Aortic Cholesterol Accumulation Research Articles

The role of cholesterol-enriched diet and paraoxonase 1 inhibition in atherosclerosis progression.

Introduction: Atherosclerosis could be deemed as a chronic, progressive, and inflammatory disease. It has been well-documented that high-density lipoprotein (HDL) can reduce the risk of the atherosclerosis occurrence through exerting some anti-atherogenic mechanisms. In recent years, the strong evidence has suggested that paraoxonase 1 (PON1) may contribute to antioxidant properties of HDL. In the present study, the impact of a diet enriched with cholesterol and also the PON1 inhibition on atheroma formation and lipid profile has been investigated. Methods: In this study, 24 New Zealand rabbits were randomly assigned to three groups receiving standard diet, atherogenic diet, and atherogenic diet plus once daily intramuscular injection of nandrolone decanoate as the PON1 inhibitor. Triglyceride, cholesterol, HDL, and low-density lipoprotein (LDL) were determined and both cholesterol accumulation in aorta and fatty streak formation were evaluated. Results: The comparison of the results in three groups reveals that cholesterol level in the group received cholesterol-enriched diet plus once daily injection of PON1 inhibitor was higher than the groups received standard diet or atherogenic diet without PON1 inhibitor (P < 0.05). Furthermore, the percentage of atheroma with type-I lesions was equal to 75% compared with the group received atherogenic diet plus nandrolone at 30%. Additionally, the differences in fatty streak formation in aorta, as well as the right and left coronary arteries in three groups given show that the difference between groups receiving atherogenic diet and standard diet was significantly lower (P < 0.05) than the difference between groups receiving atherogenic diet plus PON1 inhibitor and standard diet. Conclusion: It can be concluded that lack of paraoxanase1 or even reduced the activity of this enzyme could accelerate the progression of fatty streak lesions toward advanced atherosclerotic lesions.

The Effect of Soybean Extracts on Serum Lipid Profile and the Accumulation of Free Cholesterol and Cholesteryl Ester in the Aorta, Carotid Artery and Iliac Artery-Experimental Study

Background: We evaluated the effect of soybean extracts on serum lipoprotein profile and cholesterol accumulation on the arterial walls. Objective and design: Sixty-four female Sprague-Dawley rats were randomly divided into eight groups. Soybean extracts were given to the rats via oral gavage every day for eight weeks, after which serum was collected. In the thoracic aorta, left carotid artery, and right iliac artery, we measured the lipoprotein fractions in the serum and the accumulation of free cholesterol and cholesteryl ester, which are predictors of subclinical atherosclerosis. Results: After eight weeks of a continuous soybean diet, only two groups showed a lipid-lowering effect (n-hexane extract for 200 mg/kg dose and ethyl acetate extract for 200 mg/kg dose). We found lower free cholesterol and cholesteryl ester accumulation in the aortas and iliac arterial walls only in these two groups. Conclusion: The results indicated that soybean extract intake leads to weight change and may influence lipid metabolism. The positive effects of the soybean diet involved not only serum lipids but also aortic wall cholesterol accumulation.

Chicory, a typical vegetable in Mediterranean diet, exerts a therapeutic role in established atherosclerosis in apolipoprotein E-deficient mice.

Since protocatechuic acid exerts an atheroprotective role, we investigated how chicory (Cichorium intybus L. var. foliosum, Belgian endive) rich in protocatechuic acid, a typical vegetable in Mediterranean diet, affects preestablished atherosclerosis progression. Apolipoprotein E-deficient mice fed AIN diets containing 0.5% freeze-dried chicory for 10 weeks displayed a reduction in lesion size with a concomitant improvement in lesion stability indicated by fewer macrophages and more collagen content. Chicory consumption suppressed aortic cholesterol accumulation and intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemoattractant protein-1 expression, whereas it increased aortic ATP-binding cassette transporter A1 (ABCA1) and G1 (ABCG1) expression. Furthermore, chicory consumption improved peritoneal macrophage phenotype with less cellular cholesterol associated with an enhancement of cholesterol efflux capacity through upregulation of ABCA1 and ABCG1, less cellular oxidative stress associated with an inhibition of nicotinamide adenine dinucleotide phosphate oxidase activity, and weaker inflammatory responses associated with an inhibition of nuclear factor-κB activation. Interestingly, ABCA1 and ABCG1 silencing tended to completely block beneficial effects of chicory in peritoneal macrophages. Chicory exerts an atheroprotective role in mice possibly by regulating lesional macrophage content and phenotype, suggesting that chicory is one underrated contributor to Mediterranean Diet-induced atheroprotection.

Abstract 67: Intervention With Citrus Flavonoids Reverses Existing Metabolic Disorders and Attenuates the Progression of Advanced Atherosclerosis in High Fat--Fed LDLr-/- Mice

Previous studies demonstrated that addition of the citrus flavonoids naringenin or nobiletin to a high-fat diet prevented the development of many disorders linked to the metabolic syndrome. In the present study, we assessed the ability of intervention with nobiletin or naringenin to reverse pre-established obesity, insulin resistance, hepatic steatosis, dyslipidemia and attenuate atherogenesis. Ldlr-/- mice were fed chow or a high-fat, cholesterol-containing (HFHC) diet for 12 weeks. For an additional 12 weeks, the HFHC-fed mice: (1) continued on the HFHC diet or were transferred to (2) chow, (3) HFHC + 3% naringenin, or (4) HFHC + 0.3% nobiletin. Following rapid weight gain during HFHC-induction, intervention with naringenin or nobiletin stimulated weight loss, while maintaining caloric intake. Micro-CT imaging revealed flavonoid intervention reversed adipose tissue accumulation by 40-60% in both subcutaneous and visceral depots. At 12 weeks, the HFHC-fed mice were hyperinsulinemic (6-fold), which was accompanied by increased fasting plasma glucose. Intervention with either flavonoid normalized plasma insulin and glucose and corrected impaired insulin and glucose tolerance. The HFHC diet increased cholesterol within VLDL (10-fold) and LDL (6-fold), which was reduced (~50%) by either naringenin or nobiletin intervention. HFHC-induction significantly increased hepatic steatosis. Flavonoid intervention reduced hepatic cholesterol (&gt;50%) and triglyceride (~20%) via increased expression of Pgc1a and Cpt1a and reduced expression of Srebp1c. HFHC-induction increased atherosclerotic lesion area (13-fold), which was increased a further 2.5-fold at 24 weeks. Flavonoid intervention modestly retarded lesion size progression (16-20%). As well, intervention with naringenin or nobiletin slowed the accumulation of aortic cholesterol (~30-45%) and reduced lesional necrotic area (~25%), suggesting improved lesion morphology. These studies demonstrate in mice with pre-existing metabolic dysregulation and atherosclerosis that intervention with naringenin or nobiletin reverses obesity, dyslipidemia, hepatic steatosis and insulin resistance, and modestly attenuates the progression of advanced atherosclerosis.

The antiatherogenic effects of targeted epigallocatechin gallate ‐ loaded nanoparticles (1045.41)

Objective: The objectives of this study were to incorporate scavenger receptor target ligands on the surface of biocompatible and biodegradable epigallocatechin gallate (EGCG)‐loaded nanoparticles (E‐LNP), to evaluate their target specificity to macrophages in vitro and atherosclerotic lesions in LDLr‐/‐ mice.Method: E‐LNP were synthesized using a sonication method. Particle size, zeta potential and morphology were determined using a transmission electron microscope and Brookhaven analyzer. The target specificity to macrophages (in vitro) and to atherosclerotic lesions in LDLr‐/‐ mice (in vivo) was measured using a fluorescence microscopy and an IVIS® Lumina XR imaging system, respectively. Macrophage cholesterol content and EGCG uptake were measured using a HPLC method. After intravenous injection of E‐LNP once per week for 20 weeks, the aortic lesion was quantified by a microscope and image J software.Results— E‐LNP are negatively charged and less than 100 nm in diameter. As compared to nanoparticles without target ligands, targeted E‐LNP significantly increased macrophage EGCG content and decreased macrophage expression of monocyte chemoattractant protein 1 (MCP‐1). The target ligands significantly increased the binding and uptake of those nanoparticles to THP‐1 derived macrophages and improved the target specificity to atherosclerotic lesions in LDLr‐/‐ mice.Conclusions— Targeted E‐LNP have a potential for decreasing aortic cholesterol accumulation and inflammatory responses through targeting to macrophages and foam cells in atherosclerotic lesions.Grant Funding Source: Supported by NIH 1R15AT007013‐01

Aortic cholesterol accumulation correlates with systemic inflammation but not hepatic and gonadal adipose tissue inflammation in low-density lipoprotein receptor null mice

Inflammation is a major contributor to the development of atherosclerotic plaque, yet the involvement of liver and visceral adipose tissue inflammatory status in atherosclerotic lesion development has yet to be fully elucidated. We hypothesized that an atherogenic diet would increase inflammatory response and lipid accumulation in the liver and gonadal adipose tissue (GAT) and would correlate with systemic inflammation and aortic lesion formation in low-density lipoprotein (LDL) receptor null (LDLr−/−) mice. For 32 weeks, LDLr−/− mice (n = 10/group) were fed either an atherogenic (high saturated fat and cholesterol) or control (low fat and cholesterol) diet. Hepatic and GAT lipid content and expression of inflammatory factors were measured using standard procedures. Compared with the control diet, the atherogenic diet significantly increased hepatic triglyceride and total cholesterol (TC), primarily esterified cholesterol, and GAT triglyceride content. These changes were accompanied by increased expression of acyl-CoA synthetase long-chain family member 5, CD36, ATP-binding cassette, subfamily A, member 1 and scavenger receptor B class 1, and they decreased the expression of cytochrome P450, family 7 and subfamily a, polypeptide 1 in GAT. Aortic TC content was positively associated with hepatic TC, triglyceride, and GAT triglyceride contents as well as plasma interleukin 6 and monocyte chemoattractant protein-1 concentrations. Although when compared with the control diet, the atherogenic diet increased hepatic tumor necrosis factor α production, they were not associated with aortic TC content. These data suggest that the LDLr−/− mice responded to the atherogenic diet by increasing lipid accumulation in the liver and GAT, which may have increased inflammatory response. Aortic TC content was positively associated with systemic inflammation but not hepatic and GAT inflammatory status.

Background Diet and Fat Type Alters Plasma Lipoprotein Response but not Aortic Cholesterol Accumulation in F1B Golden Syrian Hamsters

Dietary modification alters plasma lipoprotein profiles and atherosclerotic lesion progression in humans and some animal models. Variability in response to diet induced atherosclerosis has been reported in hamsters. Assessed was the interaction between background diet composition and dietary fat type on aortic cholesterol accumulation, lipoprotein profiles, hepatic lipids and selected genes. F1B Golden Syrian hamsters (20/group) were fed (12 weeks) semi-purified or non-purified diets containing either 10 % (w/w) coconut oil or safflower oil and 0.15 % (w/w) cholesterol. The non-purified diets relative to semi-purified diets resulted in significantly higher TC (72 % [percent difference] and 38 %, coconut oil and safflower oil, respectively) and nHDL-C (84 and 61 %, coconut oil and safflower oil, respectively), and lower HDL-C (-47 and -45 %, coconut oil and safflower oil, respectively) concentrations. Plasma triacylglycerol concentrations in the hamsters fed the non-purified coconut oil-supplemented diets were three- to fourfold higher than non-purified safflower oil-supplemented, and both semi-purified diets. With the exception of HDL-C, a significant effect of fat type was observed in TC, nHDL-C and triacylglycerol (all P < 0.05) concentrations. Regardless of diet induced differences in lipoprotein profiles, there was no significant effect on aortic cholesterol accumulation. There was an inverse relationship between plasma nHDL-C and triacylglycerol, and hepatic cholesteryl ester content (P < 0.001). Diet induced differences in hepatic gene transcription (LDL receptor, apoB-100, microsomal transfer protein) were not reflected in protein concentrations. Although hamsters fed non-purified and/or saturated fatty acid-supplemented diets had more atherogenic lipoprotein profiles compared to hamsters fed semi-purified and/or polyunsaturated fatty acid-supplemented diets these differences were not reflected in aortic cholesterol accumulation.

Antisense oligonucleotide inhibition of cholesteryl ester transfer protein enhances RCT in hyperlipidemic, CETP transgenic, LDLr-/- mice

Due to their ability to promote positive effects across all of the lipoprotein classes, cholesteryl ester transfer protein (CETP) inhibitors are currently being developed as therapeutic agents for cardiovascular disease. In these studies, we compared an antisense oligonucleotide (ASO) inhibitor of CETP to the CETP small molecule inhibitor anacetrapib. In hyperlipidemic CETP transgenic (tg) mice, both drugs provided comparable reductions in total plasma cholesterol, decreases in CETP activity, and increases in HDL cholesterol. However, only mice treated with the antisense inhibitor showed an enhanced effect on macrophage reverse cholesterol transport, presumably due to differences in HDL apolipoprotein composition and decreases in plasma triglyceride. Additionally, the ASO-mediated reductions in CETP mRNA were associated with less accumulation of aortic cholesterol. These preliminary findings suggest that CETP ASOs may represent an alternative means to inhibit that target and to support their continued development as a treatment for cardiovascular disease in man.

Curcuma oil ameliorates hyperlipidaemia and associated deleterious effects in golden Syrian hamsters

Essential oil components from turmeric (Curcuma longa L.) are documented for neuroprotective, anti-cancer, anti-thrombotic and antioxidant effects. The present study aimed to investigate the disease-modifying potential of curcuma oil (C. oil), a lipophilic component from C. longa L., in hyperlipidaemic hamsters. Male golden Syrian hamsters were fed a chow or high-cholesterol (HC) and fat-rich diet with or without C. oil (30, 100 and 300 mg/kg) for 28 d. In HC diet-fed hamsters, C. oil significantly reduced plasma total cholesterol, LDL-cholesterol and TAG, and increased HDL-cholesterol when compared with the HC group. Similar group comparisons showed that C. oil treatment reduced hepatic cholesterol and oxidative stress, and improved liver function. Hyperlipidaemia-induced platelet activation, vascular dysfunction and repressed eNOS mRNA expression were restored by the C. oil treatment. Furthermore, aortic cholesterol accumulation and CD68 expression were also reduced in the C. oil-treated group. The effect of C. oil at 300 mg/kg was comparable with the standard drug ezetimibe. Delving into the probable anti-hyperlipidaemic mechanism at the transcript level, the C. oil-treated groups fed the chow and HC diets were compared with the chow diet-fed group. The C. oil treatment significantly increased the hepatic expression of PPARa, LXRa, CYP7A1, ABCA1, ABCG5, ABCG8 and LPL accompanied by reduced SREBP-2 and HMGCR expression. C. oil also enhanced ABCA1, ABCG5 and ABCG8 expression and suppressed NPC1L1 expression in the jejunum. In the present study, C. oil demonstrated an anti-hyperlipidaemic effect and reduced lipid-induced oxidative stress, platelet activation and vascular dysfunction. The anti-hyperlipidaemic effect exhibited by C. oil seems to be mediated by the modulation of PPARa, LXRa and associated genes involved in lipid metabolism and transport.

Lipid content in hepatic and gonadal adipose tissue parallel aortic cholesterol accumulation in mice fed diets with different omega-6 PUFA to EPA plus DHA ratios

Diets with low omega (ω)-6 polyunsaturated fatty acids (PUFA) to eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) ratios have been shown to decrease aortic cholesterol accumulation and have been suggested to promote weight loss. The involvement of the liver and gonadal adipose tissue (GAT) in mediating these effects is not well understood. LDL receptor null mice were used to assess the effect of an atherogenic diet with different ω-6:EPA+DHA ratios on weight gain, hepatic and GAT lipid accumulation, and their relationship to atherosclerosis. Four groups of mice were fed a high saturated fat and cholesterol diet (HSF ω-6) alone, or with ω-6 PUFA to EPA+DHA ratios up to 1:1 for 32 weeks. Liver and GAT were collected for lipid and gene expression analysis. The fatty acid profile of liver and GAT reflected the diets. All diets resulted in similar weight gains. Compared to HSF ω-6 diet, the 1:1 ratio diet resulted in lower hepatic total cholesterol (TC) content. Aortic TC was positively correlated with hepatic and GAT TC and triglyceride. These differences were accompanied by significantly lower expression of CD36, ATP-transporter cassette A1, scavenger receptor B class 1, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), acetyl-CoA carboxylase alpha, acyl-CoA synthetase long-chain family member 5, and stearoyl-coenzyme A desaturase 1 (SCD1) in GAT, and HMGCR, SCD1 and cytochrome P450 7A1 in liver. Dietary ω-6:EPA+DHA ratios did not affect body weight, but lower ω-6:EPA+DHA ratio diets decreased liver lipid accumulation, which possibly contributed to the lower aortic cholesterol accumulation.

11β-HSD1 inhibition reduces atherosclerosis in mice by altering proinflammatory gene expression in the vasculature

11β-Hydroxysteroid dehydrogenase type 1 (11β-HSD1) is implicated in the etiology of metabolic syndrome. We previously showed that pharmacological inhibition of 11β-HSD1 ameliorated multiple facets of metabolic syndrome and attenuated atherosclerosis in ApoE-/- mice. However, the molecular mechanism underlying the atheroprotective effect was not clear. In this study, we tested whether and how 11β-HSD1 inhibition affects vascular inflammation, a major culprit for atherosclerosis and its associated complications. ApoE-/- mice were treated with an 11β-HSD1 inhibitor for various periods of time. Plasma lipids and aortic cholesterol accumulation were quantified. Several microarray studies were carried out to examine the effect of 11β-HSD1 inhibition on gene expression in atherosclerotic tissues. Our data suggest 11β-HSD1 inhibition can directly modulate atherosclerotic plaques and attenuate atherosclerosis independently of lipid lowering effects. We identified immune response genes as the category of mRNA most significantly suppressed by 11β-HSD1 inhibition. This anti-inflammatory effect was further confirmed in plaque macrophages and smooth muscle cells procured by laser capture microdissection. These findings in the vascular wall were corroborated by reduction in circulating MCP1 levels after 11β-HSD1 inhibition. Taken together, our data suggest 11β-HSD1 inhibition regulates proinflammatory gene expression in atherosclerotic tissues of ApoE-/- mice, and this effect may contribute to the attenuation of atherosclerosis in these animals.

Dysfunctional HDL containing L159R ApoA-I leads to exacerbation of atherosclerosis in hyperlipidemic mice

The mutation L159R apoA-I or apoA-IL159R (FIN) is a single amino acid substitution within the sixth helical repeat of apoA-I. It is associated with a dominant negative phenotype, displaying hypoalphaproteinemia and an increased risk for atherosclerosis in humans. Mice lacking both mouse apoA-I and LDL receptor (LDL−/−, apoA-I−/−) (double knockout or DKO) were crossed>9 generations with mice transgenic for human FIN to obtain L159R apoA-I, LDLr−/−, ApoA-I−/− (FIN-DKO) mice. A similar cross was also performed with human wild-type (WT) apoA-I (WT-DKO). In addition, FIN-DKO and WT-DKO were crossed to obtain WT/FIN-DKO mice. To determine the effects of the apoA-I mutations on atherosclerosis, groups of each genotype were fed either chow or an atherogenic diet for 12weeks. Interestingly, the production of dysfunctional HDL-like particles occurred in DKO and FIN-DKO mice. These particles were distinct with respect to size, and their enrichment in apoE and cholesterol esters. Two-dimensional gel electrophoresis indicated that particles found in the plasma of FIN-DKO mice migrated as large α3-HDL. Atherosclerosis analysis showed that FIN-DKO mice developed the greatest extent of aortic cholesterol accumulation compared to all other genotypes, including DKO mice which lack any apoA-I. Taken together these data suggest that the presence of large apoE enriched HDL particles containing apoA-I L159R lack the normal cholesterol efflux promoting properties of HDL, rendering them dysfunctional and pro-atherogenic. In conclusion, large HDL-like particles containing apoE and apoA-IL159R contribute rather than protect against atherosclerosis, possibly through defective efflux properties and their potential for aggregation at their site of interaction in the aorta. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945–2010).

Enhanced Aortic Macrophage Lipid Accumulation and Inflammatory Response in LDL Receptor Null Mice Fed an Atherogenic Diet

The effect of an atherogenic diet on inflammatory response and elicited peritoneal macrophage (Mphi) cholesterol accumulation in relation to aortic lesion formation was assessed in LDL receptor null (LDLr-/-) mice. Mice were fed an atherogenic or control diet for 32 weeks. The atherogenic relative to control diet resulted in significantly higher plasma monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) concentrations, more aortic wall Mphi deposition, higher serum non HDL-cholesterol concentrations and total cholesterol to HDL-cholesterol ratios, and greater accumulation of both aortic free and esterified cholesterol. Elicited peritoneal Mphi selectively accumulated longer chain unsaturated fatty acids in their membrane, independent of the dietary fatty acid profile. Elicited peritoneal Mphi isolated from mice fed the atherogenic relative to control diet had significantly less arachidonic acid levels, accumulated significantly higher esterified cholesterol, had significantly higher mRNA levels and secretion of MCP-1, and mRNA and protein levels of ATP-binding cassette A1. Diet treatment had no significant effect in elicited peritoneal Mphi on TNFalpha and IL-6 mRNA levels and secretion. These data suggest that the atherogenic relative to control diet resulted in higher plasma inflammatory factor concentrations, less favorable lipoprotein profile, higher elicited peritoneal Mphi cholesterol accumulation and inflammatory factor secretion, and more aortic wall Mphi deposition, which in turn were associated with greater aortic cholesterol accumulation.

Atherogenic Diet Promotes Liver Inflammation, Fatty Liver Formation &amp; Atherogenesis in LDL Receptor Null Mice

The effect of an atherogenic diet on hepatic cytokine production in relation to aortic lesion formation was assessed in LDL receptor null (LDLr−/−) mice. Mice (n=11/group) were fed an atherogenic (20% fat, 0.2% cholesterol, w/w) or control (4% fat, 0.02% cholesterol, w/w) diet for 32 weeks. Cytokine concentrations and tissue lipid content were measured by ELISA and enzymatic methods, respectively. The atherogenic diet, relative to the control diet, significantly increased the hepatic production of interleukin‐6 (IL‐6, 1.4‐fold, P&lt;0.05) and tumor necrosis factor alpha (TNFα, 2.0‐fold, P&lt;0.05). The atherogenic diet, relative to the control diet, also resulted in significantly higher content of liver triglyceride (3.5‐fold, P&lt;0.01), total cholesterol (4.2‐fold, P&lt;0.01) and esterified cholesterol (7.9‐fold, P&lt;0.001). Greater accumulation of aortic esterified cholesterol (6.4‐fold, P&lt;0.001) and higher plasma concentrations of TNFα (4.4‐fold, P&lt;0.01) and IL‐6 (2.9‐fold, P&lt;0.001) were found in the mice fed the atherogenic relative to control diet. These data suggest that the atherogenic diet‐induced liver inflammation partially contributed to higher plasma cytokine concentrations, which in turn were associated with atherogenesis in LDLr−/− mice.

Low-carbohydrate diets reduce lipid accumulation and arterial inflammation in guinea pigs fed a high-cholesterol diet

Introduction Low-carbohydrate diets (LCD) efficiently induce weight loss and favorably affect plasma lipids, however, the effect of LCD on atherosclerosis is still argued. Objective To evaluate the effect of LCD on the prevention of atherosclerosis. Methods Twenty guinea pigs were fed either a LCD or a low-fat diet (LFD) in combination with high-cholesterol (0.25 g/100 g) for 12 weeks. The percentage energy of macronutrient distribution was 10:65:25 for carbohydrate:fat:protein for the LCD, and 55:20:25 for the LFD. Plasma lipids were measured using colorimetric assays. Plasma and aortic oxidized (oxLDL) were quantified using ELISA methods. Inflammatory cytokines were measured in aortic homogenates using an immunoassay. H&E stained sections of aortic sinus and Schultz stained sections of carotid arteries were examined. Results LDL cholesterol was lower in the LCD compared to the LFD group (71.9 ± 34.8 vs. 81.7 ± 26.9 mg/dL; p = 0.039). Aortic cholesterol was also lower in the LCD (4.98 ± 1.3 mg/g) compared to the LFD group (6.68 ± 2.0 mg/g); p < 0.05. The Schultz staining method confirmed less aortic cholesterol accumulation in the LCD group. Plasma oxLDL did not differ between groups, however, aortic oxLDL was 61% lower in the LCD compared to the LFD group ( p = 0.045). There was a positive correlation ( r = 0.63, p = 0.03) between oxLDL and cholesterol concentration in the aorta of LFD group, which was not observed in LCD group ( r = −0.05, p = 0.96). Inflammatory markers were reduced in guinea pigs from the LCD group ( p < 0.05) and they were correlated with the decreases in oxLDL in aorta. Conclusion These results suggest that LCD not only decreases lipid deposition, but also prevents the accumulation of oxLDL and reduces inflammatory cytokines within the arterial wall and may prevent atherosclerosis.

Atherogenic Diet Promotes Atherosclerotic Lesion Formation by Enhancing Inflammatory Response in the LDL Receptor Null Mouse

The effect of an atherogenic diet on inflammatory response in elicited peritoneal macrophages and livers in relation to aortic lesion formation was assessed in LDL receptor null (LDLr‐/‐) mice. Mice were fed an atherogenic (20% fat, 0.2% cholesterol, w/w) or control (4% fat, 0.02% cholesterol, w/w) diet for 32 weeks. The atherogenic diet, relative to the control diet, resulted in significantly higher plasma concentrations of monocyte chemoattractant protein‐1 (MCP‐1, P&lt;0.01), tumor necrosis factor alpha (TNF‐alpha, P&lt;0.01) and interleukin‐6 (IL‐6, P&lt;0.001), more aortic wall macrophage deposition, and greater accumulation of both aortic free cholesterol (4.9‐fold, P&lt;0.001) and esterified cholesterol (6.4‐fold, P&lt;0.001). Elicited peritoneal macrophages isolated from the atherogenic diet, relative to the control diet, fed mice accumulated more esterified cholesterol (P&lt;0.001), had higher mRNA levels (P&lt;0.05) and secretion (P&lt;0.01) of MCP‐1. The atherogenic diet, relative to the control diet, significantly increased the production of IL‐6 (P&lt;0.05) and TNF‐alpha (P&lt;0.05) from the livers. These data suggest that the atherogenic diet resulted in higher plasma inflammatory factor concentrations, higher elicited peritoneal macrophage secretion and liver production of inflammatory factors, which in turn were associated with greater aortic cholesterol accumulation.

Changes in liver weight are independent of hepatic lipid content in guinea pigs fed a high‐cholesterol low‐carbohydrate diet

We have used high cholesterol (HC) diets to study mechanisms of atherosclerosis in the guinea pig and shown that low carbohydrate diets (LCD) mitigate aortic cholesterol accumulation and inflammatory expression. We have also shown that HC diets induce fatty liver in guinea pigs. We evaluated whether LCD could improve hepatic steatosis in guinea pigs. Male Hartley guinea pigs were fed a HC diet (0.25g/100g) and randomly assigned (n=10/group) to consume either a LCD or high‐carbohydrate diet (HCD) for 12 wk. Plasma and whole livers were collected for lipid analysis. Plasma LDL cholesterol was lower in animals fed the LCD (P &lt; 0.01) diet while plasma triglycerides (TG) were higher (P &lt; 0.05). There were no differences in plasma free fatty acids or plasma glucose between groups. However, glucagon‐like peptide‐1 (GLP‐1) was lower in the LCD group (P &lt; 0.01). Liver weight was 40% higher in the LCD compared to the HCD group. Interestingly despite the increased liver weight in LCD there were no differences in hepatic TG, cholesterol or non‐esterified fatty acids between groups. Histological analysis performed by hematoxylin and eosin staining confirmed there were no differences in hepatic lipid accumulation or steatosis between groups. Collectively these results suggest that in the presence of a HC‐LCD, the increase in liver mass is unrelated to lipid accumulation. An increased number of hepatocytes through an accelerated regenerative process may be responsible for these observations in the LCD group.

A-002 (Varespladib), a phospholipase A2inhibitor, reduces atherosclerosis in guinea pigs

BackgroundThe association of elevated serum levels of secretory phospholipase A2 (sPLA2) in patients with cardiovascular disease and their presence in atherosclerotic lesions suggest the participation of sPLA2 enzymes in this disease. The presence of more advanced atherosclerotic lesions in mice that overexpress sPLA2 enzymes suggest their involvement in the atherosclerotic process. Therefore, the sPLA2 family of enzymes could provide reasonable targets for the prevention and treatment of atherosclerosis. Thus, A-002 (varespladib), an inhibitor of sPLA2enzymes, is proposed to modulate the development of atherosclerosis.MethodsTwenty-four guinea pigs were fed a high saturated fat, high cholesterol diet (0.25%) for twelve weeks. Animals were treated daily with A-002 (n = 12) or vehicle (10% aqueous acacia; n = 12) by oral gavage. After twelve weeks, animals were sacrificed and plasma, heart and aorta were collected. Plasma lipids were measured by enzymatic methods, lipoprotein particles size by nuclear magnetic resonance, aortic cytokines by a colorimetric method, and aortic sinus by histological analyses.ResultsPlasma total cholesterol, HDL cholesterol and triglycerides were not different among groups. However, the levels of inflammatory cytokines interleukin (IL)-10, IL-12 and granulocyte-macrophage colony-stimulating factor (GM-CSF) were significantly reduced in the treatment group. This group also had a significant 27% reduction in cholesterol accumulation in aorta compared with placebo group. Morphological analysis of aortic sinus revealed that the group treated with A-002 reduced atherosclerotic lesions by 24%.ConclusionThe use of A-002 may have a beneficial effect in preventing diet-induced atherosclerosis in guinea pigs.

Effects of Dietary Palmitoleic Acid on Plasma Lipoprotein Profile and Aortic Cholesterol Accumulation Are Similar to Those of Other Unsaturated Fatty Acids in the F1B Golden Syrian Hamster

The lower susceptibility of palmitoleic acid (16:1) to oxidation compared to PUFA may confer functional advantages with respect to finding acceptable alternatives to partially hydrogenated fats, but limited data are available on its effect on cardiovascular risk factors. This study investigated the effect of diets (10% fat, 0.1% cholesterol, wt:wt) enriched with macadamia [monounsaturated fatty acid (MUFA)16:1], palm (SFA,16:0), canola (MUFA,18:1), or safflower (PUFA,18:2) oils on lipoprotein profiles and aortic cholesterol accumulation in F1B Golden Syrian hamsters (n = 16/group). After 12 wk, 8 hamsters in each group were killed (phase 1). The remaining hamsters fed palm oil were changed to a diet containing coconut oil, while hamsters in the other diet groups continued on their original diets for an additional 6 wk (phase 2). With minor exceptions, the time course and dietary SFA source did not alter the study outcomes. Macadamia oil-fed hamsters had lower non-HDL cholesterol and triglyceride concentrations compared with the palm and coconut oil-fed hamsters and higher HDL-cholesterol compared with the coconut, canola, and safflower oil-fed hamsters. The aortic cholesterol concentration was not affected by dietary fat type. The hepatic cholesterol concentration was higher in the unsaturated compared with the saturated oil-fed hamsters. RBC membrane and aortic cholesteryl ester, triglyceride, and phospholipid fatty acid profiles reflected that of the dietary oil. These data suggest that an oil relatively high in palmitoleic acid does not adversely affect plasma lipoprotein profiles or aortic cholesterol accumulation and was similar to other unsaturated fatty acid-rich oils.

A‐002, a secretory phospholipase A2 inhibitor, reduces cholesterol accumulation in aorta and aortic cytokines in guinea pigs

Secretory phospholipase A2 enzymes (sPLA2) are involved with the generation of proinflammatory molecules such as leukotrienes and prostaglandins and are associated with atherosclerotic plaques. In this study we tested the effects of an sPLA2 inhibitor (A‐002) on aortic inflammatory cytokines and aortic lipid accumulation in a guinea pig atherosclerosis model. For this purpose, 24 male Hartley guinea pigs (12 per group) were fed a diet containing 0.25% dietary cholesterol to induce atherosclerosis, for 3 months. Animals were randomized into placebo (PL) or treated (A‐002) group, and gavaged daily either with vehicle (10% acacia, PL) or A‐002 (150 mg/kg/d, A‐002). At the end of 12 weeks, guinea pigs were sacrificed and blood was collected to measure plasma lipids and lipoprotein subfractions. The aorta was harvested for histological evaluation, measurement of inflammatory cytokines and lipid accumulation. Aortic cytokines including Interleukin (IL)‐2, IL‐10, IL‐12 and GMSCF measured by use of antibodies and Luminex technique were significantly lower (p &lt; 0.05) in the A‐002 group. In addition, the A‐002 group had 26.5% lower cholesterol accumulation in the aorta (p &lt; 0.05), but not in plasma, in association with a reduction in atherosclerotic lesion content in the aortic sinus. From these studies we conclude that A‐002 was effective in reducing atherosclerosis, as indicated by reductions in aortic cholesterol content, inflammatory cytokines and lesion content. [Study supported by Anthera Pharmaceuticals, Inc., San Mateo, CA].