Supplement to DK-38389 Lipid Transport in the Intestine

膳食脂肪的主要水解物是脂肪酸(FA)和单甘油酯(MG)。尽管 虽然在肠腔中产生了非常大量的物质，但我们对这些物质的理解仍然存在很大差距。 小肠吸收细胞吸收MG和FA的基本机制。其中包括一个 从分子水平理解两个高表达的肠细胞脂肪酸结合蛋白的个体功能 蛋白质(FABP)、肠道FABP和肝脏FABP(IFABP和LFABP)。在我们之前的研究中，使用了体外 脂质转运动力学方法，我们提供了新的证据表明IFABP和LFABP可能 在肠道细胞中至少有一些独特的功能。在父提案中，我们使用了一个集成的 细胞和动物研究的方法来解决IFABP和LFABP的功能。在目标1和目标2中，研究 正在确定IFABP和LFABP在肠细胞中的功能和结构/功能关系 FA和MG的转运和代谢。在我们目前的研究中，直接蛋白质转移和DNA转染 正在使用各种方法将FABP的野生型和特定突变形式引入培养细胞 概述肠细胞表型的模型，检查对脂肪吸收、新陈代谢和分泌的影响。 在其他研究中，我们第一次比较了IFABP或LFABP为空的小鼠，我们观察到了几个有趣的 喂养食物的小鼠的肠道表型变化，包括IFABP-/-小鼠和IFABP-/-小鼠TG合成增加 减少了LFABP基因敲除中的FA-氧化。令人惊讶的是，当动物被喂食高饱和脂肪饲料时， 观察到戏剧性的全身表型差异，LFABP基因缺失的小鼠表现出明显的肥胖和 IFABP基因缺失的小鼠表现出完全相反的表型--防止饮食诱导的肥胖！这些 综合研究，使用细胞和动物研究、蛋白质组学、脂体学和结构功能相结合的研究 方法，提供了关于肠道脂肪同化的全新信息，以及关于 肠道脂质转运和代谢在调节全身能量平衡中的作用。另一个重要的差距是 我们对肠道脂肪同化的理解关系到FA和MG在肠细胞中的代谢命运。这个 吸收上皮细胞表现出显著不同的代谢在饲料或顶端添加(AP)的FA 细胞的表面，与细胞的基侧(BL)表面相比，我们最近证明了惊人的 MG代谢的代谢极性也是如此。这种划分背后的机制仍然存在 基本上是未知的。在我们目前在目标3中的研究中，我们使用了细胞和 确定FA和MG代谢区划机制的动物研究 在肠道细胞中。我们研究的总体目标是提供肠道脂质运输的分子水平图像 为了能够控制膳食脂肪同化的速度和程度以及餐后脂肪水平，通过 调节特定的运输和代谢过程。

The primary hydrolytic products of dietary fat are fatty acids (FA) and monoacylglycerol (MG). Despite the very large quantities generated in the intestinal lumen, substantial gaps remain in our understanding of the basic mechanisms of MG and FA assimilation by the absorptive cells of the small intestine. These include a molecular level understanding of the individual functions of two highly expressed enterocyte fatty acid-binding proteins (FABP), intestinal FABP and liver FABP (IFABP and LFABP). In our previous studies using in vitro lipid transport kinetics approaches, we provided novel evidence suggesting that IFABP and LFABP are likely to have at least some unique functions in the enterocyte. In the parent proposal, we are using an integrated approach of cellular and animal studies to address the functions of IFABP and LFABP. In Aims 1 and 2, studies are determining the functions and structure/function relationships for IFABP and LFABP in enterocyte transport and metabolism of FA and MG. In our current studies, direct protein transfer and DNA transfection approaches are being used to introduce wild-type and specific mutant forms of the FABPs into cultured cell models that recapitulate the enterocyte phenotype, examining effects on lipid uptake, metabolism, and secretion. In other studies comparing, for the first time, mice null for IFABP or LFABP, we have observed several interesting intestinal phenotypic changes in chow-fed mice, including increased TG synthesis in the IFABP-/- mouse and decreased FA -oxidation in the LFABP knockout. Strikingly, when the animals are fed high saturated fat diets, dramatic whole-body phenotypic differences are observed, with LFABP null mice exhibiting marked obesity and IFABP null mice displaying a completely opposite phenotype--protection against diet-induced obesity! These integrated studies, using a combination of cellular and animal studies, proteomic, lipidomic, and structure-function approaches, are providing entirely novel information about intestinal lipid assimilation, and on the important role of intestinal lipid transport and metabolism in regulating whole-body energy homeostasis. Another important gap in our understanding of intestinal lipid assimilation concerns the metabolic fate of FA and MG in the enterocyte. The absorptive epithelial cell exhibits marked differences in the metabolism of FA added at the dietary or apical (AP) surface of the cell, compared to the basolateral (BL) surface of the cell, and we recently demonstrated striking metabolic polarity for MG metabolism as well. The mechanisms that underlie this compartmentation remain essentially unknown. In our current studies in Aim 3, we are using an integrated approach of cellular and animal studies to determine the mechanisms underlying the metabolic compartmentation of FA and MG in the enterocyte. The overall goal of our research is to provide a molecular level picture of intestinal lipid traffic in order to enable the control of the rate and extent of dietary lipid assimilation and postprandial lipid levels, by modulating specific transport and metabolic processes.