Lack of association between the MTHFR (C677T) polymorphism and atopic disease

Background: Impaired folate metabolism has been suggested as a potential risk factor for the development of asthma and atopic disease. However, there have been conflicting reports on the potential association between atopic disease and a common polymorphism of the methylene‐tetrahydrofolate reductase (MTHFR)‐gene, a well‐known marker of impaired folate metabolism. Objectives: The aim of this study was to investigate the association between the MTHFR (C677T) polymorphism and different outcome variables of asthma and atopic disease. Methods: This study was a population‐based study of 1189 participants aged 15–77 years living in Copenhagen, the Capital of Denmark. Examinations included measurements of specific IgE and skin prick tests against inhalant allergens, metacholine bronchial hyper‐reactivity, and serum eosinophilic cationic protein, and a self‐administered questionnaire about diagnoses and symptoms of allergy and asthma. In addition, participants were genotyped for the MTHFR (C677T) polymorphism. Results: None of the examined outcomes were significantly associated with the MTHFR (C677T) polymorphism. Conclusions: The results of this study using detailed objective markers of atopic disease do not support the hypothesis that impaired folate metabolism as reflected by the MTHFR genotype is involved in the development of atopic disease. Please cite this paper as: Thuesen BH, Husemoen LLN, Fenger M and Linneberg A. Lack of association between the MTHFR (C677T) polymorphism and atopic disease. The Clinical Respiratory Journal 2009; 3: 102–108.     

MTHFR C677T基因多态性与代谢综合征的相关性研究

目的探讨中国福建地区汉族人群N5,10-亚甲基四氢叶酸还原酶（MTHFR）基因C677T多态性与代谢综合征（metabolism syndrome,MS）病的关系。方法研究对象375例,其中正常对照组120例,MS组255例,采用PCR-RFLP方法和基因测序鉴定MTHFRC677T基因型,测定肌酐、尿酸、甘油三酯、空腹血糖等生化指标,统计分析采用卡方检验、方差分析、Logistic回归。结果MTHFRC677T基因型和等位基因频率在MS组和正常对照组间分布有统计学差异（P〈0.05）。MS组中CC、CT、TT各基因型的血尿酸水平依次递增,有显著性差异（P〈0.05）,经两两比较后,CT基因型的血尿酸水平较CC型高,差异有统计学意义（P〈0.05）。在调整了其它混杂因素的影响后,年龄、体重指数和携带T等位基因是MS的危险因素。结论MTHFR基因C677T多态性与尿酸水平和MS病相关。     

Methylenetetrahydrofolate reductase C677T-polymorphism and its association with alcohol withdrawal seizure

BACKGROUND: Elevated homocysteine plasma levels are considered as a risk factor for the occurrence of seizures during alcohol withdrawal. Homocysteine plasma concentrations seem to be influenced by the methylenetetrahydrofolate reductase (MTHFR) C677T-polymorphism. It was investigated whether the T-allele of the MTHFR C677T-polymorphism is associated with alcohol dependence, alcohol withdrawal seizure (WS), or the daily amount of alcohol consumption. METHODS: A group of 102 healthy controls and 221 alcoholic patients, including 97 patients with a history of mild withdrawal symptoms (MWS) and 70 patients with a history of alcohol WS, were genotyped, and personal data were collected for statistical evaluation in a case-control design. RESULTS: The T-allele is significantly associated with WS by comparing alcoholic patients with a history of WS (T-allele frequency: 0.39) and healthy controls (T-allele frequency: 0.28) (p=0.03). Although there was no significant difference between alcoholic patients with only MWS and alcoholic patients with a history of WS, a trend for the T-allele frequency among the analyzed subgroups was noticed: T-allele frequency increased from f(T)=0.28 in healthy controls to f(T)=0.33 in alcoholic patients with MWS up to f(T)=0.40 in alcohol-dependent men having a WS. Differences between healthy male controls and male alcoholic patients concerning the T-allele frequency also turned out to be significant [f(T)=0.27 vs f(T)=0.37; p=0.03]. Daily alcohol intake was independent of T-allele carrier status in alcohol-dependent patients. CONCLUSION: The present study suggests an influence of the MTHFR C677T-polymorphism on the etiology of alcohol WS and alcohol dependence in men in a western European population. An influence of MTHFR C677T on the daily amount of alcohol intake before admission among alcohol-dependent patients could not be shown.     

脑血管病与MTHFR基因A1298C多态的研究

目的探讨脑血管病与MTHFR基因A1298C多态性关系。方法对我院脑血管病患者与健康体检者各100例作病例-对照研究。运用聚合酶连反应-限制性内切酶片段长度多态性分析（PCR-RFLP）方法确定MTHFR基因型。结果患者组中CC型与T等位基因频率、AC型与C等位基因频率均明显高于健康对照组（P〈0.05）。结论 MTHFR1298AC型与C等位基因在脑血管疾病中的构成比均明显增大,MTHFR1298C多态性可能与脑血管疾病的发生存在一定的相关性。     

母亲与婴儿亚甲基四氢叶酸还原酶C677T多态性与早产和低出生体重的相关性研究

目的:探讨早产和低出生体重与母亲和婴儿5-10亚甲基四氢叶酸还原酶基因(MTHFR)C677T多态性的关系.方法:采用病例对照及核心家系的研究设计,共调查了500个核心家系,包括250个正常孕周出生的核心家系和250个早产核心家系.采用盐沉淀法提取基因组DNA,通过聚合酶链式反应(PCR)对5-10亚甲基四氢叶酸还原酶基因C677T多态性进行基因型鉴定.通过SAS软件的广义线性模型(GENMOD),选用对数线性模型(Log-linear Model)中的泊松回归进行最大拟然比检验(Maximum Likelihood Ratio Test),分析母亲和婴儿MTHFR基因分别与早产和低出生体重的关系.结果:首先,我们采用TDT方法分别检验了早产和低出生体重对照核心家系MTHFR 677T等位基因传递是否平衡,研究结果表明MTHFR 677T突变等位基因传递符合孟德尔遗传规律.之后,我们分析了MTHFR基因与早产和低出生体重的关系.结果显示:婴儿MTHFR CT 和TT基因型不但增加早产的发生危险性且具有显著的统计学意义(CT基因型:OR＝2.01,95%CI为1.21～3.32;TT基因型:OR为1.82,95%CI为1.02～3.26),而且婴儿MTHFR基因能够增加低出生体重的发生危险且具有显著的统计学意义(CT基因型:OR＝1.87,95%CI为1.08～3.24;TT基因型:OR＝1.90,95%CI为1.02～3.54).但是母亲MTHFR基因对早产和低出生体重的影响均没有显著的统计学意义.我们进一步观察了母亲与婴儿MTHER基因之间的交互作用对早产和低出生体重的影响,研究结果表明母亲与婴儿MTHFR基因之间无明显交互作用存在.结论:婴儿MTHFR基因CT和TT基因型能够增加早产和低出生体重发生风险且有显著的统计学意义,在早产核心家系中MTHFR677T突变等位基因不符合孟德尔遗传规律,可能是导致早产的遗传易感位点,并且MTHFR 基因有可能通过孕周的缩短(早产)而导致低出生体重这一生殖结局的发生.     

Association of MTHFR polymorphisms and chromosomal abnormalities in leukemia

Genetic variation in MTHFR gene might explain the interindividual differences in the reduction of DNA repaired and the increase of chromosome breakage and damage. Nowadays, chromosomal rearrangement is recognized as a major cause of lymphoid malignancies. In addition, the association of MTHFR polymorphisms with aneuploidy was found in several studies, making the MTHFR gene as a good candidate for leukemia etiology. Therefore, in this study, we investigated the common sequence variation, 677C>T and 1298A>C in the MTHFR gene of 350 fixed cell specimens archived after chromosome analysis. The distribution of the MTHFR polymorphisms frequency was compared in leukemic patients with structural chromosome abnormality and chromosome aneuploidy, as well as in those with no evidence of chromosome abnormalities. We observed a significant decrease in the distribution of T allele in 677C>T polymorphisms among patients with chromosomal abnormalities including both structural aberration and aneuploidy. The same significance result also found in patients with structural aberration when compare with the normal karyotype patients. Suggesting that polymorphism in the MTHFR gene was involved in chromosome abnormalities of leukemia. However, further investigation on the correlation with the specific types of chromosomal aberrations is needed.     

The neurobiology of depression in later-life: clinical, neuropsychological, neuroimaging and pathophysiological features

As the population ages, the economic and societal impacts of neurodegenerative and neuropsychiatric disorders are expected to rise sharply. Like dementia, late-life depressive disorders are common and are linked to increased disability, high healthcare utilisation, cognitive decline and premature mortality. Considerable heterogeneity in the clinical presentation of major depression across the life cycle may reflect unique pathophysiological pathways to illness; differentiating those with earlier onset who have grown older (early-onset depression), from those with illness onset after the age of 50 or 60 years (late-onset depression). The last two decades have witnessed significant advances in our understanding of the neurobiology of early- and late-onset depression, and has shown that disturbances of fronto-subcortical functioning are implicated. New biomedical models extend well beyond perturbations of traditional monoamine systems to include altered neurotrophins, endocrinologic and immunologic system dysfunction, inflammatory processes and gene expression alterations. This more recent research has highlighted that a range of illness-specific, neurodegenerative and vascular factors appear to contribute to the various phenotypic presentations. This review highlights the major features of late-life depression, with specific reference to its associated aetiological, clinical, cognitive, neuroimaging, neuropathological, inflammatory and genetic correlates. Data examining the efficacy of pharmacological, non-pharmacological and novel treatments for depression are discussed. Ultimately, future research must aim to evaluate whether basic biomedical knowledge can be successfully translated into enhanced health outcomes via the implementation of early intervention paradigms.     

阿尔茨海默病患者同型半胱氨酸代谢相关酶基因突变频度的研究

目的　探讨胱硫醚β合成酶 (CBS)基因 84 4ins6 8、甲硫氨酸合成酶 (MS)基因A2 75 6G、亚甲基四氢叶酸还原酶 (MTHFR)基因C6 77T三种同型半胱氨酸代谢相关酶基因突变在阿尔茨海默病 (AD)发病中的意义 .方法　PCR扩增AD 6 6例及 14 3例对照者的CBS、MS、MTHFR基因突变点 ,直接或经限制性内切酶消化后行凝胶电泳确定其基因型 .结果　AD病人MTHFR基因中 ,基因型C/T占 5 6 .0 6 % ,明显高于对照组 (p <0 .0 1) ,C/C明显低于对照组 (p <0 .0 1) ,T/T与对照组无明显差异 (p>0 .0 5 ) .AD病人中MTHFR基因等位基因C的频率相对危险率 (RR) ,T的频率与对照组的差异有显著性 (p<0 .0 5 ) .CBS 84 4ins6 8、MSA2 75 6G各种基因型频率在AD组与对照组之间无差异 .结论　AD病人中MTHFR T频率明显高于正常人 ;而MTHFR C频率则明显低于正常人 ,而CBS 84 4ins6 8、MSA2 75 6G突变可能不足以构成阿尔茨海默病的独立遗传性危险因子     

Uracil in DNA: consequences for carcinogenesis and chemotherapy

The synthesis of thymidylate (TMP) occupies a convergence of two critical metabolic pathways: folate metabolism and pyrimidine biosynthesis. Thymidylate is formed from deoxyuridylate (dUMP) using N(5),N(10)-methylene tetrahydrofolate. The metabolic relationship between dUMP, TMP, and folate has been the subject of cancer research from prevention to chemotherapy. Thymidylate stress is induced by nutritional deficiency of folic acid, defects in folate metabolism, and by antifolate and fluoropyrimidine chemotherapeutics. Both classes of chemotherapeutics remain mainstay treatments against solid tumors. Because of the close relationship between dUMP and TMP, thymidylate stress is associated with increased incorporation of uracil into DNA. Genomic uracil is removed by uracil DNA glycosylases of base excision repair (BER). Unfortunately, BER is apparently problematic during thymidylate stress. Because BER requires a DNA resynthesis step, elevated dUTP causes reintroduction of genomic uracil. BER strand break intermediates are clastogenic if not repaired. Thus, BER during thymidylate stress appears to cause genome instability, yet might also contribute to the mechanism of action for antifolates and fluoropyrimidines. However, the precise roles of BER and its components during thymidylate stress remain unclear. In particular, links between BER and downstream events remain poorly defined, including damage signaling pathways and homologous recombination (HR). Evidence is growing that HR responds to persistent BER strand break intermediates and DNA damage signaling pathways mediate cross talk between BER and HR. Examination of crosstalk among BER, HR, and damage signaling may shed light on decades of investigation and provide insight for development of novel chemopreventive and chemotherapeutic approaches.     

Supplementation with Watermelon Extract Reduces Total Cholesterol and LDL Cholesterol in Adults with Dyslipidemia under the Influence of the MTHFR C677T Polymorphism

Dyslipidemia and genetic polymorphisms are associated with increased risk for developing cardiovascular diseases, and watermelon appears to have the potential to improve hyperlipidemia due to the presence of nutrients such as arginine and citrulline.

Objective: To test the hypolipidemic effect of watermelon extract (Citrullus lanatus) and the influence of the methylenetetrahydrofolate reductase genotype (MTHFR C677T) on supplementation response.

Methods: This is an experimental clinical phase II randomized and double-blind study. Forty-three subjects with dyslipidemia were randomly divided into 2 groups: experimental (n = 22) and control (n = 21) groups. The subjects were supplemented daily for 42 days with 6 g of watermelon extract or a mixture of carbohydrates (sucrose/glucose/fructose).

Results: The use of watermelon extract reduced plasma total cholesterol (p < 0.05) and low-density lipoprotein (p < 0.01) without modifying triglycerides, high-density lipoprotein, and very low-density lipoprotein values. Only carriers of the T allele (MTHFR C677T) showed decreasing concentrations of low-density lipoprotein (p < 0.01). No changes in anthropometric parameters analyzed were observed. This is the first study to demonstrate the beneficial effect of the consumption of watermelon extract in reducing plasma levels of lipids in humans. The MTHFR C677T polymorphism did not affect the plasma lipid concentration but made individuals more responsive to treatment with watermelon.

Conclusions: The consumption of this functional food represents an alternative therapy in the combined treatment of patients with dyslipidemia, promoting health and minimizing the development of risk factors for cardiovascular diseases.