Association between Vitamin D Receptor Gene Polymorphisms and Renal Osteodystrophy in Patients on Maintenance Hemodialysis

We examined the possible involvement of vitamin D receptor (VDR) gene polymorphisms in patients on maintenance hemodialysis and further investigated the relation between VDR genotypes and bone histology. Two hundred and nine patients undergoing regular hemodialysis (male/female ratio, 124/85) were included in this study. DNA was extracted from peripheral blood leukocytes. VDR genotypes were analyzed as restriction fragment length polymorphisms, by using BsmI, ApaI, TaqI and FokI. Lumbar bone mineral density was measured by dual-energy X-ray absorptiometry, and expressed as a Z-score. Serum 1,25(OH)2D3, osteocalcin and ntact-parathyroid hormone (i-PTH) were determined by an immunoradiometric assay. In 97 patients, bone biopsy as performed and the histology was divided into osteitis fibrosa, mild lesion, dynamic bone disease and osteomalacia. Serum levels of osteocalcin, i-PTH and bone mineral density were significantly lower in the presence of B, A, t and f alleles. However, in this study, we did not find any association between bone histology and the four VDR genotypes. We concluded that renal osteodystrophy in dialysis patients was modified by environmental factors such as medication with active vitamin D, age, gender and duration of chronic renal failure, and that the impact of the VDR allelic effect may play a small role in determining on bone histology.