Effect of ACAT inhibition on the progression of coronary atherosclerosis

Regression of coronary atherosclerosis: Current evidence and future perspectives

Coronary atherosclerosis has been considered a chronic disease characterized by ongoing progression in response to systemic risk factors and local pro-atherogenic stimuli. As our understanding of the pathobiological mechanisms implicated in atherogenesis and plaque progression is evolving, effective treatment strategies have been developed that led to substantial reduction of the clinical manifestations and acute complications of coronary atherosclerotic disease. More recently, intracoronary imaging modalities have enabled detailed in vivo quantification and characterization of coronary atherosclerotic plaque, serial evaluation of atherosclerotic changes over time, and assessment of vascular responses to effective anti-atherosclerotic medications. The use of intracoronary imaging modalities has demonstrated that intensive lipid lowering can halt plaque progression and may even result in regression of coronary atheroma when the highest doses of the most potent statins are used. While current evidence indicates the feasibility of atheroma regression and of reversal of presumed high-risk plaque characteristics in response to intensive anti-atherosclerotic therapies, these changes of plaque size and composition are modest and their clinical implications remain largely elusive. Growing interest has focused on achieving more pronounced regression of coronary plaque using novel anti-atherosclerotic medications, and more importantly on elucidating ways toward clinical translation of favorable changes of plaque anatomy into more favorable clinical outcomes for our patients.

Non-invasive volumetric assessment of aortic atheroma: a core laboratory validation using computed tomography angiography

Aortic atherosclerosis has been linked with worse peri- and post-procedural outcomes following a range of aortic procedures. Yet, there are currently no standardized methods for non-invasive volumetric pan-aortic plaque assessment. We propose a novel means of more accurately assessing plaque volume across whole aortic segments using computed tomography angiography (CTA) imaging. Sixty patients who underwent CTA prior to trans-catheter aortic valve implantation were included in this analysis. Specialized software analysis (3mensio Vascular™, Pie Medical, Maastricht, Netherlands) was used to reconstruct images using a centerline approach, thus creating true cross-sectional aortic images, akin to those images produced with intravascular ultrasonography. Following aortic segmentation (from the aortic valve to the renal artery origin), atheroma areas were measured across multiple contiguous evenly spaced (10 mm) cross-sections. Percent atheroma volume (PAV), total atheroma volume (TAV) and calcium score were calculated. In our populations (age 79.9 ± 8.5 years, male 52 %, diabetes 27 %, CAD 84 %, PVD 20 %), mean ± SD number of cross sections measured for each patient was 35.1 ± 3.5 sections. Mean aortic PAV and TAV were 33.2 ± 2.51 % and 83,509 ± 17,078 mm(3), respectively. Median (IQR) calcium score was 1.5 (0.7-2.5). Mean (SD) inter-observer coefficient of variation and agreement for plaque area among 4 different analysts was 14.1 (5.4), and the mean (95 % CI) Lin's concordance correlation coefficient was 0.79 (0.62-0.89), effectively simulating a Core Laboratory scenario. We provide an initial validation of cross-sectional volumetric aortic atheroma assessment using CTA. This proposed methodology highlights the potential for utilizing non-invasive aortic plaque imaging for risk prediction across a range of clinical scenarios.

Antisense oligonucleotides, microRNAs, and antibodies

The specificity of Watson-Crick base pairing and the development of several chemical modifications to oligonucleotides have enabled the development of novel drug classes for the treatment of different human diseases. This review focuses on promising results of recent preclinical or clinical studies on targeting HDL metabolism and function by antisense oligonucleotides and miRNA-based therapies. Although many hurdles regarding basic mechanism of action, delivery, specificity, and toxicity need to be overcome, promising results from recent clinical trials and recent approval of these types of therapy to treat dyslipidemia suggest that the treatment of HDL dysfunction will benefit from these unique clinical opportunities. Moreover, an overview of monoclonal antibodies (mAbs) developed for the treatment of dyslipidemia and cardiovascular disease and currently being tested in clinical studies is provided. Initial studies have shown that these compounds are generally safe and well tolerated, but ongoing large clinical studies will assess their long-term safety and efficacy.

Atheroma progression in hyporesponders to statin therapy

OBJECTIVE

Lowering low-density lipoprotein cholesterol (LDL-C) with statins has been demonstrated to slow plaque progression. This antiatherosclerotic effect in patients with minimal LDL-C lowering has not been investigated.

APPROACH AND RESULTS

Six hundred forty-seven patients with angiographic coronary artery disease who were commenced on statin therapy underwent serial imaging with intravascular ultrasound. Responders were defined as a percentage reduction in LDL-C of <15%. Disease progression was compared in responders (n=517) and hyporesponders (n=130) to statin therapy. Twenty percentage of patients demonstrated minimal changes in LDL-C, despite commencement of statin therapy. Statin hyporesponders were younger (55 versus 57 years; P=0.01), more likely to be male (79% versus 66%; P=0.005), and obese (body mass index, 31.5 ± 6.1 versus 30.3 ± 5.9 kg/m(2); P=0.04) and less likely to have a history of dyslipidemia (50% versus 66%; P<0.001). Baseline levels of systolic blood pressure (127 ± 15 versus 132 ± 17 mm Hg; P=0.01) and LDL-C (2.5 ± 0.6 versus 3.4 ± 0.8 mmol/L; P<0.001) were lower in statin hyporesponders. Baseline percent atheroma volume was similar between statin hyporesponders and responders (36.9 ± 9.8% versus 38.3 ± 9.2%; P=0.13). On serial evaluation, greater progression of percent atheroma volume (1.19 ± 0.48% versus 0.09 ± 0.43%; P=0.003) was observed in statin hyporesponders. After adjusting for baseline clinical characteristics and measures of plaque burden, statin hyporesponders still exhibited greater atheroma progression (+0.83 ± 0.58% versus -0.21 ± 0.52%; P=0.006).

CONCLUSIONS

A substantial proportion of patients with coronary artery disease fail to achieve effective reductions in LDL-C, despite prescription of statin therapy. Greater progression of atherosclerosis is observed in these patients. Our current study underscores monitoring LDL-C level after the commencement of statin to ensure adequate response to statin therapy.

The difference between Asian and Western in the effect of LDL-C lowering therapy on coronary atherosclerotic plaque: a meta-analysis report

Background

The different effects of LDL-C levels and statins therapy on coronary atherosclerotic plaque between Western and Asian remain to be settled.

Methods

PubMed, EMBASE, and Cochrane databases were searched from Jan. 2000 to Sep. 2014 for randomized controlled or blinded end-points trials assessing the effects of LDL-C lowering therapy on regression of coronary atherosclerotic plaque (CAP) in patients with coronary heart disease by intravascular ultrasound. The significance of plaques regression was assessed by computing standardized mean difference (SMD) of the volume of CAP between the baseline and follow-up.

Results

Twenty trials (ten in the West and ten in Asia) were identified. For Westerns, Mean lowering LDL-C by 49.4% and/or to level 61.9 mg/dL in the group of patients with baseline mean LDL-C 123.2 mg/dL could significantly reduce the volume of CAP at follow up (SMD −0.156 mm³, 95% CI −0.248 ~ −0.064, p = 0.001). LDL-C lowering by rosuvastatin (mean 40 mg daily) could significantly decrease the volumes of CAP at follow up. For Asians, Mean lowering LDL-C by 36.1% and/or to level 84.0 mg/dL with baseline mean LDL-C 134.2 mg/dL could significantly reduce the volume of CAP at follow up (SMD −0.211 mm³, 95% CI −0.331 ~ −0.092, p = 0.001). LDL-C lowering by rosuvastatin (mean 14.1 mg daily) and atorvastatin (mean 18.9 mg daily) could significantly decrease the volumes of CAP at follow up.

Conclusions

There was a different effect of LDL-C lowering on CAP between Westerns and Asians. For regressing CAP, Asians need lower dosage of statins or lower intensity LDL-C lowering therapy than Westerns.

In vitro metabolism of pyripyropene A and ACAT inhibitory activity of its metabolites

Pyripyropene A (PPPA, 1) of fungal origin, a selective inhibitor of acyl-CoA:cholesterol acyltransferase 2 (ACAT2), proved orally active in atherogenic mouse models. The in vitro metabolites of 1 in liver microsomes and plasma of human, rabbit, rat and mouse were analyzed by ultra fast liquid chromatography and liquid chromatography/tandem mass spectrometry. In the liver microsomes from all species, successive hydrolysis occurred at the 1-O-acetyl residue, then at the 11-O-acetyl residue of 1, while the 7-O-acetyl residue was resistant to hydrolysis. Furthermore, dehydrogenation of the newly generated 11-alcoholic hydroxyl residue occurred in human and mouse-liver microsomes, while oxidation of the pyridine ring occurred in human and rabbit liver microsomes. On the other hand, hydrolysis of the 7-O-acetyl residue proceeded only in the mouse plasma. These data indicated that the in vitro metabolic profiles of 1 have subtle differences among animal species. All of the PPPA metabolites observed in liver microsomes and plasma markedly decreased ACAT2 inhibitory activity. These findings will help us to synthesize new PPPA derivatives more effective in in vivo study than 1.

Loss of apoptosis regulator through modulating IAP expression (ARIA) protects blood vessels from atherosclerosis

Atherosclerosis is the primary cause for cardiovascular disease. Here we identified a novel mechanism underlying atherosclerosis, which is provided by ARIA (apoptosis regulator through modulating IAP expression), the transmembrane protein that we recently identified. ARIA is expressed in macrophages present in human atherosclerotic plaque as well as in mouse peritoneal macrophages. When challenged with acetylated LDL, peritoneal macrophages isolated from ARIA-deficient mice showed substantially reduced foam cell formation, whereas the uptake did not differ from that in wild-type macrophages. Mechanistically, loss of ARIA enhanced PI3K/Akt signaling and consequently reduced the expression of acyl coenzyme A:cholesterol acyltransferase-1 (ACAT-1), an enzyme that esterifies cholesterol and promotes its storage, in macrophages. Inhibition of PI3K abolished the reduction in ACAT-1 expression and foam cell formation in ARIA-deficient macrophages. In contrast, overexpression of ARIA reduced Akt activity and enhanced foam cell formation in RAW264.7 macrophages, which was abrogated by treatment with ACAT inhibitor. Of note, genetic deletion of ARIA significantly reduced the atherosclerosis in ApoE-deficient mice. Oil red-O-positive lipid-rich lesion was reduced, which was accompanied by an increase of collagen fiber and decrease of necrotic core lesion in atherosclerotic plaque in ARIA/ApoE double-deficient mice. Analysis of bone marrow chimeric mice revealed that loss of ARIA in bone marrow cells was sufficient to reduce the atherosclerogenesis in ApoE-deficient mice. Together, we identified a unique role of ARIA in the pathogenesis of atherosclerosis at least partly by modulating macrophage foam cell formation. Our results indicate that ARIA could serve as a novel pharmacotherapeutic target for the treatment of atherosclerotic diseases.

Acyltransferase inhibitors: a patent review (2010-present)

INTRODUCTION

Acyltransferase (AT) catalyzes the transfer of an acyl moiety from acyl-coenzyme A (acyl-CoA) to an acceptor. ATs play important roles in the maintenance of homeostasis in the human body and have been linked to various diseases; therefore, several ATs have been proposed as potential targets for the treatment or prevention of such diseases. The AT family includes acyl-CoA:cholesterol AT (ACAT), diacylglycerol AT (DGAT), and monoacylglycerol AT (MGAT) for the metabolism of lipids. Furthermore, recent molecular biological studies revealed the existence of their isozymes with distinct functions in the body.

AREAS COVERED

This review summarized patent filings published between 2010 and the present date that claimed isozyme-selective inhibitors of ACAT, DGAT and MGAT, which are involved in neutral lipid metabolism.

EXPERT OPINION

Isozymes of ACAT, DGAT and MGAT play distinct functions in neutral lipid metabolism in the human body and have been considered as potential therapeutic targets. Accordingly, isozyme-selective inhibitors that could be used in the treatment or prevention of lipid metabolism disorders were searched for. Of these, pyripyropene A derivatives, ACAT2-selective inhibitors, may be potential therapeutics for the treatment of atherosclerosis, homozygous familial hypercholesterolemia and nonalcoholic fatty liver disease.

Impact of baseline lipoprotein and C-reactive protein levels on coronary atheroma regression following high-intensity statin therapy

Guidelines now recommend high-intensity statin therapy in all patients with proven atherosclerotic disease. Yet the impact of baseline lipoprotein and C-reactive protein (CRP) levels on measures of disease regression to this therapy are unknown. The aim of this study was to test the hypothesis that high-intensity statin therapy causes equivalent degrees of coronary atheroma regression irrespective of baseline lipoprotein and CRP levels. In 8 prospective randomized trials using serial coronary intravascular ultrasound, 1,881 patients who maintained or switched to 18- to 24 months of high-intensity statin therapy (rosuvastatin 40 mg or atorvastatin 80 mg) were stratified according to baseline lipoprotein and CRP levels. Changes in coronary percentage atheroma volume (PAV) and total atheroma volume (TAV) were evaluated. High-intensity statin therapy produced significant reductions from baseline in low-density lipoprotein cholesterol by 38.4%, non-high-density lipoprotein (HDL) cholesterol by 33.6%, triglycerides by 13.1%, and CRP by 33.3%, while increasing HDL cholesterol by 11.7% (p <0.001 for all). This was associated with regression of PAV by 0.7% and of TAV by 8.2 mm(3) (p <0.001 for both). No significant differences of changes in PAV and TAV were observed across baseline quintiles of low-density lipoprotein cholesterol, HDL cholesterol, non-HDL cholesterol, triglycerides, or CRP. Moreover, across all measured lipoproteins and CRP, most patients demonstrated plaque regression (defined as any change from baseline in PAV or TAV <0). In conclusion, high-intensity statin therapy attenuated the natural progression of coronary atherosclerosis in all strata of patients with coronary artery disease irrespective of baseline lipoprotein or CRP levels. These findings provide support for the latest United States guideline recommendations for the broad use of high-intensity statin therapy in all patients with atherosclerosis, regardless of baseline lipid status.

Cholesterol esters (CE) derived from hepatic sterol O-acyltransferase 2 (SOAT2) are associated with more atherosclerosis than CE from intestinal SOAT2

RATIONALE

Cholesterol esters (CE), especially cholesterol oleate, generated by hepatic and intestinal sterol O-acyltransferase 2 (SOAT2) play a critical role in cholesterol homeostasis. However, it is unknown whether the contribution of intestine-derived CE from SOAT2 would have similar effects in promoting atherosclerosis progression as for liver-derived CE.

OBJECTIVE

To test whether, in low-density lipoprotein receptor null (LDLr(-/-)) mice, the conditional knockout of intestinal SOAT2 (SOAT2(SI-/SI-)) or hepatic SOAT2 (SOAT2(L-/L-)) would equally limit atherosclerosis development compared with the global deletion of SOAT2 (SOAT2(-/-)).

METHODS AND RESULTS

SOAT2 conditional knockout mice were bred with LDLr(-/-) mice creating LDLr(-/-) mice with each of the specific SOAT2 gene deletions. All mice then were fed an atherogenic diet for 16 weeks. SOAT2(SI-/SI-)LDLr(-/-) and SOAT2(-/-)LDLr(-/-) mice had significantly lower levels of intestinal cholesterol absorption, more fecal sterol excretion, and lower biliary cholesterol levels. Analysis of plasma LDL showed that all mice with SOAT2 gene deletions had LDL CE with reduced percentages of cholesterol palmitate and cholesterol oleate. Each of the LDLr(-/-) mice with SOAT2 gene deletions had lower accumulations of total cholesterol and CE in the liver compared with control mice. Finally, aortic atherosclerosis development was significantly lower in all mice with global or tissue-restricted SOAT2 gene deletions. Nevertheless, SOAT2(-/-)LDLr(-/-) and SOAT2(L-/L-)LDLr(-/-) mice had less aortic CE accumulation and smaller aortic lesions than SOAT2(SI-/SI-)LDLr(-/-) mice.

CONCLUSIONS

SOAT2-derived CE from both the intestine and liver significantly contribute to the development of atherosclerosis, although the CE from the hepatic enzyme appeared to promote more atherosclerosis development.

Berberine decreases cholesterol levels in rats through multiple mechanisms, including inhibition of cholesterol absorption

OBJECTIVE

The objective was to determine the mechanisms of action of berberine (BBR) on cholesterol homeostasis using in vivo and in vitro models.

METHODS

Male Sprague-Dawley rats were fed the AIN-93G diet (normal control) or modified AIN-93G diet containing 28% fat, 2% cholesterol and 0.5% cholic acid with treatment of 0 (atherogenic control), 50, 100, and 150 mg/kg·d of BBR, respectively by gavaging in water for 8 weeks. Cholesterol absorption rate was measured with the dual stable isotope ratio method, and plasma lipids were determined using the enzymatic methods. Gene and protein expressions of Acyl-coenzyme A:cholesterol acyltransferase-2 were analyzed in vivo and in vitro. Cholesterol micellarization, uptake and permeability were determined in vitro.

RESULTS

Rats on the atherogenic diet showed significantly hypercholesterolemic characteristics compared to normal control rats. Treatment with BBR in rats on the atherogenic diet reduced plasma total cholesterol and nonHDL cholesterol levels by 29%-33% and 31%-41%, respectively, with no significant differences being observed among the three doses. The fractional dietary cholesterol absorption rate was decreased by 40%-51%. Rats fed the atherogenic diet showed lower plasma triacylglycerol levels, and no changes were observed after the BBR treatment. BBR interfered with cholesterol micellarization, decreased cholesterol uptake by Caco-2 cells and permeability through Caco-2 monolayer. BBR also inhibited the gene and protein expressions of acyl-coenzyme A cholesterol acyltransferease-2 in the small intestine and Caco-2 cells.

CONCLUSION

BBR lowered blood cholesterol levels at least in part through inhibiting the intestinal absorption and further by interfering with intraluminal cholesterol micellarization and decreasing enterocyte cholesterol uptake and secretion.

Hepatitis C virus infection mediates cholesteryl ester synthesis to facilitate infectious particle production

Cholesterol is a critical component of the hepatitis C virus (HCV) life cycle, as demonstrated by its accumulation within infected hepatocytes and lipoviral particles. To cope with excess cholesterol, hepatic enzymes ACAT1 and ACAT2 produce cholesteryl esters (CEs), which are destined for storage in lipid droplets or for secretion as apolipoproteins. Here we demonstrate in vitro that cholesterol accumulation following HCV infection induces upregulation of the ACAT genes and increases CE synthesis. Analysis of human liver biopsy tissue showed increased ACAT2 mRNA expression in liver infected with HCV genotype 3, compared with genotype 1. Inhibiting cholesterol esterification using the potent ACAT inhibitor TMP-153 significantly reduced production of infectious virus, but did not inhibit virus RNA replication. Density gradient analysis showed that TMP-153 treatment caused a significant increase in lipoviral particle density, suggesting reduced lipidation. These data suggest that cholesterol accumulation following HCV infection stimulates the production of CE, a major component of lipoviral particles. Inhibition of CE synthesis reduces HCV particle density and infectivity, suggesting that CEs are required for optimal infection of hepatocytes.

Relation of high-density lipoprotein cholesterol:apolipoprotein a-I ratio to progression of coronary atherosclerosis in statin-treated patients

High-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apoA-I) levels are inversely associated with adverse cardiovascular outcomes. Associations between these HDL-C-related measurements and coronary plaque progression have not been studied. We performed a retrospective analysis of 2,566 statin-treated patients with angiographic coronary artery disease who underwent serial evaluation of atheroma burden with intravascular ultrasound. Relations between achieved levels of HDL-related measurements with clinical characteristics and changes in plaque burden were determined. A strong correlation between HDL-C and apoA-I (r = 0.80, p <0.001) was observed. HDL-C, apoA-I, and the HDL-C:apoA-I ratio demonstrated negative correlations with the change in percent atheroma volume and total atheroma volume (all p ≤0.001). Increasing levels of achieved HDL-C:apoA-I (p = 0.04), but not HDL-C (p = 0.18) or apoA-I (p = 0.67), were associated with less progression of percent atheroma volume. Similar results were seen for change in total atheroma volume, with less progression seen with increased HDL-C:apoA-I (p = 0.002) but not with increases in HDL-C (p = 0.09) or apoA-I (p = 0.19). In conclusion, increasing levels of HDL-C:apoA-I associated with less progression of coronary atherosclerosis. This suggests that interventions increasing the cholesterol content of HDL particles may be of cardiovascular benefit.

Imaging plaques to predict and better manage patients with acute coronary events

Culprit lesions of patients, who have had an acute coronary syndrome commonly, are ruptured coronary plaques with superimposed thrombus. The precursor of such lesions is an inflamed thin-capped fibroatheroma. These plaques can be imaged by means of invasive techniques, such as intravascular ultrasound (and derived techniques), optical coherence tomography, and near-infrared spectroscopy. Often these patients exhibit similar (multiple) plaques beyond the culprit lesion. These remote plaques can be assessed noninvasively by computed tomographic angiography and MRI and also using invasive imaging. The detection of these remote plaques is not only feasible but also in natural history studies have been associated with clinical coronary events. Different systemic pharmacological treatments have been studied (mostly statins) with modest success and, therefore, newer approaches are being tested. Local treatment for such lesions is in its infancy and larger, prospective, and randomized trials are needed. This review will describe the pathological and imaging findings in culprit lesions of patients with acute coronary syndrome and the assessment of remote plaques. In addition, the pharmacological and local treatment options will be reviewed.

Acyl-CoA:cholesterol acyltransferase 1 mediates liver fibrosis by regulating free cholesterol accumulation in hepatic stellate cells

BACKGROUND & AIMS

Acyl-coenzyme A: cholesterol acyltransferase (ACAT) catalyzes the conversion of free cholesterol (FC) to cholesterol ester, which prevents excess accumulation of FC. We recently found that FC accumulation in hepatic stellate cells (HSCs) plays a role in progression of liver fibrosis, but the effect of ACAT1 on liver fibrosis has not been clarified. In this study, we aimed to define the role of ACAT1 in the pathogenesis of liver fibrosis.

METHODS

ACAT1-deficient and wild-type mice, or Toll-like receptor 4 (TLR4)(-/-)ACAT1(+/+) and TLR4(-/-)ACAT1(-/-) mice were subjected to bile duct ligation (BDL) for 3 weeks or were given carbon tetrachloride (CCl4) for 4 weeks to induce liver fibrosis.

RESULTS

ACAT1 was the major isozyme in mice and human primary HSCs, and ACAT2 was the major isozyme in mouse primary hepatocytes and Kupffer cells. ACAT1 deficiency significantly exaggerated liver fibrosis in the mouse models of liver fibrosis, without affecting the degree of hepatocellular injury or liver inflammation, including hepatocyte apoptosis or Kupffer cell activation. ACAT1 deficiency significantly increased FC levels in HSCs, augmenting TLR4 protein and downregulating expression of transforming growth factor-β (TGFβ) pseudoreceptor Bambi (bone morphogenetic protein and activin membrane-bound inhibitor), leading to sensitization of HSCs to TGFβ activation. Exacerbation of liver fibrosis by ACAT1 deficiency was dependent on FC accumulation-induced enhancement of TLR4 signaling.

CONCLUSIONS

ACAT1 deficiency exaggerates liver fibrosis mainly through enhanced FC accumulation in HSCs. Regulation of ACAT1 activities in HSCs could be a target for treatment of liver fibrosis.

The LRP6 rs2302685 polymorphism is associated with increased risk of myocardial infarction

Background

Abnormal lipids is one of the critical risk factors for myocardial infarction (MI), however the role of genetic variants in lipid metabolism-related genes on MI pathogenesis still requires further investigation. We herein genotyped three SNPs (LRP6 rs2302685, LDLRAP1 rs6687605, SOAT1 rs13306731) in lipid metabolism-related genes, aimed to shed light on the influence of these SNPs on individual susceptibility to MI.

Methods

Genotyping of the three SNPs (rs2302685, rs6687605 and rs13306731) was performed in 285 MI cases and 650 control subjects using polymerase chain reaction–ligation detection reaction (PCR–LDR) method. The association of these SNPs with MI and lipid profiles was performed with SPSS software.

Results

Multivariate logistic regression analysis showed that C allele (OR = 1.62, P = 0.039) and the combined CT/CC genotype (OR = 1.67, P = 0.035) of LRP6 rs2302685 were associated with increased MI risk, while the other two SNPs had no significant effect. Further stratified analysis uncovered a more evident association with MI risk among younger subjects (≤60 years old). Fascinatingly, CT/CC genotype of rs2302685 conferred increased LDL-C levels compared to TT genotype (3.0 mmol/L vs 2.72 mmol/L) in younger subjects.

Conclusions

Our data provides the first evidence that LRP6 rs2302685 polymorphism is associated with an increased risk of MI in Chinese subjects, and the association is more evident among younger individuals, which probably due to the elevated LDL-C levels.

Systematic study of the effects of lowering low-density lipoprotein-cholesterol on regression of coronary atherosclerotic plaques using intravascular ultrasound

BACKGROUND

Conflicting results currently exist on the effects of LDL-C levels and statins therapy on coronary atherosclerotic plaque, and the target level of LDL-C resulting in the regression of the coronary atherosclerotic plaques has not been settled.

METHODS

PubMed, EMBASE, and Cochrane databases were searched from Jan. 2000 to Jan. 2014 for randomized controlled or blinded end-points trials assessing the effects of LDL-C lowering therapy on regression of coronary atherosclerotic plaque (CAP) in patients with coronary heart disease by intravascular ultrasound. Data concerning the study design, patient characteristics, and outcomes were extracted. The significance of plaques regression was assessed by computing standardized mean difference (SMD) of the volume of CAP between the baseline and follow-up. SMD were calculated using fixed or random effects models.

RESULTS

Twenty trials including 5910 patients with coronary heart disease were identified. Mean lowering LDL-C by 45.4% and to level 66.8 mg/dL in the group of patients with baseline mean LDL-C 123.7 mg/dL, mean lowering LDL-C by 48.8% and to level 60.6 mg/dL in the group of patients with baseline mean LDL-C 120 mg/dL, and mean lowering LDL-C by 40.4% and to level 77.8 mg/dL in the group of patients with baseline mean LDL-C 132.4 mg/dL could significantly reduce the volume of CAP at follow up (SMD -0.108 mm3, 95% CI -0.176 ~ -0.040, p = 0.002; SMD -0.156 mm3, 95% CI -0.235 ~ -0.078, p = 0.000; SMD -0.123 mm3, 95% CI -0.199 ~ -0.048, p = 0.001; respectively). LDL-C lowering by rosuvastatin (mean 33 mg daily) and atorvastatin (mean 60 mg daily) could significantly decrease the volumes of CAP at follow up (SMD -0.162 mm3, 95% CI: -0.234 ~ -0.081, p = 0.000; SMD -0.101, 95% CI: -0.184 ~ -0.019, p = 0.016; respectively). The mean duration of follow up was from 17 ~ 21 months.

CONCLUSIONS

Intensive lowering LDL-C (rosuvastatin mean 33 mg daily and atorvastatin mean 60 mg daily) with >17 months of duration could lead to the regression of CAP, LDL-C level should be reduced by >40% or to a target level <78 mg/dL for regressing CAP.

Progression of coronary atherosclerosis in stable patients with ultrasonic features of high-risk plaques

AIM

Large plaque burden, expansive vascular remodelling, and spotty calcification have been considered as important morphologies of high-risk plaques causing acute coronary events. Although non-occlusive rupture of high-risk plaques has been proposed as a mechanism for disease progression in post-mortem studies, the natural history of coronary atherosclerosis in stable patients with high-risk plaques has not been fully elucidated. We sought to evaluate coronary atheroma progression in stable patients with greyscale intravascular ultrasound (IVUS)-derived high-risk plaques.

METHODS AND RESULTS

We analysed 4477 patients with stable coronary artery disease underwent serial greyscale IVUS imaging in eight clinical trials. We compared volumetric intravascular ultrasound (IVUS) data in the non-culprit segments between patients with and without high-risk plaques, defined as the combination of per cent atheroma volume (PAV) >63%, positive remodelling and spotty calcification. High-risk plaques were observed in 201 (4.5%) of patients. Patients with high-risk plaques exhibited a greater PAV (47.1 ± 8.4 vs. 37.7 ± 8.7%, P < 0.001) at baseline. On serial evaluation, however, regression of PAV (-0.26 ± 0.39 vs. 0.24 ± 0.32%, P = 0.03) was observed. In patients with high-risk plaques, the non-statin use was associated with the accelerated atheroma progression, whereas atheroma regression was observed under statin therapy (change in PAV: 1.87 ± 0.68% vs. -0.83 ± 0.53%, P = 0.01).

CONCLUSIONS

Patients with high-risk plaques exhibit extensive atheroma burden, which is modifiable with anti-atherosclerotic therapies. These findings underscore risk modification using a statin in patients with high-risk plaques.

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.

Association between single nucleotide polymorphism rs1044925 and the risk of coronary artery disease and ischemic stroke

The present study was performed to clarify the association between the acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) single nucleotide polymorphism (SNP) rs1044925 and the risk of coronary artery disease (CAD) and ischemic stroke (IS) in the Guangxi Han population. Polymerase chain reaction and restriction fragment length polymorphism was performed to determine the genotypes of the ACAT-1 SNP rs1044925 in 1730 unrelated subjects (CAD, 587; IS, 555; and healthy controls; 588). The genotypic and allelic frequencies of rs1044925 were significantly different between the CAD patients and controls (p = 0.015) and borderline different between the IS patients and controls (p = 0.05). The AC/CC genotypes and C allele were associated with a decreased risk of CAD and IS (CAD: p = 0.014 for AC/CC vs. AA, p = 0.022 for C vs. A; IS: p = 0.014 for AC/CC vs. AA; p = 0.017 for C vs. A). The AC/CC genotypes in the healthy controls, but not in CAD or IS patients, were associated with an increased serum high-density lipoprotein cholesterol (HDL-C) concentration. The present study shows that the C allele carriers of ACAT-1 rs1044925 were associated with an increased serum HDL-C level in the healthy controls and decreased risk in CAD and IS patients.

Exploring the natural history of atherosclerosis with intravascular ultrasound

Intravascular ultrasound has emerged as the preferred imaging modality for the characterization of atherosclerotic plaque within the coronary arteries. Ultrasonic imaging reveals the presence of more extensive atheroma than suggested by conventional angiography in patients with coronary artery disease. The ability to precisely quantify atheroma volume in an arterial segment at different time points provides the unique opportunity to investigate the factors that influence the natural history of atheroma progression. Accordingly, serial intravascular ultrasound has been incorporated into a number of clinical trials that have evaluated the impact of medical therapies that modify established risk factors and novel pathological targets. This article will review the increasing role of imaging modalities in the assessment of atherosclerosis and factors that influence its natural history.

The GALAXY Program: an update on studies investigating efficacy and tolerability of rosuvastatin for reducing cardiovascular risk

The GALAXY Program is a series of clinical studies investigating the efficacy and tolerability of rosuvastatin in line with the hypothesis that the statin with the greatest efficacy for improving the atherogenic lipid profile and beneficially modifying inflammatory markers will also slow progression of atherosclerosis and improve cardiovascular outcomes. Completed studies report that rosuvastatin is more effective than comparator statins in reducing low-density lipoprotein cholesterol, improving the lipid profile and enabling patients to achieve lipid goals, including revised, more stringent goals, even in high-risk patients. Studies have also reported that rosuvastatin can arrest and even regress atherosclerosis. Ongoing outcomes studies will determine whether these beneficial effects of rosuvastatin translate into reduced morbidity and mortality.

Combination therapy with ezetimibe and simvastatin to achieve aggressive LDL reduction

A low-density lipoprotein (LDL) cholesterol goal of less than 100 mg/dl is recommended for patients at moderate to high risk of cardiovascular disease with an optional LDL goal of less than 70 mg/dl for patients at a very high risk of cardiovascular disease. Most patients will require reductions in LDL of more than 50% in order to achieve these more aggressive goals. Only a few agents will lower LDL by at least 50%. This review will focus on the efficacy and safety ezetimibe/simvastatin coadministered as a therapy with enhanced LDL-lowering efficacy, while minimizing the adverse effects of statins in a wide range of patients. Ezetimibe 10 mg/simvastatin 80 mg lowers LDL by approximately 60% and has been demonstrated to be superior to the highest doses of atorvastatin and rosuvastatin for lowering LDL and raising high-density lipoprotein.

Atherosclerotic Plaque Destabilization

Understanding the pathophysiology of atherogenesis and the progression of atherosclerosis have been major goals of cardiovascular research during the previous decades. However, the complex molecular and cellular mechanisms underlying plaque destabilization remain largely obscure. Here, we review how lesional cells undergo cell death and how failed clearance exacerbates necrotic core formation. Advanced atherosclerotic lesions are further weakened by the pronounced local activity of matrix-degrading proteases as well as immature neovessels sprouting into the lesion. To stimulate translation of the current knowledge of molecular mechanisms of plaque destabilization into clinical studies, we further summarize available animal models of plaque destabilization. Based on the molecular mechanisms leading to plaque instability, we outline the current status of clinical and preclinical trials to induce plaque stability with a focus on induction of dead cell clearance, inhibition of protease activity, and dampening of inflammatory cell recruitment.

Myeloperoxidase levels predict accelerated progression of coronary atherosclerosis in diabetic patients: insights from intravascular ultrasound

OBJECTIVE

While inflammation has been proposed to contribute to the adverse cardiovascular outcome in diabetic patients, the specific pathways involved have not been elucidated. The leukocyte derived product, myeloperoxidase (MPO), has been implicated in all stages of atherosclerosis. The relationship between MPO and accelerated disease progression observed in diabetic patients has not been studied.

METHODS

We investigated the relationship between MPO and disease progression in diabetic patients. 881 patients with angiographic coronary artery disease underwent serial evaluation of atherosclerotic burden with intravascular ultrasound. Disease progression in diabetic (n = 199) and non-diabetic (n = 682) patients, stratified by baseline MPO levels was investigated.

RESULTS

MPO levels were similar in patients with and without diabetes (1362 vs. 1255 pmol/L, p = 0.43). No relationship was observed between increasing quartiles of MPO and either baseline (p = 0.81) or serial changes (p = 0.43) in levels of percent atheroma volume (PAV) in non-diabetic patients. In contrast, increasing MPO quartiles were associated with accelerated PAV progression in diabetic patients (p = 0.03). While optimal control of lipid and the use of high-dose statin were associated with less disease progression, a greater benefit was observed in diabetic patients with lower compared with higher MPO levels at baseline.

CONCLUSIONS

Increasing MPO levels are associated with greater progression of atherosclerosis in diabetic patients. This finding indicates the potential importance of MPO pathways in diabetic cardiovascular disease.

Recent failures in antiatherosclerotic drug development: examples from the thyroxin receptor agonist, the secretory phospholipase A2 antagonist, and the acyl coenzyme A: cholesterol acyltransferase inhibitor programs

PURPOSE OF REVIEW

To review the published data related to the rise and fall of three different therapeutic approaches, which were investigated to lower cardiovascular disease (CVD) risk.

RECENT FINDINGS

CVD remains a major burden of morbidity and mortality, despite therapeutic interventions. Novel strategies to address this residual risk are eagerly awaited, and a number of novel targets for therapy have been identified. Lipids and lipoproteins have been shown to play an eminent role in atherosclerosis progression, and as such, interventions that influence these biomarkers are crucial in CVD risk prevention. In recent years, however, clinical studies investigating the effect of novel lipid-modifying drugs on cardiovascular risk prevention have not always resulted in the anticipated beneficial outcome. Moreover, the development of therapies directed toward bioactive proteins acting at the crossroads of lipids and inflammation has also been disappointing.

SUMMARY

In this review, we will specifically address the rationale, design, and results of the clinical trials investigating the effects of three of the failing therapies: the thyroxin receptor agonist, the secretory phospholipase A2 antagonist, and the acyl coenzyme A:cholesterol acyltransferase inhibitor.

Progression of coronary atherosclerosis in African-American patients

BACKGROUND

African-Americans with coronary artery disease (CAD) demonstrate worse clinical outcomes than Caucasians. While this is partly due to a lack of accessibility to established therapies, the mechanisms underlying this difference remain to be elucidated. We aimed to characterize the progression of coronary atherosclerosis in African-Americans with CAD.

METHODS

3,479 patients with CAD underwent serial intravascular ultrasound (IVUS) imaging to evaluate atheroma progression in 7 clinical trials of anti-atherosclerotic therapies. Risk factor control and atheroma progression were compared between African-Americans (n=170) and Caucasians (n=3,309).

RESULTS

African-Americans were more likely to be female (51.8% vs. 28.1%, P<0.001), have a higher body mass index (32.8±6.0 vs. 31.3±5.8 kg/m(2), P=0.002) and greater history of hypertension (85.9% vs. 78.8%, P=0.02), diabetes (41.8% vs. 30.6%, P=0.002) and stroke (12.9% vs. 3.0%, P<0.001). Despite a high use of anti-atherosclerotic medications (93% statin, 89% aspirin, 79% β-blocker, 52% ACE inhibitor), African-Americans demonstrated higher levels of LDL-C (2.4±0.7 vs. 2.2±0.7 mmol/L, P=0.006), CRP (2.9 vs. 2.0 mg/dL, P<0.001) and systolic blood pressure (133±15 vs. 129±13 mmHg, P<0.001) at follow-up. There was no significant difference in atheroma volume at baseline (189.0±82.2 vs. 191.6±83.3 mm(3), P=0.82) between two groups. Serial evaluation demonstrated a greater increase in atheroma volume in African-Americans (0.51±2.1 vs. -3.1±1.7 mm(3), P=0.01). This difference persisted with propensity matching accounting for differences in risk factor control (0.1±2.1 vs. -3.7±1.7 mm(3), P=0.02).

CONCLUSIONS

African-Americans with CAD achieve less optimal risk factor control and greater atheroma progression. These findings support the need for more intensive risk factor modification in African-Americans.

Targeting Cholesterol Crystal-Induced Inflammation for the Secondary Prevention of Cardiovascular Disease

Cholesterol crystals are present in nascent and advanced atherosclerotic plaque. Under some conditions, they may enlarge and cause direct plaque trauma or trigger an inflammatory cascade that promotes the growth and instability of atherosclerotic plaque. Therapies that reduce the risk of cholesterol crystal formation or prevent the associated inflammatory response have the potential to improve the clinical outcome of patients with cardiovascular disease. Statins have pleiotropic effects that can reduce the size of the free cholesterol pool contained within atherosclerotic plaques and prevent the formation of cholesterol crystals. Colchicine prevents crystal-induced inflammation by virtue of its ability to inhibit macrophage and neutrophil function. Both statins and colchicine have been demonstrated to reduce the risk of cardiovascular events in patients with stable coronary disease. The efficacy of statins and colchicine for cardiovascular prevention supports the hypothesis that crystal-induced inflammation plays an integral role in the progression and instability of coronary disease. Inhibition of cholesterol crystal-induced inflammation offers a promising new target for the secondary prevention of cardiovascular disease.

Cholesterol crystals and inflammation

Chronic vascular inflammation is regarded as a crucial aspect of cardiovascular disease. However, the elicitors of this inflammatory response in the vessel wall are currently not well understood. Excessive amounts of cholesterol, an abundant and fundamental lipid molecule in mammalian cells, can initiate the development and progression of atherosclerosis. Accumulation of cholesterol in early atherosclerotic lesions results in the formation of macrophage foam cells, and crystalline cholesterol is found as a characteristic of advanced atherosclerotic plaques. Cholesterol crystals can activate the NLRP3 inflammasome, a multimolecular signaling complex of the innate immune system, resulting in caspase-1 mediated activation and secretion of proinflammatory interleukin-1 family cytokines. Furthermore, crystalline cholesterol is believed to induce plaque rupture by physical disruption of the fibrous cap covering atherosclerotic lesions. Here we review the effect of cholesterol deposition and crystallization on inflammatory responses in cardiovascular diseases.

Synthesis and structure-activity relationship of pyripyropene A derivatives as potent and selective acyl-CoA:cholesterol acyltransferase 2 (ACAT2) inhibitors: part 3

In an effort to develop potent and selective inhibitors toward ACAT2, structure-activity relationship studies were carried out using derivatives based on pyripyropene A (PPPA, 1). In particular, we investigated the possibility of introducing appropriate 1,11-O-benzylidene and 7-O-substituted benzoyl moieties into PPPA (1). The new o-substituted benzylidene derivatives showed higher selectivity for ACAT2 than PPPA (1). Among them, 1,11-O-o-methylbenzylidene-7-O-p-cyanobenzoyl PPPA derivative 7q and 1,11-O-o,o-dimethylbenzylidene-7-O-p-cyanobenzoyl PPPA derivative 7z proved to be potent ACAT2 inhibitors with unprecedented high isozyme selectivity.

Manzamine A, a marine-derived alkaloid, inhibits accumulation of cholesterol ester in macrophages and suppresses hyperlipidemia and atherosclerosis in vivo

The formation of foam cells in macrophages plays an essential role in the progression of early atherosclerotic lesions and therefore its prevention is considered to be a promising target for the treatment of atherosclerosis. We found that an extract of the marine sponge Acanthostrongylophora ingens inhibited the foam cell formation induced by acetylated low-density lipoprotein (AcLDL) in human monocyte-derived macrophages, as measured based on the accumulation of cholesterol ester (CE). Bioassay-guided purification of inhibitors from the extract afforded manzamines. Manzamine A was the most potent inhibitor of foam cell formation, and also suppressed CE formation in Chinese hamster ovary cells overexpressing acyl-CoA:cholesterol acyl-transferase (ACAT)-1 or ACAT-2. In addition, manzamine A inhibited ACAT activity. Next, we orally administered manzamine A to apolipoprotein E (apoE)-deficient mice for 80 days, and found that total cholesterol, free cholesterol, LDL-cholesterol, and triglyceride levels in serum were significantly reduced and the area of atherosclerotic lesions in the aortic sinus was also substantially diminished. These findings clearly suggest that manzamine A suppresses hyperlipidemia and atherosclerosis in apoE-deficient mice by inhibiting ACAT and is therefore a promising lead compound in the prevention or treatment of atherosclerosis. Although manzamine A has been reported to show several biological activities, this is the first report of a suppressive effect of manzamine A on atherosclerosis in vivo.

Prediction of bioactivity of ACAT2 inhibitors by multilinear regression analysis and support vector machine

Two quantitative structure-activity relationships (QSAR) models for predicting 95 compounds inhibiting Acyl-coenzyme A: cholesterol acyltransferase2 (ACAT2) were developed. The whole data set was randomly split into a training set including 72 compounds and a test set including 23 compounds. The molecules were represented by 11 descriptors calculated by software ADRIANA.Code. Then the inhibitory activity of ACAT2 inhibitors was predicted using multilinear regression (MLR) analysis and support vector machine (SVM) method, respectively. The correlation coefficients of the models for the test sets were 0.90 for MLR model, and 0.91 for SVM model. Y-randomization was employed to ensure the robustness of the SVM model. The atom charge and electronegativity related descriptors were important for the interaction between the inhibitors and ACAT2.

Acat1 knockdown gene therapy decreases amyloid-β in a mouse model of Alzheimer's disease

Both genetic inactivation and pharmacological inhibition of the cholesteryl ester synthetic enzyme acyl-CoA:cholesterol acyltransferase 1 (ACAT1) have shown benefit in mouse models of Alzheimer's disease (AD). In this study, we aimed to test the potential therapeutic applications of adeno-associated virus (AAV)-mediated Acat1 gene knockdown in AD mice. We constructed recombinant AAVs expressing artificial microRNA (miRNA) sequences, which targeted Acat1 for knockdown. We demonstrated that our AAVs could infect cultured mouse neurons and glia and effectively knockdown ACAT activity in vitro. We next delivered the AAVs to mouse brains neurosurgically, and demonstrated that Acat1-targeting AAVs could express viral proteins and effectively diminish ACAT activity in vivo, without inducing appreciable inflammation. We delivered the AAVs to the brains of 10-month-old AD mice and analyzed the effects on the AD phenotype at 12 months of age. Acat1-targeting AAV delivered to the brains of AD mice decreased the levels of brain amyloid-β and full-length human amyloid precursor protein (hAPP), to levels similar to complete genetic ablation of Acat1. This study provides support for the potential therapeutic use of Acat1 knockdown gene therapy in AD.

Making, baking, and breaking: the synthesis, storage, and hydrolysis of neutral lipids

The esterification of amphiphilic alcohols with fatty acids is a ubiquitous strategy implemented by eukaryotes and some prokaryotes to conserve energy and membrane progenitors and simultaneously detoxify fatty acids and other lipids. This key reaction is performed by at least four evolutionarily unrelated multigene families. The synthesis of this "neutral lipid" leads to the formation of a lipid droplet, which despite the clear selective advantage it confers is also a harbinger of cellular and organismal malaise. Neutral lipid deposition as a cytoplasmic lipid droplet may be thermodynamically favored but nevertheless is elaborately regulated. Optimal utilization of these resources by lipolysis is similarly multigenic in determination and regulation. We present here a perspective on these processes that originates from studies in model organisms, and we include our thoughts on interventions that target reductions in neutral lipids as therapeutics for human diseases such as obesity and diabetes.

New treatments on the horizon for familial hypercholesterolemia

Patients with familial hypercholesterolemia (FH) have higher baseline LDL cholesterol (LDLc) levels and are at high risk of developing premature cardiovascular disease. Disease is attributed to mutations in the LDLR gene, which encodes the LDL receptor protein and whose deficiency results in decreased uptake of apoB-containing cholesterol particles by the liver and elevated serum LDLc levels. Heterozygous FH is inherited in an autosomal-dominant pattern and has an incidence of 1:500 in the general population. These patients usually present with premature cardiovascular disease at 30-40 years of age and have baseline LDLc levels ranging from 190 to 230 mg/dl. Homozygous FH, however, is much rarer, occurring in one in a million births; those afflicted present with severe cardiovascular disease in childhood and have baseline LDLc levels greater than 300 mg/dl. Often FH patients do not reach their target LDLc levels on conventional therapies such as statins. Even with combination therapy, the percent of FH patients reaching target cholesterol levels is less than 30% and while apheresis is a therapeutic option for those with the most severe disease, many FH patients seek less invasive therapeutic strategies. New classes of cholesterol medications, aimed at either lowering LDLc levels or altering the progression of intra-arterial plaque, are currently in clinical development and may offer alternative or adjunctive therapies for this high-risk population.

Synthesis and structure-activity relationship of pyripyropene A derivatives as potent and selective acyl-CoA:cholesterol acyltransferase 2 (ACAT2) inhibitors: part 2

Synthesis and structure-activity relationships of 7-O-p-cyanobenzoyl pyripyropene A derivatives with modification at C1 and 11 are described. Regioselective mono-deprotection of di-tert-butylsilylene acetal was critical in their synthesis.

Exploring coronary atherosclerosis with intravascular imaging

Coronary angiography has been widely used for five decades to evaluate a range of vascular pathologies and triage patients to therapeutic interventions. The inability to directly visualize the artery wall with conventional angiographic techniques has stimulated development of a number of intravascular imaging modalities. These approaches have the potential to provide a more comprehensive characterization of the burden, composition and functionality of atherosclerotic plaque, neointimal hyperplasia and allograft vasculopathy that develop within coronary arteries. The ability to use these modalities in vivo and in a serial fashion has provided a greater insight into the factors that underlie the disease process and guide therapeutic interventions.

Paradoxical association of enhanced cholesterol efflux with increased incident cardiovascular risks

OBJECTIVE

Diminished cholesterol efflux activity of apolipoprotein B (apoB)-depleted serum is associated with prevalent coronary artery disease, but its prognostic value for incident cardiovascular events is unclear. We investigated the relationship of cholesterol efflux activity with both prevalent coronary artery disease and incident development of major adverse cardiovascular events (death, myocardial infarction, or stroke).

APPROACH AND RESULTS

Cholesterol efflux activity from free cholesterol-enriched macrophages was measured in 2 case-control cohorts: (1) an angiographic cohort (n=1150) comprising stable subjects undergoing elective diagnostic coronary angiography and (2) an outpatient cohort (n=577). Analysis of media from cholesterol efflux assays revealed that the high-density lipoprotein fraction (1.063<d<1.21) contained only a minority (≈ 40%) of [(14)C]cholesterol released, with the majority found within the lipoprotein particle-depleted fraction, where ≈ 60% was recovered after apolipoprotein A1 immunoprecipitation. Albumin immunoprecipitation recovered another ≈ 30% of radiolabeled cholesterol within this fraction. Enhanced cholesterol efflux activity from ATP-binding cassette transporter A1-stimulated macrophages was associated with reduced risk of prevalent coronary artery disease in unadjusted models within both cohorts; however, the inverse risk relationship remained significant after adjustment for traditional coronary artery disease risk factors only within the outpatient cohort. Surprisingly, higher cholesterol efflux activity was associated with increase in prospective (3 years) risk of myocardial infarction/stroke (adjusted hazard ratio, 2.19; 95% confidence interval, 1.02-4.74) and major adverse cardiovascular events (adjusted hazard ratio, 1.85; 95% confidence interval, 1.11-3.06).

CONCLUSIONS

Heightened cholesterol efflux to apoB-depleted serum was paradoxically associated with increased prospective risk for myocardial infarction, stroke, and death. The majority of released radiolabeled cholesterol from macrophages in cholesterol efflux activity assays does not reside within a high-density lipoprotein particle.

Synthesis and structure-activity relationship of pyripyropene A derivatives as potent and selective acyl-CoA:cholesterol acyltransferase 2 (ACAT2) inhibitors: part 1

In an effort to develop potent and selective inhibitors toward ACAT2, structure-activity relationship studies were carried out using derivatives based on pyripyropene A (PPPA, 1). We have successfully developed novel PPPA derivatives with a 7-O-substituted benzoyl substituent that significantly exhibit more potent ACAT2 inhibitory activity and higher ACAT2 isozyme selectivity than 1.

The UBIAD1 prenyltransferase links menaquinone-4 [corrected] synthesis to cholesterol metabolic enzymes

Schnyder corneal dystrophy (SCD) is an autosomal dominant disease characterized by germline variants in UBIAD1 introducing missense alterations leading to deposition of cholesterol in the cornea, progressive opacification, and loss of visual acuity. UBIAD1 was recently shown to synthesize menaquinone-4 (MK-4, vitamin K(2) ), but causal mechanisms of SCD are unknown. We report a novel c.864G>A UBIAD1 mutation altering glycine 177 to glutamic acid (p.G177E) in six SCD families, including four families from Finland who share a likely founder mutation. We observed reduced MK-4 synthesis by UBIAD1 altered by SCD mutations p.N102S, p.G177R/E, and p.D112N, and molecular models showed p.G177-mutant UBIAD1 disrupted transmembrane helices and active site residues. We show UBIAD1 interacts with HMGCR and SOAT1, enzymes catalyzing cholesterol synthesis and storage, respectively, using yeast two-hybrid screening and immunoprecipitation. Docking simulations indicate cholesterol binds to UBIAD1 in the substrate-binding cleft and substrate-binding overlaps with GGPP binding, an MK-4 substrate, suggesting potential competition between these metabolites. Impaired MK-4 synthesis is a biochemical defect identified in SCD suggesting UBIAD1 links vitamin K and cholesterol metabolism through physical contact between enzymes and metabolites. Our data suggest a role for endogenous MK-4 in maintaining cornea health and visual acuity.

Using self-organizing map (SOM) and support vector machine (SVM) for classification of selectivity of ACAT inhibitors

Using a self-organizing map (SOM) and support vector machine, two classification models were built to predict whether a compound is a selective inhibitor toward the two Acyl-coenzyme A: cholesterol acyltransferase (ACAT) isozymes, ACAT-1 and ACAT-2. A dataset of 97 ACAT inhibitors was collected. For each molecule, the global descriptors, 2D and 3D property autocorrelation descriptors and autocorrelation of surface properties were calculated from the program ADRIANA.Code. The prediction accuracies of the models (based on the training/ test set splitting by SOM method) for the test sets are 88.9 % for SOM1, 92.6 % for SVM1 model. In addition, the extended connectivity fingerprints (ECFP_4) for all the molecules were calculated and the structure-activity relationship of selective ACAT inhibitors was summarized, which may help find important structural features of inhibitors relating to the selectivity of ACAT isozymes.