IL18 and obesity due to melanocortin 4 receptor deficiency: Altogether the present findings demonstrate that ablation of Il18 blocks the emergence of inducible brown adipocytes and its associated thermogenesis, and this effect could contribute to the metabolic disturbances in HFD-fed Il18-KO mice, previously described2, 16, 17 and confirmed herein (i.e extreme susceptibility to dietary obesity, increased basal glucose levels and hepatic steatosis).