The prevalence of type 2 diabetes is increasing rapidly worldwide, and fasting plasma glucose levels have risen globally since 1980.1 A recent review indicated that ethnic differences in insulin sensitivity were implicated in the pathogenesis of diabetes.2 Indeed, the prevalence of type 2 diabetes and the population attributable fraction for cardiovascular disease in Japan were estimated to be markedly increased, despite a low body mass index (BMI).3 This evidence concerns the gene INS and type 2 diabetes mellitus.