Identification of urinary soluble E-cadherin as a novel biomarker for diabetic nephropathy

Background Currently, early diagnosis of diabetic nephropathy (DN) remains a major challenge. Thus, more investigations into new DN-related biomarkers are needed. Methods We employed urinary proteomic approach of fluorescence-based difference gel electrophoresis (DIGE) and mass spectrometry to identify novel biomarkers in urine samples, which were from type 2 diabetes patients with normoalbuminuria (DM group), microalbuminuria (DN1 group), macroalbuminuria (DN2 group) and control group (n = 8 in each group). The identified biomarker was further studied by western blot in urine samples (n = 6 in each group) and immunohistochemistry in renal biopsies. Besides, the urinary level of biomarker was detected and analyzed using enzyme-linked immunosorbent assay(ELISA) method (n = 40 in each group). Results A novel DN-related biomarker, urinary E-cadherin, was identified by proteomic methods, which up-regulated 1.3-fold, 5.2-fold and 8.5-fold in DM, DN1 and DN2 groups compared with control group. Meanwhile, high expression of urinary soluble 80 kDa fragment of E-cadherin (sE-cadherin) was verified in DN groups by western blot. The ELISA data also demonstrated that urinary sE-cadherin-to-creatinine ratio was significantly increased in DN1 and DN2 groups versus DM group or control group (2751.5 +/- 164 and 5839.6 +/- 428 vs 721.9 +/- 93 or 652.7 +/- 87 mu g/g; p < 0.001). The sensitivity and specificity of urinary sE-cadherin for diagnosis of DN were calculated as 78.8% (95% CI, 74-83%) and 80% (95% CI, 65-91%). Besides, immunohistochemical stain showed that E-cadherin expression was markedly decreased in renal tubular epithelial cells of patients with DN versus healthy controls. Conclusions Urinary sE-cadherin has a potential clinical diagnostic value for DN and E-cadherin may participate in the pathogenesis of DN. Copyright (c) 2009 John Wiley & Sons, Ltd.