Leucine supplementation with respect to muscle mass in human

Abstract

The branched chain amino acids (AACR/BCAA): leucine, isoleucine and valine are essential amino acids in the human diet. Lately these amino acids have gaining some attention due their physiological properties, especially leucine. The objective of this literature review is to aim for the highest number of studies and other reviews with humans, approaching the effects of leucine supplementation singly or not in anabolic processes of synthesis, muscle protein degradation and prevention of sarcopenia. Eight studies were evaluated, all of them with humans, with or without physical activity and with or without food. Among the studies reviewed, it was found that 7 studies associate the beneficial effects of leucine supplementation and only one mentions the endurance exercises had no beneficial results with the use of leucine with respect to the muscle synthesis associated with exercise. Some studies report that leucine promotes muscle protein synthesis by protein kinase mammalian target of rapamycin (mTOR) that stimulates the three key proteins: 70 kDa ribosomal protein S6 kinase (p70S6K), eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), and eukaryotic initiation factor 4G (elF4G). It also verifies that leucine acts by stimulating the translation initiation stage of messenger RNA into protein by mechanisms dependent and independent of insulin and mTOR. Although 90% of the articles have a positive standpoint regarding leucine supplementation and muscle protein synthesis further studies and research that addresses more training are needed especially endurance.