Biosynthesis of diacylglycerols by rat intestinal mucosa in vivo

Abstract

The biosynthesis of diacylglycerols was studied in rat intestinal mucosa during in vivo absorption of a low molecular weight fraction of butter oil and of the corresponding medium and long chain fatty acids. The experimental fat solutions were given by stomach tube to the animals after a 24-h fast and mucosal scrapings were collected 3 h later. The lipids were isolated and the acylglycerols determined by combined thin-layer chromatography gas–liquid chromatography techniques and stereospecific analyses. Free fatty acid feeding led mainly to, sn-1,2-diacylglycerols, which contained exogenous and endogenous fatty acids. During triacylglycerol feeding, both.sn-1,2- and sn-2,3-diacylglycerols were recovered in significant amounts from the intestinal mucosa. The composition of the sn-2,3-diacylglycerols corresponded to that with exogenous fatty acids but the sn-1,2-diacylglycerols clearly contained both exogenous and endogenous fatty acids. In all cases it was possible to isolate endogenous sn-1,2-diacylglycerols made up largely of species with linoleic and arachidonic acids in the 2 position and palmitic and stearic acids in the 1 position, which apparently were not converted to triacylglycerols. The in vivo reacylation of 2-monoacylglycerols via both sn-1,2- and sn-2,3-diacylglycerols is in agreement with similar findings in vitro with everted sacs of rat intestinal mucosa.