%0 Journal Article
%T Metabolic and Physiological Roles of Branched-Chain Amino Acids
%A Md. Monirujjaman
%A Afroza Ferdouse
%J Advances in Molecular Biology
%D 2014
%R 10.1155/2014/364976
%X Branch chain amino acids (BCAAs) have unique properties with diverse physiological and metabolic roles. They have functions other than simple nutrition. Different diseases including metabolic disease lead to protein loss, especially muscle protein. Supplementation of BCAAs promotes protein synthesis and reduces break down, as well as improving disease conditions. They are important regulators of mTOR signaling pathway and regulate protein synthesis as well as protein turnover. BCAAs facilitate glucose uptake by liver and SK muscle and also enhance glycogen synthesis. Oxidation of BCAAs seems to be beneficial for metabolic health as their catabolism increases fatty acid oxidation and reduces risk of obesity. BCAAs are also important in immunity, brain function, and other physiological aspects of well-being. All three BCAAs are absolutely required for lymphocyte growth and proliferation. They are also important for proper immune cell function. BCAAs may influence brain protein synthesis, and production of energy and may influence synthesis of different neurotransmitters. BCAAs can be used therapeutically and future studies may be directed to investigating the diverse effects of BCAAs in different tissues and their signaling pathways. 1. Introduction Amino acids (AAs) are biologically important compounds containing carboxylic and amine moiety as functional groups and are the building blocks of protein. They play important metabolic and physiological roles in all living organisms. Although more than 300 AAs have been found, only 20 AAs are known as standard AA and contain a specific side-chain specific to each AA [1]. Three branch chain amino acids (BCAAs), including isoleucine, leucine, and valine, have unique properties with diverse physiological and metabolic roles. BCAAs are primarily oxidized in the peripheral tissue, in particular in skeletal (SK) muscle, whereas the other AA catabolizes in the liver. BCAAs may regulate rate of protein synthesis and degradation in SK muscle and other organs. BCAAs and aromatic AA bind to the same carrier proteins to be transported to brain. They compete with each other and their ratio in brain may influence the synthesis of specific neurotransmitters, and that may influence the behavior of an organism [2, 3]. BCAAs have glycogen sparing action and they have an opposite relation with tryptophan levels of brain, which is the precursor of serotonin. Serotonin is a mediator of central fatigue. Thus supplementation of BCAAs may prevent fatigue during extensive exercise, and diet enriched with BCAAs may improve muscle
%U http://www.hindawi.com/journals/amb/2014/364976/