GYS1 and type 2 diabetes mellitus: A polymorphism (XbaI) in intron 14 of the glycogen synthase gene (GYS1) has been associated with lower glycogen synthase activity, T2D, features of the metabolic syndrome (MetS) and with myocardial infarction in males [4]–[8] but association to T2D has not been consistently replicated in all studies [9], [10].