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M.T. Lane, T.J. Herda, A.C. Fry, M.A. Cooper, M.J. Andre, P.M. Gallagher, J.L. Seeman. University of Kansas, Applied Physiology Laboratory, Lawrence, KS Email: mlane@ku.edu

Leucine ingestion, via circulating insulin, reportedly activates skeletal muscle activation of the mTOR pathway, contributing to a hypertrophy response. There is limited evidence of this occurring for humans in response to heavy resistance exercise. PURPOSE: To compare the post-resistance exercise effects of leucine and whey protein supplementation on muscle mTOR pathway phosphorylation and the endocrine profile. METHODS: Twenty recreationally active males (X±S D; Age = 27.8±2.8 yrs, Hgt = 1.78±0.07 m, Wgt = 81.3±11.0 kg) served as subjects. On visit 1, subjects gave a muscle biopsy of the vastus lateralis m. (baseline) and were tested for 10 repetition maximum (RM) on leg press and leg extension machines to determine baselines for strength and skeletal muscle Akt(S473), mTOR(S2448) 4E-BP1(Thr70), P70S6K(Thr 421), and S6(5G10) phosphorylation. Prior to biopsy, serum samples were collected and subsequently analyzed via ELISA for cortisol, glucose and insulin. On visit 2, subjects were randomized to ingest either leucine+whey protein (10g+10g; supplement) or a non-caloric placebo. Visit 3 was 3-5 days after the baseline session in a double-blind crossover design where subjects were given either the placebo or supplement with the order being randomized. During this visit, 5 sets of 10 RM were performed on the leg press and leg extension. Immediately after completion of each training session, subjects ingested the placebo or the supplement, followed by a serum sample 30 min and muscle biopsy 45 min later. The procedure was repeated 7-9 days later utilizing the opposite drink. SDS-PAGE and western blots were used to quantify total and phosphorylated signaling proteins. A one way repeated measures ANOVA was used to determine the differences between each group (α < 0.05; * > baseline; + > placebo). RESULTS: Phosphorylation of each signaling protein for both conditions were normalized to baseline for each subject (X±S D baseline = 1.00±0.0). Relative phosphorylations were as follows; Akt, supplement = 1.33±0.34*+, placebo = 1.12±0.32*; p70s6k, supplement = 24.69±24.29*, and placebo = 15.66±13.67*; S6, supplement = 135.17±121.16*+, and placebo = 66.86±67.45*. No differences were reported for mTOR or 4E-BP1. Insulin (pmol·L-1) was 15.4±17.3, 85.6±69.9*+, and 22.5±29.2 for baseline, supplement, and placebo, respectively. No differences were observed for cortisol or glucose. CONCLUSION: Supplementation of leucine plus whey protein directly after heavy resistance exercise increases the anabolic signaling in the muscle more than placebo ingestion.

Supported by a grant from GNC, Inc.

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