In addition, previous studies also suggested that the chronic low-grade inflammation in obesity can increase macrophage infiltration and proinflammatory adipokine secretion, including interleukin (IL)-1, -6 and tumor necrosis factor (TNF)-α by adipose tissues, which interfere with the insulin-signaling pathway in related tissues and ultimately lead to the development of insulin resistance and the subsequent progression to type 2 diabetes [7, 8]. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.