SIRT3 deficiency decreases oxidative-metabolism capacity but increases lifespan under caloric restriction

Mitochondrial NAD+-dependent protein deacetylase Sirtuin3 (SIRT3) has been proposed to mediate calorie restriction (CR)-dependent metabolic regulation and lifespan extension. Here, we investigated the role of SIRT3 in CR-mediated longevity, mitochondrial function, and aerobic fitness. We report that SIRT3 is required for whole-body aerobic capacity but is dispensable for CR-dependent lifespan extension. Under CR, loss of SIRT3 (Sirt3-/-) yielded a longer overall and maximum lifespan as compared to Sirt3+/+ mice. This unexpected lifespan extension was associated with altered mitochondrial protein acetylation in oxidative metabolic pathways, reduced mitochondrial respiration, and reduced aerobic exercise capacity. Also, Sirt3-/- CR mice exhibit lower physical activity and favor fatty acid oxidation during the postprandial period, leading to a pseudo-fasting condition that extends the fasting period. This study shows uncoupling of lifespan and healthspan parameters (aerobic fitness and spontaneous activity), and provides new insights into SIRT3 function in CR adaptation, fuel utilization, and aging.