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PubMed1995

Role of lecithin:cholesterol acyltransferase and apolipoprotein A-I in cholesterol esterification in lipoprotein-X in vitro.

Lipoprotein-X (Lp-X) is an abnormal particle present in the plasma of patients with familial lecithin:cholesterol acyltransferase (LCAT) deficiency syndromes or cholestatic liver disease. Compared to other lipoproteins, Lp-X contains a high content of unesterified cholesterol (30%, w/w) to phosphatidylcholine (60%, w/w). The objective of this study was to evaluate the role of LCAT and apolipoprotein A-I (apoA-I) in Lp-X metabolism in vitro and to elucidate the regulation of cholesterol esterification in this unique lipoprotein. Lp-X isolated from sera of patients with obstructive jaundice had a high content of unesterified cholesterol and phosphatidylcholine and contained apolipoprotein E, apoCs, and albumin. Although human recombinant LCAT used as an enzyme source did bind to isolated Lp-X, no cholesterol esterification was detected. However, addition of human apoA-I in the presence of albumin resulted in significant cholesterol esterification in Lp-X (Vmax 0.25 +/- 0.04 nmol/h per microgram LCAT protein). Exogenous apoA-I did not change the size of Lp-X particle as determined by quasi-elastic light scattering analysis. A reduction in Lp-X size was observed when both apoA-I and LCAT were included in the reaction mixture (from 47 nm to 42 nm). Furthermore, addition of apoA-I (but not HDL) dramatically changed the electrophoretic mobility of Lp-X from cathodic to anodic migration. Such changes are not due to displacement of apoC or apoE proteins from Lp-X by apoA-I. While increasing apoA-I concentration (up to 35 micrograms/ml) in the reaction mixture stimulated cholesterol esterification in Lp-X, addition of apoA-I at the concentration of 8 micrograms/ml inhibited cholesterol esterification in VLDL, LDL, and HDL by more than 50%. Albumin was required for the LCAT reaction to Lp-X. Our results suggest that while LCAT binds to isolated Lp-X, apoA-I is needed for the LCAT reaction to proceed. The presence of apoA-I does not result in the displacement of apoCs and apoE from Lp-X and addition of apoA-I changes the electrophoretic mobility but not the size of Lp-X.

Animals↗
PubMed1999

Influence of water activity on the enantioselective esterification of (R,S)-ibuprofen by Candida antarctica lipase B in solventless media.

The lipase-catalyzed enantioselective esterification of ibuprofen has been studied in a media, composed only of substrates. When racemic ibuprofen is used, the alcohol-chain length affects the esterification rates of individual enantiomers, but it does not affect the enantioselectivity. Water activity affects the esterification rates of (R)- and (S)-ibuprofen differently, leading to higher enantioselectivity at lower water activities. Experiments were also conducted at various (R)- to (S)-ibuprofen ratios. It appears that the esterification rate of (R)-ibuprofen is always proportional to its concentration, whereas at low water activity the esterification rate of (S)-ibuprofen shows a saturation at higher concentrations. Other 2-phenyl carboxylic acids were studied, and the increase in apparent enantioselectivity at low-water activity was not observed for the molecules tested.

Biotransformation↗
PubMed2000

Multidrug resistance P-glycoprotein is not involved in cholesterol esterification.

The aim of the present paper is to reinvestigate the role of multidrug resistance P-glycoprotein MDR1 and MDR-associated protein (MRP1) in cholesterol esterification using well-characterized inhibitors. Using specific substrate efflux assay, we show that GF120918 (0.2 microM) and probenecid (5 mM) were specific inhibitors of MDR1 and MRP1, respectively. In HepG2 cells, neither of them affect the esterification of cholesterol derived from the uptake of cholesterol-rich lipoprotein, while both verapamil (100 microM) and progesterone (100 microM) were able to inhibit cholesterol esterification. Similar results were obtained with verapamil, progesterone, and GF120918 in the MDR1-overexpressing cells MCF7/ADR. The capacity of progesterone to reduce cholesterol esterification is not correlated with its ability to inhibit MDR1 but is rather due to direct inhibition of acyl-CoA:cholesterol acyltransferase (ACAT). We conclude that the esterification of cholesterol is not correlated with MDR1 or MRP1 activity, thus excluding their role in the intracellular transport of endocytosis-derived cholesterol.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1998

Lipase specificity toward some acetylenic and olefinic alcohols in the esterification of pentanoic and stearic acids.

The esterification of five medium- and long-chain acetylenic alcohols (2-nonyn-1-ol, 10-undecyn-1-ol, 6-octadecyn-1-ol, 9-octadecyn-1-ol, and 13-docosyn-1-ol), seven olefinic alcohols (cis-3-nonen-1-ol, 10-undecen-1-ol, cis-6-octadecen-1-ol, cis-9-octadecen-1-ol, trans-9-octadecen-1-ol, trans-9, trans-11-octadecadien-1-ol, cis-9,cis-12-octadecadien-1-ol), and four short-chain unsaturated alcohols (allyl alcohol, 3-butyn-1-ol, 3-pentyn-1-ol, and cis-2-penten-1-ol) with pentanoic or stearic acid in the presence of various lipase preparations was studied. With the exception of 2-nonyn-1-ol, where Lipase AY-30 (Candida rugosa) was used as the biocatalyst, the esterification of C11, C18, and C22 acetylenic alcohols with pentanoic acid appeared to be generally unaffected by the presence of an acetylenic bond in the alcohol as relatively high yields of the corresponding esters (78-97%) were obtained. However, medium- and long-chain olefinic alcohols were discriminated by Lipase AY-30, Lipolase 100T (Rhizomucor miehei), and especially by porcine pancreatic lipase (PPL), when esterification was conducted with pentanoic acid. Esterification of medium- and long-chain acetylenic or olefinic alcohols with a long-chain fatty acid, stearic acid, was very efficient except when Lipase AY-30 and Lipolase 100T were used. Short-chain unsaturated alcohols were much more readily discriminated. 3-Pentyn-1-ol and 3-butyn-1-ol were difficult (<5% yield) to esterify with pentanoic or stearic acid in the presence of Lipase AY-30 and PPL, respectively. Very low yields (<26%) of esters were produced when 3-butyn-1-ol and 3-pentyn-1-ol were reacted with pentanoic or stearic acid, when catalyzed by lipase from Candida cylindracea. No reaction took place between 3-butyn-1-ol and stearic acids in the presence of Lipase AY-30. Esterification of short-chain acetylenic and olefinic alcohols was most efficiently achieved with Lipolase 100T (Rhizomucor miehei), Lipozyme IM20 (Rh. miehei), or Novozyme 435 (Candida antarctica) as the biocatalyst.

Fatty Alcohols↗
PubMed1981

Cholesterol esterification by rat adrenal gland. Inhibition by local anesthetics in vitro.

Cholesterol esterification was studied in rat adrenal gland, adrenal homogenates and isolated adrenal microsomes. In whole gland and homogenates, the local anesthetic, lidocaine, inhibited the incorporation of [1-14C]oleate and [1-14C]oleoyl-CoA, respectively, into labeled cholesteryl esters in a dose-dependent manner. Inhibition of sterol esterification in the preparations reached 50% at about 2 mM. Various other local anesthetics (tetracaine, dibucaine and benzocaine) also inhibited sterol esterification in adrenal homogenates but were more potent than lidocaine; in each case, 90% inhibition occurred at anesthetic levels of 1 mM. Since sterol esterification in the adrenal gland is a function of microsomal acyl-CoA: cholesterol acyltransferase (EC 2.3.1.26), the enzyme was assayed in isolated adrenal microsomes in the presence of lidocaine while using [14C]oleoyl-CoA as a substrate for labeled cholesteryl ester formation. Inhibition of the enzymes by lidocaine was confirmed, with 50% inhibition occurring between 0.5 and 0.75 mM lidocaine. Lidocaine may be useful as a tool in studies on the regulation of adrenal sterol esterification.

Acyl Coenzyme A↗
PubMed1984

The effect of nutritional and thyroid state on the distribution of fatty acids between oxidation and esterification in isolated rat hepatocytes.

Small amounts of glycerol (0.25 mM) simultaneously decrease oxidation and increase esterification of fatty acids in isolated rat hepatocytes, mainly by raising the intracellular concentration of alpha-glycerophosphate. These effects were obtained in all thyroid states as well as in the fed and fasted states. In normal hepatocytes, the rate of oxidation showed a poor correlation with the content of malonyl-CoA. The effects of glycerol on fatty acid metabolism were most pronounced in hepatocytes with a high capacity for esterification and a previous low concentration of alpha-glycerophosphate (glucagon-treated hepatocytes from euthyroid fed rats). Esterification capacity was influenced by the nutritional and thyroid state (decreased in fasting and in hyperthyroidism). It was not influenced by glucagon in short-term experiments. alpha-Glycerophosphate may not regulate fatty acid metabolism in vivo, but a high esterification capacity probably traps acyl-CoA for esterification, thus preventing fatty acids from being oxidized. The metabolism of alpha-glycerophosphate seems to be accelerated by hyperthyroidism and slowed down by fasting. The effect of fasting seems not to depend on thyroid hormones for its effects on fatty acid metabolism in the liver.

Animals↗
PubMed1987

Inhibition of cellular cholesterol esterification can decrease low density lipoprotein receptor number in human fibroblasts.

In fibroblasts deprived of exogenous cholesterol to induce low density lipoprotein receptors there is a continuing flux of cholesterol esterification. The structurally unrelated inhibitors of acyl-CoA; cholesterol acyl-transferase, progesterone, trimethylcyclohexanyl mandelate and 3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl] propanamide, (58035), could all inhibit this basal rate of esterification within 1h of addition. Exposure of cholesterol-deprived fibroblasts for 17h to progesterone or trimethylcyclohexanyl mandelate caused decreased specific binding and metabolism of low density lipoprotein. The effect was not a direct inhibition of lipoprotein binding; it was time dependent and followed from the reversible inhibition of cholesterol esterification by these two compounds. The irreversible inhibition of esterification by 58035 left the receptor number unaffected. The results indicate that down regulation of low density lipoprotein receptors is initiated by accumulation of cholesterol in a specific intracellular pool. Inhibition of cholesterol esterification by progesterone and trimethylcyclohexanyl mandelate causes accumulation of cholesterol in this pool but 58035 does not.

Amides↗
PubMed1993

The inhibition of cholesterol esterification by cyclandelate in transformed mouse macrophages.

Cyclandelate (trimethylcyclohexanyl mandelate) inhibited cholesterol esterification in a transformed mouse macrophage cell line (J774) with a concentration of approximately 20 microM being required for half-maximal inhibition. The intact drug was required for its inhibitory action since neither of its hydrolysis products, trimethylcyclohexanol and mandelic acid, caused any inhibition even at high concentrations. The drug entered the cells very rapidly with inhibition being apparent within the shortest time possible to measure esterification (15 min after drug addition). The rate of cholesterol esterification returned to control values when drug-inhibited cells were incubated in drug-free medium indicating a rapid loss of drug from the cells. Loading of cells with cholesterol had no effect on the inhibitory action of cyclandelate, and the inhibition of esterification of cholesterol appeared to be specific, since the syntheses of phospholipid and triacylglycerol (which also involve the action of acyltransferases) were not affected by the drug. Similar inhibitions of cholesterol esterification were seen in four other cell lines, a human osteosarcoma, Chinese hamster ovary cells, a human transformed macrophage cell line (U937) and human umbilical cord vein endothelial cells, as well as in slices of pig aorta, indicating a general action in extra-hepatic tissues where the drug is not hydrolysed.

Animals↗
PubMed1983

Role of esterified cholesterol transfers in the regulation of plasma cholesterol esterification.

The role of esterified cholesterol transfers in mediating the known effect of very low density lipoproteins (VLDL) on plasma cholesterol esterification has been examined. Advantage has been taken of the fact that pig plasma, in contrast to human plasma, is deficient in activity of the protein that transfers esterified cholesterol between plasma lipoproteins. The experimental protocol consisted of a pre-incubation in which VLDL-deficient pig plasma or isolated pig lipoproteins were incubated with added VLDL, in the presence or absence of an exogenous source of the esterified cholesterol transfer protein. After pre-incubation, any VLDL that may have been present was removed and rates of cholesterol esterification measured in subsequent incubations of the recovered VLDL-depleted fractions. It was, thus, possible to assess the effect of VLDL and/or transfer protein activity on the capacity of other lipoproteins to act as substrates for cholesterol esterification. In the absence of transfer protein activity, the presence of VLDL in pre-incubations had no effect on the subsequently measured rate of cholesterol esterification. However, when pig plasma was supplemented with human lipoprotein-free plasma (a source of esterified cholesterol transfer protein activity) the presence of VLDL in pre-incubations resulted in both a reduction in the esterified cholesterol content of the re-isolated VLDL-deficient fraction and a markedly enhanced rate of cholesterol esterification in subsequent incubations of this fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The influence of plasma lipoproteins from patients with abetalipoproteinemia on cellular cholesterol esterification.

In normal humans low density lipoproteins (LDL) constitute the major lipoprotein responsible for the delivery of cholesterol to cells and their uptake results in a decrease in cholesterol biosynthesis and an increase in cholesterol esterification. In the present study, we have examined whether plasma lipoproteins from patients with abetalipoproteinemia (ABL), who lack LDL in their plasma, can stimulate intracellular cholesterol esterification and, quantitatively, how this compares with normal LDL. Fibroblasts from normal and abetalipoproteinemic patients had similar cholesterol esterification rates when LDL was present in the medium. Esterification rates using ABL HDL2 were significantly higher than that of normal HDL2 in both normal and ABL fibroblasts. However, maximal rates of cellular cholesterol delivery are considerably greater for normal LDL than for the HDL2 particles in ABL plasma. Our results indicate that lipoprotein particles present in the HDL2 fraction of plasma from patients with ABL are able to provide sufficient cholesterol to cells so that cholesterol esterification is stimulated.

Abetalipoproteinemia↗
PubMed1990

Relationship between plasma cholesterol levels and cholesterol esterification in isolated human mononuclear cells.

We studied the relationship between plasma lipoprotein concentrations and cholesterol esterification in freshly isolated human mononuclear cells from 27 normolipidemic and 32 hyperlipidemic individuals. Cells were either incubated for 5 hours with radiolabeled oleate immediately after isolation or were preincubated for 18 hours in the presence of exogenous cholesterol, and then incubated with [14C]sodium-oleate-albumin complex. In the absence of exogenous cholesterol, control and hypercholesterolemic subjects had similarly low values of intracellular cholesterol esterification. In the presence of exogenous cholesterol, both hypertriglyceridemic and hypercholesterolemic subjects had higher cholesterol esterification than controls. There was a significant correlation between the rate of cholesterol esterification and plasma total cholesterol (r = 0.65 p less than 0.0003). These results suggest that plasma cholesterol levels may regulate mononuclear cell intra-cellular cholesterol esterification in humans.

Cholesterol↗
PubMed1986

Age-related changes in the rate of esterification of plasma cholesterol in Fischer-344 rats.

Plasma cholesterol and triglyceride levels and selected molecular species of plasma cholesteryl esters and triglycerides were determined in 6-, 12-, 15-, 18-, 21-, and 24-month-old Fischer-344 rats. Lecithin:cholesterol acyltransferase (LCAT) activity was also determined using two independent methods utilizing endogenous and exogenous substrates. Plasma cholesterol levels increased up to 18 months of age and then plateaued. Of the plasma triglyceride molecular species investigated (C50, C52, C54 and C56), only the levels of C52 increased linearly with age. The concentration of other triglyceride molecular species did not change with age. The fractional rate of plasma cholesterol esterification showed a decreasing trend with age, whereas, the net cholesterol esterification rate showed a gradual age related increase. However, this latter parameter remained unchanged with age when the data were normalized for body weight. The cholesterol esterification rates measured using an exogenous substrate (estimating LCAT enzyme levels) showed essentially no change with age. These data indicate that changes in the levels and/or composition of lipoprotein substrate(s) for LCAT are likely causes of the observed age-related changes in the fractional rate of plasma cholesterol esterification. The net esterification rate of plasma cholesterol was significantly correlated with the plasma triglyceride levels when the animals for all age groups were treated as one experimental group.

Aging↗
PubMed1985

The synthesis and esterification of cholesterol by hepatocytes and H35 hepatoma cells are independent of the level of nonspecific lipid transfer protein.

The level of the nonspecific lipid transfer protein (i.e., sterol carrier protein 2) is 16-fold lower in the Reuber H35 hepatoma cells as compared to the hepatocytes in culture (49 and 810 ng of protein per mg of 105000 X g supernatant protein, respectively). In order to establish whether there is a relationship between the level of nonspecific transfer protein and intracellular cholesterol metabolism, we have determined the biosynthesis and esterification of cholesterol in these hepatoma cells and hepatocytes. Both types of cells incorporated [3H]mevalonate into cholesterol and cholesterol ester. Incubation of both cell types with [3H]cholesterol in the medium resulted in a time-dependent uptake and subsequent conversion into cholesterol ester. In both instances, the amount of 3H label incorporated into cholesterol per mg of cellular protein was about 2-fold higher for the hepatoma cells. The kinetics of esterification of endogenously synthesized cholesterol were similar for both hepatoma cells and hepatocytes. Esterification of cholesterol derived from the medium proceeded 2-times faster in the hepatoma cells than in the hepatocytes. From the kinetics of cholesterol esterification we conclude that cells do not discriminate between cholesterol synthesized de novo and cholesterol derived from the medium. In addition, the proposition that the nonspecific lipid transfer protein is involved in cholesterol synthesis and esterification is not substantiated by this study.

Animals↗
PubMed2000

Analysis of different de-esterification mechanisms for pectin by enzymatic fingerprinting using endopectin lyase and endopolygalacturonase II from A. niger.

A series of pectins with different distribution patterns of methyl ester groups was produced by treatment with either plant (p-PME) or fungal pectin methyl esterases (f-PME) and compared with those obtained by base catalysed de-esterification. The products generated by digestion of these pectins with either endopectin lyase (PL) or endopolygalacturonase II (PG II) from Aspergillus niger were analysed using matrix assisted laser desorption ionisation mass spectrometry (MALDIMS) and high-performance anion-exchange chromatography with pulsed amperometric or UV detection (HPAEC-PAD/UV). Time course analysis using MALDIMS was used to identify the most preferred substrate for each enzyme. For PL, this was shown to be fully methyl esterified HG whereas for PG II, long regions of HG without any methyl esterification, as produced by p-PME was the optimal substrate. The blockwise de-esterification caused by p-PME treatment gave a decrease of partly methylated oligomers in PL fingerprints, which did not effect the relative composition of partly methylated oligomers. PG II fingerprints showed a constant increase of monomers and oligomers without any methyl ester groups with decreasing degree of esterification (DE), but almost no change in the concentration of partly methylated compounds. PL fingerprints of f-PME and chemically treated pectins showed decreasing amounts of partly methyl esterified oligomers with decreasing DE, together with a relative shift towards longer oligomers. PG II fingerprints were characterised by an increase of partly methylated and not methylated oligomers with decreasing DE. But differences were also seen between these two forms of homogenous de-esterification. Introduction of a certain pattern of methyl ester distribution caused by selective removal of certain methyl ester groups by f-PME is the most reasonable explanation for the detected differences.

Aspergillus niger↗
PubMed1981

Sialic acid polysaccharide antigens of Neisseria meningitidis and Escherichia coli: esterification between adjacent residues.

Colominic acid and meningococcal Group B polysaccharide, both (2 leads to 8)-alpha-linked homopolymers of sialic acid, are made water-insoluble either by reaction with a carbodiimide in aqueous solution at pH 4.75 or by treatment with 48% aqueous hydrofluoric acid at 0 degrees for 48 h. I.r. spectra of the products show a major band near 1750 cm-1, consistent with ester formation; this band virtually disappears after mild, alkali treatment. Esterification also occurs by incubating the native polysaccharides below pH 6.0, and their i.r. spectra show that the degree of esterification increases as the pH is lowered. The relatively low molecular weight of these partially esterified, water-soluble polymers is consistent with intra- rather than inter-molecular ester formation. Counter-current immunoelectrophoresis shows that esterification of approximately 9% is sufficient to abolish immunoprecipitation. 13C-N.m.r. spectroscopy of fully esterified colominic acid provides strong evidence for cross-linking between the carboxyl group of one residue and HO-9 of an adjoining residue. Meningococcal serogroup C polysaccharide, a (2 leads to 9)-alpha-linked homopolymer of sialic acid containing O-acetyl groups at C-7 and/or C-8, does not undergo intramolecular esterification after carbodiimide treatment. However, upon O-deacetylation of the polysaccharide, esterification occurs.

Escherichia coli↗
PubMed2002

Rates of cholesterol esterification and esterified cholesterol net mass transfer between high-density lipoproteins and apolipoprotein B-containing lipoproteins in Type 1 diabetes.

AIMS: Type 1 diabetes is associated with a high incidence of coronary heart disease (CHD) despite paradoxically normal or high high-density lipoprotein (HDL) cholesterol concentrations. Triglyceride (TG) concentrations have been shown to be important determinants of two aspects of HDL metabolism: cholesterol esterification rate and esterified cholesterol (EC) net mass transfer rate between HDL and the apolipoprotein B-containing lipoproteins. In order to try to explain the paradox, we aimed to assess the relationships between plasma TG and these two processes in Type 1 diabetic compared with non-diabetic subjects. METHODS: Rates of cholesterol esterification and EC net mass transfer between HDL and the apolipoprotein B-containing lipoproteins were assessed by incubating whole plasma at 37 degrees C; intra-assay coefficients of variation were 6% and 30%, respectively. RESULTS: Ten Type 1 diabetic and 10 non-diabetic subjects, with similar ages, sex distributions, body mass indices and total cholesterol and TG concentrations, were assessed. Apolipoprotein A1, HDL unesterified cholesterol, and HDL phospholipid concentrations were greater in the Type 1 diabetic subjects. There were no significant differences in the rates of cholesterol esterification or EC net mass transfer between the groups. There were strong associations between plasma TG and the rate of cholesterol esterification and between plasma TG and the rate of EC net mass transfer in Type 1 diabetic subjects (r = 0.83, P = 0.0027 and r = 0.88, P = 0.0009, respectively) and in non-diabetic subjects (r = 0.91, P = 0.0002 and r = 0.79, P = 0.0070, respectively). However, the slopes of the associations with plasma TG were significantly steeper in the Type 1 diabetic subjects (analyses of covariance P = 0.0053 and P = 0.0146, respectively). CONCLUSIONS: Increases in TG may therefore promote more EC enrichment of atherogenic apolipoprotein B-containing lipoproteins in Type 1 diabetes while also promoting more cholesterol esterification, thereby maintaining HDL cholesterol concentrations. This could contribute to the paradox of high CHD incidence despite normal or high HDL cholesterol concentrations in Type 1 diabetes.

Adult↗
PubMed1996

Disruption of the acyl-CoA:cholesterol acyltransferase gene in mice: evidence suggesting multiple cholesterol esterification enzymes in mammals.

The microsomal enzyme acyl-CoA:cholesterol acyltransferase (ACAT; EC 2.3.1.26) catalyzes the esterification of cellular cholesterol with fatty acids to form cholesterol esters. ACAT activity is found in many tissues, including macrophages, the adrenal glands, and the liver. In macrophages, ACAT is thought to participate in foam cell formation and thereby to contribute to atherosclerotic lesion development. Disruption of the gene for ACAT (Acact) in mice resulted in decreased cholesterol esterification in ACAT-deficient fibroblasts and adrenal membranes, and markedly reduced cholesterol ester levels in adrenal glands and peritoneal macrophages; the latter finding will be useful in testing the role of ACAT and macrophage foam cell formation in atherosclerosis. In contrast, the livers of ACAT-deficient mice contained substantial amounts of cholesterol esters and exhibited no reduction in cholesterol esterification activity. These tissue-specific reductions in cholesterol esterification provide evidence that in mammals this process involves more than one form of esterification enzyme.

Adrenal Glands↗
PubMed1988

Niemann-Pick disease group C: clinical variability and diagnosis based on defective cholesterol esterification. A collaborative study on 70 patients.

Seventy patients were selected to cover the range of variability in clinical expression of Niemann-Pick disease group C (NP-C). Their individual main clinical features and course of the disease (age at discovery and type of visceromegaly, age at onset and first neurological manifestation, later neurological symptoms) are schematically described. In cultured skin fibroblasts from these patients, sphingomyelinase activities measured in vitro showed decreased values only in approximately half of the cases, and when the metabolic fate of [14C]-sphingomyelin was studied in living cell cultures, still 20% of the cases had a normal hydrolysis rate. Esterification of exogenous cholesterol was investigated in cell lines from these and 5 additional patients and in 21 of their parents. Using a non-lipoprotein [3H]cholesterol source, very low esterification rates were obtained in more than 90% of the cases. All the numerous other pathological conditions studied, including Niemann-Pick disease types A and B, gave normal results. A more sensitive method was elaborated, in which the cells were challenged with pure human low density lipoproteins (LDL) and the early rate of esterification studied. With the latter procedure, a pronounced deficiency could also be demonstrated in the few cases which had shown a milder impairment using a [3H]cholesterol source, and intermediate rates of esterification were obtained in heterozygotes. Discrimination of these difficult cases and of heterozygotes could also be achieved replacing LDL with total unfrozen human serum. Correlations were established between given clinical phenotypes and the severity of the biochemical lesion. Defective intracellular cholesterol esterification is further established as an intrinsic feature of NP-C, and demonstration of this metabolic alteration appears as a major advance in diagnosing the condition.

Age Factors↗