Comparison of the uptake and secretion of carotene and xanthophyll carotenoids by Caco-2 intestinal cells

Carotenoids have been shown to have potential beneficial effects on human health which has led to an increasing interest in the study of their bioavailability. A Caco-2 cell model, as previously described, was employed to examine the percentage transfer of the carotenoids alpha-carotene, beta-carotene, lycopene, astaxanthin, beta-cryptoxanthin, lutein and zeaxanthin through an intact, highly differentiated Caco-2 cell monolayer at a range of different amounts. Our results show that astaxanthin, a carotenoid with powerful antioxidant capacity, had the highest percentage transfer overall. We examined the cellular uptake and secretion of lutein and zeaxanthin to compare two structurally similar carotenoids. Both were efficiently transported through the monolayer with a range between 5.1 (sem 1.2) % to 20.2 (sem 3.3) % and 5.5 (sem 2.5) % to 13.4 (sem 4) % for lutein and zeaxanthin, respectively. These carotenoids were compared to each other at each added amount and no significant difference was observed between the two xanthophylls. The carotene carotenoids alpha-carotene, beta-carotene and lycopene and the xanthophyll beta-cryptoxanthin were also examined and had lower uptake and secretion values when compared to lutein, zeaxanthin and astaxanthin. The xanthophyll beta-cryptoxanthin was also not significantly different when compared to the carotene carotenoids. Data generated from this study compares well with in vivo bioavailability studies. Furthermore, the model provides comparative data on the relative absorption and transfer of seven different carotenoids. Our data indicate that lower amounts of carotenoids were absorbed and transferred more efficiently than higher amounts suggesting a saturation effect at higher exposure.