Skeletal muscle interleukin-6 regulates metabolic factors in i during and exercise training

To investigate the role of skeletal muscle (SkM) interleukin (IL)-6 in the regulation of adipose tissue metabolism. Muscle-specific IL-6 knockout (IL-6 MKO) and IL-6 loxP/loxP (Floxed) mice were subjected to standard rodent diet (Chow), high-fat diet (HFD), or HFD in combination with exercise training (HFD ExTr) for 16 weeks. Total fat mass increased (P < 0.05) in both genotypes with HFD. However, HFD IL-6 MKO mice had lower (P < 0.05) inguinal adipose tissue (iWAT) mass than HFD Floxed mice. Accordingly, iWAT glucose transporter 4 (GLUT4) protein content, 5'AMP activated protein kinase (AMPK) Thr172 phosphorylation, and fatty acid synthase (FAS) mRNA content were lower (P < 0.05) in IL-6 MKO than Floxed mice on Chow. In addition, iWAT AMPK Thr172 and hormone-sensitive lipase (HSL) Ser565 phosphorylation as well as perilipin protein content was higher (P < 0.05) in HFD IL-6 MKO than HFD Floxed mice, and pyruvate dehydrogenase E1α (PDH-E1α) protein content was higher (P < 0.05) in HFD ExTr IL-6 MKO than HFD ExTr Floxed mice. These findings indicate that SkM IL-6 affects iWAT mass through regulation of glucose uptake capacity as well as lipogenic and lipolytic factors