Serum retinol-binding protein 4 is elevated and positively associated with insulin resistance in postmenopausal women

Retinol-binding protein 4 (RBP4) is a newly discovered adipokine, which is reported to be correlated with insulin resistance (IR) and type 2 diabetes (T2DM). The aim of this study was to evaluate the influence of menopausal status on RBP4 concentration and to investigate serum RBP4 with IR and the prevalence of T2DM in postmenopausal women. We conducted a cross-sectional study and enrolled 34 healthy premenopausal women, 41 healthy postmenopausal women and 37 postmenopausal women with T2DM. Serum RBP4 concentration was measured by an enzyme-linked immunosorbent assay. Anthropometric parameters, plasma glucose, insulin and sex hormones concentrations were measured, and IR was assessed by HOMA2-IR. We found RBP4 was significantly elevated after menopause, even after adjustment for age and BMI. In postmenopausal women, RBP4 correlated positively with BMI, WHR, FPI, HOMA2-IR, TG and FAI, while negatively with SHBG (p<0.05). Furthermore, RBP4 was positively associated with 17beta-estradiol in only diabetic postmenopausal women. In healthy premenopausal group, age, BMI, and TG were the independent determinants of RBP4. In two postmenopausal groups, the independent determinants of RBP4 were BMI, WHR, HOMA2-IR, TG and FAI in healthy subjects, and in group with T2DM, the determinants were BMI, WHR, FPI, HOMA2-IR, TG and FAI (p<0.05). However, serum RBP4 was not significantly associated with increased odds of T2DM in postmenopausal women (OR 0.979, 95% CI 0.610-1.637). The findings suggested serum RBP4 concentration is influenced by menopausal status and closely related to IR but not to the prevalence of T2DM in postmenopausal women.