Улога на подоцитните протеини - нефрин и подокаликсин во рана дијагноза на секундарни нефропатии

Abstract

Background: Nephrin and podocalyxin are specific podocyte proteins, they have an important role in selective permeability of the glomerular filtration barrier. Damage of podocytes - podocytopathies, result in presence of podocite proteins in urine, where they can be measured with relatively cheap and simplify methods. Podocytopathies are important in pathogenesis of secondary nephropathies. Previously, microalbuminuria was considered as a golden standard in early detection of secondary nephropathies, particularly in early detection of diabetic nephropathy, but the fact that microalbuminuria is nonspecific and nonsensitive marker, motivate us to find a novel markers in early detection and prediction of secondary nephropathies. The main aim of the PhD study is to test the significance of nephrin and podocalyxin in early detection of diabetic and hypertensive nephropathy and in prediction of preeclampsia. Material and methods: In this PhD study were included 305 subjects, divided into four groups: subjects with diabetes mellitus type 2 (30 with nephropathy and 60 without nephropathy), subjects with chronic hypertension (30 with nephropathy and 54 without nephropathy), pregnant women (41 women with high risk pregnancy and 30 with preeclampsia) and healthy subjects (30 healthy subjects and 30 healthy pregnant women). In all subjects we measured: nephrin and podocalyxin in urine with immunoenzyme assay, microalbumin and creatinine in urine with standard biochemical methods, in patients with macro- and microalbumiuria we performed electrophoretic separation of urinary proteins by polyacrylamide gel. In blood sera, we measured a few standard biochemical parameters, which were on interest of the study. Results: In all three major groups, ROC analyses showed that nephrin and podocalyxin have high discriminatory power between healthy subjects and subjects with diabetic nephropathy, hypertensive nephropathy and preeclampsia. The percent of subjects with elevated levels of urinary nephrin and podocalyxin was significant in all tested groups, but particularly is significant the fact that this percent is high in normoalbuminuric group of subjects with diabetes mellitus type 2 (82%), normoalbuminuric subjects with chronic hypertension (66,7%) and in group of women with preeclampsia (96%). Podocalyxin was elevated in all women with preeclampsia, in 63% of women with high-risk pregnancy, in 25% of hypertensive normoalbuminuric subjects and in 21% of normoalbuminuric subjects with diabetes mellitus type 2. The concentration of urinary nephrin and podocalyxin showed statistically significant differences between all groups of patients and healthy subjects (р ˂ 0.05). In group with diabetes mellitus type 2 and group with chronic hypertension we found statistically significant negative correlation between concentration of urinary nephrin, respectively podocalyxin and estimated rate of glomerular filtration. In group of pregnant women with preeclampsia and group of pregnant women with risk for development of preeclampsia we found statistically significant positive correlation between concentration of urinary nephrin, respectively podocalyxin and gestational age. Electrophoretic separation of urinary proteins showed that in patient with diabetes mellitus type 2 and macroalbuminuria the most frequent type of proteinuria was tubular proteinuria, while in all other examined groups, the most frequent type of proteinuria was mixed proteinuria, glomerular and tubular proteinuria. Conclusion: High percent of normoalbuminuric subjects with diabetes and hypertension with elevated levels of nephrin and podocalyxin and negative correlation between concentration of nephrin and podocalyxin in urine and glomerular filtration rate, indicate that these markers, separately or together, can be a useful markers for early detection of diabetic and hypertensive nephropathy. We found statistically significant differences in urinary concentration of both markers between the pregnant women with preeclampsia, pregnant women with risk for development of preeclampsia and healthy pregnant women. Also we found statistically significant positive correlation between concentration of urinary nephrin, respectively podocalyxin and gestational age. These findings in pregnant women indicate that nephrin and podocalyxin can be useful markers in follow-up of high risk pregnant women and in prediction of preeclampsia.