Serum total selenium status in Greek adults and its relation to age. The ATTICA study cohort

Selenoprotein P increases upon selenium and coenzyme Q10 supplementation and is associated with telomere length, quality of life and reduced inflammation and mortality

BACKGROUND

Selenoprotein P (SELENOP) transports selenium to extrahepatic tissues and is a biomarker of selenium status. Low soil selenium leads to low dietary selenium intake. A consequence is an increased risk of cardiovascular disease.

OBJECTIVE

To investigate clinical aspects associated with SELENOP deficiency, including biomarkers of inflammation, quality of life, and mortality within 12 years, and the effect of dietary selenium and coenzyme Q10 supplementation on SELENOP.

METHODS

SELENOP was determined at inclusion and after four years of supplementation in 403 elderly community-living participants low in selenium receiving selenium yeast (200 μg/day) and coenzyme Q10 (200 mg/day), or placebo. Pre-intervention, the average serum selenium level was 67 μg/L. T-tests, repeated measures of variance, Cox proportional regressions analyses, Kaplan-Meier graphs and ANCOVA analyses were applied. Associations with biomarkers of inflammation, telomere length, quality of life and mortality were investigated. Benchmark modelling was used to determine the serum selenium concentration at which the saturation levels of SELENOP and GPx3 was achieved. Comparison with GPx3 and serum selenium to identify increased mortality risk was performed, and the effect of supplementation on SELENOP levels were evaluated.

RESULTS

Inverse associations were observed between the level of SELENOP at inclusion and biomarkers for inflammation. At follow-up, shorter telomere lengths were seen in those with low levels of SELENOP at inclusion, whereas high levels of SELENOP were associated with better quality of life and decreased mortality. SELENOP had increased prognostic power compared to GPx3 and selenium. Saturation of SELENOP was achieved at a serum selenium level of 146 μg/L, and for GPx3 at 99 μg/L. Supplementation induced higher levels of SELENOP.

CONCLUSION

Significant associations between SELENOP and inflammation, length of telomeres, quality of life, and mortality were observed. Thus, selenium supplementation improved SELENOP expression, thereby facilitating systemic selenium bioavailability and resulting in the observed positive health effects.

Deciphering the associations of selenium distribution in serum GPx-3 and selenoprotein P with cardiovascular risk factors in a healthy population with moderate levels of selenium: The ATTICA study

BACKGROUND

Selenium (Se) is an essential micronutrient, important for human health. The relationship of Se with cardiovascular risk factors is still inconclusive, especially regarding the role of different selenoproteins. The present study evaluated the relation of total serum Se as well as its distribution in plasma selenoproteins, namely glutathione peroxidase 3 (GPx3) and selenoprotein P (SelP) with cardiovascular risk factors in a sex-specific manner, in a healthy population with moderate levels of Se.

METHODS

A sub-sample from the ATTICA Study's database, consisting of 398 participants (160 females and 238 males) with data on Se and selenoproteins levels, was considered. GPx3, SelP and the main non-specific serum selenium containing protein, selenoalbumin (SeAlb) were simultaneously determined in human plasma by high-performance liquid chromatography (HPLC) coupled with inductively coupled plasma mass spectrometry (ICP-MS) at baseline.

RESULTS

Participants that belong to the highest tertiles of GPx3 and SelP presented the lowest blood pressure. Homocysteine was inversely associated with SelP and its ratio SelP/TSe in both sexes. In males, the lowest tertile of GPx3 showed lower adiponectin levels (0.66 ± 0.21 μg/mL) in comparison to the 2nd tertile of GPx3 (p=0.002), SelP was inversely associated with visceral adipose index (VAI) (-2.29 ± 0.81, p=0.005). Particularly, in males, the middle tertile of SelP had the lowest VAI values. Regarding females, lower Lp(a) concentration by 11.96 ± 5.84 mg/dL was observed in low SelP levels while higher leptin concentration by 2.30 ± 0.73 μg/L and lower fibrinogen concentration by 27.32 ± 13.30 mg/dL was detected in low GPx3 levels.

CONCLUSION

Circulating selenoproteins exert differentiated effects on cardiovascular risk factors, some of them in a sex-specific manner.

Supplementation with selenium and coenzyme Q10 in an elderly Swedish population low in selenium - positive effects on thyroid hormones, cardiovascular mortality, and quality of life

BACKGROUND

Selenium-dependent deiodinases play a central role in thyroid hormone regulation and metabolism. In many European countries, insufficient selenium intake may consequently lead to adverse effects on thyroid function. In this randomised placebo-controlled double-blind study, we examined the effect of supplementation with selenium and coenzyme Q10 on thyroid hormonal status, cardiovascular (CV) mortality and health-related quality of life (Hr-QoL).

METHODS

Free T3, free T4, reverse T3, and TSH were determined in 414 individuals at baseline, and the effect of selenium yeast (200 µg/day) and coenzyme Q10 (200 mg/day) supplementation on hormone concentrations, CV mortality and Hr-QoL was evaluated after 48 months using Short Form 36 (SF-36). Pre-intervention plasma selenium was low, mean 67 µg/L, corresponding to an estimated intake of 35 µg/day. Changes in concentrations of thyroid hormones following the intervention were assessed using T-tests, repeated measures of variance, and ANCOVA analyses.

RESULTS

In the total population, the group with the lowest selenium concentration at baseline presented with significantly higher levels of TSH and lower levels of fT3 as compared to subjects with the highest selenium concentration. Supplementation with selenium and coenzyme Q10 for 4 years significantly increased fT3 and rT3, decreased fT4, and diminished the increase in TSH levels compared with placebo treatment (p = 0.03, all). In the placebo group, TSH and fT4 values above the median were associated with an increase in 10-year CV mortality, as compared with the mortality rate among those with TSH and fT4 below the median (p < 0.04, both), with no difference in mortality rate according to TSH and fT4 levels in the active intervention group. Similarly, TSH > median and fT3 < median were associated with a decline in mental Hr-QoL measures vs. TSH < and fT3 > median in the placebo group during 4 years of follow-up, but this was wiped out in the active group.

CONCLUSIONS

Supplementation with selenium and coenzyme Q10 had a beneficial effect on thyroid hormones with respect to CV mortality and Hr-QoL outcomes. The initial deficient selenium status was associated with an impaired thyroid function and the changes in thyroid hormone levels can be explained by increased activity of deiodinases. We conclude that a substantial part of the elderly study population might suffer from suboptimal thyroidal function with adverse clinical implications due to selenium deficiency.

TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov and has the identifier NCT01443780. Since it was not mandatory to register at the time the study began, the study has been registered retrospectively.

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.

Effects of an Intervention with Selenium and Coenzyme Q10 on Five Selected Age-Related Biomarkers in Elderly Swedes Low in Selenium: Results That Point to an Anti-Ageing Effect-A Sub-Analysis of a Previous Prospective Double-Blind Placebo-Controlled Randomised Clinical Trial

Background: Ageing is associated with cardiovascular disease (CVD). As no single biomarker reflects the full ageing process, we aimed to investigate five CVD- and age-related markers and the effects of selenium and coenzyme Q10 intervention to elucidate the mechanisms that may influence the course of ageing. Methods: This is a sub-study of a previous prospective double-blind placebo-controlled randomized clinical trial that included 441 subjects low in selenium (mean age 77, 49% women). The active treatment group (n = 220) received 200 µg/day of selenium and 200 mg/day of coenzyme Q10, combined. Blood samples were collected at inclusion and after 48 months for measurements of the intercellular adhesion molecule (ICAM-1), adiponectin, leptin, stem cell factor (SCF) and osteoprotegerin (OPG), using ELISAs. Repeated measures of variance and ANCOVA evaluations were used to compare the two groups. In order to better understand and reduce the complexity of the relationship between the biomarkers and age, factor analyses and structural equation modelling (SEM) were performed, and a structural model is presented. Results: Correlation analyses of biomarker values at inclusion in relation to age, and relevant markers related to inflammation, endothelial dysfunction and fibrosis, demonstrated the biomarkers' association with these pathological processes; however, only ICAM1 and adiponectin were directly correlated with age. SEM analyses showed, however, that the biomarkers ICAM-1, adiponectin, SCF and OPG, but not leptin, all had significant associations with age and formed two independent structural factors, both significantly related to age. While no difference was observed at inclusion, the biomarkers were differently changed in the active treatment and placebo groups (decreasing and increasing levels, respectively) at 48 months (p ≤ 0.02 in all, adjusted), and in the SEM model, they showed an anti-ageing impact. Conclusions: Supplementation with selenium/Q10 influenced the analysed biomarkers in ways indicating an anti-ageing effect, and by applying SEM methodology, the interrelationships between two independent structural factors and age were validated.

The relationship between urinary selenium levels and risk of gestational diabetes mellitus: A nested case–control study

Background

Selenium (Se) is an essential trace element for the human body. Serum Se and urinary Se are also biomarkers to assess Se exposure status. However, studies focusing on the association between urinary Se and the risk of gestational diabetes mellitus (GDM) are rare.

Objective

To investigate the association between urinary Se and the risk of GDM.

Methods

A nested case–control study based on a prospective birth cohort in Wuhan, China, which focuses on the effects of prenatal environmental factors exposure on pregnant women and children’s health was conducted. Two hundred and twenty-six cases and 452 controls were included. Maternal urine samples were collected before GDM diagnosis, and the urinary Se levels were determined. We assessed the association of urinary Se with GDM by conditional logistic regression with maternal urinary Se level as a categorical variable, and estimated the association between Se and glucose levels by multiple linear regression. The potential modifier roles of maternal age and fetal sex have also been assessed.

Results

Lower urinary level of Se was significantly associated with a higher risk of GDM (OR = 2.35 for the tertile 1, 95% CI:1.36-4.06; adjusted OR = 1.79 for the tertile 2, 95%CI:1.09-2.95; p for trend = 0.01). Fetal sex had an interaction with Se in the association with GDM. The association was more pronounced among pregnant women with female fetuses than with male fetuses.

Discussion

Our study suggested a significant negative association between urinary Se and the risk of GDM, and this association may vary depending on the fetal sex.

Serum selenium concentration in patients with autoimmune thyroid disease

Abstract.

Improved cardiovascular health by supplementation with selenium and coenzyme Q10: applying structural equation modelling (SEM) to clinical outcomes and biomarkers to explore underlying mechanisms in a prospective randomized double-blind placebo-controlled intervention project in Sweden

Purpose

Selenium and coenzyme Q10 have synergistic antioxidant functions. In a four-year supplemental trial in elderly Swedes with a low selenium status, we found improved cardiac function, less cardiac wall tension and reduced cardiovascular mortality up to 12 years of follow-up. Here we briefly review the main results, including those from studies on biomarkers related to cardiovascular risk that were subsequently conducted. In an effort, to explain underlying mechanisms, we conducted a structured analysis of the inter-relationship between biomarkers.

Methods

Selenium yeast (200 µg/day) and coenzyme Q10 (200 mg/ day), or placebo was given to 443 elderly community-living persons, for 48 months. Structural Equation Modelling (SEM) was used to investigate the statistical inter-relationships between biomarkers related to inflammation, oxidative stress, insulin-like growth factor 1, expression of microRNA, fibrosis, and endothelial dysfunction and their impact on the clinical effects. The main study was registered at Clinicaltrials.gov at 30th of September 2011, and has the identifier NCT01443780.

Results

In addition to positive clinical effects, the intervention with selenium and coenzyme Q10 was also associated with favourable effects on biomarkers of cardiovascular risk. Using these results in the SEM model, we showed that the weights of the first-order factors inflammation and oxidative stress were high, together forming a second-order factor inflammation/oxidative stress influencing the factors, fibrosis (β = 0.74; p < 0.001) and myocardium (β = 0.65; p < 0.001). According to the model, the intervention impacted fibrosis and myocardium through these factors, resulting in improved cardiac function and reduced CV mortality.

Conclusion

Selenium reduced inflammation and oxidative stress. According to the SEM analysis, these effects reduced fibrosis and improved myocardial function pointing to the importance of supplementation in those low on selenium and coenzyme Q10.

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.

Nutritional Status of Selenium and Its Association with Diet and Indoor Air Pollution among Pregnant Women in a Rural Area of Northern China

The nutritional status of selenium (Se) in pregnant women in rural areas of northern China and its association with diet and indoor air pollution are rarely reported. We recruited 273 pregnant women in early or middle term in Shanxi and Hebei province and detected their fasting blood selenium. Demographic characteristics, food habits, and indoor air pollution exposure were collected with a questionnaire. Multivariate logistic regression models were used to estimate the adjusted odds ratios (AORs) and their 95% confidence intervals for the factors and relatively low blood levels of Se (below the lower quartile). The median (interquartile range [IQR]) blood concentration of Se was 117.35 (103.90, 129.23) μg/L. The rate of Se deficiency was 4.8%, and the rate of overnutrition was 23.8%. The AORs for the risk for relatively low blood levels of Se were 2.26 (1.15, 4.44) for consuming less beef and pork/mutton; 0.39 (0.19, 0.80) for a lower frequency of vinegar consumption; and 1.41 (0.76, 2.60) and 1.18 (0.59, 2.36) for passive smoking and indoor coal pollution, respectively. In conclusion, the nutritional status of Se in pregnant women in a rural area of northern China was acceptable; diet was the main determinant; no conclusive association was found between indoor air pollution and Se nutritional status.

Oxidative Stress and Cognitive Decline: The Neuroprotective Role of Natural Antioxidants

Free- radicals (Oxygen and Nitrogen species) are formed in mitochondria during the oxidative phosphorylation. Their high reactivity, due to not-engaged electrons, leads to an increase of the oxidative stress. This condition affects above all the brain, that usually needs a large oxygen amount and in which there is the major possibility to accumulate "Reacting Species." Antioxidant molecules are fundamental in limiting free-radical damage, in particular in the central nervous system: the oxidative stress, in fact, seems to worsen the course of neurodegenerative diseases. The aim of this review is to sum up natural antioxidant molecules with the greatest neuroprotective properties against free radical genesis, understanding their relationship with the Central Nervous System.

A cross-sectional study of blood selenium concentration and cognitive function in elderly Americans: National Health and Nutrition Examination Survey 2011-2014

BACKGROUND

Cognitive decline can develop into mild cognitive impairment, a high-risk factor in the progression of Alzheimer's disease. The antioxidant micronutrient selenium may have some effect on preventing cognitive decline, but the association between whole blood selenium concentration and cognitive function remains controversial.

AIM

To investigate the association between whole blood selenium concentration and cognitive function score in elderly Americans.

SUBJECTS AND METHODS

Data was obtained from the national health and nutrition survey between 2011 and 2014. A general linear model was used to adjust for possible risk factors to analyse the association between blood selenium concentration and cognitive function.

RESULTS

2068 participants were included in our study, and the average blood selenium concentration was high at 195.08 μg/L. The risk of lower cognitive scores was higher in people with lower blood selenium concentration (p < 0.05). The lower cognition may also be associated with one or more of the following characteristics: older, male, had a low poverty-income ratio, low education level, and consumed less alcohol. Related conditions such as stroke, diabetes and high blood pressure may also affect cognitive scores.

CONCLUSIONS

Higher blood selenium is associated with higher cognitive scores in elderly Americans.

Dietary Habits, Selenium, Copper, Zinc and Total Antioxidant Status in Serum in Relation to Cognitive Functions of Patients with Alzheimer's Disease

Oxidative stress plays a crucial role in the neurodegenerative process and can impair cognitive functions. In the prevention of Alzheimer's disease (AD), an adequate consumption of dietary antioxidants may be a major factor. The objective of the study was to estimate selenium (Se), copper (Cu), zinc (Zn), and total antioxidant status (TAS) in the serum of patients with AD in relation to their cognitive functions and dietary habits. A total of 110 patients (aged 54-93 years) with early or moderate AD, as well as 60 healthy people (aged 52-83 years) were studied. The severity of the disease was assessed using the mini-mental state examination (MMSE) scale. Food-frequency questionnaires were implemented to collect the dietary data. The concentrations of Se, Cu and Zn in the sera were determined by the atomic absorption spectrometry method. TAS was estimated spectrophotometrically using ready-made kits (Randox). Significantly lower concentrations of Se, Zn and TAS, and higher Cu:Zn ratio in the serum of patients with AD, compared to healthy people, were observed. A low correlation between the MMSE score and TAS in the serum of AD patients and significantly higher MMSE values in patients with TAS above the reference range were also noted. In patients with serum Cu concentration above the norm, significantly lower MMSE values were found. Selected dietary habits such as the frequency of consumption of various food products had a significant impact on the concentration of the assessed parameters in the serum of people with AD.

Supplemental selenium and coenzyme Q10 reduce glycation along with cardiovascular mortality in an elderly population with low selenium status - A four-year, prospective, randomised, double-blind placebo-controlled trial

BACKGROUND

A low intake of selenium has been shown to increase the risk of cardiovascular mortality, and supplementation of selenium and coenzyme Q10 influences this. The mechanism behind is unclear although effects on inflammation, oxidative stress and microRNA expression have been reported. Fructosamine, a marker of long-term glycaemic control, is also a marker of increased risk of heart disease and death, even in non-diabetics.

OBJECTIVE

To analyse the impact of selenium and coenzyme Q10 supplementation on the concentration of fructosamine. Also, the relation between pre-intervention serum selenium concentration and the effect on fructosamine of the intervention was studied.

METHODS

Fructosamine plasma concentration was determined in 219 participants after six and 42 months of intervention with selenium yeast (200 μg/day) and coenzyme Q10 (200 mg/ day) (n = 118 of which 20 had diabetes at inclusion), or placebo (n = 101 of which 18 had diabetes at inclusion). Pre-intervention, the serum selenium levels were 67 μg/L (active treatment group: 66.6 μg/L; placebo group: 67.4 μg/L), corresponding to an estimated intake of 35 μg/day. Changes in concentrations of fructosamine following intervention were assessed by the use of T-tests, repeated measures of variance, and ANCOVA analyses.

RESULTS

Post-intervention selenium concentrations were 210 μg/L in the active group and 72 μg/L in the placebo group. A lower concentration of fructosamine could be seen as a result of the intervention in the total population (P = 0.001) in both the males (P = 0.04) and in the females (P = 0.01) in the non-diabetic population (P = 0.002), and in both the younger (<76 years) (P = 0.01) and the older (≥76 years) participants (P = 0.03). No difference could be demonstrated in fructosamine concentration in the diabetic patients, but the total sample was small (n = 38). In subjects with a low pre-intervention level of serum selenium the intervention gave a more pronounced decrease in fructosamine compared with those with a higher baseline selenium level.

CONCLUSION

A significantly lower concentration of fructosamine was observed in the elderly community-living participants supplemented with selenium and coenzyme Q10 for 42 months compared to those on the placebo. As oxidative mechanisms are involved in the glycation of proteins, less glycoxidation could be a result of the supplementation of selenium and coenzyme Q10, which could have contributed to lower cardiac mortality and less inflammation, as has earlier been reported. This study was registered at Clinicaltrials.gov, and has the identifier NCT01443780.

Significant decrease of von Willebrand factor and plasminogen activator inhibitor-1 by providing supplementation with selenium and coenzyme Q10 to an elderly population with a low selenium status

Purpose

Endothelial dysfunction and inflammation are conditions which fuel atherosclerosis and ischaemic heart disease. We have previously reported reduced cardiovascular (CV) mortality following supplementation with selenium and coenzyme Q10 to 443 elderly individuals with low selenium status (mean 67 μg/L) for 4 years. Here, we wanted to evaluate a possible association between the supplementation and the plasma concentrations of the von Willebrand factor (vWf), and the plasminogen activator inhibitor-1 (PAI-1), as they, besides other functions, are also strongly associated with endothelial function.

Methods

In this sub-study, 308 individuals (active substance: 157, placebo: 151) were included. Blood samples were drawn after 6 and 36 months and vWf and PAI-1 were determined in plasma by ELISA. Changes in concentrations of the biomarkers were evaluated by the use of T tests, repeated measures of variance, and ANCOVA analyses.

Results

The active treatment group presented a lower level of vWf after 36 months compared with the placebo group (1.08 U/mL vs. 5.10 U/mL; p = 0.0007). The results were validated through the repeated measures of variance evaluation. The PAI-1 levels showed an equally significant decrease in the active group (26.2 ng/mL vs. 49.2 ng/mL; p = 0.0002) and were also validated through repeated measures of variance evaluation.

Conclusion

In this sub-study on elderly receiving selenium and coenzyme Q10, or placebo we found significantly lower levels of vWf and PAI-1 in the active treatment group as compared to the placebo group. We interpret this as a better endothelial function because of the intervention, which accords with a previous finding of reduced CV mortality.

Changes of trace element status during aging: results of the EPIC-Potsdam cohort study

Purpose

We aimed to evaluate age-dependent changes of six trace elements (TE) [manganese (Mn), iron (Fe), zinc (Zn), copper (Cu), iodine (I), and selenium (Se)] over a 20-year period.

Methods

TE concentrations were determined using repeated serum samples taken at baseline and after 20 years of follow-up from 219 healthy participants of the EPIC-Potsdam study, using inductively coupled plasma tandem mass spectrometry. For each TE, absolute and relative differences were calculated between the two time points, as well as the proportion of individuals within normal reference ranges. Interdependence between age-related TE differences was investigated using principal component analysis (PCA). Relationships between selected factors (lifestyle, sociodemographic, anthropometric factors, and hypertension) and corresponding TE longitudinal variability were examined using multivariable linear regression models.

Results

Median age of our study sample was 58.32 years (4.42) at baseline and 40% were females. Median Mn, Zn, Se concentrations and Se to Cu ratio significantly decreased during aging while median Fe, Cu, I concentrations and Cu to Zn ratio significantly increased. A substantial percentage of the participants, at both time points, had Zn concentrations below the reference range. The first PCA-extracted factor reflected the correlated decline in both Mn and Zn over time while the second factor reflected the observed (on average) increase in both Cu and I over time. Overall, none of the investigated factors were strong determinants of TE longitudinal variability, except possibly dietary supplement use, and alcohol use for Fe.

Conclusions

In conclusion, in this population-based study of healthy elderly, decrease in Mn, Zn, and Se concentrations and increase in Fe, Cu, and I concentrations were observed over 20 years of follow-up. Further research is required to investigate dietary determinants and markers of TE status as well as the relationships between TE profiles and the risk of age-related diseases.

Electronic supplementary material

The online version of this article (10.1007/s00394-019-02143-w) contains supplementary material, which is available to authorized users.

Significant Changes in Metabolic Profiles after Intervention with Selenium and Coenzyme Q10 in an Elderly Population

Selenium and coenzyme Q₁₀ (SeQ₁₀) are important for normal cellular function. Low selenium intake leads to increased cardiovascular mortality. Intervention with these substances with healthy elderly persons over a period of four years in a double-blind, randomised placebo-controlled prospective study showed reduced cardiovascular mortality, increased cardiac function, and a lower level of NT-proBNP. Therefore, we wanted to evaluate changes in biochemical pathways as a result of the intervention with SeQ₁₀ using metabolic profiling. From a population of 443 healthy elderly individuals that were given 200 µg selenium and 200 mg coenzyme Q₁₀, or placebo daily for four years, we selected nine males on active intervention and nine males on placebo for metabolic profiling in the main study. To confirm the results, two validation studies (study 1 n = 60 males, study 2 n = 37 males) were conducted. Principal component analyses were used on clinical and demographic data to select representative sets of samples for analysis and to divide the samples into batches for analysis. Gas chromatography time-of-flight mass spectrometry-based metabolomics was applied. The metabolite data were evaluated using univariate and multivariate approaches, mainly T-tests and orthogonal projections to latent structures (OPLS) analyses. Out of 95 identified metabolites, 19 were significantly decreased due to the intervention after 18 months of intervention. Significant changes could be seen in the pentose phosphate, the mevalonate, the beta-oxidation and the xanthine oxidase pathways. The intervention also resulted in changes in the urea cycle, and increases in the levels of the precursors to neurotransmitters of the brain. This adds information to previous published results reporting decreased oxidative stress and inflammation. This is the first-time metabolic profiling has been applied to elucidate the mechanisms behind an intervention with SeQ₁₀. The study is small and should be regarded as hypothesis-generating; however, the results are interesting and, therefore, further research in the area is needed. This study was registered at Clinicaltrials.gov, with the identifier NCT01443780.

Analysis of the Relationship Between Hemorheologic Parameters, Aluminum, Manganese, and Selenium in Smokers

Smoking is a significant risk factor in fatal pathologies including cardio-cerebrovascular and respiratory diseases. Aluminum (Al) is a toxic element without known biological function, but with recognized toxic effects. Manganese (Mn) and selenium (Se) are essential trace elements involved in cellular antioxidant defense mechanisms. Al, Mn, and Se carry out their metabolic activities via blood flow and tissue oxygenation. The structure and number of red blood cells (RBC) play important role in tissue oxygenation throughout blood flow. Increased hematocrit (Hct) as a result of probable hypoxia induces disturbed blood flow, RBC aggregation (RBC Agg), RBC deformability index (Tk), and oxygen delivery index (ODI). Therefore, we aimed to investigate the effects of altered Al, Mn, and Se levels on number, structure, and function of RBCs (Hct, blood and plasma viscosity (BV and PV, respectively), RBC Agg, Tk, ODI) in smokers without diagnosis of chronic obstructive pulmonary disease (COPD) in a study group (n = 128) categorized as ex-smokers (ES), smokers (S), and healthy controls (HC). Elements were analyzed in serum using ICP-OES. BV and PV were measured via Brookfield and Harkness viscometers at 37 °C, respectively. Smokers had statistically higher serum Al and Mn levels, BV, RBC, Hgb, Hct, PV, fibrinogen, RBC Agg, Tk₄₅, and pulmonary blood flow rate, but lower serum Se levels and ODI₄₅ values versus HC. In conclusion, increased Al, Mn, and hemorheological parameters and decreased Se and ODI₄₅ might result from inflammatory response in defense mechanism in smokers without diagnosis of COPD. Our results point out that serum Al, Mn, and Se with hemorheological parameters may be beneficial markers of tissue oxygenation and defense mechanism before the clinic onset of COPD in smokers.

Five threads: How U-shaped thinking weaves together dogs, men, selenium, and prostate cancer risk

Prostate cancer is one of the leading causes of cancer-related mortality among men living in developed countries, making the development of safe, practical approaches to prostate cancer risk reduction a high research priority. The relationship between prostate cancer risk and selenium, an essential nutrient required for a number of metabolically important enzymes including glutathione peroxidases, has been investigated, but a satisfactory integration of results has proven elusive. Dogs, like men, naturally develop prostate cancer during aging, providing an appropriate context to study the effects of selenium supplementation on the dysregulation of homeostasis that drives cancer development within the aging prostate. In this paper, we summarize the translational significance of research results gained from dog studies on selenium and prostate cancer risk. Our discovery of a U-shaped dose-response between toenail selenium concentration and prostatic DNA damage in dogs remarkably parallels data on the relationship between selenium status and prostate cancer risk in men. Notably, the dog U-curve provides a plausible explanation for the unanticipated increase in prostate cancer incidence among men with highest baseline selenium who received selenium supplementation in the largest-ever prostate cancer prevention trial (SELECT). Moreover, the dog U-curve guided the discovery of a non-antioxidant, anti-carcinogenic mechanism of organic selenium - the preferential triggering of apoptosis in DNA damaged cells, which we have termed "homeostatic housecleaning". Taken together, the data from dogs and men indicate that increasing selenium status will not necessarily be associated with prostate cancer risk reduction. Landing in the trough of the U - achieving mid-range selenium status - is better than being too low or too high. Personalizing health promotion in a more-is-not-necessarily-better world poses distinctive challenges. Dog studies can be relied upon to contribute important insights into dose-dependent and form-dependent effects - two critical aspects of selenium biology that will have to be disentangled if the burgeoning science of selenium is to be translated into effective strategies for human disease prevention. Beyond contributing to understanding the role of selenium in biology, our work situates the concept of U-shaped thinking at the core of personalized medicine and precision nutrition.

Still reduced cardiovascular mortality 12 years after supplementation with selenium and coenzyme Q10 for four years: A validation of previous 10-year follow-up results of a prospective randomized double-blind placebo-controlled trial in elderly

BACKGROUND

Selenium and coenzyme Q10 are both necessary for optimal cell function in the body. The intake of selenium is low in Europe, and the endogenous production of coenzyme Q10 decreases as age increases. Therefore, an intervention trial using selenium and coenzyme Q10 for four years as a dietary supplement was performed. The main publication reported reduced cardiovascular mortality as a result of the intervention. In the present sub-study the objective was to determine whether reduced cardiovascular (CV) mortality persisted after 12 years, in the supplemented population or in subgroups with diabetes, hypertension, ischemic heart disease or reduced functional capacity due to impaired cardiac function.

METHODS

From a rural municipality in Sweden, four hundred forty-three healthy elderly individuals were included. All cardiovascular mortality was registered, and no participant was lost to the follow-up. Based on death certificates and autopsy results, mortality was registered.

FINDINGS

After 12 years a significantly reduced CV mortality could be seen in those supplemented with selenium and coenzyme Q10, with a CV mortality of 28.1% in the active treatment group, and 38.7% in the placebo group. A multivariate Cox regression analysis demonstrated a reduced CV mortality risk in the active treatment group (HR: 0.59; 95%CI 0.42-0.81; P = 0.001). In those with ischemic heart disease, diabetes, hypertension and impaired functional capacity we demonstrated a significantly reduced CV mortality risk.

CONCLUSIONS

This is a 12-year follow-up of a group of healthy elderly participants that were supplemented with selenium and coenzyme Q10 for four years. Even after twelve years we observed a significantly reduced risk for CV mortality in this group, as well as in subgroups of patients with diabetes, hypertension, ischemic heart disease or impaired functional capacity. The results thus validate the results obtained in the 10-year evaluation. The protective action was not confined to the intervention period, but persisted during the follow-up period. The mechanisms behind this effect remain to be fully elucidated, although various effects on cardiac function, oxidative stress, fibrosis and inflammation have previously been identified. Since this was a small study, the observations should be regarded as hypothesis-generating.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01443780.

The association between irisin levels, element distribution and oxidative stress markers in adolescent swimmers

The objective of this investigation was to compare irisin concentration and its relation with oxidative stress markers, antioxidant enzymes and element levels in both male adolescent swimmers and sedentary controls. Twelve male swimmers aged between 11 and 18 years, who performed regular swimming training for at least 2 years and 12 age- and gender-matched sedentary controls participated in this study. After anthropometric measurements were performed, fasting venous blood samples were taken at rest. Irisin, malondialdehyde (MDA) as a marker of oxidative stress, superoxide dismutase (SOD) as a marker of antioxidant enzyme and elements (Zn, Cu, Se, Cr, Ni, Al, Fe) were analyzed in these samples. MDA levels were lower but Zn levels and Zn/Cu ratio were higher in the swimmers than in sedentary controls (p < 0.05). There was no statistically significant difference in the irisin levels and SOD activities between the groups (p > 0.05). The results of the current study suggested that exercise training has antioxidant effects and may reduce oxidative damage. Exercise training has also limited effects on irisin levels in the adolescents.

Serum Trace Elements Profile in Graves' Disease Patients with or without Orbitopathy in Northeast China

Objective

The purpose of the present study was to investigate serum trace elements in Graves' disease (GD) patients with or without orbitopathy in Northeast China.

Methods

Patients with newly diagnosed Graves' disease (HyGD) (n = 66), GD patients with euthyroid status or subclinical thyroidism after treatment (EUGD) (n = 55), GO patients with euthyroid status or subclinical thyroidism after treatment (GO) (n = 57), and normal controls (NC) (n = 66) were enrolled in this study. Serum trace elements were measured with ICP-MS.

Results

Serum selenium (Se) levels in EUGD group (median: 7.53 µg/dL), HyGD group (median: 6.76 µg/dL), and GO group (median: 7.40 µg/dL) were significantly lower than those in NC group (median: 9.20 µg/dL, all P < 0.01). Serum copper (Cu) levels in GO group (median: 95.93 µg/dL) were significantly lower than those in the NC group (median: 113.59 µg/dL, P = 0.015). After being adjusted for multivariables, thyroid-specific antibodies grade was associated with low Se levels. Hyperthyroidism and thyroid-specific antibodies grade were associated with high Cu levels. In addition, orbitopathy was associated with low Cu levels.

Conclusions

Thyroid autoimmunity was associated with low Se levels. Hyperthyroidism and thyroid autoimmunity may be associated with relatively high serum Cu levels. Alternatively, ophthalmopathy may be related to low serum Cu levels.

Supplementation with Selenium and Coenzyme Q10 Reduces Cardiovascular Mortality in Elderly with Low Selenium Status. A Secondary Analysis of a Randomised Clinical Trial

Background

Selenium is needed by all living cells in order to ensure the optimal function of several enzyme systems. However, the selenium content in the soil in Europe is generally low. Previous reports indicate that a dietary supplement of selenium could reduce cardiovascular disease but mainly in populations in low selenium areas. The objective of this secondary analysis of a previous randomised double-blind placebo-controlled trial from our group was to determine whether the effects on cardiovascular mortality of supplementation with a fixed dose of selenium and coenzyme Q10 combined during a four-year intervention were dependent on the basal level of selenium.

Methods

In 668 healthy elderly individuals from a municipality in Sweden, serum selenium concentration was measured. Of these, 219 individuals received daily supplementation with selenium (200 μg Se as selenized yeast) and coenzyme Q10 (200 mg) combined for four years. The remaining participants (n = 449) received either placebo (n = 222) or no treatment (n = 227). All cardiovascular mortality was registered. No participant was lost during a median follow-up of 5.2 years. Based on death certificates and autopsy results, all mortality was registered.

Findings

The mean serum selenium concentration among participants at baseline was low, 67.1 μg/L. Based on the distribution of selenium concentration at baseline, the supplemented group was divided into three groups; <65 μg/L, 65–85 μg/L, and >85 μg/L (45 and 90 percentiles) and the remaining participants were distributed accordingly. Among the non-treated participants, lower cardiovascular mortality was found in the high selenium group as compared with the low selenium group (13.0% vs. 24.1%; P = 0.04). In the group with the lowest selenium basal concentration, those receiving placebo or no supplementation had a mortality of 24.1%, while mortality was 12.1% in the group receiving the active substance, which was an absolute risk reduction of 12%. In the middle selenium concentration group a mortality of 14.0% in the non-treated group, and 6.0% in the actively treated group could be demonstrated; thus, there was an absolute risk reduction of 8.0%. In the group with a serum concentration of >85 μg/L, a cardiovascular mortality of 17.5% in the non-treated group, and 13.0% in the actively treated group was observed. No significant risk reduction by supplementation could thus be found in this group.

Conclusions

In this evaluation of healthy elderly Swedish municipality members, two important results could be reported. Firstly, a low mean serum selenium concentration, 67 μg/L, was found among the participants, and the cardiovascular mortality was higher in the subgroup with the lower selenium concentrations <65 μg/L in comparison with those having a selenium concentration >85 μg/L. Secondly, supplementation was cardio-protective in those with a low selenium concentration, ≤85 at inclusion. In those with serum selenium>85 μg/L and no apparent deficiency, there was no effect of supplementation. This is a small study, but it presents interesting data, and more research on the impact of lower selenium intake than recommended is therefore warranted.

Trial Registration

Clinicaltrials.gov NCT01443780

Relatively high mortality risk in elderly Swedish subjects with low selenium status

Background/Objectives:

The daily dietary intake of selenium (Se), an essential trace element, is still low in Sweden in spite of decades of nutritional information campaigns and the effect of this on the public health is presently not well known. The objective of this study was to determine the serum Se levels in an elderly Swedish population and to analyze whether a low Se status had any influence on mortality.

Subjects/Methods:

Six-hundred sixty-eight (n=668) elderly participants were invited from a municipality and evaluated in an observational study. Individuals were followed for 6.8 years and Se levels were re-evaluated in 98 individuals after 48 months. Clinical examination of all individuals included functional classification, echocardiography, electrocardiogram and serum Se measurement. All mortality was registered and endpoints of mortality were assessed by Kaplan–Meier plots, and Cox proportional hazard ratios adjusted for potential confounding factors were calculated.

Results:

The mean serum Se level of the study population (n=668) was 67.1 μg/l, corresponding to relatively low Se intake. After adjustment for male gender, smoking, ischemic heart disease, diabetes, chronic obstructive pulmonary disease and impaired heart function, persons with serum Se in the lowest quartile had 43% (95% confidence interval (CI): 1.02–2.00) and 56% (95% CI: 1.03–2.36) increased risk for all-cause and cardiovascular mortality, respectively. The result was not driven by inflammatory effects on Se concentration in serum.

Conclusion:

The mean serum Se concentration in an elderly Swedish population was 67.1 μg/l, which is below the physiological saturation level for several selenoprotein enzymes. This result may suggest the value of modest Se supplementation in order to improve the health of the Swedish population.

Determination of selenium in serum in the presence of gadolinium with ICP-QQQ-MS

Triple–quadrupole ICP-MS using O₂mass-shift technology is superior for removing gadolinium interference on selenium in serum.

Plasma levels of trace elements and exercise induced stress hormones in well-trained athletes

This study analyzed the variation and relationship of several trace elements, metabolic substrates and stress hormones activated by exercise during incremental exercise. Seventeen well-trained endurance athletes performed a cycle ergometer test: after a warm-up of 10 min at 2.0 W kg(-1), the workload was increased by 0.5 W kg(-1) every 10 min until exhaustion. Prior diet, activity patterns, and levels of exercise training were controlled, and tests timed to minimize variations due to the circadian rhythm. Oxygen uptake, blood lactate concentration, plasma ions (Zn, Se, Mn and Co), serum glucose, non-esterified fatty acids (NEFAs) and several hormones were measured at rest, at the end of each stage and 3, 5 and 7 min post-exercise. Urine specific gravity was measured before and after the test, and participants drank water ad libitum. Significant differences were found in plasma Zn and Se levels as a function of exercise intensity. Zn was significantly correlated with epinephrine, norepinephrine and cortisol (r = 0.884, P < 0.01; r = 0.871, P < 0.01; and r = 0.808, P = 0.05); and Se showed significant positive correlations whit epinephrine and cortisol (r = 0.743, P < 0.05; and r = 0.776, P < 0.05). Neither Zn nor Se levels were associated with insulin or glucagon, and neither Mn nor Co levels were associated with any of the hormones or substrate metabolites studied. Further, while Zn levels were found to be associated only with lactate, plasma Se was significantly correlated with lactate and glucose (respectively for Zn: r = 0.891, P < 0.01; and for Se: r = 0.743, P < 0.05; r = 0.831, P < 0.05). In conclusion, our data suggest that there is a positive correlation between the increases in plasma Zn or Se and stress hormones variations induced by exercise along different submaximal intensities in well-hydrated well-trained endurance athletes.

The role of selenium in human conception and pregnancy

Selenium (Se) is a trace element essential for the appropriate course of vital processes in the human body. It is also a constituent of the active center of glutathione peroxidase that protects cellular membranes against the adverse effects of H2O2 lipid peroxides. Epidemiological surveys have demonstrated that selenium deficiency in the body may contribute to an increased risk for certain neoplasmic diseases (including colonic carcinoma, gastric carcinoma, pulmonary carcinoma and prostate carcinoma), as well as diseases of the cardiovascular, osseous and nervous systems. Apart from its cancer prevention and antioxidative activities, selenium protects the body against detrimental effects of heavy metals and determines the proper functioning of the immunological system. Furthermore, selenium plays a significant role in the undisturbed functioning of the reproductive system. Many studies have addressed correlations between its intake and fertility as well as disorders of procreation processes. Selenium deficiencies may lead to gestational complications, miscarriages and the damaging of the nervous and immune systems of the fetus. A low concentration of selenium in blood serum in the early stage of pregnancy has been proved to be a predictor of low birth weight of a newborn. A deficiency of this element may also cause infertility in men by causing a deterioration in the quality of semen and in sperm motility. For this reason, supplementation in the case of selenium deficiencies in the procreation period of both women and men is of utmost significance.

Selenium status in patients with autoimmune and non-autoimmune thyroid diseases from four European countries

CONTEXT

Selenium supplementation has been suggested for Hashimoto thyroiditis and Graves' ophthalmopathy. Objective, Design: Our aim is to measure selenium status (p-Se, p-SePP), urine iodine (UI) levels and urine iodine/creatinine ratio (UI/C) in different thyroid diseases (n = 416) from four European countries and to compare the results between patients with and without thyroid autoimmunity.

RESULTS

p-Se and p-SePP showed positive correlation and did not correlate with UI/C. Also, these measurements were higher in patients from Italy in comparison with the other countries. Austria had the lowest UI/C ratios. Selenium deficiency exists in these four European countries. Selenium status was lower in patients with Hashimoto thyroiditis and Graves' disease in comparison with non-autoimmune thyroid disease patients and did not differ between autoimmune patients with or without thyroid peroxidase antibodies. The latter correlated positively with age.

CONCLUSIONS

Our findings suggest that Se supplementation might have a beneficial effect in autoimmune thyroid patients.

Gender-specific distribution of selenium to serum selenoproteins: associations with total selenium levels, age, smoking, body mass index, and physical activity

The epidemiology of selenium (Se) is mainly based on the determination of total serum selenium levels (TSe) which by many aspects is an inadequate marker of Se status. In this study we applied a recently developed LC-ICP-MS method, for the determination of the selenium content of the three main serum selenium-containing proteins, in a subcohort of the ATTICA study. This enables us to investigate whether the selenium distribution to selenoproteins may correlate with demographic (age, gender) and lifestyle variables (smoking, physical activity) that are crucial for the development of chronic diseases. A sub-sample from the ATTICA Study, consisted of 236 males (40 ± 11 years) and 163 females (38 ± 12 years), was selected. The selenium content of glutathione peroxidase (GPx-3), selenoprotein P (SelP) and selenoalbumin (SeAlb) was determined in serum by LC-ICP/MS method. We found that 26% of TSe is found in GPx-3, 61% in SelP and 13% in SeAlb. We have assessed the different ratios of selenoproteins' selenium content (Se-GPX-3/Se-SelP, Se-GPX-3/Se-SeAlb, Se-SelP/Se-SeAlb), showing that people with similar TSe may have different distribution of this selenium to selenoproteins. Total selenium levels and gender are the variables that mostly affect selenium distribution to selenoproteins while age, smoking, physical activity and BMI do not significantly influence selenium distribution. In conclusion, the simultaneous determination of the selenium content of serum selenium-containing selenoproteins is necessary for a thorough estimation of selenium status. The ratio of the Se content between selenoproteins may be proven a novel, valid marker of selenium status.

Study of selenium intake and disposition in various matrices based on mathematical algorithms derived from pooled biomonitoring data

Biomonitoring is increasingly used to assess exposure to selenium (Se) in the population. However, there is little harmonization among protocols used in the different studies (varying biological matrices, differences in expression of results (concentrations versus amounts, units)). This makes inter-comparison of biomonitoring results across studies difficult. From a public health risk perspective, it also becomes challenging to estimate baseline levels in biological matrices for populations exposed by various sources. The aim of this study was thus to perform a systematic analysis of the relationship between Se intakes and biological concentrations based on published data. Inclusion and exclusion criteria were used and led to select 75 published biomonitoring data in humans from an extended review of Se biomonitoring studies. This represents 8 628 individuals who provided biological samples aiming at documenting Se exposure and/or Se concentrations in two or more biological matrices. Mathematical algorithms that relate Se intakes to biological concentrations and establish matrix-to-matrix associations were derived from these pooled biomonitoring data. Logarithmic regressions showed good correlations between Se intakes and whole blood concentrations (R(2)=0.884), plasma concentrations (R(2)=0.863) and urinary excretion rates (R(2)=0.958). Blood and plasma concentrations were also strongly related (R(2)=0.874), as were whole blood concentrations and urinary excretion rates (R(2)=0.953). The interpretation of the log-regression coefficients allowed illustrating Se physiology. Se concentrations in plasma tend to plateau when daily intake exceed 150 μg/d, whereas Se in urine increases rapidly above this threshold. The application of the algorithms to other independent data sets in order to reconstruct past Se intakes confirmed that interpretation of results on the basis of Se in integuments may be misleading if external contamination is not avoided. This approach based on pooled data covered a wide range of exposure and the large number of data integrated increased the level of confidence of results.

Influence of training frequency on serum concentrations of some essential trace elements and electrolytes in male swimmers

Elemental fluctuations during physical performances have been a point of interest. This study was designed to investigate the effect of swimming frequency on serum concentrations of some trace elements (chromium, iron, copper, zinc, selenium) and electrolytes (sodium, magnesium, potassium, calcium). Three groups of different-level male swimmers were included in the study, as elite swimmers (n = 14), amateur swimmers (n = 11), and sedentary individuals (n = 10). Elite and amateur swimmer groups followed a 3-week training program. At the end of the period, all volunteers were subjected to a controlled swimming test, and blood samples were collected at the beginning of (pre-test), immediately after (post-test), and 1 h after this activity. Element concentrations were determined by inductively coupled plasma mass spectrometry using a dilute and shoot procedure. Apart from the swimming test applied, pre-test calcium and potassium levels were higher in elite swimmers compared to amateurs and controls. The difference in pre-test levels of these elements can be associated with adaptive mechanisms emerged by the frequent training. Regarding the test applied, changes in magnesium, calcium, copper, zinc, and selenium levels exhibited a common pattern in all study groups, with higher post-test serum concentrations. Another point of note was a drop of copper, zinc, and selenium levels at 1 h after the test in elite swimmers. The decrease in serum zinc was also observed in the other groups. Results highlight the value of regular control of elemental status to provide insight into transient effects and deficiencies.

Adaptive dysfunction of selenoproteins from the perspective of the triage theory: why modest selenium deficiency may increase risk of diseases of aging

The triage theory proposes that modest deficiency of any vitamin or mineral (V/M) could increase age-related diseases. V/M-dependent proteins required for short-term survival and/or reproduction (i.e., "essential") are predicted to be protected on V/M deficiency over other "nonessential" V/M-dependent proteins needed only for long-term health. The result is accumulation of insidious damage, increasing disease risk. We successfully tested the theory against published evidence on vitamin K. Here, we review about half of the 25 known mammalian selenoproteins; all of those with mouse knockout or human mutant phenotypes that could be used as criteria for a classification of essential or nonessential. Five selenoproteins (Gpx4, Txnrd1, Txnrd2, Dio3, and Sepp1) were classified as essential and 7 (Gpx1, Gpx 2, Gpx 3, Dio1, Dio2, Msrb1, and SelN) nonessential. On modest selenium (Se) deficiency, nonessential selenoprotein activities and concentrations are preferentially lost, with one exception (Dio1 in the thyroid, which we predict is conditionally essential). Mechanisms include the requirement of a special form of tRNA sensitive to Se deficiency for translation of nonessential selenoprotein mRNAs except Dio1. The same set of age-related diseases and conditions, including cancer, heart disease, and immune dysfunction, are prospectively associated with modest Se deficiency and also with genetic dysfunction of nonessential selenoproteins, suggesting that Se deficiency could be a causal factor, a possibility strengthened by mechanistic evidence. Modest Se deficiency is common in many parts of the world; optimal intake could prevent future disease.

High-throughput quantification of selenium in individual serum proteins from a healthy human population using HPLC on-line with isotope dilution inductively coupled plasma-MS

In this study, a method, based on dual column affinity chromatography hyphenated to isotope dilution inductively coupled plasma-quadrupole MS, was developed for selenium determination in selenoprotein P, glutathione peroxidase, and selenoalbumin in human serum samples from a group of healthy volunteers (n=399). Method improvement was achieved using methanol-enhanced isotope dilution which resulted in improved sensitivity and removal of isobaric interferences. Although no human serum reference materials are currently certified for their selenium species levels, method development was conducted using human serum reference material BCR 637 and 639 as their Se species content has been reported in the previous studies, and thus comparisons were possible. The mean selenium concentrations determined for the 399 healthy volunteer serum samples were 23 ± 10 ng Se mL(-1) for glutathione peroxidase, 49 ± 15 ng Se mL(-1) for selenoprotein P and 11 ± 4 ng Se mL(-1) for selenoalbumin. These values are found to be in close agreement with published values for a limited number of healthy volunteer samples, and to establish baseline Se levels in serum proteins for an apparently healthy group of individuals, thus allowing for subsequent comparisons with respective values determined for groups of individuals with selenium related health issues, as well as assist in the discovery of potential selenium biomarkers. Also, the relationship between Se serum protein levels and some anthropometric characteristics of the volunteer population were investigated. Additionally, further development of the analytical method used in this study was achieved by adding a size exclusion chromatography column after the two affinity columns via a switching valve. This allowed for the separation of small selenium-containing molecules from glutathione peroxidase and thus enhanced the overall confidence in its identification.

Dietary habits of Greek adults and serum total selenium concentration: the ATTICA study

PURPOSE

The trace element selenium is an essential micronutrient for human health, and its low levels in serum are implicated in the pathogenesis of several chronic diseases. The determination of total serum selenium levels may contribute to the assessment of the health status of all populations. Since the serum selenium levels are highly affected by diet, we assessed its association with the dietary habits of Greek adults.

METHODS

Serum selenium levels were determined with inductively coupled plasma mass spectrometry in a cohort of 506 participants (men: 296, women: 210) aged 18-75 from the ATTICA study. Food consumption was evaluated with a validated food-frequency questionnaire.

RESULTS

Evaluation of the relationship between serum total selenium with major food groups and beverages by multi-adjusted analysis revealed that serum selenium was positively correlated with the consumption of red meat (2.37 ± 0.91, p = 0.01) while the consumption of other selenium-containing foods (i.e., fish, cereals, dairy products, vegetables) did not demonstrate such a relationship. Moreover, principal component analysis revealed that the adoption of a vegetarian type of diet is inversely correlated with total selenium (-3.94 ± 2.28, p = 0.08).

CONCLUSIONS

Among the dietary habits that were examined, red meat seems to be the major determinant of serum selenium in Greek adults.

Plasma levels of copper, manganese and selenium in an adult population in southern Spain: influence of age, obesity and lifestyle factors

Copper, manganese and selenium are elements involved in protecting the body against oxidative stress. Determining their plasma level may contribute to assessing the health and nutritional status of populations. The aim of this study was to assess factors influencing copper, manganese and selenium plasma levels in an adult Mediterranean population and to identify groups at risk of deficiency. A cross-sectional survey was carried out in Andalusia, a region in southern Spain. Blood samples were obtained in a random subsample of 340 subjects. Food consumption was assessed by 48-h recall. Height, weight, skinfolds, waist and hip circumferences were measured. Copper, manganese and selenium were measured in plasma. Information about physical exercise, educational level, alcohol and smoking habits was obtained with a structured questionnaire. Plasma copper was found to be higher in women than among men. Hypocupraemia was found in 4.4% of the population, while 9.7% presented hypomanganesemia. Moreover, 86.5% presented plasma selenium values below 125microg/L (cutoff for optimal glutathione peroxidase activity). No association was found between plasma elements, anthropometric indices and lifestyle factors; there were tendencies, no more. Copper tended to decrease in obese and increase in sedentary, while selenium tended to decrease among smokers. Plasma Cu was positively correlated with the consumption of monounsaturated and polyunsaturated fats. Plasma Mn was directly correlated with the consumption of dairy products. Levels of Se were positively correlated with age, the consumption of fruit, vegetables, energy obtained from carbohydrates, and the consumption of fibre, and inversely correlated with the consumption of meat and sweets. Our results provide an estimate of the copper, manganese and selenium status in the adult population of southern Spain. The correlations found for Se suggest that there is a tendency for Se levels to be better maintained among the population that shows a stronger preference for the traditional diet.

Nutritional status of selenium in Alzheimer's disease patients

Studies have shown that various antioxidants are decreased in different age-related degenerative diseases and thus, oxidative stress would have a central role in the pathogenesis of many disorders that involve neuronal degeneration, including Alzheimer's disease (AD). The present study aimed to assess the nutritional status of Se in AD patients and to compare with control subjects with normal cognitive function. The case–control study was carried out on a group of elderly with AD (n 28) and compared with a control group (n 29), both aged between 60 and 89 years. Se intake was evaluated by using a 3-d dietary food record. Se was evaluated in plasma, erythrocytes and nails by using the method of hydride generation atomic absorption spectroscopy. Deficient Se intake was largely observed in the AD group. AD patients showed significantly lower Se levels in plasma, erythrocytes and nails (32·59 μg/l, 43·74 μg/l and 0·302 μg/g) when compared with the control group (50·99 μg/l, 79·16 μg/l and 0·400 μg/g). The results allowed us to suggest that AD has an important relation with Se deficiency.