Interaction of Bile Acids, Phospholipids, Cholesterol and Triglyceride with Dietary Fibers in the Small Intestine of Rats

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Abstract
Certain dietary fibers have been reported to lower plasma cholesterol by binding bile acids and reducing their recycling through the enterohepatic circulation. In addition, certain fibers may delay the digestion and absorption of fat. In the present study, the interaction of bile acids with guar gum (GG), konjac mannan (KM) and chitosan (CH) was determined. Rats were fed during a 20-min period a test meal containing either 5% cellulose (CE), GG, KM or CH and also containing 14C-labeled triolein and 3H-labeled cholesterol. The group fed CE served as control, since CE does not bind bile acids or phospholipids in vivo. Two hours after presentation of the test meal, rats were killed and the stomach and small and large intestine removed. All four groups ate the same amount of the test meal, about 1.9 g. The aqueous phase of the small intestinal contents was separated by ultracentrifugation, and the amount (µmol) of bile acids and phospholipids in the total intestinal contents and in the aqueous phase was estimated. The ratio of bile acids in the aqueous phase to that in total intestinal contents was significantly higher in the GG and KM groups and significantly lower in the CH group than that in the CE group, demonstrating that the bile acids are bound or trapped by each of these fiber sources. Only CH appeared to bind phospholipids, reducing the proportion in the aqueous phase compared to that in the CE group. Of the 14C and 3H emptied from the stomach, a greater percentage remained in the small intestine of the GG and KM groups than in that of the CE group, indicating that absorption of both cholesterol and triglyceride from the small intestine was delayed due to feeding GG or KM.