Relationship of serum gamma-glutamyltransferase to atherogenic dyslipidemia and glycemic control in type 2 diabetes.

We evaluated possible interactions between BMI and serum gamma-glutamyltransferase (GGT) concentration and their effects on the prevalence of poor glycemic control and common comorbidities of diabetes. We assessed whether the association of BMI with poor glycemic control, hypertension, atherogenic dyslipidemia (i.e., high triglycerides and/or low high-density lipoprotein (HDL) cholesterol), hypercholesterolemia, and hyperuricemia differed according to serum GGT concentration in a cohort of 3,633 type 2 diabetic individuals. The associations of BMI with different outcome measures were significant, but the associations varied remarkably by GGT concentration. As GGT concentration increased, the association of BMI with atherogenic dyslipidemia and glycemic control strengthened (P = 0.01 and 0.004 for interactions, respectively); in contrast, the association of BMI with hypertension, hypercholesterolemia, and hyperuricemia did not change substantially across GGT quartiles. For example, within the lowest GGT quartile, BMI was not associated with atherogenic dyslipidemia or poor glycemic control, whereas in the highest GGT quartile, the prevalence rates ranged from 62.3 to 74.7% for dyslipidemia and from 75.3 to 83% for poor glycemic control. The results remained unchanged after adjustment for sex, age, alcohol consumption, diabetes duration, and diabetes treatment. In conclusion, our findings show that BMI was associated with atherogenic dyslipidemia and poor glycemic control only when serum GGT activity was in its high-normal range. These findings suggest that obesity itself may not be a sufficient risk factor for atherogenic dyslipidemia or poor glycemic control in people with type 2 diabetes.