Dietary BCAAs Do Not Prevent Skeletal Muscle Atrophy in Rats Injected with Glucocorticoid

This study investigated the effects of the combination of a voluntary resistance exercise (climbing) and the feeding of a high protein snack rich in Branched-Chain Amino Acids (BCAAs) on skeletal muscle weights in rats injected with glucocorticoid as a model of age-related sarcopenia (Experiment 1). Moreover, we examined whether BCAAs in the diet and/or BCAAs in snacks prevent sarcopenia in sedentary rats (Experiment 2). Male Wistar rats were injected with prednisolon (2 mg kg-1) every day. Rats in the exercise groups climbed voluntarily in the tower cage for 8 weeks. BCAAs were exchanged partly for casein in the experimental diets. Glucocorticoid injection decreased final body weight and muscle mass. The body weight gain did not differ among glucocorticoid-injected rats. Climbing exercise markedly prevented the loss of muscle mass, but the BCAA snack did not facilitate the effects of exercise (Experiment 1). In the sedentary rats, either BCAA in the diet or BCAA in the snack decreased mass and protein content of muscle (Experiment 2). These results suggest that resistance exercise is the most effective way to inhibit sarcopenia in rats. BCAAs did not depress muscle mass loss without resistance exercise. BCAAs should be used on the condition that all other essential amino acids are fully available in the diet.