Serum Levels of Adipokine Retinol-Binding Protein-4 in Relation to Renal Function

Abstract

OBJECTIVE -Retinol-binding protein (RBP)-4 was recently identified as an adipokine that induces insulin resistance. In the current study, we investigated RBP-4 serum levels in diabetic and nondiabetic patients on chronic hemodialysis (CD) compared with control subjects with a glomerular filtration rate Ͼ50 ml/min. The majority of the diabetic subjects used oral hypoglycemic agents or insulin.RESEARCH DESIGN AND METHODS -RBP-4 was determined by enzyme-linked immunosorbent assay in control subjects (n ϭ 59) and CD patients (n ϭ 58) and correlated with clinical and biochemical measures of renal function, glucose and lipid metabolism, and inflammation in both groups.RESULTS -Mean serum RBP-4 levels were almost fourfold higher in CD patients (102 Ϯ 30 mg/l) compared with control subjects (28 Ϯ 8 mg/l). Furthermore, serum creatinine independently predicted RBP-4 concentrations in multiple regression analyses in both control subjects and CD patients. In addition, C-reactive protein and systolic blood pressure independently and negatively correlated with RBP-4 serum concentrations in CD patients but not control subjects. In contrast, markers of glucose and lipid metabolism were not independently related to serum RBP-4 in control subjects or CD patients.CONCLUSIONS -We show that markers of renal function are independently related to serum RBP-4 levels.

RBP4: a controversial adipokine

“…Increased circulating RBP4 levels in T2D subjects could be the result of decreased renal clearance of RBP4 caused by different levels of renal insufficiency in these subjects (78)(79)(80). These studies are supported by the fact that patients with end-stage kidney failure have significantly higher circulating RBP4 levels than healthy controls and that serum creatinine levels independently predict RBP4 concentrations in both controls and patients with kidney failure (81). There is an ongoing debate on the possible influence of transthyretin on circulating RBP4 levels via RBP4's decreased renal clearance (24,25).…”

An Increase in Serum Retinol-Binding Protein 4 in the Type 2 Diabetic Subjects with Nephropathy

“…There was a possibility that the discrepancy of the findings from those of previous reports may result from the analysis using different assay kit of RBP4. Ziegelmeier et al [24] reported a fourfold increase in serum RBP4 levels in patients with chronic hemodialysis compared with control subjects. Their patients included both diabetic and non-diabetic patients.…”

Elevated serum retinol-binding protein 4 concentrations are associated with chronic kidney disease but not with the higher carotid intima-media thickness in type 2 diabetic subjects

“…Elevated serum RBP4 concentrations have been observed in patients of type 2 DM with nephropathy [15] and in subjects on chronic hemodialysis [16]. Serum creatinine can independently predict RBP4 concentrations even in control subjects with a GFR >50 mL/min [16].…”