Abstract
Amino acids are components of proteins that also exist free-form in the body; their functions can be divided into (1) nutritional, (2) sensory, and (3) biological regulatory roles. The skeletal muscle, which is the largest organ in the human body, representing ~40% of the total body weight, plays important roles in exercise, energy expenditure, and glucose/amino acid usage—processes that are modulated by various amino acids and their metabolites. In this review, we address the metabolism and function of amino acids in the skeletal muscle. The expression of PGC1α, a transcriptional coactivator, is increased in the skeletal muscle during exercise. PGC1α activates branched-chain amino acid (BCAA) metabolism and is used for energy in the tricarboxylic acid (TCA) cycle. Leucine, a BCAA, and its metabolite, β-hydroxy-β-methylbutyrate (HMB), both activate mammalian target of rapamycin complex 1 (mTORC1) and increase protein synthesis, but the mechanisms of activation appear to be different. The metabolite of valine (another BCAA), β-aminoisobutyric acid (BAIBA), is increased by exercise, is secreted by the skeletal muscle, and acts on other tissues, such as white adipose tissue, to increase energy expenditure. In addition, several amino acid-related molecules reportedly activate skeletal muscle function. Oral 5-aminolevulinic acid (ALA) supplementation can protect against mild hyperglycemia and help prevent type 2 diabetes. β-alanine levels are decreased in the skeletal muscles of aged mice. β-alanine supplementation increased the physical performance and improved the executive function induced by endurance exercise in middle-aged individuals. Further studies focusing on the effects of amino acids and their metabolites on skeletal muscle function will provide data essential for the production of food supplements for older adults, athletes, and individuals with metabolic diseases.
Highlights
Amino Acids and HealthAmino acids are compounds that contain an amino group (-NH2) and a carboxyl group (-COOH)and are components of proteins and materials for various bioactive molecules
The branched-chain amino acids (BCAAs; valine, leucine, and isoleucine) are thought to be metabolized and utilized as energy sources in the skeletal muscle [13], as the expression of BCAA aminotransferase (BCAT2), an enzyme that catabolizes the first step of BCAA degradation, is high in the skeletal muscle and low in the liver
Skeletal muscle proliferator-activated receptor-gamma coactivator 1α (PGC1α) and circadian transcription factors are likely to be important for muscle and systemic amino acid metabolism
Summary
Amino acids are compounds that contain an amino group (-NH2) and a carboxyl group (-COOH). Other food components, can be divided into those with nutritional, sensory, and biological regulatory functions. Their nutritional function means that eating a sufficient amount of good-quality protein. Amino acids have biological regulatory functions, for example, leucine increases the anabolism of muscle proteins [4,5], arginine has a vasodilation action and enhances immunity [6], and gamma aminobutyric acid (GABA) regulates blood pressure [7,8]. We discuss the roles of amino acids in the skeletal muscle
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
