Selenium exposure and the risk of type 2 diabetes: a systematic review and meta-analysis

Non-genetic and genetic determinants of serum selenium and selenium species in the Aragon Workers Health Study

Understanding potential determinants of selenium biomarkers can help to unravel selenium health effects. We evaluated the contribution of non-genetic (sociodemographic and lifestyle) and genetic factors to serum selenium biomarkers and selenium species (quantified as selenium) including selenium in glutathione peroxidase (GPx), selenoprotein P (SeP), selenoalbumin (SeAlb) and total selenometabolites (Se-metabolites) in the Aragon Workers Health Study (AWHS), a predominantly male cohort of car assembly factory workers in Spain. Total serum selenium and selenium species were measured by HPLC/ICP-QQQ-MS in 1624 AWHS participants. Blood and urine selenium, measured by ICP-MS, were available in a subset. A Healthy Lifestyle Score (HLS) included Mediterranean diet, physical activity, smoking, BMI and alcohol intake. Candidate gene and genome-wide discovery analyses (CGA and GDA, respectively) were based on TOPMed imputed SNPs. In sex and age-adjusted models, overall HLS, physical activity, and specific foods intake showed positive associations with serum total selenium, SeAlb and Se-metabolites concentrations. The associations between smoking status and BMI with total serum selenium; age, smoking status, BMI and meat intake with SeAlb; and smoking status with Se-metabolites, were inverse. In the GDA, we identified 20, 24, 21, 26, 16, 20 and 68 independent genetic loci for serum total selenium, GPx, SeP, SeAlb, Se-metabolites, and total blood and urine selenium, respectively, with some overlapping genes also relevant in the CGA. Enrichment analysis pointed to biological pathways including circadian rhythm regulation, immune system processes, signaling and receptor- and transporter-related pathways. The explained variability of selenium markers ranged from 15 % for SeP to 21 % for SeAlb and from 0.2 % for SeP to 3.5 % for SeAlb in environmental determinants-adjusted models with and without the specific selenium biomarker polygenic score, respectively. While the genetic contribution is substantial, selenium status might be influenced by reinforced healthy lifestyle interventions. Follow-up genetic studies to evaluate selenium health consequences are granted.

Selenium supplementation in chronic kidney disease patients undergoing haemodialysis: a systematic review of the effects on plasma selenium, antioxidant and inflammatory markers, immunological parameters and thyroid hormones

Selenium (Se) is a mineral with several biological functions, and studies have shown that its deficiency can be linked to many complications in patients with chronic kidney disease (CKD). This study aims to systematically review the effects of Se supplementation in patients with CKD undergoing haemodialysis (HD). This systematic review was carried out according to the PRISMA statement. Clinical trials were searched in PubMed, Lilacs, Embase, Scopus and Cochrane Library databases from inception to July 2021 and updated in July 2024. The protocol was registered on PROSPERO (CRD42021231444). Two independent reviewers performed the study screening and data extraction, and the risk of bias was evaluated using the Cochrane Collaboration tool. Thirteen studies were included in this review. Only nine studies showed results on Se levels; in all, reduced Se levels were observed before supplementation. A positive effect of supplementation on plasma Se level was demonstrated. Of the ten studies analysed, six demonstrated positive effects on antioxidant and inflammatory markers. Only one study analysed immunological parameters, showing a positive impact. From two studies that analysed thyroid hormones, only one showed positive results. All studies were classified as high risk of bias. The findings suggest that Se supplementation significantly increases plasma Se levels in these patients; however, there are still not enough studies to clarify the effects of Se supplementation on the antioxidant and inflammatory markers, immune system and thyroid hormones. Further studies are needed to elucidate the effects of Se supplementation and to provide a recommendation for patients with CKD undergoing HD.

Effects of Selenium Administration on Blood Lipids: A Systematic Review and Dose-Response Meta-Analysis of Experimental Human Studies

CONTEXT

Overexposure to the essential trace element selenium has been associated with adverse metabolic and cardiovascular outcomes, hypertension, and diabetes. However, dose-response meta-analyses analyzing the effects of selenium administration on the lipid profile in experimental human studies are lacking.

OBJECTIVE

Through a restricted cubic spline regression meta-analysis, the dose-response relation between the dose of selenium administered or blood selenium concentrations at the end of the trials and changes over time in blood lipids, ie, total, high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, and triglycerides was assessed.

DATA SOURCES

Searches were performed on PubMed, Web of Science, Embase, and the Cochrane Library from inception up to January 11, 2025 to identify randomized controlled trials (RCTs) investigating the impact of selenium supplementation on blood lipid profiles among adults.

DATA EXTRACTION

A total of 27 eligible RCTs that enrolled healthy individuals, pregnant individuals, and participants with specific health conditions were identified and the relevant data was extracted.

DATA ANALYSIS

Dose-response analysis indicated that selenium administration at and above 200 µg/day decreased HDL and LDL cholesterol and increased triglyceride levels. Blood selenium concentrations at the end of the trial above approximately 150 µg/L were positively associated with triglyceride and LDL cholesterol concentrations, and inversely associated with HDL cholesterol. Inorganic selenium supplementation showed stronger associations than organic selenium. At the lowest levels of baseline intake, selenium supplementation appeared instead to have beneficial effects on the lipid profile, with an overall indication of U-shaped curves, apart from HDL-cholesterol. The adverse effects of selenium were stronger in studies involving healthy participants as compared with unhealthy participants and pregnant females, in those having a longer duration of the intervention, particularly more than 3 months, and in European populations at selenium intake levels of above 300 µg/day.

CONCLUSIONS

In this dose-response meta-analysis of experimental human studies, an adverse effect of selenium administration on blood lipids at levels around or above the current upper level of intake was observed.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration No. CRD42022380432.

Dietary mineral patterns are associated with the pre-diabetes regression and progression: the Tehran lipid and glucose study (TLGS)

AIM

We investigated the potential association between dietary mineral patterns and longitudinal change of glycemic status among individuals with prediabetes (Pre-DM).

METHODS

This study included 1456 individuals with Pre-DM (mean age of 47.2 ± 12.8, and 52.5% men) who participated in the third (2006-2008) and fourth (2009-2011) examinations of the Tehran Lipid and Glucose Study (TLGS) that followed up until 2015-2017. The participants' habitual dietary intakes of minerals were assessed using a semi-quantitative food frequency questionnaire (FFQ) at baseline. Principle factor analysis (PCA) identified three major mineral patterns (with a total variance of 92.3%), including multi-mineral (MM) (characterized by higher loads of phosphorous, zinc, calcium, magnesium, and copper), chromium-selenium (Cr-Se), and iron-manganese (Fe-Mn) patterns. Cox proportional hazard models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of developing type 2 diabetes (T2D) and regression to normal glucose regulation (NGR) across tertile categories of mineral patterns score.

RESULTS

After a median follow-up of 5.8 years, the incidence rates of T2D and NGR was 23.8% and 46.8%, respectively. After adjustment of T2D risk score (i.e., composed of age, sex, family history of diabetes, history of gestational diabetes, body mass index, and physical activity level) and dietary confounders, Cr-Se and Fe-Mn patterns were associated with an increased chance of returning to NGR by 26% (HR = 1.26, 95% CI = 1.02-1.55) and 42% (HR = 1.42, 95% CI = 1.14-1.76), respectively. Fe-Mn pattern was also associated with a reduced risk of developing T2D (HR = 0.67, 95% CI = 0.49-0.92).

CONCLUSION

Our findings emphasize the potential benefits of dietary Fe-Mn and Cr-Se intakes in pre-diabetic individuals.

Association between urinary metal concentrations and hyperuricemia in Chinese community-dwelling elderly: Exploring the mediating role of estimating glomerular filtration rate

BACKGROUND

It has been shown that multiple metals exposure is associated with hyperuricemia. However, previous studies on the association and interaction between multiple metals exposure and hyperuricemia have been controversial, and there has been little evaluation of the potential mediating role of estimating glomerular filtration rate (eGFR).

METHODS

In this study, levels of 12 metals in the urine of 3756 study participants were measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The associations between urinary metals and the hyperuricemia were analyzed by multivariable logistic regression model and restricted cubic spline (RCS). Weighted Quantile Sum (WQS) regression was used to explore the weight of each metal. Bayesian Kernel Machine Regression (BKMR) was used to explore the join effect of mixed metal exposure. Mediation analysis was used to explore the role of eGFR in relationship between urinary metal concentration and hyperuricemia.

RESULTS

In the multi-metal model, the multivariate-adjusted odds ratio (OR) and 95 % confidence interval (CI) of hyperuricemia were 0.89 (0.81,0.99) for Fe, 0.79 (0.70,0.89) for Se, 0.84 (0.75,0.93) for Cd, 0.87 (0.79,0.96) for Pb, 1.36 (1.23,1.51) for Zn (all P < 0.05). The RCS regression indicated signification nonlinear associations for Zn and Pb (all P-non-linear <0.05). The WQS regression model based on the negative fit showed that the maximum weight of Cd is 43.1 %. In the BKMR model, metal mixtures showed an overall negative association with the risk of developing hyperuricemia, and we also found interactions between Zn and Pb. Mediation analysis showed that eGFR mediated the association between Fe, Se, Cd, Pb and hyperuricemia with mediation ratios of 11.18 %, 12.10 %, 9.60 %, and 12.01 %, respectively.

CONCLUSIONS

The metal mixture in urine is negatively correlated with hyperuricemia, with Cd having the greatest impact. eGFR may play a partial role in association of Fe, Se, Cd and Pb exposure with hyperuricemia.

Associations of multiple plasma metals with the risk of type 2 diabetes in Chinese adults: A cross-sectional study

Evidence regarding the associations between co-exposure to multiple metals and diabetes risk was scarce. This study aimed to evaluate the associations of multiple metals with diabetes risk using multiple statistical methods. This cross-sectional study included 192 diabetic patients and 189 healthy subjects. We employed inductively coupled plasma mass spectrometry (ICP-MS) to determine the plasma concentrations of 18 metals. Least absolute shrinkage and selection operator (LASSO) regression, logistic regression, and Bayesian kernel machine regression (BKMR) were applied to evaluate associations of multiple metals with diabetes risk comprehensively. These models consistently suggested that aluminium and selenium were positively associated with diabetes risk, while manganese, rubidium, and lead were negatively associated with diabetes risk. Age-specific differences of selenium and sex-specific differences of manganese in diabetes risk were also observed based on stratified analyses. According to RCS analyses, we obtained dose-response relationships between metals and diabetes risk:(1) there were inverted U-shaped associations of plasma aluminium and selenium with diabetes risk, with the threshold close to 20.5µg/L and 75.9µg/L, respectively (both P for overall < 0.05; both P for non-linearity < 0.05). (2) There were L-shaped associations of rubidium and lead with diabetes risk, with the turning point close to 144.5µg/L and 2.5µg/L, respectively (both P for overall < 0.05; both P for non-linearity < 0.05). (3) Manganese was linearly and negatively correlated with diabetes risk when concentrations of manganese were less than approximately 4.2 μg/L (P for overall < 0.05; P for non-linearity = 0.268). The BKMR model also revealed a negative combined effect of metal mixtures on diabetes risk and potential interactions between six pairs of metals (aluminium-manganese, aluminium-selenium, aluminium-rubidium, aluminium-lead, manganese-selenium, and manganese-rubidium). In summary, we need to pay attention to the role of low plasma levels of aluminium, selenium, manganese, rubidium, and lead in diabetes, especially regarding their safety windows.

Calling for a comprehensive risk assessment of selenium in drinking water

In the last two decades, research has elucidated that selenium, a trace element, has both nutritional and toxicological effects on human health, depending on its dose and chemical form. Recent animal, laboratory, and human studies have shown harmful effects of certain selenium species at specific exposure levels, prompting the need to reassess overall exposure to this element, including that occurring through drinking water, a primary source of inorganic selenium. Drinking water selenium standards worldwide are scarce and existing standards are inconsistent, likely because they have been informed by an incomplete and outdated assessment of the scientific evidence. Incorporating all the available human and laboratory evidence into a precautionary regulatory framework indicates that a drinking water limit of around 5 μg/L of selenium is needed to protect human health, i.e. with an uncertainty factor of 2 versus the lowest adverse effect level observed in human studies, and that higher values may pose unacceptable risks to humans. Despite the rarity of such high levels of selenium in underground and potable waters, coal mining and other sources of environmental pollution as well as geological factors may raise drinking water selenium content above a safe threshold, triggering the need to protect consumers, and to face challenging technological issues for selenium removal, currently under active investigation.

Unraveling the Link: Mendelian Randomization Reveals Causal Relationship Between Selenium and Metabolic Syndrome

Observational studies have linked selenium and metabolic syndrome (MetS), but the causality remains unclear. Therefore, this study intends to determine the causal relationship between selenium and the risk of MetS and its component features [body mass index (BMI), waist circumference adjusted for BMI (WCadjBMI), triglycerides (TC), HDL-cholesterol (HDL-C), fasting blood glucose (FBG), fasting blood insulin (FBI), systolic blood pressure (SBP), and diastolic blood pressure (DBP)]. This study was designed as the two-sample Mendelian randomization (MR), and genetic variants were obtained from the genome-wide association studies. The inverse variance weighted (IVW) was applied as the primary method, and the MR-Egger, weighted median, and MR-PRESSO were supplemented to assess its robustness. The Bonferroni method was used to correct p-values for multiple tests. Genetically incremented selenium level was related to higher odds ratios of developing the MetS (OR = 1.054, 95% CI = 1.016-1.094, p = 0.0049). As for components, significant causal links were identified between selenium and BMI (β = 0.015, p = 1.321 × 10-5), WCadjBMI (β = 0.033, p = 2.352 × 10-4), HDL-C (β = -0.036, p = 1.352 × 10-8), FBG (β = 0.028, p = 0.001), and FBI (β = 0.028, p = 0.002). No significant association was discovered for SBP (β = -0.076, p = 0.218) and DBP (β = 0.054, p = 0.227). These results were generally supported by the weighted median and MR-PRESSO methods. Our study provided evidence of the causal effect of selenium on MetS risk from the genetic perspective in the European population, and further investigation across diverse populations was warranted.

Disentangling the role of selenium in antagonizing the toxicity of arsenic and cadmium

Cadmium (Cd) and inorganic arsenic (As) compounds are considered to be among the major public health hazards. This is due to both the high intrinsic toxicity of these substances and the often difficult to avoid exposure of the general population through contaminated water and food. One proposed method to reduce the toxic effects of As and Cd on animals and humans is the use of selenium (Se). As discussed in our previous article, laboratory studies show that this micronutrient can have a beneficial effect on the detoxification of As and Cd in the body through the formation of non-toxic complexes with these elements, as well as through the antioxidant effects of selenoproteins. New data that have emerged in recent years allow for a clearer description of the interaction between Se and As and Se and Cd. Human studies show that optimal levels of Se can have a beneficial effect in reducing the toxic effects associated with exposure to As or Cd. However, as Se levels in the body increase, the protective effects of Se may be reversed. Recent laboratory studies confirm the antagonistic effects of medium doses of Se toward Cd and As through the formation of nontoxic complexes, antioxidant, anti-inflammatory effects, and induction of pro-survival pathways in cells. In conclusion, Se has a complex effect on As and Cd toxicity, with both benefits and potential risks, depending on the form of Se and its dose as a supplement or the status (level) of this micronutrient in the body.

Evaluating agreement between individual nutrition randomised controlled trials and cohort studies - a meta-epidemiological study

BACKGROUND

In nutrition research, randomised controlled trials (RCTs) and cohort studies provide complementary evidence. This meta-epidemiological study aims to evaluate the agreement of effect estimates from individual nutrition RCTs and cohort studies investigating a highly similar research question and to investigate determinants of disagreement.

METHODS

MEDLINE, Epistemonikos, and the Cochrane Database of Systematic Reviews were searched from January 2010 to September 2021. We matched individual RCTs to cohort studies based on population, intervention/exposure, comparator, and outcome (PI/ECO) characteristics. Two reviewers independently extracted study characteristics and effect estimates and rated the risk of bias using RoB2 and ROBINS-E. Agreement of matched RCTs/cohort studies was analysed by pooling ratio of risk ratios (RRR) and difference of (standardised) mean differences (DSMD).

RESULTS

We included 64 RCT/cohort study pairs with 4,136,837 participants. Regarding PI/ECO similarity, 20.3% pairs were "more or less identical", 71.9% "similar but not identical" and 7.8% "broadly similar". Most RCTs were classified as "low risk of bias" (26.6%) or with "some concerns" (65.6%); cohort studies were mostly rated with "some concerns" (46.6%) or "high risk of bias" (47.9%), driven by inadequate control of important confounding factors. Effect estimates across RCTs and cohort studies were in high agreement (RRR 1.00 (95% CI 0.91-1.10, n = 54); and DSMD - 0.26 (95% CI - 0.87-0.35, n = 7)). In meta-regression analyses exploring determinants of disagreements, risk-of-bias judgements tend to have had more influence on the effect estimate than "PI/ECO similarity" degree.

CONCLUSIONS

Effect estimates of nutrition RCTs and cohort studies were generally similar. Careful consideration and evaluation of PI/ECO characteristics and risk of bias is crucial for a trustworthy utilisation of evidence from RCTs and cohort studies.

The association between blood selenium and metabolic syndrome in adults: a systematic review and dose-response meta-analysis of epidemiologic studies

Background and aim

Although the relationship between selenium and metabolic syndrome (MetS) was previously investigated, the findings were inconsistent. Therefore, we performed a systematic review and dose-response meta-analysis to summarize the association between blood selenium and MetS in adults.

Methods

A comprehensive search was conducted in Medline (PubMed), ISI Web of Science, Scopus, and motor engineering of Google Scholar up to October 1st, 2024. Observational studies which reported the risk of MetS in relation to blood selenium in adults were included. The protocol of the current analysis was registered at PROSPERO as CRD42024486035.

Results

Overall, 16,779 participants and 6,471 cases with MetS from 5 cross-sectional and 7 case-control studies were included in the current systematic review and meta-analysis. The findings showed that participants with the highest blood values of selenium (mean: 268.5 μg/L) in comparison to those with the lowest values (mean: 75.27 μg/L) had 40% higher risk of MetS. Nevertheless, this association was not significant (95%CI: 0.99-1.97). Due to a significant between-study heterogeneity (I2 = 90.4%, p < 0.001), subgroup analysis was conducted based on potential confounders. However, this association was only significant in a few subgroups with low number effect sizes. Linear dose-response analysis illustrated each 50 μg/L increment in circulating selenium was related to 7% higher risk of MetS (RR: 1.07, 95%CI: 0.99, 1.15) However, this association was not statistically significant. Additionally, non-linear dose-response analysis indicated a U-shaped association between blood selenium and risk of MetS with the lowest risk at 160 ug/L of blood selenium (p < 0.001).

Conclusion

There is a U-shaped relationship between blood selenium levels risk of MetS. However, more longitudinal studies are needed to verify the causality of findings and clarify the underlying mechanisms.

Activation of the De Novo Serine Synthesis Pathway and Disruption of Insulin Signaling Induced by Supplemental SeMet in Vitro

Selenium (Se) intake or selenoprotein overexpression can cause abnormal glucose metabolism and increase the risk of type 2 diabetes (T2D). The purpose of this study is to observe whether glycolysis bypass in the de novo serine synthesis pathway (SSP) is activated under high-Se stress in vitro. Initially, HCT-116, L02, HepG2, and differentiated C2C12 cells were exposed to five selenomethionine (SeMet) concentrations (0.001 to 10 µmol/L) for 48 h. The expressions of glutathione peroxidase 1 (GPX1), selenoprotein P (SELENOP), 3-phosphoglycerate dehydrogenase (PHGDH), and serine hydroxy-methyltransferases 1 (SHMT1) were assessed by western blotting (WB). Then, corresponding to the peak expressions of GPX1, SELENOP, and PHGDH, 0.1 µmol/L SeMet was identified as the highest intervention concentration. With more detailed levels of SeMet (0.001 to 0.1 µmol/L) given, the differentiated C2C12 cells were treated for 48 h to analyze the expressions of selenoproteins, enzymes related with serine metabolism and insulin signaling pathway. Among the four cell lines, the expressions of selenoproteins and metabolic enzymes of serine in C2C12 cells were more sensitive to changes in Se concentrations, which was similar to that in L02 cells. In C2C12 cells, the expressions of GPX1, SELENOP, selenoprotein N (SELENON), PHGDH, and SHMT1 exhibited a parabolic inflection point at SeMet concentrations of 0.05 µmol/L or 0.075 µmol/L, while 5,10-methylenetetrahydrofolate reductase (MTHFR) and methionine synthase (MS) showed no such trend. After 15 min of insulin stimulation, glucose retained more in the culture medium due to the decreased uptake by C2C12 cells. The expressions of key enzymes (AKT, AKT (Ser-473), AKT (Thr-308), mTOR, and PI3K) in the PI3K-AKT-mTOR signaling pathway decreased with the increased level of SeMet. This study demonstrated that excessive Se intake could induce abnormal glucose metabolism via SSP and impair the normal signaling of insulin in the differentiated C2C12 cells.

Accelerated Longitudinal Glycemic Changes in Relation to Urinary Toxic/Essential Metals and Metal Mixtures Among Mexican Americans Living in Starr County, Texas

OBJECTIVE

Metal and metalloid exposures (hereafter "metals") are associated with adverse health outcomes, including type 2 diabetes; however, previous studies were largely cross-sectional or underpowered. Furthermore, underserved racial and ethnic groups are underrepresented in environmental health research despite having higher rates of type 2 diabetes and a greater risk of metal exposures. Consequently, we evaluated continuous glycemic traits in relation to baseline urinary toxic metal, essential metal, and metal mixtures in a cohort of Mexican American adults.

RESEARCH DESIGN AND METHODS

A total of 510 participants were selected based upon self-reported diabetes status and followed over 3 years. Urinary metals were assessed at baseline. Linear mixed-effects models were used to estimate per-month changes in hemoglobin A1c, fasting plasma glucose, and postload glucose in relation to urinary metal levels. Multiple statistical approaches were used to assess the associations between glycemic traits and metal mixtures.

RESULTS

After adjustment, higher urinary levels of arsenic, selenium, copper, molybdenum, nickel, and tin were associated with faster increases in measures of glycemia. The toxic metal mixture composed of arsenic, lead, cadmium, nickel, and tin was associated with faster increases in postload glucose. Using postload glucose criteria, highest versus lowest arsenic was predicted to accelerate conversion of normoglycemia to prediabetes and diabetes by 23 and 65 months, respectively.

CONCLUSIONS

In this underrepresented, high-risk Mexican American population, exposure to toxic metals and alterations in essential metal homeostasis were associated with faster increases in glycemia over time that may accelerate type 2 diabetes development.

Increased Expression of PHGDH Under High-Selenium Stress In Vivo

The purpose of this study is to explore the glycolytic remodeling under high-selenium (Se) stress. Three groups of male C57BL/6J mice were fed on diets with different Se contents (0.03, 0.15, and 0.30 mg Se/kg). Glucose tolerance test (GTT) and insulin tolerance test (ITT) were measured at the third month. Mice were killed at the fourth month. Plasma, liver, and muscle tissues were fetched for biochemistry and Se analysis. The expressions of insulin signaling pathway (PI3K-AKT-mTOR), glutathione peroxidase 1 (GPX1), selenoprotein N (SELENON), 3-phosphoglycerate dehydrogenase (PHGDH), serine hydroxymethyltransferases 1 (SHMT1), 5,10-methylenetetrahydrofolate reductase (MTHFR), and methionine synthase (MS) were analyzed by western blotting (WB) in liver and muscle tissues. The results of GTT and ITT showed that glucose tolerance and insulin tolerance were both abnormal in the 0.03 mg Se/kg and 0.3 mg Se/kg groups. Se concentrations in plasma, liver, and muscle of 0.03 mg Se/kg group were significantly lower than that of 0.15 mg Se/kg and 0.30 mg Se/kg groups (p < 0.05 or p < 0.01). The expressions of P-Akt (Thr-308) in muscle (p < 0.05) and PI3K and mTOR in liver (p < 0.001) of 0.30 mg Se/kg group were downregulated. The expressions of GPX1 in liver and muscle (p < 0.05 and p < 0.001), SELENON in muscle (p < 0.05), PHGDH in liver and muscle (p < 0.05), and SHMT1 (p < 0.05), MTHFR (p < 0.001), and MS (p < 0.001) in muscle of 0.3 mg Se/kg group were upregulated. The de novo serine synthesis pathway (SSP) was found to be activated in liver and muscle tissues of mice with a high-Se diet for the first time.

Selenium, diabetes, and their intricate sex-specific relationship

Selenium (Se) is an essential trace element, which is inserted as selenocysteine (Sec) into selenoproteins during biosynthesis, orchestrating their expression and activity. Se is associated with both beneficial and detrimental health effects; deficient supply or uncontrolled supplementation raises concerns. In particular, Se was associated with an increased incidence of type 2 diabetes (T2D) in a secondary analysis of a randomized controlled trial (RCT). In this review, we discuss the intricate relationship between Se and diabetes and the limitations of the available clinical and experimental studies. Recent evidence points to sexual dimorphism and an association of Se deficiency with gestational diabetes mellitus (GDM). We highlight the emerging evidence linking high Se status with improved prognosis in patients with T2D and lower risk of macrovascular complications.

Serum selenium accelerates the development of metabolic disorders in a metabolically healthy obese U.S. population: a retrospective cross-sectional analysis of a population-based study from the NHANES (2011-2018)

Background

Obesity represents a significant risk factor for the development of metabolic abnormalities. However, it is not inevitable that all individuals with obesity will develop these disorders. Selenium has been demonstrated to play a role in maintaining metabolic homeostasis in vivo, with the ability to regulate relevant signaling pathways involved in glucose and lipid metabolism processes. Previous studies have indicated that selenium concentrations in obese individuals are higher than those reported in the general population. These findings the question of whether altered selenium concentrations may act as important triggers for accelerating metabolic imbalances in the obese population. The aim of this study was to examine the potential correlation between serum selenium concentrations and the risk of developing metabolic abnormalities in individuals with obesity.

Methods

The present study included 6,125 participants from the 2011-2018 National Health and Nutrition Examination Survey (NHANES) who were aged between 20 and 80 years, with a body mass index (BMI) of 30 kg/m2 or greater, and met the inclusion and exclusion criteria. Weighted generalized linear regression analyses were conducted to evaluate the associations between serum selenium concentrations and the conversion of metabolically healthy obesity (MHO) to metabolically unhealthy obesity (MUO). A generalized additive model (GAM) and a two-piecewise linear regression model were employed to investigate the saturation threshold effect between selenium and MUO. The correlation between different selenium concentration intervals and metabolic diseases was evaluated by categorizing selenium concentrations according to the saturation threshold. Furthermore, this study investigated the correlation between serum selenium and lipid concentrations in obese females and between serum selenium and blood pressure in obese males.

Results

The weighted prevalence of MUO in the study population was 48.35%. After rigorous adjustment for sociodemographic, physical, and laboratory test covariates, the weighted odds ratio (OR) of MUO increased by 44% for every 1 µM increase (approximately 78.74 µg) in the serum selenium concentration (weighted OR=1.44; 95% CI=1.09 - 1.91; P=0.018). Second, GAM analysis and saturation threshold analyses revealed an inverted U-shaped relationship between serum selenium and metabolic abnormalities in males, with a corresponding inflection point (K) of 2.82 µM. When the serum selenium concentration was below the K-value, the effects of serum selenium were mainly on blood pressure, especially diastolic blood pressure (DBP) (weighted β: 3.34; 95% CI= 0.25 - 6.44; P=0.038). Conversely, the correlation between the serum selenium concentrations and metabolic homeostasis imbalance in females was linear. When the selenium concentration exceeded 2.12 µM, the increase in selenium content was accompanied by increases in total cholesterol (TC, weighted β=0.54, 95% CI=0.32 - 0.76; P=0.000) and triglyceride (TG, weighted β=0.51, 95% CI=0.27 - 0.75; P=0.000) concentrations.

Conclusions

The findings of our study indicate that selenium supplementation strategies for individuals with obesity should be tailored to the sex of the individual. In females, serum selenium concentration above the saturation threshold primarily facilitates the transition from MHO to MUO by influencing alterations in serum lipid metabolism. Maintaining selenium concentrations below the threshold levels is highly important for preventing the conversion of MHO to MUO. In males, serum selenium concentrations above the threshold were found to be effective in preventing an elevation in blood pressure, particularly in improving systolic blood pressure (SBP). Nevertheless, serum selenium concentrations below the threshold are linked to an increased risk of hypertension in obese individuals, particularly those with elevated diastolic blood pressure (DBP). Further research is needed to elucidate the optimal serum selenium concentration that exerts deleterious effects on blood pressure.

Association of Blood Selenium Levels with Diabetes and Heart Failure in American General Adults: a Cross-sectional Study of NHANES 2011-2020 pre

Selenium is an essential trace element closely related to human health; however, the relationship between blood selenium levels, diabetes, and heart failure remains inconclusive. Therefore, this study aimed to explore the relationship between blood selenium levels and the prevalence of diabetes as well as heart failure in American general adults aged 20 years or older. This study utilized data from four survey cycles from NHANES 2011-2020 pre. Blood selenium levels were considered as both a continuous variable and quartiles, and logistic regression was employed to investigate the associations between blood selenium levels with diabetes and heart failure. Nonlinear relationships were examined by restricted cubic spline regression. The analysis included a total of 16311 participants aged 20 years or older. After adjustment for all potential confounder, we found when the blood selenium levels increased by 10 ug/L, the average risk of diabetes increased by 4.2% (95% CI: 1.5%, 7.0%), and the average risk of heart failure decreased by 5.0% (95% CI: 0.1%, 9.8%). In addition, compared with the lowest reference group, blood selenium levels were significantly positively associated with risk of diabetes in participants in the fourth quartile (OR=1.458, 95% CI: 1.173, 1.812), while significantly negatively associated with the risk of heart failure in participants in the second, third and fourth quartiles (Q2, OR=0.677, 95% CI: 0.471, 0.974) (Q3, OR=0.609, 95% CI: 0.426, 0.870) (Q4, OR=0.653, 95% CI: 0.443, 0.961). There was a nonlinear and reverse L-shaped association between blood selenium and diabetes, while a negative dose-response association between blood selenium and heart failure. Furthermore, the association between blood selenium levels and heart failure was more pronounced in participants with poor glycemic control, rather than diabetic patients. High blood selenium levels may be positively related to diabetes, while low blood selenium levels may be associated to heart failure. Appropriate blood selenium levels may help prevent diabetes and heart failure.

Association of Dietary Selenium Intake with Type 2 Diabetes in Middle-Aged and Older Adults in China

The relationship between distinct dietary selenium intake and type 2 diabetes (T2D) is still a topic of uncertainty. This study examined the relationship between dietary selenium intake and T2D risk among middle-aged and older Chinese adults. Dietary selenium intake was assessed through three 24 h recalls, using data from the China Health and Nutrition Survey. To investigate the relationship and the potential dose-response pattern between selenium intake and the likelihood of developing T2D, we employed both the restricted cubic spline analysis and the Cox proportional hazards model as our analytical tools. A cohort of 5970 participants aged ≥ 50 years was followed for an average of 5.44 years. The results revealed a V-shaped correlation between selenium intake and T2D risk, with the lowest risk observed at approximately 45 µg/day. Below this level, the risk decreased with an increasing selenium intake, while the risk increased between 45 and 100 µg/day. No significant association was found beyond 100 µg/day. These findings suggest that both low and high selenium consumption may increase T2D risk, highlighting the importance of maintaining a balanced selenium intake for T2D prevention.

Selenium Species in Diabetes Mellitus Type 2

Selenium is an important trace element for humans and animals as it plays a key role in several major metabolic pathways. Several studies were conducted to better understand the role of selenium against diabetes mellitus (DM), particularly type 2 (T2DM), but the obtained conclusions are contradictory. A simple linear relationship does not exist between the risk of T2DM and selenium levels but is best represented in a dose-dependent manner, getting often the U-graph. This relation also depends on selenium chemical forms that are present in a diet or supplements. Both too low and too high selenium intakes could increase the risk of diabetes. Moreover, the baseline status of Se should be taken into consideration to avoid over-supplementation. The focus of this brief overview is to report the recent updates concerning selenium participation in diabetes mellitus.

Circulating Selenium Level Was Positively Related to Visceral Adiposity Index with a Non-linear Trend: a Nationwide Study of the General Population

Selenium plays a role in obesity. However, whether circulating selenium levels are related to the visceral adiposity index (VAI), an indicator of obesity, is still unknown. Based on the National Health and Nutrition Examination Survey (NHANES) 2011-2018, data from 12,777 individuals aged ≥ 20 years were analyzed to clarify this question. In fully adjusted models of multivariate regression analysis, natural logarithm (Ln) selenium was positively related to Ln VAI (β = 0.41; 95% confidence interval [CI], 0.27, 0.55; P < 0.001). Compared with the lowest quartile of Ln selenium, the highest quartile was also positively associated with Ln VAI (β = 0.16; 95% CI, 0.11, 0.21; P < 0.001). Moreover, we found that this positive connection was non-linear. When Ln selenium was less than the inflection point, Ln selenium was positively related to Ln VAI (β = 0.41; 95% CI, 0.31, 0.52; P < 0.001). However, when Ln selenium was greater than or equal to the inflection point, Ln selenium was not significantly related to Ln VAI (β = -0.15; 95% CI, -0.56, 0.25; P = 0.455). In subgroup analysis, significant interactions were observed with age and sex (P for interaction < 0.05). Stronger interactions were observed among middle-aged participants (β = 0.65; 95% CI, 0.31, 0.98; P = 0.002) and males (β = 0.61; 95% CI, 0.43, 0.79; P < 0.001). Overall, circulating selenium levels were positively related to VAI, with a non-linear trend. Prospective studies and interventional experiments are necessary to verify the possible mechanisms.

Recommendations for nutritional supplements for dry eye disease: current advances

Dry eye disease (DED) represents a prevalent ocular surface disease. The development of effective nutritional management strategies for DED is crucial due to its association with various factors such as inflammation, oxidative stress, deficiencies in polyunsaturated fatty acids (PUFAs), imbalanced PUFA ratios, and vitamin insufficiencies. Extensive research has explored the impact of oral nutritional supplements, varying in composition and dosage, on the symptoms of DED. The main components of these supplements include fish oils (Omega-3 fatty acids), vitamins, trace elements, and phytochemical extracts. Beyond these well-known nutrients, it is necessary to explore whether novel nutrients might contribute to more effective DED management. This review provides a comprehensive update on the therapeutic potential of nutrients and presents new perspectives for combination supplements in DED treatment.

Selenium intake in relation to all-cause and cardiovascular mortality in individuals with nonalcoholic fatty liver disease: A nationwide study in nutrition

AIMS

Limited evidence exists regarding the association of selenium with risk of death in individuals with nonalcoholic fatty liver disease (NAFLD). This study was designed to investigate the relationship between dietary selenium intake with mortality in a nationally representative sample of United States adults with NAFLD.

METHODS

Dietary selenium intake was assessed in 2274 NAFLD adults younger than 60 years of age from the National Health and Nutrition Examination Survey (NHANES) III through a 24-hour dietary recall. NAFLD was diagnosed by liver ultrasound after excluding liver disease due to other causes. Cox proportional hazards models were utilized to assess the effect of dietary selenium intake on all-cause and cardiovascular mortality among individuals with NAFLD.

RESULTS

At a median follow-up of 27.4 years, 577 deaths occurred in individuals with NAFLD, including 152 cardiovascular deaths. The U-shaped associations were discovered between selenium intake with all-cause (Pnolinear = 0.008) and cardiovascular mortality (Pnolinear < 0.001) in adults with NAFLD after multivariate adjustment, with the lowest risk around selenium intake of 121.7 or 125.9 μg/day, respectively. Selenium intake in the range of 104.1-142.4 μg/day was associated with a reduced risk of all-cause mortality and, otherwise, an increased risk. Selenium intake in the range of 104.1-150.6 μg/day was associated with a reduced risk of cardiovascular death and, otherwise, an increased risk.

CONCLUSIONS

Both high and low selenium intake increased the risk of all-cause and cardiovascular death in adults younger than 60 years of age with NAFLD, which may help guide dietary adjustments and improve outcomes in adults with NAFLD.

National trends in nine key minerals intake (quantity and source) among U.S. adults, 1999 to march 2020

BACKGROUND

Changes in economy and dietary guidelines brought a great shock to diet quality and meal behaviors, but if these transformations have extended to minerals intake and their sources was still poorly understood. It is essential to evaluate time trends in minerals intake and their sources to inform policy makers.

OBJECTIVE

To investigate trends in minerals intake and their sources among U.S. adults.

METHODS

This analysis used dietary data collected by 24-h recalls from U.S. adults (≥ 20 years) in NHANES (1999-March 2020). Minerals intake, age-adjusted percentage of participants meeting recommendations, and minerals sources were calculated among all participants and by population subgroups in each NHANES survey cycle. Weighted linear or logistic regression models were used to examine the statistical significance of time trends.

RESULTS

A total of 48223 U.S. adults were included in this analysis. From 1999 to March 2020, intake of calcium (from 0.94 to 1.02 g/day), magnesium (from 308.07 to 321.85 mg/day), phosphorus (from 1.24 to 1.30 g/day), and sodium (from 3.24 to 3.26 mg/day) from food and beverages (FB) and dietary supplements (DSs) significantly increased, and intake of iron (from 19.17 to 16.38 mg/day), zinc (from 16.45 to 14.19 mg/day), copper (from 1.79 to 1.38 mg/day), and potassium (from 2.65 to 2.50 g/day) from FB + DSs decreased (all FDR < 0.05). Additionally, age-adjusted percentage of participants meeting recommendations for calcium, phosphorus, sodium, and selenium significantly increased, that for iron, potassium, zinc, and copper decreased (all FDR < 0.05). Minerals intake and time trends in minerals intake were highly variable depending on age, gender, race/ethnicity, education, and income. For example, white, higher socioeconomic status participants had a higher minerals intake (e.g. iron, zinc, and copper), but had a greater decrease in minerals intake. Furthermore, the percentage of minerals from milks and DSs decreased, and that from beverages increased.

CONCLUSION

From 1999 to March 2020, both minerals intake and their sources experienced a significant alteration among U.S. adults. Many differences in minerals intake and their food sources across sociodemographic characteristics appeared to narrow over time. Although some improvements were observed, important challenges, such as overconsumption of sodium and underconsumption of potassium, calcium, and magnesium, still remained among U.S. adults.

Effects of selenium and iodine on Kashin-Beck disease: an updated review

Kashin-Beck disease (KBD) is an endochondral osteogenesis disorder characterised by epiphysis damage and secondary deformable arthropathy induced by multiple external factors, among which selenium (Se) and iodine deficiency are important influencing factors. Iodine deficiency is usually accompanied by a low Se content in the soil in the KBD areas of China. Se can reverse oxidative damage to chondrocytes. In addition, Se is related to the bone conversion rate and bone mineral density. Low Se will hinder growth and change bone metabolism, resulting in a decrease in the bone conversion rate and bone mineral density. Thyroid hormone imbalance caused by thyroid dysfunction caused by iodine deficiency can damage bone homeostasis. Compared with Se deficiency alone, Se combined with iodine deficiency can reduce the activity of glutathione peroxidase more effectively, which increases the vulnerability of chondrocytes and other target cells to oxidative stress, resulting in chondrocyte death. Clinical studies have shown that supplementation with Se and iodine is helpful for the prevention and treatment of KBD.

A genome-wide association study provides insights into the genetic etiology of 57 essential and non-essential trace elements in humans

Trace elements are important for human health but may exert toxic or adverse effects. Mechanisms of uptake, distribution, metabolism, and excretion are partly under genetic control but have not yet been extensively mapped. Here we report a comprehensive multi-element genome-wide association study of 57 essential and non-essential trace elements. We perform genome-wide association meta-analyses of 14 trace elements in up to 6564 Scandinavian whole blood samples, and genome-wide association studies of 43 trace elements in up to 2819 samples measured only in the Trøndelag Health Study (HUNT). We identify 11 novel genetic loci associated with blood concentrations of arsenic, cadmium, manganese, selenium, and zinc in genome-wide association meta-analyses. In HUNT, several genome-wide significant loci are also indicated for other trace elements. Using two-sample Mendelian randomization, we find several indications of weak to moderate effects on health outcomes, the most precise being a weak harmful effect of increased zinc on prostate cancer. However, independent validation is needed. Our current understanding of trace element-associated genetic variants may help establish consequences of trace elements on human health.

Evaluating agreement between evidence from randomised controlled trials and cohort studies in nutrition: a meta-research replication study

This meta-research study aims to evaluate the agreement of effect estimates between bodies of evidence (BoE) from RCTs and cohort studies included in the same nutrition evidence synthesis, to identify factors associated with disagreement, and to replicate the findings of a previous study. We searched Medline, Epistemonikos and the Cochrane Database of Systematic Reviews for nutrition systematic reviews that included both RCTs and cohort studies for the same patient-relevant outcome or intermediate-disease marker. We rated similarity of PI/ECO (population, intervention/exposure, comparison, outcome) between BoE from RCTs and cohort studies. Agreement of effect estimates across BoE was analysed by pooling ratio of risk ratios (RRR) for binary outcomes and difference of standardised mean differences (DSMD) for continuous outcomes. We performed subgroup and sensitivity analyses to explore determinants associated with disagreements. We included 82 BoE-pairs from 51 systematic reviews. For binary outcomes, the RRR was 1.04 (95% confidence interval (CI) 0.99 to 1.10, I2 = 59%, τ2 = 0.02, prediction interval (PI) 0.77 to 1.41). For continuous outcomes, the pooled DSMD was  - 0.09 (95% CI  - 0.26 to 0.09, PI  - 0.55 to 0.38). Subgroup analyses yielded that differences in type of intake/exposure were drivers towards disagreement. We replicated the findings of a previous study, where on average RCTs and cohort studies had similar effect estimates. Disagreement and wide prediction intervals were mainly driven by PI/ECO-dissimilarities. More research is needed to explore other potentially influencing factors (e.g. risk of bias) on the disagreement between effect estimates of both BoE.Trial registration: CRD42021278908.

Brazil nut consumption reduces DNA damage in overweight type 2 diabetes mellitus patients

Type 2 diabetes mellitus (T2D) is a metabolic disease, which occurs largely due to unhealthy lifestyle. As oxidative stress is believed to promote T2D, by inducing damage to lipids, proteins, and DNA, appropriate dietary interventions seem critical to prevent, manage, and even reverse this condition. Brazil nuts (Bertholletia excelsa, H.B.K.) are nature's richest source of selenium, a mineral that has shown several health benefits. Therefore, this study aims to assess the effects of selenium consumption, through Brazil nuts, on biochemical and oxidative stress parameters, and genomic instability in T2D patients. We recruited 133 patients with T2D, registered in the Integrated Clinics of the University of Southern Santa Catarina (Brazil). Participants consumed one Brazil nut a day for six months. Blood samples and exfoliated buccal cells were collected at the beginning and the end of the intervention. The glycemic profile, lipid profile, renal profile and hepatic profile, DNA damage and selenium content were evaluated. A total of 74 participants completed the intervention. Brazil nut consumption increased selenium and GSH levels, GPx, and CAT activity while DCF and nitrites levels decreased. Total thiols increased, and protein carbonyl and MDA levels decreased. Levels of baseline and oxidative DNA damage in T2D patients were significantly decreased, as well as the frequency of micronuclei and nuclear buds. The fasting glucose levels, HDL and LDL cholesterol, and GGT levels that increased significantly in patients with type 2 diabetes were significantly reduced with nut consumption. Our results show an increase in antioxidant activity, along with reductions of protein and lipid oxidation as well as DNA damage, suggesting that Brazil nut consumption could be an ally in reducing oxidative stress and modulating the genomic instability in T2D patients.

Effect of dietary selenium intake on CVD: a retrospective cohort study based on China Health and Nutrition Survey (CHNS) data

OBJECTIVE

We aimed to examine the association between dietary Se intake and CVD risk in Chinese adults.

DESIGN

This prospective cohort study included adults above 20 years old in the China Health and Nutrition Survey (CHNS), and they were followed up from 1997 to 2015 (n 16 030). Dietary data were retrieved from CHNS, and a 3-d, 24-h recall of food intake was used to assess the cumulative average intake of dietary Se, which was divided into quartiles. The Cox proportional hazards model was adopted to analyse the association between dietary Se intake and incident CVD risk.

SETTING

CHNS (1991, 1993, 1997, 2000, 2004, 2006, 2009, 2011 and 2015).

RESULTS

A total of 663 respondents developed CVD after being followed up for a mean of 9·9 years (median 9 years). The incidence of CVD was 4·3, 3·7, 4·6 and 4·0 per 1000 person-years across the quartiles of cumulative Se intake. After adjusting all potential factors, no significant associations were found between cumulative Se intake and CVD risk. No interactions were found between Se intake and income, urbanisation, sex, region, weight, hypertension and CVD risk.

CONCLUSION

We found no association between dietary Se and CVD.

Impact of age, sex, and thyroid autoimmunity on the association between selenium intake and type 2 diabetes mellitus

BACKGROUND

The association between dietary selenium(Se) intake and type 2 diabetes mellitus (T2DM) remains controversial. The present study aimed to investigate this association using data from the National Health and Nutrition Examination Survey (NHANES) database for the years 2007-2012.

METHODS

Three thousand seventy three individuals aged 20 years and above were eligible for inclusion in this cross-sectional study. The average age of the participants was 50.74 years and the proportions of males and females were nearly equal (49.12% vs. 50.88%). The odds ratios (OR) of the association between dietary Se intake (log2-transformed) and T2DM were examined through the multivariate logistic regression model. Subgroup analyses were conducted based on age, sex, and thyroid autoimmunity to assess the potential impact of these variables on the relationship. Fitted smoothing curves and threshold effect analysis were conducted to describe the nonlinear relationship.

RESULTS

In the fully adjusted model, a significant positive association between Se intake and T2DM was observed (OR = 1.49, 95% CI: 1.16, 1.90, p = 0.0017). After stratifying the data by age, sex, and thyroid autoimmunity, a significant positive association between Se intake and T2DM was observed in individuals under 65 years of age, males, and those with negative thyroid autoimmunity. A two-segment linear regression model was analyzed for sex stratification, revealing a threshold effect in males with an inflection point of 90.51 μg, and an inverted U-shaped relationship in females with an inflection point of 109.90 μg, respectively.

CONCLUSIONS

The present study found a positive relationship between Se intake and the prevalence of T2DM. This association is particularly significant in younger individuals, males, and those with negative thyroid autoimmunity. Our results should be validated in future large prospective studies in different populations.

Selenium Concentration Is Positively Associated with Triglyceride-Glucose Index and Triglyceride Glucose-Body Mass Index in Adults: Data from NHANES 2011-2018

Compiling evidence supports that selenium plays a vital role in glucose metabolism. Triglyceride-glucose index (TyG) and triglyceride-glucose-body mass index (TyG-BMI) are commonly used in epidemiologic studies to evaluate insulin resistance and cardiovascular disease (CVD) risks. This study is aimed to investigate the association between whole blood selenium concentration and TyG and TyG-BMI. A total of 6290 participants (age ≥ 20 years) from the National Health and Nutrition Examination Survey (NHANES) 2011-2018 were included. Multiple linear regression models were used to examine the association between blood selenium quartiles and TyG and TyG-BMI. Subgroup analysis stratified by diabetes status was also performed. The adjusted model showed a positive association between TyG and blood selenium concentration (β [95%CI] = 0.099 [0.063, 0.134], p < 0.001) and TyG-BMI (β [95%CI] = 3.185 [2.102, 4.268], p < 0.001). The association persisted after stratification by diabetes status (p < 0.001). Participants were stratified into four quartiles based on selenium concentration (Q1: 1.08-2.24 μmol/L, Q2: 2.25-2.42 μmol/L, Q3: 2.43-2.62 µmol/L, Q4: 2.63-8.08). Compared with the Q1 group, TyG in the Q3 and Q4 groups was significantly higher (β = 0.075 [95%CI 0.039 to 0.112] and β = 0.140 [95%CI 0.103 to 0.176], respectively). Additionally, TyG-BMI in the Q2, Q3, and Q4 groups was higher than that in the Q1 group (β = 1.189 [95%CI 0.065 to 2.314], β = 2.325 [95%CI 1.204 to 3.446], and β = 4.322 [95%CI 3.210 to 5.435], respectively). Blood level of selenium was positively associated with TyG and TyG-BMI, indicating that excessive blood selenium may be associated with impaired insulin sensitivity and increased risk of cardiovascular disease.

Adherence to the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet and exposure to selenium species: A cross-sectional study

Selenium is a trace element found in many chemical forms. Selenium and its species have nutritional and toxicologic properties, some of which may play a role in the etiology of neurological disease. We hypothesized that adherence to the Mediterranean-Dietary Approach to Stop Hypertension Intervention for Neurodegenerative Delay (MIND) diet could influence intake and endogenous concentrations of selenium and selenium species, thus contributing to the beneficial effects of this dietary pattern. We carried out a cross-sectional study of 137 non-smoking blood donors (75 females and 62 males) from the Reggio Emilia province, Northern Italy. We assessed MIND diet adherence using a semiquantitative food frequency questionnaire. We assessed selenium exposure through dietary intake and measurement of urinary and serum concentrations, including speciation of selenium compound in serum. We fitted non-linear spline-based regression models to investigate the association between MIND diet adherence and selenium exposure concentrations. Adherence to the MIND diet was positively associated with dietary selenium intake and urinary selenium excretion, whereas it was inversely associated with serum concentrations of overall selenium and organic selenium, including serum selenoprotein P-bound selenium, the most abundant circulating chemical form of the metalloid. MIND diet adherence also showed an inverted U-shaped relation with inorganic selenium and particularly with its hexavalent form, selenate. Our results suggest that greater adherence to the MIND diet is non-linearly associated with lower circulating concentrations of selenium and of 2 potentially neurotoxic species of this element, selenoprotein P and selenate. This may explain why adherence to the MIND dietary pattern may reduce cognitive decline.

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.

Selenomethionine Suppress the Progression of Poorly Differentiated Thyroid Cancer via LncRNA NONMMUT014201/miR-6963-5p/Srprb Pathway

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) is a special type of thyroid cancer that threatens the life of the patients. Unfortunately, there are no effective treatments for PDTC right now, so it is urgent to search for new efficacious drugs. This experiment was designed to elucidate the effects of selenomethionine (SeMet) on PDTC in vitro and vivo.

METHODS

A xenograft animal model was used to assay the volume and weight of PDTC. LncRNA NOMMMUT014201 expression was detected by fluorescence in situ hybridization and Real-time quantitative PCR (qRT-PCR). In vitro experiments were carried on in WRO cells. The Cell Counting Kit-8 assay was performed to test the effect of SeMet on the proliferation of cells. And the migration and invasion of WRO cells by the wound-healing assay, Transwell migration and invasion assays. The cell apoptosis was measured by flow cytometry. In addition, genes related to proliferation, migration, invasion and apoptosis were detected through qRT-PCR and Western Blot.

RESULTS

SeMet inhibited the proliferation, migration and invasion and promoted the apoptosis of WRO cells in a dose-dependent manner. Then vivo, SeMet significantly suppressed the volume and weight of PDTC. And SeMet downregulated the expressions of Ki67, PCNA, MMP2, MMP9 and BCL2, but upregulated that of BAX and Cleaved-Caspase 3. Moreover, SeMet upregulated the level of LncRNA NOMMMUT014201 both vivo and in vitro. In addition, repression of LncRNA NOMMMUT014201 removed the inhibition effect of SeMet on WRO cell growth significantly (p<0.05). Further investigation showed that LncRNA NOMMMUT014201 downregulated the expression of miR-6963-5p in PDTC cells, but miR-6963-5p inhibited the level of Srprb. In addition, sh-LncRNA NOMMMUT014201 enhanced the proliferation, migration and invasion but inhibited the apoptosis of WRO cells. However, inhibited miR-6963-5p or overexpressed Srprb relieved the effects of sh-LncRNA NOMMMUT014201on WRO cells.

CONCLUSION

Collectively, SeMet inhibits the growth of PDTC in a dose-dependent manner through LncRNA NONMMUT014201/miR-6963-5p/Srprb signal pathway, thus suggesting that SeMet might be a potential drug for PDTC treatment.

A Comprehensive Review on GLP-1 Signaling Pathways in the Management of Diabetes Mellitus - Focus on the Potential Role of GLP-1 Receptors Agonists and Selenium among Various Organ Systems

Diabetes Mellitus develops when the body becomes unable to fuel its cells with glucose, which results in the accumulation of sugar excess in the bloodstream. Because it has diverse pathophysiological impacts on the body, diabetes mellitus represents a significant issue of concern in an attempt to find suitable treatment modalities and medications for afflicted diabetic patients. Glucagon-like peptide 1 (GLP-1) plays a pivotal role in the incretin effect, emerging as a prospective treatment for diabetes mellitus and a promising means of regenerating pancreatic cells, whether directly or through its receptor agonists. It has been shown that GLP-1 efficiently increases insulin production, lowers blood sugar levels in patients with type 2 diabetes mellitus, and decreases appetite, craving, and hunger, therefore amplifying the sensation of fullness and satiety. Moreover, since they are all dependent on GLP-1 effect, intricate signaling pathways share some similarities during specific phases, although the pathways continue to exhibit significant divergence engendered by specific reactions and effects in each organ, which encompasses the rationale behind observed differences. This triggers an expanding range of GLP-1 R agonists, creating new unforeseen research and therapeutic application prospects. This review aims to explain the incretin effect, discuss how GLP-1 regulates blood glucose levels, and how it affects different body organs, as well as how it transmits signals, before introducing selenium's role in the incretin impact.

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.

A causal relationship between antioxidants, minerals and vitamins and metabolic syndrome traits: a Mendelian randomization study

BACKGROUND

The available evidence regarding the association of antioxidants, minerals, and vitamins with the risk of metabolic syndrome (MetS) traits is currently limited and inconsistent. Therefore, the purpose of this Mendelian randomization (MR) study was to investigate the potential causal relationship between genetically predicted antioxidants, minerals, and vitamins, and MetS.

METHODS

In this study, we utilized genetic variation as instrumental variable (IV) to capture exposure data related to commonly consumed dietary nutrients, including antioxidants (β-carotene, lycopene, and uric acid), minerals (copper, calcium, iron, magnesium, phosphorus, zinc, and selenium), and vitamins (folate, vitamin A, B6, B12, C, D, E, and K1). The outcomes of interest, namely MetS (n = 291,107), waist circumference (n = 462,166), hypertension (n = 463,010), fasting blood glucose (FBG) (n = 281,416), triglycerides (n = 441,016), and high-density lipoprotein cholesterol (HDL-C) (n = 403,943), were assessed using pooled data obtained from the most comprehensive genome-wide association study (GWAS) available. Finally, we applied the inverse variance weighting method as the result and conducted a sensitivity analysis for further validation.

RESULTS

Genetically predicted higher iron (OR = 1.070, 95% CI 1.037-1.105, P = 2.91E-05) and magnesium levels (OR = 1.130, 95% CI 1.058-1.208, P = 2.80E-04) were positively associated with increased risk of MetS. For each component of MetS, higher level of genetically predicted selenium (OR = 0.971, 95% CI 0.957-0.986, P = 1.09E-04) was negatively correlated with HDL-C levels, while vitamin K1 (OR = 1.023, 95% CI 1.012-1.033, P = 2.90E-05) was positively correlated with HDL-C levels. Moreover, genetically predicted vitamin D (OR = 0.985, 95% CI 0.978-0.992, P = 5.51E-5) had a protective effect on FBG levels. Genetically predicted iron level (OR = 1.043, 95% CI 1.022-1.064, P = 4.33E-05) had a risk effect on TG level.

CONCLUSIONS

Our study provides evidence that genetically predicted some specific, but not all, antioxidants, minerals, and vitamins may be causally related to the development of MetS traits.

Advances in Biosynthesis of Non-Canonical Amino Acids (ncAAs) and the Methods of ncAAs Incorporation into Proteins

The functional pool of canonical amino acids (cAAs) has been enriched through the emergence of non-canonical amino acids (ncAAs). NcAAs play a crucial role in the production of various pharmaceuticals. The biosynthesis of ncAAs has emerged as an alternative to traditional chemical synthesis due to its environmental friendliness and high efficiency. The breakthrough genetic code expansion (GCE) technique developed in recent years has allowed the incorporation of ncAAs into target proteins, giving them special functions and biological activities. The biosynthesis of ncAAs and their incorporation into target proteins within a single microbe has become an enticing application of such molecules. Based on that, in this study, we first review the biosynthesis methods for ncAAs and analyze the difficulties related to biosynthesis. We then summarize the GCE methods and analyze their advantages and disadvantages. Further, we review the application progress of ncAAs and anticipate the challenges and future development directions of ncAAs.

Selenium intake and multiple health-related outcomes: an umbrella review of meta-analyses

Selenium is an essential trace metalloid element that is associated with fundamental importance to human health. Our umbrella review aimed to evaluate the quality of evidence, validity, and biases in the relationship between selenium intake and health-related outcomes according to published systematic reviews with pooled data and meta-analyses. Selenium intake is associated with a decreased risk of digestive system cancers, all-cause mortality, depression, and Keshan disease, when in children reduce the risk of Kashin-Beck disease. Additionally, selenium supplementation can improve sperm quality, polycystic ovary syndrome, autoimmune thyroid disease, cardiovascular disease, and infective outcomes. Selenium supplementation also has relationship with a decreased concentration of serum lipids including total cholesterol and very low-density lipoprotein cholesterol. However, no evidence has shown that selenium is associated with better outcomes among patients in intensive care units. Furthermore, selenium intake may be related with a higher risk of type 2 diabetes and non-melanoma skin cancers. Moreover, most of included studies are evaluated as low quality according to our evidence assessment. Based on our study findings and the limited advantages of selenium intake, it is not recommended to receive extra supplementary selenium for general populations, and selenium supplementation should not be continued in patients whose selenium-deficient status has been corrected.

Selenium supplementation effect on glycemic control: A GRADE-assessed systematic review and dose-response meta-analysis of randomized controlled trials

Results from different studies on the effects of selenium supplementation on glycemic control are still debated. To fill this knowledge gap, we investigated the overall effects of selenium supplementation on some glycemic parameters such as fasting blood sugar (FBS), hemoglobinA1c (HbA1c), fasting insulin, quantitative insulin sensitivity check index (QUICKI), and homeostatic model assessment of insulin resistance (HOMA-IR). A comprehensive literature search was conducted from inception to April 2023 on Scopus, Web of Science, PubMed, Google Scholar, and Cochrane databases. All randomized controlled trials (RCTs) which reported an effect of selenium supplementation on glycemic parameters were included. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% CI for each outcome. Between-studies heterogeneity was assessed by the I2 and Cochran's Q test. 20 trials were included in the meta-analysis. Pooled analysis showed that selenium intake significantly reduced fasting insulin (WMD: -3.02 µIu/mL, 95% CI; -5.13, -0.90, P = 0.005) and increased QUICKI levels (WMD: 0.01, 95% CI: 0.01, 0.02, P = 0.005). However, selenium supplementation did not change FBS (WMD: -1.32 mg/dL, 95% CI; -4.02, 1.37, P = 0.332), HbA1c (WMD = 0.05%, 95% CI: -0.19, 0.28, p = 0.701), and HOMA-IR (WMD: -0.82, 95% CI; -2.14, 0.50, P = 0.223). Moreover, we found that there is a non-linear association between selenium supplementation dosage and FBS (P-nonlinearity = 0.008). In conclusion, our study findings indicate some benefits of selenium on fasting insulin, and QUICKI compared with placebo, but elicits no effect on HbA1c, HOMA-IR, and FBS. Further well-designed RCTs with larger samples are necessary to ascertain the effects of selenium supplementation on glycemic control.

Antioxidant Nutrients and Risk of Latent Autoimmune Diabetes in Adults and Type 2 Diabetes: A Swedish Case-Control Study and Mendelian Randomization Analysis

Antioxidant vitamins C and E are inversely associated with type 1 diabetes (T1D). We investigated if antioxidants are also associated with latent autoimmune diabetes in adults (LADA), with low (LADA^low) and high (LADA^high) autoantibody levels, type 2 diabetes (T2D), and estimates of beta cell function (HOMA-B) and insulin resistance (HOMA-IR). We used Swedish case-control data with incident cases of LADA (n = 584) and T2D (n = 1989) and matched population-based controls (n = 2276). Odds ratios (OR) and 95% confidence intervals (CI) were calculated per one standard deviation higher beta-carotene, vitamin C, vitamin E, selenium, and zinc intakes. Two-sample Mendelian randomization (MR) analyses assessed causality between genetically predicted circulating antioxidants and LADA, T1D, and T2D, using summary statistics from genome-wide association studies. Among the antioxidants, vitamins C and E were inversely associated with LADA^high (OR 0.84, CI 0.73, 0.98 and OR 0.80, CI 0.69, 0.94 respectively), but not with LADA^low or T2D. Vitamin E was also associated with higher HOMA-B and lower HOMA-IR. MR analyses estimated an OR of 0.50 (CI 0.20, 1.25) for the effect of vitamin E on T1D, but did not support causal relationships between antioxidants and either LADA or T2D. In conclusion, vitamin E may have a protective effect on autoimmune diabetes, possibly through preserved beta cell function and less insulin resistance.

Selenium and Selenoproteins in Health

Selenium is a trace mineral that is essential for health. After being obtained from food and taken up by the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium stimulates the activation of immune cells and is important for the activation of the immune system. Selenium is also essential for the maintenance of brain function. Selenium supplements can regulate lipid metabolism, cell apoptosis, and autophagy, and have displayed significant alleviating effects in most cardiovascular diseases. However, the effect of increased selenium intake on the risk of cancer remains unclear. Elevated serum selenium levels are associated with an increased risk of type 2 diabetes, and this relationship is complex and nonlinear. Selenium supplementation seems beneficial to some extent; however, existing studies have not fully explained the influence of selenium on various diseases. Further, more intervention trials are needed to verify the beneficial or harmful effects of selenium supplementation in various diseases.

Redox Balance in Type 2 Diabetes: Therapeutic Potential and the Challenge of Antioxidant-Based Therapy

Oxidative stress is an important factor in the development of type 2 diabetes (T2D) and associated complications. Unfortunately, most clinical studies have failed to provide sufficient evidence regarding the benefits of antioxidants (AOXs) in treating this disease. Based on the known complexity of reactive oxygen species (ROS) functions in both the physiology and pathophysiology of glucose homeostasis, it is suggested that inappropriate dosing leads to the failure of AOXs in T2D treatment. To support this hypothesis, the role of oxidative stress in the pathophysiology of T2D is described, together with a summary of the evidence for the failure of AOXs in the management of diabetes. A comparison of preclinical and clinical studies indicates that suboptimal dosing of AOXs might explain the lack of benefits of AOXs. Conversely, the possibility that glycemic control might be adversely affected by excess AOXs is also considered, based on the role of ROS in insulin signaling. We suggest that AOX therapy should be given in a personalized manner according to the need, which is the presence and severity of oxidative stress. With the development of gold-standard biomarkers for oxidative stress, optimization of AOX therapy may be achieved to maximize the therapeutic potential of these agents.

Diabetes as one of the long-term COVID-19 complications: from the potential reason of more diabetic patients' susceptibility to COVID-19 to the possible caution of future global diabetes tsunami

According to recent researches, people with diabetes mellitus (type 1 and 2) have a higher incidence of coronavirus disease 2019 (COVID-19), which is caused by a SARS-CoV-2 infection. In this regard, COVID-19 may make diabetic patients more sensitive to hyperglycemia by modifying the immunological and inflammatory responses and increasing reactive oxygen species (ROS) predisposing the patients to severe COVID-19 and potentially lethal results. Actually, in addition to COVID-19, diabetic patients have been demonstrated to have abnormally high levels of inflammatory cytokines, increased virus entrance, and decreased immune response. On the other hand, during the severe stage of COVID-19, the SARS-CoV-2-infected patients have lymphopenia and inflammatory cytokine storms that cause damage to several body organs such as β cells of the pancreas which may make them as future diabetic candidates. In this line, the nuclear factor kappa B (NF-κB) pathway, which is activated by a number of mediators, plays a substantial part in cytokine storms through various pathways. In this pathway, some polymorphisms also make the individuals more competent to diabetes via infection with SARS-CoV-2. On the other hand, during hospitalization of SARS-CoV-2-infected patients, the use of some drugs may unintentionally lead to diabetes in the future via increasing inflammation and stress oxidative. Thus, in this review, we will first explain why diabetic patients are more susceptible to COVID-19. Second, we will warn about a future global diabetes tsunami via the SARS-CoV-2 as one of its long-term complications.

The Role of Diet and Specific Nutrients during the COVID-19 Pandemic: What Have We Learned over the Last Three Years?

Nutrients and diets have an important impact on our immune system and infection risk and a huge number of papers have been published dealing with various aspects of nutrition in relation to SARS-CoV-2 infection risk or COVID-19 severity. This narrative review aims to give an update on this association and tries to summarize some of the most important findings after three years of pandemic. The analysis of major studies and systematic reviews leads to the conclusion that a healthy plant-based diet reduces the risks for SARS-CoV-2 infection and especially COVID-19 severity. Regarding micronutrients, vitamin D is to the fore, but also zinc, vitamin C and, to some extent, selenium may play a role in COVID-19. Furthermore, omega-3-fatty acids with their anti-inflammatory effects also deserve attention. Therefore, a major aim of societal nutritional efforts in future should be to foster a high quality plant-based diet, which not only exerts beneficial effects on the immune system but also reduces the risk for non-communicable diseases such as type 2 diabetes or obesity which are also primary risk factors for worse COVID-19 outcomes. Another aim should be to focus on a good supply of critical immune-effective nutrients, such as vitamin D and zinc.

Interference of altered plasma trace elements profile with hyperhomocysteinemia and oxidative stress damage to insulin secretion dysfunction in Psammomys obesus: focus on the selenium

The objective of this study is to investigate the relationship between altered plasma trace elements, particularly selenium (Se), with Hyper-homocysteinemia (HhCys) as a predictive factor of insulin secretion dysfunction. The study is carried out on adult Psammomys obesus, divided in 4 experimental groups: (I) Normoglycemic/Normoinsulinemic; (II) Normoglycemic/Hyperinsulinemic; (III) Hyperglycaemic/Hyperinsulinemic and (IV) Hyperglycaemic/Insulin deficiency with ketoacidosis. The data showed that a drastic depletion of Se plasma levels is positively correlated with HhCys (>15 µmol/L; p < .001), concomitantly with decreased GPx activity, GSH levels, and GSH/GSSG ratio in group IV both in plasma and liver. In contrast, SOD activity is increased (p ≤ .001) in group IV both in plasma and liver. However, plasma Cu and Mn levels increased, while plasma Zn levels decreased in group IV (p < .001). Our study confirms the increase of plasma hCys levels seemed to be a major contributing factor to antioxidant capacities and alters the availability of selenium metabolism by interference with homocysteine synthesis in the insulin secretion deficiency stage.

Coexposure to multiple metals and renal tubular damage: a population-based cross-sectional study in China's rural regions

Previous studies have indicated that exposure to a single toxic metal can cause renal tubular damage, while evidence about the effects of multimetal exposure on renal tubular damage is relatively limited. We aimed to evaluate the relationships of multimetal coexposure with renal tubular damage in adults in heavy metal-polluted rural regions of China. A cross-sectional study of 1918 adults in China's heavy metal-contaminated rural regions was conducted. Inductively coupled plasma-mass spectrometry (ICP-MS) was used to measure the plasma levels of 18 metals in participants, and immune turbidimetry was used to measure sensitive biological indicators, reflecting renal tubular damage (including retinol-binding protein and β2-microglobulin). Least absolute shrinkage and selection operator (LASSO) penalized regression analysis, logistic and linear regression analysis, restricted cubic spline (RCS) regression analysis and the Bayesian kernel machine regression (BKMR) method were used to explore associations of multimetal coexposure with renal tubular damage risk or renal tubular damage indicators. Plasma selenium, cadmium, arsenic, and iron were identified as the main plasma metals associated with renal tubular damage risk after dimensionality reduction. Multimetal regression models showed that selenium was positively associated, and iron was negatively associated with renal tubular damage risk or its biological indicators. Multimetal RCS analyses additionally revealed a non-linear relationship of selenium with renal tubular damage risk. The BKMR models showed that the metal mixtures were positively associated with biological indicators of renal tubular damage when the metal mixtures were above the 50th percentile of concentration. Our findings indicated that natural exposure to high levels of multimetal mixtures increases the risk of renal tubular damage. Under the conditions of multimetal exposure, selenium was positively associated, and iron was negatively associated with renal tubular damage risk or its biological indicators.

Nuts in the Prevention and Management of Type 2 Diabetes

Diabetes is a continuously growing global concern affecting >10% of adults, which may be mitigated by modifiable lifestyle factors. Consumption of nuts and their inclusion in dietary patterns has been associated with a range of beneficial health outcomes. Diabetes guidelines recommend dietary patterns that incorporate nuts; however, specific recommendations related to nuts have been limited. This review considers the epidemiological and clinical evidence to date for the role of nut consumption as a dietary strategy for the prevention and management of type 2 diabetes (T2D) and related complications. Findings suggest nut consumption may have a potential role in the prevention and management of T2D, with mechanistic studies assessing nuts and individual nut-related nutritional constituents supporting this possibility. However, limited definitive evidence is available to date, and future studies are needed to elucidate better the impact of nuts on the prevention and management of T2D.

SELENOM Knockout Induces Synaptic Deficits and Cognitive Dysfunction by Influencing Brain Glucose Metabolism

Selenium, a trace element associated with memory impairment and glucose metabolism, mainly exerts its function through selenoproteins. SELENOM is a selenoprotein located in the endoplasmic reticulum (ER) lumen. Our study demonstrates for the first time that SELENOM knockout decreases synaptic plasticity and causes memory impairment in 10-month-old mice. In addition, SELENOM knockout causes hyperglycaemia and disturbs glucose metabolism, which is essential for synapse formation and transmission in the brain. Further research reveals that SELENOM knockout leads to inhibition of the brain insulin signaling pathway [phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR/p70 S6 kinase pathway], which may impair synaptic plasticity in mice. High-fat diet (HFD) feeding suppresses the brain insulin signaling pathway in SELENOM knockout mice and leads to earlier onset of cognitive impairment at 5 months of age. In general, our study demonstrates that SELENOM knockout induces synaptic deficits via the brain insulin signaling pathway, thus leading to cognitive dysfunction in mice. These data strongly suggest that SELENOM plays a vital role in brain glucose metabolism and contributes substantially to synaptic plasticity.

Whole blood trace element and toxic metal concentration in dogs with idiopathic epilepsy and healthy dogs: A case-control study

Background

Idiopathic epilepsy (IE) is the most common neurological disease in dogs. Multiple genes and environmental factors interact to cause clinical signs, although the pathogenesis remains poorly understood. Extensive evidence from recent decades shows that trace elements play a role in epilepsy in humans, and recently it was shown for the first time that also dogs with IE have altered trace element status. On the other hand, toxic metals may cause seizures but research on their role in canine IE is lacking. Therefore, we aimed to investigate trace element and toxic metal concentrations in whole blood from dogs that had been diagnosed with IE and compare them to those of healthy dogs.

Materials and methods

Whole blood concentrations of trace elements (selenium, zinc, copper, manganese, iron, and chromium) and toxic metals (arsenic, cadmium, mercury, and lead) were analyzed from 19 dogs that had been diagnosed with IE by board-certified neurologists and 19 healthy control dogs using inductively coupled plasma mass spectrometry. The concentrations in study and control group were compared using the Mann-Whitney U test.

Results

Dogs diagnosed with IE had significantly higher blood copper concentration (P = 0.007), higher copper/zinc ratio (P = 0.04), and higher selenium concentration (P < 0.001), as well as lower chromium concentration (P = 0.01) when compared to healthy dogs. Treatment of IE with potassium bromide was associated with a significant elevation in blood arsenic concentration (P = 0.01).

Conclusion

In conclusion, the present results support the role of altered trace element status in dogs diagnosed with IE and suggest that copper, selenium, and chromium may be involved in the pathogenesis of canine epilepsy or seizures. The results also suggest that potassium bromide may alter arsenic metabolism in dogs.

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.