Polymorphisms in mitochondrial DNA genes coding for subunits in complex I differentially control lifespan and ageing-related pathways in mice.

Mitochondrial complex I, the largest enzyme complex of the mitochondrial oxidative phosphorylation machinery, has been proposed to contribute to variety of age-related pathological alterations as well as longevity. The enzyme complex-consisting proteins are encoded by both nuclear- (nDNA) and mitochondrial DNA (mtDNA). While some association studies of mtDNA-encoded complex I genes and lifespan in humans have been reported, experimental evidence and functional consequence of such variants are limited to studies using invertebrate models. Here, we present experimental evidence that a homoplasmic mutation in mitochondrially encoded complex I gene, mt-Nd2, modulates lifespan by altering cellular tryptophan levels and consequently ageing-related pathways in mice. A conplastic mouse strain carrying a mutation at m.4738C>A in mt-Nd2 lived significantly shorter than the controls. The same mutation led to higher susceptibility to glucose intolerance induced by high fat diet feeding. These phenotypes were not observed in mice carrying a mutation in another mtDNA-encoded complex I gene, mt-Nd5, suggesting functional relevance of particular mutations in complex I to ageing and age-related diseases.