Ketogenic Diet Increases Glutathione Peroxidase Activity in Rat Hippocampus

Ketogenic diets have been used in the treatment of refractory childhood epilepsy for almost 80 years; however, we know little about the underlying biochemical basis of their action. In this study, we evaluate oxidative stress in different brain regions from Wistar rats fed a ketogenic diet. Cerebral cortex appears to have not been affected by this diet, and cerebellum presented a decrease in antioxidant capacity measured by a luminol oxidation assay without changes in antioxidant enzyme activities—glutathione peroxidase, catalase, and superoxide dismutase. In the hippocampus, however, we observed an increase in antioxidant activity accompanied by an increase of glutathione peroxidase (about 4 times) and no changes in lipoperoxidation levels. We suggest that the higher activity of this enzyme induced by ketogenic diet in hippocampus might contribute to protect this structure from neurodegenerative sequelae of convulsive disorders.     

Selenium modifies glutathione peroxidase activity and glutathione concentration in mice exposed to ozone-provoked oxidative stress

The aim of this study was to show the direct effect of selenium on glutathione peroxidase (GSH-Px) activity and GSH/GSSG concentrations in 3- and 6-month-old mice. An ozone-oxygen mixture was used to provoke an oxygen stress. To measure the Se-effect mice were gavaged with sodium selenite. GSH-Px activity and total glutathione concentrations were determined in serum and in the postnuclear fraction of liver and lungs. Additionally glutathione concentrations were determined in whole blood. Both ozone and selenium, administered separately, reduced GSH-Px activity in lungs of 6-month-old animals, while in young mice an opposite effect of Se was observed. Ozone administered jointly with Se did not influence GSH-Px activity in 6-month-old mice, while in young, 3-month-old mice, a stimulatory effect in lungs was observed. There were no significant changes in GSH-Px activity in the liver of 6-month-old mice, but the stimulatory effect occurred in young mice treated with Se and Se & ozone jointly. In young mice, ozone (also ozone with Se) augmented glutathione concentrations. The response to ozone and selenium strictly depended on age and the antagonism between selenium and ozone was observed only in a few cases.     

谷胱甘肽/谷胱甘肽过氧化物酶系统在微生物细胞抗氧胁迫系统中的作用

谷胱甘肽(GSH)/谷胱甘肽过氧化物酶(GPx)系统在不同微生物细胞抵抗氧胁迫中的生理功能不尽相同。该系统在真核模式微生物酿酒酵母中是必需存在的,在维持胞内氧化还原平衡和抵抗氧胁迫中发挥主要作用。然而,在原核微生物中,该系统只是条件性的,即部分胞内存在谷胱甘肽还原酶和GPx的原核微生物,如流感嗜血杆菌和乳酸乳球菌,可通过从胞外吸收GSH,形成条件性的依赖于GSH的GPx系统,参与抵抗氧胁迫。     

Serum antioxidant enzyme activity in Parkinson's disease

Summary The activities of superoxide dismutase (SOD; EC 1.15.1.1) and glutathione peroxidase (GSHP_x; EC 1.11.1.9.), the enzymes that metabolize the superoxide anion and hydrogen peroxide, respectively, were measured in serum from healthy subjects and patients with Parkinson's disease (PD). The activities of SOD and GSHP_x in patients with PD were higher than those in normal healthy individuals. These results suggest that the increased activities of these enzymes could be due to oxidative stress in the initial stages of this disease.     

谷胱甘肽促进液体发酵体系中蛹虫草合成虫草素

虫草素是药用真菌蛹虫草Cordyceps militaris的主要活性成分,具有抗癌、抗肿瘤、抗病毒等多种生理活性.研究表明,氧化应激参与丝状真菌的次级代谢调控,然而在蛹虫草虫草素代谢中尚未见报道.本研究以蛹虫草深层液体发酵体系为研究对象,添加谷胱甘肽(glutathione,GSH)调节细胞氧化还原状态,考察其对虫草...     

Effect of acute vs chronic H2O2-induced oxidative stress on antioxidant enzyme activities

H₂O₂ can freely crosses membranes and in the presence of Fe²⁺ (or Cu⁺) it is prone to participate in Fenton reaction. This study evaluated the concentration and time-dependent effects of H₂O₂-induced oxidative stress on MnSOD, Se:GPx and catalase and on aconitase. Acute and chronic H₂O₂ treatments were able to induce oxidative stress in HeLa cells as they significantly decreased aconitase activity and also caused a very significant decrease on antioxidant enzyme activities. The inhibition of enzyme activities was time- and concentration-dependent. Chronic treatment with 5 µM H₂O₂/h after 24 h was able to decrease all enzyme activities almost at the same level as the acute treatment. Acute and chronic treatments on antioxidant enzyme activities were prevented by cell treatment with ascorbic acid or N-acetylcysteine. These results indicate that antioxidant enzymes can also be affected by the same ROS they produce or neutralize if the time of exposure is long enough.     

Reactive oxygen intermediates and glutathione regulate the expression of cytosolic ascorbate peroxidase during iron-mediated oxidative stress in bean

Excess of free iron is thought to harm plant cells by enhancing the intracellular production of reactive oxygen intermediates (ROI). Cytosolic ascorbate peroxidase (cAPX) is an iron-containing, ROI-detoxifying enzyme induced in response to iron overload or oxidative stress. We studied the expression of cAPX in leaves of de-rooted bean plants in response to iron overload. cAPX expression, i.e., mRNA and protein, was rapidly induced in response to iron overload. This induction correlated with the increase in iron content in leaves and occurred in the light as well as in the dark. Reduced glutathione (GSH), which plays an important role in activating the ROI signal transduction pathway as well as in ROI detoxification, was found to enhance the induction of APX mRNA by iron. To determine whether cAPX induction during iron overload was due to an increase in the amount of free iron, which serves as a co-factor for cAPX synthesis, or due to iron-mediated increase in ROI production, we tested the expression of APX in leaves under low oxygen pressure. This treatment, which suppresses the formation of ROI, completely abolished the induction of cAPX mRNA during iron overload, without affecting the rate of iron uptake by plants. Taken together, our results suggest that high intracellular levels of free iron in plants lead to the enhanced production of ROI, which in turn induces the expression of cAPX, possibly using GSH as an intermediate signal. We further show, using cAPX-antisense transgenic plants, that cAPX expression is essential to prevent iron-mediated tissue damage in tobacco.     

Probucol treatment reverses antioxidant and functional deficit in diabetic cardiomyopathy

Earlier we reported that probucol treatment subsequent to the induction of diabetes can prevent diabetes-associated changes in myocardial antioxidants as well as function at 8 weeks. In this study, we examined the efficacy of probucol in the reversal of diabetes induced myocardial changes. Rats were made diabetic with a single injection of streptozotocin (65 mg/kg, i.v.). After 4 weeks of induction of diabetes, a group of animals was treated on alternate days with probucol (10 mg/kg i.p.), a known lipid lowering agent with antioxidant properties. At 8 weeks, there was a significant drop in the left ventricle (LVSP) and aortic systolic pressures (ASP) in the diabetic group. Hearts from these animals showed an increase in the thiobarbituric acid reacting substances (TBARS), indicating increased lipid peroxidation. This was accompanied by a decrease in the myocardial antioxidant enzymes activities, superoxide dismutase (SOD) and glutathione peroxidase (GSHPx). Myocardial catalase activity in the diabetic group was higher. In the diabetic + probucol group both LVSP and ASP showed significant recovery. This was also accompanied by an improvement in SOD and GSHPx activities and there was further increase in the catalase activity. Levels of the TBARS were decreased in this group. These data provide evidence that diabetic cardiomyopathy is associated with an antioxidant deficit which can be reversed with probucol treatment. Improved cardiac function with probucol may be due to the recovery of antioxidants in the heart.     

A comparative study on effect of dietary selenium and vitamin E on some antioxidant enzyme activities of liver and brain tissues

Since selenium and vitamin E have been increasingly recognized as an essential element in biology and medicine, current research activities in the field of human medicine and nutrition are devoted to the possibilities of using these antioxidants for the prevention or treatment of many diseases. The present study was aimed at investigating and comparing the effects of dietary antioxidants on glutathione reductase and glutathione peroxidase activities as well as free and protein-bound sulfhydryl contents of rat liver and brain tissues. For 12–14 wk, both sex of weanling rats were fed a standardized selenium-deficient and vitamin E-deficient diet, a selenium-excess diet, or a control diet. It is observed that glutathione reductase and glutathione peroxidase activities of both tissues of the rats fed with a selenium-deficient or excess diet were significantly lower than the values of the control group. It is also shown that free and bound sulfhydryl concentrations of these tissues of both experimental groups were significantly lower than the control group. The percentage of glutathione reductase and glutathione peroxidase activities of the deficient group with respect to the control were 50% and 47% in liver and 66% and 61% in the brain, respectively; while these values in excess group were 51% and 69% in liver and 55% and 80% in brain, respectively. Free sulfhydryl contents of the tissues in both experimental groups showed a parallel decrease. Furthermore, the decrease in protein-bound sulfhydryl values of brain tissues were more pronounced than the values found for liver. It seems that not only liver but also the brain is an important target organ to the alteration in antioxidant system through either a deficiency of both selenium and vitamin E or an excess of selenium alone in the diet.     

Ozone tolerance and antioxidant enzyme activity in soybean cultivars

The current study confirmed earlier conclusions regarding differential ozone (O₃) tolerances of two soybean cultivars, Essex and Forrest, and evaluated antioxidant enzyme activities of these two varieties based on their performance under environmentally relevant, elevated O₃ conditions. The experiment was conducted in open-top chambers in the field during the 1994 and 1995 growing seasons. Exposure of plants to moderately high O₃ levels (62.9 nl l⁻¹ air, 2-year seasonal average) caused chlorophyll loss and increased membrane permeability when compared to control plants grown in charcoal filtered air (24.2 nl l⁻¹ air). The other effects of O₃ treatment were decrease in seed yield, loss of total sulfhydryl groups, reduction of soluble protein content, and increase in guaiacol peroxidase activity in leaves of both cultivars. The O₃-induced increase in guaiacol peroxidase activity was much smaller in cv. Essex leaflets. Cv. Essex had less leaf oxidative damage and smaller reduction in seed yield than cv. Forrest under elevated O₃ conditions. During ozonation, mature leaflets of the more O₃ tolerant cv. Essex had higher levels of glutathione reductase (30%), ascorbate peroxidase (13%), and superoxide dismutase (45%) activity than did mature leaflets of cv. Forrest. Cu,Zn-superoxide dismutase, which represented 95% of total superoxide dismutase activity in the two cultivars, appeared to be increased by O₃ exposure in the leaflets of O₃ tolerant cv. Essex but not in those of cv. Forrest. Cytosolic ascorbate peroxidase activity was also higher in leaflets of cv. Essex than in cv. Forrest regardless of O₃ level. Stromal ascorbate peroxidase and Mn-superoxide dismutase activity did not appear to be involved in the O₃ tolerance of the two soybean cultivars. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lymphocyte glutathione peroxidase activity during exacerbations in multiple sclerosis

Glutathione peroxidase, one of the major antioxidants in the human brain, has been found to have decreased activity in patients suffering from multiple sclerosis (MS). This study compares the activity of lymphocyte glutathione peroxidase (L-GSH-px) in MS patients suffering from acute relapses with clinically stable MS patients and with control patients referred with nondemyelinating neurological diseases. All three groups showed an increase of mean enzymatic activity (MEA) during the observation period. The highest MEA in this study was observed in the MS groups. However, there were no significant differences in the L-GSH-px activity in the three groups. These results are not in accordance with previous investigations, and the need for further research in this field is emphasized.     

Selenium depletion in patients on home parenteral nutrition

Severe selenium (Se) depletion was found in nine patients receiving long-term home parenteral nutrition because of short bowel syndrome. Plasma Se ranged from 0–0.51 (median 0.21 μmol/L) and erythrocyte Se ranged from 0.7–2.6 (median 1.8 μmol/gHgb), which was significantly lower than in the controls. Glutathione peroxidase (GSHPx) in plasma and erythrocytes was also decreased. After bolus injections with 200 μg Se/d in the form of sodium selenite for 4 mo, followed by 100 μg/d for 8 mo, plasma Se increased to values slightly but significantly higher than in the controls. Erythrocyte Se reached normal levels in most of the patients after 4 mo substitution, but it remained lower than in the controls. Following Se supplementation, plasma and erythrocyte GSHPx did not differ between patients and controls. These data suggest that all patients receiving long-term parenteral nutrition because of short bowel syndrome should receive at least 100 μg sodium selenite/d when given as bolus injections to avoid Se depletion.