ANGPTL8 and obesity due to melanocortin 4 receptor deficiency: For example, they did not demonstrate the correlation between circulating levels of betatrophin and the increase in islet mass; most of the experiments are in an artificial model of insulin-resistance, based on the use of an insulin receptor antagonist, and not in the traditional models of obesity and or insulin-resistance, mainly based on a diet-induced obesity (9, 10); and, the increase in mRNA of betatrophin is much higher in pregnancy than in ob/ob and db/db mice, but the increase in islet mass is usually higher in these genetic models compared to pregnancy (1, 11).