Mitochondrial dysfunction is associated with ageing, but the detailed causal relationship between the two is still unclear. We review the major phenomenological manifestations of mitochondrial age-related dysfunction including biochemical, regulatory and energetic features. We conclude that the complexity of these processes and their inter-relationships are still not fully understood and at this point it seems unlikely that a single linear cause and effect relationship between any specific aspect of mitochondrial biology and ageing can be established in either direction.

Mitochondrial dysfunction is a causative and/or exacerbating feature of many pathologies. We discuss below approaches to modulate mitochondrial dysfunction that involve (1) increasing their energetic efficiency by targeting gene expression regulators such as PPAR or AMPK, (2) using antioxidant compounds to reduce the toxic reactive oxygen species mitochondria produce under stress, or (3) modulating aspects on the innate mitochondrial quality control system. The latter comprise linked processes of biogenesis, dynamic morphological changes, and elimination of defective mitochondria by mitophagy. We discuss representative compounds in all three classes.