叶酸代谢相关基因多态性及血浆同型半胱氨酸与唐氏综合征关系研究

目的研究叶酸代谢相关的亚甲基四氢叶酸还原酶(methylenetetrahydrofolate reductase,MTH-FR)基因多态性与唐氏综合征(Down syndrome,DS)发生的关系。方法选择100例生育过DS患儿的汉族母亲及100名相匹配的正常对照组母亲,PCR-限制性片段长度多态性方法检测MTHFR677C/T的基因型,化学发光法检测血浆中同型半胱氨酸(homocysteine,HCY)的水平。结果病例组MTHFR677T等位基因的频率较对照组增高,差异有统计学意义(P=0.002);杂合基因型CT的比值比为2.12(95%CI:1.14～3.94);而纯合基因型TT的比值比为3.43(95%CI:1.41～8.36)。平均血浆HCY浓度在病例组[(9.04±3.85)μmol/L]较对照组[(6.53±2.06)μmol/L]增高,差异有统计学意义(P<0.01)。MTHFR677位点一个和(或)两个等位基因C→T的变异,不论在病例组还是对照组均可引起HCY水平的显著增加(P<0.01)。同为MTHFR677CC基因型,病例组中的血浆HCY浓度仍较对照组增高(P<0.01),这种增加不依赖于MTHFR的基因型。结论血浆HCY和叶酸代谢相关基因的遗传多态性是汉族妇女生育DS患儿的危险因素。

The relationship between polymorphism of gene involved in folate metabolism, homocysteine level and risk of Down syndrome

OBJECTIVE: To investigate whether the polymorphism in methylenetetrahydrofolate reductase (MTHFR) gene involved in folate metabolism is associated with Down syndrome (DS). METHODS: One hundred Chinese mothers who gave birth to babies with DS and 100 control mothers were chosen. Genotype of MTHFR 677 was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and concentration of plasma homocysteine (HCY) was measured by chemiluminescence. RESULTS: The MTHFR 677T allele frequency was significantly different among case mothers, compared with control mothers (P=0.002); the odds ratio for the heterozygous CT genotype was 2.12 (95%CI: 1.14-3.94), whereas for the homozygous TT genotype, the odds ratio was 3.43 (95%CI:1.41-8.36). The mean plasma HCY concentration [(9.04 +/- 3.85) mu mol/L] of cases was significantly different from that of controls [(6.53 +/- 2.06) mu mol/L](P <0.01). The presence of the 677C>T substitution in one or both alleles was associated with increased plasma HCY both in case mothers and control mothers (P < 0.01). Interestingly, although both being MTHFR 677CC, the plasma HCY concentrations were higher in case mothers than in control mothers, the increase was not dependent on MTHFR genotype (P < 0.01). CONCLUSION: Our results provide evidences that plasma HCY and genetic polymorphism in gene of folate pathway are risk factors for mothers to have a DS child in China.