Interactions Among Leucine, Isoleucine, and Valine with Special Reference to the Branched-Chain Amino Acid Antagonism

The branched-chain amino acids (BCAA) - leucine, isoleucine, and valine - are required preformed in the diet by mammals. Research on the BCAA antagonism has continued to give insights into how leucine exerts its unique effects. An understanding of the interrelationships among the BCAA has become critical as the use of leucine-enriched solutions in the treatment of diseases such as renal failure, hepatic encephalopathy, sepsis, and trauma has increased. Evidence of a role for leucine in stimulating protein synthesis and suppressing protein degradation in vitro has come from studies with isolated rat diaphragm and perfused rat hindquarter, heart, and liver. If increased net protein synthesis is assumed to be the mechanism responsible for the leucine-induced lowering of free amino acid pools, a number of problems surface. Stimulation specifically of BCAA oxidation by consumption of excesses of leucine could account for depletion of isoleucine and valine pools.