Triiodothyronine treatment attenuates the induction of hepatic glycine N-methyltransferase by retinoic acid and elevates plasma homocysteine concentrations in rats.

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  • Author(s): Tanghe KA;Tanghe KA; Garrow TA; Schalinske KL
  • Source:
    The Journal of nutrition [J Nutr] 2004 Nov; Vol. 134 (11), pp. 2913-8.
  • Publication Type:
    Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.
  • Language:
    English
  • Additional Information
    • Source:
      Publisher: Elsevier Country of Publication: United States NLM ID: 0404243 Publication Model: Print Cited Medium: Print ISSN: 0022-3166 (Print) Linking ISSN: 00223166 NLM ISO Abbreviation: J Nutr Subsets: MEDLINE
    • Publication Information:
      Publication: 2023- : [New York, NY] : Elsevier
      Original Publication: 1928-1933 : Springfield, Ill. : C. C. Thomas
    • Subject Terms:
      Homocysteine/*blood ; Liver/*enzymology ; Methyltransferases/*biosynthesis ; Tretinoin/*pharmacology ; Triiodothyronine/*pharmacology; 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase/metabolism ; Animals ; Betaine-Homocysteine S-Methyltransferase ; Enzyme Induction/drug effects ; Glycine N-Methyltransferase ; Hyperthyroidism/chemically induced ; Hyperthyroidism/metabolism ; Hypothyroidism/chemically induced ; Hypothyroidism/enzymology ; Hypothyroidism/metabolism ; Male ; Methyltransferases/metabolism ; Rats ; Rats, Sprague-Dawley
    • Abstract:
      Recent studies indicated that hormonal imbalances have a role in modulating the metabolism of methyl groups and homocysteine, interrelated pathways that when disrupted, are associated with a number of pathologies. Retinoic acid (RA) was shown to induce hepatic glycine N-methyltransferase (GNMT), a key regulatory protein in methyl group metabolism, and to reduce circulating homocysteine levels. Because thyroid status influences the hepatic folate-dependent one-carbon pool and retinoids can alter thyroid hormone levels, the aim of this study was to examine the interaction between retinoids and thyroid function. For hypothyroid studies, rats were administered 0.5 g/L propylthiouracil in the drinking water for 15 d, and RA [30 micromol/(kg . d)] for the final 5 d. For hyperthyroid studies, rats were treated with RA [30 micromol/(kg . d)] for 8 d and triiodothyronine [T(3); 50 microg/(100 g . d)] the last 4 d. T(3) treatment prevented the RA-mediated increase in GNMT activity. However, GNMT abundance remained elevated, indicating that GNMT regulation by T(3) in RA-treated rats may be, at least in part, at the post-translational level. In addition, T(3) treatment elevated plasma levels of homocysteine 177%, an elevation that was prevented by RA. T(3)-mediated hyperhomocysteinemia may be due to a 70% decrease in hepatic betaine-homocysteine S-methyltransferase, the enzyme that catalyzes folate-independent remethylation of homocysteine, whereas the RA-mediated stimulation of hepatic homocysteine remethylation by folate-dependent methionine synthase may contribute to lowering plasma homocysteine levels. These findings indicate that thyroid hormones, alone and in conjunction with RA, play an important role in the regulation of methyl group and homocysteine metabolism.
    • Grant Information:
      DK 52501 United States DK NIDDK NIH HHS
    • Accession Number:
      06LU7C9H1V (Triiodothyronine)
      0LVT1QZ0BA (Homocysteine)
      5688UTC01R (Tretinoin)
      EC 2.1.1.- (Methyltransferases)
      EC 2.1.1.13 (5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase)
      EC 2.1.1.20 (Glycine N-Methyltransferase)
      EC 2.1.1.20 (Gnmt protein, rat)
      EC 2.1.1.5 (Betaine-Homocysteine S-Methyltransferase)
    • Publication Date:
      Date Created: 20041030 Date Completed: 20041209 Latest Revision: 20230216
    • Publication Date:
      20231215
    • Accession Number:
      10.1093/jn/134.11.2913
    • Accession Number:
      15514252