Dehydroepiandrosterone and a beta-agonist, energy transducers, alter antioxidant enzyme systems: influence of chronic training and acute exercise in rats

The effect of DHEA treatment on the oxidative stress and myocardial fibrosis induced by Keshan disease pathogenic factors

Oxidative stress induced by the combined deficiencies of selenium (Se) and vitamin E (VE) is considered the basic factor of Keshan disease (KD). Dehydroepiandrosterone (DHEA) is a naturally occurring adrenal androgen that has antioxidant properties. We found that a Se- and VE-deficient diet induced KD lesions in rats, while 0.05, 0.125, and 0.25 g/kg DHEA caused a concentration-dependent inhibition in the development of oxidative stress and extracellular matrix (ECM) deposition in the left ventricles of the Se- and VE-deficient rats. In addition, DHEA counteracted activation of NFκB as well as the subsequent increase in TGFβ-1 and CTGF induced by the Se- and VE-deficient diet. These studies suggested that DHEA prevents oxidative stress and might be useful in treating Se and VE deficiency-related KD. These effects were based on its antioxidant effects and ECM deposition inhibition in left ventricles.

Protection of Panax ginseng in injured muscles after eccentric exercise

Panax ginseng C.A. Meyer, the root of an Araliaceae plant has been shown to possess various biological effects. Ginseng treatment (100 mg kg(-1)) protected muscles from eccentric exercise injuries. It was effective in preserving mitochondrial membrane integrity and reduced nitrate concentration in vastus and rectus (46% and 26%, respectively). It also reduced carbonyl contents by approximately 27% in all the muscles studied.

Antioxidant effects of dehydroepiandrosterone and 7alpha-hydroxy-dehydroepiandrosterone in the rat colon, intestine and liver

This study examined in healthy male Wistar rats the in vivo antioxidant effect of dehydroepiandrosterone (DHEA) and 7alpha-hydroxy-DHEA administered by intraperitoneal injections (50 mg/kg body weight) for 2 or 7 days. Markers of oxidative damage to lipids (thiobarbituric acid-reacting substances, TBARS) and to proteins (protein carbonyls) were assessed in colon, small intestine, and liver homogenates. DHEA and 7alpha-hydroxy-DHEA caused a decrease in body weight. DHEA treatment significantly increased liver, colon, and small intestine cell weights. After 7 days, DHEA exerted an antioxidant effect in all organs studied. In the colon, oxidative damage protection was accompanied by a goblet cell proliferation and increase in acidic mucus production. After 2 days, the antioxidant effect of 7alpha-hydroxy-DHEA was mainly observed in the liver. Nonprotein sulfhydryl groups (mostly glutathione levels) were altered by DHEA in the liver whereas they remained unchanged after 7alpha-hydroxy-DHEA treatment. The results indicate that in healthy animals, DHEA exerts a protective effect, particularly in the colon, by reducing the tissue susceptibility to oxidation of both lipids and proteins. This effect was not limited to a specific tissue, whereas the metabolite 7alpha-hydroxy-DHEA exerted its antioxidant effect towards the two markers of oxidative damage earlier than DHEA, and mainly in the liver.

Antioxidant enzyme expression in health and disease: effects of exercise and hypertension

Antioxidant enzymes (superoxide dismutases, catalase and glutathione peroxidase) are components of an organism's mechanisms for combating oxidative stress which is generated in normal metabolism and which may also be a reaction in response to external stimuli. This review identifies the general significance of antioxidant enzymes in health and disease, and some of the diseases that are now believed to have oxidative stress as a component. A discussion is then presented of the molecular mechanisms by which antioxidant enzyme expression is controlled at the transcriptional and post-transcriptional levels. The final sections of the review highlight the effects of exercise and hypertension on antioxidant enzyme expression in a number of different tissues, and the possibilities for future studies in these areas are discussed.

Protective effects of Panax ginseng on muscle injury and inflammation after eccentric exercise

Eccentric muscle contraction causes fibre injury associated with disruption of the myofibrillar cytoskeleton. The medicinal plant Panax ginseng C.A. Meyer, known for its therapeutic properties, was studied to explore its protective effects after eccentric contraction. A crude extract and a standardised extract (G115) of different saponin compositions were tested as to their efficacy in reducing lipid peroxidation, inflammation and release of myocellular proteins after the realisation of an eccentric contraction protocol on a rat treadmill. Plasma creatine kinase (CK) levels were significantly reduced by approximately 25% after ingestion of both extracts of ginseng. Both extracts reduced lipid peroxidation by approximately 15% as measured by malondialdehyde levels. beta-Glucuronidase concentrations and glucose-6-phosphate dehydrogenase (G6PDH) levels, which can be considered markers of inflammation, were also significantly reduced. The values of beta-glucuronidase were increased from 35.9+/-1.5 to 128.4+/-8.1 in vastus and to 131.1+/-12.1 U x g(-1) in rectus, the protection due to ginseng administration being approximately 40% in both muscles. Both extracts appeared to be equally effective in reducing injuries and inflammation caused by eccentric muscle contractions.

In vitro effects of different steroid hormones on superoxide anion production of human neutrophil granulocytes

Neutrophil granulocytes play an important role in atherogenesis also through their free radical generation. According to recent studies, a point of action by which estrogens can provide protection against atherosclerosis is their inhibiting effect on superoxide anion production. The aim of our study was to test whether this means a common effect of steroids on superoxide production, or whether various steroid hormones have different action on superoxide generation of human granulocytes. Neutrophils were separated from the blood samples of twelve healthy volunteers. Isolated cells were incubated with different concentrations (10(-9), 10(-8), 10(-7) M) of hydrocortisone, aldosterone, cortexolone, 17-beta-estradiol, progesterone, and testosterone. Superoxide anion production was determined by photometry using the reduction of ferricytochrome-C. Compared to that of control cells neutrophils incubated with 17-beta-estradiol, progesterone, testosterone and hydrocortisone showed significantly reduced superoxide production. No significant alteration of superoxide anion production was found after the incubation of cells with aldosterone and cortexolone. It is concluded that similarly to estradiol other sex steroids and cortisol can inhibit the free radical production of human granulocytes, but mineralocorticoid aldosterone and Reichstein's substance S do not show such activity. Our results provide new evidence supporting the theory that certain types of steroid hormones have antioxidant capacity. This may give further reasons for investigating the molecular background of the existence or absence of this property and thus might lead to the development of new free radical scavengers.

Dehydroepiandrosterone protects tissues of streptozotocin-treated rats against oxidative stress

Chronic hyperglycemia in diabetes determines the overproduction of free radicals, and evidence is increasing that these contribute to the development of diabetic complications. It has recently been reported that dehydroepiandrosterone possesses antioxidant properties; this study evaluates whether, administered daily for three weeks per os, it may provide antioxidant protection in tissues of rats with streptozotocin-induced diabetes. Lipid peroxidation was evaluated on liver, brain and kidney homogenates from diabetic animals, measuring both steady-state concentrations of thiobarbituric acid reactive substances and fluorescent chromolipids. Hyperglycemic rats had higher thiobarbituric acid reactive substances formation and fluorescent chromolipids levels than controls. Dehydroepiandrosterone-treatment (4 mg/day for 3 weeks) protected tissues against lipid peroxidation: liver, kidney and brain homogenates from dehydroepiandrosterone-treated animals showed a significant decrease of both thiobarbituric acid reactive substances and fluorescent chromolipids formation. The effect of dehydroepiandrosterone on the cellular antioxidant defenses was also investigated, as impaired antioxidant enzyme activities were considered proof of oxygen-dependent toxicity. In kidney and liver homogenates, dehydroepiandrosterone treatment restored to near-control values the cytosolic level of reduced glutathione, as well as the enzymatic activities of superoxide-dismutase, glutathione-peroxidase, catalase. In the brain, only an increase of catalase activity was evident (p < .05), which reverted with dehydroepiandrosterone treatment. The results demonstrate that DHEA treatment clearly reduces oxidative stress products in the tissues of streptozotocin-treated rats.

Effects of administration of the standardized Panax ginseng extract G115 on hepatic antioxidant function after exhaustive exercise

The effect of prolonged treatment with the standardized Panax ginseng extract G115 on the antioxidant capacity of the liver was investigated. For this purpose, rats that had received G115 orally at different doses for 3 months and untreated control rats were subjected to exhaustive exercise on a treadmill. A bell-shaped dose response on running time was obtained. The results showed that the administration of G115 significantly increases the hepatic glutathione peroxidase activity (GPX) and the reduced glutathione (GSH) levels in the liver, with a dose-dependent reduction of the thiobarbituric acid reactant substances (TBARS). After the exercise, there is reduced hepatic lipid peroxidation, as evidenced by the TBARS levels in both the controls and the treated animals. The GPX (glutathione peroxidase) and SOD (superoxide dismutase) activity are also significantly increased in the groups receiving G115, compared with the controls. The hepatic transaminase levels, ALT (Alanine-amino-transferase) and AST (Aspartate-amino-transferase), in the recuperation phase 48 h after the exercise, indicate a clear hepatoprotective effect related to the administration of the standardized Panax ginseng extract G115. At hepatic level, G115 increases the antioxidant capacity, with a marked reduction of the effects of the oxidative stress induced by the exhaustive exercise.

Vitamin E prevents induction of carbonyl group formation in microsomal protein by dehydroepiandrosterone

The effect of dehydroepiandrosterone (DHEA), a free radical- and lipid peroxide-inducing agent, and of vitamin E (alpha-tocopherol), a free radical chain terminator, on protein carbonyl group formation was investigated in rat liver microsomes. Administration of alpha-tocopherol at 25-50 mg/kg diet for seven days resulted in high Fe(2+)-NADPH-ADP-dependent production of protein carbonyl groups in liver microsomal protein isolated from otherwise untreated rats. However, alpha-tocopherol administered at > 100 mg/kg diet caused a decrease in the production of protein carbonyl groups. In animals simultaneously receiving alpha-tocopherol at 50 mg/kg diet and DHEA at 500 mg/kg diet, no additional stimulatory effect of the steroid on microsomal protein carbonyl group production was observed. Protein carbonyl group production was significantly enhanced by DHEA in rats given a diet containing 400 mg alpha-tocopherol/kg diet. Microsomes isolated from rats fed 1,000 mg alpha-tocopherol/kg diet with DHEA (500 mg/kg diet) and without DHEA produced small but similar amounts of protein carbonyl groups. These results provide evidence that vitamin E is an important protective agent against DHEA-mediated oxidative damage of intracellular components, including proteins.

Lower lipid peroxide levels in practitioners of the Transcendental Meditation program

OBJECTIVE

Oxidative stress or free radical activity may contribute to the pathophysiology of atherosclerosis and other chronic diseases associated with aging. Because psychosocial stress has been shown to increase oxidative stress, we conducted an exploratory study to investigate the effects of stress reduction with the Transcendental Meditation program on serum lipid peroxide levels in elderly subjects.

METHOD

Forty-one normally healthy subjects (aged 56 to 74 years, average 67 years) were recruited from the same Midwest city. Eighteen were long-term practitioners of the TM program (average 16.5 years). Twenty-three controls were not practicing a formal stress management technique. Venous blood samples were analyzed for lipid peroxides by the TBARS assay. A dietary questionnaire was used to assess fat intake, red meat consumption, antioxidant vitamin supplementation, and smoking. Differences between groups and subgroups were analyzed by t test, and correlations.

RESULTS

Significantly lower serum levels of lipid peroxides were found in the TM practitioners compared with controls (-15%, p = .026). No significant differences were found between groups on smoking, fat intake, or vitamin supplementation. TM practitioners also had lower red meat consumption but matched subgroup analysis and partial correlations did not confirm a relationship between red meat intake and lipid peroxide levels.

CONCLUSIONS

These preliminary findings suggest that lower serum lipid peroxide levels may be associated with stress reduction using the Transcendental Meditation technique. Prospective controlled trials are needed to confirm that this effect is because of TM practice rather than other lifestyle factors, such as diet.

Dietary alpha-tocopherol prevents dehydroepiandrosterone-induced lipid peroxidation in rat liver microsomes and mitochondria

Dehydroepiandrosterone (DHEA), an adrenal steroid, causes lipid peroxidation in rat liver microsomes and mitochondria and induces hepatocarcinogenesis. It was investigated whether alpha-tocopherol, a naturally occurring free radical chain terminator, could decrease lipid peroxidation. When DHEA-free diet supplemented with increasing concentrations of alpha-tocopherol (25, 50, 100, 200, 400 and 1000 mg/kg diet) was fed to rats for 7 days, a marked lipid peroxidation (measured as thiobarbituric acid reactive substances formation) was observed at concentrations 25 and 50 mg/kg in liver microsomes and mitochondria isolated from these animals. Lipid peroxidation was significantly reduced at concentrations > or = 100 mg/kg. When DHEA (500 mg/kg diet) was fed to rats simultaneously with increasing concentrations of alpha-tocopherol, strong lipid peroxidation was observed at alpha-tocopherol concentrations < or = 200 mg/kg diet. However, microsomes and mitochondria isolated from livers of rats fed alpha-tocopherol at doses of 400 and 1000 mg/kg diet produced only negligible amounts of thiobarbituric acid reactive substances. The data show that high concentrations of alpha-tocopherol in the diet decrease DHEA-induced microsomal and mitochondrial lipid peroxidation. Our results support the concept that alpha-tocopherol can protect against DHEA-induced lipid peroxidation and consequently against steroid-induced liver cell damage and, perhaps, also tumour development.

Protective effect of dehydroepiandrosterone against copper-induced lipid peroxidation in the rat

This study investigates the effectiveness and multitargeted activity of dehydroepiandrosterone (DHEA) as antioxidant in vivo. A single dose of DHEA was given IP to male rats. Liver and brain microsomes, and plasma low density lipoprotein (LDL), were isolated from rats sacrificed 17 h later. Liver and brain microsomes were challenged with CuSO(4) and, as index of lipid peroxidation, the production of thiobarbituric acid reactive substances (TBARS) was measaured. Also, plasma low-density lipoprotein (LDL) were challenged with copper and the time course of lipid peroxidation was evaluated following the formation of conjugated dienes. The onset of TBARS generation induced by copper was marked delayed in both liver and brain microsomes from DHEA-treated animals. Also, the resistance of LDL to oxidation, expressed by the duration of the lag-phase of the kinetic curve, was significantly enhanced in DHEA-treated rats. Results indicate that in vivo DHEA supplementation makes subcellular fractions isolated from different tissues and plasma constituents (LDL) more resistant to lipid peroxidation triggered by copper. The antioxidant effect on plasma LDL might be of special relevance to the proposed antiatherogenic activity of DHEA. Moreover, multitargeted antioxidant activity of DHEA might protect tissues from oxygen radicals damage.

Dehydroepiandrosterone-induced lipid peroxidation in rat liver mitochondria

Administration of dehydroepiandrosterone (DHEA), a steroid hormone of the adrenal cortex which acts as a peroxisome proliferator and hepatocarcinogen in the rat, caused an increase in NADPH-dependent lipid peroxidation in mitochondria isolated from the liver, kidney and heart, but not from the brain. The effect of DHEA on rat liver mitochondrial lipid peroxidation became discernible after feeding steroid-containing diet (0.6% w/w) for 3 days, and reached maximal levels between 1 and 2 weeks. DHEA in the concentration range 0.001-0.02% did not significantly increase lipid peroxidation compared to the control. Lipid peroxidation was significantly enhanced in animals given a diet containing > or = 0.05% DHEA. The addition of DHEA in the concentration range 0.1-100 microM to mitochondria isolated from control rats had no effect on lipid peroxidation. It seems, therefore, that the steroid effect is mediated by an intracellular process. Our data indicate that induction of mitochondrial membrane lipid peroxidation is an early effect of DHEA administration at pharmacological doses.

Review of progress in sterol oxidations: 1987-1995

Material dealing with the chemistry, biochemistry, and biological activities of oxysterols is reviewed for the period 1987-1995. Particular attention is paid to the presence of oxysterols in tissues and foods and to their physiological relevance.

Increase of lipid peroxidation in rat liver microsomes by dehydroepiandrosterone feeding

Oral administration of the adrenal steroid dehydroepiandrosterone (DHEA), a peroxisome proliferator and hepatocarcinogen in the rat, caused an increase in NADPH-dependent lipid peroxidation in microsomes isolated from rat liver and kidney cortex, but not from brain. The increase of liver microsomal lipid peroxidation was greater in male than in female rats. the effect of DHEA on lipid peroxidation became discernible after feeding steroid-containing diet (0.6%) to male and female rats for 2 and 3 days and reached maximal levels at 1 and 2 weeks, respectively. The increase of microsomal lipid peroxidation reached a plateau stimulation at 0.05% in the diet. The addition of DHEA in the concentration range 0.1-100 microM to microsomes isolated from control rats had no effect on lipid peroxidation. Furthermore, a significant increase of the endogenous concentration of thiobarbituric acid reactive substances was found in microsomes after DHEA-administration at 0.05% in the diet. These results provide in vivo evidence that DHEA can cause lipid peroxidation in rat liver. Administration of DHEA at 0.6% in the diet for 7 consecutive days also significantly enhanced NADH- and ascorbate-dependent lipid peroxidation in liver microsomes. The DHEA-stimulated rat liver microsomal lipid peroxidation was completely inhibited by EDTA but not by superoxide dismutase, catalase or mannitol applied as OH-radical scavenger. The findings indicate that membrane lipid peroxidation is an early effect of DHEA, and that this process may be involved in the steroid-induced carcinogenesis in rats.

Antioxidant enzyme activities and lipid peroxidation levels in exercised and hypertensive rat tissues

Previous studies have shown that exercise-induced changes in muscle antioxidant status occur shortly after exercise. The present studies were designed to determine if longer-term exercise-related changes in antioxidant enzyme activities in both normotensive (WKY) and hypertensive rats (SHR) occurred, and if these changes were related to the levels of lipid peroxidation. WKY and SHR rats were exercised over a 10-week period using a progressive treadmill regimen. After a 1-week detraining period, the animals were euthanized and measurements of tissue antioxidant enzyme activities and lipid peroxide levels were determined in both exercised and cage-sedentary groups. Decreases in antioxidant activities (particularly glutathione peroxidase and catalase) in liver, kidney, skeletal and cardiac were associated with exercise training in both WKy and SHR rats (e.g. left ventricular glutathione peroxidase specific activity in WKY rats was decreased from 234 +/- 25 [SD, n = 12] to 187 +/- 17 [SD, n = 11] units/mg protein). Elevations in activities of antioxidant enzymes were generally associated with hypertension in these tissues (e.g. left ventricular glutathione peroxidase specific activity in SHR rats was 275 +/- 30 [SD, n = 12] units/mg protein), but changes in activities were more variable than those seen in response to exercise. Exercise-related changes in tissue levels of thiobarbituric acid-reactive substances (an indirect measure of tissue lipid peroxide levels) generally did not correlate with exercise-related antioxidant enzyme activity changes, and hypertension had no effect on these levels except in liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular adaptations of the myocardium to chronic exercise

The heart responds positively to programs of chronic dynamic exercise. Hallmark adaptations of the heart include a training bradycardia, increases in end-diastolic dimension and maximal stroke volume, and a general improvement in ventricular performance and contractile function. Of considerable clinical significance are the general observations that chronic exercise renders the myocardium less susceptible to the deleterious effects of acute ischemic episodes and can effectively prevent and/or reverse many of the cardiac functional deficits that are known to occur in settings of chronic hypertension, advanced age, and myocardial infarction. In the text that follows, information gathered over the last 25 to 30 years has been reviewed in an attempt to identify cellular myocardial adaptations, both known and hypothetical, that are responsible for the observed effects of chronic dynamic exercise on the function and morphology of the heart in both normal and selected pathophysiologic settings. Finally, a variety of unresolved issues regarding the ability of chronic exercise to elicit adaptive cardiocyte responses has been identified. In so doing, it is hoped that creative thought and future work in the area will be stimulated.

Dehydroepiandrosterone pretreatment protects rats against the pro-oxidant and necrogenic effects of carbon tetrachloride

A single intraperitoneal injection of dehydroepiandrosterone (3 beta-hydroxy-5-androsten-17-one, DHEA) 17 hr before carbon tetrachloride (CCl4) poisoning protects rats against liver injury induced by the haloalkane. In liver homogenates, both the increase in malondialdehyde production and the formation of fluorescent lipid peroxidation products are significantly reduced. Also, liver microsomes obtained from DHEA-pretreated rats incubated in vitro with CCl4 are less susceptible to lipid peroxidation than microsomes from normal animals. The release of liver enzymes into the blood is much reduced in DHEA-pretreated rats, confirming a cause-effect relationship between lipid peroxidation and hepatocyte death. Treatment with DHEA inhibits neither glucose-6-phosphate dehydrogenase activity in the cytosol, nor the microsomal mixed function oxidase system (cytochrome P450 content, aminopyrine demethylase and ethoxycoumarin de-ethylase activities). In animals treated with DHEA, the liver content of total glutathione and vitamin E is not modified. These results support the hypothesis that DHEA protects against CCl4-induced liver injury through its own antioxidant activity, rather than by interfering with the metabolism of the toxin or with the tissue level of primary antioxidants.

Early responses of female obese rats to dehydroepiandrosterone treatment

Short-term DHEA treatment elicited an increase in catalase, long-chain fatty acid CoA hydrolase, and peroxisomal beta-oxidation together with a variable increase in mitochondrial respiration. The mechanisms involved with the antiobesity effects of DHEA have yet to be fully resolved.