维生素D受体基因起始密码子和CDX2多态性与钙剂补充对绝经后妇女骨密度作用的关系

目的了解维生素D受体（vitamin D receptor，VDR）基因（VDR）起始密码子（Fok Ⅰ位点）和启动子区CDX2结合位点多态性与绝经后妇女钙剂补充对骨密度（bone mineral density，BMD）和骨转换指标作用的关系。方法200名受试对象（均为上海市汉族无亲缘关系的绝经后妇女）分为两组：高钙组（日服元素钙1000mg和维生素D400IU）和低钙组（日服元素钙300mg和维生素D300IU）各100名，期限1年。检测治疗前后BMD和骨转换指标，以及VDR基因Fok Ⅰ位点和CDX2结合位点多态性。结果其中171名完成整个研究。研究人群础Ⅰ基因型频率分布依次为Ff（48．0％）、FF（31．0％）和ff（21．0％）；CDX2基因型频率分布依次为AG（56．7％）、GG（25．7％）和AA（17．6％），上述等位基因频率分布在整个人群或2亚组中均符合Hardy-Weinberg定律。无论在整个人群组、或是2亚组中，Fok Ⅰ或CDX2各基因型间各部位BMD和各骨转换指标的基线值差异均无统计学意义；钙剂补充1年时，各部位BMD和骨转换指标的终点值和变化的百分数与Fok Ⅰ或CDX2多态性均无相关性。结论高钙或低钙的补充对上海市汉族绝经后妇女BMD或骨转换指标的影响与VDR基因Fok Ⅰ或CDX2多态性无相关性。

Relationship between the polymorphism of start codon and CDX2 site in vitamin D receptor gene and the effect of calcium supplementation on bone mineral density of postmenopausal women

OBJECTIVE: To investigate the association of polymorphisms of start codon (Fok I site) and CDX2 binding site in vitamin D receptor gene (VDR) concerned with the effect of calcium supplementation on bone mineral density (BMD) and bone turnover markers of postmenopausal women. METHODS: Two hundreds unrelated postmenopausal women of Han ethnicity in Shanghai were randomly divided into 2 groups of 100 women: high calcium group (1000 mg element calcium and 400 units of vitamin D were given daily for 12 months) and low calcium group (300 mg element calcium and 300 units of vitamin D were given daily for 12 months). BMD and bone turnover markers were measured at baseline and 12 months after calcium supplementation. VDR gene Fok I and CDX2 polymorphisms were analyzed using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and allele-specific multiplex PCR, respectively. RESULTS: One hundred and seventy-one women completed 12-month study period. The frequency of VDR Fok I genotypes was 48.0 % for Ff, 31.0 % for FF, and 21.0 % for ff, and the frequency of CDX2 genotypes was 56.7 % for AG, 25.7% for GG, and 17.6% for AA. The frequencies distribution of Fok I and CDX2 alleles in the entire population or in two subgroups all followed the Hardy-Weinberg equilibrium. No significant difference of baseline BMD and bone turnover markers in Fok I genotypes or CDX2 genotypes was observed in the entire population or in two subgroups. Moreover, regardless of calcium supplementation given for 12 months, no significant association was found between Fok I or CDX2 polymorphisms and the endpoint values or percentage changes of any BMD and bone turnover markers in either high calcium group or low calcium group. CONCLUSION: There is no significant relationship between VDR gene Fok I or CDX2 polymorphisms and the effect of high or low doses calcium supplementation on BMD and bone turnover markers in Shanghai postmenopausal women of Han ethnicity.