MC4R and type 2 diabetes mellitus: Moreover, an intraperitoneal injection of a 5HT2CR agonist blocked an increase in blood glucose concentrations after intraperitoneal glucose injection in male mice with type 2 diabetes, and this effect of the 5HT2CR agonist on glucose downregulation requires the activation of downstream MC4R signaling because the effect of the 5HT2CR agonist was not detected in MC4R gene KO mice60.