Serum selenium is associated with plasma homocysteine concentrations in elderly humans

Relationships between minerals' intake and blood homocysteine levels based on three machine learning methods: a large cross-sectional study

BACKGROUND

Blood homocysteine (Hcy) level has become a sensitive indicator in predicting the development of cardiovascular disease. Studies have shown an association between individual mineral intake and blood Hcy levels. The effect of mixed minerals' intake on blood Hcy levels is unknown.

METHODS

Data were obtained from the baseline survey data of the Shanghai Suburban Adult Cohort and Biobank(SSACB) in 2016. A total of 38273 participants aged 20-74 years met our inclusion and exclusion criteria. Food frequency questionnaire (FFQ) was used to calculate the intake of 10 minerals (calcium, potassium, magnesium, sodium, iron, zinc, selenium, phosphorus, copper and manganese). Measuring the concentration of Hcy in the morning fasting blood sample. Traditional regression models were used to assess the relationship between individual minerals' intake and blood Hcy levels. Three machine learning models (WQS, Qg-comp, and BKMR) were used to the relationship between mixed minerals' intake and blood Hcy levels, distinguishing the individual effects of each mineral and determining their respective weights in the joint effect.

RESULTS

Traditional regression model showed that higher intake of calcium, phosphorus, potassium, magnesium, iron, zinc, copper, and manganese was associated with lower blood Hcy levels. Both Qg-comp and BKMR results consistently indicate that higher intake of mixed minerals is associated with lower blood Hcy levels. Calcium exhibits the highest weight in the joint effect in the WQS model. In Qg-comp, iron has the highest positive weight, while manganese has the highest negative weight. The BKMR results of the subsample after 10,000 iterations showed that except for sodium, all nine minerals had the high weights in the joint effect on the effect of blood Hcy levels.

CONCLUSION

Overall, higher mixed mineral's intake was associated with lower blood Hcy levels, and each mineral contributed differently to the joint effect. Future studies are available to further explore the mechanisms underlying this association, and the potential impact of mixed minerals' intake on other health indicators needs to be further investigated. These efforts will help provide additional insights to deepen our understanding of mixed minerals and their potential role in health maintenance.

Higher blood selenium level is associated with lower risk of hyperhomocysteinemia in the elderly

BACKGROUND AND AIMS

Earlier studies have reported inconsistent association between selenium (Se) and homocysteine (Hcy) levels, while no evidence could be found from Chinese population. To fill this gap, we investigated the association between blood Se and hyperhomocysteinemia (HHcy) of rural elderly population in China.

METHODS

A cross-sectional study on 1823 participants aged 65 and older from four Chinese rural counties was carried out in this study. Whole blood Se and serum Hcy concentrations were measured in fasting blood samples. Analysis of covariance and restricted cubic spline models were used to examine the association between Se and Hcy levels. Logistic regression models were used to evaluate the risk of prevalent HHcy among four Se quartile groups after adjusting for covariates.

RESULTS

For this sample, the mean blood Se concentration was 156.34 (74.65) μg/L and the mean serum Hcy concentration was 17.25 (8.42) μmol/L. A significant non-linear relationship was found between blood Se and serum Hcy, the association was inverse when blood Se was less than 97.404 μg/L and greater than 156.919 μg/L. Participants in the top three blood Se quartile groups had significantly lower risk of prevalent HHcy compared with the lowest quartile group. When defined as Hcy> 10 μmol/L, the odds ratios and 95% confidence interval of HHcy were 0.600 (0.390, 0.924), 0.616 (0.398, 0.951) and 0.479 (0.314, 0.732) for Q2, Q3, and Q4 Se quartile groups compared with the Q1 group, respectively. When defined as Hcy≥ 15 μmol/L, the odds ratios and 95% confidence interval of HHcy were 0.833 (0.633, 1.098) and 0.827 (0.626, 1.092), 0.647 (0.489, 0.857) for Q2, Q3, and Q4 Se quartile groups compared with Q1 group.

CONCLUSIONS

Our findings suggest that higher blood Se level could be a protective factor for HHcy in the elderly.

Reactive sulfur and selenium species in the regulation of bone homeostasis

Reactive oxygen species (ROS) are important modulators of physiological signaling and play important roles in bone tissue regulation. Both reactive sulfur species (RSS) and reactive selenium species (RSeS) are involved in ROS signaling, and recent work suggests RSS and RSeS involvement in the regulation of bone homeostasis. For example, RSS can promote osteogenic differentiation and decrease osteoclast activity and differentiation, and the antioxidant activity of RSeS play crucial roles in balancing bone remodeling. Here, we outline current research progress on the application of RSS and RSeS in bone disease and regeneration. Focusing on these investigations, we highlight different methods, tools, and sources of RSS and RSeS, and we also highlight future opportunities for delivery of RSS and RSeS in biological environments relating to bone.

Plasma metal concentrations and their interactions with genetic susceptibility on homocysteine levels

Limited studies have evaluated the associations of multiple metal exposures with homocysteine (Hcy) levels, which were independent risk factor for cardiovascular disease (CVD). Furthermore, the interactions between genetic variants and plasma metals in relation to Hcy levels were largely unknown. We aimed to explore the associations of multiple plasma metals (including metalloids arsenic [As] and selenium [Se]) with Hcy levels and whether their associations were modified by genetic susceptibility. We included 2989 participants from the baseline of the Dongfeng-Tongji cohort (DFTJ cohort) and conducted a cross-sectional study to explore the associations of 17 plasma metals with serum Hcy levels. Both multi-variable linear regression model (single-metal model) and LASSO penalized regression model (multiple-metal model) were used to identify the Hcy-associated metals. The weighted genetic risk score (GRS) was calculated based on 18 established Hcy-associated genetic variants. For metals that were associated with Hcy, we further assessed the gene-metal interactions on Hcy levels. Among 17 metals, plasma molybdenum (Mo), strontium (Sr), and Zinc (Zn) were positively associated with Hcy levels, whereas Se was inversely associated with Hcy levels in both single- and multiple-metal models. We also observed that the genetic predisposition to Hcy significantly modified the association between plasma Se and serum Hcy levels (P for interaction = 0.003), while no significant gene-metal interactions were found for Mo, Sr, and Zn (all P for interactions > 0.05). These findings provide novel insight into the associations of the plasma concentrations of Mo, Se, Sr and Zn with Hcy levels and address the importance of Se as a potential upstream modifiable factor for the personalized prevention of elevated Hcy levels and CVD.

Plasma selenium and the risk of first stroke in adults with hypertension: a secondary analysis of the China Stroke Primary Prevention Trial

BACKGROUND

Previous studies have indicated that selenium (Se) may play an important role in cardio-cerebrovascular disease. However, the relation between circulating selenium and risk of first stroke remains inconclusive.

OBJECTIVES

We conducted a secondary analysis of the China Stroke Primary Prevention Trial (CSPPT), using a nested case-control design, and aimed to investigate the correlation between Se concentration and first stroke risk in adults with hypertension and examine the potential effect modifiers.

METHODS

In the CSPPT, a total of 20,702 adults with hypertension were randomly assigned to a double-blind daily treatment with either 10 mg enalapril and 0.8 mg folic acid or 10 mg enalapril alone. A total of 618 first stroke cases and 618 controls matched for age, sex, treatment group, and study site were included in this study.

RESULTS

During a median follow-up duration of 4.5 y (IQR: 4.2-4.6 y), there was a significant inverse association between plasma Se and the risk of first stroke (per SD increment; adjusted OR: 0.81; 95% CI: 0.68, 0.96) and ischemic stroke (per SD increment; adjusted OR: 0.76; 95% CI: 0.62, 0.93). Furthermore, a stronger inverse association between plasma Se and first stroke was observed in participants with higher folate concentrations at baseline [≥7.7 ng/mL (median), adjusted OR: 0.67; 95% CI: 0.54, 0.85, compared with <7.7 ng/mL, adjusted OR: 0.98; 95% CI: 0.80, 1.21; P-interaction = 0.008] and those with higher time-averaged systolic blood pressure (SBP) over the treatment period (≥140 mm Hg, adjusted OR: 0.71; 95% CI: 0.58, 0.86, compared with <140 mm Hg, adjusted OR: 0.96; 95% CI: 0.77, 1.20; P-interaction = 0.023).

CONCLUSIONS

There was a significant inverse association between plasma Se and risk of first stroke in Chinese adults with hypertension, especially among those with higher baseline folate concentrations and those with higher time-averaged SBP over the treatment period. This trial was registered at clinicaltrials.gov as NCT00794885.

Treatment-resistant schizophrenia: focus on the transsulfuration pathway

Treatment-resistant schizophrenia (TRS) is a severe form of schizophrenia. The severity of illness is positively related to homocysteine levels, with high homocysteine levels due to the low activity of the transsulfuration pathway, which metabolizes homocysteine in synthesizing L-cysteine. Glutathione levels are low in schizophrenia, which indicates shortages of L-cysteine and low activity of the transsulfuration pathway. Hydrogen sulfide (H2S) levels are low in schizophrenia. H2S is synthesized by cystathionine β-synthase and cystathionine γ-lyase, which are the two enzymes in the transsulfuration pathway. Iron-sulfur proteins obtain sulfur from L-cysteine. The oxidative phosphorylation (OXPHOS) pathway has various iron-sulfur proteins. With low levels of L-cysteine, iron-sulfur cluster formation will be dysregulated leading to deficits in OXPHOS in schizophrenia. Molybdenum cofactor (MoCo) synthesis requires sulfur, which is obtained from L-cysteine. With low levels of MoCo synthesis, molybdenum-dependent sulfite oxidase (SUOX) will not be synthesized at appropriate levels. SUOX detoxifies sulfite from sulfur-containing amino acids. If sulfites are not detoxified, there can be sulfite toxicity. The transsulfuration pathway metabolizes selenomethionine, whereby selenium from selenomethionine can be used for selenoprotein synthesis. The low activity of the transsulfuration pathway decreases selenoprotein synthesis. Glutathione peroxidase (GPX), with various GPXs being selenoprotein, is low in schizophrenia. The dysregulations of selenoproteins would lead to oxidant stress, which would increase the methylation of genes and histones leading to epigenetic changes in TRS. An add-on treatment to mainline antipsychotics is proposed for TRS that targets the dysregulations of the transsulfuration pathway and the dysregulations of other pathways stemming from the transsulfuration pathway being dysregulated.

How Are Epigenetic Modifications Related to Cardiovascular Disease in Older Adults?

The rate of aging has increased globally during recent decades and has led to a rising burden of age-related diseases such as cardiovascular disease (CVD). At the molecular level, epigenetic modifications have been shown recently to alter gene expression during the life course and impair cellular function. In this regard, several CVD risk factors, such as lifestyle and environmental factors, have emerged as key factors in epigenetic modifications within the cardiovascular system. In this study, we attempted to summarized recent evidence related to epigenetic modification, inflammation response, and CVD in older adults as well as the effect of lifestyle modification as a preventive strategy in this age group. Recent evidence showed that lifestyle and environmental factors may affect epigenetic mechanisms, such as DNA methylation, histone acetylation, and miRNA expression. Several substances or nutrients such as selenium, magnesium, curcumin, and caffeine (present in coffee and some teas) could regulate epigenetics. Similarly, physical inactivity, alcohol consumption, air pollutants, psychological stress, and shift working are well-known modifiers of epigenetic patterns. Understanding the exact ways that lifestyle and environmental factors could affect the expression of genes could help to influence the time of incidence and severity of aging-associated diseases. This review highlighted that a healthy lifestyle throughout the life course, such as a healthy diet rich in fibers, vitamins, and essential elements, and specific fatty acids, adequate physical activity and sleep, smoking cessation, and stress control, could be useful tools in preventing epigenetic changes that lead to impaired cardiovascular function.

Genome-Wide Association Study of Response to Selenium Supplementation and Circulating Selenium Concentrations in Adults of European Descent

BACKGROUND

Selenium (Se) is a trace element that has been linked to many health conditions. Genome-wide association studies (GWAS) have identified variants for blood and toenail Se levels, but no GWAS has been conducted to date on responses to Se supplementation.

OBJECTIVES

A GWAS was performed to identify the single nucleotide polymorphisms (SNPs) associated with changes in Se concentrations after 1 year of supplementation. A GWAS of basal plasma Se concentrations at study entry was conducted to evaluate whether SNPs for Se responses overlap with SNPs for basal Se levels.

METHODS

A total of 428 participants aged 40-80 years of European descent from the Selenium and Celecoxib Trial (Sel/Cel Trial) who received daily supplementation with 200 µg of selenized yeast were included for the GWAS of responses to supplementation. Plasma Se concentrations were measured from blood samples collected at the time of recruitment and after 1 year of supplementation. Linear regression analyses were performed to assess the relationship between each SNP and changes in Se concentrations. We further examined whether the identified SNPs overlapped with those related to basal Se concentrations.

RESULTS

No SNP was significantly associated with changes in Se concentration at a genome-wide significance level. However, rs56856693, located upstream of the NEK6, was nominally associated with changes in Se concentrations after supplementation (P = 4.41 × 10-7), as were 2 additional SNPs, rs11960388 and rs6887869, located in the dimethylglycine dehydrogenase (DMGDH)/betaine-homocysteine S-methyltransferase (BHMT) region (P = 0.01). Alleles of 2 SNPs in the DMGDH/BHMT region associated with greater increases in Se concentrations after supplementation were also strongly associated with higher basal Se concentrations (P = 8.67 × 10-8).

CONCLUSIONS

This first GWAS of responses to Se supplementation in participants of European descent from the Sel/Cel Trial suggests that SNPs in the NEK6 and DMGDH/BHMT regions influence responses to supplementation.

Anti-Oxidant and Anti-Endothelial Dysfunctional Properties of Nano-Selenium in vitro and in vivo of Hyperhomocysteinemic Rats

Purpose

Elevation of blood homocysteine (Hcy) level (hyperhomocysteinemia) is a risk factor for cardiovascular disorders and is closely associated with endothelial dysfunction. The present study aims to investigate the protective effect and underlying mechanism of nanoscale selenium (Nano-Se) in Hcy-mediated vascular endothelial cell dysfunction in vitro and in vivo.

Materials and Methods

By incubating vascular endothelial cells with exogenous Hcy and generating hyperhomocysteinemic rat model, the effects of Nano-Se on hyperhomocysteinemia-mediated endothelial dysfunction and its essential mechanisms were investigated.

Results

Nano-Se inhibited Hcy-induced mitochondrial oxidative damage and apoptosis by preventing the downregulation of glutathione peroxidase enzyme 1 and 4 (GPX1, GPX4) in the vascular endothelial cells, thus effectively prevented the vascular damage in vitro and in vivo in the hyperhomocysteinemic rats. Nano-Se possessed similar protective effects but lower toxicity against Hcy in vascular endothelial cells when compared with other forms of Se.

Conclusion

The application of Nano-Se could serve as a novel promising strategy against Hcy-mediated vascular dysfunction with reduced risk of Se toxicity.

A disease-modifying treatment for Alzheimer's disease: focus on the trans-sulfuration pathway

High homocysteine levels in Alzheimer's disease (AD) result from low activity of the trans-sulfuration pathway. Glutathione levels are also low in AD. L-cysteine is required for the synthesis of glutathione. The synthesis of coenzyme A (CoA) requires L-cysteine, which is synthesized via the trans-sulfuration pathway. CoA is required for the synthesis of acetylcholine and appropriate cholinergic neurotransmission. L-cysteine is required for the synthesis of molybdenum-containing proteins. Sulfite oxidase (SUOX), which is a molybdenum-containing protein, could be dysregulated in AD. SUOX detoxifies the sulfites. Glutaminergic neurotransmission could be dysregulated in AD due to low levels of SUOX and high levels of sulfites. L-cysteine provides sulfur for iron-sulfur clusters. Oxidative phosphorylation (OXPHOS) is heavily dependent on iron-sulfur proteins. The decrease in OXPHOS seen in AD could be due to dysregulations of the trans-sulfuration pathway. There is a decrease in aconitase 1 (ACO1) in AD. ACO1 is an iron-sulfur enzyme in the citric acid cycle that upon loss of an iron-sulfur cluster converts to iron regulatory protein 1 (IRP1). With the dysregulation of iron-sulfur cluster formation ACO1 will convert to IRP1 which will decrease the 2-oxglutarate synthesis dysregulating the citric acid cycle and also dysregulating iron metabolism. Selenomethionine is also metabolized by the trans-sulfuration pathway. With the low activity of the trans-sulfuration pathway in AD selenoproteins will be dysregulated in AD. Dysregulation of selenoproteins could lead to oxidant stress in AD. In this article, we propose a novel treatment for AD that addresses dysregulations resulting from low activity of the trans-sulfuration pathway and low L-cysteine.

Malnutrition in obesity before and after bariatric surgery

Bariatric surgeries are considered the only effective way of weight loss therapy in morbidly obese patients, i.e. body mass index ≥ 35. However, micronutrient deficiencies and malnutrition are common after most bariatric procedures and thus, pre- and postoperative nutritional assessment and corrections are advised. The present review is presented in an effort to describe in some detail about prevalence, and mechanisms of macro- and micronutrient deficiencies in obese and post-bariatric surgery individuals. We also aimed to summarize the data on screening and supplementation of macro- and micronutrients before and after bariatric surgeries.

Selenium and Epigenetics in Cancer: Focus on DNA Methylation

Chemopreventive activity of selenium (Se) may influence epigenome. In this review, we have discussed two aspects of Se and epigenetics in cancer, related to (1) the association between Se and epigenetic regulation in cancer development and prevention; (2) epigenetic modification of selenoprotein-encoding genes in different cancers. In both issues, we focused on DNA methylation as the most investigated epigenetic mechanism. The existing evidence from experimental data in human cancer cell lines, rodents, and human studies in cancer-free subjects indicates that: high Se exposure leads to the inhibition of DNA methyltransferase expression/activity; the association between Se and global methylation remains unclear and requires further investigation with respect to the underlying mechanisms and possible nonlinear character of this relationship; Se affects methylation of specific tumor suppressor genes, possibly in a sex-dependent manner; and cancer phenotype is often characterized by altered methylation of selenoprotein-encoding genes, mainly glutathione peroxidase 3.

Epigenetic effects of selenium and their implications for health

Alterations of epigenetic marks are linked to normal development and cellular differentiation as well as to the progression of common chronic diseases. The plasticity of these marks provides potential for disease therapies and prevention strategies. Macro- and micro-nutrients have been shown to modulate disease risk in part via effects on the epigenome. The essential micronutrient selenium affects human health outcomes, e.g., cancers, cardiovascular and autoimmune diseases, via selenoproteins and through a range of biologically active dietary selenocompounds and metabolism products thereof. This review provides an assessment of the current literature regarding epigenetic effects of dietary and synthetic selenocompounds, which include the modulation of marks and editors of epigenetic information and interference with one-carbon metabolism, which provides the methyl donor for DNA methylation. The relevance of a selenium-epigenome interaction for human health is discussed, and we also indicate where future studies will be helpful to gain a deeper understanding of epigenetic effects elicited by selenium.

Genome-wide association study of selenium concentrations

Selenium (Se) is an essential trace element in human nutrition, but its role in certain health conditions, particularly among Se sufficient populations, is controversial. A genome-wide association study (GWAS) of blood Se concentrations previously identified a locus at 5q14 near BHMT. We performed a GW meta-analysis of toenail Se concentrations, which reflect a longer duration of exposure than blood Se concentrations, including 4162 European descendants from four US cohorts. Toenail Se was measured using neutron activation analysis. We identified a GW-significant locus at 5q14 (P < 1 × 10(-16)), the same locus identified in the published GWAS of blood Se based on independent cohorts. The lead single-nucleotide polymorphism (SNP) explained ∼1% of the variance in toenail Se concentrations. Using GW-summary statistics from both toenail and blood Se, we observed statistical evidence of polygenic overlap (P < 0.001) and meta-analysis of results from studies of either trait (n = 9639) yielded a second GW-significant locus at 21q22.3, harboring CBS (P < 4 × 10(-8)). Proteins encoded by genes at 5q14 and 21q22.3 function in homocysteine (Hcy) metabolism, and index SNPs for each have previously been associated with betaine and Hcy levels in GWAS. Our findings show evidence of a genetic link between Se and Hcy pathways, both involved in cardiometabolic disease.

Differential responses to selenomethionine supplementation by sex and genotype in healthy adults

A year-long intervention trial was conducted to characterise the responses of multiple biomarkers of Se status in healthy American adults to supplemental selenomethionine (SeMet) and to identify factors affecting those responses. A total of 261 men and women were randomised to four doses of Se (0, 50, 100 or 200 μg/d as L-SeMet) for 12 months. Responses of several biomarkers of Se status (plasma Se, serum selenoprotein P (SEPP1), plasma glutathione peroxidase activity (GPX3), buccal cell Se, urinary Se) were determined relative to genotype of four selenoproteins (GPX1, GPX3, SEPP1, selenoprotein 15), dietary Se intake and parameters of single-carbon metabolism. Results showed that supplemental SeMet did not affect GPX3 activity or SEPP1 concentration, but produced significant, dose-dependent increases in the Se contents of plasma, urine and buccal cells, each of which plateaued by 9-12 months and was linearly related to effective Se dose (μg/d per kg0·75). The increase in urinary Se excretion was greater for women than men, and for individuals of the GPX1 679 T/T genotype than for those of the GPX1 679 C/C genotype. It is concluded that the most responsive Se-biomarkers in this non-deficient cohort were those related to body Se pools: plasma, buccal cell and urinary Se concentrations. Changes in plasma Se resulted from increases in its non-specific component and were affected by both sex and GPX1 genotype. In a cohort of relatively high Se status, the Se intake (as SeMet) required to support plasma Se concentration at a target level (Se(pl-target)) is: Se(in) = [(Se(pl - target) - Se(pl))/(18.2ng d kg⁰.⁷⁵/ml per mu g)] .

Epigenetics and lifestyle

The concept of 'lifestyle' includes different factors such as nutrition, behavior, stress, physical activity, working habits, smoking and alcohol consumption. Increasing evidence shows that environmental and lifestyle factors may influence epigenetic mechanisms, such as DNA methylation, histone acetylation and miRNA expression. It has been identified that several lifestyle factors such as diet, obesity, physical activity, tobacco smoking, alcohol consumption, environmental pollutants, psychological stress and working on night shifts might modify epigenetic patterns. Most of the studies conducted so far have been centered on DNA methylation, whereas only a few investigations have studied lifestyle factors in relation to histone modifications and miRNAs. This article reviews current evidence indicating that lifestyle factors might affect human health via epigenetic mechanisms.

Common variants at 12q14 and 12q24 are associated with hippocampal volume

Aging is associated with reductions in hippocampal volume (HV) that are accelerated by Alzheimer’s disease and vascular risk factors. Our genome-wide association study of dementia-free persons (n=9,232) identified 46 SNPs at four loci with p-values <4.0×10^-7. Two additional samples (n=2,318) replicated associations at 12q24 within MSRB3/WIF1 (discovery + replication, rs17178006; p=5.3×10^-11) and at 12q14 near HRK/FBXW8 (rs7294919; p=2.9×10^-11). Remaining associations included one 2q24 SNP within DPP4 (rs6741949; p=2.9×10^-7) and nine 9p33 SNPs within ASTN2 (rs7852872; p=1.0×10^-7) that were also associated with HV (p<0.05) in a third younger, more heterogeneous sample (n=7,794). The ASTN2 SNP was also associated with decline in cognition in a largely independent sample (n=1,563). These associations implicate genes related to apoptosis (HRK), development (WIF1), oxidative stress (MSR3B), ubiquitination (FBXW8), enzymes targeted by new diabetes medications (DPP4), and neuronal migration (ASTN2), indicating novel genetic influences that influence hippocampal size and possibly the risk of cognitive decline and dementia.

Selenium is significantly depleted among morbidly obese female patients seeking bariatric surgery

BACKGROUND

The aim of this study was to compare serum levels of trace elements in morbidly obese female patients seeking bariatric surgery with those of age-matched females with body mass index (BMI) less than or equal to 30.

METHODS

Blood samples were collected from 66 morbidly obese female patients seeking bariatric surgery prior to undergoing surgery. Blood was collected also from 44 female patients (with BMI less than or equal to 30) prospectively from April 2009 till February 2010. Exclusion criteria in both groups were the presence of any co-morbidities on medication, patients receiving any vitamin supplement or any herbal product intake, smoking, and alcohol consumption. Serum zinc, magnesium, copper, and selenium were measured and compared between the two groups.

RESULTS

The mean age and BMI for morbidly obese female patients was 28.5 years (21.5-35.5) and 45.26 kg/m(2) (40.3-50.22). The control group had a mean age and BMI of 30.75 years (21.35-40.15) and 25.88 kg/m(2) (22.73-29.03). For morbidly obese patients, the serum level of copper, zinc, selenium, and magnesium was 1,623.84, 698.34, 86.08, and 17,830 μg/l, respectively, compared to 1,633.36, 734.82, 101.14, and 18,260 μg/l for the control group. The serum levels of the trace elements were not statistically significantly different between the two groups except for selenium, which was significantly reduced among morbidly obese female patients (p < 0.0001).

CONCLUSIONS

Serum selenium level is significantly reduced among morbidly obese female patients seeking bariatric surgery.

Glucoraphanin does not reduce plasma homocysteine in rats with sufficient Se supply via the induction of liver ARE-regulated glutathione biosynthesis enzymes

Data from human and animal trials have revealed contradictory results regarding the influence of selenium (Se) status on homocysteine (HCys) metabolism. It was hypothesised that sufficient Se reduces the flux of HCys through the transsulphuration pathway by decreasing the expression of glutathione (GSH) synthesising enzymes. Glucoraphanin (GRA) is a potent inducer of genes regulated via an antioxidant response element (ARE), including those of GSH biosynthesis. We tested the hypothesis that GRA supplementation to rat diets lowers plasma HCys levels by increasing GSH synthesis. Therefore 96 weaned albino rats were assigned to 8 groups of 12 and fed diets containing four different Se levels (15, 50, 150 and 450 μg kg(diet)(-1)), either without GRA (groups: C15, C50, C150 and C450) or in combination with 700 μmol GRA kg(diet)(-1) (groups G15, G50, G150 and G450). Rats fed the low Se diets C15 and G15 showed an impressive decrease of plasma HCys. Se supplementation increased plasma HCys and lowered GSH significantly by reducing the expression of GSH biosynthesis enzymes. As new molecular targets explaining these results, we found a significant down-regulation of the hepatic GSH exporter MRP4 and an up-regulation of the HCys exporter Slco1a4. In contrast to our hypothesis, GRA feeding did not reduce plasma HCys levels in Se supplemented rats (G50, G150 and 450) through inducing GSH biosynthesis enzymes and MRP4, but reduced their mRNA in some cases to a higher extent than Se alone. We conclude: 1. That the long-term supplementation of moderate GRA doses reduces ARE-driven gene expression in the liver by increasing the intestinal barrier against oxidative stress. 2. That the up-regulation of ARE-regulated genes in the liver largely depends on GRA cleavage to free sulforaphane and glucose by plant-derived myrosinase or bacterial β-glucosidases. As a consequence, higher dietary GRA concentrations should be used in future experiments to test if GRA or sulforaphane can be established as HCys lowering compounds.

Efeitos antioxidantes do selênio e seu elo com a inflamação e síndrome metabólica

O estado inflamatório crônico e de baixo grau bem como o estresse oxidativo associados à síndrome metabólica são fatores de risco relevantes para o desenvolvimento de doenças cardiovasculares. Neste contexto, o selênio é um mineral essencial que se encontra associado com o correto funcionamento dos principais processos metabólicos celulares. Estudos in vitro e in vivo em modelos experimentais de síndrome metabólica, bem como em humanos, tem investigado o efeito do selênio sobre a expressão e secreção de biomarcadores de inflamação e de estresse oxidativo. Para obtenção dos artigos sobre efeitos antioxidantes do selênio foram feitas pesquisas nos websites científicos. Na literatura encontramos numerosos artigos sobre os diferentes parâmetros modulados pelas concentrações plasmáticas de selênio, incluindo a proteína-C reativa, a interleucina-6, o fator de necrose tumoral-α, a interleucina-1β e a proteína transportadora de retinol-4. Esta revisão teve por objetivo discutir o papel do selênio nos processos inflamatórios e de estresse oxidativo, associados à síndrome metabólica.

Study of molecular targets influencing homocysteine and cholesterol metabolism in growing rats by manipulation of dietary selenium and methionine concentrations

Inconsistent results exist from human and animal studies for Se and methionine (Met) regarding their influence on homocysteine (HCys) and cholesterol (Chol) metabolism. To elucidate these contradictions, sixty-four weanling albino rats were divided into eight groups of 8, and were fed diets containing four different Se levels (15, 50, 150 and 450 microg/kg) either in combination with the recommended Met level of 3 g/kg (C15, C50, C150 and C450) or with an increased Met concentration of 15 g/kg (M15, M50, M150 and M450) for 8 weeks. Plasma HCys was twofold higher in the Se-supplemented C groups than in group C15. Met addition also doubled plasma HCys compared with the respective C groups. In contrast, the expression of the key enzymes of glutathione biosynthesis in the liver was significantly lowered by Se and in particular by Met. Liver Chol concentration was significantly higher in all the Se-supplemented C and M groups than in groups C15 and M15. Plasma Chol was, however, lowered. The uninfluenced expression of sterol-regulatory element-binding protein 2 and of hydroxymethyl-glutaryl-CoA reductase, the increased LDL receptor expression and the reduced expression of the hepatobiliary Chol exporter ATP-binding-cassette-transporter 8 (ABCG8) by Se and/or Met explain these findings. We conclude that the elevation of plasma HCys in rats by Se and Met results from a higher export into plasma. The fact that Se in particular combined with Met increases liver Chol but reduces plasma Chol should be addressed in future investigations focussing on the regulation of ABCG8, which is also selectively involved in the reverse transport of phytosterols in the small intestine.

Selenium in food and the human body: a review

Selenium levels in soil generally reflect its presence in food and the Se levels in human populations. Se food content is influenced by geographical location, seasonal changes, protein content and food processing. Periodic monitoring of Se levels in soil and food is necessary. Diet is the major Se source and approximately 80% of dietary Se is absorbed depending on the type of food consumed. Se bioavailability varies according to the Se source and nutritional status of the subject, being significantly higher for organic forms of Se. Se supplements can be beneficial for subjects living in regions with very low environmental levels of Se. Several strategies have been followed: (1) employment of Se-enriched fertilizers; (2) supplementation of farm animals with Se; (3) consumption of multimicronutrient supplements with Se. Nevertheless, detailed investigations of possible interactions between Se supplements and other food components and their influence on Se bioavailability are needed. Suppliers also need to provide more information on the specific type of Se used in supplements. In addition, research is lacking on the mechanisms through which Se is involved in hepatocyte damage during hepatopathies. Although Se potential as an antioxidant for the prevention of cardiovascular diseases (CVD) is promising, additional long-term intervention trials are necessary. As a result, indiscriminate Se supplements cannot be reliably recommended for the prevention of CVD in human beings. Some interesting findings reported an association of Se intake with a reduced prevalence and risk for prostate and colon cancer. However, random trials for other cancer types are inconclusive. As a final conclusion, the general population should be warned against the employment of Se supplements for prevention of hepatopathies, cardiovascular or cancer diseases, because benefits of Se supplementation are still uncertain, and their indiscriminate use could generate an increased risk of Se toxicity.

Nutritional deficiencies in morbidly obese patients: a new form of malnutrition? Part B: minerals

Even though in the Western world there is almost no limitation to a wide variety of food supply, nutritional deficiencies can be found in both normal-weight population and in the obese population. In this review, we examine the prevalence and manifestations of various mineral deficiencies in obese patients.

Environment, diet and CpG island methylation: epigenetic signals in gastrointestinal neoplasia

The epithelial surfaces of the mammalian alimentary tract are characterised by very high rates of cell proliferation and DNA synthesis, and in humans they are highly susceptible to cancer. The role of somatic mutations as drivers of carcinogenesis in the alimentary tract is well established, but the importance of gene silencing by epigenetic mechanisms is increasingly recognised. Methylation of CpG islands is an important component of the epigenetic code that regulates gene expression during development and normal cellular differentiation, and a number of genes are well known to become abnormally methylated during the development of tumours of the oesophagus, stomach and colorectum. Aberrant patterns of DNA methylation develop as a result of pathological processes such as chronic inflammation, and in response to various dietary factors, including imbalances in the supply of methyl donors, particularly folates, and exposure to DNA methyltransferase inhibitors, which include polyphenols and possibly isothiocyanates from plant foods. However the importance of these environmental interactions in human health and disease remains to be established. Recent moves to modify the exposure of human populations to folate, by mandatory supplementation of cereal foods, emphasise the importance of understanding the susceptibility of the human epigenome to dietary and other environmental effects.

Homocysteine increases the risk of mortality in elderly individuals

Although total plasma homocysteine (tHcy) has been extensively studied as a risk factor of CVD, longitudinal evidence on its association with mortality is scarce, especially among the elderly. The study cohort consisted of 215 subjects (eighty-eight male and 127 female), aged 60 years or older, recruited in fourteen elderly care institutions from Asturias (Spain). All participants were free of major chronic pathology and took no vitamin and/or mineral supplements. Baseline determinations included tHcy in plasma and folate, vitamin B12and Se in serum. Survival analyses were performed by quintiles of these factors after 6 years (mean follow-up time 4·3 years) by means of Cox regression models. During follow-up time sixty participants died. tHcy above 16·7 μmol/l was associated with an increased risk of mortality in the sample (relative risk 2·30 (95 % CI 1·02, 5·17)). Among the nutritional determinants of tHcy evaluated, folate and Se were not predictive of death risk of the cohort, while vitamin B12showed inconsistent results. Nevertheless, mortality was significantly lower at higher serum Se levels (upper quintile), but this effect was restricted to women. Higher tHcy in both sexes and lower serum Se in women were found to be independently associated with an increased risk of death in elderly subjects.

The organotellurium compound ammonium trichloro(dioxoethylene-o,o')tellurate reacts with homocysteine to form homocystine and decreases homocysteine levels in hyperhomocysteinemic mice

Ammonium trichloro(dioxoethylene-o,o')tellurate (AS101) is an organotellurium compound with pleiotropic functions that has been associated with antitumoral, immunomodulatory and antineurodegenerative activities. Tellurium compounds with a +4 oxidation state, such as AS101, react uniquely with thiols, forming disulfide molecules. In light of this, we tested whether AS101 can react with the amino acid homocysteine both in vitro and in vivo. AS101 conferred protection against homocysteine-induced apoptosis of HL-60 cells. The protective mechanism of AS101 against homocysteine toxicity was directly mediated by its chemical reactivity, whereby AS101 reacted with homocysteine to form homocystine, the less toxic disulfide form of homocysteine. Moreover, AS101 was shown here to reduce the levels of total homocysteine in an in vivo model of hyperhomocysteinemia. As a result, AS101 also prevented sperm cells from undergoing homocysteine-induced DNA fragmentation. Taken together, our results suggest that the organotellurium compound AS101 may be of clinical value in reducing total circulatory homocysteine levels.

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

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

Dietary contaminants and oxidative stress in Inuit of Nunavik

The aim of the present study was to investigate the potential deleterious effects of dietary contaminants such as polychlorinated biphenyls (PCBs) and methylmercury (MeHg) on different molecules sensitive to oxidative stress, namely, plasma oxidized low-density lipoproteins (OxLDLs), plasma homocysteine (Hcy), blood glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione (GSH). We also planned to assess the potential beneficial effects of long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) and selenium (Se) that are also present in the traditional Inuit diet. A total of 99 participants were studied. Plasma levels of PCBs, blood levels of Se and MeHg, plasma lipids (triacylglycerols, total, LDL-, and high-density lipoprotein cholesterol [LDL-C and HDL-C, respectively], apolipoprotein B-LDL), erythrocyte n-3 PUFAs, OxLDL, Hcy, blood GPx, GSH, and GR have been determined. Mean concentrations of MeHg, Se, and PCBs were respectively 10- to 14-fold, 8- to 15-fold, and 16- to 18-fold higher than reported in white population consuming little or no fish. Multivariate analyses show that variance in plasma OxLDL concentrations was predicted by LDL-C (P = .007), HDL-C (P = .005), and PCBs (P = .006). The level of LDL oxidation, represented as the ratio OxLDL/apolipoprotein B-LDL, was predicted by LDL-C (P = .0002), HDL-C (P = .002), and GSH (P = .005). Concentration of plasma Hcy was positively predicted by age (P = .02) but negatively by body mass index (P = .04) and Se (P = .005). Glutathione was predicted by the smoking status (P = .004) and the level of LDL oxidation (P = .005), whereas GR was only predicted by the smoking status (P = .0009). The variance of GPx was not predicted by any contaminant or other physiological parameter. Dietary MeHg showed no association with the examined oxidative biomarkers, whereas PCB level was a predictor of the plasma concentration of OxLDL, although this concentration remained very low. The level of GPx activity in Inuit was higher than levels previously reported to be protective in whites. Homocysteine was negatively predicted by Se, suggesting a possible beneficial effect of Se. Moreover, n-3 PUFAs were highly correlated with dietary contaminants, but had no relationships with oxidative biomarkers. This study suggests that, in adult Inuit, contaminated traditional diet seems to have no direct oxidative effects on molecules involved in oxidative stress.

High serum selenium and reduced risk of advanced colorectal adenoma in a colorectal cancer early detection program

BACKGROUND

Epidemiologic and animal studies suggest that selenium may reduce risk of colorectal cancer. However, the epidemiologic data is mainly from relatively small investigations, limiting their interpretation. Although substantial evidence suggests that smoking is a strong effect modifier for other antioxidative nutrients, little is known about smoking-selenium interactions in colorectal tumors.

METHODS

We studied the association of serum selenium and advanced colorectal adenoma, a cancer precursor, in 758 cases and 767 sex- and race-matched controls, randomly selected from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cases had at least one verified advanced adenoma (> or = 1 cm or villous elements, or high-grade dysplasia) of the distal colon, and controls had a negative sigmoidoscopy.

RESULTS

The multivariable odds ratio (OR) comparing participants in the highest quintile of serum selenium with those in the lowest quintile was 0.76 [95% confidence interval (95% CI), 0.53-1.10; P(trend) = 0.01]. The inverse association between serum selenium and advanced colorectal adenoma was significant among recent smokers (OR, 0.53; 95% CI, 0.27-1.01 for highest versus lowest tertile; P(trend) = 0.008). Serum selenium was unrelated to adenoma risk in nonsmokers and former smokers who quit smoking > or = 10 years ago.

CONCLUSION

Selenium may reduce the risk of developing advanced colorectal adenoma, particularly among the high-risk group of recent smokers.

Selenium and antioxidant vitamin status of elderly German women

OBJECTIVE

Low antioxidant intake and status have been shown to be associated with an elevated risk for various diseases. Data on the status of antioxidant vitamins, selenium and coenzyme Q10 of younger female seniors are scarce. The aim of this study was to assess the status of these antioxidants, as well as influencing factors such as dietary intake, anthropometric data and educational level in female seniors (60-70 years) in Germany.

DESIGN

Dietary intake of alpha-tocopherol, beta-carotene and ascorbic acid was determined by a 3-day diet record. Serum concentrations of alpha-tocopherol, beta-carotene, ascorbic acid, selenium and coenzyme Q10 were measured. Anthropometric measures, socioeconomic and educational status were assessed.

SETTING

In total, 178 elderly women without severe diseases in the region of Hannover, Germany, were included in the study. The mean (+/- s.d.) age and BMI of the women was 63.2 (2.73) years and 25.6 (3.77) kg/m2, respectively. The study participants were generally better educated than the overall German female population.

RESULTS

Dietary intake of the ascorbic acid and alpha-tocopherol was below RDA in six and 75% of the women, respectively. In comparison to estimated desirable serum concentrations of alpha-tocopherol, ascorbic acid, beta-carotene and selenium, lower concentrations were found in 23, 1, 6, and 39% of the women, respectively. Ascorbic acid (r = 0.205, P = 0.009) and beta-carotene (r = 0.173, P = 0.025) intake were significantly associated with serum concentrations. Beta-carotene concentrations were influenced by the type of diet, BMI, and school education (R2 = 0.128, P < 0.001). Serum selenium was positively associated with alcohol intake (r = 0.229, P = 0.003). Neither employment nor vocational training was predictive for the serum concentrations of antioxidant vitamins, selenium or coenzyme Q10.

CONCLUSIONS

Poor status of selenium and alpha-tocopherol is highly prevalent even among younger, well-educated female seniors, whereas ascorbic acid and beta-carotene status seems sufficient in most women.

Food Intake and Serum Selenium Concentration in Elderly People

BACKGROUND/AIMS

It is becoming apparent that the essential trace element selenium plays a critical role in the maintenance of optimal health status. The objective of this study was to identify the food groups that most contributed to selenium intake and its serum levels in elderly people.

METHODS

Dietary intake was assessed in 205 institutionalized elderly by means of a 1-year food frequency questionnaire (FFQ). Intake of macronutrients and minerals of the diet were estimated. Selenium was determined in serum and analyzed by graphite-furnace atomic absorption spectrometry.

RESULTS

Selenium intake and serum concentration were both within the normal range. The major contributors to selenium intake were cereals and bakery, fish and shellfish, meat and meat products and dairy products. All of them except cereals were also associated to serum selenium. Intake of animal protein, but not the vegetable one, contributed to serum selenium.

CONCLUSION

An adequate intake of fish and meat would be of importance to improve selenium status and health principally in elderly people who are at high risk of mineral deficiency.