Geographic variation of environmental, food, and human hair selenium content in an industrial region of Russia

Biological Activity of Selenium and Its Impact on Human Health

Selenium (Se) is a naturally occurring metalloid element essential to human and animal health in trace amounts but it is harmful in excess. Se plays a substantial role in the functioning of the human organism. It is incorporated into selenoproteins, thus supporting antioxidant defense systems. Selenoproteins participate in the metabolism of thyroid hormones, control reproductive functions and exert neuroprotective effects. Among the elements, Se has one of the narrowest ranges between dietary deficiency and toxic levels. Its level of toxicity may depend on chemical form, as inorganic and organic species have distinct biological properties. Over the last decades, optimization of population Se intake for the prevention of diseases related to Se deficiency or excess has been recognized as a pressing issue in modern healthcare worldwide. Low selenium status has been associated with an increased risk of mortality, poor immune function, cognitive decline, and thyroid dysfunction. On the other hand, Se concentrations slightly above its nutritional levels have been shown to have adverse effects on a broad spectrum of neurological functions and to increase the risk of type-2 diabetes. Comprehension of the selenium biochemical pathways under normal physiological conditions is therefore an important issue to elucidate its effect on human diseases. This review gives an overview of the role of Se in human health highlighting the effects of its deficiency and excess in the body. The biological activity of Se, mainly performed through selenoproteins, and its epigenetic effect is discussed. Moreover, a brief overview of selenium phytoremediation and rhizofiltration approaches is reported.

Distribution Characteristics and Influencing Factors of Bio-elements in the Human Hair of Uyghur Communities in an Oasis Area of Xinjiang, China

Located in central Asia, Xinjiang is characterized as a diverse environment in China, consisting of vast deserts, dotted oases, and high mountains. Due to the combined effect of climate conditions under such a diverse environment, there are large differences in human activities, living styles, and eating habits in farmland and grazing pastures between Xinjiang and other regions of China. This study aimed to investigate the variations and mechanisms of elemental distribution in the hair of Uyghur communities among different ages and genders and under different land use backgrounds in an oasis region in Xinjiang. Hair samples from 524 residents from four traditional farmland areas and two grazing pasture areas in Bai Cheng County in Xinjiang were collected, and the levels of thirteen elements were analyzed. The results indicated that the average levels of Cu, Mg, Mn, Zn, Ni, Co, Pb, Fe, Ca, Cd, Cr, As, and Se in the hair of Uyghur communities were within the background levels of Chinese and global residents' hair. Overall, the levels of elements in the hair of women residents were higher than those of men residents. The levels of elements in the human hair of the middle-aged group were higher than those of child and older-aged groups. Elements Cr and Se in the hair of grazing pastures were higher than those of farmland areas. The levels of Cd, Pb, As, and Zn in the hair of farmland areas were higher than those of grazing pasture areas. The levels of Ca, Mg, Cu, and Fe in the hair of Uyghur communities were higher than those of other ethnic groups, while the toxic elements in the hair of residents in Bai Cheng were lower than those in other regions of China. Middle-aged people were exposed to higher levels of toxic elements in their daily activities compared to elderly and child groups. Also, adult groups need much more nutrients for their growth and intellectual development compared to child and elderly groups. The change in land use from grazing pastures to farmland increased the toxic trace element concentration levels in human hair. The significant differences in the overall concentration levels of elements in human hair among the different ethnic groups and regions can be attributed to the differences in lifestyles, cultural customs, dietary habits, and internal and external exposure routes.

Emerging roles of selenium on metabolism and type 2 diabetes

Selenium is recognized as an essential element for human health and enters human body mainly via diet. Selenium is a key constituent in selenoproteins, which exert essential biological functions, including antioxidant and anti-inflammatory effects. Several selenoproteins including glutathione peroxidases, selenoprotein P and selenoprotein S are known to play roles in the regulation of type 2 diabetes. Although there is a close association between certain selenoproteins with glucose metabolism or insulin resistance, the relationship between selenium and type 2 diabetes is complex and remains uncertain. Here we review recent advances in the field with an emphasis on roles of selenium on metabolism and type 2 diabetes. Understanding the association between selenium and type 2 diabetes is important for developing clinical practice guidelines, establishing and implementing effective public health policies, and ultimately combating relative health issues.

A county-level spatial epidemiological study of hair selenium and Keshan disease

Background

No spatial analysis of hair selenium and Keshan disease (KD) on a nationwide county-level has been performed. Selenium deficiency is a recognized environmental risk factor for KD. Hair selenium is one of the recognized biomarkers of selenium nutrition. This study aimed to perform a geographically precise and visualized assessment of the achievement of KD prevention and control at the level of selenium nutrition in terms of etiology.

Methods

A spatial ecological study was conducted. The hair selenium content of the residents was assayed using an atomic fluorescence spectrometer. The spatial analysis was performed using ArcGIS.

Results

The median of the hair selenium levels of the 3,028 participants in the 1,174 counties was 0.38 mg/kg, and the content of inhabitants in KD endemic counties was significantly lower than that in KD non-endemic counties (0.34 vs. 0.39 mg/kg, z = −10.03, P < 0.0001). The proportion of Se-deficient and Se-marginal counties in KD endemic counties was significantly higher than that in KD non-endemic counties (59.4 vs. 29.0%, z = −7.45, P < 0.0001). The global autocorrelation analysis was not statistically significant (Moran's I = 0.0005, P = 0.68). Local autocorrelation analysis identified 174 low-low clusters of hair selenium levels, 83 (47.7%) of which are KD endemic counties located in KD endemic provinces of Henan, Gansu, Shaanxi, Inner Mongolia, Jilin, and Heilongjiang. The hair selenium featured a positive correlation with per capita GDP (rs = 0.20, P < 0.0001).

Conclusion

The median of the hair selenium levels of inhabitants living in KD endemic counties was significantly lower than that in KD non-endemic counties. All the 83 KD endemic counties with low-low clusters of hair selenium levels should be prioritized in KD precision prevention and control. These findings are geographically precise and visualized evidence of the assessment of the effectiveness of KD prevention and control at the level of selenium nutrition in terms of etiology.

Essential Trace Elements in Scalp Hair of Residents across the Caspian Oil and Gas Region of Kazakhstan

Most of the country’s oil and gas fields are situated in West Kazakhstan, mainly on the Caspian Sea coast, causing significant damage to the local environment and contributing to an imbalance in the trace element composition of the human body. The study is aimed to evaluate the relationship between the concentration of essential trace elements in scalp hair of the western Kazakhstan adult population and the remoteness of their residence from oil and gas fields. The concentration of essential trace elements (Co, Cu, Fe, I, Mn, Se, Zn) in the hair of 850 individuals aged 18−60 years was determined by inductively coupled plasma mass spectrometry. In residents of settlements located at a distance of >110 km from oil and gas fields, the concentration of Cu and I in hair was significantly higher than in those closer to 110 km (p < 0.001). The content of Cu and I were associated with the distance to oil and gas fields (0.072 (95% CI: 0.050; 0.094)) and (0.121 (95% CI: 0.058; 0.185)), respectively. We detected a significant imbalance in the distribution of some essential trace elements in residents’ scalp hair from the Caspian region of western Kazakhstan, living near oil and gas fields. The concentrations of Cu and I were significantly interrelated with the distance to oil and gas fields. The level of copper in the hair of both inhabitants of the area most remote from oil and gas facilities and the entire population of western Kazakhstan as a whole remains significantly low. The data obtained provide evidence of the possible impact of pollutants generated by the oil and gas facilities on a shortage of essential trace elements and associated subsequent health risks.

A County-Level Spatial Study of Serum Selenoprotein P and Keshan Disease

Background

Keshan disease (KD) is strongly associated with selenium deficiency. Selenoprotein P (SELENOP) is a recognized molecular biomarker of selenoproteins and an important indicator of selenium nutrition. This study was aimed at providing geographically precisely visualized evidence of selenium nutrition at molecular level for assessing KD prevention, control, and elimination on the etiological perspective.

Methods

We used spatial ecological design for this study. The serum SELENOP levels of the residents were measured by ELISA. ArcGIS version 9.0 was used for spatial description, spatial autocorrelation analysis of SELENOP levels and spatial regression with per capita disposable income.

Results

The mean serum SELENOP levels of the 6,382 residents in 1,688 counties were 4.62 ± 1.82 μg/mL. The mean serum SELENOP levels of the residents living in the townships and rural areas of KD endemic counties were not statistically significantly lower than those of the KD non-endemic counties. The mean serum SELENOP levels were globally clustered (Moran's I = 0.03, z = 6.37, and P < 0.0001), and 99.3% (553/557) of the cold spots, identified by local autocorrelation analysis (Getis-Ord-Gi^* analysis), were located in the KD endemic provinces of Shaanxi, Shanxi, Henan, Hebei, Shandong, Inner Mongolia, Gansu, Hubei, Chongqing, Yunnan, and Sichuan. The serum SELENOP level was positively correlated with per capita disposable income (t = 3.52, P = 0.0004).

Conclusions

The results of this study were the geographically precisely visualized evidence of selenium nutrition at molecular level for assessing KD elimination on the etiological perspective. The cold spot counties found by Getis-Ord-Gi^* analysis in the KD endemic provinces should be the high priority of KD precision prevention and control.

A Spatial Ecological Study on Hair Selenium Level of Residents in Keshan Disease Endemic and Non-endemic Areas in Heilongjiang Province, China

This study was aimed to provide, by mapping the spatial distribution of hair selenium levels of residents, visualized evidence for assessment of KD elimination from a perspective of selenium nutrition of the residents living in the KD-endemic and non-endemic areas. Using a spatial ecological research design, 401 male permanent residents in KD-endemic and non-endemic areas participated in this study. Demographic information and hair samples were obtained through a questionnaire survey and sample collection, respectively. Hair selenium was measured using hydride generation atomic fluorescence spectrometry. Thematic maps were created, and spatial analysis was conducted using ArcGIS 9.0. The median of hair selenium of the participants was 0.30 (IQR, 0.23-0.34) mg/kg. The median hair selenium of the residents in the KD-endemic areas was significantly lower than that of the residents of the non-endemic areas. The hair selenium levels of residents were spatially clustered, with cold spots and hot spots located in northwest and southwest regions respectively. Residents living in KD-endemic areas may still have selenium deficiency. Measuring hair selenium levels of residents in KD-endemic areas as a molecular marker of selenium nutritional status as part of KD surveillance could provide visualized evidence for the evaluation of KD elimination from a perspective of selenium nutrition of the residents living in the KD endemic areas.

A Spatial Ecological Study on Serum Selenium and Keshan Disease in Heilongjiang Province, China

BACKGROUND

There are no reports on the spatial ecology of serum selenium and Keshan disease in Heilongjiang Province in China.

OBJECTIVE

This study aimed to conduct a spatial assessment of Keshan disease elimination at the level of the etiological molecular marker.

METHODS

An ecological study design was used. The levels of serum selenium of the 571 residents aged between 17 and 35 years and living in rural areas, townships, and cities in 63 Keshan disease endemic counties and 46 non-endemic counties in Heilongjiang Province were measured using atomic fluorescence spectrometry. A spatial analysis of serum selenium levels was conducted.

RESULTS

The median serum selenium level of the 571 participants was 1.00 μmol/L, and that of participants living in Keshan disease endemic areas was 0.97 μmol/L, which was significantly lower compared to the level of those living in non-endemic areas (1.01 μmol/L, P = 0.0037). Serum selenium levels of the participants living in rural areas, townships, and cities were significantly different (P < 0.001) at 0.95 μmol/L, 1.00 μmol/L, and 1.04 μmol/L, respectively. Spatial regression analysis showed that the distribution of serum selenium levels was positively correlated with the per capita gross domestic product.

CONCLUSION

The analysis of the spatial distribution of serum selenium levels provided precise visual evidence that selenium deficiency may still be present among residents of Keshan disease endemic counties of Tangyuan, Mulan, Lingdong, Suiling, and Dongshan. Selenium levels should therefore be included in the national surveillance of Keshan disease.

A systematic review and dose-response meta-analysis of exposure to environmental selenium and the risk of type 2 diabetes in nonexperimental studies

Accumulating evidence from both experimental and nonexperimental human studies in the last 15 years indicates that exposure to high levels of the trace element selenium increases the risk of type 2 diabetes. However, the relation of dose to effect is not well understood because randomized controlled trials used only one dose (200 μg/day) of selenium supplementation. While no new trial on this topic has been published since 2018, several nonexperimental studies have appeared. We therefore updated a previous meta-analysis to include recently published observational studies, and incorporated the recently developed one-stage random-effects model to display the dose-response relation between selenium and type 2 diabetes. We retrieved 34 potentially eligible nonexperimental studies on selenium and diabetes risk up to April 15, 2021. The bulk of the evidence indicates a direct relation between blood, dietary and urinary levels of selenium and risk of diabetes, but not with nail selenium, which may be considered a less reliable biomarker. The association was nonlinear, with risk increasing above 80 μg/day of dietary selenium. Whole blood/plasma/serum selenium concentrations of 160 μg/L corresponded to a risk ratio of 1.96 (95% CI 1.27-3.03) compared with a concentration of 90 μg/L (approximately 60 μg of daily selenium intake). The cohort studies, which are less susceptible to reverse causation bias, indicated increased risk for both blood and urine selenium levels and dietary selenium intake, whereas no such pattern emerged from studies relying on nail selenium content. Overall, the nonexperimental studies agree with findings from randomized controlled trials, indicating that moderate to high levels of selenium exposure are associated with increased risk for type 2 diabetes.

Selenium as a Bioactive Micronutrient in the Human Diet and Its Cancer Chemopreventive Activity

This review answers the question of why selenium is such an important trace element in the human diet. Daily dietary intake of selenium and its content in various food products is discussed in this paper, as well as the effects of its deficiency and excess in the body. Moreover, the biological activity of selenium, which it performs mainly through selenoproteins, is discussed. These specific proteins are responsible for thyroid hormone management, fertility, the aging process, and immunity, but their key role is to maintain a redox balance in cells. Furthermore, taking into account world news and the current SARS-CoV-2 virus pandemic, the impact of selenium on the course of COVID-19 is also discussed. Another worldwide problem is the number of new cancer cases and cancer-related mortality. Thus, the last part of the article discusses the impact of selenium on cancer risk based on clinical trials (including NPC and SELECT), systematic reviews, and meta-analyses. Additionally, this review discusses the possible mechanisms of selenium action that prevent cancer development.

Selenium Nutritional Status of Rural Residents and Its Correlation with Dietary Intake Patterns in a Typical Low-Selenium Area in China

China is recognized as a selenium-deficient country, and nutritional selenium intake has always been a concern. To clarify the current inhabitants’ selenium nutrition status and the characteristics of dietary consumption in low-selenium areas, samples of human hair and grains were collected, and food frequency questionnaires were administered in Binxian County, Shaanxi Province, a typical low-selenium area in the Loess Plateau. The subject number of the study is 85, and the age range is from 11 to 81 years, with an average of 60. The results showed that the average hair selenium content of the residents was 231.7 μg/kg, and 62.4% of the participants had levels higher than the selenium deficiency threshold (200 μg/kg). There was a significant positive correlation between the hair selenium content and the food consumption score after adjusting for rice outsourcing. Three different dietary patterns were noted according to hierarchical cluster analysis. This study provides a tool for assessing the selenium nutrition of inhabitants in low-selenium areas and has considerable significance for improving the dietary pattern of residents.

Selenium and Other Elements in Wheat (Triticum aestivum) and Wheat Bread from a Seleniferous Area

The objective of the present study was to assess the levels of Se, as well as other essential and toxic trace elements in wheat grains and traditional Roti-bread from whole-grain flour in a seleniferous area of Punjab (India) using inductively-coupled plasma mass-spectrometry. Wheat grain and bread selenium levels originating from seleniferous areas exceeded the control values by a factor of more than 488 and 179, respectively. Se-rich wheat was also characterized by significantly increased Cu and Mn levels. Se-rich bread also contained significantly higher levels of Cr, Cu, I, Mn, and V. The level of Li and Sr was reduced in both Se-enriched wheat and bread samples. Roti bread from Se-enriched wheat was also characterized by elevated Al, Cd, and Ni, as well as reduced As and Hg content as compared to the respective control values. Se intake with Se-rich bread was estimated as more than 13,600% of RDA. Daily intake of Mn with both Se-unfortified and Se-fortified bread was 133% and 190% of RDA. Therefore, Se-rich bread from wheat cultivated on a seleniferous area of Punjab (India) may be considered as a potent source of selenium, although Se status should be monitored throughout dietary intervention.

Selenium⁻Fascinating Microelement, Properties and Sources in Food

Selenium is a micronutrient that is essential for the proper functioning of all organisms. Studies on the functions of selenium are rapidly developing. This element is a cofactor of many enzymes, for example, glutathione peroxidase or thioredoxin reductase. Insufficient supplementation of this element results in the increased risk of developing many chronic degenerative diseases. Selenium is important for the protection against oxidative stress, demonstrating the highest activity as a free radical scavenger and anti-cancer agent. In food, it is present in organic forms, as exemplified by selenomethionine and selenocysteine. In dietary supplementation, the inorganic forms of selenium (selenite and selenate) are used. Organic compounds are more easily absorbed by human organisms in comparison with inorganic compounds. Currently, selenium is considered an essential trace element of fundamental importance for human health. Extreme selenium deficiencies are widespread among people all over the world. Therefore, it is essential to supplement the deficiency of this micronutrient with selenium-enriched food or yeast cell biomass in the diet.