Metabolic adaptation to progressive mitochondrial dysfunction in aging POLGD257A mice

A decline in mitochondrial function is associated with neurodegeneration and aging. Progressive mitochondrial defects have diverse metabolic consequences that could drive some of the pathophysiological changes that occur with aging. Here, we comprehensively characterized metabolic alterations in PolgD257A mitochondrial DNA mutator mice. Plasma alanine increased dramatically with time, with lactate and other organic acids accumulating to a lesser extent. These changes were reflective of increased glycolysis, rapid gluconeogenesis, and hypoglycemia. Tracing with [15N]ammonium revealed impairment of the urea cycle and diversion to purine catabolism. We also measured alterations in the lipidome, observing a general reduction in canonical lipids and the accumulation of 1-deoxysphingolipids, which are synthesized from alanine via promiscuous serine palmitoyltransferase activity. Consistent with 1-deoxysphingolipid9s association with peripheral neuropathy, PolgD257A mice exhibited thermal hypoalgesia. These results highlight the distinct changes that occur in carbon and nitrogen metabolism upon mitochondrial impairment and key metabolic mechanisms which can drive aging-associated neuropathy.