Association between serum retinol-binding protein 4 concentrations and clinical indices in subjects with type 2 diabetes: A meta-analysis

Background: Retinol-binding protein (RBP4) is an adipokine that may be important in type 2 diabetes. Previous studies have examined the association between serum RBP4 concentrations and clinical indices in patients with type 2 diabetes, although the results obtained have been inconsistent. We conducted a meta-analysis aiming to investigate the association between serum RBP4 concentrations and clinical indicators of diabetes, renal function, metabolic syndrome and obesity in subjects with type 2 diabetes. Methods: MEDLINE, EMBASE and CINAHL databases were searched from 2005 through November 2011, and the search identified 21 clinical variables from seven studies (total n=1406). For each variable, summary correlation coefficients (r _s) were estimated using a random-effects meta-analysis. Results: None of the diabetes markers were correlated with serum RBP4 concentrations in subjects with type 2 diabetes, whereas all of the renal function markers and many metabolic syndrome markers were significantly correlated. Summary correlation coefficients and 95% confidence intervals (CIs) were -0.36 (95% CI=-0.51 to -0.18) for creatinine clearance, -0.39 (95% CI=-0.44 to -0.33) for estimated glomerular filtration rate and 0.53 (95% CI=0.30-0.71) for creatinine concentration. In addition, plasma triglyceride concentrations (r _s=0.22; 95% CI=0.11-0.32), plasma total cholesterol concentrations [r _s=0.14 (95% CI=0.05-0.23)] and low-density lipoprotein cholesterol level (r _s=0.14; 95% CI=0.02-0.25) were positively correlated with serum RBP4 concentrations. Conclusions: The results obtained in the present study suggest that serum RBP4 concentrations in patients with type 2 diabetes may be associated with diabetes-related renal dysfunction and imbalances in lipid metabolism.