Serum retinol binding protein 4 is negatively related to beta cell function in Chinese women with non-alcoholic fatty liver disease: a cross-sectional study

Background: To observe the relationship between serum retinol binding protein 4(RBP4) and beta cell function in Chinese subjects with non-alcoholic fatty liver disease (NAFLD) and without known diabetes. Methods: 106 patients diagnosed as fatty liver by ultrasonography (M/F: 61/45; aged 47.44 +/- 14.16 years) were enrolled in our current cross-sectional study. Subjects with known diabetes, chronic virus hepatitis and excessive alcohol consumption were excluded. Serum RBP4 was detected by ELISA and validated by quantitative Western blotting. beta cell function were assessed by HOMA in all subjects and by hyperglycemic clamp in 17 normal glucose tolerance subjects (M = 6, F = 11). Results: The levels of serum RBP4 in men were higher than that in women (55.96 +/- 11.14 vs 45.87 +/- 10.31 mu g/ml, p < 0.001). Pearson's correlation analysis demonstrated that in women, serum RBP4 levels were significantly associated with fasting blood glucose (FBG), HOMA-beta, and increment of first phase insulin secretion (1PH), but not associated with age, BMI, waist circumference, WHR, systolic (SBP) and diastolic blood pressure (DBP), TC, TG, HDL-c, LDL-c, 2 h blood glucose, HOMA-IR, ALT, AST, gamma-GT, hepatic fat content (HFC), and insulin sensitivity index (ISI). However, in men, serum RBP4 levels were significantly associated with HDL-c, ALT, AST, but not associated with any other parameters as mentioned above. A stepwise multiple linear regression analysis demonstrated that in women, HOMA-IR and RBP4 were significantly associated with HOMA-beta, while in men, HOMA-IR and BMI were significantly variables associated with HOMA-beta. Conclusions: Serum RBP4, secreted mainly by liver and adipose tissue, may involve in the pathogenesis of beta cell dysfunction in Chinese women patients with NAFLD.