Functional & molecular study of intetinal cholesterol transporters & absorption

性状（由申请方提供）：Zetia（依折麦布）通过抑制肠细胞中NPC 1-L1介导的胆固醇转运途径来抑制胆固醇吸收。我们证明了CD 36在胆固醇吸收中也起作用。研究还表明，清道夫受体SR-BI是小肠刷状缘膜上的另一种胆固醇转运蛋白。我们假设SR-BI和CD 36分别是近端和远端肠中的胆固醇转运蛋白，与NPC 1-L1（可能是细胞内的）一起工作，介导胆固醇从肠腔摄取到乳糜微粒组装发生的肠细胞的细胞内隔室。目标1：我们将确定：1）如果缺乏SR-BI、CD 36或NPC 1 L1改变了胆固醇吸收的位点和/或效率（通过改变输注的位点或剂量）;和2）如果在缺乏一种或另一种转运蛋白的情况下上调对应转运蛋白以维持胆固醇吸收。在淋巴瘘小鼠中，我们还将确定依折麦布是否仍能有效抑制这些基因敲除动物小肠的胆固醇摄取。目标二：首先，我们将确定亚有效剂量的依折麦布与亚有效剂量的熊去氧胆酸盐或普朗尼克F-68（F-68）联合使用是否抑制大鼠的肠道胆固醇吸收。此外，我们将确定同样的现象也适用于小鼠。第二，在上述基因敲除小鼠模型中，我们将确定依折麦布或熊去氧胆酸盐或F-68单独或组合是否有效抑制小肠对胆固醇的吸收。目标3：我们将利用依折麦布抑制肠道胆固醇的能力和Pluronic L-81防止乳糜微粒形成的能力，以确定途径并定量通过外排至顶侧以及通过基底外侧膜分泌为富含胆固醇脂蛋白的胆固醇的量。使用依折麦布和普朗尼克L-81的组合，我们将能够研究小肠对胆固醇的摄取和排出。完成拟议的研究将为我们提供新的见解胆固醇摄取和淋巴运输是如何调节肠道中的各种转运蛋白。这些新的数据也可能为高胆固醇血症患者的临床管理提供新的信息。

DESCRIPTION (provided by applicant): Zetia (Ezetimibe) inhibits cholesterol absorption via inhibition of NPC1-L1 mediated cholesterol transport pathway(s) in the enterocytes. We demonstrated that CD36 also plays a role in cholesterol absorption. It has also been demonstrated that the scavenger receptor SR-BI as another putative cholesterol transporter on intestinal brush border membrane. We hypothesize that SR-BI and CD36 are cholesterol transporters in the proximal and distal intestine, respectively, working in conjunction with NPC1-L1 (may be intracellular) to mediate cholesterol uptake from the lumen to intracellular compartments of the enterocytes where chylomicron assembly occurs. Aim 1: We will determine: 1) if the lack of SR-BI, CD36, or NPC1L1 alters the site and/or efficiency of cholesterol absorption (by varying the site or dose of infusion); and 2) if the counterpart transporters are upregulated to maintain cholesterol absorption in the absence of one or the other transporter protein. In lymph fistula mice, we will also determine if Ezetimibe remains effective in inhibiting cholesterol uptake by the small intestine in these knockout animals. Aim 2: First, we will determine if sub-effective doses of Ezetimibe, in combination with sub-effective doses of either ursodeoxycholate or Pluronic F-68 (F-68), inhibits intestinal cholesterol absorption in the rat. Also, we will determine the same phenomenon also works in the mouse. Second, in the knockout mice models described above, we will determine if Ezetimibe or ursodeoxycholate or F-68 alone or in combination is/are effective in inhibiting cholesterol absorption by the small intestine. Aim 3: We will take advantage of the ability of Ezetimibe to inhibit intestinal cholesterol, and the ability of Pluronic L-81 to prevent chylomicron formation to identify the pathway and quantify the amount of cholesterol exiting the enterocytes through efflux to the apical side as well as secreted through the basolateral membrane as triglyceride-rich lipoproteins. Using a combination of both Ezetimibe and Pluronic L-81, we will be able to study both the uptake and efflux of cholesterol by the small intestine. Completion of the proposed studies will provide us with new insights into how cholesterol uptake and lymphatic transport are regulated by the various transporters in the gut. These new data may also provide us with new information in the clinical management of hypercholestermic patients.