Purpurogallin in the prevention of hypercholesterolemic atherosclerosis

Effects of purpurogallin (PPG), an antioxidant on high cholesterol diet-induced atherosclerosis, and changes in blood lipid profile and lipid peroxidation product malondialdehyde (MDA), aortic tissue MDA, chemiluminescence (M-CL), a marker for antioxidant reserve and antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-P_x)] were investigated in rabbits. The rabbits were divided into three groups: Group I, regular rabbit chow; Group II, same as Group I+cholesterol (1%); and Group III, same as Group II+PPG (14 mg/kg, orally, daily). Serum concentrations of triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and blood MDA were measured before and after 4 and 10 weeks on the respective diets. The aorta was removed at the end of 10 weeks for assessment of atherosclerotic changes, MDA concentration, M-CL, and antioxidant enzymes. Coronary arteries were also examined for atherosclerotic changes. Serum TC, LDL-C, and LDL-C/HDL-C ratio increased whereas HDL-C decreased in Group II and their values were similar in Groups II and III. Aortic tissue MDA, M-CL, CAT, and GSH-P_x activity increased in Group II but these values in Group III were lower than in Group II except for MDA which was greater in Group III than in Group II. Atherosclerotic changes were greater in Group II than in Group III. Histological changes were similar in Groups II and III. Atherosclerotic changes were also observed in the coronary arteries of Groups II and III, however, they were less in Group III than in Group II. Increased levels of aortic MDA and decreased levels of antioxidant reserve, which were associated with the development of atherosclerosis, suggest a role for oxygen radicals in the pathogenesis of hypercholesterolemic atherosclerosis. The protection afforded by PPG, which was associated with reversal of the antioxidant reserve to control level, in spite of hypercholesterolemia, supports the hypothesis that oxygen radicals are involved in the development of hypercholesterolemic atherosclerosis. These results suggest that PPG retard the development of hypercholesterolemic atherosclerosis because of its antioxidant activity without lowering blood cholesterol level.     

Regression of hypercholesterolemic atherosclerosis in rabbits by secoisolariciresinol diglucoside isolated from flaxseed

Secoisolariciresinol diglucoside (SDG) isolated from flaxseed is a lipid-lowering and antioxidant agent. It suppresses the development of hypercholesterolemic atherosclerosis in rabbits. It is however not known if SDG would produce regression of atherosclerosis. The objectives of this study were to determine (i) if SDG produces regression of atherosclerosis; (ii) if regression is associated with reduction in serum lipids, oxidative stress or both; and (iii) if the duration of treatment has an effect on regression. Rabbits were assigned to five groups: Group I, regular diet (control); Group II, 0.5% cholesterol diet for 2 months (mo); Group III, same as Group II but followed by regular diet for 2 mo; Group IV, same as Group II and followed by regular diet with SDG (20mg x kg body wt(-1) x day(-1) PO) for 2 mo; and Group V, same as Group IV but SDG treatment for an additional 2 mo. Blood samples were collected from rabbits before and at monthly intervals thereafter on their respective diet regimen for measurement of triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and malondialdehyde (MDA), a lipid peroxidation product. At the end of the protocol, the aorta was removed for assessment of atherosclerotic lesions, aortic MDA and aortic chemiluminescence (Aortic-CL), a measure of antioxidant reserve. MDA and Aortic-CL provide an index of oxidative stress. Increases in serum TG, TC, LDL-C, HDL-C and the risk ratio TC/HDL-C in Group II were associated with an increase in oxidative stress and development of atherosclerosis (57% of aortic intimal surface covered with lesions). Serum lipids decreased to a similar extent in Groups III-V, however atherosclerotic lesions were 84%, 63% and 44%, respectively in Groups III-V. There were more atherosclerotic lesions in Group III (+48.9%) as compared to Group II. The atherosclerotic lesions decreased by 24% and 45%, respectively in Groups IV and V compared to Group III. The reduction in atherosclerotic lesions was associated with a reduction in oxidative stress. These results suggest that (i) regular diet following a high cholesterol diet accelerates atherosclerosis in spite of a decrease in serum lipids; (ii) SDG treatment prevents the progression of atherosclerosis on a regular diet following a high cholesterol diet; (iii) prevention of progression is associated with a reduction of aortic oxidative stress and not with reductions in serum lipids; (iv) a longer duration of treatment reduces the progression of atherosclerosis to a greater extent, and tends to regress the atherosclerosis.     

Hypocholesterolemic and antiatherosclerotic effect of flax lignan complex isolated from flaxseed

Hypercholesterolemia, low HDL-C and oxygen radicals have been implicated in the development of atherosclerosis. Lignan complex isolated from flaxseed contains secoisolariciresinol diglucoside (SDG), 3-hydroxy-3methylglutaric acid (HMGA) and cinnamic acids. SDG and cinnamic acids are antioxidants, and HMGA is a hypocholesterolemic agent. Antioxidants are known to reduce hypercholesterolemic atherosclerosis. The objectives of this study were to determine if lignan complex reduces (i) serum cholesterol, (ii) oxidative stress, and (iii) atherosclerosis in hypercholesterolemic rabbits. Rabbits were assigned to four groups: Group I, control; Group II, lignan complex control (lignan complex, 40 mg/kg body weight daily orally); Group III, 0.5% cholesterol; Group IV, 0.5% cholesterol diet+lignan complex, (40 mg/kg body weight daily orally). Blood samples were collected before (time 0) and after 1 and 2 months of experimental diets for measurement of serum triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and serum malondialdehyde (MDA), a lipid peroxidation product. At the end of the protocol, the aorta was removed for measurement of atherosclerotic plaques, MDA and aortic tissue chemiluminescence (Aortic CL), a marker of antioxidant reserve. Rabbits in Group III developed atherosclerosis (50.84+/-6.23% of the intimal surface of the aorta was covered with atherosclerotic changes) which was associated with an increase in the serum TG, TC, LDL-C, HDL-C, MDA and aortic MDA and antioxidant reserve. Lignan complex reduced the development of atherosclerosis by 34.37% and this was associated with a decrease in serum TC by 20%, LDL-C by 14%, TC/HDL-C by 34%, serum MDA by 35% and aortic MDA by 58%. Serum HDL-C was elevated by 30% in hypercholesterolemic rabbits and by 25% in normocholesterolemic rabbits with lignan complex. Lignan complex did not affect the TC and LDL-C and serum MDA in the normocholesterolemic rabbits. However, it increased the aortic MDA in the normocholesterolemic rabbits. These results suggest that lignan complex isolated from flaxseed reduced the extent of hypercholesterolemic atherosclerosis and this effect was associated with marked decreases in oxidative stress, serum total cholesterol, LDL-C and risk ratio, and elevation of serum HDL-C. Lignan complex may, therefore, be beneficial in preventing atherosclerosis, and reducing risk factors for coronary artery disease and stroke.     

Oxygen free radicals as a mechanism of hypercholesterolemic atherosclerosis: Effects of probucol

We investigated the effects of high cholesterol diet in the presence and absence of probucol on the genesis of atherosclerosis, the blood lipid profile, aortic tissue lipid peroxidation product malondialdehyde (MDA), and aortic tissue chemiluminescence (CL) a marker for antioxidant reserve in rabbits. Five groups each of 10 rabbits were studied: group I, regular rabbit chow; group II, as I + cholesterol (0.5%); group III, as I + cholesterol (0.5%) and probucol (0.5 gm/kg/day); group IV, as I + cholesterol (1%), and group V, as I + cholesterol (1%) and probucol (0.5 gm/kg/day). Blood concentrations of triglyceride (TG), total cholesterol (TC), high density lipoproteincholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), very low density lipoprotein-cholesterol (VLDL-C) were measured at monthly intervals for 4 months. The aorta was removed at the end of the protocol for assessment of atherosclerotic changes (gross and microscopic), MDA concentration and CL. TC, LDL-C, LDL-C/HDL-C ratio increased in all the groups except group I, while VLDL-C increased in group II only. HDL-C decreased in groups III, IV and V but remained unchanged in groups I and II. There was a decrease in HDL-C and VLDL-C components and an increase in LDL-C components of total cholesterol in all the groups II, III, IV and V, the changes being greater in group IV than in group II. Probucol did not appreciably affect the changes in lipid profile except that it decreased HDL-C significantly. Aortic tissue MDA increased in groups II, IV and V to a similar extent. Aortic CL which was measured only in groups I, IV and V increased to similar extent in the latter two groups. Atherosclerotic changes were greater in group II than in group III but similar to that in groups IV and V. Histological changes were practically similar in groups II, III, IV and V. The increased levels of aortic MDA and CL, which were associated with development of atherosclerosis, suggest a role for oxygen free radicals in the pathogenesis of hypercholesterolemia-induced atherosclerosis. Protection afforded by probucol was associated with a decrease in aortic MDA in spite of hypercholesterolemia. Ineffectiveness of probucol in 1% cholesterolfed rabbits was associated with its inability to reduce MDA and increase antioxidant reserve. These findings further support for the hypothesis that oxygen free radicals are involved in the genesis and maintenance of hypercholesterolemic atherosclerosis.     

Vitamin E does not slow the progression of hypercholesterolemic atherosclerosis

BACKGROUND:

Vitamin E suppresses the development of atherosclerosis but does not regress established hypercholesterolemic atherosclerosis.

OBJECTIVES:

To investigate whether vitamin E slows the progression of established atherosclerosis, and whether this effect is associated with reductions in serum lipids and oxidative stress.

METHODS:

The present study was performed in four groups of rabbits: group I, regular diet (control); group II, 0.25% cholesterol diet (two months); group III, 0.25% cholesterol diet (four months); and group IV, 0.25% cholesterol diet (two months) followed by 0.25% cholesterol and vitamin E (two months). Serum lipids and the chemiluminescent activity of white blood cells (WBC-CL), a measure of oxygen radical production by white blood cells, were measured before and at monthly intervals for the duration of the study. Aortas were removed at the end of the protocol for assessment of atherosclerosis and the chemiluminescent activity of aortic tissue (aortic-CL), a measure of antioxidant reserve.

RESULTS:

Atherosclerosis was associated with hyperlipidemia and increased oxidative stress, indicated by increased nonactivated WBC-CL and alteration of the aortic-CL. Significant areas of the intimal surfaces of the aortas from group II (26.54%±4.11%), group III (69.37%±5.34%) and group IV (65.96%±7.86%) were covered with atherosclerotic lesions. Vitamin E did not alter serum lipids, aortic antioxidant reserve or WBC-CL. Vitamin E was ineffective in slowing the progression of hypercholesterolemic atherosclerosis.

CONCLUSION:

Vitamin E did not slow the progression of hypercholesterolemic atherosclerosis, and this effect was associated with its ineffectiveness in reducing serum lipids and oxidative stress.     

Antioxidant Effects of Lovastatin and Vitamin E on Experimental Atherosclerosis in Rabbits

The effects of the administration of vitamin E (10 mg/day) plus lovastatin (2 mg/day; group A, n = 10), lovastatin alone (2 mg/day; group B, n = 10), and placebo (group C, n = 10) were compared over 24 weeks in a randomized, single-blind controlled trial. All groups of rabbits received a trans fatty acid (TFA)–rich diet (5–10 g/day) for 36 weeks. Treatment with vitamin E plus lovastatin (group A) and lovastatin (group B) started after 12 week of administration of TFA-rich diet was associated with a significant but similar decline in serum cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides in both groups at 36 weeks. Lipid peroxides and diene conjugates showed a significant decline in association with a significant increase in the plasma level of vitamin E in group A rabbits at 36 weeks. However, the lovastatin group B showed a lesser but significant decrease in lipid peroxides and diene conjugates at 36 weeks, indicating that lovastatin may have antioxidant activity. In control group C, the increase in blood lipids and oxidative stress at 36 weeks was much greater than the decrease in groups A and B. After experimental lipid peroxidation at 24 weeks in all of the rabbits, 2 of 10 group B and 3 of 10 group C rabbits died due to coronary thrombosis; there were no deaths in group A. Thus antioxidant therapy with vitamin E can provide protection against death due to free radical stress. Aortic lipids and sudanophilia indicating athorosclorosis were significantly lower in groups A and B than in group C. The atherosclerotic coronary plaque sizes were significantly smaller in group A (18.5 ± 3.6 μm) than in groups B (41.6 ± 4.2 μm) and C (85 ± 6.7 μm). Aortic plaque sizes were also smaller in group A than in group B and C. It is possible that antioxidant therapy with vitamin E, as an adjunct to lipid lowering with lovastatin, can provide additional benefit in the inhibition of oxidative stress and atherosclerosis. The antioxidant activity of lovastatin has not been reported, to our knowledge. This revised version was published online in July 2006 with corrections to the Cover Date.     

四逆汤对高胆固醇喂饲所致动脉粥样硬化形成和氧化损伤的影响

为了观察四逆汤对高胆固醇喂饲所致家兔实验性动脉粥样硬化形成和氧化损伤的影响，采用高胆固醇喂饲模型；将24只新西兰家兔随机分为3组：正常组、模型组、四逆汤组，分别给予普通饲料(正常对照组)和高胆固醇饮食(其它2组)喂养，四逆汤组另加用四逆汤方药；实验结束后，观察血管病理变化、血和血管超氧化物歧化酶活性、血浆和血管丙二醛含量、超氧化物歧化酶蛋白和基因表达。结果发现，与模型组相比，四逆汤组主动脉脂质斑块面积、内膜斑块面积和厚度明显降低；血和血管超氧化物歧化酶活性明显增加；血浆和血管丙二醛的含量明显增加；血管超氧化物歧化酶蛋白和基因表达明显增强。研究结果提示，四逆汤具有较好的抗动脉粥样硬化作用，抗氧化损伤可能是四逆汤产生抗动脉粥样硬化作用的重要机制之一。     

Attenuation of the development of hypercholesterolemic atherosclerosis by thymoquinone

Thymoquinone (TQ), derived from Nigella sativa seed, is an antioxidant. The present study investigated whether TQ attenuates the development of atherosclerosis, and/or reduces the serum lipid levels and oxidative stress in rabbits. New Zealand white female rabbits were assigned to four groups of six animals each: group I, control; group II, 1% cholesterol diet; group III, 1% cholesterol plus TQ (10 mg/kg/day; through a nasogastric tube) diet; and group IV, 1% cholesterol plus TQ (20 mg/kg/day; through a nasogastric tube) diet. Blood samples were collected at baseline and after four and eight weeks on the experimental diets for measurement of serum lipids, total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), TC/HDL-C ratio and oxidative stress biomarkers (malondialdehyde [MDA] and protein carbonyls). At the end of the eight weeks, the aorta was removed for the assessment of atherosclerotic changes, MDA and protein carbonyls. Group II animals developed atherosclerosis (45%±11% of the intimal surface of aorta was covered with atherosclerotic plaques), which was associated with an increase in the serum TC, TG, LDL-C, HDL-C, TC/HDL-C, MDA and protein carbonyls. In group III, TQ decreased serum TC, LDL-C, MDA and protein carbonyls by 26%, 29%, 85% and 62%, respectively, and aortic MDA by 73%, which was associated with a 40% reduction of the development of aortic atherosclerosis. The higher dose of TQ in group IV had effects similar to the lower dose (group III), except that this dose further decreased serum TG. It is concluded that TQ attenuates hypercholesterolemic atherosclerosis and this effect is associated with a decrease in serum lipids and oxidative stress.     

Amlodipine attenuates oxidative stress in the heart and blood of high-cholesterol diet rabbits

Introduction

Oxidative stress is a key component of atherosclerosis. It has been suggested that amlodipine inhibits oxidative stress. In this study, we evaluated the effects of amlodipine on the total antioxidant capacity of heart tissue and blood in 36 control and cholesterol-fed male New Zealand white rabbits.

Methods

The rabbits were divided into four groups (n = 9). Group 1 rabbits were fed a regular diet, group 2 were fed a diet with 2% cholesterol, group 3 were fed a regular diet plus 5 mg/kg/day oral amlodipine, and group 4 were fed 2% cholesterol diet plus amlodipine 5 mg/kg/day. At the end of eight weeks, blood samples were drawn and at the same time heart tissue was isolated and frozen in liquid nitrogen. After homogenisation, the solution was centrifuged and the light supernatant was stored at –80˚C. This was used for determination of glutathione peroxidase (GPX), superoxide dismutase (SOD) and (MDA) levels.

Results

Eight weeks of amlodipine treatment significantly reduced the levels of total cholesterol, low-density lipoprotein cholesterol and triglycerides in the group on the hypercholesterolaemic diet (p < 0.05). In the blood, the level of thiobarbituric acid-reactive substances increased in the rabbits on the 2% cholesterol diet (group 2) and 2% cholesterol-plusamlodipine diet (group 4) and decreased in the amlodipineonly group (group 3) (p < 0.05). Lipid peroxidation in the heart tissue was similar to that in the blood, except in the amlodipine-only group (group 3). In the blood, the activity of total SOD (tSOD) decreased in the group on the 2% cholesterol diet (group 2) (p < 0.05) and markedly increased in the amlodipine-only (group 3) and 2% cholesterol-plusamlodipine groups (group 4) (p < 0.05).

Conclusion

Amlodipine decreased oxidative stress in the heart and blood and improved the lipid profile in cholesterolfed rabbits. Therefore, it may be considered a useful tool for the reduction of oxidative stress and improvement of lipid profiles in diseases related to atherosclerosis.     

Suppression of hypercholesterolemic atherosclerosis by pentoxifylline and its mechanism

Reactive oxygen species (ROS) have been implicated in the development of hypercholesterolemic atherosclerosis. Hypercholesterolemia increases the levels of platelet activating factor (PAF) and cytokines which are known to stimulate granulocytes and endothelial cells to produce ROS. Pentoxifylline (PTX) is an inhibitor of cytokines and PAF and would reduce the generation of ROS by granulocytes and endothelial cells. PTX therefore would be expected to reduce the development of hypercholesterolemic atherosclerosis. New Zealand white female rabbits were assigned to four groups: Group I (n=12), control; Group II (n=5), PTX control (40 mg/kg body weight daily orally); Group III (n=13), 0.5% cholesterol; Group IV (n=9), 0.5% cholesterol+PTX (40 mg/kg body weight daily orally). Blood samples were collected before (0 time) and after 1 and 2 months on experimental diets for measurement of serum triglycerides (TG), total cholesterol (TC), LDL-C, HDL-C and serum malondialdehyde (MDA), a lipid peroxidation product. At the end of 2 months the aorta was removed for measurement of atherosclerotic plaques, MDA, and aortic tissue chemiluminescence (Ao-CL), a marker for antioxidant reserve. Rabbits in Group III developed atherosclerosis (56.61+/-6.90% of the intimal surface of aorta was covered with atherosclerotic plaques) which was associated with an increase in the serum TG, TC, LDL-C, HDL-C, TC/HDL-C, MDA and aortic MDA and antioxidant reserve. PTX reduced the development of atherosclerosis by 38.1% and this was associated with decreases in serum MDA by 32%, aortic MDA by 37%, and antioxidant reserve by 17.3% without changes in the serum lipids. These results suggest that ROS generated during hypercholesterolemia via cytokines and PAF may in part contribute to the development of hypercholesterolemic atherosclerosis and that suppression of production and activity of cytokines and PAF may reduce the development of hypercholesterolemic atherosclerosis.     

Early decrease of oxidative stress by atorvastatin in hypercholesterolaemic patients: effect on circulating vitamin E.

AIMS: Statins inhibit oxidative stress, but the interplay between cholesterol lowering and antioxidant vitamins is still unclear. Aims of the study were to assess if statins inhibit oxidative stress independently from cholesterol lowering, to assess the behaviour of vitamin E simultaneously with the changes of oxidative stress, to determine in vitro if atorvastatin was able to directly influence platelet-mediated LDL oxidation and vitamin E consumption. METHODS AND RESULTS: In 30 hypercholesterolaemic patients (HC) and 20 healthy subjects (HS), urinary isoprostanes and plasma vitamin E were determined. The HC were randomized to diet or diet plus atorvastatin 10 mg/day. Compared with HS, HC had higher isoprostanes and lower vitamin E levels. The statin-allocated group showed a reduction of isoprostanes after only 3 days (-18.8%, P < 0.01); after 30 days, a stronger reduction of isoprostanes was noted (-37.1%, P < 0.01) whereas an increase of vitamin E (+42%, P < 0.01) and a reduction of cholesterol (-24.9%, P < 0.01) were observed. The diet-allocated group showed a weak decrease of cholesterol after 30 days. In vitro study showed that atorvastatin dose-dependently inhibited platelet-mediated LDL oxidation and isoprostane formation with a mechanism involving NADPH-oxidase. CONCLUSION: The study provides the first evidence that atorvastatin exerts an early antioxidant effect that could contribute to enhancing circulating vitamin E.     

Lipid peroxidation and scavenging enzyme activity in streptozotocin-induced diabetes

The aim of this study was to evaluate lipid peroxidation and scavenging enzyme activity in streptozotocin-induced diabetes, and then to establish whether moderate doses of nonenzymatic antioxidant vitamin E play a role in the antioxidant defence system in diabetic pregnant rats and their offspring. The study group consisted of 30 normal female Wistar rats, which were given a single dose of streptozotocin (40 mg/kg) and were mated 7 days later. Subsequently, the diabetic animals were divided into two matched groups: the first supplemented with vitamin E (30 mg/100 g chow), and the other fed with a standard diet lacking vitamine E. Controls consisted of 15 pregnant rats. On the first day after delivery, the rats were decapitated and homogenates of maternal liver and uterus as well as neonatal lungs and liver were prepared. Then the following parameters were measured: malondialdehyde (MDA) concentrations in the homogenates and blood serum, glutathione (GSH) levels, the activity of CuZn-superoxide dismutase (SOD) and glutathione peroxidase (GPx), and glycaemia. The neonates of diabetic rats were smaller than the healthy ones and serum glucose concentration was markedly higher in the diabetic animals. MDA levels were significantly increased, whereas GSH, SOD and GPx were markedly diminished in the diabetic adult rats and their offspring in comparison to the control grouop. In the animals supplemented with α-tocopherol, MDA concentrations were significantly lower, GSH content and SOD activities were markedly elevated most tissues studied, whereas GPx remained unchanged. We conclude that, by monitoring the activity of selected scavenging enzymes, information on ongoing biological oxidative stress and thereby on the fetus/neonate status may be obtained. Our results suggest that diabetic pregnant rats and their neonates are exposed to an increased oxidative stress and that vitamin E supplementation may reduce its detrimental effects. Received: 20 January 2000 / Accepted in revised form: 23 February 2001     

Improvement in the endothelium-dependent relaxation in hypercholesterolemic rabbits treated with vitamin E

The authors studied the time course of the vitamin E mediated improvement in endothelium-dependent relaxation in hypercholesterolemic rabbits. A total of 40 male New Zealand white rabbits were randomly assigned to hypercholesterolemic (control) and vitamin E treated groups. The latter group was further divided in three subgroups in accordance with the duration of the vitamin E treatment (2, 4 or 6 days) at the end of the experiment. The dose of vitamin E utilized was 50 IU/day administered once a day by gavage. All the rabbits were fed a diet supplemented with cholesterol (0.5%) and coconut oil (2%) for 4 weeks. At the end of this period, the animals were sacrificed and the aorta removed for determination of the cholesterol and malondialdehyde (MDA) contents. The relaxation of the aortic strips in response to acetylcholine was also studied. In addition, the cholesterol and MDA contents of native and oxidized LDL were measured. At the end of the 4th week, the MDA level was significantly reduced in native and oxidized LDL in the rabbits treated with vitamin E for 2 days, while in aortic tissue a reduction was seen after 4 days of treatment. Endothelium-dependent relaxation improved significantly after 6 days of vitamin E administration, and there was a reduction in the total plasma and aortic cholesterol levels during this same period. We conclude that vitamin E at a dose of 50 IU/day for 6 days improves the endothelium-dependent relaxation seen in hypercholesterolemic rabbits. This effect may be mediated through an antioxidant action on LDL particles and on the aortic arterial wall.     

The effect of ethanol extract of Hypericum lysimachioides on lipid profile in hypercholesterolemic rabbits and its in vitro antioxidant activity

Hypercholesterolemia, high cholesterol diet and oxidative stress increase serum total cholesterol and LDL cholesterol levels resulting in increased risk for development of atherosclerosis. Antioxidants play an important role in inhibiting and scavenging radicals, thus providing protection to humans against infectious and degenerative diseases. Literature shows that the antioxidant activity is high in medicinal plants. Realizing the fact that, this study was carried out to determine the effect of ethanol extract of Hypericum lysimachioides Boiss var lysimachioides (Guttifera) on serum lipid levels and serum lipid peroxidation in hypercholesterolemic rabbits. The rabbits were divided into four groups and these groups were fed with diets containing standard laboratory diet (Group I), standard laboratory diet and ethanol extracts of H. lysimachioides (HL) (50mg/kg body weight) (Group II), standard laboratory diet, ethanol extracts of HL (50mg/kg body weight) and cholesterol (100mg/kg body weight) (Group III), and finally standard laboratory diet and cholesterol (100mg/kg body weight) (Group IV), for 5 weeks. Feeding cholesterol increased serum cholesterol and LDL cholesterol levels significantly in Group IV as compared to the other groups. Ethanol extract of HL with high cholesterol diet significantly lowered LDL cholesterol and total cholesterol levels in the rabbits of Group III as compared to the Group IV. The level of serum triacylglycerol was found to be similar to all comparison groups. HDL cholesterol levels were also increased significantly in Groups II and III as compared to Group IV. Statistically significant difference was found in Group IV as compared to all other groups. The ethanol extract of HL with high cholesterol diet significantly lowered the serum MDA levels in the rabbits of Group III compared to the Group IV. The histopathological findings confirmed that the ethanol extract of HL restrained the progression of the hydropic degeneration and fatty changes in the liver and some atherosclerotic lesions in the aorta. The in vitro antioxidant activities of ethanol extract of HL was also evaluated. The free radical-scavenging properties of HL (IC(50)=28 microg/ml) were studied using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay system. Since plant phenolic compound is one of the phytochemicals possessing radical scavenging activity, the amount of total phenolic compound was also determined in ethanol extract of HL and total phenolic content of one-milligram HL ethanol extract was equivalent to 307 microg of gallic acid. Total antioxidant activity of ethanol extract of HL was tested by using ferric thiocyanate (FTC) and thiobarbituric acid (TBA) methods. Antioxidative activities of ethanol extract of HL was found to be comparable with Vitamin E. In conclusion, the use of this extract could be useful in the management of cardiovascular disease in which atherosclerosis is important.     

Differential indicators of diabetes-induced oxidative stress in New Zealand White rabbits: role of dietary vitamin E supplementation

Determination of reliable bioindicators of diabetes-induced oxidative stress and the role of dietary vitamin E supplementation were investigated. Blood (plasma) chemistries, lipid peroxidation (LPO), and antioxidant enzyme activities were measured over 12 weeks in New Zealand White rabbits (control, diabetic, and diabetic + vitamin E). Cholesterol and triglyceride levels did not correlate with diabetic state. Plasma LPO was influenced by diabetes and positively correlated with glucose concentration only, not cholesterol or triglycerides. Liver glutathione peroxidase (GPX) activity negatively correlated with glucose and triglyceride levels. Plasma and erythrocyte GPX activities positively correlated with glucose, cholesterol, and triglyceride concentrations. Liver superoxide dismutase activity positively correlated with glucose and cholesterol concentration. Vitamin E reduced plasma LPO, but did not affect the diabetic state. Thus, plasma LPO was the most reliable indicator of diabetes-induced oxidative stress. Antioxidant enzyme activities and types of reactive oxygen species generated were tissue dependent. Diabetes-induced oxidative stress is diminished by vitamin E supplementation.     

The effect of vitamin E, probucol, and lovastatin on oxidative status and aortic fatty lesions in hyperlipidemic-diabetic hamsters

Diabetes mellitus is associated with an increased risk of premature atherosclerosis, which may be due in part to an increased rate of low density lipoprotein (LDL) oxidation. Previous studies have shown that vitamin E, probucol, and lovastatin can reduce the oxidative susceptibility of LDL in normoglycemic animal models; however, few studies have investigated this in conjunction with aortic fatty streak lesion formation in diabetic hyperlipidemic models. Forty-eight Syrian hamsters were made diabetic by intraperitoneal injection of low dose streptozotocin. Diabetic animals (12 animals/groups) received a high saturated fat and cholesterol diet for 12.5 weeks. At 2.5 week of dietary treatments, the diet was supplemented with either: (1) 500 IU/day vitamin E (D+E); (2) 1% probucol w/w of the diet (D+P); (3) 25 mg/kg lovastatin (D+L); or (4) diabetic control (D). An age-matched group of hamsters (n=6) receiving the same diet but not made diabetic (ND) was used as control. At the end of the study, aortic arch foam cell-rich fatty streak lesion, plasma glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), phospholipids, alpha-tocopherol, plasma lipid peroxide and the susceptibility of LDL to copper-catalyzed oxidation were determined. Diabetes increased plasma glucose, and when combined with an atherogenic diet resulted in a further increase of plasma lipids. Vitamin E, probucol, and lovastatin significantly reduced plasma TG in the diabetic hamsters fed the atherogenic diet. Vitamin E treatment increased TC, probucol reduced HDL-C without affecting TC; whereas lovastatin reduced TC and selectively decreased non-HDL-C, and significantly reduced fatty streak lesion formation in the aortic arch. While vitamin E and probucol were effective in reducing several indices of oxidative stress including plasma lipid peroxides, cholesterol oxidation products and in vitro LDL oxidation, they had no effect on fatty streak lesion formation. Our results indicate that the LDL in diabetic animals is more susceptible to oxidation than in non-diabetic hamsters and that not only vitamin E and probucol but also lovastatin provide antioxidant protection. It appears that in this combined model of diabetes and hypercholesterolemia, progression of fatty streak lesion formation is mainly associated with changes in TC and non-HDL-C as affected by lovastatin, and is less dependent on the extent of LDL oxidation, changes in plasma TG level and oxidative stress status.     

Reduction in oxidative stress and modulation of heart failure subsequent to myocardial infarction in rats

BACKGROUND:

Patients surviving myocardial infarction (MI) are at a heightened risk for the development of congestive heart failure. This clinical syndrome has been associated with an antioxidant deficit and elevated oxidative stress in the myocardium. Effects of dietary vitamin E, a lipid-soluble antioxidant, on myocardial anti-oxidant enzyme activities, oxidative stress and hemodynamic function, were examined separately in the viable left ventricle (LV) and right ventricle (RV) of rats at 16 weeks post-MI.

METHODS AND RESULTS:

Animals were fed either a basal diet or a diet enriched with 1500 U of vitamin E/kg beginning two weeks before MI-inducing surgery and continued 16 weeks post-MI. In the MI animals on the basal diet, LV systolic pressure (LVSP) and RVSP were significantly depressed and LV end-diastolic pressure (LVEDP) and RVEDP were significantly elevated. These hemodynamic alterations were accompanied by clinical signs of heart failure including dyspnea, lethargy and cyanotic limbs. Supplementation of MI animals with dietary vitamin E resulted in complete normalization of RVSP and RVEDP. An increase in LVSP and a decrease in LVEDP was observed in the vitamin E-supplemented MI animals, although mild residual LV dysfunction remained. The myocardial enzymatic antioxidants catalase and glutathione peroxidase declined substantially in each of the ventricles of unsupplemented MI animals. Myocardial levels of vitamin E were reduced by 33% in the LV and no change was observed in the RV of the MI animals. Vitamin E-supplemented control animals and MI animals showed a significant increase in vitamin E levels in both ventricles. Myocardial oxidative stress, as assessed by lipid peroxidation and the ratio of reduced to oxidized glutathione, was significantly increased in each of the respective ventricles of untreated MI animals. Supplementation with dietary vitamin E resulted in a substantial increase in the myocardial activities of catalase and glutathione peroxidase in both the LV and RV. Furthermore, an increase in the ratio of reduced to oxidized glutathione concomitant with significantly less lipid peroxidation was also observed in each of the respective ventricles of MI animals supplemented with vitamin E. No overt clinical signs of heart failure were evident in these vitamin E-supplemented animals.

CONCLUSIONS:

An improved myocardial redox state and endogenous antioxidant reserve with vitamin E therapy, coupled with the modulation of the development of heart failure, lend strong support in favour of a pathophysiological role for increased oxidative stress in the pathogenesis of heart failure, at least in experimental animals. Association between an increase in oxidative stress and cardiac events in patients requires further examination.     

Dietary vitamin E and the attenuation of early lesion development in modified Watanabe rabbits.

Modified Watanabe heritable hyperlipidemic rabbits (M-WHHL) were fed either standard rabbit diet or diet supplemented with 0.5% wt/wt of the lipophilic antioxidant vitamin E (d,l-alpha-tocopherol). Animals of 10-12 weeks of age were divided into two groups matched for distribution of serum cholesterol levels at the beginning of the 12 week study period. A significant hypocholesterolemic response to vitamin E feeding was observed throughout the study. Vitamin E supplementation increased serum vitamin E levels approximately fourfold and restricted ex-vivo copper mediated oxidative modification of low density lipoprotein (LDL) as quantitated by fluorescence at 430 nm. Post mortem examination of aortic tissue revealed a significant (32%) inhibition of surface area lesion involvement in the arch region as determined by image analysis. It is concluded that administration of vitamin E to M-WHHL rabbits brings about a significant hypocholesterolemic response, confers on LDL significant protection against oxidative modification and either or both contribute to the inhibition of early aortic lesion development.     

The correlation between markers of oxidative stress and risk factors of coronary artery disease in Thai patients

An imbalance between oxidative damage and antioxidative protection in association with the pathophysiology of atherosclerosis has been suggested. The aim of our study was to investigate the relationship between plasma lipids, the antioxidant system and oxidative damage in Thai patients with stable coronary artery disease (CAD). Sixty-one patients (40 males, 21 females), who were angiographically defined as having CAD and were clinically stable, participated in this study. Thirty-two healthy subjects (20 males, 12 females) served as normal controls. The investigation included the measurements of plasma lipid profiles and plasma total antioxidative status (TAS) such as plasma vitamin E erythrocyte glutathione (GSH) and glutathione peroxidase (GPx), as well as malondialdehyde (MDA) and total plasma total protein thiols (P-SH). In patients with CAD, erythrocyte GSH and GPx were significantly lower than those found in controls. However plasma TAS and vitamin E were not significantly different between groups. Patients with CAD also had higher MDA and lower P-SH levels than the controls, which represents the oxidative damage products of lipid and proteins. Multiple regression analysis revealed negative correlations between GSH and cholesterol, GSH and low density lipoprotein (LDL), vitamin E and MDA, as well as P-SH and MDA. This study demonstrated the status of oxidative stress in patients with stable CAD. Since oxidative stress is the imbalance between the total oxidants and antioxidants in the body, any single oxidant/antioxidant parameter may not reflect the overall oxidative stress system. Thus, in patients with CAD, diets with various types of antioxidants may be more beneficial in increasing antioxidant activity than any particular antioxidant supplementation.     

Cordycepin (3′-deoxyadenosine) attenuates age-related oxidative stress and ameliorates antioxidant capacity in rats

Free radical-induced oxidative damage is considered to be the most important consequence of the aging process. The activities and capacities of antioxidant systems of cells decline with increased age, leading to the gradual loss of pro-oxidant/antioxidant balance and resulting in increased oxidative stress. Our investigation was focused on the effects of cordycepin (3′-deoxyadenosine) on lipid peroxidation and antioxidation in aged rats. Age-associated decline in the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST), reduced glutathione (GSH), vitamin C and vitamin E, and elevated levels of malondialdehyde (MDA) were observed in the liver, kidneys, heart and lungs of aged rats, when compared to young rats. Furthermore, serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine were found to be significantly elevated in aged rats compared to young rats. Aged rats receiving cordycepin treatment show increased activity of SOD, CAT, GPx, GR and GST, and elevated levels of GSH, and vitamins C and E such that the values of most of these parameters did not differ significantly from those found in young rats. In addition, the levels of MDA, AST, ALT, urea and creatinine became reduced upon administration of cordycepin to aged rats. These results suggest that cordycepin is effective for restoring antioxidant status and decreasing lipid peroxidation in aged rats.