Methionine Synthase Reductase (MTRR) A66G polymorphism is not related to plasma homocysteine concentration and the risk for vascular disease

Epidemiological evidence has revealed that hyperhomocysteinemia increases the risk for vascular disease. Methionine Synthase Reductase (MTRR) is one of several key enzymes in the homocysteine metabolic pathway and its mutant forms have been implicated in abnormal homocysteine accumulation. In this study, we determined total plasma homocysteine levels and MTRR A66G polymorphism in 114 patients with vascular disease: 58 patients with deep-vein thrombosis, 56 patients with arterial thrombosis, and 95 healthy subjects from the Sicilian population. Our data confirmed that, as already reported, moderately elevated t-Hcy levels are correlated with an increased risk of vascular disease. In our study, the levels of t-Hcy found in both deep-vein thrombosis (13.7 ± 3.2 μmol/L) and arterial thrombosis (14.3 ± 4.3 μmol/L) patient groups were higher than levels detected in normal subjects (8.7 ± 2.7 μmol/L).We concluded that the MTRR A66G polymorphism was not associated with the t-Hcy plasma concentration because the same genotype frequency distribution was detected in both patients and healthy individuals.     

亚甲基四氢叶酸还原酶对胃癌细胞基因表达的影响

目的 分析亚甲基四氢叶酸还原酶（MTHFR）基因的真核表达质粒对人胃癌细胞生存力、DNA甲基化酶基因及肿瘤相关基因转录水平的影响。方法 分别构建含有人野生型（正义）MTHFR（W）和反义MTHFR（A）的真核表达质粒，将其转染入人胃癌MKN45细胞，噻唑蓝（MTT）法检测细胞生存活力，定量PCR检测DNA甲基化酶及胃癌相关基因的转录水平。结果 转染野生型MTHFR质粒的胃癌细胞生存活力增高（P〈0、01），而转染反义质粒者生存活力降低（P〈0．01）。野生型MTHFR质粒下调c-myc、p21WAF1a和hMLH1基因表达，反义MTHFR质粒的转染则无明显的基因调控作用。结论 重组MTHFR表达质粒可影响细胞生存活力及人胃癌细胞相关基因的表达，可望成为肿瘤基因防治的新靶点。     

尼克酰胺N-甲基化酶基因多态性对血清同型半胱氨酸的影响

目的探讨尼克酰胺N-甲基化酶(NNMT)A/G基因多态性与血清总同型半胱氨酸(tHcy)水平的关系,及其与叶酸和亚甲基四氢叶酸还原酶(MTHFR)C677T多态性的相互作用。方法采用横断面研究,选择日本某公司健康男性员工221例(40～64岁)为研究对象,应用LightTyper溶解曲线法和PCR-RLFP的方法分别检测NNMT A/G和MTHFR/C677T基因型。结果NNMT A/G各基因型受检者的血清tHcy水平间差异无统计学意义(P=0.254)。低叶酸水平者中NNMT GG基因型者与A等位基因携带者(GG和AA AG)的tHcy水平间差异有统计学意义(P=0.029),而这种差异在中、高叶酸水平者间均无统计学意义(P值分别为0.428、0.871);叶酸与NNMT A/G基因多态性存在相互作用(P=0.008)。低叶酸水平者NNMT A/G和MTHFR C677T两种基因型存在相互作用(P=0.034),携带NNMT GG基因的MTHFR TT基因型者其tHcy浓度与其他基因型个体间差异有统计学意义(P<0.001)。结论NNMTA/G多态性不是影响日本健康男性血清tHcy水平的独立危险因素,但其可能与叶酸、MTHFR C677T多态性存在相互作用而影响血清tHcy水平。     

新疆哈萨克族食管癌与叶酸摄入水平、亚甲基四氢叶酸还原酶基因多态关系的研究

目的探讨新疆哈萨克族人群食管癌与叶酸摄人水平及与叶酸代谢相关基因亚甲基四氢叶酸还原酶（MTHER）基因多态的关系。方法采用1：2配比的病例对照研究方法，收集120例哈萨克族食管癌患者，按同性别、同民族、年龄相差≤5岁、同一个居住地区等选取对照240例；选用聚合酶链反应-限制性片段长度多态性（PCR-RFLP）方法检测MTHFR C677T基因型，采用条件logistic回归进行统计分析。结果叶酸摄入量与哈萨克族食管癌有关（X^2=7．868，υ=1，P〈0．01），其OR值为0．519（95％CI：0．329-0．821），叶酸摄入水平高是保护因素；病例组和对照组MTHFR C677T基因型分布，经统计学检验，差异有统计学意义（X^2=15．823，υ=1，P〈0．01）；MTHFR 677CT、TT基因型个体发生食管癌的危险性是CC基因型个体的2．613倍（95％CI：1．628-4．194）；交互作用提示：叶酸摄入充足，可降低携带MTHFR 677CT、TT基因型个体发生食管癌的危险性。多因素条件logistic回归分析显示：饮用河水或渠水、饮食不规律、辛辣饮食、暴饮暴食、粮食存放超过1年、有食管或胃病变史√MTHFR677位点发生C→T改变等是哈萨克族食管癌的危险因素，叶酸摄入水平高是保护因素。结论叶酸摄入缺乏是新疆哈萨克族食管癌的主要危险因素；MTHFR C677T多态是哈萨克族食管癌的易感因素。     

血浆同型半胱氨酸与子(癎)前期发病的关系

目的 研究孕妇血浆同型半胱氨酸(homocysteine,Hcy)水平和亚甲基四氢叶酸还原酶(methylenetetrahydrofolate reductase,MTHFR)基因C677T的多态性,以探讨其在子癎前期发病中的作用.方法 选取子癎前期孕妇50例(子痴前期轻度14例,子癎前期重度36例),正常孕妇40例为研究对象.采用荧光偏振免疫法测定血浆Hcy水平,PCR法检测MTHFR基因C677T的多态性.结果 研究组Hcy水平显著高于对照组[(12.00±4.59)μmol/L和(7.85±1.51)μmol/L,P<0.05];轻度子癎前期组Hcy水平[(8.63±3.94)μmol/L高于对照组,但差异无统计学意义(P>0.05),重度子癎前期组Hcy水平(13.30±2.06)μmol/L]明显高于对照组(P<0.01);子痢前期组MTHFR基因677位点CT、TT基因型频率分布(C/T:42.0%;T/T:14.0%)和子癎前期组总的突变T等位基因频率(T:35.0%)均显著高于对照组(P<0.05).结论 血浆Hey水平升高可能是子瘸前期发病机制中的重要因素,而MTHFR基因C677T多态性影响了Hcy的代谢途径.可能是子癎前期的病因学机理之一.     

5,10-亚甲基四氢叶酸还原酶的基因组结构分析

目的：了解５，１０亚甲基四氢叶酸还原酶（ＭＴＨＦＲ）基因组外显子／内含子结构，为进一步的研究ＭＴＨＦＲ基因及寻找突变奠定基础。方法：根据报道的人肝ＭＴＨＦＲｍＲＮＡ序列设计引物，分段扩增基因组ＤＮＡ，进行双向测序，确定基因组序列。结果与结论：ＭＴＨＦＲ基因包括１１个外显子和１０个内含子，外显子的长度分别为９９～２５２ｂｐ，内含子长度分别为１９２～９８１ｂｐ。     

Prevalence of hyperhomocysteinemia and the MTHFR C677T polymorphism in patients with arterial and venous thrombosis from North Western Russia

Conflicting data from Western European and USA population studies led us to investigate hyperhomocysteinemia (HHcy), the methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms and thrombotic disease in North Western Russia. Plasma total homocysteine (tHcy) levels, MTHFR C677T genotype, selected life style determinants and haemostatic factor activity were determined in patients with arterial (n=33), venous (n=40), arterial+venous (n=11) thrombosis and healthy controls (n=30). We found raised median tHcy levels in all patient groups vs. controls (p<0.05), with odds ratios (95% CI) for vascular disease among patients with HHcy (defined as>15 μmol/l) of 3.9 (0.6–14.3), 4.8 (1.2–18.8) and 15.8 (2.8–87.3) respectively. tHcy levels were a function of MTHFR C677T genotype, and all patients with tHcy levels>30 μmol/l had the MTHFR C677T homozygous substitution. Elevated tHcy levels (p<0.05) were identified in smokers and coffee drinkers, with the degree of elevation dependent on MTHFR C677T genotype. Of the studied haemostatic parameters increased factor VIII activity and vWF antigen and activity was observed in HHcy subjects. We conclude that HHcy and MTHFR C677T genotype are positively associated with arterial and venous thrombotic disease in the population of North Western Russia.     

贞芪胶囊对非增殖型糖尿病视网膜病变大鼠视网膜中醛糖还原酶基因mRNA的表达

目的探讨益气养阴、祛瘀明目中药复方贞芪胶囊对糖尿病视网膜病变（Diabetic retinopathy，DR）大鼠血糖及视网膜中醛糖还原酶基因（Mdose Reductase，AR）mRNA表达的影响。方法高脂饮食喂养后采用脲链佐菌素（Streptozotocin，STZ）注射大鼠腹腔诱发糖尿病。在糖尿病大鼠病程3个月出现DR病理变化后用贞芪胶囊治疗，连续灌胃3个月，通过血糖的测定及逆转录-聚合酶链反应（RT—PCR）检测，探讨贞芪胶囊对DR大鼠血糖及视网膜中醛糖还原酶基因mRNA表达的影响。结果高脂饮食加链脲佐菌素诱导后3个月大鼠糖尿病视网膜病变造模成功；造模后及治疗前STZ大鼠血糖与空白对照组相比明显升高，差异有统计学意义（P〈0.01）；贞芪胶囊高、中、低剂量组AR mRNA水平均低于模型组和空白对照组，与模型组及空白对照组比较，差异均有统计学意义（P〈0．01）。结论贞芪胶囊可降低DR大鼠视网膜中醛糖还原酶基因mRNA表达，同时有一定降低血糖的作用。     

Prevalence of the methylenetetrahydrofolate reductase 677C > T mutation in the Mediterranean Spanish population. Association with cardiovascular risk factors

Methylenetetrahydrofolate reductase (MT-HFR) is a key enzyme involved in folate metabolism. A common cytosine (C) to a thymine (T) mutation at nucleotide 677 (677C > T) in the MTHFR gene which converts an alanine residue to a valine, has been related with several biochemical phenotypes and with cardiovascular risk, depending on the population studied. Our objective was to estimate the prevalence of the 677C > T mutation in a large and randomly selected sample (289 men and 427 women) from the Mediterranean Spanish population, and to test the association between this genetic variant and some cardiovascular risk factors. For both genders, the prevalence of CC, CT and TT subjects was 32.0, 52.2 and 15.8%, respectively. The frequency (95% confidence interval) of the 677T allele was 0.44 (0.40–0.48) in men and 0.40 (0.37–0.44) in women. This prevalence was significantly different from other European countries, and among the highest reported in the world for any healthy population. We found no association between the 677C > T gene variants and age, body mass index (BMI), total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides or diastolic blood pressure in men and women. However, in men, a statistically significant increase of systolic blood pressure with the number of mutant alleles was found (122.2 mmHg in CC, 125.1 mmHg in CT and 128.5 mmHg in TT subjects; p for trend = 0.030). This association remained significant (p = 0.047) even after adjustment for age, BMI, alcohol consumption, tobacco smoking, education and physical activity.