Effects of intravenous betaine on methionine-loading–induced plasma homocysteine elevation in rats

• Published in: The Journal of nutritional biochemistry Vol. 15; no. 11; pp. 666 - 671
• Main Authors: Yagisawa, Masako, Okawa, Nao, Shigematsu, Norihiro, Nakata, Rieko
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.11.2004; Elsevier Science
• Subjects: amino acid metabolism; animal models; Animals; Betaine; Betaine - administration & dosage; Betaine - pharmacology; biochemical pathways; Biological and medical sciences; blood serum; cardioprotective effect; Disease Models, Animal; dose response; Feeding. Feeding behavior; Fundamental and applied biological sciences. Psychology; Glycine - pharmacology; Homocysteine; Homocysteine - blood; Hyperhomocysteinemia - blood; Injections, Intravenous; intravenous injection; lipotropic agents; Male; methionine; Methionine - pharmacology; Methionine loading; Methyl group; Rats; Sarcosine - pharmacology; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Methionine loading; Rats; Homocysteine; Betaine; Methyl group; Intravenous administration; Rat; Rodentia; Methionine; Metabolism; Blood plasma; Vertebrata; Mammalia; Homocystein; Animal
• ISSN: 0955-2863; 1873-4847
• DOI: 10.1016/j.jnutbio.2004.05.004

An intravenous methionine-loading model was characterized, and the suppressive effect of betaine on plasma homocysteine elevation induced by methionine loading was examined in rats. The plasma homocysteine concentrations significantly increased 5–120 minutes after 0.34 mmol/kg of methionine loading and then returned to the baseline within 240 minutes. Betaine was then intravenously administered at the same time as the methionine loading. The total increment of plasma homocysteine was assessed using the positive incremental area under the plasma homocysteine concentration curve over the 240-minute post–methionine-loading period (ΔAUC 0-240). Betaine reduced ΔAUC 0-240 dose-dependently: 81% of the control by 1.7 mmol/kg of betaine and 33% by 3.4 mmol/kg. The effects of glycine and methylglycine, analogues of betaine, were also investigated. As observed for betaine, methylglycine decreased ΔAUC 0-240 to 44% of the control, whereas glycine showed no significant effect on ΔAUC 0-240, indicating that methyl groups of betaine and dimethylglycine were necessary to suppress plasma homocysteine elevation. These results suggest that betaine contributes to the suppression of plasma homocysteine elevation by promoting homocysteine metabolism, and seems to work as a methyl donor.