Roles of IL-6 in mastication in mice and effects of training and food hardness

Upon exercise, IL-6 produced by skeletal muscles plays a key role in glucose homeostasis in skeletal muscles during physical exercise. In this article, the role of IL-6 in masticatory activity (MA) were reviewed, especially in the unique model of gnawing behavior (GB) in mice. GB induced IL-6 mRNA expression in masseter muscles and also increased SOCS-3 mRNA expression, a downstream molecule of IL-6 signaling. Interestingly, mice fed with harder pellet food exhibited higher MA and also lower IL-6 mRNA expression in masseter muscle. IL-6-deficient mice exhibited much lower MA. In addition, in masseter muscle, the recovery. of glycogen level after GB and the Glut4 mRNA expressions were lower in IL-6-deficient mice.Taken together, IL-6 produced in masseter muscle in response to masticationplays a key role in sustaining normal masticatory activity by supporting glucose homeostasis, and that daily provision of hard food increases MA, with a decreasing dependency on IL-6 production.