(21-11-15) High folic acid consumption leads to pseudo-MTHFR deficiency, altered lipid metabolism, and liver injury in mice

1,2,3,4,5
1. Karen E Christensen,
2. Leonie G Mikael,
3. Kit-Yi Leung,
4. Nancy Lévesque,
5. Liyuan Deng,
6. Qing Wu,
7. Olga V Malysheva,
8. Ana Best,
9. Marie A Caudill,
10. Nicholas DE Greene, and
11. Rima Rozen
+ Author Affiliations
1. 1From 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).
+ Author Notes
↵2 Supported by grant MOP-43232 (RR) from the Canadian Institutes of Health Research and grant J003794 (NDEG) from the UK Medical Research Council. This is an open access article distributed under the CC-BY license (http://creativecommons.org/licenses/by/3.0/).
↵3 Supplemental Figure 1 and Supplemental Tables 1 and 2 are available from the “Supplemental data” link in the online posting of the article and from the same link in the online table of contents at http://ajcn.nutrition.org.
↵4 KEC and LGM contributed equally to this work.
↵5 Address correspondence to R Rozen, McGill University, Montreal Children's Hospital, 4060 Ste Catherine West, Room 200, Montreal, Quebec, Canada, H3Z 2Z3. E-mail: [email protected].
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.


Source: http://ajcn.nutrition.org/content/early/2015/01/07/ajcn.114.086603

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