Microarray and pathway analysis highlight Nrf2/ARE-mediated expression profiling by polyphenolic myricetin

Exploring the links between polyphenols, Nrf2, and diabetes: A review

Diabetes mellitus, a complex metabolic disorder, is marked by chronic hyperglycemia that drives oxidative stress and inflammation, leading to complications such as neuropathy, retinopathy, and cardiovascular disease. The Nrf2 pathway, a key regulator of cellular antioxidant defenses, plays a vital role in mitigating oxidative damage and maintaining glucose homeostasis. Dysfunction of Nrf2 has been implicated in the progression of diabetes and its related complications. Polyphenols, a class of plant-derived bioactive compounds, have shown potential in modulating the Nrf2 pathway. Numerous compounds have been found to activate Nrf2 through mechanisms including Keap1 interaction, transcriptional regulation, and epigenetic modification. Preclinical studies indicate their ability to reduce reactive oxygen species (ROS), improve insulin sensitivity, and attenuate inflammation in diabetic models. Clinical trials with certain polyphenols, such as resveratrol, have demonstrated improvements in glycemic parameters, though results remain inconsistent. While polyphenols show promise as a component of non-pharmacological approaches to diabetes management, challenges such as bioavailability, individual variability in response, and limited clinical evidence highlight the need for further investigation. Continued research could enhance understanding of their mechanisms and improve their practical application in mitigating diabetes-related complications.

Phenolic Compound Profiles, Antioxidant, and Cytoprotective Activity of Elaeagnus conferta Roxb. Fruit

In this paper, three varieties of Elaeagnus conferta Roxb fruits prepared by ultrasonic-assisted extraction from a subtropical region southwest of China were utilized as raw materials to investigate their phenolic profiles, antioxidant activities, and protective effects on injured human umbilical vein endothelial cells (HUVECs). The ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) findings revealed that fifteen substances, including seven phenolic acids, seven flavonoids, and one gallic acid derivative, were discovered. The dihydromyricetin, ellagic acid, gallic acid were the predominant phenolic compounds in all E.conferta fruits. These E.conferta fruits extracts shown excellent antioxidant activity varied from 2.258±0.03~7.844±0.39 μM Trolox/g and protective effect on HUVECs injured by H2O2 through decrease the level of ROS, MDA, LDH and enhance the SOD level. These finding indicate that E.conferta is a valuable source of high-capacity antioxidants that might be used as an alternative material for food industries.

Kaempferol Extends Male Lifespan Under Blue Light Irradiation in Drosophila

Short-wavelength blue light is ubiquitous in daily life and has a lasting destructive influence. Its potential harm to biological health is significant. This study used Drosophila as a model organism to investigate the protective effects of kaempferol, a flavonoid, against the toxicity of blue light. It also examined its physiological effects on Drosophila under blue light irradiation. In this experiment, fruit flies were fed with three different concentrations of kaempferol solutions (0.1, 0.01, and 0.001 mol/L) dissolved in food. The survival rate and physiological indexes of Drosophila were investigated under blue light irradiation of 2500 lux. The results showed that 0.1 mol/L kaempferol increased the activity of male flies during the day and significantly extended the male survival time under blue light irradiation. However, the study found that kaempferol did not significantly prolong the survival time of Drosophila in the oxidative stress experiment, and no significant difference was observed in the feeding experiment. In summary, our research found that kaempferol, at the concentration of 0.1 mol/L, has a protective effect on Drosophila under blue light irradiation, potentially achieved through alterations in circadian rhythm.

Evaluation of Sechium edule fruit attenuation impact on the cardiomyopathy of the STZ-induced diabetic rats

Sechium edule, commonly known as chayote is known for its low glycemic index, high fiber content, and rich nutritional profile, which suggests it may be beneficial for individuals with diabetes. While research specifically examining the impact of chayote on diabetes is limited, this study screened its biological impacts by using different biomarkers on streptozotocin-induced diabetic (STZ-ID) rats. The ethanolic extract of the Sechium edule fruits was assessed for different phytochemical, biochemical, and anti-diabetic properties. In the results, chayote extract had high phenolic and flavonoid contents respectively (39.25 ± 0.65 mg/mL and 12.16 ± 0.50 mg/mL). These high phenolic and flavonoid contents showed high implications on STZ-ID rats. Altogether 200 and 400 mg/kg of the extract considerably reduced the blood sugar level and enhanced the lipid profile of the STZ-ID rats. Additionally, they have decreased blood urea and serum creatinine levels. Besides, the levels of SGOT, SGPT, LDH, sodium, and potassium ions were significantly lowered after the administration period. More importantly, the electrocardiogram (ECG) parameters such as QT, RR, and QTc which were prolonged in the diabetic rats were downregulated after 35 days of administration of S. edule extract (400 mg/kg). And, the histological examination of the pancreas and kidney showed marked improvement in structural features of 200 and 400 mg/kg groups when compared to the diabetic control group. Where the increase in the glucose levels was positively correlated with QT, RR, and QTc (r2 = 0.76, r2 = 0.76, and r2 = 0.43) which means that ECG could significantly reflect the diabetes glucose levels. In conclusion, our findings showed that the fruit extract exerts a high potential to reduce artifacts secondary to diabetes which can be strongly suggested for diabetic candidates. However, there is a need to study the molecular mechanisms of the extract in combating artifacts secondary to diabetes in experimental animals.

The consumption of Sechium edule (chayote) has antioxidant effect and prevents telomere attrition in older adults with metabolic syndrome

OBJECTIVE

To determine the effect of the consumption of Sechium edule (1.5 g/day) for six months on oxidative stress (OxS) and inflammation markers and its association with telomere length (TL) in older adults with metabolic syndrome (MetS).

METHODS

The study was conducted in a sample of 48 older adults: placebo (EP) and experimental (EG) groups. Lipoperoxides, protein carbonylation, 8-OHdG, total oxidant status (TOS), SOD, GPx, H₂O₂ inhibition, total antioxidant status (TAS), inflammatory cytokines (IL6, IL10, TNF-α), and TL were measured before and six months post-treatment.

RESULTS

We found a significant decrease in the levels of lipoperoxides, protein carbonylation, 8-OHdG, TOS in the EG in comparison PG. Likewise, a significante increase of TAS, IL-6, and IL-10 levels was found at six months post-treatment in EG in comparison with PG. TL showed a statistically significant decrease in PG compared to post-treatment EG.

CONCLUSIONS

Our findigns showed that the supplementation of Sechium edule has antioxidant, and anti-inflammatory effects, and diminushion of shortening of telomeric DNA in older adults with MetS. This would be the first study that shows that the intervention with Sechium edule has a possible geroprotective effect by preventing telomeres from shortening as usually happens in these patients. Therefore, suggesting a protection of telomeric DNA and genomic DNA.

The Supplementation of Sechium edule var. nigrum spinosum (Chayote) Promotes Nrf2-Mediated Antioxidant Protection in Older Adults with Metabolic Syndrome

The aim was to determine the effect of Sechium edule var. nigrum spinosum (chayote) on gene expression related to antioxidant protection mechanisms and the inflammatory process in older adults with metabolic syndrome (MetS). A quasi-experimental study was carried out in a convenience sample of 46 older adults diagnosed with MetS: (i) placebo group (PG; n = 20); (ii) experimental group (EG; n = 26). The clinical, biochemical, anthropometric parameters and SOD, GPx, and CAT enzyme activity, alongside total oxidant status (TOS), total antioxidant status (TAS), oxidative stress index (OSI), cytokines (IL-6, IL-8 and TNF-α), and mRNA expression of SOD, GPx, CAT, IL-6, IL-8, TNF-α, Nrf2, NFkB p50, and NFkB p65, were measured at baseline and 6 months post-intervention. A statistically significant decrease was observed in TOS (baseline, 28.9 ± 3.6 vs. post, 23.7 ± 3.4, p < 0.01) and OSI (baseline, 24.1 ± 3.8 vs. post, 17.7 ± 4), as well as an increase in IL-6 (baseline, 10.7 ± 1.1 vs. post, 12.3 ± 2, p = 0.03), SOD activity (baseline, 167.1 ± 11.9 vs. post, 180.6 ± 7.6, p < 0.05), CAT activity (baseline, 1.0 ± 0.2 vs. post, 1.3 ± 0.2, p < 0.01), and TAS (baseline, 1.1 ± 0.1 vs. post, 1.4 ± 0.1, p < 0.01) in the EG compared to the PG. Regarding the expression of Nrf2, SOD, and IL-6, the EG showed a significant increase vs. basal levels (47%, 44%, and 43%, respectively). Our findings suggest that Sechium edule supplementation promotes the antioxidant response and decreases oxidative stress via Nrf2.

Phenylboronic Ester-Bridged Chitosan/Myricetin Nanomicelle for Penetrating the Endothelial Barrier and Regulating Macrophage Polarization and Inflammation against Ischemic Diseases

The brain and liver are more susceptible to ischemia and reperfusion (IR) injury (IRI), which triggers the reactive oxygen species (ROS) burst and inflammatory cascade and results in severe neuronal damage or hepatic injury. Moreover, the damaged endothelial barrier contributes to proinflammatory activity and limits the delivery of therapeutic agents such as some macromolecules and nanomedicine despite the integrity being disrupted after IRI. Herein, we constructed a phenylboronic-decorated chitosan-based nanoplatform to deliver myricetin, a multifunctional polyphenol molecule for the treatment of cerebral and hepatic ischemia. The chitosan-based nanostructures are widely studied cationic carriers for endothelium penetration such as the blood-brain barrier (BBB) and sinusoidal endothelial barrier (SEB). The phenylboronic ester was chosen as the ROS-responsive bridging segment for conjugation and selective release of myricetin molecules, which meanwhile scavenged the overexpressed ROS in the inflammatory environment. The released myricetin molecules fulfill a variety of roles including antioxidation through multiple phenolic hydroxyl groups, inhibition of the inflammatory cascade by regulation of the macrophage polarization from M1 to M2, and endothelial injury repairment. Taken together, our present study provides valuable insight into the development of efficient antioxidant and anti-inflammatory platforms for potential application against ischemic disease.

Why Do Dietary Flavonoids Have a Promising Effect as Enhancers of Anthracyclines? Hydroxyl Substituents, Bioavailability and Biological Activity

Anthracyclines currently play a key role in the treatment of many cancers, but the limiting factor of their use is the widespread phenomenon of drug resistance and untargeted toxicity. Flavonoids have pleiotropic, beneficial effects on human health that, apart from antioxidant activity, are currently considered small molecules-starting structures for drug development and enhancers of conventional therapeutics. This paper is a review of the current and most important data on the participation of a selected series of flavonoids: chrysin, apigenin, kaempferol, quercetin and myricetin, which differ in the presence of an additional hydroxyl group, in the formation of a synergistic effect with anthracycline antibiotics. The review includes a characterization of the mechanism of action of flavonoids, as well as insight into the physicochemical parameters determining their bioavailability in vitro. The crosstalk between flavonoids and the molecular activity of anthracyclines discussed in the article covers the most important common areas of action, such as (1) disruption of DNA integrity (genotoxic effect), (2) modulation of antioxidant response pathways, and (3) inhibition of the activity of membrane proteins responsible for the active transport of drugs and xenobiotics. The increase in knowledge about the relationship between the molecular structure of flavonoids and their biological effect makes it possible to more effectively search for derivatives with a synergistic effect with anthracyclines and to develop better therapeutic strategies in the treatment of cancer.

Activation of Nrf2 signaling: A key molecular mechanism of protection against cardiovascular diseases by natural products

Cardiovascular diseases (CVD) are a group of cardiac and vascular disorders including myocardial ischemia, congenital heart disease, heart failure, hypertension, atherosclerosis, peripheral artery disease, rheumatic heart disease, and cardiomyopathies. Despite considerable progress in prophylaxis and treatment options, CVDs remain a leading cause of morbidity and mortality and impose an extremely high socioeconomic burden. Oxidative stress (OS) caused by disequilibrium in the generation of reactive oxygen species plays a crucial role in the pathophysiology of CVDs. Nuclear erythroid 2-related factor 2 (Nrf2), a transcription factor of endogenous antioxidant defense systems against OS, is considered an ideal therapeutic target for management of CVDs. Increasingly, natural products have emerged as a potential source of Nrf2 activators with cardioprotective properties and may therefore provide a novel therapeutic tool for CVD. Here, we present an updated comprehensive summary of naturally occurring products with cardioprotective properties that exert their effects by suppression of OS through activation of Nrf2 signaling, with the aim of providing useful insights for the development of therapeutic strategies exploiting natural products.

Myricetin: targeting signaling networks in cancer and its implication in chemotherapy

The gaps between the complex nature of cancer and therapeutics have been narrowed down due to extensive research in molecular oncology. Despite gathering massive insight into the mysteries of tumor heterogeneity and the molecular framework of tumor cells, therapy resistance and adverse side effects of current therapeutic remain the major challenge. This has shifted the attention towards therapeutics with less toxicity and high efficacy. Myricetin a natural flavonoid has been under the spotlight for its anti-cancer, anti-oxidant, and anti-inflammatory properties. The cutting-edge molecular techniques have shed light on the interplay between myricetin and dysregulated signaling cascades in cancer progression, invasion, and metastasis. However, there are limited data available regarding the nano-delivery platforms composed of myricetin in cancer. In this review, we have provided a comprehensive detail of myricetin-mediated regulation of different cellular pathways, its implications in cancer prevention, preclinical and clinical trials, and its current available nano-formulations for the treatment of various cancers.

Dietary phenolic-type Nrf2-activators: implications in the control of toxin-induced hepatic disorders

Numerous studies have exemplified the importance of nuclear factor erythroid 2-related factor 2 (Nrf2) activation in the alleviation of toxin-induced hepatic disorders primarily through eliminating oxidative stress. Whereafter, increasingly more efforts have been contributed to finding Nrf2-activators, especially from dietary polyphenols. The present review summarized the phenolic-type Nrf2-activators published in the past few decades, analyzed their effectiveness based on their structural characteristics and outlined their related mechanisms. It turns out that flavonoids are the largest group of phenolic-type Nrf2-activators, followed by nonflavonoids and phenolic acids. When counting on subgroups, the top three types are flavonols, flavones, and hydroxycinnamic acids, with curcuminoids having the highest effective doses. Moreover, most polyphenols work through the phosphorylation of Nrf2. Besides, mitogen-activated protein kinases (MAPKs) and protein kinase B (Akt) are the frequent targets of these Nrf2-activators, which indirectly mediate the behavior of Nrf2. However, current data are not sufficient to conclude any structure-activity relationship.

Myricetin Improves Impaired Nerve Functions in Experimental Diabetic Rats

Diabetic peripheral neuropathy (DPN) is considered as one of the most important complications of diabetes mellitus. At present, effective treatments that might improve the damaged neurological function in DPN are sorely needed. As myricetin has been proved to possess excellent neuroprotective and antioxidant effects, it might have therapeutic potential for DPN. Therefore, the purpose of our study was to detect the potential beneficial effect of myricetin on DPN. A single dose of 50 mg/kg of streptozotocin was applied in rats for the establishment of diabetic models. Different doses of myricetin (0.5 mg/kg/day, 1.0 mg/kg/day, and 2.0 mg/kg/day) were intraperitoneally injected for 2 weeks from the 21st day after streptozotocin injection. After the final myricetin injection, behavioral, electrophysiological, biochemical, and protein analyses were performed. In the present study, myricetin significantly ameliorated diabetes-induced impairment in sensation, nerve conduction velocities, and nerve blood flow. In addition, myricetin significantly reduced the generation of advanced glycation end-products (AGEs) and reactive oxygen species (ROS), and elevated Na⁺, K⁺-ATPase activity and antioxidant activities in nerves in diabetic animals. Additional studies revealed that myricetin significantly raised the hydrogen sulfide (H₂S) levels, and elevated the expression level of heme oxygenase-1 (HO-1) as well as nuclear factor-E2-related factor-2 (Nrf2) in diabetic rats. In addition, myricetin has the capability of decreasing plasma glucose under diabetic conditions. The findings in our present study collectively indicated that myricetin could restore the impaired motor and sensory functions under diabetic conditions. The Nrf2-dependent antioxidant action and the capability of decreasing plasma glucose might be the underlying mechanisms for the beneficial effect of myricetin on impaired neural functions. Our study showed the therapeutic potential of myricetin in the management of DPN.

Ameliorative Effect of Myricetin on Nonalcoholic Fatty Liver Disease in ob/ob Mice

Obesity, insulin resistance, and oxidative stress are important risk factors for nonalcoholic fatty liver disease (NAFLD). This study aimed at determining the beneficial effects of myricetin against NAFLD in ob/ob mice. C57BL/6-Lep^ob/ob mice (n = 21) were fed an AIN-93G diet (ob/ob control group) or diet containing 0.04% (low myricetin; LMTN group) or 0.08% (high myricetin; HMTN group) myricetin, and lean heterozygous littermates (lean control group, n = 7) were fed AIN-93G diet for 10 weeks. HMTN consumption significantly lowered serum glucose levels and homeostasis model assessment for insulin resistance values in ob/ob mice. In addition to reducing serum triglyceride (TG) and cholesterol levels, HMTN significantly decreased total hepatic lipid and TG levels partly through downregulation of carbohydrate response element-binding protein and sterol regulatory element-binding protein 1c expression. The reduction in the levels of hepatic thiobarbituric acid reactive substances by HMTN likely resulted from the elevation of nuclear factor erythroid-2-related factor 2 expression. Tumor necrosis factor-α and monocyte chemoattractant protein 1 expressions were reduced by LMTN and HMTN, and HMTN also decreased interleukin-6 expression. These results suggest that myricetin has beneficial effects against NAFLD by regulating the expression of transcription factors of hepatic lipid metabolism, the antioxidant system, and pro-inflammatory cytokines.

Recent advances in research on vine tea, a potential and functional herbal tea with dihydromyricetin and myricetin as major bioactive compounds

Vine tea has been used as an herbal tea by several ethnic minorities for hundreds of years in China. Flavonoids, a kind of indispensable component in a variety of nutraceutical, pharmaceutical and cosmetic applications, are identified to be the major metabolites and bioactive ingredients in vine tea. Interestingly, vine tea exhibits a wide range of significant bioactivities including anti-oxidant, anti-inflammatory, anti-tumor, antidiabetic, neuroprotective and other activities, but no toxicity. These bioactivities, to some extent, enrich the understanding about the role of vine tea in disease prevention and therapy. The health benefits of vine tea, particularly dihydromyricetin and myricetin, are widely investigated. However, there is currently no comprehensive review available on vine tea. Therefore, this report summarizes the most recent studies investigating bioactive constituents, pharmacological effects and possible mechanisms of vine tea, which will provide a better understanding about the health benefits and preclinical assessment of novel application of vine tea.

Beetroot and leaf extracts present protective effects against prostate cancer cells, inhibiting cell proliferation, migration, and growth signaling pathways

Beet (Beta vulgaris L.) has high nutritional value, containing bioactive compounds such as betalains and flavonoids. Scientific evidence points to the use of these natural compounds in the treatment of several types of cancer, such as prostate cancer, one of the main causes of morbidity and mortality in men. Here, we compared beet roots and leaves extracts, and their main compounds, apigenin, and betanin, respectively, in DU-145 and PC-3 prostate cancer cell lines. Both cells presented the proliferation decreased for beetroot and beet leaves extracts. The apigenin treatment also reduced the proliferation of both cell lines. Regarding cell migration, beet leaves extract was able to decrease the scratch area in both cell lines, whereas apigenin affected only PC-3 cells' migration. In colony formation assay, both extracts were effective in reducing the number of colonies formed. Besides, the beet leaves extracts and apigenin presented strong inhibition of growth-related signaling pathways in both cell lines, and the beetroot extract and betanin presented effects only in DU-145 cells. Furthermore, the extracts and isolated compounds were able to reduce the levels of apoptotic and cell cycle proteins. This study reveals that beet extracts have important anti-cancer effects against prostate cancer cells.

The Hallmarks of Flavonoids in Cancer

Flavonoids represent an important group of bioactive compounds derived from plant-based foods and beverages with known biological activity in cells. From the modulation of inflammation to the inhibition of cell proliferation, flavonoids have been described as important therapeutic adjuvants against several diseases, including diabetes, arteriosclerosis, neurological disorders, and cancer. Cancer is a complex and multifactor disease that has been studied for years however, its prevention is still one of the best known and efficient factors impacting the epidemiology of the disease. In the molecular and cellular context, some of the mechanisms underlying the oncogenesis and the progression of the disease are understood, known as the hallmarks of cancer. In this text, we review important molecular signaling pathways, including inflammation, immunity, redox metabolism, cell growth, autophagy, apoptosis, and cell cycle, and analyze the known mechanisms of action of flavonoids in cancer. The current literature provides enough evidence supporting that flavonoids may be important adjuvants in cancer therapy, highlighting the importance of healthy and balanced diets to prevent the onset and progression of the disease.

Effect of myricetin on odontoblast-like cells and its potential to preserve resin-dentin Bonds

Stabilization of the resin-dentin interface to increase the durability of adhesive dental restorations is a challenging task. The use of naturally occurring collagen crosslinking agents has been proposed to prevent degradation of the hybrid layer. Myricetin (MYR) is a flavonoid with a wide variety of beneficial effects and it has been used for the treatment of different systemic pathologies. The chemical structure of MYR makes it a powerful antioxidant, an inhibitor of matrix metalloproteinase (MMP) activity, and a collagen cross-linker. This study presents MYR as a novel treatment in operative dentistry to stabilize the resin-dentin interface by inhibiting MMPs and crosslinking the collagen. Viability tests carried out using a resazurin assay showed that MYR had no cytotoxic effects on human odontoblast-like cells and the phenotype was preserved. Fluorometric MMP activity assay and fluorescence microscopy revealed that the MMPs in the demineralized dentin were effectively inhibited by the application of MYR (600 μM for 120 s). A microtensile bond strength test was performed immediately and after six months of storage. The bond strength to dentin was not affected by MYR and was preserved over time. Demineralized dentin beams were evaluated to determine the dentin biomodification using microtensile strength and elastic modulus assays. MYR improved the biomechanical behavior of the demineralized dentin similarly to glutaraldehyde, a recognized crosslinking agent. These findings indicated that MYR acts as an MMP inhibitor, collagen cross-linker, and preserver of the bond strength. Furthermore, MYR is an ethanol-soluble molecule with a lower molecular weight than the other polyphenols; hence, it can be applied for a short time and diffuses deeply through the dentin without any associated cytotoxicity. This molecule has beneficial effects on the biological and mechanical behavior of the resin-dentin interface and may be used to effectively stabilize the hybrid layer in a clinical setting.

Inhibitory Effect of Delphinidin on Oxidative Stress Induced by H2O2 in HepG2 Cells

Chronic liver diseases (CLDs) are correlated with oxidative stress induced by the accumulation of intracellular reactive oxygen species (ROS). In this study, we employed HepG2, a human liver carcinoma cell line containing many antioxidant enzymes, to explore the function of delphinidin against oxidative stress induced by H₂O₂ and to provide scientific data of the molecular mechanism. Cells were pretreated with different concentrations of delphinidin (10 μmol/L, 20 μmol/L, and 40 μmol/L) for 2 h before treatment with 750 μM H₂O₂ for 1 h. The results showed that H₂O₂ decreased the survival rate of HepG2 cells and increased the level of ROS, but delphinidin pretreatment could possess the opposite result. At the same time, the expression of Nrf2 was enhanced by the delphinidin pretreatment. This was because delphinidin promoted Nrf2 nuclear translocation and inhibited its degradation, which led to the increase expression of antioxidant protein HO-1 (Nrf2-related phase II enzyme heme oxygenase-1). Besides, we found that delphinidin could significantly alleviate the reduction of Nrf2 protein levels and the accumulation of intracellular ROS levels in Nrf2 knockdown HepG2 cells. In conclusion, our study suggested that delphinidin, as an effective antioxidant, protected HepG2 cells from oxidative stress by regulating the expression of Nrf2/HO-1.

Regulation of Nrf2/ARE Pathway by Dietary Flavonoids: A Friend or Foe for Cancer Management?

The nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) pathway is an important cell signaling mechanism in maintaining redox homeostasis in humans. The role of dietary flavonoids in activating Nrf2/ARE in relation to cancer chemoprevention or cancer promotion is not well established. Here we summarize the dual effects of flavonoids in cancer chemoprevention and cancer promotion with respect to the regulation of the Nrf2/ARE pathway, while underlying the possible cellular mechanisms. Luteolin, apigenin, quercetin, myricetin, rutin, naringenin, epicatechin, and genistein activate the Nrf2/ARE pathway in both normal and cancer cells. The hormetic effect of flavonoids has been observed due to their antioxidant or prooxidant activity, depending on the concentrations. Reported in vitro and in vivo investigations suggest that the activation of the Nrf2/ARE pathway by either endogenous or exogenous stimuli under normal physiological conditions contributes to redox homeostasis, which may provide a mechanism for cancer chemoprevention. However, some flavonoids, such as luteolin, apigenin, myricetin, quercetin, naringenin, epicatechin, genistein, and daidzein, at low concentrations (1.5 to 20 µM) facilitate cancer cell growth and proliferation in vitro. Paradoxically, some flavonoids, including luteolin, apigenin, and chrysin, inhibit the Nrf2/ARE pathway in vitro. Therefore, even though flavonoids play a major role in cancer chemoprevention, due to their possible inducement of cancer cell growth, the effects of dietary flavonoids on cancer pathophysiology in patients or appropriate experimental animal models should be investigated systematically.

Myricetin bioactive effects: moving from preclinical evidence to potential clinical applications

Several flavonoids have been recognized as nutraceuticals, and myricetin is a good example. Myricetin is commonly found in plants and their antimicrobial and antioxidant activities is well demonstrated. One of its beneficial biological effects is the neuroprotective activity, showing preclinical activities on Alzheimer, Parkinson, and Huntington diseases, and even in amyotrophic lateral sclerosis. Also, myricetin has revealed other biological activities, among them as antidiabetic, anticancer, immunomodulatory, cardiovascular, analgesic and antihypertensive. However, few clinical trials have been performed using myricetin as nutraceutical. Thus, this review provides new insights on myricetin preclinical pharmacological activities, and role in selected clinical trials.

Myricetin Alleviates Pathological Cardiac Hypertrophy via TRAF6/TAK1/MAPK and Nrf2 Signaling Pathway

Myricetin (Myr) is a common plant-derived polyphenol and is well recognized for its multiple activities including antioxidant, anti-inflammation, anticancer, and antidiabetes. Our previous studies indicated that Myr protected mouse heart from lipopolysaccharide and streptozocin-induced injuries. However, it remained to be unclear whether Myr could prevent mouse heart from pressure overload-induced pathological hypertrophy. Wild type (WT) and cardiac Nrf2 knockdown (Nrf2-KD) mice were subjected to aortic banding (AB) surgery and then administered with Myr (200 mg/kg/d) for 6 weeks. Myr significantly alleviated AB-induced cardiac hypertrophy, fibrosis, and cardiac dysfunction in both WT and Nrf2-KD mice. Myr also inhibited phenylephrine- (PE-) induced neonatal rat cardiomyocyte (NRCM) hypertrophy and hypertrophic markers' expression in vitro. Mechanically, Myr markedly increased Nrf2 activity, decreased NF-κB activity, and inhibited TAK1/p38/JNK1/2 MAPK signaling in WT mouse hearts. We further demonstrated that Myr could inhibit TAK1/p38/JNK1/2 signaling via inhibiting Traf6 ubiquitination and its interaction with TAK1 after Nrf2 knockdown in NRCM. These results strongly suggested that Myr could attenuate pressure overload-induced pathological hypertrophy in vivo and PE-induced NRCM hypertrophy via enhancing Nrf2 activity and inhibiting TAK1/P38/JNK1/2 phosphorylation by regulating Traf6 ubiquitination. Thus, Myr might be a potential strategy for therapy or adjuvant therapy for malignant cardiac hypertrophy.

Myricetin Attenuated Diabetes-Associated Kidney Injuries and Dysfunction via Regulating Nuclear Factor (Erythroid Derived 2)-Like 2 and Nuclear Factor-κB Signaling

Background/Aims: Previous studies have suggested that myricetin (Myr) could promote the expression and nuclear translocation of nuclear factor (erythroid-derived 2)-like (Nrf2). This study aimed to investigate whether Myr could attenuate diabetes-associated kidney injuries and dysfunction in wild-type (WT) and Nrf2 knockdown (Nrf2-KD) mice.

Methods: Lentivirus-mediated Nrf2-KD and WT mice were used to establish type 1 diabetes mellitus (DM) by streptozotocin (STZ) injection. WT and Nrf2-KD mice were then randomly allocated into four groups: control (CON), Myr, STZ, and STZ + Myr. Myr (100 mg/kg/day) or vehicle was administered for 6 months. Kidneys were harvested and weighed at the end of the experiment. Hematoxylin and eosin staining and Masson’s trichrome staining were used to assess the morphology and fibrosis of the kidneys, respectively. Urinary albumin-to-creatinine ratio was used to test renal function. Western blotting was performed to determine oxidative-stress- or inflammation-associated signaling pathways. Real-time polymerase chain reaction (RT-PCR) was performed to detect the expression of fibrosis or inflammatory cytokines at the message Ribonucleic Acid (mRNA) level.

Results: In WT mice, Myr alleviated DM-induced renal dysfunction, fibrosis, and oxidative damage and enhanced the expression of Nrf2 and its downstream genes. After knockdown of Nrf2, Myr treatment partially but significantly mitigated DM-induced renal dysfunction and fibrosis, which might be associated with inhibition of the I-kappa-B (IκB)/nuclear factor-κB (NF-κB) (P65) signaling pathway.

Conclusions: This study showed that Myr prevented DM-associated decreased expression of Nrf2 and inhibited IκB/NF-κB (P65) signaling pathway. Moreover, inhibition of IκB/NF-κB (P65) signaling pathway is independent of the regulation of Nrf2. Thus, Myr could be a potential treatment for preventing the development and progression of DM-associated kidney injuries and dysfunction.

Microarray Based Functional Analysis of Myricetin and Proteomic Study on Its Anti-Inflammatory Property

Myricetin has been reported as a promising chemopreventive compound with multiple biofunctions. To evaluate its influence on gene expressions in genome-wide set and further investigate its anti-inflammatory property, the present study performed Gene Ontology and Ingenuity Pathway Analysis (IPA) to describe the basic gene expression characteristics by myricetin treatment in HepG2 cells, confirmed its multi-biofunction by real-time fluorescent quantitative PCR (RT-qPCR), and further verified its anti-inflammatory property by Western blotting and bio-plex-based cytokines assay. The IPA data showed that 337 gene expressions (48% of the top molecules) are disturbed over 2-fold, and the most possible biofunctions of myricetin are the effect on “cardiovascular disease, metabolic disease, and lipid metabolism,” via regulation of 28 molecules with statistic score of 46. RT-qPCR data confirmed the accuracy of microarray data, and cytokines assay results indicated that 6 of the total 27 inflammatory cytokine secretions were significantly inhibited by myricetin pretreatment, including TNF-α, IFN-γ, IL-1α, IL-1β, IL-2, and IL-6. The present study is the first time to elucidate the multi-function of myricetin in genome-wide set by IPA analysis and verify its anti-inflammatory property by proteomics of cytokines assay. Therefore, these results enrich the comprehensive bioactivities of myricetin and reveal that myricetin has powerful anti-inflammatory property, which provides encouragement for in vivo studies to verify its possible health benefits.

Nrf2⁻ARE Signaling Acts as Master Pathway for the Cellular Antioxidant Activity of Fisetin

Fisetin, a dietary flavonoid, is reported to have cellular antioxidant activity with an unclear mechanism. In this study, we investigated the effect of fisetin on the nuclear factor, erythroid 2-like 2 (Nrf2) signaling pathway in HepG2 cells to explore the cellular antioxidant mechanism. Fisetin upregulated the mRNA expression of heme oxygenase-1 (HO-1), glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modifier subunit (GCLM), and NAD(P)H quinone oxidoreductase-1 (NQO1), and induced the protein of HO-1 but had no significant effect on the protein of GCLC, GCLM and NQO1. Moreover, nuclear accumulation of Nrf2 was clearly observed by immunofluorescence analysis and western blotting after fisetin treatment, and an enhanced luciferase activity of antioxidant response element (ARE)-regulated transactivation was obtained by dual-luciferase reporter gene assays. In addition, fisetin upregulated the protein level of Nrf2 and downregulated the protein level of Kelch-like ECH-associated protein 1 (Keap1). However, fisetin had no significant effect on Nrf2 mRNA expression. When protein synthesis was inhibited with cycloheximide (CHX), fisetin prolonged the half-life of Nrf2 from 15 min to 45 min. When blocking Nrf2 degradation with proteasome inhibitor MG132, ubiquitinated proteins were enhanced, and fisetin reduced ubiquitination of Nrf2. Taken together, fisetin translocated Nrf2 into the nucleus and upregulated the expression of downstream HO-1 gene by inhibiting the degradation of Nrf2 at the post-transcriptional level. These data provide the molecular mechanism to understand the cellular antioxidant activity of fisetin.

Lotus seed skin proanthocyanidin extract exhibits potent antioxidant property via activation of the Nrf2-ARE pathway

Lotus seed is well known as traditional food and medicine, but its skin is usually discarded. Recent studies have shown that lotus seed skin contains a high concentration of proanthocyanidins that have multi-functions, such as antioxidation, anti-inflammation, and anti-cancer effects. In the present study, we aimed to isolate and purify the proanthocyanidins from lotus seed skin by acetone extraction and rotary evaporation, identify their chemical structures by HPLC-MS-MS and NMR, and further investigate the antioxidant properties of the extract purified by macroporous resin (PMR) from lotus seed skin both in vitro and in vivo. The results showed that PMR mainly contained oligomeric proanthocyanidins, especially dimeric procyanidin B1 (PB1), procyanidin B2 and procyanidin B4. Although it had limited ability to directly scavenge radicals in vitro, PMR could significantly enhance the expressions of antioxidant proteins via activation of nuclear factor-E2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway in HepG2 cells. Molecular data revealed that PB1, a major component in PMR, stabilized Nrf2 by inhibiting the ubiquitination of Nrf2, which led to subsequent activation of the Nrf2-ARE pathway, including the enhancements of Nrf2 nuclear translocation, Nrf2-ARE binding and ARE transcriptional activity. Moreover, the in vivo results in high fat diet-induced mice further verified the powerful antioxidant property of PMR. These results revealed that lotus seed skin is a promising resource for functional food development.

Postgenomic Properties of Natural Micronutrients

Modern medical approaches to the therapy of various diseases, including cancer, are based on the use of toxic drugs. The unfavorable side effects of traditional medicine could be counterbalanced by addition of natural bioactive substances to conventional therapy due to their mild action on cells combined with the multitargeted effects. To elucidate the real mechanisms of their biological activity, versatile approaches including a number of "omics" such as genomics, transcriptomics, proteomics, and metabolomics are used. This review highlights inclusion of bioactive natural compounds into the therapy of chronic diseases from the viewpoint of modern omics-based nutritional biochemistry. The recently accumulated data argue for necessity to employ nutrigenetic and nutrimetabolomic analyses to prevent or diminish the risk of chronic diseases.

Extraction, identification, and antioxidant property evaluation of limonin from pummelo seeds

Limonin, the main bioactive phytochemical constituent of limonoids with multi-functions, is enriched in citrus fruits and often found at a high concentration in citrus seeds. The present study was attempted to introduce a new and efficient extraction method to isolate limonoids from pummelo seeds, and to evaluate the antioxidant property of the main constituent limonin in HepG2 cells. Three key single factors were identified for the extraction of limonoids from pummelo seeds using the Box-Behnken experiment design of response surface methodology (RSM), and the optimized extraction parameters were treatment with 89.68 mL of anhydrous acetone for 4.62 h at 78.94 °C, while the yield of limonoids was 11.52 mg/g. The structure of isolated main constituent of the limonoids was further identified as limonin by Fourier transform infrared (FT-IR) spectrometer and nuclear magnetic resonance (NMR) spectrum. Moreover, the molecular data in HepG2 cells revealed that limonin exerted its anti-oxidant property mainly by the activation of nuclear factor (erythroid-2)-like 2 (Nrf2)/kelch-like ECH-associated protein 1 (Keap1)- antioxidant response element (ARE) pathway in the form of transcriptional regulation of Nrf2 mRNA and posttranscriptional regulation of Nrf2/Keap1 system. These results demonstrate that pummelo seeds are an ideal source of limonoids, and limonin is proved to exert its anti-oxidant property by the activation of Nrf2/Keap1 pathway.

Myricetin alleviates cuprizone-induced behavioral dysfunction and demyelination in mice by Nrf2 pathway

Multiple sclerosis (MS) is a demyelinating disease occurring in the central nervous system. In the present study, we evaluated the function of myricetin on the alleviation of behavioral dysfunction and myelin protection in the cuprizone-induced demyelination model. Mice were daily fed with fodder including 0.2% cuprizone and were administrated myricetin (100 mg kg^-1) by gavage administration for 5 weeks. The treatment of myricetin ameliorated hyper-locomotion and behavior impairment induced by cuprizone toxicity. With the administration of myricetin, the demyelinating lesion was lessened via increasing the LFB staining area and myelin phosphatide protein (MBP) expression. In addition, myricetin evidently promoted Nrf2 translocation in the nuclear fraction and enhanced the HO-1 and NQO1 expression levels. Our data revealed that myricetin may be a potential candidate for mitigating motor defects and demyelination in a cuprizone-induced mouse model via activating the Nrf2 pathway.

Nrf2 at the heart of oxidative stress and cardiac protection

The NFE2L2 gene encodes the transcription factor Nrf2 best known for regulating the expression of antioxidant and detoxification genes. Gene knockout approaches have demonstrated its universal cytoprotective features. While Nrf2 has been the topic of intensive research in cancer biology since its discovery in 1994, understanding the role of Nrf2 in cardiovascular disease has just begun. The literature concerning Nrf2 in experimental models of atherosclerosis, ischemia, reperfusion, cardiac hypertrophy, heart failure, and diabetes supports its cardiac protective character. In addition to antioxidant and detoxification genes, Nrf2 has been found to regulate genes participating in cell signaling, transcription, anabolic metabolism, autophagy, cell proliferation, extracellular matrix remodeling, and organ development, suggesting that Nrf2 governs damage resistance as well as wound repair and tissue remodeling. A long list of small molecules, most derived from natural products, have been characterized as Nrf2 inducers. These compounds disrupt Keap1-mediated Nrf2 ubquitination, thereby prohibiting proteasomal degradation and allowing Nrf2 protein to accumulate and translocate to the nucleus, where Nrf2 interacts with sMaf to bind to ARE in the promoter of genes. Recently alternative mechanisms driving Nrf2 protein increase have been revealed, including removal of Keap1 by autophagy due to p62/SQSTM1 binding, inhibition of βTrCP or Synoviolin/Hrd1-mediated ubiquitination of Nrf2, and de novo Nrf2 protein translation. We review here a large volume of literature reporting historical and recent discoveries about the function and regulation of Nrf2 gene. Multiple lines of evidence presented here support the potential of dialing up the Nrf2 pathway for cardiac protection in the clinic.

Myricetin Possesses Potential Protective Effects on Diabetic Cardiomyopathy through Inhibiting IκBα/NFκB and Enhancing Nrf2/HO-1

Diabetic cardiomyopathy (DCM) is associated with a greater risk of mortality in patients with diabetes mellitus. Currently, no specific treatment has been suggested for DCM treatment. This study demonstrated that myricetin (M) attenuated DCM-associated cardiac injury in mice subjected to streptozotocin (SZT) and in neonatal rat cardiomyocytes (NRCM) challenged with high glucose. In vivo investigation demonstrated 6 months of M treatment (200 mg/kg/d) significantly alleviated cardiac hypertrophy, apoptosis, and interstitial fibrosis. Mechanically, M treatment significantly increased the activity of Nrf2/HO-1 pathway, strengthening antioxidative stress capacity evidenced by reversed activities of GPx and SOD, and decreased MDA production. M treatment also inhibited IκBα/NF-κB pathway, resulting in reduced secretion of inflammation cytokines including IL-1β, TNF-α, and IL-6. Besides, the TGFβ/Smad3 signaling was also blunted in DCM mice treated with M. These beneficial effects of M treatment protected cardiomyocytes from apoptosis as shown by decreased TUNEL-positive nucleus, c-caspase 3, and Bax. Similar effects of M treatment could be reproduced in NRCM treated with high glucose. Furthermore, through silencing Nrf2 in NRCM, we found that the regulation of IκBα/NFκB by M was independent on its function on Nrf2. Thus, we concluded that M possesses potential protective effects on DCM through inhibiting IκBα/NFκB and enhancing Nrf2/HO-1.

Myricetin protects cardiomyocytes from LPS-induced injury

BACKGROUND

Sepsis-induced cardiomyopathy is a well-known cause of mortality. Recent evidence has highlighted the important role of myricetin in anti-inflammation and anti-oxidative stress. However, little is known about its effect on endotoxin-induced cardiomyopathy. We examined the effect of myricetin on lipopolysaccharide (LPS)-induced cardiomyocyte injury and the underlying mechanisms in vitro.

METHODS

mRNA expression of interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha was examined via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Protein expression levels of NF-κB/p65, IκB, IL-1beta, IL-6, and TNF-alpha were assesses via Western blotting. Immunofluorescence (IF) was used to determine the nuclear translocation of p65. Commercial kits were employed to detect the level of oxidative markers and to quantify NF-κB/p65 both in the cytoplasm and the nucleus. Finally, terminal deoxy-nucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) was performed to evaluate the apoptosis of H9c2 cardiomyocytes.

RESULTS

The results showed that myricetin blunted the overexpression of IL-1beta, IL-6, and TNF-alpha markedly by inhibiting the NF-κB/P65 signaling pathway. Furthermore, myricetin treatment led to the downregulation of reactive oxygen species (ROS) accompanied by increased expression of superoxide dismutase and glutathione peroxidase. TUNEL-positive nuclei were rarely detected following myricetin treatment.

CONCLUSION

Our findings suggest that myricetin is a valuable protective agent against endotoxin-induced early inflammatory responses in H9c2 cardiomyocytes, which involves regulation of ROS and the IκB/NF-κb signaling pathway.

DNA Microarray-Based Screening and Characterization of Traditional Chinese Medicine

The application of DNA microarray assay (DMA) has entered a new era owing to recent innovations in omics technologies. This review summarizes recent applications of DMA-based gene expression profiling by focusing on the screening and characterizationof traditional Chinese medicine. First, herbs, mushrooms, and dietary plants analyzed by DMA along with their effective components and their biological/physiological effects are summarized and discussed by examining their comprehensive list and a list of representative effective chemicals. Second, the mechanisms of action of traditional Chinese medicine are summarized by examining the genes and pathways responsible for the action, the cell functions involved in the action, and the activities found by DMA (silent estrogens). Third, applications of DMA for traditional Chinese medicine are discussed by examining reported examples and new protocols for its use in quality control. Further innovations in the signaling pathway based evaluation of beneficial effects and the assessment of potential risks of traditional Chinese medicine are expected, just as are observed in other closely related fields, such as the therapeutic, environmental, nutritional, and pharmacological fields.

Regressive Effect of Myricetin on Hepatic Steatosis in Mice Fed a High-Fat Diet

Myricetin is an effective antioxidant in the treatment of obesity and obesity-related metabolic disorders. The objective of this study was to explore the regressive effect of myricetin on pre-existing hepatic steatosis induced by high-fat diet (HFD). C57BL/6 mice were fed either a standard diet or a HFD for 12 weeks and then half of the mice were treated with myricetin (0.12% in the diet, w/w) while on their respective diets for further 12 weeks. Myricetin treatment significantly alleviated HFD-induced steatosis, decreased hepatic lipid accumulation and thiobarbituric acid reactive substance (TBARS) levels, and increased antioxidative enzyme activities, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities. Microarray analysis of hepatic gene expression profiles showed that myricetin significantly altered the expression profiles of 177 genes which were involved in 12 biological pathways, including the peroxisome proliferator activated receptor (PPAR) signaling pathway and peroxisome. Further research indicated that myricetin elevated hepatic nuclear Nrf2 translocation, increased the protein expression of heme oxygenase-1 (HO-1) and NAD(P)H quinone dehydrogenase 1 (NQO1), reduced the protein expression of PPARγ, and normalized the expressions of genes that were involved in peroxisome and the PPAR signaling pathway. Our data indicated that myricetin might represent an effective therapeutic agent to treat HFD-induced hepatic steatosis via activating the Nrf2 pathway and the PPAR signaling pathway.

Myricetin ameliorates brain injury and neurological deficits via Nrf2 activation after experimental stroke in middle-aged rats

The aim of our study was to investigate the protective effects and underlying mechanisms of myricetin, a bioactive food compound, on brain injury and neurological deficits after ischemic stroke. Treatment of myricetin significantly attenuated oxygen-glucose deprivation (OGD)-induced cell death in SHSY5Y cells in vitro. In a rat model of cerebral ischemia, myricetin was administered intragastrically at 2 h before and every day after middle cerebral artery occlusion (MCAO). The effects of myricetin were evaluated by various biochemical assays and neurobehavioral tests. Treatment with myricetin resulted in decreased infarction volume, reduced neuronal loss as well as lessened production of reactive oxygen species (ROS) and malondialdehyde following MCAO. We also found evidence that myricetin treatment could enhance the activity of antioxidant enzymes and mitochondrial function. Meanwhile, myricetin treatment reversed the suppression of Nrf2 nuclear translocation, and increased HO-1 expression in the ipsilateral ischemic brain and in the normal brain. Moreover, our results suggested that myricetin treatment resulted in significant improvement in neurological function. In conclusion, treatment with myricetin attenuates brain injury and neurological deficits in a rat model of cerebral ischemia via improvement of mitochondrial function and activation of the Nrf2 pathway.

Myricetin: A Dietary Molecule with Diverse Biological Activities

Myricetin is a common plant-derived flavonoid and is well recognised for its nutraceuticals value. It is one of the key ingredients of various foods and beverages. The compound exhibits a wide range of activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities. It displays several activities that are related to the central nervous system and numerous studies have suggested that the compound may be beneficial to protect against diseases such as Parkinson's and Alzheimer's. The use of myricetin as a preserving agent to extend the shelf life of foods containing oils and fats is attributed to the compound's ability to protect lipids against oxidation. A detailed search of existing literature revealed that there is currently no comprehensive review available on this important molecule. Hence, the present work includes the history, synthesis, pharmaceutical applications and toxicity studies of myricetin. This report also highlights structure-activity relationships and mechanisms of action for various biological activities.

Detection of oxidative stress biomarkers in myricetin treated red blood cells

Effect of myricetin on RBC membrane enzymes (Na⁺, K⁺-ATPase and Ca²⁺-ATPase) and Na⁺, H⁺exchanger.

Protective effects of Chaenomeles thibetica extract against carbon tetrachloride-induced damage via the MAPK/Nrf2 pathway

Chaenomeles thibetica extract possesses antioxidant and hepatoprotective effects against carbon tetrachloride-induced damage via the MAPK/Nrf2 pathway.

Sulforaphane and Other Nutrigenomic Nrf2 Activators: Can the Clinician's Expectation Be Matched by the Reality?

The recognition that food-derived nonnutrient molecules can modulate gene expression to influence intracellular molecular mechanisms has seen the emergence of the fields of nutrigenomics and nutrigenetics. The aim of this review is to describe the properties of nutrigenomic activators of transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2), comparing the potential for sulforaphane and other phytochemicals to demonstrate clinical efficacy as complementary medicines. Broccoli-derived sulforaphane emerges as a phytochemical with this capability, with oral doses capable of favourably modifying genes associated with chemoprevention. Compared with widely used phytochemical-based supplements like curcumin, silymarin, and resveratrol, sulforaphane more potently activates Nrf2 to induce the expression of a battery of cytoprotective genes. By virtue of its lipophilic nature and low molecular weight, sulforaphane displays significantly higher bioavailability than the polyphenol-based dietary supplements that also activate Nrf2. Nrf2 activation induces cytoprotective genes such as those playing key roles in cellular defense mechanisms including redox status and detoxification. Both its high bioavailability and significant Nrf2 inducer capacity contribute to the therapeutic potential of sulforaphane-yielding supplements.

TrxR1 as a potent regulator of the Nrf2-Keap1 response system

SIGNIFICANCE

All cells must maintain a balance between oxidants and reductants, while allowing for fluctuations in redox states triggered by signaling, altered metabolic flow, or extracellular stimuli. Furthermore, they must be able to rapidly sense and react to various challenges that would disrupt the redox homeostasis.

RECENT ADVANCES

Many studies have identified Keap1 as a key sensor for oxidative or electrophilic stress, with modification of Keap1 by oxidation or electrophiles triggering Nrf2-mediated transcriptional induction of enzymes supporting reductive and detoxification pathways. However, additional mechanisms for Nrf2 regulation are likely to exist upstream of, or in parallel with, Keap1.

CRITICAL ISSUES

Here, we propose that the mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a potent regulator of Nrf2. A high chemical reactivity of TrxR1 and its vital role for the thioredoxin (Trx) system distinguishes TrxR1 as a prime target for electrophilic challenges. Chemical modification of the selenocysteine (Sec) in TrxR1 by electrophiles leads to rapid inhibition of thioredoxin disulfide reductase activity, often combined with induction of NADPH oxidase activity of the derivatized enzyme, thereby affecting many downstream redox pathways. The notion of TrxR1 as a regulator of Nrf2 is supported by many publications on effects in human cells of selenium deficiency, oxidative stress or electrophile exposure, as well as the phenotypes of genetic mouse models.

FUTURE DIRECTIONS

Investigation of the role of TrxR1 as a regulator of Nrf2 activation will facilitate further studies of redox control in diverse cells and tissues of mammals, and possibly also in animals of other classes.

Baicalein modulates Nrf2/Keap1 system in both Keap1-dependent and Keap1-independent mechanisms

Baicalein, a major component of Scutellaria baicalensis Georgi (Huang Qin), is widely used in the traditional Chinese medicine. However, the mechanisms underlying cancer chemoprevention are still not clear. The present study aimed to clarify how baicalein modulate Nrf2/Keap1 system to exert its cytoprotection and cancer chemoprevention. In the upstream cellular signaling, baicalein stimulated the phosphorylation of MEK1/2, AKT and JNK1/2, which were demonstrated to be essential for baicalein-induced Nrf2 expression by their inhibitors. Immunoprecipitation with Nrf2 found that baicalein increased the amount of phosphorylated MEK1/2, AKT and JNK1/2 bound to Nrf2, and also stabilized Nrf2 protein by inhibiting the ubiquitination and proteasomal turnover of Nrf2. Simultaneously, baicalein down-regulated Keap1 by stimulating modification and degradation of Keap1 without affecting the dissociation of Keap1-Nrf2. Silencing Nrf2 using Nrf2 siRNA markedly reduced the ARE activity under both baseline and baicalein-induced conditions. Thus, baicalein positively modulate Nrf2/Keap1 system through both Keap1-independent and -dependent pathways. These finding provide an insight to understand the mechanisms of baicalein in cytoprotection and cancer chemoprevention.

Pigs fed camelina meal increase hepatic gene expression of cytochrome 8b1, aldehyde dehydrogenase, and thiosulfate transferase

Camelina sativa is an oil seed crop which can be grown on marginal lands. Camelina seed oil is rich in omega-3 fatty acids (>35%) and γ-tocopherol but is also high in erucic acid and glucosinolates. Camelina meal, is the by-product after the oil has been extracted. Camelina meal was fed to 28 d old weaned pigs at 3.7% and 7.4% until age 56 d. The camelina meal supplements in the soy based diets, improved feed efficiency but also significantly increased the liver weights. Gene expression analyses of the livers, using intra-species microarrays, identified increased expression of phase 1 and phase 2 drug metabolism enzymes. The porcine versions of the enzymes were confirmed by real time PCR. Cytochrome 8b1 (CYP8B1), aldehyde dehydrogenase 2 (Aldh2), and thiosulfate transferase (TST) were all significantly stimulated. Collectively, these genes implicate the camelina glucosinolate metabolite, methyl-sulfinyldecyl isothiocyanate, as the main xeniobiotic, causing increased hepatic metabolism and increased liver weight.

Overview of food products and dietary constituents with antidiabetic properties and their putative mechanisms of action: a natural approach to complement pharmacotherapy in the management of diabetes

Diabetes is one of the fastest growing chronic, noncommunicable diseases worldwide. Currently, 11 major classes of pharmacotherapy are available for the management of this metabolic disorder. However, the usage of these drugs is often associated with undesirable side effects, including weight gain and hypoglycemia. There is thus a need for new, safe and effective treatment strategies. Diet is known to play a major role in the prevention and management of diabetes. Numerous studies have reported the putative association of the consumption of specific food products, or their constituents, with the incidence of diabetes, and mounting evidence now suggests that some dietary factors can improve glycemic regulation. Foods and dietary constituents, similar to synthetic drugs, have been shown to modulate hormones, enzymes, and organ systems involved in carbohydrate metabolism. The present article reviews the major classes and modes of action of antidiabetic drugs, and examines the evidence on food products and dietary factors with antidiabetic properties as well as their plausible mechanisms of action. The findings suggest potential use of dietary constituents as a complementary approach to pharmacotherapy in the prevention and/or management of diabetes, but further research is necessary to identify the active components and evaluate their efficacy and safety.

Myricetin-mediated lifespan extension in Caenorhabditis elegans is modulated by DAF-16

Myricetin is a naturally occurring flavonol found in many plant based food sources. It increases the lifespan of Caenorhabditis elegans, but the molecular mechanisms are not yet fully understood. We have investigated the impact of this flavonoid on the transcription factors DAF-16 (C. elegans FoxO homologue) and SKN-1 (Nrf2 homologue), which have crucial functions in the regulation of ageing. Myricetin is rapidly assimilated by the nematode, causes a nuclear translocation of DAF-16 but not of SKN-1, and finally prolongs the mean adult lifespan of C. elegans by 32.9%. The lifespan prolongation was associated with a decrease in the accumulation of reactive oxygen species (ROS) detected by DCF. Myricetin also decreases the formation of lipofuscin, a pigment consisting of highly oxidized and cross-linked proteins that is considered as a biomarker of ageing in diverse species. The lifespan extension was completely abolished in a daf-16 loss-of-function mutant strain (CF1038). Consistently with this result, myricetin was also not able to diminish stress-induced ROS accumulation in the mutant. These results strongly indicate that the pro-longevity effect of myricetin is dependent on DAF-16 and not on direct anti-oxidative effects of the flavonoid.