Effect of pancreatic cholesterol esterase on cholesterol absorption

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Pancreatic cholesterol esterase (CEase) is an enzyme hydrolyzing cholesterol ester to cholesterol and fatty acid. It has been reported that CEase is an essential factor for cholesterol absorption. However, other investigations did not support the observation. In this study, effect of CEase on cholesterol absorption was investigated in rat brush border membranes and Caco-2 cells. Rat pancreatic juice and bovine pancreatic CEase dose-dependently accelerated the incorporation of micellar cholesterol into rat intestinal brush border membranes. CEase bound to brush border membranes did not increase the uptake of micellar cholesterol. Since the transfer of micellar cholesterol to hydrophobic triolein was accelerated by CEase, it is thought that CEase reduces the affinity between bile salt micelles and cholesterol and hence, accelerates the release of cholesterol as a monomer. This phenomenon may cause the increase of cholesterol absorption. It is thought that physico-chemical characteristics of CEase as a protein may result in the acceleration. CEase increased the incorporation of micellar cholesterol into and the secredon from differentiated Caco-2 cells. Esterification ratios of the incorporated and secreted cholesterol were increased by the addition of CEase. The results suggest that CEase is incorporated into Caco-2 cells and accelerates the esterification of cholesterol. The increase of esterified cholesterol in the cells may accelerate the secretion as chylomicron.These results suggest that pancreatic CEase is not essential for cholesterol absorption, but it has an ability to accelerate the absorption.