High-protein diet with excess leucine prevents inactivity-induced insulin resistance in women

Abstract

Background and aimsMuscle inactivity leads to muscle atrophy and insulin resistance. The branched-chain amino acid (BCAA) leucine interacts with the insulin signaling pathway to modulate glucose metabolism. We have tested the ability of a high-protein BCAA-enriched diet to prevent insulin resistance during long-term bed rest (BR). MethodsStable isotopes were infused to determine glucose and protein kinetics in the postabsorptive state and during a hyperinsulinemic-euglycemic clamp in combination with amino acid infusion (Clamp+AA) before and at the end of 60 days of BR in two groups of healthy, young women receiving eucaloric diets containing 1 g of protein/kg per day (n=8) or 1.45 g of protein/kg per day enriched with 0.15 g/kg per day of BCAAs (leucine/valine/isoleucine=2/1/1) (n=8). Body composition was determined by Dual X-ray Absorptiometry. ResultsBR decreased lean body mass by 7.6±0.3% and 7.2±0.8% in the groups receiving conventional or high protein-BCAA diets, respectively. Fat mass was unchanged in both groups.At the end of BR, percent changes of insulin-mediated glucose uptake significantly (p=0.01) decreased in the conventional diet group from 155±23% to 84±10% while did not change significantly in the high protein-BCAA diet group from 126±20% to 141±27% (BR effect, p=0.32; BR/diet interaction, p=0.01; Repeated Measures ANCOVA). In contrast, there were no BR/diet interactions on proteolysis and protein synthesis Clamp+AA changes in the conventional diet and the high protein-BCAA diet groups. ConclusionA high protein-BCAA enriched diet prevented inactivity-induced insulin resistance in healthy women.