Specifically, a reversible Mc4r knockout mouse (Mc4rNULL) intercrossed with a Choline acetyltransferase (ChAT; the enzyme that carries out acetylcholine production)CRE line to restore Mc4r expression exclusively within preganglionic sympathetic and parasympathetic neurons (Mc4rChAT; Figure 3A) revealed that Mc4rNULL mice are hyperinsulinemic and hyperglycemic and that restoration of the MC4Rs in ChAT cells in Mc4rChAT mice improves hyerinsulinemia, hyperglycemia, hepatic insulin action, and insulin-induced suppression of hepatic glucose production, without normalizing hyperphagia [25]. The gene discussed is MC4R; the disease is Hyperglycemia.