INS and obesity due to melanocortin 4 receptor deficiency: To evaluate the role of Msr1 on obesity-associated impaired glucose metabolism and insulin resistance, 8-week-old male Msr1KO and Msr1HET mice were fed HFD to induce obesity, then assessed by glucose (GTT) and insulin tolerance tests (ITT) at 14 and 15 weeks HFD, respectively.