CATABOLISM AND EXCRETION OF CHOLESTEROL AND BILE ACIDS

描述：本提案的目标是确定两个关键途径， 胆汁酸的生物合成受饮食胆固醇的调节， 顶端Na+依赖性胆汁酸转运蛋白的调控机制 （ASBP）在回肠。该提案结合了方法和动物模型， 以前没有结合起来测试一些基本假设， 胆固醇的代谢和排泄。该提案的目标如下： 1）。为了检验胆汁酸合成的两条途径， 胆固醇7 α-羟化酶途径和甾醇27-羟化酶途径， 是独立调节的，调节模式取决于胆固醇 响应能力。这将通过三种不同的方法进行测试， 一种独特的高胆固醇血症抗性兔的优势， 德克萨斯大学申请人提出了一项纵向研究， 作为胆汁的氘代7-α-羟基胆固醇和27-羟基胆固醇 酸前体。这些研究将精确测量胆汁酸的比率， 当动物被喂食高胆固醇血症， 低胆固醇饮食这一具体目标的第二个组成部分将评估 在具有总胆汁的动物中通过两种途径的胆汁酸合成速率 酸转移这一具体目标的第三个组成部分是针对 阐明了这两种途径的调节机制。的 申请人将检查mRNA的稳态速率，并使用新的 转录测定，以评估酶生物合成速率的改变是如何 在体内实现。2）。为了检验ASBP的表达是 受转录和转录后机制的调控。这 将在正常和高胆固醇血症抗性兔中进行测试 申请人将检查活性、mRNA和转录水平， 并确定mRNA的变化是否反映在 ASBP蛋白及其定位。此外，申请人将确定 在高胆固醇血症患者中发现的ASBP等位基因的功能后果 兔子 这些研究将对理解 只有通过这些途径才能将大量胆固醇从体内排出。在这 申请人预计结果将影响 治疗心血管疾病， 控制胆固醇体内平衡的基本生物学问题。

DESCRIPTION: The goal of this proposal is to determine how two key pathways of bile acid biosynthesis are regulated by dietary cholesterol and to determine the mechanisms regulating the apical Na+ -dependent bile-acid transport protein (ASBP) in the ileum. This proposal combines approaches and animal models that have not been combined before to test some basic hypotheses regarding the metabolism and excretion of cholesterol. The proposal has the following goals: 1). To test the hypothesis that the two pathways of bile acid synthesis, the cholesterol 7alpha-hydroxylase pathway and the sterol 27-hydroxylase pathway, are regulated independently, and patterns of regulation depend on cholesterol responsiveness. This will be tested by three different approaches and will take advantage of a unique hypercholesterolemia-resistant rabbit developed at the University of Texas. The applicant proposes a longitudinal study using deuterated 7-alpha hydroxycholesterol and 27-hydroxylated cholesterol as bile acid precursors. These studies will precisely measure rates of bile acid synthesis in vivo as animals are fed a hypercholesterolemic and then a hypocholesterolemic diet. The second component of this specific aim will assess rates of bile acid synthesis by the two pathways in an animal with a total bile acid diversion. The third component of this specific aim is directed a elucidating the mechanism through which these two pathways are regulated. The applicant will examine both steady-state rates of mRNA and use a novel transcription assay to assess how altered rates of enzyme biosynthesis is achieved in vivo. 2). To test the hypothesis that expression of ASBP is regulated by both transcriptional and post-transcriptional mechanisms. This will be tested both in normal and in the hypercholesterolemia-resistant rabbits and the applicant will examine levels in the activity, mRNA, and transcription of the transporter and determine if changes in mRNA are reflected in levels of ASBP protein and localization. In addition, the applicant will determine the functional consequences of ASBP allele found in the hypercholesterolemic rabbit. These studies will make a significant contribution to the understanding of the only routes by which significant cholesterol is removed from the body. In this respect the applicant anticipates that the results will impact upon the treatment of cardiovascular diseases well as having significance for fundamental biological questions of the control of cholesterol homeostasis.