Wilm's Tumor-1 Protein Levels in Urinary Exosomes from Diabetic Patients with or without Proteinuria

Abstract

BackgroundPodocyte 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.MethodsThe 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.ResultsWT1 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 m2.ConclusionThe 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.

Extracellular Vesicles in Renal Diseases

“…WT-1 expression in uEXs was also found to be increased in patients with diabetes. 85 Exosomal WT-1 was detected in all patients with diabetes and proteinuria but only one half of those without proteinuria and only 1 of 25 healthy controls. Expression of WT-1 in uEXs also correlated significantly with decline in kidney function.…”

Urinary Podocyte Microparticles Identify Prealbuminuric Diabetic Glomerular Injury

“…Exosomes, although distinct from MPs, have been identified in urine samples and proposed as tools for the noninvasive identification of renal pathology. 14,15 Using electron microscopy, Pascual et al 12 identified 100-to 200-nm urinary vesicles containing the complement receptor-1 consistent with podocyte MPs. Subsequent studies have further confirmed the presence of MPs in human urine.…”

Urinary extracellular vesicles and the kidney: biomarkers and beyond

“…One study found that WT-1 in uEVs was increased in patients with focal segmental glomerulosclerosis but not in patients with AKI or in healthy volunteers (81,82); this finding, however, was not confirmed by others (37). The increase in uEV WT-1 was also associated with a decline in kidney function in diabetic nephropathy, suggesting early podocyte damage (33). Another podocyte injury marker is podocalyxin, which, unlike WT-1, was found in shedding vesicles (no expression of CD24 and CD63) (24,25).…”