The MTHFR 677C→T polymorphism and risk of prostate cancer: results from the CAPS study

The methylenetetrahydrafolate reductase (MTHFR) enzyme may influence cancer development by affecting DNA methylation, synthesis and repair. The MTHFR 677C→T single nucleotide polymorphism (SNP) has been associated with decreased enzyme activity and has therefore been implicated in cancer development. We analyzed the MTHFR 677C→T SNP in 2,777 incident prostate cancer cases and 1,639 population controls from the CAncer Prostate in Sweden study (CAPS). No significant association was found overall between prostate cancer risk and the 677C→T SNP (p = 0.27) with heterozygote (CT) and homozygote (TT) allele carriers showing ORs of 1.12 (95% CI: 0.98–1.27) and 1.02 (95% CI: 0.80–1.30), respectively. In the subgroup of low risk prostate cancer, heterozygote—but not homozygote—allele carriers displayed a slight over-risk with an OR of 1.21 (95% CI: 1.03–1.41). Among men under 65 years of age, the 677C→T SNP was associated with prostate cancer risk (p = 0.007), with odds ratios of 1.33 (95% CI: 1.09–1.63) for heterozygote allele carriers and 0.86 (95% CI: 0.6–1.24) for homozygote allele carriers. However, this association was attributed to a shift in the genotype distribution in the young controls. In conclusion, our results do not provide strong support for the hypothesis that the MTHFR 677C→T polymorphism is related to prostate cancer risk.     

Evaluation of the relationship between C677T variants of methylenetetrahydrofolate reductase gene and hyperhomocysteinemia in children receiving antiepileptic drug therapy

Homocysteine (Hcy) is a sulfur-containing amino acid involved in methionine metabolism. Elevated plasma Hcy concentration is a possible risk factor for vascular disease. Folate and vitamin B-12 are vitamins that are necessary for remethylization of Hcy to methionine. The methylenetetrahydrofolate reductase (MTHFR) is the key enzyme in remethylation of Hcy to methionine and supplies the required 5-methyltetrahydrofolate as the methyl donor for this reaction. It is well known that some antiepileptic drugs (AED) can lead to hyperhomocysteinemia by affecting the levels of folate and vitamin B-12. The C677T variant of MTHFR gene can also lead to hyperhomocysteinemia particularly when serum folate level is decreased. In this study, we investigated the levels of serum folate, vitamin B-12 and Hcy in epileptic patients receiving carbamazepine (CBZ) or valproic acid (VPA) as monotherapy, and we also evaluated the probable contribution of the C677T variant of MTHFR gene in hyperhomocysteinemia. A total of 93 patients with idiopathic epilepsy receiving CBZ or VPA as monotherapy were included in this study. CBZ and VPA groups consisted of 29 and 64 patients, respectively. The control group comprised 62 healthy children. We measured serum folate, vitamin B-12 and Hcy levels in each group. We found that mean serum folate level was statistically lower and mean Hcy level was higher in epileptic patients receiving CBZ or VPA when compared with those of controls'. We also determined the C677T variants of MTHFR gene (as normal, heterozygote or homozygote) in epileptic patients. We compared the variant groups for serum folate, vitamin B-12 and Hcy levels and found no significant differences among them. In conclusion, C677T variants of MTHFR gene have no contribution in hyperhomocysteinemia in epileptic patients receiving CBZ or VPA.     

Serum total homocysteine,folate, 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C→T genotype and subclinical atherosclerosis

Objective: To determine the relationship of serum total homocysteine (tHcy), serum folate and 5,10-methylenetetrahydrofolate reductase (MTHFR) 677C→T genotype with ultrasonic arterial wall measurements associated with subclinical atherosclerosis. Study design: Cross-sectional analysis of 767 participants in an ongoing prospective study. Intima-media thickness (IMT) of the common carotid (IMTcc), IMT of the internal carotid including plaque when present (IMT_max) and the sum of the thickest plaques present in both carotid and both common femoral bifurcations (total plaque thickness (TPT)) were measured using ultrasound. Results: People in the upper homocysteine quartile were more likely to have clinical cardiovascular disease (CVD) than those in the lowest three quartiles. They were also more likely to have plaques. The MTHFR 677C→T genotype was not associated with any of the measures of subclinical atherosclerosis in either men or women but was the most important determinant of total homocysteine levels in men under 60 years of age. Conclusions: Increased homocysteine levels but not MTHFR 677C→T genotype, are associated with subclinical atherosclerosis and the presence of plaques. Our results indicate that measurements of blood levels of homocysteine and folate in people at intermediate risk for atherosclerotic CVD before symptoms occur, might improve risk stratification and facilitate the decision to provide folate/B vitamin intervention in primary prevention.     

Xenobiotic and folate pathway gene polymorphisms and risk of childhood acute lymphoblastic leukaemia in Javanese children

Xenobiotic and folate metabolic pathways are important for the maintenance of genetic stability and may influence susceptibility to the development of childhood acute lymphoblastic leukaemia (ALL). In this study, we investigated 10 polymorphisms in 6 genes (GSTM1‐present/null, GSTT1‐present/null, GSTP1 1578A > G, NQO1 609C > T, MTHFR 677C > T, MTHFR 1298A > C, MTHFD1 1958G > A, 3′‐TYMS 1494 6bp‐deletion/insertion, 5′‐TYMS 28bp‐tandem repeats, and SLC19A1 80G > A) in a cohort of 185 Javanese children with ALL and 177 healthy controls. In ALL patients, none of the polymorphisms demonstrated a statistically significant association with ALL after correcting for multiple comparisons. Gender‐stratified analysis showed that in girls, GSTT1‐null genotype was associated with increased ALL risk (OR = 2.20; p = 0.027), while GSTP1 1578AG genotype was associated with reduced risk (OR = 0.43; p = 0.031). Strong linkage disequilibrium between the MTHFR 677C > T and 1298A > C polymorphisms was observed (D′ = 1.0; r² = 0.072). The haplotypes 677C‐1298C and 677T‐1298A were associated with a reduced risk of ALL (OR = 0.68 and 0.64, respectively; gender‐adjusted global p = 0.028). Classification and regression tree (CART) analysis was employed to identify potential high‐order gene‐gene interactions and cluster subjects into susceptibility groups. SLC19A1 80G > A emerged as the predominant polymorphism associated with risk of ALL. Individuals simultaneously carrying MTHFR 1298AA, 3'‐TYMS 6bp deletion(s) and SLC19A1 80A‐allele(s) were at higher disease risk (OR = 2.21; p < 0.001). On the contrary, simultaneous possession of MTHFR 1298CC, 3'‐TYMS 6bp homozygosity and SLC19A1 80A‐allele(s) conferred lower risk (OR = 0.25; p = 0.004). Carriage of NQO1 609C‐allele amongst SLC19A1 80GG genotype was associated with lower risk (OR = 0.47; p = 0.003). In conclusion, our study has demonstrated the importance of gender and gene‐gene interaction within the xenobiotic and folate pathways in modulating childhood ALL susceptibility. Copyright © 2010 John Wiley & Sons, Ltd.     

MTHFR A1298C基因多态性与高尿酸血症的相关性探讨

目的探讨亚甲基四氢叶酸还原酶(MTHFR)基因A1298C单核苷酸多态性与高尿酸血症(HUA)的关系。方法以聚合酶链反应和限制性片段长度多态性方法对116例高尿酸血症患者和110例正常对照组MTHFR A1298C基因型作比较。结果在高尿酸血症病人中MTHFR 1298AA、AC、CC基因型频率分别为73.3%、23.3%和3.4%,而在正常对照组中分别为70.0%、26.4%和3.6%,两者无显著差异。结论 MTHFR A1298C单核苷酸多态可能与高尿酸血症的遗传易感性无关。     

西安地区汉族亚甲基四氢叶酸还原酶的两种基因多态性

目的：了解西安地区汉族人MTHFR基因C677T和A1298C两个位点的遗传多态性．方法：应用聚合酶链反应-限制性片段长度多态性(PCR—RFLP)调查西安地区96个汉族人的基因型分布．结果：677T等位基因的分布频率为45％，TT纯合子占18％；1298C等位基因的分布频率为20％．CC合子占3％；双杂合子677CT，1298AC占21％．结论：调查显示这两个位点的遗传多态性与献报道不同，可能具有群体差异性．     

MTHFR、CBS基因多态性与脑血管病的相关性研究

目的 研究MTHFR、CBS基因多态性与脑血管病的遗传相关性。方法采用限制性内切酶片段长度多态性方法，对54例脑梗死、27例脑出血及96例健康人MTHFR基因C677T、CBS基因T27796C多态性位点进行检测。结果MTHFR C677T位点与脑梗死及脑出血均有显著相关，两组与对照组之间T／C等位基因频率存在差异。TT型携带者较CC型患脑血管病的风险高。CBS T27796C位点与脑血管病无明显相关。结论 MTHFR基因可能是脑血管病的一个易感基因。CBS基因T27796C多态性位点与脑血管病无明显相关。     

Associations of MTHFR DNMT3b 4977 bp deletion in mtDNA and GSTM1 deletion, and aberrant CpG island hypermethylation of GSTM1 in non-obstructive infertility in Indian men

Methylenetetrahydrofolate (MTHFR) and DNMT3b play imperative roles in DNA synthesis and de novo methylation. GSTM1 is involved in detoxification of carcinogens. Mitochondrial DNA deletion has been associated with lower motility in human sperm. We analysed if polymorphisms in MTHFR (C677T and A1298C) and DNMT3b (C46359T) are associated with non-obstructive male infertility. We also analysed if folate, vitamin B(12), homocysteine (Hcy), 8'-hydroxy-2'-deoxygnanosine (8-OHdG) levels, dietary folate intake and mtDNA deletion (4977 bp) affects fertility, such interactions are modified by deletion and methylation of GSTM1. In this case-control study, we included 179 oligoasthenoteratozoospermia patients and 200 fertile men. Single-nucleotide polymorphism analysis was performed by PCR-restriction fragment length polymorphism. The MTHFR (C677T and A1298C) and DNMT3b (C46359T) frequencies did not differ significantly in two groups. GSTM1 in association with mtDNA 4977 deletion is significantly associated with infertility. Plasma folate and vitamin B(12) levels are decreased and total Hcy is elevated in infertile men. GSTM1 methylation status was investigated by methylation-specific PCR. Methylation is significantly correlated with GSTM1 reduced/loss of expression in infertile men. Infertile men have significantly higher 8-OHdG levels. Dietary folate intake is not linked with GSTM1 methylation. Low folate intake in association with CT + TT genotypes (C677T) has significant protective effect on GSTM1 methylation. Results indicate that micronutrients, 8-OHdG levels, mtDNA deletion and GSTM1 promoter methylation are frequent alterations in infertility.     

湖北省英山县汉族女性MTHFR和MTRR的遗传多态性分析

目的分析湖北省黄冈市英山县汉族育龄女性叶酸代谢相关酶5,10-亚甲基四氢叶酸还原酶(MTHFR)和甲硫氨酸合成酶还原酶(MTRR)的基因多态性分布特征,以指导育龄女性增补叶酸和出生缺陷的一级预防。方法以英山县319例汉族女性为研究对象,提取口腔黏膜上皮细胞基因组DNA,通过荧光定量PCR法对MTHFR和MTRR的多态性位点进行分析,获得英山县妇女该基因的分布特征,并与已报道的其他地区的数据进行比较。结果英山县汉族女性MTHFR C677T基因型构成与淄博、济源、张家口、延边、乌鲁木齐、银川、眉山、南宁、琼海数据相比差异有统计学意义(x^2值为181.41~13.46,均P<0.05),与松滋、湘潭、惠州相比无统计学意义(x^2值为0.12~5.87,均P>0.05)。英山县汉族女性MTHFR A1298C基因型构成与淄博、济源、张家口、延边、银川、眉山、松滋、湘潭数据的差异均有统计学意义(x^2值为76.94~7.31,均P<0.05),与乌鲁木齐、惠州、南宁、琼海相比无统计学意义(x^2值为5.19~0.97,均P>0.05)。英山县汉族女性MTRR A66G的基因型构成与延边和琼海的差异有统计学意义(x^2值分别为6.10、17.10,均P<0.05),与淄博、济源、张家口、乌鲁木齐、银川、眉山、松滋、湘潭、惠州、南宁的差异均没有统计学意义(x^2值为0.95~5.48,均P>0.05)。结论英山县汉族女性MTHFR和MTRR基因多态性频率分布具有地域特异性。     

Methylenetetrahydrofolate reductase (MTHFR) c677t gene variant modulates the homocysteine folate correlation in a mild folate-deficient population

Background: A large body of evidence links plasma concentrations of homocysteine and cardiovascular disease. Several genetic and environmental variables may modulate such relationship. We investigated the influence of methylenetetrahydrofolate reductase (MTHFR) gene variants C677T, A1298C, and T1317C on homocysteine, folate, and cobalamin concentrations in a sample of individuals from a mild folate deficiency population to better clarify the complex interactions existing among these variables. Methods: In the present study, 209 individuals belonging to an admixed urban population characterized by mild folate deficiency were investigated. MTHFR gene variants C677T, A1298C, and T1317C were genotyped and homocysteine-, folate-, and cobalamin-determined for each individual. Results: Univariate analyses showed a significant association between the C677T variant with homocysteine (P<0.001) and cobalamin (P=0.005) as well as a significant relationship between the T allele and serum folate concentrations (P<0.05). The TT genotype of the C677T polymorphism remained significantly associated with log-transformed homocysteine even after adjustment for age, sex, smoking status, ethnicity, folate, and cobalamin concentrations (P<0.01). Both univariate and multivariate analysis have failed to show any effect of the A1298C and T1317C genetic variants in homocysteine concentrations in this population. Finally, a significant interaction between folate and C677T polymorphism in the determination of homocysteine was also disclosed (P<0.005). Conclusions: Taken together, these results demonstrate a significant interaction between serum folate and MTHFR genotype in predicting homocysteine concentrations. One may consider that a differential response of homocysteine to folic acid supplementation may depend on MTHFR genotype which may have important implications when attempting to lower homocysteine concentrations in populations with mild folate deficiency.