Expression of the selenoprotein S (SELS) gene in subcutaneous adipose tissue and SELS genotype are associated with metabolic risk factors

Endoplasmic reticulum-resident selenoproteins and their roles in glucose and lipid metabolic disorders

Glucose and lipid metabolic disorders (GLMDs), such as diabetes, dyslipidemia, metabolic syndrome, nonalcoholic fatty liver disease, and obesity, are significant public health issues that negatively impact human health. The endoplasmic reticulum (ER) plays a crucial role at the cellular level for lipid and sterol biosynthesis, intracellular calcium storage, and protein post-translational modifications. Imbalance and dysfunction of the ER can affect glucose and lipid metabolism. As an essential trace element, selenium contributes to various human physiological functions mainly through 25 types of selenoproteins (SELENOs). At least 10 SELENOs, with experimental and/or computational evidence, are predominantly found on the ER membrane or within its lumen. Two iodothyronine deiodinases (DIOs), DIO1 and DIO2, regulate the thyroid hormone deiodination in the thyroid and some external thyroid tissues, influencing glucose and lipid metabolism. Most of the other eight members maintain redox homeostasis in the ER. Especially, SELENOF, SELENOM, and SELENOS are involved in unfolded protein responses; SELENOI catalyzes phosphatidylethanolamine synthesis; SELENOK, SELENON, and SELENOT participate in calcium homeostasis regulation; and the biological significance of thioredoxin reductase 3 in the ER remains unexplored despite its established function in the thioredoxin system. This review examines recent research advances regarding ER SELENOs in GLMDs and aims to provide insights on ER-related pathology through SELENOs regulation.

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

Current views on selenoprotein S in the pathophysiological processes of diabetes-induced atherosclerosis: potential therapeutics and underlying biomarkers

Atherosclerotic cardiovascular disease (ASCVD) consistently ranks as the primary mortality factor among diabetic people. A thorough comprehension of the pathophysiological routes and processes activated by atherosclerosis (AS) caused by diabetes mellitus (DM), together with the recognition of new contributing factors, could lead to the discovery of crucial biomarkers and the development of innovative drugs against atherosclerosis. Selenoprotein S (SELENOS) has been implicated in the pathology and progression of numerous conditions, including diabetes, dyslipidemia, obesity, and insulin resistance (IR)-all recognized contributors to endothelial dysfunction (ED), a precursor event to diabetes-induced AS. Hepatic-specific deletion of SELENOS accelerated the onset and progression of obesity, impaired glucose tolerance and insulin sensitivity, and increased hepatic triglycerides (TG) and diacylglycerol (DAG) accumulation; SELENOS expression in subcutaneous and omental adipose tissue was elevated in obese human subjects, and act as a positive regulator for adipogenesis in 3T3-L1 preadipocytes; knockdown of SELENOS in Min6 β-cells induced β-cell apoptosis and reduced cell proliferation. SELENOS also participates in the early stages of AS, notably by enhancing endothelial function, curbing the expression of adhesion molecules, and lessening leukocyte recruitment-actions that collectively reduce the formation of foam cells. Furthermore, SELENOS forestalls the apoptosis of vascular smooth muscle cells (VSMCs) and macrophages, mitigates vascular calcification, and alleviates inflammation in macrophages and CD4+ T cells. These actions help stifle the creation of unstable plaque characterized by thinner fibrous caps, larger necrotic cores, heightened inflammation, and more extensive vascular calcification-features seen in advanced atherosclerotic lesion development. Additionally, serum SELENOS could function as a potential biomarker, and SELENOS single nucleotide polymorphisms (SNPs) rs4965814, rs28628459, and rs9806366, might be effective gene markers for atherosclerosis-related diseases in diabetes. This review accentuates the pathophysiological processes of atherosclerosis in diabetes and amasses current evidence on SELENOS's potential therapeutic benefits or as predictive biomarkers in the various stages of diabetes-induced atherosclerosis.

"Alphabet" Selenoproteins: Implications in Pathology

Selenoproteins are a group of proteins containing selenium in the form of selenocysteine (Sec, U) as the 21st amino acid coded in the genetic code. Their synthesis depends on dietary selenium uptake and a common set of cofactors. Selenoproteins accomplish diverse roles in the body and cell processes by acting, for example, as antioxidants, modulators of the immune function, and detoxification agents for heavy metals, other xenobiotics, and key compounds in thyroid hormone metabolism. Although the functions of all this protein family are still unknown, several disorders in their structure, activity, or expression have been described by researchers. They concluded that selenium or cofactors deficiency, on the one hand, or the polymorphism in selenoproteins genes and synthesis, on the other hand, are involved in a large variety of pathological conditions, including type 2 diabetes, cardiovascular, muscular, oncological, hepatic, endocrine, immuno-inflammatory, and neurodegenerative diseases. This review focuses on the specific roles of selenoproteins named after letters of the alphabet in medicine, which are less known than the rest, regarding their implications in the pathological processes of several prevalent diseases and disease prevention.

Serum amyloid A and metabolic disease: evidence for a critical role in chronic inflammatory conditions

Serum amyloid A (SAA) subtypes 1-3 are well-described acute phase reactants that are elevated in acute inflammatory conditions such as infection, tissue injury, and trauma, while SAA4 is constitutively expressed. SAA subtypes also have been implicated as playing roles in chronic metabolic diseases including obesity, diabetes, and cardiovascular disease, and possibly in autoimmune diseases such as systemic lupus erythematosis, rheumatoid arthritis, and inflammatory bowel disease. Distinctions between the expression kinetics of SAA in acute inflammatory responses and chronic disease states suggest the potential for differentiating SAA functions. Although circulating SAA levels can rise up to 1,000-fold during an acute inflammatory event, elevations are more modest (∼5-fold) in chronic metabolic conditions. The majority of acute-phase SAA derives from the liver, while in chronic inflammatory conditions SAA also derives from adipose tissue, the intestine, and elsewhere. In this review, roles for SAA subtypes in chronic metabolic disease states are contrasted to current knowledge about acute phase SAA. Investigations show distinct differences between SAA expression and function in human and animal models of metabolic disease, as well as sexual dimorphism of SAA subtype responses.

Selenoprotein S Interacts with the Replication and Transcription Complex of SARS-CoV-2 by Binding nsp7

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) replicates and evades detection using ER membranes and their associated protein machinery. Among these hijacked human proteins is selenoprotein S (selenos). This selenoprotein takes part in the protein quality control, signaling, and the regulation of cytokine secretion. While the role of selenos in the viral life cycle is not yet known, it has been reported to interact with SARS-CoV-2 nonstructural protein 7 (nsp7), a viral protein essential for the replication of the virus. We set to study whether selenos and nsp7 interact directly and if they can still bind when nsp7 is bound to the replication and transcription complex of the virus. Using biochemical assays, we show that selenos binds directly to nsp7. In addition, we found that selenos can bind to nsp7 when it is in a complex with the coronavirus's minimal replication and transcription complex, comprised of nsp7, nsp8, and the RNA-dependent RNA polymerase nsp12. In addition, through crosslinking experiments, we mapped the interaction sites of selenos and nsp7 in the replication complex and showed that the hydrophobic segment of selenos is essential for binding to nsp7. This arrangement leaves an extended helix and the intrinsically disordered segment of selenos-including the reactive selenocysteine-exposed and free to potentially recruit additional proteins to the replication and transcription complex.

Selenium and selenoproteins in thermogenic adipocytes

Selenium (Se) is involved in energy metabolism in the liver, white adipose tissue, and skeletal muscle, and may also play a role in thermogenic adipocytes, i.e. brown and beige adipocytes. Thereby this micronutrient is a key nutritional target to aid in combating obesity and metabolic diseases. In thermogenic adipocytes, particularly in brown adipose tissue (BAT), the selenoprotein type 2 iodothyronine deiodinase (DIO2) is essential for the activation of adaptive thermogenesis. Recent evidence has suggested that additional selenoproteins may also be participating in this process, and a role for Se itself through its metabolic pathways is also envisioned. In this review, we discuss the recognized effects and the knowledge gaps in the involvement of Se metabolism and selenoproteins in the mechanisms of adaptive thermogenesis in thermogenic (brown and beige) adipocytes.

Selenoprotein S: A versatile disordered protein

Selenoprotein S (selenos) is a small, intrinsically disordered membrane protein that is associated with various cellular functions, such as inflammatory processes, cellular stress response, protein quality control, and signaling pathways. It is primarily known for its contribution to the ER-associated degradation (ERAD) pathway, which governs the extraction of misfolded proteins or misassembled protein complexes from the ER to the cytosol for degradation by the proteasome. However, selenos's other cellular roles in signaling are equally vital, including the control of transcription factors and cytokine levels. Consequently, genetic polymorphisms of selenos are associated with increased risk for diabetes, dyslipidemia, and cardiovascular diseases, while high expression levels correlate with poor prognosis in several cancers. Its inhibitory role in cytokine secretion is also exploited by viruses. Since selenos binds multiple protein complexes, however, its specific contributions to various cellular pathways and diseases have been difficult to establish. Thus, the precise cellular functions of selenos and their interconnectivity have only recently begun to emerge. This review aims to summarize recent insights into the structure, interactome, and cellular roles of selenos.

Gene Networks of Hyperglycemia, Diabetic Complications, and Human Proteins Targeted by SARS-CoV-2: What Is the Molecular Basis for Comorbidity?

People with diabetes are more likely to have severe COVID-19 compared to the general population. Moreover, diabetes and COVID-19 demonstrate a certain parallelism in the mechanisms and organ damage. In this work, we applied bioinformatics analysis of associative molecular networks to identify key molecules and pathophysiological processes that determine SARS-CoV-2-induced disorders in patients with diabetes. Using text-mining-based approaches and ANDSystem as a bioinformatics tool, we reconstructed and matched networks related to hyperglycemia, diabetic complications, insulin resistance, and beta cell dysfunction with networks of SARS-CoV-2-targeted proteins. The latter included SARS-CoV-2 entry receptors (ACE2 and DPP4), SARS-CoV-2 entry associated proteases (TMPRSS2, CTSB, and CTSL), and 332 human intracellular proteins interacting with SARS-CoV-2. A number of genes/proteins targeted by SARS-CoV-2 (ACE2, BRD2, COMT, CTSB, CTSL, DNMT1, DPP4, ERP44, F2RL1, GDF15, GPX1, HDAC2, HMOX1, HYOU1, IDE, LOX, NUTF2, PCNT, PLAT, RAB10, RHOA, SCARB1, and SELENOS) were found in the networks of vascular diabetic complications and insulin resistance. According to the Gene Ontology enrichment analysis, the defined molecules are involved in the response to hypoxia, reactive oxygen species metabolism, immune and inflammatory response, regulation of angiogenesis, platelet degranulation, and other processes. The results expand the understanding of the molecular basis of diabetes and COVID-19 comorbidity.

Hepatic deficiency of selenoprotein S exacerbates hepatic steatosis and insulin resistance

Nonalcoholic fatty liver disease (NAFLD) is closely associated with insulin resistance (IR) and type 2 diabetes mellitus (T2DM), which are all complex metabolic disorders. Selenoprotein S (SelS) is an endoplasmic reticulum (ER) resident selenoprotein involved in regulating ER stress and has been found to participate in the occurrence and development of IR and T2DM. However, the potential role and mechanism of SelS in NAFLD remains unclear. Here, we analyzed SelS expression in the liver of high-fat diet (HFD)-fed mice and obese T2DM model (db/db) mice and generated hepatocyte-specific SelS knockout (SelS^H-KO) mice using the Cre-loxP system. We showed that hepatic SelS expression levels were significantly downregulated in HFD-fed mice and db/db mice. Hepatic SelS deficiency markedly increased ER stress markers in the liver and caused hepatic steatosis via increased fatty acid uptake and reduced fatty acid oxidation. Impaired insulin signaling was detected in the liver of SelS^H-KO mice with decreased phosphorylation levels of insulin receptor substrate 1 (IRS1) and protein kinase B (PKB/Akt), which ultimately led to disturbed glucose homeostasis. Meanwhile, our results showed hepatic protein kinase Cɛ (PKCɛ) activation participated in the negative regulation of insulin signaling in SelS^H-KO mice. Moreover, the inhibitory effect of SelS on hepatic steatosis and IR was confirmed by SelS overexpression in primary hepatocytes in vitro. Thus, we conclude that hepatic SelS plays a key role in regulating hepatic lipid accumulation and insulin action, suggesting that SelS may be a potential intervention target for the prevention and treatment of NAFLD and T2DM.

The role of selenium in type-2 diabetes mellitus and its metabolic comorbidities

This review addresses the role of the essential trace element, selenium, in type-2 diabetes mellitus (T2DM) and its metabolic co-morbidities, i.e., metabolic syndrome, obesity and non-alcoholic fatty liver disease. We refer to the dietary requirements of selenium and the key physiological roles of selenoproteins. We explore the dysregulated fuel metabolism in T2DM and its co-morbidities, emphasizing the relevance of inflammation and oxidative stress. We describe the epidemiology of observational and experimental studies of selenium in diabetes and related conditions, explaining that the interaction between selenium status and glucose control is not limited to hyperglycemia but extends to hypoglycemia. We propose that the association between high plasma/serum selenium and T2DM/fasting plasma glucose observed in many cross-sectional studies may rely on the upregulation of hepatic selenoprotein-P biosynthesis in conditions of hyperglycemia and insulin resistance. While animal studies have revealed potential molecular mechanisms underlying adverse effects of severe selenium/selenoprotein excess and deficiency in the pathogenesis of insulin resistance and β-cell dysfunction, their translational significance is rather limited. Importantly, dietary selenium supplementation does not appear to be a major causal factor for the development of T2DM in humans though we cannot currently exclude a small contribution of selenium on top of other risk factors, in particular if it is ingested at high (supranutritional) doses. Elevated selenium biomarkers that are often measured in T2DM patients are more likely to be a consequence, rather than a cause, of diabetes.

Identification of VIMP as a gene inhibiting cytokine production in human CD4+ effector T cells

Many players regulating the CD4+ T cell-mediated inflammatory response have already been identified. However, the critical nodes that constitute the regulatory and signaling networks underlying CD4 T cell responses are still missing. Using a correlation-network-guided approach, here we identified VIMP (VCP-interacting membrane protein), one of the 25 genes encoding selenoproteins in humans, as a gene regulating the effector functions of human CD4 T cells, especially production of several cytokines including IL2 and CSF2. We identified VIMP as an endogenous inhibitor of cytokine production in CD4 effector T cells via both the E2F5 transcription regulatory pathway and the Ca2+/NFATC2 signaling pathway. Our work not only indicates that VIMP might be a promising therapeutic target for various inflammation-associated diseases but also shows that our network-guided approach can significantly aid in predicting new functions of the genes of interest.

Dietary Marginal and Excess Selenium Increased Triglycerides Deposition, Induced Endoplasmic Reticulum Stress and Differentially Influenced Selenoproteins Expression in the Anterior and Middle Intestines of Yellow Catfish Pelteobagrus fulvidraco

Selenium (Se) is an essential micro-mineral and plays important roles in antioxidant responses, and also influences lipid metabolism and selenoprotein expression in vertebrates, but the effects and mechanism remain unknown. The study was undertaken to decipher the insights into dietary Se influencing lipid metabolism and selenoprotein expression in the anterior and middle intestine (AI and MI) of yellow catfish Pelteobagrus fulvidraco. Yellow catfish (weight: 8.27 ± 0.03 g) were fed a 0.03- (M-Se), 0.25- (A-Se), or 6.39- (E-Se) mg Se/kg diet for 12 wk. AI and MI were analyzed for triglycerides (TGs) and Se concentrations, histochemistry and immunofluorescence, enzyme activities, and gene and protein levelsassociated with antioxidant responses, lipid metabolism, endoplasmic reticulum (ER) stress, and selenoproteome. Compared to the A-Se group, M-Se and E-Se diets significantly decreased weight gain (WG) and increased TGs concentration in the AI and MI. In the AI, compared with A-Se group, M-Se and E-Se diets significantly increased activities of fatty acid synthase, expression of lipogenic genes, and suppressed lipolysis. In the MI, compared to the A-Se group, M-Se and E-Se diets significantly increased activities of lipogenesis and expression of lipogenic genes. Compared with A-Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the AI and MI, and M-Se diet did not significantly reduce GPX activities in the AI and MI. Compared with the A- Se group, E-Se diet significantly increased glutathione peroxidase (GPX) activities in the plasma and liver, and M-Se diet significantly reduced GPX activities in the plasma and liver. Compared with the A-Se group, M-Se and E-Se groups also increased glucose-regulated protein 78 (GRP78, ER stress marker) protein expression of the intestine. Dietary Se supplementation also differentially influenced the expression of the 28 selenoproteins in the AI and MI, many of which possessed antioxidant characteristics. Compared with the A-Se group, the M-Se group significantly decreased mRNA levels of txnrd2 and txnrd3, but made no difference on mRNA levels of these seven GPX proteins in the MI. Moreover, we characterized sterol regulatory element binding protein 1c (SREBP1c) binding sites of three ER-resident proteins (selenom, selenon, and selenos) promoters, and found that Se positively controlled selenom, selenon, and selenos expression via SREBP1c binding to the selenom, selenon, and selenos promoter. Thus, dietary marginal and excess Se increased TGs deposition of yellow catfish P. fulvidraco, which might be mediated by ER-resident selenoproteins expression and ER stress.

Selenium in Endocrinology-Selenoprotein-Related Diseases, Population Studies, and Epidemiological Evidence

Selenium (Se), apart from iodine, iron, and calcium, is one of the nutrient-derived key elements strongly affecting the endocrine system. However, no specific hormonal "feedback" regulation for Se status has yet been identified, in contrast to the fine-tuned hormone network regulating Ca2+ and phosphate balance or hepcidin-related iron status. Since its discovery as an essential trace element, the effects of Se excess or deficiency on the endocrine system or components of the hypothalamic-pituitary-periphery feedback circuits, the thyroid hormone axis, glucoregulatory and adrenal hormones, male and female gonads, the musculoskeletal apparatus, and skin have been identified. Analysis of the Se status in the blood or via validated biomarkers such as the hepatically derived selenoprotein P provides valuable diagnostic insight and a rational basis for decision making on required therapeutic or preventive supplementation of risk groups or patients. Endocrine-related epidemiological and interventional evidence linking Se status to beneficial or potentially adverse actions of selected selenoproteins mediating most of the (patho-) physiological effects are discussed in this mini-review. Autoimmune thyroid disease, diabetes and obesity, male fertility, as well as osteoporosis are examples for which observational or interventional studies have indicated Se effects. The currently prevailing concept relating Se and selenoproteins to "oxidative stress," reactive oxygen species, radical hypotheses, and related strategies of pharmacological approaches based on various selenium compounds will not be the focus. The crucial biological function of several selenoproteins in cellular redox-regulation and specific enzyme reactions in endocrine pathways will be addressed and put in clinical perspective.

The SELS rs34713741 Polymorphism Is Associated with Susceptibility to Colorectal Cancer and Gastric Cancer: A Meta-Analysis

Aims: The selenoprotein S (SELS) gene has been suggested to be an important factor in the development of multiple diseases, including gastric cancer (GC) and colorectal cancer (CRC). However, the association between the SELS gene rs34713741 polymorphism and risk of GC and CRC is inconclusive. Thus, we aimed to investigate the relationship between this polymorphism and the susceptibility to GC and CRC through a meta-analysis. Materials and Methods: Literature was retrieved through the following electronic databases: PubMed, Embase, Web of Science, and Chinese National Knowledge Infrastructure. The pooled odds ratio (OR) and 95% confidence interval (CI) were used to assess the strength of the associations of the alleles of rs4713741 locus with the risk of CRC and GC. Results: Seven studies that collectively included 2331 cases and 2233 controls were utilized for this meta-analysis. Under the allelic and dominant models, the T allele of the SELS rs34713741 polymorphism was significantly associated with CRC risk (allelic model: OR = 1.20, 95% CI = 1.08-1.33, p = 0.0004; dominant model: OR = 1.25, 95% CI = 1.10-1.43, p = 0.001). In addition, all of the genetic models (allelic, dominant, and recessive models) identified the rs34713741 T allele as being significantly associated with GC risk (allelic model: OR = 1.67, 95% CI = 1.30-2.15, p < 0.001; dominant model: OR = 1.70, 95% CI = 1.25-2.30, p = 0.0006; recessive model: OR = 2.39, 95% CI = 1.26-4.50, p = 0.007). Conclusions: The SELS gene rs34713741 T-allele is a highly probable risk factor for both CRC and GC. The results of this study will provide support for using this single nucleotide polymorphism in the diagnosis of GC and CRC.

Nomogram developed with selenoprotein S (SelS) genetic variation and clinical characteristics predicting risk of coronary artery disease in a Chinese population

BACKGROUND

Selenoprotein S (SelS) is a novel selenoprotein encoded by the SelS gene on chromosome 15q26.3. SelS is associated with the development of diabetes, dyslipidemia and macrovascular complications. However, the relationship between genetic polymorphisms of SelS and coronary artery disease (CAD) remains unclear.

METHODS

In the present study, we genotyped four single nucleotide polymorphisms (rs117613208, rs117512970, rs986500879, rs542989868) of SelS gene using direct sequencing method in a case-control study (576 CAD cases and 452 control subjects). Furthermore, we developed a predictive model using SelS genetic variation and clinical variables to predict risk of CAD.

RESULTS

We found that rs117613208 T allele was more frequent in the CAD cases than that in the controls. Logistic regression analysis suggested after adjustment of other confounders, the difference remained significant between the two groups [odds ratio (OR) =2.107, 95% confidence interval (CI): 1.239-3.583, P<0.006]. Using SelS rs117613208 T allele, age, smoking, diabetes, hypertension, apolipoprotein A1 (apoA1), and lipoprotein A [Lp(a)] (GASDLY score), we developed a diagnostic model of CAD (AUC: 0.806, 95% CI: 0.776-0.836, P<0.001, sensitivity: 74.7%, specificity:75.5%).

CONCLUSIONS

The present study suggested that genetic polymorphism of SelS was independent associated with CAD and GASDLY score may be a novel diagnostic model for CAD in a Chinese population.

Association of Selenoprotein S Expression and its Variants with Metabolic Syndrome in Subjects with Cardiovascular Disease

BACKGROUND

Selenoproteins S (SELS or VIMP) may regulate cytokine production, and thus play a key role in the control of the inflammatory response.

METHODS

This study consisted of 136 Iranian patients with cardiovascular disease (65 MetS-affected and 71 MetS un-affected individuals) in the selengene study. Expression of two variants of VIMP including VIMP I and II were analyzed in all subjects using Real-Time PCR and ELISA.

RESULTS

The level of VIMP was lower in MetS⁺ compared to the MetS^- subjects (p <0.05). We found no significant differences in quantitative expression of VIMP I and VIMP II in both groups. VIMP I reveal a reverse correlation with fasting blood sugar (FBS) (r = -0.45, p = 0.009). Moreover, SELS in protein level has negative correlation with WC (r = -0.171, p = 0.049) and positive correlation with HDL (r = 0.176, p = 0.046).

CONCLUSIONS

Our study suggests that VIMP in protein level is significantly lower in MetS and shows a reverse correlation with WC and positive correlation with HDL. Therefore, with regard to the functional role of this protein, it is possible to deduce that its lower expression leads to the higher secretion of unfolded proteins into the cytosol and outside the cell, where they cannot play their exact roles in the different pathways. Moreover, the reverse correlation of VIMP I with FBS suggests further consideration of VIMP and its variant VIMP I expression in regards to potential development of major CVD risk factors.

Selenium and Selenoproteins in Adipose Tissue Physiology and Obesity

Selenium (Se) homeostasis is tightly related to carbohydrate and lipid metabolism, but its possible roles in obesity development and in adipocyte metabolism are unclear. The objective of the present study is to review the current data on Se status in obesity and to discuss the interference between Se and selenoprotein metabolism in adipocyte physiology and obesity pathogenesis. The overview and meta-analysis of the studies on blood Se and selenoprotein P (SELENOP) levels, as well as glutathione peroxidase (GPX) activity in obese subjects, have yielded heterogenous and even conflicting results. Laboratory studies demonstrate that Se may modulate preadipocyte proliferation and adipogenic differentiation, and also interfere with insulin signaling, and regulate lipolysis. Knockout models have demonstrated that the selenoprotein machinery, including endoplasmic reticulum-resident selenoproteins together with GPXs and thioredoxin reductases (TXNRDs), are tightly related to adipocyte development and functioning. In conclusion, Se and selenoproteins appear to play an essential role in adipose tissue physiology, although human data are inconsistent. Taken together, these findings do not support the utility of Se supplementation to prevent or alleviate obesity in humans. Further human and laboratory studies are required to elucidate associations between Se metabolism and obesity.

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.

Correlation between SEPS1 gene polymorphism and type 2 diabetes mellitus: A preliminary study

Background

The protein encoded by the selenoprotein S gene is considered to be an anti‐inflammatory and antioxidant protein and is involved in a variety of diseases. Therefore, we want to study the distribution characteristics of this gene in Chinese diabetic population.

Methods

A total of 170 patients with DM (including 100 patients with T2DM and 70 patients with diabetic nephropathy [DN]) and 100 healthy controls (HC) were selected from Haikou People's Hospital (China) between January 2017 and July 2017. The polymorphisms of three SEPS1 genes (SNP ID: rs4965814, rs28665122, and rs34713741) were measured by massARRAY method, while the polymorphisms of SEPS1 genes (SNP ID: rs4965373) were detected by Sanger sequencing.

Results

Comparing three groups, the results were the following: (a) There was a significant difference in the genotype and allele distribution of rs34713741 between DN group and HC group and between T2DM group and DN group; For this gene locus, the risk of diabetic nephropathy in healthy individuals with T allele was 0.6 times higher than that in individuals with GG genotype (OR = 0.60, 95% CI: 0.46 ~ 0.77). (b) There was a significant difference in the distribution of rs4975814 genotype between DN group and HC group; for this gene locus, the risk of diabetic nephropathy in healthy individuals with T allele was 2.71 times higher than that in individuals with GG genotype (OR = 2.71, 95% CI: 1.66 ~ 4.45).

Conclusion

We conclude that rs34713741 (GT + TT) may be a protective gene for DN and the rs4975814 (GT + TT) may be a susceptibility gene for DN.

Proposal of a study protocol of a preliminary double-blind randomized controlled trial. Verifying effects of selenium supplementation on selenoprotein p and s genes expression in protein and mRNA levels in subjects with coronary artery disease: selenegene

Background: Selenium is the component of selenocystein amino acid, which itself is the building block of selenoproteins having diverse effects on various aspects of the human health. Among these proteins, selenoprotein P is the central to the distribution and homeostasis of selenium, and selenoprotein S as a transmembrane protein is associated with a range of inflammatory markers, particularly in the context of cardiovascular disease. It is known that selenium status outside of the normal range is considered to confer different benefits or adverse cardiovascular risk factors. Therefore, for the first time, we aimed to verify effects of Selenium supplementation on Selenoprotein P and S Genes Expression in Protein and mRNA Levels in Subjects with Coronary Artery Disease (CAD). Methods: This is the study protocol of a double blinded randomized clinical trial on 130 subjects with angiographically documented stenosis of more than 75% in one or more coronary artery vessels. In this 60-day study, 65 patients in each group received either a 200mg selenium yeast or placebo tablets once daily. During the study, subjects were followed by phone calls and visited our clinic twice to repeat baseline measurements. We hypothesized that our finding would enable a more basic and confirmed understanding for the effect of selenium supplementation by investigating its effect on gene expression levels in people with CAD. Discussion: Upon confirmation of this hypothesis, the beneficial effect of inflammation regulation by supplementation with micronutrients could be considered for subjects with CVD. (www.actabiomedica.it)

Differential regulation of cellular stress responses by the endoplasmic reticulum-resident Selenoprotein S (Seps1) in proliferating myoblasts versus myotubes

The antioxidant Selenoprotein S (Seps1, Selenos) is an endoplasmic reticulum (ER)-resident protein associated with metabolic and inflammatory disease. While Seps1 is highly expressed in skeletal muscle, its mechanistic role as an antioxidant in skeletal muscle cells is not well characterized. In C2C12 myotubes treated with palmitate for 24 h, endogenous Seps1 protein expression was upregulated twofold. Two different siRNA constructs were used to investigate whether decreased levels of Seps1 exacerbated lipid-induced oxidative and ER stress in C2C12 myotubes and myoblasts, which differ with regards to cell cycle state and metabolic phenotype. In myoblasts, Seps1 protein knockdown of ~50% or ~75% exacerbated cellular stress responses in the presence of palmitate; as indicated by decreased cell viability and proliferation, higher H2 O2 levels, a lower reduced to oxidized glutathione (GSH:GSSG) ratio, and enhanced gene expression of ER and oxidative stress markers. Even in the absence of palmitate, Seps1 knockdown increased oxidative stress in myoblasts. Whereas, in myotubes in the presence of palmitate, a ~50% knockdown of Seps1 was associated with a trend toward a marginal (3-5%) decrease in viability (P = 0.05), decreased cellular ROS levels, and a reduced mRNA transcript abundance of the cellular stress marker thioredoxin inhibitory binding protein (Txnip). Furthermore, no enhancement of gene markers of ER stress was observed in palmitate-treated myotubes in response to Seps1 knockdown. In conclusion, reduced Seps1 levels exacerbate nutrient-induced cellular stress responses to a greater extent in glycolytic, proliferating myoblasts than in oxidative, differentiated myotubes, thus demonstrating the importance of cell phenotype to Seps1 function.

Association of genetic polymorphisms of SelS with Type 2 diabetes in a Chinese population

Background: Selenoprotein S (SelS) gene expression is positively correlated to triglyceride (TG) concentrations and is associated with diabetes in animal model. However, the relationship between genetic polymorphisms of SelS and Type 2 diabetes (T2DM) remains unclear. Methods: In the present study, we genotyped four single nucleotide polymorphisms (rs12910524, rs1384565, rs2101171, rs4965814) of SelS gene using TaqMan genotyping method in a case-control study (1947 T2DM patients and 1639 control subjects). Results: We found both rs1384565 CC genotype (12.1 compared with 6.6%, P<0.001) and C allele (35.2 compared with 24.4%, P<0.001) were more frequent in the T2DM patients than in the controls. Logistic regression analysis suggested after adjustment of other confounders, the difference remained significant between the two groups (CC compared with TT, P=0.002, OR = 1.884, 95% CI: 1.263-2.811; CT compared with TT, P<0.001, OR = 1.764, 95% CI: 1.412-2.204). Conclusion: The present study suggested that genetic polymorphisms of SelS were associated with T2DM in a Chinese population.

Associations and interactions between variants in selenoprotein genes, selenoprotein levels and the development of abdominal aortic aneurysm, peripheral arterial disease, and heart failure

Background

Little is known on the role of selenoprotein genes in cardiovascular disease. This study examines the associations of the SEPP1, SELENOS, TXNRD1, TXNRD2, GPX4, and SOD2 polymorphisms and selenoprotein P (SeP) and thioredoxin concentrations with the development of abdominal aortic aneurysm (AAA) and aortoiliac occlusive disease (AOID), as well as their influence on cardiac phenotype.

Methods

564 patients with AAA, 400 patients with AIOD, and 543 controls were enrolled and characterized for coronary artery disease, myocardial infarction, and systolic heart failure (HF) occurrence. In AAA, the coexistence of peripheral arterial disease (PAD) was examined. Genotypes were determined using TaqMan-based assays. Selenoprotein concentration was assessed using the ELISA method.

Results

The SELENOS rs34713741T, SEPP1 rs3877899A, and GPX4 rs713041T alleles were related to a 30–60% increase in the AIOD/PAD risk in the recessive or dominant model (all associations at P < .05). The SEPP1 rs3877899A allele was a protective factor for the development of AAA without concomitant PAD (OR = 0.68 for the dominant model, P = .014), but not AAA with concomitant PAD. The cumulative two-locus effects of selenoprotein genes on the AAA/AIOD risk were observed, including the multiplicative interaction between the SELENOS rs34713741T and GPX4 rs713041T alleles (both in the recessive model) affecting the AIOD risk (OR = 5.27, P = .001) and its clinical phenotype. Coexistence of HF in aortic diseases was related to both the SEPP1 rs7579A allele (OR = 1.83 for carriers, P = .013) and increased SeP concentrations; SeP level ≥8.5 mg/mL caused a 3.5-fold increase in the risk of HF. In AAA, SeP levels were correlated with BMI (r = -0.575, P < .0001).

Conclusions

Our results provide evidence that selenoprotein polymorphisms constitute a risk factor for HF and peripheral atherosclerosis, but prevent the development of AAA. Excessive weight might result in reduced antioxidant reserve efficiency in AAA. Validation studies are required to establish whether SeP concentration may be a marker for HF.

Selenium deficiency impaired immune function of the immune organs in young grass carp (Ctenopharyngodon idella)

This study aimed to investigate the effects of dietary selenium on resistance to skin haemorrhages and lesions and on immune function as well as the underlying mechanisms of those effects in the head kidney, spleen and skin of young grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp with initial body weight (226.48 ± 0.68 g) were randomly divided into six groups and fed six separate diets with graded dietary levels of selenium (0.025, 0.216, 0.387, 0.579, 0.795 and 1.049 mg/kg diet) for 80 days. After the feeding period, an immunization trial was performed by infection with Aeromonas hydrophila for 14 days. The results showed that, compared with the optimal selenium level, (1) selenium deficiency impaired the production of antibacterial compounds and immunoglobulins and down-regulated the transcript abundances of antimicrobial peptides and selenoproteins; (2) selenium deficiency aggravated inflammatory responses in part by up-regulating pro-inflammatory cytokines and down-regulating anti-inflammatory cytokines mRNA levels, which were partially related to [IKKα, β, γ/IκBα/NF-κB] signalling and [TOR/(S6K1, 4E-BP1)] signalling, respectively. Interestingly, selenium deficiency had no effect on the expression of TGF-β2, IL-4/13B, IL-10, IL-12p35, IL-15 (skin only) or 4E-BP2 in the head kidney, spleen and skin of young grass carp. Finally, based on the percent weight gain (PWG), the morbidity of skin haemorrhages and lesions, the ACP activity in the head kidney and the lysozyme activity in spleen, the optimal dietary selenium requirements for young grass carp were estimated to be 0.546-0.604 mg/kg diet. In summary, selenium deficiency decreased the growth performance and impaired the immune function in the head kidney, spleen and skin of young grass carp.

Deficiency of selenoprotein S, an endoplasmic reticulum resident oxidoreductase, impairs the contractile function of fast-twitch hindlimb muscles

Selenoprotein S (Seps1) is an endoplasmic reticulum (ER) resident antioxidant implicated in ER stress and inflammation. In human vastus lateralis and mouse hindlimb muscles, Seps1 localization and expression were fiber-type specific. In male Seps1^+/- heterozygous mice, spontaneous physical activity was reduced compared with wild-type littermates ( d = 1.10, P = 0.029). A similar trend was also observed in Seps1^-/- knockout mice ( d = 1.12, P = 0.051). Whole body metabolism, body composition, extensor digitorum longus (EDL), and soleus mass and myofiber diameter were unaffected by genotype. However, in isolated fast EDL muscles from Seps1^-/- knockout mice, the force frequency curve (FFC; 1-120 Hz) was shifted downward versus EDL muscles from wild-type littermates ( d = 0.55, P = 0.002), suggestive of reduced strength. During 4 min of intermittent, submaximal (60 Hz) stimulation, the genetic deletion or reduction of Seps1 decreased EDL force production ( d = 0.52, P < 0.001). Furthermore, at the start of the intermittent stimulation protocol, when compared with the 60-Hz stimulation of the FFC, EDL muscles from Seps1^-/- knockout or Seps1^+/- heterozygous mice produced 10% less force than those from wild-type littermates ( d = 0.31, P < 0.001 and d = 0.39, P = 0.015). This functional impairment was associated with reduced mRNA transcript abundance of thioredoxin-1 ( Trx1), thioredoxin interacting protein ( Txnip), and the ER stress markers Chop and Grp94, whereas, in slow soleus muscles, Seps1 deletion did not compromise contractile function and Trx1 ( d = 1.38, P = 0.012) and Txnip ( d = 1.27, P = 0.025) gene expression was increased. Seps1 is a novel regulator of contractile function and cellular stress responses in fast-twitch muscles.

Emerging roles of endoplasmic reticulum-resident selenoproteins in the regulation of cellular stress responses and the implications for metabolic disease

Chronic metabolic stress leads to cellular dysfunction, characterized by excessive reactive oxygen species, endoplasmic reticulum (ER) stress and inflammation, which has been implicated in the pathogenesis of obesity, type 2 diabetes and cardiovascular disease. The ER is gaining recognition as a key organelle in integrating cellular stress responses. ER homeostasis is tightly regulated by a complex antioxidant system, which includes the seven ER-resident selenoproteins - 15 kDa selenoprotein, type 2 iodothyronine deiodinase and selenoproteins S, N, K, M and T. Here, the findings from biochemical, cell-based and mouse studies investigating the function of ER-resident selenoproteins are reviewed. Human experimental and genetic studies are drawn upon to highlight the relevance of these selenoproteins to the pathogenesis of metabolic disease. ER-resident selenoproteins have discrete roles in the regulation of oxidative, ER and inflammatory stress responses, as well as intracellular calcium homeostasis. To date, only two of these ER-resident selenoproteins, selenoproteins S and N have been implicated in human disease. Nonetheless, the potential of all seven ER-resident selenoproteins to ameliorate metabolic dysfunction warrants further investigation.

Trace Elements and Healthcare: A Bioinformatics Perspective

Biological trace elements are essential for human health. Imbalance in trace element metabolism and homeostasis may play an important role in a variety of diseases and disorders. While the majority of previous researches focused on experimental verification of genes involved in trace element metabolism and those encoding trace element-dependent proteins, bioinformatics study on trace elements is relatively rare and still at the starting stage. This chapter offers an overview of recent progress in bioinformatics analyses of trace element utilization, metabolism, and function, especially comparative genomics of several important metals. The relationship between individual elements and several diseases based on recent large-scale systematic studies such as genome-wide association studies and case-control studies is discussed. Lastly, developments of ionomics and its recent application in human health are also introduced.

Selenoprotein S: a therapeutic target for diabetes and macroangiopathy?

Inflammatory response, oxidative stress, and endoplasmic reticulum (ER) stress are important pathophysiological bases of the occurrence and development of diabetes mellitus (DM) and macroangiopathy complications. Selenoprotein S (SELENOS) is involved in the regulation of these mechanisms; therefore, its association with DM and macroangiopathy has gradually received attention from scholars worldwide. SELENOS has different biological functions in different tissues and organs: it exerts antioxidant protection and has anti-ER stress effects in the pancreas and blood vessels, while it promotes the occurrence and development of insulin resistance in the liver, adipose tissue, and skeletal muscle. In addition, studies have confirmed that some SELENOS gene polymorphisms can influence the inflammatory response and are closely associated with the risk for developing DM and macroangiopathy. Therefore, comprehensive understanding of the association between SELENOS and inflammation, oxidative stress, and ER stress may better elucidate and supplement the pathogenic mechanisms of DM and macroangiopathy complications. Furthermore, in-depth investigation of the association of SELENOS function in different tissues and organs with DM and macroangiopathy may facilitate the development of new strategies for the prevention and treatment of DM and macrovascular complications. Here, we summarize the consensus and controversy regarding functions of SELENOS on currently available evidence.

Selenoprotein SelK increases the secretion of insulin from MIN6 β cells

The expression of selenoprotein SelK triggers the secretion of insulin from MIN6 β cells by increasing the cytosolic free Ca²⁺ level, resulting from the up-regulated IP3R3 expression.

Selenoprotein P neutralizes lipopolysaccharide and participates in hepatic cell endoplasmic reticulum stress response

Low serum selenium or selenoprotein P (SePP) levels have been repetitively observed in severe sepsis. The role of SePP in sepsis is incompletely characterized. To test the hypothesis that lipopolysaccharide (LPS) interacts with SePP, we investigated the interaction between LPS and the histidine-rich (His-rich) regions of SePP. We demonstrate that both purified SePP and synthetic peptides corresponding to the His-rich motifs neutralized LPS. In addition, we used a hepatocyte model to study the fate of SePP in response to LPS or endoplasmic reticulum (ER) stress. Our findings indicate that ER stress increases the cellular level of SePP and promotes its nuclear localization.

Selenium and Metabolic Disorders: An Emphasis on Type 2 Diabetes Risk

Selenium (Se) is a micronutrient that maintains biological functions through the action of Se containing proteins known as selenoproteins. Due to the known antioxidant effects of Se, supplements containing Se have been on the rise. While Se supplementation may be beneficial for Se deficient populations, few are at risk for Se deficiency due to the transportation of food from Se-rich regions and the rise of Se-enriched foods. Alarmingly, Se supplementation may have adverse effects in people who already receive an adequate Se supply. Specifically, an increased risk of type 2 diabetes has been reported in individuals with high baseline Se levels. However, this effect was restricted to males, suggesting the relationship between Se and glucose homeostasis may be sexually dimorphic. This review will discuss the current understanding of the interaction between Se and glucose homeostasis, including any sex differences that have been described.

Diet-induced obesity in the selenocysteine lyase knockout mouse

AIMS

Selenocysteine lyase (Scly) mediates selenocysteine decomposition. It was previously demonstrated that, upon adequate caloric intake (12% kcal fat) and selenium deficiency, disruption of Scly in mice leads to development of metabolic syndrome. In this study, we investigate the effect of a high-fat (45% kcal) selenium-adequate diet in Scly knockout (KO) mice on development of metabolic syndrome. Involvement of selenoproteins in energy metabolism after Scly disruption was also examined in vitro in the murine hepatoma cell line, Hepa1-6, following palmitate treatment.

RESULTS

Scly KO mice were more susceptible to diet-induced obesity than their wild-type counterparts after feeding a high-fat selenium-adequate diet. Scly KO mice had aggravated hyperinsulinemia, hypercholesterolemia, glucose, and insulin intolerance, but unchanged inflammatory cytokines and expression of most selenoproteins, except increased serum selenoprotein P (Sepp1). Scly KO mice also exhibited enhanced hepatic levels of pyruvate and enzymes involved in the regulation of pyruvate cycling, such as pyruvate carboxylase (Pcx) and pyruvate dehydrogenase (Pdh). However, in vitro silencing of Scly in Hepa1-6 cells led to diminished Sepp1 expression, and concomitant palmitate treatment decreased Pdh expression.

INNOVATION

The role of selenium in lipid metabolism is recognized, but specific selenium-dependent mechanisms leading to obesity are unclear. This study uncovers that Scly has a remarkable effect on obesity and metabolic syndrome development triggered by high-fat exposure, independent of the expression of most selenoproteins.

CONCLUSION

Diet-induced obesity in Scly KO mice is aggravated, with effects on pyruvate levels and consequent activation of energy metabolism independent of selenoprotein levels.

Membrane-bound selenoproteins

SIGNIFICANCE

Selenoproteins employ selenium to supplement the chemistry available through the common 20 amino acids. These powerful enzymes are affiliated with redox biology, often in connection with the detection, management, and signaling of oxidative stress. Among them, membrane-bound selenoproteins play prominent roles in signaling pathways, Ca(2+) regulation, membrane complexes integrity, and biosynthesis of lipophilic molecules.

RECENT ADVANCES

The number of selenoproteins whose physiological roles, protein partners, expression, evolution, and biosynthesis are characterized is steadily increasing, thus offering a more nuanced view of this specialized family. This review focuses on human membrane selenoproteins, particularly the five least characterized ones: selenoproteins I, K, N, S, and T.

CRITICAL ISSUES

Membrane-bound selenoproteins are the least understood, as it is challenging to provide the membrane-like environment required for their biochemical and biophysical characterization. Hence, their studies rely mostly on biological rather than structural and biochemical assays. Another aspect that has not received much attention is the particular role that their membrane association plays in their physiological function.

FUTURE DIRECTIONS

Findings cited in this review show that it is possible to infer the structure and the membrane-binding mode of these lesser-studied selenoproteins and design experiments to examine the role of the rare amino acid selenocysteine.

Association analysis of selenoprotein S polymorphisms in Chinese Han with susceptibility to gastric cancer

OBJECTIVE

selenoprotein S (SelS) gene polymorphism is closely related to a variety of malignant tumours. Here, we evaluate the association between SelS polymorphism and genetic susceptibility to gastric cancer.

METHODS

A case-control study was conducted to investigate the role of two SelS single nucleotide polymorphisms (SNPs) on the susceptibility to gastric cancer. The genotypes and genotype frequencies of the SelS were determined in 260 gastric cancer patients and 278 age-matched healthy controls. Polymerase chain reaction restriction fragment length of polymorphism (PCR-RFLP) was taken to genotype rs28665122 (G-105A) and rs34713741 (G-254A) within the SelS gene. The differences in the genotypic distribution between gastric cancer patients and healthy controls were analyzed with the Chi-square test for trends. Logistic-regression analysis was used to estimate odds ratios (OR) and 95% confidence intervals (CI), adjusting for age and sex.

RESULTS

For rs34713741 in SelS, the allele frequencies analysis indicated that the allele frequency of the T was higher in patients than in controls (P=0.001). There were significant differences of genotype frequencies and allele of rs34713741 polymorphism between gastric cancer group and control group (P<0.05). The relative risk of suffering from gastric cancer in T allele was 1.62 times of CC genotype in Hunan Han population (OR=1.62, 95% CI: 1.15~2.29). But there were no differences of genotype frequencies and allele of SelS rs28665122 polymorphism between gastric cancer group and control group.

CONCLUSIONS

Allele T of SelS rs34713741 polymorphism is significantly associated with an increased risk of gastric cancer in Chinese population.

Selenoprotein S is a marker but not a regulator of endoplasmic reticulum stress in intestinal epithelial cells

Selenoproteins are candidate mediators of selenium-dependent protection against tumorigenesis and inflammation in the gut. Expression and roles of only a limited number of intestinal selenoproteins have been described so far. Selenoprotein S (SelS) has been linked to various inflammatory diseases and is suggested to be involved in endoplasmic reticulum (ER) homeostasis regulation and antioxidative protection in a cell-type-dependent manner, but its protein expression, regulation, and function in the gut are not known. We here analyzed the expression and localization of SelS in the healthy and inflamed gut and studied its regulation and function in intestinal epithelial cell lines. SelS was expressed in the intestinal epithelium of the small and large intestine and colocalized with markers of Paneth cells and macrophages. It was upregulated in inflamed ileal tissue from Crohn's disease patients and in two models of experimental colitis in mice. We detected SelS in colorectal cell lines, where it colocalized with the ER marker calnexin. SelS protein expression was unaffected by enterocytic differentiation but increased in response to selenium supplementation and after treatment with the ER stress inducer tunicamycin. On the other hand, depletion of SelS in LS174T, HT29, and Caco-2 cells by RNA interference did not cause or modulate ER stress and had no effect on hydrogen peroxide-induced cell death. In summary, we introduce SelS as a novel marker of Paneth cells and intestinal ER stress. Although it is upregulated in Crohn's disease, its role in disease etiology remains to be established.

Selenium and diabetes--evidence from animal studies

Whereas selenium was found to act as an insulin mimic and to be antidiabetic in earlier studies, recent animal experiments and human trials have shown an unexpected risk of prolonged high Se intake in potentiating insulin resistance and type 2 diabetes. Elevating dietary Se intake (0.4 to 3.0mg/kg of diet) above the nutrient requirements, similar to overproduction of selenoproteins, led to insulin resistance and/or diabetes-like phenotypes in mice, rats, and pigs. Although its diabetogenic mechanism remains unclear, high Se intake elevated activity or production of selenoproteins including GPx1, MsrB1, SelS, and SelP. This upregulation diminished intracellular reactive oxygen species and then dysregulated key regulators of β cells and insulin synthesis and secretion, leading to chronic hyperinsulinemia. Overscavenging intracellular H2O2 also attenuated oxidative inhibition of protein tyrosine phosphatases and suppressed insulin signaling. High Se intake might affect expression and/or function of key regulators of glycolysis, gluconeogenesis, and lipogenesis. Future research is needed to find out if certain forms of Se metabolites in addition to selenoproteins and if mechanisms other than intracellular redox control mediate the diabetogenic effects of high Se intake. Furthermore, a potential interactive role of high Se intake in the interphase of carcinogenesis and diabetogenesis should be explored to make optimal use of Se in human nutrition and health.

The PACAP-regulated gene selenoprotein T is abundantly expressed in mouse and human β-cells and its targeted inactivation impairs glucose tolerance

Selenoproteins are involved in the regulation of redox status, which affects several cellular processes, including cell survival and homeostasis. Considerable interest has arisen recently concerning the role of selenoproteins in the regulation of glucose metabolism. Here, we found that selenoprotein T (SelT), a new thioredoxin-like protein of the endoplasmic reticulum, is present at high levels in human and mouse pancreas as revealed by immunofluorescence and quantitative PCR. Confocal immunohistochemistry studies revealed that SelT is mostly confined to insulin- and somatostatin-producing cells in mouse and human islets. To elucidate the role of SelT in β-cells, we generated, using a Cre-Lox strategy, a conditional pancreatic β-cell SelT-knockout C57BL/6J mice (SelT-insKO) in which SelT gene disruption is under the control of the rat insulin promoter Cre gene. Glucose administration revealed that male SelT-insKO mice display impaired glucose tolerance. Although insulin sensitivity was not modified in the mutant mice, the ratio of glucose to insulin was significantly higher in the SelT-insKO mice compared with wild-type littermates, pointing to a deficit in insulin production/secretion in mutant mice. In addition, morphometric analysis showed that islets from SelT-insKO mice were smaller and that their number was significantly increased compared with islets from their wild-type littermates. Finally, we found that SelT is up-regulated by pituitary adenylate cyclase-activating polypeptide (PACAP) in β-pancreatic cells and that SelT could act by facilitating a feed-forward mechanism to potentiate insulin secretion induced by the neuropeptide. Our findings are the first to show that the PACAP-regulated SelT is localized in pancreatic β- and δ-cells and is involved in the control of glucose homeostasis.

Genetic variation in Tanis was associated with elevating plasma triglyceride level in Chinese nondiabetic subjects

BACKGROUND

The association of genetic polymorphisms of Tanis with triglyceride concentration in human has not been thoroughly examined. We aimed to investigate the relationship between triglyceride concentrations and Tanis genetic polymorphisms.

METHODS

All participants (n=1497) selected from subjects participating in the Cardiovascular Risk Survey (CRS) study were divided into two groups according to ethnicity (Han: n=1059; Uygur: n= 438). Four tagging SNPs (rs12910524, rs1384565, rs2101171, rs4965814) of Tanis gene were genotyped using TaqMan® assays from Applied Biosystems following the manufacturer's suggestions and analyzed in an ABI 7900HT Fast Real-Time PCR System.

RESULTS

We found that the SNP rs12910524 was associated with triglyceride levels by analyses of a dominant model (P<0.001), recessive model (P <0.001) and additive model (P < 0.001) not only in Han ethnic but also in Uygur ethnic group, and the difference remained significant after the adjustment of sex, age, alcohol intake, smoking, BMI and plasma glucose (GLU) level (All P < 0.001). However, this relationship was not observed in rs1384565, rs2101171, and rs4965814 before and after multivariate adjustment (All P > 0.05). Furthermore, there were significant interactions between rs12910524 and GLU on TG both in Han (P=0.001) and Uygur population (P=2.60×10(-4)).

CONCLUSION

Our results indicated that the rs12910524 in the Tanis gene was associated with triglyceride concentrations in subjects without diabetes in China.

The SEPS1 G-105A polymorphism is associated with risk of spontaneous preterm birth in a Chinese population

Inflammation plays an important role in the etiology and pathophysiology of spontaneous preterm birth (SPTB), and selenoprotein S (SEPS1) is involved in regulating the inflammatory response. Recently the G-105A promoter polymorphism in SEPS1 was shown to increase pro-inflammatory cytokine expression. We examined whether this functional polymorphism was related to the risk of SPTB in a Chinese population. We also examined the impact of premature rupture of membranes (PROM) on susceptibility to SPTB. The SEPS1 G-105A polymorphism was genotyped in 569 preterm singleton neonates and 673 term neonates by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis. χ² tests and logistic regression analyses were used to calculate the odds ratios (ORs) and 95% confidence intervals (95% CIs). We observed that, compared with the GG genotype, –105A positive genotypes (GA + AA genotypes) were associated with significantly increased susceptibility to SPTB (adjusted OR, 1.87; 95% CI, 1.36–2.57; P<0.001). The –105A positive genotypes were also significantly associated with increased susceptibility to SPTB, both in the patients with PROM (adjusted OR, 2.65; 95% CI, 1.73–4.03; P<0.001) and in those without PROM (adjusted OR, 1.56; 95% CI, 1.09–2.24; P = 0.015). The –105A positive genotypes were also significantly associated with increased susceptibility to SPTB between extremely preterm neonates and controls (adjusted OR, 4.46; 95% CI, 1.86–10.73; P = 0.002) and between moderately preterm neonates and controls (adjusted OR, 1.76; 95% CI, 1.25–2.47; P = 0.001). Our findings suggest that the SEPS1 G-105A polymorphism contributes to the risk of developing SPTB in a Chinese population.

Polymorphisms in the Selenoprotein S gene and subclinical cardiovascular disease in the Diabetes Heart Study

Selenoprotein S (SelS) has previously been associated with a range of inflammatory markers, particularly in the context of cardiovascular disease (CVD). The aim of this study was to examine the role of SELS genetic variants in risk for subclinical CVD and mortality in individuals with type 2 diabetes mellitus (T2DM). The association between 10 polymorphisms tagging SELS and coronary (CAC), carotid (CarCP) and abdominal aortic calcified plaque, carotid intima media thickness and other known CVD risk factors was examined in 1220 European Americans from the family-based Diabetes Heart Study. The strongest evidence of association for SELS SNPs was observed for CarCP; rs28665122 (5' region; β = 0.329, p = 0.044), rs4965814 (intron 5; β = 0.329, p = 0.036), rs28628459 (3' region; β = 0.331, p = 0.039) and rs7178239 (downstream; β = 0.375, p = 0.016) were all associated. In addition, rs12917258 (intron 5) was associated with CAC (β = -0.230, p = 0.032), and rs4965814, rs28628459 and rs9806366 were all associated with self-reported history of prior CVD (p = 0.020-0.043). These results suggest a potential role for the SELS region in the development subclinical CVD in this sample enriched for T2DM. Further understanding the mechanisms underpinning these relationships may prove important in predicting and managing CVD complications in T2DM.

Selenium. Role of the essential metalloid in health

Selenium is an essential micronutrient in mammals, but is also recognized as toxic in excess. It is a non-metal with properties that are intermediate between the chalcogen elements sulfur and tellurium. Selenium exerts its biological functions through selenoproteins. Selenoproteins contain selenium in the form of the 21st amino acid, selenocysteine (Sec), which is an analog of cysteine with the sulfur-containing side chain replaced by a Se-containing side chain. Sec is encoded by the codon UGA, which is one of three termination codons for mRNA translation in non-selenoprotein genes. Recognition of the UGA codon as a Sec insertion site instead of stop requires a Sec insertion sequence (SECIS) element in selenoprotein mRNAs and a unique selenocysteyl-tRNA, both of which are recognized by specialized protein factors. Unlike the 20 standard amino acids, Sec is biosynthesized from serine on its tRNA. Twenty-five selenoproteins are encoded in the human genome. Most of the selenoprotein genes were discovered by bioinformatics approaches, searching for SECIS elements downstream of in-frame UGA codons. Sec has been described as having stronger nucleophilic and electrophilic properties than cysteine, and Sec is present in the catalytic site of all selenoenzymes. Most selenoproteins, whose functions are known, are involved in redox systems and signaling pathways. However, several selenoproteins are not well characterized in terms of their function. The selenium field has grown dramatically in the last few decades, and research on selenium biology is providing extensive new information regarding its importance for human health.

The Ups and Downs of Insulin Resistance and Type 2 Diabetes: Lessons from Genomic Analyses in Humans

We are in the midst of a worldwide epidemic of type 2 diabetes (T2D) and obesity. Understanding the mechanisms underlying these diseases is critical if we are to halt their progression and ultimately prevent their development. The advent and widespread implementation of microarray technology has allowed analysis of small samples of human skeletal muscle, adipose, liver, pancreas and blood. While patterns differ in each tissue, several dominant themes have emerged from these studies, including altered expression of genes indicating increased inflammation and altered lipid and mitochondrial oxidative metabolism and insulin signaling in patients with T2D, and in some cases, in those at risk for disease. Unraveling which changes in gene expression are primary, and which are secondary to an insulin resistant or diabetes metabolic milieu remains a scientific challenge but we are one step closer.

Differential Expression ESTs Associated with Fluorosis in Rats Liver

The fluoride has volcanic activity and abundantly exists in environment combining with other elements as fluoride compounds. Recent researches indicated that the molecular mechanisms of intracellular fluoride toxicity were very complex. However, the molecular mechanisms underlying the effects on gene expression of chronic fluoride-induced damage is unknown, especially the detailed regulatory process of mitochondria. In the present study, we screened the differential expression ESTs associated with fluorosis by DDRT-PCR in rat liver. We gained 8 genes, 3 new ESTs, and 1 unknown function sequence and firstly demonstrated that microsomal glutathione S-transferase 1 (MGST1), ATP synthase H⁺ transporting mitochondrial F₀ complex subunit C1, selenoprotein S, mitochondrial IF1 protein, and mitochondrial succinyl-CoA synthetase alpha subunit were participated in mitochondria metabolism, functional and structural damage process caused by chronic fluorosis. This information will be very helpful for understanding the molecular mechanisms of fluorosis.