Hydrophobic surfactant inhibits hypercholesterolemia in pair-fed rabbits on a cholesterol-free, low-fat diet

Poloxalene, a hydrophobic surfactant, is known to prevent hypercholesterolemia in animals fed a high-fat, high-cholesterol diet. It has not been demonstrated, however, whether this agent is of benefit when hypercholesterolemia is induced in animals by means other than the feeding of a high-fat diet. In this study, hypercholesterolemia was produced in rabbits by feeding a low-fat, cholesterol-free diet with dietary protein supplied by casein for a period of 8 weeks. Controls were given this diet without poloxalene and experimentals were given the diet with poloxalene. Total serum cholesterol levels increased in both groups, but the rise was greater for the control group. Lipoprotein analysis performed at the conclusion of the study showed significantly greater low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol levels in the control group as compared to the experimental group. Total protein and apolipoprotein B (apo B) were also greater in control LDL. It was concluded that poloxalene favorably affects this model of hypercholesterolemia as total serum cholesterol, LDL cholesterol, and LDL apo B were all less and the HDL cholesterol to LDL cholesterol ratio was higher in surfactant-treated rabbits.     

泰脂安对高胆固醇血症兔血脂和主动脉内膜中巨噬细胞的影响

目的 观察泰脂安对高胆固醇血症兔血脂和主动脉内膜中巨噬细胞的影响,以探讨泰脂安在调脂和抗动脉粥样硬化中的作用.方法 给16只新西兰健康雄兔高胆固醇饮食,8周后随机给予泰脂安1.0 g·kg-1·d-1,8只为泰脂安组;淀粉干预25.0 mg·kg-1,8只为对照组;另8只兔每天分别进食普通饲料120 g(正常饮食组).6周后测定血清血清总胆固醇(TC)和低密度脂蛋白胆固醇(LDI-C),采用免疫组织化学法测定主动脉内膜中巨噬细胞阳性数.结果 与正常饮食组比较,对照组和泰脂安组TC[分别为(1.8±0.7)mmol/L与(27.8±1.0)mmol/L和(26.5±2.5)mmol/L]、LDL-C[(0.6±0.2)mmol/L与(14.5±3.3)mmol/L和(13.7±4.1)mmol/L]升高,均为P<0.05.经泰脂安干预后,主动脉粥样硬化斑块中巨噬细胞表达下降[(71.8±15.5)%与(53.8±12.7)%,P<0.05];TC[(19.0±4.3)mmol/L]和LDL-C[(11.6±2.2)mmol/L]水平下降(P<0.05).结论 泰脂安能有效地调节血脂和降低动脉粥样硬化程度.     

Attenuation of the development of hypercholesterolemic atherosclerosis by thymoquinone

Thymoquinone (TQ), derived from Nigella sativa seed, is an antioxidant. The present study investigated whether TQ attenuates the development of atherosclerosis, and/or reduces the serum lipid levels and oxidative stress in rabbits. New Zealand white female rabbits were assigned to four groups of six animals each: group I, control; group II, 1% cholesterol diet; group III, 1% cholesterol plus TQ (10 mg/kg/day; through a nasogastric tube) diet; and group IV, 1% cholesterol plus TQ (20 mg/kg/day; through a nasogastric tube) diet. Blood samples were collected at baseline and after four and eight weeks on the experimental diets for measurement of serum lipids, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), TC/HDL-C ratio and oxidative stress biomarkers (malondialdehyde [MDA] and protein carbonyls). At the end of the eight weeks, the aorta was removed for the assessment of atherosclerotic changes, MDA and protein carbonyls. Group II animals developed atherosclerosis (45%±11% of the intimal surface of aorta was covered with atherosclerotic plaques), which was associated with an increase in the serum TC, TG, LDL-C, HDL-C, TC/HDL-C, MDA and protein carbonyls. In group III, TQ decreased serum TC, LDL-C, MDA and protein carbonyls by 26%, 29%, 85% and 62%, respectively, and aortic MDA by 73%, which was associated with a 40% reduction of the development of aortic atherosclerosis. The higher dose of TQ in group IV had effects similar to the lower dose (group III), except that this dose further decreased serum TG. It is concluded that TQ attenuates hypercholesterolemic atherosclerosis and this effect is associated with a decrease in serum lipids and oxidative stress.     

Ischemic preconditioning and infarct mass: the effect of hypercholesterolemia and endothelial dysfunction

In an experimental model of atherosclerosis we investigated whether rabbits fed an atherogenic diet (0.25% cholesterol, 3% coconut oil) develop endothelial dysfunction accompanied with increased infarct mass compared to normal fed rabbits and, whether hypercholesterolemia would interfere with the beneficial outcome of ischemic preconditioning observed in normal rabbits. After four weeks on either a normal or an atherogenic diet, New Zealand White rabbits (n=7 in each group) were subjected to 30 min of myocardial ischemia by occlusion of a branch of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (infarct studies). For ischemic preconditioning experiments, LAD was additionally occluded twice for 5 min followed by 10 min reperfusion before the long-lasting (30 min) ischemia. Infarct mass was evaluated by triphenyl-tetrazolium staining. Besides the assessment of aortic endothelium-dependent function and NO-release, aortic and cardiac vessels were inspected for atherosclerotic lesions. Total cholesterol serum levels in rabbits on an atherogenic diet were significantly higher (15.3+/-2.7 mmol/L) than those on a standard diet (0.65+/-0.08 mmol/L). The aortas and heart vessels were without any histological evidence of atherosclerosis, whereas endothelial dysfunction and significantly reduced calcium-ionophore stimulated endothelial NO-release were found in isolated aortic rings of hypercholesterolemic animals. Rabbits on a standard diet showed an infarct mass (related to the area at risk) of 41+/-33%, which was reduced to 21+/-2% by ischemic preconditioning (49% decrease, p<0.05). In rabbits on an atherogenic diet, infarct mass was significantly increased to 63+/-3% (52% increase versus standard diet). Interestingly, hypercholesterolemia did not affect the beneficial influence of ischemic preconditioning; infarct mass (21+/-3%, p<0.05 vs hypercholesterolemia) was similar to rabbits on a standard diet with ischemic preconditioning. Our results show that experimental hypercholesterolemia increases infarct mass in nonpreconditioned hearts but it does not interfere with the reduction of infarct mass elicited by preconditioning. This may suggest that NO produced by the endothelium is not a prime factor in the cardioprotective mechanism of preconditioning.     

Verapamil and diet halt progression of atherosclerosis in cholesterol fed rabbits

Summary The present study was designed to evaluate the effects of oral verapamil and normal diet on regression of atherosclerotic plaque in cholesterol fed rabbits. Forty-three rabbits were separated into 6 groups and studied for 24 weeks. All groups had a cholesterol diet for the first 12 weeks. Group I was then sacrificed and had 38±23% (mean ± standard deviation) aortic plaque. During weeks 13 to 24, group II (cholesterol diet) and group III (normal diet) had similar percentages of aortic plaque: 80±7% and 78±22%, respectively. Group IV (cholesterol diet), was treated with oral verapamil for 24 weeks and had significantly less plaque (54±10%) than group II, (80±7%). In group V (cholesterol diet), treatment with oral verapamil during weeks 13 to 24 did not significantly reduce plaque (70±23%), compared to group II, (80±7%). In group VI, normal diet and verapamil during weeks 13 to 24 significantly reduced aortic plaque (46±25) when compared to group II (80±7%). Group VI (46%) did not differ from group I (38%). It is concluded that verapamil combined with a normalized diet can halt the progression of aortic atherosclerosis after a 12 week atherogenic diet in rabbits. Verapamil or diet alone was ineffective in the second 12 weeks. Overall, verapamil was effective in preventing atherosclerosis but was ineffective in causing regression of atherosclerosis.Supported in part by Susan and Don Schleicher and the George D. Smith Fund.     

Effects of anticalcifying and antifibrobrotic drugs on pre-established atherosclerosis in the rabbit.

The effects of the anticalcifying drug, ethane-hydroxydiphosphonate (EHDP) and the inhibitors of collagen biosynthesis, colchicine, penicillamine and azetidine were studied in the rabbit with pre-established atherosclerosis. The drugs were administered with a cholesterol-free diet (regression diet) for 8 weeks following the induction of atherosclerosis by feeding a hypercholesterolemic diet containing 2% cholesterol and 8% peanut oil for 8 weeks. The extent and severity of aortic atherosclerosis, as revealed by the morphological and biochemical findings, increased significantly during the regression period. In rabbits treated with EHDP (5 mg/kg/day) the aorta had fewer gross lesions and contained significantly less cholesterol, collagen and elastin than did the aorta of the rabbits fed the regression diet alone. These changes were associated with a significant reduction in aortic calcium caused by EHDP. The aortic content of cholesterol, collagen and elastin in the EHDP-treated rabbits, although less than that of the rabbits fed the regression diet alone, was about the same as that of the rabbits fed a high cholesterol diet for 8 weeks. Both colchicine (0.2 mg/kg/day) and penicillamine (100 mg/kg/day) had a selective action on the induced plaques in that they suppressed the fibrous proliferation in the lesions without preventing lipid and calcium accumulation in the lesions. Neither colchicine nor penicillamine reduced the extent of aortic atherosclerosis as determined by gross examination of the vessel. Azetidine had no significant effect on the pre-established atherosclerotic lesions. The lipid, fibrous protein and calcium content of the aorta of the azetidine-treated animals was not significantly different from that of the untreated animals. The biochemical findings in the aorta were consistent with the microscopic changes.     

Cholesterol feeding increases plasma and aortic tissue cholesterol oxide levels in parallel: further evidence for the role of cholesterol oxidation in atherosclerosis.

To determine the relationship between plasma and arterial wall oxysterols, plasma and aortic tissue from 7 New Zealand White rabbits fed a high cholesterol (1%) diet for 6 weeks was compared to plasma and aortic tissue from 7 normocholesterolemic rabbits fed standard rabbit chow. Cholesterol and cholesterol oxide fractions were isolated and analyzed by gas chromatography. Normocholesterolemic plasma and aortic tissue contained low levels of cholest-5-ene-3 beta, 7 alpha-diol, cholesta-3,5-dien-7-one, 5,6 alpha-epoxy-5 alpha-cholestan-3 alpha-ol, cholest-5-ene-3 beta, 7 beta-diol, and 5 alpha-cholestane-3 beta, 5,6 beta-triol while hypercholesterolemic plasma and atherosclerotic aorta contained significantly higher levels (P less than 0.05) of these products. Furthermore, 5,6 beta-epoxy-5 alpha-cholestan-3 beta-ol not found in normocholesterolemic plasma or aortic tissue was present in substantial amounts in both hypercholesterolemic plasma and atherosclerotic aortic tissue. Cholest-5-ene-3 beta,25-diol and 3 beta-hydroxycholest-5-ene-7- one not present in normocholesterolemic aorta were present in the atherosclerotic aorta. The oxysterol chromatographic patterns of normocholesterolemic plasma and normocholesterolemic aortic tissue were similar to each other as were the oxysterol chromatographic patterns of hypercholesterolemic plasma and atherosclerotic aortic tissue. The chromatographic patterns between the normocholesterolemic and hypercholesterolemic samples differed however. Possible absorption of the low levels of cholesterol oxides present in the cholesterol feed could account for the elevation of only some of the oxysterols. We conclude that cholesterol oxides exist at some basal level in normocholesterolemia and that these levels are increased by cholesterol-feeding which results in hypercholesterolemia. Our findings demonstrate that there is a strong relationship between plasma and aortic arterial wall levels of cholesterol oxides and suggest that in addition to exogenous sources, formation of cholesterol oxides proceeds via free radical oxidation acting upon elevated cholesterol levels resulting in the accumulation of these potentially cytotoxic and atherogenic products.     

Experimental hypercholesterolemia induces apoptosis in the aortic valve

BACKGROUND AND AIM OF THE STUDY: Aortic valve disease is presently the number one indication for valve replacement in the United States, yet its molecular mechanisms remain unknown. As apoptosis (programmed cell death) occurs in degenerative disease states, it was postulated that experimental hypercholesterolemia is associated with apoptosis in rabbit aortic valves. METHODS: New Zealand White rabbits (n = 8) were fed a 1% cholesterol diet for 12 weeks; control rabbits (n = 8) were fed a normal diet. After sacrifice of the animals, the aortic valves were dissected. Apoptosis was identified in the valvular lesion by TdT-mediated dUTP-biotin nick end-labeling (TUNEL) technique, and confirmed with transmission electron microscopy. The number of apoptotic cells was measured by computed morphometry. RESULTS: Valves from hypercholesterolemic rabbits showed an increase in apoptosis. TUNEL staining was identified in the atherosclerotic layer of hypercholesterolemic valves (0.1% of cells), but not in the cells of controls (p <0.0001). CONCLUSION: Apoptosis is increased in rabbit aortic valves during experimental hypercholesterolemia. If fatal cellular degeneration occurs in hypercholesterolemic valve disease, these data suggest that apoptosis may play a role in the mechanism of valvular disease.     

ISCHEMIC PRECONDITIONING AND INFARCT MASS: THE EFFECT OF HYPERCHOLESTEROLEMIA AND ENDOTHELIAL DYSFUNCTION

In an experimental model of atherosclerosis we investigated whether rabbits fed an atherogenic diet (0.25% cholesterol, 3% coconut oil) develop endothelial dysfunction accompanied with increased infarct mass compared to normal fed rabbits and, whether hypercholesterolemia would interfere with the beneficial outcome of ischemic preconditioning observed in normal rabbits. After four weeks on either a normal or an atherogenic diet, New Zealand White rabbits (n=7 in each group) were subjected to 30 min of myocardial ischemia by occlusion of a branch of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (infarct studies). For ischemic preconditioning experiments, LAD was additionally occluded twice for 5 min followed by 10 min reperfusion before the long-lasting (30 min) ischemia. Infarct mass was evaluated by triphenyl-tetrazolium staining. Besides the assessment of aortic endothelium-dependent function and NO-release, aortic and cardiac vessels were inspected for atherosclerotic lesions. Total cholesterol serum levels in rabbits on an atherogenic diet were significantly higher (15.3±2.7 mmol/L) than those on a standard diet (0.65±0.08 mmol/L). The aortas and heart vessels were without any histological evidence of atherosclerosis, whereas endothelial dysfunction and significantly reduced calcium-ionophore stimulated endothelial NO-release were found in isolated aortic rings of hypercholesterolemic animals. Rabbits on a standard diet showed an infarct mass (related to the area at risk) of 41±3%, which was reduced to 21±2% by ischemic preconditioning (49% decrease, p<05). In rabbits on an atherogenic diet, infarct mass was significantly increased to 63±3% (52% increase versus standard diet). Interestingly, hypercholesterolemia did not affect the beneficial influence of ischemic preconditioning; infarct mass (21±3%, p<0.05 vs hypercholesterolemia) was similar to rabbits on a standard diet with ischemic preconditioning.

Our results show that experimental hypercholesterolemia increases infarct mass in nonpreconditioned hearts but it does not interfere with the reduction of infarct mass elicited by preconditioning. This may suggest that NO produced by the endothelium is not a prime factor in the cardioprotective mechanism of preconditioning.     

Relationship between serum cholesterol and thromboxane B2 levels and atherosclerotic lesions in rabbits fed a high cholesterol diet

The aim of our study was to evaluate the effects of diet induced hypercholesterolemia and associated atherosclerosis in rabbits on serum thromboxane B2 levels. We have determined thromboxane B2 in serum of hypercholesterolemic rabbits with atherosclerosis and in normocholesterolemic rabbits without atherosclerosis. Our data show only a mildly higher serum thromboxane levels in hypercholesterolemic rabbits and extensive atherosclerosis than in controls without atherosclerosis. In conclusion, these results show that diet induced hypercholesterolemia was not associated with thromboxane B2 generation, in spite of a diffuse experimental atheromatosis.     

依那普利、硝苯吡啶和洛伐他汀对家兔实验性动脉粥样硬化的影响

为探讨依那普利、硝苯吡啶和洛伐他丁对高胆固醇兔动脉粥样硬化的影响,本文将３７只新西兰雄性白兔随机分为正常饮食组、胆固醇组、依那普利组、硝苯吡啶组和洛伐他丁组,后三组在高胆固醇饮食的基础上给相应药物。喂养１６周后处死所有动物,测定主动脉组织中胆固醇含量及斑块面积比。结果发现,依那普利和硝苯吡啶不影响血脂水平,洛伐他丁有降低胆固醇,甘油三脂及低密度脂蛋白的作用,洛伐他丁组低密度脂蛋白／高密度脂蛋白的比     

Onion, garlic, and experimental atherosclerosis.

Forty-two healthy male albino rabbits weighing around 1 Kg were divided into 4 groups. Group I (8)- fed on normal stock diet, Group II (8)- fed on stock diet plus cholesterol (0.5 gm in 5 ml of olive oil). Group III (15)- received stock diet plus cholesterol plus garlic (0.25 gm) juice. Group IV (11)- received stock diet plus cholesterol plus onion (2.5 gm) juice. The animals were closely observed and followed for 16 weeks. Approximately every 4 weeks, blood samples were collected for estimation of various parameters (S. cholesterol, S. triglycerides, S. lipoproteins, S. phospolipids, and fibrinolytic activity). At the end of experiment, animals were sacrificed and degree of aortic atherosclerosis was graded (grade 0 to 4) in different groups and compared. Experimental study revealed that both garlic and onion (garlic more than onion) had significant effect in inhibiting the rise in S. cholesterol, S. triglycerides, S. beta lipoproteins, and S. phospolipids and significant effect in enhancing the fibrinolytic activity. The beta: alpha ratio was altered favourably and the ratio was kept close to normal. As regards the degree of aortic atherosclerosis as seen on post mortem, it was significantly less in garlic and onion group when compared with pure cholesterol group.     

Experimental aortic valve stenosis in rabbits

OBJECTIVES: We studied a known rabbit model of atherosclerosis to assess the effect of a hypercholesterolemic diet on aortic valve morphology and function. We also evaluated the effects of the combination of this diet with vitamin D supplements on the development of the disease and the occurrence of valve calcification. BACKGROUND: Aortic valve stenosis (AVS) is the most common valvular heart disease. Recent observations have suggested a link between atherosclerosis and the development of AVS. However, until now, there has been no solid direct proof of this potential link. METHODS: Rabbits were divided in three groups: 1) no treatment; 2) cholesterol-enriched diet (0.5% cholesterol); and 3) cholesterol-enriched diet plus vitamin D(2) (50,000 IU/day). Echocardiographic assessment of the aortic valve was done at baseline and after 12 weeks of treatment. The aortic valve area (AVA) and maximal and mean transvalvular gradients were recorded and compared over time. RESULTS: Control animals displayed no abnormalities of the aortic valve. Despite important increases in blood total cholesterol levels, animals in group 2 did not develop any significant functional aortic valve abnormality over 12 weeks. However, eight of 10 of the animals in group 3 developed a significant decrease in AVA (p = 0.004) and significant increases in transvalvular gradients (p = 0.003). CONCLUSIONS: This study supports a potential link between atherosclerosis and the development of AVS. The differences noted between hypercholesterolemic animals with or without vitamin D(2) supplementation imply a significant role of calcium in the development of AVS, meriting further attention.     

Probucol reduces plasma and aortic wall oxysterol levels in cholesterol fed rabbits independently of its plasma cholesterol lowering effect.

To understand further the antiatherogenic mechanism of probucol, the antioxidant effect of this agent was studied on specific cholesterol oxidation products in plasma and aortic wall in equally hypercholesterolemic New Zealand white rabbits. In order to maintain equal plasma total cholesterol levels, five control rabbits (C group) received a 1% followed by a 0.5% cholesterol enriched diet, while the probucol treated rabbits (C+P group) received a graded increase in the cholesterol supplemented diet from 1% to 3%; probucol supplementation was constant at 1%. After 9 weeks of feeding, the plasma oxysterols, cholest-5-ene-3 beta,7 alpha-diol, cholest-5-ene-3 beta,7 beta-diol, 5,6 beta-epoxy-5 alpha-cholestan-3 beta-ol, 5,6 alpha-epoxy-5 alpha-cholestan-3 alpha-ol and 5 alpha-cholestane-3 beta,5,6 beta-triol significantly increased over baseline levels in both experimental groups. However, the increase in all these products in plasma was 20-60% less in the C+P group than the C group (P < 0.05). Furthermore, the C+P aortic wall cholesterol oxide concentrations were 50-90% less than the C group (P < 0.05). The oxysterol pattern of the aortic wall was similar to plasma. Additionally, the aortic wall cholesterol content in the C+P group was 50% less than the C group (P < 0.05). The plasma cholesterol levels were not significantly different at any time point during the study and the cholesterol oxide content in the diets was the same. These results are consistent with the contention that the antioxidant properties of probucol serve as the basis for its antiatherogenic effects in vivo.     

Purpurogallin in the prevention of hypercholesterolemic atherosclerosis

Effects of purpurogallin (PPG), an antioxidant on high cholesterol diet-induced atherosclerosis, and changes in blood lipid profile and lipid peroxidation product malondialdehyde (MDA), aortic tissue MDA, chemiluminescence (M-CL), a marker for antioxidant reserve and antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-P_x)] were investigated in rabbits. The rabbits were divided into three groups: Group I, regular rabbit chow; Group II, same as Group I+cholesterol (1%); and Group III, same as Group II+PPG (14 mg/kg, orally, daily). Serum concentrations of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and blood MDA were measured before and after 4 and 10 weeks on the respective diets. The aorta was removed at the end of 10 weeks for assessment of atherosclerotic changes, MDA concentration, M-CL, and antioxidant enzymes. Coronary arteries were also examined for atherosclerotic changes. Serum TC, LDL-C, and LDL-C/HDL-C ratio increased whereas HDL-C decreased in Group II and their values were similar in Groups II and III. Aortic tissue MDA, M-CL, CAT, and GSH-P_x activity increased in Group II but these values in Group III were lower than in Group II except for MDA which was greater in Group III than in Group II. Atherosclerotic changes were greater in Group II than in Group III. Histological changes were similar in Groups II and III. Atherosclerotic changes were also observed in the coronary arteries of Groups II and III, however, they were less in Group III than in Group II. Increased levels of aortic MDA and decreased levels of antioxidant reserve, which were associated with the development of atherosclerosis, suggest a role for oxygen radicals in the pathogenesis of hypercholesterolemic atherosclerosis. The protection afforded by PPG, which was associated with reversal of the antioxidant reserve to control level, in spite of hypercholesterolemia, supports the hypothesis that oxygen radicals are involved in the development of hypercholesterolemic atherosclerosis. These results suggest that PPG retard the development of hypercholesterolemic atherosclerosis because of its antioxidant activity without lowering blood cholesterol level.     

Lack of decreased contractility in hearts from atherosclerotic rabbits

Previous studies have suggested that the contractility of isolated heart muscle removed from rabbits made hypercholesterolemic is decreased. As part of a study evaluating the effects of high-lipid diets on aortic atherosclerosis, we evaluated the contractility of perfused rabbit hearts. Six rabbits were placed on a high-lipid diet for 3 months with cholesterol levels rising to 1700 ± 400 mg %. After they were killed, their hearts were studied in an isolated, perfused, working heart apparatus at 37° C. Control animals included six rabbits matched for age, six rabbits matched for weight, and six young rabbits. Measurements were made of developed pressure, maximum dP/dt, oxygen extraction, oxygen consumption, and coronary blood flow. There were no significant differences between the contractile parameters of hearts from any group. Since previous studies were conducted with isolated heart muscle at a lower temperature, it may be that hypercholesterolemic effects on membranes may have led to the previous findings of reduced contractility. Our results suggest that hypercholesterolemia, per se, does not decrease cardiac contractility in the rabbit fed a high-lipid diet.     

A high fat/high carbohydrate diet induces aortic valve disease in C57BL/6J mice.

OBJECTIVES: The purpose of this study was to compare aortic valve function and morphology in adult wild-type (WT) mice and in low-density lipoprotein receptor-deficient (LDLr-/-) mice fed or not fed a high-fat/high-carbohydrate (HF/HC) diet. BACKGROUND: Observations suggest a link between degenerative aortic valve stenosis (AS) and atherosclerosis. Aortic valve stenosis has been successfully induced in animal models of extreme hypercholesterolemia, but these models are less relevant to humans. It is not known if a proatherogenic HF/HC diet without added cholesterol could have the same negative impacts. METHODS: Forty C57BL/6J mice were divided into four groups: WT + normal diet, WT + HF/HC diet, LDLr-/- with a normal diet, and LDLr-/- with a HF/HC diet. Aortic valve function and histology were evaluated by echocardiography after four months. RESULTS: Wild-type mice on a HF/HC diet became mildly hypercholesterolemic, obese, and hyperglycemic. As expected, LDLr-/- mice became severely hypercholesterolemic. Both WT and LDLr-/- mice on a HF/HC diet displayed smaller valve areas and higher transvalvular velocities (p < 0.01) after four months. Aortic valve leaflets were thicker and infiltrated with lipids and macrophages in both HF/HC groups. CONCLUSIONS: A HF/HC diet in mice results in significant aortic valve abnormalities. Putting WT mice on a HF/HC diet reproduced a combination of atherogenic factors (obesity, mild dyslipidemia, and hyperglycemia) more commonly encountered in humans than isolated severe hypercholesterolemia. Severe hypercholesterolemia was not a prerequisite in our model. This experimental model suggests that AS development is multifactorial and that hypercholesterolemia should not be the only target in this disease.     

Effect of hypercholesterolemia on vascular reactivity in the rabbit. I. Endothelium-dependent and endothelium-independent contractions and relaxations in isolated arteries of control and hypercholesterolemic rabbits

We studied the effects of hypercholesterolemia on vascular responsiveness in different arteries isolated from rabbits: control groups of rabbits and groups receiving the atherogenic diet consisted of eight animals each. In the arteries, 16 weeks of cholesterol-rich (0.3%) diet evoked intimal lesions which were more pronounced than those noted after 8 weeks of hypercholesterolemia; the aortic arch was affected significantly more by the lesions than the abdominal aorta and the pulmonary artery. Segments of the arteries were mounted in organ chambers for isometric tension recording or for measurement of the endothelium-derived relaxant factor. Contractions caused by acetylcholine and prostaglandin F2 alpha were not altered by the hypercholesterolemia; those evoked by serotonin were moderately augmented only in the aortic arch of hypercholesterolemic rabbits. As the degree of intimal lesion formation increased, the contractions to norepinephrine and clonidine were progressively inhibited. The endothelium-independent relaxations to nitroglycerin were inhibited in only the most severely affected arteries; the endothelium-dependent relaxations to acetylcholine and adenosine triphosphate were progressively inhibited as the degree of fatty streak formation augmented. Thus, in the aortic arch, the relaxations to 3 X 10(-6) M acetylcholine, expressed as percent of the initial contraction, decreased from 86.7 +/- 3.3% in control tissues to 16.3 +/- 8.6% in the 16-week hypercholesterolemic vessels; in the abdominal aortas these relaxations averaged 93.5 +/- 2.2% in control vessels and 72.0 +/- 6.9% in the hypercholesterolemic tissues. The acetylcholine-induced release of endothelium-derived relaxant factor from the abdominal aorta was not significantly affected by the hypercholesterolemia. We conclude from these studies that in arteries obtained from hypercholesterolemic rabbits: the contractions caused by serotonergic mechanisms tend to be augmented, while those to alpha-adrenergic activation are decreased, the endothelium-independent relaxations are modified only in the more severely affected arteries, and the endothelium-dependent relaxations are progressively inhibited as the degree of fatty streak formation augments, probably because a step subsequent to the release of endothelium-derived relaxant factor is altered.     

Oxygen free radicals as a mechanism of hypercholesterolemic atherosclerosis: Effects of probucol

We investigated the effects of high cholesterol diet in the presence and absence of probucol on the genesis of atherosclerosis, the blood lipid profile, aortic tissue lipid peroxidation product malondialdehyde (MDA), and aortic tissue chemiluminescence (CL) a marker for antioxidant reserve in rabbits. Five groups each of 10 rabbits were studied: group I, regular rabbit chow; group II, as I + cholesterol (0.5%); group III, as I + cholesterol (0.5%) and probucol (0.5 gm/kg/day); group IV, as I + cholesterol (1%), and group V, as I + cholesterol (1%) and probucol (0.5 gm/kg/day). Blood concentrations of triglyceride (TG), total cholesterol (TC), high density lipoproteincholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), very low density lipoprotein-cholesterol (VLDL-C) were measured at monthly intervals for 4 months. The aorta was removed at the end of the protocol for assessment of atherosclerotic changes (gross and microscopic), MDA concentration and CL. TC, LDL-C, LDL-C/HDL-C ratio increased in all the groups except group I, while VLDL-C increased in group II only. HDL-C decreased in groups III, IV and V but remained unchanged in groups I and II. There was a decrease in HDL-C and VLDL-C components and an increase in LDL-C components of total cholesterol in all the groups II, III, IV and V, the changes being greater in group IV than in group II. Probucol did not appreciably affect the changes in lipid profile except that it decreased HDL-C significantly. Aortic tissue MDA increased in groups II, IV and V to a similar extent. Aortic CL which was measured only in groups I, IV and V increased to similar extent in the latter two groups. Atherosclerotic changes were greater in group II than in group III but similar to that in groups IV and V. Histological changes were practically similar in groups II, III, IV and V. The increased levels of aortic MDA and CL, which were associated with development of atherosclerosis, suggest a role for oxygen free radicals in the pathogenesis of hypercholesterolemia-induced atherosclerosis. Protection afforded by probucol was associated with a decrease in aortic MDA in spite of hypercholesterolemia. Ineffectiveness of probucol in 1% cholesterolfed rabbits was associated with its inability to reduce MDA and increase antioxidant reserve. These findings further support for the hypothesis that oxygen free radicals are involved in the genesis and maintenance of hypercholesterolemic atherosclerosis.     

辛伐他汀的调脂及抗动脉粥样硬化作用

采用食饵性兔动脉粥样硬化为模型 ,以舒降之为阳性对照药 ,研究辛伐他汀的调脂及抗动脉粥样硬化作用。将 5 6只雄性新西兰兔 (体重 1.96± 0 .16kg)随机分为对照组 (颗粒饲料 12 0～ 15 0g d ,n =14 )、动脉粥样硬化模型组 [颗粒饲料 +胆固醇 0 .5g (kg·d) ,n =14 ]、舒降之组 [颗粒饲料 +胆固醇 +舒降之片 5mg (kg·d) ,n =14 ]和辛伐他汀组 [颗粒饲料 +胆固醇 +辛伐他汀片 5mg (kg·d) ,n =14 ]。在实验前、实验第 8、12周末分别测定血清总胆固醇和甘油三酯 ,并分别处死 7只兔取主动脉染色测定主动脉粥样硬化斑块面积。结果发现 ,与对照组相比 ,第8、12周末时动脉粥样硬化模型组血清总胆固醇和甘油三酯均显著增高 ,总胆固醇第 8周末为 14 .86± 4 .15mmol L ,第 12周末时为 18.8± 7.6 8mmol L ;甘油三酯第 8周末为 1.83± 0 .4 9mmol L ,第 12周末时为 2 .5 9± 0 .6 3mmol L。第8、12周末时对照组主动脉粥样硬化斑块面积均为零 ,而动脉粥样硬化模型组主动脉粥样硬化斑块面积分别为 35 .2 9%± 9.4 1%和 4 2 %± 9.6 9% ;辛伐他汀组和舒降之组血清总胆固醇和甘油三酯及主动脉粥样硬化斑块面积均显著低于同期动脉粥样硬化模型组 (P <0 .0 1) ,且该两组同期总胆固醇和甘油三酯及主动脉粥样硬化斑块面