bluuebunny/crossref_metadata_2025 huggingface dataset:
A common deletion polymorphism in the apolipoprotein A4 gene and its significance in lipid metabolism.
Authors: Kamboh M I , Friedlaender J S , Ahn Y I , Ferrell R E
Published: June 2011

Apolipoprotein A-IV (apoA-IV, protein; APOA4, gene) is a major constituent of high-density lipoprotein (HDL) and triglyceride-rich lipoprotein particles, but its precise function in lipid metabolism is still uncertain. We have determined APOA4 genetic polymorphism in 285 randomly selected Melanesians from the Solomon Islands and have evaluated its significance in lipid metabolism. By using isoelectric focusing and immunoblotting techniques, a variant pattern, indistinguishable from the APOA4*2 allele uniquely found in white populations at a frequency of about 8%, was detected at a relatively high frequency (19%) in the Melanesian sample. Polymerase chain reaction (PCR) amplification and DNA sequencing of the 3' end of the APOA4 gene revealed that the Melanesian mutation is distinct from the known APOA4*2 mutation and that it involves a four-amino acid deletion in the evolutionarily conserved carboxyl-terminal region in the apoA-IV protein, which consists of four repeats of four amino acids each. After adjustment for concomitant variables, we investigated the impact of the deletion polymorphism on plasma levels of cholesterol, triglycerides, apoA-I, apoA-II, and apoE. A significant (P = .02) and gene-dosage effect was observed on the plasma levels of apoA-I and apoA-II: these levels were lowest in individuals homozygous for the deletion allele (D), intermediate in heterozygotes (ND), and highest in homozygous individuals for the normal allele (N). The average effect of the APOA4*D allele was to lower apoA-I and apoA-II by 8 mg/dL and 2 mg/dL, respectively, and the APOA4 polymorphism accounted for about 3% of the phenotypic variance in both cases.(ABSTRACT TRUNCATED AT 250 WORDS)
A gene-gender interaction affecting plasma lipoproteins in a genetic isolate.
Authors: Hegele R A , Evans A J , Tu L , Ip G , Brunt J H , Connelly P W
Published: June 2011

The Hutterite Brethren are a genetic isolate characterized by high indices of relatedness and a communal agrarian lifestyle. We hypothesized that variation in their apolipoprotein (apo) E and lipoprotein lipase (LPL) genes would be associated with variation in fasting plasma lipoproteins. We measured plasma lipids, lipoproteins, and apolipoproteins and analyzed DNA for genotypes of apoE and LPL in 803 Hutterites. We observed that apoE and LPL genotypes were significantly associated with variations in plasma total cholesterol, low-density lipoprotein (LDL) cholesterol, and apoB. When the data were subdivided by sex, apoE genotype was associated with plasma apoB-related traits in men, but LPL genotype was not. In contrast, LPL genotype was associated with plasma apoB-related traits in women, including triglycerides and LDL cholesterol. After accounting for age, body mass index, and colony of origin, the variation in these variables was much more significantly associated with LDL genotype than with apoE genotype in women but not in men. The association of LPL variation with plasma lipoproteins in women suggests that the functional effects of important structural elements within, flanking, or proximal to the LPL gene on chromosome 8p22 may be sex related.
Preferential cholesteryl ester acceptors among the LDL subspecies of subjects with familial hypercholesterolemia.
Authors: Guérin M , Dolphin P J , Chapman M J
Published: June 2011

Elevated cholesteryl ester transfer protein-mediated transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to low-density lipoprotein (LDL) may contribute to the atherogenicity of LDL in subjects with familial hypercholesterolemia (FH). To identify the major CE acceptors among LDL subspecies, we investigated the qualitative and quantitative features of CE transfer and exchange to LDL on incubation of plasma under physiological conditions. LDL subspecies were fractionated by density-gradient ultra-centrifugation. Both mass transfer and exchange of HDL CE to and with very-low-density lipoprotein plus intermediate-density lipoprotein and LDL were linear for the first 6 hours of incubation. Thereafter mass transfer ceased, but exchange continued at a comparable rate. The rate of CE mass transfer to apolipoprotein B-containing lipoproteins was significantly enhanced in heterozygous FH subjects compared with normolipidemic individuals (91.6 +/- 28.2 versus 52.9 +/- 19.6 micrograms CE/h per milliliter plasma, FH versus normal subjects, P < .02). In FH subjects the predominant LDL subspecies (LDL 3 and 4, d = 1.029 to 1.050 g/mL) accounted for 59.7 +/- 9.2% of the total CE transferred to LDL from HDL. By contrast, expression of CE mass transfer relative to the mass of each lipoprotein acceptor showed the triglyceride (TG)-rich (10.7% to 17.3%), light LDL subspecies (LDL 1 and 2, d = 1.019 to 1.029 g/mL) to represent the preferential CE acceptors (LDL 1 and 2, 94.8 to 136.5 micrograms CE/mg LDL mass; LDL 3 through 5 [d = 1.029 to 1.063 g/mL], 47.1 to 64.1 micrograms CE/mg LDL mass).(ABSTRACT TRUNCATED AT 250 WORDS)
Interaction of the allogeneic state and hypercholesterolemia in arterial lesion formation in experimental cardiac allografts.
Authors: Tanaka H , Sukhova G K , Libby P
Published: June 2011

To learn more about the interaction of allogeneic transplantation and hypercholesterolemia in the formation of arterial lesions, we performed heterotopic cardiac transplantation in rabbits. We analyzed lesions in both the coronary arteries and the proximal ascending aorta 6 weeks after surgery in both transplanted and native hearts of normocholesterolemic rabbits and those with diet-induced hypercholesterolemia (serum cholesterol, 1638 +/- 366 mg/dL, n = 6, 6 weeks after transplantation). All animals received cyclosporin A (5 mg.kg-1.d-1) for immunosuppression. The transplanted aortas of hypercholesterolemic animals had thicker intimal lesions than did the native aortas (intima/media ratio, 0.67 +/- 0.4 versus 0.08 +/- 0.1, P < .05) and contained more T cells (37.4 +/- 12.8 versus 5.7 +/- 6.2 per high-power field, P < .001). In normocholesterolemic animals (n = 5) the coronary arteries had negligible lesions in the native heart and only slight and inconsistent intimal lesions in the transplanted heart. In the hypercholesterolemic animals, more coronary arteries had intimal lesions in the transplanted hearts than in the native hearts (74% versus 43%). Coronary artery lesions in the native hearts consisted mostly of foam cells, while those in transplanted hearts had more abundant smooth muscle cells as determined by alpha-actin staining. Intimal endothelial cells in transplanted aortas expressed increased levels of vascular cell adhesion molecule-1 and intracellular adhesion molecule-1 compared with the native vessels subjected to identical levels of cholesterolemia. Medial smooth muscle cells in transplanted aortas contained much higher levels of immunoreactive tumor necrosis factor-alpha than did medial cells of the native aorta in the same hypercholesterolemic animals. The intima of transplanted aortas contained prominent microvessels compared with the native aorta of the hypercholesterolemic rabbits. We conclude that even during treatment with doses of cyclosporine that control acute myocardial rejection, hypercholesterolemia and the allogeneic state act together to augment allograft atherosclerosis, T-cell accumulation, intimal neovascularization, local cytokine expression, and indices of cell activation in arteries.
Chronic inhibition of nitric oxide production accelerates neointima formation and impairs endothelial function in hypercholesterolemic rabbits.
Authors: Cayatte A J , Palacino J J , Horten K , Cohen R A
Published: June 2011

To determine if endogenous local levels of nitric oxide (NO) modulate atherogenesis, we studied the effect of inhibiting NO with NG-nitro-L-arginine methyl ester (L-NAME) on early neointima formation in cholesterol-fed rabbits. Male rabbits were fed for 5 weeks with a 0.5% cholesterol diet alone or treated in addition during the last 4 weeks with L-NAME (12 mg/kg per day SC) via osmotic minipump. Endothelial cell function was assessed in isolated aortic rings by vascular reactivity and levels of cyclic GMP. In L-NAME-treated rabbits there was inhibition of endothelium-dependent relaxations to acetylcholine and the calcium ionophore A23187 as well as impaired cyclic GMP accumulation in response to acetylcholine. Neointima formation in the ascending thoracic aorta was assessed by determining media and intima cross-sectional areas with computerized image analysis. Compared with rabbits that consumed the cholesterol diet alone, L-NAME-treated rabbits had significant increases in lesion area (0.29 +/- 0.04 versus 0.15 +/- 0.03 mm2) and in lesion/media ratio (0.06 +/- 0.01 versus 0.03 +/- 0.01). Plasma levels of cholesterol and fluorescent lipid peroxide products were unchanged, suggesting no difference in cholesterol metabolism or oxidation. Because arterial blood pressure was not altered by L-NAME treatment, the increased atherogenesis could not be attributed to an increase in blood pressure. These results indicated that local inhibition of NO accelerates early neointima formation possibly because of modulating monocyte recruitment or foam cell lipid accumulation.
Binding and degradation of lipoprotein(a) and LDL by primary cultures of human hepatocytes. Comparison with cultured human monocyte-macrophages and fibroblasts.
Authors: Snyder M L , Hay R V , Whitington P F , Scanu A M , Fless G M
Published: June 2011

Although lipoprotein(a) (Lp[a]) has structural similarities to low-density lipoprotein (LDL) that include the presence of apolipoprotein B100, there is some disagreement over the strength of its interaction with the LDL receptor and its cellular catabolism by the LDL receptor-mediated pathway. To clarify this subject we evaluated LDL receptor-mediated binding and degradation of Lp(a) and LDL in three human cell lines. The binding of 50 nmol/L Lp(a) at 37 degrees C to the LDL receptor of primary hepatocytes, macrophages, and fibroblasts was only 10%, 29%, and 29% of the respective value obtained with 50 nmol/L LDL. Analysis of 4 degrees C binding curves indicated that Lp(a) and LDL had equal affinities for the LDL receptor of fibroblasts, whereas maximal binding of Lp(a) was remarkably lower than that of LDL. LDL receptor-mediated degradation of 50 nmol/L Lp(a) in hepatocytes, macrophages, and fibroblasts was only 17%, 22%, and 26%, respectively, of the value obtained with 50 nmol/L LDL and varied greatly among the cells in that it was lowest in hepatocytes, an order of magnitude greater in macrophages, and two orders of magnitude greater in fibroblasts. In contrast, the nonspecific degradation rate of Lp(a) was similar to that of LDL in each of the three tested cell lines. However, the proportion of the degradation of Lp(a) that was nonspecific varied greatly, being 76%, 58%, and 33% in hepatocytes, macrophages, and fibroblasts, respectively. These studies indicate that not only is Lp(a) recognized by the LDL receptor but also that, in fibroblasts, Lp(a) and LDL have equal affinities for the LDL receptor, although Lp(a) has a much lower receptor occupancy than LDL. Additionally, they show that there are great cellular differences in the LDL receptor-mediated degradation of Lp(a). If these results can be extrapolated in vivo, where normal LDL levels are 40- to 50-fold higher than those of Lp(a), it would be unlikely that the hepatic LDL receptor is significantly involved in the degradation of Lp(a).
Stimulation of PAI-1 expression in endothelial cells by cultured vascular smooth muscle cells.
Authors: Gallicchio M , Argyriou S , Ianches G , Filonzi E L , Zoellner H , Hamilton J A , McGrath K , Wojta J
Published: June 2011

Regulation of endothelial cell (EC) plasminogen activator inhibitor type-1 (PAI-1), the primary physiological inhibitor of tissue-type plasminogen activator (TPA) and urokinase-type plasminogen activator (UPA), by various stimuli has been well characterized. We report the upregulation of secreted and intracellular PAI-1 in human umbilical ECs when cocultured with human smooth muscle cells (SMCs) on amniotic membranes or incubated with SMC conditioned medium (CM) under serum-free conditions as determined by enzyme-linked immunosorbent assay. Cocultured human umbilical vein ECs and SMCs, or human umbilical artery ECs and SMCs, displayed a 73% and 68% increase, respectively, in released PAI-1. SMC-derived stimulatory factor release showed tissue specificity, since only human aortic, umbilical vein, and umbilical artery SMCs upregulated PAI-1 synthesis, whereas SMCs from human mammary artery, pulmonary artery, and saphenous vein did not. Stimulation of EC PAI-1 by SMC CM was both time and concentration dependent, with as much as five- and fourfold increases in supernatants and lysates, respectively. PAI-1 synthesis and activity in ECs from other vascular beds were also upregulated by SMC CM. Northern blot analysis paralleled the protein results, showing as much as a 2.7-fold increase in specific EC PAI-1 mRNA expression after incubation with SMC CM for 8 hours. PAI-1 stimulatory activity in SMC CM was completely abolished by boiling or incubation with protamine sulfate and was reduced by transient acidification or heparin-Sepharose pretreatment by 33% or 48%, respectively. The stimulatory factor(s) appeared to have a molecular mass of 23 kD as determined by gel filtration.(ABSTRACT TRUNCATED AT 250 WORDS)
Sex differences in susceptibility to etiologic factors for peripheral atherosclerosis. Importance of plasma fibrinogen and blood viscosity.
Authors: Fowkes F G , Pell J P , Donnan P T , Housley E , Lowe G D , Riemersma R A , Prescott R J
Published: June 2011

Cardiovascular risk factors in men, such as cigarette smoking, hypercholesterolemia, and hypertension, also increase risk in women, but the relative susceptibility to risk factors between the sexes is not established. Our aim was to investigate a wide range of possible etiologic factors in a single population study and identify those that were more strongly related to peripheral atherosclerosis in men or women. We studied personal factors (age and social class), lifestyle factors (smoking, exercise, alcohol intake, and dietary nutrients), and intermediary factors (obesity, diabetes, serum lipids, coagulation, and rheological factors). In the Edinburgh Artery Study in 1988 we measured cardiovascular risk factors in a random population sample of 1592 men and women aged 55 to 74 years. The ankle-brachial pressure index (ABPI), which is inversely related to the degree of peripheral atherosclerosis, was assessed in each subject. Lifetime cigarette smoking was correlated with a lower ABPI equally in men and women (r = -.27, P < .001). Dietary nutrients and alcohol intake were not related differently between the sexes with ABPI. However, recall of strenuous and moderate leisure time exercise during the age range of 35 to 45 years was related more strongly to a higher ABPI in men than in women (P < .05). Plasma fibrinogen, plasma viscosity, and blood viscosity were the only intermediary factors that had stronger univariate correlations with lower ABPI in men than in women. On multivariate analysis, the sex differences persisted for plasma fibrinogen (P < .05) and blood viscosity (P < .001); high-density lipoprotein cholesterol was related to ABPI in men only (sex difference, P < .1).(ABSTRACT TRUNCATED AT 250 WORDS)
The LPL gene in individuals with familial combined hyperlipidemia and decreased LPL activity.
Authors: Nevin D N , Brunzell J D , Deeb S S
Published: June 2011

Familial combined hyperlipidemia (FCHL) is an oligogenic disorder, with family members having elevated apolipoprotein B-100 levels and either elevated plasma cholesterol or triglyceride levels or both. Obligate heterozygous parents of children with lipoprotein lipase (LPL) deficiency express a mild FCHL phenotype. Of patients with FCHL, 36% have diminished postheparin LPL activity and mass values that are comparable with those of obligate heterozygotes for LPL deficiency. It is hypothesized that heterozygosity for mutations in the LPL gene could contribute to FCHL in this subset of patients. Single-strand conformation polymorphism (SSCP) analysis, direct DNA sequencing, and Southern blot analysis were used to examine exons 1 through 9 and exon-intron junctions of the LPL gene in 20 patients with FCHL and low LPL activity and mass. One subject had a substitution (GAC-->AAC) in exon 2, changing Asp9 to Asn. Two subjects had a previously undescribed "silent" substitution (GTG-->GTA) in exon 3 at Val108. Three patients had a premature termination at codon 447 in exon 9 resulting in truncation of the mature protein by two amino acids. In addition to SSCP analysis, exons 4, 5, and 6, where almost all mutations in LPL-deficient patients have been found, were sequenced and no additional mutations were found. Southern blot analysis of the LPL gene revealed one subject with heterozygous loss of an EcoRI site but without an abnormality in Stu I restriction fragments; this mutation is therefore unlikely to be functionally significant. The substitutions identified at codons 9 and 447 have previously been found not to affect lipolytic activity when expressed in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
Associations of allelic differences at the A-I/C-III/A-IV gene cluster with carotid artery intima-media thickness and plasma lipid transport in hypercholesterolemic-hypertriglyceridemic humans.
Authors: Patsch W , Sharrett A R , Chen I Y , Lin-Lee Y C , Brown S A , Gotto A M , Boerwinkle E
Published: June 2011

Individuals with elevated levels of plasma cholesterol and triglyceride may be at higher risk for coronary artery disease than those with isolated elevations of either cholesterol or triglyceride. Sequence variation in the A-I/C-III/A-IV gene cluster has been implicated in the etiology of some disorders associated with premature atherosclerosis and/or hypertriglyceridemias with or without elevations of cholesterol. This led to the hypothesis that allelic variation at this gene locus alters plasma lipid transport and affects susceptibility for atherosclerosis. The study population, from the Atherosclerosis Risk in Communities (ARIC) Study, consisted of 50 normolipidemic individuals, 48 subjects with elevated plasma cholesterol, 47 subjects with elevated plasma triglyceride, and 123 subjects with both elevated plasma cholesterol and triglyceride who were used to evaluate associations between an Xmn I polymorphic site 2.5 kilobase pairs (kbp) upstream of the structural gene for apolipoprotein (apo) A-I, intimal-medial thickening of the extracranial carotid arteries, and several plasma lipid factors. The relative allele frequencies of the 8.3-kbp allele and the 6.6-kbp allele were .86 and .14, respectively, in the entire study population and did not differ among the lipid phenotypes. In the group with elevated plasma cholesterol and triglyceride, subjects possessing the 6.6-kbp allele exhibited a greater carotid artery intimal-medial thickness (P = .034) and higher plasma levels of apoA-I, high-density lipoprotein (HDL) cholesterol, and HDL3 cholesterol (P < .02) than subjects homozygous for the 8.3-kbp allele. In contrast, subjects with the 6.6-kbp allele displayed lower mean ratios of apolipoproteins C-II to C-III, C-II to A-IV and E to A-IV in plasma (P < .05) and a lower mean ratio of apolipoprotein C-II to C-III in the triglyceride-rich lipoproteins (P = .026). Sequence variation in or near the genes encoding apolipoproteins A-I, C-III, and A-IV may therefore identify a group of hypercholesterolemic-hypertriglyceridemic persons who are at higher risk for atherosclerosis than others with the same lipoprotein phenotype.
Inhibition of PDGF receptor binding and PDGF-stimulated biological activity in vitro and of intimal lesion formation in vivo by 2-bromomethyl-5-chlorobenzene sulfonylphthalimide.
Authors: Mullins D E , Hamud F , Reim R , Davis H R
Published: June 2011

The proliferation of vascular smooth muscle cells (SMCs) is a key event in the development of atherosclerotic lesions and in the restenosis of arteries after angioplasty. Polypeptide growth factors are potent SMC mitogens in vitro and are believed to be involved in SMC proliferation in vivo. Strong data exist linking platelet-derived growth factor (PDGF) activity to human atherosclerosis. However, no low-molecular-weight antagonists of this growth factor have been discovered. We identified a compound, SCH 13929 (2-bromomethyl-5-chlorobenzene sulfonylphthalimide), which inhibits binding of 125I-PDGF BB to cell surface receptors with an IC50 of 0.13 mumol/L. This compound has a lesser effect on the binding of 125I-epidermal growth factor (EGF), 125I-basic fibroblast growth factor (bFGF), or 125I-endothelin to specific cell surface receptors. Exposure of cultured SMCs to SCH 13929 inhibits PDGF BB- and PDGF AA-stimulated DNA synthesis but not EGF- or bFGF-stimulated DNA synthesis. PDGF BB-stimulated SMC division is also inhibited by exposure to SCH 13929. Chemotaxis assays indicate that SCH 13929 inhibits PDGF-stimulated directional migration and suggest that the compound interacts with PDGF rather than with the receptor. Oral administration of SCH 13929 (100 mg/kg per day) to Sprague-Dawley rats or spontaneously hypertensive rats results in significant inhibition of lesion formation in the balloon catheter-deendothelialized carotid artery. These results suggest that SCH 13929 may be a useful tool for understanding the role of PDGF in intimal lesion formation.
A cell culture system for screening human serum for ability to promote cellular cholesterol efflux. Relations between serum components and efflux, esterification, and transfer.
Authors: de la Llera Moya M , Atger V , Paul J L , Fournier N , Moatti N , Giral P , Friday K E , Rothblat G
Published: June 2011

A cell culture system was employed to test a large number of samples of human serum for the ability to stimulate the efflux of cell cholesterol. The extent of efflux obtained with each specimen was correlated with the serum concentrations of cholesterol, triglycerides, apoprotein (apo) B, apo A-I, apo A-II, and lipoprotein subfractions (ie, high-density lipoprotein2 [HDL2], HDL3, lipoprotein [Lp] A-I, and LpA-I:A-II). In addition, the subsequent esterification of the released cholesterol and the distribution of the synthesized exogenous cholesteryl esters between HDL and low-density lipoprotein/very-low-density lipoprotein provided estimates of the lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities of each serum. The values for these activities were analyzed for correlations with cell efflux and the various serum parameters. Cell cholesterol efflux best correlated with serum total HDL cholesterol values. HDL2 and HDL3 correlated about equally well with efflux, whereas LpA-I demonstrated a much greater association with efflux than did LpA-I:A-II. Analysis of the data by partial correlation analysis indicated that HDL3 and LpA-I were the HDL subfractions most closely associated with efflux. Esterification of the released radiolabeled cholesterol was strongly and positively correlated with serum triglyceride concentrations and negatively related to the serum concentrations of HDL2. There was no relation between esterification values, which reflect LCAT activity, and efflux. The transfer of the labeled cholesteryl esters between HDL and apoB-containing lipoproteins was used as a measure of CETP activity and demonstrated a pattern in which all apoB-related parameters were positively correlated to transfer of esterified cholesterol, and all HDL associated parameters, particularly HDL3, were negatively related to transfer. No relations were observed between efflux, esterification, and transfer.
Detection and quantitation of calcific atherosclerosis by ultrafast computed tomography in children and young adults with homozygous familial hypercholesterolemia.
Authors: Hoeg J M , Feuerstein I M , Tucker E E
Published: June 2011

Ultrafast computed tomography (CT) is a new method for detecting calcific lesions in the coronary arteries. The ability of CT to detect and quantify coronary artery atherosclerosis in children and young adults at risk for malignant atherogenesis was evaluated. A total of 11 consecutive familial hypercholesterolemic (FH) homozygotes (3 to 37 years old) participated. Untreated total cholesterol concentrations were 488 to 1277 mg/dL (12.7 to 33.2 mmol/L). Angiography detected significant lesions in 7 of 11 patients. CT detected calcific atherosclerosis in all 9 of the patients older than 12 years of age, including all those with angina. CT was more sensitive in detecting aortic root and coronary ostial lesions, where atherosclerosis first appears in homozygous FH. The volume of calcification (in cubic millimeters) correlated with the severity and duration of the hypercholesterolemia (r = .62, P < .05) as well as with the presence of angina (P < .05). All patients with angina (7 of 7) had > 150 mm3 of calcified volume, whereas only 1 of 4 asymptomatic patients had a volume score > 150 mm3. We conclude that (1) coronary and aortic calcium phosphate deposits are common in young FH homozygotes; (2) these deposits are associated with the presence of angiographic stenoses, as has been seen in adults with coronary atherosclerosis; and (3) aortic calcific deposits are more common than calcific coronary lesions.
Associations of lipoprotein cholesterols, apolipoproteins A-I and B, and triglycerides with carotid atherosclerosis and coronary heart disease. The Atherosclerosis Risk in Communities (ARIC) Study.
Authors: Sharrett A R , Patsch W , Sorlie P D , Heiss G , Bond M G , Davis C E
Published: June 2011

Previous research shows generally greater proportional elevation in apolipoprotein B (apoB) levels than in low-density lipoprotein cholesterol (LDL-C) in coronary heart disease (CHD) case subjects compared with control subjects. The Atherosclerosis Risk in Communities study provided general populations of 7261 men and women free of cardiovascular symptoms for evaluating the associations between intima-media thickening in extracranial carotid arteries measured using ultrasound imaging and fasting plasma LDL-C, high-density lipoprotein cholesterol (HDL-C), apoB, apolipoprotein A-I (apoA-I), triglycerides, and HDL density subfractions. A CHD group was selected for comparison. Lipid factors show approximately linear associations with carotid thickness: positive for LDL-C and plasma apoB and negative for HDL-C and apoA-I levels. Apolipoproteins and HDL density subfractions did not contribute to the association after accounting for LDL-C and HDL-C. Compared with control subjects, persons whose carotid thickness exceeded 0.9 mm had greater proportional elevations in LDL-C than in apoB, whereas HDL-C reductions were small. CHD case subjects showed greater proportional elevations of apoB than LDL-C. Although the lipid profiles associated with asymptomatic carotid wall thickening and stenotic coronary disease are similar, the differences found suggest that LDL-C is the most important lipid factor in earlier stages of atherogenesis, whereas the metabolism of triglyceride-rich lipoproteins and its effects on LDL and HDL may be more relevant to later atherothrombotic processes.
Increased plasma cholesteryl ester transfer protein in obese subjects. A possible mechanism for the reduction of serum HDL cholesterol levels in obesity.
Authors: Arai T , Yamashita S , Hirano K , Sakai N , Kotani K , Fujioka S , Nozaki S , Keno Y , Yamane M , Shinohara E
Published: June 2011

It is well known that obesity is frequently associated with low levels of serum high-density lipoprotein (HDL) cholesterol. However, the mechanism for this reduction has not been fully clarified. Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins and plays an important role in regulating the concentration and composition of HDL. To elucidate the mechanism for the reduction of serum HDL cholesterol in obesity, we analyzed serum lipoproteins, CETP, and postheparin lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities in 30 obese subjects (17 women and 13 men, age 44 +/- 14 years, mean +/- SD). We also investigated the relationship between these variables, total adiposity, and indices of body fat distribution. The average body mass index of the obese subjects was 33.1 +/- 4.8 kg/m2 (range, 26.4 to 43.8 kg/m2). The obese subjects showed significantly lower serum HDL cholesterol levels than control subjects (1.04 +/- 0.28 versus 1.50 +/- 0.34 mmol/L, P < .01). In the obese subjects, both activities and protein mass of CETP and postheparin HTGL activities were significantly increased, whereas postheparin LPL activities were significantly decreased. CETP activities, independent of postheparin HTGL and LPL activities, were correlated negatively with HDL cholesterol (r = -.39, P < .05) and the cholesteryl ester to triglyceride ratio of HDL2 and HDL3 (r = -.36, P < .05; r = -.46, P < .05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
Characterization of subspecies of apolipoprotein A-I-containing lipoprotein in homozygotes for familial lecithin:cholesterol acyltransferase deficiency.
Authors: Ohta T , Hattori S , Nakamura R , Horiuchi S , Frohlich J , Takata K , Ikeda Y , Saito Y , Matsuda I
Published: June 2011

We characterized the two species of lipoproteins containing apolipoprotein A-I (apoA-I), one containing only apoA-I (LpA-I) and the other containing apoA-I and apoA-II (LpA-I/A-II), in four homozygotes for familial lecithin: cholesterol acyltransferase (LCAT) deficiency. Two homozygotes lacked both LCAT mass and activity, whereas the other two had some residual LCAT mass and activity. In these patients, the amount of all apoA-I-containing lipoproteins was one fourth that of normal control subjects, and > 60% was LpA-I. The chemical composition of both LpA-I and LpA-I/A-II is characterized by markedly decreased ratios of neutral to polar lipids compared with those of normals and the sizes of LpA-I and LpA-I/A-II particles are shifted to smaller and larger diameter ranges when compared with those of normal particles. Changes in particle diameter are also reflected in slower electrophoretic mobilities of both LpA-I and LpA-I/A-II particles. All of these abnormalities were more evident in the two homozygotes who lacked LCAT activity. Incubation of LCAT-deficient plasma with LCAT markedly corrected the chemical and physical abnormalities in both LpA-I and LpA-I/A-II particles. These data, taken together, emphasize the importance of LCAT in modifying the chemical composition, size, and shape of LpA-I and LpA-I/A-II particles.
An ultrastructural study of lipoprotein accumulation in cardiac valves of the rabbit.
Authors: Nievelstein-Post P , Mottino G , Fogelman A , Frank J
Published: June 2011

Heart valves are composed chiefly of extracellular matrix surrounded by an endothelial cell monolayer and as a result are an excellent model of the intima. Heart valves from rabbits fed a high-cholesterol diet accumulate lipids within the matrix and over time develop fatty streaks similar to those seen in the aorta. In this study we demonstrate that the heart valves (atrioventricular and aortic) can be isolated and used as an in vitro preparation to control and follow low-density lipoprotein (LDL) uptake and deposition. Using thin-section and freeze-etch microscopy we found that LDL rapidly associates with collagen within the extracellular matrix. As it accumulates along the collagen fibers the LDL appears to undergo structural changes in size and surface topography. This association of LDL with collagen may be a key step in lipid aggregation in the intima.
n-3 fatty acid incorporation into LDL particles renders them more susceptible to oxidation in vitro but not necessarily more atherogenic in vivo.
Authors: Whitman S C , Fish J R , Rand M L , Rogers K A
Published: June 2011

The hypothesis that n-3 fatty acid incorporation into low-density lipoprotein (LDL) particles renders them more susceptible to oxidative modification and possibly more atherogenic was tested using two groups of female Yucatan miniature swine (10 animals per group) fed an atherogenic diet for 8 months. As a supplement to the atherogenic diet, the first group received a daily oral dose of the fish oil (FO) concentrate MaxEPA, rich in n-3 fatty acids, while the second group received the same dosage of a control oil (CO) low in n-3 fatty acids but with the same ratio of polyunsaturated to monounsaturated to saturated fatty acids as MaxEPA. At 8 months, the animals were killed and perfusion fixed, and all major vessels were removed for morphological assessment of atherosclerotic lesion area. Before fixation, blood samples were collected from all 20 pigs, and LDL (d = 1.019 to 1.063 g/mL) was separated from the plasma by ultracentrifugation. A series of in vitro oxidative modification reactions were carried out by incubating the LDL with a copper sulfate solution. The susceptibility of each LDL preparation to oxidation was determined by measuring both the formation of conjugated dienes and the relative mobility of each sample in an agarose gel. The incorporation of n-3 fatty acids into LDL particles decreased the lag phase by 30%, resulting in an increased mobility of FO-LDL (compared with CO-LDL) when incubated for 0.5 to 12 hours, but at longer incubation times (18 to 24 hours), the extent of modification between the two groups became equal.(ABSTRACT TRUNCATED AT 250 WORDS)
Cytotoxicity of oxidized LDL to porcine aortic smooth muscle cells is associated with the oxysterols 7-ketocholesterol and 7-hydroxycholesterol.
Authors: Hughes H , Mathews B , Lenz M L , Guyton J R
Published: June 2011

The cytotoxicity of oxidized low-density lipoprotein (Ox-LDL) to arterial smooth muscle cells (SMCs) may contribute to atherogenesis by causing cell death in core regions of plaques. The aim of the present study was to identify the components of copper-oxidized LDL responsible for its toxicity to porcine aortic SMCs. Toxicity to SMCs was assessed as the decrease in viable cell counts after 3-day cell incubation. Extracts of LDL were tested for toxicity at concentrations equivalent to that derived from 100 micrograms LDL protein per milliliter. Lipid extracts of Ox-LDL but not native-LDL were toxic to SMCs. When separated into neutral and polar lipid classes, only the neutral lipids were toxic (89.7 +/- 0.7% cell loss). The neutral lipids were fractionated further by use of solid-phase extraction and high-performance liquid chromatography (HPLC). Two toxic fractions, causing 93.3% and 60.3% cell loss, were isolated from HPLC and analyzed by gas chromatography/mass spectrometry. The most toxic of these fractions contained 7-ketocholesterol, and the other contained 7 alpha- and 7 beta-hydroxycholesterol. Quantification of these unesterified oxysterols in LDL extracts and comparison with the toxicity of authentic standards indicate that 7-ketocholesterol and 7-hydroxycholesterol are present in Ox-LDL at levels sufficient to account for its toxicity to SMCs.
Role of the lipopolysaccharide (LPS)-binding protein/CD14 pathway in LPS induction of tissue factor expression in monocytic cells.
Authors: Steinemann S , Ulevitch R J , Mackman N
Published: June 2011

Endotoxic shock is associated with a coagulopathy, organ failure, and death. Tissue factor (TF) expression by monocytes exposed to bacterial endotoxin (lipopolysaccharide [LPS]) may mediate the coagulopathy and contribute to the high mortality of this disease. We examined the role of the LPS-binding protein (LBP)/CD14 receptor pathway in the LPS induction of TF expression in human monocytic THP-1 cells and peripheral blood monocytes. In THP-1 cells, the threshold concentration of LPS required to induce TF activity in serum-free medium was reduced 20-fold by purified LBP, which also enhanced TF mRNA synthesis. Similarly, monocytes cultured in the presence of serum were induced to express TF antigen at LPS concentrations 100 times lower than monocytes cultured in serum-free medium. An anti-LBP monoclonal antibody indicated that this effect was dependent on the presence of LBP in serum. LPS/LBP induction of TF activity and TF antigen expression in these monocytic cells were also inhibited by an anti-CD14 monoclonal antibody, indicating a requirement for the CD14 receptor. Thus, we suggest that low levels of LPS (5 to 100 pg/mL) present during sepsis induce TF expression in monocytes via the LBP/CD14-dependent pathway.
Protein kinase C-dependent desensitization of HDL3-activated phospholipase C in human platelets.
Authors: Nazih H , Nazih-Sanderson F , Magret V , Caron B , Goudemand J , Fruchart J C , Delbart C
Published: June 2011

In isolated human platelets, exposure of subfraction 3 high-density lipoprotein (HDL3) binding sites to high concentrations of HDL3 (1 mg/mL) causes rapid desensitization of HDL3 (50 micrograms/mL)-stimulated breakdown of phosphatidylcholine, as shown in approximately a 70% depression of the maximal 1,2-diacylglycerol release activity by phospholipase C. This desensitization is HDL3 dose dependent (IC50, 150 +/- 20 micrograms/mL, n = 6) and time dependent (t1/2, < 30 seconds). It requires the binding of HDL3, as pretreatment of HDL3 by tetranitromethane does not cause the desensitization of HDL3-induced phospholipase C activity. Permeabilization of human platelets with 10 micrograms/mL digitonin, used to permit access of charged inhibitors to the cytosol, does not interfere with the pattern of HDL3 (1 mg/mL)-induced desensitization of HDL3 (50 micrograms/mL)-stimulated phospholipase C. Inhibitors of protein kinase C (100 mumol/L H-7 and 10 mumol/L staurosporine) markedly inhibit desensitization of HDL3-induced phospholipase C activity, whereas cAMP-dependent protein kinase inhibitor (1 mumol/L), heparin (100 nmol/L), or concanavalin A (0.25 mg/mL) were ineffective. HDL3-induced desensitization is accompanied at least by the phosphorylation of the 94- and 110-kD proteins. Inhibition of HDL3-induced desensitization by 100 mumol/L H-7 or 10 mumol/L staurosporine is characterized by a marked reduction of the phosphorylation state of these proteins in permeabilized platelets. Whereas protein kinase C inhibitors fully inhibited the phosphorylation of the 94- and 110-kD proteins, inhibitors of protein kinase A were less effective. These data establish that phosphorylation by protein kinase C represent a step in the desensitization of HDL3 binding sites in human platelets.
Response of atherosclerotic intimal smooth muscle cells to epidermal growth factor in vitro.
Authors: Mitsumata M , Gamou S , Shimizu N , Yoshida Y
Published: June 2011

Increased proliferation of intimal smooth muscle cells (SMCs) plays an important role in the early phase of atherogenesis. To investigate growth mechanisms of these cells, we used intimal SMCs from rabbits fed an atherogenic diet and examined the sequential events that may facilitate induction of intimal SMC proliferation as well as the possible effects of growth-promoting factors secreted by these cells. In serum-free medium, epidermal growth factor (EGF) stimulated [3H]thymidine uptake by quiescent intimal SMCs at a rate six times higher than quiescent medial SMCs. There was no significant difference between the two cell types in terms of the number of specific EGF receptor per cell, the dissociation constant of EGF, and the time course of EGF binding and internalization. Furthermore, in both types of cells, c-fos, c-jun, and c-myc mRNAs were induced after 1, 1, and 4 hours of EGF treatment, respectively, whereas they required 8 hours of contact with EGF to induce proliferation. Growth response of medical SMCs to EGF was greatly enhanced when rabbit serum, deficient in lipoproteins and free of platelet-derived growth factor, was added to the medium. Moreover, EGF induced a twofold to fourfold increase in DNA synthesis in medial SMCs cocultured with intimal SMCs compared with medial SMCs incubated alone. Likewise, DNA synthesis of medial SMCs grown in medium conditioned by intimal SMCs was six times higher than that observed in medium conditioned by medical SMCs. Adding EGF to the medium conditioned by intimal SMCs increased their DNA synthesis even further.(ABSTRACT TRUNCATED AT 250 WORDS)
Impact of apolipoprotein E polymorphism on lipoproteins and risk of myocardial infarction. The ECTIM Study.
Authors: Luc G , Bard J M , Arveiler D , Evans A , Cambou J P , Bingham A , Amouyel P , Schaffer P , Ruidavets J B , Cambien F
Published: June 2011

Human apolipoprotein (apo) E, a polymorphic protein with three common alleles, epsilon 2, epsilon 3, and epsilon 4, plays an important role in lipoprotein metabolism. This article describes the association of this polymorphism with lipids, apolipoproteins, and lipoproteins with a particular regard to lipoprotein particles, as defined by their apolipoprotein content, as well as the risk of myocardial infarction in a multicenter population-based case-control study (ECTIM study). In the ECTIM study, 574 male patients aged 25 to 64 were examined 3 to 9 months after myocardial infarction in four regions participating in the World Health Organization MONICA project: Belfast (Northern Ireland) and Lille, Strasbourg, and Toulouse (France). Control subjects (n = 722) were randomly selected from the regional populations. The distribution of apoE phenotypes was significantly different across the four control samples (P = .04), with a higher frequency of the epsilon 4 allele in Belfast (14.3%) than in Toulouse (8.2%). The association of apoE polymorphism with biological measurements was studied in the control groups (n = 640) after men with coronary heart disease or those taking hypolipidemic drugs were omitted, with the apoE3/3 phenotype as a reference after adjustment for concomitant factors. Individuals carrying the epsilon 2 allele had lower levels of plasma cholesterol, low-density lipoprotein cholesterol (LDL-C), and apoB and higher levels of triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), apoC-III, apoE, lipoprotein (Lp) C-III:B, and Lp E:B. However, the effect of the epsilon 2 allele on triglyceride, VLDL-C, apoE, and Lp E:B parameters was heterogeneous across the populations.(ABSTRACT TRUNCATED AT 250 WORDS)
Thrombin plays a key role in late platelet thrombus growth and/or stability. Effect of a specific thrombin inhibitor on thrombogenesis induced by aortic subendothelium exposed to flowing rabbit blood.
Authors: Gast A , Tschopp T B , Baumgartner H R
Published: June 2011

Thrombin is involved in the pathogenesis of venous and arterial thrombosis. This study addressed the question of the relative importance of thrombin in the early and late phases of thrombogenesis. The effect of Ro 46-6240 (1.43 mg/kg bolus and 0.1 mg/kg per minute i.v.), a novel, selective thrombin inhibitor on thrombogenesis induced by rabbit aorta subendothelium, was measured ex vivo in a perfusion chamber model after a short (5-minute) and long (30-minute) exposure time to rabbit native blood. The role of the perfusion time was assessed at shear rates of 100/s, 650/s, and 2600/s. These shear rates mimic blood flow conditions found in veins, arteries, and small or stenosed arteries, respectively. Fibrin deposition and platelet thrombus formation on subendothelium were evaluated by microscopic morphometry. In the presence of Ro 46-6240, fibrin deposition was abolished at both perfusion times and at all shear rates. In the 5-minute experiments, thrombus height was reduced by Ro 46-6240 at shear rates of 100/s (85%) and 650/s (35%) but not at a shear rate of 2600/s, whereas thrombus area was not affected at any shear rate. In contrast, both thrombus height and thrombus area were reduced (60% to 90%) by Ro 46-6240 in the 30-minute perfusion groups at all wall shear rates. The antithrombotic effect of Ro 46-6240 after 30-minute perfusion was confirmed by the minimal increase in the pressure difference between the entrance and the exit of the perfusion chamber compared with the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Inhibition of hepatic ACAT decreases ApoB secretion in miniature pigs fed a cholesterol-free diet.
Authors: Huff M W , Telford D E , Barrett P H , Billheimer J T , Gillies P J
Published: June 2011

To test the hypothesis that hepatic cholesteryl ester is involved in the regulation of apolipoprotein (apo) B secretion into plasma, apoB kinetic studies were performed in six control miniature pigs and in six pigs after a 21-day administration of the acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitor DuP 128 (2.2 mg.kg-1.d-1 i.v.). Pigs were fed low-fat, cholesterol-free diets. Total plasma cholesterol, triglyceride, very-low-density lipoprotein (VLDL) triglyceride, and low-density lipoprotein (LDL) cholesterol decreased 18%, 29%, 40%, and 26% respectively (P < .03). 131I-VLDL and 125I-LDL were injected simultaneously into each animal, and apoB kinetics were analyzed by using multi-compartmental analysis (SAAM30). VLDL apoB pool size decreased significantly by 60% (0.32 versus 0.84 mg/kg), which was due to a 65% reduction in the VLDL apoB production or secretion rate (1.03 versus 2.94 mg.kg-1.h-1). The fractional catabolic rate was unchanged. LDL apoB pool size decreased nonsignificantly by 18% (5.61 versus 6.90 mg/kg) due entirely to a 24% decrease in production rate (0.26 versus 0.34 mg.kg-1.h-1). At necropsy, hepatic microsomal ACAT activity decreased by 68% (0.28 versus 0.88 nmol.min-1.mg-1; P < .0002). Although an increase in hepatic free cholesterol leading to a decreased LDL receptor expression might be expected, this did not occur. The concentration of hepatic cholesterol and the LDL apoB fractional catabolic rate were unaffected by DuP 128. In addition, the concentration of hepatic triglyceride and the activity of diacylglycerol acyltransferase were not altered by DuP 128, indicating a lack of effect of DuP 128 on hepatic triglyceride metabolism. We conclude that inhibition of hepatic cholesteryl ester synthesis in vivo decreases apoB secretion into plasma.