Biomedical subjects

B Perret

Publications and source records attributed to B Perret.

At least 19 recordsLinked to original sources

PubMed2006

Lipoprotein (a) and risk of ischemic stroke in young adults.

UNLABELLED: Lipoprotein (a) [Lp(a)] is a LDL-particle linked to apoprotein (a) [apo(a)]. High Lp(a) plasma level is a risk factor for coronary heart disease and, in older men, for ischemic stroke. The role of Lp(a) as a risk factor for ischemic stroke in young adults is uncertain. METHODS: Lp(a) concentration was prospectively measured in 100 consecutive patients with acute ischemic stroke (58 men and 42 women) aged 18-55 years, and in 100 controls matched for age and gender. RESULTS: The distribution of Lp(a) concentration was skewed toward the highest and median tertiles in male patients. In multivariate logistic regression analyses adjusting on classical risk factors for ischemic stroke and lipid variables, Lp(a) concentration in the highest and medium tertiles compared with the lowest tertile was significantly associated with ischemic stroke in men (OR 3.55, 95% CI 1.33-9.48, p = 0.012), but was not in women (OR 0.42, 95% CI 0.14-1.26, p = 0.12). Although large vessel atherosclerosis was more common in men than in women, there were no differences in Lp(a) concentration according to the cause of ischemic stroke. CONCLUSION: Among subjects aged 18-55 years, a slightly elevated Lp(a) concentration was strongly and independently associated with ischemic stroke in men, but not in women. Further studies are required to elucidate the mechanisms underlying this gender-specific association.

Adolescent↗

PubMed2006

Cell surface adenylate kinase activity regulates the F(1)-ATPase/P2Y (13)-mediated HDL endocytosis pathway on human hepatocytes.

We have previously demonstrated on human hepatocytes that apolipoprotein A-I binding to an ecto-F(1)-ATPase stimulates the production of extracellular ADP that activates a P2Y(13)-mediated high-density lipoprotein (HDL) endocytosis pathway. Therefore, we investigated the mechanisms controlling the extracellular ATP/ADP level in hepatic cell lines and primary cultures to determine their impact on HDL endocytosis. Here we show that addition of ADP to the cell culture medium induced extracellular ATP production that was due to adenylate kinase [see text] and nucleoside diphosphokinase [see text] activities, but not to ATP synthase activity. We further observed that in vitro modulation of both ecto-NDPK and AK activities could regulate the ADP-dependent HDL endocytosis. But interestingly, only AK appeared to naturally participate in the pathway by consuming the ADP generated by the ecto-F(1)-ATPase. Thus controlling the extracellular ADP level is a potential target for reverse cholesterol transport regulation.

Adenosine Diphosphate↗

PubMed2006

Metabolic syndrome and coronary heart disease risk in a population-based study of middle-aged men from France and Northern Ireland. A nested case-control study from the PRIME cohort.

Metabolic Syndrome (MetS) was found associated with an increased CHD risk in several studies but data about this relationship in Southern Europe are lacking. We studied the association of MetS according to three different indexes (the National Cholesterol Education Program's definition (NCEP), a modified World Health Organization's definition (WHO) and the recent International Diabetes Federation's definition (IDF)) with CHD risk in a case-control study nested within the PRIME cohort, composed of subjects from France (Southern Europe) and Belfast (Northern Europe). The PRIME prospective study is composed of 10 592 men, aged 50-59 at baseline and followed for 5 years. Subjects included in this nested case-control study were 296 cases of incident CHD and 540 controls, who remained free of CHD during the 5 years of follow-up of the PRIME cohort and matched for age, recruitment centre and recruitment date. All subjects had questionnaires and a medical examination at baseline, and a blood sample was taken. Using the IDF's, the WHO's and the NCEP's definitions respectively, the frequency of MetS was 38.9%, 35.5% and 29.7% in cases and 32.4%, 28.7% and 22.6% in controls. After adjustment for physical activity, smoking and drinking habits, MetS was associated with CHD risk whichever the definition used (ORIDF=1.41 [1.02-1.95], P<0.04, ORWHO=1.40 [1.01-1.94], P<0.05 and ORNCEP=1.46[1.04-2.04], P<0.04). These results were homogeneous in France (low risk of CHD) and Belfast (high risk of CHD). Our results add further evidence that MetS is predictive of CHD risk in middle-aged men from Northern and Southern Europe, and highlight differences between the three definitions studied.

Blood Glucose↗

PubMed2005

Metabolic syndrome is associated with markers of subclinical atherosclerosis in a French population-based sample.

Metabolic syndrome (MetS) is associated with increased risk of cardiovascular disease (CVD). The relation of MetS with early stages of atherosclerosis, more important from a prevention perspective, has not been evaluated extensively. We examined the association of MetS, using WHO and NCEP definitions, with number of carotid and femoral plaques; carotid intima-media thickness (IMT); pulse wave velocity (PWV) in a random population-based sample of 1153 French adults (35-65 year). Impact of inflammatory factors (C-reactive protein and soluble intercellular adhesion molecule-1) on these parameters was also evaluated. Prevalence of MetS was 14.5 (CI: 12.3-16.0) and 17.5 (CI: 15.1-20.2)%, using NCEP and WHO definitions, respectively. MetS significantly predicted number of plaques, IMT, and PWV after adjustment for traditional risk factors (P<0.05). Inflammatory factors predicted peripheral plaques only. The risk of subclinical atherosclerosis was considerably increased with MetS (P<0.05); odds ratios ranged 1.80-2.15 with NCEP definition, and 1.48-1.97 with WHO definition. Individuals meeting both NCEP and WHO definitions had slightly greater risk of increased plaques, IMT, and PWV. MetS was strongly associated with subclinical atherosclerosis and aortic stiffness, and can be used as a surrogate marker for high CVD risk, deserving aggressive treatment.

Adult↗

PubMed2005

The nucleotide receptor P2Y13 is a key regulator of hepatic high-density lipoprotein (HDL) endocytosis.

Cell surface receptors for high-density lipoprotein (HDL) on hepatocytes are major partners in the regulation of cholesterol homeostasis. We recently identified a cell surface ATP synthase as a high-affinity receptor for HDL apolipoprotein A-I (apoA-I) on human hepatocytes. Stimulation of this ectopic ATP synthase by apoA-I triggered a low-affinity-receptor-dependent HDL endocytosis by a mechanism strictly related to the generation of ADP. This suggests that nucleotide G-protein-coupled receptors of the P2Y family are molecular components in this pathway. Only P2Y1 and P2Y13 are present on the membrane of hepatocytes. Using both a pharmacological approach and small interference RNA, we identified P2Y13 as the main partner in hepatic HDL endocytosis, in cultured cells as well as in situ in perfused mouse livers. We also found a new important action of the antithrombotic agent AR-C69931MX as a strong activator of P2Y13-mediated HDL endocytosis.

Adenosine Diphosphate↗

PubMed2005

Total body composition by DXA of 241 HIV-negative men and 162 HIV-infected men: proposal of reference values for defining lipodystrophy.

The aim of this study was to define standard values for fat mass distribution by dual-energy X-ray absorptiometry in human immunodeficiency virus (HIV)-negative men and to analyze factors associated with lipodystrophy in HIV-infected men. Total-body composition was analyzed in 241 HIV-negative men (controls) and 162 HIV-infected men. We created a fat mass ratio (FMR) as the ratio of the percentage of the trunk fat mass to the percentage of the lower limbs fat mass. We defined the FMR standard values as the mean value+/-standard deviation. We compared body mass index (BMI), fat mass percentage (%FM), lean mass (LM), bone mineral density (BMD), and FMR between the control group and HIV-infected men, by age range, according to prescription of treatment and presence of clinical lipodystrophy. The FMR standard value is equal to 1.3+/-0.2. The FMR was higher in treated HIV-infected men with or without clinical lipodystrophy. The FMR was similar for naïve HIV-infected men and controls. It was positively correlated with age, cumulative time on treatment, zidovudine, stavudine, or indinavir. BMD and fat mass were lower for treated and naïve HIV-infected men than for HIV-negative men. The FMR seems to be a valuable index for measuring fat mass distribution. We defined FMR standard values from the largest group of HIV-negative men to our knowledge. Applying FMR to HIV patients could help physicians to diagnose lipodystrophy earlier.

Absorptiometry, Photon↗

PubMed2005

[Prevalence of dyslipidaemias in a representative sample of the French population].

Prevalence of dyslipidaemias in a representative sample of the French population Hypercholesterolaemia is a major factor of risk of coronary atherosclerosis. The prevalence of other types of dyslipidaemia in the general population remains poorly defined. This study was performed to measure the prevalence of various dyslipidaemias in the French population. A representative sample of 3508 men and women between the ages of 35 and 64 years was recruited by the "Multinational MONItoring of trends and determinants in CArdiovascular disease" centres of Lille, Strasbourg and Toulouse. We excluded 162 patients suffering from known cardiovascular disorders, and 409 individuals treated with lipid-lowering drugs. The prevalence of pure hypercholesterolaemia, defined as a total cholesterol concentration >6.2 mmol/l (2.4 g/l) and triglyceride concentration <2.3 mmol/l (2 g/l), was 30% (29-32%). The prevalence of HDL cholesterol concentration <1 mmol/l (0.4 g/l) in men, or <1.3 mmol/l (0.5 g/l) in women, was 12% (11-13%). The prevalence of mixed hyperlipidaemia, defined as a total cholesterol concentration >6.2 mmol/l (2.4 g/l) and triglyceride concentration >2.3 mmol/l (2 g/l) was 5% (4-6%). The prevalence of hypertriglyceridaemia, defined as a total cholesterol concentration <6.2 mmol/l (2.4 g/l) and triglyceride concentration >2.3 mmol/l (2 g/l) was 4% (3-5%). Low HDL cholesterol concentrations were associated with smoking, obesity, and absence of either regular physical exercise or alcohol consumption. This study confirmed the high prevalence of pure hypercholesterolaemia, and revealed an important prevalence of low HDL cholesterol concentration, which represents a major cardiovascular risk factor.

Adult↗

PubMed2004

New insight on the molecular mechanisms of high-density lipoprotein cellular interactions.

High-density lipoprotein (HDL) cholesterol is an independent negative risk factor for coronary artery disease and thus represents today the only protective factor against atherosclerosis. The protective effect of HDL is mostly attributed to its central function in reverse cholesterol transport (RCT), a process whereby excess cell cholesterol is taken up and processed in HDL particles, and is later delivered to the liver for further metabolism and bile excretion. This process relies on specific interactions between HDL particles and cells, both peripheral (cholesterol efflux) and hepatic (cholesterol disposal) cells, and on the maturation of HDL particles within the vascular compartment. The plasma level of HDL cholesterol will thus result also from the complex interplay with cellular partners. Among them, some contribute to HDL formation - for instance ATP binding cassette AI protein - while others are mostly involved in HDL catabolism, the scavenger receptor-class B type I or the recently described membrane-bound ATP synthase/hydrolase. The last decade has seen major breakthroughs in the identification and elucidation of the role of cellular partners of HDL metabolism, and in their transcriptional regulations, opening up new perspectives in the modulation of HDL cholesterol.

ATP Binding Cassette Transporter 1↗

PubMed2002

Types of alcoholic beverages and blood lipids in a French population.

STUDY OBJECTIVE: Prospective studies have shown a consistent relation between alcohol consumption and decreasing incidence of coronary artery disease. The protective effect of alcohol could be mediated through increased levels of HDL cholesterol (HDL-c). The aim of this study was to examine the relation between blood lipid levels and the consumption of different types of alcoholic beverages among 1581 men and 1535 women. DESIGN: Data from representative cross sectional surveys (1994-1997) in three different regions of France were used. The consumption of the different types of alcohol was quantified using a recall method according to a typical weekly consumption. MAIN RESULTS: The median daily alcohol intake was 24 g for men and 4 g for women. After adjustment for confounders, total alcohol showed a positive and significant association with HDL-c and triglycerides (TG) in both sexes. In multivariate analysis, wine was positively associated with HDL-c. Beer was positively associated with HDL-c in men and with triglycerides in men and women. When taking drinking patterns into account, wine drinkers had higher HDL-c levels than non-wine drinkers. Differences became non-significant after adjustment for confounders and particularly for socioeconomic parameters. CONCLUSIONS: In a French population sample, total alcohol was positively associated with HDL-c and triglycerides. The specific influence of any particular alcoholic beverage on blood lipids was not clearly demonstrated but wine preference found in a group with higher lifestyle standards was associated with a more favourable blood lipid profile.

Adult↗

PubMed2001

An interaction between apo C-III variants and protease inhibitors contributes to high triglyceride/low HDL levels in treated HIV patients.

BACKGROUND: Long-term therapy with protease inhibitors (PI) is associated with hypertriglyceridaemia, low high-density lipoprotein (HDL) levels and accumulation of apolipoprotein (apo) E- and apo C-III-containing lipoproteins. OBJECTIVES: To evaluate the impact, on this dyslipaemic phenotype, of three polymorphisms of the apo C-III gene: two on an insulin response element and one in the 3'-region. Apo E genotypes were evaluated also. DESIGN: Sixty consecutive male patients attending the HIV follow-up consultation were included during a 3-month period. All patients received at least one PI. Apo C-III and apo E genotypes were determined. Besides routine bio-clinical examination, a detailed exploration of lipoproteins and of insulin secretion markers was carried out. METHODS: Plasma lipoparticles, insulin, proinsulin and C-peptide were measured by specific immuno-assays. Determination of apo C-III genotypes (-455C/T, -482C/T and SstI) and of apo E alleles (epsilon2, epsilon3 and epsilon4) were performed by amplification and endonuclease digestion and were confirmed by allele-specific oligonucleotide hybridization. RESULTS: Distribution of apo C-III alleles defined four major haplotypes. Carriers of the -455C variant had 30% lower levels of HDL-cholesterol than non-carriers. Plasma triglycerides increased according to the number of variant alleles. In multivariate analysis, a model including age, body mass index, clinical stage and treatment length, plasma insulin and apo C-III haplotypes explained around 43% of the HDL-cholesterol and triglycerides variability. Measurements of lipids before and after the use of PI demonstrated synergistic effects of the treatment and apo C-III variants on triglyceride levels. CONCLUSIONS: Apo C-III polymorphisms might identify a genetic predisposition to develop dyslipidaemia under PI therapy.

Adult↗

PubMed2001

Vascular smooth muscle cell spreading onto fibrinogen is regulated by calpains and phospholipase C.

Fibrinogen deposition and smooth muscle cell migration are important causes of atherosclerosis and angiogenesis. Involvement of calpains in vascular smooth muscle cell adhesion onto fibrinogen was investigated. Using calpain inhibitors, we showed that activation of calpains was required for smooth muscle cell spreading. An increase of (32)P-labeled phosphatidic acid and phosphatidylinositol-3,4-bisphosphate, respective products of phospholipase C and phosphoinositide 3-kinase activities, was measured in adherent cells. Addition of the calpain inhibitor calpeptin strongly decreased phosphatidic acid and phosphatidylinositol-3,4-bisphosphate. However, smooth muscle cell spreading was prevented by the phospholipase C inhibitor U-73122, but poorly modified by phosphoinositide 3-kinase inhibitors wortmannin and LY-294002. Moreover, PLC was found to act upstream of the PI 3-kinase IA isoform. Thus, our data provide the first evidence that calpains are required for smooth muscle cell spreading. Further, phospholipase C activation is pointed as a key step of cell-spreading regulation by calpains.

Actins↗

PubMed2001

Differential regulation of phosphoinositide metabolism by alphaVbeta3 and alphaVbeta5 integrins upon smooth muscle cell migration.

Smooth muscle cell migration is a key step of atherosclerosis and angiogenesis. We demonstrate that alpha(V)beta(3) and alpha(V)beta(5) integrins synergistically regulate smooth muscle cell migration onto vitronectin. Using an original haptotactic cell migration assay, we measured a strong stimulation of phosphoinositide metabolism in migrating vascular smooth muscle cells. Phosphatidic acid production and phosphoinositide 3-kinase IA activation were triggered only upon alpha(V)beta(3) engagement. Blockade of alpha(V)beta(3) engagement or phospholipase C activity resulted in a strong inhibition of smooth muscle cell spreading on vitronectin. By contrast, blockade of alpha(V)beta(5) reinforced elongation and polarization of cell shape. Moreover, Pyk2-associated tyrosine kinase and phosphoinositide 4-kinase activities measured in Pyk2 immunoprecipitates were stimulated upon cell migration. Blockade of either alpha(V)beta(3) or alpha(V)beta(5) function, as well as inhibition of phospholipase C activity, decreased both Pyk2-associated activities. We demonstrated that the Pyk2-associated phosphoinositide 4-kinase corresponded to the beta isoform. Our data point to the metabolism of phosphoinositides as a regulatory pathway for the differential roles played by alpha(V)beta(3) and alpha(V)beta(5) upon cell migration and identify the Pyk2-associated phosphoinositide 4-kinase beta as a common target for both integrins.

1-Phosphatidylinositol 4-Kinase↗

PubMed2001

Characterization of a G protein-activated phosphoinositide 3-kinase in vascular smooth muscle cell nuclei.

Recent studies highlight the existence of an autonomous nuclear polyphosphoinositide metabolism related to cellular proliferation and differentiation. However, only few data document the nuclear production of the putative second messengers, the 3-phosphorylated phosphoinositides, by the phosphoinositide 3-kinase (PI3K). In the present paper, we examine whether GTP-binding proteins can directly modulate 3-phosphorylated phosphoinositide metabolism in membrane-free nuclei isolated from pig aorta smooth muscle cells (VSMCs). In vitro PI3K assays performed without the addition of any exogenous substrates revealed that guanosine 5'-(gamma-thio)triphosphate (GTPgammaS) specifically stimulated the nuclear synthesis of phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P(3)), whereas guanosine 5'-(beta-thio)diphosphate was ineffective. PI3K inhibitors wortmannin and LY294002 prevented GTPgammaS-induced PtdIns(3,4,5)P(3) synthesis. Moreover, pertussis toxin inhibited partially PtdIns(3,4,5)P(3) accumulation, suggesting that nuclear G(i)/G(0) proteins are involved in the activation of PI3K. Immunoblot experiments showed the presence of Galpha(0) proteins in VSMC nuclei. In contrast with previous reports, immunoblots and indirect immunofluorescence failed to detect the p85alpha subunit of the heterodimeric PI3K within VSMC nuclei. By contrast, we have detected the presence of a 117-kDa protein immunologically related to the PI3Kgamma. These results indicate the existence of a G protein-activated PI3K inside VSMC nucleus that might be involved in the control of VSMC proliferation and in the pathogenesis of vascular proliferative disorders.

Cell Nucleus↗

PubMed2001

Apoprotein c-III and E-containing lipoparticles are markedly increased in HIV-infected patients treated with protease inhibitors: association with the development of lipodystrophy.

Long-term therapy with protease inhibitors (PIs) can induce hypertriglyceridemia and development of a lipodystrophy. To better understand these metabolic alterations, the apoprotein and lipoparticle profile was investigated in male HIV patients under antiretroviral therapy: 49 received PIs, and 14 were given only two reverse transcriptase inhibitors. As controls, 63 male subjects were selected from a population study carried out in the Toulouse, France, area. Fasting glucose, insulin, and C-peptide were also determined. All patients under PIs displayed low levels of plasma glucose and increased insulin. PI administration was associated with moderate hypertriglyceridemia, low high-density cholesterol and apolipoprotein (apo) A-I levels. The most striking changes were a 2- to 3-fold increase in apo E and apo C-III, essentially recovered as associated to apo B-containing lipoparticles. Levels of those lipoparticles were two to eight times above control values. About 50% of PI-treated patients had developed a patent lipodystrophy. Multivariate analysis revealed that, among the investigated parameters, apo C-III was the only one found strongly associated with the occurrence of lipodystrophy (odds ratio, 5.5; P: < 0.015). Finally, 13 PI-receiving subjects with patent hypertriglyceridemia were given fenofibrate and were reevaluated 2 months later. Triglycerides, apo E, apo C-III, and the corresponding lipoparticles had returned to nearly normal levels. These results document the accumulation of potentially atherogenic lipoparticles under PIs. Apo C-III may play a pivotal role in the development of hypertriglyceridemia and lipodystrophy.

Adult↗

PubMed2000

Characterization of two high-density lipoprotein binding sites on porcine hepatocyte plasma membranes: contribution of scavenger receptor class B type I (SR-BI) to the low-affinity component.

Two HDL(3) high- and low-affinity binding sites are present on the human hepatoma cell line (HepG(2)). Recently, we have suggested that the high-affinity binding sites might modulate the endocytosis of HDL through the low-affinity binding sites [Guendouzi, K. (1998) Biochemistry 37, 14974-14980], highlighting the physiological importance of this family of HDL high-affinity binding sites. The present data demonstrate the presence of HDL(3) high-affinity (K(d) = 0.37 microg/mL, B(max) = 260 ng/mg of protein) and low-affinity (K(d) = 86.2 microg/mL, B(max) = 14 300 ng/mg of protein) binding sites on purified porcine hepatocyte plasma membranes. By contrast, free apoA-I was strictly specific to the high-affinity sites (K(d) = 0.2 microg/mL and B(max) = 72 ng/mg of protein). Competition experiments between (125)I-labeled HDL(3) and either LDL, oxidized LDL, or anti-SR-BI IgG as competitors show that SR-BI is mostly responsible (70% displacement) for the binding of HDL(3) to the low-affinity binding sites. By contrast, the same competition experiments using (125)I-labeled free apoA-I clearly excluded SR-BI as the high-affinity binding receptor. We conclude that the binding of HDL onto hepatocyte plasma membranes involves: (1) two low-affinity binding receptors, one being SR-BI; (2) one family of high-affinity binding sites unrelated to SR-BI.

Amino Acid Sequence↗

PubMed2000

Identification of an ApoA-I ligand domain that interacts with high-affinity binding sites on HepG2 cells.

We have previously described the presence of two (high- and low-affinity) HDL binding sites on the hepatoma cell line (HepG2) (R. Barbaras, X. Collet, H. Chap, and B. Perret (1994) Biochemistry 33, 2335-2340]. Moreover, apoA-I, the major HDL apolipoprotein, interacts with these two binding sites, while lipid-free apoA-I binds only to the high-affinity sites. Using tryptic HDL fragments and HepG2 cell monolayers as an "affinity matrix," we identified an apoA-I peptide of 16 amino acids, spanning between residues 62 and 77, as a ligand domain. The corresponding synthetic peptide displays high-affinity (K(d) approximately 10(-7) M) and low-capacity (B(max) 8 pmol/mg of cell protein) binding components. Competition experiments with this peptide, using (125)I-labeled free apoA-I as a ligand, show that this binding corresponds to the high-affinity binding sites already described. In conclusion, we identified the apoA-I 62-77 region as a specific high-affinity ligand domain of HDL on HepG2 cells.

Amino Acid Sequence↗

PubMed2000

Enhancement of zona binding using 2-hydroxypropyl- beta-cyclodextrin.

Since membrane cholesterol depletion is known to play an important role in sperm capacitation, we have investigated the effect of 2-hydroxypropyl-beta-cyclodextrin, a cyclic oligosaccharide that mediates cholesterol efflux, on sperm functions. Sperm treatment with cyclodextrin did not affect the motility patterns but induced an increase in sperm binding to zona pellucida (24 +/- 5 versus 13 +/- 4 in control, P < 0.01). Cyclodextrin treatment was associated with an increase in spontaneous acrosome reaction (32 +/- 8% versus 22 +/- 4% in controls after a 4 h incubation, P < 0.05; 61 +/- 10% versus 50 +/- 11% in controls after a 24 h incubation, NS) but with a decrease in acrosome response to ionophore challenge (44 +/- 5% versus 51 +/- 3% in controls, P < 0.05). Concerning cell sterols, cyclodextrin induced a rapid and dramatic fall in the cholesterol and desmosterol content of spermatozoa. We conclude that cyclodextrin is a powerful capacitating agent, but since it induces an increase in spontaneous acrosome loss, it needs to be further evaluated before routine use in assisted reproductive technology media.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed1999

Biochemical and physical properties of remnant-HDL2 and of pre beta 1-HDL produced by hepatic lipase.

The hepatic lipase acting on triglyceride-rich high-density lipoprotein2 (HDL2) induces the formation of pre beta 1-HDL, leaving a residual alpha-migrating HDL particle that was named "remnant-HDL2" (Barrans, A., Collet, X., Barbaras, R., Jaspard, B., Manent, J., Vieu, C., Chap, H., and Perret, B. (1994) J. Biol. Chem. 269, 11572-11577.]. In this study, these two product particles generated by hepatic lipase were isolated by density gradient ultracentrifugation. Particles were first characterized in terms of chemical composition, density, and mass. The pre beta 1-HDL obtained in vitro contain one to two molecules of apoA-I, associated with phospholipids, and free and esterified cholesterol. When compared to triglyceride-rich HDL2, remnant-HDL2 have lost on average one molecule of apoA-I, 60% of triacylglycerols, and 15% of phospholipids. The estimated composition is concordant with the hypothesis of the splitting of a substrate particle into one pre beta 1-HDL and one remnant-HDL2. Spectroscopic studies were carried out to monitor changes in lipid fluidity upon lipolysis. The fluorescence anisotropy was measured using (1,6)-diphenyl-hexa-(1,3, 5)-triene as a probe, and the degree of order was calculated from electron spin resonance spectra using the 5-nitroxy-derivative of stearic acid. Both approaches showed a decreased lipid fluidity in remnant-HDL2, as compared to triglyceride-rich HDL2. The immunoreactivity of apoA-I toward several monoclonal antibodies was assayed as a reflection of changes of apoA-I conformation. In remnant-HDL2, as compared to triglyceride-rich HDL2, a lower reactivity was noted with the 2G11 antibody, which interacts in the NH2 terminal part of apoA-I. Finally, remnant-HDL2 was clearly different from HDL3 with respect to all of the parameters studied, demonstrating that hepatic lipase does not promote the direct conversion of HDL2 to HDL3. Thus, hepatic lipase produces remnant-HDL2 particles, which display modifications of apoA-I conformation and of fluidity of the lipid environment. This newly described HDL2 subfraction may play a major role in the reverse cholesterol transport.

Apolipoprotein A-I↗