Cluster of Differentiation 36 (CD36) Preferentially Mediates Intestinal Absorption of Dietary Z -Astaxanthin and Especially 9- Z -Isomer via Higher Binding Affinity.

Variances in the biological functions of astaxanthin geometric isomers (i.e., all- E , Z ) are related to their intestinal absorption, but the mechanism of isomer absorption mediated by transporters remains unclear. Here, models of in vitro cell overexpression, in situ intestinal perfusion, and in vivo mouse inhibition were employed to investigate the impact of cluster of differentiation 36 (CD36) on the absorption of astaxanthin isomers. Cells overexpressing CD36 notably enhanced the uptake of Z -astaxanthin, particularly the 9- Z -isomer (47.76%). The absorption rate and permeability of Z -astaxanthin surpassed that of the all- E -isomer by the in situ model. Furthermore, the addition of the CD36-specific inhibitor sulfo- N -succinimidyl oleate significantly reduced the absorption of Z -astaxanthin in the mouse duodenum and jejunum, especially the 9- Z -isomer (57.66%). Molecular docking and surface plasmon resonance techniques further validated that 9- Z -astaxanthin binds to more amino acids of CD36 with higher affinity and in a fast-binding, fast-dissociating mode, thus favoring transport. Our findings elucidate, for the first time, the mechanism of the CD36-mediated transmembrane transport of astaxanthin geometric isomers.