INTERACTIVE EFFECTS OF BILE SALT AND LIPOLYTIC ENZYMES IN CHOLESTEROL ABSORPTION

本项目主要研究腔内脂肪消化之间的关系 和胆固醇的吸收，特别注意它的作用 胰腺磷脂酶A/2(PLA2)和胰脂酶(PL)的变化 这一过程。具体的假设是胆固醇的吸收 效率与腔内脂肪消化的效率相关， 而这又取决于胆汁酸的数量和类型以及 肠腔内脂解酶的活性。我们 假设：(1)胆汁酸和脂解酶相互作用。 肠腔脂肪在被肠细胞吸收之前的建模； (2)胰腺脂解酶表达水平的变化 导致胆固醇吸收的个体差异 效率；以及(3)胰腺脂解酶的异位表达 胆管上皮内注射是治疗脂肪吸收不良的一种可行方法 与胰腺功能不全和囊性纤维化有关。四 针对这些假设提出了具体目标：具体目标1 将决定胆汁酸成分对管腔脂肪分解的影响。 将在体外进行实验，以确定胆汁的影响 酸组成对(I)磷脂酶A2和磷脂酶活性，(Ii)胆固醇 脂肪乳剂、磷脂微囊和混合乳剂中的分布 胶束，以及(Iii)培养中肠道细胞对胆固醇的摄取 和粘膜层。体外观察将与In 补充胆汁酸对体腔脂解酶的影响 活性、胆固醇溶解和胆固醇吸收 人类受试者的效率。特定目标2将产生PLA2基因敲除 小鼠测试PLA2在胆固醇吸收中的重要性。特定的 AIM 3将产生PL基因敲除小鼠以测试PL基因的影响 脂肪和胆固醇吸收方面的缺失。PL基因敲除小鼠 这项研究产生的结果将用于具体目标4，以确定 重组腺病毒介导的胆道PL基因转移 在没有胰腺的情况下，上皮可以恢复脂肪的吸收 脂肪酶在胰腺的表达。这些研究将提供 营养学家和临床医生用机械信息来设计 对饮食引起的疾病进行有效的饮食和/或治疗- 诱发高脂血症或脂肪消化和运输异常 胰腺疾病。

This project focuses on the relationship between luminal lipid digestion and cholesterol absorption, with particular attention paid to the role of pancreatic phospholipase A/2 (PLA2) and pancreatic lipase (PL) in this process. The specific hypothesis is that cholesterol absorption efficiency is correlated to the efficiency of luminal lipid digestion, which in turn is dictated by the amount and type of bile acid and the activity of lipolytic enzymes present in the intestinal lumen. We postulate that: (1) bile acids and lipolytic enzymes interact in the re- modeling of luminal lipids prior to their absorption by the enterocytes; (2) variations in the level of pancreatic lipolytic enzyme expression contribute to individual differences in cholesterol absorption efficiency; and (3) ectopic expression of pancreatic lipolytic enzymes in the biliary epithelium is a feasible treatment for fat malabsorption associated with pancreatic insufficiency and cystic fibrosis. Four specific aims are proposed to address these hypotheses: Specific Aim 1 will determine the effect of bile acid composition on luminal lipolysis. Experiments will be performed in vitro to determine the effects of bile acid composition on (i) PLA2 and PL activities, (ii) cholesterol distribution among lipid emulsions, phospholipid vesicles, and mixed micelles, and (iii) cholesterol uptake by intestinal cells in culture and mucosal sheets. The in vitro observations will be correlated with in vivo affects of bile acid supplementation on luminal lipolytic enzyme activities, cholesterol solubilization, and cholesterol absorption efficiency in human subjects. Specific Aim 2 will produce PLA2 knockout mice to test eh importance of PLA2 in cholesterol absorption. Specific Aim 3 will produce PL knockout mice to test the impact of PL gene deletion on fat and cholesterol absorption. The PL knockout mice produced in this study will be used in Specific Aim 4 to determine if recombinant adenovirus mediated PL gene transfer to the biliary epithelium can restore fat absorption in the absence of pancreatic lipase expression by the pancreas. These studies will provide nutritionists and clinicians with mechanistic information to design effective dietary and/or therapeutic treatment for diseases due to diet- induced hyperlipidemia or to aberrant fat digestion and transport due to pancreatic diseases.