Disease relevance of retinyl esters

• These studies clearly show that activation of sensory transduction by unliganded opsin, and not the accumulation of retinyl esters, causes light-independent retinal degeneration in LCA [1].
• For comparison, concentrations of retinyl esters and retinol were determined in nine patients with type V hyperlipoproteinemia and nine control subjects, none of whom were using vitamin A supplements [2].
• Retinol and retinyl ester levels were determined in tissue samples of normal human kidney and renal cell carcinoma [3].
• Reduced levels of retinyl esters and vitamin A in human renal cancers [3].
• The clearance rate of chylomicron retinyl ester from plasma can be used to distinguish rats with cirrhosis from those with portacaval shunt [4].

Psychiatry related information on retinyl esters

• After adjusting for age, sex, race or ethnicity, education, smoking status, cotinine concentration, physical activity, fruit and vegetable intake, and vitamin or mineral use, participants with the metabolic syndrome had significantly lower concentrations of retinyl esters, vitamin C, and carotenoids, except lycopene [5].
• A concomitant alteration in vitamin-hormone status is observed with progressive metabolic alterations: low T3, T4, and elevated retinyl esters in subjects with the hypercarotenemia associated with anorexia nervosa [6].

High impact information on retinyl esters

• A genetic block of transducin signaling completely rescued degeneration irrespective of an elevated level of retinyl ester [1].
• It is not known whether the isomerization is enzyme-mediated, whether it occurs in the pigment epithelium or in the retina, or whether retinal, retinol, or a retinyl ester is the vitamin A compound that is isomerized [7].
• Lipid extract from the tissues was chromatographed on deactivated alumina to isolate retinol and retinyl esters, which were determined by specific spectrofluorometry [8].
• RESTs accumulate in Rpe65-/- mice incapable of carrying out the enzymatic isomerization, and correspondingly, are absent in the eyes of Lrat-/- mice deficient in retinyl ester synthesis [9].
• These structures form autonomous all-trans-retinyl ester-rich intracellular compartments distinct from other organelles and colocalize with adipose differentiation-related protein [9].

Chemical compound and disease context of retinyl esters

• Liver retinoid levels and the retinyl esters were examined in liver biopsy specimens from 70 patients with alcoholic and nonalcoholic liver diseases [10].
• Uptake and storage of retinol and retinyl esters in bone marrow of children with acute myeloid leukemia treated with high-dose retinyl palmitate [11].
• A significant reduction in plasma total antioxidant capacity, alpha-tocopherol, glutathione, retinol and retinyl esters content was observed in dropsy patients when compared to healthy controls [12].
• Serum vitamin A, retinyl esters and vitamin E in nephrotic syndrome [13].

Biological context of retinyl esters

• For example, the cellular retinol-binding protein, CRBP, has been implicated in retinol uptake, retinol esterification, mobilization of retinyl esters, and the initial oxidation of retinol to retinaldehyde [14].
• These results suggest that a three-compartment model of plasma retinyl ester disappearance kinetics gives important quantitative information about hepatic function [4].
• This review summarizes current knowledge about the identity, function, and regulation of the hepatic enzymes potentially involved in catalyzing the hydrolysis of retinyl esters [15].
• Rpe65 is a retinyl ester binding protein that presents insoluble substrate to the isomerase in retinal pigment epithelial cells [16].
• Retinyl ester in low density lipoprotein showed no effect either on cell differentiation or proliferation of any of the myeloid cells tested [17].

Anatomical context of retinyl esters

• Here we show that recombinant RPE65, when expressed in QBI-293A and COS-1 cells, has robust enzymatic activity of the previous unidentified isomerohydrolase, an enzyme converting all-trans retinyl ester to 11-cis retinol in the visual cycle [18].
• Our recent studies indicate that the metabolism of retinol to retinyl esters is greatly reduced in human carcinoma cell lines of the oral cavity, skin, and breast as compared with their normal epithelial counterparts, suggesting that human carcinoma cells are retinoid deficient relative to normal epithelial cells [3].
• Neither the activity of acyl coenzyme A:retinol acyl transferase nor the activity of retinyl ester hydrolase was altered in the mammary tumor compared to the normal mammary gland [19].
• Using two-photon microscopy and the intrinsic fluorescence of N-retinylamides, we showed that newly formed amides colocalize with the retinyl ester storage particles (retinosomes) in the retinal pigment epithelium [20].
• The microsomes from 3-day-old liver had greater esterifying ability than microsomes from adult liver, perhaps due to the presence of two retinyl ester synthase enzymes [21].

Associations of retinyl esters with other chemical compounds

• Effects of carbon tetrachloride treatment and portacaval shunt surgery on exogenous chylomicron retinyl ester clearance from rat plasma were analyzed assuming three-compartment model kinetics [4].
• The enzymatic properties of this neutral, bile salt-dependent retinyl ester hydrolase activity in liver homogenates are nearly identical to those observed in the present report for the in vitro hydrolysis of retinyl palmitate by purified rat pancreatic cholesteryl ester hydrolase (EC 3.1.1.13) [22].
• Lipoprotein cholesterol, triglyceride, and retinyl ester concentrations were measured in fractions separated by density gradient ultracentrifugation [23].
• The isomerization of all-trans-retinyl ester to 11-cis-retinol in the retinal pigment epithelium (RPE) is a critical step in the visual cycle and is essential for normal vision [24].
• With 21 microM IRBP and phase 2 incubations of > or = 10 min, the specific radioactivity of released 11-cis-retinal exceeded that of all-trans-retinyl ester in the RPE [25].

Gene context of retinyl esters

• We conclude that Lrat-/- mice may serve as an animal model with early onset severe retinal dystrophy and severe retinyl ester deprivation [26].
• When retinyl esters were allowed to form prior to the addition of the LRAT inhibitors, a significant amount of isomerization product was generated [27].
• Both transcription and translation were required, suggesting that signaling from the EGF receptor through the MAPK cascade controls the expression of modulators or inhibitors of the retinyl ester hydrolase(s) [28].
• During vitamin A deficiency, the additional loss of Adh1 completely prevented the excessive loss of liver retinyl esters observed in Crbp1-/- mice for the first 5 weeks of deficiency and greatly minimized this loss for up to 13 weeks [29].
• Lipoprotein lipase hydrolysis of retinyl ester. Possible implications for retinoid uptake by cells [30].

Analytical, diagnostic and therapeutic context of retinyl esters

• On the other hand, Eck fistula rats did experience dramatic increases in l3, implying that the hepatic uptake of chylomicron retinyl esters from compartment 3 was enhanced by portacaval shunting [4].
• Clinical application of the chylomicron retinyl ester clearance test is discussed for estimating hepatic function reserves and for differential diagnosis of portal hypertension [4].
• High performance liquid chromatography analysis of retinol and retinyl esters in adipocytes and media indicated that cAMP stimulated, in a time- and dose-dependent manner, retinol accumulation in the culture media and decreased cellular retinyl ester concentrations [31].
• Using data from the Third National Health and Nutrition Examination Survey (1988-1994), we compared circulating concentrations of vitamins A, C, and E; retinyl esters; five carotenoids; and selenium in 8,808 U.S. adults aged > or = 20 years with and without the metabolic syndrome [5].
• Employing anion exchange and gel filtration chromatography results in a partial purification of the retinyl ester synthetase (approximately 189-fold) [32].

References