Influence of serum selenium concentrations on hypertension: the Lipid Analytic Cologne cross-sectional study

Selenium intake in relation to all-cause and cardiovascular mortality in individuals with nonalcoholic fatty liver disease: A nationwide study in nutrition

AIMS

Limited evidence exists regarding the association of selenium with risk of death in individuals with nonalcoholic fatty liver disease (NAFLD). This study was designed to investigate the relationship between dietary selenium intake with mortality in a nationally representative sample of United States adults with NAFLD.

METHODS

Dietary selenium intake was assessed in 2274 NAFLD adults younger than 60 years of age from the National Health and Nutrition Examination Survey (NHANES) III through a 24-hour dietary recall. NAFLD was diagnosed by liver ultrasound after excluding liver disease due to other causes. Cox proportional hazards models were utilized to assess the effect of dietary selenium intake on all-cause and cardiovascular mortality among individuals with NAFLD.

RESULTS

At a median follow-up of 27.4 years, 577 deaths occurred in individuals with NAFLD, including 152 cardiovascular deaths. The U-shaped associations were discovered between selenium intake with all-cause (Pnolinear = 0.008) and cardiovascular mortality (Pnolinear < 0.001) in adults with NAFLD after multivariate adjustment, with the lowest risk around selenium intake of 121.7 or 125.9 μg/day, respectively. Selenium intake in the range of 104.1-142.4 μg/day was associated with a reduced risk of all-cause mortality and, otherwise, an increased risk. Selenium intake in the range of 104.1-150.6 μg/day was associated with a reduced risk of cardiovascular death and, otherwise, an increased risk.

CONCLUSIONS

Both high and low selenium intake increased the risk of all-cause and cardiovascular death in adults younger than 60 years of age with NAFLD, which may help guide dietary adjustments and improve outcomes in adults with NAFLD.

First review on the selenium status in Germany covering the last 50 years and on the selenium content of selected food items

INTRODUCTION

Selenium is important for human health. However, the selenium status and selenium intake of the German population has not been recorded in a representative study so far.

MATERIAL AND METHODS

Thus, literature from the last 50 years was screened in a systematic way and the results of various studies were pulled together to shed light on the selenium status of the German population. Moreover, the selenium content of selected food items that were either found on the German market or grown in Germany was researched and evaluated.

RESULTS

Of 3542 articles identified, 37 studies met the inclusion criteria. These 37 studies comprised a total of 8,010 healthy adults living in Germany with a weighted arithmetic mean of 82 μg/l selenium in plasma or serum. The results will form a basis for interpreting upcoming results from national food consumption surveys. Furthermore, 363 selenium values for 199 food items were identified out of 20 data sources-published or analysed between 2002 and 2019. An estimation of the selenium intake of the German population will be possible with this data in future nutrition surveys.

Selenoprotein K contributes to CD36 subcellular trafficking in hepatocytes by accelerating nascent COPII vesicle formation and aggravates hepatic steatosis

SelenoproteinK (SelK), an endoplasmic reticulum (ER) - resident protein, possesses the property of mediate oxidation resistance and ER - associated protein degradation (ERAD) in several tissues. Here, we found that increased SelK markedly promotes fatty acid translocase (CD36) subcellular trafficking and aggravates lipid accumulation in hepatocytes. We demonstrated that SelK is required for the assembly of COPII vesicles and accelerates transport of palmitoylated-CD36 from the ER to Golgi, thus facilitating CD36 plasma membrane distribution both in vivo and in vitro. The mechanism is that SelK increases the stability of Sar1B and triggers CD36-containing nascent COPII vesicle formation, consequently, promotes CD36 subcellular trafficking. Furthermore, we verified that the intervention of SelK SH3 binding domain can inhibit the vesicle formation and CD36 subcellular trafficking, significantly ameliorates NAFLD in mice. Collectively, our findings disclose an unexpected role of SelK in regulating NAFLD development, suggesting that targeting the SelK of hepatocytes may be a new therapeutic strategy for the treatment of NAFLD.

Single and Combined Associations of Plasma and Urine Essential Trace Elements (Zn, Cu, Se, and Mn) with Cardiovascular Risk Factors in a Mediterranean Population

Trace elements are micronutrients that are required in very small quantities through diet but are crucial for the prevention of acute and chronic diseases. Despite the fact that initial studies demonstrated inverse associations between some of the most important essential trace elements (Zn, Cu, Se, and Mn) and cardiovascular disease, several recent studies have reported a direct association with cardiovascular risk factors due to the fact that these elements can act as both antioxidants and pro-oxidants, depending on several factors. This study aims to investigate the association between plasma and urine concentrations of trace elements and cardiovascular risk factors in a general population from the Mediterranean region, including 484 men and women aged 18−80 years and considering trace elements individually and as joint exposure. Zn, Cu, Se, and Mn were determined in plasma and urine using an inductively coupled plasma mass spectrometer (ICP-MS). Single and combined analysis of trace elements with plasma lipid, blood pressure, diabetes, and anthropometric variables was undertaken. Principal component analysis, quantile-based g-computation, and calculation of trace element risk scores (TERS) were used for the combined analyses. Models were adjusted for covariates. In single trace element models, we found statistically significant associations between plasma Se and increased total cholesterol and systolic blood pressure; plasma Cu and increased triglycerides and body mass index; and urine Zn and increased glucose. Moreover, in the joint exposure analysis using quantile g-computation and TERS, the combined plasma levels of Zn, Cu, Se (directly), and Mn (inversely) were strongly associated with hypercholesterolemia (OR: 2.03; 95%CI: 1.37−2.99; p < 0.001 per quartile increase in the g-computation approach). The analysis of urine mixtures revealed a significant relationship with both fasting glucose and diabetes (OR: 1.91; 95%CI: 1.01−3.04; p = 0.046). In conclusion, in this Mediterranean population, the combined effect of higher plasma trace element levels (primarily Se, Cu, and Zn) was directly associated with elevated plasma lipids, whereas the mixture effect in urine was primarily associated with plasma glucose. Both parameters are relevant cardiovascular risk factors, and increased trace element exposures should be considered with caution.

l-selenomethionine induces zebrafish embryo cardiovascular defects via down-regulating expression of lrp2b

Selenium plays crucial roles in maintaining the growth and development of vertebrates including humans. However, excessive selenium in cells will lead to developmental defects and disease. Selenium has been reported to cause severe malformation in zebrafish embryos, but there are few studies on the mechanism of selenium excess-induced cardiovascular defects. In this study, the fertilized zebrafish embryos were treated with selenium for 96 h post fertilization (hpf). Under selenium stress, wild-type embryos showed pericardial edema, heart rate decrease, ectopic accumulation of hemoglobin; fli1-eGFP transgenic zebrafish displayed intersegmental vessel injury; and myl7-eGFP transgenic zebrafish exhibited atrial area increase. RNA-seq data and qRT-PCR results indicated that the expressions of cardiovascular development genes were up-regulated in selenium-stressed embryos. The expressions of lipid metabolism-related and selenium metabolism-related genes were evaluated in embryos. Among the tested genes, the expression of lrp2b was down-regulated in both 24 hpf and 96 hpf embryos. Furthermore, lrp2b-knockdown embryos exhibited the cardiac defects similar to selenium-stress embryos, and the over-expression of lrp2b rescued the selenium-induced defects, indicating that lrp2b might play a key role in regulating selenium cardiotoxicity. In summary, our research evaluates the cardiotoxicity of excessive selenium, and reveals the molecular mechanism of cardiovascular defects in selenium-exposed zebrafish embryos.

Cross-sectional study: Relationship between serum trace elements and hypertension

BACKGROUND

A balanced intake of trace elements is beneficial for chronic diseases such as hypertension. However, the available information regarding trace elements that may be independently associated with hypertension is limited, and the relationship between this disorder and element ratios also remains unclear.

METHODS

A total of 6,754 subjects from rural China were selected, after exclusion of patients who were under 18, had incomplete data or had additional related disorders, by multi-stage simple random and cluster sampling (participation rate: 95.22 %). Subjects were divided into a hypertensive (H) and a control (C) group. Data were collected on blood pressure and 12 serum trace elements were measured by flame atomic absorption spectrometry and inductively coupled plasma-mass spectrometry. Other basic information was collated from questionnaires and biochemical indicators were measured via kits.

RESULTS

Differences in serum levels of magnesium (Mg(mg/l): H: 27.43 ± 12.72; C: 26.33 ± 12.16), iron (Fe(mg/l): H: 1.99 ± 1.24; C: 1.84 ± 1.16), copper (Cu(mg/l): H: 1.19 ± 0.37; C: 1.10 ± 0.36), boron (B(μg/l): H: 50.00 ± 25.21; C: 47.57 ± 26.25), selenium (Se(μg/l): H: 125.12 ± 32.81; C: 118.80 ± 29.72) and chromium (Cr(μg/l): H: 8.77 ± 10.12; C: 10.12 ± 10.72) between the hypertensive and control groups were found. There were no differences in serum contents of calcium (Ca(mg/l): H: 112.43 ± 58.25; C: 111.00 ± 59.49), zinc (Zn(mg/l): H: 1.50 ± 1.97; C: 1.44 ± 1.88), arsenic (As(μg/l): H: 4.17 ± 3.94; C: 4.10 ± 4.00), manganese (Mn(μg/l): H: 4.15 ± 4.03; C: 4.07 ± 4.05), cadmium (Cd(μg/l): H: 1.14 ± 1.11; C: 1.18 ± 1.12) or lead (Pb(μg/l): H: 4.22 ± 8.90; C: 4.26 ± 10.25). The serum Cr and Cd concentrations of hypertensive men were lower than that of male controls while Mg, Cu, Ca and Se concentrations in male controls were lower. Further differences were apparent and Fe, B, Se, Mg and Cu all showed higher levels in hypertensive females whereas Cr concentrations were higher in female controls. Serum Zn and B levels showed age-related variations among hypertensive patients and concentrations of serum Cu, Zn, Se and B showed age-related variations among control subjects. For hypertensive patients, the odds ratio (OR) and 95 % confidence interval (CI) for the association of serum Cu, Se and Cr levels with hypertension were Cu: 1.36 (1.12-1.66); Se: 1.03 (1.01-1.05); Cr: 0.89 (0.83-0.96). Moreover, when the participants in the grouping with the highest copper/zinc (Cu/Zn) and magnesium/manganese (Mg/Mn) ratios were compared with the reference group, the OR and 95 % CI for hypertension were 1.22 (1.04-1.44) and 1.20 (1.01-1.42), respectively.

CONCLUSIONS

Levels of serum trace elements showed age- and sex-related differences in a group of rural Chinese adults with hypertension and healthy participants. Serum concentrations of Cu, Se and Cr may be independently associated with hypertension. Higher serum ratios of Cu:Zn and Mg:Mn may also be associated with hypertension. Further randomized trials are necessary to elucidate the true relationship between levels of Cu, Se, Cr, Cu:Zn, Mg:Mn and hypertension.

Serum selenium and non-alcoholic fatty liver disease (NAFLD) in U.S. adults: National Health and Nutrition Examination Survey (NHANES) 2011-2016

BACKGROUND

Selenium is an essential trace element that shows beneficial or adverse health effects depending on the dose. Laboratory studies suggest that high selenium may contribute to the development of non-alcoholic fatty liver disease (NAFLD). However, human evidence is limited. We evaluated the associations of serum selenium level with serum alanine aminotransferase (ALT) activity and suspected NAFLD prevalence in U.S. adults.

METHODS

We conducted the cross-sectional analysis in 3827 adults aged 20 years and older without viral hepatitis, hemochromatosis, or alcoholic liver disease who participated in the National Health and Nutrition Examination Survey (NHANES) 2011-2012, 2013-2014, and 2015-2016. Serum selenium was measured using inductively coupled plasma dynamic reaction cell mass spectrometry. Suspected NAFLD cases were defined in the presence of serum ALT >30 international units (IU)/L in men and >19 I.U./L in women in the absence of other identifiable causes of liver disease.

RESULTS

The median (interquartile range) of serum selenium level was 127.9 (117.9, 139.4) μg/L. Non-linear associations of serum selenium with NAFLD prevalence and serum ALT activity were observed in the generalized additive models with penalized splines. After adjustment for sociodemographic variables, lifestyle factors, body mass index, and NHANES survey cycles, positive associations were found at > ~130 μg/L serum selenium with both NAFLD and ALT, whereas the associations were flattened at < ~130 μg/L.

CONCLUSIONS

Our findings provide evidence of non-linear associations of serum selenium with ALT activity and NAFLD prevalence. In particular, positive associations were found above serum selenium level of 130 μg/L, whereas no association was observed below this value. This finding requires confirmation in future prospective cohort studies.

Selenium-related nutritional status in patients with common variable immunodeficiency: association with oxidative stress and atherosclerosis risk

Background

Common variable immunodeficiency (CVID) is an inborn errors of immunity, that leads to recurrent chronic infections and autoimmune/ inflammatory diseases and neoplasms. It is considered that these condition is related to persistent this immune-inflammatory stimulation and increased oxidative stress. A positive impact on the survival of patients with an inborn error of immunity was observed with advanced clinical care protocols, thus raising concerns about the risk of developing other associated chronic diseases, such as atherosclerosis. Studies suggest that selenium (Se) is a protective trace element against damage caused by oxidative stress. Thus, it is postulated that adequate consumption reduces the risk of some chronic diseases.

Results

Se median levels (ug/L) [45.6 (37.3–56.2) vs. 57.8 (46.0–66.0); p = 0.004] and GPX activity (U/L) [7682 (6548–8446) vs. 9284(8440–10,720); p = 0,002) were significantly lower in patients compared to controls. Inadequacy of Se levels was observed in 50% of the patients. There was a higher percentage of high values of C-reactive protein in the group of CVID patients compared to controls [8 (36.4%) vs. 2 (11.1%); p = 0.082]. Higher concentrations of oxidized LDL (45.3 mg/dL vs. 33.3 mg/dL; p = 0.016) and lower concentrations of Apo A-1 (98.5 mg/dL) vs. 117.0 mg/dL; p = 0.008) were observed in the CVID group compared to the control. There was a significant and positive correlation between Se plasma levels and apolipoprotein A-1 concentrations in CVID group (rho = 0.577; p = 0.001). Se values less than 46 μg / L (OR = 3.590; 95% CI 1.103 to 11.687; p = 0.034) and GPX activity below the 4th quartile (OR = 21.703; 95% CI 2.534 to 185.914; p = 0.005) were independently associated, after adjustment for age, overweight and dyslipidemia, with the CVID group (Table 5).

Conclusion

This study showed an higher percentage of high us-CRP, lower values of plasma Se and GPX activity, higher concentrations of LDLox and lower levels of Apo A-1 in CVID patients in comparison to controls, suggesting oxidative stress and cardiovascular risk.These data point to the importance of assessing the Se status and cardiovascular risk in these patients.

Impact of Micronutrients on Hypertension: Evidence from Clinical Trials with a Special Focus on Meta-Analysis

Hypertension (HT) is one of the pivotal risk factors for various detrimental diseases like cardiovascular diseases (CVDs), cerebrovascular disease, and renal dysfunction. Currently, many researchers are paying immense attention to various diet formula (dietary approach) with a special focus on micro and macronutrients along with modified lifestyle and standard anti-hypertensive drugs. Micronutrients (minerals/vitamins) play a central role in the regulation of blood pressure (BP) as they aid the function of macronutrients and also improve the anti-hypertensive functions of some anti-hypertensive agents. Even though several studies have demonstrated the beneficial effects of micronutrients on controlling BP, still some ambiguity exists among the nutritionists/doctors, which combination or individual mineral (dietary approach) contributes to better BP regulation. Therefore, this critical review article was attempted to delineate the underlying role of micronutrients (minerals and vitamins) for the management and prevention or delaying of HT and their related complications with strong affirmation from clinical trials as well as its mechanism of controlling BP. Moreover, the major source and recommended daily allowance (RDA) of various micronutrients are included in this review for guiding common readers (especially HT subjects) and dieticians to choose/recommend a better micronutrient and their combinations (other nutrients and standard anti-hypertensive drugs) for lowering the risk of HT and its related co-morbid conditions like CVDs.

Potential benefits of selenium supplementation in patients with kidney disease

Trace element deficiency is common among patients with end-stage renal disease (ESRD); the reason is that since these patients undergo dialysis, they lose these elements more than healthy people, and also the use of trace elements is restricted due to loss of appetite. Selenium (Se) is a trace element that is essential for the oxidative stress defense system. Se deficiency leads to some complications similar to those often seen in ESRD patients, such as all-cause mortality due to cardiovascular diseases, bone loss, uric acid elevation, and anemia. This article aims to review the evidence on consequences of Se deficiency in ESRD patients, as well as effects of Se supplementation in hemodialysis patients. Multiple databases were searched to summarize the available evidence on selenium's role in kidney diseases. Since the complications of ESRD and those of Se deficiency are mostly similar, this triggers the idea that Se deficiency may be considered as a cause of these problems, but it needs to be more assessed that Se deficiency is a single factor or there are other factors participated in. Also the role of Se supplementation on resolving the mentioned complications, needs to be more studied through welldesigned clinical studies.

Soil Selenium Concentration and Residents Daily Dietary Intake in a Selenosis Area: A Preliminary Study in Yutangba Village, Enshi City, China

In 1963, selenosis occurred in Yutangba Village, Enshi City, China. Subsequently, local residents migrated to a new area of Yutangba to avoid high selenium (Se) exposure. In this study, 19 soil samples, 43 food samples, 60 hair samples and 58 plasma samples from local residents were randomly collected in New Yutangba Village. The mean total Se concentrations in cultivated soil samples were 1753.6 ± 742.8 µg/kg (n = 14). The estimated daily Se intake in New Yutangba Village decreased to 63.2 ± 39.8 µg/day, slightly higher than the recommended dietary Se intake for adults in China (60 µg/day). The mean Se concentrations in hair and plasma samples were 549.7 ± 165.2 µg/kg (n = 60) and 98.4 ± 32.1 µg/L (n = 58), respectively. The result indicated that appropriate activities, such as relocation, consuming a mixture of local foods and market foods containing low Se concentration, could effectively reduce the risk of high Se exposure.

Nutrition, Bioenergetics, and Metabolic Syndrome

According to the World Health Organization (WHO), the global nutrition report shows that whilst part of the world’s population starves, the other part suffers from obesity and associated complications. A balanced diet counterparts these extreme conditions with the proper proportion, composition, quantity, and presence of macronutrients, micronutrients, and bioactive compounds. However, little is known on the way these components exert any influence on our health. These nutrients aiming to feed our bodies, our tissues, and our cells, first need to reach mitochondria, where they are decomposed into CO₂ and H₂O to obtain energy. Mitochondria are the powerhouse of the cell and mainly responsible for nutrients metabolism, but they are also the main source of oxidative stress and cell death by apoptosis. Unappropriated nutrients may support mitochondrial to become the Trojan horse in the cell. This review aims to provide an approach to the role that some nutrients exert on mitochondria as a major contributor to high prevalent Western conditions including metabolic syndrome (MetS), a constellation of pathologic conditions which promotes type II diabetes and cardiovascular risk. Clinical and experimental data extracted from in vitro animal and cell models further demonstrated in patients, support the idea that a balanced diet, in a healthy lifestyle context, promotes proper bioenergetic and mitochondrial function, becoming the best medicine to prevent the onset and progression of MetS. Any advance in the prevention and management of these prevalent complications help to face these challenging global health problems, by ameliorating the quality of life of patients and reducing the associated sociosanitary burden.

Plasma selenium levels and risk of new-onset diabetes in hypertensive adults

OBJECTIVE

The association between plasma selenium and new-onset diabetes in hypertensive adults is still unclear. We aimed to evaluate the relationship of baseline plasma selenium with new-onset diabetes and examine possible effect modifiers in a post-hoc analysis of the China Stroke Primary Prevention Trial (CSPPT).

METHODS

A total of 2367 hypertensive, non-diabetic patients with plasma selenium measurements at baseline were included. The primary outcome was new-onset diabetes, defined as physician-diagnosed diabetes or use of glucose-lowering drugs during the follow-up period, or fasting glucose (FG) ≥126.0 mg/dL at the exit visit.

RESULTS

At baseline, higher FG levels were found among participants with plasma selenium in quartile 4 (≥94.8 μg/L) (β, 1.64 mg/dL; 95%CI: 0.54, 2.73) compared to those in quartiles 1-3. During a median follow-up duration of 4.5 years, new-onset diabetes occurred in 270 (11.4%) participants. Graphic plot showed a positive association between baseline selenium levels and risk of new-onset diabetes. This was further confirmed by adjusted regression analyses; the odds ratios (OR) for new-onset diabetes comparing quartile 4 (≥94.8 μg/L) to quartiles 1-3 was 1.36 (95%CI: 1.01, 1.83). No clear trend was evident across quartiles 1-3.

CONCLUSIONS

Our data suggest that high plasma selenium (≥94.8 μg/L) was associated with increased risk of new-onset diabetes in hypertensive patients.

Environmental Selenium and Human Health: an Update

PURPOSE OF REVIEW

Selenium, a trace element, is ubiquitous in the environment. The main source of human exposure is diet. Despite its nutritional benefits, it is one of the most toxic naturally occurring elements. Selenium deficiency and overexposure have been associated with adverse health effects. Its level of toxicity may depend on its chemical form, as inorganic and organic species have distinct biological properties.

RECENT FINDINGS

Nonexperimental and experimental studies have generated insufficient evidence for a role of selenium deficiency in human disease, with the exception of Keshan disease, a cardiomyopathy. Conversely, recent randomized trials have indicated that selenium overexposure is positively associated with type 2 diabetes and high-grade prostate cancer. In addition, a natural experiment has suggested an association between overexposure to inorganic hexavalent selenium and two neurodegenerative diseases, amyotrophic lateral sclerosis and Parkinson's disease. Risk assessments should be revised to incorporate the results of studies demonstrating toxic effects of selenium. Additional observational studies and secondary analyses of completed randomized trials are needed to address the uncertainties regarding the health risks of selenium exposure.

Blood pressure levels and hypertension prevalence in a high selenium environment: results from a cross-sectional study

BACKGROUND AND AIMS

Recent human and laboratory studies have suggested the possibility that selenium overexposure may increase blood pressure. We sought to ascertain whether adults living in a seleniferous area exhibit an association between selenium exposure and both blood pressure levels as well as prevalence of hypertension.

METHODS AND RESULTS

We measured selenium levels in blood (serum), hair and nail samples obtained from 680 adult volunteers (267 men and 413 women), living in seven Punjabi villages in a seleniferous area and related them to health outcomes, including systolic and diastolic blood pressure and presence of hypertension. In a multivariable restricted cubic spline regression model, adjusted for age, sex and history of hypertension, we found a positive association between systolic blood pressure and both serum (P = 0.004) and hair (P = 0.058) selenium levels, but not with nail selenium content. Little association emerged between the three selenium biomarkers and diastolic blood pressure. Hypertension prevalence was positively associated with the three exposure indicators (P < 0.001). The associations we found were generally stronger in women than in men.

CONCLUSIONS

Overall, these findings suggest that chronic overexposure to environmental selenium may increase blood pressure, though there were inconsistencies for this association according to the choice of exposure indicator, the study endpoint and the sex.

Gender Differences with Dose⁻Response Relationship between Serum Selenium Levels and Metabolic Syndrome-A Case-Control Study

Few studies have investigated the association between selenium and metabolic syndrome. This study aimed to explore the associations between the serum selenium level and metabolic syndrome as well as examining each metabolic factor. In this case-control study, the participants were 1165 adults aged ≥40 (65.8 ± 10.0) years. Serum selenium was measured by inductively coupled plasma-mass spectrometry. The associations between serum selenium and metabolic syndrome were examined by multivariate logistic regression analyses. The least square means were computed by general linear models to compare the serum selenium levels in relation to the number of metabolic factors. The mean serum selenium concentration was 96.34 ± 25.90 μg/L, and it was positively correlated with waist circumference, systolic blood pressure, triglycerides, fasting glucose, and homeostatic model assessment insulin resistance (HOMA-IR) in women, but it was only correlated with fasting glucose and HOMA-IR in men. After adjustment, the odds ratios (ORs) of having metabolic syndrome increased with the selenium quartile groups (p for trend: <0.05), especially in women. The study demonstrated that the serum selenium levels were positively associated with metabolic syndrome following a non-linear dose⁻response trend. Selenium concentration was positively associated with insulin resistance in men and women, but it was associated with adiposity and lipid metabolism in women. The mechanism behind this warrants further confirmation.

Exposure to Trace Elements and Risk of Skin Cancer: A Systematic Review of Epidemiologic Studies

Exposure to environmental trace elements has been studied in relation to many cancers. However, an association between exposure to trace elements and skin cancer remains less understood. Therefore, we conducted a systematic review of published epidemiologic literature examining the association between exposure to trace elements, and risk of melanoma and keratinocyte carcinoma in humans. We identified epidemiologic studies investigating exposure to arsenic, cadmium, chromium, copper, iron, selenium, and zinc and risk of skin cancer in humans. Among the minerals, arsenic, selenium, and zinc had more than five studies available. Exposure to arsenic was associated with increased risk of keratinocyte carcinoma, while too few studies existed on melanoma to draw conclusions. Exposure to selenium was associated with possible increased risk of keratinocyte carcinoma. Studies of zinc and skin cancer were case-control in design and were found to have inconsistent associations. The data on the association between cadmium, chromium, copper, and iron and risk of skin cancer remain too sparse to draw any conclusions. In summary, epidemiologic studies on exposure to trace elements and cutaneous malignancies are limited. Studies with larger sample sizes and prospective designs are warranted to improve our knowledge of trace elements and skin cancer.

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

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

Cross-sectional Study: Relationship Between Serum Selenium and Hypertension in the Shandong Province of China

Although selenium, which is a necessary trace element for the human body, has been considered to be beneficial to the cardiovascular system and helpful to lower blood pressure, more and more evidence shows that high amounts of selenium are a risk factor for hypertension. A random multistage sampling which included the cluster method was performed; a total of 9076 urban and rural residents between 18 and 80 years old in the Shandong province of China were investigated by questionnaire, physical examination, and laboratory tests. The prevalence of hypertension was 42.1% in males and 35.3% in females. The mean (standard deviation) selenium concentration was 124.68 (36.32) μg/l in males and 119.54 (31.88) μg/l in females. After adjusting for potential confounders, logistic regression analysis showed that the highest selenium levels were associated with a risk of hypertension (OR = 1.192; 95% CI 1.009-1.407) in females, while there was no significant difference in males (OR = 1.043; 95% CI 0.864-1.259). Our findings suggest that high selenium levels in females are more likely to increase the risk of hypertension compared to similar levels in males. More attention should be paid to the metabolic mechanisms and physiological effects of selenium in females.

Associations of environmental exposure to metals with the risk of hypertension in China

Hypertension contributes largely to the global burden of disease and mortality. Environmental exposure to metals might be a causative factor for hypertension, but the association remains unclear. The present case-control study of 502 hypertension patients and 502 healthy participants aimed to evaluate the potential relationships between the concentrations of 20 metal in urine and the risk of hypertension in a Chinese population. Multivariate logistic analyses adjusted for potential confounders were performed separately considering the effects of single and multi-metal. We found the increasing trends of urinary Fe, Co, Ni, Cu, Zn and Sr quartiles and the decreasing trends of urinary V and Rb quartiles with the ORs for hypertension. These dose-response associations were confirmed in the RCS models and remained robust in the multi-metal model. Urinary Hg quartiles were positively associated with the risk of hypertension in the models of single-metal and multi-metal. Urinary Cd quartiles were inversely associated with the risk of hypertension in the multi-metal model. Besides, modification effects of gender, BMI and smoking status on the associations of the exposure to various metals with the risk of hypertension were also suggested in the subgroup analysis. Our findings suggest that environmental exposure to V, Fe, Co, Ni, Cu, Zn, Rb, Sr, Cd and Hg might be related with the prevalence of hypertension. Further studies with prospective design should be conducted to confirm these findings.

Effects of biological factors and health condition on mercury and selenium concentrations in the cartilage, meniscus and anterior cruciate ligament

Due the long-term nature of joint tissue remodeling processes, knee structures including meniscus and anterior cruciate ligament (ACL) can be a model for studying the bioaccumulation of mercury (Hg) and selenium (Se). The accumulation and retention of Hg in human tissues can have a negative effect on the proper functioning of homeostasis-affecting organisms. A factor of chronic poisoning with Hg forms is probably the Se:Hg ratio in tissues. Se:Hg molar ratios below one may increase Hg toxicity potentials, while molar ratios that approach or exceed one effectively may protect against Hg toxicity. Therefore, the aim of the study was to determine total mercury (THg), Se, and Se:THg molar ratios in the cartilage, meniscus and ACL of patients with osteoarthritis (OA) from northwestern Poland. In all studied samples (n=95), we observed higher Se than THg concentration. Taking into consideration the biological factors, we found significantly higher THg levels in the cartilage of women, patients under 65 years of age, patients without hypertension and in the ACL of patients with spinal degenerative disease. We found higher Se levels in the meniscus in women than in men. In all studied parts of the knee joint, we found the Se:THg molar ratio higher than one, which suggests that the joint forming structures are not much exposed to THg. Moreover the results reported here may provide a basis for establishing reference values for the meniscus and ACL in patients with OA who had undergone knee replacement surgery.

Selenium, Vanadium, and Chromium as Micronutrients to Improve Metabolic Syndrome

Trace metals play an important role in the proper functioning of carbohydrate and lipid metabolism. Some of the trace metals are thus essential for maintaining homeostasis, while deficiency of these trace metals can cause disorders with metabolic and physiological imbalances. This article concentrates on three trace metals (selenium, vanadium, and chromium) that may play crucial roles in controlling blood glucose concentrations possibly through their insulin-mimetic effects. For these trace metals, the level of evidence available for their health effects as supplements is weak. Thus, their potential is not fully exploited for the target of metabolic syndrome, a constellation that increases the risk for cardiovascular disease and type 2 diabetes. Given that the prevalence of metabolic syndrome is increasing throughout the world, a simpler option of interventions with food supplemented with well-studied trace metals could serve as an answer to this problem. The oxidation state and coordination chemistry play crucial roles in defining the responses to these trace metals, so further research is warranted to understand fully their metabolic and cardiovascular effects in human metabolic syndrome.

Selenium Exposure and Cancer Risk: an Updated Meta-analysis and Meta-regression

The objective of this study was to investigate the associations between selenium exposure and cancer risk. We identified 69 studies and applied meta-analysis, meta-regression and dose-response analysis to obtain available evidence. The results indicated that high selenium exposure had a protective effect on cancer risk (pooled OR = 0.78; 95%CI: 0.73-0.83). The results of linear and nonlinear dose-response analysis indicated that high serum/plasma selenium and toenail selenium had the efficacy on cancer prevention. However, we did not find a protective efficacy of selenium supplement. High selenium exposure may have different effects on specific types of cancer. It decreased the risk of breast cancer, lung cancer, esophageal cancer, gastric cancer, and prostate cancer, but it was not associated with colorectal cancer, bladder cancer, and skin cancer.

Selenium and its supplementation in cardiovascular disease--what do we know?

The trace element selenium is of high importance for many of the body’s regulatory and metabolic functions. Balanced selenium levels are essential, whereas dysregulation can cause harm. A rapidly increasing number of studies characterizes the wide range of selenium dependent functions in the human body and elucidates the complex and multiple physiological and pathophysiological interactions of selenium and selenoproteins. For the majority of selenium dependent enzymes, several biological functions have already been identified, like regulation of the inflammatory response, antioxidant properties and the proliferation/differentiation of immune cells. Although the potential role of selenium in the development and progression of cardiovascular disease has been investigated for decades, both observational and interventional studies of selenium supplementation remain inconclusive and are considered in this review. This review covers current knowledge of the role of selenium and selenoproteins in the human body and its functional role in the cardiovascular system. The relationships between selenium intake/status and various health outcomes, in particular cardiomyopathy, myocardial ischemia/infarction and reperfusion injury are reviewed. We describe, in depth, selenium as a biomarker in coronary heart disease and highlight the significance of selenium supplementation for patients undergoing cardiac surgery.

A review of dietary selenium intake and selenium status in Europe and the Middle East

This is a systematic review of existing data on dietary selenium (Se) intake and status for various population groups in Europe (including the United Kingdom (UK)) and the Middle East. It includes English language systematic reviews, meta-analyses, randomised controlled trials, cohort studies, cross-sectional and case-control studies obtained through PUBMED searches from January, 2002, to November, 2014, for European data and from 1990 to November 2014, for Middle Eastern data. Reports were selected if they included data on Se intake and status. The search identified 19 European/UK studies and 15 investigations in the Middle East that reported Se intake and Se concentration in water and/or food and 48 European/UK studies and 44 investigations in the Middle East reporting Se status. Suboptimal Se status was reported to be widespread throughout Europe, the UK and the Middle East, and these results agreed with previous reports highlighting the problem. Eastern European countries had lower Se intake than Western European countries. Middle Eastern studies provided varying results, possibly due to varying food habits and imports in different regions and within differing socioeconomic groups. In conclusion, Se intake and status is suboptimal in European and Middle Eastern countries, with less consistency in the Middle East.

Plasma selenium levels and oxidative stress biomarkers: a gene-environment interaction population-based study

The role of selenium exposure in preventing chronic disease is controversial, especially in selenium-repleted populations. At high concentrations, selenium exposure may increase oxidative stress. Studies evaluating the interaction of genetic variation in genes involved in oxidative stress pathways and selenium are scarce. We evaluated the cross-sectional association of plasma selenium concentrations with oxidative stress levels, measured as oxidized to reduced glutathione ratio (GSSG/GSH), malondialdehyde (MDA), and 8-oxo-7,8-dihydroguanine (8-oxo-dG) in urine, and the interacting role of genetic variation in oxidative stress candidate genes, in a representative sample of 1445 men and women aged 18-85 years from Spain. The geometric mean of plasma selenium levels in the study sample was 84.76 µg/L. In fully adjusted models the geometric mean ratios for oxidative stress biomarker levels comparing the highest to the lowest quintiles of plasma selenium levels were 0.61 (0.50-0.76) for GSSG/GSH, 0.89 (0.79-1.00) for MDA, and 1.06 (0.96-1.18) for 8-oxo-dG. We observed nonlinear dose-responses of selenium exposure and oxidative stress biomarkers, with plasma selenium concentrations above ~110 μg/L being positively associated with 8-oxo-dG, but inversely associated with GSSG/GSH and MDA. In addition, we identified potential risk genotypes associated with increased levels of oxidative stress markers with high selenium levels. Our findings support that high selenium levels increase oxidative stress in some biological processes. More studies are needed to disentangle the complexity of selenium biology and the relevance of potential gene-selenium interactions in relation to health outcomes in human populations.

The need for a reassessment of the safe upper limit of selenium in drinking water

Results of recent epidemiologic studies suggest the need to reassess the safe upper limit in drinking water of selenium, a metalloid with both toxicological and nutritional properties. Observational and experimental human studies on health effects of organic selenium compounds consumed through diet or supplements, and of inorganic selenium consumed through drinking water, have shown that human toxicity may occur at much lower levels than previously surmised. Evidence indicates that the chemical form of selenium strongly influences its toxicity, and that its biological activity may differ in different species, emphasizing the importance of the few human studies on health effects of the specific selenium compounds found in drinking water. Epidemiologic studies that investigated the effects of selenate, an inorganic selenium species commonly found in drinking water, together with evidence of toxicity of inorganic selenium at low levels in from in vitro and animal studies, indicate that health risks may occur at exposures below the current European Union and World Health Organization upper limit and guideline of 10 and 40 μg/l, respectively, and suggest reduction to 1 μg/l in order to adequately protect human health. Although few drinking waters are currently known to have selenium concentrations exceeding this level, the public health importance of this issue should not be overlooked, and further epidemiologic research is critically needed in this area.

Friend or foe? The current epidemiologic evidence on selenium and human cancer risk

Scientific opinion on the relationship between selenium and the risk of cancer has undergone radical change over the years, with selenium first viewed as a possible carcinogen in the 1940s then as a possible cancer preventive agent in the 1960s-2000s. More recently, randomized controlled trials have found no effect on cancer risk but suggest possible low-dose dermatologic and endocrine toxicity, and animal studies indicate both carcinogenic and cancer-preventive effects. A growing body of evidence from human and laboratory studies indicates dramatically different biological effects of the various inorganic and organic chemical forms of selenium, which may explain apparent inconsistencies across studies. These chemical form-specific effects also have important implications for exposure and health risk assessment. Overall, available epidemiologic evidence suggests no cancer preventive effect of increased selenium intake in healthy individuals and possible increased risk of other diseases and disorders.