INS and obesity due to melanocortin 4 receptor deficiency: The results suggest that hyperphagia and obesity, disorders of the primarily central origin, observed in IRS2-KO mice [28] and neuron-specific IRS2-KO mice [29], could be, at least partly, due to impaired ability of NG neuron to sense insulin and thereby convey its information to the brain in IRS2-KO mice.