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.     

Influence of fish protein as compared to casein and soy protein on serum and liver lipids, and serum lipoprotein cholesterol levels in the rabbit

Serum and hepatic cholesterol and triglyceride levels, and serum lipoprotein cholesterol were investigated in rabbits fed fish protein as compared to casein and soy protein as part of a 20% protein, low fat, cholesterol-free, semi-purified diet. A nonpurified diet was used as a control. After a 28-day experimental period, rabbits fed casein developed hypercholesterolemia compared to those fed the soy protein diet. Serum cholesterol levels of rabbits fed fish protein was intermediate and not different from that of the casein or the soy protein group. However, serum triglycerides were higher in the fish group than in the casein group. Feeding of fish protein resulted in a reduction of hepatic cholesterol compared to casein, indicating no direct relationship between serum and hepatic cholesterol. In addition, fish protein induced a decrease of cholesterol in the low density lipoproteins (LDL) compared to casein and an increase of cholesterol in the high density lipoproteins (HDL) compared to casein and soy protein. Reduction in LDL-cholesterol (LDL-C) and elevation in HDL-cholesterol (HDL-C) caused a 10-fold decrease in the LDL-C/HDL-C ratio of fish protein fed rabbits compared to those fed casein. This ratio was similar to that observed with soy protein which was also lower than the ratio of the casein group. Thus, since the LDL-C/HDL-C ratio has been shown to be a good indicator of the atherosclerosis risk, these results suggest that fish protein, as well as soy protein, may reduce the risk of atherosclerosis in rabbits, compared to casein.     

Hydrophobic surfactant effects on aortic cholesterol accumulation and atherosclerosis in hypercholesterolemic rabbits

Studies were performed in hypercholesterolemic rabbits to determine whether the hydrophobic surfactant, Poloxalene 2930 (Pol), is of benefit under these conditions. Lipoprotein analyses plus chemical and morphologic studies of the aorta were performed to evaluate the results. In one study, rabbits were made hypercholesterolemic by dietary means and then divided into two groups and given a cholesterol-free diet with one group additionally given Pol with treatment continued for 10 weeks. Pol treatment resulted in less atherosclerosis but the mechanism for this effect was not apparent from lipoprotein analysis. In the other study 3 groups of rabbits were given a cholesterol-rich diet for 16 weeks. Two groups received Pol supplement with one of these groups receiving a dose that was too small to prevent hypercholesterolemia. In this group plus the group on diet alone comparable degrees of hypercholesterolemia were maintained throughout the study. Lipoprotein abnormalities were similar in these two groups except that those on Pol had a more normal cholesterol to apolipoprotein B ratio. The amount of atherosclerosis in both groups was mild but aortic cholesterol content was much less for the Pol group. It is concluded that Pol limits cholesterol accumulation in the aortic wall of hypercholesterolemic rabbits and can retard the development of atherosclerosis.     

Casein-induced hypercholesterolemia in rabbits: distribution of cholesterol, triglycerides and phospholipids between serum and liver

Replacement of soy protein by casein in the cholesterol-free, semipurified diet of rabbits caused hypercholesterolemia within 7 days. After 36 days, the serum of casein-fed rabbits displayed elevated levels of free and esterified cholesterol and phospholipids, but not of triglycerides. Most of the excess of serum cholesterol in the casein group was localized in the LDL fraction, but there were marked variations in the density profile of the serum lipoproteins between individual rabbits. Dietary casein induced an increased content in liver of free and esterified cholesterol, but not of phospholipids and triglycerides. The molar ratio of free to esterified cholesterol in the liver was decreased by casein. In contrast, feeding casein resulted in an increase of this ratio in the serum.     

Transgenic overexpression of human lecithin: cholesterol acyltransferase (LCAT) in mice does not increase aortic cholesterol deposition

Results from several atherosclerosis studies using morphometric procedures have proven controversial with regard to whether over-expression of human LCAT in transgenic (Tg) mice is atherogenic. The purpose of the present study was to determine the effect of 10-fold over-expression of human LCAT on aortic free and esterified cholesterol (EC) deposition as well as plasma lipoprotein cholesteryl ester (CE) fatty acid composition in mice fed an atherogenic diet containing cholic acid. C57Bl/6 (control) and human LCAT-Tg mice were fed chow or an atherogenic diet (15% of calories from palm oil, 1.0% cholesterol and 0.5% cholic acid) for 24 weeks before measurement of aortic cholesterol content. Compared with the chow diet, control and LCAT-Tg mice fed the atherogenic diet had a 2-fold increase in plasma total, free and EC, a 7-fold increase in plasma apoB lipoprotein cholesterol, and a 40-50-fold increase in hepatic cholesterol content. The aortic EC content was increased in control (0.7 vs. 1.2 mg/g protein) and LCAT-Tg (0.3 vs. 1.5 mg/g protein) mice fed the atherogenic diet compared with those consuming the chow diet; however, there was no difference in aortic free (14.4+/-6.8 vs. 18.5+/-7.7 mg/g protein) or esterified (1.2+/-1.0 vs. 1.5+/-1.2 mg/g protein) cholesterol content between atherogenic diet-fed control and LCAT-Tg mice, respectively. LCAT-Tg mice fed the atherogenic diet had a 2-fold increase in the ratio of saturated+monounsaturated to polyunsaturated CE species in plasma apoB lipoproteins compared with control mice (9.4+/-2.4 vs. 4.9+/-0.7). We conclude that over-expression of human LCAT in Tg mice fed an atherogenic diet containing cholic acid does not result in increased aortic cholesterol deposition compared with control mice, even though the CE fatty acid saturation index of plasma apoB lipoproteins was doubled.     

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.     

Increase of serum high density lipoprotein with progression and regression of aortic lipid deposition in rats.

The progression and regression of aortic lipid deposition was studied in male ExHC rats. Rats in the progression group were fed an atherogenic diet containing 2% cholesterol, 0.4% sodium cholate and 10% olive oil for periods up to 32 weeks. Rats in the regression group were first fed the atherogenic diet for 16 weeks, and then maintained on a basal low cholesterol diet. Half the rats were killed at 4 weeks and the other half at 16 weeks after cessation of the atherogenic diet. Rat aortas of the progression group contained progressively more lipid pari passu with the duration of cholesterol feeding, but connective-tissue proliferation was absent. Deposited lipid in the aorta of cholesterol-fed rats disappeared very slowly after the rats were returned to the basal diet. serum HDL decreased in the hypercholesterolemic ExHC rats fed the atherogenic diet for 4 weeks. By contrast, serum HDL and apo A-I increased in both hypercholesterolemic ExHC rats fed the atherogenic diet for 32 weeks and slightly hypercholesterolemic ExHC rats fed the basal diet for 16 weeks in the regression period.     

Ramipril prevents impaired endothelium-dependent relaxation in arteries from rabbits fed an atherogenic diet

Endothelium-dependent relaxation in arteries is attenuated in clinical and experimental atherosclerosis. This study investigates the endothelial preservation properties of the angiotensin converting enzyme inhibitor, ramipril, by assessing its ability to restore endothelium-dependent responsiveness in blood vessels from rabbits fed an atherogenic diet (0.25% cholesterol; 3% coconut oil; 12 weeks). Seven rabbits fed the atherogenic diet received ramipril (3 mg/kg mixed into their food daily) and 6 rabbits were maintained on the atherogenic diet alone. Control rabbits (n = 6) were fed a standard diet and did not receive ramipril. At the end of the dietary intervention, the rabbits were killed and blood was collected for measurement of the lipid profile. The thoracic aorta was isolated and half was frozen for pathologic review while the other half was cut into rings and placed in a muscle bath for measurement of isometric force development. Dose response curves to phenylephrine (10⁻⁹ to 10⁻⁵ M) and angiotensin II (10⁻¹⁰ to 3 × 10⁻⁷ M) were completed. There was a minimal decrease in responsiveness to phenylephrine in vessels from rabbits eating the atherogenic diet compared with controls and no significant differences in the response to angiotensin II for any of the vessels. Following contraction by phenylephrine, acetylcholine (10⁻⁹ to 10⁻⁵ M) and nitroglycerin (10⁻¹⁰ to 10⁻⁵ M) dose response curves were completed. Relaxation to acetylcholine in aortic rings from control rabbits was observed, although in arteries from atherogenic rabbits relaxation was attenuated. This effect was prevented in the atherogenic rabbits fed ramipril. Responsiveness to the endothelium-independent vasodilator, nitroglycerin, was similar in arteries from the three rabbit groups. Total cholesterol levels were elevated in the rabbits fed the atherogenic diet and in the rabbits fed the atherogenic diet containing ramipril. High density lipoprotein (HDL) cholesterol levels were not affected by the atherogenic diet alone, but when ramipril was added, there was a significant increase in HDL cholesterol levels. The percentage of aortic surface covered with lipid streaks was not significantly different in the three rabbit groups. We conclude that ramipril prevents endothelial dysfunction in arteries from rabbits fed an atherogenic diet. Mechanistically, this effect of ramipril on the endothelium must occur prior to the release of nitric oxide as no alteration in the dose response curve to nitroglycerine could be identified. Additionally, this improvement in endothelial function in rabbits supplemented with ramipril appears to be independent of morphologic changes in response to the atherogenic diet.     

Varied effects of dietary sucrose and cholesterol on serum lipids, lipoproteins and apolipoproteins in rhesus monkeys.

Serum lipid, lipoproteins, apolipoproteins and plasma insulin and glucose were studied in rhesus monkeys (Macaca mulatta) fed high sucrose diets (69%, w/w), with and without added cholesterol. When compared to basal diet, a high sucrose diet with no added cholesterol fed for 6 weeks increased serum total cholesterol and triglycerides by factors of 1.2 and 2.8, respectively. Cholesterol supplementation of sucrose diets increased the serum total cholesterol levels by a factor of 2.2 and decreased the serum triglycerides by 0.47. The serum cholesterol response to experimental diets was reflected predominantly in beta-lipoprotein and to a lesser extent in alpha-lipoprotein. Sucrose diets without cholesterol enriched the beta- and pre-beta-lipoproteins with triglycerides and protein at the expense of cholesterol. On the same diet, the protein content of alpha-lipoprotein increased at the expense of cholesterol and triglycerides. In contrast, dietary cholesterol decreased the triglyceride content and increased the cholesterol content of all the lipoprotein classes. Sucrose feeding seems to increase ApoB more than non-ApoB proteins. The proportion of ApoC-II relative to ApcoC-III increased in each animal on a sucrose diet; exogenous cholesterol further increased this trend. While sucrose diet decreased ApoA-I/ApoA-II ratios, cholesterol supplementation reversed this trend. Dietary sucrose increased the plasma glucose, insulin, and insulin-glucose ratios. The addition of cholesterol also tended to decrease plasma glucose and insulin levels. These observations indicate varied responses of serum lipoproteins and apoproteins to dietary sucrose with and without cholesterol supplementation.     

Sunflower, virgin-olive and fish oils differentially affect the progression of aortic lesions in rabbits with experimental atherosclerosis

In this study we report the effects of sunflower, virgin olive and fish oils on the progression of aortic lesions. A total of 24 male New Zealand rabbits (six per each group) were fed for 50 days on a diet containing 3% lard and 1.3% cholesterol, to induce atherosclerosis. An atherogenic control group (A) was killed after this period and three groups were fed for an additional period of 30 days with a diet composed of (1.75 g of supplemented oil and 98.25 of standard chow): sunflower oil (S), virgin olive oil (O) and fish oil (F). A control group (n=6) was fed with a standard chow diet for 80 days. LDL lipid composition and histological analysis of aortic atherosclerotic lesions were assayed. The atherogenic diet caused a significant increase of cholesterol levels in LDL and aorta tissue. Cholesterol ester content rose significantly in the aortic arch of groups S, O and F. Fatty streaks were found in all aortic sections, although only group S showed a significant progression of the lesion compared with group A. We conclude that the replacement of a high cholesterol-saturated fat diet by another cholesterol free-unsaturated fat diet does not regress atherosclerosis in rabbit. However, sunflower oil provokes a significant progression in lesion development, whereas diet enrichment with extra virgin olive oil and, to a lesser extent, fish oil, stops this progression.     

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.     

Fish oil feeding results in an enhancement of cholesterol-induced atherosclerosis in rabbits

We investigated the influence of fish oil on cholesterol induced atherosclerosis in rabbits. Group I, a control group was fed a cholesterol-free diet, group II was fed a diet supplemented with 1.5% cholesterol, group III received in addition to cholesterol supplementation a purified fish oil concentrate (Maxepa, 2 ml/d). The animals received these diets for 5 months (100 g/d). Aortic atherosclerosis as measured by planimetry of sudanophilic lesions was significantly higher (+59%) in group III as compared with group II, even though serum cholesterol levels were comparable. No differences were found in platelet half-life times between groups II and III, but these values were significantly lower than the half-life of platelets in the control group I. Total serum peroxide levels, expressed as malondialdehyde equivalents were significantly elevated in the fish oil-treated group. This may be due to malondialdehyde modification of the lipoproteins and may be responsible for the enhanced development of atherosclerosis in these animals.     

罗格列酮对兔动脉粥样硬化血脂和组织总抗氧化能力的影响

目的:观察罗格列酮对高胆固醇饮食兔血脂和组织总抗氧化能力的影响,探讨罗格列酮对动脉粥样硬化斑块消退的机制。方法:雄性新西兰大白兔24只随机等分为3组:对照组、胆固醇组、罗格列酮组。罗格列酮从第10周开始干预,16周后,测定血脂、血糖水平,主动脉行病理形态学及颈动脉组织总抗氧化能力的检测。结果:与对照组和胆固醇组相比,16周末时罗格列酮组血清总胆固醇、低密度脂蛋白胆固醇均明显降低;主动脉壁斑块数量和斑块面积显著减少;颈动脉组织总抗氧化能力明显增强。结论:罗格列酮对动脉粥样硬化斑块消退作用的其机制之一可能与降低血清总胆固醇、低密度脂蛋白胆固醇水平及增强组织总抗氧化能力有关。     

Suppression of experimental atherosclerosis in rabbits by interferon-inducing agents

The effects of two chemically different interferon inducers on the suppression of atherosclerosis were studied in rabbits fed an atherogenic chow diet. One group (10 rabbits per group) was fed normal rabbit chow, and three groups were fed an atherogenic chow. One of the latter groups received the atherogenic feeding alone; the other two were treated with either polyinosinic-polycytidylic acid (poly I:C) or 2-amino-5-bromo-6-phenyl-4-pyrimidinone (ABPP). Neither of the drugs reduced significantly the hypercholesterolemia induced by the feeding. However, both poly I:C and ABPP treatment significantly reduced the percent area of the aortic intimal surface lesions, stained for lipid with Sudan IV, compared with that in untreated rabbits fed atherogenic chow. Microscopic sections of typical aortic plaques showed that both drug treatments significantly reduced the size and number of intimal lipid deposits compared with those observed in the aortas of untreated animals. Chemical analysis for cholesterol and collagen content revealed that interferon-inducing agents significantly reduced cholesterol deposits in the aorta, with little effect on fibrous protein deposition. The results indicate that two unrelated interferon-inducing drugs suppressed atherogenesis without reducing serum cholesterol and low density lipoprotein levels. Whether the protection against atherosclerosis is exerted by endogenous interferon production remains to be determined.     

阿托伐他汀对兔主动脉粥样硬化斑块和脂肪酸结合蛋白的抑制作用

目的观察阿托伐他汀对兔动脉粥样硬化斑块和血清脂肪细胞型脂肪酸结合蛋白(AFABP)的作用机制。方法 16只新西兰大白兔给予高TC饲料饲养8周后,随机分为高TC组(继续饲以高TC饲料4周)和阿托伐他汀组(在饲以高TC饲料的基础上给予阿托伐他汀2.5 mg·kg~(-1)·d~(-1)4周),每组8只。另选8只普通饲料饲养12周的新西兰大白兔作为对照组。分析观察前、8和12周兔血脂和AFABP水平的变化;12周末处死兔,取主动脉进行病理学检查;RT-PCR测定主动脉AFABP mRNA的表达。结果与高TC组比较,阿托伐他汀组兔12周时血清TC、LDL-C、AFABP水平和AFABP mRNA表达均明显降低(P0.01)。对照组、高TC组、阿托伐他汀组斑块/内膜面积比分别为0、(75.80±8.21)%和(46.11±3.56)%,差异显著(P0.01);内膜厚度分别为(4.12±0.29)μm、(74.18±10.25)μm和(39.45±5.68)μm;内膜/中膜比分别为0.05±0.01、0.85±0.31和0.48±0.23,差异显著(P0.01)。结论阿托伐他汀具有抗动脉粥样硬化作用,其降低兔血清AFABP水平及主动脉AFABP mRNA的表达可能是其作用机制之一。     

疏水性表面活性剂对家兔实验性高脂血症及动脉硬化的预防作用

本文将22只家兔随机分为三组。喂饲胆固醇诱发高脂血症。实验组给予疏水性表面活性剂Soluchorol,探讨其对高脂血症及动脉硬化的预防作用。结果表明,实验组血清总胆固醇及低密度脂蛋白均明显低于高脂组(P<0.01)。血清过氧化脂质亦低于高脂组(P<0.05)。二组主动脉斑块面积及厚度的对比分析均有显著性差异。提示疏水性表面活性剂具有一定的降血脂及预防动脉硬化的作用。但对Soluchorol的合成过程及其在机体内的代谢过程,使用剂量及毒性,试验等方面尚需进一步研究。     

前列腺素E1对兔动脉粥样硬化易损斑块的影响

目的研究前列腺素E1对兔动脉粥样硬化易损斑块的影响及机制。方法 22只新西兰大白兔高脂饲料(1%胆固醇)喂养2周后,进行腹主动脉球囊损伤术,术后继续高脂喂养,7周后,随机分为模型组、前列腺素E1组和辛伐他汀组,同时改为普通饲料继续喂养4周,13周末,所有兔给予中国斑点蝰蛇毒和组胺进行药物诱发。观察药物干预后血脂、斑块形态、斑块组分及炎症因子的变化。结果前列腺素E1对血脂没有影响;与模型组比较,前列腺素E1组能显著增加斑块的纤维帽厚度(101.72±34.89μm比79.86±16.98μm,P<0.01),减小斑块易损指数(0.94±0.27比3.83±1.45,P<0.01);并且能够显著抑制斑块中巨噬细胞的累积(P<0.01)及其分泌的炎症因子基质金属蛋白酶1和基质金属蛋白酶9的表达(P<0.01),前列腺素E1组与辛伐他汀组比较差异无显著性。结论前列腺素E1能够稳定兔动脉粥样硬化易损斑块,该作用与脂质代谢无关,但与抑制斑块中巨噬细胞的累积及其分泌炎症因子密切相关。     

Quantification of plasma lipids and apolipoproteins in British Halflop rabbits. A comparison between normocholesterolemic rabbits, hypercholesterolemic rabbits (modified WHHL rabbits) and rabbits fed an atherogenic diet

We have established isolation methods and developed electroimmunoassays for rabbit apolipoprotein A-I (apo A-I), apo B, apo C-III and apo E. The assays were used to characterize a hyperlipidemic strain of the British Halflop rabbits (BHL rabbits), obtained after cross-breeding with WHHL rabbits and referred to as modified WHHL rabbits, and to investigate the changes in the apolipoprotein levels induced by feeding normal BHL rabbits an atherogenic diet (0.25% cholesterol and 3% coconut oil). The modified WHHL rabbits were characterized by increased levels of apo B, apo C-III and apo E as well as cholesterol, phospholipids and triacylglycerol as compared to chow-fed BHL rabbits, while the apo A-I levels were only half of those found in the chow-fed animals. The modified WHHL rabbits had virtually no low density lipoprotein (LDL) receptor activity and a low fractional catabolic rate (FCR) of LDL. These results indicate that the modified WHHL rabbit has the homozygous form of the LDL receptor deficiency. The BHL rabbits fed the atherogenic diet showed increased levels of cholesterol, triacylglycerol, apo B, apo C-III and apo E, as compared to those of the chow-fed BHL rabbits. The apo E and apo C-III reached levels in the range of or even higher than those of the modified WHHL rabbits. The apo A-I levels on the other hand did not differ from those of the chow-fed rabbits. Feeding an atherogenic diet led to a decrease in the FCR of LDL to a level similar to that found in the modified WHHL rabbits.     

Raloxifene and estrogen reduces progression of advanced atherosclerosis--a study in ovariectomized, cholesterol-fed rabbits

The present study investigated the effect of raloxifene, a selective estrogen receptor modulator (SERM), on aortic atherosclerosis in 80 ovariectomized, cholesterol-fed rabbits with pre-induced atherosclerosis. The animals were fed an atherogenic diet containing 240 mg cholesterol/day for 15 weeks, after this period a baseline control group was sacrificed. Thereafter, oral treatment was initiated with either estradiol 4 mg/day (n=20), raloxifene (210 mg/day) or placebo (n=20). In the treatment period of 39 weeks, the dietary cholesterol content was reduced to 80 mg cholesterol/day. Postmortem evaluation showed a significantly increased uterine weight induced by estradiol treatment (10.3+/-1.2 g), whereas raloxifene intervention caused a decreased uterus weight (1.21+/-0.1 g) when compared to placebo (2.48+/-0.47 g). Throughout the study, serum lipids increased in all groups to levels seen in very high risk humans. After 58 weeks the cholesterol content in the aorta was 3.18+/-0.54 micromol/cm(2) (38% reduction) in the estradiol group, 3.66+/-0.52 micromol/cm(2) (29% reduction) in the raloxifene group and 5.12+/-0.60 micromol/cm(2) in the placebo group. Analyses of the aortic cholesterol content corrected for time-averaged serum cholesterol revealed that both estradiol and raloxifene therapy significantly reduced the progression of atherosclerosis (P<0.01 for both) as compared to placebo.     

Anti-atherosclerotic activity of colestipol hydrochloride in SEA quail

Young, male, SEA (Susceptible to Experimental Atherosclerosis) Japanese quail (Coturnix coturnix japonica) were fed an atherogenic diet consisting of yellow corn meal and soybean meal supplemented with 2% cholesterol and 1% cholic acid. A control group of ten animals was fed the atherogenic diet for eight weeks, and another group was fed the same diet containing 2% colestipol hydrochloride for the same length of time. At the end of the treatment period serum and arterial total cholesterols were measured and extent of macroscopic atherosclerotic lesions assessed. Colestipol hydrochloride treatment significantly reduced both serum and arterial total cholesterol levels by 50 and 59%, respectively. Grossly visible atherosclerosis was significantly reduced by 64%. These data further demonstrate that male SEA quail are an appropriate and relevant small animal model for examining the cardiovascular effects of bile acid sequestrants.