Anwar - Transport of vitamin E by differentiated Caco-2...

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Unformatted text preview: Transport of vitamin E by differentiated Caco-2 cells Kamran Anwar, * Herbert J. Kayden, † and M. Mahmood Hussain 1, * Departments of Anatomy & Cell Biology and Pediatrics,* State University of New York Downstate Medical Center, Brooklyn, NY; and New York University Medical Center, † New York, NY Abstract In hepatocytes, vitamin E is secreted via the ef- flux pathway and is believed to associate with apolipoprotein B (apoB)-lipoproteins extracellularly. The molecular mech- anisms involved in the uptake, intracellular trafficking, and secretion of dietary vitamin E by the intestinal cells are un- known. We observed that low concentrations of Tween-40 were better for the solubilization and delivery of vitamin E to differentiated Caco-2 cells, whereas high concentrations of Tween-40 and sera inhibited this uptake. Vitamin E uptake was initially rapid and then reached saturation. Subcellular localization revealed that vitamin E primarily accumulated in microsomal membranes. Oleic acid (OA) treatment, which induces chylomicron assembly and secretion, decreased mi- crosomal membrane-bound vitamin E in a time-dependent manner. To study secretion, differentiated Caco-2 cells were pulse-labeled with vitamin E and chased in the presence and absence of OA. Inthe absence ofOA, vitaminE wasassociated with intestinal high density lipoprotein (I-HDL), whereas OA- treated cells secreted vitamin E with I-HDL and chylomicrons. No extracellular transfer of vitamin E between these lipo- proteins was observed. Glyburide, an antagonist of ABCA1, partially inhibited its secretion with I-HDL, whereas plasma HDL increased vitamin E efflux. An antagonist of microsomal triglyceride transfer protein, brefeldin A, and monensin specificallyinhibited vitaminE secretionwithchylomicrons. These studies indicate that vitamin E taken up by Caco-2 cells is stored in the microsomal membranes and secreted with chylomicrons and I-HDL. Transport via I-HDL might contrib- ute to vitamin E absorption in patients with abetalipoprotein- emia receiving large oral doses of the vitamin.— Anwar, K., H. J. Kayden, and M. M. Hussain. Transport of vitamin E by differentiated Caco-2 cells. J. Lipid Res. 2006. 47: 1261–1273. Supplementary key words microsomal triglyceride transfer protein . lipoprotein assembly . triglycerides . cholesteryl esters . phospholipids . triacylglycerol . apolipoprotein B . tocopherol . abetalipoproteinemia Vitamin E is a major lipid-soluble antioxidant and is an essential nutrient for normal growth and development. Its deficiency results in neurological dysfunction, muscular weakness, and reproductive failure (1–3). Although a diet rich in vegetable oils and whole grains is a sufficient source of vitamin E in normal people (4), deficiency can result because of lipid malabsorption syndromes such as abeta- lipoproteinemia, a disease in which apolipoprotein B (apoB)-containing lipoproteins (chylomicrons, very low density lipoproteins, and low density lipoproteins) are...
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This note was uploaded on 11/21/2010 for the course NUT 72880 taught by Professor Clifford during the Fall '10 term at UC Davis.

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Anwar - Transport of vitamin E by differentiated Caco-2...

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