Se GSH-Px Activity Research Articles

Antibody responses of growing beef cattle fed silage diets with and without selenium supplementation

The relationships between blood Se levels and glutathione peroxidase (GSH-Px) activities and the ability of cattle to produce antibodies in response to antigen challenges with sheep red blood cells (SRBC) and ovalbumin (OA) were examined in a two-phase experiment with yearling beef cattle. There were no treatment effects on weight gains, feed intake or efficiency of feed conversion in either phase. In phase 1, cattle fed the unsupplemented control diet had lower (P ≤ 0.05) blood Se levels and GSH-Px activities by week 8 than cattle fed Se-fertilized forage, but neither was different (P > 0.05) from those of cattle fed Se-enriched yeast or inorganic Se. Antibody titers resulting from injection of SRBC at week 4 of the experiment peaked about 3 wk after injection, then declined. Differences due to Se treatment were small. The same animals were used in phase 2, where half of the animals on each of the four treatments of phase 1 were fed a supplement with Se-enriched yeast and the other half were fed an unsupplemented control. Differences in blood Se levels and GSH-Px activities due to phase-1 treatments persisted throughout phase 2. Differences due to phase-2 treatments were apparent after 9 wk. The cattle were challenged with OA at week 12 and at week 17 with both OA and SRBC. Differences in antibody titer due to Se treatment were small but tended to be higher (P > 0.05) in the Se-supplemented cattle. These results support the suggestion that blood Se levels over 100 μg L−1 are needed to maintain optimum immunocompetence. Key words: Selenium, glutathione peroxidase, immunocompetence, cattle, antibody

Effects of aurothioglucose and dietary Se on glutathione S-transferase activities and glutathione concentrations in chick tissues.

Experiments were conducted to determine whether the increased glutathione S-transferase (GSH-T) activity associated with selenium (Se) deficiency is necessarily related to losses in the activity of Se-dependent glutathione peroxidase (SeGSHpx) in chicks. Nutritional Se status was altered in two ways: by treatment with an antagonist of Se utilization, aurothioglucose (AuTG), and by feeding diets containing excess Se. Chicks given AuTG (10-30 mg AU/kg, sc) had growth rates and hepatic GSH concentrations that were comparable to those of saline-treated controls; however, their plasma GSH levels exceeded those of either Se-deficient (6-fold) or -adequate (3-fold) saline-treated chicks. Hepatic SeGSHpx activities of AuTG-treated chicks were half those of controls under conditions of Se-adequacy; however, this effect was not detected when Se was deficient. Hepatic GSH-TCDNB (assayed with 1-chloro-2,4-dinitrobenzene) activities of AuTG-treated chicks were significantly greater than those of controls when Se was deficient (i.e., when SeGSHpx activity was 12% of the Se-adequate level); however, deprivation of Se did not affect GSH-TCDNB activity in the absence of AuTG. Chicks fed excess Se (6-20 ppm as Na2SeO3) in diets containing either low (2 IU/kg) or adequate (100 IU/kg) VE, showed hepatic GSH-TCDNB activities and GSH concentrations greater than those of Se-adequate (0.2 ppm Se) chicks by 100% and 40%, respectively. That increased hepatic GSH-TCDNB activity can occur because of either AuTG or excess Se status under conditions wherein SeGSHpx activity is not affected indicates that the transferase response is not directly related to changes in the peroxidase.

Effects of dietary selenium and vitamin E on glutathione concentrations and glutathione S-transferase activities in chick liver and plasma

Studies were conducted to determine the effects of the antioxidant nutrients selenium (Se) and vitamin E (VE) on the concentrations of glutathione (GSH) and activities of two GSH-metabolizing enzymes, Se-dependent GSH-peroxidase (SeGSHpx) and GSH S-transferase (GSH-T), in the chick. The hepatic activity of GSH-T, assayed using 1-chloro-2,4-dinitrobenzene as substrate (GSH-T CDNB), was greater in chicks depleted of both Se and VE than in chicks fed adequate levels of either nutrient. This effect was only observed when the Se deficiency was severe enough to result in a very substantial loss of SeGSHpx activity (e.g., 8% of control levels); it was not observed unless chicks were also deficient in VE. Chicks fed the Se-deficient diet supplemented with a low level of VE (2 IU/kg) failed to show hepatic GSH-T CDNB activities greater than controls. Chicks fed the Se-deficient diet had plasma GSH concentrations greater than those of Se-fed chicks, which difference was intensified by concomittant VE deficiency. These results show that GSH metabolism in the chick can be affected by nutritional status with respect to VE as well as Se. It is suggested that the increased hepatic activity of GSH-T CDNB that occurs in nutritional Se- and VE-deficiency may be a response to altered GSH metabolism rather than a compensation for loss of SeGSHpx.

Effect of dietary Se intake on blood Se levels and glutathione peroxidase activities in lambs

Se metabolism in lambs was studied following Se supplementation at different levels. For 3 months, four groups of lambs were fed a basal diet containing 0.082 mg Se/kg DM (A) or the same diet plus a mineral mixture with selenite providing 0.25, 0.41 or 0.58 mg Se/kg DM (B, C and D, respectively). Se concentration in whole blood and glutathione peroxidase (GSH-Px) activity in red cells of Se-treated lambs increased during the time of experiment. Plasma Se concentration in all groups reached a plateau (2-times the initial value) after 1 month. Although plasma GSH-Px activity increased with time in Se-treated lambs, there were only slight, but not significant, differences between groups B, C and D. It was concluded that dietary Se levels of 0.25 mg/kg DM are sufficient to cover requirements of blood components for maintaining plateaus of Se concentration and GSH-Px activity in lambs.

Antioxidant enzyme systems in skeletal muscle atrophied by immobilization.

To clarify the mechanism of oxidative stress in skeletal muscle atrophied by immobilization, we investigated the change of antioxidant enzyme activities in a typical slow red muscle, the soleus. Atrophied soleus muscles were collected from male Wistar rats (16 weeks old), one ankle joint of which had been immobilized in the fully extended position for 7 days. Also, soleus muscles were collected from intact age-matched rats as control. The activities of Mn-containing superoxide dismutase (Mn-SOD), Cu,Zn-containing superoxide dismutase (Cu,Zn-SOD), Se-dependent glutathione peroxidase (Se-GSHPx), glutathione S-transferase (GST), catalase, and glutathione reductase (GSSGRx) were measured. The activities of Cu,Zn-SOD, GST, and GSSGRx were significantly higher in atrophied muscles, while the others were unchanged. Increased Cu,Zn-SOD and unchanged Mn-SOD levels might reflect increased generation of superoxide anions in the cytoplasm rather than in the mitochondria. Owing to the enhancement of Cu,Zn-SOD and the unaltered Se-GSHPx and catalase activities, hydrogen peroxide is thought to be increased in the cytoplasm. Because there is also an increase of iron in the microsomes of atrophied muscles, the production of hydroxyl radicals, the most aggressive of radicals, might consequently be elevated.

Comparison of selenium level and glutathione peroxidase activity in tissues of vitamin B 6-deficient rats fed sodium selenite or DL-selenomethionine

The effect of vitamin B 6 on the levels of tissue selenium (Se) and glutathione peroxidase (GSH-Px) was studied. Male Wistar 4-week-old rats were fed a vitamin B 6-Se-deficient basal diet for 2 weeks, then divided into 10 groups of five or six rats and fed their respective diets for 4 weeks. The experimental design was a 2×2×2 factorial with two levels of vitamin B 6, two forms of Se, and two levels of Se, plus two extra groups (vitamin B 6-supplemented and deficient without Se). Vitamin B 6 was 0 and 250 μg pyridoxine-HCl/100 g of diet; Se forms were Na 2SeO 3 and DL-selenomethionine; Se levels were 0.5 and 5.0 mg Se/kg of diet. Regardless of form or level of Se, vitamin B 6-deficient rats had lower body weights and organ weights than vitamin B 6-supplemented rats. At 5.0 mg Se/kg of diet, Na 2SeO 3 caused a further depression. Vitamin B 6 deficiency resulted in a higher Se level and GSH-Px activity in plasma of rats fed selenomethionine. However, Se content an GSH-Px activity in erythrocytes were significantly elevated in vitamin B 6-supplemented rats compared with vitamin B 6-deficient rats. Se levels in muscle and heart were significantly lower in vitamin B 6-deficient groups fed Na 2SeO 3 than in vitamin B 6-supplemented groups. Vitamin B 6-deficient rats fed selenomethionine had higher Se levels in muscle, heart, spleen, liver, and kidneys than vitamin B 6-supplemented rats. Activity of GSH-Px in muscle, heart, and spleen was significantly lower in vitamin B 6-deficient groups than in vitamin B 6-supplemented groups, regardless of form of Se. A significant decrease of GSH-Px in liver was observed in vitamin B 6-deficient rats fed selenomethionine compared with vitamin B 6-supplemented rats, whereas no significant decrease was observed in those fed Na 2SeO 3. These results suggest that vitamin B 6 is involved in the distribution and transportation of Se in body and the metabolism of selenomethionine in liver.

Selenium status of patients with Balkan endemic nephropathy.

The selenium (Se) contents in common cereals in endemic and nonendemic areas in Serbia are very low. Plasma Se levels of both patients and healthy subjects, were also low, reflecting low Se intakes. Patients with Balkan endemic nephropathy (BEN) had significantly lower (p less than 0.05) plasma Se levels than healthy individuals, both from regions close to endemic areas, and from Belgrade. Mean plasma Se of BEN patients was slightly but insignificantly higher in samples taken immediately after dialysis than in those taken before, suggesting that very little of the Se present in plasma is dialyzable. Plasma SeGSH-Px activities before and after hemodialysis in both BEN and Nonendemic chronic renal failure (NCRF) patients were not significantly different, but BEN patients had lower enzyme activities than those with NCRF and healthy controls. In BEN patients, a significant correlation between plasma Se and SeGSH-Px activity was found.

Selenium content and distribution in bovine and human milk from different regions of Poland.

Human milk and bulk cow's milk samples from 3 different areas of central Poland were analyzed for their Se content. Cow's milk specimens were also analyzed for Se distribution and GSH-Px activity. Mature human milk contained 34-68% more Se than bulk cow's milk obtained from analogous areas of central Poland. Comparison of literature values suggest, that human and cow's milk from vicinity of Warsaw and Piotrków Trubunalski were Se-adequate but milk from Siedlce area was Se-deficient. Glutathione peroxidase activity accounted for 25-31% of the total peroxidase activity of cow's milk. The majority of the Se was found in the whey fraction. It was suggested that the participation of the casein fraction in total milk selenium increased faster than milk Se content. Cow's milk obtained near Warsaw had a 2-times higher concentration of Se than in milk from Siedlce but the content of this microelement in the casein fraction (pellet) was 3-times higher.

Platelet Glutathione Peroxidase Activity in Long‐Term Total Parenteral Nutrition With and Without Selenium Supplementation

Selenium (Se) is not routinely included in total parenteral nutrition (TPN) solution; thus, patients receiving long-term TPN may be at risk of Se deficiency, which may cause fatal cardiomyopathy. Platelet glutathione peroxidase (GSH-Px) activity, as well as Se levels and GSH-Px activity in plasma and erythrocytes during prolonged TPN, was measured in six patients with chronic gastrointestinal disease. During the time course of TPN, Se administration was discontinued for 12 weeks, and then resupplemented for another 12 weeks. Before the study period, all Se indices had been maintained within the normal range. After discontinuation of Se supplementation, a significant decrease in platelet GSH-Px activity was observed after 1 week (from 64 +/- 7 [mean +/- SD] to 39 +/- 5 U/g of protein). After resupplementation, it increased after 1 week (from 44 +/- 9 to 65 +/- 10 U/g of protein). Plasma Se indices significantly changed within 3 weeks after withdrawal and reintroduction of Se (Se: from 136 +/- 28 to 75 +/- 14 and from 61 +/- 22 to 125 +/- 33 micrograms/L; GSH-Px: from 236 +/- 50 to 140 +/- 36 and from 128 +/- 32 to 220 +/- 64 U/L). Erythrocyte Se indices showed no significant changes during the study period. The results demonstrate that platelet GSH-Px activity is the most sensitive index of Se status in TPN patients.

The effect of barium selenate injection on selenium concentration and glutathione peroxidase activity in blood of pregnant ewes fed selenium-deficient diet.

Selenium (Se) levels in whole blood and plasma, and glutathione peroxidase (GSH-Px) activities in red cells and plasma were measured in ewes fed an Se-deficient diet injected with barium selenate before breeding season. Highly significant increases in Se levels and GSH-Px activities (P less than 0.001) were observed throughout the gestation period and during lactation. In the control group, Se levels and GSH-Px activities decreased significantly (P less than 0.001), and were at critically low levels during lambing and lactation periods.

Selenium in Pediatric Nutrition

Se is an essential nutrient that provides antioxidant protection in concert with vitamin E. Several selenoproteins have been identified, but only one, SeGSHpx, has a known function, that of neutralizing toxic hydroperoxides. Plasma Se concentration, being responsive to changes in Se intake, is the most practical and widely used measure of nutritional Se status. The plasma Se concentrations of the majority of healthy infants and children fall within the range of 50 to 150 micrograms/L. Although SeGSHpx activity measures the metabolically functional form of Se, the lack of a standardized analytical method has limited its usefulness as an index of nutritional Se status. Se deficiency was first observed in animals, but it is now recognized to occur in humans. Two human diseases associated with severe nutritional Se deficiency have been reported from China: a juvenile cardiomyopathy named Keshan disease and a chondrodystrophy named Kaschin-Beck disease. Long-term TPN, which provides negligible amounts of intrinsic Se, has been demonstrated in some cases to result in biochemical and clinical impairment. Although there are no consistent signs and symptoms characteristic of TPN-associated Se deficiency in addition to the low blood selenium levels, some patients will experience leg muscle pain and altered serum transaminase and creatine kinase activities. These manifestation of Se deficiency usually take years to develop. Recent information about the amount of dietary Se needed to maximize plasma SeGSHpx activity in adult men has allowed for better estimates of the Se requirement for humans. Recommended daily dietary allowances published recently by the National Academy of Sciences have been revised for infants and children in this paper by making appropriate adjustments for the protein requirements of these age-groups. These recommended intakes for Se can generally be met by consuming adequate amounts of cereals, meat, eggs, dairy products, human milk, and infant formula, which are good sources of highly available Se and are of low risk of providing excess amounts of Se. Suboptimal Se intakes by pregnant women may predispose their infants to low Se status at birth, which in turn may affect the infants ability to maintain adequate Se status during the first few months of life. In those situations where protein intake is restricted, such as in phenylketonuria and maple syrup urine disease, Se-supplemented formulas should be used. The most critical situation for Se supplementation is in pediatric patients receiving long-term TPN therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Role of Selenium‐Dependent Glutathione Peroxidase in Protecting against t‐Butyl Hydroperoxide‐Induced Damage in Hepatocytes

The role of the selenoenzyme glutathione peroxidase (Se-GSHPx) in protecting against oxidative injury was studied in hepatocytes isolated from rats fed either a low-selenium (Se-) or a selenium-adequate (Se+, control) diet. In rats fed Se- diet for eight weeks the selenium content of plasma and liver was lowered to 15 and 8%, respectively. No Se-GSHPx and only 5% of total GSHPx activity was detected in Se- hepatocytes. However, the Se- hepatocytes were as resistant as the Se+ cells to oxidative injury by 0.8 mM tert-butyl hydroperoxide (t-BuOOH), or 0.2 mM t-BuOOH plus 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of oxidized glutathione (GSSG) reductase. Only at 1.5 mM t-BuOOH or at 0.5 mM t-BuOOH with BCNU were cell damage and lipid peroxidation more evident in Se- cells. At all t-BuOOH concentrations used the depletion of cellular glutathione (GSH) was similar in magnitude in Se- and Se+ cells, but Se+ cells released more glutathione (mainly GSSG), obviously due to their higher Se-GSHPx activity. These results suggest that hepatocytes devoid of Se-GSHPx activity maintain a high capacity to resist peroxidative attack, either via residual (non-Se)GSHPx activity or other compensatory GSH-associated detoxication mechanisms.

Whole Blood Selenium Levels and Glutathione Peroxidase Activity in Erythrocytes of Black-Tailed Deer

I determined the relationship between whole blood selenium (Se) erythrocyte glutathione peroxidase (GSH-Px) activity in black-tailed deer (Odocoileus hemionus columbianus). Whole blood Se levels were linearly correlated (r 2 =0.91) to GSH-Px activities over a wide range of blood Se concentrations. The response of wole blood Se levels and GSH-Px activities to Se supplementation indicated that the Se status of indigenous deer may be established conveniently by whole blood analysis. Such monitoring may be necessary depending on known Se levels in soils and plant and the level of anthropogenic influences on Se bioavailability or requirements

Prospective study on selenium and antioxidant status during dmba-induced mammary carcinogenesis

The purpose of this study was to examine selenium (Se) and antioxidant status of rats during the development of DMBA-induced mammary carcinogenesis and to determine whether there are differences between DMBA-treated rats that remained free of tumors (NT group, n=23), animals that developed tumors (WT group, n=7) and vehicle-treated control rats (n=20). All animals were fed the recommended amount of Se (0.1 mg/kg) in a high fat (20%) diet. The activities of Se-dependent glutathione peroxidase (SeGSHPx) and Cu,Zn-superoxide dismutase (SOD) were determined in plasma and erythrocytes every 2 wks for the 21 wk duration of the experiment. Lipid peroxidation was assessed by measuring urinary malondialdehyde. SeGSHPx activity was lower in WT rats, before the appearance of tumors, compared to both NT and control rats. In contrast, SOD activity was reduced in DMBA-treated rats compared to control animals, but there were no differences between NT and WT rats. These changes in enzyme activity and the presence or absence of tumors did not affect lipid peroxidation.

Modulation of Selenium-Dependent Glutathione Peroxidase by Perfluorodecanoic Acid in Rats: Effect of Dietary Selenium

Forty-eight male Sprague-Dawley rats fed a diet containing 0.4, 0.2 or 1.0 mg of selenium (Se)/kg of diet were injected with a single dose (35 mg/kg) of perfluorodecanoic acid (PFDA) in corn oil and killed 2 wk later. Control animals were pair-fed and treated with an equal volume of vehicle. PFDA treatment significantly increased Se-dependent glutathione peroxidase (Se-GSHPx) activity in liver cytosol of rats fed the 0.04 mg of Se/kg of diet but not in rats fed the other diets. The increase in liver cytosolic Se-GSHPx activity in rats fed 0.04 mg of Se/kg of diet paralleled increases in Se content and serum Se-GSHPx activity. Determination of Se-GSHPx by an enzyme-linked immunosorbent assay showed that PFDA caused a decrease in Se-GSHPx protein in rats fed 0.2 or 1.0 mg of Se/kg of diet but not in rats fed 0.04 mg of Se/kg of diet. Further analysis revealed that the ratio of Se-GSHPx activity to antibody-reactive protein was increased by PFDA in all three groups. The in vitro addition of PFDA directly to the assay mixture for Se-GSHPx activity did not produce any effect. Reduced glutathione was significantly increased by PFDA treatment in all three groups. These data show that PFDA affects the Se content, Se-GSHPx activity and Se-GSHPx protein in rat liver and that the effect is dependent on the dietary/hepatic Se level.

Digestibility and bioavailability of dietary selenium from fishmeal, selenite, selenomethionine and selenocystine in Atlantic salmon ( Salmo salar)

Four groups of Atlantic salmon ( Salmo salar), mean weight 68 g, were given diets for 4 weeks, in which the selenium (Se) was supplied from either fishmeal, sodium selenite, DL-selenomethionine or DL-selenocystine. Selenomethionine was the most digestible (92%) and fishmeal (47%) the least digestible source of Se. This was reflected in plasma Se concentration which was highest in fish given selenomethionine, although the activity of the enzyme glutathione peroxidase (GSH-Px) which contains Se was not significantly increased. Measurement of the GSH-Px:Se ratio indicated that Se supplied as selenite or selenocystine was a better source of Se for plasma GSH-Px than was Se from selenomethionine or fishmeal. Se concentration and GSH-Px activity in liver and erythrocytes were not significantly different in fish given the experimental diets for 4 weeks.

Changes in Selenium and Antioxidant Status during DMBA-Induced Mammary Carcinogenesis in Rats

Female weanling Sprague-Dawley rats were used to examine the changes that occurred in selenium and antioxidant status during the development of 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors. Animals were fed an AIN-76 diet, modified to contain 20% fat (3:1 wt/wt, lard:corn oil) and 0.1, 0.035, 0.1, 1.0, 2.0 or 4.0 mg Se/kg diet. At wk 5, rats in groups 2-6 were administered by intragastric tube 4.32 mg of DMBA dissolved in corn oil. Control rats received corn oil only. A blood sample was removed from the tail vein and analyzed for selenium-dependent glutathione peroxidase (Se-GSHPx) and superoxide dismutase (SOD) activity at wk 5, and every 4 wk until wk 25. At the end of the experiment, rats were classified by tumor status, and each diet group was subdivided into two groups: those rats remaining free of tumors for 25 wk and those with tumors. DMBA treatment caused an initial decrease in erythrocyte SeGSHPx and SOD activity compared to untreated control rats. SeGSHPx activity in rats with tumors remained lower than controls, while SeGSHPX activity increased in rats with no tumors. These changes, however, were not associated with any changes in lipid peroxidation.

Ascorbate interacts with sodium selenite to increase glutathione peroxidase activity in selenium-deficient chick duodena cultured in vitro

Duodena from Selenium (Se)/vitamin E-depleted 19 d chick embryos were cultured in vitro for 0-30 h. The addition of sodium selenite to the culture medium was associated with increased selenium-dependent glutathione peroxidase (SeGSHpx) activity after 24 h of incubation. In the absence of Se or in the presence of sodium ascorbate supplementation alone, SeGSHpx activity showed a gradual decline over the same time period. When ascorbate was added, along with sodium selenite, SeGSHpx activity was increased earlier and to a greater extent than in the presence of Se alone. These observations show that ascorbate can influence the metabolism of sodium selenite, resulting in increased SeGSHpx activity.

Selenium Content and Glutathione Peroxidase Activity of Milk from Vegetarian and Nonvegetarian Women

The concentration of selenium (Se) in milk samples obtained from 26 lacto-ovo-vegetarian (vegetarian) women was significantly greater (22.2 +/- 0.8 ng/ml) than from 12 nonvegetarian women (16.8 +/- 1.3). Mean GSH-Px activity (EC 1.11.1.9) in milk from vegetarians was 146% of that in milk from nonvegetarians. A significant correlation between GSH-Px activity and Se concentration was observed (r = 0.76). Likewise a significant correlation was observed between milk linoleic acid content and GSH-Px activity (r = 0.68). In undialyzed samples from vegetarian women, most of the increased content of Se was found in fractions containing proteins of 100 kdaltons (kD) or more. The high glutathione peroxidase activity in milk from vegetarians was associated with selenoproteins in the 90 to 100 kD range. A distinct 40 kD Se peak was also detected in milk from vegetarians. There was no difference in Se intake between the two groups of women. Therefore, although data from the present study show that both the quantity and distribution of Se in human milk can be modified by the maternal diet, the increased Se content and GSH-Px activity in milk from vegetarians cannot be explained by an increased Se intake.

Selenium and vitamin E supplementation: activities of glutathione peroxidase in human tissues

Twenty-seven New Zealand women received daily for 4 wk, 200 micrograms selenium as sodium selenite, 170 mg alpha-tocopherol acetate, or a placebo. Se supplementation raised platelet selenoglutathione peroxidase (Se-GSHPx, p less than 0.001) and also Se and Se-GSHPx in whole blood and plasma. Se concentrations and Se-GSHPx activities in liver biopsies taken after supplementation were greater (p less than 0.05) for the Se group and a good correlation was found between Se and Se-GSHPx in liver and muscle for all subjects. Platelet Se-GSHPx correlated well with Se and Se-GSHPx in liver, indicating its suitability for assessing Se bioavailability. This is the first reported study of relationships between Se and Se-GSHPx in human liver and muscle tissue and platelet Se-GSHPx after Se supplementation. These observations verify in man relationships observe in animal studies, giving support to assumptions made in methods for assessing Se status and bioavailability in man, in particular the use of platelet GSHPx.