Selenium controls the sex-specific immune response and selenoprotein expression during the acute-phase response in mice

The relevance of selenium to viral disease with special reference to SARS-CoV-2 and COVID-19

In this review, the relevance of selenium (Se) to viral disease will be discussed paying particular attention to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease (COVID-19). Se, the active centre in selenoproteins has an ongoing history of reducing the incidence and severity of viral infections. Host Se deficiency increased the virulence of RNA viruses such as influenza A and coxsackievirus B3, the latter of which is implicated in the development of Keshan disease in north-east China. Significant clinical benefits of Se supplementation have been demonstrated in HIV-1, in liver cancer linked to hepatitis B, and in Chinese patients with hantavirus that was successfully treated with oral sodium selenite. China is of particular interest because it has populations that have both the lowest and the highest Se status in the world. We found a significant association between COVID-19 cure rate and background Se status in Chinese cities; the cure rate continued to rise beyond the Se intake required to optimise selenoproteins, suggesting an additional mechanism. Se status was significantly higher in serum samples from surviving than non-surviving COVID-19 patients. As regards mechanism, SARS-CoV-2 may interfere with the human selenoprotein system; selenoproteins are important in scavenging reactive oxygen species, controlling immunity, reducing inflammation, ferroptosis and endoplasmic reticulum (ER) stress. We found that SARS-CoV-2 significantly suppressed mRNA expression of GPX4, of the ER selenoproteins, SELENOF, SELENOM, SELENOK and SELENOS and down-regulated TXNRD3. Based on the available data, both selenoproteins and redox-active Se species (mimicking ebselen, an inhibitor of the main SARS-CoV-2 protease that enables viral maturation within the host) could employ their separate mechanisms to attenuate virus-triggered oxidative stress, excessive inflammatory responses and immune-system dysfunction, thus improving the outcome of SARS-CoV-2 infection.

Excess selenium intake is associated with microalbuminuria in female but not in male among adults with obesity: Results from NHANES 2009-2018

INTRODUCTION

Selenium is a critical trace element with antioxidant activities that has been related to the preservation of kidney function. Few studies, however, have looked at the effects of excess selenium on kidneys. The purpose of the present study was performed to investigate the relationship between dietary selenium intake and the prevalence of microalbuminuria in American adults with obesity.

METHODS

A total of 8,547 participants with obesity in the National Health and Nutrition Examination Survey (NHANES) with the age of 19 years or older were included in the present study. Multivariable regression and subgroup analyses were performed to examine the association between dietary selenium and microalbuminuria in the two genders, separately. A selenium intake above the median was defined as high selenium intake.

RESULTS

Dietary selenium intake was significantly higher in men compared to women (139.49 μg/day vs. 101.06 μg/day; P < 0.0001). Among female participants, the prevalence of microalbuminuria was significantly higher in participants with a high selenium intake compared with those without a high selenium intake (13.82 vs. 9.96%; P = 0.008), whereas this difference did not exist in male participants (10.79 vs. 11.97%; P = 0.40). Dietary selenium is not significantly correlated with microalbuminuria (P = 0.68) in the male population, whereas each 1 μg/day of increase in selenium consumption was independently associated with a 6h higher risk of microalbuminuria (OR = 1.006; 95% CI, 1.001-1.011, P = 0.01) in females.

CONCLUSION

According to our research, excessive selenium consumption is positively correlated with microalbuminuria in females with obesity, but not in males with obesity.

Antagonistic Interaction of Selenium and Cadmium in Human Hepatic Cells Through Selenoproteins

Cadmium (Cd) is a highly toxic heavy metal for humans and animals, which is associated with acute hepatotoxicity. Selenium (Se) confers protection against Cd-induced toxicity in cells, diminishing the levels of ROS and increasing the activity of antioxidant selenoproteins such as glutathione peroxidase (GPx). The aim of this study was to evaluate the antagonistic effect of selenomethionine (SeMet) against Cd toxicity in HepG2 cells, through the modulation of selenoproteins. To this end, the cells were cultured in the presence of 100 µM SeMet and 5 μM, 15 µM, and 25 µM CdCl₂ and a combination of both species for 24 h. At the end of the experiment, cell viability was determined by MTT assay. The total metal content of Cd and Se was analyzed by triple-quadrupole inductively coupled plasma–mass spectrometry (ICP-QqQ-MS). To quantify the concentration of three selenoproteins [GPx, selenoprotein P (SELENOP), and selenoalbumin (SeAlb)] and selenometabolites, an analytical methodology based on column switching and a species-unspecific isotopic dilution approach using two-dimensional size exclusion and affinity chromatography coupled to ICP-QqQ-MS was applied. The co-exposure of SeMet and Cd in HepG2 cells enhanced the cell viability and diminished the Cd accumulation in cells. Se supplementation increased the levels of selenometabolites, GPx, SELENOP, and SeAlb; however, the presence of Cd resulted in a significant diminution of selenometabolites and SELENOP. These results suggested that SeMet may affect the accumulation of Cd in cells, as well as the suppression of selenoprotein synthesis induced by Cd.

A Comprehensive Review on Selenium and Its Effects on Human Health and Distribution in Middle Eastern Countries

Selenium (Se) is an important microelement with numerous positive effects on human health and diseases. It is important to specify that the status and consumption of Se are for a specific community as the levels of Se are extremely unpredictable between different populations and regions. Our existing paper was based on the impacts of Se on human health and disease along with data on the Se levels in Middle Eastern countries. Overall, the findings of this comprehensive review show that the consumption and levels of Se are inadequate in Middle Eastern nations. Such findings, together with the growing awareness of the importance of Se to general health, require further work primarily on creating an acceptable range of blood Se concentration or other measures to determine optimal Se consumption and, consequently, to guarantee adequate Se supplementation in populations at high risk of low Se intake.

Trace elements and the thyroid

Trace elements, such as iodine and selenium (Se), are vital to human health and play an essential role in metabolism. They are also important to thyroid metabolism and function, and correlate with thyroid autoimmunity and tumors. Other minerals such as iron (Ir), lithium (Li), copper (Co), zinc (Zn), manganese (Mn), magnesium (Mg), cadmium (Cd), and molybdenum (Mo), may related to thyroid function and disease. Normal thyroid function depends on a variety of trace elements for thyroid hormone synthesis and metabolism. These trace elements interact with each other and are in a dynamic balance. However, this balance may be disturbed by the excess or deficiency of one or more elements, leading to abnormal thyroid function and the promotion of autoimmune thyroid diseases and thyroid tumors.The relationship between trace elements and thyroid disorders is still unclear, and further research is needed to clarify this issue and improve our understanding of how trace elements mediate thyroid function and metabolism. This paper systematically reviewed recently published literature on the relationship between various trace elements and thyroid function to provide a preliminary theoretical basis for future research.

High dose supplementation of selenium in left ventricular assist device implant surgery - a double-blinded, randomized controlled, pilot trial

BACKGROUND

Systemic inflammation and oxidative stress remain the main cause of complications in heart failure patients receiving a left ventricular assist device (LVAD). Selenoproteins are a cornerstone of antioxidant defense mechanisms for improving inflammatory conditions.

METHODS

We conducted a monocentric double-blinded, randomized pilot trial. Patients scheduled for LVAD implantation were randomized to receive 300μg of selenium the evening before surgery orally, followed by high-dose intravenous selenium supplementation (3000μg after anesthesia induction, 1000 μg upon intensive care unit (ICU) admission, and 1000μg daily at ICU for a maximum of 14 days), or placebo. The main outcomes of this pilot study were feasibility and effectiveness in restoring serum selenium concentrations.

RESULTS

20 out of 21 randomized patients were included in the analysis. The average recruitment rate was 1.5 patients/month (0-3). The average duration of study intervention was 12.6 days (7-14) with a 97.7% dose compliance. No patient received open-label selenium. The supplementation strategy was effective in compensating low serum selenium concentration (before surgery: control: 63.5±11.9μg/L vs. intervention: 65.8±16.5μg/L, ICU admission: control: 49.0±9.8μg/L vs. intervention: 144.2±45.4μg/L). Comparing to the control group, the serum selenium concentrations in the intervention group were significantly higher during the observation period (baseline: mean of placebo (MoP):63.1 vs. mean of selenium (MoS):64.0; ICU admission: MoP:49.0 vs. MoS:144.6; day 1:MoP:44.9 vs. MoS: 102.4; day 3: MoP:43.6 vs. MoS:100.4; day 5: MoP:48.5 vs. MoS:114.7; day 7: MoP:44.4 vs.MoS:118.3; day 13:MoP:48.0 vs. MoS:131.0).

CONCLUSIONS

Selenium supplementation in patients receiving LVAD-implantation is feasible and effective to compensate a selenium deficiency. This article is protected by copyright. All rights reserved.

Selenium can regulate the differentiation and immune function of human dendritic cells

Selenium is an essential trace element that can regulate the function of immnue cells via selenoproteins. However, the effects of selenium on human dendritic cell (DCs) remain unclear. Thus, selenoprotein levels in monocytes, immature DCs (imDCs) and mature DCs (mDCs) treated with or without Na₂SeO₃ were evaluated using RT-PCR, and then the immune function of imDCs and mDCs was detected by flow cytometry, cell counting and the CCK8 assay. In addition, the effects of Se on cytokine and surface marker expression were investigated by RT-PCR. The results revealed different expression levels of selenoprotein in monocytes, imDCs and mDCs, and selenoproeins could be regulated by Se. Moreover, it was indicated that anti-phagocytic activity was improved by 0.1 µM Se, whereas it was suppressed by 0.2 µM Se in imDCs; The migration of imDCs and mDCs was improved by 0.1 µM Se, whereas their migration was inhibited by treatment with 0.05 or 0.2 µM Se; The mixed lymphocyte reaction of mDCs was improved by 0.1 µM Se, and it was inhibited by 0.05 and 0.2 µM Se. In addition, 0.1 µM Se improved the immune function of DCs through the regulation of CD80, CD86, IL12-p35 and IL12-p40. Wheres 0.05 and 0.2 µM Se impaired immune function of DCs by up-regulation of interleukin (IL-10) in imDCs and down-regulation of CD80, CD86, IL12-p35 and IL12-p40 in mDCs. In conclusion, 0.1 µM Se might improve the immune function of human DCs through selenoproteins.

Course and Survival of COVID-19 Patients with Comorbidities in Relation to the Trace Element Status at Hospital Admission

Selenium (Se) and zinc (Zn) are essential trace elements needed for appropriate immune system responses, cell signalling and anti-viral defence. A cross-sectional observational study was conducted at two hospitals in Ghent, Belgium, to investigate whether Se and/or Zn deficiency upon hospital admission correlates to disease severity and mortality risk in COVID-19 patients with or without co-morbidities. Trace element concentrations along with additional biomarkers were determined in serum or plasma and associated to disease severity and outcome. An insufficient Se and/or Zn status upon hospital admission was associated with a higher mortality rate and a more severe disease course in the entire study group, especially in the senior population. In comparison to healthy European adults, the patients displayed strongly depressed total Se (mean ± SD: 59.2 ± 20.6 vs. 84.4 ± 23.4 µg L⁻¹) and SELENOP (mean ± SD: 2.2 ± 1.9 vs. 4.3 ± 1.0 mg L⁻¹) concentrations at hospital admission. Particularly strong associations were observed for death risk of cancer, diabetes and chronic cardiac disease patients with low Se status, and of diabetes and obese patients with Zn deficiency. A composite biomarker based on serum or plasma Se, SELENOP and Zn at hospital admission proved to be a reliable tool to predict severe COVID-19 course and death, or mild disease course. We conclude that trace element assessment at hospital admission may contribute to a better stratification of patients with COVID-19 and other similar infectious diseases, support clinical care, therapeutic interventions and adjuvant supplementation needs, and may prove of particular relevance for patients with relevant comorbidities.

Selenium Deficiency Due to Diet, Pregnancy, Severe Illness, or COVID-19-A Preventable Trigger for Autoimmune Disease

The trace element selenium (Se) is an essential part of the human diet; moreover, increased health risks have been observed with Se deficiency. A sufficiently high Se status is a prerequisite for adequate immune response, and preventable endemic diseases are known from areas with Se deficiency. Biomarkers of Se status decline strongly in pregnancy, severe illness, or COVID-19, reaching critically low concentrations. Notably, these conditions are associated with an increased risk for autoimmune disease (AID). Positive effects on the immune system are observed with Se supplementation in pregnancy, autoimmune thyroid disease, and recovery from severe illness. However, some studies reported null results; the database is small, and randomized trials are sparse. The current need for research on the link between AID and Se deficiency is particularly obvious for rheumatoid arthritis and type 1 diabetes mellitus. Despite these gaps in knowledge, it seems timely to realize that severe Se deficiency may trigger AID in susceptible subjects. Improved dietary choices or supplemental Se are efficient ways to avoid severe Se deficiency, thereby decreasing AID risk and improving disease course. A personalized approach is needed in clinics and during therapy, while population-wide measures should be considered for areas with habitual low Se intake. Finland has been adding Se to its food chain for more than 35 years-a wise and commendable decision, according to today's knowledge. It is unfortunate that the health risks of Se deficiency are often neglected, while possible side effects of Se supplementation are exaggerated, leading to disregard for this safe and promising preventive and adjuvant treatment options. This is especially true in the follow-up situations of pregnancy, severe illness, or COVID-19, where massive Se deficiencies have developed and are associated with AID risk, long-lasting health impairments, and slow recovery.

Relation of Serum Copper Status to Survival in COVID-19

The trace element copper (Cu) is part of our nutrition and essentially needed for several cuproenzymes that control redox status and support the immune system. In blood, the ferroxidase ceruloplasmin (CP) accounts for the majority of circulating Cu and serves as transport protein. Both Cu and CP behave as positive, whereas serum selenium (Se) and its transporter selenoprotein P (SELENOP) behave as negative acute phase reactants. In view that coronavirus disease (COVID-19) causes systemic inflammation, we hypothesized that biomarkers of Cu and Se status are regulated inversely, in relation to disease severity and mortality risk. Serum samples from COVID-19 patients were analysed for Cu by total reflection X-ray fluorescence and CP was quantified by a validated sandwich ELISA. The two Cu biomarkers correlated positively in serum from patients with COVID-19 (R = 0.42, p < 0.001). Surviving patients showed higher mean serum Cu and CP concentrations in comparison to non-survivors ([mean+/-SEM], Cu; 1475.9+/-22.7 vs. 1317.9+/-43.9 µg/L; p < 0.001, CP; 547.2.5 +/- 19.5 vs. 438.8+/-32.9 mg/L, p = 0.086). In contrast to expectations, total serum Cu and Se concentrations displayed a positive linear correlation in the patient samples analysed (R = 0.23, p = 0.003). Serum CP and SELENOP levels were not interrelated. Applying receiver operating characteristics (ROC) curve analysis, the combination of Cu and SELENOP with age outperformed other combinations of parameters for predicting risk of death, yielding an AUC of 95.0%. We conclude that the alterations in serum biomarkers of Cu and Se status in COVID-19 are not compatible with a simple acute phase response, and that serum Cu and SELENOP levels contribute to a good prediction of survival. Adjuvant supplementation in patients with diagnostically proven deficits in Cu or Se may positively influence disease course, as both increase in survivors and are of crucial importance for the immune response and antioxidative defence systems.

Identification of VIMP as a gene inhibiting cytokine production in human CD4+ effector T cells

Many players regulating the CD4+ T cell-mediated inflammatory response have already been identified. However, the critical nodes that constitute the regulatory and signaling networks underlying CD4 T cell responses are still missing. Using a correlation-network-guided approach, here we identified VIMP (VCP-interacting membrane protein), one of the 25 genes encoding selenoproteins in humans, as a gene regulating the effector functions of human CD4 T cells, especially production of several cytokines including IL2 and CSF2. We identified VIMP as an endogenous inhibitor of cytokine production in CD4 effector T cells via both the E2F5 transcription regulatory pathway and the Ca2+/NFATC2 signaling pathway. Our work not only indicates that VIMP might be a promising therapeutic target for various inflammation-associated diseases but also shows that our network-guided approach can significantly aid in predicting new functions of the genes of interest.

[The role of selenium in cardiology]

Selenium is an important micronutrient that is essential for the functioning of the human body. Being a component of the active center of several antioxidant enzymes selenium prevents cell injury by free radicals. Decline in selenium-containing enzymes results in progression of oxidative stress and chronic inflammation, which are considered as possible causes for the development of many cardiovascular diseases. This review focuses on mechanisms for prevention of myocardial and vascular injury through the adequate selenium supply to the body. The importance of monitoring and correction of the selenium status in appropriate patients is underlined.

Serum Selenium Status as a Diagnostic Marker for the Prognosis of Liver Transplantation

The trace element selenium (Se) is taken up from the diet and is metabolized mainly by hepatocytes. Selenoprotein P (SELENOP) constitutes the liver-derived Se transporter. Biosynthesis of extracellular glutathione peroxidase (GPx3) in kidney depends on SELENOP-mediated Se supply. We hypothesized that peri-operative Se status may serve as a useful prognostic marker for the outcome in patients undergoing liver transplantation due to hepatocellular carcinoma. Serum samples from liver cancer patients were routinely collected before and after transplantation. Concentrations of serum SELENOP and total Se as well as GPx3 activity were determined by standardized tests and related to survival, etiology of cirrhosis/carcinoma, preoperative neutrophiles, lymphocytes, thyrotropin (TSH) and Child-Pugh and Model for End-Stage Liver Disease (MELD) scores. A total of 221 serum samples from 79 transplanted patients were available for analysis. The Se and SELENOP concentrations were on average below the reference ranges of healthy subjects. Patients with ethanol toxicity-dependent etiology showed particularly low SELENOP and Se concentrations and GPx3 activity. Longitudinal analysis indicated declining Se concentrations in non-survivors. We conclude that severe liver disease necessitating organ replacement is characterized by a pronounced Se deficit before, during and after transplantation. A recovering Se status after surgery is associated with positive prognosis, and an adjuvant Se supplementation may, thus, support convalescence.

Prediction of survival odds in COVID-19 by zinc, age and selenoprotein P as composite biomarker

SARS-CoV-2 infections cause the current coronavirus disease (COVID-19) pandemic and challenge the immune system with ongoing inflammation. Several redox-relevant micronutrients are known to contribute to an adequate immune response, including the essential trace elements zinc (Zn) and selenium (Se). In this study, we tested the hypothesis that COVID-19 patients are characterised by Zn deficiency and that Zn status provides prognostic information. Serum Zn was determined in serum samples (n = 171) collected consecutively from patients surviving COVID-19 (n = 29) or non-survivors (n = 6). Data from the European Prospective Investigation into Cancer and Nutrition (EPIC) study were used for comparison. Zn concentrations in patient samples were low as compared to healthy subjects (mean ± SD; 717.4 ± 246.2 vs 975.7 ± 294.0 μg/L, P < 0.0001). The majority of serum samples collected at different time points from the non-survivors (25/34, i.e., 73.5%) and almost half of the samples collected from the survivors (56/137, i.e., 40.9%) were below the threshold for Zn deficiency, i.e., below 638.7 μg/L (the 2.5th percentile in the EPIC cohort). In view that the Se status biomarker and Se transporter selenoprotein P (SELENOP) is also particularly low in COVID-19, we tested the prevalence of a combined deficit, i.e., serum Zn below 638.7 μg/L and serum SELENOP below 2.56 mg/L. This combined deficit was observed in 0.15% of samples in the EPIC cohort of healthy subjects, in 19.7% of the samples collected from the surviving COVID-19 patients and in 50.0% of samples from the non-survivors. Accordingly, the composite biomarker (SELENOP and Zn with age) proved as a reliable indicator of survival in COVID-19 by receiver operating characteristic (ROC) curve analysis, yielding an area under the curve (AUC) of 94.42%. We conclude that Zn and SELENOP status within the reference ranges indicate high survival odds in COVID-19, and assume that correcting a diagnostically proven deficit in Se and/or Zn by a personalised supplementation may support convalescence.

The Association of Circulating Selenium Concentrations with Diabetes Mellitus

PURPOSE

The relationship between circulating selenium and diabetes mellitus (DM) remains inconsistent. Therefore, the relationship between circulating selenium and DM was investigated in the present study.

PATIENTS AND METHODS

All participants (aged ≥18 years) were included from the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Selenium concentrations from the fasting serum samples were determined using inductively coupled mass spectrometry, then grouped into quartiles. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by using multivariate logistic regression analysis and the results were stratified by age and sex.

RESULTS

A total of 2,903 (61.9±13.7 years old) participants (49.3% males) were enrolled, and 580 (19.97%) of them had DM. The mean levels of selenium were 136.4±19.6 µg/L. Patients with DM (138.76±20.02 vs 135.88±19.44, P=0.002) had higher selenium levels compared to those without DM. The OR for DM was 1.12 (95% CI=1.01-1.24; P=0.0270) for each 10 µg/L increment in selenium, and subjects in the highest quartile of selenium levels (>147.00 uµg/L) had 2.82 (95% CI=1.55-5.11; P=0.0007) times higher risk of DM compared to the lowest quartile of selenium levels. Subgroup analysis showed that selenium was independently associated with DM only in female aged <65 years.

CONCLUSION

Circulating selenium levels were positively associated with the odds of DM, but difference in sex and age.

Hepatic-Specific Decrease in the Expression of Selenoenzymes and Factors Essential for Selenium Processing After Endotoxemia

Background

Selenium (Se) levels decrease in the circulation during acute inflammatory states and sepsis, and are inversely associated with morbidity and mortality. A more specific understanding of where selenoproteins and Se processing are compromised during insult is needed. We investigated the acute signaling response in selenoenzymes and Se processing machinery in multiple organs after innate immune activation in response to systemic lipopolysaccharide (LPS).

Methods

Wild type (WT) adult male C57/B6 mice were exposed to LPS (5 mg/kg, intraperitoneal). Blood, liver, lung, kidney and spleen were collected from control mice as well as 2, 4, 8, and 24 h after LPS. Plasma Se concentration was determined by ICP-MS. Liver, lung, kidney and spleen were evaluated for mRNA and protein content of selenoenzymes and proteins required to process Se.

Results

After 8 h of endotoxemia, plasma levels of Se and the Se transporter protein, SELENOP were significantly decreased. Consistent with this timing, the transcription and protein content of several hepatic selenoenzymes, including SELENOP, glutathione peroxidase 1 and 4 were significantly decreased. Furthermore, hepatic transcription and protein content of factors required for the Se processing, including selenophosphate synthetase 2 (Sps2), phosphoseryl tRNA kinase (Pstk), selenocysteine synthase (SepsecS), and selenocysteine lyase (Scly) were significantly decreased. Significant LPS-induced downregulation of these key selenium processing enzymes was observed in isolated hepatocytes. In contrast to the acute and dynamic changes observed in the liver, selenoenzymes did not decrease in the lung, kidney or spleen.

Conclusion

Hepatic selenoenzyme production and Se processing factors decreased after endotoxemia. This was temporally associated with decreased circulating Se. In contrast to these active changes in the regulation of Se processing in the liver, selenoenzymes did not decrease in the lung, kidney or spleen. These findings highlight the need to further study the impact of innate immune challenges on Se processing in the liver and the impact of targeted therapeutic Se replacement strategies during innate immune challenge.

GPx3 dysregulation impacts adipose tissue insulin receptor expression and sensitivity

Insulin receptor signaling is crucial for white adipose tissue (WAT) function. Consequently, lack of insulin receptor (IR) in WAT results in a diabetes-like phenotype. Yet, causes for IR downregulation in WAT of patients with diabetes are not well understood. By using multiple mouse models of obesity and insulin resistance, we identify a common downregulation of IR with a reduction of mRNA expression of selenoproteins Txnrd3, Sephs2, and Gpx3 in gonadal adipose tissue. Consistently, GPX3 is also decreased in adipose tissue of insulin-resistant and obese patients. Inducing Gpx3 expression via selenite treatment enhances IR expression via activation of the transcription factor Sp1 in 3T3-L1 preadipocytes and improves adipocyte differentiation and function. Feeding mice a selenium-enriched high-fat diet alleviates diet-induced insulin resistance with increased insulin sensitivity, decreased tissue inflammation, and elevated IR expression in WAT. Again, IR expression correlated positively with Gpx3 expression, a phenotype that is also conserved in humans. Consequently, decreasing GPx3 using siRNA technique reduced IR expression and insulin sensitivity in 3T3-L1 preadipocytes. Overall, our data identify GPx3 as a potentially novel regulator of IR expression and insulin sensitivity in adipose tissue.

Selenomethionine relieves inflammation in the chicken trachea caused by LPS though inhibiting the NF-κB pathway

Selenomethionine is able to relieve the effect of inflammation in various tissues and organs. However, there are few studies about the influences of organic selenium resisting inflammation induced by LPS in chicken trachea. Therefore, the purpose of this experiment is to explore the organic selenium (selenomethionine) can raise immune function and relieve the LPS-induced inflammation of chicken trachea via inhibiting the NF-κB pathway. To investigate the mechanism of organic selenium on chicken trachea, the supplement of selenomethionine and/or LPS-induced chicken models were established. One hundred 46-week-old isa chickens were randomly divided into four groups (n = 25). The four groups were the control group, the selenomethionine group (Se group), the LPS-induced group (LPS group), and the Se and LPS interaction group (Se + LPS group). Then, the expressions of inflammatory factors (including induced nitric oxide synthase (iNOS), nuclear factor-kappa B(NF-κB), tumor necrosis factor (TNF-α), cyclooxygenase-2 (COX-2), and prostaglandin E (PTGEs) synthase), inflammation-related cytokines (including interleukin (IL-2, IL-6, IL-8, IL-17) and immunoglobulin (IgA, IgM, IgY)), the marker of immune function (avian β-defensins (AvBD6, AvBD7)), heat shock proteins (including HSP60, HSP90), and selenoproteins (including Selo, Sels, Selm, Selh, Selu, Seli, SPS2, GPx1, GPx2, Dio1, Sepx1, Sep15, Sepp1, Txnrd1) were detected in our experiment. The above genes were significantly changed in different groups (p < 0.05). We can conclude that organic selenium can increase the function of immunity and the expression of selenoproteins, and mitigate the inflammation induced by LPS via suppression of the NF-κB pathway.

The other view: the trace element selenium as a micronutrient in thyroid disease, diabetes, and beyond

Antibiotics are provided for infections caused by bacteria, and statins help to control hypercholesterolemia. When hungry, you need to eat, and when you are deficient in a particular nutrient, the diet should be chosen wisely to provide what is missing. In the matter of providing the essential trace element selenium (Se), there are two different but partly overlapping views on its nature and requirements. Some consider it a medication that should be given to a subset of more or less well-defined (thyroid) patients only, in order to alleviate symptoms, to improve the course of the disease or even to provide a cure, alone or in an adjuvant mode. Such treatment attempts are conducted for a short time period, and potential medical benefits and side effects are evaluated thoroughly. One could also approach Se in medicine in a more holistic way and evaluate primarily the nutritional status of the patient before considering supplementation. The available evidence for positive health effects of supplemental Se can be interpreted as the consequence of correcting deficiency instead of speculating on a direct pharmaceutical action. This short review provides a novel view on Se in (thyroid) disease and beyond and offers an alternative explanation for its positive health effects, i.e., its provision of the substrate needed for allowing adequate endogenous expression of those selenoproteins that are required in certain conditions. In Se deficiency, the lack of the trace element constitutes the main limitation for the required adaptation of selenoprotein expression to counteract health risks and alleviate disease symptoms. Supplemental Se lifts this restriction and enables the full endogenous response of selenoprotein expression. However, since Se does not act as a pharmacological medication per se, it should not be viewed as a dangerous drug, and, importantly, current data show that supplemental Se does not cause diabetes.

Selenium-Rich-Yeast Protects Against Aluminum-Induced Activating Nuclear Xenobiotic Receptors and Triggering Inflammation and Cytochromes P450 Systems in Mice Heart

Aluminum (Al) poisoning is linked to the development of cardiovascular diseases, and dietary supplementation with selenium-rich-yeast (SeY) has been shown to prevent inflammatory conditions. We evaluated the preventive effect of SeY on Al-induced cardiotoxicity, and the possible underlying mechanisms. Mice were treated with SeY (0.1 mg/kg) and/or Al (10 mg/kg) by oral gavage for 4 weeks. Histopathological damage was observed in the heart of Al-treated mice, in addition to the transcriptional up/downregulation of nuclear xenobiotic receptors (NXRs), inflammatory cytokines and 15 CYP450s genes. SeY significantly inhibited these Al-induced histopathological and molecular changes, and restored these indicators to the control levels. These results suggest that SeY exerts a cardio-protective effect against Al-induced toxicity through the NXR system, inflammatory cytokines, and CYP450s genes.

Selenium Pretreatment Alleviated LPS-Induced Immunological Stress Via Upregulation of Several Selenoprotein Encoding Genes in Murine RAW264.7 Cells

This study was conducted to profile selenoprotein encoding genes in mouse RAW264.7 cells upon lipopolysaccharide (LPS) challenge and integrate their roles into immunological regulation in response to selenium (Se) pretreatment. LPS was used to develop immunological stress in macrophages. Cells were pretreated with different levels of Se (0, 0.5, 1.0, 1.5, 2.0 μmol Se/L) for 2 h, followed by LPS (100 ng/mL) stimulation for another 3 h. The mRNA expression of 24 selenoprotein encoding genes and 9 inflammation-related genes were investigated. The results showed that LPS (100 ng/mL) effectively induced immunological stress in RAW264.7 cells with induced inflammation cytokines, IL-6 and TNF-α, mRNA expression, and cellular secretion. LPS increased (P < 0.05) mRNA profiles of 9 inflammation-related genes in cells, while short-time Se pretreatment modestly reversed (P < 0.05) the LPS-induced upregulation of 7 genes (COX-2, ICAM-1, IL-1β, IL-6, IL-10, iNOS, and MCP-1) and further increased (P < 0.05) expression of IFN-β and TNF-α in stressed cells. Meanwhile, LPS decreased (P < 0.05) mRNA levels of 18 selenoprotein encoding genes and upregulated mRNA levels of TXNRD1 and TXNRD3 in cells. Se pretreatment recovered (P < 0.05) expression of 3 selenoprotein encoding genes (GPX1, SELENOH, and SELENOW) in a dose-dependent manner and increased (P < 0.05) expression of another 5 selenoprotein encoding genes (SELENOK, SELENOM, SELENOS, SELENOT, and TXNRD2) only at a high level (2.0 μmol Se/L). Taken together, LPS-induced immunological stress in RAW264.7 cells accompanied with the global downregulation of selenoprotein encoding genes and Se pretreatment alleviated immunological stress via upregulation of a subset of selenoprotein encoding genes.

Effects of dietary sodium selenite and organic selenium sources on immune and inflammatory responses and selenium deposition in growing pigs

The study was conducted to compare effects of different dietary Se sources (sodium selenite [NaSe], Se-enriched yeast [Se yeast] or L-selenomethionine [SeMet]) and one Se-deficient control diet on the expression of selected genes, hematological and clinical biochemical parameters, and muscle morphology in two parallel trials with finisher pigs. Se concentrations in blood plasma and tissues were also monitored. From the pigs in one of the parallel groups, muscle samples obtained from Musculus longissimus dorsi (LD) before and during the trial were examined. The pigs in the other parallel group were challenged once with lipopolysaccharide (LPS) intravenously. Transcriptional analyses of LD showed that selenogenes SelenoW and H were higher expressed in pigs fed Se-supplemented diets compared with control. Furthermore, the expression of interferon gamma and cyclooxygenase 2 was lower in the Se-supplemented pigs versus control. In whole blood samples prior to LPS, SelenoN, SelenoS and thioredoxin reductase 1 were higher expressed in pigs fed NaSe supplemented feed compared with the other groups, possibly indicating a higher level of oxidative stress. After LPS exposure glutathione peroxidase 1 and SelenoN were more reduced in pigs fed NaSe compared with pigs fed organic Se. Products of most above-mentioned genes are intertwined with the oxidant-antioxidant system. No significant effects of Se-source were found on hematologic parameters or microscopic anatomy. The Se-concentrations in various skeletal muscles and heart muscle were significantly different between the groups, with highest concentrations in pigs fed SeMet, followed by those fed Se yeast, NaSe, and control diet. Consistent with previous reports our results indicate that dietary Se at adequate levels can support the body's antioxidant system. Our results indicate that muscle fibers of pigs fed organic Se are less vulnerable to oxidative stress compared with the other groups.

SEXUAL DIMORPHISM IN SELENIUM METABOLISM AND SELENOPROTEINS

Sexual dimorphism, the condition in which males and females in a species differ beyond the morphology of sex organs, delineates critical aspects of the biology of higher eukaryotes, including selenium metabolism. While sex differences in selenium biology have been described by several laboratories, delineation of the effects of sex in selenium function and regulation of selenoprotein expression is still in its infancy. This review encompasses the available information on sex-dependent parameters of selenium metabolism, as well as the effects of selenium on sex hormones. Gaps in the current knowledge of selenium and sex are identified and discussed.

Genetically driven antioxidant capacity in a Caucasian Southeastern European population

Previous studies have underlined the function of specific xenobiotic metabolizing phase-I or phase-II enzymes and endogenous antioxidant-related enzymes in the reduction and/or progression of oxidative stress and consequently the incidence of several diseases. In the present study, 10 polymorphic variants (rs4880, rs1799895, rs660339, rs1050450, rs1001179, rs28665122, rs1695, rs1138272, rs1051740 and rs2234922) were investigated in 1132 individuals of a Caucasian Southeastern European population. The frequency distribution of alleles and genotypes was compared to data of European (Northern, Central, Northwestern and Southwestern) and Global populations, extracted from the ensembl genome browser. The allele frequencies in the case of rs1051740 were similar to the frequencies noted in the global population. The majority of the present study allelic polymorphisms showed similar frequency distribution to those of the European or the Global populations (0.88≤OR≤1.14). The rs1051740 polymorphism demonstrated similar to the Global population frequencies (OR=1.09). In conclusion, observed distributions of the polymorphisms studied in the Southeastern population demonstrate a positive impact (rs4880, rs1799895, rs660339, rs28665122) and a negative impact (rs1050450, rs1138272, rs109179, rs1695) against oxidative stress when compared to other population groups.

Selenoprotein S: a therapeutic target for diabetes and macroangiopathy?

Inflammatory response, oxidative stress, and endoplasmic reticulum (ER) stress are important pathophysiological bases of the occurrence and development of diabetes mellitus (DM) and macroangiopathy complications. Selenoprotein S (SELENOS) is involved in the regulation of these mechanisms; therefore, its association with DM and macroangiopathy has gradually received attention from scholars worldwide. SELENOS has different biological functions in different tissues and organs: it exerts antioxidant protection and has anti-ER stress effects in the pancreas and blood vessels, while it promotes the occurrence and development of insulin resistance in the liver, adipose tissue, and skeletal muscle. In addition, studies have confirmed that some SELENOS gene polymorphisms can influence the inflammatory response and are closely associated with the risk for developing DM and macroangiopathy. Therefore, comprehensive understanding of the association between SELENOS and inflammation, oxidative stress, and ER stress may better elucidate and supplement the pathogenic mechanisms of DM and macroangiopathy complications. Furthermore, in-depth investigation of the association of SELENOS function in different tissues and organs with DM and macroangiopathy may facilitate the development of new strategies for the prevention and treatment of DM and macrovascular complications. Here, we summarize the consensus and controversy regarding functions of SELENOS on currently available evidence.

Response of Selenium and Selenogenome in Immune Tissues to LPS-Induced Inflammatory Reactions in Pigs

Circulating concentration of the essential trace element selenium (Se) was significantly lower in inflammatory disorders. Although Se plays physiological roles mainly through the function of 25 selenoproteins, the response of the selenogenome in immune tissues during inflammatory reactions remains unclear. The objective of this study was to determine the Se retention and selenogenome expression in immune tissues during the lipopolysaccharide (LPS)-induced inflammatory response in porcine. A total of 12 male pigs were randomly divided into two groups and injected with LPS or saline. After 4 h postinjection, blood samples were collected and pigs were euthanized. Pigs challenged with LPS had 36.8 and 16.6 % lower (P < 0.05) Se concentrations in the serum and spleen, respectively, than those injected with saline. Moreover, the activities of GPX decreased (P < 0.05) by 23.4, 26.6, and 30.4 % in the serum, thymus, and lymph node, respectively, in the pigs injected with LPS. Furthermore, the LPS challenge altered (P < 0.05) the mRNA expression of 14, 16, 10, and 6 selenoprotein genes in the liver, spleen, thymus, and lymph node, respectively. Along with 10 previously reported selenoprotein genes, the response of Txnrd2, Txnrd3, Sep15, Selh, Seli, Seln, Selo, Selt, Selx, and Sephs2 to inflammatory reaction in immune tissues were newly illustrated in this study. In conclusion, the LPS-induced inflammatory response impaired Se metabolism and was associated with dysregulation of the selenogenome expression in immune tissues.

Sex-specific and inter-individual differences in biomarkers of selenium status identified by a calibrated ELISA for selenoprotein P

Selenoprotein P (SELENOP) is a liver-derived transporter of selenium (Se) in blood, and a meaningful biomarker of Se status. Se is an essential trace element for the biosynthesis of enzymatically-active selenoproteins, protecting the organism from oxidative damage. The usage of uncalibrated assays hinders the comparability of SELENOP concentrations and their pathophysiological interpretation across different clinical studies. On this account, we established a new sandwich SELENOP-ELISA and calibrated against a standard reference material (SRM1950). The ELISA displays a wide working range (11.6-538.4µg/L), high accuracy (2.9%) and good precision (9.3%). To verify whether SELENOP correlates to total Se and to SELENOP-bound Se, serum samples from healthy subjects and age-selected participants from the Berlin Aging Study II were analyzed by SELENOP-ELISA and Se quantification. SELENOP was affinity-purified and its Se content was determined from a subset of samples. There was a high correlation of total Se and SELENOP concentrations in young and elderly men, and in elderly women, but not in young women, indicating a specific sexual dimorphism in these biomarkers of Se status in young subjects. The Se content of isolated SELENOP was independent of sex and age (mean±SD: 5.4±0.5). By using this calibrated SELENOP-ELISA, prior reports on pathological SELENOP concentrations in diabetes and obesity are challenged as the reported values are outside reasonable limits. Biomarkers of Se status in clinical research need to be measured by validated assays in order to avoid erroneous data and incorrect interpretations, especially when analyzing young women. The Se content of circulating SELENOP differs between individuals and may provide some important diagnostic information on Se metabolism and status.

Selenium Pretreatment for Mitigation of Ischemia/Reperfusion Injury in Cardiovascular Surgery: Influence on Acute Organ Damage and Inflammatory Response

Ischemia/reperfusion injury (IRI) contributes to morbidity and mortality after cardiovascular surgery requiring cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA). Multi-organ damage is associated with substantial decreases of blood selenium (Se) levels in patients undergoing cardiac surgery with CPB. We compared the influence of a dietary surplus of Se and pretreatment with ebselen, a mimic of the selenoenzyme glutathione peroxidase, on IRI-induced tissue damage and inflammation. Male Wistar rats were fed either a Se-adequate diet containing 0.3 ppm Se or supplemented with 1 ppm Se (as sodium selenite) for 5 weeks. Two other groups of Se-adequate rats received intraperitoneal injection of ebselen (30 mg/kg) or DMSO (solvent control) before surgery. The animals were connected to a heart-lung-machine and underwent 45 min of global ischemia during circulatory arrest at 16 °C, followed by re-warming and reperfusion. Selenite and ebselen suppressed IRI-induced leukocytosis and the increase in plasma levels of tissue damage markers (AST, ALT, LDH, troponin) during surgery but did not prevent the induction of proinflammatory cytokines (IL-6, TNF-α). Both Se compounds affected phosphorylation and expression of proteins related to stress response and inflammation: Ebselen increased phosphorylation of STAT3 transcription factor in the heart and decreased phosphorylation of ERK1/2 MAP kinases in the lungs. Selenite decreased ERK1/2 phosphorylation and HSP-70 expression in the heart. Pretreatment with selenite or ebselen protected against acute IRI-induced tissue damage during CPB and DHCA. Potential implications of their different actions with regard to molecular stress markers on the recovery after surgery represent promising targets for further investigation.

Prediagnostic selenium status and hepatobiliary cancer risk in the European Prospective Investigation into Cancer and Nutrition cohort

BACKGROUND

Selenium status is suboptimal in many Europeans and may be a risk factor for the development of various cancers, including those of the liver and biliary tract.

OBJECTIVE

We wished to examine whether selenium status in advance of cancer onset is associated with hepatobiliary cancers in the EPIC (European Prospective Investigation into Cancer and Nutrition) study.

DESIGN

We assessed prediagnostic selenium status by measuring serum concentrations of selenium and selenoprotein P (SePP; the major circulating selenium transfer protein) and examined the association with hepatocellular carcinoma (HCC; n = 121), gallbladder and biliary tract cancers (GBTCs; n = 100), and intrahepatic bile duct cancer (IHBC; n = 40) risk in a nested case-control design within the EPIC study. Selenium was measured by total reflection X-ray fluorescence, and SePP was determined by a colorimetric sandwich ELISA. Multivariable ORs and 95% CIs were calculated by using conditional logistic regression.

RESULTS

HCC and GBTC cases, but not IHBC cases, showed significantly lower circulating selenium and SePP concentrations than their matched controls. Higher circulating selenium was associated with a significantly lower HCC risk (OR per 20-μg/L increase: 0.41; 95% CI: 0.23, 0.72) but not with the risk of GBTC or IHBC. Similarly, higher SePP concentrations were associated with lowered HCC risk only in both the categorical and continuous analyses (HCC: P-trend ≤ 0.0001; OR per 1.5-mg/L increase: 0.37; 95% CI: 0.21, 0.63).

CONCLUSION

These findings from a large prospective cohort provide evidence that suboptimal selenium status in Europeans may be associated with an appreciably increased risk of HCC development.

Selenium Deficiency Affects the mRNA Expression of Inflammatory Factors and Selenoprotein Genes in the Kidneys of Broiler Chicks

The aim of this study was to investigate the influence of Se deficiency on the transcription of inflammatory factors and selenoprotein genes in the kidneys of broiler chicks. One hundred fifty 1-day-old broiler chicks were randomly assigned to two groups fed with either a low-Se diet (L group, 0.033 mg/kg Se) or an adequate Se diet (C group, 0.2 mg/kg Se). The levels of uric acid (UA) and creatinine (Cr) in the serum and the mRNA levels of 6 inflammatory factors and 25 selenoprotein genes in the kidneys were measured as the clinical signs of Se deficiency occurred at 20 days old. The results indicated that the contents of UA and Cr in the serum increased in L group (p < 0.05), and the mRNA levels of the inflammatory factors (NF-κB, iNOS, COX-2, and TNF-α) increased in L group (p < 0.05). Meanwhile, the mRNA levels of PTGEs and HO-1 were not changed. In addition, 25 selenoprotein transcripts displayed ubiquitous expression in the kidneys of the chicks. The mRNA levels of 14 selenoprotein genes (Dio1, Dio2, GPx3, Sepp1, SelH, SelI, SelK, Sepn1, SelO, SelW, Sep15, SelT, SelU, and SelS) decreased, and 9 selenoprotein genes (GPx1, GPx2, GPx4, SelPb, Txnrd1, Txnrd2, Txnrd3, SPS2, and SelM) increased in L group (p < 0.05), but the Dio3 and Sepx1 mRNA levels did not change. The results indicated that Se deficiency resulted in kidney dysfunction, activation of the NF-κB pathway, and a change in selenoprotein gene expression. The changes of inflammatory factor and selenoprotein gene expression levels were directly related to the abnormal renal functions induced by Se deficiency.

Selenium and Metabolic Disorders: An Emphasis on Type 2 Diabetes Risk

Selenium (Se) is a micronutrient that maintains biological functions through the action of Se containing proteins known as selenoproteins. Due to the known antioxidant effects of Se, supplements containing Se have been on the rise. While Se supplementation may be beneficial for Se deficient populations, few are at risk for Se deficiency due to the transportation of food from Se-rich regions and the rise of Se-enriched foods. Alarmingly, Se supplementation may have adverse effects in people who already receive an adequate Se supply. Specifically, an increased risk of type 2 diabetes has been reported in individuals with high baseline Se levels. However, this effect was restricted to males, suggesting the relationship between Se and glucose homeostasis may be sexually dimorphic. This review will discuss the current understanding of the interaction between Se and glucose homeostasis, including any sex differences that have been described.

Selenium supplementation has beneficial and detrimental effects on immunity to influenza vaccine in older adults

BACKGROUND & AIMS

Mortality resulting from influenza (flu) virus infections occurs primarily in the elderly through declining immunity. Studies in mice have suggested beneficial effects of selenium (Se) supplementation on immunity to flu but similar evidence is lacking in humans. A dietary intervention study was therefore designed to test the effects of Se-supplementation on a variety of parameters of anti-flu immunity in healthy subjects aged 50-64 years.

METHODS

A 12-week randomized, double-blinded, placebo-controlled clinical trial (ClinicalTrials.govNCT00279812) was undertaken in six groups of individuals with plasma Se levels <110 ng/mL. Four groups were given daily capsules of yeast enriched with 0 μg Se/day (SeY-0/d; n = 20), 50 μg Se/d (SeY-50/d; n = 18), 100 μg Se/d (SeY-100/d; n = 21) or 200 μg Se/d (SeY-200/d; n = 23). Two groups were given onion-containing meals with either <1 μg Se/d (SeO-0/d; n = 17) or 50 μg Se/d (SeO-50/d; n = 18). Flu vaccine was administrated at week 10 and immune parameters were assessed until week 12.

RESULTS

Primary study endpoints were changes in cellular and humoral immune responses. Supplementation with SeY and SeO affected different aspects of cellular immunity. SeY increased Tctx-ADCC cell counts in blood (214%, SeY-100/d) before flu vaccination and a dose-dependent increase in T cell proliferation (500%, SeY-50/100/200/d), IL-8 (169%, SeY-100/d) and IL-10 (317%, SeY-200/d) secretion after in vivo flu challenge. Positive effects were contrasted by lower granzyme B content of CD8 cells (55%, SeY-200/d). SeO (Se 50 μg/d) also enhanced T cell proliferation after vaccination (650%), IFN-γ (289%), and IL-8 secretion (139%), granzyme (209%) and perforin (190%) content of CD8 cells but inhibited TNF-α synthesis (42%). Onion on its own reduced the number of NKT cells in blood (38%). These effects were determined by comparison to group-specific baseline yeast or onion control groups. Mucosal flu-specific antibody responses were unaffected by Se-supplementation.

CONCLUSION

Se-supplementation in healthy human adults with marginal Se status resulted in both beneficial and detrimental effects on cellular immunity to flu that was affected by the form of Se, supplemental dose and delivery matrix. These observations call for a thorough evaluation of the risks and benefits associated with Se-supplementation.

Selenium and the thyroid

PURPOSE OF REVIEW

This article provides an update on the role of the essential trace element selenium and its interaction with the other trace elements iodine and iron that together contribute to adequate thyroid hormone status. Synthesis, secretion, metabolism and action of thyroid hormone in target tissues depend on a balanced nutritional availability or supplementation of these elements. Selenium status is altered in benign and malignant thyroid diseases and various selenium compounds have been used to prevent or treat widespread diseases such as goiter, autoimmune thyroid disease or thyroid cancer.

RECENT FINDINGS

Several studies, most with still too low numbers of cases, indicate that selenium administration in both autoimmune thyroiditis (Hashimoto thyroiditis) and mild Graves' disease improves clinical scores and well-being of patients and reduces thyroperoxidase antibody titers. However, published results are still conflicting depending on basal selenium status, dose, time and form of selenium used for intervention. Evidence for sex-specific selenium action, lack of beneficial effects in pregnancy and contribution of genetic polymorphisms (selenoprotein S) has been presented.

SUMMARY

Adequate nutritional supply of selenium that saturates expression of circulating selenoprotein P, together with optimal iodine and iron intake, is required for a healthy and functional thyroid during development, adolescence, adulthood and aging.

Chronic Kidney Disease Distinctly Affects Relationship Between Selenoprotein P Status and Serum Thyroid Hormone Parameters

INTRODUCTION

Chronic kidney disease (CKD) impairs thyroid hormone (TH) metabolism and is associated with low serum triiodothyronine (T3) concentrations in patients with a low glomerular filtration rate (GFR). Whether this results from decreased T3 formation from thyroxine (T4) by impaired 5'-deiodinase (DIO) activity and/or enhanced degradation of T3 and increased reverse triiodothyronine (rT3) formation from T4 by elevated 5-DIO activity remains unclear. Both activating 5'- and the inactivating 5-deiodination of TH are catalyzed by three selenium (Se)-dependent DIO isoenzymes. Selenoprotein P (SePP) is the major constituent of serum selenium, and functions as Se transport protein from liver to kidney and several other organs. This study tested the hypothesis that serum SePP and TH status are associated with the degree of renal impairment in patients with CKD.

PATIENTS AND METHODS

A total of 180 CKD patients (stages 1-5) and 70 chronic hemodialysis (CHD) patients undergoing hemodialysis three times per week for at least two years were prospectively investigated for clinical data, parameters of renal function, serum TH profile (thyrotropin, T4, free thyroxine [fT4], T3, free triiodothyronine (fT3), rT3, thyroxine-binding globulin [TBG]), C-reactive protein (CRP), and serum SePP.

RESULTS

In CKD patients, renal function was negatively associated with SePP concentration (standardized β = -0.17, p = 0.029); that is, SePP concentrations increased in more advanced CKD stages. In contrast, significantly lower SePP concentrations were found in patients on hemodialysis compared with CKD patients (M ± SD = 2.7 ± 0.8 mg/L vs. 3.3 ± .9 mg/L; p < 0.001). Notably, in CKD patients, the SePP concentration was negatively associated with T4 (standardized β = -0.16, p = 0.039) and fT4 (standardized β = -0.16, p = 0.039) concentrations, but no association was found with T3, fT3, rT3, T3/T4, rT3/T3, rT3/T4, or TBG concentrations. The SePP concentration was also negatively associated with CRP levels (standardized β = -0.17, p = 0.029). In the CHD group, no association was detected between SePP and the investigated TH parameters.

SUMMARY AND CONCLUSION

Impaired renal function is positively correlated with serum concentrations of SePP. In patients undergoing CHD treatment, SePP concentrations were significantly reduced, but the TH profile remained unaffected. These findings indicate an important contribution of kidney function on serum SePP homeostasis, and consequently on Se status.

Progression of micronutrient alteration and hepatotoxicity following acute PCB126 exposure

Polychlorinated Biphenyls (PCBs) are industrial chemicals that have become a persistent threat to human health due to ongoing exposure. A subset of PCBs, known as dioxin-like PCBs, pose a special threat given their potent hepatic effects. Micronutrients, especially Cu, Zn and Se, homeostatic dysfunction is commonly seen after exposure to dioxin-like PCBs. This study investigates whether micronutrient alteration is the byproduct of the ongoing hepatotoxicity, marked by lipid accumulation, or a concurrent, yet independent event of hepatic damage. A time course study was carried out using male Sprague-Dawley rats with treatments of PCB126, the prototypical dioxin-like PCB, resulting in 6 different time points. Animals were fed a purified diet, based on AIN-93G, for three weeks to ensure micronutrient equilibration. A single IP injection of either tocopherol-stripped soy oil vehicle (5 mL/kg) or 5 μmol/kg PCB126 dose in vehicle was given at various time points resulting in exposures of 9h, 18 h, 36 h, 3 days, 6 days, and 12 days. Mild hepatic vacuolar change was seen as early as 36 h with drastic changes at the later time points, 6 and 12 days. Micronutrient alterations, specifically Cu, Zn, and Se, were not seen until after day 3 and only observed in the liver. No alterations were seen in the duodenum, suggesting that absorption and excretion may not be involved. Micronutrient alterations occur with ROS formation, lipid accumulation, and hepatomegaly. To probe the mechanistic underpinnings, alteration of gene expression of several copper chaperones was investigated; only metallothionein appeared elevated. These data suggest that the disruption in micronutrient status is a result of the hepatic injury elicited by PCB126 and is mediated in part by metallothionein.

Gene-specific regulation of hepatic selenoprotein expression by interleukin-6

Sepsis is a severe inflammatory disease resulting in excessive production of pro-inflammatory cytokines including interleukin-6 (IL-6), causing oxidative stress, tissue damage and organ dysfunction. Health benefits have been observed upon selenium (Se) supplementation in severe sepsis. Selenium is incorporated into selenoproteins implicated in anti-oxidative defence, thyroid hormone metabolism and immunoregulation. Selenium metabolism is controlled by hepatocytes synthesizing and secreting the Se transporter selenoprotein P (SePP). The circulating SePP declines in sepsis causing low serum Se levels. Dysregulation of the hepatic selenoenzyme deiodinase type 1 (DIO1) potentially contributes to the low T3 (thyroid hormone) syndrome observed in severe diseases. We hypothesized that IL-6 affects hepatic selenoprotein biosynthesis directly. Testing human hepatocytes in culture, IL-6 reduced the concentrations of SePP mRNA and secreted SePP in a dose-dependent manner. In parallel, expression of DIO1 declined at the mRNA, protein and enzyme activity level. The effects of IL-6 on glutathione peroxidase (GPX) expression were isozyme-specific; GPX1 remained unaffected, while transcript concentrations of GPX2 increased and those of GPX4 decreased. This pattern of IL-6-dependent effects was mirrored in reporter gene experiments with SePP, DIO1, GPX1, and GPX2 promoter constructs pointing to direct transcriptional effects of IL-6. The redirection of hepatic selenoprotein biosynthesis by IL-6 may represent a central regulatory circuit responsible for the decline of serum Se and low T3 concentrations in sepsis. Accordingly, therapeutic IL-6 targeting may be effective for improving the Se and thyroid hormone status, adjuvant Se supplementation success and survival in sepsis.

Biomarkers of selenium status

The essential trace element, selenium (Se), has multiple biological activities, which depend on the level of Se intake. Relatively low Se intakes determine the expression of selenoenzymes in which it serves as an essential constituent. Higher intakes have been shown to have anti-tumorigenic potential; and very high Se intakes can produce adverse effects. This hierarchy of biological activities calls for biomarkers informative at different levels of Se exposure. Some Se-biomarkers, such as the selenoproteins and particularly GPX3 and SEPP1, provide information about function directly and are of value in identifying nutritional Se deficiency and tracking responses of deficient individuals to Se-treatment. They are useful under conditions of Se intake within the range of regulated selenoprotein expression, e.g., for humans <55 μg/day and for animals <20 μg/kg diet. Other Se-biomarkers provide information indirectly through inferences based on Se levels of foods, tissues, urine or feces. They can indicate the likelihood of deficiency or adverse effects, but they do not provide direct evidence of either condition. Their value is in providing information about Se status over a wide range of Se intake, particularly from food forms. There is need for additional Se biomarkers particularly for assessing Se status in non-deficient individuals for whom the prospects of cancer risk reduction and adverse effects risk are the primary health considerations. This would include determining whether supranutritional intakes of Se may be required for maximal selenoprotein expression in immune surveillance cells. It would also include developing methods to determine low molecular weight Se-metabolites, i.e., selenoamino acids and methylated Se-metabolites, which to date have not been detectable in biological specimens. Recent analytical advances using tandem liquid chromatography-mass spectrometry suggest prospects for detecting these metabolites.

Selenoprotein S is involved in maintenance and transport of multiprotein complexes

SelS (Selenoprotein S) is a selenocysteine-containing protein with roles in ER (endoplasmic reticulum) function and inflammation. It has been implicated in ERAD (ER-associated protein degradation), and clinical studies revealed an association of its promoter polymorphism with cytokine levels and human diseases. However, the pathways and interacting proteins that could shed light on pathogenesis of SelS-associated diseases have not been studied systematically. We performed a large-scale affinity isolation of human SelS and its mutant forms and analysed the proteins that interact with them. All previously known SelS targets and nearly two hundred additional proteins were identified that were remarkably enriched for various multiprotein complexes. Subsequent chemical cross-linking experiments identified the specific interacting sites in SelS and its several targets. Most of these interactions involved coiled-coil domains. The data suggest that SelS participates in intracellular membrane transport and maintenance of protein complexes by anchoring them to the ER membrane.

A polymorphism in the promoter region of the selenoprotein S gene (SEPS1) contributes to Hashimoto's thyroiditis susceptibility

CONTEXT

The association between selenium and inflammation and the relevance of selenoproteins in follicular thyroid cell physiology have pointed to a putative role of selenoproteins in the pathogenesis of autoimmune thyroid diseases.

OBJECTIVE

The aim of this study was to evaluate the role of a promoter variation in SEPS1, the selenoprotein S gene, in the risk for developing Hashimoto's thyroiditis (HT).

DESIGN

A case-control study was performed to assess the association of genetic variation in the SEPS1 gene (SEPS1 -105G/A single-nucleotide polymorphism, rs28665122) and HT.

SETTING

The study was conducted in north Portugal, Porto, in the period of 2007-2013.

PATIENTS OR OTHER PARTICIPANTS

A total of 997 individuals comprising 481 HT patients and 516 unrelated controls were enrolled in the study.

MAIN OUTCOME MEASURES

Genetic variants were discriminated by real-time PCR using TaqMan single-nucleotide polymorphism genotyping assays.

RESULTS

There is a significant association between the SEPS1 -105 GA and AA genotypes and HT [odds ratio (OR) 2.24, confidence interval (CI) 1.67-3.02, P < 5.0 × 10(-7), and OR 2.08, CI 1.09-3.97, P = .0268, respectively]. The A allele carriers are in higher proportion in the patient group than in the control population (46.2% vs 28.1%, P < 5.0 × 10(-7)) with an OR (CI) of 2.22 (1.67-2.97). The proportion of patients carrying the A allele is significantly higher in male patients with HT, representing a 3.94 times increased risk (P = 7.9 × 10(-3)).

CONCLUSION

Our findings support the existence of a link between SEPS1 promoter genetic variation and HT risk.

Acute and subacute response of iron, zinc, copper and selenium in pigs experimentally infected with Actinobacillus pleuropneumoniae

Experimental bacterial lung infection affects trace elements in blood and liver tissue.

Effects of selenoprotein S on oxidative injury in human endothelial cells

Background

Selenoprotein S (SelS) is an important endoplasmic reticulum and plasma membrane-located selenoprotein implicated in inflammatory responses and insulin resistance. However, the effects of SelS on endothelial cells (ECs) have not been reported. In the present study, the role of SelS in oxidative stress and the underlying mechanism were investigated in human ECs.

Methods

A SelS over-expression plasmid (pc-SelS) and a SelS-siRNA plasmid were transfected into human umbilical vein endothelial cells (American Type Culture Collection, USA). The cells were divided into four groups: control, SelS over-expression (transfected with pc-SelS), vector control, and SelS knockdown (transfected with siRNA-SelS). After treating the cells with H₂O₂, the effects of oxidative stress and the expression of caveolin-1 (Cav-1) and protein kinase Cα (PKCα) were investigated.

Results

Following treatment with H₂O₂, over-expression of SelS significantly increased cell viability and superoxide dismutase (SOD) activity, and decreased malondialdehyde (MDA) production and Cav-1 gene and protein expression. However, no effects on PKCα were observed. In contrast, knockdown of SelS significantly decreased cell viability, SOD activity, and PKCα gene and protein expression, and increased MDA production and Cav-1 gene and protein expression.

Conclusions

SelS protects ECs from oxidative stress by inhibiting the expression of Cav-1 and PKCα.

Serum selenium is low in newly diagnosed Graves' disease: a population-based study

CONTEXT

Selenium deficiency may play an important role in the initiation and progression of autoimmune thyroid disease.

OBJECTIVE

To compare serum selenium (s-Se) values in patients with newly diagnosed autoimmune thyroid disease and controls from the Danish population.

DESIGN AND SETTINGS

S-Se was measured in triplicate by a fluorimetric method.

PARTICIPANTS

Patients with newly diagnosed Graves' disease (GD) (n = 97) or autoimmune overt hypothyroidism (AIH) (n = 96), euthyroid subjects with high serum levels of thyroid peroxidase antibody (TPO-Ab) (TPO-Ab > 1500 U/ml, n = 92) and random controls (n = 830).

MAIN OUTCOME MEASURE

Differences in s-Se values.

RESULTS

S-Se was lower in patients with GD than in controls (mean (SD), GD: 89·9 μg/l (18·4); controls: 98·8 μg/l (19·7), P < 0·01). This was confirmed in a multivariate logistic regression model adjusting for age, sex, mineral supplements, smoking, geographical region and time of sampling (P < 0·01). In a linear model, s-Se was similar in patients with AIH (mean (SD): 98·4 μg/l (24·9)) and in controls (P = 0·86). In the multivariate model however, s-Se was marginally lower in patients with AIH compared to controls (P = 0·04). There was no significant difference in s-Se between euthyroid participants with high TPO-Ab and random controls (linear: P = 0·97; multivariate: P = 0·27).

CONCLUSION

Patients with newly diagnosed GD and AIH had significantly lower s-Se compared with random controls. Our observation supports the postulated link between inadequate selenium supply and overt autoimmune thyroid disease, especially GD.

Effects of different selenium levels on gene expression of a subset of selenoproteins and antioxidative capacity in mice

This study aimed to evaluate how excess selenium induces oxidative stress by determining antioxidant enzyme activity and changes in expression of selected selenoproteins in mice. BALB/c mice (n = 20 per group) were fed a diet containing 0.045 (Se-marginal), 0.1 (Se-adequate), 0.4 (Se-supernutrition), or 0.8 (Se-excess) mg Se/kg. Gene expression was quantified in RNA samples extracted from the liver, kidney, and testis by real-time quantitative reverse transcription-polymerase chain reaction. We found that glutathione peroxidase (GPx) and catalase activities decreased in livers of mice fed the marginal or excess dose of Se as compared to those in the Se-adequate group. Additionally, superoxide dismutase and glutathione reductase activities were significantly reduced only in mice fed the excess Se diet, compared to animals on the adequate Se diet. Se-supernutrition had no effect on hepatic mRNA levels of GPx isoforms 1 and 4 (GPx1 and GPx4), down-regulated GPx isoform 3 (GPx3), and upregulated selenoprotein W (SelW) mRNA expression. The excess Se diet led to decreased hepatic mRNA levels of GPx1, GPx3 and GPx4 but no change in testicular mRNA levels of GPx1, GPx3 or SelW. Dietary Se had no effect on testicular mRNA levels of GPx4. Thus, our results suggest that Se exposure can reduce hepatic antioxidant capacity and cause liver dysfunction. Dietary Se was found to differentially regulate mRNA levels of the GPx family or SelW, depending on exposure. Therefore, these genes may play a role in the toxicity associated with Se.

Selenistasis: epistatic effects of selenium on cardiovascular phenotype

Although selenium metabolism is intricately linked to cardiovascular biology and function, and deficiency of selenium is associated with cardiac pathology, utilization of selenium in the prevention and treatment of cardiovascular disease remains an elusive goal. From a reductionist standpoint, the major function of selenium in vivo is antioxidant defense via its incorporation as selenocysteine into enzyme families such as glutathione peroxidases and thioredoxin reductases. In addition, selenium compounds are heterogeneous and have complex metabolic fates resulting in effects that are not entirely dependent on selenoprotein expression. This complex biology of selenium in vivo may underlie the fact that beneficial effects of selenium supplementation demonstrated in preclinical studies using models of oxidant stress-induced cardiovascular dysfunction, such as ischemia-reperfusion injury and myocardial infarction, have not been consistently observed in clinical trials. In fact, recent studies have yielded data that suggest that unselective supplementation of selenium may, indeed, be harmful. Interesting biologic actions of selenium are its simultaneous effects on redox balance and methylation status, a combination that may influence gene expression. These combined actions may explain some of the biphasic effects seen with low and high doses of selenium, the potentially harmful effects seen in normal individuals, and the beneficial effects noted in preclinical studies of disease. Given the complexity of selenium biology, systems biology approaches may be necessary to reach the goal of optimization of selenium status to promote health and prevent disease.

Absence of selenoprotein P but not selenocysteine lyase results in severe neurological dysfunction

Dietary selenium restriction in mammals causes bodily selenium to be preferentially retained in the brain relative to other organs. Almost all the known selenoproteins are found in brain, where expression is facilitated by selenocysteine (Sec)-laden selenoprotein P. The brain also expresses selenocysteine lyase (Scly), an enzyme that putatively salvages Sec and recycles the selenium for selenoprotein translation. We compared mice with a genetic deletion of Scly to selenoprotein P (Sepp1) knockout mice for similarity of neurological impairments and whether dietary selenium modulates these parameters. We report that Scly knockout mice do not display neurological dysfunction comparable to Sepp1 knockout mice. Feeding a low-selenium diet to Scly knockout mice revealed a mild spatial learning deficit without disrupting motor coordination. Additionally, we report that the neurological phenotype caused by the absence of Sepp1 is exacerbated in male vs. female mice. These findings indicate that Sec recycling via Scly becomes limiting under selenium deficiency and suggest the presence of a complementary mechanism for processing Sec. Our studies illuminate the interaction between Sepp1 and Scly in the distribution and turnover of body and brain selenium and emphasize the consideration of sex differences when studying selenium and selenoproteins in vertebrate biology.