Serum Retinol-Binding Protein 4 as a Marker for Cardiovascular Disease in Women

BACKGROUND: Elevated serum level of retinol-binding protein 4 (RBP4) has been associated with obesity-related co-morbidities including insulin resistance, dyslipidemia and hypertension. OBJECTIVES: The present study examined the relationship between serum level of RBP4 and various risk factors related to cardiovascular disease (CVD) in men and women. METHODS: 284 subjects (139 males, 145 females), grouped into healthy (n = 60), obese diabetes (n = 60), non-obese diabetes (n = 60), obese non-diabetes (n = 60) and patients with CVD (n = 44), were assessed for anthropometric and biochemical parameters related to obesity, diabetes and CVD. In addition, serum levels of several adipokines, including fatty acid binding protein 4 (FABP4) and lipocalin 2 (LCN2) and RBP4 were measured using specific immunoassays. RESULTS: Serum RBP4 level correlated significantly with principal component derived from known risk factors of CVD (β = 0.20±0.06, P = 0.002). Significance of this correlation was limited to women (β = 0.20±0.06, P = 0.002) and it persisted even after adjusting for BMI (β = 0.19±0.06, P = 0.002). Overall (n = 284) serum RBP4 values significantly correlated with FABP4 (R = 0.19, p = 0.001). Serum FABP4 level of CVD subjects was significantly higher than healthy control (P = 0.001) and non-obese diabetes (P = 0.04) groups, but this difference was attributable to differences in BMI. Serum LCN2 level correlated well with RBP4 (R = 0.15, P = 0.008) and FABP4 (R = 0.36, P<0.001), but did not differ significantly between CVD and other groups. CONCLUSIONS: Results of this study indicate a significant correlation between serum RBP4 and various established risk factors for CVD and suggest RBP4 may serve as an independent predictor of CVD in women.