Parental history of early myocardial infarction is associated with decreased levels of lipoparticle AI in adolescents

Cardioprotective functions of HDLs

Multiple human population studies have established the concentration of high density lipoprotein (HDL) cholesterol as an independent, inverse predictor of the risk of having a cardiovascular event. Furthermore, HDLs have several well-documented functions with the potential to protect against cardiovascular disease. These include an ability to promote the efflux of cholesterol from macrophages in the artery wall, inhibit the oxidative modification of low density lipoproteins (LDLs), inhibit vascular inflammation, inhibit thrombosis, promote endothelial repair, promote angiogenesis, enhance endothelial function, improve diabetic control, and inhibit hematopoietic stem cell proliferation. There are undoubtedly other beneficial functions of HDLs yet to be identified. The HDL fraction in human plasma is heterogeneous, consisting of several subpopulations of particles of varying size, density, and composition. The functions of the different HDL subpopulations remain largely unknown. Given that therapies that increase the concentration of HDL cholesterol have varying effects on the levels of specific HDL subpopulations, it is of great importance to understand how distribution of different HDL subpopulations contribute to the potentially cardioprotective functions of this lipoprotein fraction. This review summarizes current understanding of the relationship of HDL subpopulations to their cardioprotective properties and highlights the gaps in current knowledge regarding this important aspect of HDL biology.

Apolipoprotein modulation of streptococcal serum opacity factor activity against human plasma high-density lipoproteins

Human plasma HDL are the target of streptococcal serum opacity factor (SOF), a virulence factor that clouds human plasma. Recombinant (r) SOF transfers cholesteryl esters (CE) from approximately 400,000 HDL particles to a CE-rich microemulsion (CERM), forms a cholesterol-poor HDL-like particle (neo HDL), and releases lipid-free (LF) apo A-I. Whereas the rSOF reaction requires labile apo A-I, the modulation effects of other apos are not known. We compared the products and rates of the rSOF reaction against human HDL and HDL from mice overexpressing apos A-I and A-II. Kinetic studies showed that the reactivity of various HDL species is apo-specific. LpA-I reacts faster than LpA-I/A-II. Adding apos A-I and A-II inhibited the SOF reaction, an effect that was more profound for apo A-II. The rate of SOF-mediated CERM formation was slower against HDL from mice expressing human apos A-I and A-II than against WT mice HDL and slowest against HDL from apo A-II overexpressing mice. The lower reactivity of SOF against HDL containing human apos is due to the higher hydropathy of human apo A-I, particularly its C-terminus relative to mouse apo A-I, and the higher lipophilicity of human apo A-II. The SOF-catalyzed reaction is the first to target HDL rather than its transporters and receptors in a way that enhances reverse cholesterol transport (RCT). Thus, effects of apos on the SOF reaction are highly relevant. Our studies show that the "humanized" apo A-I-expressing mouse is a good animal model for studies of rSOF effects on RCT in vivo.

Lipoprotein(a) levels are increased in healthy young subjects with parental history of premature myocardial infarction

BACKGROUND AND AIM

Most but not all studies in children, adolescents and young adults with a family history of coronary artery disease have reported an increase in lipoprotein(a) (Lp(a)) concentrations. The aim of this study was to assess if healthy children, adolescents and young adults with a parental history of premature myocardial infarction (PHPMI) have increased Lp(a) levels and are at higher risk of elevated (>30 mg/dl) Lp(a) concentrations.

METHODS AND RESULTS

One hundred fifty healthy children, adolescents and young adults with PHPMI (55% males; age 18+/-6.7 years) and 150 age- (+/-1 year) and gender-matched control subjects participated in the study. Concentrations of total plasma cholesterol, low-density lipoprotein (LDL)-cholesterol, high density lipoprotein (HDL)-cholesterol, apolipoprotein (Apo) A-I and B, triglycerides and Lp(a) were determined after fasting for 14 h. Participants with PHPMI had higher concentrations of LDL-cholesterol (107.9+/-31.1 vs. 99.2+/-28.7 mg/dl, p=0.01), Apo B (89.6+/-26.4 vs. 82.8+/-20.2 mg/dl, p=0.011) and Lp(a) (26.7+/-34.0 vs. 19.2+/-23.2 mg/dl, p=0.012) and lower HDL-cholesterol concentrations (47.9+/-11.3 vs. 50.7+/-13.9 mg/dl, p=0.038) than participants without PHPMI. Thirty percent of PHPMI positive subjects had elevated Lp(a) concentrations vs. 16.7% of PHPMI negative subjects (p=0.009; relative risk 2.14; 95% CI 1.23-3.73). In a conditional logistic regression analysis, Lp(a) concentration was significantly and independently associated with PHPMI.

CONCLUSIONS

Healthy young subjects with PHPMI have increased Lp(a) levels, a higher risk for elevated Lp(a) concentrations within an unfavourable lipid profile.

Rosuvastatin selectively stimulates apolipoprotein A-I but not apolipoprotein A-II synthesis in Hep G2 cells

Hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) are extensively used to regulate dyslipidemia and to reduce atherosclerotic cardiovascular disease. In addition to effectively lowering cholesterol and low-density lipoprotein levels, rosuvastatin and certain other statins can also increase plasma high-density lipoprotein (HDL) cholesterol modestly. However, the mechanism of action of rosuvastatin on HDL metabolic processes is not understood. Using cultured human hepatoblastoma cells (Hep G2) as an in vitro model system, we assessed the effect of rosuvastatin on apolipoprotein (apo) A-I and apo A-II (the major proteins of HDL) synthesis and HDL catabolic processes. Rosuvastatin dose-dependently increased messenger RNA expression and de novo synthesis of apo A-I but not apo A-II. Rosuvastatin selectively increased the synthesis of HDL particles containing only apo A-I (LP A-I) but not particles containing both apo A-I and A-II (LP A-I + A-II). The HDL(3)-protein or HDL(3)-cholesterol ester uptake by Hep G2 cells was not affected by rosuvastatin. The apo A-I-containing particles secreted by rosuvastatin-treated Hep G2 significantly increased cholesterol efflux from fibroblasts. The data indicate that rosuvastatin increases hepatic apo A-I but not apo A-II messenger RNA transcription, thereby selectively increasing the synthesis of functionally active apo A-I-containing HDL particles, which mediate cholesterol efflux from peripheral tissues. We suggest that this mechanism of action of rosuvastatin to increase apo A-I production without apo A-I/HDL removal may result in increased apo A-I turnover that results in accelerated reverse cholesterol transport.

Relationship between the concentration and antiatherogenic activity of high-density lipoproteins

PURPOSE OF REVIEW

The relationship between the concentration of high-density lipoprotein cholesterol and their protective function is addressed.

RECENT FINDINGS

Strong epidemiologic evidence indicates that the concentration of high-density lipoproteins is a powerful inverse predictor of cardiovascular risk. This is consistent with the fact that high levels of high-density lipoprotein are generally associated with an increased concentration of large high-density lipoprotein particles that are now known to be the preferred acceptors of cholesterol released from macrophages via the adenosine triphosphate-binding cassette A1 pathway. Some of the protective activity, however, of high-density lipoproteins may reflect functions of specific subpopulations or variations in the 'quality' of high-density lipoprotein particles and may be unrelated to the concentration of the total high-density lipoprotein fraction. This review summarizes the cardiovascular protective role of high-density lipoproteins and addresses how the concentration and antiatherogenic activity of high-density lipoproteins are related.

SUMMARY

Some of the protective functions of high-density lipoprotein are closely related to the simple concentration of high-density lipoproteins; others may not be related. Given the current high level of interest in therapies that raise the concentration of high-density lipoprotein, it is essential to conduct further research to identify precisely how high-density lipoproteins protect.

The effect of physical exercise on reverse cholesterol transport

High-density lipoproteins (HDL) are recognized for their role in coronary artery disease (CAD) risk reduction. Plasma HDL plays a pivotal role in the reverse cholesterol transport (RCT) process. Physical exercise is well recognized as a modality that affects HDL metabolism. The purpose of this discussion is to describe the effects of physical exercise on RCT.

Niacin and cholesterol: role in cardiovascular disease (review)

Niacin has been widely used as a pharmacologic agent to regulate abnormalities in plasma lipid and lipoprotein metabolism and in the treatment of atherosclerotic cardiovascular disease. Although the use of niacin in the treatment of dyslipidemia has been reported as early as 1955, only recent studies have yielded an understanding about the cellular and molecular mechanism of action of niacin on lipid and lipoprotein metabolism. In brief, the beneficial effect of niacin to reduce triglycerides and apolipoprotein-B containing lipoproteins (e.g., VLDL and LDL) are mainly through: a) decreasing fatty acid mobilization from adipose tissue triglyceride stores, and b) inhibiting hepatocyte diacylglycerol acyltransferase and triglyceride synthesis leading to increased intracellular apo B degradation and subsequent decreased secretion of VLDL and LDL particles. The mechanism of action of niacin to raise HDL is by decreasing the fractional catabolic rate of HDL-apo AI without affecting the synthetic rates. Additionally, niacin selectively increases the plasma levels of Lp-AI (HDL subfraction without apo AII), a cardioprotective subfraction of HDL in patients with low HDL. Using human hepatocytes (Hep G2 cells) as an in vitro model system, recent studies indicate that niacin selectively inhibits the uptake/removal of HDL-apo AI (but not HDL-cholesterol ester) by hepatocytes, thereby increasing the capacity of retained HDL-apo AI to augment cholesterol efflux through reverse cholesterol transport pathway. The studies discussed in this review provide evidence to extend the role of niacin as a lipid-lowering drug beyond its role as a vitamin.

High density lipoproteins (HDLs) and atherosclerosis; the unanswered questions

The concentration of high density lipoprotein-cholesterol (HDL-C) has been found consistently to be a powerful negative predictor of premature coronary heart disease (CHD) in human prospective population studies. There is also circumstantial evidence from human intervention studies and direct evidence from animal intervention studies that HDLs protect against the development of atherosclerosis. HDLs have several documented functions, although the precise mechanism by which they prevent atherosclerosis remains uncertain. Nor is it known whether the cardioprotective properties of HDL are specific to one or more of the many HDL subpopulations that comprise the HDL fraction in human plasma. Several lifestyle and pharmacological interventions have the capacity to raise the level of HDL-C, although it is not known whether all are equally protective. Indeed, despite the large body of information identifying HDLs as potential therapeutic targets for the prevention of atherosclerosis, there remain many unanswered questions that must be addressed as a matter of urgency before embarking wholesale on HDL-C-raising therapies as strategies to prevent CHD. This review summarises what is known and highlights what we still need to know.

Genetic susceptibility to ageing-associated diseases

The constant and rapid increase of life expectancy in western countries is associated with a major ageing of our populations. In these conditions, we can expect an epidemic progression of most chronic diseases, especially cardiovascular, neurodegenerative and metabolic disorders, the main causes of death in the world. The global burden of these diseases will have a dramatic impact on the health and on the socio-economical context of our societies. From a global point of view, the occurrence and progression of these multifactorial diseases rely upon the nature and intensity of the environmental determinants we are exposed to all life long, but also to our individual genetic susceptibility. Through the determination of this higher susceptibility to an environmental risk factor and the understanding of its mechanisms of action, prevention and management efforts will be better focused. In such multifactorial affections, the development and the transmission of the disease do not follow the simple laws of monogenic Mendelian models. The complexity of this transmission is associated with the influence, at various degrees, of several genes and of a close interaction between this particular genetic susceptibility and environmental risk factors. With the recent development of automated and high throughput molecular biology techniques and their use in epidemiological studies, gene expression regulation and post genomic studies, the determination of sub-groups facing a higher individual genetic susceptibility has begun. This determination will offer new clues for a better-targeted disease management.

Formation of spherical, reconstituted high density lipoproteins containing both apolipoproteins A-I and A-II is mediated by lecithin:cholesterol acyltransferase

Previous studies have provided detailed information on the formation of spherical high density lipoproteins (HDL) containing apolipoprotein (apo) A-I but no apoA-II (A-I HDL) by an lecithin:cholesterol acyltransferase (LCAT)-mediated process. In this study we have investigated the formation of spherical HDL containing both apoA-I and apoA-II (A-I/A-II HDL). Incubations were carried out containing discoidal A-I reconstituted HDL (rHDL), discoidal A-II rHDL, and low density lipoproteins in the absence or presence of LCAT. After the incubation, the rHDL were reisolated and subjected to immunoaffinity chromatography to determine whether A-I/A-II rHDL were formed. In the absence of LCAT, the majority of the rHDL remained as either A-I rHDL or A-II rHDL, with only a small amount of A-I/A-II rHDL present. By contrast, when LCAT was present, a substantial proportion of the reisolated rHDL were A-I/A-II rHDL. The identity of the particles was confirmed using apoA-I rocket electrophoresis. The formation of the A-I/A-II rHDL was influenced by the relative concentrations of the precursor discoidal A-I and A-II rHDL. The A-I/A-II rHDL included several populations of HDL-sized particles; the predominant population having a Stokes' diameter of 9.9 nm. The particles were spherical in shape and had an electrophoretic mobility slightly slower than that of the alpha-migrating HDL in human plasma. The apoA-I:apoA-II molar ratio of the A-I/A-II rHDL was 0.7:1. Their major lipid constituents were phospholipids, unesterified cholesterol, and cholesteryl esters. The results presented are consistent with LCAT promoting fusion of the A-I rHDL and A-II rHDL to form spherical A-I/A-II rHDL. We suggest that this process may be an important source of A-I/A-II HDL in human plasma.

High-density lipoprotein subclasses and apolipoprotein A-I

Epidemiological and clinical studies showing an association between decreased concentrations of high-density lipoprotein (HDL) cholesterol and increased risk of premature coronary artery disease have generated interest in the mechanism through which HDL prevents atherosclerosis. Recognition of the importance of apolipoproteins (apo(s)) has led to the separation of HDL into subpopulations according to their apolipoprotein composition. It is now recognised that HDL comprises at least two types of apo A-I-containing lipoproteins: LpA-I:A-II containing both apo A-I and apo A-II and LpA-I containing apo A-I but not apo A-II. A majority of studies support the fact that LpA-I is more effective than LpA-I:A-II in promoting cellular cholesterol efflux, the first step in reverse cholesterol transport. Studies in transgenic animals have revealed that the gene transfer of human apo A-I in mice and rabbits increases plasma apo A-I and HDL cholesterol levels and particularly apo A-I-rich HDL particle concentrations, leading to inhibition of the development of dietary or genetically induced atherosclerosis. On the other hand, gene transfer of apo A-II in mice gives conflicting results. The conclusions of some experiments indicate either an atherogenic, or a poorly anti-atherogenic, or even a strongly anti-atherogenic role for apo A-II and for apo A-II-rich HDL lipoproteins. Although these experimental results have been obtained in animals, they confirm previous studies obtained in human clinical studies, indicating that apo A-I-rich HDL (tested as LpA-I in clinical studies) are generally strong plasma markers of atherosclerosis protection while the clinical significance of apo A-I + apo A-II HDL (tested as LpA-I:A-II in clinical studies) is more controversial. The introduction of immunological methods to measure LpA-I and LpA-I:A-II levels in blood make large-scale studies feasible to confirm the clinical significance of these HDL particles.

Effect of apo E phenotype on plasma postprandial triglyceride levels in young male adults with and without a familial history of myocardial infarction: the EARS II study. European Atherosclerosis Research Study

The goal of the present study was to assess whether the effect of the apolipoprotein E polymorphism on postprandial lipemia explained part of the risk attributable to familial history of coronary heart disease. Cases (n = 407) were students, aged between 18 and 28 years, whose fathers had a proven myocardial infarction before the age of 55 years. Age-matched controls (n = 415) were recruited from the corresponding student registers. Blood was obtained after an overnight fast and at 2, 3, 4 and 6 h after ingestion of a fatty meal for triglyceride measurements. Apolipoprotein E phenotype was associated with postprandial triglyceride variability in both cases and controls. However, the apolipoprotein E-dependent triglyceride response was not significantly heterogeneous between cases and controls. In the pooled data, postprandial triglyceride levels were higher in carriers of the E2 and, to a lesser extent, of the E4 isoform, than in E3/3 homozygotes, independently of fasting triglyceride levels. At 6 h, triglyceride levels were increased by 21.2% (P < 0.01) in E2 carriers and 11.5% (P = 0.053) in E4 carriers by comparison to E3/3 subjects. These effects were not significantly different between regions. In conclusion, the effects of the apolipoprotein E polymorphism on postprandial triglyceridemia are similar across regions of Europe, and homogeneous in healthy young subjects with and without a family history of early myocardial infarction. This suggests that the influence of apolipoprotein E on myocardial infarction risk may be acting through mechanisms other than through effects on postprandial triglyceridemia.

Carotid atherosclerosis in patients operated for lower extremity ischemia before the age of 50: a case control study

The purpose of this study was to investigate the presence of, and to identify factors associated with carotid atherosclerosis in patients, previously operated on for lower extremity ischemia before the age of 50. Forty-eight patients were compared to sex- and age-matched controls. All subjects were examined with duplex ultrasonography of the neck arteries and analysis of serum lipoproteins. History including smoking habits, family history of cardiovascular disease, and medication was also obtained. The patients were examined clinically and their preoperative angiograms were reevaluated. Thirty-one patients (64%) and 13 controls (23%) had a carotid lesion (p < 0.0001). Patients with suprainguinal or multilevel disease had a higher proportion of carotid lesions than those with only infrainguinal disease in whom the proportion was similar to the controls. A multiple regression analysis among the patients revealed that age, level of lower extremity arterial disease, presence of family history, and the ratio apolipoproteinB/apolipoproteinA discriminated significantly between those with and without carotid disease. It is concluded that a high proportion of patients operated on for lower extremity suprainguinal arterial occlusive disease at an early age have carotid lesions at follow-up, while patients operated on due to isolated infrainguinal disease have a prevalence similar to controls.

Apolipoproteins and lipoprotein particles in Moroccan patients with previous myocardial infarction

We investigated for the first time in the Moroccan population the relationship between lipoprotein particles and the progression of coronary atherosclerosis. Plasma lipid variables, including total cholesterol, triglycerides, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, apolipoproteins AI and B, Lp AI, Lp AI: AII, and Lp(a) were measured in 40 Moroccan adults who suffered a verified myocardial infarction before the age of 50 years. The results were compared with a healthy control group. Plasma total cholesterol, triglyceride, and Lp AI: AII levels of patients did not differ significantly from control subjects. Patients had lower plasma high-density lipoprotein-cholesterol (P < 0.05), apo AI (P < 0.05), and Lp AI (P < 0.001) than control subjects, suggesting that the cholesterol reverse transport system is altered in patients with previous myocardial infarction. However, patients had higher plasma low-density lipoprotein-cholesterol (P < 0.001), apo B (P < 0.001), and Lp(a) (P < 0.001). In all patients the best predictor of cardiovascular risk was the independent risk factor Lp(a) plasma level, and the Lp AI plasma level. In this study, the increased coronary atherosclerosis risk with elevated plasma levels of apo B and Lp(a), and with reduced Lp AI, was substantially modified by smoking habits, but not by family history of myocardial infarction.

Relation of total homocysteine and lipid levels in children to premature cardiovascular death in male relatives

We assessed the relative importance of lipid, apo B, lipoprotein(a) [Lp(a)], and total homocysteine (tHcy) levels in children in relation to premature cardiovascular disease in family members. Parents of 381 girls and 375 boys age 8-12 y completed family history questionnaires. Nonfasting serum lipid and lipoproteins and plasma tHcy and cysteine levels were measured in the children. Serum folate and vitamin B12 levels were determined in a random subsample of 23% of the children, who participated in a food frequency interview. Children whose parents reported hypercholesterolemia had higher total and non-HDL cholesterol and apo B levels than the rest, but these levels were not associated with cardiovascular disease. tHcy levels were similar in girls and boys. tHcy was higher in children whose father, grandfather, or uncle died at age < or = 55 y of myocardial infarction or sudden cardiac arrest (n = 42) than in control children [5.92 mumol/L (95% confidence interval [CI] of 5.47-6.36) versus 5.25 mumol/L (95% CI, 5.16-5.34)], also after adjustment for socioeconomic group. Intake and serum levels of vitamin B12 and folate were within recommended or reference ranges. In a stepwise multiple regression analysis, serum folate (negative correlation), plasma creatinine, and sugar intake as percent of dietary energy (positive correlations) were significantly associated with tHcy (multiple r = 0.44, adjusted r2 = 18%; 95% CI, 5-30%). Our data show that a modest elevation in tHcy in children was related to premature cardiovascular death in their male relatives and may partly account for the contribution of family history to risk of cardiovascular disease. tHcy may be modifiable through the diet, even in children with apparently adequate vitamin nutriture.

High density lipoproteins and coronary heart disease

An inverse relationship between the concentration of high density lipoprotein (HDL) cholesterol and the development of coronary heart disease (CHD) is well established. It is unclear from the human studies whether this relationship reflects an ability of HDLs to protect against coronary disease or whether a low HDL in coronary patients is simply an epiphenomenon. Recent studies of transgenic mice, however, indicate that HDLs are directly antiatherogenic. The mechanism of the protection is unknown but may relate both to an involvement of HDLs in plasma cholesterol transport and to a range of non-lipid transport functions of HDLs. It is also unclear from human studies whether specific HDL subpopulations have differing abilities to protect against CHD, although such specificity is suggested from studies of transgenic mice. There is circumstantial evidence that elevating the concentration of HDL cholesterol in human subjects translates into a reduced coronary risk, although it should be stressed that there are still no reports of studies designed specifically to address this issue.

Apo B-containing lipoprotein particles in poorly controlled insulin-dependent diabetes

The goal of this study was to compare the structural and biological characteristics of apolipoprotein (apo) B-100-containing particle subfractions isolated from poorly controlled diabetic patients with insulin-dependent diabetes (IDDM), and healthy controls matched for sex, age and body mass index (BMI). Different apo B-containing particles were isolated by sequential immunochromatography and were free of apo A-I, apo A-II, apo A-IV and apo(a). Particles lipoprotein (Lp) B/C-III contained apo B and apo C-III. They were free of apo E. Particles Lp B/E contained apo B and apo E. They were free of apo C-III. Particles Lp B were devoided of apo C-III and apo E. All these particles could contain other known apolipoproteins not cited here, as for example apo C-II and/or apo C-I. The plasma levels of cholesterol, triglycerides, phospholipids, apo A-I, B-100, C-III, E, total Lp B/C-III, total Lp B/E were not different between patients and controls. The physico-chemical properties of Lp B/C-III and Lp B/E were similar in both groups. Only Lp B from patients exhibited some changes, an increase in the size and a decrease in the cholesterol and cholesteryl ester levels. The conformational properties of the lipoproteins were studied through their immunoreactivity against four different anti-apo B-100 monoclonal antibodies (MAb) for which sequential epitopes have been located on the protein, and one MAb for which the epitope is conformationally expressed. Again, minor changes were observed between patients and controls, and only a slight decrease in the immunoreactivity of the epitope encompassing amino-acid residues 405 to 539 of Lp B and of the conformationally expressed epitope of Lp B/C-III were found in patients. Nevertheless, whatever these conformational and/or physico-chemical modifications may be, they were not sufficient to induce functional alterations in the binding of the particles from the patients to the LDL-receptor of HeLa cells. This study shows that IDDM is not associated with any significant abnormalities in the apo-containing lipoprotein particles. The excessive occurrence of coronary heart disease (CHD) and other atherosclerotic vascular disease in patients with IDDM must have other causes.

HDL heterogeneity and atherosclerosis

High-density lipoprotein (HDL), the most abundant human plasma lipoprotein, plays a major role in reverse cholesterol transport, which recycles cholesterol from peripheral cells to the liver. HDL constitutes a heterogeneous group of particles differing in density, size, electrophoretic mobility, and apolipoprotein content. HDL can therefore be fractionated into discrete subclasses by different techniques according to their physicochemical properties. The clinical significance of HDL differs with the subclasses, especially with respect to coronary heart disease, alcohol intake, longevity, dyslipoproteinemia, dietary fat content, and hypolipidemic drugs. Because of their structural and functional diversity, HDL subclasses generate considerable hope that they may help to improve the identification of individuals at an increased risk of developing coronary heart disease.

Comparison of the effect of fluvastatin, an hydroxymethyl glutaryl coenzyme A reductase inhibitor, and cholestyramine, a bile acid sequestrant, on lipoprotein particles defined by apolipoprotein composition

In a double-blind, parallel-group, randomized study, the effects of fluvastatin (FLUV) 20 and 40 mg/d on lipoprotein particle levels were compared with those of cholestyramine (CME) 16 g/d. Lipoparticles were defined by apolipoprotein composition as either those containing both apolipoprotein (apo) B and apo E or CIII (lipoprotein [Lp] E-B or Lp CIII-B) or those containing apo AI alone (Lp AI) or in association with apo AII (Lp AI-AII). After an 8-week dietary stabilization period, 100 hypercholesterolemic patients were treated with FLUV 20 mg/d for 6 weeks and 40 mg/d for an additional 6 weeks and were compared with 48 hypercholesterolemic subjects treated with CME 16 g/d. Treatment with FLUV (40 mg/d) or CME (16 g/d) for 12 weeks was associated with a significant reduction in plasma cholesterol and low-density lipoprotein (LDL) cholesterol and a significant increase in high-density lipoprotein (HDL) cholesterol. However, plasma triglyceride levels decreased following FLUV treatment, whereas they increased with CME. These changes were associated with a significant reduction in the levels of apo B (FLUV, -24%, P < .001; CME, -26%, P < .001), apo E (FLUV, -36%, P < .001; CME, -32%, P < .001), and apo CIII (FLUV, -21%, P < .001; CME, -6%, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Cholesterol efflux from human monocyte-derived macrophages in the presence of LpA-I:A-II

Previous epidemiological studies have suggested that the LpA-I subfraction of HDL is more protective than the LpA-I:A-II subfraction against the development of cardiovascular disease. A possible basis for a specific anti-atherogenic function of LpA-I emerged from studies of cholesterol efflux from cultured mouse adipocytes. LpA-I efficiently removed excess cholesterol from the mouse adipocytes, while LpA-I:A-II was ineffective. On the other hand, LpA-I:A-II was able to stimulate cholesterol efflux from a number of other cell types including rodent macrophages. Because of previously reported differences in HDL stimulation of cholesterol clearance from macrophages of different origins, we determined whether LpA-I:A-II could induce cholesterol efflux from cultured human monocyte-macrophages. Our findings showed that LpA-I:A-II and HDL3 effectively stimulated cholesterol efflux from human monocyte-macrophages enriched with cholesterol by incubation with AcLDL. LpA-I:A-II also decreased by one-half the amount of cholesterol accumulated when macrophages were incubated with AcLDL and LpA-I:A-II together. Thus, it would appear that the differential anti-atherogenic effects of LpA-I:A-II and LpA-I do not derive from their effects on macrophage cholesterol efflux. Possibly these HDL subfractions differentially affect other biologic processes that modulate the development of cardiovascular disease.

Apolipoprotein A-I-containing particles and reverse cholesterol transport: evidence for connection between cholesterol efflux and atherosclerosis risk

It is now clearly established that apo A-I-containing lipoproteins exist as two major families, those containing apo A-I and apo A-II (LpA-I:A-II) and those containing apo A-I but free of apo A-II (LpA-I). Metabolic studies utilizing radiolabeled lipoprotein particles suggested that there is a kinetic difference between LpA-I and LpA-I:A-II family and support the concept that there may be important functional differences between the lipoprotein particles present within HDL. Of considerable significance was the finding that proteins stimulating reverse cholesterol transport (lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP)) are mainly present in LpA-I and not in LpA-I:A-II family. Cholesterol efflux mediated by A-I-containing particles has been studied in different cells. Long term exposure to LpA-I family promoted cholesterol efflux whereas less efflux was observed in the presence of LpA-I:A-II family. The fact that LpA-I:A-II family can inhibit the LpA-I promoted cholesterol efflux strongly supports the role of apo A-II as an antagonist in the production of cholesterol efflux. These results which emphasize that LpA-I and LpA-I:A-II families behave as distinct entities have been confirmed in other studies showing that they have different clinical significance. The results in mice transgenic for apo A-I indicate that overexpression of apo A-I induces more cholesterol efflux and protects C57BL/6 mice from atherosclerosis. Increased expression of apo A-II in mice appears to decrease cholesterol efflux and to promote rather than retard aortic fatty streak development.(ABSTRACT TRUNCATED AT 250 WORDS)