Glutathione Peroxidase 3 Serum Levels and GPX3 Gene Polymorphisms in Subjects with Metabolic Syndrome

Insights into the Role of Glutathione Peroxidase 3 in Non-Neoplastic Diseases

Reactive oxygen species (ROSs) are byproducts of normal cellular metabolism and play pivotal roles in various physiological processes. Disruptions in the balance between ROS levels and the body's antioxidant defenses can lead to the development of numerous diseases. Glutathione peroxidase 3 (GPX3), a key component of the body's antioxidant system, is an oxidoreductase enzyme. GPX3 mitigates oxidative damage by catalyzing the conversion of hydrogen peroxide into water. Beyond its antioxidant function, GPX3 is vital in regulating metabolism, modulating cell growth, inducing apoptosis and facilitating signal transduction. It also serves as a significant tumor suppressor in various cancers. Recent studies have revealed aberrant expression of GPX3 in several non-neoplastic diseases, associating it with multiple pathological processes. This review synthesizes the current understanding of GPX3 expression and regulation, highlighting its extensive roles in noncancerous diseases. Additionally, this paper evaluates the potential of GPX3 as a diagnostic biomarker and explores emerging therapeutic strategies targeting this enzyme, offering potential avenues for future clinical treatment of non-neoplastic conditions.

Current Understanding of Human Polymorphism in Selenoprotein Genes: A Review of Its Significance as a Risk Biomarker

Selenium has been proven to influence several biological functions, showing to be an essential micronutrient. The functional studies demonstrated the benefits of a balanced selenium diet and how its deficiency is associated with diverse diseases, especially cancer and viral diseases. Selenium is an antioxidant, protecting the cells from damage, enhancing the immune system response, preventing cardiovascular diseases, and decreasing inflammation. Selenium can be found in its inorganic and organic forms, and its main form in the cells is the selenocysteine incorporated into selenoproteins. Twenty-five selenoproteins are currently known in the human genome: glutathione peroxidases, iodothyronine deiodinases, thioredoxin reductases, selenophosphate synthetase, and other selenoproteins. These proteins lead to the transport of selenium in the tissues, protect against oxidative damage, contribute to the stress of the endoplasmic reticulum, and control inflammation. Due to these functions, there has been growing interest in the influence of polymorphisms in selenoproteins in the last two decades. Selenoproteins' gene polymorphisms may influence protein structure and selenium concentration in plasma and its absorption and even impact the development and progression of certain diseases. This review aims to elucidate the role of selenoproteins and understand how their gene polymorphisms can influence the balance of physiological conditions. In this polymorphism review, we focused on the PubMed database, with only articles published in English between 2003 and 2023. The keywords used were "selenoprotein" and "polymorphism". Articles that did not approach the theme subject were excluded. Selenium and selenoproteins still have a long way to go in molecular studies, and several works demonstrated the importance of their polymorphisms as a risk biomarker for some diseases, especially cardiovascular and thyroid diseases, diabetes, and cancer.

Effect of Crocetin on Basal Lipolysis in 3T3-L1 Adipocytes

Crocetin (CCT) is a natural saffron-derived apocarotenoid that possesses healthy properties such as anti-adipogenic, anti-inflammatory, and antioxidant activities. Lipolysis is enhanced in obesity and correlates with a pro-inflammatory, pro-oxidant state. In this context, we aimed to investigate whether CCT affects lipolysis. To evaluate CCT's possible lipolytic effect, 3T3-L1 adipocytes were treated with CCT10μM at day 5 post-differentiation. Glycerol content and antioxidant activity were assessed using colorimetric assays. Gene expression was measured using qRT-PCR to evaluate the effect of CCT on key lipolytic enzymes and on nitric oxide synthase (NOS) expression. Total lipid accumulation was assessed using Oil Red O staining. CCT10μM decreased glycerol release from 3T3-L1 adipocytes and downregulated adipose tissue triglyceride lipase (ATGL) and perilipin-1, but not hormone-sensitive lipase (HSL), suggesting an anti-lipolytic effect. CCT increased catalase (CAT) and superoxide dismutase (SOD) activity, thus showing an antioxidant effect. In addition, CCT exhibited an anti-inflammatory profile, i.e., diminished inducible NOS (NOS2) and resistin expression, while enhanced the expression of adiponectin. CCT10μM also decreased intracellular fat and C/EBPα expression (a transcription factor involved in adipogenesis), thus revealing an anti-adipogenic effect. These findings point to CCT as a promising biocompound for improving lipid mobilisation in obesity.

Cross-tissue omics analysis discovers ten adipose genes encoding secreted proteins in obesity-related non-alcoholic fatty liver disease

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is a fast-growing, underdiagnosed, epidemic. We hypothesise that obesity-related inflammation compromises adipose tissue functions, preventing efficient fat storage, and thus driving ectopic fat accumulation into the liver.

METHODS

To identify adipose-based mechanisms and potential serum biomarker candidates (SBCs) for NAFLD, we utilise dual-tissue RNA-sequencing (RNA-seq) data in adipose tissue and liver, paired with histology-based NAFLD diagnosis, from the same individuals in a cohort of obese individuals. We first scan for genes that are differentially expressed (DE) for NAFLD in obese individuals' subcutaneous adipose tissue but not in their liver; encode proteins secreted to serum; and show preferential adipose expression. Then the identified genes are filtered to key adipose-origin NAFLD genes by best subset analysis, knockdown experiments during human preadipocyte differentiation, recombinant protein treatment experiments in human liver HepG2 cells, and genetic analysis.

FINDINGS

We discover a set of genes, including 10 SBCs, that may modulate NAFLD pathogenesis by impacting adipose tissue function. Based on best subset analysis, we further follow-up on two SBCs CCDC80 and SOD3 by knockdown in human preadipocytes and subsequent differentiation experiments, which show that they modulate crucial adipogenesis genes, LPL, SREBPF1, and LEP. We also show that treatment of the liver HepG2 cells with the CCDC80 and SOD3 recombinant proteins impacts genes related to steatosis and lipid processing, including PPARA, NFE2L2, and RNF128. Finally, utilizing the adipose NAFLD DE gene cis-regulatory variants associated with serum triglycerides (TGs) in extensive genome-wide association studies (GWASs), we demonstrate a unidirectional effect of serum TGs on NAFLD with Mendelian Randomization (MR) analysis. We also demonstrate that a single SNP regulating one of the SBC genes, rs2845885, produces a significant MR result by itself. This supports the conclusion that genetically regulated adipose expression of the NAFLD DE genes may contribute to NAFLD through changes in serum TG levels.

INTERPRETATION

Our results from the dual-tissue transcriptomics screening improve the understanding of obesity-related NAFLD by providing a targeted set of 10 adipose tissue-active genes as new serum biomarker candidates for the currently grossly underdiagnosed fatty liver disease.

FUNDING

The work was supported by NIH grants R01HG010505 and R01DK132775. The Genotype-Tissue Expression (GTEx) Project was supported by the Common Fund of the Office of the Director of the National Institutes of Health, and by NCI, NHGRI, NHLBI, NIDA, NIMH, and NINDS. The KOBS study (J. P.) was supported by the Finnish Diabetes Research Foundation, Kuopio University Hospital Project grant (EVO/VTR grants 2005-2019), and the Academy of Finland grant (Contract no. 138006). This study was funded by the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant No. 802825 to M. U. K.). K. H. P. was funded by the Academy of Finland (grant numbers 272376, 266286, 314383, and 335443), the Finnish Medical Foundation, Gyllenberg Foundation, Novo Nordisk Foundation (grant numbers NNF10OC1013354, NNF17OC0027232, and NNF20OC0060547), Finnish Diabetes Research Foundation, Finnish Foundation for Cardiovascular Research, University of Helsinki, and Helsinki University Hospital and Government Research Funds. I. S. was funded by the Instrumentarium Science Foundation. Personal grants to U. T. A. were received from the Matti and Vappu Maukonen Foundation, Ella och Georg Ehrnrooths Stiftelse and the Finnish Foundation for Cardiovascular Research.

Systematic identification of cancer-associated-fibroblast-derived genes in patients with colorectal cancer based on single-cell sequencing and transcriptomics

Colorectal cancer (CRC) has a high incidence rate and poor prognosis, and the available treatment approaches have limited therapeutic benefits. Therefore, understanding the underlying mechanisms of occurrence and development is particularly crucial. Increasing attention has been paid to the pathophysiological role of cancer-associated fibroblasts (CAFs) in the heterogeneous tumour microenvironment. CAFs play a crucial role in tumorigenesis, tumour progression and treatment response. However, routine tissue sequencing cannot adequately reflect the heterogeneity of tumours. In this study, single-cell sequencing was used to examine the fibroblast population in CRC. After cluster analysis, the fibroblast population was divided into four subgroups. The distribution and role of these four subgroups in CRC were found to be different. Based on differential gene expression and lasso regression analysis of the main marker genes in these subgroups, four representative genes were obtained, namely, TCF7L1, FLNA, GPX3 and MMP11. Patients with CRC were divided into the low- and high-risk groups using the prognostic risk model established based on the expression of these four genes. The prognosis of patients in different risk groups varied significantly; patients with low-risk scores had a greater response to PDL1 inhibitors, significant clinical benefits and significantly prolonged overall survival. These effects may be attributed to inhibition of the function of T cells in the immune microenvironment and promotion of the function of tumour-associated macrophages.

Distinct transcriptomic profile of small arteries of hypertensive patients with chronic kidney disease identified miR-338-3p targeting GPX3 and PTPRS

OBJECTIVE

Hypertension is associated with vascular injury, which contributes to end-organ damage. MicroRNAs regulating mRNAs have been shown to play a role in vascular injury in hypertensive mice. We aimed to identify differentially expressed microRNAs and their mRNA targets in small arteries of hypertensive patients with/without chronic kidney disease (CKD) to shed light on the pathophysiological molecular mechanisms of vascular remodeling.

METHODS AND RESULTS

Normotensive individuals and hypertensive patients with/without CKD were recruited ( n  = 15-16 per group). Differentially expressed microRNAs and mRNAs were identified uniquely associated with hypertension (microRNAs: 10, mRNAs: 68) or CKD (microRNAs: 68, mRNAs: 395), and in both groups (microRNAs: 2, mRNAs: 32) with a P less than 0.05 and a fold change less than or greater than 1.3 in subcutaneous small arteries ( n  = 14-15). One of the top three differentially expressed microRNAs, miR-338-3p that was down-regulated in CKD, presented the best correlation between RNA sequencing and reverse transcription-quantitative PCR (RT-qPCR, R2  = 0.328, P  < 0.001). Profiling of human aortic vascular cells showed that miR-338-3p was mostly expressed in endothelial cells. Two of the selected top nine up-regulated miR-338-3p predicted targets, glutathione peroxidase 3 ( GPX3 ) and protein tyrosine phosphatase receptor type S ( PTPRS ), were validated with mimics by RT-qPCR in human aortic endothelial cells ( P  < 0.05) and by a luciferase assay in HEK293T cells ( P  < 0.05).

CONCLUSION

A distinct transcriptomic profile was observed in gluteal subcutaneous small arteries of hypertensive patients with CKD. Down-regulated miR-338-3p could contribute to GPX3 and PTPRS up-regulation via the canonical microRNA targeting machinery in hypertensive patients with CKD.

http://links.lww.com/HJH/C27.

Selenium and Selenoproteins at the Intersection of Type 2 Diabetes and Thyroid Pathophysiology

Type 2 diabetes (T2D) is considered one of the largest global public-health concerns, affecting approximately more than 400 million individuals worldwide. The pathogenesis of T2D is very complex and, among the modifiable risk factors, selenium (Se) has recently emerged as a determinant of T2D pathogenesis and progression. Selenium is considered an essential element with antioxidant properties, and is incorporated into the selenoproteins involved in the antioxidant response. Furthermore, deiodinases, the enzymes responsible for homeostasis and for controlling the activity of thyroid hormones (THs), contain Se. Given the crucial action of oxidative stress in the onset of insulin resistance (IR) and T2D, and the close connection between THs and glucose metabolism, Se may be involved in these fundamental relationships; it may cover a dual role, both as a protective factor and as a risk factor of T2D, depending on its basal plasma concentration and the individual’s diet intake. In this review we discuss the current evidence (from experimental, observational and randomized clinical studies) on how Se is associated with the occurrence of T2D and its influence on the relationship between thyroid pathophysiology, IR and T2D.

cDNA Characterization and Expression of Selenium-Dependent CqGPx3 Isoforms in the Crayfish Cherax quadricarinatus under High Temperature and Hypoxia

Glutathione peroxidase 3 (GPx3) is the only extracellular selenoprotein (Sel) that enzymatically reduces H2O2 to H2O and O2. Two GPx3 (CqGPx3) cDNAs were characterized from crayfish Cherax quadricarinatus. The nerve cord CqGPx3a isoform encodes for a preprotein containing an N-terminal signal peptide of 32 amino acid residues, with the mature Sel region of 192 residues and a dispensable phosphorylation domain of 36 residues. In contrast, the pereiopods CqGPx3b codes for a precursor protein with 19 residues in the N-terminal signal peptide, then the mature 184 amino acid residues protein and finally a Pro-rich peptide of 42 residues. CqGPx3 are expressed in cerebral ganglia, pereiopods and nerve cord. CqGPx3a is expressed mainly in cerebral ganglia, antennulae and nerve cord, while CqGPx3b was detected mainly in pereiopods. CqGPx3a expression increases with high temperature and hypoxia; meanwhile, CqGPx3b is not affected. We report the presence and differential expression of GPx3 isoforms in crustacean tissues in normal conditions and under stress for high temperature and hypoxia. The two isoforms are tissue specific and condition specific, which could indicate an important role of CqGPx3a in the central nervous system and CqGPx3b in exposed tissues, both involved in different responses to environmental stressors.

Selenomethionine modulates insulin secretion in the MIN6-K8 mouse insulinoma cell line

Selenium is an essential trace element of interest for its potential role in glucose homeostasis. The present study investigated the impact of selenium supplementation as selenomethionine (SeMet) on insulin secretion in MIN6-K8 cells, a pancreatic β-cell model. We found that SeMet enhanced percent glucose-induced insulin secretion, while also increasing tolbutamide- and KCl-induced percent insulin secretion. RNA-sequencing showed that SeMet supplementation altered expression of several selenoproteins, including glutathione peroxidase 3 (Gpx3) and selenoprotein P (SelP). Targeted knockdown of Gpx3 increased both percent and total insulin release, while SelP knockdown increased insulin content and insulin release. Collectively, these studies support a putative role for selenium and selenoproteins in the regulation of insulin secretion, glucose homeostasis, and diabetes risk.

Oxidative Stress Genes in Diabetes Mellitus Type 2: Association with Diabetic Kidney Disease

Diabetic type 2 patients compared to nondiabetic patients exhibit an increased risk of developing diabetic kidney disease (DKD), the leading cause of end-stage renal disease. Hyperglycemia, hypertension, oxidative stress (OS), and genetic background are some of the mechanisms and pathways implicated in DKD pathogenesis. However, data on OS pathway susceptibility genes show limited success and conflicting or inconclusive results. Our study is aimed at exploring OS pathway genes and variants which could be associated with DKD. We recruited 121 diabetes mellitus type 2 (DM2) patients with DKD (cases) and 220 DM2, non-DKD patients (control) of Greek origin and performed a case-control association study using genome-wide association data. PLINK and EIGENSOFT were used to analyze the data. Our results indicate 43 single nucleotide polymorphisms with their 21 corresponding genes on the OS pathway possibly contributing or protecting from DKD: SPP1, TPO, TTN, SGO2, NOS3, PDLIM1, CLU, CCS, GPX4, TXNRD2, EPHX2, MTL5, EPX, GPX3, ALOX12, IPCEF1, GSTA, OXR1, GPX6, AOX1, and PRNP. Therefore, a genetic OS background might underlie the complex pathogenesis of DKD in DM2 patients.

Redox Regulation of Lipid Mobilization in Adipose Tissues

Lipid mobilization in adipose tissues, which includes lipogenesis and lipolysis, is a paramount process in regulating systemic energy metabolism. Reactive oxygen and nitrogen species (ROS and RNS) are byproducts of cellular metabolism that exert signaling functions in several cellular processes, including lipolysis and lipogenesis. During lipolysis, the adipose tissue generates ROS and RNS and thus requires a robust antioxidant response to maintain tight regulation of redox signaling. This review will discuss the production of ROS and RNS within the adipose tissue, their role in regulating lipolysis and lipogenesis, and the implications of antioxidants on lipid mobilization.

The effect of sex on the mouse lens transcriptome

The transcriptome of mammalian tissues differs between males and females, and these differences can change across the lifespan, likely regulating known sexual dimorphisms in disease prevalence and severity. Cataract, the most prevalent disease of the ocular lens, occurs at similar rates in young individuals, but its incidence is elevated in older women compared to men of the same age. However, the influence of sex on the lens transcriptome was unknown. RNAseq based transcriptomic profiling of young adult C57BL/6J mouse lens epithelial and fiber cells revealed that few genes are differentially expressed between the sexes. In contrast, lens cells from aged (24 month old) male and female C57BL/6J mice differentially expressed many genes, including several whose expression is lens preferred. Like cataracts, posterior capsular opacification (PCO), a major sequela of cataract surgery, may also be more prevalent in women. Lens epithelial cells isolated from mouse eyes 24 h after lens fiber cell removal exhibited numerous transcriptomic differences between the sexes, including genes implicated in complement cascades and extracellular matrix regulation, and these differences are much more pronounced in aged mice than in young mice. These results provide an unbiased basis for future studies on how sex affects the lens response to aging, cataract development, and cataract surgery.

The aging mouse lens transcriptome

Age is a major risk factor for cataract (ARC). However, the influence of aging on the lens transcriptome is under studied. Lens epithelial (LEC) and fiber cells (LFC) were isolated from young (3 month old) and aged (24 month old) C57BL/6J mice, and the transcriptome elucidated via RNAseq. EdgeR estimated differential gene expression in pairwise contrasts, and Advaita's Ipathway guide and custom R scripts were used to evaluate the potential biological significance of differentially expressed genes (DEGs). This analysis revealed age-dependent decreases in lens differentiation marker expression in both LECs and LFCs, with gamma crystallin transcripts downregulating nearly 50 fold in aged LFCs. The expression of the transcription factors Hsf4 and Maf, which are known to activate lens fiber cell preferred genes, are downregulated, while FoxE3, which represses gamma crystallin expression, is upregulated in aged fibers. Aged LECs upregulate genes controlling the immune response, complement pathways, and cellular stress responses, including glutathione peroxidase 3 (Gpx3). Aged LFCs exhibit broad changes in the expression of genes regulating cell communication, and upregulate genes involved in antigen processing/presentation and cholesterol metabolism, while changes in the expression of mitochondrial respiratory chain genes are consistent with mitochondrial stress, including upregulation of NDufa4l2, which encodes an alternate electron transport chain protein. However, age did not profoundly affect the response of LECs to injury as both young and aged LECs upregulate inflammatory gene signatures at 24 h post injury to similar extents. These RNAseq profiles provide a rich data set that can be mined to understand the genetic regulation of lens aging and how this impinges on the pathophysiology of age related cataract.

Glutathione peroxidase 3 (extracellular isoform) levels and functional polymorphisms in fertile and infertile men

Background

Oxidative stress has an undeniable role in the impairment of sperm function and idiopathic male infertility. On the other hand, the local antioxidant system particularly glutathione peroxidase 3 (GPX3) as an extracellular enzyme protects male fertility from oxidative damages. Therefore, in the current study, we evaluated the association between two functional polymorphisms of the GPX3 gene with its levels in seminal fluid and subsequently with the risk of male infertility.

Result

We recruited 100 fertile and 100 infertile men for the study. Our results showed that the concentration of GPX3 was higher in the fertile group than infertile patients (p= <0.01), and there were positive correlations between GPX3 concentration in seminal fluid with sperm motility and morphology. The frequency of rs8177404 and rs3828599 genotypes and alleles was significantly different between the groups and we found that having the rs8177404 polymorphism (TC and CC genotypes) could increase the risk of idiopathic infertility more than 2-fold. On the other hand, the GG genotype (rs3828599) showed a protective effect against infertility. Our results demonstrated that men carrying CC genotype of rs8177404 polymorphism had significantly lower progressively motile sperm and higher immotile sperm compared with subjects carrying TT and TC genotypes. In the rs3828599 polymorphism, the GG carriers had significantly higher progressively motile and lower immotile sperm than AA carriers. Furthermore, men with genotypes of CC (rs8177404) and GG (rs3828599) had significantly lower and higher levels of GPX3 in the seminal fluid, respectively.

Conclusion

In conclusion, our results showed associations between sperm parameters with GPX3 levels and the gene polymorphisms. It seems rs8177404 and rs3828599 polymorphisms can affect GPX3 levels in seminal fluid and subsequently sperm parameters.

A pan-cancer study of selenoprotein genes as promising targets for cancer therapy

BACKGROUND

The most important health benefit of selenium (Se) is in the prevention and control of cancer. Glutathione peroxidases (GPXs) and thioredoxin reductases (TXNRDs) are selenoenzymes that are thought to play a role in oxidative stress. The differential expression of genes of the TXNRD and GPX families is closely related to carcinogenesis and the occurrence of cancer. This study comprehensively analyzed the expression profiles of seven genes in the TXNRD and GPX families, in terms of their correlations with patient survival and immune-cell subtypes, tumor microenvironment, and drug sensitivity.

RESULTS

The expression profiles of genes in the TXNRD and GPX families differ between different types of cancer, and also between and within individual cancer cases. The expression levels of the seven analyzed genes are related to the overall survival of patients. The TXNRD1 and TXNRD3 genes are mainly related to poor prognoses, while other genes are related to good or poor prognoses depending on the type of cancer. All of the genes were found to be correlated to varying degrees with immune-cell subtypes, level of mechanistic cell infiltration, and tumor cell stemness. The TXNRD1, GPX1, and GPX2 genes may exert dual effects in tumor mutagenesis and development, while the TXNRD1, GPX1, GPX2, and GPX3 genes were found to be related to drug sensitivity or the formation of drug resistance.

CONCLUSIONS

The results will greatly help in identifying the association between genes and tumorigenesis, especially in the immune response, tumor microenvironment, and drug resistance, and very important when attempting to identify new therapeutic targets.

Reduced Expression of GPX3 in Breast Cancer Patients in Correlation with Clinical Significance

Glutathione peroxidase 3 (GPX3) is the main antioxidant enzyme in plasma. Its biological roles are to protect cells from oxidative stress-induced damage. Several studies have been reported the association between GPX3 expression and its correlation with cancer carcinogenesis including breast cancer. The aim of this research was to investigate the GPX3 messenger ribonucleic acid (mRNA) expression in 82 breast tumors and paired normal breast tissues by SYBR green quantitative real-time reverse transcription-polymerase chain reaction and the association with clinicopathological data. Our results show that GPX3 reduced expression was found significantly associated with number of metastatic lymph nodes (odds ratio [OR] = 3.41, 95% confidence interval [CI] = 1.35–8.64, p  = 0.01), no distant metastasis (OR = 5.52, 95% CI = 3.74–11.89, p  = 0.04), and nonhormone usage breast cancer patients (OR = 0.19, 95% CI = 0.04–0.93, p  = 0.04). This finding suggested that GPX3 plays a role in breast carcinogenesis, and might serve as a prognostic biomarker in breast cancer patients.

Enzymatic antioxidant system and endothelial function in patients with metabolic syndrome

BACKGROUND

This study examined the relationship between serum glutathione peroxidase 1 (GPx-1) activity and endothelial dysfunction in the subjects with and without metabolic syndrome (MetS).

METHODS

This case-control study was conducted on 76 subjects, 38 were patients with MetS and 38 were without MetS. The demographic, clinical, and laboratory features of the subjects were measured and then compared. The MetS was diagnosed according to the definitions of the National Cholesterol Education Program (NCEP) and International Diabetes Federation (IDF). Serum GPx-1 activity was measured by standard methods. Endothelial dysfunction was assessed with flow-mediated dilation (FMD) technique.

RESULTS

In case-control study of 76 subjects, all of MetS risk factors including abdominal obesity, triglyceride (TG), low serum level of high-density lipoprotein cholesterol (HDL-C), hypertension (HTN), and fasting plasma glucose (FPG) were significantly higher than healthy individuals (P < 0.050). FMD was significantly lower than normal subjects (P < 0.050). Serum GP-1 activity was significantly lower in patients with MetS compared to normal subjects (21.7 ± 13.5 vs. 79.0 ± 38.6, respectively) (P = 0.001). The value of GPx-1 was significantly correlated with diastolic blood pressure (DBP) (r = -0.249, P = 0.040), C-reactive protein (CRP) (r = -0.409, P = 0.014), and FMD (r = 0.293, P = 0.050) in patients with MetS. The results of logistic regression showed that a unite increase in CRP (mg/dl), FMD (%), and endothelin-1 (ET-1) (pg/ml) and a unit decrease in GPx significantly increased the odds ratio (OR) of MetS; after adjusting for age and sex the results remained significant except for FMD (P < 0.050)

CONCLUSION

Endothelial dysfunction is related to serum GPx-1 activity in patients with MetS. GPX-1 activity is associated with risk of cardiovascular diseases (CVDs) and peripheral vascular diseases (PVDs) in patients with MetS.

An Overview of the Ferroptosis Hallmarks in Friedreich's Ataxia

BACKGROUND

Friedreich's ataxia (FRDA) is a neurodegenerative disease characterized by early mortality due to hypertrophic cardiomyopathy. FRDA is caused by reduced levels of frataxin (FXN), a mitochondrial protein involved in the synthesis of iron-sulphur clusters, leading to iron accumulation at the mitochondrial level, uncontrolled production of reactive oxygen species and lipid peroxidation. These features are also common to ferroptosis, an iron-mediated type of cell death triggered by accumulation of lipoperoxides with distinct morphological and molecular characteristics with respect to other known cell deaths.

SCOPE OF REVIEW

Even though ferroptosis has been associated with various neurodegenerative diseases including FRDA, the mechanisms leading to disease onset/progression have not been demonstrated yet. We describe the molecular alterations occurring in FRDA that overlap with those characterizing ferroptosis.

MAJOR CONCLUSIONS

The study of ferroptotic pathways is necessary for the understanding of FRDA pathogenesis, and anti-ferroptotic drugs could be envisaged as therapeutic strategies to cure FRDA.

Association between glutathione peroxidase-3 activity and carotid atherosclerosis in patients with type 2 diabetes mellitus

BACKGROUND AND AIMS

Deficiency of glutathione peroxidase 3 (GPx3) has been recognized as an independent risk factor for cardiovascular events. However, little is known regarding the role of GPx3 in carotid atherosclerosis, which is ubiquitously observed in type 2 diabetes mellitus (T2DM). This study aimed to investigate the relationship between GPx3 activity and carotid atherosclerosis among patients with T2DM.

METHODS

From January 2018 to December 2018, 245 consecutive patients with T2DM were enrolled in this observational study. Assessment of serum GPx3 activity was performed after admission. We also used carotid ultrasound to measure the mean carotid intima-media thickness (CIMT) and to assess the presence of carotid plaque.

RESULTS

Of the 245 patients, the median serum GPx3 activity was 22.5 U/ml (interquartile range, 12.4-35.9 U/ml). Carotid plaque was observed in 113 (46.1%) patients, and mean CIMT was 0.8 ± 0.1 mm. Univariate analysis showed that age, smoking, previous coronary heart disease, carotid plaque, and level of mean CIMT and hypersensitive C-reactive protein were significantly associated with decreasing tertile of GPx3. Furthermore, after adjusting for all potential confounders by multivariable logistic regression analysis, PGx3 activity was significantly and independently associated with the mean CIMT (β = -.406, p = .002) and carotid plaque (first tertile of GPx3, odds ratio, 1.870, 95% confidence intervals, 1.124-3.669, p = .024).

CONCLUSIONS

This study demonstrated that serum GPx3 activity was inversely associated with mean CIMT and carotid plaque, suggesting that lower GPx3 activity may be an independent predictor for carotid atherosclerosis in T2DM.

Extracellular Glutathione Peroxidase GPx3 and Its Role in Cancer

Mammalian cells possess a multifaceted antioxidant enzyme system, which includes superoxide dismutases, catalase, the peroxiredoxin/thioredoxin and the glutathione peroxidase systems. The dichotomous role of reactive oxygen species and antioxidant enzymes in tumorigenesis and cancer progression complicates the use of small molecule antioxidants, pro-oxidants, and targeting of antioxidant enzymes as therapeutic approaches for cancer treatment. It also highlights the need for additional studies to investigate the role and regulation of these antioxidant enzymes in cancer. The focus of this review is on glutathione peroxidase 3 (GPx3), a selenoprotein, and the only extracellular GPx of a family of oxidoreductases that catalyze the detoxification of hydro- and soluble lipid hydroperoxides by reduced glutathione. In addition to summarizing the biochemical function, regulation, and disease associations of GPx3, we specifically discuss the role and regulation of systemic and tumor cell expressed GPx3 in cancer. From this it is evident that GPx3 has a dichotomous role in different tumor types, acting as both a tumor suppressor and pro-survival protein. Further studies are needed to examine how loss or gain of GPx3 specifically affects oxidant scavenging and redox signaling in the extracellular tumor microenvironment, and how GPx3 might be targeted for therapeutic intervention.

Involvement of glutathione peroxidases in the occurrence and development of breast cancers

Glutathione peroxidases (GPxs) belong to a family of enzymes that is important in organisms; these enzymes promote hydrogen peroxide metabolism and protect cell membrane structure and function from oxidative damage. Based on the establishment and development of the theory of the pathological roles of free radicals, the role of GPxs has gradually attracted researchers' attention, and the involvement of GPxs in the occurrence and development of malignant tumors has been shown. On the other hand, the incidence of breast cancer in increasing, and breast cancer has become the leading cause of cancer-related death in females worldwide; breast cancer is thought to be related to the increased production of reactive oxygen species, indicating the involvement of GPxs in these processes. Therefore, this article focused on the molecular mechanism and function of GPxs in the occurrence and development of breast cancer to understand their role in breast cancer and to provide a new theoretical basis for the treatment of breast cancer.

GPx3 dysregulation impacts adipose tissue insulin receptor expression and sensitivity

Insulin receptor signaling is crucial for white adipose tissue (WAT) function. Consequently, lack of insulin receptor (IR) in WAT results in a diabetes-like phenotype. Yet, causes for IR downregulation in WAT of patients with diabetes are not well understood. By using multiple mouse models of obesity and insulin resistance, we identify a common downregulation of IR with a reduction of mRNA expression of selenoproteins Txnrd3, Sephs2, and Gpx3 in gonadal adipose tissue. Consistently, GPX3 is also decreased in adipose tissue of insulin-resistant and obese patients. Inducing Gpx3 expression via selenite treatment enhances IR expression via activation of the transcription factor Sp1 in 3T3-L1 preadipocytes and improves adipocyte differentiation and function. Feeding mice a selenium-enriched high-fat diet alleviates diet-induced insulin resistance with increased insulin sensitivity, decreased tissue inflammation, and elevated IR expression in WAT. Again, IR expression correlated positively with Gpx3 expression, a phenotype that is also conserved in humans. Consequently, decreasing GPx3 using siRNA technique reduced IR expression and insulin sensitivity in 3T3-L1 preadipocytes. Overall, our data identify GPx3 as a potentially novel regulator of IR expression and insulin sensitivity in adipose tissue.

Sex Differences in Glutathione Peroxidase Activity and Central Obesity in Patients with Type 2 Diabetes at High Risk of Cardio-Renal Disease

Women with type 2 diabetes (T2DM) have an increased susceptibility of developing cardio-renal disease compared to men, the reasons and the mechanisms of this vulnerability are unclear. Since oxidative stress plays a key role in the development of cardio-renal disease, we investigated the relationship between sex, plasma antioxidants status (glutathione peroxidase (GPx-3 activity), vitamin E and selenium), and adiposity in patients with T2DM at high risk of cardio-renal disease. Women compared to men had higher GPx-3 activity (p = 0.02), bio-impedance (p ≤ 0.0001), and an increase in waist circumference in relation to recommended cut off-points (p = 0.0001). Waist circumference and BMI were negatively correlated with GPx-3 activity (p ≤ 0.05 and p ≤ 0.01, respectively) and selenium concentration (p ≤ 0.01 and p ≤ 0.02, respectively). In multiple regression analysis, waist circumference and sex were independent predictors of GPx-3 activity (p ≤ 0.05 and p ≤ 0.05, respectively). The data suggest that increased central fat deposits are associated with reduced plasma antioxidants which could contribute to the future risk of cardio-renal disease. The increased GPx-3 activity in women could represent a preserved response to the disproportionate increase in visceral fat. Future studies should be aimed at evaluating if the modulation of GPx-3 activity reduces cardio-renal risk in men and women with T2DM.

Transcriptional profiling of liver tissues in chicken embryo at day 16 and 20 using RNA sequencing reveals differential antioxidant enzyme activity

Considering the high proportion of polyunsaturated fatty acids, the antioxidant defense of chick embryo tissues is vital during the oxidative stress experienced at hatching. In order to better understand the mechanisms of the defense system during chicken embryo development, we detected the activity of antioxidant enzymes during the incubation of chicken embryo. Results showed that the activity of superoxide dismutase (SOD) and (GSH-PX) in livers were higher than those in hearts. Based on these results, liver tissues were used as the follow-up study materials, which were obtained from chicken embryo at day 16 and day 20. Thus, we used RNA sequencing (RNA-Seq) analysis to identify the transcriptome from 6 liver tissues. In total, we obtained 45,552,777-45,462,856 uniquely mapped reads and 18,837 mRNA transcripts, across the 6 liver samples. Among these, 1,154 differentially expressed genes (p<0.05, foldchange≥1) were identified between the high and low groups, and 1,069 GO terms were significantly enriched (p<0.05). Of these, 10 GO terms were related to active oxygen defense and antioxidant enzyme activity. GO enrichment and KEGG pathway analysis indicated that GSTA2, GSTA4, MGST1, GPX3, and HAO2 participated in glutathione metabolism, and were considered as the most promising candidate genes affecting the antioxidant enzyme activity of chicken embryo at day 16 and day 20. Using RNA-Seq and differential gene expression, our study here investigated the complexity of the liver transcriptome in chick embryos and analyzed the key genes associated with the antioxidant enzyme.

Effects of Weight Loss on Glutathione Peroxidase 3 Serum Concentrations and Adipose Tissue Expression in Human Obesity

BACKGROUND/AIMS

Altered expression and circulating levels of glutathione peroxidase 3 (GPX3) have been observed in obesity and type 2 diabetes (T2D) across species. Here, we investigate whether GPX3 serum concentrations and adipose tissue (AT) GPX3 mRNA expression are related to obesity and weight loss.

METHODS

GPX3 serum concentration was measured in 630 individuals, including a subgroup (n = 293) for which omental and subcutaneous (SC) GPX3 mRNA expression has been analyzed. GPX3 analyses include three interventions: 6 months after bariatric surgery (n = 80) or combined exercise/hypocaloric diet (n = 20) or two-step bariatric surgery (n = 24) studies.

RESULTS

Bariatric surgery-induced weight loss (-25.8 ± 8.4%), but not a moderate weight reduction of -8.8 ± 6.5% was associated with significantly reduced GPX3 serum concentrations. GPX3 mRNA is significantly higher expressed in AT from individuals with normal glucose metabolism compared to T2D patients. SC AT GPX3 expression is significantly higher in lean compared to obese as well as in insulin-sensitive compared insulin-resistant individuals with obesity. Weight loss after bariatric surgery causes a significant increase in SC AT GPX3 expression. AT GPX3 expression significantly correlates with age, BMI, fat distribution, insulin sensitivity (only SC AT), but not with circulating GPX3.

CONCLUSION

Our data support the notion that SC AT GPX3 expression is associated with obesity, fat distribution and related to whole body insulin resistance.

Glutathione peroxidase 3 gene polymorphisms and the risk of sudden sensorineural hearing loss

The glutathione peroxidase 3 gene (GPX3) is reported to be a risk factor for arterial ischaemic stroke and cerebral venous thrombosis. GPX3 may be one of the aetiologies of sudden sensorineural hearing loss (SSNHL), which might be attributed to the genetic effect of GPX3 by influence reactive oxygen species (ROS). Unbalanced ROS have been associated with susceptibility to SSNHL. Therefore, we conducted a case-control study with 416 SSNHL cases and 255 controls. Five single nucleotide polymorphisms (SNPs) were selected. The genotypes were determined using TaqMan genotyping assays. Each SNP was tested using the Hardy-Weinberg equilibrium (HWE), and the genetic effects were evaluated using three inheritance models. All five SNPs were in HWE. As the result, the AG genotype of rs3805435 had an adjusted odds ratio (OR) of 0.54 (95% confidence interval = 0.37-0.79, p = 0.001) compared with the AA genotype in the SSNHL cases. The GG and AG genotypes of the SNP rs3805435 were associated with SSNHL under the dominant model (p = 0.002, OR = 0.58). In conclusion, these results suggest that GPX3 polymorphisms influence susceptibility to SSNHL in southern Taiwan.

Oxidative stress is associated with an increased antioxidant defense in elderly subjects: a multilevel approach

BACKGROUND

Studies of associations between plasma GSH-Px activity and cardiovascular risk factors have been done in humans, and contradictory results have been reported. The aim of our study was to assess the association between the scavenger antioxidant enzyme glutathione peroxidase (GSH-Px) activity in plasma and the presence of novel and classical cardiovascular risk factors in elderly patients.

METHODS

We performed a cross-sectional study with baseline data from a subsample of the PREDIMED (PREvención con DIeta MEDiterránea) study in Spain. Participants were 1,060 asymptomatic subjects at high risk for cardiovascular disease (CVD), aged 55 to 80, selected from 8 primary health care centers (PHCCs). We assessed classical CVD risk factors, plasma oxidized low-density lipoproteins (ox-LDL), and glutathione peroxidase (GSH-Px) using multilevel statistical procedures.

RESULTS

Mean GSH-Px value was 612 U/L (SE: 12 U/L), with variation between PHCCs ranging from 549 to 674 U/L (Variance =  013.5; P<0.001). Between-participants variability within a PHCC accounted for 89% of the total variation. Both glucose and oxidized LDL were positively associated with GSH-Px activity after adjustment for possible confounder variables (P = 0.03 and P = 0.01, respectively).

CONCLUSION

In a population at high cardiovascular risk, a positive linear association was observed between plasma GSH-Px activity and both glucose and ox-LDL levels. The high GSH-Px activity observed when an oxidative stress situation occurred, such as hyperglycemia and lipid oxidative damage, could be interpreted as a healthy defensive response against oxidative injury in our cardiovascular risk population.