Document Type

Dissertation/Thesis

Date Created

5-5-2022

Abstract

Interleukin-6 (IL6) is a pleiotropic cytokine secreted by a wide array of cells in response to different stimuli. The immune and inflammatory functions of IL6 have been widely studied, and it is well documented that IL6 plays a critical role in immune function and the inflammatory response to pathogens and damage to the organism. Interleukin-6 has also been implicated in the pathogenesis of a wide array of diseases and high circulating levels of IL6 are used as a clinical marker for many. However, recent work has found IL6 to function as a myokine in response to exercise involving muscular contractions. Myokines are proteins and cytokines released by skeletal muscle in response to contraction that have been shown to have a beneficial effect on metabolism, muscle hypertrophy, angiogenesis, and decreasing levels of chronic inflammation. These contradictory roles of IL6 make studying the potential benefits it has in response to exercise of profound importance. However, methods used to discover how and where skeletal muscle is secreting IL6 are not definitive and further research is needed to help understand muscle derived IL6. Purpose: To study whether IL6 is expressed in skeletal muscle from rats using an ex vivo model to rule out expression by other cells during exercise. Methods: Male Sprague-Dawley rats were sacrificed and had their soleus (SOL) and extensor digitorum longus (EDL) excised. Left-sided muscles were flash frozen and stored as a sedentary control. Right sided muscles were stimulated to contract until fatigued. Results: There were no significant differences between control and exercised soleus muscles IL6 (p = 0.328) or control and exercised extensor digitorum longus muscles IL6 (p = 0.41). Conclusion: There were no significant differences between groups, but a trend was noted that exercised muscles expressed less IL6 than their sedentary counterparts. This is thought to be due to muscle secretion of IL6 from the working skeletal muscle. These findings warrant further study.

Keywords

interleukin-6; myokines; inflammation; exercise; immune system; cytokines; resistance training; cardiorespiratory fitness

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