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1.  Folate and vitamin B12 in idiopathic male infertility 
Asian Journal of Andrology  2011;13(6):856-861.
Although methylenetetrahydrofolate reductase, a folate enzyme gene, has been associated with idiopathic male infertility, few studies have examined other folate-related metabolites and genes. We investigated whether idiopathic male infertility is associated with variants in folate, vitamin B12 (B12) and total homocysteine (tHcy)-related genes and measured these metabolites in blood. We conducted a case–control study that included 153 men with idiopathic infertility and 184 fertile male controls recruited at the Fertility Center and Antenatal Care Center, University Hospital, Malmö and Lund, Sweden. Serum folate, red cell folate (RCF), serum B12, plasma tHcy and semen quality were measured. Subjects were genotyped for 20 common variants in 12 genes related to folate/B12/homocysteine metabolism. Metabolite concentrations and genotype distributions were compared between cases and controls using linear and logistic regression with adjustment for covariates. The phosphatidylethanolamine N-methyltransferase (PEMT) M175V and TCblR rs173665 polymorphisms were significantly associated with infertility (P=0.01 and P=0.009, respectively), but not with semen quality. Among non-users of supplements, infertile men had lower serum folate concentrations than fertile men (12.89 vs. 14.73 nmol l−1; P=0.02), but there were no significant differences in RCF, B12 or tHcy. Folate, B12 and tHcy concentrations were not correlated with any semen parameters. This study provides little support for low folate or B12 status in the pathogenesis of idiopathic male infertility. Although additional data are needed to confirm these initial findings, our results suggest that PEMT and TCblR, genes involved in choline and B12 metabolism, merit further investigation in idiopathic male infertility.
doi:10.1038/aja.2011.96
PMCID: PMC3372894  PMID: 21857689
folate; idiopathic male infertility; semen quality; vitamin B12
2.  Alcohol increases homocysteine and reduces B vitamin concentration in healthy male volunteers—a randomized, crossover intervention study 
Background: Few studies have examined the effect of alcohol consumption on total homocysteine (tHcy) concentrations.
Aim: To assess the effect of an 8-week intervention with vodka or red wine on plasma tHcy and B vitamin concentrations in healthy male volunteers. To assess the effect on tHcy according to methylenetetrahydrofolate reductase (MTHFR) 677C>T genotype.
Design and methods: A randomized controlled crossover intervention study measuring tHcy and serum folate and vitamin B12 concentrations was conducted in 78 male subjects (21–70 years). Following a 2-week washout period during which no alcohol was consumed, all subjects consumed 24 g alcohol (either 240 ml red wine or 80 ml vodka)/day for a 2-week period. Following a further 2-week washout, participants consumed the alternate intervention for 2 weeks.
Results: A significant increase in plasma tHcy was observed after the 2-week red wine intervention (5%, P = 0.03), and a non-significant increase in tHcy with vodka intervention (3%, P = 0.09). When the two interventions were compared, the change in tHcy did not differ between the vodka and red wine interventions (P = 0.57). There were significant decreases in serum vitamin B12 and folate concentrations, and this decrease did not differ between interventions. The increase in tHcy observed in both interventions did not vary by MTHFR 677C>T genotype.
Conclusions: A 2-week alcohol intervention resulted in a decrease in folate and vitamin B12 status and an increase in plasma tHcy. The effect of alcohol intervention on tHcy, folate and vitamin B12 concentrations did not differ between the red wine and vodka intervention groups.
doi:10.1093/qjmed/hcn112
PMCID: PMC2572692  PMID: 18790817
3.  Impact of voluntary folate fortification on plasma homocysteine and serum folate in Australia from 1995 to 2001: a population based cohort study 
Study objective: To investigate the effect of the voluntary folate fortification policy in Australia on serum folate and total plasma homocysteine (tHcy) concentrations.
Design: Population based cohort study.
Setting: Perth, Western Australia.
Participants: Men and women aged 27 to 77 years (n = 468), who were originally randomly selected from the Perth electoral roll. The cohort was surveyed in 1995/96 before widespread introduction of folate fortification of a variety of foods, and followed up on two occasions, firstly in 1998/99 and again in 2001, when a moderate number of folate fortified foods were available. Subjects with abnormal serum creatinine concentrations at baseline were excluded from this analysis.
Main results: Repeated measures analysis of variance was used to determine changes in serum folate and tHcy over the three surveys and to assess whether time trends were related to age, sex, MTHFR C677T genotype, or consumption of folate fortified foods. An increase (38%) in mean serum folate (p<0.0005) and a decrease (21%) in mean tHcy (p<0.0005) were seen after introduction of the voluntary folate fortification policy in Australia. Serum folate was consistently higher (p = 0.032) and tHcy was consistently lower (p = 0.001) in subjects who consumed at least one folate fortified food compared with subjects who did not consume any folate fortified foods in the previous week. The time related changes in serum folate and tHcy were affected only by intake of folate fortified foods (p<0.0005) and not by any other measured variables including age, sex, or MTHFR genotype.
Conclusion: Voluntary fortification of foods with folate in Australia has been followed by a substantial increase in serum folate and decrease in tHcy in the general population.
doi:10.1136/jech.2004.027078
PMCID: PMC1733078  PMID: 15831684
4.  Genetic and Lifestyle Variables Associated with Homocysteine Concentrations and the Distribution of Folate Derivatives in Healthy Premenopausal Women 
Background
Low folate and high homocysteine (Hcy) concentrations are associated with pregnancy-related pathologies such as spina bifida. Polymorphisms in folate/Hcy metabolic enzymes may contribute to this potentially pathogenic biochemical phenotype.
Methods
The study comprised 26 Caucasian and 23 African-American premenopausal women. Subjects gave fasting blood samples for biochemical phenotyping and genotyping. Total Hcy (tHcy) and both plasma and red blood cell (RBC) folate derivatives [i.e. tetrahydrofolate (THF), 5-methylTHF (5-MTHF), and 5,10-methenylTHF (5,10-MTHF)] were measured using stable isotope dilution liquid chromatography, multiple reaction monitoring, mass spectrometry. Eleven polymorphisms from nine folate/Hcy pathway genes were genotyped. Tests of association between genetic, lifestyle, and biochemical variables were applied.
Results
In African American women, tHcy concentrations were associated (p<0.05) with total RBC folate, RBC 5-MTHF, B12, and polymorphisms in methionine synthase (MTR) and thymidylate synthase (TYMS). In Caucasian women, tHcy concentrations were not associated with total folate levels, but were associated (p<0.05) with RBC THF, ratios of RBC 5-MTHF: THF, and polymorphisms in 5,10-methylenetetrahydrofolate reductase (MTHFR) and MTR . In African Americans, folate derivative levels were associated with smoking, B12, and polymorphisms in MTR, TYMS, methionine synthase reductase (MTRR), and reduced folate carrier1 (RFC1). In Caucasians, folate derivative levels were associated with vitamin use, B12, and polymorphisms in MTHFR, TYMS, and RFC1.
Conclusions
Polymorphisms in the folate/Hcy pathway are associated with tHcy and folate derivative levels. In African American and Caucasian women, different factors are associated with folate/Hcy phenotypes and may contribute to race-specific differences in the risks of a range of pregnancy-related pathologies.
doi:10.1002/bdra.20683
PMCID: PMC4051228  PMID: 20544798
Genetics; folate; homocysteine; women; reproductive age; spina bifida risk
5.  Genetic and Environmental Determinants of Plasma Total Homocysteine Levels: Impact of Population-wide Folate Fortification 
Pharmacogenetics and genomics  2011;21(7):426-431.
Objectives
Folate metabolism is an important target for drug therapy. Drug-induced inhibition of folate metabolism often causes an elevation of plasma total homocysteine (tHcy). Plasma tHcy levels are influenced by several non-genetic (e.g., folate intake, age, smoking) as well as genetic factors. Over the last decade, several countries have implemented a nation-wide folate fortification program of all grain products. This investigation sought to determine the impact of folate fortification on the relative contribution of environmental and genetic factors to the variability of plasma tHcy.
Methods
Two cohorts were compared in this study, one from the U.S. (with folate fortification, n=281), and one from Austria (without folate fortification, n=139). Several environmental factors as well as previously identified gene variants important for tHcy levels (MTHFR C677T, MTHFR A1298C, MTRR A66G) were examined for their ability to predict plasma tHcy in a multiple linear regression model.
Results
Non-genetic, environmental factors had a comparable influence on plasma tHcy between the two cohorts (R2 ~ 0.19). However, after adjusting for other covariates, the tested gene variants had a substantially smaller impact among patients from the folate fortified cohort (R2= 0.021) compared to the non-folate fortified cohort (R2= 0.095). The MTHFR C677T polymorphism was the single most important genetic factor. Male gender, smoking and folate levels were important predictors for non-folate fortified patients; age for folate fortified.
Conclusions
Population-wide folate fortification had a significant effect on the variability of plasma tHcy and reduced the influence of genetic factors, most importantly the MTHFR 677TT genotype, and may be an important confounder for a personalized drug therapy.
doi:10.1097/FPC.0b013e32834741ff
PMCID: PMC3116052  PMID: 21597397
Homocysteine; folate fortification; folic acid
6.  Hyperhomocysteinemia from trimethylation of hepatic phosphatidylethanolamine during cholesterol cholelithogenesis in inbred mice 
Hepatology (Baltimore, Md.)  2011;54(2):697-706.
Because hyperhomocysteinemia can occur in cholesterol gallstone disease, we hypothesized that this may result from trimethylation of phosphatidylethanolamine (PE), which partakes in biliary phosphatidylcholine (PC) hypersecretion during cholesterol cholelithogenesis. We fed murine strains C57L/J, C57BL/6J, SWR/J, AKR/J, PE N-methyltransferase (PEMT) knockout (KO), PEMT heterozygous (HET), and wild type (WT) mice a cholesterol/cholic acid lithogenic diet (LD) for up to 56 days and documented biliary lipid phase transitions and secretion rates. We quantified plasma total homocysteine (tHcy), folate, and vitamin B12 in plasma and liver, as well as biliary tHcy and cysteine secretion rates. Rate-limiting enzyme activities of PC synthesis, PEMT and cytidine triphosphate: phosphocholine cytidylyltransferase (PCT), S-adenosylmethionine (SAM), and S-adenosylhomocysteine (SAH) were measured in liver homogenates. Other potential sources of plasma tHcy, glycine N-methyltransferase (GNMT) and guanidinoacetate N-methyltransferase (GAMT), were assayed by gene expression. Plasma tHcy and PEMT activities became elevated during cholelithogenesis in gallstone-susceptible C57L, C57BL/6, and SWR mice, but not in the gallstone-resistant AKR mice. Persisting in C57L mice, which exhibit the greatest Lith gene burden, these increases were accompanied by elevated hepatic SAM/SAH ratios and augmented biliary tHcy secretion rates. Counter-regulation included remethylation of Hcy to methionine concurrent with decreased folate and vitamin B12 levels and Hcy transsulfuration to cysteine. Concomitantly, methylenetetrahydrofolate reductase (Mthfr), betaine-homocysteine methyltransferase (Bhmt), and cystathionine-β-synthase (Cbs) were upregulated, but Gnmt and Gamt genes were downregulated. PEMT KO and HET mice displayed biliary lipid secretion rates and high gallstone prevalence rates similar to WT mice without any elevation in plasma tHcy levels.
Conclusion
This work implicates upregulation of PC synthesis by the PEMT pathway as a source of elevated plasma and bile tHcy during cholesterol cholelithogenesis.
doi:10.1002/hep.24428
PMCID: PMC3145001  PMID: 21567442
phosphatidylethanolamine N-methyltransferase; folate; vitamin B12; cysteine; bile
7.  Glycine and l-Arginine Treatment Causes Hyperhomocysteinemia in Cerebral Creatine Transporter Deficiency Patients 
JIMD Reports  2011;4:13-16.
Our aim was to monitor folate status in five creatine transporter deficient (CRTR) patients undergoing glycine/l-arginine (Gly/Arg) therapy after the finding of severe hyperhomocysteinemia in one of these cases.
Five male patients (age range: 12–20; median = 13 years) genetically confirmed of CRTR deficiency, who were treated with oral glycine (200 mg/kg/day) and l-arginine (400 mg/kg/day) twice a day for 9 months. Clinical follow-up was done at baseline and every 3 months after the start of the therapy. Serum folate was assayed by automated procedures, and plasma total homocysteine (tHcys) by HPLC with fluorescence detection. The 677C→T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene was analyzed by PCR.
Case 1 presented severe hyperhomocysteinemia (81 μmol/L; control values <10.8) 3 months after Gly/Arg therapy. Three out of the other four cases disclosed mildly increased plasma tHcys values. Serum folate was normal in all cases before therapy, but 3 months after, a deficient status was detected in two cases and a clear decrement in the others when compared with baseline conditions. Two cases were homozygous for the 677C→T polymorphism of the MTHFR, presenting the highest plasma tHcys values. In all cases, after 3 months of folate supplementation (5 mg/day), both serum folate and tHcys concentrations returned to normal values.
In conclusion, prior to the start of long-term Gly/Arg therapy, the monitoring of folate and plasma tHcys values, together with study of the 677C→T polymorphism of the MTHFR gene, seems necessary in order to correct hyperhomocysteinemia by means of folate supplementation.
doi:10.1007/8904_2011_41
PMCID: PMC3509873  PMID: 23430891
8.  Functional COMT Val158Met Polymorphism, Risk of Acute Coronary Events and Serum Homocysteine: The Kuopio Ischaemic Heart Disease Risk Factor Study 
PLoS ONE  2007;2(1):e181.
Background
The role of circulating levels of total homocysteine tHcy in the development of coronary heart disease (CHD) is still under debate. One reason for conflicting results between previous studies on homocysteine and heart diseases could be consequence of different interactions between homocysteine and genes in different study populations. Many genetic factors play a role in folate-homocysteine metabolism, like functional polymorphism (Val108Met) in the Catechol-O-methyltransferase (COMT) gene.
Methodology and Findings
Our aim was to examine the role of COMT Val158Met polymorphism and interaction of this polymorphism with serum tHcy and folate concentration on the risk of acute coronary and events in middle-aged men from eastern Finland. A population-based prospective cohort of 792 men aged 46–64 years was examined as part of the Kuopio Ischaemic Heart Disease Risk Factor Study. During an average follow-up of 9.3 years, there were 69 acute coronary events in men with no previous history of CHD. When comparing the COMT low activity genotype with the others, we found an age and examination year adjusted hazard rate ratio (HRR) of 1.73 (95% confidence interval (CI), 1.07–2.79), and an age, examination year, serum LDL and HDL cholesterol, and triglyceride concentration, systolic blood pressure and smoking adjusted HRR of 1.77 (95% CI, 1.05–2.77). Although serum tHcy concentration was not statistically significantly associated with acute coronary events (HRR for the highest third versus others 1.52, 95% CI, 0.93–2.49), subjects with both high serum tHcy and the COMT low activity genotype had an additionally increased adjusted risk of HRR 2.94 (95% CI 1.50–5.76) as compared with other men.
Conclusions
This prospective cohort study suggests that the functional COMT Val158Met polymorphism is associated with increased risk of acute coronary events and it may interact with high serum tHcy levels.
doi:10.1371/journal.pone.0000181
PMCID: PMC1779620  PMID: 17264883
9.  Effects of differences in serum total homocysteine, folate, and vitamin B12 on cognitive impairment in stroke patients 
BMC Neurology  2014;14:217.
Background
Vascular cognitive impairment-no dementia (VCIND) refers to the early or mild cognitive impairment induced by cerebral vascular injury. Research shows that serum total homocysteine (tHcy) level is an independent risk factor for cerebral vascular disease and may be closely related to cognitive function.Current studies on the tHcy level in VCIND patients are limited, and the relationship of tHcy with cognitive function remains unclear. This study aims to investigate the tHcy levels in patients with VCIND and to determine their correlation with cognitive function, as well as to provide useful clues for preventing and treating VCIND.
Methods
The tHcy, folate, and vitamin B12 levels in 82 patients with VCIND were reviewed retrospectively and compared with those of 80 stroke patients without cognitive impairment and 69 healthy controls by using the Montreal Cognitive Assessment (MoCA) scale and the event-related potential P300 to evaluate cognitive function.
Results
The tHcy levels in the VCIND group were higher than those in the other two groups, whereas the folate and Vitamin B12 levels in the VCIND group were lower than those of the other two groups. The tHcy levels in the stroke group were higher than those in the control group, and the folate and vitamin B12 levels in the stroke group were lower than those in the control group. The patients in the VCIND group with high tHcy exhibited lower MoCA scores and prolonged P300 latency than those in with normal tHcy. Correlation analysis showed that tHcy level is positively correlated with P300 latency period and negatively correlated with MoCA score.
Conclusion
The tHcy levels were significantly higher and the vitamin B12 and folate levels were significantly lower in the patients with VCIND than those in the other groups. The high tHcy levels in the VCIND patients may be correlated with impaired cognitive function.
doi:10.1186/s12883-014-0217-9
PMCID: PMC4333896  PMID: 25433800
Cognitive impairment; Cerebrovascular disorder; Neuropsychology; Event related potentials P300; Homocysteine
10.  Folate, Cobalamin, Cysteine, Homocysteine, and Arsenic Metabolism among Children in Bangladesh 
Environmental Health Perspectives  2009;117(5):825-831.
Background
Approximately 35 million people in Bangladesh are chronically exposed to inorganic arsenic (InAs) in drinking water. Methylation of InAs to monomethylarsonic (MMA) and dimethylarsinic acids (DMA) relies on folate-dependent one-carbon metabolism and facilitates urinary arsenic (uAs) elimination.
Objectives
We examined the relationships between folate, cobalamin, cysteine, total homocysteine (tHcys), and uAs metabolites in a sample of 6-year-old Bangladeshi children (n = 165).
Methods
Children provided blood samples for measurement of tHcys, folate, cobalamin, and cysteine, and urine specimens for the measurement of total uAs and As metabolites.
Results
Consistent with our studies in adults, mean tHcys concentrations (7.9 μmol/L) were higher than those reported among children of similar ages in other populations. Nineteen percent of the children had plasma folate concentrations < 9.0 nmol/L. The proportion of total uAs excreted as InAs (%InAs) was inversely correlated with folate (r = −0.20, p = 0.01) and cysteine (r = −0.23, p = 0.003), whereas the correlations between %DMA and both folate (r = 0.12, p = 0.14) and cysteine (r = 0.11, p = 0.15) were positive. Homocysteine was inversely correlated (r = −0.27, p = 0.009) with %MMA in males, and the correlation with %DMA was positive (r = 0.13, p = 0.10).
Conclusions
These findings suggest that, similar to adults, folate and cysteine facilitate As methylation in children. However, the inverse correlation between tHcys and %MMA, and positive correlation with %DMA, are both opposite to our previous findings in adults. We propose that upregulation of one-carbon metabolism, presumably necessary to meet the considerable demands for DNA and protein biosynthesis during periods of rapid growth, results in both increased tHcys biosynthesis and increased As methylation.
doi:10.1289/ehp.0800164
PMCID: PMC2685848  PMID: 19479028
arsenic; Bangladesh; children; cobalamin; creatinine; cysteine; dimethylarsinic acid; folate; homocysteine; monomethylarsonic acid; one-carbon metabolism
11.  Circulating folate, vitamin B12, homocysteine, vitamin B12 transport proteins and risk of prostate cancer: a case-control study, systematic review and meta-analysis 
Background
Disturbed folate metabolism is associated with an increased risk of some cancers. Our objective was to determine whether blood levels of folate, vitamin B12 and related metabolites were associated with prostate cancer risk.
Methods
Matched case-control study nested within the UK population-based ProtecT study of PSA-detected prostate cancer in men aged 50–69 years. Plasma concentrations of folate, B12 (cobalamin), holo-haptocorrin, holo- and total-transcobalamin, and total homocysteine (tHcy) were measured in 1,461 cases and 1,507 controls. ProtecT study estimates for associations of folate, B12, and tHcy with prostate cancer risk were included in a meta-analysis, based on a systematic review.
Results
In the ProtecT study, increased B12 and holo-haptocorrin concentrations showed positive associations with prostate cancer risk (highest vs lowest quartile of B12 odds ratio (OR)=1.17 (95% CI 0.95–1.43), P-for-trend=0.06; highest vs lowest quartile of holo-haptocorrin OR=1.27 (1.04–1.56), P-for-trend=0.01); folate, holo-transcobalamin and tHcy were not associated with prostate cancer risk. In the meta-analysis, circulating B12 levels were associated with an increased prostate cancer risk (pooled OR=1.10 (1.01–1.19) per 100 pmol/L increase in B12, P=0.002); the pooled OR for the association of folate with prostate cancer was positive (OR=1.11 (0.96–1.28) per 10 nmol/L, P=0.2) and conventionally statistically significant if ProtecT (the only case-control study) was excluded (OR=1.18 (1.00–1.40) per 10 nmol/L, P=0.02).
Conclusion
Vitamin B12 and (in cohort studies) folate were associated with increased prostate cancer risk.
Impact
Given current controversies over mandatory fortification, further research is needed to determine whether these are causal associations.
doi:10.1158/1055-9965.EPI-10-0180
PMCID: PMC3759018  PMID: 20501771
folate; vitamin B12; cobalamin; transcobalamin; haptocorrin; homocysteine; folate-mediated one-carbon metabolism; prostate cancer
12.  Bioinformatic and Genetic Association Analysis of MicroRNA Target Sites in One-Carbon Metabolism Genes 
PLoS ONE  2011;6(7):e21851.
One-carbon metabolism (OCM) is linked to DNA synthesis and methylation, amino acid metabolism and cell proliferation. OCM dysfunction has been associated with increased risk for various diseases, including cancer and neural tube defects. MicroRNAs (miRNAs) are ∼22 nt RNA regulators that have been implicated in a wide array of basic cellular processes, such as differentiation and metabolism. Accordingly, mis-regulation of miRNA expression and/or activity can underlie complex disease etiology. We examined the possibility of OCM regulation by miRNAs. Using computational miRNA target prediction methods and Monte-Carlo based statistical analyses, we identified two candidate miRNA “master regulators” (miR-22 and miR-125) and one candidate pair of “master co-regulators” (miR-344-5p/484 and miR-488) that may influence the expression of a significant number of genes involved in OCM. Interestingly, miR-22 and miR-125 are significantly up-regulated in cells grown under low-folate conditions. In a complementary analysis, we identified 15 single nucleotide polymorphisms (SNPs) that are located within predicted miRNA target sites in OCM genes. We genotyped these 15 SNPs in a population of healthy individuals (age 18–28, n = 2,506) that was previously phenotyped for various serum metabolites related to OCM. Prior to correction for multiple testing, we detected significant associations between TCblR rs9426 and methylmalonic acid (p  =  0.045), total homocysteine levels (tHcy) (p  =  0.033), serum B12 (p < 0.0001), holo transcobalamin (p < 0.0001) and total transcobalamin (p < 0.0001); and between MTHFR rs1537514 and red blood cell folate (p < 0.0001). However, upon further genetic analysis, we determined that in each case, a linked missense SNP is the more likely causative variant. Nonetheless, our Monte-Carlo based in silico simulations suggest that miRNAs could play an important role in the regulation of OCM.
doi:10.1371/journal.pone.0021851
PMCID: PMC3134459  PMID: 21765920
13.  Red cell N5-methyltetrahydrofolate concentrations and C677T methylenetetrahydrofolate reductase genotype in patients with stroke 
Journal of Clinical Pathology  2004;57(1):54-57.
Aims: To investigate the relation between total red cell folate, red cell N5-methyltetrahydrofolate (N5MTHF) concentrations, and N5N10-methylenetetrahydrofolate reductase (MTHFR) genotypes in stroke.
Methods: The study comprised 120 consecutive patients presenting to hospital with acute stroke. Multivitamin supplement use was recorded. Serum and red cell folate were measured by microbiological assays using Lactobacillus casei and Enterococcus faecalis, and by the DPC-BioMediq Immulite™ 2000 analyser. Total plasma homocysteine (tHcy), serum cobalamin, and serum vitamin B6 were measured and the C677T MTHFR genotype determined.
Results: There were no significant differences in blood tHcy or vitamin concentrations according to MTHFR genotype in the overall patient cohort. However, when patients taking vitamins were excluded, total red cell folate and red cell N5MTHF were significantly lower in patients with the TT genotype compared with CT or CC genotypes. In the overall cohort, irrespective of genotype, red cell folate was significantly lower when assayed microbiologically than with the Immulite assay. This discrepancy remained after exclusion of patients taking vitamins.
Conclusion: Total red cell folate and red cell N5MTHF are significantly lower in stroke patients with the TT compared with the CT and TT MTHFR genotypes, particularly those not taking vitamin supplements. Microbiological assays that measure biologically active folates provide substantially lower estimates of folate than the Immulite™ assay. Because folate is a key determinant of blood homocysteine values, these findings may impact on the interpretation of the strength and independence of the association between raised blood concentrations of homocysteine and atherothrombosis risk reported in most epidemiological studies.
PMCID: PMC1770163  PMID: 14693836
stroke; folate; methylenetetrahydrofolate reductase; homocysteine
14.  Folate Intake at RDA Levels Is Inadequate for Mexican American Men with the Methylenetetrahydrofolate Reductase 677TT Genotype123 
The Journal of nutrition  2008;138(1):67-72.
Since the establishment of the 1998 folate recommended dietary allowance (RDA), the methylenetetrahydrofolate reductase (MTHFR) 677C→T variant has emerged as a strong modifier of folate status. This controlled feeding study investigated the adequacy of the RDA, 400 μg/d as dietary folate equivalents (DFE), for Mexican American men with the MTHFR 677CC or TT genotype. Because of the interdependency between folate and choline, the influence of choline intake on folate status was also assessed. Mexican American men (n = 60; 18–55 y) with the MTHFR 677CC (n = 31) or TT (n = 29) genotype consumed 438 μg DFE/d and total choline intakes of 300, 550 (choline adequate intake), 1100, or 2200 mg/d for 12 wk. Folate status response was assessed via serum folate (SF), RBC folate, plasma total homocysteine (tHcy), and urinary folate. SF decreased (P < 0.001) 66% to 7.9 ± 0.7 nmol/L (means ± SEM) in men with the 677TT genotype and 62% to 11.3 ± 0.9 nmol/L in the 677CC genotype. Plasma tHcy increased (P < 0.0001) 170% to 31 ± 3 μmol/L in men with the 677TT genotype and 18% to 11.6 ± 0.3 μmol/L in the 677CC genotype. At the end of the study, 34% (677TT) and 16% (677CC) had SF concentrations <6.8 nmol/L and 79% (677TT) and 7% (677CC) had tHcy concentrations >14 μmol/L. Choline intake did not influence the response of the measured variables. These data showed that the folate RDA is not adequate for men of Mexican descent, particularly for those with the MTHFR 677TT genotype, and demonstrated a lack of influence of choline intake on the folate status variables measured in this study.
PMCID: PMC2646848  PMID: 18156406
15.  The maternal folate hydrolase gene polymorphism is associated with neural tube defects in a high-risk Chinese population 
Genes & Nutrition  2012;8(2):191-197.
Folate hydrolase 1 (FOLH1) gene encodes intestinal folate hydrolase, which regulates intestinal absorption of dietary folate. Previous studies on the association between polymorphisms rs202676 and rs61886492 and the risk of neural tube defects (NTDs) were inconclusive. A case–control study of women with NTD-affected pregnancies (n = 160) and controls (n = 320) was conducted in the Chinese population of Lvliang, a high-risk area for NTDs. We genotyped the polymorphic sites rs202676 and rs61886492 and assessed maternal plasma folate and total homocysteine (tHcy). Our results showed that in case group, plasma folate concentrations were 18 % lower compared with those of control group (8.32 vs. 6.79 nmol/L, p = 0.033) and tHcy concentrations were 17 % higher (10.47 vs. 12.65 μmol/L, p = 0.047). Almost all samples had the rs61886492 GG genotype (99.78 %). The result showed that the frequency of GG genotype in rs202676 was significantly higher in group with multiple NTDs than in controls (p = 0.030, OR = 2.157, 95 % CI, 1.06–4.38). The multiple-NTD group showed higher maternal plasma concentrations of tHcy (10.47 vs. 13.96 μmol/L, p = 0.024). The GG genotype of rs202676 had a lower maternal folate and higher tHcy concentrations than other genotypes with no significant differences. The result of structural prediction indicated that this variation might change the spatial structure of the protein. These results suggested that the maternal polymorphism rs202676 was a potential risk factor for multiple NTDs in this Chinese population. The allele G might affect maternal plasma folate and tHcy concentration.
doi:10.1007/s12263-012-0309-3
PMCID: PMC3575888  PMID: 22918695
Association study; Chinese population; FOLH1; Neural tube defects; Single-nucleotide polymorphism
16.  Maternal vitamin levels in pregnancies affected by congenital malformations other than neural tube defects 
Background
Periconceptional use of folic acid prevents most neural tube defects (NTDs). Whether folic acid and/or multivitamins can prevent other congenital anomalies is not clear. This study tested whether maternal blood levels of folate and vitamin B12 in pregnancies affected by congenital malformations excluding NTDs are lower when compared to non-affected pregnancies.
Methods
We measured pregnancy red cell folate (RCF), vitamin B12, and homocysteine (tHcy) concentrations in blood samples taken at the first antenatal clinic in Dublin maternity hospitals in 1986–1990 when vitamin supplementation was rare. The cases were mothers who delivered a baby with a congenital malformation other than NTD identified by the Dublin EUROCAT Registry; controls were a systematic sample of mothers of offspring without congenital malformations from the same hospitals in the same time period.
Results
The median maternal levels of RCF and tHcy did not differ significantly between cases and controls for any of the congenital malformation groups examined (RCF: all malformations 275.9 ug/L v controls 271.2; p=0.77; tHcy: all malformations 7.5 umol/L v controls 7.6; p=0.57). In an unadjusted analysis vitamin B12 was significantly higher in case-mothers whose babies had cleft palate only (p=0.006), musculoskeletal malformations (p=0.034) and midline defects (p=0.039) but not after adjustment for multiple testing.
Conclusions
Our data suggest that low maternal folate and B12 levels or high tHcy levels in early pregnancy are not associated with all congenital malformations excluding NTDs. Fortification with folic acid or B12 may not have a beneficial effect in the prevention of these anomalies.
doi:10.1002/bdra.20817
PMCID: PMC3372895  PMID: 21591245
17.  Homocysteine concentration, related B vitamins, and betaine in pregnant women recruited to the Seychelles Child Development Study123 
Background
Both folate and betaine are important predictors of total homocysteine (tHcy) during pregnancy. However, studies to date have only been undertaken in populations with Western dietary patterns.
Objective
We investigated the predictors of tHcy in pregnant women recruited in the Seychelles, a population where access to fortified foods is limited and where women habitually consume diets rich in fish, eggs, rice, and fruit.
Design
Pregnant women (n = 226) provided blood samples at enrollment, at week 28 of gestation, and at delivery. Cord blood was obtained from a subset of participants (n = 135).
Results
As in other studies, maternal tHcy was lower during pregnancy than at delivery, whereas folate and vitamin B-12 status declined significantly to delivery. Despite low maternal folate status at delivery (median: 9.0 nmol/L), with 35% of women in the deficient range (serum folate: <6.8 nmol/L), cord blood folate status (median: 40.2 nmol/L) was similar to concentrations reported in Western populations. Folate was a significant predictor of tHcy at all time points (P < 0.001). In contrast with previous studies, betaine was only a significant predictor of maternal tHcy (P < 0.001) when the essential amino acid methionine was low.
Conclusions
The current study reports 2 important findings. First, fetal requirements for folate are paramount, such that cord blood folate status is maintained, even when maternal status is low. Second, betaine is a significant predictor of tHcy in pregnant women with low serum folate and low serum methionine concentrations.
PMCID: PMC2258320  PMID: 18258630
Homocysteine; folate; betaine; vitamin B-12; pregnancy; maternal status
18.  Transient Increase in Homocysteine but Not Hyperhomocysteinemia during Acute Exercise at Different Intensities in Sedentary Individuals 
PLoS ONE  2012;7(12):e51185.
Considering that hyperhomocysteinemia is an independent risk factor for cardiovascular disease, the purpose of this study was to determine the kinetics of serum homocysteine (tHcy) and the vitamins involved in its metabolism (folates, B12, and B6) in response to acute exercise at different intensities. Eight sedentary males (18–27 yr) took part in the study. Subjects were required to complete two isocaloric (400 kcal) acute exercise trials on separate occasions at 40% (low intensity, LI) and 80% VO2peak (high intensity, HI). Blood samples were drawn at different points before (pre4 and pre0 h), during (exer10, exer20, exer30, exer45, and exer60 min), and after exercise (post0, post3, and post19 h). Dietary, genetic, and lifestyle factors were controlled. Maximum tHcy occurred during exercise, both at LI (8.6 (8.0–10.1) µmol/L, 9.3% increase from pre0) and HI (9.4 (8.2–10.6) µmol/L, 25.7% increase from pre0), coinciding with an accumulated energy expenditure independent of the exercise intensity. From this point onwards tHcy declined until the cessation of exercise and continued descending. At post19, tHcy was not different from pre-exercise values. No values of hyperhomocysteinemia were observed at any sampling point and intensity. In conclusion, acute exercise in sedentary individuals, even at HI, shows no negative effect on tHcy when at least 400 kcal are spent during exercise and the nutritional status for folate, B12, and B6 is adequate, since no hyperhomocysteinemia has been observed and basal concentrations were recovered in less than 24 h. This could be relevant for further informing healthy exercise recommendations.
doi:10.1371/journal.pone.0051185
PMCID: PMC3517465  PMID: 23236449
19.  Effects of second-generation antipsychotics on selected markers of one-carbon metabolism and metabolic syndrome components in first-episode schizophrenia patients 
Purpose
Alterations in one-carbon metabolism (OCM) have been repeatedly reported in schizophrenia. However, there is a scarcity of studies addressing the effects of antipsychotics on selected OCM markers in schizophrenia and provided results are inconsistent.
Methods
We recruited 39 first-episode schizophrenia (FES) patients and determined serum profile of total homocysteine (tHcy), folate, vitamin B12, lipoproteins and glucose at baseline and after 12 weeks of treatment with second-generation antipsychotics (SGA) including olanzapine and risperidone in monotherapy.
Results
After 12 weeks of treatment, all patients had significantly higher body mass index (BMI), serum levels of total cholesterol (TC), low-density lipoproteins (LDL), triglycerides (TG) and tHcy together with significantly lower levels of folate and vitamin B12. The analysis of differences between SGA revealed the same biochemical alterations in patients treated with olanzapine as in the whole group, while those receiving risperidone had no statistically significant changes in serum folate, vitamin B12 and TG. There was a significantly higher increase in BMI and TC in patients treated with olanzapine in comparison with those treated with risperidone. Patients receiving olanzapine had a higher decrease in vitamin B12 than those assigned to the treatment with risperidone. Changes in folate, vitamin B12, tHcy and TC levels were significant only in males, even after Bonferroni correction. Multiple regression analysis revealed that changes in tHcy levels are associated with gender and baseline metabolic parameters (BMI, glucose, TC, LDL and HDL) but not with selected SGA.
Conclusions
These results indicate that SGA may influence OCM, especially in first-episode schizophrenia (FES) males.
Electronic supplementary material
The online version of this article (doi:10.1007/s00228-014-1762-2) contains supplementary material, which is available to authorized users.
doi:10.1007/s00228-014-1762-2
PMCID: PMC4226930  PMID: 25291992
One-carbon metabolism; Homocysteine; First-episode schizophrenia; Second-generation antipsychotics; Olanzapine; Risperidone
20.  Hyperhomocysteinemia exacerbates the development of intimal hyperplasia in Sprague-Dawley rats: Alleviation by rosiglitazone 
The amino acid intermediate homocysteine (Hcy) is formed during the metabolism of methionine to cysteine. Hyperhomocysteinemia (HHcy) is recognized as an independent risk factor for coronary atherosclerosis. The circulating levels of total Hcy (tHcy) can increase due to intake of foods rich in methionine or deficiencies of vitamins such as folate, pyridoxine and cyanocobalamin, which are required for the metabolism of Hcy. In addition, mutations in the genes coding for Hcy metabolizing enzymes can contribute to an increase in tHcy levels. Clinical and epidemiological studies have shown that an elevated level of tHcy measured in serum or plasma is a strong predictor of cardiovascular disease risk, which appears to be greatest in patients who have HHcy following a methionine load. Intimal hyperplasia (IH) (intima/media [I/M] ratio) is the universal response of a vessel to injury and may result in vasoconstriction when left unattended. The effect of dietary HHcy on balloon catheter-injured carotid artery and its modulation (if any) by the peroxisome proliferator-activated receptor agonist gamma rosiglitazone was evaluated in 12-week-old female Sprague-Dawley rats fed either a control diet or a diet containing 1% L-methionine. Once the rats were established on the diet, the group that was fed 1% L-methionine was further subdivided and either given an aqueous preparation of 3 mg/kg/day rosiglitazone or the vehicle via oral gavage for one week. This was followed by surgically injuring the left carotid artery using a Maverick Over-The-Wire catheter (2.0 mm × 20 mm, 3.2F; Boston Scientific, USA). The rats were continued on their respective diets and drug regimen for 21 days postsurgery. On day 22 of the procedure, the rats were sacrificed for collection of blood, the carotid arteries and liver for biochemical and histological evaluation. Compared with controls there was a significant increase in both tHcy levels and I/M ratio in the rats fed 1% L-methionine (5.4±0.28 μM versus 32.8±3.01 μM, P<0.002; and 0.175±0.05 versus 1.05±0.23, P<0.005, respectively). The effect of rosiglitazone in rats fed the control diet was not prominent. On the other hand, administration of rosiglitazone to the rats on the 1% L-methionine diet significantly reduced the levels of serum tHcy (16.6±2.1 μM versus 32.8±3.01 μM, P<0.001); however, the tHcy levels remained significantly elevated compared with animals on the control diet (P<0.002). The group receiving the L-methionine diet plus rosiglitazone had an inhibition in the development of IH compared with those receiving the L-methionine diet alone (I/M of 0.278±0.041 versus 1.05±0.23, P<0.01). Moreover, the development of IH in the group receiving the L-methionine diet plus rosiglitazone treatment was not significantly different from that observed in the group on the control diet without rosiglitazone (0.278±0.041 versus 0.175±0.05, respectively). These findings may have important implications in deciphering the molecular mechanisms involved in the augmentation of IH in HHcy and modulation of this process by rosiglitazone.
PMCID: PMC2716244  PMID: 19641680
Carotid; Hyperhomocysteinemia; Metabolism; Methionine; Vasoconstriction
21.  No associations of Helicobacter pylori infection and gastric atrophy with plasma total homocysteine in Japanese 
Recent studies have suggested that Helicobacter pylori (H. pylori) infection might be a risk factor for atherosclerosis. Since the bacterium has not been isolated from atherosclerotic lesions, a direct role in atherogenesis is not plausible. We examined associations of plasma total homocysteine (tHcy) and serum folate, independent risk factors for atherosclerosis, with H. pylori infection and subsequent gastric atrophy among 174 patients (78 males and 96 females) aged 20 to 73 years, who visited an H. pylori eradication clinic of Nagoya University from July 2004 to October 2005. Polymorphism genotyping was conducted for methylenetetrahydrofolate reductase (MTHFR) C677T and thymidylate synthase (TS) 28-bp tandem repeats by PCR with confronting two-pair primers and PCR, respectively. H. pylori infection and gastric atrophy were not significantly associated with hyperhomocysteinemia (tHcy ≥ 12 nmol/ml), when adjusted by sex, age, smoking, alcohol, and genotypes of MTHFR and TS. The adjusted odds ratio of gastric atrophy for low folate level (≤ 4mg/ml) was 0.21 (95% confidence interval = 0.05-0.78). The associations of tHcy with serum folate and MTHFR genotype were clearly observed in this dataset. The present study demonstrated that folate and MTHFR genotype were the deterministic factors of plasma tHcy, but not H. pylori infection and subsequent gastric atrophy, indicating that even if H. pylori infection influences the risk of atherosclerosis, the influence may not be through the elevation of homocysteine.
PMCID: PMC1838822  PMID: 17396161
Helicobacter pylori; homocysteine; methylenetetrahydrofolate reductase (MTHFR); thymidylate synthase (TS); gastric atrophy
22.  Blood Concentrations of Homocysteine and Methylmalonic Acid among Demented and Non-Demented Swedish Elderly with and without Home Care Services and Vitamin B12 Prescriptions 
Background and Aims
Total plasma homocysteine (tHcy) has been suggested as a risk factor of dementia. Our aim was to investigate potential differences in tHcy status in relation to the prescription of vitamin B12 and dementia diagnosis. We examined whether vitamin B12 prescriptions, a family history of dementia, or the need for home care service might be associated with tHcy values.
Methods
A cross-sectional monocenter study comprising 926 consecutive subjects attending our Memory Care Unit was conducted.
Results
Demented subjects being prescribed vitamin B12 had higher serum vitamin B12 (p = 0.025) but also higher tHcy (p < 0.001) and serum methylmalonate (p = 0.032), and lower serum folate (p < 0.001) than those who did not receive vitamin B12 prescriptions. tHcy levels were significantly higher in non-demented subjects receiving home care service (p = 0.007). This group also had lower serum albumin (dementia: p < 0.001; non-dementia: p = 0.004). There was no difference in renal function (estimated glomerular filtration rate) in demented or non-demented subjects with or without vitamin B12 prescriptions (dementia with/without vitamin B12 prescription: p = 0.561; non-dementia with/without vitamin B12 prescription: p = 0.710).
Conclusion
Despite vitamin B12 prescriptions, demented subjects had higher tHcy and methylmalonate values. The elevated metabolite values could not be explained by differences in renal function. Thus, elderly subjects on vitamin B12 prescription appear to have unmet nutritional needs.
doi:10.1159/000339669
PMCID: PMC3522456  PMID: 23277779
Homocysteine; Dementia; Vitamin B12; Folate; Home care service
23.  Genome-Wide Meta-Analysis of Homocysteine and Methionine Metabolism Identifies Five One Carbon Metabolism Loci and a Novel Association of ALDH1L1 with Ischemic Stroke 
PLoS Genetics  2014;10(3):e1004214.
Circulating homocysteine levels (tHcy), a product of the folate one carbon metabolism pathway (FOCM) through the demethylation of methionine, are heritable and are associated with an increased risk of common diseases such as stroke, cardiovascular disease (CVD), cancer and dementia. The FOCM is the sole source of de novo methyl group synthesis, impacting many biological and epigenetic pathways. However, the genetic determinants of elevated tHcy (hyperhomocysteinemia), dysregulation of methionine metabolism and the underlying biological processes remain unclear. We conducted independent genome-wide association studies and a meta-analysis of methionine metabolism, characterized by post-methionine load test tHcy, in 2,710 participants from the Framingham Heart Study (FHS) and 2,100 participants from the Vitamin Intervention for Stroke Prevention (VISP) clinical trial, and then examined the association of the identified loci with incident stroke in FHS. Five genes in the FOCM pathway (GNMT [p = 1.60×10−63], CBS [p = 3.15×10−26], CPS1 [p = 9.10×10−13], ALDH1L1 [p = 7.3×10−13] and PSPH [p = 1.17×10−16]) were strongly associated with the difference between pre- and post-methionine load test tHcy levels (ΔPOST). Of these, one variant in the ALDH1L1 locus, rs2364368, was associated with incident ischemic stroke. Promoter analyses reveal genetic and epigenetic differences that may explain a direct effect on GNMT transcription and a downstream affect on methionine metabolism. Additionally, a genetic-score consisting of the five significant loci explains 13% of the variance of ΔPOST in FHS and 6% of the variance in VISP. Association between variants in FOCM genes with ΔPOST suggest novel mechanisms that lead to differences in methionine metabolism, and possibly the epigenome, impacting disease risk. These data emphasize the importance of a concerted effort to understand regulators of one carbon metabolism as potential therapeutic targets.
Author Summary
Elevated homocysteine (tHcy) is strongly associated with risk for common disorders such as stroke, cardiovascular disease and Alzheimer disease. Lowering tHcy levels has proven to have variable success in reducing clinical risk, so the question remains, “Are we correctly targeting these disorders by lowering tHcy?” Understanding folate one-carbon metabolism pathway (FOCM) genetic variation will aid us in developing new targets for therapy. The FOCM is essential in regulation of the epigenome, which controls genes in ways beyond nucleotide sequence. We present data generated from stroke-only and general populations where we identify strong association of genetic risk factors for variation in one-carbon metabolism function, characterized by the post-methionine load test. We show that GNMT harbors genetic and epigenetic differences that influence gene function, which may have downstream effects on the epigenome of the cell, affecting disease risk. We developed a genetic risk score that predicts post-methionine load homocysteine levels that may be useful in clinic. Finally, we identified a novel association between ischemic stroke and ALDH1L1, which emphasizes the clinical importance of this work. Our results highlight the importance of a concerted effort to target the FOCM (beyond tHcy) and parallel pathways in future pharmacogenetic work using the genetic variation we describe here.
doi:10.1371/journal.pgen.1004214
PMCID: PMC3961178  PMID: 24651765
24.  Significant Impact of the MTHFR Polymorphisms and Haplotypes on Male Infertility Risk 
PLoS ONE  2013;8(7):e69180.
Background
Methylenetetrahydrofolate reductase (MTHFR) converts 5,10-methylene tetrahydrofolate to 5-methyl tetrahydrofolate and affects the activity of cellular cycles participating in nucleotide synthesis, DNA repair, genome stability, maintenance of methyl pool, and gene regulation. Genetically compromised MTHFR activity has been suggested to affect male fertility. The objective of the present study was to find the impact on infertility risk of c.203G>A, c.1298A>C, and c.1793G>A polymorphisms in the MTHFR gene.
Methods
PCR-RFLP and DNA sequencing were used to genotype the common SNPs in the MTHFR gene in 630 infertile and 250 fertile males. Chi-square test was applied for statistical comparison of genotype data. Linkage disequilibrium between the SNPs and the frequency of common haplotypes were assessed using Haploview software. Biochemical levels of total homocysteine (tHcy) and folic acid were measured. Meta-analysis on c.1298A>C polymorphism was performed using data from ten studies, comprising 2734 cases and 2737 controls.
Results
c.203G>A and c.1298A>C were found to be unrelated to infertility risk. c.1793G>A was protective against infertility (P = 0.0008). c.677C>T and c.1793G>A were in significant LD (D’ = 0.9). Folic acid and tHcy level did not correlate with male infertility. Pooled estimate on c.1298A>C data from all published studies including our data showed no association of this polymorphism with male infertility (Odds ratio = 1.035, P = 0.56), azoospermia (Odds ratio = 0.97, P = 0.74), or oligoasthenoteratozoospermia (Odds ratio = 0.92, p = 0.29). Eight haplotypes with more than 1% frequency were detected, of which CCGA was protective against infertility (p = 0.02), but the significance of the latter was not seen after applying Bonferroni correction.
Conclusion
Among MTHFR polymorphisms, c.203G>A and c.1298A>C do not affect infertility risk and c.1793G>A is protective against infertility. Haplotype analysis suggested that risk factors on the MTHFR locus do not extend too long on the DNA string.
doi:10.1371/journal.pone.0069180
PMCID: PMC3715460  PMID: 23874907
25.  Plasma folate, but not homocysteine, is associated with Apolipoprotein A1 levels in a non-fortified population 
Background
Elevated total plasma homocysteine (tHcy) in humans is associated with cardiovascular disease but prevention trials have failed to confirm causality. Reported reasons for this association have been that homocysteine and its major genetic determinant methylenetetrahydrofolate reductase (MTHFR) may have an effect on HDL and Apolipoprotein (Apo) A1 levels. We wanted to study if tHcy and its major determinants were correlated with Apo A1 levels in a large population without folate fortification.
Methods
This study was a prospective incident nested case-referent study within the Northern Sweden Health and Disease Study Cohort (NSHDSC), including 545 cases with first myocardial infarction and 1054 matched referents, median age at inclusion was 59 years. Univariate and multiple regression analyzes was used to study the associations between apolipoproteins Apo A1 and B, tHcy, folate and vitamin B12 in plasma as well as MTHFR polymorphisms 677C>T and 1298A>C.
Results
Apo A1 and Apo B were strongly associated with the risk of a first myocardial infarction. tHcy was not associated with Apo A1 levels. Instead, folate had an independent positive association with Apo A1 levels in univariate and multiple regression models. The associations were seen in all men and women, among referents but not among cases. MTHFR polymorphisms had no clear effect on Apo A1 levels.
Conclusions
Analyzing over 1500 subjects we found an independent positive association between plasma folate (major dietary determinant of tHcy) and Apo A1 levels among those who later did not develop a first myocardial infarction. No association was seen between tHcy and Apo A1.
doi:10.1186/1476-511X-12-74
PMCID: PMC3679998  PMID: 23697869
Apolipoprotein; Homocysteine; Myocardial infarction; Folate; Epidemiology

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