FATTY ACID TRANSPORT IN THE INTESTINE

脂肪酸(FFA)和单甘油(MG)是主要的消化物质 膳食脂肪的产品。肠道构成了一道屏障。 FFA和MG必须通过的，但它们所依据的机制 运输问题在很大程度上仍未得到解决。这项研究的目的是 计划是继续解决我们对分子的认识上的空白 游离脂肪酸从两种脂相转移的机制 肠腔、胶束和囊泡，通向肠细胞；b)穿过 肠细胞的微绒毛膜(MVM)；以及c)在 肠细胞胞浆。后一方面的研究将集中在 肠道和肝脏脂肪酸结合蛋白(I-和L-FABP)。这些 被认为在细胞内的FFA运输中发挥作用，但他们的 确切的功能仍不清楚。拟议的研究也将开始。 分析MG的吸收动力学和吸收机理。 实验方法将结合使用纯化的模型脂 细胞膜和细胞质的重组系统 Caco-2肠道细胞培养系统。 现已知在此过程中会形成两个产品阶段 肠道脂肪消化分为胶束期和囊泡期。这个 FFA和MG从这两个相中转移的动力学将用 荧光FFA和MG衍生物，以及共振能量转移 化验。研究将继续确定从 每一个阶段，它们对脂肪摄取的相对贡献，以及 它们通过结构和生理上重要的解决方案进行调节 变量。 FFA穿越MVM的机制目前存在争议，以及 对肠道中的MG摄取知之甚少。确定…的角色 质膜蛋白与脂类扩散途径，研究将使用 直接监测跨膜转运的荧光显微镜 FFA和MG在单个Caco-2细胞水平上的表达。 为了确定I-和L-FABP在FFA同化中的作用， 拟议的研究将使用FABP的蛋白质荧光和一种 系列荧光FFA衍生物，比较其结构 I-FABP与FFA的相互作用与L-FABP。与MG的互动将 也是第一次接受检查。 拟议的研究还将系统地分析 游离脂肪酸和微球蛋白从I-vs.L-FABP向模型和亚细胞转移 膜，以及这些FABP在细胞膜间FFA运输中的作用 肠细胞。荧光和天然配体都将用于这些 调查。 更好地理解FFA和MG的分子机制 在肠道内的同化可能使更有效的治疗 吸收不良综合征--肠内药物的持续发展 提供系统，以及饮食能量利用的调节。

Fatty acids (ffa) and monoacylglycerol (MG) are the major digestive products of dietary lipid. The intestine presents a barrier through which the ffa and MG must pass, yet the mechanisms by which they are transported remain largely unresolved. The objective of this research plan is to continue to address the gaps in our knowledge of the molecular mechanisms of ffa transfer a) from the two lipid phases present in the intestinal lumen, micelles and vesicles, to the enterocyte; b) across the microvillus membrane (MVM) of the intestinal cell; and c) within the enterocyte cytoplasm. The latter studies will focus on the functions of intestinal and liver fatty acid binding proteins (I- and L-FABP). These are thought to play a role in intracellular ffa transport, but their precise functions remain unknown. The proposed studies will also begin to analyze the kinetics and mechanism of MG absorption. The experimental approach will combine the use of purified model lipid systems, reconstituted systems of cell membranes and cytoplasmic components, and the Caco-2 intestinal cell culture system. Two product phases are now known to be formed during the course of intestinal lipid digestion, a micelle phase and a vesicle phase. The kinetics of ffa and MG transfer from the two phases will be studied using fluorescent ffa and MG derivatives, and a resonance energy transfer assay. Studies will continue to define the mechanisms of transfer from each of these phases, their relative contributions to lipid uptake, and their regulation by structural and physiologically important solution variables. The mechanism by which ffa cross the MVM is presently controversial, and little is known about intestinal MG uptake. To determine the role of plasma membrane protein vs. lipid diffusion pathways, studies will use fluorescence microscopy to directly monitor the transmembrane transport of ffa and MG at the level of the single Caco-2 cell. In order to define the role that I- and L-FABP play in ffa assimilation, the proposed studies will use the protein fluorescence of the FABP and a series of fluorescent ffa derivatives, to compare the structural interactions with ffa for I-FABP vs. L-FABP. Interactions with MG will also be examined for the first time. The proposed studies will also systematically analyze the mechanisms of ffa and MG transfer from I- vs. L-FABP to model and subcellular membranes, and the role of these FABP in intermembrane ffa traffic in the enterocyte. Both fluorescent and natural ligands will be used for these investigations. A better understanding of the molecular mechanisms underlying ffa and MG assimilation in the intestine may enable more effective treatment of malabsorption syndromes, the continued development of enteral drug delivery systems, and the regulation of dietary energy utilization.