The Insulin-Facilitated Increase of Muscle Protein Synthesis after Resistance Exercise Involves a MAP-Kinase Pathway : Medicine & Science in Sports & Exercise

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Annual Meeting Abstracts: D-49 – Free Communication/Slide: Skeletal Muscle Genomics/Gene Expression II

The Insulin-Facilitated Increase of Muscle Protein Synthesis after Resistance Exercise Involves a MAP-Kinase Pathway

Fluckey, James D.1; Knox, Micheal1; Smith, Latasha1; Dupont-Versteegden, Esther E.1; Gaddy, Dana1; Tesch, Per A. FACSM2; Peterson, Charlotte A.1

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Medicine & Science in Sports & Exercise 36(5):p S183-S184, May 2004.
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Recent studies have implicated the mTOR signaling pathway as a primary component for muscle growth in mammals. PURPOSE: To examine signaling pathways for muscle protein synthesis in rats after resistance exercise. METHODS: Twenty-eight, 6-month old, male Sprague-Dawley rats were assigned to either resistance exercise or control groups (n = 14 each). Resistance exercise was accomplished in operantly conditioned animals using a specially designed flywheel apparatus. Rats performed two sessions of resistance exercise, separated by 48 h, each consisting of 2 sets of 25 repetitions. Sixteen hours after the second session, animals were sacrificed, and soleus muscles were examined for rates of protein synthesis with and without insulin and/or rapamycin (mTOR inhibitor) and/or (PD)098059 (MAPk-kinase inhibitor). RESULTS: Rates of synthesis were higher (p<0.05) with insulin after exercise in comparison to without insulin, or in control muscles, regardless of insulin. Rapamycin lowered (p<0.05) rates of synthesis in controls, with or without insulin, and after exercise without insulin. However, insulin was able to overcome the inhibition of rapamycin after exercise (p<0.05). PD had no effect (p>0.05) on protein synthesis in control rats, but was lower (p<0.05) than control after resistance exercise and was not rescued by insulin. CONCLUSION: Together, these results suggest that the insulin-facilitated increase of muscle protein synthesis after resistance exercise may operate through MAP-kinase signaling pathways. Supported by NIH/NIAMSD grant R01 AR47577.

©2004The American College of Sports Medicine