Selenoproteins and Cancer Prevention

50 Years of Organoselenium Chemistry, Biochemistry and Reactivity: Mechanistic Understanding, Successful and Controversial Stories

In 1973, two major discoveries changed the face of selenium chemistry: the identification of the first mammal selenoenzyme, glutathione peroxidase 1, and the discovery of the synthetic utility of the so-called selenoxide elimination. While the chemical mechanism behind the catalytic activity of glutathione peroxidases appears to be mostly unveiled, little is known about the mechanisms of other selenoproteins and, for some of them, even the function lies in the dark. In chemistry, the capacity of organoselenides of catalyzing hydrogen peroxide activation for the practical manipulation of organic functional groups has been largely explored, and some mechanistic details have been clearly elucidated. As a paradox, despite the long-standing experience in the field, the nature of the active oxidant in various reactions still remains matter of debate. While many successes characterize these fields, the pharmacological use of organoselenides still lacks any true application, and while some organoselenides were found to be non-toxic and safe to use, to date no therapeutically approved use was granted. In this review, some fundamental and chronologically aligned topics spanning organoselenium biochemistry, chemistry and pharmacology are discussed, focusing on the current mechanistic picture describing their activity as either bioactive compounds or catalysts.

Selenoprotein S (SELENOS) is a potential prognostic biomarker for brain lower grade glioma

BACKGROUND

Selenium, an essential micronutrient, primarily exists as selenocysteine in various selenoproteins. Selenoprotein S (SELENOS) is crucial in the development of human cancer. This study aimed to explore the correlation between SELENOS gene expression and the prognosis of brain lower-grade glioma (LGG).

METHODS

SELENOS protein and mRNA expression in human normal and tumor tissues were explored through the HPA database. SELENOS expression differences between normal and tumor tissues, along with its prognostic significance in gliomas, were analyzed using the TCGA, GTEx datasets, while the CGGA dataset was used to further assess its prognostic potential in a Chinese cohort. The association between SELENOS expression and tumor immune infiltration was also assessed. Multivariate and univariate Cox models were used to screen for clinicopathological parameters associated with SELENOS expression. The GDSC datasets was utilized to explore the connection between SELENOS and chemotherapeutic responses in LGG. A protein-protein interaction network for SELENOS was created. SELENOS expression in LGG cell lines were determined by Western blotting and qRT-PCR, and its functions were ascertained by routine in vitro experiments.

RESULTS

SELENOS was upregulated in 11 cancers and downregulated in 10 cancers relative to the corresponding normal tissues, and correlated significantly with the prognosis, especially for GBM, LGG and GBMLGG. Furthermore, It displayed a positive correlation with immune cell infiltration levels in LGG. Multivariate and Univariate Cox analyses confirmed that the impact of SELENOS on the prognosis of LGG is the combined result of factors such as age and tumor grade. The expression of SELENOS was significantly negatively correlated with temozolomide IC50 in LGG. We found that SELENOS interacts with 10 proteins, which are upregulated in LGG compared to human normal tissues. The expression of these interactors is positively correlated with SELENOS expression and LGG survival/prognosis. In vitro experiments confirmed the aberrant expression of SELENOS in LGG cell lines, and siRNA-mediated knockdown of SELENOS reduced the proliferation, viability, invasion and migration of LGG cells, and induced apoptosis.

CONCLUSIONS

SELENOS is a potential prognostic marker and therapeutic target for LGG, and its low expression is associated with favorable prognosis in LGG.

PRDX6 augments selenium utilization to limit iron toxicity and ferroptosis

Ferroptosis is a form of regulated cell death induced by iron-dependent accumulation of lipid hydroperoxides. Selenoprotein glutathione peroxidase 4 (GPX4) suppresses ferroptosis by detoxifying lipid hydroperoxides via a catalytic selenocysteine (Sec) residue. Sec, the genetically encoded 21st amino acid, is biosynthesized from a reactive selenium donor on its cognate tRNA[Ser]Sec. It is thought that intracellular selenium must be delivered 'safely' and 'efficiently' by a carrier protein owing to its high reactivity and very low concentrations. Here, we identified peroxiredoxin 6 (PRDX6) as a novel selenoprotein synthesis factor. Loss of PRDX6 decreases the expression of selenoproteins and induces ferroptosis via a reduction in GPX4. Mechanistically, PRDX6 increases the efficiency of intracellular selenium utilization by transferring selenium between proteins within the selenocysteyl-tRNA[Ser]Sec synthesis machinery, leading to efficient synthesis of selenocysteyl-tRNA[Ser]Sec. These findings highlight previously unidentified selenium metabolic systems and provide new insights into ferroptosis.

Selenoprotein GPX3 is a novel prognostic indicator for stomach adenocarcinoma and brain low-grade gliomas: Evidence from an integrative pan-cancer analysis

Background

The antioxidant enzyme GPX3 is a selenoprotein that transports selenium in blood and maintains its levels in peripheral tissues. Aberrant GPX3 expression is strongly linked to the development of some tumors. However, there is a scarcity of studies examining the pan-cancer expression patterns and prognostic relevance of GPX3.

Methods

GPX3 expression levels in normal tissues and multiple tumors were analyzed using TCGA, CCLE, GTEx, UALCAN and HPA databases. Forest plots and KM survival curves were utilized to evaluate the correlation between GPX3 expression and the outcome of tumor patients. The prognostic value of GPX3 in LGG was assessed utilizing the CGGA datasets, and that in STAD was tested by TCGA and GEO databases. A nomogram was then constructed to predict OS in STAD using R software. Additionally, the impact of GPX3 on post-chemoradiotherapy OS in patients with LGG and STAD was evaluated using the KM method. The multiplicative interaction of GPX3 expression, chemotherapy and radiotherapy on STAD and LGG was analyzed using logistic regression models. The correlation of GPX3 with the immune infiltration, immune neoantigens and MMR genes were investigated in TCGA cohort.

Results

GPX3 exhibited downregulation across 21 tumor types, including STAD, with its decreased expression significantly associated with improved OS, DFS, PFS and DSS. Conversely, in LGG, low levels of GPX3 expression were indicative of a poorer prognosis. Univariate and multivariate Cox models further identified GPX3 as an independent predictor of STAD, and a nomogram based on GPX3 expression and other independent factors showed high level of predictive accuracy. Moreover, low GPX3 expression and chemotherapy prolonged the survival of STAD. In LGG patients, chemoradiotherapy, GPX3 and chemotherapy, and GPX3 and chemoradiotherapy may improve prognosis. Our observations reveal a notable connection between GPX3 and immune infiltration, immune neoantigens, and MMR genes.

Conclusions

The variations in GPX3 expression are linked to the controlling tumor development and could act as a promising biomarker that impacts the prognosis of specific cancers like STAD and LGG.

Micronutrient Status and Breast Cancer: A Narrative Review

Breast cancer is one of the most common cancers worldwide, at the same time being one of the most prevalent causes of women's death. Many factors such as alcohol, weight fluctuations, or hormonal replacement therapy can potentially contribute to breast cancer development and progression. Another important factor in breast cancer onset includes micronutrient status. In this narrative review, we analyzed 23 micronutrients and their possible influence on breast cancer onset and progression. Further, the aim of this study was to investigate the impact of micronutrient status on the prevention of breast cancer and its possible influence on various therapeutic pathways. We researched meta-analyses, systemic and narrative reviews, retrospective studies, as well as original studies on human and animal models. The results of these studies indicate a possible correlation between the different levels of micronutrients and a decreased risk of breast cancer as well as a better survival rate. However, further studies are necessary to establish adequate doses of supplementation of the chosen micronutrients and the exact mechanisms of micronutrient impact on breast cancer therapy.

Seleno-Warfare against Cancer: Decoding Antitumor Activity of Novel Acylselenoureas and Se-Acylisoselenoureas

Currently, cancer remains a global health problem. Despite the existence of several treatments, including chemotherapy, immunotherapy, and radiation therapy, the survival rate for most cancer patients, particularly those with metastasis, remains unsatisfactory. Thus, there is a continuous need to develop novel, effective therapies. In this work, 22 novel molecules containing selenium are reported, including seven Se-acylisoselenoureas synthesized from aliphatic carbodiimides as well as acylselenoureas with the same carbo- and heterocycles and aliphatic amines. After an initial screening at two doses (50 and 10 µM) in MDA-MB-231 (breast), HTB-54 (lung), DU-145 (prostate), and HCT-116 (colon) tumor cell lines, the ten most active compounds were identified. Additionally, these ten hits were also submitted to the DTP program of the NCI to study their cytotoxicity in a panel of 60 cancer cell lines. Compound 4 was identified as the most potent antiproliferative compound. The results obtained showed that compound 4 presented IC50 values lower than 10 µM in the cancer cell lines, although it was not the most selective one. Furthermore, compound 4 was found to inhibit cell growth and cause cell death by inducing apoptosis partially via ROS production. Overall, our results suggest that compound 4 could be a potential chemotherapeutic drug for different types of cancer.

Applications of peptide-functionalized or unfunctionalized selenium nanoparticles for the passivation of SARS-CoV-2 variants and the respiratory syncytial virus (RSV)

The SARS-CoV-2 Omicron subvariants BA.4, BA. 5 and XBB are currently causing a COVID resurgence due to their increased spreading and infectivity. These latest subvariants have been shown to be somewhat resistant to the most common vaccines even with the third dose. Moreover, it has been well documented that when patients stop taking some commercial therapies (such as Paxlovid), COVID from these variants may return and may even be more contagious. Herein, we tested unfunctionalized and functionalized selenium (Se) nanoparticles with three novel peptides (NapFFTLUFLTUTEKKKK, NapFFMLUFLMUMEKKKK, and NapFFSAVLQSGFKKKK) previously shown by themselves to passivate the Omicron SARS-CoV-2 BA.4, BA.5 and XBB variants. Se is a natural element in our diet and is well known to boost the immune system, thus, providing a complementary approach to viral infections. NapFFMLUFLMUMEKKKK showed a stronger inhibition ability at 98 % for Omicron BA.4 % and 96 % for Omicron BA.5 after just 15 min in vitro. Two types of Se nanoparticles (those made chemically or biogenically by cells) were tested to passivate the new SARS-CoV-2 XBB variant. Results showed that the combination of any peptide and using either type of Se NP, the Omicron subvariant XBB was inhibited by 100 % after just 15 min in vitro. Interestingly, the use of Se NPs alone outperformed the peptides in terms of XBB passivation. Also, in order to determine a mechanism of action, functionalizing Se nanoparticles with the NapFFSAVLQSGFKKKK peptide showed a high binding ability toward the chemotrypsin-like cysteine protease (SARS CoV-2 3CLpro). Further, as a demonstration of their versatility, these functionalized peptides also passivated the Respiratory Syncytial Virus (RSV). NapFFTLUFLTUTEKKKK and NapFFMLUFLMUMEKKKK showed in silico interactions with the fusion glycoprotein of RSV prompting in vitro RSV pseudo virus testing. Compared to the conventionally precipitated synthetic Se nanoparticles, in vitro results showed that biogenic Se functionalized with the peptides enhanced the inhibition RSV to 100 % after just 15 min of incubation. NapFFTLUFLTUTEKKKK and NapFFMLUFLMUMEKKKK also showed no potential genotoxicity or carcinogenic effects. The peptides showed good gastro-intestinal (GI) tract absorption and bioavailability as predicted using the partition coefficient (QP logPo/w), and high-water solubility as detected by QPlogS. According to these promising results, functionalizing biogenic Se nanoparticles with these novel peptides should be further studied in vivo for the improved diagnosis, prevention, and treatment of SARS-CoV-2, RSV, and other respiratory virus infections.

Matched analysis of circulating selenium with the breast cancer selenotranscriptome: a multicentre prospective study

INTRODUCTION

Low serum selenium and altered tumour RNA expression of certain selenoproteins are associated with a poor breast cancer prognosis. Selenoprotein expression stringently depends on selenium availability, hence circulating selenium may interact with tumour selenoprotein expression. However, there is no matched analysis to date.

METHODS

This study included 1453 patients with newly diagnosed breast cancer from the multicentric prospective Sweden Cancerome Analysis Network - Breast study. Total serum selenium, selenoprotein P and glutathione peroxidase 3 were analysed at time of diagnosis. Bulk RNA-sequencing was conducted in matched tumour tissues. Fully adjusted Cox regression models with an interaction term were employed to detect dose-dependent interactions of circulating selenium with the associations of tumour selenoprotein mRNA expression and mortality.

RESULTS

237 deaths were recorded within ~ 9 years follow-up. All three serum selenium biomarkers correlated positively (p < 0.001). All selenoproteins except for GPX6 were expressed in tumour tissues. Single cell RNA-sequencing revealed a heterogeneous expression pattern in the tumour microenvironment. Circulating selenium correlated positively with tumour SELENOW and SELENON expression (p < 0.001). In fully adjusted models, the associations of DIO1, DIO3 and SELENOM with mortality were dose-dependently modified by serum selenium (p < 0.001, p = 0.020, p = 0.038, respectively). With increasing selenium, DIO1 and SELENOM associated with lower, whereas DIO3 expression associated with higher mortality. Association of DIO1 with lower mortality was only apparent in patients with high selenium [above median (70.36 µg/L)], and the HR (95%CI) for one-unit increase in log(FPKM + 1) was 0.70 (0.50-0.98).

CONCLUSIONS

This first unbiased analysis of serum selenium with the breast cancer selenotranscriptome identified an effect-modification of selenium on the associations of DIO1, SELENOM, and DIO3 with prognosis. Selenium substitution in patients with DIO1-expressing tumours merits consideration to improve survival.

Selenium in Prostate Cancer: Prevention, Progression, and Treatment

Selenium, a trace mineral with various biological functions, has become a focal point in prostate cancer research. This review aims to present a comprehensive overview of selenium's involvement in prostate cancer, covering its impact on prevention, development, treatment, and underlying mechanisms. Observational studies have revealed a link between selenium levels and selenoproteins with prostate cancer progression. However, randomized controlled studies have shown that selenium supplementation does not prevent prostate cancer (HR: 0.95; 95% CI 0.80-1.13). This discrepancy might be attributed to selenoprotein single nucleotide polymorphisms. In the context of combinatorial therapy, selenium has demonstrated promising synergistic potential in the treatment of prostate cancer. Emerging evidence highlights the significant role of selenium and selenoproteins in prostate cancer, encompassing AR signaling, antioxidative properties, cell death, cell cycle regulation, angiogenesis, epigenetic regulation, immunoregulation, epithelial-mesenchymal transformation, and redox signal. In conclusion, selenium's diverse properties make it a promising trace mineral in prostate cancer prevention, development, and treatment and as a platform for exploring novel agents.

Ameliorative effect of selenium nanoparticles on testicular toxicity induced by cisplatin in adult male rats

Cisplatin (Cis) is a treatment for testicular germ-cell tumors (TGCTs). Unfortunately, it causes testicular toxicity due to releasing reactive oxygen species (ROS) causing damage to testicular cells and chromosomes. The current study aimed to investigate the ameliorative effect of selenium nanoparticles (SeNPs) against cisplatin testicular toxicity in male rats by assessment of body weight, testis weight, oxidative stress markers in testis homogenates as (malondialdehyde (MDA), Superoxide dismutase (SOD), Glutathione reduced (GSH), Glutathione peroxidase (GSH ∼ PX) and Catalase (CAT)), gene expression, testosterone concentration (T), sperm characteristics (count, motility and abnormality) and testicular histopathology. Methods: Thirty adult male rats divided equally into four groups; a single dose intraperitoneally injection of cisplatin (10 mg/kg) and selenium nanoparticles (2 mg/kg/day) were administrated alone or in combination. Cis group showed a decrease in body weight, testis weight, antioxidant activities (SOD, GSH, GSH ∼ PX and CAT), T concentration and steroidogenetic expression, the data recorded an increase in MDA levels and sperm abnormality, meanwhile histopathology of testis sections showed degenerative changes in the seminiferous tubules. The co-administration of selenium nanoparticles ameliorated the harmful effects of cisplatin. In conclusion; SeNPs through its antioxidant potential may be useful to prevent the testicular toxicity induced by cisplatin to the rat testis by reducing oxidative stress.

Natural Sources of Selenium as Functional Food Products for Chemoprevention

Cancer is one of the leading causes of death worldwide, the incidence of which is increasing annually. Interest has recently grown in the anti-cancer effect of functional foods rich in selenium (Se). Although clinical studies are inconclusive and anti-cancer mechanisms of Se are not fully understood, daily doses of 100-200 µg of Se may inhibit genetic damage and the development of cancer in humans. The anti-cancer effects of this trace element are associated with high doses of Se supplements. The beneficial anti-cancer properties of Se and the difficulty in meeting the daily requirements for this micronutrient in some populations make it worth considering the use of functional foods enriched in Se. This review evaluated studies on the anti-cancer activity of the most used functional products rich in Se on the European market.

An Assessment of Serum Selenium Concentration in Women with Ovarian Cancer

BACKGROUND

Available studies on the effect of serum selenium levels on the risk of malignancies show some conflicting results. In this study, we investigated the correlation between serum selenium levels and ovarian cancer occurrence.

METHODS

314 women (157 diseased patients and 157 healthy ones) matched in terms of age and BMI were included in the study. The measurements of selenium in the collected blood samples were performed using an ICP mass spectrometer. Univariable and multivariable analyzes were performed to determine the relationship between the factors under the study and the occurrence of ovarian cancer.

RESULTS

The mean concentration of selenium was lower among diseased ones than among controls (53.31 μg/L vs. 78.99 μg/L). A decrease in selenium concentration was noticed with the advancement of ovarian cancer. In univariable and multivariable analyzes, a clear relationship between low selenium concentration and the occurrence of ovarian cancer was found (35.3 (95% CI: 11.2-111; p < 0.001) and 45.8 (95% CI: 12.8-164; p < 0.001)).

CONCLUSION

The studied patients with ovarian cancer are characterized by statistically significant lower serum selenium levels than patients from the control group. Among the study group, a decrease in selenium concentration was observed with an increase in the FIGO stage. The determination of the role of selenium as a prophylactic factor in ovarian cancer requires further prospective studies.

Dysfunctional tRNA reprogramming and codon-biased translation in cancer

Many cancers hijack translation to increase the synthesis of tumor-driving proteins, the messenger mRNAs of which have specific codon usage patterns. Termed 'codon-biased translation' and originally identified in stress response regulation, this mechanism is supported by diverse studies demonstrating how the 50 RNA modifications of the epitranscriptome, specific tRNAs, and codon-biased mRNAs are used by oncogenic programs to promote proliferation and chemoresistance. The epitranscriptome writers METTL1-WDR4, Elongator complex protein (ELP)1-6, CTU1-2, and ALKBH8-TRM112 illustrate the principal mechanism of codon-biased translation, with gene amplifications, increased RNA modifications, and enhanced tRNA stability promoting cancer proliferation. Furthermore, systems-level analyses of 34 tRNA writers and 493 tRNA genes highlight the theme of tRNA epitranscriptome dysregulation in many cancers and identify candidate tRNA writers, tRNA modifications, and tRNA molecules as drivers of pathological codon-biased translation.

Biogenic Selenium Nanoparticles and Their Anticancer Effects Pertaining to Probiotic Bacteria—A Review

Selenium nanoparticles (SeNPs) can be produced by biogenic, physical, and chemical processes. The physical and chemical processes have hazardous effects. However, biogenic synthesis (by microorganisms) is an eco-friendly and economical technique that is non-toxic to human and animal health. The mechanism for biogenic SeNPs from microorganisms is still not well understood. Over the past two decades, extensive research has been conducted on the nutritional and therapeutic applications of biogenic SeNPs. The research revealed that biogenic SeNPs are considered novel competitors in the pharmaceutical and food industries, as they have been shown to be virtually non-toxic when used in medical practice and as dietary supplements and release only trace amounts of Se ions when ingested. Various pathogenic and probiotic/nonpathogenic bacteria are used for the biogenic synthesis of SeNPs. However, in the case of biosynthesis by pathogenic bacteria, extraction and purification techniques are required for further useful applications of these biogenic SeNPs. This review focuses on the applications of SeNPs (derived from probiotic/nonpathogenic organisms) as promising anticancer agents. This review describes that SeNPs derived from probiotic/nonpathogenic organisms are considered safe for human consumption. These biogenic SeNPs reduce oxidative stress in the human body and have also been shown to be effective against breast, prostate, lung, liver, and colon cancers. This review provides helpful information on the safe use of biogenic SeNPs and their economic importance for dietary and therapeutic purposes, especially as anticancer agents.

First Time Identification of Selenoneine in Seabirds and Its Potential Role in Mercury Detoxification

Birds are principally exposed to selenium (Se) through their diet. In long-lived and top predator seabirds, such as the giant petrel, extremely high concentrations of Se are found. Selenium speciation in biota has aroused great interest in recent years; however, there is a lack of information about the chemical form of Se in (sea)birds. The majority of publications focus on the growth performance and antioxidant status in broilers in relation to Se dietary supplementation. The present work combines elemental and molecular mass spectrometry for the characterization of Se species in wild (sea)birds. A set of eight giant petrels (Macronectes sp.) with a broad age range from the Southern Ocean were studied. Selenoneine, a Se-analogue of ergothioneine, was identified for the first time in wild avian species. This novel Se-compound, previously reported in fish, constitutes the major Se species in the water-soluble fraction of all of the internal tissues and blood samples analyzed. The levels of selenoneine found in giant petrels are the highest reported in animal tissues until now, supporting the trophic transfer in the marine food web. The characterization of selenoneine in the brain, representing between 78 and 88% of the total Se, suggests a crucial role in the nervous system. The dramatic decrease of selenoneine (from 68 to 3%) with an increase of Hg concentrations in the liver strongly supports the hypothesis of its key role in Hg detoxification.

Selenium concentration is associated with occurrence and diagnosis of three cardiovascular diseases: A systematic review and meta-analysis

BACKGROUND

Selenium (Se) is a vital trace element playing its biological functions through selenoprotein, which has been implicated in various physiological and pathological processes. A growing number of studies indicate that low Se increases the risk of cardiovascular diseases (CVDs). This meta-analysis aimed to compare and analyze differences in Se levels between patients with heart failure (HF), myocardial infarction (MI), coronary heart disease (CHD), and healthy people. This will provide ideas with the potential to improve clinical intervention and prevention of CVDs.

METHODS

The PubMed, Embase, Chinese National Knowledge Infrastructure (CNKI) and Chinese Biomedical databases were systematically searched for relevant publications until November 20, 2020. The following combination keywords were used: "(heart failure disease OR myocardial infarction OR coronary heart disease) AND (selenium OR Se)". The identified studies were screened against inclusion and exclusion criteria and extracted data were analyzed using RevMan5.3 and State 16.0 software.

RESULTS

A total of 49 eligible studies (including 61 cohorts) were obtained. Results of the meta-analysis showed that there was a significant difference in Se levels between HF, MI, CHD patients and healthy people. The standard mean difference (SMD) level of Se in HF patients [SMD = -0.98, 95 % CI (-1.34, -0.62)], MI patients [MI: SMD = -3.46, 95 % CI (-4.43, -2.85)], and CHD patients [CHD: SMD = -0.47, 95 % CI (-0.64, -0.28)] were all significantly lower compared to healthy controls. Analysis of the correlation between Se level and publication year showed that SMD of Se levels in HF and controls was positively correlated with time. Se level was found to be a good diagnostic marker of MI (AUC = 0.7107, P = 0.0167, Sensitivity = 77.27 %, Specificity = 72.73 %).

CONCLUSIONS

This meta-analysis shows that Se levels in patients with HF, MI, and CHD are generally lower compared with healthy controls. However, due to the small number of included studies, further studies are needed to confirm the present results.

Genetic Variation Interacts with Selenium Exposure Regarding Breast Cancer Risk: Assessing Dietary Intake, Serum Levels and Genetically Elevated Selenium Levels

Selenium has been suggested to be protective regarding breast cancer risk but no overall effect has been established. Genetics may modify the effect. This study compares the effect of selenium exposure on breast cancer risk between women with different alleles in single-nucleotide polymorphisms (SNPs). The Malmö Cancer and Diet Study, a cohort including 17,035 women and >25 years of follow-up on breast cancer diagnosis, was used. Five promising SNPs regarding interaction with selenium exposure were selected from the literature: rs1050450, rs4880, rs3877899, rs7579, and rs71304. Selenium exposure was assessed in three ways: genetically elevated (n = 16,429), dietary intake (n = 15,891) and serum levels (n = 2037) at baseline. Cox regression and logistic regression analyses evaluated breast cancer risk from selenium exposure, stratified for the SNPs and adjusted for risk factors. A total of 1946 women were diagnosed with breast cancer. Women with T/T alleles in rs1050450 had lower breast cancer risk compared with C/C, HR 0.81 (0.68–0.96). Interaction by rs1050450 limited a protective effect of higher selenium intake to T/T carriers, HR 0.68 (0.43–1.08) for intermediate intake and HR 0.63 (0.40–1.00) for high intake. No interactions or risk differences were seen for other SNPs or for serum selenium or genetically elevated selenium. The results indicate that genetic variation in rs1050450 might affect breast cancer risk and that selenium exposure could be a possible modifiable risk factor for breast cancer among women with that variation.

Thioredoxin reductase 3 suppression promotes colitis and carcinogenesis via activating pyroptosis and necrosis

BACKGROUND

Txnrd3 as selenoprotein plays key roles in antioxidant process and sperm maturation. Inflammatory bowel diseases, such as ulcerative colitis and Crohn's disease, are becoming significantly increasing disease worldwide in recent years which are proved relative to diet, especially selenium intake.

METHODS

In the present study, 8-week-old C57BL/6N male Txnrd3-/-, Txnrd3-/ + , Txnrd3 + / + mice, weight 25-30 g, were randomly chosen and each group with 30 mice. Feed 3.5% DSS drinking water and normal water continuously for 7 days. Mouse colon cancer cells (CT26) were cultured in vitro to establish Txnrd3 overexpressed/knocked-down model by cell transfection technology. Morphology and ultrastructure, calcium levels, ROS level, cell death were observed and detected in vivo and vitro.

RESULTS

In Txnrd3-/-mice, ulcerative colitis was more severe, the morphological and ultrastructural lesions were also more prominent compared with wild-type mice, accompanied by the significantly increased expression of NLRP3, Caspase1, RIPK3, and MLKL. Overexpression of Txnrd3 could lead to increased oxidative stress through intracellular calcium outflow-induced oxidative stress increase followed by necrosis and pyroptosis pathway activation and further inhibit the growth and proliferation of colon cancer cells.

CONCLUSION

Txnrd3 overexpression leads to intracellular calcium outflow and increased ROS, which eventually leads to necrosis and focal death of colon cancer cells, while causing Txnrd3-/- mice depth of the crypt deeper, weakened intestinal secretion and immune function and aggravate the occurrence of ulcerative colitis. The present study lays a foundation for the prevention and treatment of ulcerative colitis and colon carcinoma in clinic treatment.

An Assessment of GPX1 (rs1050450), DIO2 (rs225014) and SEPP1 (rs7579) Gene Polymorphisms in Women with Endometrial Cancer

Background: Numerous studies indicate a relationship between the presence of GPX1 (rs1050450), DIO2 (rs225014) and SEPP1 (rs7579) gene polymorphisms and the development of chronic or neoplastic diseases. However, there are no reports on the influence of these polymorphisms on the development of endometrial cancer. Methods: 543 women participated in the study. The study group consisted of 269 patients with diagnosed endometrial cancer. The control group consisted of 274 healthy women. Blood samples were drawn from all the participants. The PCR-RFLP method was used to determine polymorphisms in the DIO2 (rs225014) and GPX1 (rs1050450) genes. The analysis of polymorphisms in the SEPP1 (rs7579) gene was performed by means of TaqMan probes. Results: There was a 1.99-fold higher risk of developing endometrial cancer in CC homozygotes, DIO2 (rs225014) polymorphism (95% Cl 1.14–3.53, p = 0.017), compared to TT homozygotes. There was no correlation between the occurrence of GPX1 (rs1050450) and SEPP1 (rs7579) polymorphisms and endometrial cancer. Conclusion: Carriers of the DIO2 (rs225014) polymorphism may be predisposed to the development of endometrial cancer. Further research confirming this relationship is recommended.

Effects of Selenium as a Dietary Source on Performance, Inflammation, Cell Damage, and Reproduction of Livestock Induced by Heat Stress: A Review

Heat stress as a result of global warming has harmful consequences for livestock and is thus becoming an urgent issue for animal husbandry worldwide. Ruminants, growing pigs, and poultry are very susceptible to heat stress because of their fast growth, rapid metabolism, high production levels, and sensitivity to temperature. Heat stress compromises the efficiency of animal husbandry by affecting performance, gastrointestinal health, reproductive physiology, and causing cell damage. Selenium (Se) is an essential nutritional trace element for livestock production, which acts as a structural component in at least 25 selenoproteins (SELs); it is involved in thyroid hormone synthesis, and plays a key role in the antioxidant defense system. Dietary Se supplementation has been confirmed to support gastrointestinal health, production performance, and reproductive physiology under conditions of heat stress. The underlying mechanisms include the regulation of nutrient digestibility influenced by gastrointestinal microorganisms, antioxidant status, and immunocompetence. Moreover, heat stress damage to the gastrointestinal and mammary barrier is closely related to cell physiological functions, such as the fluidity and stability of cellular membranes, and the inhibition of receptors as well as transmembrane transport protein function. Se also plays an important role in inhibiting cell apoptosis and reducing cell inflammatory response induced by heat stress. This review highlights the progress of research regarding the dietary supplementation of Se in the mitigation of heat stress, addressing its mechanism and explaining the effect of Se on cell damage caused by heat stress, in order to provide a theoretical reference for the use of Se to mitigate heat stress in livestock.

Inherited Disorders of Thyroid Hormone Metabolism Defect Caused by the Dysregulation of Selenoprotein Expression

Consistent activation and functioning of thyroid hormones are essential to the human body as a whole, especially in controlling the metabolic rate of all organs and systems. Impaired sensitivity to thyroid hormones describes any process that interferes with the effectiveness of thyroid hormones. The genetic origin of inherited thyroid hormone defects and the investigation of genetic defects upon the processing of thyroid hormones are of utmost importance. Impaired sensitivity to thyroid hormone can be categorized into three conditions: thyroid hormone cell membrane transport defect (THCMTD), thyroid hormone metabolism defect (THMD), and thyroid hormone action defect (THAD). THMD is caused by defects in the synthesis and processing of deiodinases that convert the prohormone thyroxine (T4) to the active hormone triiodothyronine (T3). Deiodinase, a selenoprotein, requires unique translation machinery that is collectively composed of the selenocysteine (Sec) insertion sequence (SECIS) elements, Sec-insertion sequence-binding protein 2 (SECISBP2), Sec-specific eukaryotic elongation factor (EEFSEC), and Sec-specific tRNA (TRU-TCA1-1), which leads to the recognition of the UGA codon as a Sec codon for translation into the growing polypeptide. In addition, THMD could be expanded to the defects of enzymes that are involved in thyroid hormone conjugation, such as glucuronidation and sulphation. Paucity of inherited disorders in this category leaves them beyond the scope of this review. This review attempts to specifically explore the genomic causes and effects that result in a significant deficiency of T3 hormones due to inadequate function of deiodinases. Moreover, along with SECISBP2, TRU-TCA1-1, and deiodinase type-1 (DIO1) mutations, this review describes the variants in DIO2 single nucleotide polymorphism (SNP) and thyroid stimulating hormone receptor (TSHR) that result in the reduced activity of DIO2 and subsequent abnormal conversion of T3 from T4. Finally, this review provides additional insight into the general functionality of selenium supplementation and T3/T4 combination treatment in patients with hypothyroidism, suggesting the steps that need to be taken in the future.

The Effects of Selenium on Bone Health: From Element to Therapeutics

Osteoporosis, characterized by low bone mass and a disruption of bone microarchitecture, is traditionally treated using drugs or lifestyle modifications. Recently, several preclinical and clinical studies have investigated the effects of selenium on bone health, although the results are controversial. Selenium, an important trace element, is required for selenoprotein synthesis and acts crucially for proper growth and skeletal development. However, the intake of an optimum amount of selenium is critical, as both selenium deficiency and toxicity are hazardous for health. In this review, we have systematically analyzed the existing literature in this field to determine whether dietary or serum selenium concentrations are associated with bone health. In addition, the mode of administration of selenium as a supplement for treating bone disease is important. We have also highlighted the importance of using green-synthesized selenium nanoparticles as therapeutics for bone disease. Novel nanobiotechnology will be a bridgehead for clinical applications of trace elements and natural products.

Trace elements and the thyroid

Trace elements, such as iodine and selenium (Se), are vital to human health and play an essential role in metabolism. They are also important to thyroid metabolism and function, and correlate with thyroid autoimmunity and tumors. Other minerals such as iron (Ir), lithium (Li), copper (Co), zinc (Zn), manganese (Mn), magnesium (Mg), cadmium (Cd), and molybdenum (Mo), may related to thyroid function and disease. Normal thyroid function depends on a variety of trace elements for thyroid hormone synthesis and metabolism. These trace elements interact with each other and are in a dynamic balance. However, this balance may be disturbed by the excess or deficiency of one or more elements, leading to abnormal thyroid function and the promotion of autoimmune thyroid diseases and thyroid tumors.The relationship between trace elements and thyroid disorders is still unclear, and further research is needed to clarify this issue and improve our understanding of how trace elements mediate thyroid function and metabolism. This paper systematically reviewed recently published literature on the relationship between various trace elements and thyroid function to provide a preliminary theoretical basis for future research.

Dark Side of Cancer Therapy: Cancer Treatment-Induced Cardiopulmonary Inflammation, Fibrosis, and Immune Modulation

Advancements in cancer therapy increased the cancer free survival rates and reduced the malignant related deaths. Therapeutic options for patients with thoracic cancers include surgical intervention and the application of chemotherapy with ionizing radiation. Despite these advances, cancer therapy-related cardiopulmonary dysfunction (CTRCPD) is one of the most undesirable side effects of cancer therapy and leads to limitations to cancer treatment. Chemoradiation therapy or immunotherapy promote acute and chronic cardiopulmonary damage by inducing reactive oxygen species, DNA damage, inflammation, fibrosis, deregulation of cellular immunity, cardiopulmonary failure, and non-malignant related deaths among cancer-free patients who received cancer therapy. CTRCPD is a complex entity with multiple factors involved in this pathogenesis. Although the mechanisms of cancer therapy-induced toxicities are multifactorial, damage to the cardiac and pulmonary tissue as well as subsequent fibrosis and organ failure seem to be the underlying events. The available biomarkers and treatment options are not sufficient and efficient to detect cancer therapy-induced early asymptomatic cell fate cardiopulmonary toxicity. Therefore, application of cutting-edge multi-omics technology, such us whole-exome sequencing, DNA methylation, whole-genome sequencing, metabolomics, protein mass spectrometry and single cell transcriptomics, and 10 X spatial genomics, are warranted to identify early and late toxicity, inflammation-induced carcinogenesis response biomarkers, and cancer relapse response biomarkers. In this review, we summarize the current state of knowledge on cancer therapy-induced cardiopulmonary complications and our current understanding of the pathological and molecular consequences of cancer therapy-induced cardiopulmonary fibrosis, inflammation, immune suppression, and tumor recurrence, and possible treatment options for cancer therapy-induced cardiopulmonary toxicity.

Serum Selenium Level and 10-Year Survival after Melanoma

Melanoma is one of the most aggressive human malignancies. The determination of prognostic biomarkers is important for the early detection of recurrence and for the enrollment of the patients into different treatment regimens. Herein, we report the 10-year survival of 375 melanoma patients depending on their serum selenium levels. The study group was followed up from the date of melanoma diagnosis until death or 2020. Patients were assigned to one of four categories, in accordance with the increasing selenium level (I-IV quartiles). The subgroup with low selenium levels had a significant lower survival rate in relation to patients with high selenium levels, HR = 8.42; p = 0.005 and HR = 5.83; p = 0.02, for uni- and multivariable models, respectively. In the univariable analysis, we also confirmed the association between Breslow thickness, Clark classification and age at melanoma prognosis. In conclusion, a low serum selenium level was associated with an increased mortality rate in the 10 years following melanoma diagnosis. Future studies in other geographic regions with low soil selenium levels should be conducted to confirm our findings.

Food Sources of Selenium and Its Relationship with Chronic Diseases

Selenium (Se) is an essential micronutrient for mammals, and its deficiency seriously threatens human health. A series of biofortification strategies have been developed to produce Se-enriched foods for combating Se deficiency. Although there have been some inconsistent results, extensive evidence has suggested that Se supplementation is beneficial for preventing and treating several chronic diseases. Understanding the association between Se and chronic diseases is essential for guiding clinical practice, developing effective public health policies, and ultimately counteracting health issues associated with Se deficiency. The current review will discuss the food sources of Se, biofortification strategies, metabolism and biological activities, clinical disorders and dietary reference intakes, as well as the relationship between Se and health outcomes, especially cardiovascular disease, diabetes, chronic inflammation, cancer, and fertility. Additionally, some concepts were proposed, there is a non-linear U-shaped dose-responsive relationship between Se status and health effects: subjects with a low baseline Se status can benefit from Se supplementation, while Se supplementation in populations with an adequate or high status may potentially increase the risk of some diseases. In addition, at supra-nutritional levels, methylated Se compounds exerted more promising cancer chemo-preventive efficacy in preclinical trials.

Gene expression evaluation of antioxidant enzymes in patients with hepatocellular carcinoma: RT-qPCR and bioinformatic analyses

Any condition leading to chronic liver disease is a potential oncogenic agent for hepatocellular carcinoma (HCC). Alterations in the expression of antioxidant enzymes could alter the redox balance. Our aim was to evaluate the expression of the genes GPX1, GPX4, SEP15, SELENOP, SOD1, SOD2, GSR, CAT, and NFE2L2 in patients with HCC. Differential gene expression analysis was performed using RNA-Seq data from the TCGA and GTEx databases, and RT-qPCR data from HCC patient samples. Bioinformatic analysis revealed significant differential expression in most genes. GPX4 expression was significantly increased (p=0.02), while SOD2 expression was significantly decreased (p=0.04) in experimental data. In TCGA samples, alpha-fetoprotein levels (mg/dL) were negatively correlated with the expression of SEP15 (p<0.001), SELENOP (p<0.001), SOD1 (p<0.001), SOD2 (p<0.001), CAT (p<0.001), and NFE2L2 (p=0.004). Alpha-fetoprotein levels were positively correlated with the expression of GPX4 (p=0.02) and SELENOP (p=0.01) in the experimental data. Low expression of GPX1 (p=0.006), GPX4 (p=0.01), SELENOP (p=0.006), SOD1 (p=0.007), CAT (p<0.001), and NFE2L2 (p<0.001), and higher levels of GSR, were associated with low overall survival at 12 months. These results suggest a significant role for these antioxidant enzymes in HCC pathogenesis and severity.

Serum Selenium Level Predicts 10-Year Survival after Breast Cancer

In a recent prospective study, we reported an association between a low serum selenium level and five-year survival among breast cancer patients. We now have updated the cohort to include 10-year survival rates. A blood sample was obtained from 538 women diagnosed with first primary invasive breast cancer between 2008 and 2015 in the region of Szczecin, Poland. Blood was collected before initiation of treatment. Serum selenium levels were quantified by mass spectroscopy. Each patient was assigned to one of four quartiles based on the distribution of serum selenium levels in the whole cohort. Patients were followed from diagnosis until death or last known alive (mean follow-up 7.9 years). The 10-year actuarial cumulative survival was 65.1% for women in the lowest quartile of serum selenium, compared to 86.7% for women in the highest quartile (p < 0.001 for difference). Further studies are needed to confirm the protective effect of selenium on breast cancer survival. If confirmed this may lead to an investigation of selenium supplementation on survival of breast cancer patients.

Selenium at the eural arriers: eview

Selenium (Se) is known to contribute to several vital physiological functions in mammals: antioxidant defense, fertility, thyroid hormone metabolism, and immune response. Growing evidence indicates the crucial role of Se and Se-containing selenoproteins in the brain and brain function. As for the other essential trace elements, dietary Se needs to reach effective concentrations in the central nervous system (CNS) to exert its functions. To do so, Se-species have to cross the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCB) of the choroid plexus. The main interface between the general circulation of the body and the CNS is the BBB. Endothelial cells of brain capillaries forming the so-called tight junctions are the primary anatomic units of the BBB, mainly responsible for barrier function. The current review focuses on Se transport to the brain, primarily including selenoprotein P/low-density lipoprotein receptor-related protein 8 (LRP8, also known as apolipoprotein E receptor-2) dependent pathway, and supplementary transport routes of Se into the brain via low molecular weight Se-species. Additionally, the potential role of Se and selenoproteins in the BBB, BCB, and neurovascular unit (NVU) is discussed. Finally, the perspectives regarding investigating the role of Se and selenoproteins in the gut-brain axis are outlined.

The importance of selenium and zinc deficiency in cardiovascular disorders

Cardiovascular diseases often linked with lifestyle are among the main causes of death, especially in the elderly population. The role of trace elements in health and disease has been emphasized in multiple scientific research. Moreover, supplementation of trace elements to improve health is becoming increasingly popular. The following paper presents current views on the relationship between the concentration of trace elements such as selenium and zinc in the body, as well as morphology and function of the cardiovascular system. Research discussing the effect of selenium and zinc supplementation on the function of the heart and blood vessels was also reviewed. The relationship between selenium and zinc concentration and morphology and function of the cardiovascular system is equally unclear, and therefore there is currently no scientific evidence for its supplementation for preventing cardiovascular diseases. It seems justified to continue scientific research on this subject due to the small number of experimental studies available on the topic of selenium and zinc deficiency and their impact on the cardiovascular system.

Effects of Fish Oil and Dietary Antioxidant Supplementation on Bone Health of Growing Lambs

Simple Summary

The current study investigated the bone status of growing lambs fed diets supplemented with bioactive components (fish oil, carnosic acid, SeY, and Na₂SeO₃) improving bone parameters. The study provides new information with regards to the positive role of bioactive components supplemented to diets for growing lambs on their femur characteristics (bone content, bone mineral density, geometry, and strength).

Abstract

The aim of the present study was to assess the effects of partial replacement of rapeseed oil (RO) with fish oil (FO) combined with dietary supplementation of various antioxidants on the characteristics of lamb femur. Thirty male lambs were assigned to five dietary treatments and fed isoproteinous and isoenergetic diets for 35 days. The control diet was enriched with 3.0% RO, while the experimental diets were enriched either only with 2.0% RO and 1.0% FO or additionally with 0.1% carnosic acid, 0.1% carnosic acid and 0.35 ppm Se as selenized yeast, or 0.1% carnosic acid and 0.35 ppm Se as sodium selenite. After 35 days, the lambs were slaughtered, and the femur was dissected from the carcass of each animal and analyzed for morphometric, geometric, densitometric, and biomechanical properties. The dietary modifications, specifically the supplementation of FO and selenized yeast, significantly improved the geometric, densitometric, and biomechanical properties of lamb femur.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The changes of serum zinc, copper, and selenium levels in epileptic patients: a systematic review and meta-analysis

INTRODUCTION

It is widely accepted that trace elements have been implicated in various metabolic processes. Valproic acid (VPA) is a remarkably safe and effective antiepileptic drug. There is no consensus option regarding the fluctuations in serum zinc (Zn), copper (Cu), and selenium (Se) in epileptic patients treated with VPA. We applied a meta-analysis to systematically assess the effects of VPA on serum ions in these patients.

AREAS COVERED

In this study, we performed a meta-analysis of the changes in serum Zn, Cu, and Se levels in human samples of healthy controls, epileptic patients, and patients treated with VPA. Twenty-two published analyzable studies were selected by searching the databases of PubMed, China National Knowledge Infrastructure (CNKI), Google Scholar, Web of Science, EMBASE, WAN FANG and Vip.

EXPERT OPINION

Serum Se levels in epileptic patients were decreased compared to healthy controls. Serum Zn levels in patients with VPA treatment were significantly lower than those in epileptic patients. The results of this meta-analysis are instructive for the intake of trace elements such as Zn, Cu, and Se in the diet balance of patients with epilepsy treated with VPA. Meanwhile, this study provides a theoretical basis for the combined use of other drugs that affect the intake and absorption of trace elements and VPA.

The role of selenium metabolism and selenoproteins in cartilage homeostasis and arthropathies

As an essential nutrient and trace element, selenium is required for living organisms and its beneficial roles in human health have been well recognized. The role of selenium is mainly played through selenoproteins synthesized by the selenium metabolic system. Selenoproteins have a wide range of cellular functions including regulation of selenium transport, thyroid hormones, immunity, and redox homeostasis. Selenium deficiency contributes to various diseases, such as cardiovascular disease, cancer, liver disease, and arthropathy—Kashin–Beck disease (KBD) and osteoarthritis (OA). A skeletal developmental disorder, KBD has been reported in low-selenium areas of China, North Korea, and the Siberian region of Russia, and can be alleviated by selenium supplementation. OA, the most common form of arthritis, is a degenerative disease caused by an imbalance in matrix metabolism and is characterized by cartilage destruction. Oxidative stress serves as a major cause of the initiation of OA pathogenesis. Selenium deficiency and dysregulation of selenoproteins are associated with impairments to redox homeostasis in cartilage. We review the recently explored roles of selenium metabolism and selenoproteins in cartilage with an emphasis on two arthropathies, KBD and OA. Moreover, we discuss the potential of therapeutic strategies targeting the biological functions of selenium and selenoproteins for OA treatment.

Selenium, a micronutrient found in brazil nuts, shiitake mushrooms, and most meats, may aid in treating joint diseases, including the most common form of arthritis, osteoarthritis (OA). In addition to thyroid hormone metabolism and immunity, selenium is important in antioxidant defense. Oxidative damage can destroy cartilage and harm joints, and selenium deficiency is implicated in several joint diseases. Jin-Hong Kim at Seoul National University in South Korea and co-workers reviewed selenium metabolism, focusing on OA and and Kashin–Beck disease, a skeletal development disorder prevalent in selenium-deficient areas of northeast Asia. They report that selenium-containing proteins protect cells against oxidative damage and that selenium is crucial to cartilage production. Further investigation of selenium metabolism may point the way to new treatments for OA and other joint diseases.

The Interaction between Dietary Selenium Intake and Genetics in Determining Cancer Risk and Outcome

There is considerable interest in the trace element selenium as a possible cancer chemopreventive dietary component, but supplementation trials have not indicated a clear benefit. Selenium is a critical component of selenium-containing proteins, or selenoproteins. Members of this protein family contain selenium in the form of selenocysteine. Selenocysteine is encoded by an in-frame UGA codon recognized as a selenocysteine codon by a regulatory element, the selenocysteine insertion sequence (SECIS), in the 3′-untranslated region of selenoprotein mRNAs. Epidemiological studies have implicated several selenoprotein genes in cancer risk or outcome based on associations between allelic variations and disease risk or mortality. These polymorphisms can be found in or near the SECIS or in the selenoprotein coding sequence. These variations both function to control protein synthesis and impact the efficiency of protein synthesis in response to the levels of available selenium. Thus, an individual’s genetic makeup and nutritional intake of selenium may interact to predispose them to acquiring cancer or affect cancer progression to lethality.

Prediagnostic serum selenium levels in relation to breast cancer survival and tumor characteristics

Women with lower levels of serum selenium (Se) may have a worse survival in breast cancer than women with higher levels, despite no difference in incidence of the disease. Our study was conducted to test whether Se is associated with the aggressiveness of breast tumors. Both the risk of having a tumor characteristic associated with worse prognosis, as well as the overall and breast cancer-specific mortality, were studied. We identified breast cancer cases and controls within the Malmö Diet and Cancer Study, a population-based cohort with 17 035 women recruited between 1991 and 1996. Inclusion criteria were incident breast cancer. Exclusion criteria were carcinoma in situ and bilateral breast cancer. Controls were selected among breast cancer-free women both from matching (n = 694) as well as randomization (n = 492). After exclusion, 1066 cases remained and were compared to controls regarding their prediagnostic serum Se levels and subsequent risk of having a certain tumor characteristic or intrinsic subtype. We also followed breast cancer patients regarding overall and breast cancer-specific mortality, comparing different Se quartiles. No association between serum Se quartile and any tumor characteristic or intrinsic subtype was found. Lower overall mortality was found among women in the highest Se quartile compared to the lowest using an adjusted Cox proportional hazards model, hazard ratio 0.63 (95% confidence interval: 0.44-0.89). Similar results were seen for breast cancer-specific mortality, 0.60 (0.37-0.98). The results of our study support that Se is associated with a lower mortality in breast cancer, not related to established prognostic factors.

Low selenium levels are associated with decreased bone mineral densities

PURPOSE

Osteoporosis has a high worldwide prevalence and detrimental consequences (e.g., increased fracture risk). The amount of bone mineral in bone tissue (i.e., bone mineral density [BMD]) is most widely used indicator of osteoporosis in clinical medicine. Selenium is an essential micronutrient for animals and humans. It is a cofactor for antioxidant enzyme reduction (e.g., glutathione peroxidase). It also enhances immune surveillance and modulates cell proliferation. Study findings on the associations between BMD and selenium levels are inadequate and contradictory. The purpose of this study was to examine the associations between hair selenium levels and lumbar spine and femur BMD values.

METHODS

Using a cross-sectional study design, we assessed the associations between hair selenium levels and BMD values in 1,167 Korean adults who underwent a health check-up. Each subject was assigned to one of two groups based on BMD (normal group [T-score ≥ -1.0] or low BMD group [T-score < -1.0]). The associations between hair selenium levels and the risk for low BMD were estimated using multivariate logistic regression models.

RESULTS

Study participants with lower hair selenium levels were older and had higher phosphorous, alkaline phosphatase, and osteocalcin levels. They also had lower BMDs, corrected serum calcium levels, uric acid levels, and creatinine clearance. Participants with low BMDs had significantly lower hair selenium levels (P < 0.001). After adjusting for osteoporosis-related risk factors, the risk of a low BMD was significantly greater for the lower hair selenium quartile groups (P = 0.045).

CONCLUSION

In conclusion, this study found that lower hair selenium levels were associated with low BMD values, independent of the other osteoporosis risk factors examined. Further prospective studies are warranted to determine the role of selenium in the development of osteoporosis.

Cul5-type Ubiquitin Ligase KLHDC1 Contributes to the Elimination of Truncated SELENOS Produced by Failed UGA/Sec Decoding

The UGA codon signals protein translation termination, but it can also be translated into selenocysteine (Sec, U) to produce selenocysteine-containing proteins (selenoproteins) by dedicated machinery. As Sec incorporation can fail, Sec-containing longer and Sec-lacking shorter proteins co-exist. Cul2-type ubiquitin ligases were recently shown to destabilize such truncated proteins; however, which ubiquitin ligase targets truncated proteins for degradation remained unclear. We report that the Cul5-type ubiquitin ligase KLHDC1 targets truncated SELENOS, a selenoprotein, for proteasomal degradation. SELENOS is involved in endoplasmic reticulum (ER)-associated degradation, which is linked to reactive oxygen species (ROS) production, and the knockdown of KLHDC1 in U2OS cells decreased ER stress-induced cell death. Knockdown of SELENOS increased the cell population with lower ROS levels. Our findings reveal that, in addition to Cul2-type ubiquitin ligases, KLHDC1 is involved in the elimination of truncated oxidoreductase-inactive SELENOS, which would be crucial for maintaining ROS levels and preventing cancer development.

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KLHDC1 is a Cul5-type ubiquitin ligase

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KLHDC1 targets immature SELENOS for proteasomal degradation

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KLHDC1 knockdown in U2OS cells decreases ER stress-induced cell death

Selenium and selenoproteins: it's role in regulation of inflammation

Abstract

Selenium is an essential immunonutrient which holds the human’s metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body are selenocysteine and selenoproteins. These forms have a unique way of synthesis and translational coding. Selenoproteins act as antioxidant warriors for thyroid regulation, male-fertility enhancement, and anti-inflammatory actions. They also participate indirectly in the mechanism of wound healing as oxidative stress reducers. Glutathione peroxidase (GPX) is the major selenoprotein present in the human body, which assists in the control of excessive production of free radical at the site of inflammation. Other than GPX, other selenoproteins include selenoprotein-S that regulates the inflammatory cytokines and selenoprotein-P that serves as an inducer of homeostasis. Previously, reports were mainly focused on the cellular and molecular mechanism of wound healing with reference to various animal models and cell lines. In this review, the role of selenium and its possible routes in translational decoding of selenocysteine, synthesis of selenoproteins, systemic action of selenoproteins and their indirect assimilation in the process of wound healing are explained in detail. Some of the selenium containing compounds which can acts as cancer preventive and therapeutics are also discussed. These compounds directly or indirectly exhibit antioxidant properties which can sustain the intracellular redox status and these activities protect the healthy cells from reactive oxygen species induced oxidative damage. Although the review covers the importance of selenium/selenoproteins in wound healing process, still some unresolved mystery persists which may be resolved in near future.

Graphic abstract

Selenium Anticancer Properties and Impact on Cellular Redox Status

(1) Background: In this review, we provide information published in recent years on the chemical forms, main biological functions and especially on antioxidant and prooxidant activities of selenium. The main focus is put on the impact of selenoproteins on maintaining cellular redox balance and anticancerogenic function. Moreover, we summarize data on chemotherapeutic application of redox active selenium compounds. (2) Methods: In the first section, main aspects of metabolism and redox activity of selenium compounds is reviewed. The second outlines multiple biological functions, asserted when selenium is incorporated into the structure of selenoproteins. The final section focuses on anticancer activity of selenium and chemotherapeutic application of redox active selenium compounds as well. (3) Results: optimal dietary level of selenium ensures its proper antioxidant and anticancer activity. We pay special attention to antioxidant activities of selenium compounds, especially selenoproteins, and their importance in antioxidant defence. It is worth noting, that data on selenium anticancer properties is still contraversive. Moreover, selenium compounds as chemotherapeutic agents usually are used at supranutritional doses. (4) Conclusions: Selenium play a vital role for many organism systems due to its incorporation into selenoproteins structure. Selenium possesses antioxidant activity at optimal doses, while at supranutritional doses, it displays prooxidant activity. Redox active selenium compounds can be used for cancer treatment; recently special attention is put to selenium containing nanoparticles.

Chemoprevention of Colorectal Cancer

Although colorectal cancer (CRC) screening has reduced the incidence of and mortality from CRC, chemoprevention strategies have the potential to further reduce CRC incidence and mortality. Chemoprevention agents might be used for average-risk as well as high-risk groups, and to prevent CRC recurrence after therapy. CRC chemoprevention agents that have been studied include aspirin, nonaspirin nonsteroidal anti-inflammatory drugs, statins, agents that target metabolic pathways, and vitamins and minerals. We review the prospect of chemoprevention of CRC, results from preclinical and human studies, challenges, and future directions.

Structural analysis of human SEPHS2 protein, a selenocysteine machinery component, over-expressed in triple negative breast cancer

Selenophosphate synthetase 2 (SEPHS2) synthesizes selenide and ATP into selenophosphate, the selenium donor for selenocysteine (Sec), which is cotranslationally incorporated into selenoproteins. The action and regulatory mechanisms of SEPHS2 as well as its role in carcinogenesis (especially breast cancer) remain ambiguous and need further clarification. Therefore, lacking an experimentally determined structure for SEPHS2, we first analyzed the physicochemical properties of its sequence, modeled its three-dimensional structure and studied its conformational behavior to identify the key residues (named HUB nodes) responsible for protein stability and to clarify the molecular mechanisms by which it induced its function. Bioinformatics analysis evidenced higher amplification frequencies of SEPHS2 in breast cancer than in other cancer types. Therefore, because triple negative breast cancer (TNBC) is biologically the most aggressive breast cancer subtype and its treatment represents a challenge due to the absence of well-defined molecular targets, we evaluated SEPHS2 expression in two TNBC cell lines and patient samples. We demonstrated mRNA and protein overexpression to be correlated with aggressiveness and malignant tumor grade, suggesting that this protein could potentially be considered a prognostic marker and/or therapeutic target for TNBC.

Association of the selenoprotein 15-kDa (SEP15) polymorphisms with cancer risk: a meta-analysis

Selenoproteins are involved in antioxidant defense, the redox signaling pathway and cell homeostasis. Primary studies have shown that single-nucleotide polymorphisms in the selenoprotein gene (SEP15) are associated with cancer risk. However, conflicting outcomes warrant a meta-analysis to obtain more precise estimates. Literature search yielded 18 case-control studies from 12 articles. We calculated pooled odds ratios (OR) and 95% confidence intervals (CI) of two SEP15 polymorphisms (rs5845 and rs5859) using standard genetic models (homozygous, recessive, dominant and codominant). Subgroup analysis was based on statistical power (80% cutoff) and cancer type (breast/respiratory/genitourinary/colorectal). Heterogeneity of the outcomes necessitated examining their sources (outlier treatment). Multiple comparison outcomes were corrected with the False Discovery Rate (P^aF). Our core findings lay in the post-outlier recessive subgroup outcomes, where risks in the powered study (≥ 80%) was increased (OR 1.26, 95% CI 1.02-1.57, P^aF = 0.047) while that in genitourinary cancer was protective (OR 0.29, 95% CI 0.20-0.43, P^aF < 10^-4). The potency of outlier treatment in unmasking significant associations and generating homogeneity provides good evidence of SEP15's role in cancer. In the clinical sense, selenium chemo-intervention may be of benefit among persons with particular SEP15 genotypes.AbbreviationsAnumber of unduplicated articles that contributed to instabilityAManalysis modelBnumber of robust comparisonsBCbreast cancerBLCbladder cancercDNAcomplementary deoxyribonucleic acidCIconfidence intervalCIDconfidence interval differenceCRCcolorectal cancerDdecreased riskEHeliminated heterogeneityFfixed-effectsFDRFalse Discovery RateGUCgenitourinary cancersGSgained significanceHBhospital-basedHWEHardy-Weinberg EquilibriumIincreased riskI²measure of heterogeneitykDakiloDaltonLAClaryngeal cancerLUClung cancermafminor allele frequencynnumber of studiesNnumber of comparisonsNMnot mentionedNOSNewcastle-Ottawa ScaleORodds ratioP^aP value for associationP^aδP value for association (pre-FDR)P^aFP value for association FDR-correctedP^bP value for heterogeneityPBpopulation-basedPCprostate cancerPRISMAPreferred Reporting Items for Systematic Reviews and Meta-AnalysesPROpre-outlierPSOpost-outlierRrandom-effects[R]referenceRCrespiratory cancersRNSretained non-significanceROSreactive oxygen speciesSEPselenoproteinsSEP15selenoprotein geneSNPsingle nucleotide polymorphismSWShapiro-Wilk testUSAUnited States of Americavvvariantwvheterozygouswwwild-type.

From Selenium Absorption to Selenoprotein Degradation

Selenium is an essential dietary micronutrient. Ingested selenium is absorbed by the intestines and transported to the liver where it is mostly metabolized to selenocysteine (Sec). Sec is then incorporated into selenoproteins, including selenoprotein P (SELENOP), which is secreted into plasma and serves as a source of selenium to other tissues of the body. Herein, we provide an overview of the biology of selenium from its absorption and distribution to selenoprotein uptake and degradation, with a particular focus on the latter. Molecular mechanisms of selenoprotein degradation include the lysosome-mediated pathway for SELENOP and endoplasmic reticulum-mediated degradation of selenoproteins via ubiquitin-activated proteasomal pathways. Ubiquitin-activated pathways targeting full-length selenoproteins include the peroxisome proliferator-activated receptor gamma-dependent pathway and substrate-dependent ubiquitination. An alternate mechanism is utilized for truncated selenoproteins, in which cullin-RING E3 ubiquitin ligase 2 targets the defective proteins for ubiquitin-proteasomal degradation. Selenoproteins, particularly SELENOP, may have their Sec residues reutilized for new selenoprotein synthesis via Sec decomposition. This review will explore these aspects in selenium biology, providing insights to knowledge gaps that remain to be uncovered.

Selenium and thyroid cancer: a systematic review

The aim of the study was to investigate the association between blood and tissue levels of selenium and thyroid cancer through a systematic review. We searched for observational studies written in English, Spanish, and Portuguese indexed in PubMed, LILACS, and Scielo without date restriction, that evaluated the association between selenium levels in whole-blood, serum, or plasma and/or thyroid tissue and thyroid cancer, both in individuals with cancer of thyroid as in healthy individuals. Then data were extracted and analyzed. Of the 570 articles identified, five cross-sectional studies were included in the review. In one study, lower concentrations of selenium were found in whole-blood (0.543 μg/ml) and in the thyroid (0.88 μg/g) of thyroid cancer patients compared to controls. Another study showed a decrease in serum selenium concentrations in patients with follicular carcinoma and papillary types (0.077 ± 0.021 μg/ml and 0.080 ± 0.020 μg/ml, respectively). On the other hand, other studies showed no difference in plasma selenium content or glutathione peroxidase activity among patients and healthy volunteers. The available evidence on this issue is inconclusive. Additional studies are needed to elucidate the association between serum and/or tissue levels of selenium and the development of thyroid cancer.

Redox-Active Selenium in Health and Disease: A Conceptual Review

Although it is generally accepted that selenium (Se) is important for life, it is not well known which forms of organic and/or inorganic Se compound are the most biologically active. In nature Se exists mostly in two forms, namely as selenite with fourvalent and selenate with sixvalent cations, from which all other inorganic and organic species are derived. Despite a small difference in their electronic structure, these two inorganic parent compounds differ significantly in their redox properties. Hence, only selenite can act as an oxidant, particularly in the reaction with free and/or protein- bound sulhydryl (SH) groups. For example, selenite was shown to inhibit the hydroxyl radicalinduced reduction and scrambled reoxidation of disulfides in human fibrinogen thus preventing the formation of highly hydrophobic polymer, termed parafibrin. Such a polymer, when deposited within peripheral and/or cerebral circulation, may cause irreversible damage resulting in the development of cardiovascular, neurological and other degenerative diseases. In addition, parafibrin deposited around tumor cells produces a protease-resistant coat protecting them against immune recognition and elimination. On the other hand, parafibrin generated by Ebola's protein disulfide isomerase can form a hydrophobic 'spike' that facilitates virus attachment and entry to the host cell. In view of these specific properties of selenite this compound is a potential candidate as an inexpensive and readily available food supplement in the prevention and/or treatment of cardiovascular, neoplastic, neurological and infectious diseases.

Metabolomics signature associated with circulating serum selenoprotein P levels

PURPOSE

Selenoprotein P (SELENOP) has been previously related to various metabolic traits with partially conflicting results. The identification of SELENOP-associated metabolites, using an untargeted metabolomics approach, may provide novel biological insights relevant to disentangle the role of SELENOP in human health.

METHODS

In this cross-sectional study, 572 serum metabolites were identified by comparing the obtained LC-MS/MS spectra with spectra stored in Metabolon's spectra library. Serum SELENOP levels were measured in 832 men and women using an ELISA kit.

RESULTS

Circulating SELENOP levels were associated with 24 out of 572 metabolites after accounting for the number of independent dimensions in the metabolomics data, including inverse associations with alanine, glutamate, leucine, isoleucine and valine, an unknown compound X-12063, urate and the peptides gamma-glutamyl-leucine, and N-acetylcarnosine. Positive associations were observed between SELENOP and several lipid compounds. Of the identified metabolites, each standard deviation increase in the branched-chain amino acids (isoleucine, leucine, valine), alanine and gamma-glutamyl-leucine was related to higher odds of having T2DM [OR (95% CI): 1.96 (1.41-2.73); 1.62 (1.15-2.28); 1.94 (1.45-2.60), 1.57 (1.17-2.11), and 1.52 (1.13-2.05), respectively].

CONCLUSIONS

Higher serum SELENOP levels were associated with an overall healthy metabolomics profile, which may provide further insights into potential mechanisms of SELENOP-associated metabolic disorders.

Interaction of NKX3.1 and SELENOP genotype with prostate cancer recurrence

BACKGROUND

NKX3.1 is a tumor suppressor frequently lost in prostate cancer. Previous studies by others indicated that the risks associated with reduced NKX3.1 levels can be enhanced by anti-oxidant supplementation. Selenium is an essential component of several proteins with anti-oxidant functions and lower levels of selenium have been associated with greater risk of prostate cancer. In contrast, participants of the select prostate cancer prevention trial were at increased risk of prostate cancer when supplemented with selenium when their baseline selenium levels were high.

METHODS

In order to investigate whether there was an interaction between a functional polymorphism in NKX3.1 that results in less protein and selenium status with prostate cancer grade or outcome, plasma selenium levels and the genotypes of NKX3.1 and the selenium carrier protein SELENOP were determined from a cohort of men who underwent radical protatectomy.

RESULTS

NKX3.1 and SELENOP genotypes were associated with a more aggressive prostate tumor grade at the time of prostatectomy, but there were no significant interactions of NKX3.1 genotype with either selenium status or SELENOP genotype. There was also a significant association between NKX3.1 genotype and prostate cancer recurrence, however this association was modified by SELENOP genotype, but not with plasma selenium levels.

CONCLUSIONS

These data indicate that the impact of selenium status on prostate cancer may be influenced by factors other than the amount of selenium in circulation.