Cross-sectional and longitudinal association of serum alanine aminotransaminase and γ-glutamyltransferase with metabolic syndrome in middle-aged and elderly Chinese people.

BACKGROUND Although associations of the liver enzymes alanine aminotransaminase (ALT) and γ-glutamyltransferase (GGT) with metabolic syndrome (MetS) are well recognized, whether they are independent of insulin resistance and which enzyme is more effective are yet to be clarified. METHODS A total of 5404 subjects aged ≥ 40 years were recruited from two urban communities in Shanghai for cross-sectional analyses. A subgroup of 681 participants without MetS at baseline was included in the longitudinal analyses. Insulin resistance was measured using the homeostasis model assessment of insulin resistance (HOMA-IR), and the modified National Cholesterol Education Program Adult Treatment Panel III criteria were adopted to diagnose MetS. RESULTS Both GGT and ALT were strongly and positively associated with MetS risks in simple and multivariate analyses. Further adjustment for HOMA-IR and ALT did not change the association of GGT and MetS materially, whereas adjustment for HOMA-IR and GGT substantially attenuated the ALT-MetS association. In longitudinal analyses, risks of developing MetS were increased across GGT quartiles in a dose-dependent manner after extensive adjustments (odds ratios were 1.00, 1.38, 1.62, and 2.29 for GGT, quartile 1 through quartile 4; P for trend = 0.01). In contrast, ALT was no longer associated with MetS development after final adjustment for GGT (P for trend = 0.09). CONCLUSIONS Our study confirmed significant and independent associations of GGT and ALT with MetS in adult Chinese people. Moreover, GGT might be more effective for indicating the future development of MetS.