β-Carotene in the human body: metabolic bioactivation pathways – from digestion to tissue distribution and excretion
Résumé
β-Carotene intake and tissue/blood concentrations have been associated with reduced inci-
dence of several chronic diseases. Further bioactive carotenoid-metabolites can modulate
the expression of specific genes mainly via the nuclear hormone receptors: retinoic acid
receptor- and retinoid X receptor-mediated signalling. To better understand the metabolic
conversion of β-carotene, inter-individual differences regarding β-carotene bioavailability
and bioactivity are key steps that determine its further metabolism and bioactivation and
mediated signalling. Major carotenoid metabolites, the retinoids, can be stored as esters
or further oxidised and excreted via phase 2 metabolism pathways. In this review, we aim
to highlight the major critical control points that determine the fate of β-carotene in the
human body, with a special emphasis on β-carotene oxygenase 1. The hypothesis that higher
dietary β-carotene intake and serum level results in higher β-carotene-mediated signalling is
partly questioned. Alternative autoregulatory mechanisms in β-carotene / retinoid-mediated
signalling are highlighted to better predict and optimise nutritional strategies involving β-carotene-related health beneficial mediated effects.
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