A Divergent Response In Cytokines And Soluble Receptors Between Trained And Untrained Participants After Exercise

Exercise-induced changes in circulating cytokines are involved in acute and chronic exercise responses. Soluble receptors represent an additional regulatory and modulatory layer of cytokine signaling that has not been toughly investigated in the context of exercise. PURPOSE: To determine how cytokines and their soluble receptors change in the serum of both trained and untrained men after vigorous exercise. METHODS: Seven endurance-trained and five untrained men participated in this study. Anthropometrics, cardiorespiratory fitness, and cardiorespiratory compensation point (second ventilatory threshold: VT2) were assessed during the baseline testing. At the experimental session, participants performed 1 hour of cycling at a workload that corresponded with their VT2. Blood was sampled before and 3 hours post-exercise. The serum concentrations of ten cytokines and 12 soluble cytokine receptors were measured using a MAGPIX multiplexing system. RESULTS: In the untrained group, all pro-inflammatory cytokines (IL-6, TNF-α, IL-1β, CCL2, and VEGF-A) were significantly increased after exercise (average log2 fold change = +0.8180 all p < 0.05); however, anti-inflammatory IL-10 decreased significantly (log2 fold change = - 0.8813, p < 0.05). In the trained group, almost all cytokines showed no changes (average log2 fold change = 0.2883, all p > 0.05), except for IL-10, which had a significant increase after exercise (log2 fold change = 0.0892, p < 0.05). Regarding soluble cytokine receptors, untrained individuals experienced a decrease in soluble GP130, IL-6R, and VEGF-A3 (average log2 fold change = - 0.2262 all p < 0.05), alongside an increase in VEGF-A1 and IL-4R levels (average log2 fold change = +0.5737 all p < 0.05). Conversely, there was a significant increase in all soluble cytokine receptors in the trained group (average log2 fold change = 0.2422 all p < 0.05), except for VEGF-A2, IL-2R, and IL-4R, which showed no changes (average log2 fold change = 0.1203 all p > 0.05). sIL-1RII was also significantly higher in trained people at baseline (10.3 ± 0.3 .v.s 9.0 ± 0.2 ng/ml, p < 0.05). CONCLUSIONS: Our results highlight a novel anti-inflammatory adaptaion to exercise through elevated soluble receptors that reduce cytokine bioavailability and decreased secretion of inflammatory cytokines themselves.