GGT1 and type 2 diabetes mellitus: In the T2DM subjects, ever-smoking, drinking, the ALDH2*2 allele and the transaminase, diastolic BP and triglyceride levels were significantly associated with the GGT levels, irrespective of the GGT1 genotype, while the HbA1c level was significantly associated with the GGT level only in non-carriers (Additional file 1: Table S1).