Selenium and the brain: a review

Assessment of dietary Selenium and its role in Mercury fate in cultured fish rainbow trout with two sustainable aquafeeds

This study enhances the current limited understanding of the interaction between mercury (Hg) and selenium (Se) species in fish. Rainbow trout (Oncorhynchus mykiss), a model aquaculture fish, was exposed to Hg and Se species through controlled dietary conditions. Over a 6-month feeding trial, the impact of dietary Se on Hg bioaccumulation in fish, including flesh, brain, and liver, was tracked. Twelve dietary conditions were tested, including plant-based diets (0.25 µgSe g-1) and tuna byproduct diets (0.25 µgHg g-1, 8.0 µgSe g-1) enriched with methylmercury and/or Se as selenite or selenomethionine. The tuna byproduct diet resulted in lower Hg levels than the plant-based diets, with muscle Hg content below the European Commission's safe threshold. This study highlights the significant impact of specific Se compounds in the diet, particularly from tuna-based aquafeed, on Hg bioaccumulation. These promising results provide a strong recommendation for future use of fisheries byproducts in sustainable aquafeeds.

Prenatal Metal Exposures and Child Social Responsiveness Scale Scores in 2 Prospective Studies

Background

Prenatal exposure to metals is hypothesized to be associated with child autism. We aim to investigate the joint and individual effects of prenatal exposure to urine metals including lead (Pb), mercury (Hg), manganese (Mn), and selenium (Se) on child Social Responsiveness Scale (SRS) scores.

Methods

We used data from 2 cohorts enriched for likelihood of autism spectrum disorder (ASD): Early Autism Risk Longitudinal Investigation (EARLI) and the Markers of Autism Risk in Babies-Learning Early Signs (MARBLES) studies. Metal concentrations were measured in urine collected during pregnancy. We used Bayesian Kernel Machine Regression and linear regression models to investigate both joint and independent associations of metals with SRS Z-scores in each cohort. We adjusted for maternal age at delivery, interpregnancy interval, maternal education, child race/ethnicity, child sex, and/or study site.

Results

The final analytic sample consisted of 251 mother-child pairs. When Pb, Hg, Se, and Mn were at their 75th percentiles, there was a 0.03 increase (95% credible interval [CI]: -0.11, 0.17) in EARLI and 0.07 decrease (95% CI: -0.29, 0.15) in MARBLES in childhood SRS Z-scores, compared to when all 4 metals were at their 50th percentiles. In both cohorts, increasing concentrations of Pb were associated with increasing values of SRS Z-scores, fixing the other metals to their 50th percentiles. However, all the 95% credible intervals contained the null.

Conclusions

There were no clear monotonic associations between the overall prenatal metal mixture in pregnancy and childhood SRS Z-scores at 36 months. There were also no clear associations between individual metals within this mixture and childhood SRS Z-scores at 36 months. The overall effects of the metal mixture and the individual effects of each metal within this mixture on offspring SRS Z-scores might be heterogeneous across child sex and cohort. Further studies with larger sample sizes are warranted.

Potential role of selenium in modifying the effect of maternal methylmercury exposure on child neurodevelopment - A review

Selenium (Se) is an essential trace element for normal neurodevelopment. It is incorporated into multiple selenoenzymes which have roles in the brain and neurological function, the synthesis of thyroid hormones, the antioxidant defense system, DNA synthesis, and reproduction. Fish is a source of both Se and neurotoxic methylmercury (MeHg). Selenium is known to ameliorate the effects of MeHg in experimental animals, but studies in children exposed to both Se and MeHg through prenatal fish consumption have been inconclusive. Research on Se's implications for pregnancy and child neurodevelopment is limited. The aims of this review are to summarize the literature on the biological roles of Se during pregnancy and the potential role in mitigating the effects of MeHg exposure from fish consumption on human health. This review has shown that Se concentrations among pregnant women globally appear insufficient, with the majority of pregnant women reporting Se concentrations below 70 µg/L during pregnancy. The role of Se in child development and its interactions with MeHg in children are inconclusive. Further investigation of the interaction between Se and MeHg in relation to child neurodevelopment in high fish-eating populations is required to fully elucidate effects.

Effects of Dietary Selenium Yeast Supplementation on Oxidative Biomarkers of the Brain and Blood in Goats

The present study evaluated the effects of dietary selenium yeast (SY) on the brain, CSF, and blood of 30 crossbreed goats (5-6 months of age) of both sexes. After the acclimatization of 2 weeks, they were randomly separated into two groups (n = 15) named C and SY groups. The C group received only a basal diet, while SY received a basal diet along with 0.3 mg/kg/diet of SY (Sel-Plex®) in total 0.035 mg/kg/diet of SY for 10 weeks. Se concentration (µg /g dry weight) in 15 different parts of the goat's brain was accessed, and results showed that the highest concentration was found in the occipital cerebrum (322.0 ± 6.146), whereas the lowest concentration was found in the midbrain (10.33 ± 0.232). Besides, the oxidative biomarkers including GSH (12.13 ± 0.191), GSH-Px (206.7 ± 2.362), GST (23.80 ± 0.279), CAT (14.80 ± 0.279), and SOD (152.5 ± 9.540) were increased in SY as compared to GSH (8.200 ± 0.144), GSH-Px (112.9 ± 1.183), GST (18.93 ± 0.284), CAT (12.53 ± 0.215), and SOD (109.0 ± 1.966) of C. The level of cholesterol was also significantly decreased in the serum of the SY group (84.87 ± 0.960) as compared to C (110.5 ± 0.592). In addition, the cholesterol level in CSF decreased significantly in SY (0.3567 ± 0.016) as compared to C (0.509 ± 0.009). The current research suggests that SY supplementation has improved the brain's antioxidant status, blood biochemistry, and cholesterol levels in both serum and CSF of goats.

Association of dietary mineral mixture with depressive symptoms: A combination of Bayesian approaches

The relationships between mixtures of multiple minerals and depression have not been explored. Therefore, we analyzed the relationship between the mixture of nine dietary minerals [calcium (Ca), phosphorus, magnesium (Mg), iron (Fe), zinc, copper (Cu), sodium, potassium (K), and selenium (Se)] and depressive symptoms in the general population. We screened 20,342 participants from the National Health and Nutrition Examination Survey (NHANES) 2007-2018. We fitted the general linear regression, Bayesian kernel machine regression (BKMR), and Bayesian semiparametric regression models to explore associations and interactions. We obtained the relative importance of dietary minerals by calculating posterior inclusion probabilities (PIPs). The dietary intakes of minerals were obtained using the 24-h dietary recall interview, and depressive symptoms were assessed using the Patient Health Questionnaire-9 (PHQ-9). The linear analysis showed that nine minerals were negatively associated with PHQ-9 scores. The BKMR analysis showed a negative association between the dietary mineral mixture and PHQ-9 scores, with Se having the largest PIP at 1.0000, followed by K (0.7784). We also observed potential interactions between Ca and Fe, Se and Fe, and K and Mg. Among them, the interaction of Ca and Fe had the largest PIP of 0.986. In addition, the overall effect was more pronounced in females than males, and Cu's PIP (0.8376) was higher in females. Two sensitivity analyses showed that our results were robust. Our study provides a basis for formulating nutritional intervention programs for depression in the future.

Association of Selenium Levels with Neurodegenerative Disease: A Systemic Review and Meta-Analysis

BACKGROUND

Neurodegenerative diseases (NDs) have posed significant challenges to public health, and it is crucial to understand their mechanisms in order to develop effective therapeutic strategies. Recent studies have highlighted the potential role of selenium in ND pathogenesis, as it plays a vital role in maintaining cellular homeostasis and preventing oxidative damage. However, a comprehensive analysis of the association between selenium and NDs is still lacking.

METHOD

Five public databases, namely PubMed, Web of Science, EMBASE, Cochrane and Clinical Trials, were searched in our research. Random model effects were chosen, and Higgins inconsistency analyses (I2), Cochrane's Q test and Tau2 were calculated to evaluate the heterogeneity.

RESULT

The association of selenium in ND patients with Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS) and Huntington's disease (HD) was studied. A statistically significant relationship was only found for AD patients (SMD = -0.41, 95% CI (-0.64, -0.17), p < 0.001), especially for erythrocytes. However, no significant relationship was observed in the analysis of the other four diseases.

CONCLUSION

Generally, this meta-analysis indicated that AD patients are strongly associated with lower selenium concentrations compared with healthy people, which may provide a clinical reference in the future. However, more studies are urgently needed for further study and treatment of neurodegenerative diseases.

Dissecting the microbial community structure of internal organs during the early postmortem period in a murine corpse model

BACKGROUND

Microorganisms distribute and proliferate both inside and outside the body, which are the main mediators of decomposition after death. However, limited information is available on the postmortem microbiota changes of extraintestinal body sites in the early decomposition stage of mammalian corpses.

RESULTS

This study investigated microbial composition variations among different organs and the relationship between microbial communities and time since death over 1 day of decomposition in male C57BL/6 J mice by 16S rRNA sequencing. During 1 day of decomposition, Agrobacterium, Prevotella, Bacillus, and Turicibacter were regarded as time-relevant genera in internal organs at different timepoints. Pathways associated with lipid, amino acid, carbohydrate and terpenoid and polyketide metabolism were significantly enriched at 8 h than that at 0.5 or 4 h. The microbiome compositions and postmortem metabolic pathways differed by time since death, and more importantly, these alterations were organ specific.

CONCLUSION

The dominant microbes differed by organ, while they tended toward similarity as decomposition progressed. The observed thanatomicrobiome variation by body site provides new knowledge into decomposition ecology and forensic microbiology. Additionally, the microbes detected at 0.5 h in internal organs may inform a new direction for organ transplantation.

The Role and Mechanism of Essential Selenoproteins for Homeostasis

Selenium (Se) is one of the essential trace elements that plays a biological role in the body, mainly in the form of selenoproteins. Selenoproteins can be involved in the regulation of oxidative stress, endoplasmic reticulum (ER) stress, antioxidant defense, immune and inflammatory responses and other biological processes, including antioxidant, anti-inflammation, anti-apoptosis, the regulation of immune response and other functions. Over-loading or lack of Se causes certain damage to the body. Se deficiency can reduce the expression and activity of selenoproteins, disrupt the normal physiological function of cells and affect the body in antioxidant, immunity, toxin antagonism, signaling pathways and other aspects, thus causing different degrees of damage to the body. Se intake is mainly in the form of dietary supplements. Due to the important role of Se, people pay increasingly more attention to Se-enriched foods, which also lays a foundation for better research on the mechanism of selenoproteins in the future. In this paper, the synthesis and mechanism of selenoproteins, as well as the role and mechanism of selenoproteins in the regulation of diseases, are reviewed. Meanwhile, the future development of Se-enriched products is prospected, which is of great significance to further understand the role of Se.

Are Essential Trace Elements Effective in Modulation of Mental Disorders? Update and Perspectives

The emergence of mental disorders is associated with several risk factors including genetic and environmental susceptibility. A group of nutrients serves an especially important role in a number of essential neurodevelopmental processes through brain areas promoting the high degree of brain metabolism during early life, although almost all nutrients are needed. These include macronutrients and micronutrients (e.g., iron, magnesium, zinc, copper, selenium). Numerous nutritional psychiatry trials have been performed to examine the correlation of many individual nutrients with mental health, such as essential trace elements. The increased accumulation or lack of such components will facilitate an alternative metabolic pathway that can lead to many diseases and conditions of neurodevelopment. Mental functions have biochemical bases, so the impairment of such neurochemical mechanisms due to lack of trace elements can have mental effects. In psychological conditions such as depression, anxiety, schizophrenia, and autism, scientific studies demonstrate the putative role of trace element deficiency. Therefore, given the critical roles played by essential trace elements in the neurodevelopment and mental health, the effect of these elements' intake on the modulation of psychological functioning is reviewed.

Effect of antioxidant, malondialdehyde, macro-mineral, and trace element serum concentrations in Bangladeshi patients with schizophrenia: A case-control study

BACKGROUND

Schizophrenia (SCZ) is an incurable neuropsychiatric disorder generally described by impaired social behavior and altered recognition of reality. For the first time, this study explored serum levels of antioxidants (vitamin A, E, and C), malondialdehyde (MDA), macro-minerals (calcium, potassium, and sodium), and trace elements (zinc, iron, and selenium) in Bangladeshi patients with SCZ and thereby, discovering any pathophysiological correlation.

METHODS

This case-controlled study evaluated 63 patients with SCZ as cases and 63 healthy individuals as controls. Vitamin A and E levels were defined by RP-HPLC. MDA and vitamin C levels were measured by using UV spectrophotometry, and macro and trace elements by atomic absorption spectroscopy.

RESULTS

This study found significantly (P ≤ 0.05) elevated MDA levels and decreased levels of antioxidants-vitamin A, C, and E and significantly (P ≤ 0.05) diminished levels of macro and trace elements in cases in contrast to the controls. Serum levels of zinc (Zn), selenium (Se), iron (Fe), potassium (K), calcium (Ca), and sodium (Na) were determined to be 0.33 ± 0.008, 0.0252 ± 0.00060, 0.24 ± 0.01, 64.18 ± 2.72, 36.88 ± 2.56, and 2657.5 ± 53.32 mg/L, respectively, in cases, whereas 0.79 ± 0.03, 0.0650 ± 0.00355,0.78 ± 0.03, 168.01 ± 2.85, 86.43 ± 2.55, and 3200.8 ± 29.96 mg/L, respectively, were determined in controls. Pearson's correlation analysis revealed a negative correlation between Zn and Na, Zn and K, Zn and Ca, Zn and Fe, Zn and Se, Fe and Na, and Fe and Se in patients.

CONCLUSIONS

The findings connect that the pathogenesis of SCZ may have a correlation with altered levels of antioxidants, MDA, macro-minerals, and trace elements.

Nutrition and neurodevelopment: the search for candidate nutrients in the Seychelles Child Development Nutrition Study

This review examines the role of nutrients in child development and outlines the key nutrients identified as potentially important to neurodevelopment among high fish consumers in the Seychelles Child Development Nutrition Study (SCDNS). It describes the clinical assessment of these nutrients in the blood and breast milk samples collected from the cohort of 300 pregnant women who were recruited, at their first antenatal visit, on the SCDNS. These key nutrients include the long chain polyunsaturated fatty acids (LCPUFA), docosohexaenoic acid (DHA) and arachidonic acid (AA), both of which may affect neurodevelopment in the later stages of fetal growth. Only DHA, however, is strongly associated with fish consumption, the predominant source of the neurotoxicant methyl mercury (MeHg). Any benefits of increased selenium status on neurodevelopment are likely to accrue via detoxification of MeHg during fetal growth, while benefits of optimal iodine or thyroid status are likely to be directly related to neurodevelopment during late fetal growth. Unlike LCPUFA, Se, and I, the status of the B vitamins, folate, vitamin B12, vitamin B6, and riboflavin are unlikely to be closely related to fish consumption but the status of each of these B vitamins is likely to impinge on overall status of choline, which is expected to have direct effects on neurodevelopment both prenatally and postnatally and may also impact on MeHg toxicity. Choline status, together with the status of two other candidate nutrients, zinc and copper, which are also likely to have effects on neurodevelopment prenatally and postnatally, are expected to have some correlation with fish consumption.

Selenium intake and status of postpartum women and postnatal depression during the first year after childbirth in New Zealand - Mother and Infant Nutrition Investigation (MINI) study

BACKGROUND

Selenium (Se) plays an important role in selenoproteins as an antioxidant, and is involved in thyroid function, mental health and child development. Selenium is low in the local food supplies in NZ. Low selenium intake has been reported in women of childbearing age and postmenopausal women, however, there is little research relating to breastfeeding women and their infants.

PURPOSE

The study investigates maternal and infant selenium intake and status during the first year postpartum, and possible relationships to postnatal depression and anxiety.

BASIC PROCEDURES

The Mother and Infant Nutrition Investigation (MINI) study is an observational longitudinal cohort study. In total 87 breastfeeding mother-infant pairs were recruited and followed up at 3, 6 and 12 months postpartum. Maternal selenium intake was estimated from a four-day diet diary (4DDD). Selenium concentrations were measured in maternal spot urine, breastmilk and plasma; and infant spot urine samples. Postnatal depression was screened by the Edinburgh Postnatal Depression Scale (EPDS) questionnaire.

MAIN FINDINGS

Median maternal selenium intake was 62 (50, 84) μg/day, with 56 % below the Estimated Average Requirement (EAR) of 65 μg/day. At 3, 6, and 12 months postpartum, median maternal urinary selenium:creatinine ratios were 29.0 (22.4, 42.0), 29.5 (23.1, 28.4), and 30.9 (24.3, 35.3) μg/g; median infant urinary selenium concentrations (IUSC) were 8 (6,13), 11 (6, 15), and 24 (10, 40) μg/L; median breastmilk selenium concentrations (BMSC) were 13 (11, 14), 11 (9, 11) and 12 (11, 13) μg/L; 18 %, 11 % and 14 % of women reported probable minor depression based on the EPDS scores equal or above 10. Estimated median infant selenium intake at 3 and 6 months were 9 (8, 11) and 8 (7, 10) μg/day with 85 % and 93 % below the Adequate Intake of 12 μg/day. Median maternal plasma selenium was 105.8 μg/L at 6 months postpartum. Minor depression at three months postpartum was significantly different across tertiles of plasma selenium concentrations (p = 0.041).

PRINCIPLE CONCLUSIONS

Suboptimal selenium intake was observed among breastfeeding mothers and their infants in the MINI study. Potentially, some women had insufficient selenium status. Relation between selenium status and risk of postnatal depression and anxiety was inconclusive.Further research is required to explore effects on maternal thyroid function and infant neurodevelopment among women with inadequate selenium intake and status.

Impact of selenium co-administration on methylmercury exposed eleutheroembryos and adult zebrafish (Danio rerio): Changes in bioaccumulation and gene expression

Mercury still represents one of the most hazardous threats for the aquatic ecosystem due to its high toxicity, and the fact that it can be easily incorporated into the food chain by accumulation in fish as MeHg. On the other hand, selenium is a micronutrient that is part of different antioxidant enzymes that regulate the cellular redox state, and whose complex interaction with Hg has been extensively studied from a toxicological point of view. In order to evaluate the protective effect of Se(IV) co-administration against MeHg accumulation and toxicity, we have selected an in-vivo model at two developmental stages: zebrafish eleutheroembryos and adult fish. Embryos were exposed during 48 h to MeHg (5 or 25 μg/l) and a concentration of Se (IV) representing a molar ratio close to one (2.5 or 12.5 μg/l), while adult zebrafish were exposed during 72 h to either 25 μg/l of MeHg alone or co-exposed with 12.5 μg/l of Se (IV). A significant decrease in MeHg bioaccumulation factor was observed in eleutheroembryos co-exposed to Se(IV). A time-dependent accumulation of MeHg was observed in all the analyzed organs and tissues of adult fish, which was significantly reduced in the muscular tissue and the intestine by Se(IV) co-administration. However, such protection against MeHg bioaccumulation was not maintained in the brain and liver. The data derived from the gene expression analysis also demonstrated the protective effect of Se(IV) against MeHg-induced oxidative stress and the activation of different defense mechanisms by Se(IV) co-administration.

Effects of Selenium and Cadmium on Breast Muscle Fatty-Acid Composition and Gene Expression of Liver Antioxidant Proteins in Broilers

The present work was part of a project intended to evaluate whether organic selenium (Se) has the potential to protect against toxic effects exerted by cadmium (Cd). For this reason, 300 as-hatched, one-day-old broiler chickens were randomly allocated in four dietary treatments with five replicate pens per treatment. Chickens in T1 treatment, were offered a diet supplemented with 0.3 ppm Se (as Se-yeast), without added Cd; in T2 treatment, they were offered a diet with 0.3 ppm Se and 10 ppm Cd; in T3 treatment, they were offered a diet with 0.3 ppm Se and 100 ppm Cd; in T4 treatment, chickens were offered a diet supplemented with 3 ppm Se and 100 ppm Cd. Cadmium was added to the diets in T2, T3, and T4 as CdCl₂. On the fourth and sixth weeks, liver and breast samples were obtained from two broilers per replicate pen. Relative gene expression levels of catalase (CAT), superoxide dismutase 1 (SOD1) and 2 (SOD2), methionine sulfoxide reductase A (MSRA) and B3 (MSRB3), iodothyronine deiodinase 1 (DIO1), 2 (DIO2), and 3 (DIO3), glutathione peroxidase 1 (GPX1) and 4 (GPX4), thioredoxin reductase 1 (TXNRD1) and 3 (TXNRD3), and metallothionein 3 (MT3) were analyzed by real-time quantitative PCR in liver, whereas the fatty-acid (FA) profile of breast muscle was determined by gas chromatography. Broilers supplemented with 0.3 ppm Se could tolerate low levels of Cd present in the diets, as there were no significant changes in the breast muscle FA profile, whereas excess Cd led to decreased polyunsaturated fatty acids (PUFAs), and in particular n-6 PUFA. Furthermore, treatments mainly affected the messenger RNA (mRNA) expression of SOD2, TXNRD3, and MT3, while age affected CAT, MSRB3, DIO2, DIO3, GPX4, TXNRD1, and MT3. In conclusion, dietary Se may help against the negative effects of Cd, but cannot be effective when Cd is present at excessive amounts in the diet.

Blood and hair as non-invasive trace element biological indicators in growing rabbits

<p>The suitability of blood and hair as non-invasive tools to monitor trace element contents was studied in 48 Hyla male growing rabbits. Three diets with increasing organic selenium (Se) addition (0.1, 0.5 and 2.5 mg/kg) were used to induce alterations in the concentrations of trace elements vs. an unsupplemented diet. In blood, a linear decrease in Co (P&lt;0.001), Cu (<em>P</em>&lt;0.001), Mn (<em>P</em>&lt;0.05), Zn (<em>P</em>&lt;0.05), Sb (<em>P</em>&lt;0.001), As (<em>P</em>&lt;0.001), Cr (<em>P</em>&lt;0.001), Mo (<em>P</em>&lt;0.001), Ni (<em>P</em>&lt;0.001) and Cd (<em>P</em>&lt;0.001) concentrations with increasing dietary Se was observed. In hair, a cubic effect of dietary Se on Co (<em>P</em>&lt;0.01), Cu (<em>P</em>&lt;0.05), Mn (<em>P</em>&lt;0.001), Pb (<em>P</em>&lt;0.05), Mo (<em>P</em>&lt;0.05) and Cd (<em>P</em>&lt;0.05) concentrations was found, while As, Cr and Ni concentrations decreased linearly (<em>P</em>&lt;0.01, <em>P</em>&lt;0.01 and <em>P</em>&lt;0.001, respectively) with increasing dietary Se. Selenium was negatively correlated to Sb, As, Cr, Mo, Ni and Cd, (P&lt;0.001) in blood, and to As (<em>P</em>&lt;0.05), Cr, Ni (<em>P</em>&lt;0.01) and Pb (P&lt;0.05) in hair. The contents of Se, As, Cr and Ni in blood were highly correlated (<em>P</em>&lt;0.001) to those in hair. Blood appeared to be more sensitive than hair in detecting small changes in the trace element profile in rabbits, as was indicated by the discriminant analysis. In conclusion, blood and hair can be suitable biological indicators of essential, toxic and potentially toxic trace element status in rabbits, particularly when used complementarily.</p>

Effects of soft electrophiles on selenium physiology

This review examines the effects of neurotoxic electrophiles on selenium (Se) metabolism. Selenium-dependent enzymes depend on the unique and elite functions of selenocysteine (Sec), the 21st proteinogenic amino acid, to perform their biochemical roles. Humans possess 25 selenoprotein genes, ~ half of which are enzymes (selenoenzymes) required for preventing, controlling, or reversing oxidative damage, while others participate in regulating calcium metabolism, thyroid hormone status, protein folding, cytoskeletal structure, Sec synthesis and Se transport. While selenoproteins are expressed in tissue dependent distributions and levels in all cells of all vertebrates, they are particularly important in brain development, health, and functions. As the most potent intracellular nucleophile, Sec is subject to binding by mercury (Hg) and other electron poor soft neurotoxic electrophiles. Epidemiological and environmental studies of the effects of exposures to methyl-Hg (CH₃Hg⁺), elemental Hg (Hg°), and/or other metallic/organic neurotoxic soft electrophiles need to consider the concomitant effects of all members of this class of toxicants in relation to the Se status of their study populations. The contributions of individual electrophiles' discrete and cooperative rates of Se sequestration need to be evaluated in relation to tissue Se reserves of the exposed populations to identify sensitive subgroups which may be at accentuated risk due to poor Se status. Additional study is required to examine possibilities of inherited, acquired, or degenerative neurological disorders of Se homeostasis that may influence vulnerability to soft electrophile exposures. Investigations of soft electrophile toxicity will be enhanced by considering the concomitant effects of combined exposures on tissue Se-availability in relation to pathological consequences during fetal development or in relation to etiologies of neurological disorders and neurodegenerative diseases. Since selenoenzymes are molecular "targets" of soft electrophiles, concomitant evaluation of aggregate exposures to these toxicants in relation to dietary Se intakes will assist regulatory agencies in their goals of improving and protecting public health.

Effects of Selol 5% supplementation on tissue antioxidant enzyme levels and peroxidation marker in healthy mice

BACKGROUND

Selenium (Se) is an essential micronutrient for animals and humans used in the prevention or treatment of cancer. Selol is a mixture of selenitetriglycerides, containing Se(IV). It does not exhibit mutagenic activity and is less toxic than inorganic sodium selenite containing Se(IV). The antioxidant properties of the Selol were demonstrated using the blood of healthy animals. The aim of the study was to evaluate Selol as a Se supplement by determining the effect of its administration on the Se level and the antioxidant status in the tissues.

METHODS

We examined the effect of long-term (28-day) Selol 5% supplementation on the activity of antioxidant enzymes, including the main selenoenzymes in healthy mice organs, such as liver, brain, lungs, and testis. Enzyme activities of the tissue homogenates and the concentration of malondialdehyde (MDA) as a biomarker of oxidative stress were measured using spectrophotometric methods. The selenium concentrations in the tissues were determined by inductively coupled plasma mass spectrometer (ICP-MS) as well.

RESULTS

A significant increase in glutathione peroxidase, thioredoxin reductase, and glutathione S-transferase activity as well as the MDA concentration was observed in most of the studied tissues during the Selol 5% supplementation.

CONCLUSIONS

Long-term supplementation with the new Se(IV) compound - Selol 5% significantly affects the activity of antioxidant enzymes and the redox state in healthy mice organs. In the healthy population Selol 5% seems to be a promising new antioxidant compound.

Selenium-Dependent Antioxidant Enzymes: Actions and Properties of Selenoproteins

Unlike other essential trace elements that interact with proteins in the form of cofactors, selenium (Se) becomes co-translationally incorporated into the polypeptide chain as part of 21st naturally occurring amino acid, selenocysteine (Sec), encoded by the UGA codon. Any protein that includes Sec in its polypeptide chain is defined as selenoprotein. Members of the selenoproteins family exert various functions and their synthesis depends on specific cofactors and on dietary Se. The Se intake in productive animals such as chickens affect nutrient utilization, production performances, antioxidative status and responses of the immune system. Although several functions of selenoproteins are unknown, many disorders are related to alterations in selenoprotein expression or activity. Selenium insufficiency and polymorphisms or mutations in selenoproteins' genes and synthesis cofactors are involved in the pathophysiology of many diseases, including cardiovascular disorders, immune dysfunctions, cancer, muscle and bone disorders, endocrine functions and neurological disorders. Finally, heavy metal poisoning decreases mRNA levels of selenoproteins and increases mRNA levels of inflammatory factors, underlying the antagonistic effect of Se. This review is an update on Se dependent antioxidant enzymes, presenting the current state of the art and is focusing on results obtained mainly in chicken.

Selenium status of children in Kashin-Beck disease endemic areas in Shaanxi, China: assessment with mercury

The causes of Kashin-Beck disease (KBD) in children are multifactorial, and particular consideration has been given to childhood selenium (Se) deficiency. In this study, dietary intake of Se and mercury (Hg) was determined at KBD areas to investigate the Se status and risks. Therefore, total Hg and Se levels were investigated in scalp hair samples and in daily intake food samples of 150 schoolchildren in Yongshou County of Shaanxi, China. The results showed that the average concentration of Se in children's hair has risen to 302 ng g^-1 and significantly increased compared to the data reported decades ago. Children at KBD endemic areas likely have improved Se status due to the Se supplementation in food at recent decades. However, all the children in the study areas still showed lower Se status compared to those in other non-KBD areas of China. The probable daily intake of Se in the study areas was still lower after stopping Se supplementation in food at KBD areas, which is 17.96 μg day^-1. Food produced locally cannot satisfy the lowest demand for Se nutrition for local residents. If the interactions of Se-Hg detoxification are considered, Hg intake from food exacerbates Se deficiency at the KBD areas.

Responses of an American eel brain endothelial-like cell line to selenium deprivation and to selenite, selenate, and selenomethionine additions in different exposure media

The effect of selenium deprivation and addition on the American eel brain endothelial cell line (eelB) was studied in three exposure media: complete growth medium (L15/FBS), serum-free medium (L15), and minimal medium (L15/ex). L15/ex contains only galactose and pyruvate and allowed the deprivation of selenium on cells to be studied. In L15/ex, without any obvious source of selenium, eelB cells survived for at least 7 d, formed capillary-like structures (CLS) on Matrigel, and migrated to heal wounds. Three selenium compounds were added to cultures: selenite, selenate, and selenomethionine (SeMet). Adding selenite or selenate to eelB cell cultures for 24 h caused dose-dependent declines in cell viability, regardless of the exposure media. Although varying with exposure media and viability end point, selenite was approximately 70-fold more cytotoxic than selenate. By contrast, 24 h exposures to either DL- or L-SeMet in the three media caused little or no cytotoxicity. However for 7 d exposures in L15/ex, DL- and L-SeMet were very cytotoxic, even at the lowest tested concentration of 31 μM. By contrast in L15 and L15/FBS, cytotoxicity was only observed with 500 and 1000 μM L-SeMet. In L15/FBS, eelB continued to migrate and form CLS in the presence of SeMet but at 500 μM, cell migration appeared stimulated. As judged from a colony-forming assay over 14 d in L15/FBS, 500 and 1000 μM DL- and L-SeMet inhibited cell proliferation. Overall, the responses of eel cells to selenium depended on the selenium form, concentration, and exposure media, with responses to SeMet being most dependent on exposure media.

Hg and Se exposure in brain tissues of striped dolphin (Stenella coeruleoalba) and bottlenose dolphin (Tursiops truncatus) from the Tyrrhenian and Adriatic Seas

In this study we analyzed Hg and Se concentrations in dolphin brain tissues of fifteen specimens of striped dolphin (Stenella coeruleoalba) and eight specimens of bottlenose dolphin (Tursiops truncatus) stranded in the Tyrrhenian and Adriatic Seas, in order to assess the toxicological risks associated with Hg exposure. High Hg concentrations were found in brain tissues of both analyzed specie (1.86-243 mg/kg dw for striped dolphin and 2.1-98.7 mg/kg dw for bottlenose dolphin), exceeding levels associated with marine mammals neurotoxicity. Althougth the results clearly suggest that the protective effects of Se against Hg toxicity occur in cetaceans' brain tissues, a molar excess of mercury with respect to selenium was found, particularly in adult specimens of Stenella coeruleoalba. On contrary, negligible neurotoxicological risks were found for Tursiops truncatus specimens, due to detoxification processes. Data obtained allowed to prove a more marked neurotoxicological risk for adult specimens of Stenella coeruleoalba in both Tyrrhenian and Adriatic Seas.

Sodium Selenite Prevents Paraquat-Induced Neurotoxicity in Zebrafish

Considering the antioxidant properties of sodium selenite (Na₂SeO₃) and the involvement of oxidative stress events in paraquat-induced neurotoxicity, this study investigated the protective effect of dietary Na₂SeO₃ on biochemical and behavioral parameters of zebrafish exposed to paraquat (PQ). Fish were pretreated with a Na₂SeO₃ diet for 21 days and then PQ (20 mg/kg) was administered intraperitoneally with six injections for 16 days. In the novel tank test, the Na₂SeO₃ diet prevented the locomotor impairments, as well as the increase in the time spent in the top area of the tank, and the exacerbation of freezing episodes. In the preference for conspecifics and in the mirror-induced aggression (MIA) tasks, Na₂SeO₃ prevented the increase in the latency to enter the area closer to conspecifics and the agonistic behavior of PQ-treated animals, respectively. Na₂SeO₃ prevented the increase of carbonylated protein (CP), reactive oxygen species (ROS), and nitrite/nitrate (NOx) levels, as well as the decrease in non-protein thiols (NPSH) levels. Regarding the antioxidant enzymatic defenses, Na₂SeO₃ prevented the increase in catalase (CAT) and glutathione peroxidase (GPx) activities caused by PQ. Altogether, dietary Na₂SeO₃ improves behavioral and biochemical function impaired by PQ treatment in zebrafish, by modulating not only redox parameters, but also anxiety- and aggressive-like phenotypes in zebrafish.

Molecular cloning and sequence analysis of selenoprotein W gene and its mRNA expression patterns in response to metabolic status and cadmium exposure in goldfish, Carassius auratus

Selenoprotein W (SelW) is a low molecular weight and selenocysteine containing protein with redox activity involved in the antioxidant response. In the present study, the full-length cDNA of goldfish (Carassius auratus) selenoprotein W (gfSelW) was successfully cloned from the liver tissue by rapid amplification of cDNA ends technique. The obtained gfSelW cDNA was 730 bp long with a 79 bp 5'-untranslated region (UTR), a 390 bp 3'-UTR containing the consensus polyadenylation signal AATAAA and a 261 bp open reading frame coding a protein of 86 amino acid residues. gfSelW mRNA was observed in all regions of brain and peripheral tissues by semi-quantitative RT-PCR, and the most abundant was detected in testis. After fasting for 1 week, gfSelW mRNA expression levels were significantly decreased compared to the fed group in hypothalamus and liver. After refeeding for 7 days, gfSelW mRNA expression levels were increased back. Furthermore, the mRNA expressions of gfSelW in hypothalamus and liver were varied in periprandial changes and significantly up-regulated after meal 2 h and 4 h, respectively. With cadmium exposure for 24 h, gfSelW mRNA expression levels in gill and leucocytes were significantly decreased at different cadmium concentrations changing from 0.5 ppm to 10 ppm. However, the gfSelW mRNA expression level was sharply increased in liver, relatively to the control about 4.98-fold at 0.5 ppm. The results in this study provide molecular characterization of SelW in goldfish and imply that SelW mRNA expression may be associated with metabolic status and oxidative stress and regulated by metabolic factors and cadmium in fish.

Investigations on light induced stress model and on the role of Phyllanthus amarus in attenuation of stress related depression with focus on 5HT2Am- RNA expression

Background

There is an increasing evidence that psychological stress and depression trigger changes in various biochemical parameters in animals and human subjects. Chronic stress in rats, and psychosocial stress in humans, is implicated in the pathophysiology of mood and anxiety disorders.

Purpose

The current study was been designed to investigate the behavioral, anatomical status of rat brain and expression of serotonin receptor (5HT_2A) mRNA related to pathophysiology of stress after high light (HL) illumination and to evaluate the effect of Phyllanthus amarus (PA) over such stress induced changes in mid brain and prefrontal cortex region of rat brain.

Methods

Bright light illumination was used to induce stress in wistar rats. Established methods were used to analyse biochemical and histopathological tests.

Results

PA administration to HL stressed animals for 7 days prevented stress-induced oxidative damage, as evidenced by significant enhancement of key endogenous antioxidant defense components. HL stress also caused reduced activities of membrane bound enzymes in synaptic membrane along with reduced levels of lipid profile and glycoprotein in the midbrain region. Stress induced changes in the locomotor activity, time spent for exploring the center of the arena, frequency of rearing and grooming, and frequency of facing the corner of the arena, were altered on PA administration.

Conclusion

The findings suggest that the therapeutic efficacy of PA may be mediated, atleast partially, via reversal of oxidative damage. Further the study demonstrates the promising intervention by PA on the mRNA expression of 5HT 2A in the brain. These preliminary results pave the way for further validation of PA against stress.

Potential Role of Selenoenzymes and Antioxidant Metabolism in relation to Autism Etiology and Pathology

Autism and autism spectrum disorders (ASDs) are behaviorally defined, but the biochemical pathogenesis of the underlying disease process remains uncharacterized. Studies indicate that antioxidant status is diminished in autistic subjects, suggesting its pathology is associated with augmented production of oxidative species and/or compromised antioxidant metabolism. This suggests ASD may result from defects in the metabolism of cellular antioxidants which maintain intracellular redox status by quenching reactive oxygen species (ROS). Selenium-dependent enzymes (selenoenzymes) are important in maintaining intercellular reducing conditions, particularly in the brain. Selenoenzymes are a family of ~25 genetically unique proteins, several of which have roles in preventing and reversing oxidative damage in brain and endocrine tissues. Since the brain's high rate of oxygen consumption is accompanied by high ROS production, selenoenzyme activities are particularly important in this tissue. Because selenoenzymes can be irreversibly inhibited by many electrophiles, exposure to these organic and inorganic agents can diminish selenoenzyme-dependent antioxidant functions. This can impair brain development, particularly via the adverse influence of oxidative stress on epigenetic regulation. Here we review the physiological roles of selenoproteins in relation to potential biochemical mechanisms of ASD etiology and pathology.

New insights into traditional health risk assessments of mercury exposure: implications of selenium

There is increasing evidence that selenium (Se) has a significant effect on mercury (Hg) toxicology; however, Hg exposure risk assessments usually consider only the amount of Hg present in the environment or in food. On the basis of the present understanding of mechanisms of interaction between Se and Hg, the physiology/toxicology of Se, and the toxicology of Hg, we propose a new criterion for Se/Hg exposure assessment. This criterion, which is based on Se-Hg interactions, considers not only the toxicological consequences of Hg exposure but also the benefits and/or adverse effects of Se intake, especially the adverse effects related to a Se deficiency/excess. According to an illustrative assessment based on the new criterion and nine existing criteria, large knowledge gaps in the traditional assessments of exposure to Hg and/or Se were found, including those that assessed the interactions between Hg and Se. These results suggest that future assessments of Hg exposure (or Se intake) should include both Se and Hg.

Selenium neurotoxicity in humans: bridging laboratory and epidemiologic studies

Selenium is a metalloid of considerable interest in the human from both a toxicological and a nutritional perspective, with a very narrow safe range of intake. Acute selenium intoxication is followed by adverse effects on the nervous system with special clinical relevance, while the neurotoxicity of long-term overexposure is less characterized and recognized. We aimed to address this issue from a public health perspective, focusing on both laboratory studies and the few epidemiologic human studies available, with emphasis on their methodological strengths and limitations. The frequently overlooked differences in toxicity and biological activity of selenium compounds are also outlined. In addition to lethargy, dizziness, motor weakness and paresthesias, an excess risk of amyotrophic lateral sclerosis is the effect on the nervous system which has been more consistently associated with chronic low-level selenium overexposure, particularly to its inorganic compounds. Additional research efforts are needed to better elucidate the neurotoxic effects exerted by selenium overexposure.

Selenoprotein W expression and regulation in mouse brain and neurons

Background Selenoprotein W (Sepw1) is a selenium-containing protein that is abundant in brain and muscle of vertebrate animals. Muscular expression of Sepw1 is reduced by dietary selenium (Se) deficiency in mammals, whereas brain expression is maintained. However, expression of Sepw1 depends on the Se transporter selenoprotein P (Sepp1). Methods We assessed the regional and cellular expression of Sepw1 in the mouse brain and neuronal cultures. Results We found that Sepw1 is widespread in neurons and neuropil of mouse brain and appears in both the soma and processes of neurons in culture. Pyramidal neurons of cortex and hippocampus express high levels of Sepw1. It is also abundant in Purkinje neurons and their dendritic arbors in the cerebellum. Analysis of synaptosome fractions prepared from mice brains indicated that Sepw1 is present at synapses, as were several proteins involved in selenoprotein synthesis. Synaptic expression of Sepw1 expression is reduced in mice lacking Sepp1 compared with control mice, although selenoprotein synthesis factors were similarly expressed in both genotypes. Lastly, Sepw1 mRNA coimmunoprecipitates with Staufen 2 protein in a human neuronal cell line. Conclusions Our results suggest that Sepw1 may be locally synthesized in distal compartments of neurons including synapses.

Dietary selenium supplementation modifies breast tumor growth and metastasis

The survival rate for breast cancer drops dramatically once the disease progresses to the metastatic stage. Selenium (Se) is an essential micronutrient credited with having high anticancer and chemopreventive properties. In our study, we investigated if dietary Se supplementation modified breast cancer development in vivo. Three diets supplemented with sodium selenite, methylseleninic acid (MSA) or selenomethionine (SeMet), as well as a Se-deficient and a Se-adequate diet were fed to mice before mammary gland inoculation of 4T1.2 cells. The primary tumor growth, the numbers of cancer cells present in lungs, hearts, livers, kidneys and femurs and several proinflammatory cytokines were measured. We found that inorganic selenite supplementation provided only short-term delay of tumor growth, whereas the two organic SeMet and MSA supplements provided more potent growth inhibition. These diets also affected cancer metastasis differently. Mice fed selenite developed the most extensive metastasis and had an increased incidence of kidney and bone metastasis. On the other hand, mice fed the SeMet diet showed the least amount of cancer growth at metastatic sites. The MSA diet also provided some protection against breast cancer metastasis although the effects were less significant than those of SeMet. The cytokine profiles indicated that serum levels of interlukin-2, interleukin-6, interferon γ and vascular endothelial growth factor were elevated in SeMet-supplemented mice. There was no significant difference in tumor growth and the patterns of metastasis between the Se-deficient and Se-adequate groups. Our data suggest that organic Se supplementation may reduce/delay breast cancer metastasis, while selenite may exacerbate it.

Is selenium a potential treatment for cancer metastasis?

Selenium (Se) is an essential micronutrient that functions as a redox gatekeeper through its incorporation into proteins to alleviate oxidative stress in cells. Although the epidemiological data are somewhat controversial, the results of many studies suggest that inorganic and organic forms of Se negatively affect cancer progression, and that several selenoproteins, such as GPXs, also play important roles in tumor development. Recently, a few scientists have examined the relationship between Se and metastasis, a late event in cancer progression, and have evaluated the potential of Se as an anti-angiogenesis or anti-metastasis agent. In this review, we present the current knowledge about Se compounds and selenoproteins, and their effects on the development of metastasis, with an emphasis on cell migration, invasion, and angiogenesis. In the cancers of breast, prostate, colorectal, fibrosarcoma, melanoma, liver, lung, oral squamous cell carcinoma, and brain glioma, there is either clinical evidence linking selenoproteins, such as thioredoxin reductase-1 to lymph node metastasis; in vitro studies indicating that Se compounds and selenoproteins inhibited cell motility, migration, and invasion, and reduced angiogenic factors in some of these cancer cells; or animal studies showing that Se supplementation resulted in reduced microvessel density and metastasis. Together, these data support the notion that Se may be an anti-metastastatic element in addition to being a cancer preventative agent.

Differential effects of organic and inorganic selenium compounds on adenosine deaminase activity and scavenger capacity in cerebral cortex slices of young rats

Selenium (Se) has anti-inflammatory and antioxidant properties and is necessary for the development and normal function of the central nervous system. This study was aimed to compare the in vitro effects of 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one (C21H2HOSe; organoselenium) and sodium selenate (inorganic Se) on adenosine deaminase (ADA) activity, cell viability, lipid peroxidation, scavenger of nitric oxide (NO) and nonprotein thiols (NP-SH) content in the cerebral cortex slices of the young rats. A decrease in ADA activity was observed when the slices were exposed to organoselenium at the concentrations of 1, 10 and 30 µM. The same compound showed higher scavenger capacity of NO than the inorganic compound. Inorganic Se was able to protect against sodium nitroprusside-induced oxidative damage and increased the NP-SH content. Both the compounds displayed distinctive antioxidant capacities and were not cytotoxic for the cerebral cortex slices in the conditions tested. These findings are likely to be related to immunomodulatory and antioxidant properties of this compound.

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration

An evidence-based systematic review of vanadium by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Selenium modulates oxidative stress-induced TRPM2 cation channel currents in transfected Chinese hamster ovary cells

It has been recently reported that the essential antioxidant element selenium has protective effects on cytosolic Ca(2+) levels in cell lines. However, the effects of selenium on like transient receptor potential melastatin 2 (TRPM2) in response to oxidative stress (H(2) O(2) ) are not well understood. We investigated the effects of selenium on H(2) O(2) -induced TRPM2 channel currents in the Chinese hamster ovary (CHO) cell line using patch-clamp and fura-2 fluorescence imaging techniques.

Oxidative stress in patients with primary insomnia

OBJECTIVE

Many physiological and pathological processes, such as infections, environmental toxins, and ionizing radiation increase bodily concentrations of oxidizing substances, known as free radicals, which lead to neurodegenerative disorders. Sleep is one of the most important factors contributing to health; however, insomnia is among the most prevalent health complaints.

METHODS

In this study, for the first time in the literature, we investigated the effects of primary insomnia on certain oxidative stress biomarkers. For this purpose, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and myeloperoxidase (MPO) activities and levels of reduced glutathione (GSH) and malondialdehyde (MDA) were measured in 30 patients with primary insomnia and 30 healthy volunteers

RESULTS

Our results show that the patients with primary insomnia had significantly lower GSH-Px activity and higher MDA levels compared with the controls.

CONCLUSION

These results may indicate the important role of sleep in attenuating oxidative stress.

Biostrome communities and mercury and selenium bioaccumulation in the Great Salt Lake (Utah, USA)

The Great Salt Lake has a salinity near 150 g/L and is habitat for over 200 species of migratory birds. The diet of many of these birds is dependent on the food web of carbonaceous biostromes (stromatolites) that cover 260 km(2) of the lake's littoral zone. We investigated the biostrome community to understand their production processes and to assess whether they are a potential vector for bioconcentration of high mercury and selenium levels in the lake. The periphyton community of the biostromes was >99% colonial cyanobacteria. Periphyton chlorophyll levels averaged 900 mg m(-2) or nine times that of the lake's phytoplankton. Lake-wide estimates of chlorophyll suggest that their production is about 30% of that of the phytoplankton. Brine fly (Ephydra gracilis) larval densities on the biostromes increased from 7000 m(-2) in June to 20000m(-2) in December. Pupation and adult emergence halted in October and larvae of various instars overwintered at temperatures <5°C. Mean total dissolved and dissolved methyl mercury concentrations in water were 5.0 and 1.2 ηg L(-1). Total mercury concentrations in the periphyton, fly larvae, pupae, and adults were, respectively, 152, 189, 379 and 659 ηg g(-1) dry weight, suggesting that bioconcentration is only moderate in the short food web and through fly developmental stages. However, common goldeneye ducks (Bucephala clangula) that feed primarily on brine fly larvae at the Great Salt Lake had concentrations near 8000 ηg Hg g(-1) dry weight in muscle tissue. Data from a previous study indicated that selenium concentrations in periphyton, brine fly larvae and goldeneye liver tissue were high (1700, 1200 and 24,000 ηg g(-1), respectively) and Hg:Se molar ratios were <1.0 in all tissues, suggesting that the high mercury concentration in the ducks may be partially detoxified by combining with selenium. The study demonstrated that the high mercury levels in the Great Salt Lake are routed through the biostrome community resulting in invertebrate prey that may provide health risks for birds and humans that consume them.