Selenoproteins and the aging brain

Selenium spatial distribution and bioavailability of soil-plant systems in China: a comprehensive review

Selenium (Se) has a dual nature, with beneficial and harmful effects on plants, essential for both humans and animals, playing a crucial role in ecosystem regulation. Insufficient Se in specific terrestrial environments raises concerns due to its potential to cause diseases, while excess Se can lead to severe toxicity. Thus, maintaining an optimal Se level is essential for living organisms. This review focuses first on Se transformation, speciation, and geochemical properties in soil, and then provides a concise overview of Se distribution in Chinese soil and crops, with a focus on the relationship between soil Se levels and parent materials. Additionally, this paper explores Se bioavailability, considering parent materials and soil physicochemical properties, using partial least squares path modeling for analysis. This paper aimed to be a valuable resource for effectively managing Se-enriched soil resources, contributing to a better understanding of Se role in ecosystems.

Selenium intake is an effective strategy for the improvement of cognitive decline in low cognition older Americans

Age-related cognitive decline is a prominent concern in older adults and selenium (Se) deficiency has been found to be associated with cognitive deficits. For the first time, the present study explored the association between Se intake and cognitive performance in older people with/without cognitive impairment using the data from the National Health and Nutrition Examination Survey 2011-2014. Weighted linear regression models were conducted to evaluate the association between dietary Se/total Se intakes and cognitive assessments. A total of 2387 participants were included. The significant positive association between dietary Se/total Se intakes and total scores of cognitive functioning tests existed only in the older people with low cognitive performance (p < 0.001), not in those with normal cognitive performance. In conclusion, Se intake was beneficial for cognitive decline only in the low cognition older people but failed in normal cognition older people.

New horizons for the role of selenium on cognitive function: advances and challenges

Cognitive deficits associated with oxidative stress and the dysfunction of the central nervous system are present in some neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. Selenium (Se), an essential microelement, exhibits cognition-associated functions through selenoproteins mainly owing to its antioxidant property. Due to the disproportionate distribution of Se in the soil, the amount of Se varies greatly in various foods, resulting in a large proportion of people with Se deficiency worldwide. Numerous cell and animal experiments demonstrate Se deficiency-induced cognitive deficits and Se supplementation-improved cognitive performances. However, human studies yield inconsistent results and the mechanism of Se in cognition still remains elusive, which hinder the further exploration of Se in human cognition. To address the urgent issue, the review summarizes Se-contained foods (plant-based foods, animal-based foods, and Se supplements), brain selenoproteins, mechanisms of Se in cognition (improvement of synaptic plasticity, regulation of Zn2+ level, inhibition of ferroptosis, modulation of autophagy and de novo synthesis of L-serine), and effects of Se on cognitive deficits, as well as consequently sheds light on great potentials of Se in the prevention and treatment of cognitive deficits.

Knocking out Selenium Binding Protein 1 Induces Depressive-Like Behavior in Mice

Selenium binding protein 1 (SELENBP1) is involved in neurologic disorders, such as multiple sclerosis, spinal cord injury, Parkinson's disease, epilepsy, and schizophrenia. However, the role of SELENBP1 in the neurogenesis of depression, which is a neurologic disorder, and the underlying mechanisms of oxidative stress and inflammation in depression remain unknown. In this study, we evaluated the changes in the expression levels of SELENBP1 in the hippocampus of a mouse model of depression and in the serum of human patients with depression using the Gene Expression Omnibus database. These changes were validated using blood samples from human patients with depression and mouse models with chronic unpredictable mild stress (CUMS)-induced depressive-like behavior. We also investigated the effects of SELENBP1 knockout (KO) on inflammation, oxidative stress, and hippocampal neurogenesis in mice with CUMS-induced depression. Our results revealed that SELENBP1 levels was decreased in the blood of human patients with depression and in the hippocampus of mice with CUMS-induced depression. SELENBP1 KO increased CUMS-induced depressive behavior in mice and caused dysregulation of inflammatory cytokines and oxidative stress. This led to a decrease in the numbers of doublecortin- and Ki67-positive cells, which might aggravate CUMS-induced depressive symptoms. These findings suggest that SELENBP1 might be involved in the regulation of neurogenesis in mice with depression and could be served as a potential target for diagnosing and treating depression.

Selenium- and/or Zinc-Enriched Egg Diet Improves Oxidative Damage and Regulates Gut Microbiota in D-Gal-Induced Aging Mice

Eggs, with their high nutritional value, are great carriers for enriching nutrients. In this study, selenium- and/or zinc-enriched eggs (SZE) were obtained and their effects on ameliorating oxidative stress injury, alleviating cognitive impairment, and maintaining intestinal flora balance in a D-gal-induced aging mice model were investigated. As determined by the Y-maze test, SZE restored the learning and memory abilities and increased the Ach level and AChE activity of aging mice (p < 0.05). Meanwhile, supplementation of low-dose SZE increased antioxidant levels and decreased inflammation levels (p < 0.05). High-dose SZE increased anti-inflammatory levels but were less effective than low dose. Additionally, SZE maintained the intestinal flora balance and significantly increased the ratio of Firmicutes and Bacteroidota. Blautia, as a probiotic, was negatively correlated with pro-inflammatory factors and positively correlated with antioxidant levels (p < 0.05). These results suggest that SZE might improve organ damage and cognitive function by attenuating oxidative stress and inflammatory response and maintaining healthy gut flora.

Review on the health-promoting effect of adequate selenium status

Selenium is an essential microelement involved in various biological processes. Selenium deficiency increases the risk of human immunodeficiency virus infection, cancer, cardiovascular disease, and inflammatory bowel disease. Selenium possesses anti-oxidant, anti-cancer, immunomodulatory, hypoglycemic, and intestinal microbiota-regulating properties. The non-linear dose-response relationship between selenium status and health effects is U-shaped; individuals with low baseline selenium levels may benefit from supplementation, whereas those with acceptable or high selenium levels may face possible health hazards. Selenium supplementation is beneficial in various populations and conditions; however, given its small safety window, the safety of selenium supplementation is still a subject of debate. This review summarizes the current understanding of the health-promoting effects of selenium on the human body, the dietary reference intake, and evidence of the association between selenium deficiency and disease.

Different Effects and Mechanisms of Selenium Compounds in Improving Pathology in Alzheimer’s Disease

Owing to the strong antioxidant capacity of selenium (Se) in vivo, a variety of Se compounds have been shown to have great potential for improving the main pathologies and cognitive impairment in Alzheimer’s disease (AD) models. However, the differences in the anti-AD effects and mechanisms of different Se compounds are still unclear. Theoretically, the absorption and metabolism of different forms of Se in the body vary, which directly determines the diversification of downstream regulatory pathways. In this study, low doses of Se-methylselenocysteine (SMC), selenomethionine (SeM), or sodium selenate (SeNa) were administered to triple transgenic AD (3× Tg-AD) mice for short time periods. AD pathology, activities of selenoenzymes, and metabolic profiles in the brain were studied to explore the similarities and differences in the anti-AD effects and mechanisms of the three Se compounds. We found that all of these Se compounds significantly increased Se levels and antioxidant capacity, regulated amino acid metabolism, and ameliorated synaptic deficits, thus improving the cognitive capacity of AD mice. Importantly, SMC preferentially increased the expression and activity of thioredoxin reductase and reduced tau phosphorylation by inhibiting glycogen synthase kinase-3 beta (GSK-3β) activity. Glutathione peroxidase 1 (GPx1), the selenoenzyme most affected by SeM, decreased amyloid beta production and improved mitochondrial function. SeNa improved methionine sulfoxide reductase B1 (MsrB1) expression, reflected in AD pathology as promoting the expression of synaptic proteins and restoring synaptic deficits. Herein, we reveal the differences and mechanisms by which different Se compounds improve multiple pathologies of AD and provide novel insights into the targeted administration of Se-containing drugs in the treatment of AD.

Review: Advances in the Accuracy and Traceability of Metalloprotein Measurements Using Isotope Dilution Inductively Coupled Plasma Mass Spectrometry

Advances in inductively coupled plasma mass spectrometry and the methods used to prepare isotopically enriched standards, allow for the high accuracy measurement of metalloproteins by isotope dilution mass spectrometry. This technique has now reached a level of maturity whereby a step change in the accuracy, precision, and traceability of, in particular, clinical, and biomedical measurements is achievable. Current clinical measurements, which require low limits of detection in the presence of complex sample matrices, use indirect methods based on immunochemistry for the study of human disease. However, this approach suffers from poor traceability, requiring comparisons based on provision of matrix-based reference materials, used as analytical standards. This leads to difficulty when changes in the reference material are required, often resulting in a lack of interlaboratory and temporal comparability in clinical results and reference ranges. In this review, we focus on the most important metalloproteins for clinical studies, to illustrate how the attributes of chromatography coupled to inorganic mass spectrometry can be used for the direct measurement of metalloproteins such as hemoglobin, transferrin, and ceruloplasmin. By using this approach, we hope to demonstrate how isotope dilution analysis can be used as a reference method to improve traceability and underpin clinical, biomedical, and other biological measurements.

Selenium Intake and its Interaction with Iron Intake Are Associated with Cognitive Functions in Chinese Adults: A Longitudinal Study

Studies on the relation between selenium intake and cognitive function are inconclusive. This study aimed to examine the associations between dietary selenium intake and cognitive function among Chinese adults and tested the interaction effect of selenium intake and iron intake on cognition. Data from 4852 adults aged 55 years and above who attended the 1991–2006 China Health and Nutrition Survey (CHNS) were used. Cognitive function was assessed through face-to-face interviews in 1997, 2000, 2004, and 2006. A 3-day, 24-hour recall was used to collect dietary selenium intake. Multivariable mixed linear regression and logistic regression were used in the analyses. In fully adjusted regression models, the regression coefficients (95% confidence interval) were 0.00, 0.29 (−0.12–0.70), 0.26 (−0.18–0.70), and 0.50 (0.02–0.97) across the quartiles of selenium intake. In the subgroup analysis, the positive association between selenium intake and cognitive function was only observed in the participants who live in the southern region but not those in the northern region. The selenium-intake-to-iron-intake ratio was inversely associated with low global cognition scores. Furthermore, only those with a normal BMI had a positive association between selenium and cognition. In conclusion, high selenium intake was linked to better cognitive function and a lower risk of cognition decline in Chinese adults among those with low iron intake. A substantial interaction was found between selenium intake and BMI or region.

Dietary supplementation with biogenic selenium nanoparticles alleviate oxidative stress-induced intestinal barrier dysfunction

Selenium (Se) is an essential micronutrient that promotes body health. Endemic Se deficiency is a major nutritional challenge worldwide. The low toxicity, high bioavailability, and unique properties of biogenic Se nanoparticles (SeNPs) allow them to be used as a therapeutic drug and Se nutritional supplement. This study was conducted to investigate the regulatory effects of dietary SeNPs supplementation on the oxidative stress-induced intestinal barrier dysfunction and its association with mitochondrial function and gut microbiota in mice. The effects of dietary SeNPs on intestinal barrier function and antioxidant capacity and its correlation with gut microbiota were further evaluated by a fecal microbiota transplantation experiment. The results showed that Se deficiency caused a redox imbalance, increased the levels of pro-inflammatory cytokines, altered the composition of the gut microbiota, and impaired mitochondrial structure and function, and intestinal barrier injury. Exogenous supplementation with biogenic SeNPs effectively alleviated diquat-induced intestinal barrier dysfunction by enhancing the antioxidant capacity, inhibiting the overproduction of reactive oxygen species (ROS), preventing the impairment of mitochondrial structure and function, regulating the immune response, maintaining intestinal microbiota homeostasis by regulating nuclear factor (erythroid-derived-2)-like 2 (Nrf2)-mediated NLR family pyrin domain containing 3 (NLRP3) signaling pathway. In addition, Se deficiency resulted in a gut microbiota phenotype that is more susceptible to diquat-induced intestinal barrier dysfunction. Supranutritional SeNPs intake can optimize the gut microbiota to protect against intestinal dysfunctions. This study demonstrates that dietary supplementation of SeNPs can prevent oxidative stress-induced intestinal barrier dysfunction through its regulation of mitochondria and gut microbiota.

The Role and Mechanism of Essential Selenoproteins for Homeostasis

Selenium (Se) is one of the essential trace elements that plays a biological role in the body, mainly in the form of selenoproteins. Selenoproteins can be involved in the regulation of oxidative stress, endoplasmic reticulum (ER) stress, antioxidant defense, immune and inflammatory responses and other biological processes, including antioxidant, anti-inflammation, anti-apoptosis, the regulation of immune response and other functions. Over-loading or lack of Se causes certain damage to the body. Se deficiency can reduce the expression and activity of selenoproteins, disrupt the normal physiological function of cells and affect the body in antioxidant, immunity, toxin antagonism, signaling pathways and other aspects, thus causing different degrees of damage to the body. Se intake is mainly in the form of dietary supplements. Due to the important role of Se, people pay increasingly more attention to Se-enriched foods, which also lays a foundation for better research on the mechanism of selenoproteins in the future. In this paper, the synthesis and mechanism of selenoproteins, as well as the role and mechanism of selenoproteins in the regulation of diseases, are reviewed. Meanwhile, the future development of Se-enriched products is prospected, which is of great significance to further understand the role of Se.

Multivariate Assessment of Lipoxidative Metabolites, Trace Biometals, and Antioxidant and Detoxifying Activities in the Cerebrospinal Fluid Define a Fingerprint of Preclinical Stages of Alzheimer’s Disease

Background: There exists considerable interest in the identification of molecular traits during early stages of Alzheimer’s disease (AD). Mild cognitive impairment (MCI) is considered the closest prodromal stage of AD, and to develop gradually from earlier stages although not always progresses to AD. Classical cerebrospinal fluid (CSF) AD biomarkers, amyloid-β peptides and tau/p-tau proteins, have been measured in prodromal stages yet results are heterogeneous and far from conclusive. Therefore, there exists a pressing need to identify a neurochemical signature for prodromal stages and to predict which cases might progress to AD. Objective: Exploring potential CSF biomarkers related to brain oxidative and inorganic biochemistry during prodromal stages of the disease. Methods: We have analyzed CSF levels of lipoxidative markers (MDA and 8-isoF2α), biometals (Cu, Zn, Se, Mn, and Fe), iron-transport protein transferrin (TFER), antioxidant enzymes (SOD and GPx4), detoxifying enzymes (GST and BuChE), as well as classical amyloid-β and total and phosphorylated tau, in cognitively healthy controls, patients with MCI, and subjects exhibiting subjective memory complaints (SMC). Results: Inter-group differences for several variables exhibit differentiable trends along the HC ⟶ SMC ⟶ MCI sequence. More interestingly, the combination of Se, Cu, Zn, SOD, TFER, and GST variables allow differentiable fingerprints for control subjects and each prodromal stage. Further, multivariate scores correlate positively with neurocognitive In-Out test, hence with both episodic memory decline and prediction to dementia. Conclusion: We conclude that changes in the CSF biochemistry related to brain oxidative defense and neurometallomics might provide more powerful and accurate diagnostic tools in preclinical stages of AD.

N-γ-(L-glutamyl)-L-selenomethionine shows neuroprotective effects against Parkinson's disease associated with SKN-1/Nrf2 and TRXR-1 in Caenorhabditis elegans

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease, yet fundamental treatments for the disease remain sparse. Thus, the search for potentially efficacious compounds from medicinal plants that can be used in the treatment of PD has gained significant interest.

PURPOSE

In many medicinal plants, selenium is primarily found in an organic form. We investigated the neuroprotective potential of an organic form of selenium, N-γ-(L-glutamyl)-L-selenomethionine (Glu-SeMet) in a Caenorhabditis elegans PD model and its possible molecular mechanisms.

METHODS

We used a C. elegans pharmacological PD strain (BZ555) that specifically expresses green fluorescent protein (GFP) in dopaminergic neurons and a transgenic PD strain (NL5901) that expresses human α-synuclein (α-syn) in muscle cells to investigate the neuroprotective potential of Glu-SeMet against PD.

RESULTS

We found that Glu-SeMet significantly ameliorated 6-hydroxydopamine (6-OHDA)-induced dopaminergic neuron damage in the transgenic BZ555 strain, with corresponding improvements in slowing behavior and intracellular ROS levels. In addition, compared with clinical PD drugs (L-DOPA and selegiline), Glu-SeMet demonstrated stronger ameliorated effects on 6-OHDA-induced toxicity. Glu-SeMet also triggered the nuclear translocation of SKN-1/Nrf2 and significantly increased SKN-1, GST-4, and GCS-1 mRNA levels in the BZ555 strain. However, Glu-SeMet did not increase mRNA levels or ameliorate the damage to dopaminergic neurons when the BZ555 strain was subjected to skn-1 RNA interference (RNAi). Glu-SeMet also upregulated the mRNA levels of the selenoprotein TRXR-1 in both the BZ555 and BZ555; skn-1 RNAi strains and significantly decreased α-syn accumulation in the NL5901 strain, although this was not observed in the NL5901; trxr-1 strain.

CONCLUSION

We found that Glu-SeMet has a neuroprotective effect against PD in a C. elegans PD model and that the anti-PD effects of Glu-SeMet were associated with SKN-1/Nrf2 and TRXR-1. Glu-SeMet may thus have the potential for use in therapeutic applications or supplements to slow the progression of PD.

Oxidative Stress and Cognitive Decline: The Neuroprotective Role of Natural Antioxidants

Free- radicals (Oxygen and Nitrogen species) are formed in mitochondria during the oxidative phosphorylation. Their high reactivity, due to not-engaged electrons, leads to an increase of the oxidative stress. This condition affects above all the brain, that usually needs a large oxygen amount and in which there is the major possibility to accumulate "Reacting Species." Antioxidant molecules are fundamental in limiting free-radical damage, in particular in the central nervous system: the oxidative stress, in fact, seems to worsen the course of neurodegenerative diseases. The aim of this review is to sum up natural antioxidant molecules with the greatest neuroprotective properties against free radical genesis, understanding their relationship with the Central Nervous System.

DHA and Its Elaborated Modulation of Antioxidant Defenses of the Brain: Implications in Aging and AD Neurodegeneration

DHA (docosahexaenoic acid) is perhaps the most pleiotropic molecule in nerve cell biology. This long-chain highly unsaturated fatty acid has evolved to accomplish essential functions ranging from structural components allowing fast events in nerve cell membrane physiology to regulation of neurogenesis and synaptic function. Strikingly, the plethora of DHA effects has to take place within the hostile pro-oxidant environment of the brain parenchyma, which might suggest a molecular suicide. In order to circumvent this paradox, different molecular strategies have evolved during the evolution of brain cells to preserve DHA and to minimize the deleterious effects of its oxidation. In this context, DHA has emerged as a member of the “indirect antioxidants” family, the redox effects of which are not due to direct redox interactions with reactive species, but to modulation of gene expression within thioredoxin and glutathione antioxidant systems and related pathways. Weakening or deregulation of these self-protecting defenses orchestrated by DHA is associated with normal aging but also, more worryingly, with the development of neurodegenerative diseases. In the present review, we elaborate on the essential functions of DHA in the brain, including its role as indirect antioxidant, the selenium connection for proper antioxidant function and their changes during normal aging and in Alzheimer’s disease.

A comprehensive review on the neuropathophysiology of selenium

As an essential micronutrient, selenium (Se) exerts its biological function as a catalytic entity in a variety of enzymes. From a toxicological perspective, however, Se can become extremely toxic at concentrations slightly above its nutritional levels. Over the last few decades, there has been a growing level of concern worldwide regarding the adverse effects of both inorganic and organic Se compounds on a broad spectrum of neurological functions. A wealth of evidence has shown that exposure to excess Se may compromise the normal functioning of various key proteins, neurotransmitter systems (the glutamatergic, dopaminergic, serotonergic, and cholinergic systems), and signaling molecules involved in the control and regulation of cognitive, behavioral, and neuroendocrine functions. Elevated Se exposure has also been suspected to be a risk factor for the development of several neurodegenerative and neuropsychiatric diseases. Nonetheless, despite the various deleterious effects of excess Se on the central nervous system (CNS), Se neurotoxicity and negative behavioral outcomes are still disregarded at the expense of its beneficial health effects. This review focuses on the current state of knowledge regarding the neurobehavioral effects of Se and discusses its potential mode of action on different aspects of the central and peripheral nervous systems. This review also provides a brief history of Se discovery and uses, its physicochemical properties, biological roles in the CNS, environmental occurrence, and toxicity. We also review potential links between exposure to different forms of Se compounds and aberrant neurobehavioral functions in humans and animals, and identify key knowledge gaps and hypotheses for future research.

Selenium supplementation inhibits IGF-1 signaling and confers methionine restriction-like healthspan benefits to mice

Methionine restriction (MR) dramatically extends the healthspan of several organisms. Methionine-restricted rodents have less age-related pathology and increased longevity as compared with controls, and recent studies suggest that humans might benefit similarly. Mechanistically, it is likely that the decreased IGF-1 signaling that results from MR underlies the benefits of this regimen. Thus, we hypothesized that interventions that decrease IGF-1 signaling would also produce MR-like healthspan benefits. Selenium supplementation inhibits IGF-1 signaling in rats and has been studied for its putative healthspan benefits. Indeed, we show that feeding mice a diet supplemented with sodium selenite results in an MR-like phenotype, marked by protection against diet-induced obesity, as well as altered plasma levels of IGF-1, FGF-21, adiponectin, and leptin. Selenomethionine supplementation results in a similar, albeit less robust response, and also extends budding yeast lifespan. Our results indicate that selenium supplementation is sufficient to produce MR-like healthspan benefits for yeast and mammals.

Selenium at the eural arriers: eview

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

Dietary Habits, Selenium, Copper, Zinc and Total Antioxidant Status in Serum in Relation to Cognitive Functions of Patients with Alzheimer's Disease

Oxidative stress plays a crucial role in the neurodegenerative process and can impair cognitive functions. In the prevention of Alzheimer's disease (AD), an adequate consumption of dietary antioxidants may be a major factor. The objective of the study was to estimate selenium (Se), copper (Cu), zinc (Zn), and total antioxidant status (TAS) in the serum of patients with AD in relation to their cognitive functions and dietary habits. A total of 110 patients (aged 54-93 years) with early or moderate AD, as well as 60 healthy people (aged 52-83 years) were studied. The severity of the disease was assessed using the mini-mental state examination (MMSE) scale. Food-frequency questionnaires were implemented to collect the dietary data. The concentrations of Se, Cu and Zn in the sera were determined by the atomic absorption spectrometry method. TAS was estimated spectrophotometrically using ready-made kits (Randox). Significantly lower concentrations of Se, Zn and TAS, and higher Cu:Zn ratio in the serum of patients with AD, compared to healthy people, were observed. A low correlation between the MMSE score and TAS in the serum of AD patients and significantly higher MMSE values in patients with TAS above the reference range were also noted. In patients with serum Cu concentration above the norm, significantly lower MMSE values were found. Selected dietary habits such as the frequency of consumption of various food products had a significant impact on the concentration of the assessed parameters in the serum of people with AD.

Selenium and L-carnitine protects from valproic acid-Induced oxidative stress and mitochondrial damages in rat cortical neurons

Oxidative stress and mitochondrial dysfunction have been associated with valproic acid (VPA) induced neurotoxicity. Mitochondria are vulnerable to oxidative damage and are also a major source of superoxide free radicals. Therefore, the need for mitochondrial protective and antioxidant agents for reducing valporic acid toxicity in central nerve system (CNS) is essential. In the present study, we investigated the potential beneficial effects of sodium selenite (SS) and L-carnitine (LC) against valproic acid -induced oxidative stress and mitochondrial dysfunction in isolated rat cortical neurons. Valproic acid (50, 100 and 200 µM) treatment caused a significant decrease in cellular viability, which was accompanied by increases in reactive oxygen species (ROS) generation, GSSG and GSH content, lipid peroxidation and lysosomal and mitochondrial damages. Sodium selenite (1 µM) and L-carnitine (1 mM) pretreatment attenuated valproic acid-induced decrease in cell viability. In addition, sodium selenite (1 µM) and L-carnitine (1 mM) pretreatment significantly protected against valproic acid-induced raise in oxidative stress, mitochondrial and lysosomal dysfunction, lipid peroxidation levels and depletion of GSH content. Our results in the current study provided insights into the protective mechanism by L-carnitine and sodium selenite, which is liked, to neuronal ROS generation and mitochondrial and lysosomal damages.

Metabolomics and lipidomics study unveils the impact of polybrominated diphenyl ether-47 on breast cancer mice

Polybrominated diphenyl ether-47 (BDE-47) is a congener of polybrominated diphenyl ethers (PBDEs) and relates to different health risks. However, in vivo study of the association between BDE-47 and breast cancer was scarce. In this study, we performed in vivo exposure of BDE-47 to breast cancer nude mice and conducted mass spectrometry-based metabolomics and lipidomics analysis to investigate the metabolic changes in mice. Results showed that the tumor sizes were positively associated with the dosage of BDE-47. Metabolomics and lipidomics profiling analysis indicated that BDE-47 induced significant alterations of metabolic pathways in livers, including glutathione metabolism, ascorbate and aldarate metabolism, and lipids metabolism, etc. The upregulations of phosphatidylcholines (PCs) and phosphatidylethanolamines (PEs) suggested the membrane remodeling, and the downregulations of Lyso-PCs and Lyso-PEs might be associated with the tumor growth. Targeted metabolomics analysis revealed that BDE-47 inhibited fatty acid β-oxidation (FAO) and induced incomplete FAO. The inhibition of FAO and downregulation of PPARγ would contribute to inflammation, which could promote tumor growth. In addition, BDE-47 elevated the expression of the cytokines TNFRSF12A, TNF-α, IL-1β and IL-6, and lowered the cytokines SOCS3 and the nuclear receptor PPARα. The changes of cytokines and receptor may contribute to the tumor growth of mice.

Selenium Status in Elderly People: Longevity and Age-Related Diseases

BACKGROUND

Selenium (Se) is a trace element active in selenoproteins, which can regulate oxidative stress. It is generally perceived as an import factor for maintaining health in the elderly.

METHODS

The goal of this review is to discuss selenium concentration in biological samples, primarily serum or plasma, as a function of age and its relation with longevity. The elemental level in various age-related diseases is reviewed.

CONCLUSION

Highest selenium values were observed in healthy adults, while in an elderly population significantly lower concentrations were reported. Variables responsible for contradictory findings are mentioned. Risk and benefits of Se-supplementation still remain under debate.

Selenoprotein P and its potential role in Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disease associated with cognitive decline, loss of memory, and progressive cerebral atrophy. The trace element selenium (Se) is known to be involved in brain pathology. Selenoprotein P (SELENOP), as the main Se transport protein, is, to a great extent, responsible for maintaining Se homeostasis and the hierarchy of selenoprotein expression in the body. Adequate Se supply through SELENOP is vital for proper brain development and function. Additionally, SELENOP may be implicated in pathological processes in the central nervous system, including those in AD. The current review summarizes recent findings on the possible role of SELENOP in AD, with a focus on probable mechanisms: Se delivery to neurons, antioxidant activity, cytoskeleton assembly, interaction with redox-active metals (e.g., copper and iron), and misfolded proteins (amyloid beta and tau protein). The use of SELENOP as a biomarker of Se status is also briefly discussed. Epidemiological studies on Se supplementation are beyond the scope of the current review.

Melatonin and insulin modulates the cellular biochemistry, histoarchitecture and receptor expression during hepatic injury in diabetic rats

Aims; The present study was designed to ameliorate the integrated efficacy of exogenous melatonin and insulin on tissue biochemical, serological, histopathological architecture and receptor expression of melatonin (MT1, MT2) and insulin receptor (IR) expression against the hepatic injury in diabetic rats. Materials and Method; the rats were randomly allocated into nine different experimental groups. Diabetes was induced by streptozotocin (15 mg/kg) for 6 days. Rats having blood glucose level above 250 mg/dl were considered as diabetic. Animals euthanized after 4 weeks, blood and liver samples were collected to perform various biochemical, serological, histopathological and receptor expression of melatonin (MT1, MT2) and insulin receptor (IR). Key findings; Diabetic rats revealed significant increase in lipid peroxidation (LPO) of liver tissue, liver function tests (ALT, AST and ALP), increase in serum cholesterol, LDL, VLD, but decrease in HDL level. Further, diabetic rats exhibited significant decrement in antioxidative enzymatic system (GSH, SOD, CAT, GR, GPX, G6PDH and GST), total tissue protein and glycogen content. Histomicrograph of liver of diabetic rats resulted in vacuolization indicating cellular damages as well as upregulation in liver MT1, MT2 and IR protein expression. However, the combined therapy (Melatonin and insulin treatment) revealed significant recovery and restoration in biochemical, cellular architecture of liver cells and receptor expression pattern of MT1, MT2 and IR. Significance; It may establish a synergistic action of melatonin and insulin, which might be a novel evidence for clinicians to combat the hepatic complication along with controlling diabetes.

Organic selenium derived from chelation of soybean peptide-selenium and its functional properties in vitro and in vivo

Organic selenium has been widely explored as an important source of selenium (Se) supplement due to its low toxicity and easy absorption. In the present study, a new type of organic selenium was fabricated by chelating Se with soybean protein isolate peptides (SPIPs), and its physio-chemical properties, structural characteristics, and antioxidant activities were investigated. Results indicated that the structure of the SPIP molecule was folded and aggregated during the chelation process. SPIP-Se exhibited stronger hydroxyl radical scavenging activity and reducing power than SPIP in vitro. In addition, SPIP-Se could repair the H2O2-induced oxidative damage of Caco-2 cells by enhancing the activities of antioxidant enzymes. The in vivo assay showed that SPIP-Se showed much less toxicity than inorganic Se supplements, and exhibited a more positive effect on the activities of key enzymes including superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and aspartate aminotransferase (AST). These findings suggest that SPIP-Se could be developed as an effective dietary Se supplement in the food or pharmaceutical field in the future.

An in silico investigation on the inhibitory potential of the constituents of Pomegranate juice on antioxidant defense mechanism: Relevance to neurodegenerative diseases

Elevation in the levels of reactive oxygen and nitrogen species (RONS), and downregulation of cellular antixoidants, have ubiquitously been reported from studies in animal models of neurodegenerative diseases, including Parkinson’s disease (PD) and Alzheimer’s disease (AD). Thus, plant-derived compounds are widely being investigated for their beneficial effects in these models. However, while studies have reported antioxidant potentials of several phytochemicals, a large number of studies have demonstrated different phytochemicals to be rather pro-oxidant and exaggerate oxidative stress (OS). One such study aimed to investigate possible ameliorative effect of Pomegranate juice (PJ) in rat model of toxin-induced parkinsonism revealed that PJ exacerbates OS, inflammation and promotes neurodegeneration. Thus, it remains to be investigated whether different constituents and metabolites of PJ are pro-oxidant or anti-oxidant. Using computational modeling, we investigated possible inhibitory potential of different constituents of PJ and their metabolites viz. delphinidin-3-glucoside, dimethylellagic acid-glucuronide, ellagic acid, ellagitannin, gallic acid, gallotannin 23, pelargonidin, punicalagin, urolithin A, urolithin A-glucuronide and urolithin B, on anti-oxidant defense system of the brain. The results indicate that the constituents of PJ have the potential to inhibit five key enzymes of the neuronal antioxidant defense system, viz. catalase, superoxide dismutase, glutathione peroxidase 4, glutathione reductase and glutathione-S-transferase. Thus, it is surmised that the constituents of PJ may contribute to OS and neurodegeneration by way of affecting antioxidant defense mechanism. This may particularly be more pronounced in neurodegenerative diseases, since neurons are known to be more vulnerable to OS. Thus, the present findings caution the use of PJ in patients prone to OS, especially those suffering from neurodegenerative diseases, and warrant further experimental studies to unveil the effects of individual components and metabolites of PJ on antioxidant defense system of brain.

Redox Mechanisms in Neurodegeneration: From Disease Outcomes to Therapeutic Opportunities

SIGNIFICANCE

Once considered to be mere by-products of metabolism, reactive oxygen, nitrogen and sulfur species are now recognized to play important roles in diverse cellular processes such as response to pathogens and regulation of cellular differentiation. It is becoming increasingly evident that redox imbalance can impact several signaling pathways. For instance, disturbances of redox regulation in the brain mediate neurodegeneration and alter normal cytoprotective responses to stress. Very often small disturbances in redox signaling processes, which are reversible, precede damage in neurodegeneration. Recent Advances: The identification of redox-regulated processes, such as regulation of biochemical pathways involved in the maintenance of redox homeostasis in the brain has provided deeper insights into mechanisms of neuroprotection and neurodegeneration. Recent studies have also identified several post-translational modifications involving reactive cysteine residues, such as nitrosylation and sulfhydration, which fine-tune redox regulation. Thus, the study of mechanisms via which cell death occurs in several neurodegenerative disorders, reveal several similarities and dissimilarities. Here, we review redox regulated events that are disrupted in neurodegenerative disorders and whose modulation affords therapeutic opportunities.

CRITICAL ISSUES

Although accumulating evidence suggests that redox imbalance plays a significant role in progression of several neurodegenerative diseases, precise understanding of redox regulated events is lacking. Probes and methodologies that can precisely detect and quantify in vivo levels of reactive oxygen, nitrogen and sulfur species are not available.

FUTURE DIRECTIONS

Due to the importance of redox control in physiologic processes, organisms have evolved multiple pathways to counteract redox imbalance and maintain homeostasis. Cells and tissues address stress by harnessing an array of both endogenous and exogenous redox active substances. Targeting these pathways can help mitigate symptoms associated with neurodegeneration and may provide avenues for novel therapeutics. Antioxid. Redox Signal. 30, 1450-1499.

Insights into the Potential Role of Mercury in Alzheimer's Disease

Mercury (Hg), which is a non-essential element, is considered a highly toxic pollutant for biological systems even when present at trace levels. Elevated Hg exposure with the growing release of atmospheric pollutant Hg and rising accumulations of mono-methylmercury (highly neurotoxic) in seafood products have increased its toxic potential for humans. This review aims to highlight the potential relationship between Hg exposure and Alzheimer's disease (AD), based on the existing literature in the field. Recent reports have hypothesized that Hg exposure could increase the potential risk of developing AD. Also, AD is known as a complex neurological disorder with increased amounts of both extracellular neuritic plaques and intracellular neurofibrillary tangles, which may also be related to lifestyle and genetic variables. Research reports on AD and relationships between Hg and AD indicate that neurotransmitters such as serotonin, acetylcholine, dopamine, norepinephrine, and glutamate are dysregulated in patients with AD. Many researchers have suggested that AD patients should be evaluated for Hg exposure and toxicity. Some authors suggest further exploration of the Hg concentrations in AD patients. Dysfunctional signaling pathways in AD and Hg exposure appear to be interlinked with some driving factors such as arachidonic acid, homocysteine, dehydroepiandrosterone (DHEA) sulfate, hydrogen peroxide, glucosamine glycans, glutathione, acetyl-L carnitine, melatonin, and HDL. This evidence suggests the need for a better understanding of the relationship between AD and Hg exposure, and potential mechanisms underlying the effects of Hg exposure on regional brain functions. Also, further studies evaluating brain functions are needed to explore the long-term effects of subclinical and untreated Hg toxicity on the brain function of AD patients.

Sodium selenite protects from 3-nitropropionic acid-induced oxidative stress in cultured primary cortical neurons

Selenium (Se) is an essential trace element for humans; its intake is needed to allow the proper synthesis of 25 different selenoproteins that are necessary to the normal functioning of several organs, including the brain. Accordingly, decreased Se levels have been associated with neurological disorders. In the present study, we investigated the potential beneficial effects of Se, as sodium selenite, against 3-nitropropionic acid (3-NP)-induced oxidative stress in primary cultures of mouse cortical neurons. 3-NP treatment caused a significant decrease in cellular viability, which was accompanied by decreases in mitochondrial complex II activity and reduced glutathione (GSH) content, as well as increases in reactive oxygen species (ROS) generation and oxidized glutathione (GSSG) levels. Sodium selenite pretreatment (6 days) attenuated 3-NP-induced decrease in cell viability. In addition, sodium selenite pretreatment significantly protected against 3-NP-induced increase in ROS generation and decrease in GSH/GSSG ratio. Of note, sodium selenite pretreatment did not change 3-NP-induced decrease of mitochondrial complex II activity, suggesting that Se modulates secondary events resultant from 3-NP-induced mitochondrial dyshomeostasis. In addition, sodium selenite pretreatment significantly increased glutathione peroxidase (GPx) activity. Our data provide insights into the mechanism of protection by sodium selenite, which is related, at least in part, to GPx induction.

Selenium Status Is Not Associated with Cognitive Performance: A Cross-Sectional Study in 154 Older Australian Adults

Selenium was suggested to play a role in modulating cognitive performance and dementia risk. Thus, this study aimed to investigate the association between selenium status and cognitive performance, as well as inflammatory and neurotrophic markers in healthy older adults. This cross-sectional study included 154 older adults (≥60 years) from Victoria, Australia. Participants were assessed for cognitive performance (Cogstate battery), dietary selenium intake (two 24-h food recalls), plasma selenium concentration, inflammatory markers (interleukin (IL)-6, -8, -10, tumor necrosis factor-alpha and adiponectin) and neurotrophic factors (brain-derived neurotrophic factor, vascular endothelial growth factor and insulin-like growth factor 1). Dietary selenium intake was adequate for 85% of all participants. The prevalence of selenium deficiency was low; only 8.4% did not have the minimum concentration in plasma required for optimization of iodothyronine 5' deiodinases activity. Multiple linear regression analysis revealed that plasma selenium was not associated with cognitive performance, inflammatory markers nor neurotrophic factors, independent of age, sex, body mass index (BMI), habitual physical activity, APOE status, education, and history of cardiovascular disease. The lack of association might be due to the optimization of selenoproteins synthesis as a result of adequate selenium intake. Future prospective studies are recommended to explore potential associations of selenium status with age-associated cognitive decline.

Nutritional interventions and cognitive-related outcomes in patients with late-life cognitive disorders: A systematic review

There have been a large number of observational studies on the impact of nutrition on neuroprotection, however, there was a lack of evidence from randomized clinical trials (RCTs). In the present systematic review, from the 32 included RCTs published in the last four years (2014-2017) in patients aged 60 years and older with different late-life cognitive disorders, nutritional intervention through medical food/nutraceutical supplementation and multidomain approach improved magnetic resonance imaging findings and other cognitive-related biomarkers, but without clear effect on cognition in mild Alzheimer's disease (AD) and mild cognitive impairment (MCI). Antioxidant-rich foods (nuts, grapes, cherries) and fatty acid supplementation, mainly n-3 polyunsaturated fatty acids (PUFA), improved specific cognitive domains and cognitive-related outcomes in MCI, mild-to-moderate dementia, and AD. Antioxidant vitamin and trace element supplementations improved only cognitive-related outcomes and biomarkers, high-dose B vitamin supplementation in AD and MCI patients improved cognitive outcomes in the subjects with a high baseline plasma n-3 PUFA, while folic acid supplementation had positive impact on specific cognitive domains in those with high homocysteine.

Roles for selenium and selenoprotein P in the development, progression, and prevention of intestinal disease

Selenium (Se) is a micronutrient essential to human health, the function of which is mediated in part by incorporation into a class of proteins known as selenoproteins (SePs). As many SePs serve antioxidant functions, Se has long been postulated to protect against inflammation and cancer development in the gut by attenuating oxidative stress. Indeed, numerous studies over the years have correlated Se levels with incidence and severity of intestinal diseases such as inflammatory bowel disease (IBD) and colorectal cancer (CRC). Similar results have been obtained with the Se transport protein, selenoprotein P (SELENOP), which is decreased in the plasma of both IBD and CRC patients. While animal models further suggest that decreases in Se or SELENOP augment colitis and intestinal tumorigenesis, large-scale clinical trials have yet to show a protective effect in patient populations. In this review, we discuss the function of Se and SELENOP in intestinal diseases and how research into these mechanisms may impact patient treatment.

Selenium, selenoprotein P, and Alzheimer's disease: is there a link?

The essential trace element, selenium (Se), is crucial to the brain but it may be potentially neurotoxic, depending on dosage and speciation; Se has been discussed for decades in relation to Alzheimer's disease (AD). Selenoprotein P (SELENOP) is a secreted heparin-binding glycoprotein which serves as the main Se transport protein in mammals. In vivo studies showed that this protein might have additional functions such as a contribution to redox regulation. The current review focuses on recent research on the possible role of SELENOP in AD pathology, based on model and human studies. The review also briefly summarizes results of epidemiological studies on Se supplementation in relation to brain diseases, including PREADViSE, EVA, and AIBL. Although mainly positive effects of Se are assessed in this review, possible detrimental effects of Se supplementation or exposure, including potential neurotoxicity, are also mentioned. In relation to AD, various roles of SELENOP are discussed, i.e. as the means of Se delivery to neurons, as an antioxidant, in cytoskeleton assembly, in interaction with redox-active metals (copper, iron, and mercury) and with misfolded proteins (amyloid-beta and hyperphosphorylated tau-protein).

Effects of topography and soil properties on soil selenium distribution and bioavailability (phosphate extraction): A case study in Yongjia County, China

Selenium (Se) is an essential trace element for humans. In order to investigate how soil Se is influenced by topography and soil properties, we selected Yongjia County, an area with mountainous topography, as a study area. This study used cultivated soil data to comprehensively analyze the effects of topography and soil properties on Se mobility and bioavailability and to identify the key factors influencing Se distribution in the environment. Factors considered in this study were elevation, slope, topographic wetness index, the coefficient of weathering and eluviation, pH, organic matter, and Fe₂O₃. The concentration of total soil Se (0.382±0.123mgkg^-1) was far higher than the background value of soil in China, and 98% of the soil samples were classified as having moderate Se levels (>0.175mgkg^-1), indicating Yongjia County is a Se-rich region in China. Phosphate extracted Se accounted for an average of 9% of the total Se and was significantly associated with soil total Se, Fe₂O₃, pH, and the coefficient of weathering and eluviation. Fe₂O₃ primarily controlled Se adsorption, fixation, and availability in soil. Under the geo-environmental conditions in the study area, the total Se in the soil increased first and then decreased with increases in elevation, slope, and the topographic wetness index, and the phosphate extracted Se showed similar patterns except for the elevation. The findings showed that topographical attributes and soil physicochemical properties synthetically influenced the distribution and bioavailability of Se in soil.

Effect of Sodium Selenate on Hippocampal Proteome of 3×Tg-AD Mice-Exploring the Antioxidant Dogma of Selenium against Alzheimer's Disease

Selenium (Se), an antioxidant trace element, is an important nutrient for maintaining brain functions and is reported to be involved in Alzheimer's disease (AD) pathologies. The present study has been designed to elucidate the protein changes in hippocampus of 3×Tg-AD mice after supplementing sodium selenate as an inorganic source of selenium. By using iTRAQ proteomics technology, 113 differentially expressed proteins (DEPs) are found in AD/WT mice with 37 upregulated and 76 downregulated proteins. Similarly, in selenate-treated 3×Tg-AD (ADSe/AD) mice, 115 DEPs are found with 98 upregulated and 17 downregulated proteins. The third group of mice (ADSe/WT) showed 75 DEPs with 46 upregulated and 29 downregulated proteins. Among these results, 42 proteins (40 downregulated and 2 upregulated) in the diseased group showed reverse expression when treated with selenate. These DEPs are analyzed with different bioinformatics tools and are found associated with various AD pathologies and pathways. Based on their functions, selenate-reversed proteins are classified as structural proteins, metabolic proteins, calcium regulating proteins, synaptic proteins, signaling proteins, stress related proteins, and transport proteins. Six altered AD associated proteins are successfully validated by Western blot analysis. This study shows that sodium selenate has a profound effect on the hippocampus of the triple transgenic AD mice. This might be established as an effective therapeutic agent after further investigation.

Associations of Spatial Disparities of Alzheimer's Disease Mortality Rates with Soil Selenium and Sulfur Concentrations and Four Common Risk Factors in the United States

BACKGROUND

Associations between environmental factors and spatial disparity of mortality rates of Alzheimer's disease (AD) in the US are not well understood.

OBJECTIVE

To find associations between 41 trace elements, four common risk factors, and AD mortality rates in the48 contiguous states.

METHODS

Isopleth maps of AD mortality rates of the 48 states and associated factors were examined. Correlations between state average AD mortality rates and concentrations of 41 soil elements, wine consumption, percentage of current smokers, obesity, and diagnosed diabetes of the 48 states between 1999 and 2014 were analyzed.

RESULTS

Among 41 elements, soil selenium concentrations have the most significant inverse correlations with AD mortality rates. Rate ratio (RR) of the 6 states with the lowest product of soil selenium and sulfur concentrations is 53% higher than the 6 states with the highest soil selenium sulfur product in the 48 states (RR = 1.53, CI95% 1.51-1.54). Soil tin concentrations have the most significant inverse correlation with AD mortality growth rates between 1999 and 2014, followed by soil sulfur concentrations. Percentages of obesity, diagnosed diabetes, smoking, and wine consumption per capita also correlate significantly with AD mortality growth rates.

CONCLUSIONS

High soil selenium and sulfur concentrations and wine consumption are associated with low AD mortality rates. Given that average soil selenium and sulfur concentrations are indicators of their intakes from food, water, and air by people in a region, long-term exposure to high soil selenium and sulfur concentrations might be beneficial to AD mortality rate reduction in a region.

Proteins enriched in charged amino acids control the formation and stabilization of selenium nanoparticles in Comamonas testosteroni S44

Elemental selenium nanoparticles (SeNPs) are useful in medicine, environmental remediation and in material science. Biosynthesized SeNPs (BioSeNPs) by bacteria are cheap, eco-friendly and have a lower cytotoxicity in comparison with chemically synthesized ones. Organic matters were found to cap on the surface of BioSeNPs, but the functions were still not entirely clear. The purified BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy (TEM). Fourier Transform Infrared (FT-IR) and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins, 23 mg carbohydrates and only very limited amounts of lipids. Proteomics of BioSeNPs showed more than 800 proteins bound to BioSeNPs. Proteins enriched in charged amino acids are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria. In view of the results reported here, a schematic model for the molecular mechanism of BioSeNPs formation in bacteria is proposed. These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs for medicine application.

Association of soil selenium, strontium, and magnesium concentrations with Parkinson's disease mortality rates in the USA

Among the 41 soil elements analyzed from 4856 sites across the contiguous 48 states, average Parkinson's disease (PD) mortality rates between 1999 and 2014 have the most significant positive correlation with the average soil strontium (Sr) concentrations (correlation r = 0.47, significance level p = 0.00), and average PD mortality rates have the most significant inverse correlation with the average soil selenium (Se) concentrations (r = -0.44, p = 0.00). Multivariate regression models indicate that soil Sr and Se concentrations can explain 35.4% of spatial disparities of the state average PD mortality rates between 1999 and 2014 (R ² = 0.354). When the five outlier states were removed from the model, concentrations of soil Sr and Se can explain 62.4% (R ² = 0.624) of the spatial disparities of PD mortality rates of the 43 remaining states. The results also indicate that high soil magnesium (Mg) concentrations suppressed the growth rate of the PD mortality rates between 1999 and 2014 in the 48 states (r = -0.42, p = 0.000). While both Se and Sr have been reported to affect the nervous system, this study is the first study that reported the statistically significant association between the PD mortality rates and soil concentrations of Se, Sr, and Mg in the 48 states. Given that soil elemental concentration in a region is broad indicator of the trace element intake from food, water, and air by people, implications of the results are that high soil Se and Mg concentrations helped reduce the PD mortality rates and benefited the PD patients in the 48 states.

Effect of selenium on testicular damage induced by varicocele in adult male Wistar rats

PROJECT

Varicocele is an abnormal tortuosity and distension of the veins of the pampiniform plexus in the spermatic cord. It is the most common surgically correctable cause of male infertility. Several studies have revealed the effects of increased oxidative stress on serum, semen, and testicular tissues in patients with varicocele or in animal models. The aim of this study was to investigate the effects of sodium selenite on testicular damage induced by experimental left varicocele in male Wistar rats.

PROCEDURE

In the present study, the effects of oral administration of sodium selenite (at doses of 0.05, 0.1, 0.2, and 0.4mg/kg bw) were assessed in normal and varicocelized rats.

RESULTS

The varicocelized control rats showed decrease in sperm quality parameters, decreased activity of testes CAT, GPX and SOD, increased levels of MDA, and damage in testicular architecture. Administration of sodium selenite significantly reduced these changes to nearly normal levels, but did not change these parameters in normal rats. Histopathological studies further confirmed the protective effects of sodium selenite on varicocele-induced testicular damage in rats. Administrations of sodium selenite did not change these parameters in normal rats.

CONCLUSIONS

Taken together, the results of this study suggest that sodium selenite treatment may have beneficial effect on the testes of varicocelized rats.

Dysregulation of serum NADPH oxidase1 and ferritin levels provides insights into diagnosis of Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) is a common neurodegenerative disease. Oxidative stress is considered as a key modulator in the development of PD. This study aimed to investigate associations between serum NOX1 (NADPH oxidase1), ferritin, selenium (Se), and uric acid (UA) levels and clinical parameters in patients with PD.

DESIGN AND METHODS

Serum levels of NOX1, ferritin, Se, and UA were measured in 40 PD patients and 40 healthy individuals. Receiver operating characteristic (ROC) analysis was performed to investigate incremental diagnostic value of each factor in the study groups.

RESULTS

Mean serum NOX1 levels were markedly higher in patient group (22.36±5.80ng/mL) versus healthy individuals (8.89±2.37ng/mL) (p<0.001). Significant differences were also observed in the serum concentrations of ferritin (p=0.005) and Se (p=0.001) between patients with PD and healthy individuals. However, the serum concentrations of UA were not statistically significant between the study groups (p=0.560). ROC analysis revealed a diagnostic ability of serum NOX1 and ferritin levels for PD with an area under ROC curve of ≥0.7 (p<0.05) and relatively high sensitivity and specificity. Combination of serum NOX1 and Se along with ferritin and UA levels increased the sensitivity up to 85%, specificity up to 97% and area under the ROC curve up to 0.94 (95% confidence interval (95% CI): 0.89 to 0.99, p<0.001).

CONCLUSION

Our findings indicated that serum concentrations of NOX1, ferritin, and Se are significantly higher in the patients with PD. Therefore, these factors can be considered as potential diagnostic biomarkers for diagnosis and monitoring of PD patients. Further studies are required with larger sample size to provide more detailed information about the cognitive profile of participants and the outcome measures.

Sodium selenate activated Wnt/β-catenin signaling and repressed amyloid-β formation in a triple transgenic mouse model of Alzheimer's disease

Accumulating evidences show that selenium dietary intake is inversely associated with the mortality of Alzheimer's disease (AD). Sodium selenate has been reported to reduce neurofibrillary tangles (NFT) in the tauopathic mouse models, but its effects on the Wnt/β-catenin signaling pathway and APP processing remain unknown during AD formation. In this paper, triple transgenic AD mice (3×Tg-AD) had been treated with sodium selenate in drinking water for 10month before the detection of hippocampal pathology. Increased Aβ generation, tau hyperphosphorylation and neuronal apoptosis were found in the hippocampus of AD model mouse. Down-regulation of Wnt/β-catenin signaling is closely associated with the alteration of AD pathology. Treatment with sodium selenate significantly promoted the activity of protein phosphatases of type 2A (PP2A) and repressed the hallmarks of AD. Activation of PP2A by sodium selenate could increase active β-catenin level and inhibit GSK3β activity in the hippocampal tissue and primarily cultured neurons of AD model mouse, leading to activation of Wnt/β-catenin signaling and transactivation of target genes, including positively-regulated genes c-myc, survivin, TXNRD2 and negatively-regulated gene BACE1. Meanwhile, APP phosphorylation was also reduced on the Thr668 residue after selenate treatment, causing the decreases of APP cleavage and Aβ generation. These findings reveal that the Wnt/β-catenin signaling is a potential target for prevention of AD and sodium selenate may be developed as a new drug for AD treatment.

Chiral penicillamine-modified selenium nanoparticles enantioselectively inhibit metal-induced amyloid β aggregation for treating Alzheimer's disease

Nanometer-scale chirality has gained significant interest from different research fields due to its fundamental importance in nature and living matter. In this study, we design and synthesize chiral penicillamine-capped selenium nanoparticles (l-/d-Pen@Se NPs) that can act as a novel class of chiral amyloid-β (Aβ) inhibitors. In this work, d-Pen@Se NPs demonstrate higher inhibition efficiency, as well as ameliorate cognition and memory impairments. We used rat pheochromocytoma (PC12) cells to perform real-time cell analysis assay (RTCA) to probe the potential cytotoxicity of l-/d-Pen@Se NPs. At any given time point, the cell index decreases as d-Pen@Se NPs concentration increases, demonstrating a concentration-dependent cytotoxic effect on PC12 cells. In addition, d-Pen@Se NPs also reduced Zn²⁺-induced intracellular Aβ₄₀ fibrillation, while l-Pen@Se NPs did not. The histological analysis demonstrates that mice treated with d-Pen@Se NPs did not exhibit signs of in vivo systemic toxicity in major organs. Our findings are highly encouraging in terms of providing substantial evidence of the safety of chiral d-Pen@Se NPs for biomedical application. We expect that these results will be relevant for other chiral NPs for treatment of Alzheimer's disease and have broad implications in NP-based studies and applications.

N-γ-(L-Glutamyl)-L-selenomethionine enhances stress resistance and ameliorates aging indicators via the selenoprotein TRXR-1 in Caenorhabditis elegans

SCOPE

Selenium is an essential trace nutrient for human health. This study investigates the organic form of selenium, N-γ-(L-Glutamyl)-L-selenomethionine (Glu-SeMet), for its effects on aging indicators and stress resistance. The role of the selenoprotein TRXR-1 was also evaluated in Caenorhabditis elegans.

METHODS AND RESULTS

Glu-SeMet-treated wild-type N2 worms showed increased survival upon oxidative and thermal stress challenges. However, Glu-SeMet treatment did not extend the lifespan of wild-type N2 C. elegans under normal conditions (p = 0.128 for 0.01 μM and p = 0.799 for 10 μM Glu-SeMet). Under stress conditions, Glu-SeMet significantly increased the survival of wild-type N2 C. elegans, but the phenomenon was absent from trxr-1 null mutant worms. Furthermore, Glu-SeMet treatments significantly ameliorated aging indicators, including body bends, pumping rate, defecation duration, and lipofuscin accumulation in wild-type N2 nematodes. Nevertheless, the ameliorative effects by Glu-SeMet were absent in the trxr-1 null mutant worms.

CONCLUSION

The findings indicate that enhanced stress resistance and improved aging indicators by Glu-SeMet in C. elegans are mediated by the selenoprotein TRXR-1. Glu-SeMet has potential for improving health and also provides new insights into selenium's regulatory mechanisms in intact organisms.

Glutathione peroxidase 4: a new player in neurodegeneration?

Glutathione peroxidase 4 (GPx4) is an antioxidant enzyme reported as an inhibitor of ferroptosis, a recently discovered non-apoptotic form of cell death. This pathway was initially described in cancer cells and has since been identified in hippocampal and renal cells. In this Perspective, we propose that inhibition of ferroptosis by GPx4 provides protective mechanisms against neurodegeneration. In addition, we suggest that selenium deficiency enhances susceptibility to ferroptotic processes, as well as other programmed cell death pathways due to a reduction in GPx4 activity. We review recent studies of GPx4 with an emphasis on neuronal protection, and discuss the relevance of selenium levels on its enzymatic activity.

Selenoproteins in Tumorigenesis and Cancer Progression

Selenium is a micronutrient essential to human health and has long been associated with cancer prevention. Functionally, these effects are thought to be mediated by a class of selenium-containing proteins known as selenoproteins. Indeed, many selenoproteins have antioxidant activity which can attenuate cancer development by minimizing oxidative insult and resultant DNA damage. However, oxidative stress is increasingly being recognized for its "double-edged sword" effect in tumorigenesis, whereby it can mediate both negative and positive effects on tumor growth depending on the cellular context. In addition to their roles in redox homeostasis, recent work has also implicated selenoproteins in key oncogenic and tumor-suppressive pathways. Together, these data suggest that the overall contribution of selenoproteins to tumorigenesis is complicated and may be affected by a variety of factors. In this review, we discuss what is currently known about selenoproteins in tumorigenesis with a focus on their contextual roles in cancer development, growth, and progression.

Selenium in the Therapy of Neurological Diseases. Where is it Going?

Selenium (₃₄Se), an antioxidant trace element, is an important regulator of brain function. These beneficial properties that Se possesses are attributed to its ability to be incorporated into selenoproteins as an amino acid. Several selenoproteins are expressed in the brain, in which some of them, e.g. glutathione peroxidases (GPxs), thioredoxin reductases (TrxRs) or selenoprotein P (SelP), are strongly involved in antioxidant defence and in maintaining intercellular reducing conditions. Since increased oxidative stress has been implicated in neurological disorders, including Parkinson’s disease, Alzheimer’s disease, stroke, epilepsy and others, a growing body of evidence suggests that Se depletion followed by decreased activity of Se-dependent enzymes may be important factors connected with those pathologies. Undoubtedly, the remarkable progress that has been made in understanding the biological function of Se in the brain has opened up new potential possibilities for the treatment of neurological diseases by using Se as a potential drug. However, further research in the search for optimal Se donors is necessary in order to achieve an effective and safe therapeutic income.