Association between selenium nutritional status and metabolic risk factors in men with visceral obesity

Serum Selenium Levels and Lipid Profile: A Systematic Review and Meta-analysis of Observational Studies

Selenium is a trace element with pivotal roles in metabolic processes. Studies suggested that selenium deficiency could lead to impaired lipid profiles. However, inconsistent results have been reported regarding the association between serum selenium concentrations and lipid profile (triglycerides, LDL, HDL, VLDL, and total cholesterol). Thus, we aimed to review the correlation between them. A systematic literature search was conducted in PubMed, Embase, Web of Science, Scopus, and Google Scholar until 31 December 2023. The relevant correlation coefficients were used as desired effect sizes to assess the correlation between selenium level and lipid profile. Among 8291 records found in the primary search, 47 and 34 articles were included in the systematic review and meta-analysis, respectively. All included studies were observational investigations and had acceptable quality. Our results failed to reach strong evidence supporting the correlation between serum selenium level and lipid profiles, except for HDL, which showed a weak correlation among both adults (r = 0.1 [0.03:0.17]; I2 = 71%) and pediatrics (r = 0.08 [0.03:0.14]; I2 = 38%). Subgroup analyses based on gender did not reveal a significant or strong correlation with selenium levels (except for total cholesterol in males (r = 0.12 [0.01:0.22]; I2 = 52%)). The results did not change after the sensitivity analysis. Although some previous studies have suggested that selenium deficiency could lead to impaired lipid profile, the findings of this study indicate no strong correlation between serum selenium levels and lipid profile.

The influence of serum selenium in differential epigenetic and transcriptional regulation of CPT1B gene in women with obesity

INTRODUCTION

The increasing prevalence of obesity has become a major health problem worldwide. The causes of obesity are multifactorial and could be influenced by dietary patterns and genetic factors. Obesity has been associated with a decrease in micronutrient intake and consequently decreased blood concentrations. Selenium is an essential micronutrient for human health, and its metabolism could be affected by obesity, especially severe obesity. This study aimed to identify differential methylation genes associated with serum selenium concentration in women with and without obesity.

METHODOLOGY

Thirty-four patients were enrolled in the study and divided into two groups: Obese (Ob) n = 20 and Non-Obese (NOb) n = 14, according to the Body Mass Index (BMI). Anthropometry, body composition, serum selenium, selenium intake, and biochemical parameters were evaluated. DNA extraction and bisulfite conversion were performed to hybridize the samples on the 450k Methylation Chip Infinium Beadchip (Illumina). Bioinformatics analysis was performed using the R program and the Champ package. The differentially methylated regions (DMRs) were identified using the Bumphunter method. In addition, logarithmic conversion was performed for the analysis of serum selenium and methylation.

RESULTS

In the Ob group, the body weight, BMI, fat mass, and free fat mass were higher than in the NOb group, as expected. Interestingly, the serum selenium was lower in the Ob than in the NOb group without differences in selenium intake. One DMR corresponding to the CPT1B gene, involved in lipid oxidation, was related to selenium levels. This region was hypermethylated in the Ob group, indicating that the intersection between selenium deficiency and hypermethylation could influence the expression of the CPT1B gene. The transcriptional analysis confirmed the lower expression of the CPT1B gene in the Ob group.

CONCLUSION

Studies connecting epigenetics to environmental factors could offer insights into the mechanisms involving the expression of genes related to obesity and its comorbidities. Here we demonstrated that the mineral selenium might play an essential role in lipid oxidation via epigenetic and transcriptional regulation of the CPT1B gene in obesity.

Selenium as a predictor of metabolic syndrome in middle age women

BACKGROUND

Selenium plays an important role in metabolic homeostasis. It has been suggested that it may also affect the expression and activity of PPAR-γ. The aim of study was to analyze the relationships between these variables in the context of the health of women, for whom the risk of MetS increases with age.

MATERIAL AND METHODS

The study involved 390 women in middle age. The stages of study: a survey-based part; anthropometric measurements; analysis of biological material (blood) in terms of glycemia, triglyceride, HDL, and selenium levels, as well as genetic analysis of the PPAR-γ polymorphisms.

RESULTS

It was found that selenium may moderate the effect of the G allele of the PPAR-γ gene on the occurrence of elevated waist circumference (OR=1.030, 95%CI 1.005-1.057, p=0.020); and the effect of the C (OR=1.077, 95%CI 1.009-1.149, p=0.026) and the G alleles (OR=1.052, 95%CI 1.025-1.080, p<0.000) on the odds of elevated blood pressure. Women in whom HDL levels were not significantly reduced, had higher selenium levels (p=0.007).

CONCLUSIONS

1. The effect of selenium on MetS and its components has not been demonstrated. 2. The effect of individual alleles of the PPAR-γ gene on MetS and its components was not demonstrated. 3. The concentration of selenium may affect waist circumference in carriers of the G allele, and arterial hypertension in carriers of the C and G alleles by affecting the expression of PPAR-γ. 4. Higher selenium concentrations increased the odds of higher HDL levels in the group of subjects meeting the MetS criteria.

RELATIONSHIP BETWEEN SELENIUM NUTRITIONAL STATUS AND MARKERS OF LOW-GRADE CHRONIC INFLAMMATION IN OBESE WOMEN

Low-grade chronic inflammation is one of the main disorders that characterize adipose tissue dysfunction in obesity and is an important element in the pathogenesis of several comorbidities. In this context, selenium is an essential micronutrient that exerts important anti-inflammatory functions, and the role of selenium in controlling inflammation associated with obesity is not well defined. Thus, this study aimed to evaluate the relationship between markers of the nutritional status of selenium and low-grade chronic inflammation in obese women. This cross-sectional study included 81 women aged between 18 and 50 years, who were divided into two groups according to body mass index (BMI): the obesity group (n = 38) and normal weight group (n = 43). Selenium intake was assessed by 3-day diet records. The plasma, erythrocyte, and urinary selenium concentrations were determined using inductively coupled plasma optical emission spectrometry. The analysis of serum cytokines interleukin (IL)-8, IL-1β, IL-6, IL-10, and tumor necrosis factor alpha (TNFα) was performed using flow cytometry. The results of this study revealed that the obese women had higher dietary intake of selenium than eutrophic women. However, obese participants showed decreased selenium concentrations in plasma and erythrocytes, in parallel with increased concentrations of selenium in the urine. Regarding the inflammatory parameters, obese women exhibited higher concentrations of IL-6 and lower concentrations of the cytokines IL-8, IL-1β, and TNFα than eutrophic women. In the binary logistic regression analysis, erythrocyte selenium was considered an independent predictor of the serum concentrations of cytokine IL-8 in obese women, reflecting the anti-inflammatory action of this micronutrient.

Dietary selenium intake and the risk of kidney stones in adults, an analysis of 2007-2018 National Health and Nutrition Examination Survey, a cross-sectional study

Purpose

To evaluate the association between dietary selenium intake and the risk of kidney stones in adults.

Materials and methods

We performed a cross-sectional analysis using data from 2007 to 2018 National Health and Nutrition Examination Survey (NHANES). Dietary intake information of 30,184 participants was obtained using first 24-h dietary recall interview, and kidney stones were presented by a standard questionnaire. The quartile analysis, stratified analysis and non-linearity analysis were used to estimate the association between dietary selenium intake and kidney stones after an adjustment for potential confounders.

Results

The multiple logistic regression indicated that the fourth quantile (Q4) of dietary selenium intake had a lower risk of kidney stones than the first quantile (Q1) in Model 3 (OR 0.82, P < 0.05). The stratified analyses indicated there were statistical differences between dietary selenium intake and kidney stones among younger (age < 50) (OR 0.65, P < 0.01), male (OR 0.73, P < 0.01) and overweight/obese (BMI ≥ 25.0) (OR 0.80, P < 0.05) individuals in Model 3. The non-linear relationship was founded between dietary selenium intake and kidney stones in all participants, younger, male and overweight/obese individuals after adjusting for confounding factors.

Conclusion

Our study revealed an inverse relation between the level of dietary selenium intake and the risk of kidney stones for the United States population, especially for younger (age < 50), male and overweight/obese (BMI ≥ 25.0) individuals. The study provides preliminary guidance on dietary selenium intake for the prevention of kidney stones in different populations. Further studies are required to confirm our findings and clarified the biological mechanisms.

Selenium Supplementation during Puberty and Young Adulthood Mitigates Obesity-Induced Metabolic, Cellular and Epigenetic Alterations in Male Rat Physiology

Selenium (Se) role in obesity is not clear. In addition, information on Se’s role in male physiology, specifically in obesity, is scarce. We conducted this study to evaluate the efficacy of Se supplementation, specifically during puberty until young adulthood, against obesity-induced deregulation of metabolic, cellular, and epigenetic parameters in epididymal fat and/or sperm cells in a rat model. High-fat-diet consumption by male rats during puberty and young adulthood significantly increased body weight, adipocyte size, oxidative stress, deregulated expression of genes associated with inflammation (Adiponectin, IL-6, TNF-α), adipogenesis (CEBPα), estrogen biosynthesis (CYP19) and epigenetic processes in epididymal adipose tissue (Dnmt3a), as well as altered microRNA expression vital for spermatogenesis in sperm cells (miR-15b and miR-497). On the other hand, Se supplementation significantly decreased oxidative stress and mitigated these molecular/epigenetic alterations in epididymal adipose tissue or sperm cells. Our results indicate that selenium supplementation during puberty/young adulthood could improve male physiology in the context of obesity. In addition, it suggests that Se could potentially positively affect offspring health.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

High Dietary Fat and Selenium Concentrations Exert Tissue- and Glutathione Peroxidase 1-Dependent Impacts on Lipid Metabolism of Young-Adult Mice

BACKGROUND

Excessive dietary selenium (Se; 3 mg/kg) or fat (>25%) intakes and overproduction of glutathione peroxidase 1 (GPX1) adversely affect body lipid metabolism.

OBJECTIVE

The objective was to reveal impacts and mechanisms of a moderately high Se and a high fat intake on lipid metabolism in Gpx1 knockout (KO) and wild-type (WT) mice.

METHODS

The KO and WT mice (males, 12-wk-old, body weight = 24.8 ± 0.703 g) were allotted to 4 groups each (n = 5) and fed a sucrose-torula yeast basal diet (5% corn oil) supplemented with 0.3 or 1.0 mg (+Se) Se/kg (as sodium selenite) and 0% or 25% [high-fat (HF)] lard for 6 wk. Multiple physiological and molecular biomarkers (68) related to lipid metabolism and selenogenome expression in plasma, liver, and/or adipose tissue were analyzed by 2-way (+Se by HF) ANOVA.

RESULTS

Compared with the control diet, the +Se diet decreased (P < 0.05) body-weight gain and plasma and liver concentrations of lipids (22-66%) but elevated (≤1.5-fold, P < 0.05) adipose tissue concentrations of lipids in the WT mice. The +Se diet up- and downregulated (P < 0.05) mRNA and/or protein concentrations of factors related to lipogenesis, selenogenome, and transcription, stress, and cell cycle in the liver (26% to 176-fold) and adipose tissues (14% to 1-fold), respectively, compared with the control diet in the WT mice. Many of these +Se diet effects were different (P < 0.05) from those of the HF diet and were eliminated or altered (P < 0.05) by the KO.

CONCLUSIONS

The +Se and HF diets exerted tissue-specific and GPX1 expression-dependent impacts on lipid metabolism and related gene expression in the young-adult mice. Our findings will help reveal metabolic potential and underlying mechanisms of supplementing moderately high Se to subjects with HF intakes.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

Selenium and RNA Virus Interactions: Potential Implications for SARS-CoV-2 Infection (COVID-19)

SARS-CoV-2 is an RNA virus responsible for the COVID-19 pandemic that already claimed more than 340,000 lives worldwide as of May 23, 2020, the majority of which are elderly. Selenium (Se), a natural trace element, has a key and complex role in the immune system. It is well-documented that Se deficiency is associated with higher susceptibility to RNA viral infections and more severe disease outcome. In this article, we firstly present evidence on how Se deficiency promotes mutations, replication and virulence of RNA viruses. Next, we review how Se might be beneficial via restoration of host antioxidant capacity, reduction of apoptosis and endothelial cell damages as well as platelet aggregation. It also appears that low Se status is a common finding in conditions considered at risk of severe COVID-19, especially in the elderly. Finally, we present a rationale for Se use at different stages of COVID-19. Se has been overlooked but may have a significant place in COVID-19 spectrum management, particularly in vulnerable elderly, and might represent a game changer in the global response to COVID-19.

Sex Differences in Glutathione Peroxidase Activity and Central Obesity in Patients with Type 2 Diabetes at High Risk of Cardio-Renal Disease

Women with type 2 diabetes (T2DM) have an increased susceptibility of developing cardio-renal disease compared to men, the reasons and the mechanisms of this vulnerability are unclear. Since oxidative stress plays a key role in the development of cardio-renal disease, we investigated the relationship between sex, plasma antioxidants status (glutathione peroxidase (GPx-3 activity), vitamin E and selenium), and adiposity in patients with T2DM at high risk of cardio-renal disease. Women compared to men had higher GPx-3 activity (p = 0.02), bio-impedance (p ≤ 0.0001), and an increase in waist circumference in relation to recommended cut off-points (p = 0.0001). Waist circumference and BMI were negatively correlated with GPx-3 activity (p ≤ 0.05 and p ≤ 0.01, respectively) and selenium concentration (p ≤ 0.01 and p ≤ 0.02, respectively). In multiple regression analysis, waist circumference and sex were independent predictors of GPx-3 activity (p ≤ 0.05 and p ≤ 0.05, respectively). The data suggest that increased central fat deposits are associated with reduced plasma antioxidants which could contribute to the future risk of cardio-renal disease. The increased GPx-3 activity in women could represent a preserved response to the disproportionate increase in visceral fat. Future studies should be aimed at evaluating if the modulation of GPx-3 activity reduces cardio-renal risk in men and women with T2DM.

VEGF gene polymorphism interactions with dietary trace elements intake in determining the risk of metabolic syndrome

There is a complex association among genetic, metabolic, and environmental factors in determining the risk of metabolic syndrome (MetS). The aim of this study was to investigate the role of the association between the dietary intake of iron, copper, zinc, manganese, selenium, and iodine (assessed by 24 recall) with vascular endothelial growth factor variants (rs6921438, rs4416670, rs6993770, and rs10738760), on the risk of MetS. Two-hundred and forty-eight individuals with MetS and 100 individuals without MetS were recruited. The dietary intake and the daily average of energy and nutrient intake were obtained by a questionnaire and quantified using Diet Plan 6 software. DNA was extracted from EDTA anticoagulated whole blood. The SNPs were assessed using using a Sequenom iPLEX Gold assay. Data analysis was undertaken using the Student t test, χ2 test and logistic regression using SPSS 11.5 software. There was a significant association between low dietary iron intake and rs6993770 (β = .10, P < .05), and a low dietary zinc and a high manganese intake with rs6921438 in relation to the presence of MetS (β = -.17, P < .05, β = -.30, P < .05, respectively). Our data showed the association of rs6993770 with iron intake and rs6921438 with zinc and manganese intake, indicating further investigation in a larger population to evaluate their values.

Biomarkers of the metabolic syndrome: Influence of minerals, oligo- and trace elements

Influences of minerals, oligo- and trace elements on the concentration of biomarkers of the metabolic syndrome (MetS) are reviewed. Since food is a complex mixture of caloric compounds and essential non-caloric food components with multiple interactions and varying bioavailability, it is hard to separate or identify the effect of one single component in a total meal or diet. Moreover the diet contains various non-nutritive biologically active components, which may add some beneficial characteristics. Therefore, conclusions on the effect of components on various biomarkers of MetS are sometimes quite contradictory. Reasons therefore are mentioned. Literature data should be studied in detail to conclude whether a component is related to a reduction of MetS-related symptoms or whether its influence is merely affecting a biomarker.

Transcriptomic signature of high dietary organic selenium supplementation in sheep: A nutrigenomic insight using a custom microarray platform and gene set enrichment analysis

The objective of this study was to investigate the effect of a high dietary Se supplementation on the whole transcriptome of sheep. A custom sheep whole-transcriptome microarray, with more than 23,000 unique transcripts, was designed and then used to profile the global gene expression of sheep after feeding a high dietary supplementation of organic Se. Lactating crossbred ewes ( = 10; 3 to 4 yr of age and 55 to 65 kg BW) at late lactation (100 ± 8 d in milk) were acclimated to indoor individual pen feeding of a basal control diet (0.40 mg Se/d, sodium selenite) for 4 wk. Sheep were then kept on a diet with an extra (high) supplementation of organic Se (1.45 mg Se/d as Sel-Plex; Alltech Biotechnology Pty Ltd, Dandenong, Victoria, Australia) for 40 d. Whole blood was collected at 2 time points (last day of the acclimatization period [T0] and after 40 d of the organic Se supplementation [T40]), and then total RNA was isolated and labeled for the subsequent microarray analysis. Significance Analysis of Microarrays, using the -statistic, of the microarray data (T40 versus T0) evidenced the up- and downregulation of 942 and 244 transcripts (false discovery rate < 0.05), respectively. Seven genes showed the same trend of expression (up- or downregulation) when tested by quantitative real-time PCR (qPCR) in a cross-validation step. The microarray showed significant upregulation of the following selenoproteins at T40: selenium binding protein 1 (SELENBP1), selenoprotein W1 (SEPW1), glutathione peroxidase 3 (GPX3), and septin 8 (SEPT8). And the expression trends for SEPW1 and SEPT8 were validated using qPCR. Functional annotation of the differentially expressed genes showed the enrichment of several immune system-related biological processes (lymphocyte activation, cytokine binding, leukocyte activation, T cell differentiation, and B cell activation) and pathways (cytokine and interleukin signaling). Moreover, Gene Set Enrichment Analysis evidenced the enrichment of B and T cell receptors signaling pathways, with an enrichment score of 0.63 and 0.59, respectively. Overall, from a global gene expression (whole-transcriptome) point of view, short-term supplementation of a high dietary organic Se to Se-nondeficient sheep results in a transcriptomic signature that mainly reflects an induced immune system and a modulation of transcription effect. Also, the present study provides a custom whole-transcriptome microarray platform that can be used in further global gene expression studies in the ovine species.

High Dietary Selenium Intake Alters Lipid Metabolism and Protein Synthesis in Liver and Muscle of Pigs

BACKGROUND

Prolonged high intakes of dietary selenium have been shown to induce gestational diabetes in rats and hyperinsulinemia in pigs.

OBJECTIVE

Two experiments were conducted to explore metabolic and molecular mechanisms for the diabetogenic potential of high dietary selenium intakes in pigs.

METHODS

In Expt. 1, 16 Yorkshire-Landrace-Hampshire crossbred pigs (3 wk old, body weight = 7.5 ± 0.81 kg, 50% males and 50% females) were fed a corn-soybean meal basal diet supplemented with 0.3 or 1.0 mg Se/kg (as selenium-enriched yeast for 6 wk). In Expt. 2, 12 pigs of the same crossbreed (6 wk old, body weight = 16.0 ± 1.8 kg) were fed a similar basal diet supplemented with 0.3 or 3.0 mg Se/kg for 11 wk. Biochemical and gene and protein expression profiles of lipid and protein metabolism and selenoproteins in plasma, liver, muscle, and adipose tissues were analyzed.

RESULTS

In Expt. 1, the 1-mg-Se/kg diet did not affect body weight or plasma concentrations of glucose and nonesterified fatty acids. In Expt. 2, the 3-mg-Se/kg diet, compared with the 0.3-mg-Se/kg diet, increased (P < 0.05) concentrations of plasma insulin (0.2 compared with 0.4 ng/mL), liver and adipose lipids (41% to 2.4-fold), and liver and muscle protein (10-14%). In liver, the 3-mg-Se/kg diet upregulated (P < 0.05) the expression, activity, or both of key factors related to gluconeogenesis [phosphoenolpyruvate carboxykinase (PEPCK); 13%], lipogenesis [sterol regulatory element binding protein 1 (SREBP1), acetyl-coenzyme A carboxylase (ACC), and fatty acid synthase (FASN); 46-90%], protein synthesis [insulin receptor (INSR), P70 ribosomal protein S6 kinase (P70), and phosphorylated ribosomal protein S6 (P-S6); 88-105%], energy metabolism [AMP-activated protein kinase (AMPK); up to 2.8-fold], and selenoprotein glutathione peroxidase 3 (GPX3; 1.4-fold) and suppressed (P < 0.05) mRNA levels of lipolysis gene cytochrome P450, family 7, subfamily A, polypeptide 1 (CYP7A1; 88%) and selenoprotein gene selenoprotein W1 (SEPW1; 46%). In muscle, the 3-mg-Se/kg diet exerted no effect on the lipid profiles but enhanced (P < 0.05) expression of P-S6 and mammalian target of rapamycin (mTOR; 42-176%; protein synthesis); selenoprotein P (SELP; 40-fold); and tumor suppressor protein 53 (P53) and peroxisome proliferator-activated receptor γ (PPARG; 52-58%; lipogenesis) and suppressed (P < 0.05) expression of INSR (59%; insulin signaling); selenoprotein S (SELS); deiodinases, iodothyronine, type I (DIO1); and thioredoxin reductase 1 (TXNRD1; 50%; selenoproteins); and ACC1 and FASN (35-51%; lipogenesis).

CONCLUSION

Our research showed novel roles, to our best knowledge, and mechanisms of high selenium intakes in regulating the metabolism of protein, along with that of lipid, in a tissue-specific fashion in pigs.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

A systematic review on the association of serum selenium and metabolic syndrome

BACKGROUND

This systematic review paper aims to study the experimental and human studies on the relationship between metabolic syndrome (MetS), its component and selenium (Se) concentration.

MATERIALS AND METHODS

The literature was searched in PubMed, Scopus, and Google Scholar databases with no time limitation using MetS X and Se key words in medical subject heading. The related papers were selected in three phases. After quality assessment, two reviewers extracted the data, whereas the third reviewer checked their extracted data. All evidence comes from experimental and laboratory studies.

RESULTS

Finally, 18 articles were included. While, some studies documented that as an antioxidant agent, Se might be correlated with endothelial function, large controversy exists about the type of correlation including positive, negative, and no correlation between MetS and Se levels in body. Some of the reviewed studies were focused on antioxidant supplementation effects on MetS, results also varied in this regard.

CONCLUSION

This inconsistency could be because of diversity in study design, population, lack of special focus on Se and MetS, and finally the complex nature of MetS.

Associations between Dietary Antioxidant Intake and Metabolic Syndrome

Background

The objective of this study was to evaluate the association between dietary antioxidant intake (carotenoid, vitamin C, E and selenium) intake and metabolic syndrome (MS).

Method

This cross-sectional study included 2069 subjects undergoing a regular health checkup. Biochemical test results and data on dietary intakes were collected for analysis. Adjustment for energy intake and multi-variable logistic regression were performed to determine adjusted odds ratios (ORs) and corresponding 95% confidence intervals (95%CI) for the relationship between dietary antioxidants intake and MS. The lowest quartile of antioxidant intake was regarded as the reference category.

Result

Dietary vitamin C intake (P values for trend were 0.02 in energy adjusted analysis and 0.08 in multivariable adjusted analysis) had a negative association with MS, as did selenium intake in the second quartile (energy adjusted OR: 0.60, 95%CI: 0.43 to 0.85; multivariable adjusted OR: 0.60, 95%CI: 0.43 to 0.86). However, there was no significant relationship between dietary carotenoid and vitamin E intake and MS.

Conclusion

Subjects with low intake of vitamin C might be predisposed to development of MS, while dietary selenium intake had a moderate negative association with MS. Dietary carotenoid and vitamin E intake was not associated with MS.

Serum and urinary selenium levels in obese children: a cross-sectional study

OBJECTIVE

To determine serum and urinary selenium (Se) levels in children with and without obesity, and to assess if Se influences the risk of obesity.

SUBJECTS AND METHODS

High-resolution-continuum source-atomic absorption spectrometry (HR-CS-AAS) was used to determine the content of Se in 80 children (age 6-17; 40 boys, 40 girls). Correlations between variables were tested with the use of Spearman's correlation coefficient. U Mann-Whitney test was applied to assess the difference of Se contents in samples. Measured metabolic risk factors (blood pressure, glucose level, triglycerides (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), and total cholesterol), age, gender, and BMI were correlated. Logistic regression models were fitted to identify predictors of obesity interacting with selenium content in serum and urine, separately.

RESULTS

Obese children, regardless of gender, had lower Se content. Se level in serum (p=0.001, OR 0.74, 95%CI 0.62-0.88) and total cholesterol (p=0.001, OR 1.19, 95%CI 1.08-1.31) were the independent factors significantly influencing the risk of obesity in children. Two separate models were observed for Se in urine: (i) Se level (p<0. 0001, OR 0.70, 95%CI 0.58-0.84) and glucose level (p<0.0001, OR 1.22, 95%CI 1.10-1.35), and (ii) Se level (p=0.002, OR 0.60 95%CI 0.43-0.83) and total cholesterol level (p=0.003, OR 1.16, 95%CI 1.05-1.28).

CONCLUSION

The current study suggests a possible role of Se in obesity. Further research needs to be performed to check if obese children are an at-risk group for Se deficiency.

Differential protein expression of Caco-2 cells treated with selenium nanoparticles compared with sodium selenite and selenomethionine

The study was designed to determine the differential protein expression of Caco-2 cells treated with different forms of selenium including sodium selenite, selenomethionine (Se-Met), and selenium nanoparticles (nano-Se). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry (MS) were used to identify the differentially expressed proteins. The results indicated that seven protein spots, ubiquitin-conjugating enzyme E2 (E2), glutathione synthetases (GS), triosephosphate isomerase (TSP), T-complex protein 1 subunit zeta (TCPZ), lamin-B1, heterogeneous nuclear ribonucleoprotein F (hnRNP F), and superoxide dismutase [Cu-Zn] (Cu, Zn-SOD) were significantly different among all the groups. According to the order of control, sodium selenite, Se-Met, and Nano-Se, the expression levels of two proteins (E2 and GS) increased and the other differential proteins were reverse. Except for E2, there were no significant differences in other protein expressions between the groups treated with nano-Se and Se-Met.

[Selenium supplementation trials for cancer prevention and the subsequent risk of type 2 diabetes mellitus: selenium and vitamin E cancer prevention trial and after]

The essential trace element selenium has long been considered to exhibit cancer-preventive, antidiabetic and insulin-mimetic properties. However, recent epidemiological studies have indicated that supranutritional selenium intake and high plasma selenium levels are not necessarily preventive against cancer, and are possible risk factors for developing type 2 diabetes mellitus. The results of the SELECT, Selenium and Vitamin E Cancer Prevention Trial, in which it is hypothesized that the supplementations with selenium and/or vitamin E decrease the prostate cancer incidence among healthy men in the U.S., showed that the supplementation did not prevent the development of prostate cancer and that the incidence of newly diagnosed type 2 diabetes mellitus increased among the selenium-supplemented participants. The Nutritional Prevention of Cancer (NPC) trial showed a decreased risk of prostate cancer among participants taking 200 μg of selenium daily for 7.7 years. However, the results of the NPC trial also showed an increased risk of type 2 diabetes mellitus in the participants with plasma selenium levels in the top tertile at the start of the study. Recently, the association of serum selenium with adipocytokines, such as TNF-α, VCAM-1, leptin, FABP-4, and MCP-1, has been observed. Selenoprotein P has been reported to associated with adiponectin, which suggests new roles of selenoprotein P in cellular energy metabolism, possibly leading to the increased risk of type 2 diabetes mellitus and also the development of cancer. Further studies are required to elucidate the relationship between selenium and adipocytokines and the role of selenoprotein P in the development of type 2 diabetes mellitus and cancer at high levels of selenium.