INS and obesity due to melanocortin 4 receptor deficiency: However, type 2 diabetes or obesity disrupts signaling mediated by IRS-1 in the skeletal muscle, by inhibiting the tyrosine phosphorylation of IRS-1 and/or activating the serine/threonine phosphorylation of IRS-1, thereby inactivating or downregulating insulin cascade that reduces glucose disposal, known as insulin resistance [3,5].