Vitamin E and atherosclerosis: beyond prevention of LDL oxidation

Protective effects of paraoxonase-1, vitamin E and selenium, and oxidative stress index on the susceptibility of low density lipoprotein to oxidation in diabetic patients with/without coronary artery disease

BACKGROUND

The oxidative modification of low density lipoprotein (LDL) is closely associated with an increased risk for coronary artery disease (CAD) in diabetic patients. The purpose of this study is to investigate the relation between serum vitamin E and selenium, paraoxonase-1 (PON1) activity, total antioxidant capacity (TAC), total oxidant status (TOS), malondialdehyde (MDA), and oxidative stress index (OSI) values with the susceptibility of LDL to oxidative modification and the possibility of CAD in diabetic patients.

METHOD

This study was designed as a case control survey of 82 diabetes patients divided into two groups including T2DM alone (as group I) and both T2DM and CAD (as group II). Fasting blood samples were taken to the assay of fasting blood glucose (FBG), HbA1c, total cholesterol (TC), TAC, TOS, MDA, OSI, vitamin E, selenium, oxidized low density lipoprotein (Ox-LDL), and activity of PON1.

RESULTS

Ox-LDL, MDA, TOS, and OSI values in groups II were significantly higher compared with group I (all with P value = 0.000). TAC, vitamin E, selenium, and PON1 activity values were significantly lower in group II compared with groups I (P value = 0.000; P value = 0.000; P value = 0.007; P value = 0.003, respectively). There were significant relationships between the amounts of TAC, TOS, OSI, and vitamin E with the amounts of PON1 activity and Ox-LDL (p < 0.05). But Ox-LDL and PON1 activity correlated weakly with together (p = 0.094).

CONCLUSION

Results of this study support the belief that oxidative stress might be an important etiologic factor which makes some diabetics more susceptible to CAD. Increased oxidative stress may be a potential therapeutic target in the prevention and management of CAD in diabetic patients.

D-Pinitol Content and Antioxidant and Antidiabetic Activities of Five Bougainvillea spectabilis Willd. Cultivars

Diabetes mellitus is a major challenge for global health, and Bougainvillea spectabilis Willd. (B. spectabilis) is a widely used herbal remedy with diverse cultivars traditionally used for diabetes treatment. However, the comparative efficacy of these cultivars remains ambiguous. This study aimed to evaluate the D-pinitol content and DPPH radical-scavenging activity of methanolic leaves extracts of five B. spectabilis cultivars. Furthermore, the effects of these cultivars on various parameters, including blood glucose levels, oxidative stress markers, inflammatory cytokines, lipid profiles, liver enzymes, renal function markers, and histopathological changes, were assessed in STZ-induced diabetic rats after one month of oral daily treatment. All tested cultivars demonstrated significant improvements in the measured parameters, albeit to varying extents. Notably, the LOE cultivar, distinguished by its orange bracts, exhibited the highest efficacy, surpassing the effectiveness of glibenclamide, an antidiabetic medication, and displayed the highest concentration of D-pinitol. These findings underscore the importance of carefully selecting the appropriate B. spectabilis cultivar to maximize the antidiabetic efficacy, with a particular emphasis on the correlation between antidiabetic activity and D-pinitol concentrations.

Lipophilic and Hydrophilic Compounds from Arthrospira platensis and Its Effects on Tissue and Blood Cells—An Overview

The cyanobacterium Arthrospira platensis (Spirulina platensis) is a natural source of considerable amounts of ingredients that are relevant for nutra- and pharmaceutical uses. Different hydrophilic and hydrophobic substances can be obtained by extraction from the biomass. The respective extraction techniques determine the composition of substances in the extract and thus its biological activity. In this short review, we provide an overview of the hydrophilic compounds (phenols, phycobiliproteins, polysaccharides, and vitamins) and lipophilic ingredients (chlorophylls, vitamins, fatty acids, and glycolipids) of Arthrospira platensis. The principal influences of these substances on blood and tissue cells are briefly summarized.

Recapsoma®: A Novel Mixture Based on Bergamot, Ipomoea Batatas, Policosanol Extracts and Liposomal Berberine for the Treatment of Hypercholesterolemia

Cardiovascular disease (CVD) is considered one of the major causes of mortality worldwide. Epidemiological studies have shown that regular consumption of phenols is inversely associated with cardiovascular disease, and the use of nutraceuticals and functional foods can provide protective, preventive, and possibly curative effects in CVD. A novel mixture of different natural substances named Recapsoma^® (bergamot, liposomal berberine, Ipomoea batatas, oleuropein, polycosanols, and vitamin E) has been produced, and its anti-dyslipidaemic efficacy has been tested, specifically studying the in vitro effects on the mechanisms of action underlying cholesterol synthesis, triglycerides, and LDL-cholesterol oxidation. The work has demonstrated the ability of this herbal extract mixture to inhibit the action of PCSK, ACAT, PAP, and HMGR and to increase the LDL receptor (LDLR), underlying the synergistic effect of the mixture over the single components. Such results suggest that the Recapsoma^® mixture could be used as a tool for controlling hypercholesterolemia, and an alternative to statins, especially for those patients with metabolic syndrome.

Atherosclerosis: nexus of vascular dynamics and cellular cross talks

Cardiovascular diseases (CVDs) are the foremost cause of mortality worldwide. Atherosclerosis is the underlying pathology behind CVDs. Atherosclerosis is manifested predominantly by lipid deposition, plaque formation, and inflammation in vascular intima. Initiation and progression of plaque require many years. With aging, atherosclerotic plaques become vulnerable. Localization of these plaques in the coronary artery leads to myocardial infarction. A complete understanding of the pathophysiology of this multifaceted disease is necessary to achieve the clinical goal to provide early diagnosis and the best therapeutics. The triggering factors of atherosclerosis are biomechanical forces, hyperlipidemia, and chronic inflammatory response. The current review focuses on crucial determinants involved in the disease, such as location, hemodynamic factors, oxidation of low-density lipoproteins, and the role of endothelial cells, vascular smooth muscle cells, and immune cells, and better therapeutic targets.

Vitamins E and C do not effectively inhibit low density lipoprotein oxidation by ferritin at lysosomal pH

Low density lipoprotein (LDL) might be oxidized by iron in the lysosomes of macrophages in atherosclerotic lesions. We have shown previously that the iron-storage proteinferritin can oxidize LDL at lysosomal pH. We have now investigated the roles of the most important antioxidant contained in LDL, α-tocopherol (the main form of vitamin E) and of ascorbate (vitamin C), a major water-soluble antioxidant, on LDL oxidation by ferritin at lysosomal pH (pH 4.5). We incubated LDL with ferritin at pH 4.5 and 37 °C and measured its oxidation by monitoring the formation of conjugated dienes at 234 n min a spectrophotometer. α-Tocopherol is well known to inhibit LDL oxidation at pH 7.4, but enrichment of LDL with α-tocopherol was unable to inhibit LDL oxidation by ferritin at pH 4.5. Ascorbate had a complex effect on LDL oxidation by ferritin at lysosomal pH and exhibited both antioxidant and pro-oxidant effects. It had no antioxidant effect on partially oxidized LDL, only a pro-oxidant effect. Ascorbate completely inhibited LDL oxidation by copper at pH 7.4 for a long period, but in marked contrast did not inhibit LDL oxidation by copper at lysosomal pH. Dehydroascorbate, the oxidation product of ascorbate, had a pronounced pro-oxidant effect on LDL incubated with ferritin at pH 4.5. The inability of α-tocopherol and ascorbate to effectively inhibit LDL oxidation by ferritin at lysosomal pH might help to explain why the large clinical trials with these vitamins failed to show protection against cardiovascular diseases.

Association Between Fat-soluble Vitamins and Lipid Profile in the Overweight Population

BACKGROUND & AIMS

It is well-known that the coronary artery stenosis is related to lipid profile. This is a descriptive cross-sectional study to investigate the relationship between the serum fat-soluble vitamins (A, E and D), circulating proprotein convertase subtilisin/kexin type 9 (PCSK9), and lipid profile in the study population.

METHODS

A total of 120 overweight subjects were participated in this study. The circulating PCSK9 and vitamin D were measured by ELISA technique. The serum vitamin A and vitamin E amounts were simultaneously measured by the HPLC method. The Serum Small Dense LDLCholesterol (sdLDL-C) values were evaluated using heparin-Mg2+ precipitation technique. The lipid profile was measured by routine laboratory techniques.

RESULTS

The serum vitamin E values correlated significantly to vitamin A (r= 0.47, P= 0.0001), VLDL-C (r= 0.30, P= 0.002), total cholesterol (r= 0.309, P= 0.001), PCSK9 (r= 0.233, P= 0.01) and total triglyceride (r= 0.61, P= 0.0001) values. The circulating PCSK9 values correlated significantly to LDL-C (r= 0.17, P= 0.05) and total cholesterol (r= 0.23, P= 0.009) values. However, there were not correlations between the levels of serum D and A vitamins, the serum LDL-C, sdLDL-C and total cholesterol values.

CONCLUSION

The data showed the correlations between serum vitamin E and PCSK9-related LDLC values lower than the normal range. Furthermore, the results suggested a nutritional need on the patents considering supplementation or fortification of vitamin E for the overweight subjects with higher LDL-C levels.

VPO1 mediates oxidation of LDL and formation of foam cells

Deposition of oxidized-LDL in vascular walls is essential in the initiation of atherosclerosis. Oxidation of LDL has been attributed to myeloperoxidase as its generation of potent oxidants. However, the exact mechanism of LDL oxidation and foam cell formation in atherosclerosis remains to be elucidated. Vascular peroxidase-1 (VPO1), a newly-identified heme-containing peroxidase, is primarily expressed in cardiovascular systems, and secreted into the circulation. The present study evaluates VPO1-mediated LDL oxidation and its role in atherosclerosis. VPO1 was first demonstrated binding to LDL. VPO1-mediated oxidation of proteins and lipids in LDL was verified by a variety of methods including immunoblot analysis, free tryptophan assay, UV absorbance, and thiobarbituric acid assay. VPO1-oxidized LDL caused accumulation of LDL in monocyte-like cells and promoted formation of foam cells. Administration of inflammation factors, LPS or TNF-α, induced increasing expression of VPO1 in aorta and secretion to plasma. TNF-α also promoted formation and retention of VPO1-oxidized LDL in aortic walls. Our data suggest that VPO1 contributes to oxidation and retention of LDL in vessel walls, and formation foam cells, indicating VPO1 as a novel potential mediator of atherosclerosis.

Gender differences and typical nutrition concerns of the diets of preschool children - the results of the first stage of an intervention study

BACKGROUND

Nutrition in children has an important influence on health both in childhood and adulthood. Actions aimed at improving children's nutrition are essential, not only to the children and their families, but also to the whole society. The aim of the study was to present the results of nutrient intake before starting a nutrition and physical activity intervention programme, to investigate gender differences in nutrient intake and to discuss whether the preschoolers' nutrient intake is similar to the intake of their peers from other countries.

METHODS

Nutrient intake was estimated from seven-day weighed food records kept by parents and preschool staff individually for 122 4-6-year-old children who attended two preschools in Piła, north-western Poland. Nutrient intake was calculated using Dieta 4.0 computer programme including water intake and intake of nutrients from dietary supplements. Statistical analysis was performed using the IBM SPSS Statistics computer programme, version 21.0, according to gender. The study was approved by the Bioethics Committee of the Poznan University of Medical Sciences (reference number 886/08).

RESULTS

Boys, in comparison to girls, were found to have statistically significantly higher intakes of total protein, total protein per kg of body weight, saturated fatty acids, total carbohydrates, available carbohydrates, lactose, sucrose, total water, vitamin A, beta-carotene, vitamin B2, vitamin B12, vitamin C, calcium, phosphorus, and magnesium. Statistically significantly higher percentage of girls than boys had intakes of vitamin E below AI.

CONCLUSIONS

Gender was a significant factor of nutrient intake in the studied preschool children. The main nutritional concerns in the studied preschoolers' diets, irrespective of gender, are typical of the diets of preschool children from various parts of Europe and indicate the need to work out common nutritional strategies to improve preschoolers' nutrition across Europe to reduce future burden of diet-related diseases to the European societies.

Anti-aging pharmacology: Promises and pitfalls

Life expectancy has grown dramatically in modern times. This increase, however, is not accompanied by the same increase in healthspan. Efforts to extend healthspan through pharmacological agents targeting aging-related pathological changes are now in the spotlight of geroscience, the main idea of which is that delaying of aging is far more effective than preventing the particular chronic disorders. Currently, anti-aging pharmacology is a rapidly developing discipline. It is a preventive field of health care, as opposed to conventional medicine which focuses on treating symptoms rather than root causes of illness. A number of pharmacological agents targeting basic aging pathways (i.e., calorie restriction mimetics, autophagy inducers, senolytics etc.) are now under investigation. This review summarizes the literature related to advances, perspectives and challenges in the field of anti-aging pharmacology.

Biological Properties of Tocotrienols: Evidence in Human Studies

Vitamin E has been recognized as an essential vitamin since their discovery in 1922. Although the functions of tocopherols are well established, tocotrienols have been the unsung heroes of vitamin E. Due to their structural differences, tocotrienols were reported to exert distinctive properties compared to tocopherols. While most vegetable oils contain higher amount of tocopherols, tocotrienols were found abundantly in palm oil. Nature has made palm vitamin E to contain up to 70% of total tocotrienols, among which alpha-, gamma- and delta-tocotrienols are the major constituents. Recent advancements have shown their biological properties in conferring protection against cancer, cardiovascular diseases, neurodegeneration, oxidative stress and immune regulation. Preclinical results of these physiological functions were translated into clinical trials gaining global attention. This review will discuss in detail the evidence in human studies to date in terms of efficacy, population, disease state and bioavailability. The review will serve as a platform to pave the future direction for tocotrienols in clinical settings.

Meta-analysis of risk factors associated with atherosclerosis in patients with Kawasaki disease

BACKGROUND

Kawasaki disease (KD) has now become the leading cause of acquired heart disease among children in developed countries. This study investigated whether patients with KD have an increased risk of atherosclerosis.

METHODS

Electronic databases, including PubMed, Embase and Springer link, were searched through June 1, 2015, for eligible studies. Studies were included when they met the following criteria: 1) an observational study focusing on evaluating the risk factors for atherosclerosis in patients with KD; 2) KD was diagnosed clinically according to the Japan Kawasaki Disease Research Committee or American Heart Association's diagnostic criteria; 3) the study subjects were KD patients without coronary heart disease or related cardiovascular disease (KD group) and non-KD patients as control (control group), and 4) investigation of important atherosclerosis risk factors, total cholesterol (TC), low-density lipoprotein cholesterol (LDL), triglycerides (TG), systolic blood pressure (SBP), and flowmediated dilatation (FMD). The methodological quality of the included studies was evaluated using the Newcastle- Ottawa Scale. Mean difference (MD) and relative risk (RR) and corresponding 95% confidence intervals (CI) were used to calculate the pooled results.

RESULTS

Sixteen studies were included with a total of 870 patients, including 421 KD patients and 449 non-KD controls. Differences in TG and SBP between KD patients and controls were not significant; in contrast, TC and LDL levels were significantly higher in KD patients than the controls, whereas FMD in the KD patients was significantly lower.

CONCLUSIONS

KD patients may have an increased risk of developing atherosclerosis.

Vitamin E-gene interactions in aging and inflammatory age-related diseases: implications for treatment. A systematic review

Aging is a complex biological phenomenon in which the deficiency of the nutritional state combined with the presence of chronic inflammation and oxidative stress contribute to the development of many age-related diseases. Under this profile, the free radicals produced by the oxidative stress lead to a damage of DNA, lipids and proteins with subsequent altered cellular homeostasis and integrity. In young-adult age, the cell has a complex efficient system to maintain a proper balance between the levels of free radicals and antioxidants ensuring the integrity of cellular components. In contrast, in old age this balance is poorly efficient compromising cellular homeostasis. Supplementation with Vitamin E can restore the balance and protect against the deteriorating effects of oxidative stress, progression of degenerative diseases, and aging. Experiments in cell cultures and in animals have clearly shown that Vitamin E has a pivotal role as antioxidant agent against the lipid peroxidation on cell membranes preserving the tissue cells from the oxidative damage. Such a role has been well documented in immune, endothelial, and brain cells from old animals describing how the Vitamin E works both at cytoplasmatic and nuclear levels with an influence on many genes related to the inflammatory/immune response. All these findings have supported a lot of clinical trials in old humans and in inflammatory age-related diseases with however contradictory and inconsistent results and even indicating a dangerous role of Vitamin E able to affect mortality. Various factors can contribute to all the discrepancies. Among them, the doses and the various isoforms of Vitamin E family (α,β,γ,δ tocopherols and the corresponding tocotrienols) used in different trials. However, the more plausible gap is the poor consideration of the Vitamin E-gene interactions that may open new roadmaps for a correct and personalized Vitamin E supplementation in aging and age-related diseases with satisfactory results in order to reach healthy aging and longevity. In this review, this peculiar nutrigenomic and/or nutrigenetic aspect is reported and discussed at the light of specific polymorphisms affecting the Vitamin E bioactivity.

Effects of vitamin e on bone biomechanical and histomorphometric parameters in ovariectomized rats

The present study examined the dose-dependent effect of vitamin E in reversing bone loss in ovariectomized (Ovx) rats. Sprague-Dawley rats were either Sham-operated (Sham) or Ovx and fed control diet for 120 days to lose bone. Subsequently, rats were divided into 5 groups (n = 12/group): Sham, Ovx-control, low dose (Ovx + 300 mg/kg diet; LD), medium dose (Ovx + 525 mg/kg diet; MD), and high dose (Ovx + 750 mg/kg diet; HD) of vitamin E and sacrificed after 100 days. Animals receiving MD and HD of vitamin E had increased serum alkaline phosphatase compared to the Ovx-control group. Bone histomorphometry analysis indicated a decrease in bone resorption as well as increased bone formation and mineralization in the Ovx groups supplemented with MD and HD of vitamin E. Microcomputed tomography findings indicated no effects of vitamin E on trabecular bone of fifth lumbar vertebrae. Animals receiving HD of vitamin E had enhanced fourth lumbar vertebra quality as evidenced by improved ultimate and yield load and stress when compared to Ovx-control group. These findings demonstrate that vitamin E improves bone quality, attenuates bone resorption, and enhances the rate of bone formation while being unable to restore bone density and trabecular bone structure.

Early superoxide scavenging accelerates renal microvascular rarefaction and damage in the stenotic kidney

Renal artery stenosis (RAS), the main cause of chronic renovascular disease (RVD), is associated with significant oxidative stress. Chronic RVD induces renal injury partly by promoting renal microvascular (MV) damage and blunting MV repair in the stenotic kidney. We tested the hypothesis that superoxide anion plays a pivotal role in MV dysfunction, reduction of MV density, and progression of renal injury in the stenotic kidney. RAS was induced in 14 domestic pigs and observed for 6 wk. Seven RAS pigs were chronically treated with the superoxide dismutase mimetic tempol (RAS+T) to reduce oxidative stress. Single-kidney hemodynamics and function were quantified in vivo using multidetector computer tomography (CT) and renal MV density was quantified ex vivo using micro-CT. Expression of angiogenic, inflammatory, and apoptotic factors was measured in renal tissue, and renal apoptosis and fibrosis were quantified in tissue sections. The degree of RAS and blood pressure were similarly increased in RAS and RAS+T. Renal blood flow (RBF) and glomerular filtration rate (GFR) were reduced in the stenotic kidney (280.1 ± 36.8 and 34.2 ± 3.1 ml/min, P < 0.05 vs. control). RAS+T kidneys showed preserved GFR (58.5 ± 6.3 ml/min, P = not significant vs. control) but a similar decreases in RBF (293.6 ± 85.2 ml/min) and further decreases in MV density compared with RAS. These changes were accompanied by blunted angiogenic signaling and increased apoptosis and fibrosis in the stenotic kidney of RAS+T compared with RAS. The current study shows that tempol administration provided limited protection to the stenotic kidney. Despite preserved GFR, renal perfusion was not improved by tempol, and MV density was further reduced compared with untreated RAS, associated with increased renal apoptosis and fibrosis. These results suggest that a tight balance of the renal redox status is necessary for a normal MV repair response to injury, at least at the early stage of RVD, and raise caution regarding antioxidant strategies in RAS.

Management of diabetes mellitus: could simultaneous targeting of hyperglycemia and oxidative stress be a better panacea?

The primary aim of the current management of diabetes mellitus is to achieve and/or maintain a glycated hemoglobin level of ≤6.5%. However, recent evidence indicates that intensive treatment of hyperglycemia is characterized by increased weight gain, severe hypoglycemia and higher mortality. Besides, evidence suggests that it is difficult to achieve and/or maintain optimal glycemic control in many diabetic patients; and that the benefits of intensively-treated hyperglycemia are restricted to microvascular complications only. In view of these adverse effects and limitations of intensive treatment of hyperglycemia in preventing diabetic complications, which is linked to oxidative stress, this commentary proposes a hypothesis that “simultaneous targeting of hyperglycemia and oxidative stress” could be more effective than “intensive treatment of hyperglycemia” in the management of diabetes mellitus.

Pollock oil supplementation modulates hyperlipidemia and ameliorates hepatic steatosis in mice fed a high-fat diet

Background

Hyperlipidemia associated with obesity is closely related to the development of atherosclerosis. Both n-3 polyunsaturated fatty acids (PUFAs) and long-chain monounsaturated fatty acids (MUFAs; i.e., C20:1 and C22:1 isomers) supplementation modulate risk factors for metabolic syndrome via multiple mechanisms, including the restoration of impaired lipid metabolism. We therefore examined the effects of pollock oil, which contains a considerable amount of n-3 PUFAs as well as long-chain MUFAs, on plasma hyperlipidemia and hepatic steatosis in diet-induced obese mice.

Methods

Male C57BL/6J mice (24-26 g) were divided into two groups (n = 10/group) and were fed a high-fat diet containing 32% lard (control group) or 17% lard plus 15% pollock oil (experimental group) for 6 weeks. For both groups, fat comprised 60% of the total caloric intake.

Results

Although body and liver masses for the two groups did not differ significantly, hepatic lipids concentrations (triglycerides and total cholesterols) were lower (P < 0.05) after pollock oil ingestion. After 2 weeks on the specified diets, plasma lipid levels (total cholesterol, LDL cholesterol, and triglycerides) significantly decreased (P < 0.05) in the experimental group compared with the control group, although plasma HDL cholesterol levels did not differ. At the end of 6 weeks, plasma adiponectin levels increased (P < 0.05), whereas plasma resistin and leptin levels decreased (P < 0.05) in the experimental mice. Increased levels of long-chain MUFAs and n-3 PUFAs in plasma, liver and adipose tissue by ingesting pollock oil were possibly correlated to these favorable changes. Expression of hepatic genes involved in cholesterol metabolism (SREBP2, HMGCR, and ApoB) and lipogenesis (SREPB1c, SCD-1, FAS, and Acacα) was suppressed in the experimental group, and may have favorably affected hyperlipidemia and hepatic steatosis induced by the high-fat diet.

Conclusions

We demonstrated that pollock oil supplementation effectively improved hyperlipidemia, attenuated hepatic steatosis, and downregulated the express of hepatic genes involved in cholesterol and lipid metabolism in mice with diet-induced obesity.

Inhibitory effect of three C-glycosylflavonoids from Cymbopogon citratus (Lemongrass) on human low density lipoprotein oxidation

This study assessed the inhibitory effect of three C-glycosylflavonoids from Cymbopogon citratus leaves − isoorientin (1), swertiajaponin (2) and isoorientin 2"-O-rhamnoside (3) − on human LDL oxidation. Isolated LDL was incubated with compounds 1-3 and the kinetics of lipid peroxidation were assessed by conjugated diene and malondialdehyde-thiobarbituric acid reactive substances (MDA-TBARS) formation after addition of copper ions. Significant differences (p < 0.05) between the lag time phase of the control and the lag time phase in the presence of the compounds 1 (0.25 µM) and 2 (0.50 µM) were observed. After five hours of incubation all three compounds showed a significant inhibitory effect on MDA-TBARS formation with respect to the control. After six hours of incubation only compound 1 kept a remarkable antioxidant effect. This study demonstrates that isoorientin (1) is an effective inhibitor of in vitro LDL oxidation. As oxidative damage to LDL is a key event in the formation of atherosclerotic lesions, the use of this natural antioxidant may be beneficial to prevent or attenuate atherosclerosis.

The role of vitamin E in reversing bone loss

BACKGROUND AND AIMS

A positive correlation between intake of antioxidants including vitamins E and C on bone mass has been established by a number of investigators. The present study was conducted to evaluate the extent to which higher doses of vitamin E than normal dose (75 IU per kg diet) can reverse bone loss in aged osteopenic orchidectomized male rats.

METHODS

Forty 12-month old male Sprague- Dawley rats were either sham-operated (Sham) or orchidectomized (Orx), and fed control diet for 120 days to establish bone loss. Thereafter, rats were assigned to their corresponding treatment groups (n= 10 per group): Sham and one Orx groups received 75 IU vitamin E and served as controls, and the other two Orx groups received either 250 or 500 IU vitamin E per kg diet for 90 days.

RESULTS

Higher doses of vitamin E did not improve bone mineral density (BMD) or content (BMC) of whole body, femur and lumbar vertebra or alter the orchidectomy-induced deterioration of trabecular microarchitecture of the distal femur metaphysis in comparison with Orx controls that received adequate vitamin E. Biochemical markers of bone formation and bone resorption, i.e. serum osteocalcin and urinary deoxypyridinoline crosslinks, were also unaffected by vitamin E supplementation.

CONCLUSIONS

Overall, the findings of the present study suggest that supplemental doses of vitamin E do not increase BMD values in male rat model of osteoporosis. However, human studies are needed to confirm the population findings indicating that individuals with higher vitamin E intake have higher bone mass.

Antiatherogenic effects of kaempferol and rhamnocitrin

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Kaempferol and rhamnocitrin (kaempferol 7-O-methyl ether) are two anti-inflammatory flavonoids commonly found in plants. The aim of this study is to investigate the function of kaempferol and rhamnocitrin on prevention of atherosclerosis. Chemical analyses demonstrated that kaempferol and rhamnocitrin were scavengers of DPPH (1,1-diphenyl-2-picrylhydrazyl) with IC50 of 26.10 +/- 1.33 and 28.38 +/- 3.07 microM, respectively. Copper-induced low-density lipoprotein (LDL) oxidation was inhibited by kaempferol and rhamnocitrin, with similar potency, as measured by decreased formation of malondialdehyde and relative electrophoretic mobility (REM) on agarose gel, while rhamnocitrin reduced delayed formation of conjugated dienes better than kaempferol. Cholesterol-laden macrophages are the hallmark of atherogenesis. The class B scavenger receptor, CD36, binds oxidized low-density lipoprotein (oxLDL), is found in atherosclerotic lesions, and is up-regulated by oxLDL. Addition of kaempferol and rhamnocitrin (20 microM) caused significant reductions in cell surface CD36 protein expression in THP-1-derived macrophages (p < 0.05). Reverse transcription quantitative PCR (RT-Q-PCR) showed that kaempferol and rhamnocitrin (20 microM) decreased oxLDL-induced CD36 mRNA expression (p < 0.01 and p < 0.05, respectively). Kaempferol- and rhamnocitrin-treated macrophages also showed reduction in 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanide perchlorate (DiI)-labeled oxLDL uptake. Current evidences indicate that kaempferol and rhamnocitrin not only protect LDL from oxidation but also prevent atherogenesis through suppressing macrophage uptake of oxLDL.

Histopathological observations on protective effects of vitamin E on endosulfan induced cardiotoxicity in rats

The protective effects of vitamin E was investigated on the cardiotoxicity induced by endosulfan administration. Male rats in different groups were given endosulfan (2 mg per kg body weight per day in corn oil through gavage), vitamin E (200 mg per kg body weight twice a week in corn oil through gavage) and endosulfan and vitamin E at the same dose and route, to the control group corn oil is given at the dose rate of 2 mL per rat per day through gavage, for a period of28 days. The animals were sacrificed and heart tissues were collected and subjected to histopathology. The result indicated, sever congestion, haemorrhages with interstitial oedema. In some places there was diapedesis of leukocytes. Myocardium showed different degrees of degeneration, some of the myofibrils were found to be granular with pyknotic nuclei. Thickening of wall of arteries were seen. In the Vitamin E and endosulfan treated group the above mentioned lesions were significantly decreased in their severity. This study brought to light the protective effects of vitamin E on the toxic pathological lesions caused by endosulfan administration.

Cyclosporine A induced changes to plasma and erythrocyte antioxidant defences

Organ transplant recipients develop pronounced cardiovascular disease, and decreased antioxidant capacity in plasma and erythrocytes is associated with the pathogenesis of this disease. These experiments tested the hypothesis that the immunosuppressant cyclosporine A (CsA) alters erythrocyte redox balance and reduces plasma antioxidant capacity. Female Sprague-Dawley rats were randomly assigned to a control or CsA treated group. Treatment animals received 25 mg/kg/day of CsA via intraperitoneal injection for 18 days. Control rats were injected with the same volume of the vehicle. Three hours after the final CsA injection, rats were exsanguinated and plasma analysed for total antioxidant status (TAS), alpha-tocopherol, malondialdehyde (MDA), and creatinine. Erythrocytes were analysed for superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glucose-6-phosphate dehydrogenase (G6PD) activities, alpha-tocopherol, and MDA. CsA administration resulted in a significant (P < 0.05) decrease in plasma TAS and significant increases (P < 0.05) in plasma creatinine and MDA. Erythrocyte CAT was significantly (P < 0.05) increased in CsA treated rats compared to controls. There were no significant differences (P > 0.05) in erythrocyte SOD, GPX, G6PD, alpha-tocopherol or MDA between groups. In summary, CsA alters erythrocyte antioxidant defence and decreases plasma total antioxidant capacity.

Vitamin E inhibits CD36 scavenger receptor expression in hypercholesterolemic rabbits

A numerous studies suggest that Vitamin E has a preventive role in atherosclerosis, although the mechanism of action still remains unclear. CD36, a member of the scavenger receptor family is centrally involved in the uptake of oxidized low density proteins (oxLDLs) from bloodstream. During the atherosclerotic process, the lipid cargo of oxLDL accumulates in macrophages and smooth muscle cells, inducing their pathological conversion to foam cells. In the present study, we investigate the role of Vitamin E on CD36 expression in an in vivo model. Atherosclerosis was induced by a 2% cholesterol containing Vitamin E poor diet. Three groups of six rabbits each were studied. The first group (control) was fed on Vitamin E poor diet. The second group was fed with Vitamin E poor diet containing 2% cholesterol and the rabbits in the third group were fed with Vitamin E poor diet containing 2% cholesterol and received injections of 50 mg/kg of Vitamin E i.m. After 4 weeks, aortas were removed and analysed by light microscopy for atherosclerotic lesions. Aortic samples were analysed for CD36 mRNA expression. The aortas of cholesterol-fed rabbits showed typical atherosclerotic lesions, detected by macroscopic and microscopic examination, and exhibited an increase in CD36 mRNA expression. Vitamin E fully prevented cholesterol induced atherosclerotic lesions and the induction of CD36 mRNA expression. The effects observed at the level of CD36 scavenger receptor expression in vivo suggest an involvement of reduced foam cell formation in the protective effect of Vitamin E against atherosclerosis.

Antioxidant activity of Glossogyne tenuifolia

Glossogyne tenuifolia is a native traditional anti-inflammatory herb in Taiwan. It has previously been shown that the ethanol extract of G. tenuifolia (GT) inhibited the LPS-induced inflammatory mediator release from murine macrophage cell line and human whole blood. In the present work, the ethanol extracts of G. tenuifolia and its major constituent, luteolin-7-glucoside, were shown to be scavengers of 1,1-diphenyl-2-picrylhydrazyl, superoxide, and hydroxyl radicals. Moreover, copper-induced low-density lipoprotein oxidation was suppressed by GT and luteolin-7-glucoside as measured by decreased formation of malondialdehyde and conjugated diene as well as reduced electrophoretic mobility. GT and luteolin-7-glucoside were also against N-formyl-methionyl-leucyl-phenylalanine-induced reactive oxygen species (ROS) production in human polymorphonuclear neutrophils and peripheral blood mononuclear cells. In summary, these data indicated that GT is a potential ROS scavenger and may prevent atherosclerosis via inhibiting LDL oxidation or ROS production in human leukocytes. Moreover, luteolin-7-glucoside may serve as the active principal of GT.

Effects of combined administration of low dose atorvastatin and vitamin E on inflammatory markers and endothelial function in patients with heart failure

BACKGROUND

Heart failure has been associated with impaired endothelial function, increased inflammatory process and elevated oxidative stress status. Both statins and vitamin E separately improve endothelial function in patients with hypercholesterolemia and/or advanced atherosclerosis.

AIM

To evaluate the effect of atorvastatin alone or in combination with vitamin E on endothelial function and serum levels of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha) and vascular cells adhesion molecule (sVCAM-1) in patients with ischemic heart failure.

METHODS

Thirty-eight male patients with ischemic cardiomyopathy were randomly divided into three groups and received either atorvastatin 10 mg/day (n = 14), a combination of atorvastatin 10 mg/day plus vitamin E 400 IU/day (n = 12), or no statin or antioxidant treatment (n=12, controls) for 4 weeks. Forearm blood flow (FBF) was measured using venous occlusion strain-gauge plethysmography. Forearm vasodilatory response to reactive hyperemia (RH%) or to nitrate (NTG%) was defined as the percent change of FBF from rest to the maximum flow during reactive hyperemia or after nitrate administration, respectively.

RESULTS

RH% was significantly improved in both the atorvastatin-treated (p < 0.01) and atorvastatin plus vitamin E groups (p < 0.05), but the increase was significantly higher in the atorvastatin-treated group (p < 0.05). Serum levels of IL-6, TNF-alpha and sVCAM-1 were decreased in the atorvastatin-treated group (p < 0.05 for all), but remained unaffected in the other two groups (p = NS for all).

CONCLUSIONS

Low dose atorvastatin treatment improves endothelial function and reduces the expression of proinflammatory cytokines and adhesion molecules in patients with ischemic heart failure, an effect partly depressed by vitamin E.

Redox modulation of insulin signaling and endothelial function

Reactive oxygen and nitrogen species (ROS and RNS) recently emerged as critical signaling molecules in cardiovascular research. Several studies over the past decade have shown that physiological effects of vasoactive factors are mediated by these reactive species and, conversely, that altered redox mechanisms are implicated in the occurrence of metabolic and cardiovascular diseases. Oxidant stress occurs when ROS and/or RNS production exceeds the cell natural antioxidant systems, and pathological events ensue. Cardiovascular risk factors are associated with an imbalance of the redox equilibrium toward oxidative stress, leading to endothelial activation and proinflammatory processes implicated in atherogenesis and metabolic disorders. Recent studies indicate that insulin and insulin-sensitizing drugs activate antiinflammatory pathways that may limit oxidant stress in insulin target tissues. The main goal of this brief review is to discuss recent progress in the field of cellular redox signaling as it pertains to insulin modulation of vascular endothelial function in cardiovascular diseases.

Vitamin E supplementation suppresses macrophage accumulation and endothelial cell expression of adhesion molecules in the aorta of hypercholesterolemic rabbits

Suppression of cell adhesion molecule expression and macrophage accumulation by the endothelium is believed to play an important role in preventing the development of atherosclerosis. Earlier, we have shown that in vitro supplementation of human aortic endothelial cells with Vitamin E dose-dependently reduced expression of adhesion molecules and monocyte adhesion. Here, we report the in vivo down-regulation of endothelial cell adhesion molecules expression and macrophage accumulation in the aortas of hypercholesterolemic rabbits supplemented with Vitamin E. To this end, New Zealand White rabbits were fed a semi-purified diet containing 30 (control) or 1000 IU/kg Vitamin E. After 4 weeks, both groups' diets were switched to an atherogenic diet (0.3% cholesterol, 9% hydrogenated coconut oil, and 1% corn oil) containing the respective levels of Vitamin E and fed for 2, 4, and 6 weeks. Vitamin E supplemented rabbits had significantly higher levels of Vitamin E in their plasma and aortas. Frozen aorta sections were fixed and stained by an avidin-biotin complex method using Rb2/3 and Rb1/9 monoclonal antibodies against rabbit ICAM-1 and VCAM-1, respectively, and with RAM-11 for macrophage and von Willebrand factor for endothelial cells, followed by staining with secondary antibodies and counterstaining and evaluation under the microscope. At 6 weeks on atherogenic diet treatment, a trend (P = 0.08) toward a lower score of ICAM-1 expression by endothelial cells was observed in the aorta of Vitamin E treated rabbits compared to the control. However, a decrease in the score of VCAM-1 expression by endothelial cells in Vitamin E treated rabbits did not reach to a statistical significance. At 4 and 6 weeks on atherogenic diet, Vitamin E supplementation also significantly (P = 0.003) inhibited the accumulation of macrophages in the aorta. These results support the concept that down-regulation of adhesion molecule expression and suppression of monocyte/macrophage activation by Vitamin E in vivo is one of the potential mechanisms by which Vitamin E may suppress the development of aortic lesions in a rabbit model of atherosclerosis.

Effect of cigarette smoking on serum α-tocopherol and the lipid profile in a Portuguese population

BACKGROUND

The present study was conducted to determine the effects of cigarette smoking on the levels of serum alpha-tocopherol and on the lipid profile in humans from the Lisbon population.

METHODS

Serum alpha-tocopherol was evaluated by a reverse-phase HPLC method with UV detection. Enzymatic tests were used for the evaluation of the lipid profile.

RESULTS

Smokers in general and female smokers in particular had decreased alpha-tocopherol levels when compared with nonsmokers. Smokers had also lower HDL cholesterol (HDL-C) contents, but this difference was statistically significant only for females. Regardless of sex, in smokers, there was a positive correlation between alpha-tocopherol and triglyceride (TG) levels. Cluster analysis showed a sex-independent separation between smokers and nonsmokers.

CONCLUSION

These results suggest a different interaction of these blood parameters in smokers versus nonsmokers that should be further investigated.

Effects of oxidant-induced injury on heme oxygenase and glutathione in cultured aortic endothelial cells from atherosclerosis-susceptible and -resistant Japanese quail

Recent studies on cultured aortic endothelial cells (AECs) from atherosclerosis-susceptible (SUS) and -resistant (RES) strains of Japanese quail suggest that differences in atherosclerosis susceptibility between RES and SUS may be due to differences in endothelial heme oxygenase (HO) and antioxidant components. We have now investigated the effects of oxidant-induced injury on HO and glutathione (GSH) in AECs from SUS and RES quail. We report that cultured AECs from SUS and RES birds differ in their response to oxidative stress. AECs from the SUS strain cells are more susceptible than those from the RES strain to oxidative stress induced by tert-butylhydroperoxide, as judged by lower HO activity, HO-1 expression, ferritin and GSH levels. Aortic endothelial cells from SUS birds also showed higher levels of catalytic iron, TBARS production and LDH release compared with RES cells, indicating that SUS AECs are more susceptible to oxidative stress than cells from the resistant strain. Furthermore, independently of genetic status, AECs from old birds have higher TBARS and lower levels of HSP70 induction than AECs from younger birds, suggesting that aging is associated with a decreased ability of AECs to respond to oxidative stress, and this may be relevant to the permissive effect of aging on the process of atherogenesis. Our results indicate that genetic factors and endogenous antioxidant systems in the blood vessel wall may be important in determining the susceptibility of vascular cells to oxidative stress and atherosclerotic plaque formation.

The role of alpha-tocopherol in preventing disease: from epidemiology to molecular events

The function of vitamin E has been attributed to its capacity to protect the organism against the attack of free radicals by acting as a lipid based radical chain breaking molecule. More recently, alternative non-antioxidant functions of vitamin E have been proposed and in particular that of a "gene regulator". Effects of vitamin E have been observed at the level of mRNA or protein and could be consequent to regulation of gene transcription, mRNA stability, protein translation, protein stability and post-translational events. Given the high priority functions assigned to vitamin E, it can be speculated that it would be inefficient to consume it as a radical scavenger. Rather, it would be important to protect vitamin E through a network of cellular antioxidant defences, similarly to what occurs with proteins, nucleic acids and lipids.

Comparison of acute and chronic antioxidant interventions in experimental renovascular disease

Reactive oxygen species (ROS) can modulate renal hemodynamics and function both directly, by leading to vasoconstriction, and indirectly, by inducing renal inflammation and tissue growth. The involvement of oxidative stress in the pathogenesis of renovascular disease (RVD) is increasingly recognized, but the relative contribution of long-term tissue injury to renal dysfunction remains unclear. We hypothesized that functional and structural alterations elicited by oxidative stress in RVD would be more effectively modulated by chronic than by acute antioxidant intervention. Renal hemodynamics and function were quantified in vivo in pigs using electron-beam computed tomography at baseline and after vasoactive challenge (ACh and sodium nitroprusside); after 12 wk of RVD (simulated by concurrent hypercholesterolemia and renal artery stenosis, n = 7); RVD acutely infused with the SOD-mimetic tempol (RVD+tempol, n = 7); RVD chronically supplemented with antioxidant vitamins C (1 g) and E (100 IU/kg; RVD+vitamins, n = 7); or control (normal, n = 7). Renal tissue was studied ex vivo using immunoblotting and immunohistochemistry. Basal renal blood flow (RBF) and glomerular filtration rate were similarly decreased in all RVD groups. ACh-stimulated RBF remained unchanged in RVD, increased in RVD+tempol, but further increased (similarly to normal) in RVD+vitamins ( P < 0.05 vs. RVD). Furthermore, RVD+vitamins also showed a decreased presence of superoxide anion, decreased NAD(P)H-oxidase and nitrotyrosine expression, increased endothelial nitric oxide synthase expression, and attenuated renal fibrosis. Chronic antioxidant intervention in early RVD improved renal hemodynamic responses more effectively than acute intervention, likely due to increased nitric oxide bioavailability and decreased structural injury. These suggest that chronic tissue changes play an important role in renal compromise mediated by oxidative stress in RVD.

The role of vitamin E in atherosclerosis

Epidemiological and biochemical studies infer that oxidative processes, including the oxidation of low-density lipoprotein (LDL), are involved in atherosclerosis. Vitamin E has been the focus of several large supplemental studies of cardiovascular disease, yet its potential to attenuate or even prevent atherosclerosis has not been realised. The scientific rationale for vitamin E supplements protecting against atherosclerosis is based primarily on the oxidation theory of atherosclerosis, the assumption that vitamin E becomes depleted as disease progresses, and the expectation that vitamin E prevents the oxidation of LDL in vivo and atherogenic events linked to such oxidation. However, it is increasingly clear that the balance between vitamin E and other antioxidants may be crucial for in vivo antioxidant protection, that vitamin E is only minimally oxidised and not deficient in atherosclerotic lesions, and that vitamin E is not effective against two-electron oxidants that are increasingly implicated in both early and later stages of the disease. It also remains unclear as to whether oxidation plays a bystander or a casual role in atherosclerosis. This lack of knowledge may explain the ambivalence of vitamin E and other antioxidant supplementation in atherosclerosis.

Vitamin E and its role in the prevention of atherosclerosis and carcinogenesis: a review

Epidemiological and experimental studies suggest that antioxidants like vitamin E (alpha-tocopherol) may play an important role in prevention of chronic disease. Several observational surveys have linked populations with a large intake of vitamin E with reduced incidence of heart disease. These observations have been strengthened by the demonstration of strong antioxidant activity by vitamin E in cellular, molecular and animal experiments. These results have highlighted a potential role for vitamin E supplementation in the prevention of chronic disease in humans. Interestingly however, large-scale clinical trials of vitamin E and other antioxidants in preventing specific disease processes (e.g., coronary artery disease) have generated conflicting and mixed outcomes. In this review, the role of vitamin E in the prevention of atherosclerosis and carcinogenesis has been carefully examined with particular emphasis on salient human studies (clinical trials) and their limitations. In addition, pertinent biochemical, physiological and metabolic features of vitamin E have also been incorporated. A list of common natural food sources of vitamin E has been provided. Important in vitro and animal studies related to the antiatherosclerotic and anticarcinogenic actions of vitamin E have been discussed in detail. Finally, the direction of future investigations in primary and secondary prevention of chronic diseases by vitamin E supplementation has been outlined.

Alpha-tocopherol protects against diet induced atherosclerosis in New Zealand white rabbits

In this study, we asked the question "does alpha-tocopherol supplementation prevent an increase in total plasma cholesterol (TPC) concentration and reduce the deposition of cholesterol in arterial plaques of rabbits fed atherogenic diets?" Isocaloric diets containing 0.1% cholesterol to induce atherosclerosis were enriched in one of three fats: saturated fats (SAT), monounsaturated fats (MONO), or n-6 polyunsaturated fats (POLY). Half of each of the three diets were supplemented with 2,500 IU alpha-tocopherol/kg-diet. Unsupplemented diets contained 25 IU alpha-tocopherol/kg-diet. Rabbits supplemented with alpha-tocopherol had plasma alpha-tocopherol concentrations 10-fold higher and an average TPC concentration 31% lower, P = 0.017, than rabbits fed unsupplemented diets. Among the three fat-fed groups, the difference was greatest for the POLY fat fed group (54%, P = 0.041). POLY fat-fed rabbits without alpha-tocopherol supplementation had plasma HDL cholesterol concentrations that were less than half that of rabbits fed other fats, P < or = 0.0001. In general, differences in mean esterified artery cholesterol concentrations among the three fat-fed groups, with and without alpha-tocopherol supplementation, paralleled differences in TPC concentration among the groups. This study suggests that for rabbits fed high pharmacological doses of alpha-tocopherol, atherosclerosis can be diminished in situations where the plasma cholesterol concentrations are also significantly lower.

Dietary supplementation with vitamins C and E prevents downregulation of endothelial NOS expression in hypercholesterolemia in vivo and in vitro

Impaired endothelium-dependent vasodilation has been associated with decreased NO bioavailability in hypercholesterolemia. This study aimed to determine whether antioxidant vitamins C and E could improve hypercholesterolemia-derived endothelial dysfunction in the porcine model, and whether observed in vivo results could be reproduced in vitro by incubation of coronary endothelial cells (EC) in the presence of native low-density lipoproteins (LDL). Adult mini-pigs were fed standard (C), cholesterol rich (HC) or cholesterol rich diet supplemented with vitamins C and E (HCV). Endothelium-dependent blood flow increase in response to acetylcholine was determined. Endothelial nitric oxide synthase (eNOS) expression was measured in arterial samples and in EC incubated with LDL isolated from porcine plasma. Vasomotor response to acetylcholine in HC was significantly lower (P<0.05) than control and HCV. There was a significant (P<0.05) decrease in eNOS immunoreactivity in HC, compared with HCV and control. Native LDL from HC, but not from HCV, induced a significant decrease in eNOS expression. Vitamins C and E treatment improved the endothelium-dependent vasomotor capacity and prevented decreased expression of eNOS in hypercholesterolemic pigs. A similar effect could be demonstrated in vitro, by incubation of EC with native LDL, suggesting that the effect of physiologically-modified LDL on eNOS could have a role in recovering vascular function.

Metabolism of oxidized and chemically modified low density lipoproteins in rainbow trout--clearance via scavenger receptors

Oxidative modifications of low density lipoprotein (LDL) convert LDL into a ligand recognized by a variety of scavenger receptors (SR) in mammals. This oxidized LDL (oxLDL) activate several cell types, and have been shown to induce expression of a variety of genes in mammals. Lipoproteins of poikilothermic animals like salmonid fishes contain high levels of polyunsaturated fatty acids susceptible to oxidative modifications. We have investigated, and found trout LDL to be susceptible to oxidation in the presence of Cu(2+). When oxidized or acetylated trout LDL was injected intravenously, the clearance rate was increased compared to that of native LDL. Modified LDL was taken up almost exclusively in the kidney, whereas native LDL was also taken up in the liver. Uptake of both oxLDL and acetylated LDL in the kidney was significantly inhibited by lipoteichoic acid (LTA) and formaldehyde treated BSA (fBSA), both of which are known ligands of SR.

[Molecular mechanisms of the protective effect of vitamin e against atherosclerosis]

Oxidation of low-density lipoproteins constitutes the first step of a very complex process leading to atherosclerosis. Vitamin E, and principally a-tocopherol, is considered as the principal inhibitor of lipid peroxidation. Some studies showed the beneficial role of vitamin E in the prevention and reduction of atherosclerosis and its associated pathologies. However, other in vitro studies advance a prooxidant role of vitamin E. The results of the epidemiologic studies are difficult to generalize without taking account of the clinical randomized tests. In this work, we reviewed the principal studies devoted to the role of vitamin E and discussed the assumption of a prooxidant effect of this molecule.