INS and obesity due to melanocortin 4 receptor deficiency: T2DM is a complex disease developed by the progressive loss of insulin secretion in β cells of the pancreas and/or by decreased insulin sensitivity in peripheral target organs that is often associated with age, obesity, lack of physical activity, first-degree family history, and/or with a strong genetic predisposition [5]; however, the genetic etiology of T2DM is still poorly studied.