Future of cholesteryl ester transfer protein inhibitors

Unlocking the mysteries of VLDL: exploring its production, intracellular trafficking, and metabolism as therapeutic targets

Reducing circulating lipid levels is the centerpiece of strategies for preventing and treating atherosclerotic cardiovascular disease (ASCVD). Despite many available lipid-lowering medications, a substantial residual cardiovascular risk remains. Current clinical guidelines focus on plasma levels of low-density lipoprotein (LDL). Recent attention has been given to very low-density lipoprotein (VLDL), the precursor to LDL, and its role in the development of coronary atherosclerosis. Preclinical investigations have revealed that interventions targeting VLDL production or promoting VLDL metabolism, independent of the LDL receptor, can potentially decrease cholesterol levels and provide therapeutic benefits. Currently, methods, such as mipomersen, lomitapide, and ANGPTL3 inhibitors, are used to reduce plasma cholesterol and triglyceride levels by regulating the lipidation, secretion, and metabolism of VLDL. Targeting VLDL represents an avenue for new lipid-lowering strategies. Interventions aimed at reducing VLDL production or enhancing VLDL metabolism, independent of the LDL receptor, hold promise for lowering cholesterol levels and providing therapeutic benefits beyond LDL in the management of ASCVD.

Dissecting the Structural Dynamics of Authentic Cholesteryl Ester Transfer Protein for the Discovery of Potential Lead Compounds: A Theoretical Study

Current structural and functional investigations of cholesteryl ester transfer protein (CETP) inhibitor design are nearly entirely based on a fully active mutation (CETPMutant) constructed for protein crystallization, limiting the study of the dynamic structural features of authentic CETP involved in lipid transport under physiological conditions. In this study, we conducted comprehensive molecular dynamics (MD) simulations of both authentic CETP (CETPAuthentic) and CETPMutant. Considering the structural differences between the N- and C-terminal domains of CETPAuthentic and CETPMutant, and their crucial roles in lipid transfer, we identified the two domains as binding pockets of the ligands for virtual screening to discover potential lead compounds targeting CETP. Our results revealed that CETPAuthentic displays greater flexibility and pronounced curvature compared to CETPMutant. Employing virtual screening and MD simulation strategies, we found that ZINC000006242926 has a higher binding affinity for the N- and C-termini, leading to reduced N- and C-opening sizes, disruption of the continuous tunnel, and increased curvature of CETP. In conclusion, CETPAuthentic facilitates the formation of a continuous tunnel in the "neck" region, while CETPMutant does not exhibit such characteristics. The ligand ZINC000006242926 screened for binding to the N- and C-termini induces structural changes in the CETP unfavorable to lipid transport. This study sheds new light on the relationship between the structural and functional mechanisms of CETP. Furthermore, it provides novel ideas for the precise regulation of CETP functions.

Differential distribution of cholesterol pools across arteries under high-cholesterol diet

Excessive cholesterol constitutes a major risk factor for vascular disease. Within cells, cholesterol is distributed in detergent-sensitive and detergent-resistant fractions, with the largest amount of cholesterol residing in cellular membranes. We set out to determine whether various arteries differ in their ability to accumulate esterified and non-esterified cholesterol in detergent-sensitive versus detergent-resistant fractions throughout the course of a high-cholesterol diet. Male Sprague-Dawley rats were placed on 2 % cholesterol diet while a control group was receiving iso-caloric standard chow. Liver, aorta, and pulmonary, mesenteric, and cerebral arteries were collected at 2-6, 8-12, 14-18, and 20-24 weeks from the start of high-cholesterol diet. After fraction separation, esterified and free non-esterified cholesterol levels were measured. In all arteries, largest cholesterol amounts were present in detergent-sensitive fractions in the non-esterified form. Overall, cholesterol in aorta and cerebral arteries was elevated during 14-18 weeks of high-cholesterol diet. Cerebral arteries also exhibited increase in esterified cholesterol within detergent-sensitive domains, as well as increase in cholesterol level in the detergent-resistant fraction at earlier time-points of diet. Pulmonary artery and mesenteric artery were largely resistant to cholesterol accumulation. Quantitative polymerase chain reaction (qPCR) analysis revealed up-regulation of low-density lipoprotein receptor (Ldlr) and low-density lipoprotein receptor-related protein 1 (Lrp1) gene expression in cerebral arteries when compared to mesenteric and pulmonary arteries, respectively. In summary, we unveiled the differential ability of arteries to accumulate cholesterol over the course of a high-cholesterol diet. The differential accumulation of cholesterol seems to correlate with the up-regulated gene expression of proteins responsible for cholesterol uptake.

Mathematical Modelling of Material Transfer to High-Density Lipoprotein (HDL) upon Triglyceride Lipolysis by Lipoprotein Lipase: Relevance to Cardioprotective Role of HDL

High-density lipoprotein (HDL) contributes to lipolysis of triglyceride-rich lipoprotein (TGRL) by lipoprotein lipase (LPL) via acquirement of surface lipids, including free cholesterol (FC), released upon lipolysis. According to the reverse remnant-cholesterol transport (RRT) hypothesis recently developed by us, acquirement of FC by HDL is reduced at both low and extremely high HDL concentrations, potentially underlying the U-shaped relationship between HDL-cholesterol and cardiovascular disease. Mechanisms underlying impaired FC transfer however remain indeterminate. We developed a mathematical model of material transfer to HDL upon TGRL lipolysis by LPL. Consistent with experimental observations, mathematical modelling showed that surface components of TGRL, including FC, were accumulated in HDL upon lipolysis. The modelling successfully reproduced major features of cholesterol accumulation in HDL observed experimentally, notably saturation of this process over time and appearance of a maximum as a function of HDL concentration. The calculations suggested that the both phenomena resulted from competitive fluxes of FC through the HDL pool, including primarily those driven by FC concentration gradient between TGRL and HDL on the one hand and mediated by lecithin-cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) on the other hand. These findings provide novel opportunities to revisit our view of HDL in the framework of RRT.

Phospholipid transfer to high-density lipoprotein (HDL) upon triglyceride lipolysis is directly correlated with HDL-cholesterol levels and is not associated with cardiovascular risk

BACKGROUND AND AIMS

While low concentrations of high-density lipoprotein-cholesterol (HDL-C) represent a well-established cardiovascular risk factor, extremely high HDL-C is paradoxically associated with elevated cardiovascular risk, resulting in the U-shape relationship with cardiovascular disease. Free cholesterol transfer to HDL upon lipolysis of triglyceride-rich lipoproteins (TGRL) was recently reported to underlie this relationship, linking HDL-C to triglyceride metabolism and atherosclerosis. In addition to free cholesterol, other surface components of TGRL, primarily phospholipids, are transferred to HDL during lipolysis. It remains indeterminate as to whether such transfer is linked to HDL-C and cardiovascular disease.

METHODS AND RESULTS

When TGRL was labelled with fluorescent phospholipid 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), time- and dose-dependent transfer of DiI to HDL was observed upon incubations with lipoprotein lipase (LPL). The capacity of HDL to acquire DiI was decreased by -36% (p<0.001) in low HDL-C patients with acute myocardial infarction (n = 22) and by -95% (p<0.001) in low HDL-C subjects with Tangier disease (n = 7), unchanged in low HDL-C patients with Type 2 diabetes (n = 17) and in subjects with high HDL-C (n = 20), and elevated in subjects with extremely high HDL-C (+11%, p<0.05) relative to healthy normolipidemic controls. Across all the populations combined, HDL capacity to acquire DiI was directly correlated with HDL-C (r = 0.58, p<0.001). No relationship of HDL capacity to acquire DiI with both overall and cardiovascular mortality obtained from epidemiological studies for the mean HDL-C levels observed in the studied populations was obtained.

CONCLUSIONS

These data indicate that the capacity of HDL to acquire phospholipid from TGRL upon LPL-mediated lipolysis is proportional to HDL-C and does not reflect cardiovascular risk in subjects widely differing in HDL-C levels.

Modulation of the Gut Microbiota and Liver Transcriptome by Red Yeast Rice and Monascus Pigment Fermented by Purple Monascus SHM1105 in Rats Fed with a High-Fat Diet

Hyperlipidemia can easily cause atherosclerosis and induce cardiovascular and cerebrovascular diseases. Red yeast rice (RYR) contains a variety of active ingredients and is commonly used as medicine and food, and has pharmacological effects such as lowering blood lipids. In this study, we select Monascus strain SHM1105 with a high yield of Monacolin K and monascus pigment (PIG), and studied the effects of the RYR and PIG fermented by this strain on blood lipids, intestinal flora, and liver transcriptome in hyperlipidemia model rats. The experimental results show that, compared with the high-fat model group, the weight growth rate, liver weight ratio, kidney weight ratio, spleen weight ratio, and fat weight ratio of rats in the gavage lovastatin (LOV), RYR, and PIG group were all significantly decreased (p < 0.05). Intervention with RYR and PIG can significantly reduce the serum TC, TG, and LDL-C levels, which has the effect of lowering blood lipids. The 16SrDNA sequencing results showed that the ratio of Firmicutes/Bacteroidetes decreased significantly (p ≤ 0.01) after the intervention of LOV, RYR, and PIG; the abundance of the ratio of Lachnospiraceae, Ruminococcaceae, Prevotellaceae, and Bacteroidales-S24-7-group also changed. The combined analysis of transcriptome and metabolome showed that lovastatin, RYR, and PIG can all improve lipid metabolism in rats by regulating Steroid hormone biosynthesis, Glycerolipid metabolism, and the Arachidonic acid metabolism pathway. In addition, RYR and PIG also have a unique way of regulating blood lipids. Although a lot of research on the lipid-lowering components of Monascus rice and the single pigment component of Monascus has been carried out, the actual application is RYR and pigments as mixtures, as a mixture of RYR and PIG contains a variety of biologically active ingredients, and each component may have a synergistic effect. Hence it has a lipid-lowering mechanism that lovastatin does not have. Therefore, RYR and PIG are effective in reducing lipid potential development and can be utilized in functional foods.

Development of an effective liposomal cholesterol ester transfer protein (CETP) vaccine for protecting against atherosclerosis in rabbit model

Clinical trials of cholesterol ester transfer protein (CETP) peptide vaccine were stopped after disappointing results in humans due to the inadequacy of adjuvant aluminum hydroxide in stimulating the immune response against the self-antigen of CETP. To increase the efficacy of the CETP vaccine, we developed a novel liposomal form of tetanus toxoid-CETP (TT-CETP) peptide (Lip CETP) with well-characterized properties and high encapsulation efficiency. The vaccine efficacy against atherosclerosis was evaluated in rabbits challenged with a high cholesterol diet. Rabbits were immunized with Lip-CETP or liposome containing CETP with CpG ODN (Lip CETP/CpG). Control groups received empty liposomes or buffer. Anti-TT-CETP specific antibodies in serum were determined and gene expression of cytokine IFN-γ and IL-4 were measured in blood peripheral mononuclear cells. Therapeutic response was evaluated by titration of plasma lipoproteins during the study and pathologic analysis of aorta atherosclerotic lesions at the end. Lip-CETP/CpG elicited strong anti-TT-CETP antibodies and a higher IFN-γ level than the buffer. IL-4 was lower than the buffer in all vaccinated groups. Plasma lipoproteins showed no significant difference in the studied groups. Atherosclerosis thickness grade of the aorta was lower than the buffer group (p < 0.001) in rabbits vaccinated with Lip-CETP but not with Lip-CETP/CpG. In conclusion, Lip-CETP showed a strong atheroprotective effect.

Cholesteryl Ester Transfer Protein Inhibition for Preventing Cardiovascular Events: JACC Review Topic of the Week

Cholesteryl ester transfer protein (CETP) facilitates exchange of triglycerides and cholesteryl ester between high-density lipoprotein (HDL) and apolipoprotein B100–containing lipoproteins. Evidence from genetic studies that variants in the CETP gene were associated with higher blood HDL cholesterol, lower low-density lipoprotein cholesterol, and lower risk of coronary heart disease suggested that pharmacological inhibition of CETP may be beneficial. To date, 4 CETP inhibitors have entered phase 3 cardiovascular outcome trials. Torcetrapib was withdrawn due to unanticipated off-target effects that increased risk of death, and major trials of dalcetrapib and evacetrapib were terminated early for futility. In the 30,000-patient REVEAL (Randomized Evaluation of the Effects of Anacetrapib through Lipid Modification) trial, anacetrapib doubled HDL cholesterol, reduced non-HDL cholesterol by 17 mg/dl (0.44 mmol/l), and reduced major vascular events by 9% over 4 years, but anaceptrapib was found to accumulate in adipose tissue, and regulatory approval is not being sought. Therefore, despite considerable initial promise, CETP inhibition provides insufficient cardiovascular benefit for routine use.

Molecular modeling and rational design of hydrocarbon-stapled/halogenated helical peptides targeting CETP self-binding site: Therapeutic implication for atherosclerosis

The human plasma cholesteryl ester transfer protein (CETP) collects triglycerides from very-/low-density lipoproteins (V/LDL) and exchanges them for cholesteryl esters from high-density lipoproteins (HDL), which has recognized as an important therapeutic target for atherosclerosis. The protein has a C-terminal amphipathic α-helix that serves as self-binding peptide to fulfill biological function by dynamically binding to/unbinding from its cognate site (termed self-binding site) in the same protein. Previously, we successfully derived and halogenated the helical peptide to competitively disrupt the self-binding behavior of CETP C-terminal tail. However, the halogenated peptides have only a limited affinity increase as compared to native helical peptide (∼3-fold), thus exhibiting only a moderate competitive potency. Here, instead of optimizing the direct intermolecular interaction of peptide with CETP self-binding site we attempt to further improve the peptide competitive potency by reducing its conformational flexibility with hydrocarbon-stapling technique. Computational analysis reveals that the helical peptide has large intrinsic disorder in unbound free state, which would incur a considerable entropy penalty upon rebinding to the self-binding site. All-hydrocarbon bridge is designed and optimized on native and halogenated peptides in terms of the helical pattern and binding mode of self-binding peptide. Dynamics simulation and circular dichroism indicate that the stapling can considerably reduce peptide disorder in free state. Energetics calculation and fluorescence assay conform that the binding affinity of stapled/halogenated peptides is improved substantially (by > 5-fold), thus exhibiting an effective competition potency with native peptide for the self-binding site. Structural examination suggests that the binding modes and nonbonded interactions of native and halogenated peptides are not influenced essentially due to the stapling.

Association of CETP Gene Variants With Risk for Vascular and Nonvascular Diseases Among Chinese Adults

Question

What is the association of genetic variants in the CETP gene that lower cholesteryl ester transfer protein activity with risk for cardiovascular and other diseases?

Findings

In this biobank study of 151 217 Chinese adults, CETP gene variants were associated with higher levels of high-density lipoprotein cholesterol but not with lower levels of low-density lipoprotein cholesterol and were not associated with risk for cardiovascular disease.

Meaning

Increasing levels of high-density lipoprotein cholesterol by cholesteryl ester transfer protein inhibition in the absence of lower levels of low-density lipoprotein cholesterol may not confer significant benefits for cardiovascular disease.

Importance

Increasing levels of high-density lipoprotein (HDL) cholesterol through pharmacologic inhibition of cholesteryl ester transfer protein (CETP) is a potentially important strategy for prevention and treatment of cardiovascular disease (CVD).

Objective

To use genetic variants in the CETP gene to assess potential risks and benefits of lifelong lower CETP activity on CVD and other outcomes.

Design, Setting, and Participants

This prospective biobank study included 151 217 individuals aged 30 to 79 years who were enrolled from 5 urban and 5 rural areas of China from June 25, 2004, through July 15, 2008. All participants had baseline genotype data, 17 854 of whom had lipid measurements and 4657 of whom had lipoprotein particle measurements. Median follow-up of 9.2 years (interquartile range, 8.2-10.1 years) was completed January 1, 2016, through linkage to health insurance records and death and disease registries.

Exposures

Five CETP variants, including an East Asian loss-of-function variant (rs2303790), combined in a genetic score weighted to associations with HDL cholesterol levels.

Main Outcomes and Measures

Baseline levels of lipids and lipoprotein particles, cardiovascular risk factors, incidence of carotid plaque and predefined major vascular and nonvascular diseases, and a phenome-wide range of diseases.

Results

Among the 151 217 individuals included in this study (58.4% women and 41.6% men), the mean (SD) age was 52.3 (10.9) years. Overall, the mean (SD) low-density lipoprotein (LDL) cholesterol level was 91 (27) mg/dL; HDL cholesterol level, 48 (12) mg/dL. CETP variants were strongly associated with higher concentrations of HDL cholesterol (eg, 6.1 [SE, 0.4] mg/dL per rs2303790-G allele; P = 9.4 × 10⁻⁴⁷) but were not associated with lower LDL cholesterol levels. Within HDL particles, cholesterol esters were increased and triglycerides reduced, whereas within very low-density lipoprotein particles, cholesterol esters were reduced and triglycerides increased. When scaled to 10-mg/dL higher levels of HDL cholesterol, the CETP genetic score was not associated with occlusive CVD (18 550 events; odds ratio [OR], 0.98; 95% CI, 0.91-1.06), major coronary events (5767 events; OR, 1.08; 95% CI, 0.95-1.22), myocardial infarction (3118 events; OR, 1.14; 95% CI, 0.97-1.35), ischemic stroke (13 759 events; OR, 0.94; 95% CI, 0.86-1.02), intracerebral hemorrhage (6532 events; OR, 0.94; 95% CI, 0.83-1.06), or other vascular diseases or carotid plaque. Similarly, rs2303790 was not associated with any vascular diseases or plaque. No associations with nonvascular diseases were found other than an increased risk for eye diseases with rs2303790 (4090 events; OR, 1.43; 95% CI, 1.13-1.80; P = .003).

Conclusions and Relevance

CETP variants were associated with altered HDL metabolism but did not lower LDL cholesterol levels and had no significant association with risk for CVD. These results suggest that in the absence of reduced LDL cholesterol levels, increasing HDL cholesterol levels by inhibition of CETP may not confer significant benefits for CVD.

Efferocytosis and Atherosclerosis: Regulation of Phagocyte Function by MicroRNAs

There is evidence of the critical role of efferocytosis, the clearance of apoptotic cells (ACs) by phagocytes, in vascular cell homeostasis and protection against atherosclerosis. Specific microRNAs (miRs) can regulate atherogenesis by controlling the accumulation of professional phagocytes (e.g., macrophages) and nonprofessional phagocytes (i.e., neighboring tissue cells with the ability to acquire a macrophage-like phenotype) within the arterial wall, the differentiation of phagocytes into foam cells, the efferocytosis of apoptotic foam cells by phagocytes, and the phagocyte-mediated inflammatory response. A better understanding of the mechanisms involved in miR-regulated phagocyte function might lead to novel therapeutic antiatherosclerotic strategies. In this review, we try to shed light on the relationship between miRs and cellular players in the process of efferocytosis in the context of atherosclerotic plaque and their potential as molecular targets for novel antiatherosclerotic therapies.

Genetic Dissection of the Impact of miR-33a and miR-33b during the Progression of Atherosclerosis

As an important regulator of macrophage cholesterol efflux and HDL biogenesis, miR-33 is a promising target for treatment of atherosclerosis, and numerous studies demonstrate that inhibition of miR-33 increases HDL levels and reduces plaque burden. However, important questions remain about how miR-33 impacts atherogenesis, including whether this protection is primarily due to direct effects on plaque macrophages or regulation of lipid metabolism in the liver. We demonstrate that miR-33 deficiency in Ldlr^-/- mice promotes obesity, insulin resistance, and hyperlipidemia but does not impact plaque development. We further assess how loss of miR-33 or addition of miR-33b in macrophages and other hematopoietic cells impact atherogenesis. Macrophage-specific loss of miR-33 decreases lipid accumulation and inflammation under hyperlipidemic conditions, leading to reduced plaque burden. Therefore, the pro-atherogenic effects observed in miR-33-deficient mice are likely counterbalanced by protective effects in macrophages, which may be the primary mechanism through which anti-miR-33 therapies reduce atherosclerosis.

Beneficial Effects of Monascus sp. KCCM 10093 Pigments and Derivatives: A Mini Review

The production of Monascus pigments and related byproducts, via microbial fermentation, has been broadly utilized as coloring by traditional food industries and as a natural textile dye. In addition to these traditional purposes, Monascus pigments have been recently favored for a variety of commercial and academic purposes. Pigments and derivatives formed during Monascus fermentation have pharmaceutical and clinical properties that can counteract common diseases, including obesity, type-2 diabetes, and cancer. Various research attempts have investigated the optimum conditions for this derived compound synthesis, as well as the still-unknown bio-functional effects. Recently, several studies were conducted using Monascus sp. KCCM 10093 and its derivatives. These experimental outcomes potentially reflect the bio-functional features of Monascus sp. KCCM 10093. However, no publication to date provides an overview of Monascus sp. KCCM 10093's unique metabolite products, functionalities, or biological pathways. In order to develop profitable commercial applications of Monascus sp. KCCM 10093, it is necessary not only to conduct continuous research, but also to systematically organize previous Monascus studies. The goals of this review are to investigate the current derivatives of Monascus sp. KCCM 10093 pigments-some of which have demonstrated newly-identified functionality-and the relevant uses of these molecules for pharmaceutical or nutraceutical purposes.

Sphingosine 1-Phosphate and Atherosclerosis

Sphingosine 1-phosphate (S1P) is a potent lipid mediator that works on five kinds of S1P receptors located on the cell membrane. In the circulation, S1P is distributed to HDL, followed by albumin. Since S1P and HDL share several bioactivities, S1P is believed to be responsible for the pleiotropic effects of HDL. Plasma S1P levels are reportedly lower in subjects with coronary artery disease, suggesting that S1P might be deeply involved in the pathogenesis of atherosclerosis. In basic experiments, however, S1P appears to possess both pro-atherosclerotic and anti-atherosclerotic properties; for example, S1P possesses anti-apoptosis, anti-inflammation, and vaso-relaxation properties and maintains the barrier function of endothelial cells, while S1P also promotes the egress and activation of lymphocytes and exhibits pro-thrombotic properties. Recently, the mechanism for the biased distribution of S1P on HDL has been elucidated; apolipoprotein M (apoM) carries S1P on HDL. ApoM is also a modulator of S1P, and the metabolism of apoM-containing lipoproteins largely affects the plasma S1P level. Moreover, apoM modulates the biological properties of S1P. S1P bound to albumin exerts both beneficial and harmful effects in the pathogenesis of atherosclerosis, while S1P bound to apoM strengthens anti-atherosclerotic properties and might weaken the pro-atherosclerotic properties of S1P. Although the detailed mechanisms remain to be elucidated, apoM and S1P might be novel targets for the alleviation of atherosclerotic diseases in the future.

Involvement of CETP (Cholesteryl Ester Transfer Protein) in the Shift of Sphingosine-1-Phosphate Among Lipoproteins and in the Modulation of its Functions

OBJECTIVE

Sphingosine-1-phosphate (S1P) is a vasoprotective lipid mediator. About two thirds of plasma S1P rides on high-density lipoprotein (HDL), and several pleiotropic properties of HDL have been ascribed to S1P. In human subjects, CETP (cholesteryl ester transfer protein) greatly influences HDL quantities. In this study, we attempted to elucidate the roles of CETP in the metabolism of S1P.

APPROACH AND RESULTS

We overexpressed CETP in mice that lacked CETP and found that CETP overexpression decreased the HDL level but failed to modulate the levels of S1P and apolipoprotein M (apoM), a carrier of S1P, in the total plasma. We observed, however, that the distribution of S1P and apoM shifted from HDL to apoB-containing lipoproteins. When we administered C₁₇S1P bound to apoM-containing lipoprotein, C₁₇S1P and apoM were rapidly transferred to apoB-containing lipoproteins in CETP-overexpressing mice. When HDL containing C₁₇S1P was mixed with low-density lipoprotein ex vivo, C₁₇S1P shifted to the low-density lipoprotein fraction independent of the presence of CETP. Concordant with these results, apoM was distributed mainly to the same fraction as apo AI in a CETP-deficient subject, although apoM was also detected in apo AI-poor fractions in a corresponding hypercholesterolemia subject. About the bioactivities of S1P carried on each lipoprotein, S1P riding on apoB-containing lipoproteins induced the phosphorylation of Akt (AKT8 virus oncogene cellular homolog) and eNOS (endothelial nitric oxide synthase) in human umbilical vein endothelial cells, and CETP overexpression increased insulin secretion and sensitivity, which was inhibited by an S1P receptor 1 or 3 antagonist.

CONCLUSIONS

CETP modulates the distribution of S1P among lipoproteins, which affects the bioactivities of S1P.

A novel atheroprotective role of MF59-like adjuvant when co-administered with CETP vaccine in rabbit model of atherosclerosis

OBJECTIVES

In this study, for the first time, MF59 adjuvant was used to develop a cholesteryl ester transfer protein (CETP) vaccine. The efficacy of the vaccine was compared with the efficacy of CETP vaccine formulated with Alum/CpG, the formulation that its immunogenicity has been already demonstrated in rabbit and mice.

MATERIALS AND METHODS

Tetanus toxoid- CETP peptide (TT-CETP) was mixed with Alum/CpG or MF59-like and administered subcutaneously for total five times in rabbit model of atherosclerosis. Anti-TT-CETP specific antibody, CETP activity in sera and mRNA level of cytokine IL-4 and IFN-γ in peripheral mononuclear cells were determined. Therapeutic response was also examined by tracking serum lipoprotein levels and pathologic observation of atherosclerotic lesions at aortic site.

RESULTS

More anti-TT-CETP antibody was found in Alum/CpG vaccinated rabbits compared to buffer (P<0.001). Antibody induced by MF59-like formulation was not significantly higher than buffer. CETP activity and lipoprotein levels were not significantly different between vaccinated and control rabbits. The mRNA level of IL-4 was significantly lower than buffer while, IFN-γ gene expression was significantly higher in both vaccinated groups. Atherosclerosis thickness grade of aorta was dramatically lower than buffer (P<0.01) in both vaccinated groups.

CONCLUSION

It is concluded that MF59-adjuvanted CETP vaccine showed anti-atherosclerosis properties, but the protective effect could not be directly attributed to the immune response induced by anti TT-CETP antibody and CETP inhibition. Further studies are needed to explain the anti-atherosclerosis properties of MF59 in the presence of TT-CETP peptide.

Lipid Management in Diabetes with a Focus on Emerging Therapies

We reviewed the current and potential future management of dyslipidemia in patients with diabetes, with a focus on reduction of risk for macrovascular disease. We considered novel dyslipidemia therapies, in particular, inhibitors of proprotein convertase subtilisin kexin 9 (PCSK9), which have been approved in Canada for reducing low-density lipoprotein (LDL) cholesterol in certain patient groups. We searched for English-language randomized clinical trials (RCTs) of lipid-lowering modalities, mainly since 2012, that included patients with diabetes. The results from some RCTs may have future impacts on the approach to patients with diabetes. In particular, ezetimibe added to statins in the context of acute coronary syndromes seems to have particular benefits in patients with diabetes. Also, patients with diabetes show no differences, so far, from patients without diabetes with respect to efficacy of PCSK9 inhibitors in LDL cholesterol reduction and also in the frequency of adverse effects. RCTs of clinical outcomes with PCSK9 inhibitors performed exclusively in patients with diabetes are desirable, but approval of these agents for use in Canada has occurred before the availability of such results. Clinicians will have to gauge whether certain subjects with diabetes might benefit from this therapy, such as those with superimposed familial dyslipidemia, those with recurrent cardiovascular events and recalcitrant LDL cholesterol levels despite maximally tolerated statin therapy and those with high cardiovascular risk who cannot tolerate any dose of statins.

Re-evaluation of cholesteryl ester transfer protein function in atherosclerosis based upon genetics and pharmacological manipulation

PURPOSE OF REVIEW

To re-evaluate the functions of plasma cholesteryl ester transfer protein (CETP) in atherosclerosis based upon recent findings from human genetics and pharmacological CETP manipulation.

RECENT FINDINGS

CETP is involved in the transfer of cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins, a key step of reverse cholesterol transport (RCT). CETP inhibitors have been developed to raise serum HDL-cholesterol (HDL-C) levels and reduce cardiovascular events. However, outcome studies of three CETP inhibitors (torcetrapib, dalcetrapib and evacetrapib) were prematurely terminated because of increased mortality or futility despite marked increases in HDL-cholesterol and decreases in LDL-cholesterol except for dalcetrapib. Patients with CETP deficiency show remarkable changes in HDL and LDL and are sometimes accompanied by atherosclerotic cardiovascular diseases. Recent prospective epidemiological studies demonstrated atheroprotective roles of CETP. CETP inhibition induces formation of small dense LDL and possibly dysfunctional HDL and downregulates hepatic scavenger receptor class B type I (SR-BI). Therefore, CETP inhibitors may interrupt LDL receptor and SR-BI-mediated cholesterol delivery back to the liver.

SUMMARY

For future drug development, the opposite strategy, namely enhancers of RCT via CETP and SR-BI activation as well as the inducers of apolipoprotein A-I or HDL production might be a better approach rather than delaying HDL metabolism by inhibiting a main stream of RCT in vivo.

Adipose-Derived Mesenchymal Stem Cells Ameliorate Lipid Metabolic Disturbance in Mice

: Adipose-derived mesenchymal stem cells (AD-MSCs) have been shown to ameliorate hyperglycemia in diabetic animals and individuals. However, little is known about whether AD-MSCs affect lipid metabolism. Here we have demonstrated for the first time that AD-MSC infusion can significantly suppress the increase in body weight and remarkably improve dyslipidemia in db/db obese mice and diet-induced obesity mice. Induction of white fat tissue "browning" and activation of adenosine monophosphate-activated protein kinase and its downstream hormone-sensitive lipase in adipose tissue contribute to the antiobesity and lipid-lowering effects. Thus, AD-MSC infusion holds great therapeutic potential for dyslipidemia and associated cardiovascular diseases.

SIGNIFICANCE

Mesenchymal stem cells (MSCs) are considered one of the most promising types of stem cells for translational application because of their rich tissue sources, multilineage differentiation capacity, and easy amplification in vitro and unique immunobiological properties. This study demonstrated that adipose-derived MSCs (AD-MSCs) infusion can significantly suppress the increase in body weight and remarkably improve dyslipidemia in obese mice. Induction of white fat tissue "browning" and activation of adenosine monophosphate-activated protein kinase and its downstream hormone-sensitive lipase in adipose tissue were demonstrated to contribute to the antiobesity and lipid-lowering effects. Thus, AD-MSC infusion holds great therapeutic potential for dyslipidemia.

Managing dyslipidaemia in type 2 diabetes mellitus

Glucose-control has a modest beneficial effect on cardiovascular outcomes in patients with type 2 diabetes mellitus. Thus, managing other atherogenic risk factors including hypertriglyceridemia, low HDL-cholesterol and moderately elevated LDL-cholesterol levels with increased small dense LDL-cholesterol fraction, is crucial. Insulin resistance is a key pathophysiologic factor in this population. Treatment starts with lifestyle modifications, but current best programmes have not translated into positive cardiovascular outcomes. Lowering LDL-cholesterol with statins is currently the main treatment strategy, but significant residual risk remains. Attempts to elevate HDL-cholesterol and to reduce triglycerides levels, with niacin or fibrates have not improved cardiovascular prognosis, but addition of ezetimibe, or fibrates in specific patients subgroups, have shown modest benefit. Some glucose-lowering medications and bariatric surgery may also improve diabetic dyslipidemia. Results of three major cardiovascular outcome trials evaluating the effect of lowering LDL-cholesterol with PCSK9 inhibitors in large cohorts that include thousands of diabetic patients are pending.

Recent advances in the pharmacological management of hypercholesterolaemia

The recent developments in pharmacological interventions that reduce LDL cholesterol have been remarkable, coming more than a decade after the approval of the last LDL-cholesterol-lowering drug, the cholesterol absorption inhibitor ezetimibe. Within just a few years, four new LDL-cholesterol-lowering agents have received regulatory approval. Lomitapide and mipomersen inhibit the production of LDL, but also increase hepatic fat and are licensed specifically for homozygous familial hypercholesterolaemia. Alirocumab and evolocumab are monoclonal antibodies that bind to proprotein convertase subtilisin/kexin type 9 (PCSK9), lowering LDL by about 50-60%. These drugs are approved for use in patients with cardiovascular disease or familial hypercholesterolaemia whose LDL cholesterol levels are insufficiently controlled on standard agents. Although definitive clinical efficacy and long-term safety data are still needed, antibody-based PCSK9 inhibitors promise to meet much of the unmet medical need in the treatment of raised LDL cholesterol. However, several additional approaches to inhibiting PCSK9, as well as other classes of LDL-lowering therapies, are in clinical development. Here we summarise the science behind the development of the newly approved LDL-cholesterol-lowering drugs and critically review their efficacy and safety data, highlighting unanswered research questions. Finally, we discuss emerging LDL-lowering therapies in clinical development.

Statin combination therapy and cardiovascular risk reduction

In numerous clinical trials, lowering LDL-C with statin therapy has been demonstrated to reduce the risk of cardiovascular disease (CVD) in primary and secondary prevention settings. Guidelines recommend statins for first-line therapy in cholesterol-lowering management of patients with CVD risk. Despite increased statin monotherapy use over the last decade, a number of patients with high CVD risk do not achieve optimal LDL-C lowering. Guidelines recommend consideration of statin combination therapy with nonstatin agents for these patients. However, combination therapy approaches have been hampered by neutral findings. Recently, ezetimibe added to simvastatin therapy reduced cardiovascular events in acute coronary syndrome patients, more than simvastatin alone. This article provides an overview of various agents in combination with statin therapy on cardiovascular outcomes. Other lipid-lowering agents in development, including PCSK9 and CETP inhibitors in development, are also described.

Candidate gene resequencing to identify rare, pedigree-specific variants influencing healthy aging phenotypes in the long life family study

Background

The Long Life Family Study (LLFS) is an international study to identify the genetic components of various healthy aging phenotypes. We hypothesized that pedigree-specific rare variants at longevity-associated genes could have a similar functional impact on healthy phenotypes.

Methods

We performed custom hybridization capture sequencing to identify the functional variants in 464 candidate genes for longevity or the major diseases of aging in 615 pedigrees (4,953 individuals) from the LLFS, using a multiplexed, custom hybridization capture. Variants were analyzed individually or as a group across an entire gene for association to aging phenotypes using family based tests.

Results

We found significant associations to three genes and nine single variants. Most notably, we found a novel variant significantly associated with exceptional survival in the 3’ UTR OBFC1 in 13 individuals from six pedigrees. OBFC1 (chromosome 10) is involved in telomere maintenance, and falls within a linkage peak recently reported from an analysis of telomere length in LLFS families. Two different algorithms for single gene associations identified three genes with an enrichment of variation that was significantly associated with three phenotypes (GSK3B with the Healthy Aging Index, NOTCH1 with diastolic blood pressure and TP53 with serum HDL).

Conclusions

Sequencing analysis of family-based associations for age-related phenotypes can identify rare or novel variants.

Electronic supplementary material

The online version of this article (doi:10.1186/s12877-016-0253-y) contains supplementary material, which is available to authorized users.

Cholesteryl Ester Transfer Protein Inhibition With Anacetrapib Decreases Fractional Clearance Rates of High-Density Lipoprotein Apolipoprotein A-I and Plasma Cholesteryl Ester Transfer Protein

OBJECTIVE

Anacetrapib (ANA), an inhibitor of cholesteryl ester transfer protein (CETP) activity, increases plasma concentrations of high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-I (apoA)-I, apoA-II, and CETP. The mechanisms responsible for these treatment-related increases in apolipoproteins and plasma CETP are unknown. We performed a randomized, placebo (PBO)-controlled, double-blind, fixed-sequence study to examine the effects of ANA on the metabolism of HDL apoA-I and apoA-II and plasma CETP.

APPROACH AND RESULTS

Twenty-nine participants received atorvastatin (ATV) 20 mg/d plus PBO for 4 weeks, followed by ATV plus ANA 100 mg/d for 8 weeks (ATV-ANA). Ten participants received double PBO for 4 weeks followed by PBO plus ANA for 8 weeks (PBO-ANA). At the end of each treatment, we examined the kinetics of HDL apoA-I, HDL apoA-II, and plasma CETP after D3-leucine administration as well as 2D gel analysis of HDL subspecies. In the combined ATV-ANA and PBO-ANA groups, ANA treatment increased plasma HDL-C (63.0%; P<0.001) and apoA-I levels (29.5%; P<0.001). These increases were associated with reductions in HDL apoA-I fractional clearance rate (18.2%; P=0.002) without changes in production rate. Although the apoA-II levels increased by 12.6% (P<0.001), we could not discern significant changes in either apoA-II fractional clearance rate or production rate. CETP levels increased 102% (P<0.001) on ANA because of a significant reduction in the fractional clearance rate of CETP (57.6%, P<0.001) with no change in CETP production rate.

CONCLUSIONS

ANA treatment increases HDL apoA-I and CETP levels by decreasing the fractional clearance rate of each protein.

Discovery of Novel Indoline Cholesterol Ester Transfer Protein Inhibitors (CETP) through a Structure-Guided Approach

Using the collective body of known (CETP) inhibitors as inspiration for design, a structurally novel series of tetrahydroquinoxaline CETP inhibitors were discovered. An exemplar from this series, compound 5, displayed potent in vitro CETP inhibition and was efficacious in a transgenic cynomologus-CETP mouse HDL PD (pharmacodynamic) assay. However, an undesirable metabolic profile and chemical instability hampered further development of the series. A three-dimensional structure of tetrahydroquinoxaline inhibitor 6 was proposed from (1)H NMR structural studies, and this model was then used in silico for the design of a new class of compounds based upon an indoline scaffold. This work resulted in the discovery of compound 7, which displayed potent in vitro CETP inhibition, a favorable PK-PD profile relative to tetrahydroquinoxaline 5, and dose-dependent efficacy in the transgenic cynomologus-CETP mouse HDL PD assay.

The potential of cholesteryl ester transfer protein as a therapeutic target

INTRODUCTION

Over recent decades, attempts to ascertain the pro-atherogenic nature of plasma cholesteryl ester transfer protein (CETP) and to establish the relevance of its pharmacological blockade as a promising high density lipoproteins-raising and anti-atherogenic therapy have been disappointing.

AREAS COVERED

The current review focuses on CETP as a multifaceted protein, on genetic variations at the CETP gene and on their possible consequences for cardiovascular risk in human populations. Specific attention is given to physiological modulation of endogenous CETP activity by the apoC1 inhibitor. Finally, the rationale behind the need for selection of patients to treat is discussed in the light of recent studies.

EXPERT OPINION

At this stage one can only speculate on the clinical outcome of pharmacological CETP inhibitors in high-risk populations, but recent advances give cause to adjust the expectations from now on. The CETP effect is probably largely influenced by the overall metabolic state, and whether CETP blockade may be relevant or not in promoting cholesterol disposal is still questioned. The possible need for a careful stratification of patients to treat with CETP inhibitors is outlined. Finally, manipulation of CETP activity should be considered with caution in the context of sepsis and infectious diseases.

Regulation of Hepatic Cholesteryl Ester Transfer Protein Expression and Reverse Cholesterol Transport by Inhibition of DNA Topoisomerase II

Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from high density lipoprotein to triglyceride-rich lipoproteins. CETP expression can be transcriptionally activated by liver X receptor (LXR). Etoposide and teniposide are DNA topoisomerase II (Topo II) inhibitors. Etoposide has been reported to inhibit atherosclerosis in rabbits with un-fully elucidated mechanisms. In this study we determined if Topo II activity can influence cholesterol metabolism by regulating hepatic CETP expression. Inhibition of Topo II by etoposide, teniposide, or Topo II siRNA increased CETP expression in human hepatic cell line, HepG2 cells, which was associated with increased CETP secretion and mRNA expression. Meanwhile, inhibition of LXR expression by LXR siRNA attenuated induction of CETP expression by etoposide and teniposide. Etoposide and teniposide induced LXRα expression and LXRα/β nuclear translocation while inhibiting expression of receptor interacting protein 140 (RIP140), an LXR co-repressor. In vivo, administration of teniposide moderately reduced serum lipid profiles, induced CETP expression in the liver, and activated reverse cholesterol transport in CETP transgenic mice. Our study demonstrates a novel function of Topo II inhibitors in cholesterol metabolism by activating hepatic CETP expression and reverse cholesterol transport.

A multivariate genome-wide association analysis of 10 LDL subfractions, and their response to statin treatment, in 1868 Caucasians

We conducted a genome-wide association analysis of 7 subfractions of low density lipoproteins (LDLs) and 3 subfractions of intermediate density lipoproteins (IDLs) measured by gradient gel electrophoresis, and their response to statin treatment, in 1868 individuals of European ancestry from the Pharmacogenomics and Risk of Cardiovascular Disease study. Our analyses identified four previously-implicated loci (SORT1, APOE, LPA, and CETP) as containing variants that are very strongly associated with lipoprotein subfractions (log₁₀Bayes Factor > 15). Subsequent conditional analyses suggest that three of these (APOE, LPA and CETP) likely harbor multiple independently associated SNPs. Further, while different variants typically showed different characteristic patterns of association with combinations of subfractions, the two SNPs in CETP show strikingly similar patterns - both in our original data and in a replication cohort - consistent with a common underlying molecular mechanism. Notably, the CETP variants are very strongly associated with LDL subfractions, despite showing no association with total LDLs in our study, illustrating the potential value of the more detailed phenotypic measurements. In contrast with these strong subfraction associations, genetic association analysis of subfraction response to statins showed much weaker signals (none exceeding log₁₀Bayes Factor of 6). However, two SNPs (in APOE and LPA) previously-reported to be associated with LDL statin response do show some modest evidence for association in our data, and the subfraction response proles at the LPA SNP are consistent with the LPA association, with response likely being due primarily to resistance of Lp(a) particles to statin therapy. An additional important feature of our analysis is that, unlike most previous analyses of multiple related phenotypes, we analyzed the subfractions jointly, rather than one at a time. Comparisons of our multivariate analyses with standard univariate analyses demonstrate that multivariate analyses can substantially increase power to detect associations. Software implementing our multivariate analysis methods is available at http://stephenslab.uchicago.edu/software.html.

Cardiovascular pharmacotherapy: Innovation stuck in translation

Systematic reviews of animal studies have revealed serious limitations in internal and external validity strongly affecting the reliability of this research. In addition inter-species differences are likely to further limit the predictive value of animal research for the efficacy and tolerability of new drugs in humans. Important changes in the research process are needed to allow efficient translation of preclinical discoveries to the clinic, including improvements in the laboratory and publication practices involving animal research and early incorporation of human proof-of-concept studies to optimize the interpretation of animal data for its predictive value for humans and the design of clinical trials.

Beyond the genetics of HDL: why is HDL cholesterol inversely related to cardiovascular disease?

There is unequivocal evidence that high-density lipoprotein (HDL) cholesterol levels in plasma are inversely associated with the risk of cardiovascular disease (CVD). Studies of families with inherited HDL disorders and genetic association studies in general (and patient) population samples have identified a large number of factors that control HDL cholesterol levels. However, they have not resolved why HDL cholesterol and CVD are inversely related. A growing body of evidence from nongenetic studies shows that HDL in patients at increased risk of CVD has lost its protective properties and that increasing the cholesterol content of HDL does not result in the desired effects. Hopefully, these insights can help improve strategies to successfully intervene in HDL metabolism. It is clear that there is a need to revisit the HDL hypothesis in an unbiased manner. True insights into the molecular mechanisms that regulate plasma HDL cholesterol and triglycerides or control HDL function could provide the handholds that are needed to develop treatment for, e.g., type 2 diabetes and the metabolic syndrome. Especially genome-wide association studies have provided many candidate genes for such studies. In this review we have tried to cover the main molecular studies that have been produced over the past few years. It is clear that we are only at the very start of understanding how the newly identified factors may control HDL metabolism. In addition, the most recent findings underscore the intricate relations between HDL, triglyceride, and glucose metabolism indicating that these parameters need to be studied simultaneously.

A vaccine targeted at CETP alleviates high fat and high cholesterol diet-induced atherosclerosis and non-alcoholic steatohepatitis in rabbit

Low HDL-C levels are associated with atherosclerosis and non-alcoholic steatohepatitis, and increased levels may reduce the risk of these diseases. Inhibition of cholesteryl ester transfer protein (CETP) activity is considered a promising strategy for increasing HDL-C levels. Since CETP is a self-antigen with low immunogenicity, we developed a novel CETP vaccine (Fc-CETP₆) to overcome the low immunogenicity of CETP and for long-term inhibition of CETP activity. The vaccine consists of a rabbit IgG Fc domain for antigen delivery to antigen-presenting cells fused to a linear array of 6 repeats of a CETP epitope to efficiently activate B cells. Rabbits were fed a high fat/cholesterol (HFC) diet to induce atherosclerosis and NASH, and immunized with Fc-CETP₆ vaccine. The Fc-CETP₆ vaccine successfully elicited anti-CETP antibodies and lowered plasma CETP activity. The levels of plasma HDL-C and ApoA-I were higher, and plasma ox-LDL lower, in the Fc-CETP₆-immunized rabbits as compared to the unimmunized HFC diet-fed rabbits. Pathological analyses revealed less lipid accumulation and inflammation in the aorta and liver of the Fc-CETP₆-immunized rabbits. These results show that the Fc-CETP₆ vaccine efficiently elicited antibodies against CETP and reduced susceptibility to both atherosclerosis and steatohepatitis induced by the HFC diet. Our findings suggest that the Fc-CETP₆ vaccine may improve atherosclerosis and NASH and has high potential for clinical use.

Ectopic visceral fat: a clinical and molecular perspective on the cardiometabolic risk

Worldwide, cardiovascular diseases (CVDs) are a leading cause of mortality. While in many westernized societies there has been a decrease prevalence of smoking and that a special emphasis has been put on the urgency to control the, so called, classical risk factors, it is more and more recognized that there remains a residual risk, which contributes to the development of CVDs. Imaging studies conducted over two decades have highlighted that the accumulation of ectopic visceral fat is associated with a plethora of metabolic dysfunctions, which have complex and intertwined interactions and participate to the development/progression/events of many cardiovascular disorders. The contribution of visceral ectopic fat to the development of coronary artery disease (CAD) is now well established, while in the last several years emerging evidence has pointed out that accumulation of harmful ectopic fat is associated with other cardiovascular disorders such as calcific aortic valve disease (CAVD), atrial fibrillation and left ventricular dysfunction. We review herein the key molecular processes linking the accumulation of ectopic fat to the development of CVDs. We have attempted, whenever possible, to use a translational approach whereby the pathobiology processes are linked to clinical observations.

HDL and cardiovascular disease

The cholesterol contained within HDL is inversely associated with risk of coronary heart disease and is a key component of predicting cardiovascular risk. However, despite its properties consistent with atheroprotection, the causal relation between HDL and atherosclerosis is uncertain. Human genetics and failed clinical trials have created scepticism about the HDL hypothesis. Nevertheless, drugs that raise HDL-C concentrations, cholesteryl ester transfer protein inhibitors, are in late-stage clinical development, and other approaches that promote HDL function, including reverse cholesterol transport, are in early-stage clinical development. The final chapters regarding the effect of HDL-targeted therapeutic interventions on coronary heart disease events remain to be written.

LDL cholesterol: controversies and future therapeutic directions

Lifelong exposure to raised concentrations of LDL cholesterol increases cardiovascular event rates, and the use of statin therapy as an adjunct to diet, exercise, and smoking cessation has proven highly effective in reducing the population burden associated with hyperlipidaemia. Yet, despite consistent biological, genetic, and epidemiological data, and evidence from randomised trials, there is controversy among national guidelines and clinical practice with regard to LDL cholesterol, its measurement, the usefulness of population-based screening, the net benefit-to-risk ratio for different LDL-lowering drugs, the benefit of treatment targets, and whether aggressive lowering of LDL is safe. Several novel therapies have been introduced for the treatment of people with genetic defects that result in loss of function within the LDL receptor, a major determinant of inherited hyperlipidaemias. Moreover, the usefulness of monoclonal antibodies that extend the LDL-receptor lifecycle (and thus result in substantial lowering of LDL cholesterol below the levels achieved with statins alone) is being assessed in phase 3 trials that will enrol more than 60,000 at-risk patients worldwide. These trials represent an exceptionally rapid translation of genetic observations into clinical practice and will address core questions of how low LDL cholesterol can be safely reduced, whether the mechanism of LDL-cholesterol lowering matters, and whether ever more aggressive lipid-lowering provides a safe, long-term mechanism to prevent atherothrombotic complications.

HDL and cognition in neurodegenerative disorders

High-density lipoproteins (HDLs) are a heterogeneous group of lipoproteins composed of various lipids and proteins. HDL is formed both in the systemic circulation and in the brain. In addition to being a crucial player in the reverse cholesterol transport pathway, HDL possesses a wide range of other functions including anti-oxidation, anti-inflammation, pro-endothelial function, anti-thrombosis, and modulation of immune function. It has been firmly established that high plasma levels of HDL protect against cardiovascular disease. Accumulating evidence indicates that the beneficial role of HDL extends to many other systems including the central nervous system. Cognition is a complex brain function that includes all aspects of perception, thought, and memory. Cognitive function often declines during aging and this decline manifests as cognitive impairment/dementia in age-related and progressive neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. A growing concern is that no effective therapy is currently available to prevent or treat these devastating diseases. Emerging evidence suggests that HDL may play a pivotal role in preserving cognitive function under normal and pathological conditions. This review attempts to summarize recent genetic, clinical and experimental evidence for the impact of HDL on cognition in aging and in neurodegenerative disorders as well as the potential of HDL-enhancing approaches to improve cognitive function.

Testing cardiovascular drug safety and efficacy in randomized trials

Randomized trials provide the gold standard evidence on which rests the decision to approve novel therapeutics for clinical use. They are large and expensive and provide average but unbiased estimates of efficacy and risk. Concern has been expressed about how unrepresentative populations and conditions that pertain in randomized trials might be of the real world, including concerns about the homogeneity of the biomedical and adherence characteristics of volunteers entered into such trials, the dose and constancy of drug administration and the mixture of additional medications that are restricted in such trials but might influence outcome in practice. A distinction has been drawn between trials that establish efficacy and those that demonstrate effectiveness, drugs that patients actually consume in the real world for clinical benefit. However, randomized controlled trials remain the gold standard for establishing efficacy and the testing of effectiveness with less rigorous approaches is a secondary, albeit important consideration. Despite this, there is an appreciation that average results may conceal considerable interindividual variation in drug response, leading to a failure to appreciate clinical value or risk in subsets of patients. Thus, attempts are now being made to individualize risk estimates by modulating those derived from large randomized trials with the individual baseline risk estimates based on demographic and biological criteria-the individual Numbers Needed to Treat to obtain a benefit, such as a life saved. Here, I will consider some reasons why large phase 3 trials-by far the most expensive element of drug development-may fail to address the unmet medical needs, which should justify such effort and investment.