Muscle-derived interleukin-6: possible biological effects

Interleukin-6 (IL-6) is produced locally in working skeletal muscle and can account for the increase in plasma IL-6 during exercise. The production of IL-6 during exercise is related to the intensity and duration of the exerc ise, and low muscle glycogen content stimulates the production. Muscle-deri ved IL-6 is released into the circulation during exercise in high amounts a nd is likely to work in a hormone-like fashion, exerting an effect on the l iver and adipose tissue, thereby contributing to the maintenance of glucose homeostasis during exercise and mediating exercise-induced lipolysis. Musc le-derived IL-6 may also work to inhibit the effects of pro-inflammatory cy tokines such as tumour necrosis factor alpha. The latter cytokine is produc ed by adipose tissue and inflammatory cells and appears to play a pathogene tic role in insulin resistance and atherogenesis.