Potential Links between Impaired One-Carbon Metabolism Due to Polymorphisms, Inadequate B-Vitamin Status, and the Development of Alzheimer's Disease

Alzheimer's disease (AD) is the major cause of dementia and no preventive or effective treatment has been established to date. The etiology of AD is poorly understood, but genetic and environmental factors seem to play a role in its onset and progression. In particular, factors affecting the one-carbon metabolism (OCM) are thought to be important and elevated homocysteine (Hcy) levels, indicating impaired OCM, have been associated with AD. We aimed at evaluating the role of polymorphisms of key OCM enzymes in the etiology of AD, particularly when intakes of relevant B-vitamins are inadequate. Our review indicates that a range of compensatory mechanisms exist to maintain a metabolic balance. However, these become overwhelmed if the activity of more than one enzyme is reduced due to genetic factors or insufficient folate, riboflavin, vitamin B6 and/or vitamin B12 levels. Consequences include increased Hcy levels and reduced capacity to synthetize, methylate and repair DNA, and/or modulated neurotransmission. This seems to favor the development of hallmarks of AD particularly when combined with increased oxidative stress e.g., in apolipoprotein E (ApoE) ε4 carriers. However, as these effects can be compensated at least partially by adequate intakes of B-vitamins, achieving optimal B-vitamin status for the general population should be a public health priority.

Novel Approaches to Investigate One-Carbon Metabolism and Related B-Vitamins in Blood Pressure

Hypertension, a major risk factor for heart disease and stroke, is the world's leading cause of preventable, premature death. A common polymorphism (677C→T) in the gene encoding the folate metabolizing enzyme methylenetetrahydrofolate reductase (MTHFR) is associated with increased blood pressure, and there is accumulating evidence demonstrating that this phenotype can be modulated, specifically in individuals with the MTHFR 677TT genotype, by the B-vitamin riboflavin, an essential co-factor for MTHFR. The underlying mechanism that links this polymorphism, and the related gene-nutrient interaction, with hypertension is currently unknown. Previous research has shown that 5-methyltetrahydrofolate, the product of the reaction catalysed by MTHFR, appears to be a positive allosteric modulator of endothelial nitric oxide synthase (eNOS) and may thus increase the production of nitric oxide, a potent vasodilator. Blood pressure follows a circadian pattern, peaking shortly after wakening and falling during the night, a phenomenon known as 'dipping'. Any deviation from this pattern, which can only be identified using ambulatory blood pressure monitoring (ABPM), has been associated with increased cardiovascular disease (CVD) risk. This review will consider the evidence linking this polymorphism and novel gene-nutrient interaction with hypertension and the potential mechanisms that might be involved. The role of ABPM in B-vitamin research and in nutrition research generally will also be reviewed.

The model homologue of the partially defective human 5,10-methylenetetrahydrofolate reductase, considered as a risk factor for stroke due to increased homocysteine level, can be protected and reactivated by heat shock proteins

The A222 V substitution in the human MTHFR gene product (5,10-methylenetetrahydrofolate reductase) is responsible for a decreased activity of this enzyme. This may cause an increased homocysteine level, considered as a risk factor for arteriosclerosis and stroke. The bacterial homologue of the human enzyme, MetF, has been found to be a useful model in genetic and biochemical studies. The similarity of Escherichia coli MetF and human MTHFR proteins is so high that particular mutations in the corresponding human gene can be reflected by the bacterial mutants. For example, the A222 V substitution in MTHFR (caused by the C667T substitution in the MTHFR gene) can be ascribed to the A117 V substitution in MetF. Here, it is reported that a temperature-sensitive MetF117 (A117 V) protein can be partially protected from a thermal inactivation by the heat shock proteins from the Hsp70/100 systems. Moreover, activity of the thermally denatured enzyme can be partially restored by the same heat shock proteins. High temperature protein G (HtpG) had no effect on MetF117 activity in both experimental systems. The presented results indicate that functions of heat shock proteins may be required for maintenance of the MetF117 function. This may have implications for the mechanisms of arteriosclerosis and stroke, especially in the light of previous findings that the A222 V MTHFR polymorphism may be a risk factor for stroke, as well as recently published results which demonstrated the increased levels of antibodies against heat shock proteins in stroke patients.

Artificial Neural Networks Link One-Carbon Metabolism to Gene-Promoter Methylation in Alzheimer's Disease

BACKGROUND

There is increasing interest in DNA methylation studies in Alzheimer's disease (AD), but little is still known concerning the relationship between gene-promoter methylation and circulating biomarkers of one-carbon metabolism in patients.

OBJECTIVE

To detect the connections among circulating folate, homocysteine (hcy) and vitamin B12 levels and promoter methylation levels of PSEN1, BACE1, DNMT1, DNMT3A, DNMT3B, and MTHFR genes in blood DNA.

METHODS

We applied a data mining system called Auto Contractive Map to an existing database of 100 AD and 100 control individuals.

RESULTS

Low vitamin B12 was linked to the AD condition, to low folates, and to high hcy. Low PSEN1 methylation was linked to low folate levels as well as to low promoter methylation of BACE1 and DNMTs genes. Low hcy was linked to controls, to high folates and vitamin B12, as well as to high methylation levels of most of the studied genes.

CONCLUSIONS

The present pilot study suggests that promoter methylation levels of the studied genes are linked to circulating levels of folates, hcy, and vitamin B12.

The Frequency of Factor V Leiden and Concomitance of Factor V Leiden With Prothrombin G20210A Mutation and Methylene Tetrahydrofolate Reductase C677T Gene Mutation in Healthy Population of Denizli, Aegean Region of Turkey

Factor V Leiden causing activated protein C resistance is the most common inherited form of thrombophilia leading to thrombosis. Its frequency shows great ethnic and geographic variations. The aim of this study was to determine the frequency of FV Leiden and coinheritance of FV Leiden with two other frequent hereditary thrombophilia causes, namely, prothrombin G20210A and methylene-tetrahydrofolate reductase ( MTHFR) C677T mutation in the Aegean region of Turkey. The study population consisted of 1030 (500 men and 530 women) apparently healthy subjects. Functional resistance to activated protein C (APC) was measured by using the test kit STA staclot APC-R ((Diagnostica Stago, Asnieres, France, Cat. No. 00721). In subjects with APC resistance, molecular analyses of FV Leiden and of prothrombin G20210A and MTHFR C677T mutation were performed by using FV-PTH-MTHFR StripA (Vienna Lab, Labordiagnostika GmbH, Austria) kit, which was based on hybridization of polymerase chain reaction (PCR) amplified DNA products with mutation-specific oligonucleotide probes. Functional APC resistance was present in 93 subjects (9%). FV Leiden mutation was found in 87 of 93 subjects with APC resistance by PCR method. The FV Leiden carrier frequency was found to be 8.4% (87/1030). Seventy-six individuals were heterozygous (7.3%), and 11 were homozygous (1.06%). Among the 87 subjects with FV Leiden mutation, 45 subjects had MTHFR C677T gene mutation (7 homozygous, 38 heterozygous) and 4 subjects had heterozygote prothrombin G20210A gene mutation. A combination of FV Leiden and prothrombin G20210A and MTHFR C677T gene mutation was detected in 3 subjects. The results indicate that FV Leiden prevalence is quite high and coexistence of FV Leiden with other hereditary causes of thrombosis such as prothrombin G20210A mutation and MTHFR enzyme defect is not rare in healthy population of Aegean region of Turkey.

Murine diet/tissue and human brain tumorigenesis alter Mthfr/MTHFR 5'-end methylation

Polymorphisms and decreased activity of methylenetetrahydrofolate reductase (MTHFR) are linked to disease, including cancer. However, epigenetic regulation has not been thoroughly studied. Our goal was to generate DNA methylation profiles of murine/human MTHFR gene regions and examine methylation in brain and liver tumors. Pyrosequencing in four murine tissues revealed minimal DNA methylation in the CpG island. Higher methylation was seen in liver or intestine in the CpG island shore 5' to the upstream translational start site or in another region 3' to the downstream start site. In the latter region, there was negative correlation between expression and methylation. Three orthologous regions were investigated in human MTHFR, as well as a fourth region between the two translation start sites. We found significantly increased methylation in three regions (not the CpG island) in pediatric astrocytomas compared with control brain, with decreased expression in tumors. Methylation in hepatic carcinomas was also increased in the three regions compared with normal liver, but the difference was significant for only one CpG. This work, the first overview of the Mthfr/MTHFR epigenetic landscape, suggests regulation through methylation in some regions, demonstrates increased methylation/decreased expression in pediatric astrocytomas, and should serve as a resource for future epigenetic studies.

Choline metabolites: gene by diet interactions

PURPOSE OF REVIEW

The review highlights recent advances in our understanding of the interactions between genetic polymorphisms in genes that metabolize choline and the dietary requirements of choline and how these interactions relate to human health and disease.

RECENT FINDINGS

The importance of choline as an essential nutrient has been well established, but our appreciation of the interaction between our underlying genetic architecture and dietary choline requirements is only beginning. It has been shown in both human and animal studies that choline deficiencies contribute to diseases such as nonalcoholic fatty liver disease and various neurodegenerative diseases. An adequate supply of dietary choline is important for optimum development, highlighted by the increased maternal requirements during fetal development and in breast-fed infants. We discuss recent studies investigating variants in PEMT and MTHFR1 that are associated with a variety of birth defects. In addition to genetic interactions, we discuss several recent studies that uncover changes in fetal global methylation patterns in response to maternal dietary choline intake that result in changes in gene expression in the offspring. In contrast to the developmental role of adequate choline, there is now an appreciation of the role choline has in cardiovascular disease through the gut microbiota-mediated metabolite trimethylamine N-oxide. This pathway highlights some of our understanding of how the microbiome affects nutrient processing and bioavailability. Finally, to better characterize the genetic architecture regulating choline requirements, we discuss recent results focused on identifying polymorphisms that regulate choline and its derivative products.

SUMMARY

Here we discuss recent studies that have advanced our understanding of how specific alleles in key choline metabolism genes are related to dietary choline requirements and human disease.

Functional variants of gene encoding folate metabolizing enzyme and methotrexate-related toxicity in children with acute lymphoblastic leukemia

Methotrexate (MTX) is commonly used agent in therapy of malignancies, including acute lymphoblastic leukemia (ALL). Based on the literature data it is known that MTX elimination and toxicity can be affected by polymorphisms in genes encoding enzymes involved in MTX metabolism. The aim of our study was to investigate the influence of C677T and A1298C polymorphisms in methylenetetrahydrofolate reductase (MTHFR) gene on MTX-induced toxicity during treatment of children with ALL. We also tried to answer the question whether simultaneous occurrence of these two polymorphisms has a clinical significance. MTHFR polymorphisms were assessed in 47 pediatric ALL patients, treated according to intensive chemotherapy for childhood ALL, ALL IC BFM 2009. Prolonged MTX elimination and higher incidence of toxicity were observed for patients with 677T-1298A haplotype. On the other hand, occurrence of 677C-1298A haplotype had protective effect on MTX clearance and toxicity, that was not observed in carriers of 677C-1298C haplotype. In patients with coexistence of studied variants 677CT/1298AC heterozygotes as well as in 677TT/1298AA homozygotes more frequently toxicity incidents were noted. The obtained results suggest that occurrence of 677T allele and coexistence of 677T and 1298C alleles may be associated with lower MTX clearance and elevated risk of adverse effects during MTX-treatment of pediatric ALL patients.

[C677T AND A1298C ALLELE POLYMORPHISM GENE OF METHYLENETETRAHYDRAFOLATEREDUCTASE IN PATIENTS WITH NONALCOHOLIC FATTY LIVER DISEASE AND TYPE 2 DIABETES]

The article presents the results of the study C677T and A1298C polymorphisms of MTHFR gene and their influence on plasma homocysteine levels in patients with nonalcoholic fatty liver disease (NAFLD). The study involved 100 patients with NAFLD and 40 apparently healthy individuals (control group). Determination of allelic polymorphism was performed by polymerase chain reaction with the detection results of hybridization by fluorescence in real-time. Determination of plasma homocysteine levels was performed by ELISA. As a result, studies have not found significant differences in the distribution of genotypes investigated C677T and A1298C MTHFR gene between patients with NAFLD and control group. We have detected statistically significant relationship between the level of homocysteine plasma C677T polymorphism of the MTHFR gene in patients with NAFLD and lack of connection with the A1298C polymorphism of the gene MTHFR.

Obstructive heart defects associated with candidate genes, maternal obesity, and folic acid supplementation

Right-sided and left-sided obstructive heart defects (OHDs) are subtypes of congenital heart defects, in which the heart valves, arteries, or veins are abnormally narrow or blocked. Previous studies have suggested that the development of OHDs involved a complex interplay between genetic variants and maternal factors. Using the data from 569 OHD case families and 1,644 control families enrolled in the National Birth Defects Prevention Study (NBDPS) between 1997 and 2008, we conducted an analysis to investigate the genetic effects of 877 single nucleotide polymorphisms (SNPs) in 60 candidate genes for association with the risk of OHDs, and their interactions with maternal use of folic acid supplements, and pre-pregnancy obesity. Applying log-linear models based on the hybrid design, we identified a SNP in methylenetetrahydrofolate reductase (MTHFR) gene (C677T polymorphism) with a main genetic effect on the occurrence of OHDs. In addition, multiple SNPs in betaine-homocysteine methyltransferase (BHMT and BHMT2) were also identified to be associated with the occurrence of OHDs through significant main infant genetic effects and interaction effects with maternal use of folic acid supplements. We also identified multiple SNPs in glutamate-cysteine ligase, catalytic subunit (GCLC) and DNA (cytosine-5-)-methyltransferase 3 beta (DNMT3B) that were associated with elevated risk of OHDs among obese women. Our findings suggested that the risk of OHDs was closely related to a combined effect of variations in genes in the folate, homocysteine, or glutathione/transsulfuration pathways, maternal use of folic acid supplements and pre-pregnancy obesity.

High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice

BACKGROUND

Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions.

OBJECTIVE

Our goal was to investigate the impact of high folic acid intake on liver disease and methyl metabolism.

DESIGN

Folic acid-supplemented diet (FASD, 10-fold higher than recommended) and control diet were fed to male Mthfr(+/+) and Mthfr(+/-) mice for 6 mo to assess gene-nutrient interactions. Liver pathology, folate and choline metabolites, and gene expression in folate and lipid pathways were examined.

RESULTS

Liver and spleen weights were higher and hematologic profiles were altered in FASD-fed mice. Liver histology revealed unusually large, degenerating cells in FASD Mthfr(+/-) mice, consistent with nonalcoholic fatty liver disease. High folic acid inhibited MTHFR activity in vitro, and MTHFR protein was reduced in FASD-fed mice. 5-Methyltetrahydrofolate, SAM, and SAM/S-adenosylhomocysteine ratios were lower in FASD and Mthfr(+/-) livers. Choline metabolites, including phosphatidylcholine, were reduced due to genotype and/or diet in an attempt to restore methylation capacity through choline/betaine-dependent SAM synthesis. Expression changes in genes of one-carbon and lipid metabolism were particularly significant in FASD Mthfr(+/-) mice. The latter changes, which included higher nuclear sterol regulatory element-binding protein 1, higher Srepb2 messenger RNA (mRNA), lower farnesoid X receptor (Nr1h4) mRNA, and lower Cyp7a1 mRNA, would lead to greater lipogenesis and reduced cholesterol catabolism into bile.

CONCLUSIONS

We suggest that high folic acid consumption reduces MTHFR protein and activity levels, creating a pseudo-MTHFR deficiency. This deficiency results in hepatocyte degeneration, suggesting a 2-hit mechanism whereby mutant hepatocytes cannot accommodate the lipid disturbances and altered membrane integrity arising from changes in phospholipid/lipid metabolism. These preliminary findings may have clinical implications for individuals consuming high-dose folic acid supplements, particularly those who are MTHFR deficient.

Folate metabolism gene polymorphisms and risk for down syndrome offspring in Turkish women

AIMS

Down syndrome (DS) is the most common chromosomal abnormality. Many studies have assessed the association between maternal gene polymorphisms involved in folate metabolism and the risk of having a DS offspring, but data are conflicting. Six common polymorphisms in folate-metabolizing genes were analayzed to determine possible risk factors for a child to be born having DS (DS mothers); these samples were taken from 47 Turkish mothers having DS children (case group) and 49 control mothers. Investigated polymorphisms include methylenetetrahydrofolate reductase (MTHFR) C677T (rs1801133), A1298C (rs1801131), methionine synthase reductase (MTRR) A66G (rs1801394), methylenetetrahydrofolate dehydrogenase (MTHFD1) G1958A (rs2236225), reduced folate carrier (RFC1) A80G (rs1051266), and cystathionine β-synthase (CBS) 844ins68.

RESULTS

The frequency of the MTHFR 677C allele in DS mothers (79.8%) was significantly higher than in controls (66.3%), with a 0.499-fold increased risk of having a DS offspring (p=0.038 and 95% confidence interval [CI], 0.259-0.961). Mothers with the MTHFD1 1958A allele had a 1.880-fold increased risk of having a child with DS (p=0.031 and 95% CI, 1.060-3.335). No significant association was found for the other polymorphic variants in this study. Gene-gene interactions were not statistically significant.

CONCLUSION

Polymorphic variants of the enzymes involved in folate metabolism may play an important role in determining the susceptibility of having a DS offspring. The gene-nutrition, gene-gene interactions and ethnicity are important variables to be considered in future studies.

[A STUDY OF OCCURRENCE FREQUENCY OF C677T POLYMORPHISM OF THE GENE MTHFR AND PLASMA FOLATE LEVELS IN PATIENTS WITH UNIPOLAR DEPRESSION]

This study focuses on the problem of finding an effective diagnostic algorithm to identify unipolar depression by examining the C677T MTHFR gene polymorphism and features of folate metabolism in patients with unipolar depression. The study proves that C677T MTHFR gene polymorphism is significantly associated with unipolar depression, which can be used to improve the quality of depression identification, as well as forming new ways of diagnosis.

Nutri-epigenetics ameliorates blood-brain barrier damage and neurodegeneration in hyperhomocysteinemia: role of folic acid

Epigenetic mechanisms underlying nutrition (nutrition epigenetics) are important in understanding human health. Nutritional supplements, for example folic acid, a cofactor in one-carbon metabolism, regulate epigenetic alterations and may play an important role in the maintenance of neuronal integrity. Folic acid also ameliorates hyperhomocysteinemia, which is a consequence of elevated levels of homocysteine. Hyperhomocysteinemia induces oxidative stress that may epigenetically mediate cerebrovascular remodeling and leads to neurodegeneration; however, the mechanisms behind such alterations remain unclear. Therefore, the present study was designed to observe the protective effects of folic acid against hyperhomocysteinemia-induced epigenetic and molecular alterations leading to neurotoxic cascades. To test this hypothesis, we employed 8-weeks-old male wild-type (WT) cystathionine-beta-synthase heterozygote knockout methionine-fed (CBS+/− + Met), WT, and CBS+/− + Met mice supplemented with folic acid (FA) [WT + FA and CBS+/− + Met + FA, respectively, 0.0057-μg g−1 day−1 dose in drinking water/4 weeks]. Hyperhomocysteinemia in CBS+/− + Met mouse brain was accompanied by a decrease in methylenetetrahydrofolate reductase and an increase in S-adenosylhomocysteine hydrolase expression, symptoms of oxidative stress, upregulation of DNA methyltransferases, rise in matrix metalloproteinases, a drop in the tissue inhibitors of metalloproteinases, decreased expression of tight junction proteins, increased permeability of the blood-brain barrier, neurodegeneration, and synaptotoxicity. Supplementation of folic acid to CBS+/− + Met mouse brain led to a decrease in the homocysteine level and rescued pathogenic and epigenetic alterations, showing its protective efficacy against homocysteine-induced neurotoxicity.

Pharmacogenomics in lung cancer chemotherapy: a review of what the oncologist should know

Lung cancer is the leading cause of cancer-related death around the world; the addition of chemotherapy to treatment of this disease has been shown to significantly increase progression-free survival and overall survival. Despite newer chemotherapies, it is important to personalize the care (treatment and dose) upon each single patient's susceptibility for controlling and reducing adverse side-effects, at best. The present review describes the current status of pharmacogenomics studies regarding germline DNA variants that may alter response and tolerability to chemotherapeutic agents used to treat lung cancer, including perspective studies.

Folic acid pathway single nucleotide polymorphisms associated with methotrexate significant adverse events in United States veterans with rheumatoid arthritis

OBJECTIVES

Methotrexate (MTX) is the cornerstone medication in the treatment of rheumatoid arthritis (RA). We examined whether single nucleotide polymorphisms (SNPs) in enzymes of the folic acid pathway (folylpoly-gamma-glutamate synthetase [FPGS], gamma-glutamyl hydrolase [GGH], and methylenetetrahydrofolate reductase [MTHFR]) associate with significant adverse events (SigAE).

METHODS

Patients (n=319) enrolled in the Veterans Affairs RA (VARA) registry taking MTX were genotyped for HLA-DRB1-SE and the following SNPs: FPGS (rs7033913, rs10760503, rs10106), GGH (12548933, rs7010484, rs4617146, rs719235, rs11988534), MTHFR (rs1801131, rs1801133). AE were abstracted from the medical record using a structured instrument. SigAE were defined as an AE leading to MTX discontinuation. Covariates included: age, gender, race, RA antibody status, tobacco, RA disease duration between diagnosis and MTX course, Charlson-Deyo comorbidity index, glucocorticoids, use of prior RA medications, and mean 4-variable disease activity score. Cox regression was performed to determine factors associated with time-to-SigAE. A p-value ≤ 0.005 established significance in the final model.

RESULTS

The presence of ≥ 1 copy of the minor allele in MTHFR rs1801131 was associated with an increased hazard ratio (HR) of SigAE (HR 3.05, 95% CI 1.48-6.29, p-value 0.003 and HR 3.88, 95% CI 1.62-9.28, p-value 0.002 for heterozygotes and homozygotes for the minor allele, respectively). An interaction term, between FPGS rs7033913 heterozygotes and GGH rs11988534 homozygotes for the minor allele, had a p-value <0.0001.

CONCLUSIONS

RA subjects taking MTX may have decreased time-to-SigAE with ≥ 1 copy of the minor allele in MTHFR rs1801131. Further investigation is warranted, as these SNPs may indicate susceptibility to MTX toxicity.

The maize brown midrib2 (bm2) gene encodes a methylenetetrahydrofolate reductase that contributes to lignin accumulation

The midribs of maize brown midrib (bm) mutants exhibit a reddish-brown color associated with reductions in lignin concentration and alterations in lignin composition. Here, we report the mapping, cloning, and functional and biochemical analyses of the bm2 gene. The bm2 gene was mapped to a small region of chromosome 1 that contains a putative methylenetetrahydrofolate reductase (MTHFR) gene, which is down-regulated in bm2 mutant plants. Analyses of multiple Mu-induced bm2-Mu mutant alleles confirmed that this constitutively expressed gene is bm2. Yeast complementation experiments and a previously published biochemical characterization show that the bm2 gene encodes a functional MTHFR. Quantitative RT-PCR analyses demonstrated that the bm2 mutants accumulate substantially reduced levels of bm2 transcript. Alteration of MTHFR function is expected to influence accumulation of the methyl donor S-adenosyl-L-methionine (SAM). Because SAM is consumed by two methyltransferases in the lignin pathway (Ye et al., ), the finding that bm2 encodes a functional MTHFR is consistent with its lignin phenotype. Consistent with this functional assignment of bm2, the expression patterns of genes in a variety of SAM-dependent or -related pathways, including lignin biosynthesis, are altered in the bm2 mutant. Biochemical assays confirmed that bm2 mutants accumulate reduced levels of lignin with altered composition compared to wild-type. Hence, this study demonstrates a role for MTHFR in lignin biosynthesis.

MTHFR C677T genotype and cardiovascular risk in a general population without mandatory folic acid fortification

PURPOSE

Meta-analyses have suggested an effect of MTHFR C677T genotype (rs1801133), a proxy for blood total homocysteine, on cardiovascular disease (CVD) in populations with low population dietary folate. The aim was to examine the association and effect modification by serum folate and vitamin B12 levels between MTHFR and CVD-related outcomes in a general population with no mandatory folic acid fortification policy.

METHODS

The study population included 13,748 adults retrieved from pooling of four population-based studies conducted in Denmark. MTHFR genotype, serum folate (measured in approximately 9,356 individuals), and serum vitamin B12 (9,215 individuals), hypertension, and dyslipidemia were measured at baseline, and participants were followed for a mean of 10.5-11.7 years in central registries for diagnoses of stroke (623 incidents), ischaemic heart disease (IHD) (835 incidents), and all-cause mortality (1,272 incidents).

RESULTS

The MTHFR genotype (TT vs. CC/CT) was not associated with hypertension [OR (95% CI) 1.09 (0.95-1.25)], dyslipidemia [OR (95% CI) 0.97 (0.84-1.11)], stroke [HR (95% CI) 0.92 (0.69-1.23)], and all-cause mortality [HR (95% CI) 0.94 (0.77-1.14)], either overall, or in participants with low serum folate or B12 status (P values for interactions 0.15-0.94). Individuals with the MTHFR TT genotype had a higher risk of IHD (HR (95% CI) 1.38 (1.11-1.71)), but this association was not modified by folate status (P value for interaction 0.45).

CONCLUSIONS

Our results do not support a causal relationship between homocysteine and CVD. However, we cannot exclude a direct causal effect of MTHFR C677T genotype on IHD.

[Analysis of the effect of N5, N10-methylenetetrahydrofolate reductase gene C(677)-->T polymorphism on the ischemic stroke development in persons with various risk factors]

The results ofMTHFR gene C(677)-->T (rs1801133) polymorphism determined in 170 patients with ischemic atherothrombotic stroke (IATS) and 124 healthy subjects (control group) are presented in the paper. It has been shown that in patients with IATS, the frequencies of main homozygotes (CC), heterozygotes (CT) and minor homozygotes (TT) are 52.4, 35.9, 11.8% (in control--46.0, 48.4, 5.6%, P = 0.044 by chi2-test). TT homozygotes have a greater chance of developing IATS than carriers of main C-allele (CT + CC) (OR = 2.3, CI = 0.911-5.449, P = 0.049). In the representatives of the Ukrainian population there is a relationship between the frequency of MTHFR gene C(677)-->T polymorphism genotypes and the risk of IATS. This connection is manifested in male patients, in persons with normal blood pressure, and in people who do not have the habit of smoking. The sex of the patients, body mass index, blood pressure and smoking affect the level of the studied polymorphism association with stroke.

The effect of MTHFR C677T polymorphism on type 2 diabetes mellitus with vascular complications in Chinese Han population: a meta-analysis

Methylenetetrahydrofolate reductase plays an important role in folate metabolism. Individuals who are type 2 diabetes mellitus have greatest risk for the development of vascular complications. The results of studies which assessed the association between MTHFR C677T polymorphism and T2DM with vascular complications were inconsistent in the Chinese Han population. The purpose of this meta-analysis was to assess the associations between MTHFR C677T polymorphism and T2DM with vascular complications in the Chinese Han population. We collected all relevant articles on MTHFR C677T polymorphisms and T2DM with vascular complications in the Chinese Han population in multiple electronic databases which were searched to December 2013. Fixed-effects and random-effects meta-analyses were performed to assess the odds ratios (ORs). Stratified Analysis, sensitivity Analysis and publication bias were examined. A total of 1984 diabetic patients with vascular complications and 1703 single diabetic patients were found in meta-analysis. There was a significant association between MTHFR C677T polymorphisms and T2DM with vascular complications under recessive genetic model, dominant genetic model, homozygous genetic model, heterozygous genetic model and allele comparison. Sensitivity analysis indicated that the overall result was dependable. Our meta-analysis suggests the MTHFR C677T polymorphisms is associated with T2DM with vascular complications in the Chinese Han population.

DNA methylation of IGF2DMR and H19 is associated with fetal and infant growth: the generation R study

Changes in epigenetic programming of embryonic growth genes during pregnancy seem to affect fetal growth. Therefore, in a population-based prospective birth cohort in the Netherlands, we examined associations between fetal and infant growth and DNA methylation of IGF2DMR, H19 and MTHFR. For this study, we selected 69 case children born small-for-gestational age (SGA, birth weight <-2SDS) and 471 control children. Fetal growth was assessed with serial ultrasound measurements. Information on birth outcomes was retrieved from medical records. Infant weight was assessed at three and six months. Methylation was assessed in DNA extracted from umbilical cord white blood cells. Analyses were performed using linear mixed models with DNA methylation as dependent variable. The DNA methylation levels of IGF2DMR and H19 in the control group were, median (90% range), 53.6% (44.5-61.6) and 30.0% (25.6-34.2) and in the SGA group 52.0% (43.9-60.9) and 30.5% (23.9-32.9), respectively. The MTHFR region was found to be hypomethylated with limited variability in the control and SGA group, 2.5% (1.4-4.0) and 2.4% (1.5-3.8), respectively. SGA was associated with lower IGF2DMR DNA methylation (β = -1.07, 95% CI -1.93; -0.21, P-value = 0.015), but not with H19 methylation. A weight gain in the first three months after birth was associated with lower IGF2DMR DNA methylation (β = -0.53, 95% CI -0.91; -0.16, P-value = 0.005). Genetic variants in the IGF2/H19 locus were associated with IGF2DMR DNA methylation (P-value<0.05), but not with H19 methylation. Furthermore, our results suggest a possibility of mediation of DNA methylation in the association between the genetic variants and SGA. To conclude, IGF2DMR and H19 DNA methylation is associated with fetal and infant growth.

The association between MTHFR 677C>T genotype and folate status and genomic and gene-specific DNA methylation in the colon of individuals without colorectal neoplasia

BACKGROUND

Decreased genomic and increased gene-specific DNA methylation predispose to colorectal cancer. Dietary folate intake and the methylenetetrahydrofolate reductase polymorphism (MTHFR 677C>T) may influence risk by modifying DNA methylation.

OBJECTIVE

We investigated the associations between MTHFR 677C>T genotype, folate status, and DNA methylation in the colon.

DESIGN

We conducted a cross-sectional study of 336 men and women (age 19-92 y) in the United Kingdom without colorectal neoplasia. We obtained blood samples for measurement of serum and red blood cell folate, plasma homocysteine, and MTHFR 677C>T genotype and colonic tissue biopsies for measurement of colonic tissue folate and DNA methylation (genomic- and gene-specific, estrogen receptor 1, ESR1; myoblast determination protein 1, MYOD1; insulin-like growth factor II, IGF2; tumor suppressor candidate 33, N33; adenomatous polyposis coli, APC; mut-L homolog 1, MLH1; and O(6)-methylguanine-DNA methyltransferase, MGMT) by liquid chromatography/electrospray ionization mass spectrometry and pyrosequencing, respectively.

RESULTS

Of the 336 subjects recruited, 185 (55%) carried the CC, 119 (35%) the CT, and 32 (10%) the TT alleles. No significant differences in systemic markers of folate status and colonic tissue folate between genotypes were found. The MTHFR TT genotype was not associated with genomic or gene-specific DNA methylation. Biomarkers of folate status were not associated with genomic DNA methylation. Relations between biomarkers of folate status and gene-specific methylation were inconsistent. However, low serum folate was associated with high MGMT methylation (P = 0.001).

CONCLUSION

MTHFR 677C>T genotype and folate status were generally not associated with DNA methylation in the colon of a folate-replete population without neoplasia.

[Influence of the MTHFR gene C677T polymorphism with physical performance and function of cardiovascular system in athletes]

The aim of the was to investigate the interrelation between MTHFR gene C677T polymorphism and morphometric echocardiography and physiologic parameters in male ski racers (n = 23). Genotyping was performed by RFLP. Echocardiography was performed by ultrasound scanner Nemio MX (Toshiba, Japan). We found that the MTHFR C677 allele was associated with low myocardial growth and high physical performance of athletes.

A population model of folate-mediated one-carbon metabolism

Background: Previous mathematical models for hepatic and tissue one-carbon metabolism have been combined and extended to include a blood plasma compartment. We use this model to study how the concentrations of metabolites that can be measured in the plasma are related to their respective intracellular concentrations. Methods: The model consists of a set of ordinary differential equations, one for each metabolite in each compartment, and kinetic equations for metabolism and for transport between compartments. The model was validated by comparison to a variety of experimental data such as the methionine load test and variation in folate intake. We further extended this model by introducing random and systematic variation in enzyme activity. Outcomes and Conclusions: A database of 10,000 virtual individuals was generated, each with a quantitatively different one-carbon metabolism. Our population has distributions of folate and homocysteine in the plasma and tissues that are similar to those found in the NHANES data. The model reproduces many other sets of clinical data. We show that tissue and plasma folate is highly correlated, but liver and plasma folate much less so. Oxidative stress increases the plasma S-adenosylmethionine/S-adenosylhomocysteine (SAM/SAH) ratio. We show that many relationships among variables are nonlinear and in many cases we provide explanations. Sampling of subpopulations produces dramatically different apparent associations among variables. The model can be used to simulate populations with polymorphisms in genes for folate metabolism and variations in dietary input.

The human MTHFR rs4846049 polymorphism increases coronary heart disease risk through modifying miRNA binding

BACKGROUND AND AIMS

Abnormal functioning of 5,10-methylenetetrahydrofolate reductase (MTHFR) enhances the risk for coronary heart disease (CHD). Here, we tested whether a single-nucleotide polymorphism (SNP) located in the 3' untranslated region (UTR) of MTHFR was associated with CHD susceptibility by affecting microRNAs binding.

METHODS AND RESULTS

We first analyzed in silico the SNPs localized in the 3' UTR of MTHFR for their ability to modify miRNA binding. We observed that rs4846049 (G > T) was a potential candidate SNP to modulate miRNAs:MTHFR mRNA complex, with the greatest changed binding free energy for has-miR-149. Based on luciferase analysis, hsa-miR-149 inhibited the activity of the reporter vector carrying -T allele, but not -G allele. We further conducted a case-control study (654 vs 455) in a Chinese Han population. rs4846049 was significantly associated with increased risk for CHD. In addition, the T allele was associated with decreased levels of HDL-cholesterol and apoA. Finally, we observed a reduced MTHFR protein level in peripheral blood mononuclear cells of CHD patients with TT carriers compared to GG carriers of rs4846049.

CONCLUSION

Our results suggest that rs4846049 (G > T) of MTHFR is associated with increased risk for CHD. We also identified a potentially pathogenetic mechanism of SNP-modified posttranscriptional gene regulation by miRNAs to MTHFR.