A cross-sectional study of middle-aged Japanese men [42], including 139 cases of IFG (impaired fasting glycemia), 421 of IGT (impaired glucose tolerance), 180 of type 2 diabetes, and a control group with normal glucose tolerance, studied two different SNPs: CYP1A2 -3860G>A (CYP1A2*1C, rs2069514) and CYP1A2 -163C>A (CYP1A2*1F, rs762551). This evidence concerns the gene CYP1A2 and type 2 diabetes mellitus.