Serum retinol-binding protein 4 levels are elevated but do not contribute to insulin resistance in newly diagnosed Chinese hypertensive patients

BACKGROUND: Insulin resistance (IR) is closely correlated with cardiovascular disease (CVD). Retinol-binding protein 4 (RBP4) is a novel adipokine that modulates the action of insulin in various diseases. This study addressed the relationship between RBP4 and IR in newly diagnosed essential hypertension. METHODS: Serum RBP4, anthropometric and metabolic parameters were determined in 267 newly diagnosed essential hypertensive patients not taking antihypertensive medications. The patients along with 64 control (NC) normotensive and lean subjects paired by age and sex were divided into two groups depending on body mass index (BMI), hypertension with obesity (HPO) and hypertension without obesity (HP). RESULTS: A striking difference was observed in RBP4 levels between the HP and NC groups. Significantly higher levels were noted in the HP group compared with the NC group; slightly, but not significantly, lower levels were observed in the HPO group compared with the HP group. After adjusting for BMI, WC and WHR, a modestly linear relationship was observed between RBP4 levels and SBP (r = 0.377; p = 0.00), DBP (r = 0.288; p = 0.00) and HOMA-β(r = 0.121; p = 0.028). Multiple stepwise regression analysis showed that SBP, WHR and drinking were independently related with serum RBP4 levels. CONCLUSIONS: The results of this study indicated that RBP4 levels were increased in naive hypertensive patients; however, no differences were observed in obese or non-obese hypertensive subjects. Our data suggest for the first time that RBP4 levels are significantly increased but do not contribute to the development of IR in newly diagnosed hypertensive Chinese patients.