INTESTINAL DIGESTION, ABSORPTION, AND TRANSPORT OF STRUCTURED TRIGLYCERIDES AND CHOLESTEROL IN RATS

We compared the intestinal absorption of trilinolein (1,2,3-tri-[1-C-1 4]linoleyl-sn-glycerol) with two different structured triglycerides co ntaining one linoleic acid (C18:2) and two octanoic acids (C8:0), 1,3- dioctanoyl-2-[1-C-14]linoleyl-sn-glycerol (2-linoleate) and 1,2-di[1-C -14] octanoyl-3-linoleyl-sn-glycerol (1,2-octanoate), respectively. Ly mphatic radioactive lipid output of 2-linoleate resembled that of tril inolein rats but remained significantly lower during the lipid infusio n. Radioactive lipid was recovered along the entire small intestinal l umen, with a significantly higher amount of [C-14]lipid recovered in t he lower small intestine and cecum in the 2-linoleate group. Delayed u ptake of radioactive 2-linoleate was not due to poor digestion. In con trast, 1,2-octanoate was efficiently digested, and both the free fatty acid (FFA) and the monoacylglycerol (MG) containing octanoate were ra pidly absorbed. Irrespective of its position on the triglyceride molec ule, C-14-labeled octanoate was poorly transported into lymph. In addi tion, intestinal luminal and mucosal recovery of [C-14]octanoate was s ignificantly lower in the 1,2-octanoate group compared with [C-14]lino leate recovery in the 2-linoleate or trilinolein groups. Total recover y of infused radioactive lipid was significantly less in the 1,2-octan oate group than in the 2-linoleate or trilinolein groups. Thus radioac tive octanoate in the form of FFA or 2-MG was rapidly absorbed and tra nsported via the portal vein. The infusion of either 2-linoleate or 1, 2-octanoate did not affect the absorption and lymphatic transport of c holesterol compared with trilinolein. In summary, the type of the fatt y acid on the structured triglyceride molecule affects its digestion, absorption, and lymphatic transport. Structured triglycerides containi ng octanoic acid in the 1- and 3-positions and linoleic acid in the a- position may not be advantageous to use as a sole source of dietary li pid, but should be supplemented with long-chain triglycerides.