Accumulation and retention of micellar β-carotene and lutein by Caco-2 human intestinal cells

Despite the interest in the diverse roles of dietary carotenoids in human health, little is known about the transfer of these plant pigments from foods to micelles during digestion and their subsequent transfer across the intestinal epithelium. We conducted this study to characterize the intestinal uptake of micellarized carotenoids using monolayers of differentiated Caco-2 human intestinal cells. Crystalline beta-carotene (BC) and lutein (LUT), solubilized in mixed micelles for delivery to cells, were stable in a tissue culture environment for 20 hours. Cellular accumulation of micellar BC and LUT was proportional to the media content of carotenoids at greater than or equal to 2 mu mol/L and the length of exposure. Cellular accumulation of BC routinely exceeded LUT and was dire in part to the enhanced efflux or possible metabolism of LUT. Cellular BC content increased in a curvilinear manner when cultures were incubated in micellar medium containing 2 to 27 mu mol/L BC prepared from water miscible beadlets: cellular BC content was maximum when medium BC was greater than or equal to 18 mu mol/L. There was no indication that high levels of BC in medium or within cells adversely affected micellar LUT accumulation. These data support the use of the Caco-2 human cell line as a model for studying the intestinal uptake, absorption, and possible interactions of dietary carotenoids. (C) Elsevier Science Inc. 1999. All rights reserved.