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Journal of Lipid Research, Vol. 48, 2028-2038, September 2007
Copyright © 2007 by American Society for Biochemistry and Molecular Biology

Mechanisms involved in vitamin E transport by primary enterocytes and in vivo absorption

Kamran Anwar^*,, Jahangir Iqbal and M. Mahmood Hussain^1,,

^* Molecular and Cellular Biology Program, School of Graduate Studies, State University of New York Downstate Medical Center, Brooklyn, NY 11203
Department of Anatomy and Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY 11203
Department of Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203

Published, JLR Papers in Press, June 20, 2007.

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

It is generally believed that vitamin E is absorbed along with chylomicrons. However, we previously reported that human colon carcinoma Caco-2 cells use dual pathways, apolipoprotein B (apoB)-lipoproteins and HDLs, to transport vitamin E. Here, we used primary enterocytes and rodents to identify in vivo vitamin E absorption pathways. Uptake of [³H]-tocopherol by primary rat and mouse enterocytes increased with time and reached a maximum at 1 h. In the absence of exogenous lipid supply, these cells secreted vitamin E with HDL. Lipids induced the secretion of vitamin E with intermediate density lipoproteins, and enterocytes supplemented with lipids and oleic acid secreted vitamin E with chylomicrons. The secretion of vitamin E with HDL was not affected by lipid supply but was enhanced when incubated with HDL. Microsomal triglyceride transfer protein inhibition reduced vitamin E secretion with chylomicrons without affecting its secretion with HDL. Enterocytes from Mttp-deficient mice also secreted less vitamin E with chylomicrons. In vivo absorption of [³H]-tocopherol by mice after poloxamer 407 injection to inhibit lipoprotein lipase revealed that vitamin E was associated with triglyceride-rich lipoproteins and small HDLs containing apoB-48 and apoA-I. These studies indicate that enterocytes use two pathways for vitamin E absorption. Absorption with chylomicrons is the major pathway of vitamin E absorption. The HDL pathway may be important when chylomicron assembly is defective and can be exploited to deliver vitamin E without increasing fat consumption.

Supplementary key words lipoproteins • tocopherol • HDL • chylomicrons • oleic acid

Abbreviations: apoA-I, apolipoprotein A-I; FPLC, fast-performance liquid chromatography; IDL, intermediate density lipoprotein; MTP, microsomal triglyceride transfer protein; OA, oleic acid; P407, poloxamer 407; pIpC, polyinosinic-polycytidylic ribonucleic acid

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