Omega 3 rich diet modulates energy metabolism via GPR120-Nrf2 crosstalk in a novel antioxidant mouse model
With obesity rates reaching epidemic proportions, more studies concentrated on reducing the risk and treating this epidemic are vital. Redox stress is an important metabolic regulator involved in the pathophysiology of cardiovascular disease, Type 2 diabetes, and obesity. Oxygen and nitrogen-derived free radicals alter glucose and lipid homeostasis in key metabolic tissues, leading to increases in risk of developing metabolic syndrome. Oxidants derived from dietary fat differ in their metabolic regulation, with numerous studies showing benefits from a high omega 3 rich diet compared to the frequently consumed "western diet" rich in saturated fat. Omega 3 (OM3) fatty acids improve lipid profile, lower inflammation, and ameliorate insulin resistance, possibly through maintaining redox homeostasis. This study is based on the hypothesis that altering endogenous antioxidant production and/or increasing OM3 rich diet consumption will improve energy metabolism and maintain insulin sensitivity. We tested the comparative metabolic effects of a diet rich in saturated fat (HFD) and an omega 3-enriched diet (OM3) in the newly developed 'stress-less' mice model that overexpresses the endogenous antioxidant catalase. Eight weeks of dietary intervention showed that mice overexpressing endogenous catalase compared to their wild-type controls when fed an OM3 enriched diet, in contrast to HFD, activated GPR120-Nrf2 cross-talk to maintain balanced energy metabolism, normal circadian rhythm, and insulin sensitivity. These findings suggest that redox regulation of GPR120/FFAR4 might be an important target in reducing risk of metabolic syndrome and associated diseases.
SGLT2 inhibition with empagliflozin attenuates myocardial oxidative stress and fibrosis in diabetic mice heart
Hyperglycaemia associated with myocardial oxidative stress and fibrosis is the main cause of diabetic cardiomyopathy. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor has recently been reported to improve glycaemic control in patients with type 2 diabetes in an insulin-independent manner. The aim of this study was to investigate the effect of empagliflozin on myocardium injury and the potential mechanism in type 2 diabetic KK-Ay mice.
Protective role of sitagliptin against oxidative stress in a kainic acid-induced status epilepticus in rats models via Nrf2/HO-1 pathway
Preclinical Research & Development Aim: Sitagliptin (Sita) is a dipeptidyl peptidase-4 inhibitor which has been approved as a curing medicine for Type 2 diabetes (T2D) and has also reported its neuroprotective and antioxidant activity. This article describes the therapeutic eﬀects of Sita on induced rat model of SE by kainic acid (KA) and investigated the antioxidative pathway of sita.
Absence of TXNIP in Human Gives Lactic Acidosis and Low Serum Methionine Linked to Deficient Respiration on Pyruvate
Thioredoxin Interacting Protein (TXNIP) is an alpha arrestin that can bind to and inhibit the antioxidant protein thioredoxin (TXN). TXNIP expression is induced by glucose, promotes ß-cell apoptosis in the pancreas and deletion of its gene in mouse models protects against diabetes. TXNIP is currently studied as a potential new target for antidiabetic drug therapy. Here we describe a family with a mutation in the gene leading to non-detectable expression of TXNIP protein. Symptoms of affected family members include lactic acidosis and low serum methionine levels. Using patient-derived TXNIP-deficient fibroblasts and myoblasts we show that oxidative phosphorylation is impaired in these cells when given glucose and pyruvate but normalized with malate. Isolated mitochondria from these cells appear to have normal respiratory function. The cells also display a transcriptional pattern suggestive of a high basal activation of the Nrf2 transcription factor. We conclude that a complete lack of TXNIP in human is non-lethal and leads to specific metabolic distortions that are, at least in part, linked to a deficient respiration on pyruvate. The results give important insights into the impact of TXNIP in human and thus help to further advance the development of antidiabetic drugs targeting this protein.
Genetic risk score combining six genetic variants associated with the cellular NRF2 expression levels correlates with Type 2 diabetes in the human population
Type 2 diabetes (T2D) is known as an inflammatory disease. NRF2 (Nuclear Factor Erythroid 2 Like2) encodes a transcription factor that binds to antioxidant response elements (AREs) and regulates the expression of genes involved in many antioxidant responses.
PCB 126 induces monocyte/macrophage polarization and inflammation through AhR and NF-κB pathways
Polychlorinated biphenyls (PCBs) are persistent organic pollutants that contribute to inflammatory diseases such as atherosclerosis, and macrophages play a key role in the overall inflammatory response. Depending on specific environmental stimuli, macrophages can be polarized either to pro-inflammatory (e.g., M1) or anti-inflammatory (e.g., M2) phenotypes. We hypothesize that dioxin-like PCBs can contribute to macrophage polarization associated with inflammation. To test this hypothesis, human monocytes (THP-1) were differentiated to macrophages and subsequently exposed to PCB 126. Exposure to PCB 126, but not to PCB 153 or 118, significantly induced the expression of inflammatory cytokines, including TNFα and IL-1β, suggesting polarization to the pro-inflammatory M1 phenotype. Additionally, monocyte chemoattractant protein-1 (MCP-1) was increased in PCB 126-activated macrophages, suggesting induction of chemokines which regulate immune cell recruitment and infiltration of monocytes/macrophages into vascular tissues. In addition, oxidative stress sensitive markers including nuclear factor (erythroid-derived 2)-like 2 (NFE2L2; Nrf2) and down-stream genes, such as heme oxygenase 1 (HMOX1) and NAD(P)H quinone oxidoreductase 1 (NQO1), were induced following PCB 126 exposure. Since dioxin-like PCBs may elicit inflammatory cascades through multiple mechanisms, we then pretreated macrophages with both aryl hydrocarbon receptor (AhR) and NF-κB antagonists prior to PCB treatment. The NF-κB antagonist BMS-345541 significantly decreased mRNA and protein levels of multiple cytokines by approximately 50% compared to PCB treatment alone, but the AhR antagonist CH-223191 was protective to a lesser degree. Our data demonstrate the involvement of PCB 126 in macrophage polarization and inflammation, indicating another important role of dioxin-like PCBs in the pathology of atherosclerosis.
Nrf2 represses the onset of type 1 diabetes in non-obese diabetic mice
The transcription factor Nrf2 (NF-E2-related factor 2) plays a critical role in oxidative stress responses. While activation of Nrf2 signaling is known to exert anti-inflammatory effects, Nrf2 function in inflammation-mediated autoimmune disorders, such as type 1 diabetes, is not well established. To address the roles of Nrf2 in protection against autoreactive T-cell-induced type 1 diabetes, we used non-obese diabetic (NOD) mice, a polygenic model of human type 1 diabetes, to generate a genetic model that allowed us to assess the contribution of Nrf2 activation to preventing and/or treating type 1 diabetes. As Keap1 negatively regulates Nrf2, we used Keap1 gene knockdown driven by either hypomorphic or knockout alleles of Keap1,which enhances Nrf2 signaling to moderate and excess levels, respectively. We found that Nrf2 activation in NOD::Keap1FA/- mice inhibited T-cell infiltration within or near the islets, ameliorated impairment of insulin secretion, and prevented development of diabetes mellitus in the NOD mice. Notably, Nrf2 activation decreased both plasma interferon-γ (IFN-γ) levels and IFN-γ-positive cell numbers in the pancreatic islets. These findings were also observed in mice with two hypomorphic Keap1 alleles (Keap1FA/FA). Both NOD::Keap1FA/- and NOD::Keap1FA/FA mice had decreased incidence of diabetes mellitus, demonstrating that the activation of Nrf2 signaling prevents the onset of type 1 diabetes mellitus in NOD mice. Thus, Nrf2 appears to be a potential target for preventing and treating type 1 diabetes.
Notoginsenoside R1 Protects db/db Mice against Diabetic Nephropathy via Upregulation of Nrf2-Mediated HO-1 Expression
Diabetic nephropathy (DN) is a leading cause of end-stage renal failure, and no effective treatment is available. Notoginsenoside R1 (NGR1) is a novel saponin that is derived from , and our previous studies showed the cardioprotective and neuroprotective effects of NGR1. However, its role in protecting against DN remains unexplored. Herein, we established an experimental model in / mice and HK-2 cells exposed to advanced glycation end products (AGEs). The in vivo investigation showed that NGR1 treatment increased serum lipid, β2-microglobulin, serum creatinine, and blood urea nitrogen levels of / mice. NGR1 attenuated histological abnormalities of kidney, as evidenced by reducing the glomerular volume and fibrosis in diabetic kidneys. In vitro, NGR1 treatment was further found to decrease AGE-induced mitochondria injury, limit an increase in reactive oxygen species (ROS), and reduce apoptosis in HK-2 cells. Mechanistically, NGR1 promoted nucleus nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expressions to eliminate ROS that induced apoptosis and transforming growth factor beta (TGF-β) signaling. In summary, these observations demonstrate that NGR1 exerts renoprotective effects against DN through the inhibition of apoptosis and renal fibrosis caused by oxidative stress. NGR1 might be a potential therapeutic medicine for the treatment of DN.
Exendin-4 prevented pancreatic beta cells from apoptosis in (Type I) diabetic mouse via keap1-Nrf2 signaling
Nrf2 is an essential part of the defense mechanism of vertebrates and protects them from surrounding stress via participation in stimulated expression of detoxification as well as antioxidant enzymes. It also exerts a role in defending hosts from different stress in the environment, including reactive oxygen species. Our study investigates the role of exendin-4 on Nrf2 pathway as well as cell death in pancreatic β-cell and in non-obese diabetic mice. Result of study indicates exendin-4 mediates activation of Keap1-Nrf2-ARE pathway and may serve as a potential agent to treat type I diabetes mellitus. In our research, we observed excessive reactive oxygen species production, low level of cell death, and PKC phosphorylation on exendine-4 treatment. Nrf2 knockdown led to suppression of reactive oxygen species generation as well as increasing apoptosis. Moreover, siRNA-mediated Nrf2 down-regulation attenuated the suppressive effect of exendin-4 in pancreatic β-cell viability, via modulating apoptosis promoting- and counteracting-proteins, Bax, and Bcl-2.
Host nuclear factor erythroid 2-related factor-2 defense system determines the outcome of dextran sulfate sodium-induced colitis in mice
Administration of dextran sulfate sodium (DSS) in drinking water led to significant bout of colitis simulating ulcerative colitis of human. However, colitis usually developed 5 - 7 days after DSS administration. Therefore, we hypothesized host defense system might protect colitis up to 5 days of DSS administration. 2.5% DSS-induced colitis were administered to C57BL/6 mice and sequential measurements of pathology, cyclooxygenase-2 (COX-2), nuclear factor-κB (NF-κB), heme oxygenase-1 (HO-1), NADPH quinone oxidoreductase-1 (NQO1), γ-glutamylcysteine synthetase (γ-GCS), nuclear factor erythroid 2-related factor-2 (Nrf2), and keap1 were done at 2, 6, 12, 24, 48, 96, 120, and 168 hour of DSS administration, respectively. DSS-induced colitis was repeated in either COX-2 or Nrf2 mice. On serial pathological analysis, significant colitis was noted after 120 h of DSS administration, during which both activations of COX-2/NF-κB and HO-1/Nrf2 were noted. Nrf2 activations after keap1 inactivation led to significant increases in HO-1 after 168 hours of DSS administration, when NF-κB nuclear translocation was noted. Significantly attenuated colitis was noted in DSS-challenged COX-2 mice, in which the levels of HO-1 were significantly decreased compared to DSS-challenged WT littermates (p < 0.01), while the levels of NQO1 were significantly increased. On DSS administration to Nrf2 mice, colitis was significantly aggravated (p < 0.01), in which the expressions of COX-2 as well as expressions of HO-1 and γ-GCS were significantly increased (p < 0.01). Reciprocal activations of inflammatory and antioxidative defense signaling after DSS administration might be prerequisite to make intestinal homeostasis and host defense Nrf2 system can determine colitis.
Novel Curcumin C66 That Protects Diabetes-Induced Aortic Damage Was Associated with Suppressing JNK2 and Upregulating Nrf2 Expression and Function
Diabetes-related cardiovascular diseases are leading causes of the mortality worldwide. Our previous study has explored the protective effect of curcumin analogue C66 on diabetes-induced pathogenic changes of the aorta. In the present study, we sought to reveal the underlying protective mechanisms of C66. Diabetes was induced in male WT and JNK2 mice with a single intraperitoneal injection of streptozotocin. Diabetic mice and age-matched nondiabetic mice were randomly treated with either vehicle (WT, WT DM, JNK2, and JNK2DM) or C66 (WT + C66, WT DM + C66, JNK2 + C66, and JNK2DM + C66) for three months. Aortic oxidative stress, cell apoptosis, inflammatory changes, fibrosis, and Nrf2 expression and function were assessed by immunohistochemical staining for the protein level and real-time PCR method for mRNA level. The results suggested that either C66 treatment or JNK2 deletion can reverse diabetes-induced aortic oxidative stress, cell apoptosis, inflammation, and fibrosis. Nrf2 was also found to be activated either by C66 or JNK2 deletion. However, C66 had no extra effect on diabetic aortic damage or Nrf2 activation without JNK2. These results suggest that diabetes-induced pathological changes in the aorta can be protected by C66 mainly via inhibition of JNK2 and accompanied by the upregulation of Nrf2 expression and function.
Enhanced Oxidative Damage and Nrf2 Downregulation Contribute to the Aggravation of Periodontitis by Diabetes Mellitus
Diabetes mellitus is a well-recognized risk factor for periodontitis. The goal of the present study was to elucidate whether oxidative stress and nuclear factor erythroid 2-related factor 2 (Nrf2) participate in the aggravation of periodontitis by diabetes. For this purpose, we assigned Wistar rats to control, periodontitis, diabetes, and diabetic periodontitis groups. Two weeks after induction of diabetes by streptozotocin, periodontitis was induced by ligation. Two weeks later, periodontal tissues and blood were harvested and analyzed by stereomicroscopy, immunohistochemistry, and real-time polymerase chain reaction. We found that ligation induced more severe bone loss and periodontal cell apoptosis in diabetic rats than in normal rats ( < 0.05). Compared with the control group, periodontitis significantly enhanced local oxidative damage (elevated expression of 3-nitrotyrosine, 4-hydroxy-2-nonenal, and 8-hydroxy-deoxyguanosine), whereas diabetes significantly increased systemic oxidative damage and suppressed antioxidant capacity (increased malondialdehyde expression and decreased superoxide dismutase activity) ( < 0.05). Simultaneous periodontitis and diabetes synergistically aggravated both local and systemic oxidative damage ( < 0.05); this finding was strongly correlated with the more severe periodontal destruction in diabetic periodontitis. Furthermore, gene and protein expression of Nrf2 was significantly downregulated in diabetic periodontitis ( < 0.05). Multiple regression analysis indicated that the reduced Nrf2 expression was strongly correlated with the aggravated periodontal destruction and oxidative damage in diabetic periodontitis. We conclude that enhanced local and systemic oxidative damage and Nrf2 downregulation contribute to the development and progression of diabetic periodontitis.
Inhalation of hydrogen gas elevates urinary 8-hydroxy-2'-deoxyguanine in Parkinson's disease
Hyposmia is one of the earliest and the most common symptoms in Parkinson's disease (PD). The benefits of hydrogen water on motor deficits have been reported in animal PD models and PD patients, but the effects of hydrogen gas on PD patients have not been studied. We evaluated the effect of inhalation of hydrogen gas on olfactory function, non-motor symptoms, activities of daily living, and urinary 8-hydroxy-2'-deoxyguanine (8-OHdG) levels by a randomized, double-blinded, placebo-controlled, crossover trial with an 8-week washout period in 20 patients with PD. Patients inhaled either ~1.2-1.4% hydrogen-air mixture or placebo for 10 minutes twice a day for 4 weeks. Inhalation of low dose hydrogen did not significantly influence the PD clinical parameters, but it did increase urinary 8-OHdG levels by 16%. This increase in 8-OHdG is markedly less than the over 300% increase in diabetes, and is more comparable to the increase after a bout of strenuous exercise. Although increased reactive oxygen species is often associated with toxicity and disease, they also play essential roles in mediating cytoprotective cellular adaptations in a process known as hormesis. Increases of oxidative stress by hydrogen have been previously reported, along with its ability to activate the Nrf2, NF-κB pathways, and heat shock responses. Although we did not observe any beneficial effect of hydrogen in our short trial, we propose that the increased 8-OHdG and other reported stress responses from hydrogen may indicate that its beneficial effects are partly or largely mediated by hormetic mechanisms. The study was approved by the ethics review committee of Nagoya University Graduate School of Medicine (approval number 2015-0295). The clinical trial was registered at the University Hospital Medical Information Network (identifier UMIN000019082).
Protective Effects of Siebold Fruit Extract against Palmitate-Induced Lipotoxicity in Mesangial Cells
Diabetic nephropathy is one of the most serious complications of diabetes. Lipotoxicity in glomerular mesangial cells is associated with the progression of diabetic nephropathy. Paper mulberry, Siebold (BK), has been used in oriental medicine for human health problems. However, to date, the beneficial effect of BK fruit has not been studied. In this study, we investigated the protective effect of an ethanolic extract of BK fruit (BKFE) against palmitate- (PA-) induced toxicity in mesangial cells. BKFE significantly increased the viability of PA-treated SV40 MES13 cells. BKFE significantly inhibited PA-induced apoptosis and decreased the expression of apoptotic genes, cleaved caspase-3, and cleaved PARP. Moreover, BKFE inhibited the expression of endoplasmic reticulum (ER) stress-related genes, such as BiP, phosphorylated eIF2, cleaved ATF6, and spliced XBP-1, in PA-treated SV40 MES13 cells. BKFE decreased PA-induced ROS production. In addition, BKFE activated the transcription factor Nrf2 and increased the expression of antioxidant enzymes. However, knockdown of Nrf2 using siRNA suppressed this BKFE-induced increase in antioxidant enzyme expression. Furthermore, the protective effect of BKFE on PA-induced apoptosis was significantly reduced by Nrf2 knockdown. In conclusion, BKFE induced the expression of antioxidant enzymes via activation of Nrf2 and protected against PA-induced lipotoxicity in mesangial cells.
Treatment With Naringenin Elevates the Activity of Transcription Factor Nrf2 to Protect Pancreatic β-Cells From Streptozotocin-Induced Diabetes and
Chronic hyperglycemia and unusually high oxidative stress are the key contributors for diabetes in humans. Since nuclear factor E2-related factor 2 (Nrf2) controls the expression of antioxidant- and detoxification genes, it is hypothesized that targeted activation of Nrf2 using phytochemicals is likely to protect pancreatic β-cells, from oxidative damage, thereby mitigates the complications of diabetes. Naringenin is one such activator of Nrf2. However, it is currently not known whether the protective effect of naringenin against streptozotocin (STZ) induced damage is mediated by Nrf2 activation. Hence, the potential of naringenin to activate Nrf2 and protect pancreatic β-cells from STZ-induced damage in MIN6 cells is studied. In MIN6 cells, naringenin could activate Nrf2 and its target genes GST and NQO1, thereby inhibit cellular apoptosis. In animals, administration of 50 mg/kg body weight naringenin, for 45 days, significantly decreased STZ-induced blood glucose levels, normalized the lipid profile, and augmented the levels of antioxidants in pancreatic tissues. Immunohistochemical analysis measuring the number of insulin-positive cells in pancreas showed restoration of insulin expression similar to control animals. Furthermore, naringenin promoted glycolysis while inhibiting gluconeogenesis. In conclusion, naringenin could be a good anti-diabetic agent, which works by promoting Nrf2 levels and by decreasing cellular oxidative stress.