Effects of Bile Diversion on the Lipid-Reesterifying Capacity of the Rat Small Bowel

Abstract

Intestinal absorption of lipid by the small bowel proceeds via enzymatic processes by which the products of lipid digestion are reesterified to triglyceride. This study was done to determine whether bile diversion which causes steatorrhea due to impairment of micelle formation also has an adverse effect on the small bowel itself by producing a reduction in its lipid-reesterifying capacity. Two methods were employed to investigate this question. The first utilized the everted gut sac technique incubating jejunal sacs in a micellar solution of radioactive free fatty acid. Rates of esterification of the fatty acid were determined in both control and experimental sacs incubated for brief periods in solutions of varying concentrations of free fatty acid. Morphological studies were also performed on these sacs both before and after incubation. The other method used to determine the reesterifying capacity of the intestine was the direct enzymatic assays of acyl-coenzyme A ligase and acyl-coenzyme A: monoglyceride acyltransferase. All studies were performed 72 hr after surgery. Maximal rates of esterification of oleic acid by sacs were sustained for only brief periods. Histological examination demonstrated slight but definite abnormalities of the epithelial cells after only 5 min and partial villous sloughing after 15 min of incubation. Using brief periods of incubation, studies were performed on sacs from both nonfasting and fasting control and bile fistula rats. Rates of esterification were greater in sacs from either nonfasting or fasting control rats compared with sacs from experimental rats under comparable conditions of nonfasting and fasting. The activities of the mucosal lipid-reesterifying enzymes were also found to be greater in the control rats. Enzymatic activities were determined to be greater in either the nonfasting or fasting control groups compared with the respective nonfasting and fasting experimental groups. Similar enzyme assays were performed in rats infused intraduodenally with a synthetic diet at a constant rate. Under these conditions, enzymatic activities were still greater in control rats. Additional studies in experimental rats demonstrated that these enzymatic activities could be maintained in the normal range by infusing artificial bile intraduodenally. It is concluded that, in addition to causing lipid malabsorption by impairing micelle formation, bile diversion also has an adverse effect on the intracellular process of lipid absorption by producing a reduction in the lipid-reesterifying capacity of the small bowel.