Abstract

Objective: Retinol Binding Protein 4 (RBP4) has been identified as a novel adipokine mediating systemic insulin resistance, and elevated serum RBP4 indicated overt or impending insulin resistance in lean, obese and type 2 diabetic subjects. As insulin resistance is present in nearly all patients with liver cirrhosis, we evaluated RBP4 in patients with chronic liver diseases (CLD).

Research Design and Methods: Serum RBP4 was measured 111 CLD patients. 99 age- and sex-matched healthy blood donors served as controls. RBP4 gene expression was also quantified in normal and cirrhotic rat liver.

Results: In CLD patients, serum RBP4 was significantly reduced compared with healthy controls, and closely correlated with the stage of liver cirrhosis. CLD patients without cirrhosis showed normal RBP4 concentrations, which correlated with serum glucose, insulin secretion and inversely with insulin sensitivity. In patients with Child A-C liver cirrhosis, however, RBP4 was not correlated with glucose metabolism or other adipokines such as adiponectin or resistin, but closely linked to the hepatic biosynthetic capacity, fibrotic changes in liver histology or clinical complications such as portal hypertension. In an animal model of experimental cirrhosis, hepatic RBP4 gene expression decreased in cirrhotic liver.

Conclusions: RBP4 appears, unlike in obesity or type 2 diabetes, not to be a relevant systemic factor in the pathogenesis of insulin resistance in liver cirrhosis. Liver function has a tremendous impact on RBP4 levels, and future studies will need to take liver function into account when examining serum RBP4 levels.