Distribution of medium-chain FA in different lipid classes after administration of specific structured TAG in rats

Structured TAG (STAG) containing medium-chain FA (MCFA) in the sn-1,3 positions and essential FA in the sn-2 position were synthesized by lipase-catalyzed acidolysis. In our previous studies we found that part of the MCFA from STAG could be absorbed in the small intestine; however, it was unclear how they were absorbed. In order to get a better understanding of the metabolism of STAG to improve future design and application of STAG, in the present study lymph lipids collected after feeding STAG were fractionated into different classes and the FA composition of each lipid class was studied by GC after methylation to FAME. Caprylic acid was detected in the fraction of TAG only after administration of 1,3-dioctanoyl-2-linoleyl-sn-glycerol (8∶0/18∶2/8∶0), whereas lauric acid was detected in TAG, DAG, and FFA as well as phospholipids after administration of 1,3-didodecanoyl-2-linoleyl-sn-glycerol (12∶0/18∶2/12∶0). We conclude that the enterocyte has the ability to reacylate the MCFA into TAG and that the intestinal absorption of MCFA from STAG mainly occurs by resynthesis of TAG. Caprylic acid from STAG is not incorporated into phospholipids, whereas lauric acid from STAG can be incorporated into phospholipids.