Amino Acid Supplementation Increases Lean Body Mass, Basal Muscle Protein Synthesis, and IGF-1 Expression in Older Women

Amino Acid Supplementation Increases Lean Body Mass, Basal Muscle Protein Synthesis, and IGF-1 Expression in Older Women.

Dillon EL, Sheffield-Moore M, Paddon-Jones D, Gilkison C, Sanford AP, Casperson SL, Jiang J, Chinkes DL, Urban RJ.

Department of Internal Medicine (M.S.-M., D.P.J., C.G., S.L.C., J.J., E.L.D., R.J.U.), Department of Surgery (A.P.S., D.L.C.), Department of Physical Therapy and Rehabilitation Sciences (D.P.J.), University of Texas Medical Branch at Galveston, Texas 77555-1060.

Context: Inadequate dietary protein intake has been implicated in sarcopenia. Objective and Design: The objective of this study was to determine 1) if chronic essential amino acid (EAA) supplementation improves post-absorptive muscle protein fractional synthesis rate (FSR), lean body mass (LBM) and 1 repetition maximum (1RM) muscle strength, and androgen receptor (AR) and IGF-1 muscle protein expression, and 2) if the acute anabolic response to EAA ingestion is preserved following a 3 month supplementation period. Using a randomized, double-blinded, placebo controlled design, older women (68 +/- 2 yr) were assigned to receive either placebo (Placebo, n=7), or 15g EAA/day (SUP, n=7) for three months. Metabolic outcomes were assessed in association with stable isotope studies conducted at 0 and 3 months. Setting: The study was performed at the UTMB General Clinical Research Center (GCRC). Results: Ingestion of 7.5g EAA acutely stimulated FSR in both groups at 0 months (P<0.05). Basal FSR at three months was increased in SUP only. The magnitude of the acute response to EAA was unaltered after 3 months in SUP. LBM increased in SUP only (P<0.05). 1RM strength remained unchanged in both groups. Basal IGF-1 protein expression increased in SUP after 3 months (P=0.05), with no changes in AR or total and phosphorylated Akt, mTOR, S6K1 and 4E-BP1. Conclusion: EAA improved lean body mass and basal muscle protein synthesis in older individuals. The acute anabolic response to EAA supplementation is maintained over time and can improve lean body mass, possibly offsetting the debilitating effects of sarcopenia.