DOES THE VITAMIN-D-RECEPTOR GENOTYPE PREDICT BONE-MINERAL LOSS IN HEMODIALYZED PATIENTS

Background. It has been suggested that the vitamin D receptor (VDR) ge ne BsmI-polymorphism is a genetic determinant of bone metabolism. Desi gn. To test this hypothesis, the relationship between VDR genotypes, b one mineral density (baseline and after 18 months) and parameters of c alcium metabolism and bone turnover were investigated prospectively in 88 haemodialysed patients not receiving active vitamin D metabolites. Methods. Whole body, lumbar spine and femoral neck bone mineral densi ty (BMD) were assessed by dual energy X-ray absorptiometry (DEXA). In addition calcium, phosphorus, 25(OH)D3, 1,25(OH)(2)D3, osteocalcin ser um concentrations, alkaline phosphatase activity and intact 1,84 PTH l evels were measured. Results. VDR genotype BE, Bb and bb were found in 27, 49 and 24% of patients. Initial BMD (g/cm(2)) of whole body, lumb ar spine and femoral neck did not differ between genotypes (whole body : BE 1.055+/-0.120, Bb 1.082+/-0.102, bb 1.128+/-0.120; lumbar spine: BE 1.075+/-0.199, Bb 1.079+/-0.185, bb 1.099+/-0.170; femoral neck: BE 0.808+/-0.160, Bb 0.862+/-0.127, bb 0.842+/-0.125; mean+/-SD), but th e decrease of whole body and femoral neck BMD during 18 months was sig nificantly (P < 0.02) different between the genotype groups (whole bod y: BE -0.048 +/- 0.028, Bb -0.031+/-0.029, bb -0.024+/-0.023; femoral neck BE -0.044+/-0.069, Bb -0.032+/-0.081, bb -0.012+/-0.029 g/cm(2)). Conclusion. This preliminary study suggests faster mineral loss in BE genotype of VDR in haemodialysed patients.