The molecular basis by which dietary restricted feeding reduces mitochondrial reactive oxygen species generation

▶ The paper explains why mitochondria from DR rats generate lower rates of mitochondrial H 2O 2. ▶ Enhanced proton leak through the ANT induces mild uncoupling of the mitochondria in DR rats. ▶ The enhanced proton leak lowers the membrane potential and free radical generation rates. ▶ Proton leak through the ANT is induced by free fatty acids mobilized in response to DR feeding. ▶ The proton leak can be inhibited by exogenous insulin that inhibits free fatty acid mobilisation. Restricted feeding regimes in rodents that extend longevity lower the rate of mitochondrial reactive oxygen species generation. This effect is not dependent upon the depression of the state III and IV mitochondrial respiration rates. Mitochondria from liver, skeletal muscle and brown adipose tissue adapt to DR feeding with a lowered membrane potential that results from an enhanced proton leak across the inner membrane. Mitochondrial ROS generation is very sensitive to the magnitude of the membrane potential and the enhanced proton leak and ROS generation rates are reversible by exogenous insulin in liver and heart mitochondria. The adenine nucleotide translocase (ANT) was shown to be the dominant proton leak channel induced under DR feeding regimes in these tissues, while in brown fat mitochondria, UCP1 was activated, but this was not sensitive to exogenous insulin treatment. The effect of DR to modify the proton leak, membrane potential and ROS generation rate can be simulated by a range of non-esterified free fatty acids (NEFA) acting on the ANT to enhance its protonophoric activity. Mobilisation of NEFA under DR feeding, when insulin plasma concentrations are extremely low, explains the indirect action of insulin to counteract the effects of DR feeding on mitochondrial ROS generation.