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

Christensen KE, Mikael LG, Leung KY, Lévesque N, Deng L, Wu Q, Malysheva OV, Best A, Caudill MA, Greene ND, Rozen R - Am. J. Clin. Nutr. (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: From the Departments of Human Genetics and Pediatrics, McGill University, and the Montreal Children's Hospital site of the McGill University Health Centre Research Institute, Montreal, Quebec, Canada (KEC, LGM, NL, LD, QW, and RR); Developmental Biology and Cancer Programme, Institute of Child Health, University College London, London, United Kingdom (K-YL and NDEG); the Division of Nutritional Sciences and Genomics, Cornell University, Ithaca, NY (OVM and MAC); and the Department of Mathematics and Statistics, McGill University, Montreal, Quebec, Canada (AB).

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.

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High folic acid consumption reduces methylTHF and methylation capacity. (A) Total liver folate content did not differ between groups. (B) The proportion of unmetabolized folic acid (percentage of total folates) in liver was ∼60% higher in FASD-fed mice (borderline significant, P = 0.074). (C) The proportion of methylTHF was significantly lower in FASD-fed mice. (D) SAM concentrations were significantly lower in FASD-fed mice. (E) There was a significant interaction between the effects of diet and Mthfr genotype on SAH concentrations, but there was no significant difference between groups by Tukey post hoc comparisons. (F) Methylation capacity as measured by SAM/SAH ratio. There was a significant interaction between diet and genotype; CD+/− and FASD+/+ groups were borderline significantly different from CD+/+ by Tukey post hoc analysis (ΔP = 0.062–0.074). White bars: Mthfr+/+; gray bars: Mthfr+/−. n = 4–5 per group, mean ± SEM, analyzed by 2-factor ANOVA. CD, control diet; D, diet; FASD, folic acid–supplemented diet; G, genotype; SAH, S-adenosylhomocysteine; SAM, S-adenosylmethionine.
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fig3: High folic acid consumption reduces methylTHF and methylation capacity. (A) Total liver folate content did not differ between groups. (B) The proportion of unmetabolized folic acid (percentage of total folates) in liver was ∼60% higher in FASD-fed mice (borderline significant, P = 0.074). (C) The proportion of methylTHF was significantly lower in FASD-fed mice. (D) SAM concentrations were significantly lower in FASD-fed mice. (E) There was a significant interaction between the effects of diet and Mthfr genotype on SAH concentrations, but there was no significant difference between groups by Tukey post hoc comparisons. (F) Methylation capacity as measured by SAM/SAH ratio. There was a significant interaction between diet and genotype; CD+/− and FASD+/+ groups were borderline significantly different from CD+/+ by Tukey post hoc analysis (ΔP = 0.062–0.074). White bars: Mthfr+/+; gray bars: Mthfr+/−. n = 4–5 per group, mean ± SEM, analyzed by 2-factor ANOVA. CD, control diet; D, diet; FASD, folic acid–supplemented diet; G, genotype; SAH, S-adenosylhomocysteine; SAM, S-adenosylmethionine.

Mentions: Key folate derivatives were evaluated in the liver (Figure 3 and Supplemental Table 2). There was no significant change in the concentration of total folate due to diet or genotype (Figure 3A), as previously observed in mice fed folate-supplemented diets (53). Therefore, to compare folate distributions, individual concentrations were normalized to the total and expressed as percent total folates. Folic acid in the liver was ∼60% greater in mice fed FASD (Figure 3B). MethylTHF was lower in all groups compared with CD+/+ (Figure 3C), consistent with reduced expression and activity of MTHFR (Figure 2). There were no significant changes due to diet or genotype in the proportion of other folates (dihydrofolate, THF, methenylTHF, methyleneTHF, and formylTHF) (Supplemental Table 2). These findings suggest that the substrate of MTHFR, methyleneTHF, is being redistributed among the other nonmethyl forms. High folic acid intake appears to be altering methylation potential, without dramatically changing the availability of folate substrates for nucleotide synthesis and other functions. However, some variability between mice in the levels of non-methylTHF may have contributed to this lack of significance.


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

Christensen KE, Mikael LG, Leung KY, Lévesque N, Deng L, Wu Q, Malysheva OV, Best A, Caudill MA, Greene ND, Rozen R - Am. J. Clin. Nutr. (2015)

High folic acid consumption reduces methylTHF and methylation capacity. (A) Total liver folate content did not differ between groups. (B) The proportion of unmetabolized folic acid (percentage of total folates) in liver was ∼60% higher in FASD-fed mice (borderline significant, P = 0.074). (C) The proportion of methylTHF was significantly lower in FASD-fed mice. (D) SAM concentrations were significantly lower in FASD-fed mice. (E) There was a significant interaction between the effects of diet and Mthfr genotype on SAH concentrations, but there was no significant difference between groups by Tukey post hoc comparisons. (F) Methylation capacity as measured by SAM/SAH ratio. There was a significant interaction between diet and genotype; CD+/− and FASD+/+ groups were borderline significantly different from CD+/+ by Tukey post hoc analysis (ΔP = 0.062–0.074). White bars: Mthfr+/+; gray bars: Mthfr+/−. n = 4–5 per group, mean ± SEM, analyzed by 2-factor ANOVA. CD, control diet; D, diet; FASD, folic acid–supplemented diet; G, genotype; SAH, S-adenosylhomocysteine; SAM, S-adenosylmethionine.
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Related In: Results  -  Collection

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fig3: High folic acid consumption reduces methylTHF and methylation capacity. (A) Total liver folate content did not differ between groups. (B) The proportion of unmetabolized folic acid (percentage of total folates) in liver was ∼60% higher in FASD-fed mice (borderline significant, P = 0.074). (C) The proportion of methylTHF was significantly lower in FASD-fed mice. (D) SAM concentrations were significantly lower in FASD-fed mice. (E) There was a significant interaction between the effects of diet and Mthfr genotype on SAH concentrations, but there was no significant difference between groups by Tukey post hoc comparisons. (F) Methylation capacity as measured by SAM/SAH ratio. There was a significant interaction between diet and genotype; CD+/− and FASD+/+ groups were borderline significantly different from CD+/+ by Tukey post hoc analysis (ΔP = 0.062–0.074). White bars: Mthfr+/+; gray bars: Mthfr+/−. n = 4–5 per group, mean ± SEM, analyzed by 2-factor ANOVA. CD, control diet; D, diet; FASD, folic acid–supplemented diet; G, genotype; SAH, S-adenosylhomocysteine; SAM, S-adenosylmethionine.
Mentions: Key folate derivatives were evaluated in the liver (Figure 3 and Supplemental Table 2). There was no significant change in the concentration of total folate due to diet or genotype (Figure 3A), as previously observed in mice fed folate-supplemented diets (53). Therefore, to compare folate distributions, individual concentrations were normalized to the total and expressed as percent total folates. Folic acid in the liver was ∼60% greater in mice fed FASD (Figure 3B). MethylTHF was lower in all groups compared with CD+/+ (Figure 3C), consistent with reduced expression and activity of MTHFR (Figure 2). There were no significant changes due to diet or genotype in the proportion of other folates (dihydrofolate, THF, methenylTHF, methyleneTHF, and formylTHF) (Supplemental Table 2). These findings suggest that the substrate of MTHFR, methyleneTHF, is being redistributed among the other nonmethyl forms. High folic acid intake appears to be altering methylation potential, without dramatically changing the availability of folate substrates for nucleotide synthesis and other functions. However, some variability between mice in the levels of non-methylTHF may have contributed to this lack of significance.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: From the Departments of Human Genetics and Pediatrics, McGill University, and the Montreal Children's Hospital site of the McGill University Health Centre Research Institute, Montreal, Quebec, Canada (KEC, LGM, NL, LD, QW, and RR); Developmental Biology and Cancer Programme, Institute of Child Health, University College London, London, United Kingdom (K-YL and NDEG); the Division of Nutritional Sciences and Genomics, Cornell University, Ithaca, NY (OVM and MAC); and the Department of Mathematics and Statistics, McGill University, Montreal, Quebec, Canada (AB).

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.

Show MeSH
Related in: MedlinePlus