Background: Podocyte loss plays an important role in the pathogenesis of diabetic nephropathy. We hypothesize that messenger RNA expression of podocyte-associated molecules in urinary sediment may provide important clinical information in patients with diabetic nephropathy.
Method: We studied 21 patients with biopsy-proven diabetic nephropathy and 9 healthy controls. The mRNA expression of nephrin, podocin, synaptopodin, Wilms' tumor-1 (WT-1) and alpha-actinin-4 in urinary sediment were measured by real-time quantitative polymerase chain reaction. The degree of histological damage was quantified by morphometric analysis. Patients were then followed for an average of 25.63 +/- 10.76 months. The rate of glomerular filtration rate (GFR) decline was calculated by the least-square regression.
Results: There were significant differences in nephrin, podocin, synaptopodin, alpha-actinin-4 (p < 0.01 for all comparisons) and WT-1 (p = 0.028) expression between patients and normal controls. Urinary nephrin expression was significantly correlated with proteinuria (r = 0.502, p = 0.020); urinary synaptopodin was significantly correlated with proteinuria (r = 0.585, p = 0.005), serum creatinine (r = 0.516, p = 0.017) and estimated GFR (r = -0.560, p = 0.008), and urinary WT-1 expression was significantly correlated with the degree of tubulointerstitial fibrosis (r = 0.558, p = 0.009). There was no significant correlation between GFR decline and urinary expression of target genes.
Conclusion: Urinary mRNA expressions of nephrin, podocin, synaptopodin, WT-1 and alpha-actinin-4 are higher in patients with diabetic nephropathy than in normal controls. Urinary nephrin and synaptopodin expressions are correlated with baseline clinical parameters such as proteinuria or renal function, while WT-1 expression is related to the degree of histological damage. Our results suggest that urinary mRNA expression of podocyte-associated molecules may be used for risk stratification of diabetic nephropathy.
Copyright 2007 S. Karger AG, Basel.