1 The role of gut microbiota on regulation of growth and metabolism by branched-chain amino acids

Abstract Branched-chain amino acids (BCAA) including leucine, isoleucine and valine are essential amino acids, which are involved in energy homeostasis and regulation of many physiological paradigms including growth. The BCAA serve not only as an essential substrate in the synthesis of body proteins, but also have an important role in regulation of protein turnover. The effects of BCAA on growth and metabolism are likely mediated through different pathways including shifts in metabolic profile in peripheral organs, oxidative capacity of muscle, gut development, and protein metabolism in muscle. Although it has not been appropriately studied or fully dissected, the impact of BCAA on growth and metabolism is thought to lie in the alteration of gut microbiota by BCAA. It has long been believed that gut microbiota, more specifically, the activity of the microbiome and its metabolic products, directly influence a variety of aspects in metazoan physiology. For example, deregulation of bacterial community structure has been linked with host longevity and stress resistance, the pathogenesis of several disorders, regulation of appetite. Multiple studies have demonstrated that modulation of dietary BCAA levels could elicit clear shifts in gut microbial community structure. As part of “Physiology Symposium: The Microbiome and the Host: Functional Role in Metabolism, Immunity, and Gut-Brain Axis”, the possible involvement of intestinal microbiota on regulatory roles of BCAA on growth and metabolism will be discussed.