Investigation of beta-carotene and lutein transport in Caco-2 cells: carotenoid-carotenoid interactions and transport inhibition by ezetimibe.

Carotenoid bioavailability is influenced by a number of factors including the presence of other carotenoids, which may enhance or inhibit the transport of one another by intestinal cells. Therefore, the objectives of the present study were: first, to determine carotenoid uptake and secretion (i. e. transport) by supplementing differentiated Caco-2 cells with increasing concentrations of either lutein or beta-carotene (0 - 1 microM); second, to assess any interactions between beta-carotene and lutein on their cellular uptake and secretion; and third, to a minor extent, to determine the effects of a carotenoid absorption inhibitor, ezetimibe, on beta-carotene and lutein transport. The carotenoid mixes were used at molar ratios of 1:1 and 4:1. At equimolar concentrations, lutein had a negative impact on beta-carotene transport and vice versa. However, these effects were not seen when the ratios were adjusted to 4:1. Following treatment with ezetimibe (25 - 100 microM) for 16 hours there was a reduction in beta-carotene transport, whereas a non-significant reduction in lutein transport was observed. In conclusion, this study confirmed that beta-carotene and lutein interact during their absorption, depending on the concentration/ratios used, and that carotenoid absorption is partially affected by ezetimibe.