Apolipoprotein E and atherosclerosis

Genetically Predicted Apolipoprotein E Levels with the Risk of Panvascular Diseases: A Mendelian Randomization Study

The aim of this study was to comprehensively assess the causal relationship between the overall genetic effect of circulating ApoE levels and panvascular lesions using newer genome-wide association data and two-sample bidirectional Mendelian randomization (MR) analysis. Two-way MR using single-nucleotide polymorphisms of circulating ApoE as instrumental variables was performed using the highest-priority Genome-wide association study (GWAS) data, with factor-adjusted and data-corrected statistics, to estimate causal associations between circulating ApoE levels and 10 pan-vascular diseases in > 500,000 UK Biobank participants, > 400,000 participants of Finnish ancestry, and numerous participants in a consortium of predominantly European ancestry. Meta-analysis was conducted to assess positive results. After correcting for statistical results, elevated circulating ApoE levels were shown to have a significant protective effect against Cerebral ischemia (CI) [IVW odds ratio (OR) 0.888, 95% Confidence Interval (CI): 0.823-0.958, p = 2.3 × 10-3], Coronary heart disease [IVW OR 0.950,95% CI: 0.924-0.976, p = 2.0 × 10-4] had a significant protective effect and potentially suggestive protective causality against Angina pectoris [IVW odds ratio (OR) 0.961, 95%CI: 0.931-0.991, p = 1.1 × 10-2]. There was a potential causal effect for increased risk of Heart failure (HF) [IVW ratio (OR) 1.040, 95%CI: 1.006-1.060, p = 1.8 × 10-2]. (Bonferroni threshold p < 0.0026, PFDR < 0.05) Reverse MR analysis did not reveal significant evidence of a causal effect of PVD on changes in circulating ApoE levels. Meta-analysis increases reliability of results. Elevated circulating ApoE levels were particularly associated with an increased risk of heart failure. Elevated ApoE levels reduce the risk of cerebral ischemia, coronary heart disease, and angina pectoris, reflecting a protective effect. The possible pathophysiological role of circulating ApoE levels in the development of panvascular disease is emphasized.

ApoE enhances mitochondrial metabolism via microRNA-142a/146a-regulated circuits that suppress hematopoiesis and inflammation in hyperlipidemia

Apolipoprotein E (ApoE) is recognized for its pleiotropic properties that suppress inflammation. We report that ApoE serves as a metabolic rheostat that regulates microRNA control of glycolytic and mitochondrial activity in myeloid cells and hematopoietic stem and progenitor cells (HSPCs). ApoE expression in myeloid cells increases microRNA-146a, which reduces nuclear factor κB (NF-κB)-driven GLUT1 expression and glycolytic activity. In contrast, ApoE expression reduces microRNA-142a, which increases carnitine palmitoyltransferase 1a (CPT1A) expression, fatty acid oxidation, and oxidative phosphorylation. Improved mitochondrial metabolism by ApoE expression causes an enrichment of tricarboxylic acid (TCA) cycle metabolites and nicotinamide adenine dinucleotide (NAD+) in macrophages. The study of mice with conditional ApoE expression supports the capacity of ApoE to foster microRNA-controlled immunometabolism. Modulation of microRNA-146a and -142a in the hematopoietic system of hyperlipidemic mice using RNA mimics and antagonists, respectively, improves mitochondrial metabolism, which suppresses inflammation and hematopoiesis. Our findings unveil microRNA regulatory circuits, controlled by ApoE, that exert metabolic control over hematopoiesis and inflammation in hyperlipidemia.

ApoE expression in macrophages communicates immunometabolic signaling that controls hyperlipidemia-driven hematopoiesis & inflammation via extracellular vesicles

While apolipoprotein E (apoE) expression by myeloid cells is recognized to control inflammation, whether such benefits can be communicated via extracellular vesicles is not known. Through the study of extracellular vesicles produced by macrophages derived from the bone marrow of Wildtype (WT-BMDM-EV) and ApoE deficient (EKO-BMDM-EV) mice, we uncovered a critical role for apoE expression in regulating their cell signaling properties. WT-BMDM-EV communicated anti-inflammatory properties to recipient myeloid cells by increasing cellular levels of apoE and miR-146a-5p, that reduced NF-κB signalling. They also downregulated cellular levels of miR-142a-3p, resulting in increased levels of its target carnitine palmitoyl transferase 1A (CPT1A) which improved fatty acid oxidation (FAO) and oxidative phosphorylation (OxPHOS) in recipient cells. Such favorable metabolic polarization enhanced cell-surface MerTK levels and the phagocytic uptake of apoptotic cells. In contrast, EKO-BMDM-EV exerted opposite effects by reducing cellular levels of apoE and miR-146a-5p, which increased NF-κB-driven GLUT1-mediated glucose uptake, aerobic glycolysis, and oxidative stress. Furthermore, EKO-BMDM-EV increased cellular miR-142a-3p levels, which reduced CPT1A levels and impaired FAO and OxPHOS in recipient myeloid cells. When cultured with naïve CD4+ T lymphocytes, EKO-BMDM-EV drove their activation and proliferation, and fostered their transition to a Th1 phenotype. While infusions of WT-BMDM-EV into hyperlipidemic mice resolved inflammation, infusions of EKO-BMDM-EV increased hematopoiesis and drove inflammatory responses in myeloid cells and T lymphocytes. ApoE-dependent immunometabolic signaling by macrophage extracellular vesicles was dependent on transcriptional axes controlled by miR-146a-5p and miR-142a-3p that could be reproduced by infusing miR-146a mimics & miR-142a antagonists into hyperlipidemic apoE-deficient mice. Together, our findings unveil a novel property for apoE expression in macrophages that modulates the immunometabolic regulatory properties of their secreted extracellular vesicles.

Diversity of arterial cell and phenotypic heterogeneity induced by high-fat and high-cholesterol diet

Lipid metabolism disorder is the basis of atherosclerotic lesions, in which cholesterol and low-density lipoprotein (LDL) is the main factor involved with the atherosclerotic development. A high-fat and high-cholesterol diet can lead to this disorder in the human body, thus accelerating the process of disease. The development of single-cell RNA sequencing in recent years has opened the possibility to unbiasedly map cellular heterogeneity with high throughput and high resolution; alterations mediated by a high-fat and high-cholesterol diet at the single-cell transcriptomic level can be explored with this mean afterward. We assessed the aortic arch of 16-week old Apoe-/- mice of two control groups (12 weeks of chow diet) and two HFD groups (12 weeks of high fat, high cholesterol diet) to process single-cell suspension and use single-cell RNA sequencing to anatomize the transcripts of 5,416 cells from the control group and 2,739 from the HFD group. Through unsupervised clustering, 14 cell types were divided and defined. Among these cells, the cellular heterogeneity exhibited in endothelial cells and immune cells is the most prominent. Subsequent screening delineated ten endothelial cell subsets with various function based on gene expression profiling. The distribution of endothelial cells and immune cells differs significantly between the control group versus the HFD one. The existence of pathways that inhibit atherosclerosis was found in both dysfunctional endothelial cells and foam cells. Our data provide a comprehensive transcriptional landscape of aortic arch cells and unravel the cellular heterogeneity brought by a high-fat and high-cholesterol diet. All these findings open new perspectives at the transcriptomic level to studying the pathology of atherosclerosis.

Endometriosis promotes atherosclerosis in a murine model

BACKGROUND

Epidemiologic studies have demonstrated an association between endometriosis and the subsequent development of cardiovascular disease. The direct effect of endometriosis on the progression of atherosclerotic, if any, has not been previously characterized. Endometriosis leads to systemic inflammation that could have consequences for cardiovascular health. Here, we reported the effects of endometriosis on the development of atherosclerosis in a murine model.

OBJECTIVE

This study aimed to determine the contribution of endometriosis in promoting cardiovascular disease in a murine model of endometriosis.

STUDY DESIGN

Endometriosis was induced in 18 apolipoprotein E-null mice, the standard murine model used to study atherosclerosis. Mice of the same strain were used as controls (n=18) and underwent sham surgery without inducing endometriosis. The formation of endometriotic lesions was confirmed after 25 weeks of induction. Atherosclerotic lesions were subjected to hematoxylin and eosin staining followed by measurement of the aortic root luminal area and wall thickness. The whole aorta was isolated, and Oil Red O staining was performed to quantify the lipid deposits or plaque formation; moreover, biochemical assays were carried out in serum to determine the levels of lipids and inflammatory-related cytokines.

RESULTS

Apolipoprotein E mice with endometriosis exhibited increased aortic atherosclerosis compared with controls as measured using Oil Red O staining (7.9% vs 3.1%, respectively; P=.0004). Mice with endometriosis showed a significant 50% decrease in the aortic luminal area compared with sham mice (0.85 mm² vs 1.46 mm²; P=.03) and a significant increase in aortic root wall thickness (0.22 mm vs 0.15 mm; P=.04). There was no difference in the lipoprotein profile (P<.05) between mice with endometriosis and sham mice. The serum levels of inflammatory cytokines interleukin 1 alpha, interleukin 6, interferon gamma, and vascular endothelial growth factor were significantly (P<.05)increased in the endometriosis mice.

CONCLUSION

Our study used a murine model to determine the effect of endometriosis on atherosclerosis. Inflammation-related cytokines interleukin 1 alpha, interleukin 6, interferon gamma, and vascular endothelial growth factor (angiogenic factor) released by endometriotic lesions may contribute to the increased cardiovascular risks in women with endometriosis. To reduce the risk of cardiovascular disease, early identification and treatment of endometriosis are essential. Future treatments targeting inflammatory cytokines may help reduce the long-term risk of cardiovascular disease in women with endometriosis.

The role of hepatic Surf4 in lipoprotein metabolism and the development of atherosclerosis in apoE-/- mice

Elevated plasma levels of low-density lipoprotein-C (LDL-C) increase the risk of atherosclerotic cardiovascular disease. Circulating LDL is derived from very low-density lipoprotein (VLDL) metabolism and cleared by LDL receptor (LDLR). We have previously demonstrated that cargo receptor Surfeit 4 (Surf4) mediates VLDL secretion. Inhibition of hepatic Surf4 impairs VLDL secretion, significantly reduces plasma LDL-C levels, and markedly mitigates the development of atherosclerosis in LDLR knockout (Ldlr^-/-) mice. Here, we investigated the role of Surf4 in lipoprotein metabolism and the development of atherosclerosis in another commonly used mouse model of atherosclerosis, apolipoprotein E knockout (apoE^-/-) mice. Adeno-associated viral shRNA was used to silence Surf4 expression mainly in the liver of apoE^-/- mice. In apoE^-/- mice fed a regular chow diet, knockdown of Surf4 expression significantly reduced triglyceride secretion and plasma levels of non-HDL cholesterol and triglycerides without causing hepatic lipid accumulation or liver damage. When Surf4 was knocked down in apoE^-/- mice fed the Western-type diet, we observed a significant reduction in plasma levels of non-HDL cholesterol, but not triglycerides. Knockdown of Surf4 did not increase hepatic cholesterol and triglyceride levels or cause liver damage, but significantly diminished atherosclerosis lesions. Therefore, our findings indicate the potential of hepatic Surf4 inhibition as a novel therapeutic strategy to reduce the risk of atherosclerotic cardiovascular disease.

Triglyceride-Rich Lipoprotein Remnants and Cardiovascular Disease

BACKGROUND

Triglycerides, cholesterol, and their metabolism are linked due to shared packaging and transport within circulating lipoprotein particles. While a case for a causal role of cholesterol-carrying low-density lipoproteins (LDLs) in atherosclerosis is well made, the body of scientific evidence for a causal role of triglyceride-rich lipoproteins (TRLs) is rapidly growing, with multiple lines of evidence (old and new) providing robust support.

CONTENT

This review will discuss current perspectives and accumulated evidence that an overabundance of remnant lipoproteins stemming from intravascular remodeling of nascent TRLs-chylomicrons and very low-density lipoproteins (VLDL)-results in a proatherogenic milieu that augments cardiovascular risk. Basic mechanisms of TRL metabolism and clearance will be summarized, assay methods reviewed, and pivotal clinical studies highlighted.

SUMMARY

Remnant lipoproteins are rendered highly atherogenic by their high cholesterol content, altered apolipoprotein composition, and physicochemical properties. The aggregate findings from multiple lines of evidence suggest that TRL remnants play a central role in residual cardiovascular risk.

apoA2 correlates to gestational age with decreased apolipoproteins A2, C1, C3 and E in gestational diabetes

INTRODUCTION

Pregnant women with gestational diabetes mellitus (GDM) are at risk of adverse outcomes, including gestational hypertension, pre-eclampsia, and preterm delivery. This study was undertaken to determine if apolipoprotein (apo) levels differed between pregnant women with and without GDM and if they were associated with adverse pregnancy outcome.

RESEARCH DESIGN AND METHODS

Pregnant women (46 women with GDM and 26 women without diabetes (ND)) in their second trimester were enrolled in the study. Plasma apos were measured and correlated to demographic, biochemical, and pregnancy outcome data.

RESULTS

apoA2, apoC1, apoC3 and apoE were lower in women with GDM compared with control women (p=0.0019, p=0.0031, p=0.0002 and p=0.015, respectively). apoA1, apoB, apoD, apoH, and apoJ levels did not differ between control women and women with GDM. Pearson bivariate analysis revealed significant correlations between gestational age at delivery and apoA2 for women with GDM and control women, and between apoA2 and apoC3 concentrations and C reactive protein (CRP) as a measure of inflammation for the whole group.

CONCLUSIONS

Apoproteins apoA2, apoC1, apoC3 and apoE are decreased in women with GDM and may have a role in inflammation, as apoA2 and C3 correlated with CRP. The fact that apoA2 correlated with gestational age at delivery in both control women and women with GDM raises the hypothesis that apoA2 may be used as a biomarker of premature delivery, and this warrants further investigation.

Association of Apolipoprotein E Polymorphism with Adipokines and Cardiovascular Disease Risk in Rheumatoid Arthritis Patients

Apolipoprotein E (ApoE) polymorphism and adipokines are linked to atherosclerosis. We aimed to investigate the associations of apoE genotypes with adipokines, inflammatory parameters, and cardiovascular disease (CVD) risks in rheumatoid arthritis (RA) patients. We enrolled 152 RA patients and 49 healthy control (HC) subjects. The apoE genotyping was determined by a polymerase chain reaction, while plasma levels of adipokines and inflammatory cytokines were measured with ELISA. Although apoE genotypes distributions were indistinguishable between RA patients and HC, we found significantly higher levels of apoE and adipokines in RA patients compared with HC. RA patients with ε2ε3 genotype had lower levels of TNF-α, IL-6, resistin, and visfatin, but higher leptin levels compared with ε3ε3 genotype patients. Patients with ε3ε4 genotype had significantly higher low-density lipoprotein-cholesterol (LDL-C) levels and atherogenic index scores compared with ε2ε3 genotype carriers. Moreover, patients with ε2ε3 genotype had significantly lower 10-year CVD risk than ε3ε3 or ε3ε4 genotype patients. ε3ε4 genotype and adiponectin levels were independent predictors of a high 10-year CVD risk. RA patients with ε2ε3 genotype are associated with lower levels of TNF-α, IL-6, resistin, visfatin, and CVD risk, while RA patients with ε3ε4 genotype exhibited higher levels of LDL-C, insulin resistance, and higher CVD risks.

Knockdown of phosphatase and tensin homolog (PTEN) inhibits fatty acid oxidation and reduces very low density lipoprotein assembly and secretion in calf hepatocytes

Dairy cows with fatty liver exhibit hepatic lipid accumulation and disturbances in fatty acid oxidation and lipid transport. Phosphatase and tensin homolog (PTEN), a lipid phosphatase, regulates intrahepatic fatty acid oxidation and lipid transport in mice. Whether PTEN play a role in fatty acid oxidation and very low density lipoprotein (VLDL) assembly in calf hepatocytes are unknown. Hepatocytes isolated from 3 healthy female Holstein calves (1 d old, 30-40 kg) were infected with empty adenovirus with green fluorescent protein for 48 h (Ad-GFP group) or infected with PTEN knockdown adenovirus for 48 h (Ad-shPTEN group), or cultured in RPMI-1640 without Ad-shPTEN or Ad-GFP (control group). Compared with the Ad-GFP group, PTEN knockdown decreased mRNA and protein abundance and the activity of fatty acid oxidation-related molecules, including acyl-coA synthetase long-chain 1, carnitine palmitoyltransferase 1, carnitine palmitoyltransferase 2, and 3-hydroxy acyl-coA dehydrogenase. Furthermore, PTEN knockdown decreased mRNA and protein abundance of VLDL assembly-related molecules, including apolipoprotein B100, apolipoprotein E, microsomal triglyceride transfer protein, and low density lipoprotein receptor. Importantly, PTEN knockdown promoted triglyceride accumulation in hepatocytes and reduced the VLDL content in culture medium. A subsequent study was conducted on the following 4 groups: cells infected with Ad-GFP for 48 h and then treated with 2% BSA for another 24 h (Ad-GFP + BSA); cells infected with Ad-GFP for 48 h and then treated with 1.2 mM free fatty acids (FFA) and 2% BSA for another 24 h (Ad-GFP + 1.2 mM FFA); cells infected with Ad-shPTEN for 48 h and then treated with 2% BSA for another 24 h (Ad-shPTEN + BSA); cells infected with Ad-shPTEN for 48 h and then treated with 1.2 mM FFA and 2% BSA for another 24 h (Ad-shPTEN + 1.2 mM FFA). Compared with Ad-GFP + BSA, the abundances of PTEN and of fatty acid oxidation- and VLDL assembly-related proteins were lower in the Ad-GFP + 1.2 mM FFA group. Importantly, PTEN knockdown heightened the increase in triglyceride accumulation of hepatocytes and the decrease in VLDL content in culture medium induced by FFA. Overall, these in vitro data indicate that FFA inhibits PTEN expression, leading to triglyceride accumulation and the inhibition of VLDL assembly in calf hepatocytes. These findings suggest that PTEN may be a potential therapeutic target for FFA-induced hepatic steatosis in dairy cows.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

Apolipoprotein E and plasminogen activator inhibitor 1 gene polymorphism in children with chronic renal insufficiency associated with cardiovascular disease

Background

Cardiovascular disease (CVD) is considered a major cause of death in renal insufficiency (RI). Contributing genetic factors is a recent focus of research. This study aims to elucidate apolipoprotein E (APO-E) and plasminogen activator inhibitor 1 (PAI-1) gene polymorphisms in RI children associated with CVD.

Methods

We studied 50 cases with chronic kidney disease (CKD) associated with CVD, and 30 healthy controls. Study sample was grouped as one on conservative treatment, the second on hemodialysis and the third was posttransplant. PAI-1 and APO-E gene polymorphisms were investigated using allele-specific polymerase chain reaction (AS-PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) respectively.

Results

4G4G and 4G5G were the most common PAI-1 polymorphism denoting high association of 4 G allele in renal insufficiency associated with CVD with absent link to dyslipidemia, echocardiography changes or thrombosis. E3E3 was the most common among APO-E polymorphism without relation to dyslipidemia or thrombosis. Dyslipidemia was significantly linked to thrombosis. The study confirmed the role of dyslipidemia and hemodialysis in promoting thrombosis.

Conclusion

Although PAI 4G Genotyping did not show significant association with echocardiography severity or thrombotic severity, yet genetic expression for high levels of PAI in plasma is expected in response to CRI factors known to trigger its release, in addition to those related to dialysis. APO-E3E3 genotyping showed a significant association with echocardiography severity as it enhances APO-A which contributes to CVD. The current study confirmed a significant association between dyslipidemia and CVD; however, the prevalent patterns 4G and E3E3 did not show a significant association with dyslipidemia. The genetic role for APO-A, B, O, or even other isomers for APO-E should be further studied as well.

Genital Chlamydia infection in hyperlipidemic mouse models exacerbates atherosclerosis

BACKGROUND AND AIMS

Atherosclerosis is a chronic inflammatory disease, and recent studies have shown that infection at remote sites can contribute to the progression of atherosclerosis in hyperlipidemic mouse models. In this report, we tested the hypothesis that genital Chlamydia infection could accelerate the onset and progression of atherosclerosis.

METHODS

Apolipoprotein E (Apoe^-/-) and LDL receptor knockout (Ldlr^-/-) mice on a high-fat diet were infected intra-vaginally with Chlamydia muridarum. Atherosclerotic lesions on the aortic sinuses and in the descending aorta were assessed at 8-weeks post-infection. Systemic, macrophage, and vascular site inflammatory responses were assessed and quantified.

RESULTS

Compared to the uninfected groups, infected Apoe^-/- and Ldlr^-/- mice developed significantly more atherosclerotic lesions in the aortic sinus and in the descending aorta. Increased lesions were associated with higher circulating levels of serum amyloid A-1, IL-1β, TNF-α, and increased VCAM-1 expression in the aortic sinus, suggesting an association with inflammatory responses observed during C. muridarum infection. Genital infection courses were similar in Apoe^-/-, Ldlr^-/-, and wild type mice. Further, Apoe^-/- mice developed severe uterine pathology with increased dilatations. Apoe-deficiency also augmented cytokine/chemokine response in C. muridarum infected macrophages, suggesting that the difference in macrophage response could have contributed to the genital pathology in Apoe^-/- mice.

CONCLUSIONS

Overall, these studies demonstrate that genital Chlamydia infection exacerbates atherosclerotic lesions in hyperlipidemic mouse and suggest a novel role for Apoe in full recovery of uterine anatomy after chlamydial infection.

Plasma ApoE elevations are associated with NAFLD: The PREVEND Study

Non-alcoholic fatty liver disease (NAFLD) is featured by increased plasma very low density lipoproteins (VLDL). The extent to which plasma apolipoprotein E (ApoE) levels are elevated in NAFLD is unclear. We determined whether plasma ApoE is elevated in subjects with suspected NAFLD. Plasma ApoE and genotypes were determined in 6,762 participants of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort. A Fatty Liver Index (FLI) ≥ 60 was used as a proxy of NAFLD. A total of 1,834 participants had a FLI ≥ 60, which coincided with increased triglycerides, non-HDL cholesterol, ApoB and ApoE (all P<0.001). In multivariable linear regression analysis, plasma ApoE levels were positively associated with an elevated FLI when taking account of ApoE genotypes and other clinical and laboratory covariates (fully adjusted model: β = 0.201, P<0.001). Stratified analysis for ApoE genotypes (ApoE ε3ε3 homozygotes, ApoE ε2 carriers, and ApoE ε3ε4 and ε4ε4 carriers combined), also showed positive associations of plasma ApoE levels with an elevated FLI in each group (all P<0.001). In conclusion, it is suggested that NAFLD is characterized by increased plasma ApoE levels, even when taking account of the various ApoE genotypes. Increased plasma ApoE may contribute to altered VLDL metabolism and to increased atherosclerosis susceptibility in NAFLD.

Placental secretion of apolipoprotein A1 and E: the anti-atherogenic impact of the placenta

High levels of atherogenic lipids in pregnancy are associated with health complications for the mother, the fetus and the newborn. As endocrine secretory tissue, the human placenta releases apolipoproteins (apos), particularly apoA1 and apoE. However, the magnitude and the directionality of the apo secretions remain unknown. We aimed to 1) determine the amount and orientation (apical-maternal versus basal-fetal) of placentally secreted apoA1 and apoE using human perfused placenta and primary trophoblast cell (PTC) culture, 2) compare apoA1 and apoE secretions of PTC with that of hepatocytes and 3) associate the obtained results with human blood levels by determining apoA1 and apoE concentrations in maternal and fetal serum samples. In perfused placenta and serum samples, apoA1 and apoE concentrations were significantly higher at the maternal compared to the fetal side. For apoE a similar trend was found in PTC. For apoA1, the secretion to the apical side declined over time while release to the basal side was stable resulting in significantly different apoA1 concentrations between both sides. Unexpectedly, PTC secreted significantly higher amounts of apoA1 and apoE compared to hepatocytes. Our data indicate that the placenta may play an important role in maternal and fetal cholesterol homeostasis via secretion of anti-atherogenic apos.

Effects of atorvastatin and/or probucol on recovery of atherosclerosis in high-fat-diet-fed apolipoprotein E-deficient mice

INTRODUCTION

We have investigated the possible effects and mechanism of atorvastatin, a statin, and/or probucol, a powerful antioxidant used to lower cholesterol before 1995, on the atherosclerosis development.

METHODS

Apolipoprotein-E-deficient (ApoE^-/-) mice fed with the high fat diet were randomly divided into 3 groups (n = 10/each group): Placebo, Atorvastatin (10 mg/ kg/d), and atorvastatin (10 mg/kg/d) plus probucol (10 mg/kg/d) groups. C57BL/6 J mice were fed with normal diet as the control group (n = 10). Animals were sacrificed 10 weeks after the intervention. To evaluate the experimental atherosclerosis, blood tests were used for measuring serum lipoprotein profile, Western blots for endoplasmic reticulum (ER) stress protein expression, H&E staining for plaque lesions, immunohistology for macrophages, inflammatory cytokines, innate immune receptor TLR-4, transcription factor NF-κB, and atherosclerosis plaques.

RESULTS

Compared with the control group, ApoE^-/- mice in the placebo group showed with the significantly (p < 0.05) higher levels of serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL) and oxidized low density lipoprotein (ox-LDL), PERK, GRP78, CHOP, IL-1β, TNF-α and NF-κB, but with the lower levels of high-density lipoprotein cholesterol (HDL) and TLR-4, and also the increase in macrophages and the aortic media collagen, and the decrease in the elastic fibers (p < 0.01). Treatment with atorvastatin recovered all these features (p < 0.05 or p < 0.01) near to the levels in the control group. In addition, the combination of atorvastatin and probucol has shown the slightly stronger effect than the use of atorvastatin alone without statistical significances when comparing most bio-markers of atherosclerosis, but with significant differences in the reduction of the plaque lesion areas and macrophages (p < 0.05).

CONCLUSIONS

Atorvastatin and/or probucol suppresses ER stress and increase the level of TLR-4, which lowers NF-κB, resulting in the recovery of atherosclerosis in the ApoE^-/- mouse model.

APOE ε4 Genotype and Cognitive Reserve Effects on the Cognitive Functioning of Healthy Elders

AIM

To test the association between cognitive performance and APOE genotype, and to assess potential modifications of this association by sociodemographic and neuroanatomical factors in a sample of 74 healthy elders.

METHODS

Firstly, we explored the isolated role of the APOE ɛ4 genotype (i.e., APOE4) in different neuropsychological tests, and then the effects of its interaction with sociodemographic (i.e., age, gender, and educational level) and neuroanatomical (i.e., hippocampal volumes) variables. Subsequently, we performed the same analyses after dividing the sample into two subgroups according to their Mini-Mental State Examination scores (control-high group ≥29 and control-low group < 29).

RESULTS

In the whole group, APOE4 carriers exhibited a significantly poorer execution in several cognitive domains including global cognitive functioning, episodic memory, verbal fluency, and naming. This effect was more noticeable in older and less educated subjects. The separated analyses revealed that APOE4 carriers in the control-low group exhibited lower scores in global cognitive functioning and episodic memory, while no effects were observed in the control-high group. Neither gender nor hippocampal volumes showed a significant interaction effect with APOE genotype.

CONCLUSIONS

Current results point out that APOE4 genotype influences healthy aged cognition, although factors such age or educational attainment seem to modulate its effects.

Nuclear factor E2-related factor 2 deficiency impairs atherosclerotic lesion development but promotes features of plaque instability in hypercholesterolaemic mice

Aims

Oxidative stress and inflammation play an important role in the progression of atherosclerosis. Transcription factor NF-E2-related factor 2 (Nrf2) has antioxidant and anti-inflammatory effects in the vessel wall, but paradoxically, global loss of Nrf2 in apoE deficient mice alleviates atherosclerosis. In this study, we investigated the effect of global Nrf2 deficiency on early and advanced atherogenesis in alternative models of atherosclerosis, LDL receptor deficient mice (LDLR−/−), and LDLR−/− mice expressing apoB-100 only (LDLR−/− ApoB100/100) having a humanized lipoprotein profile.

Methods and results

LDLR−/− mice were fed a high-fat diet (HFD) for 6 or 12 weeks and LDLR−/−ApoB100/100 mice a regular chow diet for 6 or 12 months. Nrf2 deficiency significantly reduced early and more advanced atherosclerosis assessed by lesion size and coverage in the aorta in both models. Nrf2 deficiency in LDLR−/− mice reduced total plasma cholesterol after 6 weeks of HFD and triglycerides in LDLR−/−ApoB100/100 mice on a chow diet. Nrf2 deficiency aggravated aortic plaque maturation in aged LDLR−/−ApoB100/100 mice as it increased plaque calcification. Moreover, ∼36% of Nrf2−/−LDLR−/−ApoB100/100 females developed spontaneous myocardial infarction (MI) or sudden death at 5 to 12 months of age. Interestingly, Nrf2 deficiency increased plaque instability index, enhanced plaque inflammation and calcification, and reduced fibrous cap thickness in brachiocephalic arteries of LDLR−/−ApoB100/100 female mice at age of 12 months.

Conclusions

Absence of Nrf2 reduced atherosclerotic lesion size in both atherosclerosis models, likely via systemic effects on lipid metabolism. However, Nrf2 deficiency in aged LDLR−/−ApoB100/100 mice led to an enhanced atherosclerotic plaque instability likely via increased plaque inflammation and oxidative stress, which possibly predisposed to MI and sudden death.

Apolipoprotein E and Atherosclerosis: From Lipoprotein Metabolism to MicroRNA Control of Inflammation

Apolipoprotein (apo) E stands out among plasma apolipoproteins through its unprecedented ability to protect against atherosclerosis. Although best recognized for its ability to mediate plasma lipoprotein clearance in the liver and protect against macrophage foam cell formation, our recent understanding of the influence that apoE can exert to control atherosclerosis has significantly widened. Among apoE’s newfound athero-protective properties include an ability to control exaggerated hematopoiesis, blood monocyte activation and aortic stiffening in mice with hyperlipidemia. Mechanisms responsible for these exciting new properties extend beyond apoE’s ability to prevent cellular lipid excess. Rather, new findings have revealed a role for apoE in regulating microRNA-controlled cellular signaling in cells of the immune system and vascular wall. Remarkably, infusions of apoE-responsive microRNA mimics were shown to substitute for apoE in protecting against systemic and vascular inflammation to suppress atherosclerosis in mice with hyperlipidemia. Finally, more recent evidence suggests that apoE may control the release of microvesicles that could modulate cellular signaling, inflammation and atherosclerosis at a distance. These exciting new findings position apoE within the emerging field of intercellular communication that could introduce new approaches to control atherosclerosis cardiovascular disease.

PCSK9: A potential regulator of apoE/apoER2 against inflammation in atherosclerosis?

Atherosclerosis is characterized by chronic inflammation and lipid accumulation in arterial walls, resulting in several vascular events. Proprotein convertase subtilisin kexin 9 (PCSK9), a serine protease, has a pivotal role in the degradation of hepatic low-density lipoprotein receptor (LDLR). It can increase plasma concentrations of low-density lipoprotein cholesterol and affect lipid metabolism. Recently, PCSK9 has been found to accelerate atherosclerosis via mechanisms apart from that involving the degradation of LDLR, with an emerging role in regulating the inflammatory response in atherosclerosis. Apolipoprotein E receptor 2 (apoER2), one of the LDLR family members expressed in macrophages, can bind to its ligand apolipoprotein E (apoE), exhibiting an anti-inflammatory role in atherosclerosis. Evidence suggests that apoER2 is a target of PCSK9. This review aims to discuss PCSK9 as a potential regulator of apoE/apoER2 against inflammation in atherosclerosis.

Addition of Estradiol to Cross-Sex Testosterone Therapy Reduces Atherosclerosis Plaque Formation in Female ApoE-/- Mice

The contributions of estradiol and testosterone to atherosclerotic lesion progression are not entirely understood. Cross-sex hormone therapy (XHT) for transgender individuals dramatically alters estrogen and testosterone levels and consequently could have widespread consequences for cardiovascular health. Yet, no preclinical research has assessed atherosclerosis risk after XHT. We examined the effects of testosterone XHT after ovariectomy on atherosclerosis plaque formation in female mice and evaluated whether adding low-dose estradiol to cross-sex testosterone treatments after ovariectomy reduced lesion formation. Six-week-old female ApoE-/- C57BL/6 mice underwent ovariectomy and began treatments with testosterone, estradiol, testosterone with low-dose estradiol, or vehicle alone until euthanized at 23 weeks of age. Atherosclerosis lesion progression was measured by Oil Red O stain and confirmed histologically. We found reduced atherosclerosis in the estradiol- and combined testosterone/estradiol-treated mice compared with those treated with testosterone or vehicle only in the whole aorta (-75%), aortic arch (-80%), and thoracic aorta (-80%). Plaque size was similarly reduced in the aortic sinus. These reductions in lesion size after combined testosterone/estradiol treatment were comparable to those obtained with estrogen alone. Testosterone/estradiol combined therapy resulted in less atherosclerosis plaque formation than either vehicle or testosterone alone after ovariectomy. Testosterone/estradiol therapy was comparable to estradiol replacement alone, whereas mice treated with testosterone only fared no better than untreated controls after ovariectomy. Adding low-dose estrogen to cross-sex testosterone therapy after oophorectomy could improve cardiovascular outcomes for transgender patients. Additionally, these results contribute to understanding of the effects of estrogen and testosterone on atherosclerosis progression.

Protease-Activated Receptor-2 Deficiency Attenuates Atherosclerotic Lesion Progression and Instability in Apolipoprotein E-Deficient Mice

Inflammatory mechanisms are involved in the process of atherosclerotic plaque formation and rupture. Accumulating evidence suggests that protease-activated receptor (PAR)-2 contributes to the pathophysiology of chronic inflammation on the vasculature. To directly examine the role of PAR-2 in atherosclerosis, we generated apolipoprotein E/PAR-2 double-deficient mice. Mice were fed with high-fat diet for 12 weeks starting at ages of 6 weeks. PAR-2 deficiency attenuated atherosclerotic lesion progression with reduced total lesion area, reduced percentage of stenosis and reduced total necrotic core area. PAR-2 deficiency increased fibrous cap thickness and collagen content of plaque. Moreover, PAR-2 deficiency decreased smooth muscle cell content, macrophage accumulation, matrix metallopeptidase-9 expression and neovascularization in plaque. Relative quantitative PCR assay using thoracic aorta revealed that PAR-2 deficiency reduced mRNA expression of inflammatory molecules, such as vascular cell adhesion molecule-1, intercellular adhesion molecule-1, tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1. In vitro experiment, we found that PAR-2 deficiency reduced mRNA expression of interferon-γ, interleukin-6, TNF-α and MCP-1 in macrophage under unstimulated and lipopolysaccharide-stimulated conditions. These results suggest that PAR-2 deficiency attenuates the progression and instability of atherosclerotic plaque.

MicroRNA‑146a promotes the proliferation of rat vascular smooth muscle cells by downregulating p53 signaling

The present study aimed to detect and verify gene expression profile differences for microRNA (miR)‑146a and its role in the proliferation of vascular smooth muscle cells (VSMCs). Artificially synthesized miR‑146a mimics, miR‑146 inhibitor, scramble‑miRNA or PBS was transfected into cultured primary rat VSMCs in vitro. Reverse transcription‑quantitative polymerase chain reaction confirmed that the miR‑146a expression level was significantly decreased in VSMCs treated with miR‑146a inhibitor (P<0.01). Cell Counting Kit‑8 was used to determine the proliferation ability, which demonstrated that proliferation was significantly decreased in VSMCs treated with miR‑146a inhibitor (P<0.01). Microarray expression profiling analysis revealed that the p53 signal pathway was upregulated in VSMCs treated with the miR‑146a inhibitor. Compared with untransfected VSMCs, the mRNA and protein expression levels of caspase‑3 and phosphatase and tensin homolog (PTEN) in p53 signal transduction pathway did not exhibit a significant difference (P>0.05); however, the mRNA and protein expression levels of p53 were significantly decreased in cells transfected with miR‑146a mimics and increased in miR‑146a inhibitor transfected cells (both P<0.01). The mRNA and protein expression levels of cyclin D1 significantly increased in miR‑146a mimics transfected cells and decreased in cells transfected with the miR‑146a inhibitor (both P<0.05). The present data indicated that miR‑146a may promote the proliferation of rat VSMCs by downregulating p53 and upregulating cyclin D1 expression.

Cytokines and MicroRNA in Coronary Artery Disease

Cardiovascular disease (CVD) is a major health problem globally. The high incidence and case fatality of CVD are, to a large extent, a consequence of its late diagnosis and lack of highly sensitive and specific markers. Only a very small number of biomarkers, such as troponin, detect late disease. There is some evidence of an association and dysregulation between specific cytokines in the pathogenesis of CVD. These molecules are involved in inflammatory and immune mechanisms associated with atherogenesis. Several molecular/cellular pathways that include STAT, MAPK, and SMAD are modulated by cytokines. Against this background, microRNAs (miRNAs) are a class of noncoding RNAs with important roles in pathological events, leading to atherosclerotic CVD. It has been shown that the latter could affect cytokine production and contribute to progression of atherosclerotic CVD. Moreover, modulation of miRNAs appears to inhibit cardiomyocyte apoptosis, attenuate infarct size, and reduce cardiac dysfunction. This review highlights several recent preclinical and clinical studies on the role of cytokines in CVD, novel miRNA-based therapeutic approaches for therapeutic intervention, and potential circulating cytokines that have promise as biomarkers in CVD.

Increased maternal and fetal cholesterol efflux capacity and placental CYP27A1 expression in preeclampsia

Preeclampsia is a pregnancy-specific condition that leads to increased cardiovascular risk in later life. A decrease in cholesterol efflux capacity is linked to CVD. We hypothesized that in preeclampsia there would be a disruption of maternal/fetal plasma to efflux cholesterol, as well as differences in the concentrations of both placental sterol 27-hydroxylase (CYP27A1) and apoA1 binding protein (AIBP). Total, HDL-, and ABCA1-mediated cholesterol effluxes were performed with maternal and fetal plasma from women with preeclampsia and normotensive controls (both n = 17). apoA1 and apoE were quantified by chemiluminescence, and 27-hydroxycholesterol (27-OHC) by GC-MS. Immunohistochemistry was used to determine placental expression/localization of CYP27A1, AIBP, apoA1, apoE, and SRB1. Maternal and fetal total and HDL-mediated cholesterol efflux capacities were increased in preeclampsia (by 10-20%), but ABCA1-mediated efflux was decreased (by 20-35%; P < 0.05). Maternal and fetal apoE concentrations were higher in preeclampsia. Fetal plasma 27-OHC levels were decreased in preeclamptic samples (P < 0.05). Placental protein expression of both CYP27A1 and AIBP were localized around fetal vessels and significantly increased in preeclampsia (P = 0.04). Placental 27-OHC concentrations were also raised in preeclampsia (P < 0.05). Increased HDL-mediated cholesterol efflux capacity and placental CYP27A1/27-OHC could be a rescue mechanism in preeclampsia, to remove cholesterol from cells to limit lipid peroxidation and increase placental angiogenesis.

Apolipoprotein E levels and apolipoprotein E genotypes in incident cardiovascular disease risk in subjects of the Prevention of Renal and Vascular End-stage disease study

BACKGROUND

Apolipoprotein E (apoE) is a component of all major lipoprotein classes with multiple functions including clearance of circulating triglyceride-rich lipoprotein particles and hepatic production of triglyceride-rich lipoprotein, thus affording several avenues for apoE involvement in atherosclerosis development. ApoE has 3 isoforms (E2, E3, and E4) based on a common genetic polymorphism. Numerous studies have been performed assessing cardiovascular disease (CVD) risk relative to the 6 resulting genotypes; however, surprisingly, few studies have been performed assessing risk attributable to apoE plasma levels either alone or in addition also taking into account apoE genotypes.

OBJECTIVE

To examine the role of apoE levels together with apoE genotypes on incident CVD risk in a large population-based cohort and also to afford preliminary characterization of atherogenic apoE-containing lipoprotein particles.

METHODS

Cox multivariable proportional hazards modeling was performed on a cohort of the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study as a function of apoE levels and apoE genotypes adjusted for age, gender, and past history of CVD. Further modeling was performed with single addition of clinical and biomarker parameters to elucidate the nature of apoE-associated risk.

RESULTS

High apoE levels were demonstrated to be associated with CVD risk (hazard ratio per apoE standard deviation, 1.20; 95% confidence interval, 1.11-1.31; P < .0001) both overall and within the high-frequency apoE genotype groups (ε2ε3, ε3ε3, and ε3ε4). Only on addition of apoB-containing lipoprotein parameters to models, did apoE levels lose association with risk.

CONCLUSIONS

ApoE levels positively associate with incident CVD risk with apoE-associated risk likely residing in apoB-containing lipoproteins.

Apolipoprotein E enhances microRNA-146a in monocytes and macrophages to suppress nuclear factor-κB-driven inflammation and atherosclerosis

RATIONALE

Apolipoprotein E (apoE) exerts anti-inflammatory properties that protect against atherosclerosis and other inflammatory diseases. However, mechanisms by which apoE suppresses the cellular activation of leukocytes commonly associated with atherosclerosis remain incompletely understood.

OBJECTIVE

To test the hypothesis that apoE suppresses inflammation and atherosclerosis by regulating cellular microRNA levels in these leukocytes.

METHODS AND RESULTS

An assessment of apoE expression among such leukocyte subsets in wild-type mice revealed that only macrophages and monocytes express apoE abundantly. An absence of apoE expression in macrophages and monocytes resulted in enhanced nuclear factor-κB signaling and an exaggerated inflammatory response on stimulation with lipopolysaccharide. This correlated with reduced levels of microRNA-146a, a critical negative regulator of nuclear factor-κB signaling. Ectopic apoE expression in Apoe(-/-) macrophages and monocytes raised miR-146a levels, whereas its silencing in wild-type cells had an opposite effect. Mechanistically, apoE increased the expression of transcription factor purine-rich PU-box-binding protein 1, which raised levels of pri-miR-146 transcripts, demonstrating that apoE exerts transcriptional control over miR-146a. In vivo, even a small amount of apoE expression in macrophages and monocytes of hypomorphic apoE mice led to increased miR-146a levels, and inhibited macrophage proinflammatory responses, Ly-6C(high) monocytosis, and atherosclerosis in the settings of hyperlipidemia. Accordingly, cellular enrichment of miR-146a through the systemic delivery of miR-146a mimetics in Apoe(-/-)Ldlr(-/-) and Ldlr(-/-) mice attenuated monocyte/macrophage activation and atherosclerosis in the absence of plasma lipid reduction.

CONCLUSIONS

Our data demonstrate that cellular apoE expression suppresses nuclear factor-κB-mediated inflammation and atherosclerosis by enhancing miR-146a levels in monocytes and macrophages.

Vascular calcifications on hand radiographs in rheumatoid arthritis and associations with autoantibodies, cardiovascular risk factors and mortality

OBJECTIVE

To examine whether vascular calcifications on hand films in RA might aid in determining mortality risk.

METHODS

Hand radiographs from 906 RA patients were scored as positive or negative for vascular calcifications. Patient characteristics associated with vascular calcifications were assessed using multivariable logistic regression, and associations with mortality were examined using Cox proportional hazards regression. Cytokines and multiplex ACPA were measured in both groups.

RESULTS

A total of 99 patients (11%) demonstrated radiographic vascular calcifications. Factors independently associated with vascular calcifications included diabetes [odds ratio (OR) 2.85; 95% CI 1.43, 5.66], cardiovascular disease at enrolment (OR 2.48; 95% CI 1.01, 6.09), prednisone use (OR 1.90; 95% CI 1.25, 2.91), current smoking (OR 0.06; 95% CI 0.01, 0.23) and former smoking (OR 0.36; 95% CI 0.27, 0.48) vs never smoking. In cytokine and ACPA subtype analysis, IL-4 and anti-citrullinated apolipoprotein E were significantly increased in patients with vascular calcifications in fully adjusted multivariable models. After multivariable adjustment, vascular calcifications were associated with an increase in all-cause mortality (hazard ratio 1.41; 95% CI 1.12, 1.78; P = 0.004).

CONCLUSION

Vascular calcifications on hand radiographs were independently associated with increased all-cause mortality in RA. Mechanisms underpinning the associations of IL-4 and select ACPA with vascular calcifications and their utility as biomarkers predictive of cardiovascular disease risk in RA merit further study.

Animal models of diabetic macrovascular complications: key players in the development of new therapeutic approaches

Diabetes mellitus is a lifelong, incapacitating metabolic disease associated with chronic macrovascular complications (coronary heart disease, stroke, and peripheral vascular disease) and microvascular disorders leading to damage of the kidneys (nephropathy) and eyes (retinopathy). Based on the current trends, the rising prevalence of diabetes worldwide will lead to increased cardiovascular morbidity and mortality. Therefore, novel means to prevent and treat these complications are needed. Under the auspices of the IMI (Innovative Medicines Initiative), the SUMMIT (SUrrogate markers for Micro- and Macrovascular hard end points for Innovative diabetes Tools) consortium is working on the development of novel animal models that better replicate vascular complications of diabetes and on the characterization of the available models. In the past years, with the high level of genomic information available and more advanced molecular tools, a very large number of models has been created. Selecting the right model for a specific study is not a trivial task and will have an impact on the study results and their interpretation. This review gathers information on the available experimental animal models of diabetic macrovascular complications and evaluates their pros and cons for research purposes as well as for drug development.

Selective suppression of adipose tissue apoE expression impacts systemic metabolic phenotype and adipose tissue inflammation

apoE is a multi-functional protein expressed in several cell types and in several organs. It is highly expressed in adipose tissue, where it is important for modulating adipocyte lipid flux and gene expression in isolated adipocytes. In order to investigate a potential systemic role for apoE that is produced in adipose tissue, mice were generated with selective suppression of adipose tissue apoE expression and normal circulating apoE levels. These mice had less adipose tissue with smaller adipocytes containing fewer lipids, but no change in adipocyte number compared with control mice. Adipocyte TG synthesis in the presence of apoE-containing VLDL was markedly impaired. Adipocyte caveolin and leptin gene expression were reduced, but adiponectin, PGC-1, and CPT-1 gene expression were increased. Mice with selective suppression of adipose tissue apoE had lower fasting lipid, insulin, and glucose levels, and glucose and insulin tolerance tests were consistent with increased insulin sensitivity. Lipid storage in muscle, heart, and liver was significantly reduced. Adipose tissue macrophage inflammatory activation was markedly diminished with suppression of adipose tissue apoE expression. Our results establish a novel effect of adipose tissue apoE expression, distinct from circulating apoE, on systemic substrate metabolism and adipose tissue inflammatory state.

Identification of a non-growth factor role for GM-CSF in advanced atherosclerosis: promotion of macrophage apoptosis and plaque necrosis through IL-23 signaling

RATIONALE

Granulocyte macrophage colony-stimulating factor (GM-CSF, Csf2) is a growth factor for myeloid-lineage cells that has been implicated in the pathogenesis of atherosclerosis and other chronic inflammatory diseases. However, the role of GM-CSF in advanced atherosclerotic plaque progression, the process that gives rise to clinically dangerous plaques, is unknown.

OBJECTIVE

To understand the role of GM-CSF in advanced atherosclerotic plaque progression.

METHODS AND RESULTS

Ldlr(-/-) mice and Csf2(-/-)Ldlr(-/-) mice were fed a Western-type diet for 12 weeks, and then parameters of advanced plaque progression in the aortic root were quantified. Lesions from the GM-CSF-deficient mice showed a substantial decrease in 2 key hallmarks of advanced atherosclerosis, lesional macrophage apoptosis and plaque necrosis, which indicates that GM-CSF promotes plaque progression. Based on a combination of in vitro and in vivo studies, we show that the mechanism involves GM-CSF-mediated production of interleukin-23, which increases apoptosis susceptibility in macrophages by promoting proteasomal degradation of the cell survival protein Bcl-2 (B-cell lymphoma 2) and by increasing oxidative stress.

CONCLUSIONS

In low-density lipoprotein-driven atherosclerosis in mice, GM-CSF promotes advanced plaque progression by increasing macrophage apoptosis susceptibility. This action of GM-CSF is mediated by its interleukin-23-inducing activity rather than its role as a growth factor.

Anti-inflammatory and cholesterol-reducing properties of apolipoprotein mimetics: a review

Reduced levels of HDL cholesterol (HDL-C) are a strong independent predictor of coronary artery disease (CAD) risk. The major anti-atherogenic function of HDL is to mediate reverse cholesterol transport. This response is highly dependent on apoA-I and apoE, protein components of HDL. Randomized clinical trials have assessed effects of several classes of drugs on plasma cholesterol levels in CAD patients. Agents including cholestyramine, fibrates, niacin, and statins significantly lower LDL cholesterol (LDL-C) and induce modest increases in HDL-C, but tolerance issues and undesirable side effects are common. Additionally, residual risk may be present in patients with persistently low HDL-C and other complications despite a reduction in LDL-C. These observations have fueled interest in the development of new pharmacotherapies that positively impact circulating lipoproteins. The goal of this review is to discuss the therapeutic potential of synthetic apolipoprotein mimetic peptides. These include apoA-I mimetic peptides that have undergone initial clinical assessment. We also discuss newer apoE mimetics that mediate the clearance of atherogenic lipids from the circulation and possess anti-inflammatory properties. One of these (AEM-28) has recently been given orphan drug status and is undergoing clinical trials.

RP5-833A20.1/miR-382-5p/NFIA-dependent signal transduction pathway contributes to the regulation of cholesterol homeostasis and inflammatory reaction

OBJECTIVE

Cardiovascular disease caused by atherosclerosis is the number one cause of death in Western countries and threatens to become the major cause of morbidity and mortality worldwide. Long noncoding RNAs are emerging as new players in gene regulation, but how long noncoding RNAs operate in the development of atherosclerosis remains unclear.

APPROACH AND RESULTS

Using microarray analysis, we found that long noncoding RNA RP5-833A20.1 expression was upregulated, whereas nuclear factor IA (NFIA) expression was downregulated in human acute monocytic leukemia macrophage-derived foam cells. Moreover, we showed that long noncoding RNA RP5-833A20.1 may decreases NFIA expression by inducing hsa-miR-382-5p expression in vitro. We found that the RP5-833A20.1/hsa-miR-382-5p/NFIA pathway is essential to the regulation of cholesterol homeostasis and inflammatory responses in human acute monocytic leukemia macrophages. Lentivirus-mediated NFIA overexpression increased high-density lipoprotein cholesterol circulation, reduced low-density lipoprotein cholesterol, and very-low-density lipoprotein cholesterol circulation, decreased circulation of inflammatory cytokines, including interleukin-1β, interleukin-6, tumor necrosis factor-α, and C-reactive protein, enhanced reverse cholesterol transport, and promoted regression of atherosclerosis in apolipoprotein E-deficient mice.

CONCLUSIONS

Our findings indicated that the RP5-833A20.1/miR-382-5p/NFIA pathway was essential to the regulation of cholesterol homeostasis and inflammatory reactions and suggested that NFIA may represent a therapeutic target to ameliorate cardiovascular disease.

Does low birth weight affect the presence of cardiometabolic risk factors in overweight and obese children?

Recent findings suggest that low-birth-weight children with current obesity are more likely to have higher systolic blood pressure levels and impaired β-cell function than those who are obese with normal birth weight. It seems possible, however, that concurrent low birth weight with excess weight gain can exacerbate other risk factors for cardiometabolic diseases. The purpose of this study is to investigate the influence of birth weight on the lipid/apolipoprotein profile, visfatin levels, and insulin parameters in overweight/obese children. A cross-sectional study of 68 overweight/obese children was conducted. Among these children, 28 were identified with low birth weight and 40 were of normal birth weight. Blood lipid profile, apolipoproteins, visfatin, glucose, and insulin were measured. Our results show that systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels, triglycerides (TG), very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDLc), apolipoprotein B and E, insulin, apolipoprotein B/A1 ratio, and homeostasis model assessment insulin resistance (HOMA-IR) were significantly elevated in overweight/obese low-birth-weight (LBW) children. There was a significant association of the SBP levels with TG (P=0.027), LDLc (P=0.001), HOMA-IR (P<0.001), apolipoprotein B (P=0.001), and apolipoprotein E (P=0.039).

CONCLUSION

Our findings suggest that LBW children with overweight or obesity have an additional risk factor for both atherogenic and insulinogenic profile.

The roles of genetic polymorphisms and human immunodeficiency virus infection in lipid metabolism

Dyslipidemia has been frequently observed among individuals infected with human immunodeficiency virus type 1 (HIV-1), and factors related to HIV-1, the host, and antiretroviral therapy (ART) are involved in this phenomenon. This study reviews the roles of genetic polymorphisms, HIV-1 infection, and highly active antiretroviral therapy (HAART) in lipid metabolism. Lipid abnormalities can vary according to the HAART regimen, such as those with protease inhibitors (PIs). However, genetic factors may also be involved in dyslipidemia because not all patients receiving the same HAART regimen and with comparable demographic, virological, and immunological characteristics develop variations in the lipid profile. Polymorphisms in a large number of genes are involved in the synthesis of structural proteins, and enzymes related to lipid metabolism account for variations in the lipid profile of each individual. As some genetic polymorphisms may cause dyslipidemia, these allele variants should be investigated in HIV-1-infected patients to identify individuals with an increased risk of developing dyslipidemia during treatment with HAART, particularly during therapy with PIs. This knowledge may guide individualized treatment decisions and lead to the development of new therapeutic targets for the treatment of dyslipidemia in these patients.

Liver X receptor modulators: a review of recently patented compounds (2009 - 2012)

INTRODUCTION

The development of small molecule agonists of the liver X receptors (LXRs) has been an area of interest for over a decade, given the critical role of those receptors in cholesterol metabolism, glucose homeostasis, inflammation, innate immunity and lipogenesis. Many potential indications have been characterized over time including atherosclerosis, diabetes, inflammation, Alzheimer's disease and cancer. However, concerns about the lipogenic effects of full LXRα/β agonists have required extensive efforts aimed at identifying LXRβ agonist with limited activity on the LXRα receptor to increase the safety margins.

AREAS COVERED

This review includes a summary of the LXR agonists that have reached the clinic and summarizes the patent applications for LXR modulators from September 2009 to December 2012 with emphasis on chemical matters, biological data associated with selected analogs and therapeutic indications.

EXPERT OPINION

As LXR agonists have the potential to be useful for many indications, the scientific community, despite setbacks due to on-target side effects, has maintained interest and devised strategies to overcome safety hurdles. While a clinical proof of concept still remains elusive, the recent advancement of compounds into the clinic highlights that acceptable safety margins in preclinical species have been achieved.

Liver ABCA1 deletion in LDLrKO mice does not impair macrophage reverse cholesterol transport or exacerbate atherogenesis

OBJECTIVE

Hepatic ATP binding cassette transporter A1 (ABCA1) expression is critical for maintaining plasma high-density lipoprotein (HDL) concentrations, but its role in macrophage reverse cholesterol transport and atherosclerosis is not fully understood. We investigated atherosclerosis development and reverse cholesterol transport in hepatocyte-specific ABCA1 knockout (HSKO) mice in the low-density lipoprotein (LDL) receptor KO (LDLrKO) C57BL/6 background.

APPROACH AND RESULTS

Male and female LDLrKO and HSKO/LDLrKO mice were switched from chow at 8 weeks of age to an atherogenic diet (10% palm oil, 0.2% cholesterol) for 16 weeks. Chow-fed HSKO/LDLrKO mice had HDL concentrations 10% to 20% of LDLrKO mice, but similar very low-density lipoprotein and LDL concentrations. Surprisingly, HSKO/LDLrKO mice fed the atherogenic diet had significantly lower (40% to 60%) very low-density lipoprotein, LDL, and HDL concentrations (50%) compared with LDLrKO mice. Aortic surface lesion area and cholesterol content were similar for both genotypes of mice, but aortic root intimal area was significantly lower (20% to 40%) in HSKO/LDLrKO mice. Although macrophage (3)H-cholesterol efflux to apoB lipoprotein-depleted plasma was 24% lower for atherogenic diet-fed HSKO/LDLrKO versus LDLrKO mice, variation in percentage efflux among individual mice was <2-fold compared with a 10-fold variation in plasma HDL concentrations, suggesting that HDL levels, per se, were not the primary determinant of plasma efflux capacity. In vivo reverse cholesterol transport, resident peritoneal macrophage sterol content, biliary lipid composition, and fecal cholesterol mass were similar between both genotypes of mice.

CONCLUSIONS

The markedly reduced plasma HDL pool in HSKO/LDLrKO mice is sufficient to maintain macrophage reverse cholesterol transport, which, along with reduced plasma very low-density lipoprotein and LDL concentrations, prevented the expected increase in atherosclerosis.

Hypercholesterolemia in pregnant mice increases the susceptibility to atherosclerosis in adult life

PURPOSE

To determine the effects of hypercholesterolemia in pregnant mice on the susceptibility to atherosclerosis in adult life through a new animal modeling approach.

METHODS

Male offspring from apoE-/- mice fed with regular (R) or high (H) cholesterol chow during pregnancy were randomly subjected to regular (Groups R-R and H-R, n = 10) or high cholesterol diet (Groups R-H and H-H, n = 10) for 14 weeks. Plasma lipid profiles were determined in all rats. The abdominal aorta was examined for the severity of atherosclerotic lesions in offspring.

RESULTS

Lipids significantly increased while high-density lipoprotein-cholesterol/low-density lipoprotein-cholesterol decreased in mothers fed high cholesterol chow after delivery compared with before pregnancy (p < 0.01). Groups R-H and H-R indicated dyslipidemia and significant atherosclerotic lesions. Group H-H demonstrated the highest lipids, lowest high-density lipoprotein-cholesterol/low-density lipoprotein-cholesterol, highest incidence (90%), plaque area to luminal area ratio (0.78 ± 0.02) and intima to media ratio (1.57 ± 0.05).

CONCLUSION

Hypercholesterolemia in pregnant mice may increase susceptibility to atherosclerosis in their adult offspring.

Oxysterol generation and liver X receptor-dependent reverse cholesterol transport: not all roads lead to Rome

Cell cholesterol metabolism is a tightly regulated process, dependent in part on activation of nuclear liver X receptors (LXRs) to increase expression of genes mediating removal of excess cholesterol from cells in the reverse cholesterol transport pathway. LXRs are thought to be activated predominantly by oxysterols generated enzymatically from cholesterol in different cell organelles. Defects resulting in slowed release of cholesterol from late endosomes and lysosomes or reduction in sterol-27-hydroxylase activity lead to specific blocks in oxysterol production and impaired LXR-dependent gene activation. This block does not appear to be compensated by oxysterol production in other cell compartments. The purpose of this review is to summarize current knowledge about oxysterol-dependent activation by LXR of genes involved in reverse cholesterol transport, and what these defects of cell cholesterol homeostasis can teach us about the critical pathways of oxysterol generation for expression of LXR-dependent genes.

Roles of apolipoprotein E (ApoE) and inducible nitric oxide synthase (iNOS) in inflammation and apoptosis in preeclampsia pathogenesis and progression

Objectives

To investigate potential roles of inducible nitric oxide synthase (iNOS) and apolipoprotein (apoE) in inflammation and apoptosis promoting pathological changes in preeclampsia in pregnant mice with apoE and/or iNOS knock out.

Methods

B6.129 mice were crossed to produce WT, apoE^−/−, apoE^+/−, iNOS^−/−, iNOS^+/− and apoE^−/−iNOS^−/− groups. Variants were confirmed by PCR. Serum lipid parameters (triglycerides, TG; total cholesterol, TC; high density lipoprotein, HDL; and low density lipoprotein, LDL), NO levels and placental electronic microscopic ultrastructures were evaluated, and blood pressure (BP), 24-hour urine protein and pregnancy outcomes were recorded for pregnant F1 generation mice. Placental expressions of inflammatory (tumor necrosis factor-α, TNF-α; interleukin-6, IL-6; nuclear factor-κB, NF-κb) and apoptotic markers (Bcl-2 associated X protein, Bax, B-cell lymphoma/leukemia-2, Bcl-2, and Caspase-3) were evaluated via Western blot.

Results

Serum lipids, BP and 24-hour urine protein levels were shown to be significantly higher and parturition and placenta weights were lower in apoE^−/− and apoE^−/−iNOS^−/− groups (p<0.05). NO levels were lower in the apoE^−/−iNOS^−/− group. In addition, inflammatory/apoptosis parameters, including TNF-α, IL-6, NF-κb, Bax, Bcl-2 and Caspase-3 in the apoE^−/−iNOS^−/− group (p<0.01), as well as in the apoE^−/− group (p<0.05), and NF-κB, Bax in iNOS^−/− group (p<0.05) were higher compared with WT group. However, most of the inflammatory/apoptosis parameters in the iNOS^+/− and the apoE^+/− groups (p>0.05) showed no differences. In addition, placenta vascular endothelial and trophoblast cell morphological changes were demonstrated in both the apoE^−/−iNOS^−/− and apoE^−/− groups.

Conclusion

Elevated lipid metabolism and inflammatory/apoptosis parameters suggest a potentially significant role of apoE in preeclampsia pathology, as well as a relationship between iNOS and preeclampsia progression.

The absence of macrophage Nrf2 promotes early atherogenesis

AIMS

The loss of nuclear factor E2-related factor 2 (Nrf2) has been shown to protect against atherogenesis in apoE-deficient mice. The mechanism by which Nrf2 deficiency affords atheroprotection in this model is currently unknown, but combined systemic and local vascular effects on lesion macrophages have been proposed. We investigated the effect of bone marrow-specific loss of Nrf2 on early atherogenesis in low-density lipoprotein (LDL) receptor-deficient (LDLR(-/-)) mice, and assessed the effect of Nrf2 on cellular accumulation of modified LDLs and the expression of inflammatory markers in macrophages.

METHODS AND RESULTS

The effect of bone marrow-specific loss of Nrf2 on atherogenesis was studied using bone marrow transplantation of wild-type (WT) or Nrf2(-/-) bone marrow to LDLR(-/-) mice. Mice transplanted with Nrf2(-/-) bone marrow and fed a high-fat diet for 6 weeks exhibited significantly larger atherosclerotic lesions than WT bone marrow transplanted mice. Moreover, in thioglycollate-elicited Nrf2(-/-) macrophages, the uptake of acetylated and malondialdehyde-modified LDLs was increased in comparison with WT controls, with the concomitant increase in the expression of scavenger receptor A and toll-like receptor 4. In addition, the expression of pro-inflammatory monocyte chemoattractant protein-1 and interleukin-6 were increased in Nrf2(-/-) vs. WT macrophages.

CONCLUSION

Nrf2 deficiency specific to bone marrow-derived cells aggravates atherosclerosis in LDLR(-/-) mice. Furthermore, the loss of Nrf2 in macrophages enhances foam cell formation and promotes the pro-inflammatory phenotype.

Effect of fenofibrate and atorvastatin on VLDL apoE metabolism in men with the metabolic syndrome

We examined the effects of fenofibrate and atorvastatin on very low density lipoprotein (VLDL) apolipoprotein (apo)E metabolism in the metabolic syndrome (MetS). We studied 11 MetS men in a randomized, double-blind, crossover trial. VLDL-apoE kinetics were examined using stable isotope methods and compartmental modeling. Compared with placebo, fenofibrate (200 mg/day) and atorvastatin (40 mg/day) decreased plasma apoE concentrations (P < 0.05). Fenofibrate decreased VLDL-apoE concentration and production rate (PR) and increased VLDL-apoE fractional catabolic rate (FCR) compared with placebo (P < 0.05). Compared with placebo, atorvastatin decreased VLDL-apoE concentration and increased VLDL-apoE FCR (P < 0.05). Fenofibrate and atorvastatin had comparable effects on VLDL-apoE concentration. The increase in VLDL-apoE FCR with fenofibrate was 22% less than that with atorvastatin (P < 0.01). With fenofibrate, the change in VLDL-apoE concentration was positively correlated with change in VLDL-apoB concentration, and negatively correlated with change in VLDL-apoB FCR. In MetS, fenofibrate and atorvastatin decreased plasma apoE concentrations. Fenofibrate decreased VLDL-apoE concentration by lowering VLDL-apoE production and increasing VLDL-apoE catabolism. By contrast, atorvastatin decreased VLDL-apoE concentration chiefly by increasing VLDL-apoE catabolism. Our study provides new insights into the mechanisms of action of two different lipid-lowering therapies on VLDL-apoE metabolism in MetS.

ApoE derived from adipose tissue does not suppress atherosclerosis or correct hyperlipidemia in apoE knockout mice

The synthesis of apoE by adipocytes has profound effects on adipose tissue lipid flux and gene expression. Using adipose tissue transplantation from wild-type (WT) to apoE knockout (EKO) mice, we show that adipose tissue also contributes to circulating apoE. Different from circulating apoE produced by bone marrow transplantation (BMT), however, adipose tissue-derived apoE does not correct hyperlipidemia or suppress atherosclerosis. ApoE secreted by macrophages has a more acidic isoform distribution, and it increases binding of reconstituted VLDL particles to hepatocytes and fibroblasts more effectively than apoE secreted by adipocytes. The incremental binding can be entirely accounted for by binding to the LDL receptor. After BMT into EKO hosts, plasma cholesterol and macrophage-derived apoE are largely within IDL/LDL- and HDL-sized particles. After adipose tissue transplantation, most cholesterol and adipocyte apoE remain in VLDL. After BMT, circulating apoE no longer demonstrates predominance of acidic isoforms compared with that circulating after fat transplantation. In conclusion, fat transplantation provides circulating apoE levels similar to those provided by bone marrow transplantation, but it does not suppress hyperlipidemia or atherosclerosis. A potential mechanism contributing to this difference is differential binding to cell surface lipoprotein receptors.

Apolipoprotein E regulation of myeloid cell plasticity in atherosclerosis

PURPOSE OF REVIEW

Apolipoprotein (apo) E is a multifunctional protein that has long been recognized for its ability to safeguard against atherosclerosis. Among its pleiotropic roles known to suppress atherosclerosis, mechanisms by which apoE regulates cells of the immune system have remained elusive. Because atherosclerosis is a chronic inflammatory disease that remains on the rise, understanding in more detail how apoE controls immune cell activation and function is of much interest.

RECENT FINDINGS

Literature reported in the past year introduces apoE as a regulator of monocyte and macrophage plasticity. Through signals delivered by its interaction with cell surface receptors, apoE has been shown to influence the polarity and inflammatory phenotypes of the macrophage. By promoting cellular cholesterol efflux in a cell autonomous manner and through its ability to enhance HDL function in hyperlipidemic plasma, apoE is now known to suppress atherosclerosis by controlling myeloid cell proliferation, monocyte activation and their capacity to infiltrate the vascular wall. Lastly, the structural basis for apoE isoform-specific effects in macrophage dysfunction and atherosclerosis susceptibility is beginning to emerge.

SUMMARY

Collectively, these findings introduce a new dimension to our understanding of how apoE links lipoprotein biology to monocyte and macrophage function in atherosclerosis susceptibility.

Lipid metabolism and neuroinflammation in Alzheimer's disease: a role for liver X receptors

Liver X receptors (LXR) are nuclear receptors that have emerged as key regulators of lipid metabolism. In addition to their functions as cholesterol sensors, LXR have also been found to regulate inflammatory responses in macrophages. Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive cognitive decline associated with inflammation. Evidence indicates that the initiation and progression of AD is linked to aberrant cholesterol metabolism and inflammation. Activation of LXR can regulate neuroinflammation and decrease amyloid-β peptide accumulation. Here, we highlight the role of LXR in orchestrating lipid homeostasis and neuroinflammation in the brain. In addition, diabetes mellitus is also briefly discussed as a significant risk factor for AD because of the appearing beneficial effects of LXR on glucose homeostasis. The ability of LXR to attenuate AD pathology makes them potential therapeutic targets for this neurodegenerative disease.