Absorption, transport and metabolism of vitamin E

Lipid peroxidation and urinary excretion of vitamin E in rats submitted to an immunological inflammatory process

Inflammation is a protective physiologic response, generally controlled by the organism at the injury site. Vitamin E is the most important antioxidant in the lipid phase present in nature and acts by interrupting the chain reaction produced by free radicals. The objective of this study was to evaluate the effect of inflammation on vitamin E levels and lipid peroxidation in rats. Forty Wistar rats (four groups of 10 rats each) were studied over a period of 15 days. Two substances inducing the inflammatory process were parenterally administered, anti-rat basement membrane serum (ABMG) and Freund's complete adjuvant (FAG). Lipid peroxidation levels in hepatic and renal tissue and in plasma and urine were analyzed and compared with the control (CG). Vitamin E was determined by HPLC and lipid peroxidation by quantification of thiobarbituric acid reactive substances (TBARS). ABMG produced more (p < 0.05) TBARS in renal and hepatic tissues (0.7 +/- 0.11 and 1.28 +/- 0.27 nmol/g protein, respectively) compared to CG (0.65 +/- 0.81 and 0.69 +/- 0.13 nmol/g protein). Analysis of TBARS in urine did not show statistically significant differences between the experimental groups and the control. Vitamin E levels in the hepatic tissue of ABMG and FAG (40.7 +/- 10.04 and 44.26 +/- 20.24 micrograms/g tissue) were higher than in CG (22.37 +/- 8.20 micrograms/g tissue) while in kidney tissue and plasma these values were lower (P < 0.05). Renal excretion was increased (P < 0.05) in the group that received anti-rat basement membrane serum (22.39 +/- 0.11 mmol/mL) compared to CG (0.56 +/- 0.056 mmol/mL). We conclude that the acute inflammatory process causes important alterations in the metabolism of vitamin E and lipid peroxidation leading to a significantly increased excretion of this vitamin in the urine.

Age-related macular degeneration and nutritional supplementation: a review of randomised controlled trials

Age-related macular degeneration (AMD) is the leading cause of severe vision loss in the developed world. The lack of effective treatment modalities, coupled with evidence supporting an oxidative pathogenesis, has increased interest in the potential preventative role of nutritional supplementation. This article reviews seven randomised controlled trials (RCTs) that have investigated the role of nutritional supplementation in AMD. Three of these trials reported a positive effect of nutritional supplementation on AMD; the Age-related eye study (AREDS), the Lutein Antioxidant Supplementation Trial (LAST), and the oral zinc trial by Newsome et al. (1988). However, the oral zinc trial by Newsome et al. (1988) was unlikely to detect any difference between treatments smaller than 72%, and the AREDS results were based on a subgroup of their study population. Lutein was considered for the AREDS formulation, but was not commercially available at that time. The findings of the LAST support a possible therapeutic role of lutein in AMD.

Factors affecting intestinal absorption of highly lipophilic food microconstituents (fat-soluble vitamins, carotenoids and phytosterols)

Highly lipophilic food microconstituents (HLFMs) with octanol-water partition coefficients log10 P(c) > 8 include the fat-soluble vitamins (A, E, D and K) and phytochemicals with potential health benefits, the carotenoids and phytosterols. It has been assumed that these compounds have the same metabolism in the human upper gastrointestinal tract and that they follow the same fate as lipids. However, a literature review shows that the metabolism of HLFMs in the upper gastrointestinal tract depends on each HLFM species. For example, some HLFM esters are hydrolyzed mainly by pancreatic lipase, others by bile salt-stimulated lipase; some HLFMs are apparently absorbed by passive diffusion, others by a transporter. Also, although some factors (HLFM molecular species, fat, food matrix) affect absorption efficiency of most HLFMs, other factors (fibers, microconstituents) apparently affect absorption only of some HLFMs. The mnemonic acronym SLAMENGHI, previously proposed to list the factors affecting the bioavailability of carotenoids, was used here to review current knowledge of the factors suspected to affect the intestinal absorption of HLFMs. The available data reveal numerous gaps in the knowledge of the metabolism of HLFMs and the factors that affect their absorption. These gaps need to be filled to be able to formulate HLFMs so as to promote greater absorption efficiency.

Effect of vitamin E on glutathione-dependent enzymes

Reactive oxygen species and various electrophiles are involved in the etiology of diseases varying from cancer to cardiovascular and pulmonary disorders. The human body is protected against damaging effects of these compounds by a wide variety of systems. An important line of defense is formed by antioxidants. Vitamin E (consisting of various forms of tocopherols and tocotrienols) is an important fat-soluble, chain-breaking antioxidant. Besides working as an antioxidant, this compound possesses other functions with possible physiological relevance. The glutathione-dependent enzymes form another line of defense. Two important enzymes in this class are the free radical reductase and glutathione S-transferases (GSTs). The GSTs are a family of phase II detoxification enzymes. They can catalyze glutathione conjugation with various electrophiles. In most cases the electrophiles are detoxified by this conjugation, but in some cases the electrophiles are activated. Antioxidants do not act in isolation but form an intricate network. It is, for instance, known that vitamin E, together with glutathione (GSH) and a membrane-bound heat labile GSH-dependent factor, presumably an enzyme, can prevent damaging effects of reactive oxygen species on polyunsaturated fatty acids in biomembranes (lipid peroxidation). This manuscript reviews the interaction between the two defense systems, vitamin E and glutathione-dependent enzymes. On the simplest level, antioxidants such as vitamin E have protective effects on glutathione-dependent enzymes; however, we will see that reality is somewhat more complicated.

Plasma lipoproteins in transport of silibinin, an antioxidant flavonolignan from Silybum marianum

To assess the role of plasma lipoproteins in the transport of silibinin, an antioxidant flavonolignan, (125)I-labelled silibinin ((125)I-SB) administered perorally to the rat was used. The plasma (125)I-SB derived radioactivity was distributed among plasma lipoproteins according to their lipophilicity (TAG-rich lipoproteins 30-40% > LDL 15% > HDL 5%), and in the fraction of d > 1.215 containing albumin and other proteins a minority amount of radioactivity was found. Administration of (125)I-SB in a complex with phosphatidylcholine resulted in proportionally higher radioactivities in all fractions as well as in tissues. Dietary olive oil had a slightly decreasing effect on plasma concentrations of silibinin measured by HPLC as well as on (125)I-SB derived radioactivity in plasma and liver. In the TAG-rich lipoprotein fraction and HDL no effects of olive oil on the levels of (125)I-SB derived radioactivities were observed, however, at a 30 min interval the levels of (125)I-SB derived radioactivity in LDL and the heart were significantly decreased in the olive oil group. These results suggest that (i) silibinin is not resorbed by the chylomicron pathway, and (ii) the endogenous lipoprotein pathway VLDL --> LDL may play a role in the transport of silibinin from the liver to the extrahepatic tissues concurrently facilitating the lipoprotein antioxidant influence of silibinin.

Interaction of dietary vitamin E with Eimeria maxima infections in chickens

In two trials, broiler chickens, processed similarly to those placed in commercial operation, were fed, from 1 d of age, a range (13 to 200 ppm) of DL-alpha-tocopheryl acetate (VE-AC) levels, and the effects on the pathology of Eimeria maxima infections were assessed at 6 d postinoculation (PI). In Trial 1, dietary levels of VE-AC had little significant effect on variables characterizing pathology except for the number of oocysts shed, which was significantly increased in chicks treated with higher VE-AC levels. The infection was judged to be mild based on moderate lesion scores (2.2+/-0.2), lack of significant effects on weight gain (7+/-1.6% decrease), moderate reduction in plasma carotenoids (21+/-2%) and small increases in plasma NO2-+NO3- (141+/-12%). In uninfected and infected chickens, plasma alpha-tocopherol (AT) increased with dietary levels of VE-AC; however, E. maxima infection caused a fairly constant decrease in AT of 35.3+/-3.2% across these levels. Plasma gamma-tocopherol (GT) levels were unaffected by dietary VE-AC or E. maxima infection. In Trial 2, pathology, again, was relatively unaffected by dietary VE-AC level. The infection was judged to be severe based on lesion scores (3.5+/-0.1), reduction in weight gain (30.7+/-3%), plasma carotenoids (72.4+/-1.5%), uric acid (16.3+/-3.4), albumin (37.8+/-2.8%), large increases (261+/-8%) in plasma NO2-+NO3-, and high numbers of oocysts shed per chick (4.12+/-0.4 x 10(7)). Plasma AT again increased with increasing dietary VE-AC levels in uninfected and infected chicks, but the mean decrease across VE-AC levels caused by E. maxima infection was 73.14+/-3.3%. GT levels were erratic and unrelated to dietary VEAC or infection. Thus, in processed broiler chickens, high dietary VE-AC did not prevent or lessen the pathology caused by mild or severe infections with E. maxima. The main effect of E. maxima infection appeared to be reduction in plasma AT levels. We postulate that this reduction may be due to malabsorption of AT, which results from physical damage to the absorptive mucosa, reduction in esterases required to hydrolyze the VE-AC, and a generalized lipid malabsorption, preventing movement of the free AT to circulating blood and infected tissues.

Necrosis and apoptosis in lymphoma cell lines exposed to eicosapentaenoic acid and antioxidants

The present study is focused on the role of oxidative stress in the induction of either necrosis or apoptosis by eicosapentaenoic acid (EPA) in the lymphoma cell lines Raji and Ramos, respectively. To investigate the different death modes induced by EPA, we assessed the importance of some antioxidants and reactive oxygen species in the two cell lines. We observed that different antioxidants counteracted the necrotic effect of EPA on Raji cells to a different extent, and that vitamin E counteracted EPA-induced accumulation of superoxide anion in this cell line. On the contrary, no effects of antioxidants were observed on development of apoptosis induced by EPA in Ramos cells, and vitamin E did not counteract EPA-induced accumulation of superoxide anions in Ramos cells. Moreover, apoptosis was partly inhibited by transcription inhibitors (actinomycin D) and protein synthesis inhibitors (cycloheximide), suggesting dependency upon new protein synthesis prior to apoptosis. Kinase inhibitors (staurosporin and calphostin C) did not alter the EPA-induced apoptosis. The observed cellular accumulation of superoxide anion following EPA incubation may be important for induction of necrosis in Raji cells. In contrast, none of the other investigated parameters indicated a role of oxidative stress promoted by EPA in the induction of apoptosis in Ramos cells.

Serum concentrations of beta-carotene and alpha-tocopherol are associated with diet, smoking, and general and central adiposity

BACKGROUND

Previous studies of associations between diet, obesity, and blood concentrations of alpha-tocopherol and beta-carotene have been equivocal. Furthermore, most studies used only body mass index (BMI) as an obesity measure.

OBJECTIVES

Our objectives were to examine the associations between energy and nutrient intakes, alcohol consumption, tobacco use, and serum cholesterol and serum concentrations of alpha-tocopherol and beta-carotene, and to examine the associations between different measures of general and central adiposity and serum concentrations of alpha-tocopherol and beta-carotene.

DESIGN

This was a cross-sectional, population-based study of 253 men and 276 women aged 46-67 y. Nutrient data were collected by a modified diet history method. Measures of obesity included BMI, percentage of body fat (impedance analysis), waist-to-hip ratio, and waist circumference. The associations between serum nutrient concentrations and the other factors were examined by multiple linear regression.

RESULTS

Twenty-one percent of men and 34% of women used antioxidant supplements. The mean BMI was 26.1 in men and 25.4 in women. Serum beta-carotene concentration was positively associated with serum cholesterol concentration, fiber intake, and beta-carotene intake, and negatively associated with smoking and all measures of obesity. In men, serum beta-carotene concentration was not significantly associated with central adiposity after adjustment for body fat. Serum alpha-tocopherol concentration was positively correlated with serum cholesterol, obesity, and vitamin E intake. In women, serum alpha-tocopherol concentration was also positively associated with intakes of ascorbic acid and selenium. Serum alpha-tocopherol concentration was associated with central adiposity after adjustment for body fat.

CONCLUSION

Serum beta-carotene and alpha-tocopherol concentrations have different associations with diet, smoking, general adiposity, and central adiposity.

Fourier-transform infrared spectroscopy: a pharmacotoxicologic tool for in vivo monitoring radical aggression

Among the physico-chemical methods that can be used to investigate induced peroxidation in living cells, Fourier transform infrared (FT-IR) spectroscopy appears to be a valuable technique as it is non-destructive and sensitive for monitoring changes in the vibrational spectra of samples. We examined microsomal fractions from rat liver and brain by FT-IR to study the effect of radical aggression induced in vivo by carbon tetrachloride (CCl4). The length of the acyl chains was increased as a consequence of peroxidation induced by the xenobiotic. Moreover, an enhanced level of cholesterol esters and an increase in phospholipids were observed in the liver and the brain, respectively. The conformational structure of the membrane proteins was changed in both the liver and the brain. In the polysaccharide region, we observed an important loss in glucidic structures, such as a decrease in liver glycogen and in some brain glycolipids. These alterations are probably due to the interactions between cells and CCl4and the metabolic changes caused by CCl4. Thus, FT-IR spectroscopy appears to be an useful tool and an accurate means for rapidly investigating the in vivo biochemical alterations induced by CCl4in microsomes, and for correlating them with biochemical and physiological data.Key words: brain, carbon tetrachloride, FT-IR, liver, microsomes.

The role of oxidative stress in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blind registration in the developed world, and yet its pathogenesis remains poorly understood. Oxidative stress, which refers to cellular damage caused by reactive oxygen intermediates (ROI), has been implicated in many disease processes, especially age-related disorders. ROIs include free radicals, hydrogen peroxide, and singlet oxygen, and they are often the byproducts of oxygen metabolism. The retina is particularly susceptible to oxidative stress because of its high consumption of oxygen, its high proportion of polyunsaturated fatty acids, and its exposure to visible light. In vitro studies have consistently shown that photochemical retinal injury is attributable to oxidative stress and that the antioxidant vitamins A, C, and E protect against this type of injury. Furthermore, there is strong evidence suggesting that lipofuscin is derived, at least in part, from oxidatively damaged photoreceptor outer segments and that it is itself a photoreactive substance. However, the relationships between dietary and serum levels of the antioxidant vitamins and age-related macular disease are less clear, although a protective effect of high plasma concentrations of alpha-tocopherol has been convincingly demonstrated. Macular pigment is also believed to limit retinal oxidative damage by absorbing incoming blue light and/or quenching ROIs. Many putative risk-factors for AMD have been linked to a lack of macular pigment, including female gender, lens density, tobacco use, light iris color, and reduced visual sensitivity. Moreover, the Eye Disease Case-Control Study found that high plasma levels of lutein and zeaxanthin were associated with reduced risk of neovascular AMD. The concept that AMD can be attributed to cumulative oxidative stress is enticing, but remains unproven. With a view to reducing oxidative damage, the effect of nutritional antioxidant supplements on the onset and natural course of age-related macular disease is currently being evaluated.

Pharmacologic application of fourier transform IR spectroscopy: in vivo toxicity of carbon tetrachloride on rat liver

Microsomal fractions from rat liver were examined by means of Fourier transform IR (FTIR) spectroscopy to study the in vivo toxic effect of carbon tetrachloride administered by intraperitoneal injection. Lipid content was significantly enhanced in the liver of treated rats compared with untreated ones. The level of saturated fatty acids largely increased while that of unsaturated acids slightly decreased as a consequence of lipid peroxidation induced by the xenobiotic compound. The conformational structure of membrane proteins was changed, which was shown by the large decrease in the alpha-helical configuration. In the polysaccharide region we observed an important loss in glucidic structures that could be related to the metabolic changes caused by carbon tetrachloride intoxication. Thus, FTIR spectroscopy appears to be a useful tool to rapidly investigate the chemical alterations induced by this drug in liver microsomes and to correlate them with biochemical and physiological data.

Lipid peroxidation of isolated chylomicrons and oxidative status in plasma after intake of highly purified eicosapentaenoic or docosahexaenoic acids

Fourteen healthy male volunteers were given two separate high-saturated-fat meals with and without the addition of 4 g highly purified ethyl esters of either eicosapentaenoic acid (EPA) (95% pure, n = 7) or docosahexaenoic acid (DHA) (90% pure, n = 7) supplied as 1-g capsules each containing 3.4 mg vitamin E. The chylomicrons were isolated 6 h after the meals, at peak concentrations of n-3 fatty acids (FA). Addition of n-3 FA with the meal caused a 10.4-fold increase in the concentration of n-3 FA in chylomicrons compared to the saturated fat meal without addition of n-3 FA. After the saturated-fat meal, the concentration of thiobarbituric acid-reactive substances (TBARS) was 327.6 +/- 34.6 nmol/mmol triacylglycerol (TAG), which increased to 1015.8 +/- 212.0 nmol/mmol TAG (P < 0.0001, n = 14) after EPA and DHA were added to the meal. There was no significant correlation between the concentrations of TBARS and vitamin E in the chylomicrons collected 6 h after the test meal. The present findings demonstrate an immediate increase in chylomicron peroxidation ex vivo provided by intake of highly purified n-3 FA. The capsular content of vitamin E was absorbed into chylomicrons, but the amount of vitamin E was apparently not sufficient to protect chylomicrons against lipid peroxidation ex vivo. Daily intake of 4 g n-3 FA either as EPA or DHA for 5 wk did not change the plasma concentration of TBARS. Although not significantly different between groups, DHA supplementation decreased total glutathione in plasma (P < 0.05) and EPA supplementation increased plasma concentration of vitamin E (P < 0.05). The other lipid-soluble and polar antioxidants in plasma remained unchanged during 5 wk of intervention with highly purified n-3 FA.

Low doses of eicosapentaenoic acid, docosahexaenoic acid, and hypolipidemic eicosapentaenoic acid derivatives have no effect on lipid peroxidation in plasma

It was of interest to investigate the influence of both high doses of eicosapentaenoic acid (EPA) and low doses of 2- or 3-methylated EPA on the antioxidant status, as they all cause hypolipidemia, but the dose required is quite different. We fed low doses (250 mg/d/kg body wt) of different EPA derivatives or high doses (1500 mg/d/kg body wt) of EPA and DHA to rats for 5 and 7 d, respectively. The most potent hypolipidemic EPA derivative, 2,2-dimethyl-EPA, did not change the malondialdehyde content in liver or plasma. Plasma vitamin E decreased only after supplementation of those EPA derivatives that caused the greatest increase in the fatty acyl-CoA oxidase activity. Fatty acyl-CoA oxidase activity increased after administration of both EPA and DHA at high doses. High doses of EPA and DHA decreased plasma vitamin E content, whereas only DHA elevated lipid peroxidation. In liver, however, both EPA and DHA increased lipid peroxidation, but the hepatic level of vitamin E was unchanged. The glutathione-requiring enzymes and the glutathione level were unaffected, and no significant changes in the activities of xanthine oxidase and superoxide dismutase were observed in either low- or high-dose experiments. In conclusion, increased peroxisomal beta-oxidation in combination with high amounts of polyunsaturated fatty acids caused elevated lipid peroxidation. At low doses of polyunsaturated fatty acids, lipid peroxidation was unchanged, in spite of increased peroxisomal beta-oxidation, indicating that polyunsaturation is the most important factor for lipid peroxidation.

Plasma levels of glutathione, alpha-tocopherol and lipid peroxides in polytraumatized patients; evidence for a stimulating effect of TNF alpha on glutathione synthesis

Prognosis and outcome of polytraumatized patients are determined by the possible development of multiple organ failure (MOF). Among the direct traumatic organ damage, it is caused by a systemic inflammatory reaction. This might be triggered by an activation of the inflammatory mediator cascade following hemorrhagic-traumatic shock as well as by oxygen-derived free radicals (ROS). The aim of our present study was to answer the following questions: 1. Is the "oxidative stress" measurable during the development of MOF after polytraumatic injury? 2. Is there a relation between the activation of the inflammatory mediator cascade and changes of the organism's antioxidative system? The study group included 26 patients (15 survivors, 11 non-survivors) suffering from severe polytraumatic injury (Hannover Polytrauma Score 12-63 points). Plasma levels of reduced (GSH) and oxidized (GSSG) glutathione alpha-tocopherol (TOC), lipid peroxides (expressed in terms of thiobarbituric acid reagible substances = TBARS), and tumor necrosis factor alpha (TNF) were measured each day from the point of admission on the ICU until the discharge or death of the patients. The following results were obtained: Independent from the outcome, we observed a continuous loss of plasma sulfhydryl groups and TOC. In the patients developing a MOF score > 5 on 10th day after injury (n = 6), a significant increase in plasma GSSG level was measurable. Additionally, a total loss of plasma GSH was seen in some of these patients indicating the collapse of the GSH-dependent antioxidative system. Similar changes were never observed in patients with MOF score < or = 5 on 10th day after injury (n = 15). In this group, a significant correlation between plasma TNF peaks and short time GSH boosts was obtained as a possible indicative for a stimulating effect of TNF on GSH synthesis. It can be concluded that processes of oxidative stress in connection with a consumption of endogenic antioxidants might be able to promote the development of MOF after polytraumatic injury.

Vitamin E analogues reduce the incidence of ventricular fibrillations and scavenge free radicals

The aim of our study was to analyse the protective effects of different alpha-tocopherol analogues 1) against fibrillations induced by an ischemia-reperfusion sequence, and 2) to further investigate in vitro the radical scavenging properties of these analogues by two sensitive methods. Concerning 1: isolated rat hearts underwent 10 min of coronary ligation followed by reperfusion and the alpha-tocopherol analogues were infused 15 min before occlusion. Functional parameters including heart rate and fibrillations were recorded. Concerning 2: the beta-phycoerythrin assay was utilised to determine the oxygen radical absorbing capacity (ORAC) of these vitamin E analogues against peroxyl radicals. Electron paramagnetic resonance (EPR) was used to measure their scavenger abilities on hydroxyl radical and superoxide anion production. Concerning 1: ventricular fibrillation times were reduced for all analogues treated hearts at concentrations of 1 microM and 5 microM, with Trolox being the most efficacious. Concerning 2: in our experimental conditions of intense production of free radicals, scavenging IC50 values for hydroxyl radical were 1.15, 2.17 and 4.04 mM for Trolox, MDL 74270 and MDL 74366 respectively. Superoxide anion IC50 values were 1.0 and 6.75 mM for Trolox and MDL 74270. Our results show that water-soluble analogues of vitamin E are effective in the prevention of coronary ligation induced reperfusion arrhythmia, under our experimental conditions. Moreover, our data demonstrate that these vitamin E analogues are effective scavengers for a variety of radicals. Our studies support the view that compounds that can either inhibit the formation or scavenge free radicals can protect the heart against arrhythmia associated with ischemia-reperfusion.

Fixed-point methods for computing the equilibrium composition of complex biochemical mixtures

The fixed-point algebraic method [Storer and Cornish-Bowden (1976) Biochem. J. 159, 1-5] for computing the concentrations at equilibrium of complex biochemical mixtures fails for many binding stoichiometries, especially those that include molecular self-association. A typical example is the monomer-dimer-tetramer equilibrium. This paper reports two main results. First, the above algorithm is analysed theoretically to predict for which binding stoichiometries it succeeds and for which it will fail. Secondly, an alternative algorithm is described for self-associating biochemical systems. Illustrative examples are based on the dimeric proteinase from HIV.

alpha- and delta-tocopherol induce expression of hepatic alpha-tocopherol-transfer-protein mRNA

alpha-Tocopherol transfer protein (alpha-TTP) supplements nascent very-low-density lipoprotein (VLDL) preferentially with alpha-tocopherol by selecting the alpha-isomers against other stereoisomers of tocopherol. It is exclusively expressed in liver. We investigated whether the expression of the hepatic alpha-TTP can be induced by dietary tocopherols. Vitamin E-depleted rats were fed with a diet containing alpha- and delta-tocopherol (ratio 1:3). The expression of alpha-TTP mRNA was measured in liver tissue. The ratio of tocopherol stereoisomers was determined in plasma, plasma lipoproteins and tissues to measure the metabolic action of alpha-TTP. Refeeding a diet containing either alpha- or delta-tocopherol, or both, caused a steady increase of the expression of alpha-TTP mRNA. In parallel the alpha/delta-tocopherol ratio increased in plasma, VLDL, high-density lipoprotein and low-density lipoprotein as well as in liver tissue, when the diet was fed containing both isomers. The alpha-tocopherol/delta-tocopherol ratio of heart, kidney, lung, lamellar bodies of lung and in lung lavage showed no or a comparatively low increase. The data show that both tocopherol isomers were able to induce alpha-TTP mRNA in rat liver and, thus, the ability of liver to select for the alpha-isomer. On the other hand, tocopherol depletion did not change the expression of hepatic alpha-TTP mRNA in the rat.

Antioxidant properties of indapamide, 5-OH indapamide and hydrochlorothiazide evaluated by oxygen-radical absorbing capacity and electron paramagnetic resonance

The aim of these experiments was to investigate the radical scavenging properties of three diuretics: indapamide (IND) and its major metabolite, 5-OH indapamide (5-OH IND), compared to a reference diuretic, hydrochlorothiazide (HTZ). Electron Paramagnetic Resonance (EPR) was used to determine the scavenging abilities of these compounds on enzymatically produced superoxide radical anion, with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) used as a spin-trap. These experiments revealed that IND and specially 5-OH IND were effective superoxide radical anion scavengers at 0.2 mg/ml. In the second part of these studies, allophycocyanin was used as an indicator of free radical mediated protein damage. In the assay, 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH) was used as a peroxyl radical generator, Trolox (a water-soluble analogue of vitamin E) as a control standard, and the loss of allophycocyanin fluorescence was monitored. The antioxidant effects of the diuretics were expressed in oxygen-radical absorbing capacity (ORAC), where one ORAC unit equals the net protection produced by 1 microM Trolox. HTZ showed no protection up to 100 microM final concentration, whereas IND and 5-OH IND showed linear correlation with respect to concentration when expressed in ORAC units: 5-OH IND induced the highest protection against peroxyl radical. The above observations suggested that IND and 5-OH IND are potent radical scavengers, with the metabolite 5-OH IND having a superior antioxidant potency than IND. By contrast, HTZ had no effect. These radical scavenging properties of 5-OH IND may be of clinical interest for vascular protection and may help to protect the heart from oxidative injury.

Tocopherols and the etiology of colon cancer

Colorectal cancer is the second most common cause of cancer deaths in the United States for both sexes. Considerable evidence suggests that the risk of this cancer is increased by the mutagenic actions of free radicals, which are produced during oxidation reactions. Dietary factors, the intestinal flora (bacteria), and endogenously produced metabolites contribute to the production of free radicals in the colon. Dietary antioxidants, such as vitamin E, should reduce the levels of these harmful oxidation products. In the absence of vitamin E, polyunsaturated fats can be oxidized in the colon to produce mutagens, such as lipid hydroperoxides and malondialdehyde. Furthermore, fecal bacteria can generate a high flux of reactive oxygen species (e.g., the superoxide radical [O2*-]) at the surface of the intestinal lumen, and inflammatory cells in close proximity to the colon can produce reactive nitrogen species (e.g., nitrogen dioxide [NO2]). Increasing evidence suggests that the different chemical (e.g., alpha- and gamma-tocopherol) and stereochemical (e.g., RRR- and all-racemic-alpha-tocopherol) forms of vitamin E have distinct biologic potencies, pharmacokinetics, and different abilities to prevent neoplastic transformation. This review considers and evaluates recent studies relating vitamin E and oxidative stress to colon cancer, emphasizing the distinct roles of alpha- and gamma-tocopherols. In addition, recent findings on the antioxidant/pro-oxidant status of the digesta (ingested food) are discussed with respect to the use of antioxidants in chemo-prevention trials for colon cancer.

Oxidative stress and antioxidant status in mouse liver: effects of dietary lipid, vitamin E and iron

The purpose of this study was to determine the effects of dietary fat, vitamin E and iron on oxidative damage and antioxidant status. Male Swiss-Webster mice (1 mo old) were fed a basal vitamin E-deficient diet that contained either 8% fish oil + 2% corn oil or 10% lard with or without 1 g dl-alpha-tocopheryl acetate. The diets without vitamin E contained either 0.21 or 0.95 g ferric citrate/kg. Diets were fed for 4 wk/kg diet. Compared with the vitamin E-supplemented groups, mice fed diets without vitamin E (with or without supplemental iron) had significantly (P < 0.05) higher hepatic levels of thiobarbituric acid-reactive substances (TBARS), conjugated dienes and protein carbonyls when they were fed fish oil, but not lard. The levels of TBARS were further increased by iron supplementation in the mice fed fish oil. Significantly lower concentrations of alpha-tocopherol and higher glutathione (GSH) were found in the liver of mice fed fish oil and vitamin E than in those fed lard and vitamin E (P < 0.05). The activities of superoxide dismutase and glucose-6-phosphate dehydrogenase were lower in the fish oil-fed mice than in those fed lard (P < 0.05). The activities of Se-GSH peroxidase, non-Se-GSH peroxidase, catalase, and glutathione reductase were not altered by dietary fat or vitamin E/iron. The results obtained provide experimental evidence of the prooxidative effects of high dietary fish oil and iron, and suggest that vitamin E protects not only lipid-soluble compounds, but also water-soluble constituents, against oxidative damage. Further, dietary lipid plays a key role in determining cellular susceptibility to oxidative stress.

Effect of hyperoxia on the composition of the alveolar surfactant and the turnover of surfactant phospholipids, cholesterol, plasmalogens and vitamin E

Experimental and clinical studies have provided evidence for the involvement of oxygen free radicals in development of acute and chronic lung diseases. Hyperoxia is very often an indispensable therapeutic intervention which seems to impose oxidative stress on lung tissue. We measured the effect of hyperoxia (80% O2 for 20 h) (1) on the lipid composition of pulmonary surfactant treated in vitro, (2) on surfactant lipid synthesis and secretion of type II pneumocytes in primary culture, (3) on the lipid composition and on the SP-A content of rat lung lavages and (4) on the turnover of phospholipids, cholesterol, plasmalogens and vitamin E in type II pneumocytes, lamellar bodies and lavages of adult rat lungs. (1) Hyperoxia of lung lavages in vitro reduces the vitamin E content significantly but does not change the relative proportion of PUFA or the content of plasmalogens. (2) Hyperoxia does not affect the biosynthesis or secretion of surfactant lipids and plasmalogens by type pneumocytes in primary culture. (3) Hyperoxic treatment of rats increases the SP-A content and reduces the vitamin E content significantly but does not change the concentration of other lipid components of lung lavage. (4) The vitamin E turnover, measured in type II pneumocytes, lamellar bodies and lung lavages, is increased 2-fold in these fractions. In contrast, the turnover of surfactant cholesterol and surfactant lipids does not change. (5) Hyperoxia caused an increase of the vitamin E uptake by type II pneumocytes resulting in a vitamin E enrichment of lamellar bodies. From these results we conclude that type II pneumocytes are able to regulate the turnover of lipophilic constituents of the alveolar surfactant independently of each other. Hyperoxia caused type II pneumocytes to increase the vitamin E content of lamellar bodies. The lipid and SP-A content of alveolar fluid can be regulated independently each other.

alpha-Tocopherol concentrations in milk and plasma during clinical Escherichia coli mastitis

Eighteen cows were challenged by intramammary infusion with Escherichia coli 727 to determine the effects of acute clinical mastitis on alpha-tocopherol concentrations in plasma and milk. Cows were fed diets supplemented with 1000 IU of vitamin E/d from calving through the experimental period. At challenge, geometric mean DIM was 33 d. Each mammary quarter was diagnosed with an IMI and clinical mastitis at 24 and 48 h after challenge. The alpha-tocopherol concentrations in milk from challenged quarters were approximately 60% greater by 24 and 48 h after challenge than concentrations at prechallenge and 168 h postchallenge. Plasma alpha-tocopherol concentrations did not change after intramammary challenge. The alpha-tocopherol in plasma and milk was correlated at 48 and 168 h postchallenge but not at prechallenge or 24 h postchallenge. Milk alpha-tocopherol and SCC were correlated positively across all sample periods. Milk fat and milk alpha-tocopherol concentrations were correlated at each sample period except 24 h postchallenge. Increases in milk alpha-tocopherol during clinical mastitis were not correlated to milk production, DMI, or BSA concentration in milk. Changes in milk alpha-tocopherol concentration during clinical mastitis were similar to the dynamics of milk SCC.

Antimalarial properties of soy-bean fat emulsions

Intralipid and Ivelip are commercial preparations of soy-bean lipid extracts used for intravenous supplementation of lipids in various clinical conditions. They were found to inhibit the growth of Plasmodium falciparum in culture with an IC50 of 8.07 +/- 2.13 and 13.32 +/- 2.05 mg.ml-1, respectively. Intralipid rapidly and efficiently inhibited nucleic acid synthesis in cultured P. falciparum, exhibiting full inhibitory activity in less than 2 h. Ivelip injected intraperitoneally, was found by the 4-day suppressive test to be active in vivo against P. vinckei petteri within the normal recommended regimen for dietary lipid supply (0.5-4 g.kg-1), but it was impossible to obtain a radical cure even with very high doses (6.4 g.kg-1). Ivelip was less effective against P. berghei and P. yoelii nigeriensis. As Ivelip showed no interference with the antimalarial activity of chloroquine, it could be considered for use in the treatment of severe human malaria in association with 4-aminoquinolines to expedite the clearance of parasites.

Biokinetics in humans of RRR-alpha-tocopherol: the free phenol, acetate ester, and succinate ester forms of vitamin E

The bioavailability of RRR-alpha-tocopherol from the oral administration of RRR-alpha-tocopherol itself and its acetate and succinate esters was determined in healthy human subjects. Venous blood samples were withdrawn periodically over a 51-h period following oral administration of a gelatin capsule containing an equimolar mixture of RRR-alpha-tocopherol and RRR-alpha-tocopheryl acetate. In a second study, subjects received a capsule containing an equimolar mixture of RRR-alpha-tocopheryl acetate and RRR-alpha-tocopheryl succinate. In Study 1, RRR-alpha-tocopherol was absorbed at similar rates from both the free phenol, and the acetate ester and maximum plasma levels occurred at 12 h in most subjects. The extent of absorption of RRR-alpha-tocopherol varied considerably between subjects in absolute terms, but the relative absorption from the two forms was remarkably consistent, and a ratio of 1.0 was found for parameters of relative bioavailability in plasma. The concentration of RRR-alpha-tocopherol from each form was maximal at approximately 27 h in red blood cells and, as seen with the plasma data, there was a large interindividual variability. In Study 2, there was no significant difference in the extent of absorption of RRR-alpha-tocopherol from the acetate ester and the succinate ester, although there was an apparently higher initial rate of absorption from the acetate ester.

Effect of dietary antioxidants on puromycin aminonucleoside nephrotic syndrome

Several studies indicate the pathophysiological importance of reactive oxygen species in rats with nephrotic syndrome induced by puromycin aminonucleoside, an experimental model of the human minimal change disease. The role of reactive oxygen species in these rats was further evaluated, examining the effect of dietary deficiency and supplementation of antioxidants (vitamin E and selenium) on biochemical and renal ultrastructural alterations induced by puromycin aminonucleoside. Male Wistar rats, weaned at 3 weeks, were placed on diets normal, deficient or supplemented in vitamin E and selenium for 4 weeks. At the end of this period, rats were divided in two groups: control (sacrificed without any further treatment) and nephrotic (injected with puromycin aminonucleoside and sacrificed 7 and 22 days later). In control rats, the dietary deficiency or supplementation of antioxidants resulted in no significative differences in renal function, proteinuria or kidney ultrastructure. However, kidney lipoperoxidation, kidney glutathione peroxidase activity and circulating levels of vitamin E changed according to the amount of antioxidants in the diet. Seven days after the injection of puromycin aminonucleoside, rats fed normal, deficient or supplemented diets, developed nephrotic syndrome. However, proteinuria, hypoproteinemia, renal dysfunction and ultrastructural alterations were higher in rats fed a deficient diet. In contrast, proteinuria and kidney ultrastructural alterations were lower in rats fed a supplemented diet. Kidney lipoperoxidation and glutathione peroxidase activity increased on day 7 in rats fed a normal or a deficient diet, but not in rats fed a supplemented diet. This study shows that nephrotic syndrome induced by puromycin aminonucleoside in rats is modified by dietary antioxidants (vitamin E and selenium). Dietary supplementation ameliorates it and dietary deficiency exacerbates it.(ABSTRACT TRUNCATED AT 250 WORDS)

Monitoring oxidative damage in patients with liver cirrhosis and different daily alcohol intake

This study looked at the possible association between alcohol abuse and free radical mediated oxidative injury by examining the presence of oxidative damage, as monitored by erythrocyte malonildialdehyde and plasma lipid hydroperoxides, in patients with liver cirrhosis and different lifetime daily alcohol intake. All patients with an alcohol intake above 100 g/day (ALC) showed concentrations of malonildialdehyde and lipid hydroperoxide on average four to fivefold higher than cirrhotic patients with alcohol intake below 100 g/day (NAC) or healthy controls. Further subgrouping of ALC patients showed that those with alcohol intake ranging between 100 and 200 g/day (ALC1) had malonildialdehyde and lipid hydroperoxide concentrations significantly lower than those with an intake higher than 200 g/day (ALC2). These differences were not related to the extent of liver injury or to the liver derangement as assessed by Child's classification. The increase in lipid peroxidation markers in ALC cirrhotic patients was associated with a decrease in, respectively, plasma alpha-tocopherol and erythrocyte glutathione concentrations. Significant differences were also seen between ALC1 and ALC2 groups in plasma alpha-tocopherol, but not in erythrocyte glutathione concentrations. The concentrations of alpha-tocopherol and glutathione in the blood of NAC patients were in contrast not substantially different from those of healthy controls. The close association between oxidative damage and alcohol abuse suggested that free radical intermediates produced during ethanol metabolism might be responsible for causing oxidative damage.

Oxidative stress: free radical production in neural degeneration

It is not yet established whether oxidative stress is a major cause of cell death or simply a consequence of an unknown pathogenetic factor. Concerning chronic diseases, as Parkinson's and Alzheimer's disease are assumed to be, it is possible that a gradual impairment of cellular defense mechanisms leads to cell damage because of toxic substances being increasingly formed during normal cellular metabolism. This point of view brings into consideration the possibility that, besides exogenous factors, the pathogenetic process of neurodegeration is triggered by endogenous mechanisms, either by an endogenous toxin or by inherited metabolic disorders, which become progressively more evident with aging. In the following review, we focus on the oxidative stress theory of neurodegeneration, on excitotoxin-induced cell damage and on impairment of mitochondrial function as three major noxae being the most likely causes of cell death either independently or in connection with each other. First, having discussed clinical, pathophysiological, pathological and biochemical features of movement and cognitive disorders, we discuss the common features of these biochemical theories of neurodegeneration separately. Second, we attempt to evaluate possible biochemical links between them and third, we discuss experimental findings that confirm or rule out the involvement of any of these theories in neurodegeneration. Finally, we report some therapeutic strategies evolved from each of these theories.

Rat vitamin E status and heart lipid peroxidation: effect of dietary alpha-linolenic acid and marine n-3 fatty acids

Three groups of sixteen male rats each were fed semi-purified diets containing 15% by weight of lipid for a period of 4 wk. The diets contained the same amount of polyunsaturated fatty acids (PUFA) (20% of total fatty acids) and saturated fatty acids (19% of total fatty acids). Dietary PUFA were represented exclusively by linoleic acid (18:2 diet), or 10% linoleic acid and 10% linolenic acid (18:3 diet), or 10% linoleic acid and 10% long-chain n-3 fatty acids (LCn-3 diet). The overall amount of vitamin E was similar in the three diets, i.e., 140, 133 and 129 mg/kg diet, respectively. Following appropriate extraction, tocopherol levels in heart, liver, brain, adipose tissue (AT) and plasma were measured by high-performance liquid chromatography. The level of vitamin E in the heart decreased with n-3 PUFA diets, most markedly with LCn-3 PUFA. Liver and AT vitamin E contents also decreased with n-3 PUFA diets when expressed as micrograms/mg total lipids and micrograms/mg phospholipids, respectively. Total plasma vitamin E was lower in rats fed the LCn-3 diet, but there was no significant difference when expressed as microgram/mg total lipids. Brain vitamin E was not affected by the various diets. In vitro cardiac lipid peroxidation was quantified by the thiobarbituric acid reactive substances (TBARS) test. Heart homogenates were incubated at 37 degrees C for 15 and 30 min in both the absence (uninduced) or presence (induced) of a free radical generating system (1 mM xanthine, 0.1 IU per mL xanthine oxidase, 0.2 mM/0.4 mM Fe/ethylenediaminetetraacetic acid). TBARS release was time-independent but significantly higher when LCn-3 fatty acids were fed to rats in either the uninduced or induced system. The study demonstrated that n-3 PUFA diets can influence vitamin E status of rats even in short-term experiments and can change the susceptibility of the heart to in vitro lipid peroxidation.

Effect of dietary supplementation with very-long-chain n-3 fatty acids in patients with psoriasis

BACKGROUND

In several studies dietary fish oil has been found to have beneficial effect on psoriasis, but the results are contradictory and based mainly on open studies or studies of small numbers of patients.

METHODS

In a four-month double-blind, multicenter trial, we randomly assigned 145 patients with moderate-to-severe psoriasis to receive in their diet either highly purified ethyl esters of n-3 fatty acids ("fish oil"; 6 g of oil per day, containing 5 g of eicosapentaenoic and docosahexaenoic acid) or an isoenergetic amount of corn oil containing mainly n-6 fatty acids. All the patients were advised to reduce their intake of saturated fatty acids. A 48-hour dietary recall was performed, and the fatty-acid pattern in the serum phospholipids was monitored in a subgroup of patients.

RESULTS

In the fish-oil group, n-3 fatty acids were increased in serum phospholipids (P < 0.001), the ratio of arachidonic acid to eicosapentaenoic acid decreased (P < 0.001), and the level of n-6 fatty acids decreased (P < 0.001). In the corn-oil group, only docosahexaenoic acid increased significantly (P < 0.05). The ratio of polyunsaturated to saturated fatty acids increased in both groups. Plasma concentrations of triacylglycerol decreased from base line in the fish-oil group (P < 0.05). The score on the Psoriasis Area and Severity Index, as evaluated by the physicians, did not change significantly during the trial in either group. This was also true of a total subjective score reported by the patients, but a selected area of skin in the corn-oil group showed a significant reduction in the clinical signs (P < 0.05). Scaling was reduced from base line in both groups (P < 0.01). The fish-oil group had less cellular infiltration (P < 0.01), and the corn-oil group had improvement in desquamation and redness (P < 0.05). There was no significant difference in clinical manifestations between the groups. Among the patients in the fish-oil group, an increase in the concentration of n-3 fatty acids in serum phospholipids was not accompanied by clinical improvement, whereas in the corn-oil group there was a significant correlation between clinical improvement and an increase in eicosapentaenoic acid and total n-3 fatty acids.

CONCLUSIONS

Dietary supplementation with very-long-chain n-3 fatty acids was no better than corn-oil supplementation in treating psoriasis. Clinical improvement was not correlated with an increase in the concentration of n-3 fatty acids in serum phospholipids among the patients in the fish-oil group, whereas there was a significant correlation between clinical improvement and an increase in eicosapentaenoic acid and total n-3 fatty acids in the corn-oil group.

Comparison of supplementation of RRR-alpha-tocopherol and racemic alpha-tocopherol in humans. Effects on lipid levels and lipoprotein susceptibility to oxidation

It has been suggested that alpha-tocopherol, a safe and effective antioxidant, be used in clinical trials to evaluate the ability of antioxidant therapy to inhibit atherosclerosis. Recent reports, however, have raised the possibility that there may be greater enrichment of plasma low density lipoprotein (LDL) in alpha-tocopherol resulting from the use of the naturally occurring RRR-alpha-tocopherol isomer compared with the other isomers present in the synthetic racemic form of alpha-tocopherol. Therefore, we fed equal dosages (1,600 mg/day) of the two forms of vitamin E to 16 men and women for 8 weeks and compared the effects of this supplementation on the susceptibility of isolated lipoproteins to oxidation. Neither form of vitamin E had appreciable effects on lipid or lipoprotein levels. alpha-Tocopherol levels in LDL increased at a similar rate in both groups and were nearly twofold higher than baseline levels by the end of the study. The susceptibility of LDL to oxidation was measured by formation of conjugated dienes, lipid peroxides, and thiobarbituric acid-reactive substances, as well as by macrophage degradation of LDL exposed to oxidizing conditions in vitro. The susceptibility of LDL to oxidation was decreased in both vitamin E groups compared with the baseline value, and this reduction occurred to a similar extent in both vitamin E-supplemented groups. alpha-Tocopherol levels in LDL also strongly correlated with all measures of LDL oxidation. This study demonstrates that, at this dosage, supplementation with either the natural or synthetic form of alpha-tocopherol provided equal antioxidant protection to LDL.

Increased ethane exhalation, an in vivo index of lipid peroxidation, in alcohol-abusers

Ethane exhalation was measured in 42 control subjects, 52 patients with various non-alcoholic liver diseases, and 89 alcohol abusers who had been admitted to hospital for alcohol withdrawal and assessment of liver disease (six with normal liver tests, 10 with steatosis with or without fibrosis, six with alcoholic hepatitis, 29 with cirrhosis, 34 with both cirrhosis and alcoholic hepatitis, and four with both cirrhosis and a hepatocellular carcinoma). Ethane exhalation was similar in control subjects and in patients with non-alcoholic liver diseases, but was five times higher in alcohol abusers. Ethane exhalation in alcohol abusers was significantly, but very weakly, correlated with the daily ethanol intake before hospital admission, and the histological score for steatosis, but not with the inflammation or alcoholic hepatitis scores. Ethane exhalation was inversely correlated with the duration of abstinence before the test. In nine alcoholic patients, the exhalation of ethane was measured repeatedly, and showed slow improvement during abstinence. Ethane exhalation was significantly but weakly correlated with the Pugh's score in patients with alcoholic cirrhosis. It is concluded that the mean ethane exhalation is increased in alcohol abusers. One of the possible mechanisms may be the presence of oxidizable fat in the liver. The weak correlation with the Pugh's score is consistent with the contribution of many other factors in the progression to severe liver disease.

Effect of supplementing periparturient cows with vitamin E on distribution of alpha-tocopherol in blood

Holstein cows were fed 0 or 1000 IU/d of supplemental vitamin E during the dry period and injected with placebo or 3000 IU of vitamin E at 10 and 5 d prior to anticipated calving. Blood was collected at various times, starting at 60 d prepartum (dry off) and concluding 30 d postpartum, and separated into plasma, red blood cells, and neutrophils. Oral supplementation increased concentrations of alpha-tocopherol in plasma and red blood cells on 10 d, but not on 5 d prepartum. Injection of vitamin E increased alpha-tocopherol in plasma, red blood cells, and neutrophils at d 5 prior to and on the day of parturition. Concentrations of alpha-tocopherol and cholesterol in plasma were correlated, and both were at their nadir at parturition. Concentrations of alpha-tocopherol in plasma and red blood cells were correlated, but the correlation increased when plasma alpha-tocopherol was expressed per unit of cholesterol. alpha-Tocopherol in plasma and neutrophils had a low correlation. Injection of alpha-tocopherol increased its concentration in plasma, red blood cells, and neutrophils during the periparturient period. Concentration of alpha-tocopherol in plasma of periparturient cows may be limited by its low lipid content, and transport mechanisms for alpha-tocopherol may differ between red blood cells and neutrophils.

Vitamin E dietary supplementation protects against carbon tetrachloride-induced chronic liver damage and cirrhosis

Previous studies have shown that alpha-tocopherol (vitamin E) pretreatment of experimental animals can protect against acute liver necrosis induced by carbon tetrachloride. In this study we investigated whether the increase of vitamin E liver content by dietary supplementation influences chronic liver damage and cirrhosis induced by carbon tetrachloride in the rat. Our data indicate that vitamin E supplementation did not interfere with the growth rate of the animals and increased about threefold the liver's content of the vitamin. Vitamin E supplementation significantly reduced oxidative liver damage, but it was not effective in protecting against development of fatty liver and did not interfere with metabolic activation of carbon tetrachloride. Moreover, vitamin E-fed animals showed incomplete but significant prevention of liver necrosis and cirrhosis induced by carbon tetrachloride. This has been shown by means of histological examination, analysis of serum parameters and biochemical evaluation of collagen content. These results show that an increased liver content of vitamin E can afford a significant degree of protection against carbon tetrachloride-induced chronic liver damage and cirrhosis.