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Mitochondrial Dysfunction Module

Metabolism Aging Module mitochondrial_dysfunction 36 disorders Pathograph 18
A conserved mechanism module for the hallmark of aging (Lopez-Otin et al.) termed mitochondrial dysfunction: the age-associated decline of mitochondrial quality and bioenergetic capacity and its downstream consequences. Because mitochondria convert dietary calories into ATP by oxidative phosphorylation while generating reactive oxygen species (ROS) as a by-product, and because mitochondrial DNA (mtDNA) is present in many copies and encodes essential respiratory-chain subunits, post-mitotic tissues accumulate somatic mtDNA mutations and respiratory-chain dysfunction with age. Declining bioenergetics and rising oxidative stress are incompletely counteracted because mitophagy (autophagic clearance of damaged mitochondria) also wanes, so dysfunctional, ROS-producing, pro-inflammatory mitochondria accumulate. Mitochondrial dysfunction feeds several other hallmarks - cellular senescence, chronic inflammation, and the decline in stem-cell activity - and converges on age-related tissue dysfunction. Individual disorder entries declare conformance via conforms_to on their pathophysiology nodes, substituting the disease-specific lesion (e.g. primary mtDNA/nuclear respiratory-chain defects in mitochondrial disease, or secondary mitochondrial injury in neurodegeneration and metabolic disease) while preserving the conserved damage -> bioenergetic-decline/ROS -> impaired-clearance -> tissue-decline chain. A pharmacological arm is curated alongside the chain, because the central question this module raises - whether age-related bioenergetic decline is a reversible regulatory state or only the readout of accumulated damage - has been tested directly: the cardiolipin-binding peptide elamipretide (SS-31) reverses the bioenergetic, redox, proton-leak, and organ-function phenotypes in naturally aged mice without increasing mitochondrial content, while the one randomized human test produced target engagement without functional benefit.
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Pathophysiology Nodes

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5 shared nodes are defined in this module.
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Cell Types

0
No cell types are annotated for this module.
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Biological Processes

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Aerobic Respiration GO:0009060 ↓ DECREASED Gene Ontology (GO) Relation: this mechanism module involves this biological process This mechanism module involves decreased Aerobic Respiration (GO:0009060). GO:0009060 is a biological process from the Gene Ontology. Oxidative Phosphorylation GO:0006119 ↓ DECREASED Gene Ontology (GO) Relation: this mechanism module involves this biological process This mechanism module involves decreased Oxidative Phosphorylation (GO:0006119). GO:0006119 is a biological process from the Gene Ontology. Reactive Oxygen Species Metabolism GO:0072593 ↑ INCREASED Gene Ontology (GO) Relation: this mechanism module involves this biological process This mechanism module involves increased Reactive Oxygen Species Metabolism (GO:0072593). GO:0072593 is a biological process from the Gene Ontology. Mitophagy GO:0000422 ↓ DECREASED Gene Ontology (GO) Relation: this mechanism module involves this biological process This mechanism module involves decreased Mitophagy (GO:0000422). GO:0000422 is a biological process from the Gene Ontology. Inflammatory Response GO:0006954 ↑ INCREASED Gene Ontology (GO) Relation: this mechanism module involves this biological process This mechanism module involves increased Inflammatory Response (GO:0006954). GO:0006954 is a biological process from the Gene Ontology.
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Notes

This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "mitochondrial_dysfunction#Bioenergetic Decline and Oxidative Stress"). Conforming nodes in disorder files should include the corresponding biological processes and causal edges, specialized to their disease context. The module is intentionally kept lean and deliberately does NOT adjudicate the contested mitochondrial free-radical theory of aging or embed disease-specific mtDNA lesions; such claims belong on the relevant disorder entry. Complements cellular_senescence and inflammaging (mitochondrial dysfunction is an upstream driver of both) and deregulated_nutrient_sensing (mitophagy is an autophagic quality-control arm). Key conformance target: "mitochondrial_dysfunction#Bioenergetic Decline and Oxidative Stress". A naked mole-rat (Heterocephalus glaber) comparative negative model is attached under animal_models, and is this module's clearest counterexample to a simple oxidative-damage-to-aging chain: the oxidative arm of the central effector node is exaggerated relative to the mouse while the age-related tissue-dysfunction consequence is never reached. It is a species comparison, not a disease model, and conforming disorder entries do NOT inherit those links. The module also carries a pharmacological-probe arm - elamipretide (SS-31) under treatments, the naturally aged wild-type mouse under animal_models, and the elamipretide_aging_translation_gap discussion. That arm exists to record which of these nodes have been shown to be reversible and in what system; it is not an endorsement of the drug, and a conforming disorder entry should substitute its own disease-specific target node rather than copy the module targets.
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Discussions and Knowledge Gaps

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Does the reversal of mitochondrial and organ-level aging phenotypes that elamipretide produces in aged rodents occur in human aging, given that the only randomized human test showed target engagement on the bioenergetic node without any functional benefit?
HUMAN MODEL MISMATCH OPEN elamipretide_aging_translation_gap
Attached to: Bioenergetic Decline and Oxidative Stress Age-Related Tissue Dysfunction Elamipretide (SS-31) Naturally aged wild-type mouse
In aged mice the chain from drug to mitochondrial state to organ function is complete and reproducible across three organs and several laboratories. In humans only the first half has been observed. A randomized crossover trial in 39 older adults selected for poor mitochondrial function found a single infusion raised in vivo ATPmax but left fatigue resistance unchanged, and the phase-3 MMPOWER-3 trial in primary mitochondrial myopathy - a disease population, not an aging one, but the largest test of the drug's functional effect - missed both of its primary endpoints. The mismatch is specifically at the "Bioenergetic Decline and Oxidative Stress" to "Age-Related Tissue Dysfunction" edge, not at target engagement, which makes it a translational validity question rather than a pharmacology one. Candidate explanations are not mutually exclusive: single-dose exposure in humans against 8 weeks to 8 months in mice; a human muscle endpoint (first dorsal interosseous fatigue) less energetically limited than murine treadmill endurance; or a genuine species difference in how much of human age-related functional loss is downstream of reversible mitochondrial regulation as opposed to structural damage, denervation, and sarcopenic fiber loss. Until a chronic-dosing human trial with a functional endpoint is reported, module conformers should treat the rodent reversal as evidence about mechanism and not as evidence of a treatable human phenotype.
Proposed experiments: Chronic elamipretide dosing in older adults with a matched-modality functional endpoint
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Animal Models

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Naked mole-rat (Heterocephalus glaber) comparative longevity model
Comparative negative model, and the clearest counterexample this module has to a simple oxidative-damage-to-aging chain. The naked mole-rat lives in a more pro-oxidative cellular environment than the mouse and carries more accrued oxidative damage to lipids, DNA and protein, yet reaches none of the age-related tissue dysfunction this chain terminates in over a lifespan above 30 years. It is curated here to mark where the chain is broken in a naturally long-lived mammal, not as a model of a disease.
Species
Naked mole-rat
Genotype
Wild type
Publication
PMID:17054663
Pathograph links
Bioenergetic Decline and Oxidative Stress partially recapitulates fidelity: moderate The oxidative-stress arm of this node is present and, relative to the mouse, exaggerated: lower reduced glutathione and a lower GSH/GSSG ratio, about tenfold higher in vivo lipid peroxidation, and higher accrued oxidative damage to lipids, DNA and protein.
Limitations: Only the oxidative arm is recapitulated. This node also asserts falling ATP output by oxidative phosphorylation, and the cited comparison does not measure respiration, ATP production or mitochondrial content. The oxidative state is also present in young naked mole-rats rather than developing with age, so it is a species baseline and not the age-progressive decline the node describes. All measurements are cross-species against mice at matched physiological ages.
Readouts
Glutathione redox status
Direction: DECREASED
Interpretation: Poorer antioxidant buffering than the short-lived comparator, so the oxidative arm of this node is not avoided by this species.
Evidence: 1
Accrued oxidative damage to lipids, DNA and protein
Direction: INCREASED
Interpretation: The downstream macromolecular damage attributed to this node is present at higher levels than in the mouse.
Evidence: 1
Age-Related Tissue Dysfunction fails to recapitulate fidelity: low With the oxidative input present and elevated, the consequence node is still not reached: the naked mole-rat shows no age-related increase in mortality and only delayed or attenuated age-associated physiological decline. The dissociation is the reason the source authors conclude that something other than attenuated oxidative stress explains this species' longevity.
Limitations: The supporting argument is organism-level and demographic, from captive colony records, so it establishes that age-related mortality is absent rather than that mitochondria-driven tissue dysfunction specifically is absent. It also does not tell this module which node is broken: a species that tolerates oxidative damage without aging may be protecting the proteome, the genome, or mitochondrial quality control, and the proteostasis and genomic-instability modules carry competing candidates for the same phenotype. Naked mole-rat mitophagy has not been measured across the lifespan.
Evidence: 2
Aging turquoise killifish mitochondria (Nothobranchius furzeri) Naturally short-lived vertebrate aging model
Hartmann and colleagues asked whether the shortest-lived vertebrate held in captivity shows the mitochondrial changes canonically attributed to aging. Mitochondrial DNA copy number, biogenesis-factor expression, respiratory chain complex content, and respiration all decline with age, but the large-scale mtDNA deletions expected from the mutation-accumulation account were not detectable. The model therefore separates the module's copy-number and bioenergetic facets from its somatic-mutation facet.
Species
Turquoise killifish (Nothobranchius furzeri)
Genotype
Wild type
Background
Young versus old fish assayed in skeletal muscle, brain, liver, skin, and dorsal fin, with the complete mitochondrial genome sequenced for this study.
Publication
PMID:21624037
Pathograph links
Mitochondrial Damage and mtDNA Mutation partially recapitulates fidelity: moderate Mitochondrial genome content falls with age across five tissues, together with downregulation of the factors that maintain and replicate it. The deletion burden that the node's mutation half predicts was, however, not detectable in this species.
Limitations: The absence of detectable deletions is a limit-of-detection result at the assay sensitivity used, not proof that none accumulate, and the compressed killifish lifespan may simply be too short for clonal deletion expansion. Point mutations and heteroplasmy were not quantified. Copy-number loss and mutation load are separate mechanisms and this model supports only the former, so it should not be cited for mtDNA mutation accumulation.
Readouts
Mitochondrial DNA copy number across tissues
mtDNA copy number in skeletal muscle, brain, liver, skin, and dorsal fin of young versus old fish.
Direction: DECREASED
Interpretation: A consistent multi-tissue decline is the direct measurement supporting the genome-content half of this node.
Evidence: 1
Large-scale mtDNA deletion burden
Screen for age-related large-scale deletions in the sequenced killifish mitochondrial genome.
Direction: UNCHANGED
Interpretation: No detectable deletion accumulation, which is a genuine negative result against the mutation half of this node in this species.
Evidence: 1
Expression of mtDNA maintenance and biogenesis factors
Transcript levels of the mitochondrial biogenesis coactivator and the mtDNA binding factors Tfam and mtSsbp in young versus old fish.
Direction: DECREASED
Interpretation: Coordinated downregulation of the maintenance machinery is the mechanistic correlate of the copy-number loss rather than an independent finding.
Evidence: 1
Evidence: 1
Bioenergetic Decline and Oxidative Stress recapitulates fidelity: moderate Respiratory chain complex content and mitochondrial respiration both fall in aged killifish, giving the module's bioenergetic node a direct functional measurement rather than an expression proxy.
Limitations: Functional respirometry was performed in skeletal muscle only, so the bioenergetic claim is not established for the other tissues in which copy number falls. Reactive oxygen species production and oxidative damage markers were not measured, so the oxidative-stress half of this node is not covered by this model as curated here.
Readouts
Respiratory chain complex III and IV content in skeletal muscle
Content of respiratory chain complexes in skeletal muscle of old versus young fish.
Direction: DECREASED
Interpretation: Loss of complex content is the structural basis of the respiration defect measured in the same tissue.
Evidence: 1
ADP-stimulated and succinate-dependent respiration
Respirometry on mitochondria isolated from old versus young fish.
Direction: DECREASED
Interpretation: A functional respiration deficit is the most direct available evidence for the bioenergetic node in this model.
Evidence: 1
Evidence: 1
Curated as part of a tranche adding turquoise killifish models across the hallmarks-of-aging modules. The deletion-burden readout is the point of interest: the canonical mtDNA mutation-accumulation account does not reproduce in the shortest-lived vertebrate model, while copy-number and bioenergetic decline do.
Naturally aged wild-type mouse
Chronologically aged, genetically unmodified mice are the system in which most of this module's nodes were measured and in which they have been pharmacologically reversed. There is no engineered lesion: the phenotype is whatever normal aging produces by 24-27 months, which one of the studies below equates to a human of about 79 years. The model is curated here because the module's central claim - that age-related bioenergetic decline is a reversible regulatory state rather than only accumulated damage - rests almost entirely on measurements made in it.
Species
Mouse
Genotype
Wild-type (C57BL/6 and C57BL/6Nia), studied at 24-27 months against 5-6-month young adults
Publication
PMID:23692570
Pathograph links
Bioenergetic Decline and Oxidative Stress recapitulates fidelity: moderate Aged mice reproduce the full node: reduced in vivo ATP production and oxidative-phosphorylation coupling, a more oxidized glutathione and protein-thiol redox state, increased mitochondrial ROS, and an increased proton leak. Each of these has been measured directly and each is corrected by elamipretide.
Limitations: Fidelity is MODERATE rather than HIGH because the in vivo deficits are not reproduced ex vivo - respiration in permeabilized fibers from the same aged muscles is not different from young, so the phenotype depends on the intact cellular environment and does not transfer to isolated mitochondria. Mouse lifespan compresses the exposure history of human aging, cohorts are typically single-sex, and the mtDNA mutation burden of an inbred laboratory mouse is not that of an outbred human.
Readouts
In vivo mitochondrial phosphorylation capacity (ATPmax) and P/O coupling in skeletal muscle
Combined optical and 31P magnetic resonance spectroscopy of hindlimb muscle in the intact animal.
Oxidative Phosphorylation GO:0006119 ↓ DECREASED Gene Ontology (GO) Relation: this readout reports on this biological process This readout reports on decreased Oxidative Phosphorylation (GO:0006119). GO:0006119 is a biological process from the Gene Ontology.
Direction: DECREASED
Interpretation: The quantitative form of the node's bioenergetic arm, measured without removing mitochondria from their cellular context.
Evidence: 1
In vivo ATPmax and P/O coupling after elamipretide treatment
The same spectroscopic measures repeated after 8 weeks of 3 mg/kg/day SS-31 in aged mice.
Direction: RESTORED
Interpretation: Pharmacological reversal of the node in the model, and the basis for treating the age-related deficit as regulatory rather than structural.
Evidence: 1
Mitochondrial proton leak in cardiomyocytes
Direct measurement of proton entry in cardiomyocytes from naturally aging mice and rats, localized to ANT1.
Direction: INCREASED
Interpretation: Establishes a coupling-efficiency lesion distinct from ROS production within this node.
Evidence: 1
Cysteine S-glutathionylation of the cardiac proteome
Shotgun redox proteomics of mouse hearts, comparing 24-month with 5-6-month animals before and after 8 weeks of elamipretide.
Direction: RESTORED
Interpretation: A proteome-wide molecular correlate of the node's oxidative-stress arm, and the most specific evidence that the drug shifts redox state rather than only functional output.
Evidence: 1
Evidence: 1
Age-Related Tissue Dysfunction recapitulates fidelity: moderate The same animals show the organ-level consequence arm - diastolic dysfunction, glomerulosclerosis, and loss of endurance and fatigue resistance - and each improves when the upstream mitochondrial node is treated in late life.
Limitations: The organ phenotypes are those of a short-lived quadruped: murine cardiac aging is dominated by diastolic dysfunction without the atherosclerotic and hypertensive comorbidity that shapes human cardiac aging, and murine sarcopenia is not the human syndrome. The functional gains are also regimen-dependent - intermittent rather than continuous dosing preserved exercise tolerance and left ventricular mass but did not reproduce the renal benefit.
Readouts
Left ventricular diastolic function in old mice
Echocardiographic diastolic function after 8 weeks of SS-31 begun in old age.
Direction: RESTORED
Interpretation: The organ-level endpoint most consistently reversed by acting on the upstream mitochondrial nodes.
Evidence: 1
Treadmill endurance capacity in aged mice
Forced treadmill running to exhaustion after 8 weeks of treatment, compared with both pretreatment and untreated aged controls.
Direction: RESTORED
Interpretation: Whole-animal function, the least reducible of the readouts and the one whose human counterpart has not reproduced.
Evidence: 1
Glomerulosclerosis and glomerular mitochondrial morphology
Light and transmission electron microscopy of glomeruli in mice randomized at 24 months to 8 weeks of SS-31 or saline.
Direction: RESTORED
Interpretation: A structural, non-functional readout of the consequence node in a second organ.
Evidence: 1
Evidence: 1
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Computational Models

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Kowald-Kirkwood Transcription-Based mtDNA Deletion Selection Model AGENT_BASED
Stochastic simulation of mitochondrial DNA populations within a cell, testing candidate explanations for why deletion-bearing mtDNA molecules clonally expand to take over a cell during ageing. The model supports a transcription-linked selection advantage: deleted genomes, being shorter and less transcribed, incur less transcription-associated degradation and so replicate to dominance.
PMID:24569805
Pathograph links
Mitochondrial Damage and mtDNA Mutation recapitulates fidelity: moderate Models clonal expansion of deletion mutants as the outcome of a replicative selection advantage rather than random drift alone.
Explains why a rare somatic mtDNA deletion becomes cell-wide, which is the step that converts a stochastic mutation into the focal respiratory-deficient cells seen in aged tissue.
Resolving the Clonal Expansion of mtDNA Deletions AGENT_BASED
Systematic comparison of the competing mechanistic hypotheses for mtDNA deletion clonal expansion - random drift, replicative advantage of shorter genomes, selection through impaired mitophagy - evaluated against the constraint that the expansion must complete within a mammalian lifespan.
PMID:29495484
Pathograph links
Mitochondrial Damage and mtDNA Mutation recapitulates fidelity: moderate Discriminates among candidate expansion mechanisms using lifespan-scale timing as the discriminating constraint.
Impaired Mitophagy and Quality Control partially recapitulates fidelity: low Evaluates selective-mitophagy failure as one candidate route to expansion.
Limitations: Mitophagy enters as an alternative selection hypothesis under test, not as a mechanistically resolved quality-control pathway.
Sizek2023 MiDAS Boolean Model SBML-qual BOOLEAN_NETWORK
Boolean regulatory network model of mitochondrial dynamics coupled to cell-cycle control and apoptosis, capturing hyper-fusion at the G1/S boundary and fission in mitosis. It offers a mechanistic hypothesis, with testable predictions, for Mitochondrial Dysfunction-Associated Senescence (MiDAS) - the state in which reactive oxygen species and an energy deficit push a cell into senescence with an altered secretome and chronic oxidative stress, and examines NAD+ as an intervention point.
Repository ↗ PMID:39163758
Pathograph links
Bioenergetic Decline and Oxidative Stress recapitulates fidelity: moderate Couples low NAD+/NADH and reduced ATP output to ROS production as a single regulatory state rather than as independent readouts.
Mitochondrial Contribution to Senescence and Inflammation recapitulates fidelity: moderate Distinguishes MiDAS from deep senescence by secretome state, and predicts NAD+ repletion as the lever that separates them.
Limitations: Boolean formalism yields qualitative state transitions without rates or concentrations, and the MiDAS mechanism is offered as a hypothesis with testable predictions rather than as a validated pathway.
The explicit bridge from this module into cellular_senescence - a mitochondrial state, not a DNA-damage state, determines which senescent secretome results. The "Sizek2023" label follows the BioModels record name, which encodes the 2023 deposit; the paper itself (PMID:39163758) published in 2024. Encoded with the SBML qual package, so a plain SBML reader will not load it.
Kowald-Kirkwood Network Theory of Ageing Model KINETIC
Integrated model treating ageing as the interaction of defective mitochondria, aberrant proteins, free radicals, and scavenger systems, rather than as any one of these damage processes acting alone. An early attempt to make the interdependence of the damage pathways quantitative.
PMID:8649456
Pathograph links
Bioenergetic Decline and Oxidative Stress partially recapitulates fidelity: low Places mitochondrial free-radical production inside a feedback network with protein damage and scavenging capacity.
Age-Related Tissue Dysfunction partially recapitulates fidelity: low Derives an organism-level ageing trajectory from the coupled damage processes.
Limitations: A 1996 synthesis predating most of the molecular detail in this module; its value is the coupling structure it proposes, not its parameterization.
Historically the origin of the "damage processes interact" framing that the hallmarks-of-aging modules now represent as separate but cross-linked entries.
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Module Collections

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Hallmarks of Aging as Mitochondrial dysfunction
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Used By Disorder Entries

36
Alzheimer Disease via Mitochondrial Quality-Control Failure → Impaired Mitophagy and Quality Control
Combined Oxidative Phosphorylation Defect Type 13 via Combined Respiratory Chain Complex Deficiency → Bioenergetic Decline and Oxidative Stress
Combined Oxidative Phosphorylation Defect Type 23 via Combined Respiratory Chain Complex Deficiency → Bioenergetic Decline and Oxidative Stress
Combined Oxidative Phosphorylation Deficiency 34 via Impaired Oxidative Phosphorylation → Bioenergetic Decline and Oxidative Stress
Combined Oxidative Phosphorylation Deficiency 35 via Impaired Oxidative Phosphorylation → Bioenergetic Decline and Oxidative Stress
Combined oxidative phosphorylation deficiency 42 via Combined Respiratory Chain Enzyme Deficiency → Bioenergetic Decline and Oxidative Stress
Combined oxidative phosphorylation deficiency 48 via Combined Respiratory Chain Enzyme Deficiency → Bioenergetic Decline and Oxidative Stress
Combined Oxidative Phosphorylation Deficiency 51 via Combined Respiratory Chain Deficiency with Complex II Spared → Bioenergetic Decline and Oxidative Stress
FBXL4-Related Mitochondrial DNA Depletion Syndrome via Combined Respiratory Chain Deficiency → Bioenergetic Decline and Oxidative Stress
Fontaine Progeroid Syndrome via Abnormal mitochondrial energy metabolism → Bioenergetic Decline and Oxidative Stress
Ischemic Stroke via Post-Ischemic Mitochondrial Dysfunction → Bioenergetic Decline and Oxidative Stress
Kearns-Sayre syndrome via Mitochondrial Translation and OXPHOS Deficiency → Bioenergetic Decline and Oxidative Stress
LETM1-Related Childhood-Onset Neurodegeneration via Respiratory Chain Complex Deficiency → Bioenergetic Decline and Oxidative Stress
MELAS Syndrome via Oxidative phosphorylation deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency Nuclear Type 3 via Isolated Complex I Deficiency and Bioenergetic Failure → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 11 via Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 13 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 14 via Impaired Mitochondrial NADH Reoxidation and ATP Synthesis → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 15 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 17 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 18 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 22 via Reduced Complex I Amount and Activity → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 24 via Reduced Complex I Amount and Activity → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 33 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 34 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex I Deficiency, Nuclear Type 36 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Complex V (ATP Synthase) Deficiency, Nuclear Type 3 via Isolated Complex V Deficiency with Preserved Respiratory Chain → Bioenergetic Decline and Oxidative Stress
Mitochondrial DNA Depletion Syndrome 14B (Cardioencephalomyopathic Type) via Combined Respiratory Chain Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial DNA Depletion Syndrome 3 (Hepatocerebral Type) via Combined Respiratory Chain Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial DNA Depletion Syndrome, Myopathic Form via Combined Respiratory Chain Deficiency → Bioenergetic Decline and Oxidative Stress
Mitochondrial Spastic Paraplegia via Homoplasmic MT-TV m.1661A>G Variant → Mitochondrial Damage and mtDNA Mutation , Reduced Mitochondrial DNA Copy Number → Bioenergetic Decline and Oxidative Stress
Multiple Sclerosis via Clonally Expanded Neuronal mtDNA Deletions → Mitochondrial Damage and mtDNA Mutation , CNS Mitochondrial Respiratory Deficiency → Bioenergetic Decline and Oxidative Stress
Pearson syndrome via Mitochondrial Translation and OXPHOS Deficiency → Bioenergetic Decline and Oxidative Stress
Sarcopenia via Mitochondrial Dysfunction and Oxidative Stress → Bioenergetic Decline and Oxidative Stress
SUCLA2-Related Mitochondrial DNA Depletion Syndrome via Combined Respiratory Chain Deficiency → Bioenergetic Decline and Oxidative Stress
Werner Syndrome via Impaired Mitophagy and Mitochondrial Quality Control → Impaired Mitophagy and Quality Control
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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence-backed metadata.
Pathograph: causal mechanism network for Mitochondrial Dysfunction Module Interactive directed graph showing how this shared module's pathophysiology nodes connect.
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Pathophysiology

5
Mitochondrial Damage and mtDNA Mutation
trigger
With age, post-mitotic tissues accumulate somatic mitochondrial DNA (mtDNA) mutations and respiratory-chain damage. Because mtDNA encodes essential subunits of the oxidative-phosphorylation machinery and exists in many copies per cell, this heritable mitochondrial damage is the initiating lesion that compromises energy production.
Aerobic Respiration GO:0009060 ↓ DECREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Aerobic Respiration (GO:0009060). GO:0009060 is a biological process from the Gene Ontology.
Used by disorders
Mitochondrial Spastic Paraplegia as Homoplasmic MT-TV m.1661A>G Variant
Multiple Sclerosis as Clonally Expanded Neuronal mtDNA Deletions
Downstream
  • Bioenergetic Decline and Oxidative Stress
Show evidence (2 references)
PMID:23454757 SUPPORT Other
"Somatic mitochondrial DNA (mtDNA) mutations and respiratory chain dysfunction accompany normal aging"
Establishes accumulation of somatic mtDNA mutations and respiratory-chain dysfunction with normal aging, the initiating lesion of this module. Evidence source is OTHER because this is a review.
PMID:16285865 SUPPORT Other
"I propose that the delayed-onset and progressive course of the age-related diseases results from the accumulation of somatic mutations in the mtDNAs of post-mitotic tissues."
Proposes accumulation of somatic mtDNA mutations in post-mitotic tissues as the basis of age-related disease, supporting this trigger node. Evidence source is OTHER because this is a review.
Bioenergetic Decline and Oxidative Stress
central effector
Damaged mitochondria produce less ATP by oxidative phosphorylation while generating more reactive oxygen species (ROS) as a toxic by-product. This fall in mitochondrial quality and activity - correlated with the development of a wide range of age-related diseases - is the central effector state that disease-specific mitochondrial lesions converge upon.
Oxidative Phosphorylation GO:0006119 ↓ DECREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Oxidative Phosphorylation (GO:0006119). GO:0006119 is a biological process from the Gene Ontology. Reactive Oxygen Species Metabolism GO:0072593 ↑ INCREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Reactive Oxygen Species Metabolism, annotated with reactive oxygen species metabolic process (GO:0072593). GO:0072593 is a biological process from the Gene Ontology.
Used by disorders
Combined Oxidative Phosphorylation Defect Type 13 as Combined Respiratory Chain Complex Deficiency
Combined Oxidative Phosphorylation Defect Type 23 as Combined Respiratory Chain Complex Deficiency
Combined Oxidative Phosphorylation Deficiency 34 as Impaired Oxidative Phosphorylation
Combined Oxidative Phosphorylation Deficiency 35 as Impaired Oxidative Phosphorylation
Combined oxidative phosphorylation deficiency 42 as Combined Respiratory Chain Enzyme Deficiency
Combined oxidative phosphorylation deficiency 48 as Combined Respiratory Chain Enzyme Deficiency
Combined Oxidative Phosphorylation Deficiency 51 as Combined Respiratory Chain Deficiency with Complex II Spared
FBXL4-Related Mitochondrial DNA Depletion Syndrome as Combined Respiratory Chain Deficiency
Fontaine Progeroid Syndrome as Abnormal mitochondrial energy metabolism
Ischemic Stroke as Post-Ischemic Mitochondrial Dysfunction
Kearns-Sayre syndrome as Mitochondrial Translation and OXPHOS Deficiency
LETM1-Related Childhood-Onset Neurodegeneration as Respiratory Chain Complex Deficiency
MELAS Syndrome as Oxidative phosphorylation deficiency
Mitochondrial Complex I Deficiency Nuclear Type 3 as Isolated Complex I Deficiency and Bioenergetic Failure
Mitochondrial Complex I Deficiency, Nuclear Type 11 as Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 13 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 14 as Impaired Mitochondrial NADH Reoxidation and ATP Synthesis
Mitochondrial Complex I Deficiency, Nuclear Type 15 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 17 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 18 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 22 as Reduced Complex I Amount and Activity
Mitochondrial Complex I Deficiency, Nuclear Type 24 as Reduced Complex I Amount and Activity
Mitochondrial Complex I Deficiency, Nuclear Type 33 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 34 as Isolated Complex I Deficiency
Mitochondrial Complex I Deficiency, Nuclear Type 36 as Isolated Complex I Deficiency
Mitochondrial Complex V (ATP Synthase) Deficiency, Nuclear Type 3 as Isolated Complex V Deficiency with Preserved Respiratory Chain
Mitochondrial DNA Depletion Syndrome 14B (Cardioencephalomyopathic Type) as Combined Respiratory Chain Deficiency
Mitochondrial DNA Depletion Syndrome 3 (Hepatocerebral Type) as Combined Respiratory Chain Deficiency
Mitochondrial DNA Depletion Syndrome, Myopathic Form as Combined Respiratory Chain Deficiency
Mitochondrial Spastic Paraplegia as Reduced Mitochondrial DNA Copy Number
Multiple Sclerosis as CNS Mitochondrial Respiratory Deficiency
Pearson syndrome as Mitochondrial Translation and OXPHOS Deficiency
Sarcopenia as Mitochondrial Dysfunction and Oxidative Stress
SUCLA2-Related Mitochondrial DNA Depletion Syndrome as Combined Respiratory Chain Deficiency
Downstream
  • Impaired Mitophagy and Quality Control
  • Mitochondrial Contribution to Senescence and Inflammation
Show evidence (2 references)
PMID:26942670 SUPPORT Other
"A decline in mitochondrial quality and activity has been associated with normal aging and correlated with the development of a wide range of age-related diseases."
Establishes the decline in mitochondrial quality/activity as an aging correlate and driver of age-related disease, the central effector modeled here. Evidence source is OTHER because this is a review.
PMID:16285865 SUPPORT Other
"Since the mitochondria use oxidative phosphorylation (OXPHOS) to convert dietary calories into usable energy, generating reactive oxygen species (ROS) as a toxic by-product"
Describes oxidative phosphorylation and ROS generation, the bioenergetic and oxidative-stress axes of this node. Evidence source is OTHER because this is a review.
Impaired Mitophagy and Quality Control
amplifier
Autophagic turnover specific for mitochondria (mitophagy) normally eliminates dysfunctional or damaged mitochondria, counteracting degeneration and dampening inflammation. When mitophagy and general autophagy decline with age, damaged mitochondria are not cleared and accumulate, amplifying bioenergetic failure and pro-inflammatory, pro-apoptotic signaling.
Mitophagy GO:0000422 ↓ DECREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves decreased Mitophagy, annotated with autophagy of mitochondrion (GO:0000422). GO:0000422 is a biological process from the Gene Ontology.
Used by disorders
Alzheimer Disease as Mitochondrial Quality-Control Failure
Werner Syndrome as Impaired Mitophagy and Mitochondrial Quality Control
Downstream
  • Age-Related Tissue Dysfunction
Show evidence (1 reference)
PMID:21868666 SUPPORT Other
"Autophagic turnover of cellular constituents, be it general or specific for mitochondria (mitophagy), eliminates dysfunctional or damaged mitochondria, thus counteracting degeneration, dampening inflammation, and preventing unwarranted cell loss."
Establishes mitophagy as the quality-control mechanism whose decline permits accumulation of damaged mitochondria, the amplifying step modeled here. Evidence source is OTHER because this is a review.
Mitochondrial Contribution to Senescence and Inflammation
amplifier
Beyond energy failure, dysfunctional mitochondria drive other aging hallmarks: they contribute to cellular senescence, chronic inflammation (via pro-inflammatory signaling), and the age-dependent decline in stem-cell activity. This node is the conserved interface at which mitochondrial dysfunction feeds the senescence and inflammaging modules.
Inflammatory Response GO:0006954 ↑ INCREASED Gene Ontology (GO) Relation: this pathophysiological event involves this biological process This pathophysiological event involves increased Inflammatory Response (GO:0006954). GO:0006954 is a biological process from the Gene Ontology.
Downstream
  • Age-Related Tissue Dysfunction
Show evidence (2 references)
PMID:26942670 SUPPORT Other
"we discuss how mitochondria contribute to specific aspects of the aging process, including cellular senescence, chronic inflammation, and the age-dependent decline in stem cell activity"
Establishes that mitochondria contribute to senescence, chronic inflammation, and stem-cell decline, the cross-hallmark interface modeled here. Evidence source is OTHER because this is a review.
PMID:21868666 SUPPORT Other
"Moreover, mitochondria have an important role in pro-inflammatory signaling."
States the role of mitochondria in pro-inflammatory signaling, linking this node to inflammaging. Evidence source is OTHER because this is a review.
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Treatments

3
Elamipretide (SS-31)
Pharmacotherapy NCIT:C15986 NCI 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.
Agent: elamipretide CHEBI:233331 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses elamipretide (CHEBI:233331). CHEBI:233331 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Peptide
Elamipretide (SS-31, MTP-131) is a synthetic aromatic-cationic tetrapeptide that concentrates in the inner mitochondrial membrane independently of membrane potential and binds cardiolipin. Occupying cardiolipin preserves cristae structure and the organization of the respiratory complexes into supercomplexes, keeps the cardiolipin-cytochrome c interaction from converting cytochrome c into a peroxidase, and reduces the age-associated proton leak attributed to ANT1 - raising ATP output and lowering mitochondrial reactive oxygen species without increasing mitochondrial content. It is curated here as the reference pharmacological probe of this module rather than as an established anti-aging therapy. Because it acts on the regulatory redox and structural state of mitochondria that already exist, and not on accumulated mtDNA lesions, a benefit from elamipretide is evidence that the central-effector node is reversible in situ; it is deliberately NOT linked to "Mitochondrial Damage and mtDNA Mutation" for that reason. Whether the rodent effect translates to human aging is unsettled - see the elamipretide_aging_translation_gap discussion. A conforming disorder entry that curates elamipretide should substitute its own disease-specific target node (as Barth_Syndrome does, targeting the cardiolipin remodeling defect) rather than copying these module targets.
Mechanism target:
INHIBITS Bioenergetic Decline and Oxidative Stress — Binding cardiolipin protects cristae architecture and respiratory supercomplex organization and blocks the peroxidase conversion of cytochrome c, so oxidative phosphorylation recovers while mitochondrial ROS production falls. In aged muscle the recovery of ATPmax, P/O coupling and PCr/ATP occurs within an hour of a single dose and without any change in mitochondrial content, which places the drug's action on the regulatory state of existing mitochondria rather than on mitochondrial biogenesis or the repair of damaged organelles. Evidence: 5
INHIBITS Age-Related Tissue Dysfunction — Correcting the bioenergetic and redox state of aged mitochondria improves organ-level function that had already declined - diastolic function in the aged heart, glomerular architecture in the aged kidney, and fatigue resistance and endurance in aged skeletal muscle. Treatment begun in late life is sufficient, so this is reversal of an established phenotype rather than prevention. Evidence: 4
INHIBITS Mitochondrial Contribution to Senescence and Inflammation — Because mitochondrial damage is upstream of senescence, correcting it pharmacologically in old animals lowers senescence markers. The evidence for this link is from a single tissue - the aged mouse glomerulus, where a late-life course of SS-31 lowered p16 and senescence-associated beta-galactosidase - so it is narrower than the other two links here and should be read as kidney-specific until a second tissue is curated. Within that scope it is the drug-side counterpart of the module's claim that this node is driven by, rather than merely correlated with, mitochondrial dysfunction, and it differs from a senolytic, which removes senescent cells that have already formed. Evidence: 1
Not approved for any aging indication. Elamipretide's only approved use is in Barth syndrome; its phase-3 trial in primary mitochondrial myopathy (MMPOWER-3) missed both primary endpoints. Those results are curated on the relevant disorder entries and summarized in the discussion attached to this treatment; they are recorded here so the module is not read as asserting clinical efficacy in aging.
Methylene Blue (Alternative Electron Carrier)
Pharmacotherapy NCIT:C15986 NCI 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.
Agent: methylene blue CHEBI:6872 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses methylene blue (CHEBI:6872). CHEBI:6872 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Methylene blue is a redox-cycling compound that can accept electrons from NADH and donate them to cytochrome c, bypassing damaged proximal respiratory-chain complexes. Its effect on reactive oxygen species is substrate-dependent rather than uniformly antioxidant - it lowers H2O2 production with complex II substrate but raises it with complex I substrates - so it is curated here as modulating, not simply correcting, the bioenergetic and oxidative node. Ranked joint third of nine (9/12) by Kulkarni et al.
Mechanism target:
MODULATES Bioenergetic Decline and Oxidative Stress — Methylene blue raises mitochondrial oxygen consumption with both complex I and complex II substrates, but its effect on reactive oxygen species runs in opposite directions depending on the substrate, so the net effect on this node is directionally mixed.
Evidence: 2
Metformin (Mitochondrial Bioenergetic Restoration)
Pharmacotherapy NCIT:C15986 NCI 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.
Agent: metformin CHEBI:6801 Chemical Entities of Biological Interest (CHEBI) Relation: this treatment uses this therapeutic agent This treatment uses metformin (CHEBI:6801). CHEBI:6801 is a therapeutic agent from Chemical Entities of Biological Interest.
Platform: Small molecule
Metformin normalizes mitochondrial bioenergetics in cells from older human donors, in which respiratory capacity is impaired and associated with redox imbalance. In the aged-T-cell system its mitochondrial and autophagic actions were found to run largely in parallel rather than one through the other, which is why this module and the disabled-macroautophagy module each carry the treatment separately.
Mechanism target:
RESTORES Bioenergetic Decline and Oxidative Stress — Metformin improves mitochondrial bioenergetics in cells from older donors that show a measured bioenergetic defect relative to younger donors, recovering function toward the younger-donor baseline.
Evidence: 2