Transport of vitamin E by differentiated Caco-2 cells

J Lipid Res. 2006 Jun;47(6):1261-73. doi: 10.1194/jlr.M500523-JLR200. Epub 2006 Mar 28.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Apolipoproteins A / metabolism
  • Biological Transport
  • Caco-2 Cells
  • Carrier Proteins / metabolism
  • Carrier Proteins / physiology
  • Cell Differentiation*
  • Cholesterol Esters / metabolism
  • Chylomicrons / metabolism
  • Chylomicrons / physiology
  • Humans
  • Intestinal Mucosa / metabolism
  • Intestines / cytology
  • Lipoproteins, HDL / metabolism
  • Models, Biological
  • Signal Transduction / physiology
  • Vitamin E / metabolism*
  • Vitamin E / pharmacokinetics

Substances

  • Apolipoproteins A
  • Carrier Proteins
  • Cholesterol Esters
  • Chylomicrons
  • Lipoproteins, HDL
  • microsomal triglyceride transfer protein
  • Vitamin E