Supplemental file for Training alters cytokine and soluble receptor responses

Endurance training contributes to immune system changes that help manage exercise-induced stress and promote an anti-inflammatory effect. However, the specific mechanisms underlying these adaptations are still being explored. Cytokines play a key role in both acute and chronic exercise responses through interactions with their receptors, which are present in both membrane-bound and soluble forms. Yet, the impact of exercise on cytokines and soluble receptors in parallel remains understudied. Therefore, the purpose of this study was to assess how cytokines and their soluble receptors change in serum after vigorous exercise in endurance-trained and untrained men. Following 1-hour of cycling at their respiratory compensation point, untrained men (n=5) exhibited a significant increase in pro-inflammatory cytokines, including IL-6, TNF-α, IL-1β, CCL2, and VEGFA. In contrast, anti-inflammatory cytokines such as IL-10 and IL-1Ra were reduced. These effects were not observed in the trained group (n=7). Instead, pro-inflammatory cytokine levels remained close to baseline, while the levels of anti-inflammatory cytokines IL-10 and IL-1Ra increased. In the trained group, these cytokine changes were accompanied by a marked increase in the expression of soluble receptors known to inhibit cytokine-mediated signaling, such as sIL-1RII, sGP130, sTNFRI, sTNFRII, sVEGFR1, and sVEGFR2, indicating reduced cytokine bioavailability. However, in the untrained group, the expression of these soluble receptors either remained unchanged or decreased, suggesting greater cytokine bioavailability. Together these findings highlight a novel potential anti-inflammatory adaptation such that trained men present a blunted inflammatory response by both reduced inflammatory cytokines and increased soluble receptors post-exercise compared to untrained men.