Effect of 8.5% and 25% caloric restriction on mitochondrial free radical production and oxidative stress in rat liver
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Previous studies have consistently shown that 40% caloric restriction (CR) decreases the rate of mitochondrial ROS production and steady-state levels of markers of oxidative damage to macromolecules including mitochondrial DNA. However, few investigations have studied whether these changes also occur in lower CR regimes. This is of potential interest since moderate levels of dietary restriction are more practicable for humans. In this investigation male Wistar rats were subjected to 8.5% and 25% caloric restriction. Neither 8.5% nor 25% CR changed mitochondrial ROS production, oxygen consumption or mtDNA oxidative damage in rat liver mitochondria. However, both 8.5% and 25% CR significantly decreased the five different markers of protein oxidation, glycoxidation and lipoxidation measured, aminoadipic and glutamic semialdehyde, carboxyethyl-lysine, carboxymethyl-lysine, and malondialdehyde-lysine. The fatty acid composition of liver mitochondria was also affected and led to a moderate decrease in the degree of membrane unsaturation in both 8.5% and 25% CR. While 8.5% CR only affected complex I concentration (which was decreased), 25% CR decreased complexes I and IV and increased complexes II and III of the respiratory chain. Apoptosis-inducing factor (AIF) significantly decreased in 25% CR but not in 8.5% CR. The results show that moderate levels of caloric restriction can have beneficial effects including decreases in oxidative protein modification and a lower sensitivity of membranes to lipid peroxidation, in association with a reprogramming of the respiratory chain complexes and AIF content.