The Intraluminal Phase of Fat Digestion in Man: The Lipid Content of the Micellar and Oil Phases of Intestinal Content Obtained during Fat Digestion and Absorption*

Abstract

After the feeding of a test meal containing corn oil, human small intestinal content was collected by intubation and heated for 10 minutes at 70[degree] C to inactivate pancreatic lipase. The intestinal content was then centrifuged for 18 hours at 100,000 x g at 37 to 40[degree] C and thus separated into a transparent, aqueous, micellar phase and a supernatant oil phase. The fatty acid and glyceride content of each phase was determined by titration and silicic acid chromatography. The lipids of the lower, micellar phase were chiefly fatty acid and mono-glyceride with smaller amounts of diglyceride and triglyceride. The lipids of the micellar phase differed from those of the oil phase in containing significantly more fatty acid and significantly less diglyceride and triglyceride. Thin-layer chromatography showed the diglyceride to be largely 1,2 isomer. Five specimens of intestinal content were analyzed for 1- and 2-monoglyceride content by periodate titration; two-thirds of the monoglyceride was present as the 2-isomer, on an average. The results are consistent with the hypotheses that intestinal lipid, during fat digestion, is selectively partitioned between a micellar and an oil phase and that absorption of dietary lipid takes place from a micellar solution containing chiefly fatty acid and 2-monoglyceride.