Effects of leucine supplementation on the body composition and protein status of rats submitted to food restriction

Acute administration of leucine has been shown to stimulate certain protein synthesis related anabolic processes. However, the effect of chronic leucine administration in a catabolic situation caused by food restriction (FR) has not been established. We therefore evaluated the effect of chronic leucine supplementation on the body composition and some indicators of protein nutritional status of rats submitted to FR. Adult male Wistar rats were submitted to 50% FR for 6 weeks. The control group received the AIN-93M diet and the leucine group received the same diet supplemented with 5.91 g L-leucine/kg ration. We then determined carcass chemical composition, serum leptin, albumin and total protein concentrations, and protein, DNA and RNA concentrations in gastrocnemius muscle and liver. No difference in final body weight was observed between groups. However, the leucine group presented a lower amount of body fat ( P < 0.05). Leptin concentration showed a directly proportional correlation with the amount of body fat (r = 0.88, P < 0.05), but no significant difference in serum leptin concentration was observed between groups ( P = 0.08). Regarding protein nutritional status, liver protein concentration was higher in the leucine group ( P < 0.05). In the gastrocnemius muscle, a higher RNA concentration ( P < 0.05) and a tendency towards higher DNA concentration ( P = 0.06) were observed in the leucine group. The results indicate that low-dose leucine supplementation increases body fat loss and improves liver protein status and the capacity of muscle protein synthesis in rats submitted to FR.