Elevated serum γ-glutamyltransferase levels are independently associated with insulin resistance in non-diabetic subjects

We investigated the associations of γ-glutamyltransferase (GGT) with visceral obesity, adiponectin and retinol binding protein 4 (RBP4), and insulin resistance (IR) and compared these associations with other liver enzymes in non-diabetes. We enrolled 94 healthy subjects 30-69 years old. Clinical and biochemical metabolic parameters were measured. Adiponectin and RBP4 were determined by ELISA. IR was examined by HOMA-IR. Visceral fat was determined by computed tomography scan. GGT and alanine aminotransferase (ALT) were positively correlated with waist circumference (WC), waist-to-hip ratio (WHR), visceral fat area (VFA), visceral-to-subcutaneous fat area ratio (VSR), HOMA-IR, and RBP4, but was negatively correlated with adiponectin (p < 0.05). In multivariate regression, GGT was associated with male sex, HOMA-IR, and RBP4 (R² = 0.48, p < 0.05) and ALT was associated with HOMA-IR (R² = 0.22, p < 0.05). By logistic regression after adjusted for age and sex, the odds ratio (OR) for IR in the highest tertile of sex-specific GGT and ALT were significantly increased compared to those in the lowest [OR (95% CI); 6.90 (2.08-22.82), 3.38 (1.08-10.57), respectively]. However, these relationships after further adjustments for RBP4, adiponectin, VFA, VSR, WHR, WC, TG, and HDL remained significant in only GGT. In conclusions, GGT may be a useful marker of IR in non-diabetes.