On the other hand, obesity, a major risk factor for type 2 diabetes mellitus (T2DM), could lead to the dysfunction of β cell in the pancreas, which is characterized by abnormalities in insulin synthesis and secretion (Ashcroft and Rorsman, 2012; Fu et al., 2013; Zhang et al., 2019; Lei et al., 2021). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.