Skeletal muscle produces a range of myokines, which have various effects throughout the body. Two new studies published in Nature Metabolism have identified a myokine that they have termed feimin, and characterized its effects on glucose homeostasis and exercise performance.

Using mice with whole-body knockout of the gene encoding feimin or one of various organ-specific knockout models (for example, intestine or muscle), the authors demonstrated that feimin was secreted from the skeletal muscle in response to feeding. Furthermore, mice with skeletal muscle knockout of the gene encoding feimin had increased blood levels of glucose and decreased hepatic and muscle glycogen storage following feeding, compared with wild-type mice. This finding suggests that feimin has a role in regulating glucose homeostasis. “In contrast to the action of insulin, our findings demonstrate that feimin signalling operates through a distinct mechanism; it exerts a slower, weaker, yet more sustained effect on AKT activation and glucose regulation,” explains Wang. “This suggests that insulin functions as a coarse adjustment mechanism, while feimin finetunes glucose homeostasis.”