Low serum selenium and total carotenoids predict mortality among older women living in the community: the women's health and aging studies

Association between plasma metal exposure and health span in very elderly adults: a prospective cohort study with mixture statistical approach

BACKGROUND

Metals have been linked to a diverse spectrum of age-related diseases; however, the effects of metal exposure on health span remains largely unknown. This cohort study aims to determine the association between plasma metal and health span in elder adults aged ≥ 90 years.

METHODS

The plasma concentrations of seven metals were measured at baseline in 300 elder adults. The end of the health span (EHS) was identified as the occurrence of one of eight major morbidities or mortality events. We used Cox regression to assess hazard ratios (HR). The combined effects of multiple metal mixtures were estimated using grouped-weighted quantile sum (GWQS), quantile g-computation (Q-gcomp), and Bayesian kernel machine regression (BKMR) methods.

RESULTS

The estimated HR for EHS with an inter-quartile range (IQR) increment for selenium (Se) was 0.826 (95% confidence interval [CI]: 0.737-0.926); magnesium (Mg), 0.806 (95% CI: 0.691-0.941); iron (Fe), 0.756 (95% CI: 0.623-0.917), and copper (Cu), 0.856 (95% CI: 0.750-0.976). The P for trend of Se, Mg, and Fe were all < 0.05. In the mixture analyses, Q-gcomp showed a negative correlation with EHS (P = 0.904), with the sum of the negative coefficients being -0.211.

CONCLUSION

Higher plasma Se, Mg, and Fe reduced the risk of premature end of health span, suggesting that essential metal elements played a role in health maintenance in elder adults.

Strong associations of serum selenoprotein P with all-cause mortality and mortality due to cancer, cardiovascular, respiratory and gastrointestinal diseases in older German adults

BACKGROUND

Selenium is an essential trace mineral. The main function of selenoprotein P (SELENOP) is to transport selenium but it has also been ascribed anti-oxidative effects.

METHODS

To assess the association of repeated measurements of serum SELENOP concentration with all-cause and cause-specific mortality serum SELENOP was measured at baseline and 5-year follow-up in 7,186 and 4,164 participants of the ESTHER study, a German population-based cohort aged 50-74 years at baseline.

RESULTS

During 17.3 years of follow-up, 2,126 study participants (30%) died. The relationship of serum SELENOP concentration with all-cause mortality was L-shaped, with mortality being significantly higher at SELENOP concentrations < 4.1 mg/L, which is near the bottom tertile's cut-off (4.2 mg/L). All-cause mortality of participants in the bottom SELENOP tertile was significantly increased compared to subjects in the top tertile (hazard ratio [95% confidence interval]: 1.35 [1.21-1.50]). SELENOP in the bottom tertile was further associated with increased cardiovascular mortality (1.24 [1.04-1.49]), cancer mortality (1.31 [1.09-1.58]), respiratory disease mortality (2.06 [1.28-3.32]) and gastrointestinal disease mortality (2.04 [1.25-3.32]). The excess risk of all-cause mortality for those in the bottom SELENOP tertile was more than twice as strong in men as in women (interaction of SELENOP and sex; p = 0.008).

CONCLUSIONS

In this large cohort study, serum SELENOP concentration was inversely associated with all-cause and cause-specific mortality. Consistent inverse associations with multiple mortality outcomes might be explained by an impaired selenium transport and selenium deficiency in multiple organs. Trials testing the efficacy of selenium supplements in subjects with low baseline SELENOP concentration are needed.

TRIAL REGISTRATION

Retrospectively registered in the German Clinical Trials Register on Feb 14, 2018 (ID: DRKS00014028).

Selenium - a scoping review for Nordic Nutrition Recommendations 2023

Selenium is an essential trace element in humans, critical to the normal physiology in all animal species. The main form of selenium in food is selenomethionine, selenocysteine and a variety of organic compounds, while inorganic salts mainly occur in food supplements. In animals and humans, selenium occurs as selenocysteine in selenoproteins encoded by 25 genes (specific selenium pool). Several selenoproteins are part of the antioxidant enzyme system and serve as oxido-reductases and in thyroid hormone regulation. SelenoproteinP (SELENOP) transports selenium to peripheral tissues, is the main plasma selenoprotein, and has been used as biomarker of selenium status and intake. SELENOP in plasma represents a saturable pool of selenium and is maximised at a selenium concentration in plasma of about 110 µg/L or an intake of selenomethionine at about 1.2 µg/kg body weight in adults. In Finland, with an estimated selenium intake of 88 µg/day in men and 68 µg/day in women, the average selenium concentration in plasma is about 110 µg/L. Imported wheat from selenium rich areas is an important dietary source in Norway. Dietary intakes in the Nordic and Baltic area vary from 39 to 88 µg/day in men and 22 to 68 µg/day in women, the highest levels were from Finland. Most intervention trials on the effect of selenium supplementation on health outcomes have been carried out in 'selenium-replete'-populations and show no beneficial effect, which from a nutritional point of view would rather not be expected. Some intervention studies conducted in populations low in selenium have showed a beneficial effect. Observational studies suggest an inverse relationship between selenium status and risk of cardiovascular diseases (CVDs), cancer and all-cause mortality, and some other outcomes at low levels of intake (<55 µg/day) or in plasma or serum (<100 µg/L). However, a lack of quantitative data and inconsistencies between studies precludes these studies to be used to derive dietary reference values. At high intakes above 330 to 450 µg/day selenium may cause toxic effects affecting liver, peripheral nerves, skin, nails, and hair. An upper tolerable level (UL) of 255 µg selenium/day in adults was established by EFSA.

Could Selenium Supplementation Prevent COVID-19? A Comprehensive Review of Available Studies

The purpose of this review is to systematically examine the scientific evidence investigating selenium's relationship with COVID-19, aiming to support, or refute, the growing hypothesis that supplementation could prevent COVID-19 etiopathogenesis. In fact, immediately after the beginning of the COVID-19 pandemic, several speculative reviews suggested that selenium supplementation in the general population could act as a silver bullet to limit or even prevent the disease. Instead, a deep reading of the scientific reports on selenium and COVID-19 that are available to date supports neither the specific role of selenium in COVID-19 severity, nor the role of its supplementation in the prevention disease onset, nor its etiology.

Relationships Between Hair Chemical Elements and Nutritional Status in Oldest-Old and Centenarian Populations

Background

Hair chemical elements reflect physical condition over time. Collection, transporting, and storing hair is more convenient than handling blood. Hair elements show higher levels for a long time, which allows for more accurate and sensitive results than using blood. Studies explored the relationships between elements and age, without full consideration of nutritional status, in older people. This study explored the relationships between hair chemical elements and Geriatric Nutritional Risk Index (GNRI) in oldest-old and centenarian populations to provide an updated reference for nutritional evaluation of older people.

Methods

A total of 152 participants over 80 years old underwent home interviews and physical examinations. An inductively coupled plasma mass spectrometer was used to detect hair chemical elements.

Results

Women accounted for 77.0% of participants. Women had lower levels of zinc, and higher levels of selenium, manganese, lead, iron, and copper than men (P<0.05 for all). Ninety-two participants formed the 80-99 year group, and 60 participants formed the 100+ year group. Centenarians had lower levels of selenium, lead, iron, and copper than those aged 80-99 years (P<0.05 for all). Hair selenium levels were positively associated with GNRI (odds ratio: 11.55, 95% confidence interval: 3.42-19.68, P < 0.05) based on a multivariate linear regression analysis. Other chemical elements had no significant associations with GNRI based on a multivariate linear regression analysis.

Conclusion

Chemical elements and nutrient status were altered based on age and gender, and an association existed between hair selenium and nutritional status in older people. Chemical elements may influence and indicate nutritional status in older people.

Scientific opinion on the tolerable upper intake level for selenium

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver a scientific opinion on the tolerable upper intake level (UL) for selenium. Systematic reviews of the literature were conducted to identify evidence regarding excess selenium intake and clinical effects and potential biomarkers of effect, risk of chronic diseases and impaired neuropsychological development in humans. Alopecia, as an early observable feature and a well-established adverse effect of excess selenium exposure, is selected as the critical endpoint on which to base a UL for selenium. A lowest-observed-adverse-effect-level (LOAEL) of 330 μg/day is identified from a large randomised controlled trial in humans (the Selenium and Vitamin E Cancer Prevention Trial (SELECT)), to which an uncertainty factor of 1.3 is applied. A UL of 255 μg/day is established for adult men and women (including pregnant and lactating women). ULs for children are derived from the UL for adults using allometric scaling (body weight0.75). Based on available intake data, adult consumers are unlikely to exceed the UL, except for regular users of food supplements containing high daily doses of selenium or regular consumers of Brazil nuts. No risk has been reported with the current levels of selenium intake in European countries from food (excluding food supplements) in toddlers and children, and selenium intake arising from the natural content of foods does not raise reasons for concern. Selenium-containing supplements in toddlers and children should be used with caution, based on individual needs.

Selenium: An Antioxidant with a Critical Role in Anti-Aging

Aging is characterized by an imbalance between damage inflicted by reactive oxygen species (ROS) and the antioxidative defenses of the organism. As a significant nutritional factor, the trace element selenium (Se) may remodel gradual and spontaneous physiological changes caused by oxidative stress, potentially leading to disease prevention and healthy aging. Se is involved in improving antioxidant defense, immune functions, and metabolic homeostasis. An inadequate Se status may reduce human life expectancy by accelerating the aging process or increasing vulnerability to various disorders, including immunity dysfunction, and cancer risk. This review highlights the available studies on the effective role of Se in aging mechanisms and shows the potential clinical implications related to its consumption. The main sources of organic Se and the advantages of its nanoformulations were also discussed.

Impact of Selenium on Biomarkers and Clinical Aspects Related to Ageing. A Review

Selenium (Se) is an essential dietary trace element that plays an important role in the prevention of inflammation, cardiovascular diseases, infections, and cancer. Selenoproteins contain selenocysteine in the active center and include, i.a., the enzymes thioredoxin reductases (TXNRD1–3), glutathione peroxidases (GPX1–4 and GPX6) and methionine sulfoxide reductase, involved in immune functions, metabolic homeostasis, and antioxidant defense. Ageing is an inevitable process, which, i.a., involves an imbalance between antioxidative defense and reactive oxygen species (ROS), changes in protein and mitochondrial renewal, telomere attrition, cellular senescence, epigenetic alterations, and stem cell exhaustion. These conditions are associated with mild to moderate inflammation, which always accompanies the process of ageing and age-related diseases. In older individuals, Se, by being a component in protective enzymes, operates by decreasing ROS-mediated inflammation, removing misfolded proteins, decreasing DNA damage, and promoting telomere length. Se-dependent GPX1–4 and TXNRD1–3 directly suppress oxidative stress. Selenoprotein H in the cell nucleus protects DNA, and selenoproteins residing in the endoplasmic reticulum (ER) assist in the removal of misfolded proteins and protection against ER stress. In this review, we highlight the role of adequate Se status for human ageing and prevention of age-related diseases, and further its proposed role in preservation of telomere length in middle-aged and elderly individuals.

Therapeutic Potential of Selenium in Glioblastoma

Little progress has been made in the long-term management of malignant brain tumors, leaving patients with glioblastoma, unfortunately, with a fatal prognosis. Glioblastoma remains the most aggressive primary brain cancer in adults. Similar to other cancers, glioblastoma undergoes a cellular metabolic reprogramming to form an oxidative tumor microenvironment, thereby fostering proliferation, angiogenesis and tumor cell survival. Latest investigations revealed that micronutrients, such as selenium, may have positive effects in glioblastoma treatment, providing promising chances regarding the current limitations in surgical treatment and radiochemotherapy outcomes. Selenium is an essential micronutrient with anti-oxidative and anti-cancer properties. There is additional evidence of Se deficiency in patients suffering from brain malignancies, which increases its importance as a therapeutic option for glioblastoma therapy. It is well known that selenium, through selenoproteins, modulates metabolic pathways and regulates redox homeostasis. Therefore, selenium impacts on the interaction in the tumor microenvironment between tumor cells, tumor-associated cells and immune cells. In this review we take a closer look at the current knowledge about the potential of selenium on glioblastoma, by focusing on brain edema, glioma-related angiogenesis, and cells in tumor microenvironment such as glioma-associated microglia/macrophages.

Selenium supplementation inhibits IGF-1 signaling and confers methionine restriction-like healthspan benefits to mice

Methionine restriction (MR) dramatically extends the healthspan of several organisms. Methionine-restricted rodents have less age-related pathology and increased longevity as compared with controls, and recent studies suggest that humans might benefit similarly. Mechanistically, it is likely that the decreased IGF-1 signaling that results from MR underlies the benefits of this regimen. Thus, we hypothesized that interventions that decrease IGF-1 signaling would also produce MR-like healthspan benefits. Selenium supplementation inhibits IGF-1 signaling in rats and has been studied for its putative healthspan benefits. Indeed, we show that feeding mice a diet supplemented with sodium selenite results in an MR-like phenotype, marked by protection against diet-induced obesity, as well as altered plasma levels of IGF-1, FGF-21, adiponectin, and leptin. Selenomethionine supplementation results in a similar, albeit less robust response, and also extends budding yeast lifespan. Our results indicate that selenium supplementation is sufficient to produce MR-like healthspan benefits for yeast and mammals.

Frailty syndrome: A target for functional nutrients?

Frailty is a late life phenotype characterized by a decline in physiological reserve across several organ systems, resulting in the increased susceptibility to endogenous and/or exogenous stressors. Although the etiology of frailty remains poorly understood, an interconnected network of putative mechanisms linked to the ageing process has been proposed. However, frailty is a dynamic process that may be prevented, delayed, or even reversed. The syndromic nature of frailty requires a multidomain approach, such as proper nutrition, as part of modifiable environmental factors, and represents one of the most promising and least costly ways to prevent and reduce frailty among older adults. Nutrient deficiencies have been consistently associated with frailty; however, mounting evidence also supports the hypothesis that beyond the traditional nutritional value, specific dietary components may exert function-enhancing effects and mitigate the extent of frailty. Thus, further mechanistic studies, along with large clinical trials, are imperative to establish the exact role of functional nutrients in the clinical management of frailty. Here, we provide a contemporary discussion of how emerging functional nutrients may contribute to modify the trajectory of the frailty syndrome.

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.

Spatial variations in soil selenium and residential dietary selenium intake in a selenium-rich county, Shitai, Anhui, China

Shitai, a selenium (Se)-rich county in Anhui, China, has been reported for its resident longevity in the last 20 years. A recent survey by the Anhui Bureau of Geological Survey showed that soil Se contents in the Shitai area ranged from 0.05 to 51.20 mg/kg, with an average of 0.56 mg/kg. To explore the potential relationship between longevity and natural-occurring Se contents in Shitai county, Se concentrations were determined in Shitai's food chain (including soils and foods) and the daily Se intakes and hair Se contents were calculated for the residents. In the present study, 33 soil samples, 66 food samples and 82 hair samples were randomly collected from field sites, local food markets and male and female residents in downtown Shitai and in four nearby villages (Dashan, Xianyu, Yongfu and Yuantou). The total Se contents in all samples and the levels of water soluble, exchangeable, acid soluble, organic bound and residual Se in soil samples were determined with hydride generation - atomic fluorescence spectrometry. The total Se contents in soils ranged from 227 to 2603 μg/kg, with the averages of 1607 ± 242 μg/kg in Dashan, 1149 ± 118 μg/kg in Xianyu, 521 ± 157 μg/kg in Yongfu, and 363 ± 140 μg/kg in Yuantou. The soil bioavailable Se content (soluble and exchangeable Se) in Dashan was highest (14.98%), followed by Xianyu (13.69%), Yongfu (13.18%) and Yuantou (9.38%). For food samples, the highest Se concentration of grains was 468.5 μg/kg in Dashan, while lowest was observed in downtown (41.7 μg/kg). The estimated daily Se intake of residents in Dashan reached 298.4 μg/d/adult, which is about 5 times higher than the recommend nutrient intake in China (60 μg/d/adult), and 6-10 times higher than the levels observed in Xianyu (47.6 μg/d/adult), Yuantou (46.1 μg/d/adult), Yongfu (40.0 μg/d/adult), and downtown (30.0 μg/d/adult). Although hair Se contents in Dashan (male: 709.2 μg/kg; female: 589.2 μg/kg) were significantly higher than those at the other study sites, no significant relationships between daily Se intakes and hair Se contents were observed. The present study demonstrated that Se levels in soils, foods, resident dietary intake and human hairs in Shitai County varied significantly; therefore, the region could be a unique field site to study the direct relationship between Se and human health.

Effect of long-term selenium supplementation on mortality: Results from a multiple-dose, randomised controlled trial

BACKGROUND

Selenium, an essential trace element, is incorporated into selenoproteins with a wide range of health effects. Selenoproteins may reach repletion at a plasma selenium concentration of ~ 125 µg/L, at which point the concentration of selenoprotein P reaches a plateau; whether sustained concentrations higher than this are beneficial, or indeed detrimental, is unknown.

OBJECTIVE

In a population of relatively low selenium status, we aimed to determine the effect on mortality of long-term selenium supplementation at different dose levels.

DESIGN

The Denmark PRECISE study was a single-centre, randomised, double-blinded, placebo-controlled, multi-arm, parallel clinical trial with four groups. Participants were 491 male and female volunteers aged 60-74 years, recruited at Odense University Hospital, Denmark. The trial was initially designed as a 6-month pilot study, but supplemental funding allowed for extension of the study and mortality assessment. Participants were randomly assigned to treatment with 100, 200, or 300 µg selenium/d as selenium-enriched-yeast or placebo-yeast for 5 years from randomization in 1998-1999 and were followed up for mortality for a further 10 years (through March 31, 2015).

RESULTS

During 6871 person-years of follow-up, 158 deaths occurred. In an intention-to-treat analysis, the hazard ratio (95% confidence interval) for all-cause mortality comparing 300 µg selenium/d to placebo was 1.62 (0.66, 3.96) after 5 years of treatment and 1.59 (1.02, 2.46) over the entire follow-up period. The 100 and 200 µg/d doses showed non-significant decreases in mortality during the intervention period that disappeared after treatment cessation. Although we lacked power for endpoints other than all-cause mortality, the effects on cancer and cardiovascular mortality appeared similar.

CONCLUSIONS

A 300 µg/d dose of selenium taken for 5 years in a country with moderately-low selenium status increased all-cause mortality 10 years later. While our study was not initially designed to evaluate mortality and the sample size was limited, our findings indicate that total selenium intake over 300 µg/d and high-dose selenium supplements should be avoided.

Beneficial and paradoxical roles of selenium at nutritional levels of intake in healthspan and longevity

Accumulation of genome and macromolecule damage is a hallmark of aging, age-associated degeneration, and genome instability syndromes. Although processes of aging are irreversible, they can be modulated by genome maintenance pathways and environmental factors such as diet. Selenium (Se) confers its physiological functions mainly through selenoproteins, but Se compounds and other proteins that incorporate Se nonspecifically also impact optimal health. Bruce Ames proposed that the aging process could be mitigated by a subset of low-hierarchy selenoproteins whose levels are preferentially reduced in response to Se deficiency. Consistent with this notion, results from two selenotranscriptomic studies collectively implicate three low-hierarchy selenoproteins in age or senescence. Experimental evidence generally supports beneficial roles of selenoproteins in the protection against damage accumulation and redox imbalance, but some selenoproteins have also been reported to unexpectedly display harmful functions under sporadic conditions. While longevity and healthspan are usually thought to be projected in parallel, emerging evidence suggests a trade-off between longevity promotion and healthspan deterioration with damage accumulation. We propose that longevity promotion under conditions of Se deficiency may be attributed to 1) stress-response hormesis, an advantageous event of resistance to toxic chemicals at low doses; 2) reduced expression of selenoproteins with paradoxical functions to a lesser extent. In particular, selenoprotein H is an evolutionally conserved nuclear selenoprotein postulated to confer Se functions in redox regulation, genome maintenance, and senescence. This review highlights the need to pinpoint roles of specific selenoproteins and Se compounds in healthspan and lifespan for a better understanding of Se contribution at nutritional levels of intake to healthy aging.

Antioxidant effects of selenocysteine on replicative senescence in human adipose-derived mesenchymal stem cells

In most clinical applications, human mesenchymal stem cells (hMSCs) are expanded in large scale before their administration. Prolonged culture in vitro results in cellular senescence-associated phenotypes, including accumulation of reactive oxygen species (ROS) and decreased cell viabilities. Profiling of stem cell-related genes during in vitro expansion revealed that numerous canonical pathways were significantly changed. To determine the effect of selenocysteine (Sec), a rare amino acid found in several antioxidant enzymes, on the replicative senescence in hMSCs, we treated senescent hMSCs with Sec. Supplementation of Sec in the culture medium in late-passage hMSCs reduced ROS levels and improved the survival of hMSCs. In addition, a subset of key antioxidant genes and Sec-containing selenoproteins showed increased mRNA levels after Sec treatment. Furthermore, ROS metabolism and inflammation pathways were predicted to be downregulated. Taken together, our results suggest that Sec has antioxidant effects on the replicative senescence of hMSCs.

Selenium supplementation lowers insulin resistance and markers of cardio-metabolic risk in patients with congestive heart failure: a randomised, double-blind, placebo-controlled trial

This study was carried out to evaluate the effects of Se supplementation on metabolic profiles in patients with congestive heart failure (CHF). This randomised double-blind, placebo-controlled trial was performed among fifty-three subjects with CHF, aged 45–85 years old. Subjects were randomly allocated into two groups to take either 200 µg/d of Se as Se yeast (n 26) or placebo (n 27) for 12 weeks. Metabolic profiles were assessed at baseline and at the end of trial. Compared with the placebo, Se supplementation led to significant reductions in serum insulin (−18·41 (sd 27·53) v. +13·73 (sd 23·63) pmol/l, P<0·001), homoeostatic model of assessment for insulin resistance (−1·01 (sd 1·61) v. +0·55 (sd 1·20), P<0·001) and a significant increase in quantitative insulin sensitivity check index (QUICKI) (+0·007 (sd 0·03) v. −0·01 (sd 0·01), P=0·007). In addition, Se supplementation significantly decreased LDL-cholesterol (−0·23 (sd 0·29) v. −0·04 (sd 0·28) mmol/l, P=0·03) and total-:HDL-cholesterol ratio (−0·47 (sd 0·31) v. −0·06 (sd 0·42), P<0·001), and significantly increased HDL-cholesterol levels (+0·18 (sd 0·19) v. +0·02 (sd 0·13) mmol/l, P=0·001) compared with the placebo. In addition, taking Se supplements was associated with a significant reduction in high-sensitivity C-reactive protein (hs-CRP) (−1880·8 (sd 3437·5) v. +415·3 (sd 2116·5) ng/ml, P=0·01), and a significant elevation in plasma total antioxidant capacity (TAC) (+30·9 (sd 118·0) v. −187·9 (sd 412·7) mmol/l, P=0·004) and total glutathione levels (+33·7 (sd 130·4) v. −39·2 (sd 132·8) µmol/l, P=0·003) compared with the placebo. When we applied Bonferroni correction for multiple outcome testing, QUICKI (P=0·11), LDL-cholesterol (P=0·51), hs-CRP (P=0·17), TAC (P=0·06) and GSH (P=0·05) became non-significant, and other metabolic profiles did not alter. Overall, our study supported that Se supplementation for 12 weeks to patients with CHF had beneficial effects on insulin metabolism and few markers of cardio-metabolic risk.

Developmental selenium exposure and health risk in daily foodstuffs: A systematic review and meta-analysis

Selenium (Se) is a trace mineral and an essential nutrient of vital importance to human health in trace amounts. It acts as an antioxidant in both humans and animals, immunomodulator and also involved in the control of specific endocrine pathways. The aim of this work is to provide a brief knowledge on selenium content in daily used various foodstuffs, nutritional requirement and its various health consequences. In general, fruits and vegetables contain low content of selenium, with some exceptions. Selenium level in meat, eggs, poultry and seafood is usually high. For most countries, cereals, legumes, and derivatives are the major donors to the dietary selenium intake. Low level of selenium has been related with higher mortality risk, dysfunction of an immune system, and mental failure. Selenium supplementation or higher selenium content has antiviral outcomes and is necessary for effective reproduction of male and female, also decreases the threat of chronic disease (autoimmune thyroid). Generally, some advantages of higher content of selenium have been shown in various potential studies regarding lung, colorectal, prostate and bladder cancers risk, nevertheless results depicted from different trials have been diverse, which perhaps indicates the evidence that supplementation will merely grant advantage if the intakes of a nutrient is deficient. In conclusion, the over-all people should be advised against the usage of Se supplements for prevention of cardiovascular, hepatopathies, or cancer diseases, as advantages of Se supplements are still ambiguous, and their haphazard usage could result in an increased Se toxicity risk. The associations among Se intake/status and health, or disease risk, are complicated and need exposition to notify medical practice, to improve dietary recommendations, and to develop adequate communal health guidelines.

Age-Dependent Protective Effect of Selenium against UVA Irradiation in Primary Human Keratinocytes and the Associated DNA Repair Signature

Few studies have focused on the protective role of selenium (Se) against skin aging and photoaging even though selenoproteins are essential for keratinocyte function and skin development. To the best of our knowledge, the impact of Se supplementation on skin cells from elderly and young donors has not been reported. Therefore, the main objective of our study was to evaluate the effects of Se supplementation on skin keratinocytes at baseline and after exposure to ultraviolet A (UVA) irradiation. Low doses of Se (30 nM) were very potently protective against UVA-induced cytotoxicity in young keratinocytes, whereas the protection efficiency of Se in old keratinocytes required higher concentrations (240 nM). Additionally, the DNA repair ability of the old keratinocytes drastically decreased compared with that of the young keratinocytes at baseline and after the UVA exposure. The Se supplementation significantly enhanced the DNA repair of 8-oxoguanine (8oxoG) only in the keratinocytes isolated from young donors. Therefore, aged keratinocytes have an increased vulnerability to oxidative DNA damage, and the Se needs in the elderly should be considered. Strengthening DNA repair activities with Se supplementation may represent a new strategy to combat aging and skin photoaging.

Selenium preserves keratinocyte stemness and delays senescence by maintaining epidermal adhesion

Skin is constantly exposed to environmental factors such as pollutants, chemicals and ultra violet radiation (UV), which can induce premature skin aging and increase the risk of skin cancer. One strategy to reduce the effect of oxidative stress produced by environmental exposure is the application of antioxidant molecules. Among the endogenous antioxidants, selenoproteins play a key role in antioxidant defense and in maintaining a reduced cellular environment. Selenium, essential for the activity of selenoproteins, is a trace element that is not synthesized by organisms and must be supplied by diet or supplementation. The aim of this study is to evaluate the effect of Selenium supplementation on skin aging, especially on keratinocytes, the main cells of the epidermis. Our results demonstrate for the first time to our knowledge, the major role of Selenium on the replicative life span of keratinocytes and on aging skin. Selenium protects keratinocyte stem cells (KSCs) against senescence via preservation of their stemness phenotype through adhesion to the basement membrane. Additionally, Selenium supplementation maintains the homeostasis of skin during chronological aging in our senescent skin equivalent model. Controlled supplementation with Selenium could be a new strategy to protect skin against aging.

Selenium for preventing cancer

BACKGROUND

This review is the third update of the Cochrane review "Selenium for preventing cancer". Selenium is a naturally occurring element with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancer.

OBJECTIVES

To gather and present evidence needed to address two research questions:1. What is the aetiological relationship between selenium exposure and cancer risk in humans?2. Describe the efficacy of selenium supplementation for cancer prevention in humans.

SEARCH METHODS

We updated electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 2), MEDLINE (Ovid, 2013 to January 2017, week 4), and Embase (2013 to 2017, week 6), as well as searches of clinical trial registries.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and longitudinal observational studies that enrolled adult participants.

DATA COLLECTION AND ANALYSIS

We performed random-effects (RE) meta-analyses when two or more RCTs were available for a specific outcome. We conducted RE meta-analyses when five or more observational studies were available for a specific outcome. We assessed risk of bias in RCTs and in observational studies using Cochrane's risk assessment tool and the Newcastle-Ottawa Scale, respectively. We considered in the primary analysis data pooled from RCTs with low risk of bias. We assessed the certainty of evidence by using the GRADE approach.

MAIN RESULTS

We included 83 studies in this updated review: two additional RCTs (10 in total) and a few additional trial reports for previously included studies. RCTs involved 27,232 participants allocated to either selenium supplements or placebo. For analyses of RCTs with low risk of bias, the summary risk ratio (RR) for any cancer incidence was 1.01 (95% confidence interval (CI) 0.93 to 1.10; 3 studies, 19,475 participants; high-certainty evidence). The RR for estimated cancer mortality was 1.02 (95% CI 0.80 to 1.30; 1 study, 17,444 participants). For the most frequently investigated site-specific cancers, investigators provided little evidence of any effect of selenium supplementation. Two RCTs with 19,009 participants indicated that colorectal cancer was unaffected by selenium administration (RR 0.99, 95% CI 0.69 to 1.43), as were non-melanoma skin cancer (RR 1.16, 95% CI 0.30 to 4.42; 2 studies, 2027 participants), lung cancer (RR 1.16, 95% CI 0.89 to 1.50; 2 studies, 19,009 participants), breast cancer (RR 2.04, 95% CI 0.44 to 9.55; 1 study, 802 participants), bladder cancer (RR 1.07, 95% CI 0.76 to 1.52; 2 studies, 19,009 participants), and prostate cancer (RR 1.01, 95% CI 0.90 to 1.14; 4 studies, 18,942 participants). Certainty of the evidence was high for all of these cancer sites, except for breast cancer, which was of moderate certainty owing to imprecision, and non-melanoma skin cancer, which we judged as moderate certainty owing to high heterogeneity. RCTs with low risk of bias suggested increased melanoma risk.Results for most outcomes were similar when we included all RCTs in the meta-analysis, regardless of risk of bias. Selenium supplementation did not reduce overall cancer incidence (RR 0.99, 95% CI 0.86 to 1.14; 5 studies, 21,860 participants) nor mortality (RR 0.81, 95% CI 0.49 to 1.32; 2 studies, 18,698 participants). Summary RRs for site-specific cancers showed limited changes compared with estimates from high-quality studies alone, except for liver cancer, for which results were reversed.In the largest trial, the Selenium and Vitamin E Cancer Trial, selenium supplementation increased risks of alopecia and dermatitis, and for participants with highest background selenium status, supplementation also increased risk of high-grade prostate cancer. RCTs showed a slightly increased risk of type 2 diabetes associated with supplementation. A hypothesis generated by the Nutritional Prevention of Cancer Trial - that individuals with low blood selenium levels could reduce their risk of cancer (particularly prostate cancer) by increasing selenium intake - has not been confirmed. As RCT participants have been overwhelmingly male (88%), we could not assess the potential influence of sex or gender.We included 15 additional observational cohort studies (70 in total; over 2,360,000 participants). We found that lower cancer incidence (summary odds ratio (OR) 0.72, 95% CI 0.55 to 0.93; 7 studies, 76,239 participants) and lower cancer mortality (OR 0.76, 95% CI 0.59 to 0.97; 7 studies, 183,863 participants) were associated with the highest category of selenium exposure compared with the lowest. Cancer incidence was lower in men (OR 0.72, 95% CI 0.46 to 1.14, 4 studies, 29,365 men) than in women (OR 0.90, 95% CI 0.45 to 1.77, 2 studies, 18,244 women). Data show a decrease in risk of site-specific cancers for stomach, colorectal, lung, breast, bladder, and prostate cancers. However, these studies have major weaknesses due to study design, exposure misclassification, and potential unmeasured confounding due to lifestyle or nutritional factors covarying with selenium exposure beyond those taken into account in multi-variable analyses. In addition, no evidence of a dose-response relation between selenium status and cancer risk emerged. Certainty of evidence was very low for each outcome. Some studies suggested that genetic factors might modify the relation between selenium and cancer risk - an issue that merits further investigation.

AUTHORS' CONCLUSIONS

Well-designed and well-conducted RCTs have shown no beneficial effect of selenium supplements in reducing cancer risk (high certainty of evidence). Some RCTs have raised concerns by reporting a higher incidence of high-grade prostate cancer and type 2 diabetes in participants with selenium supplementation. No clear evidence of an influence of baseline participant selenium status on outcomes has emerged in these studies.Observational longitudinal studies have shown an inverse association between selenium exposure and risk of some cancer types, but null and direct relations have also been reported, and no systematic pattern suggesting dose-response relations has emerged. These studies suffer from limitations inherent to the observational design, including exposure misclassification and unmeasured confounding.Overall, there is no evidence to suggest that increasing selenium intake through diet or supplementation prevents cancer in humans. However, more research is needed to assess whether selenium may modify the risk of cancer in individuals with a specific genetic background or nutritional status, and to investigate possible differential effects of various forms of selenium.

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.

Selenium Concentrations for Maximisation of Thioredoxin Reductase 2 Activity and Upregulation of Its Gene Transcripts in Senescent Human Fibroblasts

Thioredoxin reductase 2 (TR2) activity, its gene transcripts, and hydrogen peroxide (H₂O₂) generation were examined in biochemically identified early-senescent P20 and senescent P30 fibroblasts subcultured in media (MEM2–MEM8) containing Se concentrations at 1.25, 2.5, 3.5, 5.0, 6.0, 7.0, and 8.0 µM, respectively. Although TR2 activity was moderately increased in P20 and P30 cells subcultured in routine growth medium (MEM1), there were progressive significant activity increases in the same cells subcultured in MEM2–MEM8. Such increases were proportional to Se concentration and peaked in P30 cells incubated with MEM7 and MEM8. H₂O₂ generation underwent progressive increases in MEM1-incubated P20 and P30 cells, peaking in the latter, but was gradually lowered in those incubated with MEM2–MEM8, reaching its lowest values when cells were incubated with MEM7 and MEM8. In parallel, TR2 gene transcripts underwent significant upregulation in P20 cells and higher magnitude upregulation in P30 cells subcultured in MEM2, MEM4, and MEM8 compared to those recorded for P5 pre-senescent cells subcultured in the same media. The computed Km Se values with respect to TR2 activity equaled 3.34 and 4.98 µM for P20 and P30 cells, respectively, with corresponding V_max activities of 55.9 and 96.2 nmol/min/mg protein. It is concluded that senescent P30 cells utilize more Se and achieve maximal TR2 activity to combat oxidative injury.

Prenatal exposure to selenium may protect against wheezing in children by the age of 3

Introduction

It has been suggested that human in utero exposure to heavy metals such as selenium can reduce the prevalence of childhood asthma and allergic diseases. However, data on this topic are scarce. The objective of the present study was to assess the putative associations between maternal selenium level during pregnancy and the risk of asthma, wheezing, allergic rhinitis, and atopic dermatitis in children from the EDEN birth cohort by the age of 1 and 3 years.

Methods

Plasma selenium concentrations were measured in maternal blood during mid‐pregnancy (24–28 weeks of gestation) in 861 mothers. Cohort children were followed up from birth to 3 years using health questionnaires filled out by the parents for asthma, wheezing, allergic rhinitis, and atopic dermatitis. Maternal plasma selenium was related to the childhood outcomes by the age of 1 and 3 years.

Results

Our results showed a significant negative association between a high maternal plasma selenium level during pregnancy and the risk of wheezing in the child by the age of 1 and 3 years. However, maternal plasma selenium during pregnancy was not associated with the prevalence of asthma, allergic rhinitis or atopic dermatitis.

Conclusions

The results of this study suggest that the level of fetal exposure to maternal selenium could have an influence on the risk of wheezing in infancy and potentially on the risk of developing asthma later in life.

Happily (n)ever after: Aging in the context of oxidative stress, proteostasis loss and cellular senescence

Aging is a complex phenomenon and its impact is becoming more relevant due to the rising life expectancy and because aging itself is the basis for the development of age-related diseases such as cancer, neurodegenerative diseases and type 2 diabetes. Recent years of scientific research have brought up different theories that attempt to explain the aging process. So far, there is no single theory that fully explains all facets of aging. The damage accumulation theory is one of the most accepted theories due to the large body of evidence found over the years. Damage accumulation is thought to be driven, among others, by oxidative stress. This condition results in an excess attack of oxidants on biomolecules, which lead to damage accumulation over time and contribute to the functional involution of cells, tissues and organisms. If oxidative stress persists, cellular senescence is a likely outcome and an important hallmark of aging. Therefore, it becomes crucial to understand how senescent cells function and how they contribute to the aging process. This review will cover cellular senescence features related to the protein pool such as morphological and molecular hallmarks, how oxidative stress promotes protein modifications, how senescent cells cope with them by proteostasis mechanisms, including antioxidant enzymes and proteolytic systems. We will also highlight the nutritional status of senescent cells and aged organisms (including human clinical studies) by exploring trace elements and micronutrients and on their importance to develop strategies that might increase both, life and health span and postpone aging onset.

Glutathione peroxidase 3 localizes to the epithelial lining fluid and the extracellular matrix in interstitial lung disease

Aberrant antioxidant activity and excessive deposition of extracellular matrix (ECM) are hallmarks of interstitial lung diseases (ILD). It is known that oxidative stress alters the ECM, but extracellular antioxidant defence mechanisms in ILD are incompletely understood. Here, we extracted abundance and detergent solubility of extracellular antioxidant enzymes from a proteomic dataset of bleomycin-induced lung fibrosis in mice and assessed regulation and distribution of glutathione peroxidase 3 (GPX3) in murine and human lung fibrosis. Superoxide dismutase 3 (Sod3), Gpx3, and Gpx activity were increased in mouse BALF during bleomycin-induced lung fibrosis. In lung tissue homogenates, Gpx3, but not Sod3, was upregulated and detergent solubility profiling indicated that Gpx3 associated with ECM proteins. Immunofluorescence analysis showed that Gpx3 was expressed by bronchial epithelial cells and interstitial fibroblasts and localized to the basement membrane and interstitial ECM in lung tissue. As to human ILD samples, BALF of some patients contained high levels of GPX3, and GPX3 was upregulated in lung homogenates from IPF patients. GPX3 expression in primary human bronchial epithelial cells and lung fibroblasts was downregulated by TNF-α, but more variably regulated by TGF-β1 and menadione. In conclusion, the antioxidant enzyme GPX3 localizes to lung ECM and is variably upregulated in ILD.

Micronutrient intake and food sources in the very old: analysis of the Newcastle 85+ Study

A number of socio-economic, biological and lifestyle characteristics change with advancing age and place very old adults at increased risk of micronutrient deficiencies. The aim of this study was to assess vitamin and mineral intakes and respective food sources in 793 75-year-olds (302 men and 491 women) in the North-East of England, participating in the Newcastle 85+ Study. Micronutrient intakes were estimated using a multiple-pass recall tool (2×24 h recalls). Determinants of micronutrient intake were assessed with multinomial logistic regression. Median vitamin D, Ca and Mg intakes were 2·0 (interquartile range (IQR) 1·2-6·5) µg/d, 731 (IQR 554-916) mg/d and 215 (IQR 166-266) mg/d, respectively. Fe intake was 8·7 (IQR 6·7-11·6) mg/d, and Se intake was 39·0 (IQR 27·3-55·5) µg/d. Cereals and cereal products were the top contributors to intakes of folate (31·5 %), Fe (49·2 %) and Se (46·7 %) and the second highest contributors to intakes of vitamin D (23·8 %), Ca (27·5 %) and K (15·8 %). More than 95 % (n 756) of the participants had vitamin D intakes below the UK's Reference Nutrient Intake (10 µg/d). In all, >20 % of the participants were below the Lower Reference Nutrient Intake for Mg (n 175), K (n 238) and Se (n 418) (comparisons with dietary reference values (DRV) do not include supplements). As most DRV are not age specific and have been extrapolated from younger populations, results should be interpreted with caution. Participants with higher education, from higher social class and who were more physically active had more nutrient-dense diets. More studies are needed to inform the development of age-specific DRV for micronutrients for the very old.

Dietary selenium intake and mortality in two population-based cohort studies of 133 957 Chinese men and women

OBJECTIVE

To investigate the potential influence of dietary Se intake on mortality among Chinese populations.

DESIGN

We prospectively evaluated all-cause, CVD and cancer mortality risks associated with dietary Se intake in participants of the Shanghai Women's Health Study (SWHS) and the Shanghai Men's Health study (SMHS). Dietary Se intake was assessed by validated FFQ during in-person interviews. Cox proportional hazards models were used to calculate hazard ratios (HR) and 95 % CI.

SETTING

Urban city in China.

SUBJECTS

Chinese adults (n 133 957).

RESULTS

During an average follow-up of 13·90 years in the SWHS and 8·37 years in the SMHS, 5749 women and 4217 men died. The mean estimated dietary Se intake was 45·48 μg/d for women and 51·34 μg/d for men, respectively. Dietary Se intake was inversely associated with all-cause mortality and CVD mortality in both women and men, with respective HR for the highest compared with the lowest quintile being 0·79 (95 % CI 0·71, 0·88; P trend<0·0001) and 0·80 (95 % CI 0·66, 0·98; P trend=0·0268) for women, and 0·79 (95 % CI 0·70, 0·89; P trend=0·0001) and 0·66 (95 % CI 0·54, 0·82; P trend=0·0002) for men. No significant associations were observed for cancer mortality in both women and men. Results were similar in subgroup and sensitivity analyses.

CONCLUSIONS

Dietary Se intake was inversely associated with all-cause and cardiovascular mortality in both sexes, but not cancer mortality.

BMI and all cause mortality: systematic review and non-linear dose-response meta-analysis of 230 cohort studies with 3.74 million deaths among 30.3 million participants

OBJECTIVE

To conduct a systematic review and meta-analysis of cohort studies of body mass index (BMI) and the risk of all cause mortality, and to clarify the shape and the nadir of the dose-response curve, and the influence on the results of confounding from smoking, weight loss associated with disease, and preclinical disease.

DATA SOURCES

PubMed and Embase databases searched up to 23 September 2015.

STUDY SELECTION

Cohort studies that reported adjusted risk estimates for at least three categories of BMI in relation to all cause mortality.

DATA SYNTHESIS

Summary relative risks were calculated with random effects models. Non-linear associations were explored with fractional polynomial models.

RESULTS

230 cohort studies (207 publications) were included. The analysis of never smokers included 53 cohort studies (44 risk estimates) with >738 144 deaths and >9 976 077 participants. The analysis of all participants included 228 cohort studies (198 risk estimates) with >3 744 722 deaths among 30 233 329 participants. The summary relative risk for a 5 unit increment in BMI was 1.18 (95% confidence interval 1.15 to 1.21; I(2)=95%, n=44) among never smokers, 1.21 (1.18 to 1.25; I(2)=93%, n=25) among healthy never smokers, 1.27 (1.21 to 1.33; I(2)=89%, n=11) among healthy never smokers with exclusion of early follow-up, and 1.05 (1.04 to 1.07; I(2)=97%, n=198) among all participants. There was a J shaped dose-response relation in never smokers (Pnon-linearity <0.001), and the lowest risk was observed at BMI 23-24 in never smokers, 22-23 in healthy never smokers, and 20-22 in studies of never smokers with ≥20 years' follow-up. In contrast there was a U shaped association between BMI and mortality in analyses with a greater potential for bias including all participants, current, former, or ever smokers, and in studies with a short duration of follow-up (<5 years or <10 years), or with moderate study quality scores.

CONCLUSION

Overweight and obesity is associated with increased risk of all cause mortality and the nadir of the curve was observed at BMI 23-24 among never smokers, 22-23 among healthy never smokers, and 20-22 with longer durations of follow-up. The increased risk of mortality observed in underweight people could at least partly be caused by residual confounding from prediagnostic disease. Lack of exclusion of ever smokers, people with prevalent and preclinical disease, and early follow-up could bias the results towards a more U shaped association.

PEG functionalized selenium nanoparticles as a carrier of crocin to achieve anticancer synergism

Schematic representation of crocin extraction from saffron stigmas and possible mechanism of pH based crocin delivery system of PEG-SeNP induced apoptosis in lung cancer cell.

Update on selenoprotein biosynthesis

SIGNIFICANCE

Selenium is an essential trace element that is incorporated in the small but vital family of proteins, namely the selenoproteins, as the selenocysteine amino acid residue. In humans, 25 selenoprotein genes have been characterized. The most remarkable trait of selenoprotein biosynthesis is the cotranslational insertion of selenocysteine by the recoding of a UGA codon, normally decoded as a stop signal.

RECENT ADVANCES

In eukaryotes, a set of dedicated cis- and trans-acting factors have been identified as well as a variety of regulatory mechanisms, factors, or elements that control the selenoprotein expression at the level of the UGA-selenocysteine recoding process, offering a fascinating playground in the field of translational control. It appeared that the central players are two RNA molecules: the selenocysteine insertion sequence (SECIS) element within selenoprotein mRNA and the selenocysteine-tRNA([Ser]Sec); and their interacting partners.

CRITICAL ISSUES

After a couple of decades, despite many advances in the field and the discovery of many essential and regulatory components, the precise mechanism of UGA-selenocysteine recoding remains elusive and more complex than anticipated, with many layers of control. This review offers an update of selenoproteome biosynthesis and regulation in eukaryotes.

FUTURE DIRECTIONS

The regulation of selenoproteins in response to a variety of pathophysiological conditions and cellular stressors, including selenium levels, oxidative stress, replicative senescence, or cancer, awaits further detailed investigation. Clearly, the efficiency of UGA-selenocysteine recoding is the limiting stage of selenoprotein synthesis. The sequence of events leading Sec-tRNA([Ser]Sec) delivery to ribosomal A site awaits further analysis, notably at the level of a three-dimensional structure.

Revised reference values for selenium intake

The German, Austrian and Swiss nutrition societies are the joint editors of the 'reference values for nutrient intake'. They have revised the reference values for the intake of selenium and published them in February 2015. The saturation of selenoprotein P (SePP) in plasma is used as a criterion for the derivation of reference values for selenium intake in adults. For persons from selenium-deficient regions (China) SePP saturation was achieved with a daily intake of 49μg of selenium. When using the reference body weights the D-A-CH reference values are based upon, the resulting estimated value for selenium intake is 70μg/day for men and 60μg/day for women. The estimated value for selenium intake for children and adolescents is extrapolated using the estimated value for adults in relation to body weight. For infants aged 0 to under 4 months the estimated value of 10μg/day was derived from the basis of selenium intake via breast milk. For infants aged 4 to under 12 months this estimated value was used and taking into account the differences regarding body weight an estimated value of 15μg/day was derived. For lactating women compared to non-lactating women a higher reference value of 75μg/day is indicated due to the release of selenium with breast milk. The additional selenium requirement for pregnant women is negligible, so that no increased reference value is indicated.

Cognitive impairment, genomic instability and trace elements

Cognitive impairments are often related to aging and micronutrient deficiencies. Various essential micronutrients in the diet are involved in age-altered biological functions such as, zinc, copper, iron, and selenium that play pivotal roles either in maintaining and reinforcing the antioxidant performances or in affecting the complex network of genes (nutrigenomic approach) involved in encoding proteins for biological functions. Genomic stability is one of the leading causes of cognitive decline and deficiencies or excess in trace elements are two of the factors relating to it. In this review, we report and discuss the role of micronutrients in cognitive impairment in relation to genomic stability in an aging population. Telomere integrity will also be discussed in relation to aging and cognitive impairment, as well as, the micronutrients related to these events. This review will provide an understanding on how these three aspects can relate with each other and why it is important to keep a homeostasis of micronutrients in relation to healthy aging. Micronutrient deficiencies and aging process can lead to genomic instability.

Selenium action in neuro-oncology

The trace element selenium and selenocysteine-carrying selenoproteins play a pivotal role in the brain. Beside the essential function during development and maintenance of brain action, selenium has also been associated with several neurological and neuro-oncological conditions. Reliable supply of selenium is important since selenium compounds can affect tumor microenvironment and neoangiogenesis in malignant gliomas (WHO grade III and IV [glioblastoma, GBM]) via induction of apoptosis and alteration of matrix metalloproteinases expression. Here, we summarize recent findings focusing on the anti-toxicity and cancer-preventive properties of selenium and their implication in current multimodal therapies including temozolomide (Temodal), cyclophosphamide (Endoxan), and cisplatin (DDP, Platiblastin, and Platinol). We shed light on unintended side effects in chemotherapy and the developments of novel combinatorial chemotherapeutics with selenium compounds. We found that selenium and selenium compounds have dual action profiles with direct anti-cancer and chemotherapy-intensifier effects as well as neuroprotective and cytoprotective agents. Current selenium trials and selenium supplementation with focus on neuro-oncology will be discussed with regard to low-adequate-to-high/toxic selenium status.

Associations between antioxidants and all-cause mortality among US adults with obstructive lung function

Chronic obstructive pulmonary disease is characterised by oxidative stress, but little is known about the associations between antioxidant status and all-cause mortality in adults with this disease. The objective of the present study was to examine the prospective associations between concentrations of α- and β-carotene, β-cryptoxanthin, lutein/zeaxanthin, lycopene, Se, vitamin C and α-tocopherol and all-cause mortality among US adults with obstructive lung function. Data collected from 1492 adults aged 20-79 years with obstructive lung function in the National Health and Nutrition Examination Survey III (1988-94) were used. Through 2006, 629 deaths were identified during a median follow-up period of 14 years. After adjustment for demographic variables, the concentrations of the following antioxidants modelled as continuous variables were found to be inversely associated with all-cause mortality among adults with obstructive lung function: α-carotene (P= 0·037); β-carotene (P= 0·022); cryptoxanthin (P= 0·022); lutein/zeaxanthin (P= 0·004); total carotenoids (P= 0·001); vitamin C (P< 0·001). In maximally adjusted models, only the concentrations of lycopene (P= 0·013) and vitamin C (P= 0·046) were found to be significantly and inversely associated with all-cause mortality. No effect modification by sex was detected, but the association between lutein/zeaxanthin concentrations and all-cause mortality varied by smoking status (P interaction= 0·048). The concentrations of lycopene and vitamin C were inversely associated with all-cause mortality in this cohort of adults with obstructive lung function.

Carotenoids and health in older people

As the proportion of older people increases, so will chronic disease incidence and the proportion of the population living with disability. Therefore, new approaches to maintain health for as long as possible in this age group are required. Carotenoids are a group of polyphenolic compounds found predominantly in fruit and vegetables that have been proposed to have anti-inflammatory and antioxidant effects. Such properties may impact on the risk diseases which predominate in older people, and also ageing-related physiological changes. Working out the effect of carotenoid intake versus fruit and vegetable intake is difficult, and the strong correlation between individual carotenoid intakes also complicates any attempt to examine individual carotenoid health effects. Similarly, research to determine whether carotenoids consumed as supplements have similar benefits to increased dietary intake through whole foods, is still required. However, reviewing the recent evidence suggests that carotenoid intake and status are relatively consistently associated with reduced CVD risk, although β-carotene supplementation does not reduce CVD risk and increases lung cancer risk. Increased lycopene intake may reduce prostate cancer progression, with a potential role for carotenoids at other cancer sites. Lutein and zeaxanthin have a plausible role in the maintenance of eye health, whilst an association between carotenoid intake and cognitive and physical health appears possible, although research is limited to date. Given this accruing evidence base to support a specific role for certain carotenoids and ageing, current dietary advice to consume a diet rich in fruit and vegetables would appear prudent, and efforts maintained to encourage increased intake.

Dietary and circulating lycopene and stroke risk: a meta-analysis of prospective studies

Epidemiological studies support a protective role of lycopene against stroke occurrence or mortality, but the results have been conflicting. We conducted a meta-analysis to assess the relationship between dietary or circulating lycopene and stroke risk (including stroke occurrence or mortality). Relevant papers were collected by screening the PubMed database through October 2013. Only prospective studies providing relative risk estimates with 95% confidence intervals for the association between lycopene and stroke were included. A random-effects model was used to calculate the pooled estimate. Subgroup analysis was conducted to investigate the effects of various factors on the final results. The pooled analysis of seven prospective studies, with 116,127 participants and 1,989 cases, demonstrated that lycopene decreased stroke risk by 19.3% (RR = 0.807, 95% CI = 0.680–0.957) after adjusting for confounding factors. No heterogeneity was observed (p = 0.234, I² = 25.5%). Circulating lycopene, not dietary lycopene, was associated with a statistically significant decrease in stroke risk (RR = 0.693, 95% CI = 0.503–0.954). Lycopene could protect European, or males against stroke risk. Duration of follow-up had no effect on the final results. There was no evidence of publication bias. Lycopene, especially circulating lycopene, is negatively associated with stroke risk.

Reduction of selenite to red elemental selenium by Rhodopseudomonas palustris strain N

The trace metal selenium is in demand for health supplements to human and animal nutrition. We studied the reduction of selenite (SeO₃⁻²) to red elemental selenium by Rhodopseudomonas palustris strain N. This strain was cultured in a medium containing SeO₃⁻² and the particles obtained from cultures were analyzed using transmission electron microscopy (TEM), energy dispersive microanalysis (EDX) and X ray diffraction analysis (XRD). Our results showed the strain N could reduce SeO₃⁻² to red elemental selenium. The diameters of particles were 80-200 nm. The bacteria exhibited significant tolerance to SeO₃⁻² up to 8.0 m mol/L concentration with an EC₅₀ value of 2.4 m mol/L. After 9 d of cultivation, the presence of SeO₃²⁻ up to 1.0 m mol/L resulted in 99.9% reduction of selenite, whereas 82.0% (p<0.05), 31.7% (p<0.05) and 2.4% (p<0.05) reduction of SeO₃⁻² was observed at 2.0, 4.0 and 8.0 m mol/L SeO₃²⁻ concentrations, respectively. This study indicated that red elemental selenium was synthesized by green technology using Rhodopseudomonas palustris strain N. This strain also indicated a high tolerance to SeO₃⁻². The finding of this work will contribute to the application of selenium to human health.

Associations of the antioxidant capacity and hemoglobin levels with functional physical performance of the upper and lower body limbs

Herein we considered the role of oxidative stress on deficiencies of functional physical performance that could affect a future pre-frailty condition. Using principal component analyses (PCA), we created new variables to better describe the functionality regarding the physical performance of the upper and lower body limbs. Gait speed and the Short Physical Performance Battery (SPPB) score were classified by PCA to describe functional performance of the lower body limbs. Variables describing the general physical status, including weekly consumption of kilocalories and the musculoskeletal index, were classified together with grip strength of the dominant hand as indicators of functional performance of the upper body limbs. An intimate association between the functional physical performance of the upper body limbs and the total antioxidant capacity was observed in older subjects. Low levels of total antioxidant capacity were found in women 76 years or younger with deficiencies in the physical performance of both upper and lower body limbs. Similarly, we observed a close association between the functional physical performance of the lower body limbs and the levels of hemoglobin. In particular, low levels of hemoglobin were mostly found in men older than 76 years of age, showing impaired functional physical performance. In addition, the physical performance of the lower body limbs was shown to be more important than that of the upper body limbs in the statistical association with pre-frailty in the elderly. Therefore, specific low levels of hemoglobin and deficient oxidative defense in the elderly could significantly affect the functional physical performance and future outcomes of pre-frailty.

Selenium for preventing cancer

BACKGROUND

This review is an update of the first Cochrane publication on selenium for preventing cancer (Dennert 2011).Selenium is a metalloid with both nutritional and toxicological properties. Higher selenium exposure and selenium supplements have been suggested to protect against several types of cancers.

OBJECTIVES

Two research questions were addressed in this review: What is the evidence for:1. an aetiological relation between selenium exposure and cancer risk in humans? and2. the efficacy of selenium supplementation for cancer prevention in humans?

SEARCH METHODS

We conducted electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, 2013, Issue 1), MEDLINE (Ovid, 1966 to February 2013 week 1), EMBASE (1980 to 2013 week 6), CancerLit (February 2004) and CCMed (February 2011). As MEDLINE now includes the journals indexed in CancerLit, no further searches were conducted in this database after 2004.

SELECTION CRITERIA

We included prospective observational studies (cohort studies including sub-cohort controlled studies and nested case-control studies) and randomised controlled trials (RCTs) with healthy adult participants (18 years of age and older).

DATA COLLECTION AND ANALYSIS

For observational studies, we conducted random effects meta-analyses when five or more studies were retrieved for a specific outcome. For RCTs, we performed random effects meta-analyses when two or more studies were available. The risk of bias in observational studies was assessed using forms adapted from the Newcastle-Ottawa Quality Assessment Scale for cohort and case-control studies; the criteria specified in the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias in RCTs.

MAIN RESULTS

We included 55 prospective observational studies (including more than 1,100,000 participants) and eight RCTs (with a total of 44,743 participants). For the observational studies, we found lower cancer incidence (summary odds ratio (OR) 0.69, 95% confidence interval (CI) 0.53 to 0.91, N = 8) and cancer mortality (OR 0.60, 95% CI 0.39 to 0.93, N = 6) associated with higher selenium exposure. Gender-specific subgroup analysis provided no clear evidence of different effects in men and women (P value 0.47), although cancer incidence was lower in men (OR 0.66, 95% CI 0.42 to 1.05, N = 6) than in women (OR 0.90, 95% CI 0.45 to 1.77, N = 2). The most pronounced decreases in risk of site-specific cancers were seen for stomach, bladder and prostate cancers. However, these findings have limitations due to study design, quality and heterogeneity that complicate interpretation of the summary statistics. Some studies suggested that genetic factors may modify the relation between selenium and cancer risk-a hypothesis that deserves further investigation.In RCTs, we found no clear evidence that selenium supplementation reduced the risk of any cancer (risk ratio (RR) 0.90, 95% CI 0.70 to 1.17, two studies, N = 4765) or cancer-related mortality (RR 0.81, 95% CI 0.49 to 1.32, two studies, N = 18,698), and this finding was confirmed when the analysis was restricted to studies with low risk of bias. The effect on prostate cancer was imprecise (RR 0.90, 95% CI 0.71 to 1.14, four studies, N = 19,110), and when the analysis was limited to trials with low risk of bias, the interventions showed no effect (RR 1.02, 95% CI 0.90 to 1.14, three studies, N = 18,183). The risk of non-melanoma skin cancer was increased (RR 1.44, 95% CI 0.95 to 1.17, three studies, N = 1900). Results of two trials-the Nutritional Prevention of Cancer Trial (NPCT) and the Selenium and Vitamin E Cancer Trial (SELECT)-also raised concerns about possible increased risk of type 2 diabetes, alopecia and dermatitis due to selenium supplements. An early hypothesis generated by NPCT that individuals with the lowest blood selenium levels at baseline could reduce their risk of cancer, particularly of prostate cancer, by increasing selenium intake has not been confirmed by subsequent trials. As the RCT participants were overwhelmingly male (94%), gender differences could not be systematically assessed.

AUTHORS' CONCLUSIONS

Although an inverse association between selenium exposure and the risk of some types of cancer was found in some observational studies, this cannot be taken as evidence of a causal relation, and these results should be interpreted with caution. These studies have many limitations, including issues with assessment of exposure to selenium and to its various chemical forms, heterogeneity, confounding and other biases. Conflicting results including inverse, null and direct associations have been reported for some cancer types.RCTs assessing the effects of selenium supplementation on cancer risk have yielded inconsistent results, although the most recent studies, characterised by a low risk of bias, found no beneficial effect on cancer risk, more specifically on risk of prostate cancer, as well as little evidence of any influence of baseline selenium status. Rather, some trials suggest harmful effects of selenium exposure. To date, no convincing evidence suggests that selenium supplements can prevent cancer in humans.

Interplay between selenium levels, selenoprotein expression, and replicative senescence in WI-38 human fibroblasts

Selenium is an essential trace element, which is incorporated as selenocysteine into at least 25 selenoproteins using a unique translational UGA-recoding mechanism. Selenoproteins are important enzymes involved in antioxidant defense, redox homeostasis, and redox signaling pathways. Selenium levels decline during aging, and its deficiency is associated with a marked increase in mortality for people over 60 years of age. Here, we investigate the relationship between selenium levels in the culture medium, selenoprotein expression, and replicative life span of human embryonic lung fibroblast WI-38 cells. Selenium levels regulate the entry into replicative senescence and modify the cellular markers characteristic for senescent cells. Whereas selenium supplementation extends the number of population doublings, its deficiency impairs the proliferative capacity of WI-38 cells. We observe that the expression of several selenoproteins involved in antioxidant defense is specifically affected in response to cellular senescence. Their expression is selectively controlled by the modulation of mRNA levels and translational recoding efficiencies. Our data provide novel mechanistic insights into how selenium impacts the replicative life span of mammalian cells by identifying several selenoproteins as new targets of senescence.

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.

Resonance Raman based skin carotenoid measurements in newborns and infants

We describe Resonance Raman based skin carotenoid measurements in newborns and infants. Skin- and serum carotenoid levels correlate with high statistical significance in healthy newborns and infants, and with reduced accuracy also in prematurely born infants, who in general feature very low carotenoid levels and thin transparent skin giving rise to large background absorption effects. Skin carotenoid levels can be easily compared among subjects and/or tracked in longitudinal studies with the highly molecule-specific Raman method. It therefore holds promise as a rapid, non-invasive, carotenoid antioxidant assessment method for newborns and infants in the field of pediatrics.