Insulin is a potential antioxidant for diabetes-associated cognitive decline via regulating Nrf2 dependent antioxidant enzymes

Mechanistic Insights and Potential Therapeutic Implications of NRF2 in Diabetic Encephalopathy

Diabetic encephalopathy (DE) is a complication of diabetes, especially type 2 diabetes (T2D), characterized by damage in the central nervous system and cognitive impairment, which has gained global attention. Despite the extensive research aimed at enhancing our understanding of DE, the underlying mechanism of occurrence and development of DE has not been established. Mounting evidence has demonstrated a close correlation between DE and various factors, such as Alzheimer's disease-like pathological changes, insulin resistance, inflammation, and oxidative stress. Of interest, nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor with antioxidant properties that is crucial in maintaining redox homeostasis and regulating inflammatory responses. The activation and regulatory mechanisms of NRF2 are a relatively complex process. NRF2 is involved in the regulation of multiple metabolic pathways and confers neuroprotective functions. Multiple studies have provided evidence demonstrating the significant involvement of NRF2 as a critical transcription factor in the progression of DE. Additionally, various molecules capable of activating NRF2 expression have shown potential in ameliorating DE. Therefore, it is intriguing to consider NRF2 as a potential target for the treatment of DE. In this review, we aim to shed light on the role and the possible underlying mechanism of NRF2 in DE. Furthermore, we provide an overview of the current research landscape and address the challenges associated with using NRF2 activators as potential treatment options for DE.

Insulin-Loaded Chitosan-Cellulose-Derivative Hydrogels: In Vitro Permeation of Hormone through Strat-M® Membrane and Rheological and Textural Analysis

This work is part of the current research trend to develop a hydrogel carrier of insulin to promote wound healing. Topically applied insulin promotes keratinocyte proliferation and migration, increases collagen synthesis, reduces inflammation and oxidative stress, and exhibits antimicrobial activity. The aim of this study was to design an insulin hydrogel matrix based on selected cellulose derivatives (methylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose) and chitosan. Rheological parameters of the formulations were evaluated using rotational rheometry and an oscillation test. Textural tests were performed. In vitro pharmaceutical insulin availability studies were carried out using the innovative Strat-M® membrane to imitate the skin barrier. It was found that the pharmaceutical formulation of insulin based on chitosan and methylcellulose showed an acceptable balance between rheological and textural parameters and ease of application. The API was released from the carrier in a prolonged manner, eliminating the need to apply the formulation several times per day. The developed hydrogel shows potential for use in clinical practice.

Advancing the understanding of diabetic encephalopathy through unravelling pathogenesis and exploring future treatment perspectives

Diabetic encephalopathy (DE), a significant micro-complication of diabetes, manifests as neurochemical, structural, behavioral, and cognitive alterations. This condition is especially dangerous for the elderly because aging raises the risk of neurodegenerative disorders and cognitive impairment, both of which can be made worse by diabetes. Despite its severity, diagnosis of this disease is challenging, and there is a paucity of information on its pathogenesis. The pivotal roles of various cellular pathways, activated or influenced by hyperglycemia, insulin sensitivity, amyloid accumulation, tau hyperphosphorylation, brain vasculopathy, neuroinflammation, and oxidative stress, are widely recognized for contributing to the potential causes of diabetic encephalopathy. We also reviewed current pharmacological strategies for DE encompassing a comprehensive approach targeting metabolic dysregulations and neurological manifestations. Antioxidant-based therapies hold promise in mitigating oxidative stress-induced neuronal damage, while anti-diabetic drugs offer neuroprotective effects through diverse mechanisms, including modulation of insulin signaling pathways and neuroinflammation. Additionally, tissue engineering and nanomedicine-based approaches present innovative strategies for targeted drug delivery and regenerative therapies for DE. Despite significant progress, challenges remain in translating these therapeutic interventions into clinical practice, including long-term safety, scalability, and regulatory approval. Further research is warranted to optimize these approaches and address remaining gaps in the management of DE and associated neurodegenerative disorders.

Neuroprotective Effects of Sodium-Glucose Cotransporter-2 (SGLT2) Inhibitors (Gliflozins) on Diabetes-Induced Neurodegeneration and Neurotoxicity: A Graphical Review

Diabetes is a chronic endocrine disorder that negatively affects various body systems, including the nervous system. Diabetes can cause or exacerbate various neurological disorders, and diabetes-induced neurodegeneration can involve several mechanisms such as mitochondrial dysfunction, activation of oxidative stress, neuronal inflammation, and cell death. In recent years, the management of diabetes-induced neurodegeneration has relied on several types of drugs, including sodium-glucose cotransporter-2 (SGLT2) inhibitors, also called gliflozins. In addition to exerting powerful effects in reducing blood glucose, gliflozins have strong anti-neuro-inflammatory characteristics that function by inhibiting oxidative stress and cell death in the nervous system in diabetic subjects. This review presents the molecular pathways involved in diabetes-induced neurodegeneration and evaluates the clinical and laboratory studies investigating the neuroprotective effects of gliflozins against diabetes-induced neurodegeneration, with discussion about the contributing roles of diverse molecular pathways, such as mitochondrial dysfunction, oxidative stress, neuro-inflammation, and cell death. Several databases-including Web of Science, Scopus, PubMed, Google Scholar, and various publishers, such as Springer, Wiley, and Elsevier-were searched for keywords regarding the neuroprotective effects of gliflozins against diabetes-triggered neurodegenerative events. Additionally, anti-neuro-inflammatory, anti-oxidative stress, and anti-cell death keywords were applied to evaluate potential neuronal protection mechanisms of gliflozins in diabetes subjects. The search period considered valid peer-reviewed studies published from January 2000 to July 2023. The current body of literature suggests that gliflozins can exert neuroprotective effects against diabetes-induced neurodegenerative events and neuronal dysfunction, and these effects are mediated via activation of mitochondrial function and prevention of cell death processes, oxidative stress, and inflammation in neurons affected by diabetes. Gliflozins can confer neuroprotective properties in diabetes-triggered neurodegeneration, and these effects are mediated by inhibiting oxidative stress, inflammation, and cell death.

Elucidating PAR1 as a therapeutic target for delayed traumatic brain injury: Unveiling the PPAR-γ/Nrf2/HO-1/GPX4 axis to suppress ferroptosis and alleviate NLRP3 inflammasome activation in rats

Repetitive traumatic brain injury (RTBI) is acknowledged as a silent overlooked public health crisis, with an incomplete understanding of its pathomechanistic signaling pathways. Mounting evidence suggests the involvement of thrombin and its receptor, the protease-activated receptor (PAR)1, in the development of secondary injury in TBI; however, the consequences of PAR1 modulation and its impact on ferroptosis-redox signaling, and NLRP3 inflammasome activation in RTBI, remain unclear. Further, the utilitarian function of PAR1 as a therapeutic target in RTBI has not been elucidated. To study this crosstalk, RTBI was induced in Wistar rats by daily weight drops on the right frontal region for five days. Three groups were included: normal control, untreated RTBI, and RTBI+SCH79797 (a PAR1 inhibitor administered post-trauma at 25 μg/kg/day). The concomitant treatment of PAR1 antagonism improved altered behavior function, cortical histoarchitecture, and neuronal cell survival. Moreover, the receptor blockade downregulated mRNA expression of PAR1 but upregulatedthat of the neuroprotective receptor PPAR-γ. The anti-inflammatory impact of SCH79797 was signified by the low immune expression/levels of NF-κB p65,TNF-α, IL-1β, and IL-18. Consequently, the PAR1 blocker hindered the formation of inflammasome components NLRP3, ASC, and activated caspase-1. Ultimately, SCH79797 treatment abated ferroptosis-dependent iron redox signaling through the activation of the antioxidant Nrf2/HO-1 axis and its subsequent antioxidant machinery (GPX4, SOD) to limit lipid peroxidation, iron accumulation, and transferrin serum increment. Collectively, SCH79797 offered putative preventive mechanisms against secondary RTBI consequences in rats by impeding ferroptosis and NLRP3 inflammasome through activating the PPAR-γ/Nrf2 antioxidant cue.

Effect of recurrent severe insulin-induced hypoglycemia on the cognitive function and brain oxidative status in the rats

BACKGROUND

Episodes of recurrent or severe hypoglycemia can occur in patients with diabetes mellitus, insulinoma, neonatal hypoglycemia, and medication errors. However, little is known about the short-term and long-term effects of repeated episodes of acute severe hypoglycemia on the brain, particularly in relation to hippocampal damage and cognitive dysfunction.

METHODS

Thirty-six wistar rats were randomly assigned to either the experimental or control group. The rats were exposed to severe hypoglycemia, and assessments were conducted to evaluate oxidative stress in brain tissue, cognitive function using the Morris water maze test, as well as histopathology and immunohistochemistry studies. The clinical and histopathological evaluations were conducted in the short-term and long-term.

RESULTS

The mortality rate attributed to hypoglycemia was 34%, occurring either during hypoglycemia or within 24 h after induction. Out of the 14 rats monitored for 7 to 90 days following severe/recurrent hypoglycemia, all exhibited clinical symptoms, which mostly resolved within three days after the last hypoglycemic episode, except for three rats. Despite the decrease in catalase activity in the brain, the total antioxidant capacity following severe insulin-induced hypoglycemia increased. The histopathology findings revealed that the severity of the hippocampal damage was higher compared to the brain cortex 90 days after hypoglycemia. Memory impairments with neuron loss particularly pronounced in the dentate gyrus region of the hippocampus were observed in the rats with severe hypoglycemia. Additionally, there was an increase in reactive astrocytes indicated by GFAP immunoreactivity in the brain cortex and hippocampus.

CONCLUSION

Recurrent episodes of severe hypoglycemia can lead to high mortality rates, memory impairments, and severe histopathological changes in the brain. While many histopathological and clinical changes improved after three months, it seems that the vulnerability of the hippocampus and the development of sustained changes in the hippocampus were greater and more severe compared to the brain cortex following severe and recurrent hypoglycemia. Furthermore, it does not appear that oxidative stress plays a central role in neuronal damage following severe insulin-induced hypoglycemia. Further research is necessary to assess the consequences of repeated hypoglycemic episodes on sustained damage across various brain regions.

Inhibition of MST1 ameliorates neuronal apoptosis via GSK3β/β-TrCP/NRF2 pathway in spinal cord injury accompanied by diabetes

AIMS

Spinal cord injury (SCI) is a devastating neurological disease that often results in tremendous loss of motor function. Increasing evidence demonstrates that diabetes worsens outcomes for patients with SCI due to the higher levels of neuronal oxidative stress. Mammalian sterile 20-like kinase (MST1) is a key mediator of oxidative stress in the central nervous system; however, the mechanism of its action in SCI is still not clear. Here, we investigated the role of MST1 activation in induced neuronal oxidative stress in patients with both SCI and diabetes.

METHODS

Diabetes was established in mice by diet induction combined with intraperitoneal injection of streptozotocin (STZ). SCI was performed at T10 level through weight dropping. Advanced glycation end products (AGEs) were applied to mimic diabetic conditions in PC12 cell line in vitro. We employed HE, Nissl staining, footprint assessment and Basso mouse scale to evaluate functional recovery after SCI. Moreover, immunoblotting, qPCR, immunofluorescence and protein-protein docking analysis were used to detect the mechanism.

RESULTS

Regarding in vivo experiments, diabetes resulted in up-regulation of MST1, excessive neuronal apoptosis and weakened motor function in SCI mice. Furthermore, diabetes impeded NRF2-mediated antioxidant defense of neurons in the damaged spinal cord. Treatment with AAV-siMST1 could restore antioxidant properties of neurons to facilitate reactive oxygen species (ROS) clearance, which subsequently promoted neuronal survival to improve locomotor function recovery. In vitro model found that AGEs worsened mitochondrial dysfunction and increased cellular oxidative stress. While MST1 inhibition through the chemical inhibitor XMU-MP-1 or MST1-shRNA infection restored NRF2 nuclear accumulation and its transcription of downstream antioxidant enzymes, therefore preventing ROS generation. However, these antioxidant effects were reversed by NRF2 knockdown. Our in-depth studies showed that over-activation of MST1 in diabetes directly hindered the neuroprotective AKT1, and subsequently fostered NRF2 ubiquitination and degradation via the GSK3β/β-TrCP pathway.

CONCLUSION

MST1 inhibition significantly restores neurological function in SCI mice with preexisting diabetes, which is largely attributed to the activation of antioxidant properties via the GSK3β(Ser 9)/β-TrCP/NRF2 pathway. MST1 may be a promising pharmacological target for the effective treatment of spinal cord injury patients with diabetes.

Assessing the impact of body composition, metabolic and oxidative stress parameters on insulin resistance as a prognostic marker for reactive hypoglycemia: a cross-sectional study in overweight, obese, and normal weight individuals

Oxidative stress (OS) plays a pivotal role in the pathogenesis of insulin resistance (IR), particularly in its association with obesity. This study evaluate both the diagnostic and clinical significance of assessing oxidative status in patients affected by overweight and obesity displaying IR, especially with reactive hypoglycemic episodes (RH). A comprehensive examination of OS biomarkers was carried out, encompassing measurements of total oxidative capacity (TOC) and total antioxidant capacity (TAC). Our analysis results reveal noteworthy connections between OS levels and the severity of IR in overweight and obese patients. Moreover, in the study, we demonstrated the diagnostic utility of serum concentrations of TAC and TOC as indicators of the risk of RH, the occurrence of which, even at the stage of overweight, may be associated with increased OS and further development of obesity. Our findings imply that the evaluation of oxidative status could serve as a crucial diagnostic and prognostic tool for patients observed with IR and overweight and obesity. In conclusion, our study underscores the potential utility of assessing oxidative status in the context of IR and highlights the possibility of identifying novel therapeutic targets for the treatment of overweight and obese patients.

Duodenal-jejunal bypass improves hypothalamic oxidative stress and inflammation in diabetic rats via glucagon-like peptide 1-mediated Nrf2/HO-1 signaling

BACKGROUND

Type 2 diabetes mellitus (T2DM) is often accompanied by impaired glucose utilization in the brain, leading to oxidative stress, neuronal cell injury and infla-mmation. Previous studies have shown that duodenal jejunal bypass (DJB) surgery significantly improves brain glucose metabolism in T2DM rats, the role and the metabolism of DJB in improving brain oxidative stress and inflammation condition in T2DM rats remain unclear.

AIM

To investigate the role and metabolism of DJB in improving hypothalamic oxidative stress and inflammation condition in T2DM rats.

METHODS

A T2DM rat model was induced via a high-glucose and high-fat diet, combined with a low-dose streptozotocin injection. T2DM rats were divided into DJB operation and Sham operation groups. DJB surgical intervention was carried out on T2DM rats. The differential expression of hypothalamic proteins was analyzed using quantitative proteomics analysis. Proteins related to oxidative stress, inflammation, and neuronal injury in the hypothalamus of T2DM rats were analyzed by flow cytometry, quantitative real-time PCR, Western blotting, and immunofluorescence.

RESULTS

Quantitative proteomics analysis showed significant differences in proteins related to oxidative stress, inflammation, and neuronal injury in the hypothalamus of rats with T2DM-DJB after DJB surgery, compared to the T2DM-Sham groups of rats. Oxidative stress-related proteins (glucagon-like peptide 1 receptor, Nrf2, and HO-1) were significantly increased (P < 0.05) in the hypothalamus of rats with T2DM after DJB surgery. DJB surgery significantly reduced (P < 0.05) hypothalamic inflammation in T2DM rats by inhibiting the activation of NF-κB and decreasing the expression of interleukin (IL)-1β and IL-6. DJB surgery significantly reduced (P < 0.05) the expression of factors related to neuronal injury (glial fibrillary acidic protein and Caspase-3) in the hypothalamus of T2DM rats and upregulated (P < 0.05) the expression of neuroprotective factors (C-fos, Ki67, Bcl-2, and BDNF), thereby reducing hypothalamic injury in T2DM rats.

CONCLUSION

DJB surgery improve oxidative stress and inflammation in the hypothalamus of T2DM rats and reduce neuronal cell injury by activating the glucagon-like peptide 1 receptor-mediated Nrf2/HO-1 signaling pathway.

Oyster-derived dipeptides RI, IR, and VR promote testosterone synthesis by reducing oxidative stress in TM3 cells

Short peptides have gained widespread utilization as functional constituents in the development of functional foods due to their remarkable biological activity. Previous investigations have established the positive influence of oysters on testosterone biosynthesis, although the underlying mechanism remains elusive. This study aims to assess the impact of three dipeptides derived from oysters on the oxidative stress state of TM3 cells induced by AAPH while concurrently examining alterations in cellular testosterone biosynthesis capacity. The investigation encompasses an analysis of reactive oxygen species (ROS) content, antioxidant enzyme activity, apoptotic status, and expression levels of crucial enzymes involved in the testosterone synthesis pathway within TM3 cells, thus evaluating the physiological activity of the three dipeptides. Additionally, molecular docking was employed to investigate the inhibitory activity of the three dipeptides against ACE. The outcomes of this study imply that the oxidative stress state of cells impedes the synthesis of testosterone by inhibiting the expression of essential proteins in the testosterone synthesis pathway. These three dipeptides derived from oysters ameliorate cellular oxidative stress by directly scavenging excess ROS or reducing ROS production rather than enhancing cellular antioxidant capacity through modulation of antioxidant enzyme activity. These findings introduce a novel avenue for developing and utilizing antioxidant peptides derived from food sources.

A comparative study of the therapeutic effect of bone marrow mesenchymal stem cells versus insulin on mandibular dento-alveolar complex collagen formation and beta-catenin expression in experimentally induced type I diabetes

Objective

To assess and compare the therapeutic effect of bone marrow mesenchymal stem cells (BM-MSCs) versus insulin on mandibular dento-alveolar complex collagen formation and beta-catenin (β-catenin) expression in experimentally induced type I diabetes in albino rat.

Design

Twenty-eight male albino rats were equally divided as follows; Group I: was composed of rats which received no drug. The remaining rats were administrated a single streptozotocin (STZ) (40 mg/kg) intra-peritoneal injection. After affirmation of diabetes induction, the rats were divided into: Group II: Diabetic rats were given no treatment. Group III: Diabetic rats received a single BM-MSCs intravenous injection (1x106 cells). Group IV: Diabetic rats were given a daily insulin subcutaneous injection (5 IU/kg). After 28 days, mandibles were processed and stained by Hematoxylin & Eosin (H&E), Masson's trichrome and anti-β-catenin antibody. A statistical analysis was performed to measure positive area% of Masson's trichrome and β-catenin.

Results

Dento-alveolar complex tissues and cells of Group II showed destructive changes histologically, while Groups III and IV demonstrated improved histological features. Group II presented almost old collagen in all dento-alveolar complex tissues, and nearly negative β-catenin expression. Groups III and IV revealed a newly formed collagen intermingled with very few areas of old collagen, and both groups showed positive β-catenin immunoreactivity. Statistically, Groups III and IV represented the highest mean values of Masson's trichrome area% and β-catenin area%, while Group II reported the lowest mean.

Conclusions

Streptozotocin has a destructive effect on the dento-alveolar complex structure and function. BM-MSCs and insulin show regenerative capacity in STZ-affected periodontal tissues, and statistically, they increase collagen formation and β-catenin expression.

The role of hormones in sepsis: an integrated overview with a focus on mitochondrial and immune cell dysfunction

Sepsis is a dysregulated host response to infection that results in life-threatening organ dysfunction. Virtually every body system can be affected by this syndrome to greater or lesser extents. Gene transcription and downstream pathways are either up- or downregulated, albeit with considerable fluctuation over the course of the patient's illness. This multi-system complexity contributes to a pathophysiology that remains to be fully elucidated. Consequentially, little progress has been made to date in developing new outcome-improving therapeutics. Endocrine alterations are well characterised in sepsis with variations in circulating blood levels and/or receptor resistance. However, little attention has been paid to an integrated view of how these hormonal changes impact upon the development of organ dysfunction and recovery. Here, we present a narrative review describing the impact of the altered endocrine system on mitochondrial dysfunction and immune suppression, two interlinked and key aspects of sepsis pathophysiology.

Is metformin neuroprotective against diabetes mellitus-induced neurodegeneration? An updated graphical review of molecular basis

Diabetes mellitus (DM) is a metabolic disease that activates several molecular pathways involved in neurodegenerative disorders. Metformin, an anti-hyperglycemic drug used for treating DM, has the potential to exert a significant neuroprotective role against the detrimental effects of DM. This review discusses recent clinical and laboratory studies investigating the neuroprotective properties of metformin against DM-induced neurodegeneration and the roles of various molecular pathways, including mitochondrial dysfunction, oxidative stress, inflammation, apoptosis, and its related cascades. A literature search was conducted from January 2000 to December 2022 using multiple databases including Web of Science, Wiley, Springer, PubMed, Elsevier Science Direct, Google Scholar, the Core Collection, Scopus, and the Cochrane Library to collect and evaluate peer-reviewed literature regarding the neuroprotective role of metformin against DM-induced neurodegenerative events. The literature search supports the conclusion that metformin is neuroprotective against DM-induced neuronal cell degeneration in both peripheral and central nervous systems, and this effect is likely mediated via modulation of oxidative stress, inflammation, and cell death pathways.

Artemisia ordosica polysaccharide ameliorated LPS-induced growth inhibition and intestinal injury in broilers through enhancing immune-regulation and antioxidant capacity

The study investigated the effects of dietary Artemisia ordosica polysaccharide (AOP) on growth, intestinal morphology, immune responses and antioxidant capacity of broilers challenged with lipopolysaccharide (LPS). A total of 192 1-d-old broilers were randomly allotted to four treatments with 6 replicates (n = 8): (1) CON group, non-challenged broilers fed basal diet; (2) LPS group, LPS-challenged broilers fed basal diet; (3) AOP group, non-challenged broilers fed basal diet supplemented with 750 mg/kg AOP; (4) LPS+AOP group, LPS-challenged broilers fed basal diet supplemented with 750 mg/kg AOP. The trial included starter phase (d 1 to 14), stress period Ⅰ (d 15 to 21), convalescence Ⅰ (d 22 to 28), stress period Ⅱ (d 29 to 35) and convalescence Ⅱ (d 36 to 42). During stress period Ⅰ and Ⅱ, broilers were injected intra-abdominally either with LPS solution or with equal sterile saline. The results showed that AOP alleviated LPS-induced growth inhibition by prompting protein digestibility, and decreasing serum stress hormones and pro-inflammatory cytokines content of broilers. Moreover, AOP decreased LPS-induced over-production of IL-1β and IL-6 through suppressing TLR4/NF-κB pathway, and alleviated LPS-induced decreasing of T-AOC, CAT and GPx activities by activating Nrf2/Keap1 pathway, which ultimately improved jejunum morphology. In conclusion, AOP alleviated LPS-induced growth inhibition and intestinal damage by enhancing anti-inflammatory and antioxidant capacities of broilers.

Supportive effect of naringenin on NaCl-induced toxicity in Carthamus tinctorius seedlings

In the present study, we used exogenous naringenin (0.5 mM) pretreatment before the stress (25 mM NaCl) on the growth and tolerance of safflower seedlings under non-salinity conditions and salinity conditions. Our results showed that salinity treatment significantly declined the biomass, leaf relative water content, chlorophyll content, K⁺ content, and K⁺/Na⁺ ratio by 28%, 28%, 12%, 36%, and 56%, respectively, as compared to untreated control. The results obtained in the present study showed the beneficial effects of the pretreatment of naringenin in safflower seedlings under non-salinity conditions concerning increasing plant biomass, total phenolic compound, radical scavenging activity (RSA), soluble sugar content, proline, glutathione, enzymatic antioxidants, and K⁺ content. Nevertheless, naringenin pretreated plants showed a clear increment in the values of biomass, RSA, total phenolic compound, and catalase enzyme activity parameters under salinity stress. Salinity stress caused ionic phytotoxicity and oxidative stress by enhancing Na⁺ content, H₂O₂ accumulation, malondialdehyde (MDA), and antioxidants. However, naringenin alleviated salt-induced oxidative stress by decreasing H₂O₂ and MDA content in the leaves and improving the catalase activity in treated plants. Generally, it could be concluded pretreatment of naringenin before stress could partly diminish NaCl-caused oxidative stress in safflower seedlings, probably due to improvement in enzymatic and non-enzymatic antioxidants and reduced cell membrane damage.

Protective effects of black onion polysaccharide on liver and kidney injury in T2DM rats through the synergistic impact of hypolipidemic and antioxidant abilities

In this study, the synergistic effects of black onion on the hypolipidemic and antioxidant activities in T2DM rats induced by a high-fat-diet and alloxan were investigated. The results showed that the fasting blood glucose of diabetic rats was significantly decreased after treatment with black onion polysaccharide (p < 0.01). Blood lipid analysis indicated that black onion polysaccharide could significantly improve the abnormal metabolism of blood lipids caused by diabetes. In addition, the MDA and ROS of the diabetic rats treated with black onion polysaccharide were significantly reduced; moreover, SOD was increased, indicating the excellent antioxidant activity of black onion polysaccharide. A histological examination clearly showed that black onion polysaccharide could improve the histological morphology of the liver and kidney. Furthermore, the indices of liver and kidney function were restored. These results indicate that black onion polysaccharide can reduce blood glucose and simultaneously show synergistic effects of hypoglycemic and antioxidant activities in diabetic rats. Therefore, black onion polysaccharide may alleviate liver and kidney function injury by improving the "two-hit" mechanism and can thus be used as a potential functional food to prevent diabetes and its complications.

Facilitation of Insulin Effects by Ranolazine in Astrocytes in Primary Culture

Ranolazine (Rn) is a drug used to treat persistent chronic coronary ischemia. It has also been shown to have therapeutic benefits on the central nervous system and an anti-diabetic effect by lowering blood glucose levels; however, no effects of Rn on cellular sensitivity to insulin (Ins) have been demonstrated yet. The present study aimed to investigate the permissive effects of Rn on the actions of Ins in astrocytes in primary culture. Ins (10−8 M), Rn (10−6 M), and Ins + Rn (10−8 M and 10−6 M, respectively) were added to astrocytes for 24 h. In comparison to control cells, Rn and/or Ins caused modifications in cell viability and proliferation. Rn increased protein expression of Cu/Zn-SOD and the pro-inflammatory protein COX-2 was upregulated by Ins. On the contrary, no significant changes were found in the protein expression of NF-κB and IκB. The presence of Rn produced an increase in p-ERK protein and a significant decrease in COX-2 protein expression. Furthermore, Rn significantly increased the effects of Ins on the expression of p-AKT, p-eNOS, p-ERK, Mn-SOD, and PPAR-γ. In addition, Rn + Ins produced a significant decrease in COX-2 expression. In conclusion, Rn facilitated the effects of insulin on the p-AKT, p-eNOS, p-ERK, Mn-SOD, and PPAR-γ signaling pathways, as well as on the anti-inflammatory and antioxidant effects of the hormone.

Evaluation of a single dose of intra-testicular insulin treatment in heat-stressed mice model

Insulin plays important role in testicular functions such as germ cell proliferation and steroidogenesis, despite its conventional role as a hypoglycaemic agent. It is also well known that testicular activity is severely get affected by heat stress and heat stress induces testicular pathogenesis. The effect of insulin on heat-induced testicular impairment has not been investigated. Thus, it is hypothesized that insulin might modulate testicular activity in a heat-stressed model. Experimental mice were separated into 4 groups; the first group was the normal control (CN), and the second group was subjected to heat stress (HS) by submerging the lower body part in a thermostatically controlled water bath maintained at 43°C for 15 min. The third and fourth groups were treated with a single dose of intra-testicular insulin (0.6 IU/mice) before and after heat stress. Animal tissue samples were collected after 14 days of heat treatment. Insulin treatment did not improve the sperm parameters; however, both insulin pre and post-treatment improved the markers of spermatogenesis such as Johnsen score, germinal epithelium height and the number of stages VII/VIII. The histoarchitecture of testis also showed amelioration from heat-induced pathogenesis in the insulin-treated groups. Insulin treatment has also increased the proliferation of germ cells (increased PCNA and GCN), survival (Bcl2), and decreased apoptosis (active caspase-3). Furthermore, insulin treatment decreased MDA levels, without pronounced effects on the activities of antioxidant enzymes. Heat stress also decreased the circulating testosterone and oestrogen levels, and insulin treatment significantly increased oestrogen levels only. Although testosterone showed an increasing trend, it was insignificant. The expression of aromatase, AR, ER-α, and ER-β was down regulated by heat-stress and insulin treatment up regulated these markers. In conclusion, our results showed the amelioration of heat-induced testicular impairment by pre and post-intra-testicular insulin treatments. Insulin-associated improvements in the pre-and post-treatment groups suggested a preventive mechanism of insulin against heat stress in the testis.

Benfotiamine protects against hypothalamic dysfunction in a STZ-induced model of neurodegeneration in rats

The neurodegeneration of Alzheimer's disease (AD) affects not only brain structures associate with cognition early in the progression of the disease, but other areas such as the hypothalamus, a region involved in the control of metabolism and appetite. In this context, we evaluated the effects of benfotiamine (BFT), a vitamin B1 analog that is being proposed as a therapeutical approach for AD-related cognitive alterations, which were induced by intracerebroventricular injection of streptozotocin (STZ). In addition to the already described effect of STZ on cognition, we show that this drug also causes metabolic changes which are linked to changes in hypothalamic insulin signaling and orexigenic and anorexigenic circuitries, as well as a decreased cellular integrated stress response. As expected, the supplementation with 150 mg/kg of BFT for 30 days increased blood concentrations of thiamine and its phosphate esters. This led to the prevention of body weight and fat loss in STZ-ICV-treated animals. In addition, we also found an improvement in food consumption, despite hypothalamic gene expression linked to anorexia after STZ exposure. Additionally, decreased apoptosis signaling was observed in the hypothalamus. In in vitro experiments, we noticed a high ability of BFT to increase insulin sensitivity in hypothalamic neurons. Furthermore, we also observed that BFT decreases the mitochondrial unfolded stress response damage by preventing the loss of HSP60 and reversed the mitochondria dysfunction caused by STZ. Taken together, these results suggest that benfotiamine treatment is a potential therapeutic approach in the treatment of hypothalamic dysfunction and metabolic disturbances associated with sporadic AD.

New Advances on Pathophysiology of Diabetes Neuropathy and Pain Management: Potential Role of Melatonin and DPP-4 Inhibitors

Pre-diabetes and diabetes are growing threats to the modern world. Diabetes mellitus (DM) is associated with comorbidities such as hypertension (83.40%), obesity (90.49%), and dyslipidemia (93.43%), creating a substantial burden on patients and society. Reductive and oxidative (Redox) stress level imbalance and inflammation play an important role in DM progression. Various therapeutics have been investigated to treat these neuronal complications. Melatonin and dipeptidyl peptidase IV inhibitors (DPP-4i) are known to possess powerful antioxidant and anti-inflammatory properties and have garnered significant attention in the recent years. In this present review article, we have reviewed the recently published reports on the therapeutic efficiency of melatonin and DPP-4i in the treatment of DM. We summarized the efficacy of melatonin and DPP-4i in DM and associated complications of diabetic neuropathy (DNP) and neuropathic pain. Furthermore, we discussed the mechanisms of action and their efficacy in the alleviation of oxidative stress in DM.

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

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

Is the insulin necessary for the struggle against oxidative stress in diabetes mellitus type 2: A pilot study

Background/Aim. Hyperglycaemia has a detrimental effect on the progress of micro/macrovascular complications in patients with diabetes mellitus type 2 (T2DM). Additionally, all known complications in T2DM are coupled with oxidative stress developed from different metabolic pathways. The aim of this study was to estimate the quality of glucoregulation and the degree of oxidative stress in T2DM patients depending on the applied therapeutic protocol and assess their correlation with clinical data and crucial biochemical parameters important for the development of diabetes complications. Methods. All included patients were divided into two groups: those treated with oral antidiabetic drugs (OAD) and those treated with oral antidiabetic drugs and insulin (OA-DINS). Thiobarbituric acid reactive substances (TBARS), total sulfhydryl groups (TSH), the activity of superoxide dismutase (SOD), total nitrites (NOx), vascular endothelial growth factor (VEGF), and activities of matrix metalloproteinase 9 (MMP9) were measured, together with lipid profile and routine biochemical parameters. All subjects were analyzed for demographic characteristics and detailed medical history as well as smoking habits and calculated for body mass index (BMI). Results. All patients were uniformly poor glucoregulated and dyslipidemic. SOD activity was decreased, and lipid peroxidation was increased in the OAD group compared to OADINS. Deficient glucoregulation in both the OAD and the OADINS groups did not associate with an oxidative state outcome. In both of these groups, the concentrations of VEGF and MMP9 were significantly higher than in controls. Conclusion. The better antioxidative outcome, expressed with a normalized concentration of TBARS, preserved TSH, and normalized SOD activity in T2DM patients treated with OADINS compared to those treated exclusively with OAD, suggests the need for more careful consideration of earlier insulin introduction into T2DM therapy in order to prevent the development of complications.

CAPE-pNO2 ameliorates diabetic brain injury through modulating Alzheimer's disease key proteins, oxidation, inflammation and autophagy via a Nrf2-dependent pathway

AIMS

CAPE-pNO₂, an active derivative of caffeic acid phenethyl ester, has been verified to exert protection of diabetic cardiomyopathy and diabetic nephropathy. The present study aims to explore the brain protection effects and potential mechanisms of CAPE-pNO₂ on streptozotocin-induced diabetic brain injury in vivo and in vitro.

MAIN METHODS

Biochemical indexes including triglyceride, total cholesterol, superoxide dismutase and malondialdehyde contents were detected. The histopathological structure of hippocampus and cerebral cortex were determined. Immunofluorescence and immunoblot methods were used to assess expression of oxidative stress, inflammation and autophagy pathway-related proteins of diabetic brain in vivo. Alzheimer's disease (AD)-associated key proteins were also checked in vivo. DCFH-DA assay, immunofluorescence and immunoblot methods were applied to verify the master role of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in vitro.

KEY FINDINGS

First, CAPE-pNO₂ could rescue the diabetic brain atrophy and diminish CA1 and CA3 cells of hippocampus and cerebral cortex. Second, CAPE-pNO₂ could decrease Aβ and p-tau (S396) expression through anti-oxidation, anti-inflammation and autophagy induction in vivo. Last, CAPE-pNO₂ could down-regulate p-tau (S396) expression through Nrf2-related anti-oxidation mechanisms in vitro.

SIGNIFICANCE

CAPE-pNO₂ may exert brain protection via Nrf2-dependent way in diabetes. Additionally, Nrf2 was capable of regulating p-tau (S396) expression that is critical to AD.

Artemisia ordosica Polysaccharide Alleviated Lipopolysaccharide-induced Oxidative Stress of Broilers via Nrf2/Keap1 and TLR4/NF-κB Pathway

Artemisia ordosica is one of the main shrubby perennials belonging to Artemisia species of Asteraceae and could be used in folk Chinese/Mongolian medicine to treat symptoms of various inflammatory ailments. The present study was conducted to investigate the protective effects of dietary Artemisia ordosica polysaccharide (AOP) against lipopolysaccharide (LPS) induced oxidative stress in broilers via Nrf2/Keap1 and TLR4/NF-κB pathway. A total of 192 1-day-old Arbor Acres male broilers were randomly allotted to four treatments with 6 replicates (n = 8): (1) CON group, non-challenged broilers fed basal diet; (2) LPS group, LPS-challenged broilers fed basal diet; (3) AOP group, non-challenged broilers fed basal diet supplemented with 750 mg/kg AOP; (4) LPS+AOP group, LPS-challenged broilers fed basal diet supplemented with 750 mg/kg AOP. The trial included starter phase (d 1-14), stress period Ⅰ (d 15-21), convalescence Ⅰ (d 22-28), stress period Ⅱ (d 29-35) and convalescence Ⅱ (d 36-42). During stress period Ⅰ (on d 15, 17, 19 and 21) and stress period Ⅱ (on d 29, 31, 33 and 35), broilers were injected intra-abdominally either with LPS solution or with an equal amount of sterile saline. The results showed that dietary AOP supplementation alleviated LPS-induced reduction in antioxidant enzyme activity and excessive production of ROS, 8-OHdG and PC in serum of broilers challenged with LPS. Moreover, dietary AOP supplementation alleviated the decrease of T-AOC and activities of SOD, CAT and GPx in liver of broilers challenged with LPS by increasing expression of Nrf2, and inhibiting over-expression of Keap1 both at gene and protein level. Additionally, dietary AOP supplementation decreased the over-production of IL-1β and IL-6 in liver of broilers challenged by LPS through decreasing mRNA expression of TLR4, MyD88, NF-κB P65, IL-1β and IL-6, and alleviating the increase of protein expression of TLR4, IKKβ, NF-κB P65, IL-1β, IL-6, and the decrease of protein expression of IkBα. In conclusion, dietary AOP supplementation could alleviate LPS-induced oxidative stress through Nrf2/Keap1 and TLR4/NF-κB pathway.

Oxidative Stress in Optic Neuropathies

Increasing evidence indicates that changes in the redox system may contribute to the pathogenesis of multiple optic neuropathies. Optic neuropathies are characterized by the neurodegeneration of the inner-most retinal neurons, the retinal ganglion cells (RGCs), and their axons, which form the optic nerve. Often, optic neuropathies are asymptomatic until advanced stages, when visual impairment or blindness is unavoidable despite existing treatments. In this review, we describe systemic and, whenever possible, ocular redox dysregulations observed in patients with glaucoma, ischemic optic neuropathy, optic neuritis, hereditary optic neuropathies (i.e., Leber's hereditary optic neuropathy and autosomal dominant optic atrophy), nutritional and toxic optic neuropathies, and optic disc drusen. We discuss aspects related to anti/oxidative stress biomarkers that need further investigation and features related to study design that should be optimized to generate more valuable and comparable results. Understanding the role of oxidative stress in optic neuropathies can serve to develop therapeutic strategies directed at the redox system to arrest the neurodegenerative processes in the retina and RGCs and ultimately prevent vision loss.

Insulin signaling alters antioxidant capacity in the diabetic heart

Diabetic cardiomyopathy is associated with an increase in oxidative stress. However, antioxidant therapy has shown a limited capacity to mitigate disease pathology. The molecular mechanisms responsible for the modulation of reactive oxygen species (ROS) production and clearance must be better defined. The objective of this study was to determine how insulin affects superoxide radical (O₂^•–) levels. O₂^•– production was evaluated in adult cardiomyocytes isolated from control and Akita (type 1 diabetic) mice by spin-trapping electron paramagnetic resonance spectroscopy. We found that the basal rates of O₂^•– production were comparable in control and Akita cardiomyocytes. However, culturing cardiomyocytes without insulin resulted in a significant increase in O₂^•– production only in the Akita group. In contrast, O₂^•– production was unaffected by high glucose and/or fatty acid supplementation. The increase in O₂^•– was due in part to a decrease in superoxide dismutase (SOD) activity. The PI3K inhibitor, LY294002, decreased Akita SOD activity when insulin was present, indicating that the modulation of antioxidant activity is through insulin signaling. The effect of insulin on mitochondrial O₂^•– production was evaluated in Akita mice that underwent a 1-week treatment of insulin. Mitochondria isolated from insulin-treated Akita mice produced less O₂^•– than vehicle-treated diabetic mice. Quantitative proteomics was performed on whole heart homogenates to determine how insulin affects antioxidant protein expression. Of 29 antioxidant enzymes quantified, thioredoxin 1 was the only one that was significantly enhanced by insulin treatment. In vitro analysis of thioredoxin 1 revealed a previously undescribed capacity of the enzyme to directly scavenge O₂^•–. These findings demonstrate that insulin has a role in mitigating cardiac oxidative stress in diabetes via regulation of endogenous antioxidant activity.

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Insulin decreases ROS production in T1D Akita cardiomyocytes.

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Insulin signaling downstream of PI3K is required for this effect.

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Insulin increases the antioxidant capacity in the Akita heart.

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Trx1 is upregulated by insulin in the Akita heart in vivo.

Effects of Antioxidant in Adjunct with Periodontal Therapy in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis

This review investigated whether the adjunctive use of antioxidants with periodontal therapy improves periodontal parameters in patients with type 2 diabetes. A systematic and extensive literature search for randomized controlled trials (RCTs) conducted before April 2021 was performed on the PubMed, Cochrane Library, and Web of Science databases. The risk of bias was assessed using the Cochrane risk-of-bias tool. A meta-analysis was performed to quantitatively evaluate the clinical outcomes following periodontal therapy. After independent screening of 137 initial records, nine records from eight RCTs were included. The risk-of-bias assessment revealed that all RCTs had methodological weaknesses regarding selective bias, although other risk factors for bias were not evident. This meta-analysis of two RCTs showed that periodontal pocket depths were significantly reduced in the groups treated with combined non-surgical periodontal therapy and melatonin than in those treated with non-surgical periodontal therapy alone. The present systematic review and meta-analysis suggest that the adjunctive use of melatonin, resveratrol, omega-3 fatty acids with cranberry juice, propolis, and aloe vera gel with periodontal therapy significantly improves periodontal disease parameters in patients with type 2 diabetes, and melatonin application combined with non-surgical periodontal therapy might significantly reduce periodontal pocket depth. However, there are still limited studies of melatonin in combination with non-surgical periodontal therapy in Type 2 diabetic patients, and more well-designed RCTs are required to be further investigated.

Astaxanthin-s-allyl cysteine diester against high glucose-induced neuronal toxicity in vitro and diabetes-associated cognitive decline in vivo: Effect on p53, oxidative stress and mitochondrial function

Neuroprotective effect of astaxanthin-s-allyl cysteine diester (AST-SAC) against high glucose (HG)-induced oxidative stress in in vitro and cognitive decline under diabetes conditions in in vivo has been explored. Pretreatment of AST-SAC (5, 10 and 15 μM) dose-dependently preserved the neuronal cells (SH-SY5Y) viability against HG toxicity through i) decreasing oxidative stress (decreasing reactive oxygen species generation and increasing endogenous antioxidants level); ii) protecting mitochondrial function [oxidative phosphorylation (OXPHOS) complexes activity and mitochondrial membrane potential (MMP)]; and iii) decreasing p53 level thereby subsequently decreasing the level of apoptotic marker proteins. Male Spraque-Dawley rats were orally administered AST-SAC (1 mg/kg/day) for 45 days in streptozotocin-induced diabetes mellitus (DM) rats. AST-SAC administration prevented the loss of spatial memory in DM rats as determined using the novel object location test. AST-SAC administration alleviated the DM-induced injury in brain such as increased cholinesterases activity, elevated oxidative stress and mitochondrial dysfunction. Altogether, the results from the present study demonstrated that AST-SAC averted the neuronal apoptosis and preserved the cognitive function against HG toxicity under DM conditions.

LncRNA MEG3 Alleviates Diabetic Cognitive Impairments by Reducing Mitochondrial-Derived Apoptosis through Promotion of FUNDC1-Related Mitophagy via Rac1-ROS Axis

Mitochondrial dysfunction and elevated ROS generation are predominant contributors of neuronal death that is responsible for the diabetes-related cognitive impairments. Emerging evidence has demonstrated that long noncoding RNA-MEG3 can serve as an important regulator in the pathogenesis of diabetes. However, the underlying mechanisms remain to be further clarified. Here, it was observed that MEG3 was significantly down-regulated in STZ (streptozotocin)-induced diabetic rats. MEG3 overexpression noticeably improved diabetes-induced cognitive dysfunctions, accompanied by the abatement of Rac1 activation and ROS production, as well as the inhibition of mitochondria-associated apoptosis. Furthermore, either MEG3 overexpression or Rac1 inhibition promoted FUNDC1 dephosphorylation and suppressed oxidative stress and neuro-inflammation. Similarly, in vitro studies confirmed that hyperglycemia also down-regulated MEG3 expression in PC12 cells. MEG3 reintroduction protected PC12 cells against hyperglycemia-triggered neurotoxicity by improving mitochondrial fitness and repressing mitochondria-mediated apoptosis. Moreover, these neuroprotective effects of MEG3 relied on FUNDC1-related mitophagy, since silencing of FUNDC1 abolished these beneficial outcomes. Additionally, MEG3 rescued HG-induced neurotoxicity was involved in inhibiting Rac1 expression via interaction with Rac1 3'UTR. Conversely, knockdown of MEG3 showed opposite effects. NSC23766, a specific inhibitor of Rac1, fully abolished harmful effects of MEG3 depletion. Consistently, knockdown of Rac1 potentiated FUNDC1-associated mitophagy. Meanwhile, colocalization of Rac1 and FUNDC1 was found in mitochondria under hyperglycemia, which was interrupted by MEG3 overexpression. Furthermore, silencing of Rac1 promoted PGAM5 expression, and FUNDC1 strongly interacted with LC3 in Rac1-deleted cells. Altogether, our findings suggested that the Rac1/ROS axis may be a downstream signaling pathway for MEG3-induced neuroprotection, which was involved in FUNDC1-associated mitophagy.

Effects of date seeds administration on anxiety and depressive symptoms in streptozotocin-induced diabetic rats: biochemical and behavioral evidences

OBJECTIVES

Several epidemiological data indicate that chronic hyperglycemia is associated with behavioral changes such as anxiety and depressive symptoms. Date seeds, one of the most potent products with potential antioxidant activities and possess many benefits against hyperglycemia and its complication. The aim of the current study was to explore the potential effect of date seeds extract on biochemical and behavioral changes (anxiety and depression) in streptozotocin (STZ)-diabetic rats.

METHODS

Rats were divided into four groups as follows: normal control, diabetic control, diabetic treated with the lyophilized aqueous extract of the date seed (2,000 mg/kg) (LAE-DS) and diabetics treated with insulin (4 UI/day). Experimental diabetes was induced by a single intraperitoneal injection of STZ (60 mg/kg). After 24 days treatment period, anxiety and depressive behaviors were evaluated using four behavioral tests. After sacrifice, blood samples were collected to evaluate lipid parameters. In addition, rat organs (kidney, liver and brain) were dissected out in order to estimate lipid peroxidation levels as oxidative stress marker.

RESULTS

Oral administration of the lyophilized aqueous extract of date seeds and insulin injection for 30 days significantly decreased blood glucose levels in STZ-diabetic rats and protected them against undesirable changes in lipid parameters, including cholesterol, triglycerides, LDL cholesterol, VLDL cholesterol and atherosclerosis index. Compared to untreated diabetic rat, a significant decrease in lipid peroxidation levels in kidney, liver and brain (Hippocampus and prefrontal cortex) were observed after treatment with insulin or LAE-DS in diabetic rats. Furthermore, insulin and LAE-DS administration prevented anxiety-related behaviors in STZ-diabetic rats.

CONCLUSIONS

Therefore, it would be possible to combine this extract with insulin and use it as an antioxidant supplement for type 1 diabetic patients.

DL-3-n-butylphthalide ameliorates diabetes-associated cognitive decline by enhancing PI3K/Akt signaling and suppressing oxidative stress

DL-3-n-Butylphthalide (DL-NBP), a small molecular compound extracted from the seeds of Apium graveolens Linn (Chinese celery), has been shown to exert neuroprotective effects due to its anti-inflammatory, anti-oxidative and anti-apoptotic activities. DL-NBP not only protects against ischemic cerebral injury, but also ameliorates vascular cognitive impairment in dementia patients including AD and PD. In the current study, we investigated whether and how DL-NBP exerted a neuroprotective effect against diabetes-associated cognitive decline (DACD) in db/db mice, a model of type-2 diabetes. db/db mice were orally administered DL-NBP (20, 60, 120 mg· kg-1· d-1) for 8 weeks. Then the mice were subjected to behavioral test, their brain tissue was collected for morphological and biochemical analyses. We showed that oral administration of DL-NBP significantly ameliorated the cognitive decline with improved learning and memory function in Morris water maze testing. Furthermore, DL-NBP administration attenuated diabetes-induced morphological alterations and increased neuronal survival and restored the levels of synaptic protein PSD95, synaptophysin and synapsin-1 as well as dendritic density in the hippocampus, especially at a dose of 60 mg/kg. Moreover, we revealed that DL-NBP administration suppressed oxidative stress by upregulating Nrf2/HO-1 signaling, and increased brain-derived neurotrophic factor (BDNF) expression by activating PI3K/Akt/CREB signaling in the hippocampus. These beneficial effects of DL-NBP were observed in high glucose-treated PC12 cells. Our results suggest that DL-NBP may be a potential pharmacologic agent for the treatment of DACD.

Structural characterization of a polysaccharide from Suillellus luridus and its antidiabetic activity via Nrf2/HO-1 and NF-κB pathways

A heteropolysaccharide designated SLPC-1S with the Mw of 9.4 kDa was purified from the caps of Suillellus luridus. Monosaccharide composition analysis revealed that SLPC-1S was composed of galactose, glucose, arabinose and mannose in a molar ratio of 44.9:27.6:14.7:12.8. Structural characterization indicated that SLPC-1S had a backbone principally composed of 1,3 linked α-D-Galp, 1,3 linked β-D-Glcp and 1,6 linked β-D-Glcp with the branches mainly composed of 1,3 linked β-D-Glcp, 1,3 linked α-L-Arap, 1,3 linked α-D-Manp and T-linked α-D-Galp. Furthermore, SLPC-1S exhibited excellent antidiabetic activities in the streptozotocin-induced diabetic mice. Protein expression and mRNA levels in NF-kB and Nrf2/HO-1 signaling pathways were detected by western blots and real-time polymerase chain reaction (RT-PCR), respectively. The results strongly proved that SLPC-1S can be treated as a potential agent for preventing and treating diabetes via regulating Nrf2-mediated oxidative stress and NF-κB-mediated inflammatory responses.

Metabolic Inflammation-A Role for Hepatic Inflammatory Pathways as Drivers of Comorbidities in Nonalcoholic Fatty Liver Disease?

Nonalcoholic fatty liver disease (NAFLD) is a global and growing health concern. Emerging evidence points toward metabolic inflammation as a key process in the fatty liver that contributes to multiorgan morbidity. Key extrahepatic comorbidities that are influenced by NAFLD are type 2 diabetes, cardiovascular disease, and impaired neurocognitive function. Importantly, the presence of nonalcoholic steatohepatitis and advanced hepatic fibrosis increase the risk for systemic comorbidity in NAFLD. Although the precise nature of the crosstalk between the liver and other organs has not yet been fully elucidated, there is emerging evidence that metabolic inflammation-in part, emanating from the fatty liver-is the engine that drives cellular dysfunction, cell death, and deleterious remodeling within various body tissues. This review describes several inflammatory pathways and mediators that have been implicated as links between NAFLD and type 2 diabetes, cardiovascular disease, and neurocognitive decline.

Carvacryl acetate, a semisynthetic monoterpenic ester obtained from essential oils, provides neuroprotection against cerebral ischemia reperfusion-induced oxidative stress injury via the Nrf2 signalling pathway

Carvacryl acetate (CA) is a semisynthetic monoterpenic ester obtained from essential oils, and it exerts an antioxidation effect.

Depression-like behavior, hyperglycemia, oxidative stress, and neuroinflammation presented in diabetic mice are reversed by the administration of 1-methyl-3-(phenylselanyl)-1H-indole

Oxidative stress and neuroinflammation are found both in diabetes mellitus and major depressive disorder (MDD). In addition to damage in peripheral organs, such as liver and kidney, diabetic patients have a higher risk of developing depression. In this sense, the objective of the present study was to characterize the antidepressant-like effect of a selenium-containing compound, the 1-methyl-3-(phenylselanyl)-1H-indole (MFSeI), in streptozotocin (STZ)-induced diabetic mice. STZ (200 mg/kg, i.p.) was used to induce diabetes mellitus type I, and after seven days, the administration of MFSeI (10 mg/kg, i.g.) was initiated and followed for the next 14 days. Twenty-four hours after the last administration of MFSeI, the behavioral tests were performed, followed by euthanasia. The treatment with MFSeI was able to reverse the hyperglycemia induced by STZ. MFSeI also decreased the plasma levels of biomarkers of liver and kidney damage. Importantly, MFSeI reversed the depression-like behavior induced by STZ in the tail suspension test and forced swimming test without promoting locomotor alterations. Furthermore, MFSeI reversed the increased levels of reactive species and lipid peroxidation in the prefrontal cortex (PFC), hippocampus (HC), liver, and kidney of STZ-treated mice. Treatment with MFSeI also decreased the expression of tumor necrosis factor-alpha, inducible nitric oxide synthase and indoleamine 2,3-dioxygenase, while increasing the expression of interleukin-10, insulin receptor substrate-1 and glucose transport-4 in the PFC and HC of mice. Taken together, the results indicate the effectiveness of MFSeI against depression-like behavior and central and peripheral complications caused by diabetes in mice.

The neuroprotective effect and action mechanism of polyphenols in diabetes mellitus-related cognitive dysfunction

BACKGROUND

Diabetes mellitus (DM) is a complex and prevalent metabolic disorder worldwide. Strong evidence has emerged that DM is a risk factor for the accelerated rate of cognitive decline and the development of dementia. Though traditional pharmaceutical agents are efficient for the management of DM and DM-related cognitive decrement, long-term use of these drugs are along with undesired side effects. Therefore, tremendous studies have focused on the therapeutic benefits of natural compounds at present. Ample evidence exists to prove that polyphenols are capable to modulate diabetic neuropathy with minimal toxicity and adverse effects.

PURPOSE

To describe the benefits and mechanisms of polyphenols on DM-induced cognitive dysfunction. In this review, we introduce an updated overview of associations between DM and cognitive dysfunction. The risk factors as well as pathological and molecular mechanisms of DM-induced cognitive dysfunction are summarized. More importantly, many active polyphenols that possess preventive and therapeutic effects on DM-induced cognitive dysfunction and the potential signaling pathways involved in the action are highlighted.

CONCLUSIONS

The therapeutic effects of polyphenols on DM-related cognitive dysfunction pave a novel way for the management of diabetic encephalopathy.

The Protective Effect of Insulin on Rat Cortical Neurons in Oxidative Stress and Its Dependence on the Modulation of Akt, GSK-3beta, ERK1/2, and AMPK Activities

Insulin is a promising drug for the treatment of diseases associated with brain damage. However, the mechanism of its neuroprotective action is far from being understood. Our aim was to study the insulin-induced protection of cortical neurons in oxidative stress and its mechanism. Immunoblotting, flow cytometry, colorimetric, and fluorometric techniques were used. The insulin neuroprotection was shown to depend on insulin concentration in the nanomolar range. Insulin decreased the reactive oxygen species formation in neurons. The insulin-induced modulation of various protein kinase activities was studied at eight time-points after neuronal exposure to prooxidant (hydrogen peroxide). In prooxidant-exposed neurons, insulin increased the phosphorylation of GSK-3beta at Ser⁹ (thus inactivating it), which resulted from Akt activation. Insulin activated ERK1/2 in neurons 5–30 min after cell exposure to prooxidant. Hydrogen peroxide markedly activated AMPK, while it was for the first time shown that insulin inhibited it in neurons at periods of the most pronounced activation by prooxidant. Insulin normalized Bax/Bcl-2 ratio and mitochondrial membrane potential in neurons in oxidative stress. The inhibitors of the PI3K/Akt and MEK1/2/ERK1/2 signaling pathways and the AMPK activator reduced the neuroprotective effect of insulin. Thus, the protective action of insulin on cortical neurons in oxidative stress appear to be realized to a large extent through activation of Akt and ERK1/2, GSK-3beta inactivation, and inhibition of AMPK activity increased by neuronal exposure to prooxidant.

Nrf2 mediates the protective effect of edaravone after chlorpyrifos-induced nervous system toxicity

We aim to confirm the impairment of chlorpyrifos (CPF) in PC12 cells, evaluate the protective effect of edaravone on CPF-induced injury, and try to unravel its underlying mechanism perspective from Nrf2 signaling pathway. Viability of PC12 cells treated with CPF and edaravone (Ed) were evaluated by MTT assay. Cell apoptosis was observed by the Hoechst 33342 stain. The level of reactive oxygen species (ROS), the content of malondialdehyde (MDA), and the activity of superoxide dismutase (SOD) were detected to evaluate the oxidative stress injury. The expression of Nrf2 was detected by Western blot; profoundly, RNA interference was conducted to construct Nrf2 gene knockdown PC12 cells and to uncover its underlying mechanism. MTT results showed CPF injured PC12 cells in a concentration-dependent manner. Increased ROS and MDA content, decreased total SOD activity, or even apoptosis were occurred in PC12 cells when treated with CPF. Interestingly, CPF-induced cell injury was conspicuously reversed after Ed administration. Nrf2 signaling pathway was activated after Ed treatment and the neuroprotective effect of Ed was not significant in cells after Nrf2 gene knockdown. In conclusion, Ed exerts neuroprotective effect on CPF-induced oxidative stress injury and its mechanism was correlated with the Nrf2 signaling pathway.

Insulin Signaling Impairment in the Brain as a Risk Factor in Alzheimer's Disease

Type 2 diabetes is a risk factor for developing Alzheimer’s disease (AD). The underlying mechanism that links up the two conditions seems to be the de-sensitization of insulin signaling. In patients with AD, insulin signaling was found to be de-sensitized in the brain, even if they did not have diabetes. Insulin is an important growth factor that regulates cell growth, energy utilization, mitochondrial function and replacement, autophagy, oxidative stress management, synaptic plasticity, and cognitive function. Insulin desensitization, therefore, can enhance the risk of developing neurological disorders in later life. Other risk factors, such as high blood pressure or brain injury, also enhance the likelihood of developing AD. All these risk factors have one thing in common – they induce a chronic inflammation response in the brain. Pro-inflammatory cytokines block growth factor signaling and enhance oxidative stress. The underlying molecular processes for this are described in the review. Treatments to re-sensitize insulin signaling in the brain are also described, such as nasal insulin tests in AD patients, or treatments with re-sensitizing hormones, such as leptin, ghrelin, glucagon-like peptide 1 (GLP-1),and glucose-dependent insulinotropic polypeptide (GIP). The first clinical trials show promising results and are a proof of concept that utilizing such treatments is valid.

Rosmarinic acid exerts an antagonistic effect on vascular calcification by regulating the Nrf2 signalling pathway

Vascular calcification (VC) is a process in which calcium phosphate crystals deposit within the intima and middle membrane of the vascular wall. Rosmarinic acid (RA) is a common phenolic compound. It possesses antioxidation, anti-inflammatory, antimicrobial effects. Our experiment aims to investigate the role and molecular mechanism of RA in VC. Rats were fed high-fat feed and injected with vitamin D3 to establish a VC model. β-Glyerophosphate (β GP) was selected to stimulate rat aortic smooth muscle cells (VSMCs) in order to establish the cell calcification model. Kits were used to detect the antioxidant index and calcification index. RA significantly reduced the levels of ALP, MDA, Ca, and P but increased SOD levels. Quantitative real-time polymerase chain reaction (RT-qPCR) and western blot analysis were used to detect various antioxidant-related genes and calcified genes on an mRNA and protein level. The results showed that nuclear factor red cell-2 related factors (Nrf2), haem oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase (NQO1), and osteoprotegerin (OPG) were up regulated by RA at both the mRNA and protein levels, but kelch-like ECH-associated protein 1 (Keap1), nuclear factor kappa B(NF-κB), cadherin associated protein (β-catenin) and osteogenic transcription factor (Runx2) expression at both the mRNA and protein levels was significantly inhibited. Microscopic examination showed that RA significantly decreased the content of calcified nodules and the production of reactive oxygen species (ROS). When Nrf2 is disturbed, the role of RA is significantly blocked. Our results showed that RA can improve VC by regulating the Nrf2 pathway.

Antioxidative, inflammatory and immune responses in hydrogen peroxide-induced liver injury of tilapia (GIFT, Oreochromis niloticus)

Oxidative stress has been implicated in the pathogenesis of many liver diseases in fish, but the molecular mechanism is still obscure. Here, we used hydrogen peroxide (H₂O₂) as a reactive oxygen species (ROS) to induce liver injury and assess underlying molecular mechanism linking oxidative stress and liver injury in fish. Tilapia were injected with various concentrations of H₂O₂ (0, 40, 120, 200, 300 and 400 mM) for 72 h. The blood and liver were collected to assay biochemical parameters and genes expression after 24, 48 and 72 h of injection. The results showed that treatments with higher H₂O₂ levels (300 and/or 400 mM) significantly increased the levels of GPT, GOT, AKP and MDA, and apparently decreased the levels of TP, ALB, SOD, GSH, CAT, GST and T-AOC throughout of the 72 h. The gene expression data showed that treatments with 200, 300 and/or 400 H₂O₂ suppressed Nrf2/keap1 pathway and its downstream genes including ho-1, nqo1 and gsta, activated inflammatory response via enhancing the mRNA levels of nf-κb, tnf-α, il-1β and il-8, and attenuating il-10 mRNA level, and caused immunotoxicity through downregulating the genes expression of c3, hep, lzm and Igm for 24, 48 and/or 72 h. Additionally, there was a mild or strong increase in levels of nrf2 and its subsequent antioxidant genes or enzymes such as ho-1, nqo1, gst, CAT and SOD in treatments with lower concentrations of H₂O₂ (40 or 120 mM) for 24 and/or 48 h. Overall results suggested that H₂O₂ hepatotoxicity was mainly concerned with lipid peroxidation, impairment antioxidant defense systems, inflammatory response and immunotoxicity, and Nrf2/Keap1 and NF-κB signaling pathways played important roles in oxidative stress-induced liver injury in fish.