Zinc supplementation inhibits lipid peroxidation and the development of atherosclerosis in rabbits fed a high cholesterol diet

Developing atherosclerotic lesions in hypercholesterolemic rabbits are depleted in zinc, while iron accumulates. This study examined the influence of zinc supplementation on the development of atherosclerosis and used isotope dilution gas chromatography-mass spectrometry techniques to measure biomarkers of oxidative lipid damage in atherosclerotic rabbit aorta. Our previous method for F(2)-isoprostane measurement was adapted to include the quantitation of cholesterol oxidation products in the same sample. Two groups of New Zealand white rabbits were fed a high cholesterol (1% w/w) diet and one group was also supplemented with zinc (1 g/kg) for 8 weeks. Controls were fed a normal diet. Zinc supplementation did not significantly alter the increase in total plasma cholesterol levels observed in animals fed high cholesterol. However, in cholesterol-fed animals zinc supplementation significantly reduced the accumulation of total cholesterol levels in aorta which was accompanied by a significant reduction in average aortic lesion cross-sectional areas of the animals. Elevated levels of cholesterol oxidation products (5,6-alpha and beta cholesterol epoxides, 7beta-hydroxycholesterol, 7-ketocholesterol) in aorta and total F(2)-isoprostanes in plasma and aorta of rabbits fed a cholesterol diet were significantly decreased by zinc supplementation. Our data indicate that zinc has an antiatherogenic effect, possibly due to a reduction in iron-catalyzed free radical reactions.     

Impact of a cholesterol enriched diet on maternal and fetal plasma lipids and fetal deposition in pregnant rabbits.

Pregnancy is associated with a hypercholesterolemic and a hyperlipidemic state. The totality of the essential fatty acids and 50% of the lipids needed by the fetus are transferred by the placenta from the maternal circulation. The hypothesis of this study is that an augmentation of the maternal plasmatic cholesterol is modifying the fetal lipids accumulation and development during rabbit pregnancy. To demonstrate the impact of a cholesterol enriched diet on plasma lipids during rabbit's pregnancy and on their fetus, we have established two groups: control and hypercholesterolemic rabbits (fed with a 0.2% cholesterol diet). Blood samples were collected before mating and at each trimester of pregnancy for analysis of lipid fractions and their lipoproteins. Plasma analysis shows that starting the 10th day of pregnancy the concentration of total-cholesterol and lipoproteins decreases for both groups. We have demonstrated that for the hypercholesterolemic group, concentrations of total-cholesterol (631%) and lipoproteins are significantly higher at the end of pregnancy than those for the control group. For both groups, after 20 days of pregnancy, triglycerides metabolism was biphasic showing a significant increase followed by a diminution in their concentration. In both groups, free fatty acids increases significantly at the end of the pregnancy (537.5% for the control group and 462.5% for the hypercholesterolemic group). Furthermore, the offsprings of hypercholesterolemic dams manifest a lower birth weight (15.5%) than those of control group. Our results demonstrate that a cholesterol enriched diet modifies greatly the fetal development and lipid metabolism during rabbit's pregnancy. These modifications could be useful for the understanding of the interaction between diet and fetal development in rabbit and probably during human pregnancy.     

CETP activity in liver perfusates and plasma from rabbits hypo- or hyperresponsive to dietary cholesterol

We investigated the relationship between the development of hypercholesterolemia in rabbits and cholesteryl ester transfer protein (CETP) activity secretion by their perfused livers. Two inbred strains of rabbits were compared which differ markedly in their hypercholesterolemic response to dietary cholesterol. Feeding a high-cholesterol (0.3%) diet, increased plasma and liver cholesterol levels in the two strains, the increments being 15 mM and 30 μmol/g greater in the hyperresponders, respectively. The high-cholesterol diet caused an about 2-fold increased hepatic secretion of CETP activity, but there was no difference between the two rabbit strains. Feeding a lower amount of dietary cholesterol (0.08%) also caused higher cholesterolemic (2 mM) and hepatocholesterolic (28 μmol/g) responses in hyper- than in hyporesponsive rabbits. The activity of hepatic CETP secretion was not increased by the low-cholesterol diet, and there was no difference between hypo- and hyperresponsive rabbits. Cholesterol feeding increased plasma CETP activity by 90% in both rabbit strains, but there was no difference between the strains. Our combined data suggest that with increasing plasma cholesterol levels, hepatic CETP secretion may be increased in a parabolic manner, reaching its maximum rate far before plasma cholesterol concentrations are maximal. There were no differences in hepatic CETP activity secretion or plasma CETP activity levels between the genetically different strains of hypo- and hyperresponsive rabbits.     

Improving effect of dietary taurine supplementation on the oxidative stress and lipid levels in the plasma,liver and aorta of rabbits fed on a high-cholesterol diet

The effect of a high-cholesterol diet with or without taurine on lipids and oxidative stress in the plasma, liver and aorta of rabbits was investigated. The animals were maintained on a basal diet (control), a high-cholesterol diet (HC, 1% w/w), or a high- cholesterol diet supplemented with taurine (HCHT, 2.5% w/w) for two months. Taurine has an ameliorating effect on atherosclerosis together with a decreasing effect on the cholesterol and triglyceride levels in rabbits fed on an HC diet. The HCHT diet caused a significant decrease in the malondialdehyde (MDA) and diene conjugate (DC) levels in the plasma, liver and aorta of rabbits as compared to the HC group. This treatment did not alter the antioxidant system in the liver of rabbits in the HC group. Our findings indicate that taurine ameliorated oxidative stress and cholesterol accumulation in the aorta of rabbits fed on the HC diet and that this effect may be related to its antioxidative potential as well as its reducing effect on serum lipids.     

Comparison of cholesterol transport in pulmonary, peritoneal, and blood-derived macrophages from normo- and hypercholesterolemic rabbits

The influx and efflux components of cholesterol transport were separately determined in pulmonary, peritoneal, and monocyte-derived macrophages from rabbits fed a diet containing either 4.5% fat or 4.5% fat plus 2% cholesterol. Both influx and efflux in pulmonary macrophages increased with increasing concentration of either normal or hypercholesterolemic serum in the medium. The mass of cholesterol entering the macrophages continued to increase beyond the mass of cholesterol effluxed, leading to an increase in cholesterol mass. Similar results were obtained with peritoneal macrophages. Cholesterol-enriched peritoneal macrophages in most cases had a net efflux of sterol when incubated with normocholesterolemic serum. Pulmonary and peritoneal macrophages from cholesterol-fed rabbits tended to have slower sterol influx and a slightly faster sterol efflux than pulmonary and peritoneal macrophages from control rabbits, but the combined effect of these mechanisms did not prevent these macrophages from accumulating sterol ester from hypercholesterolemic serum. Hypercholesterolemic rabbit serum was fractionated by heparin-Sepharose affinity chromatography into a beta-VLDL-deficient nonadsorbed fraction, which had very little effect on pulmonary macrophage sterol content, and an adsorbed beta-VLDL-containing fraction which promoted a large increase in macrophage sterol. As with unfractionated hypercholesterolemic serum, macrophages incubated with the adsorbed beta-VLDL-containing fraction accumulated large amounts of cellular sterol. Monocyte-macrophages cultured in vitro for 21 hr, in contrast to extravascular macrophages, closely regulated their cellular sterol, primarily by limiting the rate of sterol influx.     

Enhancement of rat liver catalase activity dietary cholesterol

The effects of a fat-supplemented diet and clofibrate (ethylchlorophenoxyisobutirate) upon serum lipids and liver catalase activity were studied in male rats. A butter-supplemented diet produced a striking increase of serum triglycerides but did not affect the liver catalase activity. Cholesterol (1%, w/w), added to the butter supplemented diet markedly increased liver catalase activity. This diet produced a hypercholesterolemic state higher than that induced by a butter-supplemented diet only, although the hypertriglyceridemic effect was less pronounced. Clofibrate given a butter-supplemented diet produced a marked increase of liver catalase activity (about four-fold). When clofibrate is administered with the cholesterol-supplemented diet, the increment observed in the liver catalase activity was the same as that induced with the cholesterol supplemented diet alone. Clofibrate, in either lipid-rich diet, failed to induce a hypocholesterolemic response, although a clear hypotrigliceridemic effect was evident. This effect appears to be potentiated with clofibrate and the cholesterol supplemented diet. Thus the increment in liver catalase activity induced by dietary cholesterol and clofibrate seems to be related to a hypotriglyceridemic effect which gives support to a role of liver peroxisomes in lipid metabolism. The role that liver catalase would play, in this regard, remains unclear from these results.     

Different responses of fluvastatin to cholesterol‐induced oxidative modifications in rabbits: evidence for preventive effect against DNA damage

Hypercholesterolemia is a major risk factor for atherosclerosis and related occlusive vascular diseases. We investigated the effect of low‐dose fluvastatin (2 mg kg^?1 day^?1) on antioxidant enzyme activities [superoxide dismutase (SOD), catalase], vascular reactivity changes and oxidatively induced DNA damage in early stage of atherosclerosis in hypercholesterolemic rabbits. The animals were divided into three groups each composed of 10 rabbits. The control group received a regular rabbit chow diet, and the cholesterol group had hypercholesterolemic diet (2%, 4 weeks). The fluvastatin group was given hypercholesterolemic diet plus fluvastatin. Dietary intake of cholesterol significantly increased total cholesterol levels in rabbits (control, 0.85 ± 0.29; cholesterol, 12.04 ± 4.61; fluvastatin, 8.07 ± 2.72 mmol l^?1 ). Hypercholesterolemic diet revealed discernible fatty streaks in arcus aortae. Fluvastatin significantly reduced the areas of the lesions. The diet significantly increased SOD activities in both erythrocyte and tissue. Treatment with fluvastatin normalized the increased activity of SOD in both erythrocyte and aortic tissues from the cholesterol group. Cholesterol feeding decreased the sensitivity to acetylcholine, and treatment with fluvastatin significantly restored the diminished sensitivity to acetylcholine in thoracic aortae. Cholesterol feeding caused oxidatively induced DNA damage in liver tissues determined by the increased levels of 8‐hydroxyguanine (8‐OH‐Gua) and 2,6‐diamino‐4‐hydroxy‐5‐formamidopyrimidine (FapyGua). Fluvastatin decreased only FapyGua level in liver. In conclusion, our results may suggest that fluvastatin seems to play a protective role on high cholesterol‐induced oxidative stress and DNA damage. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of dietary flaxseed on vascular contractile function and atherosclerosis during prolonged hypercholesterolemia in rabbits

Dietary flaxseed has significant anti-atherogenic effects. However, the limits of this action and its effects on vascular contractile function are not known. We evaluated the effects of flaxseed supplementation on atherosclerosis and vascular function under prolonged hypercholesterolemic conditions in New Zealand White rabbits assigned to one of four groups for 6, 8, or 16 wk of feeding: regular diet (RG), 10% flaxseed-supplemented diet (FX), 0.5% cholesterol-supplemented diet (CH), and 0.5% cholesterol- and 10% flaxseed-supplemented diet (CF). Cholesterol feeding resulted in elevated plasma cholesterol levels and the development of atherosclerosis. The CF group had significantly less atherosclerotic lesions in the aorta and carotid arteries after 6 and 8 wk than the CH animals. However, the anti-atherogenic effect of flaxseed supplementation was completely attenuated by 16 wk. Maximal tension induced in aortic rings either by KCl or norepinephrine was not impaired by dietary cholesterol until 16 wk. This functional impairment was not prevented by including flaxseed in the high-cholesterol diet. Aortic rings from the cholesterol-fed rabbits exhibited an impaired relaxation response to acetylcholine at all time points examined. Including flaxseed in the high-cholesterol diet completely normalized the relaxation response at 6 and 8 wk and partially restored it at 16 wk. No significant changes in the relaxation response induced by sodium nitroprusside were observed in any of the groups. In summary, dietary flaxseed is a valuable strategy to limit cholesterol-induced atherogenesis as well as abnormalities in endothelial-dependent vasorelaxation. However, these beneficial effects were attenuated during prolonged hypercholesterolemic conditions.     

Cytotoxicity of cholesterol oxidase to cells of hypercholesterolemic guinea pigs

1. A high cholesterol diet caused guinea pig erythrocytes to become sensitive to lysis by cholesterol oxidase (CO), a protein not hemolytic to normal cells. 2. Lysis was associated with conversion of membrane cholesterol to its oxidation product (delta-4-cholesten-3-one). 3. Intravenous injection of CO to hypercholesterolemic guinea pigs produced a reduction in serum cholesterol, but was not lethal as it was in rabbits. 4. Homogenized spleen, liver and kidney from the hyperlipidemic animals were sensitive to in vitro cholesterol oxidation while tissues from non-lipemic animals were resistant to modification.     

Cholesterol and copper in the liver of rabbit inbred strains with differences in dietary cholesterol response

In order to investigate whether cholesterol intake influences the hepatic copper content of rabbits, we compared the hepatic copper content of two rabbit inbred strains after feeding the animals a control or a cholesterol-rich diet. One strain was not reactive to dietary cholesterol (IIIVO/JU), whereas the other strain was reactive to dietary cholesterol (AX/JU). The coefficient of inbreeding (F) >0.95 for both strains. Dietary cholesterol-reactive rabbits when compared with their non-reactive counterparts had a higher hepatic copper content. The consumption of a hypercholesterolemic diet decreased liver copper concentration (expressed in micro g/g dry weight) in both strains of rabbits, which was (in part) due to dietary-induced hepatomegaly. A decrease in the absolute hepatic copper content was found only in the dietary cholesterol-reactive inbred strain. It is discussed that differences in glucocorticoid levels may be responsible for the strain difference in liver copper content. The cholesterol effect on the hepatic copper content in the reactive strain might be caused by an increased bilirubin secretion.     

Effects of Selenium- and Chromium-Enriched Diets on Growth Performance,Lipid Profile,and Mineral Concentration in Different Tissues of Growing Rabbits

The aim of this study was to investigate the effect of dietary supplementation with different sources of selenium and/or organic chromium on the growth performance, digestibility, lipid profile, and mineral content of hair, liver, and fore and hind limb of growing rabbits. A total of 150 weanling New Zealand White (NZW) male rabbits were randomly allotted to six dietary treatment groups: (1) basal diet (control group), (2) basal diet + 0.6 mg sodium selenite/kg diet, (3) basal diet + 0.6 mg selenium yeast/kg diet, (4) basal diet + 0.3 mg sodium selenite/kg diet + 0.3 mg selenium yeast/kg diet, (5) basal diet + 0.6 mg chromium yeast/kg diet + 0.6 mg selenium yeast/kg diet, (6) basal diet + 0.6 mg chromium yeast/kg diet. Only the combination between inorganic and organic selenium led to significant improvement in body weight, body weight gain, and feed conversion ratio. Carcass traits were not different in all groups. Selenium (Se) and chromium (Cr) were deposited in the tissues of rabbits fed diets supplemented with Se and Cr, respectively. Blood serum in both of selenium- and chromium-supplemented groups showed declined total cholesterol, triglycerides, and low-density lipoprotein (LDL). Group supplemented with organic chromium showed higher high-density lipoprotein (HDL) than the other groups. It could be concluded that using a mixture of inorganic and organic Se has a positive effect on the growth performance of growing rabbits. Both Se and Cr have hypocholesterolemic effect. Both of Se and Cr can be deposited in the meat and other tissues of rabbits and that improves meat quality which positively reflects on human acceptance. The combination between inorganic (0.3 mg sodium selenite/kg diet) and organic selenium (0.6 mg selenium yeast/kg diet) improved growth performance traits of growing rabbits.

     

Phytosterols and lecithin do not have an additive effect in lowering plasma and hepatic cholesterol levels in diet-induced hypercholesterolemic rats

Both plant sterols and lecithin are used as dietary supplements for lowering blood cholesterol in Western countries. This study evaluated the possibility of an additive effect of these ingredients on the regulation of lipid concentrations and cholesterol metabolism. Male Sprague-Dawley rats were randomly divided into three groups, and fed one of the following diets for 5 weeks; high cholesterol diet (HCD), phytosterol mixture-supplemented diet (PD, HCD+0.25% phytosterols), or phytosterol mixture and lecithin-supplemented diet (PLD, PD+0.15% lecithin). Feeding the PD for 5 weeks resulted in a 34% and 41% decrease in plasma total- and VLDL+LDL-cholesterol levels, respectively, and a 23% decrease in hepatic cholesterol content compared to those for the HCD rats (p < 0.05). These cholesterol-lowering properties of the phytosterol mixture were also associated with the down-regulation of hepatic acyl CoA:cholesterol acytransferase (ACAT) activity (p < 0.05). Addition of lecithin plus phytosterol mixture to the hypercholesterolemic diet did not significantly affect blood and hepatic lipid concentrations (with the exception of 36% decrease in hepatic triglyceride level, p < 0.05) as well as hepatic ACAT activity compared to feeding the hypercholesterolemic diet supplemented with phytosterol alone. These results indicate that combining lecithin, at a 0.15% level, with a phytosterol mixture-supplemented diet does not exhibit an additive effect in regulating hepatic ACAT activity or lowering blood cholesterol in hypercholesterolemic rats.     

Effects of added dietary taurine on erythrocyte lipids and oxidative stress in rabbits fed a high cholesterol diet

Lipid peroxidation leads to damage of polyunsaturated fatty acids of membrane phospholipids. The contribution of oxidative stress to hypercholesterolemia-induced hemolytic anemia and the effects of addition of taurine on erythrocyte lipid composition, oxidative stress, and hematological data were studied in rabbits fed on a high cholesterol (HC) diet (1%, w/w) for 2 months. The effects of taurine on erythrocyte hemolysis and H2O2-induced lipid peroxidation were investigated in normal rabbit erythrocytes in vitro. The HC diet resulted in increases in plasma lipids and lipid peroxide levels as well as increases in cholesterol levels and the cholesterol:phospholipid ratio in the erythrocytes. This diet caused a hemolytic anemia, but lipid peroxide levels remained unchanged in the erythrocytes of the rabbits. Taurine (2.5%, w/w) added to the food has an ameliorating effect on plasma lipids and lipid peroxide levels in rabbits fed on a HC diet. This treatment also caused decreases in elevated erythrocyte cholesterol levels and cholesterol:phospholipid ratio due to the HC diet, but it did not prevent the hemolytic anemia and did not change erythrocyte lipid peroxide levels. In addition, in an in vitro study, taurine did not protect erythrocytes against H2O2-induced hemolysis or lipid peroxidation. These results show that the HC diet causes hemolytic anemia without any changes in erythrocyte lipid peroxidation, and taurine treatment was not effective against hemolytic anemia caused by the HC diet.     

The effect of heat-stable extract from bovine sublingual salivary gland on serum cholesterol and triglyceride levels in normal and hypercholesterolemic rabbits

An extract of bovine sublingual glands (SLF3) reduced the serum cholesterol levels of normal rabbits 34.6% and serum triglyceride levels 19.6% when injected intraperitoneally (i.p.) at 20 mg/kg body wt on alternate days for 7 days. SLF3 also reduced serum cholesterol levels 69.0% and triglyceride levels 46.5% in hypercholesterolemic rabbits, while in similar rabbits injected with a control muscle tissue extract, the rate of decrease in serum cholesterol levels was 33.3% and triglyceride levels 26.7%.     

Synthesis of long-chain polyunsaturated fatty acids is inhibited in vivo in hypercholesterolemic rabbits and in vitro by oxysterols

Plasma total lipids, total cholesterol (cholesterol esters and free cholesterol) and oxysterol (mainly 7 beta-hydroxycholesterol (7 beta OH)) concentrations were significantly elevated in New Zealand rabbits fed a 2% cholesterol-containing diet with respect to controls fed the same diet without cholesterol. In addition, linoleic (18:2 n-6) and alpha-linolenic acid (18:3 n-3) plasma concentrations were significantly elevated in hypercholesterolemic rabbits, while concentrations of long-chain n-6 and n-3 derivatives were reduced. Studies in monocytic cell line THP-1 revealed that 7 beta OH markedly inhibited the conversion of 18:2 to 20:4 n-6 and of 18:3 to 22:6 n-3, indicating depression of the desaturation steps; in particular the inhibition was greater for the Delta 5 desaturation step. Furthermore, experiments of Real-Time PCR showed that 5-10 microM 7 beta OH decreased the Delta 5 gene expression. In conclusion, atherogenic oxysterols interfere with the production of long-chain polyunsaturated fatty acids from their precursors both in hypercholesterolemic rabbits and in cultured cells.     

The content of phospholipids and free fatty acids in the sarcoplasmic reticulum membranes in the early stage of an x-ray radiation lesion

One and 24 h following single X-irradiation (0.21 C/kg) of rabbit hind leg the content of free fatty acids and phospholipid lysoforms increased in the sarcoplasmic reticulum (SR) membrane of skeletal muscles. The results obtained are important in estimating the mechanisms of action of ionizing radiation on the structural and functional properties of SR.     

Dietary polyenylphosphatidylcholine decreases cholesterolemia in hypercholesterolemic rabbits: role of the hepato-biliary axis

The aim of this work was to study the cholesterol-lowering mechanisms induced by dietary soybean lecithin in hypercholesterolemic rabbits. Male New Zealand white rabbits (n = 6 in each group) were fed for 10 weeks either a low-fat control C diet, containing 27 g fat/kg, or high-fat diets enriched with 2 g cholesterol/kg and 77 g fat/kg. The high-fat diets contained 50 g lard (L), 50 g soybean triacylglycerol (SO), or 50 g pure soybean phosphatidylcholine (PLE). PLE diet decreased by 30% beta-VLDL-cholesterol, compared with SO diet. HDL2-, HDL3- and LDL-lipid contents were unchanged in the L, SO and PLE groups. In gallbladder bile, amounts of phospholipids, bile salts and cholesterol were significantly increased in PLE group by respectively 45%, 11% and 44%, in comparison with SO group. Intestinal and hepatic Hydroxy Methyl Glutaryl Coenzyme A reductase activities were not increased by PLE diet. Triacylglycerol hepatic content was lower in PLE group than in L or SO groups. Compared with triacylglycerol enriched diet, phosphatidylcholine enriched diet developed significant higher cholesterol- and triacylglycerol-lowering effects by a two-step mechanism: i) by reducing the beta-VLDLs, ii) by enhancing the secretion of bile cholesterol. Such results constitute promising effects of soybean phosphatidylcholine at the hepato-biliary level, in the treatment or prevention of hyperlipidemia and related atherosclerosis.     

Different palm oil preparations reduce plasma cholesterol concentrations and aortic cholesterol accumulation compared to coconut oil in hypercholesterolemic hamsters

Several studies have reported on the effect of refined, bleached and deodorized palm oil (RBD-PO) incorporation into the diet on blood cholesterol concentrations and on the development of atherosclerosis. However, very little work has been reported on the influence of red palm oil (RPO), which is higher in carotenoid and tocopherol content than RBD-PO. Thus, we studied the influence of RPO, RBD-PO and a RBD-PO plus red palm oil extract (reconstituted RBD-PO) on plasma cholesterol concentrations and aortic accumulation vs. hamsters fed coconut oil. Forty-eight F1B Golden Syrian hamsters (Mesocricetus auratus) (BioBreeders, Watertown, MA) were group housed (three/cage) in hanging polystyrene cages with bedding in an air-conditioned facility maintained on a 12-h light/dark cycle. The hamsters were fed a chow-based hypercholesterolemic diet (HCD) containing 10% coconut oil and 0.1% cholesterol for 2 weeks at which time they were bled after an overnight fast and segregated into four groups of 12 with similar plasma cholesterol concentrations. Group 1 continued on the HCD, Group 2 was fed the HCD containing 10% RPO in place of coconut oil, Group 3 was fed the HCD containing 10% RBD-PO in place of coconut oil and Group 4 was fed the HCD with 10% reconstituted RBD-PO for an additional 10 weeks. Plasma total cholesterol (TC) and non-high-density lipoprotein-cholesterol (HDL-C) (very low- and low-density lipoprotein) concentrations were significantly lower in the hamsters fed the RPO (-42% and -48%), RBD-PO (-32% and -36%) and the reconstituted RBD-PO (-37% and -41%) compared to the coconut oil-fed hamsters. Plasma HDL-C concentrations were significantly higher by 14% and 31% in hamsters fed the RBD-PO and RPO compared to the coconut oil-fed hamsters. Plasma triglyceride (TG) concentrations were significantly lower in hamsters fed RBD-PO (-32%) and the reconstituted RBD-PO (-31%) compared to the coconut oil-fed hamsters. The plasma gamma-tocopherol concentrations were higher in the coconut oil-fed hamsters compared to the hamsters fed the RPO (60%), RBD-PO (42%) and the reconstituted RBD-PO (49%), while for plasma alpha-tocopherol concentrations, the coconut oil-fed hamsters were significantly higher than only the RPO-fed hamsters (21%). The coconut oil-fed hamsters also had significantly higher plasma lipid hydroperoxide concentrations compared to RBD-PO (112%) and the reconstituted RBD-PO (485%). The hamsters fed the coconut oil diet excreted significantly more fecal total neutral sterols and cholesterol compared to the hamsters fed the RBD-PO (158% and 167%, respectively). The coconut oil-fed hamsters had significantly higher levels of aortic total, free and esterified cholesterol compared to the hamsters fed the RPO (74%, 50% and 225%, respectively), RBD-PO (57%, 48% and 92%, respectively) and the reconstituted RBD-PO (111%, 94% and 94%, respectively). Also, aortic free/ester cholesterol ratio in the aortas of hamsters fed RPO was significantly higher than in those fed the coconut oil (124%). In conclusion, hamsters fed the three palm oil preparations had lower plasma TC and non-HDL-C and higher HDL-C concentrations while accumulating less aortic cholesterol concentrations compared to hamsters fed coconut oil.     

Anti-atherogenic effects of seabuckthorn (Hippophaea rhamnoides) seed oil

Seabuckthorn (SBT) seed oil is a rich source of unsaturated fatty acids, phytosterols, carotenoids and flavonoids, which are known to have significant anti-atherogenic and cardioprotective activity. The anti-atherogenic activity of supercritical CO(2) extracted SBT seed oil was evaluated in white albino rabbits fed on high cholesterol diet for 60 days. The study was performed on 20 male healthy rabbits divided into four groups of 5 animals each. Group I - control, group II - SBT seed oil, group III - cholesterol (1%) for 60 days, group IV - cholesterol+SBT seed oil. After 30 days of high cholesterol diet, group IV rabbits received 1 ml of SBT seed oil daily for 30 days. Blood total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C) and triglyceride (TG) levels were measured before and after the administration of SBT seed oil. The vasorelaxant activity of the seed oil was studied in vitro using aortic ring model technique and changes in isometric force were recorded using a polygraphic recording system. Accumulation of cholesterol in the aorta was studied using Sudan-IV staining technique. SBT seed oil feeding to normal rabbits for 18 days caused a significant decline in plasma cholesterol, LDL-C, atherogenic index (AI) and LDL/HDL ratio. The HDL-C levels, HDL-C/TC ratio (HTR) and vasorelaxant activity of the aorta were significantly increased. In cholesterol-fed animals the TC, TG, LDL-C and AI were significantly increased and showed a decline following seed oil administration. The increase in HDL-C was more marked in seed oil treated hypercholesterolemic animals. The acetylcholine-induced vasorelaxant activity was significantly decreased in cholesterol-fed animals and could be restored to that of normal values by seed oil administration. These observations suggest that supercritical CO(2) extracted SBT seed oil has significant anti-atherogenic and cardioprotective activity.     

Early pathological changes of endothelia in a model using LDL perfusion at physiological LDL-cholesterol concentration.

The aim of the present research was to provide further insight into the debated problem of the existence of modified LDL in vivo. For this purpose a novel model was devised for studying LDL injurious effect on endothelial cells (EC) by infusing native cholesterol rich LDL, diluted to physiological LDL cholesterol concentration. Normal rabbits were infused with LDL separated from rabbits previously fed either with standard food (I-LDL Group), 1% cholesterol (II-LDL Group) or 1% cholesterol plus probucol (IV-LDL Group). Cu++ modified II-LDL was infused as well (III-LDL Group). After dilution as above, lipid oxide (LP) significantly increased in III- and II-LDL media, as compared to I- and IV-LDL media. EC of III- and II-LDL Groups showed irregular shape and surface pattern. Further, they showed adhering clusters of monocytes, platelets and erythrocytes. Endocytic vesicles and ruthenium red-positive particles increased too. EC of IV-LDL Group were only slightly affected as compared to I-LDL Group. These data suggest that native LDL from hypercholesterolemic rabbits contain an oxidized form which is noxious to EC even when LDL is infused at physiological LDL-cholesterol concentration. This early injury is in part LP-associated and actively involves platelets and monocytes.