Serum levels of retinol-binding protein-4 are associated with the presence and severity of coronary artery disease

Background: The interplay between the novel adipokine retinol-binding protein-4 (RBP4) and coronary artery disease (CAD) is still obscure. We investigated the relationship between RBP4 levels and the presence and severity of angiographically proven CAD and determined its possible role in acute myocardial infarction (AMI). Methods: 305 individuals with angiographically proven CAD (CAD-patients), were classified into 2 subgroups: 1) acute myocardial infarction (AMI, n = 141), and 2) stable angina (SA, n = 164). Ninety-one age-and sex-matched individuals without CAD, but with at least 2 classical cardiovascular risk factors, served as controls (non-CAD group). RBP4 serum levels were measured at hospital admission and were analyzed in relation to the coronary severity stenosis, assessed by the Gensini-score and the number of coronary narrowed vessels. Other clinical parameters, including insulin levels, HOMA-IR, hsCRP, glycaemic and lipid profile, and left-ventricular ejection fraction were also assessed. Results: Serum RBP4 levels were significantly elevated in patients with CAD compared to non-CAD patients (39.29 +/- 11.72 mg/L vs. 24.83 +/- 11.27 mg/L, p < 0.001). We did not observe a significant difference in RBP4 levels between AMI and SA subgroups (p = 0.734). Logistic regression analysis revealed an independent association of CAD presence with serum RBP4 (beta = 0.163, p = 0.006), and hsCRP (beta = 0.122, p = 0.022) levels, in the whole study group. Among variables, hsCRP (beta = 0.220), HDL (beta = -0.150), and RBP4 (beta = 0.297), correlated in both univariate and multivariate analysis with CAD severity (R-2 = 0.422, p < 0.001). Similarly, RBP4 concentrations increased with the number of coronary narrowed vessels (p < 0.05). Conclusion: Patients with CAD, both SA and AMI, showed elevated RBP4 serum levels. Notably, increased RBP4 concentration seemed to independently correlate with CAD severity, but no with AMI.