13cIMH, 13-cis isomerohydrolase, ARAT, acyl-CoA:retinol acyltransferase, AREH, acid retinyl ester hydrolase, ATGL, adipose triglyceride lipase, BBB, blood-brain-barrier, BPL-B, brush-border phospholipase B, CE, cholesteryl ester, CEL, carboxyl ester lipase, CES, carboxylesterase, CGI-58, comparative gene identification 58, CM, chylomicron, CRBP1, cellular retinol-binding protein 1, DGAT1, acyl-CoA:diacylglycerol acyltransferase 1, ER, endoplasmic reticulum, Es2, esterase 2, Es3, esterase 3, Es4, esterase 4, Es10, esterase 10, Es22, esterase 22, FA, fatty acid, GPIHBP1, glycosylphosphatidylinositol-anchored high-density-lipoprotein binding protein 1 , GS2, gene sequence 2, HL, hepatic lipase, HSC, hepatic stellate cell, HSL, hormone-sensitive lipase, HSPG, heparan sulphate proteoglycan, ko, knock-out, LD, lipid droplet, LRAT, lecithin:retinol acyltransferase, LRP-1, low-density lipoprotein-receptor protein 1, LPL, lipoprotein lipase, MG, monoacylglycerol, MGL, monoglyceride lipase, NREH, neutral retinyl ester hydrolase, PL, phospholipid, PLRP2, pancreatic lipase-related protein 2, PNPLA, patatin-like phospholipase domain containing, PTL, pancreatic triglyceride lipase, RA, retinoic acid, RARα/β, retinoic acid receptor alpha/beta, RBP4, retinol-binding protein 4, RPE, retinal pigment epithelium, RXRα/β/γ, retinoid X receptor alpha/beta/gamma, RE, retinyl ester, REH, retinyl ester hydrolase, STRA6, stimulated by retinoic acid gene 6, STS, steroid sulfatase, TG, triacylglycerol, TIP47, tail-interacting protein of 47 kDa, VLDL, very low-density lipoprotein, wt, wild-type, Vitamin A, Retinyl ester hydrolase, Lipid droplet, Mobilization, Neutral lipid, Store
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.
► 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.