Anti-hyperlipidemic and anti-peroxidative role of pterostilbene via Nrf2 signaling in experimental diabetes

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.

Antihyperglycemic activity of 14-deoxy, 11, 12-didehydro andrographolide on streptozotocin-nicotinamide induced type 2 diabetic rats

BACKGROUND

Diabetic Mellitus is characterized by a lack or failure of insulin to bind to its target receptor or failure of the pancreas to yield insulin. This study evaluated the antihyperglycemic activity of 14-deoxy, 11, 12-didehydro andrographolide on streptozotocin-nicotinamide-induced type 2 diabetic rats. Diabetic conditions were induced by administering streptozotocin at a dosage of 45 mg/kg body weight and nicotinamide at a dosage of 110 mg/kg body weight through intraperitoneal injection.

MATERIALS AND METHODS

Diabetic-induced rats were treated with 14-deoxy, 11, 12-didehydro andrographolide concentrations between 10 and 500 mg/kg body weight. The blood glucose level and body weight of the rats were periodically examined. The pancreas was isolated and the histopathological staining was performed after making fine sections of the pancreas using a microtome. The influence of 14-deoxy, 11, 12-didehydro andrographolide on the expression level of various insulin signaling cascades was determined with q-PCR and western blotting.

RESULTS

The blood glucose level of the diabetic-induced rats was significantly (p < 0.05) higher when compared with the control group and resulted in a drop in the blood glucose level of the diabetic rats. Oral glucose level was also reduced in the treatment group and no significant reduction was noted in the untreated. The lipid profiling revealed that the atherogenic index and cholesterol ratio was increased in the diabetic group over the control group. Upregulation of the insulin cascades like IRTK and GLUT4 was observed by the q-PCR and upregulation of GLUT4 and IR-β was observed by the western blot analysis.

CONCLUSION

Overall, the finding indicates that 14-deoxy, 11, 12-didehydro andrographolide exhibited antihyperglycemic activity by modulating the expression of insulin cascades.

The association between circulatory, local pancreatic PCSK9 and type 2 diabetes mellitus: The effects of antidiabetic drugs on PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent modulator of cholesterol metabolism and plays a crucial role in the normal functioning of pancreatic islets and the progression of diabetes. Islet autocrine PCSK9 deficiency can lead to the enrichment of low-density lipoprotein (LDL) receptor (LDLR) and excessive LDL cholesterol (LDL-C) uptake, subsequently impairing the insulin secretion in β-cells. Circulatory PCSK9 levels are primarily attributed to hepatocyte secretion. Notably, anti-PCSK9 strategies proposed for individuals with hypercholesterolemia chiefly target liver-derived PCSK9; however, these anti-PCSK9 strategies have been associated with the risk of new-onset diabetes mellitus (NODM). In the current review, we highlight a new direction in PCSK9 inhibition therapy strategies: screening candidates for anti-PCSK9 from the drugs used in type 2 diabetes mellitus (T2DM) treatment. We explored the association between circulating, local pancreatic PCSK9 and T2DM, as well as the relationship between PCSK9 monoclonal antibodies and NODM. We discussed the emergence of artificial and natural drugs in recent years, exhibiting dual benefits of antidiabetic activity and PCSK9 reduction, confirming that the diverse effects of these drugs may potentially impact the progression of diabetes and associated disorders, thereby introducing novel avenues and methodologies to enhance disease prognosis.

Toxicological and histopathological alterations in the heart of young and adult albino rats exposed to mosquito coil smoke

Mosquito coil repellents are well-known indoor air pollutant with significant health concerns. The present study investigated the toxic effects of mosquito coil smoke on the heart of young and adult male rats. The animals were subjected to the smoke for 6 h/day, 6 days/week, for 4 weeks. Within the first hour after lighting the coil, significant amounts of formaldehyde, total volatile organic compounds, and particulate matter (PM2.5 and PM10) were detected. Both exposed ages, particularly the young group, showed a significant increase in the activities of serum aspartate aminotransferase, lactate dehydrogenase, creatine kinase-MB, and the levels of troponin I, myoglobin, Na+ levels, lipid profile, and inflammatory markers (interleukin-6 and C-reactive protein) as well as a significant decrease in K+ levels and cardiac Na-K ATPase activity, indicating development of cardiac inflammation and dysfunction. Furthermore, the toxic stress response was validated by significant downregulation at expression of the detoxifying enzyme cytochrome p450. Histopathological studies in both age groups, especially the young group, revealed cardiomyocyte degeneration and necrotic areas. Moreover, upregulation at the pro-apoptotic markers, caspase3, P53, and cytochrome C expressions, was detected by immunohistochemical approach in heart sections of the exposed groups. Finally, the myocardial dysfunctional effects of the coil active ingredient, meperfluthrin, were confirmed by the docking results which indicated a high binding affinity of meperfluthrin, with Na-K ATPase and caspase 3. In conclusion, both the young and adult exposed groups experienced significant cardiac toxicity changes evidenced by cell apoptosis and histopathological alterations as well as disruption of biochemical indicators.

Potential Chemopreventive Role of Pterostilbene in Its Modulation of the Apoptosis Pathway

Cancer incidence keeps increasing every year around the world and is one of the leading causes of death worldwide. Cancer has imposed a major burden on the human population, including the deterioration of physical and mental health as well as economic or financial loss among cancer patients. Conventional cancer treatments including chemotherapy, surgery, and radiotherapy have improved the mortality rate. However, conventional treatments have many challenges; for example, drug resistance, side effects, and cancer recurrence. Chemoprevention is one of the promising interventions to reduce the burden of cancer together with cancer treatments and early detection. Pterostilbene is a natural chemopreventive compound with various pharmacological properties such as anti-oxidant, anti-proliferative, and anti-inflammatory properties. Moreover, pterostilbene, due to its potential chemopreventive effect on inducing apoptosis in eliminating the mutated cells or preventing the progression of premalignant cells to cancerous cells, should be explored as a chemopreventive agent. Hence, in the review, we discuss the role of pterostilbene as a chemopreventive agent against various types of cancer via its modulation of the apoptosis pathway at the molecular levels.

Co-administration of exercise training and melatonin on the function of diabetic heart tissue: a systematic review and meta-analysis of rodent models

PURPOSE

Diabetes mellitus (DM), a hyperglycemic condition, occurs due to the failure of insulin secretion and resistance. This study investigated the combined effects of exercise training and melatonin (Mel) on the function of heart tissue in diabetic rodent models.

METHODS

A systematic search was conducted in Embase, ProQuest, Cochrane library, Clinicaltrial.gov, WHO, Google Scholar, PubMed, Ovid, Scopus, Web of Science, Ongoing Trials Registers, and Conference Proceedings in July 2022 with no limit of date or language. All trials associated with the effect of Mel and exercise in diabetic rodent models were included. Of the 962 relevant publications, 58 studies met our inclusion criteria as follows; Mel and type 1 DM (16 studies), Mel and type 2 DM (6 studies), exercise and type 1 DM (24 studies), and exercise and type 2 DM (12 studies). Meta-analysis of the data was done using the Mantel Haenszel method.

RESULTS

In most of these studies, antioxidant status and oxidative stress, inflammatory response, apoptosis rate, lipid profiles, and glucose levels were monitored in diabetic heart tissue. According to our findings, both Mel and exercise can improve antioxidant capacity by activating antioxidant enzymes compared to the control diabetic groups (p < 0.05). The levels of pro-inflammatory cytokines, especially TNF-α were reduced in diabetic rodents after being treated with Mel and exercise. Apoptotic changes were diminished in diabetic rodents subjected to the Mel regime and exercise in which p53 levels and the activity of Caspases reached near normal levels (p < 0.05). Based on the data, both Mel and exercise can change the lipid profile in diabetic rodents, especially rats, and close it to near-to-control levels.

CONCLUSION

These data showed that exercise and Mel can reduce the harmful effects of diabetic conditions on the heart through the regulation of lipid profile, antioxidant capacity, apoptosis, and inflammation.

Subacute oral toxicology and toxicokinetics of pterostilbene, a novel Top1/Tdp1 inhibiting anti-tumor reagent

This study evaluated the subacute toxicity and toxicokinetics of a potential anti-cancer drug candidate, pterostilbene, in rats. Animals were orally administered at two repeated doses of 200 and 500 mg/kg for 28 days. No mortality was observed during the 28 days of continuous administration of pterostilbene. Body weight and food consumption in each group increased steadily, while no significant difference was found. Liver weight in the 500 mg/kg female, but not male group increased with mild cytoplasmic vacuoles observed in histopathological study. Toxicokinetics was assessed by measuring plasma concentrations of pterostilbene on the first and 28th day of administration using UPLC-MS/MS. Toxicokinetic parameters showed that AUC_0-t significantly increased in all animals, while the increase in females was greater than males. System exposure of pterostilbene appeared to be linear within the administrated dose range. In conclusion, our findings suggested a minimal subacute toxicity profile of pterostilbene, which could strongly support further development of this compound as a novel anti-cancer agent.

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.

Antiretroviral Therapy-Induced Dysregulation of Gene Expression and Lipid Metabolism in HIV+ Patients: Beneficial Role of Antioxidant Phytochemicals

Human immunodeficiency virus (HIV) infection has continued to be the subject of study since its discovery nearly 40 years ago. Significant advances in research and intake of antiretroviral therapy (ART) have slowed the progression and appearance of the disease symptoms and the incidence of concomitant diseases, which are the leading cause of death in HIV+ persons. However, the prolongation of ART is closely related to chronic degenerative diseases and pathologies caused by oxidative stress (OS) and alterations in lipid metabolism (increased cholesterol levels), both of which are conditions of ART. Therefore, recent research focuses on using natural therapies to diminish the effects of ART and HIV infection: regulating lipid metabolism and reducing OS status. The present review summarizes current information on OS and cholesterol metabolism in HIV+ persons and how the consumption of certain phytochemicals can modulate these. For this purpose, MEDLINE and SCOPUS databases were consulted to identify publications investigating HIV disease and natural therapies and their associated effects.

Fatty acid synthase inhibition ameliorates diabetes induced liver injury in rodent experimental model

The abnormal dietary life style leads to hyperlipidemia and insulin resistance with ectopic lipid accumulation and elevated levels of hepatic glucose development which are the underlying pathological characteristics of fatty liver diseases. The pharmacological inhibition of fatty acid synthase of de novo lipogenesis may regulate the dysfunctional lipid biotransformation and reverse the pathological state of diabetic liver injury. The three pharmacological interventions (PTS; Pterostilbene, ARB; Arbutin, PUR; Purpurin) were administered to manage the condition of diabetic liver injury against the high fat diet (HFD) + Streptozotocin (STZ) 30 mg/kg b.wt. rodent animal model to observe the effect of abnormal fatty acid synthesis. The qRT-PCR was used to evaluate the fatty acid synthase (FASN) expression which is independently allied with diabetes associated fatty liver disorders. To determine the therapeutic potential of three selected drugs, the biochemical parameters and histopathological considerations were utilized. Three subsequent dosage of PTS, ARB and PUR administered (i.e., 30,60 & 120 mg/kg/p.o.) for five weeks significantly alter the serum parameters, oxidative burden in HFD-STZ which, in turn, resulted in diabetic liver injury. It was also revealed that increased mRNA expression of fatty acid synthase (FASN), which is known to promote abnormal fatty acid synthesis through different molecular signaling pathways, was associated with the development of diabetes associated liver injury, this expression was observed to be significantly suppressed by PTS, ARB and PUR treatment. Moreover, the studies of histopathology showed that there was substantial structural improvement after PTS, ARB and PUR treatment. All three selected drugs have been shown to be effective for Diabetic liver injury (DLI) care but PTS shows impressive results compared to other selected drugs.

Pterostilbene prevents methylglyoxal-induced cytotoxicity in endothelial cells by regulating glyoxalase, oxidative stress and apoptosis

Methylglyoxal (MGO), a cytotoxic byproduct of glycolysis in biological systems, can induce endothelial cells dysfunction, implicated in diabetic vascular complications. Pterostilbene (PTS), a naturally occurring resveratrol derivative, is involved in various pharmacological activities. This study aimed to explore the effects of PTS on MGO induced cytotoxicity in human umbilical vein endothelial cells (HUVECs) and the underlying mechanisms for the first time. In the current study, it has been demonstrated that PTS could enhance the level of glyoxalase 1 (GLO-1) and elevate glutathione (GSH) content to active the glyoxalase system, resulting in elimination of the toxic MGO as well as advanced glycation end products (AGEs) in HUVECs. Meanwhile, PTS could also suppress oxidative stress and thus exert cytoprotective effects by elevating Nrf2 nuclear translocation and the corresponding down-stream antioxidant enzymes in MGO induced HUVECs. In addition, PTS could alleviate MGO induced apoptosis in HUVECs via inhibition of oxidative stress and associated downstream mitochondria-dependent signaling apoptotic cascades, as characterized by preventing caspases family activation. Taken together, these findings suggest that PTS could protect against MGO induced endothelial cell cytotoxicity by regulating glyoxalase, oxidative stress and apoptosis, suggesting that PTS could be beneficial in the treatment of diabetic vascular complications.

Melatonin protects the heart and pancreas by improving glucose homeostasis, oxidative stress, inflammation and apoptosis in T2DM-induced rats

Cardiomyopathy and pancreatic injury are health issues associated with type 2 diabetes mellitus (T2DM) and are characterized by elevated oxidative stress, inflammation and apoptosis. Melatonin (MLT) is a hormone with multifunctional antioxidant activity. The protective effects of MLT on the heart and pancreas during the early development of diabetic cardiomyopathy and pancreatic injury were investigated in male Wistar rats with T2DM. MLT (10 mg/kg) was administered daily by gavage for 15 days after diabetic induction. Treatment of diabetic rats with MLT significantly normalized the levels of serum glucose, HbA1-c, and the lipid profile and improved the insulin levels and insulin resistance compared with diabetic rats, affirming its antidiabetic effect. MLT significantly prevented the development of oxidative stress and sustained the levels of glutathione and glutathione peroxidase activity in the heart and pancreas of diabetic animals, indicating its antioxidant capacity. Additionally, MLT prevented the increase in proinflammatory cytokines and expression of Bax, caspase-3 and P53. Furthermore, MLT enhanced the anti-inflammatory cytokine IL-10 and antiapoptotic protein Bcl-2. MLT controlled the levels of troponin T and creatine kinase-MB and lactate dehydrogenase activity, indicating its anti-inflammatory and antiapoptotic effects. Histological examinations confirmed the protective effects of MLT on T2DM-induced injury in the myocardium, pancreas and islets of Langerhans. In conclusion, the protective effects of melatonin on the heart and pancreas during the early development of T2DM are attributed to its antihyperglycemic, antilipidemic and antioxidant influences as well as its remarkable anti-inflammatory and antiapoptotic properties.

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.

Molecular basis for drug repurposing to study the interface of the S protein in SARS-CoV-2 and human ACE2 through docking, characterization, and molecular dynamics for natural drug candidates

A novel coronavirus (SARS-CoV-2) identified in Wuhan state of China in 2019 is the causative agent of deadly disease COVID-19. It has spread across the globe (more than 210 countries) within a short period. Coronaviruses pose serious health threats to both humans and animals. A recent publication reported an experimental 3D complex structure of the S protein of SARS-CoV-2 showed that the ectodomain of the SARS-CoV-2 S protein binds to the peptidase domain (PD) of human ACE2 with a dissociation constant (Kd) of ~ 15 nM. In this study, we focused on inhibitors for ACE2: S protein complex using virtual screening and inhibition studies through molecular docking for over 200,000 natural compounds. Toxicity analysis was also performed for the best hits, and the final complex structures for four complexes were subjected to 400 ns molecular dynamics simulations for stability testing. We found two natural origin inhibitors for the S protein: human ACE2 complex (Andrographolide and Pterostilbene) which displayed better inhibition potential for ACE2 receptor and its binding with the S protein of SARS-CoV-2. Comparative studies were also performed to test and verify that these two drug candidates are also better than hydroxychloroquine which is known to inhibit this complex. However, we needed better potential drug candidates to overcome the side effects of hydroxychloroquine. Supplementary experimental studies need to be carried forward to corroborate the viability of these two new inhibitors for ACE2: S protein complex so as to curb down COVID-19.

In vitro targeted screening and molecular docking of stilbene, quinones, and flavonoid on 3T3-L1 pre-adipocytes for anti-adipogenic actions

In metabolic disorders like obesity, NAFLD and T2DM, adipocytes are dysfunctional. Hence, pharmacological interventions have importance in preventing differentiation of adipocytes and stimulating lipid uptake. We, therefore, investigated the effects of arbutin (ARB), purpurin (PUR), quercetin (QR), and pterostilbene (PTS) on adipocyte differentiation and lipid uptake using 3T3-L1 adipocytes. Further, in silico docking studies were achieved to investigate interactions of ARB, PUR, QR, and PTS with beta-ketoacyl reductase (KR) and thioesterase (TE) domains of fatty acid synthase (FAS) enzyme. Mature 3T3-L1 adipocytes were used to investigate the anti-adipogenic effect of selected pharmacological agents by Oil Red O staining and in vitro fatty acid uptake analysis. Molecular docking studies were performed to predict the binding interactions of selected compounds with KR and TE domains of FAS enzyme. All these agents significantly decrease the adipocyte differentiation and showed the stimulatory effect on fatty acid uptake in 3T3-L1 adipocytes. However, PTS and PUR proved to be anti-adipogenic, whereas ARB and QR showed significant effect on fatty acid uptake, compared to others. Similarly, all the compounds displayed significant binding interactions with KR and TE domains of FAS enzyme, supporting the results of in vitro studies. Graphical abstract.

Protective effects of natural compounds against oxidative stress in ischemic diseases and cancers via activating the Nrf2 signaling pathway: A mini review

Oxidative stress, an imbalance between reactive oxygen species and antioxidants, has been seen in the pathological states of many disorders such as ischemic diseases and cancers. Many natural compounds (NCs) have long been recognized to ameliorate oxidative stress due to their inherent antioxidant activities. The modulation of oxidative stress by NCs via activating the Nrf2 signaling pathway is summarized in the review. Three NCs, ursolic acid, betulinic acid, and curcumin, and the mechanisms of their cytoprotective effects are investigated in myocardial ischemia, cerebral ischemia, skin cancer, and prostate cancer. To promote the therapeutic performance of NCs with poor water solubility, the formulation approach, such as the nano drug delivery system, is elaborated as well in this review.

In silico virtual screening, characterization, docking and molecular dynamics studies of crucial SARS-CoV-2 proteins

The ongoing pandemic COVID-19 (COrona Virus Immuno Deficiency-2019) which is caused by SARS-CoV-2 (Severe Acute Respiratory Syndrome–CoronaVirus-2) has emerged as a pandemic with 400,000 plus deaths till date. We do not have any drug or vaccine available for the inhibition of this deadly virus. The expedition for searching a potential drug or vaccine against COVID-19 will be of massive potential and favor. This study is focused on finding an effective natural origin compound which can put a check on the activity of this virus. We chose important proteins from the SARS-CoV-2 genome such as NSP4, NSP15 and RdRp along-with the human ACE2 receptor which is the first point of contact with the virus. Virtual screening and followed up molecular docking resulted in Baicalin and Limonin as the final lead molecules. 200 ns of MD simulation for each protein-ligand complex provides the insights that Baicalin has a potential to target NSP4, NSP15 and RdRp proteins. Limonin which is largely used in traditional Indian medicine system is found to inhibit the human ACE2 receptor (making it inefficient in binding to the receptor binding domain of SARS-CoV-2). Our studies propose Baicalin and Limonin in combination to be studied in vitro and in vivo against COVID-19.

Communicated by Ramaswamy H. Sarma

Artesunate inhibits atherosclerosis by upregulating vascular smooth muscle cells-derived LPL expression via the KLF2/NRF2/TCF7L2 pathway

Lipoprotein lipase (LPL) plays a central role in hydrolyzing triglyceride and its deficiency leads to atherosclerosis. Artesunate (ART), a derivative of artemisinin, has been demonstrated that ART reduces the formation of atherosclerotic plaques. However, it remains unclear whether ART-alleviated atherosclerotic lesion is involved in regulating lipid metabolism. ApoE^-/- mice were fed a high-fat diet to form atherosclerotic plaques and then injected with artesunate or not. Oil Red O, HE and Masson staining were performed to assess atherosclerotic plaques. Both Western blot and qRT-PCR were applied to detect protein expression. The Luciferase reporter gene and Chromatin immunoprecipitation assays were used to assess the interaction between proteins. Immunofluorescence assay was performed to show the localization of target proteins. In vitro, our data shown that ART increased LPL expression and inhibition of NRF2 blocked the binding of TCF7L2 to LPL promoter region in VSMCs. Downregulated Klf2 could decrease the nuclear enrichment of NRF2, TCF7L2 and LPL expression. In vivo, ART decreased atherosclerotic plaque formation and increased VSMC counts and LPL expression within atherosclerotic plaques. We observed the reduced tendency of serum lipids, and increased in serum LPL activity in mice. In support of vitro data, the markedly increased KLF2, TCF7L2 and LPL expression have been detected in aorta. Our study suggests that ART may be a novel therapeutic drug for inhibition of atherosclerotic plaque formation. The molecular mechanism may involve in upregulation of LPL expression via the KLF2/NRF2/TCF7L2 pathway in VSMCs.

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.

Comparison of the protective effects of resveratrol and pterostilbene against intestinal damage and redox imbalance in weanling piglets

BACKGROUND

Evidence indicates that early weaning predisposes piglets to intestinal oxidative stress and increases the risk of intestinal dysfunction; however, there are minimal satisfactory treatment strategies for these conditions. This study investigated the potential of resveratrol and its analog, pterostilbene, as antioxidant protectants for regulating intestinal morphology, barrier function, and redox status among weanling piglets.

METHODS

A total of 144 piglets were selected at 21 days of age and randomly allocated into one of four treatment groups, each of which included six replicates. Piglets in a sow-reared control group were suckling normally between ages 21 and 28 days, while those in weaned groups were fed a basal diet, supplemented with either 300 mg/kg of resveratrol or with 300 mg/kg of pterostilbene. Parameters associated with intestinal injury and redox status were analyzed at the end of the feeding trial.

RESULTS

Early weaning disrupted the intestinal function of young piglets, with evidence of increased diamine oxidase activity and D-lactate content in the plasma, shorter villi, an imbalance between cell proliferation and apoptosis, an impaired antioxidant defense system, and severe oxidative damage in the jejunum relative to suckling piglets. Feeding piglets with a resveratrol-supplemented diet partially increased villus height (P = 0.056) and tended to diminish apoptotic cell numbers (P = 0.084) in the jejunum compared with those fed a basal diet. Similarly, these beneficial effects were observed in the pterostilbene-fed piglets. Pterostilbene improved the feed efficiency of weanling piglets between the ages of 21 and 28 days; it also resulted in diminished plasma diamine oxidase activity and D-lactate content relative to untreated weaned piglets (P < 0.05). Notably, pterostilbene restored jejunal antioxidant capacity, an effect that was nearly absent in the resveratrol-fed piglets. Pterostilbene reduced the malondialdehyde and 8-hydroxy-2´-deoxyguanosine contents of jejunal mucosa possibly through its regulatory role in facilitating the nuclear translocation of nuclear factor erythroid-2-related factor 2 and the expression levels of NAD(P)H quinone dehydrogenase 1 and superoxide dismutase 2 (P < 0.05).

CONCLUSIONS

The results indicate that pterostilbene may be more effective than its parent compound in alleviating early weaning-induced intestinal damage and redox imbalance among young piglets.

Stilbene-based natural compounds as promising drug candidates against COVID-19

The pandemic coronavirus disease (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents a great threat to public health. Currently, no potent medicine is available to treat COVID-19. Quest for new drugs especially from natural plant sources is an area of immense potential. The current study aimed to repurpose stilbenoid analogs, reported for some other biological activities, against SARS-CoV-2 spike protein and human ACE2 receptor complex for their affinity and stability using molecular dynamics simulation and binding free energy analysis based on molecular docking. Four compounds in total were probed for their binding affinity using molecular docking. All of the compounds showed good affinity (> -7 kcal/mol). However, fifty nanoseconds molecular dynamic simulation in aqueous solution revealed highly stable bound conformation of resveratrol to the viral protein: ACE2 receptor complex. Net free energy of binding using MM-PBSA also affirmed the stability of the resveratrol-protein complex. Based on the results, we report that stilbene based compounds in general and resveratrol, in particular, can be promising anti-COVID-19 drug candidates acting through disruption of the spike protein. Our findings in this study are promising and call for further in vitro and in vivo testing of stiblenoids, especially resveratrol against the COVID-19. [Formula: see text] Communicated by Ramaswamy H. SarmaHighlightsStilbenoid analogs could be potential disruptors of SARS-CoV-2 spike protein and human ACE2 receptor complex.In particular, resveratrol revealed highly stable conformation to the viral protein: ACE2 receptor complex.The strong interaction of resveratrol is affirmed by molecular dynamic simulation studies and better net free energies.

Pterostilbene Improves Hepatic Lipid Accumulation via the MiR-34a/Sirt1/SREBP-1 Pathway in Fructose-Fed Rats

High fructose intake promotes hepatic lipid accumulation. Pterostilbene, a natural analogue of resveratrol found in diet berries, exhibits a hepatoprotective property. Here, we studied the protection by pterostilbene against fructose-induced hepatic lipid accumulation and explored its possible mechanism. We observed a high expression of microRNA-34a (miR-34a, P < 0.05) and a low expression of its target, sirtuin1 (Sirt1, mRNA: P < 0.01; protein: P < 0.001), with the overactivation of downstream sterol regulatory element-binding protein-1 (SREBP-1) lipogenic pathway (nuclear SREBP-1 protein: P < 0.05; FAS and SCD1 mRNA: P < 0.01), in rat livers, as well as BRL-3A and HepG2 cells, stimulated by fructose. More interestingly, pterostilbene recovered the fructose-disturbed miR-34a expression (0.3-0.5-fold vs fructose control, P < 0.05), Sirt1 protein level (1.2- to 1.5-fold vs fructose control, P < 0.05), and SREBP-1 lipogenic pathway, resulting in significant amelioration of hepatocyte lipid accumulation in animal [hepatic triglyceride and total cholesterol (TG&TC) mg/g·wet tissue: 4.90 ± 0.19, 5.23 ± 0.16, 5.20 ± 0.29 vs fructose control 9.73 ± 1.06, P < 0.001; 3.18 ± 0.30, 3.31 ± 0.39, 3.37 ± 0.47 vs 5.67 ± 0.28, P < 0.001] and cell models (BRL-3A TG&TC mmol/g·protein: 0.123 ± 0.011 vs 0.177 ± 0.004, P < 0.001; 0.169 ± 0.011 vs 0.202 ± 0.008, P < 0.05; HepG2: 0.257 ± 0.005 vs 0.303 ± 0.016, P < 0.05; 0.143 ± 0.004 vs 0.201 ± 0.008, P < 0.001). These results provide the experimental evidence supporting the anti-lipogenic effect of pterostilbene against fructose-induced hepatic lipid accumulation via modulating the miR-34a/Sirt1/SREBP-1 pathway.

Antioxidative and Hypoglycemic Effect of Ta-ermi Extracts on Streptozotocin-Induced Diabetes

INTRODUCTION

The purpose of the present study was to reveal the potential positive effect of the Ta-ermi extracts on oxidative stress and streptozotocin (STZ)-diabetic mice and rats treated with Ta-ermi water- and alcohol-extracts.

METHODS

The study was carried out using three experimental model: 1) in vitro experiments whereby Ta-ermi extracts were incubated with free radical generators such as 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) to evaluate Ta-ermi's antioxidant effects; 2) testing the hypoglycemic effects of Ta-ermi extracts in streptozotocin (STZ)-induced diabetic mice; and 3) testing the beneficial effects of Ta-ermi extracts on mitochondrial complex I function using STZ-diabetic rats.

RESULTS

In vitro antioxidant experiments showed that both of the extracts could scavenge free radicals and exhibited inhibitory effects on glucosidase and aldose reductase with differential effects between water extract and alcohol extract. In the STZ mouse diabetic model, both the water- and alcohol-extracts attenuated body weight decrease, decreased blood glucose levels in a concentration-dependent manner, improved insulin sensitivity, and increased oral glucose tolerance ability. In the STZ-diabetic rat model, both the water- and alcohol-extracts were found to be able to lower blood glucose levels in the diabetic animals with no effects on body weight changes. Moreover, in the STZ-diabetic rats, both the water- and alcohol-extracts of Ta-ermi could inhibit the increase of mitochondrial NADH/ubiquinone oxidoreductase (complex I) activity in the pancreas and enhanced complex I activity in the liver but showed no effect on lung or kidney mitochondrial complex I.

DISCUSSION

The present study points to the potential medicinal value of Ta-ermi's water and alcohol extracts in lowering blood glucose and decreasing diabetic oxidative stress. One limitation of our study is that the compound or compounds that actually have this beneficial effect in the extracts remain unknown at this time. Therefore, the future studies should be focused on the identification of the components in the extracts that exhibit anti-oxidative and hypoglycemic effects.

CONCLUSION

Taken together, our studies using different experimental paradigms indicate that Ta-ermi extracts possess antioxidant and anti-diabetic properties and may be employed as functional food ingredients for the remission of diabetes.

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.

Antidiabetic effects of pterostilbene through PI3K/Akt signal pathway in high fat diet and STZ-induced diabetic rats

Pterostilbene (PTE) is a natural dimethylated analog of resveratrol, which exerts antioxidative, hypolipidemic and hypoglycemic effects; however, the underlying mechanism is not yet clear. In this study, we evaluated the effects of PTE on diabetic rats and clarified the underlying mechanism. Diabetes was induced in rats by streptozotocin (STZ) and a high-sugar and high-fat diet. Rats were then treated with PTE (20, 40 and 80 mg/kg/d) for 8 weeks. Oral glucose tolerance test (OGTT) was performed to measure the glycometabolism of the diabetic rats at the end of the treatment. Fasting blood glucose (FBG), fasting insulin (FINS) and lipid profile were determined using an automatic biochemistry analyzer and serum inflammatory factors were analyzed by enzyme-linked immunosorbent assay. Serum superoxide dismutase (SOD) and malondialdehyde (MDA) were also analyzed by spectrophotometry to evaluate the anti-oxidant effects. The expression of proteins of PPARγ and PI3K/Akt signaling pathway related proteins in adipose tissue of the diabetic rats was analyzed by Western blotting. PTE treatment significantly reduced weight loss, FBG, insulin resistance, serum lipid levels and inflammatory factors. PTE treatment also inhibited oxidative stress by decreasing MDA expression and increasing SOD expression. Simultaneously, PTE treatment significantly ameliorated morphological impairment of the pancreas in diabetic rats. Furthermore, PTE treatment significantly increased the protein expression of PPARγ, PI3K, p-Akt, GLUT4 and IRS-1 in adipose tissues of diabetic rats. This study suggests that PTE can exert antidiabetic effects via the PI3K/Akt signaling pathway.

Pterostilbene prevents hepatocyte epithelial-mesenchymal transition in fructose-induced liver fibrosis through suppressing miR-34a/Sirt1/p53 and TGF-β1/Smads signalling

BACKGROUND AND PURPOSE

Excessive fructose consumption is a risk factor for liver fibrosis. Pterostilbene protects against liver fibrosis. Here, we investigated the potential role and the mechanisms underlying the hepatocyte epithelial-mesenchymal transition (EMT) in fructose-induced liver fibrosis and protection by pterostilbene.

EXPERIMENTAL APPROACH

Characteristic features of liver fibrosis in 10% fructose-fed rats and EMT in 5 mM fructose-exposed BRL-3A cells with or without pterostilbene and the change of miR-34a/Sirt1/p53 and transforming growth factor-β1 (TGF-β1)/Smads signalling were examined. MiR-34a inhibitor, miR-34a minic, or p53 siRNA were used to explore the role of miR-34a/Sirt1/p53 signalling in fructose-induced EMT and the action of pterostilbene.

KEY RESULTS

Pterostilbene prevented fructose-induced liver injury with fibrosis in rats. Fructose caused hepatocyte undergoing EMT, gaining fibroblast-specific protein 1 and vimentin, and losing E-cadherin, effects attenuated by pterostilbene. Moreover, fructose induced miR-34a overexpression in hepatocytes with down-regulated Sirt1, increased p53 and ac-p53, and activated TGF-β1/Smads signalling, whereas these disturbances were suppressed by miR-34a inhibitor. Additionally, miR-34a inhibitor and p53 siRNA prevented TGF-β1-driven hepatocyte EMT under fructose exposure. Pterostilbene down-regulated miR-34a, up-regulated Sirt1, and suppressed p53 activation and TGF-β1/Smads signalling in fructose-stimulated animals and cells but showed no additional effects with miR-34a inhibitor on miR-34a/Sirt1/p53 signalling in fructose-exposed hepatocytes.

CONCLUSIONS AND IMPLICATIONS

These results strongly suggest that activation of miR-34a/Sirt1/p53 signalling is required for fructose-induced hepatocyte EMT mediated by TGF-β1/Smads signalling, contributing to liver fibrosis in rats. Pterostilbene exhibits a protective effect against liver fibrosis at least partly through inhibiting miR-34a/Sirt1/p53 signalling activation.

Nrf2 exerts mixed inflammation and glucose metabolism regulatory effects on murine RAW264.7 macrophages

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a transcription factor that mediates a broad range of cellular antioxidative, detoxification and anti-inflammatory effects. However, the precise mechanism by which Nrf2 regulates inflammation and metabolism in macrophages remains controversial and unclear. To further clarify the roles of Nrf2 in inflammation and glucose metabolism regulation, retrovirus-mediated knockdown of Nrf2 was performed in murine RAW264.7 macrophages, and the cells were stimulated with 100 ng/mL lipopolysaccharide for 24 h for M1 activation. qPCR and western blotting results indicated that Nrf2 knockdown significantly enhanced expression of the inflammatory genes Il1a and Il1b in unstimulated macrophages and increased expression of the inflammatory genes Il1a, Il1b, Il6, Il10, Ccl2, Ccl22, and CD38 but decreased that of Tnfa and Tgfb1 in M1 macrophages. Nrf2 knockdown also significantly elevated IL6 and IL10 secretion by M1 macrophages. Western blotting showed that Nrf2 knockdown reduced iNOS protein levels in resting macrophages and enhanced CD38 protein levels in both resting and M1 macrophages. The differential regulation of these macrophage inflammation and polarization markers by Nrf2 reveals multiple roles for Nrf2 in regulating inflammation in macrophages. Moreover, Nrf2 knockdown increased the Glu4 protein level and decreased AKT and GSK3β protein phosphorylation in M1 macrophages, suggesting multiple roles for Nrf2 in regulating glucose metabolism in macrophages. Overall, our results are the first to demonstrate mixed inflammation and glucose metabolism regulatory effects of Nrf2 in macrophages that may occur independent of its classic function in redox regulation. These findings support the potential of Nrf2 as a therapeutic target for the prevention and treatment of inflammation- and obesity-associated syndromes, including diabetes and atherosclerosis.

Encapsulation of pterostilbene in nanoemulsions: influence of lipid composition on physical stability, in vitro digestion, bioaccessibility, and Caco-2 cell monolayer permeability

Nanoemulsions fabricated using medium chain triglycerides as carrier lipid are more effective for delivering pterostilbene than long chain triglycerides.

Pterostilbene alleviates hydrogen peroxide-induced oxidative stress via nuclear factor erythroid 2 like 2 pathway in mouse preimplantation embryos

Pterostilbene (PTS) in blueberries is a phytoalexin with antioxidant properties. PTS exerts strong cytoprotective effects on various cells via Nuclear Factor Erythroid 2 like 2 (NFE2L2) pathway. We evaluated the antioxidant PTS treatment in mouse preimplantation embryos. In vitro culture media were supplemented with different concentrations of PTS. Treatment of zygotes with 0.25 μM PTS improved the development of day 4 blastocysts (P < 0.05). Moreover, H₂O₂ treatment significantly increased the reactive oxygen species level and reduced the glutathione level in mouse blastocyst, whereas PTS treatment counteracted these effects. The fluorescence intensity of apoptotic positive cell was higher in the H₂O₂ group than in the PTS group. Furthermore, PTS-treated embryos significantly increased the protein expression of NFE2L2 in the nucleus and decreased Kelch-like ECH-associated protein1 (KEAP1). PTS treatment significantly increased the expression of downstream target genes involved in the NFE2L2 pathway, such as catalase (CAT), heme oxygenase1 (HMOX1), glutathione peroxidase (GPX), and superoxide dismutase (SOD); these genes confer cellular protection. In addition, PTS treatment significantly increased the expression of anti-apoptotic B-cell lymphoma 2 (BCL2), with a concomitant reduction in the apoptotic Bcl-2-associated X protein (BAX) and Caspase-3 genes in the embryo. PTS treatment also increased the protein expression of BCL2 and reduced the protein expression of BAX in the mouse embryo. In conclusion, PTS activated NFE2L2 signaling pathway in the development of mouse embryos by altering downstream expression of genes involved in the antioxidant mechanisms and apoptosis.

Activation of Nrf2 signaling by natural products-can it alleviate diabetes?

Type 2 diabetes mellitus (DM) has reached pandemic proportions and effective prevention strategies are wanted. Its onset is accompanied by cellular distress, the nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor boosting cytoprotective responses, and many phytochemicals activate Nrf2 signaling. Thus, Nrf2 activation by natural products could presumably alleviate DM. We summarize function, regulation and exogenous activation of Nrf2, as well as diabetes-linked and Nrf2-susceptible forms of cellular stress. The reported amelioration of insulin resistance, β-cell dysfunction and diabetic complications by activated Nrf2 as well as the status quo of Nrf2 in precision medicine for DM are reviewed.

Nrf2, a novel molecular target to reduce type 1 diabetes associated secondary complications: The basic considerations

Oxidative stress and inflammation are the mediators of diabetes and related secondary complications. Oxidative stress arises because of the excessive production of reactive oxygen species and diminished antioxidant production due to impaired Nrf2 activation, the master regulator of endogenous antioxidant. It has been established from various animal models that the transcription factor Nrf2 provides cytoprotection, ameliorates oxidative stress, inflammation and delays the progression of diabetes and its associated complications. Whereas, deletion of the transcription factor Nrf2 amplifies tissue level pathogenic alterations. In addition, Nrf2 also regulates the expression of numerous cellular defensive genes and protects against oxidative stress-mediated injuries in diabetes. The present review provides an overview on the role of Nrf2 in type 1 diabetes and explores if it could be a potential target for the treatment of diabetes and related complications. Further, the rationality of different agent's intervention has been discussed to mitigate organ damages induced by diabetes.

Dexpanthenol reduces diabetic nephropathy and renal oxidative stress in rats

Hyperglycemia increases reactive oxygen species (ROS) and the resulting oxidative stress contributes to the development of diabetic complications. Dexpanthenol (Dxp) is the biological active form of pantothenic acid. We investigated whether Dxp administration could decrease oxidative stress as a way to treat renal complications of diabetes mellitus (DM). Thirty-two male Wistar albino rats were divided into four groups: control, Dxp, DM and DM + Dxp. Experimental diabetes was induced by a single dose of streptozotocin (STZ). After administration of STZ, the DM + Dxp group was administered 500 mg/kg Dxp intraperitoneally every day for 6 weeks. At the end of the study, blood glucose levels were measured and rats were sacrificed. Kidneys were embedded in paraffin, sectioned and stained with hematoxylin and eosin, and periodic acid-Schiff. The mean malondialdehyde levels, glutathione peroxidase, superoxide dismutase and catalase activities, and total antioxidant and total oxidant status also were measured. The control group was normal in histological appearance. We observed congestion, inflammation, glomerulosclerosis, tubular desquamation, loss of villi and hydropic degeneration in tubule cells in the DM group. Indicators of oxidative stress were elevated and antioxidant activity was reduced in the DM group compared to controls. In the DM + Dxp group, oxidative stress was decreased, antioxidant activity was increased and histopathological changes were reduced compared to the DM group. We found that Dxp exhibited ameliorative effects on STZ induced diabetic nephropathy by increasing antioxidant activity.

Therapeutic Potential of Pterostilbene and Resveratrol on Biomechanic, Biochemical, and Histological Parameters in Streptozotocin-Induced Diabetic Rats

AIMS

The aim of this study was to investigate the effects of pterostilbene (PTS) (trans-3,5-dimethoxy-4'-hydroxystilbene) and resveratrol (RSV) (trans-3,5,4' trihydroxystilbene) applied at different doses for the treatment of streptozotocin- (STZ-) induced diabetic rats.

MATERIALS AND METHODS

At the end of the 5-week experimental period, the right gastrocnemius muscles of the rats were examined biomechanically, while the left ones were examined histologically. In addition, blood glucose, serum insulin, and malondialdehyde (MDA) levels were analyzed in blood samples taken from the rats.

RESULTS

The skeletal muscle isometric contraction forces, which showed a decrease with diabetes, were observed to increase with antioxidant applications. Blood glucose, serum insulin, and MDA levels in diabetic rats approached normal levels after applying PTS. When the electron microscopic images of the rat skeletal muscle were examined, those in the combination treatment group were observed to show a better enhancement in the skeletal muscle morphological structure compared to the other diabetic and treatment groups.

CONCLUSION

According to the findings, we suggest that these antioxidant treatments might have good therapeutic nutraceutical potential for some muscle diseases that coexist with diabetes. These treatments should be comprehensively investigated in the future.

Oxidative stress biomarkers in type 2 diabetes mellitus for assessment of cardiovascular disease risk

AIMS

Type-2 Diabetes Mellitus (T2DM) is one of the most prevalent and progressive metabolic conditions affecting approximately 8.5% of the global population. Individuals with T2DM have a significantly increased risk of developing chronic conditions such as cardiovascular disease (CVD) and its associated complications, therefore, it is of great importance to establish strategies for combatting T2DM and its associated chronic conditions. Current literature has identified several biomarkers that are known to play a key role in the pathogenesis of CVD. Many of these biomarkers affecting CVD are influenced by an increase in oxidative stress as seen in T2DM. The purpose of this review is to analyse and correlate the oxidative stress-related biomarkers that have been identified in the literature to provide an updated summary of their significance in CVD risk factors.

DATA SYNTHESIS

This review has analysed current research on T2DM, CVD, and oxidative stress. Four key cardiovascular risk factors: thrombosis, inflammation, vascular homeostasis and cellular proliferation were searched to identify potential biomarkers for this review. These biomarkers stem from seven major cellular pathways; NF-κB, Keap1-Nrf2, protein kinase-C, macrophage activation, arachidonic acid mobilisation, endothelial dysfunction and advanced glycation end products.

CONCLUSIONS

The pathways and biomarkers were analysed to show their role as contributing factors to CVD development and a summary is made regarding the assessment of cardiovascular risk in T2DM individuals.

Pterostilbene inhibits inflammation and ROS production in chondrocytes by activating Nrf2 pathway

Pterostilbene has been reported as a potential drug to inhibit oxidative stress and inflammation. However, the effect of pterostilbene on chondrocytes and osteoarthritis remains to be elucidated. We sought to investigate whether pterostilbene could protect chondrocytes from inflammation and ROS production through factor erythroid 2-related factor 2 (Nrf2) activation. The pterostilbene toxicity on chondrocytes collected from cartilages of Sprague-Dawley rats was assessed by CCK-8 test. Immunofluorescence and Western blotting explored the nuclear translocation of Nrf2. Nrf2 expression was silenced by siRNA to evaluate the involvement of Nrf2 in the effect of pterostilbene on chondrocytes. Finally, osteoarthritis model was established by the transection of anterior cruciate ligament and partial medial meniscectomy in rats, and then these rats received pterostilbene 30 mg/kg, daily, p.o. for 8 weeks. Histology and immunohistochemistry were used to assess histopathological change and Nrf2 expression in cartilage. Nuclear translocation of Nrf2 was stimulated by pterostilbene without cellular toxicity. Pterostilbene inhibited the level of COX-2, iNOS, PGE2, and NO, as well as the mitochondrial and total intracellular ROS production induced by IL-1β in chondrocytes, partially reversed by the Nrf2 silencing. Pterostilbene prevented cartilage degeneration and promoted the nuclear translocation of Nrf2 in cartilage. These results suggest that pterostilbene could inhibit the IL-1β-induced inflammation and ROS production in chondrocytes by stimulating the nuclear translocation of Nrf2.

Beneficial effects of N-acetylcysteine on hepatic oxidative stress in streptozotocin-induced diabetic rats

Diabetes is one of the leading diseases worldwide and, thus, finding new therapeutic alternatives is essential. The development of non-alcoholic fatty liver disease is a notable diabetic complication. Therefore, antioxidant therapy became a leading topic in the world of diabetes research. The objective of this present study was to evaluate the effects of antioxidant N-acetylcysteine (NAC) administration on serum biochemical parameters and oxidative stress parameters in hepatic tissue of the diabetic rats. Thirty-two animals were divided in 4 groups (n = 8): G1, normal rats; G2, normal rats + NAC; G3, diabetic rats; and G4, diabetic rats + NAC. Diabetes was induced in diabetic groups through streptozotocin. NAC administration was effective in improving hyperglycemia and hypoinsulinemia, as well as reducing serum alanine-aminotransferase and urea, hepatic triglycerides accumulation, and oxidative stress biomarkers in the diabetic liver, as well as improving the activity of hepatic antioxidant enzymes. This effect was likely due to NAC’s ability of restoring intracellular glutathione, an important compound for the antioxidant defense, as well as due to NAC’s direct antioxidant properties. Thus, NAC administration was useful for reducing hepatic oxidative stress and decreased the deposit of triacylglycerols, minimizing diabetic hepatic damage, making it a promising therapeutic adjuvant in the future.

Pterostilbene modulates the suppression of multidrug resistance protein 1 and triggers autophagic and apoptotic mechanisms in cisplatin-resistant human oral cancer CAR cells via AKT signaling

Pterostilbene is a natural polyphenolic compound that is primarily found in fruits, such as blueberries and has a similar structure to resveratrol. Pterostilbene exhibits antioxidant, anti-inflammatory and antitumor activity but the effects of pterostilbene on drug-resistant oral cancer cells and its underlying mechanisms of action have not yet been explored. Therefore, the present study was performed to clarify the anticancer effects of pterostilbene on cisplatin-resistant human oral cancer CAR cells. The results demonstrated that CAR cells exhibited marked shrinkage, cell membrane breakage and autophagic vacuole formation following treatment with pterostilbene. Pterostilbene also effectively inhibited cell viability and suppressed cell confluence in a time- and concentration-dependent manner. Probing with acridine orange, monodansylcadaverine and LysoTracker Red demonstrated that the number of acidic vesicular organelles was increased, indicating increased autophagy. Furthermore, Heochst 33342 staining determined that DNA condensation, a characteristic of apoptosis, was enhanced following treatment with pterostilbene. Furthermore, pterostilbene upregulated mRNA levels of LC3-II and Atg12, as well as the expression of Atgs/Beclin-1/LC3-associated signaling, suggesting that it enhances autophagy. The autophagy inhibitors 3-methyladenine and chloroquine were used to confirm that pterostilbene induces autophagy. It was also determined that pterostilbene triggered caspase-dependent apoptosis by directly testing DNA breakage and using the pan-caspase inhibitor carbobenzoxyvalyl-alanyl-aspartyl fluoromethyl ketone. The results demonstrated that pterostilbene mediates the apoptosis of CAR cells via the intrinsic apoptotic cascade. In addition, pterostilbene inhibited MDR1 expression and the phosphorylation of AKT on the Ser473 site in CAR cells. Therefore, pterostilbene may elicit an oral anticancer response in drug-resistant cells and may be used as a chemotherapeutic adjuvant to treat patients with oral cancer.

Effect of resveratrol and pterostilbene on aging and longevity

Over the past years, several studies have found that foods rich in polyphenols protect against age-related disease, such as atherosclerosis, cardiovascular disease, cancer, arthritis, cataracts, osteoporosis, type 2 diabetes (T2D), hypertension and Alzheimer's disease. Resveratrol and pterostilbene, the polyphenol found in grape and blueberries, have beneficial effects as anti-aging compounds through modulating the hallmarks of aging, including oxidative damage, inflammation, telomere attrition and cell senescence. In this review, we discuss the relationship between resveratrol and pterostilbene and possible aging biomarker, including oxidative stress, inflammation, and high-calorie diets. Moreover, we also discuss the positive effect of resveratrol and pterostilbene on lifespan, aged-related disease, and health maintenance. Furthermore, we summarize a variety of important mechanisms modulated by resveratrol and pterostilbene possibly involved in attenuating age-associated disorders. Overall, we describe resveratrol and pterostilbene potential for prevention or treatment of several age-related diseases by modulating age-related mechanisms. © 2017 BioFactors, 44(1):69-82, 2018.

Pterostilbene inhibits inflammation by promoting the nuclear translocation of Nrf2 in the rat nucleus pulposus

Pterostilbene (PTE), a natural plant extract, has an anti-inflammatory effect; however, whether PTE could protect nucleus pulposus cells (NPCs) in the intervertebral disk from inflammation remains unclear. Primary NPCs isolated from Sprague-Dawley (SD) rats were cultured, and Cell Counting Kit-8 (CCK-8) analysis was used to test the cytotoxicity of PTE. The effect of PTE on interleukin-1β (IL-1β)-induced inflammation was analyzed using an enzyme-linked immunosorbent assay, real-time polymerase chain reaction (PCR), and a Griess test. Western blotting, immunofluorescence, and a nuclear factor erythroid 2-related factor 2 (Nrf2) small interfering RNA (siRNA) transfection were used to assess the involvement of Nrf2 in the anti-inflammatory mechanism of PTE on NPCs. The results of the CCK-8 analysis showed that PTE produced no cytotoxicity in NPCs at 20 μM for 24 h. PTE suppressed the production of nitric oxide (NO) and prostaglandin E2 (PGE2) and inhibited the messenger RNA (mRNA) expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) induced by IL-1β. PTE could promote the nuclear translocation of Nrf2 in NPCs. In addition, Nrf2 silence reversed the inhibitory effect of PTE on the production of NO and PGE2 and the expression of COX-2 and iNOS. These results indicate that PTE inhibits inflammation in the rat nucleus pulposus by promoting the nuclear translocation of Nrf2.

Metabolism and pharmacokinetics of resveratrol and pterostilbene

Beneficial properties of resveratrol and pterostilbene, a dimethyl ether analog of resveratrol, have attracted increasing interest in recent years. Resveratrol and pterostilbene exhibit many pharmacological similarities and both of them are generally considered to be safe for human consumption. Beyond the structural and general bioactivity similarities between them, large amounts of data are now available to reveal the metabolic fate and pharmacological differences between them. Pterostilbene was found to be more metabolically stable and usually exhibited stronger pharmacological activities than that of resveratrol. As a contribution to clarify and compare aspects like metabolic stability and pharmacokinetics of resveratrol and pterostilbene, as well as explain the pharmacological similarities and differences between them, this review presents and compares recent data on the metabolism and pharmacokinetics of resveratrol and pterostilbene. © 2018 BioFactors, 44(1):16-25, 2018.

Pterostilbene attenuates myocardial ischemia-reperfusion injury via the phosphatidylinositol 3'-kinase-protein kinase B signaling pathway

The current study aimed to evaluate the cardioprotective effects of pterostilbene (PTB) on myocardial ischemia-reperfusion (I/R) injury in rats and identify its possible underlying mechanisms of action. A rat I/R model was established by ligating the left anterior descending coronary artery for 30 min and releasing the ligature to induce reperfusion for 120 min. Serum creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) levels were measured using CK-MB and LDH assay kits and myeloperoxidase (MPO) activity in the myocardium was evaluated using an MPO assay kit. Tumor necrosis factor-α, interleukin (IL)-6 and IL-8 levels were assayed using ELISA kits. Cardiomyocyte apoptosis was measured using terminal deoxynucleotidyl transferase dUTP nick end labeling staining. Levels of protein kinase B (Akt) and phosphorylated Akt (p-Akt) were measured using western blotting. The results demonstrated that treatment with PTB significantly reduced cardiomyocyte apoptosis, significantly increased Bcl-2 and p-Akt levels and decreased Bax expression in the hearts of rats subjected to I/R injury. However, the protective effects induced by PTB were attenuated by LY294002, which inhibits Akt activation. The results of the current study suggest that PTB treatment may reduce the I/R injury-induced apoptosis of cardiomyocytes, which is mediated by the phosphoinositide 3-kinase/Akt signaling pathway.

Pterostilbene suppresses human endometrial cancer cells in vitro by down-regulating miR-663b

Resveratrol has long been known as an antioxidant and a chemopreventive agent. Similar to resveratrol, pterostilbene (PT) is also a phenolic compound extracted from the Vitis species. However, there are few studies on the antitumor effect of PT. Thus, we investigated the effects of PT on the endometrial cancer (EC) cells in vitro and the related molecular mechanisms. Treatment of EC cell lines HTB-111 and Ishikawa with PT (25-100 μmol/L) dose-dependently suppressed the cell viability and induced apoptosis. Using miR microarrays, we examined the miR expression profile in Ishikawa cells with or without PT, and revealed that miR-663b was the most decreased in PT-treated Ishikawa cells. Furthermore, we predicted and verified that the pro-apoptosis factor BCL2L14 is the direct target of miR-663b. Over-expression of miR-663b and knock-down of BCL2L14 counteracted the suppressing effects of PT on HTB-111 and Ishikawa cells. In addition, we evaluated the miR-663b levels in EC tissues of 51 patients using an in situ hybridization technique. With the median of the score of miR-663b as a cut-off value, these EC patients were divided into two groups, and the patients with high miR-663b expression had significantly poor prognosis.

Pterostilbene ameliorates insulin sensitivity, glycemic control and oxidative stress in fructose-fed diabetic rats

AIMS

The present investigation was designed to explore the effectiveness of pterostilbene (PT) on insulin resistance, metabolic syndrome and oxidative stress in fructose-fed insulin resistant rats.

MAIN METHODS

Age-matched, male Sprague-Dawley rats (330±30g body weight) were allocated into five groups (n=10). Control (C) group received 65% cornstarch, and the diabetic (D) group received 65% fructose for eight weeks. The third group (D+PT20) received 65% fructose and PT 20mg/kg/day for eight weeks. The fourth group (D+PT40) received 65% fructose and PT 40mg/kg/day for eight weeks. The fifth group (D+M) received 65% fructose and metformin (M) 100mg/kg/day for eight weeks. PT was dissolved in 10% β-cyclodextrin and given orally to rats. Several biochemical parameters were determined to assess the PT efficacy against insulin resistance, metabolic complications, and hepatic oxidative stress.

KEY FINDINGS

Significantly high HOMA-IR (p<0.001) values in D group compared to C group indicate the presence of insulin resistance. Significantly high levels of TBARS (p<0.001) and decreased levels of SOD (p<0.001) and GSH (p<0.001) in hepatic tissues of D group indicate oxidative stress associated with insulin resistance. Pterostilbene treatment to fructose-fed diabetic rats significantly decreased HOMA-IR (p<0.001) values. Furthermore, PT treatment significantly decreased hepatic TBARS (p<0.001) and increased SOD (p<0.001) and GSH (p<0.001) levels in fructose-fed diabetic rats.

SIGNIFICANCE

Current study reveals that PT is successful in ameliorating glycemic control, insulin sensitivity while diminishing metabolic disturbances and hepatic oxidative stress in a fructose-induced T2DM rat model.

Nuclear factor E2-related factor 2 knockdown enhances glucose uptake and alters glucose metabolism in AML12 hepatocytes

Nuclear factor E2-related factor 2 (Nrf2) is a transcription factor known to induce the expression of a variety of antioxidant and detoxification genes. Recently, increasing evidence has revealed roles for Nrf2 in glucose, lipid, and energy metabolism; however, the exact functions of Nrf2 in hepatocyte biology are largely unclear. In the current study, the transient knockdown of Nrf2 via siRNA transfection enhanced the glucose uptake of fasting AML12 hepatocytes to 325.3 ± 11.1% ( P < 0.05) of that of untransfected control cells. The impacts of Nrf2 knockdown (NK) on the antioxidant system, inflammatory response, and glucose metabolism were then examined in AML12 cells under both high-glucose (33 mmol/L) and low-glucose (4.5 mmol/L) conditions. NK lowered the gene and protein expression of the anti-oxidases heme oxygenase-1 and NAD(P)H: quinone oxidoreductase 1 and increased p-eukaryotic initiation factor-2α^S51, p-nuclear factor-κB p65^S276, and its downstream proinflammatory factors, including interleukin-1 beta, tumor necrosis factor-α, matrix metalloproteinase 2, and matrix metalloproteinase 9, at the protein level. NK also altered the protein expression of fibroblast growth factor 21, glucose transporter type 4, insulin-like growth factor 1, forkhead box protein O1, p-AKT^S473, and p-GSK3α/β^Y279/Y216, which are involved in glucose uptake, glycogenesis, and gluconeogenesis in AML12 cells. Our results provide a comprehensive understanding of the central role of Nrf2 in the regulation of glucose metabolism in AML12 hepatocytes, in addition to its classical roles in the regulation of redox signaling, endoplasmic reticulum stress and proinflammatory responses, and support the potential of Nrf2 as a therapeutic target for the prevention and treatment of obesity and other associated metabolic syndromes. Impact statement Increasing evidence supports the complexity of Nrf2 functions beyond the antioxidant and detoxification response. Previous in vivo studies employing either Nrf2-knockout or Nrf2-activated mice have achieved a similar endpoint: protection against an obese and insulin-resistant phenotype that includes impaired lipogenesis and gluconeogenesis in the liver. These apparently paradoxical observations led us to evaluate the impact of Nrf2 in liver cells in the absence of any influence from the systemic environment, including changes in the secretion of adipokines and proinflammatory cytokines by adipose tissues. In the present study, Nrf2 knockdown was sufficient to induce fundamental changes in the glucose metabolism of AML12 hepatocytes in addition to its classical cytoprotective functions. We also discuss similarities and differences between our in vitro study and previous in vivo studies, which may be helpful to dissect and better understand in vivo data that represents the culmination of both local and systemic alterations.