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J C Fruchart

Publications and source records attributed to J C Fruchart.

At least 289 records · Page 16Linked to original sources
PubMed1993

Immunological properties of apoB-containing lipoprotein particles in human atherosclerotic arteries.

In this study, we have documented immunochemical properties of apolipoprotein (apo) B-containing particles (LpB) extracted from human atherosclerotic lesions obtained during vascular reconstructive surgery of patients. These properties were compared to those of particles purified from corresponding atherosclerotic plasma and healthy control plasma. LpB immunoreactivities were tested in solid phase competitive binding radioimmunoassays using five anti-apoB monoclonal antibodies (MAb) for which epitopes have been previously located on the protein. The regions encompassed amino acids 405 to 539 (MAb B1), 1854 to 1879 (MAb B4), 3506 (MAb BA11), and 4355 (MAb BL3). The fifth antibody (MAb BL5) recognizes a conformationally expressed epitope. LpB from lesions presented a significantly decreased immunoreactivity as compared to LpB from respective plasma except for the epitope recognized by MAb BA11 located precisely in the low density lipoprotein (LDL) receptor binding site. The accessibility of the four sequential epitopes was similar on LpB from atherosclerotic and healthy plasma while it was decreased for the conformational one in LpB from atherosclerotic samples. These altered immunoreactivities were not related to changes in chemical composition of LpB as this was quite comparable in all preparations. With regard to electronegativity, apoB fragmentation, immunological accessibility, and size distribution of the particles, changes seem to increase in the following order from healthy plasma, atherosclerotic plasma, and the corresponding lesions. The results confirm some structural characteristics of oxidatively modified particles from human atherosclerotic lesions and to a lesser degree from respective plasma, but more specifically demonstrate a global conformational change in LpB from lesions, this change being perhaps initiated in the plasma.

Aged↗
PubMed1993

Human very low density lipoprotein structure: interaction of the C apolipoproteins with apolipoprotein B-100.

Very low density lipoproteins (VLDL) are a heterogenous population of particles differing in size and composition. Heparin-Sepharose chromatography yields three VLDL subfractions. Two subfractions, VLDLNR-1 and VLDLNR-2, which are not retained by heparin, contain little or no detectable apolipoprotein (apo)E. According to negative stain electron microscopy, VLDLNR-1 is slightly larger than VLDLNR-2. The third fraction, VLDLR, is composed of smaller particles that are retained by the heparin-Sepharose and contain apoE. The C apolipoproteins of the respective VLDL subfractions transfer to 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) single bilayer vesicles giving three subfractions designated VLDLNR-1-C, VLDLNR-2-C, and VLDLR-C. The protein, phospholipid, and cholesterol (free + esterified) contents decrease in the order VLDLR > VLDLNR-2 > VLDLNR-1. Triglyceride content decreases in the opposite order. POPC treatment of each VLDL subfraction increases the phospholipid and decreases the protein, triglyceride, and cholesteryl ester contents, while free cholesterol remains unchanged. According to immunological analysis of each subfraction with well-characterized monoclonal antibodies, the accessibility of some epitopes of apoB-100 on VLDL is changed by POPC treatment. Electron-microscopic analysis of POPC-treated VLDL subfraction reveals vacancies on the surfaces of each particle. VLDLNR-1, VLDLNR-2, and VLDLR are resistant to thrombin cleavage, whereas the lipoproteins lacking C apolipoproteins are not. Thrombin cleavage (8 h) of apoB-100 of VLDLNR-2-C and VLDLR-C gives two fragments, T1 and T2, that are converted to smaller fragments only after prolonged treatment. In contrast, apoB-100 of VLDLNR-1-C is converted into small fragments after 8 h thrombin treatment. These results suggest that removal of apoCs affects the accessibility and conformation of apoB-100 in the individual VLDL subfractions in the region near residue 3249, which is the primary thrombin cleavage site and the epitope of monoclonal antibody 4C11.

Apolipoprotein B-100↗
PubMed1993

Heterogeneity of high density lipoprotein particles.

Human high density lipoprotein (HDL) contains at least two types of lipoprotein-containing A-I particles: one contains both apolipoproteins (apo) A-I and A-II (Lp A-I:A-II) as main protein components, whereas in the other, apo A-II is absent (Lp A-I). The two subpopulations have different metabolisms and physiological roles. Studies indicate that apo A-II is an antagonist of cholesterol efflux. Lp A-I but not Lp A-I:A-II is increased in women compared with men. The lower apo A-I levels in patients with coronary artery disease reflect a decrease in Lp A-I. Lp A-I also is decreased in children with a family history of coronary artery disease, and increased in elderly subjects. Despite cholesterol intake remaining constant, a high polyunsaturated:saturated fat diet leads to a decrease in Lp A-I but not Lp A-I:A-II. Chronic alcohol consumption induces an increase in Lp A-I:A-II and a decrease in Lp A-I, although short bouts of drinking produce increases in both Lp A-I and Lp A-I:A-II. Hypolipidemic drugs have specific effects on discrete apo A-I particles.

Alcoholism↗
PubMed1993

Sequential ultracentrifugation micromethod for separation of serum lipoproteins and assays of lipids, apolipoproteins, and lipoprotein particles.

We describe a fast sequential separation of very-low-density, low-density, and high-density lipoproteins from 400 microL of serum, using the Beckman TL100 ultracentrifuge. The cumulative centrifugation time is 9.5 h. The purity of lipoprotein fractions was verified by a gel-filtration procedure. The major contaminant is the serum albumin, which can be eliminated by a second centrifugation at the same density. Enzymatic measurement of lipids shows good recovery (> 91%) and weak within-sample variation (< 7%). In comparison with a density-gradient procedure, the deleterious effects on the lipoprotein structure appear to be limited, as shown by the low concentrations of apolipoprotein (apo) E and apo A-I in the fraction > 1.21 kg/L. Furthermore, the micro-ultracentrifugation also gives a better recovery rate. Finally, we have studied the distribution of lipids, apolipoproteins, and lipoprotein particles (LpA-I:A-II, LpB:C-III, LpB:E) in each fraction separated from 10 serum samples from healthy subjects.

Adult↗
PubMed1992

Pertussis toxin sensitive G-protein coupling of HDL receptor to phospholipase C in human platelets.

Initially we established that, in human platelets, low concentrations of HDL3 stimulate phosphatidylcholine (PC) hydrolysis and a transient increase in 1,2-diacylglycerol (DAG). In (3H) PC prelabelled platelets, phosphocholine is released into the medium during HDL3 induced PC turnover with a 1.5 to 2 fold increment, indicating that HDL3 stimulated DAG generation in platelets is likely due to phospholipase C (PLC). GTP or GTP-gamma-S augments, and pertussis toxin inhibits HDL3 stimulated DAG production. Treatment of platelet membranes with HDL3 or with proteoliposome containing apo A-I or A-II substantially prevents 41 kDa protein ADP-ribosylation that was induced by pertussis toxin, with apo A-II having an inhibitory potency greater than apo A-I. These data provide strong evidence that the pertussis sensible G protein (Go or Gi) is directly involved in coupling PLC to HDL3 receptor in platelets.

Apolipoprotein A-I↗
PubMed1992

Isolation and characterization of two sub-species of Lp(a), one containing apo E and one free of apo E.

Lipoprotein Lp(a) was isolated by immunoaffinity chromatography using anti apolipoprotein B and anti apolipoprotein (a) immunosorbents. Besides apolipoproteins (a) and B, this fraction was shown to contain apolipoproteins C and E. Therefore, it was decided to further purify this crude Lp(a) into particles containing apolipoprotein E and particles free of apo E, using chromatography with an anti apolipoprotein E immunosorbent. Lp(a), free of apolipoprotein E was cholesterol ester rich and triacylglycerol poor and was found mainly in the LDL size range. In contrast, Lp(a) containing apolipoprotein E was triacylglycerol rich and was distributed mainly in the VLDL and IDL size range. Binding of these two fractions, one containing apo E and one free of it, to the apo B/E receptor of HeLa cells was studied. Both fractions bound to the receptor but the one containing apo E had a better affinity than the one free of apo E. Further studies are needed to identify the clinical importance of these two different entities.

Apolipoproteins↗
PubMed1992

Oxidized low density lipoproteins exert arrhythmogenic effects in rabbit Purkinje fibers.

The electrophysiological effects of oxidized low density lipoproteins (ox-LDLs) have been studied in rabbit Purkinje fibers using standard microelectrode techniques, in comparison with native LDLs (n-LDLs) and lysophosphatidylcholine (LPC). At the concentration of 100 micrograms protein/ml, ox-LDL but never n-LDL induced the abrupt occurrence of abnormal electrical activities during the basic stimulation of 1 Hz (6/13 fibers) and the development of either early afterdepolarizations (6/13 fibers) or abnormal automaticity (4/13 fibers) at low frequencies (0.1 and 0.03 Hz). Short trains of rapid stimulation (2, 3, 4 and 5 Hz) did not trigger delayed afterdepolarizations. However, early afterhyperpolarizations were commonly seen after each action potential. 30 microM LPC caused quite similar electrophysiological derangements. The results suggest that ox-LDLs may exert arrhythmogenic effects partly explained by their LPC content.

Action Potentials↗
PubMed1992

The polymorphism ApoB/4311 in patients with myocardial infarction and controls: the ECTIM Study.

The polymorphism affecting codon 4311 of the apolipoprotein B gene (ApoB/4311) was investigated in a large case-control study in two French and one Northern Irish geographically defined populations. Cases were recruited 3 to 9 months after a myocardial infarction (MI) and controls were randomly selected from the population. The polymorphism was assessed using allele-specific oligonucleotides (ASO). The genotype frequencies of the ApoB/4311 polymorphism did not differ in Northern Ireland and France and were in Hardy-Weinberg equilibrium in all groups; strong associations with three other polymorphisms of the ApoB gene (XbaI, EcoRI, VNTR(34 repeats)) were observed and it was possible to identify highly sensitive and specific markers of the ApoB/4311 rare variant. Homozygotes for the ApoB 4311 rare variant were slightly less frequent in cases than in controls: 22 (4.4%) and 35 (6.7%) respectively (population adjusted chi 2 = 3.3 P less than 0.07), especially in Belfast: 6 (3.1%) and 12 (7.6%), respectively (P less than 0.06). Several lipid and lipoprotein parameters were measured. Consistently among control groups, rare homozygotes had lower mean levels of ApoB (P less than 0.02), triglycerides (P less than 0.02), and lipoprotein particles containing ApoE and ApoB (LpE:B; P less than 0.001) and a higher mean level of lipoprotein particles containing ApoAI and not ApoAII (LpAI; P less than 0.02) than heterozygotes and frequent homozygotes combined. The strong association between the ApoB/4311 polymorphism and LpE:B was also observed in patients with MI. When present in the homozygous form, the ApoB/4311 Asn----Ser variant is associated with a lipoprotein profile that is apparently favourable.

Apolipoproteins B↗
PubMed1992

Increased triglyceride levels in shift workers.

PURPOSE: To assess an independent relationship between shift work and serum lipid levels. DESIGN: Cross-sectional survey. SETTING: Two plants of northern France: a chemical one and a nuclear power station. PARTICIPANTS: All the shift workers of the chemical plant and of one part of the nuclear station. One hundred nine persons were selected, 25 were excluded or absent during the study, and 11 refused to participate. Day workers matched with shift workers according to age, educational level, birthplace, and occupational physical activity level served as controls; 109 were selected, 26 were excluded or absent, and 10 refused to participate. MAIN OUTCOME MEASURES: Fasting venous plasma concentration of total cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol; dietary intake assessed by a 3-day record, smoking habits, and body mass index (BMI). RESULTS: Shift workers had significantly higher levels of serum triglyceride (1.26 versus 1.03 mmol/L, p = 0.01). Cholesterol and HDL cholesterol levels were similar for the two groups. There was no difference in energy and nutrient intake, but day workers had a higher alcohol intake (15.64 g/d versus 9.3 g/d, p = 0.03). Multivariate analysis conducted with triglycerides as dependent variable and shift work, BMI, smoking, age, leisure time physical activity level, energy intake, and alcohol intake as independent variables confirmed that shift work has a significant explanatory power for triglyceride levels (beta = 0.134, p = 0.0005). CONCLUSION: This study confirms that shift work is associated with an increase of triglyceride levels independent of dietary intake. We did not find any influence of shift work on cholesterol and HDL cholesterol. Despite this latter fact, our findings are to be considered in the explanation of coronary risk among shift workers. Further studies are needed to elucidate the mechanism of this relative hypertriglyceridemia: stress induced by shift work or diurnal rhythm disturbances.

Adult↗
PubMed1992

Plasma level of lipoprotein Lp(a) is high in predialysis or hemodialysis, but not in CAPD.

Plasma Lp(a) lipoprotein level was determined in chronic renal failure (CRF) patients, 24 before initiation of dialysis, 18 undergoing hemodialysis, and 24 on continuous ambulatory peritoneal dialysis (CAPD). Eighteen healthy subjects were studied as controls. Median of Lp(a) level in both predialysis and dialysis patients was significantly increased: 23.5 mg/dl (range: 0 to 109) and 24.0 mg/dl (range: 1.4 to 90), respectively, as compared to healthy controls: 4.7 mg/dl (range: 1.8 to 27; P less than 0.001). By contrast, the median Lp(a) level in CAPD patients, 2.4 mg/dl (range: 0 to 39.5), was similar to the control group. Whether the CAPD procedure reduces the Lp(a) level in CRF patients has to be established in a prospective study.

Female↗
PubMed1992

Drug transfer across the blood-brain barrier: correlation between in vitro and in vivo models.

To assess the drug transport across the blood-brain barrier (BBB), we compared the maximal brain extraction values at time 0 [E(0) values] obtained using either in vitro or in vivo methods. The in vitro BBB model consisted of a coculture of brain capillary endothelial cells growing on one side of a filter and astrocytes on the other. The in vivo model used intracarotid injection in anesthetized rats. Eleven compounds were tested. They were selected because they exhibit quantitatively different brain extraction rates: very low for inulin and sucrose, low for oxicam-related nonsteroidal antiinflammatory drugs and diclofenac, and high for propranolol and diazepam. As these compounds are apparently transferred by a passive diffusion mechanism, two others, glucose and leucine, were added that cross the BBB by a known carrier-mediated process. The in vivo and in vitro E(0) values showed a strong correlation as indicated by the Spearman's correlation coefficient (r = 0.88, p less than 0.01). The relative ease with which such cocultures can be produced in large quantities could facilitate the screening of new centrally acting drugs.

Animals↗
PubMed1992

Apolipoprotein A-I-containing particles and reverse cholesterol transport in IDDM.

Lipoprotein particles containing apoA-I but not apoA-II are, among high-density lipoproteins, effective protectors against atherosclerosis that act by promoting the efflux of cellular cholesterol and the reverse cholesterol transport process. Because previous studies showed that in vitro nonenzymatic glycosylation of HDL impairs HDL receptor-mediated cholesterol efflux, we isolated Lp A-I from two poorly controlled insulin-dependent diabetic patients and compared the chemical composition and ability to promote cholesterol efflux with the same particles purified from two matched nondiabetic control subjects. No differences in lipid composition or in the ability to promote cholesterol efflux from cultured adipose cells were noted between the two types of Lp A-I preparations. However, when we separated Lp A-I from diabetic subjects by degree of glycosylation, the specifically glycosylated subfractions were about 50% less effective in producing cholesterol efflux than the nonglycosylated particles.

Adult↗
PubMed1992

Apo AIV in plasma and dialysate fluid of CAPD patients: comparison with other apolipoproteins.

Plasma lipids and apolipoproteins were determined in 18 patients with chronic renal failure on haemodialysis (HD), 18 patients on continuous ambulatory peritoneal dialysis (CAPD), and 18 healthy controls. Significant differences were observed between the two dialysis procedures, CAPD patients showed elevated plasma cholesterol, apo AI and apoB. No significant difference in plasma apo AIV concentration was observed between the two dialysis groups. Measurement of apolipoproteins in the dialysate fluid of five patients on CAPD showed losses of all apolipoproteins (AI, AII, AIV, B, CII, CIII and E). Although daily losses of apo AI and apo AIV were similar (255 and 221 mg/day respectively), the peritoneal clearance of apo AIV was threefold that of apo AI and 12-fold that of apo B. In view of the inverse correlation between peritoneal clearance and the molecular mass of proteins, about 13% of total plasma apo AIV was lost daily as lipoprotein-free form.

Adult↗
PubMed1992

Thrombin cleavage of apolipoprotein Bh of rabbit LDL: structural comparisons with human apolipoprotein B-100.

Rabbit plasma low density lipoprotein (LDL) contains one major apolipoprotein of apparent molecular weight of 320 kDa, designated apolipoprotein (apo) Bh, while another component termed apoB1 of apparent molecular weight of 220 kDa is found in chylomicrons. The fragments generated by thrombin digestion of the protein moieties of rabbit and human LDL were separated by polyacrylamide gradient gel electrophoresis and compared. As in the human species, the enzyme produced limited cleavage patterns of rabbit LDL apoB. Within the first 2 h, two fragments (Tr1 and Tr2, with apparent molecular weights 280,000 and 44,000, respectively) appeared. Longer incubations led to the production of two additional peptides, Tr3 and Tr4 (apparent molecular weights 180,000 and 96,000, respectively). Ten monoclonal antibodies, developed against rabbit LDL and designated P01 to P10, were found to react with rabbit apoB. Some also cross-reacted with human apoB. Epitope mapping, performed with these antibodies, showed that Tr3 and Tr4 were derived from the further degradation of Tr1. The rabbit is one of the most frequently used animals in atherosclerosis research. Its LDL receptor has been characterized and there exists a strain of homozygous LDL receptor-deficient rabbits referred to as WHHL rabbits. Despite this, little has been done to characterize the structure of rabbit apoB; only a short region has been sequenced and shown to be the carboxyl-terminal region, the rabbit apoB1. The molecular weight of human apoB (550,000) is much larger than rabbit apoBh. In both species, a primary and secondary thrombin cleavage occur, but the size of the fragments produced is very different between the two species. Identification of the thrombolytic fragments of the rabbit apoB have afforded the opportunity to compare the structures of both apoB species.

Animals↗
PubMed1992

Inhibition of lipoprotein lipase activity by synthetic peptides of apolipoprotein C-III.

In this study we have examined effects of synthetic polypeptide fragments of apoC-III on the kinetic properties of lipoprotein lipase (LPL) activity. Based on the loss of 79% of LPL-inhibitory activity after CNBr cleavage at the N-terminal portion of apoC-III and a systematic search for synthetic peptides with LPL-inhibitory activity spanning the apoC-III sequence, we concluded that the N-terminal domain is the most important in the modulation of LPL activity. In addition, there are multiple attachment sites in apoC-III for its interaction with LPL and these sites reside in the hydrophilic sequences of apoC-III. Probably for this reason the intact apo-CIII exhibited higher inhibitory potential than its peptide components. Based on the deduced inhibition constants derived for the synthetic apoC-III1-79 we concluded that apoC-III is likely to exhibit a physiological role in regulating LPL activity since the derived dissociation constants for the LPL-apoC-III interaction are within the physiological concentration range of plasma apoC-III. In addition, as the synthetic apoC-III1-79 lacks the carbohydrate moiety, we also concluded that the presence of the oligosaccharide in native apoC-III is not essential for its inhibitory activity on LPL. The fact that the I50 (concentration for inhibition of LPL at 50% activity) decreases for apoC-III-1 when assayed in the presence of apoC-II indicated that the activator actually caused an increased affinity between LPL and apoC-III and demonstrated that apoC-III does not compete for the activator site of apoC-II.

Amino Acid Sequence↗
PubMed1992

Apolipoprotein A-containing lipoprotein particles: physiological role, quantification, and clinical significance.

High-density lipoprotein (HDL) particles are made up of two major populations of particles, differing in composition and metabolism. Both contain apolipoprotein (apo) A-I but only one contains apo A-II. Lipoprotein particles that contain only apo A-I (LpA-I particles) can increase cellular cholesterol efflux from cultured cells in vitro. LpA-I:A-II particles, however, do not increase cholesterol efflux. LpA-I:A-II can be determined directly with an enzyme-linked differential antibody immunosorbent assay. LpA-I is determined by differential electroimmunoassay: in the presence of a large excess of anti-apo A-II, LpA-I:A-II particles are retained in one peak, whereas LpA-I migrates grates as a second peak. Both lipoprotein forms of apo A-I-containing particles are present mainly in HDL, but the relative proportion of LpA-I is greater in HDL2 than in HDL3. Concentrations of LpA-I in plasma samples from normolipemic subjects average approximately 10% higher in women than in men. The lower apo A-I concentrations in patients with significant coronary artery disease reflect a decrease in the LpA-I particles. Data obtained in octogenarians also support the possibility that LpA-I might represent the anti-atherogenic fraction of HDL. Moreover, the concentration of LpA-I in children of parents with premature coronary heart disease was lower than that of a control group without any family history of this disease. Nutrients and hypolipidemic drugs seem to affect the two kinds of particles differently.

Adipose Tissue↗