ROS Acts as a Double-Edged Sword in the Pathogenesis of Type 2 Diabetes Mellitus: Is Nrf2 a Potential Target for the Treatment?

HINT2 may be One Clinical Significance Target for Patient with Diabetes Mellitus and Reduced ROS-Induced Oxidative Stress and Ferroptosis by MCU

The World Health Organization (WHO) predicted that patients with diabetes around the world will increase to 600 million by 2040, of which about 1/3 will develop diabetic nephropathy (DN). Therefore, the present study aimed to uncover therapeutic effect of HINT2 and determined its possible mechanisms. Patients with diabetes mellitus and normal volunteers were enrolled at our hospital. Male C57BL/6 mice were fed with a high fat diet and injected intraperitoneally with STZ for once (100 mg/kg body weight). Mouse podocytes (MPC5) cells were induced with 20 mmol/l D-glucose. Inhibition of HINT2 mRNA expression levels in patients with DN was observed, compared with normal group. The serum of HINT2 mRNA expression was negative in correlation with blood sugar, tubulo-interstitial damage, glomerular damage score or urine protein level in patients with DN. HINT2 expression in kidney tissue of mice with DN were downregulated. HINT2 presented reduced DN and inflammation and ROS-induced oxidative stress in model of DN. HINT2 promoted ferroptosis in model of DN by mitochondrial membrane potential. HINT2 suppressed MCU expression in model of DN. HINT2 protein combined with MCU protein increased MCU protein ubiquitination. HINT2 triggers mitochondrial Ca2+ influx to increase ROS production level by MCU. Taken together, these findings demonstrated that HINT2 reduced ROS-induced Oxidative stress and ferroptosis by MCU, suggesting that HINT2 may be a feasible strategy to treat DN.

Arginase: Biological and Therapeutic Implications in Diabetes Mellitus and Its Complications

Arginase is a ubiquitous enzyme in the urea cycle (UC) that hydrolyzes L-arginine to urea and L-ornithine. Two mammalian arginase isoforms, arginase1 (ARG1) and arginase2 (ARG2), play a vital role in the regulation of β-cell functions, insulin resistance (IR), and vascular complications via modulating L-arginine metabolism, nitric oxide (NO) production, and inflammatory responses as well as oxidative stress. Basic and clinical studies reveal that abnormal alterations of arginase expression and activity are strongly associated with the onset and development of diabetes mellitus (DM) and its complications. As a result, targeting arginase may be a novel and promising approach for DM treatment. An increasing number of arginase inhibitors, including chemical and natural inhibitors, have been developed and shown to protect against the development of DM and its complications. In this review, we discuss the fundamental features of arginase. Next, the regulatory roles and underlying mechanisms of arginase in the pathogenesis and progression of DM and its complications are explored. Furthermore, we review the development and discuss the challenges of arginase inhibitors in treating DM and its related pathologies.

Triplication of HSA21 on alterations in structure and function of mitochondria

Triplication of genes encoded in human chromosome 21 (HSA21) is responsible for the phenotypes of Down syndrome (DS). The dosage-imbalance of the nuclear genes and the extra-nuclear mitochondrial DNA (mtDNA) jointly contributes to patho-mechanisms in DS. The mitochondrial organelles are the power house of cells for generation of ATP and maintaining cellular calcium and redox homeostasis, and cellular energy-metabolism processes. Each cell contains hundreds to thousands of mitochondria depending on their energy consumption. The dynamic structure of mitochondria is maintained with continuous fission and fusion events, and thus, content of mtDNA and its genetic composition are widely variable among cells. Cells of brain and heart tissues of DS patients and DS-mouse models have demonstrated elevated number but reduced amount of mtDNA due to higher fission process. This mechanism perturbs the oxidative phosphorylation (OXPHOS) and generates more free radicals such as reactive oxygen species (ROS), suggesting contribution of mtDNA in proliferation and protection of cells from endogenous toxic environment and external stressors. Gene-dosage in DS population collectively contributes to mitochondrial dysfunction by lowering energy production and respiratory capacity via the impaired OXPHOS, and damaged redox homeostasis and mitochondrial dynamics in all types of cells in DS. The context is highly complex and affects the functioning of all organs. The effect in brain and heart tissues promotes myriads of neurodegenerative diseases and cardiac complexities in individuals with DS. Crosstalk between trisomic nuclear and mitochondrial genome has been crucial for identification of potential therapeutic targets.

Recent Advances in Understanding Nrf2 Agonism and Its Potential Clinical Application to Metabolic and Inflammatory Diseases

Oxidative stress is a major component of cell damage and cell fat, and as such, it occupies a central position in the pathogenesis of metabolic disease. Nuclear factor-erythroid-derived 2-related factor 2 (Nrf2), a key transcription factor that coordinates expression of genes encoding antioxidant and detoxifying enzymes, is regulated primarily by Kelch-like ECH-associated protein 1 (Keap1). However, involvement of the Keap1–Nrf2 pathway in tissue and organism homeostasis goes far beyond protection from cellular stress. In this review, we focus on evidence for Nrf2 pathway dysfunction during development of several metabolic/inflammatory disorders, including diabetes and diabetic complications, obesity, inflammatory bowel disease, and autoimmune diseases. We also review the beneficial role of current molecular Nrf2 agonists and summarize their use in ongoing clinical trials. We conclude that Nrf2 is a promising target for regulation of numerous diseases associated with oxidative stress and inflammation. However, more studies are needed to explore the role of Nrf2 in the pathogenesis of metabolic/inflammatory diseases and to review safety implications before therapeutic use in clinical practice.

A System-Level Mechanism of Anmyungambi Decoction for Obesity: A Network Pharmacological Approach

Obesity is a low-grade systemic inflammatory disease involving adipocytokines. As though Anmyungambi decoction (AMGB) showed significant improvement on obesity in a clinical trial, the molecular mechanism of AMGB in obesity remains unknown. Therefore, we explored the potential mechanisms of action of AMGB on obesity through network pharmacological approaches. We revealed that targets of AMGB are significantly associated with obesity-related and adipocyte-elevated genes. Evodiamine, berberine, genipin, palmitic acid, genistein, and quercetin were shown to regulate adipocytokine signaling pathway proteins which mainly involved tumor necrosis factor receptor 1, leptin receptor. In terms of the regulatory pathway of lipolysis in adipocytes, norephedrine, pseudoephedrine, quercetin, and limonin were shown to affect adrenergic receptor-beta, protein kinase A, etc. We also found that AMGB has the potentials to enhance the insulin signaling pathway thereby preventing type II diabetes mellitus. Additionally, AMGB was discovered to be able to control not only insulin-related proteins but also inflammatory mediators and apoptotic regulators and caspases, hence reducing hepatocyte injury in nonalcoholic fatty liver disease. Our findings help develop a better understanding of how AMGB controls obesity.

Tonsil-derived mesenchymal stem cells incorporated in reactive oxygen species-releasing hydrogel promote bone formation by increasing the translocation of cell surface GRP78

Controlling the senescence of mesenchymal stem cells (MSCs) is essential for improving the efficacy of MSC-based therapies. Here, a model of MSC senescence was established by replicative subculture in tonsil-derived MSCs (TMSCs) using senescence-associated β-galactosidase, telomere-length related genes, stemness, and mitochondrial metabolism. Using transcriptomic and proteomic analyses, we identified glucose-regulated protein 78 (GRP78) as a unique MSC senescence marker. With increasing cell passage number, GRP78 gradually translocated from the cell surface and cytosol to the (peri)nuclear region of TMSCs. A gelatin-based hydrogel releasing a sustained, low level of reactive oxygen species (ROS-hydrogel) was used to improve TMSC quiescence and self-renewal. TMSCs expressing cell surface-specific GRP78 (csGRP78+), collected by magnetic sorting, showed better stem cell function and higher mitochondrial metabolism than unsorted cells. Implantation of csGRP78+ cells embedded in ROS-hydrogel in rats with calvarial defects resulted in increased bone regeneration. Thus, csGRP78 is a promising biomarker of senescent TMSCs, and the combined use of csGRP78+ cells and ROS-hydrogel improved the regenerative capacity of TMSCs by regulating GRP78 translocation.

Cr (VI) induces abnormalities in glucose and lipid metabolism through ROS/Nrf2 signaling

The hexavalent form of chromium, Cr (VI), has been associated with various diseases in humans. In this study, we examined the mechanisms underlying the effect of Cr (VI) on glucose and lipid metabolism in vivo and in vitro. We found that Cr (VI) induced abnormal liver function, increased fasting blood glucose (FBG), as well as glucose and insulin intolerance in mice. Furthermore, Cr (VI) decreased glucose-6-phosphate (G6P) level and glucose transporter-2 (GLUT2) expression, increased the levels of triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C), reduced high-density lipoprotein-cholesterol (HDL-C), and increased sterol regulatory element-binding proteins 1 (SREBP1) and fat synthase (FAS) in vitro and in vivo. Moreover, Cr (VI) promoted intracellular ROS production in vitro, and induced reduction of antioxidant enzyme level and Nrf2/HO-1 expression in vitro and in vivo. Also, N-acetyl cysteine (NAC, effective antioxidant and free radical scavenger) pretreatment inhibited the production of intracellular ROS, significantly suppressed Cr (VI)-induced oxidative stress, lipid accumulation, decreased G6P and GLUT2, and improved impaired glucose tolerance and glucose and insulin intolerance caused by Cr (VI) in mice. Dh404 activated expression of Nrf2 decreased ROS level, increased HO-1 expression, ameliorated activity of the antioxidant enzyme, inhibited Cr (VI) increase of SREBP1, FAS level, and reduction of G6P and GLUT2. To sum up, these data suggest that dysregulation of ROS/Nrf2/HO-1 has an important role in Cr (VI)-induced glucose/lipid metabolic disorder.

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.

Serum carotenoid concentrations and their association with ethnic differences in type 2 diabetes within the Healthy Life in an Urban Setting (HELIUS) study

OBJECTIVE

Studies have reported an inverse association between a diet rich in fruits and vegetables and type 2 diabetes (T2D), but data on high-risk ethnic minority groups is limited. We investigated whether serum carotenoids, as biomarkers for fruit and vegetable intake, mediate ethnic differences in the prevalence of T2D.

DESIGN

Age-adjusted serum carotenoid concentrations were compared using ANCOVA. A cross-sectional analysis was performed using Cox regression to estimate prevalence ratios (PR) and their 95 % CI of the association between serum carotenoid concentrations and T2D. To study whether serum carotenoids potentially mediate the differences in the prevalence of T2D across ethnic groups, we compared PR of the model including known risk factors and the model additionally adjusted for serum carotenoid concentrations using the Dutch group as reference.

SETTING

A study among six ethnic groups living in Amsterdam, the Netherlands.

PARTICIPANTS

Data on 204 Dutch, 203 South Asian Surinamese, 204 African Surinamese, 203 Turkish and 200 Moroccan-origin participants from the Healthy Life in an Urban Setting (HELIUS) study were used.

RESULTS

Serum carotenoid concentrations differed across ethnic groups. After adjusting for confounders, the serum concentrations of total carotenoids (PR 0·67, 95 % CI 0·54, 0·84), α-carotene (PR 0·57, 95 % CI 0·42, 0·77), β-carotene (PR 0·45, 95 % CI 0·32, 0·63) and β-cryptoxanthin (PR 0·73, 95 % CI 0·58, 0·92) were inversely associated with T2D. Despite the associations, serum carotenoids did not mediate the ethnic differences in the prevalence of T2D.

CONCLUSIONS

The limited contribution of serum carotenoids to ethnic differences in T2D suggests that a focus on increasing fruit and vegetable intake alone will not likely eliminate ethnic differences in T2D prevalence.

Perilipin 5 Reduces Oxidative Damage Associated With Lipotoxicity by Activating the PI3K/ERK-Mediated Nrf2-ARE Signaling Pathway in INS-1 Pancreatic β-Cells

Oxidative stress induced by free fatty acid overload in pancreatic β-cells is a potential contributory factor to dysfunction of insulin secretion and apoptotic cell death. Perilipin 5 (Plin5) has been reported to ameliorate oxidative stress-mediated damage in non-insulin-secreting tissues. We tested the hypothesis that Plin5 plays a similar role in pancreatic β-cells, which are extremely sensitive to oxidative stress. Here, our in vitro data showed that Plin5-mediated alleviation of palmitate-triggered apoptosis involves the mitochondrial pathway. And the protective role of Plin5 on β-cells was partially dependent on its modulation in oxidative stress. Upregulation of Plin5 in INS-1 cells decreased reactive oxygen species production, enhanced cellular glutathione levels, and induced expression of antioxidant enzymes glutamate-cysteine ligase catalytic subunit and heme oxygenase-1. However, knocking out of Plin5 abolished all of these beneficial effects. Furthermore, by using the O^2- scavenger MnTMPyP, we verified that altering Plin5 expression impacted lipotoxic cell death partially via modulating oxidative stress. Mechanistic experiments revealed that Plin5 induced Nrf2-ARE system, a master regulator in the cellular adaptive response to oxidative stress, by activating PI3K/Akt and ERK signal pathways, contributing to the increase of antioxidant defense and consequently improving β-cell function and survival in the presence of lipotoxic oxidative stress. Overall, our findings indicate that Plin5 abrogates oxidative damage in INS-1 β-cells during lipotoxic stress partially through the enhancement of antioxidant defense involving the PI3K/Akt and ERK mediated Nrf2-ARE system.

Tertiary butylhydroquinone alleviates gestational diabetes mellitus in C57BL/KsJ-Lep db/+ mice by suppression of oxidative stress

Gestational diabetes mellitus (GDM) is a common disorder characterized by abnormal glucose metabolism during pregnancy, affecting 2% to 5% of pregnant women. Currently, clinical treatment for GDM is very limited. The present study was designed to investigate the effect and underlying molecular mechanism of tertiary butylhydroquinone (TBHQ) in a pregnant C57BL/KsJ-Lep db/+ (referred to as db+) GDM mouse model. The results showed that nonpregnant db/+ mice did not show a diabetic phenotype, and TBHQ had no effect on glucose and insulin tolerance in these mice. Moreover, in db/+ pregnant mice exhibiting typical diabetes symptoms, such as hyperglycemia and hypoinsulinemia, TBHQ could remarkably decrease the blood glucose level, increase insulin level, and improve glucose and insulin intolerance. The results also revealed that TBHQ could inhibit oxidative stress in pregnant db/+ mice. Furthermore, TBHQ greatly improved offspring survival rate, glucose metabolism, and insulin tolerance. In addition, TBHQ inhibited oxidative stress by reducing malondialdehyde (MDA) and reactive oxygen species (ROS) levels and increased superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities. Moreover, we found that TBHQ activated the nuclear factor erythroid 2-related factor 2 (Nrf2), thereby increasing the levels of Nrf2, and ultimately upregulating the expression of heme oxygenase 1 (NO-1) and superoxide dismutase 2 (SOD2). In conclusion, our findings demonstrated that TBHQ alleviated GDM via Nrf2 activation.

Tempol improves oxidant/antioxidant parameters in testicular tissues of diabetic rats

AIMS

Oxidative stress induced by diabetes mellitus (DM) is considered as one of the main causes of infertility in diabetic patients. The aim of the present study was to assess the effect of Tempol - as a synthetic antioxidant- on the testis oxidative stress and sperm parameters in type 2 diabetic (T2D) rats.

MAIN METHODS

Twenty male Wistar rats were divided into 4 groups. Control groups (C) and diabetic groups (D); the control and diabetic groups received Tempol (100 mg/kg) for one month. Sperm parameters and oxidative stress biomarkers were evaluated in testicular tissue.

KEY FINDINGS

The results demonstrated that administration of Tempol in diabetic rats improved sperm motility and viability and decreased the count of abnormal sperms. Also Tempol decreased the fasting blood sugar (FBS) and lipid peroxidation (LPO). In addition, Tempol significantly increased total antioxidant capacity (TAC) levels in testis tissue of T2D rats. Histopathological changes were also improved in the diabetic treated group.

SIGNIFICANCE

Taken together, the results indicated that Tempol improved fertility parameters in a diabetic rat through reducing oxidative stress.

The Main Determinants of Diabetes Mellitus Vascular Complications: Endothelial Dysfunction and Platelet Hyperaggregation

Diabetes mellitus is a common disease that affects 3–5% of the general population in Italy. In some countries of northern Europe or in North America, it can even affect 6–8% of the population. Of great concern is that the number of cases of diabetes is constantly increasing, probably due to the increase in obesity and the sedentary nature of the population. According to the World Health Organization, in the year 2030 there will be 360 million people with diabetes, compared to 170 million in 2000. This has important repercussions on the lives of patients and their families, and on health systems that offer assistance to patients. In this review, we try to describe in an organized way the pathophysiological continuity between diabetes mellitus, endothelial dysfunction, and platelet hyperaggregation, highlighting the main molecular mechanisms involved and the interconnections.

The PI3K/AKT pathway in obesity and type 2 diabetes

Obesity and type 2 diabetes mellitus are complicated metabolic diseases that affect multiple organs and are characterized by hyperglycaemia. Currently, stable and effective treatments for obesity and type 2 diabetes mellitus are not available. Therefore, the mechanisms leading to obesity and diabetes and more effective ways to treat obesity and diabetes should be identified. Based on accumulated evidences, the PI3K/AKT signalling pathway is required for normal metabolism due to its characteristics, and its imbalance leads to the development of obesity and type 2 diabetes mellitus. This review focuses on the role of PI3K/AKT signalling in the skeletal muscle, adipose tissue, liver, brain and pancreas, and discusses how this signalling pathway affects the development of the aforementioned diseases. We also summarize evidences for recently identified therapeutic targets of the PI3K/AKT pathway as treatments for obesity and type 2 diabetes mellitus. PI3K/AKT pathway damaged in various tissues of the body leads to obesity and type 2 diabetes as the result of insulin resistance, and in turn, insulin resistance exacerbates the PI3K/AKT pathway, forming a vicious circle.

Polychlorinated biphenyls-153 induces metabolic dysfunction through activation of ROS/NF-κB signaling via downregulation of HNF1b

Polychlorinated biphenyls (PCB) is a major type of persistent organic pollutants (POPs) that act as endocrine-disrupting chemicals. In the current study, we examined the mechanism underlying the effect of PCB-153 on glucose and lipid metabolism in vivo and in vitro. We found that PCB-153 induced per se and worsened high fat diet (HFD)-resulted increase of blood glucose level and glucose and insulin intolerance. In addition, PCB-153 induced per se and worsened HFD-resulted increase of triglyceride content and adipose mass. Moreover, PCB-153 concentration-dependently inhibited insulin-dependent glucose uptake and lipid accumulation in cultured hepatocytes and adipocytes. PCB-153 induced the expression and nuclear translocation of p65 NF-κB and the expression of its downstream inflammatory markers, and worsened HFD-resulted increase of those inflammatory markers. Inhibition of NF-κB significantly suppressed PCB-153-induced inflammation, lipid accumulation and decrease of glucose uptake. PCB-153 induced oxidative stress and decreased hepatocyte nuclear factor 1b (HNF1b) and glutathione peroxidase 1 (GPx1) expression in vivo and in vitro. Overexpression of HNF1b increased GPx1 expression, decreased ROS level, decreased Srebp1, ACC and FAS expression, and inhibited PCB-153-resulted oxidative stress, NF-κB-mediated inflammation, and final glucose/lipid metabolic disorder. Our results suggest that dysregulation of HNF1b/ROS/NF-κB plays an important role in PCB-153-induced glucose/lipid metabolic disorder.

Exposure to sodium molybdate results in mild oxidative stress in Drosophila melanogaster

OBJECTIVES

The study was conducted to assess the redox status of Drosophila flies upon oral intake of insulin-mimetic salt, sodium molybdate (Na₂MoO₄).

METHODS

Oxidative stress parameters and activities of antioxidant and associated enzymes were analyzed in two-day-old D. melanogaster insects after exposure of larvae and newly eclosed adults to three molybdate levels (0.025, 0.5, or 10 mM) in the food.

RESULTS

Molybdate increased content of low molecular mass thiols and activities of catalase, superoxide dismutase, glutathione-S-transferase, and glucose-6-phosphate dehydrogenase in males. The activities of these enzymes were not affected in females. Males exposed to molybdate demonstrated lower carbonyl protein levels than the control cohort, whereas females at the same conditions had higher carbonyl protein content and catalase activity than ones in the control cohort. The exposure to 10 mM sodium molybdate decreased the content of protein thiols in adult flies of both sexes. Sodium molybdate did not affect the activities of NADP-dependent malate dehydrogenase and thioredoxin reductase in males or NADP-dependent isocitrate dehydrogenase in either sex at any concentration.

DISCUSSION

Enhanced antioxidant capacity in upon Drosophila flies low molybdate levels in the food suggests that molybdate can be potentially useful for the treatment of certain pathologies associated with oxidative stress.

Kukoamine A attenuates insulin resistance and fatty liver through downregulation of Srebp-1c

Nonalcoholic fatty liver disease (NAFLD) refers to a pathological condition of hepatic steatosis. Insulin resistance is believed to be the key mechanism mediating initial accumulation of fat in the liver, resulting in hepatic steatosis. Kukoamine A (KuA), a spermine alkaloid, is a major bioactive component extracted from the root barks of Lycium chinense (L. chinense) Miller. In the current study, we aimed to explore the possible effect of KuA on insulin resistance and fatty liver. We showed that KuA significantly inhibited the increase of fasting blood glucose level and insulin level, and the glucose levels in response to glucose and insulin load in HFD-fed mice, which was in a dose-dependent manner. KuA dose-dependently decreased the histological injury of liver, levels of hepatic triglyceride (TG), and serum AST and ALT activities in HFD-fed mice. The increase of serum levels of TNFɑ, IL-1β, IL-6 and C reactive protein in HFD-fed mice was inhibited by KuA. HFD feeding-induced increase of hepatic expression of Srebp-1c and its target genes, including fatty acid synthase (FAS) and acetyl CoA carboxylase 1 (ACC1), was significantly inhibited by KuA. Moreover, upregulation of Srebp-1c notably inhibited KuA-induced improvement of insulin-stimulated glucose uptake, decrease of lipid accumulation and H₂O₂ level in palmitic acid-treated AML-12 cells. In conclusion, we reported that KuA inhibited Srebp-1c and downstream genes expression and resulted in inhibition of lipid accumulation, inflammation, insulin resistance and oxidative stress. Overall, our results provide a better understanding of the pharmacological activities of KuA against insulin resistance and hepatic steatosis.

Evolution of metabolic disorder in rats fed high sucrose or high fat diet: Focus on redox state and mitochondrial function

Glucotoxicity and lipotoxicity are major hallmarks of metabolic disorder. High consumption of fat or carbohydrate rich food is a major risk of metabolic disorder. However, the evolution of high fat or high carbohydrate diet-induced metabolic disorder is not clear. In the study, we tried to find distinguished and common ways involved in the pathogenesis of insulin resistance induced by high fat (HF) and high sucrose (HS) diet. We found that HS diet induced mild glucose intolerance (2month), followed by a "temporary non-symptom phase" (3month), and then induced significant metabolic abnormality (4month). HF diet induced an early "responsive enhancement phase" (2month), and then gradually caused severe metabolic dysfunction (3-4month). After a mild induction of mitochondrial ROS generation (2month), HS diet resulted in a "temporary non-symptom phase" (3month), and then induced a more significant mitochondrial ROS production (4month). The impairment of mitochondrial function induced by HS diet was progressive (2-4month). HF diet induced gradual mitochondrial ROS generation and hyperpolarization. HF diet induced an early "responsive enhancement" of mitochondrial function (2month), and then gradually resulted in severe decrease of mitochondrial function (3-4month). Despite the patterns of HS and HF diet-induced insulin resistance were differential, final mitochondrial ROS generation combined with mitochondrial dysfunction may be the common pathway. These findings demonstrate a novel understanding of the mechanism of insulin resistance and highlight the pivotal role of mitochondrial ROS generation and mitochondrial dysfunction in the pathogenesis of metabolic disorder.

The Keap1-Nrf2-ARE Pathway As a Potential Preventive and Therapeutic Target: An Update

The Keap1-Nrf2-ARE ((Kelch-like ECH-Associating protein 1) nuclear factor erythroid 2 related factor 2-antioxidant response element) pathway is one of the most important defense mechanisms against oxidative and/or electrophilic stresses, and it is closely associated with inflammatory diseases, including cancer, neurodegenerative diseases, cardiovascular diseases, and aging. In recent years, progress has been made in strategies aimed at modulating the Keap1-Nrf2-ARE pathway. The Nrf2 activator DMF (Dimethylfumarates) has been approved by the FDA as a new first-line oral drug to treat patients with relapsing forms of multiple sclerosis, while a phase 3 study of another promising candidate, CDDO-Me, was terminated for safety reasons. Directly inhibiting Keap1-Nrf2 protein-protein interactions as a novel Nrf2-modulating strategy has many advantages over using electrophilic Nrf2 activators. The development of Keap1-Nrf2 protein-protein interaction inhibitors has become a topic of intense research, and potent inhibitors of this target have been identified. In addition, inhibiting Nrf2 activity has attracted an increasing amount of attention because it may provide an alternative cancer therapy. This review summarizes the molecular mechanisms and biological functions of the Keap1-Nrf2-ARE system. The main focus of this review is on recent progress in studies of agents that target the Keap1-Nrf2-ARE pathway and the therapeutic applications of such agents.

Hormetic and regulatory effects of lipid peroxidation mediators in pancreatic beta cells

Nutrient sensing mechanisms of carbohydrates, amino acids and lipids operate distinct pathways that are essential for the adaptation to varying metabolic conditions. The role of nutrient-induced biosynthesis of hormones is paramount for attaining metabolic homeostasis in the organism. Nutrient overload attenuate key metabolic cellular functions and interfere with hormonal-regulated inter- and intra-organ communication, which may ultimately lead to metabolic derangements. Hyperglycemia and high levels of saturated free fatty acids induce excessive production of oxygen free radicals in tissues and cells. This phenomenon, which is accentuated in both type-1 and type-2 diabetic patients, has been associated with the development of impaired glucose tolerance and the etiology of peripheral complications. However, low levels of the same free radicals also induce hormetic responses that protect cells against deleterious effects of the same radicals. Of interest is the role of hydroxyl radicals in initiating peroxidation of polyunsaturated fatty acids (PUFA) and generation of α,β-unsaturated reactive 4-hydroxyalkenals that avidly form covalent adducts with nucleophilic moieties in proteins, phospholipids and nucleic acids. Numerous studies have linked the lipid peroxidation product 4-hydroxy-2E-nonenal (4-HNE) to different pathological and cytotoxic processes. Similarly, two other members of the family, 4-hydroxyl-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE), have also been identified as potential cytotoxic agents. It has been suggested that 4-HNE-induced modifications in macromolecules in cells may alter their cellular functions and modify signaling properties. Yet, it has also been acknowledged that these bioactive aldehydes also function as signaling molecules that directly modify cell functions in a hormetic fashion to enable cells adapt to various stressful stimuli. Recent studies have shown that 4-HNE and 4-HDDE, which activate peroxisome proliferator-activated receptor δ (PPARδ) in vascular endothelial cells and insulin secreting beta cells, promote such adaptive responses to ameliorate detrimental effects of high glucose and diabetes-like conditions. In addition, due to the electrophilic nature of these reactive aldehydes they form covalent adducts with electronegative moieties in proteins, phosphatidylethanolamine and nucleotides. Normally these non-enzymatic modifications are maintained below the cytotoxic range due to efficient cellular neutralization processes of 4-hydroxyalkenals. The major neutralizing enzymes include fatty aldehyde dehydrogenase (FALDH), aldose reductase (AR) and alcohol dehydrogenase (ADH), which transform the aldehyde to the corresponding carboxylic acid or alcohols, respectively, or by biding to the thiol group in glutathione (GSH) by the action of glutathione-S-transferase (GST). This review describes the hormetic and cytotoxic roles of oxygen free radicals and 4-hydroxyalkenals in beta cells exposed to nutritional challenges and the cellular mechanisms they employ to maintain their level at functional range below the cytotoxic threshold.

Genistein alleviates lead-induced neurotoxicity in vitro and in vivo: Involvement of multiple signaling pathways

Lead (Pb) is a ubiquitous environmental and industrial pollutant. It induces neurotoxicity and cell death by disrupting the pro- and anti-oxidative balance; however, the mechanisms of its toxicity have yet to be fully understood. The soy-derived isoflavonoid, genistein (GEN), was reported to possess neuroprotective and antioxidative properties. The present study investigated the molecular mechanisms of Pb-induced neurotoxicity in vivo and in vitro, addressing the efficacy of GEN in protecting against Pb-induced toxicity. Pb exposure was associated with reduction of cell viability and cell apoptosis, concomitant with reactive oxygen species (ROS) generation in vitro, and pre-treatment with GEN markedly ameliorated the Pb-induced oxidative injury by increasing the expression of key antioxidant enzymes and the antioxidant transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2). Next, PKC-α activation was found after Pb exposure in vitro and pretreatment with GEN attenuated Pb-induced ROS generation by PKC-α inhibition. MAPK-NF-κB activation triggered by Pb was also inhibited by GEN. In summary, our study establishes that GEN alleviates Pb-induced impairment in spatial memory, and reduces cell apoptosis caused by Pb exposure and GEN protects neurons from Pb-induced neurotoxicity by downstream activation of antioxidant and anti-apoptotic pathways via regulation of Nrf2 and MAPK-NF-κB signaling.

Redox modulation of adipocyte differentiation: hypothesis of "Redox Chain" and novel insights into intervention of adipogenesis and obesity

In view of the global prevalence of obesity and obesity-associated disorders, it is important to clearly understand how adipose tissue forms. Accumulating data from various laboratories implicate that redox status is closely associated with energy metabolism. Thus, biochemical regulation of the redox system may be an attractive alternative for the treatment of obesity-related disorders. In this work, we will review the current data detailing the role of the redox system in adipocyte differentiation, as well as identifying areas for further research. The redox system affects adipogenic differentiation in an extensive way. We propose that there is a complex and interactive "redox chain," consisting of a "ROS-generating enzyme chain," "combined antioxidant chain," and "transcription factor chain," which contributes to fine-tune the regulation of ROS level and subsequent biological consequences. The roles of the redox system in adipocyte differentiation are paradoxical. The redox system exerts a "tridimensional" mechanism in the regulation of adipocyte differentiation, including transcriptional, epigenetic, and posttranslational modulations. We suggest that redoxomic techniques should be extensively applied to understand the biological effects of redox alterations in a more integrated way. A stable and standardized "redox index" is urgently needed for the evaluation of the general redox status. Therefore, more effort should be made to establish and maintain a general redox balance rather than to conduct simple prooxidant or antioxidant interventions, which have comprehensive implications.

Sodium chromate demonstrates some insulin-mimetic properties in the fruit fly Drosophila melanogaster

The effects of food supplementation with sodium chromate at concentrations of 1-500 μM on development of Drosophila melanogaster larvae and food intake, carbohydrate and lipid pools in adult fruit flies were investigated. Food supplementation with hexavalent chromium (Na2CrO4) at high concentrations delayed larval development and decreased the percentage of larvae that pupated which indicated a relatively low toxicity. The supplement decreased glucose levels in fly hemolymph, but at concentrations of 5-25 μM increased fly carbohydrate reserves: hemolymph trehalose and whole body trehalose and glycogen. The data on parameters of carbohydrate metabolism show that chromate possesses some insulin-mimetic properties. The changes in metabolism of carbohydrates under chromate exposure were also accompanied by an increase in total lipid levels and in the portion of triacylglycerides among all lipids. Chromate addition to fly food did not affect male or female body mass, but reduced food consumption by females at all concentrations used, whereas in males only 500 μM chromate decreased food consumption. The data show that: (1) Cr(6+) has many of the same effects as Cr(3+) suggesting that it might be just as effective to treat diabetic states, likely as a result of intracellular reduction of Cr(6+) ions, and (2) the Drosophila model can be used to develop new approaches to investigate the molecular mechanisms of chromium as an insulin-mimetic. Although it is usually believed that hexavalent chromium possesses higher toxicity than the trivalent ion, due to its easier penetration into the cell, application of hexavalent chromium may substantially decrease the chromium doses needed to get the desired effects.

Certain Diet and Lifestyle May Contribute to Islet β-cells Protection in Type-2 Diabetes via the Modulation of Cellular PI3K/AKT Pathway

PI3K/AKT pathway has been shown to play a pivotal role on islet β-cell protection, enhancing β-cell survival by stimulating cell proliferation and inhibiting cell apoptosis. Accordingly, this pathway appears to be crucial in type-2 diabetes. Understanding the regulations of this pathway may provide a better efficacy of new therapeutic approaches. In this review, we summarize advances on the involvement of the PI3K/AKT pathway in hypothetical intra-cellular signaling of islet β-cells. As recent findings may show the nutritional regulation of the survival pathway in the islet β-cells through activation of the PI3K/AKT pathway, we also review studies on the features of several diets, correlated lifestyle, and its signaling pathway involved in type-2 diabetes. The molecular mechanisms contributing to the disease are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies against a condition of the disease.

Association between oxidative stress index and post-CPR early mortality in cardiac arrest patients: A prospective observational study

Objective:

Cardiopulmonary resuscitation (CPR) is a series of lifesaving actions that improve the chance of survival following cardiac arrest (CA). Many clinical and laboratory parameters, such as the presence of asystole, out-of-hospital CPR, and duration of cardiac arrest, are associated with failed CPR in patients with CA. Asystole is a state of no cardiac electrical activity, along with the absence of contractions of the myocardium and absence of cardiac output. Oxidative stress index (OSI), which is the ratio of total oxidative status to total antioxidant status, increases by ischemia-reperfusion injury. We investigated whether OSI levels in patients with CA could predict early mortality after CPR.

Methods:

This study has a prospective observational cohort design. Five patients with a history of cancer, four patients who developed hemolysis in their blood, six patients who were transferred to our hospital from other hospitals, and six patients in whom blood samples for OSI could not be stored properly were excluded. Finally, a total of 90 in-hospital or out-of-hospital CA patients and 40 age- and sex-matched healthy volunteers as the control group were evaluated prospectively. The patients were classified according to the CPR response into a successful group (n=46) and a failed group (n=44). Comparisons between groups were performed using one-way ANOVA with post hoc analysis by Tukey’s HSD or independent samples t-test and the Kruskal-Wallis tests or Mann-Whitney U test for normally and abnormally distributed data, respectively. Also, we used chi-square test, Spearman’s correlation test, univariate and multible logistic regression analyses, and receiver operator characteristic curve analysis.

Results:

OSI was 3.0±4.0, 5.6±4.3, and 8.7±3.8 in the control group, the successful CPR group, and the failed CPR group, respectively (p<0.001 for the 2 comparisons). OSI on admission, ischemia-modified albumin, presence of asystole, mean duration of cardiac arrest, out-of-hospital CPR, pH, and potassium and sodium levels were found to have prognostic significance in the univariate analysis. In the multivariate logistic regression model, OSI on admission (OR=1.325, p=0.003), ischemia-modified albumin (OR=1.008, p=0.005), presence of asystole (OR=13.576, p<0.001), and sodium level (OR=1.132, p=0.029) remained associated with an increased risk of early mortality. In addition, the optimal cut-off value of OSI to predict post-CPR mortality was measured as >6.02, with 84.1% sensitivity and 76.1% specificity.

Conclusion:

Elevated OSI levels can predict failed CPR in CA patients.

Tocopherol inhibits the relaxing effect of terbutaline in the respiratory and reproductive tracts of the rat: the role of the oxidative stress index

AIMS

Reactive oxygen species play a role in the signal transduction of beta-adrenergic receptors. We investigated whether an antioxidant (tocopherol) can reduce the effect of terbutaline in beta-2-adrenergic receptor (β2-AR)-regulated smooth muscles.

MAIN METHODS

Contractility of the tissues from nonpregnant (trachea) and 22-day-pregnant (myometrium and cervix) rats was investigated in an isolated organ bath. The tracheal and uterine β2-AR expressions were increased by 17-beta-estradiol valerate (E2) and progesterone (P4), respectively. The accumulation of cyclic-AMP (cAMP), and the total oxidant (TOS) and total antioxidant status (TAS) were also measured. The oxidative stress index (OSI) was defined as the ratio of TOS and TAS.

KEY FINDINGS

Terbutaline (10(-10)-10(-5)M) decreased the contractions in the nontreated and the P4-pretreated myometria, but tocopherol (10(-7)M) did not alter these actions. Terbutaline (10(-6)M) increased the cervical resistance both in the nontreated and in the P4-treated samples, while tocopherol reduced this action only in the P4-treated cervices. Terbutaline (10(-9)-10(-4)M) reduced the tracheal tones both in the nontreated and in the E2-treated tissues, while tocopherol reduced these effects. The changes in the intracellular cAMP levels of the tissues were in harmony with the isolated organ results. The OSI was highest in the trachea and lowest in the pregnant myometrium.

SIGNIFICANCE

A higher OSI is linked to a higher tocopherol sensitivity of beta-mimetic-induced relaxation. Our results suggest that the antiasthmatic effect of beta-mimetics may worsen, while their tocolytic effect may remain unchanged during parallel tocopherol administration.

Neuroprotective effects of tetramethylpyrazine against dopaminergic neuron injury in a rat model of Parkinson's disease induced by MPTP

Parkinson's disease (PD) is the second most prevalent progressive neurodegenerative disease. Although several hypotheses have been proposed to explain the pathogenesis of PD, apoptotic cell death and oxidative stress are the most prevalent mechanisms. Tetramethylpyrazine (TMP) is a biological component that has been extracted from Ligusticum wallichii Franchat (ChuanXiong), which exhibits anti-apoptotic and antioxidant roles. In the current study, we aimed to investigate the possible protective effect of TMP against dopaminergic neuron injury in a rat model of Parkinson's disease induced by MPTP and to elucidate probable molecular mechanisms. The results showed that TMP could notably prevent MPTP-induced dopaminergic neurons damage, reflected by improvement of motor deficits, enhancement of TH expression and the content of dopamine and its metabolite, DOPAC. We observed MPTP-induced activation of mitochondrial apoptotic death pathway, evidenced by up-regulation of Bax, down-regulation of Bcl-2, release of cytochrome c and cleavage of caspase 3, which was significantly inhibited by TMP. Moreover, TMP could prevent MPTP-increased TBARS level and MPTP-decreased GSH level, indicating the antioxidant role of TMP in PD model. And the antioxidant role of TMP attributes to the prevention of MPTP-induced reduction of Nrf2 and GCLc expression. In conclusion, in MPTP-induced PD model, TMP prevents the down-regulation of Nrf2 and GCLc, maintaining redox balance and inhibiting apoptosis, leading to the attenuation of dopaminergic neuron damage. The effectiveness of TMP in treating PD potentially leads to interesting therapeutic perspectives.

Signaling properties of 4-hydroxyalkenals formed by lipid peroxidation in diabetes

Peroxidation of polyunsaturated fatty acids is intensified in cells subjected to oxidative stress and results in the generation of various bioactive compounds, of which 4-hydroxyalkenals are prominent. During the progression of type 2 diabetes mellitus, the ensuing hyperglycemia promotes the generation of reactive oxygen species (ROS) that contribute to the development of diabetic complications. It has been suggested that ROS-induced lipid peroxidation and the resulting 4-hydroxyalkenals markedly contribute to the development and progression of these pathologies. Recent findings, however, also suggest that noncytotoxic levels of 4-hydroxyalkenals play important signaling functions in the early phase of diabetes and act as hormetic factors to induce adaptive and protective responses in cells, enabling them to function in the hyperglycemic milieu. Our studies and others' have proposed such regulatory functions for 4-hydroxynonenal and 4-hydroxydodecadienal in insulin secreting β-cells and vascular endothelial cells, respectively. This review presents and discusses the mechanisms regulating the generation of 4-hydroxyalkenals under high glucose conditions and the molecular interactions underlying the reciprocal transition from hormetic to cytotoxic agents.

Protective nature of mangiferin on oxidative stress and antioxidant status in tissues of streptozotocin-induced diabetic rats

Oxidative stress plays an important role in the progression of diabetes complications. The aim of the present study was to investigate the beneficial effect of oral administration of mangiferin in streptozotocin (STZ)-induced diabetic rats by measuring the oxidative indicators in liver and kidney as well as the ameliorative properties. Administration of mangiferin to diabetic rats significantly decreased blood glucose and increased plasma insulin levels. The activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) and level of reduced glutathione (GSH) were significantly (P < 0.05) decreased while increases in the levels of lipidperoxidation (LPO) markers were observed in liver and kidney tissues of diabetic control rats as compared to normal control rats. Oral treatment with mangiferin (40 mg/kg b.wt/day) for a period of 30 days showed significant ameliorative effects on all the biochemical and oxidative parameters studied. Diabetic rats treated with mangiferin restored almost normal architecture of liver and kidney tissues, which was confirmed by histopathological examination. These results indicated that mangiferin has potential ameliorative effects in addition to its antidiabetic effect in experimentally induced diabetic rats.

Oleanolic acid improves hepatic insulin resistance via antioxidant, hypolipidemic and anti-inflammatory effects

Insulin resistance is the hallmark of type 2 diabetes mellitus (T2DM), which is closely related to disorder of lipid metabolism. The study was designed to evaluate the effects of oleanolic acid (OA) on hepatic insulin resistance and underlying mechanisms in Lep(db)(/)(db) obese diabetic mice. db/db Mice were administered with OA (20mg/kg/day, i.p.) for two weeks. OA reduced body weight, liver weight, and fat weight, and protected liver morphology and function. OA decreased fasting blood glucose, improved glucose and insulin tolerance, enhanced insulin signaling and inhibited gluconeogenesis. In livers, mitochondrial biogenesis, ultrastructure and function were influenced, accompanied by increased cellular and mitochondrial ROS production. OA inhibited all these changes, in which process Nrf2-GCLc mediated stabilization of mitochondrial glutathione pool may be involved. Moreover, OA decreased serum triglyceride, total cholesterol, LDL, HDL, and free fatty acids, increased serum HDL, and reduced hepatic lipid accumulation. Furthermore, inflammatory condition in db/db mice was improved by OA, as evidenced by decreased level of IL-1 β, IL-6, and TNFα in circulation and in liver. The evidence suggests that OA improves hepatic insulin resistance through inhibition of mitochondrial ROS, hypolipidemic and anti-inflammatory effects. The effectiveness of OA leads to interesting therapeutic perspectives.

Update on the protective molecular pathways improving pancreatic beta-cell dysfunction

The primary function of pancreatic beta-cells is to produce and release insulin in response to increment in extracellular glucose concentrations, thus maintaining glucose homeostasis. Deficient beta-cell function can have profound metabolic consequences, leading to the development of hyperglycemia and, ultimately, diabetes mellitus. Therefore, strategies targeting the maintenance of the normal function and protecting pancreatic beta-cells from injury or death might be crucial in the treatment of diabetes. This narrative review will update evidence from the recently identified molecular regulators preserving beta-cell mass and function recovery in order to suggest potential therapeutic targets against diabetes. This review will also highlight the relevance for novel molecular pathways potentially improving beta-cell dysfunction.

Roles for PI3K/AKT/PTEN Pathway in Cell Signaling of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver pathologies and is associated with obesity and the metabolic syndrome, which represents a range of fatty liver diseases associated with an increased risk of type 2 diabetes. Molecular mechanisms underlying how to make transition from simple fatty liver to nonalcoholic steatohepatitis (NASH) are not well understood. However, accumulating evidence indicates that deregulation of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway in hepatocytes is a common molecular event associated with metabolic dysfunctions including obesity, metabolic syndrome, and the NAFLD. A tumor suppressor PTEN negatively regulates the PI3K/AKT pathways through its lipid phosphatase activity. Molecular studies in the NAFLD support a key role for PTEN in hepatic insulin sensitivity and the development of steatosis, steatohepatitis, and fibrosis. We review recent studies on the features of the PTEN and the PI3K/AKT pathway and discuss the protein functions in the signaling pathways involved in the NAFLD. The molecular mechanisms contributing to the diseases are the subject of considerable investigation, as a better understanding of the pathogenesis will lead to novel therapies for a condition.

Oxidative stress during pregnancy in the sheep

During physiological pregnancy, all tissues and, mostly, placenta and foetus require high amounts of oxygen. Reactive oxygen species (ROS), generated both by mother and foetus, are implicated in foetal growth because they promote replication, differentiation and maturation of cells and organs. Nevertheless, ROS excess, if not properly counterbalanced, may lead to an alteration in cell constituents, with harmful effects both on mother and foetus.ROS exert a biphasic effect because adequate ROS concentration is essential for embryo development, implant, foetal defence against uterine infections, steroidogenesis, pregnancy maintainance and partum. On the other hand, an uncontrolled ROS generation, beyond physiological antioxidant defences, may lead to embryo resorption, placental degeneration with subsequent alteration in maternal-foetal exchanges, delay in foetal growth, pregnancy interruption, stillbirths. This review investigates the mechanisms underlying ROS generation and effects, throughout physiological and pathological pregnancy in sheep, with a look to antioxidants and their importance in such a critical phase of the reproductive cycle of the sheep.

S-adenosylmethionine-dependent protein methylation is required for expression of selenoprotein P and gluconeogenic enzymes in HepG2 human hepatocytes

Cellular methylation processes enable expression of gluconeogenic enzymes and metabolism of the nutrient selenium. Selenium status has been proposed to relate to type II diabetes risk, and plasma levels of selenoprotein P (SEPP1) have been positively correlated with insulin resistance. Increased expression of gluconeogenic enzymes glucose-6-phosphatase (G6PC) and phosphoenolpyruvate carboxykinase 1 (PCK1) has negative consequences for blood glucose management in type II diabetics. Transcriptional regulation of SEPP1 is directed by the same transcription factors that control the expression of G6PC and PCK1, and these factors are activated by methylation of arginine residues. We sought to determine whether expression of SEPP1 and the aforementioned glucoconeogenic enzymes are regulated by protein methylation, the levels of which are reliant upon adequate S-adenosylmethionine (SAM) and inhibited by S-adenosylhomocysteine (SAH). We treated a human hepatocyte cell line, HepG2, with inhibitors of adenosylhomocysteine hydrolase (AHCY) known to increase concentration of SAH before analysis of G6PC, PCK1, and SEPP1 expression. Increasing SAH decreased 1) the SAM/SAH ratio, 2) protein-arginine methylation, and 3) expression of SEPP1, G6PC, and PCK1 transcripts. Furthermore, hormone-dependent induction of gluconeogenic enzymes was reduced by inhibition of protein methylation. When protein-arginine methyltransferase 1 expression was reduced by siRNA treatment, G6PC expression was inhibited. These findings demonstrate that hepatocellular SAM-dependent protein methylation is required for both SEPP1 and gluconeogenic enzyme expression and that inhibition of protein arginine methylation might provide a route to therapeutic interventions in type II diabetes.

Age- and diet-dependent requirement of DJ-1 for glucose homeostasis in mice with implications for human type 2 diabetes

Elderly patients often suffer from multiple age-related diseases. Here we show that the expression of DJ-1, an antioxidant protein with reduced expression in the central nervous system of patients with Parkinson's disease, is reduced in pancreatic islets of patients with type 2 diabetes mellitus (T2DM). In contrast, under non-diabetic conditions, DJ-1 expression increases in mouse and human islets during aging. In mouse islets, we show that DJ-1 prevents an increase in reactive oxygen species levels as the mice age. This antioxidant function preserves mitochondrial integrity and physiology, prerequisites for glucose-stimulated insulin secretion. Accordingly, DJ-1-deficient mice develop glucose intolerance and reduced β cell area as they age or gain weight. Our data suggest that DJ-1 is more generally involved in age- and lifestyle-related human diseases and show for the first time that DJ-1 plays a key role in glucose homeostasis and might serve as a novel drug target for T2DM.

Does insulin bolster antioxidant defenses via the extracellular signal-regulated kinases-protein kinase B-nuclear factor erythroid 2 p45-related factor 2 pathway?

Oxidative stress plays a fundamental role in the development of diabetes, which has become a great threaten for health in the whole world. In recent years, it has been found that, in addition to the effect on metabolism, insulin plays an antioxidant role. However, the effect of insulin on the whole antioxidant enzyme system, especially in vivo, is not completely understood. We note that, in vitro and in vivo, insulin administration could sequentially and transiently increase a battery of antioxidant enzymes through the activation of the key transcription factor nuclear factor erythroid 2 p45-related factor 2 (Nrf2). The sequential activation of extracellular signal-regulated kinases (ERK)-protein kinase B (Akt) pathway maybe required for insulin-induced enhancement of antioxidant defense regulated by Nrf2. Our observation leads to the hypothesis that insulin regulates the redox balance and insulin bolsters antioxidant defenses via the ERK-Akt-Nrf2 pathway.

Small molecule modulators of Keap1-Nrf2-ARE pathway as potential preventive and therapeutic agents

Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elements (ARE) pathway represents one of the most important cellular defense mechanisms against oxidative stress and xenobiotic damage. Activation of Nrf2 signaling induces the transcriptional regulation of ARE-dependent expression of various detoxifying and antioxidant defense enzymes and proteins. Keap1-Nrf2-ARE signaling has become an attractive target for the prevention and treatment of oxidative stress-related diseases and conditions including cancer, neurodegenerative, cardiovascular, metabolic, and inflammatory diseases. Over the last few decades, numerous Nrf2 inducers have been developed and some of them are currently undergoing clinical trials. Recently, overactivation of Nrf2 has been implicated in cancer progression as well as in drug resistance to cancer chemotherapy. Thus, Nrf2 inhibitors could potentially be used to improve the effectiveness of cancer therapy. Herein, we review the signaling mechanism of Keap1-Nrf2-ARE pathway, its disease relevance, and currently known classes of small molecule modulators. We also discuss several aspects of Keap1-Nrf2 interaction, Nrf2-based peptide inhibitor design, and the screening assays currently used for the discovery of direct inhibitors of Keap1-Nrf2 interaction.

Oxidative Stress and Mitochondrial Dysfunction in Down's Syndrome: Relevance to Aging and Dementia

Genome-wide gene deregulation and oxidative stress appear to be critical factors determining the high variability of phenotypes in Down's syndrome (DS). Even though individuals with trisomy 21 exhibit a higher survival rate compared to other aneuploidies, most of them die in utero or early during postnatal life. While the survivors are currently predicted to live past 60 years, they suffer higher incidence of age-related conditions including Alzheimer's disease (AD). This paper is centered on the mechanisms by which mitochondrial factors and oxidative stress may orchestrate an adaptive response directed to maintain basic cellular functions and survival in DS. In this context, the timing of therapeutic interventions should be carefully considered for the successful treatment of chronic disorders in the DS population.