High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice.
ABSTRACT: BACKGROUND:Increased consumption of folic acid is prevalent, leading to concerns about negative consequences. The effects of folic acid on the liver, the primary organ for folate metabolism, are largely unknown. Methylenetetrahydrofolate reductase (MTHFR) provides methyl donors for S-adenosylmethionine (SAM) synthesis and methylation reactions. OBJECTIVE:Our goal was to investigate the impact of high folic acid intake on liver disease and methyl metabolism. DESIGN:Folic acid-supplemented diet (FASD, 10-fold higher than recommended) and control diet were fed to male Mthfr(+/+) and Mthfr(+/-) mice for 6 mo to assess gene-nutrient interactions. Liver pathology, folate and choline metabolites, and gene expression in folate and lipid pathways were examined. RESULTS:Liver and spleen weights were higher and hematologic profiles were altered in FASD-fed mice. Liver histology revealed unusually large, degenerating cells in FASD Mthfr(+/-) mice, consistent with nonalcoholic fatty liver disease. High folic acid inhibited MTHFR activity in vitro, and MTHFR protein was reduced in FASD-fed mice. 5-Methyltetrahydrofolate, SAM, and SAM/S-adenosylhomocysteine ratios were lower in FASD and Mthfr(+/-) livers. Choline metabolites, including phosphatidylcholine, were reduced due to genotype and/or diet in an attempt to restore methylation capacity through choline/betaine-dependent SAM synthesis. Expression changes in genes of one-carbon and lipid metabolism were particularly significant in FASD Mthfr(+/-) mice. The latter changes, which included higher nuclear sterol regulatory element-binding protein 1, higher Srepb2 messenger RNA (mRNA), lower farnesoid X receptor (Nr1h4) mRNA, and lower Cyp7a1 mRNA, would lead to greater lipogenesis and reduced cholesterol catabolism into bile. CONCLUSIONS:We suggest that high folic acid consumption reduces MTHFR protein and activity levels, creating a pseudo-MTHFR deficiency. This deficiency results in hepatocyte degeneration, suggesting a 2-hit mechanism whereby mutant hepatocytes cannot accommodate the lipid disturbances and altered membrane integrity arising from changes in phospholipid/lipid metabolism. These preliminary findings may have clinical implications for individuals consuming high-dose folic acid supplements, particularly those who are MTHFR deficient.
Project description:Methylenetetrahydrofolate reductase (MTHFR) generates methyltetrahydrofolate for methylation reactions. Severe MTHFR deficiency results in homocystinuria and neurologic impairment. Mild MTHFR deficiency (677C?>?T polymorphism) increases risk for complex traits, including neuropsychiatric disorders. Although low dietary folate impacts brain development, recent concerns have focused on high folate intake following food fortification and increased vitamin use. Our goal was to determine whether high dietary folate during pregnancy affects brain development in murine offspring. Female mice were placed on control diet (CD) or folic acid-supplemented diet (FASD) throughout mating, pregnancy and lactation. Three-week-old male pups were evaluated for motor and cognitive function. Tissues from E17.5 embryos, pups and dams were collected for choline/methyl metabolite measurements, immunoblotting or gene expression of relevant enzymes. Brains were examined for morphology of hippocampus and cortex. Pups of FASD mothers displayed short-term memory impairment, decreased hippocampal size and decreased thickness of the dentate gyrus. MTHFR protein levels were reduced in FASD pup livers, with lower concentrations of phosphocholine and glycerophosphocholine in liver and hippocampus, respectively. FASD pup brains showed evidence of altered acetylcholine availability and Dnmt3a mRNA was reduced in cortex and hippocampus. E17.5 embryos and placentas from FASD dams were smaller. MTHFR protein and mRNA were reduced in embryonic liver, with lower concentrations of choline, betaine and phosphocholine. Embryonic brain displayed altered development of cortical layers. In summary, high folate intake during pregnancy leads to pseudo-MTHFR deficiency, disturbed choline/methyl metabolism, embryonic growth delay and memory impairment in offspring. These findings highlight the unintended negative consequences of supplemental folic acid.
Project description:Impaired utilization of folate is caused by insufficient dietary intake and/or genetic variation and has been shown to prompt changes in related pathways, including choline and methionine metabolism. These pathways have been shown to be sensitive to variation within the Mthfd1 gene, which codes for a folate-metabolizing enzyme responsible for generating 1-carbon (1-C)-substituted folate derivatives. The Mthfd1(gt/+) mouse serves as a potential model of human Mthfd1 loss-of-function genetic variants that impair MTHFD1 function. This study investigated the effects of the Mthfd1(gt/+) genotype and folate intake on markers of choline, folate, methionine, and transsulfuration metabolism. Male Mthfd1(gt/+) and Mthfd1(+/+) mice were randomly assigned at weaning (3 wk of age) to either a control (2 mg/kg folic acid) or folate-deficient (0 mg/kg folic acid) diet for 5 wk. Mice were killed at 8 wk of age following 12 h of food deprivation; blood and liver samples were analyzed for choline, methionine, and transsulfuration biomarkers. Independent of folate intake, mice with the Mthfd1(gt/+) genotype had higher hepatic concentrations of choline (P = 0.005), betaine (P = 0.013), and dimethylglycine (P = 0.004) and lower hepatic concentrations of glycerophosphocholine (P = 0.002) relative to Mthfd1(+/+) mice. Mthfd1(gt/+) mice also had higher plasma concentrations of homocysteine (P = 0.0016) and cysteine (P < 0.001) as well as lower plasma concentrations of methionine (P = 0.0003) and cystathionine (P = 0.011). The metabolic alterations observed in Mthfd1(gt/+) mice indicate perturbed choline and folate-dependent 1-C metabolism and support the future use of Mthfd1(gt/+) mice as a tool to investigate the impact of impaired 1-C metabolism on disease outcomes.
Project description:Supplementation with high doses of folic acid, an important mediator of one-carbon transfers for DNA methylation, is used clinically to improve sperm parameters in infertile men. We recently detected an unexpected loss of DNA methylation in the sperm of idiopathic infertile men after 6 months of daily supplementation with 5mg folic acid (>10× the daily recommended intake-DRI), exacerbated in men homozygous for a common variant in the gene encoding an important enzyme in folate metabolism, methylenetetrahydrofolate reductase (MTHFR 677C>T). To investigate the epigenomic impact and mechanism underlying effects of folic acid on male germ cells, wildtype and heterozygote mice for a targeted inactivation of the Mthfr gene were fed high-dose folic acid (10× the DRI) or control diets for six months. No changes were detected in general health, sperm counts or methylation of imprinted genes. Reduced representation bisulfite sequencing revealed sperm DNA hypomethylation in Mthfr+/- mice on the 10× diets. Wildtype mice demonstrated sperm hypomethylation only with a very high dose (20×) of folic acid for 12 months. Testicular MTHFR protein levels decreased significantly in wildtype mice on the 20× diet but not in those on the 10× diet, suggesting a possible role for MTHFR deficiency in sperm DNA hypomethylation. In-depth analysis of the folic acid-exposed sperm DNA methylome suggested mouse/human susceptibility of sequences with potential importance to germ cell and embryo development. Our data provide evidence for a similar cross-species response to high dose folic acid supplementation, of sperm DNA hypomethylation, and implicate MTHFR downregulation as a possible mechanism. Overall design: 27 total samples, n=3-5 for each group compared treated (10FS/20FS) to specific Control samples (CD)
Project description:Supplementation with high doses of folic acid, an important mediator of one-carbon transfers for DNA methylation, is used clinically to improve sperm parameters in infertile men. We recently detected an unexpected loss of DNA methylation in the sperm of idiopathic infertile men after 6 months of daily supplementation with 5 mg folic acid (>10×?the daily recommended intake-DRI), exacerbated in men homozygous for a common variant in the gene encoding an important enzyme in folate metabolism, methylenetetrahydrofolate reductase (MTHFR 677C>T). To investigate the epigenomic impact and mechanism underlying effects of folic acid on male germ cells, wild-type and heterozygote mice for a targeted inactivation of the Mthfr gene were fed high-dose folic acid (10×?the DRI) or control diets (CDs) for 6 months. No changes were detected in general health, sperm counts or methylation of imprinted genes. Reduced representation bisulfite sequencing revealed sperm DNA hypomethylation in Mthfr+/- mice on the 10×?diets. Wild-type mice demonstrated sperm hypomethylation only with a very high dose (20×) of folic acid for 12 months. Testicular MTHFR protein levels decreased significantly in wild-type mice on the 20×?diet but not in those on the 10×?diet, suggesting a possible role for MTHFR deficiency in sperm DNA hypomethylation. In-depth analysis of the folic acid-exposed sperm DNA methylome suggested mouse/human susceptibility of sequences with potential importance to germ cell and embryo development. Our data provide evidence for a similar cross-species response to high dose folic acid supplementation, of sperm DNA hypomethylation, and implicate MTHFR downregulation as a possible mechanism.
Project description:Both taking folic acid-containing vitamins around conception and consuming food fortified with folic acid have been reported to reduce omphalocele rates. Genetic factors are etiologically important in omphalocele as well; our pilot study showed a relationship with the folate metabolic enzyme gene methylenetetrahydrofolate reductase (MTHFR). We studied 169 non-aneuploid omphalocele cases and 761 unaffected, matched controls from all New York State births occurring between 1998 and 2005 to look for associations with single nucleotide polymorphisms (SNPs) known to be important in folate, vitamin B12, or choline metabolism. In the total study population, variants in the transcobalamin receptor gene (TCblR), rs2232775 (p.Q8R), and the MTHFR gene, rs1801131 (c.1298A>C), were significantly associated with omphalocele. In African-Americans, significant associations were found with SNPs in genes for the vitamin B12 transporter (TCN2) and the vitamin B12 receptor (TCblR). A SNP in the homocysteine-related gene, betaine-homocysteine S-methyltransferase (BHMT), rs3733890 (p.R239Q), was significantly associated with omphalocele in both African-Americans and Asians. Only the TCblR association in the total population remained statistically significant if Bonferroni correction was applied. The finding that transcobalamin receptor (TCblR) and transporter (TCN2) SNPs and a BHMT SNP were associated with omphalocele suggests that disruption of methylation reactions, in which folate, vitamin B12, and homocysteine play critical parts, may be a risk factor for omphalocele. Our data, if confirmed, suggest that supplements containing both folic acid and vitamin B12 may be beneficial in preventing omphaloceles.
Project description:OBJECTIVE:We evaluated the interaction of serum folate and vitamin B12 with methylenetetrahydrofolate reductase (MTHFR) C677T genotypes on the risk of first ischemic stroke and on the efficacy of folic acid treatment in prevention of first ischemic stroke. METHODS:A total of 20,702 hypertensive adults were randomized to a double-blind treatment of daily enalapril 10 mg and folic acid 0.8 mg or enalapril 10 mg alone. Participants were followed up every 3 months. RESULTS:Median values of folate and B12 concentrations at baseline were 8.1 ng/mL and 280.2 pmol/L, respectively. Over a median of 4.5 years, among those not receiving folic acid, participants with baseline serum B12 or serum folate above the median had a significantly lower risk of first ischemic stroke (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.57-0.96), especially in those with MTHFR 677 CC genotype (wild-type) (HR, 0.49; 95% CI, 0.31-0.78). Folic acid treatment significantly reduced the risk of first ischemic stroke in participants with both folate and B12 below the median (2.3% in enalapril-folic acid group vs 3.6% in enalapril-only group; HR, 0.62; 95% CI, 0.46-0.86), particularly in MTHFR 677 CC carriers (1.6% vs 4.9%; HR, 0.24; 95% CI, 0.11-0.55). However, TT homozygotes responded better with both folate and B12 levels above the median (HR, 0.28; 95% CI, 0.10-0.75). CONCLUSIONS:The risk of first ischemic stroke was significantly higher in hypertensive patients with low levels of both folate and B12. Effect of folic acid treatment was greatest in patients with low folate and B12 with the CC genotype, and with high folate and B12 with the TT genotype.
Project description:Folic acid supplementation prevents the occurrence and recurrence of neural tube defects (NTDs), but the causal metabolic pathways underlying folic acid-responsive NTDs have not been established. Serine hydroxymethyltransferase (SHMT1) partitions folate-derived one-carbon units to thymidylate biosynthesis at the expense of cellular methylation, and therefore SHMT1-deficient mice are a model to investigate the metabolic origin of folate-associated pathologies.We examined whether genetic disruption of the Shmt1 gene in mice induces NTDs in response to maternal folate and choline deficiency and whether a corresponding disruption in de novo thymidylate biosynthesis underlies NTD pathogenesis.Shmt1 wild-type, Shmt1(+/-), and Shmt1(-/-) mice fed either folate- and choline-sufficient or folate- and choline-deficient diets were bred, and litters were examined for the presence of NTDs. Biomarkers of impaired folate metabolism were measured in the dams. In addition, the effect of Shmt1 disruption on NTD incidence was investigated in Pax3(Sp) mice, an established folate-responsive NTD mouse model.Shmt1(+/-) and Shmt1(-/-) embryos exhibited exencephaly in response to maternal folate and choline deficiency. Shmt1 disruption on the Pax3(Sp) background exacerbated NTD frequency and severity. Pax3 disruption impaired de novo thymidylate and purine biosynthesis and altered amounts of SHMT1 and thymidylate synthase protein.SHMT1 is the only folate-metabolizing enzyme that has been shown to affect neural tube closure in mice by directly inhibiting folate metabolism. These results provide evidence that disruption of Shmt1 expression causes NTDs by impairing thymidylate biosynthesis and shows that changes in the expression of genes that encode folate-dependent enzymes may be key determinates of NTD risk.
Project description:Choline and folate are interrelated in 1-carbon metabolism, mostly because of their shared function as methyl donors for homocysteine remethylation. Folate deficiency and mutations of methylenetetrahydrofolate reductase (MTHFR) reduce the availability of a major methyl donor, 5-methyltetrahydrofolate, which in turn may lead to compensatory changes in choline metabolism. This study investigated the hypothesis that reductions in methyl group supply, either due to dietary folate deficiency or Mthfr gene deletion, would modify tissue choline metabolism in a sex-specific manner. Mthfr wild type (+/+) or heterozygous (+/-) knockout mice were randomized to a folate-deficient or control diet for 8 wk during which time deuterium-labeled choline (d9-choline) was consumed in the drinking water (~10 ?mol/d). Mthfr heterozygosity did not alter brain choline metabolite concentrations, but it did enhance their labeling in males (P < 0.05) and tended to do so in females (P < 0.10), a finding consistent with greater turnover of dietary choline in brains of +/- mice. Dietary folate deficiency in females yielded 52% higher (P = 0.027) hepatic glycerophosphocholine, which suggests that phosphatidylcholine (PtdCho) degradation was enhanced. Labeling of the hepatic PtdCho in d3 form was also reduced (P < 0.001) in females, which implies that fewer of the dietary choline-derived methyl groups were used for de novo PtdCho biosynthesis under conditions of folate insufficiency. Males responded to folate restriction with a doubling (P < 0.001) of hepatic choline dehydrogenase transcripts, a finding consistent with enhanced conversion of choline to the methyl donor, betaine. Collectively, these data show that several adaptations in choline metabolism transpire as a result of mild perturbations in folate metabolism, presumably to preserve methyl group homeostasis.
Project description:BACKGROUND:Neural tube defects (NTDs) are birth defects of the brain, spine, or spinal cord invoked by the insufficient intake of folic acid in the early stages of pregnancy and have a complex etiology involving both genetic and environmental factors. So the study aimed to explore the association between alterations in maternal one-carbon metabolism and NTDs in the offspring. METHODS:We conducted a case-control study to get a deeper insight into this association, as well as into the role of genetic polymorphisms. Plasma concentrations of folate, homocysteine (Hcy), S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH) and genotypes and alleles distributions of 52 SNPs in 8 genes were compared for 61 women with NTDs-affected offspring and 61 women with healthy ones. RESULTS:There were significant differences between groups with regard to plasma folate, SAM, SAH and SAM/SAH levels. Logistic regression results revealed a significant association between maternal plasma folate level and risk of NTDs in the offspring. For MTHFD1 rs2236225 polymorphism, mothers having GA genotype and A allele exhibited an increased risk of NTDs in the offspring (OR = 2.600, 95%CI: 1.227-5.529; OR = 1.847, 95%CI: 1.047-3.259). For MTHFR rs1801133 polymorphism, mothers having TT and CT genotypes were more likely to affect NTDs in the offspring (OR = 4.105, 95%CI: 1.271-13.258; OR = 3.333, 95%CI: 1.068-10.400). Moreover, mothers carrying T allele had a higher risk of NTDs in the offspring (OR = 1.798, 95%CI: 1.070-3.021). For MTRR rs1801394 polymorphism, the frequency of G allele was significantly higher in cases than in controls (OR = 1.763, 95%CI: 1.023-3.036). Mothers with NTDs-affected children had higher AG genotype in RFC1 rs1051226 polymorphism than controls, manifesting an increased risk for NTDs (OR = 3.923, 95%CI: 1.361-11.308). CONCLUSION:Folic acid deficiency, MTHFD1 rs2236225, MTHFR rs1801133, MTRR rs1801349 and RFC1 rs1051226 polymorphisms may be maternal risk factors of NTDs.
Project description:Moderate hyperhomocysteinemia-induced low folate status is an independent risk factor for cardiovascular disease, dementia, and depression. Folate is an essential cofactor in the one-carbon metabolism pathway and is necessary in amino acid metabolism, purine and thymidylate synthesis, and DNA methylation. In the folate cycle and homocysteine metabolism, folate, vitamin B12, vitamin B6, and vitamin B2 are important cofactors. Many enzymes are involved in folate transport and uptake, the folate pathway, and homocysteine (Hcy) metabolism, and various polymorphisms have been documented in these enzymes. Serum folate and total Hcy (tHcy) levels are influenced by folate intake and genetic polymorphisms in 5,10-methylenetertahydrofolate reductase (MTHFR) such as C677T. The prevalence of the MTHFR 677TT genotype varies across ethnic groups and regions, with a frequency of approximately 15% in Japanese populations. Individuals with the TT genotype have significantly higher tHcy levels and lower folate levels in serum than those with the CT and TT genotypes. However, administration of folic acid has been shown to eliminate these differences. Moreover, data have suggested that interventions based on genotype may be effective for motivating individuals to change their lifestyle and improve their nutrition status. Accordingly, in this review, we discuss the effects of MTHFR C677T polymorphisms on serum tHcy and folate levels with folic acid intervention and evaluate approaches for overcoming folic acid deficiency and related symptoms.