Alanine Aminotransferase and Total Bilirubin Are Synergistically Associated with Metabolic Syndrome Among Middle-Aged and Elderly Japanese Women.

Background: Metabolic syndrome (MetS) is associated with an increased risk of major cardiovascular events. Alanine aminotransferase (ALT) at high levels and total bilirubin (T-BiL) at low levels were oxidative potentials, but it was uncertain whether ALT and T-BiL had an additive interaction for the risk of MetS.

Methods: From a single community, we recruited 864 women (70 ± 8 years) during their annual health examination. We cross-sectionally investigated whether ALT and T-BiL are associated with MetS and its components based on the modified criteria of the National Cholesterol Education Program's Adult Treatment Panel (NCEP-ATP) III report.

Results: Of these subjects, 415 women (48.0%) had MetS. Participants with MetS had a higher ALT and lower T-BiL level than those without MetS. The adjusted-odds ratios (OR) (95% confidence interval [CI]) for MetS across tertiles of ALT and T-BiL were 1.00, 1.19 (0.78-1.81), and 1.86 (1.24-2.80) and 1.00, 0.96 (0.65-1.43), and 0.54 (0.36-0.81), respectively. When ALT and T-BiL were categorized into three binary characteristics by tertiles of ALT and T-BiL, high T-BiL was associated with decreased risk for MetS in a multivariable model (OR: 0.55, 95% CI: 0.37-0.82), especially among those with 1st tertile ALT. Similarly, high ALT was also associated with increased risk for MetS in a multivariate model (OR: 1.81, 95% CI: 1.20-2.71), especially among those with 2nd & 3rd tertiles of T-BiL. In the formal testing of addictive interaction between ALT and T-BiL for MetS, presence of T-BiL <0.72 mg/dL (1st and 2nd tertile) alone was not associated with increased risk of MetS in a multivariate analysis, and presence of ALT ≥16 IU/L (2nd and 3rd tertile) alone was not associated with increased risk of MetS.

Conclusions: These results suggested that higher ALT and lower T-BiL levels were synergistically associated with MetS, independent of other confounding factors among Japanese women.