Molecular composition of the phosphatidylcholines produced by the phospholipid methylation pathway in rat brain in vivo

Abstract

We examined the formation in vivo of molecular subspecies of brain phosphatidylcholine (PC) via the phospholipid-methylation pathway. [3H]Methionine was infused into a lateral cerebral ventricle, and 3H-labelled PC was isolated from brains of rats 0.1-18 h after the infusions. Three major subspecies of this PC, differing in their fatty acid compositions, were separated on silver-impregnated t.l.c. plates, and the proportions of radioactivities in these three PC fractions were determined. The results indicate that newly-formed PC synthesized by methylation of phosphatidylethanolamine at 0.1 h after [3H]methionine contains a significantly higher proportion of polyunsaturated subspecies (i.e. those with six or four double bonds) than does PC obtained later times after injection of [3H]methionine. This change in the composition of 3H-labelled brain PC occurs gradually and is not due to an influx of radioactive PC from the periphery. Our data suggest that polyunsaturated PC (hexaenes and tetraenes) produced in the brain by methylation of phosphatidylethanolamine turns over faster than does that containing more-saturated fatty acids.

Entry of polyunsaturated fatty acids into the brain: evidence that high-density lipoprotein-induced methylation of phosphatidylethanolamine and phospholipase A2 are involved

“…An attractive hypothesis about the PEMT function would be to supply a cellular pool of PUFA-rich PC to the brain. This is consistent with previous reports indicating that in the brain, tetraenoic and hexaenoic PCs were the major products formed by methylation [13,32], and that PEMT activity in cerebrum, which decreases during the myelination process, is 40 % lower in 50-day-old animals than at birth, whereas the PEMT activity of the cerebellum is unchanged throughout the postnatal period [33]. Moreover, in cortical synaptic membranes, a transient rise in PE methylation in the early days of life correlates with the transient increase in the level of arachidonic acid-rich PC species [23].…”

Imaging Lipid Synthesis in Hepatocellular Carcinoma with [Methyl-11C]Choline: Correlation with In Vivo Metabolic Studies

“…Molecular species of phosphatidylcholine were resolved according to their degree of unsaturation by an argentation thin-layer chromatography method, which can separate phosphatidylcholine into 3 major bands (8). Briefly, individual eluting phosphatidylcholine peaks were collected from HPLC eluant of the lipid-soluble phase of liver tissue and spotted on the argentation thin-layer chromatography plate.…”

“…Betaine can also provide the methyl group to methionine and subsequently produce s-adenosylmethionine, which can eventually incorporate into phosphatidylcholine through a reaction with phosphatidylethanolamine in the phosphatidylethanolamine methylation pathway. There is a profound distinction in phosphatidylcholine species between the CDP-choline pathway and the phosphatidylethanolamine methylation pathway (7,8). This distinction may contribute to the different functions of these 2 pathways in the liver.…”