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THE EFFECT OF LEUCINE SUPPLEMENTATION ON INFLAMMATION DURING SKELETAL MUSCLE REGENERATION

Abstract

Alyssa M. Papineau, Lemuel A. Brown, and Tyrone A. Washington, Exercise Muscle Biology Laboratory and Human Performance Lab, University of Arkansas, Fayetteville, AR

Skeletal muscle regeneration requires the coordinated regulation of inflammation, extracellular matrix remodeling, and myofiber growth. Disruptions to any of these processes can alter the skeletal muscle regenerative response. Leucine supplementation has been shown to increase protein translation and muscle protein synthesis by activating the mammalian target of rapamycin signaling pathway. Leucine supplementation appears to modulate inflammatory status and protein turnover of muscle cells by altering protein synthesis and protein degradation pathways. However, it is not known how leucine supplementation modifies the inflammatory response during skeletal muscle regeneration. PURPOSE: To examine the effects of leucine supplementation on inflammatory markers during skeletal muscle regeneration. METHODS: Twenty female C57/BL6 mice (12 weeks) were randomly assigned to one of four groups: uninjured, uninjured + leucine, injured, injured + leucine. To induce damage, bupivacaine was injected into the tibialis anterior (TA) of the injured group. In the uninjured groups, phosphate buffered saline was injected into TA. Three days post-injection injection, the TA was extracted and quantitative PCR and western blot analysis was performed to determine gene expression and protein expression, respectively. RESULTS: In the no leucine group, there was a 9% decrease in TA mass to tibia length (2.2 ± 0.1 mg/mm vs. 2.0 ± 0.1 mg/mm, p < 0.05) whereas, in the leucine group there was a 19% decrease in TA mass to tibia length (2.1 ± 0.1 mg/mm vs. 1.7 ± 0.0 mg/mm, p < 0.05) 3 days post-bupivacaine injection. In the no leucine group, TNF-α gene expression was increased 2-fold (p < 0.05) 3 days post-bupivacaine injection. However, in the leucine group, TNF-α gene expression was not altered at 3 days post-bupivacaine injection. In the no leucine group, p-STAT protein expression was not affected 3 days post-bupivacaine injection. However, in the leucine group, p-STAT protein expression was decreased 48% (p < 0.05) 3 days post-bupivacaine injection. CONCLUSION: Leucine supplementation decreased markers of inflammation at the onset of skeletal muscle regeneration and could lead to an improved skeletal muscle regenerative response.

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