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Inhibition of Betaine‐Homocysteine Methyltransferase (BHMT) increases plasma total homocysteine (tHcy) in mice
Author(s) -
Strakova Jana,
Slow Sandy,
Williams Kelly,
Schalinske Kevin,
Garrow Timothy
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a609-d
Subject(s) - cystathionine beta synthase , homocysteine , chemistry , methionine , methyltransferase , thymidylate synthase , methionine synthase , western blot , medicine , biochemistry , endocrinology , methylation , biology , gene , amino acid , fluorouracil , chemotherapy
Elevation of tHcy is an independent risk factor for vascular disease. Hcy can be methylated by BHMT and folate‐dependent methionine synthase (MS) to form methionine (Met), or it can be converted to cystathionine by cystathionine‐β‐synthase (CBS). Disruption of flux through CBS or MS elevates tHcy, but BHMT’s role in the tHcy regulation has not been characterized. We describe the effect of S‐(δ‐carboxybutyl) homocysteine (CBHcy), a specific inhibitor of BHMT, on tHcy, BHMT and CBS. Mice (n = 8/treatment) were given intraperitoneal injections of saline (control) or CBHcy (1mg) at 12 h intervals. Four animals within each group were euthanized after 28 h (3 doses), and 4 at 76 h (7 doses). tHcy was measured by HPLC, liver BHMT and CBS expression were assessed using enzymatic, Western blot and real‐time PCR. tHcy increased several‐fold at both 28 and 76 h in the CBHcy‐treated animals. Compared to controls, BHMT activity was significantly lower in CBHcy‐treated animals (77 ± 8.3, 45 ± 5.1 U/mg) at 28 h, but its activity increased to 114 ± 9.9 U/mg at 76 h. Increases in BHMT immunodetectable protein and a 4‐fold increase in BHMT mRNA were also observed at 76 h. CBS activity decreased from 0.25 ± 0.13 U/mg (control) to 0.13 ± 0.01 U/mg in the CBHcy‐treated mice. These data show that inhibition of BHMT activity by CBHcy elevates tHcy. The loss of BHMT activity is compensated for by an increase in expression. Reduction of CBS protein and activity may also contribute to the elevation of tHcy observed. This work was supported by NIDDK (DK52501); ADA (1‐04‐RA‐96).