The relationship between the degree of dietary-induced hypercholesterolemia in the rabbit and atherosclerotic lesion formation

Cholesteryl Ester Transfer Protein (CETP) Variations in Relation to Lipid Profiles and Cardiovascular Diseases: An Update

Lipid metabolism plays an essential role in the pathogenesis of cardiovascular and metabolic diseases. Cholesteryl ester transfer protein (CETP) is a crucial glycoprotein involved in lipid metabolism by transferring cholesteryl esters (CE) and triglycerides (TG) between plasma lipoproteins. CETP activity results in reduced HDL-C and increased VLDL- and LDL-C concentrations, thus increasing the risk of cardiovascular and metabolic diseases. In this review, we discuss the structure of CETP and its mechanism of action. Furthermore, we focus on recent experiments on animal CETP-expressing models, deciphering the regulation and functions of CETP in various genetic backgrounds and interaction with different external factors. Finally, we discuss recent publications revealing the association of CETP single nucleotide polymorphisms (SNPs) with the risk of cardiovascular and metabolic diseases, lifestyle factors, diet and therapeutic interventions. While CETP SNPs can be used as effective diagnostic markers, diet, lifestyle, gender and ethnic specificity should also be considered for effective treatment.

Effects of atherogenic diet supplemented with fermentable carbohydrates on metabolic responses and plaque formation in coronary arteries using a Saddleback pig model

Fermentable carbohydrates are gaining interest in the field of human nutrition because of their benefits in obesity-related comorbidities. The aim of this study was to investigate the influence of fermentable carbohydrates, such as pectin and inulin, in an atherogenic diet on metabolic responses and plaque formation in coronary arteries using a Saddleback pig model. Forty-eight healthy pigs aged five months were divided into four feeding groups (n = 10) and one baseline group (n = 8). Three feeding groups received an atherogenic diet (38% crisps, 10% palm fat, and 2% sugar with or without supplementation of 5% pectin or inulin), and one group received a conventional diet over 15 weeks. Feed intake, weight gain, body condition score, and back fat thickness were monitored regularly. Blood and fecal samples were collected monthly to assess the metabolites associated with high cardiovascular risk and fat content, respectively. At the end of 15 weeks, the coronary arteries of the pigs were analyzed for atherosclerotic plaque formation. Independent of supplementation, significant changes were observed in lipid metabolism, such as an increase in triglycerides, bile acids, and cholesterol in serum, in all groups fed atherogenic diets in comparison to the conventional group. Serum metabolome analysis showed differentiation of the feeding groups by diet (atherogenic versus conventional diet) but not by supplementation with pectin or inulin. Cardiovascular lesions were found in all feeding groups and in the baseline group. Supplementation of pectin or inulin in the atherogenic diet had no significant impact on cardiovascular lesion size. Saddleback pigs can develop naturally occurring plaques in coronary arteries. Therefore, this pig model offers potential for further research on the effects of dietary intervention on obesity-related comorbidities, such as cardiovascular lesions, in humans.

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

•

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

•

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

•

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

•

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.

A modified animal model of hepatic regeneration induced by hilar bile duct ligation

Mechanisms of the proliferation of liver are mainly studied in animal model of liver regeneration after partial hepatectomy (PH). However, the PH model involves complex regeneration mechanisms, including hemodynamic factors, cytokines, growth factors, and metabolites. Among liver metabolites, bile acid (BA) is a key signaling molecule that regulates liver regeneration. This study aimed to establish a new type of rapid liver hyperplasia model induced mainly by bile acid pathway through hepatoenteral circulation with hilar bile duct ligation (HBDL). We first established the HBDL model by ligating the bile duct of all hepatic lobes but the right lateral lobe in rabbits and compared with the PVL model and sham operation group. Changes in the liver lobe and hemodynamics were observed. Liver function and the bile acid level were also analyzed. Then we verified the HBDL model in mice. Liver function and the levels of bile acids and cytokines were tested. The protein and mRNA levels of FXR, FGF15, CYP7A1 and FoxM1b in liver tissue were also analyzed. After hilar ligation of the biliary tract, the unligated liver lobes proliferated significantly. Compared with those in the sham group, the volume and weight of the unligated right lateral lobe of the liver in the HBDL group and the PVL group increased significantly (P < 0.05). Transient liver function impairment occurred both in the HBDL group and PVL group in the rabbit model as well as the mouse models. The bile acid levels in the HBDL groups of the rabbit model and mouse model increased significantly within first week after surgery (P < 0.05). The immunohistochemistry results confirmed the proliferation of hepatocytes in the unligated liver lobe. Compared with those in the sham group, the levels of FXR, FGF15 and FoxM1b in the HBDL group were significantly increased (P < 0.05), while the expression of CYP7A1 was inhibited. Compared with those in the HBDL group, the postoperative hemodynamic changes in the PVL group were significant (P < 0.05). The levels of IL-6 and TNF-α in the HBDL group were higher than those in the sham group. The HBDL model is simple to establish and exhibits good surgical tolerance. The model has definite proliferative effect and strong specificity of bile acid pathway. This is an ideal animal model to study the mechanism of liver regeneration through bile acid pathway.

Daily White kwao krua dietary supplement alleviates LDL oxidative susceptibility, plasma LDL level and improves vasculature in a hypercholesterolemia rabbit model

BACKGROUND AND AIM

White kwao krua is an edible plant that grows in Southeast Asia. It is very rich in natural phytoestrogens. Previous clinical studies revealed that the use of White kwao krua as a hormone replacement therapy has beneficial effects on the lipid profile of menopause women. In this present study, we utilized the hypercholesterolemia rabbit model to demonstrate the effect of White kwao krua on the daily intake of high-fat diet.

EXPERIMENTAL PROCEDURE

We induced hypercholesterolemia in rabbits by feeding with high-fat diet (1% cholesterol-containing diet). The animals were maintained 12 weeks for the experimentation. The White kwao krua supplement was administered 100 mg/kg/day, and the effects were monitored comparing with Statins and turmeric. Blood was collected periodically to monitor the plasma cholesterol level and the oxidative susceptibility of isolated LDL-cholesterol. At the end of the experiment, the aorta was collected from the animal and performed endothelial-dependent relaxation and endothelial-independent relaxation assays. The relative ratio of intima to media layer was microscopically evaluated from hematoxylin/eosin-stained tissues.

RESULTS AND CONCLUSION

We showed that the White kwao krua supplement reduced LDL-cholesterol about 40% compared with high-fat diet consumption alone. Administration of White kwao krua had significantly prolonged the susceptibility of LDL-cholesterol to oxidation. Besides, it led to the improvement of vascular function by recovering endothelium-dependent relaxation and alleviating vascular structure impairment induced by high-fat dietary intake. Together, we suggest that White kwao krua should be used as a dietary supplement to reduce the atherogenesis in high-fat dietary consumption.

SECTION

Dietary therapy/nutrients supplements.

TAXONOMY

Inflammation, Disease.

Large-scale gene analysis of rabbit atherosclerosis to discover new biomarkers for coronary artery disease

Atherosclerosis is the pathological basis of coronary artery disease (CAD) and causes high mortality. Thus, early detection is thought to be crucial in reducing the risk of CAD. Uncovering the mechanisms of the progression and regression of atherosclerosis will provide insights into discovering novel biomarkers to identify subjects at risk for CAD and improve prevention. We established atherosclerosis progression and regression in a rabbit model. Then, we extracted mRNA of the abdominal aorta from control, model and recovery groups to perform gene chip analysis. Candidate biomarkers were screened by large-scale gene analysis and validated in patients with CAD or with CAD recovery by ELISA. The differentially expressed genes in the progression and regression of atherosclerosis were mainly enriched in four clusters. Genes associated with inflammation and extracellular matrix were returned to normal or close-to-normal levels much earlier than genes associated with metabolism and sarcoplasmic proliferation, and they were maintained downregulated or upregulated after feeding a normal diet. We then selected four candidate biomarkers and found that lipoprotein lipase (LPL), bone morphogenetic protein 7 and somatostatin concentrations could indicate CAD diagnosis. In addition, LPL and macrophage cationic peptide 2 can be indicators of the prognosis of CAD. Molecular changes during the progression and regression of atherosclerosis in rabbits were revealed, and candidate regulators were identified. The identified factors could be used as novel biomarkers and targets for improving the diagnosis and prognosis of human CAD in the future.

Immunization with the Gly1127-Cys1140 amino acid sequence of the LRP1 receptor reduces atherosclerosis in rabbits. Molecular, immunohistochemical and nuclear imaging studies

Background: The LRP1 (CR9) domain and, in particular, the sequence Gly1127-Cys1140 (P3) plays a critical role in the binding and internalization of aggregated LDL (agLDL). We aimed to evaluate whether immunization with P3 reduces high-fat diet (HFD)-induced atherosclerosis. Methods: Female New Zealand White (NZW) rabbits were immunized with a primary injection and four reminder doses (R1-R4) of IrP (irrelevant peptide) or P3 conjugated to the carrier. IrP and P3-immunized rabbits were randomly divided into a normal diet group and a HFD-fed group. Anti-P3 antibody levels were determined by ELISA. Lipoprotein profile, circulating and tissue lipids, and vascular pro-inflammatory mediators were determined using standardized methods while atherosclerosis was determined by confocal microscopy studies and non-invasive imaging (PET/CT and Doppler ultrasonography). Studies treating human macrophages (hMΦ) and coronary vascular smooth muscle cells (hcVSMC) with rabbit serums were performed to ascertain the potential impact of anti-P3 Abs on the functionality of these crucial cells. Results: P3 immunization specifically induced the production of anti-P3 antibodies (Abs) and did not alter the lipoprotein profile. HFD strongly induced cholesteryl ester (CE) accumulation in the aorta of both the control and IrP groups, and their serum dose-dependently raised the intracellular CE of hMΦ and hcVSMC, promoting TNFR1 and phospho-NF-kB (p65) overexpression. These HFD pro-inflammatory effects were dramatically decreased in the aorta of P3-immunized rabbits and in hMΦ and hcVSMC exposed to the P3 rabbit serums. Microscopy studies revealed that P3 immunization reduced the percentage of lipids, macrophages, and SMCs in the arterial intima, as well as the atherosclerotic extent and lesion area in the aorta. PET/CT and Doppler ultrasonography studies showed that the average standardized uptake value (SUVmean) of the aorta and the arterial resistance index (ARI) of the carotids were more upregulated by HFD in the control and IrP groups than the P3 group. Conclusions: P3 immunization counteracts HFD-induced fatty streak formation in rabbits. The specific blockade of the LRP1 (CR9) domain with Anti-P3 Abs dramatically reduces HFD-induced intracellular CE loading and harmful coupling to pro-inflammatory signaling in the vasculature.

Vitamin E: Regulatory role in the cardiovascular system

Cardiovascular disease (CVD) is one of the major causes of morbidity and mortality, all around the world. Vitamin E is an important nutrient influencing key cellular and molecular mechanisms as well as gene expression regulation centrally involved in the prevention of CVD. Cell culture and animal studies have focused on the identification of vitamin E regulated signaling pathways and involvement on inflammation, lipid homeostasis, and atherosclerotic plaque stability. While some of these vitamin E functions were verified in clinical trials, some of the positive effects were not translated into beneficial outcomes in epidemiological studies. In recent years, the physiological metabolites of vitamin E, including the liver derived (long- and short-chain) metabolites and phosphorylated (α-, γ-tocopheryl phosphate) forms, have also provided novel mechanistic insight into CVD regulation that expands beyond the vitamin E precursor. It is certain that this emerging insight into the molecular and cellular action of vitamin E will help to design further studies, either in animal models or clinical trials, on the reduction of risk for CVDs. This review focuses on vitamin E-mediated preventive cardiovascular effects and discusses novel insights into the biology and mechanism of action of vitamin E metabolites in CVD. © 2019 IUBMB Life, 71(4):507-515, 2019.

Glabridin attenuates endothelial dysfunction and permeability, possibly via the MLCK/p-MLC signaling pathway

Atherosclerosis is caused by various factors, and Glabridin may have protective effects on the cardiovascular system. The purpose of the present study was to evaluate the effects of Glabridin on atherosclerosis and evaluate whether Glabridin attenuates arteriosclerosis and endothelial permeability by suppressing the myosin light chain (MLC) kinase (MLCK)/phosphorylated (p)-MLC system via the mitogen activated protein kinase (MAPK) signaling pathway. Male New Zealand rabbits were randomly divided into 3 groups: The control group was administered an ordinary diet, whereas the high fat group and the Glabridin (2 mg/kg/d) intervention group were administered a high fat diet. Following 12 weeks, the blood lipid levels of rabbits, the morphological structure of the arterial wall, the arterial intimal permeability, the endothelial function and the mRNA levels of MLCK were measured. Western blot analysis was used to detect the levels of MLCK, p-c-Jun N-terminal kinase (JNK), p-extracellular signal regulated kinase (ERK), and p-p38. The high-fat diet group exhibited significantly increased total cholesterol and triglycerides, and endothelial dysfunction, which were attenuated by Glabridin treatment. Notably, the aortic endothelial permeability was increased in the high-fat diet group but was ameliorated in the Glabridin treatment group. Hyperlipidemia enhanced the expression of p-MLC and MLCK, which were associated with the increased phosphorylation of ERK, p38 and JNK. These changes were also ameliorated by Glabridin. In conclusion, the results of the present study suggested that atherosclerosis may be associated with upregulated MLCK expression and activity, which was downregulated by Glabridin. The mechanism of action of Glabridin was thought to proceed through modulating MAPK pathway signal transduction. However, further studies are required to adequately illuminate the exact regulatory mechanisms involved.

Cholesteryl ester transfer protein and its inhibitors

Most of the cholesterol in plasma is in an esterified form that is generated in potentially cardioprotective HDLs. Cholesteryl ester transfer protein (CETP) mediates bidirectional transfers of cholesteryl esters (CEs) and triglycerides (TGs) between plasma lipoproteins. Because CE originates in HDLs and TG enters the plasma as a component of VLDLs, activity of CETP results in a net mass transfer of CE from HDLs to VLDLs and LDLs, and of TG from VLDLs to LDLs and HDLs. As inhibition of CETP activity increases the concentration of HDL-cholesterol and decreases the concentration of VLDL- and LDL-cholesterol, it has the potential to reduce atherosclerotic CVD. This has led to the development of anti-CETP neutralizing monoclonal antibodies, vaccines, and antisense oligonucleotides. Small molecule inhibitors of CETP have also been developed and four of them have been studied in large scale cardiovascular clinical outcome trials. This review describes the structure of CETP and its mechanism of action. Details of its regulation and nonlipid transporting functions are discussed, and the results of the large scale clinical outcome trials of small molecule CETP inhibitors are summarized.

Recent Advances in Managing Atherosclerosis via Nanomedicine

Atherosclerosis, driven by chronic inflammation of the arteries and lipid accumulation on the blood vessel wall, underpins many cardiovascular diseases with high mortality rates globally, such as stroke and ischemic heart disease. Engineered bio-nanomaterials are now under active investigation as carriers of therapeutic and/or imaging agents to atherosclerotic plaques. This Review summarizes the latest bio-nanomaterial-based strategies for managing atherosclerosis published over the past five years, a period marked by a rapid surge in preclinical applications of bio-nanomaterials for imaging and/or treating atherosclerosis. To start, the biomarkers exploited by emerging bio-nanomaterials for targeting various components of atherosclerotic plaques are outlined. In addition, recent efforts to rationally design and screen for bio-nanomaterials with the optimal physicochemical properties for targeting plaques are presented. Moreover, the latest preclinical applications of bio-nanomaterials as carriers of imaging, therapeutic, or theranostic agents to atherosclerotic plaques are discussed. Finally, a mechanistic understanding of the interactions between bio-nanomaterials and the plaque ("athero-nano" interactions) is suggested, the opportunities and challenges in the clinical translation of bio-nanomaterials for managing atherosclerosis are discussed, and recent clinical trials for atherosclerotic nanomedicines are introduced.

Development and Multiparametric Evaluation of Experimental Atherosclerosis in Rabbits

Several animal models have been developed to study atherosclerosis. Here we present a rabbit atherosclerosis model generated by surgical denudation of the aortic endothelium in combination with a high-fat and cholesterol-enriched diet. This model is characterized by the formation of vascular lesions that exhibit several hallmarks of human atherosclerosis. Due to the rabbit's relative large size, as compared to rodents, this model is suited for the imaging-guided evaluation of novel therapeutic strategies using clinical scanners. In this chapter, we present an extensive outline of the procedures to induce aortic atherosclerotic lesions in rabbits as well as methods to evaluate the disease, including noninvasive in vivo multiparametric imaging and histopathology.

Animal models of atherosclerosis

Atherosclerosis is a significant cause of morbidity and mortality globally. Many animal models have been developed to study atherosclerosis, and permit experimental conditions, diet and environmental risk factors to be carefully controlled. Pathophysiological changes can be produced using genetic or pharmacological means to study the harmful consequences of different interventions. Experiments using such models have elucidated its molecular and pathophysiological mechanisms, and provided platforms for pharmacological development. Different models have their own advantages and disadvantages, and can be used to answer different research questions. In the present review article, different species of atherosclerosis models are outlined, with discussions on the practicality of their use for experimentation.

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.

Effect of a hypercholesterolemia as a starting factor on spinal degeneration in rabbits and role of Vitamin E (α-tocopherol)

Background:

To identify the role of the hypercholesterolemia as a starting factor in discovertebral degeneration that ultimately causes lower back pain, and investigate the role of Vitamin E in this process.

Methods:

The rabbits (n = 32) were divided into two broad experimental groups: A control group, and a hypercholesterolemia group, namely cholesterol, and cholesterol plus Vitamin E groups and they were fed sequentially for 4 or 8 weeks. Serum cholesterol and Vitamin E (α-tocopherol) levels were determined; vascular tissue was prepared for histopathological analyses and vertebra was decalcified for the study.

Results:

Cholesterol diet group resulted approximately 44-fold of increase plasma cholesterol levels over the 4-week control values. Additional supplementation with Vitamin E group induced a plasma cholesterol level increase of only 37-fold as compared to the control group. In the cholesterol groups, light microscope examination revealed atherosclerotic plaque in major arteries. However, in the cholesterol plus Vitamin E treatment groups, no lipid accumulation or foam cell formation was visible in the abdominal aorta and vertebral segmental artery. In histopathological examination, we found degenerative changes in the discovertebral unit in cholesterol treated groups.

Conclusion:

Hypercholesterolemia causes fat accumulation in the disc endplate and vertebral body that causes blood supply disturbances which might be a starting factor of discovertebral degeneration. This event was not reversed by the elimination of cholesterol from the diet. Vitamin E supplementation was not effective in reducing fat accumulation in vertebral bone marrow. As a result, we conclude that degeneration of the discovertebral unit is not related to atherosclerotic changes in the major blood vessels.

Antihypercholesterolemic and antioxidant efficacies of zerumbone on the formation, development, and establishment of atherosclerosis in cholesterol-fed rabbits

Owing to the high incidence of cholesterol-induced cardiovascular disease, particularly atherosclerosis, the current study was designed to investigate the preventive and therapeutic efficacies of dietary zerumbone (ZER) supplementation on the formation and development of atherosclerosis in rabbits fed with a high cholesterol diet. A total of 72 New Zealand white rabbits were divided randomly on two experimental studies carried out 8 weeks apart. The first experiment was designed to investigate the prophylactic efficacy of ZER in preventing early developed atheromatous lesion. The second experimental trial was aimed at investigating the therapeutic effect of ZER in reducing the atherosclerotic lesion progression and establishment. Sudanophilia, histopathological, and ultrastructural changes showed pronounced reduction in the plaque size in ZER-medicated aortas. On the other hand, dietary supplementation of ZER for almost 10 weeks as a prophylactic measure indicated substantially decreasing lipid profile values, and similarly, plaque size in comparison with high-cholesterol non-supplemented rabbits. Furthermore, the results of oxidative stress and antioxidant biomarker evaluation indicated that ZER is a potent antioxidant in suppressing the generation of free radicals in terms of atherosclerosis prevention and treatment. ZER significantly reduced the value of malondialdehyde and augmented the value of superoxide dismutase. In conclusion, our data indicated that dietary supplementation of ZER at doses of 8, 16, and 20 mg/kg alone as a prophylactic measure, and as a supplementary treatment with simvastatin, significantly reduced early plague formation, development, and establishment via significant reduction in serum lipid profile, together with suppression of oxidative damage, and therefore alleviated atherosclerosis lesions.

Modelling atherosclerosis by proteomics: Molecular changes in the ascending aortas of cholesterol-fed rabbits

The cholesterol-fed rabbit is commonly used as a model to study the vascular effects of hypercholesterolemia and resulting atherosclerotic lesions. Here we undertook a proteomic case-control investigation of ascending aortas from male New Zealand White rabbits after 10 weeks on a high-cholesterol (2% w/w) diet (HCD, n = 5) or control diet (n = 5), in order to determine the changes in response to the HCD. Histology confirmed intimal thickening in the HCD group consistent with atherosclerosis, and LC-MS/MS analysis of individually-obtained ascending aortic extracts labelled with isobaric (iTRAQ) tags enabled the identification and quantitation of 453 unique proteins above the 1% false discovery rate threshold. Of 67 proteins showing significant differences in relative abundance (p < 0.05), 62 were elevated and five decreased in ascending aortas from HCD-fed rabbits compared to controls. Six proteins were selected for validation using Multiple Reaction Monitoring, which confirmed the iTRAQ results. Many of the observed protein changes are consistent with known molecular perturbations in the ascending aorta that occur in response to hypercholesterolemia, e.g. elevation of tissue levels of apolipoproteins, extracellular matrix adhesion proteins, glycolytic enzymes, heat shock proteins and proteins involved in immune defense. We also made a number of novel observations, including a 15-fold elevation of glycoprotein (trans-membrane) nmb-like (Gpnmb) in response to HCD. Gpnmb has previously been linked to angiogenesis but not to atherosclerosis. This and additional novel observations merit further investigation as these perturbations may play important and as yet undiscovered roles in the pathogenesis of atherosclerosis in rabbits as well as humans.

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.

Insights into the antiatherogenic molecular mechanisms of andrographolide against Porphyromonas gingivalis-induced atherosclerosis in rabbits

Atherosclerosis is the commonest and most important vascular disease. Andrographolide (AND) is the main bioactive component of the medicinal plant Andrographis paniculata and is used in traditional medicine. This study was aimed to evaluate the antiatherogenic effect of AND against atherosclerosis induced by Porphyromonas gingivalis in White New Zealand rabbits. Thirty rabbits were divided into five groups as follows: G1, normal group; G2-5, were orally challenged with P. gingivalis five times a week over 12 weeks; G2, atherogenic control group; G3, standard group treated with atorvastatin (AV) 5 mg/kg; and G4 and G5, treatment groups treated with AND 10 and 20 mg/kg, respectively over 12 weeks. Serums were subjected to antioxidant enzymatic and anti-inflammatory activities, and the aorta was subjected to histological analyses. Groups treated with AND showed a significant reversal of liver and renal biochemical changes, compared with the atherogenic control group. In the same groups, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), total glutathione (GSH) levels in serum were significantly increased (P < 0.05), and lipid peroxidation (malondialdehyde (MDA)) levels were significantly decreased (P < 0.05), respectively. Furthermore, treated groups with AV and AND showed significant decrease in the level of VCAM-1 and ICAM-1 compared with the atherogenic control group. In aortic homogenate, the level of nitrotyrosine was significantly increased, while the level of MCP1 was significantly decreased in AV and AND groups compared with the atherogenic control group. In addition, staining the aorta with Sudan IV showed a reduction in intimal thickening plaque in AV and AND groups compared with the atherogenic control group. AND has showed an antiatherogenic property as well as the capability to reduce lipid, liver, and kidney biomarkers in atherogenic serum that prevents atherosclerosis complications caused by P. gingivalis.

Effect of shear stress alteration on atherosclerotic plaque vulnerability in cholesterol-fed rabbits

Previously, we created an experimental murine model for the induction of vulnerable plaque (VP). Although this murine model offers the opportunity to study the different molecular biological pathways that regulate plaque destabilization, the size of the animals severely limits the use of the model for in vivo diagnostics and percutaneous interventions. This study aimed to create a VP model in the rabbit, based on the murine model, to aid the assessment and development of novel diagnostic and interventional tools. New Zealand white rabbits were fed on a 2% cholesterol diet. After 1 week, a shear stress-altering device was implanted around the right carotid artery. Twelve weeks after cast placement, the carotid artery was isolated and processed for (immuno-)histological analysis to evaluate the presence of a VP phenotype. Atherosclerotic plaques with high lipid and macrophage content, low vascular smooth muscle cell content and intimal neovascularization were located upstream and downstream of the cast. The plaques lacked a significant necrotic core. In conclusion, we were able to create atherosclerotic plaques with a phenotype beyond that of a fatty streak, with a high percentage of lipids and macrophages, a thick cap with some vascular smooth muscle cells and neovascularization. However, as there was only a small necrotic core, the overall phenotype seems less vulnerable as compared to the thin fibrous cap atheroma in patients.

Dietary cholesterol increases ventricular volume and narrows cerebrovascular diameter in a rabbit model of Alzheimer's disease

Using structural magnetic resonance imaging in a clinical scanner at 3.0T, we describe results showing that following 12weeks on a diet of 2% cholesterol, rabbits experience a significant increase in the volume of the third ventricle compared to rabbits on a diet of 0% cholesterol. Using time-of-flight magnetic resonance angiography, we find cholesterol-fed rabbits also experience a decrease in the diameter of a number of cerebral blood vessels including the basilar, posterior communicating, and internal carotid arteries. Taken together, these data confirm that, despite the inability of dietary cholesterol to cross the blood-brain barrier, it does significantly enlarge ventricular volume and decrease cerebrovascular diameter in the rabbit - effects that are also seen in patients with Alzheimer's disease.

Antiatherosclerotic Effect of Canarium odontophyllum Miq. Fruit Parts in Rabbits Fed High Cholesterol Diet

The effect of C. odontophyllum (CO) fruit parts was investigated in hypercholesterolemic rabbits. Forty-nine rabbits, which were randomly divided into seven groups of seven animals (n = 7), received a diet containing different parts of CO fruit parts for 8 weeks. The groups were as follows: (1) normal diet: NC group and (2) hypercholesterolemic diet: PC, HS (10 mg/kg/day simvastatin), HPO (20 g kg(-1) oil extracted from the pulp of CO), HKO (20 g kg(-1) oil extracted from the kernel of CO), HF (50 g kg(-1) fullfat pulp of CO), and HD (50 g kg(-1) defatted pulp of CO). Among these groups, rabbits receiving defatted pulp of CO showed the greatest cholesterol lowering effect as it had reduced plasma LDL-C, TC, and thiobarbiturate reactive substance (TBARS) levels as well as atherosclerotic plaques. The presence of high dietary fiber and antioxidants activity are potential factors contributing to the cholesterol lowering effect. Consequently, these results indicate the potential use of CO defatted pulp as a cholesterol lowering and antioxidant agent.

Dietary Cholesterol Concentration and Duration Degrade Long-Term Memory of Classical Conditioning of the Rabbit's Nictitating Membrane Response

A rabbit model of Alzheimer's disease based on feeding a cholesterol diet for eight weeks shows sixteen hallmarks of the disease, including learning and memory changes. Although we have shown 2% cholesterol and copper in water can retard learning, other studies show feeding dietary cholesterol before learning can improve acquisition whereas feeding cholesterol after learning can degrade long-term memory. We explored this issue by manipulating cholesterol concentration and duration following classical trace conditioning of the rabbit's nictitating membrane response and assessed conditioned responding after eight weeks on cholesterol. First, rabbits given trace classical conditioning followed by 0.5%, 1%, or 2% cholesterol for eight weeks showed body weight and serum cholesterol levels that were a function of dietary cholesterol. Although all concentrations of cholesterol showed some sign of retarding long-term memory, the level of memory retardation was correlated with serum cholesterol levels. Second, rabbits given trace conditioning followed by different durations of a 2% cholesterol diet combined with different durations of a 0% control diet for 8 weeks showed duration and timing of a 2% cholesterol diet were important in affecting recall. The data support the idea that dietary cholesterol may retard long-term memory.

Animal models of atherosclerosis

Atherosclerosis is a chronic inflammatory disorder that is the underlying cause of most cardiovascular disease. Both cells of the vessel wall and cells of the immune system participate in atherogenesis. This process is heavily influenced by plasma lipoproteins, genetics, and the hemodynamics of the blood flow in the artery. A variety of small and large animal models have been used to study the atherogenic process. No model is ideal as each has its own advantages and limitations with respect to manipulation of the atherogenic process and modeling human atherosclerosis or lipoprotein profile. Useful large animal models include pigs, rabbits, and nonhuman primates. Due in large part to the relative ease of genetic manipulation and the relatively short time frame for the development of atherosclerosis, murine models are currently the most extensively used. Although not all aspects of murine atherosclerosis are identical to humans, studies using murine models have suggested potential biological processes and interactions that underlie this process. As it becomes clear that different factors may influence different stages of lesion development, the use of mouse models with the ability to turn on or delete proteins or cells in tissue specific and temporal manner will be very valuable.

Animal models of atherosclerosis

Cardiovascular disease is currently the predominant cause of mortality worldwide and its incidence is expected to increase significantly during the next decades owing to the unhealthy effects of modern lifestyle habits (e.g., obesity and lack of physical exercise). Cardiovascular death is frequently associated with acute myocardial infarction or stroke, which are generally the ultimate consequence of an underlying atherosclerotic process. Small and big animal models are valuable tools to understand the molecular mechanisms underlying atherosclerotic plaque formation and progression, as well as the occurrence of associated ischemic events. Moreover, animal models of atherosclerosis are pivotal for testing mechanistic hypothesis and for translational research, including the assessment of dietary and/or pharmacological interventions and the development of imaging technologies and interventional devices. In this chapter, we will describe the most widely used animal models that have permitted major advances in atherosclerosis research and significant improvements in the treatment and diagnosis of atherosclerotic disease.

Protective effects of vitamin E against hypercholesterolemia-induced age-related diseases

Hypercholesterolemia is a major risk factor for age-related diseases such as atherosclerosis and Alzheimer's disease (AD). Changes in human plasma cholesterol levels results from the interaction between multiple genetic and environmental factors. The accumulation of excess cholesterol in blood vessels leads to atherosclerosis. Many studies on this field show that differential expression of oxidative stress-related proteins, lipid metabolism-related enzymes, and receptors response to atherogenic diet. Additionally, excess brain cholesterol has been associated with increased formation and deposition of amyloid-β peptide from amyloid precursor protein which may contribute to the risk and pathogenesis of AD. To consider genetically, more than 50 genes have been reported to influence the risk of late-onset AD. Some of these genes might be also important in cholesterol metabolism and transport. Epidemiological studies have shown an association between high intake and high serum concentrations of antioxidant vitamins like vitamin E and lower rates of ischemic heart diseases. It has been known that vitamin E also inhibits smooth muscle cell proliferation by non-antioxidant mechanism. On the basis of the previous results, vitamin E has been accepted as an important protective factor against hypercholesterolemia-induced age-related diseases.

Animal models for the atherosclerosis research: a review

Atherosclerosis is a leading cause of death worldwide, and its mechanisms are still unclear. However, various animal models have significantly advanced our understanding of the mechanisms involved in atherosclerosis and have allowed the evaluation of therapeutic options. The aim of this paper is to review those animal models (i.e., rabbits, mice, rats, guinea pigs, hamsters, avian, carnivores, swine, and, non-human primates) that have been used to study atherosclerosis. Though there is no single perfect animal model that completely replicates the stages of human atherosclerosis, cholesterol feeding and mechanical endothelial injury are two common features shared by most models of atherosclerosis. Further, with the development of genetically modified animals, these models are significantly broadening our understanding of the pathogenesis of atherosclerosis.

Hypercholesterolemia increases vasospasm resulting from basilar artery subarachnoid hemorrhage in rabbits which is attenuated by Vitamin E

BACKGROUND

Aneurysm rupture results in subarachnoid hemorrhage (SAH) with subsequent vasospasm in the cerebral and cerebellar major arteries. In recent years, there has been increasing evidence that hypercholesterolemia plays a role in the pathology of SAH. It is known that hypercholesterolemia is one of the major risk factors for the development of atherosclerosis. Among the factors that have been found to retard the development of atherosclerosis is the intake of a sufficient amount of Vitamin E. An inverse association between serum Vitamin E and coronary heart disease mortality has been demonstrated in epidemiologic studies. Therefore, we tested, in an established model of enhanced cholesterol feed in rabbits, the effects of hypercholesterolemia on vasospasm after SAH by using computed tomography (CT) angiograms of the rabbit basilar artery; in addition, we tested the effects of Vitamin E on these conditions, which have not been studied up to now.

METHODS

In this study rabbits were divided into 3 major groups: control, cholesterol fed, and cholesterol + Vitamin E fed. Hypercholesterolemia was induced by a 2% cholesterol-containing diet. Three rabbit groups were fed rabbit diet; one group was fed a diet that also contained 2% cholesterol and another group was fed a diet containing 2% cholesterol and they received i.m. injections of 50 mg/kg of Vitamin E. After 8 weeks, SAH was induced by the double-hemorrhage method and distilled water was injected into cisterna magna. Blood was taken to measure serum cholesterol and Vitamin E levels. Basilar artery samples were taken for microscopic examination. CT angiography and measurement of basilar artery diameter were performed at days 0 and 3 after SAH.

RESULTS

Two percent cholesterol diet supplementation for 8 weeks resulted in a significant increase in serum cholesterol levels. Light microscopic analysis of basilar artery of hypercholesterolemic rabbits showed disturbances in the subendothelial and medial layers, degeneration of elastic fibers in the medial layer from endothelial cell desquamation, and a reduction of waves in the endothelial layer. However, the cholesterol + Vitamin E group did not exhibit these changes. The mean diameter of the basilar artery after SAH induction in the cholesterol-treated group was decreased 47% compared with the mean diameter of the control group. This value was less affected in cholesterol + Vitamin E-treated rabbits, which decreased 18% compared with the mean diameter of the control group.

CONCLUSIONS

Hypercholesterolemia-related changes in the basilar artery aggravate vasospasm after SAH. Adding Vitamin E to cholesterol-treated rabbits decreased the degree of vasospasm following SAH in the rabbit basilar artery SAH model. We suggest that Vitamin E supplements and a low cholesterol diet may potentially diminish SAH complicated by vasospasm in high-risk patients.

Astaxanthin Reduces Oxidative Stress, but not Aortic Damage in Atherosclerotic Rabbits

We evaluated whether carotenoid astaxanthin (ASX) could prevent oxidative and atherosclerotic damage in rabbits. Rabbits received regular chow (control) or an atherogenic diet (1% cholesterol) alone or supplemented with 50, 100, and 500 mg% ASX for 60 days (n = 5-9 per group). The atherogenic diet increased the serum cholesterol levels and the ratio of the intima/media area in the aortic arch. These changes were not prevented by ASX. Atherosclerotic rabbits showed increased aortic lipid peroxidation and nonprotein thiol group (NPSH) levels along with inhibition of glutathione peroxidase (GSH-Px). All ASX doses attenuated lipid peroxidation and the increase in NPSH but not the inhibition of GSH-Px. Aortic superoxide dismutase (SOD), catalase (CAT), and thioredoxin reductase (TrxR) activities were enhanced in atherosclerotic rabbits. Although all ASX doses prevented the increase in SOD activity, only 100 and 500 mg% ASX prevented the increase in CAT activity. Furthermore, these same doses partially prevented the increase in TrxR activity, while 50 mg% ASX completely prevented the effects of the atherogenic diet on this enzyme. However, ASX did not attenuate the hypercholesterolemia or the atherosclerotic lesions caused by the atherogenic diet at any of the doses evaluated. Our results indicate that although ASX did not prevent hypercholesterolemia or atherosclerotic lesions, it could play a beneficial role by preventing lipid peroxidation and changes in antioxidant enzyme activities.

von Willebrand factor, C-reactive protein, nitric oxide, and vascular endothelial growth factor in a dietary reversal model of hypercholesterolemia in rabbit

AIMS

Endothelial dysfunction is considered a sign of the early vascular changes preceding atherosclerosis. We studied the alteration of von Willebrand Factor (vWF), C - reactive protein (CRP), nitrite and Vascular Endothelial Growth Factor (VEGF) in a dietary reversal model of hypercholesterolemia in rabbit.

METHODS

This project was designed in two phases. In phase I, male rabbits (n = 11) were fed a 1% high cholesterol diet for 30 days. Then the diet was replaced with normal rabbit chow for other 30 days (cholesterol withdrawal phase, phase II). To compare the fatty streak formation with normal condition, a control group (n = 6) received normal diet during the study. The serum lipid levels, vWF, CRP, nitrite, and VEGF were measured before the experiment and by the end of each phase. Fatty streak formation in the walls of the aortas in both groups (high cholesterol diet and control group) was determined using intima thickness/media thickness (IMT) ratio.

RESULTS

The results indicate that the level of cholesterol, Low Density Lipoproteins (LDL), vWF and CRP increased significantly in phase I, and decreased after hypercholesterolemic diet withdrawal (p < 0.05). No statistically significant changes were found in VEGF levels but the serum level of nitrite increased significantly during both phases of the study (p < 0.05). The IMT ratio in the walls of aortas was significantly different between the groups in both phases of studies (p < 0.05). There was a significant correlation between nitrite and cholesterol levels in both phases (r = 0.62 and r = 0.98, p < 0.05). Nitrite concentration also correlated with IMT ratio in both phases of the study (r = 0.75 and r = -0.99, p < 0.05). vWF did not correlate with cholesterol but it correlated with IMT ratio in both phases of the study (r = 0.87 and r = 0.84, p < 0.05). CRP only correlated with cholesterol in the first phase (r = 0.91, p < 0.05).

CONCLUSIONS

Among the endothelial biomarkers, vWF was found to be a biological marker for identifying the risk of developing atherosclerosis; however a single biomarker may not provide appropriate information.

The in vitro and ex vivo antioxidant properties, hypolipidaemic and antiatherosclerotic activities of water extract of Moringa oleifera Lam. leaves

Moringa oleifera is used in Thai traditional medicine as cardiotonic. Recent studies demonstrated its hypocholesterolaemic effect. However, to be clinically useful, more scientific data are needed.

AIM OF THE STUDY

We investigated the antioxidant, hypolipidaemic and antiatherosclerotic activities of Moringa oleifera leaf extract.

MATERIALS AND METHODS

Scavenging activity of the extract on 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH), and the inhibitory effect on Cu(2+)-induced low-density lipoprotein (LDL) oxidation were determined in in vitro experiment. The effects of the extract on cholesterol levels, conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) and plaque formations in cholesterol-fed rabbits were investigated.

RESULTS

We found that in scavenging DPPH radicals the extract and Trolox had IC(50) of 78.15+/-0.92 and 2.14+/-0.12microg/ml, respectively. The extract significantly (P<0.05) prolonged the lag-time of CD formation and inhibited TBARS formation in both in vitro and ex vivo experiments in a dose-dependent manner. In hypercholesterol-fed rabbits, at 12 weeks of treatment, it significantly (P<0.05) lowered the cholesterol levels and reduced the atherosclerotic plaque formation to about 50 and 86%, respectively. These effects were at degrees comparable to those of simvastatin.

CONCLUSIONS

The results indicate that this plant possesses antioxidant, hypolipidaemic and antiatherosclerotic activities and has therapeutic potential for the prevention of cardiovascular diseases.

The effect of temporary aneurysm clip on the common carotid artery of atherosclerotic rabbits

BACKGROUND

We compared the effect of temporary aneurysm clips on atherosclerotic and nonatherosclerotic CCA of rabbits by morphometric and ultrastructural methods.

METHODS

The rabbits (N = 12) were divided into 2 groups: the first group was fed a 2% cholesterol diet, and the second group, a normal diet for 4 weeks. Atherosclerotic lesions developed after 4 weeks. Temporary aneurysm clips were placed on the left CCA of both groups; the right CCA of both groups served as control. Thus, a total of 4 groups were used: atherosclerotic (A), atherosclerotic/clip (AC), nonatherosclerotic (NA), and nonatherosclerotic/clip (NAC). Temporary aneurysm clips were applied for 1, 5, and 10 minutes in the AC and NAC groups. No temporary clip was placed on the right CCA (A and NA groups). The affected parts of the CCA via clips were examined under light microscope and SEM.

RESULTS

Comparison of atherosclerotic and nonatherosclerotic CCA of rabbits under light microscope indicated that the wall of atherosclerotic CCA was thicker than that of nonatherosclerotic CCA. The difference between the thickness of atherosclerotic and nonatherosclerotic CCAs was significant. SEM analyses showed that in nonatherosclerotic CCAs, the effect of temporary aneurysm clips was seen after 10 minutes, but in atherosclerotic CCAs, the effect was seen within the 1st minute of clipping and continued in the 5th and 10th minutes.

CONCLUSION

The duration of temporary clipping should be decreased for the neurovascular surgery of atherosclerotic patients.

Chronically gorgingv. nibbling fat and cholesterol increases postprandial lipaemia and atheroma deposition in the New Zealand White rabbit

In the present study, we compared the effects of nibbling and gorging on postprandial lipaemia and lipoproteins, hepatic lipid uptake and atheroma deposition. New Zealand White rabbits were fed on a low-fat (LF) control diet or a peanut oil- (10 g/d) and cholesterol- (0·5 g/d) enriched (HF) diet with the fat and cholesterol components given either by nibbling (HF-N) or gorging (HF-G). After 4 and 8 weeks, rabbits were given a test meal, which was either nibbled or taken as a bolus. The LF diet did not noticeably alter postprantial lipid variables. Triacylglycerol levels, 0–35 h lipid responses and plasma accumulation of dietary lipids were significantly higher in the HF-G group than in the HF-N group, despite higher post-heparin plasma lipase activities. Furthermore, as studied on cultured isolated hepatocytes, the higher the rate of supply of triacylglycerol- and cholesterol-rich lipoproteins (TCRL), the lower the rate of lipid uptake and bile salt secretion. Atheroma deposition was significantly increased by gorging the HF diet and was correlated with levels of most postprandial lipid variables. We conclude that gorgingv. nibbling a fat and cholesterol-enriched diet exacerbates postprandial lipaemia by reducing the rate of TCRL clearance and favours atheroma deposition.

Concord grape juice attenuates platelet aggregation, serum cholesterol and development of atheroma in hypercholesterolemic rabbits

Intake of Concord grape juice (CGJ), rich in polyphenolics, inhibits platelet aggregation (PA), a risk factor for cardiovascular disease (CVD), in normocholesterolemic animals and humans. It is unclear whether CGJ can attenuate hypercholesterolemia-enhanced PA. The effects of daily CGJ consumption on hypercholesterolemia-enhanced PA and the development of atherosclerosis were investigated. Two groups of rabbits (Control and Treated; n=10 each) were fed a hypercholesterolemic diet for 48 days. Treated group then received supplemental CGJ (225mL/day) while Control group received supplemental iso-caloric sugar water for 48 days. Collagen-, collagen+epinephrine- and phorbol-12-myristate-13-acetate-induced whole blood PA responses were measured on Days 0, 48 and 96; total serum cholesterol and blood pressure were also measured. The development of aortic atheroma was quantified at the end. Both groups showed significant increases in PA and serum cholesterol at Day 48. However, at Day 96, Treated group showed significantly lower PA and development of atheroma (30.7+/-3.9% lower (p<0.001)) than Control group; Treated group also had significantly lower total serum cholesterol and blood pressure than Control group. In conclusion, daily consumption of CGJ attenuates hypercholesterolemia-enhanced PA, blood pressure, total serum cholesterol and development of atheroma in rabbits.

O processo aterosclerótico em artérias de coelhos submetidos a dieta suplementada com gema de ovo: modelo experimental de baixo custo

OBJETIVO: Verificar a aterogenicidade do modelo de hipercolesterolemia por suplementação alimentar com gema de ovo em coelhos e seu uso como modelo de aterosclerose experimental de baixo custo. MATERIAL E MÉTODO: Foram utilizados 14 coelhos divididos em dois grupos de sete animais: grupo controle (G1), que recebeu ração comercial ad libitum, e grupo tratado (G2), que foi alimentado com dieta suplementada com gema de ovo. Ambos os grupos foram alimentados por 90 dias. Foram realizadas dosagens do perfil lipídico dos animais nos momentos 0, 30, 60 e 90 dias. Ao término do período experimental, os animais foram submetidos a eutanásia e retirada da aorta e de seus ramos diretos para realização de estudo anatomopatológico. RESULTADOS Apenas no grupo G2 houve aumento significativo nos níveis de colesterol total e frações. Ao exame macroscópico, foram observadas estrias gordurosas no arco aórtico e aorta abdominal e, à microscopia, acúmulos lipídicos discretos na íntima da aorta abdominal, renal, carótida, transição toracoabdominal e femoral. Portanto, a dieta com gema de ovo provocou aterosclerose leve no animal de experimentação e alterações equivalentes àquelas provocadas pelo colesterol purificado comercial quando fornecido em baixa dosagem. Assim sendo, a gema de ovo pode ser utilizada como fonte de colesterol alimentar de baixo custo em modelos de aterosclerose experimental.

Evaluation of rat and rabbit sera lipoproteins in experimentally induced hyperlipidemia by analytical ultracentrifugation

Animals of various species are widely used as models with which to study atherosclerosis and the lipoprotein metabolism. The objective of this study was to investigate the lipoprotein profiles in Wistar rats and New Zealand white rabbits with experimentally induced hyperlipidemia by means of ultracentrifugation. The Schlieren curves were utilized to compare suckling and adult rat sera to determine whether aging causes alterations in lipoprotein profiles. A striking feature of the data is the high concentration of low-density lipoproteins (LDL), (>5.2 mmol/l cholesterol) in the 2-week old rat serum pool which was greatly decreased in the 3-weeks rat serum pool (<1.3 mmol/l cholesterol). Additional experiments were performed to permit a direct comparison of the amounts of lipoprotein present in rat sera in experimental hyperlipidemia post-Triton WR 1339 administration. Rapid changes in concentrations in very low-density lipoproteins (VLDL), LDL and high-density lipoproteins (HDL) were observed after Triton injection. The administration of Triton WR 1339 to fasted rats resulted in an elevation of serum cholesterol levels. Triton physically alters VLDL, rendering them refractive to the action of lipolytic enzymes in the blood and tissues, preventing or delaying their removal from the blood. Whereas the VLDL concentration was increased markedly, those of LDL and HDL were decreased at 20 h after Triton treatment. Rabbits were fed a diet containing 2% cholesterol for 60 days to develop hyperlipidemia and atheromatous aortic plaques. A combination of preparative and analytical ultracentrifugation was used to investigate of LDL aliquots, to prepare radioactive-labeled lipoproteins and to study induced hyperlipidemia in rabbits. Analytical ultracentrifugation was applied to investigate the LDL flotation peaks before and after cholesterol feeding of rabbits. Modified forms of LDL were detected in the plasma of rabbits with experimentally induced atherosclerosis. ApoB-containing particles, migrating as LDL, intermediate density lipoproteins and VLDL were the most abundant lipoproteins. Gamma camera in vivo scintigraphy on rabbits with radiolabeled lipoproteins revealed visible signals corresponding to atherosclerotic plaques of the aorta and carotid arteries.

Hemodynamics simulation and identification of susceptible sites of atherosclerotic lesion formation in a model abdominal aorta

Employing the rabbit's abdominal aorta as a suitable atherosclerotic model, transient three-dimensional blood flow simulations and monocyte deposition patterns were used to evaluate the following hypotheses: (i) simulation of monocyte transport through a model of the rabbit abdominal aorta yields cell deposition patterns similar to those seen in vivo, and (ii) those deposition patterns are correlated with hemodynamic wall parameters related to atherosclerosis. The deposition pattern traces a helical shape down the aorta with local elevation in monocyte adhesion around vessel branches. The cell deposition pattern was altered by an exercise waveform with fewer cells attaching in the upper abdominal aorta but more attaching around the renal orifices. Monocyte deposition was correlated with the wall shear stress gradient and the wall shear stress angle gradient. The wall stress gradient, the wall shear stress angle gradient and the normalized monocyte deposition fraction were correlated with the distribution of monocytes along the abdominal aorta and monocyte deposition is correlated with the measured distribution of monocytes around the major abdominal branches in the cholesterol-fed rabbit. These results suggest that the transport and deposition pattern of monocytes to arterial endothelium plays a significant role in the localization of lesions.

Effect of phytosterols in dietary diacylglycerol on atherosclerosis in cholesterol-fed rabbits

OBJECTIVE

The present study investigated the effects of phytosterols (PS) in combination with diacylglycerol (DAG) versus PS in combination with triacylglycerol (TAG) on serum lipids and atherosclerosis in cholesterol-fed rabbits.

METHODS

Cholesterol-fed (0.3%) New Zealand white rabbits were treated with a control diet, a 0.3% PS and 7% TAG diet, or a 0.3% PS and 7% DAG diet for 14 wk.

RESULTS

Serum total cholesterol level in the PS/DAG group was statistically lower than that in the control and PS/TAG groups, whereas serum high-density lipoprotein cholesterol and triacylglycerol levels were not statistically different between these two groups. The ratio of the atherosclerotic lesion area and the mean thickness of the intima in the aortas of the PS/DAG group were statistically lower than those of the control group, whereas there was no statistical difference between the PS/TAG and control groups. In particular, the ratio of the lesion area in the abdominal aorta and the mean thickness of the intima in the thoracic and total aortas of the PS/DAG group were statistically lower than those of the PS/TAG group. The ratio of the atherosclerotic lesion area and the mean thickness of the intima in the aortas correlated positively with total cholesterol exposure level.

CONCLUSIONS

These findings suggested that PS in combination with DAG as opposed to TAG prevents the development of atherosclerosis via a decrease in total cholesterol exposure level and might be useful as a dietary oil for the prevention of atherosclerosis.

Molecular mechanisms of cholesterol or homocysteine effect in the development of atherosclerosis: Role of vitamin E

The development of atherosclerosis is a multifactorial process in which both elevated plasma cholesterol levels and proliferation of smooth muscle cells play a central role. Numerous studies have suggested the involvement of oxidative processes in the pathogenesis of atherosclerosis and especially of oxidized low density lipoprotein. Some epidemiological studies have shown an association between high dietary intake and high serum concentrations of vitamin E and lower rates of ischemic heart disease. Cell culture studies have shown that alpha-tocopherol brings about inhibition of smooth muscle cell proliferation. This takes place via inhibition of protein kinase C activity. alpha-Tocopherol also inhibits low density lipoprotein induced smooth muscle cell proliferation and protein kinase C activity. The following animal studies showed that vitamin E protects development of cholesterol induced atherosclerosis by inhibiting protein kinase C activity in smooth muscle cells in vivo. Elevated plasma levels of homocysteine have been identified as an important and independent risk factor for cerebral, coronary and peripheral atherosclerosis. However the mechanisms by which homocysteine promotes atherosclerotic plaque formation are not clearly defined. Earlier reports have been suggested that homocysteine exert its effect via H2O2 produced during its metabolism. To evaluate the contribution of homocysteine in the pathogenesis of vascular diseases, we examined whether the homocysteine effect on vascular smooth muscle cell growth is mediated by H2O2. We show that homocysteine induces DNA synthesis and proliferation of vascular smooth muscle cells in the presence of peroxide scavenging enzyme, catalase. Our data suggest that homocysteine induces smooth muscle cell growth through the activation of an H2O2 independent pathway and accelerate the progression of atherosclerosis. The results indicate a cellular mechanism for the atherogenicity of cholesterol or homocysteine and protective role of vitamin E in the development of atherosclerosis.