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Strakova J , Williams KT , Gupta S , Schalinske KL , Kruger WD , Rozen R , Jiracek J , Li L , Garrow TA
Dietary intake of S-(alpha-carboxybuty1)-DL-homocysteine induces hyperhomocysteinemia in rats
Nutrition Research. 2010 Jul;30(7) :492-500
PMCID: PMC2929918   
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Abstract
Betaine homocysteine S-methyltransferase (BHMT) catalyzes the transfer of a methyl group from betaine to homocysteine (Hey), forming dimethylglycine and methionine. We previously showed that inhibiting BHMT in mice by intraperitoneal injection of S-(alpha-carboxybutyl)-DL-homocysteine (CBHcy) results in hyperhomocysteinemia. In the present study, CBHcy was fed to rats to determine whether it could be absorbed and cause hyperhomocysteinemia as observed in the intraperitoneal administration of the compound in mice. We hypothesized that dietary administered CBHcy will be absorbed and will result in the inhibition of BHMT and cause hyperhomocysteinemia. Rats were meal-fed every 8 hours an L-amino acid defined diet either containing or devoid of CBHcy (5 mg per meal) for 3 days. The treatment decreased liver BHMT activity by 90% and had no effect on methionine synthase, methylenetetrahydrofolate reductase, phosphatidylethanolamine N-methyl-transferase, and CTP:phosphocholine cytidylyltransferase activities. In contrast, cystathionine beta-synthase activity and immunodetectable protein decreased (56% and 26%, respectively) and glycine N-methyltransferase activity increased (52%) in CBHcy-treated rats. Liver S-adenosylmethionine levels decreased by 25% in CBHcy-treated rats, and S-adenosylhomocysteine levels did not change. Furthermore, plasma choline decreased (22%) and plasma betaine increased (15-fold) in CBHcy-treated rats. The treatment had no effect on global DNA and CpG island methylation, liver histology, and plasma markers of liver damage. We conclude that CBHcy-mediated BHMT inhibition causes an elevation in total plasma Hey that is not normalized by the folate-dependent conversion of Hey to methionine. Furthermore, metabolic changes caused by BHMT inhibition affect cystathionine P-synthase and glycine N-methyltransferase activities, which further deteriorate plasma Hey levels. (C) 2010 Elsevier Inc. All rights reserved.
Notes
Strakova, Jana Williams, Kelly T. Gupta, Sapna Schalinske, Kevin L. Kruger, Warren D. Rozen, Rima Jiracek, Jiri Li, Lucas Garrow, Timothy A. Pergamon-elsevier science ltd Oxford 648no