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

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.

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.

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.

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.

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.

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.

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.

Selenium and immune function: a systematic review and meta-analysis of experimental human studies

BACKGROUND

Selenium is an essential trace element with both beneficial and detrimental effects on health depending on dose and chemical form. Currently, there is debate on recommendations for selenium supplementation as a public health measure to improve immune function and reduce infectious disease susceptibility.

OBJECTIVES

We performed a systematic review and meta-analysis of experimental studies assessing the effect of selenium supplementation on immunity-related outcomes in healthy people.

METHODS

We undertook a search of published and unpublished studies in literature databases such as PubMed/MEDLINE, Embase, and clinicaltrials.gov up to 17 October, 2022, and performed a meta-analysis comparing the effects on immunity-related outcomes between Se-supplemented versus control arms. Whenever possible we assessed the nonlinear relation using a dose-response approach.

RESULTS

9 trials were included, 5 in North America, and 4 in Europe, with a duration between 8 and 48 weeks and supplementation of both inorganic and organic selenium forms. Selenium supplementation did not substantially affect immunoglobulin or white blood cell concentrations, and the dose-response meta-analysis indicated that an increase in plasma selenium concentrations above 100 μg/L did not further increase IgA levels nor T cells. An inverted U-shaped relation emerged for NK cell count, with a lower number of these cells both below and above 120 μg/L. The only beneficial effect of selenium supplementation was the increased activity for NK lysis, but the available data did not permit dose-response analysis. Cytokine levels were substantially unaffected by selenium supplementation.

CONCLUSIONS

Although some of the data suggested beneficial effects of selenium supplementation on immune function, the overall picture appears to be inconsistent and heterogeneous due to differences in trial duration and interventions, plus evidence of null and even detrimental effects. Overall, the evidence that we extracted from the literature in this systematic review does not support the need to supplement selenium beyond the recommended dietary intake to obtain beneficial effects on immune function. This trial was registered at PROSPERO (CRD42022312280).

Thyroid Carcinoma: A Review for 25 Years of Environmental Risk Factors Studies

Environmental factors are established contributors to thyroid carcinomas. Due to their known ability to cause cancer, exposure to several organic and inorganic chemical toxicants and radiation from nuclear weapons, fallout, or medical radiation poses a threat to global public health. Halogenated substances like organochlorines and pesticides can interfere with thyroid function. Like phthalates and bisphenolates, polychlorinated biphenyls and their metabolites, along with polybrominated diethyl ethers, impact thyroid hormones biosynthesis, transport, binding to target organs, and impair thyroid function. A deeper understanding of environmental exposure is crucial for managing and preventing thyroid cancer. This review aims to investigate the relationship between environmental factors and the development of thyroid cancer.

Chemical Compounds and Ambient Factors Affecting Pancreatic Alpha-Cells Mass and Function: What Evidence?

The exposure to different substances present in the environment can affect the ability of the human body to maintain glucose homeostasis. Some review studies summarized the current evidence about the relationships between environment and insulin resistance or beta-cell dysfunction. Instead, no reviews focused on the relationships between the environment and the alpha cell, although in recent years clear indications have emerged for the pivotal role of the alpha cell in glucose regulation. Thus, the aim of this review was to analyze the studies about the effects of chemical, biological, and physical environmental factors on the alpha cell. Notably, we found studies focusing on the effects of different categories of compounds, including air pollutants, compounds of known toxicity present in common objects, pharmacological agents, and compounds possibly present in food, plus studies on the effects of physical factors (mainly heat exposure). However, the overall number of relevant studies was limited, especially when compared to studies related to the environment and insulin sensitivity or beta-cell function. In our opinion, this was likely due to the underestimation of the alpha-cell role in glucose homeostasis, but since such a role has recently emerged with increasing strength, we expect several new studies about the environment and alpha-cell in the near future.

Correlation between dietary selenium intake and stroke in the National Health and Nutrition Examination Survey 2003-2018

BACKGROUND

Epidemiologic evidence of the effect of dietary selenium intake on stroke risk remains controversial. This study aimed to examine the cross-sectional correlation between dietary selenium intake and the risk of stroke in adults.

MATERIALS AND METHODS

We retrospectively analysed 39,438 participants from the National Health and Nutrition Examination Survey 2003-2018, aged 20-85 years. Participants were divided into quartiles depending on daily dietary selenium intake: quartile 1 (0-77 μg), quartile 2 (77-108 μg), quartile 3 (108-148 μg), and quartile 4 (148-400 μg). The dose-response relationship was assessed using the restricted cubic spline function.

RESULTS

The adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of stroke were 0.70 (0.55, 0.88) for participants in quartile 2, 0.71 (0.53, 0.93) for quartile 3, and 0.61 (0.43, 0.85) for quartile 4 compared with that in quartile 1. p-Value for trend through quartiles was .007. A non-linear negative correlation between dietary selenium intake and stroke was observed in the threshold effect analysis and restricted cubic spline function (p-value for non-linearity < .001). An initial decrease in odds of stroke lower than 105 μg/day selenium intake (0.61 [0.44, 0.85], p = .004) was followed by a platform beyond 105 μg/day (0.97 [0.81, 1.16], p = .723). In the subgroup analysis, adjusted ORs (95% CIs) of stroke were 0.51 (0.36, 0.70) for female participants, 0.63 (0.40, 0.99) for participants with age <60 years, 0.63 (0.47, 0.85) for participants with poverty-income ratio < 2.14, 0.66 (0.50, 0.87) for participants with overweight and obesity, 0.66 (0.52, 0.84) for participants with hypertension, 0.72 (0.53, 0.97) for participants without diabetes, and 0.72 (0.56, 0.92) for non-anaemic participants.

CONCLUSIONS

Dietary selenium had a negative and non-linear correlation with the risk of stroke in adults. The correlation varied across different population subgroups.KEY MESSAGESDietary selenium had a negative and non-linear correlation with the risk of stroke in adults.Non-linear negative correlation trends were observed in subpopulations of females, age <60 years, poverty-income ratio <2.14, overweight and obesity, hypertension, non-diabetes, and non-anaemia.Dietary selenium intake of approximately 105 μg per day has an optimum effect on stroke.

Dihydroflavonoid glycosides from Viscum album and their inhibitory effects on hepatic lipid accumulation and target identification

Five undescribed dihydroflavonoid glycoside derivatives, namely albvisosides A‒E, together with two known compounds were isolated from the roots and stem leaves of Viscum album L. var. album. (European mistletoe). Their structures were determined by HRESIMS, 1D and 2D NMR, and ECD analysis. Albvisoside B exhibits significant inhibitory effect on hepatic lipid accumulation in HepG2 cells at very low concentrations (EC50: 0.7 nM). Using proteome integral solubility alteration assay, the direct targets or downstream effectors of albvisoside B were elucidated. As a result, 97 proteins were identified based on ligand-induced alterations in the protein thermal stability. Bioinformatics analysis indicated that albvisoside B primarily ameliorated oleic acid-induced lipid accumulation by regulating the selenoamino acids metabolism signaling pathway. RPL3, ADAM17, and RPL14 were likely to be involved in mediating the lipid-lowering effect of albvisoside B.

Emerging roles of selenium on metabolism and type 2 diabetes

Selenium is recognized as an essential element for human health and enters human body mainly via diet. Selenium is a key constituent in selenoproteins, which exert essential biological functions, including antioxidant and anti-inflammatory effects. Several selenoproteins including glutathione peroxidases, selenoprotein P and selenoprotein S are known to play roles in the regulation of type 2 diabetes. Although there is a close association between certain selenoproteins with glucose metabolism or insulin resistance, the relationship between selenium and type 2 diabetes is complex and remains uncertain. Here we review recent advances in the field with an emphasis on roles of selenium on metabolism and type 2 diabetes. Understanding the association between selenium and type 2 diabetes is important for developing clinical practice guidelines, establishing and implementing effective public health policies, and ultimately combating relative health issues.

Antioxidant, Anti-inflammatory, and Immunomodulatory Roles of Nonvitamin Antioxidants in Anti-SARS-CoV-2 Therapy

Viral pathologies encompass activation of pro-oxidative pathways and inflammatory burst. Alleviating overproduction of reactive oxygen species and cytokine storm in COVID-19 is essential to counteract the immunogenic damage in endothelium and alveolar membranes. Antioxidants alleviate oxidative stress, cytokine storm, hyperinflammation, and diminish the risk of organ failure. Direct antiviral roles imply: impact on viral spike protein, interference with the ACE2 receptor, inhibition of dipeptidyl peptidase 4, transmembrane protease serine 2 or furin, and impact on of helicase, papain-like protease, 3-chyomotrypsin like protease, and RNA-dependent RNA polymerase. Prooxidative environment favors conformational changes in the receptor binding domain, promoting the affinity of the spike protein for the host receptor. Viral pathologies imply a vicious cycle, oxidative stress promoting inflammatory responses, and vice versa. The same was noticed with respect to the relationship antioxidant impairment-viral replication. Timing, dosage, pro-oxidative activities, mutual influences, and interference with other antioxidants should be carefully regarded. Deficiency is linked to illness severity.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Plasma and vitreous selenium concentrations in patients with type 2 diabetes and diabetic retinopathy

BACKGROUND

This work aimed to determine and compare plasma and vitreous selenium (Se) concentrations in patients with type 2 diabetes and diabetic retinopathy (DR).

METHODS

A total of 60 type-2-diabetes patients including 20 without DR, 20 with non-proliferative DR (NPDR), and 20 with proliferative diabetic retinopathy (PDR), were involved in this study. Blood plasma samples were collected from above 60 patients and 20 normal controls (without diabetes). Twenty control vitreous samples were obtained from the eyes presenting a macular hole and epimacular membrane. Vitreous samples were also collected from PDR patients receiving one-week intravitreal anti-VEGF therapy or not. Plasma and vitreous Se concentrations were determined by inductively coupled plasma mass spectrometry.

RESULTS

Plasma Se concentrations in PDR patients (163.74 ± 32.68 μg/L) were significantly higher than those in normal control patients (121.59 ± 28.33 μg/L), NPDR patients (130.34 ± 29.11 μg/L), and the patients without DR (81.23 ± 20.59 μg/L) (all P < .001). Similarly, Se concentrations in vitreous samples of PDR patients (56.30 ± 12.03 μg/L) were consistently higher than those in control vitreous samples (26.26 ± 6.53 μg/L). In addition, vitreous Se concentrations in PDR patients decreased to 47.76 ± 9.72 μg/L after intravitreal injection of the anti-VEGF drug ranibizumab for one week, which was significantly lower than those before injection (P = .02). Plasma VEGF levels of diabetic patients were lower than those of the normal controls (P < .001). On the contrary, the vitreous VEGF level in the PDR group (913.61 ± 193.32 pg/mL) was significantly higher than that of the normal control group (101.23 ± 21.33 pg/mL) (P < .001).

CONCLUSION

The elevation of Se concentrations may be an important risk factor in plasma and vitreous with diabetic retinopathy among type-2-diabetes patients. The elevated VEGF may be also closely related to the intraocular Se concentration in PDR patients.

Higher selenium was associated with higher risk of diabetes: Consistent evidence from longitudinal and cross-sectional studies based on nail and serum selenium measures

Although the association between selenium (Se) and diabetes has been well-discussed in recent years, few studies have focused on the effects of long-term natural Se exposure and rarely concerned the effects of different Se biomarkers. To address this question, we carried out a 7-year longitudinal study on older adults aged over 65 and another cross-sectional study on middle-aged and older adults aged 40 and above from Chinese soil Se-deplete and Se-optimum areas. Cox proportional hazard models were used to evaluate the associations between nail Se levels and incidence risk of diabetes. Unconditional logistic regression models and analysis of variance models were used to examine the associations between serum Se levels and the prevalence risk of diabetes. The nail and serum Se levels were 0.47 ± 0.20 μg/g and 111.09 ± 55.01 μg/L for the two study populations, respectively. For both of the independent studies, higher Se levels were observed to be associated with a higher risk of diabetes and prediabetes. Compared with the Second nail Se quartile (Q2), the adjusted hazard ratios (HRs) and 95 % confidence intervals (95 % CIs) of diabetes for Q1, Q3 and Q4 were 1.24(0.70, 2.21), 1.53(0.98, 2.39) and 1.31(0.76, 2.26), respectively, and the adjusted HRs (95 % CIs) of prediabetes were 1.47(0.77, 2.81), 1.38(0.83, 2.30), and 1.97(1.13, 3.44), respectively. Compared with the first serum Se quintile (Q1), the adjusted odds ratios (ORs) and 95 % CIs of diabetes for higher quintiles were 1.12(0.75, 1.66), 1.05(0.71, 1.57), 1.09(0.73, 1.62) and 1.51(1.02, 2.19), and the adjusted ORs (95 % CIs) of prediabetes were 1.27(0.77, 2.09), 1.70(1.05, 2.74), 1.94(1.21, 3.11) and 1.67(1.03, 2.71). Our findings consistently suggest that higher Se status is associated with a higher risk of diabetes in adults.

Comparison of Serum Selenium Levels Between Patients with Newly Diagnosed Atrial Fibrillation and Normal Controls

Atrial fibrillation (AF) is the most common sustained dysrhythmia in the elderly population. It is estimated to affect more than 30 million people worldwide. AF occurs when abnormal electrical impulses start to activate in the atria and override the heart's natural pacemaker, which can no longer control the heart's rhythm. Since atrial contractility is impaired in AF, blood flow in the atria becomes stasis over time and causes thrombus formation. This thrombus causes the risk of embolism and causes complications such as stroke. Therefore, it is a fundamental cause of cardiovascular mortality and morbidity. The diagnosis of AF is usually made with the help of electrocardiography (ECG). The absence of P waves in ECG and irregular R-R interval is sufficient for diagnosis. AF is most commonly associated with advanced age, hypertension, diabetes mellitus, thyroid dysfunction, obesity, alcohol use, physical inactivity, and underlying ischemic heart diseases. As well as to all these usual risk factors, electrolyte disorders and mineral deficiencies also play an essential role in the etiology of AF. Previous studies have clearly demonstrated that serum electrolyte changes have a role in the etiology of AF. These include electrolytes such as serum magnesium, calcium, potassium, and chloride. However, there is not enough information in the literature about the effects of trace elements on AF. Selenium is a trace element that plays an important role in many systems in the human body. It has a vital role in inflammation, regulation of antioxidant reactions, and fibrosis of tissues in both animals and humans. It is known that selenium deficiency causes many cardiovascular diseases such as heart failure, coronary artery disease, and arrhythmia. Our study aimed to compare serum selenium levels in newly diagnosed AF patients with the healthy control group.

Sex-Specific Association between Fasting Plasma Glucose and Serum Selenium Levels in Adults from Southern Mexico

Selenium (Se) is an essential trace element that by its antioxidant properties has been studied to elucidate its participation in the development of obesity and type 2 diabetes. We evaluated the association between cardiometabolic traits and serum Se levels in a sample of adults from southern Mexico. In 96 nondiabetic individuals, anthropometric data and clinical biochemistry measurements were analyzed. Serum total Se levels were measured with inductively coupled plasma mass spectrometry (ICP-MS). Serum Se level in the whole sample was 10.309 ± 3.031 μg mL⁻¹ and no difference between the women and men was observed (p = 0.09). Additionally, fasting plasma glucose (FPG) was significantly associated with serum Se level (β = −0.07 ± 0.03, p = 0.02, analysis adjusted for age, sex and BMI). Furthermore, sex shows significant interaction with FPG on the serum Se levels (p = 0.01). A follow-up analysis revealed the particular association between FPG and Se levels in women (β = −0.10 ± 0.04, p = 0.01). In conclusion, our data evidenced a women-specific association between FPG and serum Se levels in a sample of adults from southern Mexico.

The role of glutathione peroxidase-1 in health and disease

Glutathione peroxidase 1 (GPx1) is an important cellular antioxidant enzyme that is found in the cytoplasm and mitochondria of mammalian cells. Like most selenoenzymes, it has a single redox-sensitive selenocysteine amino acid that is important for the enzymatic reduction of hydrogen peroxide and soluble lipid hydroperoxides. Glutathione provides the source of reducing equivalents for its function. As an antioxidant enzyme, GPx1 modulates the balance between necessary and harmful levels of reactive oxygen species. In this review, we discuss how selenium availability and modifiers of selenocysteine incorporation alter GPx1 expression to promote disease states. We review the role of GPx1 in cardiovascular and metabolic health, provide examples of how GPx1 modulates stroke and provides neuroprotection, and consider how GPx1 may contribute to cancer risk. Overall, GPx1 is protective against the development and progression of many chronic diseases; however, there are some situations in which increased expression of GPx1 may promote cellular dysfunction and disease owing to its removal of essential reactive oxygen species.

Selenium Status and Its Antioxidant Role in Metabolic Diseases

Selenium (Se), in the form of selenoproteins, is an essential micronutrient that plays an important role in human health and disease. To date, there are at least 25 selenoproteins in humans involved in a wide variety of biological functions, including mammalian development, metabolic progress, inflammation response, chemoprotective properties, and most notably, oxidoreductase functions. In recent years, numerous studies have reported that low Se levels are associated with increased risk, poor outcome, and mortality of metabolic disorders, mainly related to the limited antioxidant defense resulting from Se deficiency. Moreover, the correlation between Se deficiency and Keshan disease has received considerable attention. Therefore, Se supplementation as a therapeutic strategy for preventing the occurrence, delaying the progression, and alleviating the outcomes of some diseases has been widely studied. However, supranutritional levels of serum Se may have adverse effects, including Se poisoning. This review evaluates the correlation between Se status and human health, with particular emphasis on the antioxidant benefits of Se in metabolic disorders, shedding light on clinical treatment.

Clinical Relevance of Selenium with Liver Stiffness and Steatosis Detected by Transient Elastography in Adults

The associations between selenium and liver stiffness and steatosis remain uncertain. This study aimed to explore the clinical relevance of selenium with liver stiffness and steatosis in adults from the 2017-2018 National Health and Nutrition Examination Survey. Subjects with excessive alcohol consumption and hepatitis B or C infection were excluded. Liver stiffness and steatosis were detected by transient elastography. Dietary selenium intakes and blood selenium concentrations were included as exposures. In multivariate analysis without adjustment for obesity, higher dietary selenium intakes (tertile 3 vs. tertile 1) were positively associated with liver stiffness in females (odds ratio (95% confidence interval): 2.64 (1.88-3.70)), and were positively associated with liver steatosis overall (1.54 (1.20-1.97)) and also in males (1.55 (1.06-2.26)). In multivariate analysis without adjustment for obesity, higher blood selenium concentrations (tertile 3 vs. tertile 1) were positively associated with liver steatosis overall (1.33 (1.02-1.76)) and also in males (1.56 (1.13-2.16)). After further adjustment for obesity, the abovementioned associations remain significant between dietary selenium intakes and liver stiffness in females (2.29 (1.69-3.12)) and liver steatosis overall (1.37 (1.01-1.86)), and between blood selenium concentrations and liver steatosis in males (1.67 (1.25-2.21)). Dose-response analysis showed that the abovementioned associations were linear. However, dietary selenium intakes meeting the recommended daily allowance (≥ 55 µg/day) were not associated with liver stiffness (0.99 (0.62-1.55)) and steatosis (1.01 (0.69-1.49)). In conclusion, higher dietary selenium intakes and blood selenium concentrations were positively associated with liver stiffness and steatosis, and obesity may partially account for the observed associations.

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.