Association between nephrinuria, podocyturia, and proteinuria in women with pre-eclampsia

Podocyte depletion in the kidney is associated with end-stage kidney disease (ESKD). Pre-eclampsia (PE) increases the risk of ESKD in later life. This study was performed to determine whether nephrinuria (soluble nephrin in the urine) is correlated with proteinuria and/or podocyturia (podocytes in the urine) in PE women.

Eighty-three urine samples, consisting of 45 and 38 samples from 27 normotensive and nine PE women, respectively, underwent simultaneous determination of nephrin, protein, and creatinine concentrations in the urine supernatant and quantitative analysis of podocyte-specific protein mRNA expression. This included podocin (Pod-mRNA) and nephrin (Nep-mRNA), using real-time polymerase chain reaction in the pelleted urine. Nephrinuria and proteinuria were corrected by creatinine concentration. Pod- and Nep-mRNA expression levels were corrected by GAPDH.

Nephrinuria, proteinuria, Pod-mRNA expression, and Nep-mRNA expression all increased with advancing gestation in PE women, while not in normotensive women. The nephrinuria was strongly correlated with proteinuria (R = 0.901, P <  0.001), Pod-mRNA expression level (R = 0.824, P < 0.001), and Nep-mRNA expression level (R  =  0.724, P <  0.001) in urine samples from PE women, while the nephrinuria was significantly correlated with proteinuria alone (R  =  0.419, P <  0.005) in urine samples from normotensive women.

Nephrinuria reflected well the degrees of proteinuria and podocyturia in PE women. This suggested that increased nephrinuria/proteinuria was associated with podocyte loss in the kidneys of PE women.