In this context, pro-opiomelanocortin (POMC)-expressing neurons located into the hypothalamic arcuate nucleus (ARC) are critically involved in leptin’s effects on glucose homeostasis in obesity and insulin resistance states (Huo et al., 2009; Berglund et al., 2012). The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.