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Expression of renal vitamin D receptors and metabolizing enzymes in IgA nephropathy

Introduction: IgA nephropathy (IgAN) is principal cause of ESRD worldwide and the most common form of glomerulonephritis. Since kidney is a key player in vitamin D metabolism, disturbances of vitamin D metabolism are consequence of renal damage of different causality. There is no study investigating the expression pattern of renal vitamin D receptors (VDR) and metabolizing enzymes in IgA nephropathy. Material & methods: Immunoflurescent staining was used to determine the expression of VDR, 25-Hydroxyvitamin D3 1-alpha-hydroxylase (1α- OHase) and vitamin D3 24-hydroxylase (CYP24A1). There were 5 renal biopsies from adult patients and 10 from paediatric patients, as well as 6 control samples. Results: The expression of VDR was prominent in distal tubular cells (DTCs), while immunoreactivity of VDR in proximal tubular cells (PTCs) was weak. There was no difference between expression of VDR in tissues from control group and both, bioptate from IgA- nephritis patients (IgAN-P) from paediatric or adult populations. The expression of 1α-OHase, calcitriol synthesizing enzyme, was significantly lower in both paediatric and adult IgAN-P, in comparison with control renal tissues (p<0.05). In opposite, the expression of CYP24A1, vitamin D degrading enzyme, was significantly higher in both paediatric and adult IgAN-P, in comparison with control renal tissues (p<0.05). However, we did not find difference between bioptates from paediatric and adult IgAN-P in expression of both, 1α- OHase or CYP24A1. Conclusions: Our result indicate substantially decreased renal calcitriol production and increased vitamin D degradation in kidneys of both, paediatric and adult IgAN-P. These changes do not differ between paediatric and adult population of patients.

IgA nephropathy ; VDR ; 1-alpha-hydroxylase ; CYP24A1

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