Associations among circulating branched-chain amino acids and tyrosine with muscle volume and glucose metabolism in individuals without diabetes

Abstract Objectives Amino acid metabolites, including branched-chain amino acids (BCAA) and tyrosine (Tyr), affect glucose metabolism. The effects of BCAA on insulin resistance in patients with diabetes seem to conflict with mechanisms determined in animal models and cultured cells. The aim of this study was to clarify the controversy surrounding the effects of BCAA by investigating the physiological effects of BCAA and Tyr on glucose metabolism in healthy community dwellers. Methods We investigated associations among BCAA and Tyr and metabolic parameters in 78 residents (median age, 52 y) of Mie, Japan, who did not have prediabetes, diabetes, or a body mass index >30 kg/m2. Results Muscle volume, serum BCAA, and Tyr levels were higher in men than in women (n = 32 and 46, respectively; all P