DIETARY CAROTENOIDS - LIPOPROTEIN/CELL INTERACTIONS

人类从水果和蔬菜中获取类胡萝卜素。类胡萝卜素作为抗氧化剂的作用一直是我们在脂蛋白氧化方面工作的重点。虽然很明显，脂蛋白是类胡萝卜素运输的主要载体，但对肠道吸收类胡萝卜素的机制知之甚少。我们现在试图确定肠道吸收类胡萝卜素及其在血细胞中的分布机制。我们关注类胡萝卜素与人类单核细胞/巨噬细胞的相互作用，因为这种相互作用可能在动脉粥样硬化的发展中发挥作用。具体目标是：1.；培养CACO-2细胞肠道吸收类胡萝卜素及其进入乳糜微粒的机制。我们将测试其他脂溶性营养素抑制β -胡萝卜素进入乳糜微粒的假设。我们将验证SRB1、CD-36、FAT和其他假定的脂质转运体介导β -胡萝卜素进入细胞的摄取的假设。我们将检验β -胡萝卜素15,15'双加氧酶表达的增加会增加β -胡萝卜素通过细胞的总通量的假设。2. -胡萝卜素在人体中的肠道吸收。我们将使用稳定同位素方法来研究人类肠道吸收β -胡萝卜素的机制。正在研究的一般问题是，是否存在吸收各种脂溶性膳食营养素的共同机制。我们将检验肠道吸收胆固醇的效率与肠道吸收β -胡萝卜素的效率正相关的假设。我们将测试β -胡萝卜素仅在肠道内转化为维生素A的假设。我们将量化β -胡萝卜素转化为维生素A的过程，以检验β -胡萝卜素吸收增加与维生素A转化增加有关的假设。膳食类胡萝卜素对巨噬细胞功能的调节。我们将使用U937细胞系以及人外周血单核-巨噬细胞来检测类胡萝卜素在血源性细胞中的分配以及类胡萝卜素富集对单核-巨噬细胞功能的影响。我们将测试血浆类胡萝卜素分裂成各种血细胞以及血浆脂蛋白的假设。我们将测试类胡萝卜素富集改变单核巨噬细胞表型的假设，增强或抑制细胞功能的潜在促动脉粥样硬化方面，包括对趋化刺激的反应、与内皮细胞的粘附、向巨噬细胞的分化、氧化LDL的能力和形成泡沫细胞的能力。

Humans obtain carotenoids in the diet from fruits and vegetables. The role of carotenoids as antioxidants has been the focus of our work on lipoprotein oxidation. While it is clear that lipoproteins are the main vehicles for transport of carotenoids, little is known about mechanisms of intestinal absorption of carotenoids. We now seek to define the mechanism(s) of intestinal absorption of carotenoids and their distribution into blood cells. We focus on the interaction of carotenoids and the human monocyte/macrophage since this interaction may play a role in the development of atherosclerosis. Specific aims are: 1. Mechanisms of intestinal absorption of carotenoids and their incorporation into chylomicrons in CACO-2 cells in culture. We will test the hypothesis that other fat-soluble nutrients inhibit the incorporation of beta-carotene into chylomicrons. We will test the hypothesis that SRB1, CD-36, FAT, and other putative lipid transporters mediate the uptake of beta-carotene into the cell. We will test the hypothesis the increasing the expression of beta-carotene 15,15' dioxygenase increases the total flux of beta-carotene through the cell. 2. Intestinal absorption of beta-carotene in humans. We will use stable isotope methodology to study the mechanisms of the intestinal absorption of beta- carotene in humans. The general question under investigation is whether there are common mechanisms for the absorption of various fat-soluble dietary nutrients. We will test the hypothesis that the efficiency of intestinal absorption of cholesterol is positively correlated with the efficiency of the intestinal absorption of beta-carotene. We will test the hypothesis that beta-carotene is converted to vitamin A solely in the intestine. We will quantify the conversion of beta-carotene to vitamin A to test the hypothesis that increased absorption of beta-carotene is associated with increased conversion to vitamin A. 3. Modulation of macrophage function by dietary carotenoids. We will use the U937 cell line as well as human peripheral blood monocyte- macrophages to examine the partitioning of carotenoids into blood-borne cells and the effects of carotenoid enrichment on monocyte-macrophage function. We will test the hypothesis that plasma carotenoids partition into various blood cells as well as into plasma lipoproteins. We will test the hypothesis that carotenoid enrichment alters monocyte-macrophage phenotype, either enhancing or inhibiting potentially pro-atherosclerotic aspects of cell function including response to chemotactic stimuli, adhesion to endothelial cells, differentiation into macrophages, ability to oxidize LDL, and ability to form foam cells.