L-精氨酸对原发性高血压影响的临床研究

目的:从血流动力学及神经内分泌学两方面探讨左旋精氨酸(L-Arg)-一氧化氮(NO)通路对原发性高血压的影响。方法: 选择24例高血压病人随机分为两组,一组静滴L-Arg ,一组静滴生理盐水,观察其血压、心率及心功能,同时检测血浆中NO、血管紧张素Ⅱ(AngⅡ)、内皮素(ET)、血栓素A₂(TXA₂)以及前列环素(PGI₂)以探讨其降压机理。 结果:L-Arg治疗后,病人血压下降、心率增快,心输出量(CO)、每搏输出量(SV)、射血分数(EF)增加,总外周阻力(TPR)降低,血浆NO、PGI₂含量升高,ET、AngⅡ、TXA₂水平降低。静滴80 min时,随NO浓度降低CO、SV、EF也随之降低,而TPR又回升,血浆ET、AngⅡ发生相应变化,TXA₂、PGI₂无明显改变。结论:L-Arg通过直接升高血浆NO水平引起血流动力学改变,通过间接反馈效应改变ET、AngⅡ水平,并可抑制血小板聚集。     

MTHFR基因C677T多态性与冠心病患者血浆同型半胱氨酸和叶酸水平相关

目的研究宁夏地区汉族人群5,10-亚甲基四氢叶酸还原酶基因(MTHFR)C677T多态性、同型半胱氨酸水平(Hcy)及叶酸水平与冠心病(CHD)的相关性。方法用病例-对照研究方法、应用限制性片段长度多态性扩增技术(PCR-RFLP)分析宁夏地区汉族202例冠心病患者及199例正常人群MTHFRC677T基因型频率及基因频率的分布特点。荧光偏振免疫分析法测定血浆Hcy水平,化学发光免疫分析法测定血清叶酸、VitB12浓度。结果 (1)病例组与对照组MTHFRC677T基因型频率分别为CC型23.3%vs20.7%、CT型52.3%vs54.5%和TT型24.4%vs24.8%,两组间基因型及等位基因频率分布无差异。(2)冠心病患者组中MTHFR基因C677TCC基因型患者血浆Hcy浓度(10.84μmol/L)较T基因携带者(12.24μmol/L)低(P<0.01)。CC基因型患者血浆叶酸浓度(5.38μg/L)较T基因携带者(3.72μg/L)高(P<0.05)。结论 MTHFRC677T的3种基因型频率在宁夏汉族冠心病患者和正常人群中的分布无统计学意义。MTHFR基因C677T多态性与冠心病的危险因素Hc...     

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。     

亚甲基四氢叶酸还原酶基因677C→T突变与糖尿病微血管病

目的 研究中国人群2型糖尿病患者中,亚甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase,MTHFR)基因677C→T突变与糖尿病微血管病的关系。方法 将168名研究对象分为正常对照组、糖尿病和糖尿病微血管病（diabetic microangiopathy,DMA)组,采用PCR－RFLP检测各组MTHFR677C→T突变,统计各组对象的突变频率。结果 与无糖尿病微血管病患者和正常人相比,糖尿病微血管病患者MTHFR677C→T（T／T基因型）变频率更高（22．6％vs6.7%和5．5％,P＜0．01）,MTHFRT／T基因型对MDA的OR值为3．36,P＜0．001。结论 糖尿病患者中MTHFR677C→T突变为其发生微血管病的一种遗传易感因素。     

血浆Hcy水平及MTHFR和MTRR基因多态性与复发性流产的相关性研究

目的探讨血清同型半胱氨酸(Hcy)水平及亚甲基四氢叶酸还原酶(MTHFR)、甲硫氨酸合成酶还原酶(MTRR)基因多态性与不明原因复发性流产的相关性。方法以84例复发性自然流产的患者作为病例组,60例已有1次正常生育史,且既往无不良孕产史的妇女作为对照组,应用荧光定量PCR技术检测MTHFR基因C677T、A1298C和MTRR A66G位点的多态性,同时应用比色法检测血清Hcy水平。比较病例组和对照组间各种基因型和血清Hcy水平的差异。结果病例组血清Hcy水平明显高于对照组;高Hcy是先兆流产的危险因素(OR=2.132,P=0.021);MTHFR C677位点TT基因型携带者血清Hcy水平明显高于其他基因型;A1298位点CC基因型携带者血清Hcy水平明显高于AA野生型;MTRR A66位点GG基因型携带者血清Hcy水平明显高于其他基因型,差异均有统计学意义(P0.05)。结论 Hcy升高是导致复发性流产的重要危险因素;MTHFR基因C677T、A1298C和MTRR A66G位点的多态性改变均可致血清Hcy水平升高,与复发性流产的发生有一定的相关性。     

血管紧张素Ⅱ对心房颤动患者外向钾电流的作用

目的：研究血管紧张素Ⅱ(AngⅡ)对心房颤动(AF)患者心房肌外向钾电流的作用及其受体机制。方法: 采用急性酶解法获取游离心房肌细胞，应用膜片钳全细胞技术记录外向钾电流。结果: (1) 在钳制电位-10 mV~+50 mV时, AF组瞬时外向钾电流(I_to1)密度明显低于窦性心律(SR)组（P<0.01），而持续性外向钾电流（I_sus）密度与SR组无明显差异。(2) 以0.1 μmol/L AngⅡ灌流后，在钳制电位0 mV~+50 mV时，SR患者的Ito1密度明显低于灌流前（P<0.01），其动力学特性没有改变，AngⅡ对AF组I_to1的抑制作用明显低于SR组 (P<0.01)。0.1 μmol/L AngⅡ对两组I_sus没有影响。(3) AngⅡ对Ito1的抑制作用可逆，10 μmol/L缬沙坦（valsartan）以及1 μmol/L沙拉新(saralasin)均能完全消除0.1 μmol/L AngⅡ对Ito1的抑制，以10 μmol/L valsartan灌流后，膜电位+50 mV时I_to1的电流密度增加（22.46±4.30）%。结论: AngⅡ通过Ⅰ型受体（AT₁R）介导，明显抑制心房肌细胞膜I_to1，是AF患者心房肌瞬时外向钾通道电重构的机制之一。     

Ang Ⅱ对成年大鼠心肌成纤维细胞分泌ET-1、NO功能的影响

目的：探讨血管紧张素Ⅱ（Ang Ⅱ）对成年大鼠心肌成纤维细胞（MFs）分泌内皮素-1（ET-1）、一氧化氮（NO）的影响。方法：采用酶消化法和差速贴壁分离法获取MFs，应用放射免疫分析法、硝酸还原酶法分别测定不同条件下培养的第二代心肌MFs培养液中的ET-1、NO水平。结果：一定浓度范围内的Ang Ⅱ可按剂量依赖方式促MFs分泌ET-1, 血管紧张素Ⅱ1型受体（AT₁R）拮抗剂losartan可阻断Ang Ⅱ的上述作用；Ang Ⅱ可抑制心肌MFs分泌NO，加losartan后再加Ang Ⅱ培养发现，MFs分泌NO能力不但不降低，而且还高于对照组（P<0.01）。结论：Ang Ⅱ可通过AT₁R促成年大鼠心肌MFs分泌ET-1，主要通过AT₁R影响MFs分泌NO，从而改变ET-1/NO比值。Ang Ⅱ可能通过影响MFs分泌的生物活性物质网络平衡关系改变，发挥其促心肌肥厚及心力衰竭效应。     

河源地区汉族女性MTHFR基因多态性调查及其与血清HCY水平相关性的研究

目的调查广东省河源地区汉族女性5,10-亚甲基四氢叶酸还原酶(MTHFR)C677T、A1298C位点基因多态性分布特征,研究分析遗传因素与血清同型半胱氨酸(HCY)的相关性,为本地区育龄妇女个性化补服叶酸及出生缺陷的一级预防提供依据。方法以该地区1423位汉族女性为研究对象,检测其MTHFR C677T、A1298C基因位点多态性,与我国其他南北各地区既有数据对比,采用统计学方法分析基因的多态性分布特征;对其中418位孕期女性测定血清同型半胱氨酸浓度,分析该生化指标与遗传因素的相关性。结果本地区的汉族女性MTHFR 677TT基因型频率(7.4%),MTHFR 1298CC基因型频率(5.6%)。C677T和A1298C位点三种基因型间血清HCY水平差异无统计学意义(P0.05)。结论本地区汉族女性MTHFR基因C677T、A1298C位点多态性分布特征有其自身的特点;基因位点的多态性变化对血清同型半胱氨酸水平无显著性影响。     

MTHFR C677 T基因多态性及血浆HCY与复发性流产的关系

目的探讨亚甲基四氢叶酸还原酶基因多态性(MTHFR C677T)及血浆同型半胱氨酸(HCY)与复发性流产的关系。方法非孕期复发性流产患者100例,对照组50例,MTHFR基因C677T多态性采用聚合酶链反应-限制性片段长度多态性技术检测,HCY检测采用酶循环法于全自动生化分析仪上完成。结果病例组的HCY水平明显高于对照组,差异有统计学意义(P0.05);对两组进行MTHFR基因型及频率分析,病例组TT基因型虽较对照组高,但差异无统计学意义(P0.05);组别和基因型间的HCY水平的比较,得出组别和基因型之间HCY水平差异均具有统计学意义(P0.05)。不同基因型进行组内两两比较,得出TT与CT、CC均具有统计学差异,CT、CC之间没有统计学差异。结论患者MTHFR C677T突变及血浆HCY水平的增高与复发性流产关系密切。     

MTHFR C677T多态性与脓毒血症的关系

目的 探讨MTHFR C677T基因多态性（SNP）与脓毒血症的关系。方法 选择2014年1月~2018年6月我院住院的脓毒血症患者98例,采用梯度PCR及DNA测序技术,检测MTHFR C677T基因型,比较不同T淋巴细胞凋亡比例脓毒血症患者MTHFR C677T基因型分布情况及MTHFR C677T多态性与脓毒血症的关系。结果 MTHFR C677各位点基因型在T淋巴细胞中的凋亡比例方面比较,差异均无统计学意义（P＞0.05）;APACHEⅡ＜4分,SOFA＜2分的CT比例高于CC与TT基因型,降钙素原减少比例TT低于CC基因型与CT基因型,差异均有统计学意义（P＜0.05）,28 天死亡人数比例TT低于CC基因型与CT基因型,差异均有统计学意义（P＜0.05）。结论 MTHFR C677T与脓毒血症患者预后有关,可根据MTHFR C677T的基因多态性预测脓毒血症的预后。     

Methylenetetrahydrofolate reductase polymorphism and pre-eclampsia.

A common missense mutation in the methylenetetrahydrofolate reductase (MTHFR) gene, a C to T substitution at nucleotide 677, is responsible for reduced MTHFR activity and associated with modestly increased plasma homocysteine concentrations. Since underlying maternal vascular disease increases the risk of pre-eclampsia, we had the working hypothesis that pre-eclampsia patients would have an increased T677 allele frequency compared with controls. The MTHFR genotypes were determined in 67 pre-eclampsia patients, 98 normal pregnant women, and 260 healthy adults by the PCR/RFLP method. The T677 allele and the genotype homozygous for the T677 allele were significantly increased in the pre-eclamptic group compared with the controls (p < 0.02 and p < 0.004, respectively). The data indicate that the T677 variant of the MTHFR gene is one of the genetic risk factors for pre-eclampsia.     

同型半胱氨酸代谢酶基因多态性与深静脉血栓的相关性研究

目的探讨亚甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase，MTHFR）基因C677T、甲硫氨酸合成酶（methionine synthase，MS）基因A2756G和胱硫醚β-合成酶（cystathionine β-synthase，CBS）基因844ins68这3种基因突变在深静脉血栓发病中的意义。方法应用聚合酶链反应-限制性片段长度多态性方法对103例深静脉血栓患者和250名健康对照者进行MTHFR C677T、MS A2756G和CBS 844ins68基因多态性的分析，并进行基因型及等位基因频率的计数。对MTHFR C677T和MS A2756G两位点进行单倍型分析。结果MTHFR C677T TT基因型在深静脉血栓组的分布频率（27．2％）高于对照组（17．2％），经χ^2检验差异有统计学意义（P〈0．05）。MS A2756G AG基因型在深静脉血栓组的分布频率（9．7％）低于对照组（19．2％），经χ^2检验差异有统计学意义（P〈0．05）。单倍型分析显示病例组中677T-2756A单倍型频率明显高于对照组（P〈0．05），677C-2756A单倍型频率明显低于对照组（P〈0．05）。CBS 844ins68基因型在两组的分布频率差异无统计学意义。结论MTHFR C677T多态性中TT基因型可能是深静脉血栓形成的一个遗传风险因子，MS 2756 AG基因型可能会减少深静脉血栓的发生。677T-2756A单倍型可能是静脉血栓的危险因素，677C-2756A单倍型可能是静脉血栓的保护因素。CBS 844ins68基因突变可能存在种族或地域的差异。     

Role of a common mutation in the homocysteine regulatory enzyme methylenetetrahydrofolate reductase in ischemic stroke.

A common mutation in methylenetetrahydrofolate reductase (MTHFR), a homocysteine metabolic pathway enzyme, has been associated with increased homocysteine levels and increased risk for premature cardiovascular disease. The purpose of this study was to assess the association between the prevalence of the MTHFR mutation, hyperhomocysteinemia, and subtypes of ischemic stroke in an elderly population comprised of three age-balanced groups of patients. The presence of the C677T MTHFR mutation was determined by a direct polymerase chain reaction-based assay performed on blood samples from 136 patients with acute ischemic stroke, 95 patients with atherosclerotic risk factors for stroke (including some with a history of previous stroke or transient ischemic attack), and 52 healthy control subjects. The prevalence of the homozygous C677T mutation was not significantly higher in the elderly stroke patients (7%) than in the atherosclerotic risk (8%) or healthy elderly control (2%) groups. Plasma homocysteine levels were higher in the acute stroke patient group (14.5+/-4.5 micromol/L) and atherosclerotic risk patient group (14.6+/-6.2 micromol/L) compared with the control subjects (10.3+/-3.1 micromol/ L, P < 0.03). Homozygotes for the C677T MTHFR mutation did not have significantly higher homocysteine levels than non-homozygotes. Moderate hyperhomocysteinemia, though common in older patients with ischemic cerebrovascular disease, is not attributable, at least in this patient group, to a higher prevalence of the C677T MTHFR mutation.     

Methylenetetrahydrofolate reductase and spina bifida: evaluation of level of defect and maternal genotypic risk in Hispanics

The C677T and A1298C mutations in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene are each associated with reduced MTHFR activity. The C677T mutation in the heterozygous and homozygous state correlates with increased enzyme thermolability, with homozygous mutant genotypes showing significantly elevated plasma homocysteine levels and decreased plasma folate levels. The A1298C mutation results in decreased MTHFR activity, but changes in neither homocysteine nor folate levels are associated with A1298C variant genotypes. Our study determined the frequencies of the C677T and A1298C MTHFR mutations for spina bifida (SB) cases, mothers and fathers of SB cases, and controls in Hispanics of Mexican-American descent. In addition, our subject population was further categorized as to whether the spina bifida lesion occurred as an upper or lower level defect, according to the Van Allen "multi-site closure" model. Hispanic SB cases with upper level defects and their mothers were homozygous for the C677T variant allele at a higher rate than their respective controls (OR = 1.5 [95% CI 0.8-2.9], P = 0.30; OR = 2.3 [1.1-4.8], P = 0.04, respectively), with statistically significant results seen only for the maternal homozygous genotype. Homozygosity for the A1298C mutation was seen at a higher rate only in Hispanic mothers of both upper and lower level SB cases when compared to controls, but these results were not statistically significant. Our study provides evidence that the maternal C677T MTHFR homozygous mutant genotype is a risk factor for upper level spina bifida defects in Hispanics.     

Methylenetetrahydrofolate reductase polymorphism (c677t) in muslim population of eastern uttar pradesh, India

Objective : The aim of the present study was to investigate the distribution of methylenetetrahydrofolate reductase (C677T) polymorphism in the Muslim population of eastern Uttar Pradesh. Materials and Methods: Total 56 subjects were analysed for MTHFR C677T polymorphism. C677T mutation analysis was done according to the PCR-RFLP (Polymerase chain reaction-Restriction fragment length polymorphism) method. Results : The frequencies of three genotypes CC, CT, and TT were 0.857, 0.125, and 0.07, respectively, and the frequency of mutated T allele was found to be 0.080. Conclusion : Genotypes and allele frequencies revealed the low prevalence of MTHFR C677T polymorphism in Indian Muslims. C677T mutation has been suggested to be positively associated with the risk of several congenital and multifactorial disorders. The low frequency of T/T genotype in the Muslim population may be due to malnutrition in pregnant women, because of insufficient intake of folate is considered to be a survival disadvantage for foetuses with T/T genotype.     

甲基四氢叶酸还原酶基因多态性与糖尿病肾病关系的研究

目的：探讨甲基四氢叶酸还原酶（methylenetetrahydrofolate reductase,MTHFR)基因多态性与糖尿病肾病（diabetic nephropathy,DN)发生的关系。方法：利用聚合酶链反应－限制性片段长度多态性分析法（PCR－RFLP）检测了85名健康人和经尿微量白蛋白检测确诊的82例合并DN和79例无DN的2型糖尿病患者MTHFR基因第677位碱基多态性。结果：DN患者MTHFR基因变异型纯合子和等位基因频率均明显高于无肾病患者及健康者,P＜0．01。结论：MTHFR基因第677位碱基变异可能是中国汉族人DN发生的一个遗传危险因子。     

MTHFR基因C677T多态性与Down综合征发生的相关研究

目的研究亚甲基四氢叶酸还原酶(MTHFR)基因C677T多态性与Down综合征关系。方法采用聚合酶链反应—限制性片段长度多态性(PCR-RFLP)法对32例DS患儿母亲,70例未生育DS患儿女性MTHFR的C677T进行基因分析。比较上述各组基因型和等位基因频率分布有无差异。结果MTHFR基因C677T突变型等位基因(T)频率在实验组和对照组中有显著性差异,CC、TT基因型频率分布差异有显著性(P<0.05)。CT基因型比CC基因型生育DS患儿风险高2.84倍,TT基因型比CC基因型生育DS患儿风险高9.26倍。结论MTHFRC677T基因多态性与Down综合征发生相关,TT基因型增加了Down综合征的发生风险,CC基因型是降低Down综合征发生的保护性因素。     

Polymorphisms of methylenetetrahydrofolate reductase gene among women of childbearing age from Shiyan areaCSCD

Objective: To assess the association of methylenetetrahydrofolate reductase (MTHFR) gene 677C>T polymorphism with blood homocysteine (Hey) level among women of childbearing age from Shiyan area. Methods: PCR - chip hybridization was used to determine the genotype of MTHFR 6770T, and a biochemical assay was used to determine the total Hey level among 428 healthy women of childbearing age. Association of MTHFR 677>T with total Hey level was assessed. Results: Heterozygous CT mutation was most common form for the MTHFR 677>T polymorphisms and amounted for 49. 77% among the group, while the CC wild type and homozygous TT mutation respectively accounted for 30. 61% and 19. 63%. These gave a frequency of 44. 51% for the 677T allele. The dominant genotype among different age groups were the CT type. Of note, the proportion of MTHFR 677CC is higher in women above 30 years of age. The distribution of MTHFR 677>T genotypes has differed significantly among different age groups (P<0. 05). Compared with those with wild type alleles, carriers of MTHFR mutations had a higher plasma Hey level. The genotypic frequencies of MTHFR C677T in Shiyan region differed significantly from those of Sichuan, Hebei, Henan and Shandong (P < 0. 05) but were similar to those of Jiangsu, Guangdong, Ningxia and Xinjiang. Conclusion: The distribution of MTHFR C677T polymorphism among women of childbearing age in Shiyan area is influenced by age and is geographically specific and associated with plasma Hey level. Nearly 50% of women have carried the high risk alleles, for whom folic acid supplementation is crucial for the reduction of birth defect rate. © 2018 MeDitorial Ltd. All rights reserved.     

The C677 mutation in methylene tetrahydrofolate reductase gene: correlation with uric acid and cardiovascular risk factors in elderly Korean men

The C677T mutation in the methylene tetrahydrofolate reductase (MTHFR) gene results in elevated homocysteine levels and, presumably, in increased cardiovascular risk. Moreover, elevated homocysteine levels are reportedly associated with high serum uric acid levels. We evaluated the MTHFR genotype and a panel of biochemical, hematological variables, and lifestyle characteristics in 327 elderly Korean men (age range 40-81 yr; mean, 51.87). This study shows that mutation of the MTHFR gene may be a risk for hyperuricemia. The mean uric acid levels for the C/C, C/T and T/T genotypes were 5.54, 5.91 and 6.33 mg/dL, respectively (p=0.000). The T/T genotype was significantly more frequent in subjects with high uric acid levels (p=0.003). Thus, this mutation of the MTHFR gene is implied by the study results to be a risk factor of hyperuricemia in elderly Korean men. However, the relationship between the MTHFR mutation and uric acid metabolism remains unclear. Therefore, further studies are necessary to explain the associated between the MTHFR mutation and elevated uric acid levels, and to examine potential relationships between it and conventional cardiovascular risk factors.     

Association of methylenetetrahydrofolate reductase C677T and A1298C polymorphisms with myocardial infarction in Tunisian young patients

Myocardial infarction (MI) is an important clinical problem because of its large contribution to mortality. The objective of this study is to assess whether two methylenetetrahydrofolate reductase (MTHFR) polymorphisms, C677T and A1298C, were associated with MI among Tunisian patients. One hundred young patients (<47 years old) with MI were recruited and compared with 200 control subjects with no history of MI. The most common MI risk factors were investigated. Fasting plasma homocysteine levels were measured. Genotypes of the MTHFR C677T and A1298 polymorphisms were studied by polymerase chain reaction. The mean plasma homocysteine level in the study group was raised when compared with the control group. Homozygous MTHFR C677T mutation was observed in 2 (2 %) patients and in 17 (8.5 %) control subjects, whereas heterozygous MTHFR C677T mutation was detected in 82 (82 %) patients versus only 79 (39.5 %) in control subjects. The mean total homocysteine concentrations were significantly higher in individuals with the 677TT and CT genotypes. Our results indicate that C677T and A1298C MTHFR mutations and hyperhomocysteinemia contributed to the risk factors for MI.