Relationships between serum total bilirubin levels and metabolic syndrome in Korean adults

Background and aims: Metabolic syndrome (MS) is associated with insulin resistance in all parts of its natural history, which is accompanied by oxidative stress. Bilirubin is a potent endogenous antioxidant and cytoprotectant. The current study was performed to identify the major predictors of the total bilirubin level and to assess the relationships between the total bilirubin levels and MS in Korean adults. Methods and results: This is a cross-sectional study involving 12342 adults aged 20 years and over who visited a Health Promotion Center. Physical examinations and laboratory tests including total and direct bilirubin levels were performed. MS was defined based on the modified NCEP-ATP III definition and the determinations of the Korean Society for the Study of Obesity. The results showed that hemoglobin had the strongest influence on the total bilirubin levels after adjusting for age, gender, and all other variables. The high-bilirubin group (>= 15.4 mmol/L in males and >= 12.1 mmol/L in females) was associated with significantly decreased odds of MS compared to the low-bilirubin group (OR 0.74 [95% CI 0.64-0.86]). High levels of bilirubin also were negatively associated with abdominal obesity and hypertriglyceridemia. The total bilirubin levels decreased with an increase in the number of MS components after adjustment for all covariates. Conclusion: Within the physiological range, the serum total bilirubin level was negatively associated with the MS in subjects without overt metabolic or cardiovascular diseases. This may be partially due to the negative association between the total bilirubin level and abdominal obesity and hypertriglyceridemia. (C) 2011 Elsevier B.V. All rights reserved.