Genetic polymorphisms that affect selenium status and response to selenium supplementation in United Kingdom pregnant women

Selenium and Arsenic Levels, Prevalence of Common Variants of Genes Involved in Their Metabolism, and Psoriasis Disease

Using an Inductively Coupled Plasma Mass Spectrometer we measured the concentration of selenium and arsenic in serum and blood samples from 336 unselected psoriatic patients and 336 matched healthy controls to evaluate any associations with the clinical course of the disease. We genotyped 336 patients and 903 matched controls to evaluate the prevalence of SOD2 (rs4880), CAT (rs1001179), GPX1 (rs1050450), and DMGDH (rs921943) polymorphisms using Taqman assays. The mean selenium (Se) level in serum was 74 µg/L in patients and 86 µg/L in controls (p < 0.001). The mean Se level in blood was 95 µg/L in patients and 111 µg/L in controls (p < 0.001). Psoriasis risk was greatest among participants with the lowest serum (<68.75 µg/L, OR: 8.30; p < 0.001) and lowest blood concentrations of Se (<88.04 µg/L, OR: 10.3; p < 0.001). Similar results were observed in subgroups of males and females. We found an inverse correlation of selenium levels with PASI, NAPSI, and BSA scores. There was no significant difference in the distribution of the CAT, GPX1, DMGDH, and SOD2 polymorphisms. Among carriers of rs4880, rs1001179, and rs921943 polymorphisms, blood selenium levels were significantly lower. The mean arsenic level in serum was 0.79 µg/L in patients and 0.7 µg/L in controls (p = 0.2). The mean concentration in blood was 1.1 µg/L in patients and 1.3 µg/L in controls (p < 0.001). In conclusion, we found that lower selenium levels, in blood and serum, are associated with psoriasis risk and its more severe course. Future prospective studies should focus on the optimalisation of the concentration of this trace element not only for prophylactic guidance but also to support the treatment of this disease.

Genetic and Environmental Factors in Autoimmune Thyroid Disease: Exploring Associations with Selenium Levels and Novel Loci in a Latvian Cohort

The interplay of genetic, immune and environmental factors strongly contributes to the development of autoimmune thyroid disease (AITD), which can be classified as Graves' disease (GD) or Hashimoto thyroiditis (HT). One of the most studied exogenous factors in the pathogenesis of AITD is selenium, which, in the form of selenoproteins, strengthens the antioxidative defence system of thyroid cells against superoxide production. Furthermore, it modulates inflammatory cytokine release and autoantibody production. The aim of this study was to assess the associations of genetic factors with selenium levels in a cohort of adults with HT and GD and healthy controls from Latvia. A total of 148 GD patients, 102 HT patients and 2442 control participants were included in the study. The genotypes were determined using genome-wide genotyping; imputation was carried out using the TOPMed r2 imputation panel; and association analysis was performed with PLINK v1.90b7. We found three loci associated with GD (LSAMP, HNRNPA3P5, and NTN1) and one locus associated with HT (VAT1L); furthermore, one locus was associated with a serum selenium concentration > 80 µg/L (LINC01544/RNF152/PIGN). The detected associations could be attributed to population-specific effects or unknown stratification in our cohort, and further assessment of these results is required to explain the relationships of genetic traits with AITD and other phenotypes.

The regulation of methylation on the Z chromosome and the identification of multiple novel Male Hyper-Methylated regions in the chicken

DNA methylation is a key regulator of eukaryote genomes, and is of particular relevance in the regulation of gene expression on the sex chromosomes, with a key role in dosage compensation in mammalian XY systems. In the case of birds, dosage compensation is largely absent, with it being restricted to two small Male Hyper-Methylated (MHM) regions on the Z chromosome. To investigate how variation in DNA methylation is regulated on the Z chromosome we utilised a wild x domestic advanced intercross in the chicken, with both hypothalamic methylomes and transcriptomes assayed in 124 individuals. The relatively large numbers of individuals allowed us to identify additional genomic MHM regions on the Z chromosome that were significantly differentially methylated between the sexes. These regions appear to down-regulate local gene expression in males, but not remove it entirely (unlike the lncRNAs identified in the initial MHM regions). These MHM regions were further tested and the most balanced genes appear to show decreased expression in males, whilst methylation appeared to be far more correlated with gene expression in the less balanced, as compared to the most balanced genes. In addition, quantitative trait loci (QTL) that regulate variation in methylation on the Z chromosome, and those loci that regulate methylation on the autosomes that derive from the Z chromosome were mapped. Trans-effect hotspots were also identified that were based on the autosomes but affected the Z, and also one that was based on the Z chromosome but that affected both autosomal and sex chromosome DNA methylation regulation. We show that both cis and trans loci that originate from the Z chromosome never exhibit an interaction with sex, whereas trans loci originating from the autosomes but affecting the Z chromosome always display such an interaction. Our results highlight how additional MHM regions are actually present on the Z chromosome, and they appear to have smaller-scale effects on gene expression in males. Quantitative variation in methylation is also regulated both from the autosomes to the Z chromosome, and from the Z chromosome to the autosomes.

Prediagnostic selenium status, selenoprotein gene variants and association with breast cancer risk in a European cohort study

Selenium (Se) may help prevent breast cancer (BC) development. Owing to limited observational evidence, we investigated whether prediagnostic Se status and/or variants in the selenoprotein genes are associated with BC risk in a large European cohort. Se status was assessed by plasma measures of Se and its major circulating proteins, selenoprotein P (SELENOP) and glutathione peroxidase 3 (GPX3), in matched BC case-control pairs (2208 for SELENOP; 1785 for GPX3 and Se) nested within the European Prospective Investigation into Cancer and Nutrition (EPIC). Single nucleotide polymorphisms (SNPs, n = 452) in 55 selenoprotein and Se metabolic pathway genes and an additional 18 variants previously associated with Se concentrations were extracted from existing genotyping data within EPIC for 1564 case-control pairs. Multivariable-adjusted logistic regression models were used to calculate the odds ratios (ORs) and 95 % confidence intervals (CIs) of the association between Se status markers, SNP variants and BC risk. Overall, there was no statistically significant association of Se status with BC risk. However, higher GPX3 activity was associated with lower risk of premenopausal BC (4th versus 1st quartile, OR = 0.54, 95 % CI: 0.30-0.98, Ptrend = 0.013). While none of the genetic variant associations (P ≤ 0.05) retained significance after multiple testing correction, rs1004243 in the SELENOM selenoprotein gene and two SNPs in the related antioxidant TXN2 gene (rs4821494 and rs5750261) were associated with respective lower and higher risks of BC at a significance threshold of P ≤ 0.01. Fourteen SNPs in twelve Se pathway genes (P ≤ 0.01) in interaction with Se status were also associated with BC risk. Higher Se status does not appear to be associated with BC risk, although activity of the selenoenzyme GPX3 may be inversely associated with premenopausal BC risk, and SNPs in the Se pathway alone or in combination with suboptimal Se status may influence BC risk.

The effect of selenium supplementation in pregnant women on maternal, fetal, and newborn outcomes: a systematic review and meta-analysis

OBJECTIVE

Low maternal selenium status has been associated with poor pregnancy outcomes, including preterm birth. This study aimed to evaluate available evidence of the effects of selenium supplementation during pregnancy on preterm birth and related maternal, fetal, and newborn outcomes.

DATA SOURCES

MEDLINE, Embase, CINAHL, Global Index Medicus, and the Cochrane Library were systematically searched on June 23, 2022, without language or time restrictions.

STUDY ELIGIBILITY CRITERIA

Randomized controlled trials and nonrandomized interventional studies were included if they compared the effects of selenium supplementation with placebo or no treatment among pregnant women. The review protocol was registered in the International Prospective Register of Systematic Reviews (identification number: CRD42022383669).

METHODS

For outcomes reported by ≥1 study, a meta-analysis was conducted. Because of the small number of studies and high clinical heterogeneity between populations, random-effects models were used. The Risk of Bias 2 and Risk Of Bias In Non-randomized Studies - of Interventions tools were used to assess study quality, and Grading of Recommendations Assessment, Development, and Evaluation analysis was used to determine the certainty of evidence for each outcome.

RESULTS

Literature searches identified 5105 unique records, and 32 studies met the eligibility criteria. Of note, 11 reports were not included for analysis following research integrity assessments. Moreover, 10 trials and 3 observational studies met the inclusion criteria; however, only 8 trials (1851 women) and 1 prospective cohort study (71,728 women) reported on at least 1 review outcome. Our results could not determine the effect of selenium supplementation on preterm birth at <37 weeks of gestation (relative risk, 0.65; 95% confidence interval, 0.26-1.63; very low certainty evidence) and <34 weeks of gestation (relative risk, 1.05; 95% confidence interval, 0.59-1.44; very low certainty evidence).

CONCLUSION

There is limited evidence on the effects of selenium supplementation during pregnancy. Further trials, with larger sample sizes, more representative populations, and reliable assessment of maternal selenium status at trial entry, are required.

SELENOP rs3877899 Variant Affects the Risk of Developing Advanced Stages of Retinopathy of Prematurity (ROP)

The significance of selenoproteins for the incidence of prematurity and oxidative-damage-related diseases in premature newborns is poorly understood. The latter are at risk for ROP as well as BPD, IVH, PDA, RDS, and NEC, which is particularly high for newborns with extremely low gestational age (ELGA) and extremely low birth weight (ELBW). This study evaluates the hypothesis that variation in the selenoprotein-encoding genes SELENOP, SELENOS, and GPX4 affects the risk of ROP and other comorbidities. The study included infants born ≤ 32 GA, matched for onset and progression of ROP into three groups: no ROP, spontaneously remitting ROP, and ROP requiring treatment. SNPs were determined with predesigned TaqMan SNP genotyping assays. We found the association of the SELENOP rs3877899A allele with ELGA (defined as <28 GA), ROP requiring treatment, and ROP not responsive to treatment. The number of RBC transfusions, ELGA, surfactant treatment, and coexistence of the rs3877899A allele with ELGA were independent predictors of ROP onset and progression, accounting for 43.1% of the risk variation. In conclusion, the SELENOP rs3877899A allele associated with reduced selenium bioavailability may contribute to the risk of ROP and visual impairment in extremely preterm infants.

Metabolism and Anticancer Mechanisms of Selocompounds: Comprehensive Review

Selenium (Se) is an essential micronutrient with several functions in cellular and molecular anticancer processes. There is evidence that Se depending on its chemical form and the dosage use could act as a modulator in some anticancer mechanisms. However, the metabolism of organic and inorganic forms of dietary selenium converges on the main pathways. Different selenocompounds have been reported to have crucial roles as chemopreventive agents, such as antioxidant activity, activation of apoptotic pathways, selective cytotoxicity, antiangiogenic effect, and cell cycle modulation. Nowadays, great interest has arisen to find therapies that could enhance the antitumor effects of different Se sources. Herein, different studies are reported related to the effects of combinatorial therapies, where Se is used in combination with proteins, polysaccharides, chemotherapeutic agents or as nanoparticles. Another important factor is the presence of single nucleotide polymorphisms in genes related to Se metabolism or selenoprotein synthesis which could prevent cancer. These studies and mechanisms show promising results in cancer therapies. This review aims to compile studies that have demonstrated the anticancer effects of Se at molecular levels and its potential to be used as chemopreventive and in cancer treatment.

Associations between Circulating SELENOP Level and Disorders of Glucose and Lipid Metabolism: A Meta-Analysis

Selenoprotein P (SELENOP) is an extracellular antioxidant, selenium transporter, and hepatokine interfering with glucose and lipid metabolism. To study the association between the circulating SELENOP concentration and glucose and lipid metabolic diseases (GLMDs), including gestational diabetes (GD), metabolic syndrome (MetS), non-alcoholic fatty liver disease, obesity, and type 2 diabetes, as well as the individual markers, a meta-analysis was conducted by searching multiple databases from their establishment through March 2022 and including 27 articles published between October 2010 and May 2021, involving 4033 participants. Participants with GLMDs had higher levels of SELENOP than those without GLMDs (standardized mean difference = 0.84, 95% CI: 0.16 to 1.51), and the SELENOP levels were positively correlated with the markers of GLMDs (pooled effect size = 0.09, 95% CI: 0.02 to 0.15). Subgroup analyses showed that the SELENOP concentrations were higher in women with GD and lower in individuals with MetS than their counterparts, respectively. Moreover, SELENOP was positively correlated with low-density lipoprotein cholesterol, but not with the other markers of GLMDs. Thus, the heterogenicity derived from diseases or disease markers should be carefully considered while interpreting the overall positive association between SELENOP and GLMDs. Studies with a larger sample size and advanced design are warranted to confirm these findings.

Genetic Variation Interacts with Selenium Exposure Regarding Breast Cancer Risk: Assessing Dietary Intake, Serum Levels and Genetically Elevated Selenium Levels

Selenium has been suggested to be protective regarding breast cancer risk but no overall effect has been established. Genetics may modify the effect. This study compares the effect of selenium exposure on breast cancer risk between women with different alleles in single-nucleotide polymorphisms (SNPs). The Malmö Cancer and Diet Study, a cohort including 17,035 women and >25 years of follow-up on breast cancer diagnosis, was used. Five promising SNPs regarding interaction with selenium exposure were selected from the literature: rs1050450, rs4880, rs3877899, rs7579, and rs71304. Selenium exposure was assessed in three ways: genetically elevated (n = 16,429), dietary intake (n = 15,891) and serum levels (n = 2037) at baseline. Cox regression and logistic regression analyses evaluated breast cancer risk from selenium exposure, stratified for the SNPs and adjusted for risk factors. A total of 1946 women were diagnosed with breast cancer. Women with T/T alleles in rs1050450 had lower breast cancer risk compared with C/C, HR 0.81 (0.68–0.96). Interaction by rs1050450 limited a protective effect of higher selenium intake to T/T carriers, HR 0.68 (0.43–1.08) for intermediate intake and HR 0.63 (0.40–1.00) for high intake. No interactions or risk differences were seen for other SNPs or for serum selenium or genetically elevated selenium. The results indicate that genetic variation in rs1050450 might affect breast cancer risk and that selenium exposure could be a possible modifiable risk factor for breast cancer among women with that variation.

Evaluating the Diagnostic Value of a Combined Indicator of Vitamin B12 Status (cB12) Throughout Pregnancy

Background

Inadequate provision of vitamin B₁₂ during pregnancy is associated with a number of adverse maternal and fetal outcomes. We set out to (1) suggest pregnancy-specific reference ranges for a range of biomarkers of vitamin B₁₂; (2) assess the temporal behaviors of these markers over the course of pregnancy; and (3) test whether any biomarkers, including the genetic marker HIBCH rs291466 strongly associated with MMA measured early in pregnancy could reliably and significantly predict future B₁₂ status within a healthy UK population of pregnant women.

Materials and Methods

We used existing biobank samples from the placebo arm of the UK Selenium in PRegnancy Intervention (SPRINT) study, to generate biochemical data for serum folate, B₁₂, holotranscobalamin (HoloTC), total homocysteine (tHcy), and MMA, calculate cB₁₂, and genotyped the polymorphism rs291466 in gene HIBCH on a total of n=114 women across trimesters 1–3 of their pregnancy. We performed a series of exploratory cross-sectional and longitudinal analyses to investigate levels at each trimester, suggest references ranges, evaluate changes and correlations between the B₁₂ biomarkers, and assess the predictive capabilities of each biomarker from 12-weeks to 35-weeks of gestation.

Results

Significant changes in all vitamin B₁₂ biomarker values were observed over the three trimesters (P < 0.05). Our study shows that cB₁₂ values were largely constant and stable throughout trimester 1 (T1) and T2 (i.e., up to week 20), but declined significantly in T3 (−66% | P < 0.001). Yet, cB₁₂ generally remained within the normal boundaries. We identified pregnancy and trimester-specific reference ranges for each biomarker at each trimester, notably for total serum B₁₂. This marker fell below the recommended cut-offs in 1/3 of the cohort at the third trimester, contrasting other markers (mostly normal). Our multivariate analyses indicated that none of the biomarkers could reliably and accurately predict any other biomarkers than themselves later in pregnancy. Yet, HoloTC seems to be a promising predictor within the limitations of our cohort, constituted of B₁₂-replete individuals. Most notably, cB₁₂ did not significantly predict itself between trimesters. Finally, we show that the HIBCH variant has little predictive power for MMA or cB₁₂ as it does not explain the significant increase in MMA concentrations nor the decline of cB₁₂ throughout pregnancy.

Conclusion

Trimester-specific reference ranges for biomarkers of vitamin B₁₂ in normal pregnancy are suggested. However, these biomarkers have limited predictive value in identifying mothers at elevated risk of vitamin B₁₂ insufficiency/deficiency during pregnancy.

Supranutritional selenium suppresses ROS-induced generation of RANKL-expressing osteoclastogenic CD4+ T cells and ameliorates rheumatoid arthritis

OBJECTIVE

The benefit of Se supplementation in rheumatoid arthritis (RA) has been tested in clinical trials, but results remain inconclusive. The objective of this study was to specifically investigate the potential benefit of supranutritional Se by examining human samples from an area with supranutritional Se intake and testing a mouse model of RA.

METHODS

Peripheral blood mononuclear cells (PBMCs) from RA patients (N = 57) and healthy controls (HC, N = 71) from an area of supranutritional Se intake (Enshi, Hubei, China) were analysed by flow cytometry. Serum cytokine and Se levels were measured by cytometric beads array (CBA) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. With sufficient or supranutritional selenium intake, mice were induced with collagen-induced arthritis (CIA) and examined for disease activity and immunopathology. The influence of Se supplementation in the generation of RANKL-expressing osteoclastogenic CD4+ T cells was investigated by in vitro assays.

RESULTS

In Enshi city, HC showed the above-normal concentrations of serum Se concentrations while RA patients were enriched in the normal range (70-150 ng mL-1) or below. RA patients with higher Se levels demonstrated milder disease and lower levels of C-reactive protein, IL-6, RANKL and Th17 cells. In the mouse CIA model, supranutritional Se supplementation delayed disease onset, ameliorated joint pathology and reduced CD4+CD44+RANKL+ T cells. Se supplementation could suppress RANKL expression in cultured mouse Th17 cells.

CONCLUSION

Supranutritional Se suppresses RANKL-expressing osteoclastogenic CD4+ T cells and could be beneficial to RA, which warrants formal testing in randomised clinical trials.

The Association of Familial Hypertension and Risk of Gestational Hypertension and Preeclampsia

It has not been established how history of hypertension in the father or mother of pregnant women, combined with obesity or smoking, affects the risk of main forms of pregnancy-induced hypertension. A cohort of 912 pregnant women, recruited in the first trimester, was assessed; 113 (12.4%) women developed gestational hypertension (GH), 24 (2.6%) developed preeclampsia (PE) and 775 women remained normotensive (a control group). Multiple logistic regression was used to calculate adjusted odds ratios (AOR) (and 95% confidence intervals) of GH and PE for chronic hypertension in the father or mother of pregnant women. Some differences were discovered. (1) Paternal hypertension (vs. absence of hypertension in the family) was an independent risk factor for GH (AOR-a = 1.98 (1.2–3.28), p = 0.008). This odds ratio increased in pregnant women who smoked in the first trimester (AOR-a = 4.71 (1.01–21.96); p = 0.048) or smoked before pregnancy (AOR-a = 3.15 (1.16–8.54); p = 0.024), or had pre-pregnancy overweight (AOR-a = 2.67 (1.02–7.02); p = 0.046). (2) Maternal hypertension (vs. absence of hypertension in the family) was an independent risk factor for preeclampsia (PE) (AOR-a = 3.26 (1.3–8.16); p = 0.012). This odds ratio increased in the obese women (AOR-a = 6.51 (1.05–40.25); p = 0.044) and (paradoxically) in women who had never smoked (AOR-a = 5.31 (1.91–14.8); p = 0.001). Conclusions: Chronic hypertension in the father or mother affected the risk of preeclampsia and gestational hypertension in different ways. Modifiable factors (overweight/obesity and smoking) may exacerbate the relationships in question, however, paradoxically, beneficial effects of smoking for preeclampsia risk are also possible. Importantly, paternal and maternal hypertension were not independent risk factors for GH/PE in a subgroup of women with normal body mass index (BMI).

Fetal Programming Is Deeply Related to Maternal Selenium Status and Oxidative Balance; Experimental Offspring Health Repercussions

Nutrients consumed by mothers during pregnancy and lactation can exert permanent effects upon infant developing tissues, which could represent an important risk factor for diseases during adulthood. One of the important nutrients that contributes to regulating the cell cycle and tissue development and functionality is the trace element selenium (Se). Maternal Se requirements increase during gestation and lactation. Se performs its biological action by forming part of 25 selenoproteins, most of which have antioxidant properties, such as glutathione peroxidases (GPxs) and selenoprotein P (SELENOP). These are also related to endocrine regulation, appetite, growth and energy homeostasis. In experimental studies, it has been found that low dietary maternal Se supply leads to an important oxidative disruption in dams and in their progeny. This oxidative stress deeply affects gestational parameters, and leads to intrauterine growth retardation and abnormal development of tissues, which is related to endocrine metabolic imbalance. Childhood pathologies related to oxidative stress during pregnancy and/or lactation, leading to metabolic programing disorders like fetal alcohol spectrum disorders (FASD), have been associated with a low maternal Se status and intrauterine growth retardation. In this context, Se supplementation therapy to alcoholic dams avoids growth retardation, hepatic oxidation and improves gestational and breastfeeding parameters in FASD pups. This review is focused on the important role that Se plays during intrauterine and breastfeeding development, in order to highlight it as a marker and/or a nutritional strategy to avoid diverse fetal programming disorders related to oxidative stress.

The Prevalence of Inorganic Mercury in Human Kidneys Suggests a Role for Toxic Metals in Essential Hypertension

The kidney plays a dominant role in the pathogenesis of essential hypertension, but the initial pathogenic events in the kidney leading to hypertension are not known. Exposure to mercury has been linked to many diseases including hypertension in epidemiological and experimental studies, so we studied the distribution and prevalence of mercury in the human kidney. Paraffin sections of kidneys were available from 129 people ranging in age from 1 to 104 years who had forensic/coronial autopsies. One individual had injected himself with metallic mercury, the other 128 were from varied clinicopathological backgrounds without known exposure to mercury. Sections were stained for inorganic mercury using autometallography. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) was used on six samples to confirm the presence of autometallography-detected mercury and to look for other toxic metals. In the 128 people without known mercury exposure, mercury was found in: (1) proximal tubules of the cortex and Henle thin loops of the medulla, in 25% of kidneys (and also in the man who injected himself with mercury), (2) proximal tubules only in 16% of kidneys, and (3) Henle thin loops only in 23% of kidneys. The age-related proportion of people who had any mercury in their kidney was 0% at 1-20 years, 66% at 21-40 years, 77% at 41-60 years, 84% at 61-80 years, and 64% at 81-104 years. LA-ICP-MS confirmed the presence of mercury in samples staining with autometallography and showed cadmium, lead, iron, nickel, and silver in some kidneys. In conclusion, mercury is found commonly in the adult human kidney, where it appears to accumulate in proximal tubules and Henle thin loops until an advanced age. Dysfunctions of both these cortical and medullary regions have been implicated in the pathogenesis of essential hypertension, so these findings suggest that further studies of the effects of mercury on blood pressure are warranted.

The influence of nutrigenetics on biomarkers of selenium nutritional status

Selenium (Se) is an essential micronutrient for human biology that executes its functions as the amino acid selenocysteine via selenoproteins, which have important functions in, for example, antioxidation, immunomodulation, thyroid metabolism, and human fertility. Se nutritional status is assessed using the quantification of blood Se biomarkers, which are influenced by several factors, including diet, age, gender, smoking status, alcohol consumption, health condition, and the genetic characteristics of individuals. Nutrigenetic studies have identified single nucleotide polymorphisms in selenoproteins that might clarify the high variability in values reported for biomarkers of Se nutritional status in different populations, and the response of these biomarkers to Se supplementation with either organic or inorganic forms of Se. This review aims to (1) define the basic aspects of Se biology, (2) describe the current most commonly used biomarkers of Se nutritional status, and (3) provide a summary of associations between functional single nucleotide polymorphisms in selenoproteins and biomarkers of Se status in healthy populations.

Genome-Wide Association Study of Response to Selenium Supplementation and Circulating Selenium Concentrations in Adults of European Descent

BACKGROUND

Selenium (Se) is a trace element that has been linked to many health conditions. Genome-wide association studies (GWAS) have identified variants for blood and toenail Se levels, but no GWAS has been conducted to date on responses to Se supplementation.

OBJECTIVES

A GWAS was performed to identify the single nucleotide polymorphisms (SNPs) associated with changes in Se concentrations after 1 year of supplementation. A GWAS of basal plasma Se concentrations at study entry was conducted to evaluate whether SNPs for Se responses overlap with SNPs for basal Se levels.

METHODS

A total of 428 participants aged 40-80 years of European descent from the Selenium and Celecoxib Trial (Sel/Cel Trial) who received daily supplementation with 200 µg of selenized yeast were included for the GWAS of responses to supplementation. Plasma Se concentrations were measured from blood samples collected at the time of recruitment and after 1 year of supplementation. Linear regression analyses were performed to assess the relationship between each SNP and changes in Se concentrations. We further examined whether the identified SNPs overlapped with those related to basal Se concentrations.

RESULTS

No SNP was significantly associated with changes in Se concentration at a genome-wide significance level. However, rs56856693, located upstream of the NEK6, was nominally associated with changes in Se concentrations after supplementation (P = 4.41 × 10-7), as were 2 additional SNPs, rs11960388 and rs6887869, located in the dimethylglycine dehydrogenase (DMGDH)/betaine-homocysteine S-methyltransferase (BHMT) region (P = 0.01). Alleles of 2 SNPs in the DMGDH/BHMT region associated with greater increases in Se concentrations after supplementation were also strongly associated with higher basal Se concentrations (P = 8.67 × 10-8).

CONCLUSIONS

This first GWAS of responses to Se supplementation in participants of European descent from the Sel/Cel Trial suggests that SNPs in the NEK6 and DMGDH/BHMT regions influence responses to supplementation.

Minerals in Pregnancy and Their Impact on Child Growth and Development

During pregnancy, women undergo metabolic and physiological changes, and their needs are higher, to maintain growth and development of the fetus. If the nutritional status of the expectant mother is not satisfactory, some maternal and neonatal complications can occur. In the second and third trimester of pregnancy, there is a reserve of nutrients in the fetus that can be utilized after birth; thereby, children present an accelerated growth in the first years of life, which is a proven response to the available nutrition pattern. However, if such a pattern is insufficient, there will be deficits during development, including brain function. Therefore, despite many recent published works about gestational nutrition, uncertainties still remain on the mechanisms of absorption, distribution, and excretion of micronutrients. Further elucidation is needed to better understand the impacts caused either by deficiency or excess of some micronutrients. Thus, to illustrate the contributions of minerals during prenatal development and in children, iodine, selenium, iron, zinc, calcium, and magnesium were selected. Our study sought to review the consequences related to gestational deficiency of the referred minerals and their impact on growth and development in children born from mothers with such deficiencies

Selenium and at-risk pregnancy: challenges and controversies

Selenium (Se), an essential trace element, is inserted as selenocysteine into an array of functional proteins and forms the core of various enzymes that play a cardinal role in antioxidant defense mechanisms, in redox regulation, and in thyroid hormone metabolism. Variations in plasma Se are due to nutritional habits, geographic and ethnic differences, and probably to genetic polymorphisms, the latter still to be conclusively established. Se concentrations were reported to be low in women of reproductive age in the UK, decreasing further during pregnancy, this resulting in low plasma and placental antioxidant enzyme activities. Since low serum Se levels have been found in women with preeclampsia, it has been hypothesized that low maternal Se status during early gestation may be an indicator of preterm birth. Moreover, it is documented that Se administration during pregnancy tendentially reduced the markers of thyroid autoimmunity and the incidence of maternal hypothyroidism in the postpartum period. Importantly, low Se levels in pregnant women affect fetal growth and augment the risk of delivering a small-for-gestational age infant by reducing placental antioxidant defense, while low Se in the third trimester is thought to indicate increased demands by the placenta, an issue which requires further confirmation. There is evidently a need for double-blind, placebo-controlled studies to better determine the efficacy and safety of Se supplementation in pregnancy at high risk for complications, and for measurement of Se levels or of selenoprotein P, the most reliable parameter of Se status, particularly in selenopenic regions.

Trace elements and APOE polymorphisms in pregnant women and their new-borns

We investigated the relationship between lipid binding glycoprotein apolipoprotein E (apoE; gene APOE) polymorphisms (ε4 allele carriers versus no carriers = ε4+/ε4-) and trace elements (TEs) (e.g., (methyl)mercury, arsenic, lead, cadmium, selenium, manganese, copper, and zinc) in mothers (N = 223) and their new-borns (N = 213) exposed to potentially toxic metal(loid)s from seafood consumption. The apoE isoform encoded by the ε4 allele is believed to have beneficial effects in early life but represents a risk factor for age-associated diseases. Under certain conditions ε4 carriers are more susceptible to oxidative stress and metal(loid) toxicity. DNA from Croatian pregnant women (N = 223, third trimester) and their new-borns (N = 176), was genotyped for APOE by TaqMan® SNP assay - rs429358 and rs7412. Seafood intake data and TE levels in maternal urine, milk, hair, peripheral venous blood, mixed cord blood, and new-borns' urine were available from previous studies. We compared TEs between ε4+ and ε4- carriers using Mann-Whitney U tests and applied multiple linear regression models to analyse the TE's dependence on the presence of allele ε4 (genotypes ε3/ε4, ε4/ε4) in combination with other explanatory variables. We identified 17% (n = 37) and 20% (n = 35) ε4 allele carriers in mothers and new-borns, respectively. The Mann-Whitney U test showed that mothers with the ε4 allele had significantly higher mean levels of (methyl)mercury in peripheral venous blood, cord blood, and hair; arsenic in urine and cord blood; and selenium in peripheral venous blood and plasma. However, taking confounders into account, only the maternal plasma selenium remained statistically significant in the linear regression models (ε4 carriers vs non-carriers: 62.6 vs 54.9 ng/mL, p < 0.001). Literature suggestions of possible ε4 allele impact on Hg levels were not observed, while superior selenium status observed in healthy pregnant women carrying allele ε4 could be linked to the proposed APOE ε4 beneficial effects early in life.

Concentrations of toxic metals and essential trace elements vary among individual neurons in the human locus ceruleus

Objective

Damage to locus ceruleus neurons could play a part in the pathogenesis of neurodegenerative disorders such as Alzheimer’s disease, Parkinson’s disease, and multiple sclerosis because of impairment of the blood-brain barrier and enhanced neuroinflammation. The locus ceruleus has connections throughout the brain and spinal cord, so the characteristic widespread multifocal pathology in these disorders could be due to damage to different subsets of locus ceruleus neurons. Previous studies have shown that only certain locus ceruleus neurons accumulate the neurotoxic metal mercury. To find out if concentrations of other toxic metals or of essential trace elements also vary between individual locus ceruleus neurons, we used synchrotron X-ray fluorescence microscopy on frozen sections of locus ceruleus neurons taken from people with multiple sclerosis, in whom the locus ceruleus is structurally intact.

Materials and methods

Paraffin embedded sections containing the locus ceruleus from seven people with multiple sclerosis were stained with autometallography that demonstrates accumulations of mercury, silver and bismuth. These were compared to maps of multiple elements obtained from frozen sections of locus ceruleus neurons from the same people using X-ray fluorescence microscopy. Neurons in the anterior pons from three of these donors were used as internal controls.

Results

Autometallography staining was observed in scattered locus ceruleus neurons from three of the seven donors. X-ray fluorescence microscopy showed variations among individual locus ceruleus neurons in levels of mercury, selenium, iron, copper, lead, bromine, and rubidium. Variations between donors of locus ceruleus neuronal average levels of mercury, iron, copper, and bromine were also detected. Anterior pons neurons contained no mercury, had varied levels of iron, and had lower copper levels than locus ceruleus neurons.

Conclusions

Individual human locus ceruleus neurons contain varying levels of toxic metals and essential trace elements. In contrast, most toxic metals are absent or at low levels in nearby anterior pons neurons. The locus ceruleus plays a role in numerous central nervous system functions, including maintaining the blood-brain-barrier and limiting neuroinflammation. Toxic metals, or alterations in essential trace metals within individual locus ceruleus neurons, could be one factor determining the non-random destruction of locus ceruleus neurons in normal aging and neurodegenerative diseases, and subsequently the sites of the widespread multifocal central nervous system pathology in these disorders.

First Trimester Microelements and their Relationships with Pregnancy Outcomes and Complications

Microelements involved in the oxidative balance have a significant impact on human health, but their role in pregnancy are poorly studied. We examined the relationships between first trimester levels of selenium (Se), iron (Fe), zinc (Zn), and copper (Cu), as well as maternal characteristics and pregnancy results. The data came from a Polish prospective cohort of women in a single pregnancy without chronic diseases. A group of 563 women who had a complete set of data, including serum microelements in the 10–14th week was examined, and the following were found: 47 deliveries <37th week; 48 cases of birth weight <10th and 64 newborns >90th percentile; 13 intrauterine growth restriction (IUGR) cases; 105 gestational hypertension (GH) and 15 preeclampsia (PE) cases; and 110 gestational diabetes mellitus (GDM) cases. The microelements were quantified using mass spectrometry. The average concentrations (and ranges) of the elements were as follows: Se: 60.75 µg/L (40.91–125.54); Zn: 618.50 µg/L (394.04–3238.90); Cu: 1735.91 µg/L (883.61–3956.76); and Fe: 1018.33 µg/L (217.55–2806.24). In the multivariate logistic regression, we found that an increase in Se of 1 µg/L reduces the risk of GH by 6% (AOR = 0.94; p = 0.004), the risk of IUGR by 11% (AOR = 0.89; p = 0.013), and the risk of birth <34th week by 7% (but close to the significance) (AOR = 0.93; p = 0.061). An increase in Fe of 100 µg/L reduces the risk of PE by 27% (AOR = 0.73; p = 0.009). In the multivariable linear regression, we found negative strong associations between prepregnancy BMI, Se (β = −0.130; p = 0.002), and Fe (β = −0.164; p < 0.0001), but positive associations with Cu (β = 0.320; p < 0.000001). The relationships between Se and maternal age (β = 0.167; p < 0.0001), Se and smoking (β = −0.106; p = 0.011) and Cu, and gestational age from the 10–14th week (β = 0.142; p < 0.001) were also found. Secondary education was associated with Zn (β = 0.132; p = 0.004) and higher education was associated with Cu (β = −0.102; p = 0.023). A higher financial status was associated with Fe (β = 0.195; p = 0.005). Other relationships were statistically insignificant. Further research is needed to clarify relationships between first trimester microelements and pregnancy complications. In addition, attention should be paid to lifestyle-related and socioeconomic factors that affect microelement levels.

Serum Microelements in Early Pregnancy and their Risk of Large-for-Gestational Age Birth Weight

Excessive birth weight has serious perinatal consequences, and it “programs” long-term health. Mother’s nutritional status can be an important element in fetal “programming”; microelements such as selenium (Se), zinc (Zn), copper (Cu), and iron (Fe) are involved in many metabolic processes. However, there are no studies assessing the relationship of the microelements in the peri-conceptual period with the risk of excessive birth weight. We performed a nested case control study of serum microelements’ levels in the 10–14th week of pregnancy and assessed the risk of large-for-gestational age (LGA) newborns using the data from a prospective cohort of pregnant women recruited in 2015–2016 in Poznań, Poland. Mothers delivering LGA newborns (n = 66) were examined with matched mothers delivering appropriate-for-gestational age (AGA) newborns (n = 264). Microelements’ levels were quantified using mass spectrometry. The odds ratios of LGA (and 95% confidence intervals) were calculated by multivariate logistic regression. In the whole group, women with the lowest quartile of Se had a 3 times higher LGA risk compared with women in the highest Se quartile (AOR = 3.00; p = 0.013). Importantly, the result was sustained in the subgroup of women with the normal pre-pregnancy BMI (AOR = 4.79; p = 0.033) and in women with a male fetus (AOR = 6.28; p = 0.004), but it was not sustained in women with a female fetus. There were no statistical associations between Zn, Cu, and Fe levels and LGA. Our study provides some preliminary evidence for the relationships between lower serum Se levels in early pregnancy and a higher risk of large-for-gestational age birth weight. Appropriate Se intake in the periconceptual period may be important for optimal fetal growth.

Pregnancy, thyroid, and the potential use of selenium

The management of pregnant women is a major concern of health care around the world. There is growing evidence regarding the influence of selenium (Se) on pregnancy and fetus outcomes. However, due to as yet insufficient evidence, lack of measurable markers to assess the effect of Se supplementation on the human metabolism, and Se's narrow therapeutic index, the majority of experts and the current guidelines published by several scientific societies do not recommend the use of Se in pregnancy and in women of childbearing age. Further research based on well-designed studies, including assessment of the complex interactions between different micronutrients and individual response to different doses of Se, is needed.

From Selenium Absorption to Selenoprotein Degradation

Selenium is an essential dietary micronutrient. Ingested selenium is absorbed by the intestines and transported to the liver where it is mostly metabolized to selenocysteine (Sec). Sec is then incorporated into selenoproteins, including selenoprotein P (SELENOP), which is secreted into plasma and serves as a source of selenium to other tissues of the body. Herein, we provide an overview of the biology of selenium from its absorption and distribution to selenoprotein uptake and degradation, with a particular focus on the latter. Molecular mechanisms of selenoprotein degradation include the lysosome-mediated pathway for SELENOP and endoplasmic reticulum-mediated degradation of selenoproteins via ubiquitin-activated proteasomal pathways. Ubiquitin-activated pathways targeting full-length selenoproteins include the peroxisome proliferator-activated receptor gamma-dependent pathway and substrate-dependent ubiquitination. An alternate mechanism is utilized for truncated selenoproteins, in which cullin-RING E3 ubiquitin ligase 2 targets the defective proteins for ubiquitin-proteasomal degradation. Selenoproteins, particularly SELENOP, may have their Sec residues reutilized for new selenoprotein synthesis via Sec decomposition. This review will explore these aspects in selenium biology, providing insights to knowledge gaps that remain to be uncovered.

Combined Omics Reveals That Disruption of the Selenocysteine Lyase Gene Affects Amino Acid Pathways in Mice

Selenium is a nonmetal trace element that is critical for several redox reactions and utilized to produce the amino acid selenocysteine (Sec), which can be incorporated into selenoproteins. Selenocysteine lyase (SCL) is an enzyme which decomposes Sec into selenide and alanine, releasing the selenide to be further utilized to synthesize new selenoproteins. Disruption of the selenocysteine lyase gene (Scly) in mice (Scly-/- or Scly KO) led to obesity with dyslipidemia, hyperinsulinemia, glucose intolerance and lipid accumulation in the hepatocytes. As the liver is a central regulator of glucose and lipid homeostasis, as well as selenium metabolism, we aimed to pinpoint hepatic molecular pathways affected by the Scly gene disruption. Using RNA sequencing and metabolomics, we identified differentially expressed genes and metabolites in the livers of Scly KO mice. Integrated omics revealed that biological pathways related to amino acid metabolism, particularly alanine and glycine metabolism, were affected in the liver by disruption of Scly in mice with selenium adequacy. We further confirmed that hepatic glycine levels are elevated in male, but not in female, Scly KO mice. In conclusion, our results reveal that Scly participates in the modulation of hepatic amino acid metabolic pathways.

The Role of Early Pregnancy Maternal Selenium Levels on the Risk for Small-for-Gestational Age Newborns

It has not yet been established, whether or not the maternal serum selenium (Se) in early pregnancy may be a risk marker of small-for-gestational age (SGA) birth weight. Selenium is important for human health and is involved in oxidative balance, a key element in the development of the placenta and fetus. This innovative study was nested in a prospective cohort of 750 women recruited in the 10–14th week of a single pregnancy, all of whom were healthy during recruitment. We examined mothers delivering SGA infants (with birth weight <10th percentile) (n = 48) and matched mothers delivering appropriate-for-gestational age (AGA) infants (between 10–90th percentile) (n = 192). We measured the maternal microelement concentrations in the serum from the 10–14th gestational week, using the inductively coupled plasma mass spectrometry (ICP-MS). The odds ratios of SGA (and 95% confidence intervals) were assessed in logistic regression. The mean maternal Se concentrations were lower in mothers in the SGA group compared to the AGA group (59.60 vs. 62.54 µg/L; p = 0.020). Women in the lowest Q₁ quartile of Se (≤56.60 µg/L) have about three times higher risk of SGA compared to women in the higher quartiles (Q₂ or Q₄); the odds ratio of SGA was OR = 3.02 (p = 0.019) for Q₁ vs. Q₂ quartile. The risk profile graph confirms the results. We found that excessive pre-pregnancy BMI (body mass index) affected the estimated SGA odds ratios. Early pregnancy maternal serum selenium status can be a risk marker of SGA newborns and more research is needed in larger groups.

A Spatial Ecology Study of Keshan Disease and Hair Selenium

Few spatial ecological studies on hair selenium (Se) and Keshan disease (KD) have been reported. To investigate the relationships of hair Se with KD and economic indicators and to visualize the evidence for KD precise prevention. An ecological study design was employed. The levels of hair Se of 636 adult men (≥ 18 years old) living in rural, general cities and developed cities in 15 KD endemic provinces and 11 KD non-endemic provinces in mainland China were measured using hydride generation atomic fluorescence spectrometry. Spatial description and spatial analysis of hair Se were conducted. The subjects were adults aged. The hair Se level of the residents of KD endemic areas was 0.30 mg/kg, statistically significantly lower than that of non-endemic areas 0.34 mg/kg (Mann-Whitney U test, p = 0.007). The hair Se level of the 636 people was 0.33 mg/kg. The hair Se levels of the residents of the developed cities, general cities, and rural were 0.35 mg/kg, 0.33 mg/kg, and 0.32 mg/kg, respectively, with statistical significance (Kruskal-Wallis H test, P = 0.032). Spatial regression analysis showed that the spatial distribution of hair Se was positively correlated with per capita GDP. Selenium deficiency may still exist among residents living in the KD endemic areas. The results of spatial description and analysis of hair Se provided visualized evidence for targeting key provinces for precise prevention of Keshan disease, including assessment of KD elimination. The hair Se level of the mainland Chinese males was probably between 0.31 and 0.33 μg/g in 2015.

Serum Selenium Level in Early Healthy Pregnancy as a Risk Marker of Pregnancy Induced Hypertension

Selenium (Se) is an antioxidant nutrient whose deficiency can influence adverse outcomes of pregnancy. The aim of this study is to determine whether serum Se level in early healthy pregnancy may be a risk marker for pregnancy induced hypertension. We obtained data from our prospective study in which we recruited healthy women in weeks 10–14 of a single pregnancy. In this analysis, we examined 121 women who subsequently developed pregnancy-induced hypertension and matched 363 women who remained normotensive. We measured Se levels (using the ICP-MS technique) in the serum in weeks 10–14 of the pregnancy. The odds ratios of pregnancy-induced hypertension (95% confidence intervals) were calculated using multivariate logistic regression. We found that the mean Se level was lower in the case group compared to the control (57.51 vs. 62.89 μg/L; p = 2.6 × 10⁻¹⁰). Excessive body mass index (BMI) and smoking influenced the estimated odds ratios. In the subgroup of women who had never smoked with normal pre-pregnancy BMI, the adjusted odds ratio (AOR) of pregnancy-induced hypertension was 15.34 (95% CI: 2.73–86.31, p = 0.002) for Se levels in the lowest quartile (≤57.68 µg/L), as compared to the highest quartile (>66.60 µg/L), after adjusting for all the accepted confounders. In the whole cohort, the prognostic value of Se by logistic regression showed that the area under curve (AUC) = 0.814. In our study, one can consider the role of Se as a risk marker of pregnancy-induced hypertension.

Arsenic metabolites; selenium; and AS3MT, MTHFR, AQP4, AQP9, SELENOP, INMT, and MT2A polymorphisms in Croatian-Slovenian population from PHIME-CROME study

The relationships between inorganic arsenic (iAs) metabolism, selenium (Se) status, and genetic polymorphisms of various genes, commonly studied in populations exposed to high levels of iAs from drinking water, were studied in a Croatian-Slovenian population from the wider PHIME-CROME project. Population consisted of 136 pregnant women in the 3^rd trimester and 176 non-pregnant women with their children (n = 176, 8-9 years old). Their exposure to iAs, defined by As (speciation) analyses of biological samples, was low. The sums of biologically active metabolites (arsenite + arsenate + methylated As forms) for pregnant women, non-pregnant women, and children, respectively were: 3.23 (2.84-3.68), 1.83 (1.54-2.16) and 2.18 (1.86-2.54) ng/mL_SG; GM (95 CI). Corresponding plasma Se levels were: 54.8 (52.8-56.9), 82.3 (80.4-84.0) and 65.8 (64.3-67.3) ng/mL; GM (95 CI). As methylation efficiency indexes confirmed the relationship between pregnancy/childhood and better methylation efficiency. Archived blood and/or saliva samples were used for single nucleotide polymorphism (SNP) genotyping of arsenic(3+) methyltransferase - AS3MT (rs7085104, rs3740400, rs3740393, rs3740390, rs11191439, rs10748835, rs1046778 and the corresponding AS3MT haplotype); methylene tetrahydrofolate reductase - MTHFR (rs1801131, rs1801133); aquaporin - AQP 4 and 9 (rs9951307 and rs2414539); selenoprotein P1 - SELENOP (rs7579, rs3877899); indolethylamine N-methyltransferase - INMT (rs6970396); and metallothionein 2A - MT2A (rs28366003). Associations of SNPs with As parameters and urine Se were determined through multiple regression analyses adjusted using appropriate confounders (blood As, plasma Se, ever smoking, etc.). SNPs' influence on As methylation, defined particularly by the secondary methylation index (SMI), confirmed the 'protective' role of minor alleles of six AS3MT SNPs and their haplotype only among non-pregnant women. Among the other investigated genes, the carriers of AQP9 (rs2414539) were associated with more efficient As methylation and higher urine concentration of As and Se among non-pregnant women; poorer methylation was observed for carriers of AQP4 (rs9951307) among pregnant women and SELENOP (rs7579) among non-pregnant women; MT2A (rs28366003) was associated with higher urine concentration of AsIII regardless of the pregnancy status; and INMT (rs6970396) was associated with higher As and Se concentration in non-pregnant women. Among confounders, the strongest influence was observed for plasma Se; it reduced urine AsIII concentration during pregnancy and increased secondary methylation index among non-pregnant women. In the present study of populations with low As exposure, we observed a few new As-gene associations (particularly with AQPs). More reliable interpretations will be possible after their confirmation in larger populations with higher As exposure levels.

A spatial ecological study of selenoprotein P and Keshan disease

Few spatial ecological studies on selenoprotein P (SePP) and Keshan disease (KD) have been reported. The main objective of this study is to investigate the relationships of SePP with KD, economic indicators and soil selenium and to visualize the evidence for KD precise prevention and control. An ecological study design was employed. The serum SePP of 2351 subjects living in rural areas, general cities and developed cities in 15 KD endemic provinces and 13 KD non-endemic provinces in China were measured. Spatial description and spatial analysis of SePP were conducted. The subjects were adults aged. The mean serum SePP level of KD endemic area residents was 14.20 mg/L, significantly lower than that in non-endemic areas, 15.30 mg/L (t = - 3.19, P = 0.0010). Serum SePP levels were low among the people in the KD endemic provinces of Shandong, Inner Mongolia, Heilongjiang, etc. The mean serum SePP level of the 2351 people was 15.04 (95% CI: 14.76 and 15.31) mg/L. The mean serum SePP levels of residents in developed cities, general cities and rural areas were 16.54 mg/L, 14.98 mg/L and 14.44 mg/L, respectively, and were significantly different (F = 17.00, P < 0.0010). Spatial regression analysis showed that the spatial distribution of SePP was positively correlated with per capita consumption expenditure and soil selenium. Selenium deficiency may still exist among residents living in the KD endemic provinces. Shandong, Inner Mongolia, and Heilongjiang should be the target provinces, visualized by spatial analysis, for KD precise prevention and control.

Decreased Thyroid Peroxidase Antibody Titer in Response to Selenium Supplementation in Autoimmune Thyroiditis and the Influence of a Selenoprotein P Gene Polymorphism: A Prospective, Multicenter Study in China

Background: Recent intervention studies have suggested that selenium (Se) is an effective treatment for autoimmune thyroiditis (AIT). However, the exact effect of Se on AIT is unclear as well as the mechanism of action. The aim of the present study was to explore the effect of Se on thyroid peroxidase antibody (TPOAb) titers in patients with AIT and to analyze the potential impact of the genetic background on the effect of Se supplementation. Methods: This was a randomized, placebo-controlled, double-blind trial. Three hundred and sixty-four patients with elevated TPOAb (>300 IU/mL) were recruited and randomized to receive Se yeast 200 μg/day supplementation or placebo. Urinary iodine concentration, serum thyrotropin, free thyroxine, TPOAb, Se, malondialdehyde, and serum glutathione peroxidase activity were measured at baseline and follow-up. Ninety-six patients were genotyped for single nucleotide polymorphism r25191G/A in the selenoprotein P (SEPP1/SELENOP) gene. Results: The median urinary iodine concentration was 182 μg/L. Serum Se increased significantly (p < 0.001) after Se treatment. TPOAb titer decreased by 10.0% at 3 months and by 10.7% at 6 months after Se supplementation, while there was a moderate increase in TPOAb titers over the follow-up period in patients receiving placebo. Glutathione peroxidase activity significantly increased (p < 0.001), and malondialdehyde significantly decreased (p < 0.001) after 6 months of Se supplementation. TPOAb titers decreased to variable extents in patients with different genotypes of single nucleotide polymorphism r25191G/A after Se supplementation. Serum TPOAb titers in patients with the AA genotype showed a more significant decrease (by 46.2%) than those with the GA and GG genotypes (by 14.5 and 9.8% respectively) at 3 months of Se supplementation (p = 0.070). Conclusions: Se supplementation significantly reduced TPOAb titers in patients with AIT, and there may be an important genetic component influencing interindividual differences in the decrease in TPOAb titers.

Selenium Analysis and Speciation in Dietary Supplements Based on Next-Generation Selenium Ingredients

Selenium is essential for humans and the deficit of Se requires supplementation. In addition to traditional forms such as Se salts, amino acids, or selenium-enriched yeast supplements, next-generation selenium supplements, with lower risk for excess supplementation, are emerging. These are based on selenium forms with lower toxicity, higher bioavailability, and controlled release, such as zerovalent selenium nanoparticles (SeNPs) and selenized polysaccharides (SPs). This article aims to focus on the existing analytical systems for the next-generation Se dietary supplement, providing, at the same time, an overview of the analytical methods available for the traditional forms. The next-generation dietary supplements are evaluated in comparison with the conventional/traditional ones, as well as the analysis and speciation methods that are suitable to reveal which Se forms and species are present in a dietary supplement. Knowledge gaps and further research potential in this field are highlighted. The review indicates that the methods of analysis of next-generation selenium supplements should include a step related to chemical species separation. Such a step would allow a proper characterization of the selenium forms/species, including molecular mass/dimension, and substantiates the marketing claims related to the main advantages of these new selenium ingredients.

Circulating Selenium and Prostate Cancer Risk: A Mendelian Randomization Analysis

In the Selenium and Vitamin E Cancer Prevention Trial (SELECT), selenium supplementation (causing a median 114 μg/L increase in circulating selenium) did not lower overall prostate cancer risk, but increased risk of high-grade prostate cancer and type 2 diabetes. Mendelian randomization analysis uses genetic variants to proxy modifiable risk factors and can strengthen causal inference in observational studies. We constructed a genetic instrument comprising 11 single nucleotide polymorphisms robustly (P < 5 × 10-8) associated with circulating selenium in genome-wide association studies. In a Mendelian randomization analysis of 72 729 men in the PRACTICAL Consortium (44 825 case subjects, 27 904 control subjects), 114 μg/L higher genetically elevated circulating selenium was not associated with prostate cancer (odds ratio [OR] = 1.01, 95% confidence interval [CI] = 0.89 to 1.13). In concordance with findings from SELECT, selenium was weakly associated with advanced (including high-grade) prostate cancer (OR = 1.21, 95% CI = 0.98 to 1.49) and type 2 diabetes (OR = 1.18, 95% CI = 0.97 to 1.43; in a type 2 diabetes genome-wide association study meta-analysis with up to 49 266 case subjects and 249 906 control subjects). Our Mendelian randomization analyses do not support a role for selenium supplementation in prostate cancer prevention and suggest that supplementation could have adverse effects on risks of advanced prostate cancer and type 2 diabetes.

Selenium in Complicated Pregnancy. A Review

Selenium (Se) is an essential trace element of significant importance in human health. Diet is the major source of Se, and intake of this element depends on its concentration in food sources as well as the amount of those sources consumed. Unfortunately, daily dietary intake of Se in most European countries is generally low, ∼30-40μg/day, compared with the recommended dietary allowance, ∼55 and 70μg/day for adult females and males, respectively. The importance of Se as an essential trace element is linked to its role as selenocysteine in a number of selenoproteins including antioxidant enzymes glutathione peroxidases (GSH-Pxs), thioredoxin reductases (TrxRs), and selenoprotein P (SePP). These enzymes protect tissues against the damaging effect of reactive oxygen species (ROS) and other endogenous products of cellular metabolism implicated in DNA damage and potentially leading to mutagenesis, cell death, and carcinogenesis. Reduced body Se and antioxidant enzyme activity during pregnancy results in oxidative stress within tissues contributing to premature birth, miscarriage, preeclampsia, and intrauterine growth retardation. Because placenta development is highly dependent on oxygen status, uncontrolled ROS formation is likely detrimental. Despite these findings, the role of Se and Se-dependent enzymes in pregnancy remains controversial. The objective of this review is to explore Se status in pregnancy with respect to adverse outcomes. Effects related to decreased antioxidant activity and increased oxidative stress will be highlighted.

Selenoproteins in human body: focus on thyroid pathophysiology

Selenium (Se) has a multilevel, complex and dynamic effect on the human body as a major component of selenocysteine, incorporated into selenoproteins, which include the selenocysteine-containing enzymes iodothyronine deiodinases. At the thyroid level, these proteins play an essential role in antioxidant protection and hormone metabolism. This is a narrative review based on PubMed/Medline database research regarding thyroid physiology and conditions with Se and Se-protein interferences. In humans, Se-dependent enzyme functions are best expressed through optimal Se intake, although there is gap in our knowledge concerning the precise mechanisms underlying the interrelation. There is a good level of evidence linking low serum Se to autoimmune thyroid diseases and, to a lesser extent, differentiated thyroid cancer. However, when it comes to routine supplementation, the results are heterogeneous, except in the case of mild Graves' orbitopathy. Autoimmune hypothyroidism is associated with a state of higher oxidative stress, but not all studies found an improvement of thyroid function after Se was introduced as antioxidant support. Meanwhile, no routine supplementation is recommended. Low Se intake is correlated with an increased risk of developing antithyroid antibodies, its supplementation decreasing their titres; there is also a potential reduction in levothyroxine replacement dose required for hypothyroidism and/or the possibility that it prevents progression of subclinical hypothyroidism, although not all studies agree. In thyroid-associated orbitopathy, euthyroidism is more rapidly achieved if the micronutrient is added to traditional drugs, while controls appear to benefit from the microelement only if they are deficient; thus, a basal assay of Se appears advisable to better select patients who need substitution. Clearly, further Se status biomarkers are required. Future introduction of individual supplementation algorithms based on baseline micronutrient levels, underlying or at-risk clinical conditions, and perhaps selenoprotein gene polymorphisms is envisaged.

Genetic variants in selenoprotein genes modulate biomarkers of selenium status in response to Brazil nut supplementation (the SU.BRA.NUT study)

BACKGROUND

The beneficial effects of selenium (Se) to human health are exerted by selenoproteins, which can be quantified in blood and used as biomarkers of Se status. Different responses of Se biomarkers after supplementation with selenomethionine and sodium selenite have been observed and some of them could be due to genetic polymorphisms, mainly single nucleotide polymorphisms (SNPs). Brazil nuts are known to be the richest natural source of Se.

OBJECTIVE

Investigate how genetic variations in selenoprotein genes modulate biomarkers of Se status in response to Brazil nut supplementation.

METHODS

The SU.BRA.NUT study was a four month interventional trial which involved healthy volunteers of both genders, selected in University of Sao Paulo. The supplementation was done with one Brazil nut a day for 8 weeks, followed by 8 weeks of washout. Blood samples were collected at 5 time points: baseline, 4 and 8 weeks of supplementation and 4 and 8 weeks of washout for analysis of five biomarkers of Se status - erythrocyte GPx1 (Glutathione Peroxidase 1) activity, plasma GPx3 activity, plasma Se, erythrocyte Se, and plasma selenoprotein P. The gene expression of GPX1, SELENOP, SELENOF and SELENOS was done before and after 8 weeks of supplementation. The volunteers were genotyped for SNPs in GPX1 (rs1050450, rs3811699 and rs1800699), GPX4 (rs713041), SELENOP (rs3877899 and rs7579), SELENOF (rs5845) and SELENOS (rs34713741).

RESULTS

A total of 130 volunteers finished the protocol. The concentrations of four biomarkers of Se status increased significantly after 4 and 8 weeks of supplementation, being modulated by gender. In addition, erythrocyte GPx1 activity was associated with rs1050450, rs713041 and rs5845. Plasma Se was associated with rs7579 and selenoprotein P with plasma Se at baseline. Nut supplementation significantly increased GPX1 mRNA expression only in subjects with CC genotype at rs1050450. SELENOP mRNA expression was significantly lower in subjects with GG genotype at rs7579 before and after supplementation.

CONCLUSION

Genetic variations in GPX1 and SELENOP genes are associated with different responses of molecular and biochemical biomarkers of Se status after Brazil nut supplementation in healthy Brazilians. The SU.BRA.NUT study was registred at www.clinicaltrials.gov as NCT 03111355.

Severe selenium deficits in pregnant women irrespective of autoimmune thyroid disease in an area with marginal selenium intake

OBJECTIVES

Selenium (Se) deficiency is related to an increased risk of preterm labor, miscarriage, preeclampsia, gestational diabetes, and other obstetric complications. As the Se status declines during pregnancy, we hypothesized that the decline may be exacerbated in women with autoimmune thyroid disease (AITD).

MATERIAL AND METHODS

Pregnant women (n=74; 30 [23-38] years) were consecutively recruited from the district of Warsaw, Poland, and divided into healthy subjects (HS, n=45), and women with a diagnosis of AITD (AITD, n=29). Thyroglobulin antibodies (TG-aAb), thyroid peroxidase antibodies (TPO-aAb), TSH, free T3, free T4, total T3, and total T4, as well as urine iodine excretion were determined. Se status was assessed by serum Se and selenoprotein P (SELENOP) concentrations. Thyroid volume was evaluated by ultrasonography.

RESULTS

Serum Se and SELENOP concentrations were relatively low in both control and AITD women. A Se deficit according to WHO definition (<45μg/l) was observed in 0%, 3.4%, 28.6% and 4.5%, 18.2%, 35.5% of women in the AITD and HS group, respectively, during the 1st, 2nd, and 3rd trimester. From first to third trimester, TPO-aAb and TG-aAb declined in AITD by 71% and 60%, respectively. The decline in TPO- and TG-aAb was unrelated to the Se status.

CONCLUSIONS

In this area of habitual low Se intake, a high proportion of women developed a severe Se deficit during pregnancy, irrespective of AITD status. This decline must be considered as a preventable risk factor for pregnancy complications of relevance to both the unborn child and the pregnant mother.

Single step genome-wide association studies based on genotyping by sequence data reveals novel loci for the litter traits of domestic pigs

In this study, data genotyping by sequence (GBS) was used to perform single step GWAS (ssGWAS) to identify SNPs associated with the litter traits in domestic pigs and search for candidate genes in the region of significant SNPs. After quality control, 167,355 high-quality SNPs from 532 pigs were obtained. Phenotypic traits on 2112 gilt litters from 532 pigs were recorded including total number born (TNB), number born alive (NBA), and litter weight born alive (LWB). A single-step genomic BLUP approach (ssGBLUP) was used to implement the genome-wide association analysis at a 5% genome-wide significance level. A total of 8, 23 and 20 significant SNPs were associated with TNB, NBA, and LWB, respectively, and these significant SNPs accounted for 62.78%, 79.75%, and 58.79% of genetic variance. Furthermore, 1 (SSC14: 16314857), 4 (SSC1: 81986236, SSC1: 66599775, SSC1: 161999013, and SSC1: 267883107), and 5 (SSC9: 29030061, SSC2: 32368561, SSC5: 110375350, SSC13: 45619882 and SSC13: 45647829) significant SNPs for TNB, NBA, and LWB were inferred to be novel loci. At SSC1, the AIM1 and FOXO3 genes were found to be associated with NBA; these genes increase ovarian reproductive capacity and follicle number and decrease gonadotropin levels. The genes SLC36A4 and INTU are involved in cell growth, cytogenesis and development were found to be associated with LWB. These significant SNPs can be used as an indication for regions in the Sus scrofa genome for variability in litter traits, but further studies are expected to confirm causative mutations.

Selenium levels in human breast carcinoma tissue are associated with a common polymorphism in the gene for SELENOP (Selenoprotein P)

Selenium supplementation of the diets of rodents has consistently been shown to suppress mammary carcinogenesis and some, albeit not all, human epidemiological studies have indicated an inverse association between selenium and breast cancer risk. In order to better understand the role selenium plays in breast cancer, 30 samples of tumor tissue were obtained from women with breast cancer and analyzed for selenium concentration, the levels of several selenium-containing proteins and the levels of the MnSOD anti-oxidant protein. Polymorphisms within the genes for these same proteins were determined from DNA isolated from the tissue samples. There was a wide range of selenium in these tissues, ranging from 24 to 854ng/gm. The selenium levels in the tissues were correlated to the genotype of the SELENOP selenium carrier protein, but not to other proteins whose levels have been reported to be responsive to selenium availability, including GPX1, SELENOF and SBP1. There was an association between a polymorphism in the gene for MnSOD and the levels of the encoded protein. These studies were the first to examine the relationship between selenium levels, genotypes and protein levels in human tissues. Furthermore, the obtained data provide evidence for the need to obtain data about the effects of selenium in breast cancer by examining samples from that particular tissue type.