Incremental replacement of saturated fats by n-3 fatty acids in high-fat, high-cholesterol diets reduces elevated plasma lipid levels and arterial lipoprotein lipase, macrophages and atherosclerosis in LDLR-/- mice.

OBJECTIVE: Effects of progressive substitution of dietary n-3 fatty acids (FA) for saturated FA (SAT) on modulating risk factors for atherosclerosis have not been fully defined. Our previous reports demonstrate that SAT increased, but n-3 FA decreased, arterial lipoprotein lipase (LpL) levels and arterial LDL-cholesterol deposition early in atherogenesis. We now questioned whether incremental increases in dietary n-3 FA can counteract SAT-induced pro-atherogenic effects in atherosclerosis-prone LDL-receptor knockout (LDLR-/-) mice and have identified contributing mechanisms. METHODS AND RESULTS: Mice were fed chow or high-fat diets enriched in SAT, n-3, or a combination of both SAT and n-3 in ratios of 3:1 (S:n-3 3:1) or 1:1 (S:n-3 1:1). Each diet resulted in the expected changes in fatty acid composition in blood and aorta for each feeding group. SAT-fed mice became hyperlipidemic. By contrast, n-3 inclusion decreased plasma lipid levels, especially cholesterol. Arterial LpL and macrophage levels were increased over 2-fold in SAT-fed mice but these were decreased with incremental replacement with n-3 FA. n-3 FA partial inclusion markedly decreased expression of pro-inflammatory markers (CD68, IL-6, and VCAM-1) in aorta. SAT diets accelerated advanced atherosclerotic lesion development, whereas all n-3 FA-containing diets markedly slowed atherosclerotic progression. CONCLUSION: Mechanisms whereby dietary n-3 FA may improve adverse cardiovascular effects of high-SAT, high-fat diets include improving plasma lipid profiles, increasing amounts of n-3 FA in plasma and the arterial wall. Even low levels of replacement of SAT by n-3 FA effectively reduce arterial lipid deposition by decreasing aortic LpL, macrophages and pro-inflammatory markers.

Pharmacological inhibition of C-C chemokine receptor 2 decreases macrophage infiltration in the aortic root of the human C-C chemokine receptor 2/apolipoprotein E-/- mouse: magnetic resonance imaging assessment.

UNLABELLED: Purpose- This study assessed the pharmacological effect of a novel selective C-C chemokine receptor (CCR) 2 antagonist (GSK1344386B) on monocyte/macrophage infiltration into atherosclerotic plaque using magnetic resonance imaging (MRI) in an atherosclerotic mouse model. METHODS AND RESULTS: Apolipoprotein E(-/-) mice expressing human CCR2 were fed a Western diet (vehicle group) or a Western diet plus10 mg/kg per day of GSK1344386B (GSK1344386B group). After the baseline MRI, mice were implanted with osmotic pumps containing angiotensin II, 1000 ng/kg per minute, to accelerate lesion formation. After five weeks of angiotensin II administration, mice received ultrasmall superparamagnetic iron oxide, an MRI contrast agent for the assessment of monocyte/macrophage infiltration to the plaque, and underwent imaging. After imaging, mice were euthanized, and the heart and aorta were harvested for ex vivo MRI and histopathological examination. After 5 weeks of dietary dosing, there were no significant differences between groups in body or liver weight or plasma cholesterol concentrations. An in vivo MRI reflected a decrease in ultrasmall superparamagnetic iron oxide contrast agent uptake in the aortic arch of the GSK1344386B group (P<0.05). An ex vivo MRI of the aortic root also reflected decreased ultrasmall superparamagnetic iron oxide uptake in the GSK1344386B group and was verified by absolute iron analysis (P<0.05). Although there was no difference in aortic root lesion area between groups, there was a 30% reduction in macrophage area observed in the GSK1344386B group (P<0.05). CONCLUSIONS: An MRI was used to noninvasively assess the decreased macrophage content in the atherosclerotic plaque after selective CCR2 inhibition.

One-month administration of hydroxytyrosol, a phenolic antioxidant present in olive oil, to hyperlipemic rabbits improves blood lipid profile, antioxidant status and reduces atherosclerosis development.

The present study analysed the effects of hydroxytyrosol (HT) on blood lipids, antioxidant status and the progression of aortic lesions in hyperlipemic rabbits. Sixty-four rabbits were distributed into eight groups of animals (n = 8). Animal groups C, A and H were fed for 1-month with a control diet containing sunflower oil (C), an atherogenic diet (A) high in saturated fat and cholesterol or the A diet together with HT, respectively. The other five groups were fed for 2-months with diets C or A (groups CC or AA, respectively), or for 1-month with the A-diet followed by a further month with diet C, extra virgin olive oil diet (O) or diet C with HT (groups AC, AO and AH, respectively). Four milligram of HT/kg body weight were used in the study. Fifty and 42% decrease in total cholesterol and triacylglycerols, respectively, and a 2.3-fold increase in HDL-cholesterol were observed in the AH group but not in the H group. The HT-supplemented groups improved their antioxidant status and reduced the size of atherosclerotic lesions measured as intimal layer areas of the aortic arch when compared with control animals. We conclude that HT supplementation may have cardioprotective effects in vivo.

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.

Atherosclerosis. Chronic effects of fish oil and a therapeutic diet in nonhuman primates.

Prolonged testing of marine fish oil (FO) as a dietary supplement is necessary because of widespread claims that it is antiatherogenic. The basis for such claims is inadequate because atherogenesis is chronic and may not respond to short-term changes induced by dietary treatments. A proven (vervet) model of atherosclerosis promoted by an atherogenic diet (AD) was used to test dietary supplementation with Atlantic pilchard FO for 20 months in 47 omnivorous nonhuman primates. Responses were controlled against known favorable effects of changing from the AD to a therapeutic diet (TD). Compliance was achieved, and tissue responses to the FO dose were confirmed. Compromise of reflex vasoconstriction by atherosclerosis was demonstrated for the first time in the model. Aortic, peripheral, coronary, and cerebral atherosclerosis were assessed by light microscopy and computerized image analysis. No component of atherosclerosis regressed after dietary FO, and several deteriorated. After a change to the TD, stainable lipid was cleared from aortas and there were few lipophages, but advanced atherosclerosis was not reduced. Male vervets developed more severe atherosclerosis than did females, and the association among aortic, peripheral, and coronary atherosclerosis was positive in males. Females were resistant to coronary atherosclerosis. Only mild cerebral atherosclerosis was detected. In conclusion, the FO used was not antiatherogenic in the model, and there is a need for caution. The TD regresses some components of atherosclerosis, but it was not effective against fibrosis, mineralization, and cholesterol crystals within 20 months.

Use of 3H-cholesteryl linoleyl ether as a quantitative marker for loss of cholesteryl ester during regression of cholesterol-induced aortic atheromas in rabbits.

In this study, use was made of 3H-cholesteryl linoleyl ether (3H-CLE) to follow regression of aortic atheromatosis induced by feeding cholesterol to rabbits. After a 3-month induction period, the rabbits were divided into two groups with an attempt to match them by plasma cholesterol levels. They were injected with rabbit plasma labeled with 3H-CLE, and the baseline group rabbits were killed 10 to 12 days after injection. The experimental (regression) group rabbits were given rabbit chow containing 3% cholestyramine and were killed up to 330 days thereafter. Aortic 3H-CLE of both the baseline and the regression groups correlated highly with the plasma cholesterol levels at the time of injection of label. The radioactivity recovered in the aortas of the baseline and regression groups was not significantly different, indicating retention of label between day 12 and 330 days after injection. During that time, the mean aortic cholesteryl ester content decreased from 7.6 +/- 1.3 mg to 3.1 +/- 0.7 mg (p less than 0.01). The specific activity of 3H-CLE/cholesteryl ester determined in the aortic arch and the thoracic and abdominal aorta was significantly increased in all three regions examined in the regression group as compared to the baseline group. The present data show that 3H-CLE is retained in the atheromatous aorta for at least 330 days and that its use may add another dimension to the quantitative evaluation of regression of atherosclerotic lesions.