INS and obesity due to melanocortin 4 receptor deficiency: It is the M1 macrophages that create the proinflammatory environment that blocks the action of insulin on the adipocytes, so promoting the development of insulin resistance and type 2 diabetes, and obesity not only stimulates their infiltration and migration into the adipose tissues, but also induces a redistribution of the macrophage population in favor of the M1 phenotype with overexpression of TNF-α and IL-6 [24,29].