Safety and efficacy of dalcetrapib on atherosclerotic disease using novel non-invasive multimodality imaging (dal-PLAQUE): a randomised clinical trial

Molecular imaging of atherosclerosis for improving diagnostic and therapeutic development

Despite recent progress, cardiovascular and allied metabolic disorders remain a worldwide health challenge. We must identify new targets for therapy, develop new agents for clinical use, and deploy them in a clinically effective and cost-effective manner. Molecular imaging of atherosclerotic lesions has become a major experimental tool in the last decade, notably by providing a direct gateway to the processes involved in atherogenesis and its complications. This review summarizes the current status of molecular imaging approaches that target the key processes implicated in plaque formation, development, and disruption and highlights how the refinement and application of such tools might aid the development and evaluation of novel therapeutics.

Established and emerging approaches for the management of dyslipidaemia

The key role of dyslipidaemia in determining cardiovascular disease (CVD) has been proved beyond reasonable doubt, and therefore several dietary and pharmacological approaches have been developed. The discovery of statins has provided a very effective approach in reducing cardiovascular risk as documented by the results obtained in clinical trials and in clinical practice. The current efficacy of statins or other drugs, however, comes short of providing the benefit that could derive from a further reduction of LDL cholesterol (LDL-C) in high-risk and very high risk patients. Furthermore, experimental data clearly suggest that other lipoprotein classes beyond LDL play important roles in determining cardiovascular risk. For these reasons a number of new potential drugs are under development in this area. Aim of this review is to discuss the available and the future pharmacological strategies for the management of dyslipidemia.

Clinical value of drugs targeting inflammation for the management of coronary artery disease

Atherosclerosis and cardiovascular disease are the leading cause of death worldwide. Atherosclerosis is a complex inflammatory disease that results from lipid accumulation and oxidation in the arterial wall combined with an active inflammatory reaction involving transmigration of monocytes and other inflammatory cells from the blood stream into the vessel wall. Many therapeutic approaches have been tested to treat atherosclerosis and prevent its complications, with statins being the most efficient therapy by reducing the levels of atherogenic lipoproteins and preventing major cardiovascular events. However, the risk of atherothrombotic complications still remains high, causing millions of deaths around the world each year. Extensive research has shed light on the cascade of cellular and molecular events that lead from atherosclerotic plaque formation to its rupture and have highlighted promising new therapeutic targets, each being implicated at different stages of the atherosclerotic plaque formation and progression. In this review, we briefly discuss the potential of high-density lipoprotein-based therapies, given the anti-inflammatory properties of high-density lipoprotein. We then present different approaches that tackle inflammation, including inhibition of 5-lipoxygenase, blockade of P-selectin, use of a viral-derived serpin, and interleukin-1β inhibition. All these targets have shown encouraging results in clinical trials and support the idea that targeting inflammation could reduce cardiovascular complications in patients with coronary artery disease.

Diet intervention reduces uptake of αvβ3 integrin-targeted PET tracer 18F-galacto-RGD in mouse atherosclerotic plaques

BACKGROUND

Expression of α(v)β(3) integrin has been proposed as a marker for atherosclerotic lesion inflammation. We studied whether diet intervention reduces uptake of α(v)β(3) integrin-targeted positron emission tomography tracer (18)F-galacto-RGD in mouse atherosclerotic plaques.

METHODS AND RESULTS

Hypercholesterolemic LDLR(-/-) ApoB(100/100) mice on high-fat diet for 4 months were randomized to further 3 months on high-fat diet (high-fat group, n = 8) or regular mouse chow (intervention group, n = 7). Intima-media ratio describing plaque burden was comparable between intervention and high-fat groups (2.0 ± 0.5 vs 2.3 ± 0.8, P = .5). Uptake of (18)F-galacto-RGD in the aorta was lower in the intervention than high-fat group (%ID/g 0.16 vs 0.23, P < .01). Autoradiography showed 35% lower uptake of (18)F-galacto-RGD in the atherosclerotic plaques in the intervention than high-fat group (P = .007). Uptake of (18)F-galacto-RGD in plaques correlated with uptake of (3)H-deoxyglucose and nuclear density, which was lower in the intervention than high-fat group (P = .01). Flow cytometry demonstrated macrophages expressing α(v) and β(3) integrins in the aorta.

CONCLUSIONS

Uptake of (18)F-galacto-RGD in mouse atherosclerotic lesions was reduced by lipid-lowering diet intervention. Expression of α(v)β(3) integrin is a potential target for evaluation of therapy response in atherosclerosis.

HDL functionality

PURPOSE OF REVIEW

HDL cholesterol concentration is inversely correlated with cardiovascular disease and has a wide range of functions involved in many systems. The purpose of this review is to summarize HDL functionality, its relevance to atherosclerosis and factors affecting HDL functions.

RECENT FINDINGS

The contribution of HDL to reverse cholesterol transport may not be as great as first envisaged. However, it still plays an important role in cholesterol efflux from peripheral tissues. The capacity of HDL to promote cellular cholesterol efflux in an ex-vivo model has been reported to correlate more closely with carotid intima-media thickness than HDL cholesterol concentration. Recently, a variety of other functions of HDL have been described including antimicrobial, antioxidant, antiglycation, anti-inflammatory, nitric oxide--inducing, antithrombotic and antiatherogenic activity and immune modulation as well as a potential role in glucose homeostasis, diabetes pathophysiology and complications.

SUMMARY

HDL has a wide range of functions some of which are independent of its cholesterol content. Its cargo of apolipoproteins, various proteins and phospholipids contributes most to its various functions. These functions are affected by a number of genetic, physiological and pathological factors.

Rationale for cholesteryl ester transfer protein inhibition

PURPOSE OF REVIEW

Raising HDL cholesterol (HDL-C) has become an attractive therapeutic target to lower cardiovascular risk in addition to statins. Inhibition of the cholesteryl ester transfer protein (CETP), which mediates the transfer of cholesteryl esters from HDL to apolipoprotein B-containing particles, leads to a substantial increase in HDL-C levels. Various CETP inhibitors are currently being evaluated in phase II and phase III clinical trials. However, the beneficial effect of CETP inhibition on cardiovascular outcome remains to be established.

RECENT FINDINGS

Torcetrapib, the first CETP inhibitor tested in a phase III clinical trial (ILLUMINATE), failed in 2006 because of an increase in all-cause mortality and cardiovascular events that subsequently were attributed to nonclass-related off-target effects (particularly increased blood pressure and low serum potassium) related to the stimulation of aldosterone production. Anacetrapib, another potent CETP inhibitor, raises HDL-C levels by approximately 138% and decreases LDL cholesterol (LDL-C) levels by approximately 40%, without the adverse off-targets effects of torcetrapib (DEFINE study). The CETP modulator dalcetrapib raises HDL-C levels by approximately 30% (with only minimal effect on LDL-C levels) and proved safety in the dal-VESSEL and dal-PLAQUE trials involving a total of nearly 600 patients. Evacetrapib, a relatively new CETP inhibitor, exhibited favorable changes in the lipid profile in a phase II study.

SUMMARY

The two ongoing outcome trials, dal-OUTCOMES (dalcetrapib) and REVEAL (anacetrapib), will provide more conclusive answers for the concept of reducing cardiovascular risk by raising HDL-C with CETP inhibition.

Current imaging modalities for atherosclerosis

Atherosclerotic disease is responsible for nearly half of all deaths in the western world. During the past three decades, considerable efforts have been made towards detection and assessment of atherosclerosis plaques in various vascular beds using different imaging techniques. Recently, both noninvasive and invasive modalities have frequently been used to refine cardiovascular risk assessment in high-risk individuals, to evaluate the natural history of atheroma burden and to reveal the impact of anti-atherosclerotic medical therapies on disease progression. In this review, we provide an overview of the currently available imaging modalities. This article will underscore arterial wall imaging to assess the impact of medical therapies on atherosclerosis and to develop the effective therapeutic strategies, resulting in the prevention of cardiovascular complications.

Arterial inflammation in patients with HIV

CONTEXT

Cardiovascular disease is increased in patients with human immunodeficiency virus (HIV), but the specific mechanisms are unknown.

OBJECTIVE

To assess arterial wall inflammation in HIV, using 18fluorine-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET), in relationship to traditional and nontraditional risk markers, including soluble CD163 (sCD163), a marker of monocyte and macrophage activation.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study of 81 participants investigated between November 2009 and July 2011 at the Massachusetts General Hospital. Twenty-seven participants with HIV without known cardiac disease underwent cardiac 18F-FDG-PET for assessment of arterial wall inflammation and coronary computed tomography scanning for coronary artery calcium. The HIV group was compared with 2 separate non-HIV control groups. One control group (n = 27) was matched to the HIV group for age, sex, and Framingham risk score (FRS) and had no known atherosclerotic disease (non-HIV FRS-matched controls). The second control group (n = 27) was matched on sex and selected based on the presence of known atherosclerotic disease (non-HIV atherosclerotic controls).

MAIN OUTCOME MEASURE

Arterial inflammation was prospectively determined as the ratio of FDG uptake in the arterial wall of the ascending aorta to venous background as the target-to-background ratio (TBR).

RESULTS

Participants with HIV demonstrated well-controlled HIV disease (mean [SD] CD4 cell count, 641 [288] cells/μL; median [interquartile range] HIV-RNA level, <48 [<48 to <48] copies/mL). All were receiving antiretroviral therapy (mean [SD] duration, 12.3 [4.3] years). The mean FRS was low in both HIV and non-HIV FRS-matched control participants (6.4; 95% CI, 4.8-8.0 vs 6.6; 95% CI, 4.9-8.2; P = .87). Arterial inflammation in the aorta (aortic TBR) was higher in the HIV group vs the non-HIV FRS-matched control group (2.23; 95% CI, 2.07-2.40 vs 1.89; 95% CI, 1.80-1.97; P < .001), but was similar compared with the non-HIV atherosclerotic control group (2.23; 95% CI, 2.07-2.40 vs 2.13; 95% CI, 2.03-2.23; P = .29). Aortic TBR remained significantly higher in the HIV group vs the non-HIV FRS-matched control group after adjusting for traditional cardiovascular risk factors (P = .002) and in stratified analyses among participants with undetectable viral load, zero calcium, FRS of less than 10, a low-density lipoprotein cholesterol level of less than 100 mg/dL (<2.59 mmol/L), no statin use, and no smoking (all P ≤ .01). Aortic TBR was associated with sCD163 level (P = .04) but not with C-reactive protein (P = .65) or D-dimer (P = .08) among patients with HIV.

CONCLUSION

Participants infected with HIV vs noninfected control participants with similar cardiac risk factors had signs of increased arterial inflammation, which was associated with a circulating marker of monocyte and macrophage activation.

Progression of experimental lesions of atherosclerosis: assessment by kinetic modeling of black-blood dynamic contrast-enhanced MRI

Pharmacokinetic modeling of dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) is used to noninvasively characterize neovasculature and inflammation in atherosclerotic vessels by estimating perfusion characteristics, such as fractional plasma volume vp and transfer constant Ktrans. DCE-MRI has potential to study the evolution of nascent lesions involving early pathological changes. However, currently used bright-blood DCE-MRI approaches are difficult to apply to small lesions because of the difficulty in separating the signal in the thin vessel wall from the adjacent lumen. By suppressing the lumen signal, black-blood DCE-MRI techniques potentially provide a better tool for early atherosclerotic lesion assessment. However, whether black-blood DCE-MRI can detect temporal changes in physiological kinetic parameters has not been investigated for atherosclerosis. This study of balloon-injured New Zealand White rabbits used a reference-region-based pharmacokinetic model of black-blood DCE-MRI to evaluate temporal changes in early experimental atherosclerotic lesions of the abdominal aorta. Six rabbits were imaged at 3 and 6 months after injury. Ktrans was found to increase from 0.10±0.03 min(-1) to 0.14±0.05 min(-1) (P=0.01). In histological analysis of all twelve rabbits, Ktrans showed a significant correlation with macrophage content (R=0.70, P=0.01). These results suggest black-blood DCE-MRI and a reference-region kinetic model could be used to study plaque development and therapeutic response in vivo.

Recent clinical studies of the effects of lipid-modifying therapies

Results from multiple clinical trials, primarily with the class of lipid-lowering agents known as statins, have shown that reductions in low-density lipoprotein (LDL) cholesterol are associated with reduced risk of coronary artery disease. Although LDL cholesterol is the primary target of cholesterol management strategies, increasing attention has focused on the role of inflammation, high-density lipoprotein cholesterol, and triglycerides in atherosclerosis and cardiovascular disease. We review major trials with lipid-modifying therapies published since the 2004 update of the Adult Treatment Panel (ATP) III guidelines. A pivotal trial was the Justification for the Use of Statins in Primary Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER), which demonstrated significant reductions in cardiovascular morbidity and mortality in healthy individuals without elevated LDL cholesterol but with high levels of the inflammatory marker high-sensitivity C-reactive protein. Additional trials demonstrated the efficacy of intensive statin therapy in secondary prevention, whereas other agents, including fibrates, omega-3 fatty acids, niacin, ezetimibe, and experimental cholesteryl ester transfer protein inhibitors, have been evaluated for their ability to reduce residual cardiovascular risk.

An update on the clinical development of dalcetrapib (RO4607381), a cholesteryl ester transfer protein modulator that increases HDL cholesterol levels

CETP is the target of CETP inhibitors such as anacetrapib and the modulator dalcetrapib. Both molecules have entered Phase III clinical trials, with the ultimate goal of reducing cardiovascular events by raising HDL cholesterol. At the 600-mg dose selected for the dal-OUTCOMES study, dalcetrapib is expected to inhibit CETP activity by approximately 30% and raise HDL-C by approximately 30% with limited effects on LDL cholesterol. Importantly, dalcetrapib does not raise blood pressure or aldosterone levels, two effects previously associated with the CETP inhibitor torcetrapib. Dalcetrapib has been well tolerated at the 600-mg dose. In the dal-PLAQUE atherosclerosis imaging study, dalcetrapib reduced the enlargement of total vessel area over time. In May 2012, following the results of the second interim analysis of dal-OUTCOMES, the Data and Safety Monitoring Board recommended stopping the study owing to a lack of clinically significant benefit, which was followed by Roche’s (Basel, Switzerland) decision to terminate the study and the dalcetrapib program (dal-HEART). Contrary to anacetrapib, a potent CETP inhibitor that markedly increases HDL cholesterol and significantly reduces LDL cholesterol, dalcetrapib has allowed us to test the hypothesis that an isolated, moderate elevation in HDL cholesterol prevents cardiovascular events.

Nuclear perfusion imaging for functional evaluation of patients with known or suspected coronary artery disease: the future is now

Nuclear imaging, with both single-photon emission computed tomography and PET, has a well-established role in the assessment of patients with known or suspected coronary artery disease. There is a large body of evidence regarding the diagnostic accuracy and prognostic value of these modalities, however, they continue to evolve rapidly with advances in camera and tracer technology, as well as changes in imaging protocols to increase lab efficiency, improve image quality and to decrease radiation exposure to patients. Nuclear imaging also provides insights into atherogenesis at a molecular level and can be combined with other imaging modalities, providing both functional and structural data and complimentary information on the presence of coronary disease and its functional implications.

Cardiovascular defense challenges at the basic, clinical, and population levels

Cardiovascular disease (CVD) is now the leading cause of mortality worldwide. Particularly in low and middle income countries, rapid urbanization and secondary factors, such as increasing obesity, poor diet, and lack of exercise, have combined to propel CVD into this position. Given the enormous scope of this problem and the complex cultural, societal, and political issues that are involved, an equally sophisticated and multipronged approach is required to combat CVD at the global level. In this review, we outline the basic, clinical, and population level challenges that we face in defending ourselves against this disease.

Dalcetrapib , a cholesteryl ester transfer protein modulator

INTRODUCTION

Cholesteryl ester transfer protein (CETP) plays an important role in reverse cholesterol transport by transferring cholesteryl esters from high-density lipoprotein (HDL) to the apolipoprotein B-containing lipoproteins. Inhibition of CETP is a target to increase HDL-cholesterol and potentially reduce atherosclerosis. Dalcetrapib is an orally administered CETP inhibitor developed for the treatment of primary hypercholesterolaemia and mixed hyperlipidaemia.

AREAS COVERED

AREAS COVERED are: mode of action, preclinical development and clinical trials of dalcetrapib, a CETP modulator. The article provides an understanding of the pharmacokinetic and pharmacodynamic characteristics of dalcetrapib and insight into its clinical efficacy and safety. In clinical trials, dalcetrapib produced significant elevations in HDL-cholesterol when taken alone or in combination with statin with no effect on blood pressure or expression of genes involved in the renin-angiotensin-aldosterone system.

EXPERT OPINION

Although dalcetrapib is the least potent CETP inhibitor, it does not impair the formation of CETP-induced pre-β HDL, which might be needed to increase reverse cholesterol transport. While dalcetrapib is well-tolerated and does not show major side effects, the recent interim results of the Phase III dal-OUTCOMES trial have shown the lack of a clinically meaningful benefit, and further testing of the drug has been halted.

Non-FDG imaging of atherosclerosis: will imaging of MMPs assess plaque vulnerability?

Acute ruptures of atherosclerotic plaques with subsequent occlusion account for the vast majority of clinical events such as myocardial infarction or stroke. New imaging approaches focusing on the visualization of inflammation in the vessel wall could emerge as tools for individualized risk assessment and prevention of events. To this end, PET employing (18)F-fluorodeoxyglucose (FDG) has recently been introduced for the first clinical trials. Although this approach nicely visualizes plaques inflammation questions remain with respect to if and how this inflammatory signal can be employed for predicting individual plaque rupture. Molecular imaging of proteases such as matrix-metalloproteinases (MMPs) involved in several steps in plaque progression driving plaques into vulnerable, rupture-prone states seems a promising alternative approach. This review introduces and discusses the vulnerable plaque concept, animal models with human-like plaque ruptures and the potential of a FDG versus a non-FDG MMP-targeted strategy to image rupture-prone plaques.

Cholesteryl ester transfer protein inhibition as a strategy to reduce cardiovascular risk

Human and rabbit plasma contain a cholesteryl ester transfer protein (CETP) that promotes net mass transfers of cholesteryl esters from high density lipoproteins (HDL) to other plasma lipoprotein fractions. As predicted, inhibition of CETP in both humans and rabbits increases the concentration of cholesterol in the potentially protective HDL fraction, while decreasing it in potentially proatherogenic non-HDL fractions. Inhibition of CETP in rabbits also inhibits the development of diet-induced atherosclerosis. However, use of the CETP inhibitor torcetrapib in humans did not reduce atheroma in three imaging trials and caused an excess of deaths and cardiovascular events in a large clinical outcome trial. The precise explanation for the harm caused by torcetrapib is unknown but may relate to documented, potentially harmful effects unrelated to inhibition of CETP. More recently, a trial using the weak CETP inhibitor dalcetrapib, which raises HDL levels less effectively than torcetrapib and does not lower non-HDL lipoprotein levels, was terminated early for reasons of futility. There was no evidence that dalcetrapib caused harm in that trial. Despite these setbacks, the hypothesis that CETP inhibitors will be antiatherogenic in humans is still being tested in studies with anacetrapib and evacetrapib, two CETP inhibitors that are much more potent than dalcetrapib and that do not share the off-target adverse effects of torcetrapib.

Cholesteryl ester transfer-protein modulator and inhibitors and their potential for the treatment of cardiovascular diseases

Elevated low-density lipoprotein (LDL) cholesterol and lowered high-density lipoprotein (HDL) cholesterol are important risk factors for cardiovascular disease. Accordingly, raising HDL cholesterol induced by cholesteryl ester transfer protein (CETP) inhibition is an attractive approach for reducing the residual risk of cardiovascular events that persist in many patients receiving low-density LDL cholesterol-lowering therapy with statins. The development of torcetrapib, a CETP inhibitor, was terminated due to its adverse cardiovascular effects. These adverse effects did not influence the mechanism of CETP inhibition, but affected the molecule itself. Therefore a CETP modulator, dalcetrapib, and a CETP inhibitor, anacetrapib, are in Phase III of clinical trials to evaluate their effects on cardiovascular outcomes. In the dal-VESSEL (dalcetrapib Phase IIb endothelial function study) and the dal-PLAQUE (safety and efficacy of dalcetrapib on atherosclerotic disease using novel non-invasive multimodality imaging) clinical studies, dalcetrapib reduced CETP activity by 50% and increased HDL cholesterol levels by 31% without changing LDL cholesterol levels. Moreover, dalcetrapib was associated with a reduction in carotid vessel-wall inflammation at 6 months, as well as a reduced vessel-wall area at 24 months compared with the placebo. In the DEFINE (determining the efficacy and tolerability of CETP inhibition with anacetrapib) clinical study, anacetrapib increased HDL cholesterol levels by 138% and decreased LDL cholesterol levels by 36%. In contrast with torcetrapib, anacetrapib had no adverse cardiovascular effects. The potential of dalcetrapib and anacetrapib in the treatment of cardiovascular diseases will be revealed by two large-scale clinical trials, the dal-OUTCOMES (efficacy and safety of dalcetrapib in patients with recent acute coronary syndrome) study and the REVEAL (randomized evaluation of the effects of anacetrapib through lipid modification, a large-scale, randomized placebo-controlled trial of the clinical effects of anacetrapib among people with established vascular disease) study. The dal-OUTCOMES study is testing whether dalcetrapib can reduce cardiovascular events and the REVEAL study is testing whether anacetrapib can reduce cardiovascular events. These reports are expected to be released by 2013 and 2017, respectively.

Coronary arterial 18F-sodium fluoride uptake: a novel marker of plaque biology

OBJECTIVES

With combined positron emission tomography and computed tomography (CT), we investigated coronary arterial uptake of 18F-sodium fluoride (18F-NaF) and 18F-fluorodeoxyglucose (18F-FDG) as markers of active plaque calcification and inflammation, respectively.

BACKGROUND

The noninvasive assessment of coronary artery plaque biology would be a major advance particularly in the identification of vulnerable plaques, which are associated with specific pathological characteristics, including micro-calcification and inflammation.

METHODS

We prospectively recruited 119 volunteers (72 ± 8 years of age, 68% men) with and without aortic valve disease and measured their coronary calcium score and 18F-NaF and 18F-FDG uptake. Patients with a calcium score of 0 were used as control subjects and compared with those with calcific atherosclerosis (calcium score >0).

RESULTS

Inter-observer repeatability of coronary 18F-NaF uptake measurements (maximum tissue/background ratio) was excellent (intra-class coefficient 0.99). Activity was higher in patients with coronary atherosclerosis (n = 106) versus control subjects (1.64 ± 0.49 vs. 1.23 ± 0.24; p = 0.003) and correlated with the calcium score (r = 0.652, p < 0.001), although 40% of those with scores >1,000 displayed normal uptake. Patients with increased coronary 18F-NaF activity (n = 40) had higher rates of prior cardiovascular events (p = 0.016) and angina (p = 0.023) and higher Framingham risk scores (p = 0.011). Quantification of coronary 18F-FDG uptake was hampered by myocardial activity and was not increased in patients with atherosclerosis versus control subjects (p = 0.498).

CONCLUSIONS

18F-NaF is a promising new approach for the assessment of coronary artery plaque biology. Prospective studies with clinical outcomes are now needed to assess whether coronary 18F-NaF uptake represents a novel marker of plaque vulnerability, recent plaque rupture, and future cardiovascular risk. (An Observational PET/CT Study Examining the Role of Active Valvular Calcification and Inflammation in Patients With Aortic Stenosis; NCT01358513).

Cardiovascular molecular imaging: the road ahead

Despite significant advancements in medical and device-based therapies, cardiovascular disease remains the number one cause of death in the United States. Early detection of atherosclerosis, prevention of myocardial infarction and sudden cardiac death, and modulation of adverse ventricular remodeling still remain elusive goals. Molecular imaging focuses on identifying critical cellular and molecular targets and therefore plays an integral role in understanding these biologic processes in vivo. Because many imaging targets are upregulated before irreversible tissue damage occurs, early detection could ultimately lead to development of novel, preventive therapeutic strategies. This review addresses recent work on radionuclide imaging of cardiovascular inflammation, infection, and infarct healing. We further discuss opportunities provided by multimodality approaches such as PET/MRI and PET/optical imaging.

Constitutive inhibition of plasma CETP by apolipoprotein C1 is blunted in dyslipidemic patients with coronary artery disease

Plasma cholesteryl ester transfer protein (CETP) promotes the cholesterol enrichment of apoB-containing lipoproteins (VLDL and LDL) at the expense of HDL. Recent studies demonstrated that apoC1 is a potent CETP inhibitor in plasma of healthy, normolipidemic subjects. Our goal was to establish whether the modulation of CETP activity by apoC1 is influenced by dyslipidemia in patients with documented coronary artery disease (CAD). In the total CAD population studied (n = 240), apoC1 levels correlated negatively with CETP activity, independently of apoE-epsilon, CETP-Taq1B, and apoC1-Hpa1 genotypes. In multivariate analysis, the negative relationship was observed only in normolipidemic patients, not in those with hypercholesterolemia, hypertriglyceridemia, or combined hyperlipidemia. In the normolipidemic subjects, apoC1 levels were positively associated with higher HDL- to LDL-cholesterol ratio (r = 0.359, P < 0.001). It is concluded that apoC1 as a CETP inhibitor no longer operates on cholesterol redistribution in high-risk patients with dyslipidemia, probably due to increasing amounts of VLDL-bound apoC1, which is inactive as a CETP inhibitor. Patients with dyslipidemia could experience major benefits from treatment with pharmacological CETP inhibitors, which might compensate for blunted endogenous inhibition.

Molecular mechanisms of vascular effects of High-density lipoprotein: alterations in cardiovascular disease

Low high-density lipoprotein (HDL)-cholesterol levels are associated with an increased risk of coronary artery disease (CAD) and myocardial infarction, which has triggered the hypothesis that HDL, in contrast to low-density lipoprotein (LDL), acts as an anti-atherogenic lipoprotein. Moreover, experimental studies have identified potential anti-atherogenic properties of HDL, including promotion of macrophage cholesterol efflux and direct endothelial-protective effects of HDL, such as stimulation of endothelial nitric oxide production and repair, anti-apoptotic, anti-inflammatory and anti-thrombotic properties. Studies in gene-targeted mice, however, have also indicated that increasing HDL-cholesterol plasma levels can either limit (e.g. apolipoprotein A-I) or accelerate (e.g. Scavenger receptor class B type I) atherosclerosis. Moreover, vascular effects of HDL have been observed to be heterogenous and are altered in patients with CAD or diabetes, a condition that has been termed 'HDL dysfunction'. These alterations in biological functions of HDL may need to be taken into account for HDL-targeted therapies and considering raising of HDL-cholesterol levels alone is likely not sufficient in this respect. It will therefore be important to further determine, which biological functions of HDL are critical for its anti-atherosclerotic properties, as well as how these can be measured and targeted.

New lipid-lowering drugs: an update

Lipid lowering is established as a proven intervention to reduce atherosclerosis and its complications. Statins form the basis of care but are not able to treat all aspects of dyslipidaemia. Many novel therapeutic compounds are being developed. These include additional therapeutics for low-density lipoprotein cholesterol, for example, thyroid mimetics (thyroid receptor beta-agonists), antisense oligonucleotides or microsomal transfer protein inhibitors (MTPI); triglycerides, for example, novel peroxosimal proliferator activating receptors agonists, MTPIs, diacylglycerol acyl transferase-1 inhibitors and high-density lipoprotein cholesterol (HDL-C), for example, mimetic peptides; HDL delipidation strategies and cholesterol ester transfer protein inhibitors and modulators of inflammation, for example, phospholipase inhibitors. Gene therapy for specific rare disorders, for example, lipoprotein lipase deficiency using alipogene tiparvovec is also in clinical trials. Lipid-lowering drugs are likely to prove a fast-developing area for novel treatments as possible synergies exist between new and established compounds for the treatment of atherosclerosis.

Non-invasive imaging of atherosclerosis

Atherosclerosis is an inflammatory disease that causes most myocardial infarctions, strokes, and acute coronary syndromes. Despite the identification of multiple risk factors and widespread use of drug therapies, it still remains a global health concern with associated costs. It is well known that the risks of atherosclerotic plaque rupture are not well correlated with stenosis severity. Lumenography has a central place for defining the site and severity of vascular stenosis as a prelude to intervention for relief of symptoms due to blood flow limitation. Atherosclerosis develops within the arterial wall; this is not imaged by lumenography and hence it provides no information regarding underlying processes that may lead to plaque rupture. For this, we must rely on other imaging modalities such as ultrasound, computed tomography, magnetic resonance imaging, and nuclear imaging methods. These are capable of reporting on the underlying pathology, in particular the presence of inflammation, calcification, neovascularization, and intraplaque haemorrhage. Additionally, non-invasive imaging can now be used to track the effect of anti-atherosclerosis therapy. Each modality alone has positives and negatives and this review will highlight these, as well as speculating on future developments in this area.

Preclinical mouse models and methods for the discovery of the causes and treatments of atherosclerosis

INTRODUCTION

Atherosclerosis is the leading cause of death in the Western world. Despite huge advances in understanding its pathophysiological mechanisms, current treatment is mostly based on 'traditional' risk factors. The introduction of statins more than 20 years ago reduced morbidity and mortality of atherosclerosis by 30%, leaving a residual cardiovascular risk. Therefore, efforts continue toward the development of novel therapies that can be added to established treatments. Besides targeting dyslipidemia, recent focus has been put on preventing or resolving inflammatory processes involved in atherosclerosis.

AREAS COVERED

The article discusses therapeutic and diagnostic targets in atherosclerosis and how they can be discovered and studied in preclinical animal models. The roles of immune cells, specifically macrophages and monocytes, in plaque inflammation are discussed. The article also describes current preclinical models of atherosclerosis, specifically the mouse, study designs (for progression and regression studies), basic and advanced methods of analysis of atherosclerotic lesions, and discusses the challenges of translating the findings to humans.

EXPERT OPINION

Advances in genomics, proteomics, lipidomics and the development of high-throughput screening techniques help to improve our understanding of atherosclerosis disease mechanisms immensely and facilitate the discovery of new diagnostic and therapeutic targets. Preclinical studies in animals are still indispensable to uncover pathways involved in atherosclerotic disease and to evaluate novel drug targets. The translation of these targets, however, from animal studies to humans remains challenging. There is a strong need for novel biomarkers that can be used to prove the concept of a new target in humans.

HDL-cholesterol: perfection is the enemy of good?

An inverse relationship between the plasma concentration of high-density lipoprotein (HDL)-cholesterol and the risk of having a cardiovascular event has been shown in several epidemiologic studies. It is likely that this relationship is causal because HDL has several intrinsic properties that can potentially reverse atherosclerosis. However, this has not been conclusively shown in humans, and trying to achieve perfection with pharmacotherapy is possibly the enemy of good (ie, a healthy lifestyle). Patients with low HDL should be advised to change their lifestyle, including smoking cessation, weight reduction, and regular exercise.

Imaging the efficacy of anti-inflammatory liposomes in a rabbit model of atherosclerosis by non-invasive imaging

Nanomedicine can provide a potent alternative to current therapeutic strategies for atherosclerosis. For example, the encapsulation of anti-inflammatory drugs into liposomes improves their pharmacokinetics and biodistribution, thereby enhancing bioavailability to atherosclerotic plaques and improving therapeutic efficacy. The evaluation of this type of experimental therapeutics can greatly benefit from in vivo evaluation to assess biological changes, which can be performed by non-invasive imaging techniques, such as ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) and dynamic contrast enhanced magnetic resonance imaging (DCE-MRI). Here, we will illustrate the methods for inducing atherosclerosis in a rabbit model, the production of anti-inflammatory liposomes and monitoring of therapeutic efficacy of experimental therapeutics with the above-mentioned imaging techniques.

Lipids, blood pressure, kidney - what was new in 2011?

The year 2011 was very interesting regarding new studies, trials and guidelines in the field of lipidology, hypertensiology and nephrology. Suffice it to mention the new European Society of Cardiology (ESC)/European Atherosclerosis Society (EAS) guidelines on the management of dyslipidaemias, American College of Cardiology Foundation (ACCF)/American Heart Association (AHA) guidelines on hypertension in the elderly, and many important trials presented among others during the American Society of Nephrology (ASN) Annual Congress in Philadelphia and the AHA Annual Congress in Orlando. The paper is an attempt to summarize the most important events and reports in the mentioned areas in the passing year.