Factors associated with longitudinal plasma selenium decline in the elderly: the EVA study

Influence of smoking status on the relationship between serum selenium and cause-specific mortality in US adults

Selenium, a crucial antioxidant in the body, has been linked to all-cause and cause-specific mortality. However, the relationship between selenium and mortality in the general population remains unclear. A total of 5449 participants in the National Health and Nutrition Examination Survey (NHANES) (2003-2004, 2011-2016) were analyzed to track participant mortality until December 31, 2019. The COX proportional hazard model, Kaplan‒Meier survival analysis and restricted cubic spline regression analysis were used to investigate the associations. Subgroup analysis was conducted on the basis of age (≤ 60, > 60), sex (male, female), and smoking status (nonsmoker, former smoker, and current smoker). The second quartile was associated with lower all-cause mortality and noncardiovascular mortality (HR and 95% CI 0.61,0.45-0.83;0.59,0.42-0.83, respectively). The third quartile was associated with lower cardiovascular-related mortality (HR and 95% CI 0.49, 0.32-0.76). Elevated serum selenium concentrations were associated with lower all-cause mortality, noncardiovascular mortality (range ≤ 129.82 μg/L), and cardiovascular mortality (range ≤ 129.08 μg/L). Subgroup analysis revealed a positive correlation between the serum selenium concentration (range ≥ 129.82 μg/L) and all-cause mortality among the subgroup of current smokers (p < 0.001). This study indicates that the protective effect of the serum selenium concentration on cause-specific mortality decreases beyond a certain range in the general population, potentially increasing the risk of death among current smokers.

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.

Nontoxic Levels of Se-Containing Compounds Increase Survival by Blocking Oxidative and Inflammatory Stresses via Signal Pathways Whereas High Levels of Se Induce Apoptosis

Selenium is a main group element and an essential trace element in human health. It was discovered in selenocysteine (SeC) by Stadtman in 1974. SeC is an encoded natural amino acid hailed as the 21st naturally occurring amino acid (U) present in several enzymes and which exquisitely participates in redox biology. As it turns out, selenium bears a U-shaped toxicity curve wherein too little of the nutrient present in biology leads to disorders; concentrations that are too great, on the other hand, pose toxicity to biological systems. In light of many excellent previous reviews and the corpus of literature, we wanted to offer this current review, in which we present aspects of the clinical and biological literature and justify why we should further investigate Se-containing species in biological and medicinal contexts, especially small molecule-containing species in biomedical research and clinical medicine. Of central interest is how selenium participates in biological signaling pathways. Several clinical medical cases are recounted; these reports are mainly pertinent to human cancer and changes in pathology and cases in which the patients are often terminal. Selenium was an option chosen in light of earlier chemotherapeutic treatment courses which lost their effectiveness. We describe apoptosis, and also ferroptosis, and senescence clearly in the context of selenium. Other contemporary issues in research also compelled us to form this review: issues with CoV-2 SARS infection which abound in the literature, and we described findings with human patients in this context. Laboratory scientific studies and clinical studies dealing with two main divisions of selenium, organic (e.g., methyl selenol) or inorganic selenium (e.g., sodium selenite), are discussed. The future seems bright with the research and clinical possibilities of selenium as a trace element, whose recent experimental clinical treatments have so far involved dosing simply and inexpensively over a set of days, amounts, and time intervals.

Selenium concentration is associated with occurrence and diagnosis of three cardiovascular diseases: A systematic review and meta-analysis

BACKGROUND

Selenium (Se) is a vital trace element playing its biological functions through selenoprotein, which has been implicated in various physiological and pathological processes. A growing number of studies indicate that low Se increases the risk of cardiovascular diseases (CVDs). This meta-analysis aimed to compare and analyze differences in Se levels between patients with heart failure (HF), myocardial infarction (MI), coronary heart disease (CHD), and healthy people. This will provide ideas with the potential to improve clinical intervention and prevention of CVDs.

METHODS

The PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI) and Chinese Biomedical databases were systematically searched for relevant publications until November 20, 2020. The following combination keywords were used: "(heart failure disease OR myocardial infarction OR coronary heart disease) AND (selenium OR Se)". The identified studies were screened against inclusion and exclusion criteria and extracted data were analyzed using RevMan5.3 and State 16.0 software.

RESULTS

A total of 49 eligible studies (including 61 cohorts) were obtained. Results of the meta-analysis showed that there was a significant difference in Se levels between HF, MI, CHD patients and healthy people. The standard mean difference (SMD) level of Se in HF patients [SMD = -0.98, 95 % CI (-1.34, -0.62)], MI patients [MI: SMD = -3.46, 95 % CI (-4.43, -2.85)], and CHD patients [CHD: SMD = -0.47, 95 % CI (-0.64, -0.28)] were all significantly lower compared to healthy controls. Analysis of the correlation between Se level and publication year showed that SMD of Se levels in HF and controls was positively correlated with time. Se level was found to be a good diagnostic marker of MI (AUC = 0.7107, P = 0.0167, Sensitivity = 77.27 %, Specificity = 72.73 %).

CONCLUSIONS

This meta-analysis shows that Se levels in patients with HF, MI, and CHD are generally lower compared with healthy controls. However, due to the small number of included studies, further studies are needed to confirm the present results.

Serum Zinc and Selenium Concentrations in Patients with Hypertrophy and Remodelling of the Left Ventricle Secondary to Arterial Hypertension

The aim of the study was to assess the relationship between serum selenium and zinc concentrations (Se-S and Zn-S) and the left ventricle geometry in patients suffering from arterial hypertension. A total of 78 people with arterial hypertension (mean age: 53.72 ± 12.74 years) participated in the study. Se-S and Zn-S were determined in all patients. The type of left ventricular remodelling and hypertrophy was determined by the left ventricular mass index (LVMI) and relative wall thickness (RWT) measured by echocardiography. Se-S and Zn-S in the whole group were 89.84 ± 18.75 µg/L and 0.86 ± 0.13 mg/L. Normal left ventricular geometry was found in 28.2% of patients; left ventricular hypertrophy (LVH) in 71.8%, including concentric remodelling in 28.2%, concentric hypertrophy in 29.5%, and eccentric hypertrophy in 14.1%. LVH was statistically significantly more frequent in patients with Se-S < median compared to patients with Se-S ≥ median (87.2% vs. 56.4%, p < 0.05), as well as in patients with Zn-S < median compared to patients with Zn-S ≥ median (83.8% vs. 60.9%, p < 0.05). In hypertensive patients, older age, higher LDL cholesterol, higher fasting glucose, lower Se-S, and lower Zn-S were independently associated with LVH. In conclusion, in hypertensive patients, left ventricular hypertrophy may be associated with low levels of selenium and zinc in the serum.

The association between blood metals and hypertension in the GuLF study

BACKGROUND

Both essential and non-essential metals come from natural and anthropogenic sources. Metals can bioaccumulate in humans and may impact human health, including hypertension.

METHODS

Blood metal (cadmium, lead, mercury, manganese, and selenium) concentrations were measured at baseline for a sample of participants in the Gulf Long-Term Follow-up (GuLF) Study. The GuLF Study is a prospective cohort study focused on potential health effects following the 2010 Deepwater Horizon oil spill. Hypertension was defined as high systolic (≥140 mm Hg) or diastolic (≥90 mm Hg) blood pressure or taking anti-hypertensive medications. A total of 957 participants who had blood measurement for at least one metal, baseline blood pressure measurements, information on any anti-hypertensive medication use, and relevant covariates were included in this cross-sectional analysis. We used Poisson regression to explore the association between individual blood metal levels and hypertension. Quantile-based g-computation was used to investigate the association between the metal mixture and hypertension. We also explored the association between individual blood metal levels and continuous blood pressure measurements using general linear regression.

RESULTS

Comparing the highest quartile of blood metals with the lowest (Q4vs1), the hypertension prevalence ratio (PR) was 0.92 (95 % confidence interval (CI) = 0.73,1.15) for cadmium, 0.86 (95%CI = 0.66,1.12) for lead, 0.89 (95%CI = 0.71,1.12) for mercury, 1.00 (95%CI = 0.80,1.26) for selenium, and 1.22 (95%CI = 0.95,1.57) for manganese. We observed some qualitative differences across race and BMI strata although none of these differences were statistically significant. In stratified analyses, the PR (Q4vs1) for mercury was 0.69 (95%CI = 0.53, 0.91) in White participants and 1.29 (95%CI = 0.86,1.92) in Black participants (p for interaction = 0.5). The PR (Q4vs1) for manganese was relatively higher in Black participants (PR = 1.37, 95%CI = 0.92,2.05) than in White participants (PR = 1.15, 95%CI = 0.83,1.60, p for interaction = 0.5), with a suggestive dose-response among Blacks. After stratifying by obesity (BMI ≥30 and < 30), positive associations of of hypertension with cadmium (PR [Q4vs1] = 1.19, 95%CI = 0.91,1.56, p for interaction = 0.5), lead (PR [Q4vs1] = 1.14, 95%CI = 0.84,1.55, p for interaction = 1.0) and manganese (PR = 1.25, 95%CI = 0.93,1.68, p for interaction = 0.8) were observed in participants with BMI≥30, but not in participants with BMI<30. The joint effect of the metal mixture was 0.96 (95%CI = 0.73,1.27). We did not observe clear associations between blood metal levels and continuous blood pressure measurements.

CONCLUSION

We did not find overall cross-sectional associations between blood cadmium, lead, mercury, selenium levels and hypertension or blood pressure. We found some evidence suggesting that manganese might be positively associated with risk of hypertension. Associations varied somewhat by race and BMI.

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.

Associations between urinary heavy metal concentrations and blood pressure in residents of Asian countries

BACKGROUND

Previous studies have suggested that exposures to heavy metals (arsenic, cadmium, lead, and selenium) may be associated with differences in blood pressure. However, the findings of these studies have been inconsistent. This study was performed to examine the associations between urinary heavy metal concentrations and blood pressure among residents of four Asian countries (Bangladesh, Indonesia, Nepal, and Vietnam).

METHODS

This cross-sectional study examined 1899 adults in four Asian countries. Urinary concentrations of heavy metals were measured by inductively coupled plasma mass spectrometry. A questionnaire survey was administered regarding individual characteristics. Anthropometric measurements (height and weight) were performed. Systolic and diastolic blood pressures were measured after a short rest. Multiple linear regression models were applied to investigate associations between urinary heavy metal concentrations and blood pressure after adjustments for age, sex, and body mass index.

RESULTS

The geometric means of the urinary concentrations of arsenic, cadmium, lead, and selenium were 84.6, 0.885, 2.09, and 16.5 μg/g creatinine, respectively. The urinary arsenic concentrations were slightly higher than those typically reported in non-polluted populations, while urinary cadmium, lead, and selenium concentrations were equivalent or slightly lower. The urinary lead concentrations were positively associated with both systolic and diastolic blood pressure, but urinary selenium concentrations were negatively associated with them.

CONCLUSIONS

Variations in the urinary concentrations of lead and selenium were associated with blood pressure at low levels of exposure/intake.

The importance of selenium and zinc deficiency in cardiovascular disorders

Cardiovascular diseases often linked with lifestyle are among the main causes of death, especially in the elderly population. The role of trace elements in health and disease has been emphasized in multiple scientific research. Moreover, supplementation of trace elements to improve health is becoming increasingly popular. The following paper presents current views on the relationship between the concentration of trace elements such as selenium and zinc in the body, as well as morphology and function of the cardiovascular system. Research discussing the effect of selenium and zinc supplementation on the function of the heart and blood vessels was also reviewed. The relationship between selenium and zinc concentration and morphology and function of the cardiovascular system is equally unclear, and therefore there is currently no scientific evidence for its supplementation for preventing cardiovascular diseases. It seems justified to continue scientific research on this subject due to the small number of experimental studies available on the topic of selenium and zinc deficiency and their impact on the cardiovascular system.

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.

Aging affects sex- and organ-specific trace element profiles in mice

A decline of immune responses and dynamic modulation of the redox status are observed during aging and are influenced by trace elements such as copper, iodine, iron, manganese, selenium, and zinc. So far, analytical studies have focused mainly on single trace elements. Therefore, we aimed to characterize age-specific profiles of several trace elements simultaneously in serum and organs of adult and old mice. This allows for correlating multiple trace element levels and to identify potential patterns of age-dependent alterations. In serum, copper and iodine concentrations were increased and zinc concentration was decreased in old as compared to adult mice. In parallel, decreased copper and elevated iron concentrations were observed in liver. The age-related reduction of hepatic copper levels was associated with reduced expression of copper transporters, whereas the increased hepatic iron concentrations correlated positively with proinflammatory mediators and Nrf2-induced ferritin H levels. Interestingly, the age-dependent inverse regulation of copper and iron was unique for the liver and not observed in any other organ. The physiological importance of alterations in the iron/copper ratio for liver function and the aging process needs to be addressed in further studies.

Circulating Selenium and Cardiovascular or All-Cause Mortality in the General Population: a Meta-Analysis

The association of circulating selenium level with mortality remains controversial. This meta-analysis investigated the association between elevated circulating selenium level and cardiovascular or all-cause mortality in the general population. PubMed and Embase databases (up to January 20, 2019) were searched for observational studies or post hoc analyses of randomized controlled trials that evaluated the association between elevated circulating selenium level and cardiovascular or all-cause mortality in the general population. Twelve observational studies (ten cohort and two case-control studies) with a total of 25,667 individuals were included. Comparison with the lowest and the highest circulating selenium level showed that the pooled risk ratio (RR) values of all-cause mortality and cardiovascular mortality were 1.36 (95% confidence intervals [CI] 1.18-1.58) and 1.35 (95% CI 1.13-1.62), respectively. When analyzed selenium level as a continuous variable, each standard deviation selenium increase significantly reduced 20% all-cause mortality risk. However, the lowest circulating selenium level was not associated with a high risk of coronary mortality (RR 1.43; 95% CI 0.93-2.19). This meta-analysis indicated that low circulating selenium level was associated with higher risk of cardiovascular or all-cause mortality in the general population. Low circulating selenium level did not confer significant effect on coronary death.

Selenium Status in Elderly People: Longevity and Age-Related Diseases

BACKGROUND

Selenium (Se) is a trace element active in selenoproteins, which can regulate oxidative stress. It is generally perceived as an import factor for maintaining health in the elderly.

METHODS

The goal of this review is to discuss selenium concentration in biological samples, primarily serum or plasma, as a function of age and its relation with longevity. The elemental level in various age-related diseases is reviewed.

CONCLUSION

Highest selenium values were observed in healthy adults, while in an elderly population significantly lower concentrations were reported. Variables responsible for contradictory findings are mentioned. Risk and benefits of Se-supplementation still remain under debate.

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.

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.

Selenium intake and metabolic syndrome: A systematic review

BACKGROUND & AIMS

Metabolic syndrome is a multi-causal disease. Its treatment includes lifestyle changes with a focus on weight loss. This systematic review assessed the association between Selenium intake and metabolic syndrome.

METHODS

Data were collected mainly from four databases: PubMed, CENTRAL (Cochrane), Scopus and Web of Knowledge. Keywords related to metabolic syndrome, selenium, as well as metabolic syndrome features were searched. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement. A systematic review protocol was registered at PROSPERO (n. 42016046321). Two reviewers independently screened 2957 abstracts. Six studies were included to perform data extraction with standardized spreadsheets. The risk of bias was assessed by using specific tools according to the design of the relevant studies. An assessment was carried out based on the appropriateness of the study reports accordingly to STROBE and the CONSORT-based checklist for each study design.

RESULTS

Three studies found no association between Selenium intake and metabolic syndrome; two of them found an inverse association; and one study found a direct association between Selenium intake and metabolic syndrome. One study also showed an inverse association between Selenium intake and the prevalence of high waist circumference, high diastolic blood pressure, and hyperglycaemia in women.

CONCLUSIONS

Overall, based on the argumentation and results of this study, it is possible to conclude that Selenium intake and metabolic syndrome are not clearly associated in adults and elderly.

Selenium Concentrations and Mortality among Community-Dwelling Older Adults: Results from IlSIRENTE Study

BACKGROUND

Selenium has a wide range of pleiotropic effects, influencing redox homeostasis, thyroid hormone metabolism, and protecting from oxidative stress and inflammation. Serum selenium levels are reduced in the older population.

OBJECTIVES

to investigate the association of serum selenium levels with all-cause mortality in a sample of community-dwelling older adults.

DESIGN AND SETTING

Data are from the 'Invecchiamento e Longevità nel Sirente' (Aging and Longevity in the Sirente geographic area, ilSIRENTE) study, a prospective cohort study that collected information on individuals aged 80 years and older living in an Italian mountain community (n=347). The main outcome was risk of death after ten years of follow-up.

PARTICIPANTS AND MEASUREMENTS

Participants were classified according to the median value of selenium (105.3 μg/L) in two groups: high selenium and low selenium.

RESULTS

A total of 248 deaths occurred during a 10-year follow-up. In the unadjusted model, low levels of selenium was associated with increased mortality (HR, 0.66; 95% CI 0.51-0.85). After adjusting for potential confounders the relationship remained significant (HR, 0.71; 95% CI 0.54-0.92).

CONCLUSIONS

Low serum levels of selenium are associated with reduced survival in elderly, independently of age and other clinical and functional variables.

Association of Antioxidant Supplement Use and Dementia in the Prevention of Alzheimer's Disease by Vitamin E and Selenium Trial (PREADViSE)

Importance

Oxidative stress is an established dementia pathway, but it is unknown if the use of antioxidant supplements can prevent dementia.

Objective

To determine if antioxidant supplements (vitamin E or selenium) used alone or in combination can prevent dementia in asymptomatic older men.

Design, Setting, and Participants

The Prevention of Alzheimer's Disease by Vitamin E and Selenium (PREADViSE) trial began as a double-blind randomized clinical trial in May 2002, which transformed into a cohort study from September 2009 to May 2015. The PREADViSE trial was ancillary to the Selenium and Vitamin E Cancer Prevention Trial (SELECT), a randomized clinical trial of the same antioxidant supplements for preventing prostate cancer, which closed in 2009 owing to findings from a futility analysis. The PREADViSE trial recruited 7540 men, of whom 3786 continued into the cohort study. Participants were at least 60 years old at study entry and were enrolled at 130 SELECT sites, and Cox proportional hazards models were used in a modified intent-to-treat analysis to compare hazard rates among the study arms.

Interventions

Participants were randomized to vitamin E, selenium, vitamin E and selenium, or placebo. While taking study supplements, enrolled men visited their SELECT site and were evaluated for dementia using a 2-stage screen. During the cohort study, men were contacted by telephone and assessed using an enhanced 2-stage cognitive screen. In both phases, men were encouraged to visit their physician if the screen results indicated possible cognitive impairment.

Main Outcomes and Measures

Dementia case ascertainment relied on a consensus review of the cognitive screens and medical records for men with suspected dementia who visited their physician for an evaluation or by review of all available information, including a functional assessment screen.

Results

The mean (SD) baseline age of the 7540 participants was 67.5 (5.3) years, with 3936 (52.2%) reporting a college education or better, 754 (10.0%) reporting black race, and 505 (6.7%) reporting Hispanic ethnicity. Dementia incidence (325 of 7338 men [4.4%]) was not different among the 4 study arms. A Cox model, which adjusted incidence for participant demographic information and baseline self-reported comorbidities, yielded hazard ratios of 0.88 (95% CI, 0.64-1.20) for vitamin E, 0.83 (0.60-1.13) for selenium, and 1.00 (0.75-1.35) for the combination compared with placebo.

Conclusions and Relevance

Neither supplement prevented dementia. To our knowledge, this is the first study to investigate the long-term association of antioxidant supplement use and dementia incidence among asymptomatic men.

Low preoperative selenium is associated with post-operative atrial fibrillation in patients having intermediate-risk coronary artery surgery

BACKGROUND/OBJECTIVES

Post-operative atrial fibrillation (POAF) is a frequent complication of cardiac surgery. Oxidative stress and reduced antioxidant function have major roles in its development. Selenium is a key to normal antioxidant function, and levels are often low before cardiac surgery. This study investigated whether low preoperative selenium levels were associated with POAF in cardiac surgical patients.

SUBJECTS/METHODS

Using the Society of Thoracic Surgeons (STS) Mortality risk score, 50 patients having primary coronary artery bypass grafts (CABG) surgery were divided into two groups: (i) low-risk group (STS ⩽0.5%; n=26) and (ii) intermediate-risk group (STS ⩾2.0%; n=24). Plasma levels of selenium, glutathione peroxidase (GPx) and malondialdehyde (MDA) were measured in all patients at anaesthetic induction, after aortic cross-clamp removal, 3 h post cardiopulmonary bypass and on post-operative days 1 and 5. Multiple logistic regression was used to assess whether selenium levels were associated with POAF development.

RESULTS

Seventeen patients developed POAF (14 patients in the intermediate-risk group and 3 patients in the low-risk group). Preoperative selenium was lower in patients who developed POAF compared with those with normal sinus rhythm (0.73±0.16 vs 0.89±0.13 μmol/l, P=0.005), and this was independently associated with POAF (PR 0.32; 95% confidence credible interval (95%cI) 0.06-0.85, P=0.016). Regardless of POAF, preoperative selenium was lower in the intermediate-risk patients than in the low-risk patients (0.77±0.15 vs 0.89±0.14 μmol/l; P=0.004).

CONCLUSIONS

Intermediate-risk patients with low preoperative selenium levels may be at a greater risk of developing POAF following CABG. This raises the question of whether selenium supplementation in select cardiac surgical patients may reduce their POAF risk.

Longitudinal Association between Selenium Levels and Hypertension in a Rural Elderly Chinese Cohort

OBJECTIVES

Results from previous studies have been inconsistent on the association between selenium and hypertension, and very few studies on this subject have focused on the elderly population. The purpose of this study is to examine the relationship between selenium level and hypertension in a rural elderly Chinese cohort.

DESIGN

A longitudinal study was implemented and data were analyzed using logistic regression models and Cox proportional hazards regression model adjusting for potential confounders. The associations between selenium level and prevalent hypertension at baseline and between selenium and incident hypertension were examined.

SETTING

Community-based setting in four rural areas in China.

SUBJECTS

A total of 2000 elderly aged 65 years and over (mean 71.9±5.6 years) participated in this study.

MEASUREMENTS

Nail selenium levels were measured in all subjects at baseline. Blood pressure measures and self-reported hypertension history were collected at baseline, 2.5 years and 7 years later. Hypertension was defined as systolic blood pressure 140 mmHg or higher, diastolic blood pressure 90 mmHg or higher, or reported use of anti-hypertensive medication.

RESULTS

The rate of baseline hypertension was 63.50% in this cohort and the mean nail selenium level is 0.413±0.183μg/g. Multi-covariate adjusted cross-sectional analyses indicated that higher selenium level was associated with higher blood pressure measures at baseline and higher rates of hypertension. For the 635 participants with normal blood pressure at baseline, 360 had developed hypertension during follow-up. The incidence rate for hypertension was 45.83%, 52.27%, 62.50%, 70.48%, and 62.79% from the first selenium quintile to the fifth quintile respectively. Comparing to the lowest quintile group, the hazard ratios were 1.41 (95%CI: 1.03 to1.94), 1.93 (95%CI: 1.40 to 2.67), 2.35 (95%CI: 1.69 to 3.26) and 1.94 (95%CI: 1.36 to 22.77) for the second selenium quintile to the fifth quintile respectively.

CONCLUSIONS

Our findings suggest that high selenium may play a harmful role in the development of hypertension. Future studies are needed to confirm our findings and to elucidate a plausible biological mechanism.

Selenium: an element for life

This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto's thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se's ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves' Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a 'Janus-effect' of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to be more advantageous in long-term prevention, and supplementation efforts, while the inorganic form (sodium selenite) has proven effective in an acute, e.g., sepsis, clinical setting. Recent data indicate that functional selenoprotein single-nucleotide polymorphisms (SNPs) may interfere with Se utilization and effectiveness.

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.

XAS studies of Se speciation in selenite-fed rats

The biological activity of selenium is dependent on its chemical form. Therefore, knowledge of Se chemistry in vivo is required for efficacious use of selenium compounds in disease prevention and treatment. Using X-ray absorption spectroscopy, Se speciation in the kidney, liver, heart, spleen, testis and red blood cells of rats fed control (∼0.3 ppm Se) or selenite-supplemented (1 ppm or 5 ppm Se) diets for 3 or 6 weeks, was investigated. X-ray absorption spectroscopy revealed the presence of Se-Se and Se-C species in the kidney and liver, and Se-S species in the kidney, but not the liver. X-ray absorption near edge structure (XANES) spectra showed that there was variation in speciation in the liver and kidneys, but Se speciation was much more uniform in the remaining organs. Using principal component analysis (PCA) to interpret the Se K-edge X-ray absorption spectra, we were able to directly compare the speciation of Se in two different models of selenite metabolism--human lung cancer cells and rat tissues. The effects of Se dose, tissue type and duration of diet on selenium speciation in rat tissues were investigated, and a relationship between the duration of the diet (3 weeks versus 6 weeks) and selenium speciation was observed.

Interaction between essential elements selenium and zinc with cadmium and mercury in samples from hypertensive patients

The abnormal metabolism of metal ions plays an important role in health and disease conditions; hence, the studies about them have received much interest. The objective of this study was to evaluate the association between trace and toxic elements zinc (Zn), cadmium (Cd), selenium (Se), and mercury (Hg) in biological samples (scalp hair, blood, and urine) of hypertensive patients (n = 257), residents of Hyderabad, Pakistan. For comparison purpose, the biological samples of age-matched healthy controls were selected as referents. The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The validity and accuracy of the methodology was checked using certified reference materials and by the conventional wet acid digestion method. The recovery of all studied elements was found in the range of 96.4-99.1 % in certified reference materials. The results of this study showed that the mean values of Cd and Hg were significantly higher in scalp hair, blood, and urine samples of hypertensive patients than in referents (P < 0.001), whilst the concentrations of Zn and Se were lower in the scalp hair and blood, but higher in the urine samples of hypertensive patients. The deficiency of Zn and Se and the high exposure of toxic metals may be synergistic with risk factors associated with hypertension.

Micronutrient-gene interactions related to inflammatory/immune response and antioxidant activity in ageing and inflammation. A systematic review

Recent longitudinal studies in dietary daily intake in human centenarians have shown that a satisfactory content of some micronutrients within the cells maintain several immune functions, a low grade of inflammation and preserve antioxidant activity. Micronutrients (zinc, copper, selenium) play a pivotal role in maintaining and reinforcing the performances of the immune and antioxidant systems as well as in affecting the complex network of the genes (nutrigenomic) with anti- and pro-inflammatory tasks. Genes of pro- and anti-inflammatory cytokines and some key regulators of trace elements homeostasis, such as Metallothioneins (MT), are involved in the susceptibility to major geriatric disease/disorders. Moreover, the genetic inter-individual variability may affect the nutrients' absorption (nutrigenetic) with altered effects on inflammatory/immune response and antioxidant activity. The interaction between genetic factors and micronutrients (nutrigenomic and nutrigenetic approaches) may influence ageing and longevity because the micronutrients may become also toxic. This review reports the micronutrient-gene interactions in ageing and their impact on the healthy state with a focus on the method of protein-metal speciation analysis. The association between micronutrient-gene interactions and the protein-metal speciation analysis can give a complete picture for a personalized nutrient supplementation or chelation in order to reach healthy ageing and longevity.

Selenium levels and hypertension: a systematic review of the literature

OBJECTIVE

Se is an antioxidant micronutrient and has been studied for its potential role in CVD prevention. The purpose of the present study was to conduct a systematic review of the literature on the relationship between Se and hypertension.

DESIGN

We conducted a systematic literature search in PubMed and OVID of studies on Se levels and hypertension or blood pressure published in English up to June 2011. Articles meeting inclusion criteria were reviewed and the following information was gathered from each publication: study setting, participant demographics, exclusion criteria, intervention if applicable, medium of Se measure, mean level of Se, outcome definition, relationship between Se and the outcome variable, significance of this relationship, and covariates. In studies that also reported glutathione peroxidase levels, we extracted results on the relationship between glutathione peroxidase and hypertension.

RESULTS

Twenty-five articles were included. Approximately half of the studies reported no significant relationship between Se and hypertension. Of the remaining studies, about half found that higher Se levels were associated with lower blood pressure and the other half found the opposite relationship. The studies varied greatly in terms of study population, study design and Se levels measured in participants.

CONCLUSIONS

Based on the present systematic review, there is no conclusive evidence supporting an association between Se and hypertension. Randomized controlled trials and prospective studies with sufficient sample size in populations with different Se levels are needed to fully investigate the relationship between Se and hypertension.

Trace elements in the blood of institutionalized elderly in the Czech Republic

Whole blood selenium, copper, zinc and manganese concentrations of 197 institutionalized senior citizens (46 males, 151 females) aged 61-100 years (mean age 83.6 years) were determined using atomic absorption spectrometry and inductively coupled plasma mass spectrometry from two localities in the Czech Republic (Prague and Teplice) from 2009 through 2011. Geometric means (GM) of whole blood selenium (B-Se), copper (B-Cu), zinc (B-Zn) and manganese (B-Mn) levels were 74.0 μg/l, 941.0 μg/l, 5898.0 μg/l and 10.9 μg/l, respectively. Gender-related differences were found with significantly higher B-Cu levels in women and significantly higher B-Zn levels in men. The percentage of seniors with B-Se levels lower than 56 μg/l (which is equivalent to the critical value of 45 μg/l of Se in serum (S-Se)) was 8.6%. A negative correlation between age and B-Se levels was found. B-Zn positively correlated with serum albumin and prealbumin whereas a negative correlation between age and B-Zn was observed. Seniors with diabetes mellitus and atherosclerosis had higher B-Cu and B-Mn levels, respectively, than those without these diagnoses. The elderly from Prague had significantly higher B-Mn concentrations than those from Teplice. We found no evidence of serious essential elements deficiencies or excesses in the seniors who participated in this study.

The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities

Dietary selenium (]Se), mainly through its incorporation into selenoproteins, plays an important role in inflammation and immunity. Adequate levels of Se are important for initiating immunity, but they are also involved in regulating excessive immune responses and chronic inflammation. Evidence has emerged regarding roles for individual selenoproteins in regulating inflammation and immunity, and this has provided important insight into mechanisms by which Se influences these processes. Se deficiency has long been recognized to negatively impact immune cells during activation, differentiation, and proliferation. This is related to increased oxidative stress, but additional functions such as protein folding and calcium flux may also be impaired in immune cells under Se deficient conditions. Supplementing diets with above-adequate levels of Se can also impinge on immune cell function, with some types of inflammation and immunity particularly affected and sexually dimorphic effects of Se levels in some cases. In this comprehensive article, the roles of Se and individual selenoproteins in regulating immune cell signaling and function are discussed. Particular emphasis is given to how Se and selenoproteins are linked to redox signaling, oxidative burst, calcium flux, and the subsequent effector functions of immune cells. Data obtained from cell culture and animal models are reviewed and compared with those involving human physiology and pathophysiology, including the effects of Se levels on inflammatory or immune-related diseases including anti-viral immunity, autoimmunity, sepsis, allergic asthma, and chronic inflammatory disorders. Finally, the benefits and potential adverse effects of intervention with Se supplementation for various inflammatory or immune disorders are discussed.

Selenium and cognitive impairment: a brief-review based on results from the EVA study

Preventing cognitive impairment and dementia in the elderly is a major public health challenge for our century and all hypotheses should be explored. Selenium (Se) is one of the factors that may affect the risk of cognitive decline. Its importance in the health and aging process has been documented. Because of the potential of selenoproteins to protect against oxidative stress, Se raises significant expectations for the prevention of chronic diseases including cancer, cardiovascular disease, and type 2 diabetes conditions commonly associated with oxidative stress. Thus, the relationships between Se and cognitive impairment or dementia can be examined through vascular risk factors for dementia, with particular interest in diabetes and dyslipidemia. In addition, in cases of Se deficiency, the brain is the organ that remains Se replete the longest suggesting that Se plays an important role in brain functions. This article presents results obtained in the frame of a longitudinal study on Se and cognitive impairment. They are consistent with the hypothesis that low Se status is a risk factor for cognitive decline even after taking into account vascular risk factors. The concomitant evolution between plasma Se decrease over a 9-year period and cognitive decline suggested that optimal Se status is potentially important to maintain neuropsychological functions in aging people. However, as our understanding of Se biology is incomplete, epidemiological studies are needed to define the groups of population that could benefit from Se supplementation.

Assessment of lifestyle effect on oxidative stress biomarkers in free-living elderly in rural Japan

BACKGROUND

Oxidative stress is believed to play a crucial role in aging and age-related diseases, and is widely thought to increase morbidity and mortality in the elderly. Assessment of biomarkers of oxidative stress, such as 8-isoprostane and 8-hydroxy-2-deoxyguanosine, are considered to be useful in predicting disease risks at the population level.

OBJECTIVE

The aim of the present study was to assess the health status of the elderly by comparing their lifestyles and levels of oxidative stress biomarkers.

METHODS

We carried out a cross-sectional study where urine samples from a total of 100 elderly men and women were assayed for 8-isoprostane, 8-hydroxy-2-deoxyguanosine, selenium, cadmium and creatinine. They were asked to answer a questionnaire that included questions about their lifestyle.

RESULTS

Most of the participants were prehypertensive, non-alcohol users and on a rich plant-based diet. There were no differences in any biomarkers of oxidative stress between men and women. 8-Isoprostane was found to correlate positively with systolic blood pressure in women, but not in men. There was a slight increase of 8-isoprostane in participants with a poor intake of vegetables, and a decrease of 8-hydroxy-2-deoxyguanosine in participants who consumed fish. Multiple regression analysis showed that oxidative stress biomarkers were positively associated with cadmium, and negatively associated with selenium and fish intake in all participants, 89% of which were non-smokers.

CONCLUSION

Results from the present study show that fish intake has the potential of decreasing oxidative stress among elderly persons.

Age related changes in selenium and glutathione levels in different lobes of the rat prostate

Aging represents a major risk factor for prostate cancer; however, mechanisms responsible for this relationship remain unclear. Preclinical and some clinical investigations support the protective role of selenium against prostate cancer possibly through the reduction of oxidative stress. While increased levels of oxidative stress together with decreases in selenium and the major cellular antioxidant glutathione (GSH) are common in tissues of old animals, there is little data available on these parameters in the prostate. In the present study we have compared the levels of selenium, GSH and protein-bound GSH (GSSP) in blood and prostate tissues in young (4-month), mature (12-month), old (18 month), and very old (24 month) male F344 rats. Each prostate lobe (dorsolateral, DL; anterior, AL; ventral, VL) was analyzed separately based upon their differing potential for prostate cancer development. At all ages, selenium levels were lowest in DL<VL<AL. After 12 mo, an 85% reduction in selenium in the DL was observed (P<0.05), while levels in other lobes were unchanged. In animals of all ages, levels of GSH were lowest in the VL<DL=AL and no significant changes were observed in GSH levels by 18 mo. However, GSSP, a marker of oxidative stress, was increased 90% after 18 mo in the DL only (P<0.01). These findings of age-related changes in GSSP and selenium in the DL prostate are consistent with the sensitivity of this lobe to carcinogenesis and, thus, may be playing a mechanistic role.

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.

Alcohol and the older adult: a comprehensive review

Alcohol consumption in the older adult is of major concern with the advent of baby boomers coming into the over 65-age bracket. Alcohol consumption has been touted as beneficial for health, and while that may be accurate for moderate consumption in younger persons, there is considerable risk associated with increased alcohol intake in older adults. This increase is partially due to age-related physiological changes, existing diagnoses, number of comorbid conditions, and increased use of prescribed and/or over-the-counter medications, coupled with other concerns. This review addresses the current research regarding ethanol consumption in older adults and all-cause mortality as well as several conditions more frequently seen in the geriatric population. These conditions include vascular diseases, hypertension, type 2 diabetes, gastrointestinal disorders, hepatic disorders, dental and oro-facial problems, bone density decline, and falls and fractures. In addition, drug interactions and recent research into select vitamin and mineral considerations with increased alcohol intake in older persons are addressed. While recommendations for alcohol intake have not been specifically established for age ranges within the 65-year-and-older bracket, and practitioners do not routinely assess alcohol intake or ethanol related adverse events in this population, common sense approaches to monitoring will become increasingly important as the generation of "boomers" who believe that alcohol intake improves health comes of age.

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.

The effect of microelements supplementation on beta-oxidation activity in healthy and type 1 diabetic rats

Diabetes mellitus type 1 disease changes the activity of fatty acid degradation as compared to healthy animals. Supplementation in vitro with microelements chromium Cr3+ and selenium Se4+ and Se2- in non-toxic ([96.15 pmol (5 ppm) for chromium and 6.33 micromol (0.5 ppm) for selenium] concentrations strongly stimulates the activity of this process in diabetic rats. In healthy animals only chromium Cr3+ in concentration of 96.15 micromol (5 ppm) stimulated beta-oxidation activity in lymphocytes. It may indicate the beneficial effect of supplementation of the diet with microelements, chromium Cr3 and selenium Se4+ or Se2- at concentrations as low as 100 micromol for chromium and 6 micromol for selenium, respectively.

On the importance of selenium and iodine metabolism for thyroid hormone biosynthesis and human health

The trace elements iodine and selenium (Se) are essential for thyroid gland functioning and thyroid hormone biosynthesis and metabolism. While iodine is needed as the eponymous constituent of the two major thyroid hormones triiodo-L-thyronine (T3), and tetraiodo-L-thyronine (T4), Se is essential for the biosynthesis and function of a small number of selenocysteine (Sec)-containing selenoproteins implicated in thyroid hormone metabolism and gland function. The Se-dependent iodothyronine deiodinases control thyroid hormone turnover, while both intracellular and secreted Se-dependent glutathione peroxidases are implicated in gland protection. Recently, a number of clinical supplementation trials have indicated positive effects of increasing the Se status of the participants in a variety of pathologies. These findings enforce the notion that many people might profit from improving their Se status, both as a means to reduce the individual health risk as well as to balance a Se deficiency which often develops during the course of illness. Even though the underlying mechanisms are still largely uncharacterised, the effects of Se appear to be exerted via multiple different mechanisms that impact most pronounced on the endocrine and the immune systems.

Fibrates but not statins increase plasma selenium in dyslipidemic aged patients--the EVA study

This secondary analysis of "Etude du Vieillissement Artériel" (EVA) study reports the effect of fibrates and statins on plasma selenium concentration and its 9-year change in free-living dyslipidemic elderly. Dyslipidemic patients were categorized in three sub-groups according to final low-density lipoprotein (LDL)-cholesterol level or hypolipidemic treatment: non-treated dyslipidemic (LDL-cholesterol >4.41 mmol/L, n=84); dyslipidemics who were treated exclusively by fibrates (n=47) or by statins (n=25) whatever their serum LDL-cholesterol concentration. The influence of lipid-lowering treatments on plasma selenium concentrations and its 9-year change was evaluated by analysis of variance (ANOVA) and multivariate linear regression models taking into account cardiovascular risk and changes in lipid-profile parameters. Multivariate linear regression indicated that the plasma selenium decline was associated with the longitudinal variation in LDL (beta=-0.039+/-0.019, p=0.04) and high-density lipoprotein (HDL)-cholesterol concentrations (beta=0.187+/-0.059, p=0.002) but not with triglycerides (beta=-0.018+/-0.031, p=0.57). During the 9-year follow-up, similar plasma selenium declines were observed in all the sub-groups (p=0.33) despite plasma selenium levels being higher in fibrate users and lower in statin users (p=0.0004). The mechanisms underlying these data are not yet totally understood, but considering the risk of selenium deficiency in the elderly and its relationship with poor health status further clinical trial is needed to verify the proposed hypotheses.

The prediction of cardiovascular disease based on trace element contents in hair and a classifier of boosting decision stumps

The early discovery of cardiovascular disease (CVD) is crucial for performing successful treatments. This study aims at exploring the feasibility of Adaboost (ensemble from machining learning) using decision stumps as weak classifier, combined with trace element analysis of hair, for accurately predicting early CVD. A total of 124 hair samples composed of two groups of samples (one is healthy group from 100 healthy persons aged 24-72 while the other is patient group from 24 cardiovascular disease patients aged 36-81) were used. Nine kinds of trace elements, i.e., chromium (Cr), manganese (Mn), cadmium (Cd), copper (Cu), zinc (Zn), selenium (Se), iron (Fe), aluminum (Al), and nickel (Ni), were selected. In a preliminary analysis, no obvious linear correlations between elements can be observed and the concentration of Cr, Fe, Al, Cd, Ni, or Se for healthy group is higher than that for patient group while the opposite is true for Mn, Cu, or Zn, indicating that both low Se/Fe and high Mn/Cu can be identified as major risk factors. Based on the proposed approach, the final ensemble classifier, constructed on the training set and contained only four decision stumps, achieved an overall identification accuracy of 95.2%, a sensitivity of 100% and a specificity of 94% on the independent test set. The results suggested that integrating Adaboost and trace element analysis of hair sample can serve as a useful tool of diagnosing CVD in clinical practice.

Selenium status of the Australian population: effect of age, gender and cardiovascular disease

Selenium (Se) is an essential trace element and the clinical consequences of Se deficiency have been well-documented. Se is primarily obtained through the diet and recent studies have suggested that the level of Se in Australian foods is declining. Currently there is limited data on the Se status of the Australian population so the aim of this study was to determine the plasma concentration of Se and glutathione peroxidase (GSH-Px), a well-established biomarker of Se status. Furthermore, the effect of gender, age and presence of cardiovascular disease (CVD) was also examined. Blood plasma samples from healthy subjects (140 samples, mean age = 54 years; range, 20-86 years) and CVD patients (112 samples, mean age = 67 years; range, 40-87 years) were analysed for Se concentration and GSH-Px activity. The results revealed that the healthy Australian cohort had a mean plasma Se level of 100.2 +/- 1.3 microg Se/L and a mean GSH-Px activity of 108.8 +/- 1.7 U/L. Although the mean value for plasma Se reached the level required for optimal GSH-Px activity (i.e. 100 microg Se/L), 47% of the healthy individuals tested fell below this level. Further evaluation revealed that certain age groups were more at risk of a lowered Se status, in particular, the oldest age group of over 81 years (females = 97.6 +/- 6.1 microg Se/L; males = 89.4 +/- 3.8 microg Se/L). The difference in Se status between males and females was not found to be significant. The presence of CVD did not appear to influence Se status, with the exception of the over 81 age group, which showed a trend for a further decline in Se status with disease (plasma Se, 93.5 +/- 3.6 microg Se/L for healthy versus 88.2 +/- 5.3 microg Se/L for CVD; plasma GSH-Px, 98.3 +/- 3.9 U/L for healthy versus 87.0 +/- 6.5 U/L for CVD). These findings emphasise the importance of an adequate dietary intake of Se for the maintenance of a healthy ageing population, especially in terms of cardiovascular health.

The role of selenium in chronic disease

Selenium functions as a part of proteins known as selenoproteins. Through these selenoproteins, selenium functions as a defensive mechanism for oxidative stress, for the regulation of thyroid hormone activity, and for the redox status of vitamin C and other molecules. In several of its roles, selenium functions as a dietary antioxidant and thus has been studied for its possible role in chronic diseases. This article reviews recent studies regarding selenium status or supplementation in hypertension, cardiovascular disease, cancer, and diabetes mellitus. A few studies regarding aging and mortality are also included. What can be ascertained from this current review is that the maintenance of adequate selenium nutriture and, at minimum, the prevention of a deficiency in selenium would be advisable for all individuals. In addition, the indiscriminant use of selenium supplements should be approached with caution until further randomized, controlled trials monitor the effects of such supplementation, especially on a long-term basis.

Food-chain selenium and human health: emphasis on intake

Following the publication of the landmark trial of Clark et al. in 1996 that appeared to show that Se could reduce the risk of cancer, awareness of the importance of Se to human health has markedly increased. As a result, there is now much more aggressive marketing of Se supplements and functional foods, even in situations where additional consumption of Se is inappropriate. The present review addresses how Se gets into the food chain, the wide variability in Se content of foods and the very different levels of intake between countries and regions. Though it is clear that there are adverse consequences for health of both deficient and excessive intake, health effects at intermediate levels of intake are less certain. Thus it is difficult to define optimal intake which depends on a large number of factors, such as which functions of Se are most relevant to a particular disease state, which species of Se is most prominent in the Se source, which health condition is being considered, the adequacy or otherwise of intake of other nutrients, the presence of additional stressors, and lastly whether the ability to make selenoproteins may be compromised. These complexities need to be understood, particularly by policy makers, in order to make informed judgments. Potential solutions for increasing Se intake, where required, include agronomic biofortification and genetic biofortification or, for individuals, increased intake of naturally Se-rich foods, functional foods or supplements. The difficulties of balancing the risks and benefits in relation to Se intake are highlighted.