Correlation between serum YKL-40 (Chitinase-3-like protein 1) level and proteinuria in renal transplant recipients

BACKGROUND YKL-40 (chitinase-3-like protein 1) is a novel inflammation and endothelial dysfunction biomarker. Although YKL-40 is associated with albuminuria and predicts cardiovascular morbidity and mortality in a non-uremic population, it's status is not known in renal transplant recipients. The aim of this study was to investigate plausible links between serum YKL-40 and proteinuria. MATERIAL AND METHODS A total of 110 renal transplant recipients were included in this study. The level of proteinuria was calculated from spot urine using the protein/creatinine ratio. The estimated glomerular filtration rate (GFR) was calculated using the Modification of Diet in Renal Disease (MDRD) formula. Serum YKL-40 was determined by ELISA (R&D Systems, USA). RESULTS The mean patient age was 40.5 ± 10 years. The mean YKL-40, GFR, and proteinuria levels were 66 ± 46 ng/ml, 49 ± 24 ml/min/1.73 m2, and 0.77 ± 1.15 g/day, respectively. Increases in the YKL-40 tertiles were correlated with increases in proteinuria and C-reactive protein and decreases in the GFR and serum albumin. An adjusted linear regression analysis demonstrated that the YKL-40 level (t=3.28, P=0.001), GFR (t=-3.00, P=0.003), and systolic blood pressure (t=2.51, P=0.01) were independently associated with proteinuria. CONCLUSIONS This is the first study to show that increased serum YKL-40 levels are independently associated with proteinuria in renal transplant recipients. YKL-40 may be responsible for the pathogenesis of cardiovascular injury in this patient population.