L-Leucine supplemented whey protein. Dose–response effect on heart mTOR activation of sedentary and trained rats

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The aim of the study was to investigate the effect of leucine supplementation combined with exercise and whey protein in cardiac mTOR anabolic pathway. Ninety-six weanling male Wistar rats were divided into eight groups and fed diets containing either casein or WP plus increasing levels (0, 3, 4.5 and 6% of diet) of l-leucine for 30days. A parallel set of eight groups was exercised for comparison. Serum aspartate amino transferase, alanine aminotransferase, creatine kinase, lactate dehydrogenase and branched chain amino acids were determined by standard methods, and mammalian target of rapamycin (mTOR) and p70S6K by the Western blot analysis. Chronic l-leucine supplementation was capable of increasing both mTOR and p70S6K phosphorylation in the heart in a dose-dependent fashion, independent of the type of dietary protein in both groups, sedentary and exercised, but the exercise potentialized the activation of the anabolic pathway. The content of protein in heart increase with l-leucine supplementation and the heart mass relativized by body mass did not change. In conclusion, the combination of l-leucine and milk proteins (casein or whey protein) has the potential to increase the mTOR pathway in the cardiac muscle without increasing the heart mass. The novelty of this study is to show the effectiveness of a blend of leucine and whey protein as a viable alternative to maximize the activation of the anabolic pathway of cardiac muscle and that the exercise can improve this process.