INS and obesity due to melanocortin 4 receptor deficiency: Following the feeding on high-fat diet for 10 weeks, mice became obese, and exhibited significant increases in the body weight, plasma glucose level, plasma insulin concentration, insulin resistance (HOMA-IR: control vs. DIO = 0.70 vs. 2.0), mesenteric adipose tissue weight, epididymal adipose tissue weight, content of hepatic triglyceride and the content of hepatic total-cholesterol, indicating the development of diet-induced obesity in mice (i.e., DIO mice), as compared to the control mice fed on normal diet.