Association of plasma retinol-binding protein 4, adiponectin, and high molecular weight adiponectin with insulin resistance in non-diabetic hypertensive patients

Abstract

Purpose: The aim of this study was to determine whether retinol-binding protein 4 (RBP4), adiponectin and high molecular weight (HMW) adiponectin are associated with insulin resistance (IR) and metabolic parameters in non-diabetic hypertensive patients. Also, we sought to compare the predictive values of these adipocytokines for IR in non-diabetic hypertensive patients.

Materials and methods: Analyses of RBP4, adiponectin, and HMW adiponectin were performed on 308 non-diabetic hypertensives (148 males, age 58 +/- 10 years, 189 non-metabolic syndrome and 119 metabolic syndrome). The homeostasis model assessment (HOMA) index for IR, lipid profiles, and anthropometric measurements were assessed.

Results: There was no significant difference in RBP4 levels according to the presence of metabolic syndrome, although adiponectin and HMW adiponectin were significantly lower in metabolic syndrome. Correlation analysis of log RBP4 with IR and metabolic indices revealed that there was no significant correlation of RBP4 with waist circumference (r = 0.056, p = 0.324), HDL cholesterol (r = 0.005, p = 0.934), ApoB/ApoAI ratio (r = 0.066, p = 0.270), and the HOMA index (r = 0.017, p = 0.756). However, adiponectin and HMW adiponectin showed significant correlations with the HOMA index (r = - 0.247, p < 0.001; r = - 0.296, p < 0.001) and metabolic parameters. With IR defined as HOMA index >or= 2.5, HMW adiponectin did not demonstrate a superior predictive value for IR compared to adiponectin (AUC = 0.680 vs. 0.648, p = 0.083). The predictive value of RBP4 for IR was minimal (AUC = 0.534).

Conclusion: RBP4 was not associated with IR or metabolic indices and the predictive value for IR was minimal in hypertensives. HMW adiponectin didn't have a superior predictive value for IR compared to adiponectin. Therefore, we can suggest that RBP4 and HMW adiponectin don't have more additive information than adiponectin in non-diabetic hypertensives.

Fig. 1

Correlation of RBP4, adiponectin, and HMW adiponectin with metabolic parameters in hypertensive subjects. (A) Log RBP4, (B) Log adiponectin, (C) Log HMW adiponectin. RBP4, retinol-binding protein 4; HMW, high-molecular weight.

Fig. 2

ROC curves of adipocytokines for prediction of insulin resistance, defined as HOMA-IR index > 2.5 (n = 308), in hypertensive subjects. (A) Plasma adiponectin and HMW adiponectin. (B) Plasma RBP4. AUC, area under curve; ROC, receiver operating characteristics; HOMA, homeostasis model assessment; RBP4, retinol-binding protein 4.