Influence of vitamin D receptor gene polymorphisms on secondary hyperparathyroidism and bone density after kidney transplantation

Abstract

Secondary hyperparathyroidism and immunosuppressive treatments are the most important pathogenetic factors for bone disease after kidney transplantation. The aim of study was to compare the influence of vitamin D receptor (VDR) genotype on the PTH level and bone mineral density (BMD) in 67 patients, including 45 immunosuppressed with cyclosporine (CsA) and 22 with tacrolimus (Tac) versus 147 healthy volunteers. Two VDR polymorphisms: BsmI and FokI were assayed with RFLP-PCR. Scantibodies were utilized to evaluate 1-84 PTH. BMD was measured by DEXA. Hormone levels were measured on the third day and sixth month after transplantation. BMD was examined at the third and ninth month. The distribution of FokI genotype differed, but the BsmI genotypes did not differ between the transplant patients and the control group. All transplanted patients showed an elevated tPTH at the first examination. The highest PTH values, which were observed in bb genotype, significantly decreased after the transplant procedure. Patients with the FF genotype who were treated with CsA showed higher levels of tPTH than those with the Ff genotype. At 6 months, a decrease in tPTH occurred in both the CsA and the Tac patients. A low BMD at the third month was more frequent among patients of the BB genotype treated with CsA. The Z-score remained low at the third month and at the ninth month. In conclusion, kidney graft recipients show overrepresentation of the Ff genotype. Our preliminary data suggest that the bb genotype exhibits a protective effect on bone loss after renal transplantation.