IL-6 regulates exercise and training-induced adaptations in subcutaneous adipose tissue in mice

Aim: The aim of this study was to test the hypothesis that IL‐6 regulates exercise‐induced gene responses in subcutaneous adipose tissue in mice. Methods: Four‐month‐old male IL‐6 whole body knockout (KO) mice and C57B wild‐type (WT) mice performed 1 h of treadmill exercise, where subcutaneous adipose tissue (AT) was removed either immediately after, 4 h or 10 h after exercise as well as from mice not running acutely. Moreover, AT was sampled at resting conditions after 5 weeks of exercise training. Results: AT leptin mRNA decreased immediately after a single running exercise bout in both genotypes and returned to baseline within 10 h of recovery in IL‐6 KO mice, but not WT mice. Leptin mRNA content decreased in WT and increased in IL‐6 KO mice with training, but without significant alterations in leptin protein. Acute exercise induced a decrease in the AT TNFα mRNA content in WT, but not in IL‐6‐KO mice, while training lowered resting levels of TNFα mRNA in both genotypes. In addition, an exercise‐induced decline in AT PPARγ mRNA content was absent in IL‐6 KO mice and in line training increased PPARγ mRNA only in IL‐6 KO mice. Conclusion: The present findings indicate a role of IL‐6 in regulating exercise‐ and training‐induced leptin and PPARγ expression in adipose tissue. In addition, while IL‐6 is required for TNF‐α mRNA reduction in response to acute exercise, IL‐6 does not appear to be mandatory for anti‐inflammatory effects of exercise training in adipose tissue.