title: The effect of a methyl-deficient diet on the global DNA methylation and the DNA methylation regulatory pathways.
abstract: Methyl-deficient diets are known to induce various liver disorders, in which DNA methylation changes are implicated. Recent studies have clarified the existence of the active DNA demethylation pathways that start with oxidization of 5-methylcytosine (5meC) to 5-hydroxymethylcytosine by ten-eleven translocation (Tet) enzymes, followed by the action of base-excision-repair pathways. Here, we investigated the effects of a methionine-choline-deficient (MCD) diet on the hepatic DNA methylation of mice by precisely quantifying 5meC using a liquid chromatography-electrospray ionization-mass spectrometry and by investigating the regulatory pathways, including DNA demethylation. Although feeding the MCD diet for 1 week induced hepatic steatosis and lower level of the methyl donor S-adenosylmethionine, it did not cause a significant reduction in the 5meC content. On the other hand, the MCD diet significantly upregulated the gene expression of the Tet enzymes, Tet2 and Tet3, and the base-excision-repair enzymes, thymine DNA glycosylase and apurinic/apyrimidinic-endonuclease 1. At the same time, the gene expression of DNA methyltransferase 1 and a, was also significantly increased by the MCD diet. These results suggest that the DNA methylation level is precisely regulated even when dietary methyl donors are restricted. Methyl-deficient diets are well known to induce oxidative stress and the oxidative-stress-induced DNA damage, 8-hydroxy-2'-deoxyguanosine (8OHdG), is reported to inhibit DNA methylation. In this study, we also clarified that the increase in 8OHdG number per DNA by the MCD diet is approximately 10 000 times smaller than the reduction in 5meC number, suggesting the contribution of 8OHdG formation to DNA methylation would not be significant.
authors.affiliation: Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan.|Department of Public Health and Environmental Medicine, The Jikei University School of Medicine, Tokyo, 105-8461, Japan.
authors.forename: Shota
authors.initials: S
authors.lastname: Takumi
authors.affiliation: Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan.
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Okamura
authors.affiliation: Department of Public Health and Environmental Medicine, The Jikei University School of Medicine, Tokyo, 105-8461, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Yanagisawa
authors.affiliation: Center for Environmental Measurement and Analysis, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Sano
authors.affiliation: Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan.
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Kobayashi
authors.affiliation: Center for Environmental Health Sciences, National Institute for Environmental Studies, Tsukuba, 305-8506, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Nohara
mesh_terms: D044503:5-Methylcytosine / Q000378:metabolism / Q000031:analogs & derivatives; D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D002796:Choline Deficiency / Q000150:complications / Q000235:genetics / Q000378:metabolism*; D003596:Cytosine / Q000031:analogs & derivatives / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D005234:Fatty Liver / Q000209:etiology / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D008099:Liver / Q000378:metabolism*; D008297:Male; D008715:Methionine / Q000172:deficiency*; D008810:Mice, Inbred C57BL; D018384:Oxidative Stress / Q000235:genetics; D012435:S-Adenosylhomocysteine / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism
chemical_list: C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D012436:S-Adenosylmethionine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003596:Cytosine; D012435:S-Adenosylhomocysteine; D008715:Methionine; D003849:Deoxyguanosine
keywords: 5-methylcytosine (5meC); Tet family proteins; Thymine DNA glycosylase (Tdg); active DNA demethylation; hepatic DNA methylation; methyl-deficient diet