COMT和MTHFR基因单体型及其血浆蛋白的表达与神经管畸形的相关性研究

Our previous study have shown that daily tea drinking during the periconceptional period was associated with a 3-fold elevated risk of NTDs (neural tube defects, NTDs) in the study population of North China. The active compounds in tea are believed to be tea polyphenols (primarily catechins and gallocatechins). Due to the similarity in molecular structure to folic acid, tea polyphenols competitively inhibit dihydrofolate reductase (DHFR) in cellular folate metabolism pathways and hence to decrease availability of folate or impaired folate metabolism. Methylation catalyzed by catechol-Omethyl transferase (COMT) represents a major metabolic pathway for tea polyphenols. Since the metabolic pathways of COMT and MTHFR are interconnected, variations in methylenetetrahydrofolate reductase (MTHFR) and COMT have been associated with elevated homocysteine, a risk factor for NTDs. In the present case-control study (600 cases and 600 controls), we would investigate the association between COMT/MTHFR haplotypes and NTDs. Enzymatic activity in the protein level would be evaluated to test the relationship of the functional variation linked to COMT and MTHFR haplotypes and NTDs. Environmental factors, such as smoking/passive smoking, folate, tea drinking, pesticide, organic solvent, heavy metal and nutrition status, would be considered as confounding factors. Finally, we would assess if there exist an interaction between COMT and MTHFR SNPs and environmental factors (tea drinking and exposure of heavy metal). The result would contribute to clarify the mechanism of NTDs and provide more specific preventive measures of birth defects.

本课题组前期研究发现孕前及孕早期饮茶增加生育神经管畸形（NTDs）患儿的风险，推测茶叶中活性物质儿茶酚影响叶酸的代谢可能与儿茶酚胺氧位甲基转移酶（COMT）和5,10-亚甲基四氢叶酸还原酶（MTHFR）的基因多态性有关。本课题拟通过分析已收集到的600对病例对照（病例组为生育NTDs患儿的母亲，对照组为同期生育正常儿的母亲）的调查问卷和生物标本信息（血液和胎盘），通过检测COMT和MTHFR基因的多态性并构建单体型，同时测定血浆中COMT和MTHFR的蛋白表达、血浆和胎盘中重金属含量，分析环境因素（饮茶、重金属）和遗传因素（COMT和MTHFR多态性）的交互作用对NTDs发生的影响。该研究对于进一步阐明NTDs的发病机制和确定筛选高危人群或易感个体的分子标志物具有理论意义，从而为实施目标明确的个体预防、制定基于人群的预防干预措施提供理论依据。

神经管畸形（neural tube defects，NTDs）是最常见和严重的出生缺陷，是围产儿死亡和儿童肢体残疾的主要原因之一。本课题组前期研究发现妇女孕前及孕早期饮茶增加生育NTDs患儿的风险，但是机制不明。有报道欧洲人群中儿茶酚胺氧位甲基转移酶（Catechol-O-methyltransferase，COMT)基因多态性与后代脊柱裂有关，中国人群中有待验证。.本课题通过在出生缺陷高发区以人群为基础的出生缺陷监测系统收集NTDs病例资料，采用1:1匹配病例——对照研究，利用问卷调查收集研究对象人口学特征、居住环境、营养状况、生活方式等背景因素，收集研究对象的全血和胎盘标本进行检测，探讨中国妇女COMT和MTHFR基因多态性、环境因素（饮茶、重金属）和遗传因素（COMT和MTHFR多态性）交互作用与NTDs易感性的关系。.研究完成576例神经管畸形和594例正常对照母亲血液的COMT和MTHFR基因型检测，结果发现，在控制了混杂因素的作用下，COMT基因的rs737865位点CC基因型显著增加NTDs（OR = 2.04, 95% CI, 1.24–3.35)和无脑儿发生风险(OR = 1.99, 95% CI, 1.17–3.39)。rs4633位点CC基因型与NTDs的发生风险显著相关(OR = 3.66, 95% CI, 1.05–12.83)。饮茶和 rs4680AA/AG 基因型的交互作用可能在脊柱裂的发生中起作用(P=0.08)。MTHFR C677T TT基因型增加NTDs(OR=1.37, 95 % CI=0.93–2.03)和无脑儿的发生风险(OR=1.67, 95 % CI=0.98–2.84)。COMT rs737865 CC 和MTHFR rs1801133 TT 交互作用显著增加NTDs(OR=3.02, 95 % CI=1.00–9.14)和无脑儿(OR =3.39, 95 % CI=0.94–12.18)发生风险。.该研究初步验证了我国神经管缺陷高发区域育龄妇女COMT基因多态性与后代NTDs的发生有关；在NTDs的发生中，环境（饮茶）和基因（COMT）、基因和基因之间（COMT和MTHFR）存在交互作用。研究对于进一步阐明NTDs的发病机制，确定筛选高危人群的分子标志物，制定实施基于人群的预防措施提供重要理论依据。