Apolipoprotein E-rich High Density Lipoproteins Research Articles

Low plasma apolipoprotein E-rich high-density lipoprotein levels in patients with metabolic syndrome

BackgroundHigh-density lipoprotein (HDL) containing apolipoprotein E (apoE-rich HDL) represents a small portion of plasma HDL. We recently established a method for measuring plasma apoE-rich HDL. This study aimed to investigate the relationship between metabolic syndrome (MetS) and apoE-rich HDL levels. MethodsThe apoE-rich HDL-cholesterol (HDL-C) levels and metabolic characteristics of 113 patients were analyzed. ResultsThe MetS group (n = 58) had significantly lower apoE-rich HDL-C and a lower apoE-rich HDL-C/HDL-C ratio (apoE-HDL (%)) compared to the non-MetS group. The prevalence of MetS was increased when apoE-HDL (%) decreased. In simple regression analyses, apoE-HDL (%) was significantly inversely correlated with visceral fat area (rs = −0.370, P < 0.001) and plasma triglycerides (rs = −0.447, P < 0.001) and positively correlated with low-density lipoprotein (LDL) mean particle size (rs = 0.599, P < 0.001) and HDL mean particle size (rs = 0.512, P < 0.001). Stepwise multiple regression analysis revealed that LDL mean particle size, a component of the atherogenic lipoprotein profile, was an independent predictor of apoE-HDL (%) (adjusted R2 = 0.409). ConclusionsPlasma apoE-rich HDL levels might be a valuable indicator of MetS. These findings may help further understand HDL subfraction analysis in cardiometabolic diseases.

Upregulating Reverse Cholesterol Transport With Cholesteryl Ester Transfer Protein Inhibition Requires Combination With the LDL-Lowering Drug Berberine in Dyslipidemic Hamsters

This study aimed to investigate whether cholesteryl ester transfer protein inhibition promotes in vivo reverse cholesterol transport in dyslipidemic hamsters. In vivo reverse cholesterol transport was measured after an intravenous injection of (3)H-cholesteryl-oleate-labeled/oxidized low density lipoprotein particles ((3)H-oxLDL), which are rapidly cleared from plasma by liver-resident macrophages for further (3)H-tracer egress in plasma, high density lipoprotein (HDL), liver, and feces. A first set of hamsters made dyslipidemic with a high-fat and high-fructose diet was treated with vehicle or torcetrapib 30 mg/kg (TOR) over 2 weeks. Compared with vehicle, TOR increased apolipoprotein E-rich HDL levels and significantly increased (3)H-tracer appearance in HDL by 30% over 72 hours after (3)H-oxLDL injection. However, TOR did not change (3)H-tracer recovery in liver and feces, suggesting that uptake and excretion of cholesterol deriving from apolipoprotein E-rich HDL is not stimulated. As apoE is a potent ligand for the LDL receptor, we next evaluated the effects of TOR in combination with the LDL-lowering drug berberine, which upregulates LDL receptor expression in dyslipidemic hamsters. Compared with TOR alone, treatment with TOR+berberine 150 mg/kg resulted in lower apolipoprotein E-rich HDL levels. After (3)H-oxLDL injection, TOR+berberine significantly increased (3)H-tracer appearance in fecal cholesterol by 109%. Our data suggest that cholesteryl ester transfer protein inhibition alone does not stimulate reverse cholesterol transport in dyslipidemic hamsters and that additional effects mediated by the LDL-lowering drug berberine are required to upregulate this process.

Multidimensional profiling of plasma lipoproteins by size exclusion chromatography followed by reverse-phase protein arrays

The composition of lipoproteins and the association of proteins with various particles are of much interest in the context of cardiovascular disease. Here, we describe a technique for the multidimensional analysis of lipoproteins and their associated apolipoproteins. Plasma is separated by size exclusion chromatography (SEC), and fractions are analyzed by reverse-phase arrays. SEC fractions are spotted on nitrocellulose slides and incubated with different antibodies against individual apolipoproteins or antibodies against various apolipoproteins. In this way, tens of analytes can be measured simultaneously in 100 μl of plasma from a single SEC separation. This methodology is particularly suited to simultaneous analysis of multiple proteins that may change their distribution to lipoproteins or alter their conformation, depending on factors that influence circulating lipoprotein size or composition. We observed changes in the distribution of exchangeable apolipoproteins following addition of recombinant apolipoproteins or interaction with exogenous compounds. While the cholesteryl ester transfer protein (CETP)-dependent formation of pre-β-HDL was inhibited by the CETP inhibitors torcetrapib and anacetrapib, it was not reduced by the CETP modulator dalcetrapib. This finding was elucidated using this technique.

Reduced Apolipoprotein E-Rich High-Density Lipoprotein Level at Birth Is Restored to the Normal Range in Patients with Familial Hypercholesterolemia in the First Year of Life

High-density lipoprotein (HDL) consists of apolipoprotein E (apoE)-rich and apoE-poor HDL particles. ApoE-rich HDL level is high at birth but decreases after birth with reciprocal elevation in low-density lipoprotein (LDL)-cholesterol. The objective of the study was to clarify whether apoE-rich HDL decreases after birth in children with familial hypercholesterolemia (FH), a disorder caused by impaired LDL clearance. We measured apoE-rich HDL-cholesterol and LDL-cholesterol during the first year of life in 10 FH children (one homozygote and nine heterozygotes), 12 non-FH siblings, and 75 healthy controls. At birth, apoE-rich HDL-cholesterol was undetectable in a homozygous FH child and lower in heterozygous FH children than non-FH siblings and controls (4+/-2 vs. 12+/-4 and 11+/-4 mg/dl, P<0.001). At 3-4 months, apoE-rich HDL-cholesterol increased in homozygous and heterozygous FH children and decreased in non-FH siblings and controls. At 12 months, apoE-rich HDL-cholesterol levels were similar among these four groups (6-7 mg/dl). In contrast, LDL-cholesterol concentration was always twice as high in heterozygous FH children as non-FH siblings and controls (at birth, 50+/-15 vs. 25+/-7 and 25+/-5 mg/dl, P<0.001; at 3-4 months of age, 159+/-29 vs. 71+/-16 and 73+/-15 mg/dl, P<0.001; at 12 months of age, 156+/-29 vs. 75+/-18 and 76+/-17 mg/dl, P<0.001). ApoE-rich HDL level is low at birth in FH children and increases to the normal level in the first year of life, opposite to the change in normal children.

Functional LCAT deficiency in human apolipoprotein A-I transgenic, SR-BI knockout mice

Reduction of plasma LCAT activity has been observed in several conditions in which the size of HDL particles is increased; however, the mechanism of this reduction remains elusive. We investigated the plasma activity, mass, and in vivo catabolism of LCAT and its association with HDL particles in human apolipoprotein A-I transgenic, scavenger receptor class B type I knockout (hA-ITg SR-BI-/-) mice. Compared with hA-ITg mice, hA-ITg SR-BI-/- mice had a 4-fold higher total plasma cholesterol concentration, which occurred predominantly in 13-18 nm diameter HDL particles, a significant reduction in plasma esterified cholesterol-total cholesterol (EC/TC) ratio, and significantly lower plasma LCAT activity, suggesting a decrease in LCAT protein. However, LCAT protein in plasma, hepatic mRNA for LCAT, and in vivo turnover of 35S-radiolabeled LCAT were similar in both genotypes of mice. HDL from hA-ITg SR-BI-/- mice was enriched in sphingomyelin (SM), relative to phosphatidylcholine, and had less associated [35S]LCAT radiolabel and endogenous LCAT activity compared with HDL from hA-ITg mice. We conclude that the decreased EC/TC ratio in the plasma of hA-ITg SR-BI-/- mice is attributed to a reduction in LCAT reactivity with SM-enriched HDL particles.

Effects of Ionizing Radiation (Neutrons/Gamma Rays) on Plasma Lipids and Lipoproteins in Rats

Male Wistar rats weighing 250 g were exposed to 4 Gy of neutrons/gamma radiation (3.33 Gy of neutrons and 0.66 Gy of gamma rays). After whole-body irradiation, plasma cholesterol and phospholipid levels increased up to 62 and 37%, respectively, at day 4 and then returned to control values 12 days after irradiation. Plasma triglyceride concentrations decreased concomitantly with decreased food intake after irradiation but remained higher than in pair-fed control rats. Plasma lipoproteins were separated by ultracentrifugation on a density gradient (1.006-1.210 g/ml). Four days after irradiation, most of the cholesterol (62% compared to 31% in controls, P < 0.001) is transported by apolipoprotein E-rich high-density lipoproteins. At the same time, plasma levels of apolipoproteins B and E were increased by 28 and 65%, respectively, while those of apolipoproteins AI and AIV were reduced by 21 and 59%, respectively. While in the liver of irradiated rats the apolipoprotein B/E receptor number was not modified, the hydroxymethylglutaryl coenzyme A reductase activity was fivefold higher than in control pair-fed rats. Four days after irradiation, the susceptibility of lipoproteins to peroxidation, as measured by the formation of conjugated dienes in the presence of Cu2+, was markedly increased while plasma vitamin E levels were decreased, demonstrating that irradiation reduces antioxidant stores markedly. These results suggest that such modified lipoproteins could be involved in radiation-induced vascular damage.

Effects of Simvastatin on Plasma Lipoprotein Concentrations and Very-Low-Density Lipoprotein Secretion in the Rat.

The effects of simvastatin, a cholesterol biosynthesis inhibitor, on plasma lipoprotein concentrations and very-low-density lipoprotein (VLDL) secretion were investigated in the rat. The results showed that simvastatin did not significantly modify plasma lipid levels but did increase the cholesterol level of apolipoprotein E-rich high-density lipoproteins (+31%). The treatment significantly reduced total VLDL secretion (-26%), assessed by VLDL-triacylglycerol accumulation in plasma after lipolysis inhibition by Triton WR 1379. Since intestinal VLDL production, which was measured in rats fed orotic acid in order to block the hepatic secretion of lipoproteins, was not changed, we deduced that simvastatin reduced by 50% the hepatic VLDL secretion. Furthermore, whole-body cholesterol production, assessed by the sterol balance, appeared inhibited in the rat after long-term simvastatin treatment.

Identification of apolipoprotein B-100 low density lipoproteins, apolipoprotein B-48 remnants, and apolipoprotein E-rich high density lipoproteins in the mouse.

Plasma lipoprotein fractions from inbred C57BL/6J mice and outbred ICR mice were prepared by sequential density ultracentrifugation using density ranges that were optimized for separating mouse lipoproteins, or by Superose 6 HR10/30 fast performance liquid chromatography (FPLC). The lipoproteins were characterized by migration behavior in agarose, apolipoprotein (apo) composition, lipid composition, and particle size distribution. Both sequential density ultracentrifugation and Superose 6 FPLC were adapted for the separation of lipoproteins from a single mouse. In the plasma of ICR and C57BL/6J mice, in contrast to human plasma, alpha-migrating high density lipoproteins (HDL) and beta-migrating low density lipoproteins (LDL) had overlapping density ranges. For example, beta-migrating apoB-100 LDL, slow pre-beta-migrating apoB-48 remnants, and alpha-migrating HDL1 were found together in the d 1.02-1.04 g/ml fraction. The d 1.04-1.06 g/ml fraction contained beta-migrating apoB-100 LDL and alpha-migrating HDL1. Large HDL1 that were found at d 1.02-1.06 g/ml were apoE-rich HDL1, characteristic of cholesteryl ester transfer protein-deficient mammals. The d 1.10-1.21 g/ml fraction, in addition to alpha-migrating HDL, included unique slow beta-migrating particles that contained apoE and apoA-I but was deficient in neutral lipids. These slow beta-HDL eluted in the same FPLC fractions as dense alpha-migrating HDL. Compared to ICR mouse plasma, C57BL/6J mouse plasma contained more LDL and less HDL1, which might contribute to the susceptibility of C57BL/6J and the resistance of ICR mice to the development of aortic fatty streak lesions when challenged with an atherogenic diet.

Increased plasma apolipoprotein E-rich high-density lipoprotein and its effect on serum high-density lipoprotein cholesterol determination in patients with familial hyperalphalipoproteinemia due to cholesteryl ester transfer activity deficiency.

Plasma apo E-rich HDL was studied in regard to its quantity and chemical composition in the members of a family with cholesteryl ester transfer activity deficiency, exhibiting familial hyperalphalipoproteinemia. The approach involved a simple precipitation method established in our laboratory. Serum apo E-rich HDL concentrations for two homozygous members were elevated up to 66 and 60 mg/dl in terms of cholesterol (normal, 6.7 +/- 2.3 mg/dl, n = 38), and to 9.4 and 10.8 mg/dl in terms of apo E (normal, 2.6 +/- 1.5 mg/dl, n = 38). The cholesterol/apo E ratio (mole/mole) of apo E-rich HDL was higher in two homozygotes (669 and 531) than in two cholestatic patients with elevated apo E-rich HDL (268 and 149) and in normal subjects (242 +/- 115, n = 38). Chromatographic studies of the serum from a homozygote showed enlargement of all HDL subclasses and apo E in the larger HDL subclass. These facts indicate that the increase of apo E-rich HDL in this disease occurs secondarily to the enlargement of HDL particles, which require substances to cover their cores, having expanded due to the accumulation of cholesteryl ester. The sera from the homozygotes gave HDL cholesterol concentrations which were remarkably discrepant among commercial precipitating reagents, because of the difference in recovery of apo E-rich HDL with these reagents.

A rapid and simple quantification of human apolipoprotein E-rich high-density lipoproteins in serum

A rapid and simple method for the quantitative determination of human serum apo E-rich high-density lipoproteins is described. A sample was divided into two parts; one part was mixed with an equal volume of 13% polyethylene glycol 6000, and the other part was mixed with a solution containing dextran sulfate, sodium phosphotungstate, and Mg2+, respectively. The mixed solutions were centrifuged (2000 g; 15 min). The supernate obtained by the former procedure contained both apo E-rich HDL and apo E-poor HDL, but that obtained by the latter procedure contained solely apo E-poor HDL. The serum apo E-rich HDL concentration in terms of apo E (E) and cholesterol (C), was given by the following equations: E = EP x 2, and C = (CP - CD) x 2, where EP and CP were the concentrations of apo E and cholesterol, respectively, in the supernate obtained with 13% polyethylene glycol, and CD was the concentration of cholesterol in the supernate obtained with the mixture solution of dextran sulfate, sodium phosphotungstate, and Mg2+. Normal serum apo E-rich HDL concentrations were 2.6 +/- 1.5 and 6.7 +/- 2.3 mg/dl (means +/- SD, n = 38) in terms of apo E and cholesterol, respectively. Apo E-rich HDL was increased strikingly in the sera from three patients with hepatobiliary diseases.

Accumulation of apolipoprotein E-rich high density lipoproteins in hyperalphalipoproteinemic human subjects with plasma cholesteryl ester transfer protein deficiency.

This study characterized the plasma lipoproteins of familial hyperalphalipoproteinemic patients with or without deficiency of cholesteryl ester transfer protein (CETP) activity. The subjects with CETP deficiency have increased levels of apolipoprotein (apo) E. The increased concentration of apo E in these subjects was correlated to the appearance of apo E-rich high density lipoproteins (HDL). Sodium dodecyl sulfate-polyacrylamide gel analysis revealed that these lipoproteins contained predominantly the apo E (82%) and little amount of apo A-I (18%). These apo E-rich HDL displayed a much higher affinity than human LDL in binding to LDL receptors on human fibroblasts. Furthermore, 3.5 times fewer apo E-rich HDL than LDL were required to saturate the receptors on fibroblasts. These data indicated that the apo E-rich HDL in CETP-deficient human subjects contained multiple copies of apo E and bound to the LDL receptor through multiple interactions. The apo E-rich HDL, with similar properties as cholesterol-induced apo E HDLc, were not detectable in normal human subjects or in hyperalphalipoproteinemic subjects with normal CETP activity. The apo E-containing HDL in the latter subjects were smaller and contained only small amounts of apo E (14%). The difference in apo E-containing HDL in these subjects suggests a correlation between CETP level and the appearance of apo E-rich HDL.

The acute effect of prolonged walking and dietary changes on plasma lipoprotein concentrations and high-density lipoprotein subfractions

The effect of diet on exercise-induced changes in the plasma concentrations of lipoproteins was examined in six healthy male subjects during walks of 37 km on each of four successive days. With a high-carbohydrate diet (85% of the calories as carbohydrate) there was an increase ( P < .05) in the concentration of very-low-density lipoprotein (VLDL)-cholesterol and VLDL-triglyceride and a decrease ( P < .01) in the concentration of high density lipoprotein (HDL)-cholesterol, due mainly to a decrease in HDL 3-cholesterol ( P < .01), and HDL-protein ( P < .001). In contrast, a high-fat diet (75% fat) produced a decrease ( P < .01) in the concentration of VLDL-cholesterol and VLDL-triglyceride with increases ( P < .01) in HDL-protein concentration and in HDL-cholesterol concentrations that arose largely from an increase ( P < .001) in HDL 2-cholesterol. Gradient gel electrophoretic analysis showed an increase ( P < .01) in the relative concentration of HDL 2b (subspecies of diameter 10.57 nm) with a decrease ( P < .01) in the concentration of HDL 2a (9.16 nm) plus HDL 3a (8.44 nm) with the high-fat diet, but no significant or consistent change with the high-carbohydrate diet. There was no change in the level of the apolipoprotein E-rich HDL subfraction with either diet. Plasma lecithin:cholesterol acyltransferase activity decreased ( P < .05) with the high-fat diet but not with the high-carbohydrate diet. Thus, diet can strongly influence the changes that occur in plasma lipoprotein concentrations during prolonged low-intensity exercise.

Effect of Copper Deficiency on the Apolipoprotein E-Rich High Density Lipoproteins in Rats

Twenty-four male weanling Sprague-Dawley rats were randomly divided into two treatments, namely a copper-adequate (8 mg Cu/kg diet) or a copper-deficient (0.85 mg Cu/kg diet) group. Feed and distilled-demineralized water were provided ad libitum. After 7 wk, plasma high density lipoproteins (HDL) were isolated by ultracentrifugation and agarose column chromatography. A heparin-Sepharose affinity column chromatographic method was used to subfractionate HDL into apolipoprotein E (apoE) -rich and apoE-poor subfractions. Significantly higher protein and cholesterol contents of HDL and the second retained (RII) subfraction (apoE-rich) were observed in copper-deficient than in control rats. The apoE contents of HDL and the apoE-rich (RII) subfraction were about threefold higher in copper-deficient rats. The increase in apoE in the HDL fraction was due primarily to the increased apoE concentration of the RII subfraction. In addition to a higher apoE concentration, apolipoprotein A-I concentration was also higher in the RII subfraction of the copper-deficient rats as compared to controls. However, the percentage of these apolipoproteins remained unaltered by copper deficiency. The present data suggest that the hypercholesterolemia observed in copper deficiency was associated with marked increases in cholesterol and apolipoprotein contents of the apoE-rich HDL.

Effects of injecting exogenous lipid transfer protein into rats

Rats were injected intravenously with preparations of partially purified lipid transfer protein isolated from human plasma. Cholesteryl ester transfer activity disappeared from the plasma of recipient rats with a t 1 2 of about 10 h and after 24 h had fallen to a level comparable to that in human plasma. By contrast there was no measurable cholesteryl ester transfer activity in the plasma of control rats. Plasma collected from rats 24 h after the injection was subjected to ultracentrifugation at 1.225 g/ml; lipoproteins in the 1.225 g/ml supernatant were subsequently separated by both gel filtration chromatography and gradient gel electrophoresis. The major change in the treated animals was a total loss of the large, cholesteryl ester-rich, apolipoprotein E-rich high-density lipoproteins, HDL 1, which are prominent in the plasma of control rats. This loss of HDL 1 unmasked an obvious peak of low-density lipoproteins that had been obscured in the control rats. Other changes in the treated rats included an increase in the relative cholesteryl ester content of very-low-density lipoproteins and the emergence of a peak of triacylglycerol in the high-density lipoproteins.

Saturated fat feeding, hyperlipidemia and hyperinsulinemia

The effects of feeding saturated and eucaloric unsaturated fat-rich diets on lipemia and insulinemia in female Brown Norway rats have been compared. The relative hyperlipemia in the unsaturated fat group at 8 a.m. has declined at 10 a.m., whereas the saturated fat group at 8 a.m. gives lower values than at 10 a.m. It suggests that saturated fat feeding requires a longer absorption period. The insulin levels in the unsaturated fat groups are higher at 8 a.m. than at 10 a.m., whereas insulin levels in the saturated fat group are higher at 10 a.m. than at 8 a.m. It also suggests retarded resorption of food in the saturated fat group. The relative hyperlipemia at 10 a.m. in the saturated fat group applies to triacylglycerol, free cholesterol, free fatty acids and particularly phosphatidylcholine. It was almost 50% higher than phosphatidylcholine in the unsaturated fat group and coincided with the accumulation of an apolipoprotein E-rich high density lipoprotein.

Separation of rat plasma hdl subfractions by density gradient centrifugation and the effect of incubation on these fractions

The conditions for the separation of rat high density lipoproteins (HDL) in a single ultracentrifuge run are described. By this method six serum samples can be processed simultaneously. HDL is separated into two main fractions, one with apolipoprotein E and the other with apolipoprotein A-I as the major protein component. The apolipoprotein E-rich HDL contains a relatively high amount of phospholipid and unesterified cholesterol and therefore resembles HDL-1 or apolipoprotein E HDL as isolated by other methods. The other HDL fraction resembles HDL-2. The two HDL fractions appeared to be heterogeneous with respect to apolipoprotein composition. The HDL-1 consisted of particles with and without a low percentage of apolipoprotein A-I. The HDL-2 consisted of particles with a variable amount of apolipoprotein E and A-IV. During incubation of rat serum for 5 h at 37° C in the presence of dithiobis(2-nitrobenzoic acid) (DTNB) a small shift of the HDL-2 peak to lower densities occurred. Incubation of the serum without DTNB led to a loss of cholesterol from the ‘light’ HDL-1 fractions and an increase in cholesterol ester in fractions at densities intermediate between those of HDL-1 and HDL-2 and in fractions at the densest part of the gradient.

Plasma lipoprotein composition in alcoholic hepatitis: accumulation of apolipoprotein E-rich high density lipoprotein and preferential reappearance of "light'-HDL during partial recovery.

Abnormal lipoproteins accumulate in the plasma of alcoholic hepatitis patients in association with a deficiency of the cholesterol esterifying enzyme, lecithin:cholesterol acyl-transferase. Most of these abnormal lipoproteins are found in the d > 1.006 g/ml density fraction. To investigate the composition and morphology of the lipoproteins at various times during the illness in four patients, we have employed density gradient ultracentrifugation combined with analyses of gradient fractions by polyacrylamide gel electrophoresis, electroimmunoassay, and electron microscopy. At the onset of the illness, plasma cholesteryl esters ranged from 19-34% of total cholesterol; high density lipoprotein (HDL) cholesterol and apoA-I, the major HDL apoprotein, were <10% of normal; and most of the d > 1.006 g/ml triglycerides and phospholipids were found in the LDL density region. A linear correlation (r = 0.964, P < 0.001) was found between the d > 1.006 g/ml apoB concentration and the summation of the triglyceride and esterified cholesterol for that fraction, indicating a constant ratio of apoB to the summation of these two "core lipids". ApoA-I was primarily found in the fraction d > 1.18 g/ml (HDL(3) and VHDL) but not at all in the HDL(2) density range of the gradient. No cholesteryl esters were present in the apoA-I containing fractions. In contrast to normal, large amounts of apoE accumulated in lipoproteins isolated at d 1.055-1.114 g/ml. The apoE-rich fractions contained primarily phospholipids and unesterified cholesterol; they appeared by electron microscopy to be mixtures of spherical particles, vesicular particles, and chains of bilamellar discs. Analyses of the density gradient fractions by SDS polyacrylamide gel electrophoresis under reducing conditions indicated that apoA-II levels and distribution paralleled apoA-I, not apoE, providing evidence against appreciable concentrations of apoE-apoA-II complexes. During partial recovery from alcoholic hepatitis in three patients, the d > 1.006 g/ml unesterified cholesterol and triglyceride levels decreased, while esterified cholesterol, HDL-cholesterol, and apoA-I levels increased. The first HDL fractions to reappear were lipoproteins with HDL(2) density characteristics, as evidenced by simultaneous increases of apoA-I, apoA-II, cholesteryl esters and phospholipids. Lipoproteins with HDL(3) density characteristics appeared later. Long-term (6-10 months) follow-up studies indicated a substantial elevation of HDL cholesterol and apoA-I in three of the four patients that appeared to have resulted from further increases in their HDL(2)-like subspecies. The above results illustrate the diversity of abnormal lipoproteins in alcoholic hepatitis and the ability of density gradient ultra-centrifugation combined with lipid and apolipoprotein quantitation, electron microscopy, and polyacrylamide gel electrophoresis to partially resolve those lipoproteins in the d > 1.006 g/ml plasma fraction.-Weidman, S. W., J. B. Ragland, and S. M. Sabesin. Plasma lipoprotein composition in alcoholic hepatitis: accumulation of apolipoprotein E-rich high density lipoprotein and preferential reappearance of "light"-HDL during partial recovery.

Characterization of apolipoprotein E-rich high density lipoproteins in familial lecithin:cholesterol acyltransferase deficiency.

We have isolated and charachterized a subfraction of high density lipoproteins, rich in apolipoprotein E, from the plasma of patients afflicted with familial lecithin:cholesterol acyltransferase deficiency. Prepared by successive ultracentrifugal flotation, affinity chromatography on heparin-agarose, and affinity chromatography on conconavalin A-agarose, the subfraction contained disc-shaped lipoproteins that measured 14--40 nm in diameter and 4.4--4.5 nm in thickness. The major components were apolipoprotein E, phosphatidylcholine, and unesterified cholesterol, though other apolipoproteins and lipids were present in small amounts. A second subfraction of high density lipoproteins, isolated during the chromatography, contained apolipoproteins A-I and A-II, but no apolipoprotein E. This subfraction included disc-shaped lipoproteins, 13--24 nm in diameter, as well as small round particles, 5.7 nm in diameter. Both subfractions contained similar proportions of total protein relative to lipid, similar amounts of unesterified cholesterol relative to phosphatidylcholine, and a similar distribution of phosphatidylcholine fatty acid.