Comparison of whole-blood glutathione peroxidase activity, levels of serum selenium, and lipid peroxidation in subjects from the fishing and rural communities of "Rabo de Peixe" village, San Miguel Island, the Azores' Archipelago, Portugal

Associations between serum selenium and serum lipids in adolescents aged 12-19: A cross-sectional study

BACKGROUND

Selenium is an essential trace element in the human body and is important in lipid metabolism. Previous studies on the relationship between selenium and serum lipids were almost conducted in adults, and the research conclusions were inconsistent. Evidence linking selenium and lipids in adolescents is very limited. As an important stage of growth and development, studying the effects of trace elements on the body during adolescence is meaningful.

OBJECTIVE

This study examined the association between serum selenium and serum lipids in adolescents aged 12-19.

METHODS

This cross-sectional study analyzed 2209 adolescents aged 12-19 years from NHANES 2011 to 2016. Multiple linear regression analyses were performed to evaluate selenium's association with serum lipids (containing TC, TG, LDL-C, and HDL-C). Moreover, a generalized additive model (GAM) and a fitted smoothing curve (penalized spline method) were conducted to explore the exact curve shape between them.

RESULTS

In the fully adjusted model, it showed a positive association between selenium and TC, TG, LDL-C [TC (β = 0.144 (, 95 % CI (0.084, 0.204), P < 0.001), TG (β = 0.285, 95 % CI (0.134, 0.437), P < 0.001), LDL-C (β = 0.098, 95 % CI (0.022, 0.174), P = 0.011)], whereas a negative association [(β = -0.031, 95 % CI (-0.054, - 0.009), P = 0.006)] between Se and HDL-C. Subgroup analysis showed that the above associations were more significant in females aged 12-19 (P for trend < 0.05). Furthermore, linear associations were performed in Se between TC and LDL-C.

CONCLUSION

This is the first study to find evidence demonstrating associations between serum Se and serum lipids in adolescents aged 12-19. The validation of our findings will require further research.

Trace Elements Levels in Major Depressive Disorder-Evaluation of Potential Threats and Possible Therapeutic Approaches

The multifactorial etiology of major depressive disorder (MDD) includes biological, environmental, genetic, and psychological aspects. Recently, there has been an increasing interest in metallomic studies in psychiatry, aiming to evaluate the role of chosen trace elements in the MDD etiology as well as the progression of symptoms. This narrative review aims to summarize the available literature on the relationship between the concentration of chosen elements in the serum of patients with MDD and the onset and progression of this psychiatric condition. The authors reviewed PubMed, Web of Science, and Scopus databases searching for elements that had been investigated so far and further evaluated them in this paper. Ultimately, 15 elements were evaluated, namely, zinc, magnesium, selenium, iron, copper, aluminium, cadmium, lead, mercury, arsenic, calcium, manganese, chromium, nickel, and phosphorus. The association between metallomic studies and psychiatry has been developing dynamically recently. According to the results of current research, metallomics might act as a potential screening tool for patients with MDD while at the same time providing an assessment of the severity of symptoms. Either deficiencies or excessive amounts of chosen elements might be associated with the progression of depressive symptoms or even the onset of the disease among people predisposed to MDD.

Selenium and Redox Enzyme Activity in Pregnant Women Exposed to Methylmercury

Selenium (Se) is a micronutrient with essential physiological functions achieved through the production of selenoproteins. Adequate Se intake has health benefits and reduces mercury (Hg) toxicity, which is important due to its neurotoxicity. This study determined the Se status and redox enzyme, including selenoproteins', activity in pregnant women highly exposed to Hg (between 1 to 54 µg Hg/L blood) via fish consumption. A cross-sectional study enrolling 513 women between the first and third trimester of pregnancy from Madeira, Portugal was conducted, encompassing collection of blood and plasma samples. Samples were analyzed for total Se and Hg levels in whole blood and plasma, and plasma activity of redox-active proteins, such as glutathione peroxidase (GPx), thioredoxin reductase (TrxR) and thioredoxin (Trx). Enzyme activities were related to Se and Hg levels in blood. Se levels in whole blood (65.0 ± 13.1 µg/L) indicated this population had a sub-optimal Se status, which translated to low plasma GPx activity (69.7 ± 28.4 U/L). The activity of TrxR (12.3 ± 5.60 ng/mL) was not affected by the low Se levels. On the other hand, the decrease in Trx activity with an increase in Hg might be a good indicator to prevent fetal susceptibility.

The role of selenium in depression: a systematic review and meta-analysis of human observational and interventional studies

The results of human studies are inconsistent regarding selenium and depressive disorders. Therefore, we aimed to conduct a systematic review and meta-analysis of observational and interventional studies and provided an overview of the role of selenium in depression. Three databases including Medline, Scopus, and Web of Science were searched on June 30, 2020 and updated on April 12, 2021. Also, we searched in electronical databases of WHO Global Index Medicus and ClinicalTrials.gov. No time or language restrictions were used for the search. A random effects model was used to pool effect sizes. In total, 20 studies were included in the systematic review, and 15 studies were included in the meta-analysis. There were no significant differences in serum selenium levels between patients with depression and healthy subjects (WMD: 2.12 mg/L; 95% CI: - 0.11, 4.36; I2 = 98.0%, P < 0.001). Also, no significant correlation was found between serum levels of selenium and depression scores (r: - 0.12; 95% CI: - 0.33, 0.08; I2 = 73.5%, P = 0.010). Nevertheless, there was a significant negative association between high selenium intake and the risk of postpartum depression (OR: 0.97; 95% CI: 0.95, 0.99; I2 = 0.0%, P = 0.507). In addition, selenium supplementation significantly reduced depressive symptoms (WMD: - 0.37; 95% CI: - 0.56, - 0.18; I2 = 0.0%, P = 0.959). Taken these results together, selenium seems to have a protective role against postpartum depression and can be considered as a beneficial adjuvant therapy in patients with depression. Further studies are necessary to draw definitive conclusions.

The Oxidative Stress Markers in the Erythrocytes and Heart Muscle of Obese Rats: Relate to a High-Fat Diet but Not to DJOS Bariatric Surgery

Obesity and high-fat diet (HF) are prevalent causes of oxidative stress (OS). Duodenal-jejunal omega switch (DJOS) is a bariatric procedure used for body mass reduction, extensively tested in animal models. We studied the long-term impact of bariatric surgery and an HF diet on the oxidative stress markers in erythrocytes and heart muscles of rats. We analyzed superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx) activity and malondialdehyde (MDA) concentration in DJOS or SHAM (control) operated rats fed with different dietary protocols (control diet (CD) and high-fat diet (HF)), before and after the surgery (CD/CD, HF/HF, CD/HF, and HF/CD). We observed higher erythrocytes CAT, GST and GPx activity in DJOS-operated (vs. SHAM) rats fed with an HF/HF diet. For DJOS-operated rats, erythrocytes CAT and GPx activity and MDA concentration were significantly lower in CD/CD group. We observed increased heart muscle GR activity in SHAM-operated rats (vs. DJOS bariatric surgery) fed with an HF/HF diet. Change from HF to CD diet increased heart muscle GPx activity after DJOS bariatric surgery. Heart muscle SOD activity was lower in HF/HF and CD/CD groups after DJOS bariatric surgery (vs. SHAM). DJOS surgery significantly reduced heart muscle MDA concentration in HF/HF and HF/CD groups (vs. SHAM). We conclude that the selected dietary patterns had a stronger impact on oxidative stress markers in erythrocytes and heart muscle than DJOS bariatric surgery.

Relationship between serum selenium, sociodemographic variables, other trace elements and lipid profile in an adult Spanish population

INTRODUCTION

Several studies have shown an inverse relationship between selenium status and cardiovascular health, although epidemiologic evidence yielded by the randomized trials did not find a beneficial effect of selenium administration. The aim of this study was to analyze the association between serum selenium levels and lipid profile adjusted by age, sex and other associated factors among a general adult population in Spain.

MATERIALS AND METHODS

We recruited 372 hospital employee volunteers (60 men and 312 women) with a mean age of 47 (SD: 10.9), whom were given a standardized questionnaire. Serum selenium concentration was measured by electrothermal atomization atomic absorption spectrometry. Serum copper and zinc concentrations were measured using flame atomic absorption spectrometry.

RESULTS

The mean of serum selenium was 79.5μg/L (SD: 11.7) with no sex-dependent differences. In the multivariate linear regression analysis, the associated factors with the mean levels of selenium were: age (β=0.223; CI 95%: 0.101-0.345), p<0.001; widowhood (β=-9.668; CI 95%: -17.234 to -2.102), p=0.012; calcium supplements (β=3.949; CI 95%: 0.059-7.838), p=0.047; zinc (β=0.126; CI 95%: 0.013-0.238), p=0.028 and glucose (β=0.172; CI 95%: 0.062- 0.281), p=0.002; Participants with serum selenium≥79.5μg/L were 1.98 (OR=1.98; CI 95% 1.17-3.35; p=0.011) and 2.04 times (OR=2.04; CI 95% 1.06-3.97; p=0.034) more likely to have cholesterol ≥200mg/dL and LDL-c ≥100mg/dL respectively than those with serum selenium <79.5μg/L.

CONCLUSIONS

Higher selenium was positively associated with increased total and LDL cholesterol but not with HDL-c and triglycerides. More studies are needed in order to confirm the lower serum selenium findings in widows.

Modulators of erythrocyte glutathione peroxidase activity in healthy adults: an observational study

The aim of this study was to investigate the potential modulators of erythrocyte glutathione peroxidase (GPx) activity in young and apparently healthy individuals. One hundred one individuals (53 women and 48 men) were evaluated for anthropometric measurements, biochemical markers, clinical, dietary, and endogenous and exogenous components of the antioxidant defense system. Statistical analysis was performed to detect differences among subjects by the median of GPx activity. A linear regression model and Spearman correlation coefficients were used to screen the associations between GPx activity and interest variables. Individuals with higher GPx enzymatic activity were older and higher circulating levels of oxidized low-density lipoprotein (ox-LDL) values, but conversely lower nail concentrations of selenium and copper (P < 0.05). The GPx activity was positively correlated to truncal fat percentage values (r = 0.24, P = 0.016), circulating levels of ox-LDL (r = 0.28, P = 0.004), and daily vitamin C intake (r = 0.28, P = 0.007), and negatively correlated to the nail concentration of selenium (r = -0.24, P = 0.026). Interesting, it was noticed that the truncal fat percentage and circulating levels of ox-LDL explained 5.9 and 7.4% of the GPx enzymatic activity. Thus, preventive measures such as adequate antioxidant intake and proper fat percentage would be a priority in the nutritional care of young and apparently healthy individuals.

Dietary selenium intake is negatively associated with serum sialic acid and metabolic syndrome features in healthy young adults

Low-grade and chronic inflammation related to excessive body weight can increase the risk for type 2 diabetes and cardiovascular disease, whereas the intake of antioxidant nutrients appears to produce anti-inflammatory effects. The purpose of this observational study was to assess the potential relationships between serum SA levels, metabolic syndrome features, and dietary selenium intake to test the hypothesis that this antioxidant micronutrient may also have anti-inflammatory properties in healthy young adults. Forty-three healthy participants with a mean age of 18.0 +/- 0.93 years and a mean body mass index of 22.2 +/- 2.7 kg/m(2) were enrolled. Anthropometric, body composition, and blood pressure determinations were measured as well as serum lipid profile, glucose, insulin, and SA concentrations. Nutritional intake was estimated by a computerized, validated semiquantitative food frequency questionnaire. The findings included a positive correlation between SA and triacylglycerol levels (r = 0.317, P = .038) and a trend to significance with the homeostatic model assessment of insulin resistance index (r = 0.297, P = .053). Moreover, subjects with higher dietary selenium intake showed statistically lower SA levels compared with subjects with lower dietary selenium intake (1.8 +/- 0.4 vs 2.1 +/- 0.4 mmol/L, P = .037), while dietary selenium negatively correlated with SA (r = -0.331, P = .030) and triacylglycerol levels (r = -0.312, P = .041). It can be concluded that a relationship of SA, an inflammatory marker, with metabolic syndrome features such as lipid profile impairment and insulin resistance has been envisaged. In addition, we report (apparently for the first time) a negative association between SA and selenium intake, a recognized antioxidant trace element, in healthy young subjects, reinforcing the view of selenium as a potential anti-inflammatory nutrient.

Essential and non-essential trace metals in scalp hair of men chronically exposed to volcanogenic metals in the Azores, Portugal

Volcanoes produce and release large amounts of toxicants, and the concentration of metals in hair can be used as a biomarker of exposure to trace metals. In order to investigate whether humans exposed to volcanic emissions demonstrate higher concentrations of essential and non-essential trace metals, scalp hair of men (3-89 years) living in two areas of the Azores, one exposed to volcanic emissions and the other not, was sampled, and their content in Cd, Cu, Pb, Rb, Se, and Zn was quantified by using High Resolution Inductively Coupled Plasma Mass Spectrometry. In average, men exposed to volcanic emissions presented higher concentrations of Cd (96.9 ppb), Cu (16.2 ppm), Pb (3417.6 ppb), Rb (216.3 ppb), and Zn (242.8 ppm), but not Se (469.6 ppb). Also, strong and significant correlations were found between Cd-Rb and Pb-Rb in the exposed men. In conclusion, humans living chronically exposed to volcanic emissions show high concentrations of essential and non-essential trace metals in scalp hair, and is suggested that this type of exposure may be as harmful as living close to industrial facilities.

Whole blood glutathione peroxidase and erythrocyte superoxide dismutase activities, serum trace elements (Se, Cu, Zn) and cardiovascular risk factors in subjects from the city of Ponta Delgada, Island of San Miguel, The Azores Archipelago, Portugal

Activities of whole blood glutathione peroxidase (GSH-Px) and erythrocyte superoxide dismutase (SOD) and serum levels of selenium (Se), copper (Cu) and zinc (Zn) were measured in 118 apparently healthy subjects aged 20-60 years from the city of Ponta Delgada, Island of San Miguel, The Azores Archipelago, Portugal. Data were analysed by age/gender, lipid profile and blood pressure as cardiovascular risk factors searching for their relevance when assessing reference values for antioxidant biomarkers. GSH-Px was in the same range, but SOD was significantly lower than in other Portuguese populations. Neither activity differed with gender. GSH-Px activity increased with age, namely in normolipidemic men versus the hyperlipidemic group in which a decrease was observed. This suggests a progressive impairment of GSH-Px with age caused by an enhanced production of oxidant species in hyperlipidemia. GSH-Px was 30% lower in male hypertensives versus normotensives. SOD activity did not relate to age or blood pressure but was 17% higher in the hyperlipidemic men versus the normolipidemic group, suggesting a better antioxidant protection by SOD than by GSH-Px in hyperlipidemia and hypertension. Se was higher in men versus women, particularly in the older subjects, and partly related to hyperlipidemia. Zn levels showed a similar dependency on gender, not related to age or lipid profile. Cu levels were much higher in women than in men in all age or lipid profile classes and decreased in hyperlipidemia. They were lowered with age in both genders, particularly in normolipidemic women. The present research therefore suggests that hyperlipidemia and hypertension do affect antioxidant status and should be considered when assessing antioxidant biomarkers in blood.

Plasma selenium levels in healthy blood bank donors in the central-eastern part of Belgium

Graphite furnace atomic absorption spectrometry, with Zeeman background correction and after improved matrix modification, was used to measure the plasma selenium content of healthy blood bank donors in the central part of Belgium. The mean plasma selenium concentration of 80 men and 80 women was 79.7+/-4.4ng/mL with a range of 55.0-117.4ng/mL. There was no gender difference observed. Plasma selenium level was significantly highest for the adult group, aged 45-64 years, compared to the others, except the young adults (18-24 years). The mean plasma selenium concentration measured corresponded well with literature data for Belgium. The obtained values were found to be in the medium range, compared with recent literature values for the European countries.

Elevated blood selenium levels in the Brazilian Amazon

Contaminated fish poses a difficult challenge throughout the world, on the one hand, fish is a very nutritious food source, while on the other hand it accumulates many toxic substances, including mercury (Hg). As part of our efforts in the Brazilian Amazon to maximize nutritional input from fish consumption, a dietary mainstay, and minimize toxic risk, we have been studying the role of selenium (Se), an essential element, that may influence the distribution of Hg in the body and influence Hg neurotoxicity. Se, which is naturally present in the soil, is ingested through consumption of various foods, notably fish, mammals and certain plants. The objectives of the present study were: (i) evaluate whole blood Se (B-Se) and Hg (B-Hg); (ii) characterize B-Se variations with respect to socio-demographic and dietary variables; and (iii) examine the relation between B-Se and B-Hg. A total of 236 persons from six riparian communities of the Tapajós River Basin, a tributary of the Amazon, participated in this study. Whole blood Se and Hg were measured and interview administered questionnaires were used to obtain data on socio-demographic variable, smoking and drinking habits, and fish and fruit consumption. The results show that B-Se are in the upper normal range (median=284.3 microg/L, range=142.1-2029.3 microg/L). No individuals presented B-Se deficiency, but 9 participants from the same extended family had relatively high B-Se levels, potentially a threat to their health. B-Se varied between communities, was significantly higher among alcohol drinkers and farmers, but not associated with age, sex or tobacco consumption. A significant positive relation between B-Se and B-Hg was noted, independently of the overall fish consumption. B-Se increased with consumption of Peacock bass (Cichla sp.), a piscivorous fish species, and coconut pulp (Cocos nucifera L.). The B-Se intercommunity variations may reflect geographic differences in local soil Se levels as well as traditional land use practices in the different ecosystems of the Tapajós River Basin. In this population with relatively high exposure to Hg, Se may play an important role. Further studies should examine, in this region, the sources of Se, its transmission through the terrestrial and aquatic ecosystem and its role with respect to human health.

Serum selenium determinants in French adults: the SU.VI.M.AX study

The objective of the present work was to assess the relationship between serum Se concentrations and environmental determinants (i.e. lifestyle, social activity, geographic region, urban status, education, familial status, physical activity, BMI, tobacco, and food and alcohol consumption). Baseline results from 13 017 subjects (7876 women aged 35-60 and 5141 men aged 45-60) who participated in the SU.VI.M.AX (Supplémentation en Vitamines et Minéraux Antioxydants) study were analysed. Fewer than 2 % of the volunteers had a serum Se status under 0.75 micromol/l, which has been quoted as the cut-off of biological Se sub-deficiency. Women had significantly lower serum Se concentrations than men (1.09 (sd 0.19) micromol/l (n 7423) and 1.14 (sd 0.20) micromol/l (n 4915), P<0.0001, respectively). Significant differences in serum Se concentrations were observed between geographic areas. In both sexes, the serum Se concentration increased with alcohol, meat and fish consumption, and decreased with smoking. In premenopausal women, the serum Se concentration was higher in contraceptive-pill users than in non-users. In women only, age was associated with increased serum Se concentrations, and obesity (BMI> or =30 kg/m2) was associated with decreased serum Se levels. In men, we observed a decrease in serum Se concentrations with increased consumption of vegetables and fruits. In conclusion, though few of the volunteers participating in the SU.VI.M.AX study had Se status in the sub-deficiency range, 83 % of women and 75 % of men had serum concentrations below the value considered optimal for glutathione peroxidase activity. The largest Se associations in both sexes were found with regions, smoking, alcohol, meat and fish consumption. Further studies are needed to understand the difference in Se status between genders.

Comparison of the serum selenium content of healthy adults living in the Antwerp region (Belgium) with recent literature data

Graphite furnace atomic absorption spectrometry, after improved matrix modification and using Zeeman background correction, was used to measure the serum selenium content of healthy adults living in the Antwerp region (Belgium). The mean serum concentration of 13 men and 13 women, sampled once a month during 1 year, was 84.3 +/- 9.4ng/ml with a broad range of 51.4-121.7 ng/ml. The intra-individual variation was remarkably high. Recent literature on selenium concentrations is reviewed and values are tabulated, with limitation to healthy adults and European countries. The mean serum selenium concentration measured corresponded well to older literature data for Belgium. The obtained values were found to be in the medium range compared with the literature data for other European countries.