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The Nutritional Requirements and Toxicity to Fish of Dietary and Waterborne Selenium
Selenium is found throughout aquatic ecosystems but generally at very low concentrations. However,
there are examples of aquatic ecosystems affected by industrial activity that have selenium con
centrations at 5-100 times those found in clean areas. Therefore it is conceivable that there could be
both inadequate and excessive levels of selenium in aquatic environments. This paper reviews new
and published data to show that:
1. selenium is a nutrient for freshwater fish but, at levels observed in the water and food chain,
deficiencies are unlikely to occur;
2. dietary selenium is relatively more toxic than waterborne selenium and dietary toxicity to fish is
observed at concentrations close to those of food chain organisms;
3. uptake of selenium from the diet appears very efficient and independent of dietary loading, but
bioconcentration factors are limited at high dietary loadings by active excretion processes;
4. uptake of selenium from the water appears very efficient at low waterborne concentrations but
bioconcentration factors at high waterborne concentrations appear limited by saturation of gill
absorption processes. Elimination rates are passive so that bioconcentration factors are a
function of uptake rates rather than elimination rates; and
5. the tissue distribution of selenium varies with exposure concentration because the selenium
elimination rates of liver tissue decrease as exposure increases.
We speculate that waterborne selenium is stored predominantly in the inorganic form whereas
dietary selenium may be metabolized and stored as an organic form. As such, it may be more toxic
but more easily excreted than selenium taken up from water.
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Selenium accumulation, reproductive status, and histopathological changes in environmentally exposed redear sunfish
Comparisons were made of the accumulation of selenium, histopathological damage, and reproductive status of redear sunfish (Lepomis microlophus) collected in July 1986 from Martin Lake (a contaminated site) and Lake Tyler (a reference site). Hepatic concentrations of selenium were four times higher in Martin Lake sunfish (7.6±0.5 ppm) than in fish from the reference lake (2.1±0.2 ppm). Redears collected from the contaminated lake had lower condition factors than individuals collected from the reference site. Sunfish with elevated levels of hepatic selenium had substantial alterations in the liver including necrosis, cytoplasmic vacuolation, and Kupffer cell proliferation. The ovaries of mature fish collected from Martin Lake frequently had atretic follicles, abnormally shaped follicles, connective tissue hypertrophy, asynchronous oocyte development, and an overall reduction in the number of developing oocytes. These histopathological changes in the ovaries of Martin Lake sunfish were not accompanied by alterations in gonadal steroid titers in the blood. No histopathological lesions could be detected in the testes of Martin Lake fish. Most of the males collected from the contaminated site were immature and had lower circulating levels of sex steroid hormones than reference males. The results show that tissue burdens of selenium have declined by 25% since this sunfish population was sampled last in 1981. Further, the results of this study indicate that the overall health and reproductive status of selenium-contaminated fish collected from Martin Lake is still seriously impaired.
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Selenium replacement in patients with severe systemic inflammatory response syndrome improves clinical outcome
Critical Care Medicine:
September 1999 - Volume 27 - Issue 9 - pp 1807-1813
Clinical Investigations
Angstwurm, Matthias W. A. MD; Schottdorf, Juergen MS; Schopohl, Jochen MD; Gaertner, Roland MD
Objective: To determine the effect of selenium replacement on morbidity and mortality in patients with systemic inflammatory response syndrome (SIRS).
Design: Controlled, randomized prospective open-label pilot study comparing patients with and without selenium replacement.
Setting: Intensive care unit of a university hospital for internal medicine.
Conclusions: Selenium replacement in patients with SIRS seems to improve clinical outcome and to reduce the incidence of acute renal failure requiring hemodialysis.
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Selenium in Intensive Care (SIC): Results of a prospective randomized, placebo-controlled, multiple-center study in patients with severe systemic inflammatory response syndrome, sepsis, and septic shock*
Critical Care Medicine:
January 2007 - Volume 35 - Issue 1 - pp 118-126
doi: 10.1097/01.CCM.0000251124.83436.0E
Clinical Investigations
Angstwurm, Matthias W. A. MD; Engelmann, Lothar MD; Zimmermann, Thomas MD; Lehmann, Christian MD; Spes, Christoph H. MD; Abel, Peter MD; Strau, Richard MDß; Meier-Hellmann, Andreas MD; Insel, Rudolf MD; Radke, Joachim MD; Schüttler, Jürgen MD; Gärtner, Roland MD
Objective: Sepsis is associated with an increase in reactive oxygen species and low endogenous antioxidative capacity. We postulated that high-dose supplementation of sodium-selenite would improve the outcome of patients with severe sepsis and septic shock.
Design: Prospective randomized, placebo-controlled, multiple-center trial.
Setting: Eleven intensive care units in Germany.
Patients: Patients were 249 patients with severe systemic inflammatory response syndrome, sepsis, and septic shock and an Acute Physiology and Chronic Health Evaluation (APACHE) III score >70.
Interventions: Patients received 1000 μg of sodium-selenite as a 30-min bolus injection, followed by 14 daily continuous infusions of 1000 μg intravenously, or placebo.
Conclusions: The adjuvant treatment of patients with high-dose sodium-selenite reduces mortality rate in patients with severe sepsis or septic shock.
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Selenium Deficiency and Toxicity in the Environment.
Fordyce, F. M. (2012). Essentials of Medical Geology, 375–416. doi:10.1007/978-94-007-4375-5_16
Selenium (Se) is a naturally occurring metalloid element,
which is essential to human and other animal health in trace
amounts but is harmful in excess. Of all the elements, selenium
has one of the narrowest ranges between dietary defi-
ciency (<40 mg day ) and toxic levels (>400 ug day*)
(WHO 1996), which makes it necessary to carefully control
intakes by humans and other animals, hence, the importance
of understanding the relationships between environmental
exposure and health.
* Disputed.
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Would selenium supplementation aid in therapy for Chagas Disease?
Chagas disease, a neglected tropical disease discovered over 100 years ago, is caused by the intracellular parasite Trypanosoma cruzi and is most frequently associated with chronic cardiomyopathy and digestive disorders. Initial invasion of cells is followed by progressive inflammatory destruction of heart, muscles, nerves, and gastrointestinal (GI) tract tissue. Approximately 30% of patients progress to a chronic cardiomyopathy associated with increased morbidity and mortality. Seven to 10% of patients develop megasyndromes involving the GI tract, in particular, the esophagus and the colon. Results from several studies suggest that selenium (Se) deficiency could be an important factor in the pathogenesis of Chagas disease. In this opinion article, Se supplementation is proposed as an adjuvant therapy for treatment of chronic Chagas disease.
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Coping with two-headed fish and other effects of selenium
Both humans and animals need tiny amounts for good health, but too much is dangerous. In areas with a lot of selenium in the soil, including Utah's Middle Green River Basin and Nevada's Stillwater National Wildlife Refuge, activities that bring soil into contact with water -- irrigating, mining, drilling and road building -- boost natural concentrations, and can cause illness and deformities in people, livestock and wildlife.
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The pathology of selenium deficiency in Cyprinus carpio L.
360 juvenile carp were allocated to three treatments. Each treatment containing 120 fish was randomly divided into four groups, fed with purified diets containing selenium at 0, 0.15, 0.30 and 0.45 mg kg(-1). The results indicated that the morbidity and mortality rates of the test groups were negatively correlated with the level of selenium in the diets. The morbidity and mortality rates were, respectively, 46.7%, 33.3%, 13.3%, 0 and 26.7% 16.7%, 6.7%, 0.
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Too much selenium is bad for reproduction
High Hg reduced the growth and survival of female fish, but these effects were largely prevented with high Se.
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A small-molecule antivirulence agent for treating Clostridium difficile infection
Clostridium difficile infection (CDI) is a worldwide health threat that is typically triggered by the use of broad-spectrum antibiotics, which disrupt the natural gut microbiota and allow this Gram-positive anaerobic pathogen to thrive. The increased incidence and severity of disease coupled with decreased response, high recurrence rates, and emergence of multiple antibiotic-resistant strains have created an urgent need for new therapies. We describe pharmacological targeting of the cysteine protease domain (CPD) within the C. difficile major virulence factor toxin B (TcdB). Through a targeted screen with an activity-based probe for this protease domain, we identified a number of potent CPD inhibitors, including one bioactive compound, ebselen, which is currently in human clinical trials for a clinically unrelated indication. This drug showed activity against both major virulence factors, TcdA and TcdB, in biochemical and cell-based studies. Treatment in a mouse model of CDI that closely resembles the human infection confirmed a therapeutic benefit in the form of reduced disease pathology in host tissues that correlated with inhibition of the release of the toxic glucosyltransferase domain (GTD). Our results show that this non-antibiotic drug can modulate the pathology of disease and therefore could potentially be developed as a therapeutic for the treatment of CDI.
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Selenium Supplementation in Fish: A Combined Chemical and Biomolecular Study to Understand Sel-Plex Assimilation and Impact on Selenoproteome Expression in Rainbow Trout (Oncorhynchus mykiss)
Selenium (Se) is an essential oligonutrient, as a component of several Se-containing proteins (selenoproteins), which exert important biological functions within an organism. In livestock, Se-enriched products have been proposed as dietary supplements to be included into functional feeds for animal preventive health care. To this end, it is important to understand the optimal range of concentrations for supplementation and how long it takes to be assimilated into the organism.
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The human body absorbs more than 90% of selenomethionine but only about 50% of selenium from selenite
Selenium is available in multivitamin/multimineral supplements and as a stand-alone supplement, often in the forms of selenomethionine or of selenium-enriched yeast (grown in a high-selenium medium) or as sodium selenite or sodium selenate [2,5,6]. The human body absorbs more than 90% of selenomethionine but only about 50% of selenium from selenite [6].
Few studies have compared the relative absorption and bioavailability of different forms of selenium. In one investigation, 10 groups of selenium-replete subjects were randomly assigned to receive a placebo or either 200 or 600 mcg/day selenium as selenomethionine, sodium selenite, or high-selenium yeast (in which an estimated 75% of selenium was in the form of selenomethionine) for 16 weeks [16]. Selenium bioavailability, based on urinary excretion, was greatest for selenomethionine and lowest for selenite. However, supplementation with any of these forms only affected plasma selenium levels and not glutathione peroxidase activity or selenoprotein P concentration, confirming that study participants were selenium replete before they began taking selenium supplements.
In the United States, 18% to 19% of adults and children use a dietary supplement containing selenium
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Dietary Selenium in Adjuvant Therapy of Viral and Bacterial Infections
Viral and bacterial infections are often associated with deficiencies in macronutrients and micronutrients, including the essential trace element selenium. In selenium deficiency, benign strains of Coxsackie and influenza viruses can mutate to highly pathogenic strains. Dietary supplementation to provide adequate or supranutritional selenium supply has been proposed to confer health benefits for patients suffering from some viral diseases, most notably with respect to HIV and influenza A virus (IAV) infections. In addition, selenium-containing multimicronutrient supplements improved several clinical and lifestyle variables in patients coinfected with HIV and Mycobacterium tuberculosis. Selenium status may affect the function of cells of both adaptive and innate immunity. Supranutritional selenium promotes proliferation and favors differentiation of naive CD4-positive T lymphocytes toward T helper 1 cells, thus supporting the acute cellular immune response, whereas excessive activation of the immune system and ensuing host tissue damage are counteracted through directing macrophages toward the M2 phenotype. This review provides an up-to-date overview on selenium in infectious diseases caused by viruses (e.g., HIV, IAV, hepatitis C virus, poliovirus, West Nile virus) and bacteria (e.g., M. tuberculosis, Helicobacter pylori). Data from epidemiologic studies and intervention trials, with selenium alone or in combination with other micronutrients, and animal experiments are discussed against the background of dietary selenium requirements to alter immune functions.
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Selenium levels in fish raise concerns about pollution from Red Chris mine
Selenium levels have doubled in fish samples taken from Ealue Lake near the Red Chris copper mine in northwestern British Columbia, raising concerns about a naturally occurring chemical element that can be toxic to aquatic life.
The source of the selenium pollution hasn't been determined and the levels are not high enough to pose a human-health concern. But selenium can cause deformities or reproductive failure in fish and that is raising alarms in the small native community of Iskut, near the mine operated by Imperial Metals.
"Until further tests are done by the mine … we are advising you to not fish in Ealue Lake & at this point suggesting Eddontenajon [Lake] as well," Iskut band councillor Jodi Payne wrote in a recent Facebook posting. "I don't want to cause a huge panic right now, just know we have been made aware and made this a priority to assure it gets dealt with ASAP."
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Genetic Adaptation and Selenium Uptake in Vertebrates
Of the essential micronutrients, selenium is unusual in that it has a
very narrow margin between nutritionally optimal and potentially
toxic (Wilber, 1980), making its uneven environmental distribution
a challenge to the needs of the vertebrate diet.
In humans, mild selenium deficiency can cause immune dysfunction,
reduced fertility, cognitive decline and increased risk of
mortality (Rayman, 2012). In severely selenium-deficient parts
of China, a disease of the heart muscle (Keshan disease), which
has a high mortality rate in children, and a disabling disease of
the bone and cartilage (Kashin–Beck disease).
Levels of selenium in waters worldwide also vary a hundredfold
(Selinus et al., 2005), but oceans, seas and other aquatic
environments are generally an environmental sink for land
selenium (Selinus et al., 2005) with inorganic forms of selenium
being rapidly and efficiently bioaccumulated in phytoplankton
(100–1 000 000-fold enrichment from the water concentration
(Stewart et al., 2010)) and converted into organic forms of selenium
that can enter the animal diet (Ogle et al., 1988). Indeed,
selenium bioaccumulation through the aquatic food chain has
made fish foods a major source of selenium in the human diet.
Thus, vertebrate species from different land and aquatic environments
have evolved under different levels of selenium in their
diets.
The element selenium (with symbol Se) was first discovered in
1817, and owing to its similarity to tellurium (named after Tellus,
the Roman god of the earth), it was named after the titanic goddess
of the moon, Selena (Berzelius, 1818). The role of selenium
in biology was, however, neither discovered nor investigated
until much later. Once selenium started being heavily used in
various industries in the late nineteenth century, its toxic effect on
humans came to the foreground (Dudley, 1938). In the 1930s, a
systematic study of poisoning symptoms of farm animals showed
their feed and the soil in which it is grown to have toxic levels of
selenium (Painter, 1941). Yet, it wasn’t until 1957 that selenium
was seen as an element essential to life despite its toxicity when
ingested in large amounts (Schwarz and Foltz, 1957).
While the approaches required to correctly identify selenoproteins
have been known for many years, most genomic databases
still wrongly annotate selenium-containing genes. This is mainly
because most databases use the UGA codon, a termination codon,
to identify the end of the open reading frame (ORF) (see Glossary)
of each gene and ignore the possibility of the codon being
in-frame and co-translationally incorporating selenocysteine. To
address this problem, dedicated databases to selenoprotein genes
now exist.
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Dietary Selenium Deficiency or Excess Reduces Sperm Quality and Testicular mRNA Abundance of Nuclear Glutathione Peroxidase 4 in Rats
Methods: After weaning, male Sprague-Dawley rats were fed a Se-deficient basal diet (BD) for 5 wk until they were 9 wk old [mean ± SEM body weight (BW) = 256 ± 5 g]. They were then fed the BD diet alone (deficient) or with 0.25 (adequate), 3 (excess), or 5 (excess) mg Se/kg for 4 wk. Testis, liver, blood, and semen were collected to assay for selenoprotein mRNA and protein abundances, selenium concentration, GPX activity, 8-hydroxy-deoxyguanosine concentration, and sperm quality.
Results: Dietary selenium supplementations elevated (P < 0.05) tissue selenium concentrations and GPX activities. Compared with those fed BD + 0.25 mg Se/kg, rats fed BD showed lower (P < 0.05) BW gain (86%) and sperm density (57%) but higher (P < 0.05) plasma 8-hydroxy-deoxyguanosine concentrations (189%), and nonprogressive sperm motility (4.4-fold). Likewise, rats fed BD + 5 mg Se/kg had (P = 0.06) lower BW gain and higher (1.9-fold) sperm deformity rates than those in the selenium-adequate group. Compared with the selenium-adequate group, dietary selenium deficiency (BD) or excess (BD + 3 or 5 mg Se/kg) resulted in 45–77% lower (P < 0.05) nuclear Gpx4 (nGpx4) mRNA abundance in the testis. Rats fed BD had lower (P < 0.05) mRNA levels of 2 Selenop variants in both testis and liver than those in the other groups. Testicular SELENOP was 155–170% higher (P < 0.05) in rats fed BD + 5 mg Se/kg and hepatic c/mGPX4 was 13–15% lower (P < 0.05) in rats fed BD than in the other groups.
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Selenium as a Protective Agent against Pests: A Review
The aim of the present review is to summarize selenium’s connection to pests. Phytopharmaceuticals for pest control, which increase the pollution in the environment, are still widely used nowadays regardless of their negative characteristics. The use of trace elements, including selenium, can be an alternative method of pest control. Selenium can repel pests, reduce their growth, or cause toxic effects while having a positive effect on the growth of plants. In conclusion, accumulated selenium protects plants against aphids, weevils, cabbage loopers, cabbage root flies, beetles, caterpillars, and crickets due to both deterrence and toxicity.
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Europeans are in need of selenium
British researcher Professor Margaret P. Rayman, University of Surrey, Guildford, published a report called “Selenium and Human Health” in The Lancet. In her report, Rayman points, among other things, to the interesting fact that in low-selenium areas like Europe there seems to be clear benefits associated with increased selenium intake.
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Selenium and Selenoproteins - Impact of Statins
by Duane Graveline, MD, MPH
The predominant biochemical action of selenium in humans is to serve as an antioxidant via the selenium-dependent enzyme, glutathione peroxidase, and thus protect cellular membranes and organelles from peroxidative damage.
In the absence of this antioxidant, mitochondrial lipid peroxidation results in a marked loss of both cytochrome c oxidase activity and cardiolipin content, offering yet another mechanism by which statins adversely affect mitochondria.
Bottom line of this technical jargon is the reality of more reduced adenosine triphosphate (ATP) and increased mitochondrial damage from reactive oxygen species (ROS).
I have warned in other articles that the primary effect of statins on the mevalonate pathway was to inhibit CoQ10 availability for antioxidation at complexes I and II of the mitochondria.
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Effect of Micronutrient Supplementation on Mood in Nursing Home Residents
One third of older people in nursing and/or residential homes have significant symptoms of depression. In younger people, deficiencies in selenium, vitamin C and folate are associated with depression. This study examines the association between micronutrient status and mood before and after supplementation. The objective was to determine whether the administration of selenium, vitamin C and folate improved mood in frail elderly nursing home residents. Mood was assessed using the Hospital Anxiety and Depression rating scale (HAD), and Montgomery-Åsberg Depression Rating Scale (MADRS). Micronutrient supplementation was provided for 8 weeks in a double-blinded randomised controlled trial. Significant symptoms of depression (29%) and anxiety (24%) were found at baseline. 67% of patients had low serum concentrations of vitamin C, but no-one was below the reference range for selenium. Depression was significantly associated with selenium levels, but not with folate or vitamin C levels. No individual with a HAD depression score of ≧8, had selenium levels >1.2 µM. In those patients with higher HAD depression scores, there was a significant reduction in the score and a significant increase in serum selenium levels after 8 weeks of micronutrient supplementation. Placebo group scores were unchanged. This small study concluded that depression was associated with low levels of selenium in frail older individuals. Following 8 weeks of micronutrient supplementation, there was a significant increase in selenium levels and improved symptoms of depression occurred in a subgroup.
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Dietary vitamins and selenium diminish the development of mechanically induced osteoarthritis and increase the expression of antioxidative enzymes in the knee joint of STR/1N mice.
A diet supplemented with vitamins/selenium might be important in prevention or therapy of mechanically induced OA. We hypothesize that free oxygen radical species might be involved in the mechanical induction of OA.
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