Retinol-binding protein 4 as a novel risk factor for cardiovascular disease in patients with coronary artery disease and hyperinsulinemia.

Retinol-binding protein 4 (RBP4) is an adipokine associated with insulin resistance (IR) and obesity-related metabolic disorders. To evaluate its association with cardiovascular disease, we compared serum RBP4 concentrations in patients with coronary artery disease (CAD) and in controls. Sixty patients with coronary angiography-confirmed CAD, including 30 with CAD and 30 with CAD and hyperinsulinemia (CAD/HIns group), and 29 healthy subjects were enrolled. Serum RBP4, IR indexes and cardiovascular risk factors were assessed in these subjects. Serum RBP4 concentrations were significantly higher in the CAD/HIns than in the CAD and control groups (P < 0.01 each). RBP4 concentration was significantly associated with cardiovascular risk factors, including body mass index and concentrations of triglycerides, high-density lipoprotein cholesterol, uric acid, high-sensitivity C reactive protein and adiponectin (P < 0.01 each). Two-hour postprandial insulin (β = 0.224), homeostatic model assessment of IR score (β = 0.456) and adiponectin concentration (β = 0.294) were independent factors associated with RBP4 (P < 0.01 each). RBP4 concentration is associated with cardiovascular risk factors related to IR and CAD. Circulating RBP4 could be a marker of metabolic complications and atherosclerosis and could be used to assess CAD.