β-Apo-13-carotenone

β-apo-13-Carotenone is identified as enzymatic cleavage products of β-carotene in homogenates of intestinal mucosa of rat. β-apo-13-carotenone is found to antagonize the activation of RXRα by 9-cis-retinoic acid and is effective at concentrations as low as 1nM. Molecular modeling studies reveal that β-apo-13-carotenone makes molecular interactions like an antagonist of RXRα. β-apo-13-carotenone competes for 9cRA binding to RXRα with an affinity (7–8 nM) identical to 9cRA itself. β-apo-13-carotenone antagonizes 9cRA activation of full-length hRXRα with a similar efficiency as the known antagonist UVI3003. β-apo-13-carotenone induces formation of the RXRα transcriptionally silent tetramer but does not inhibit coactivator recruitment to the isolated LBD. The uptake and/or metabolism of β-apo-13-carotenone does not allow for accumulation of these β-carotene metabolites in cells. 3T3-L1 adipocyte marker gene expression is induced by β-apo-carotenoid treatment.