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

The aim of this study was to test the hypothesis that IL-6 regulates exercise-induced gene responses in subcutaneous adipose tissue in mice.

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.

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.

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.