Exercise Training, Plasma Levels of Branched-Chain Amino Acids, and Insulin Resistance in Metabolic Diseases: A Narrative Review

Branched-chain amino acids (BCAAs), including valine, leucine, and isoleucine, are essential amino acids that modulate glucose homeostasis, neurotransmission, immune responses, and mitochondrial biogenesis, and thereby, contributing a role in the development of metabolic disorders such as obesity and diabetes. In this review, the relationship between the catabolism of BCAAs and insulin resistance (IR), as well as the effect of exercise training on this pathway, was discussed. Epidemiological studies and review articles published between 1964 and 2023 were collected from PubMed, Google Scholar, and Web of Science databases. Also, to reach Persian language articles, Iranian scientific databases, including the Scientific Information Database (SID), Iran’s Information and Scientific Documents Research Institute (Irandoc), and Iran’s publications database (Magiran), were searched to find relevant papers published between 2001 and 2023. The results of various studies show that plasma BCAAs are either upregulated or downregulated by the first two enzymes in their catabolic pathway, i.e., branched-chain aminotransferase (BCAT) and branched-chain alpha-acid dehydrogenase (BCKD). Therefore, the disruption of the enzymatic complexes that limit the catabolic rate of BCAAs lowers their catabolism and increases the plasma levels of BCAAs, greatly predisposing to the development of diabetes. Exercise training can reduce the accumulation of BCAAs catabolic mediators and reduce or even prevent IR. Improving BCAAs’ catabolism through exercise training and diet control can lead to the recovery or prevention of metabolic diseases such as obesity and diabetes.