Cholesterol Acyltransferase Inhibitor Research Articles

Acyl-coenzyme A: cholesterol acyltransferase inhibitor avasimibe suppresses tumorigenesis and induces G1-phase cell-cycle arrest by activating PPARγ signaling pathway in bladder cancer.

Reprogramming of energy metabolism is one of the most important characteristics of tumors. Bladder cancer (BLCA) cells contain higher levels of cholesterol content compared to normal cells, and acyl-coenzyme A (CoA): cholesterol acyltransferase-1 (ACAT1) plays a crucial role in the esterification of cholesterol. Avasimibe is a drug that has been used in the treatment of atherosclerosis, and it can effectively inhibit ACAT1. We observed that ACAT1 was significantly up-regulated in BLCA and positively correlated with tumor grade. By avasimibe administration, the proliferation and migration ability of BLCA cells were reduced, while the production of ROS was strongly increased, accompanied by the up-regulated expression of ROS metabolism-related proteins SOD2 and catalase. Furthermore, BLCA cell cycle was arrested at the G1 phase, accompanied by the downregulation of cell cycle-related proteins (CCNA1/2, CCND1, CDK2 and CDK4), while the PPARγ was found to be up-regulated at both transcriptional and protein levels after avasimibe treatment. Then we found that the PPARγ antagonist GW9662 could reverse the effect of avasimibe on the cell cycle. Moreover, xenograft and pulmonary metastasis models further demonstrated that avasimibe could inhibit tumor cell growth and metastasis in vivo. Taken together, our results for the first time revealed that avasimibe can inhibit BLCA progression and metastasis, and PPARγ signaling pathway may play a key role in regulation of cell cycle distribution induced by avasimibe.

A study on cholesterol-cholesteryl ester metabolic homeostasis and drug intervention in hyperlipidemic hamsters using UHPLC-MS/MS

Hyperlipidemia is a global metabolic disorder characterized by dysregulation of lipid metabolism. This dysregulation is closely associated with the altered homeostasis of cholesterol-cholesteryl ester (CE) metabolism in systemic circulation, and some organs. Additionally, the relationship between oxidized cholesteryl ester (oxCE) and the disease has also gained attention. Currently, there is a lack of comprehensive research on the alterations in cholesterol-CE metabolism in the context of hyperlipidemia, as well as the characteristics of lipid-lowering agents in regulating this metabolic state. Therefore, 40 oxCEs were identified in the hamster liver sample, and novel ultrahigh performance liquid chromatography−tandem mass spectrometry (UHPLC-MS/MS) methods were established for simultaneous analysis of cholesterol, 57 CEs, and 40 oxCEs in the serum, liver, adipose tissue, and intestine of hyperlipidemic hamsters. This study investigated the metabolic alterations between cholesterol-CE/oxCE in hyperlipidemic hamsters and those treated with lipid-lowering agents, including the Niemann-Pick-C1 like-1 protein (NPC1L1) inhibitor ezetimibe and the acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitor avasimibe. The study findings demonstrate metabolic disorders in cholesterol-CE/oxCE homeostasis in hyperlipidemic hamsters. Lipid-lowering agent therapy can improve the metabolic dysregulation caused by hyperlipidemia, with distinct characteristics: ezetimibe is more effective in reducing cholesterol, while avasimibe is more effective in reducing CEs/oxCEs. Eight potential biomarkers indicating the dysregulation of cholesterol-CE metabolism caused by hyperlipidemia and its improvement by lipid-lowering agents have been identified in the serum. This study offers new insights into the hyperlipidemia pathophysiology and the mechanisms of lipid-lowering agents from a novel perspective on cholesterol-CE/oxCE metabolic homeostasis.

TMET-31. CHOLESTEROL ESTERIFICATION IN A PATIENT WITH DIFFUSE ASTROCYTOMA PROGRESSING TO GLIOBLASTOMA

Abstract Metabolic profiles of diffuse astrocytoma and recurrent tumor tissues were compared in a patient with diffuse astrocytoma who showed tumor recurrence and progressed to glioblastoma (GBM). The patient presented with a diffuse infiltrating tumor and was operated in April 2018. The pathology report showed that the tumor was a diffusely infiltrating astrocytoma with Ki-67 of 5% (WHO Grade II). In addition, the molecular testing results indicated that the tumor was IDH1wt with TERTp mutation and showed an indeterminate MGMT promoter status. Given diffuse brain involvement and IDH1wt status, an aggressive behavior was suggested for this tumor. After ~3.5 years (January 2022), the MRI examination showed tumor recurrence and the patient underwent craniotomy for the resection of the recurrent tumor. The pathology report showed a high-grade glial neoplasm composed of ovoid tumor cells with nuclear pleomorphism (GBM, WHO Grade IV). We collected the tumor specimens from both surgeries and compared the metabolic profiles using 1H NMR spectroscopy. The tumor specimens were extracted using methanol-chloroform (2:1 ratio) extraction-method. The methanol-layer of the recurrent tumor showed decreased levels of N-acetylaspartate (NAA) and myo-inositol, and the elevated levels of phosphocholine (PC) and glycine, compared to the diffuse astrocytoma. Decreased NAA and elevated PC and glycine are metabolic features of high-grade gliomas, suggesting progression of the low-grade astrocytoma to GBM. The chloroform-layers of both tumors showed the presence of cholesterol; however, cholesteryl ester (CE) was detected only in the recurrent tumor (GBM). The ratio of CE to cholesterol was 0.44, suggesting that 44% of cholesterol pool was esterified in GBM. Cholesterol esterification is dysregulated in GBM and targeting this metabolic pathway using AcylCoA:cholesterol acyltransferase (ACAT) inhibitors would be promising in the treatment of GBM and astrocytomas with TERTp mutation which transform to GBM.

YM750, an ACAT Inhibitor, Acts on Adrenocortical Cells to Inhibit Aldosterone Secretion Due to Depolarization.

Primary aldosteronism (PA) is considered the most common form of secondary hypertension, which is associated with excessive aldosterone secretion in the adrenal cortex. The cause of excessive aldosterone secretion is the induction of aldosterone synthase gene (CYP11B2) expression by depolarization of adrenocortical cells. In this study, we found that YM750, an Acyl-coenzyme A: cholesterol acyltransferase (ACAT) inhibitor, acts on adrenocortical cells to suppress CYP11B2 gene expression and aldosterone secretion. YM750 inhibited the induction of CYP11B2 gene expression by KCl stimulation, but not by angiotensin II and forskolin stimulation. Interestingly, YM750 did not inhibit KCl-stimulated depolarization via an increase in intracellular calcium ion concentration. Moreover, ACAT1 expression was relatively abundant in the zona glomerulosa (ZG) including these CYP11B2-positive cells. Thus, YM750 suppresses CYP11B2 gene expression by suppressing intracellular signaling activated by depolarization. In addition, ACAT1 was suggested to play an important role in steroidogenesis in the ZG. YM750 suppresses CYP11B2 gene expression and aldosterone secretion in the adrenal cortex, suggesting that it may be a potential therapeutic agent for PA.

Repurposing Avasimibe to Inhibit Bacterial Glycosyltransferases.

We are interested in identifying and characterizing small molecule inhibitors of bacterial virulence factors for their potential use as anti-virulence inhibitors. We identified from high-throughput screening assays a potential activity for avasimibe, a previously characterized acyl-coenzyme A: cholesterol acyltransferase inhibitor, in inhibiting the NleB and SseK arginine glycosyltransferases from Escherichia coli and Salmonella enterica, respectively. Avasimibe inhibited the activity of the Citrobacter rodentium NleB, E. coli NleB1, and S. enterica SseK1 enzymes, without affecting the activity of the human serine/threonine N-acetylglucosamine (O-GlcNAc) transferase. Avasimibe was not toxic to mammalian cells at up to 200 µM and was neither bacteriostatic nor bactericidal at concentrations of up to 125 µM. Doses of 10 µM avasimibe were sufficient to reduce S. enterica abundance in RAW264.7 macrophage-like cells, and intraperitoneal injection of avasimibe significantly reduced C. rodentium survival in mice, regardless of whether the avasimibe was administered pre- or post-infection. We propose that avasimibe or related derivates created using synthetic chemistry may have utility in preventing or treating bacterial infections by inhibiting arginine glycosyltransferases that are important to virulence.

Facile method to incorporate high-affinity ACAT/SOAT1 inhibitor F12511 into stealth liposome-based nanoparticle and demonstration of its efficacy in blocking cholesteryl ester biosynthesis without overt toxicity in neuronal cell culture

BackgroundAcyl-CoA:cholesterol acyltransferase (ACAT) inhibitors have been considered as potential therapeutic agents to treat several diseases, including Alzheimer’s disease, atherosclerosis, and cancer. While many ACAT inhibitors are readily available, methods to encapsulate them as nanoparticles have not been reported. New methodWe report a simple method to encapsulate ACAT inhibitors, using the potent hydrophobic ACAT inhibitor F12511 as an example. By mixing DSPE-PEG2000, egg phosphatidylcholine (PC), and F12511 in ethanol, followed by drying, resuspension and sonication in buffer, we show that F12511 can be encapsulated as stealth liposomes at high concentration. ResultsWe successfully incorporated F12511 into nanoparticles and found that increasing PC in the nanoparticles markedly increased the amount of F12511 incorporated in stealth liposomes. The nanoparticles containing F12511 (Nanoparticle F) exhibit average size of approximately 200 nm and are stable at 4 ºC for at least 6 months. Nanoparticle F is very effective at inhibiting ACAT in human and mouse neuronal and microglial cell lines. Toxicity tests using mouse primary neuronal cells show that F12511 alone or Nanoparticle F added at concentrations from 2 to 10 µM for 24-, 48-, and 72-hours produces minimal, if any, toxicity. Comparison with existing method(s)Unlike existing methods, the current method is simple, cost effective, and can be expanded to produce tagged liposomes to increase specificity of delivery. This also offers opportunity to embrace water soluble agent(s) within the aqueous compartment of the nanoparticles for potential combinatorial therapy. ConclusionsThis method shows promise for delivery of hydrophobic ACAT inhibitors at high concentration in vivo.

Pharmacophore-based Screening for Identification of Human Acyl-CoA Cholesterol Acyltransferase Inhibitors: An In-silico Study

Aims: A pharmacophore based in silico study for screening out Human Acyl-CoA cholesterol acyltransferase (ACAT) inhibitors. Background: Human Acyl-CoA cholesterol acyltransferase (ACAT) plays an important role in catalysis of reaction which converts cholesterol into cholesteryl esters and long-chain fatty acyl coenzyme A. The inhibition of ACAT has therapeutically potential roles in hypercholestrolemia, atherosclerosis and coronary heart disease. Objective: As no 3D structure of Human Acyl-CoA cholesterol acyltransferase (ACAT) is reported, ligand based design of the inhibitors is required that which converts cholesterol into cholesteryl esters. Methods: For better understanding of essential chemical features for ACAT inhibition and identifying novel inhibitors, a three-dimensional (3D) chemical-feature-based quantitative QSAR pharmacophore model for available ACAT inhibitors have been developed for first time using Discovery Studio 2.5. Results: The best model (Hypo1) having lowest total cost (84.14), highest cost difference (69.67), highest correlation coefficient (0.94), and lowest RMS (1.15Å), constitutes of one hydrogen bond acceptor, one hydrogen bond donor, two hydrophobic aromatic and one hydrophobic aliphatic feature. The pharmacokinetic properties and toxicities of top 10 active hits obtained from virtual screening were predicted for ZINC33073636 and ZINC33073625. Conclusion: These studies thus provide a pharmacophore model, which will be helpful in designing novel human ACAT inhibitors.

Targeting the Cholesterol Paradigm in the Risk Reduction for Atherosclerotic Cardiovascular Disease: Does the Mechanism of Action of Pharmacotherapy Matter for Clinical Outcomes?

Hypercholesterolemia is a well-established risk factor for atherosclerotic cardiovascular disease (ASCVD). Low-density lipoprotein cholesterol (LDL-C) has been labeled as "bad" cholesterol and high-density lipoprotein cholesterol (HDL-C) as "good" cholesterol. The prevailing hypothesis is that lowering blood cholesterol levels, especially LDL-C, reduces vascular deposition and retention of cholesterol or apolipoprotein B (apoB)-containing lipoproteins which are atherogenic. We review herein the clinical trial data on different pharmacological approaches to lowering blood cholesterol and propose that the mechanism of action of cholesterol lowering, as well as the amplitude of cholesterol reduction, are critically important in leading to improved clinical outcomes in ASCVD. The effects of bile acid sequestrants, fibrates, niacin, cholesteryl ester transfer protein (CETP) inhibitors, apolipoprotein A-I and HDL mimetics, apoB regulators, acyl coenzyme A: cholesterol acyltransferase (ACAT) inhibitors, cholesterol absorption inhibitors, statins, and proprotein convertase subtilisin kexin 9 (PCSK9) inhibitors, among other strategies are reviewed. Clinical evidence supports that different classes of cholesterol lowering or lipoprotein regulating approaches yielded variable effects on ASCVD outcomes, especially in cardiovascular and all-cause mortality. Statins are the most widely used cholesterol lowering agents and have the best proven cardiovascular event and survival benefits. Manipulating cholesterol levels by specific targeting of apoproteins or lipoproteins has not yielded clinical benefit. Understanding why lowering LDL-C by different approaches varies in clinical outcomes of ASCVD, especially in survival benefit, may shed further light on our evolving understanding of how cholesterol and its carrier lipoproteins are involved in ASCVD and aid in developing effective pharmacological strategies to improve the clinical outcomes of ASCVD.

General Perspectives for the Treatment of Atherosclerosis

:Atherosclerosis, a cardiovascular disease, is at the top of the list among the diseases leading to death. Although the biochemical and pathophysiological cascades involved within the development of atherosclerosis have been identified clearly, its nature is quite complex to be treated with a single agent targeting a pathway. Therefore, many natural and synthetic compounds have been suggested for the treatment of the disease. The majority of the drugs employed target one of the single components of the pathological outcomes, resulting in many times less effective and longterm treatments. In most cases, treatment options prevent further worsening of the symptoms rather than a radical treatment. Consequently, the current review has been prepared to focus on the validated and non-validated targets of atherosclerosis as well as the alternative treatment options such as hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors, acyl-CoA cholesterol acyl transferase (ACAT) inhibitors, lipoprotein lipase stimulants, bile acid sequestrants, and some antioxidants. Related to the topic, both synthetic compounds designed employing medicinal chemistry skills and natural molecules becoming more popular in drug development are scrutinized in this mini review.

Short-Term Acyl-CoA:Cholesterol Acyltransferase Inhibition, Combined with Apoprotein A1 Overexpression, Promotes Atherosclerosis Inflammation Resolution in Mice.

Acyl-CoA:cholesterol acyltransferase (ACAT) mediates cellular cholesterol esterification. In atherosclerotic plaque macrophages, ACAT promotes cholesteryl ester accumulation, resulting in foam cell formation and atherosclerosis progression. Its complete inactivation in mice, however, showed toxic effects because of an excess of free cholesterol (FC) in macrophages, which can cause endoplasmic reticulum stress, cholesterol crystal formation, and inflammasome activation. Our previous studies showed that long-term partial ACAT inhibition, achieved by dietary supplementation with Fujirebio F1394, delays atherosclerosis progression in apoprotein E-deficient (Apoe -/-) mice by reducing plaque foam cell formation without inflammatory or toxic effects. Here, we determined whether short-term partial inhibition of ACAT, in combination with an enhanced systemic FC acceptor capacity, has synergistic benefits. Thus, we crossbred Apoe -/- with human apoprotein A1-transgenic (APOA1 tg/tg) mice, which have elevated cholesterol-effluxing high-density lipoprotein particles, and subjected Apoe -/- and APOA1 tg/tg/Apoe -/- mice to an atherogenic diet to develop advanced plaques. Then mice were either euthanized (baseline) or fed purified standard diet with or without F1394 for 4 more weeks. Plaques of APOA1 tg/tg/Apoe -/- mice fed F1394 showed a 60% reduction of macrophages accompanied by multiple other benefits, such as reduced inflammation and favorable changes in extracellular composition, in comparison with Apoe -/- baseline mice. In addition, there was no accumulation of cholesterol crystals or signs of toxicity. Overall, these results show that short-term partial ACAT inhibition, coupled to increased cholesterol efflux capacity, favorably remodels atherosclerosis lesions, supporting the potential of these combined therapies in the treatment of advanced atherosclerosis. SIGNIFICANCE STATEMENT: Short-term pharmacological inhibition of acyl-CoA:cholesterol acyltransferase-mediated cholesterol esterification, in combination with increased free cholesterol efflux acceptors, has positive effects in mice by 1) reducing the inflammatory state of the plaque macrophages and 2) favoring compositional changes associated with plaque stabilization. These effects occur without toxicity, showing the potential of these combined therapies in the treatment of advanced atherosclerosis.

Avasimibe inhibits the proliferation, migration and invasion of glioma cells by suppressing linc00339

Glioma is one of the most destructive human tumours. Although standard treatment has improved the prognosis for glioma patients, the survival of glioma patients is still unsatisfactory. Avasimibe, an effective inhibitor of cholesterol acyltransferase 1 (ACAT1), has shown anti-tumour efficacy in many kinds of tumours. However, its role and related mechanism in glioma has not been fully elucidated. In the present study, we show that avasimibe effectively inhibits the proliferation, migration and invasion of glioma cell lines. Through LncRNA microarrays, we found that linc00339 levels were closely related to the anti-tumour effect of avasimibe. With the help of a series of functional assays, we show that avasimibe inhibits the proliferation, migration and invasion of glioma cell lines by suppressing linc00339 in vitro and in vivo. Our findings may provide a new approach for glioma therapy.

Genome mining and biosynthesis of the Acyl-CoA:cholesterol acyltransferase inhibitor beauveriolide I and III in Cordyceps militaris

Ascomycete fungi Cordyceps are widely used in traditional Chinese medicine, and numerous investigations have been carried out to uncover their biological activities. However, primary researches on the physiological effects of Cordyceps were committed using crude extracts. At present, there are only a few compounds which were comprehensively characterized from Cordyceps, partial owing to the low production. In order to scientifically take advantage of Cordyceps, we used the strategy of genome mining to discover bioactive compounds from Cordyceps militaris. We found the putative biosynthetic gene cluster of the acyl-CoA:cholesterol acyltransferase inhibitor beauveriolides in the genome of C. militaris, and produced the compounds by heterologous expression in Aspergillus nidulans. Production of beauveriolide I and III also was detected in both ferment mycelia and fruiting bodies of C. militaris. The possible biosynthetic pathway was proposed. Our studies unveil the active compounds of C. militaris against atherosclerosis and Alzheimer’s disease and provide the enzyme resources for the biosynthesis of new cyclodepsipeptide molecules.

Rapid methods for the separation of natural mixtures of beauverolides, cholesterol acyltransferase inhibitors, isolated from the fungus Isaria fumosorosea.

Beauverolides (beauveriolides) are abundant, biologically active cyclodepsipeptides produced by many entomopathogenic fungi, including those that are used as biopesticides. Beauverolides act as cholesterol acyltransferase inhibitors in humans; thus, their mode of action has been the subject of pharmacological and clinical research. The cost-effective analytical methods are needed for fast, routine laboratory analysis of beauverolides. We isolated beauverolides from the fungal strain Isaria fumosorosea PFR 97-Apopka and opened the rings of the isolated beauverolides using a pyridine alkaline medium. We separated fractions of cyclic and linearized beauverolides by thin-layer chromatography, and found the chloroform-acetate (9:1, v/v) and chloroform-acetonitrile-acetate (8:1:1, v/v/v) mobile phases, respectively, to be the most efficient. We examined all the fractions by liquid chromatography-mass spectrometry using ion trap and Orbitrap high resolution mass spectrometry. For rapid screening of the contents of cyclic, and, particularly, linearized beauverolides, we developed a novel analytical method that consisted of using capillary electrophoresis coupled with contactless conductivity detection. Furthermore, we improved the separation of the peptides by applying capillary micellar electrokinetic chromatography with the N-cyclohexyl-2-aminoethanesulfonic acid:SDS:NaOH buffer, pH 9.8 as the background electrolyte. The described novel methods allow fast and cost-effective separation of chemically related groups of beauverolides.

Acyl-Coenzyme A: Cholesterol Acyltransferase Inhibition in Cancer Treatment.

Overexpression of acyl-coenzyme A:cholesterol acyltransferase (ACAT) results in increased cholesteryl ester levels and has been involved in a variety of cancer types. As a consequence, cholesterol metabolism has raised interest as a potential target for cancer treatment. Inhibition of ACAT results in suppression of proliferation in a range of cancer cell types both in vitro and in vivo. The exact mechanism of this phenomenon is being investigated, and the most important findings are presented in this review.

Cholesterol Esterification Enzyme Inhibition Enhances Antitumor Effects of Human Chimeric Antigen Receptors Modified T Cells.

Chimeric antigen receptor-modified T cell (CART) therapy has been demonstrated to have significant effect on hematologic tumor in patients. However, many persistent obstacles and challenges still limit the application. It is known that CD8 T cells are a key component of antitumor immunity. An avasimibe-induced inhibition of cholesterol esterification has been shown to improve the antitumor response of CD8 T cells in mice. In this study, using human CD19-directed CART cells as effector cells and CD19-overexpressing K562 cells as target cells, we detected whether cholesterol acyltransferase inhibition by avasimibe can enhance the antitumor effect of human CART cells. After avasimibe treatment, the infection rate was dropped by up to 50% (P<0.05). The cytotoxic effect of CART cells was significantly increased than the control group in a dose-dependent manner. Moreover, the level of secreted interferon-γ increased in almost half of the cases (P<0.05); the ratio of CD8CD4 T cells was increased among the total T cells and the CART cells in some of cases (P<0.05). Our study suggests that inhibition of cholesterol acyltransferase can promote the antitumor effect of CART cells, and provides a new option for a combination therapy by regulating T-cell metabolism to enhance antitumor effects.

Cholesterol esterification inhibition and imatinib treatment synergistically inhibit growth of BCR-ABL mutation-independent resistant chronic myelogenous leukemia.

Since the advent of tyrosine kinase inhibitors (TKIs) such as imatinib, nilotinib, and dasatinib, chronic myelogenous leukemia (CML) prognosis has improved greatly. However, ~30–40% of patients develop resistance to imatinib therapy. Although most resistance is caused by mutations in the BCR-ABL kinase domain, 50–85% of these patients develop resistance in the absence of new mutations. In these cases, targeting other pathways may be needed to regain clinical response. Using label-free Raman spectromicroscopy, we evaluated a number of leukemia cell lines and discovered an aberrant accumulation of cholesteryl ester (CE) in CML, which was found to be a result of BCR-ABL kinase activity. CE accumulation in CML was found to be a cancer-specific phenomenon as untransformed cells did not accumulate CE. Blocking cholesterol esterification with avasimibe, a potent inhibitor of acyl-CoA cholesterol acyltransferase 1 (ACAT-1), significantly suppressed CML cell proliferation in Ba/F3 cells with the BCR-ABLT315I mutation and in K562 cells rendered imatinib resistant without mutations in the BCR-ABL kinase domain (K562R cells). Furthermore, the combination of avasimibe and imatinib caused a profound synergistic inhibition of cell proliferation in K562R cells, but not in Ba/F3T315I. This synergistic effect was confirmed in a K562R xenograft mouse model. Analysis of primary cells from a BCR-ABL mutation-independent imatinib resistant patient by mass cytometry suggested that the synergy may be due to downregulation of the MAPK pathway by avasimibe, which sensitized the CML cells to imatinib treatment. Collectively, these data demonstrate a novel strategy for overcoming BCR-ABL mutation-independent TKI resistance in CML.

Emerging antiplatelet and lipid lowering therapies

Antiplatelet therapy is used widely with proven benefit for the primary prevention of cardiovascular disease as well as for the prevention of further ischemic cardiovascular events in patients with proven coronary artery disease (CAD) and in those with a history of acute coronary syndrome (ACS). The limitations of conventional antiplatelet therapy with aspirin, clopidogrel, or prasugrel, as well as the fact that rates of recurrent ischemic events still remain high with use of these agents, underscore the need to investigate alternative molecules that may be effective in further reducing the occurrence of events without increasing the risk of bleeding. The armamentarium of antiplatelet therapy has been further enriched by ticagrelor, cangrelor, vorapaxar, prasugrel and atopaxar. Ticagrelor was approved in 2011 by the European Medicines Agency swiftly followed by the US Food and Drug Administration. Reversible antiplatelet agents acting as P2Y12 antagonists similar to ticagrelor are cangrelor, and elinogrel. A new class of oral protease-activated receptor-1 (PAR-1) inhibitors, vorapaxar and atopaxar has also been proposed as effective antiplatelets but their clinical benefit is still under debate. The P2Y12 antagonists prasugrel and ticagrelor prevent adverse cardiac outcomes albeit their absolute benefit is very small. The beneficial effect of prasugrel and ticagrelor comes at a cost of an increased risk of bleeding. Furthermore, new adverse effects have also become evident with the new P2Y12 antagonists and these include dyspnea (for all of the reversible P2Y12 antagonists: ticagrelor, cangrelor, and elinogrel) and ventricular pauses for ticagrelor. In addition, the newer P2Y12 antagonists have a peculiar pharmacodynamic profile with a fast onset and offset. Two of these agents, cangrelor and elinogrel, are available as intravenous formulations, which may provide additional benefits in patients who undergo coronary artery bypass graft (CABG) surgery. Trials with the PAR-1 inhibitors have also shown trends toward reductions in cardiac events, but not without the possibility of increased bleeding. Physicians must carefully assess patient-specific factors such as risk of thrombosis, concomitant disease states, age, drug adherence, and aspirin dose, and plan for those patients who will be undergoing CABG when selecting antiplatelet therapy in order to optimally balance bleeding and thrombosis risk. In addition to adequate anti-platelet therapy the treatment of blood lipids is important for the primary and secondary prevention of cardiovascular disease. Elevated low-density lipoprotein cholesterol is an important risk factor for cardiovascular and cerebrovascular events. HMG-CoA reductase inhibitors, or statins, are very effective in lowering cholesterol levels, and in reducing mortality and cardiovascular events in patients with and without cardiovascular disease. The evidence cumulated with the studies conducted with statin has led to the recent recommendations that all patients with known vascular disease, or who are at high risk for vascular disease, should be considered candidates for statin therapy. Nonstatin therapies (either as monotherapy or in addition to statins) to reduce LDL cholesterol by mechanisms that do not involve inhibition of HMG-CoA reductase are likely to be useful for patients in need of LDL reduction; particularly those who either cannot take statins or respond only partially or not at all to statins alone. These therapies include cholesterol absorption inhibitors, Acyl-CoA cholesterol acyl transferase inhibitors, farnesoid X receptor antagonists, sterolregulating binding protein cleavage activating protein, and microsomal triglyceride transfer protein. Recent studies with the PCSK9 have shown that these drugs significantly reduce total and LDL cholesterol in patients with familial hypercholesterolaemia and that are effective in further reducing plasma cholesterol levels in patients receiving statins. Therefore, therapeutic options are becoming available for patients who cannot tolerate full dose statin therapy or for those few patients who are intolerant to statin therapy.

Chlamydia trachomatis growth depends on eukaryotic cholesterol esterification and is affected by Acyl-CoA:cholesterol acyltransferase inhibition.

Chlamydia trachomatis is auxotrophic for a variety of essential metabolites. Inhibitors that interrupt host cell catabolism may inhibit chlamydial growth and reveal Chlamydia metabolite requirements. We used the known indoleamine-2,3-dioxygenase (IDO)-inhibitor 4-phenyl imidazole (4-PI) to reverse Interferon (IFN)-γ-induced chlamydial growth inhibition. However, at elevated inhibitor concentrations chlamydial growth was arrested even in the absence of IFN-γ. Since 4-PI is known to interfere with cholesterol metabolism, the effect of cholesterol add-back was tested. Chlamydia growth was restored in the presence of cholesterol in serum-containing, but not serum-free medium suggesting that cholesterol and other serum components are required for growth recovery. When serum factors were tested, either cholesteryl linoleate or the combination of cholesterol and linoleic acid restored chlamydial growth. However, growth was not restored when either cholesterol or linoleic acid were added alone, suggesting that the production of cholesteryl esters from cholesterol and fatty acids was affected by 4-PI treatment. In eukaryotic cells, the enzyme Acyl-CoA:cholesterol acyltransferase (ACAT) catalyzes the production of cholesteryl esters. When HeLa cells were treated with the ACAT-specific inhibitor 4-hydroxycinnamicacid amide C. trachomatis growth was interrupted, but was restored by the addition of cholesteryl linoleate, suggesting that ACAT activity is necessary for intracellular Chlamydia growth.

HCV 3a core protein increases lipid droplet cholesteryl ester content via a mechanism dependent on sphingolipid biosynthesis.

Hepatitis C virus (HCV) infected patients often develop steatosis and the HCV core protein alone can induce this phenomenon. To gain new insights into the pathways leading to steatosis, we performed lipidomic profiling of HCV core protein expressing-Huh-7 cells and also assessed the lipid profile of purified lipid droplets isolated from HCV 3a core expressing cells. Cholesteryl esters, ceramides and glycosylceramides, but not triglycerides, increased specifically in cells expressing the steatogenic HCV 3a core protein. Accordingly, inhibitors of cholesteryl ester biosynthesis such as statins and acyl-CoA cholesterol acyl transferase inhibitors prevented the increase of cholesteryl ester production and the formation of large lipid droplets in HCV core 3a-expressing cells. Furthermore, inhibition of de novo sphingolipid biosynthesis by myriocin - but not of glycosphingolipid biosynthesis by miglustat - affected both lipid droplet size and cholesteryl ester level. The lipid profile of purified lipid droplets, isolated from HCV 3a core-expressing cells, confirmed the particular increase of cholesteryl ester. Thus, both sphingolipid and cholesteryl ester biosynthesis are affected by the steatogenic core protein of HCV genotype 3a. These results may explain the peculiar lipid profile of HCV-infected patients with steatosis.

An overview of the new frontiers in the treatment of atherogenic dyslipidemias.

Cardiovascular diseases (CVDs) are the leading cause of morbidity/mortality worldwide. Dyslipidemia is a major risk factor for premature atherosclerosis and CVD. Lowering low-density-lipoprotein cholesterol (LDL-C) levels is well established as an intervention for the reduction of CVDs. Statins are the first-line drugs for treatment of dyslipidemia, but they do not address all CVD risk. Development of novel therapies is ongoing and includes the following: (i) reduction of LDL-C concentrations using antibodies to proprotein convertase subtilisin/kexin-9, antisense oligonucleotide inhibitors of apolipoprotein B production, microsomal transfer protein (MTP) inhibitors, and acyl-coenzyme A cholesterol acyl transferase inhibitors; (ii) reduction in levels of triglyceride-rich lipoproteins with ω-3 fatty acids, MTP inhibitors, and diacylglycerol acyl transferase-1 inhibitors; and (iii) increase of high-density-lipoprotein (HDL) cholesterol levels, HDL particle numbers, and/or HDL functionality using cholesteryl ester transfer protein inhibitors, HDL-derived agents, apolipoprotein AI mimetic peptides, and microRNAs. Large prospective outcome trials of several of these emerging therapies are under way, and thrilling progress in the field of lipid management is anticipated.