High Cholesterol Diet Rabbits Research Articles

Effects of Water-Based Contrast Media on Experimentally Induced Established Atherosclerotic Plaques in Rabbits

INTRODUCTION: Imaging techniques involving optical coherence tomography, computed tomography (CT) and high-resolution magnetic resonance imaging (MRI) are used as tools to identify atherosclerotic plaques. However, the effects of water-based contrast media used in Post Mortem Computed Tomography Angiography (PMCTA) on the histopathology of atherosclerotic plaques have not been widely explored. The objective of this study is to determine the effects of water-based contrast media used in PMCTA on the histopathology of atherosclerotic plaques and biomarkers of atherosclerosis in experimentally induced established atherosclerotic rabbits. MATERIALS AND METHODS: Twenty male New Zealand white rabbits were divided into 2 groups. One group was given a high cholesterol diet (HCD) for 12 weeks to establish atherosclerosis and the control group normal diet (ND). Five rabbits from each group were then given intravenous water-based contrast media before being sacrificed. The entire length of aorta was dissected and submitted for histopathological examination and determination of tissue biomarkers α-SMA and MMP-9. RESULTS: Histopathological examination of the aorta including percentage of area covered by plaque and foam cell formation showed no significant difference in atheromatous plaque formation in both groups of HCD rabbits with or without intravenous contrast media injection (plaque: 55±41 vs. 63±15, p=0.731; foam cells: 124±83 vs. 171±55, p=0.325). Similarly, α-SMA and MMP-9 protein expression also showed no significant difference in both groups (α-SMA: 70±20 vs. 67±26, p=0.807; MMP-9: 60±12 vs. 57±17, p=0.785). CONCLUSION: Water-based contrast media used in PMCTA does not affect the morphology or the immunohistochemistry staining of SMA and MMP-9 in atherosclerotic plaques.

Antioxidant and anti-inflammatory effects of dimethyl fumarate in hypercholesterolemic rabbits

The present study aimed to determine the possible beneficial effects of dimethyl fumarate (DMF) against oxidative stress and inflammation in hypercholesterolemic rabbits. Twenty four New Zealand male rabbits were randomly allocated into 4 groups as the following: Group I (control): rabbits received standard rabbit chow; Group II high cholesterol diet (HCD): rabbits received 1% cholesterol-enriched chow for 4weeks; Group III (HCD-DMF): rabbits received 1% cholesterol-enriched chow and administered DMF (12.5mg/kg/day, orally) for 4weeks; Group IV (DMF): rabbits received standard chow plus DMF (12.5mg/kg/day, orally) for 4weeks. At the end of experiment (day 30), blood samples were collected for measuring serum total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C) and C-reactive protein (CRP). In addition, the aorta was removed for measurement of malondialdehyde (MDA), superoxide dismutase (SOD), mRNA expression of cholesteryl ester transfer protein (CETP) and histological assessment of intima/media (I/M) ratio. HCD-fed rabbits showed significant increases in TGs, TC, low-density lipoprotein cholesterol (LDL-C), aortic MDA and aortic I/M ratio levels while they significantly exhibited a reduced SOD level relative to control animals. Moreover, HCD rabbits demonstrated upregulated mRNA expression of CETP. DMF administration significantly decreased HCD-induced elevations in serum TC and LDL-C. Additionally, DMF decreased aortic level of MDA while increased SOD level. Moreover, DMF significantly downregulated mRNA expression of CETP and reduced the elevation in I/M ratio.In conclusion, this study suggests that DMF has the ability to improve HCD-induced vascular irregularities, possibly via its anti-inflammatory and antioxidant effect.

Antihyperlipidemic Effect of Syrian Mesquite (Prosopis farcta) Root in High Cholesterol Diet-Fed Rabbits.

Prosopis farcta root has been proposed as an efficacious natural drug for cardiovascular disorders in traditional medicine. The present study evaluates the efficacy of aqueous extract of Prosopis farcta root on experimental atherosclerosis development in rabbits with high cholesterol diet-induced hypercholesterolemia. Serum lipid parameters were significantly increased in the high cholesterol diet groups in comparison with the normal control group (P < .050). Histopathological findings revealed that atheromatous plaques were formed in both thoracic and abdominal aorta of hypercholestrolemic rabbits. Treatment with Prosopis farcta root significantly reduced total cholesterol, triglyceride, high-density lipoprotein, low-density lipoprotein, and very low density lipoprotein levels compared to high cholesterol diet rabbits (P < .050). This finding may reflect a reduction of chest pain or the beneficial effects of this plant root extract on cardiovascular health. The present study can serve as a basis for future investigations on the other effects of this plant on cardiovascular health.

Atorvastatin delays the glucose clearance rate in hypercholesterolemic rabbits

The administration of statin might increase the risk of new-onset diabetes in hypercholesterolemic patients based on the recent clinical evidence. However, the causal relationship must be clarified and confirmed in animal experiments. Therefore, we mimicked hypercholesterolemia by feeding rabbits a high-cholesterol diet (HCD) and performed 16 weeks of atorvastatin administration to investigate the effect of statin on glucose metabolism. The intravenous glucose tolerance test showed that plasma glucose levels in the statin-treated rabbits were consistently higher and that there was a slower rate of glucose clearance from the blood than in HCD rabbits. The incremental area under the curve for glucose in the statin-treated rabbits was also significantly larger than in the HCD rabbits. However, there was no significant difference between the two groups in the intravenous insulin tolerance test. The glucose-lowering ability of exogenous insulin was not impaired by statin treatment in hypercholesterolemic rabbits. The administration of a single dose of statin did not affect glucose metabolism in normal rabbits. The statin also significantly increased the levels of high-density lipoprotein cholesterol, alanine aminotransferase and aspartate transaminase and decreased plasma levels of total cholesterol, triglycerides and low-density lipoprotein cholesterol in the hypercholesterolemic rabbits, whereas it did not affect plasma levels of glucose and insulin. The current results showed that atorvastatin treatment resulted in a significant delay of glucose clearance in hypercholesterolemic rabbits, and this rabbit model could be suitable for studying the effects of statin on glucose metabolism.

SIMVASTATIN PREVENT RABBIT ARTERIAL ATHEROSCLEROSIS DEVELOPMENT THROUGH INTERFERING NUCLEAR FACTOR-κB ACTIVATION

ObjectivesTo explore the effects of simvastatin on NF-κB activation in cholesterol diet rabbit artery and the underlying mechanisms of the beneficial effects of simvastatin on atherosclerosis (AS).MethodsTwenty-four male rabbits were...

Amlodipine attenuates oxidative stress in the heart and blood of high-cholesterol diet rabbits.

Oxidative stress is a key component of atherosclerosis. It has been suggested that amlodipine inhibits oxidative stress. In this study, we evaluated the effects of amlodipine on the total antioxidant capacity of heart tissue and blood in 36 control and cholesterol-fed male New Zealand white rabbits. The rabbits were divided into four groups (n = 9). Group 1 rabbits were fed a regular diet, group 2 were fed a diet with 2% cholesterol, group 3 were fed a regular diet plus 5 mg/kg/day oral amlodipine, and group 4 were fed 2% cholesterol diet plus amlodipine 5 mg/kg/day. At the end of eight weeks, blood samples were drawn and at the same time heart tissue was isolated and frozen in liquid nitrogen. After homogenisation, the solution was centrifuged and the light supernatant was stored at -80°C. This was used for determination of glutathione peroxidase (GPX), superoxide dismutase (SOD) and (MDA) levels. Eight weeks of amlodipine treatment significantly reduced the levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides in the group on the hypercholesterolaemic diet (p < 0.05). In the blood, the level of thiobarbituric acid-reactive substances increased in the rabbits on the 2% cholesterol diet (group 2) and 2% cholesterol-plusamlodipine diet (group 4) and decreased in the amlodipineonly group (group 3) (p < 0.05). Lipid peroxidation in the heart tissue was similar to that in the blood, except in the amlodipine-only group (group 3). In the blood, the activity of total SOD (tSOD) decreased in the group on the 2% cholesterol diet (group 2) (p < 0.05) and markedly increased in the amlodipine-only (group 3) and 2% cholesterol-plusamlodipine groups (group 4) (p < 0.05). Amlodipine decreased oxidative stress in the heart and blood and improved the lipid profile in cholesterolfed rabbits. Therefore, it may be considered a useful tool for the reduction of oxidative stress and improvement of lipid profiles in diseases related to atherosclerosis.

Association of aorta intima permeability with myosin light chain kinase expression in hypercholesterolemic rabbits

The development of hypercholesterolemia is a multifactorial process in which elevated plasma cholesterol levels play a central role. This study analyzed the variability of the expression and activity of myosin light chain kinase (MLCK) and endothelial permeability in the artery wall of rabbits after feeding the animals with a normal or a high-cholesterol diet. Hypercholesterolemia was induced by a high-cholesterol diet for 4 weeks. Aortas were removed and analyzed for endothelial permeability and MLCK expression. Samples of the arterial media were analyzed for MLCK activity and expression. A selective MLCK inhibitor 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML7) were used in hypercholesterolemia rabbit (1 mg/kg body weight). The aortas of high-cholesterol diet rabbits showed an increase in MLCK expression and activity (nearly threefold compare with control) as well as endothelial permeability. ML7 inhibit MLC phosphorylation and MLCK activity (nearly twofold compare with control) and endothelial permeability stimulated by cholesterol. These results indicate for the first time that hypercholesterolemia may be associated with MLCK expression and activity through which endothelial permeability is increased.

Amlodipine Ameliorates Up-Regulation of ET-1 in Left Ventricle of Hypercholesterolemia Rabbits

Objective(s) In addition to antihypertensive effects, amlodipine may exhibit cardiovascular protective effects in heart tissue. The aim of this study was to evaluate the effects of amlodipine and/or high cholesterol diet on blood, heart tissue concentration and mRNA expression of endothelin-1 (ET-1) in male New Zealand white rabbits. Materials and Methods A total of 40 male New Zealand rabbits were divided into four groups: the normal control group, normal group receiving amlodipine, high-cholesterol diet group and high-cholesterol diet with amlodipine group. After 8 weeks, all the animals anesthetized and blood or tissues samples were collected. Results After 8 weeks of a high cholesterol diet, the group with such a diet had a significantly higher ratio of left ventricle (LV) weight to body weight than the control group (P= 0.0001). After treatment with amlodipine for 8 weeks, ET-1 level was reduced considerably in comparison with the control (P= 0.01) and highcholesterol diet groupes (P= 0.01). Amlodipine consumption caused significant reduction (P= 0.01) in the level of ET-1 in heart tissues of high-cholesterol diet group but it had no remarkable effect on the reduction of heart tissue ET-1 in amlodipine group compared with the control group. Conclusion The present study demonstrates that ventricular prepro-ET-1 mRNA quantitatively increases in the highcholesterol diet rabbits which results in development of ventricular hypertrophy. It seems that the treatment with amlodipine retards the progression of LV hypertrophy through attenuation of ET-1 levels independent of lipid changes.

Cloning of rabbit adiponectin and its relationship to age and high-cholesterol diet

Secreted by adipocytes, adiponectin is a collagen-like protein with significant roles in regulating the metabolism of glucose and fatty acids and in preventing atherosclerosis. However, information about adiponectin in rabbit is limited. In this study, we cloned rabbit ADIPOQ gene by RT-PCR using mRNA from adipose tissue and sequenced the open reading frame. The rabbit adiponectin sequence shares approximately 86.39% and 81.45% homology with those of humans and mice respectively, and 85.66% and 85.25% similarity with humans and mice proteins at the amino acid level respectively, based on the translated rabbit sequence and GenBank submissions of other species. We also evaluated ADIPOQ gene mRNA expression in adipose tissue in rabbits fed on high-cholesterol diet and in different age groups by real-time PCR. ADIPOQ gene mRNA expression was significantly different in different age rabbits and correlated positively with the level of plasma HDL in high-cholesterol diet rabbits. These results suggest similar function of ADIPOQ gene in rabbits as in other species and indicate the relationship between ADIPOQ gene mRNA expression and high-cholesterol diet and age.

Effect of amlodipine on blood and aortic tissue concentration of endothelin in male rabbits receiving atherogenic diet

<b>Background:</b> Different factors are involved in the induction and progress of atherosclerosis. One of these factors is endothelin-1. Since, in atherosclerotic vessels, there are certain obvious changes, with abnormality in the transfer of calcium ions, some researchers have suggested that calcium channel blockers can slow down the process of atherosclerosis. In this study, we evaluated the effects of amlodipine and/or a high cholesterol diet on the blood and aortic concentration of endothelin in rabbits.<br><b> Materials and Methods:</b> Thirty-six male New Zealand white rabbits were divided into four groups: the normal control group, normal diet plus amlodipine group, high-cholesterol diet group, and high-cholesterol diet plus amlodipine group. After 8 weeks all animals were anesthetized and blood or tissue samples were collected.<br><b> Results and Conclusions:</b> Eight weeks of amlodipine treatment significantly reduced total cholesterol, low density lipoproteins (LDL), and triglycerides (TG) in the hypercholesterolemic diet group. Although amlodipine treatment tended to enhance HDL/LDL and HDL/cholesterol ratios in the mentioned group, these effects were not statistically significant. The observed significant increase in plasma high density lipoprotein cholesterol (HDL-C) and decrease in TG is considered to be the main effect of amlodipine treatment on the serum lipid profile in the control group. The plasma level of endothelin-1 in the atherosclerotic model group was significantly increased as compared to the control group (<i> P</i> < 0.01). After treatment with amlodipine, the ET-1 level reduced significantly in the control and high-cholesterol diet rabbits (<i> P</i> < 0.01). A high-cholesterol diet induced atherosclerotic lesions and thickening of the intima in the thoracic aorta. Amlodipine consumption reduced atherotic injuries in high-cholesterol diet rabbits. There were no lesions in the normal diet groups or the normal diet with amlodipine group. High cholesterol causes increase in plasma and tissue endothelin. Amlodipine treatment reduced the levels of total cholesterol, LDL, and TG and, in a high lipid intake situation reduced endothelin levels in plasma and aortic tissue. Our data shows that amlodipine treatment may be considered as one of the important interventions for prevention and regression of atherosclerosis.

Attenuation of Tissue P-Selectin and MCP-1 Expression and Intimal Proliferation by AT1 Receptor Blockade in Hyperlipidemic Rabbits

Angiotensin-II (Ang-II) participates in the development and progression of atherosclerosis by activating type 1 (AT1) receptors. In vitro studies show that inflammatory factors, such as P-selectin and MCP-1, which can be upregulated by Ang-II, play an important role in atherogenesis. We examined the effect of AT1 receptor blockade with losartan on the expression of P-selectin and MCP-1 in hypercholesterolemic rabbits. Since AT1 receptor blockade is associated with feedback upregulation of renin-angiotensin system (RAS), we also examined alterations in plasma Ang-II levels by losartan therapy. Male NZW rabbits were fed regular chow (high cholesterol diet or high cholesterol diet + losartan 25 mg/kg/day). As expected, there was a marked intimal proliferation in association with increase in serum cholesterol (P < 0.001). In addition, there was a modest increase in plasma Ang-II levels (P < 0.05), and a significant increase in the expression of AT1 receptors, P-selectin and MCP-1 in aortas of high cholesterol diet rabbits. Concurrent administration of losartan with high cholesterol diet attenuated aortic intimal proliferation induced a fivefold increase in plasma Ang-II levels and caused a marked decrease in expression of P-selectin and MCP-1 without change in serum lipid levels and aortic AT1 receptor expression. These observations in hypercholesterolemic animal models show that AT1 receptor blockade is associated with modulation of P-selectin and MCP-1 expression concurrent with reduction in intimal proliferation. The rise in plasma Ang-II does not appear to limit the potential beneficial effect of losartan.

High resolution miniature trans-esophageal echocardiography is useful to evaluate atherosclerosis and the effects of alacepril in hyper-cholesterol rabbits.

This study tested the efficacy of high resolution miniature transesophageal echocardiography (m-TEE; 3.5 mm-diameter probe, 7.5 MHz, axial resolution of 0.25 mm) in the evaluation of atherosclerotic lesions of the thoracic aorta rabbits exposed to a high cholesterol diet. The effects of the ACE inhibitor Alacepril (90 mg/kg) on atherosclerosis were also assessed in normotensive, high cholesterol-diet rabbits by m-TEE, both in situ and in vitro. Oral treatment with Alacepril was begun on confirmation of atherosclerosis after a three month high cholesterol diet (group AL). Ultrasound examination reliably distinguished the lesions of atherosclerosis in situ. A three month course of Alacepril treatment decreased the systolic and diastolic blood pressures by approximately 20 and 5 mmHg, produced a regression of atherosclerosis and significantly decreased the intimal plus medial thickness compared with hyperlipidemic-controls (group HC) (1.0 + 0.3 vs 1.6 + 0.4 mm, p < 0.02). The intimal surface involvement area in group AL was marginally smaller than in group HC (57 + 23 vs 76 + 23%, p = 0.06). The high dose of Alacepril in this study did not affect the serum levels of t-cholesterol, HDL-C, LDL-C, triglycerides, or apoproteins A-I and B. These results suggest that Alacepril can produce regression of atherosclerosis, without changing circulating lipoprotein or apoprotein levels. Further miniature TEE offers high repeatability and is useful both in situ and in vitro for determining changes in arterial wall thickness and the severity of atherosclerosis.

Lipid characterization in an animal model of atherosclerosis using NMR spectroscopy and imaging

High resolution 1H and 13C NMR spectroscopic measurements including 1H/13C 2D correlation and magnetic resonance imaging (MRI) studies, have been carried out on intact rabbit aortic tissues ex vivo using animals fed both normal and high cholesterol diets. The results show that 1H and 13C NMR spectroscopy can distinguish mobile lipids and can differentiate between normal triglyceride content and cholesterol-enriched lipids, in intact tissue, There were considerable differences in the level of deposition of cholesteryl esters in animals all fed on the same diet. Confirmation is presented of temperature-dependent differences in mobility and organization between the triglycerides found in control tissue and the cholesteryl esters found in aortas from high lipid diet animals. Water-suppressed MRI showed evidence of lipid accumulation in the aortas of high cholesterol diet rabbits. It is concluded that the hypercholesterolaemic rabbit model of atherosclerosis, coupled with such NMR methods, may offer a noninvasive method of monitoring disease development, allowing the evaluation of the effect of therapeutic agents on the progress of atherosclerosis.