Natural Nrf2 activators in diabetes

Single-cell RNA sequencing reveals that NRF2 regulates vascular smooth muscle cell phenotypic switching in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening disease characterized by extensive membrane destruction in the vascular wall that is closely associated with vascular smooth muscle cell (VSMC) phenotypic switching. A thorough understanding of the changes in regulatory factors during VSMC phenotypic switching is essential for managing AAA therapy. In this study, we revealed the impact of NRF2 on the modulation of VSMC phenotype and the development of AAA based on single-cell RNA sequencing analysis. By utilizing a murine model of VSMC-specific knockout of nuclear factor E2-related factor 2 (NRF2), we observed that the absence of NRF2 in VSMCs exacerbated AAA formation in an angiotensin II-induced AAA model. The downregulation of NRF2 promoted VSMC phenotypic switching, leading to an enhanced inflammatory response. Through genome-wide transcriptome analysis and loss- or gain-of-function experiments, we discovered that NRF2 upregulated the expression of VSMC contractile phenotype-specific genes by facilitating microRNA-145 (miR-145) expression. Our data identified NRF2 as a novel regulator involved in maintaining the VSMC contractile phenotype while also influencing AAA formation through an miR-145-dependent regulatory mechanism.

Redox Regulation of Immunometabolism in Microglia Underpinning Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness among the working-age population. Microglia, resident immune cells in the retina, are recognized as crucial drivers in the DR process. Microglia activation is a tightly regulated immunometabolic process. In the early stages of DR, the M1 phenotype commonly shifts from oxidative phosphorylation to aerobic glycolysis for energy production. Emerging evidence suggests that microglia in DR not only engage specific metabolic pathways but also rearrange their oxidation-reduction (redox) system. This redox adaptation supports metabolic reprogramming and offers potential therapeutic strategies using antioxidants. Here, we provide an overview of recent insights into the involvement of reactive oxygen species and the distinct roles played by key cellular antioxidant pathways, including the NADPH oxidase 2 system, which promotes glycolysis via enhanced glucose transporter 4 translocation to the cell membrane through the AKT/mTOR pathway, as well as the involvement of the thioredoxin and nuclear factor E2-related factor 2 antioxidant systems, which maintain microglia in an anti-inflammatory state. Therefore, we highlight the potential for targeting the modulation of microglial redox metabolism to offer new concepts for DR treatment.

Phytochemicals and Their Usefulness in the Maintenance of Health

Inflammation is the immune system's first biological response to infection, injury, or irritation. Evidence suggests that the anti-inflammatory effect is mediated by the regulation of various inflammatory cytokines, such as nitric oxide, interleukins, tumor necrosis factor alpha-α, interferon gamma-γ, as well as the non-cytokine mediator, prostaglandin E2. Currently, the mechanism of action and clinical usefulness of phytochemicals is known; their action on the activity of cytokines, free radicals, and oxidative stress. The latter are of great relevance in the development of diseases, such that the evidence collected demonstrates the beneficial effects of phytochemicals in maintaining health. Epidemiological evidence indicates that regular consumption of fruits and vegetables is related to a low risk of developing cancer and other chronic diseases.

Annona Muricata L. extract restores renal function, oxidative stress, immunohistochemical structure, and gene expression of TNF-α, IL-β1, and CYP2E1 in the kidney of DMBA-intoxicated rats

Introduction: 7,12-dimethylbenz (a) anthracene (DMBA) is a harmful polycyclic aromatic hydrocarbon derivative known for its cytotoxic, carcinogenic, and mutagenic effects in mammals and other species. Annona muricata, L. (Graviola; GRV) is a tropical fruit tree traditionally well-documented for its various medicinal benefits. This investigation is the first report on the potential antioxidant and antinfammatory reno-protective impact of GRV against DMBA-induced nephrotoxicity in rats. Methods: Forty male albino rats were allocated into four equal groups (n = 10). The 1st group served as the control, the 2nd group (GRV) was gastro-gavaged with GRV (200 mg/kg b.wt), the 3rd group (DMBA) was treated with a single dose of DMBA (15 mg/kg body weight), and the 4th group (DMBA + GRV) was gastro-gavaged with a single dose of DMBA, followed by GRV (200 mg/kg b.wt). The GRV administration was continued for 8 weeks. Results and Discussion: Results revealed a significant improvement in renal function, represented by a decrease in urea, creatinine, and uric acid (UA) in the DMBA + GRV group. The antioxidant potential of GRV was confirmed in the DMBA + GRV group by a significant decline in malondialdehyde (MDA) and a significant increase in catalase (CAT), superoxide dismutase (SOD), glutathione S transferase (GST), and reduced glutathione (GSH) compared to DMBA-intoxicated rats; however, it was not identical to the control. Additionally, the antiinflammatory role of GRV was suggested by a significant decline in mRNA expression of cytochrome P450, family 2, subfamily e, polypeptide 1 (CYP2E1), tumor necrosis factor-alpha (TNF-α), and interleukin 1 beta (IL-1β) in the DMBA + GRV group. Moreover, GRV improved the histopathologic and immunohistochemical expression of TNF-α, CYP450, and IL1β in DMBA-intoxicated kidney tissue. Conclusively, GRV is a natural medicinal product that can alleviate the renal injury resulting from environmental exposure to DMBA. The reno-protective effects of GRV may involve its anti-inflammatory and/or antioxidant properties, which are based on the presence of phytochemical compounds such as acetogenins, alkaloids, and flavonoids.

Nrf2 modulates the benefits of evening exercise in type 2 diabetes

Exercise has well-characterized therapeutic benefits in the management of type 2 diabetes mellitus (T2DM). Most of the beneficial effects of exercise arise from the impact of nuclear factor erythroid 2 related factor-2 (Nrf2) activation of glucose metabolism. Nrf2 is an essential controller of cellular anti-oxidative capacity and circadian rhythms. The circadian rhythm of Nrf2 is influenced by circadian genes on its expression, where the timing of exercise effects the activation of Nrf2 and the rhythmicity of Nrf2 and signaling, such that the timing of exercise has differential physiological effects. Exercise in the evening has beneficial effects on diabetes management, such as lowering of blood glucose and weight. The mechanisms responsible for these effects have not yet been associated with the influence of exercise on the circadian rhythm of Nrf2 activity. A better understanding of exercise-induced Nrf2 activation on Nrf2 rhythm and signaling can improve our appreciation of the distinct effects of morning and evening exercise. This review hypothesizes that activation of Nrf2 by exercise in the morning, when Nrf2 level is already at high levels, leads to hyperactivation and decrease in Nrf2 signaling, while activation of Nrf2 in the evening, when Nrf2 levels are at nadir levels, improves Nrf2 signaling and lowers blood glucose levels and increases fatty acid oxidation. Exploring the effects of Nrf2 activators on rhythmic signaling could also provide valuable insights into the optimal timing of their application, while also holding promise for timed treatment of type 2 diabetes.

Capsiate-Rich Fraction of Capsicum annuum Induces Muscular Glucose Uptake, Ameliorates Rosiglitazone-Induced Adipogenesis, and Exhibits Activation of NRs Regulating Multiple Signaling Pathways

Capsiate is a key ingredient in the fruits of a nonpungent cultivar of Capsicum annuum. We investigated the effects of a C. annuum extract (CE) and a capsiate-rich fraction of CE (CR) on nuclear receptors involved in multiple signaling pathways, glucose uptake, and adipogenesis in comparison to pure capsiate (Ca). Similar to the effect of Ca (100 μM), CE (500 μg/mL) and CR (100 μg/mL) caused the activation of PPARα and PPARγ (>3-fold), while CR also activated LXR and NRF2 (>2 fold). CR (200 μg/mL) and Ca (100 μM) decreased lipid accumulation (22.6 ± 14.1 and 49.7 ± 7.3%, respectively) in adipocytes and increased glucose uptake (44.7 ± 6.2 and 30.1 ± 12.2%, respectively) in muscle cells and inhibited the adipogenic effect induced by rosiglitazone by 41.2 ± 5.6 and 13.9 ± 4.3%, respectively. This is the first report to reveal the agonistic action of CR and Ca on multiple nuclear receptors along with their enhanced glucose uptake and antiadipogenic effects. The results indicate the potential utility of the capsiate-rich fraction of C. annuum in alleviating the symptoms of metabolic syndrome and in preventing the undesired adipogenic effects of full PPARγ agonists such as rosiglitazone.

Screening of the phytochemical constituents of Teucrium polium extract and evaluation of their prophylactic role against the oxidative damage and cytotoxicity of Aflatoxin B1 in rats

Aflatoxin B1 (AFB1) is common carcinogen causing acute and chronic hepatocyte injuries. This study aimed to determine the bioactive components of Teucrium polium methanolic extract (TPE) and to evaluate their protective role against AFB1-induced oxidative damage, cytotoxicity, and genotoxicity in rats. Six groups of male albino rats were treated orally for 4 weeks including the control group, the ِAFB1-treated group (80 μg/kg b.w.), the groups treated with low (LD) or high (HD) dose TPE (50 or 100 mg/kg b.w.), and the groups treated with AFB1 plus TEP (LD) or TPE (HD). Blood and serum samples were collected for different assays. The GC-MS identified 34 compounds, the major compounds were pinene, germacrene D, α-cadinol, α-thujene, epi-bicyclosesquiphellandrene, and limonene. Animals that received AFB1 showed significant changes in all indicators of oxidative stress, biochemistry, cytokines, MNPCEs, comet tail formation in bone marrow, mRNA expression of inflammatory-related genes, Nrf2, and iNOS beside histological changes in the liver. TPE at the two doses tested showed insignificant changes in all tested parameters. The extract could normalize most of these parameters and the hepatic structure in AFB1-treated animals in a dose-dependent fashion. therefore, we concluded that TPE supplementation is effective for protection against AFB1 in endemic areas.

Tripeptide Leu-Pro-Phe from Corn Protein Hydrolysates Attenuates Hyperglycemia-Induced Neural Tube Defect in Chicken Embryos

Neural tube defect (NTD) is the most common and severe embryopathy causing embryonic malformation and even death associated with gestational diabetes mellitus (GDM). Leu-Pro-Phe (LPF) is an antioxidative tripeptide isolated from hydrolysates of corn protein. However, the biological activity of LPF in vivo and in vitro remains unclear. This study is aimed at investigating the protective effects of tripeptide LPF against NTD in the high glucose exposure condition and delineate the underlying biological mechanism. We found that LPF alleviated NTD in the high glucose-exposed chicken embryo model. In addition, DF-1 chicken embryo fibroblast was loaded with high glucose for induction of oxidative stress and abnormal O-GlcNAcylation in vitro. LPF significantly decreased accumulation of reactive oxygen species and content of malondialdehyde in DF-1 cells but increased the ratio of reduced glutathione and oxidized glutathione in chick embryo. Oxygen radical absorbance capacity results showed that LPF itself had good free radical scavenging capacity and could enhance antioxidant activity of the cell content. Mechanistic studies suggested that the resistance of LPF to oxidative damage may be related to promotion of NRF2 expression and nuclear translocation. LPF alleviated the overall O-GlcNAcylation level of cellular proteins under high glucose conditions and restored the level of Pax3 protein. Collectively, our findings indicate that LPF peptide could act as a nutritional supplement for the protection of development of embryonic neural tube affected by GDM.

Quercetin ameliorates oxidative stress‑induced cell apoptosis of seminal vesicles via activating Nrf2 in type 1 diabetic rats

It was known that diabetes may affect the male reproductive function by inhibiting the secretion of male accessory glands including seminal vesicles. Increased cell apoptosis induced by oxidative stress is thought to be an important pathological change in the seminal vesicles in diabetic patients. Quercetin is a potent anti-oxidative bioflavonoid. In this study, we explore the effect of quercetin on cell apoptosis of seminal vesicles and its underlying mechanism. The STZ-induced type 1 diabetic rat model was established. Three doses (low, medium and high) of quercetin were administrated to the STZ-induced type 1 diabetic rats for 4 months. Fasting blood glucose, the fructose in seminal plasma, total antioxidant capacity (T-AOC) and malondialdehyde (MDA) in seminal vesicles were determined by colorimetric method. Nuclear transcription factor- Nrf2 was observed by immunofluorescent staining. Biomarkers related to cell apoptosis, such as Bcl-2, Bax and cleaved -Caspase3 were measured by Western blotting and immumohistochemical staining. The body weight and seminal vesicle weight indexes were also determined. The results showed that T-AOC and Nrf2 were decreased, the levels of MDA were increased, the cleaved Caspase-3 was increased and the ratio of Bax to BCL-2 was decreased in seminal vesicles of diabetic rats, along with the severe hyperglycemia. When diabetic rats were treated by quercetin for 4 months, all the indexes were reversed at different degree except the fasting blood glucose. Our results suggested that quercetin could ameliorate oxidative stress‑induced cell apoptosis of seminal vesicles via inhibiting Nrf2 in type 1 diabetic rats, which indicated that quercetin could be used for preventing lesions of seminal vesicles in type 1 diabetes.

An update of Nrf2 activators and inhibitors in cancer prevention/promotion

NF-E2-related factor 2 (Nrf2) protein is a basic-region leucine zipper transcription factor that defends against endogenous or exogenous stressors. By inducing several cytoprotective and detoxifying gene expressions, Nrf2 can increase the sensitivity of the cells to oxidants and electrophiles. Transient Nrf2 activation, by its specific activators, has protective roles against carcinogenesis and cancer development. However, permanent activation of Nrf2 promotes various cancer properties, comprising malignant progression, chemo/radio resistance, and poor patient prognosis. Taken together, these findings suggest that reaching an optimal balance between paradoxical functions of Nrf2 in malignancy may render a selective improvement to identify therapeutic strategies in cancer treatment. In this review, we describe lately discovered Nrf2 inducers and inhibitors, and their chemopreventive and/or anticancer activities.

The Nrf2 pathway signifies one of the most significant cell defense procedures against exogenous or endogenous stressors. Certainly, by increasing the expression of several cytoprotective genes, the transcription factor Nrf2 can shelter cells and tissues from multiple sources of damage including electrophilic, xenobiotic, metabolic, and oxidative stress. Notably, the aberrant activation or accumulation of Nrf2, a common event in many tumors, confers a selective advantage to cancer cells and is connected to malignant progression, therapy resistance, and poor prognosis. Therefore, lately, Nrf2 has arisen as a hopeful target in treatment of cancer, and many struggles have been made to detect therapeutic strategies intended at disrupting its pro-oncogenic role. By summarizing the outcomes from past and recent studies, this review provided an overview concerning the Nrf2 pathway and the molecular mechanisms causing Nrf2 hyperactivation in cancer cells. Finally, this paper also described some of the most promising therapeutic approaches that have been successfully employed to counteract Nrf2 activity in tumors, with a particular emphasis on the development of natural compounds and the adoption of drug repurposing strategies.

3,3′,4,5′-Tetramethoxy-trans-stilbene Improves Insulin Resistance by Activating the IRS/PI3K/Akt Pathway and Inhibiting Oxidative Stress

The potential anti-diabetic effect of resveratrol derivative, 3,3′,4,5′-tetramethoxy-trans-stilbene (3,3′,4,5′-TMS) and its underlying mechanism in high glucose (HG) and dexamethasone (DXMS)-stimulated insulin-resistant HepG2 cells (IR-HepG2) were investigated. 3,3′,4,5′-TMS did not reduce the cell viability of IR-HepG2 cells at the concentrations of 0.5–10 µM. 3,3′,4,5′-TMS increased the potential of glucose consumption and glycogen synthesis in a concentration-dependent manner in IR-HepG2 cells. 3,3′,4,5′-TMS ameliorated insulin resistance by enhancing the phosphorylation of glycogen synthase kinase 3 beta (GSK3β), inhibiting phosphorylation of insulin receptor substrate-1 (IRS-1), and activating phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) pathway in IR-HepG2 cells. Furthermore, 3,3′,4,5′-TMS significantly suppressed levels of reactive oxygen species (ROS) with up-regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) expression. To conclude, the beneficial effect of 3,3′,4,5′-TMS against insulin resistance to increase glucose consumption and glycogen synthesis was mediated through activation of IRS/PI3K/Akt signaling pathways in the IR-HepG2 cells, accomplished with anti-oxidative activity through up-regulation of Nrf2.

The Multifunctional Role of Herbal Products in the Management of Diabetes and Obesity: A Comprehensive Review

Obesity and diabetes are the most demanding health problems today, and their prevalence, as well as comorbidities, is on the rise all over the world. As time goes on, both are becoming big issues that have a big impact on people’s lives. Diabetes is a metabolic and endocrine illness set apart by hyperglycemia and glucose narrow-mindedness because of insulin opposition. Heftiness is a typical, complex, and developing overall wellbeing worry that has for quite some time been connected to significant medical issues in individuals, all things considered. Because of the wide variety and low adverse effects, herbal products are an important hotspot for drug development. Synthetic compounds are not structurally diverse and lack drug-likeness properties. Thus, it is basic to keep on exploring herbal products as possible wellsprings of novel drugs. We conducted this review of the literature by searching Scopus, Science Direct, Elsevier, PubMed, and Web of Science databases. From 1990 until October 2021, research reports, review articles, and original research articles in English are presented. It provides top to bottom data and an examination of plant-inferred compounds that might be utilized against heftiness or potentially hostile to diabetes treatments. Our expanded comprehension of the systems of activity of phytogenic compounds, as an extra examination, could prompt the advancement of remedial methodologies for metabolic diseases. In clinical trials, a huge number of these food kinds or restorative plants, as well as their bioactive compounds, have been shown to be beneficial in the treatment of obesity.

Capsaicinoid-Glucosides of Fresh Hot Pepper Promotes Stress Resistance and Longevity in Caenorhabditis elegans

In this study, capsaicin-glucoside and dihydro-capsaicin-glucoside derived from fresh hot-red pepper were isolated and identified using UPLC-ESI-Q-TOF-MS/PDA. Synchronized worms were treated with capsaicinoid-glucosides (CG), and then lifespan and stress resistance were examined. The 50 µg/ml concentration of CG-intake could effectively protect the Caenorhabditis elegans (C. elegans) against stresses factors including oxidation and heat as well as reactive oxygen species (ROS), thereby enhancing the survival of CG-treated worms under stress. Enhancing stress resistance in CG-treated worms could be due to the increased expressions of stress-related genes in C. elegans such as daf-16, skn-1 and their downstream target genes (sod-3, hsp-16.2, gst-4 and gcs-1). Lifespan study of different C. elegans strains and RT-PCR showed that the CG-mediated lifespan extension was dependent on DAF-16/FOXO and SKN-1/Nrf2 transcription factors. The study is a step forward in exploring the stress resistance and anti-aging properties of this beneficial extract. Thus, this study will be useful in formulating remedies for stresses factors and age associated disorders.

Malnutrition and Dietary Habits Alter the Immune System Which May Consequently Influence SARS-CoV-2 Virulence: A Review

COVID-19, resulting from the SARS-CoV-2 virus, is a major pandemic that the world is fighting. SARS-CoV-2 primarily causes lung infection by attaching to the ACE2 receptor on the alveolar epithelial cells. However, the ACE2 receptor is also present in intestinal epithelial cells, suggesting a link between nutrition, virulence and clinical outcomes of COVID-19. Respiratory viral infections perturb the gut microbiota. The gut microbiota is shaped by our diet; therefore, a healthy gut is important for optimal metabolism, immunology and protection of the host. Malnutrition causes diverse changes in the immune system by repressing immune responses and enhancing viral vulnerability. Thus, improving gut health with a high-quality, nutrient-filled diet will improve immunity against infections and diseases. This review emphasizes the significance of dietary choices and its subsequent effects on the immune system, which may potentially impact SARS-CoV-2 vulnerability.

Targeting Neuroimmune Interactions in Diabetic Neuropathy with Nanomedicine

Significance: Diabetes is a major source of neuropathy and neuropathic pain that is set to continue growing in prevalence. Diabetic peripheral neuropathy (DPN) and pain associated with diabetes are not adequately managed by current treatment regimens. Perhaps the greatest difficulty in treating DPN is the complex pathophysiology, which involves aspects of metabolic disruption and neurotrophic deficits, along with neuroimmune interactions. There is, therefore, an urgent need to pursue novel therapeutic options targeting the key cellular and molecular players. Recent Advances: To that end, cellular targeting becomes an increasingly compelling drug delivery option as our knowledge of neuroimmune interactions continues to mount. These nanomedicine-based approaches afford a potentially unparalleled specificity and longevity of drug targeting, using novel or established compounds, all while minimizing off-target effects. Critical Issues: The DPN therapeutics directly targeted at the nervous system make up the bulk of currently available treatment options. However, there are significant opportunities based on the targeting of non-neuronal cells and neuroimmune interactions in DPN. Future Directions: Nanomedicine-based agents represent an exciting opportunity for the treatment of DPN with the goals of improving the efficacy and safety profile of analgesia, as well as restoring peripheral neuroregenerative capacity. Antioxid. Redox Signal. 36, 122-143.

The Potential Role of Curcumin in Modulating the Master Antioxidant Pathway in Diabetic Hypoxia-Induced Complications

Oxidative stress is the leading player in the onset and development of various diseases. The Keap1-Nrf2 pathway is a pivotal antioxidant system that preserves the cells' redox balance. It decreases inflammation in which the nuclear trans-localization of Nrf2 as a transcription factor promotes various antioxidant responses in cells. Through some other directions and regulatory proteins, this pathway plays a fundamental role in preventing several diseases and reducing their complications. Regulation of the Nrf2 pathway occurs on transcriptional and post-transcriptional levels, and these regulations play a significant role in its activity. There is a subtle correlation between the Nrf2 pathway and the pivotal signaling pathways, including PI3 kinase/AKT/mTOR, NF-κB and HIF-1 factors. This demonstrates its role in the development of various diseases. Curcumin is a yellow polyphenolic compound from Curcuma longa with multiple bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Since hyperglycemia and increased reactive oxygen species (ROS) are the leading causes of common diabetic complications, reducing the generation of ROS can be a fundamental approach to dealing with these complications. Curcumin can be considered a potential treatment option by creating an efficient therapeutic to counteract ROS and reduce its detrimental effects. This review discusses Nrf2 pathway regulation at different levels and its correlation with other important pathways and proteins in the cell involved in the progression of diabetic complications and targeting these pathways by curcumin.

A Nature-Inspired Nrf2 Activator Protects Retinal Explants from Oxidative Stress and Neurodegeneration

Oxidative stress (OS) plays a key role in retinal dysfunctions and acts as a major trigger of inflammatory and neurodegenerative processes in several retinal diseases. To prevent OS-induced retinal damage, approaches based on the use of natural compounds are actively investigated. Recently, structural features from curcumin and diallyl sulfide have been combined in a nature-inspired hybrid (NIH1), which has been described to activate transcription nuclear factor erythroid-2-related factor-2 (Nrf2), the master regulator of the antioxidant response, in different cell lines. We tested the antioxidant properties of NIH1 in mouse retinal explants. NIH1 increased Nrf2 nuclear translocation, Nrf2 expression, and both antioxidant enzyme expression and protein levels after 24 h or six days of incubation. Possible toxic effects of NIH1 were excluded since it did not alter the expression of apoptotic or gliotic markers. In OS-treated retinal explants, NIH1 strengthened the antioxidant response inducing a massive and persistent expression of antioxidant enzymes up to six days of incubation. These effects resulted in prevention of the accumulation of reactive oxygen species, of apoptotic cell death, and of gliotic reactivity. Together, these data indicate that a strategy based on NIH1 to counteract OS could be effective for the treatment of retinal diseases.

Food Containing Bioactive Flavonoids and Other Phenolic or Sulfur Phytochemicals With Antiviral Effect: Can We Design a Promising Diet Against COVID-19?

Since in late 2019, when the coronavirus 2 (SARS-CoV-2) pathogen of coronavirus disease 2019 (COVID-19) started to spread all over the world, causing the awful global pandemic we are still experiencing, an impressive number of biologists, infectious disease scientists, virologists, pharmacologists, molecular biologists, immunologists, and other researchers working in laboratories of all the advanced countries focused their research on the setting up of biotechnological tools, namely vaccines and monoclonal antibodies, as well as of rational design of drugs for therapeutic approaches. While vaccines have been quickly obtained, no satisfactory anti-Covid-19 preventive, or therapeutic approach has so far been discovered and approved. However, among the possible ways to achieve the goal of COVID-19 prevention or mitigation, there is one route, i.e., the diet, which until now has had little consideration. In fact, in the edible parts of plants supplying our food, there are a fair number of secondary metabolites mainly belonging to the large class of the flavonoids, endowed with antiviral or other health beneficial activities such as immunostimulating or anti-inflammatory action that could play a role in contributing to some extent to prevent or alleviate the viral infection and/or counteract the development of SARS induced by the novel coronavirus. In this review, a number of bioactive phytochemicals, in particular flavonoids, proven to be capable of providing some degree of protection against COVID-19, are browsed, illustrating their beneficial properties and mechanisms of action as well as their distribution in cultivated plant species which supply food for the human diet. Furthermore, room is also given to information regarding the amount in food, the resistance to cooking processes and, as a very important feature, the degree of bioavailability of these compounds. Concluding, remarks and perspectives for future studies aimed at increasing and improving knowledge and the possibility of using this natural complementary therapy to counteract COVID-19 and other viral pathologies are discussed.

Trans-resveratrol imparts disparate effects on transcription of DNA damage sensing/repair pathway genes in euglycemic and hyperglycemic rat testis

Prevention or repair of DNA damage is critical to inhibit carcinogenesis in living organisms. Using quantitative RT2 Profiler™ PCR array, we investigated if trans-resveratrol could modulate the transcription of DNA damage sensing/repair pathway genes in euglycemic and non-obese type 2 diabetic Goto-Kakizaki rat testis. Trans-resveratrol imparted disparate effects on gene expressions. In euglycemic rats, it downregulated 79% and upregulated 2% of genes. However, in diabetic rats, it upregulated only 2% and downregulated 4% of genes. As such, diabetes upregulated 16% and downregulated 4% of genes. Trans-resveratrol normalized the expression of 9 (60%) out of 15 upregulated genes in diabetic rats. In euglycemic rats, trans-resveratrol inhibited ATM/ATR, DNA damage repair, pro-cell cycle progression, and apoptosis signaling genes. However, it increased Cdkn1a and Sumo1, indicating cell cycle arrest, apoptosis, and cytostasis in conjunction with increased DNA double-strand breaks and apoptosis. Diabetes increased DNA damage and apoptosis but did not affect ATM/ATR and double-strand break repair genes, although it increased few single-strand repair genes. Diabetes increased Abl1 and Sirt1, which may be related to apoptosis, but their increase may well suggest the enhanced cell cycle progression and putative carcinogenicity. The transcription of Rad17 and Smc1a increased in diabetic rats indicating G2 phase arrest and increases in a few DNA single-strand breaks repair genes suggesting DNA damage repair. Trans-resveratrol inhibits the cell cycle and causes cell death in euglycemic rat testis but normalizes diabetes-induced genes related to DNA damage and cell cycle control, suggesting its usefulness in maintaining DNA integrity in diabetes.

Oxidative stress and redox signaling in CRPC progression: therapeutic potential of clinically-tested Nrf2-activators

Androgen deprivation therapy (ADT) is the mainstay regimen in patients with androgen-dependent prostate cancer (PCa). However, the selection of androgen-independent cancer cells leads to castrate resistant prostate cancer (CRPC). The aggressive phenotype of CRPC cells underscores the need to elucidate mechanisms and therapeutic strategies to suppress CRPC outgrowth. Despite ADT, the activation of androgen receptor (AR) transcription factor continues via crosstalk with parallel signaling pathways. Understanding of how these signaling cascades are initiated and amplified post-ADT is lacking. Hormone deprivation can increase oxidative stress and the resultant reactive oxygen species (ROS) may activate both AR and non-AR signaling. Moreover, ROS-induced inflammatory cytokines may further amplify these redox signaling pathways to augment AR function. However, clinical trials using ROS quenching small molecule antioxidants have not suppressed CRPC progression, suggesting that more potent and persistent suppression of redox signaling in CRPC cells will be needed. The transcription factor Nrf2 increases the expression of numerous antioxidant enzymes and downregulates the function of inflammatory transcription factors, e.g., nuclear factor kappa B. We documented that Nrf2 overexpression can suppress AR-mediated transcription in CRPC cell lines. Furthermore, two Nrf2 activating agents, sulforaphane (a phytochemical) and bardoxolone-methyl (a drug in clinical trial) suppress AR levels and sensitize CRPC cells to anti-androgens. These observations implicate the benefits of potent Nrf2-activators to suppress the lethal signaling cascades that lead to CRPC outgrowth. This review article will address the redox signaling networks that augment AR signaling during PCa progression to CRPC, and the possible utility of Nrf2-activating agents as an adjunct to ADT.

Therapeutic potential of curcumin in diabetic retinopathy (Review)

Diabetic retinopathy (DR) is a type of retinal microangiopathy caused by diabetes mellitus. It has become the leading cause of blindness among working individuals worldwide. DR is becoming increasingly common among younger diabetic patients and there is a need for lifelong treatment. The pathogenic mechanisms of DR are influenced by a number of factors, such as hyperglycemia, hyperlipidemia, inflammatory response and oxidative stress, among others. Currently, the treatment methods for DR mainly include retinal photocoagulation, vitrectomy, or anti‑vascular endothelial growth factor (VEGF) therapy. However, these methods have some disadvantages and limitations. Therefore, it is a matter of great interest and urgency to discover drugs that can target the pathogenesis of DR. Since ancient times, traditional Chinese medicine practitioners have accumulated extensive experiences in the use of Chinese herbal medicine for the prevention and treatment of diseases. In the theory of traditional Chinese medicine, curcumin has the effects of promoting blood circulation and relieving pain. A number of studies have also demonstrated that curcumin has multiple biological activities, including exerting anti‑apoptotic, anti‑inflammatory, antioxidant and antitumor properties. In recent years, studies have also confirmed that curcumin can prevent a variety of diabetic complications, including diabetic nephropathy (DN). However, the preventive and curative effects of curcumin on DR and its mechanisms of action have not yet been fully elucidated. The present review aimed to explore the therapeutic potential of curcumin in diabetes mellitus and DR.

Jares E, Jarvis D, Jassem E, Jenko K, Jiméneracruz Uscanga RD, Johnston SL, Joos G, Jošt M, Julge K, Jung K, Just J, Jutel M, Kaidashev I, Kalayci O, Kalyoncu F, Kapsali J, Kardas P, Karjalainen J, Kasala CA, Katotomichelakis M, Kavaliukaite L, Kazi BS, Keil T, Keith P, Khaitov M, Khaltaev N, Kim Y, Kirenga B, Kleine‐Tebbe J, Klimek L, Koffi N’Goran B, Kompoti E, Kopač P, Koppelman G, KorenJeverica A, Koskinen S, Košnik M, Kostov KV, Kowalski ML, Kralimarkova T, Kramer Vrščaj K, Kraxner H, Kreft S, Kritikos V, Kudlay D, Kuitunen M, Kull I, Kuna P, Kupczyk M, Kvedariene V, Kyriakakou M, Lalek N, Landi M, Lane S, Larenas‐Linnemann D, Lau S, Laune D, Lavrut J, Le L, Lenzenhuber M, Lessa M, Levin M, Li J, Lieberman P, Liotta G, Lipworth B, Liu X, Lobo R, Lodrup Carlsen KC, Lombardi C, Louis R, Loukidis S, Lourenço O, Luna Pech JA, Madjar B, Maggi E, Magnan A, Mahboub B, Mair A, Mais Y, Maitland van der Zee A, Makela M, Makris M, Malling H, Mandajieva M, Manning P, Manousakis M, Maragoudakis P, Marseglia G, Marshall G, Reza Masjedi M, Máspero JF, Matta Campos JJ, Maurer M, Mavale‐Manuel S, Meço C, Melén E, Melioli G, Melo‐Gomes E, Meltzer EO, Menditto E, Menzies‐Gow A, Merk H, Michel J, Micheli Y, Miculinic N, Midão L, Mihaltan F, Mikos N, Milanese M, Milenkovic B, Mitsias D, Moalla B, Moda G, Mogica Martínez MD, Mohammad Y, Moin M, Molimard M, Momas I, Mommers M, Monaco A, Montefort S, Mora D, Morais‐Almeida M, Mösges R, Mostafa B, Mullol J, Münter L, Muraro A, Murray R, Musarra A, Mustakov T, Naclerio R, Nadeau KC, Nadif R, Nakonechna A, Namazova‐Baranova L, Navarro‐Locsin G, Neffen H, Nekam K, Neou A, Nettis E, Neuberger D, Nicod L, Nicola S, Niederberger‐Leppin V, Niedoszytko M, Nieto A, Novellino E, Nunes E, Nyembue D, O’Hehir R, Odjakova C, Ohta K, Okamoto Y, Okubo K, Oliver B, Onorato GL, Pia Orru M, Ouédraogo S, Ouoba K, Paggiaro PL, Pagkalos A, Pajno G, Pala G, Palaniappan S, Pali‐Schöll I, Palkonen S, Palmer S, Panaitescu Bunu C, Panzner P, Papadopoulos NG, Papanikolaou V, Papi A, Paralchev B, Paraskevopoulos G, Park H, Passalacqua G, Patella V, Pavord I, Pawankar R, Pedersen S, Peleve S, Pellegino S, Pereira A, Pérez T, Perna A, Peroni D, Pfaar O, Pham‐Thi N, Pigearias B, Pin I, Piskou K, Pitsios C, Plavec D, Poethig D, Pohl W, Poplas Susic A, Popov TA, Portejoie F, Potter P, Poulsen L, Prados‐Torres A, Prarros F, Price D, Prokopakis E, Puggioni F, Puig‐Domenech E, Puy R, Rabe K, Raciborski F, Ramos J, Recto MT, Reda SM, Regateiro FS, Reider N, Reitsma S, Repka‐Ramirez S, Ridolo E, Rimmer J, Rivero Yeverino D, Angelo Rizzo J, Robalo‐Cordeiro C, Roberts G, Roche N, Rodríguez González M, Rodríguez Zagal E, Rolla G, Rolland C, Roller‐Wirnsberger R, Roman Rodriguez M, Romano A, Romantowski J, Rombaux P, Romualdez J, Rosado‐Pinto J, Rosario N, Rosenwasser L, Rossi O, Rottem M, Rouadi P, Rovina N, Rozman Sinur I, Ruiz M, Ruiz Segura LT, Ryan D, Sagara H, Sakai D, Sakurai D, Saleh W, Salimaki J, Samitas K, Samolinski B, Sánchez Coronel MG, Sanchez‐Borges M, Sanchez‐Lopez J, Sarafoleanu C, Sarquis Serpa F, Sastre‐Dominguez J, Savi E, Sawaf B, Scadding GK, Scheire S, Schmid‐Grendelmeier P, Schuhl JF, Schunemann H, Schvalbová M, Schwarze J, Scichilone N, Senna G, Sepúlveda C, Serrano E, Shields M, Shishkov V, Siafakas N, Simeonov A, FER Simons E, Carlos Sisul J, Sitkauskiene B, Skrindo I, SokličKošak T, Solé D, Sooronbaev T, Soto‐Martinez M, Soto‐Quiros M, Sousa Pinto B, Sova M, Soyka M, Specjalski K, Spranger O, Stamataki S, Stefanaki L, Stellato C, Stelmach R, Strandberg T, Stute P, Subramaniam A, Suppli Ulrik C, Sutherland M, Sylvestre S, Syrigou A, Taborda Barata L, Takovska N, Tan R, Tan F, Tan V, Ping Tang I, Taniguchi M, Tannert L, Tantilipikorn P, Tattersall J, Tesi F, Thijs C, Thomas M, To T, Todo‐Bom A, Togias A, Tomazic P, Tomic‐Spiric V, Toppila‐Salmi S, Toskala E, Triggiani M, Triller N, Triller K, Tsiligianni I, Uberti M, Ulmeanu R, Urbancic J, Urrutia Pereira M, Vachova M, Valdés F, Valenta R, Valentin Rostan M, Valero A, Valiulis A, Vallianatou M, Valovirta E, Van Eerd M, Van Ganse E, Hage M, Vandenplas O, Vasankari T, Vassileva D, Velasco Munoz C, Ventura MT, Vera‐Munoz C, Vicheva D, Vichyanond P, Vidgren P, Viegi G, Vogelmeier C, Von Hertzen L, Vontetsianos T, Vourdas D, Tran Thien Quan V, Wagenmann M, Walker S, Wallace D, Wang DY, Waserman S, Wickman M, Williams S, Williams D, Wilson N, Wong G, Woo K, Wright J, Wroczynski P, Xepapadaki P, Yakovliev P, Yamaguchi M, Yan K, Yeow Yap Y, Yawn B, Yiallouros P, Yorgancioglu A, Yoshihara S, Young I, Yusuf OB, Zaidi A, Zaitoun F, Zar H, Zedda M, Zernotti ME, Zhang L, Zhong N, Zidarn M, Zubrinich C. Cabbage and fermented vegetables: From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19

Large differences in COVID‐19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS‐CoV‐2 binds to its receptor, the angiotensin‐converting enzyme 2 (ACE2). As a result of SARS‐CoV‐2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT₁R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID‐19. The nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT₁R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof‐of‐concept of dietary manipulations that may enhance Nrf2‐associated antioxidant effects, helpful in mitigating COVID‐19 severity.

Artemisia judaica L. diminishes diabetes-induced reproductive dysfunction in male rats via activation of Nrf2/HO-1-mediated antioxidant responses

Diabetes mellitus is a well-known danger element for the progression of male reproductive dysfunctions. Available evidence supports oxidative stress to be the underlying mechanism for the manifestation of testicular dysfunctions during diabetes, and this relation represents an attractive target to antagonize these complications. Artemisia judaica L. is known to have antidiabetic and antioxidant characteristics. The possible protective effect of Artemisia judaica against diabetes-induced testicular disorders was not explored. In this investigation, we planned to estimate the possible protective effect of Artemisia judaica extract against diabetes-induced testicular disorders in male rats. The blood levels of insulin, glucose, glycosylated hemoglobin, testosterone, luteinizing hormone and follicle stimulating hormone were evaluated in rats after 12 weeks of Artemisia judaica treatment. Further, oxidative stress markers were determined in their testicular tissue. Epididymal fluid and testicular histological changes were also assessed. Expression of proliferating cell nuclear antigen has been evaluated in testis. Testicular mRNA expression of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 as the significant transcription factors in controlling antioxidant system were evaluated by real-time polymerase chain reaction. Artemisia judaica extracts have the ability to ameliorate the elevation in the serum glucose and blood glycosylated hemoglobin and the reduction in insulin, testosterone, follicle stimulating hormone and luteinizing hormone caused by streptozotocin-induced diabetes. It induced a significant recovery of the testicular oxidative stress markers, sperm characteristics and improved histopathological findings of the testes. Treatment with Artemisia judaica extracts led to an increase in proliferating cell nuclear antigen protein expression. Reduction of testicular oxidative stress potential in streptozotocin-treated groups was confirmed by upregulation of nuclear factor erythroid 2-related factor 2 and heme oxygenase-1.

Diabetic neuropathy and neuropathic pain: a (con)fusion of pathogenic mechanisms?

Neuropathy is a common complication of long-term diabetes that impairs quality of life by producing pain, sensory loss and limb amputation. The presence of neuropathy in both insulin-deficient (type 1) and insulin resistant (type 2) diabetes along with the slowing of progression of neuropathy by improved glycemic control in type 1 diabetes has caused the majority of preclinical and clinical investigations to focus on hyperglycemia as the initiating pathogenic lesion. Studies in animal models of diabetes have identified multiple plausible mechanisms of glucotoxicity to the nervous system including post-translational modification of proteins by glucose and increased glucose metabolism by aldose reductase, glycolysis and other catabolic pathways. However, it is becoming increasingly apparent that factors not necessarily downstream of hyperglycemia can also contribute to the incidence, progression and severity of neuropathy and neuropathic pain. For example, peripheral nerve contains insulin receptors that transduce the neurotrophic and neurosupportive properties of insulin, independent of systemic glucose regulation, while the detection of neuropathy and neuropathic pain in patients with metabolic syndrome and failure of improved glycemic control to protect against neuropathy in cohorts of type 2 diabetic patients has placed a focus on the pathogenic role of dyslipidemia. This review provides an overview of current understanding of potential initiating lesions for diabetic neuropathy and the multiple downstream mechanisms identified in cell and animal models of diabetes that may contribute to the pathogenesis of diabetic neuropathy and neuropathic pain.

Systematic review of the nuclear factor erythroid 2-related factor 2 (NRF2) system in human chronic kidney disease: alterations, interventions, and relation to morbidity

BACKGROUND

NRF2 and its effectors NAD(P)H:quinoneoxidoreductase 1 (NQO1) and heme oxygenase 1 (HO-1) are of interest in kidney disease. We therefore reviewed studies about their status in patients with chronic kidney disease (CKD).

METHODS

We undertook systematic searches of PubMed and EMBASE databases. Alterations of NRF2, NQO1 and HO-1 in CKD, their responses to interventions and their relation to clinically relevant parameters were reported.

RESULTS

We identified 1373 articles, of which 32 studies met the inclusion criteria. NRF2 levels were decreased in the majority of analyses of CKD patients. Half of the analyses showed a similar or increased NQO1 level vs. control, whereas NQO1 was decreased in half of the analyses. Most of the studies reported either an increased or similar HO-1 level in CKD patients compared to controls. For patients with CKD stages 1-4, studies reported positive correlations to markers of kidney disease severity. Also, positive associations of NQO1/HO-1 levels to inflammation and comorbidities were reported. One third of the studies showed discordant changes between gene expression and protein level of NRF2 system components. Two thirds of intervention studies (50% dietary, such as using resistant starch) reported an increase of NRF2, NQO1, or HO-1.

CONCLUSIONS

In patients with CKD, NRF2 expression was downregulated, while NQO1 and HO-1 showed varying alterations related to inflammation, comorbidities, and severity of kidney damage. Interventions that increased NRF2 system components were described, but their effectiveness and clinical relevance require further clinical studies of high quality. Research on gene expression together with protein analyses is indispensable to understand NRF2 system alterations in CKD.

Microdose Lithium Protects against Pancreatic Islet Destruction and Renal Impairment in Streptozotocin-Elicited Diabetes

Psychiatric use of lithium has been associated with hypoglycemic effects, but its effect on type 1 diabetes mellitus (T1D) is unknown. In streptozotocin (STZ) induced murine models of T1D, microdose lithium therapy improved hyperglycemia, attenuated body weight loss and prevented early signs of diabetic kidney injury. This beneficial effect was associated with preservation of pancreatic islet histology and β-cell production of insulin as well as mitigated oxidative damage of islets. Mechanistically, lithium in islets cells induced inhibitory phosphorylation of glycogen synthase kinase 3β (GSK3β), the major molecular target of lithium that has been recently implicated in non-canonical regulation of Nrf2 activity. In turn, Nrf2 antioxidant response was potentiated in islets, marked by nuclear translocation of Nrf2 and augmented expression of its target antioxidant enzyme heme oxygenase 1 (HO-1). Conversely, cotreatment with trigonelline, a selective blockade of Nrf2, offset the lithium enhanced Nrf2 antioxidant response in islets, blunted the protective effect of lithium on pancreatic islets and β-cells, and abolished the hypoglycemic activity of lithium in STZ-injured mice. Collectively, our findings suggest that microdose lithium confers a protective effect on islet β-cells via targeting the GSK3β-regulated Nrf2 antioxidant response and thereby ameliorates T1D and its related kidney impairment.

NRF2-Related Epigenetic Modifications in Cardiac and Vascular Complications of Diabetes Mellitus

Diabetes mellitus (DM) is a highly prevalent chronic disease that is accompanied with serious complications, especially cardiac and vascular complications. Thus, there is an urgent need to identify new strategies to treat diabetic cardiac and vascular complications. Nuclear factor erythroid 2-related factor 2 (NRF2) has been verified as a crucial target for the prevention and treatment of diabetic complications. The function of NRF2 in the treatment of diabetic complications has been widely reported, but the role of NRF2-related epigenetic modifications remains unclear. The purpose of this review is to summarize the recent advances in targeting NRF2-related epigenetic modifications in the treatment of cardiac and vascular complications associated with DM. We also discuss agonists that could potentially regulate NRF2-associated epigenetic mechanisms. This review provides a better understanding of strategies to target NRF2 to protect against DM-related cardiac and vascular complications.

DhHP-6 ameliorates hepatic oxidative stress and insulin resistance in type 2 diabetes mellitus through the PI3K/AKT and AMPK pathway

Insulin resistance is one major features of type 2 diabetes mellitus (T2DM). Deuterohemin-βAla-His-Thr-Val-Glu-Lys (DhHP-6), a novel microperoxidase mimetic designed and synthesized based on microperoxidase 11 (MP-11), can scavenge reactive oxygen species (ROS) in vivo. In our previous studies, we showed that oral DhHP-6 could reduce blood glucose and improve insulin resistance. To investigate the mechanisms of how DhHP-6 ameliorates oxidative stress and insulin resistance, we established T2DM mouse models and glucosamine-induced HepG2 cell insulin resistance models. The results suggested that DhHP-6 decreased blood glucose, increased antioxidant enzyme activity, and inhibited glycogen synthesis in T2DM mice. In addition, DhHP-6 improved insulin resistance by activating phosphatidylinositol 3-kinase (PI3K)/AKT, and AMP-activated protein kinase (AMPK) pathway in T2DM mice. Furthermore, DhHP-6 also activated PI3K/AKT and AMPK pathway in glucosamine-induced HepG2 cells. However, LY294002 did not completely inhibit AKT phosphorylation, and partially inhibited AMPK phosphorylation, whilst compound C only partially reduced AMPK phosphorylation, and also partially inhibited AKT phosphorylation, suggesting that AKT and AMPK interact to improve insulin resistance. Thus, these data suggest that DhHP-6 attenuates insulin resistance via the PI3K/AKT and AMPK pathway.

Anti-Viral Potential and Modulation of Nrf2 by Curcumin: Pharmacological Implications

Nuclear factor erythroid 2-related factor 2 (Nrf2) is an essential transcription factor that maintains the cell's redox balance state and reduces inflammation in different adverse stresses. Under the oxidative stress, Nrf2 is separated from Kelch-like ECH-associated protein 1 (Keap1), which is a key sensor of oxidative stress, translocated to the nucleus, interacts with the antioxidant response element (ARE) in the target gene, and then activates the transcriptional pathway to ameliorate the cellular redox condition. Curcumin is a yellow polyphenolic curcuminoid from Curcuma longa (turmeric) that has revealed a broad spectrum of bioactivities, including antioxidant, anti-inflammatory, anti-tumor, and anti-viral activities. Curcumin significantly increases the nuclear expression levels and promotes the biological effects of Nrf2 via the interaction with Cys151 in Keap1, which makes it a marvelous therapeutic candidate against a broad range of oxidative stress-related diseases, including type 2 diabetes (T2D), neurodegenerative diseases (NDs), cardiovascular diseases (CVDs), cancers, viral infections, and more recently SARS-CoV-2. Currently, the multifactorial property of the diseases and lack of adequate medical treatment, especially in viral diseases, result in developing new strategies to finding potential drugs. Curcumin potentially opens up new views as possible Nrf2 activator. However, its low bioavailability that is due to low solubility and low stability in the physiological conditions is a significant challenge in the field of its efficient and effective utilization in medicinal purposes. In this review, we summarized recent studies on the potential effect of curcumin to activate Nrf2 as the design of potential drugs for a viral infection like SARS-Cov2 and acute and chronic inflammation diseases in order to improve the cells' protection.

Nrf2-interacting nutrients and COVID-19: time for research to develop adaptation strategies

There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPARγ:Peroxisome proliferator-activated receptor, NFκB: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2α:Elongation initiation factor 2α). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT₁R axis (AT₁R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity.

Sargassum fusiforme Fucoidan Alleviates High-Fat Diet-Induced Obesity and Insulin Resistance Associated with the Improvement of Hepatic Oxidative Stress and Gut Microbiota Profile

Sargassum fusiforme fucoidan (SFF) exhibits diverse biological activities. Insulin resistance (IR) implicated in type 2 diabetes (T2D) has become an epidemic health issue worldwide. In this study, we investigated whether SFF can improve insulin sensitivity in high-fat diet (HFD)-fed mice. Our present data showed that SFF significantly reduced fasting blood glucose and IR index along with improved glucose tolerance. Impaired phosphorylation of Akt was also restored by SFF. Furthermore, SFF decreased the levels of MDA and 4-HNE-modified protein and increased GSH/GSSG ratio as well as elevated antioxidant enzymes and activated Nrf2 signaling. SFF also increased the abundance and diversity of gut microbiota in the obese mice, as well as improved intestinal integrity and inflammation. Our findings suggested that SFF ameliorated HFD-induced IR through activating the Nrf2 pathway, remodeling gut microbiota, and reducing intestinal inflammation, thus providing a novel perspective into the treatment strategy on metabolic disease.

Quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) increases Nrf2 expression via miR-27a mediation to prevent memory dysfunction in diabetic rats

Oxidative stress is one of the earliest defects involved in the development of diabetes-induced cognitive impairment. Nrf2 is the master regulator of the cellular antioxidant system can be regulated by some microRNAs. The study aimed to evaluate the effects of quercetin (QC) and quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) on Nrf2-controlled antioxidant genes through the redox-sensitive miR-27a. Expression levels of miR-27a, Nrf2, SOD1, GPX1, and CAT were measured by quantitative real-time PCR. Moreover, the oxidative stress parameters including total antioxidant capacity (TAC) and histological alterations were investigated. The expression level of miR-27a was significantly up-regulated in diabetic rats. While expression levels of Nrf2, SOD1, GPX1, and CAT were significantly down-regulated under diabetic condition. Interestingly, QCSPIONs decreased expression level of miR-27a and subsequently enhanced the expression levels of Nrf2, SOD1, and CAT to the control level. No significant difference was observed in the expression level of GPX1. Besides, QC in pure and especially conjugated form was able to normalize TAC and regenerate pathological lesions in STZ-diabetic rats. Our result demonstrates that QCSPIONs as an effective combined therapy can decrease miR-27a expression, which in turn increases the Nrf2 expression and responsive antioxidant genes, resulting in improvement of memory dysfunction in diabetic rats.

NRF-2 and nonalcoholic fatty liver disease

Currently, chronic liver diseases have conditioned morbidity and mortality, many of these with a metabolic, toxicologic, immunologic, viral, or other etiology. Thus, a transcription factor that has been of huge importance for biomedical research is NRF-2. The latter is considered a principal component of the antioxidant mechanism, and it has been acknowledged that it impairs the function of NRF-2 in many liver diseases and that it forms an essential part of the pathologic changes that occur in the liver to contain inflammation and damage. Within the investigations and experiments carried out, there are isolated drugs, many of them related to plants and natural extracts that possess antioxidant properties through the NRF-2 signaling pathway, or even involving the stimulation of the transcription target proteins of NRF-2. Notwithstanding all of these experimental findings, to date there is not sufficient clinical evidence to justify the use of NRF-2 in medical practice.

Sodium butyrate protects against high-fat diet-induced oxidative stress in rat liver by promoting expression of nuclear factor E2-related factor 2

Oxidative stress is closely related to metabolic disorders, which can lead to various diseases. Nuclear factor E2-related factor 2 (Nrf2) is a central regulator of oxidative stress. Sodium butyrate (NaB) has been shown to alleviate oxidative stress and insulin resistance, yet how Nrf2 is involved in the action of NaB remains unclear. In the present study, rats were rendered obese by feeding a high-fat diet for 9 weeks. NaB (300 mg/kg), which was gavaged every 2 d for 7 weeks, significantly alleviated high-fat diet-induced oxidative stress and insulin resistance. Additionally, the insulin signalling pathway in the liver was activated by NaB, associated with significant activation of Nrf2, superoxide dismutase and glutathione. Furthermore, hepatic up-regulation of Nrf2 in NaB-treated rats was associated with reduced protein content of histone deacetylase 1 and increased histone H3 acetyl K9 (H3K9Ac) modification on the Nrf2 promoter. The actions of NaB were completely abolished when Nrf2 was knocked down in vitro. Taken together, NaB acts as a histone deacetylase inhibitor to up-regulate Nrf2 expression with enhanced H3K9Ac modification on its promoter. NaB-induced Nrf2 activation stimulates transcription of downstream antioxidant enzymes, thus contributing to the amelioration of high-fat diet-induced oxidative stress and insulin resistance.

P38 MAPK and Nrf2 Activation Mediated Naked Gold Nanoparticle Induced Heme Oxygenase-1 Expression in Rat Aortic Vascular Smooth Muscle Cells

BACKGROUND AND AIMS

Heme oxygenase 1 (HO-1) is mainly regulated by the redox-sensitive transcription factor, namely nuclear factor erythroid 2-related factor 2 (Nrf2). We previously found a physically-made gold nanoparticle (GNP) can affect migration, adhesion, and proliferation of rat aortic vascular smooth muscle cells (VSMCs). This study was sought to investigate whether the GNP can affect HO-1 expression level in VSMCs.

METHODS

Cellular fractionation, Western blotting, and immunofluorescence microscopy were used to determine Nrf2 translocation and phosphorylation. SiRNA interference was used to examine role of Nrf2 in GNP-induced HO-1 expression.

RESULTS

The GNP concentration- and time-dependently enhanced HO-1 protein and mRNA expression; however, the mRNA induction was declined after 16 h treatment. The GNP treatment caused Nrf2 expression level and phosphorylation. In addition, it induced cytosolic Nrf2 translocation into nucleus. The HO-1 induction was inhibited by a ROS scavenger N-acetylcysteine (NAC), thiol-containing antioxidants (glutathione [GSH] and dithiothreitol [DTT]), JNK and p38 MAPK inhibitors, and nuclear transport inhibitor leptomycin. Meanwhile, the GNP-induced Nrf2 translocation (activation) was also reduced by NAC, JNK and p38 MAPK inhibitors, and nuclear transport inhibitor. Intriguingly, the GNP only enhanced activation of p38 MAPK but not JNK1/2. Finally, introduction of Nrf2 siRNA to cells to knockdown Nrf2 expression significantly inhibited GNP-induced HO-1 protein expression.

CONCLUSIONS

This study elucidates the action mechanism that the naked physically-made GNP can enhance HO-1 expression in rat aortic VSMCs by inducing Nrf2 expression and phosphorylation and translocation into nucleus. The Nrf2 activation is mediated through a redox-related reaction and p38 MAPK activation.

Curcumin analog A13 alleviates oxidative stress by activating Nrf2/ARE pathway and ameliorates fibrosis in the myocardium of high-fat-diet and streptozotocin-induced diabetic rats

BACKGROUND

Diabetes mellitus is an important risk factor for cardiomyopathy. Increasing oxidative stress may be one of the main factors of diabetic cardiomyopathy. A13, a newly synthesized curcumin analog, was proved to be superior to curcumin in biological activity. However, little know about how A13 performed in diabetic models. In this study, we evaluated the ability of curcumin analog A13 to alleviate oxidative stress and ameliorate fibrosis in the myocardium, and explore the underlying mechanisms.

METHODS

Intraperitoneal injection of streptozotocin (30 mg/kg in 0.1 M sodium citrate buffer, pH 4.5) induced diabetes in high-fat fed rats. The rats were respectively treated with a daily dose of curcumin or A13 via intragastric intubation for 8 weeks. Myocardial tissue sections were stained with hematoxylin-eosin; oxidative stress was detected by biochemical assays; activation of the Nrf2/ARE pathway was detected by Western blot, immunohistochemical staining and RT-qPCR; myocardial fibrosis was identified by Western blot and Masson trichrome staining.

RESULTS

Treatment with curcumin analog A13 reduced the histological lesions of the myocardium in diabetic rats. Curcumin and A13 treatment decreased the malondialdehyde level and increased the activity of superoxide dismutase in the myocardium of diabetic rats. Molecular analysis and immunohistochemical staining demonstrated that dose of 20 mg/kg of A13 could activate the Nrf2/ARE pathway. Molecular analysis and Masson staining showed that curcumin analog A13 treatment significantly ameliorated fibrosis in myocardium of these diabetic rats.

CONCLUSION

Treatment with curcumin analog A13 protects the morphology of myocardium, restores the MDA levels and SOD activity, activates the Nrf2/ARE pathway and ameliorates myocardial fibrosis in diabetic rats. It may be a useful therapeutic agent for some aspects of diabetic cardiomyopathy.

1-Palmitoyl-2-Linoleoyl-3-Acetyl-rac-Glycerol Attenuates Streptozotocin-Induced Pancreatic Beta Cell Damage by Promoting Glucose Transporter 2 Endocytosis

Streptozotocin (STZ) is widely used to induce diabetic rodent models. It is specifically toxic to pancreatic beta cells and causes severe destruction and dysfunction. We investigated the effect of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) on an STZ-induced diabetic mouse model. PLAG attenuated the glucose increase and maintained serum insulin at levels similar to those seen with control mice.

Streptozotocin (STZ) is widely used to induce diabetic rodent models. It is specifically toxic to pancreatic beta cells and causes severe destruction and dysfunction. We investigated the effect of 1-palmitoyl-2-linoleoyl-3-acetyl-rac-glycerol (PLAG) on an STZ-induced diabetic mouse model. PLAG attenuated the glucose increase and maintained serum insulin at levels similar to those seen with control mice. In pancreatic beta cell line INS-1, STZ-induced cell apoptosis and intracellular reactive oxygen species (ROS) generation were significantly reduced to nearly normal levels after PLAG treatment. Glucose transporter 2 (GLUT2) localization analyses and glucose uptake assays showed that PLAG accelerated GLUT2 internalization, which ameliorated excessive entry of glucose, as well as STZ. STZ-induced cytotoxic effects were significantly reduced in PLAG-treated groups. The biological activity of PLAG was further confirmed in GLUT2-silenced cells, and the specificity of PLAG was verified using its derivative 1-palmitoyl-2-linoleoyl-3-hydroxyl-rac-glycerol (PLH). Our results suggest that PLAG may be a useful agent for protecting beta cells in the setting of excessive glucose influx.

DNA Methylome and Transcriptome Alterations in High Glucose-Induced Diabetic Nephropathy Cellular Model and Identification of Novel Targets for Treatment by Tanshinone IIA

Diabetic nephropathy (DN) is a diabetes complication that comes from overactivation of Renin-Angiotensin System, excessive pro-inflammatory factors, reactive oxygen species (ROS) overproduction, and potential epigenetic changes. Tanshinone IIA (TIIA), a diterpene quinone phytochemical, has been shown to possess powerful antioxidant, anti-inflammatory, epigenetics, and protective effects against different diseases including DN by inhibiting ROS induced by high glucose (HG). However, epigenomic and transcriptomic study of DN and the protective effect of TIIA are lacking. In this study, next-generation sequencing of RNA and DNA methylation profiles on the potential underlying mechanisms of a DN model in mouse kidney mesangial mes13 cells challenged with HG and treatment with TIIA were conducted. Bioinformatic analysis coupled with Ingenuity Pathway analysis of RNA-seq was performed, and 1780 genes from HG/LG and 1416 genes from TIIA/HG were significantly altered. Several pro-inflammatory pathways like leukotriene biosynthesis and eicosanoid signaling pathways were activated by HG stimulation, while TIIA treatment would enhance glutathione-mediated detoxification pathway to overcome the excess oxidative stress and inflammation triggered by HG. Combination analysis of RNA-seq and Methyl-seq data sets, DNA methylation, and RNA expression of a list of DN associated genes, Nmu, Fgl2, Glo, and Kcnip2, were found to be altered in HG-induced mes13 DN model, and TIIA treatment would effectively restore the alterations. Taken together, these findings provide novel insights into the understanding of how epigenetic/epigenomic modifications could affect the progression of DN and the potential preventive effect of TIIA in DN.

Glutathione-dependent enzyme activities of peripheral blood mononuclear cells decrease during the winter season compared with the summer in normal-weight and severely obese adolescents

Oxidative stress-related inflammation is known to play a vital role in obesity-associated cardiovascular disease, contributing to the early stages of the pathology as well as during its development. Therefore, it is of great interest to understand how obesity-induced stress modulates antioxidant enzyme activity during puberty. To this end, 27 severely obese adolescents (body mass index > 30, z-score > 3.7) were recruited from a paediatric weight management centre. Eighteen were recruited during the summer and nine in the winter. All underwent a 4-month weight loss programme consisting in diet and physical activity. Twenty normal-weight age-matched adolescents were recruited from the same geographical area to serve as controls. Blood samples were extracted, and antioxidant enzyme activities were determined in peripheral blood mononuclear cells (PBMCs) and erythrocytes. The enzymes studied included catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase. Severely obese adolescents presented lower PBMC-glutathione reductase activity than their corresponding normal-weight counterparts. In addition, glutathione-dependent activities tended to be lower in both groups during the winter compared with summer. These changes coincided with differences in circulating vitamin D levels. Results may suggest that season-dependent factors such as vitamin D could affect glutathione-dependent activities in severely obese as well as in normal-weight adolescents.

Basic Concepts on the Role of Nuclear Factor Erythroid-Derived 2-Like 2 (Nrf2) in Age-Related Diseases

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) is one of the most important oxidative stress regulator in the human body. Once Nrf2 regulates the expression of a large number of cytoprotective genes, it plays a crucial role in the prevention of several diseases, including age-related disorders. However, the involvement of Nrf2 on these conditions is complex and needs to be clarified. Here, a brief compilation of the Nrf2 enrollment in the pathophysiology of the most common age-related diseases and bring insights for future research on the Nrf2 pathway is described. This review shows a controversial response of this transcriptional factor on the presented diseases. This reinforces the necessity of more studies to investigate modulation strategies for Nrf2, making it a possible therapeutic target in the treatment of age-related disorders.

Oxidative stress pathways in pancreatic β-cells and insulin-sensitive cells and tissues: importance to cell metabolism, function, and dysfunction

It is now accepted that nutrient abundance in the blood, especially glucose, leads to the generation of reactive oxygen species (ROS), ultimately leading to increased oxidative stress in a variety of tissues. In the absence of an appropriate compensatory response from antioxidant mechanisms, the cell, or indeed the tissue, becomes overwhelmed by oxidative stress, leading to the activation of intracellular stress-associated pathways. Activation of the same or similar pathways also appears to play a role in mediating insulin resistance, impaired insulin secretion, and late diabetic complications. The ability of antioxidants to protect against the oxidative stress induced by hyperglycemia and elevated free fatty acid (FFA) levels in vitro suggests a causative role of oxidative stress in mediating the latter clinical conditions. In this review, we describe common biochemical processes associated with oxidative stress driven by hyperglycemia and/or elevated FFA and the resulting clinical outcomes: β-cell dysfunction and peripheral tissue insulin resistance.

Probucol promotes high glucose-induced proliferation and inhibits apoptosis by reducing reactive oxygen species generation in Müller cells

PURPOSE

To explore the protective effect of probucol on human retinal Müller cells cultured in high glucose.

METHODS

Primary Müller cells from human retinas were cultured in complete DMEM. Third-generation Müller cells were identified using glutamine synthetase (GS) antibody and randomly divided into three groups: normoglycemia (NG, 5.5 mmol/L); hyperglycemia (HG, 30 mmol/L); and hyperglycemia (30 mmol/L) with probucol (10 μmol/L; HGPB). After a 24-h intervention, cell proliferation, apoptosis, and cellular reactive oxygen species (ROS) were measured with a CCK-8 kit, flow cytometry, and DCFH-DA probe, respectively. Kelch-like ECH-associated protein 1 (Keap1), NF-E2-related factor 2 (Nrf2), and glutamate cysteine ligase catalytic subunit (GCLC) protein expression were detected by immunofluorescence staining.

RESULTS

For NG, HG, and HGPB, optical density (OD) values for cell proliferation were 0.98 ± 0.23, 0.58 ± 0.11, and 0.73 ± 0.11; apoptotic rates were 2.79 ± 0.52%, 7.70 ± 0.44%, and 4.00 ± 0.95%; and intracellular ROS were 20.89 ± 5.14, 55.17 ± 14.07, and 26.28 ± 4.73, respectively. Compared to NG, OD was markedly decreased (P < 0.01), apoptosis was increased (P < 0.001), and intracellular ROS level was significantly higher than in HG (P < 0.01). Compared to HG, OD was markedly increased (P < 0.01), apoptosis was meaningfully decreased (P < 0.01), and intracellular ROS level was significantly lower than in HGPB (P < 0.01). GS, Keap1, Nrf2, and GCLC had positive expression.

CONCLUSIONS

Probucol could inhibit intracellular ROS generation, promote proliferation, and decrease apoptosis of human retinal Müller cells cultured in high glucose. This might also be associated with Keap1/Nrf2/ARE oxidative stress signaling pathway activation.

Resveratrol increases stem cell function in the treatment of damaged pancreas

Pancreatic damage results in insufficient insulin secretion, leading to type 1 diabetes. Stem cell-based therapy has recently shown potential in the treatment of type 1 diabetes. Resveratrol supplementation has demonstrated a beneficial effect in treating diabetes. This study investigates if adipose-derived stem cells (ADSC), preconditioned with resveratrol, show better effects on experimental diabetic animals. Wistar rats were randomly divided into four groups including sham (normal rats), DM (diabetic rats induced by SZT injection), DM+ADSC (DM rats with receiving autologous ADSC transplantation) and DM+R-ADSC (DM rats receiving resveratrol preconditioned ADSC). The experimental results show that SZT induced pancreatic damage (DM group), including reduction of islet size, fibrosis pathway activation, survival signaling suppression, and apoptotic pathway expression, lead to serum glucose elevation. Autologous ADSC (DM+ADSC group) transplantation shows improvement in the above observations in DM rats. Furthermore, ADSC precondition with resveratrol (DM+R-ADSC group) reveals significant improvement in the above pathological observations over both DM and DM+ADSC groups. We found that ADSC precondition with resveratrol increases the survival marker p-Akt expression, leading to enhanced ADSC viability. This study suggests that ADSC precondition with resveratrol shows potential in the treatment of patients with type 1 DM.