C3H apoE(-/-) mice have less atherosclerosis than C57BL apoE(-/-) mice despite having a more atherogenic serum lipid profile

Wild-type C57BL mice are known to be susceptible to diet-induced atherosclerosis, whilst C3H mice are resistant. We investigated the effect of these background strains on the hyperlipidaemia and atherosclerosis that develops in mice deficient in apolipoprotein E (apoE(-/-)). Male and female apoE(-/-) mice on C3H/HeNHsd (C3H) and C57BL/6J (C57) backgrounds were fed atherogenic Western diet for 12 weeks. Serum cholesterol and triglyceride concentrations were measured and atherosclerosis quantified in the aortic sinus. C3H apoE(-/-) mice fed normal diet had 1.5 2 fold higher serum cholesterol levels than C57 apoE(-/-) mice and 4-5 fold higher serum triglyceride concentrations. Feeding Western diet caused a 4-5 fold increase in serum cholesterol in all mice, but levels of triglyceride were either attenuated or were unaffected in C3H apoE(-/-) and C57 apoE(-/-) mice, respectively. C3H apoE(-/-) mice had approximately 2 fold higher serum cholesterol and 4 fold higher triglyceride concentrations than the C57 apoE(-/-) mice throughout the study. Serum triglyceride concentrations were 35-108% higher in male C3H apoE(-/-) than female C3H apoE(-/-) mice. Most of the lipids were present in the very low density lipoprotein (VLDL)/chylomicron fraction in both strains of mice whether they were fed normal or Western diet. Notwithstanding the lower plasma lipid concentrations, atherosclerotic lesion areas were more than 2-fold larger in C57 apoE(-/-) than in C3H apoE(-/-) mice (males 68 +/- 11 x 10(3) vs 30 +/- 6 x 10(3) females 102 +/- 12 x 10(3) vs 41 +/- 8 x 10(3) microm2. mean +/- SEM).     

Increased atherosclerosis in ApoE and LDL receptor gene knock-out mice as a result of human cholesteryl ester transfer protein transgene expression

The plasma cholesteryl ester transfer protein (CETP) plays a major role in the catabolism of HDL cholesteryl ester (CE). CETP transgenic mice have decreased HDL cholesterol levels and have been reported to have either increased or decreased early atherosclerotic lesions. To evaluate the impact of CETP expression on more advanced forms of atherosclerosis, we have cross-bred the human CETP transgene into the apoE knock-out (apoE0) background with and without concomitant expression of the human apo A-I transgene. In this model the CETP transgene is induced to produce plasma CETP levels 5 to 10 times normal human levels. CETP expression resulted in moderately reduced HDL cholesterol (34%) in apoE0 mice and markedly reduced HDL cholesterol (76%) in apoE0/apoA1 transgenic mice. After injection of radiolabeled HDL CE, the CETP transgene significantly delayed the clearance of CE radioactivity from plasma in apoE0 mice, but accelerated the clearance in apoE0/apoA1 transgenic mice. ApoE0/CETP mice displayed an increase in mean atherosclerotic lesion area on the chow diet (approximately 2-fold after 2 to 4 months, and 1.4- to 1.6-fold after 7 months) compared with apoE0 mice (P<0.02). At 7 months apoA1 transgene expression resulted in a 3-fold reduction in mean lesion area in apoE0 mice (P<0.001). In the apoE0/apoA1 background, CETP produced an insignificant 1.3- to 1.7-fold increase in lesion area. In further studies the CETP transgene was bred onto the LDL receptor knock-out background (LDLR0). After 3 months on the Western diet, the mean lesion area was increased 1.8-fold (P<0.01) in LDLR0/CETP mice, compared with LDLR0 mice. These studies indicate that CETP expression leads to a moderate increase in atherosclerosis in apoE0 and LDLR0 mice, and suggest a proatherogenic effect of CETP activity in metabolic settings in which clearance of remnants or LDL is severely impaired. However, apoA1 overexpression has more dramatic protective effects on atherosclerosis in apoE0 mice, which are not significantly reversed by concomitant expression of CETP.     

The TNF alpha converting enzyme (TACE/ADAM17) is expressed in the atherosclerotic lesions of apolipoprotein E-deficient mice: possible contribution to elevated plasma levels of soluble TNF alpha receptors

TNF alpha converting enzyme (TACE) critically regulates the inflammatory processes as it releases from the cell surface several transmembrane proteins, including TNFalpha (TNF) and its receptors TNFR1 and TNFR2. We investigated the expression of TACE in atherosclerotic lesions of apolipoproteinE-deficient (apoE (-/-)) mice. Five-week-old apoE(-/-) male mice were fed a high-fat diet and examined at 5, 10, 15 and 25 weeks of age. A group of wild-type C57BL/6 mice (WT) fed the high-fat diet for 25 weeks was included. In apoE(-/-) mice, lesions progressed with time in both aortic sinus and arch, in which TACE immunostaining also increased particularly between 5 and 15 weeks. TACE expression was also observed in human atherosclerotic plaques. The plasma levels of soluble TNFR1 and TNFR2 rose with atherosclerosis. In the 25-week-old WT mice, no lesions were observed and the plasma levels of TNFRs were 17% of those of age-matched apoE(-/-) mice. Incubated aortas of 25-week-old apoE(-/-) mice released much higher amounts of sTNF and sTNFRs than did aortas of 5-week-old apoE(-/-) mice or 25-week-old WT mice. Active TACE was expressed at the surface of macrophages isolated from apoE(-/-) mice. In conclusion, TACE expression is associated with lesions in atherosclerosis-prone sites. Our data suggest that atherosclerotic lesions-expressing TACE may contribute to the elevated levels of circulating sTNFRs.     

Leptin deficiency suppresses progression of atherosclerosis in apoE-deficient mice

Both experimental and epidemiological studies suggest that leptin is one of the molecules responsible for accelerated atherosclerosis in obese humans. To confirm the notion, we studied whether leptin accelerates atherosclerosis in apoE(-/-) mice. Leptin deficient hyperlipidemic mice (ob/ob;apoE(-/-) mice) developed significantly less atherosclerosis than apoE(-/-) mice, when fed an atherogenic diet for 16 weeks from 8 weeks of age. Histological analysis revealed that most of the atherosclerotic lesions in ob/ob;apoE(-/-) mice remained as fatty streaks, while those in apoE(-/-) mice were mainly fibrous plaques. The decrease in atherosclerosis was not due to changes in the serum levels of cholesterol, TNF-alpha, or adiponectin. Exogenous leptin significantly increased atherosclerotic areas in apoE(-/-) mice, even though it decreased food intake and body weight. Our findings support the notion that leptin accelerates atherosclerosis.     

T and B lymphocytes play a minor role in atherosclerotic plaque formation in the apolipoprotein E-deficient mouse

Cellular and humoral immunity have been implicated in the pathogenesis of atherosclerosis. To determine whether an intact immune system is necessary for the formation of atherosclerotic lesions, we have generated immunodeficient mice with hypercholesterolemia and atherosclerosis by crossbreeding the apolipoprotein E (apoE)-deficient mouse with the recombinase activating gene 1 (Rag-1) knockout mouse. Chow-fed immunodeficient mice with targeted disruption in both apoE and Rag-1 (E0/R0) had a 2-fold decrement in aortic root lesion size at 16 weeks of age, compared with immunocompetent littermates, which were heterozygotes at the Rag-1 locus (E0/R1). Nearly all atherosclerotic lesions from chow-fed animals were limited to raised foam cell fatty streaks. In contrast, when a second group of animals was fed a high-fat Western-type diet to accelerate lesion development, there were no differences in either aortic root lesion size or the percent of the total aorta occupied by lesions. Fibrous plaques with well-defined caps and necrotic cores were detected in both Western diet-fed E0/R0 and E0/R1 animals. We conclude that T and B lymphocytes play only a minor role in the rate of forming foam cell lesions, and they are not necessary for the formation of fibroproliferative plaques.     

Accelerated atherosclerosis in C57Bl/6 mice transplanted with ApoE-deficient bone marrow

Apolipoprotein E (apoE), a high affinity ligand for lipoprotein receptors, is synthesized by the liver and extrahepatic tissues, including cells of the monocyte/macrophage cell lineage. The role of monocyte/macrophage-derived apoE in atherogenesis was assessed by transplantation of apoE-deficient (apoE-/-) bone marrow into normolipidemic C57Bl/6 mice. No significant effect could be demonstrated on serum apoE levels in C57Bl/6 mice, transplanted with apoE-deficient bone marrow compared with control transplanted mice. Furthermore, no consistent effect on serum cholesteryl esters and triglyceride concentrations could be demonstrated on either a standard chow diet or a high cholesterol diet. Quantitative analysis of atherosclerosis in mice transplanted with apoE-deficient bone marrow, after two months on a high cholesterol diet, revealed a 4-fold increase in the atherosclerotic lesion area as compared to animals transplanted with apoE+/+ bone marrow. Analysis of the ability of apoE-deficient macrophages to release cholesterol after loading with acetylated LDL revealed that the release of cholesterol from apoE-deficient macrophages was impaired as compared to wild-type macrophages in the absence and the presence of specific cholesterol acceptors. In conclusion, apoE production by macrophages retards the formation of atherosclerotic plaques, possibly by mediating cholesterol efflux. We anticipate that pharmacological approaches to increase apoE synthesis and/or secretion by macrophages might be beneficial for the treatment of atherosclerosis.     

Genetic background determines the extent of atherosclerosis in ApoE-deficient mice.

Two strains of ApoE-deficient mice were found to have markedly different plasma lipoprotein profiles and susceptibility to atherosclerosis when fed either a low-fat chow or a high-fat Western-type diet. FVB/NJ ApoE-deficient (FVB E0) mice had higher total cholesterol, HDL cholesterol, ApoA1, and ApoA2 levels when compared with C57BL/6J ApoE-deficient (C57 E0) mice. At 16 weeks of age, mean aortic root atherosclerotic lesion area was 7- to 9-fold higher in chow diet-fed C57 E0 mice and 3.5-fold higher in Western diet-fed C57 E0 mice compared with FVB E0 mice fed similar diets. Lesion area in chow diet-fed first-generation mice from a strain intercross was intermediate in size compared with parental values. The distribution of the lesion area in 150 chow diet-fed second-generation progeny spanned the range of the lesion area in both parental strains. There were no correlations between total cholesterol, non-HDL cholesterol, HDL cholesterol, ApoA1, ApoA2, ApoJ, or anti-cardiolipin antibodies and lesion area in the second-generation progeny. Thus, a genomic approach may succeed in identifying the genes responsible for the variation in atherosclerosis susceptibility in these 2 strains of ApoE-deficient mice, which could not be explained by measured plasma parameters.     

High-fat, high-cholesterol diet increases the incidence of gastritis in LDL receptor-negative mice

Transgenic and knockout mice are widely used as models for atherogenesis studies. While developing a Helicobacter infection model in LDL receptor-negative (LDLR(-/-)) mice, we noticed that mice fed a high-fat, high-cholesterol diet often contracted gastritis independent of infection. To further investigate this finding, we studied 27 male and 18 female LDLR(-/-) mice fed high-fat, 1% or 1.25% cholesterol diets for 3 to 4 months. The extent of atherosclerosis was morphometrically analyzed in the whole aorta, and the degree of gastric inflammation was scored histologically in hematoxylin-eosin-stained stomach sections. The autoantibody titers to epitopes of oxidized LDL were also measured. Mice fed high-fat, high-cholesterol diets had a significantly higher incidence of gastritis than mice fed normal chow, 62% versus 5%, respectively (P<0.0001). This effect was specific for LDLR(-/-) mice, because no difference in gastritis was found in wild-type mice fed either diet. Animals with gastritis showed slightly more atherosclerosis than animals without gastritis: 16.3+/-6.4% versus 12.8+/-3.4% in males and 9.4+/-3.5% versus 6.5+/-3.3% in females. Cholesterol-fed mice also had significantly higher IgG autoantibody titers against modified LDL than normal chow-fed animals, but no difference was seen between the gastritis and nongastritis groups. We conclude that the standard high-fat, high-cholesterol diet commonly used in many murine models to induce atherosclerosis increased the incidence of gastritis significantly in LDLR(-/-) mice.     

Reduced atherosclerosis in chow-fed mice expressing high levels of a catalytically inactive human hepatic lipase

Increased expression of catalytically inactive hepatic lipase (ciHL) lowers remnants and low-density lipoproteins (LDL) and may reduce atherosclerosis in mice lacking both LDLreceptors (LDLR) and murine (m) HL. However, in a previous study, ciHL expression failed to reduce atherosclerosis but increased liver fat accumulation after a 3-month high-fat diet, suggesting that diet-induced metabolic changes compromised the antiatherogenic effects of ciHL. Therefore, we hypothesized that reduced dietary fat would reduce atherosclerosis in ciHL expressing mice. Mice lacking both LDLR and mHL, alone, or expressing ciHL were fed a low-fat (chow) diet for 9 months to match the cumulative cholesterol exposure resulting from a 3-month high-fat diet. Plasma lipids and lipoproteins as well as atherosclerosis were determined at sacrifice. Also, liver expression of receptors and proteins contributing to cholesterol delivery including the LDLreceptor related protein (LRP), scavenger receptor (SR)-B1 and apoE were determined. At 9 months, ciHL expression reduced plasma cholesterol by approximately 20% and atherosclerosis by 79% (from 2.67+/-0.61% of aortic surface, Ldlr-/-hl-/-, n=9, to 0.55+/-0.32% of aortic surface, Ldlr-/-hl-/-ciHL, n=7, P=0.01). Also, LRP-expression increased approximately 4-fold, whereas SR-B1 and apoE remained unchanged. These results demonstrate that ciHL expression reduces atherosclerosis. Also, these results demonstrate that ciHL increases LRP expression and suggest increased LRP-mediated lipoprotein clearance as a pathway for ciHL-mediated atherosclerosis reduction.     

Hyperlipidemia and atherosclerotic lesion development in LDL receptor-deficient mice fed defined semipurified diets with and without cholate.

Past studies of atherosclerosis in mice have used chow-based diets supplemented with cholesterol, lipid, and sodium cholate to overcome species resistance to lesion formation. Similar diets have been routinely used in studies with LDL receptor-deficient (LDLR(-/-)) mice. The nonphysiological nature and potential toxicity of cholate-containing diets have led to speculation that atherogenesis in these mice may not accurately reflect the human disease process. We have designed a semipurified AIN-76A-based diet that can be fed in powdered, pelleted, or liquid form and manipulated for the precise evaluation of diet-genetic interactions in murine atherosclerosis. LDLR(-/-) mice were randomly assigned among 4 diets (n=6/diet) as follows: 1, control, 10% kcal lipid; 2, high fat (40% kcal), moderate cholesterol (0.5% by weight); 3, high fat, high cholesterol (1.25% by weight); and 4, high fat, high cholesterol, and 0.5% (wt/wt) sodium cholate. Fasting serum cholesterol was increased in all cholesterol-supplemented mice compared with controls after 6 or 12 weeks of feeding (P<0.01). The total area of oil red O-stained atherosclerotic lesions was determined from digitally scanned photographs. In contrast to the control group, all mice in cholesterol-supplemented dietary groups 2 to 4 had lesions involving 7.01% to 12.79% area of the thoracic and abdominal aorta at 12 weeks (P<0.002, for each group versus control). The distribution pattern of atherosclerotic lesions was highly reproducible and comparable. The histological features of lesions in mice fed cholate-free or cholate-containing diets were similar. This study shows that sodium cholate is not necessary for the formation of atherosclerosis in LDLR(-/-) mice and that precisely defined semipurified diets are a valuable tool for the examination of diet-gene interactions.     

载脂蛋白E基因敲除小鼠动脉粥样硬化斑块中血小板因子4和Toll样受体2的表达

目的观察高脂饲养的载脂蛋白E基因敲除小鼠动脉粥样硬化斑块表达Toll样受体2和血小板因子4的情况,探讨血小板因子4对内皮细胞Toll样受体2表达的影响。方法高脂饲料喂养载脂蛋白E基因敲除小鼠12周,建立动脉粥样硬化模型。安乐死处死动物,原位灌流固定,取主动脉于10%中性缓冲福尔马林中固定,石蜡包埋连续切片,HE染色观察动脉粥样硬化斑块形态,免疫组织化学检测斑块中Toll样受体2和血小板因子4的表达。结果载脂蛋白E基因敲除小鼠血脂水平明显增高,主动脉HE染色可见态动脉粥样硬化病变。在载脂蛋白E基因敲除小鼠主动脉富含脂质斑块中Toll样受体2表达上调,其中血管内皮细胞、巨噬细胞表达Toll样受体2明显增多。载脂蛋白E基因敲除小鼠主动脉斑块中也发现有血小板因子4表达,主要在内皮细胞和动脉粥样硬化斑块肩部。结论1.载脂蛋白E基因敲除小鼠粥样斑块中Toll样受体2表达上调,并且Toll样受体2主要表达在粥样斑块的内皮细胞和巨噬细胞上。2.载脂蛋白E基因敲除小鼠动脉粥样硬化斑块中可见血小板因子4表达。     

Vascular effects of a low-carbohydrate high-protein diet

The cardiovascular complications of obesity have prompted interest in dietary interventions to reduce weight, including low-carbohydrate diets that are generally high in protein and fat. However, little is known about the long-term effects of these diets on vascular health. We examined the cardiovascular effects of a low-carbohydrate, high-protein diet (LCHP) in the ApoE^−/− mouse model of atherosclerosis and in a model of ischemia-induced neovascularization. Mice on a LCHP were compared with mice maintained on either the standard chow diet (SC) or the Western diet (WD) which contains comparable fat and cholesterol to the LCHP. LCHP-fed mice developed more aortic atherosclerosis and had an impaired ability to generate new vessels in response to tissue ischemia. These changes were not explained by alterations in serum cholesterol, inflammatory mediators or infiltrates, or oxidative stress. The LCHP diet substantially reduced the number of bone marrow and peripheral blood endothelial progenitor cells (EPCs), a marker of vascular regenerative capacity. EPCs from mice on a LCHP diet also manifest lower levels of activated (phosphorylated) Akt, a serine-threonine kinase important in EPC mobilization, proliferation, and survival. Taken together, these data demonstrate that in animal models LCHP diets have adverse vascular effects not reflected in serum markers and that nonlipid macronutrients can modulate vascular progenitor cells and pathophysiology.     

Recombinant antibodies to an oxidized low-density lipoprotein epitope induce rapid regression of atherosclerosis in apobec-1(-/-)/low-density lipoprotein receptor(-/-) mice.

OBJECTIVES: The present study tested the hypothesis that treatment with human recombinant immunoglobulin G1 (IgG1) antibodies against a specific oxidized low-density lipoprotein (oxLDL) epitope will induce regression of existing atherosclerotic lesions in LDL receptor-deficient mice expressing apolipoprotein B-100 (apoB-100) (Apobec-1(-/-)/LDLR(-/-)). BACKGROUND: Oxidized LDL plays an essential role in the pathogenesis of atherosclerosis. We previously showed that an antibody against oxLDL reduces progression of atherosclerosis in mice. METHODS: Apobec-1(-/-)/LDLR(-/-) mice were fed a high-fat diet until they were 24 weeks and were subsequently transferred to chow. Starting at 25 weeks, mice were given 3 weekly injections of either of 2 recombinant human IgG1 antibodies (IEI-E3 or 2D03) against a malondialdehyde-modified apoB-100 peptide sequence. RESULTS: At 25 weeks, atherosclerotic lesions covered 10.3 +/- 3.7% of the descending aorta. Transfer to chow diet resulted in a modest regression of atherosclerosis over a 5-week period (8.28 +/- 4.36%; p = NS). Antibody treatment induced additional regression of atherosclerosis by 50% (2D03; p = 0.001) and 36% (IEI-E3; p = 0.004) compared with control IgG1. The 2D03 treatment also reduced plaque inflammation, enhanced plaque expression of the adenosine triphosphate-binding cassette transporter A1, and inhibited expression of monocyte chemoattractant protein-1 in cultured monocytes. CONCLUSIONS: Human IgG1 against a specific oxLDL epitope can induce rapid and substantial regression of atherosclerotic lesions, possibly by stimulating lipid efflux and inhibiting macrophage recruitment. These recombinant human antibodies could represent a novel strategy for rapid regression/stabilization of atherosclerotic lesions.     

In vivo uptake of radiolabeled MDA2, an oxidation-specific monoclonal antibody, provides an accurate measure of atherosclerotic lesions rich in oxidized LDL and is highly sensitive to their regression

To determine whether labeled antibodies against oxidized LDL (OxLDL) offer advantages for quantifying atherosclerosis, we compared in vivo aortic uptake of (125)I-labeled MDA2, a monoclonal antibody against malondialdehyde-lysine epitopes), atherosclerotic surface area, and aortic weight in Watanabe heritable hyperlipidemic and New Zealand White rabbits and in low density lipoprotein receptor-deficient (LDLR(-/-)) and apolipoprotein E-deficient (apoE(-/-)) mice. Absolute and specific uptakes of (125)I-MDA2 were significantly greater in plaque than in normal aortas. Uptake of (125)I-MDA2 significantly correlated with aortic weight and percent atherosclerotic surface area in rabbits and mice. To assess whether (125)I-MDA2 uptake reflects changes in lesion content of OxLDL, in a separate study, extensive atherosclerosis was induced in 4 groups of LDLR(-/-) mice by feeding them a high fat/cholesterol diet for 6 months. A baseline group was euthanized at this time. The remaining groups were fed "regression" diets (chow or chow+1% vitamin E+0.05% vitamin C) or the high fat/cholesterol diet for 6 more months. When atherosclerosis was measured as percent surface area or aortic weight, there was strong progression in the high fat/cholesterol group, moderate progression in the chow group, and no progression in the chow+vitamin E+vitamin C group compared with the baseline group. The (125)I-MDA2 method also yielded a significant increase in atherosclerosis in the high fat/cholesterol group but significant decreases in the chow and chow+vitamin E+vitamin C groups. Immunocytochemistry showed fewer oxidation-specific epitopes in lesions from the chow and chow+vitamin E+vitamin C groups. Thus, the uptake of (125)I-MDA2 correlates well with traditional measures of atherosclerosis but also reflects reduced plaque OxLDL content after hypocholesterolemic intervention.     

巨细胞病毒感染加剧apoE基因敲除小鼠动脉粥样硬化

目的建立巨细胞病毒(MCMV)感染的动脉粥样硬化动物模型,观察CMV感染是否可促使动脉粥样硬化发生。方法apoE基因敲除的C57BL/6雌性小鼠,随机分为四组,根据不同处理分为对照组、高脂高胆固醇饮食组、注射MCMV组和联合高脂高胆固醇饮食并注射MCMV组,每组9只。分别于饲养8、12和16周时处死小鼠,分离主动脉,病理切片观察动脉粥样硬化改变。结果对照组8周开始有内膜增厚,炎症细胞浸润,至16周尚无明显斑块形成;CMV感染组各阶段的炎症细胞浸润及泡沫细胞形成均比对照组和高脂饮食组严重,16周有明显的粥样斑块形成。而CMV感染合并高脂饮食组的病变最为严重。结论MCMV感染ApoE-KO小鼠可导致动脉粥样硬化的发生,高脂饮食与CMV感染对促动脉粥样硬化有协同作用。     

Beta3 integrin deficiency promotes atherosclerosis and pulmonary inflammation in high-fat-fed,hyperlipidemic mice

Hyperlipidemia promotes the chronic inflammatory disease atherosclerosis through poorly understood mechanisms. Atherogenic lipoproteins activate platelets, but it is unknown whether platelets contribute to early inflammatory atherosclerotic lesions. To address the role of platelet aggregation in diet-induced vascular disease, we studied beta3 integrin-deficient mice (lacking platelet integrin alphaIIbbeta3 and the widely expressed nonplatelet integrin alphavbeta3) in two models of atherosclerosis, apolipoprotein E (apoE)-null and low-density lipoprotein receptor (LDLR)-null mice. Unexpectedly, a high-fat, Western-type (but not a low-fat) diet caused death in two-thirds of the beta3-/-apoE-/- and half of the beta3-/-LDLR-/- mice due to noninfectious pneumonitis. In animals from both models surviving high-fat feeding, pneumonitis was absent, but aortic atherosclerosis was 2- to 6-fold greater in beta3-/- compared with beta+/+ littermates. Expression of CD36, CD40L, and CD40 was increased in lungs of beta3-/-LDLR-/- mice. Each was also increased in smooth muscle cells cultured from beta3-deficient mice and suppressed by retroviral reconstitution of beta3. These data show that the platelet defect caused by alphaIIbbeta3 deficiency does not impair atherosclerotic lesion initiation. They also suggest that alphavbeta3 has a suppressive effect on inflammation, the loss of which induces atherogenic mediators that are amplified by diet-induced hyperlipidemia.     

Increased atherosclerotic lesion area in apoE deficient mice overexpressing bovine growth hormone

Human growth hormone (GH) excess is linked to increased cardiovascular morbidity and mortality. However, little is known about the effect of GH excess on atherosclerosis. We developed a new mouse model to assess the hypothesis that GH overexpression accelerates atherosclerotic lesion formation. apoE(-/-) mice were crossed with bovine GH (bGH) transgenic mice to yield apoE(-/-) mice overexpressing bGH (apoE(-/-)/bGH). The mice were fed either standard or Western diet. At 22 weeks, atherosclerotic lesion area of thoracic aorta was larger in apoE(-/-)/bGH mice compared with littermate apoE(-/-) mice fed either diet (standard: +161+/-50%, Western: +430+/-134%). Aortic sinus lesions were more severe in apoE(-/-)/bGH mice fed standard diet compared with littermate apoE(-/-) mice. apoE(-/-)/bGH mice had lower (VLDL+LDL)/HDL ratios compared with littermate apoE(-/-) mice, while systolic blood pressure was higher in apoE(-/-)/bGH mice, irrespective of diet. The levels of serum amyloid A and hepatic CRP mRNA were higher in apoE(-/-)/bGH mice than in littermate apoE(-/-) mice. In conclusion, this study shows that excess GH augments the development of atherosclerosis in apoE(-/-) mice. The mechanisms could be direct effects of GH on cellular processes in the vessel wall or the result of concomitant processes such as hypertension or a general inflammatory state.     

Dietary cholesterol suppresses the ability of olive oil to delay the development of atherosclerotic lesions in apolipoprotein E knockout mice

To test the hypothesis that cholesterol might suppress the beneficial effect of olive oil in atherosclerosis, we fed apoE KO mice diets containing extra virgin olive oil, either with or without cholesterol, for 10 weeks and assessed the development of atherosclerosis. Within each sex, mice were assigned randomly to one of the following four experimental groups: (1) a standard chow diet, (2) a chow diet supplemented with 0.1% cholesterol (w/w) cholesterol, (3) a chow diet enriched with 20% (w/w) extra virgin olive oil and (4) a chow diet containing 0.1% cholesterol and 20% extra virgin olive oil. On the standard chow diet, average plasma cholesterol levels were higher in males than in females. Olive oil- and cholesterol-enriched diets, separately or in combination, induced hypercholesterolemia in both sexes, and abolished the difference between the sexes in plasma cholesterol levels. The addition of cholesterol to chow or olive oil diets decreased apolipoprotein A-I significantly in females and serum paraoxonase activities in males. The latter activity was higher in females than in males. In both sexes, the size of aortic atherosclerotic lesions was similar in olive oil- and chow-fed animals and smaller than in cholesterol-supplemented groups. Size of aortic lesions were positively correlated with circulating paraoxonase activity, particularly in males, and the relationship remained after adjusting for apolipoprotein A-I and HDL cholesterol levels. Our results demonstrate that the nutritional regulation of paraoxonase is an important determinant of atherosclerotic lesions dependent on sex. They also suggest that the mere inclusion of olive oil in Western diets is insufficient and the adoption of Mediterranean diet would be more effective in retarding the development of atherosclerotic lesions.     

瑞舒伐他汀对载脂蛋白E基因敲除小鼠动脉粥样硬化的影响

目的 探讨瑞舒伐他汀对载脂蛋白E基因敲除(apoE-/-)小鼠主动脉粥样硬化的影响.方法 取apoE-/-小鼠18只建立动脉粥样硬化模型,C57BL/6小鼠12只为对照组.apoE-/-小鼠予高脂饲料,C57BL/6小鼠予普通饲料.12周后,随机抽取C57BL/6小鼠和apoE-/-小鼠各6只,判断是否成模.将成模后余下的12只apoE-/-小鼠随机分为模型组和瑞舒伐他汀治疗组(瑞舒伐他汀10 mg·kg-1·d-1灌胃),每组6只.余下的6只C57BL/6小鼠作为对照组.再过12周后处死小鼠,行血脂及主动脉HE、Masson、油红O染色观察动脉斑块,免疫组织化学方法检测主动脉组织平滑肌肌动蛋白(α-SMA)、转化生长因子β1(TGF-β1)、巨噬细胞表面分子-3(Mac-3)表达.结果 模型组小鼠胆固醇、低密度脂蛋白水平均高于对照组(P均＜0.01),甘油三酯水平与对照组比较差异无统计学意义.模型组小鼠主动脉组织内可见明显动脉粥样硬化斑块形成,α-SMA、TGF-β1和Mac-3表达均较高于对照组(P均＜0.01).瑞舒伐他汀治疗组小鼠胆固醇、低密度脂蛋白、甘油三酯水平与模型组比较差异无统计学意义,但斑块内脂肪含量少于模型组,胶原含量多于模型组.治疗组α-SMA表达与模型组比较差异无统计学意义,治疗组TGF-β1、Mac-3表达均低于较模型组(P均＜0.01).结论 瑞舒伐他汀可以减轻apoE-/-小鼠动脉粥样硬化模型中的脂质沉积和炎症反应,可以增加其胶原含量,利于斑块的稳定,具有抗动脉粥样硬化的作用,对血脂无影响.

Abstract：

Objective To investigate the effect of rosuvastatin on atherosclerosis in apoE-knockout ( apoE - / - ) mice. Methods Eighteen 6-week-old apoE - / - mice fed with high fat diet were used as atherosclerosis models, twelve 6-week-old C57BL/6 mice fed with normal diet were used as control. After twelve weeks, six apoE -/ - mice were used to observe the formation of atherosclerosis. Another 12 apoE -/- mice were divided into placebo treated group (n =6) and rosuvastatin group (n =6,10 mg· kg-1 ·d -1 per gavage) and treated for 12 weeks. Then, blood was collected for measuring lipid, aorta was prepared for morphologic study (HE, Oil red O, Masson) and immunohistochemical analysis (α-smooth activor protein, transforming growth factor β1, macrophage surface molecule-3 ). Results Serum cholesterol and low density lipoprotein levels were significantly higher in apoE -/- mice fed with high fat diet than in C57/ BL6 mice( all P ＜0. 01 )while triglyceride level was similar between the two groups, these were not affected by rosuvastatin. Similarly, atherosclerotic lesion area in apoE -/ - mice fed with high fat diet was also not significantly reduced by rosuvastatin, while lipid deposition could be significantly reduced and collagen deposition could be significantly increased in the aortic atherosclerotic lesions by treatment with rosuvastatin.Upregulated TGF-β1 and Mac-3 expression in the aortic atherosclerotic lesions in apoE -/- mice fed with high fat diet could also be significantly reduced by rosuvastatin (all P ＜ 0. 01 ), suggesting reduce inflammatory responses in the atherosclerotic lesion and stable atherosclerotic plaque post rosuvastatin treatment. Conclusion Reducing inflammatory responses and stabilizing plaque properties might contribute to the anti-atherosclerosis effects of rosuvastatin in mice high fat diet fed apoE -/- mice.