NAD(P)H:quinone oxidoreductase 1 activity reduces hypertrophy in 3T3-L1 adipocytes

Regulation of Nrf2 and NF-κB activities may contribute to the anti-inflammatory mechanism of xylopic acid

Xylopic acid (XA) is a kaurene diterpene which naturally exists in African plants such as Xylopia aethiopica. It has been established to exhibit acute and chronic anti-inflammatory activities from our earlier studies. This current work sets out to shed light on the potential molecular target(s) of xylopic acid. Selection of investigated targets (NF-κB, Nrf2 and PTP1B) was based on an unbiased approach, using the SPiDER in silico prediction tool, and a candidate approach, examining well-known anti-inflammatory targets. Reporter gene assays were used to test for altered NF-κB and Nrf2 activities in transfected HEK or CHO cells, respectively, and immunoblot and flow cytometric analyses examined protein expression of the Nrf2/NF-kB target genes HO-1 and VCAM-1 in HUVEC. An effect of XA on PTP1B activity assay was studied using an in vitro enzyme assay with recombinant human enzyme and pNPP as substrate as well as by looking at insulin receptor phosphorylation in HepG2 cells. XA at 30 µM significantly (p < 0.001) inhibited the NF-κB-dependent reporter gene expression and enhanced activation of Nrf2 in a concentration-dependent manner when compared to the control. XA also marginally increased HO-1 protein expression levels while expression of VCAM-1 was reduced to 70% in XA-treated endothelial cells. However, XA did not show any sign of inhibition of PTP1B or a related phosphatase. Our findings suggest that the anti-inflammatory mechanism of XA entails the inhibitory effect on NF-κB and an increased activity of Nrf2, accompanied by increased expression of HO-1 and reduced expression of VCAM-1.

Ozone Activates the Nrf2 Pathway and Improves Preservation of Explanted Adipose Tissue In Vitro

In clinical practice, administration of low ozone (O₃) dosages is a complementary therapy for many diseases, due to the capability of O₃ to elicit an antioxidant response through the Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2)-dependent pathway. Nrf2 is also involved in the adipogenic differentiation of mesenchymal stem cells, and low O₃ concentrations have been shown to stimulate lipid accumulation in human adipose-derived adult stem cells in vitro. Thus, O₃ treatment is a promising procedure to improve the survival of explanted adipose tissue, whose reabsorption after fat grafting is a major problem in regenerative medicine. In this context, we carried out a pilot study to explore the potential of mild O₃ treatment in preserving explanted murine adipose tissue in vitro. Scanning and transmission electron microscopy, Western blot, real-time polymerase chain reaction and nuclear magnetic resonance spectroscopy were used. Exposure to low O₃ concentrations down in the degradation of the explanted adipose tissue and induced a concomitant increase in the protein abundance of Nrf2 and in the expression of its target gene Hmox1. These findings provide a promising background for further studies aimed at the clinical application of O₃ as an adjuvant treatment to improve fat engraftment.

Inhibitory Effect of Betanin FromHylocereus ocamponisAgainst Steatohepatitis in Mice Fed a High-Fat Diet

Betanin is a phytocompound whose effect in steatohepatitis has not yet been tested. Betanin was extracted from the fruits of Hylocereus ocamponis, and its effects were evaluated in a mice model for non-alcoholic fatty liver disease. Six-week-old male BALB/c mice fed with a high-fat diet received 9.6 mg of betanin per day during 40 days. Body, liver, and epididymal fat pad weights and the levels of blood serum total cholesterol, triglycerides, high-density lipoproteins, alanine aminotransferase, blood nitrogen urea, creatinine, and total antioxidant capacity were measured. Hepatosteatosis and inflammatory infiltration were categorized, and the relative cell area of hepatocytes was determined. Betanin inhibited the inflammatory infiltration of the liver ( P = 4.000 × 10−6) and the necrosis of hepatocytes ( P = 9.634 × 10−7); it also produced a predominance of microvesicular steatosis ( P = 9.634 × 10−7), decreased epididymal fat pad weight ( P = 8.250 × 10−4), and increased blood serum total cholesterol ( P = 0.011). Betanin is a promising compound for fatty liver, steatohepatitis, and chronic liver disease.

The Role of Nrf2 in the Antioxidant Cellular Response to Medical Ozone Exposure

Ozone (O3) is a natural, highly unstable atmospheric gas that rapidly decomposes to oxygen. Although not being a radical molecule, O3 is a very strong oxidant and therefore it is potentially toxic for living organisms. However, scientific evidence proved that the effects of O3 exposure are dose-dependent: high dosages stimulate severe oxidative stress resulting in inflammatory response and tissue injury, whereas low O3 concentrations induce a moderate oxidative eustress activating antioxidant pathways. These properties make O3 a powerful medical tool, which can be used as either a disinfectant or an adjuvant agent in the therapy of numerous diseases. In this paper, the cellular mechanisms involved in the antioxidant response to O3 exposure will be reviewed with special reference to the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) and its role in the efficacy of ozone therapy.

Schlafen 3 knockout mice display gender-specific differences in weight gain, food efficiency, and expression of markers of intestinal epithelial differentiation, metabolism, and immune cell function

Self-renewal and differentiation are essential for intestinal epithelium absorptive functioning and adaptation to pathological states such as short gut syndrome, ulcers, and inflammatory bowel disease. The rodent Slfn3 and its human analog Slfn12 are critical in regulating intestinal epithelial differentiation. We sought to characterize intestinal function in Slfn3 knockout (KO) mice. Male and female pair-fed Slfn3KO mice gained less weight with decreased food efficiency than wild type (WT) mice, with more pronounced effects in females. RNA sequencing performed on intestinal mucosa of Slfn3KO and WT mice showed gene ontology decreases in cell adhesion molecule signaling, tumor necrosis factor receptor binding, and adaptive immune cell proliferation/functioning genes in Slfn3KO mice, with greater effects in females. qPCR analysis of fatty acid metabolism genes, Pla2g4c, Pla2g2f, and Cyp3c55 revealed an increase in Pla2g4c, and a decrease in Pla2g2f in Slfn3KO females. Additionally, adipogenesis genes, Fabp4 and Lpl were decreased and ketogenesis gene Hmgcs2 was increased in female Slfn3KO mice. Sequencing did not reveal significant changes in differentiation markers, so qPCR was utilized. Slfn3KO tended to have decreased expression of intestinal differentiation markers sucrase isomaltase, dipeptidyl peptidase 4, villin 1, and glucose transporter 1 (Glut1) vs. WT males, although these trends did not achieve statistical significance unless data from several markers was pooled. Differentiation markers, Glut2 and sodium-glucose transporter 1 (SGLT1), did show statistically significant sex-dependent differences. Glut2 mRNA was reduced in Slfn3KO females, while SGLT1 increased in Slfn3KO males. Notch2 and Cdx2 were only increased in female Slfn3KO mice. Although Slfn3KO mice gain less weight and decreased food efficiency, their biochemical phenotype is more subtle and suggests a complex interplay between gender effects, Slfn3, and another regulatory pathway yet to be identified that compensates for the chronic loss of Slfn3.

RETRACTED: MicroRNA-494 inhibition alleviates acute lung injury through Nrf2 signaling pathway via NQO1 in sepsis-associated acute respiratory distress syndrome

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 5G,H+I, which appear to have a similar phenotype as many other publications, as detailed here: https://pubpeer.com/publications/7C9483B2551952AD53CCFCE206C4EB; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. The journal requested that the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

Inactivation of glycogen synthase kinase-3β (GSK-3β) enhances skeletal muscle oxidative metabolism

BACKGROUND

Aberrant skeletal muscle mitochondrial oxidative metabolism is a debilitating feature of chronic diseases such as chronic obstructive pulmonary disease, type 2 diabetes and chronic heart failure. Evidence in non-muscle cells suggests that glycogen synthase kinase-3β (GSK-3β) represses mitochondrial biogenesis and inhibits PPAR-γ co-activator 1 (PGC-1), a master regulator of cellular oxidative metabolism. The role of GSK-3β in the regulation of skeletal muscle oxidative metabolism is unknown.

AIMS

We hypothesized that inactivation of GSK-3β stimulates muscle oxidative metabolism by activating PGC-1 signaling and explored if GSK-3β inactivation could protect against physical inactivity-induced alterations in skeletal muscle oxidative metabolism.

METHODS

GSK-3β was modulated genetically and pharmacologically in C2C12 myotubes in vitro and in skeletal muscle in vivo. Wild-type and muscle-specific GSK-3β knock-out (KO) mice were subjected to hind limb suspension for 14days. Key constituents of oxidative metabolism and PGC-1 signaling were investigated.

RESULTS

In vitro, knock-down of GSK-3β increased mitochondrial DNA copy number, protein and mRNA abundance of oxidative phosphorylation (OXPHOS) complexes and activity of oxidative metabolic enzymes but also enhanced protein and mRNA abundance of key PGC-1 signaling constituents. Similarly, pharmacological inhibition of GSK-3β increased transcript and protein abundance of key constituents and regulators of mitochondrial energy metabolism. Furthermore, GSK-3β KO animals were protected against unloading-induced decrements in expression levels of these constituents.

CONCLUSION

Inactivation of GSK-3β up-regulates skeletal muscle mitochondrial metabolism and increases expression levels of PGC-1 signaling constituents. In vivo, GSK-3β KO protects against inactivity-induced reductions in muscle metabolic gene expression.

Phenethyl isothiocyanate protects against H2O2-induced insulin resistance in 3T3-L1 adipocytes

Obesity is associated with systemic oxidative stress and leads to insulin resistance. Phenethyl isothiocyanate (PEITC), a natural dietary isothiocyanate, has been shown to have beneficial effects in improving cellular defense activities against oxidative stress through activation of nuclear factor erythroid-2 related factor 2 (Nrf2) pathway. However, little evidence exists if the antioxidative activity has beneficial effects on glucose metabolism. Here, we tested the preventive potential of PEITC for impaired insulin-induced glucose uptake by oxidative stress in 3T3-L1 adipocytes. Treatment with PEITC increased the expression of antioxidative enzymes regulated by Nrf2 such as γ-glutamylcysteine-synthetase, heme oxygenase 1, NAD(P)H:quinone oxidoreductase 1 and glutathione S-transferase, and reduced oxidative stress induced by H₂O₂. Furthermore, PEITC restored impaired insulin-stimulated glucose uptake, translocation of glucose transporter 4 and insulin signaling by H₂O₂. These results indicate that PEITC protected insulin-regulated glucose metabolism impaired by oxidative stress through the antioxidative activity in 3T3-L1 adipocytes.

Pulicaria jaubertii E. Gamal-Eldin reduces triacylglyceride content and modifies cellular antioxidant pathways in 3T3-L1 adipocytes

Levels of obesity in Middle Eastern countries are increasing. Phytochemicals have anti-obesogenic properties as evidenced by prevention of adipocyte differentiation and blocking triacylglyceride (TG) accumulation. In Yemen, Pulicaria jaubertii E. Gamal-Eldin (PJ) is a food additive and a traditional medicine. We tested the hypothesis that phytochemicals present in PJ inhibit adipocytic responses during differentiation of 3T3-L1 preadipocytes to adipocytes. Methanolic extracts of PJ did not block expression of fatty acid binding protein 4 (FABP4) a marker of differentiation but did inhibit TG accumulation. Treatment of 3T3-L1 preadipocytes increased NADPH:quinone oxidoreductase 1 (NQO1), a suppressor of TG accumulation. Further fractionation of the methanolic PJ extract with hexane and dichloromethane (DCM) demonstrated that bioactivity towards TG reduction and elevated expression of NQO1 and other antioxidant genes (glutamate cysteine ligase catalytic unit, glutathione disulfide reductase, glutathione peroxidase (GPx) 4 resided in the DCM fraction. Activity towards depleting GSH and elevating the expression of catalase and GPx3 were found in the DCM and hexane fractions. Analysis by gas chromatography and liquid chromatography coupled with mass spectrometry demonstrated the presence of catechin-like moieties in the DCM and methanolic fractions and suggest that these components were partially responsible for the bioactivity of these fractions. In summary, our data indicate that fractions derived PJ exhibit anti-adipogenic properties in part through the presence of catechin-like compounds.

Cellular localization of NRF2 determines the self-renewal and osteogenic differentiation potential of human MSCs via the P53-SIRT1 axis

NRF2 (nuclear factor erythroid-derived 2-like 2) plays an important role in defense against oxidative stress at the cellular level. Recently, the roles of NRF2 in embryonic and adult stem cells have been reported, but its role in maintaining self-renewal and differentiation potential remains unknown. We studied the mechanisms of NRF2 action in mesenchymal stem cells (MSCs) derived from human bone marrow. We found that the cellular localization of NRF2 changed during prolonged cell passage and osteogenic differentiation. Blocking the nuclear import of NRF2 using ochratoxin A (OTA) induced the loss of the self-renewal and osteogenic potential of early-passage (EP) MSCs. Conversely, reinforcing the nuclear import of NRF2 using tert-butylhydroquinone (t-BHQ) improved the self-renewal capacity and maintained the differentiation potential in the osteogenic lineage of EP MSCs. Real-time quantitative PCR and western blot analysis showed that NRF2 positively regulates sirtuin 1 (SIRT1) at the mRNA and protein levels via the negative regulation of p53. The self-renewal and osteogenic potential suppressed in OTA-treated or NRF2-targeting small hairpin RNA (shRNA)-infected EP MSCs were rescued by introducing small interfering RNA (siRNA) targeting p53. t-BHQ treatment in late-passage (LP) MSCs, which lost their self-renewal and osteogenic potential, reversed these effects. In LP MSCs treated with t-BHQ for ∼7 days, the phosphorylation and nuclear localization of NRF2 improved and SIRT1 protein level increased, whereas p53 protein levels decreased. Therefore, our results suggest that NRF2 plays an important role in regulating p53 and SIRT1 to maintain MSC stemness. This study is the first to establish a functional link between NRF2 and SIRT1 expression in the maintenance of MSC self-renewal and differentiation potential.

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.

Effects of dipeptidyl-peptidase 4 inhibitor about vascular inflammation in a metabolic syndrome model

Background

In this study, we used vidagliptin(V) to examine the role of the DDP-IV, incretin system component, in the activation of different molecular inflammatory cytokines, NF-kB and VCAM-1 to generate a microenvironment that supports cardiovascular remodeling.

Methods

Male WKY and SHR were separated into five groups: Control, FFR: WKY rats receiving a 10% (w/v) fructose solution during all 12 weeks, SHR, FFHR: SHR receiving a 10% (w/v) fructose solution during all 12 weeks and FFHR+V: (5 mg/kg per day for 6 weeks) (n = 8 each group). Metabolic variables and systolic blood pressure were measured. The TBRAS, eNOS activity, and NAD(P)H oxidase activity were estimated to evaluate oxidative stress. Cardiac and vascular remodeling were evaluated. To assess the cytokine, NF-kB and VCAM-1 immunostaining techniques were used.

Results

The FFHR experimental model presents metabolic syndrome criteria, vascular and cardiac remodeling, vascular inflammation due to increased expression of NF-kB, VCAM-1, and pro-atherogenic cytokines. Chronic treatment with V was able to reverse total or partiality of variables studied.

Conclusions

Data demonstrated an important effect of DDP-IV in reducing vascular inflammation, accompanied by a favorable reduction in metabolic and structural parameters.

Genetics of oxidative stress in obesity

Obesity is a multifactorial disease characterized by the excessive accumulation of fat in adipose tissue and peripheral organs. Its derived metabolic complications are mediated by the associated oxidative stress, inflammation and hypoxia. Oxidative stress is due to the excessive production of reactive oxygen species or diminished antioxidant defenses. Genetic variants, such as single nucleotide polymorphisms in antioxidant defense system genes, could alter the efficacy of these enzymes and, ultimately, the risk of obesity; thus, studies investigating the role of genetic variations in genes related to oxidative stress could be useful for better understanding the etiology of obesity and its metabolic complications. The lack of existing literature reviews in this field encouraged us to gather the findings from studies focusing on the impact of single nucleotide polymorphisms in antioxidant enzymes, oxidative stress-producing systems and transcription factor genes concerning their association with obesity risk and its phenotypes. In the future, the characterization of these single nucleotide polymorphisms (SNPs) in obese patients could contribute to the development of controlled antioxidant therapies potentially beneficial for the treatment of obesity-derived metabolic complications.

Akt and ERK/Nrf2 activation by PUFA oxidation-derived aldehydes upregulates FABP4 expression in human macrophages

OBJECTIVE

In macrophages, adipocyte fatty acid-binding protein (FABP4) coordinates key events in oxidized LDL-induced foam cell formation, such as cholesterol trafficking and inflammatory responses. Nrf2 is a redox-sensitive transcription factor with antioxidant and anti-inflammatory properties. We investigated the involvement of the Nrf2 signaling pathway in FABP4-upregulation in response to aldehydes that are derived from polyunsaturated fatty acid (PUFA) oxidation.

METHODS AND RESULTS

Using RT-PCR and western blotting, we found that the aldehyde 2,4-decadienal (2,4-DDE) produced a marked increase in FABP4 mRNA and protein levels. 2,4-DDE acts at the transcriptional level of FABP4 by promoting mRNA synthesis and prolonging the half-life of the de novo synthesized mRNA. 2,4-DDE consistently enhanced nuclear translocation of phosphorylated Nrf2, which was mediated by the activation of the Akt and ERK signaling pathways. A chromatin immunoprecipitation assay showed the in vivo binding of activated Nrf2 to a newly identified ARE site in the human FABP4 promoter.

CONCLUSIONS

We propose an Akt and ERK/Nrf2-dependent FABP4 upregulation pathway in response to PUFA oxidation end-products in human macrophages. These results open a new avenue for putative therapeutic targets addressed to control atherogenesis.

Emerging role of Nrf2 in adipocytes and adipose biology

Maintenance of a balanced redox state within the cell is of critical importance to a wide variety of biological systems. Nuclear factor erythroid-derived 2-like 2 (Nrf2) is a critical regulator of key aspects of the antioxidant defense pathway and has long been a subject of interest regarding conditions of chronic stress such as inflammation and cancer. Recent data have emerged demonstrating that oxidative stress and Nrf2 also play critical roles in the biology of adipose tissue. This review examines data identifying the roles of Nrf2 and oxidative stress in the biological process of adipose cell differentiation as well as the implications of Nrf2 modulation on obesity. Working to understand the complex interplay among Nrf2, oxidative stress, and adipose biology could lead to a variety of possible treatments for obesity and other related disorders.