Selenium deficiency-induced alterations in the vascular system of the rat

To enunciate the mechanisms whereby Se protects against cardiovascular diseases, weanling male Wistar rats were fed deficient (0.022 mg/kg diet) and adequate (0.159 mg/kg diet) Se diets for 14 and/or 39 wk. As the Se content and glutathione peroxidase activity were decreased and the lipid peroxide level was increased, the plasma 6-keto-PGF_1α concentration of the Se-deficient group was markedly decreased in blood and tissues of the Se-deficient rats, as compared with the Se-adequate animals. Furthermore, the Se-deficient group had significantly lower plasma nitric oxide content and vascular nitric oxide synthase activity, higher erythrocyte sedimentation equation K value and aggregation index, and lower erythrocyte deformability than the Se-adequate group. Experimental Se deficiency also resulted in significant increases in serum total cholesterol and low-density lipoprotein cholesterol levels and a significant decrease in serum high-density lipoprotein cholesterol level. These results give some experimental supports to the hypothesis that low Se status and lipid peroxidation are involved in the etiology of cardiovascular diseases.     

Minimum Selenium Requirements Increase When Repleting Second-Generation Selenium-Deficient Rats but Are Not Further Altered by Vitamin E Deficiency

Second-generation selenium-deficient weanling rats fed graded levels of dietary Se were used (a) to study the impact of initial Se deficiency on dietary Se requirements; (b) to determine if further decreases in selenoperoxidase expression, especially glutathione peroxidase 4 (Gpx4), affect growth or gross disease; and (c) to examine the impact of vitamin E deficiency on biochemical and molecular biomarkers of Se status. Rats were fed a vitamin E-deficient and Se-deficient crystalline amino acid diet (3 ng Se/g diet) or that diet supplemented with 100 μg/g all-rac-α-tocopheryl acetate and/or 0, 0.02, 0.05, 0.075, 0.1, or 0.2 μg Se/g diet as Na₂SeO₃ for 28 days. Se-supplemented rats grew 6.91 g/day as compared to 2.17 and 3.87 g/day for vitamin E-deficient/Se-deficient and vitamin E-supplemented/Se-deficient groups, respectively. In Se-deficient rats, liver Se, plasma Gpx3, red blood cell Gpx1, liver Gpx1 and Gpx4 activities, and liver Gpx1 mRNA levels decreased to <1, <1, 21, 1.6, 49, and 11 %, respectively, of levels in rats fed 0.2 μg Se/g diet. For all biomarkers, ANOVA indicated significant effects of dietary Se, but no significant effects of vitamin E or vitamin E × Se interaction, showing that vitamin E deficiency, even in severely Se-deficient rat pups, does not result in compensatory changes in these biochemical and molecular biomarkers of selenoprotein expression. Se requirements determined in this study, however, were >50 % higher than in previous studies that started with Se-adequate rats, demonstrating that dietary Se requirements determined using initially Se-deficient animals can result in overestimation of Se requirements.     

Selenium regulation of thioredoxin reductase activity and mRNA levels in rat liver

Mammalian thioredoxin reductase (TRR; NADPH₂:oxidized thioredoxin oxidoreductase, E.C. 1.6.4.5) is a new member of the family of selenocysteine-containing proteins. TRR activity in Se-deficient rat liver is reported to decrease to 4.5 to 15% of the activity in Se-adequate rat liver, similar to the fall in Se-dependent glutathione peroxidase-1 activity. Both glutathione peroxidase-1 enzyme activity and mRNA levels decrease dramatically in Se deficiency, whereas glutathione peroxidase-4 activity only decreases to 40% of Se-adequate levels and mRNA level is little affected by Se deficiency. The purpose of these experiments is to study the effect of Se status on TRR mRNA levels and enzyme activity in our well-characterized rat model, and to compare this regulation directly to the regulation of other Se-dependent proteins in male weanling rats fed Se-deficient diets or supplemented with dietary Se for 28 days. In two experiments, TRR activity in Se-deficient liver decreased to 15% of Se-adequate activity as compared to 2% and 40% of Se-adequate levels for GPX1 and GPX4, respectively. Using ribonuclease protection analysis, we found that TRR mRNA levels in Se-deficient rat liver decreased to 70% of Se-adequate levels. This decrease in TRR mRNA was similar to the GPX4 mRNA decrease in Se-deficient liver in these experiments, whereas GPX1 mRNA levels decreased to 23% of Se-adequate levels. This study clearly shows that TRR represents a third pattern of Se regulation with dramatic down-regulation of enzyme activity in Se deficiency but with only a modest decrease in mRNA level. The conservation of TRR mRNA in Se deficiency suggests that this is a valued enzyme; the loss of TRR activity in Se deficiency may be the cause of some signs of Se deficiency.     

Effect of selenium status on mRNA levels for glutathione peroxidase in rat liver

To determine the effect of Se status on the level of mRNA for Se-dependent glutathione peroxidase (EC 1.11.1.9), rats were fed either a Se-deficient torula yeast diet (less than 0.02 mg Se/kg diet) or a Se-adequate diet (+0.2 mg Se/kg as Na2SeO3) for greater than 135 d. Liver glutathione peroxidase activity was 0.025 for Se-deficient versus 0.615 EU/mg protein for Se-adequate rats. Total liver RNA and polyadenylated RNA were isolated and subjected to Northern blot analysis using a 700 bp DNA probe from cloned murine glutathione peroxidase. Autoradiography showed that Se-deficient liver had 7-17% of the mRNA for glutathione peroxidase present in Se-adequate liver, suggesting that Se status may regulate the level of mRNA for this selenoenzyme.     

Effect of long-term Se deficiency on the antioxidant capacities of rat vascular tissue

Selenium (Se) is an essential micronutrient in human health and Se deficiency has been incriminated in the etiology of cardiovascular diseases. However, the effect of long-term Se deficiency on the antioxidant capacities of vascular tissue has not been elucidated. This study was to determine whether long-term Se deficiency might affect the antioxidant capacity of rat vascular tissue and whether the diet Se might affect the activities of glutathione peroxidase (GPx) and thioredoxin reductase (TR) in rat vascular tissue. Weanling male Wister rats were fed Se-deficient and Se-adequate diets for 12 mo. Se was supplemented in drinking water (1 μg Se/mL) for 1 mo. The arterial walls isolated from various groups were used in the assay. In comparison with the control, Se-deficient rats exhibited significant decreases of GPx activity and total antioxidant capacity in the arterial wall. Similar decreases appeared in the heart, liver, and kidney. The superoxide dismutase activity was also decreased in the Se-deficient rat’s arterial wall. Followed by Se supplementation, they were restored to different extent. TR activity was decreased in the heart, liver, and kidney, but increased in the arterial wall. The content of malondialdehyde was increased markedly in Se-deficient rats. In conclusion, a positive correlation exists between dietary Se and antioxidant capacity of rat vascular tissue except TR. It seems that the activities of GPx and TR in the rat arterial wall were mediated in different pathways by the Se status.     

Mineral status in selenium-deficient rats compared to selenium-sufficient rats fed vitamin-free casein-based or torula yeast-based diet

To clarify the mineral status in selenium (Se)-deficient rats fed a vitamin-free casein (VFC)-based or torula yeast (TY)-based diet, 24 weanling male Wistar rats were divided into 4 groups fed diets using VFC or TY as the protein source and containing Se at sufficient (0.5 μg/g,⁺Se) or deficient (0.019 μg/g for VFC-based and <0.005 μg/g for TY-based diets,⁻Se) level for 8 wk. TY supplied a larger amount of extra minerals (Na, K, Ca, Mg, Fe, Mn, Zn, and Cu) except Se than VFC. Se concentration and glutathione peroxidase activity were significantly lower in TY-fed rats than in VFC-fed rats, as well as in⁻Se rats compared to⁺Se rats. Compared to⁺Se rats, Fe concentration was higher in liver and muscle of⁻Se rats fed the VFC-based diet and in plasma, heart, liver, and tibia of⁻Se rats fed the TY-based diet. Compared to⁺Se rats, decreases of Mn concentration appeared in plasma, heart, and tibia of VFC-fed⁻Se rats and in brain, heart, liver and tibia of TY-fed⁻Se rats. There was also a little imbalance in Ca, Mg, Na, K, and Cu caused by Se deficiency. The results indicated that Se deficiency induced the mineral imbalance in rats, especially an increase in Fe and decrease in Mn, which was more severe in TY-fed rats than VFC-fed rats. However, TY cannot be used as a model for both Se and other mineral deficiency because of the extra minerals except Se found in TY. Instead, VFC can be employed, which contains fewer minerals except Se than TY and also can produce a severe degree of Se deficiency.     

Effect of selenium and protein deficiency on selenium and glutathione peroxidase in rats

Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium (0.5 ppm [+ Se] or <0.02 ppm [−Se] and protein (15% [+Pro] or 5% [−Pro]), but adequate levels of all other nutrients for 4 wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient groups. In Se-deficient groups, Se and GSHPx were significantly higher in −Se−Pro rats in heart, liver, and kidney. Data analysis showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed that under the condition of Se deficiency. a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis, and result in Se redistribution. This could account for high levels of Se and GSHPx in the −Se−Pro rats compared to −Se+Pro rats.     

Comparison of selenium level and glutathione peroxidase activity in tissues of vitamin B6-deficient rats fed sodium selenite or DL-selenomethionine

The effect of vitamin B₆ on the levels of tissue selenium (Se) and glutathione peroxidase (GSH-Px) was studied. Male Wistar 4-week-old rats were fed a vitamin B₆-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 B₆, two forms of Se, and two levels of Se, plus two extra groups (vitamin B₆-supplemented and deficient without Se). Vitamin B₆ was 0 and 250 μg pyridoxine-HCl/100 g of diet; Se forms were Na₂SeO₃ and DL-selenomethionine; Se levels were 0.5 and 5.0 mg Se/kg of diet. Regardless of form or level of Se, vitamin B₆-deficient rats had lower body weights and organ weights than vitamin B₆-supplemented rats. At 5.0 mg Se/kg of diet, Na₂SeO₃ caused a further depression. Vitamin B₆ 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 B₆-supplemented rats compared with vitamin B₆-deficient rats. Se levels in muscle and heart were significantly lower in vitamin B₆-deficient groups fed Na₂SeO₃ than in vitamin B₆-supplemented groups. Vitamin B₆-deficient rats fed selenomethionine had higher Se levels in muscle, heart, spleen, liver, and kidneys than vitamin B₆-supplemented rats. Activity of GSH-Px in muscle, heart, and spleen was significantly lower in vitamin B₆-deficient groups than in vitamin B₆-supplemented groups, regardless of form of Se. A significant decrease of GSH-Px in liver was observed in vitamin B₆-deficient rats fed selenomethionine compared with vitamin B₆-supplemented rats, whereas no significant decrease was observed in those fed Na₂SeO₃. These results suggest that vitamin B₆ is involved in the distribution and transportation of Se in body and the metabolism of selenomethionine in liver.     

Disruption of endoplasmic reticulum is the primary ultrastructural lesion of the pancreas in the selenium-deficient chick

Severe uncomplicated selenium (Se) deficiency was produced in chicks by feeding, from 1 day of age, a purified diet that contained 0.010 ppm Se but was adequate with respect to all other known nutrients. The deficiency was characterized by depressions in rate of growth and efficiency of feed utilization and by reductions in the plasma activity of Se-dependent glutathione peroxidase (SeGSHpx) by 85-97% from levels in chicks fed the basal diet supplemented with 0.20 ppm Se as Na2SeO3. Histological observations of the target organ of Se deficiency in the chick, i.e., the pancreas, using transmission electron microscopy, showed severe losses of endoplasmic reticulum (ER) and absence of secretory granules in acinar cells of Se-deficient animals. These effects were not uniform within individuals, as Se-deficient pancreases also showed areas of unaffected acini. By 14 days of age, Se-deficient pancreases contained many apparently undifferentiated cells, which were absent from pancreases of Se-fed chicks. It is noteworthy that abnormal mitochondria were not observed in any pancreas sections. It is concluded that the metabolic consequences of severe uncomplicated Se deficiency in the chick result from the disruption of ER and loss of functional acinar cells, rather than to damage to mitochondria as previously suggested.     

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 Na₂SeO₃ 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.     

Influence of selenium deficiency on the acute cardiotoxicity of adriamycin in rats

The influence of selenium (Se) deficiency on the acute cardiotoxicity induced by the anticancer drug adriamycin (ADR) has been studied in rats by electrocardiography. Two categories were formed by feeding groups of rats a Se-supplemented and a Se-deficient diet. The supplemented animals were taken as normals. The two categories were treated with iv injections of saline solution containing ADR at doses of 0, 7.5, and 15 mg/kg body wt. The cardiac Se concentration and glutathione peroxidase (GSH-Px) activity in the Se-deficient groups were <2% lower than in the normals. The normal groups showed significant widening of the SaT and QaT durations when given 15 mg/kg ADR. The Se-deficient groups exhibited a dose-dependent widening of the SaT and QaT duration at 7.5 and 15 mg/kg and narrowing of the PQ duration at 15 mg/kg ADR. No heart rate or QRS duration changes were detected in both categories. Our results suggest that an imbalance of the antioxidant system is associated with Se deficiency and that Se plays a role in preventing the cardiac functional disorder attributable to oxygen free radical formation induced by ADR.     

Effects of selenium deficiency on Ca transport function of sarcoplasmic reticulum and lipid peroxidation in rat myocardium

Two groups of weanling Sprague-Dawley rats were fed a low-selenium basal diet (Se 0.009 mg/kg) and the same diet supplemented with sodium selenite (Se 0.25 mg/kg), respectively, for 1, 2, and 3 months. At each feeding time, the Ca²⁺-ATPase activity, Ca²⁺ uptake rate and the capacity of Ca²⁺ uptake in isolated cardiac sacroplasmic reticulum from the Se-deficient rats were decreased significantly compared to those from the Se-supplemented rats, the contents of lipid peroxide in postmitochondrial supernatant and isolated sarcoplasmic reticulum from the Se-deficient rats were significantly higher than that from Se-supplemented rats. Compared to the Se-supplemented rats, the cytosolic glutathione peroxidase activity in Se-deficient rats decreased significantly. In addition, significant linear negative correlations of lipid peroxide in postmitochondrial supernatant to sarcoplasmic reticular Ca²⁺-ATPase activity, Ca²⁺ uptake rate and to whole blood selenium concentration were observed. The results suggest that the enhancement of lipid peroxidation via the depressed glutathione peroxidase activity might be responsible for the decrease of Ca²⁺-ATPase and Ca²⁺ uptake activities in sarcoplasmic reticulum in Se-deficient animals.     

Long-Term Selenium-Deficient Diet Induces Liver Damage by Altering Hepatocyte Ultrastructure and MMP1/3 and TIMP1/3 Expression in Growing Rats

The effects of selenium (Se)-deficient diet on the liver were evaluated by using growing rats which were fed with normal and Se-deficient diets, respectively, for 109 days. The results showed that rats fed with Se-deficient diet led to a decrease in Se concentration in the liver, particularly among male rats from the low-Se group. This causes alterations to the ultrastructure of hepatocytes with condensed chromatin and swelling mitochondria observed after low Se intake. Meanwhile, pathological changes and increased fibrosis in hepatic periportal were detected by hematoxylin and eosin and Masson’s trichrome staining in low-Se group. Furthermore, through immunohistochemistry (IHC) staining, higher expressions of metalloproteinases (MMP1/3) and their tissue inhibitors of metalloproteinases (TIMP1/3) were observed in the hepatic periportal of rats from the low-Se group. However, higher expressions of MMP1/3 and lower expressions of TIMP1/3 were detected in hepatic central vein and hepatic sinusoid. In addition, upregulated expressions of MMP1/3 and downregulated expressions of TIMP1/3 at the messenger RNA (mRNA) and protein levels also appeared to be relevant to low Se intake. In conclusion, Se-deficient diet could cause low Se concentration in the liver, alterations of hepatocyte ultrastructure, differential expressions of MMP1/3 and TIMP1/3 as well as fibrosis in the liver hepatic periportal.     

Effects of dietary iron overload on glutathione peroxidase knockout mice

Excess iron (Fe) intake has been associated with an increased risk of cardiovascular disease in humans, presumably the result of increased oxidative stress. Previous work by us has shown that feeding a high-Fe diet to selenium (Se)-deficient weanling mice for 4 wk resulted in elevated plasma cholesterol and triglycerides and increased hepatic thiobarbituric acid reactive substances (TBARS). Here, we report the effect of Fe overload in mice lacking cellular glutathione peroxidase (GPX1 knockout [KO] mice), the selenoenzyme thought to account for much of the antioxidant action of Se. Four groups of 9–13 weanling wild-type (WT) or GPX1 KO mice were randomly assigned, then fed either an Fe-adequate (35 ppm Fe) or high-Fe (1100 ppm Fe) casein-based diet for 4 wk. Iron was added as ferric citrate. Both diets also contained 0.2 ppm Se added as sodium selenite. As expected, liver GPX1 activity was essentially absent in the KO mice. Another Se parameter measured (hepatic thioredoxin reductase activity) did not vary across groups. Although liver Fe was elevated in mice fed the high-Fe diet, liver TBARS was largely unaffected either by mouse genotype or diet fed. Moreover, plasma lipids were not elevated in the Fe-overloaded GPX1 KO mice. Thus, decreased GPX1 activity cannot account for the pro-oxidant hyperlipidemic effects observed earlier in mice fed the high-Fe Se-deficient diet. This suggests that impairment of Se functions other than GPX1 activity may be responsible for the elevated plasma lipids and hepatic TBARS seen in the Fe-overloaded Se-deficient mice.     

Effects of dietary selenium and vitamin E concentrations on phospholipid hydroperoxide glutathione peroxidase expression in reproductive tissues of pubertal maturing male rats

Phospholipid hydroperoxide glutathione peroxidase (PHGPX) is the second intracellular selenium (Se)-dependent glutathione peroxidase (GSH-Px) identified in mammals. Our objectives were to determine the effect of dietary vitamin E and Se levels on PHGPX activity expression in testis, epididymis, and seminal vesicles of pubertal maturing rats, and the relationship of PHGPX expression with testicular development and sperm quality. Forty Sprague-Dawley male weanling rats (21-d old), were initially fed for 3 wk a torula yeast basal diet (containing 0.05 mg Se/kg) supplemented with marginal levels of Se (0.1 mg/kg as Na₂SeO₃) and vitamin E (25 IU/kg as all-rac-α-tocopheryl acetate). Then, rats were fed the basal diets supplemented with 0 or 0.2 mg Se/kg and 0 or 100 IU vitamin E/kg diet during the 3-wk period of pubertal maturing. Compared with the Se-supplemented rats, those fed the Se-deficient diets retained 31, 88, 67, and 50% of Se-dependent GSH-Px activities in liver, testis, epididymis, and seminal vesicles, respectively. Testes and seminal vesicles had substantially higher (5-to 20-fold) PHGPX activity than liver. Dietary Se deficiency did not affect PHGPX activities in the reproductive tissues, but reduced PHGPX activity in liver by 28% (P < 0.0001). Dietary vitamin E supplementation did not affect PHGPX activity in liver, whereas it raised PHGPX activity in seminal vesicles by 43% (P < 0.005). Neither dietary vitamin E nor Se levels affected body weight gains, reproductive organ weights, or sperm counts and morphology. In conclusion, expression of PHGPX activity in testis and seminal vesicles was high and regulated by dietary Se and vitamin E differently from that in liver.     

Activation of superoxide dismutase in selenium-deficient mice infected with influenza virus.

Selenium (Se) deficiency is associated with decreased activities of Se-dependent antioxidant enzymes, glutathione peroxidase (GPx) and thioredoxin reductase (TR), and with changes in the cellular redox status. We have previously shown that host Se deficiency is responsible for increased virulence of influenza virus in mice due to changes in the viral genome. The present study examines the antioxidant defense systems in the lung and liver of Se-deficient and Se-adequate mice infected with influenza A/Bangkok/1/79. Results show that neither Se status nor infection changed glutathione (GSH) concentration in the lung. Hepatic GSH concentration was lower in Se-deficient mice, but increased significantly day 5 post infection. No significant differences due to Se status or influenza infection were found in catalase activities. As expected, Se deficiency was associated with significant decreases in GPx and TR activities in both lung and liver. GPx activity increased in the lungs and decreased in the liver of Se-adequate mice in response to infection. Both Se deficiency and influenza infection had profound effects on the activity of superoxide dismutase (SOD). The hepatic SOD activity was higher in Se-deficient than Se-adequate mice before infection. However, following influenza infection, hepatic SOD activity in Se-adequate mice gradually increased. Influenza infection was associated with a significant increase of SOD activity in the lungs of Se-deficient, but not Se-adequate mice. The maximum of SOD activity coincided with the peak of pathogenesis in infected lungs. These data suggest that SOD activation in the lung and liver may be a part of a compensatory response to Se deficiency and/or influenza infection. However, SOD activation that leads to increased production of H(2)O(2) may also contribute to pathogenesis and to influenza virus mutation in lungs of Se-deficient mice.     

克山病病区粮喂养大鼠红细胞膜脂流动性的变化

本文观察了低硒的克山病病区粮和克山病病区粮补硒后喂养大鼠对其红细胞膜脂流动性的影响。实验结果表明克山病病区粮喂养的大鼠红细胞膜脂流动性较正常对照降低,其原因可能与机体处于低硒状态下红细胞膜结合硒含量降低、红细胞膜胆固醇含量及脂质过氧化产物升高有关,克山病病区粮补硒后喂养大鼠,其红细胞膜脂流动性恢复至正常对照。     

Bioavailability of selenium from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine, and sodium selenite assessed in selenium-deficient rats

The bioavailability of selenium (Se) from veal, chicken, beef, pork, lamb, flounder, tuna, selenomethionine (SeMet), and sodium selenite was assessed in Se-deficient Fischer-344 rats. Se as veal, chicken, beef, pork, lamb, flounder, tuna, SeMet, and sodium selenite was added to torula yeast (TY) basal diets to comprise Se-inadequate (0.05 mg Se/kg) diets. Se as sodium selenite was added to a TY basal diet to comprise a Se-adequate (0.10 mg Se/kg), Se-control diet. The experimental diets were fed to weanling Fischer-344 rats that had been subjected to dietary Se depletion for 6 wk. After 9 wk of the dietary Se repletion, relative activity of liver glutathione peroxidase (GSHPx) from the different dietary groups compared with control rats (100%) was: flounder 106%, tuna 101%, pork 86%, sodium selenite 81%, SeMet 80%, beef 80%, chicken 77%, veal 77%, and lamb 58%. Se from flounder was the most efficient at restoring Se concentrations in the liver and skeletal muscle. Se from sodium selenite, SeMet, beef, veal, chicken, pork, lamb, and tuna was not dietarily sufficient to restore liver and muscle Se after 9 wk of recovery following a 6-wk period of Se depletion.