Jean-Marie Bard

Modulation of Lipoprotein B Binding to the LDL Receptor by Exogenous Lipids and Apolipoproteins CI, CII, CIII, and E

We have recently shown that apo B-containing lipoproteins isolated by immunoaffinity chromatography bind to the LDL receptor with an affinity dependent on their apo E or apo CIII content. However, these lipoproteins--LpB:E, LpB:CIII, and LpB:CIII:E--isolated from whole plasma have variable lipid and apolipoprotein contents, and it is difficult to consider each parameter separately, particularly because an increase in the apo CIII content is always associated with an increase in the content of other C apolipoproteins. Therefore, we used affinity-purified LpB free of other apolipoproteins. Lipid content of LpB was increased by incubation with a lipid emulsion, and this triglyceride-enriched LpB was named TG-LpB. Free apo CI, apo CII, apo CIII, and apo E were added to LpB and TG-LpB and their associations to the lipoprotein were assessed by gel filtration, nondenaturing electrophoresis, and immunoblotting. Molar ratios of 6 (apo E), 30 (apo CII), 20 (apo CIII), and 30 (apo CI) for 1 apo B were obtained. The association of apo CII to LpB and TG-LpB induced modifications to the LpB structure and a redistribution of lipids and apolipoproteins on the lipoprotein particles. The binding of these LpBs and TG-LpBs with and without added apo CI, CII, CIII, and E was tested at 4 degrees C on the LDL receptors of HeLa cells. The increased content of lipids reduced TG-LpB binding to the LDL receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating soluble adhesion molecules ICAM-1 and VCAM-1 and incident coronary heart disease: The PRIME Study

The Epidemiological Study of Myocardial Infarction Study which enrolled 9758 apparently healthy men aged 50-59 years, is a prospective cohort study designed to evaluate markers of coronary risk. Soluble forms of the intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) levels were measured in plasma obtained at baseline from 317 subjects who suffered a coronary event during the 5-year follow-up and in twice the number of control subjects who were matched for center, age and day of inclusion in a nested case-control design. The relative risk associated with the highest compared with the lowest thirds of ICAM-1 (>625 versus <502 ng/ml) was 2.45 (95% CI: 1.64-3.65, P<0.001) without adjustment; it decreased moderately (RR: 2.09; 95% CI: 1.34-3.24, P<0.001) after control for lipid and non-lipid factors and remained significantly elevated after adjustment for C-reactive protein (CRP) (RR: 1.90; 95% CI: 1.21-2.96, P=0.005). Plasma ICAM-1 was essentially associated with the risk of myocardial infarction or coronary death and also with angina pectoris. Subjects with CRP presented elevated coronary risk only if ICAM-1 was high. An elevated level of VCAM-1 was not associated with any risk of future acute coronary event, or with angina pectoris. This data indicates that plasma levels of ICAM-1 may serve as risk markers for future coronary events whatever their clinical presentation and that risk is better defined using simultaneous measurements of ICAM-1 and CRP than any of these levels separately.

A multicenter comparison of the effects of simvastatin and fenofibrate therapy in severe primary hypercholesterolemia, with particular emphasis on lipoproteins defined by their apolipoprotein composition

This multicenter, double-blind, randomized study was designed to compare the effects of simvastatin (20 mg/d and 40 mg/d) and fenofibrate (400 mg/d) on plasma lipids, lipoproteins, apolipoproteins (apo), and lipoprotein particles defined by their apo composition (Lp A-I, Lp A-II:A-I, Lp E:B, Lp C-III:B) in primary hypercholesterolemia. After 6 and 10 weeks of therapy, both drugs lowered plasma cholesterol, low-density lipoprotein (LDL) cholesterol, and apo B. The effect on LDL and apo B was significantly more pronounced for simvastatin (P = .01). Simvastatin increased Lp A-I, but did not change Lp A-II:A-I, while fenofibrate decreased Lp A-I and increased Lp A-II:A-I. Lp E:B and Lp C-III:B were decreased with both drugs, but fenofibrate was significantly more effective in reducing these particles than simvastatin. This study demonstrates that both drugs have beneficial effects on the parameters positively or negatively correlated with the atherosclerotic risk, with simvastatin being more effective in reducing some of them. These results suggest that the drugs led to different structural modifications of the lipoproteins, which would not be revealed by examination of lipoprotein density classes. These differences are probably related to the different mechanisms of action of the agents.

Logistic discriminant analysis of lipids and apolipoproteins in a population of coronary bypass patients and the significance of apolipoproteins C-III and E

The lipid and apolipoprotein states of 74 men (mean age 49.96 +/- 5.9 years) were studied 24 h before coronary bypass surgery and their results were compared with those of a control group of 78 men (mean age 48.88 +/- 5.41 years). Apolipoproteins C-III (apo C-III) and E (apo E) were determined in particles with (LpB) and without (nonLpB) apo B separated using a concanavalin A reagent. Apo C-III was significantly increased in LpB particles (P less than 0.001), and apo E in LpB (P less than 0.001) and nonLpB (P less than 0.001) particles. The significant variables selected in logistic discriminant stepwise analysis were total cholesterol/HDL-cholesterol, apo E-nonLpB and apo C-III-LpB. This last parameter, which is more discriminant than triglycerides, provides a more specific indication of dyslipoproteinemia in coronary bypass patients; in association with the other two variables, it significantly improved the percentage of correctly classified individuals.

Lipoprotein composition changes induced by fenofibrate in dysbetalipoproteinemia type III

Fenofibrate (300 mg daily) was given to 9 subjects (7 men, 2 women) with dysbetalipoproteinemia type III. The treatment brought about important plasma level reductions in cholesterol (-35%), triglycerides (-56%), VLDL-cholesterol (-63%) and VLDL-triglycerides (-59%). The VLDL-C/TG ratio, which was 0.40 before treatment, was 0.30 after 4 weeks of fenofibrate, still suggestive of type III. LDL-C, when measured by conventional methods, was unchanged but isolation of the IDL (1.006-1.019 g/ml) fraction from the 1.006 g/ml infranatant revealed that true LDL-C levels actually increased in 6 individuals while IDL-C decreased considerably. The total HDL-C increase was mostly due to a 33% HDL3-C change. Apolipoprotein levels were considerably modified, notably apo B, C-III and E which were decreased, as well as the lipoprotein particles containing combinations of these apolipoproteins, namely LpE:B and LpC-III:B. Apo A-I was slightly modified as LpA-I: A-II particle levels increased and LpA-I decreased. There were marked compositional modifications of apo B-containing lipoproteins which corresponded to changes of the whole lipoprotein profile. Some abnormal classes of lipoproteins (e.g., beta-VLDL, dense LDL), characteristic of this disease, tended to disappear and were in some cases replaced by material of different size and density.

Effect of pravastatin, an HMG CoA reductase inhibitor, and cholestyramine, a bile acid sequestrant, on lipoprotein particles defined by their apolipoprotein composition.

This study compares the effects of cholestyramine (16 g/d) and pravastatin (40 mg/d) on lipoprotein particles defined by their apolipoprotein composition (Lp A-I, Lp A-II:A-I, Lp E:B, and Lp C-III:B). Analysis was performed after 4, 8, and 12 weeks of therapy. Low-density lipoprotein (LDL) cholesterol decreased by 25.1% to 35.0% with cholestyramine and 26.2% to 30.7% with pravastatin, while triglycerides decreased slightly with pravastatin therapy and increased slightly during cholestyramine administration. The fall in cholesterol was mainly due to a decrease in very-low-density lipoprotein (VLDL) and LDL cholesterol; high-density lipoprotein (HDL) cholesterol increased. Apolipoprotein B was reduced dramatically (by 21.7% to 30.5% with cholestyramine and 27.7% to 37.4% with pravastatin). No significant effect on apolipoproteins C-III and E was observed with cholestyramine, while pravastatin reduced these parameters slightly. Apolipoprotein A-I increased during therapy with both drugs, while apolipoprotein A-II was slightly decreased. Although the drugs had nearly the same effects on plasma lipids, their influence on lipoprotein particles defined by their apolipoprotein composition was substantially different. Lp A-II:A-I was increased by both drugs (+8.1% to +41.2% for cholestyramine and +7.2% to +32.6% for pravastatin). Lp A-I was also increased with both drugs, but cholestyramine had a more constant and pronounced effect than pravastatin (+15.1% to +21.7% for cholestyramine and +1.7% to +13.0% for pravastatin). Lp E:B and Lp C-III:B were consistently decreased by pravastatin (-10.2% to -36.5% for LP E:B and -7.2% to -20.9% for Lp C-III:B), while cholestyramine had variable effects on these particles.(ABSTRACT TRUNCATED AT 250 WORDS)

High-density lipoprotein particles in octogenarians☆

High-density lipoprotein (HDL) particles exhibit considerable heterogeneity, specifically in apolipoprotein (apo) composition. Thus, apo A-I, the major protein of HDL, is present in two types of particles: one species contains both apo A-I and apo A-II (Lp A-I/A-II) while in the other (Lp A-I), apo A-II is absent. We used the hypothesis that octogenarians, who survived periods in life when the incidence of coronary heart disease (CHD) is very high, have several protective factors. We compared HDL-cholesterol (HDL-C), HDL2-cholesterol (HDL2-C), HDL3-cholesterol (HDL3-C), apo A-I, and apo A-II in octogenarians and younger control subjects smoking less than 10 cigarettes/d and not taking drugs known to affect lipid metabolism. Using a new procedure, we also compared the levels of Lp A-I and Lp A-I/A-II. The cholesterol content of total HDL was similar in octogenarian and control (38 +/- 8 years) men while HDL2-C was higher and HDL3-C, apo A-I, and A-II were lower in octogenarian than in control men. In women, the level of HDL-C and apo A-I was similar in premenopausal and octogenarian subjects but higher in postmenopausal women than in octogenarians, while HDL2-C and apo A-II were similar in the three groups. In contrast, HDL3-C was higher in the two groups of control women (premenopausal and postmenopausal) than in octogenarians. However, Lp A-I was significantly elevated in octogenarian men and women (men: 61 +/- 14 mg/dL; women: 70 +/- 14 mg/dL) by comparison with younger control subjects (men: 48 +/- 12 mg/dL; premenopausal women: 53 +/- 11 mg/dL; postmenopausal women: 63 +/- 19 mg/dL).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Quantitative determination of different apolipoprotein B containing lipoproteins by an enzyme linked immunosorbent assay: apo B with apo C-III and apo B with apo E.

A non competitive enzyme-linked immunosorbent assay (ELISA) for total apolipoprotein (apo) B, apo B with apo C-III (LpC-III:B), and apo B with apo E (LpE:B), was developed. Microtiter plates were used as solid-phase, and subdivided into three parts, coated respectively with affinity purified antibodies to apo B, to apo C-III and to apo E. After incubating the antigen with coated plates, a horseradish peroxidase-labelled antibody to apo B was added to all the plates to estimate total apo B, LpC-III:B and LpE:B.

The increased plasma Lp(a) : B lipoprotein particle concentration in angina pectoris is not associated with hypofibrinolysis

The structural homology between plasminogen and apolipoprotein (a), the specific glycoprotein of Lp(a) lipoprotein, raises the possibility of a relationship between this lipoprotein and the plasma fibrinolytic system. The present study examines this proposal by studying 66 patients with angina pectoris. As compared to normal controls, the patients had raised concentrations of Lp(a): B lipoprotein particles. No correlation was found between circulating Lp(a): B and the fibrinolytic system. The pathogenic role of Lp(a): B lipoprotein seems therefore not mediated by its effect on the plasma fibrinolytic system.