Recently medium chain triglyceride has been used for the treatment of fat malabsorption syndromes, as it has been widely thought that MCT is more easily hydrolyzed and absorbed than LCT.
The purpose of this study is to investigate the mechanism by which MCT is more readily absorbed than LCT.
The intestinal lipolysis and absorption of MCT were compared with those of LCT under various experimental conditions. Male albino rats weighing 120-150g were used in four groups, that is normal, bile duct ligated, pancreatic duct ligated, and both bile and pancreatic duct ligated group. Test meals containing trioctanoin-1-
14C or tripalmitin-1-
14C were administered into the duodenum. Lipids of intestinal contents, intestinal wall and portal blood were extracted, assayed for radioactivity and then analyzed by thin-layer chromatography and autoradiography therof. In the other series of experiments in vitro, trioctanoin-1-
14C or tripalmitin-1-
14C were incubated with albumin solution (phosphate buffer, pH 7.4), varying taurocholic acid concentration, varying steapsin concentration at 37.5°C and analyzed with florisil column chromatography. In the further experiments, steapsin was replaced by the rat pancreatic juice or the rat intestinal mucosal homogenates.
MCT is in need of intraluminal lipolysis prior to the intestinal absorption. Both MCT and LCT are injured in absorption in the case of insufficiency of the flow of bile or pancreatic juice. But the extent of disturbance in absorption is smaller in MCT than LCT. Taurocholic acid and steapsin show lipolytic activity to MCT as equal as to LCT. Retention ratio in intestinal mucosa of MCT and that of LCT are very low, but the former is lesser than the latter. MCT is mostly hydrolyzed by pancreatic lipase with the aid of bile acid in the intestinal lumen, and a small amount of intact MCT and its lower glycerides, which are not hydrolyzed in the intestinal lumen, are hydrolyzed completely by intestinal lipase in mucosa. Most of released FA from MCT enter the portal vein. It is thought that a little of intact MCT enter the intestinal mucosa, but it cannot enter the portal vein.
The mechanism, by which MCT is more easily and rapidly absorbed than LCT, is that the released FA from MCT is transported via portal flow, which is more rapid than lymphatic flow.
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