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At least 19 recordsLinked to original sources
PubMed2000

Accumulated lipids, aberrant fatty acid composition and defective cholesterol ester hydrolase activity in cholesterol ester storage disease.

We confirmed accumulation of glycogen and lipids, particularly cholesterol esters, in the liver of a patient with cholesterol ester storage disease (CESD). Hepatic cholesterol ester concentration was 100-200 times that found in normal livers. Analysis of the fatty acid composition indicated a higher proportion (41%) of cholesterol linoleate (C18-2), a slightly lower proportion (33%) of cholesterol oleate (C18-1) and normal proportions (14%) of cholesterol palmitate (C16-0) in the CESD patient compared with the control. This fatty acid composition of cholesterol esters and the fatty acid composition of other classes of lipids in the patient's liver resembled that of LDL. We also found that acid cholesterol ester hydrolase activity in the CESD liver was reduced to 5% of that in the control liver, while neutral cholesterol ester hydrolase activity remained at the control level. These results suggest that accumulated cholesterol esters were derived mainly from serum LDL and that the accumulation resulted from lack of acid cholesterol ester hydrolase.

Child, Preschool↗
PubMed1975

The effect of dietary rape-seed oil on cholesterol-ester metabolism and cholesterol-ester-hydrolase activity in the rat adrenal.

The effects of stock diet and stock diet supplemented by olive oil and rape seed on rat adrenal cholesterol ester metabolism have been studied. Rats fed rape seed oil failed to gain weight at the same rate as rats fed olive oil. A prominent feature of the rats fed rape seed oil was an accumulation of high concentrations of cholesterol erucate in the adrenal lipid droplets. When these rats were subjected to an ether stress no percentage decrease in the amount of cholesterol erucate was observed. Adrenal cholesterol ester hydrolase activity was higher in rats fed the olive oil and rape seed oil diets than rats fed the stock diet. In rats fed stock or olive oil diets, a ten-minute ether anaesthesia stress resulted in a two-fold increase in activity of adrenal cholesterol ester hydrolase. Cofactor addition of ATP, cyclic AMP and MgCl-2 in vitro resulted in a stimulation of cholesterol ester hydrolase to a similar activity in both quiescent and ether-stressed rats. By contrast rats fed the rape seed oil diet gave no significant stimulation of cholesterol ester hydrolase activity when given an ether stress or when cofactors were added in vitro. Cholesterol erucate was hydrolysed at only 25% to 30% of the rate of cholesterol oleate in vitro in all groups of animals. Oleic acid added in vitro gave an inhibition of cholesterol ester hydrolase activity in rats fed stock diet while erucic acid activated the enzyme. The accumulation of cholesterol erucate in the adrenal when rats are fed rape seed oil could be due to the reduced ability of cholesterol ester hydrolase to hydrolyse this ester.

Adenosine Triphosphate↗
PubMed1997

Omega-3 fatty acid intake results in a relationship between the fatty acid composition of LDL cholesterol ester and LDL cholesterol content in humans.

The relationship between the fatty acid composition of the low density lipoprotein (LDL) cholesterol ester and LDL cholesterol content was assessed in 26 free-living, normal subjects. Dietary intakes of 14:0, 16:0, 18:0, 18:1, 18:2omega6, 18:3omega3, 20:4omega6, 20:5omega3, 22:6omega3 were calculated from seven-day food records kept by each subject at baseline and after three months of supplementation with olive, flaxseed or fish oil, respectively. A randomized cross-over design was used. The fatty acid content of specific foods was calculated. Fasting blood samples, taken at the beginning and end of each supplementation period, were analyzed for the fatty acid content present in individual lipoproteins. There was a significant correlation between 20:5omega3 and 22:6omega3 intake and the content of these fatty acids in the LDL cholesterol ester fraction. During the fish oil treatment period the 16:0 and 18:0 content of the LDL cholesterol ester was highly predictive of LDL cholesterol content. This relationship was not observed during the baseline or placebo (olive oil) supplement period.

Adult↗
PubMed2002

Interaction of the Vibrio cholerae cytolysin (VCC) with cholesterol, some cholesterol esters, and cholesterol derivatives: a TEM study.

The Vibrio cholerae cytolysin (VCC) 63-kDa monomer has been shown to interact in aqueous suspension with cholesterol microcystals to produce a ring/pore-like heptameric oligomer approximately 8 nm in outer diameter. Transmission electron microscopy data were produced from cholesterol samples adsorbed to carbon support films, spread across the holes of holey carbon films, and negatively stained with ammonium molybdate. The VCC oligomers initially attach to the edge of the stacked cholesterol bilayers and with increasing time cover the two planar surfaces. VCC oligomers are also released into solution, with some tendency to cluster, possibly via the hydrophobic membrane-spanning domain. At the air/water interface, the VCC oligomers are likely to be selectively oriented with the hydrophobic domain facing the air. Despite some molecular disorder/plasticity within the oligomers, multivariate statistical analysis and rotational self-correlation using IMAGIC-5 strongly suggest the presence of sevenfold rotational symmetry. To correlate the electron microscopy data with on-going biochemical and permeability studies using liposomes of varying lipid composition, the direct interaction of VCC with several cholesterol derivatives and other steroids has been examined. 19-Hydroxycholesterol and 7 beta-hydroxycholesterol both induce VCC oligomerization. beta-Estradiol, which does not possess an aliphatic side chain, also efficiently induces VCC oligomer formation, as does cholesteryl acetate. Cholesteryl stearate and oleate and the C22 (2-trifluoroacetyl)naphthyloxy analogue of cholesterol fail to induce VCC oligomerization, but binding of the monomer to the surface of these steroids does occur. Stigmasterol has little tendency to induce oligomer formation, and oligomers are largely confined to the edge of the bilayers; ergosterol has even less oligomerization ability. Attempts to solubilize and stabilize the VCC oligomers from cholesterol suspensions have been pursued using the neutral surfactant octylglucoside. Although individual solubilized oligomers have been defined which exhibit a characteristic cytolysin channel conformation in the side-on orientation, a tendency remains for the oligomers to cluster via their hydrophobic domains.

Cholesterol↗
PubMed1984

Cholesterol ester and triglyceride metabolism in intact fibroblasts from patients with Wolman's disease and cholesterol ester storage disease.

Cholesterol ester and triglyceride metabolism was examined in intact fibroblast monolayers from normal individuals and patients with Wolman's disease and cholesterol ester storage disease. Cholesterol esters were introduced into cells by incubation in medium containing [3H]cholesteryl linoleate (CL) bound to human low density lipoprotein. Triglycerides were introduced by incubation with glycerol tri[1-14C]oleate (triolein) bound to human very low-density lipoprotein. Both types of mutant cell lines accumulated the unhydrolyzed substrates to a greater extent than did normal cells with the greatest accumulation observed in Wolman's disease cells. Wolman's disease cells hydrolyzed CL at 10-22% and triolein at 11-19% the rate of normal cells; cholesterol ester storage disease cells hydrolyzed these substrates at 28-49 and 30-47% the normal rate, respectively. In contrast, assays of acid lipase activity in cell lysates revealed less than 1% of control activity in both disorders. The data suggest that the mutant acid lipase present in Wolman's disease and cholesterol ester storage disease is more active in the intact cell than assays of cell lysates would indicate. In addition, the differences observed between the two disorders provide a biochemical explanation for the different phenotypes associated with the two disorders.

Cell Line↗
PubMed2004

Metabolism of cholesterol ester of apolipoprotein B100-containing lipoproteins in dogs: evidence for disregarding cholesterol ester transfer.

BACKGROUND: It has been shown that dogs exhibit no cholesterol ester transfer protein (CETP) activity in vitro, in contrast to humans. The aim of our study was to determine modalities of in vivo plasma cholesterol ester turnover in this species, using a kinetic approach with stable isotopes. MATERIALS AND METHODS: Kinetics of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) were studied in seven adult male Beagle dogs using a dual isotope approach through endogenous labelling of both their cholesterol moiety and their protein moiety. A primed constant infusion of both [1,2(13)C]acetate and [5,5,5-2H3]leucine enabled us to obtain measurable deuterium enrichments by gas chromatography-mass spectrometry for plasma leucine and apoB100, as well as measurable 13C enrichment by gas chromatography-combustion-isotopic ratio mass spectrometry for unesterified cholesterol and cholesterol ester in the VLDL and LDL. Two identical multicompartmental models (SAAM II) were used together for the analysis of tracer kinetics' data of proteins and cholesterol. RESULTS: Characterization of the apoB100-containing lipoprotein cholesterol ester model allowed determination of kinetic parameters of VLDL and LDL cholesterol ester metabolism. We succeeded in modelling VLDL and LDL cholesterol ester metabolism and apoB100 metabolism simultaneously. Fractional catabolic rate (FCR) of apoB100 and CE had the same values. Introducing cholesterol ester transfer between lipoproteins in the model did not significantly improve the fit. Total VLDL FCR was 2.97 +/- 01.47 h(-1). Approximately one-quarter corresponded to the direct removal of VLDL (0.81 +/- 00.34 h(-1)) and the remaining three-quarters corresponded to the fraction of VLDL converted to LDL, which represented a conversion of VLDL into LDL of 2.16 +/- 01.16 h(-1). Low-density lipoproteins were produced exclusively from VLDL conversion and were then removed (0.031 +/- 0.004 h(-1)) from plasma. CONCLUSION: These kinetic data showed that VLDL cholesterol ester and LDL cholesterol ester metabolism followed VLDL and LDL apoB100 metabolism, and that consequently there is no in vivo transfer of cholesterol ester in dogs.

Animals↗
PubMed1977

Cholesterol ester accumulation in cultured aortic smooth muscle cells. Induction of cholesterol ester retention by chloroquine and low density lipoprotein and its reversion by mixtures of high density apolipoprotein and sphingomyelin.

Accretion of cholesterol ester was studied in rat aortic smooth muscle cells in culture. Confluent multilayers of smooth muscle cells were exposed to human low density lipoprotein (LDL) and chloroquine and this treatment resulted in a very marked increase in cellular cholesterol ester. The degree of enrichment in cholesterol ester was related inversely to the cell density in the petri dish and was maximal in 48 h. The morphological changes after 48 h incubation with chloroquine and LDL consisted of accumulation of numerous membrane-bound inclusions containing electron-dense and electron-lucent material, some of which resembled secondary lysosomes. These changes resembled some of the changes observed in human and experimental atheromatosis. Similar inclusions were seen also in cultured human skin fibroblasts which accumulated large amounts of cholesterol ester during 48 h incubation with LDL and chloroquine. Removal of the accumulated cellular cholesterol ester was studied in the two cell types and it was markedly enhanced in the presence of lipoprotein-deficient serum and high density apolipoprotein-sphingomyelin mixture. The morphological findings after 24 h of post incubation revealed the presence of empty vacuoles, membrane whorls and cytoplasmic lipid droplets. The present results indicate that aortic smooth muscle cells in culture can serve as a good model to study the role of the lysosomal system in atherogenesis.

Adult↗
PubMed1989

Lipolytic enzymes of the human pancreas. II. Purification and properties of cholesterol ester hydrolase.

Cholesterol ester hydrolase (sterol-ester acylhydrolase, EC 3.1.1.13) was purified from human pancreatic tissue by column chromatography and acetone precipitation, leading to a 400-fold enrichment. Isoelectric focusing of this product reveals a double-band at pH 4.5 and 4.6. The molecular weight was estimated at 320 kDa by means of Sephadex filtration on calibrated columns. Obviously these large molecules represent a tetrameric form of the monomeric subunit (molecular mass 76-80 kDa), which is also enzymatically active. It was found together with the dimeric form in pancreatic juice, where the tetrameric enzyme is responsible for the major part of the hydrolytic activity, splitting cholesterol ester as well as synthetic substrates, such as fluorescein or p-nitrophenyl esters. Attempts to split the tetrameric cholesterol ester hydrolase, isolated from pancreatic tissue, into active subunits found additionally in pancreatic juice by the influence of bile acids and proteolytic enzymes failed. The spectral shift method using Rhodamine fluorescence was employed in order to prove that fluorescein dilaurate forms micellar solutions and mixed micelles when bile salts are present.

Acetone↗
PubMed1982

Relationships between circadian cycles of rat adrenal cholesterol ester metabolizing enzymes, cholesterol, ascorbic acid, and corticosteroid secretion.

The circadian changes in rat adrenal cholesterol ester (CE) metabolism have been studied and related to the circadian changes in adrenal ascorbic acid and corticosterone levels and plasma corticosterone levels. Significant declines in the ratio of CE/C, cholesterol esterase (CEase) and acyl CoA:cholesterol acyl transferase (ACAT) activities occur during the peak and declining phases of adrenal and plasma corticosteroids, suggesting that when there is a decreased need for steroid precursors the amount of stored CE is decreased, and that the enzymes involved in CE metabolism decline in activity. Adrenal ascorbic acid has a biphasic rhythm with peaks at 0900 and 2200 h. The rhythm of ascorbic acid appears to be inverse to that of ACAT activity, suggesting possible relationships between the two parameters.

Acyltransferases↗
PubMed1975

Increased cholesterol-ester formation during forced cholesterol synthesis in rat hepatocytes.

By comparing the incorporation of 3H20 and [14C]mevalonate into cholesterol in suspensions of rat hepatocytes, it was calculated that the cholesterol biosynthesis could be stimulated 4--7-fold by addition of mevalonate. The addition of 3.3--6.7 mM mevalonate also caused a 5--6-fold increase in the proportion of newly synthesized cholesterol that was esterifield. The esterification of radioactive cholesterol, entering the cells by exchange with surrounding plasma lipoproteins was also increased, indicating that a true increase in the rate of cholesterol ester formation rather than a more selective utilization of newly synthesized cholesterol for esterification, occurred. The increase in cholesterol esterification was not abolished by cycloheximide, indicating that it did not require an increased synthesis of cholesterol esterifying enzyme. Instead the data suggest that the supply of cholesterol to the esterifiable pool may be an important factor, regulating the rate of cholesterol ester formation in rat liver. The addition of 0.5 mM oleic acid to the medium did not increase the degree of cholesterol esterification significantly, whereas 2 mM oleic acid bound to 1% albumin increased the proportion of newly synthesized cholesterol that was esterified, by about 70%. The cells secreted radioactive cholesterol esters into the medium. Cycloheximide inhibited this secretion to about 80% but did not affect the rate at which newly synthesized cholesterol was transferred to surrounding plasma lipoproteins.

Animals↗
PubMed1978

Study of cultured skin fibroblasts from patients with and without ischemic heart disease. Metabolism of low density lipoprotein and cholesterol ester, synthesis of cellular lipids and effect of chloroquine on accumulation of cholesterol ester.

The aim of the present study was to determine whether skin fibroblasts derived from patients with ischemic heart disease (IHD), which could not be related to accepted risk factors, would show a metabolic abnormality with respect to lipid or lipoprotein metabolism. Male patients 30-52 years old suffering from IHD were subdivided into two groups: those in whom IHD was not associated with risk factors such as hypertension, hyperlipoproteinemia, diabetes or smoking (group I); and those in whom heavy smoking was the only major risk factor recognized (group II). The controls were patients with angiographically normal coronary arteries (group III). Skin fibroblasts obtained from these patients were cultured and investigated with respect to metabolism of low density lipoprotein (LDL), synthesis of cellular lipids and induction of cholesterol ester accumulation in the presence of chloroquine, an inhibitor of lysosomal hydrolases. After 24 h incubation, the uptake and degradation of LDL protein in cells from patients of group II was significantly higher than in the controls, group III, but not different from those of group I. Hydrolysis of [3H] cholesterol linoleate, and incorporation of [3H] oleic acid into total lipids and into cholesterol esters was similar in cell cultures of the 3 groups studied. After exposure to chloroquine and LDL, the cells from the different donors accumulated cholesterol ester to a similar extent. Thus, whereas no significant difference was encountered in the lipid and lipoprotein metabolism in cells of patients with IHD without risk factors and controls, some increase in LDL metabolism was seen in cells from patients with IHD and with a history of smoking. It remains to be determined whether this increase was causally related to smoking.

Adult↗
PubMed1993

Cholesterol esters selectively delivered in vivo by high-density-lipoprotein subclass LpA-I to rat liver are processed faster into bile acids than are LpA-I/A-II-derived cholesterol esters.

High-density lipoprotein (HDL) subclass LpA-I has been reported to promote cholesterol efflux from mouse adipose cells in vitro, whereas subclass LpA-I/A-II has no effect. To investigate whether the apolipoprotein composition of HDL plays a role in the selective delivery of cholesterol esters to the liver in vivo, we labelled HDL in its cholesterol ester moiety and separated [3H]cholesterol oleate-labelled HDL into subclasses LpA-I and LpA-I/A-II by immuno-affinity chromatography. Serum decay and liver association of LpA-I and LpA-I/A-II were compared for the apoprotein and cholesterol ester moieties. Both LpA-I and LpA-I/A-II selectively delivered cholesterol esters to the liver with similar kinetics. The kinetics of biliary secretion of processed cholesterol esters, initially associated with LpA-I or LpA-I/A-II, were studied in rats equipped with permanent catheters in bile, duodenum and heart. For both LpA-I and LpA-I/A-II, liver association was coupled to bile acid synthesis, with an increase in secretion rate during the night. During the first night period, the biliary secretion of LpA-I-derived radio-activity was significantly greater than for LpA-I/A-II. The data indicate that with both LpA-I and LpA-I/A-II selective delivery of cholesterol esters from HDL to the liver occurs, but that cholesterol esters delivered by LpA-I are more efficiently coupled to bile acid synthesis.

Animals↗
PubMed1986

Cholesterol ester hydrolase(s) in mammalian brain: is there a myelin-specific cholesterol ester hydrolase?

The present study compared the properties of cholesterol ester hydrolase(s) in myelin and microsomes from rat, mouse and human brain. The results indicated that the enzyme activity in both myelin and microsomes from rat, mouse and human brain was optimal at pH 6.5 and required Triton X-100 for optimal activity. The enzyme activity in myelin was 3- to 4-fold higher in the presence of Triton X-100 than taurocholate. Addition of phosphatidyl serine enhanced (2 to 4 fold) the hydrolase activity in both myelin and microsomes. The properties of the enzyme in solubilized preparation of myelin were also similar to the properties of the enzyme in partially delipidated and solubilized preparations of microsomes. The activity was again optimal at pH 6.5, required Triton X-100 for optimal activity and was stimulated by phosphatidyl serine. These results indicate that the properties of cholesterol ester hydrolase in myelin are similar to those of the microsomal enzyme and that this is true for the fractions from both human and rodent brain. The data thus lead us to believe that the hydrolase activity in mammalian brain myelin and microsomes may reflect the distribution of a single enzyme in the two fractions rather than two distinct enzymes, one being specific to each fraction.

Animals↗
PubMed1990

Pancreatic cholesterol esterases. 3. Kinetic characterization of cholesterol ester resynthesis by the pancreatic cholesterol esterases.

The ability of cholesterol esterase to catalyze the synthesis of cholesterol esters has been considered to be of limited physiological significance because of its bile salt requirements for activity, though detailed kinetic studies have not been reported. This study was performed to determine the taurocholate, pH, and substrate requirements for optimal cholesterol ester synthesis catalyzed by various pancreatic lipolytic enzymes, including the bovine 67- and 72-kDa cholesterol esterases, human 100-kDa cholesterol esterase, and human 52-kDa triglyceride lipase. In contrast to current beliefs, cholesterol esterase exhibits a bile salt independent as well as a bile salt dependent synthetic pathway. For the bovine pancreatic 67- and 72-kDa cholesterol esterases, the bile salt independent pathway is optimal at pH 6.0-6.5 and is stimulated by micromolar concentrations of taurocholate. For the bile salt dependent synthetic reaction for the 67-kDa enzyme, increasing the taurocholate concentration from 0 to 1.0 mM results in a progressive shift in the pH optimum from pH 6.0-6.5 to pH 4.5 or lower. In contrast, cholesterol ester hydrolysis by the 67-, 72-, and 100-kDa enzymes was characterized by pH optima from 5.5 to 6.5 at all taurocholate concentrations. Optimum hydrolytic activity for these three enzyme forms occurred with 10 mM taurocholate. Since hydrolysis is minimal at low taurocholate concentrations, the rate of synthesis actually exceeds hydrolysis when the taurocholate concentration is less than 1.0 mM. The 52-kDa enzyme exhibits very low cholesterol ester synthetic and hydrolytic activities, and for this enzyme both activities are bile salt independent. Thus, our data show that cholesterol esterase has both bile salt independent and bile salt dependent cholesterol ester synthetic activities and that it may catalyze the net synthesis of cholesterol esters under physiological conditions.

Animals↗