Accordingly, diabetes mellitus can be divided into types 1 and 2, with the former caused by the abnormal function of the immune system, leading to the destruction of β cells in islets and impairment of insulin secretion, while the latter is caused by insulin resistance and inadequate insulin secretion due to poor living habit and obesity [17]. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.