Mitochondrial Dysfunction Module

Metabolism Aging Module mitochondrial_dysfunction 12 disorders Pathograph 6

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.

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Pathophysiology Nodes

5 shared nodes are defined in this module.

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Cell Types

No cell types are annotated for this module.

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Biological Processes

Aerobic Respiration GO:0009060 DECREASED Oxidative Phosphorylation GO:0006119 DECREASED Reactive Oxygen Species Metabolism GO:0072593 INCREASED Mitophagy GO:0000422 DECREASED Inflammatory Response GO:0006954 INCREASED

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.

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Used By Disorder Entries

Ageing Associated Decline in Intrinsic Capacity via Mitochondrial Bioenergetic Decline → Bioenergetic Decline and Oxidative Stress

Alzheimer Disease via Mitochondrial Quality-Control Failure → Impaired Mitophagy and Quality Control

Combined oxidative phosphorylation deficiency 42 via Combined Respiratory Chain Enzyme Deficiency → Bioenergetic Decline and Oxidative Stress

Fontaine Progeroid Syndrome via Abnormal mitochondrial energy metabolism → Bioenergetic Decline and Oxidative Stress

Kearns-Sayre syndrome via Mitochondrial Translation and OXPHOS Deficiency → Bioenergetic Decline and Oxidative Stress

MELAS Syndrome via Oxidative phosphorylation deficiency → 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 34 via Isolated Complex I Deficiency → Bioenergetic Decline and Oxidative Stress

Mitochondrial DNA Depletion Syndrome 14B (Cardioencephalomyopathic Type) via Combined Respiratory Chain 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

Werner Syndrome via Impaired Mitophagy and Mitochondrial Quality Control → Impaired Mitophagy and Quality Control

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Pathograph

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Pathophysiology

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

Downstream

Bioenergetic Decline and Oxidative Stress

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 Reactive Oxygen Species Metabolism GO:0072593 INCREASED

Used by disorders

Ageing Associated Decline in Intrinsic Capacity as Mitochondrial Bioenergetic Decline

Combined oxidative phosphorylation deficiency 42 as Combined Respiratory Chain Enzyme Deficiency

Fontaine Progeroid Syndrome as Abnormal mitochondrial energy metabolism

Kearns-Sayre syndrome as Mitochondrial Translation and OXPHOS Deficiency

MELAS Syndrome as Oxidative phosphorylation deficiency

Mitochondrial Complex I Deficiency, Nuclear Type 24 as Reduced Complex I Amount and Activity

Mitochondrial Complex I Deficiency, Nuclear Type 34 as Isolated Complex I Deficiency

Mitochondrial DNA Depletion Syndrome 14B (Cardioencephalomyopathic Type) as Combined Respiratory Chain Deficiency

Pearson syndrome as Mitochondrial Translation and OXPHOS Deficiency

Sarcopenia as Mitochondrial Dysfunction and Oxidative Stress

Downstream

Impaired Mitophagy and Quality Control
Mitochondrial Contribution to Senescence and Inflammation

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

Used by disorders

Alzheimer Disease as Mitochondrial Quality-Control Failure

Werner Syndrome as Impaired Mitophagy and Mitochondrial Quality Control

Downstream

Age-Related Tissue Dysfunction

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

Downstream

Age-Related Tissue Dysfunction