Abstract
A growing literature is dedicated to the understanding of carotenoid beneficial health effects. However, the absorption process of this broad family of molecules is still poorly understood. These highly lipophilic plant metabolites are usually weakly absorbed. It was long believed that β-carotene absorption (the principal provitamin A carotenoid in the human diet), and thus all other carotenoid absorption, was driven by passive diffusion through the brush border of the enterocytes. The identification of transporters able to facilitate carotenoid uptake by the enterocytes has challenged established statements. After a brief overview of carotenoid metabolism in the human upper gastrointestinal tract, a focus will be put on the identified proteins participating in the transport and the metabolism of carotenoids in intestinal cells and the regulation of these processes. Further progress in the understanding of the molecular mechanisms regulating carotenoid intestinal absorption is still required to optimize their bioavailability and, thus, their health effects.
Highlights
Carotenoids are hydrophobic molecules synthesized by plants and by some microorganisms
Other carotenes derive from lycopene by cyclization and dehydrogenation, and xanthophylls derive from carotenes by oxidation [4] (Table 1)
As SR-BI is involved in the uptake of vitamin D [37], E [38], and K [39], in cultured cells and in mice, we suggest that another primary role of SR-BI in the gut is the transport of minor molecules, such as fat-soluble vitamins and carotenoids
Summary
Carotenoids are hydrophobic molecules synthesized by plants and by some microorganisms (bacteria, algae, or fungi). New investigations have carotenoid are, atatat least inin vitro, powerful radical quenchers. New investigations have carotenoid are, least in vitro, powerful radical quenchers. After a short description of carotenoid fate the human upper gastrointestinal lumen, afocus focus will be put on the identified proteins participating in carotenoid transport and metabolism in will be put on the identified proteins participating in carotenoid transport and metabolism in cells and on the regulation of these processes.
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