Effects of Eccentric and Concentric Emphasized Resistance Exercise on IL-15 Serum Levels and Its Relation to Inflammatory Markers in Athletes and Non-Athletes

BACKGROUND Cytokines play an important role in modulating the muscle's metabolic and immunological responses to exercise. OBJECTIVES In the present study, we investigated changes in the serum levels of Interleukin (IL)-15 as well as tumor necrosis factor (TNF)-α and high sensitivity C-reactive protein (hs-CRP), as markers of inflammation, in athlete and non-athlete young men following eccentric (ECC) and concentric (CON) emphasized resistance exercise (RE). PATIENTS AND METHODS This study recruited 28 young males, 14 athletes and 14 non-athletes. Subjects completed two bouts of ECC and CON emphasized RE five days apart. Each bout included seven exercises that emphasized all major muscle groups with weight loads of 70% - 80% of one repetition maximum (1RM) for CON RE and 90% - 100% of 1RM for ECC RE. We analyzed subjects' blood samples before and immediately after each bout of exercise to determine cytokine and hs-CRP serum levels according to enzyme-linked immunosorbent assay. RESULTS Statistical analysis showed a significant difference between IL-15 serum levels before and after ECC and CON RE in non-athletes (P = 0.03). In athletes, IL-15 serum level only increased after ECC RE (P = 0.01), which was noted to be the highest degree of change in IL-15 levels in all subjects. For athletes, the hs-CRP levels significantly decreased (P < 0.05). The serum levels of both TNF-α and hs-CRP were also significantly down-regulated after ECC RE in non-athletes. CONCLUSIONS These results indicated that fitness level and RE could modulate circulating levels of IL-15 and suggest the potential anti-inflammatory effects of IL-15 during RE.