Feeding Medium-Chain Triglycerides to Rats Decreases Degradation of Sucrase-Isomaltase Complex in the Jejunum

Abstract

We demonstrated previously that feeding a diet containing medium-chain triglycerides (MCT) to rats causes an increase in the sucrase activity in jejunum relative to diets containing long-chain triglycerides (LCT). To explore the mechanism whereby MCT affect jejunal sucrase activity, 7-wk-old rats were fed a high LCT diet for 7 d, and then they were force-fed either the high LCT diet, a high MCT diet or a high carbohydrate (alpha-methylglucoside) diet for the subsequent 12 h. Feeding the high carbohydrate diet produced significantly greater sucrase and isomaltase activities in both upper and lower jejunum than feeding the LCT diet. Feeding the high MCT diet led to significantly greater sucrase activity in the lower jejunum, but isomaltase activity was not elevated. Rocket immunoelectrophoresis revealed that in the lower jejunum of the rats fed the high MCT diet the proportion of sucrase-isomaltase complex to its degradation product (i.e., isomaltase monomer) was elevated, suggesting that dietary MCT affects sucrase activity by retardation of degradation of sucrase-isomaltase. Because the amounts of total bile acids in the upper jejunum were 50% lower in rats fed the high MCT diet relative to animals fed the high LCT diet, it is likely that MCT feeding decreases secretion of bile into the lumen, which in turn decreases degradation of the sucrase subunit of the sucrase-isomaltase complex.