Novel large apolipoprotein E-containing lipoproteins of density 1.006-1.060 g/ml in human cerebrospinal fluid

Although the critical role of apolipoprotein E (apoE) allelic variation in Alzheimer's disease and in the outcome of CNS injury is now recognized, the functions of apoE in the CNS remain obscure, particularly with regard to lipid metabolism. We used density gradient ultracentrifugation to identify apoE-containing lipoproteins in human CSF. CSF apoE lipoproteins, previously identified only in the 1.063-1.21 g/ml density range, were also demonstrated in the 1.006-1.060 g/ml density range. Plasma lipoproteins in this density range include low-density lipoprotein and high-density lipoprotein (HDL) subfraction 1 (HDL1). The novel CSF apoE lipoproteins are designated HDL1. No immunoreactive apolipoprotein A-I (apo A-I) or B could be identified in the CSF HDL1 fractions. Large lipoproteins 18.3 +/- 6.6 nm in diameter (mean +/- SD) in the HDL1 density range were demonstrated by electron microscopy. Following fast protein liquid chromatography of CSF at physiologic ionic strength, apoE was demonstrated in particles of average size greater than particles containing apoA-I. The largest lipoproteins separated by this technique contained apoE without apoA-I. Thus, the presence of large apoE-containing lipoproteins was confirmed without ultracentrifugation. Interconversion between the more abundant smaller apoE-HDL subfractions 2 and 3 and the novel larger apoE-HDL1 is postulated to mediate a role in cholesterol redistribution in brain.     

Oxidative susceptibility of low density lipoprotein subfractions is related to their ubiquinol-10 and alpha-tocopherol content

The conjugated polyene fatty acid parinaric acid (PnA) undergoes a stoichiometric loss in fluorescence upon oxidation and can be used to directly monitor peroxidative stress within lipid environments. We evaluated the course of potentially atherogenic oxidative changes in low density lipoproteins (LDL) by monitoring the oxidation of PnA following its incorporation into buoyant (p = 1.026-1.032 g/ml) and dense (p = 1.040-1.054 g/ml) LDL subfractions. Copper-induced oxidation of LDL-associated PnA exhibited an initial lag phase followed by an increased rate of loss until depletion. Increased PnA oxidation occurred immediately after the antioxidants ubiquinol-10 and alpha-tocopherol were consumed but before there were marked elevations in conjugated dienes. Despite differences in sensitivity to early oxidation events, PnA oxidation and conjugated diene lag times were correlated (r = 0.582; P = 0.03), and both indicated a greater susceptibility of dense than buoyant LDL in accordance with previous reports. The greater susceptibility of PnA in dense LDL was attributed to reduced levels of ubiquinol-10 and alpha-tocopherol, which were approximately 50% lower than in buoyant LDL (mol of antioxidant/mol of LDL) and together accounted for 80% of the variation in PnA oxidation lag times. These results suggest that PnA is a useful probe of LDL oxidative susceptibility and may be superior to conjugated dienes for monitoring the initial stages of LDL lipid peroxidation. Differences in oxidative susceptibility among LDL density subfractions are detected by the PnA assay and are due in large part to differences in their antioxidant content.     

Lipoprotein distribution and composition in obesity: their association with central adiposity

OBJECTIVE: To examine the relationships between the distribution and composition of subfractions of very low density (VLDL), low density (LDL) and high density (HDL) lipoproteins and central fat deposition as measured by the waist-to-hip ratio (WHR). DESIGN: Participants (n = 62, 44 women and 18 men; body mass index (BMI) > or = 25.0) were recruited from those consecutively attending the outpatient obesity clinic at the University Hospital, Geneva. MEASUREMENTS: Lipoprotein subfractions were isolated from fasting blood samples by cumulative flotation or density gradient ultracentrifugation. Concentration and composition were analysed as a function of obesity indices. RESULTS: There were significant correlations between the WHR and the profiles of the three major lipoprotein subclasses. Central obesity was associated with larger VLDL, small, dense LDL and lower levels of HDL-2 independently of other indices of obesity and plasma triglycerides. Central obesity was also significantly and independently associated with compositional anomalies, specifically an increased free cholesterol content of VLDL and LDL. CONCLUSIONS: Central body fat was associated with modifications of an atherogenic nature to lipoprotein distribution and composition. The data are consistent with an impact of body fat distribution on cardiovascular disease (CVD) via the agency of modified lipoprotein metabolism independently of raised triglycerides.     

The prevalence of gentamicin 2''-N-acetyltransferase in the Proteeae and its role in the O-acetylation of peptidoglycan

The purpose of this study was to investigate the effects of an intensive diet and exercise program on the quantity and quality of LDL as well as its susceptibility to in vitro oxidation. The diet was low in fat (< 10% kcal) and cholesterol (< 100 mg/d), while high in complex, unrefined carbohydrates (> 70% kcal) and fiber (35 g/1000 kcal). The study was composed of 80 participants in a 3-week residential program where food was provided ad libitum and there was daily aerobic exercise, primarily walking. In each subject, preparticipation and postparticipation fasting blood samples were drawn and LDL was isolated via density gradient ultracentrifugation. LDL particle diameter was determined by gradient gel electrophoresis of serum (n = 23). Isolated LDL was either separated into 6 subfractions by saline gradient equilibrium ultracentrifugation (n = 26) or subjected to in vitro copper oxidation (n = 32). Significant reductions (P < .01) in serum levels of cholesterol (20%). LDL-cholesterol (20%), HDL-cholesterol (17%), triglycerides (26%), and glucose (16%) as well as in body weight (4%) were noted for the total population. The mean particle diameter of the LDL increased (24.2 +/- 0.2 to 25.1 +/- 0.14 nm, P < .01) and was correlated with the reduction in serum triglycerides (r = .58, P < .01). Six of 22 subjects changed in LDL phenotype from B (< or = 25.5 nm) to A (> 25.5 nm). The percentage of LDL-cholesterol carried in the more dense subfractions fell significantly, while that carried by the less dense fractions increased. Initial oxidation levels fell (21%), while the lag time before copper-induced oxidation increased (13%). Reductions were observed in both the rate of oxidation (16%) and peak oxidation (20%). All of these changes should result in a dramatic reduction in the risk for atherosclerosis and its clinical sequelae.     

Small, dense LDL particle concentration correlates with plasminogen activator inhibitor type-1 (PAI-1) activity

The relation between LDL subfractions and fibrinolytic activity was studied in 150 men aged 53 to 63 years. Apolipoprotein B (apoB) concentration in the most dense LDL-5 (r = 0.39, p <0.001) and LDL-6 (r = 0.43, p <0.001) subfractions associated with plasminogen activator inhibitor type-1 (PAI-1) activity. Subjects in the highest LDL-6 apoB tertile had higher PAI-1 (24.7 vs. 13.1 AU/ml, p <0.001) and lower t-PA (0.26 vs. 0.54 IU/ml, p <0.001) activities than men in the lowest tertile. The difference in PAI-1 remained after adjusting for either triglycerides (p = 0.039) or insulin (p = 0.015) with cardiorespiratory fitness as an additional covariate, and history of cardiovascular disease and smoking as factors. In a regression analysis, plasma insulin and LDL-6 apoB, but not plasma triglycerides and body mass index, entered the model, and explained 30.6 and 3.9% of the variance in PAI-1 activity, respectively. The novel finding of the present study was the independent association between small, dense LDL particles and PAI-1 activity in middle-aged men.     

Differences in lipoprotein lipid concentration and composition modify the plasma distribution of cyclosporine

PURPOSE: The purpose of this study was to define the relationship between lipoprotein (LP) lipid concentration and composition and the distribution of cyclosporine (CSA) in human plasma. METHODS: 3H-CSA LP distribution was determined in normolipidemic human plasma that had been separated into different LP and lipoprotein-deficient plasma (LPDP) fractions by either affinity chromatography coupled with ultracentrifugation, density gradient ultracentrifugation or fast protein liquid chromatography. 3H-CSA LP distribution (at a concentration of 1000 ng/ml) was also determined in patient plasma samples with defined dyslipidemias. Furthermore, 3H-CSA LP distribution was determined in patient plasma samples of varying LP lipid concentrations. Following incubation, the plasma samples were separated into their LP and LPDP fractions by sequential phosphotungistic acid precipitation in the dyslipidemia studies and by density gradient ultracentrifugation in the specific lipid profile studies and assayed for CSA by radioactivity. Total plasma and lipoprotein cholesterol (TC), triglyceride (TG) and protein (TP) concentrations in each sample were determined by enzymatic assays. RESULTS: When the LP distribution of CSA was determined using three different LP separation techniques, the percent of CSA recovered in the LP-rich fraction was greater than 90% and the LP binding profiles were similar with most of the drug bound to plasma high-density (HDL) and low-density (LDL) lipoproteins. When 3H-CSA was incubated in dyslipidemic human plasma or specific patient plasma of varying LP lipid concentrations the following relationships were observed. As the very low-density (VLDL) and LDL cholesterol and triglyceride concentrations increased, the percent of CSA recovered within the VLDL and LDL fractions increased. The percent of CSA recovered within the HDL fraction significantly decreased as HDL triglyceride concentrations increased. The percent of CSA recovered in the LPDP fraction remained constant except in hypercholesterolemic/hypertriglyceridemic plasma where the percent of CSA recovered decreased. Furthermore, increases in VLDL and HDL TG/TC ratio resulted in a greater percentage of CSA recovered in VLDL but less in HDL. CONCLUSIONS: These findings suggest that changes in the total and plasma LP lipid concentration and composition influence the LP binding of CSA and may explain differences in the pharmacological activity and toxicity of CSA when administered to patients with different lipid profiles.     

Neutral lipid mass transfer among lipoproteins in plasma from normolipidemic subjects is not an equimolar heteroexchange

To further characterize the cholesteryl ester transfer protein (CETP)-mediated distribution of neutral lipids that occurs among lipoproteins in plasma, the net mass transfer of core lipids between donor and acceptor lipoproteins in intact plasma was measured in ten healthy normolipidemic subjects. The rate of loss of cholesteryl ester (CE) from high density lipoprotein-3 (HDL3) (19.5 +/- 8.8 nmol/ml per h) was linear and increased significantly (P < 0.01) during the 6-h incubation. Approximately 50% of the CE transferred from HDL3 (118.7 +/- 54.3 nmol/ml) went to very low density lipoprotein (VLDL); the remainder was distributed to low density lipoprotein (LDL) (approximately 30%) and HDL2 (approximately 20%). The rate of loss of triglyceride (TG) from VLDL (14.5 +/- 6.6 nmol/ml per h) to the HDL subfractions and LDL also was linear and increased significantly with time (P < 0.01). About 50% of the TG mass lost from VLDL (85.2 +/- 38.4 nmol/ml) was transferred to LDL and the remainder was recovered in HDL2 (approximately 10%) and HDL3 (approximately 40%). As the number of nmoles of CE lost from HDL3 was almost three times greater than the nmoles of TG it acquired, these findings indicate that the exchange of core lipids in plasma that result from the interaction between CETP-VLDL-HDL3 is not equimolar. Even in the absence of VLDL, HDL3 continued to donate CE to LDL and HDL2 to almost the same degree as in intact plasma (plasma minus VLDL: 17.5 +/- 5.9 nmol/ml per h vs. intact plasma: 20.2 +/- 7.5 nmol/ml per h) without accepting any TG. Our findings demonstrate that independent pathways exist for the transfer of CE and TG among the plasma lipoproteins and, contrary to what is generally believed, a heteroexchange of TG for CE during cholesteryl ester transfer is not obligatory.     

Characteristics of ten charge-differing subfractions isolated from human native low-density lipoproteins (LDL). No evidence of peroxidative modifications

Native plasma low-density lipoproteins (LDL) were fractionated into ten subfractions with increasingly negative charges (LDL-1, the least electronegative, to LDL-10) using an anion-exchange column coupled to a fast protein-liquid chromatography system. Prior to fractionation, contaminating Lp(a) and apo A-I-containing lipoproteins were removed from LDL preparations by immunoaffinity chromatography. No significant difference in thiobarbituric acid-reactive substances, vitamin E or free aminogroup was found among subfractions, and no peptide with a higher molecular weight than apo B was observed on SDS-PAGE. We observed a gradual increase in cholesterol esters and a concomitant decrease in triglycerides from LDL-1 to LDL-7, and a reverse tendency from LDL-8 to LDL-10 (P < 0.01). Free cholesterol increased linearly from LDL-1 to LDL-10 (P < 0.01). LDL-1 to -3 had a homogeneous density profile, while other more electronegative subfractions showed a bimodal distribution with a second, minor peak of slightly higher density. A gradual increase in apolipoprotein C-III content related to LDL electronegativity was observed (P < 0.001). Apolipoprotein E content was also increased in the last two subfractions (P < 0.01). LDL subfractions displayed a similar binding fate on human fibroblasts, with the exception of the most electronegative subfractions [LDL-(9 + 10)], which bound more actively to apo B/E receptors (P < 0.05). This study shows that charge heterogeneity of native LDL is not related to lipid peroxidation or derivatization of free aminogroups of apolipoprotein B. In contrast, the enrichment of LDL in apolipoproteins other than apo B may explain, in part, the difference in their particle charge.     

Studies of anti-Xa activity in human plasma. II: The role of lipoproteins

The major plasma inhibitor of factor Xa is thought to be anti-thrombin III (At III). However, adsorption of plasma by aluminium hydroxide (A1(OH)3) increases its rate of neutralisation 7-8 fold, and this 'fast-acting' anti-Xa activity has been shown to be independent of At III. Gel filtration of plasma indicated that the anti-Xa activity after A1(OH)3 adsorption was located largely in the high molecular weight (greater than 200,000) fractions, which contain most of the plasma lipoproteins. Purified lipoproteins of very low-density (VLDL), low-density (LDL) and high density (HDL) were prepared by ultracentrifugation and their anti-Xa activities measured before and after adsorption by A1(OH)3. Both LDL and HDL had significant anti-Xa activities by clotting and amidolytic assays. A1(OH)3 adsorption of LDL and HDL gave a marked increase in anti-Xa clotting activity and a decrease in amidolytic activity. Incubation of the adsorbed lipoproteins with phospholipase enzymes destroyed the anti-Xa activity, and prior incubation of Factor Xa with Ca++ and phospholipid protected it against inactivation, indicating that the anti-Xa activity of the adsorbed lipoproteins is mediated via binding of Xa to phospholipid in the lipoproteins. These results indicate that lipoproteins, especially LDL and HDL, are responsible for the increased anti-Xa activity of plasma after A1(OH)3 adsorption. These lipoproteins appear to contain high affinity phospholipid binding sites for Xa which are revealed by A1(OH)3 adsorption.     

Charge properties of low density lipoprotein subclasses

Measurements of electrophoretic mobility and particle size of low density lipoproteins (LDL) allowed use of standard electrokinetic theory to quantitate LDL charge characteristics from subjects with predominance of large LDL (pattern A, n = 9) or small LDL (pattern B, n = 8). Pattern A LDL was found to have significantly lower (P < or = 0.001) mobility (-0.22 +/- 0.01 micron s-1 cm V-1), surface potential (-4.2 +/- 0.3 mV) and charge density (-500 +/- 34 esu/cm2) than pattern B LDL (-0.25 +/- 0.01 micron s-1 cm V-1, -4.9 +/- 0.3 mV, and -580 +/- 30 esu/cm2), but no significant difference in particle valence (-22.0 +/- 1.4 for pattern A vs. -21.8 +/- 1.9 for pattern B). Thus, the greater mobility of pattern B LDL is due to similar net charge residing on a smaller particle. Comparison of subfractions in pattern B relative to pattern A LDL revealed greater surface potential in all pattern B subfractions and greater charge density in fractions of d > or = 1.032 g/ml. In a subset of subjects incubation with neuraminidase produced significant reductions in all LDL charge parameters for all subfractions, but did not abolish the differences between pattern A and B. Thus increased surface potential and charge density of unfractionated pattern B LDL is due both to charge properties of particles across the size and density spectrum as well as enrichment of pattern B LDL with smaller, denser particles that have higher surface charge density.     

Generation of reactive oxygen species and activity of platelet-activating factor acetylhydrolase in human monocyte-derived macrophages

Monocytes were prepared from healthy human volunteers and were allowed to differentiate into macrophages by adhesion to plastic surface and cultured over 7 days in presence of either 10% fetal calf serum (FCS), human control serum or serum from hyperlipaemic patients. Hyperlipaemic serum stimulated the differentiation (measured as an increase in cellular protein and DNA content) to a higher extent when compared to control serum and FCS. With all sera a marked increase of the cellular activity of the enzyme platelet-activating factor acetylhydrolase (PAF-AH) and a tremendous decrease in the capacity of cells to generate reactive oxygen species (ROS) was observed. After seven days of culture the increase in PAH-AH activity was about 19-fold with hyperlipaemic serum, 11-fold with control serum and 6-fold with FCS. During the same period of time ROS generation measured as zymosan-induced chemiluminescence decreased by about 98% and no significant differences between the three types of serum were found. The results indicate that the activity of PAF-AH and the capacity of ROS generation which are both assumed to play an important role in the oxidation of low-density lipoproteins (LDL) and thus in the development of atherosclerosis, change in opposite direction during the differentiation of blood monocytes into macrophages, and that hyperlipaemic serum stimulates PAF-AH activity but not ROS generation.     

Acute and delayed effects of prolonged exercise on serum lipoproteins. II. Concentration and composition of low-density lipoprotein subfractions and very low-density lipoproteins

To investigate the effects of a single period of prolonged exercise on lipoprotein concentration and composition, 13 healthy endurance-trained men were examined before and after (1 h, 20 h) a cross-country run [30 km, time: 130 (SD 7.4) min]. The data show that following acute exercise, serum triglyceride (TG) concentration were reduced (36%) as a consequence of a reduced number (31%) of very low density lipoprotein (VLDL) particles. Changes in composition of VLDL were present but less evident. In contrast to this, acute exercise did not induce significant changes in the average concentration of individual low-density lipoprotein (LDL) subfractions. However, changes in dense LDL [density (d) > 1.044 g.ml-1] concentration were significantly correlated to changes in serum TG: a reduction of dense LDL occurred in subjects with large reductions in serum TG. In addition, LDL composition changed significantly. Immediately (1 h) after exercise the TG content of all LDL subfractions was reduced. These reductions were significant in large (d = 1.006-1.037 g.ml-1) and small LDL (1.044-1.063 g.ml-1). It can be concluded therefore from our study that acute exercise primarily altered the composition of LDL subfractions while their concentration remained stable.     

Significant association of lipid peroxidation products with high density lipoproteins

In this study the role of high density lipoproteins in lipoprotein peroxidation process was investigated. Under basal conditions, HDL isolated from human plasma or from total lipoprotein fraction (density > 1.21) using precipitation technique carried nearly 35-40% of the total plasma fatty acid peroxidation product (measured as malonaldehyde, MDA). HDL associated MDA was reduced to < 20% when HDL was isolated by ultracentrifugation from plasma treated with Cu++. Under these conditions, 45% of the cholesterol peroxidation products (oxysterols) were associated with HDL. HDL isolated from Cu++ treated plasma significantly lost its ability to inhibit LDL peroxidation. These results suggest that HDL plays an important role in lipid peroxidation a) by carrying significant amounts of cholesterol and lipid peroxidation products, and b) its ability to inhibit LDL oxidation is compromised when HDL itself is oxidized.     

Initial clinical experience with the Ahmed Glaucoma Valve implant in pediatric patients

There is evidence that a low-density lipoprotein (LDL) subfraction profile of increased concentrations of small, dense LDL particles is less common among trained than among sedentary normocholesterolemic men, but it is still uncertain whether there is a similar association in hypercholesterolemia also. Therefore, we determined the lipid and apolipoprotein concentration and composition of six LDL subfractions (density gradient ultracentrifugation) in 20 physically fit, regularly exercising (>three times per week) hypercholesterolemic men and 20 sedentary hypercholesterolemic controls. Trained (maximal oxygen consumption [VO2max], 57.3 +/- 7.4 mL/kg/min) and sedentary (VO2max, 37.5 +/- 8.8 mL/kg/min) individuals (aged 35 +/- 11 years; body mass index [BMI], 23.9 +/- 2.7 kg/m2) were matched for LDL apolipoprotein (apo) B levels (108 +/- 23 and 112 +/- 36 mg/dL, respectively). Trained subjects had significantly lower serum triglyceride (P < .05) and very-low-density lipoprotein (VLDL) cholesterol levels (P < .05) and higher high-density lipoprotein 2 (HDL2) cholesterol levels (P < .01) than sedentary controls. LDL particle distribution showed that trained individuals had significantly less small, dense LDL (d = 1.040 to 1.063 g/mL) and more large LDL (d = 1.019 to 1.037 g/mL) subfraction particles than sedentary controls, despite equal total LDL particle number. Analysis of LDL composition showed that LDL particles of hypercholesterolemic trained men had a higher free cholesterol content than LDL of untrained hypercholesterolemic men. Small, dense LDL in hypercholesterolemic trained men were richer in phospholipids than those in sedentary controls. These data demonstrate the significant influence of aerobic fitness on lipoprotein subfraction concentration and composition, thereby emphasizing the role of exercise in the treatment and risk reduction of hypercholesterolemia.     

An efficient chromatographic system for lipoprotein fractionation using whole plasma

We have validated a semi-automatic procedure for the efficient isolation of plasma lipoproteins from 300 microl of whole plasma (actual injection volume 200 microl) by Fast Phase Liquid Chromatography (FPLC). Modified enzymatic assays were established to allow the determination of low concentrations (1-20 mg/dl) of triglycerides and cholesterol using the Beckman CX-5 Autoanalyzer. The sum of the cholesterol contents in the fractions corresponding to low density (LDL) and high density lipoprotein (HDL) can be demonstrated to be highly correlated to values obtained with dextran sulfate/MgCl2 precipitation for HDLc (slope = 0.98, r2 = 0.997) and ultracentrifugation (beta-quant) for LDLc (slope = 1.03, r2 = 0.988). Using pure lipoprotein fractions isolated by ultracentrifugation, linear ranges of detection for HDLc and HDL apoA-I were performed at 18-95 mg/dl and 59-262 mg/dl, respectively. The ranges for LDLc were 41-435 mg/dl and 21-280 mg/dl for LDL apoB. The mean (range) fractional standard deviations for quadruplicate runs for 15 individual plasma samples ranging widely in lipoprotein concentrations were 0.97 (0.29-2.86%) for LDLc (range: 101.5-258.5 mg/dl), 3.67 (0.62-14.11%) for HDLc (range: 27.1-85.1 mg/dl) and 2.19 (0.16-6.56%) for VLDL-TG (range: 6.1-515.0 mg/dl).     

Granulocytic-macrophagic and macrophagic colony stimulating factors elicit colonies of mast cells in mouse bone marrow agar culture. An electron microscope study

The aim of this paper is to describe a new methodology for the separation of human high-density lipoproteins (HDL) into apolipoprotein (apo) E-poor and apo E-rich subfractions by fast protein liquid chromatography (FPLC) using a heparin affinity column. Recoveries for apolipoproteins AI, AII, CI, CII, CIII, and E were 68.9, 74.7, 71.9, 73.5, 40.0, and 55.8%, respectively. We provide suggestive evidence that apo E-rich HDL is produced from apo E-poor HDL by the displacement of apo AI by apo E. Apo E-poor HDL was the predominant fraction. The molar ratio of apo E to apo AI in apo E-poor HDL was 0.02 and 0.01 for the subjects studied while in apo E-rich HDL it was 1.86 and 1.25. The molar ratios of the C apolipoproteins to apo AI are markedly different between the subfractions.     

Influence of plasma cholesteryl ester transfer activity on the LDL and HDL distribution profiles in normolipidemic subjects

The relations of cholesteryl ester transfer protein (CETP) activity to the distribution of low density lipoproteins (LDLs) and high density lipoproteins (HDLs) were investigated in fasting plasma samples from 27 normolipidemic subjects. LDL and HDL subfractions were separated by electrophoresis on 20-160 g/L and 40-300 g/L polyacrylamide gradient gels, respectively. Subjects were subdivided into two groups according to their LDL pattern. Monodisperse patterns were characterized by the presence of a single LDL band, whereas polydisperse patterns were characterized by the presence of several LDL bands of different sizes. To investigate the influence of lipid transfers on LDL patterns, total plasma was incubated at 37 degrees C in the absence of lecithin:cholesterol acyltransferase (LCAT) activity. The incubation induced a progressive transformation of polydisperse patterns into monodisperse patterns. Under the same conditions, initially monodisperse patterns remained unchanged. Measurements of the rate of radiolabeled cholesteryl esters transferred from HDL3s to very low density lipoproteins (VLDLs) and LDLs revealed that subjects with a monodisperse LDL pattern presented a significantly higher plasma CETP activity than subjects with a polydisperse LDL pattern (301 +/- 85%/hr per milliliter versus 216 +/- 47%/hr per milliliter, respectively; p < 0.02). In addition, when total plasma was incubated for 24 hours at 37 degrees C in the absence of LCAT activity, the relative mass of cholesteryl esters transferred from HDLs to apolipoprotein B-containing lipoproteins was greater in plasma with monodisperse LDL than in plasma with polydisperse LDL (0.23 +/- 0.06 versus 0.17 +/- 0.06, respectively; p < 0.02). These results indicated that in normolipidemic plasma, CETP could play an important role in determining the size distribution of LDL particles. The analysis of lipoprotein cholesterol distribution in the two groups of subjects sustained this hypothesis. Indeed, HDL cholesterol levels, the HDL:VLDL+LDL cholesterol ratio, and the esterified cholesterol:triglyceride ratio in HDL were significantly lower in plasma with the monodisperse LDL pattern than in plasma with the polydisperse LDL pattern (p < 0.01, p < 0.01, and p < 0.02, respectively). Plasma LCAT activity did not differ in the two groups. Plasma CETP activity correlated positively with the level of HDL3b (r = 0.542, p < 0.01) in the entire study population. Whereas plasma LCAT activity correlated negatively with the level of HDL2b (r = -0.455, p < 0.05) and positively with the levels of HDL2a (r = 0.475, p < 0.05) and HDL3a (r = 0.485, p < 0.05), no significant relation was observed with the level of HDL3b.(ABSTRACT TRUNCATED AT 400 WORDS)     

Biological and molecular characterization of Newcastle disease virus (NDV) field isolates with comparisons to reference NDV strains

3T3-L1 and human preadipocyte differentiation was significantly (P < 0.001) enhanced by HDL2, LDLII/III and LDLIV. The concentrations of lipoproteins required for maximal differentiation in human preadipocytes were not achieved over the concentration range 50-150 micrograms lipoprotein protein ml-1, whereas maximal differentiation in 3T3-L1 preadipocytes was achieved for all lipoprotein subfractions at approximately 75 micrograms lipoprotein ml-1, a level almost double that required for complete HDL and LDL fractions in 3T3-L1 cells. Despite the enhanced extent of differentiation caused by certain lipoprotein subfractions, the time needed for the conversion process was unaffected. GPDH activity development in both cell types was most pronounced in response to LDLIV, with HDL2 resulting in the lowest activity. In both cell types, the enhancement of differentiation was only evident when the cells were exposed to lipoproteins during the early stage of the program, i.e. before visible formation of lipid droplets.     

Hyperbetalipoproteinemia with small low-density lipoprotein, a characteristic disorder of lipoprotein in essential hypertension

The purpose of the present study was to elucidate the characteristic lipoprotein disorder in essential hypertension. Twenty-six patients with essential hypertension (HT) but without diabetes mellitus or obesity and 24 healthy subjects (control) were recruited into this study. Lipoproteins of HT and controls were separated by ultracentrifugation to very-low-density lipoprotein (VLDL), intermediate density lipoprotein (IDL), low-density liproprotein (LDL), and (HDL) fractions. Cholesterol and triglycerides were determined with enzyme assay, and apoB were determined by highly sensitive latex agglutination (Kyowa-hakko Co. LD). There was no difference in age (mean +/- SE; HT, 63 +/- 2 versus control, 60 +/- 2 years) or body-mass index (22.7 +/- 0.4 versus 21.7 +/- 0.5 kg/m2) between HT and controls. Blood pressure in HT and controls was 158 +/- 2/87 +/- 12 mm Hg and 123 +/- 3/72 +/- 2 mm Hg, respectively. Cholesterol did not change significantly in plasma (192.1 +/- 7.0 versus 176.4 +/- 4.2 mg/dL), VLDL (15.2 +/- 2.4 versus 11.8 +/- 1.7 mg/dL), IDL (14.8 +/- 2.4 versus 10.7 +/- 1.6 mg/dL), LDL (93.7 +/- 4.6 versus 83.1 +/- 3.9 mg/dL), nor in HDL (51.9 +/- 2.7 versus 58.1 +/- 3.2 mg/dL). Triglycerides (TG) increased in plasma (120.0 +/- 10.0 versus 87.5 +/- 9.3 mg/dL, p < 0.05), although TG did not change in all subfractions. ApoB increased in plasma (105.5 +/- 5.1 versus 85.6 +/- 3.6 mg/dL, p < 0.01), IDL (9.0 +/- 1.3 versus 5.4 +/- 0.6 mg/dL, p < 0.05), and LDL (76.3 +/- 4.3 versus 59.4 +/- 3.7 mg/dL, p < 0.01) in HT compared with controls. The ratio of cholesterol to apoB in LDL decreased (1.27 +/- 0.06 versus 1.48 +/- 0.08, p < 0.05). In essential HT, number of apoB containing lipoproteins (IDL, LDL) increased. Low ratio of cholesterol to apoB was noted in LDL, indicating the presence of small, dense LDL. As cholesterol in LDL was normal, hyperbetalipoproteinemia is also a characteristic disorder of essential HT.     

Lipoprotein heterogeneity and apolipoprotein B metabolism

The apolipoprotein B containing lipoproteins VLDL, IDL, and LDL exhibit variation in their structure, function, and metabolism. These major lipoprotein classes can be fractionated into apparently discrete components by density gradient centrifugation or affinity chromatography. Examination of the behavior of subfractions in vivo reveals the presence of metabolic channels within the VLDL-LDL delipidation cascade so that the pedigree of a lipoprotein in part determines its metabolic fate. Evidence from VLDL and LDL apoB turnovers together with epidemiological data allows the construction of a quantitative model for the generation of small, dense LDL. This lipoprotein subspecies is one component of the dyslipidemic syndrome known as the atherogenic lipoprotein phenotype, a common disorder in those at risk for coronary heart disease. Understanding lipoprotein heterogeneity is an essential step in the further discovery of the pathogenesis of atherosclerosis and in the tailoring of pharmacologic treatment for subjects at risk.