Dietetic supplementation with branched chain amino acids attenuates the severity of streptozotocin-induced diabetes in rats.

Previous studies showed that the diabetogenic action of streptozotocin is reduced in rats adapted to a high-protein, carbohydrate-free diet, that have markedly elevated plasma concentrations of valine, leucine and isoleucine. In order to test the role of these branched chain amino acids (BCAA) in the beneficial effects of the high-protein diets, rats adapted (15 days) either to a balanced synthetic diet, or to the same diet supplemented with BCAA were injected with streptozotocin (STZ) (40 mg/kg body weight) and maintained on the same diets after drug injection. Rats previously fed the BCAA enriched diet showed a partial but significant reduction in the severity of diabetes, as indicated by higher rates of body weight gain, lower food and water intake, lower excretion of glucose and higher serum insulin levels. Rats previously fed the control diet for 14 days, but transferred to the BCAA diet 3 days after STZ injection, also showed reduced severity of diabetes, as indicated by rates of body weight gain, water and food ingestion, glucose and insulin levels. The data suggest that the increased supply of BCAA is responsible, at least in part, for the previously reported beneficial effects of high-protein diets in rats with STZ-induced diabetes.