The present study sought to demonstrate the effect of dietary intake of medium-chain triacylglycerides (MCTs) on the intestinal absorption of a poorly permeable compound of intermediate molecular weight (FITC-dextran 4000 [FD-4]). As a model of MCTs, C8-C12 fatty acid triacylglyceride (COCONAD ML) was mainly used, and the dose strength of each triglyceride was set with consideration of the dietary ingestion dose (12.5 mg/rat). When FD-4 with MCTs dispersed in fasted state simulated intestinal fluid containing surfactants was administered into the rat jejunum, the intestinal absorption of FD-4 was significantly higher than when administered with a similar solution with or without corn oil (long-chain triglycerides). The effects of pretreatment by MCT lipolysis, inhibition of endogenous lipases, and different dose timings of MCTs and FD-4 on the intestinal absorption of FD-4 indicated that medium-chain fatty acids, such as caprylic acid and capric acid, released from MCTs by lipolysis in the small intestine significantly enhanced the intestinal absorption of FD-4, but the effect was transient. In addition, a similar effect was observed when MCTs were dispersed in soymilk, although large interindividual variation was detected. These findings suggested that dietary intake of MCTs might affect the intestinal absorption of poorly permeable compounds.
Keywords: Triglyceride; fluorescein isothiocyanate-dextran 4000; lipolysis; medium-chain fatty acid; medium-chain triacylglyceride; poorly permeable compound.