ILEAL BILE ACID TRANSPORTER METABOLISM AND REGULATION

在脂肪代谢中，胆汁酸在消化中起关键作用。 膳食脂肪与膳食代谢物和胆固醇的吸收。至 维持其肠-肝循环，胆汁酸被 主动回肠摄取。利用分离的肠道切片和肠道细胞， 回肠胆汁酸的动力学性质和化学特异性 已经对运输进行了审查。然而，负责 运输还没有被分离出来，这个过程也没有在 分子水平。这阻碍了人们对其机制的理解。 回肠胆汁酸转运、调节及其在胆汁酸和胆汁酸代谢中的作用 胆固醇代谢。拟议的研究将采用最近的 鉴定胆汁酸转运蛋白的cDNA克隆以检测其调控和 回肠胆汁酸转运的机制。以下问题将 收信人： 1.回肠胆汁酸转运体的一般特性是什么？ 胆汁酸的回肠转运被认为是由Na+-介导的。 依赖于刷子边缘膜上的转运体。以识别和 鉴定转运蛋白，我的实验室使用了一种表达克隆 回肠胆汁酸候选基因克隆(IBAT)的分离策略 传送器。以验证候选cDNA的身份并扩展 转运蛋白、IBAT的转运和表达的研究进展 属性将被确定。 2.回肠胆汁酸转运体是否受胆汁酸供应的调节？ 最近的体内研究表明，回肠胆汁酸运输 活性受胆汁酸可获得性的调节，可能是至关重要的 胆汁酸和胆固醇动态平衡的决定因素。要确定) 转运蛋白是否受仓鼠肠道胆汁变化的调节 酸的可用性(如先前假设的)以及b)这是什么级别 排尿发生，回肠Na+依赖的胆汁酸转运体活动， 将检测蛋白质、信使核糖核酸和基因转录水平。 3.回肠胆汁酸转运体是如何运输胆汁酸的 穿过肠上皮细胞？开始研究胆汁的细胞机制 酸运输，Caco-2细胞将作为模型系统来表达 回肠胆汁酸转运蛋白基因。将研究IBAT的传输特性 要检验刷子边界膜转运体是 胆汁酸跨细胞转运的限速步骤 回肠上皮。

In lipid metabolism, bile acids play a critical role in the digestion of dietary fat and the absorption of dietary metabolites and cholesterol. To maintain their enterohepatic circulation, bile acids are conserved by active ileal uptake. Using isolated intestinal sections and enterocytes, the kinetic properties and chemical specificity of ileal bile acid transport has been examined. However, the proteins responsible for transport have not been isolated, and the process has not been studied at the molecular level. This has hindered understanding the mechanism of ileal bile acid transport, its regulation, and its role in bile acid and cholesterol metabolism. The proposed research will employ a recently identified bile acid transporter cDNA clone to examine the regulation and mechanism of the ileal bile acid transport. The following questions will be addressed: 1. What are the general properties of the ileal bile acid transporter? Bile acid transport across the ileum is believed to be mediated by a Na+- dependent transporter on the brush border membrane. To identify and characterize the transporter, my laboratory used an expression cloning strategy to isolate a candidate cDNA clone (IBAT) for the ileal bile acid transporter. To verify the identity of the candidate cDNA and extend previous studies of the transporter, IBAT's transport and expression properties will be determined. 2. Is the ileal bile acid transporter regulated by bile acid availability? Very recent in vivo studies have suggested that ileal bile acid transport activity is regulated by bile acid availability and may be a crucial determinant of bile acid and cholesterol homeostasis. To determine a) whether the transporter is regulated by changes in hamster intestinal bile acid availability (as previously hypothesized) and b) what level this reulation occurs, ileal Na+-dependent bile acid transporter activity, protein, mRNA, and gene transcription levels will be examined. 3. How does the ileal bile acid transporter function to carry bile acids across the enterocyte? To begin studying the cellular mechanism of bile acid transport, CaCo-2 cells will be used as a model system to express the ileal bile acid transporter cDNA. IBAT's transport properties will studied to test the hypothesis that the brush border membrane transporter is the rate limiting step in transcellular trafficking of bile acids across the ileal epithelium.