Imbalance of dietary nutrients and the associated differentially expressed genes and pathways may play important roles in juvenile Kashin-Beck disease

Effects of selenium and iodine on Kashin-Beck disease: an updated review

Kashin-Beck disease (KBD) is an endochondral osteogenesis disorder characterised by epiphysis damage and secondary deformable arthropathy induced by multiple external factors, among which selenium (Se) and iodine deficiency are important influencing factors. Iodine deficiency is usually accompanied by a low Se content in the soil in the KBD areas of China. Se can reverse oxidative damage to chondrocytes. In addition, Se is related to the bone conversion rate and bone mineral density. Low Se will hinder growth and change bone metabolism, resulting in a decrease in the bone conversion rate and bone mineral density. Thyroid hormone imbalance caused by thyroid dysfunction caused by iodine deficiency can damage bone homeostasis. Compared with Se deficiency alone, Se combined with iodine deficiency can reduce the activity of glutathione peroxidase more effectively, which increases the vulnerability of chondrocytes and other target cells to oxidative stress, resulting in chondrocyte death. Clinical studies have shown that supplementation with Se and iodine is helpful for the prevention and treatment of KBD.

Comparative Analysis of Differentially Expressed Genes in Chondrocytes from Rats Exposed to Low Selenium and T-2 Toxin

The aim of this study was to construct rat models of environmental risk factors for Kashin-Beck disease (KBD) with low selenium and T-2 toxin levels and to screen the differentially expressed genes (DEGs) between the rat models exposed to environmental risk factors. The Se-deficient (SD) group and T-2 toxin exposure (T-2) group were constructed. Knee joint samples were stained with hematoxylin-eosin, and cartilage tissue damage was observed. Illumina high-throughput sequencing technology was used to detect the gene expression profiles of the rat models in each group. Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway enrichment analysis were performed and five differential gene expression results were verified by quantitative real-time polymerase chain reaction (qRT‒PCR). A total of 124 DEGs were identified from the SD group, including 56 upregulated genes and 68 downregulated genes. A total of 135 DEGs were identified in the T-2 group, including 68 upregulated genes and 67 downregulated genes. The DEGs were significantly enriched in 4 KEGG pathways in the SD group and 9 KEGG pathways in the T-2 group. The expression levels of Dbp, Pc, Selenow, Rpl30, and Mt2A were consistent with the results of transcriptome sequencing by qRT‒PCR. The results of this study confirmed that there were some differences in DEGs between the SD group and the T-2 group and provided new evidence for further exploration of the etiology and pathogenesis of KBD.

Selenium intake and multiple health-related outcomes: an umbrella review of meta-analyses

Selenium is an essential trace metalloid element that is associated with fundamental importance to human health. Our umbrella review aimed to evaluate the quality of evidence, validity, and biases in the relationship between selenium intake and health-related outcomes according to published systematic reviews with pooled data and meta-analyses. Selenium intake is associated with a decreased risk of digestive system cancers, all-cause mortality, depression, and Keshan disease, when in children reduce the risk of Kashin-Beck disease. Additionally, selenium supplementation can improve sperm quality, polycystic ovary syndrome, autoimmune thyroid disease, cardiovascular disease, and infective outcomes. Selenium supplementation also has relationship with a decreased concentration of serum lipids including total cholesterol and very low-density lipoprotein cholesterol. However, no evidence has shown that selenium is associated with better outcomes among patients in intensive care units. Furthermore, selenium intake may be related with a higher risk of type 2 diabetes and non-melanoma skin cancers. Moreover, most of included studies are evaluated as low quality according to our evidence assessment. Based on our study findings and the limited advantages of selenium intake, it is not recommended to receive extra supplementary selenium for general populations, and selenium supplementation should not be continued in patients whose selenium-deficient status has been corrected.

Dietary Intake of Multiple Nutrient Elements and Associated Health Effects in the Chinese General Population from a Total Diet Study

Nutrient elements are essential for human health. The intake of nutrient elements (Na, K, Ca, Mg, P, Mn, Fe, Zn, Cu, Se, Mo, and Cr) in the general Chinese population was comprehensively evaluated via a recent total diet study (2016-2019), covering more than two-thirds of the total population. The contents of nutrient elements in 288 composite dietary samples were determined by ICP-MS. The dietary sources, regional distribution, the relationship with the earth's crust, dietary intake, and health effects were discussed. Plant foods were the main source of both macro-elements and trace elements, accounting for 68-96% of total intake. Trace elements in food were compatible with their abundance in the earth's crust. Na intake reduced by 1/4 over the last decade but was still high. The average intake of Ca, Mg, Zn, and Se did not reach the health guidance values, while the average intake of K, P, Mn, Fe, Cu, Mo, and Cr fell within a reasonable range. No element exceeded the UL. However, an imbalance was identified in the dietary Na/K ratio and Ca/P ratio. This paper provides a most recent and national-representative assessment of nutrient element intake, indicating the significance of salt reduction and dietary structure optimization for the population.

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.

The Prevalence of Kashin-Beck Disease in China: a Systematic Review and Meta-analysis

Kashin-Beck disease (KBD) is a serious degenerative chronic joint disease. However, there are few quantitative syntheses of KBD prevalence studies. In this study, an initial systematic review and meta-analysis were performed to study the prevalence of KBD in China. Five databases (PubMed, Web of Science, Chinese National Knowledge Infrastructure (CNKI), WanFang Data, and the China Science-Technology Journal Database (VIP)) were searched by performing an overall search method to identify studies of KBD prevalence in China that were published from the inception of the database to May 30, 2022. The risk of bias was assessed with the standardized risk of bias tool. Heterogeneity was assessed with the I² statistic. A random-effect meta-analysis was performed to study the prevalence of KBD through an analysis of published studies. A total of 34 studies involving 24,820 patients with KBD were included in this meta-analysis. These studies were geographically divided into 3 endemic areas. The pooled overall prevalence rate for KBD was 0.06% (95% CI, 0.04-0.08%). The pooled prevalence estimates were 0.05% (95% CI, 0.01-0.12%) for northeast endemic areas, 0.06% (95% CI, 0.03-0.09%) for northwest endemic areas, and 0.04% (95% CI, 0-0.14%) for southwest endemic areas. There was a negative correlation between KBD prevalence and the publication year. No potential risk of publication bias was found by Begg's test and Egger's test. The publication year and quality score were significantly associated with the detected heterogeneity. Our study indicates that the occurrence and development of KBD have been effectively controlled in recent decades. More effective strategies are needed to prevent and treat KBD.

A Cross-Sectional Study of the Distribution Patterns and Potential Determinants in Plasma Selenium Status Among Chinese Adults With Hypertension

Selenium (Se) is an essential trace element in selenoproteins biosynthesis for the human body and plays an important role in the prevention and control of subsequent cardiovascular disease in adults with hypertension. However, reports on Se status and its potential determinants in populations from different regions of China are limited, especially data on adults with hypertension, a high-risk group more vulnerable to oxidative stress. Thus, we conducted a cross-sectional study from February 2017 to May 2018 of 2,599 participants (1,389 men and 1,210 women) on middle-aged to elderly adults with hypertension with a mean age of 63.1 years (SD 13.3) from 14 provinces of China and aimed to examine the relationship of plasma Se status with demographic characteristics and lifestyles. Overall, the male participants (mean value 75.0 μg/L) tended to have higher plasma Se concentrations than the female participants (73.7 μg/L) when controlling for relevant factors. There were significant differences among regions, and in age and body mass index (BMI) in plasma Se distribution, and plasma Se concentrations were significantly lower among those in the regions with relatively lower Se, aged 60 years or older, and with BMI lower than 28 kg/m². Moreover, a higher frequency of meat consumption (1-2 or ≥3 times/week vs. <1 time/week) was significantly associated with higher plasma Se concentrations in men and women, and male alcohol drinkers had significantly higher plasma Se concentrations than non-alcohol drinkers. Adequate consumption of fruits and vegetables (0.5-1.5 kg/week) was associated with higher plasma Se concentrations among women, but was associated with relatively lower plasma Se concentrations in men. Our results indicated relatively low plasma Se status in Chinese adults with hypertension from 14 provinces, while specific factors including geographic, demographic, and lifestyle characteristics and blood pressure were significantly associated with plasma Se status in this hypertensive population. In addition, more studies are required to further evaluate dietary structure and other lifestyle factors that influence circulating Se status.

Investigation of selenium nutritional status and dietary pattern among children in Kashin-Beck disease endemic areas in Shaanxi Province, China using duplicate portion sampling method

BACKGROUND AND OBJECTIVES

Selenium deficiency is a primary risk factor of Kashin-Beck disease (KBD). This study aimed to investigate whether children in endemic areas could maintain sufficient selenium intake after termination of selenium supplement administration, and evaluate their comprehensive nutritional status and dietary structure.

METHODS

Duplicate portion sampling combined with a questionnaire was adopted to collect data on categories and quantity of all food ingested in three consecutive days. Occipital hair was also collected to detect selenium content by hydride generation atomic fluorescence spectrometry (HGAFS). CDGSS3.0 software and factor analysis were integrated to assess the children's comprehensive nutritional status and dietary structure.

RESULTS

This study included 240 sex-matched (1:1) children aged 7-12 years from KBD endemic (n = 120) and non-endemic (n = 120) areas. Overall, 720 solid food, 720 liquid, and 240 hair samples were collected for selenium determination. The mean selenium level in hair of children in endemic areas (0.38 ± 0.16 mg/kg) was significantly lower than that in children in non-endemic areas (0.56 ± 0.28 mg/kg, Z = -5.249, p < 0.001). The dietary selenium intake of children in endemic areas was 40.0% lower than that in children in non-endemic areas (Z = -9.374, p < 0.001). Children in endemic areas consumed significantly less diverse dietary items leading to significantly less intake of multiple nutrients compared to children in non-endemic areas.

CONCLUSIONS

The dietary selenium intake of most children in endemic areas was less than the recommended amount. The dietary structure of children was undiversified, which limited the intake of multiple nutrients. Therefore, comprehensive nutrition rather than sole selenium intake should be the primary concern in the future.

Comparative analysis of the gut microbiota composition between knee osteoarthritis and Kashin-Beck disease in Northwest China

Background

Osteoarthritis (OA) and Kashin-Beck disease (KBD) both are two severe osteochondral disorders. In this study, we aimed to compare the gut microbiota structure between OA and KBD patients.

Methods

Fecal samples collected from OA and KBD patients were used to characterize the gut microbiota using 16S rDNA gene sequencing. To identify whether gut microbial changes at the species level are associated with the genes or functions of the gut bacteria between OA and KBD groups, metagenomic sequencing of fecal samples from OA and KBD subjects was performed.

Results

The OA group was characterized by elevated Epsilonbacteraeota and Firmicutes levels. A total of 52 genera were identified to be significantly differentially abundant between the two groups. The genera Raoultella, Citrobacter, Flavonifractor, g__Lachnospiraceae_UCG-004, and Burkholderia-Caballeronia-Paraburkholderia were more abundant in the OA group. The KBD group was characterized by higher Prevotella_9, Lactobacillus, Coprococcus_2, Senegalimassilia, and Holdemanella. The metagenomic sequencing showed that the Subdoligranulum_sp._APC924/74, Streptococcus_parasanguinis, and Streptococcus_salivarius were significantly increased in abundance in the OA group compared to those in the KBD group, and the species Prevotella_copri, Prevotella_sp._CAG:386, and Prevotella_stercorea were significantly decreased in abundance in the OA group compared to those in the KBD group by using metagenomic sequencing.

Conclusion

Our study provides a comprehensive landscape of the gut microbiota between OA and KBD patients and provides clues for better understanding the mechanisms underlying the pathogenesis of OA and KBD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02819-5.

The Status of Selenium and Zinc in the Urine of Children From Endemic Areas of Kashin-Beck Disease Over Three Consecutive Years

Selenium deficiency is one of the main risk factors for Kashin-Beck disease (KBD). This study aimed to detect the status of selenium and zinc in the urine of children from endemic areas of KBD over three consecutive years and to evaluate whether selenium and zinc levels in children in Shaanxi Province remain normal after stopping selenium supplementation. The samples of urine were collected in consecutive years (2017–2019) to detect selenium content by hydride generation atomic fluorescence spectrometry (HGAFS) and to detect zinc content by atomic absorption spectrophotometry (AAS). Generalized estimation equation (GEE) analysis was integrated to assess the comprehensive nutritional status and dietary structure of children. Data were processed in duplicate and analyzed by SPSS 18.0. This study included 30 X-ray-positive KBD cases and 123 healthy children aged 7–12 years. A total of 424 urine and 137 hair samples were collected over three consecutive years for selenium determination. The mean value of urinary selenium in all subjects was 6.86 μg/l (2017), 8.26 μg/l (2018), and 4.04 μg/l (2019), and the mean value of urinary zinc in all subjects was 0.36 mg/l (2017), 0.39 mg/l (2018), and 0.31 mg/l (2019) for the three consecutive years of 2017–2019. The mean values of urinary selenium were 6.56 and 6.94 μg/l (2017), 8.69 and 8.14 μg/l (2018), and 4.57 and 3.90 μg/l (2019) in the KBD-X and normal groups, respectively; and the mean value of urinary zinc were 0.38 and 0.35 mg/l (2017), 0.41 and 0.39 mg/l (2018), and 0.43 and 0.28 mg/l (2019) in the KBD-X and normal groups, respectively. The mean value of hair selenium in 137 subjects was 275.08 μg/kg and the mean values of hair selenium were 267.48 and 276.61 μg/kg in the KBD-X group and normal group, respectively. The level of selenium/zinc showed a trend of increasing first and then decreasing during the three consecutive years. The level of selenium in all subjects from the endemic areas was lower than normal, which reminds us to monitor the state of KBD constantly and adjust selenium salt supplementation in accordance with the changes in the KBD state.

Effect of Low Nutrition and T-2 Toxin on C28/I2 Chondrocytes Cell Line and Chondroitin Sulfate-Modifying Sulfotransferases

OBJECTIVE

To investigate the effects of low nutrition and trichothecenes-2 toxin (T-2) on human chondrocytes cell line C28/I2 and the gene expression levels of some chondroitin sulfate (CS)-modifying sulfotransferases.

METHODS

The chondrocytes were divided into 4 intervention groups: (a) control group (Dulbecco's modified Eagle's medium/Nutrient Mixture F-12 [DMEM/F-12] with fetal bovine serum [FBS]), (b) low-nutrition group (DMEM/F-12 without FBS), (c) T-2 group (DMEM/F-12 with FBS plus 20 ng/mL T-2), and (d) combined group (DMEM/F-12 without FBS plus 20 ng/mL T-2). Twenty-four hours postintervention, ultrastructural changes in the chondrocytes were observed by transmission electron microscopy (TEM). Live cell staining and methyl thiazolyl tetrazolium (MTT) assay were performed to observe cell viability. The expression of CS-modifying sulfotransferases, including carbohydrate sulfotransferase 3, 12, 13, 15 (CHST-3, CHST-12, CHST-13, and CHST-15, respectively), and uronyl 2-O-sulfotransferase (UST) were examined by quantitative real-time polymerase chain reaction (RT-qPCR) analysis.

RESULTS

The cells in the T-2 group and combined group had significantly lower live cell counts and relative survival rates than the control group. TEM pictures revealed decreased electron density of mitochondria in the low-nutrition group. The T-2 group and combined group both caused mitochondrial swelling, damage, and reduction in mitochondrial number. RT-qPCR showed a trend of altered expression of CHST and increased expression of UST genes under low-nutrition, T-2 toxin and combined interventions.

CONCLUSIONS

These results show early-stage Kashin-Beck disease chondrocyte pathophysiology, consisting of chondrocyte cell damage and compensatory upregulation of CHST and UST genes.

Association of selenium levels with the prevention and control of Keshan disease: A cross-sectional study

PURPOSE

The prevalence of Keshan disease (KD) is low and has reached controlled or eliminated levels even in counties that had a high KD prevalence in the past. Few nationwide surveys on selenium levels in KD areas have been conducted in the past 2 decades. We conducted a cross-sectional study to investigate the selenium levels and their association with KD control and prevention in areas where KD is prevalent.

METHODS

We collected 2143 human-hair, 698 soil, 701 rice, 607 flour, 521 corn, and 330 other-food samples from 49 counties with KD and 19 non-KD counties of nine KD provinces of China. The selenium content of samples was examined with hydride generation atomic fluorescence spectrometry. The difference in selenium levels between the KD and non-KD areas was analyzed. Cochran-Armitage trend tests were used to evaluate the association between selenium levels and KD control.

RESULTS

The selenium levels in human hair, soil, staple foods, and other foods in the KD areas (0.2996 mg/kg, 0.1380 mg/kg, 0.0190 mg/kg and 0.0076 mg/kg, respectively) were lower than those in the non-KD areas (0.3700 mg/kg, 0.1930 mg/kg, 0.0240 mg/kg and 0.0165 mg/kg, respectively). The Cochran-Armitage tests showed that there was a trend for the selenium standard ratio in the counties to increase in the order of KD uncontrolled, to controlled, to eliminated (Z = 2.229, P < 0.05).

CONCLUSION

The residents in the KD areas were found to be selenium-deficient. Improving the supply of staple foods containing selenium levels exceeding 0.025 mg/kg and abundant foodstuffs might contribute to KD control and prevention.

Alterations in the gut microbiota and metabolite profiles of patients with Kashin-Beck disease, an endemic osteoarthritis in China

Kashin-Beck disease (KBD) is a severe osteochondral disorder that may be driven by the interaction between genetic and environmental factors. We aimed to improve our understanding of the gut microbiota structure in KBD patients of different grades and the relationship between the gut microbiota and serum metabolites. Fecal and serum samples collected from KBD patients and normal controls (NCs) were used to characterize the gut microbiota using 16S rDNA gene and metabolomic sequencing via liquid chromatography-mass spectrometry (LC/MS). To identify whether gut microbial changes at the species level are associated with the genes or functions of the gut bacteria in the KBD patients, metagenomic sequencing of fecal samples from grade I KBD, grade II KBD and NC subjects was performed. The KBD group was characterized by elevated levels of Fusobacteria and Bacteroidetes. A total of 56 genera were identified to be significantly differentially abundant between the two groups. The genera Alloprevotella, Robinsoniella, Megamonas, and Escherichia_Shigella were more abundant in the KBD group. Consistent with the 16S rDNA analysis at the genus level, most of the differentially abundant species in KBD subjects belonged to the genus Prevotella according to metagenomic sequencing. Serum metabolomic analysis identified some differentially abundant metabolites among the grade I and II KBD and NC groups that were involved in lipid metabolism metabolic networks, such as that for unsaturated fatty acids and glycerophospholipids. Furthermore, we found that these differences in metabolite levels were associated with altered abundances of specific species. Our study provides a comprehensive landscape of the gut microbiota and metabolites in KBD patients and provides substantial evidence of a novel interplay between the gut microbiome and metabolome in KBD pathogenesis.

Sex difference in the association between plasma selenium and first stroke: a community-based nested case-control study

BACKGROUND

To date, there is no clearly defined association between plasma selenium levels and first stroke. We aimed to investigate the association between baseline plasma selenium and first stroke risk in a community-based Chinese population.

METHODS

Using a nested case-control study design, a total of 1255 first stroke cases and 1255 matched controls were analyzed. Participant plasma selenium concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS), and the association of plasma selenium with first stroke risk was estimated by conditional logistic regression models.

RESULTS

Overall, a non-linear negative association between plasma selenium and first total stroke and first ischemic stroke risks was found in males but not in females. Compared with participants with lower selenium levels (tertile 1-2, < 94.1 ng/mL), participants with higher selenium levels (tertile 3, ≥ 94.1 ng/mL) had significantly lower risks of first total stroke (OR 0.63; 95% CI 0.48, 0.83) and first ischemic stroke (OR 0.61; 95% CI 0.45, 0.83) in males but not in females with first total stroke (OR 0.92; 95% CI 0.69, 1.22) and first ischemic stroke (OR 0.89; 95% CI 0.65, 1.22). Furthermore, a stronger association between plasma selenium and first total stroke was found in males with higher vitamin E levels (≥ 13.5 μg/mL vs. < 13.5 μg/mL P-interaction = 0.007). No significant association was observed between plasma selenium and first hemorrhagic stroke risk in either males or females.

CONCLUSION

Our study indicated a significant, non-linear, negative association between plasma selenium and first stroke in males but not in females.

TRIAL REGISTRATION

ChiCTR1800017274 .

Comparison of the major cell populations among osteoarthritis, Kashin-Beck disease and healthy chondrocytes by single-cell RNA-seq analysis

Chondrocytes are the key target cells of the cartilage degeneration that occurs in Kashin–Beck disease (KBD) and osteoarthritis (OA). However, the heterogeneity of articular cartilage cell types present in KBD and OA patients and healthy controls is still unknown, which has prevented the study of the pathophysiology of the mechanisms underlying the roles of different populations of chondrocytes in the processes leading to KBD and OA. Here, we aimed to identify the transcriptional programmes and all major cell populations in patients with KBD, patients with OA and healthy controls to identify the markers that discriminate among chondrocytes in these three groups. Single-cell RNA sequencing was performed to identify chondrocyte populations and their gene signatures in KBD, OA and healthy cells to investigate their differences as related to the pathogenetic mechanisms of these two osteochondral diseases. We performed immunohistochemistry and quantitative reverse-transcription PCR (qRT-PCR) assays to validate the markers for chondrocyte population. Ten clusters were labelled by cell type according to the expression of previously described markers, and one novel population was identified according to the expression of a new set of markers. The homeostatic and mitochondrial chondrocyte populations, which were identified by the expression of the unknown markers MT1X and MT2A and MT-ND1 and MT-ATP6, were markedly expanded in KBD. The regulatory chondrocyte population, identified by the expression of CHI3L1, was markedly expanded in OA. Our study allows us to better understand the heterogeneity of chondrocytes in KBD and OA and provides new evidence of differences in the pathogenetic mechanisms between these two diseases.

Association between fatality rate of COVID-19 and selenium deficiency in China

BACKGROUND

COVID-19 has impacted populations around the world, with the fatality rate varying dramatically across countries. Selenium, as one of the important micronutrients implicated in viral infections, was suggested to play roles.

METHODS

An ecological study was performed to assess the association between the COVID-19 related fatality and the selenium content both from crops and topsoil, in China.

RESULTS

Totally, 14,045 COVID-19 cases were reported from 147 cities during 8 December 2019-13 December 2020 were included. Based on selenium content in crops, the case fatality rates (CFRs) gradually increased from 1.17% in non-selenium-deficient areas, to 1.28% in moderate-selenium-deficient areas, and further to 3.16% in severe-selenium-deficient areas (P = 0.002). Based on selenium content in topsoil, the CFRs gradually increased from 0.76% in non-selenium-deficient areas, to 1.70% in moderate-selenium-deficient areas, and further to 1.85% in severe-selenium-deficient areas (P < 0.001). The zero-inflated negative binomial regression model showed a significantly higher fatality risk in cities with severe-selenium-deficient selenium content in crops than non-selenium-deficient cities, with incidence rate ratio (IRR) of 3.88 (95% CIs: 1.21-12.52), which was further confirmed by regression fitting the association between CFR of COVID-19 and selenium content in topsoil, with the IRR of 2.38 (95% CIs: 1.14-4.98) for moderate-selenium-deficient cities and 3.06 (1.49-6.27) for severe-selenium-deficient cities.

CONCLUSIONS

Regional selenium deficiency might be related to an increased CFR of COVID-19. Future studies are needed to explore the associations between selenium status and disease outcome at individual-level.

Dietary Selenium Regulates microRNAs in Metabolic Disease: Recent Progress

Selenium (Se) is an essential element for the maintenance of a healthy physiological state. However, due to environmental and dietary factors and the narrow safety range of Se, diseases caused by Se deficiency or excess have gained considerable traction in recent years. In particular, links have been identified between low Se status, cognitive decline, immune disorders, and increased mortality, whereas excess Se increases metabolic risk. Considerable evidence has suggested microRNAs (miRNAs) regulate interactions between the environment (including the diet) and genes, and play important roles in several diseases, including cancer. MiRNAs target messenger RNAs to induce changes in proteins including selenoprotein expression, ultimately generating disease. While a plethora of data exists on the epigenetic regulation of other dietary factors, nutrient Se epigenetics and especially miRNA regulated mechanisms remain unclear. Thus, this review mainly focuses on Se metabolism, pathogenic mechanisms, and miRNAs as key regulatory factors in Se-related diseases. Finally, we attempt to clarify the regulatory mechanisms underpinning Se, miRNAs, selenoproteins, and Se-related diseases.

Analysis of Bioavailability and Induction of Glutathione Peroxidase by Dietary Nanoelemental, Organic and Inorganic Selenium

Dietary organic selenium (Se) is commonly utilized to increase formation of selenoproteins, including the major antioxidant protein, glutathione peroxidase (GPx). Inorganic Se salts, such as sodium selenite, are also incorporated into selenoproteins, and there is evidence that nanoelemental Se added to the diet may also be effective. We conducted two trials, the first investigated inorganic Se (selenite), organic Se (L-selenomethionine) and nanoelemental Se, in conventional mice. Their bioavailability and effectiveness to increase GPx activity were examined. The second trial focused on determining the mechanism by which dietary Se is incorporated into tissue, utilising both conventional and germ-free (GF) mice. Mice were fed a diet with minimal Se, 0.018 parts per million (ppm), and diets with Se supplementation, to achieve 0.07, 0.15, 0.3 and 1.7 ppm Se, for 5 weeks (first trial). Mass spectrometry, Western blotting and enzymatic assays were used to investigate bioavailability, protein levels and GPx activity in fresh frozen tissue (liver, ileum, plasma, muscle and feces) from the Se fed animals. Inorganic, organic and nanoelemental Se were all effectively incorporated into tissues. The high Se diet (1.7 ppm) resulted in the highest Se levels in all tissues and plasma, independent of the Se source. Interestingly, despite being ~11 to ~25 times less concentrated than the high Se, the lower Se diets (0.07; 0.15) resulted in comparably high Se levels in liver, ileum and plasma for all Se sources. GPx protein levels and enzyme activity were significantly increased by each diet, relative to control. We hypothesised that bacteria may be a vector for the conversion of nanoelemental Se, perhaps in exchange for S in sulphate metabolising bacteria. We therefore investigated Se incorporation from low sulphate diets and in GF mice. All forms of selenium were bioavailable and similarly significantly increased the antioxidant capability of GPx in the intestine and liver of GF mice and mice with sulphate free diets. Se from nanoelemental Se resulted in similar tissue levels to inorganic and organic sources in germ free mice. Thus, endogenous mechanisms, not dependent on bacteria, reduce nanoelemental Se to the metabolite selenide that is then converted to selenophosphate, synthesised to selenocysteine, and incorporated into selenoproteins. In particular, the similar efficacy of nanoelemental Se in comparison to organic Se in both trials is important in the view of the currently limited cheap sources of Se.

Magnetic resonance imaging at 7.0 T for evaluation of early lesions of epiphyseal plate and epiphyseal end in a rat model of Kashin-Beck disease

Background

Kashin–Beck disease (KBD) is a disabling osteoarticular disease involving growth and joint cartilage. Early diagnosis can effectively prevent the progress of the disease. However, the early diagnosis of it is still very difficult. Our aim was to study the knee joint lesions of a rat KBD model using ultra-high field magnetic resonance imaging (MRI) and compare it with X-ray imaging to analyze the possible MRI manifestations of KBD, and to further explore ways to determine the pathological damage of KBD in the early stage.

Methods

A total of 96 Wistar rats were selected and randomly divided into 4 groups: normal diet (Group A), KBD-affected diet (Group B), normal diet+T-2 toxin (Group C), and KBD-affected diet+T-2 toxin (Group D). T-2 toxin was administered at a dose of 0.1 mg/kg/day. In the 4th week, 8th week, and 12th week, eight rats randomly selected in each group were sacrificed by cervical dislocation after undergoing X-ray and 7.0 T MRI imaging, and then knee joints were harvested, sliced, and subjected to hematoxylin-eosin (H&E) staining.

Results

Characteristic image changes including of continuity interruption and early closure and fusion of epiphyseal plates were observed on T1WI in rat model of KBD. The total necrosis rates in the H&E stain of group A to group D were 4.35, 52.38, 33.3, and 73.68%, respectively. The positive rate of image change under 7.0 T MRI was 0.833 VS. that under X-ray was 0.33 (P = 0.001).

Conclusions

MRI at 7.0 T is highly sensitive to the early pathological changes of the epiphysis, epiphyseal plate, and metaphyseal end, which can improve imaging positive rate of KBD and decrease the rate of missed diagnosis. This imaging modality can be used for research on early joint lesions and for early diagnosis of KBD.

Hair multi-bioelement profile of Kashin-Beck disease in the endemic regions of China

BACKGROUND

Kashin-Beck disease (KBD) is a serious chronic osteochondral disease that is endemic in humans. Selenium (Se) has been considered in hypotheses of the aetiology of KBD, but few studies have explored the relationship between other elements and KBD.

OBJECTIVE

This study explored the relationship between 39 elements and KBD.

METHODS

In this retrospective study, 150 boys aged 6 to 14 years were randomly selected from a total population of 1,214 children. Subjects from endemic areas were divided into five groups: (KBD -Bin, N = 30; KBD + Se-Yongshou, N = 30; Control -Bin, N = 30; Control + Se -Yongshou, N = 30; and Control External -Chang'an, N = 30). Samples of occipital hair were collected from each subject, and thirty-nine elements, including 15 toxic elements, 19 nutrient elements, and 5 other elements were assayed by inductively coupled plasma mass spectrometry (ICP-MS). Correlation analysis of the elements in each group was performed by ggcorrplot (visualization of a correlation matrix using 'ggplot2') and PerformanceAnalytics packages in the program R Project.

RESULTS

Among the 15 toxic elements, the levels of aluminum (Al) and bismuth (Bi) in the KBD -Bin were significantly higher than in the other groups, and the levels of silver (Ag), beryllium (Be), platinum (Pt), antimony (Sb), tin (Sn) and lead (Pb) in the KBD -Bin were significantly lower than in the other groups. Among the 19 nutrient elements, the levels of selenium (Se), iodine (I), sulfur (S), and boron (B) in the KBD -Bin were significantly lower than in the other groups. The levels of calcium (Ca), iron (Fe), manganese (Mn), chromium (Cr), strontium (Sr) and phosphorus (P) in the KBD -Bin were significantly higher than in the other groups. Correlations between various elements were remarkably different among the groups. There were positive correlations between As and Pb, Cd and Sb, Pb and Sb, Sb and U in the Control External -Chang'an, between Al and Ni, Cd and Pb, Tl and Ni, Ti and U in the Se-S KBD, and between B and I, B and Mo, Mn and V in the Control External -Chang'an.

CONCLUSIONS

These findings indicate that the interactions between elements do not represent a simple reciprocal relationship in the occurrence of KBD. In fact, KBD was associated with an imbalance in multiple elements that play a dynamic and interactive role in the development of the disease.

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.

Selenium-Related Transcriptional Regulation of Gene Expression

The selenium content of the body is known to control the expression levels of numerous genes, both so-called selenoproteins and non-selenoproteins. Selenium is a trace element essential to human health, and its deficiency is related to, for instance, cardiovascular and myodegenerative diseases, infertility and osteochondropathy called Kashin–Beck disease. It is incorporated as selenocysteine to the selenoproteins, which protect against reactive oxygen and nitrogen species. They also participate in the activation of the thyroid hormone, and play a role in immune system functioning. The synthesis and incorporation of selenocysteine occurs via a special mechanism, which differs from the one used for standard amino acids. The codon for selenocysteine is a regular in-frame stop codon, which can be passed by a specific complex machinery participating in translation elongation and termination. This includes a presence of selenocysteine insertion sequence (SECIS) in the 3′-untranslated part of the selenoprotein mRNAs. Nonsense-mediated decay is involved in the regulation of the selenoprotein mRNA levels, but other mechanisms are also possible. Recent transcriptional analyses of messenger RNAs, microRNAs and long non-coding RNAs combined with proteomic data of samples from Keshan and Kashin–Beck disease patients have identified new possible cellular pathways related to transcriptional regulation by selenium.