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Homocysteinemia in Mice with Genetic Betaine Homocysteine S-Methyltransferase Deficiency Is Independent of Dietary Folate Intake123
Elevated homocysteine (Hcy) concentrations are associated with increased risk of several chronic diseases. Hcy can be removed by methylating it to form methionine via either the betaine homocysteine S -methyltransferase (BHMT) or the methionine synthase (MS) pathway. BHMT uses betaine as the methyl...
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Published in: | The Journal of nutrition 2012-09, Vol.142 (11), p.1964-1967 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Elevated homocysteine (Hcy) concentrations are associated with increased risk of several chronic diseases. Hcy can be removed by methylating it to form methionine via either the betaine homocysteine
S
-methyltransferase (BHMT) or the methionine synthase (MS) pathway. BHMT uses betaine as the methyl donor, whereas MS uses 5-methyltetrahydrofolate. We previously found that mice with the gene encoding
Bhmt
deleted (
Bhmt
−/−
) had altered Hcy metabolites in tissues. This study aimed to determine whether folate supplementation of
Bhmt
−/−
mice reverses, and folate deficiency exacerbates, these metabolic changes.
Bhmt
−/−
mice and their littermates (
Bhmt
+/+
mice) were fed a folate-deficient (FD; 0 mg/kg diet), a folate control (FC; 2 mg/kg diet), or a folate-supplemented (FS; 20 mg/kg diet) diet for 4 wk.
Bhmt
−/−
mice had higher plasma Hcy and hepatic
S
-adenosylhomocysteine (AdoHcy) concentrations and had lower hepatic
S
-adenosylmethionine (AdoMet) concentrations compared with
Bhmt
+/+
mice for all diets. Although the FD diet increased plasma Hcy (
P
< 0.05) and hepatic AdoHcy (
P
< 0.001) concentrations in
Bhmt
+/+
mice compared with FC and FS mice, the FD diet had no effect on the metabolites measured in
Bhmt
−/−
mice. The FS diet did not ameliorate elevated plasma Hcy and elevated hepatic AdoHcy concentrations but did increase hepatic AdoMet concentrations in
Bhmt
−/−
mice (
P
< 0.001) compared with FD and FC mice. We conclude that the BHMT pathway is a major route for the elimination of Hcy in mice and that the MS pathway has little excess capacity to methylate the Hcy that accumulates when the BHMT pathway is blocked. |
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ISSN: | 0022-3166 1541-6100 |
DOI: | 10.3945/jn.112.166835 |