Plasma Concentration of Branched Chain Amino Acids are Not Related to Improvements in Insulin Sensitivity after 12 W of Intensive Exercise in Sedentary Dysglycemic and Normoglycemic Men

Plasma concentration of branched-chain amino acids (BCAAs) is associated with insulin resistance. However, it is unknown if the insulin sensitizing effect of exercise can be explained by BCAAs. In agreement with previous reports, we found that plasma BCAAs concentration was higher, and transcription of BCAA catabolic enzymes in skeletal muscle (SkM) and subcutaneous white adipose tissue (ScWAT) was lower in dysglycemic (DG) than normoglycemic (NG) men. Twelve weeks of intensive exercise enhanced insulin sensitivity by ~40% in both groups, as quantified by euglycemic hyperinsulinemic clamp, but no changes were observed in plasma BCAAs concentrations. However, pathway analyses of mRNA sequencing data predicted enhanced BCAA catabolism in both SkM and ScWAT, which mediated the effect of exercise on insulin sensitivity. Our results suggest that the insulin sensitizing effect of exercise cannot be explained by plasma BCAAs, but imply that tissue catabolism of BCAAs may be linked to regulation of insulin sensitivity.