Therapeutic potential of pterostilbene against pancreatic beta-cell apoptosis mediated through Nrf2

Genetics, Nutrition, and Health: A New Frontier in Disease Prevention

The field of nutrition research has traditionally focused on the effects of macronutrients and micronutrients on the body. However, it has become evident that individuals have unique genetic makeups that influence their response to food. Nutritional genomics, which includes nutrigenetics and nutrigenomics, explores the interaction between an individual's genetic makeup, diet, and health outcomes. Nutrigenetics studies the impact of genetic variation on an individual's response to dietary nutrients, while nutrigenomics investigates how dietary components affect gene regulation and expression. These disciplines seek to understand the impact of diet on the genome, transcriptome, proteome, and metabolome. It provides insights into the mechanisms underlying the effect of diet on gene expression. Nutrients can cause the modification of genetic expression through epigenetic changes, such as DNA methylation and histone modifications. The aim of nutrigenomics is to create personalized diets based on the unique metabolic profile of an individual, gut microbiome, and genetic makeup to prevent diseases and promote health. Nutrigenomics has the potential to revolutionize the field of nutrition by combining the practicality of personalized nutrition with knowledge of genetic factors underlying health and disease. Thus, nutrigenomics offers a promising approach to improving health outcomes (in terms of disease prevention) through personalized nutrition strategies based on an individual's genetic and metabolic characteristics.

Dietary pterostilbene exerts potential protective effects by regulating lipid metabolism and enhancing antioxidant capacity on liver in broilers

Intensive breeding of broilers met the increasing demands of human for broiler products, but it raised their increased susceptibility to various stressors resulting in the disorder of lipid metabolism. Pterostilbene, the methoxylated analogue of resveratrol, exhibits astonishing functions of antioxidant, anti-inflammatory and glycolipid regulatory. The study aimed to elucidate the protective effects of pterostilbene on broiler liver and to explore the potential mechanisms. A total of 480 one-day-old male Arbor Acres (AA) broilers were randomly divided into four groups: the control group (basal diet) and pterostilbene groups (PT200, PT400, and PT600 feeding with basal diet containing 200, 400 and 600 mg/kg pterostilbene, respectively). The results showed that the dietary pterostilbene supplementation significantly improved the ADG of broilers. Dietary pterostilbene supplementation regulated the expression levels of the genes Sirt1 and AMPK and the downstream genes related to lipid metabolism to protect liver function and reduce lipid accumulation in broilers. Dietary pterostilbene supplementation upregulated the expression levels of the Nrf2 gene and its downstream antioxidant genes (SOD, CAT, HO-1, NQO-1, GPX) and phase II detoxification enzyme-related genes (GST, GCLM, GCLC). Collectively, pterostilbene was confirmed the positive effects as a feed additive on lipid metabolism and antioxidant via regulating Sirt1/AMPK and Nrf2 signalling pathways in broilers.

E-Stilbenes: General Chemical and Biological Aspects, Potential Pharmacological Activity Based on the Nrf2 Pathway

Stilbenes are phytoalexins, and their biosynthesis can occur through a natural route (shikimate precursor) or an alternative route (in microorganism cultures). The latter is a metabolic engineering strategy to enhance production due to stilbenes recognized pharmacological and medicinal potential. It is believed that in the human body, these potential activities can be modulated by the regulation of the nuclear factor erythroid derived 2 (Nrf2), which increases the expression of antioxidant enzymes. Given this, our review aims to critically analyze evidence regarding E-stilbenes in human metabolism and the Nrf2 activation pathway, with an emphasis on inflammatory and oxidative stress aspects related to the pathophysiology of chronic and metabolic diseases. In this comprehensive literature review, it can be observed that despite the broad number of stilbenes, those most frequently explored in clinical trials and preclinical studies (in vitro and in vivo) were resveratrol, piceatannol, pterostilbene, polydatin, stilbestrol, and pinosylvin. In some cases, depending on the dose/concentration and chemical nature of the stilbene, it was possible to identify activation of the Nrf2 pathway. Furthermore, the use of some experimental models presented a challenge in comparing results. In view of the above, it can be suggested that E-stilbenes have a relationship with the Nrf2 pathway, whether directly or indirectly, through different biological pathways, and in different diseases or conditions that are mainly related to inflammation and oxidative stress.

Pterostilbene accelerates wound healing response in diabetic mice through Nrf2 regulation

Pterostilbene (PTS), known for its diverse beneficial effects via Nuclear factor erythroid-2 related factor (Nrf2) activation, holds potential for Diabetic Foot Ulcer (DFU) treatment. However, PTS-mediated Nrf2 regulation in diabetic wounds has yet to be elucidated. We used IC21 macrophage-conditioned media to simulate complex events that can influence the fibroblast phenotype using L929 cells during the wound healing process under a hyperglycemic microenvironment. We found that PTS attenuated fibroblast migration and alpha-smooth muscle actin (α-SMA) levels and hypoxia-inducible factor- 1 alpha (HIF1α). Furthermore, we demonstrated that wounds in diabetic mice characterized by impaired wound closure in a heightened inflammatory milieu, such as the NOD-like receptor P3 (NLRP3) and intercellular adhesion molecule 1 (ICAM1), and deficient Nrf2 response accompanying lowered Akt signaling and heme oxygenase1 (HO1) expression along with the impaired macrophage M2 marker CD206 expression, was rescued by administration of PTS. Such an elicited response was also compared favorably with the standard treatment using Regranex, a commercially available topical formulation for treating DFUs. Our findings suggest that PTS regulates Nrf2 in diabetic wounds, triggering a pro-wound healing response mediated by macrophages. This insight holds the potential for developing targeted therapies to heal chronic wounds, including DFUs.

Discovery of pterostilbene analogs as novel NLRP3 inflammasome inhibitors for potential treatment of DSS-induced colitis in mice

The pterostilbene skeleton is a promising chemical scaffold that exerts anti-inflammatory, anti-depressant, and anti-tumor effects. In this study, we aim to reduce in vivo and in vitro toxicity of compound 32 (preliminary work) and maintain its biological activity. A series of novel pterostilbene derivatives (D1-D43) were designed and synthesized, and their anti-inflammatory activities were screened. All compounds were screened to evaluate their inhibitory effect on LPS/Nigericin-induced IL-1β production and pyroptosis. The structure-activity relationships was deduced, and finally 1-((E)-4-(2-ethoxyethoxy)styryl)-3,5-dimethoxy-2-((E)-2-nitrovinyl)benzene (D22) was found to be a low-toxic compound with most potent inhibitory efficacy (against IL-1β: IC₅₀ = 2.41 μM). Preliminary mechanism studies showed that compound D22 may affect the assembly of NLRP3 inflammasome by targeting NLRP3 protein, thereby inhibiting the activation of NLRP3 inflammasome. The in vivo anti-inflammatory activity indicated that compound D22 had significant therapeutic effects on DSS-induced mouse acute colitis models.

Modulation of transcription factors by small molecules in β-cell development and differentiation

Transcription factors regulate gene expression and play crucial roles in development and differentiation of pancreatic β-cell. The expression and/or activities of these transcription factors are reduced when β-cells are chronically exposed to hyperglycemia, which results in loss of β-cell function. Optimal expression of such transcription factors is required to maintain normal pancreatic development and β-cell function. Over many other methods of regenerating β-cells, using small molecules to activate transcription factors has gained insights, resulting in β-cells regeneration and survival. In this review, we discuss the broad spectrum of transcription factors regulating pancreatic β-cell development, differentiation and regulation of these factors in normal and pathological states. Also, we have presented set of potential pharmacological effects of natural and synthetic compounds on activities of transcription factor involved in pancreatic β-cell regeneration and survival. Exploring these compounds and their action on transcription factors responsible for pancreatic β-cell function and survival could be useful in providing new insights for development of small molecule modulators.

The neuroprotective effect of pterostilbene on oxaliplatin-induced peripheral neuropathy via its anti-inflammatory, anti-oxidative and anti-apoptotic effects: Comparative study with celecoxib

BACKGROUND

Oxaliplatin is one of the first-line drugs in solid tumors treatment. However, neuropathy is a devastating side effect leading to poor compliance and treatment cessation.

AIM

The current study explored pterostilbene plausible neuroprotective effects aiming to ascertain the potential mechanisms involved in relieving oxaliplatin-induced peripheral neuropathy (OIPN) and investigating whether pterostilbene and celecoxib combination could show better relief.

MAIN METHODS

Rats were divided into six groups; control, pterostilbene (40 mg/kg/day, p.o. for 5 weeks), oxaliplatin (4 mg/kg, i.p. twice per week for 4.5 weeks), celecoxib (30 mg/kg/day, p.o. for 5 weeks) and combination of pterostilbene and celecoxib. Behavioral tests and histopathological analysis of sciatic nerves were done. MAPKs, cytokines, COX-2, and PGE₂ gene and protein expressions were estimated using qRT-PCR, western, and ELISA techniques. Malondialdehyde (MDA) and total antioxidant capacity (TAC) were assessed by colorimetric assay while apoptotic markers by immunohistochemical analysis and qRT-PCR.

KEY FINDINGS

The study revealed that pterostilbene and celecoxib averted oxaliplatin-induced behavioral and motor impairments along with restoration of histopathological changes. Moreover, pterostilbene and celecoxib have significantly attenuated sciatic nerve: p38 MAPK, JNK, ERK1/2, NF-κB, COX-2, PGE₂, TNF-α, and interleukins levels. Pterostilbene and celecoxib have reduced caspase-3, Bax, and MDA while increasing Bcl-2 level and TAC.

SIGNIFICANCE

Altogether, Pterostilbene mitigates OIPN by interrupting the vicious cycle of inflammation, oxidation, and apoptosis. Furthermore, pterostilbene and celecoxib show comparable attenuation on MAPKs cascades, inflammatory cytokines, oxidative and apoptotic markers. Likewise, co-administration of pterostilbene and celecoxib shows further relief of neuropathic pain.

Role of ferroptosis inhibitors in the management of diabetes

Ferroptosis, the iron-dependent, lipid peroxide-mediated cell death, has garnered attention due to its critical involvement in crucial physiological and pathological cellular processes. Indeed, several studies have attributed its role in developing a range of disorders, including diabetes. As accumulating evidence further the understanding of ferroptotic mechanisms, the impact this specialized mode of cell death has on diabetic pathogenesis is still unclear. Several in vivo and in vitro studies have highlighted the association of ferroptosis with beta-cell death and insulin resistance, supported by observations of marked alterations in ferroptotic markers in experimental diabetes models. The constant improvement in understanding ferroptosis in diabetes has demonstrated it as a potential therapeutic target in diabetic management. In this regard, ferroptosis inhibitors promise to rescue pancreatic beta-cell function and alleviate diabetes and its complications. This review article elucidates the key ferroptotic pathways that mediate beta-cell death in diabetes, and its complications. In particular, we share our insight into the cross talk between ferroptosis and other hallmark pathogenic mediators such as oxidative and endoplasmic reticulum stress regulators relevant to diabetes progression. Further, we extensively summarize the recent developments on the role of ferroptosis inhibitors and their therapeutic action in alleviating diabetes and its complications.

Increased brain uptake of pterostilbene loaded folate modified micellar delivery system

Effective chemotherapy for clinical treatment of brain diseases is still lacking due to the poor penetration of the blood-brain barrier (BBB). The aim of this study was to construct a folate modified pterostilbene (Pt) loaded polymeric micellar delivery system (F-Pt/M) with mPEG-PCL as carrier material to aim at penetrating the BBB for brain tissue targeting via receptor-mediated endocytosis. In this study, F-Pt/M was prepared using thin-film hydration method and then optimized by response surface methodology (RSM) with the entrapment efficiency (EE), drug loading (DL) and hydrodynamic diameter (HD) as indexes. The average hydrodynamic diameter and zeta potential of optimal F-Pt/M were 133.2 nm and 24.6 mV, respectively. DL (18.3%) and EE (98.6%) made the solubility of Pt in water about 25 times higher than that of crude Pt. Results of DSC evaluation revealed that drugs were successfully encapsulated inside the polymeric micelles. TEM images showed that homogeneous spherical micellar structures with a narrow size distribution were developed. The release result in vitro showed that F-Pt/M presented sustained release behavior compared to control free Pt solution. Compared to non-targeted Pt/M, F-Pt/M had a significantly higher cytotoxicity against FR-overexpressing A172 cells. In vitro cellular uptake tests illustrated that the micellar delivery system could significantly improve the accumulation of drugs in target cells via receptor-mediated endocytosis. BBB penetration value (P) of F-Pt/M was about 4 folds higher than that of free Pt group. In addition, drug targeting index (DTI) was calculated to determine targeting of F-Pt/M to the brain which was found to be 4.89, implying improved brain targeting was achieved. Hence, the developed F-Pt/M exhibited great potential for delivering more drug molecules across the BBB for the treatment of brain diseases.

MYB transcription factors-master regulators of phenylpropanoid biosynthesis and diverse developmental and stress responses

Phenylpropanoids, the largest class of natural products including flavonoids, anthocyanins, monolignols and tannins perform multiple functions ranging from photosynthesis, nutrient uptake, regulating growth, cell division, maintenance of redox homeostasis and biotic and abiotic stress responses. Being sedentary life forms, plants possess several regulatory modules that increase their performance in varying environments by facilitating activation of several signaling cascades upon perception of developmental and stress signals. Of the various regulatory modules, those involving MYB transcription factors are one of the extensive groups involved in regulating the phenylpropanoid metabolic enzymes in addition to other genes. R2R3 MYB transcription factors are a class of plant-specific transcription factors that regulate the expression of structural genes involved in anthocyanin, flavonoid and monolignol biosynthesis which are indispensable to several developmental pathways and stress responses. The aim of this review is to present the regulation of the phenylpropanoid pathway by MYB transcription factors via Phospholipase D/phosphatidic acid signaling, downstream activation of the structural genes, leading to developmental and/or stress responses. Specific MYB transcription factors inducing or repressing specific structural genes of anthocyanin, flavonoid and lignin biosynthetic pathways are discussed. Further the roles of MYB in activating biotic and abiotic stress responses are delineated. While several articles have reported the role of MYB's in stress responses, they are restricted to two or three specific MYB factors. This review is a consolidation of the diverse roles of different MYB transcription factors involved both in induction and repression of anthocyanin, flavonoid, and lignin biosynthesis.

Intercellular mitochondrial transfer as a means of revitalizing injured glomerular endothelial cells

BACKGROUND

Recent studies have demonstrated that mesenchymal stem cells (MSCs) can rescue injured target cells via mitochondrial transfer. However, it has not been fully understood how bone marrow-derived MSCs repair glomeruli in diabetic kidney disease (DKD).

AIM

To explore the mitochondrial transfer involved in the rescue of injured glomerular endothelial cells (GECs) by MSCs, both in vitro and in vivo.

METHODS

In vitro experiments were performed to investigate the effect of co-culture with MSCs on high glucose-induced GECs. The transfer of mitochondria was visualized using fluorescent microscopy. GECs were freshly sorted and ultimately tested for apoptosis, viability, mRNA expression by real-time reverse transcriptase-polymerase chain reaction, protein expression by western blot, and mitochondrial function. Moreover, streptozotocin-induced DKD rats were infused with MSCs, and renal function and oxidative stress were detected with an automatic biochemical analyzer and related-detection kits after 2 wk. Kidney histology was analyzed by hematoxylin and eosin, periodic acid-Schiff, and immunohistochemical staining.

RESULTS

Fluorescence imaging confirmed that MSCs transferred mitochondria to injured GECs when co-cultured in vitro. We found that the apoptosis, proliferation, and mitochondrial function of injured GECs were improved following co-culture. Additionally, MSCs decreased pro-inflammatory cytokines [interleukin (IL)-6, IL-1β, and tumor necrosis factor-α] and pro-apoptotic factors (caspase 3 and Bax). Mitochondrial transfer also enhanced the expression of superoxide dismutase 2, B cell lymphoma-2, glutathione peroxidase (GPx) 3, and mitofusin 2 and inhibited reactive oxygen species (ROS) and dynamin-related protein 1 expression. Furthermore, MSCs significantly ameliorated functional parameters (blood urea nitrogen and serum creatinine) and decreased the production of malondialdehyde, advanced glycation end products, and ROS, whereas they increased the levels of GPx and superoxide dismutase in vivo. In addition, significant reductions in the glomerular basement membrane and renal interstitial fibrosis were observed following MSC treatment.

CONCLUSION

MSCs can rejuvenate damaged GECs via mitochondrial transfer. Additionally, the improvement of renal function and pathological changes in DKD by MSCs may be related to the mechanism of mitochondrial transfer.

New Insights into Dietary Pterostilbene: Sources, Metabolism, and Health Promotion Effects

Pterostilbene (PTS), a compound most abundantly found in blueberries, is a natural analog of resveratrol. Several plant species, such as peanuts and grapes, produce PTS. While resveratrol has been extensively studied for its antioxidant properties, recent evidence also points out the diverse therapeutic potential of PTS. Several studies have identified the robust pharmacodynamic features of PTS, including better intestinal absorption and elevated hepatic stability than resveratrol. Indeed, due to its higher bioavailability paired with reduced toxicity compared to other stilbenes, PTS has become an attractive drug candidate for the treatment of several disease conditions, including diabetes, cancer, cardiovascular disease, neurodegenerative disorders, and aging. This review article provides an extensive summary of the nutraceutical potential of PTS in various disease conditions while discussing the crucial mechanistic pathways implicated. In particular, we share insights from our studies about the Nrf2-mediated effect of PTS in diabetes and associated complications. Moreover, we elucidate the important sources of PTS and discuss in detail its pharmacokinetics and the range of formulations and routes of administration used across experimental studies and human clinical trials. Furthermore, this review also summarizes the strategies successfully used to improve dietary availability and the bio-accessibility of PTS.

Pterostilbene improves CFA-induced arthritis and peripheral neuropathy through modulation of oxidative stress, inflammatory cytokines and neurotransmitters in Wistar rats

Pterostilbene is a stilbene flavonoid that occurs naturally in various plants as well as produced by genetic engineering. It exhibits anti-inflammatory, analgesic, anti-oxidant and neuroprotective activities. This research was aimed to determine the potential of pterostilbene against arthritis and peripheral neuropathy in Complete Freund's Adjuvant (CFA) induced arthritis. Rat hind paw was injected with 0.1 ml CFA to induce arthritis. Standard control animals received oral methotrexate (3 mg/kg/week). Pterostilbene at 12.5, 25 and 50 mg/kg was given orally to different groups of arthritic rats from day 7-28 for 21 days. Pterostilbene significantly reduced paw diameter and retarded the decrease in body weight of arthritic rats. It profoundly (p < 0.05-0.0001) reduced lipid peroxidation and nitrites, while increased superoxide dismutase (SOD) in the liver tissue. Pterostilbene treatment significantly (p < 0.0001) reduced TNF-α and IL-6 levels. Pterostilbene markedly improved (p < 0.05-0.001) motor activity and showed analgesic effect in arthritic rats at 25 and 50 mg/kg as compared to disease control rats. Furthermore, it notably (p < 0.05-0.0001) increased SOD activity, nitrites, noradrenaline and serotonin levels in the sciatic nerve of arthritic rats. Treatment with pterostilbene also ameliorated the CFA-induced pannus formation, cartilage damage and synovial hyperplasia in the arthritic rat paws. It is determined from the current study that pterostilbene was effective in reducing CFA-induced arthritis in rats through amelioration of oxidative stress and inflammatory mediators. It was also effective to treat peripheral neuropathy through modulation of oxidative stress and neurotransmitters in sciatic nerves.

Mechanistic Insight into Oxidative Stress-Triggered Signaling Pathways and Type 2 Diabetes

Oxidative stress (OS) is a metabolic dysfunction mediated by the imbalance between the biochemical processes leading to elevated production of reactive oxygen species (ROS) and the antioxidant defense system of the body. It has a ubiquitous role in the development of numerous noncommunicable maladies including cardiovascular diseases, cancers, neurodegenerative diseases, aging and respiratory diseases. Diseases associated with metabolic dysfunction may be influenced by changes in the redox balance. Lately, there has been increasing awareness and evidence that diabetes mellitus (DM), particularly type 2 diabetes, is significantly modulated by oxidative stress. DM is a state of impaired metabolism characterized by hyperglycemia, resulting from defects in insulin secretion or action, or both. ROS such as hydrogen peroxide and the superoxide anion introduce chemical changes virtually in all cellular components, causing deleterious effects on the islets of β-cells, in turn affecting insulin production. Under hyperglycemic conditions, various signaling pathways such as nuclear factor-κβ (NF-κβ) and protein kinase C (PKC) are also activated by ROS. All of these can be linked to a hindrance in insulin signaling pathways, leading to insulin resistance. Hyperglycemia-induced oxidative stress plays a substantial role in complications including diabetic nephropathy. DM patients are more prone to microvascular as well as atherosclerotic macrovascular diseases. This systemic disease affects most countries around the world, owing to population explosion, aging, urbanization, obesity, lifestyle, etc. However, some modulators, with their free radical scavenging properties, can play a prospective role in overcoming the debilitating effects of OS. This review is a modest approach to summarizing the basics and interlinkages of oxidative stress, its modulators and diabetes mellitus. It may add to the understanding of and insight into the pathophysiology of diabetes and the crucial role of antioxidants to weaken the complications and morbidity resulting from this chronic disease.

Targeting Nrf2/Keap1 signaling pathway by bioactive natural agents: Possible therapeutic strategy to combat liver disease

BACKGROUND

Nuclear factor erythroid 2-related factor (Nrf2), a stress-activated transcription factor, has been documented to induce a defense mechanism against oxidative stress damage, and growing evidence considers this signaling pathway a key pharmacological target for the treatment of liver diseases.

PURPOSE

The present review highlights the role of phytochemical compounds in activating Nrf2 and mitigate toxicant-induced stress on liver injury.

METHODS

A comprehensive search of published articles was carried out to focus on original publications related to Nrf2 activators against liver disease using various literature databases, including the scientific Databases of Science Direct, Web of Science, Pubmed, Google, EMBASE, and Scientific Information (SID).

RESULTS

Nrf2 activators exhibited promising effects in resisting a variety of liver diseases induced by different toxicants in preclinical experiments and in vitro studies by regulating cell proliferation and apoptosis as well as an antioxidant defense mechanism. We found that the phytochemical compounds, such as curcumin, naringenin, sulforaphane, diallyl disulfide, mangiferin, oleanolic acid, umbelliferone, daphnetin, quercetin, isorhamnetin-3-O-galactoside, hesperidin, diammonium glycyrrhizinate, corilagin, shikonin, farrerol, and chenpi, had the potential to improve the Nrf2-ARE signaling thereby combat hepatotoxicity.

CONCLUSION

Nrf2 activators may offer a novel potential strategy for the prevention and treatment of liver diseases. More extensive studies are essential to identify the underlying mechanisms and establish future therapeutic potentials of these signaling modulators. Further clinical trials are warranted to determine the safety and effectiveness of Nrf2 activators for hepatopathy.

Purification and antioxidant properties of triterpenic acids from blackened jujube (Ziziphus jujuba Mill.) by macroporous resins

In order to investigate the purification process and antioxidant activity of triterpenic acids from blackened jujube, the macroporous resin was applied to purify the crude extract from blackened jujube. The adsorption and desorption characterizations of five different macroporous adsorption resins (AB-8, D-101, X-5, HPD-100, S-8) for triterpenic acids of blackened jujube were compared, the optimum purification resins were screened, and the purification parameters were optimized. The antioxidant activity of crude extracts and purified products from blackened jujube was analyzed. The results showed that D-101 resin possessed the best effect on the purification of blackened jujube triterpenic acids. The optimum purification parameters were as follows: sample concentration 25.5 μg/ml, 130 ml of the sample volume was with a flow rate of 2.0 ml/min, eluted with 95% ethanol, and speed flow was 1.0 ml/min. The purity of triterpenic acids was increased by 2.49 times after purification with a recovery rate of (78.58 ± 0.67)%. Furthermore, the IC50 values of hydroxyl radical scavenging capacity from triterpenic acids crude extract and purified substances were 0.900 and 0.850 mg/ml, respectively, and the IC50 values of superoxide anion radical were 0.745 and 0.594 mg/ml, respectively, indicating that the antioxidative capacity of the purified product was stronger than the crude extract. The purified triterpenic acids (PTA) groups at different doses had excellent protective effects on H2O2-induced damage HUVEC cells. Results have revealed that triterpenic acids of blackened jujube have good antioxidant function and utilization and development prospects.

The pivotal role of Nrf2 activators in adipocyte biology

Adipose tissue is instrumental in maintaining metabolic homeostasis by regulating energy storage in the form of triglycerides. In the case of over-nutrition, adipocytes favorably regulate lipogenesis over lipolysis and accumulate excess triglycerides, resulting in increased adipose tissue mass. An abnormal increase in hypertrophic adipocytes is associated with chronic complications such as insulin resistance, obesity, diabetes, atherosclerosis and nonalcoholic fatty liver disease. Experimental studies indicate the occurrence of oxidative stress in the pathogenesis of obesity. A common underlying link between increasing adipose tissue mass and oxidative stress is the Nuclear Factor Erythroid 2-related factor 2 (Nrf2), Keap1-Nrf2-ARE signaling, which plays an indispensable role in metabolic homeostasis by regulating oxidative and inflammatory responses. Additionally, Nrf2 also activates CCAAT/enhancer-binding protein α, (C/EBP-α), C/EBP-β and peroxisome proliferator-activated receptor γ (PPARγ) the crucial pro-adipogenic factors that promote de novo adipogenesis. Hence, at the forefront of research is the quest for prospecting novel compounds to modulate Nrf2 activity in the context of adipogenesis and obesity. This review summarizes the molecular mechanism behind the activation of the Keap1-Nrf2-ARE signaling network and the role of Nrf2 activators in adipocyte pathophysiology.

Nutrigenomics in Regulating the Expression of Genes Related to Type 2 Diabetes Mellitus

Nutrigenomics is the study of the gene-nutrient interaction and it indicates that some nutrients, called bioactive compounds, can mold the genetic expression or change the nucleotide chain. Polyphenols are secondary metabolites found in plants that are regularly consumed in functional foods and help prevent or delay the onset of type 2 diabetes mellitus (T2DM) and its complications. This article objected to review studies about the interaction of diet with polyphenols and Mediterranean diet in the expression of human genes related to T2DM. Resveratrol acts as an antioxidant, anti-inflammatory, and increases mitochondrial function. Regular consumption of quercetin resulted in improvement of hypertension and suppression of diabetes-induced vasoconstriction. Genistein also showed positive results in T2DM, such as increased cell mass and improved glucose tolerance and insulin levels. Catechins showed efficiency in inducing genes in triacylglycerol biosynthesis, inhibition of fatty acids and cholesterol, and resulting in their participation in mitigating complications of diabetes. Lastly, curcumin was demonstrated to be a protector of the pancreatic islets against streptozotocin-induced oxidative stress. Growing evidence suggest that bioactive compounds such as polyphenols have an important role in T2DM and the prevention and treatment of its complication, as they cause activation or inhibition of related genes.

Dysregulation of Nrf2 redox pathway in macrophages under diabetic microenvironment

In the present study, we characterized the aberration in Nrf2 signaling in macrophages under a hyperglycemic microenvironment that reflects diabetic wounds in vitro and studied the effect of an Nrf2 activator pterostilbene (PTS) in these experimental conditions. Macrophages were exposed to pro-inflammatory cytokines TNFα and IFNγ with (HG+) or without high glucose (NG+) followed by the treatment with or without PTS. Western blotting was undertaken to assess the Nrf2 translocation from cytosol to nucleus followed by its downstream and upstream mediators, heme oxygenase-1 and Akt, respectively, the latter via phosphorylation. Quantitative PCR was also carried out to check the expression of macrophage mannose receptor CD206. We found a 2-fold reduction in the activation of Nrf2 in the HG+ group at 24 h compared to NG+, which was significantly improved by the treatment with PTS. Reduction in the levels of heme oxygenase-1 and phosphorylation of Akt in the HG+ group was also ameliorated by PTS. Furthermore, the gene expression of CD206 that was significantly reduced in the HG+ group was also restored by PTS treatment. The disruption of Nrf2 signaling in macrophages in a hyperglycemic microenvironment in vitro may indeed reflect diabetic wounds, as opposed to other non-diabetic wounds.

Protective effects of upregulated HO-1 gene against the apoptosis of human retinal pigment epithelial cells in vitro

AIM

To investigate the protective effect of heme oxygenase-1 (HO-1) against H₂O₂-induced apoptosis in human ARPE-19 cells.

METHODS

The lentiviral vector expressing HO-1 was prepared and transfected into apoptotic ARPE-19 cells induced by H₂O₂. Functional experiments including cell counting kit-8 (CCK-8) assay, flow cytometry (FCM) and mitochondrial membrane potential assay were conducted.

RESULTS

The ultrastructure of ARPE-19 cells was observed using transmission electron microscope (TEM). It was found that exogenous HO-1 significantly ameliorated H₂O₂-induced loss of cell viability, apoptosis and intracellular levels of reactive oxygen species (ROS) in ARPE-19 cells. The overexpression of HO-1 facilitated the transfer of nuclear factor erythroid-2-related factor 2 (Nrf2) from cytoplasm to nucleus, which in turn upregualted expressions HO-1 and B-cell lymphoma-2 (Bcl-2). Furthermore, HO-1 upregulation further inhibited H₂O₂-induced release of cysteinyl aspartate specific proteinase-3 (caspase-3).

CONCLUSION

Exogenous HO-1 protect ARPE-19 cells against H₂O₂-induced oxidative stress by regulating the expressions of Nrf2, HO-1, Bcl-2, and caspase-3.

Therapeutic Potential of Polyphenols in the Management of Diabetic Neuropathy

Diabetic neuropathy (DN) is a common and serious diabetes-associated complication that primarily takes place because of neuronal dysfunction in patients with diabetes. Use of current therapeutic agents in DN treatment is quite challenging because of their severe adverse effects. Therefore, there is an increased need of identifying new safe and effective therapeutic agents. DN complications are associated with poor glycemic control and metabolic imbalances, primarily oxidative stress (OS) and inflammation. Various mediators and signaling pathways such as glutamate pathway, activation of channels, trophic factors, inflammation, OS, advanced glycation end products, and polyol pathway have a significant contribution to the progression and pathogenesis of DN. It has been indicated that polyphenols have the potential to affect DN pathogenesis and could be used as potential alternative therapy. Several polyphenols including kolaviron, resveratrol, naringenin, quercetin, kaempferol, and curcumin have been administered in patients with DN. Furthermore, chlorogenic acid can provide protection against glutamate neurotoxicity via its hydrolysate, caffeoyl acid group, and caffeic acid through regulating the entry of calcium into neurons. Epigallocatechin-3-gallate treatment can protect motor neurons by regulating the glutamate level. It has been demonstrated that these polyphenols can be promising in combating DN-associated damaging pathways. In this article, we have summarized DN-associated metabolic pathways and clinical manifestations. Finally, we have also focused on the roles of polyphenols in the treatment of DN.

Pharmacological Activation of Nrf2 by Rosolic Acid Attenuates Endoplasmic Reticulum Stress in Endothelial Cells

Endoplasmic reticulum (ER) plays a key role in the folding, modification, and trafficking of proteins. When the homeostasis of the ER is disturbed, un/misfolded proteins accumulate in the ER which leads to ER stress. Sustained ER stress results in apoptosis, which is associated with various diseases. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a major transcription factor in redox homeostasis by regulating various genes associated with detoxification and cell-protective mechanisms. We found that Rosolic acid (RA) treatment dose-dependently activates Nrf2 in endothelial cells using the enzyme fragment complementation assay. The cytoprotective role of RA against ER stress-induced endothelial apoptosis and its molecular mechanism was explored in the present study. The Nrf2 and its target genes, as well as ER stress marker expressions, were measured by qPCR in ER stress-exposed endothelial cells. The contribution of Nrf2 in RA-mediated defense mechanism in endothelial cells was established by knockout studies using Nrf2-CRISPR/Cas9. The treatment with RA to ER stress-induced endothelial cells exhibited activation of Nrf2, as demonstrated by Nrf2 translocation and reduction of ER stress markers. We found that the Nrf2 knockout sensitized the endothelial cells against ER stress, and further, RA failed to mediate its cytoprotective effect. Proteomic studies using LC-MS/MS revealed that among the 1370 proteins detected, we found 296 differentially regulated proteins in ER stress-induced endothelial cells, and RA administration ameliorated 71 proteins towards the control levels. Of note, the ER stress in endothelial cells was attenuated by the treatment with the RA, suggesting the role of the Nrf2 activator in the pathological conditions of ER stress-associated diseases.

Effect of Rosolic acid on endothelial dysfunction under ER stress in pancreatic microenvironment

Endothelial cell (EC) dysfunction is the underlying cause for the development of several pathologies, and the interdependency between the pancreatic β-cells and ECs has been established in the pathophysiology of diabetes. ECs release several factors that govern the expression of genes involved in the proliferation, physiology, and survival of the β-cells. Of the known factors that collapse this intricately balanced system, endothelial dysfunction is the crucial condition that manifests as the causative factor for micro and macrovascular diseases. Our earlier studies demonstrated that activation of nuclear factor erythroid-related factor (Nrf2) renders protection to the ECs experiencing ER stress. In this study, using a co-culture system, the crosstalk between pancreatic cells under ER stress and ECs and the effect of a novel Nrf2 activator Rosolic Acid (RA), on the crosstalk was investigated. ECs pre-treated with different concentrations RA and co-cultured with thapsigargin-induced ER stressed pancreatic β-cells showed increased levels of Nrf2 and its downstream targets such as heme oxygenase-1 (HO-1) and NADPH-quinone oxidoreductase-1 (NQO-1), and reduction of ER stress evinced by the decreased levels of glucose-regulated protein (GRP) 78 and C/ERB homologous protein (CHOP). The sensitization of ECs using RA, offered protection to pancreatic cells against ER stress as displayed by increased intracellular insulin and upregulated expression of cell survival and proliferative genes BCl2 and PDX-1. In addition, RA treatment resulted in elevated levels of various angiogenic factors, while inflammatory (TNF-α and IL-1β) and apoptotic markers (CXCL10 and CCL2) decreased. RA treatment normalized the levels of 115 proteins of the 277, which were differentially regulated as revealed by proteomic studies of ER stressed pancreatic β-cells in co-culture conditions. These findings clearly indicate the role of small molecule activators of Nrf2 not only in restoring the functioning of pancreatic cells but also in increasing the cell mass. Further, the study impinges on the strategies that can be developed to balance the pancreatic microenvironment, leading to the restoration of β-cell mass and their normophysiology in diabetic patients.

MicroRNA mediated regulation of the major redox homeostasis switch, Nrf2, and its impact on oxidative stress-induced ischemic/reperfusion injury

Ischemia/reperfusion injury (IRI) initiates from oxidative stress caused by lack of blood supply and subsequent reperfusion. It is often associated with sterile inflammation, cell death and microvascular dysfunction, which ultimately results in myocardial, cerebral and hepatic IRIs. Reportedly, deregulation of Nrf2 pathway plays a significant role in the oxidative stress-induced IRIs. Further, microRNAs (miRNAs/miRs) are proved to regulate the expression and activation of Nrf2 by targeting either the 3'-UTR or the upstream regulators of Nrf2. Additionally, compounds (crocin, ZnSO4 and ginsenoside Rg1) that modulate the levels of the Nrf2-regulating miRNAs were found to exhibit a protective effect against IRIs of different organs. Therefore, the current review briefs the impact of ischemia reperfusion (I/R) pathogenesis in various organs, role of miRNAs in the regulation of Nrf2 and the I/R protective effect of compounds that alter their expression.

Identification of Crucial Genes and Pathways Associated with Atherosclerotic Plaque in Diabetic Patients

Background

Patients with diabetes have more calcification in atherosclerotic plaque and a higher occurrence of secondary cardiovascular events than patients without diabetes. The objective of this study was to identify crucial genes involved in the development of diabetic atherosclerotic plaque using a bioinformatics approach.

Methods

Microarray dataset GSE118481 was downloaded from the Gene Expression Omnibus (GEO) database; the dataset included 6 patients with diabetic atherosclerotic plaque (DBT) and 6 nondiabetic patients with atherosclerotic plaque (Ctrl). Differentially expressed genes (DEG) between the DBT and Ctrl groups were identified and then subjected to functional enrichment analysis. Based on the enriched pathways of DEGs, diabetic atherosclerotic plaque-related pathways were screened using the comparative toxicogenomics database (CTD). We then constructed a protein–protein interaction (PPI) network and transcription factor (TF)–miRNA–mRNA network.

Results

A total of 243 DEGs were obtained in the DBT group compared with the Ctrl group, including 85 up-regulated and 158 down-regulated DEGs. Functional enrichment analysis showed that up-regulated DEGs were mainly enriched in isoprenoid metabolic process, DNA-binding TF activity, and response to virus. Additionally, DEGs participating in the toll-like receptor signaling pathway were closely related to diabetes, carotid stenosis, and insulin resistance. The TF–miRNA–mRNA network showed that toll-like receptor 4 (TLR4), BCL2-like 11 (BCL2L11), and glutamate-cysteine ligase catalytic subunit (GCLC) were hub genes. Furthermore, TLR4 was regulated by TF signal transducer and activator of transcription 6 (STAT6); BCL2L11 was targeted by hsa-miR-24-3p; and GCLC was regulated by nuclear factor, erythroid 2 like 2 (NFE2L2).

Conclusion

Identification of hub genes and pathways increased our understanding of the molecular mechanisms underlying the atherosclerotic plaque in patients with or without diabetes. These crucial genes (TLR4, BC2L11, and GCLC) might function as molecular biomarkers for diabetic atherosclerotic plaque.

Effects of Pterostilbene on Diabetes, Liver Steatosis and Serum Lipids

Pterostilbene, a phenolic compound derived from resveratrol, possesses greater bioavailability than its parent compound due to the presence of two methoxyl groups. In this review, the beneficial effects of pterostilbene on diabetes, liver steatosis and dyslipidemia are summarized. Pterostilbene is a useful bioactive compound in preventing type 1 diabetes, insulin resistance and type 2 diabetes in animal models. Concerning type 1 diabetes, the main mechanisms described to justify the positive effects of this phenolic compound are increased liver glycogen content and hepatic glucokinase and phosphofructokinase activities, the recovery of pancreatic islet architecture, cytoprotection and a decrease in serum and pancreatic pro-inflammatory cytokines. As for type 2 diabetes, increased liver glucokinase and glucose-6-phosphatase and decreased fructose-1,6-biphosphatase activities are reported. When insulin resistance is induced by diets, a greater activation of insulin signaling cascade has been reported, increased cardiotrophin-1 levels and liver glucokinase and glucose- 6-phosphatase activities, and a decreased fructose-1,6-biphosphatase activity. Data concerning pterostilbene and liver steatosis are scarce so far, but the reduction in oxidative stress induced by pterostilbene may be involved since oxidative stress is related to the progression of steatosis to steatohepatitis. Finally, pterostilbene effectively reduces total cholesterol, LDL-cholesterol and serum triglyceride levels, while increases HDL-cholesterol in animal models of dyslipidemia.

Flavonoid-rich wheatgrass (Triticum aestivum L.) diet attenuates diabetes by modulating antioxidant genes in streptozotocin-induced diabetic rats

Wheatgrass, young germinated shoots of Triticum aestivum L., is proclaimed as antidiabetic nutraceutical by traditional medicines across the world. In this study, the effects of the wheatgrass diet in ameliorating oxidative stress (OS) induced during diabetes were investigated. Total phenolic and flavonoid contents (TPC and TFC) and in vitro antioxidant activity of wheatgrass extract were estimated at different days (5, 7, 9, 11, 13, and 15) after germination. Correlating the TPC and TFC with in vitro antioxidant activity, 9th DAG wheatgrass was found to possess maximum antioxidant potential. UHPLC-MS/MS analysis also revealed the presence of nine flavonoids. For in vivo studies, diabetes was induced by streptozotocin in Wistar rats fed with a high-fat diet. Concomitant administration of 9th-day wheatgrass diet (200 and 400 mg/kg) for 60 days exhibited significant improvements in hyperglycemia, body weight, lipid profile, biochemical indices (AST, ALT, GSH, GPx), and restoration of tissue architectures equivalent to normal rats. Further, qRT-PCR-based expression profiling revealed a significant modulation of major antioxidant marker genes and insulin gene which substantiated that the wheatgrass diet is effective in reducing OS during diabetes. Therefore, flavonoid-rich 9th-day wheatgrass could be used as a functional food to control diabetes. PRACTICAL APPLICATIONS: The present research supported that wheatgrass protects against oxidative stress and therefore could be utilized to ameliorate diabetes. The findings may contribute to the development and formulation of wheatgrass-based functional food or dietary supplement for diabetes by nutraceutical industries.

Role of long non-coding RNAs on the regulation of Nrf2 in chronic diseases

Studies have identified dysregulated long non-coding RNA (lncRNA) in several diseases at transcriptional, translational, and post-translational levels. Although our mechanistic knowledge on the regulation of lncRNAs is still limited, one of the mechanisms of action attributed is binding and regulating transcription factors, thus controlling gene expression and protein function. One such transcription factor is nuclear factor erythroid 2-related factor 2 (Nrf2), which plays a critical biological role in maintaining cellular homeostasis at multiple levels in physiological and pathophysiological conditions. The levels of Nrf2 were found to be down-regulated in many chronic diseases, signifying that Nrf2 can be a key therapeutic target. Few lncRNAs like lncRNA ROR, ENSMUST00000125413, lncRNA ODRUL, Nrf2-lncRNA have been associated with the Nrf2 signaling pathway in response to various stimuli, including stress. This review discusses the regulation of Nrf2 in different responses and the potential role of specific lncRNA in modulating its transcriptional activities. This review further helps to enhance our knowledge on the regulatory role of the critical antioxidant transcription factor, Nrf2.

Pterostilbene Alleviates Aβ1-42 -Induced Cognitive Dysfunction via Inhibition of Oxidative Stress by Activating Nrf2 Signaling Pathway

SCOPE

In the present study, effect of pterostilbene on β-amyloid 1-42 (Aβ_1-42 ) induced cognitive impairment in mice is investigated and explored its possible mechanism of action.

METHODS AND RESULTS

The behavior results show that pterostilbene alleviated Aβ_1-42 -induces cognitive dysfunction assessed using the Y-maze test, novel object recognition task, Morris water maze test, and passive avoidance test. Pterostilbene alleviates neuron loss and accumulation of reactive oxygen species in Aβ_1-42 treated mouse brain. Additionally, pterostilbene promotes nuclear factor-E2 p45-related factor 2 (Nrf2) nuclear translocation and enhance the transcription and expression of antioxidant genes such as heme oxygenase-1 and superoxide dismutase both in vivo and in vitro. Nrf2 inhibitor ML385 reverses the antioxidant function of pterostilbene in SH-SY5Y cells. Nrf2 is the master regulator of oxidative homeostasis and can be activated by substrate adaptor sequestosome-1 (also named p62). Pterostilbene promotes the binding of Kelch-like ECH-associated protein 1 and p62, which enhanced activation of Nrf2.

CONCLUSION

The present study reports that pterostilbene alleviated Aβ_1-42 -induces cognitive dysfunction in mice. The mechanism of pterostilbene can be associated to the inhibition of oxidative stress through the Nrf2 signaling pathway.

Recent Advances in Synthesis, Bioactivity, and Pharmacokinetics of Pterostilbene, an Important Analog of Resveratrol

Pterostilbene is a natural 3,5-dimethoxy analog of resveratrol. This stilbene compound has a strong bioactivity and exists widely in Dalbergia and Vaccinium spp. Besides natural extraction, pterostilbene can be obtained by biosynthesis. Pterostilbene has become popular because of its remarkable pharmacological activities, such as anti-tumor, anti-oxidation, anti-inflammation, and neuroprotection. Pterostilbene can be rapidly absorbed and is widely distributed in tissues, but it does not seriously accumulate in the body. Pterostilbene can easily pass through the blood-brain barrier because of its low molecular weight and good liposolubility. In this review, the studies performed in the last three years on resources, synthesis, bioactivity, and pharmacokinetics of pterostilbene are summarized. This review focuses on the effects of pterostilbene on certain diseases to explore its targets, explain the possible mechanism, and look for potential therapeutic applications.

Vitexin restores pancreatic β-cell function and insulin signaling through Nrf2 and NF-κB signaling pathways

Chronic hyperglycemia induces pancreatic β-cell dysfunction through several cell signaling pathways. The β-cell loss by apoptosis appears to play a crucial role in the onset and progression of diabetes. This study was aimed to investigate the role of vitexin against high glucose-induced β-cells apoptosis and the underlying mechanisms involved therein. INS-1 cells were pretreated with vitexin (20 and 40 μM) followed by high glucose (33 mM) exposure and the cytotoxicity was assessed by MTT. The effect of vitexin on nuclear factor erythroid 2-related factor 2 (Nrf2) and NF-kB signaling molecules have been studied. Vitexin-mediated stimulation of Nrf2 was assessed. Vitexin protected the cells against high glucose toxicity in a concentration-dependent manner. Vitexin improved insulin signaling as analyzed by the levels of functional proteins in the insulin pathways, viz., insulin receptor (IR), insulin receptor substrate (IRS)-1 and IRS-2, glucose transporter -2, and glucose-stimulated insulin secretion. Vitexin improved the high glucose-induced nuclear transcription factor system by suppressing Rel A, Rel B, P50/p105, and IκB expression resulting in decreased cell apoptosis, further confirmed by the reduction in the percentage of Annexin-V positive cells. Our data suggest that vitexin improves insulin secretion by activating key proteins, including NF-κB and Nrf2 in β-cells regulating apoptosis.

Pterostilbene protects cochlea from ototoxicity in streptozotocin-induced diabetic rats by inhibiting apoptosis

Diabetes mellitus (DM) causes ototoxicity by inducing oxidative stress, microangiopathy, and apoptosis in the cochlear sensory hair cells. The natural anti-oxidant pterostilbene (PTS) (trans-3,5-dimethoxy-4-hydroxystylbene) has been reported to relieve oxidative stress and apoptosis in DM, but its role in diabetic-induced ototoxicity is unclear. This study aimed to investigate the effects of dose-dependent PTS on the cochlear cells of streptozotocin (STZ)-induced diabetic rats. The study included 30 albino male Wistar rats that were randomized into five groups: non-diabetic control (Control), diabetic control (DM), and diabetic rats treated with intraperitoneal PTS at 10, 20, or 40 mg/kg/day during the four-week experimental period (DM + PTS10, DM + PTS20, and DM + PTS40). Distortion product otoacoustic emission (DPOAE) tests were performed at the beginning and end of the study. At the end of the experimental period, apoptosis in the rat cochlea was investigated using caspase-8, cytochrome-c, and terminal deoxyribonucleotidyl transferase-mediated dUTP-biotin end labeling (TUNEL). Quantitative real-time polymerase chain reaction was used to assess the mRNA expression levels of the following genes: CASP-3, BCL-associated X protein (BAX), and BCL-2. Body weight, blood glucose, serum insulin, and malondialdehyde (MDA) levels in the rat groups were evaluated. The mean DPOAE amplitude in the DM group was significantly lower than the means of the other groups (0.9–8 kHz; P < 0.001 for all). A dose-dependent increase of the mean DPOAE amplitudes was observed with PTS treatment (P < 0.05 for all). The Caspase-8 and Cytochrome-c protein expressions and the number of TUNEL-positive cells in the hair cells of the Corti organs of the DM rat group were significantly higher than those of the PTS treatment and control groups (DM > DM + PTS10 > DM + PTS20 > DM + PTS40 > Control; P < 0.05 for all). PTS treatment also reduced cell apoptosis in a dose-dependent manner by increasing the mRNA expression of the anti-apoptosis BCL2 gene and by decreasing the mRNA expressions of both the pro-apoptosis BAX gene and its effector CASP-3 and the ratio of BAX/BCL-2 in a dose-dependent manner (P < 0.05 compared to DM for all). PTS treatment significantly improved the metabolic parameters of the diabetic rats, such as body weight, blood glucose, serum insulin, and MDA levels, consistent with our other findings (P < 0.05 compared to DM for all). PTS decreased the cochlear damage caused by diabetes, as confirmed by DPOAE, biochemical, histopathological, immunohistochemical, and molecular findings. This study reports the first in vivo findings to suggest that PTS may be a protective therapeutic agent against diabetes-induced ototoxicity.

Strawberry Leaf Extract Treatment Alleviates Cognitive Impairment by Activating Nrf2/HO-1 Signaling in Rats With Streptozotocin-Induced Diabetes

Diabetes-associated cognitive impairment (DACI) is a common complication of diabetes mellitus (DM) that affects the central nervous system. Cognitive impairment, such as learning and memory impairment, and even dementia, is the main clinical manifestation of DACI. Unfortunately, there is no effective means by which to delay the cognitive symptoms of DM. Evidence has shown that strawberry leaf extract could alleviate cognitive decline, suppress oxidative stress, and reduce inflammatory responses in rats. In the present study, we evaluated the effect of strawberry leaf extract on cognitive function in a rat model of streptozotocin (STZ)-induced diabetes. After the continuous administration of strawberry leaf extract for 4 weeks, the Morris Water Maze (MWM) test results showed that the cognitive impairment of the rats was alleviated. Moreover, strawberry leaf extract significantly reduced the level of reactive oxygen species (ROS), decreased the level of malondialdehyde (MDA), improved the activity of superoxide dismutase (SOD) and catalase (CAT), decreased the mRNA expression of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) and decreased the protein expression of caspase-3 and caspase-9 in the hippocampus of DM rats. Also, transcription factor nuclear factor erythroid 2 (NF-E2)-related factor 2 (Nrf2)/hemeoxygenase-1(HO-1) signaling was activated by the administration of strawberry leaf extract. Our findings indicate that strawberry leaf extract may be a potential drug candidate for the treatment of DACI and may be used as a basis for further research on the development of drugs for cognitive impairment in diabetes.

Pharmacological activation of Nrf2 promotes wound healing

Wound repair and regeneration is a complex orchestrated process, comprising several phases interconnecting various cellular events and triggering multiple intracellular molecular pathways in damaged cells and tissues. In several metabolic disorders including diabetes mellitus, delay in wound healing due to elevated levels of cellular stress poses a key challenge. Several therapeutic wound dressing materials and strategies including hyperbaric oxygen therapy and negative pressure wound therapy have been developed to accelerate repair and restore cellular homeostasis at the wound site. Further, tremendous progress has been made in identification of transcriptional regulators involved in the process of wound healing. Nuclear factor erythroid 2-related factor 2 (Nrf2), a redox sensitive transcription factor, is the key regulator of intracellular redox homeostasis which induces the expression of cytoprotective genes and increases the production of antioxidants that scavenge free radicals. Activators of Nrf2 have been reported to combat oxidative stress and enhance the process of wound healing in several pathophysiological conditions, including diabetes and its complications such as diabetic foot ulcer, and chronic kidney disease, and diabetic nephropathy. Several bioactive compounds have been reported to reduce cellular stress, and thus accelerate cell proliferation, neovascularization results in repairing damaged tissues by the activation of the transcription factor, Nrf2. This review is focused on the strategies for diabetic wound healing and the highlights the role of bioactive compounds that activate the Nrf2 signaling and revitalize the cellular and molecular mechanism in the chronic wound niche, regulate and restore redox homeostasis thereby promoting wound repair and regeneration.

Pterostilbene Protects Against Lipopolysaccharide/D-Galactosamine-Induced Acute Liver Failure by Upregulating the Nrf2 Pathway and Inhibiting NF-κB, MAPK, and NLRP3 Inflammasome Activation

The purpose of this study was to evaluate the protective effect of pterostilbene (Psb) against lipopolysaccharide and D-galactosamine (L/D)-induced acute liver failure (ALF) in mice and its potential mechanisms. Histology of liver was detected by H&E staining. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in serum and malondialdehyde (MDA), myeloperoxidase (MPO), glutathione (GSH), and superoxide dismutase (SOD) contents in liver were examined using detection kits. The levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) secretion were detected by ELISA. Meanwhile, MAPK, NF-κB, NLRP3 inflammasome, and Nrf2 were assessed by western blotting. Our findings showed that pretreatment with Psb protected against L/D-induced ALF by lowering the lethality, improving liver histology, reducing ALT, AST, IL-6, IL-1β, TNF-α, MDA, and MPO levels, and boosting liver GSH content and SOD activity. Moreover, Psb pretreatment effectively suppressed inflammation by decreasing NLRP3 inflammasome, MAPK, and NF-κB pathway activations. Moreover, Psb pretreatment efficiently enhanced the expression of several antioxidant enzymes, mainly depending on Nrf2 activation. This was the first study to demonstrate that Psb protects against L/D-induced ALF by inactivating MAPK, NF-κb, and NLRP3 inflammasome and upregulating the Nrf2 signaling pathway, indicating a potential therapeutic application for ALF treatment.

Polysaccharide from Echinacea purpurea reduce the oxidant stress in vitro and in vivo

Echinacea purpurea polysaccharides (EPPS) were extracted through water extract and alcohol precipitate method. Three polysaccharides were purified by DEAE cellulose, named EPPS-1, EPPS-2 and EPPS-3. The antioxidant activities in three polysaccharides were screened by free radical scavenging test and EPPS-3 possessed the best antioxidant function. Then the antioxidant activities of EPPS-3 were further explored in oxidative damage model in vitro and in vivo for the first time. The results showed that the antioxidases and the metabolism content were significantly improved in EPPS-3 group. EPPS-3 could protect hepatic tissue from the injury of CCl₄ compared with the oxidative damage model. The mechanism research demonstrated that EPPS-3 restrained cell apoptosis and promoted Nrf2 cell signal pathway to play an antioxidant impact. Therefore, EPPS-3 an ingredient could be served as amazing gift for food industry and feed additive.

Pterostilbene Prevents Early Diabetic Retinopathy Alterations in a Rabbit Experimental Model

Oxidative stress generated by diabetes plays a key role in the development of diabetic retinopathy (DR), a common diabetic complication. DR remains asymptomatic until it reaches advanced stages, which complicate its treatment. Although it is known that good metabolic control is essential for preventing DR, knowledge of the disease is incomplete and an effective treatment with no side effects is lacking. Pterostilbene (Pter), a natural stilbene with good antioxidant activity, has proved to beneficially affect different pathologies, including diabetes. Therefore, our study aimed to analyse the protective and/or therapeutic capacity of Pter against oxidant damage by characterising early retinal alterations induced by hyperglycaemia, and its possible mechanism of action in a rabbit model of type 1 diabetes mellitus. Pter reduced lipid and protein oxidative damage, and recovered redox status and the main activities of antioxidant enzymes. Moreover, the redox regulation by Pter was associated with activation of the PI3K/AKT/GSK3β/NRF2 pathway. Our results show that Pter is a powerful protective agent that may delay early DR development.

The pivotal role of nuclear factor erythroid 2-related factor 2 in diabetes-induced endothelial dysfunction

Endothelial dysfunction (ED) is a key event in the onset and progression of vascular complications associated with diabetes. Regulation of endothelial function and the underlying signaling mechanisms in the progression of diabetes-induced vascular complications have been well established. Recent studies indicate that increased oxidative stress is an important determinant of endothelial injury and patients with hypertension display ED mediated by impaired Nitric Oxide (NO) availability. Further, oxidative stress is known to be associated with inflammation and ED in vascular remodeling and diabetes-associated hypertension. Numerous strategies have been developed to improve the function of endothelial cells and increasing number of evidences highlight the indispensable role of antioxidants in modulation of endothelium-dependent vasodilation responses. Nuclear factor Erythroid 2-related factor 2 (Nrf2), is the principal transcriptional regulator, that is central in mediating oxidative stress signal response. Having unequivocally established the relationship between type 2 diabetes mellitus (T2DM) and oxidative stress, the pivotal role of Nrf2/Keap1/ARE network, has taken the center stage as target for developing therapies towards maintaining the cellular redox environment. Several activators of Nrf2 are known to combat diabetes-induced ED and few are currently in clinical trials. Focusing on their therapeutic value in diabetes-induced ED, this review highlights some natural and synthetic molecules that are involved in the modulation of the Nrf2/Keap1/ARE network and its underlying molecular mechanisms in the regulation of ED. Further emphasis is also laid on the therapeutic benefits of directly up-regulating Nrf2-mediated antioxidant defences in regulating endothelial redox homeostasis for countering diabetes-induced ED.

Oxidative Stress and Microvascular Alterations in Diabetic Retinopathy: Future Therapies

Diabetes is a disease that can be treated with oral antidiabetic agents and/or insulin. However, patients' metabolic control is inadequate in a high percentage of them and a major cause of chronic diseases like diabetic retinopathy. Approximately 15% of patients have some degree of diabetic retinopathy when diabetes is first diagnosed, and most will have developed this microvascular complication after 20 years. Early diagnosis of the disease is the best tool to prevent or delay vision loss and reduce the involved costs. However, diabetic retinopathy is an asymptomatic disease and its development to advanced stages reduces the effectiveness of treatments. Today, the recommended treatment for severe nonproliferative and proliferative diabetic retinopathy is photocoagulation with an argon laser and intravitreal injections of anti-VEGF associated with, or not, focal laser for diabetic macular oedema. The use of these therapeutic approaches is severely limited, such as uncomfortable administration for patients, long-term side effects, the costs they incur, and the therapeutic effectiveness of the employed management protocols. Hence, diabetic retinopathy is the widespread diabetic eye disease and a leading cause of blindness in adults in developed countries. The growing interest in using polyphenols, e.g., resveratrol, in treatments related to oxidative stress diseases has spread to diabetic retinopathy. This review focuses on analysing the sources and effects of oxidative stress and inflammation on vascular alterations and diabetic retinopathy development. Furthermore, current and antioxidant therapies, together with new molecular targets, are postulated for diabetic retinopathy treatment.

A novel chalcone derivative exerts anti-inflammatory and anti-oxidant effects after acute lung injury

We explored the effects of compound 33, a synthetic chalcone derivative with antioxidant activity, on lipopolysaccharide (LPS)-induced acute lung injury (ALI). Compound 33, dexamethasone or vehicle was administered intragastrically to mice 6 h before intratracheal instillation of LPS. After 24 h, the effects of compound 33 on alveolar structural damage were evaluated by assessing lung morphology and the wet/dry weight ratio. Protein and proinflammatory cytokine levels and superoxide dismutase activity were also examined in the cell free supernatant of bronchoalveolar lavage fluid. Additionally, we investigated the anti-inflammatory and antioxidant activity of compound 33 in vitro and its effects on the MAPK/NF-κB and Nrf2/HO-1 pathways. Pretreatment with compound 33 prevented LPS-induced structural damage, tissue edema, protein exudation, and overproduction of proinflammatory mediators. The effects of compound 33 were similar to or greater in magnitude than those of the positive control, dexamethasone. Moreover, compound 33 exerted anti-inflammatory and antioxidant effects in vitro by inhibiting the MAPK/NF-κB pathway and activating the Nrf2/HO-1 pathway. Compound 33 may therefore be a promising candidate treatment for ALI.

Boron containing compounds promote the survival and the maintenance of pancreatic β-cells

Diabetes mellitus is worldwide disease. The life of diabetic patients are dependent on exogenous insulin. Pancreas or particularly islet transplantations are performed for reducing external insulin dependency. External substances are also used to protect the β-cells from the death or increase insulin secretion. In the current study, two different boron containing compounds (sodium pentaborate pentahydrate-NaB and boric acid-BA) were investigated for their effect on pancreatic cells in terms of pro-apoptotic and anti-apoptotic markers, genes related to insulin production mechanism, pancreatic development and glucose metabolism, some antioxidant enzymes, and genes for the initiation of diabetes, insulin secretion and antioxidant enzyme activities in vitro. The results revealed that boron containing compounds did not lead to apoptosis. On the contrary, they increased cell viability, antioxidant enzyme activities and the level of genes related to insulin production. Overall evaluation, data in the current study showed that boron containing compounds might be promising therapeutic agents for type 1 diabetes. However, additional investigations are strictly needed to elucidate molecular mechanisms of boron containing compounds.

Tissue-specific role of Nrf2 in the treatment of diabetic foot ulcers during hyperbaric oxygen therapy

Hyperbaric oxygen (HBO) therapy is proven to be very successful for diabetic foot ulcer (DFU) treatment due to its antimicrobial effect, increased angiogenesis and enhanced collagen synthesis. The molecular mechanism underlying HBO therapy particularly the involvement of Nrf2 in the wound healing process was investigated in the present study. In addition, we have studied the levels of angiogenic markers in ulcer tissues and their correlation with Nrf2 during HBO therapy compared with standard therapy (Non-HBO) for DFU. A total of 32 Patients were recruited and randomized to standard wound care procedure alone (n = 17) or HBO therapy in combination with standard wound care procedure (n = 15) for 20 days. Our results showed that the tissue levels of Nrf2 along with its downstream targets were significantly increased in patients who underwent HBO therapy when compared to Non-HBO therapy. Further, HBO therapy induced angiogenesis as assessed by increased levels of angiogenesis markers such as EGF, VEGF, PDGF, FGF-2 and CXCL10 in the tissue samples. The expressions of eNOS and nitrite concentrations were also significantly increased in HBO therapy when compared to Non-HBO therapy subjects. Moreover, HBO therapy sensitises the macrophages to release FGF-2 and EGF thereby promotes angiogenesis. Further, it increased the levels of neutrophil attractant CXCL-8 thereby promotes the release of chemokine CCL2, a well-known mediator of neovascularization. The Pearson correlation showed that Nrf2 has a positive correlation with EGF, VEGF and PDGF. In conclusion, the findings of the present study suggest that HBO therapy promotes wound healing by increasing oxygen supply and distribution to damaged tissues, stimulating angiogenesis, decreasing inflammation, and increasing the nitrite levels. Increased levels of Nrf2 transiently regulate the expression of angiogenic genes in wound biopsies, which may result in accelerated healing of chronic wounds.

Resveratrol increases stem cell function in the treatment of damaged pancreas

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

Metabolic signatures suggest o-phosphocholine to UDP-N-acetylglucosamine ratio as a potential biomarker for high-glucose and/or palmitate exposure in pancreatic β-cells

INTRODUCTION

Chronic exposure to high-glucose and free fatty acids (FFA) alone/or in combination; and the resulting gluco-, lipo- and glucolipo-toxic conditions, respectively, have been known to induce dysfunction and apoptosis of β-cells in Diabetes. The molecular mechanisms and the development of biomarkers that can be used to predict similarities and differences behind these conditions would help in easier and earlier diagnosis of Diabetes.

OBJECTIVES

This study aims to use metabolomics to gain insight into the mechanisms by which β-cells respond to excess-nutrient stress and identify associated biomarkers.

METHODS

INS-1E cells were cultured in high-glucose, palmitate alone/or in combination for 24 h to mimic gluco-, lipo- and glucolipo-toxic conditions, respectively. Biochemical and cellular experiments were performed to confirm the establishment of these conditions. To gain molecular insights, abundant metabolites were identified and quantified using ¹H-NMR.

RESULTS

No loss of cellular viability was observed in high-glucose while exposure to FFA alone/in combination with high-glucose was associated with increased ROS levels, membrane damage, lipid accumulation, and DNA double-strand breaks. Forty-nine abundant metabolites were identified and quantified using ¹H-NMR. Chemometric pair-wise analysis in glucotoxic and lipotoxic conditions, when compared with glucolipotoxic conditions, revealed partial overlap in the dysregulated metabolites; however, the dysregulation was more significant under glucolipotoxic conditions.

CONCLUSION

The current study compared gluco-, lipo- and glucolipotoxic conditions in parallel and elucidated differences in metabolic pathways that play major roles in Diabetes. o-phosphocholine and UDP-N-acetylglucosamine were identified as common dysregulated metabolites and their ratio was proposed as a potential biomarker for these conditions.

Pterostilbene Decreases Cardiac Oxidative Stress and Inflammation via Activation of AMPK/Nrf2/HO-1 Pathway in Fructose-Fed Diabetic Rats

PURPOSE

Oxidative stress has a pivotal role in the pathogenesis of diabetes-associated cardiovascular problems, which has remained a primary cause of the increased morbidity and mortality in diabetic patients. It is of paramount importance to prevent the diabetes-associated cardiac complications by reducing oxidative stress with the help of nutritional or pharmacological agents. Pterostilbene (PT), the primary antioxidant in blueberries, has recently gained attention for its promising health benefits in metabolic and cardiac diseases. However, the mechanism whereby PT reduces diabetic cardiac complications is currently unknown.

METHODS

Sprague-Dawley rats were fed with 65% fructose diet with or without PT (20 mg kg^-1 day^-1) for 8 weeks. Heart rate and blood pressure were measured by tail-cuff apparatus. Real-time PCR and western blot experiments were executed to quantify the expression levels of mRNA and protein, respectively.

RESULTS

Fructose-fed rats demonstrated cardiac hypertrophy, hypertension, enhanced myocardial oxidative stress, inflammation and increased NF-κB expression. Administration of PT significantly decreased cardiac hypertrophy, hypertension, oxidative stress, inflammation, NF-κB expression and NLRP3 inflammasome. We demonstrated that PT improved mitochondrial biogenesis as evidenced by increased protein expression of PGC-1α, complex III and complex V in fructose-fed diabetic rats. Further, PT increased protein expressions of AMPK, Nrf2, HO-1 in cardiac tissues, which may account for the prevention of cardiac oxidative stress and inflammation in fructose-fed rats.

CONCLUSIONS

Collectively, PT reduced cardiac oxidative stress and inflammation in diabetic rats through stimulation of AMPK/Nrf2/HO-1 signalling.