Retinoic acid homeostasis: Retinoic acid regulates liver retinol esterification as well as its own catabolic oxidation in liver

Abstract

Retinol is stored in liver in the form of its esters. The retinol-esterifying enzyme lecithin:retinol acyltransferase (LRAT) catalyzes the conversion of retinol into its storage form. Expression of the LRAT mRNA is induced by retinoic acid (RA), or by dietary vitamin A, and is downregulated upon vitamin A depletion. RA also induces the expression in liver of the mRNA for CYP26, the enzyme that disposes of excess RA by oxidizing RA to 4-oxo-RA. CYP26 is downregulated upon vitamin A depletion.