Value of High-Density Lipoprotein (HDL) Subpopulations in Predicting Recurrent Cardiovascular Events in the Veterans Affairs HDL Intervention Trial

Associations of genetic variants in ATP-binding cassette A1 and cholesteryl ester transfer protein and differences in lipoprotein subclasses in the multi-ethnic study of atherosclerosis

BACKGROUND

ATP-binding cassette A1 (ABCA1) and cholesteryl ester transfer protein (CETP) play important roles in the reverse cholesterol transport pathway. The associations of ABCA1 and CETP polymorphisms with lipoprotein subclasses have not been extensively studied.

METHODS

We genotyped 2 ABCA1 and 5 CETP polymorphisms in 999 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) and studied their associations with HDL and LDL subclass particle concentrations, measured by nuclear magnetic resonance spectroscopy.

RESULTS

ABCA1 and CETP polymorphisms were associated with different and distinct changes in lipoprotein subclass concentrations. The ABCA1 1051G/A AA genotype, previously found to be associated with cardioprotective effects in this cohort, was associated with a 5.5% higher concentration of small HDL particles (P = 0.024). The CETP TaqIB B2B2, -2505C/A AA, and -629C/A AA genotypes, previously demonstrated to lack cardioprotective effects, were associated with 15.2%, 15.4%, and 11.7% higher HDL cholesterol concentrations, respectively, and 36.5%, 40.7%, and 25.4% higher large HDL particle concentrations (P < 0.0001). The minor alleles of the A373P and R451Q polymorphisms were associated with lower large HDL particle concentrations.

CONCLUSIONS

Our study of the influence of ABCA1 and CETP genetic variants on lipoprotein subclasses demonstrates the importance of interpreting lipoprotein subclasses within the context of the biochemical processes involved in the alterations. In the case of HDL, the study of subclass particle numbers and sizes may not be sufficiently informative. Assays for HDL function may be needed to supplement quantification of HDL cholesterol and HDL particle numbers and sizes.

Atorvastatin in Factorial with Omega-3 EE90 Risk Reduction in Diabetes (AFORRD): a randomised controlled trial

AIMS/HYPOTHESIS

The aim of the study was to examine the impact of statin or omega-3-acid ethyl esters 90 (omega-3 EE90; omega-3-acid ethyl esters 90 refers to a mixture of ethyl esters of n-3 fatty acids) on estimated cardiovascular disease (CVD) risk in community-based people with type 2 diabetes but without known CVD and not taking lipid-lowering therapy.

METHODS

A central computer randomised 800 patients in 59 UK general practices to atorvastatin (n = 401, 20 mg/day) or placebo (n = 399) and omega-3 EE90 (n = 397, 2 g/day) or placebo (n = 403) in a concealed factorial manner. Participants with LDL-cholesterol <2.6 mmol/l, triacylglycerol <1.5 mmol/l and estimated 10-year CVD risk <20% were compared at 4 months.

RESULTS

Mean (SD) age was 63.5 (11.7) years, HbA(1c) 6.9 (1.1) % and known diabetes duration (median [interquartile range]) was 4 (2-8) years. Fifty-seven per cent were men, 90% white and 74% had an estimated 10-year CVD risk >or=20%. Of 732 patients with 4-month data, more allocated atorvastatin (n = 371) compared with placebo (n = 361) achieved LDL-cholesterol <2.6 mmol/l (91% vs 24%, p < 0.001) and had estimated 10-year CVD risks <20% (38% vs 26%, p < 0.001). No differences were seen between those allocated omega-3 EE90 (n = 371) compared with placebo (n = 361) for participants achieving triacylglycerol <1.5 mmol/l (65% vs 60%, p = 0.18) or estimated 10-year CVD risks <20% (34% vs 30%, p = 0.18). There were no side effects of note.

CONCLUSIONS/INTERPRETATION

Many community-based diabetic patients without known CVD remain at high CVD risk despite statin treatment and require additional risk-reduction strategies. The impact of omega-3 EE90 on CVD risk will remain uncertain until clinical endpoint trial results are available.

TRIAL REGISTRATION

ISRCT no. 76737502.

Apolipoproteins and long-term prognosis in coronary heart disease patients

BACKGROUND

Apolipoproteins have been recently suggested as an alternative to lipoproteins in prediction of cardiovascular risk. Data regarding their added value in predicting the prognosis of coronary heart disease (CHD) patients are scarce. Our aim was to examine the association between lipoprotein cholesterol and related apolipoproteins with long-term mortality among CHD patients.

METHODS

Patients (4,472 men; 624 women, 40-74 years old) with total cholesterol <270 mg/dL (<7.0 mmol/L), high-density lipoprotein cholesterol (HDL-C) <45 mg/dL (<1.16 mmol/L), and triglycerides <300 mg/dL (< or =3.39 mmol/L); excluded from the Bezafibrate Infarction Prevention study; or included in the placebo arm were followed up for a median of 12.3 years.

RESULTS

Among both men and women, the association of apolipoproteins A-I and B with mortality was comparable to their corresponding lipids (HDL-C, non-HDL-C respectively). Adjusting for age, disease history, comorbidities, smoking and baseline glucose, the risk associated with the upper versus the lower tertile (lower vs upper for HDL-C and apolipoprotein A-I) among men were 1.04 (95% CI 0.91-1.19) for non-HDL-C; 1.11 (0.97-1.27) for apolipoprotein B; 1.24 (1.09-1.41) for HDL-C; and 1.30 (1.14-1.49) for apolipoprotein A-I. Atherogenic to nonatherogenic particle ratios (lipids or apolipoproteins) were in line with the results of their individual components pointing to a less atherogenic profile among women. Models including either apolipoprotein or cholesterol subfractions had similar predictive power.

CONCLUSION

Lipoprotein cholesterol and associated apolipoprotein have comparable ability to predict long-term mortality. The measurement of apolipoproteins constitutes an acceptable alternative to the use of blood lipids in assessing prognosis for CHD patients.

Lipid-lowering therapy today: treating the high-risk cardiovascular patient

Diseases of the heart and vascular systems are the leading cause of death in the United States and worldwide. High-risk patients have been the focus of lipid-lowering trials and treatment guidelines, which recognize that more intensive reduction of low-density lipoprotein cholesterol is appropriate for a redefined, broader high-risk population. Lifestyle modifications and lipid-lowering drug therapy form the foundation of primary- and secondary-prevention programs for patients at moderate to very high risk. Evidence shows that despite the availability of effective agents, such as HMG CoA reductase inhibitors (statins), many patients still do not achieve low-density lipoprotein cholesterol goals. Nurse-centered case management programs that support early and continued adherence with lifestyle and medical therapies have been consistently successful at improving the rates of achieving lipid goals in high-risk patients.

Effects of intensive atorvastatin and rosuvastatin treatment on apolipoprotein B-48 and remnant lipoprotein cholesterol levels

Atorvastatin and rosuvastatin at maximal doses are both highly effective in lowering low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) levels. Rosuvastatin has been shown to be more effective than atorvastatin in lowering LDL-C, small dense LDL-C and in raising high-density lipoprotein (HDL) and its subclasses. Intestinal lipoproteins containing apolipoprotein (apo) B-48 are also thought to be atherogenic particles. Our purpose in this study was to compare the effects of daily oral doses of atorvastatin 80 mg/day and rosuvastatin 40 mg/day over a 6-week period on serum apo B-48 (a marker of intestinal lipoproteins) and remnant lipoprotein cholesterol (RemL-C) levels (a marker of partially metabolized lipoproteins of both intestinal and liver origin), using novel direct assays in 270 hyperlipidemic men and women. Both atorvastatin and rosuvastatin caused significant (p<0.0001) and similar median decreases in TG (-33.0%, -27.6%), RemL-C (-58.7%, -61.5%), and apoB-48 (-37.5%, -32.1%) as compared to baseline. Our findings utilizing a specific immunoassay and a fairly large number of subjects extend prior studies indicating that statins significantly lower apolipoprotein B containing lipoproteins of both intestinal and liver origin.

High-density lipoproteins are abnormal in young women with uncomplicated systemic lupus erythematosus

Little is known about qualitative abnormalities of high-density lipoproteins (HDL) in systemic lupus erythematosus (SLE). We studied distribution and composition of HDL subclasses in 30 premenopausal women with uncomplicated SLE, and 18 controls matched for age and sex. Plasma and HDL lipids were determined by colorimetric enzymatic assays, HDL size distribution by native gradient polyacrylamide gel electrophoresis (PAGE) and apolipoproteins in HDL by sodium dodecyl sulphate denaturing PAGE. Compared with controls, SLE patients had significantly lower proportions of HDL2b (−14.7%) and higher proportions of HDL3b (+8.8%) and HDL3c (+23.3%). Cholesteryl ester (−18%) and apolipoprotein AI (−9%) were lower, whereas triglycerides (+32%) and apolipoprotein E (+27%) were higher in SLE HDL ( P < 0.05; for all). In the whole population, stepwise regression analysis showed that only insulin concentrations (R2 = 0.327) and plasma total apo AI (R2 = 0.114) accounted independently to the variance in HDL size. This study shows that HDL distribution and composition are abnormal in non-complicated SLE patients. These HDL abnormalities have been reported to be associated to impaired atheroprotective properties of HDL and prevalence of coronary heart disease. Therefore, they may contribute to the premature atherosclerosis observed in young women with SLE.

Alterations in the high density lipoprotein phenotype and HDL-associated enzymes in subjects with metabolic syndrome

Patients with metabolic syndrome (MetS) usually have low high density lipoprotein cholesterol (HDL-C) levels. We determined the HDL distribution profile as well as the HDL-related lipoprotein associated phospholipase A(2) (HDL-LpPLA(2)) and paraoxonase-1 (PON1) activities in subjects with MetS (n = 189) but otherwise healthy. Age and sex-matched individuals (n = 166) without MetS served as controls. The lower HDL-C concentration in MetS patients was due to a reduction in both large and small HDL subclasses (P < 0.001 and P < 0.05, respectively). As the number of MetS components increased, the HDL phenotype comprised of a greater percentage of small HDL-3 and less large HDL-2 subclasses, resulting in a decreased HDL-2/HDL-3 ratio (P < 0.001 for all trends). Multivariate analysis revealed that HDL-2 levels and the HDL-2/HDL-3 ratio significantly and independently correlated with HDL-C (positively) and TG (negatively) levels. HDL-3 concentration significantly and independently positively correlated with HDL-C and TG levels. HDL-LpPLA(2) activity was decreased in MetS patients (P < 0.01), a phenomenon that may contribute to the defective antiatherogenic activity of HDL in MetS. PON1 activity did not differ between groups. We conclude that MetS, in addition to the decrease in HDL-C concentration, is associated with alterations in the HDL phenotype, which is comprised of a greater percentage of small HDL subclasses. Furthermore, HDL-LpPLA(2) activity is decreased in MetS patients.

Metformin increases HDL3-cholesterol and decreases subcutaneous truncal fat in nondiabetic patients with HIV-associated lipodystrophy

The purpose of this study was to assess metformin effects on high-density lipoprotein (HDL) composition of patients with HIV-associated lipodystrophy (LDHIV). Twenty-four adult outpatients were enrolled to receive metformin (1700 mg/d) during 6 months, but 2 were lost to follow-up and 6 stopped the drug due to adverse events (gastrointestinal in 5, and excessive weight loss in 1). From the 16 subjects who completed the study, 69% were female. At baseline, 3 and 6 months, we assessed: weight, waist and hip circumferences, blood pressure, fasting glucose and insulin, homeostasis model assessment of insulin resistance (HOMA2-IR), lipids, and HDL subfractions by microultracentrifugation. At 0 and 6 months, body fat distribution was assessed by computed tomography (CT) scan (L4 and middle femur). Metformin use was associated with reduction of mean weight (-2.4Kg at 6 months; p < 0.001), body mass index, waist, waist-to-hip ratio and a marked decrease in blood pressure (p < 0.001). Subcutaneous (p = 0.01) and total abdominal fat (p = 0.002) were reduced, but no change was found in visceral or thigh fat. No difference was detected on plasma glucose, insulin, HOMA2-IR, cholesterol or triglycerides, except for an increase in HDL3-cholesterol (from 21 mg/dL to 24 mg/dL, p = 0.002) and a reduction of nascent HDL (the fraction of plasma HDL-cholesterol not associated to subfractions HDL2 or HDL3) (p = 0.008). Adverse effects were very common, but most were gastrointestinal and mild. Thus, metformin use in LDHIV increases HDL3-cholesterol (probably due to improved maturation of HDL) and decreases blood pressure, weight, waist, and subcutaneous truncal fat, making this an attractive option for preventing cardiovascular disease in this population.

HDL atheroprotection by aerobic exercise training in type 2 diabetes mellitus

PURPOSE

In this study we analyzed the role played by aerobic exercise training in the plasma lipoprotein profile, prebeta 1-HDL concentration, and in the in vitro HDL3 ability to remove cholesterol from macrophages and inhibit LDL oxidation in type 2 diabetes mellitus (DM) patients and control subjects, in the fasting and postprandial states.

METHODS

Healthy controls (HTC, N = 11; 1 M/10 F) and subjects with type 2 diabetes mellitus (DMT, N = 11; 3M/8F) were engaged in a 4-month aerobic training program, and compared with a group of sedentary subjects with type 2 diabetes mellitus (DMS, N = 10; 4 M/6 F). All groups were submitted to an oral fat load test to analyze all parameters, both at the beginning of the investigation protocol (basal) and at the end of the study period (final).

RESULTS

Exercising did not modify body weight, BMI, plasma concentrations of total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides (TG), glucose, insulin, or HOMA-IR, but it reduced the waist circumference. The HDL3 composition did not change, and its ability to remove cell cholesterol was unaltered by aerobic training. In DMT but not in HTC, aerobic training improved 15% the HDL3 protective effect against LDL maximal oxidation rate in the fasting state, and reduced 24% the plasma prebeta 1-HDL concentration in the postprandial state, suggesting an enhanced prebeta 1-HDL conversion into larger, more mature HDL particles. In this regard, regular aerobic exercise enriched HDL2 with TG in the fasting and postprandial states in HTC and in the fasting phase in DMT.

CONCLUSION

Our results show that aerobic exercise training in diabetes mellitus improves the HDL efficiency against LDL oxidation and favors HDL maturation. These findings were independent of changes in insulin resistance and of the rise of plasma HDL cholesterol concentration.

Altered lipoprotein metabolism in chronic inflammatory states: proinflammatory high-density lipoprotein and accelerated atherosclerosis in systemic lupus erythematosus and rheumatoid arthritis

In this review, the authors discuss the formation and structure of high-density lipoproteins (HDLs) and how those particles are altered in inflammatory or stress states to lose their capacity for reverse cholesterol transport and for antioxidant activity. In addition, abnormal HDLs can become proinflammatory (piHDLs) and actually contribute to oxidative damage. The assay by which piHDLs are identified involves studying the ability of test HDLs to prevent oxidation of low-density lipoproteins. Finally, the authors discuss the potential role of piHDLs (found in some 45% of patients with systemic lupus erythematosus and 20% of patients with rheumatoid arthritis) in the accelerated atherosclerosis associated with some chronic rheumatic diseases.

Effects of statins on high-density lipoproteins: a potential contribution to cardiovascular benefit

PURPOSE

The objective was to systematically review clinical trial data on the effects of statins on high-density lipoproteins (HDL) and to examine the possibility that this provides cardiovascular benefits in addition to those derived from reductions in low-density lipoproteins (LDL).

METHODS

The PubMed database was searched for publications describing clinical trials of atorvastatin, pravastatin, rosuvastatin, and simvastatin. On the basis of predefined criteria, 103 were selected for review.

RESULTS

Compared with placebo, statins raise HDL, measured as HDL-cholesterol (HDL-C) and apolipoprotein A-I (apo A-I); these elevations are maintained in the long-term. In hypercholesterolemia, HDL-C is raised by approximately 4% to 10%. The percentage changes are greater in patients with low baseline levels, including those with the common combination of high triglycerides (TG) and low HDL-C. These effects do not appear to be dose-related although there is evidence that, with the exception of atorvastatin, the changes in HDL-C are proportional to reductions in apo B-containing lipoproteins. The most likely explanation is a reduced rate of cholesteryl ester transfer protein (CETP)-mediated flow of cholesterol from HDL. There is some evidence that the statin effects on HDL reduce progression of atherosclerosis and risk of cardiovascular disease independently of reductions in LDL.

CONCLUSION

Statins cause modest increases in HDL-C and apo A-I probably mediated by reductions in CETP activity. It is plausible that such changes independently contribute to the cardiovascular benefits of the statin class but more studies are needed to further explore this possibility.

Clinical presentation, laboratory values, and coronary heart disease risk in marked high-density lipoprotein-deficiency states

Our purpose is to provide a framework for diagnosing the inherited causes of marked high-density lipoprotein (HDL) deficiency (HDL cholesterol levels <10 mg/dL in the absence of severe hypertriglyceridemia or liver disease) and to provide information about coronary heart disease (CHD) risk for such cases. Published articles in the literature on severe HDL deficiencies were used as sources. If apolipoprotein (Apo) A-I is not present in plasma, then three forms of ApoA-I deficiency, all with premature CHD,and normal low-density lipoprotein (LDL) cholesterol levels have been described: ApoA-I/C-III/A-IV deficiency with fat malabsorption, ApoA-I/C-III deficiency with planar xanthomas, and ApoA-I deficiency with planar and tubero-eruptive xanthomas (pictured in this review for the first time). If ApoA-I is present in plasma at a concentration <10 mg/dL, with LDL cholesterol that is about 50% of normal and mild hypertriglyceridemia, a possible diagnosis is Tangier disease due to mutations at the adenosine triphosphate binding cassette protein A1 (ABCA1) gene locus. These patients may develop premature CHD and peripheral neuropathy, and have evidence of cholesteryl ester-laden macrophages in their liver, spleen, tonsils, and Schwann cells, as well as other tissues. The third form of severe HDL deficiency is characterized by plasma ApoA-I levels <40 mg/dL, moderate hypertriglyceridemia, and decreased LDL cholesterol, and the finding that most of the cholesterol in plasma is in the free rather than the esterified form, due to a deficiency in lecithin:cholesterol acyltransferase activity. These patients have marked corneal opacification and splenomegaly, and are at increased risk of developing renal failure, but have no clear evidence of premature CHD. Marked HDL deficiency has different etiologies and is generally associated with early CHD risk.

Computational lipidology: predicting lipoprotein density profiles in human blood plasma

Monitoring cholesterol levels is strongly recommended to identify patients at risk for myocardial infarction. However, clinical markers beyond "bad" and "good" cholesterol are needed to precisely predict individual lipid disorders. Our work contributes to this aim by bringing together experiment and theory. We developed a novel computer-based model of the human plasma lipoprotein metabolism in order to simulate the blood lipid levels in high resolution. Instead of focusing on a few conventionally used predefined lipoprotein density classes (LDL, HDL), we consider the entire protein and lipid composition spectrum of individual lipoprotein complexes. Subsequently, their distribution over density (which equals the lipoprotein profile) is calculated. As our main results, we (i) successfully reproduced clinically measured lipoprotein profiles of healthy subjects; (ii) assigned lipoproteins to narrow density classes, named high-resolution density sub-fractions (hrDS), revealing heterogeneous lipoprotein distributions within the major lipoprotein classes; and (iii) present model-based predictions of changes in the lipoprotein distribution elicited by disorders in underlying molecular processes. In its present state, the model offers a platform for many future applications aimed at understanding the reasons for inter-individual variability, identifying new sub-fractions of potential clinical relevance and a patient-oriented diagnosis of the potential molecular causes for individual dyslipidemia.

Synthetic HDL as a new treatment for atherosclerosis regression: has the time come?

Plasma high-density lipoprotein cholesterol (HDL-C) has received considerable attention as a potential therapeutic target to further reduce cardiovascular events in the statin era. One therapeutic approach to enhance HDL-mediated atheroprotection involves the use of small, synthetic and orally-active compounds that substantially raise plasma HDL-C levels. However, doubts on the clinical benefit achievable with such treatments have been raised by the premature termination of a large Phase III trial with torcetrapib, the most potent and furthest developed HDL-C raising compound, because of excess mortality in patients receiving the drug. The alternative is the direct administration of synthetic HDL (sHDL), discoidal lipoprotein particles which mimic most, if not all, of the atheroprotective properties of plasma HDL. Short-term treatments with sHDL of different composition caused consistent and remarkable reductions of atheroma volume in patients with acute coronary syndromes (ACS). Although at early stages of drug development, sHDL hold vast promise for plaque stabilization/regression, and cardiovascular event reduction.

Laboratory assessment of HDL heterogeneity and function

BACKGROUND

Plasma concentrations of HDL cholesterol (HDL-C) and its major protein component apolipoprotein (apo) A-I are strongly inversely associated with cardiovascular risk, leading to the concept that therapy to increase HDL-C and apoA-I concentrations would be antiatherosclerotic and protective against cardiovascular events. The recent failure of the drug torcetrapib, a cholesteryl ester transfer protein inhibitor that substantially increased HDL-C concentrations, has brought focus on the issues of HDL heterogeneity and function as distinct from HDL-C concentrations.

CONTENT

This review addresses the current state of knowledge regarding assays of HDL heterogeneity and function and their relationship to cardiovascular disease. HDL is highly heterogeneous, with subfractions that can be identified on the basis of density, size, charge, and protein composition, and the concept that certain subfractions of HDL may be better predictors of cardiovascular risk is attractive. In addition, HDL has been shown to have a variety of functions that may contribute to its cardiovascular protective effects, including promotion of macrophage cholesterol efflux and reverse cholesterol transport and antiinflammatory and nitric oxide-promoting effects.

SUMMARY

Robust laboratory assays of HDL subfractions and functions and validation of the usefulness of these assays for predicting cardiovascular risk and assessing response to therapeutic interventions are critically important and of great interest to cardiovascular clinicians and investigators and clinical chemists.

High-density lipoprotein subclasses distribution and composition in Mexican adolescents with low HDL cholesterol and/or high triglyceride concentrations, and its association with insulin and C-reactive protein

We tested whether low high-density lipoprotein cholesterol (HDL-C) and/or high triglycerides are associated to abnormal HDL subclasses distribution and composition, and their relationships with fasting insulin and C-reactive protein (CRP). Four groups of adolescents were studied: group 1 (HDL-C< or =35 mg/dl+TG> or =150 mg/dl; n=16); group 2 (isolated HDL-C< or =35 mg/dl; n=31); group 3 (isolated TG> or =150 mg/dl; n=20); and group 4 (CT<200 mg/dl, HDL-C>35 mg/dl, LDL-C<130 mg/dl, and TG<150 mg/dl; n=39). Tanner score-adjusted proportions of large subspecies (HDL(2b), HDL(2a)) were lower, and small (HDL(3b), HDL(3c)) were higher in groups 1, 2 and 3 than in group 4. As a result, HDL particle size in the three dyslipidemic groups was smaller than in group 4 (p<0.001). HDL CE, FC, PL, and apo AI percent contents were lower, whereas HDL TG percent content was higher in groups 1, 2 and 3 compared to group 4. CRP median values were also significantly higher in the three groups with dyslipidemia than in normolipidemic subjects (group 4). Fasting Insulin concentration and HOMA-IR were significantly higher in group 1 than in the other three groups. In stepwise multivariate analysis HDL subclass distribution and composition were independently associated only with HDL-C and waist circumference. As reported in adults, adolescents with low HDL-C and/or high TG have abnormalities in HDL subclasses distribution and lipid composition, which may render their HDL dysfunctional. In addition, these subjects have high CRP and insulin levels suggesting the presence of chronic low-grade inflammation.

Cholesterol efflux pathways and other potential mechanisms involved in the athero-protective effect of high density lipoproteins

Plasma high density lipoprotein (HDL) levels bear a strong independent inverse relationship with atherosclerotic cardiovascular disease. Although HDL has anti-oxidant, anti-inflammatory, vasodilating and anti-thrombotic properties, the central anti-atherogenic activity of HDL is likely to be its ability to remove cholesterol and oxysterols from macrophage foam cells, smooth muscle cells and endothelial cells in the arterial wall. To some extent, the pleotropic athero-protective properties of HDL may be related to its ability to promote sterol and oxysterol efflux from arterial wall cells, as well as to detoxify oxidized phospholipids. In cholesterol-loaded macrophages, activation of liver X receptors (LXRs) leads to increased expression of adenosine triphosphate (ATP) binding cassetter transporter (ABCA1), ATP binding cassetter transporter gene (ABCG1) and apoE and promotes cholesterol efflux. ABCA1 stimulates cholesterol efflux to lipid-poor apolipoproteins, whilst ABCG1 promotes efflux of cholesterol and oxysterols to HDL. Despite some recent setbacks in the clinical arena, there is still intense interest in therapeutically targeting HDL and macrophage cholesterol efflux pathways, via treatments with niacin, cholesterol ester transfer protein inhibitors, LXR activators and infusions of apoA-1, phospholipids and peptides.

Is raising HDL a futile strategy for atheroprotection?

The dramatic failure of clinical trials evaluating the cholesterol ester transfer protein inhibitor torcetrapib has led to considerable doubt about the value of raising high-density lipoprotein cholesterol (HDL-C) as a treatment for cardiovascular disease. These results have underscored the intricacy of HDL metabolism, with functional quality perhaps being a more important consideration than the circulating quantity of HDL. As a result, HDL-based therapeutics that maintain or enhance HDL functionality warrant closer investigation. In this article, we review the complexity of HDL metabolism, discuss clinical-trial data for HDL-raising agents, including possible reasons for the failure of torcetrapib, and consider the potential for future HDL-based therapies.

Effects of maximal doses of atorvastatin versus rosuvastatin on small dense low-density lipoprotein cholesterol levels

Maximal doses of atorvastatin and rosuvastatin are highly effective in lowering low-density lipoprotein (LDL) cholesterol and triglyceride levels; however, rosuvastatin has been shown to be significantly more effective than atorvastatin in lowering LDL cholesterol and in increasing high-density lipoprotein (HDL) and its subclasses. Our purpose in this post hoc subanalysis of an open-label study was to compare the effects of daily oral doses of rosuvastatin 40 mg with atorvastatin 80 mg over a 6-week period on direct LDL cholesterol and small dense LDL (sdLDL) cholesterol in 271 hyperlipidemic men and women versus baseline values. Rosuvastatin was significantly (p<0.01) more effective than atorvastatin in decreasing sdLDL cholesterol (-53% vs -46%), direct LDL cholesterol (-52% vs -50%), total cholesterol/HDL cholesterol ratio (-46% vs -39%), and non-HDL cholesterol (-51% vs -48%), The magnitude of these differences was modest, and the 2 statins caused similar decreases in triglyceride levels (-24% and -26%). In conclusion, our data indicate that the 2 statins, given at their maximal doses, significantly and beneficially alter the entire spectrum of lipoprotein particles, but that rosuvastatin is significantly more effective than atorvastatin in lowering direct LDL cholesterol and sdLDL cholesterol.

Plasma levels of HDL subpopulations and remnant lipoproteins predict the extent of angiographically-defined coronary artery disease in postmenopausal women

OBJECTIVE

The association of coronary heart disease (CHD) with subpopulations of triglyceride (TG)-rich lipoproteins and high-density lipoproteins (HDL) is established in men, but has not been well characterized in women.

METHODS AND RESULTS

Plasma HDL subpopulation concentrations, quantified by 2-dimensional gel electrophoresis, and plasma remnant-like particle cholesterol (RLP-C) concentrations were measured in 256 postmenopausal women with established CHD and in 126 CHD-free postmenopausal women. Coronary artery disease was assessed in women with CHD by quantitative coronary angiography. Plasma RLP-C and prebeta1 HDL concentrations were higher and alpha1 and alpha2 HDL concentrations were lower in CHD than in CHD-free women. After adjustment for conventional CHD-risk factors, plasma levels of RLP-C were positively associated with the degree of coronary artery disease. In similar analyses, plasma prebeta1 HDL particle concentrations were positively associated and alpha2 HDL particle concentrations were inversely associated with the extent of coronary atherosclerosis. Plasma TG, low density lipoprotein cholesterol, and HDL cholesterol levels were not associated with the degree of coronary atherosclerosis.

CONCLUSIONS

The degree of coronary atherosclerosis in postmenopausal women is linked to a dysregulation of the TG/HDL metabolism. Subpopulations of TG-rich and HDL lipoproteins are better predictors of disease than TG and HDL cholesterol concentrations.

Relation of gemfibrozil treatment and high-density lipoprotein subpopulation profile with cardiovascular events in the Veterans Affairs High-Density Lipoprotein Intervention Trial

The significant cardiovascular disease (CVD) event reduction in the Veterans Affairs High-Density Lipoprotein Intervention Trial (VA-HIT) could not be fully explained by the 6% increase in high-density lipoprotein (HDL) cholesterol with the fibrate gemfibrozil. We examined whether measurement of HDL subpopulations provided additional information relative to CVD risk reduction. The HDL subpopulations were characterized by 2-dimensional gel electrophoresis in subjects who were treated with gemfibrozil (n = 754) or placebo (n = 741). In this study, samples obtained at the 3-month visit were used; and data were analyzed prospectively using CVD events (coronary heart disease death, myocardial infarction, or stroke) during the 5.1 years of follow-up. Analyses in the gemfibrozil arm showed that subjects with recurrent CVD events had significantly higher prebeta-1 and had significantly lower alpha-1 and alpha-2 HDL levels than those without such events. Prebeta-1 level was a significant positive predictor; alpha-1 and alpha-2 levels were significant negative risk factors for future CVD events. alpha-2 level was superior to HDL cholesterol level in CVD-risk assessment after adjustment for established risk factors. Gemfibrozil treatment was associated with 3% to 6% decreases in the small, lipid-poor prebeta-1 HDL and in the large, lipid-rich alpha-1 and alpha-2 HDL and with increases in the small alpha-3 (3%) and prealpha-3 (16%) HDLs. Although the use of gemfibrozil has been associated with reduction in CVD events in VA-HIT, HDL subpopulation analysis indicates that gemfibrozil-mediated improvement in CVD risk might not be the result of its effects on HDL. It is quite possible that much of the cardiovascular benefits of gemfibrozil are due to a much wider spectrum of effects on metabolic processes that is not reflected by changes in blood lipids and HDL subpopulations.

Lipoprotein predictors of cardiovascular events in statin-treated patients with coronary heart disease. Insights from the Incremental Decrease In End-points Through Aggressive Lipid-lowering Trial (IDEAL)

BACKGROUND

Few studies have looked into the ability of measurements of apolipoprotein B (apoB) and apolipoprotein A-1 (apoA-1) or apoB/apoA-1 to predict new coronary heart disease (CHD) events in patients with CHD on statin treatment.

AIMS

In the IDEAL trial, to compare lipoprotein components to predict CHD events and to what degree differences in those parameters could explain the observed outcome.

METHODS

We compared the ability of treatment with atorvastatin 80 mg/day to that of simvastatin 20-40 mg/day to prevent CHD events in patients with CHD and used Cox regression models to study the relationships between on-treatment levels of lipoprotein components to subsequent major coronary events (MCE).

FINDINGS

Variables related to low-density lipoprotein cholesterol (LDL-C) carried more predictive information than those related to high-density lipoprotein cholesterol (HDL-C), but LDL-C was less predictive than both non-HDL-C and apoB. The ratio of apoB to apoA-1 was most strongly related to MCE. However, for estimating differences in relative risk reduction between the treatment groups, apoB and non-HDL-C were the strongest predictors.

INTERPRETATION

The on-treatment level of apoB/apoA-1 was the strongest predictor of MCE in the pooled patient population, whereas apoB and non-HDL-C were best able to explain the difference in outcome between treatment groups. Measurements of apoB and apoA-1 should be more widely available for routine clinical assessments.

Increasing high-density lipoprotein cholesterol, inhibition of cholesteryl ester transfer protein, and heart disease risk reduction

Our purpose is to review recent research in the area of high-density lipoprotein (HDL) cholesterol raising and coronary artery disease (CAD) risk reduction. It is known that a decreased HDL cholesterol level is an important CAD risk factor and that raising HDL cholesterol has been associated with CAD risk reduction. A relative new strategy for raising HDL cholesterol, inhibition of cholesteryl ester transfer protein (CETP), is markedly effective. CETP inhibitors prevent the transfer of cholesteryl ester from HDL to triglyceride-rich lipoproteins in exchange for triglyceride. One inhibitor, torcetrapib, binds to CETP on HDL, markedly increases HDL cholesteryl ester, has no effect on fecal cholesterol excretion, but can raise blood pressure. A large clinical trial in patients with CAD who were taking atorvastatin was recently stopped prematurely because of excess mortality in those receiving torcetrapib versus placebo, and 2 other trials reported no benefit of torcetrapib on coronary atherosclerosis or carotid intima-media thickness as compared with subjects on atorvastatin alone. The adverse effects of torcetrapib may be compound specific, and because the crystal structure of CETP is now known, it should be possible to develop more optimal CETP inhibitors that do not form a nonproductive complex with CETP on the HDL particle, as has been reported for torcetrapib. Another alternative for increasing HDL levels is to develop more effective and better tolerated niacin preparations.

Lipid and lipoprotein profiles and prevalence of dyslipidemia in Mexican adolescents

The objective of the study was to determine the prevalence of different forms of dyslipidemia in an urban population of Mexican adolescents. A cross-sectional study was conducted in 1846 students from 8 randomly selected public junior high schools in Mexico City. Anthropometry, blood pressure, and 12-hour fasting lipids and lipoproteins were measured. We studied 770 male and 1076 female adolescents (13.2 +/- 1 years). The most prevalent dyslipidemia was low high-density lipoprotein cholesterol (HDL-C) (<35 mg/dL) either combined with other abnormalities (17.5% for male and 12.9% for female subjects, P < .001) or isolated (13.5% and 9.6% for male and female subjects, respectively, P < .001). Obese subjects showed the highest prevalence of low HDL-C (47.2% for male and 34.4% for female subjects) and of high total cholesterol, low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) (19.4%, 27.8%, and 36.1%, respectively, for male subjects; 9.8%, 13.1%, and 24.6%, respectively, for female subjects). Multiple regression analysis showed that waist circumference was negatively associated with HDL-C and positively associated with LDL-C and TG levels, whereas Tanner stages were negatively associated but sex was positively associated with total cholesterol, LDL-C, and TG concentrations. As in Mexican adults, low HDL-C and high TG levels were the most prevalent dyslipidemias. Increased blood lipids over long periods suggest that, as adults, these adolescents will be facing a higher risk for atherosclerosis.

Apolipoprotein A-II Is Inversely Associated With Risk of Future Coronary Artery Disease

Background— Although the vasculoprotective effects of apolipoprotein A-I (apoA-I), the major protein associated with high-density lipoprotein, have been universally accepted, apoA-II has been suggested to have poor antiatherogenic or even proatherogenic properties. To study this suggestion more closely, we evaluated how serum levels of apoA-II and apoA-I relate to the risk of future coronary artery disease (CAD) in a large, prospective study.

Methods and Results— We performed a nested case-control study in the prospective EPIC-Norfolk (European Prospective Investigation into Cancer and Nutrition–Norfolk) cohort. Case subjects (n=912) were apparently healthy men and women aged 45 to 79 years who developed fatal or nonfatal CAD during a mean follow-up of 6 years. Control subjects (n=1635) were matched by age, gender, and enrollment time. Conditional logistic regression was used to quantify the relationship between serum apoA-II levels and risk of CAD. Serum apoA-II concentration was significantly lower in case subjects (34.5±6.3 mg/dL) than in control subjects (35.2±5.8 mg/dL) and was inversely associated with risk of CAD, such that patients in the upper quartile (>38.1 mg/dL) had an odds ratio of 0.59 (95% confidence interval 0.46 to 0.76) versus those in the lowest quartile (<31.1 mg/dL; P for linearity <0.0001). After adjustment for fasting time, alcohol use, and cardiovascular risk factors (systolic blood pressure, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, body mass index, smoking, diabetes mellitus, and C-reactive protein), the corresponding risk estimate was 0.48 (95% confidence interval 0.34 to 0.67, P for linearity <0.0001). Surprisingly, additional adjustment for serum apoA-I levels did not affect risk prediction of apoA-II for future CAD (odds ratio 0.49, 95% confidence interval 0.34 to 0.68, P for linearity <0.0001). Also, after adjustment for high-density lipoprotein particle number and size, apoA-II was still associated with the risk of future CAD (odds ratio 0.62, 95% confidence interval 0.43 to 0.90, P for linearity 0.02).

Conclusions— ApoA-II is associated with a decreased risk of future CAD in apparently healthy people. These findings imply that apoA-II itself exerts effects on specific antiatherogenic pathways. On the basis of these findings, discussion of the potential proatherogenic effects of apoA-II can cease.

Long-term effects of fenofibrate on VLDL and HDL subspecies in participants with type 2 diabetes mellitus

AIMS/HYPOTHESIS

Low HDL-cholesterol (HDL-C) is frequently accompanied by high triacylglycerol levels in diabetic dyslipidaemia, increasing the risk of CHD. In the Fenofibrate Intervention and Event Lowering in Diabetes (FIELD) study, fenofibrate treatment lowered triacylglycerol levels, but the initial 5% increase in HDL-C attenuated over 5 years. We explored the changes in VLDL and HDL subspecies during fenofibrate treatment in a statin-free FIELD cohort.

METHODS

We randomised 171 participants with type 2 diabetes mellitus, who had been recruited to the FIELD study in Helsinki, to micronised fenofibrate (200 mg/day) or placebo in double-blind study design. VLDL and HDL subspecies were separated by ultracentrifugation at baseline and at the second and fifth year. Apolipoprotein (apo)A-I and apoA-II were measured by immunoturbidometric methods and lipoprotein (Lp)A-I and LpAI-AII particles by differential immunoassay.

RESULTS

Fenofibrate reduced plasma triacylglycerol levels by 26%, resulting from a marked reduction in VLDL1 triacylglycerol (0.62 vs 0.29 mmol/l, p < 0.001). Fenofibrate caused an increase in LDL size (Delta 0.80 nm, p < 0.001). HDL-C was similar between the groups. HDL2-C was decreased by fenofibrate (-27.5% at 5th year, p < 0.001) and HDL3-C increased (13.0% at 5th year, p < 0.001). Fenofibrate had no effect on apoA-I, whereas apoA-II increased. Thus, LpA-I decreased while LpAI-AII increased. Activities of cholesteryl ester transfer protein, phospholipids transfer protein and lecithin:cholesterylacyl transferase were unchanged by fenofibrate. High homocysteine levels were associated with a slight decrease in HDL-C and apoA-I.

CONCLUSIONS/INTERPRETATION

Fenofibrate markedly reduced large VLDL particles and produced a clear shift in HDL subspecies towards smaller particles. The HDL3-C increase in conjunction with unchanged apoA-I [corrected] levels is a dilemma with regard to cardiovascular disease.

Where are we with high-density lipoprotein raising and inhibition of cholesteryl ester transfer for heart disease risk reduction?

PURPOSE OF REVIEW

To review recent research in the area of high-density lipoprotein raising and coronary heart disease risk reduction.

RECENT FINDINGS

A decreased high-density lipoprotein-cholesterol is an important coronary heart disease risk factor and raising high-density lipoprotein-cholesterol has been associated with coronary heart disease risk reduction. A relative new strategy for raising high-density lipoprotein-cholesterol, i.e. inhibition of cholesteryl ester transfer protein, is markedly effective. Cholesteryl ester transfer protein inhibitors prevent the transfer of cholesteryl ester from high-density lipoprotein to triglyceride-rich lipoproteins in exchange for triglyceride. One inhibitor, torcetrapib, binds to cholesteryl ester transfer protein on high-density lipoprotein, markedly raises high-density lipoprotein-cholesteryl ester and has no effect on fecal cholesterol excretion, but can raise blood pressure. A large clinical trial in coronary heart disease patients on atorvastatin was recently stopped prematurely because of excess mortality in those receiving torcetrapib vs. placebo and two other trials reported no benefit of torcetrapib on coronary atherosclerosis or carotid artery intimal medial thickness as compared with subjects on atorvastatin alone.

SUMMARY

The adverse effects of torcetrapib may be compound-specific and, since the crystal structure of cholesteryl ester transfer protein is now known, it should be possible to develop more optimal cholesteryl ester transfer protein inhibitors that do not form a nonproductive complex with cholesteryl ester transfer protein on the high-density lipoprotein particle, as has been reported for torcetrapib. The alternative for high-density lipoprotein raising is to develop more effective and better tolerated niacin preparations.

HDL Cholesterol: Physiology, Pathophysiology, and Management

Numerous epidemiological studies have identified high-density lipoprotein cholesterol (HDL) to be an independent risk factor for coronary heart disease (CHD). HDL is an emerging therapeutic target that could rival the impact of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase inhibitors (statins) on LDL and CHD risk reduction. HDL metabolism, HDL kinetics, the concentration of various HDL subclasses, and other genetic factors affecting HDL functionality may all contribute to the anti-atherogenic properties of HDL; thus, standard plasma measurement may not capture the full range of HDL effects. Algorithms have been suggested to treat low HDL levels in subgroups of patients; however, no formal HDL target goals or treatment guidelines have been implemented as there is a lack of strong clinical evidence to support effective pharmacologic therapy for primary risk reduction. Available therapies have a modest impact on serum HDL levels; however, emerging therapies could have a more significant influence.

The relationship between physical activity and lipoprotein subclasses in postmenopausal women: the influence of hormone therapy

OBJECTIVE

This study's objective was to determine if the association between physical activity and lipids and lipoprotein subclasses in postmenopausal women varies by hormone therapy (HT) use.

DESIGN

The cross-sectional relationship between physical activity and lipid and lipoprotein subclass relationship was examined before group randomization in 485 postmenopausal (mean age 56.9 [2.9] y) white and African American women from the Woman On the Move through Activity and Nutrition study. This study is a randomized clinical trial designed to test whether a lifestyle intervention will reduce subclinical cardiovascular disease measures.

RESULTS

Hormone therapy users (n = 286) were significantly (P < 0.05) younger, less likely to be African American, reported higher levels of physical activity, large very low-density lipoprotein particles (VLDL-P), and medium high-density lipoprotein particles (HDL-P), had a larger mean HDL-P size, and lower levels of total cholesterol, low-density lipoprotein (LDL) cholesterol, small HDL-P, and small VLDL-P than nonusers (n = 196). Physical activity was significantly associated with favorable lipoprotein and lipid levels, regardless of HT use. Some relationships were found to vary significantly by HT use. In nonusers, mean HDL-P and LDL particles (LDL-P) size was significantly larger (P = 0.01 and 0.05, respectively) and total and small LDL-P were significantly lower (both P = 0.02) as activity increased. These relationship were not found in HT users.

CONCLUSIONS

Physical activity was significantly related to some lipoprotein subclasses regardless of HT; however, several key lipoprotein subclasses were associated with higher levels of activity only among non-HT users.

Comparison of the effects of high doses of rosuvastatin versus atorvastatin on the subpopulations of high-density lipoproteins

Atorvastatin and rosuvastatin are both highly effective in decreasing low-density lipoprotein cholesterol and triglyceride levels. However, rosuvastatin was shown to be more effective in increasing high-density lipoprotein (HDL) cholesterol levels. The purpose of the study is to compare the effects of daily doses of rosuvastatin 40 mg with atorvastatin 80 mg during a 6-week period on HDL subpopulations in 306 hyperlipidemic men and women. We previously showed that increased levels of large alpha-1 and alpha-2 HDLs decrease the risk of coronary heart disease and protect against progression of coronary atherosclerosis (superior to HDL cholesterol). In this study, both statins caused significant increases in large alpha-1 (p <0.001) and alpha-2 (p <0.001 for rosuvastatin, p <0.05 for atorvastatin) and significant (p <0.001) decreases in small pre-beta-1 HDL levels; however, increases in the 2 large HDL particles were significantly higher for rosuvastatin than atorvastatin (alpha-1, 24% vs 12%; alpha-2, 13% vs 4%; p <0.001). Statin-induced increases in alpha-1 and alpha-2 correlated with increases in HDL cholesterol, whereas decreases in pre-beta-1 were associated with decreases in triglycerides. In subjects with low HDL cholesterol (<40 mg/dl for men, <50 mg/dl for women, n = 99), increases in alpha-1 were 32% versus 11%, and in alpha-2, 21% versus 5% for rosuvastatin and atorvastatin, respectively. In conclusion, our data show that both statins, given at their maximal doses, favorably alter the HDL subpopulation profile, but also that rosuvastatin is significantly more effective in this regard than atorvastatin.

Abnormal HDL subclasses distribution in overweight children with insulin resistance or type 2 diabetes mellitus

BACKGROUND

Small HDL particles have emerged as significant predictors of incident type 2 diabetes mellitus (T2DM) in adults with impaired glucose tolerance (IGT). However, no previous study has investigated HDL size in pediatric subjects with these clinical conditions.

METHODS

We studied the HDL size distribution by native polyacrilamide gradient gel electrophoresis in 106 overweight children, 47 with T2DM, 43 with normal glucose tolerance (NGT), 16 with IGT, and 39 healthy weight controls.

RESULTS

Diabetic children had significantly lower proportions of HDL2b and HDL2a, and higher proportions of HDL3b and HDL3c than the other 3 groups. Overweight subjects showed HDL size distributions similar to those of controls. However, insulin-resistant children had lower proportions of HDL2b, and HDL2a, and higher proportions of HDL3b when compared with the insulin-sensitive overweight subjects. Multiple linear regression analyses showed that homeostasis model assessment correlated inversely with HDL2b and HDL2a, and directly with HDL3b, while BMI was independently associated only with HDL3a.

CONCLUSIONS

This study showed that HDL size distribution was shifted toward smaller particles in T2DM pediatric patients and in overweight children with insulin resistance, independent of their glucose tolerance status. Insulin resistance was the main factor associated with these HDL size abnormalities. This parameter could be useful as an early risk marker of incident diabetes and, probably, of coronary heart disease.

Polyacrylamide gradient gel electrophoresis of lipoprotein subclasses

High-density (HDL), low-density (LDL), and very-low-density (VLDL) lipoproteins are heterogeneous cholesterol-containing particles that differ in their metabolism, environmental interactions, and association with disease. Several protocols use polyacrylamide gradient gel electrophoresis (GGE) to separate these major lipoproteins into known subclasses. This article provides a brief history of the discovery of lipoprotein heterogeneity and an overview of relevant lipoprotein metabolism, highlighting the importance of the subclasses in the context of their metabolic origins, fates, and clinical implications. Various techniques using polyacrylamide GGE to assess HDL and LDL heterogeneity are described, and how the genetic and environmental determinations of HDL and LDL affect lipoprotein size heterogeneity and the implications for cardiovascular disease are outlined.

Alterations of high-density lipoprotein subclasses in hypercholesterolemia and combined hyperlipidemia

BACKGROUND

Alterations in plasma lipid levels can influence the composition, content, and distribution of plasma lipoprotein subclasses that effect atherosclerosis risk. Hypercholesterolemia and combined hyperlipidemia are common forms of atherogenic dyslipoproteinemia. This study evaluates the alterations of high-density lipoprotein (HDL) subclasses in hypercholesterolemic and combined hyperlipidemic subjects.

METHODS

Apolipoprotein A-I contents of plasma HDL subclasses were quantitated by 2-dimensional gel electrophoresis in 242 normolipidemic subjects, 66 hypercholesterolemic subjects and 59 combined hyperlipidemic subjects.

RESULTS

Compared with the normolipidemic subjects, apolipoprotein A-I contents of small-sized pre-beta1-HDL, HDL3c, HDL3b and HDL3a were significantly higher in both hypercholesterolemic subjects (p<.01, p<.05, p<.01 and p<.05, respectively) and combined hyperlipidemic subjects (p<.01, p<.05, p<.01 and p<.01, respectively). In contrast, apolipoprotein A-I contents of large-sized HDL2a and HDL2b were significantly lower in hypercholesterolemic subjects (p<.05 and p<.01, respectively) as well as combined hyperlipidemic subjects (p<.01 and p<.01, respectively). In addition, pre-beta1-HDL increased significantly (p<.05) while HDL2a and HDL2b decreased significantly (p<.05 and p<.01, respectively) in combined hyperlipidemic group versus hypercholesterolemic subjects. With the elevation of triglyceride levels, pre-beta1-HDL, and HDL3a increased successively, however, HDL2a and HDL2b decreased successively in subjects with total cholesterol levels greater than 240 mg/dl.

CONCLUSIONS

The particle size of HDL shifted towards smaller size in hypercholesterolemic subjects, and that the shift was more prominent in combined hyperlipidemic subjects. The alternations mentioned above indicate that HDL maturation might be abnormal, and reverse cholesterol transport (RCT) might be weakened.

Functionally defective high-density lipoprotein: a new therapeutic target at the crossroads of dyslipidemia, inflammation, and atherosclerosis

High-density lipoproteins (HDL) possess key atheroprotective biological properties, including cellular cholesterol efflux capacity, and anti-oxidative and anti-inflammatory activities. Plasma HDL particles are highly heterogeneous in physicochemical properties, metabolism, and biological activity. Within the circulating HDL particle population, small, dense HDL particles display elevated cellular cholesterol efflux capacity, afford potent protection of atherogenic low-density lipoprotein against oxidative stress and attenuate inflammation. The antiatherogenic properties of HDL can, however be compromised in metabolic diseases associated with accelerated atherosclerosis. Indeed, metabolic syndrome and type 2 diabetes are characterized not only by elevated cardiovascular risk and by low HDL-cholesterol (HDL-C) levels but also by defective HDL function. Functional HDL deficiency is intimately associated with alterations in intravascular HDL metabolism and structure. Indeed, formation of HDL particles with attenuated antiatherogenic activity is mechanistically related to core lipid enrichment in triglycerides and cholesteryl ester depletion, altered apolipoprotein A-I (apoA-I) conformation, replacement of apoA-I by serum amyloid A, and covalent modification of HDL protein components by oxidation and glycation. Deficient HDL function and subnormal HDL-C levels may act synergistically to accelerate atherosclerosis in metabolic disease. Therapeutic normalization of attenuated antiatherogenic HDL function in terms of both particle number and quality of HDL particles is the target of innovative pharmacological approaches to HDL raising, including inhibition of cholesteryl ester transfer protein, enhanced lipidation of apoA-I with nicotinic acid and infusion of reconstituted HDL or apoA-I mimetics. A preferential increase in circulating concentrations of HDL particles possessing normalized antiatherogenic activity is therefore a promising therapeutic strategy for the treatment of common metabolic diseases featuring dyslipidemia, inflammation, and premature atherosclerosis.

Lipoprotein particles, insulin, adiponectin, C-reactive protein and risk of coronary heart disease among men with metabolic syndrome

We tested the hypotheses whether nuclear magnetic resonance (NMR) determined lipoprotein particles, insulin and adiponectin, and C-reactive protein (CRP) and white blood cell (WBC) count as markers of inflammation predicted risk of coronary heart disease (CHD) death among 428 men age 35-57 years with metabolic syndrome (MetSyn) in a matched case control study within the multiple risk factor intervention trial. Blood samples collected at entry into the study and stored at -60 degrees C were obtained from central storage for blood analyte analysis. Two hundred and fourteen men with MetSyn who died of CHD were matched with 214 men with MetSyn who did not die of CHD during 18 years of follow-up. Cases were matched to controls on age, study group, number of factors present in the MetSyn, and presence or absence of a nonfatal CVD event during the trial. Mortality follow-up was determined using the National Death Index. Higher levels of high density lipoprotein particles (HDL-P), especially medium-sized HDL-P [hazard ratio (95% confidence interval) 0.45 (0.25-0.83, P<0.01), quartile 1 as compared to quartile 4], were associated with lower risk of CHD death. Low density lipoprotein (LDL) particles were not associated with increased risk of CHD. Elevated LDL cholesterol (LDL-C), smoking and WBC count were, but levels of adiponectin, insulin and CRP were not significantly related to CHD death. In multivariate models adjusting for smoking and LDL-C, medium HDL-P and WBC count remained independent predictors of CHD death. Number of HDL particles, especially medium-sized HDL particles and WBC count were independent predictors of CHD death among men with MetSyn.