Mitochondrial dysfunction

Mitochondrial dysfunction is impaired mitochondrial activity that disrupts energy production or other cellular processes. It can arise from genetic changes, acquired damage, or broader cellular stress.

Oxidative phosphorylation: The mitochondrial process that uses an electron transport chain and proton gradient to produce ATP. Its failure can reduce ATP output and disrupt the proton gradient.
Mitochondrial DNA: The small circular genome found in mitochondria, encoding a subset of mitochondrial proteins and RNAs. Variants in this genome can directly impair respiratory-chain components.
Lactic acidosis: A condition in which lactate accumulation is associated with an abnormally low blood pH. Impaired oxidative metabolism can increase lactate production, though this finding has many causes.
Mitochondrial biogenesis: The cellular processes that produce new mitochondria and expand mitochondrial capacity. Increased biogenesis can compensate for impaired organelles, but it is not itself restored function.
Mitochondrial membrane potential: The electrical and chemical gradient across the inner mitochondrial membrane. Loss of this gradient signals damage and impairs ATP synthesis.
Nuclear genes encoding mitochondrial proteins: Nuclear genes whose products are imported into mitochondria to support their structure and function. Most mitochondrial proteins are nuclear-encoded, so these genes are another major source of inherited defects.
Mitochondrial myopathy: A muscle disorder caused by mitochondrial dysfunction, often producing weakness or exercise intolerance. Skeletal muscle reveals the effects of limited energy supply during exertion.
Mitochondrial disease versus mitochondrial dysfunction: The distinction between a clinical disorder caused by mitochondrial defects and impaired mitochondrial activity more broadly. Dysfunction can occur without meeting criteria for a specific mitochondrial disease.
Reactive oxygen species: Chemically reactive oxygen-containing molecules produced in cells, including during mitochondrial respiration. Excess production can damage mitochondrial components and amplify dysfunction.
Heteroplasmy: The coexistence of genetically distinct mitochondrial DNA molecules within a cell or individual. The proportion of mutant mitochondrial genomes can determine whether dysfunction crosses a damaging threshold.

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