ABSTRACT
This chapter highlights the role of branched-chain amino acids (BCAA) in insulin resistance and type 2 diabetes, conditions of which sarcopenia may be a major contributing risk factor. Infusion of BCAA in humans elevated the phosphorylation and activation of p70S6 kinase and 4E binding protein 1 in skeletal muscle. In addition to the potential for BCAA to benefit metabolic health through hypertrophic or insulinotropic pathways, there is emerging evidence that BCAA may also influence skeletal muscle metabolism. Insulinotropic effects of leucine and/or BCAA may help to improve net muscle protein balance by increasing muscle protein synthesis, decreasing muscle protein breakdown, or both. The insulinotropic effects of BCAA may exert further influence on positive muscle protein balance by reducing muscle protein breakdown. A loss of skeletal muscle mass, for example, reduces overall glucose disposal capacity, which can result in elevated circulating glucose concentrations, unrelated to the level of insulin sensitivity.
