Red Blood Cell Glutathione Peroxidase Research Articles

Effect of polyphenols extracted from tamarind (Tamarindus indica L.) seed coat on pathophysiological changes and red blood cell glutathione peroxidase activity in heat-stressed broilers

The purpose of this study was to determine the effect of polyphenols extracted from the tamarind seed coat (PETSC) on glutathione peroxidase (GPx) activity, red blood cell parameters and bilirubin in heat-stressed broilers. One hundred forty-seven broilers, 18-days old were divided into two groups. In group 1, broilers were maintained at an environmental temperature of 26 ± 2 °C throughout the experimental period. In group 2, the broilers were maintained at 38 ± 2 °C (cyclic temperature: 26 ± 2 °C; -38 ± 2 °C; and -26 ± 2 °C, and broilers were maintained at 38 ± 2 °C for 6h/ day) and received PETSC at a concentration of 0, 100, 200, 300, 400 or 500mg/kg in their diet ad libitum. Parameters were investigated on days 1, 7, 14 and 21 of the experimental period. Results showed that GPx activity of heat-stressed broilers that received 100mg/kg of PETSC in their diet was lower (P < 0.05) than that in broilers fed the other concentrations. The mean total red blood cell count and hemoglobin concentration of heat-stressed broilers that received 100mg/kg PETSC was higher (P < 0.05) than those in broilers in group 1 and those fed the other concentrations. The mean bilirubin level in the excreta of heat-stressed broilers that received 100mg/kg of PETSC was lower (P < 0.05) than that in broilers that received 0, 300, 400 and 500mg/kg of PETSC. This showed that PETSC could reduce GPx activity and bilirubin in feces, and increase red blood cell parameters in heat-stressed broilers.

The effect of short-term canola oil ingestion on oxidative stress in the vasculature of stroke-prone spontaneously hypertensive rats

BackgroundThis study aimed to determine if 25 days of canola oil intake in the absence of excess dietary salt or together with salt loading affects antioxidant and oxidative stress markers in the circulation. A further aim was to determine the mRNA expression of NADPH oxidase subunits and superoxide dismutase (SOD) isoforms in the aorta of stroke-prone spontaneously hypertensive (SHRSP) rats.MethodsMale SHRSP rats, were fed a defatted control diet containing 10% wt/wt soybean oil or a defatted treatment diet containing 10% wt/wt canola oil, and given tap water or water containing 1% NaCl. Blood was collected at the end of study for analysis of red blood cell (RBC) antioxidant enzymes, RBC and plasma malondialdehyde (MDA), plasma 8-isoprostane and plasma lipids. The aorta was removed and the mRNA expression of NOX2, p22phox, CuZn-SOD, Mn-SOD and EC-SOD were determined.ResultsIn the absence of salt, canola oil reduced RBC SOD and glutathione peroxidase, and increased total cholesterol and LDL cholesterol compared with soybean oil. RBC glutathione peroxidase activity was significantly lower in both the salt loaded groups compared to the soybean oil only group. In addition, RBC MDA and plasma HDL cholesterol were significantly higher in both the salt loaded groups compared to the no salt groups. Plasma MDA concentration was higher and LDL cholesterol concentration lower in the canola oil group loaded with salt compared to the canola oil group without salt. The mRNA expression of NADPH oxidase subunits and SOD isoforms were significantly reduced in the canola oil group with salt compared to canola oil group without salt.ConclusionIn conclusion, these results indicate that canola oil reduces antioxidant status and increases plasma lipids, which are risk factors for cardiovascular disease. However, canola oil in combination with salt intake increased MDA, a marker of lipid peroxidation and decreased NAPDH oxidase subunits and aortic SOD gene expression.

The effects of organic selenium (Sel-Plex) on the viability of pneumonic Holstein suckling calves

The objective of this study was to determine the effects of supplemented selenium (Se) on plasma cortisol, red blood cell glutathione peroxidase activity (RBC GSH-PX-1), concentration of immunoglobulin G (IgG) and body weight in pneumonic suckling calves. Ten Holstein suckling male calves were randomly allocated to two groups and fed either unsupplemented milk (control) or with milk supplemented with 0.3 mg/kg DM Se (Sel-Plex) for two months. Sel-Plex had no significant effect on cortisol plasma concentration. A significant increase in red blood cell GSH-PX-1, body weight and serum concentration of IgG was observed in the treated group, along with a non-significant increase in body weight. The results indicate that Sel-Plex supplementation of suckling calves with a marginal selenium status increases GSH-PX-1, serum concentration of IgG and body weight of calves. The objective of this study was to determine the effects of supplemented selenium (Se) on plasma cortisol, red blood cell glutathione peroxidase activity (RBC GSH-PX-1), concentration of immunoglobulin G (IgG) and body weight in pneumonic suckling calves. Ten Holstein suckling male calves were randomly allocated to two groups and fed either unsupplemented milk (control) or with milk supplemented with 0.3 mg/kg DM Se (Sel-Plex) for two months. Sel-Plex had no significant effect on cortisol plasma concentration. A significant increase in red blood cell GSH-PX-1, body weight and serum concentration of IgG was observed in the treated group, along with a non-significant increase in body weight. The results indicate that Sel-Plex supplementation of suckling calves with a marginal selenium status increases GSH-PX-1, serum concentration of IgG and body weight of calves.

Effects of long-term antidepressant treatment on oxidative status in major depressive disorder: A 24-week follow-up study

Major depressive disorder (MDD) is a devastating disease that afflicts large populations and has also been accepted to be an independent risk factor for cardiovascular disease (CVD). Oxidative stress seems to play an essential role in the relationship of MDD and CVD. We aimed to determine the level of oxidative stress in patients with MDD and to investigate the effects of long-term antidepressant (AD) treatment on the oxidative-antioxidative system parameters and CVD risk factors. Fifty patients who fully met the fourth Diagnostic and Statistical Manual of Mental Disorders criteria for MDD and 44 healthy control subjects were included in the study. Control visits of the patients were repeated 6weeks, 12weeks and 24weeks after beginning of the AD treatment. Lipid profiles, oxidation and oxidizability of apolipoprotein B-containing lipoproteins (expressed as apo B-b-MDA and apo B-Δ-MDA, respectively), levels of plasma malondialdehyde (p-MDA), total antioxidative capacity (TAOC), antioxidant molecules and antioxidant enzyme activities including paraoxonase/arylesterase, red blood cell superoxide dismutase (RBC-SOD) and glutathione peroxidase were determined during 24-week of follow-up period. According to the results of the study, p-MDA, apo B-b-MDA and RBC-SOD activity were increased and arylesterase activity was decreased in MDD patients. Body mass index (BMI), vitamin A and total cholesterol levels in MDD patients increased after 24-weeks of AD treatment. RBC-SOD activity, TAOC, p-MDA and apo B-b-MDA levels were decreased; paraoxonase/arylesterase activities and apo B-Δ-MDA were increased at the end of 24th week. Oxidative stress, demonstrated in MDD patients, was partly improved during 24weeks of AD treatment. Increase in paraoxonase/arylesterase activities and decrease in p-MDA and apo B-b-MDA levels after 24weeks seem to be beneficial for reduction of CVD risk in MDD patients. However increased BMI and apo B-Δ-MDA levels are negative cardiovascular effects of long-term AD treatment.

Comparative Effects of Silymarin and Vitamin E Supplementation on Oxidative Stress Markers, and Hemoglobin Levels Among Patients on Hemodialysis

Background: The incidence of accelerated atherosclerosis among patients on hemodialysis is very high and oxidative stress (OS) is a potentially major contributor to their morbidity and mortality. Objective: To evaluate the effects of Silymarin and/or vitamin E on OS markers and hemoglobin levels in patients on hemodialysis. Methods: Eighty patients on hemodialysis were randomized into four groups: Group 1 received silymarin 140 mg 3 times daily; Group 2 received vitamin E 400 IU/day; Group 3 received silymarin 140 mg 3 times daily and vitamin E 400 IU/day; and Group 4 was the control. Samples were obtained at baseline and on day 21 for measurement of malondialdehyde (MDA), red blood cell (RBC) glutathione peroxidase (GPX), and hemoglobin. Results: Combination of silymarin and vitamin E led to a reduction in the MDA levels (7.84 ± 1.84 vs. 9.20 ± 2.74 nmol/mL; p = 0.008). There was a significant increase in RBC GPX levels in all treatment groups compared with controls after 3 weeks. This was more pronounced in the group receiving combination compared with the group receiving vitamin E or the control group (5.78 ± 3.51, 4.22 ± 1.63, and 3.16 ± 1.89 IU/grHb, respectively; p < 0.001). There was also a significant increase in mean hemoglobin of all treatment groups compared with the control. Conclusions: Oral supplementation with silymarin and vitamin E leads to reduction in MDA, increase in RBC GPX, and increase in hemoglobin levels in patients with end-stage renal disease. Studies with larger sample sizes and longer follow-up are required to investigate the effect of silymarin on cardiovascular outcomes and erythropoietin requirement.

Surgery-induced changes in red blood cell and plasma lipid peroxidation, enzymatic and non-enzymatic antioxidants, and blood hematology of female rats: protective role of methylene blue and vitamin E

Objective The aim was to determine the effects on red blood cell (RBC) and plasma lipid peroxidation, antioxidants and blood hematology of intraperitoneally administered vitamin E (VE) and 1% methylene blue (MB) solutions for prevention of adhesions in rats. Study design Thirty-seven female Sprague–Dawley rats were randomized into four groups. An adhesion model was constituted on the left uterine horn in three of the groups. They were then given intraperitoneally 0.9% saline (C group), 10 mg VE (VE group) and 1% MB (MB group) solutions, respectively. A sham group (Sh group), on which laparotomy was performed, received 2 ml of 0.9% saline solution. Results In the C group, the adhesion scores were significantly higher than in the VE ( p < 0.01), MB ( p < 0.01) and Sh groups ( p < 0.005). Results showed that adhesion formation significantly induced nitric oxide (NO) ( p < 0.01) and malondialdehyde (MDA) in plasma ( p < 0.01). The levels of RBC glutathione (GSH) ( p < 0.05) and plasma VE ( p < 0.01) significantly increased after VE administration, whereas the levels of MDA (RBC and plasma) ( p < 0.01), plasma NO ( p < 0.01), blood lymphocyte count ( p < 0.05) and blood white blood cell (WBC) counts ( p < 0.01) decreased. Treatment with MB caused a significant increase in plasma VE ( p < 0.01). On the other hand, results showed that MB significantly decreased blood WBC counts ( p < 0.01), plasma paraoxonase (PON1) ( p < 0.001) and NO ( p < 0.01), and RBC glutathione peroxidase (GPx) activity ( p < 0.05) and MDA levels ( p < 0.01). Conclusion Intraperitoneal administration of MB and VE is significantly effective in preventing intraabdominal adhesion formation in a rat model. Further investigations are necessary, however, to better understand the underlying biochemical mechanisms on lipid peroxidation and antioxidants of MB.

Are Great Tits (Parus major) Inhabiting the Vicinity of a Pulp Mill Healthy? Impacts on Physiology and Breeding Performance

The evaluation of pollution effects on wildlife provides biologically meaningful information concerning environmental quality and possible impacts on populations and can be used as an early warning of environmental change. We aimed to assess the potential effects of exposure to atmospheric pollution from pulp mill emissions on the morphology, physiology, and reproductive performance of the great tit (Parus major). Great tits from a population inhabiting the vicinity of a pulp mill had significantly higher feather mercury levels and were physiologically distinct from other birds not under the direct influence of the pollution source. This distinction, due to significantly higher levels of red blood cell-glutathione peroxidase antioxidant activity, in birds from the vicinity of the pulp mill, was observed both in autumn and winter and was repeatable between years. No detectable effects were observed on breeding performance or nestling morphology and physiology. The effects of pollution in this study seem to be related to increased levels of oxidative stress.

Effect Of Avenanthramide Supplementation On Responses To Eccentric Exercise In Young Women

Avenanthramides (AVA) are a group of nitrogen-containing diphenolic phytochemicals found exclusively in oats that have exhibited antioxidant and anti-inflammatory potential in vitro and in rodents; however, the effects of chronic AVA consumption in humans have been unexplored. PURPOSE: To investigate the effects of 8 weeks of AVA supplementation on the inflammatory and oxidative responses to a single bout of downhill running in college-aged women. METHODS: Ten women aged 18-29 yr were randomly assigned to receive cookies fortified with either high-AVA (23.5 mg/day) oat flour (O, Ceapro Inc., Canada) or with equal content of wheat flour as a placebo (PL). They were instructed to eat one 115 g cookie per day for 8 wks, during which dietary and physical activity levels were recorded. Before and after the supplementation period, subjects ran on a treadmill at -9% grade at a speed that elicited 75% of their maximal heart rate for 4 x 15 min bouts with 3 rest intervals of 5 min each. Blood samples were collected before and immediately and 24-h post exercise. RESULTS: There was no difference in pain and soreness ratings between O and PL groups post-exercise. During the post-supplementation test, O showed a higher plasma reduced to oxidized glutathione ratio (P<0.05) at 24 h post-exercise vs. PL group. Red blood cell (RBC) glutathione peroxidase activity decreased (P<0.05) immediately after exercise in O, but not in PL. RBC superoxide dismutase activity was higher (P<0.05) in O vs. PL post-exercise. There were trends toward lower plasma tumor necrosis factor (TNF)-alpha levels and white blood cell reactive oxygen species production in O compared to PL immediately and 24-h after exercise. CONCLUSIONS: High-AVA oat supplementation appears to attenuate downhill exercise-induced oxidative stress and blood inflammatory markers in college-aged women.

Dietary selenium requirements based on tissue selenium concentration and glutathione peroxidase activities in old female rats

Dietary nutrient requirements for older animals have been studied far less than have requirements for young growing animals. To determine dietary selenium (Se) requirements in old rats, we fed female weanling rats a Se-deficient diet (0.007 μg Se/g) or supplemented rats with graded levels of dietary Se (0–0.3 μg Se/g) as Na 2SeO 3 for 52 weeks. At no point did Se deficiency or level of Se supplementation have a significant effect ( P>0.05) on growth. To determine Se requirements, Se response curves were determined for 7 Se-dependent parameters. We found that minimum dietary Se requirements in year-old female rats were at or below 0.05 μg Se/g diet based on liver Se, red blood cell glutathione peroxidase (Gpx1) activity, plasma Gpx3 activity, liver and kidney Gpx1 activity, and liver and kidney Gpx4 activity. In conclusion, this study found that dietary Se requirements in old female rats were decreased at least 50% relative to requirements found in young, rapidly growing female rats. Collectively, this indicates that the homeostatic mechanisms related to retention and maintenance of Se status are still fully functional in old female rats.

Variation of adult Great Tit Parus major body condition and blood parameters in relation to sex, age, year and season

In recent years, an increasing number of studies have focused on the ranges of variation of health related biochemical and haematological parameters in wildlife, but information is still scarce for enzymatic activities which can be extremely important in detecting potential responses to environmental change. In a Great Tit (Parus major) population, we describe the variation in relation to age, sex, season and year of: (1) morphological: body condition index, fat and muscle, (2) haematological: hematocrit, haemoglobin, white blood cell count and heterophil/lymphocyte ratio, and (3) biochemical parameters: plasma protein and activities of plasma cholinesterases (acetylcholinesterase and butyrylcholinesterase) activity and red blood cell glutathione peroxidase. Sex had significant effects on all morphological parameters except fat. Age significantly affected cholinesterase activities, H/L ratio and haemoglobin, and there was a significant interaction between sex and age affecting hematocrit. There were significant interactions of year and season affecting almost all parameters studied—body condition index, fat, protein, acetyl and butyrylcholinesterase activities, glutathione peroxidase activity and haemoglobin. This study indicates that these parameters are largely influenced by year and seasonal effects, besides the individual’s intrinsic variation. Therefore, when evaluating experimental or environmental change effects, appropriate controls should be used.

Red blood cell glutathione peroxidase activity in female nulligravid and pregnant rats

BackgroundThe alterations of the glutathione peroxidase enzyme complex system occur in physiological conditions such as aging and oxidative stress consequent to strenuous exercise.MethodsAuthors optimize the spectrophotometric method to measure glutathione peroxidase activity in rat red blood cell membranes.ResultsThe optimization, when applied to age paired rats, both nulligravid and pregnant, shows that pregnancy induces, at seventeen d of pregnancy, an increase of both reactive oxygen substance concentration in red blood cells and membrane glutathione peroxidase activity.ConclusionThe glutathione peroxidase increase in erythrocyte membranes is induced by systemic oxidative stress long lasting rat pregnancy.

Effect of dietary supplementation with vitamins E and C on production performance, immune responses and antioxidant status of White Leghorn layers under tropical summer conditions

1. The effects of vitamin E (DL-α-tocopheryl acetate) and vitamin C (ascorbic acid) supplementation on performance, some immune variables and antioxidant status of White Leghorn layers (aged 44–56 weeks) exposed to tropical summer conditions were investigated. 2. Both vitamins E and C significantly improved the egg production, food conversion efficiency, antibody responses to inoculated sheep red blood cells (SRBC) and Newcastle disease virus (NDV) vaccine, lymphocyte proliferation in response to mitogen and activities of antioxidant enzymes red blood cell catalase (RBCC) and glutathione peroxidase (GSH-PX) in layers. Vitamin C increased the inflammatory response to phytohaemagglutinin-P (PHA-P) inoculation. 3. Supplemental vitamin C at 200 mg/kg diet significantly increased eggshell weight, eggshell thickness, and shell breaking strength. However, no effect of supplemental vitamin E on eggshell quality was observed. 4. Vitamins E and C, as well as interactions between them, significantly influenced the activities of glutathione reductase and lipid peroxidase. A combination of vitamin E at 125 IU/kg with vitamin C at 200 mg/kg diet had an additive effect on reducing the activity of oxidative enzyme lipid peroxidase (LP) and increasing the activity of antioxidant enzyme glutathione reductase (GSHR). 5. It is concluded that vitamin E (125 IU/kg) and vitamin C (200 mg/kg) could independently alleviate the effects of heat stress on production performance and immunological variables of layers. However, combination of both the vitamins at the above-mentioned concentrations is beneficial in eliciting higher antioxidant status in laying hens exposed to tropical summer conditions.

Effect of Different Levels of Selenium Supplementation on Growth Rate, Nutrient Utilization, Blood Metabolic Profile, and Immune Response in Lambs

Eighteen male lambs (8-9 months of age, 25.00 +/- 0.90 kg body weight) were divided into three groups of six animals in each and fed a total mixed ration (TMR) containing concentrate mixture (30% maize grain, 27% soybean meal, 40% wheat bran, 2% mineral mixture, and 1% common salt) and wheat straw in 65:35 ratio and supplemented with selenium (Se) as sodium selenite at 0 (T1, control), 0.15 (T2), and 0.30 ppm (T3) levels. Experimental feeding was done for a period of 90 days including a 6-day metabolism trial. To assess the growth performance, lambs were weighed every 15 days throughout the experimental period. All the lambs were intramuscularly inoculated with a single dose (2 ml) of haemorrhagic septicaemia oil adjuvant vaccine on 0 day to evaluate the humoral immune response. Blood samples were collected on 0 day and thereafter at 30 days interval. Results revealed that supplementation of Se both at 0.15 and 0.30 ppm levels had no significant (P > 0.05) effect on intake and digestibility of dry matter, organic matter, crude protein (CP), ether extract, neutral detergent fiber, acid detergent fiber, and hemicellulose; balances of calcium and phosphorus; and level and intake of digestible CP and total digestible nutrients. Se supplementation also had no significant (P > 0.05) effect on the levels of serum total cholesterol, total protein, albumin, globulin, albumin/globulin ratio, tri-iodothyronine (T(3)), thyroxine (T(4)), and T(4)/T(3) ratio; and serum glutamate oxaloacetate transaminase and serum glutamate pyruvate transaminase enzyme activity in the lambs. However, there was a significant (P < 0.05) increase in the plasma Se levels, red blood cell glutathione peroxidase enzyme activity, and humoral immune response in both the Se-supplemented groups. Feed (TMR) required per kilogram gain was less by 11.1% and 16.5% in groups T2 and T3, respectively, as compared to control (T1) group. Average daily gain was highest (108.5 g) in group T3, followed by group T2 (98.2 g), and lowest (89.06 g) in the control group (T1). These results indicated that supplementation of 0.15 and 0.3 ppm Se in the diet (having 0.19 ppm Se) of lambs significantly improves their immune response and antioxidant status.

Repeatability and Method-Dependent Variation of Blood Parameters in Wild-Caught Great TitsParus major

When interpreting responses to experimental manipulations or particular environmental cues, it is necessary to have previous knowledge about the natural variation of the response traits. We studied how nine blood parameters, including four enzymatic activities, varied with time in wild Great Tits by assessing their repeatabilities over periods of 45 days, in the same season (Spring or Autumn/Winter), in the same year and over a four years period. The accuracy of the measurements of these blood parameters was also assessed. Measurement error reflected essentially sample and time of storage rather than assay effects. Hematocrit and haemoglobin had low repeatabilities within Spring, ranging from 0.26 to 0.31; Heterophil/Lymphocyte ratio (H/L), white blood cell count (WBC), total plasma cholinesterase and red blood cell glutathione peroxidase (GSH-Px) activities had moderate to high repeatabilities over periods of 45 days (repeatabilities ranged from 0.47 to 0.81 for GSH-Px and H/L, respectively), but also during longer periods such as during Spring (total plasma cholinesterase activity) and Autumn/Winter (WBC, H/L and GSH-Px). Of the blood parameters measured, total plasma cholinesterase, glutathione peroxidase and the haematological parameters WBC and H/L seem relatively constant and therefore reliable indicators of Great Tit's physiological condition within, at least, a 45 days time frame.

Effect of extremely low frequency magnetic field on antioxidant activity in plasma and red blood cells in spot welders

The purpose of this study was to determine a possible relation between exposure to extremely low frequency magnetic field (ELF-MF) and the human antioxidant activity. The total serum antioxidant status (TAS), red blood cells (RBCs) glutathione peroxidase (GPX) and superoxide dismutase (SOD) were measured in 46 spot welders who were occupationally exposed to ELF-MF (magnetic field strength = 8.8-84 microTesla (microT), frequency = 50 Hertz (Hz) and electric field strength = 20-133 V/m). The results were compared with a nonexposed ELF-MF control group. The correlation between magnetic field strength and antioxidant activity in RBCs and plasma was then assessed. No significant differences in TAS levels were observed (P value = 0.065). However, in RBCs of exposed group, a significant decrease in SOD and GPX activities was observed (P value = 0.001 and 0.003, respectively). This decrease was measured as 22 and 12.3%, respectively. Furthermore, a significant negative correlation between SOD/GPX activities and magnetic field intensity was observed (coefficients of SOD: -0.625, significance: 0.0001 and coefficients of GPX: -0.348, significance: 0.018). The results of this study indicate that ELF-MF could influence the RBC antioxidant activity and might act as an oxidative stressor. Intracellular antioxidant enzymes such as SOD and GPX were found to be the most important markers involving in this process. The influence of magnetic field on the antioxidant activity of RBCs might occur even at the recommended levels of exposure.

Effect of One‐year Oral α‐Tocopherol Administration on the Antioxidant Defense System in Hemodialysis Patients

Oxidative stress is increased in hemodialysis (HD) patients and contributes to the increased morbidity and mortality in this population. Vitamin E is an antioxidant agent. In the present study the effect of prolonged oral alpha-tocopherol administration on the antioxidant defense system was evaluated. The antioxidant factors plasma total antioxidant status (TAS), red blood cell superoxide dismutase (SOD) activity and glutathione peroxidase (GPX) activity were evaluated with spectrometry in 27 HD patients. Measurements were performed before and after oral administration of alpha-tocopherol at a dose of 500 mg/d for a one-year period. Twenty HD patients received a placebo and 22 healthy volunteers served as controls. TAS was increased in HD patients. No difference was detected in SOD and GPX activity between HD patients and healthy volunteers. Tocopherol administration induced a significant decrease in TAS and SOD activity. Levels of GPX activity remained unaffected. All the evaluated factors remained stable in the HD patients receiving a placebo. Prolonged oral alpha-tocopherol administration in HD patients induces a decrease in some components of the antioxidant defense system, raising the possibility for a pro-oxidative role of vitamin E. Vitamin E is an antioxidant agent, but it is also known to have pro-oxidant action under special conditions that can be encountered in HD patients.

Cognitive functions and the antioxidant system in phenylketonuric patients.

The authors studied the relationship between the antioxidant system and cognitive functions in a group of 36 early and continuously treated phenylketonuric (PKU) patients (mean age=9.7 years) and 29 controls. The authors measured antioxidant cofactors and free radical damage markers in plasma (selenium, retinol, tocopherol, coenzyme Q10, malondialdehide) and antioxidant enzymes in red blood cells (glutathione peroxidase, catalase, superoxide dismutase). The authors used neuropsychological tests to screen for several cognitive functions. PKU patients showed significantly lower values of selenium, coenzyme Q10, and catalase, and significantly higher levels of malondialdehide. PKU patients showed a significantly negative correlation between plasma selenium concentrations and several Conner's Continuous Performance Test measures (more omission errors, fluctuating attention and inconsistency of response times, and slowing reaction time as the test progressed). Selenium deficiency was thus associated with a worsened performance on the Conner's Continuous Performance Test among PKU patients. In conclusion, it is important not only to control blood Phe levels in PKU but also other nutritional components such as selenium. Selenium status seems to be associated with attention functions in these PKU patients.

A Probable Causative Factor for an Old Problem: Selenium and Glutathione Peroxidase Appear to Play Important Roles in Epilepsy Pathogenesis

Only recently has it become known that oxidative stress and generation of reactive oxygen species are the cause and the consequence of epileptic seizures. Due to the protective role of selenium (Se) and selenoproteins against oxidative damage and the ability to promote neuronal cell survival, we compared serum selenium level and red blood cell Glutathione peroxidase activity (RBC GPx) between epileptic and healthy children. In a case control study, 53 epileptic children were compared with 57 healthy children in the same age and community of residence. Serum Se and RBC GPx activity were measured with an atomic absorption spectrophotometry and Cayman standard glutathione assay kit, respectively. The mean (+/-standard deviation) of serum Se was 72.90 microg/L (+/-22.20) and 86.00 microg/L (+/-15.00) in patient and control groups, respectively. For RBC GPx activity the mean (+/-standard deviation) was 440.57 nmol/min/ml (+/-264.00) and 801.00 nmol/min/ml (+/-267.00) in patient and control groups, respectively. Statistical analysis showed a significant lower means of serum Se and RBC GPx activity in patient group compared to that of healthy control group (p < 0.001). Lower serum Se and RBC GPx activity in epileptic patients compared to healthy children may support the proposed crucial role of Se and GPx activity in the pathogenesis of epilepsy. However, RBC GPx activity in the case of selenium deficiency could not be a sensitive and specific indicator of Se status in serum that led us to supplant Se measurement with RBC GPx activity.

Red blood cell and plasma glutathione peroxidase activities and selenium concentration in patients with chronic kidney disease: a review.

The metabolism of oxygen in aerobic organisms leads to generation of reactive oxygen species (ROS). These entities are able to oxidize almost all classes of macromolecules, including proteins, lipids and nucleic acids. The physiological level of ROS is usually regulated by antioxidant defense mechanisms. There are at least three groups of antioxidant enzymes: superoxide dismutases, catalases and glutathione peroxidases (GSH-Pxs) which neutralize ROS. The trace elements (copper, zinc and selenium) bound to the active sites of the above listed enzymes play an important role in the antioxidant defense system. In mammals, a major function of selenium (Se) and Se-dependent GSH-Pxs is to protect cells from oxidative stress. Selenium concentrations and GSH-Px activities are altered in blood components of chronic kidney disease (CKD) patients. The Se level is frequently lower than in healthy subjects and the concentration very often decreases gradually with advancing stage of the disease. Studies on red cell GSH-Px activity in CKD patients reported its values significantly lower, significantly higher and lower or higher, but not significantly as compared with healthy subjects. On the other hand, all authors who studied plasma GSH-Px activity have shown significantly lower values than in healthy subjects. The degree of the reduction decreases gradually with the progression of the disease. High inverse correlations were seen between plasma GSH-Px activity and creatinine level. A gradual decrease in plasma GSH-Px activity in CKD patients is due to the fact that this enzyme is synthesized predominantly in the kidney and thus the impairment of this organ is the cause of the enzyme's lower activity. Se supplementation to CKD patients has a slightly positive effect in the incipient stage of the disease, but usually no effect was observed in end-stage CKD. Presently, kidney transplantation is the only treatment that may restore plasma Se level and GSH-Px activity in patients suffering from end-stage CKD. A few studies have shown that in kidney recipients, plasma Se concentration and GSH-Px activity are restored to normal values within a period of 2 weeks to 3 months following surgery and thus it can be acknowledged that Se supplementation to those patients has a positive effect on plasma GSH-Px activity.

Oral vitamin E supplementation on oxidative stress, vitamin and antioxidant status in intensely exercised horses

Vitamin E is the most commonly supplemented antioxidant in horses; however, previous research is not conclusive as to the recommended level for exercising horses. To evaluate the effects of 3 levels of vitamin E supplementation on oxidative stress and vitamin/antioxidant status in intensely exercised horses to determine the optimal level of vitamin E supplementation. Twelve unfit Standardbreds were divided into 3 groups, supplemented orally with 0 (CON), 5000 (MOD), or 10,000 (HI) iu/day of DL-alpha-tocopheryl acetate. The 3 x 3 Latin square design consisted of three 4 week supplementation periods with 4 week wash out periods between. After each period, horses underwent a treadmill interval exercise test. Blood samples were collected and heart rate (HR) measured before, during and after exercise. Data were analysed using ANOVA with repeated measures in SAS. The CON group had lower HR throughout the test compared to the MOD and HI groups (P<0.05). There was an increase in plasma retinol (RET), beta-carotene (BC), red blood cell total glutathione and glutathione peroxidase with exercise (P<0.05), but all groups returned to baseline after 24 h. Plasma alpha-tocopherol (TOC) increased from baseline with exercise (P<0.0001) in all groups; treatment differences were observed at 24 h (P<0.05). The HI and CON groups had lower BC compared to the MOD group (P = 0.05). Horses supplemented with vitamin E, at nearly 10-times the 1989 NRC recommended level, did not experience lower oxidative stress compared to control horses. Additionally, lower plasma BC levels observed in the HI group, which may indicate that vitamin E has an inhibitory effect on BC metabolism. Supplementation above control levels is not more beneficial to oxidative stress and antioxidant status in intensely exercising horses; indeed, levels 10 times in excess may be detrimental to BC and should be avoided.