Potential Role Of Selenium Research Articles

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.

Selenium and Its Compounds in the Treatment of Anxiety and Related Disorders: A Scoping Review of Translational and Clinical Research

Anxiety disorders are among the most common mental disorders worldwide and often respond incompletely to existing treatments. Selenium, a micronutrient that is a component of several biologically active selenoproteins, is also involved in several aspects of brain functioning and may exert antidepressant and anxiolytic effects through multiple pathways. The current paper is a scoping review of translational, observational, and interventional evidence on the potential role of selenium and its compounds in the management of anxiety and related disorders. Evidence from animal models suggests that this approach may be promising. Though evidence from observational studies in humans is inconsistent and affected by several confounding factors, the available evidence from randomized controlled trials suggests that selenium supplementation may be beneficial in the management of certain anxiety-related conditions, such as anxiety in medically ill patients, prevention of anxiety following exposure to traumatic stress, and obsessive-compulsive disorder. This paper provides a critical evaluation of the existing evidence base, including unanswered questions that could serve as the focus of further research, and outlines the potential benefits and risks associated with the use of selenium in anxiety disorders.

Selenium Status in Patients with Chronic Liver Disease: A Systematic Review and Meta-Analysis.

Background: The potential role of selenium in preventing chronic liver diseases remains controversial. This meta-analysis aimed to summarize the available evidence from observational studies and intervention trials that had evaluated the associations between body selenium status and chronic liver diseases. Methods: We comprehensively searched MEDLINE, Embase, Web of Science, and Cochrane Library from inception to April 2021. The study protocol was registered at PROSPERO (CRD42020210144). Relative risks (RR) for the highest versus the lowest level of selenium and standard mean differences (SMD) with 95% confidence intervals (CI) were pooled using random-effects models. Heterogeneity and publication bias were evaluated using the I2 statistic and Egger’s regression test, respectively. Results: There were 50 studies with 9875 cases and 12975 population controls in the final analysis. Patients with hepatitis (SMD = −1.78, 95% CI: −2.22 to −1.34), liver cirrhosis (SMD = −2.06, 95% CI: −2.48 to −1.63), and liver cancer (SMD = −2.71, 95% CI: −3.31 to −2.11) had significantly lower selenium levels than controls, whereas there was no significant difference in patients with fatty liver diseases (SMD = 1.06, 95% CI: −1.78 to 3.89). Moreover, the meta-analysis showed that a higher selenium level was significantly associated with a 41% decrease in the incidence of significant advanced chronic liver diseases (RR = 0.59, 95% CI: 0.49 to 0.72). Conclusion: Our meta-analysis suggested that both body selenium status and selenium intake were negatively associated with hepatitis, cirrhosis, and liver cancer. However, the associations for fatty liver diseases were conflicting and need to be established in prospective trials.

Potential Role of Selenium in the Treatment of Cancer and Viral Infections.

Selenium has been extensively evaluated clinically as a chemopreventive agent with variable results depending on the type and dose of selenium used. Selenium species are now being therapeutically evaluated as modulators of drug responses rather than as directly cytotoxic agents. In addition, recent data suggest an association between selenium base-line levels in blood and survival of patients with COVID-19. The major focus of this mini review was to summarize: the pathways of selenium metabolism; the results of selenium-based chemopreventive clinical trials; the potential for using selenium metabolites as therapeutic modulators of drug responses in cancer (clear-cell renal-cell carcinoma (ccRCC) in particular); and selenium usage alone or in combination with vaccines in the treatment of patients with COVID-19. Critical therapeutic targets and the potential role of different selenium species, doses, and schedules are discussed.

Potential Role of Selenium Against Hepatotoxicity Induced by 2,4-Dichlorophenoxyacetic Acid in Albino Wistar Rats.

The present study aims to investigate the hepatoprotective effects of selenium on toxicity induced by 'Désormone Lourd' based on 2,4-dichlorophenoxyacetic acid in Wistar rats. Male Wistar rats were divided into four groups and were treated orally. The (C) group was used as a control, while the test groups were treated with Se (0.2mg/kg b.w.), 2,4-D (5mg/kg b.w.) or both (2,4-D + Se) for 4weeks. Our results showed that chronic treatment with 2,4-D resulted in hepatotoxicity, as revealed by an increase in liver function markers Aminotransferases (ALT, AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and total bilirubin (TB), along with reduced total protein content and albumin. An overall pro-oxidant effect was associated with a decrease in the reduced glutathione (GSH) content and the enzymatic activity of glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx), and an increase in malondialdehyde (MDA) and protein carbonyl levels (PCO). Microscopic observation of liver in 2,4-D-treated rats reveals lesions, which results in perivascular inflammatory infiltration around the vessel, sinusoidal dilatation and vacuolization of hepatocytes. However, selenium supplementation in 2,4-D-treated rats elicited a reduction in the toxic effects of the pesticide by improving the studied parameters, which was confirmed by the histological study of the liver. Selenium appears to have a promising prophylactic effect through its effective anti-radical action against the hepatotoxic effects of 2,4-D.

Effects of ultrasound and selenium on human neurons in vitro.

As the effects of ultrasound on human brain functions might bear therapeutic potential, in this study, we examined the effects of diagnostic, i.e. non-thermal, ultrasound, on morphology, networking, and metabolic activity of SH- SY5Y human neurons in culture, as well as on the expression of GAP-43, Hsp90 and VEGF proteins, with and without selenium in the culture medium. The rationale for studying selenium lays in the observation that selenium improves functional neurologic outcome in traumatic brain injury and, therefore, analysis of the interactions between ultrasound and selenium may be of clinical interest. In the presence of selenium, ultrasound increased the overall number and length of elongations arising from the neuron bodies, thus reflecting an increase in the complexity of neuronal networks and circuits. The expression of GAP-43, Hsp90 and VEGF and metabolic activity of SH-SY5Y neurons, studied as markers of cell damage, were not affected by ultrasound or selenium. This study suggests that ultrasound may modulate neuronal networking in vitro without inducing cellular or molecular damage and highlights the potential role of selenium in the ultrasound-elicited cellular responses.

Protective role of selenium against chromium stress involving metabolites and essential elements in Brassica juncea L. seedlings.

The present study aimed at the potential role of selenium in providing protection to plants subjected to chromium toxicity. The study was carried out on 15-day-old seedlings of Brassica juncea raised in the solutions of Cr (300µM) and Se (2, 4 and 6µM), both alone and in combinations under controlled laboratory environment. The effects were studied on growth, plant metabolites (involved in osmotic homeostasis and stress protection), and essential elements. The results showed that the exposure of B. juncea seedlings to 300µM Cr led to an increase in the contents of total sugars, reducing sugars, non-reducing sugars, total phenols and flavonoids. However, a significant decline in growth characteristics, the contents of proteins and free amino acids was observed. The essential elements (Na, K, Ca, Mg, C, H, N) also decreased in response to Cr. Se application in binary combinations, on the other hand, aided in improving seed germination (19%), root (88.3%) and shoot (18.2%) lengths. It also helped to increase the contents of sugars [total (16.3%), reducing (21.6%) and non-reducing (15.2%)], phenols (36.7%) and flavonoids (27.4%), thereby aiding in alleviating the phytotoxicity of Cr. The profiling of polyphenols and amino acids, and histological study of phenols supported the above results. The contents of essential elements also showed a significant increase, while Cr uptake was observed to decline by Se supplementation. The observations from the present study indicate that Se has the ability to influence primary and secondary metabolism, improve mineral nutrition and reduce Cr uptake in B. juncea seedlings to combat the Cr phytotoxicity and enhance the tolerance against stress.

Higher Serum Selenium Concentration is Associated with a Higher Prevalence of Esophageal Squamous Dysplasia in Bomet, Kenya

Abstract 15 Background: East Africa is a region of high esophageal squamous cell carcinoma (ESCC) incidence, and is known to have low soil selenium levels. Low selenium status measured in blood has been associated with ESCC risk. We measured serum selenium in a cross-sectional study of subjects from Bomet, Kenya, a region with a high incidence of ESCC and esophageal squamous dysplasia (ESD), its precursor lesion. Methods: An age and sex-stratified sample of 294 asymptomatic adult residents completed questionnaires and underwent endoscopy with Lugol's iodine and biopsy for detection of ESD in this community-based study. Serum selenium concentrations were measured using instrumental neutron activation analysis. Odds ratios (OR) and confidence intervals (95% CI) for associations between serum selenium and ESD were calculated using unconditional logistic regression, adjusting for multiple potential confounders. Ethical approval was obtained from the National Cancer Institute, Tenwek Hospital, and Kenyatta National Hospital. Results: Higher serum selenium (quartile 4) was associated with prevalence of ESD (OR: 3.03; 95% CI:1.05, 8.74) relative to lower serum selenium (quartile 1). This association remained significant after adjusting for potential confounders (Q4 vs Q1: OR: 4.24; 95% CI: 1.16, 15.46). Serum selenium concentration did differ significantly by geographic location (p=0.001); however, this did not explain the association between selenium and ESD. Conclusions: We found a significant adverse association between higher serum selenium levels and risk of ESD. These results are in contrast to our hypothesis derived from previous observations of an inverse association between selenium and ESCC. The discrepancy may be due to the difference in endpoint of ESD rather than ESCC. Further work is needed to better understand the potential role of selenium in esophageal cancer prevention and control strategies. Funding: This work was supported by the Intramural Research Program, Division of Cancer Epidemiology & Genetics, National Cancer Institute, NIH. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST: Natalie R. Pritchett No relationship to disclose Michael M. Mwachiro No relationship to disclose Stephen L. Burgert Employment: Centers for Gastroenterology, Fort Collins, Colorado, USA Research Funding: Covidien Gwen Murphy No relationship to disclose John D. Brockman No relationship to disclose Christian C. Abnet No relationship to disclose Sanford M. Dawsey No relationship to disclose

Selenium and its supplementation in cardiovascular disease--what do we know?

The trace element selenium is of high importance for many of the body’s regulatory and metabolic functions. Balanced selenium levels are essential, whereas dysregulation can cause harm. A rapidly increasing number of studies characterizes the wide range of selenium dependent functions in the human body and elucidates the complex and multiple physiological and pathophysiological interactions of selenium and selenoproteins. For the majority of selenium dependent enzymes, several biological functions have already been identified, like regulation of the inflammatory response, antioxidant properties and the proliferation/differentiation of immune cells. Although the potential role of selenium in the development and progression of cardiovascular disease has been investigated for decades, both observational and interventional studies of selenium supplementation remain inconclusive and are considered in this review. This review covers current knowledge of the role of selenium and selenoproteins in the human body and its functional role in the cardiovascular system. The relationships between selenium intake/status and various health outcomes, in particular cardiomyopathy, myocardial ischemia/infarction and reperfusion injury are reviewed. We describe, in depth, selenium as a biomarker in coronary heart disease and highlight the significance of selenium supplementation for patients undergoing cardiac surgery.

Has Selenium a Chemopreventive Effect on Hepatocellular Carcinoma?

Hepatocellular carcinoma (HCC) is one of the most lethal cancers in the world. Its etiology includes chronic liver disease, viral hepatitis, alcoholism, and hepatic cirrhosis. Both oxidative stress and inflammatory mechanisms have been implicated in HCC pathophysiology. Surgical resection and liver transplants are currently used to treat HCC. Consequently, there exists a decisive requirement to explore possible alternative chemopreventive and therapeutic strategies for HCC. The use of dietary antioxidants and micronutrients has been proposed as a useful means for the HCC management. Trace elements such as selenium are involved in several major metabolic pathways as well as antioxidant defense systems. In particular, selenium is an important oligo-element that plays a central role in cellular redox processes even if the amount necessary for the cell functions is in a very narrow range. However, selenium is involved in the prevention of numerous chronic diseases and cancers. This review will examine the potential role of selenium in HCC prevention and treatment and, in detail, focus on: i) description of selenium in biological systems and in mammalian proteins, ii) involvement of selenium in HCC, iii) in vivo and in vitro effects of selenium in preclinical models of HCC and iv) potential challenges involved in the selenium use in the prevention and treatment of HCC.

Selenium and Risk of Bladder Cancer: A Population-Based Case-Control Study

Emerging evidence indicates a potential role of selenium in the prevention of several types of cancer, including bladder cancer. We investigated the association between toenail selenium concentrations and bladder cancer risk in a population-based case-control study in New Hampshire. We analyzed data from 857 incidence cases diagnosed between July 1, 1994 and June 30, 2001 and 1,191 general population controls. Newly diagnosed cases of bladder cancer were identified from the New Hampshire State Cancer Registry, which operates a rapid reporting system. Controls were selected from population lists (driver's license and Medicare enrollment). We used logistic regression analyses to generate odds ratios (OR) and 95% confidence intervals (95% CI), controlling for age, sex, and pack-years of smoking and conducted separate analyses according to the intensity of p53 immunohistochemical staining of the tumor. Overall, toenail selenium concentrations were not significantly related to bladder cancer [OR Q4 versus Q1, 0.90 (95% CI, 0.68-1.19); P(trend) = 0.15]. However, within specific subgroups there were inverse associations, i.e., among moderate smokers [OR, 0.61 (95% CI, 0.39-0.96); P(trend) = 0.004], women [OR, 0.66 (95% CI, 0.40-1.10); P(trend) = 0.11], and those with p53-positive cancers [OR Q4 versus Q1, 0.57 (95% CI, 0.34-0.94); P(trend) = 0.01]. Our results indicate that selenium is not inversely related to risk of bladder cancer overall; however, they raise the possibility that selenium may be preventive in certain molecular phenotypes of tumors (e.g., p53 positive) or within certain subsets of a population (e.g., women or moderate smokers).

Relationship of Low Serum Selenium to Anemia among Primary School Children Living in Rural Vietnam

A cross-sectional study of 292 primary school children was conducted in rural Vietnam to investigate the relationship among micronutrient deficiencies, and other risk factors for anemia. Serum levels of iron, copper, zinc, selenium and magnesium were determined by inductively coupled plasma mass spectrometry and that of retinol by high performance liquid chromatography. Hemoglobin concentration in whole blood was measured by the cyanmethemoglobin method. The incidence of low serum zinc, selenium, magnesium, and copper in the children was 91.4, 75.6, 59.5, and 8.6%, respectively. Forty-five percent of the children were anemic and 11.3% suffered from vitamin A deficiency. A parameter significant associated with anemia was low serum selenium and vice versa (OR 1.85, 95% CI 1.06-3.24, p<0.05). Other factors associated with anemia were serum retinol <1.05 micromol/L (OR 2.05, 95% CI 1.25-3.36, p<0.01), and age in years (OR 1.59, 95% CI 1.16-2.18, p<0.01). The study showed that low selenium is associated with anemia among school children in Vietnam. Interventions are required to gain insight into the potential role of selenium on prevention and control of anemia.