Effect of Vitamin B₁₂deficiency on phosphatidylethanolamine methylation in rat liver

Abstract

I. In vitamin B12 deficiency the activity of tetrahydropteroylglutamate methyltransferase (EC 2 . I . I .13) is depressed and the synthesis of methionine is reduced. Because the methyl group of methionine is largely utilized for the methylation of phosphatidylethanolamine, we investigated the effects of vitamin Bla deficiency on phosphatidylcholine synthesis. Chemical analysis of liver phospholipids showed that the vitamin Bl,-deficient rats had a higher proportion of phosphatidylethanolamine and a lower proportion of phosphatidylcholine, indicating that the impaired synthesis of phosphatidylcholine by methylation leads to changes in membrane phospholipid composition.

The Regulatory Roles of Liver and Kidney in Cobalamin (Vitamin B12) Metabolism in the Rat: the Uptake and Intracellular Binding of Cobalamin and the Activity of the Cobalamin-Dependent Enzymes in Response to Varying Cobalamin Supply

“…Previous studies on the response of methyltransferase to cobalamin deficiency have shown a reduction in hepatic enzyme activity in rats [21], fruit bats [25] and chickens [26]. In contrast, the present studies did not show a decrease in either holoenzyme or total enzyme activity, but instead an increase in hepatic holoenzyme activity.…”

Effect of methionine on the metabolic fate of liver folates in vitamin B12-deficient rats

“…The present study also confirms a previous report (Akesson et al 1978), where vitamin B,,-deficient rats were shown to have reduced ability to methylate phospholipids in their livers. This is consistent with a depressed activity of the vitamin BIZ-dependent methyltransferase reaction producing less methionine for methyl group transfer (Fig.…”

Vitamin B₁₂ Is a Strong Determinant of Low Methionine Synthase Activity and DNA Hypomethylation in Gastrectomized Rats

“…No change of vitamin B 12 plasma level was observed in MD diet-fed rats. This emphasizes that a vitamin B 12 -free diet cannot be considered efficient enough to provide a severe and permanent vitamin B 12 deficiency in rats [19, 23]. It is therefore likely that coprophagy provides enough vitamin B 12 , even when the vitamin B 12 diet is restricted.…”