Evidence That Kidney Function but Not Type 2 Diabetes Determines Retinol-Binding Protein 4 Serum Levels
- Andrea Henze1,
- Simone K. Frey1,
- Jens Raila1,
- Martin Tepel2,
- Alexandra Scholze2,
- Andreas F. H. Pfeiffer34,
- Martin O. Weickert34,
- Joachim Spranger34 and
- Florian J. Schweigert1
- 1Department of Physiology and Pathophysiology of Nutrition, Institute of Nutritional Science, University of Potsdam, Potsdam, Germany
- 2Department of Nephrology, Charité-Universitätsmedizin Berlin, Charité Campus Benjamin Franklin, Berlin, Germany
- 3Department of Endocrinology, Diabetes and Nutrition, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
- 4Department of Clinical Nutrition, German Institute of Human Nutrition, Potsdam-Rehbruecke, Germany
- Corresponding author: Andrea Henze, henze{at}rz.uni-potsdam.de
Abstract
OBJECTIVE— It has been suggested that retinol-binding protein 4 (RBP4) links adiposity, insulin resistance, and type 2 diabetes. However, circulating RBP4 levels are also affected by kidney function. Therefore, the aim of this study was to test whether RBP4 serum levels are primarily associated with kidney function or type 2 diabetes.
RESEARCH DESIGN AND METHODS— RBP4 serum concentration was determined by enzyme-linked immunosorbent assay in 126 nondiabetic and 104 type 2 diabetic subjects. The study population was divided according to estimated glomerular filtration rate (eGFR) into the following groups: eGFR >90 ml/min per 1.73 m2 (n = 53), 60–90 ml/min per 1.73 m2 (n = 90), 30–60 ml/min per 1.73 m2 (n = 38), and <30 ml/min per 1.73 m2 (n = 49). Each group was subdivided into nondiabetic and type 2 diabetic subjects.
RESULTS— RBP4 serum concentration was elevated (2.65 vs. 2.01 μmol/l; P < 0.001) and eGFR was reduced (56 vs. 74 ml/min per 1.73 m2; P < 0.001) in type 2 diabetic vs. nondiabetic subjects, respectively. By stratifying for eGFR, no more differences in RBP4 serum concentration were detectable between type 2 diabetic and nondiabetic subjects. A linear regression analysis revealed an influence of eGFR (r = −0.477; P < 0.001) but not A1C (r = 0.093; P = 0.185) on RBP4 serum concentration.
CONCLUSIONS— Existing human data showing elevated RBP4 levels in type 2 diabetic patients may be the result of moderate renal insufficiency rather than support for the suggestion that RBP4 links obesity to type 2 diabetes.
Footnotes
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Published ahead of print at http://diabetes.diabetesjournals.org on 16 September 2008.
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- Accepted September 11, 2008.
- Received June 27, 2008.
- DIABETES
