Effects of short- and medium-term calorie restriction on muscle mitochondrial proton leak and reactive oxygen species production

Reductions in cellular oxygen consumption ((V) over dot o(2)) and reactive oxygen species (ROS) production have been proposed as mechanisms underlying the anti-aging effects of calorie restriction (CR). Mitochondria are a cell's greatest sink for oxygen and also its primary source of ROS. The mitochondrial proton leak pathway is responsible for 20-30% of (V) over dot o(2) in resting cells. We hypothesized that CR leads to decreased proton leak with consequential decreases in (V) over dot o(2), ROS production, and cellular damage. Here, we report the effects of short-term (2-wk, 2-mo) and medium-term (6-mo) CR (40%) on rat muscle mitochondrial proton leak, ROS production, and whole animal (V) over dot o(2). Whole body (V) over dot o(2) decreased with CR at all time points, whereas mass-adjusted (V) over dot o(2) was normal until the 6-mo time point, when it was 40% lower in CR compared with control rats. At all time points, maximal leak-dependent (V) over dot o(2) was lower in CR rats compared with controls. Proton leak kinetics indicated that mechanisms of adaptation to CR were different between short- and medium-term treatments, with the former leading to decreases in protonmotive force (Deltap) and state 4 (V) over dot o(2) and the latter to increases in Deltap and decreases in state 4 (V) over dot o(2). Results from metabolic control analyses of oxidative phosphorylation are consistent with the idea that short- and medium-term responses are distinct. Mitochondrial H2O2 production was lower in all three CR groups compared with controls. Overall, this study details the rapid effects of short- and medium-term CR on proton leak, ROS production, and metabolic control of oxidative phosphorylation. Results indicate that a reduction in mitochondrial (V) over dot o(2) and ROS production may be a mechanism for the actions of CR.