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Hsu FY, Liou JY, Tang FY, Sou NL, Peng JH, Chiang EPI. Ketogenic Diet Consumption Inhibited Mitochondrial One-Carbon Metabolism. Int J Mol Sci 2022; 23:ijms23073650. [PMID: 35409009 PMCID: PMC8998878 DOI: 10.3390/ijms23073650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 03/01/2022] [Accepted: 03/04/2022] [Indexed: 11/17/2022] Open
Abstract
Given the popularity of ketogenic diets, their potential long-term consequences deserve to be more carefully monitored. Mitochondrially derived formate has a critical role in mammalian one-carbon (1C) metabolism and development. The glycine cleavage system (GCS) accounts for another substantial source for mitochondrially derived 1C units. Objective: We investigated how the ketogenic state modulates mitochondrial formate generation and partitioning of 1C metabolic fluxes. Design: HepG2 cells treated with physiological doses (1 mM and 10 mM) of β-hydroxybutyrate (βHB) were utilized as the in vitro ketogenic model. Eight-week male C57BL/6JNarl mice received either a medium-chain fatty-acid-enriched ketogenic diet (MCT-KD) or a control diet AIN 93M for 8 weeks. Stable isotopic labeling experiments were conducted. Results and Conclusions: MCT-KD is effective in weight and fat loss. Deoxythymidine (dTMP) synthesis from the mitochondrial GCS-derived formate was significantly suppressed by βHB and consumption of MCT-KD. Consistently, plasma formate concentrations, as well as the metabolic fluxes from serine and glycine, were suppressed by MCT-KD. MCT-KD also decreased the fractional contribution of mitochondrially derived formate in methionine synthesis from serine. With the worldwide application, people and medical professionals should be more aware of the potential metabolic perturbations when practicing a long-term ketogenic diet.
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Affiliation(s)
- Fan-Yu Hsu
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan; (F.-Y.H.); (J.-Y.L.); (N.-L.S.); (J.-H.P.)
| | - Jia-Ying Liou
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan; (F.-Y.H.); (J.-Y.L.); (N.-L.S.); (J.-H.P.)
| | - Feng-Yao Tang
- Biomedical Science Laboratory, Department of Nutrition, China Medical University, Taichung 402, Taiwan;
| | - Nga-Lai Sou
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan; (F.-Y.H.); (J.-Y.L.); (N.-L.S.); (J.-H.P.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University, Taichung 402, Taiwan
| | - Jian-Hau Peng
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan; (F.-Y.H.); (J.-Y.L.); (N.-L.S.); (J.-H.P.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University, Taichung 402, Taiwan
- Ph.D. Program in Microbial Genomics, National Chung Hsing University, Taichung 402, Taiwan
| | - En-Pei Isabel Chiang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 402, Taiwan; (F.-Y.H.); (J.-Y.L.); (N.-L.S.); (J.-H.P.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University, Taichung 402, Taiwan
- Ph.D. Program in Microbial Genomics, National Chung Hsing University, Taichung 402, Taiwan
- Correspondence: ; Tel.: +886-4-22853049
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Downregulation of Methionine Cycle Genes MAT1A and GNMT Enriches Protein-Associated Translation Process and Worsens Hepatocellular Carcinoma Prognosis. Int J Mol Sci 2022; 23:ijms23010481. [PMID: 35008908 PMCID: PMC8745498 DOI: 10.3390/ijms23010481] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/27/2021] [Accepted: 12/28/2021] [Indexed: 01/27/2023] Open
Abstract
The major biological methyl donor, S-adenosylmethionine (adoMet) synthesis occurs mainly in the liver. Methionine adenosyltransferase 1A (MAT1A) and glycine N-methyltransferase (GNMT) are two key enzymes involved in the functional implications of that variation. We collected 42 RNA-seq data from paired hepatocellular carcinoma (HCC) and its adjacent normal liver tissue from the Cancer Genome Atlas (TCGA). There was no mutation found in MAT1A or GNMT RNA in the 42 HCC patients. The 11,799 genes were annotated in the RNA-Seq data, and their expression levels were used to investigate the phenotypes of low MAT1A and low GNMT by Gene Set Enrichment Analysis (GSEA). The REACTOME_TRANSLATION gene set was enriched and visualized in a heatmap along with corresponding differences in gene expression between low MAT1A versus high MAT1A and low GNMT versus high GNMT. We identified 43 genes of the REACTOME_TRANSLATION gene set that are powerful prognosis factors in HCC. The significantly predicted genes were referred into eukaryotic translation initiation (EIF3B, EIF3K), eukaryotic translation elongation (EEF1D), and ribosomal proteins (RPs). Cell models expressing various MAT1A and GNMT proved that simultaneous restoring the expression of MAT1A and GNMT decreased cell proliferation, invasion, as well as the REACTOME_TRANSLATION gene EEF1D, consistent with a better prognosis in human HCC. We demonstrated new findings that downregulation or defect in MAT1A and GNMT genes can enrich the protein-associated translation process that may account for poor HCC prognosis. This is the first study demonstrated that MAT1A and GNMT, the 2 key enzymes involved in methionine cycle, could attenuate the function of ribosome translation. We propose a potential novel mechanism by which the diminished GNMT and MAT1A expression may confer poor prognosis for HCC.
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Wu MT, Ye WT, Wang YC, Chen PM, Liu JY, Tai CK, Tang FY, Li JR, Liu CC, Chiang EPI. MTHFR Knockdown Assists Cell Defense against Folate Depletion Induced Chromosome Segregation and Uracil Misincorporation in DNA. Int J Mol Sci 2021; 22:ijms22179392. [PMID: 34502300 PMCID: PMC8431311 DOI: 10.3390/ijms22179392] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 08/11/2021] [Accepted: 08/19/2021] [Indexed: 12/14/2022] Open
Abstract
Folate depletion causes chromosomal instability by increasing DNA strand breakage, uracil misincorporation, and defective repair. Folate mediated one-carbon metabolism has been suggested to play a key role in the carcinogenesis and progression of hepatocellular carcinoma (HCC) through influencing DNA integrity. Methylenetetrahydrofolate reductase (MTHFR) is the enzyme catalyzing the irreversible conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate that can control folate cofactor distributions and modulate the partitioning of intracellular one-carbon moieties. The association between MTHFR polymorphisms and HCC risk is inconsistent and remains controversial in populational studies. We aimed to establish an in vitro cell model of liver origin to elucidate the interactions between MTHFR function, folate status, and chromosome stability. In the present study, we (1) examined MTHFR expression in HCC patients; (2) established cell models of liver origin with stabilized inhibition of MTHFR using small hairpin RNA delivered by a lentiviral vector, and (3) investigated the impacts of reduced MTHFR and folate status on cell cycle, methyl group homeostasis, nucleotide biosynthesis, and DNA stability, all of which are pathways involved in DNA integrity and repair and are critical in human tumorigenesis. By analyzing the TCGA/GTEx datasets available within GEPIA2, we discovered that HCC cancer patients with higher MTHFR had a worse survival rate. The shRNA of MTHFR (shMTHFR) resulted in decreased MTHFR gene expression, MTHFR protein, and enzymatic activity in human hepatoma cell HepG2. shMTHFR tended to decrease intracellular S-adenosylmethionine (SAM) contents but folate depletion similarly decreased SAM in wildtype (WT), negative control (Neg), and shMTHFR cells, indicating that in cells of liver origin, shMTHFR does not exacerbate the methyl group supply in folate depletion. shMTHFR caused cell accumulations in the G2/M, and cell population in the G2/M was inversely correlated with MTHFR gene level (r = −0.81, p < 0.0001), MTHFR protein expression (r = −0.8; p = 0.01), and MTHFR enzyme activity (r = −0.842; p = 0.005). Folate depletion resulted in G2/M cell cycle arrest in WT and Neg but not in shMTHFR cells, indicating that shMTHFR does not exacerbate folate depletion-induced G2/M cell cycle arrest. In addition, shMTHFR promoted the expression and translocation of nuclei thymidine synthetic enzyme complex SHMT1/DHFR/TYMS and assisted folate-dependent de novo nucleotide biosynthesis under folate restriction. Finally, shMTHFR promoted nuclear MLH1/p53 expression under folate deficiency and further reduced micronuclei formation and DNA uracil misincorporation under folate deficiency. In conclusion, shMTHFR in HepG2 induces cell cycle arrest in G2/M that may promote nucleotide supply and assist cell defense against folate depletion-induced chromosome segregation and uracil misincorporation in the DNA. This study provided insight into the significant impact of MTHFR function on chromosome stability of hepatic tissues. Data from the present study may shed light on the potential regulatory mechanism by which MTHFR modulates the risk for hepatic malignancies.
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Affiliation(s)
- Ming-Tsung Wu
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
- Department of Civil and Environmental Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ, UK
| | - Wei-Ting Ye
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
| | - Yi-Cheng Wang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
| | - Po-Ming Chen
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
| | - Jun-You Liu
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
| | - Chien-Kuo Tai
- Department of Biomedical Sciences, National Chung Cheng University, Chia-Yi 62102, Taiwan;
| | - Feng-Yao Tang
- Department of Nutrition, China Medical University, Taichung 40402, Taiwan;
| | - Jian-Rong Li
- Institute of Genomics and Bioinformatics, National Chung Hsing University, Taichung 40227, Taiwan; (J.-R.L.); (C.-C.L.)
| | - Chun-Chi Liu
- Institute of Genomics and Bioinformatics, National Chung Hsing University, Taichung 40227, Taiwan; (J.-R.L.); (C.-C.L.)
| | - En-Pei Isabel Chiang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan; (M.-T.W.); (W.-T.Y.); (Y.-C.W.); (P.-M.C.); (J.-Y.L.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University, Taichung 40227, Taiwan
- Correspondence:
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Sou NL, Huang YH, Chen DY, Chen YM, Tang FY, Ko HA, Fan YH, Lin YY, Wang YC, Chih HM, Shane B, Huang WN, Chiang EPI. Folinate Supplementation Ameliorates Methotrexate Induced Mitochondrial Formate Depletion In Vitro and In Vivo. Int J Mol Sci 2021; 22:1350. [PMID: 33572934 PMCID: PMC7866403 DOI: 10.3390/ijms22031350] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 12/13/2022] Open
Abstract
(1) Background: Antifolate methotrexate (MTX) is the most common disease-modifying antirheumatic drug (DMARD) for treating human rheumatoid arthritis (RA). The mitochondrial-produced formate is essential for folate-mediated one carbon (1C) metabolism. The impacts of MTX on formate homeostasis in unknown, and rigorously controlled kinetic studies can greatly help in this regard. (2) Methods: Combining animal model (8-week old female C57BL/6JNarl mice, n = 18), cell models, stable isotopic tracer studies with gas chromatography/mass spectrometry (GC/MS) platforms, we systematically investigated how MTX interferes with the partitioning of mitochondrial and cytosolic formate metabolism. (3) Results: MTX significantly reduced de novo deoxythymidylate (dTMP) and methionine biosyntheses from mitochondrial-derived formate in cells, mouse liver, and bone marrow, supporting our postulation that MTX depletes mitochondrial 1C supply. Furthermore, MTX inhibited formate generation from mitochondria glycine cleavage system (GCS) both in vitro and in vivo. Folinate selectively rescued 1C metabolic pathways in a tissue-, cellular compartment-, and pathway-specific manner: folinate effectively reversed the inhibition of mitochondrial formate-dependent 1C metabolism in mouse bone marrow (dTMP, methionine, and GCS) and cells (dTMP and GCS) but not methionine synthesis in liver/liver-derived cells. Folinate failed to fully recover hepatic mitochondrial-formate utilization for methionine synthesis, suggesting that the efficacy of clinical folinate rescue in MTX therapy on hepatic methionine metabolism is poor. (4) Conclusion: Conducting studies in mouse and cell models, we demonstrate novel findings that MTX specifically depletes mitochondrial 1C supply that can be ameliorated by folinate supplementation except for hepatic transmethylation. These results imply that clinical use of low-dose MTX may particularly impede 1C metabolism via depletion of mitochondrial formate. The MTX induced systematic and tissue-specific formate depletion needs to be addressed more carefully, and the efficacy of folinate with respect to protecting against such depletion deserves to be evaluated in medical practice.
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Grants
- 108-2321-B-005-004 Ministry of Science and Technology, Taiwan
- 107-2320-B005-003-MY3 Ministry of Science and Technology, Taiwan
- 107-2621-M005-008-MY3 Ministry of Science and Technology, Taiwan
- 107-2321-B-005-009 Ministry of Science and Technology, Taiwan
- 108-2321-B-005 -004 Ministry of Science and Technology, Taiwan
- 107-2320-B039-008-MY3 Ministry of Science and Technology, Taiwan
- 104-2320-B-039-041-MY3 Ministry of Science and Technology, Taiwan
- CMU103-ASIA-20 China Medical University, Taiwan
- CMU103-S-46 China Medical University, Taiwan
- CMU104-S-32 China Medical University, Taiwan
- 997608 Taipei Veterans General Hospital
- 1077602 Taipei Veterans General Hospital
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Affiliation(s)
- Nga-Lai Sou
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University (NCHU), Taichung 402, Taiwan
| | - Yu-Hsuan Huang
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University (NCHU), Taichung 402, Taiwan
| | - Der-Yuan Chen
- Allergy Immunology Rheumatology, Taichung Veterans General Hospital (TVGH), Taichung 402, Taiwan; (D.-Y.C.); (Y.-M.C.); (W.-N.H.)
- Allergy Immunology Rheumatology, China Medical University Hospital, Taichung 402, Taiwan
| | - Yi-Ming Chen
- Allergy Immunology Rheumatology, Taichung Veterans General Hospital (TVGH), Taichung 402, Taiwan; (D.-Y.C.); (Y.-M.C.); (W.-N.H.)
| | - Feng-Yao Tang
- Department of Nutrition, China Medical University, Taichung 402, Taiwan;
| | - Hsin-An Ko
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
| | - Yi-Hsuan Fan
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
| | - Yi-Ying Lin
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
| | - Yi-Cheng Wang
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
| | - Hui-Ming Chih
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
- Department of Nursing and Pediatrics, Taichung Veterans General Hospital (TVGH), Taichung 402, Taiwan
| | - Barry Shane
- Nutritional Sciences and Toxicology, UC Berkeley, Berkeley, CA 94701, USA;
| | - Wen-Nan Huang
- Allergy Immunology Rheumatology, Taichung Veterans General Hospital (TVGH), Taichung 402, Taiwan; (D.-Y.C.); (Y.-M.C.); (W.-N.H.)
| | - En-Pei Isabel Chiang
- Food Science and Biotechnology, National Chung Hsing University (NCHU), Taichung 402, Taiwan; (N.-L.S.); (Y.-H.H.); (H.-A.K.); (Y.-H.F.); (Y.-Y.L.); (Y.-C.W.); (H.-M.C.)
- Innovation and Development Center of Sustainable Agriculture (IDCSA), National Chung Hsing University (NCHU), Taichung 402, Taiwan
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Minović I, Riphagen IJ, van den Berg E, Kootstra-Ros JE, van Faassen M, Gomes Neto AW, Geleijnse JM, Gans RO, Eggersdorfer M, Navis GJ, Kema IP, Bakker SJ. Vitamin B-6 deficiency is common and associated with poor long-term outcome in renal transplant recipients. Am J Clin Nutr 2017; 105:1344-1350. [PMID: 28468895 DOI: 10.3945/ajcn.116.151431] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 03/31/2017] [Indexed: 11/14/2022] Open
Abstract
Background: Previous studies have reported low circulating concentrations of pyridoxal-5-phospate (PLP) in renal transplant recipients (RTRs). It is unknown whether this is because of low intake or altered handling, and it is also unknown whether variation in circulating concentrations of PLP influences long-term outcome.Objective: We compared vitamin B-6 intake and circulating PLP concentrations of RTRs with those of healthy controls and investigated long-term clinical implications of vitamin B-6 deficiency in stable outpatient RTRs.Design: In a longitudinal cohort of 687 stable RTRs (57% male; mean ± SD age: 53 ± 13 y) with a median (IQR) follow-up of 5.3 y (4.8-6.1 y) and 357 healthy controls (47% male; age 54 ± 11 y), baseline vitamin B-6 was measured as plasma PLP by high-performance liquid chromatography (HPLC). Vitamin B-6 deficiency was defined as PLP <20 nmol/L, and insufficiency as PLP 20-30 nmol/L. Dietary intake was assessed by validated food-frequency questionnaires.Results: At inclusion [5.3 y (1.8-12.1 y) after transplantation], the mean vitamin B-6 intakes in RTRs and healthy controls were 1.77 ± 0.49 and 1.85 ± 0.56 mg/d, respectively (P = 0.23). In these groups, the median plasma PLP concentrations were 29 nmol/L (17-50 nmol/L) and 41 nmol/L (29-60 nmol/L), respectively (P < 0.001). Accordingly, deficiency was present in 30% of RTRs compared with 11% of healthy controls. PLP concentrations were inversely associated with glucose homeostasis variables and inflammation variables (all P < 0.01). During follow-up, 149 (21%) RTRs died and 82 (12%) developed graft failure. In RTRs, vitamin B-6 deficiency was associated with considerably higher mortality risk (HR 2.14; 95% CI: 1.48, 3.08) than a sufficient vitamin B-6 status, independent of potential confounders. No associations were observed for graft failure (P = 0.18).Conclusions: Vitamin B-6 deficiency is common in RTRs and does not seem to be a consequence of inadequate intake. In addition, this deficient state is clinically relevant and independently associated with an increased risk of mortality in RTRs. The cohort on which the study was based [TransplantLines Food and Nutrition Biobank and Cohort Study (TxL-FN)] was registered at clinicaltrials.gov as NCT02811835.
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Affiliation(s)
- Isidor Minović
- Department of Internal Medicine, .,Department of Laboratory Medicine, and.,Top Institute Food and Nutrition, Wageningen, Netherlands
| | | | | | | | | | - Antonio W Gomes Neto
- Department of Internal Medicine.,TransplantLines Food and Nutrition Biobank and Cohort Study, University of Groningen, University Medical Center Groningen, Groningen, Netherlands
| | - Johanna M Geleijnse
- Division of Human Nutrition, Wageningen University, Wageningen, Netherlands; and
| | | | - Manfred Eggersdorfer
- Division of Human Nutrition, Wageningen University, Wageningen, Netherlands; and.,DSM Nutritional Products, Kaiseraugst, Switzerland
| | | | | | - Stephan Jl Bakker
- Department of Internal Medicine.,TransplantLines Food and Nutrition Biobank and Cohort Study, University of Groningen, University Medical Center Groningen, Groningen, Netherlands.,Top Institute Food and Nutrition, Wageningen, Netherlands
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Ueland PM, McCann A, Midttun Ø, Ulvik A. Inflammation, vitamin B6 and related pathways. Mol Aspects Med 2016; 53:10-27. [PMID: 27593095 DOI: 10.1016/j.mam.2016.08.001] [Citation(s) in RCA: 182] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 08/27/2016] [Indexed: 12/11/2022]
Abstract
The active form of vitamin B6, pyridoxal 5'-phosphate (PLP), serves as a co-factor in more than 150 enzymatic reactions. Plasma PLP has consistently been shown to be low in inflammatory conditions; there is a parallel reduction in liver PLP, but minor changes in erythrocyte and muscle PLP and in functional vitamin B6 biomarkers. Plasma PLP also predicts the risk of chronic diseases like cardiovascular disease and some cancers, and is inversely associated with numerous inflammatory markers in clinical and population-based studies. Vitamin B6 intake and supplementation improve some immune functions in vitamin B6-deficient humans and experimental animals. A possible mechanism involved is mobilization of vitamin B6 to the sites of inflammation where it may serve as a co-factor in pathways producing metabolites with immunomodulating effects. Relevant vitamin B6-dependent inflammatory pathways include vitamin B6 catabolism, the kynurenine pathway, sphingosine 1-phosphate metabolism, the transsulfuration pathway, and serine and glycine metabolism.
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Affiliation(s)
- Per Magne Ueland
- Department of Clinical Science, University of Bergen, 5021 Bergen, Norway; Laboratory of Clinical Biochemistry, Haukeland University Hospital, 5021 Bergen, Norway.
| | | | | | - Arve Ulvik
- Bevital A/S, Laboratoriebygget, 5021 Bergen, Norway
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Chang HY, Tang FY, Chen DY, Chih HM, Huang ST, Cheng HD, Lan JL, Chiang EPI. Clinical use of cyclooxygenase inhibitors impairs vitamin B-6 metabolism. Am J Clin Nutr 2013; 98:1440-9. [PMID: 24153347 DOI: 10.3945/ajcn.113.064477] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND A low circulating vitamin B-6 concentration, which is an independent risk factor for cardiovascular disease, is commonly seen in human inflammation. OBJECTIVE We investigated whether cyclooxygenase inhibitors alter vitamin B-6 metabolism. DESIGN To investigate whether subjects taking a cyclooxygenase inhibitor had an altered vitamin B-6 profile, we conducted a cross-sectional study that involved 150 rheumatoid arthritis patients, with and without cyclooxygenase inhibitor treatments. C57BL/6J mice and hyperlipidemic Syrian hamsters received drug regimens that reflected clinical nonsteroidal antiinflammatory drug (NSAID) uses in treating human inflammation. The impact of long-term physiologic use of selective and nonselective cyclooxygenase inhibitors on vitamin B-6 metabolism was systematically investigated in these independent in vivo models. RESULTS Patients who were taking cyclooxygenase inhibitors had lower circulating pyridoxal-5'-phosphate, especially those taking NSAIDs >6 mo. Long-term celecoxib and naproxen use reduced hepatic pyridoxal-5'-phosphate in mice. Nonselective cyclooxygenase inhibitor naproxen significantly decreased vitamin B-6 vitamers in the kidney. CONCLUSIONS To our knowledge, we show novel findings that long-term physiologic doses of cyclooxygenase inhibitor may impede the synthesis of the coenzymatically active form of vitamin B-6. Because the cause of vitamin B-6 depletion in inflammation remains unknown, this study provides a potential mechanism that could account for the poor vitamin B-6 status in human inflammation. Moreover, this study further raises concerns about the long-term clinical use of antiinflammatory NSAIDs in humans. Vitamin B-6 status should be carefully monitored in long-term NSAID users. Future randomized placebo-controlled studies are needed to determine the impacts of antiinflammatory cyclooxygenase inhibitor use on vitamin B-6 metabolism in humans.
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Affiliation(s)
- Hsin-Yueh Chang
- Department of Food Science and Biotechnology (H-YC, H-MC, S-TH, H-DC, and E-PIC), the National Chung Hsing University-UCD Plant and Food Biotechnology Program and Agricultural Biotechnology Center (E-PIC), and the Agricultural Biotechnology Center (E-PIC), National Chung Hsing University, Taichung, Taiwan ; the Biomedical Science Laboratory, Department of Nutrition, China Medical University, Taichung, Taiwan (F-YT); and the Division of Allergy Immunology Rheumatology (D-YC and J-LL) and the Department of Nursing and Pediatrics (H-MC), Taichung Veterans General Hospital, Taichung, Taiwan
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Wang YC, Lin WL, Lin YJ, Tang FY, Chen YM, Chiang EPI. A novel role of the tumor suppressor GNMT in cellular defense against DNA damage. Int J Cancer 2013; 134:799-810. [PMID: 23922098 DOI: 10.1002/ijc.28420] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 07/22/2013] [Indexed: 12/28/2022]
Abstract
Glycine N-methyltransferase (GNMT) is a folate binding protein commonly diminished in human hepatoma yet its role in tumor development remains to be established. GNMT binds to methylfolate but is also inhibited by it; how such interactions affect human carcinogenesis is unclear. We postulated that GNMT plays a role in folate-dependent methyl group homeostasis and helps maintain genome integrity by promoting nucleotide biosynthesis and DNA repair. To test the hypothesis, GNMT was over-expressed in GNMT-null cell lines cultured in conditions of folate abundance or restriction. The partitioning of folate dependent 1-carbon groups was investigated using stable isotopic tracers and GC/MS. DNA damage was assessed as uracil content in cell models, as well as in Gnmt wildtype (Gnmt(+/+)), heterozygote (Gnmt(+/-)) and knockout (Gnmt(-/-)) mice under folate deplete, replete, or supplementation conditions. Our study demonstrated that GMMT 1) supports methylene-folate dependent pyrimidine synthesis; 2) supports formylfolate dependent purine syntheses; 3) minimizes uracil incorporation into DNA when cells and animals were exposed to folate depletion; 4) translocates into nuclei during prolonged folate depletion. In conclusion, loss of GNMT impairs nucleotide biosynthesis. Over-expression of GNMT enhances nucleotide biosynthesis and improves DNA integrity by reducing uracil misincorporation in DNA both in vitro and in vivo. To our best knowledge, the role of GNMT in folate dependent 1-carbon transfer in nucleotide biosynthesis has never been investigated. The present study gives new insights into the underlying mechanism by which GNMT can participate in tumor prevention/suppression in humans.
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Affiliation(s)
- Yi-Cheng Wang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung, Taiwan, Republic of China
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Wang YC, Chiang EPI. Low-dose methotrexate inhibits methionine S-adenosyltransferase in vitro and in vivo. Mol Med 2012; 18:423-32. [PMID: 22193356 DOI: 10.2119/molmed.2011.00048] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Accepted: 12/19/2011] [Indexed: 12/29/2022] Open
Abstract
Methionine S-adenosyltransferase (MAT) catalyzes the only reaction that produces the major methyl donor in mammals. Low-dose methotrexate is the most commonly used disease-modifying antirheumatic drug in human rheumatic conditions. The present study was conducted to test the hypothesis that methotrexate inhibits MAT expression and activity in vitro and in vivo. HepG2 cells were cultured under folate restriction or in low-dose methotrexate with and without folate or methionine supplementation. Male C57BL/6J mice received methotrexate regimens that reflected low-dose clinical use in humans. S-adenosylmethionine and MAT genes, proteins and enzyme activity levels were determined. We found that methionine or folate supplementation greatly improved S-adenosylmethionine in folate-depleted cells but not in cells preexposed to methotrexate. Methotrexate but not folate depletion suppressed MAT genes, proteins and activity in vitro. Low-dose methotrexate inhibited MAT1A and MAT2A genes, MATI/II/III proteins and MAT enzyme activities in mouse tissues. Concurrent folinate supplementation with methotrexate ameliorated MAT2A reduction and restored S-adenosylmethionine in HepG2 cells. However, posttreatment folinate rescue failed to restore MAT2A reduction or S-adenosylmethionine level in cells preexposed to methotrexate. Our results provide both in vitro and in vivo evidence that low-dose methotrexate inhibits MAT genes, proteins, and enzyme activity independent of folate depletion. Because polyglutamated methotrexate stays in the hepatocytes, if methotrexate inhibits MAT in the liver, then the efficacy of clinical folinate rescue with respect to maintaining hepatic S-adenosylmethionine synthesis and normalizing the methylation reactions would be limited. These findings raise concerns on perturbed methylation reactions in humans on low-dose methotrexate. Future studies on the clinical physiological consequences of MAT inhibition by methotrexate and the potential benefits of S-adenosylmethionine supplementation on methyl group homeostasis in clinical methotrexate therapies are warranted.
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Affiliation(s)
- Yi-Cheng Wang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung, Taiwan, Republic of China
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Wang YC, Chen YM, Lin YJ, Liu SP, Chiang EPI. GNMT expression increases hepatic folate contents and folate-dependent methionine synthase-mediated homocysteine remethylation. Mol Med 2011; 17:486-94. [PMID: 21210071 DOI: 10.2119/molmed.2010.00243] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 12/30/2010] [Indexed: 11/06/2022] Open
Abstract
Glycine N-methyltransferase (GNMT) is a major hepatic enzyme that converts S-adenosylmethionine to S-adenosylhomocysteine while generating sarcosine from glycine, hence it can regulate mediating methyl group availability in mammalian cells. GNMT is also a major hepatic folate binding protein that binds to, and, subsequently, may be inhibited by 5-methyltetrafolate. GNMT is commonly diminished in human hepatoma; yet its role in cellular folate metabolism, in tumorigenesis and antifolate therapies, is not understood completely. In the present study, we investigated the impacts of GNMT expression on cell growth, folate status, methylfolate-dependent reactions and antifolate cytotoxicity. GNMT-diminished hepatoma cell lines transfected with GNMT were cultured under folate abundance or restriction. Folate-dependent homocysteine remethylation fluxes were investigated using stable isotopic tracers and gas chromatography/mass spectrometry. Folate status was compared between wild-type (WT), GNMT transgenic (GNMT(tg)) and GNMT knockout (GNMT(ko)) mice. In the cell model, GNMT expression increased folate concentration, induced folate-dependent homocysteine remethylation, and reduced antifolate methotrexate cytotoxicity. In the mouse models, GNMT(tg) had increased hepatic folate significantly, whereas GNMT(ko) had reduced folate. Liver folate levels correlated well with GNMT expressions (r = 0.53, P = 0.002); and methionine synthase expression was reduced significantly in GNMT(ko), demonstrating impaired methylfolate-dependent metabolism by GNMT deletion. In conclusion, we demonstrated novel findings that restoring GNMT assists methylfolate-dependent reactions and ameliorates the consequences of folate depletion. GNMT expression in vivo improves folate retention and bioavailability in the liver. Studies on how GNMT expression impacts the distribution of different folate cofactors and the regulation of specific folate dependent reactions are underway.
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Affiliation(s)
- Yi-Cheng Wang
- Department of Food Science and Biotechnology, National Chung Hsing University, Taichung, Taiwan, R.O.C
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