Exposure to a high selenium environment in Punjab, India: Effects on blood chemistry

Comprehensive Insights into the Health Effects of Selenium Exposure and Supplementation Among the Chinese Community Middle-Aged and Elderly: a Combined Retrospective Cohort Study and Intervention Study

Selenium (Se) is an essential trace element for maintaining human health, for example, plays a crucial role in preventing aging-related diseases. However, most studies on the health effects of Se among the community middle-aged and elderly have been observational or the health indices were single, and the related study among the Chinese population is limited. Additionally, China is recognized as among the countries facing a significant deficiency in Se, and Se contents in the human body may decrease with age. Therefore, a two-step study was conducted to explore the health effects of Se exposure and supplementation among such populations in China. Firstly, a retrospective cohort study was conducted to compare the health outcomes between such populations residing in Se-rich regions and non-Se-rich regions, involving a total of 102 subjects, with 51 residing in Se-rich regions and 51 in non-Se-rich regions. The hair-Se (H-Se) contents, serum-Se (S-Se) contents, and total cholesterol of subjects from Se-rich regions were significantly higher than their counterparts. Notably, significant positive associations were observed between S-Se and lipids. Secondly, a before-after self-control Se supplementation study among subjects residing in non-Se-rich regions was conducted. A total of 40 subjects administered Se tablets orally for 30 days, with Se of 120 μg/day. The results showed significant increases in H-Se and S-Se. Se supplementation also exhibited positive effects on alanine aminotransferase, homocysteine, and fasting glucose; however, high-density lipoprotein cholesterol significantly decreased. Overall, the community middle-aged and elderly residing in Se-rich regions or receiving quantitative Se supplementation could effectively improve Se contents in bodies and certain health indices, excluding lipids. These improvements encompass liver function, cardiovascular health, and glucose metabolism. These findings enhance our understanding of how Se impacts the health of the middle-aged and elderly, emphasizing the significance of targeted interventions for such populations in non-Se-rich regions. Trial registration: ChiCTR2000040987 ( https://www.chictr.org.cn ).

Invasive Round Goby (Neogobius melanostomus) Fish from the Southern Baltic as a Source of Arsenic and Selenium-Food Safety Aspects

Minimizing human exposure to arsenic (As) and ensuring an adequate dietary intake of selenium (Se) are significant issues in research on food sources. This study measured the content of As and Se in the muscles, gills, liver, and gonads of the fish round goby (Neogobius melanostomus) to assess the benefits and risks associated with their consumption. This was achieved by using dietary reference intake (DRI), estimated daily intake (EDI), target hazard quotient (THQ), and carcinogenic risk (CR). The elements were analyzed by atomic absorption spectrometry. The mean concentrations of As and Se (in μg kg-1 wet weight) were 25.1 and 161.4 in muscle, 58.8 and 367.4 in liver, 47.4 and 635.3 in gonads, and 16.4 and 228.5 in gills, respectively. Arsenic in the muscle portion of fish accounted for up to 0.5% of the DRI, while Se constituted approximately 30% of the DRI. The EDI values were below the reference oral dose (RfD). The THQ were much below the permissible levels (THQ < 1), and the CR were at least within the permissible limit (CR < 10-4). With regard to the As content, round goby muscles can be deemed safe for consumers. They may also be a valuable source of Se in the human diet. However, round goby consumption should be monitored for the proper and safe intake of these elements.

Does fluoride exposure affect thyroid function? A systematic review and dose-response meta-analysis

INTRODUCTION

Fluoride exposure may have various adverse health effects, including affecting thyroid function and disease risk, but the pattern of such relation is still uncertain.

METHODS

We systematically searched human studies assessing the relation between fluoride exposure and thyroid function and disease. We compared the highest versus the lowest fluoride category across these studies, and we performed a one-stage dose-response meta-analysis for aggregated data to explore the shape of the association.

RESULTS

Most retrieved studies (27 of which with a cross-sectional design) were conducted in Asia and in children, assessing fluoride exposure through its concentrations in drinking water, urine, serum, or dietary intake. Twenty-four studies reported data on thyroid function by measuring thyroid-related hormones in blood (mainly thyroid-stimulating-hormone - TSH), 9 reported data on thyroid disease, and 4 on thyroid volume. By comparing the highest versus the lowest fluoride categories, overall mean TSH difference was 1.05 μIU/mL. Dose-response curve showed no change in TSH concentrations in the lowest water fluoride exposure range, while the hormone levels started to linearly increase around 2.5 mg/L, also dependending on the risk of bias of the included studies. The association between biomarkers of fluoride exposure and TSH was also positive, with little evidence of a threshold. Evidence for an association between fluoride exposure and blood concentrations of thyroid hormones was less evident, though there was an indication of inverse association with triiodothyronine. For thyroid disease, the few available studies suggested a positive association with goiter and with hypothyroidism in both children and adults.

CONCLUSIONS

Overall, exposure to high-fluoride drinking water appears to non-linearly affect thyroid function and increase TSH release in children, starting above a threshold of exposure, and to increase the risk of some thyroid diseases.

Genetically determined circulating micronutrients and the risk of nonalcoholic fatty liver disease

Evidence from epidemiological literature on the association of circulating micronutrients with risk of nonalcoholic fatty liver disease (NAFLD) is inconsistent. We aimed to elucidate the causal relationships using Mendelian randomization (MR). Single-nucleotide polymorphisms associated with 14 circulating micronutrients (β-carotene, calcium, copper, folate, iron, magnesium, phosphorus, selenium, vitamin B6, B12, C, D, K1 and zinc) were employed as instrumental variables. Summary level data for NAFLD were obtained from a genome-wide association study (GWAS) meta-analysis of 8434 cases and 770,180 controls (discovery stage) and another two datasets including 1483 NAFLD cases and 17,781 controls (replication stage 1) and 2134 NAFLD cases and 33,433 controls (replication stage 2). Inverse variance-weighted method (IVW) was used as primary analysis, supplemented with a series of sensitivity analysis. Genetically predicted higher β‑carotene levels were suggestively associated with reduced NAFLD risk [odds ratio (OR) 0.81, 95% confidence interval (CI) 0.66-0.99; P = 0.047], whereas the association did not survive the false discovery rates (FDR) correction (PFDR = 0.164). Genetically predicted circulating iron (OR 1.16, 95% CI 1.05-1.29; P = 0.006, PFDR = 0.028), selenium (OR 1.11, 95% CI 1.03-1.20; P = 0.005, PFDR = 0.028) and vitamin B12 (OR 1.08, 95% CI 1.03-1.13; P = 0.002, PFDR = 0.028) were significantly associated with increased risk of NAFLD. Moreover, the findings were consistent in individual datasets (Pheterogeneity > 0.05) and confirmed in sensitivity analysis. Our study provided evidence that circulating iron, selenium and vitamin B12 might be causally linked to the risk of NAFLD, which deserves further exploration of the potential biological mechanism.

A preliminary predictive model for selenium nutritional status in residents based on three selenium biomarkers

BACKGROUND

Selenium (Se) is an essential nutrient and an important component of many selenoproteins that possess fundamental importance to human health. Selenium deficiency and excess will cause corresponding diseases in the human body. The nutritional health of Se in the human body mainly depends on the daily dietary Se intake of the human body, which in turn depends to a certain extent on the content of Se transmitted along the food chain. This study aims to research the transport of Se through the soil-crop-human chain in regions with different Se levels, and to establish the model between the residents' dietary Se intake and the three Se biomarkers (hair, nails, and plasma), to predict the nutritional health status of Se in residents through Se biomarkers.

METHOD

Carry out field and cross-sectional surveys of populations in Loujiaba Village and Longshui Village. Samples were collected from soil, crops, drinking water, residents' hair, nails, plasma, and diet. The concentration of available Se fractions was extracted from soil samples using 0.1 mol/L K2HPO4. The concentration of total Se for all samples was determined by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), and the relative standard deviation was less than 5%. In this study, hair, nails, and blood samples were collected from volunteers according to the Declaration of Helsinki and the Ethics Committee of Soochow University. The dietary nutritional structure and dietary Se intake of the population were randomly selected by 12 volunteers using the duplicate portion method. Data were described using mean ± standard deviation. We performed saliency analysis and correlation analysis (with Pearson correlation coefficient), and fitted a regression to evaluate the associations between these variables.

RESULTS

The soil total Se (5201 ± 609.2 μg/kg) and available Se (307.7 ± 83.5 μg/kg) in Luojiaba Village (LJB) were significantly higher than the soil total Se (229.2 ± 32.5 μg/kg) and available Se (21.9 ± 4.0 μg/kg) in Longshui Village (LS). The residents' dietary Se intake of LJB (150.3 ± 2.2 μg/d) was within the World Health Organization (WHO) recommended intake range, while LS (16.0 ± 0.4 μg/d) was close to the range of Keshan disease occurrence, and there was a risk of insufficient Se intake. The correlation analysis found significant positive correlations between residents' dietary Se intake and the three Se biomarkers. According to the preliminary model established in this study, if the daily dietary Se intake of residents reaches the WHO recommended value of 55-400 μg, the hair, nails, and plasma of Se concentration will be 522.1-2850.5 μg/kg, 1069.0-6147.4 μg/kg, and 128.3-661.36 μg/L, respectively.

CONCLUSION

Selenium is transmitted through the soil-crop-human chain, and the Se concentration that enters the human body through the food chain in high-Se areas is significantly higher than that in low-Se areas. The nutritional health status of Se in the human body depends on the daily dietary intake of the human body, and there is a significant correlation between the daily dietary Se intake of the human body and the three biomarkers of Se levels in the human body, so the three biomarkers can be used to evaluate the Se nutritional health of the human.

Associations of 10 trace element levels in the whole blood with risk of three types of obesity in the elderly

BACKGROUND

Currently, over 2 billion people worldwide suffer from obesity, which poses a serious health risk. More and more attention is being given to the effects of trace elements on obesity in recent years. Synergistic or antagonistic interactions among these elements can adversely or positively impact human health. However, epidemiological evidence on the relationship between trace element exposure levels and obesity has been inconclusive.

METHODS

Baseline data of 994 participants from the Cohort of Elderly Health and Environment Controllable Factors were used in the present study. ICP-MS was used to measure the concentrations of 10 trace elements in the whole blood of the older population. Binary logistic regression, restricted cubic splines (RCS) models, and Bayesian kernel machine regression (BKMR) models were employed to assess single, nonlinear, and mixed relationships between 10 trace element levels and three types of obesity based on body mass index (BMI), waist circumference (WC), and body fat percentage (BFP) in the elderly.

RESULTS

Based on BMI, WC and BFP, 51.8% of the included old population were defined as general overweight/obesity, 67.1% as abdominal obesity, and 36.2% as having slightly high/high BFP. After multivariable adjustment, compared with the lowest tertile, the highest tertile of blood selenium (Se) concentration was associated with an increased risk of all three types of obesity. Additionally, compared with the lowest tertile, higher tertiles of strontium (Sr) concentrations were associated with a lower risk of general overweight/obesity and having slightly high/high BFP, and the highest tertile of barium (Ba) was associated with a lower risk of having slightly high BFP, while higher tertiles of arsenic (As) concentrations were associated with an increased risk of having slightly high/high BFP, and the highest tertile of manganese (Mn) was associated with a higher risk of abdominal obesity. BKMR analyses showed a strong linear positive association between Se and three types of obesity. Higher blood levels of trace element mixture were associated with increased obesity risks in a dose-response pattern, with Se having the highest value of the posterior inclusion probability (PIP) within the mixture.

CONCLUSIONS

In this study, we found higher Se levels were associated with an elevated risk of obesity and high levels of Ba, Pb and Cr were associated with a decreased risk of obesity. Studies with larger samples are needed to confirm these findings.

The accessibility, necessity, and significance of certified reference materials for total selenium content and its species to improve food laboratories' performance

Micronutrients are one of the most important groups of nutrients that our body needs daily in trace amounts to tackle deficiencies. Selenium (Se) is a mineral that occurs naturally in foods and is an essential component of selenoproteins that support the healthy functioning of the human body. Therefore, monitoring dietary Se concentrations must be a higher priority to meet daily intakes. Fulfillment can be addressed through applying various analytical techniques, and the certified reference materials (CRMs) tool plays a crucial role in quality assurance/quality control (QA/QC). The availability of certified CRMs for total Se content with addition to their species is presented. The review emphasizes the necessity of incorporating more food matrix CRMs certifying Se species, apart from total Se content, to meet method validation requirements for food analysis laboratories. This would help CRM producers bridge the gap between available food matrix materials that are not certified for Se species.

Selenium exposure and urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine: Major effects of chemical species and sex

Selenium is an element present in trace amounts and different chemical forms. It may exert both beneficial and adverse effects on cellular redox status and on the generation of reactive oxygen species. 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG) is an oxidized derivative of deoxyguanosine, and a sensitive biomarker of oxidative stress and genotoxicity. The present study assessed the extent to which selenium status was associated with urinary 8-oxodG concentrations in a Northern Italian population. We recruited healthy, non-smoking blood donors living in the Reggio Emilia province during 2017-2019. We measured urinary 8-oxodG concentrations and used restricted cubic spline regression analyses to investigate the association between selenium status (estimated using food frequency questionnaires, urinary concentrations, and serum concentrations of selenium and selenium species) and 8-oxodG/g creatinine. Among 137 participants aged 30-60 years, median urinary selenium and 8-oxodG concentrations were 22.02 μg/L and 3.21 μg/g creatinine, respectively. Serum samples and selenium speciation analyses were available for 104 participants. Median total serum selenium levels and dietary intake were 116.5 μg/L and 78.7 μg/day, respectively. In spline regression analysis, there was little association between dietary, serum, or urinary selenium with 8-oxodG concentrations. In sex-specific analyses, urinary selenium showed a positive association with the endpoint among males. For single selenium species, we observed positive associations with urinary 8-oxodG for serum organic selenium species, and negative associations for inorganic selenium forms. In the most adjusted analysis, urinary 8-oxodG concentrations showed a strong positive association with selenomethione-bound selenium (Se-Met) and a negative association with inorganic tetravalent selenium, selenite. In sex-specific analyses, these associations were considerably stronger in males than in females. Overall, study findings indicate that selenium species exhibited very different patterns of associations with the biomarker of oxidative stress, and that these associations also depended on sex. Background exposure to Se-Met appears to be strongly and positively associated with oxidative stress.

Selenium Content in Freshwater and Marine Fish from Southern Brazil Coastal Plain: a Comparative Analysis on Environmental and Dietary Aspects

The coastal plain of Rio Grande do Sul is considered to be a Se-deficient region in terms of its population dietary habit, making it the focus of this study. Selenium dietary deficiency is a concern when we consider its potential critical health effects on the local population. Therefore, this study contributes new information on the levels of Se in several species of marine and freshwater fish in the region of the Patos-Mirim Lagoon system, coupled with a comparative analysis of the metalloid contents between both fish groups. The Se contents in the fish species ranged from 88 ± 13 to 688 ± 19 μg.kg^-1. The average Se concentration in the muscle tissue of the freshwater species (251 ± 96 μg kg^-1) was significantly lower than that of the marine species (412 ± 143 μg kg^-1). Likewise, no evidence of Se biomagnification was found among the fish from both the marine and freshwater environments, suggesting the absence of trophic transfer of Se. We note that to ensure that the RDA (Recommended Daily Allowance, 55 μg day^-1) of Se dietary intake for adults is met, at least 134 g of freshwater or 82 g of marine fish fillet could be incorporated into the diet of the population of Rio Grande do Sul. According to target hazard quotients (THQ) and the permissible safety limits, consumption of the fish species analyzed is safe for human health.

Scientific opinion on the tolerable upper intake level for selenium

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for selenium. Systematic reviews of the literature were conducted to identify evidence regarding excess selenium intake and clinical effects and potential biomarkers of effect, risk of chronic diseases and impaired neuropsychological development in humans. Alopecia, as an early observable feature and a well-established adverse effect of excess selenium exposure, is selected as the critical endpoint on which to base a UL for selenium. A lowest-observed-adverse-effect-level (LOAEL) of 330 μg/day is identified from a large randomised controlled trial in humans (the Selenium and Vitamin E Cancer Prevention Trial (SELECT)), to which an uncertainty factor of 1.3 is applied. A UL of 255 μg/day is established for adult men and women (including pregnant and lactating women). ULs for children are derived from the UL for adults using allometric scaling (body weight0.75). Based on available intake data, adult consumers are unlikely to exceed the UL, except for regular users of food supplements containing high daily doses of selenium or regular consumers of Brazil nuts. No risk has been reported with the current levels of selenium intake in European countries from food (excluding food supplements) in toddlers and children, and selenium intake arising from the natural content of foods does not raise reasons for concern. Selenium-containing supplements in toddlers and children should be used with caution, based on individual needs.

Correlation of Serum Selenium in Asthma Patients with Severity of the Disorder

Asthma is characterized by reversible airway obstruction, increased bronchial hyper-responsiveness and chronic inflammation, as well as higher levels of oxidative stress mainly due to decreased antioxidant defenses. Our primary aim was to investigate the correlation of serum selenium (Se) levels with the severity of asthma across gender, age, family history, and prevalence from childhood. Selenium levels in blood samples in 103 asthmatic patients and 103 healthy individuals were evaluated. The obtained data indicated that the mean serum Se levels in asthma patients were found to be twofold lower as compared to the controls (p < 0.001). However, there were no significant differences in the asthmatic patients when gender and age were considered. Patients characterized by family history of asthma and inhaler usage had 8% and 7% lower serum Se concentrations, although the difference was only border significant (p = 0.05). Multiple regression analysis demonstrated a significant inverse association of inhaler usage (β =  - 0.226; p < 0.001) with serum Se levels even after adjustment for asthma severity (β =  - 0.644; p < 0.001). While this report clearly necessitates a more detailed study, it is plausible that Se deficiency leads to impaired immune response, and therefore, Se supplementation might modulate oxidative stress in the lung and could potentially alleviate asthma pathophysiology.

SELENIUM-ASSOCIATED MECHANISMS OF PROGRESSION OF NONALCOHOLIC FATTY LIVER DISEASE IN HYPERTENSIVE PATIENTS

OBJECTIVE

The aim: To determine the role of selenium and Selenoprotein P in the intensification of inflammation processes, deviations of the functional state of the liver and the progression of changes in its parenchyma in patients with NAFLD and hypertension.

PATIENTS AND METHODS

Material and methods: Study included 100 gender and age matched NAFLD patients: 49 (67.3 % women) hypertensive (main group) and 51 (58.8 % women) non-hypertensive NAFLD patients. 20 individuals (55.0 % women) formed control group. Diagnosis of NAFLD and hypertension was made according to respective guidelines. All patients underwent measurement of liver transferases, selenium, Selenoprotein P, IL-8 and IL-10.

RESULTS

Results: In both study groups, ALT and AST levels were significantly predominant in patients with steatohepatitis than steatosis. Increase in IL-8 and IL-10 was found in main study groups but not in subgroup analysis. In hypertensive NAFLD patients with steatosis, ALT correlated with selenium and Selenoprotein P. A direct correlation was between the de Ritis index and IL-8. Selenium correlated with IL-8 but not IL-10. Selenoprotein P correlated inversely with IL-8 and directly with IL-10.

CONCLUSION

Conclusions: Intensification of inflammation and depletion of antioxidant protection under presence of hypertension deepen redox violations in NAFLD patients. Such changes can be only partially compensated by anti-inflammatory and antioxidative activity. Selenium and Selenoprotein P are important substances in progression of NAFLD and should be assessed regarding diagnosis and treatment of NAFLD patients.

Sex-specific relationship between blood selenium levels and platelet count in a large cohort representative of the United States population

While several small studies have found that selenium deficiency is associated with low platelet counts, they lack generalizability. We used data from the National Health and Nutrition Examination Surveys collected over a 12-year period. We examined the relationship between selenium quartiles and platelet count using survey-weighted linear regression models adjusting for age, sex, race, household income to poverty threshold income, highest education attainment, smoking status, red blood cell folate, and body mass index. Of the 21,764 participants, 51% were females, 23% African Americans, and 25% were >65 years of age. Mean (SD) platelet count was 243(64) 10⁹/L and selenium was 183(32) µg/L. Women had significantly higher platelet count but lower selenium levels than men (258 vs. 227 10⁹/L and 181 vs. 185 µg/L respectively; both P < 0.0001). In adjusted analysis, participants in the highest selenium quartile had 8.0x10⁹/L higher platelet count as compared to those in the lowest selenium quartile (95%CI = 4.1 to 11.9; P < 0.0001). Gender modified the relationship between the two; although there was no difference in women, platelet count was higher in the highest than the lowest selenium quartile in men (interaction p-value = 0.001). These findings highlight the importance of selenium and gender in platelet biology which needs to be explored.

Novel mechanistic insights of selenium induced microscopic, histochemical and physio-biochemical changes in tomato (Solanum lycopersicum L.) plant. An account of beneficiality or toxicity

Selenium (Se) is a well-known beneficial element in plants. The window of Se between toxic and optimal concentration is narrow and uneven which fluctuates with plants species. This experiment was aimed to investigate the morpho-physiological, microscopic and histochemical responses of two different varieties of tomato (S-22 and PKM-1), exposed to different concentrations of Se (0, 10, 40 or 80 µM), applied to soil at 30 days after transplantation (DAT). At 40 DAT, it was observed that high concentrations (40 or 80 µM) of Se radically increased oxidative stress examined by elevated reactive oxygen species (ROS), malondialdehyde (MDA) content, cell death, electrolyte leakage and decreased chlorophyll content leading phenotypic symptoms of Se-induced toxicity like stunted growth and chlorosis. Furthermore, high doses of Se altered the chloroplast and stomatal organisation, and adversely affected the photosynthetic performance of plants. But low concentration of Se improved the plant dry mass, photosynthesis, Rubisco activity, protein content and maintained the steady-state equilibrium among ROS generation and antioxidant enzymes like catalase, peroxidase and superoxide dismutase. Our outcomes proposed that high concentration of Se generated toxicity (phyto-selenosis), whereas lower concentration of Se-triggered positive impact by improving growth, photosynthetic traits and maintaining steady-state equilibrium between scavenging-system and ROS generation.

Update on thyroid eye disease: Regional variations in prevalence, diagnosis, and management

Thyroid eye disease (TED) is a rare disease that can lead to decreased quality of life, permanent disfigurement, and vision loss. Clinically, TED presents with exophthalmos, periorbital edema, extraocular muscle dysfunction, and eyelid retraction, and can lead to vision-threatening complications such as exposure to keratopathy and dysthyroid optic neuropathy (DON). Over the last several years, significant advancements have been made in the understanding of its pathophysiology as well as optimal management. Ethnic variations in the prevalence, clinical presentation, and risk of vision-threatening complications of TED are summarized, and risk factors associated with TED are discussed. Additionally, significant advances have been made in the management of TED. The management of TED traditionally included anti-inflammatory medications, orbital radiation therapy, orbital surgical decompression, and biologic therapies. Most recently, targeted therapies such as teprotumumab, an insulin-like growth factor-1 receptor antagonist, have been studied in the context of TED, with promising initial data. In this review, updates in the understanding and management of TED are presented with a focus on the international variations in presentation and management.

Selenium-enriched Polysaccharide: an Effective and Safe Selenium Source of C57 Mice to Improve Growth Performance, Regulate Selenium Deposition, and Promote Antioxidant Capacity

Selenium-enriched polysaccharide (SeEPS) was prepared by reducing Se(IV) to elemental selenium and organic selenium in polysaccharide medium by the obtained Enterobacter cloacae strain Z0206 under aerobic conditions. In the present study, we focused on investigating the role of short-term supplementation of SeEPS at supernutritional doses in the regulation of growth performance, liver damage, antioxidant capacity, and selenium (Se) accumulation in C57 mice. Thirty-two C57 mice were randomly divided into four groups: the control group was gavaged with equal volume of phosphate-buffered saline, while the sodium selenite (Na2SeO3), selenomethionine (SeMet), and SeEPS groups were gavaged with 0.5 mg Se/kg BW of Na2SeO3, SeMet, and selenium-enriched polysaccharide (n = 8), respectively. We examined liver injury indicators, antioxidant capacity in the serum and liver, selenium deposition at different sites, selenoprotein levels, and selenocysteine-synthesizing and degradation-associated gene expression in mouse livers. SeEPS supplementation dramatically increased average daily weight gain but reduced the feed-to-gain ratio (F/G) of mice (P < 0.05). Compared to Na2SeO3 and SeMet supplementation, SeEPS supplementation at supernutritional doses did not cause the liver damage. SeEPS supplementation also markedly enhanced total antioxidant capacity (T-AOC), catalase (CAT), glutathione peroxidase (GSH-PX), and total superoxide dismutase (T-SOD) activities but reduced malondialdehyde (MDA) levels in the liver and serum (P < 0.05), while significantly increasing selenocysteine-synthesizing and degradation-related gene (SEPHS2, SEPSECS, Secisbp, Scly) expression at the mRNA level (P < 0.05), thus upregulating the mRNA levels of selenoproteins (SELENOP, SELENOK) (P < 0.05). We suggest that SeEPS could be a potential replacement for inorganic selenium to improve animals' growth performance, promote antioxidant capacity, and regulate selenium deposition.

The beneficial and hazardous effects of selenium on the health of the soil-plant-human system: An overview

Selenium (Se), which can be both hazardous and beneficial to plants, animals and humans, plays a pivotal role in regulating soil-plant-human ecosystem functions. The biogeochemical behavior of Se and its environmental impact on the soil-plant-human system has received broad attention in the last decades. This review provides a comprehensive understanding of Se biogeochemistry in the soil-plant-human system. The speciation, transformation, bioavailability as well as the beneficial and hazardous effects of Se in the soil-plant-human system are summarized. Several important aspects in Se in the soil-plant-human system are detailed mentioned, including (1) strategies for biofortification in Se-deficient areas and phytoremediation of soil Se in seleniferous areas; (2) factors affecting Se uptake and transport by plants; (3) metabolic pathways of Se in the human body; (4) the interactions between Se and other trace elements in plant and animals, in particular, the detoxification of heavy metals by Se. Important research hotspots of Se biogeochemistry are outlined, including (1) the coupling of soil microbial activity and the Se biogeochemical cycle; (2) the molecular mechanism of Se metabolic in plants and animals; and (3) the application of Se isotopes as a biogeochemical tracer in research. This review provides up-to-date knowledge and guidelines on Se biogeochemistry research.

A Functional Variant in SEPP1 Interacts With Plasma Selenium Concentrations on 3-Year Lipid Changes: A Prospective Cohort Study

Background: Excess selenium has been related with adverse lipid levels in previous epidemiological studies. Meanwhile, a functional variant in SEPP1 (encodes selenoprotein P), namely rs7579, has been suggested to modulate lipid metabolism. However, the interactions between selenium status and rs7579 polymorphism on lipid changes remain unclear.

Objective: To examine whether the associations between plasma selenium and 3-year lipid changes is modified by rs7579 polymorphism.

Methods: A prospective cohort study was conducted among 1,621 individuals to examine the associations between baseline plasma selenium and 3-year lipid changes, as well as the interactions between plasma selenium and rs7579 polymorphism on lipid changes.

Results: The median (interquartile range) concentration of plasma selenium was 91.68 (81.55–104.92) μg/L. Higher plasma selenium was associated with adverse 3-year lipid changes. Comparing the highest to the lowest quartiles of plasma selenium concentrations, 3-year lipid changes were elevated by 8.25% (95% CI: 1.54–14.96%) for triglycerides (P = 0.016), 5.88% (3.13–8.63%) for total cholesterol (P < 0.001), 7.37% (3.07–11.67%) for low-density lipoprotein cholesterol (P = 0.0008), 6.44% (2.66–10.21%) for non-high-density lipoprotein cholesterol (P = 0.0009), 4.99% (0.62–9.36%) for total cholesterol/high-density lipoprotein cholesterol ratio (P = 0.025), and 7.00% (1.55–12.46%) for low-density lipoprotein cholesterol/high-density lipoprotein cholesterol ratio (P = 0.012). In analyses stratified by rs7579 genotypes, positive associations between plasma selenium concentrations and 3-year changes in triglycerides, TC, LDL-C, non-HDL-C, TC/HDL-C ratio, and LDL-C/HDL-C ratio were observed among CC genotype carriers, but negative associations between plasma selenium and TC/HDL-C ratio, and LDL-C/HDL-C ratio were observed among TT genotype carriers.

Conclusions: Our findings suggested that plasma selenium was associated with 3-year lipid changes differentially by rs7579 genotypes, and higher plasma selenium was associated with adverse lipid changes among rs7579 CC genotype carriers, but not among T allele carriers.

A Spatial Ecological Study on Hair Selenium Level of Residents in Keshan Disease Endemic and Non-endemic Areas in Heilongjiang Province, China

This study was aimed to provide, by mapping the spatial distribution of hair selenium levels of residents, visualized evidence for assessment of KD elimination from a perspective of selenium nutrition of the residents living in the KD-endemic and non-endemic areas. Using a spatial ecological research design, 401 male permanent residents in KD-endemic and non-endemic areas participated in this study. Demographic information and hair samples were obtained through a questionnaire survey and sample collection, respectively. Hair selenium was measured using hydride generation atomic fluorescence spectrometry. Thematic maps were created, and spatial analysis was conducted using ArcGIS 9.0. The median of hair selenium of the participants was 0.30 (IQR, 0.23-0.34) mg/kg. The median hair selenium of the residents in the KD-endemic areas was significantly lower than that of the residents of the non-endemic areas. The hair selenium levels of residents were spatially clustered, with cold spots and hot spots located in northwest and southwest regions respectively. Residents living in KD-endemic areas may still have selenium deficiency. Measuring hair selenium levels of residents in KD-endemic areas as a molecular marker of selenium nutritional status as part of KD surveillance could provide visualized evidence for the evaluation of KD elimination from a perspective of selenium nutrition of the residents living in the KD endemic areas.

Association of Urinary and Dietary Selenium and of Serum Selenium Species with Serum Alanine Aminotransferase in a Healthy Italian Population

The trace element selenium is of considerable interest due to its toxic and nutritional properties, which markedly differ according to the dose and the chemical form. It has been shown that excess selenium intake increases the risk of type 2 diabetes and, possibly, other metabolic diseases like hyperlipidemia and non-alcoholic fatty liver disease (NAFLD). For the latter, however, epidemiologic evidence is still limited. We carried out a cross-sectional study recruiting 137 healthy blood donors living in Northern Italy and assessed their exposure to selenium through different methods and measuring serum selenium species. We performed linear and spline regression analyses to assess the relation of selenium and its forms with serum alanine aminotransferase (ALT) levels, a marker of NAFLD. Urinary selenium levels were positively and somewhat linearly correlated with ALT (beta regression coefficient (β) 0.11). Conversely, the association of dietary selenium intake with ALT was positive up to 100 µg/day and null above that amount (β 0.03). Total serum selenium was inversely associated with ALT up to 120 µg/L, and slightly positive above that amount. Concerning the different serum selenium species, ALT positively correlated with two organic forms, selenocysteine (β 0.27) and glutathione peroxidase-bound selenium (β 0.09), showed a U-shaped relation with the inorganic tetravalent form, selenite, and an inverse association with human serum albumin-bound selenium (β -0.56). Our results suggest that overall exposure to selenium, and more specifically to some of its chemical forms, is positively associated with ALT, even at levels so far generally considered to be safe. Our findings add to the evidence suggesting that low-dose selenium overexposure is associated with NAFLD.

Role for Selenium in Metabolic Homeostasis and Human Reproduction

Selenium (Se) is a micronutrient essential for life. Dietary intake of Se within the physiological range is critical for human health and reproductive functions. Selenium levels outside the recommended range have been implicated in infertility and variety of other human diseases. However, presently it is not clear how different dietary Se sources are processed in our bodies, and in which form or how much dietary Se is optimum to maintain metabolic homeostasis and boost reproductive health. This uncertainty leads to imprecision in published dietary guidelines and advice for human daily intake of Se and in some cases generating controversies and even adverse outcomes including mortality. The chief aim for this review is to describe the sources of organic and inorganic Se, the metabolic pathways of selenoproteins synthesis, and the critical role of selenprotenis in the thyroid gland homeostasis and reproductive/fertility functions. Controversies on the use of Se in clinical practice and future directions to address these challenges are also described and discussed herein.

Serum selenium and non-alcoholic fatty liver disease (NAFLD) in U.S. adults: National Health and Nutrition Examination Survey (NHANES) 2011-2016

BACKGROUND

Selenium is an essential trace element that shows beneficial or adverse health effects depending on the dose. Laboratory studies suggest that high selenium may contribute to the development of non-alcoholic fatty liver disease (NAFLD). However, human evidence is limited. We evaluated the associations of serum selenium level with serum alanine aminotransferase (ALT) activity and suspected NAFLD prevalence in U.S. adults.

METHODS

We conducted the cross-sectional analysis in 3827 adults aged 20 years and older without viral hepatitis, hemochromatosis, or alcoholic liver disease who participated in the National Health and Nutrition Examination Survey (NHANES) 2011-2012, 2013-2014, and 2015-2016. Serum selenium was measured using inductively coupled plasma dynamic reaction cell mass spectrometry. Suspected NAFLD cases were defined in the presence of serum ALT >30 international units (IU)/L in men and >19 I.U./L in women in the absence of other identifiable causes of liver disease.

RESULTS

The median (interquartile range) of serum selenium level was 127.9 (117.9, 139.4) μg/L. Non-linear associations of serum selenium with NAFLD prevalence and serum ALT activity were observed in the generalized additive models with penalized splines. After adjustment for sociodemographic variables, lifestyle factors, body mass index, and NHANES survey cycles, positive associations were found at > ~130 μg/L serum selenium with both NAFLD and ALT, whereas the associations were flattened at < ~130 μg/L.

CONCLUSIONS

Our findings provide evidence of non-linear associations of serum selenium with ALT activity and NAFLD prevalence. In particular, positive associations were found above serum selenium level of 130 μg/L, whereas no association was observed below this value. This finding requires confirmation in future prospective cohort studies.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

Selenium and Nano-Selenium Biofortification for Human Health: Opportunities and Challenges

Selenium is an essential micronutrient required for the health of humans and lower plants, but its importance for higher plants is still being investigated. The biological functions of Se related to human health revolve around its presence in 25 known selenoproteins (e.g., selenocysteine or the 21st amino acid). Humans may receive their required Se through plant uptake of soil Se, foods enriched in Se, or Se dietary supplements. Selenium nanoparticles (Se-NPs) have been applied to biofortified foods and feeds. Due to low toxicity and high efficiency, Se-NPs are used in applications such as cancer therapy and nano-medicines. Selenium and nano-selenium may be able to support and enhance the productivity of cultivated plants and animals under stressful conditions because they are antimicrobial and anti-carcinogenic agents, with antioxidant capacity and immune-modulatory efficacy. Thus, nano-selenium could be inserted in the feeds of fish and livestock to improvise stress resilience and productivity. This review offers new insights in Se and Se-NPs biofortification for edible plants and farm animals under stressful environments. Further, extensive research on Se-NPs is required to identify possible adverse effects on humans and their cytotoxicity.