Effect of exercise, training, and glycogen availability on IL-6 receptor expression in human skeletal muscle

The cytokine interleukin-6 (IL-6) exerts it actions via the IL-6 receptor (IL-6R) in conjunction with the ubiquitously expressed gp130 receptor. IL-6 is tightly regulated in response to exercise, being affected by factors such as exercise intensity and duration, as well as energy availability. Although the IL-6 response to exercise has been extensively studied, little is known about the regulation of the IL-6R response. In the present study, we aimed to investigate the effect of exercise, training, and glycogen availability, factors known to affect IL-6, on the regulation of gene expression of the IL-6R in human skeletal muscle. Human subjects performed either 10 wk of training with an acute exercise bout before and after the training period, or a low-glycogen vs. normal-glycogen acute exercise trial. The IL-6R mRNA response was evaluated in both trials. In response to acute exercise, an increase in IL-6R mRNA levels was observed. Neither training nor intramuscular glycogen levels had an effect on the IL-6R mRNA response to exercise. However, after 10 wk of training, the skeletal muscle expressed a higher mRNA level of IL-6R compared with before training. The present study demonstrated that the IL-6R gene expression levels in skeletal muscle are increased in response to acute exercise, a response that is very well conserved, being affected by neither training status nor intramuscular glycogen levels, as opposed to IL-6. However, after the training period, IL-6R mRNA production was increased in skeletal muscle, suggesting a sensitization of skeletal muscle to IL-6 at rest.