Effect of pancreatic cholesterol esterase on cholesterol absorption

胰腺胆固醇酯酶是一种将胆固醇酯分解为胆固醇和脂肪酸的酶。据报道，停滞是胆固醇吸收的一个重要因素。然而，其他调查并不支持这一观察。本研究在大鼠刷状缘膜和Caco-2细胞上观察了停药对胆固醇吸收的影响。大鼠胰液和牛胰腺停止剂量依赖地促进胶束胆固醇掺入大鼠肠道刷状缘膜。停止结合刷边界膜并不能增加胶束胆固醇的摄取。由于胶束胆固醇向疏水三油酸脂的转移被加速，人们认为停止会降低胆盐胶束与胆固醇之间的亲和力，从而加速胆固醇作为单体的释放。这种现象可能会导致胆固醇吸收增加。有人认为，作为蛋白质的Stop的物理化学特性可能导致了加速。Stop可增加胶束胆固醇进入分化的Caco-2细胞及其分泌的量。加入STOP后，结合胆固醇和分泌胆固醇的酯化率增加。结果表明，STOP被整合到Caco-2细胞中，并加速了胆固醇的酯化。细胞中酯化胆固醇的增加可能会加速乳糜体的分泌。这些结果表明，胰腺停止对胆固醇的吸收并不是必不可少的，但它有促进吸收的能力。

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.