Wilm's tumor-1 protein levels in urinary exosomes from diabetic patients with or without proteinuria

PLoS One. 2013;8(3):e60177. doi: 10.1371/journal.pone.0060177. Epub 2013 Mar 27.

Abstract

Background: Podocyte injury is an early feature of diabetic nephropathy (DN). Recently, urinary exosomal Wilm's tumor-1 protein (WT1), shed by renal epithelial cells, has been proposed as a novel biomarker for podocyte injury. However, its usefulness as biomarker for early diabetic nephropathy has not been verified yet. We investigated urinary exosomal WT1 in type-1 diabetic patients to confirm its role as a non-invasive biomarker for predicting early renal function decline.

Methods: The expression of WT1 protein in urinary exosomes from spot urine samples of type-1 diabetes mellitus patients (n = 48) and healthy controls (n = 25) were analyzed. Patients were divided based on their urinary albumin excretion, ACR (mg/g creatinine) into non- proteinuria group (ACR<30 mg/g, n = 30) and proteinuria group (ACR>30 mg/g, n = 18). Regression analysis was used to assess the association between urinary exosomal levels of WT1 with parameters for renal function. Receiver Operating Characteristic (ROC) curve analysis was used to determine the diagnostic performance of exosomal WT-1.

Results: WT1 protein was detected in 33 out of 48 diabetic patients and in only 1 healthy control. The levels of urinary exosomal WT1 protein is significantly higher (p = 0.001) in patients with proteinuria than in those without proteinuria. In addition, all the patients with proteinuria but only half of the patients without proteinuria were positive for exosomal WT1. We found that the level of exosomal WT1 were associated with a significant increase in urine protein-to-creatinine ratio, albumin-to-creatinine ratio, and serum creatinine as well as a decline in eGFR. Furthermore, patients exhibiting WT1-positive urinary exosomes had decreased renal function compared to WT1-negative patients. ROC analysis shows that WT-1 effectively predict GFR<60 ml. min-1/1.73 m(2).

Conclusion: The predominant presence of WT1 protein in urinary exosomes of diabetic patients and increase in its expression level with decline in renal function suggest that it could be useful as early non-invasive marker for diabetic nephropathy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Case-Control Studies
  • Diabetes Mellitus, Type 1 / complications*
  • Diabetes Mellitus, Type 1 / physiopathology
  • Diabetes Mellitus, Type 1 / urine*
  • Exosomes / metabolism*
  • Female
  • Glomerular Filtration Rate / physiology
  • Humans
  • Male
  • Proteinuria / complications*
  • Proteinuria / physiopathology
  • Proteinuria / urine*
  • WT1 Proteins / urine*

Substances

  • WT1 Proteins

Grant support

This work was supported by SGPGI- Intramural research grant and the Department of Science and Technology, Government of India (SR/FR/LS-143/2010) grant to ST. AM was supported by a Junior Research Fellowship from University Grant Commission, India (F 2-89/98; SA I). AK was supported by a Research Associate Fellowship from Department of Biotechnology, India. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.