The effect of vitamin D receptor BsmI genotype on the response to osteoporosis treatment in postmenopausal women: A pilot study

Aim: The purpose of our study was to investigate the possible effect of BsmI vitamin D receptor (VDR's) polymorphism on changes in bone mineral density (BMD) and bone turnover markers in postmenopausal women receiving different treatments. Material and Methods: This pilot study included 42 postmenopausal women with elevated fracture risk, randomized into 1-year treatment with weekly oral alendronate or daily subcutaneous teriparatide. Both groups received daily supplements of 1000 mg calcium and 800 IU vitamin D. Blood samples were obtained for biochemical evaluation and genotyping. BMD at the lumbar spine and femoral neck were assessed with dual energy X-ray absorptiometry. Baseline, follow-up BMD and markers of bone turnover were assessed according to the BsmI genotype. Results: BMD at the lumbar spine increased in patients carrying at least one b allele, while it decreased in patients with the BB genotype (P = 0.041). Whereas no gene-treatment interaction was observed in teriparatide-receiving patients, women with the BB genotype receiving alendronate resulted in negative BMD (-0.056 +/- 0.032 g/m(2)) and T-score (-0.295 +/- 0.190) gradient, compared to carriers of the b allele (BMD: +0.020 +/- 0.017 g/m(2), P = 0.054; T-score: +0.217 +/- 0.100, P = 0.030). No effect of genotype was apparent with respect to gradients of biochemical bone markers. Conclusions: These preliminary results indicate that alendronate has a differential effect on BMD, depending on the VDR genotype. Carriers of the b allele may be more responsive to treatment compared to patients with the BB genotype. The interaction of VDR's BsmI polymorphism with the efficacy of the anti-osteoporotic treatment needs further investigation by larger prospective studies.