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Biomedical subjects

C Fievet

Publications and source records attributed to C Fievet.

At least 37 records · Page 2Linked to original sources
PubMed1996

Apolipoproteins C-III and E in apoB- and non-apoB-containing lipoproteins in two populations at contrasting risk for myocardial infarction: the ECTIM study. Etude Cas Témoins sur 'Infarctus du Myocarde.

Apolipoprotein (apo) C-III and apoE are components of two major classes of plasma lipoproteins, i.e., apoB- and non-apoB-containing lipoproteins. To analyze the relationship between the distribution of apoC-III and apoE among lipoproteins and coronary heart disease, we compared the distribution of these two apolipoproteins in survivors of myocardial infarction (MI) and control subjects, within and between populations at contrasting risk for MI. ApoC-III and apoE concentrations were determined in plasma devoid of apoB-containing lipoproteins by immunoprecipitation using a specific anti-apoB antiserum. These assays referred to apoC-III-Lp non-B and apoE-Lp non-B, respectively. By examining the difference with total plasma apoC-III and apoE levels, we calculated apoC-III and apoE in apoB-containing lipoproteins (apoCIII-LpB and apoE-LpB, respectively). These determinations were performed in control subjects and in survivors of MI, all males aged 25 to 64 years. They were recruited in Northern Ireland and France, countries characterized by a large difference in the incidence of coronary heart disease. In univariate analysis, apoCIII-LpB appeared significantly higher and the apoC-III ratio (apoC-III-Lp non-B/apoC-III-LpB) significantly lower in MI survivors than in control subjects in both countries. ApoE-LpB was higher in MI survivors than in control subjects in Northern Ireland but not in France. The two French and Irish control populations differed for apoC-ILL-Lp non-B, apoC-III ratio, and apoE ratio, which were higher in France than in Northern Ireland, and for apoC-III-LpB, apoE, and apoE-LpB, which were lower. Multivariate analysis showed that no parameter involving apoC-III and apoE was more discriminatory than HDL-cholesterol, cholesterol, and triglycerides or apoA-I, apoB, and triglycerides between controls and MI subjects. In contrast, the apoC-III ratio was a better discriminatory parameter between the two control populations than the listed parameters. The differences between the two control populations are of particular interest because they are not biased by the presence of disease or the large difference of the incidence in coronary heart disease between the two countries. It is suggested that the distribution of apoC-III among lipoproteins may play a role in the different susceptibility of the two populations to the atherogenic process.

Adult↗
PubMed1995

Tissue-specific expression of the human gene for lecithin: cholesterol acyltransferase in transgenic mice alters blood lipids, lipoproteins and lipases towards a less atherogenic profile.

Lecithin:cholesterol acyltransferase (LCAT) is a key enzyme in the reverse cholesterol pathway but its role in lipid metabolism is still unclear. We have generated mice transgenic for a 7-kb genomic DNA fragment comprising the 6 exons and 5 introns of the LCAT gene with 1932 bp of 5' flanking and 908 bp of 3' flanking sequences. One line had integrated about 30 copies and expressed about 40-fold increased LCAT activity in a human test system. The expression showed correct tissue specificity of the human LCAT gene. Increased LCAT activity resulted in a decrease of plasma triacylglycerols below 50% of fasting controls. This reduction was seen in all lipoprotein fractions. Lipoprotein lipase activity did not change significantly, whereas hepatic triacylglycerol lipase increased markedly. Plasma total cholesterol was similar in fasting transgenic and control mice, but low-density lipoprotein and very low-density lipoprotein cholesterol were reduced to about 50%. High-density lipoprotein cholesterol increased about 20%, accompanied by a correspondingly increased size and a higher cholesterol efflux-stimulating activity of transgenic LCAT high-density lipoprotein. Both apolipoprotein A-I and A-II plasma concentrations increased in transgenic mice. Plasma triacylglycerol and cholesteryl ester fatty acid distribution showed an increased proportion of palmitic acid, whereas oleic, linoleic and arachidonic acid decreased, thus resembling more closely the human situation. Overexpression of the human LCAT gene provokes major changes in plasma lipoprotein and apolipoprotein concentrations, resulting in a less atherogenic plasma lipoprotein profile through a reduction in atherogenic and an increase in anti-atherogenic lipoproteins.

Animals↗
PubMed1995

A 700-bp fragment of the human antithrombin III promoter is sufficient to confer high, tissue-specific expression on human apolipoprotein A-II in transgenic mice.

The human antithrombin III-encoding gene (hAT-III) promoter (phAT-III) was used to generate transgenic mice producing a human hepatic apolipoprotein, apolipoprotein A-II (hApoA-II). Integration of the transgene into the mouse genome resulted in the efficient production of hApoA-II in plasma, reaching up to 0.40 g/l in two transgenic lines. The human ApoA-II mRNA was detected at high levels, both in the liver and in the kidney of transgenic mice. The rat AT-III gene shows the same expression pattern. In contrast, as previously described, the same promoter permitted the expression of the SV40 large T antigen only in the liver of transgenic mice. In view of the extra-hepatic distribution of the ApoA-II mRNA, a preliminary characterization of the hAT-III proximal promoter (phAT-III), driving the expression of the transgene, was realized. Using DNase I footprinting analysis with liver nuclear extracts, four protected regions (I-IV) were identified in the first 175 bp of the 5' region of hAT-III. Electrophoretic mobility shift assays performed with liver and kidney nuclear extracts indicate that region III (nucleotides (nt) -67 to -90) interacts with the liver-enriched HNF4 nuclear factor. Furthermore, our data suggest that region I (nt -123 to -138) interacts with the liver-enriched HNF3 transcription factor family, both in liver and kidney. Taken together, these results demonstrate that phAT-III is a useful tool to create transgenic mice producing high plasma levels of a human apolipoprotein due to expression of the transgene in liver and kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Immunological and functional properties of in vitro oxidized low density lipoprotein.

We studied the effect of in vitro moderate oxidation on low density lipoprotein (LDL) conformation and metabolism. LDL was modified with either copper ions or phospholipase A2 plus lipoxygenase and, in both cases, mild oxidative conditions were used. The resulting conformational changes were investigated by studying immunological and biological properties of oxidized LDL. The immunoreactivity of apolipoprotein (apo) B-100 was examined using seven monoclonal antibodies. The biological implications of conformational changes were provided by cell-lipoprotein interaction studies using human fibroblasts and mouse peritoneal macrophages. Enzymatically treated LDL presented a relatively less oxidative degree of modification because it generated lower levels of TBARS, and displayed a lower electronegativity and more comparable cellular interactions with those of native LDL. Nevertheless, dramatic immunological changes were measured on both forms of LDL, i.e., a significant increase in the immunoreactivity of an epitope located in the B/E receptor binding domain, but also at epitopes far from this site and located in the N-terminal part of the apoB-100 molecule. The immunoreactivity of the C-terminal region was in contrast, decreased. Yet, as compared with enzymatically oxidized LDL, much more dramatic structural changes with chemically modified LDL were observed, resulting in such a particular conformation of lipoprotein that its interaction with the macrophagic scavenger receptor was favored, but its recognition by the B/E receptor of fibroblast was abolished. In contrast, despite a lower interaction between enzymatically modified LDL and the B/E receptor, the metabolism of this lipoprotein was quite comparable with that of native LDL and its degradation with cultured macrophages was poor. The use of in vitro models is common for study of the relationship between oxidized LDL and atherogenesis in humans. The choice of the more appropriate way to modify lipoproteins is of interest and is discussed.

Antibodies, Monoclonal↗
PubMed1993

Expression of apolipoprotein B epitopes in low density lipoproteins of hemodialyzed patients.

Serum and isolated low-density lipoprotein (LDL) composition abnormalities were investigated in 20 hemodialyzed patients with chronic renal failure and 15 healthy normolipidemic subjects for comparison. LDL apolipoprotein B (apo B) epitope accessibility was determined by the use of seven monoclonal antibodies (Mabs). These Mabs recognize fragments on the N-terminal part of apo B (Mabs B1, B4), on the middle part (Mab BL7), on the C-terminal (Mabs BA11, BL3), and the two remaining Mabs recognize conformational epitopes of apo B (BL5, DA7). Mab BA11 recognizes a fragment of apo B which interacts with the B/E receptor. In hemodialyzed patients, LDL content of triglycerides (P < 0.001) and apo CIII (P < 0.005) was increased, while cholesteryl esters (P < 0.005) were decreased. The accessibility of BL5 epitopes of LDL apo B was enhanced (P < 0.05), while BA11 epitope expression was decreased (P < 0.01). The conformation of patients' LDL (CRF-LDL) was probably abnormal and seemed to be related to some modification of the lipidic environment. It is important to consider a structural modification as it alters the B/E receptor recognition domain of apo B. These results confirm LDL abnormalities in hemodialyzed patients and suggest a possible modification of the recognition of the LDL by cells.

Adult↗
PubMed1993

Modulation of the expression of human LDL-Apo B-100 epitopes by lipids and apolipoproteins.

The purpose of the present study was to determine the immunochemical properties of apolipoprotein (apo) B-100 associated with low density lipoprotein (LDL) in relation to lipid and apolipoprotein composition. LDLs were isolated by sequential ultracentrifugation (1.019 < d < 1.050 g/mL) from two healthy volunteers and 21 dyslipidemic patients to obtain heterogeneous samples of LDL. Lipid (free cholesterol, cholesteryl esters, triglycerides, and phospholipids) and apolipoprotein contents (apo B, apo C-III, apo E) were determined in each LDL sample. Immunoreactivities of apo B were tested in solid-phase competitive-binding radioimmunoassays using seven monoclonal anti-LDL antibodies that reacted with defined epitopes of apo B-100. The relation between lipid and/or protein variables and the immunoreactivity of apo B was evaluated by successive use of Spearman's rank simple correlation, partial correlation, and canonical correlation analyses. The canonical correlation analysis showed that apo B-100 immunoreactivity on LDL is highly dependent on lipid and apolipoprotein composition simultaneously. The results confirmed the influence of surface and core lipids on the expression of the apo B-100 epitopes, independent of their location on the molecule. However, the lipid requirement of LDL strongly influences the expression of epitopes mapped in the LDL receptor-recognition domain. In contrast to apo E, apo C-III does not seem to influence the expression of the apo B-100 epitopes in the LDL range studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
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↗
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

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↗
PubMed1990

[Determination of blood profile of atherogenic lipids using immunologic techniques].

Apolipoprotein B (Apo B) exists in different types of particles in human plasma: Lp B containing only Apo B, Lp B:E containing Apo B and Apo E, Lp B:C-III containing Apo B and Apo C-III, Lp B: (a) containing Apo B and Apo (a) and so on. The physicochemically defined lipoproteins were found to be heterogeneous with respect to this concept. A particle such as Lp B, for example, may occur in any segment of the density spectrum depending on the composition and content of its lipid complement. These particles are metabolically distinct and their quantification is essential for better understanding of lipid transport disorders. Using new immunological procedures, we have identified some subpopulations of Apo B containing lipoproteins which are more abondant in atherosclerotic patients and which characterize some dyslipoproteinemic states. Drugs decreasing Apo B act differently on these different types of particles. The results presented substantiate the usefulness of the study of lipoprotein particles defined by their apolipoprotein composition for future clinical, pharmacological and epidemiological studies.

Apolipoproteins B↗
PubMed1989

Apolipoprotein B immunochemical heterogeneity in dialysed patients with chronic renal failure and patients with coronary artery stenosis.

Serum cholesterol, triglyceride, apolipoprotein B (apo B) and the cholesterol and phospholipid content of apo-B-containing particles was determined in 41 male patients on dialysis for chronic renal failure, in 41 male patients with coronary artery disease selected on the basis of a total cholesterol level below 6.72 mmol/l and in 41 male control subjects of similar age. Apo B was assessed as total B protein determined using polyclonal antibodies and also by measuring the expression of epitopes recognized by three different monoclonal antibodies (BL3, BL5 and BL7). Triglyceride was increased (p less than 0.01) and cholesterol was decreased (p less than 0.01) in the dialysed patients with chronic renal failure. Total apo B was similar in the three tested groups while the expression of the BL7 epitope was increased in the group of dialysed patients with chronic renal failure (p less than 0.001). The expression of BL3 and BL5 epitopes was increased in patients with coronary artery disease (BL3: p less than 0.05; BL5: p less than 0.02) but not in dialysed patients with chronic renal failure. These results suggest an abnormal composition and an immunological heterogeneity of apo-B-containing lipoprotein particles in patients with coronary artery stenosis and in dialysed patients with chronic renal failure.

Antibodies, Monoclonal↗
PubMed1989

Rat monoclonal antibodies to human apolipoprotein B: advantages and applications.

Eight monoclonal antibodies (Mabs) to human serum low density lipoprotein (LDL) were derived from the fusion of spleen cells, from LOU rats immunized with human LDL, and the rat myeloma line IR983F. These Mabs were characterized in terms of isotype, specificity, and affinity. Competitive experiments indicated that the epitopes that were recognized could be grouped into three patterns depending on their apparent affinity for apoB-containing lipoprotein particles such as LDL, very low density lipoproteins (VLDL), or intermediate density lipoproteins (IDL). Six epitopes have been mapped in relation to elements of the sequence of apolipoprotein B-100 (apoB-100) and some have been assigned to the middle part of the median thrombolytic fragment T3, a region not yet well targeted by mouse Mabs. The presence of lipids for the expression of the epitopes was studied and confirmed a lipid dependence for epitopes that are close to the T2/T3 cleavage site. The capacity of binding to the LDL receptor was also tested; among the Mabs we described, one inhibited the uptake and degradation of LDL to HeLa cells receptor. Finally, some antibodies were able to precipitate LDL in gel.

Animals↗
PubMed1988

Antibodies of predetermined specificity to apolipoprotein C-II elicited with a synthetic peptide. Characterization and use for immunoassays.

Antibodies of predetermined specificity raised against a synthetic peptide corresponding to the C-terminal region of apolipoprotein C-II (Apo C-II) 63-79 were shown to be specific for the apolipoprotein by Western blot. The recognition by these antibodies of Apo C-II containing lipoprotein particles (both isolated and in plasma) was studied in a fluid-phase radioimmunoassay and the affinity constant for plasma was determined. The role of lipids in the expression of epitopes was studied by comparing the antigenicity of intact and delipidated Apo C-II containing fractions. The antibodies proved to be as suitable as conventional anti-protein antibodies in an immunoenzymometric assay and, moreover, were able to develop 'rockets' in an electroimmunoassay.

Antibodies↗