LIVER/INTESTINAL METABOLISM OF BILE ACIDS AND LIPIDS

该计划项目的总体目标是：a)扩大我们的 对胆固醇和胆汁酸代谢调节的认识 在肝脏和肠道中；b)定义途径和酶 参与肠道细菌次级胆汁酸的形成； 和c)确定疏水性胆盐引起细胞的机制 并探讨其保肝作用的基础。 熊去氧胆酸盐。这项建议的具体目标是： 1)胆汁中关键酶的纯化、鉴定和克隆 酸的生物合成途径(胆固醇7α羟基酶(C7alphaH)， 3β-羟基类固醇脱氢酶/异构酶(3β-HSD)和12α- 羟基酶(12alphaH)；2)胆汁分子基础的测定 酸、胆固醇和选定的激素调节C7alphaH；3)研究 3β-HSD和12alphaH的调节；4)决定了 胆汁酸对HMG-CoA还原酶(HMG-CoA-R)的调节 肝胆固醇酯的纯化、鉴定及克隆 水解酶(CEH)；6)研究胆汁酸对CEH的调节， 胆固醇和其他调节剂与其他酶的结合 参与维持肝脏胆固醇动态平衡；7) 代谢相关酶的纯化、鉴定和克隆 初级胆汁酸向次级胆汁酸的细菌转化；8)克隆 和细菌胆汁酸转运(结合)蛋白的序列分析 选定的细菌；9)阐明疏水性的机理 胆汁酸可引起肝脏损伤，熊去氧胆酸可通过胆汁酸引起肝脏损伤。 具有代表性的亲水性胆汁盐保护细胞膜免受毒性胆汁的伤害 盐；10)以确定不同胆盐单独或在 结合UDCA，对膜的流动性梯度采用 用荧光探头评估不同深度的各向异性 以及11)确定疏水性胆汁的作用机制 盐会影响胆固醇和磷脂的转移。

The overall objectives of this program project are to: a) broaden our understanding of the regulation of cholesterol and bile acid metabolism in the liver and in the intestines; b) define the pathway and enzymes involved in the formation of secondary bile acids by intestinal bacteria; and c) determine the mechanism by which hydrophobic bile salts cause cell injury and explore the basis for hepatoprotective action of ursodeoxycholate. The specific aims of this proposal are: 1)purification, characterization, and cloning of key enzymes in the bile acid biosynthetic pathway (cholesterol 7alpha-hydroxylase (C7alphaH), 3beta-hydroxysteroid dehydrogenase/isomerase (3beta-HSD) and 12alpha- hydroxylase (12alphaH); 2) determination of molecular basis by which bile acids, cholesterol and selected hormones regulate C7alphaH; 3) to study the regulation of 3beta-HSD and 12alphaH; 4)determine the mechanism of regulation of HMG-CoA reductase (HMG-CoA-R) by bile acids; 5) purification, characterization and cloning of hepatic cholesteryl ester hydrolase (CEH); 6) to study the regulation of CEH by bile acids, cholesterol and other regulatory agents in conjunction with other enzymes involved in the maintenance of hepatic cholesterol homeostasis; 7) purification, characterization and cloning of enzymes responsible for bacterial transformation of primary to secondary bile acids; 8) cloning and sequencing of bacterial bile acid transport (binding) protein from selected bacteria; 9) elucidation of the mechanism by which hydrophobic bile acids cause hepatic injury, and by which ursodeoxycholic acid, a representative hydrophilic bile salt protects membranes from toxic bile salts; 10) to determine the effects of different bile salts alone or in combination with UDCA, on the membrane fluidity gradient employing fluoroscopic probes to assess anisotropy at different depths within the membranes; and 11) to determine the mechanism by which hydrophobic bile salts affect cholesterol and phospholipid transfer.