Carotenoid uptake and secretion by CaCo-2 cells: β-carotene isomer selectivity and carotenoid interactions

Abstract

In presence of oleate and taurocholate, differentiated CaCo-2 cell monolayers on membranes were able to assemble and secrete chylomicrons. Under these conditions, both cellular uptake and secretion into chylomicrons of ␤ -carotene ( ␤ -C) were curvilinear, time-dependent (2-16 h), saturable, and concentration-dependent (apparent K m of 7-10 M) processes. Under linear concentration conditions at 16 h incubation, the extent of absorption of all-trans ␤ -C was 11% (80% in chylomicrons), while those of 9-cis-and 13-cis-␤ -C were significantly lower (2-3%). The preferential uptake of the all-trans isomer was also shown in hepatic stellate HSC-T6 cells and in a cell-free system from rat liver (microsomes), but not in endothelial EAHY cells or U937 monocyte-macrophages. Moreover, extents of absorption of ␣ -carotene ( ␣ -C), lutein (LUT), and lycopene (LYC) in CaCo-2 cells were 10%, 7%, and 2.5%, respectively. Marked carotenoid interactions were observed between LYC/ ␤ -C and ␤ -C/ ␣ -C. The present results indicate that ␤ -C conformation plays a major role in its intestinal absorption and that cis isomer discrimination is at the levels of cellular uptake and incorporation into chylomicrons. Moreover, the kinetics of cellular uptake and secretion of ␤ -C, the inhibition of the intestinal absorption of one carotenoid by another, and the cellular specificity of isomer discrimination all suggest that carotenoid uptake by intestinal cells is a facilitated process. -During, A., M. M. Hussain, D. W. Morel, and E. H. Harrison. Carotenoid uptake and secretion by CaCo-2 cells: ␤ -carotene isomer selectivity and carotenoid interactions. J.

Multiple, Independently Regulated Pathways of Cholesterol Transport across the Intestinal Epithelial Cells

“…For experiments, cells from 70 to 80% confluent flasks were seeded on polycarbonate micropore membrane inserts (Transwells®, 6-well plate, 24 mm diameter, 3 m pore size, Corning Costar Corp., Cambridge, MA) at a density of 1 ϫ 10 5 cells/cm 2 . To induce differentiation of these cells, media were changed every other day for 21 days (17)(18)(19). Experiments were conducted using two different pulse and pulse-chase labeling protocols.…”

Restoration of Central Macular Pigment Dip with Dietary RR Zeaxanthin Supplementation in Patients with AMD

“…The patients that received Mz supplementation showed no additional benefits in visual performance or macular pigment when compared to the subjects that received the traditional AREDS2 formula. Taken together, the respective papers by Nolan et al [30] and Akuffo et al [31] provide important insight in understanding how carotenoid supplementation affects AMD progression, but they ignore the effects of dietary Z in re-pigmenting the macula by using a small and non-variable supplemental dose of Z. Xanthophyll carotenoids were initially thought to be absorbed by passive diffusion, but identification of apical membrane transporters in intestinal enterocytes now point to an active absorption process [32]. This is supported by research demonstrating competitive inhibition between carotenoids [33], though the details of this physiological mechanism are still being researched.…”

Applicability of <i>in Vitro</i> Models in Predicting the <i>in Vivo</i> Bioavailability of Lycopene and <i>β</i>-Carotene from Differently Processed Soups

“…Lycopene uptake was higher for the optimised soup in Cell study 1, but not in Cell study 2. Cellular uptake of carotenoids has previously been shown to be linearly dependent on the amount of carotenoids added to the cells [17,23,24,34]. The higher uptake of β-carotene from the optimised soup may therefore have been due to the higher carotene concentration in the micellar fraction ( Table 2, Figures 3(a), (b)).…”

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