Diabetes mellitus is a pathological condition in which the body displays impaired capacity to maintain coordinated systemic fuel metabolism upon various nutrient perturbations, particularly perturbations of glucose, due to (1) pancreatic β-cell dysfunction followed by reduced serum levels of insulin (Type I diabetes), and/or (2) reduced insulin sensitivity of systemic cells and relatively reduced insulin secretion from pancreatic β-cells (Type II diabetes) [83]. The gene discussed is INS; the disease is diabetes mellitus.