Search

Introduction: Green tea is associated with decreased risk for cardiovascular disease and stroke. Matcha is a special kind of powdered green tea known for its use in the Japanese tea ceremony. Due to its influence on lipoprotein parameters, it has been postulated to exert antiatherogenic effects. This study investigates whether it modulates the high-density lipoprotein (HDL) function and thereby influences the atherogenic process in an animal model with a strong influence on humans' situation., Methods and Results: After a pretreatment phase based on a standard diet, 10 female New Zealand White (NZW) rabbits are fed a high-fat diet for 20 weeks. The treatment group is additionally administered 1% matcha during the whole experiment. Long-term matcha treatment leads to lowered HDL cholesterol, impaired cholesterol transport manifested by reduced in vitro cholesterol efflux capacity, reduced cholesteryl ester transfer protein (CETP)-mediated cholesterol ester (CE) transfer between HDL and triglyceride-rich particles, and reduced macrophage-specific in vivo transfer, where ian increased absorption of cholesterol in the liver but a decreased secretion into bile is observed. Pulse wave velocity, assessed by nuclear magnetic resonance, is increased in matcha-treated animals, and a similar trend is observed for atherosclerotic lesion formation., Conclusion: Long-term matcha green tea treatment of hypercholesterolemic rabbits cause impaired reverse cholesterol transport and increased vascular stiffness, and susceptibility for atherosclerotic lesion development., (© 2021 The Authors. Molecular Nutrition & Food Research published by Wiley-VCH GmbH.)

Cholesterol-ester transfer protein (CETP) plays a role in atherosclerosis, the inflammatory response to endotoxemia and in experimental and human sepsis. Functional alterations in lipoprotein (LP) metabolism and immune cell populations, including macrophages, occur during sepsis and may be related to comorbidities such as chronic obstructive pulmonary disease (COPD). Macrophages are significantly associated with pulmonary emphysema, and depending on the microenvironment, might exhibit an M1 or M2 phenotype. Macrophages derived from the peritoneum and bone marrow reveal CETP that contributes to its plasma concentration. Here, we evaluated the role of CETP in macrophage polarization and elastase-induced pulmonary emphysema (ELA) in human CETP-expressing transgenic (huCETP) (line 5203, C57BL6/J background) male mice and compared it to their wild type littermates. We showed that bone marrow-derived macrophages from huCETP mice reduce polarization toward the M1 phenotype, but with increased IL-10. Compared to WT, huCETP mice exposed to elastase showed worsened lung function with an increased mean linear intercept (Lm), reflecting airspace enlargement resulting from parenchymal destruction with increased expression of arginase-1 and IL-10, which are M2 markers. The cytokine profile revealed increased IL-6 in plasma and TNF, and IL-10 in bronchoalveolar lavage (BAL), corroborating with the lung immunohistochemistry in the huCETP-ELA group compared to WT-ELA. Elastase treatment in the huCETP group increased VLDL-C and reduced HDL-C. Elastase-induced pulmonary emphysema in huCETP mice promotes lung M2-like phenotype with a deleterious effect in experimental COPD, corroborating the in vitro result in which CETP promoted M2 macrophage polarization. Our results suggest that CETP is associated with inflammatory response and influences the role of macrophages in COPD., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Santana, Righetti, Breda, Domínguez-Amorocho, Ramalho, Dantas, Nunes, Tibério, Soriano, Câmara, Quintão and Cazita.)

The cholesteryl ester transfer protein (CETP) system moves cholesteryl esters (CE) from high density lipoproteins (HDL) to lower density lipoproteins, i.e. very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) in exchange for triglycerides (TGs). This shuttle process will ultimately form complexes facilitating a bidirectional exchange of CE and TGs, the end process being CE delivery to catabolic sites. The CETP system is generally characteristic of higher animal species; lower species, not provided with this system, have higher and enlarged HDL enriched with apo E, suitable for tissue receptor interaction. Discovery of the CETP system has led to the development of agents interfering with CETP, thus elevating HDL-C and potentially preventing cardiovascular (CV) disease. Activation of CETP leads instead to reduced HDL-C levels, but also to an enhanced removal of CE from tissues. CETP antagonists are mainly small molecules (torcetrapib, anacetrapib, evacetrapib, dalcetrapib) and have provided convincing evidence of a HDL-C raising activity, but disappointing results in trials of CV prevention. In contrast, the CETP agonist probucol leads to HDL-C lowering followed by an increment of tissue cholesterol removal (reduction of xanthomas, xanthelasmas) and positive findings in secondary prevention trials. The drug has an impressive anti-inflammatory profile (markedly reduced interleukin-1β expression). Newer agents, some of natural origin, have additional valuable pharmacodynamic properties. The pharmacological approach to the CETP system remains enigmatic, although the failure of CETP antagonists has dampened enthusiasm. Studies on the system, a crossroad for any investigation on cholesterol metabolism, have however provided crucial contributions and will still be confronting any scientist working on CV prevention., (Copyright © 2018. Published by Elsevier B.V.)

The tubular lipid-binding (TULIP) superfamily has emerged in recent years as a major mediator of lipid sensing and transport in eukaryotes. It currently encompasses three protein families, SMP-like, BPI-like, and Takeout-like, which share a common fold. This fold consists of a long helix wrapped in a highly curved anti-parallel β-sheet, enclosing a central, lipophilic cavity. The SMP-like proteins, which include subunits of the ERMES complex and the extended synaptotagmins (E-Syts), appear to be mainly located at membrane contacts sites (MCSs) between organelles, mediating inter-organelle lipid exchange. The BPI-like proteins, which include the bactericidal/permeability-increasing protein (BPI), the LPS (lipopolysaccharide)-binding protein (LBP), the cholesteryl ester transfer protein (CETP), and the phospholipid transfer protein (PLTP), are either involved in innate immunity against bacteria through their ability to sense lipopolysaccharides, as is the case for BPI and LBP, or in lipid exchange between lipoprotein particles, as is the case for CETP and PLTP. The Takeout-like proteins, which are comprised of insect juvenile hormone-binding proteins and arthropod allergens, transport, where known, lipid hormones to target tissues during insect development. In all cases, the activity of these proteins is underpinned by their ability to bind large, hydrophobic ligands in their central cavity and segregate them away from the aqueous environment. Furthermore, where they are involved in lipid exchange, recent structural studies have highlighted their ability to establish lipophilic, tubular channels, either between organelles in the case of SMP domains or between lipoprotein particles in the case of CETP. Here, we review the current knowledge on the structure, versatile functions, and evolution of the TULIP superfamily. We propose a deep evolutionary split in this superfamily, predating the Last Eukaryotic Common Ancestor, between the SMP-like proteins, which act on lipids endogenous to the cell, and the BPI-like proteins (including the Takeout-like proteins of arthropods), which act on exogenous lipids. This article is part of a Special Issue entitled: The cellular lipid landscape edited by Tim P. Levine and Anant K. Menon., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Elevated plasma TGs increase risk of cardiovascular disease in women. Estrogen treatment raises plasma TGs in women, but molecular mechanisms remain poorly understood. Here we explore the role of cholesteryl ester transfer protein (CETP) in the regulation of TG metabolism in female mice, which naturally lack CETP. In transgenic CETP females, acute estrogen treatment raised plasma TGs 50%, increased TG production, and increased expression of genes involved in VLDL synthesis, but not in nontransgenic littermate females. In CETP females, estrogen enhanced expression of small heterodimer partner (SHP), a nuclear receptor regulating VLDL production. Deletion of liver SHP prevented increases in TG production and expression of genes involved in VLDL synthesis in CETP mice with estrogen treatment. We also examined whether CETP expression had effects on TG metabolism independent of estrogen treatment. CETP increased liver β-oxidation and reduced liver TG content by 60%. Liver estrogen receptor α (ERα) was required for CETP expression to enhance β-oxidation and reduce liver TG content. Thus, CETP alters at least two networks governing TG metabolism, one involving SHP to increase VLDL-TG production in response to estrogen, and another involving ERα to enhance β-oxidation and lower liver TG content. These findings demonstrate a novel role for CETP in estrogen-mediated increases in TG production and a broader role for CETP in TG metabolism., (Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.)

Lipoproteins play a key role in the development of CVD, but the dynamics of lipoprotein metabolism are difficult to address experimentally. This article describes a novel two-step combined in vitro and in silico approach that enables the estimation of key reactions in lipoprotein metabolism using just one blood sample. Lipoproteins were isolated by ultracentrifugation from fasting plasma stored at 4°C. Plasma incubated at 37°C is no longer in a steady state, and changes in composition may be determined. From these changes, we estimated rates for reactions like LCAT (56.3 µM/h), β-LCAT (15.62 µM/h), and cholesteryl ester (CE) transfer protein-mediated flux of CE from HDL to IDL/VLDL (21.5 µM/h) based on data from 15 healthy individuals. In a second step, we estimated LDL's HL activity (3.19 pools/day) and, for the very first time, selective CE efflux from LDL (8.39 µM/h) by relying on the previously derived reaction rates. The estimated metabolic rates were then confirmed in an independent group (n = 10). Although measurement uncertainties do not permit us to estimate parameters in individuals, the novel approach we describe here offers the unique possibility to investigate lipoprotein dynamics in various diseases like atherosclerosis or diabetes., (Copyright © 2016 by the American Society for Biochemistry and Molecular Biology, Inc.)

The cholesteryl ester transfer protein (CETP) plays a crucial role in high-density lipoprotein (HDL) metabolism. Genetic variants that alter CETP concentration may cause significant alterations in HDL-cholesterol (HDL-C) concentration. In this case-control study, we analyzed the genotype frequencies of CETP Taq1B polymorphisms in coronary artery disease patients (CAD; n=210) and controls (n=100). We analyzed the role of the CETP Taq1B variant in severity of CAD, and its association with plasma lipids and CETP concentration. DNA was extracted from 310 patients undergoing coronary angiography. The Taq1B polymorphism was genotyped using polymerase chain reaction-restriction fragment length polymorphism (RFLP) analysis. Lipid concentrations were measured by an auto analyzer and CETP level by a commercial enzyme-linked immunosorbent assay (ELISA) kit. In our study population, the B2 allele frequency was higher in control subjects than patients with single, double or triple vessel disease. B2B2 genotype carriers had a significantly higher high-density lipoprotein cholesterol (HDL-C) concentration than those with the B1B1 genotype in controls (51.93±9.47versus 45.34±9.93; p<0.05) and in CAD patients (45.52±10.81 versus 40.38±9.12; p<0.05). B2B2 genotype carriers had a significantly lower CETP concentration than those with the B1B1 genotype in controls (1.39±0.58 versus 1.88±0.83; p< 0.05) and in CAD patients (2.04±1.39versus 2.81±1.68; p< 0.05). Our data suggest that the B2 allele is associated with higher concentrations of HDL-C and lower concentrations of CETP, which confer a protective effect on coronary artery disease.

Cholesterol has been implicated in the pathogenesis of late-onset Alzheimer's disease (LOAD) and the cholesteryl ester transfer protein (CETP) is critical to cholesterol regulation within the cell, making CETP an Alzheimer's disease candidate gene. Several studies have suggested that CETP I405V (rs5882) is associated with cognitive function and LOAD risk, but findings vary and most studies have been conducted using relatively small numbers of samples. To test whether this variant is involved in cognitive function and LOAD progression, we genotyped 4486 subjects with up to 12 years of longitudinal cognitive assessment. Analyses revealed an average 0.6-point decrease per year in the rate of cognitive decline for each additional valine (p < 0.011). We failed to detect the association between CETP I405V and LOAD status (p < 0.28). We conclude that CETP I405V is associated with preserved cognition over time but is not associated with LOAD status., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The objective of this study was to determine the combined effects of HL and cholesteryl ester transfer protein (CETP), derived exclusively from bone marrow (BM), on plasma lipids and atherosclerosis in high-fat-fed, atherosclerosis-prone mice. We transferred BM expressing these proteins into male and female double-knockout HL-deficient, LDL receptor-deficient mice (HL(-/-)LDLr(-/-)). Four BM chimeras were generated, where BM-derived cells expressed 1) HL but not CETP, 2) CETP and HL, 3) CETP but not HL, or 4) neither CETP nor HL. After high-fat feeding, plasma HDL-cholesterol (HDL-C) was decreased in mice with BM expressing CETP but not HL (17 ± 4 and 19 ± 3 mg/dl, female and male mice, respectively) compared with mice with BM expressing neither CETP nor HL (87 ± 3 and 95 ± 4 mg/dl, female and male mice, respectively, P < 0.001 for both sexes). In female mice, the presence of BM-derived HL mitigated this CETP-mediated decrease in HDL-C. BM-derived CETP decreased the cholesterol component of HDL particles and increased plasma cholesterol. BM-derived HL mitigated these effects of CETP. Atherosclerosis was not significantly different between BM chimeras. These results suggest that BM-derived HL mitigates the HDL-lowering, HDL-modulating, and cholesterol-raising effects of BM-derived CETP and warrant further studies to characterize the functional properties of these protein interactions., (Copyright © 2014 by the American Society for Biochemistry and Molecular Biology, Inc.)

Epidemiological research over the last 50 years has discovered a plethora of biomarkers (including molecules, traits or other diseases) that associate with coronary artery disease (CAD) risk. Even the strongest association detected in such observational research precludes drawing conclusions about the causality underlying the relationship between biomarker and disease. Mendelian randomization (MR) studies can shed light on the causality of associations, i.e whether, on the one hand, the biomarker contributes to the development of disease or, on the other hand, the observed association is confounded by unrecognized exogenous factors or due to reverse causation, i.e. due to the fact that prevalent disease affects the level of the biomarker. However, conclusions from a MR study are based on a number of important assumptions. A prerequisite for such studies is that the genetic variant employed affects significantly the biomarker under investigation but has no effect on other phenotypes that might confound the association between the biomarker and disease. If this biomarker is a true causal risk factor for CAD, genotypes of the variant should associate with CAD risk in the direction predicted by the association of the biomarker with CAD. Given a random distribution of exogenous factors in individuals carrying respective genotypes, groups represented by the genotypes are highly similar except for the biomarker of interest. Thus, the genetic variant converts into an unconfounded surrogate of the respective biomarker. This scenario is nicely exemplified for LDL cholesterol. Almost every genotype found to increase LDL cholesterol level by a sufficient amount has also been found to increase CAD risk. Pending a number of conditions that needed to be fulfilled by the genetic variant under investigation (e.g. no pleiotropic effects) and the experimental set-up of the study, LDL cholesterol can be assumed to act as the functional component that links genotypes and CAD risk and, more importantly, it can be assumed that any modulation of LDL cholesterol-by whatever mechanism-would have similar effects on disease risk. Therefore, MR analysis has tremendous potential for identifying therapeutic targets that are likely to be causal for CAD. This review article discusses the opportunities and challenges of MR studies for CAD, highlighting several examples that involved multiple biomarkers, including various lipid and inflammation traits as well as hypertension, diabetes mellitus, and obesity., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.)

Objective: Low-density lipoprotein receptor (LDLR) is degraded by inducible degrader of LDLR (Idol) and protein convertase subtilisin/kexin type 9 (PCSK9), thereby regulating circulating LDL levels. However, it remains unclear whether, and if so how, these LDLR degraders affect each other. We therefore investigated effects of liver-specific expression of Idol on LDL/PCSK9 metabolism in mice and hamsters., Approach and Results: Injection of adenoviral vector expressing Idol (Ad-Idol) induced a liver-specific reduction in LDLR expression which, in turn, increased very-low-density lipoprotein/LDL cholesterol levels in wild-type mice because of delayed LDL catabolism. Interestingly, hepatic Idol overexpression markedly increased plasma PCSK9 levels. In LDLR-deficient mice, plasma PCSK9 levels were already elevated at baseline and unchanged by Idol overexpression, which was comparable with the observation for Ad-Idol-injected wild-type mice, indicating that Idol-induced PCSK9 elevation depended on LDLR. In wild-type mice, but not in LDLR-deficient mice, Ad-Idol enhanced hepatic PCSK9 expression, with activation of sterol regulatory element-binding protein 2 and subsequently increased expression of its target genes. Supporting in vivo findings, Idol transactivated PCSK9/LDLR in sterol regulatory element-binding protein 2/LDLR-dependent manners in vitro. Furthermore, an in vivo kinetic study using (125)I-labeled PCSK9 revealed delayed clearance of circulating PCSK9, which could be another mechanism. Finally, to extend these findings into cholesteryl ester transfer protein-expressing animals, we repeated the above in vivo experiments in hamsters and obtained similar results., Conclusions: A vicious cycle in LDLR degradation might be generated by PCSK9 induced by hepatic Idol overexpression via dual mechanisms: sterol regulatory element-binding protein 2/LDLR. Furthermore, these effects would be independent of cholesteryl ester transfer protein expression., (© 2014 American Heart Association, Inc.)

High-density lipoprotein cholesterol (HDL-C) contains dozens of apoproteins that participate in normal cholesterol metabolism with a reliance on renal catabolism for clearance from the body. The plasma pool of HDL-C has been an excellent inverse predictor of cardiovascular events. However, when HDL-C concentrations have been manipulated with the use of niacin, fibric acid derivatives, and cholesteryl ester transferase protein inhibitors, there has been no improvement in outcomes in patients where the low-density lipoprotein cholesterol has been well treated with statins. Apolipoprotein L1 (APOL1) is one of the minor apoproteins of HDL-C, newly discovered in 1997. Circulating APOL1 is a 43-kDa protein mainly found in the HDL3 subfraction. In patients with chronic kidney disease (CKD), mutant forms of APOL1 have been associated with rapidly progressive CKD and end-stage renal disease (ESRD). Because mutant forms of APOL1 are more prevalent in African Americans compared to Caucasians, it may explain some of the racial disparities seen in the pool of patients with ESRD in the United States. Thus, HDL-C is an important lipoprotein carrying apoproteins that play roles in vascular and kidney disease., (2014 S. Karger AG, Basel.)

High-density lipoprotein (HDL) intravascular metabolism is complex, and the major HDL functions are esterification of cholesterol and reverse cholesterol transport, in which cholesterol from cells is excreted in bile. HDL has also several other antiatherogenic functions: antioxidative, vasodilatatory, anti-inflammatory, antiapoptotic, anti thrombotic, and anti infectious. Low HDL cholesterol is a major risk factor for cardiovas cular disease (CVD) and high HDL cholesterol may favor the many protective abilities of HDL. However, aspects of HDL function can be independent of HDL cholesterol levels, including the efflux of cholesterol from cells to HDL. Some populations show low incidence of CVD despite their low HDL cholesterol. Lipid exchange between HDL and other lipoproteins and cells is fundamental in HDL metabolism and reverse cholesterol transport. By determining HDL composition, lipid transfers can also affect HDL functions that depend on proteins that anchor on HDL particle surface. Cholesteryl ester protein (CETP) and phospholipid transfer protein facilitate lipid transfers among lipoprotein classes, but the role of the lipid transfers and transfer proteins in atherosclerosis and other diseases is not well established. CETP has become a therapeutic target because CETP inhibitors increase HDL cholesterol, but to date the clinical trials failed to show benefits for the patients. Recently, we introduced a practical in vitro assay to evaluate the simultaneous transfer from a donor nanoemulsion to HDL of unesterified and esterified cho lesterol, phospholipids, and triglycerides. Groups of subjects at different clinical, nutritional, and training conditions were tested, and among other findings, lower transfer ratios of unesterified cholesterol to HDL were predictors of the presence of CVD.

Objective: To investigate the CETP suppression by 10-dehydrogingerdione, a compound in Zingiber officinale, and its effect on the progression of atherosclerosis in dyslipidemic rabbits and the underlying oxidative and inflammatory consequences., Methods: Twenty-four New Zealand male rabbits were fed either a normal diet or an atherogenic diet. The rabbits on the atherogenic diet received treatments of atorvastatin or 10-dehydrogingerdione and placebo concurrently (n = 6/group). Blood samples were collected after three and six weeks for biochemical analysis., Results: 10-Dehydrogingerdione-treated rabbits showed a significant improvement in serum lipids especially HDL-C in a time-dependant manner. This effect was correlated to its ability to lower CETP. Lp(a), ox-LDL, hsCRP, homocysteine and MMP9 decreased significantly in both 10-dehydrogingerdione- and atorvastatin-treated rabbits compared with placebo (p < 0.001). Lp(a) achieved normal values by both treatments, while homocysteine did not reach normal values by either treatments. Conversely, MMP9 returned below normal values by 10-dehydrogingerdione (p < 0.001), hsCRP and ox-LDL were slightly below normal values (hsCRP: p < 0.001; ox-LDL: p < 0.001 and p < 0.05 in 10-dehydrogingerdione and atorvastatin groups, respectively). The effect achieved by 10-dehydrogingerdione was similar to that of atorvastatin on hsCRP and Lp(a). However, 10-dehydrogingerdione exerted better effect than atorvastatin on homocysteine, MMP9 (p < 0.001) and ox-LDL (p < 0.05)., Conclusions: In a rabbit dyslipidemic model, 10-dehydrogingerdione lowers LDL-C and raises HDL-C by suppressing CETP; an effect that modulates inflammatory and oxidative risk factors of CVD. These findings suggested that the naturally occurring 10-dehydrogingerdione might be a potential CETP inhibitor for the treatment of atherosclerosis and residual risk in CVD., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

The risk for myocardial infarction can be reduced by almost 50% solely by lowering LDL cholesterol. Despite success reducing LDL and cholesterol, atherosclerosis and myocardial infarction remain significant challenges. However, mechanisms of the reverse cholesterol transport system might be used more effectively in the foreseeable future. Although the benefit of high HDL cholesterol appears to be obvious, most clinical trials aimed at increasing HDL cholesterol failed to generate convincing results. Therefore, the question arises as to whether indeed only HDL level or perhaps rather more HDL function is of considerable therapeutic relevance. If function is the crucial issue drugs such as CETP (cholesteryl ester transfer protein) activators or SR-B1 (scavenger receptor type B-1) upregulators could be beneficial. These types of drugs could improve HDL metabolism and might have beneficial effects despite the fact that they lower HDL levels. Ongoing studies on next generation CETP inhibitors and nicotinic acid will clarify this question and might help in our struggle against atherosclerosis.

Among the noteworthy recent stories in the management and prevention of atherosclerotic cardiovascular disease (CVD) is the saga of the development of pharmacological inhibitors of cholesteryl ester transfer protein (CETP). Inhibiting CETP significantly raises plasma concentrations of high-density lipoprotein cholesterol, which has long been considered a marker of reduced CVD risk. However, the first CETP inhibitor, torcetrapib, showed a surprising increase in CVD events, despite a dramatic increase in high-density lipoprotein cholesterol levels. This paradox was explained by putative off-target effects not related to CETP inhibition that were specific to torcetrapib. Subsequently, three newer CETP inhibitors, namely dalcetrapib, anacetrapib, and evacetrapib, were at various phases of clinical development in 2012. Each of these had encouraging biochemical efficacy and safety profiles. Dalcetrapib even had human arterial imaging results that tended to look favorable. However, the dalcetrapib development program was recently terminated, presumably because interim analysis of a large CVD outcome trial indicated no benefit. These events raise important questions regarding the validity of the mechanism of CETP inhibition and the broader issue of whether pharmacological raising of high-density lipoprotein cholesterol itself is a useful strategy for CVD risk reduction.

Cholesteryl ester transfer protein (CETP) inhibition is a promising experimental strategy to raise high-density lipoprotein cholesterol (HDL-C) and reduce cardiovascular risk. This review focuses on the highly selective and potent CE TP inhibitor anacetrapib and discusses the available preclinical and clinical information pertaining to it. We also describe strategies to target HDL-C, discuss the mechanism underlying CETP inhibition and its effects on lipid biology, and give an overview of other CETP inhibitors that are currently in development.

Objectives: To identify the genetic variant in the CETP gene of the proband with high HDL-C and low CETP activity and to investigate whether HDL from the CETP-deficient subject was dysfunctional in the reverse cholesterol transport (RCT) pathway., Methods: We sequenced the CETP gene and assessed its promoter activity. Cholesterol efflux and hepatic cholesteryl ester delivery studies were also performed using the proband's HDL., Results: A proband was a compound heterozygote for a known D459G variant and a novel 18-bp deletion mutation in the CETP promoter. This promoter mutation markedly reduced the transcriptional activity in HepG2 cells. HDL2 from this subject increased SR-BI-mediated cholesterol efflux, whereas cholesteryl ester delivery into hepatocytes was maintained., Conclusion: A novel deletion mutation in the CETP promoter is associated with high HDL-C and decreased promoter activity. HDL from this CETP-deficient subject was not dysfunctional in mediating two main steps of RCT assessed in vitro., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Background: Taq1B polymorphism of cholesteryl ester transfer protein (CETP) is believed to associate with high-density lipoprotein-cholesterol (HDL-C) levels and may alter the susceptibility to atherosclerosis., Aim of the Study: This study investigated the effects of Taq1B polymorphism on HDL-C and coronary artery disease (CAD) risk in angiographically defined CAD patients., Methods: One hundred thirty-five CAD patients and 112 healthy controls were screened for the CETP Taq1B genotype and plasma lipids., Results: The genotype frequency of CAD patients and controls were similar. The HDL-C levels of all genotypes in the CAD group were significantly lower than the corresponding controls. Smoking and plasma triglycerides were the predictors of the HDL-C level in B1B1 bearers, whereas the subjects with a polymorphic B2 allele were affected by smoking and sex., Conclusion: CETP Taq1B polymorphism neither plays a role in determining HDL-C levels nor is a useful predictor of the risk of CAD.

Large epidemiological studies have consistently shown that plasma levels of high-density lipoprotein (HDL) correlate inversely with cardiovascular risk. The apparent cardioprotective role of HDL has primarily been attributed to its participation in reverse cholesterol transport (RCT) but there is also substantial evidence that supports the concept of HDL and apoA-I preventing oxidative damage, inhibiting systemic inflammation, promoting vascular integrity and preventing thrombosis. Besides conventional therapy to increase HDL like physical exercise, weight loss and dietary changes new strategies to intervene at various steps of its metabolism have been proposed and are in development. One of the most promising approaches is inhibiting cholesteryl ester transfer protein (CETP)which plays a central role in RCT by transferring cholesteryl esters from HDL to apoB containing lipoproteins in exchange for triglycerides. The failure of the CETP inhibitor torcetrapib, however, to cause any benefit on cardiovascular outcomes despite significantly increased HDL levels in several clinical trials casted doubts upon the concept of CETP inhibition. Meanwhile, off target toxicity could be shown for torcetrapib and a new generation of CETP inhibitors stands ready to be tested in large clinical trials. This article describes the formation and remodeling of HDL, how HDL is thought to be beneficial for the vasculature and what options we have today to increase HDL levels with a special focus on CETP inhibition.

Despite optimal treatment of high low density lipoprotein (LDL) cholesterol with statins many cardiovascular events are not prevented. Additional therapeutic strategies are required to reduce the residual cardiovascular risk. Large epidemiological studies show an inverse correlation between the plasma concentration of high density lipoprotein (HDL) cholesterol and the incidence of cardiovascular events. Under physiological conditions, HDL is vasculoprotective and mediates the reverse cholesterol transport. However, new studies suggest that HDL particles represent a heterogeneous population. Under several pathophysiological conditions, HDL was shown to promote atherogenesis and inflammation. Interventional studies and metaanalyses examining the effect of increasing HDL cholesterol have reported mixed results. Inhibition of cholesteryl ester transfer protein (CETP) is a new and potent strategy to increase HDL concentrations. However, the first CETP-inhibitor torcetrapib increased blood-pressure and increased cardiovascular events despite increasing HDL. The blood-pressure increasing effects are not known for more recently developed CETP inhibitors such as dalcetrapib and anacetrapib nor in patients with genetic CETP deficiency. An increase of HDL cholesterol does not necessarily imply an improvement of the functional properties of HDL such as reverse cholesterol transport. An important open question remains the functional characterization of HDL generated by CETP inhibition. Important current clinical endpoint studies with new CETP inhibitors will elucidate whether increasing HDL by CETP inhibition leads to a reduction of cardiovascular events., (Georg Thieme Verlag KG Stuttgart, New York.)

Subnormal plasma levels of high-density lipoprotein cholesterol (HDL-C) constitute a major cardiovascular risk factor; raising low HDL-C levels may therefore reduce the residual cardiovascular risk that frequently presents in dyslipidaemic subjects despite statin therapy. Cholesteryl ester transfer protein (CETP), a key modulator not only of the intravascular metabolism of HDL and apolipoprotein (apo) A-I but also of triglyceride (TG)-rich particles and low-density lipoprotein (LDL), mediates the transfer of cholesteryl esters from HDL to pro-atherogenic apoB-lipoproteins, with heterotransfer of TG mainly from very low-density lipoprotein to HDL. Cholesteryl ester transfer protein activity is elevated in the dyslipidaemias of metabolic disease involving insulin resistance and moderate to marked hypertriglyceridaemia, and is intimately associated with premature atherosclerosis and high cardiovascular risk. Cholesteryl ester transfer protein inhibition therefore presents a preferential target for elevation of HDL-C and reduction in atherosclerosis. This review appraises recent evidence for a central role of CETP in the action of current lipid-modulating agents with HDL-raising potential, i.e. statins, fibrates, and niacin, and compares their mechanisms of action with those of pharmacological agents under development which directly inhibit CETP. New CETP inhibitors, such as dalcetrapib and anacetrapib, are targeted to normalize HDL/apoA-I levels and anti-atherogenic activities of HDL particles. Further studies of these CETP inhibitors, in particular in long-term, large-scale outcome trials, will provide essential information on their safety and efficacy in reducing residual cardiovascular risk.

The beneficial therapeutic effects of raising HDL cholesterol are proving difficult to confirm in humans. The evaluation of antiatherogenic functions of HDL is an important area of research which includes the role of HDL in reverse cholesterol transport (RCT), especially macrophage-specific RCT, and its antioxidant and antiinflammatory roles. The antioxidant and antiinflammatory functions of HDL can be assessed using cell-free and cell-based assays. Also, a new approach was developed to measure RCT from labeled-cholesterol macrophages to liver and feces of mice. Studies in genetically engineered animals indicate that these major HDL antiatherogenic functions are better predictors of atherosclerosis susceptibility than HDL cholesterol or total RCT. Thus, functional testing of the antiatherogenic functions of HDL in experimental animal models may facilitate the development of new strategies for the prevention and treatment of atherosclerosis.

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

Objective: To analyze the cholesteryl ester transfer protein (CETP) gene and the plasma HDL phenotype in a Caucasian subject with extremely elevated plasma high density lipoprotein-cholesterol (HDL-C)., Methods and Results: The proband, a 63-year-old male of Swedish ancestry with elevated HDL-C (208mg/dl) and apoA-I (and 272mg/dl), was found to be homozygous for a point mutation in exon 2 of CETP gene (c.109 C>T) resulting in a premature termination codon (R37X). Plasma CETP mass and activity were undetectable. Plasma HDL were characterized by predominance of large HDL with enhanced prebeta-HDL content. The proband's sons, heterozygotes for the mutation, had reduced plasma CETP activity and moderately elevated HDL-C. Serum of CETP deficient subjects showed a normal or enhanced cholesterol efflux capacity via ABCG1/SR-BI; cholesterol efflux via ABCA1 and macrophage cholesterol removal were lower than normal. The proband was healthy and had no atherosclerotic plaques in carotid or femoral arteries., Conclusion: Complete CETP deficiency caused by mutations in CETP gene is exceedingly rare in Caucasians; the description of this single case indicates that CETP deficiency does not predispose to atherosclerosis in the absence of major cardiovascular risk factors.

High-density lipoprotein (HDL) is a proven biomarker for the monitoring of changes in antioxidant and anti-inflammation capability of body fluids. The beneficial virtues of HDL are highly dependent on its lipids and protein compositions, and their ratios. In normal state, the HDL particle is enriched with lipids and several HDL-associated enzymes, which are responsible for its antioxidant activity. Lower HDL-cholesterol levels (40 mg/dL) have been recognized as an independent risk factor for coronary artery disease, as well as being a known component of metabolic syndrome. Functional and structural changes of HDL have been recognized as factors pivotal to the evaluation of HDL-quality. In this review, I have elected to focus on the functional and structural correlations of HDL and the roles of HDL-associated apolipoproteins and enzymes. Recent clinical applications of HDL have also been reviewed, particularly the therapeutic targeting of HDL metabolism and reconstituted HDL; these techniques represent promising emerging strategies for the treatment of cardiovascular disease, for drug or gene therapy.

A common dose-limiting side effect of treatment with the retinoid X receptor agonist bexarotene is dyslipidemia. We evaluated the effects of bexarotene on plasma lipid metabolism in patients with metastatic differentiated thyroid carcinoma and investigated the underlying mechanism(s) in apolipoprotein (APO) E*3-Leiden mice without (E3L) and with human cholesteryl ester transfer protein (CETP; E3L.CETP). To this end, 10 patients with metastatic differentiated thyroid carcinoma were treated with bexarotene (300 mg/d) for 6 wk. Bexarotene increased plasma triglyceride (TG; +150%), primarily associated with very low-density lipoprotein (VLDL), and raised plasma total cholesterol (+50%). However, whereas bexarotene increased VLDL-cholesterol (C) and low-density lipoprotein (LDL)-C (+63%), it decreased high-density lipoprotein (HDL)-C (-30%) and tended to decrease apoAI (-18%) concomitant with an increase in endogenous CETP activity (+44%). To evaluate the cause of the bexarotene-induced hypertriglyceridemia and the role of CETP in the bexarotene-induced shift in cholesterol distribution, E3L and E3L.CETP mice were treated with bexarotene through dietary supplementation [0.03% (wt/wt)]. Bexarotene increased VLDL-associated TG in both E3L (+47%) and E3L.CETP (+29%) mice by increasing VLDL-TG production (+68%). Bexarotene did not affect the total cholesterol levels or distribution in E3L mice but increased VLDL-C (+11%) and decreased HDL-C (-56%) as well as apoAI (-31%) in E3L.CETP mice, concomitant with increased endogenous CETP activity (+41%). This increased CETP activity by bexarotene-treatment is likely due to the increase in VLDL-TG, a CETP substrate that drives CETP activity. In conclusion, bexarotene causes combined dyslipidemia as reflected by increased TG, VLDL-C, and LDL-C and decreased HDL-C, which is the result of an increased VLDL-TG production that causes an increase of the endogenous CETP activity.

Background: The role of CETP in the development of atherosclerosis is debatable, and few data exist regarding the total impact of CETP inhibition on cholesterol efflux., Methods: Acceptor capacities of whole serum and HDL subfractions separated by HPLC were compared using 2 different cell systems. Subjects with CETP deficiency (2 homozygous, 1 compound heterozygous, and 5 heterozygous) were analyzed along with 10 normolipidemic controls. The fractional efflux from cholesterol-labeled Fu5AH hepatoma cells was determined to be SR-BI mediated. The efflux difference between control and liver X receptor (LXR) agonist-induced ABCA1-upregulated J774 macrophages was considered as a measure of ABCA1-mediated efflux., Results: For the Fu5AH cell system, the total acceptor capacities of whole serum and HPLC-separated HDL fraction 2 obtained from the homozygous subjects were 38% and 116% higher than the corresponding values for the controls, respectively (p<0.05). For the J774 cell system, the total acceptor capacities of whole serum and HPLC-separated HDL fractions were similar among the CETP-deficient subjects and controls., Conclusions: Serum from homozygous subjects with CETP-null defects exhibited enhanced acceptor capacity via an SR-BI dependent pathway, which is regulated by the middle HPLC-separated HDL fraction. Further, the cholesterol acceptor capacity of serum obtained from patients having complete and partial CETP deficiency was preserved via an ABCA1-dependent pathway.

Epidemiological studies have demonstrated an inverse correlation between plasma concentrations of high-density lipoprotein cholesterol (HDL-C) and incidence of coronary heart disease (CHD); thus new therapies for raising HDL-C levels have been the focus of significant efforts by the cardiovascular medicine community. Inhibition of cholesteryl ester transfer protein (CETP) is one approach to increasing HDL-C concentrations. CETP is a plasma glycoprotein that mediates the transfer of cholesteryl esters from HDL to the apoB-containing lipoproteins, with a balanced transfer of triglycerides. Inhibition of CETP results in an accumulation of cholesteryl esters in HDL, thus resulting in increased HDL-C. Pharmacological inhibition of CETP in humans has been shown to result in increased levels of HDL-C, although any beneficial effect of this inhibition on CHD has yet to be established. This review article will discuss the complex role of CETP in lipid metabolism, recent developments for small-molecule inhibitors of CETP, and future prospects for CETP inhibitors in the treatment of CHD.

Genetic variation in CETP (cholesteryl ester transfer protein) has been clearly associated with HDL cholesterol levels but its association with cardiovascular disease and related phenotypes has been more controversial, possibly due to variability of polymorphisms and their frequencies across different ethnic populations. To see if there are undetected polymorphisms affecting protein sequence in individuals of Asian ancestry and to determine the functionality of such variants, all exons and adjacent intronic segments were resequenced in 96 individuals and the observed variants cloned and analyzed. Two novel SNPs, including one coding change, S332 to Y332, were identified. Y332 and all other reported variants in Asians were cloned for study in vitro. Secretion efficiency was determined by Western blotting of protein from cell lysates and media. Cholesteryl ester transfer activity was measured in vitro by following the extent of transfer of fluorescently labeled substrate. Y332, Q296 and G442 are all secreted less well than wild type protein but retain significant transfer activity. P151 is not secreted and no transfer activity was detected. These protein variants should all contribute to higher HDL cholesterol in individuals carrying them. Additionally, a splicing variation that causes a protein truncation and non-functional CETP that has been reported predominantly in Asians was also found in two individuals of European ancestry and was on the same haplotype background in the two populations, suggesting a common origin of this null variant. This improved understanding of CETP variation in Asians will allow a more effective comparison of studies across populations.

Mice expressing human cholesteryl ester transfer protein (huCETP) are more resistant to Escherichia coli bacterial wall LPS because death rates 5 days after intraperitoneal inoculation of LPS were higher in wild-type than in huCETP+/+ mice, whereas all huCETP+/+ mice remained alive. After LPS inoculation, plasma concentrations of TNF-alpha and IL-6 increased less in huCETP+/+ than in wild-type mice. LPS in vitro elicited lower TNF-alpha production by CETP expressing than by wild-type macrophages. In addition, TNF-alpha production by RAW 264.7 murine macrophages increased on incubation with LPS but decreased in a dose-dependent manner when human CETP was added to the medium. Human CETP in vitro enhanced the LPS binding to plasma high-density lipoprotein/low-density lipoprotein. The liver uptake of intravenous infused 14C-LPS from Salmonella typhimurium was greater in huCETP+/+ than in wild-type mice. Present data indicate for the first time that CETP is an endogenous component involved in the first line of defense against an exacerbated production of proinflammatory mediators.

Background: Despite reduction in low-density lipoprotein cholesterol, there is still a considerable amount of residual atherosclerosis-related disease. Epidemiological and pathophysiological data strongly favour increasing plasma high-density lipoprotein (HDL) cholesterol levels as antiatherogenic therapy, for example with cholesteryl ester transfer inhibition (CETP). However, negative Phase III studies on clinical end points with the CETP inhibitor torcetrapib challenge the future perspectives of other CETP inhibitors such as JTT-705., Objective: Is there potential for CETP inhibition with JTT-705 after torcetrapib's collapse?, Methods: Search of articles in Pubmed citing JTT-705, torcetrapib and anacetrapib, or citing effects of pharmacological HDL-cholesterol raising or CETP inhibition., Results/conclusion: There is possibly a future for HDL-cholesterol raising therapies. Phase III clinical studies with either JTT-705 or anacetrapib will determine whether CETP inhibition is beneficial.

Obesity often co-presents with other cardiometabolic risk factors such as dyslipidaemia, insulin resistance and hypertension. Less well appreciated is that dysregulation of adipokine production by excess adipose tissue also promotes a state of low-level systemic chronic inflammation and a prothrombotic state, implicated in the development of both atherosclerosis and subsequently cardiovascular events. Lifestyle modification and pharmacological therapy can reduce cardiometabolic risk, a benefit that may be partly due to their effects on adipokine levels.

Objectives: The effect of glucocorticoid substitution on the prevalence of metabolic syndrome components (NCEP ATP III criteria) and serum lipid levels was determined in GH-replaced hypopituitary patients. As glucocorticoid replacement is associated with a pronounced decrease in plasma cholesteryl ester transfer protein (CETP) activity, we also tested associations of HDL cholesterol with the -629C>A CETP promoter polymorphism in subjects with and without ACTH deficiency., Design and Patients: In a university setting, we retrieved protocolized clinical and laboratory data from 165 adult hypopituitary patients, who had received GH for 1 year., Results: After adjustment for age, sex and smoking, non-HDL cholesterol (P = 0.05) and triglycerides (P = 0.004) were higher, but HDL cholesterol was not decreased in 117 glucocorticoid (mainly cortisone acetate in two divided doses) receiving subjects compared to 48 ACTH-sufficient subjects. The prevalence of elevated plasma glucose and/or diabetes (P = 0.04) and hypertriglyceridaemia (P = 0.005), but not of other metabolic syndrome components, was higher in glucocorticoid-replaced subjects. HDL cholesterol was higher in -629 A allele carriers compared to -629CC homozygotes in ACTH-sufficient subjects (P = 0.04), but not in glucocorticoid-treated subjects (P = 0.13). Multiple linear regression analysis demonstrated that only in ACTH-sufficient subjects, HDL cholesterol was independently related to this CETP gene variation (P = 0.03)., Conclusions: In GH- and glucocorticoid-replaced hypopituitary patients, serum non-HDL cholesterol and triglycerides are higher and the prevalence of hyperglycaemia is increased, but HDL cholesterol is not decreased. Conventional glucocorticoid replacement appears to diminish the association of HDL cholesterol with a common CETP gene variation.

A number of therapeutic strategies targeting high-density lipoprotein (HDL) cholesterol and reverse cholesterol transport are being developed to halt the progression of atherosclerosis or even induce regression. However, circulating HDL cholesterol levels alone represent an inadequate measure of therapeutic efficacy. Evaluation of the potential effects of HDL-targeted interventions on atherosclerosis requires reliable assays of HDL function and surrogate markers of efficacy. Promotion of macrophage cholesterol efflux and reverse cholesterol transport is thought to be one of the most important mechanisms by which HDL protects against atherosclerosis, and methods to assess this pathway in vivo are being developed. Indexes of monocyte chemotaxis, endothelial inflammation, oxidation, nitric oxide production, and thrombosis reveal other dimensions of HDL functionality. Robust, reproducible assays that can be performed widely are needed to move this field forward and permit effective assessment of the therapeutic potential of HDL-targeted therapies.

CETP inhibition increases HDL cholesterol levels and presumably could contribute to human atheroprotection via increasing macrophage-specific reverse cholesterol transport (RCT) and antioxidant properties of HDL. However, the impact of CETP activity variation on these two antiatherogenic functions of HDL remain unknown. In this study, we assessed the effects of overexpressing CETP in transgenic (Tg) mice on macrophage-specific RCT and HDL ability to protect against LDL oxidative modification. [(3)H]cholesterol-labeled macrophages were injected intraperitoneally into mice maintained on a chow diet or an atherogenic diet, after which the appearance of [(3)H]cholesterol in plasma, liver and feces over 48 h was determined. The degree of protection of oxidative modification of LDL coincubated with HDL was evaluated by measuring relative electrophoretic mobility and dichlorofluorescein fluorescence. CETP-Tg mice presented decreased radiolabeled HDL-bound [(3)H]cholesterol 24 and 48 h after the label injection. However, the magnitude of macrophage-derived [(3)H]cholesterol in liver and feces did not differ between CETP-Tg and control mice on either diet. Similar results were found when [(3)H]cholesterol-labeled endogenous peritoneal macrophages were injected into the CETP-Tg and control mice. Further, the injection of endogenous macrophages from CETP-Tg mice did not alter macrophage RCT in control mice. HDL from CETP-Tg and control mice protected LDL from oxidative modification similarly, and paraoxonase 1, platelet activated factor acetyl-hydrolase and lecithin-cholesterol acyl transferase activities of transgenic mice did not differ from those of control mice. In conclusion, CETP overexpression in transgenic mice does not affect RCT from macrophages to feces in vivo or the protection conferred by HDL against LDL oxidative modification.

We tested whether hypertriglyceridemia associated with type 2 diabetes mellitus is accompanied by alterations in pre beta-HDL, which are considered to be initial acceptors of cell-derived cholesterol, and by changes in the ability of plasma to promote cellular cholesterol efflux. In 28 hypertriglyceridemic and 56 normotriglyceridemic type 2 diabetic patients, and in 56 control subjects, we determined plasma lipids, HDL cholesterol and phospholipids, plasma pre beta-HDL and pre beta-HDL formation, phospholipid transfer protein (PLTP) activity, plasma cholesterol esterification (EST) and cholesteryl ester transfer (CET) and the ability of plasma to stimulate cholesterol efflux out of cultured human fibroblasts. HDL cholesterol and HDL phospholipids were lower, whereas plasma PLTP activity, EST and CET were higher in hypertriglyceridemic diabetic patients than in the other groups. Pre beta-HDL levels and pre beta-HDL formation were unaltered, although the relative amount of pre beta-HDL (expressed as % of total plasma apo A-I) was increased in hypertriglyeridemic diabetic patients. Cellular cholesterol efflux to plasma from hypertriglyceridemic diabetic patients was increased compared to efflux to normotriglyceridemic diabetic and control plasma, but efflux to normotriglyceridemic diabetic and control plasma did not differ. Multiple linear regression analysis demonstrated that cellular cholesterol efflux to plasma was positively and independently related to pre beta-HDL formation, PLTP activity and EST (multiple r=0.48), but not to the diabetic state. In conclusion, cholesterol efflux from fibroblasts to normotriglyceridemic diabetic plasma is unchanged. Efflux to hypertriglyceridemic diabetic plasma is enhanced, in association with increased plasma PLTP activity and cholesterol esterification. Unaltered pre beta-HDL formation in diabetic hypertriglyceridemia, despite low apo A-I, could contribute to maintenance of cholesterol efflux.

Human atherosclerotic intima contains mast cells that secrete the neutral protease chymase into the intimal fluid, which also contains HDL-modifying proteins, such as cholesteryl ester transfer protein (CETP), in addition to abundant amounts of nascent discoidal HDL particles. Here, we studied chymase-dependent degradation of a) CETP isolated from human plasma and b) CETP-HDL complexes as well as the functional consequences of such degradations. Incubation with chymase caused a rapid cleavage of CETP, yielding a specific proteolytic pattern with a concomitant reduction in its cholesteryl ester transfer activity. These chymase-dependent effects were attenuated after CETP was complexed with HDL. This attenuation was more effective when CETP was complexed with HDL(3) and HDL(2) than with discoidal reconstituted high density lipoprotein (rHDL). Conversely, rHDL, but not spherical HDLs, was protected in such CETP complexes against functional inactivation by chymase. Thus, in contrast to the complexes of CETP with spherical HDLs, the ability of the CETP-rHDL complexes to promote cholesterol efflux from macrophage foam cells remained unchanged, despite treatment with chymase. In summary, complexation of CETP and HDL modifies their resistance to proteolytic inactivation: spherical HDLs protect CETP, and CETP protects discoidal HDL. These results suggest that in inflamed atherosclerotic intima, CETP, via its complexation with HDL, has a novel protective role in early steps of reverse cholesterol transport.

Cholesteryl ester transfer protein (CETP) plays an important role in cholesterol metabolism because it is responsible for the transfer of cholesteryl esters from high-density lipoprotein (HDL) to very-low-density lipoproteins and low-density lipoproteins (LDLs). The development of CETP inhibitors represented a novel approach for raising HDL cholesterol and reducing LDL cholesterol levels to alter atherogenesis. However, results from recent clinical trials question the therapeutic use of at least 1 CETP inhibitor, torcetrapib (Pfizer Inc, New York, NY), which was demonstrated to increase blood pressure and have no effect on decreasing the progression of coronary atherosclerosis. This article discusses the use of CETP inhibitors and their effects on lipoprotein metabolism and whether they can ultimately lead to reductions in cardiovascular events.

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

Objective: We recently described that hypertriglyceridemic apolipoprotein (apo) CIII transgenic mice show increased whole body metabolic rate. In this study, we used these apo CIII-expressing mice, combined or not with the expression of the natural promoter-driven CETP gene, to test the hypothesis that both proteins modulate diet-induced obesity., Measurements and Results: Mice expressing apo CIII, CIII/CETP, CETP and nontransgenic (NonTg) mice were maintained on a high-fat diet (14% fat by weight) during 20 weeks after weaning. At the end of this period, all groups exhibited the expected lipemic phenotype. Fasting glucose levels were neither affected by the high-fat diet nor by the distinct genotypes. However, apo CIII mice showed significantly higher glycemia ( approximately 35%) and lower insulin levels ( approximately 45%) in the fed state, compared with the NonTg mice. The apo CIII mice presented significantly increased body weight, lipid content of the carcass ( approximately 25%), visceral adipose tissue mass (about twofold) and adipocyte size ( approximately 25%) compared with the CETP and NonTg mice. The CETP expression in the apo CIII background normalized the subcutaneous adipose depot and visceral adipocyte size to the levels of NonTg mice. Plasma leptin levels were lower in CETP groups (25-50%) and higher in the apo CIII mice. Similar core body temperature in all groups and similar liver mitochondrial resting respiration rates in CIII and NonTg mice indicate no differences in basal energy expenditure rates among these mice fed a high-fat diet., Conclusion: The elevation of plasma apo CIII levels aggravates diet-induced obesity and the expression of physiological levels of circulating CETP reverses this adipogenic effect, indicating a novel role for CETP in modulating adiposity.

Associations between cholesteryl ester transfer protein (CETP) polymorphisms and high-density lipoprotein cholesterol (HDL-c) levels before and after 20 wk of endurance training were investigated in the HERITAGE Family Study. Plasma HDL-c, HDL(2)-c, HDL(3)-c, and apolipoprotein (apo)A1 levels were measured, and 13 CETP single nucleotide polymorphisms (SNPs) were genotyped in 265 blacks and 486 whites. Three haplotypes defined by SNPs at the -1337, -971, and -629 sites were strongly associated with baseline HDL-c levels in whites. Both C-1337T and C-629A were associated with baseline HDL-c (P < 0.001) and apoA1 (P < 0.01) when tested separately. However, only C-629A remained significant in a combined model. G-971A was not associated with HDL phenotypes, but showed significant interactions with C-629A (P = 0.002) on baseline traits. Genotype-by-sex interactions were observed at the -629 locus for HDL(3)-c (P = 0.004) and apoA1 (P = 0.02) training responses in whites. In women, the -629 A/A homozygotes showed greater increases in HDL(3)-c (P = 0.02) and apoA1 (P = 0.02) levels than the other genotypes. Finally, apolipoprotein E (APOE) genotype and the CETP C-629A locus contributed independently and in additive fashion to the HDL traits, explaining 6.0-8.8% of the variance. The CETP -1337T and -629A alleles are associated with higher baseline HDL-c and apoA1 levels. The beneficial effects of endurance training on plasma HDL(3)-c and apoA1 levels are evident in white women homozygous for the -629A allele. The CETP and APOE genotypes account for up to 9% of the variance in HDL-c phenotypes in the HERITAGE Family Study.