Retinyl ester hydrolases and their roles in vitamin A homeostasis ^☆

Abstract

In mammals, dietary vitamin A intake is essential for the maintenance of adequate retinoid (vitamin A and metabolites) supply of tissues and organs. Retinoids are taken up from animal or plant sources and subsequently stored in form of hydrophobic, biologically inactive retinyl esters (REs). Accessibility of these REs in the intestine, the circulation, and their mobilization from intracellular lipid droplets depends on the hydrolytic action of RE hydrolases (REHs). In particular, the mobilization of hepatic RE stores requires REHs to maintain steady plasma retinol levels thereby assuring constant vitamin A supply in times of food deprivation or inadequate vitamin A intake. In this review, we focus on the roles of extracellular and intracellular REHs in vitamin A metabolism. Furthermore, we will discuss the tissue-specific function of REHs and highlight major gaps in the understanding of RE catabolism. This article is part of a Special Issue entitled Retinoid and Lipid Metabolism.

Highlights

► For the maintenance of constant vitamin A supply retinyl ester hydrolases are required. ► This review summarizes the current knowledge on the roles of retinyl ester hydrolyses in vitamin A metabolism. ► In addition, it discusses tissue-specific functions of retinyl ester hydrolases and highlights major gaps in the understanding of retinyl ester catabolism.