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1.  Polymorphisms in Methionine Synthase, Methionine Synthase Reductase and Serine Hydroxymethyltransferase, Folate and Alcohol Intake, and Colon Cancer Risk 
Background/Aims
We examined associations among folate and alcohol intake, SNPs in genes involved in one-carbon metabolism and colon cancer risk.
Methods
Colon cancer cases (294 African Americans and 349 whites) were frequency matched to population controls (437 African Americans and 611 whites) by age, race and sex from 33 North Carolina counties from 1996 to 2000. Folate and alcohol intakes were collected by dietary interview. Five SNPs were genotyped using DNA from whole blood: SHMT C1420T; MTRR A66G; MTR A2756G, and the previously-reported MTHFR C677T and MTHFR A1298C. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression.
Results
An inverse association was observed for SHMT TT genotype as compared to CC genotype in whites (OR=0.6, 95%CI=0.4, 1.0), but not in African Americans. Inverse associations were observed for high folate intake in individuals carrying 0 or 1 variant allele [OR 0.2 (95%CI 0.06 – 0.8) for African Americans; OR 0.2 (95%CI 0.1– 0.6) for whites] compared to low folate intake. Modest interactions between these SNPs and alcohol or folate intakes were observed.
Conclusions
Our results are consistent with other findings and provide needed data on these associations among African Americans.
doi:10.1159/000136651
PMCID: PMC2758622  PMID: 19776626
Alcohol; case-control study; colon cancer; folate; polymorphism
2.  Dietary intake of folate, vitamin B6, and vitamin B12, genetic polymorphism of related enzymes, and risk of breast cancer: a case-control study in Brazilian women 
BMC Cancer  2009;9:122.
Background
Several studies have determined that dietary intake of B vitamins may be associated with breast cancer risk as a result of interactions between 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) in the one-carbon metabolism pathway. However, the association between B vitamin intake and breast cancer risk in Brazilian women in particular has not yet been investigated.
Methods
A case-control study was conducted in São Paulo, Brazil, with 458 age-matched pairs of Brazilian women. Energy-adjusted intakes of folate, vitamin B6, and vitamin B12 were derived from a validated Food Frequency Questionnaire (FFQ). Genotyping was completed for MTHFR A1298C and C677T, and MTR A2756G polymorphisms. A logistical regression model was used to calculate odds ratios (ORs) and 95% confidence intervals (95% CIs).
Results
Neither dietary intake of folate, vitamin B6, or vitamin B12 nor MTHFR polymorphisms were independently associated with breast cancer risk. Analysis stratified by menopausal status showed a significant association between placement in the highest tertile of folate intake and risk of breast cancer in premenopausal women (OR = 2.17, 95% CI: 1.23–3.83; Ptrend = 0.010). The MTR 2756GG genotype was associated with a higher risk of breast cancer than the 2756AA genotype (OR = 1.99, 95% CI = 1.01–3.92; Ptrend = 0.801), and statistically significant interactions with regard to risk were observed between the MTHFR A1298C polymorphism and folate (P = 0.024) or vitamin B6 (P = 0.043), and between the MTHFR C677T polymorphism and folate (P = 0.043) or vitamin B12 (P = 0.022).
Conclusion
MTHFR polymorphisms and dietary intake of folate, vitamin B6, and vitamin B12 had no overall association with breast cancer risk. However, increased risk was observed in total women with the MTR 2756GG genotype and in premenopausal women with high folate intake. These findings, as well as significant interactions between MTHFR polymorphisms and B vitamins, warrant further investigation.
doi:10.1186/1471-2407-9-122
PMCID: PMC2684745  PMID: 19389261
3.  No association between cSHMT genotypes and risk of breast cancer in the Nurses’ Health Study 
Objective
Increased breast cancer risk has been observed with both low folate status and a functional polymorphism in methylenetetrahydrofolate reductase (MTHFR 677C→T). Cytoplasmic serine hydroxymethyltransferase (cSHMT) affects the flow of one-carbon units through the folate metabolic network, but there is little research on a role for genetic variation in cSHMT in determining breast cancer risk.
Methods
A nested case-control study within the Nurses’ Health Study was used to investigate an association between cSHMT (1420C→T) and breast cancer risk.
Results
No evidence for an association of cSHMT genotype and breast cancer was 10 observed. There was also no evidence of a gene-gene interaction between cSHMT and MTHFR.
Conclusions
There was no evidence of an association between cSHMT genotype and breast cancer occurrence. Further research in populations with differing average folate intake may be needed to fully understand the interactions of folate nutrition, sequence variation in folate genes, and breast cancer risk.
doi:10.1038/ejcn.2009.104
PMCID: PMC3033771  PMID: 19707223
breast cancer; cSHMT; MTHFR; folate
4.  Association between dietary intake of folate, vitamin B6, B12 & MTHFR, MTR Genotype and breast cancer risk 
Objective: we conducted a case-control study to investigate the association between dietary folate, vitamin B6 and vitamin B12 intake, MTHFR and MTR genotype, and breast cancer risk.
Methods: Genotyping for MTHFR C677T and A1298C and MTR A2756G polymorphisms were performed using polymerase chain reaction-restriction fragment length polymorphism analysis (PCR-RFLP) method. The intake of folate, vitamin B6 and vitamin B12 were calculated by each food item from questionnaire.
Results: Subjects with breast cancer tended to have more first-degree relatives (χ2=30.77, P<0.001) and have high intake of folate (t=2.42, P=0.008) and Vitamin B6 (t=2.94, P=0.002). Compared to the reference group, women with MTHFR 677 TT genotype and T allele had a significantly increased risk of breast cancer, with ORs (95%CI) of 1.8(1.08-2.27) and 1.39(1.02-1.92), respectively. For those who had folate intake<450 ug/day, MTHFR 667TT genotype was associated with a higher risk of breast cancer (OR=2.45, 95% CI=1.09-5.82, P=0.02). Similarly, subjects with Vitamin B6 intake<0.84 mg/day and MTHFR 667T allele genotype was correlated with a marginally increased risk of breast cancer. A significant interaction was observed between MTHFR C667T polymorphism and folate intake on the risk of breast cancer (P for interaction was 0.025).
Conclusion: This case-control study found a significant association between MTHFR C667T polymorphism, folate intake and vitamin B6 and breast cancer risk, and a significant interaction was observed between MTHFR C667T polymorphism and folate intake on the risk of breast cancer.
doi:10.12669/pjms.301.4189
PMCID: PMC3955552  PMID: 24639841
Breast cancer; Folate; MTHFR; MTR; Polymorphism; Vitamin
5.  Genetic variants in the folate pathway and risk of childhood acute lymphoblastic leukemia 
Cancer causes & control : CCC  2011;22(9):1243-1258.
Objective
Folate is involved in the one-carbon metabolism that plays an essential role in the synthesis, repair and methylation of DNA. We examined whether child’s germline genetic variation in the folate pathway is associated with childhood acute lymphoblastic leukemia (ALL), and whether periconception maternal folate and alcohol intake modify the risk.
Methods
Seventy-six single nucleotide polymorphisms (SNPs), including 66 haplotype-tagging SNPs in 10 genes (CBS, DHFR, FOLH1, MTHFD1, MTHFR, MTR, MTRR, SHMT1, SLC19A1, and TYMS) were genotyped in 377 ALL cases and 448 controls. Log-additive associations between genotypes and ALL risk were adjusted for age, sex, Hispanic ethnicity (when appropriate), and maternal race.
Results
Single and haplotype SNPs analyses showed statistically significant associations between SNPs located in (or adjacent to) CBS, MTRR, TYMS/ENOFS and childhood ALL. Many regions of CBS were associated with childhood ALL in Hispanics and non-Hispanics (P <0.01). Levels of maternal folate intake modified associations with SNPs in CBS, MTRR, and TYMS.
Conclusion
Our data suggest the importance of genetic variability in the folate pathway and childhood ALL risk.
doi:10.1007/s10552-011-9795-7
PMCID: PMC3744066  PMID: 21748308
Case-control study; Children; DNA methylation; Folate; Genetic polymorphisms; Leukemia
6.  Investigating Multiple Candidate Genes and Nutrients in the Folate Metabolism Pathway to Detect Genetic and Nutritional Risk Factors for Lung Cancer 
PLoS ONE  2013;8(1):e53475.
Purpose
Folate metabolism, with its importance to DNA repair, provides a promising region for genetic investigation of lung cancer risk. This project investigates genes (MTHFR, MTR, MTRR, CBS, SHMT1, TYMS), folate metabolism related nutrients (B vitamins, methionine, choline, and betaine) and their gene-nutrient interactions.
Methods
We analyzed 115 tag single nucleotide polymorphisms (SNPs) and 15 nutrients from 1239 and 1692 non-Hispanic white, histologically-confirmed lung cancer cases and controls, respectively, using stochastic search variable selection (a Bayesian model averaging approach). Analyses were stratified by current, former, and never smoking status.
Results
Rs6893114 in MTRR (odds ratio [OR] = 2.10; 95% credible interval [CI]: 1.20–3.48) and alcohol (drinkers vs. non-drinkers, OR = 0.48; 95% CI: 0.26–0.84) were associated with lung cancer risk in current smokers. Rs13170530 in MTRR (OR = 1.70; 95% CI: 1.10–2.87) and two SNP*nutrient interactions [betaine*rs2658161 (OR = 0.42; 95% CI: 0.19–0.88) and betaine*rs16948305 (OR = 0.54; 95% CI: 0.30–0.91)] were associated with lung cancer risk in former smokers. SNPs in MTRR (rs13162612; OR = 0.25; 95% CI: 0.11–0.58; rs10512948; OR = 0.61; 95% CI: 0.41–0.90; rs2924471; OR = 3.31; 95% CI: 1.66–6.59), and MTHFR (rs9651118; OR = 0.63; 95% CI: 0.43–0.95) and three SNP*nutrient interactions (choline*rs10475407; OR = 1.62; 95% CI: 1.11–2.42; choline*rs11134290; OR = 0.51; 95% CI: 0.27–0.92; and riboflavin*rs8767412; OR = 0.40; 95% CI: 0.15–0.95) were associated with lung cancer risk in never smokers.
Conclusions
This study identified possible nutrient and genetic factors related to folate metabolism associated with lung cancer risk, which could potentially lead to nutritional interventions tailored by smoking status to reduce lung cancer risk.
doi:10.1371/journal.pone.0053475
PMCID: PMC3553105  PMID: 23372658
7.  MTHFR Polymorphisms, Folate Intake, and Carcinogen DNA Adducts in the Lung 
The methylenetetrahydrofolate reductase (MTHFR) genes and folate in one-carbon metabolism are essential for DNA methylation and synthesis. However, their role in carcinogen DNA damage in target lung tissue, a dosimeter for cancer risk, is not known. Our study aimed to investigate the association between genetic and nutritional one-carbon metabolism factors and DNA adducts in target lung. Data on 135 lung cancer cases from the Massachusetts General Hospital were studied. Genotyping was completed for MTHFR C677T (rs1801133) and A1298C (rs1801131). Information on dietary intake for one-carbon related micronutrients, folate and other B vitamin, was derived from a validated food frequency questionnaire. DNA adducts in lung were measured by 32P-postlabeling. After adjusting for potential confounders, DNA adduct levels in lung significantly increased by 69.2% [95% confidence interval (CI), 5.5% to 171.5%] for the MTHFR 1298AC+CC genotype. The high risk group, combining the A1298C (AC+CC) plus C677T (CT+TT) genotypes, had significantly enhanced levels of lung adducts by 210.7% (95% CI, 21.4% to 695.2%) in contrast to the A1298C (AA) plus C677T (CC) genotypes. Elevation of DNA adduct was pronounced - 111.3% (95% CI, −3.0 to 360.5%) among 1298AC+CC patients who consumed the lowest level of folate intake as compared with 1298AA individuals with highest tertile of intake. These results indicate that DNA adducts levels are influenced by MTHFR polymorphisms and low folate consumption, suggesting an important role of genetic and nutritional factors in protecting DNA damage from lung carcinogen in at-risk populations.
doi:10.1002/ijc.27338
PMCID: PMC3293105  PMID: 22052259
MTHFR; folate; genetic polymorphisms; DNA adducts; one carbon metabolism
8.  Effects of methionine synthase and methylenetetrahydrofolate reductase gene polymorphisms on markers of one-carbon metabolism 
Genes & Nutrition  2013;8(6):571-580.
Genetic and nutritional factors play a role in determining the functionality of the one-carbon (1C) metabolism cycle, a network of biochemical reactions critical to intracellular processes. Genes encoding enzymes for methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR) may determine biomarkers of the cycle including homocysteine (HCY), S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH). MTHFR C677T is an established genetic determinant of HCY but less is known of its effect on SAM and SAH. Conversely, the relationship between MTR A2756G and HCY remains inconclusive, and its effect on SAM and SAH has only been previously investigated in a female-specific population. Folate and vitamin B12 are essential substrate and cofactor of 1C metabolism; thus, consideration of gene–nutrient interactions may clarify the role of genetic determinants of HCY, SAM and SAH. This cross-sectional study included 570 healthy volunteers from Kingston, Ontario, Ottawa, Ontario and Halifax, Nova Scotia, Canada. Least squares regression was used to examine the effects of MTR and MTHFR polymorphisms on plasma HCY, SAM and SAH concentrations; gene–gene and gene–nutrient interactions were considered with the inclusion of cross-products in the model. Main effects of MTR and MTHFR polymorphisms on HCY concentrations were observed; however, no gene–gene or gene–nutrient interactions were found. No association was observed for SAM. For SAH, interactions between MTR and MTHFR polymorphisms, and MTHFR polymorphism and serum folate were found. The findings of this research provide evidence that HCY and SAH, biomarkers of 1C metabolism, are influenced by genetic and nutritional factors and their interactions.
doi:10.1007/s12263-013-0358-2
PMCID: PMC3824834  PMID: 24101362
Methionine synthase; Methylenetetrahydrofolate reductase; Homocysteine; S-adenosylmethionine; S-adenosylhomocysteine; One-carbon metabolism
9.  DNA promoter methylation in breast tumors: No association with genetic polymorphisms in MTHFR and MTR 
Aberrant promoter methylation is recognized as an important feature of breast carcinogenesis. We hypothesized that genetic variation of genes for methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MTR), two critical enzymes in one-carbon metabolism, may alter DNA methylation levels, and thus influence DNA methylation in breast cancer. We evaluated case-control association of MTHFR C677T, A1298C, and MTR A2756G polymorphisms for cases strata defined by promoter methylation status for each of three genes, E- cadherin, p16, and RAR-β2 in breast cancer; in addition, we evaluated case-case comparisons of likelihood of promoter methylation in relation to genotypes using a population-based case-control study conducted in Western New York State. Methylation was evaluated with real time methylation-specific PCRs for 803 paraffin embedded breast tumor tissues from women with primary, incident breast cancer. We applied unordered polytomous regression and unconditional logistic regression to derive adjusted odds ratios (OR) and 95% confidence intervals (CI). We did not find any association of MTHFR and MTR polymorphisms with breast cancer risk stratified by methylation status nor between polymorphisms and likelihood of promoter methylation of any of the genes. There was no evidence of difference within strata defined by menopausal status, ER status, folate intake and lifetime alcohol consumption. Overall, we found no evidence that these common polymorphisms of the MTHFR and MTR genes are associated with promoter methylation of E- cadherin, p16, and RAR-β2 genes in breast cancer.
doi:10.1158/1055-9965.EPI-08-0916
PMCID: PMC3837294  PMID: 19240236
promoter methylation; MTHFR; MTR; breast cancer; epidemiology; genetic polymorphisms
10.  Cardiac Autonomic Dysfunction: Effects from Particulate Air Pollution and Protection by Dietary Methyl Nutrients and Metabolic Polymorphisms 
Circulation  2008;117(14):1802-1809.
Background
Particulate air pollution is associated with cardiovascular mortality and morbidity. To help identify mechanisms of action and protective/susceptibility factors, we evaluated whether the effect of particulate matter <2.5 µm in aerodynamic diameter (PM2.5) on heart rate variability (HRV) was modified by dietary intakes of methyl nutrients (folate, vitamin B6, B12, methionine) and related gene polymorphisms (C677T MTHFR and C1420T cSHMT).
Methods and Results
HRV and dietary data were obtained between 2000–2005 from 549 elderly men from the Normative Aging Study. In carriers of [CT/TT] MTHFR genotypes, the standard deviation of normal-to-normal intervals (SDNN) was 17.1% (95% CI, 6.5, 26.4; p=0.002) lower than in CC MTHFR subjects. In the same [CT/TT] MTHFR subjects, each 10 µg/m3 increase in PM2.5 in the 48 hours before the examination was associated with a further 8.8% (95%CI: 0.2, 16.7; p=0.047) decrease in SDDN. In [CC] cSHMT carriers, PM2.5 was associated with a 11.8% (95%CI: 1.8, 20.8; p=0.02) decrease in SDDN. No PM2.5-SSDN association was found in subjects with either [CC] MTHFR or [CT/TT] cSHMT genotypes. The negative effects of PM2.5 were abrogated in subjects with higher intakes (>median levels) of B6, B12, or methionine. PM2.5 was negatively associated with HRV in subjects with lower intakes, but no PM2.5 effect was found in the higher intake groups.
Conclusions
Genetic and nutritional variations in the methionine cycle affect HRV, either independently or by modifying the effects of PM2.5.
doi:10.1161/CIRCULATIONAHA.107.726067
PMCID: PMC3093965  PMID: 18378616
heart rate; nervous system; autonomic; metabolism; aging; epidemiology
11.  MTHFR C677T and postmenopausal breast cancer risk by intakes of one-carbon metabolism nutrients: a nested case-control study 
Introduction
The C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene has been hypothesized to increase breast cancer risk. However, results have been inconsistent, and few studies have reported the association by menopausal status or by intakes of nutrients participating in one-carbon metabolism. Our aims were to investigate whether MTHFR C677T was associated with postmenopausal breast cancer risk and whether this relation was modified by intakes of folate, methionine, vitamins B2, B6, and B12, and alcohol.
Methods
We studied 318 incident breast cancer cases and 647 age- and race-matched controls participating in a nested case-control study of postmenopausal women within the VITamins And Lifestyle (VITAL) cohort. Genotyping was conducted for MTHFR C677T and dietary and supplemental intakes were ascertained from a validated questionnaire. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression.
Results
We observed a 62% increased risk of breast cancer among postmenopausal women with the TT genotype (OR = 1.62; 95% CI: 1.05 to 2.48). Women with a higher number of variant T alleles had higher risk of breast cancer (P for trend = 0.04). Evidence of effect-modification by intakes of some B vitamins was observed. The most pronounced MTHFR-breast cancer risks were observed among women with the lowest intakes of dietary folate (P for interaction = 0.02) and total (diet plus supplemental) vitamin B6 (P for interaction = 0.01), with no significant increased risks among women with higher intakes.
Conclusions
This study provides support that the MTHFR 677TT genotype is associated with a moderate increase in risk of postmenopausal breast cancer and that this risk may be attenuated with high intakes of some one-carbon associated nutrients.
doi:10.1186/bcr2462
PMCID: PMC2815555  PMID: 20030812
12.  Comprehensive Evaluation of One-Carbon Metabolism Pathway Gene Variants and Renal Cell Cancer Risk 
PLoS ONE  2011;6(10):e26165.
Introduction
Folate and one-carbon metabolism are linked to cancer risk through their integral role in DNA synthesis and methylation. Variation in one-carbon metabolism genes, particularly MTHFR, has been associated with risk of a number of cancers in epidemiologic studies, but little is known regarding renal cancer.
Methods
Tag single nucleotide polymorphisms (SNPs) selected to produce high genomic coverage of 13 gene regions of one-carbon metabolism (ALDH1L1, BHMT, CBS, FOLR1, MTHFR, MTR, MTRR, SHMT1, SLC19A1, TYMS) and the closely associated glutathione synthesis pathway (CTH, GGH, GSS) were genotyped for 777 renal cell carcinoma (RCC) cases and 1,035 controls in the Central and Eastern European Renal Cancer case-control study. Associations of individual SNPs (n = 163) with RCC risk were calculated using unconditional logistic regression adjusted for age, sex and study center. Minimum p-value permutation (Min-P) tests were used to identify gene regions associated with risk, and haplotypes were evaluated within these genes.
Results
The strongest associations with RCC risk were observed for SLC19A1 (Pmin-P = 0.03) and MTHFR (Pmin-P = 0.13). A haplotype consisting of four SNPs in SLC19A1 (rs12483553, rs2838950, rs2838951, and rs17004785) was associated with a 37% increased risk (p = 0.02), and exploratory stratified analysis suggested the association was only significant among those in the lowest tertile of vegetable intake.
Conclusions
To our knowledge, this is the first study to comprehensively examine variation in one-carbon metabolism genes in relation to RCC risk. We identified a novel association with SLC19A1, which is important for transport of folate into cells. Replication in other populations is required to confirm these findings.
doi:10.1371/journal.pone.0026165
PMCID: PMC3198392  PMID: 22039442
13.  Dietary intake of folate and co-factors in folate metabolism, MTHFR polymorphisms, and reduced rectal cancer 
Cancer causes & control : CCC  2007;18(2):153-163.
Little is known about the contribution of polymorphisms in the methylenetetrahydrofolate reductase gene (MTHFR) and the folate metabolism pathway in rectal cancer alone. Data were from participants in a case-control study conducted in Northern California and Utah (751 cases and 979 controls). We examined independent associations and interactions of folate, B vitamins, methionine, alcohol, and MTHFR polymorphisms (MTHFR C677T and A1298C) with rectal cancer. Dietary folate intake was associated with a reduction in rectal cancer OR 0.66, 95% CI 0.48-0.92 (>475 mcg day compared to < = 322 mcg) as was a combination of nutrient intakes contributing to higher methyl donor status (OR 0.79, 95% CI 0.66-0.95). Risk was reduced among women with the 677 TT genotype (OR 0.54, 95% CI 0.30-0.9), but not men (OR 1.11, 95% CI 0.70-1.76) and with the 1298 CC genotype in combined gender analysis (OR 0.67, 95% CI 0.46-0.98). These data are consistent with a protective effect of increasing dietary folate against rectal cancer and suggest a protective role of the MTHFR 677 TT genotype in women and 1298 CC in men and women. Folate intake, low methyl donor status, and MTHFR polymorphisms may play independent roles in the etiology of rectal cancer.
doi:10.1007/s10552-006-0099-2
PMCID: PMC2366030  PMID: 17245555
Diet; Pteroylpolyglutamic Acids; Rectal Neoplasms; Polymorphism; Genetic
14.  Green tea intake, MTHFR/TYMS genotype and breast cancer risk: the Singapore Chinese Health Study 
Carcinogenesis  2008;29(10):1967-1972.
The tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) has been reported to act as a cancer preventive agent through folate pathway inhibition in experimental studies. We hypothesized that if folate pathway inhibition is the mechanism of cancer preventive activities of EGCG, then the protective effect against breast cancer would be stronger among women with low dietary folate intake and the high-activity methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TYMS) genotypes. In a nested case–control study of 380 women with incident breast cancer and 662 controls within the Singapore Chinese Health Study, we found no association between either green tea intake or gene polymorphisms of MTHFR (C677T and A1298C) and TYMS (1494 ins/del) and breast cancer risk. However, among women with low folate intake (<133.4 μg/day), weekly/daily green tea intake was inversely associated with breast cancer risk compared with less green tea intake [odds ratio (OR) = 0.45, 95% confidence interval (CI) = 0.26–0.79, P for interaction = 0.02]. Among women with high folate intake (≥133.4 μg/day), green tea intake was not associated with breast cancer. Similarly, among women possessing the high-activity MTHFR/TYMS genotypes (0–1 variant allele), weekly/daily versus less frequent green tea intake was associated with lower breast cancer risk (OR = 0.66, 95% CI = 0.45–0.98), which was observed even more strongly among those who also had low folate intake (OR = 0.44, 95% CI = 0.22–0.89) than high folate intake (OR = 0.92, 95% CI = 0.55–1.54). This association was not observed among women possessing the low-activity genotypes (2–4 variant alleles). Our findings suggest that folate pathway inhibition may be one mechanism through which green tea protects against breast cancer in humans.
doi:10.1093/carcin/bgn177
PMCID: PMC2574755  PMID: 18669903
15.  Green tea intake, MTHFR/TYMS genotype, and breast cancer risk: The Singapore Chinese Health Study 
Carcinogenesis  2008;29(10):1967-1972.
The tea polyphenol (-)-epigallocatechin gallate (EGCG) has been reported to act as a cancer preventive agent through folate pathway inhibition in experimental studies. We hypothesized that if folate pathway inhibition is the mechanism of cancer preventive activities of EGCG, then the protective effect against breast cancer would be stronger among women with low dietary folate intake and the high activity methylenetetrahydrofolate reductase (MTHFR) and thymidylate synthase (TYMS) genotypes. In a nested case-control study of 380 women with incident breast cancer and 662 controls within the Singapore Chinese Health Study, we found no association between either green tea intake or gene polymorphisms of MTHFR (C677T, A1298C) and TYMS (1494 ins/del) and breast cancer risk. However, among women with low folate intake (<133.4mcg/day), weekly/daily green tea intake was inversely associated with breast cancer risk compared with less green tea intake (odds ratio (OR)=0.45, 95% confidence interval (CI)=0.26-0.79, P for interaction=0.02). Among women with high folate intake (≥133.4mcg/day), green tea intake was not associated with breast cancer. Similarly, among women possessing the high activity MTHFR/TYMS genotypes (0-1 variant allele), weekly/daily vs. less frequent green tea intake was associated with lower breast cancer risk (OR=0.66, 95%CI=0.45-0.98), which was observed even more strongly among those who also had low folate intake (OR=0.44, 95%CI=0.22-0.89) than high folate intake (OR=0.92, 95%CI=0.55-1.54). This association was not observed among women possessing the low activity genotypes (2-4 variant alleles). Our findings suggest that folate pathway inhibition may be one mechanism through which green tea protects against breast cancer in humans.
doi:10.1093/carcin/bgn177
PMCID: PMC2574755  PMID: 18669903
green tea; MTHFR; TYMS; breast cancer; folate
16.  The association between first trimester micronutrient intake, MTHFR genotypes, and global DNA methylation in pregnant women 
Objective
Our aim was to evaluate possible associations between consumption of micronutrients involved in one-carbon metabolism, MTHFR genotypes, and global DNA methylation in pregnant women.
Methods
A semi-quantitative dietary questionnaire was administered to 195 women during their first trimester in Morelos, Mexico. Two functional polymorphisms of the key folate-metabolizing gene, i.e. MTHFR 677 C>T and 1298 A>C, as well as global DNA methylation were assessed in peripheral blood drawn during the interview.
Results
Independent of maternal age and caloric intake, vitamin B6 deficiency was associated with 1.8 fold increased risk of hypomethylation in women carrying the MTHFR 677 T allele.
Conclusions
There exists a subpopulation that is more susceptible to B vitamin deficiencies.
doi:10.3109/14767058.2011.564242
PMCID: PMC3279137  PMID: 21443409
Vitamin B6; epigenetics; one carbon metabolism; MTHFR 677; micronutrient deficiency
17.  One-Carbon Metabolism Pathway Gene Variants and Risk of Clear Cell Renal Cell Carcinoma in a Chinese Population 
PLoS ONE  2013;8(11):e81129.
Background
One-carbon metabolism is the basement of nucleotide synthesis and the methylation of DNA linked to cancer risk. Variations in one-carbon metabolism genes are reported to affect the risk of many cancers, including renal cancer, but little knowledge about this mechanism is known in Chinese population.
Methods
Each subject donated 5 mL venous blood after signing the agreement. The study was approved by the Institutional Review Board of the Nanjing Medical University, Nanjing, China. 18 SNPs in six one-carbon metabolism-related genes (CBS, MTHFR, MTR, MTRR, SHMT1, and TYMS) were genotyped in 859 clear cell renal cell carcinoma (ccRCC) patients and 1005 cancer-free controls by the Snapshot.
Results
Strong associations with ccRCC risk were observed for rs706209 (P = 0.006) in CBS and rs9332 (P = 0.027) in MTRR. Compared with those carrying none variant allele, individuals carrying one or more variant alleles in these two genes had a statistically significantly decreased risk of ccRCC [P = 0.001, adjusted odds ratio (OR) = 0.73, 95% confidence interval (CI) = 0.06–0.90]. In addition, patients carrying one or more variant alleles were more likely to develop localized stage disease (P = 0.002, adjusted OR = 1.37, 95%CI = 1.11–1.69) and well-differentiated ccRCC (P<0.001, adjusted OR = 1.42, 95%CI = 0.87–1.68). In the subgroup analysis, individuals carrying none variant allele in older group (P = 0.007, adjusted OR = 0.67, 95%CI = 0.49–0.91), male group (P = 0.007, adjusted OR = 0.71, 95%CI = 0.55–0.92), never smoking group (P = 0.002, adjusted OR = 0.68, 95%CI = 0.53–0.88) and never drinking group (P<0.001, adjusted OR = 0.68, 95%CI = 0.53–0.88) had an increased ccRCC risk.
Conclusions
Our results suggest that the polymorphisms of the one-carbon metabolism-related genes are associated with ccRCC risk in Chinese population. Future population-based prospective studies are required to confirm the results.
doi:10.1371/journal.pone.0081129
PMCID: PMC3837692  PMID: 24278388
18.  Gene–gene interaction in folate-related genes and risk of neural tube defects in a UK population 
Journal of Medical Genetics  2004;41(4):256-260.
Objective: To investigate the contribution of polymorphic variation in genes involved in the folate-dependent homocysteine pathway in the aetiology of neural tube defects (NTD).
Design: Case-control association study.
Subjects: A total of 530 individuals from families affected by NTD, 645 maternal controls, and 602 healthy newborn controls from the northern UK.
Main outcome measures: Seven polymorphisms in six genes coding for proteins in the folate-dependent homocysteine pathway (MTHFR 677C→T, MTHFR 1298A→C, MTRR 66A→G, SHMT 1420C→T, CßS 844ins68, GCPII 1561C→T, RFC-1 80G→A). The impact of each polymorphism and the effect of gene–gene interactions (epistasis) upon risk of NTD were assessed using logistic regression analysis.
Results: The MTHFR 677C→T polymorphism was shown to represent a risk factor in NTD cases (CC v CT+TT odds ratio (OR) 2.03 [95% confidence interval (CI) 1.09, 3.79] p = 0.025) and the MTRR 66A→G polymorphism was shown to exert a protective effect in NTD cases (AA v AG+GG OR 0.31 [95% CI 0.10, 0.94] p = 0.04). When statistical tests for interaction were conducted, three genotype combinations in cases (MTRR/GCPII; MTHFR 677/CßS; MTHFR 677/MTRR) and one combination in case mothers (CßS/RFC-1) were shown to elevate NTD risk. Maternal–fetal interaction was also detected when offspring carried the MTHFR 677C→T variant and mothers carried the MTRR 66A→G variant, resulting in a significantly elevated risk of NTD.
Conclusion: Both independent genetic effects and gene–gene interaction were observed in relation to NTD risk. Multi-locus rather than single locus analysis might be preferable to gain an accurate assessment of genetic susceptibility to NTD.
doi:10.1136/jmg.2003.010694
PMCID: PMC1735724  PMID: 15060097
19.  Association of Genetic Variation in Cystathionine-β-Synthase and Arsenic Metabolism 
Environmental research  2010;110(6):580-587.
Variation in individual susceptibility to arsenic-induced disease may be partially explained by genetic differences in arsenic metabolism. Mounting epidemiological evidence and in vitro studies suggest that methylated arsenic metabolites, particularly monomethylarsonic (MMA3), are more acutely toxic than inorganic arsenic; thus, MMA3 may be the primary toxic arsenic species. To test the role of genetic variation in arsenic metabolism, polymorphisms in genes involved in one-carbon metabolism [methylenetetrahydrofolate reductase (MTHFR), methionine synthase (MTR), cystathionine-β-synthase (CBS), thymidylate synthase (TYMS), dihydrofolate reductase (DHFR), serine hydroxymethyltransferase 1 (SHMT1] and glutathione biosynthesis [glutathione S-transferase omega 1 (GSTO1)] were examined in an arsenic exposed population to determine their influence in urinary arsenic metabolite patterns. In 142 subjects in Cordoba Province, Argentina, variant genotypes for CBS rs234709 and rs4920037 SNPs compared with wild-type homozygotes were associated with 24% and 26% increases, respectively, in the mean proportion of arsenic excreted as monomethylarsonic acid (%MMA). This difference is within the range of differences in %MMA seen between people with arsenic-related disease and those without such disease in other studies. Small inverse associations with CBS rs234709 and rs4920037 variants were also found for the mean levels of the proportion of arsenic excreted as dimethylarsinous acid (%DMA). No other genetic associations were found. These findings are the first to suggest that CBS polymorphisms may influence arsenic metabolism in humans and susceptibility to arsenic-related disease.
doi:10.1016/j.envres.2010.05.001
PMCID: PMC2913479  PMID: 20670920
arsenic; polymorphism; cystathionine-β-synthase; CBS; SNP
20.  Genetic variation of fifteen folate metabolic pathway associated gene loci and the risk of incident head and neck carcinoma: The Women’s Genome Health Study 
Objective
Recent studies have demonstrated the importance of folate metabolic pathway (FMP) in the pathogenesis of head and neck cancinoma (HNC). Whether the genetic variation within the FMP associated genes modulates HNC remains elusive. To date, prospective, epidemiological data on the relationship of FMP gene variation with the risk of HNC are sparse.
Methods
The association between 203 tag-SNPs (tSNPs) of 15 FMP associated genes (CBS, BHMT, DHFR, FOLR1, FOLR2, FOLR3, MTHFR, MTR, MTRR, MTHFD1, RFC1, SHMT1, SLC19A1, TCN2, and TYMS) and incident HNC was investigated in 23,294 Caucasian female participants of the prospective Women’s Genome Health Study. All were free of known cancer at baseline. During a 15-year follow-up period, 55 participants developed a first ever HNC. Multivariable Cox regression analysis was performed to investigate the relationship between genotypes and HNC risk assuming an additive genetic model. Haplotype-block analysis was also performed.
Results
A total of 11 tSNPs within DHFR, MTHFR, RFC1, and TYMS were associated with HNC risk (all p-uncorrected <0.050). Further investigation using the haplotype-block analysis revealed an association of several prespecified haplotypes of RFC1 with HNC risk (all p-uncorrected <0.050).
Conclusion
If corroborated in other large prospective studies, the present findings suggest that genetic variation within the folate metabolic pathway gene loci examined, in particular, the replication factor C-1 (RFC1) gene variation may influence HNC risk.
doi:10.1016/j.cca.2012.11.030
PMCID: PMC3582777  PMID: 23276522
Head and Neck; cancer; genetic epidemiology; single nucleotide polymorphisms; folate; homocysteine; Incident head and neck carcinoma; Risk factors; Polymorphisms
21.  Polymorphisms in folate-metabolizing genes, chromosome damage, and risk of Down syndrome in Italian women: identification of key factors using artificial neural networks 
BMC Medical Genomics  2010;3:42.
Background
Studies in mothers of Down syndrome individuals (MDS) point to a role for polymorphisms in folate metabolic genes in increasing chromosome damage and maternal risk for a Down syndrome (DS) pregnancy, suggesting complex gene-gene interactions. This study aimed to analyze a dataset of genetic and cytogenetic data in an Italian group of MDS and mothers of healthy children (control mothers) to assess the predictive capacity of artificial neural networks assembled in TWIST system in distinguish consistently these two different conditions and to identify the variables expressing the maximal amount of relevant information to the condition of being mother of a DS child.
The dataset consisted of the following variables: the frequency of chromosome damage in peripheral lymphocytes (BNMN frequency) and the genotype for 7 common polymorphisms in folate metabolic genes (MTHFR 677C>T and 1298A>C, MTRR 66A>G, MTR 2756A>G, RFC1 80G>A and TYMS 28bp repeats and 1494 6bp deletion). Data were analysed using TWIST system in combination with supervised artificial neural networks, and a semantic connectivity map.
Results
TWIST system selected 6 variables (BNMN frequency, MTHFR 677TT, RFC1 80AA, TYMS 1494 6bp +/+, TYMS 28bp 3R/3R and MTR 2756AA genotypes) that were subsequently used to discriminate between MDS and control mothers with 90% accuracy. The semantic connectivity map provided important information on the complex biological connections between the studied variables and the two conditions (being MDS or control mother).
Conclusions
Overall, the study suggests a link between polymorphisms in folate metabolic genes and DS risk in Italian women.
doi:10.1186/1755-8794-3-42
PMCID: PMC2949778  PMID: 20868477
22.  Association of IL-1 RN*2 allele and methionine synthase 2756 AA genotype with dementia severity of sporadic Alzheimer's disease 
Objective: To determine whether these polymorphisms and the genetic determinants of homocysteine (methylenetetrahydrofolate reductase, MTHFR; methionine synthase, MTR; transcobalamin, TC) are associated with an increased risk of severe dementia in Alzheimer's disease.
Methods: 152 patients with Alzheimer's disease and 136 controls were studied. The association of occurrence and dementia severity (Reisberg score <6 and ⩾6) of Alzheimer's disease with APO-E, IL-1A, IL-1B, IL-1RN, MTHFR677 C→T and 1298A→C, MTR 2756 A→G, and TC 776 C→G polymorphisms was evaluated by multivariate logistic regression analysis after adjustment for age, sex, and age of onset of Alzheimer's disease.
Results: IL-1A TT and IL-1B CT/TT associated genotypes were at risk of Alzheimer's disease (odds ratio 4.80 (95% confidence interval, 1.32 to 17.40), p = 0.017); the MTR 2756 AA genotype was at risk of severe dementia (OR 2.97 (1.23 to 7.21), p = 0.016); IL-1 RN*2 was protective (OR 0.28, (0.11 to 0.69), p = 0.006). Allele ϵ4 of the APO-E and IL-1B CC genotypes increased the risk of severe Alzheimer's disease associated with the MTR 2756 AA genotype by 3.3-fold and 1.5-fold, respectively.
Conclusions: Distinct determinants of the IL-1 gene cluster are related to the generation and progression of Alzheimer's disease. MTR only influences progression of the disease, which may be enhanced by carriage of allele ϵ4 of APO-E.
doi:10.1136/jnnp.2003.025866
PMCID: PMC1739095  PMID: 15201366
23.  Intake of vitamins D and A, and calcium and risk of non-Hodgkin lymphoma: San Francisco Bay Area population-based case-control study 
Nutrition and Cancer  2012;64(5):674-684.
Several nutrients identified as potentially cancer protective have been inconsistently associated with non-Hodgkin lymphoma (NHL) risk. Dietary history data, including use of vitamin supplements, were collected using a semi-quantitative food frequency questionnaire administered during in-person interviews with 4,133 participants (2052 cases, 2081 controls) in a San Francisco Bay Area population-based case-control. Data were used to determine the association of intake levels of vitamins D, A and calcium with risk of NHL and NHL subtypes. Odds ratios (OR) and 95% confidence intervals (CI) were computed as estimates of relative risk using adjusted unconditional logistic regression. Increasing vitamin D intake from food and supplements was positively associated with NHL risk in men (5th quintile: OR=1.6, 95% CI= 1.0-2.4, Ptrend=0.07) and with diffuse large B-cell lymphoma (DLBCL) in women and men (5th quintile: OR=1.6, 95% CI=1.0-2.5, Ptrend=0.02), that was largely due to the effect in men (Ptrend=0.03). These results do not support a strong role for vitamin D intake with NHL risk with the exception of a potential association for DLBCL risk in men. Our results should be interpreted conservatively until further investigation in larger pooled studies can be conducted to better assess the role of vitamin D intake in lymphomagenesis.
doi:10.1080/01635581.2012.689916
PMCID: PMC3403694  PMID: 22697504
lymphoma, non-Hodgkin; case-control studies; vitamin D; vitamin A; calcium
24.  Folate Pathway Polymorphisms Predict Deficits in Attention and Processing Speed after Childhood Leukemia Therapy 
Pediatric blood & cancer  2011;57(3):454-460.
Background
Neurocognitive impairment occurs in 20%-40% of childhood acute lymphoblastic leukemia (ALL) survivors, possibly mediated by folate depletion and homocysteine elevation following methotrexate treatment. We evaluated the relationship between folate pathway polymorphisms and neurocognitive impairment after childhood ALL chemotherapy.
Procedure
Seventy-two childhood ALL survivors treated with chemotherapy alone underwent a neurocognitive battery consisting of: Trail Making Tests A (TMTA) and B (TMTB), Grooved Pegboard Test Dominant-Hand and Nondominant-Hand, Digit Span subtest, and Verbal Fluency Test. We performed genotyping for: 10-methylenetetrahydrofolate reductase (MTHFR 677C>T and MTHFR 1298A>C), serine hydroxymethyltransferase (SHMT 1420C>T), methionine synthase (MS 2756 A>G), methionine synthase reductase (MTRR 66A>G), and thymidylate synthase (TSER). Student's two sample t-test and analysis of covariance were used to compare test scores by genotype.
Results
General impairment on the neurocognitive battery was related to MTHFR 1298A>C (p=0.03) and MS 2756A>G (p=0.05). Specifically, survivors with MTHFR 1298AC/CC genotypes scored, on average, 13 points lower on TMTB than those with MTHFR 1298AA genotype (p=0.001). The MS 2756AA genotype was associated with a 12.2 point lower mean TMTA score, compared to MS 2756 AG/GG genotypes (p=0.01). The TSER 2R/3R and 3R/3R genotypes were associated with an 11.4 point lower mean score on TMTB, compared to the TSER 2R/2R genotype (p=0.03). Survivors with >6 folate pathway risk alleles demonstrated a 9.5 point lower mean TMTA score (p=0.06) and 14.5 point lower TMTB score (p=0.002) than survivors with <6 risk alleles.
Conclusions
Folate pathway polymorphisms are associated with deficits in attention and processing speed after childhood ALL therapy.
doi:10.1002/pbc.23162
PMCID: PMC3134130  PMID: 21618410
folate; leukemia; neurocognitive; survivor
25.  MTHFR Genetic Polymorphism As a Risk Factor in Egyptian Mothers with Down Syndrome Children 
Disease markers  2007;24(1):19-26.
Recent reports linking Down syndrome (DS) to maternal polymorphisms at the methylenetetrahydrofolate reductase (MTHFR) gene locus have generated great interest among investigators in the field. The present study aimed at evaluation of MTHFR 677C/T and 1298A/C polymorphisms in the MTHFR gene as maternal risk factors for DS. Forty two mothers of proven DS outcomes and forty eight control mothers with normal offspring were included. Complete medical and nutritional histories for all mothers were taken with special emphasis on folate intake. Folic acid intake from food or vitamin supplements was significantly low (below the Recommended Daily Allowance) in the group of case mothers compared to control mothers. Frequencies of MTHFR 677T and MTHFR 1298C alleles were significantly higher among case mothers (32.1% and 57.1%, respectively) compared to control mothers (18.7% and 32.3%, respectively). Heterozygous and homozygous genotype frequencies of MTHFR at position 677 (CT and TT) were higher among case mothers than controls (40.5% versus 25% and 11.9% versus 6.2%, respectively) with an odds ratio of 2.34 (95% confidence interval [CI] 0.93–5.89) and 2.75 (95% CI 0.95–12.77), respectively. Interestingly, the homozygous genotype frequency (CC) at position 1298 was significantly higher in case mothers than in controls (33.3% versus 2.1% respectively) with an odds ratio of 31.5 (95% CI 3.51 to 282.33) indicating that this polymorphism may have more genetic impact than 677 polymorphism. Heterozygous genotype (AC) did not show significant difference between the two groups. We here report on the first pilot study of the possible genetic association between DS and MTHFR 1298A/C genotypes among Egyptians. Further extended studies are recommended to confirm the present work.
doi:10.1155/2008/214027
PMCID: PMC3850629  PMID: 18057532
Methylenetetrahydrofolate reductase (MTHFR); Down syndrome; polymorphism; MTHFR 677C/T polymorphism; MTHFR 1298A/C polymorphism; Egyptian

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