Effect of short and medium term calorie restriction on skeletal muscle protein synthesis and mitochondrial enzyme activities in rats

The aim of the present study was to investigate the effect of different duration of moderate (40%) calorie restriction on skeletal muscle fractional protein synthesis rate and mitochondrial enzyme activities in rats. Sixty rats were randomly divided into five groups i.e. with Ad libitum Food intake as controls (AL), 5 days calorie restricted (CR 5), 10 days calorie restricted (CR 10), 15 days calorie restricted (CR 15), and 30 days calorie restricted (CR 30). Fractional protein synthesis rate, ATP production rate, electron transport chain activity and plasma amino acids levels, Insulin, IGF-1 levels were measured. Muscle protein fractional synthesis rate was decreased (P<0.05) in CR 10, CR 15 and CR 30 groups in comparison to AL. Fractional synthesis rate was unaltered in CR 5 group in comparison to other CR groups. Levels of essential amino acids (EAA) and branched chain amino acids (BCAA) decreased (P<0.05) in CR 10, CR 15 and CR 30 groups. ATP production rate was not significantly affected in CR groups compared to AL group. Citrate synthase activity was reduced (P<0.01) in all CR groups and Complex I activity significantly reduced in CR 10, CR 15 and CR 30 groups. No significant change was observed in Complex II, III and IV enzyme activities CR10 and CR15 groups compared to AL group. Complex IV activity was increased (P<0.05) in CR 5 group. Insulin levels were unaltered in other CR groups; IGF-1 levels were decreased in all CR groups. In conclusion, result suggests that the skeletal muscle fractional protein synthesis rate decreased in 10, 15 and 30 days calorie restricted groups and it was maintained in CR 5 group, along with mitochondrial enzyme activities.