Human apolipoprotein A-II protects against diet-induced atherosclerosis in transgenic rabbits

Enhanced atherosclerosis in apolipoprotein E knockout rabbits: role of apoB48-rich remnant lipoproteins

Introduction

Apolipoprotein E (apoE) acts as a binding molecule for both the low-density lipoprotein receptor and the lipoprotein receptor-related protein and this function is essential for facilitating the hepatocyte uptake of lipoproteins containing apoB. The absence of apoE leads to increased atherogenicity in both humans and mice, although the precise molecular mechanisms remain incompletely understood.

Objectives

This study aimed to investigate the susceptibility of apoE knockout (KO) rabbits, in comparison with wild-type (WT) rabbits, to diet-induced hyperlipidemia and atherosclerosis.

Methods

ApoE KO rabbits and WT rabbits were fed a diet containing 0.3% cholesterol for 16 weeks. Plasma lipid levels, lipoproteins, and apolipoproteins were analyzed. Atherosclerosis was evaluated at the endpoint of experiments. In addition, we evaluated the oxidizability of those lipoproteins containing apoB to investigate the possible mechanisms of atherosclerosis.

Results

Male apoE KO rabbits showed significantly elevated levels of total cholesterol and triglycerides compared to WT rabbits, while female apoE KO rabbits displayed similar high total cholesterol levels, albeit with significantly higher triglycerides levels than WT controls. Notably, both male (2.1-fold increase) and female (1.6-fold increase) apoE KO rabbits exhibited a significantly augmented aortic lesion area compared to WT controls. Pathological examination showed that the increased intimal lesions in apoE KO rabbits were featured by heightened infiltration of macrophages (2.7-fold increase) and smooth muscle cells (2.5-fold increase). Furthermore, coronary atherosclerotic lesions were also increased by 1.3-fold in apoE KO rabbits. Lipoprotein analysis revealed that apoB48-rich beta-very-low-density lipoproteins were notably abundant in apoE KO rabbits, suggesting that these remnant lipoproteins of intestinal origin serve as the primary atherogenic lipoproteins. Moreover, apoB48-rich remnant lipoproteins isolated from apoE KO rabbits exhibited heightened susceptibility to copper-induced oxidation.

Conclusions

The findings indicate that apoB48-rich remnant lipoproteins, resulting from apoE deficiency, possess greater atherogenic potential than apoB100-rich remnant lipoproteins, regardless of plasma TC levels.

Metabolomic Profiling of Cholesterol Efflux Capacity in a Multiethnic Population: Insights From MESA

BACKGROUND

Impaired cholesterol efflux capacity (CEC) is a novel lipid metabolism trait associated with atherosclerotic cardiovascular disease. Mechanisms underlying CEC variation are unknown. We evaluated associations of circulating metabolites with CEC to advance understanding of metabolic pathways involved in cholesterol efflux regulation.

METHODS

Participants enrolled in the MESA (Multi-Ethnic Study of Atherosclerosis) who underwent nuclear magnetic resonance metabolome profiling and CEC measurement (N=3543) at baseline were included. Metabolite associations with CEC were evaluated using standard linear regression analyses. Repeated ElasticNet and multilayer perceptron regression were used to assess metabolite profile predictive performance for CEC. Features important for CEC prediction were identified using Shapley Additive Explanations values.

RESULTS

Greater CEC was significantly associated with metabolite clusters composed of the largest-sized particle subclasses of VLDL (very-low-density lipoprotein) and HDL (high-density lipoprotein), as well as their constituent apo A1, apo A2, phospholipid, and cholesterol components (β=0.072-0.081; P<0.001). Metabolite profiles had poor accuracy for predicting in vitro CEC in linear and nonlinear analyses (R2<0.02; Spearman ρ<0.18). The most important feature for CEC prediction was race, with Black participants having significantly lower CEC compared with other races.

CONCLUSIONS

We identified independent associations among CEC, the largest-sized particle subclasses of VLDL and HDL, and their constituent apolipoproteins and lipids. A large proportion of variation in CEC remained unexplained by metabolites and traditional clinical risk factors, supporting further investigation into genomic, proteomic, and phospholipidomic determinants of CEC.

Apolipoproteins as potential communicators play an essential role in the pathogenesis and treatment of early atherosclerosis

Atherosclerosis as the leading cause of the cardiovascular disease is closely related to cholesterol deposition within subendothelial areas of the arteries. Significantly, early atherosclerosis intervention is the critical phase for its reversal. As atherosclerosis progresses, early foam cells formation may evolve into fibrous plaques and atheromatous plaque, ulteriorly rupture of atheromatous plaque increases risks of myocardial infarction and ischemic stroke, resulting in high morbidity and mortality worldwide. Notably, amphiphilic apolipoproteins (Apos) can concomitantly combine with lipids to form soluble lipoproteins that have been demonstrated to associate with atherosclerosis. Apos act as crucial communicators of lipoproteins, which not only can mediate lipids metabolism, but also can involve in pro-atherogenic and anti-atherogenic processes of atherosclerosis via affecting subendothelial retention and aggregation of low-density lipoprotein (LDL), oxidative modification of LDL, foam cells formation and reverse cholesterol transport (RCT) in macrophage cells. Correspondingly, Apos can be used as endogenous and/or exogenous targeting agents to effectively attenuate the development of atherosclerosis. The article reviews the classification, structure, and relationship between Apos and lipids, how Apos serve as communicators of lipoproteins to participate in the pathogenesis progression of early atherosclerosis, as well as how Apos as the meaningful targeting mass is used in early atherosclerosis treatment.

HDL functionality in type 1 diabetes: enhancement of cholesterol efflux capacity in relationship with decreased HDL carbamylation after improvement of glycemic control

Background

Reduced cholesterol efflux capacity (CEC) of HDLs is likely to increase cardiovascular risk in type 1 diabetes (T1D). We aimed to assess whether improvement of glycemic control in T1D patients is associated with changes in CEC in relation with changes in carbamylation of HDLs.

Methods

In this open-label trial, 27 uncontrolled T1D patients were given a three-month standard medical intervention to improve glycemic control. HDL fraction was isolated from plasma, and CEC was measured on THP-1 macrophages. Carbamylation of HDLs was evaluated by an immunoassay. Control HDLs from healthy subjects were carbamylated in vitro with potassium cyanate.

Results

HbA_1c decreased from 11.4% [10.2–12.9] (median [1st–3rd quartiles]) at baseline to 8.1% [6.6–9.0] after the three-month intervention (P < 0.00001). The CEC of HDLs increased after intervention in 19 (70%) patients (P = 0.038). At the same time, the carbamylation of HDLs decreased in 22 (82%) patients after intervention (P = 0.014). The increase in CEC significantly correlated with the decrease in carbamylated HDLs (r = −0.411, P = 0.034), even after adjustment for the change in HbA_1c (β = −0.527, P = 0.003). In vitro carbamylation of control HDLs decreased CEC by 13% (P = 0.041) and 23% (P = 0.021) using 1 and 10 mmol/L of potassium cyanate, respectively.

Conclusions

The improvement of CEC in relation to a decrease in the carbamylation of HDLs may likely contribute to the beneficial cardiovascular effect of glycemic control in T1D patients.

Trial registration: NCT02816099 ClinicalTrials.gov.

Unraveling the Transcriptional Dynamics of NASH Pathogenesis Affecting Atherosclerosis

The prevalence of non-alcoholic steatohepatitis (NASH) is rapidly increasing and associated with cardiovascular disease (CVD), the major cause of mortality in NASH patients. Although sharing common risk factors, the mechanisms by which NASH may directly contribute to the development to CVD remain poorly understood. The aim of this study is to gain insight into key molecular processes of NASH that drive atherosclerosis development. Thereto, a time-course study was performed in Ldlr-/-.Leiden mice fed a high-fat diet to induce NASH and atherosclerosis. The effects on NASH and atherosclerosis were assessed and transcriptome analysis was performed. Ldlr-/-.Leiden mice developed obesity, hyperlipidemia and insulin resistance, with steatosis and hepatic inflammation preceding atherosclerosis development. Transcriptome analysis revealed a time-dependent increase in pathways related to NASH and fibrosis followed by an increase in pro-atherogenic processes in the aorta. Gene regulatory network analysis identified specific liver regulators related to lipid metabolism (SC5D, LCAT and HMGCR), inflammation (IL1A) and fibrosis (PDGF, COL3A1), linked to a set of aorta target genes related to vascular inflammation (TNFA) and atherosclerosis signaling (CCL2 and FDFT1). The present study reveals pathogenic liver processes that precede atherosclerosis development and identifies hepatic key regulators driving the atherogenic pathways and regulators in the aorta.

Interaction between Apo A-II -265T > C polymorphism and dietary total antioxidant capacity on some oxidative stress and inflammatory markers in patients with type 2 diabetes mellitus

This work aims to examine the interaction between apo A2 (Apo A-II) -265T > C SNP and dietary total antioxidant capacity (DTAC) on inflammation and oxidative stress in patients with type 2 diabetes mellitus. The present cross-sectional study included 180 patients (35-65 years) with identified Apo A-II genotype. Dietary intakes were assessed by a FFQ. DTAC was computed using the international databases. IL-18 (IL18), high-sensitivity C-reactive protein (hs-CRP), pentraxin (PTX3), serum total antioxidant capacity (TAC), superoxide dismutase (SOD) activity and 8-isoprostaneF2α (PGF2α) markers were obtained according to standard protocols. General linear model was used to evaluate the interaction. The interaction of gene and DTAC (P_FRAP = 0·039 and P_ORAC = 0·042) on PGF2α level was significant after adjusting for confounders. A significant interaction was observed on IL18 level (P_ORAC = 0·018 and P_FRAP = 0·048) and SOD (P_TEAC = 0·037) in obese patients. Among patients whose DTAC was higher than the median intake, the levels of hs-CRP and PGF2α were significantly higher only in individuals with CC genotype. Serum TAC (P_FRAP = 0·030, P_ORAC = 0·049) and SOD were significantly lower in the CC genotype. There was a favourable relationship between the high-DTAC and SOD (obese: P_TEAC = 0·034, non-obese: P_FRAP = 0·001, P_TRAP < 0·0001, P_TEAC = 0·003 and P_ORAC = 0·001) and PGF2α (non-obese: P_ORAC = 0·024) in T-allele carriers. The rs5082 SNP interacts with DTAC to influence several cardiometabolic risk factors. Also, we found dietary recommendations for antioxidant-rich foods intake might be useful in the prevention of diabetes complications in the T carrier more effectively than the CC genotype. Future large studies are required to confirm these results.

HDL-apoA-II Is Strongly Associated with 1-Year Mortality in Acute Heart Failure Patients

The prognostic value of the subset of high-density lipoprotein (HDL) particles containing apolipoprotein (apo)A-II (HDL-apoA-II) in acute heart failure (AHF) remains unexplored. In this study, baseline serum levels of HDL-apoA-II (total and subfractions 1−4) were measured in 315 AHF patients using NMR spectroscopy. The mean patient age was 74.2 ± 10.5 years, 136 (43.2%) were female, 288 (91.4%) had a history of cardiomyopathy, 298 (94.6%) presented as New York Heart Association class 4, and 118 (37.5%) patients died within 1 year after hospitalization for AHF. Multivariable Cox regression analyses, adjusted for age and sex as well as other clinical and laboratory parameters associated with 1-year mortality in the univariable analyses, revealed a significant inverse association of HDL-apoA-II (hazard ratio (HR) 0.67 per 1 standard deviation (1 SD) increase, 95% confidence interval (CI) 0.47−0.94, p = 0.020), HDL2-apoA-II (HR 0.72 per 1 SD increase, 95% CI 0.54−0.95, p = 0.019), and HDL3-apoA-II (HR 0.59 per 1 SD increase, 95% CI 0.43−0.80, p < 0.001) with 1-year mortality. We conclude that low baseline HDL-apoA-II, HDL2-apoA-II, and HDL3-apoA-II serum levels are associated with increased 1-year mortality in AHF patients and may thus be of prognostic value in AHF.

Apolipoprotein A-II, a Player in Multiple Processes and Diseases

Apolipoprotein A-II (apoA-II) is the second most abundant apolipoprotein in high-density lipoprotein (HDL) particles, playing an important role in lipid metabolism. Human and murine apoA-II proteins have dissimilar properties, partially because human apoA-II is dimeric whereas the murine homolog is a monomer, suggesting that the role of apoA-II may be quite different in humans and mice. As a component of HDL, apoA-II influences lipid metabolism, being directly or indirectly involved in vascular diseases. Clinical and epidemiological studies resulted in conflicting findings regarding the proatherogenic or atheroprotective role of apoA-II. Human apoA-II deficiency has little influence on lipoprotein levels with no obvious clinical consequences, while murine apoA-II deficiency causes HDL deficit in mice. In humans, an increased plasma apoA-II concentration causes hypertriglyceridemia and lowers HDL levels. This dyslipidemia leads to glucose intolerance, and the ensuing high blood glucose enhances apoA-II transcription, generating a vicious circle that may cause type 2 diabetes (T2D). ApoA-II is also used as a biomarker in various diseases, such as pancreatic cancer. Herein, we provide a review of the most recent findings regarding the roles of apoA-II and its functions in various physiological processes and disease states, such as cardiovascular disease, cancer, amyloidosis, hepatitis, insulin resistance, obesity, and T2D.

ApoA2-256T > C polymorphism interacts with Healthy Eating Index, Dietary Quality Index-International and Dietary Phytochemical Index to affect biochemical markers among type 2 diabetic patients

Several investigations revealed the association between ApoA2 concentration and lipid profile, inflammation and oxidative stress markers. Dietary habits also play a major role in the health status of individuals with type 2 diabetes mellitus (T2DM). This study aimed to investigate the interaction of ApoA2-256T > C with dietary indexes on ghrelin and leptin hormones together with biochemical markers among individuals with T2DM. A cross-sectional study was conducted on 726 randomly selected individuals with T2DM. A validated FFQ was used to evaluate Healthy Eating Index, Dietary Quality Index-International (DQI-I) and Dietary Phytochemical Index (DPI). ApoA2-256T > C genotypes were detected by real-time-PCR. Ghrelin, leptin and biochemical markers were also assessed. ANCOVA was used for the interaction between the polymorphism and dietary indexes. A significant interaction was observed between ApoA2-256T > C and DQI-I on high-sensitivity C-reactive protein (hs-CRP) level and superoxide dismutase (SOD) activity. Besides, the interaction of the SNP and DPI significantly affected hs-CRP and 8-isoprostane F2α (PGF2α) levels. CC in the second tertile of DPI had the lowest hs-CRP level, and it was elevated due to adhering to DQI-I (P_interaction = 0·01 and 0·04, respectively). Moreover, T-allele (protective allele) carriers with the highest level of PGF2α and SOD activity were those in the second tertile of DPI and DQI-I, respectively (P_interaction = 0·03 and 0·007, respectively). SOD activity, hs-CRP and PGF2α concentration may be modified in T-allele carriers and CC by the adherence to DPI and DQI-I, though additional studies are required to confirm these findings.

Genetically modified rabbit models for cardiovascular medicine

Genetically modified (GM) rabbits are outstanding animal models for studying human genetic and acquired diseases. As such, GM rabbits that express human genes have been extensively used as models of cardiovascular disease. Rabbits are genetically modified via prokaryotic microinjection. Through this process, genes are randomly integrated into the rabbit genome. Moreover, gene targeting in embryonic stem (ES) cells is a powerful tool for understanding gene function. However, rabbits lack stable ES cell lines. Therefore, ES-dependent gene targeting is not possible in rabbits. Nevertheless, the RNA interference technique is rapidly becoming a useful experimental tool that enables researchers to knock down specific gene expression, which leads to the genetic modification of rabbits. Recently, with the emergence of new genetic technology, such as zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), clustered regularly interspaced short palindromic repeats (CRISPR), and CRISPR-associated protein 9 (CRISPR/Cas9), major breakthroughs have been made in rabbit gene targeting. Using these novel genetic techniques, researchers have successfully modified knockout (KO) rabbit models. In this paper, we aimed to review the recent advances in GM technology in rabbits and highlight their application as models for cardiovascular medicine.

Determinants of high-density lipoprotein (HDL) functions beyond proteome in Asian Indians: exploring the fatty acid profile of HDL phospholipids

Impaired high-density lipoprotein (HDL) functions are associated with development of coronary artery disease. In this study, we explored the quantitative differences in HDL (i.e. HDL proteome and fatty acid profile of HDL phospholipids) underlying the functional deficits associated with acute coronary syndrome (ACS). The relationship between HDL function and composition was assessed in 65 consecutive ACS patients and 40 healthy controls. Cholesterol efflux capacity (CEC) of HDL and lecithin cholesterol acyl transferase (LCAT) activity were significantly lower in patients with ACS compared to controls. In HDL proteome analysis, HDL isolated from ACS individuals was enriched in apolipoprotein C2 (inhibitor of LCAT), apolipoprotein C4 and serum amyloid A proteins and was deficient in apolipoprotein A-I and A-II. The fatty acid profile of HDL phospholipids analyzed using gas chromatography showed significantly lower percentages of stearic acid (17.4 ± 2.4 vs 15.8 ± 2.8, p = 0.004) and omega-3 fatty acids [eicosapentaenoic acid (1.0 (0.6-1.4) vs 0.7 (0.4-1.0), p = 0.009) and docosahexaenoic acid (1.5 ± 0.7 vs 1.3 ± 0.5, p = 0.03)] in ACS patients compared to controls. Lower percentages of these fatty acids in HDL were associated with higher odds of developing ACS. Our results suggest that distinct phospholipid fatty acid profiles found in HDL from ACS patients could be one of the contributing factors to the deranged HDL functions in these patients apart from the protein content and the inflammatory conditions.

Animal Models of Neointimal Hyperplasia and Restenosis: Species-Specific Differences and Implications for Translational Research

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Neointimal hyperplasia is the major factor contributing to restenosis after angioplasty procedures.

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Multiple animal models exist to study basic and translational aspects of restenosis formation.

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Animal models differ substantially, and species-specific differences have major impact on the pathophysiology of the model.

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Genetic, dietary, and mechanical interventions determine the translational potential of the animal model used and have to be considered when choosing the model.

The process of restenosis is based on the interplay of various mechanical and biological processes triggered by angioplasty-induced vascular trauma. Early arterial recoil, negative vascular remodeling, and neointimal formation therefore limit the long-term patency of interventional recanalization procedures. The most serious of these processes is neointimal hyperplasia, which can be traced back to 4 main mechanisms: endothelial damage and activation; monocyte accumulation in the subintimal space; fibroblast migration; and the transformation of vascular smooth muscle cells. A wide variety of animal models exists to investigate the underlying pathophysiology. Although mouse models, with their ease of genetic manipulation, enable cell- and molecular-focused fundamental research, and rats provide the opportunity to use stent and balloon models with high throughput, both rodents lack a lipid metabolism comparable to humans. Rabbits instead build a bridge to close the gap between basic and clinical research due to their human-like lipid metabolism, as well as their size being accessible for clinical angioplasty procedures. Every different combination of animal, dietary, and injury model has various advantages and disadvantages, and the decision for a proper model requires awareness of species-specific biological properties reaching from vessel morphology to distinct cellular and molecular features.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

Integration of Transformative Platforms for the Discovery of Causative Genes in Cardiovascular Diseases

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide. Genome-wide association studies (GWAS) are powerful epidemiological tools to find genes and variants associated with cardiovascular diseases while follow-up biological studies allow to better understand the etiology and mechanisms of disease and assign causality. Improved methodologies and reduced costs have allowed wider use of bulk and single-cell RNA sequencing, human-induced pluripotent stem cells, organoids, metabolomics, epigenomics, and novel animal models in conjunction with GWAS. In this review, we feature recent advancements relevant to cardiovascular diseases arising from the integration of genetic findings with multiple enabling technologies within multidisciplinary teams to highlight the solidifying transformative potential of this approach. Well-designed workflows integrating different platforms are greatly improving and accelerating the unraveling and understanding of complex disease processes while promoting an effective way to find better drug targets, improve drug design and repurposing, and provide insight towards a more personalized clinical practice.

Role of lipid metabolism and systemic inflammation in the development of atherosclerosis in animal models

Systemic inflammation makes a significant contribution to the pathogenesis of atherosclerosis and has been the subject of numerous studies. Works aiming to analyze the mechanisms of atherosclerosis development often include experiments on animals. A primary task of such research is the characterization, justification, and selection of an adequate model. Aim. To evaluate the peculiarities of lipid metabolism and systemic inflammation in chronic obstructive pulmonary disease (COPD) in the development of atherosclerosis in animal models. Materials and Methods. Analyses of cross-links between species-specific peculiarities of lipid metabolism and the immune response, as well as a bioinformatic analysis of differences in Toll-like receptor 4 (TLR4) in mice, rats, and rabbits in comparison with its human homolog, were carried out. A search for and analysis of the amino acid sequences of human, mouse, rat, and rabbit TLR4 was performed in the International database GenBank of National Center of Biotechnical Information and in The Universal Protein Resource (UniProt) database. Multiple alignments of the TLR4 amino acid sequences were implemented in the Clustal Omega program, version 1.2.4. Reconstruction and visualization of molecular phylogenetic trees were performed using the MEGA7 program according to the Neighbor-Joining and Maximum Parsimony methods. Results. Species-specific differences of the peculiarities of lipid metabolism and the innate immune response in humans, mice, and rabbits were shown that must be taken into account in analyses of study results. Conclusion.Disorders in lipid metabolism and systemic inflammation mediated by the innate immune system participating in the pathogenesis of atherosclerosis in COPD possess species-specific differences that should be taken into account in analyses of study results.

Interaction between Apo A-II -265T>C polymorphism and dietary total antioxidant capacity on some anthropometric indices and serum lipid profile in patients with type 2 diabetes mellitus

The present study aimed to investigate the interaction of Apo A-II polymorphism and dietary total antioxidant capacity (DTAC) with lipid profile and anthropometric markers in patients with type 2 diabetes (T2DM) that are at risk for atherosclerosis. This cross-sectional study was conducted on 778 patients with T2DM (35–65 years). Dietary intakes were assessed by a 147-item food frequency questionnaire. DTAC was computed using international databases. Participants were categorised into two groups based on rs5082 genotypes. The gene–diet interaction was analysed by an ANCOVA multivariate interaction model. Total cholesterol, TC; triacylglycerol, TG; high- and low-density lipoprotein, HDL and LDL; TC–HDL ratio; waist circumference, WC and body mass index, BMI were obtained according to standard protocols. Overall, the frequency of CC homozygous was 12⋅1 % among study participants. We found that a significant interaction between rs5082 variants and DTAC on mean WC (P_TEAC = 0⋅044), TC concentration (P_FRAP = 0⋅049 and P_TEAC = 0⋅031) and TC/HDL (P_FRAP = 0⋅031 and P_TRAP = 0⋅040). Among patients whose DTAC was higher than the median intake, the mean of weight, WC and TC/HDL were significantly higher only in individuals with CC genotype. Also, the high DTAC was associated with a lower TC concentration only in T-allele carriers (P_FRAP = 0⋅042). We found that adherence to a diet with high total antioxidant capacity can improve the complications of diabetes and atherosclerosis in the T carrier genotype more effectively than the CC genotype. These results could indicate the anti-atherogenic properties of Apo A-II. However, further studies are needed to shed light on this issue.

Genetically Modified Rabbits for Cardiovascular Research

Rabbits are one of the most used experimental animals for investigating the mechanisms of human cardiovascular disease and lipid metabolism because they are phylogenetically closer to human than rodents (mice and rats). Cholesterol-fed wild-type rabbits were first used to study human atherosclerosis more than 100 years ago and are still playing an important role in cardiovascular research. Furthermore, transgenic rabbits generated by pronuclear microinjection provided another means to investigate many gene functions associated with human disease. Because of the lack of both rabbit embryonic stem cells and the genome information, for a long time, it has been a dream for scientists to obtain knockout rabbits generated by homologous recombination-based genomic manipulation as in mice. This obstacle has greatly hampered using genetically modified rabbits to disclose the molecular mechanisms of many human diseases. The advent of genome editing technologies has dramatically extended the applications of experimental animals including rabbits. In this review, we will update genetically modified rabbits, including transgenic, knock-out, and knock-in rabbits during the past decades regarding their use in cardiovascular research and point out the perspectives in future.

Gene Editing in Rabbits: Unique Opportunities for Translational Biomedical Research

The rabbit is a classic animal model for biomedical research, but the production of gene targeted transgenic rabbits had been extremely challenging until the recent advent of gene editing tools. More than fifty gene knockout or knock-in rabbit models have been reported in the past decade. Gene edited (GE) rabbit models, compared to their counterpart mouse models, may offer unique opportunities in translational biomedical research attributed primarily to their relatively large size and long lifespan. More importantly, GE rabbit models have been found to mimic several disease pathologies better than their mouse counterparts particularly in fields focused on genetically inherited diseases, cardiovascular diseases, ocular diseases, and others. In this review we present selected examples of research areas where GE rabbit models are expected to make immediate contributions to the understanding of the pathophysiology of human disease, and support the development of novel therapeutics.

Human apolipoprotein A-II reduces atherosclerosis in knock-in rabbits

BACKGROUND AND AIMS

Apolipoprotein A-II (apoAII) is the second major apolipoprotein of the high-density lipoprotein (HDL) particle, after apoAI. Unlike apoAI, the biological and physiological functions of apoAII are unclear. We aimed to gain insight into the specific roles of apoAII in lipoprotein metabolism and atherosclerosis using a novel rabbit model.

METHODS

Wild-type (WT) rabbits are naturally deficient in apoAII, thus their HDL contains only apoAI. Using TALEN technology, we replaced the endogenous apoAI in rabbits through knock-in (KI) of human apoAII. The newly generated apoAII KI rabbits were used to study the specific function of apoAII, independent of apoAI.

RESULTS

ApoAII KI rabbits expressed exclusively apoAII without apoAI, as confirmed by RT-PCR and Western blotting. On a standard diet, the KI rabbits exhibited lower plasma triglycerides (TG, 52%, p < 0.01) due to accelerated clearance of TG-rich particles and higher lipoprotein lipase activity than the WT littermates. ApoAII KI rabbits also had higher plasma HDL-C (28%, p < 0.05) and their HDL was rich in apoE, apoAIV, and apoAV. When fed a cholesterol-rich diet for 16 weeks, apoAII KI rabbits were resistant to diet-induced hypertriglyceridemia and developed significantly less aortic atherosclerosis compared to WT rabbits. HDL isolated from rabbits with apoAII KI had similar cholesterol efflux capacity and anti-inflammatory effects as HDL isolated from the WT rabbits.

CONCLUSIONS

ApoAII KI rabbits developed less atherosclerosis than WT rabbits, possibly through increased plasma HDL-C, reduced TG and atherogenic lipoproteins. These results suggest that apoAII may serve as a potential target for the treatment of atherosclerosis.

The pharmaceutical solvent N-methyl-2-pyrollidone (NMP) attenuates inflammation through Krüppel-like factor 2 activation to reduce atherogenesis

N-methyl-2-pyrrolidone (NMP) is a versatile water-miscible polar aprotic solvent. It is used as a drug solubilizer and penetration enhancer in human and animal, yet its bioactivity properties remain elusive. Here, we report that NMP is a bioactive anti-inflammatory compound well tolerated in vivo, that shows efficacy in reducing disease in a mouse model of atherosclerosis. Mechanistically, NMP increases the expression of the transcription factor Kruppel-like factor 2 (KLF2). Monocytes and endothelial cells treated with NMP express increased levels of KLF2, produce less pro-inflammatory cytokines and adhesion molecules. We found that NMP attenuates monocyte adhesion to endothelial cells inflamed with tumor necrosis factor alpha (TNF-α) by reducing expression of adhesion molecules. We further show using KLF2 shRNA that the inhibitory effect of NMP on endothelial inflammation and subsequent monocyte adhesion is KLF2 dependent. Enhancing KLF2 expression and activity improves endothelial function, controls multiple genes critical for inflammation, and prevents atherosclerosis. Our findings demonstrate a consistent effect of NMP upon KLF2 activation and inflammation, biological processes central to atherogenesis. Our data suggest that inclusion of bioactive solvent NMP in pharmaceutical compositions to treat inflammatory disorders might be beneficial and safe, in particular to treat diseases of the vascular system, such as atherosclerosis.

Macrophage-derived MMP-9 enhances the progression of atherosclerotic lesions and vascular calcification in transgenic rabbits

Matrix metalloproteinase‐9 (MMP‐9), or gelatinase B, has been hypothesized to be involved in the progression of atherosclerosis. In the arterial wall, accumulated macrophages secrete considerable amounts of MMP‐9 but its pathophysiological functions in atherosclerosis have not been fully elucidated. To examine the hypothesis that macrophage‐derived MMP‐9 may affect atherosclerosis, we created MMP‐9 transgenic (Tg) rabbits to overexpress the rabbit MMP‐9 gene under the control of the scavenger receptor A enhancer/promoter and examined their susceptibility to cholesterol diet‐induced atherosclerosis. Tg rabbits along with non‐Tg rabbits were fed a cholesterol diet for 16 and 28 weeks, and their aortic and coronary atherosclerosis was compared. Gross aortic lesion areas were significantly increased in female Tg rabbits at 28 weeks; however, pathological examination revealed that all the lesions of Tg rabbits fed a cholesterol diet for either 16 or 28 weeks were characterized by increased monocyte/macrophage accumulation and prominent lipid core formation compared with those of non‐Tg rabbits. Macrophages isolated from Tg rabbits exhibited higher infiltrative activity towards a chemoattractant, MCP‐1 in vitro and augmented capability of hydrolysing extracellular matrix in granulomatous tissue. Surprisingly, the lesions of Tg rabbits showed more advanced lesions with remarkable calcification in both aortas and coronary arteries. In conclusion, macrophage‐derived MMP‐9 facilitates the infiltration of monocyte/macrophages into the lesions thereby enhancing the progression of atherosclerosis. Increased accumulation of lesional macrophages may promote vascular calcification.

The Absence of Calponin 2 in Rabbits Suggests Caution in Choosing Animal Models

While the rapid development of CRISPR/CAS9 technology has allowed for readily performing site-specific genomic editing in non-rodent species, an emerging challenge is to select the most suitable species to generate animal models for the study of human biology and diseases. Improving CRISPR/CAS9 methodology for more effective and precise editing in the rabbit genome to replicate human disease is an active area of biomedical research. Although rabbits are more closely related to humans than mice (based on DNA sequence analysis), our whole-genome protein database search revealed that rabbits have more missing human protein sequences than mice. Hence, precisely replicating human diseases in rabbits requires further consideration, especially in studies involving essential functions of the missing proteins. For example, rabbits lack calponin 2, an actin-associated cytoskeletal protein that is important in the pathogenesis of inflammatory arthritis, atherosclerosis, and calcific aortic valve disease. The justification of using rabbits as models for human biomedical research is based on their larger size and their closer phylogenetic distance to humans (based on sequence similarity of conserved genes), but this may be misleading. Our findings, which consider whole-genome protein profiling together with actual protein expressions, serve as a warning to the scientific community to consider overall conservation as well as the conservation of specific proteins when choosing an animal model to study a particular aspect of human biology prior to investing in genetic engineering.

MicroRNA-144 Silencing Protects Against Atherosclerosis in Male, but Not Female Mice

OBJECTIVE

Atherosclerosis is a leading cause of death in developed countries. MicroRNAs act as fine-tuners of gene expression and have been shown to have important roles in the pathophysiology and progression of atherosclerosis. We, and others, previously demonstrated that microRNA-144 (miR-144) functions to post-transcriptionally regulate ABCA1 (ATP binding cassette transporter A1) and plasma HDL (high-density lipoprotein) cholesterol levels. Here, we explore how miR-144 inhibition may protect against atherosclerosis. Approach and Results: We demonstrate that miR-144 silencing reduced atherosclerosis in male, but not female low-density lipoprotein receptor null (Ldlr-/-) mice. MiR-144 antagonism increased circulating HDL cholesterol levels, remodeled the HDL particle, and enhanced reverse cholesterol transport. Notably, the effects on HDL and reverse cholesterol transport were more pronounced in male mice suggesting sex-specific differences may contribute to the effects of silencing miR-144 on atherosclerosis. As a molecular mechanism, we identify the oxysterol metabolizing enzyme CYP7B1 (cytochrome P450 enzyme 7B1) as a miR-144 regulated gene in male, but not female mice. Consistent with miR-144-dependent changes in CYP7B1 activity, we show decreased levels of 27-hydroxycholesterol, a known proatherogenic sterol and the endogenous substrate for CYP7B1 in male, but not female mice.

CONCLUSIONS

Our data demonstrate silencing miR-144 has sex-specific effects and that treatment with antisense oligonucleotides to target miR-144 might result in enhancements in reverse cholesterol transport and oxysterol metabolism in patients with cardiovascular disease.

Sex hormones affect endothelial lipase-mediated lipid metabolism and atherosclerosis

BACKGROUND

Endothelial lipase (EL) plays an important role in lipoprotein metabolism and atherosclerosis. To study the functional roles of EL, we recently generated transgenic (Tg) rabbits and reported that increased hepatic expression of EL in male Tg rabbits significantly reduced diet-induced hypercholesterolemia compared with non-Tg controls. This gender difference suggests that sex hormones may mediate EL functions thereby influencing lipoprotein metabolism. To examine this hypothesis, we compared the effects of orchiectomy and ovariectomy on plasma lipids and diet-induced atherosclerosis in both Tg and non-Tg rabbits.

METHODS

Male rabbits were under orchiectomy whereas female rabbits were under ovariectomy. We compared plasma lipids, lipoproteins, and apolipoproteins of rabbits before and after surgery in each group fed either a chow diet or cholesterol-rich diet.

RESULTS

On a chow diet, both male and female Tg rabbits showed lower plasma lipids than non-Tg counterparts and this lipid-lowering effect of EL was not affected by either orchiectomy in male or ovariectomy in female Tg rabbits. On a cholesterol diet; however, male Tg rabbits but not female Tg rabbits showed significant resistance to diet-induced hypercholesterolemia and atherosclerosis. The EL-mediated atheroprotective effect was eliminated after orchiectomy in male Tg rabbits. Female Tg rabbits showed similar levels of total cholesterol and lesion size of atherosclerosis compared with non-Tg rabbits and ovariectomy did not affect diet-induced hypercholesterolemia or atherosclerosis.

CONCLUSION

These results suggest that increased EL protects against diet-induced hypercholesterolemia and atherosclerosis. The beneficial effect of EL was dependent upon the presence of androgenic hormones.

Dietary supplementation of defatted kenaf (Hibiscus cannabinus L.) seed meal and its phenolics-saponins rich extract effectively attenuates diet-induced hypercholesterolemia in rats

Kenaf is one of the important commercial fiber crops worldwide and defatted kenaf seed meal (DKSM) is a secondary by-product from the kenaf industry. Thus, efforts to turn this low-cost agricultural waste into value-added functional food ingredients will definitely bring advantageous impacts to the community health, environment and economy. The present study was aimed to investigate the cardioprotective properties of DKSM and its phenolics-saponins rich extract (PSRE) in diet-induced hypercholesterolemic rat model. Hypercholesterolemia was induced in Sprague-Dawley rats via atherogenic diet feeding and dietary interventions were conducted by incorporating DKSM (15% and 30%) and equivalent levels of PSRE (2.3% and 4.6%, respectively, equivalent to the total content of phenolics and saponins in DKSM groups) into the atherogenic diets. After 10 weeks of DKSM and PSRE supplementation, the hepatosomatic index, hepatosteatosis, serum lipid profile, Castelli risk indexes as well as hepatic and renal functions of hypercholesterolemic rats were significantly improved (p < 0.05). Besides, the levels of hepatic Hmgcr and serum Pcsk9 were lowered, along with transcriptional upregulations of hepatic Cyp7a1, Abca1, Lcat, ApoA2 and ApoE (p < 0.05). The gene expression of hepatic Ldlr was marginally enhanced by DKSM supplementation (p > 0.05), but superiorly upregulated by PSRE (p < 0.05). The combined results showed that hypercholesterolemia and the atherogenic risk in rats were effectively attenuated by DKSM and PSRE supplementation, possibly via modulations of multiple vital processes in hepatic cholesterol metabolism. Furthermore, phenolics and saponins may be the bioactives conferring DKSM and PSRE with their anti-hypercholesterolemic properties. In conclusion, DKSM and PSRE are prospective cardioprotective functional food ingredients for hypercholesterolemic individuals.

Principles and Applications of Rabbit Models for Atherosclerosis Research

Rabbits are one of the most used experimental animals for biomedical research, particularly as a bioreactor for the production of antibodies. However, many unique features of the rabbit have also made it as an excellent species for examining a number of aspects of human diseases such as atherosclerosis. Rabbits are phylogenetically closer to humans than rodents, in addition to their relatively proper size, tame disposition, and ease of use and maintenance in the laboratory facility. Due to their short life spans, short gestation periods, high numbers of progeny, low cost (compared with other large animals) and availability of genomics and proteomics, rabbits usually serve to bridge the gap between smaller rodents (mice and rats) and larger animals, such as dogs, pigs and monkeys, and play an important role in many translational research activities such as pre-clinical testing of drugs and diagnostic methods for patients. The principle of using rabbits rather than other animals as an experimental model is very simple: rabbits should be used for research, such as translational research, that is difficult to accomplish with other species. Recently, rabbit genome sequencing and transcriptomic profiling of atherosclerosis have been successfully completed, which has paved a new way for researchers to use this model in the future. In this review, we provide an overview of the recent progress using rabbits with specific reference to their usefulness for studying human atherosclerosis.

Determinants of HDL Cholesterol Efflux Capacity after Virgin Olive Oil Ingestion: Interrelationships with Fluidity of HDL Monolayer

SCOPE

Cholesterol efflux capacity of HDL (CEC) is inversely associated with cardiovascular risk. HDL composition, fluidity, oxidation, and size are related with CEC. We aimed to assess which HDL parameters were CEC determinants after virgin olive oil (VOO) ingestion.

METHODS AND RESULTS

Post-hoc analyses from the VOHF study, a crossover intervention with three types of VOO. We assessed the relationship of 3-week changes in HDL-related variables after intervention periods with independence of the type of VOO. After univariate analyses, mixed linear models were fitted with variables related with CEC and fluidity. Fluidity and Apolipoprotein (Apo)A-I content in HDL was directly associated, and HDL oxidative status inversely, with CEC. A reduction in free cholesterol, an increase in triglycerides in HDL, and a decrease in small HDL particle number or an increase in HDL mean size, were associated to HDL fluidity.

CONCLUSIONS

HDL fluidity, ApoA-I concentration, and oxidative status are major determinants for CEC after VOO. The impact on CEC of changes in free cholesterol and triglycerides in HDL, and those of small HDL or HDL mean size, could be mechanistically linked through HDL fluidity. Our work points out novel therapeutic targets to improve HDL functionality in humans through nutritional or pharmacological interventions.

Comparative studies of three cholesteryl ester transfer proteins and their interactions with known inhibitors

Cholesteryl ester transfer protein (CETP) is a plasma protein that mediates bidirectional transfers of cholesteryl esters and triglycerides between low-density lipoproteins and high-density lipoproteins (HDL). Because low levels of plasma CETP are associated with increased plasma HDL-cholesterol, therapeutic inhibition of CETP activity is considered an attractive strategy for elevating plasma HDL-cholesterol, thereby hoping to reduce the risk of cardiovascular disease. Interestingly, only a few laboratory animals, such as rabbits, guinea pigs, and hamsters, have plasma CETP activity, whereas mice and rats do not. It is not known whether all CETPs in these laboratory animals are functionally similar to human CETP. In the current study, we compared plasma CETP activity and characterized the plasma lipoprotein profiles of these animals. Furthermore, we studied the three CETP molecular structures, physicochemical characteristics, and binding properties with known CETP inhibitors in silico. Our results showed that rabbits exhibited higher CETP activity than guinea pigs and hamsters, while these animals had different lipoprotein profiles. CETP inhibitors can inhibit rabbit and hamster CETP activity in a similar manner to human CETP. Analysis of CETP molecules in silico revealed that rabbit and hamster CETP showed many features that are similar to human CETP. These results provide novel insights into understanding CETP functions and molecular properties.

Associations among apolipoproteins, oxidized high-density lipoprotein and cardiovascular events in patients on hemodialysis

Apolipoproteins are associated with survival among patients on hemodialysis (HD), but these associations might be influenced by dysfunctional (oxidized) high-density lipoprotein (HDL). We assessed associations among apolipoproteins and oxidized HDL, mortality and cardiovascular disease (CVD) events in patients on HD. This prospective observational study examined 412 patients on prevalent HD. Blood samples were obtained before dialysis at baseline to measure lipids, apolipoproteins, oxidized LDL, oxidized HDL, high-sensitivity C-reactive protein (hs-CRP) and interleukin (IL)-6 at baseline, and HDL-C and hs-CRP were measured 12 months later. Patients were then prospectively followed-up (mean, 40 months) and all-cause mortality and composite CVD events were analyzed. Associations between variables at baseline and clinical outcome were assessed by Cox proportional hazards modeling (n = 412) and Cox hazards modeling with a time-varying covariate with HDL-C and hs-CRP (n = 369). Quartiles of apolipoproteins and oxidized HDL were not associated with all-cause mortality. However, Cox proportional hazards models with quartiles of each variable adjusted for confounders and hs-CRP or IL-6 identified apolipoprotein (apo)B-to-apoA-I ratio (apoB/apoA-I) and oxidized HDL, but not apoA-I or apoA-II, as independent risk factors for composite CVD events. These associations were confirmed by Cox proportional hazards modeling with time-varying covariates for hs-CRP. ApoB/apoA-I was independently associated with composite CVD events in 1-standard deviation (SD) increase-of-variables models adjusted for the confounders, oxidized HDL and hs-CRP. However, these associations disappeared from the model adjusted with IL-6 instead of hs-CRP, and oxidized HDL and IL-6 were independently associated with composite CVD events. Findings resembled those from Cox proportional hazards modeling using time-varying covariates with HDL-C adjusted with IL-6. In conclusion, both oxidized HDL and apoB/apoA-I might be associated with CVD events in patients on prevalent HD, while associations of apoB/apoA-I with CVD events differed between models of apoB/apoA-I quartiles and 1-SD increases, and were influenced by IL-6.

Study of the relationship between APOA-II -265T>C polymorphism and HDL function in response to weight loss in overweight and obese type 2 diabetic patients

BACKGROUND

It has been reported that people may respond differently to the same environmental changes because of genome variations.

OBJECTIVE

The main purpose of the present study is to determine gene-diet interactions between -265T>C apolipoprotein A-II polymorphisms and evaluate the effect of weight loss on parameters related to HDL function.

METHODS

In the present study, 56 overweight and obese type 2 diabetic patients were chosen from 697 genotype-specified subjects. After matching for gender, age and BMI, an equal number of patients were chosen for each genotype of APOA-II (TT/TC and CC group). After six-week calorie restriction programme, 44 patients completed the study. Serum paraoxonase-1 (PON1), paraoxonase-3 (PON3), pentraxin-3 (PTX3), and PTX3 gene expression in peripheral blood mononuclear cells were compared between two genotypes and also before and after the intervention separated in each genotype.

RESULTS

The mean differences of PON enzymes and PTX3 between groups were not significant at the baseline. After weight loss, the mean weight, BMI and serum concentration of PON1 and PON3 decreased significantly and PTX3 increased in total population. Although, the mean differences of PON enzymes and PTX3 between two groups were not significant. However, in comparison of mean differences within the groups, decreased PON3 and increased PTX3 have been observed only in TT group.

CONCLUSION

A comparison of the mean differences in PON3 and PTX3 within two genotype groups showed that T allele carriers are more sensitive to lifestyle modification, and serum PON3 and PTX3 levels significantly changed only in the TT/TC group.

Antimicrobial growth promoters modulate host responses in mice with a defined intestinal microbiota

Antibiotics can promote growth in livestock (antimicrobial growth promoters, AGPs), however lack of knowledge regarding mechanisms has hampered the development of effective non-antibiotic alternatives. Antibiotics affect eukaryotic cells at therapeutic concentrations, yet effects of AGPs on host physiology are relatively understudied, partially due to the complexity of host-microorganism interactions within the gastrointestinal tract. To determine the direct effects of AGPs on the host, we generated Altered Schaedler Flora (ASF) mice, and administered chlortetracycline (CTC) and tylosin phosphate (TYL) in feed. Mice were challenged with Citrobacter rodentium to determine how AGPs alter host responses to physiological stress. Although CTC and TYL had inconsistent effects on the ASF taxa, AGPs protected mice from weight loss following C. rodentium inoculation. Mice treated with either CTC or TYL had lower expression of βd1 and Il17a in the intestine and had a robust induction of Il17a and Il10. Furthermore, AGP administration resulted in a lower hepatic expression of acute phase proteins (Saa1, Hp, and Cp) in liver tissue, and ameliorated C. rodentium-induced reductions in the expression of genes involved in lipogenesis (Hmgcl and Fabp1). Collectively, this indicates that AGPs directly affect host physiology, and highlights important considerations in the development of non-antibiotic alternatives.

The interaction between ApoA2 -265T>C polymorphism and dietary fatty acids intake on oxidative stress in patients with type 2 diabetes mellitus

INTRODUCTION

Apolipoprotein A2 (APOA2) -265T>C polymorphism has been studied in relation to oxidative stress and various dietary fatty acids. Since the interaction between APOA2 polymorphism and dietary fatty acids on oxidative stress has not yet discussed, we aimed to investigate the interaction on oxidative stress in type 2 diabetes mellitus (T2DM) patients.

METHODS

The subjects were 180 T2DM patients with known APOA2 genotype, either TT, TC or CC. Superoxide dismutase (SOD) activity was determined by colorimetric method. Total antioxidant capacity (TAC) and serum level of 8-isoprostane F2α were measured by spectrophotometry and ELISA, respectively. Dietary intake was collected through a food frequency questionnaire. Based on the median intake, fatty acids intake was dichotomized into high or low groups. The interaction between APOA2 polymorphism and dietary fatty acids intake was analyzed by ANCOVA multivariate interaction model.

RESULTS

Higher than median intake of omega-6 polyunsaturated fatty acids (n-6 PUFA) was associated with increased serum level of 8-isoprostane F2α in subjects with TT/TC genotype (p = 0.004), and higher than median intake of omega-3 polyunsaturated fatty acids (n-3 PUFA) was associated with increased serum SOD activity in CC genotype (p < 0.001). There was a statistically significant interaction between APOA2 polymorphism and n-6 PUFA intake on 8-isoprostane F2α concentration as well as n-3 PUFA intake on serum SOD activity (p-interaction = 0.04 and 0.02, respectively).

CONCLUSIONS

The current study shows the interaction between APOA2 polymorphism and dietary fatty acids intake on oxidative stress. More investigations on different populations are required to confirm the interaction.

APO A2 -265T/C Polymorphism Is Associated with Increased Inflammatory Responses in Patients with Type 2 Diabetes Mellitus

BACKGROUND

Apolipoprotein A2 (APO A2) is the second most abundant structural apolipoprotein in high density lipoprotein. Several studies have examined the possible effect of APO A2 on atherosclerosis incidence. Due to the role of inflammation in atherosclerosis, we aimed to determine the relationship between APO A2 -265T/C polymorphism and inflammation as a risk factor in type 2 diabetes mellitus (T2DM) patients.

METHODS

In total, 180 T2DM patients, with known APO A2 -265T/C polymorphism, were recruited for this comparative study and were grouped equally based on their genotypes. Dietary intakes, anthropometric parameters, lipid profile, and inflammatory markers (i.e., pentraxin 3 [PTX3], high-sensitivity C-reactive protein [hs-CRP], and interleukin 18) were measured. The data were analyzed using an independent t-test, a chi-square test, and the analysis of covariance.

RESULTS

After adjusting for confounding factors, in the entire study population and in the patients with or without obesity, the patients with the CC genotype showed higher hs-CRP (P=0.001, P=0.008, and P=0.01, respectively) and lower PTX3 (P=0.01, P=0.03, and P=0.04, respectively) in comparison with the T allele carriers. In the patients with the CC genotype, no significant differences were observed in the inflammatory markers between the obese or non-obese patients. However, regarding the T allele carriers, the plasma hs-CRP level was significantly higher in the obese patients compared to the non-obese patients (P=0.01).

CONCLUSION

In the T2DM patients, the CC genotype could be considered as a risk factor and the T allele as a protective agent against inflammation, which the latter effect might be impaired by obesity. Our results confirmed the anti-atherogenic effect of APO A2, though more studies are required to establish this effect.

Anagliptin, a dipeptidyl peptidase-4 inhibitor, decreases macrophage infiltration and suppresses atherosclerosis in aortic and coronary arteries in cholesterol-fed rabbits

INTRODUCTION

Several studies have demonstrated suppression of aortic atherosclerosis by dipeptidyl peptidase-4 (DPP-4) inhibitors in hypercholesterolemic mice. However, it remains unknown whether DPP-4 inhibitors also exert anti-atherogenic effects in coronary arteries. We examined the effect of anagliptin, a DPP-4 inhibitor, on atherosclerosis development in the aorta and coronary arteries in a high-cholesterol diet-fed rabbits.

METHODS

Japanese white rabbits were fed either normal chow (n=8) or a diet containing 0.5% cholesterol (n=34) for 14weeks. Cholesterol-fed rabbits were given 0.3% anagliptin or not in drinking water (each n=16 and 18) for 12weeks.

RESULTS

Dietary cholesterol intake markedly increased serum total cholesterol (TC) levels (1464±150mg/dL, mean±SE), and the most striking increase was observed among the major lipoproteins in very low-density lipoprotein (VLDL) as determined by high-performance liquid chromatography. No significant changes were observed in body weight, water intake, hemoglobin A1c, or glucose response to intravenous glucose loading following anagliptin administration. Anagliptin decreased TC and VLDL-cholesterol as well as cholesterol absorption markers sitosterol and campesterol slightly, although not significantly. Serum DPP-4 activity was suppressed by 82%, and active glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide levels were increased 2- to 3-fold by anagliptin treatment. Severe hypercholesterolemia resulted in the development of atherosclerosis in the aorta, and the ratio of atherosclerotic lesions to the total aortic surface area was 22±2%. Anagliptin suppressed the lesion ratio to 9±2% (p<0.001). Atherosclerotic lesions were clearly observed in the coronary arteries, where the mean intima-media area was enlarged, and intimal formation was developed. Anagliptin treatment attenuated the intima-media area and the intimal area by 43%. Alpha-smooth muscle actin-positive and macrophage-positive areas in the coronary arteries were suppressed by 66 and 75%, respectively, after anagliptin treatment. The aortic lesion ratio and the coronary intima area were correlated with each other (r=0.506, p<0.01), and each lesion correlated with TC in the whole cholesterol-fed rabbits. Gene expression of the proinflammatory cytokines tumor necrosis factor-alpha and interleukin-6 in the carotid arteries was markedly reduced by approximately 90%, and vascular DPP-4 activity was reduced by 66% after anagliptin treatment.

CONCLUSIONS

We demonstrated for the first time that a DPP-4 inhibitor can substantially suppress plaque formation in coronary arteries with a marked reduction in macrophage accumulation likely via its anti-inflammatory properties.

Efficient Generation of Myostatin Gene Mutated Rabbit by CRISPR/Cas9

CRISPR/Cas9 has been widely used in generating site-specific genetically modified animal models. Myostatin (MSTN) is a negative regulator of muscle mass, related to muscle growth and differentiation. The knockout of MSTN with the desired phenotype of double muscle has been successfully generated in mice, goats, pigs and cattle, but not in rabbits. In this study, the MSTN knockout (KO) rabbits were generated by co-injection of Cas9 mRNA and sgRNA into zygotes. The typical phenotype of double muscle with hyperplasia or hypertrophy of muscle fiber was observed in MSTN KO rabbits. Furthermore, a similar phenotype was found in the F1 generation, suggesting that the mutation of MSTN could be stably inherited in the MSTN KO rabbits. In summary, we have successfully generated MSTN KO rabbits using CRISPR/Cas9 system with high efficiency, which is a reliable and effective animal model for the study of muscle development and related diseases.

Anti-atherogenic and anti-inflammatory properties of glucagon-like peptide-1, glucose-dependent insulinotropic polypepide, and dipeptidyl peptidase-4 inhibitors in experimental animals

We reported that native incretins, liraglutide and dipeptidyl peptidase‐4 inhibitors (DPP‐4i) all confer an anti‐atherosclerotic effect in apolipoprotein E‐null (Apoe^−/−) mice. We confirmed the anti‐atherogenic property of incretin‐related agents in the mouse wire injury model, in which the neointimal formation in the femoral artery is remarkably suppressed. Furthermore, we showed that DPP‐4i substantially suppresses plaque formation in coronary arteries with a marked reduction in the accumulation of macrophages in cholesterol‐fed rabbits. DPP‐4i showed an anti‐atherosclerotic effect in Apoe^−/− mice mainly through the actions of glucagon‐like peptide‐1 and glucose‐dependent insulinotropic polypepide. However, the dual incretin receptor antagonists partially attenuated the suppressive effect of DPP‐4i on atherosclerosis in diabetic Apoe^−/− mice, suggesting an incretin‐independent mechanism. Exendin‐4 and glucose‐dependent insulinotropic polypepide elicited cyclic adenosine monophosphate generation, and suppressed the lipopolysaccharide‐induced gene expression of inflammatory molecules, such as interleukin‐1β, interleukin‐6 and tumor necrosis factor‐α, in U937 human monocytes. This suppressive effect, however, was attenuated by an inhibitor of adenylate cyclase and mimicked by 8‐bromo‐cyclic adenosine monophosphate or forskolin. DPP‐4i substantially suppressed the lipopolysaccharide‐induced expression of inflammatory cytokines without affecting cyclic adenosine monophosphate generation or cell proliferation. DPP‐4i more strongly suppressed the lipopolysaccharide‐induced gene expression of inflammatory molecules than incretins, most likely through inactivation of CD26. Glucagon‐like peptide‐1 and glucose‐dependent insulinotropic polypepide suppressed oxidized low‐density lipoprotein‐induced macrophage foam cell formation in a receptor‐dependent manner, which was associated with the downregulation of acyl‐coenzyme A cholesterol acyltransferase‐1 and CD36, as well as the up‐regulation of adenosine triphosphate‐binding cassette transporter A1. Our studies strongly suggest that incretin‐related agents have favorable effects on macrophage‐driven atherosclerosis in experimental animals.

Association between ApoA-II -265T/C polymorphism and oxidative stress in patients with type 2 diabetes mellitus

BACKGROUND

Apolipoprotein A-II (ApoA-II) constitutes approximately 20% of the total HDL protein content. The results of various studies on the relationship between cardiovascular diseases (CVD) and the plasma ApoA-II level are contradictory. The aim of this study was to determine the relationship between ApoA-II polymorphism and oxidative stress (OS) as a risk factor for CVD.

METHODS

The present comparative study was carried out on 180 obese and non-obese patients with type 2 diabetes, with equal numbers of CC, TC, and TT genotypes of ApoA-II -265T/C gene. The ApoA-II genotype was determined by the TaqMan assay method. The anthropometric measurements and serum levels of lipid profile, superoxide dismutase activity (SOD), total antioxidant capacity (TAC), and 8-isoprostaneF2α were measured.

RESULTS

After adjusting for confounding factors, in the total study population and in obese and non-obese groups, the subjects with CC genotype had a lower mean serum SOD activity (p=0.002, p=0.007 and p=0.005, respectively) and higher mean 8-isoprostaneF2α concentration (p<0.001, p=0.003 and p=0.004, respectively) than the T-allele carriers. In the TT/TC group, the mean 8-isoprostanF2α concentration was significantly higher in the obese subjects than the non-obese subjects (p=0.009). In the CC group, no significant differences were found in the OS factors between obese and non-obese groups.

CONCLUSION

The T allele in patients with type 2 diabetes is a protective factor against OS; obesity inhibits this protective effect. The results of this study represent the anti-atherogenic properties of ApoA-II. However, further studies are needed in this field.

High-fructose and high-fat diet-induced insulin resistance enhances atherosclerosis in Watanabe heritable hyperlipidemic rabbits

Background

Individuals with insulin resistance and resulting impaired glucose tolerance along with type 2 diabetes showed an increased prevalence of atherosclerosis. Our aim in this study was to address whether diet-induced insulin resistance plays any roles in the development of aortic and coronary atherosclerosis in hyperlipidemic rabbits.

Methods

We fed Watanabe heritable hyperlipidemic (WHHL) rabbits with a high-fructose and high-fat diet (HFFD) with restricted normal calories and compared the lesions of both aortic and coronary atherosclerosis with those of control WHHL rabbits fed a normal chow diet.

Results

HFFD-fed WHHL rabbits showed insulin resistance and impaired glucose tolerance accompanied by elevated plasma lipid levels and accumulation of adipose tissue even though their body weight was unchanged compared to the control rabbits. At 8 weeks, the aortic gross lesion area of HFFD-fed WHHL rabbits was increased by 40 % over the controls and their lesions were characterized by increased number of macrophages and smooth muscle cells. At 16 weeks, the lesions of HFFD-fed WHHL rabbits showed more advanced lesions such as lipid core formation and calcification. In addition, coronary atherosclerosis was significantly increased in HFFD-fed WHHL rabbits.

Conclusions

These results suggest that insulin resistance accelerates lesion formation of atherosclerosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0024-3) contains supplementary material, which is available to authorized users.

Rabbit models for the study of human atherosclerosis: from pathophysiological mechanisms to translational medicine

Laboratory animal models play an important role in the study of human diseases. Using appropriate animals is critical not only for basic research but also for the development of therapeutics and diagnostic tools. Rabbits are widely used for the study of human atherosclerosis. Because rabbits have a unique feature of lipoprotein metabolism (like humans but unlike rodents) and are sensitive to a cholesterol diet, rabbit models have not only provided many insights into the pathogenesis and development of human atherosclerosis but also made a great contribution to translational research. In fact, rabbit was the first animal model used for studying human atherosclerosis, more than a century ago. Currently, three types of rabbit model are commonly used for the study of human atherosclerosis and lipid metabolism: (1) cholesterol-fed rabbits, (2) Watanabe heritable hyperlipidemic rabbits, analogous to human familial hypercholesterolemia due to genetic deficiency of LDL receptors, and (3) genetically modified (transgenic and knock-out) rabbits. Despite their importance, compared with the mouse, the most widely used laboratory animal model nowadays, the use of rabbit models is still limited. In this review, we focus on the features of rabbit lipoprotein metabolism and pathology of atherosclerotic lesions that make it the optimal model for human atherosclerotic disease, especially for the translational medicine. For the sake of clarity, the review is not an attempt to be completely inclusive, but instead attempts to summarize substantial information concisely and provide a guideline for experiments using rabbits.

High-density lipoprotein: a novel target for antirestenosis therapy

Restenosis is an integral pathological process central to the recurrent vessel narrowing after interventional procedures. Although the mechanisms for restenosis are diverse in different pathological conditions, endothelial dysfunction, inflammation, vascular smooth muscle cell (SMC) proliferation, and myofibroblasts transition have been thought to play crucial role in the development of restenosis. Indeed, there is an inverse relationship between high-density lipoprotein (HDL) levels and risk for coronary heart disease (CHD). However, relatively studies on the direct assessment of HDL effect on restenosis are limited. In addition to involvement in the cholesterol reverse transport, many vascular protective effects of HDL, including protection of endothelium, antiinflammation, antithrombus actions, inhibition of SMC proliferation, and regulation by adventitial effects may contribute to the inhibition of restenosis, though the exact relationships between HDL and restenosis remain to be elucidated. This review summarizes the vascular protective effects of HDL, emphasizing the potential role of HDL in intimal hyperplasia and vascular remodeling, which may provide novel prophylactic and therapeutic strategies for antirestenosis.

HDL cholesterol, apolipoproteins, and cardiovascular risk in hemodialysis patients

High concentrations of HDL cholesterol are considered to indicate efficient reverse cholesterol transport and to protect from atherosclerosis. However, HDL has been suggested to be dysfunctional in ESRD. Hence, our main objective was to investigate the effect of HDL cholesterol on outcomes in maintenance hemodialysis patients with diabetes. Moreover, we investigated the associations between the major protein components of HDL (apoA1, apoA2, and apoC3) and end points. We performed an exploratory, post hoc analysis with 1255 participants (677 men and 578 women) of the German Diabetes Dialysis study. The mean age was 66.3 years and the mean body mass index was 28.0 kg/m(2). The primary end point was a composite of cardiac death, myocardial infarction, and stroke. The secondary end point included all-cause mortality. The mean duration of follow-up was 3.9 years. A total of 31.3% of the study participants reached the primary end point and 49.1% died from any cause. HDL cholesterol and apoA1 and apoC3 quartiles were not related to end points. However, there was a trend toward an inverse association between apoA2 and all-cause mortality. The hazard ratio for death from any cause in the fourth quartile compared with the first quartile of apoA2 was 0.63 (95% confidence interval, 0.40 to 0.89). The lack of an association between HDL cholesterol and cardiovascular risk may support the concept of dysfunctional HDL in hemodialysis. The possible beneficial effect of apoA2 on survival requires confirmation in future studies.

Generation of knockout rabbits using transcription activator-like effector nucleases

Zinc-finger nucleases and transcription activator-like effector nucleases are novel gene-editing platforms contributing to redefine the boundaries of modern biological research. They are composed of a non-specific cleavage domain and a tailor made DNA-binding module, which enables a broad range of genetic modifications by inducing efficient DNA double-strand breaks at desired loci. Among other remarkable uses, these nucleases have been employed to produce gene knockouts in mid-size and large animals, such as rabbits and pigs, respectively. This approach is cost effective, relatively quick, and can produce invaluable models for human disease studies, biotechnology or agricultural purposes. Here we describe a protocol for the efficient generation of knockout rabbits using transcription activator-like effector nucleases, and a perspective of the field.

Probucol inhibits the initiation of atherosclerosis in cholesterol-fed rabbits

BACKGROUND

Probucol and statin are often prescribed for treating atherosclerosis. These two drugs exhibit different mechanisms but it is unknown whether they have the same anti-atherogenic properties. In the current study, we examined whether these two drugs at optimal doses could inhibit the initiation of atherosclerosis in cholesterol-fed rabbits in the same way.

METHODS

New Zealand White rabbits were fed a cholesterol-rich diet for 5 weeks to produce the early-stage lesions of atherosclerosis. Drug-treated rabbits were administered either probucol or atorvastatin and serum lipids and aortic atherosclerotic lesions were compared with those in a control group.

RESULTS

Atorvastatin treatment significantly reduced serum total cholesterol levels while probucol treatment led to significant reduction of high-density lipoprotein cholesterol levels without changing total cholesterol levels compared with those in the control group. Compared with the control, probucol treatment led to 65% (p < 0.01) reduction while atorvastatin treatment led to 23% (p = 0.426) reduction of the aortic lesion area. Histological and immunohistochemical analyses revealed that the lesions of the probucol-treated group were characterized by remarkable reduction of monocyte adherence to endothelial cells and macrophage accumulation in the intima compared with those of both atorvastatin and control groups. Furthermore, low-density lipoprotein (LDL) isolated from the probucol group exhibited prominent anti-oxidative reaction, which was not present in LDL isolated from either the atorvastatin-treated or the control group.

CONCLUSIONS

This study suggests that probucol inhibits the initiation of atherosclerosis by reducing monocyte adherence and infiltration into the subintima. Anti-oxidization of LDL by probucol protects more effectively against early-stage lesion formation than statin-mediated lipid-lowering effects.

Molecular biology of atherosclerosis

At least 468 individual genes have been manipulated by molecular methods to study their effects on the initiation, promotion, and progression of atherosclerosis. Most clinicians and many investigators, even in related disciplines, find many of these genes and the related pathways entirely foreign. Medical schools generally do not attempt to incorporate the relevant molecular biology into their curriculum. A number of key signaling pathways are highly relevant to atherogenesis and are presented to provide a context for the gene manipulations summarized herein. The pathways include the following: the insulin receptor (and other receptor tyrosine kinases); Ras and MAPK activation; TNF-α and related family members leading to activation of NF-κB; effects of reactive oxygen species (ROS) on signaling; endothelial adaptations to flow including G protein-coupled receptor (GPCR) and integrin-related signaling; activation of endothelial and other cells by modified lipoproteins; purinergic signaling; control of leukocyte adhesion to endothelium, migration, and further activation; foam cell formation; and macrophage and vascular smooth muscle cell signaling related to proliferation, efferocytosis, and apoptosis. This review is intended primarily as an introduction to these key signaling pathways. They have become the focus of modern atherosclerosis research and will undoubtedly provide a rich resource for future innovation toward intervention and prevention of the number one cause of death in the modern world.