A variety of diseases and conditions result in muscle atrophy. Muscle atrophy causes a decrease of mobility, increased susceptibility to injuries and reduced Quality of Life (QOL). The various types of muscle atrophy are due to increased protein breakdown, decreased protein synthesis or both. Muscle mass is maintained by the balance between muscle protein synthesis and degradation.
To prevent muscle atrophy, several types of intervention have been tried. Branched-chain amino acid (BCAA) administration is one of the interventions because BCAAs have been reported to stimulate protein synthesis and attenuate protein degradation in muscles. BCAAs are components of proteins that also function as signals that regulate cellular signaling pathways activated in the protein synthesis and protein degradation. In this review, the regulatory functions of the BCAAs in cellular signaling are discussed first, and the effects of the BCAAs on several types of muscle atrophy in human and animals are described thereafter.