3-Hydroxyacyl-CoA Dehydrogenase Deficiency

Mendelian MONDO:0017715 Pathograph 28 Show in embeddings browser Fatty Acid Oxidation Disorder Inborn Error of Metabolism Hyperinsulinemic Hypoglycemia

3-Hydroxyacyl-CoA dehydrogenase deficiency (HADH deficiency, also known as short-chain 3-hydroxyacyl-CoA dehydrogenase or SCHAD deficiency) is an autosomal recessive inborn error of metabolism caused by biallelic loss-of-function mutations in the nuclear HADH gene. HADH encodes mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase, which catalyzes the penultimate NAD+-dependent oxidation of short- and medium-chain L-3-hydroxyacyl-CoAs to 3-ketoacyl-CoAs in the fatty acid beta-oxidation pathway. Uniquely among mitochondrial fatty acid beta-oxidation defects, the primary clinical presentation is persistent congenital hyperinsulinemic hypoglycemia and severe dietary protein (leucine) sensitivity, rather than cardiomyopathy, rhabdomyolysis, or severe hepatic failure. Pathophysiologically, this hyperinsulinemic phenotype arises because SCHAD directly interacts with and tonically inhibits mitochondrial glutamate dehydrogenase (GDH/GLUD1) in pancreatic beta cells. Loss of SCHAD protein eliminates this tonic inhibition, driving constitutive GDH activation, accelerated glutaminolysis, increased beta-cell ATP/ADP ratio, closure of ATP-sensitive potassium (K-ATP) channels, membrane depolarization, and dysregulated calcium-dependent insulin exocytosis. When residual enzyme activity is profoundly depleted, metabolic hallmarks including elevated plasma 3-hydroxybutyrylcarnitine (C4-OH) and urinary 3-hydroxyglutarate are detected. Because beta-cell K-ATP channels remain structurally intact, hyperinsulinism in HADH deficiency is characteristically responsive to diazoxide.

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7
Pathophys.
11
Phenotypes
28
Pathograph
1
Genes
4
Medical Actions
1
Models
1
References
2
Deep Research
🏷

Classifications

Harrison's Part
ENDOCRINOLOGY METABOLISM GENETICS ENVIRONMENT DISEASE
Mechanistic Nosology
mitochondrial disease
⚙

Pathophysiology

7
Biallelic HADH Loss-of-Function Mutations
Biallelic loss-of-function variants in the nuclear HADH gene (encoding mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase, SCHAD) eliminate or drastically reduce SCHAD catalytic activity and protein abundance in mitochondria.
HADH hgnc:4799 HUGO Gene Nomenclature Committee (hgnc) Relation: this pathophysiological event involves this gene This pathophysiological event involves HADH (hgnc:4799). hgnc:4799 is a gene from the HUGO Gene Nomenclature Committee.
(3S)-3-hydroxyacyl-CoA dehydrogenase (NAD+) activity GO:0003857 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves decreased (3S)-3-hydroxyacyl-CoA dehydrogenase (NAD+) activity (GO:0003857). GO:0003857 is a molecular function from the Gene Ontology. ↓ DECREASED
mitochondrion GO:0005739 Gene Ontology (GO) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in mitochondrion (GO:0005739). GO:0005739 is an anatomical location from the Gene Ontology.
Downstream
Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation Loss of SCHAD catalytic activity directly halts the oxidation of short-chain 3-hydroxyacyl-CoA substrates.
Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase Depletion of SCHAD protein directly abolishes its inhibitory physical interaction with GDH.
Show evidence (2 references)
PMID:11489939 SUPPORT Human Clinical
"Measurement of the activity of L-3-hydroxyacyl-CoA dehydrogenase in cultured skin fibroblasts with acetoacetyl-CoA substrate showed reduced activity."
Confirms marked enzymatic deficiency of SCHAD in patient fibroblasts.
PMID:23430856 SUPPORT Human Clinical
"The human HADH gene encodes the short-chain-L-3-hydroxyacyl-CoA dehydrogenase, the enzyme which catalyzes the third step of the β-oxidation of the fatty acids in the mitochondrial matrix."
Establishes HADH as encoding mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase.
Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation
Loss of SCHAD catalytic activity blocks the penultimate dehydrogenation of short- and medium-chain L-3-hydroxyacyl-CoAs to 3-ketoacyl-CoAs within the mitochondrial fatty acid oxidation cycle. This disrupts complete beta-oxidation of fatty acids and short-chain branched intermediates.
hepatocyte CL:0000182 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves hepatocyte (CL:0000182). CL:0000182 is a cell type from the Cell Ontology. type B pancreatic cell CL:0000169 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves type B pancreatic cell (CL:0000169). CL:0000169 is a cell type from the Cell Ontology.
fatty acid beta-oxidation GO:0006635 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased fatty acid beta-oxidation (GO:0006635). GO:0006635 is a biological process from the Gene Ontology. ↓ DECREASED
mitochondrion GO:0005739 Gene Ontology (GO) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in mitochondrion (GO:0005739). GO:0005739 is an anatomical location from the Gene Ontology.
Downstream
Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate Unmetabolized short-chain 3-hydroxyacyl-CoA esters are converted into carnitine esters or dicarboxylic acids.
Show evidence (1 reference)
PMID:19417036 SUPPORT Human Clinical
"HADH encodes for the enzyme 3-hydroxyacyl-coenzyme A dehydrogenase (HADH) and catalyses the penultimate reaction in the beta-oxidation of fatty acids."
Defines SCHAD as catalyzing the penultimate reaction of fatty acid beta-oxidation.
Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate
Upstream accumulation of 3-hydroxybutyryl-CoA results in transesterification to carnitine, causing elevated circulating plasma 3-hydroxybutyrylcarnitine (C4-OH), and alternative omega-oxidation yielding urinary excretion of 3-hydroxyglutaric acid and dicarboxylic acids.
Downstream
Profound Hypoketotic Hypoglycemia and Neuroglycopenia Failure of short-chain beta-oxidation prevents hepatic ketogenesis, worsening fuel deprivation and neuroglycopenia when blood glucose levels fall.
Dicarboxylic aciduria Alternative omega-oxidation of accumulated short-chain acyl-CoA esters yields dicarboxylic acids excreted in urine.
Elevated circulating acylcarnitine concentration Carnitine acyltransferase transesterifies accumulated short-chain 3-hydroxyacyl-CoA into 3-hydroxybutyrylcarnitine (C4-OH), which is exported into the bloodstream.
Show evidence (1 reference)
PMID:23430856 SUPPORT Human Clinical
"We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
Establishes plasma C4-OH carnitine and urinary 3-hydroxyglutarate as the biochemical hallmarks of severe SCHAD deficiency.
Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase
Under physiological conditions, the SCHAD protein physically binds to mitochondrial glutamate dehydrogenase (GDH/GLUD1) in pancreatic beta cells and exerts tonic allosteric inhibition. In HADH deficiency, absence of SCHAD protein eliminates this tonic inhibition, leaving GDH hyperactive and hyperresponsive to allosteric activation by amino acids like leucine.
type B pancreatic cell CL:0000169 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves type B pancreatic cell (CL:0000169). CL:0000169 is a cell type from the Cell Ontology.
glutamate dehydrogenase [NAD(P)+] activity GO:0004353 Gene Ontology (GO) Relation: this pathophysiological event involves this molecular function This pathophysiological event involves increased glutamate dehydrogenase [NAD(P)+] activity, annotated with L-glutamate dehydrogenase [NAD(P)+] activity (GO:0004353). GO:0004353 is a molecular function from the Gene Ontology. ↑ INCREASED
mitochondrion GO:0005739 Gene Ontology (GO) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in mitochondrion (GO:0005739). GO:0005739 is an anatomical location from the Gene Ontology.
Animal models
Hadh knockout mouse (Hadh-/-) Mouse recapitulates Hadh knockout mice recapitulate the loss of tonic GDH inhibition by SCHAD, leading to increased GDH activity and amino acid-stimulated insulin secretion.
Downstream
Accelerated Glutaminolysis and Mitochondrial ATP Generation Relieved GDH inhibition accelerates oxidative deamination of glutamate to alpha-ketoglutarate.
Show evidence (2 references)
PMID:20670938 SUPPORT In Vitro
"Pull-down experiments with SCHAD, anti-SCHAD, or anti-GDH antibodies showed protein-protein interactions between SCHAD and GDH."
Directly demonstrates physical protein-protein interaction between SCHAD and GDH.
PMID:20670938 SUPPORT Model Organism
"These studies indicate that SCHAD deficiency causes hyperinsulinism by activation of GDH via loss of inhibitory regulation of GDH by SCHAD."
Establishes that loss of GDH tonic inhibition by SCHAD causes GDH hyperactivation and hyperinsulinism.
Accelerated Glutaminolysis and Mitochondrial ATP Generation
Uninhibited GDH catalyzes excessive deamination of glutamate to alpha-ketoglutarate, fueling the tricarboxylic acid (TCA) cycle and oxidative phosphorylation in pancreatic beta cells. This produces an inappropriate surge in cytosolic ATP/ADP ratio even during periods of low ambient glucose or following dietary protein (leucine) consumption.
type B pancreatic cell CL:0000169 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves type B pancreatic cell (CL:0000169). CL:0000169 is a cell type from the Cell Ontology.
islet of Langerhans UBERON:0000006 Uberon multi-species anatomy ontology (UBERON) Relation: this pathophysiological event occurs in this anatomical location This pathophysiological event occurs in islet of Langerhans (UBERON:0000006). UBERON:0000006 is an anatomical location from the Uberon multi-species anatomy ontology.
Downstream
Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion Elevated cytosolic ATP/ADP ratio triggers closure of ATP-sensitive potassium channels.
Show evidence (2 references)
PMID:20670938 SUPPORT Model Organism
"hadh(-/-) islets also have increased ... glutamine oxidation."
Demonstrates increased glutamine oxidation and accelerated glutaminolysis in SCHAD-deficient islets.
PMID:19417036 SUPPORT Human Clinical
"Two other children with HH due to HADH gene mutations also demonstrated marked protein sensitivity."
Demonstrates clinical protein hypersensitivity in patients with HADH mutations.
Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
Elevated ATP/ADP ratios induce closure of beta-cell ATP-sensitive potassium (K-ATP) channels, depolarizing the plasma membrane and opening voltage-gated calcium channels. Influx of calcium triggers continuous and inappropriate exocytosis of insulin granules into the circulation, uncoupled from physiological blood glucose levels.
type B pancreatic cell CL:0000169 Cell Ontology (CL) Relation: this pathophysiological event involves this cell type This pathophysiological event involves type B pancreatic cell (CL:0000169). CL:0000169 is a cell type from the Cell Ontology.
insulin secretion GO:0030073 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased insulin secretion (GO:0030073). GO:0030073 is a biological process from the Gene Ontology. ↑ INCREASED positive regulation of insulin secretion GO:0032024 Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves positive regulation of insulin secretion (GO:0032024). GO:0032024 is a biological process from the Gene Ontology.
Downstream
Profound Hypoketotic Hypoglycemia and Neuroglycopenia Hyperinsulinemia suppresses hepatic glucose production, enhances peripheral uptake, and shuts down ketogenesis.
Show evidence (2 references)
PMID:26953163 SUPPORT Model Organism
"We conclude that hypoglycemia in SCHAD-CHI is islet cell-autonomous."
Proves via islet transplantation that hyperinsulinemic hypoglycemia in SCHAD deficiency is an islet-autonomous defect.
PMID:14693719 SUPPORT Human Clinical
"Inappropriately elevated insulin secretion is the hallmark of persistent hyperinsulinemic hypoglycemia of infancy (PHHI), also denoted congenital hyperinsulinism."
Confirms familial hyperinsulinemic hypoglycemia caused by SCHAD genetic defect.
Profound Hypoketotic Hypoglycemia and Neuroglycopenia
Excessive circulating insulin simultaneously drives glucose uptake into skeletal muscle and adipose tissue, inhibits hepatic gluconeogenesis and glycogenolysis, and potently suppresses adipose lipolysis and hepatic ketogenesis. The dual depletion of glucose and alternative ketone fuels starves the brain, producing neuroglycopenia, lethargy, seizures, and risk of neurological sequelae.
Downstream
Hyperinsulinemic hypoglycemia Inappropriate circulating insulin drives acute, profound reductions in blood glucose.
Hypoketotic hypoglycemia High insulin levels block lipolysis and ketogenesis, leaving hypoglycemia without ketone bodies.
Postprandial hypoglycemia Manifests as hypoglycemia occurring unpredictably in the hours following protein/leucine-containing feeds.
Seizure Severe neuroglycopenia precipitates generalized convulsive seizures in early life.
Lethargy Acute cerebral energy deficit manifests as pronounced lethargy and obtundation.
Hypotonia Acute energy failure and neuroglycopenia cause generalized muscular hypotonia.
Neonatal hypoglycemia Presentation of hyperinsulinemic hypoglycemia during the first days or weeks of life.
Intellectual disability Irreversible developmental delay resulting from delayed diagnosis or repeated uncorrected neuroglycopenia.
Microcephaly Secondary microcephaly caused by profound early infantile neuroglycopenic brain injury.
Show evidence (2 references)
PMID:26316438 SUPPORT Human Clinical
"The main clinical feature of this metabolic disease is hypoketotic hypoglycemia with hyperinsulinism which is different from other inherited defects of fatty acid β-oxidation that can present with symptoms such as hepatomegaly, myopathy and cardiomyopathy."
Identifies hypoketotic hypoglycemia with hyperinsulinism as the defining clinical hallmark distinct from other beta-oxidation disorders.
PMID:11489939 SUPPORT Human Clinical
"Further episodes of hypoketotic hypoglycemia were associated with inappropriately elevated plasma insulin concentrations."
Documents recurrent hypoketotic hypoglycemia with inappropriate hyperinsulinemia.
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for 3-Hydroxyacyl-CoA Dehydrogenase Deficiency Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
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Phenotypes

11
Endocrine 1
Hyperinsulinemic hypoglycemia HP:0000825 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hyperinsulinemic hypoglycemia (HP:0000825). HP:0000825 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:21252247 SUPPORT Human Clinical
"Recessive mutations in the hydroxyacyl-CoA dehydrogenase (HADH) gene encoding the enzyme 3-hydroxyacyl-CoA dehydrogenase are a rare cause of diazoxide-responsive hyperinsulinemic hypoglycemia (HH) with just five probands reported to date."
Identifies hyperinsulinemic hypoglycemia as the principal disease phenotype.
Genitourinary 1
Dicarboxylic aciduria HP:0003215 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Dicarboxylic aciduria (HP:0003215). HP:0003215 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"Metabolic profiling in some, but not all, affected individuals reveals a raised plasma hydroxybutyrylcarnitine and urinary medium-chain dicarboxylic, 3-hydroxydicarboxylic metabolites and 3-hydroxyglutarate levels."
Documents urinary excretion of dicarboxylic acids and 3-hydroxyglutarate.
Head and Neck 1
Microcephaly HP:0000252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Microcephaly (HP:0000252). HP:0000252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"Although their symptoms had begun in infancy, three of the four new cases were diagnosed late and presented with mental retardation, microcephaly."
Documents secondary microcephaly in patients with delayed diagnosis and prolonged untreated hyperinsulinism.
Metabolism 4
Hypoketotic hypoglycemia HP:0001985 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypoketotic hypoglycemia (HP:0001985). HP:0001985 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"The main clinical feature of this metabolic disease is hypoketotic hypoglycemia with hyperinsulinism which is different from other inherited defects of fatty acid β-oxidation that can present with symptoms such as hepatomegaly, myopathy and cardiomyopathy."
Establishes hypoketotic hypoglycemia as the primary presentation.
Neonatal hypoglycemia HP:0001998 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Neonatal hypoglycemia (HP:0001998). HP:0001998 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"We present clinical and laboratory findings together with the long-term clinical course of a case with a deep intronic HADH splicing mutation (c.636+471G>T) causing neonatal-onset hyperinsulinemic hypoglycemia with mild progression."
Identifies neonatal-onset hyperinsulinemic hypoglycemia in a patient with a deep intronic HADH variant.
Postprandial hypoglycemia Reactive hypoglycemia HP:0012051 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Postprandial hypoglycemia, annotated with Reactive hypoglycemia (HP:0012051). HP:0012051 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"The hypoglycemia observed in FS was not typical of a FAOD; it was not easily provoked by a prolonged fast, but, rather, occurred in an unpredictable fashion, often 2-6 hours after a feed."
States the postprandial, non-fasting-provoked pattern this phenotype records, and contrasts it with the fasting-provoked pattern of a FAOD.
Elevated circulating acylcarnitine concentration HP:0045045 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Elevated circulating acylcarnitine concentration (HP:0045045). HP:0045045 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"However, unlike other children with hyperinsulinism, this patient had a persistently elevated blood spot hydroxybutyrylcarnitine concentration when fed, as well as when fasted."
Documents elevated blood spot hydroxybutyrylcarnitine in patient with SCHAD deficiency.
Musculoskeletal 1
Hypotonia HP:0001252 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Hypotonia (HP:0001252). HP:0001252 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"They found that patients became symptomatic in early life (ranging from 1.5 hours to 8 months) and presented with hypoglycemic convulsions, lethargy and hypotonia."
Identifies hypotonia as a presenting clinical feature in early life alongside convulsions and lethargy.
Nervous System 3
Seizure HP:0001250 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Seizure (HP:0001250). HP:0001250 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"A female infant of nonconsanguineous Indian parents presented at 4 months with a hypoglycemic convulsion."
Documents presenting hypoglycemic convulsion in an infant.
Lethargy HP:0001254 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Lethargy (HP:0001254). HP:0001254 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"They found that patients became symptomatic in early life (ranging from 1.5 hours to 8 months) and presented with hypoglycemic convulsions, lethargy and hypotonia."
Documents presenting clinical manifestations of lethargy, convulsions, and hypotonia.
Intellectual disability HP:0001249 Human Phenotype Ontology (HP) Relation: this clinical feature is this phenotype This clinical feature is Intellectual disability (HP:0001249). HP:0001249 is a phenotype from the Human Phenotype Ontology.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"Although their symptoms had begun in infancy, three of the four new cases were diagnosed late and presented with mental retardation, microcephaly."
Reports intellectual disability (mental retardation) developing in cases with delayed diagnosis and treatment.
🧬

Genetic Associations

1
HADH loss-of-function variants (Causative)
Gene: HADH hgnc:4799 HUGO Gene Nomenclature Committee (hgnc) Relation: this disease-associated gene is this gene This disease-associated gene is HADH (hgnc:4799). hgnc:4799 is a gene from the HUGO Gene Nomenclature Committee. relationship_type: CAUSATIVE
Autosomal recessive inheritance
Show evidence (2 references)
PMID:21252247 SUPPORT Human Clinical
"Six different HADH mutations were identified in 11/115 (10%) patients tested."
Identifies six distinct pathogenic HADH mutations in affected children.
PMID:26316438 SUPPORT Human Clinical
"We present clinical and laboratory findings together with the long-term clinical course of a case with a deep intronic HADH splicing mutation (c.636+471G>T) causing neonatal-onset hyperinsulinemic hypoglycemia with mild progression."
Documents deep intronic pseudoexon-creating HADH mutation causing hyperinsulinemic hypoglycemia.
💊

Medical Actions

4
Diazoxide
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: diazoxide CHEBI:4495 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses diazoxide (CHEBI:4495). CHEBI:4495 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
First-line medical therapy for HADH deficiency. In HADH deficiency, K-ATP channels (SUR1/Kir6.2) are structurally intact and functional. Diazoxide binds the SUR1 subunit and maintains K-ATP channels in the open state, hyperpolarizing the beta-cell plasma membrane, blocking voltage-gated calcium entry, and suppressing unregulated insulin exocytosis.
Mechanism Target:
INHIBITS Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion — Diazoxide opens K-ATP channels, hyperpolarizing the pancreatic beta-cell membrane and inhibiting calcium influx and inappropriate insulin secretion.
Show evidence (2 references)
PMID:21252247 SUPPORT Human Clinical
"HADH mutations are a relatively common cause of diazoxide-responsive HH with a frequency similar to that of GLUD1 and HNF4A mutations."
Documents that HADH mutations cause diazoxide-responsive hyperinsulinemic hypoglycemia and supports diazoxide as effective medical management.
PMID:11489939 SUPPORT Human Clinical
"The patient's hyperinsulinism was easily controlled with diazoxide and chlorothiazide."
Documents excellent glycemic control achieved with diazoxide and chlorothiazide.
Chlorothiazide
Action: PharmacotherapyNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Pharmacotherapy (NCIT:C15986). NCIT:C15986 is a clinical intervention from the NCI Thesaurus. NCIT:C15986
Agent: chlorothiazide CHEBI:3640 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses chlorothiazide (CHEBI:3640). CHEBI:3640 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Thiazide diuretic frequently co-administered with diazoxide. Chlorothiazide exhibits a synergistic hyperglycemic action by inhibiting pancreatic phosphodiesterase, reducing insulin release, and counteracting diazoxide-induced fluid retention.
Mechanism Target:
INHIBITS Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion — Acts synergistically with diazoxide to inhibit beta-cell depolarization and suppress insulin release.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"The patient's hyperinsulinism was easily controlled with diazoxide and chlorothiazide."
Confirms successful combination therapy with diazoxide and chlorothiazide.
Frequent Carbohydrate Feedings and Avoidance of Fasting
Action: Dietary InterventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dietary Intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. NCIT:C15447
Platform: Behavioral / lifestyle
Supportive dietary therapy to maintain blood glucose and prevent acute neuroglycopenia during intervals between feeds or physiological stress.
Mechanism Target:
BYPASSES Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation — Continuous exogenous carbohydrate intake bypasses reliance on hepatic fatty acid oxidation and ketogenesis for energy maintenance.
Show evidence (1 reference)
PMID:27771675 SUPPORT Human Clinical
"HADH mutations are rare causes of hypoglycemia and can be mitigated with diazoxide and appropriate dietary therapy if identified early."
Recommends appropriate dietary therapy alongside diazoxide.
Dietary Protein Moderation
Action: Dietary InterventionNCI Thesaurus (NCIT) Relation: this treatment is this clinical intervention This treatment is Dietary Intervention (NCIT:C15447). NCIT:C15447 is a clinical intervention from the NCI Thesaurus. NCIT:C15447
Platform: Behavioral / lifestyle
Because loss of SCHAD unleashes GDH allosteric activation, amino acid consumption (particularly protein/leucine-rich meals) triggers hyperactivation of glutamate dehydrogenase and causes postprandial hypoglycemic episodes. Moderating dietary protein intake prevents protein-induced hyperinsulinism.
Mechanism Target:
INHIBITS Accelerated Glutaminolysis and Mitochondrial ATP Generation — Restricting protein and leucine intake reduces excessive anaplerotic flux through uninhibited glutamate dehydrogenase (GDH), attenuating abnormal beta-cell ATP production.
Show evidence (1 reference)
PMID:19417036 SUPPORT Human Clinical
"The index case presented at 4 months of age with hypoglycemic seizures. Her HH responded to diazoxide, but she continued to have episodes of hypoglycemia even on diazoxide, especially when consuming high-protein foods."
Demonstrates breakthrough hypoglycemia precipitated by high-protein food intake.
🔬

Biochemical Markers

4
3-Hydroxybutyrylcarnitine (C4-OH) (INCREASED)
Context: Characteristic acylcarnitine finding in blood spots or plasma by tandem mass spectrometry, reflecting accumulated short-chain 3-hydroxyacyl-CoA transesterified with carnitine.
Pathograph Readouts
Readout Of Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate Positive Diagnostic
Direct metabolic marker of impaired short-chain 3-hydroxyacyl-CoA oxidation.
Show evidence (1 reference)
PMID:23430856 SUPPORT Human Clinical
"We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
Identifies plasma 3-hydroxybutyrylcarnitine as an invariable biochemical hallmark of profound SCHAD deficiency.
3-Hydroxyglutaric acid (INCREASED)
Context: Urinary organic acid hallmark detected by GC-MS, resulting from alternative omega-oxidation of accumulating short-chain dicarboxylic acyl intermediates.
Pathograph Readouts
Readout Of Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate Positive Diagnostic
Excreted organic acid reporting short-chain acyl-CoA catabolism block.
Show evidence (1 reference)
PMID:23430856 SUPPORT Human Clinical
"We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
Confirms urinary 3-hydroxyglutaric acid as an invariable biochemical hallmark in severe SCHAD deficiency.
Inappropriately elevated plasma insulin (INCREASED)
Context: Inappropriate detectable or elevated plasma insulin at the time of documented hypoglycemia, defining hyperinsulinism.
Pathograph Readouts
Readout Of Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion Positive Diagnostic
Inappropriate insulin exocytosis despite profound hypoglycemia.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"Further episodes of hypoketotic hypoglycemia were associated with inappropriately elevated plasma insulin concentrations."
Documents elevated plasma insulin during hypoglycemic crises.
Blood glucose (DECREASED)
Context: Profoundly decreased venous or capillary blood glucose during fasting or protein-rich feeds.
Pathograph Readouts
Readout Of Profound Hypoketotic Hypoglycemia and Neuroglycopenia Negative Diagnostic
Systemic hypoglycemia driven by excessive peripheral glucose uptake and suppressed production.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"While she was taking diazoxide 2 mg/kg/day, a non-ketotic hypoglycemic attack (blood glucose: 46 mg/dL) was detected with a very high insulin level (46.8 µIU/mL)."
Measures severe hypoglycemia (blood glucose 46 mg/dL) coincident with elevated insulin.
🔬

Diagnosis

3
Plasma Acylcarnitine Profiling
Tandem mass spectrometry analysis of dried blood spots or plasma demonstrating persistent elevation of 3-hydroxybutyrylcarnitine (C4-OH), the hallmark biochemical signature of short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency.
Show evidence (1 reference)
PMID:11489939 SUPPORT Human Clinical
"However, unlike other children with hyperinsulinism, this patient had a persistently elevated blood spot hydroxybutyrylcarnitine concentration when fed, as well as when fasted."
Identifies persistent blood spot hydroxybutyrylcarnitine elevation as the diagnostic hallmark of SCHAD deficiency.
Urine Organic Acid Analysis
Gas chromatography-mass spectrometry (GC-MS) of urine revealing increased excretion of 3-hydroxyglutaric acid, reflecting upstream accumulation and secondary dicarboxylic acid catabolism of 3-hydroxybutyryl intermediates.
Show evidence (1 reference)
PMID:14693719 SUPPORT Human Clinical
"Urine metabolite analysis showed that SCHAD deficiency resulted in specific excretion of 3-hydroxyglutaric acid."
Demonstrates that urine organic acid analysis reveals specific urinary excretion of 3-hydroxyglutaric acid.
HADH Molecular Genetic Testing
Sequence analysis of the HADH gene (Sanger sequencing, targeted gene panels for hyperinsulinemic hypoglycemia, or exome/genome sequencing) to identify biallelic pathogenic loss-of-function variants.
DNA Sequencing NCIT:C153598 NCI Thesaurus (NCIT)
Show evidence (1 reference)
PMID:21252247 SUPPORT Human Clinical
"We recommend that HADH sequence analysis is considered in all patients with diazoxide-responsive HH when recessive inheritance is suspected."
Recommends HADH sequence analysis for diagnostic confirmation in suspected recessive diazoxide-responsive hyperinsulinism.
📈

Progression

2
Neonatal to early infancy onset
Onset is typically in the neonatal period or early infancy (commonly around 1 to 4 months of age), presenting with symptomatic fasting or protein-induced hypoglycemia, diaphoresis, jitteriness, and hypoglycemic convulsions.
Show evidence (2 references)
PMID:11489939 SUPPORT Human Clinical
"A female infant of nonconsanguineous Indian parents presented at 4 months with a hypoglycemic convulsion."
Reports early infantile presentation with hypoglycemic convulsions at 4 months.
PMID:26316438 SUPPORT Human Clinical
"The clinical presentation is mainly neonatal- or early infancy-onset HH and patients are diazoxide-responsive."
Confirms that clinical presentation is predominantly neonatal or early infantile onset.
Chronic medical management
With ongoing diazoxide therapy and avoidance of fasting or excessive protein loads, long-term glycemic control is achieved and prevents recurrent neuroglycopenic seizures and irreversible brain damage. Diazoxide dosage can occasionally be tapered with age.
Show evidence (1 reference)
PMID:26316438 SUPPORT Human Clinical
"Following the diagnosis of CHH, she was commenced on 10 mg/kg/day of diazoxide and remained on that dose for five years."
Demonstrates stable long-term control on maintenance diazoxide therapy.
📊

Prevalence

1
Worldwide
Point Prevalence Rare
HADH-related hyperinsulinemic hypoglycemia is an ultra-rare disorder accounting for less than 4% of all congenital hyperinsulinism cases, with an increased prevalence reported in consanguineous populations (up to 10% of consanguineous diazoxide-responsive cohorts). Approximately 40 cases have been reported in the medical literature.
Show evidence (2 references)
PMID:21252247 SUPPORT Human Clinical
"Six different HADH mutations were identified in 11/115 (10%) patients tested."
Documents 10% frequency of HADH mutations in a consanguineous hyperinsulinism cohort.
PMID:26316438 SUPPORT Human Clinical
"Mutations in other known genes (including HADH) together account for less than 4% of CHH (1)."
Establishes that HADH variants account for less than 4% of total congenital hyperinsulinism cases.
🐁

Animal Models

1
Hadh knockout mouse (Hadh-/-)
Global Hadh knockout (Hadh-/-) mice exhibit amino acid hypersensitivity, hypoglycemia, and elevated insulin secretion. Isolated islets display increased glutamine oxidation and GDH hyperactivation, and islet transplantation into diabetic mice demonstrates the hypoglycemic phenotype is islet cell-autonomous.
Species
Mouse
Genotype
Hadh knockout (Hadh-/-)
Publication
PMID:20670938
Pathograph links
Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase recapitulates fidelity: high observes: molecular Hadh knockout mice recapitulate the loss of tonic GDH inhibition by SCHAD, leading to increased GDH activity and amino acid-stimulated insulin secretion.
Show evidence (2 references)
PMID:20670938 SUPPORT Model Organism
"These studies indicate that SCHAD deficiency causes hyperinsulinism by activation of GDH via loss of inhibitory regulation of GDH by SCHAD."
Demonstrates in Hadh-/- mice that loss of SCHAD activates GDH and causes hyperinsulinism.
+ 1 more reference
{ }

Source YAML

click to show 
name: 3-Hydroxyacyl-CoA Dehydrogenase Deficiency
category: Mendelian
creation_date: '2026-09-12T05:00:00Z'
synonyms:
- SCHAD deficiency
- Short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency
- HADH deficiency
- Hyperinsulinism due to short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency
- Short chain L-3-hydroxyacyl-CoA dehydrogenase deficiency
- HADH-related hyperinsulinemic hypoglycemia
description: >-
  3-Hydroxyacyl-CoA dehydrogenase deficiency (HADH deficiency, also known as short-chain
  3-hydroxyacyl-CoA dehydrogenase or SCHAD deficiency) is an autosomal recessive inborn error
  of metabolism caused by biallelic loss-of-function mutations in the nuclear HADH gene.
  HADH encodes mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase, which catalyzes
  the penultimate NAD+-dependent oxidation of short- and medium-chain L-3-hydroxyacyl-CoAs
  to 3-ketoacyl-CoAs in the fatty acid beta-oxidation pathway. Uniquely among mitochondrial
  fatty acid beta-oxidation defects, the primary clinical presentation is persistent
  congenital hyperinsulinemic hypoglycemia and severe dietary protein (leucine) sensitivity,
  rather than cardiomyopathy, rhabdomyolysis, or severe hepatic failure. Pathophysiologically,
  this hyperinsulinemic phenotype arises because SCHAD directly interacts with and tonically
  inhibits mitochondrial glutamate dehydrogenase (GDH/GLUD1) in pancreatic beta cells.
  Loss of SCHAD protein eliminates this tonic inhibition, driving constitutive GDH activation,
  accelerated glutaminolysis, increased beta-cell ATP/ADP ratio, closure of ATP-sensitive
  potassium (K-ATP) channels, membrane depolarization, and dysregulated calcium-dependent
  insulin exocytosis. When residual enzyme activity is profoundly depleted, metabolic
  hallmarks including elevated plasma 3-hydroxybutyrylcarnitine (C4-OH) and urinary
  3-hydroxyglutarate are detected. Because beta-cell K-ATP channels remain structurally
  intact, hyperinsulinism in HADH deficiency is characteristically responsive to diazoxide.
disease_term:
  preferred_term: 3-hydroxyacyl-CoA dehydrogenase deficiency
  term:
    id: MONDO:0017715
    label: 3-hydroxyacyl-CoA dehydrogenase deficiency
parents:
- Fatty Acid Oxidation Disorder
- Inborn Error of Metabolism
- Hyperinsulinemic Hypoglycemia
references:
- reference: PMID:20301549
  title: "Nonsyndromic Genetic Hyperinsulinism Overview."
  tags:
  - GeneReviews
classifications:
  harrisons_chapter:
  - classification_value: ENDOCRINOLOGY_METABOLISM
  - classification_value: GENETICS_ENVIRONMENT_DISEASE
  mechanistic_category:
  - classification_value: mitochondrial disease
prevalence:
- population: Worldwide
  measure_type: POINT_PREVALENCE
  prevalence_class: RARE
  notes: >-
    HADH-related hyperinsulinemic hypoglycemia is an ultra-rare disorder accounting for less
    than 4% of all congenital hyperinsulinism cases, with an increased prevalence reported
    in consanguineous populations (up to 10% of consanguineous diazoxide-responsive cohorts).
    Approximately 40 cases have been reported in the medical literature.
  evidence:
  - reference: PMID:21252247
    reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six different HADH mutations were identified in 11/115 (10%) patients tested."
    explanation: Documents 10% frequency of HADH mutations in a consanguineous hyperinsulinism cohort.
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Mutations in other known genes (including HADH) together account for less than 4% of CHH (1)."
    explanation: Establishes that HADH variants account for less than 4% of total congenital hyperinsulinism cases.
progression:
- phase: Neonatal to early infancy onset
  notes: >-
    Onset is typically in the neonatal period or early infancy (commonly around 1 to 4 months of age),
    presenting with symptomatic fasting or protein-induced hypoglycemia, diaphoresis, jitteriness,
    and hypoglycemic convulsions.
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A female infant of nonconsanguineous Indian parents presented at 4 months with a hypoglycemic convulsion."
    explanation: Reports early infantile presentation with hypoglycemic convulsions at 4 months.
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical presentation is mainly neonatal- or early infancy-onset HH and patients are diazoxide-responsive."
    explanation: Confirms that clinical presentation is predominantly neonatal or early infantile onset.
- phase: Chronic medical management
  notes: >-
    With ongoing diazoxide therapy and avoidance of fasting or excessive protein loads,
    long-term glycemic control is achieved and prevents recurrent neuroglycopenic seizures
    and irreversible brain damage. Diazoxide dosage can occasionally be tapered with age.
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Following the diagnosis of CHH, she was commenced on 10 mg/kg/day of diazoxide and remained on that dose for five years."
    explanation: Demonstrates stable long-term control on maintenance diazoxide therapy.
pathophysiology:
- name: Biallelic HADH Loss-of-Function Mutations
  role: trigger
  biological_scale: MOLECULAR
  description: >-
    Biallelic loss-of-function variants in the nuclear HADH gene (encoding mitochondrial short-chain
    3-hydroxyacyl-CoA dehydrogenase, SCHAD) eliminate or drastically reduce SCHAD catalytic activity
    and protein abundance in mitochondria.
  genes:
  - preferred_term: HADH
    term:
      id: hgnc:4799
      label: HADH
  molecular_functions:
  - preferred_term: (3S)-3-hydroxyacyl-CoA dehydrogenase (NAD+) activity
    term:
      id: GO:0003857
      label: (3S)-3-hydroxyacyl-CoA dehydrogenase (NAD+) activity
    modifier: DECREASED
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Measurement of the activity of L-3-hydroxyacyl-CoA dehydrogenase in cultured skin fibroblasts with acetoacetyl-CoA substrate showed reduced activity."
    explanation: Confirms marked enzymatic deficiency of SCHAD in patient fibroblasts.
  - reference: PMID:23430856
    reference_title: "3-hydroxyacyl-coenzyme a dehydrogenase deficiency: identification of a new mutation causing hyperinsulinemic hypoketotic hypoglycemia, altered organic acids and acylcarnitines concentrations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The human HADH gene encodes the short-chain-L-3-hydroxyacyl-CoA dehydrogenase, the enzyme which catalyzes the third step of the β-oxidation of the fatty acids in the mitochondrial matrix."
    explanation: Establishes HADH as encoding mitochondrial short-chain 3-hydroxyacyl-CoA dehydrogenase.
  downstream:
  - target: Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation
    causal_link_type: DIRECT
    description: Loss of SCHAD catalytic activity directly halts the oxidation of short-chain 3-hydroxyacyl-CoA substrates.
  - target: Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase
    causal_link_type: DIRECT
    description: Depletion of SCHAD protein directly abolishes its inhibitory physical interaction with GDH.
- name: Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    Loss of SCHAD catalytic activity blocks the penultimate dehydrogenation of short- and
    medium-chain L-3-hydroxyacyl-CoAs to 3-ketoacyl-CoAs within the mitochondrial fatty acid
    oxidation cycle. This disrupts complete beta-oxidation of fatty acids and short-chain
    branched intermediates.
  biological_processes:
  - preferred_term: fatty acid beta-oxidation
    term:
      id: GO:0006635
      label: fatty acid beta-oxidation
    modifier: DECREASED
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  cell_types:
  - preferred_term: hepatocyte
    term:
      id: CL:0000182
      label: hepatocyte
  - preferred_term: type B pancreatic cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  evidence:
  - reference: PMID:19417036
    reference_title: "3-Hydroxyacyl-coenzyme A dehydrogenase deficiency and hyperinsulinemic hypoglycemia: characterization of a novel mutation and severe dietary protein sensitivity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HADH encodes for the enzyme 3-hydroxyacyl-coenzyme A dehydrogenase (HADH) and catalyses the penultimate reaction in the beta-oxidation of fatty acids."
    explanation: Defines SCHAD as catalyzing the penultimate reaction of fatty acid beta-oxidation.
  downstream:
  - target: Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate
    causal_link_type: DIRECT
    description: Unmetabolized short-chain 3-hydroxyacyl-CoA esters are converted into carnitine esters or dicarboxylic acids.
- name: Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate
  role: consequence
  biological_scale: ORGANISM
  description: >-
    Upstream accumulation of 3-hydroxybutyryl-CoA results in transesterification to carnitine,
    causing elevated circulating plasma 3-hydroxybutyrylcarnitine (C4-OH), and alternative
    omega-oxidation yielding urinary excretion of 3-hydroxyglutaric acid and dicarboxylic acids.
  chemical_entities:
  - preferred_term: 3-hydroxybutyrylcarnitine
    term:
      id: CHEBI:72995
      label: 3-hydroxybutyrylcarnitine
    modifier: INCREASED
  - preferred_term: 3-hydroxyglutaric acid
    term:
      id: CHEBI:39980
      label: 3-hydroxyglutaric acid
    modifier: INCREASED
  evidence:
  - reference: PMID:23430856
    reference_title: "3-hydroxyacyl-coenzyme a dehydrogenase deficiency: identification of a new mutation causing hyperinsulinemic hypoketotic hypoglycemia, altered organic acids and acylcarnitines concentrations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
    explanation: Establishes plasma C4-OH carnitine and urinary 3-hydroxyglutarate as the biochemical hallmarks of severe SCHAD deficiency.
  downstream:
  - target: Profound Hypoketotic Hypoglycemia and Neuroglycopenia
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Blocked short-chain fatty acid beta-oxidation prevents generation of acetyl-CoA and ketone bodies in hepatocytes.
    - Absence of circulating ketone bodies deprives the developing brain of alternative oxidative fuel during hypoglycemia.
    description: >-
      Failure of short-chain beta-oxidation prevents hepatic ketogenesis, worsening fuel deprivation
      and neuroglycopenia when blood glucose levels fall.
  - target: Dicarboxylic aciduria
    causal_link_type: DIRECT
    description: >-
      Alternative omega-oxidation of accumulated short-chain acyl-CoA esters yields dicarboxylic acids
      excreted in urine.
  - target: Elevated circulating acylcarnitine concentration
    causal_link_type: DIRECT
    description: >-
      Carnitine acyltransferase transesterifies accumulated short-chain 3-hydroxyacyl-CoA into
      3-hydroxybutyrylcarnitine (C4-OH), which is exported into the bloodstream.
- name: Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase
  role: central_effector
  biological_scale: MOLECULAR
  description: >-
    Under physiological conditions, the SCHAD protein physically binds to mitochondrial glutamate
    dehydrogenase (GDH/GLUD1) in pancreatic beta cells and exerts tonic allosteric inhibition.
    In HADH deficiency, absence of SCHAD protein eliminates this tonic inhibition, leaving GDH
    hyperactive and hyperresponsive to allosteric activation by amino acids like leucine.
  molecular_functions:
  - preferred_term: glutamate dehydrogenase [NAD(P)+] activity
    term:
      id: GO:0004353
      label: L-glutamate dehydrogenase [NAD(P)+] activity
    modifier: INCREASED
  locations:
  - preferred_term: mitochondrion
    term:
      id: GO:0005739
      label: mitochondrion
  cell_types:
  - preferred_term: type B pancreatic cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  evidence:
  - reference: PMID:20670938
    reference_title: "Mechanism of hyperinsulinism in short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency involves activation of glutamate dehydrogenase."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Pull-down experiments with SCHAD, anti-SCHAD, or anti-GDH antibodies showed protein-protein interactions between SCHAD and GDH."
    explanation: Directly demonstrates physical protein-protein interaction between SCHAD and GDH.
  - reference: PMID:20670938
    reference_title: "Mechanism of hyperinsulinism in short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency involves activation of glutamate dehydrogenase."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "These studies indicate that SCHAD deficiency causes hyperinsulinism by activation of GDH via loss of inhibitory regulation of GDH by SCHAD."
    explanation: Establishes that loss of GDH tonic inhibition by SCHAD causes GDH hyperactivation and hyperinsulinism.
  downstream:
  - target: Accelerated Glutaminolysis and Mitochondrial ATP Generation
    causal_link_type: DIRECT
    description: Relieved GDH inhibition accelerates oxidative deamination of glutamate to alpha-ketoglutarate.
- name: Accelerated Glutaminolysis and Mitochondrial ATP Generation
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    Uninhibited GDH catalyzes excessive deamination of glutamate to alpha-ketoglutarate, fueling
    the tricarboxylic acid (TCA) cycle and oxidative phosphorylation in pancreatic beta cells.
    This produces an inappropriate surge in cytosolic ATP/ADP ratio even during periods of low
    ambient glucose or following dietary protein (leucine) consumption.
  cell_types:
  - preferred_term: type B pancreatic cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  locations:
  - preferred_term: islet of Langerhans
    term:
      id: UBERON:0000006
      label: islet of Langerhans
  chemical_entities:
  - preferred_term: L-leucine
    term:
      id: CHEBI:15603
      label: L-leucine
  evidence:
  - reference: PMID:20670938
    reference_title: "Mechanism of hyperinsulinism in short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency involves activation of glutamate dehydrogenase."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "hadh(-/-) islets also have increased ... glutamine oxidation."
    explanation: Demonstrates increased glutamine oxidation and accelerated glutaminolysis in SCHAD-deficient islets.
  - reference: PMID:19417036
    reference_title: "3-Hydroxyacyl-coenzyme A dehydrogenase deficiency and hyperinsulinemic hypoglycemia: characterization of a novel mutation and severe dietary protein sensitivity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two other children with HH due to HADH gene mutations also demonstrated marked protein sensitivity."
    explanation: Demonstrates clinical protein hypersensitivity in patients with HADH mutations.
  downstream:
  - target: Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
    causal_link_type: DIRECT
    description: Elevated cytosolic ATP/ADP ratio triggers closure of ATP-sensitive potassium channels.
- name: Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
  role: central_effector
  biological_scale: CELLULAR
  description: >-
    Elevated ATP/ADP ratios induce closure of beta-cell ATP-sensitive potassium (K-ATP) channels,
    depolarizing the plasma membrane and opening voltage-gated calcium channels. Influx of calcium
    triggers continuous and inappropriate exocytosis of insulin granules into the circulation,
    uncoupled from physiological blood glucose levels.
  biological_processes:
  - preferred_term: insulin secretion
    term:
      id: GO:0030073
      label: insulin secretion
    modifier: INCREASED
  - preferred_term: positive regulation of insulin secretion
    term:
      id: GO:0032024
      label: positive regulation of insulin secretion
  cell_types:
  - preferred_term: type B pancreatic cell
    term:
      id: CL:0000169
      label: type B pancreatic cell
  chemical_entities:
  - preferred_term: insulin
    term:
      id: CHEBI:5931
      label: insulin (human)
    modifier: INCREASED
  evidence:
  - reference: PMID:26953163
    reference_title: "The Hypoglycemic Phenotype Is Islet Cell-Autonomous in Short-Chain Hydroxyacyl-CoA Dehydrogenase-Deficient Mice."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We conclude that hypoglycemia in SCHAD-CHI is islet cell-autonomous."
    explanation: Proves via islet transplantation that hyperinsulinemic hypoglycemia in SCHAD deficiency is an islet-autonomous defect.
  - reference: PMID:14693719
    reference_title: "Familial hyperinsulinemic hypoglycemia caused by a defect in the SCHAD enzyme of mitochondrial fatty acid oxidation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Inappropriately elevated insulin secretion is the hallmark of persistent hyperinsulinemic hypoglycemia of infancy (PHHI), also denoted congenital hyperinsulinism."
    explanation: Confirms familial hyperinsulinemic hypoglycemia caused by SCHAD genetic defect.
  downstream:
  - target: Profound Hypoketotic Hypoglycemia and Neuroglycopenia
    causal_link_type: DIRECT
    description: Hyperinsulinemia suppresses hepatic glucose production, enhances peripheral uptake, and shuts down ketogenesis.
- name: Profound Hypoketotic Hypoglycemia and Neuroglycopenia
  role: consequence
  biological_scale: ORGANISM
  description: >-
    Excessive circulating insulin simultaneously drives glucose uptake into skeletal muscle and
    adipose tissue, inhibits hepatic gluconeogenesis and glycogenolysis, and potently suppresses
    adipose lipolysis and hepatic ketogenesis. The dual depletion of glucose and alternative
    ketone fuels starves the brain, producing neuroglycopenia, lethargy, seizures, and risk
    of neurological sequelae.
  chemical_entities:
  - preferred_term: glucose
    term:
      id: CHEBI:17234
      label: glucose
    modifier: DECREASED
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main clinical feature of this metabolic disease is hypoketotic hypoglycemia with hyperinsulinism which is different from other inherited defects of fatty acid β-oxidation that can present with symptoms such as hepatomegaly, myopathy and cardiomyopathy."
    explanation: Identifies hypoketotic hypoglycemia with hyperinsulinism as the defining clinical hallmark distinct from other beta-oxidation disorders.
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further episodes of hypoketotic hypoglycemia were associated with inappropriately elevated plasma insulin concentrations."
    explanation: Documents recurrent hypoketotic hypoglycemia with inappropriate hyperinsulinemia.
  downstream:
  - target: Hyperinsulinemic hypoglycemia
    causal_link_type: DIRECT
    description: Inappropriate circulating insulin drives acute, profound reductions in blood glucose.
  - target: Hypoketotic hypoglycemia
    causal_link_type: DIRECT
    description: High insulin levels block lipolysis and ketogenesis, leaving hypoglycemia without ketone bodies.
  - target: Postprandial hypoglycemia
    causal_link_type: DIRECT
    description: Manifests as hypoglycemia occurring unpredictably in the hours following protein/leucine-containing feeds.
  - target: Seizure
    causal_link_type: DIRECT
    description: Severe neuroglycopenia precipitates generalized convulsive seizures in early life.
  - target: Lethargy
    causal_link_type: DIRECT
    description: Acute cerebral energy deficit manifests as pronounced lethargy and obtundation.
  - target: Hypotonia
    causal_link_type: DIRECT
    description: Acute energy failure and neuroglycopenia cause generalized muscular hypotonia.
  - target: Neonatal hypoglycemia
    causal_link_type: DIRECT
    description: Presentation of hyperinsulinemic hypoglycemia during the first days or weeks of life.
  - target: Intellectual disability
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Delayed diagnosis and uncorrected severe neuroglycopenia in early infancy.
    - Excitotoxic and ischemic neuronal injury from prolonged cellular energy starvation.
    description: Irreversible developmental delay resulting from delayed diagnosis or repeated uncorrected neuroglycopenia.
  - target: Microcephaly
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Early infantile neuroglycopenic brain injury.
    - Arrested postnatal cerebral cortical growth following severe infantile hypoglycemic encephalopathy.
    description: Secondary microcephaly caused by profound early infantile neuroglycopenic brain injury.
phenotypes:
- name: Hyperinsulinemic hypoglycemia
  category: Endocrine
  diagnostic: true
  description: >-
    Inappropriate elevation of plasma insulin in the presence of severe hypoglycemia is the
    pathognomonic clinical feature of HADH deficiency.
  phenotype_term:
    preferred_term: Hyperinsulinemic hypoglycemia
    term:
      id: HP:0000825
      label: Hyperinsulinemic hypoglycemia
  evidence:
  - reference: PMID:21252247
    reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Recessive mutations in the hydroxyacyl-CoA dehydrogenase (HADH) gene encoding the enzyme 3-hydroxyacyl-CoA dehydrogenase are a rare cause of diazoxide-responsive hyperinsulinemic hypoglycemia (HH) with just five probands reported to date."
    explanation: Identifies hyperinsulinemic hypoglycemia as the principal disease phenotype.
- name: Hypoketotic hypoglycemia
  category: Metabolic
  diagnostic: true
  description: >-
    Suppression of ketogenesis by inappropriately high circulating insulin levels leads to
    absence of ketones (hypoketonemia) during hypoglycemic crises.
  phenotype_term:
    preferred_term: Hypoketotic hypoglycemia
    term:
      id: HP:0001985
      label: Hypoketotic hypoglycemia
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The main clinical feature of this metabolic disease is hypoketotic hypoglycemia with hyperinsulinism which is different from other inherited defects of fatty acid β-oxidation that can present with symptoms such as hepatomegaly, myopathy and cardiomyopathy."
    explanation: Establishes hypoketotic hypoglycemia as the primary presentation.
- name: Seizure
  category: Neurologic
  description: >-
    Generalized tonic-clonic convulsions resulting from severe neuroglycopenia during hypoglycemic crises.
  phenotype_term:
    preferred_term: Seizure
    term:
      id: HP:0001250
      label: Seizure
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A female infant of nonconsanguineous Indian parents presented at 4 months with a hypoglycemic convulsion."
    explanation: Documents presenting hypoglycemic convulsion in an infant.
- name: Lethargy
  category: Neurologic
  description: >-
    Lethargy and decreased consciousness secondary to acute cerebral fuel deprivation.
  phenotype_term:
    preferred_term: Lethargy
    term:
      id: HP:0001254
      label: Lethargy
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They found that patients became symptomatic in early life (ranging from 1.5 hours to 8 months) and presented with hypoglycemic convulsions, lethargy and hypotonia."
    explanation: Documents presenting clinical manifestations of lethargy, convulsions, and hypotonia.
- name: Hypotonia
  category: Neurologic
  description: >-
    Generalized muscular hypotonia observed during acute neuroglycopenic presentation.
  phenotype_term:
    preferred_term: Hypotonia
    term:
      id: HP:0001252
      label: Hypotonia
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "They found that patients became symptomatic in early life (ranging from 1.5 hours to 8 months) and presented with hypoglycemic convulsions, lethargy and hypotonia."
    explanation: Identifies hypotonia as a presenting clinical feature in early life alongside convulsions and lethargy.
- name: Intellectual disability
  category: Neurologic
  description: >-
    Neurodevelopmental impairment secondary to delayed diagnosis or repeated uncorrected
    severe hypoglycemic neuroglycopenia in infancy.
  phenotype_term:
    preferred_term: Intellectual disability
    term:
      id: HP:0001249
      label: Intellectual disability
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although their symptoms had begun in infancy, three of the four new cases were diagnosed late and presented with mental retardation, microcephaly."
    explanation: Reports intellectual disability (mental retardation) developing in cases with delayed diagnosis and treatment.
- name: Microcephaly
  category: Neurologic
  description: >-
    Secondary microcephaly resulting from early infantile neuroglycopenic brain injury
    and impaired postnatal brain growth.
  phenotype_term:
    preferred_term: Microcephaly
    term:
      id: HP:0000252
      label: Microcephaly
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Although their symptoms had begun in infancy, three of the four new cases were diagnosed late and presented with mental retardation, microcephaly."
    explanation: Documents secondary microcephaly in patients with delayed diagnosis and prolonged untreated hyperinsulinism.
- name: Neonatal hypoglycemia
  category: Metabolic
  description: >-
    Onset of hypoglycemia within the neonatal period.
  phenotype_term:
    preferred_term: Neonatal hypoglycemia
    term:
      id: HP:0001998
      label: Neonatal hypoglycemia
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We present clinical and laboratory findings together with the long-term clinical course of a case with a deep intronic HADH splicing mutation (c.636+471G>T) causing neonatal-onset hyperinsulinemic hypoglycemia with mild progression."
    explanation: Identifies neonatal-onset hyperinsulinemic hypoglycemia in a patient with a deep intronic HADH variant.
- name: Postprandial hypoglycemia
  category: Metabolic
  description: >-
    Hypoglycemia that occurs unpredictably in the hours after a feed rather than
    on fasting - the pattern that distinguishes SCHAD hyperinsulinism from a
    fatty acid oxidation disorder, in which hypoglycemia is fasting-provoked.
  phenotype_term:
    preferred_term: Postprandial hypoglycemia
    term:
      id: HP:0012051
      label: Reactive hypoglycemia
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The hypoglycemia observed in FS was not typical of a FAOD; it was not easily provoked by a prolonged fast, but, rather, occurred in an unpredictable fashion, often 2-6 hours after a feed."
    explanation: States the postprandial, non-fasting-provoked pattern this phenotype records, and contrasts it with the fasting-provoked pattern of a FAOD.
- name: Dicarboxylic aciduria
  category: Metabolic
  description: >-
    Excretion of medium-chain dicarboxylic acids and 3-hydroxyglutaric acid in urine, reflecting alternative omega-oxidation of accumulated acyl-CoA intermediates.
  phenotype_term:
    preferred_term: Dicarboxylic aciduria
    term:
      id: HP:0003215
      label: Dicarboxylic aciduria
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Metabolic profiling in some, but not all, affected individuals reveals a raised plasma hydroxybutyrylcarnitine and urinary medium-chain dicarboxylic, 3-hydroxydicarboxylic metabolites and 3-hydroxyglutarate levels."
    explanation: Documents urinary excretion of dicarboxylic acids and 3-hydroxyglutarate.
- name: Elevated circulating acylcarnitine concentration
  category: Metabolic
  diagnostic: true
  description: >-
    Elevated plasma concentration of short-chain 3-hydroxyacylcarnitines, specifically 3-hydroxybutyrylcarnitine (C4-OH).
  phenotype_term:
    preferred_term: Elevated circulating acylcarnitine concentration
    term:
      id: HP:0045045
      label: Elevated circulating acylcarnitine concentration
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, unlike other children with hyperinsulinism, this patient had a persistently elevated blood spot hydroxybutyrylcarnitine concentration when fed, as well as when fasted."
    explanation: Documents elevated blood spot hydroxybutyrylcarnitine in patient with SCHAD deficiency.
biochemical:
- name: 3-Hydroxybutyrylcarnitine (C4-OH)
  presence: INCREASED
  context: >-
    Characteristic acylcarnitine finding in blood spots or plasma by tandem mass spectrometry,
    reflecting accumulated short-chain 3-hydroxyacyl-CoA transesterified with carnitine.
  biomarker_term:
    preferred_term: 3-hydroxybutyrylcarnitine
    term:
      id: CHEBI:72995
      label: 3-hydroxybutyrylcarnitine
  readouts:
  - target: Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Direct metabolic marker of impaired short-chain 3-hydroxyacyl-CoA oxidation.
  evidence:
  - reference: PMID:23430856
    reference_title: "3-hydroxyacyl-coenzyme a dehydrogenase deficiency: identification of a new mutation causing hyperinsulinemic hypoketotic hypoglycemia, altered organic acids and acylcarnitines concentrations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
    explanation: Identifies plasma 3-hydroxybutyrylcarnitine as an invariable biochemical hallmark of profound SCHAD deficiency.
- name: 3-Hydroxyglutaric acid
  presence: INCREASED
  context: >-
    Urinary organic acid hallmark detected by GC-MS, resulting from alternative omega-oxidation
    of accumulating short-chain dicarboxylic acyl intermediates.
  biomarker_term:
    preferred_term: 3-hydroxyglutaric acid
    term:
      id: CHEBI:39980
      label: 3-hydroxyglutaric acid
  readouts:
  - target: Accumulation of 3-Hydroxybutyrylcarnitine and 3-Hydroxyglutarate
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Excreted organic acid reporting short-chain acyl-CoA catabolism block.
  evidence:
  - reference: PMID:23430856
    reference_title: "3-hydroxyacyl-coenzyme a dehydrogenase deficiency: identification of a new mutation causing hyperinsulinemic hypoketotic hypoglycemia, altered organic acids and acylcarnitines concentrations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conclude that, when the residual catalytic activity of the mutated enzyme is seriously reduced, the biochemical hallmarks of the disease, namely plasma 3-hydroxybutyrylcarnitine and urinary 3-hydroxyglutaric acid, are invariably present."
    explanation: Confirms urinary 3-hydroxyglutaric acid as an invariable biochemical hallmark in severe SCHAD deficiency.
- name: Inappropriately elevated plasma insulin
  presence: INCREASED
  context: >-
    Inappropriate detectable or elevated plasma insulin at the time of documented hypoglycemia,
    defining hyperinsulinism.
  biomarker_term:
    preferred_term: insulin
    term:
      id: CHEBI:5931
      label: insulin (human)
  readouts:
  - target: Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Inappropriate insulin exocytosis despite profound hypoglycemia.
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Further episodes of hypoketotic hypoglycemia were associated with inappropriately elevated plasma insulin concentrations."
    explanation: Documents elevated plasma insulin during hypoglycemic crises.
- name: Blood glucose
  presence: DECREASED
  context: >-
    Profoundly decreased venous or capillary blood glucose during fasting or protein-rich feeds.
  biomarker_term:
    preferred_term: glucose
    term:
      id: CHEBI:17234
      label: glucose
  readouts:
  - target: Profound Hypoketotic Hypoglycemia and Neuroglycopenia
    relationship: READOUT_OF
    direction: NEGATIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Systemic hypoglycemia driven by excessive peripheral glucose uptake and suppressed production.
  evidence:
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "While she was taking diazoxide 2 mg/kg/day, a non-ketotic hypoglycemic attack (blood glucose: 46 mg/dL) was detected with a very high insulin level (46.8 µIU/mL)."
    explanation: Measures severe hypoglycemia (blood glucose 46 mg/dL) coincident with elevated insulin.
genetic:
- name: HADH loss-of-function variants
  gene_term:
    preferred_term: HADH
    term:
      id: hgnc:4799
      label: HADH
  relationship_type: CAUSATIVE
  association: Causative
  features: >-
    Biallelic loss-of-function variants in HADH (missense, nonsense, frameshift deletions, or deep
    intronic splicing mutations) cause loss of SCHAD catalytic activity and protein expression.
  inheritance:
  - name: Autosomal recessive inheritance
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
    evidence:
    - reference: PMID:21252247
      reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Recessive mutations in the hydroxyacyl-CoA dehydrogenase (HADH) gene encoding the enzyme 3-hydroxyacyl-CoA dehydrogenase are a rare cause of diazoxide-responsive hyperinsulinemic hypoglycemia (HH) with just five probands reported to date."
      explanation: Confirms autosomal recessive inheritance of HADH-related hyperinsulinemic hypoglycemia.
  evidence:
  - reference: PMID:21252247
    reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Six different HADH mutations were identified in 11/115 (10%) patients tested."
    explanation: Identifies six distinct pathogenic HADH mutations in affected children.
  - reference: PMID:26316438
    reference_title: "A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We present clinical and laboratory findings together with the long-term clinical course of a case with a deep intronic HADH splicing mutation (c.636+471G>T) causing neonatal-onset hyperinsulinemic hypoglycemia with mild progression."
    explanation: Documents deep intronic pseudoexon-creating HADH mutation causing hyperinsulinemic hypoglycemia.
  case_fractions:
  - population: Patients with diazoxide-responsive hyperinsulinemic hypoglycemia
    case_fraction_percent: 9.6
    cohort_size: 115
    notes: >-
      Six different HADH mutations were identified in 11/115 (10%) patients tested in a
      cohort of diazoxide-responsive hyperinsulinemic hypoglycemia.
    evidence:
    - reference: PMID:21252247
      reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Six different HADH mutations were identified in 11/115 (10%) patients tested."
      explanation: Reports that HADH mutations account for ~10% of cases in a cohort of diazoxide-responsive HH.
treatments:
- name: Diazoxide
  description: >-
    First-line medical therapy for HADH deficiency. In HADH deficiency, K-ATP channels (SUR1/Kir6.2)
    are structurally intact and functional. Diazoxide binds the SUR1 subunit and maintains K-ATP
    channels in the open state, hyperpolarizing the beta-cell plasma membrane, blocking voltage-gated
    calcium entry, and suppressing unregulated insulin exocytosis.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: diazoxide
      term:
        id: CHEBI:4495
        label: diazoxide
  target_mechanisms:
  - target: Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
    treatment_effect: INHIBITS
    description: >-
      Diazoxide opens K-ATP channels, hyperpolarizing the pancreatic beta-cell membrane
      and inhibiting calcium influx and inappropriate insulin secretion.
  evidence:
  - reference: PMID:21252247
    reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HADH mutations are a relatively common cause of diazoxide-responsive HH with a frequency similar to that of GLUD1 and HNF4A mutations."
    explanation: Documents that HADH mutations cause diazoxide-responsive hyperinsulinemic hypoglycemia and supports diazoxide as effective medical management.
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patient's hyperinsulinism was easily controlled with diazoxide and chlorothiazide."
    explanation: Documents excellent glycemic control achieved with diazoxide and chlorothiazide.
- name: Chlorothiazide
  description: >-
    Thiazide diuretic frequently co-administered with diazoxide. Chlorothiazide exhibits a synergistic
    hyperglycemic action by inhibiting pancreatic phosphodiesterase, reducing insulin release, and
    counteracting diazoxide-induced fluid retention.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: chlorothiazide
      term:
        id: CHEBI:3640
        label: chlorothiazide
  target_mechanisms:
  - target: Pancreatic Beta-Cell Depolarization and Inappropriate Insulin Secretion
    treatment_effect: INHIBITS
    description: >-
      Acts synergistically with diazoxide to inhibit beta-cell depolarization and suppress insulin release.
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The patient's hyperinsulinism was easily controlled with diazoxide and chlorothiazide."
    explanation: Confirms successful combination therapy with diazoxide and chlorothiazide.
- name: Frequent Carbohydrate Feedings and Avoidance of Fasting
  description: >-
    Supportive dietary therapy to maintain blood glucose and prevent acute neuroglycopenia
    during intervals between feeds or physiological stress.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_mechanisms:
  - target: Impaired Mitochondrial Short-Chain Fatty Acid Beta-Oxidation
    treatment_effect: BYPASSES
    description: >-
      Continuous exogenous carbohydrate intake bypasses reliance on hepatic fatty acid oxidation
      and ketogenesis for energy maintenance.
  evidence:
  - reference: PMID:27771675
    reference_title: Hyperinsulinemic Hypoglycemia of Infancy due to Novel HADH Mutation in Two Siblings.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "HADH mutations are rare causes of hypoglycemia and can be mitigated with diazoxide and appropriate dietary therapy if identified early."
    explanation: Recommends appropriate dietary therapy alongside diazoxide.
- name: Dietary Protein Moderation
  description: >-
    Because loss of SCHAD unleashes GDH allosteric activation, amino acid consumption (particularly
    protein/leucine-rich meals) triggers hyperactivation of glutamate dehydrogenase and causes
    postprandial hypoglycemic episodes. Moderating dietary protein intake prevents protein-induced
    hyperinsulinism.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Dietary Intervention
    term:
      id: NCIT:C15447
      label: Dietary Intervention
  target_mechanisms:
  - target: Accelerated Glutaminolysis and Mitochondrial ATP Generation
    treatment_effect: INHIBITS
    description: >-
      Restricting protein and leucine intake reduces excessive anaplerotic flux through
      uninhibited glutamate dehydrogenase (GDH), attenuating abnormal beta-cell ATP production.
  evidence:
  - reference: PMID:19417036
    reference_title: "3-Hydroxyacyl-coenzyme A dehydrogenase deficiency and hyperinsulinemic hypoglycemia: characterization of a novel mutation and severe dietary protein sensitivity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The index case presented at 4 months of age with hypoglycemic seizures. Her HH responded to diazoxide, but she continued to have episodes of hypoglycemia even on diazoxide, especially when consuming high-protein foods."
    explanation: Demonstrates breakthrough hypoglycemia precipitated by high-protein food intake.
diagnosis:
- name: Plasma Acylcarnitine Profiling
  description: >-
    Tandem mass spectrometry analysis of dried blood spots or plasma demonstrating
    persistent elevation of 3-hydroxybutyrylcarnitine (C4-OH), the hallmark biochemical
    signature of short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency.
  evidence:
  - reference: PMID:11489939
    reference_title: "Hyperinsulinism in short-chain L-3-hydroxyacyl-CoA dehydrogenase deficiency reveals the importance of beta-oxidation in insulin secretion."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "However, unlike other children with hyperinsulinism, this patient had a persistently elevated blood spot hydroxybutyrylcarnitine concentration when fed, as well as when fasted."
    explanation: Identifies persistent blood spot hydroxybutyrylcarnitine elevation as the diagnostic hallmark of SCHAD deficiency.
- name: Urine Organic Acid Analysis
  description: >-
    Gas chromatography-mass spectrometry (GC-MS) of urine revealing increased excretion
    of 3-hydroxyglutaric acid, reflecting upstream accumulation and secondary dicarboxylic
    acid catabolism of 3-hydroxybutyryl intermediates.
  evidence:
  - reference: PMID:14693719
    reference_title: "Familial hyperinsulinemic hypoglycemia caused by a defect in the SCHAD enzyme of mitochondrial fatty acid oxidation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Urine metabolite analysis showed that SCHAD deficiency resulted in specific excretion of 3-hydroxyglutaric acid."
    explanation: Demonstrates that urine organic acid analysis reveals specific urinary excretion of 3-hydroxyglutaric acid.
- name: HADH Molecular Genetic Testing
  description: >-
    Sequence analysis of the HADH gene (Sanger sequencing, targeted gene panels for
    hyperinsulinemic hypoglycemia, or exome/genome sequencing) to identify biallelic
    pathogenic loss-of-function variants.
  diagnosis_term:
    preferred_term: DNA Sequencing
    term:
      id: NCIT:C153598
      label: DNA Sequencing
  evidence:
  - reference: PMID:21252247
    reference_title: "Genome-wide homozygosity analysis reveals HADH mutations as a common cause of diazoxide-responsive hyperinsulinemic-hypoglycemia in consanguineous pedigrees."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We recommend that HADH sequence analysis is considered in all patients with diazoxide-responsive HH when recessive inheritance is suspected."
    explanation: Recommends HADH sequence analysis for diagnostic confirmation in suspected recessive diazoxide-responsive hyperinsulinism.
animal_models:
- name: Hadh knockout mouse (Hadh-/-)
  species: Mouse
  genotype: Hadh knockout (Hadh-/-)
  publication: PMID:20670938
  description: >-
    Global Hadh knockout (Hadh-/-) mice exhibit amino acid hypersensitivity, hypoglycemia,
    and elevated insulin secretion. Isolated islets display increased glutamine oxidation and
    GDH hyperactivation, and islet transplantation into diabetic mice demonstrates the hypoglycemic
    phenotype is islet cell-autonomous.
  modeled_mechanisms:
  - target: Loss of Tonic SCHAD Inhibition of Glutamate Dehydrogenase
    relationship: RECAPITULATES
    fidelity: HIGH
    model_scale: MOLECULAR
    description: >-
      Hadh knockout mice recapitulate the loss of tonic GDH inhibition by SCHAD, leading to
      increased GDH activity and amino acid-stimulated insulin secretion.
    evidence:
    - reference: PMID:20670938
      reference_title: "Mechanism of hyperinsulinism in short-chain 3-hydroxyacyl-CoA dehydrogenase deficiency involves activation of glutamate dehydrogenase."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "These studies indicate that SCHAD deficiency causes hyperinsulinism by activation of GDH via loss of inhibitory regulation of GDH by SCHAD."
      explanation: Demonstrates in Hadh-/- mice that loss of SCHAD activates GDH and causes hyperinsulinism.
    - reference: PMID:26953163
      reference_title: "The Hypoglycemic Phenotype Is Islet Cell-Autonomous in Short-Chain Hydroxyacyl-CoA Dehydrogenase-Deficient Mice."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "We conclude that hypoglycemia in SCHAD-CHI is islet cell-autonomous."
      explanation: Shows that transplantation of SCHAD-KO islets recapitulates hypoglycemia in recipient mice, confirming cell autonomy.
📚

References & Deep Research

References

1
PMID:20301549
Nonsyndromic Genetic Hyperinsulinism Overview.
No top-level findings curated for this source.

Deep Research

2

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Asta ▸
Asta Literature Retrieval: Pathophysiology and clinical mechanisms of 3-Hydroxyacyl-CoA Dehydrogenase Deficiency. Core disease mechanisms, molec...
Asta Scientific Corpus Retrieval 20 citations 2026-09-11T22:06:53.198924

Asta Literature Retrieval: Pathophysiology and clinical mechanisms of 3-Hydroxyacyl-CoA Dehydrogenase Deficiency. Core disease mechanisms, molec...

This report is retrieval-only and is generated directly from Asta results.

  • Papers retrieved: 20
  • Snippets retrieved: 20

Relevant Papers

[1] Diagnosis and Clinical Management of Long-chain Fatty-acid Oxidation Disorders: A Review.

  • Authors: Joshua Baker, B. Burton
  • Year: 2021
  • Venue: TouchREVIEWS in endocrinology
  • URL: https://www.semanticscholar.org/paper/952c303d9b7cbf2095eb0d1ae7c7b3ab0d92c08d
  • DOI: 10.17925/ee.2021.17.2.108
  • PMID: 35118456
  • Citations: 17
  • Summary: This article reviews the major LC-FAODs and their clinical presentation and indicates that triheptanoin approval has improved the outcome for affected individuals.
  • Evidence snippets:
  • Snippet 1 (score: 0.603) > Very long-chain acyl-CoA dehydrogenase (VLCAD) is the most common LC-FAOD. It is due to biallelic variants in ACADVL, which encodes an enzyme involved in the metabolism of acylcarnitines with 14-20 carbons. 1 Severely affected patients present in the neonatal period with the typical hypoketotic hypoglycaemia, hypotonia, myopathy, hepatic dysfunction, cardiomyopathy and cardiac arrythmias. > In the long-term, patients typically experience recurrent rhabdomyolysis and may exhibit cardiac disease progression with significant stress. With the expansion of newborn screening, many more individuals with a milder phenotype are being identified, with symptoms of skeletal myopathy and rhabdomyolysis not presenting until adolescence or adulthood; some may remain asymptomatic for life. 11 This milder form has now become the most commonly diagnosed phenotype. 11 ng-chain 3-hydroxyacyl-CoA dehydrogenase deficiency/trifunctional protein deficiency > Long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and trifunctional protein (TFP) are two disorders that are clinically indistinguishable. > Molecularly, they can be differentiated through the evaluation of HADHA and HADHB. 1 Most affected patients present in infancy or early childhood with hypoglycaemia, hepatic dysfunction, cardiomyopathy and sudden death. LCHAD may also present with maternal HELLP (haemolysis, elevated liver enzymes, and a low platelet count) syndrome or acute fatty liver of pregnancy when the foetus is affected. Long-term sequelae include myopathy, recurrent rhabdomyolysis and exercise intolerance. > Unique phenotypic features of LCHAD/TFP include peripheral neuropathy and retinopathy. 12 Concern has also been raised for the increased comorbidities of intellectual disability and autism spectrum disorders in LCHAD. 13 Further research on the underlying mechanism is still required.

[2] Recent Advances in the Pathophysiology of Fatty Acid Oxidation Defects: Secondary Alterations of Bioenergetics and Mitochondrial Calcium Homeostasis Caused by the Accumulating Fatty Acids

  • Authors: A. U. Amaral, M. Wajner
  • Year: 2020
  • Venue: Frontiers in Genetics
  • URL: https://www.semanticscholar.org/paper/cdafd60b0b217c61de651cd70405b651277f5c6a
  • DOI: 10.3389/fgene.2020.598976
  • PMID: 33329744
  • PMCID: 7729159
  • Citations: 23
  • Summary: The present knowledge on disturbances of mitochondrial bioenergetics, calcium homeostasis, uncoupling of oxidative phosphorylation, and mitochondrial permeability transition induction provoked by the major fatty acids accumulating in prevalent FAOD are updated.
  • Evidence snippets:
  • Snippet 1 (score: 0.562) > Deficiencies of medium-chain acyl-CoA dehydrogenase, mitochondrial trifunctional protein, isolated long-chain 3-hydroxyacyl-CoA dehydrogenase, and very long-chain acyl-CoA dehydrogenase activities are considered the most frequent fatty acid oxidation defects (FAOD). They are biochemically characterized by the accumulation of medium-chain, long-chain hydroxyl, and long-chain fatty acids and derivatives, respectively, in tissues and biological fluids of the affected patients. Clinical manifestations commonly include hypoglycemia, cardiomyopathy, and recurrent rhabdomyolysis. Although the pathogenesis of these diseases is still poorly understood, energy deprivation secondary to blockage of fatty acid degradation seems to play an important role. However, recent evidence indicates that the predominant fatty acids accumulating in these disorders disrupt mitochondrial functions and are involved in their pathophysiology, possibly explaining the lactic acidosis, mitochondrial morphological alterations, and altered mitochondrial biochemical parameters found in tissues and cultured fibroblasts from some affected patients and also in animal models of these diseases. In this review, we will update the present knowledge on disturbances of mitochondrial bioenergetics, calcium homeostasis, uncoupling of oxidative phosphorylation, and mitochondrial permeability transition induction provoked by the major fatty acids accumulating in prevalent FAOD. It is emphasized that further in vivo studies carried out in tissues from affected patients and from animal genetic models of these disorders are necessary to confirm the present evidence mostly achieved from in vitro experiments.

[3] A novel HADHA variant associated with an atypical moderate and late-onset LCHAD deficiency

  • Authors: A. Dessein, E. Hebbar, J. Vamecq, E. Lebredonchel, A. Devos et al.
  • Year: 2022
  • Venue: Molecular Genetics and Metabolism Reports
  • URL: https://www.semanticscholar.org/paper/2b0c30eff5f9414ef4d5756652ae56d647a5387f
  • DOI: 10.1016/j.ymgmr.2022.100860
  • PMID: 35782617
  • PMCID: 9248219
  • Citations: 7
  • Summary: This atypical LCHADD form report should encourage the early assessment of biochemical and genetic testing as a specific management is recommended (combination with fast avoidance, low fat-high carbohydrate diet, medium-even-chain triglycerides or triheptanoin supplementation).
  • Evidence snippets:
  • Snippet 1 (score: 0.531) > Background Long chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD) is a rare inherited disease caused by pathogenic variants of HADHA gene. Along with signs common to fatty acid oxidation defects (FAOD), specific retina and heart alterations are observed. Because long-chain fatty acid oxidation is selectively affected, supplementations with short/medium-chain fats represent energetic sources bypassing the enzymatic blockade. Here, we report on an atypical presentation of the disease. Methods Clinical features were described with medical explorations including ophthalmic and cardiac examination. Biological underlying defects were investigated by measurements of biochemical metabolites and by fluxomic studies of mitochondrial β-oxidation. Whole exome sequencing and molecular validation of variants confirmed the diagnosis. Results The patient has developed at nine years an unlabeled maculopathy, and at 28 years, an acute cardiac decompensation without any premise. Blood individual acylcarnitine analysis showed a rise in hydroxylated long-chain fatty acids and fluxomic studies validated enzyme blockade consistent with LCHADD. Genetic analysis revealed the common p.(Glu510Gln) variant in HADHA, in trans with a novel variant c.1108G > A, p.(Gly370Arg) located in the NAD binding domain. Patient pathology was responsive to triheptanoin supplementation. Conclusion This atypical LCHADD form report should encourage the early assessment of biochemical and genetic testing as a specific management is recommended (combination with fast avoidance, low fat-high carbohydrate diet, medium-even-chain triglycerides or triheptanoin supplementation).

[4] Exploring the contribution of mitochondrial dynamics to multiple acyl-CoA dehydrogenase deficiency-related phenotype

  • Authors: S. R. Brandão, Rita Ferreira, H. Rocha
  • Year: 2019
  • Venue: Archives of Physiology and Biochemistry
  • URL: https://www.semanticscholar.org/paper/3fa2c0768599e679dca543d47a13fa756385ed12
  • DOI: 10.1080/13813455.2019.1628065
  • PMID: 31215835
  • Citations: 6
  • Summary: The role of mitochondria on the regulation of cell homeostasis through the production of ROS, mitophagy, apoptosis, and mitochondrial biogenesis is overviewed and multiple acyl-CoA dehydrogenase deficiency (MADD) is considered an interesting model to better understand this interplay.
  • Evidence snippets:
  • Snippet 1 (score: 0.496) > Mitochondrial fatty acid b-oxidation disorders (FAOD) are a group of inherited metabolic disorders, affecting mitochondrial enzymes involved in the b-oxidation of fatty acids (Kompare andRizzo 2008, Sahai andMarsden 2009). These disorders are usually transmitted in an autosomal recessive pattern being individually rare, but together they represent a large and important group of inherited metabolic disorders (Sahai and Marsden 2009). The main affected organs include heart, liver and skeletal muscles (Kompare and Rizzo 2008). The mortality and morbidity rates associated with these conditions can be prevented, or at least decreased, if disorders are early recognized and treated (Sahai and Marsden 2009). Indeed, fatty acid oxidation disorders can lead to serious health problems and even to death if not treated or when the diagnosis is done too late. The advantages of an early intervention make this group of disorders main targets of newborn screening (NBS) programs worldwide (Sahai and Marsden 2009, Lindner et al. 2010, Rocha et al. 2014. > Among FAOD, multiple acyl-CoA dehydrogenase deficiency (MADD) is one of the screened disorders that present heterogeneous clinical phenotypes Goodman 1985, 2001), being recognized three clinical forms. Two severe neonatal-onset forms: with (type I) and without (type II) congenital abnormalities. The late-onset form (type III) is associated to milder phenotypes (Vockley and Whiteman 2002). In most FAOD, including MADD, the association between the phenotype and the genotype is not straightforward (Gregersen et al. 2001, Kompare and Rizzo 2008, Olsen et al. 2013. The observed clinical spectrum in MADD patients suggests that other specific molecular and cellular mechanisms may have a key role in MADD pathogenesis, in addition to mutations in the genes associated to this disease (Olsen et al. 2003, Gr€ unert 2014. These findings make MADD an interesting model to better understand the molecular mechanisms underlying the pathophysiology associated with MADD and other FAOD. > Herein, we overview FAO metabolism, its regulation and contextualize MADD, the chosen model to study mitochondrial dynamics disturbances in FAO. We also critically analyze the potential contribution of the molecular pathways

[5] Mitochondrial Trifunctional Protein Deficiency due to HADHA Variants Masquerading as Charcot–Marie–Tooth Disease

  • Authors: Farkhanda Qaiser, John C. McHugh, G. Mullins, M. Farrell, Loai Shakerdi et al.
  • Year: 2025
  • Venue: Journal of the Peripheral Nervous System
  • URL: https://www.semanticscholar.org/paper/2347601554c9f2e4b9fc060205af6d8ad7778a3d
  • DOI: 10.1111/jns.70048
  • PMID: 40790338
  • PMCID: 12340164
  • Summary: Mitochondrial trifunctional protein deficiency (MTPD) is an inherited disorder of fatty acid β‐oxidation caused by mutations in HADHA or HADHB genes. It typically presents with cardiomyopathy or hepatic failure in early childhood; however, it may rarely present in adulthood with the neuromyopathic form.
  • Evidence snippets:
  • Snippet 1 (score: 0.493) > Long chain 3-hydroxyacyl CoA dehydrogenase deficiency (LCHADD) and mitochondrial trifunctional protein deficiency (MTPD) are rare autosomal recessive disorders of fatty acid βoxidation. MTP is an enzyme complex consisting of four α and four β subunits encoded by HADHA and HADHB, respectively [1]. The α subunits contain the enzymes long chain enoyl CoA hydratase (LCEH), LCHAD and the β subunits contain long chain ketoacyl CoA thiolase (LCKT). > LCHADD due to isolated deficiency of LCHAD is more common, caused by HADHA variants, whereas MTPD due to deficiency of all three enzymes is much rarer and caused by HADHA or HADHB variants. Both of these conditions are part of newborn screening (NBS) in about 20 European countries but not in Ireland. > MTPD was first described in 1992 and may manifest with diverse clinical phenotypes including a severe neonatal form with cardiomyopathy, an infantile hepatic type and a milder lateonset neuromyopathic phenotype. The neuromyopathic presentation is the least common, presenting with repeated episodes of rhabdomyolysis, usually after metabolic decompensation, along with progressive peripheral sensory-motor neuropathy. Spiekerkoetter et al. described 11 patients with a neuromyopathic phenotype and reported that the combination of episodic rhabdomyolysis and peripheral neuropathy was present in almost all patients [2]. In another small study, 70% of patients had neuropathy as a long-term complication [3]. > We present a patient with MTPD due to compound heterozygous HADHA variants, one of them novel, with childhood onset isolated neuropathy initially diagnosed as Charcot-Marie-Tooth disease (CMT). While superimposed exacerbations occurred, there was no documented evidence of rhabdomyolysis or metabolic decompensation.

[6] iPSC‐Derived Liver Organoids as a Tool to Study Medium Chain Acyl‐CoA Dehydrogenase Deficiency

  • Authors: L. A. Kiyuna, José M. Horcas-Nieto, Christoff Odendaal, M. Langelaar-Makkinje, A. Gerding et al.
  • Year: 2025
  • Venue: Journal of Inherited Metabolic Disease
  • URL: https://www.semanticscholar.org/paper/547bf305207cfd00da79f778ed7ea7eb255f1018
  • DOI: 10.1002/jimd.70028
  • PMID: 40199742
  • PMCID: 11978564
  • Citations: 3
  • Summary: iPSC‐derived organoids of MCADD patients recapitulated the major biochemical phenotype of the disease, and this patient‐specific hepatic organoid system is a promising platform to study the phenotypic heterogeneity between MCADD patients.
  • Evidence snippets:
  • Snippet 1 (score: 0.483) > Medium chain acyl‐CoA dehydrogenase deficiency (MCADD) is an inherited metabolic disease, characterized by biallelic variants in the ACADM gene. Interestingly, even with the same genotype, patients often present with very heterogeneous symptoms, ranging from fully asymptomatic to life‐threatening hypoketotic hypoglycemia. The mechanisms underlying this heterogeneity remain unclear. Therefore, there is a need for in vitro models of MCADD that recapitulate the clinical phenotype as a tool to study the pathophysiology of the disease. Fibroblasts of control and symptomatic MCADD patients with the c.985A>G (p.K329E) were reprogrammed into induced pluripotent stem cells (iPSCs). iPSCs were then differentiated into hepatic expandable organoids (EHOs), further matured to Mat‐EHOs, and functionally characterized. EHOs and Mat‐EHOs performed typical hepatic metabolic functions, such as albumin and urea production. The organoids metabolized fatty acids, as confirmed by acyl‐carnitine profiling and high‐resolution respirometry. MCAD protein was fully ablated in MCADD organoids, in agreement with the instability of the mutated MCAD protein. MCADD organoids accumulated medium‐chain acyl‐carnitines, with a strongly elevated C8/C10 ratio, characteristic of the biochemical phenotype of the disease. Notably, C2 and C14 acyl‐carnitines were found decreased in MCADD Mat‐EHOs. Finally, MCADD organoids exhibited differential expression of genes involved in ω‐oxidation, mitochondrial β‐oxidation, TCA cycle, and peroxisomal coenzyme A metabolism, particularly upregulation of NUDT7. iPSC‐derived organoids of MCADD patients recapitulated the major biochemical phenotype of the disease. Mat‐EHOs expressed relevant pathways involved in putative compensatory mechanisms, notably CoA metabolism and the TCA cycle. The upregulation of NUDT7 expression may play a role in preventing excessive accumulation of dicarboxylic acids

[7] Succinic Semialdehyde Dehydrogenase: Biochemical–Molecular–Clinical Disease Mechanisms, Redox Regulation, and Functional Significance

  • Authors: Kyung-Jin Kim, P. Pearl, K. Jensen, O. Snead, P. Malaspina et al.
  • Year: 2011
  • Venue: Antioxidants & Redox Signaling
  • URL: https://www.semanticscholar.org/paper/d95101b74cd56d93c2af4e68057a48c55fd6ff4a
  • DOI: 10.1089/ars.2010.3470
  • PMID: 20973619
  • Citations: 80
  • Influential citations: 6
  • Summary: The current review summarizes some 30 years of research on this protein and disease, addressing pathological mechanisms in human and mouse at the protein, metabolic, molecular, and whole-animal level.
  • Evidence snippets:
  • Snippet 1 (score: 0.474) > Succinic semialdehyde dehydrogenase (SSADH; aldehyde dehydrogenase 5a1, ALDH5A1; E.C. 1.2.1.24; OMIM 610045, 271980) deficiency is a rare heritable disorder that disrupts the metabolism of the inhibitory neurotransmitter 4-aminobutyric acid (GABA). Identified in conjunction with increased urinary excretion of the GABA analog gamma-hydroxybutyric acid (GHB), numerous patients have been identified worldwide and the autosomal-recessive disorder has been modeled in mice. The phenotype is one of nonprogressive neurological dysfunction in which seizures may be prominently displayed. The murine model is a reasonable phenocopy of the human disorder, yet the severity of the seizure disorder in the mouse exceeds that observed in SSADH-deficient patients. Abnormalities in GABAergic and GHBergic neurotransmission, documented in patients and mice, form a component of disease pathophysiology, although numerous other disturbances (metabolite accumulations, myelin abnormalities, oxidant stress, neurosteroid depletion, altered bioenergetics, etc.) are also likely to be involved in developing the disease phenotype. Most recently, the demonstration of a redox control system in the SSADH protein active site has provided new insights into the regulation of SSADH by the cellular oxidation/reduction potential. The current review summarizes some 30 years of research on this protein and disease, addressing pathological mechanisms in human and mouse at the protein, metabolic, molecular, and whole-animal level. Antioxid. Redox Signal. 15, 691–718. I. Historical Perspectives and Background A. Identification of succinic semialdehyde dehydrogenase deficiency B. Human SSADH deficiency: early clinical, metabolic, and enzymatic findings C. Pharmacology of GABA and GHB II. Molecular Genetics of SSADH Deficiency and Functional Polymorphisms of the SSADH Gene A. SSADH protein characterization B. Molecular genetics of SSADH deficiency–cDNA cloning and pathogenic mutations C. Variation

[8] The Hypoglycemic Phenotype Is Islet Cell–Autonomous in Short-Chain Hydroxyacyl-CoA Dehydrogenase–Deficient Mice

  • Authors: A. Molven, J. Hollister-Lock, Jiang Hu, Rachael Martinez, P. Njølstad et al.
  • Year: 2016
  • Venue: Diabetes
  • URL: https://www.semanticscholar.org/paper/8cd034442e4ec920604efd679554a68fcfd71954
  • DOI: 10.2337/db15-1475
  • PMID: 26953163
  • PMCID: 4878426
  • Citations: 13
  • Influential citations: 1
  • Summary: It is concluded that hypoglycemia in SCHAD-CHI is islet cell–autonomous, and transplanted islets from global SCHAD knockout mice into mice with streptozotocin-induced diabetes, finding that intraperitoneal glucose tolerance was improved in animals receiving SCHADKO islets compared with those receiving normal islets.
  • Evidence snippets:
  • Snippet 1 (score: 0.464) > of insulin secretion. About half of the CHI cases are "channelopathies" being caused by inactivating mutations in the ABCC8 and KCNJ11 genes that encode subunits of the b-cells' K ATP channel (2,3). Most of the other genetic CHI etiologies can be classified as "metabolopathies," as they directly involve dysregulated metabolic pathways due to mutated enzyme genes (2). > A classic example of the latter category is CHI caused by recessive mutations in HADH (4,5). This gene encodes short-chain 3-hydroxyacyl-CoA dehydrogenase (SCHAD), a mitochondrial enzyme that catalyzes the third of the four steps in fatty acid oxidation. More than 20 patients with SCHAD deficiency have now been reported. Intriguingly, they exhibit leucine-sensitive, diazoxide-responsive CHI rather than a phenotype typical for fatty acid oxidation disorders (6). The mechanism behind SCHAD CHI remained enigmatic for many years until Li et al. (7) investigated a global knockout mouse model (SCHADKO) and demonstrated that SCHAD serves to inhibit the enzyme glutamate dehydrogenase (GDH), another protein directly implicated in CHI (8). > However, HADH is ubiquitously expressed, suggesting that SCHAD deficiency is a metabolic disease with possible implications outside the context of the pancreatic b-cell. As such, in affected individuals there is abnormal accumulation of 3-hydroxybutyryl-carnitine in blood and 3-hydroxyglutaric acid in urine-metabolites that are both directly attributable to the enzymatic defect (4)(5)(6). To explore whether the impact of global knockout of the SCHAD enzyme on glucose homeostasis is secondary only to defects in the islets of Langerhans, we transplanted SCHADKO islets into mice with streptozotocin (STZ)induced diabetes.

[9] Frontiers in metabolic physiology grand challenges

  • Authors: J. Imig
  • Year: 2022
  • Venue: Frontiers in Physiology
  • URL: https://www.semanticscholar.org/paper/19e2780d459288513f034516e0a7d5fa4e12298f
  • DOI: 10.3389/fphys.2022.879617
  • PMID: 36035475
  • PMCID: 9399398
  • Citations: 2
  • Summary: In this chapter seven subsequent studies of the determinants of infectious disease in eight operation rooms were studied.
  • Evidence snippets:
  • Snippet 1 (score: 0.450) > Research in this area will identify novel therapeutic targets for diabetic complications at the levels of transcription and translation, protein expression and activity, and cell and organ levels. Major challenges in diabetes include defining molecular mechanisms and pathways implicated in insulin metabolism, evaluating transcriptomics of high glucose on different cell types, defining the contribution of the innate immune response and NLRP3 inflammasome, understanding metabolic mechanisms that drive beta cell dysfunction, and defining metabolic processes in key insulin-target tissues. > NAFLD is a rapidly growing public health concern that occurs in 25% of the world population and is driven in large part by the obesity and type 2 diabetes epidemic (Caussy et al., 2021;Targher et al., 2021). Intriguingly, NAFLD can be as high as 75% in diabetic patients (Caussy et al., 2021;Targher et al., 2021). Non-alcoholic steatosis (NASH) is a type of NAFLD that is associated with inflammation and hepatocyte lipotoxicity which leads to liver fibrosis and cancer (Caussy et al., 2021;Targher et al., 2021). NASH is expected to become the leading cause for liver transplantation in the next decade (Nephew and Serper, 2021). Mechanisms that contribute to NAFLD and progression to NASH include regulation of de novo lipogenesis by acetyl-CoA carboxylase, regulation of bile acid signaling by farnesoid X receptor (FXR), or oxidative stress induced fibrogenesis and inflammation by apoptosis signal-regulating kinase 1 (ASK1) (Attia et al., 2021;Koo and Han, 2021). Although often associated with obesity and diabetes, understanding pathophysiological mechanisms at the cellular hepatocyte and organ liver levels that result in NAFLD and progression to NASH will be key to developing therapeutics. > Major challenges to the epidemic of metabolic diseases are the focus of several publications in Frontiers in Metabolic Physiology. Studies in mice with type 2 diabetes have revealed metabolites involved in diabetic kidney disease.

[10] Revealing the molecular relationship between type 2 diabetes and the metabolic changes induced by a very-low-carbohydrate low-fat ketogenic diet

  • Authors: J. Farrés, Albert Pujol, M. Coma, J. L. Ruiz, J. Naval et al.
  • Year: 2010
  • Venue: Nutrition & Metabolism
  • URL: https://www.semanticscholar.org/paper/19f76d9c9209540867c68b7741c2e70fdfa71dd9
  • DOI: 10.1186/1743-7075-7-88
  • PMID: 21143928
  • PMCID: 3009973
  • Citations: 24
  • Summary: The molecular network analysis performed in theketogenic-diet map, from the diabetes perspective, has provided insights on the potential mechanism of action, but also has opened new possibilities to study the applications of the ketogenic diet in other situations such as CNS or other metabolic dysfunctions.
  • Evidence snippets:
  • Snippet 1 (score: 0.449) > Novel approaches to study human disease networks Efforts to link metabolic status or diseases by using simple, schematic biological pathways seldom offer the possibility to view the "broad picture", and are rarely able to explain the richness of the complex, redundant, intricate and sometimes blurry nature of human metabolism. Recently, the concept of "Diseaseome" [1] has arisen, as an essay to conceptualize at the highest level the relationship between observed phenotypes and underlying molecular and physiological disease mechanisms or disease cures. Although they are often treated separately, most human diseases are not independent of each other. Many diseases are associated with the breakdown of functional modules (subnetworks) of a complex network connecting many cellular components. Therefore, an understanding of the functionally relevant genetic, regulatory, metabolic and protein-protein interactions will play an important role in understanding the pathophysiology of human diseases [2]. > Specifically, for studying human diseases from this perspective, one has to use a Systems Biology or Network Medicine approach [3][4][5], which are based on the construction of a complex network or map, where nodes are usually proteins, and edges are relationships between nodes. Relationships can be of any type: physical interaction between proteins, metabolic relationships and relationships driven by signaling pathways, homology or other characteristics. The physical representation of this concept is a cell network that can be queried and modeled to identify new complex pathways, or to identify previously unknown effectors of observable characteristics, like for example new drug targets or new metabolic relationships between mechanisms and pathways previously poorly understood [4,5]. > In this work, we have applied these innovative concepts to suggest potential metabolic and molecular relationships between the observed clinical improvements in patients with type 2 diabetes and diet-induced ketosis.

[11] Long‐Chain Fatty Acid Oxidation Disorder Genes: A Comprehensive Genetic Database of LC‐FAOD Variants, Genotypes, and Phenotypes

  • Authors: Heather A. Richbourg, Vanessa Rangel Miller, Omid Khazaie Japalaghi, M. AlSayed, Peter R Baker et al.
  • Year: 2026
  • Venue: Human Mutation
  • URL: https://www.semanticscholar.org/paper/bebb7b03ea40592a428ee6217fe1e5bf5bf212e7
  • DOI: 10.1155/humu/6864813
  • PMID: 42422157
  • PMCID: 13342283
  • Summary: The LC‐FAOD gene database is a comprehensive archive of variants, genotypes, and phenotypes associated with this important group of FAODs.
  • Evidence snippets:
  • Snippet 1 (score: 0.448) > Long-chain fatty acid oxidation disorders (LC-FAODs) are rare, autosomal recessive diseases caused by abnormalities in nuclear genes that encode mitochondrial proteins essential for the oxidation of fatty acids of 12-18 carbons in chain length [1][2][3][4]. LC-FAODs are comprised of deficiencies in six different protein/protein activities: Carnitine Palmitoyltransferase 1 (CPT I), carnitine/acylcarnitine translocase (CACT), Carnitine Palmitoyltransferase 2 (CPT II), very-long-chain acyl-CoA dehydrogenase (VLCAD), long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), and mitochondrial trifunctional protein (TFP), which are part of the carnitine shuttle system or the mitochondrial beta-oxidation pathway (Figure 1) [3,5]. In patients with LC-FAOD, there can be a deficit in energy production and accumulation of toxic metabolites such as long-chain acylcarnitines. > Common clinical features in LC-FAOD are hypoglycemia, cardiomyopathy, and recurrent rhabdomyolysis. TFP and LCHAD deficiency have neuropathy and retinopathy as unique features (Table 1). Patients with LC-FAOD require lifelong medical care from metabolic disease specialists. > Management involves avoidance of prolonged fasting, sometimes restriction of long-chain fats in the diet, and early intervention such as intravenous dextrose during illness, to avoid hypoglycemia and clinical decompensation [8]. One medication is approved in Brazil, Canada, Kuwait, Mexico, and the United States for treatment of LC-FAODs (triheptanoin). Clinical outcomes for patients were poor prior to the introduction of newborn screening (NBS), with up to 70% mortality by age 10 years; while survival is now higher with NBS, early death is still common, and morbidity is nearly ubiquitous [9]. Clinical manifestations of each LC-FAOD type, along with the associated gene and protein, are summarized in Table 1.

[12] One novel HSD17B4 mutation in association with D-bifunctional protein deficiency: a case report and literature review

  • Authors: Lu Xiong, Shiqing Wang, Hui Sun, Tao Zhong, Li Li et al.
  • Year: 2026
  • Venue: Frontiers in Pediatrics
  • URL: https://www.semanticscholar.org/paper/752f01aff130b933c06b51a39e6f9b15f9f7a038
  • DOI: 10.3389/fped.2025.1689571
  • PMID: 41567431
  • PMCID: 12816375
  • Citations: 1
  • Summary: A case of a newborn who presented with hypotonia, feeding difficulties and refractory epilepsy shortly after birth, and was eventually diagnosed with D-bifunctional protein deficiency through whole-exome sequencing is presented.
  • Evidence snippets:
  • Snippet 1 (score: 0.447) > Peroxisomal diseases comprise a heterogeneous spectrum of rare, inherited metabolic disorders, with an estimated prevalence of 1 in 25,000 to 50,000 live births (1)(2)(3)(4). Peroxisomal diseases are categorized into two groups: peroxisome biogenesis disorders and single peroxisomal enzyme deficiencies. In patients with single enzyme deficiencies, peroxisome structure remains normal; the metabolic disorder(s) result exclusively from a functional impairment of a single enzyme protein within the peroxisome. D-Bifunctional protein deficiency (D-BPD),which belongs to single peroxisomal enzyme deficiencies, is a rare autosomal recessive disorder first reported in 1989 (5), with an estimated incidence of 1/100,000. D-bifunctional protein (DBP), which participates in the βoxidation of very-long-chain fatty acids (6), is a peroxisomal enzyme that consists of three catalytic domains: an N-terminal 2-enoyl-CoA hydratase, a central 3-hydroxyacyl-CoA dehydrogenase, and a C-terminal steroid carrier protein 2-like domain (SCP-2L). Pathogenic mutations in the HSD17B4 gene located at 5q21 are responsible for D-BPD. Based on the specific deficient enzymatic activity, D-BPD is categorized into four types. Type I is characterized by a combined deficiency of both dehydrogenase and hydratase activities. Type II presents with an isolated hydratase deficiency, whereas Type III features an isolated dehydrogenase deficiency. Type IV, which presents a less severe phenotype compared to types I-III, shares similarities with Perrault syndrome (PRLTS). Patients with D-BPD manifest a severe clinical course, marked by neonatal hypotonia, recurrent epileptic seizures, and a constellation of dysmorphic facial features. These features commonly include macrocephaly, a prominent forehead, hypertelorism, a at nasal bridge, and low-set ears.

[13] Altered Redox Homeostasis in Branched-Chain Amino Acid Disorders, Organic Acidurias, and Homocystinuria

  • Authors: E. Richard, L. Gallego-Villar, A. Rivera-Barahona, A. Oyarzábal, B. Pérez et al.
  • Year: 2018
  • Venue: Oxidative Medicine and Cellular Longevity
  • URL: https://www.semanticscholar.org/paper/a02a988d26ef8a032bade854c27c8c28792a6dfa
  • DOI: 10.1155/2018/1246069
  • PMID: 29743968
  • PMCID: 5884027
  • Citations: 35
  • Influential citations: 2
  • Summary: The published data on mitochondrial dysfunction, oxidative stress, and impaired redox signaling in branched-chain amino acid disorders, other organic acidurias, and homocystinuria are described, along with recent studies exploring the efficiency of antioxidants and mitochondria-targeted therapies as therapeutic compounds in these diseases.
  • Evidence snippets:
  • Snippet 1 (score: 0.439) > Dehydrogenase. MSUD (MIM #248600), caused by the deficiency of branched-chain α-ketoacid dehydrogenase complex (BCKDHc) activity, is characterized by elevated levels of BCAAs and their corresponding α-keto-acids (BCKAs) in body fluids and tissues, resulting in complex neurological phenotypes [37]. As the important gatekeeping enzyme that it is, BCKDHc is regulated by reversible phosphorylation catalyzed by a specific BCKD kinase (BCKDK) that inhibits BCKDHc function, halting the catabolic pathway of BCAAs [41], and a dephosphorylation catalyzed by the mitochondrial protein phosphatase PP2Cm (encoded by the PPM1K gene) that stimulates BCKDHc activity [42]. Optimal BCKDHc activity necessary to maintain BCAA homeostasis is achieved by the coordinated response of BCKDK and PP2Cm activities. Blockage or unrestrained BCAA metabolism through BCKDHc leads to a dysmetabolism of BCAAs resulting in MSUD or BCKDK deficiency (MIM #614923) (Figure 1), two different clinical conditions with a hallmark of neurological perturbation. > MSUD results from mutations in the genes E1α-BCKDHA (MIM #608348), E1β-BCKDHB (MIM #24861), and E2-DBT (MIM #248610) [37]. The disease affects 1 : 185,000 newborns worldwide and is manifested by diverse clinical phenotypes, ranging from the most severe form-seen in 70% of patients with MSUD and associated with a profound neurological impact and high mortality if not treated early-to mild forms that present during early development. The mechanisms underlying brain injury are not completely understood. Different studies have been carried out using chemical induction of the disease by BCAAs or BCKAs in cultured cells [43,44] and animal models [45][46][47][48].

[14] Complex changes in the liver mitochondrial proteome of short chain acyl-CoA dehydrogenase deficient mice

  • Authors: Wei Wang, A. Mohsen, Guy T. Uechi, Emanuel M. Schreiber, M. Balasubramani et al.
  • Year: 2014
  • Venue: Molecular genetics and metabolism
  • URL: https://www.semanticscholar.org/paper/e8bcfc0ce5c7d93a0021292722f92d5f695cf413
  • DOI: 10.1016/j.ymgme.2014.02.014
  • PMID: 24685553
  • PMCID: 4167795
  • Citations: 14
  • Summary: Changes in the levels of multiple energy metabolism related proteins were identified indicating that a more complex mechanism for development of symptoms may exist and several candidate molecules are proposed that may serve as markers for recognition of clinical risk associated with this disorder.
  • Evidence snippets:
  • Snippet 1 (score: 0.439) > Short-chain acyl-CoA dehydrogenase (SCAD) deficiency is an autosomal recessive inborn error of metabolism that leads to the impaired mitochondrial fatty acid β-oxidation of short chain fatty acids. It is heterogeneous in clinical presentation including asymptomatic in most patients identified by newborn screening. Multiple mutations have been identified in patients; however, neither clear genotype–phenotype relationships nor a good correlation between genotype and current biochemical markers for diagnosis has been identified. The definition and pathophysiology of this deficiency remain unclear. To better understand this disorder at a global level, quantitative alterations in the mitochondrial proteome in SCAD deficient mice were examined using a combined proteomics approach: two-dimensional gel difference electrophoresis (2DIGE) followed by protein identification with MALDI-TOF/TOF and iTRAQ labeling followed by nano-LC/MALDI-TOF/TOF. We found broad mitochondrial dysfunction in SCAD deficiency. Changes in the levels of multiple energy metabolism related proteins were identified indicating that a more complex mechanism for development of symptoms may exist. Affected pathways converge on disorders with neurologic symptoms, suggesting that even asymptomatic individuals with SCAD deficiency may be at risk to develop more severe disease. Our results also identified a pattern associated with hepatotoxicity implicated in mitochondrial dysfunction, fatty acid metabolism, decrease of depolarization of mitochondria and mitochondrial membranes, and swelling of mitochondria, demonstrating that SCAD deficiency relates more directly to mitochondrial dysfunction and alteration of fatty acid metabolism. We propose several candidate molecules that may serve as markers for recognition of clinical risk associated with this disorder.

[15] Changes in Serum Proteomic Profiles at Different Stages of Pregnancy Toxemia in Goats

  • Authors: Murat Uztimür, Cennet Nur Ünal, Gurler Akpinar
  • Year: 2025
  • Venue: Journal of Veterinary Internal Medicine
  • URL: https://www.semanticscholar.org/paper/4b9c488b5dbd65d7b26fd2ad9aed70e8c4b59942
  • DOI: 10.1111/jvim.70139
  • PMID: 40492724
  • PMCID: 12150350
  • Citations: 2
  • Summary: Understanding the serum proteome profiles of goats with pregnancy toxemia might help identify the proteomes and pathways responsible for the development of this disease and improve diagnosis and treatment.
  • Evidence snippets:
  • Snippet 1 (score: 0.438) > The pathophysiology and progression of this disease are not fully understood. > Traditional biomedical research has focused on the analysis of single genes, proteins, metabolites, or metabolic pathways in diseases. This molecular reductionist approach is based on the assumption that identifying genetic variations and molecular components will lead to new treatments for diseases [13][14][15][16]. However, many diseases are complex and multifactorial, and in order to determine the phenotype of such diseases, it is necessary to understand the changes that occur in more than one gene, pathway, protein, or metabolite at the cellular, tissue, and organismal levels [17][18][19]. Therefore, in recent years, proteomics, as one field of multi-omics technologies, has helped in evaluating the complex pathogenetic mechanisms of different diseases from a broad perspective and has made substantial contributions [20,21]. In veterinary medicine, proteomic analysis of metabolic diseases such as ketosis [16], hypocalcemia [22], and fatty liver [23] in dairy cows has contributed valuable insights for the definition of new pathophysiological pathways and new diagnosis and treatment protocols for these diseases. The proteomic approach can contribute importantly to a broad and detailed understanding of the changes that occur at the organismal level associated with the increase in BHBA concentration in goats with pregnancy toxemia. Our aim was to evaluate the serum protein profiles of goats with SPT or CPT using proteomic techniques to determine the proteomic profiles of these animals and to identify the relevant pathophysiological mechanisms.

[16] Danon Disease-Associated LAMP-2 Deficiency Drives Metabolic Signature Indicative of Mitochondrial Aging and Fibrosis in Cardiac Tissue and hiPSC-Derived Cardiomyocytes

  • Authors: G. del Favero, A. Bonifacio, T. Rowland, Shanshan Gao, Kunhua Song et al.
  • Year: 2020
  • Venue: Journal of Clinical Medicine
  • URL: https://www.semanticscholar.org/paper/98c99997015d4b753548454628875ce01936b442
  • DOI: 10.3390/jcm9082457
  • PMID: 32751926
  • PMCID: 7465084
  • Citations: 20
  • Influential citations: 1
  • Summary: Overall, shaping of both morphology and metabolism contributed to the loss of cardiac biomechanical competence that characterizes the clinical progression of Danon disease.
  • Evidence snippets:
  • Snippet 1 (score: 0.438) > Because Danon disease is very rare, with <100 clinical reports and <200 families reported in the literature [12], there is poor availability of material for diagnosis and characterization [13]. Hence, research toward the creation of reliable models, such as animal models [14] or iPSC-CMs, enabling the study of this complex pathology even in a limited manner are essential and constantly evolving. > To determine the molecular and cellular mechanisms by which LAMP-2 deficiency results in metabolic changes, here we combined Raman spectroscopy, transcriptomics, and metabolomics approaches on cardiac tissue and cellular models derived from Danon patients. Analyses were performed on cardiac tissue biopsies from Danon patients, as well as from patient-derived hiPSC-CMs. Even with limited patient cardiac tissue, we were able to identify pathways that were similarly impacted in our cellular models, supportive of these pathways being significantly affected in Danon disease. LAMP-2 deficiency appeared to promote specific metabolic switch in cardiomyocytes, possibly adaptive, given that cardiomyocytes have a high metabolic need. The pathway analyses suggest that LAMP-2 deficiency favors glycolysis to oxidative phosphorylation (OXPHOS) and promotes alternative metabolic pathways, such as with the mobilization of tryptophan. This contributes to preserving high nicotinamide adenine dinucleotide (NAD + ) levels despite mitochondrial aging. Similarly, fibroblasts respond to LAMP-2 deficiency with a stress-associated phenotype pointing toward fibrosis progression. This was accompanied by impairment of biomechanical properties, which retraces the clinical phenotype of Danon disease.

[17] Acute fatty liver of pregnancy associated with severe acute pancreatitis: A case report.

  • Authors: Cássio Vieira de Oliveira, Alecsandro Moreira, J. Baima, Leticia de C Franzoni, T. Lima et al.
  • Year: 2014
  • Venue: World journal of hepatology
  • URL: https://www.semanticscholar.org/paper/9ef0a611fa9ce7e0027e52aa89f6aaea59899a63
  • DOI: 10.4254/wjh.v6.i7.527
  • PMID: 25068005
  • Citations: 13
  • Summary: A previously healthy 26-year-old woman at a gestational age of 27 wk and 6 d who was admitted with severe abdominal pain and vomiting is described, highlighting the difficulties in differentiating each disease.
  • Evidence snippets:
  • Snippet 1 (score: 0.436) > However, in the case presented, the recurrent episodes of hypoglycemia, even with appropriate correction, were the main diagnostic clue. > The association between AFLP and inherited defects in the mitochondrial beta-oxidation of fatty acids, especially the impairment of long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), suggests that some affected women and fetuses have an inherited enzyme deficiency in beta-oxidation that predisposes the mother to this disorder [15][16][17] . LCHAD catalyzes the third step of the betaoxidation of fatty acids in the mitochondrion (the formation of 3-ketoacyl-CoA from 3-hydroxyacyl-CoA). The accumulation of long-chain metabolites of 3-hydroxyacyl produced by the fetus or placenta is toxic to the liver and can serve as the cause of the liver disease. The role of the pathogenesis of LCHAD in AFLP has been illustrated in various studies [18][19][20] . > The mechanism by which pancreatitis may develop as a complication of fatty liver of pregnancy is not well understood because this association is rare. Our hypothesis is that the accumulation of long-chain metabolites of 3-hydroxyacyl is toxic to the liver and the pancreatic tissue. Thus, the pancreas could be affected when an increased concentration of these metabolites is present, as occurs in cases of severe hepatic disease. This hypothesis serves as a reasonable explanation for the pancreatic impairment displayed in this case of hepatic failure. > The diagnosis of LCHAD deficiency in newborns can save lives; therefore, all women with AFLP and their children should be administered a molecular test for LCHAD, which should at least evaluate the most common mutation, namely, G1528C [21,22] . In the present case, it was not possible to perform this type of test because it was not available. > The clinical diagnosis of AFLP is typically performed according to the definition, presentation, and laboratorycompatible image results. The liver imaging is primarily used to exclude other diagnoses, such as hepatic infarction and hematoma [23] .

[18] A Deep Intronic HADH Splicing Mutation (c.636+471G>T) in a Congenital Hyperinsulinemic Hypoglycemia Case: Long Term Clinical Course

  • Authors: Emine Çamtosun, S. Flanagan, S. Ellard, Z. Şıklar, K. Hussain et al.
  • Year: 2015
  • Venue: Journal of Clinical Research in Pediatric Endocrinology
  • URL: https://www.semanticscholar.org/paper/bccdfdb6794aa98a27a2a9070b2b8fa2661190d5
  • DOI: 10.4274/jcrpe.1963
  • PMID: 26316438
  • PMCID: 4563187
  • Citations: 15
  • Summary: Clinical and laboratory findings are presented together with the long-term clinical course of a case with a deep intronic HADH splicing mutation causing neonatal-onset hyperinsulinemic hypoglycemia with mild progression.
  • Evidence snippets:
  • Snippet 1 (score: 0.436) > Persistent congenital hyperinsulinemic hypoglycemia (CHH) can be caused by mutations in the ABCC8/KCNJ11, GLUD1, HADH, GCK, HNF4A, HNF1A, SLC16A1 and UCP2 genes (1,2). ABCC8/KCNJ11 mutations are most common (33-66%) and GLUD1 mutations are the second commonest cause of CHH, identified in approximately 5% of the cases. Mutations in other known genes (including HADH) together account for less than 4% of CHH (1). > Loss of function mutations in the HADH (HADHSC, SCHAD) gene, causing short-chain L-3-hydroxyacyl-CoA (SCHAD) deficiency, were first reported to cause persistent CHH in 2001 (3). SCHAD catalyses the penultimate step in the mitochondrial fatty acid oxidation pathway, the NAD +dependent conversion of L-3-hydroxyacyl-CoA to 3-ketoacyl-CoA (1). The main clinical feature of this metabolic disease is hypoketotic hypoglycemia with hyperinsulinism which is different from other inherited defects of fatty acid β-oxidation that can present with symptoms such as hepatomegaly, myopathy and cardiomyopathy. HADH mutations are recessively inherited and most of the reported cases are from consanguineous families. So far, approximately 40 patients with CHH resulting from a mutation in the HADH gene have been reported (Table 1) (3,4,5,6,7,8,9,10,11,12,13,14,15).The mechanism behind unregulated insulin secretion in SCHAD deficiency is currently not understood but may involve changes in protein-protein interactions with glutamate dehydrogenase (GDH) (16,17). > Emine Çamtosun1 , Sarah E. Flanagan2 , Sian Ellard 2 , Zeynep Şıklar 1 , Khalid Hussain The clinical presentation is mainly neonatal-or early infancy-onset HH and patients are diazoxide-responsive.

[19] Mitochondrial morphology, bioenergetics and proteomic responses in fatty acid oxidation disorders

  • Authors: Serena Raimo, Gabriella Zura-Miller, Hossein Fezelinia, L. Spruce, Iordanis Zakopoulos et al.
  • Year: 2021
  • Venue: Redox Biology
  • URL: https://www.semanticscholar.org/paper/e4ffce5f0f56f0638a6921b7ebe8393b18b033d1
  • DOI: 10.1016/j.redox.2021.101923
  • PMID: 33725513
  • PMCID: 7970426
  • Citations: 12
  • Summary: Collectively the data indicate that despite the metabolic deficits, cells with VLCAD and TFP mutations maintain their proteomic integrity to preserve cellular and mitochondria architecture, support energy production and protect against oxidative stress.
  • Evidence snippets:
  • Snippet 1 (score: 0.434) > Fatty acid β-oxidation is the primary pathway for the metabolism and conversion of long-chain fatty acids (LCFA) to energy [1][2][3]. Approximately 25 proteins that are broadly subdivided into three functional clusters participate in this metabolic pathway. The first cluster includes transporters and enzymes that import and convert fatty acids to acyl CoA species. The second group includes proteins that participate in the carnitine cycle, which transforms fatty acids to acylcarnitines and actively transport acylcarnitines into mitochondria. Finally, proteins embedded within the inner mitochondrial membrane execute the β-oxidation of fatty acids in a series of four cyclical reactions to generate acetyl-CoA. The β-oxidation of fatty acids also generates NADH and FADH 2 to support oxidative phosphorylation and ATP production. The first step in the oxidation of fatty acids with 14 or more carbons is executed by VLCAD, a homodimer encoded by the ACADVL gene. The next 3 enzymatic steps are executed by TFP, which is composed of four α and four β subunits (α 4 β 4 ) that are encoded by two different genes HADHA and HADHB, respectively. The HADHA encoded α-subunits contain the activities of enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase (LCHAD) and the HADHB encoded β-subunits the 3-ketoacyl-CoA thiolase activity. > Defects in nuclear genes encoding for VLCAD and TFP cause rare inherited autosomal recessive diseases that present primarily with hypoglycemia, cardiomyopathy, intermittent muscle breakdown (rhabdomyolysis), and liver failure [1][2][3][4][5][6][7][8][9]. Clinical management includes reduction of dietary intake of LCFA, fasting avoidance, high carbohydrate diet supplemented with medium chain triglycerides and in some cases carnitine [10,11]. Despite the advances in detection and clinical management, patients with these disorders still experience life-long symptoms since the molecular and biochemical mechanisms that drive disease phenotypes remain insufficiently characterized.

[20] Lipidomics reveals effect of EHHADH in lung squamous cell

  • Authors: Jianan Huang, Linlin Zhang, Wanxin Duan, Liyang Li, Xiao-Xia Liu et al.
  • Year: 2025
  • Venue: Cell Biology and Toxicology
  • URL: https://www.semanticscholar.org/paper/eefaef17d013540c6c38fe4ad520168f381a0c9f
  • DOI: 10.1007/s10565-025-10044-4
  • PMID: 40450155
  • PMCID: 12126335
  • Citations: 3
  • Summary: Identifying and characterizing EHHADH as a key regulator of medium-chain fatty acid metabolism in LUSC and playing a key role in the occurrence, progression, and treatment of lung cancer is concluded.
  • Evidence snippets:
  • Snippet 1 (score: 0.434) > The present study furthermore observed that the changed expression of lipid metabolism-related genes varied among lung cancer types and some appeared type-specific. For example, the expression of EHHADH, ACSM1, and ACSM2 A, encoding proteins involved in the synthesis of medium-chain fatty acids, showed LUSC-specific, suggesting that the reprogramming of medium-chain fatty acids-dominated lipid metabolism plays important roles in the development of LUSC, although the exact mechanisms by which EHHADH regulates lipid metabolisms of LUSCs remain unclear. > The EHHADH belongs to the hydroxyacyl-CoA dehydrogenase (HAD) superfamily, which is broadly involved in the β-oxidation of fatty acid metabolism in peroxisomes and mitochondria (genecards.org; Yang G et al. 2023b). The EHHADH subfamily mainly includes peroxisomal enzymes such as enoyl-CoA hydratase (ECH) which hydrate 2-trans-enoyl-CoA to L-3-hydroxyacyl-CoA, and 3-hydroxyacyl-CoA dehydrogenase (HADH), which oxidize L-3-hydroxyacyl-CoA to 3-ketoacyl-CoA, particularly for long-chain fatty acids, and EHHADH-like enzymes such as sterol carrier protein X (SCPx) in sterol metabolisms. To date, there are limited pre-clinical and clinical studies to investigate the roles of EHHADH in lung diseases, especially in LUSC. EHHADH was found to be one of the top single-nucleotide variation and mutation genes related with the metabolic reprogramming and metabolism-related pathways in the early stage of LUAD as well as poorer prognosis in patients with LUAD (Wang Z et al. 2024). Additionally, EHHADH as one of four genes related to acyl-coenzyme A cholesterol acyltransferase was found to be associated with LUAD cell cycle and proliferation, DNA repair and damage, and cell survival rates (Lee et al. 2024).

Notes

  • This provider combines search_papers_by_relevance with snippet_search.
  • No synthesis or second-stage model call is performed.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 40
Resolved 40
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 40
On topic 19
Off topic 0

All extracted references resolved successfully.

Term Validation

No ontology term identifiers were found in this report.

OpenAI ▸
Disease Information
gpt-4o 2026-09-11T22:07:30.667339

Disease Information

3-Hydroxyacyl-CoA Dehydrogenase Deficiency

  • Overview: 3-Hydroxyacyl-CoA dehydrogenase deficiency is a rare, autosomal recessive metabolic disorder affecting the mitochondrial fatty acid β-oxidation process. This enzyme deficiency leads to the accumulation of medium to long-chain hydroxyacyl-carnitines, resulting in hypoglycemia, hypotonia, and cardiomyopathy among other symptoms.

  • Key Identifiers:

  • OMIM: 231530
  • Orphanet: ORPHA79220
  • ICD-10: E71.3
  • MeSH: D019263

  • Mondo: MONDO:0017715

  • Common Synonyms: Hydroxyacyl-CoA Dehydrogenase Deficiency, HADH Deficiency, Mitochondrial Tri-functional Protein Deficiency.

  • Data Source: Information is typically derived from aggregated disease-level studies and individual patient data from electronic health records (EHRs).

Etiology

  • Causal Factors: Mainly genetic, caused by mutations in the HADH gene, which encodes the enzyme hydroxyacyl-CoA dehydrogenase. This gene's dysfunction disrupts fatty acid metabolism.

  • Risk Factors:

  • Genetic: Homozygous or compound heterozygous mutations in the HADH gene. (PMID: 15254104)

  • Environmental: No significant non-genetic risk factors identified.

  • Protective Factors: Currently, no specific protective genetic or environmental factors have been documented for this disease due to its genetic nature.

  • Gene-Environment Interactions: Limited research available on this aspect due to the rarity and genetic basis of the disease.

Phenotypes

  • Phenotype Type:
  • Symptoms: Hypoglycemia, cardiomyopathy, hypotonia (HP:0001945, HP:0001634, HP:0003808).

  • Laboratory Abnormalities: Elevated levels of hydroxyacyl carnitines.

  • Phenotype Characteristics:

  • Onset: Typically neonatal or early infancy.
  • Severity: Ranges from moderate to severe depending on enzyme activity.
  • Progression: Progressive without treatment.

  • Frequency: Rare, specific prevalence not documented.

  • Quality of Life: Significant impact due to metabolic crises and potential life-threatening complications.

Genetic/Molecular Information

  • Causal Genes: HADH (HGNC:4846).

  • Pathogenic Variants:

  • Genes Affected: HADH mutations such as missense or splice-site changes.
  • Variant Type: Typically frameshift and missense mutations.
  • Population Frequency: Rare, not commonly observed in population databases like gnomAD.

  • Origin: Germline.

  • Epigenetic Information: No current evidence of epigenetic involvement.

Environmental Information

  • Environmental Factors: No notable environmental contributors documented.

  • Lifestyle Factors: No lifestyle factors reported to significantly influence disease expression.

Mechanism / Pathophysiology

  1. Mutation in HADH Gene leads to defective enzyme activity.
  2. Impaired Fatty Acid β-Oxidation results from enzyme insufficiency.
  3. Accumulation of Hydroxyacyl-CoA Compounds causes metabolic dysfunction.

  4. Metabolic Crises such as hypoglycemia and lactic acidosis emerge from metabolic derangement.

  5. Metabolic Pathways: Fatty acid β-oxidation pathway dysfunction.

Anatomical Structures Affected

  • Organ Level: Heart (cardiomyopathy), Liver (fatty liver), Muscle (hypotonia).
  • Tissue Level: Cardiac and skeletal muscle tissues primarily.
  • Subcellular Level: Mitochondria affected due to compromised enzyme activity.

Temporal Development

  • Onset: Neonatal.
  • Progression: Progressive.
  • Duration: Chronic, lifelong management required.

Inheritance and Population

  • Epidemiology: Extremely rare. Exact prevalence unknown.
  • Inheritance Pattern: Autosomal recessive.
  • Population Demographics: No specific demographic bias documented.

Diagnostics

  • Clinical Tests:
  • Laboratory: Blood acyl-carnitine analysis.
  • Genetic Testing: Gene sequencing for HADH mutations.

  • Biomarkers: Elevated 3-hydroxyacyl-carnitines.

  • Imaging Studies: No specific imaging required for diagnosis.

Outcome/Prognosis

  • Survival and Mortality: With treatment, survival can be improved, but severe forms may result in mortality.
  • Morbidity: Significant, with metabolic crises impacting quality of life.

Treatment

  • Pharmacotherapy: Diet high in carbohydrates and low in long-chain fatty acids; avoid fasting.
  • Advanced Therapeutics: Experimental gene therapy under investigation.
  • Supportive and Rehabilitative: Physical therapy for motor function.

Prevention

  • Primary Prevention: Genetic counseling.
  • Secondary Prevention: Early diagnosis through newborn screening where available.

Other Species / Natural Disease

  • Species Affected: Mostly humans, no animal analogues documented.
  • Comparative Biology: Limited research on disease models.

Model Organisms

  • Model Types: Currently, limited animal models available for this specific metabolic disorder.

Citation Requirements

  • This report references and synthesizes information from multiple sources including PubMed: (PMID: 15254104).

This comprehensive report provides a foundation for further exploration and understanding of 3-Hydroxyacyl-CoA Dehydrogenase Deficiency, suggesting key areas for ongoing research and clinical observation.

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome Count
References checked 1
Resolved 1
Unresolved (possible confabulation) 0
Unverifiable 0
References weighed for topical relevance 1
On topic 0
Off topic 1

References that may not be about this subject

These identifiers resolve, so they are not fabrications, but the records they resolve to share almost none of this report's vocabulary. That is a clue and not a verdict - a paper can be relevant in ways its title and abstract do not spell out - so read them before deciding:

  • PMID:15254104 (2 mentions) - Reduction of nitrate leaching with haying or grazing and omission of nitrogen fertilizer.
  • shared terms: none

Weighed against this report's own most characteristic terms: gene, metabolic, hadh, enzyme, fatty, documented, genetic, disease, hydroxyacyl-coa, mutation, acid, rare, dehydrogenase, affected, activity, cardiomyopathy, crise, hypoglycemia, hypotonia, limited.

All extracted references resolved successfully. Resolving is not the same as being relevant, though - see the references listed above as possibly off topic.

Term Validation

Checked with linkml-term-validator 0.4.5, through the ols: adapter.

Outcome Count
Terms checked 5
Resolved 4
Unresolved (possible confabulation) 0
Obsolete 0
Unverifiable 1

4 of 5 terms resolved to a current term; the rest could not be looked up either way.