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Journal of Lipid Research, Vol. 47, 1261-1273, June 2006
Copyright © 2006 by American Society for Biochemistry and Molecular Biology

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
New York University Medical Center, New York, NY

Published, JLR Papers in Press, March 28, 2006.

¹ To whom correspondence should be addressed. e-mail: mahmood.hussain{at}downstate.edu

In hepatocytes, vitamin E is secreted via the efflux pathway and is believed to associate with apolipoprotein B (apoB)-lipoproteins extracellularly. The molecular mechanisms involved in the uptake, intracellular trafficking, and secretion of dietary vitamin E by the intestinal cells are unknown. 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 microsomal 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. In the absence of OA, vitamin E was associated 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 lipoproteins 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 specifically inhibited vitamin E secretion with chylomicrons. 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 contribute to vitamin E absorption in patients with abetalipoproteinemia receiving large oral doses of the vitamin.

Supplementary key words microsomal triglyceride transfer protein • lipoprotein assembly • triglycerides • cholesteryl esters • phospholipids • triacylglycerol • apolipoprotein B • tocopherol • abetalipoproteinemia

Abbreviations: apoB, apolipoprotein B; I-HDL, intestinal high density lipoprotein; MTP, microsomal triglyceride transfer protein; OA, oleic acid; SFM, serum-free medium; TC, taurocholate; TTP, -tocopherol transfer protein

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