Plasma Levels of Cholesteryl Ester Transfer Protein and the Risk of Future Coronary Artery Disease in Apparently Healthy Men and Women

Inhibition of CETP activity by torcetrapib reduces susceptibility to diet-induced atherosclerosis in New Zealand White rabbits

Cholesteryl ester transfer protein (CETP) inhibitors increase high density lipoprotein-cholesterol (HDL-C) in animals and humans, but whether CETP inhibition will be antiatherogenic is still uncertain. We tested the CETP inhibitor torcetrapib in rabbits fed an atherogenic diet at a dose sufficient to increase HDL-C by at least 3-fold (207 +/- 32 vs. 57 +/- 6 mg/dl in controls at 16 weeks). CETP activity was inhibited by 70-80% throughout the study. Non-HDL-C increased in both groups, but there was no difference apparent by the study's end. At 16 weeks, aortic atherosclerosis was 60% lower in torcetrapib-treated animals (16.4 +/- 3.4% vs. 39.8 +/- 5.4% in controls) and aortic cholesterol content was reduced proportionally. Sera from a separate group of rabbits administered torcetrapib effluxed 48% more cholesterol from Fu5AH cells than did sera from control animals, possibly explaining the reduced aortic cholesterol content. Regression analyses indicated that lesion area in the torcetrapib-treated group was strongly correlated with the ratio of total plasma cholesterol to HDL-C but not with changes in other lipid or lipoprotein levels. CETP inhibition with torcetrapib retards atherosclerosis in rabbits, and the reduced lesion area is associated with increased levels of HDL-C.

Concerted actions of cholesteryl ester transfer protein and phospholipid transfer protein in type 2 diabetes: effects of apolipoproteins

PURPOSE OF REVIEW

Type 2 diabetes frequently coincides with dyslipidemia, characterized by elevated plasma triglycerides, low high-density lipoprotein cholesterol levels and the presence of small dense low-density lipoprotein particles. Plasma lipid transfer proteins play an essential role in lipoprotein metabolism. It is thus vital to understand their pathophysiology and determine which factors influence their functioning in type 2 diabetes.

RECENT FINDINGS

Cholesteryl ester transfer protein-mediated transfer is increased in diabetic patients and contributes to low plasma high-density lipoprotein cholesterol levels. Apolipoproteins A-I, A-II and E are components of the donor lipoprotein particles that participate in the transfer of cholesteryl esters from high-density lipoprotein to apolipoprotein B-containing lipoproteins. Current evidence for functional roles of apolipoproteins C-I, F and A-IV as modulators of cholesteryl ester transfer is discussed. Phospholipid transfer protein activity is increased in diabetic patients and may contribute to hepatic very low-density lipoprotein synthesis and secretion and vitamin E transfer. Apolipoprotein E could stimulate the phospholipid transfer protein-mediated transfer of surface fragments of triglyceride-rich lipoproteins to high-density lipoprotein, and promote high-density lipoprotein remodelling.

SUMMARY

Both phospholipid and cholesteryl ester transfer proteins are important in very low and high-density lipoprotein metabolism and display concerted actions in patients with type 2 diabetes.

Multiple less common genetic variants explain the association of the cholesteryl ester transfer protein gene with coronary artery disease

OBJECTIVES

The objective of this study was to identify associations of the cholesteryl ester transfer protein (CETP) gene with coronary artery disease (CAD) with tagging (t) single nucleotide polymorphisms (SNPs) chosen to optimally account for intra-genic variation.

BACKGROUND

The CETP gene plays a critical role in lipoprotein metabolism, but the common and well-studied TaqIB variant is inconsistently predictive of CAD.

METHODS

From a deoxyribonucleic acid bank of 10,020 individuals, nondiabetic nonsmoking patients (n = 4,811) with angiographically defined, clinically significant CAD (> or =70% stenosis) or normal coronaries were genotyped for 11 CETP tSNPs. Myocardial infarction (MI) and lipid levels were evaluated as secondary end points.

RESULTS

Analysis of single tSNPs, corrected for multiple comparisons (p < 0.00485), identified allele +1086A to be associated with CAD (p = 0.0034). Suggestive allelic and significant genotypic associations were found for -631AA (odds ratio [OR] = 3.95, p = 0.004 vs. CC) and +2389GA (OR = 1.21, p = 0.003 vs. GG). Haplotype analysis by linkage disequilibrium (LD) group revealed a CAD association for LD group B (p = 0.0025 across T+1086A, C+878T, C+408T) and near significance for LD group A (p = 0.013 across C-631A, MspI, G+2389A). A weak protective trend for TaqIB was eliminated by adjustment for other tSNPs, and haplotype analyses suggested that TaqIB was simply a marker for other tSNPs or haplotypes. No tSNP or haplotype associations with MI were found.

CONCLUSIONS

Multiple, less common SNPs and haplotype variants underlie CETP-related CAD risk, for which the common TaqIB variant is simply a poor marker. The occurrence of risk-related variants on separate haplotypes suggests genetic-risk complexity and allelic heterogeneity. (Database Registry of the Intermountain Heart Collaborative Study; http://clinicaltrials.gov/ct/show/NCT00406185?order=1; NCT00406185).

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.

Effect of torcetrapib on carotid atherosclerosis in familial hypercholesterolemia

BACKGROUND

Torcetrapib, an inhibitor of cholesteryl ester transfer protein, may reduce atherosclerotic vascular disease by increasing levels of high-density lipoprotein (HDL) cholesterol.

METHODS

A total of 850 patients with heterozygous familial hypercholesterolemia underwent B-mode ultrasonography at baseline and at follow-up to measure changes in carotid intima-media thickness. The patients completed an atorvastatin run-in period and were subsequently randomly assigned to receive either atorvastatin monotherapy or atorvastatin combined with 60 mg of torcetrapib for 2 years.

RESULTS

After 24 months, in the atorvastatin-only group, the mean (+/-SD) HDL cholesterol level was 52.4+/-13.5 mg per deciliter and the mean low-density lipoprotein (LDL) cholesterol level was 143.2+/-42.2 mg per deciliter, as compared with 81.5+/-22.6 mg per deciliter and 115.1+/-48.5 mg per deciliter, respectively, in the torcetrapib-atorvastatin group. During the study, average systolic blood pressure increased by 2.8 mm Hg in the torcetrapib-atorvastatin group, as compared with the atorvastatin-only group. The increase in maximum carotid intima-media thickness, the primary measure of efficacy, was 0.0053+/-0.0028 mm per year in the atorvastatin-only group and 0.0047+/-0.0028 mm per year in the torcetrapib-atorvastatin group (P=0.87). The secondary efficacy measure, annualized change in mean carotid intima-media thickness for the common carotid artery, indicated a decrease of 0.0014 mm per year in the atorvastatin-only group, as compared with an increase of 0.0038 mm per year in the torcetrapib-atorvastatin group (P=0.005).

CONCLUSIONS

In patients with familial hypercholesterolemia, the use of torcetrapib with atorvastatin, as compared with atorvastatin alone, did not result in further reduction of progression of atherosclerosis, as assessed by a combined measure of carotid arterial-wall thickness, and was associated with progression of disease in the common carotid segment. These effects occurred despite a large increase in HDL cholesterol levels and a substantial decrease in levels of LDL cholesterol and triglycerides. (ClinicalTrials.gov number, NCT00136981 [ClinicalTrials.gov].).

Genetic factors affecting HDL levels, structure, metabolism and function

PURPOSE OF REVIEW

HDL is a recognized negative risk factor for the cardiovascular diseases. Establishing the genetic determinants of HDL concentration and functions would add to the prediction of cardiovascular risk and point to the biochemical mechanisms underlying this risk. The present review focuses on various approaches to establish genetic determinants of the HDL concentration, structure and function.

RECENT FINDINGS

While many genes contribute to the HDL concentration and collectively account for half of the variability, polymorphism of individual candidate genes contributes little. There are strong interactions between environmental and genetic influences. Recent findings have confirmed that APOA1 and ABCA1 exert the strongest influence on HDL concentrations and risk of atherosclerosis. CETP and lipases also affect the HDL concentration and functionality, but their connection to the atherosclerosis risk is conditional on the interaction between environmental and genetic factors.

SUMMARY

Analysis of genetic determinants of HDL-cholesterol in patients with specific disease states or in response to the environmental condition may be a more accurate way to assess variations in HDL concentration. This may result in defining the rules of interaction between genetic and environmental factors and lead to understanding the mechanisms responsible for the variations in HDL concentration and functionality.

Circulating secretory phospholipase A2 activity and risk of incident coronary events in healthy men and women: the EPIC-Norfolk study

OBJECTIVE

To assess the association between secretory phospholipase A2 (sPLA2) activity, which encompasses several types of sPLA2, and cardiovascular disease (CAD) in healthy individuals.

METHODS AND RESULTS

We investigated this association in a nested case-control study among the 25,663 participants in EPIC-Norfolk cohort. Cases (n=991) were subjects in whom CAD developed during the 6 years of mean follow-up. Controls (n=1806) matched by age, sex, and enrollment time remained free of any CAD during follow-up. The risk of incident CAD was associated with increasing quartiles of sPLA2 activity (P<0.001). After adjustment for risk factors, C-reactive protein and sPLA2 type IIA concentration, the odds ratios of incident CAD in the second, third, and fourth quartiles of sPLA2 activity were 1.41, 1.33, and 1.56 (P=0.003), compared with the lowest quartile. sPLA2 activity and CRP were poorly correlated (r=0.15), and their combined values were more informative for incident risk of CAD than either biomarker alone. Subjects in the highest quartiles of sPLA2 activity and CRP had an adjusted odds ratio of 2.89 (95% confidence interval, 1.78 to 4.68; P<0.001) for CAD compared with those with the lowest quartiles of both markers.

CONCLUSIONS

Measurement of serum sPLA2 activity provides additive prognostic value to traditional risk factors and CRP levels, and identifies a subgroup of individuals at high risk for incident CAD. Measurement of sPLA2 type II concentration had little added prognostic utility.

High-density lipoprotein and transport of cholesterol and triglyceride in blood

High-density lipoproteins (HDL) contain approximately 25% of the cholesterol and <5% of the triglyceride in the plasma of human blood. However, the dynamic exchange of lipids and lipid-binding proteins is not revealed by simply considering the mass of material at any point in time. HDL are the most complex of lipoprotein species with multiple protein constituents, which facilitate cholesterol secretion from cells, cholesterol esterification in plasma, and transfer of cholesterol to other lipoproteins and to the liver for excretion. They also play a major role in triglyceride transport by providing for activation of lipoprotein lipase, exchange of triglyceride among the lipoproteins, and removal of triglyceride rich remnants of chylomicrons and very-low-density lipoproteins after lipase action. In addition, antioxidative enzymes and phospholipid transfer proteins are important components of HDL. Many of the proteins of HDL are exchangeable with other lipoproteins, including chylomicrons and very-low-density lipoproteins. The constantly changing content of lipids and apolipoproteins in HDL particles generate a series of structures that can be analyzed by using separation techniques that depend on size or charge of the particles. Interaction of these various structures can be very different with cell surfaces depending on the size or apolipoprotein content. A series of different transport proteins preferentially exchange lipids with specific structures among the HDL but interact poorly or not at all with others. The role of these differing forms of HDL and their interactions with cells and other lipoprotein species in plasma is the subject of intense study stimulated by the potential for reducing atherogenesis. The strength of this is only partially indicated by the correlation of higher total levels of the HDL particles with reduced incidence of vascular disease in various clinical trials and epidemiological studies.

EPIC-Heart: the cardiovascular component of a prospective study of nutritional, lifestyle and biological factors in 520,000 middle-aged participants from 10 European countries

EPIC-Heart is the cardiovascular component of the European Prospective Investigation into Cancer and Nutrition (EPIC), a multi-centre prospective cohort study investigating the relationship between nutrition and major chronic disease outcomes. Its objective is to advance understanding about the separate and combined influences of lifestyle (especially dietary), environmental, metabolic and genetic factors in the development of cardiovascular diseases by making best possible use of the unusually informative database and biological samples in EPIC. Between 1992 and 2000, 519,978 participants (366,521 women and 153,457 men, mostly aged 35-70 years) in 23 centres in 10 European countries commenced follow-up for cause- specific mortality, cancer incidence and major cardiovascular morbidity. Dietary information was collected with quantitative questionnaires or semi-quantitative food frequency questionnaires, including a 24-h dietary recall sub-study to help calibrate the dietary measurements. Information was collected on physical activity, tobacco smoking, alcohol consumption, occupational history, socio-economic status, and history of previous illnesses. Anthropometric measurements and blood pressure recordings were made in the majority of participants. Blood samples were taken from 385,747 individuals, from which plasma, serum, red cells, and buffy coat fractions were separated and aliquoted for long-term storage. By 2004, an estimated 10,000 incident fatal and non-fatal coronary and stroke events had been recorded. The first cycle of EPIC-Heart analyses will assess associations of coronary mortality with several prominent dietary hypotheses and with established cardiovascular risk factors. Subsequent analyses will extend this approach to non-fatal cardiovascular outcomes and to further dietary, biochemical and genetic factors.

Mechanisms of disease: HDL metabolism as a target for novel therapies

Plasma concentrations of HDL cholesterol are inversely correlated with risk of coronary heart disease, and low HDL-cholesterol levels are a risk factor even in patients aggressively treated for LDL reduction. Thus, there is great interest in targeting HDL cholesterol therapeutically. The existing approaches are limited in their ability to raise HDL-cholesterol levels, and there has, therefore, been a major focus on the development of novel therapies. The goal of new approaches is to either raise HDL-cholesterol levels or improve the function of HDL. Here, the current status of the development of novel therapies targeted toward HDL metabolism is reviewed.

CETP inhibition in cardiovascular risk management: a critical appraisal

In view of the cardioprotective effect of high-density lipoproteins (HDL) and the limited effects of statin and fibrate therapy on HDL cholesterol, it is clinically relevant to test whether pharmacological treatment aimed at raising HDL lowers cardiovascular risk. Cholesteryl ester transfer protein (CETP) is a new therapeutic target, because the cholesteryl ester transfer process lowers HDL cholesterol and contributes to an atherogenic lipoprotein profile, particularly when plasma triglycerides are high. Clinical evidence suggests that coronary artery calcification as well as intima media thickness is positively related to plasma cholesteryl ester transfer, and that high plasma CETP concentration is associated with increased cardiovascular risk in hypertriglyceridaemia. However, CETP could also have anti-atherogenic potential, since it provides a potentially beneficial route for delivery of HDL-derived cholesteryl esters to the liver. In addition, CETP could also favourably stimulate peripheral cell cholesterol removal and enhance hepatic cholesterol uptake. Recent evidence suggests that a high CETP level may confer lower cardiovascular risk in the context of low triglycerides. At maximal doses, the CETP inhibitors JTT-705 and torcetrapib elicit a marked rise in HDL cholesterol of up to 34% and 91-106%, respectively. The effectiveness of these drugs on (intermediate) clinical outcome measures is currently being tested in large-scale phase III clinical trials, with torcetrapib being only evaluated in combination therapy with atorvastatin. When and how to use CETP inhibitors, e.g. in combination with a statin or a fibrate, is a major challenge. We propose that low HDL cholesterol in the context of high triglycerides, such as found in type 2 diabetes mellitus, could become an important indication area for this new class of drugs.

Elevated cholesteryl ester transfer protein concentration is associated with an increased risk for cardiovascular disease in women, but not in men, with Type 2 diabetes: the Hoorn Study

AIMS

Cholesteryl ester transfer protein (CETP) exchanges neutral lipids between lipoproteins. As the role of CETP in the atherogenic process is still not fully clarified, we studied the association of CETP concentration with the prevalence of cardiovascular disease (CVD) and with intima-media thickness of the carotid artery (IMT) in subjects with normal glucose tolerance (NGT), impaird fasting glucose and/or impaired glucose tolerance (IFG/IGT) and Type 2 diabetes mellitus.

METHODS

Subjects (n = 566) were recruited from the 2000-2001 follow-up examination of the Hoorn study. CETP concentration was determined by immunoassay. CVD was defined as self-reported history of arterial surgery, cerebral vascular event, amputation, angina, claudication, possible infarction, measured ankle-brachial index < 0.90 or ECG abnormalities. The right common carotid artery IMT was measured by ultrasound at 10 mm proximal to the carotid bulb.

RESULTS

In men, CETP concentration was not associated with CVD, irrespective of glucose tolerance status. In women with NGT or IGT, there was also no relationship. However, in women with Type 2 diabetes, the risk of CVD was increased in those with high CETP concentration [odds ratio = 3.34 (1.56; 7.14)]. No statistically significant association was found between CETP concentration and IMT in the entire cohort.

CONCLUSIONS

In an elderly Caucasian population, associations of CETP concentration with CVD were dependent on glucose tolerance status and gender. The finding that high CETP concentration was strongly associated with increased prevalence of CVD in women with Type 2 diabetes warrants further investigation.

Molecular regulation of HDL metabolism and function: implications for novel therapies

HDL metabolism represents a major target for the development of therapies intended to reduce the risk of atherosclerotic cardiovascular disease. HDL metabolism is complex and involves dissociation of HDL apolipoprotein and HDL cholesterol metabolism. Advances in our understanding of the molecular regulation of HDL metabolism, macrophage cholesterol efflux, and HDL function will lead to a variety of novel therapeutics.

High-Density Lipoprotein Cholesterol: A Potential Therapeutic Target for Prevention of Coronary Artery Disease

High-density lipoprotein cholesterol has an important role in the pathophysiology of coronary artery disease. High-density lipoprotein cholesterol is becoming an increasingly important prognostic and therapeutic target. The purpose of this paper is to review the biochemical pathways involved in reverse cholesterol transport and to discuss potential, clinically based high-density lipoprotein therapies that may contribute to reduction in risk of atherosclerosis.

Cholesteryl ester transfer protein promotes the formation of cholesterol-rich remnant like lipoprotein particles in human plasma

BACKGROUND

Cholesteryl ester transfer protein (CETP) is suggested to be involved in the cholesterol level in remnant like lipoprotein particles (RLP), but there is no direct evidence that CETP increases cholesterol-rich RLP in plasma.

METHODS

Human plasma was incubated with or without HDL containing [(3)H]-labeled cholesteryl ester ([(3)H]CE), recombinant CETP or CETP inhibitors at 37 degrees C in vitro.

RESULTS

The RLP-cholesterol (RLP-C) level increased time-dependently and the amount of RLP-C increase (DeltaRLP-C) by the incubation was positively correlated with triglyceride (TG) level in plasma (r=0.597, P=0.0070). [(3)H]CE in HDL was transferred to RLP fraction under 37 degrees C incubation, and the amount of [(3)H]CE transferred to RLP correlated significantly with DeltaRLP-C in plasma (r=0.611, P=0.0156). Human recombinant CETP enhanced the RLP-C increase, while CETP inhibitor JTT-705 and anti-human CETP monoclonal antibody inhibited both the RLP-C increase and [(3)H]CE transfer to RLP. On the other hand, an inhibition of lecithin: cholesterol acyltransferase (LCAT) did not affect the RLP-C increase. In triglyceride-rich lipoproteins (TRL) fraction, JTT-705 inhibited [(3)H]CE transfer to RLP more strongly than that to non-RLP.

CONCLUSIONS

CETP promotes the formation of cholesterol-rich RLP through the transfer of CE from HDL to TRL and CETP inhibitors are useful to reduce RLP-C.

Will torcetrapib be the next big thing in coronary heart disease risk reduction?

Scientists are seeking ways to increase high-density lipoprotein (HDL) cholesterol to lower coronary heart disease (CHD). Emerging from this search is torcetrapib, a partial inhibitor of cholesteryl ester transfer protein. Via this mechanism, cholesteryl ester is prevented from being transferred to apolipoprotein B-containing lipoproteins and is retained in HDL particles, where ostensibly it may be delivered directly to the liver for elimination. Proof that this may reduce atherosclerotic vascular disease is provided by population studies of cholesteryl ester transfer protein (CETP) deficiencies and single nucleotide polymorphisms of CETP, and experiments in animal models treated with torcetrapib. Torcetrapib effectively raises HDL cholesterol when used alone and when added to background therapy with atorvastatin. The drug appears to be well tolerated. Large surrogate and survival outcome trials are underway to document its impact on CHD.

The dyslipidemia of chronic renal disease: effects of statin therapy

PURPOSE OF REVIEW

Dyslipidemia is a prevalent condition in patients with chronic renal disease, but is often left untreated. Statin treatment constitutes an effective way to improve lipid abnormalities. This review summarizes present studies on dyslipidemia and its treatment in patients with chronic renal disease.

RECENT FINDINGS

The specific dyslipidemia in renal disease is associated with the presence of proteinuria and decreased creatinine clearance, and may even adversely affect the progression of chronic renal disease. Statin therapy may have renoprotective effects due to a combination of lipid lowering and pleiotropic effects. Statins exert several anti-inflammatory properties and lead to a decrease of proteinuria. Post-hoc analyses of large-scale lipid lowering trials have shown that the reduction of cardiovascular risk was equivalent to the reduction achieved in patients without chronic renal failure. We feel, however, that if intervention with statins is postponed until patients reach end-stage renal disease, statins have limited benefit.

SUMMARY

Present studies suggest that patients with renal disease should be screened early for dyslipidemia and that statins have to be considered as the lipid lowering therapy of choice. These drugs reduce cardiovascular risk. Further studies are needed to firmly establish whether statins preserve renal function.

The potential for CETP inhibition to reduce cardiovascular disease risk

BACKGROUND

Although reductions in cardiovascular risk can be achieved by lowering low-density lipoprotein cholesterol, treated patients remain at substantial risk. Epidemiological studies have established that higher levels of high-density lipoprotein cholesterol (HDL-C) are strongly associated with reduced cardiovascular risk, and therefore raising levels of HDL-C may be beneficial. The activity of cholesteryl ester transfer protein (CETP) appears to be inversely correlated with HDL-C levels and thus CETP is an attractive target for intervention to raise levels of HDL-C and potentially reduce residual cardiovascular risk.

OBJECTIVES

This paper reviews the evidence for an atheroprotective role of higher levels of HDL-C, the function of CETP in cholesterol metabolism, and the concept of CETP inhibition as a potential new strategy for decreasing cardiovascular risk. An analysis of clinical studies of CETP inhibition was also performed.

METHODS

MEDLINE (1966 to June 2006), EMBASE (1974 to June 2006), and cardiology conference proceedings were searched for clinical trials of CETP inhibition.

RESULTS

Thirteen reports involving vaccine-based and pharmacological inhibition of CETP were found. Modest and inconsistent elevation of HDL-C was observed with vaccine-based therapy, whereas HDL-C elevation with pharmacological inhibitors was greater and more consistent.

CONCLUSIONS

Elevation of HDL-C via CETP inhibition appears to be a potentially promising approach to reduce cardiovascular disease. Preliminary studies suggest benefits of CETP inhibition on serum lipid levels, and ongoing studies should establish the effects on atherosclerosis and cardiovascular events.

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.

Tissue factor serum levels and the risk of future coronary artery disease in apparently healthy men and women: the EPIC-Norfolk prospective population study

INTRODUCTION

Tissue factor (TF) has been implicated in coronary artery disease (CAD). High levels of circulating TF are found in patients with acute atherothrombotic events. Whether high serum TF levels predict risk of future CAD independent of known risk factors remains unknown.

METHODS

We conducted a prospective case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC)-Norfolk population study. Cases (n=1037) were apparently healthy men and women, aged 45-79 years, who developed fatal or non-fatal CAD during follow-up. Controls (n=2005) were matched by age, sex, and enrolment time. Serum TF levels were measured using high-affinity antibodies.

RESULTS

In men, median TF levels were not significant higher in cases than in controls (59.0 pg mL-1, range: 16.7-370.4 vs. 54.9 pg mL-1, range: 16.2-452.4). In women, median TF levels were not significant higher in controls than in cases (73.4 pg mL-1, range: 16.7-492.3 vs. 50.5 pg mL-1, range: 16.5-376.7). The incidence of smoking was about double in the lowest compared with the highest TF quartile. Correcting for sex, age, body mass index, smoking, diabetes, systolic blood pressure, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol and C-reactive protein levels, the risk of future CAD was 1.05 (95% CI: 0.81-1.36) for people in the highest TF quartile, compared with those in the lowest (P-value for linearity=0.8).

CONCLUSION

High levels of serum TF were not independently associated with an increased risk of future CAD in apparently healthy individuals.

Cholesteryl Ester Transfer Protein Decreases High-Density Lipoprotein and Severely Aggravates Atherosclerosis in APOE*3-Leiden Mice

Objective— The role of cholesteryl ester transfer protein (CETP) in the development of atherosclerosis is still undergoing debate. Therefore, we evaluated the effect of human CETP expression on atherosclerosis in APOE*3-Leiden ( E3L ) mice with a humanized lipoprotein profile.

Methods and Results— E3L mice were crossbred with human CETP transgenic mice. On a chow diet, CETP expression increased plasma total cholesterol (TC) (+43%; P <0.05). To evaluate the effects of CETP on the development of atherosclerosis, mice were fed a Western-type diet containing 0.25% cholesterol, leading to 4.3-fold elevated TC levels in both E3L and CETP.E3L mice ( P <0.01). On both diets, CETP expression shifted the distribution of cholesterol from high-density lipoprotein (HDL) toward very-low-density lipoprotein (VLDL)/low-density lipoprotein (LDL). Moreover, plasma of CETP.E3L mice had reduced capacity (−39%; P <0.05) to induce SR-BI–mediated cholesterol efflux from Fu5AH cells than plasma of E3L mice. After 19 weeks on the Western-type diet, CETP.E3L mice showed a 7.0-fold increased atherosclerotic lesion area in the aortic root compared with E3L mice ( P <0.0001).

Conclusions— CETP expression in E3L mice shifts the distribution of cholesterol from HDL to VLDL/LDL, reduces plasma-mediated SR-BI–dependent cholesterol efflux, and represents a clear pro-atherogenic factor in E3L mice. We anticipate that the CETP.E3L mouse will be a valuable model for the preclinical evaluation of HDL-raising interventions on atherosclerosis development.

Fibrinogen plasma levels modify the association between the factor XIII Val34Leu variant and risk of coronary artery disease: the EPIC-Norfolk prospective population study

BACKGROUND

The factor (F) XIII Val34Leu variant has been implicated in coronary artery disease (CAD). In vitro evidence suggests an interaction between this variant and fibrinogen concentrations in determining thrombus structure.

OBJECTIVES

To test whether this interaction is relevant in influencing coronary risk in apparently healthy individuals.

METHODS

In an 8-year prospective population study of 25 663 men and women, we compared 898 apparently healthy men and women developing incident CAD with 1580 matched controls.

RESULTS

Overall, the FXIII Val34Leu variant was not associated with the risk of future CAD. However, a significant interaction existed between the Val34Leu variant and fibrinogen levels for the risk of future CAD (P = 0.004). Among people in the lowest tertile of fibrinogen concentrations, LeuLeu carriers had an odds ratio (OR) of 2.88 (95% confidence interval; CI 1.24-6.74) compared to wild-type individuals (P for linearity = 0.003). By contrast, among those in the highest fibrinogen tertile, LeuLeu carriers were had a lower risk than wild-type individuals (OR 0.47, 95% CI 0.18-1.17, P for linearity = 0.1).

CONCLUSIONS

Our results suggest that a significant gene-covariate interaction exists between the FXIII Val34Leu variant and fibrinogen levels. Relationships between genotype and disease risk may be altered by biological covariates. Simplistic paradigms of gene or biomarker associations are unlikely to fully characterize disease risk in populations.

Plasma cholesteryl ester transfer protein concentrations predict cardiovascular events in patients with coronary artery disease treated with pravastatin

OBJECTIVE

The B1B1 variant of the cholesteryl ester transfer protein (CETP) TaqIB polymorphism and high plasma CETP concentrations are associated with favourable angiographic outcomes in pravastatin-treated patients suffering from coronary artery disease (CAD). The purpose of the present study was to test whether CETP TaqIB genotypes and/or plasma CETP concentrations at baseline also predict clinical end-points in patients with CAD.

DESIGN

Prospective longitudinal observational study.

SETTING

Primary care doctors (n=88) and hospitals (n=7) in Austria.

SUBJECTS

A total of 1620 men and women with preexisting CAD were recruited and plasma lipids were determined at study entry. 1389 hypercholesterolaemic patients were included and 1002 patients completed the follow-up.

INTERVENTIONS

In all patients treatment with pravastatin was started and patients were followed up for 2 years.

MAIN OUTCOME MEASURES

Cardiovascular events.

RESULTS

One hundred patients suffered at least one cardiovascular event. We observed significantly more events in patients within the lowest compared with the highest quartile of plasma CETP concentrations (odds ratio 3.20, CI95 1.65-6.23; P=0.001, adjusted for known risk factors of CAD). No significantly different numbers of cardiovascular events were found between CETP TaqIB genotypes.

CONCLUSIONS

Plasma CETP concentrations, but not CETP TaqIB genotypes, predict cardiovascular events in patients with CAD treated with pravastatin. Despite higher LDL cholesterol concentrations, high plasma CETP concentrations at baseline are associated with fewer cardiovascular events compared with low plasma CETP concentrations in CAD patients treated with pravastatin.

A role for CETP TaqIB polymorphism in determining susceptibility to atrial fibrillation: a nested case control study

Background

Studies investigating the genetic and environmental characteristics of atrial fibrillation (AF) may provide new insights in the complex development of AF. We aimed to investigate the association between several environmental factors and loci of candidate genes, which might be related to the presence of AF.

Methods

A nested case-control study within the PREVEND cohort was conducted. Standard 12 lead electrocardiograms were recorded and AF was defined according to Minnesota codes. For every case, an age and gender matched control was selected from the same population (n = 194). In addition to logistic regression analyses, the multifactor-dimensionality reduction (MDR) method and interaction entropy graphs were used for the evaluation of gene-gene and gene-environment interactions. Polymorphisms in genes from the Renin-angiotensin, Bradykinin and CETP systems were included.

Results

Subjects with AF had a higher prevalence of electrocardiographic left ventricular hypertrophy, ischemic heart disease, hypertension, renal dysfunction, elevated levels of C-reactive protein (CRP) and increased urinary albumin excretion as compared to controls. The polymorphisms of the Renin-angiotensin system and Bradykinin gene did not show a significant association with AF (p > 0.05). The TaqIB polymorphism of the CETP gene was significantly associated with the presence of AF (p < 0.05). Using the MDR method, the best genotype-phenotype models included the combination of micro- or macroalbuminuria and CETP TaqIB polymorphism, CRP >3 mg/L and CETP TaqIB polymorphism, renal dysfunction and the CETP TaqIB polymorphism, and ischemic heart disease and CETP TaqIB polymorphism (1000 fold permutation testing, P < 0.05). Interaction entropy graph showed that the combination of albuminuria and CETP TaqIB polymorphism removed the most entropy.

Conclusion

CETP TaqIB polymorphism is significantly associated with the presence of AF in the context of micro- or macroalbuminuria, elevated C-reactive protein, renal dysfunction, and ischemic heart disease.

Cholesteryl ester transfer protein (CETP) inhibition beyond raising high-density lipoprotein cholesterol levels: pathways by which modulation of CETP activity may alter atherogenesis

Raising high-density lipoprotein cholesterol (HDL-C) is a promising strategy in the struggle to prevent cardiovascular disease, and cholesteryl ester transfer protein (CETP) inhibitors have been developed to accomplish this. The first results are encouraging, and, in fact, in rabbits, inhibition of CETP reduces atherosclerosis. Because human data regarding the reduction of atheroma burden require more time, the biochemical mechanisms underlying the putative atheroprotection of CETP inhibitors are currently dissected, and several pathways have emerged. First, CETP inhibition increases HDL-C and reduces low-density lipoprotein cholesterol (LDL-C) levels consistent with CETP lipid transfer activity and its role in reverse cholesterol transport (RCT). This coincides with putative beneficial increases in both HDL and LDL size. However, many aspects regarding the impact of CETP inhibition on the RCT pathway remain elusive, in particular whether the first step concerning cholesterol efflux from peripheral tissues to HDL is influenced. Moreover, the relevance of scavenger receptor BI and consequently the central role of HDL in human RCT is still unclear. Second, CETP inhibition was shown recently to increase antioxidant enzymes associated with HDL, in turn associated with decreased oxidation of LDL. Atheroprotection in man is currently anticipated based on the improvement of these biochemical parameters known to influence atherosclerosis, but final confirmation regarding the impact of CETP inhibition on cardiovascular outcome will have to come from trials evaluating clinical end points.

Inhibitors of cholesteryl ester transfer protein – a new approach to coronary artery disease

Despite the use of the statins to lower low-density lipoprotein-cholesterol, leading to major reductions in the mortality and morbidity that is associated with coronary artery disease, considerable mortality and morbidity remains. Increasing high-density lipoprotein (HDL)-cholesterol levels has been associated with reduced coronary artery disease mortality and morbidity in several studies. Inhibition of cholesteryl ester transfer protein (CETP) activity leads to increased HDL-cholesterol. In cholesterol-fed rabbits, antibodies against CETP increased HDL-cholesterol and decreased atherosclerotic lesions. In healthy subjects with mild dyslipidaemia, the CETP inhibitors JTT-705 and torcetrapib increased HDL-cholesterol and decreased low-density lipoprotein-cholesterol. Increasing HDL-cholesterol with CETP inhibitors is a new approach to dyslipidaemia that requires further investigation, especially in patients who have coronary artery disease.

Targeting cholesteryl ester transfer protein for the prevention and management of cardiovascular disease

Epidemiologic studies have shown that the concentration of high-density lipoprotein cholesterol (HDL-C) is a strong, independent, inverse predictor of coronary heart disease risk. This identifies HDL-C as a potential therapeutic target. Compared with low-density lipoprotein cholesterol (LDL-C)-lowering agents, however, currently available HDL-raising drugs are relatively ineffective. Consequently, recent years have seen considerable efforts expended on identifying new drugs that can raise HDL-C. Cholesteryl ester transfer protein (CETP) plays an important role in cholesterol metabolism, being responsible for the transfer of cholesteryl esters from HDL to very low-density lipoproteins and LDLs. The observation that Japanese populations with CETP deficiency exhibited high levels of HDL-C has led to the concept that drugs targeting CETP activity may elevate HDL-C levels and potentially decrease cardiovascular risk. Support of this proposition has been obtained in rabbits where inhibition of CETP activity is markedly antiatherogenic. Two CETP inhibitors-torcetrapib and JTT-705-are currently in the preliminary stages of clinical development. Initial studies with these drugs in humans show that they substantially increase HDL-C levels and modestly decrease LDL-C levels. Larger, long-term, randomized, clinical end point trials are required to determine whether the beneficial effects of CETP inhibitors on lipoprotein metabolism can translate into reductions in cardiovascular events.

High-density lipoprotein cholesterol therapies: the next frontier in lipid management

Current cholesterol treatment guidelines target low-density lipoprotein cholesterol as the primary goal of therapy and recommend statins as first line therapy. However, despite aggressive treatment and success at reaching the recommended goals, coronary heart disease is still a leading cause of morbidity and mortality. Thus, other lipoproteins, such as high-density lipoprotein, are now being looked to as the next promising targets of therapy to help reduce the burden of coronary heart disease and atherosclerosis. This review details currently available strategies to raise high-density lipoprotein cholesterol, and then turns to several new compounds in development that target the varying components of the complex metabolism of high-density lipoprotein.

Serum lipoprotein lipase concentration and risk for future coronary artery disease: the EPIC-Norfolk prospective population study

BACKGROUND

Lipoprotein lipase (LPL) is associated with coronary artery disease (CAD) risk, but prospective population data are lacking. This is mainly because of the need for cumbersome heparin injections, which are necessary for LPL measurements. Recent retrospective studies, however, indicate that LPL concentration can be reliably measured in serum that enabled evaluation of the prospective association between LPL and future CAD.

METHODS AND RESULTS

LPL concentration was determined in serum samples of men and women in the EPIC-Norfolk population cohort who developed fatal or nonfatal CAD during 7 years of follow-up. For each case (n=1006), 2 controls, matched for age, sex, and enrollment time, were identified. Serum LPL concentration was lower in cases compared with controls (median and interquartile range: 61 [43-85] versus 66 [46-92] ng/mL; P<0.0001). Those in the highest LPL concentration quartile had a 34% lower risk for future CAD compared with those in the lowest quartile (odds ratio [OR] 0.66; confidence interval [CI], 0.53 to 0.83; P<0.0001). This effect remained significant after adjustment for blood pressure, diabetes, smoking, body mass index, and low-density lipoprotein (LDL) cholesterol (OR, 0.77; CI, 0.60-0.99; P=0.02). As expected from LPL biology, additional adjustments for either high-density lipoprotein cholesterol (HDL-C) or triglyceride (TG) levels rendered loss of statistical significance. Of interest, serum LPL concentration was positively linear correlated with HDL and LDL size.

CONCLUSIONS

Reduced levels of serum LPL are associated with an increased risk for future CAD. The data suggest that high LPL concentrations may be atheroprotective through decreasing TG levels and increasing HDL-C levels.

Plasma cholesteryl ester transfer is a determinant of intima-media thickness in type 2 diabetic and nondiabetic subjects: role of CETP and triglycerides

We tested whether carotid artery intima-media thickness (IMT) is associated with plasma cholesteryl ester transfer (CET) and/or the plasma cholesteryl ester transfer protein (CETP) concentration in type 2 diabetic and control subjects. In 87 male and female subjects with type 2 diabetes (nonsmokers, no insulin or lipid-lowering drug treatment) and 82 control subjects, IMT, plasma CET, CETP mass, and lipids were determined. HDL cholesterol was lower, whereas IMT, pulse pressure, plasma triglycerides, and plasma CET and CETP concentration were higher in diabetic patients versus control subjects. In diabetic patients, plasma CET was positively determined by triglycerides (P < 0.001), non-HDL cholesterol (P < 0.001), CETP (P = 0.002), and the interaction between CETP and triglycerides (P = 0.004). In control subjects, plasma CET was positively related to triglycerides (P < 0.001) and non-HDL cholesterol (P < 0.001). HDL cholesterol was inversely related to plasma CET in each group (P < 0.01 for both). IMT was positively associated with plasma CET in diabetic (P = 0.05) and control (P < 0.05) subjects after adjustment for age, sex, and pulse pressure. No independent relationship with plasma CETP mass was found. Plasma CET is a positive determinant of IMT. Plasma CETP mass, in turn, is a determinant of CET with an increasing effect at higher triglycerides. These data, therefore, provide a rationale to evaluate the effects of CETP inhibitor treatment on plasma CET and on cardiovascular risk in diabetes-associated hypertriglyceridemia.

Modifying plasma low-density lipoprotein and high-density lipoprotein cholesterol: what combinations are available in the future?

Despite a growing body of research on the benefit of combination drug therapy for dyslipidemia in the metabolic syndrome or diabetes mellitus, there are insufficient outcome data on the use of combination therapy as well as inadequate data to compare certain combination regimens. The focus of the therapeutic approach in treating the metabolic syndrome has been almost exclusively on low-density lipoprotein (LDL) cholesterol for approximately the past 10 years, and specifically on statin therapy. Although results of epidemiologic studies as well as clinical trials using angiographic and clinical end points confirm the association of LDL cholesterol and risk of coronary artery disease, data are lacking regarding the effects of combination therapy in the management of coronary artery disease. Management of the metabolic syndrome focusing on the modification of plasma LDL as well as high-density lipoprotein cholesterol is reviewed. Future management strategies with the use of novel combination therapy is also discussed.

Molecular Mechanism of the Blockade of Plasma Cholesteryl Ester Transfer Protein by Its Physiological Inhibitor Apolipoprotein CI

Genetically engineered mice demonstrated that apolipoprotein (apo) CI is a potent, physiological inhibitor of plasma cholesteryl ester transfer protein (CETP) activity. The goal of this study was to determine the molecular mechanism of the apoCI-mediated blockade of CETP activity. Kinetic analyses revealed that the inhibitory property of apoCI is independent of the amount of active CETP, but it is tightly dependent on the amount of high density lipoproteins (HDL) in the incubation mixtures. The electrostatic charge of HDL, i.e. the main carrier of apoCI in human plasma, is gradually modified with increasing amounts of apoCI, and the neutralization of apoCI lysine residues by acetylation produces a marked reduction in its inhibitory potential. The inhibitory property of full-length apoCI is shared by its C-terminal alpha-helix with significant electrostratic properties, whereas its N-terminal alpha-helix with no CETP inhibitory property has no effect on HDL electronegativity. Finally, binding experiments demonstrated that apoCI and to a lower extent its C-terminal alpha-helix are able to disrupt CETP-lipoprotein complexes in a concentration-dependent manner. It was concluded that the inhibition of CETP activity by apoCI is in direct link with its specific electrostatic properties, and the apoCI-mediated reduction in the binding properties of lipoproteins results in weaker CETP-HDL interactions and fewer cholesteryl ester transfers.

C-reactive protein levels and coronary artery disease incidence and mortality in apparently healthy men and women: the EPIC-Norfolk prospective population study 1993-2003

INTRODUCTION

Measurement of C-reactive protein (CRP) levels has been proposed as a useful marker to improve the prediction of future coronary artery disease (CAD) risk, but this notion has been challenged recently.

METHODS AND RESULTS

We performed a prospective case-control study among apparently healthy men and women. The odds ratio (OR) for future CAD incidence was 2.49 (95% CI=2.02-3.08, p for linearity <0.0001) unadjusted, and 1.66 (95% CI=1.31-2.12, p for linearity <0.0001), after adjustment for classical cardiovascular risk factors, for top versus bottom quartile of the CRP distribution. Notably, the risk factor adjusted predictive value was substantially stronger for fatal CAD (OR=2.92, 95% CI=1.83-4.67, p for linearity <0.0001) than for non-fatal CAD (OR=1.25, 95% CI=0.93-1.66, p for linearity=0.06). CRP levels were among the strongest predictors of CAD incidence and mortality. CRP levels remained a statistically significant predictor of future CAD, even after adjustment for the Framingham risk score.

CONCLUSIONS

In this British cohort with risk factor levels representative of a contemporary Western population, CRP concentration was among the strongest predictors of CAD incidence and mortality. We suggest that current guidelines on CRP measurement in clinical practice should be based on contemporary and representative populations.

Drugs in development: targeting high-density lipoprotein metabolism and reverse cholesterol transport

PURPOSE OF REVIEW

This review summarizes currently available therapies for raising high-density lipoprotein cholesterol (HDL-C) and expands on therapies currently in development that target high-density lipoprotein cholesterol.

RECENT FINDINGS

In the realm of new high-density lipoprotein-raising therapies, there is a strong focus on high-density lipoprotein metabolism and the reverse cholesterol transport pathway. Several infusions of recombinant apoA-I Milano/phospholipid complexes appeared to reduce atheroma volume as measured by intravascular ultrasound. Both intravenous and oral apoA-I mimetic peptides are in early clinical trials. Next generation PPAR-alpha agonists are more potent at high-density lipoprotein-raising than currently available fibrates, and dual PPAR-alpha/PPAR-gamma agonists are under investigation to help correct atherogenic dyslipidemia seen in many diabetics. Two small molecule inhibitors of the cholesteryl ester transfer protein have shown promise in clinical trials at substantially raising high-density lipoprotein cholesterol.

SUMMARY

Larger scale clinical trials, including those with additional surrogate outcome measures as well as cardiovascular event outcomes are needed to further assess the benefit of newer high-density lipoprotein-raising therapies. Additional therapeutics are currently in development that target other parts of the reverse cholesterol transport pathway and, in addition to providing new potential pharmaceuticals, will help to further elucidate the atheroprotective mechanisms of high-density lipoprotein cholesterol.

Coronary heart disease and polymorphisms in genes affecting lipid metabolism and inflammation

Several biologic systems contribute to the pathophysiology of atherosclerosis and its complications, and within each of these systems many genes have been explored to establish the possible implication of their variability in coronary heart disease (CHD) risk. This report is focused on recent results pertaining to lipid and inflammatory genes, their variability, and their relationship with intermediate phenotypes and CHD. For both systems, there is no evidence at the present time that testing genetic polymorphisms might be of any benefit to the patient, for the diagnosis or prognosis of CHD, or for tailoring drug prescription. Understanding the genetics of complex traits like CHD will require a system approach that allows a modeling of the interaction among genes as well as between genetic and nongenetic sources of variation.

Serum Levels of Type II Secretory Phospholipase A2 and the Risk of Future Coronary Artery Disease in Apparently Healthy Men and Women

OBJECTIVES

To study the prospective relationship between serum levels of type II secretory phospholipase A2 (sPLA2) and the risk of future coronary artery disease (CAD) in apparently healthy men and women.

METHODS AND RESULTS

We conducted a prospective nested case-control study among apparently healthy men and women aged 45 to 79 years. Cases (n=1105) were people in whom fatal or nonfatal CAD developed during follow-up. Controls (n=2209) were matched by age, sex, and enrollment time. sPLA2 levels were significantly higher in cases than controls (9.5 ng/mL; interquartile range [IQR], 6.4 to 14.8 versus 8.3 ng/mL; IQR, 5.8 to 12.6; P<0.0001). sPLA2 plasma levels significantly correlated with age, body mass index, systolic blood pressure, high-density lipoprotein (HDL) cholesterol levels, and C-reactive protein (CRP) levels. Taking into account matching for sex and age and adjusting for body mass index, smoking, diabetes, systolic blood pressure, low-density lipoprotein cholesterol, HDL cholesterol, and CRP levels, the risk of future CAD was 1.34 (1.02 to 1.71; P=0.02) for people in the highest sPLA2 quartile, compared with those in the lowest (P for linearity=0.03).

CONCLUSIONS

Elevated levels of sPLA2 were associated with an increased risk of future CAD in apparently healthy individuals. The magnitude of the association was similar to that observed between CRP and CAD risk, and both associations were independent.

Raising high-density lipoprotein cholesterol: Innovative strategies against an old adversary

The lipid hypothesis, which was proposed over 100 years ago, is based on the premise that dyslipidemia is central to the process of atherosclerosis. Low-density lipoprotein and lipoprotein(a) are clearly atherogenic, whereas the role of very low-density lipoprotein as an independent factor is controversial. The only lipoprotein that is clearly antiatherogenic is high-density lipoprotein (HDL), which is thought to reduce coronary risk by mediating cholesterol efflux from the periphery by way of transportation to the liver for excretion. Traditionally, fibric acid derivatives and nicotinic acid were the major pharmacologic agents used to raise circulating levels of HDL. Recent therapeutic advances have been made in the ability to increase HDL. Apolipoprotein A-I Milano and cholesterol ester transfer protein represent novel approaches to the pharmacologic therapy of individuals with low HDL levels. The mechanisms and clinical implications of these interventions are discussed here.

Cholesteryl ester transfer protein TaqIB variant, high-density lipoprotein cholesterol levels, cardiovascular risk, and efficacy of pravastatin treatment: individual patient meta-analysis of 13,677 subjects

BACKGROUND

Several studies have reported that the cholesteryl ester transfer protein (CETP) TaqIB gene polymorphism is associated with HDL cholesterol (HDL-C) levels and the risk of coronary artery disease (CAD), but the results are inconsistent. In addition, an interaction has been implicated between this genetic variant and pravastatin treatment, but this has not been confirmed.

METHODS AND RESULTS

A meta-analysis was performed on individual patient data from 7 large, population-based studies (each >500 individuals) and 3 randomized, placebo-controlled, pravastatin trials. Linear and logistic regression models were used to assess the relation between TaqIB genotype and HDL-C levels and CAD risk. After adjustment for study, age, sex, smoking, body mass index (BMI), diabetes, LDL-C, use of alcohol, and prevalence of CAD, TaqIB genotype exhibited a highly significant association with HDL-C levels, such that B2B2 individuals had 0.11 mmol/L (0.10 to 0.12, P<0.0001) higher HDL-C levels than did B1B1 individuals. Second, after adjustment for study, sex, age, smoking, BMI, diabetes, systolic blood pressure, LDL-C, and use of alcohol, TaqIB genotype was significantly associated with the risk of CAD (odds ratio=0.78 [0.66 to 0.93]) in B2B2 individuals compared with B1B1 individuals (P for linearity=0.008). Additional adjustment for HDL-C levels rendered a loss of statistical significance (P=0.4). Last, no pharmacogenetic interaction between TaqIB genotype and pravastatin treatment could be demonstrated.

CONCLUSIONS

The CETP TaqIB variant is firmly associated with HDL-C plasma levels and as a result, with the risk of CAD. Importantly, this CETP variant does not influence the response to pravastatin therapy.

Role of CETP inhibitors in the treatment of dyslipidemia

PURPOSE OF REVIEW

This review summarizes novel human data on cholesteryl ester-transfer protein (CETP) and atherosclerosis and the possible use of CETP inhibitors in the treatment of dyslipidemia. In addition, it will underline that therapeutic targeting of the high-density lipoprotein (HDL) metabolism entails more than simply observing changes in cholesterol levels of this lipoprotein.

RECENT FINDINGS

Two pharmacological small-molecule inhibitors of CETP, JTT-705 and torcetrapib, have recently been shown to effectively raise HDL cholesterol in humans without serious side effects when either used as a monotherapy or combined with statins that lower low-density lipoprotein cholesterol. Importantly, prospective data from the Epic-Norfolk study furthermore indicate that elevated CETP concentration in conjunction with elevated triglyceride levels are associated with increased odds for cardiovascular events. Data from the Diabetic Atherosclerosis Intervention Study furthermore show that elevated CETP concentration is associated with increased progression of coronary atherosclerosis in patients with type 2 diabetes who use fenofibrate.

SUMMARY

Long-term studies will have to show whether CETP inhibition decreases the risk of atherosclerotic disease in dyslipidemic patients. Increased CETP activity might be detrimental under hypertriglyceridemic conditions which is of importance when considering that a large proportion of patients at increased risk from coronary artery disease exhibit elevated triglyceride levels. Studies into the effects of CETP inhibition in hypertriglyceridemic patients therefore seem warranted. Awaiting the first data on the effect of CETP inhibition on surrogate endpoints for atherosclerosis, this review furthermore outlines that the complexity of HDL metabolism will necessitate a wide variety of studies on many aspects of this intriguing lipoprotein.