Epidemiologically, Type 2 diabetes mellitus (T2DM) characterized by glucose intolerance accounts for approximately 90% of all diabetic patients worldwide (2, 3), and is a complex multifactorial metabolic disorder involving genetic (e.g. Tcf7l2, Kcnq1) and environmental lifestyle factors (e.g. intake of energy-dense refined food, sedentary behavior) (4–7). The gene discussed is TCF7L2; the disease is type 2 diabetes mellitus.