Asiaticoside attenuates diabetes-induced cognition deficits by regulating PI3K/Akt/NF-κB pathway

Effects of High-Intensity Interval Training (HIIT) on miR-29c and miR-146a Expression in the Hippocampus of Streptozotocin-Induced Diabetic Rats

BACKGROUND

MicroRNAs like miR-146a and miR-29c are potential biomarkers for diabetes, which is linked to brain impairments such as cognitive decline and hippocampal dysfunction due to hyperglycemia and inflammation. This study investigates the effects of high-intensity interval training (HIIT) on hippocampal miR-146a and miR-29c expression and serum TNF-α levels in diabetic rats, highlighting its role in reducing inflammation and improving brain function.

METHODS

Twenty-four male Wistar rats were divided into four groups: Control (Normal), 1-week diabetes (Diabetes 1W), 6-week diabetes (Diabetes 6W), and diabetic HIIT (Diabetes-Exe). Diabetes was induced using streptozotocin (55mg/kg) and rats with blood glucose >250mg/dL were included. HIIT was conducted for six weeks, and hippocampal miR-146a, miR-29c expression, and TNF-α serum levels were assessed using Real-Time PCR and ELISA. TNF-α serum levels were measured as a marker of systemic inflammation.

RESULTS

Diabetic rats exhibited decreased miR-146a and increased miR-29c expression in the hippocampus compared to controls. Additionally, TNF-α serum levels were significantly higher in the diabetic groups, indicating an elevated inflammatory state. HIIT in the Diabetes-Exe group resulted in a non-significant change in miR-29c expression and TNF-α serum levels, accompanied by a significant increase in miR-146a expression compared to the Diabetes 6W group.

CONCLUSION

HIIT exercise may help reduce hippocampal neuronal damage in diabetic rats by modulating miR-146a expression, improving blood glucose control, and reducing inflammation. Although HIIT did not significantly alter miR-29c expression, its potential as an effective non-pharmacological strategy for managing diabetic neuropathy complications cannot be excluded.

Studying targeted oxidation in diabetic cognitive dysfunction based on scientometrics analysis: research progress of natural product approaches

PURPOSE

The aim is to provide new insights for researchers studying the pathogenesis of diabetic cognitive dysfunction and promoting the wider use of natural products in their treatment.

METHOD

First, the Web of Science Core Collection was selected as the data source for a computerized literature search on oxidative stress and diabetic cognitive dysfunction (DCD). Next, Biblimetrix and VOSviewer performed statistical analysis focusing on publication countries, institutions, authors, research hotspots, and emerging directions in the field. Then, through the analysis of keywords and key articles, the forefront of the field is identified. Finally, we discussed the pathogenesis of DCD, the influence of oxidative stress on DCD and the antioxidant effect of natural products on DCD.

RESULT

293 valid papers were obtained. Bibliometrics showed that oxidative stress, diabetes, Alzheimer's disease (AD), cognitive decline, insulin resistance and quercetin were the key words of the symbiotic network.

CONCLUSION

The antioxidant effects of natural products in improving DCD have been extensively studied in preclinical studies, providing potential for their treatment in DCD, but their evaluation in clinical trials is currently uncommon.

Effects of asiaticoside on the model of gestational diabetes mellitus in HTR-8/svneo cells via PI3K/AKT pathway

BACKGROUND

Asiaticoside (AS) has been reported to improve the changes induced by high glucose stimulation, and it may have potential therapeutic effects on gestational diabetes mellitus (GDM). This study aims to explore the effect of AS on the cell model of GDM and the action mechanism of the PI3K/AKT pathway.

METHODS

The GDM model was established in HTR-8/Svneo cells with a high glucose (HG) medium. After the cytotoxicity assay of AS, cells were divided into the control group, HG group and HG + AS group to conduct control experiment in cells. The cell proliferation and migration were detected by CCK-8 assay and scratch test, respectively. The mRNA levels of PI3K, AKT2, mTORC1, and GLUT4 in PI3K/AKT signalling pathway were measured by RT-PCR, and the protein expressions of these signalling molecules were monitored by western blot.

RESULTS

AS showed a promotion effect on the cell proliferation rate of HTR-8/Svneo cells, and 80 μmol/L AS with a treatment time of 48 h had no cytotoxicity. The cell proliferation rate, migration rate, mRNA levels and protein expressions of PI3K, AKT2, mTORC1, and GLUT4 in the HG group were significantly lower than those in the control group, which were significantly increased in the HG + AS group (p < 0.05).

CONCLUSIONS

AS can facilitate the cell proliferation and migration in the cell model of GDM, and might play a role in GDM treatment via PI3K/AKT pathway.

Progress in the Pathogenesis of Diabetic Encephalopathy: The Key Role of Neuroinflammation

Diabetic encephalopathy (DE) is a severe complication that occurs in the central nervous system (CNS) and leads to cognitive impairment. DE involves various pathophysiological processes, and its pathogenesis is still unclear. This review summarised current research on the pathogenesis of diabetic encephalopathy, which involves neuroinflammation, oxidative stress, iron homoeostasis, blood-brain barrier disruption, altered gut microbiota, insulin resistance, etc. Among these pathological mechanisms, neuroinflammation has been focused on. This paper summarises some of the molecular mechanisms involved in neuroinflammation, including the Mammalian Target of Rapamycin (mTOR), Lipocalin-2 (LCN-2), Pyroptosis, Advanced Glycosylation End Products (AGEs), and some common pro-inflammatory factors. In addition, we discuss recent advances in the study of potential therapeutic targets for the treatment of DE against neuroinflammation. The current research on the pathogenesis of DE is progressing slowly, and more research is needed in the future. Further study of neuroinflammation as a mechanism is conducive to the discovery of more effective treatments for DE in the future.

Asiaticoside protected brain injury in hypertensive intracerebral hemorrhage via activation of the PI3K/AKT pathway

Hypertensive intracerebral hemorrhage (HICH) is a destructive disease with high mortality, incidence, and disability. Asiaticoside (AC) is a triterpenoid derivative that has demonstrated to exert a protective effect on neuron and blood vessel. To investigate the function and potential mechanism of AC on HICH. Human brain microvascular endothelial cells (hBMECs) were treated with 20 U/mL thrombin for 24 h to establish the HICH model in vitro, and AC with the concentration of 1, 2 and 4 µM were used to incubate hBMECs. The effect and potential mechanism of AC on HICH were investigated by using cell counting kit-8, flow cytometry, tube forming assays, vascular permeability experiments and western blot assays. In vivo, rats were injected with 20 µL hemoglobin with a concentration of 150 mg/mL, and then intragastrically administrated with 1.25, 2.5 and 5 mg/kg AC. Behavioral tests, brain water content measurement, hematoxylin-eosin (HE) staining, terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling assays, and western blot were used to assess the effect and potential mechanism of AC on HICH. AC (at 2 and 4 µM) improved the proliferation, apoptosis, angiogenesis and vascular permeability in thrombin-induced hBMECs (p < 0.05). Besides, AC (2.5 and 5 mg/kg) ameliorated behavioral scores, brain water content, pathological lesion, apoptosis and the expression of vascular permeability-related proteins in rats with HICH (p < 0.05). In addition, AC elevated the expression of PI3K/AKT pathway after HICH both in cell and animal models (p < 0.05). Application of LY294002, an inhibitor of PI3K/AKT pathway, reversed the ameliorative effect of AC on the proliferation, apoptosis, angiogenesis and vascular permeability in thrombin-induced hBMECs (p < 0.05). AC reduced brain damage by increasing the expression of the PI3K/AKT pathway after HICH.

Flavonols as a Potential Pharmacological Intervention for Alleviating Cognitive Decline in Diabetes: Evidence from Preclinical Studies

Diabetes mellitus is a complex metabolic disease associated with reduced synaptic plasticity, atrophy of the hippocampus, and cognitive decline. Cognitive impairment results from several pathological mechanisms, including increased levels of advanced glycation end products (AGEs) and their receptors, prolonged oxidative stress and impaired activity of endogenous mechanisms of antioxidant defense, neuroinflammation driven by the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), decreased expression of brain-derived neurotrophic factor (BDNF), and disturbance of signaling pathways involved in neuronal survival and cognitive functioning. There is increasing evidence that dietary interventions can reduce the risk of various diabetic complications. In this context, flavonols, a highly abundant class of flavonoids in the human diet, are appreciated as a potential pharmacological intervention against cognitive decline in diabetes. In preclinical studies, flavonols have shown neuroprotective, antioxidative, anti-inflammatory, and memory-enhancing properties based on their ability to regulate glucose levels, attenuate oxidative stress and inflammation, promote the expression of neurotrophic factors, and regulate signaling pathways. The present review gives an overview of the molecular mechanisms involved in diabetes-induced cognitive dysfunctions and the results of preclinical studies showing that flavonols have the ability to alleviate cognitive impairment. Although the results from animal studies are promising, clinical and epidemiological studies are still needed to advance our knowledge on the potential of flavonols to improve cognitive decline in diabetic patients.

Standardized extract of Glehnia Littoralis abrogates memory impairment and neuroinflammation by regulation of CREB/BDNF and NF-κB/MAPK signaling in scopolamine-induced amnesic mice model

Mild cognitive impairment is a typical symptom of early Alzheimer's disease (AD). Glehnia littoralis (G. littoralis), a medicinal halophyte plant commonly used to treat strokes, has been shown to possess some therapeutic qualities. In this study, we investigated the neuroprotective and anti-neuroinflammatory effects of a 50% ethanol extract of G. littoralis (GLE) on lipopolysccharide (LPS)-stimulated BV-2 cells and scopolamine-induced amnesic mice. In the in vitro study, GLE treatment (100, 200, and 400 µg/mL) markedly attenuated the translocation of NF-κB to the nucleus concomitantly with the significant mitigation of the LPS-induced production of inflammatory mediators, including NO, iNOS, COX-2, IL-6, and TNF-α. In addition, the GLE treatment suppressed the phosphorylation of MAPK signaling in the LPS-stimulated BV-2 cells. In the in vivo study, mice were orally administered with the GLE (50, 100, and 200 mg/kg) for 14 days, and cognitive loss was induced via the intraperitoneal injection of scopolamine (1 mg/kg) from 8 to 14 days. We found that GLE treatment ameliorated memory impairment and simultaneously improved memory function in the scopolamine-induced amnesic mice. Correspondingly, GLE treatment significantly decreased the AChE level and upregulated the protein expression of neuroprotective markers, such as BDNF and CREB, as well as Nrf2/HO-1 and decreased the levels of iNOS and COX-2 in the hippocampus and cortex. Furthermore, GLE treatment attenuated the increased phosphorylation of NF-κB/MAPK signaling in the hippocampus and cortex. These results suggest that GLE has a potential neuroprotective activity that may ameliorate learning and memory impairment by regulating AChE activity, promoting CREB/BDNF signaling, and inhibiting NF-κB/MAPK signaling and neuroinflammation.

Effects of Dietary Inclusion of Asiaticoside on Growth Performance, Lipid Metabolism, and Gut Microbiota in Yellow-Feathered Chickens

Excessive abdominal fat deposition in chickens is a major concern in the poultry industry. Nutritional interventions are a potential solution, but current options are limited. Asiaticoside (Asi), a herbal extract, has shown positive effects in animals, but its impact on poultry lipid metabolism is still unknown. In this study, the effects of dietary Asi on yellow-feathered chicken lipid metabolism and its potential mechanisms were investigated. A total of 120 chickens were randomly divided into three groups, with five replicates per group and 8 chickens per replicate. The chickens were fed a basal diet supplemented with 0, 0.01, or 0.05% Asi for 6 wk. The results showed that Asi down-regulated lipogenic gene expression and up-regulated lipid-breakdown-related genes in both the liver and fat tissues of the chickens, which resulted in a half reduction in abdominal fat while not affecting meat yield. Mechanistically, the hepatic and adipose PI3K/AKT pathway may be involved in Asi-induced fat loss in chickens as revealed by computer-aided reverse drug target prediction and gene expression analysis. Moreover, Asi ingestion also significantly modified the cecal microbiota of the chickens, resulting in a reduced Firmicutes to Bacteroidetes ratio and decreased abundance of bacteria positively correlated with abdominal fat deposition such as Ruminococcus, while increasing the abundance of bacteria inversely correlated with abdominal fat deposition such as Lactobacillus, Bacteroides, and Blautia. Collectively, these data suggest that Asi could ameliorate the abdominal fat deposition in yellow-feathered chickens, probably through modulating the PI3K/AKT pathway and gut microbiota function.

A review of pharmacokinetic and pharmacological properties of asiaticoside, a major active constituent of Centella asiatica (L.) Urb

ETHNOPHARMACOLOGICAL RELEVANCE

Centella asiatica (L.) Urb., a potential medicinal plant, is widely used in orient traditional medicine. Its major active constituents include asiaticoside (AS), madecassoside (MS), asiatic acid and madecassic acid. Thereinto, AS is a pentacyclic triterpenoid saponin with a variety of pharmacological effects including antitumor, neuroprotective and wound healing effects.

AIM OF THE STUDY

In this review, we summarize the pharmacokinetics, safety and pharmacological properties of AS.

MATERIALS AND METHODS

We gathered information about AS from articles published up to 2022 and listed in Google scholar, PubMed, Web of Science, Elsevier, and similar databases. The keywords used in our search included "asiaticoside", "Centella asiatica", "pharmacokinetics", "nerve", "cancer", "skin", etc. RESULTS: AS appeared to degrade through a first-order reaction and had low biotoxicity. However, the pharmacokinetic properties of AS differed according to species. AS is highly blood-brain-barrier permeable without any harmful side effect. It has a variety of pharmacological effects including anti-neural inflammation and anti-cancer properties, as well as protective properties for the skin, cardiovascular system, and pulmonary system.

CONCLUSION

This review comprehensively summarized current information regarding the pharmacokinetic and pharmacological properties of AS, and supported the pharmaceutical value of this compound. Future research should focus on improving bioavailability of AS and conducting clinical assessment.

A systematic review on anti-diabetic plant essential oil compounds: Dietary sources, effects, molecular mechanisms, and safety

Type 2 diabetes mellitus (T2DM) is a multifaceted metabolic syndrome defined through the dysfunction of pancreatic β-cells driven by a confluence of genetic and environmental elements. Insulin resistance, mediated by interleukins and other inflammatory elements, is one of the key factors contributing to the progression of T2DM. Many essential oils derived from dietary plants are beneficial against various chronic diseases. We reviewed the anti-diabetic properties of dietary plant-derived essential oil compounds, with a focus on their molecular mechanisms by modulating specific signaling pathways and other critical inflammatory mediators involved in insulin resistance. High-quality literature published in the last 12 years, from 2010 to 2022, was collected from the Scopus, Web of Science, PubMed, and Embase databases using the search terms "dietary plants," "essential oils," "anti-diabetic," "insulin resistance," "antihyperglycemic," "T2DM," "anti-diabetic essential oils," and anti-diabetic mechanism." According to the results, the essential oil compounds, including cinnamaldehyde, carvacrol, zingerone, sclareol, zerumbone, myrtenol, thujone, geraniol, citral, eugenol, thymoquinone, thymol, citronellol, α-terpineol, and linalool have been demonstrated to contain strong anti-diabetic effects via modulating various signal transduction pathways linked to glucose metabolism. Additionally, in diabetes-related animal models, they can also considerably reduce the expression of TNF-α, IL-1β, IL-4, IL-6, iNOS, and COX-2. The main signaling molecules regulated by these compounds include AMPK, GLUT4, Caspase-3, PPARγ, PPARα, NF-κB, p-IκBα, MyD88, MCP-1, SREBP-1c, AGEs, RAGE, VEGF, Nrf2/HO-1, and SIRT-1. They can also significantly inhibit the generation of TBARS and MDA, reduce oxidative stress, increase insulin levels, adiponectin, and glycoprotein enzymes, boost antioxidant enzymes like SOD, CAT, and GPx, as well as reduce glutathione and vital glycolytic enzymes. Besides, they can significantly lower the levels of liver enzymes and lipid profile markers. Moreover, most essential oil compounds are generally safe based on animal studies. In conclusion, dietary plant-derived essential oil compounds have potential anti-diabetic effects by influencing different signaling pathways and molecular targets linked to glucose metabolism, and should be safe and beneficial against diabetes and related complications.

Hypoglycemic medicines in the treatment of Alzheimer's disease: Pathophysiological links between AD and glucose metabolism

Alzheimer's Disease (AD) is a global chronic disease in adults with beta-amyloid (Aβ) deposits and hyperphosphorylated tau protein as the pathologic characteristics. Although the exact etiology of AD is still not fully elucidated, aberrant metabolism including insulin signaling and mitochondria dysfunction plays an important role in the development of AD. Binding to insulin receptor substrates, insulin can transport through the blood-brain barrier (BBB), thus mediating insulin signaling pathways to regulate physiological functions. Impaired insulin signaling pathways, including PI3K/Akt/GSK3β and MAPK pathways, could cause damage to the brain in the pathogenesis of AD. Mitochondrial dysfunction and overexpression of TXNIP could also be causative links between AD and DM. Some antidiabetic medicines may have benefits in the treatment of AD. Metformin can be beneficial for cognition improvement in AD patients, although results from clinical trials were inconsistent. Exendin-4 may affect AD in animal models but there is a lack of clinical trials. Liraglutide and dulaglutide could also benefit AD patients in adequate clinical studies but not semaglutide. Dipeptidyl peptidase IV inhibitors (DPP4is) such as saxagliptin, vildagliptin, linagliptin, and sitagliptin could boost cognitive function in animal models. And SGLT2 inhibitors such as empagliflozin and dapagliflozin were also considerably protective against new-onset dementia in T2DM patients. Insulin therapy is a promising therapy but some studies indicated that it may increase the risk of AD. Herbal medicines are helpful for cognitive function and neuroprotection in the brain. For example, polyphenols, alkaloids, glycosides, and flavonoids have protective benefits in cognition function and glucose metabolism. Focusing on glucose metabolism, we summarized the pharmacological mechanism of hypoglycemic drugs and herbal medicines. New treatment approaches including antidiabetic synthesized drugs and herbal medicines would be provided to patients with AD. More clinical trials are needed to produce definite evidence for the effectiveness of hypoglycemic medications.

Asiaticoside Prevents Oxidative Stress and Apoptosis in Endothelial Cells by Activating ROS-dependent p53/Bcl-2/Caspase-3 Signaling Pathway

BACKGROUND

Asiaticoside (AC) is a triterpenoid saponin found in Centella asiatica (L.) urban extract that has a wide range of pharmacological properties. Our previous study demonstrated that AC could promote angiogenesis in diabetic wounds, but the specific mechanisms remain unknown.

OBJECTIVE

This study aimed to examine the effectiveness and mechanism of AC on human umbilical vein endothelial cells (HUVECs) exposed to tert-butyl hydroperoxide (t-BHP) toxicity.

METHODS

Senescence was confirmed using senescence-associated betagalactosidase (SA-β-gal) activity and expression of the cell cycle phase markers p16 and p21. The levels of SOD, NO, MDA, GSH-Px, and ROS were tested. Furthermore, several cell death-related genes and proteins (p53, Bax, Bcl-2 and Caspase-3) were assessed with RT-qPCR and Western blotting.

RESULTS

AC significantly reduced SA-β-gal activity, with both the suppression of cellcycle inhibitors p16 and p21. We also found that the induced oxidative stress and apoptosis caused by t-BHP treatment resulted in the decrease of antioxidant enzymes activities, the surge of ROS and MDA, the up-regulation of p53, Bax and caspase-3, and the decrease of SOD, NO, GSH-Px and Bcl-2. These biochemical changes were all reversed by treatment with varying doses of AC.

CONCLUSION

AC alleviates t-BHP-induced oxidative injury and apoptosis in HUVECs through the ROS-dependent p53/Bcl-2/Caspase-3 signaling pathway. It may be a potential antioxidant applied in metabolic disorders and pharmaceutical products.

Isoflavone-Enriched Soybean Leaves (Glycine Max) Alleviate Cognitive Impairment Induced by Ovariectomy and Modulate PI3K/Akt Signaling in the Hippocampus of C57BL6 Mice

(1) Background: The estrogen decline during perimenopause can induce various disorders, including cognitive impairment. Phytoestrogens, such as isoflavones, lignans, and coumestans, have been tried as a popular alternative to avoid the side effects of conventional hormone replacement therapy, but their exact mechanisms and risk are not fully elucidated. In this study, we investigated the effects of isoflavone-enriched soybean leaves (IESLs) on the cognitive impairment induced by ovariectomy in female mice. (2) Methods: Ovariectomy was performed at 9 weeks of age to mimic menopausal women, and the behavior tests for cognition were conducted 15 weeks after the first administration. IESLs were administered for 18 weeks. (3) Results: The present study showed the effects of IESLs on the cognitive function in the OVX (ovariectomized) mice. Ovariectomy markedly increased the body weight and fat accumulation in the liver and perirenal fat, but IESL treatment significantly inhibited them. In the behavioral tests, ovariectomy impaired cognitive functions, but administration of IESLs restored it. In addition, in the OVX mice, administration of IESLs restored decreased estrogen receptor (ER) β and PI3K/Akt expression in the hippocampus. (4) Conclusions: The positive effects of IESLs on cognitive functions may be closely related to the ER-mediated PI3/Akt signaling pathway in the hippocampus.

Terpenoid natural products exert neuroprotection via the PI3K/Akt pathway

PI3K/Akt, an essential signaling pathway widely present in cells, has been shown to be relevant to neurological disorders. As an important class of natural products, terpenoids exist in large numbers and have diverse backbones, so they have a great chance to be identified as neuroprotective agents. In this review, we described and summarized recent research for a range of terpenoid natural products associated with the PI3K/Akt pathway by classifying their basic chemical structures of the terpenes, identified by electronic searches on PubMed, Web of Science for research, and Google Scholar websites. Only articles published in English were included. Our discussion here concerned 16 natural terpenoids and their mechanisms of action, the associated diseases, and the methods of experimentation used. We also reviewed the discovery of their chemical structures and their derivatives, and some compounds have been concluded for their structure–activity relationships (SAR). As a result, terpenoids are excellent candidates for research as natural neuroprotective agents, and our content will provide a stepping stone for further research into these natural products. It may be possible for more terpenoids to serve as neuroprotective agents in the future.

An injectable thermosensitive Pluronic F127/hyaluronic acid hydrogel loaded with human umbilical cord mesenchymal stem cells and asiaticoside microspheres for uterine scar repair

Uterine scar was one of the long-term complications cesarean section. In this study, an thermo-responsive injectable hydrogel loaded with human umbilical cord mesenchymal stem cells (UCMSCs) and asiaticoside microspheres (AMs) was used for uterine scar repair, which was prepared by optimizing the mixed ratio of aldehyde-functionalized Pluronic F127 (F127-CHO) and adipic dihydrazide-modified hyaluronic acid (AHA). The asiaticoside was loaded in Poly (DL-lactide-co-gycolide) (PLGA) by emulsion- diffusion-evaporation method. The hydrogel had appropriate pore size, good mechanical property, and slow release ability of asiaticoside. In vitro cell experiments demonstrated that F127-CHO/AHA/AMs could effectively promote stem cell adhesion and proliferation, promote angiogenesis, and provide a suitable microenvironment for cell survival. The F127-CHO/AHA/AMs/UCMSCs hydrogel was further used to repair uterine scar in female SD rats. The results showed that the prepared hydrogel could promote the proliferation of rat endometrial cells, promote the regeneration of glands, reduce the degree of endometrial fibrosis and restore the morphology of uterine cavity. The hydrogel could upregulate expression of Ki67 and IGF-1, downregulate TGF-β1 expression and promote M1-M2 transition of macrophages. This study confirmed that the prepared hydrogel could be used as an effective transplantation strategy, which could be expected to achieve clinical transformation of uterine scar repair.

The modulation of cAMP/PKA pathway by asiaticoside ameliorates high glucose-induced inflammation and apoptosis of retinal pigment epithelial cells

Asiaticoside, the major bioactive constituent purified from Centella asiatica, is a pentacyclic triterpene saponin with sugar moieties (glucose-glucose-rhamnose). Its biological activities including anti-inflammation and antioxidant have been widely reported. This study aimed to investigate the role of asiaticoside in diabetic retinopathy (DR). Human retinal pigment epithelium (RPE) cells ARPE-19 were induced by high glucose. Then, cell survival rate, expression of inflammatory factors, oxidative stress, and apoptosis were measured by MTT method, western blot, oxidative stress detection kits and TUNEL respectively. To uncover the underlying mechanism, the levels of cyclic AMP (cAMP) and protein kinase A (PKA) were measured by Enzyme linked immunosorbent assay (ELISA) and PKA activities were detected by the Kemptide phosphorylation assay. Furthermore, cAMP inhibitor SQ22536 was also used to validate the mechanism. Asiaticoside suppressed the inflammation and apoptosis of ARPE-19 cells, and the activities of cAMP and PKA were inhibited upon HG induction while again released after further administration of asiaticoside. However, these effects were all abolished by SQ22536. In conclusion, we have demonstrated in this paper that asiaticoside ameliorates high glucose-induced inflammation and apoptosis of RPE cells by activating cAMP/PKA signaling pathway. asiaticoside-mediated activation of cAMP/PKA signaling pathway may serve as a potential target for the management of DR.

Acute enhancing effect of a standardized extract of Centella asiatica (ECa 233) on synaptic plasticity: an investigation via hippocampal long-term potentiation

CONTEXT

ECa 233 is the standardized extract of Centella asiatica (L.) Urban. (Apiaceae). It contains at least 85% of triterpenoid glycosides and yields neuroprotective and memory-enhancing effects. However, the exact molecules exerting the effects might be triterpenic acid metabolites reproduced through gut metabolism after orally ingesting C. asiatica, not triterpenoid glycosides.

OBJECTIVE

This study demonstrates the effect of unmetabolized ECa 233 on hippocampal synaptic plasticity after directly perfusing ECa 233 over acute brain slices.

MATERIALS AND METHODS

The brain slices obtained from 7-week-old male Wistar rats were randomly divided into 4 groups. We perfused either artificial cerebrospinal fluid (ACSF), 0.01% DMSO, 10 µg/mL ECa 233, or 100 µg/mL on brain slices, and measured the long-term potentiation (LTP) magnitude to determine the synaptic plasticity of hippocampal circuits in each group.

RESULTS

The LTP magnitude of ACSF, DMSO, 10 ug/mL ECa 233, and 100 ug/mL ECa 233 groups increased from 100% to 181.26 ± 38.19%, 148.74 ± 5.40%, 273.71 ± 56.66%, 182.17 ± 18.61%, respectively. ECa 233 at the concentration of 10 µg/mL robustly and significantly enhanced hippocampal LTP magnitude. The data indicates an improvement of the hippocampal synaptic plasticity.

DISCUSSION AND CONCLUSIONS

This study emphasizes the effectiveness of triterpenoid glycosides in ECa 233 on synaptic plasticity enhancement. Therefore, this study supported and complimented the known effects of C. asiatica extract on the enhancement of synaptic plasticity, and subsequently, learning and memory, suggesting that ECa 233 could be a promising memory enhancing agent.

Actions and Therapeutic Potential of Madecassoside and Other Major Constituents of Centella asiatica: A Review

Centella asiatica is a popular herb well-known for its wide range of therapeutic effects and its use as a folk medicine for many years. Its therapeutic properties have been well correlated with the presence of asiaticoside, madecassoside, asiatic and madecassic acids, the pentacyclic triterpenes. The herb has been extensively known to treat skin conditions; nevertheless, several pre-clinical and clinical studies have scientifically demonstrated its effectiveness in other disorders. Among the active constituents that have been identified in Centella asiatica, madecassoside has been the subject of only a relatively small number of scientific reports. Therefore, this review, while including other major constituents of this plant, focuses on the therapeutic potential, pharmacokinetics and toxicity of madecassoside.

Huang-Pu-Tong-Qiao Formula Ameliorates the Hippocampus Apoptosis in Diabetic Cognitive Dysfunction Mice by Activating CREB/BDNF/TrkB Signaling Pathway

Background

Huang-Pu-Tong-Qiao formula (HPTQ), a traditional Chinese medicine (TCM) formula used to improve cognitive impairment. However, the underlying neuroprotective mechanism of HPTQ treated for diabetic cognitive dysfunction (DCD) remains unclear. The purpose of this study was to investigate the neuroprotective mechanism of HPTQ in DCD mice based on molecular docking.

Methods

To investigate the neuroprotective effect of HPTQ in DCD, the Morris water maze (MWM), novel object recognition (NOR) test was used to detect the learning and memory changes of mice; hematoxylin-eosin (HE) staining was used to investigate the damage of hippocampal neurons; the western blot (WB) was used to examine the level of brain-derived neurotrophic factor (BDNF) of hippocampus. To investigate the neuroprotective mechanism of HPTQ in DCD, molecular docking was used to predict the possible target proteins of different active components in HPTQ and then the WB was used to verify the expression of key target proteins in the hippocampus of mice.

Results

HPTQ improved the learning and memory ability, hippocampal neuron damage, and the level of BDNF in the hippocampus of the DCD model treated with HFD/STZ for 12 weeks. Besides, the results of molecular docking showed that the main chemical components of HPTQ could be well combined with the targets of Bcl-2-associated X (Bax) and B-cell lymphoma2 (Bcl-2) and caspase-3. The levels of Bax/Bcl-2 protein ratio and caspase-3 increased in the DCD model while the HPTQ inhibited it. In addition, HPTQ restored DCD-induced decline of p-CREB, BDNF, TrkB, and p-Akt in the hippocampus.

Conclusions

These data indicated that HPTQ ameliorates the hippocampus apoptosis in diabetic cognitive dysfunction mice by activating CREB/BDNF/TrkB signaling pathway.

Curcumin and its analog alleviate diabetes-induced damages by regulating inflammation and oxidative stress in brain of diabetic rats

BACKGROUND

Diabetic encephalopathy is a severe diabetes complication with cognitive dysfunction and neuropsychiatric disability. The mechanisms underlying diabetic encephalopathy is believed to be relevant with oxidative stress, vascular amylin deposition, immune receptors, inflammation, etc. This study wanted to evaluate the ability of curcumin and its analog A13 to alleviate oxidative stress and inflammation in diabetes-induced damages in brain.

METHODS

Sixty adult male Sprague-Dawley rats were divided into 5 groups: normal control (NC) group, diabetes mellitus (DM) group, curcumin-treated diabetes mellitus (CUR) group, high dose of A13-treated diabetes mellitus (HA) group, low dose of A13-treated diabetes mellitus (LA) group. Activation of the nuclear factor kappa-B (NF-κB p65) pathway was detected by RT-qPCR, immunohistochemical (IHC) staining and Western blot; oxidative stress was detected by biochemical detection kit; brain tissue sections were stained with hematoxylin-eosin (HE) staining and Myelin staining.

RESULTS

RT-qPCR, IHC staining and Western blot showed that curcumin and A13 treatment could inhibit the NF-κB p65 pathway. Curcumin and A13 increased the activity of superoxide dismutase and decreased the malondialdehyde level in the brain of diabetic rats. Furthermore, HE staining and Myelin staining demonstrated that the histological lesions of the brain in diabetic rats could be significantly ameliorated by curcumin and A13.

CONCLUSION

Curcumin analog A13 could alleviate the damages in the brain of diabetes rats by regulating the pathways of inflammation and oxidative stress. A13 may be a new potential therapeutic agent for diabetic encephalopathy.

Asiaticoside and polylysine-releasing collagen complex for effectively reducing initial inflammatory response using inflamed induced in vitro model

Inflammation is a significant clinical problem that can arise from full-thickness wounds or burn injuries or microbial disease. Although topical wound healing substances could promote rapid wound healing by preventing or reducing the consequences of inflammation, there still remains a need for the development of novel substances that can effectively reduce infection and inflammation in initial wound healing phase. In this study, collagen was combined with asiaticoside (AS) and ε-poly-l-lysine (εPLL). This complex was then applied to in vitro models of infection and inflammation. Collagen-AS coatings inhibited the initial inflammatory response to LPS through a sustained release of AS, and a bilayer coating-εPLL showed a notable antimicrobial effect using microbial infection test. In this study, we determined whether asiaticoside and εPLL have anti-inflammatory and antibacterial effects through different mechanisms. Collectively, the collagen-AS/εPLL complex indicated great therapeutic potentials for accelerate wound healing and the complex may be considered as a artificial scaffold substitute product to full-thickness wound healing.

Asiaticoside suppresses cell proliferation by inhibiting the NF‑κB signaling pathway in colorectal cancer

Colorectal cancer (CRC) is one of the leading causes of cancer-associated mortality. Asiaticoside (AC) exhibits antitumor effects; however, to the best of our knowledge, the biological function of AC in CRC cells remains unclear. Therefore, the aim of the present study was to investigate the effect of AC on CRC cells. In the present study, CCK-8 and colony formation assays were performed to assess the effects of AV on human CRC cell lines (HCT116, SW480 and LoVo). Mitochondrial membrane potential was examined by JC-1 staining. Cell apoptosis and cell cycle were monitored by flow cytometry, and the expression of genes was evaluated using RT-qPCR and western blot analysis. Furthermore, the biological effect of AC in vivo was detected using a xenograft mouse model. The findings revealed that 2 µM AC suppressed the proliferation of CRC cells in a time- and dose-dependent manner, but had no adverse effects on normal human intestinal FHC cells at a range of concentrations. AC decreased the mitochondrial membrane potential and increased the apoptosis of CRC cells in a dose-dependent manner. Furthermore, AC induced cell cycle arrest at the G0/G1 phase. AC attenuated IκBα phosphorylation in a dose-dependent manner, thereby preventing P65 from entering the nucleus, and resulting in inhibition of the NF-κB signaling pathway. In addition, AC significantly reduced the expression of CDK4 and Cyclin D1 in a dose-dependent manner, significantly upregulated the activation of caspase-9 and caspase-3, and decreased the Bcl-2/Bax mRNA ratio. Furthermore, treatment with the NF-κB signaling pathway inhibitor JSH-23 significantly increased the cytotoxicity of AC in CRC cells. Findings of the xenograft mice model experiments revealed that AC significantly inhibited colorectal tumor growth in a dose-dependent manner. Overall, AC suppressed activation of the NF-κB signaling pathway by downregulating IκBα phosphorylation. This resulted in inhibition of CRC cell viability and an increase of cell apoptosis, which may form the basis of AC use in the treatment of patients with CRC.

Terpenoids as Potential Geroprotectors

Terpenes and terpenoids are the largest groups of plant secondary metabolites. However, unlike polyphenols, they are rarely associated with geroprotective properties. Here we evaluated the conformity of the biological effects of terpenoids with the criteria of geroprotectors, including primary criteria (lifespan-extending effects in model organisms, improvement of aging biomarkers, low toxicity, minimal adverse effects, improvement of the quality of life) and secondary criteria (evolutionarily conserved mechanisms of action, reproducibility of the effects on different models, prevention of age-associated diseases, increasing of stress-resistance). The number of substances that demonstrate the greatest compliance with both primary and secondary criteria of geroprotectors were found among different classes of terpenoids. Thus, terpenoids are an underestimated source of potential geroprotectors that can effectively influence the mechanisms of aging and age-related diseases.

Mechanisms behind Retinal Ganglion Cell Loss in Diabetes and Therapeutic Approach

Diabetes produces several changes in the body triggered by high glycemia. Some of these changes include altered metabolism, structural changes in blood vessels and chronic inflammation. The eye and particularly the retinal ganglion cells (RGCs) are not spared, and the changes eventually lead to cell loss and visual function impairment. Understanding the mechanisms resulting in RGC damage and loss from diabetic retinopathy is essential to find an effective treatment. This review focuses mainly on the signaling pathways and molecules involved in RGC loss and the potential therapeutic approaches for the prevention of this cell death. Throughout the manuscript it became evident that multiple factors of different kind are responsible for RGC damage. This shows that new therapeutic agents targeting several factors at the same time are needed. Alpha-1 antitrypsin as an anti-inflammatory agent may become a suitable option for the treatment of RGC loss because of its beneficial interaction with several signaling pathways involved in RGC injury and inflammation. In conclusion, alpha-1 antitrypsin may become a potential therapeutic agent for the treatment of RGC loss and processes behind diabetic retinopathy.

Elucidating the mechanism of action of alpha-1-antitrypsin using retinal pigment epithelium cells exposed to high glucose. Potential use in diabetic retinopathy

BACKGROUND

Alpha-1-antitrypsin is a protein involved in avoidance of different processes that are seen in diabetic retinopathy pathogenesis. These processes include apoptosis, extracellular matrix remodeling and damage of vessel walls and capillaries. Furthermore, because of its anti-inflammatory effects, alpha-1-antitrypsin has been proposed as a possible therapeutic approach for diabetic retinopathy. Our group tested alpha-1-antitrypsin in a type 1 diabetes mouse model and observed a reduction of inflammation and retinal neurodegeneration. Thus, shedding light on the mechanism of action of alpha-1-antitrypsin at molecular level may explain how it works in the diabetic retinopathy context and show its potential for use in other retinal diseases.

METHODS

In this work, we evaluated alpha-1-antitrypsin in an ARPE-19 human cell line exposed to high glucose. We explored the expression of different mediators on signaling pathways related to pro-inflammatory cytokines production, glucose metabolism, epithelial-mesenchymal transition and other proteins involved in the normal function of retinal pigment epithelium by RT-qPCR and Western Blot.

RESULTS

We obtained different expression patterns for evaluated mediators altered with high glucose exposure and corrected with the use of alpha-1-antitrypsin.

CONCLUSIONS

The expression profile obtained in vitro for the evaluated proteins and mRNA allowed us to explain our previous results obtained on mouse models and to hypothesize how alpha-1-antitrypsin hinder diabetic retinopathy progression on a complex network between different signaling pathways.

GENERAL SIGNIFICANCE

This network helps to understand the way alpha-1-antitrypsin works in diabetic retinopathy and its scope of action.

The protective effect of Geniposide on diabetic cognitive impairment through BTK/TLR4/NF-κB pathway

The purpose of the present study was to elucidate the pharmacological effects of Geniposide (GEN) on high diet fed and streptozotocin (STZ)-caused diabetic cognitive impairment. The mice were fed with high fat diet (HFD) for 4 weeks and intraperitoneally injected with 60 mg/kg STZ for three times within 72 h. The mice with glucose level over 15 mmol/l were regarded as diabetic and selected for further studies. The animals were intragastrically treated with metformin or GEN once daily for 4 weeks. Afterwards, the animals were applied for Y maze, novel object recognition (NOR) test, step-through passive avoidance test, and Morris water maze (MWM) test. The blood glucose and body weight were examined. The SH-SY5Y cells were treated with GEN in the presence or absence of ibrutinib and stimulated with high-glucose culture medium. The tumor necrosis factor-a (TNF-α) and interleukin (IL)-6 in serum, hippocampus, and supernatant were measured using ELISA method. The protein expressions of Bruton's tyrosine kinase (BTK), Toll-like receptor 4 (TLR4), myeloid differentiating factor 88 (MyD88), nuclear factor kappa-B (NF-κB), p-NF-κB, brain-derived neurotrophic factor (BDNF), cAMP-response element binding protein (CREB), p-CREB, and glucagon-like peptide-1 receptor (GLP-1R) were detected by western blot analyses. As a result, the GEN treatment notably attenuated the body weight, blood glucose, and cognitive decline. GEN also inhibited the generations of inflammatory cytokines. Furthermore, the administrations of GEN ameliorated the alterations of BTK, TLR4, MyD88, NF-κB, and BDNF in HFD + STZ-induced mice. With the application of ibrutinib, the selective inhibitor of BTK, it was also found that BTK/TLR4/NF-κB pathway was associated with the GEN treatment in high glucose-induced SH-SY5Y cells. In summary, the results suggested that GEN exerted the protective effect on STZ-induced cognitive impairment possibly through the modulation of BTK/TLR4/NF-κB signaling.

Inverted U-shaped response of a standardized extract of Centella asiatica (ECa 233) on memory enhancement

The herb Centella asiatica has long been considered a memory tonic. A recent review found no strong evidence for improvement of cognitive function, suggesting negative results were due to limitations in dose, standardization and product variation. We used a standardized extract of C. asiatica (ECa 233) to study behavioral, cellular and molecular effects on learning and memory enhancement. ECa 233 (10, 30, and 100 mg/kg) was given orally to normal rats twice a day for 30 days. We used the Morris water maze to test spatial learning and performed acute brain slice recording to measure changes of synaptic plasticity in the hippocampus, a core brain region for memory formation. Plasticity-related protein expressions (NR2A, NR2B, PSD-95, BDNF and TrkB) in hippocampus was also measured. Rats receiving 10 and 30 mg/kg doses showed significantly enhanced memory retention, and hippocampal long-term potentiation; however, only the 30 mg/kg dose showed increased plasticity-related proteins. There was an inverted U-shaped response of ECa 233 on memory enhancement; 30 mg/kg maximally enhanced memory retention with an increase of synaptic plasticity and plasticity-related proteins in hippocampus. Our data clearly support the beneficial effect on memory retention of a standardized extract of Centella asiatica within a specific therapeutic range.

Soursop fruit extract mitigates scopolamine-induced amnesia and oxidative stress via activating cholinergic and Nrf2/HO-1 pathways

Current therapeutic interventions for memory loss are inadequate and are associated with numerous adverse effects. There is an urgent need for new alternative agents for the treatment of memory loss and related disorders. Here, we investigated the potential neuroprotective role of soursop fruit extract (SSFE) in scopolamine (SCO)-induced amnesia and oxidative damage in the hippocampus of rats. Thirty-five rats were randomly allocated into 5 groups: control, SCO, SSFE, SCO, SSFE+SCO and N-acetylcysteine (NAC) + SCO. SCO-treatment increased acetylcholine esterase activity and decreased hippocampal levels of acetylcholine, serotonin, dopamine, norepinephrine, and histamine. The level of ATP increased. SCO-treated rats showed a disturbance in oxidative status, which was evident through the increase in malondialdehyde, and nitrites/nitrates and a decrease in cellular antioxidant molecules including glutathione, superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase. A disturbance was also observed via downregulation of the nuclear factor erythroid 2-related factor 2 and heme oxygenase-1 defense pathways. SCO-treatment enhances a neuroinflammatory state, as indicated by the release of tumor necrosis factor- α and interleukin-1β and increased inducible nitric oxide synthase and mRNA expression. SCO-treatment decreased the expression of the anti-apoptotic protein, B cell lymphoma 2 and increased the expression of the pro-apoptotic protein, Bcl-2 associated X protein, caspase-3 and cytochrome c in hippocampal neurons. SSFE pretreatment markedly ameliorated hippocampal changes. Our findings revealed that SSFE exerts its potential anti-amnestic effect mainly through the activation of the cholinergic system and Nrf2/HO-1 pathway.

Effects of Asiaticoside Treatment on the Survival of Random Skin Flaps in Rats

Background: Asiaticoside (AS) is extracted from the traditional herbal medicine Centella asiatica, and has angiogenic, antioxidant, anti-inflammatory, and wound-healing effects. We investigated the effects of AS on skin flap survival. Methods: Dorsal McFarlane flaps were harvested from 36 rats and divided into two groups: an experimental group treated with 40 mg/kg AS administered orally once daily, and a control group administered normal saline in an identical manner. On day 2, superoxide dismutase (SOD) and malondialdehyde (MDA) levels, and production of the cytokines tumor necrosis factor-α and interleukin (IL)-6 were evaluated. On day 7, tissue slices were stained with hematoxylin and eosin. The expression of vascular endothelial growth factor (VEGF), IL-6, and IL-1β were immunohistochemically evaluated. Microcirculatory flow was measured using laser Doppler flowmetry. Flap angiography, using the lead oxide-gelatin injection technique, was performed with the aid of a soft X-ray machine. Results: The AS group exhibited greater mean flap survival area, improved microcirculatory flow, and higher expression levels of SOD and VEGF compared with the control group. However, MDA levels and the inflammatory response were significantly reduced. Conclusions: AS exhibits promise as a therapeutic option due to its effects on the viability and function of random skin flaps in rats.

Protective effect of Centella asiatica against D-galactose and aluminium chloride induced rats: Behavioral and ultrastructural approaches

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder and the commonest cause of dementia among the aged people. _D-galactose (D-gal) is a senescence agent, while aluminium is a known neurotoxin linked to pathogenesis of AD. The combined administration of rats with d-gal and aluminium chloride (AlCl₃) is considered to be an easy and a cheap method to obtain an animal model of AD. The plant Centella asiatica (CA) is reported to exert neuroprotective effects both in vitro and in vivo. Therefore, this study explored the protective effects of CA on cognition and brain ultrastructure in d-gal and AlCl₃ induced rats.

MATERIALS AND METHODS

Rats were exposed to d-gal 60 mg/kg/b.wt/day + AlCl₃ 200 mg/kg/b.wt/day and CA (200, 400 and 800 mg/kg/b.wt/day) and 1 mg/kg/b.wt/day of donepezil for 70 days. Different cognitive paradigms viz. T maze spontaneous alternation, modified elevated plus maze and novel object recognition test, were used to evaluate full lesions of the hippocampus, spatial learning and memory and non-spatial learning and memory respectively. Nissl's staining was used to determine the survival of hippocampus CA1 pyramidal cells, while transmission electron microscopy was used to check the ultrastructural changes.

RESULTS

The results revealed that d-gal and AlCl₃ could significantly impair behavior and cognitive functions, besides causing damage to the hippocampal CA1 pyramidal neurons in rats. In addition, it also caused ultrastructural morphological alterations in rat hippocampus. Conversely, co-administration o;f CA, irrespective of the dosage used, alleviated the cognitive impairments and pathological changes in the rats comparable to donepezil.

CONCLUSION

In conclusion the results suggest that CA could protect cognitive impairments and morphological alterations caused by d-gal and AlCl₃ toxicity in rats. Biochemical and molecular studies are ongoing to elucidate the probable pharmacodynamics of CA.

Salidroside prevents diabetes‑induced cognitive impairment via regulating the Rho pathway

In previous years, it has been found that Rhodiola has a wide range of pharmacological effects in diseases of the cardiovascular system, as it can remove superoxide anions and hydroxyl radicals in chemical reactions. Behavioral assessment was used to measure cognitive impairment. Inflammation, oxidative stress and caspase‑3 activity were measured using commercial kits. Western blot analysis was used to measure Rho/Rho‑associated kinase (ROCK)/sirtuin 1 (SIRT1)/nuclear factor (NF)‑κB protein expression. The objective of the present study was to investigate the protective effect of salidroside on diabetes and diabetes‑induced cognitive impairment. The results of the study demonstrated that salidroside prevented cognitive impairment, decreased serum blood glucose levels and increased body weight, reduced fasting blood glucose levels and blood lipid levels, and inhibited oxidative stress, inflammation and nerve cell apoptosis in the diabetic rat model. Salidroside suppressed ROCK/ SIRT1 NF‑κB pathway and protein expression in the diabetic rats. These data showed that salidroside prevented diabetes‑induced cognitive impairment by regulating the Rho/ROCK/SIRT1/NF‑κB pathway.

Brain-derived neurotrophic factor inhibits hyperglycemia-induced apoptosis and downregulation of synaptic plasticity-related proteins in hippocampal neurons via the PI3K/Akt pathway

It is not known whether brain-derived neurotrophic factor (BDNF) protects hippocampal neurons from high glucose-induced apoptosis and/or synaptic plasticity dysfunction. The present study aimed to assess whether BDNF exerted a neuroprotective effect in rat hippocampal neurons exposed to high glucose and examine the underlying mechanisms. The apoptosis of primary hippocampal neurons was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide staining. The mRNA and protein expression levels were measured by reverse transcription- quantitative polymerase chain reaction and western blot experiments, respectively. Synaptic plasticity was evaluated by the immunolocalization of synaptophysin (Syn). Exposure of the hippocampal neurons to high glucose (75 mM for 72 h) resulted in cell apoptosis, decreased mRNA and protein expression levels of three synaptic plasticity-related proteins (Syn, Arc and cyclic AMP response element-binding protein), and changes in the cellular distribution of Syn, indicating loss of synaptic density. These effects of high glucose were partially or completely reversed by prior administration of BDNF (50 ng/ml for 24 h). Pre-treatment with wortmannin, a phosphatidylinositol-3-kinase (PI3K) inhibitor, suppressed the ability of BDNF to inhibit the effects of high glucose. In addition, BDNF significantly upregulated the tropomyosin-related kinase B, its cognate receptor, Akt and phosphorylated Akt at the protein levels under high glucose conditions. In conclusion, high glucose induced apoptosis and downregulated synaptic plasticity-related proteins in hippocampal neurons. These effects were reversed by BDNF via the PI3K/Akt signaling pathway.

Asiaticoside, a component of Centella asiatica attenuates RANKL-induced osteoclastogenesis via NFATc1 and NF-κB signaling pathways

Identification of natural compounds that inhibit osteoclastogenesis will facilitate the development of antiresorptive treatment of osteolytic bone diseases. Asiaticoside is a triterpenoid derivative isolated from Centella asiatica, which exhibits varying biological effects like angiogenesis, anti-inflammation, wound healing, and osteogenic differentiation. However, its role in osteoclastogenesis remains unknown. Here, we show that Asiaticoside can suppress RANKL-induced osteoclast formation and bone resorption in a dose-dependent manner. Asiaticoside attenuated the expression of osteoclast marker genes including Ctsk, Atp6v0d2, Nfatc1, Acp5, and Dc-stamp. Furthermore, Asiaticoside inhibited RANKL-mediated NF-κB and NFATc1 activities, and RANKL-induced calcium oscillation. Collectively, this study demonstrates that Asiaticoside inhibited osteoclast formation and function through attenuating RANKL-induced key signaling pathways, which may indicate that Asiaticoside is a potential antiresorptive agent against osteoclast-related osteolytic bone diseases.

MicroRNA-146a: A Comprehensive Indicator of Inflammation and Oxidative Stress Status Induced in the Brain of Chronic T2DM Rats

Objective: It was demonstrated that inflammation and oxidative stress induced by hyperglycemia were closely associated with alteration of miR-146a. Here, we investigated the role of miR-146a in mediating inflammation and oxidative stress in the brain of chronic T2DM rats.

Methods: The chronic T2DM (cT2DM) models were induced by intraperitoneal administration of STZ (35 mg/kg) after being fed a high-fat, high-sugar diet for 6 weeks. H&E staining was conducted to observe the morphological impairment of the rat hippocampus. The expressions of inflammatory mediators (COX-2, TNF-α, IL-1β) and antioxidant proteins (Nrf2, HO-1) were measured by western blot. The levels of MDA and SOD were detected by the respective activity assay kit. The levels of p22phox and miR-146a were examined by quantitative real-time PCR (qRT-PCR). The expressions of IRAK1, TRAF6 and NF-κB p65 were measured by western blot and qRT-PCR. Pearson correlation analysis was performed to investigate the correlations between miR-146a and inflammatory mediators as well as oxidative stress indicators.

Results: The expression of miR-146a was negatively correlated with inflammation and oxidative stress status. In the brain tissues of cT2DM rats, it was observed that the expressions of inflammatory mediators (COX-2, TNF-α, IL-1β) and oxidative stress indicators including MDA and p22phox were elevated, which were negatively correlated with the expression of miR-146a. While, the antioxidant proteins (Nrf2, HO-1, SOD) levels decreased in the brain of cT2DM rats, which were positively correlated with the miR-146a level. The expressions of NF-κB p65 and its specific modulators (IRAK1&TRAF6) were elevated in the brain of cT2DM rats, which might be inhibited by miR-146a.

Conclusion: Our results implied that increased inflammation and oxidative stress status were associated with brain impairment in cT2DM rats, which were negatively correlated with miR-146a expression. Thus, miR-146a may serve as a negative comprehensive indicator of inflammation and oxidative stress status in the brain of chronic T2DM rats.

Down-regulated long non-coding RNA ANRIL restores the learning and memory abilities and rescues hippocampal pyramidal neurons from apoptosis in streptozotocin-induced diabetic rats via the NF-κB signaling pathway

Diabetes often causes learning and memory deficits, which leads to unfavorable behavioral performance. In this study, we investigated the effects of long non-coding RNA (lncRNA) ANRIL on learning, memory abilities, and hippocampal neuronal apoptosis via the NF-κB signaling pathway in streptozotocin (STZ)-induced diabetic rats. After successful establishment of diabetic rat models, the subjects were then assigned into the DM, DM + si-ANRIL, DM + si-negative control (si-NC) groups, as well as an additional normal group. Morris water maze test was employed to assess behavioral performance of rats, followed by the recording of body weight and blood glucose levels. Expressions of ANRIL, NF-κB signaling pathway-related, and apoptosis-related genes were examined by qRT-PCR and western blotting. Rat hippocampus expression levels of cleaved-caspase-3 were determined by immunofluorescence. Cell apoptosis was examined by TUNEL assay. Versus to the normal group, revealed there to be activation of the NF-κB signaling pathway, decreased weight, increased blood glucose, increased escape latency, reduced residence time, memory impairment, increased cleaved-caspase-3 expression, and increased apoptosis were detected in the DM and DM + si-NC groups. The DM + si-ANRIL group exhibited inhibited NF-κB signaling pathway, weight loss, decreased blood glucose, recovered memory, decreased cleaved-caspase-3 expression and reduced apoptosis compared to the DM group, with higher weight of rats, lower blood glucose levels, and stronger memory abilities in the DM + si-ANRIL group. Taken together, these findings indicate that silencing lncRNA ANRIL promotes memory recovery and decreases hippocampal neurons apoptosis in diabetic rats through the inhibition of the NF-κB signaling pathway.

Asiaticoside Attenuates Cell Growth Inhibition and Apoptosis Induced by Aβ1-42 via Inhibiting the TLR4/NF-κB Signaling Pathway in Human Brain Microvascular Endothelial Cells

Alzheimer's disease (AD) is a very common progressive neurodegenerative disorder with the highest incidence in the world. Dysfunction of the blood-brain barrier (BBB) may be responsible for the pathogenesis and pathology of AD for abnormally transporting amyloid-β (Aβ, the main component of the senile plaques) from the sera into the central nervous system. Aβ peptides induce apoptosis in human brain microvascular endothelial cells (hBMECs), the main component of BBB. Apoptosis in neuronal cells plays a critical role in the pathogenesis of AD. Asiaticoside, a natural glycoside extracted from Centella asiatica (L.) Urban, has an anti-apoptotic effect on hBMECs but the molecule mechanism remains unclear. Therefore, we investigate the protective effect of asiaticoside on Aβ_1-42-induced cytotoxicity and apoptosis as well as associated mechanism in hBMECs with commonly used in vitro methods for clinical development of asiaticoside as a novel anti-AD agent. In the present study, we investigated the effects of asiaticoside on cytotoxicity by Cell Counting Kit-8 assay, mitochondrial membrane potential by JC-1 fluorescence analysis, anti-apoptosis by Hoechst 33258 staining and Annexin V-FITC (fluorescein isothiocyanate) and propidium iodide (PI) analyses, the expressions of TNF-α and IL-6 by enzyme-linked immunosorbent assay (ELISA) and TLR4, MyD88, TRAF6, p-NF-κB p65, and total NF-κB p65 by Western blotting, and nuclear translocation of NF-κB p65 by immunofluorescence analysis in hBMECs. The results showed that pretreatment of asiaticoside (25, 50, and 100 μM) for 12 h significantly attenuated cell growth inhibition and apoptosis, and restored declined mitochondrial membrane potential induced by Aβ_1-42 (50 μM) in hBMECs. Asiaticoside also significantly downregulated the elevated expressions of TNF-α, IL-6, TLR4, MyD88, TRAF6, and p-NF-κB p65, as well as inhibited NF-κB p65 translocation from cytoplasm to nucleus induced by Aβ_1-42 in hBMECs in a concentration-dependent manner. The possible underlying molecular mechanism of asiaticoside may be through inhibiting the TLR4/NF-κB signaling pathway. Therefore, asiaticoside may be developed as a novel agent for the prevention and/or treatment of AD clinically.

Ferulic acid attenuates diabetes-induced cognitive impairment in rats via regulation of PTP1B and insulin signaling pathway

Cognitive impairment has been recognized as a typical characteristic of neurodegenerative disease in diabetes mellitus (DM) and this cognitive dysfunction may be a risk factor for Alzheimer's disease (AD). Ferulic acid, a phenolic compound commonly found in a range of plants, has emerged various properties including anti-inflammatory and neuroprotective effects. In the present study, the protective activities and relevant mechanisms of ferulic acid were evaluated in diabetic rats with cognitive deficits, which were induced by a high-glucose-fat (HGF) diet and low dose of streptozotocin (STZ). It was observed that ferulic acid significantly increased body weight and decreased blood glucose levels. Meanwhile, ferulic acid could markedly ameliorate spatial memory of diabetic rats in Morris water maze (MWM) and decrease AD-like pathologic changes (Aβ deposition and Tau phosphorylation) in the hippocampus, which might be correlated with the inhibition of inflammatory cytokines release and reduction of protein tyrosine phosphatase 1B (PTP1B) expression. Moreover, the levels of brain insulin signal molecules p-IRS, p-Akt and p-GSK3β were also investigated. We found that ferulic acid administration restored the alterations in insulin signaling. In conclusion, ferulic acid exhibited beneficial effects on diabetes-induced cognition lesions, which was involved in the regulation of PTP1B and insulin signaling pathway. We suppose that PTP1B inhibition may represent a promising approach to correct abnormal signaling linked to diabetes-induced cognitive impairment.

Inhibition of NF-κB activity by aminoguanidine alleviates neuroinflammation induced by hyperglycemia

Neuroinflammation is a key feature of cerebral complication which is associated with diabetes mellitus (DM). Inducible nitric oxide synthase (iNOS) is implicated in the pathogenesis of neuroinflammation. However, how iNOS facilitates the development of inflammation in brain is still unidentified. The aim of the present study was to investigate the association of iNOS and neuroinflammation in diabetic mice, and elucidate the potential mechanisms underlying aminoguanidine (AG), the selective inhibitor of iNOS, protected neurons against inflammation in diabetic mice. In present experiment, diabetic mice model were established by a single intraperitoneal injection of streptozotocin (STZ). AG was administered to diabetic mice for ten weeks after this disease induction. Then we measured iNOS activity in the serum and brain, detected the glial fibrillary acidic protein (GFAP) and ionised calcium binding adaptor molecule-1 (Iba-1) expressions in the brain. Moreover, nuclear factor-kappa B (NF-κB) in cytoplasm and nucleus were tested by IP and WB. Results revealed that high expression of iNOS in serum and brain could be reversed by AG treatment. Furthermore, AG could also inhibit GFAP and Iba-1 expressions, and NF-κB nuclear translocation by inhibiting it from binding to iNOS in cytoplasm. Our findings indicated that iNOS can combine with NF-κB in cytoplasm and promote its nuclear transfer in diabetic mice. Furthermore, AG decreased neuroinflammation through inhibiting iNOS activity and reducing NF-κB nuclear translocation by promoting its dissociation with iNOS in cytoplasm.

The protective effect of Epimedii Folium and Curculiginis Rhizoma on Alzheimer's disease by the inhibitions of NF-κB/MAPK pathway and NLRP3 inflammasome

The purpose of the current study was to explore the effects of the water extracts of Epimedii Folium and Curculiginis Rhizoma (EX) on Aβ-induced Alzheimer's disease. Aβ1-42 was stereotaxically injected bilaterally into the dorsal hippocampus, and then the rats were orally received EX at the doses of 2 g/kg and 6 g/kg for 30 days. Behavior was monitored through Morris water maze test. The neuroprotective effect of EX were examined with methods of histochemistry and biochemistry. EX reduced the contents of pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) in hippocampus and cortex. EX also reduced the levels of malondialdehyde (MDA) and increased superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and glutathione peroxidase (GSH-Px) in the serum. Immunohistochemical analysis demonstrated that EX inhibited the expressions of NLRP3. In addition, we further confirmed that EX suppressed the expression of the NLRP3 inflammasome. EX inhibited the phosphorylations MAPKs, nuclear factor κB (NF-κB), myeloid differentiation factor 88(MyD88), cathepsin B. In conclusion, these results suggest that EX may be a potential agent for treating Alzheimer's disease.

Zeaxanthin improves diabetes-induced cognitive deficit in rats through activiting PI3K/AKT signaling pathway

Published studies have shown that cognitive deficit is a characteristic manifestation of neurodegenerative disease in diabetes. However, there is no effective prevention and treatment for this diabetes-associated behavior disorder. In the present study, we attempted to elucidate the effect of zeaxanthin on cognitive deficit and the change in the hippocampus correlated with cognitive decline in diabetic rats. Diabetic rats in this study were induced by high-fat diet and low-dose streptozocin (STZ), cognitive ability of rats were evaluated use morris water maze (MWM) and morphology change in hippocampus was assessed by cresyl violet stain. Moreover, we detected the expression of phosphorylated serine/threonine kinase (p-AKT) and Cleaved caspase-3, and the activity of nuclear factor-κB (NF-κB) use western-blot (WB). Results displayed that supplementation with zeaxanthin reduce blood glucose, improve cognitive deficit, survive neural cell, increase p-AKT level, inhibit Cleaved caspase-3 level and NF-κB nuclear transcription in hippocampus. This study demonstrated that zeaxanthin ameliorate diabetes-related cognitive deficit may by means of protecting neural cell from hyperglycemia involved in AKT/NF-κB signaling pathway. This study may provide a potential therapeutic approach for the prevention of diabetes- associated cognitive deficit.

Thymol improves high-fat diet-induced cognitive deficits in mice via ameliorating brain insulin resistance and upregulating NRF2/HO-1 pathway

The impaired insulin signaling has been recognized as a common pathogenetic mechanism between diabetes and Alzheimer's disease (AD). In the progression of AD, brain is characterized by defective insulin receptor substrate-1 (IRS-1) and increased oxidative stress. Thymol, a monoterpene phenol isolated from medicinal herbs, has exhibited robust neuroprotective effects. The present study was designed to investigate the protective effect of thymol on HFD-induced cognitive deficits, and explore the possible mechanisms. C57BL/6 J mice were fed for 12 weeks with either HFD or normal diet. The mice fed with HFD were dosed with metformin (200 mg/kg) or thymol (20, 40 mg/kg) daily. It was observed that thymol treatment significantly reversed the gain of body weight and peripheral insulin resistance induced by HFD. Meanwhile, thymol improved the cognitive impairments in the Morris Water Maze (MWM) test and decreased HFD-induced Aβ deposition and tau hyperphosphorylation in the hippocampus, which may be correlated with the inhibition of hippocampal oxidative stress and inflammation. In addition, thymol down-regulated the level of P-Ser307 IRS-1, and hence enhancing the expression of P-Ser473 AKT and P-Ser9 GSK3β. We further found that the protective effects of thymol on cognitive impairments were associated with the up-regulation of nuclear respiratory factor (Nrf2)/heme oxygenase-1(HO-1) pathway. In conclusion, thymol exhibited beneficial effects on HFD-induced cognitive deficits through improving hippocampal insulin resistance, and activating Nrf2/HO-1 signaling.

Brain injury with diabetes mellitus: evidence, mechanisms and treatment implications

Diabetes mellitus is a risk for brain injury. Brain injury is associated with acute and chronic hyperglycaemia, insulin resistance, hyperinsulinemia, diabetic ketoacidosis (DKA) and hypoglycaemic events in diabetic patients. Hyperglycemia is a cause of cognitive deterioration, low intelligent quotient, neurodegeneration, brain aging, brain atrophy and dementia. Areas covered: The current review highlights the experimental, clinical, neuroimaging and neuropathological evidence of brain injury induced by diabetes and its associated metabolic derangements. It also highlights the mechanisms of diabetes-induced brain injury. It seems that the pathogenesis of hyperglycemia-induced brain injury is complex and includes combination of vascular disease, oxidative stress, neuroinflammation, mitochondrial dysfunction, apoptosis, reduction of neurotrophic factors, acetylcholinesterase (AChE) activation, neurotransmitters' changes, impairment of brain repair processes, impairment of brain glymphatic system, accumulation of amyloid β and tau phosphorylation and neurodegeneration. The potentials for prevention and treatment are also discussed. Expert commentary: We summarize the risks and the possible mechanisms of DM-induced brain injury and recommend strategies for neuroprotection and neurorestoration. Recently, a number of drugs and substances [in addition to insulin and its mimics] have shown promising potentials against diabetes-induced brain injury. These include: antioxidants, neuroinflammation inhibitors, anti-apoptotics, neurotrophic factors, AChE inhibitors, mitochondrial function modifiers and cell based therapies.

Paeoniflorin ameliorates cognitive dysfunction via regulating SOCS2/IRS-1 pathway in diabetic rats

Paeoniflorin is a natural monoterpene glycoside in Paeonia lactiflora pall with various biological properties including promising anti-inflammatory activity. Current evidences support that inflammatory reaction, oxidative stress, as well as abnormal insulin signaling in the hippocampus are potential causes of tau hyperphosphorylation and finally induce cognitive dysfunction. The present study aims to explore the effects of paeoniflorin on the cognitive deficits and investigate the underlying mechanisms in diabetic rats induced by a high-sucrose, high-fat diet and low dose of streptozotocin (STZ). Paeoniflorin treatment effectively improved the performance of diabetic rats in the Morris water maze test via decreasing escape latency and increasing the spent time in the target quadrant. Immunohistochemistry staining also had shown that tau hyperphosphorylation in the hippocampus was prevented after paeoniflorin administration. This function was correlated with its abilities of reducing the brain inflammatory cytokines (IL-1β and TNF-α), decreasing suppressor of cytokine signaling 2 (SOCS2) expressions and promoting insulin receptor substrate-1 (IRS-1) activity. Additionally, we also found paeoniflorin administration significantly promoted the phosphorylation levels of protein kinase B (Akt) and glycogen synthase kinase-3β (GSK-3β). Together, these results showed that paeoniflorin had beneficial effects on relieving diabetes-associated cognitive deficits via regulating SOCS2/IRS-1 pathway and might provide a feasible method for the treatment of diabetes-associated cognitive dysfunction.