An in vitro model to study the intestinal absorption of carotenoids

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 β-carotene, α-carotene, lutein, lycopene were 11%, 2%, 3%, 10%, 7%, and 3%, respectively. Saturation of β-carotene transport through Caco-2 cells occurred at concentrations (>15 μM) higher than “physiological” concentrations. Finally, retinol supplementation resulted in an 1.7-fold increase in β-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 β-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.