ATP-binding cassette transporter A1 is significantly involved in the intestinal absorption of α- and γ-tocopherol but not in that of retinyl palmitate in mice

Abstract

Background: It has long been assumed that newly absorbed vitamin A and E enter the body only via enterocyte-produced chylomicrons. However, recent results in cell cultures have shown that a fraction of α-tocopherol is secreted with intestinal HDL. Objectives: The aims of this study were to identify this transporter and to assess whether it is significantly implicated in the in vivo intestinal absorption of the 2 main dietary forms of vitamin E (ie, α-and γ-tocopherol) and in that of retinyl palmitate (vitamin A). Design: Having performed preliminary experiments in the Caco-2 cell model, we compared fasting and postprandial plasma concentrations of vitamins A and E in mice deficient in ATP-binding cassette A1 (ABCA1) transporter and in wild-type mice. Results: A substantial efflux of α- and γ-tocopherol, but not of retinyl esters, was induced by the presence of apolipoprotein A-I at the basolateral side of Caco-2 monolayers. The efflux of α- and γ-tocopherol was also impaired by glyburide and 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. The postprandial response of plasma γ-tocopherol was 4-fold lower in ABCA1-/- mice (P = 0.025) than in wild-type mice, whereas no significant difference was observed for retinyl esters. Fasting plasma α-tocopherol, but not vitamin A, concentrations were lower in mice bearing the genetic deletion. Conclusions: ABCA1 is the transporter responsible for the in vivo secretion of α- and γ-tocopherol with intestinal HDL, and this pathway is significantly implicated in the intestinal absorption and plasma status of vitamin E but not of vitamin A. © 2009 American Society for Nutrition.