Selenoprotein S Is Highly Expressed in the Blood Vessels and Prevents Vascular Smooth Muscle Cells From Apoptosis

Protective effect of soluble protein hydrolysate against H2O2‑induced intestinal injury: An interventional study

The present study aimed to investigate whether soluble protein hydrolysate (SPH) protects against intestinal oxidative stress injury. An in vitro lactate dehydrogenase assay was used to assess the cytotoxicity and protective effect of SPH. For in vivo assessment, friend virus B NIH Jackson mouse pups aged 21 days were administered with 5% w/v soluble protein hydrolysate (SPH) through drinking water for 14 days and then luminally injected with 0.3% or 0.6% H2O2. Thereafter, the fecal samples of mice were collected, and the mice were sacrificed. Intestinal epithelial injury was assessed, and the expressions of 84 oxidative stress‑related genes in intestinal tissues was determined. SPH prophylactically protected against H2O2‑induced oxidative stress injury in human intestinal epithelial cells. An animal model of oxidative stress‑induced intestinal injury was established using 0.3 and 0.6% H2O2. SPH treatment reduced oxidative stress (0.3% H2O2)‑induced gut injury in mice. As no accelerated body growth was observed in SPH‑treated mice, it was hypothesized that the underlying protective mechanism of SPH is not related to nutrient oversupply. Treatment with SPH upregulated five oxidative protective genes that were not consistent between the sexes. Some antioxidative genes, including ferritin heavy polypeptide‑1 (Fth1), heme oxygenase‑1 (Hmox1), NAD(P)H dehydrogenase quinone 1 (Nqo1) and superoxide dismutase 1 (Sod1), were commonly upregulated in both male and female mice. Overall, an antioxidative protective effect was observed following SPH treatment, which may be attributed to the upregulation of genes that protect against oxidative damage. The findings of the present study highlight the promising potential of SPH as a functional food for alleviating intestinal oxidative stress injury.

Genetically Elevated Selenoprotein S Levels and Risk of Stroke: A Two-Sample Mendelian Randomization Analysis

Selenoprotein S (SELENOS), one of the carrier proteins of dietary selenium (Se), is a key regulator of inflammation, oxidative stress, and endoplasmic reticulum (ER) stress, all of which are implicated in the pathogenesis of stroke. However, the causality between SELENOS and stroke risk remains poorly understood. This study aimed to explore the association between genetically determined plasma SELENOS levels and the risk of all-cause stroke, ischemic stroke, and intracerebral hemorrhage (ICH) using a two-sample Mendelian randomization (MR) approach. We analyzed data from three large-scale Genome-Wide Association Study (GWAS) meta-analyses of individuals of European descent. The fixed-effect inverse-variance weighted (IVW) model analysis revealed that genetically elevated SELENOS levels were associated with an increased risk of all-cause stroke, ischemic stroke, and ICH. Sensitivity analyses showed no evidence of pleiotropy or heterogeneity, and leave-one-out analyses confirmed the robustness of our results. Here, we show that elevated plasma SELENOS levels are causally linked to increased stroke risk. Although the effect sizes were modest, these findings suggest SELENOS may play a role in stroke pathogenesis, emphasizing the need for further mechanistic and functional studies. Finally, our findings shed light on the importance of tailored Se intake management in the context of stroke prevention.

The role and mechanism of various trace elements in atherosclerosis

Atherosclerosis is a slow and complex disease that involves various factors, including lipid metabolism disorders, oxygen-free radical production, inflammatory cell infiltration, platelet adhesion and aggregation, and local thrombosis. Trace elements play a crucial role in human health. Many trace elements, especially metallic ones, not only maintain the normal functions of organs but also participate in basic metabolic processes. The latest studies have revealed a close correlation between trace elements and the occurrence and progression of atherosclerosis. The imbalance of these trace elements can induce atherosclerosis or accelerate its progression through various mechanisms, which poses a significant threat to human health. Therefore, exploring the specific mechanism of trace elements on atherosclerosis is highly significant. In this review, we summarized the roles and mechanisms of iron, copper, zinc, magnesium, and selenium homeostasis and imbalance in atherosclerosis development, in order to identify novel targets and therapeutic strategies for treating atherosclerosis.

Low expression of selenoprotein S induces oxidative damage in cartilages

Low levels of the indispensable trace element selenium (Se) can cause oxidative stress and disrupt environmental homeostasis in humans and animals. Selenoprotein S (Selenos), of which Se is a key component, is a member of the selenoprotein family involved in various biological processes. This study aimed to investigate whether low-level SELENOS gene expression can induce oxidative stress and decrease the antioxidative capacity of chondrocytes. Compared with control cells, SELENOS-knockdown ATDC5 cells showed substantially higher dihydroethidium, reactive oxygen species and malondialdehyde levels, and lower superoxide dismutase (SOD) expression. Knockout of the gene in C57BL/6 mice increased the 8-hydroxy-2-deoxyguanosine level considerably and decreased SOD expression in cartilages relative to the levels in wild-type mice. The results showed that the increased nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling mediated by low-level SELENOS expression was involved in oxidative damage. The proliferative zone of the cartilage growth plate of SELENOS-knockout mice was shortened, suggesting cartilage differentiation dysfunction. In conclusion, this study confirmed that low-level Selenos expression plays a role in oxidative stress in cartilages.

Selenium Deficiency Promotes Dilatation of the Aorta by Increasing Expression and Activity of Vascular Smooth Muscle Cell Derived Matrix Metalloproteinase-2

OBJECTIVE

Selenium (Se) is a key part of the body's oxidation defence system. However, it is unclear whether Se affects the development of aortic aneurysm (AA). An animal experiment was conducted to clarify the role of Se in AA development.

METHODS

C57BL/6N male mice were fed with a Se deficient (Se-D, < 0.05 mg/kg), Se adequate (Se-A, 0.2 mg/kg), or Se supplemented (Se-S, 1 mg/kg) diet for 8 weeks. Subsequently, an AA murine model (Se-D, n = 11; Se-A, n = 12; Se-S, n = 15) was established using angiotensin II (Ang II, 1 mg/kg/min) for four weeks plus β-aminopropionitrile (BAPN, 1 mg/mL) for the first two weeks. Saline replaced Ang II, and BAPN was removed during the modelling process for sham mice (Se-A, n = 9). To determine whether Se deficiency promoted aortic dilation via matrix metalloproteinase-2 (MMP-2), the non-specific MMP inhibitor doxycycline (Dox, 100 mg/kg/day) was given to Se-D AA mice (n = 7) for two weeks.

RESULTS

The maximum aortic diameter in Se-D AA model mice was significantly increased compared with Se-A AA model mice. MMP-2 expression and activity in the aortic media of Se-D AA model mice was significantly increased compared with Se-A AA model mice. A large number of vascular smooth muscle cells (VSMCs) were found aggregating in the media of the non-dilated aorta of Se-D AA model mice, which was completely inhibited by Dox. The percentage of VSMCs in aortic media of Se-D AA model mice was significantly higher than in Se-A AA model mice. The maximum aortic diameter and occurrence rate of AA in Se-D AA model mice with Dox were significantly reduced compared with Se-D AA model mice.

CONCLUSION

Se deficiency promoted dilatation of the aorta in AA model mice by increasing expression and activity of VSMC derived MMP-2, causing abnormal aggregation and proliferation of VSMCs in aortic media.

The mechanism of selenium regulating the permeability of vascular endothelial cells through selenoprotein O

Vascular diseases, a leading cause of death in human, are strongly associated with pathological damage to blood vessels. The selenoprotein (Sel) have been reported to play important roles in vascular disease. However, the role of SelO in vascular disease has not been conclusively investigated. The present experiment was to investigate the regulatory mechanism of the effect of SelO on the permeability of vascular endothelial. The H.E staining, FITC-Dextran staining, Dil-AC-LDL staining and FITC-WGA staining showed that vascular structure was damaged, and intercellular junctions were disrupted with selenium (Se)-deficient. Immunohistochemistry, qPCR and Western blot revealed decreased expression of the adhesion plaque proteins vinculin, talin and paxillin, decreased expression of the vascular connectivity effector molecules connexin, claudin-1 and E-cadherin and increased expression of JAM-A and N-cadherin, as well as decreased expression of the ZO-1 signaling pathways ZO-1, Rock, rhoGEF, cingulin and MLC-2. In a screening of 24 Sel present in mice, SelO showed the most pronounced changes in vascular tissues, and a possible association between SelO and vascular intercellular junction effectors was determined using IBM SPSS Statistics 25. Silencing of SelO, vascular endothelial intercellular junction adverse effects present. The regulatory relationship between SelO and vascular endothelial intercellular junctions was determined. The results showed that Se deficiency lead to increased vascular endothelial permeability and vascular tissue damage by decreasing SelO expression, suggesting a possible role for SelO in regulating vascular endothelial permeability.

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.

Selenoprotein deficiency disorder predisposes to aortic aneurysm formation

Aortic aneurysms, which may dissect or rupture acutely and be lethal, can be a part of multisystem disorders that have a heritable basis. We report four patients with deficiency of selenocysteine-containing proteins due to selenocysteine Insertion Sequence Binding Protein 2 (SECISBP2) mutations who show early-onset, progressive, aneurysmal dilatation of the ascending aorta due to cystic medial necrosis. Zebrafish and male mice with global or vascular smooth muscle cell (VSMC)-targeted disruption of Secisbp2 respectively show similar aortopathy. Aortas from patients and animal models exhibit raised cellular reactive oxygen species, oxidative DNA damage and VSMC apoptosis. Antioxidant exposure or chelation of iron prevents oxidative damage in patient's cells and aortopathy in the zebrafish model. Our observations suggest a key role for oxidative stress and cell death, including via ferroptosis, in mediating aortic degeneration.

The Role of Selenium in Atherosclerosis Development, Progression, Prevention and Treatment

Selenium is an essential trace element that is essential for various metabolic processes, protection from oxidative stress and proper functioning of the cardiovascular system. Se deficiency has long been associated with multiple cardiovascular diseases, including endemic Keshan's disease, common heart failure, coronary heart disease, myocardial infarction and atherosclerosis. Through selenoenzymes and selenoproteins, Se is involved in numerous crucial processes, such as redox homeostasis regulation, oxidative stress, calcium flux and thyroid hormone metabolism; an unbalanced Se supply may disrupt these processes. In this review, we focus on the importance of Se in cardiovascular health and provide updated information on the role of Se in specific processes involved in the development and pathogenesis of atherosclerosis (oxidative stress, inflammation, endothelial dysfunction, vascular calcification and vascular cell apoptosis). We also discuss recent randomised trials investigating Se supplementation as a potential therapeutic and preventive agent for atherosclerosis treatment.

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.

Emerging roles of selenium on metabolism and type 2 diabetes

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

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.

Maternal Organic Selenium Supplementation Relieves Intestinal Endoplasmic Reticulum Stress in Piglets by Enhancing the Expression of Glutathione Peroxidase 4 and Selenoprotein S

Endoplasmic reticulum (ER) stress, which can be induced by reactive oxygen species (ROS) and multiple factors, is associated with numerous intestinal diseases. The organic selenium source 2-hydroxy-4-methylselenobutanoic acid (HMSeBA), has been proved to decrease intestinal inflammation and autophagy by improving the expression of selenoproteins. However, it remains unclear whether HMSeBA could alleviate intestinal ER stress by decreasing excessive production of ROS products. This study was conducted to investigate the effect of maternal HMSeBA supplementation on the regulation of intestinal ER stress of their offspring and the regulatory mechanism. Sows were supplemented with HMSeBA during gestation and jejunal epithelial (IPEC-J2) cells were treatment with HMSeBA. Results showed that maternal HMSeBA supplementation significantly upregulated mRNA level of selenoprotein S (SELS) in the jejunum of newborn and weaned piglets compared with the control group, while decreased the gene expression and protein abundance of ER stress markers in the jejunum of LPS challenged weaned piglets. In addition, HMSeBA treatment significantly increased the expression of glutathione peroxidase 4 (GPX4) and SELS, while decreased ROS level and the expression of ER stress markers induced by hydrogen peroxide (H₂O₂) in IPEC-J2 cells. Furthermore, knockdown of GPX4 did not enhance the ERS signal induced by H₂O₂, but the lack of GPX4 would cause further deterioration of ER stress signal in the absence of SELS. In conclusion, maternal HMSeBA supplementation might alleviate ROS induced intestinal ER stress by improving the expression of SELS and GPX4 in their offspring. Thus, maternal HMSeBA supplementation might be benefit for the intestinal health of their offspring.

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.

Molecular characterization and tissue distribution of nine selenoprotein genes in grass carp Ctenopharyngodon idella and their mRNA expressions in response to high-fat diet and high-fat diet supplemented with selenium

Our previous study has found that selenium (Se) can alleviate lipid accumulation caused by high-fat diet (HFD) in fish. This study aims to explore the selenoproteins (SePs) in grass carp Ctenopharyngodon idella by characterizing cDNAs of nine SeP genes (SELENOF, SELENOM, SELENOS, SELENOP1, SELENOP2, SELENOE, SELENOL, SELENOU1a and SELENOU1b) and measuring their transcriptional activity in response to HFD and HFD supplemented with 0.3 mg/Kg and 0.6 mg/Kg of Se (HSe 0.3 and HSe 0.6). Firstly, the nine SeP genes in grass carp encoded proteins with conserved functional protein regions in fish and other vertebrates. Secondly, the nine SeP genes except SELENOS showed high expression levels in the hepatopancreas, but in the adipose tissue, only SELENOS, SELENOE and SELENOU1b showed high expression levels. Further, HFD significantly up-regulated the expressions of SELENOF and SELENOS in the hepatopancreas and SELENOM in the adipose tissue of grass carp (P < 0.05), but significantly down-regulated the expressions of SELENOU1b in the hepatopancreas, SELENOP2, SELENOE, SELENOL and SELENOU1a in the adipose tissue and SELENOM in the muscle of grass carp (P < 0.05). In addition, for the hepatopancreas, the expressions of SELENOS in the HSe 0.3 group and SELENOF, SELENOM and SELENOP2 in the HSe 0.6 group significantly decreased compared with the HFD group (P < 0.05). For the adipose tissue, the expressions of SELENOF, SELENOP2, SELENOL, SELENOU1a and SELENOU1b in the HSe 0.3 group and SELENOP2, SELENOE, SELENOU1a and SELENOU1b in the HSe 0.6 group significantly increased compared with the HFD group (P < 0.05). In summary, the transcriptional activities of the nine SeP genes were regulated by the HFD and HFD supplemented with Se, indicating the potential role of these genes in the Se regulated lipid metabolism processes in grass carp, which is worthy of in-depth study.

Selenium, a Micronutrient That Modulates Cardiovascular Health via Redox Enzymology

Selenium (Se) is a trace nutrient that promotes human health through its incorporation into selenoproteins in the form of the redox-active amino acid selenocysteine (Sec). There are 25 selenoproteins in humans, and many of them play essential roles in the protection against oxidative stress. Selenoproteins, such as glutathione peroxidase and thioredoxin reductase, play an important role in the reduction of hydrogen and lipid hydroperoxides, and regulate the redox status of Cys in proteins. Emerging evidence suggests a role for endoplasmic reticulum selenoproteins, such as selenoproteins K, S, and T, in mediating redox homeostasis, protein modifications, and endoplasmic reticulum stress. Selenoprotein P, which functions as a carrier of Se to tissues, also participates in regulating cellular reactive oxygen species. Cellular reactive oxygen species are essential for regulating cell growth and proliferation, protein folding, and normal mitochondrial function, but their excess causes cell damage and mitochondrial dysfunction, and promotes inflammatory responses. Experimental evidence indicates a role for individual selenoproteins in cardiovascular diseases, primarily by modulating the damaging effects of reactive oxygen species. This review examines the roles that selenoproteins play in regulating vascular and cardiac function in health and disease, highlighting their antioxidant and redox actions in these processes.

Disparity of selenourea and selenocystine on methaemoglobinemia in non-diabetics and diabetics

Organoselenium drugs like selenourea (SeU) and selenocystine (SeC) are found to exhibit several medicinal properties and have reported roles in the field of cancer prevention. However, studies related to their interactions with the major erythroid protein, haemoglobin (HbA) are still in dearth despite being of prime importance. In view of this, it was considered essential to investigate the interaction of these two anticancer drugs with Hb. Both the drugs showed significant changes in absorption spectra of Hb at wavelength of maximum absorption (λmax) 630 nm. SeU itself had no effect on the absorbance value at 630 nm with respect to time even with 400 µM concentration. However, it was rapidly converted to nanoselenium in presence of nitrite and there was an increase in the absorbance rate at 630 nm from 3.39 × 10-3 min-1 (without nitrite) to 8.94 × 10-3 min-1 in presence of nitrite (200 µM) owing to the generation of reactive oxygen species in the medium. Although the generation and increase in peak intensity at 630 nm in Hb generally indicates the formation and rise in the levels of methaemoglobin (metHb), nanoselenium was observed to follow a different path. Instead of causing oxidation of Fe2+ to Fe3+ responsible for metHb formation, nanoselenium was found to interact with the protein part, thereby causing changes in its secondary structure which is reflected in the increasing absorbance at 630 nm. SeC, however, showed a different effect. It was shown to act as a novel agent to reduce nitrite-induced metHb formation in a dose-dependent manner. The efficiency of SeC was again found to be less in diabetic blood samples as compared to the non-diabetic ones. For similar ratio of metHb to SeC (1:8), % reduction of metHb was found to be 27.46 ± 0.82 and 16.1 ± 2.4 for non-diabetic and diabetic samples, respectively, with a two tailed P-value much <0.05 which implies that the data are highly significant.

Selenium and viral infection: are there lessons for COVID-19?

Se is a micronutrient essential for human health. Sub-optimal Se status is common, occurring in a significant proportion of the population across the world including parts of Europe and China. Human and animal studies have shown that Se status is a key determinant of the host response to viral infections. In this review, we address the question whether Se intake is a factor in determining the severity of response to coronavirus disease 2019 (COVID-19). Emphasis is placed on epidemiological and animal studies which suggest that Se affects host response to RNA viruses and on the molecular mechanisms by which Se and selenoproteins modulate the inter-linked redox homeostasis, stress response and inflammatory response. Together these studies indicate that Se status is an important factor in determining the host response to viral infections. Therefore, we conclude that Se status is likely to influence human response to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and that Se status is one (of several) risk factors which may impact on the outcome of SARS-CoV-2 infection, particularly in populations where Se intake is sub-optimal or low. We suggest the use of appropriate markers to assess the Se status of COVID-19 patients and possible supplementation may be beneficial in limiting the severity of symptoms, especially in countries where Se status is regarded as sub-optimal.

Role of Endoplasmic Reticulum Stress in Atherosclerosis and Its Potential as a Therapeutic Target

Endoplasmic reticulum (ER) stress is closely associated with atherosclerosis and related cardiovascular diseases (CVDs). It occurs due to various pathological factors that interfere with ER homeostasis, resulting in the accumulation of unfolded or misfolded proteins in the ER lumen, thereby causing ER dysfunction. Here, we discuss the role of ER stress in different types of cells in atherosclerotic lesions. This discussion includes the activation of apoptotic and inflammatory pathways induced by prolonged ER stress, especially in advanced lesional macrophages and endothelial cells (ECs), as well as common atherosclerosis-related ER stressors in different lesional cells, which all contribute to the clinical progression of atherosclerosis. In view of the important role of ER stress and the unfolded protein response (UPR) signaling pathways in atherosclerosis and CVDs, targeting these processes to reduce ER stress may be a novel therapeutic strategy.

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.

Role of Selenoproteins in Redox Regulation of Signaling and the Antioxidant System: A Review

Selenium is a vital trace element present as selenocysteine (Sec) in proteins that are, thus, known as selenoproteins. Humans have 25 selenoproteins, most of which are functionally characterized as oxidoreductases, where the Sec residue plays a catalytic role in redox regulation and antioxidant activity. Glutathione peroxidase plays a pivotal role in scavenging and inactivating hydrogen and lipid peroxides, whereas thioredoxin reductase reduces oxidized thioredoxins as well as non-disulfide substrates, such as lipid hydroperoxides and hydrogen peroxide. Selenoprotein R protects the cell against oxidative damage by reducing methionine-R-sulfoxide back to methionine. Selenoprotein O regulates redox homeostasis with catalytic activity of protein AMPylation. Moreover, endoplasmic reticulum (ER) membrane selenoproteins (SelI, K, N, S, and Sel15) are involved in ER membrane stress regulation. Selenoproteins containing the CXXU motif (SelH, M, T, V, and W) are putative oxidoreductases that participate in various cellular processes depending on redox regulation. Herein, we review the recent studies on the role of selenoproteins in redox regulation and their physiological functions in humans, as well as their role in various diseases.

Impaired exercise performance is independent of inflammation and cellular stress following genetic reduction or deletion of selenoprotein S

Selenoprotein S (Seps1) can be protective against oxidative, endoplasmic reticulum (ER), and inflammatory stress. Seps1 global knockout mice are less active, possess compromised fast muscle ex vivo strength, and, depending on context, heightened inflammation. Oxidative, ER, and inflammatory stress modulates contractile function; hence, our aim was to investigate the effects of Seps1 gene dose on exercise performance. Seps1^-/- knockout, Seps1^-/+ heterozygous, and wild-type mice were randomized to 3 days of incremental, high-intensity treadmill running or a sedentary control group. On day 4, the in situ contractile function of fast tibialis anterior (TA) muscles was determined. Seps1 reduction or deletion compromised exercise capacity, decreasing distance run. TA strength was also reduced. In sedentary Seps1^-/- knockout mice, TA fatigability was greater than wild-type mice, and this was ameliorated with exercise. Whereas, in Seps1^+/- heterozygous mice, exercise compromised TA endurance. These impairments in exercise capacity and TA contractile function were not associated with increased inflammation or a dysregulated redox state. Seps1 is highly expressed in muscle fibers and blood vessels. Interestingly, Nos1 and Vegfa mRNA transcripts were decreased in TA muscles from Seps1^-/- knockout and Seps1^-/+ heterozygous mice. Impaired exercise performance with Seps1 reduction or deletion cannot be attributed to heightened cellular stress, but it may potentially be mediated, in part, by the effects of Seps1 on the microvasculature.

Selenium nanoparticles alleviate hyperlipidemia and vascular injury in ApoE-deficient mice by regulating cholesterol metabolism and reducing oxidative stress

Atherosclerosis and related cardiovascular diseases represent the greatest threats to human health worldwide. This study was designed to investigate the anti-atherosclerotic activity of selenium nanoparticles (SeNPs) in apolipoprotein E deficient (ApoE^-/-) mice fed a high-cholesterol, high-fat diet. The results demonstrated that animals either treated with SeNPs (50 μg Se per kg per day) or with atorvastatin (10 mg per kg per day) alone showed significant relief of vascular injury after 8 weeks of treatment. SeNPs could obviously decrease the level of serum total cholesterol, triglyceride and low-density lipoprotein cholesterol, whereas increase serum high-density lipoprotein cholesterol. At the same time, SeNPs regulated the expression levels of key genes associated with cholesterol metabolism in the liver. Furthermore, SeNPs significantly reduced the lipid peroxidation level, but increased the NO level and the activities of glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase in the serum and liver. SeNPs also increased the expression levels of antioxidant selenoenzymes or selenoproteins in the liver. In addition, SeNPs could alleviate H₂O₂-induced cytotoxicity and oxidative stress by upregulating the activities of SOD and GPx in endothelial cells cultured in vitro. These results suggested that SeNPs could significantly alleviate hyperlipidemia and vascular injury in ApoE^-/- mice, possibly by regulating cholesterol metabolism and reducing oxidative stress through antioxidant selenoenzymes/selenoproteins. SeNPs might be a potential candidate for the prevention of atherosclerosis.

Selenoprotein S protects against high glucose-induced vascular endothelial apoptosis through the PKCβII/JNK/Bcl-2 pathway

Vascular endothelial apoptosis is closely associated with the pathogenesis and progression of diabetic macrovascular diseases. Selenoprotein S (SelS) participates in the protection of vascular endothelial and smooth muscle cells from oxidative and endoplasmic reticulum stress-induced injury. However, whether SelS can protect vascular endothelium from high glucose (HG)-induced apoptosis and the underlying mechanism remains unclear. The present study preliminarily analyzed aortic endothelial apoptosis and SelS expression in diabetic rats in vivo and the effects of HG on human umbilical vein endothelial cell (HUVEC) apoptosis and SelS expression in vitro. Subsequently, SelS expression was up- or downregulated in HUVECs using the pcDNA3.1-SelS recombinant plasmid and SelS-specific small interfering RNAs, and the effects of high/low SelS expression on HG-induced HUVEC apoptosis and a possible molecular mechanism were analyzed. As expected, HG induced vascular endothelial apoptosis and upregulated endothelial SelS expression in vivo and in vitro. SelS overexpression in HUVECs suppressed HG-induced increase in apoptosis and cleaved caspase3 level, accompanied by reduced protein kinase CβII (PKCβII), c-JUN N-terminal kinase (JNK), and B-cell lymphoma/leukemia-2 (Bcl-2) phosphorylation. In contrast, inhibiting SelS expression in HUVECs further aggravated HG-induced increase in apoptosis and cleaved caspase3 level, which was accompanied by increased PKCβII, JNK, and Bcl-2 phosphorylation. Pretreatment with PKC activators blocked the protective effects of SelS and increased the apoptosis and cleaved caspase3 level in HUVECs. In summary, SelS protects vascular endothelium from HG-induced apoptosis, and this was achieved through the inhibition of PKCβII/JNK/Bcl-2 pathway to eventually inhibit caspase3 activation. SelS may be a promising target for the prevention and treatment of diabetic macrovascular complications.

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.

Selenoprotein S protects against adipocyte death through mediation of the IRE1α-sXBP1 pathway

As the most conserved branch of the unfolded protein response (UPR), the inositol-requiring enzyme 1a (IRE1a)/X-box binding protein 1 (XBP1) pathway plays crucial roles in cell survival and cell death by upregulating UPR-associated genes involved in protein entry into the endoplasmic reticulum (ER) and ER-associated degradation (ERAD). Selenoprotein S (SelS) is localized to the ER membrane and involved in ERAD. Although SelS plays an important role in restoring ER stress, the SelS-dependent protective mechanisms against cell death remain unclear. Here, using an inducible SelS knockdown (KD) 3T3-L1 cell model, we showed that SelS KD resulted adipocyte death, which was associated with imbalance of the Bcl-2 family members. Furthermore, SelS KD decreased spliced XBP1 (sXBP1), increased IRE1α and p-JNK, suggesting a role of SelS in the modulation of the IRE1α-sXBP1 pathway. Moreover, adipocyte death induced by SelS suppression can be inhibited by overexpression of sXBP1. Thus, it is proposed that SelS promotes cell survival through the IRE1α-XBP1 signaling pathway.

Selenium-Dependent Antioxidant Enzymes: Actions and Properties of Selenoproteins

Unlike other essential trace elements that interact with proteins in the form of cofactors, selenium (Se) becomes co-translationally incorporated into the polypeptide chain as part of 21st naturally occurring amino acid, selenocysteine (Sec), encoded by the UGA codon. Any protein that includes Sec in its polypeptide chain is defined as selenoprotein. Members of the selenoproteins family exert various functions and their synthesis depends on specific cofactors and on dietary Se. The Se intake in productive animals such as chickens affect nutrient utilization, production performances, antioxidative status and responses of the immune system. Although several functions of selenoproteins are unknown, many disorders are related to alterations in selenoprotein expression or activity. Selenium insufficiency and polymorphisms or mutations in selenoproteins' genes and synthesis cofactors are involved in the pathophysiology of many diseases, including cardiovascular disorders, immune dysfunctions, cancer, muscle and bone disorders, endocrine functions and neurological disorders. Finally, heavy metal poisoning decreases mRNA levels of selenoproteins and increases mRNA levels of inflammatory factors, underlying the antagonistic effect of Se. This review is an update on Se dependent antioxidant enzymes, presenting the current state of the art and is focusing on results obtained mainly in chicken.

Selenoprotein S inhibits inflammation-induced vascular smooth muscle cell calcification

Vascular calcification is a prominent feature of many diseases including atherosclerotic cardiovascular disease (CVD), leading to high morbidity and mortality rates. A significant association of selenoprotein S (SelS) gene polymorphism with atherosclerotic CVD has been reported in epidemiologic studies, but the underlying mechanism is far from clear. To investigate the role of SelS in inflammation-induced vascular calcification, osteoblastic differentiation and calcification of vascular smooth muscle cells (VSMCs) induced by lipopolysaccharide (LPS) or tumor necrosis factor (TNF)-α were compared between the cells with and without SelS knockdown. LPS or TNF-α induced osteoblastic differentiation and calcification of VSMCs, as showed by the increases of runt-related transcription factor 2 (Runx2) protein levels, Runx2 and type I collagen mRNA levels, alkaline phosphatase activity, and calcium deposition content. These changes were aggravated when SelS was knocked down by small interfering RNA. Moreover, LPS activated both classical and alternative pathways of nuclear factor-κB (NF-κB) signaling in calcifying VSMCs, which were further enhanced under SelS knockdown condition. SelS knockdown also exacerbated LPS-induced increases of proinflammatory cytokines TNF-α and interleukin-6 expression, as well as increases of endoplasmic reticulum (ER) stress markers glucose-regulated protein 78 and inositol-requiring enzyme 1α expression in calcifying VSMCs. In conclusion, the present study suggested that SelS might inhibit inflammation-induced VSMC calcification probably by suppressing activation of NF-κB signaling pathways and ER stress. Our findings provide new understanding of the role of SelS in vascular calcification, which will be potentially beneficial to the prevention of atherosclerotic CVD.

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.

Selenoprotein S Attenuates Tumor Necrosis Factor-α-Induced Dysfunction in Endothelial Cells

Endothelial dysfunction, partly induced by inflammatory mediators, is known to initiate and promote several cardiovascular diseases. Selenoprotein S (SelS) has been identified in endothelial cells and is associated with inflammation; however, its function in inflammation-induced endothelial dysfunction has not been described. We first demonstrated that the upregulation of SelS enhances the levels of nitric oxide and endothelial nitric oxide synthase in tumor necrosis factor- (TNF-) α-treated human umbilical vein endothelial cells (HUVECs). The levels of TNF-α-induced endothelin-1 and reactive oxygen species are also reduced by the upregulation of SelS. Furthermore, SelS overexpression blocks the TNF-α-induced adhesion of THP-1 cells to HUVECs and inhibits the increase in intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Moreover, SelS overexpression regulates TNF-α-induced inflammatory factors including interleukin-1β, interleukin-6, interleukin-8, and monocyte chemotactic protein-1 and attenuates the TNF-α-induced activation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways. Conversely, the knockdown of SelS with siRNA results in an enhancement of TNF-α-induced injury in HUVECs. These findings suggest that SelS protects endothelial cells against TNF-α-induced dysfunction by inhibiting the activation of p38 MAPK and NF-κB pathways and implicates it as a possible modulator of vascular inflammatory diseases.

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.

Overexpression of pig selenoprotein S blocks OTA-induced promotion of PCV2 replication by inhibiting oxidative stress and p38 phosphorylation in PK15 cells

Porcine circovirus type 2 (PCV2) is the primary cause of porcine circovirus disease, and ochratoxin A (OTA)-induced oxidative stress promotes PCV2 replication. In humans, selenoprotein S (SelS) has antioxidant ability, but it is unclear whether SelS affects viral infection. Here, we stably transfected PK15 cells with pig pCDNA3.1-SelS to overexpress SelS. Selenium (Se) at 2 or 4 μM and SelS overexpression blocked the OTA-induced increases of PCV2 DNA copy number and infected cell numbers. SelS overexpression also increased glutathione (GSH), NF-E2-related factor 2 (Nrf2) mRNA, and γ-glutamyl-cysteine synthetase mRNA levels; decreased reactive oxygen species (ROS) levels; and inhibited p38 phosphorylation in PCV2-infected PK15 cells, regardless of OTA treatment. Buthionine sulfoximine reversed all of the above SelS-induced changes. siRNA-mediated SelS knockdown decreased Nrf2 mRNA and GSH levels, increased ROS levels, and promoted PCV2 replication in OTA-treated PK15 cells. These data indicate that pig SelS blocks OTA-induced promotion of PCV2 replication by inhibiting the oxidative stress and p38 phosphorylation in PK15 cells.

Selenium in the prevention of atherosclerosis and its underlying mechanisms

Atherosclerosis and related cardiovascular diseases (CVDs) represent the greatest threats to human health worldwide. Selenium, an essential trace element, is incorporated into selenoproteins that play a crucial role in human health and disease. Although findings from a limited number of randomized trials have been inconsistent and cannot support a protective role of Se supplementation in CVDs, prospective observational studies have generally shown a significant inverse association between selenium or selenoprotein status and CVD risk. Furthermore, a benefit of selenium supplementation in the prevention of CVDs has been seen in population with low baseline selenium status. Evidence from animal studies shows consistent results that selenium and selenoproteins might prevent experimental atherosclerosis, which can be explained by the molecular and cellular effects of selenium observed both in animal models and cell cultures. Selenoproteins of particular relevance to atherosclerosis are glutathione peroxidases, thioredoxin reductase 1, selenoprotein P, selenoprotein S. The present review is focusing on the existing evidence that supports the concept that optimal selenium intake can prevent atherosclerosis. Its underlying mechanisms include inhibiting oxidative stress, modulating inflammation, suppressing endothelial dysfunction, and protecting vascular cells against apoptosis and calcification. However, the benefit of selenium supplementation in the prevention of atherosclerosis remains insufficiently documented so far. Future studies with regard to the effects of selenium supplementation on atherosclerosis should consider many factors, especially the baseline selenium status, the dose and forms of selenium supplementation, and the selenoprotein genotype. Additionally, much more studies are needed to confirm the roles of selenoproteins in atherosclerosis prevention and clarify the underlying mechanisms.

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.

Immune-Inflammatory Activation in Acute Coronary Syndromes: A Look into the Heart of Unstable Coronary Plaque

In the last twenty years, our comprehension of the molecular mechanisms involved in the formation, progression and complication of atherosclerotic plaque has advanced significantly and the main role of inflammation and immunity in this phenomenon is now largely accepted. Accumulating evidence highlight the crucial role of different inflammatory and immune cells, such as monocytes and T-lymphocytes, in the pathophysiology of atherosclerotic lesion, particularly in contributing to its complications, such as rupture or ulceration. According to the new terminology, "vulnerable plaque" identifies an inflamed atherosclerotic lesion that is particularly prone to rupture. Once disrupted, prothrombotic material is exposed to the flowing blood, thus activating coagulation cascade and platelet aggregation, ultimately leading to acute thrombus formation within the coronary vessel. To date this is the key event underlying the clinical manifestations of acute coronary syndromes (ACS). The degree of vessel occlusion (complete vs. incomplete) and the time of blood flow cessation will define the severity of clinical picture. This phenomenon seems to be the final effect of a complex interaction between different local and systemic factors, involving the degree of inflammation, type of cells infiltration and the rheological characteristics of blood flow at the site of plaque rupture, thrombogenic substrates within the atherosclerotic lesion and different soluble mediators, already present or acutely released in the circulating blood. This article will review currently available data on the pathophysiology of ACS, emphasizing the immunological and inflammatory aspects of vulnerable plaque. We may postulate that intraplaque antigens and local microenvironment will define the immune-inflammatory response and cells phenotype, thus determining the severity of clinical manifestations.

The source of circulating selenoprotein S and its association with type 2 diabetes mellitus and atherosclerosis: a preliminary study

Background

Selenoprotein S (SelS) is a transmembrane protein that is expressed in the liver, skeletal muscle, adipose tissue, pancreatic islets, kidney, and blood vessels. In addition to its transmembrane localization, SelS is also secreted from hepatoma HepG2 cells (but not L6 skeletal muscle cells, 3T3-L1 adipocytes, Min6 pancreatic β cells and human embryonic kidney 293 cells) and has been detected in the serum of some human subjects, with a detection rate of 31.1 %. These findings prove that serum SelS is secreted by hepatocytes. However, whether vascularly expressed SelS can be secreted has not been reported. Transmembrane SelS has been suggested to play different roles in the pathogenesis and progression of diabetes mellitus (DM) and atherosclerosis (AS), but the association of secreted SelS with DM and macroangiopathy remains unclear.

Research design and methods

Supernatants were collected from human umbilical vein endothelial cells (HUVECs), human aortic vascular smooth muscle cells (HA/VSMCs) and human hepatoma HepG2 cells that were untransfected or transfected with the indicated plasmid and concentrated for western blotting. Serum samples were collected from 158 human subjects with or without type 2 DM (T2DM) and/or AS. Serum SelS levels were measured using an enzyme-linked immunosorbent assay.

Results

Secreted SelS was only detected in the supernatants of hepatoma HepG2 cells. The SelS detection rate among the 158 human serum samples was 100 %, and the average SelS level was 64.81 ng/dl. The serum SelS level in the isolated DM subjects was lower than the level in the healthy control subjects (52.66 ± 20.53 vs 70.40 ± 21.38 ng/dl). The serum SelS levels in the DM complicated with SAS subjects (67.73 ± 21.41 ng/dl) and AS subjects (71.69 ± 27.00 ng/dl) were significantly increased compared with the serum SelS level in the isolated DM subjects. There was a positive interaction effect between T2DM and AS on the serum SelS level (P = 0.002). Spearman correlation analysis showed that the serum SelS level was negatively correlated with fasting plasma glucose.

Conclusions

Vascular endothelial and vascular smooth muscle cells could not secrete SelS. Serum SelS was primarily secreted by hepatocytes. SelS was universally detected in human serum samples, and the serum SelS level was associated with T2DM and its macrovascular complications. Thus, regulating liver and serum SelS levels might become a new strategy for the prevention and treatment of DM and its macrovascular complications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12933-016-0388-3) contains supplementary material, which is available to authorized users.