Effects of branched chain amino acids infusion on whole‐body plasma glucose disposal: a pilot study

Abstract

The physiological importance of the inhibition of muscle glucose uptake simultaneously with the stimulation of muscle protein synthesis, when the plasma concentrations of both glucose and amino acids are elevated, as in the fed state, is not clear. We tested the hypothesis that a branched chain amino acids (BCAA) infusion, known to increase protein accumulation, impairs insulin‐stimulated whole‐body glucose disposal. Two groups of young, healthy males and females (n = 5/group) were studied in the postabsorptive state (3 hours) and during a 3 hour euglycemic, hyperinsulinemic (40 mIU/m‐2/min) clamp. The control group (BAS) was infused with BCAA sufficient to maintain plasma BCAA at the basal concentrations during the clamp, while the other group (HI) received a six hour BCAA infusion (1.66 umol/kg/min) to increase BCAA 4‐fold. Subjects in both groups were insulin sensitive as determined by the HOMA index. Glucose disposal rate during the clamp, as determined by 6,6‐d2 glucose infusion and adjusted to the prevailing plasma insulin concentrations, was lower in the HI group (0.53 umol/kg/min +/− 0.05 vs. 0.93 umol/kg/min +/− 0.11; HI vs. BAS; p=0.005). We conclude that increased concentrations of plasma BCAA decrease whole‐body glucose disposal in healthy humans. This protocol will allow us to study the role of plasma amino acids in modulating glucose uptake in skeletal muscle in humans.