AN INVITRO MODEL TO STUDY THE INTESTINAL ABSORPTION OF CAROTENOIDS

Authors: DURING, ALEXANDRINE - JHU, BALTIMORE, MD; Harrison, Earl

Submitted to: Food Research International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2005
Publication Date: 10/4/2005
Citation: During, A., Harrison, E.H. 2005. An invitro model to study the intestinal absorption of carotenoids. Food Research International. 38:1001-1008.

Interpretive Summary: Fundamental aspects of the intestinal absorption of carotenoids are still unknown. Given the limitations of using humans for these kinds of investigations, an in vitro intestinal cell culture system using the human colonic adenocarcinoma cell line, Caco-2, and mimicking the in vivo intestinal absorption of carotenoids was reported here. The data generated from the in vitro system were validated against in vivo data from human studies. For example, the extent of absorption (11%) of all-trans b-C through Caco-2 cell monolayers was within the in vivo data range (3-22%). These data and several in vivo reports also converge to indicate that 1) there is a discrimination between b-C isomers occurring during the intestinal absorption process, 2) LYC is poorly absorbed compared to other carotenoids, and 3) vitamin A supplementation resulted in the increase of intestinal transport of b-C. Additional mechanistic information given by using the in vitro model suggest that 1) the intestinal absorption of carotenoids is facilitated by the participation of a specific epithelial transporter and 2) retinol increases beta-carotene absorption by facilitating its incorporation into larger, retinyl ester-enriched chylomicrons. The present in vitro cell culture system is a relevant and simple model to study the molecular mechanisms of the intestinal absorption of carotenoids.

Technical Abstract: An in vitro cell culture model to assess the intestinal absorption of carotenoids is described. When supplemented with taurocholate and oleic acid, differentiated Caco-2 cells on membranes are able to produce chylomicrons. Under conditions mimicking the in vivo postprandial state, Caco-2 cells take up carotenoids and secrete them incorporated into chylomicrons; the extents of absorption of all-trans-, 9-cis-, 13-cis- beta-carotene, '-carotene, lutein, lycopene were 11%, 2%, 3%, 10%, 7%, and 3%, respectively. Saturation of beta-carotene transport through Caco-2 cells occurred at concentrations (>15'M) higher than “physiological” concentrations. Finally, retinol supplementation resulted in a 1.7-fold increase in beta-carotene transport. The data suggest that 1) the intestinal absorption of carotenoids is facilitated by the participation of a specific epithelial transporter and 2) retinol promotes beta-carotene incorporation into larger, retinyl ester-enriched chylomicrons. The present in vitro cell culture system is a relevant model to study the intestinal absorption of carotenoids at the molecular level.