7, 8-Dihydroxycoumarin (daphnetin) protects INS-1 pancreatic β-cells against streptozotocin-induced apoptosis

Evaluation of toxicity and anti-amylase activity of 7, 8 dihydroxy coumarin (Daphnetin), a novel α-amylase blocker in vitro and in vivo

Management of postprandial blood glucose is a measure in regulating the blood sugar concentration. This paper evaluates the anti-amylase property of a natural compound 7,8 dihydroxycoumarin (daphnetin) both in vitro and in vivo. The inhibitory effect of daphnetin was evaluated against salivary (HSA) and pancreatic α-amylases (PPA) and α-glucosidase (AG) in vitro. Enzyme kinetics studies revealed that the inhibition of HSA, PPA and AG by daphnetin was competitive in nature. Pretreatment with daphnetin was found to inhibit the amylases in vivo as confirmed by the oral starch tolerance test (OSTT). No adverse effect of daphnetin was observed on serum markers and organs like liver, kidney and small intestine. The impact of the inhibitory effect of daphnetin in in vivo was comparable to the positive control, acarbose in all aspects.

Daphnetin ameliorates diabetic cardiomyopathy by regulating inflammation and endoplasmic reticulum stress-induced apoptosis

Daphnetin has been demonstrated to exert beneficial effects on diabetes mellitus and renal complications. However, the role and molecular mechanism of daphnetin in diabetic cardiomyopathy (DCM) remain unclear. In this study, rats were injected with streptozotocin (STZ) to induce diabetes. The diabetic rats were then administered daphnetin (1 and 4 mg/kg) or dimethyl sulfoxide (DMSO) daily for 12 weeks. The results demonstrated that the diabetic rats exhibited elevated blood glucose levels, which were dose-dependently ameliorated by daphnetin. At 13 weeks following STZ injection, the rats exhibited typical diabetic signs, cardiac dysfunction, and evident pathological alterations in myocardial tissues. The administration of daphnetin to diabetic rats resulted in improvement in cardiac function, reductions in myocardial injury biomarkers, and the inhibition of myocardial fibrosis. Furthermore, daphnetin treatment suppressed inflammation and endoplasmic reticulum stress-induced apoptosis in a dose-dependent manner. Additionally, daphnetin exhibited partial blockade of the activation of mitogen-activated protein kinase pathways induced by diabetes. These findings indicate that daphnetin may be a promising therapeutic agent for the treatment of DCM.

Daphnetin ameliorates hepatic steatosis by suppressing peroxisome proliferator-activated receptor gamma (PPARG) in ob/ob mice

Non-alcoholic fatty liver disease (NAFLD) is the predominant metabolic liver disorder and currently lacks effective and safe pharmaceutical interventions. Daphnetin (DA), a natural coumarin derivative with anti-inflammatory and antioxidant activities, is a promising agent for NAFLD treatment. In this study, we evaluated the effects and mechanisms of DA on hepatic lipid metabolism in ob/ob mice. Our results showed that DA effectively ameliorates glucose metabolism and hepatic lipid accumulation in ob/ob mice. Metabolomics and RNA sequencing (RNA-seq), combined with GEO data analysis, suggest that DA primarily modulates the peroxisome proliferator-activated receptor gamma (PPARG) pathway, as validated in vivo in ob/ob mice. Mechanistically, DA selectively targets PPARG in hepatic cells by inhibiting PPARG promoter activity and downregulating its expression, resulting in decreased transcription of downstream lipid metabolism-related genes, including fatty acid binding protein 4 (Fabp4), cluster of differentiation 36 (Cd36), and fatty acid synthase (Fasn). This effect was abolished in PPARG-deficient HepG2 cells subjected to palmitic acid (PA) insult. Our findings provide evidence that DA acts as a selective suppressor of hepatic PPARG, suggesting an attractive strategy by targeting PPARG for the prevention of hepatic steatosis.

Daphnetin modulates GLP-1R to alleviate cognitive dysfunction in diabetes: implications for inflammation and oxidative stress

Daphnetin exerts certain pharmacological function on a variety of diseases, but its role in diabetic cognitive dysfunction has not been elucidated. In this study, we carried a series of pharmacological studies of GLP-1R with daphnetin. In rats and PC12 cells, we found that daphnetin could alleviate diabetic cognitive dysfunction and increase the expression level of GLP-1R. Additionally, the anti-diabetic cognitive dysfunction effect of DAP was accompanied by the inhibition of inflammation and oxidative stress. Further in-depth studies demonstrated that the inhibition GLP-1R enhanced the protective effect of daphnetin, whilst, the overexpression of GLP-1R weakened the protective effect of daphnetin. These results indicated that daphnetin protects diabetes cognitive dysfunction by regulating GLP-1R-mediated inflammation and oxidative stress, act as a GLP-1R agonist. The study further demonstrated that daphnetin has great value in preventing cognitive dysfunction in type 2 diabetes, and GLP-1R is a key potential target for the treatment of related diseases.

Pharmacological and phytochemical insights on the pancreatic β-cell modulation by Angelica L. roots

ETHNOPHARMACOLOGICAL RELEVANCE

Angelica roots are a significant source of traditional medicines for various cultures around the northern hemisphere, from indigenous communities in North America to Japan. Among its many applications, the roots are used to treat type 2 diabetes mellitus; however, this application is not mentioned often. Ethnopharmacological studies have reported the use of A. japonica var. hirsutiflora, A. furcijuga, A. shikokiana, and A. keiskei to treat diabetes symptoms, and further reports have demonstrated the three angelica roots, i.e., A. japonica var. hirsutiflora, A. reflexa, and A. dahurica, exhibit insulin secretagogue activity.

AIM OF THE STUDY

This study aimed to phytochemically characterize and compare angelica roots monographed in the European Pharmacopeia 11th, isolate major plant metabolites, and assess extracts and isolates' capability to modulate pancreatic β-cell function.

MATERIALS AND METHODS

Root extracts of Angelica archangelica, Angelica dahurica, Angelica biserrata, and Angelica sinensis were phytochemically profiled using liquid chromatography method coupled with mass spectrometry. Based on this analysis, simple and furanocoumarins were isolated using chromatography techniques. Extracts (1.6-50 μg/mL) and isolated compounds (5-40 μmol/L) were studied for their ability to modulate insulin secretion in the rat insulinoma INS-1 pancreatic β-cell model. Insulin was quantified by the homogeneous time-resolved fluorescence method.

RESULTS

Forty-one secondary metabolites, mostly coumarins, were identified in angelica root extracts. A. archangelica, A. dahurica, and A. biserrata root extracts at concentration of 12.5-50 μg/mL potentiated glucose-induced insulin secretion, which correlated with their high coumarin content. Subsequently, 23 coumarins were isolated from these roots and screened using the same protocol. Coumarins substituted with the isoprenyl group were found to be responsible for the extracts' insulinotropic effect.

CONCLUSIONS

Insulinotropic effects of three pharmacopeial angelica roots were found, the metabolite profiles and pharmacological activities of the roots were correlated, and key structures responsible for the modulation of pancreatic β-cell function were identified. These findings may have implications for the traditional use of angelica roots in treating diabetes. Active plant metabolites may also become lead structures in the search for new antidiabetic treatments.

Protective effects of madecassoside, a triterpenoid from Centella asiatica, against oxidative stress in INS-1E cells

Progressive decline in β cell function and reduction in the β cell mass is important in type 2 diabetes. Here, we tested the hypothesis that madecassoside's previously demonstrated in vivo protective effects on the β cell in experimental diabetes were exerted directly. We investigated the effects of madecassoside in protecting a β cell line (INS-1E) against a variety of agents. INS-1E cells were treated with madecassoside in the presence of high glucose (HG), a cytokine mixture, hydrogen peroxide (H2O2), or streptozotocin (STZ). HG, the cytokine mixture, H2O2 and STZ each produced a significant decrease in cell viability; this was significantly reversed by madecassoside. Pre-treatment with madecassoside reduced the number of apoptotic cells induced by HG, the cytokine mixture, H2O2, and STZ, and concentration-dependently reduced ROS production. Madecassoside also significantly enhanced glucose-induced insulin secretion. The results suggest that madecassoside's in vivo effects are exerted directly on the β cell.

Rosemarinic acid protects β-cell from STZ-induced cell damage via modulating NF-κβ pathway

Rosmarinic acid (RA), a natural ester phenolic compound, is known to have antioxidant and anti-inflammatory properties. RA has also been reported to exhibit a hypoglycemic effect; however, the mechanisms underlying this effect have yet to be investigated. Therefore, the present study focused on the anti-diabetic effects and mechanism of RA in INS-1 cells using in vitro model. Streptozotocin (STZ) at a concentration of 3 mM was applied to INS-1 cells for 4 h to create a diabetic model. The cells were pretreated for 24 h with various concentrations (1 and 2.5 μM) of RA. The Cell viability, glucose-stimulated insulin secretion (GSIS), glucose uptake, lipid peroxidation, reactive oxygen species (ROS), apoptosis, and protein expression of Bcl-2, NF-κB, 1L-1β, and PARP were assessed. Results showed that STZ-treated INS-1 cells exhibited reduced cell viability, insulin release, insulin content, glucose uptake, and elevated MDA and ROS levels. Cells pretreated with RA maintained the function and morphology of β-cells against STZ-induced damage. Moreover, RA sustained high protein expression levels of Bcl-2 and low expression levels of NF-κB, IL-1β, and PARP. In conclusion, RA preserved β-cells function against STZ-induced damage by altering NF-κB and Bcl-2 pathways.

Daphnetin, a Coumarin with Anticancer Potential against Human Melanoma: In Vitro Study of Its Effective Combination with Selected Cytostatic Drugs

(1) The treatment of metastatic or drug-resistant melanoma is still a significant therapeutic problem. The aim of this study was to evaluate the anticancer potential of daphnetin (7,8-dihydroxycoumarin) and its combinations with five different cytostatic drugs (mitoxantrone, docetaxel, vemurafenib, epirubicin and cisplatin). (2) The viability, proliferation and cytotoxicity of daphnetin against four human malignant melanoma cell lines were evaluated. The interactions were assessed using isobolographic analysis for the combinations of daphnetin with each of the five cytostatic drugs. (3) Daphnetin showed anticancer activity against malignant melanoma, with IC₅₀ values ranging from 40.48 ± 10.90 µM to 183.97 ± 18.82 µM, depending on the cell line. The combination of daphnetin with either vemurafenib or epirubicin showed an antagonistic interaction. Moreover, additive interactions were observed for the combinations of daphnetin with cisplatin and docetaxel. The most desirable synergistic interactions for human melanoma metastatic cell lines were observed for the combination of daphnetin with mitoxantrone. (4) The obtained results suggest that daphnetin should not be combined with vemurafenib or epirubicin in the treatment of malignant melanoma due to the abolition of their anticancer effects. The combination of daphnetin with mitoxantrone is beneficial in the treatment of metastatic melanoma due to their synergistic interaction.

Daphnetin: A bioactive natural coumarin with diverse therapeutic potentials

Daphnetin (DAP), a coumarin derivative extracted from Daphne species, is biologically active phytochemical with copious bioactivities including anti-inflammatory, anti-oxidant, neuroprotective, analgesic, anti-pyretic, anti-malarial, anti-bacterial, anti-arthritic, neuroprotective, hepatoprotective, nephroprotective, and anti-cancer activities. A wide range of studies have been conducted exploring the significance and therapeutic potential of DAP. This study reviewed various databases such as NCBI, PubMed, Web of Science, Scopus and Google Scholar for published research articles regarding the sources, synthesis, and various bioactivities of DAP using different key words, including but not limited to "pharmacological activities," "sources," "neuroprotective effect," "synthesis," "cancer," "anti-inflammatory effect" of "daphnetin." Furthermore, this review encompasses both in-vivo and in-vitro studies on DAP for treating various diseases. A comprehensive review of the literature revealed that the DAP had a promising pharmacological and safety profile, and could be employed as a pharmaceutical moiety to treat a variety of illnesses including microbial infections, cancer, arthritis, hepatic damage, inflammation and neurological anomalies. The current review intends to provide an in-depth focus on all pharmacological activities and therapeutic approaches for the pharmaceutical and biomedical researchers.

Daphnetin, a Coumarin in Genus Stellera Chamaejasme Linn: Chemistry, Bioactivity and Therapeutic Potential

Coumarins is a huge family of phenolic compounds containing a common structure of 2 H -1-benzopyran-2-one. Nowadays, more than 1,300 natural-based coumarins have been identified in a variety of plants, bacteria and fungi, many of them exhibited promising biomedical performance. Daphnetin (7,8-dihydroxycoumarin) is a typical coumarin associated with a couple of bioactivities such as anti-cancer, antibacterial, anti-inflammatory and anti-arthritis. In the treatment of diseases, it has been verified that daphnetin has outstanding therapeutic effects on diabetes, arthritis, transplant rejection, cancer and even on central nervous system diseases. Herein, we summarized the chemical synthetic methodologies, bioactivities, therapeutic potentials and structure-activity relationships of daphnetin and its derivatives. Hopefully, this review would be beneficial for the discovery of new coumarin-based biomedicine in the near future.

Antioxidation of a proteoglycan from Ganoderma lucidum protects pancreatic β-cells against oxidative stress-induced apoptosis in vitro and in vivo

Oxidative stress is one of the major factors in induction of pancreatic β-cell apoptosis and diabetes. Here, we investigated systematically the roles of a proteoglycan (namely, FYGL) from Ganoderma lucidum in protection and repair of pancreatic β-cells against oxidative stress-induced injury and apoptosis on molecular, cellular and animal basis. FYGL in vitro had antioxidant activity in terms of scavenging of free radicals and reduction power. FYGL improved cells viability, insulin secretion, redox indicator expressions, and mitochondrial membrane potential in H2O2-induced INS-1 cell via regulating the activations of apoptosis-related mitogen-activated protein kinases (MAPK) and nuclear factor kappa B (NF-κB) pathways as well as the insulin secretion-related pathway. Thrillingly in vivo, FYGL repaired the injured pancreas, reduced the pancreatic β-cells apoptosis, and improved insulin secretion because of regulating the balance of oxidation-reduction, therefore well managed blood glucose in db/db diabetic mice. These results demonstrated that FYGL is promising to be used as a novel natural remedy for protection of pancreatic β-cells against oxidative stress in diabetes treatment.

Coumarins and Gastrointestinal Cancer: A New Therapeutic Option?

Cancers of the gastrointestinal (GI) tract are often life-threatening malignancies, which can be a severe burden to the health care system. Globally, the mortality rate from gastrointestinal tumors has been increasing due to the lack of adequate diagnostic, prognostic, and therapeutic measures to combat these tumors. Coumarin is a natural product with remarkable antitumor activity, and it is widely found in various natural plant sources. Researchers have explored coumarin and its related derivatives to investigate their antitumor activity, and the potential molecular mechanisms involved. These mechanisms include hormone antagonists, alkylating agents, inhibitors of angiogenesis, inhibitors of topoisomerase, inducers of apoptosis, agents with antimitotic activity, telomerase inhibitors, inhibitors of human carbonic anhydrase, as well as other potential mechanisms. Consequently, drug design and discovery scientists and medicinal chemists have collaborated to identify new coumarin-related agents in order to produce more effective antitumor drugs against GI cancers. Herein, we summarize the therapeutic effects of coumarin and its derivatives against GI cancer.

Flavonoids-rich extract from Bidens bipinnata L. protects pancreatic β-cells against oxidative stress-induced apoptosis through intrinsic and extrinsic pathways

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese medicinal, Bidens bipinnata L. has been used to treat many diseases with a long history in China. The anti-diabetic effects of extract from B. bipinnata have been demonstrated in the previous reports.

AIM OF THE STUDY

The protective effects of flavonoids-rich extract from B. bipinnata (BBTF) on cell damage induced by H₂O₂ in pancreatic β cell and its potential mechanisms were evaluated.

MATERIALS AND METHODS

MTT, ROS production, nuclear staining and flow cytometry assays were adopted to determine the effects of BBTF on cell viability, production of ROS and cell apoptosis in H₂O₂-treated INS-1 cell. Cell apoptosis-related proteins expressions were detected by Western blot assay.

RESULTS

Pre-treatment of BBTF could significantly increase INS-1 cell viability, inhibit the production of intracellular ROS and reduced the characteristic features of cell apoptosis induced by H₂O₂ in INS-1 cells. The studies of the underlying mechanism showed that BBTF could regulate Bax and Bcl-2 proteins expressions, suppress the phosphorylation of JNK, ERK and p38, as well as down-regulate Fas and FasL proteins expressions induced by H₂O₂. The expressions of caspase-8, caspase-9 and caspase-3 were therefore decreased.

CONCLUSION

The results indicated that flavonoids-rich extract from B. bipinnata could be a natural agent in diabetic prevention and therapy.

The synergistic protection of EGCG and quercetin against streptozotocin (STZ)-induced NIT-1 pancreatic β cell damage via upregulation of BCL-2 expression by miR-16-5p

EGCG and quercetin are flavonoids which usually co-exist in edible plants and they exhibit anti-diabetes effects. This study aimed to explore the mechanisms by which quercetin and EGCG synergistically protected pancreatic β-cells from streptozotocin-induced apoptosis. EGCG, quercetin, and their combinations (both 15 μM) all reversed STZ-induced cells damage and enhanced glucose-stimulated insulin secretion, with the combination being more effective than a single compound. At the molecular level, the EGCG-quercetin combination upregulated BCL-2 expression and caused a greater reduction in miR-16-5p level than EGCG alone or quercetin alone. Overexpression of miR-16-5p could offset the down-regulated apoptotic genes caused by the synergistic action of the combination. These findings suggest that EGCG and quercetin exert synergistic anti-diabetes effect, possibly via decreasing the expression of miR-16-5p that targets directly BCL-2. This is the first report on a miRNA-based mechanism underlying the synergistic protective effect of EGCG and quercetin against pancreatic cell damage.

Daphnetin Preconditioning Decreases Cardiac Injury and Susceptibility to Ventricular Arrhythmia following Ischaemia-Reperfusion through the TLR4/MyD88/NF-Κb Signalling Pathway

BACKGROUND/AIMS

Daphnetin (7,8-dihydroxycoumarin, DAP) exhibits various bioactivities, such as anti-inflammatory and antioxidant activities. However, the role of DAP in myocardial ischaemia/reperfusion (I/R) injury and I/R-related arrhythmia is still uncertain. This study aimed to investigate the mechanisms underlying the effects of DAP on myocardial I/R injury and electrophysiological properties in vivo and in vitro.

METHODS

Myocardial infarct size was measured by triphenyltetrazolium chloride staining. Cardiac function was assessed by echocardiographic and haemodynamic analyses. The levels of creatine kinase-MB, lactate dehydrogenase, malondialdehyde, superoxide dismutase, interleukin-6 (IL-6), and tumour necrosis factor-alpha (TNF-α) were detected using commercial kits. Apoptosis was measured by terminal deoxynucleotidyl-transferase-mediated dUTP nick-end labelling staining and flow cytometry. The viability of H9c2 cells was determined by the Cell Counting Kit-8 assay. In vitro, the levels of IL-6 and TNF-α were measured by quantitative PCR. The expression levels of proteins associated with apoptosis, inflammation, and the Toll-like receptor 4/myeloid differentiation factor 88/nuclear factor kappa B (TLR4/MyD88/NF-κB) signalling pathway were detected by Western blot analysis. The RR, PR, QRS, and QTc intervals were assessed by surface ECG. The 90% action potential duration (APD90), threshold of APD alternans, and ventricular tachycardia inducibility were measured by the Langendorff perfusion technique.

RESULTS

DAP preconditioning decreased myocardial I/R injury and hypoxia/reoxygenation (H/R) injury in cells. DAP preconditioning improved cardiac function after myocardial I/R injury. DAP preconditioning also suppressed apoptosis, attenuated oxidative stress, and inhibited inflammatory responses in vivo and in vitro. Furthermore, DAP preconditioning decreased the susceptibility to ventricular arrhythmia after myocardial I/R. Finally, DAP preconditioning inhibited the expression of TLR4, MyD88, and phosphorylated NF-κB (p-NF-κB)/P65 in mice subjected to I/R and cells subjected to H/R.

CONCLUSIONS

DAP preconditioning protected against myocardial I/R injury and decreased susceptibility to ventricular arrhythmia by inhibiting the TLR4/MyD88/NF-κB signalling pathway.

The Influence of Plant Extracts and Phytoconstituents on Antioxidant Enzymes Activity and Gene Expression in the Prevention and Treatment of Impaired Glucose Homeostasis and Diabetes Complications

Diabetes is a complex metabolic disorder resulting either from insulin resistance or an impaired insulin secretion. Prolonged elevated blood glucose concentration, the key clinical sign of diabetes, initiates an enhancement of reactive oxygen species derived from glucose autoxidation and glycosylation of proteins. Consequently, chronic oxidative stress overwhelms cellular endogenous antioxidant defenses and leads to the acute and long-standing structural and functional changes of macromolecules resulting in impaired cellular functioning, cell death and organ dysfunction. The oxidative stress provoked chain of pathological events over time cause diabetic complications such as nephropathy, peripheral neuropathy, cardiomyopathy, retinopathy, hypertension, and liver disease. Under diabetic conditions, accompanying genome/epigenome and metabolite markers alterations may also affect glucose homeostasis, pancreatic β-cells, muscle, liver, and adipose tissue. By providing deeper genetic/epigenetic insight of direct or indirect dietary effects, nutrigenomics offers a promising opportunity to improve the quality of life of diabetic patients. Natural plant extracts, or their naturally occurring compounds, were shown to be very proficient in the prevention and treatment of different pathologies associated with oxidative stress including diabetes and its complications. Considering that food intake is one of the crucial components in diabetes’ prevalence, progression and complications, this review summarizes the effect of the major plant secondary metabolite and phytoconstituents on the antioxidant enzymes activity and gene expression under diabetic conditions.

Therapeutic Potential of Lindera obtusiloba: Focus on Antioxidative and Pharmacological Properties

Lindera obtusiloba (LO) BLUME from the genus Lindera (Lauraceae) is a medicinal herb traditionally used in Southeast Asian countries. Indigenously, extracts of different parts of the plant have been used to improve blood circulation and treat allergy, inflammation, rheumatism, and liver diseases. LO is a rich source of therapeutically beneficial antioxidative phytochemicals, such as flavonoids, butenolides, lignans and neolignans. Moreover, recent studies have unravelled the pharmacological properties of several newly found active constituents of LO, such as anti-inflammatory antioxidants (+)-syringaresinol, linderin A, anti-atherosclerotic antioxidant (+)-episesamin, anti-melanogenic antioxidants quercitrin and afzelin, cytotoxic 2-(1-methoxy-11-dodecenyl)-penta-2,4-dien-4-olide, (2Z,3S,4S)-2-(11-dodecenylidene)-3-hydroxy-4-methyl butanolide, anti-allergic koaburaside, (6-hydroxyphenyl)-1-O-beta-d-glucopyranoside and 2,6-dimethoxy-4-hydroxyphenyl-1-O-beta-d-glucopyranoside and the antiplatelet-activity compound Secolincomolide A. These findings demonstrate that LO can be a potential source of antioxidants and other prospective therapeutically active constituents that can lead to the development of oxidative stress-mediated diseases, such as cardiovascular disorders, neurodegenerative disorders, allergies, inflammation, hepatotoxicity, and cancer. Here, the antioxidant properties of different species of Lindera genus are discussed briefly. The traditional use, phytochemistry, antioxidative and pharmacological properties of LO are also considered to help researchers screen potential lead compounds and design and develop future therapeutic agents to treat oxidative stress-mediated disorders.

Bioguided fractionation of hypoglycaemic component in methanol extract of Vernonia amygdalina: an in vivo study

Nine components (C1-C9) were isolated from chloroform fraction of fractionated methanol extracts of Vernonia amygdalina leaves (FMEVA) by column chromatography. All the components C1 to C9 were purified and screened for hypoglycaemic activities in type-2 diabetic rats. The most potent hypoglycaemic component was elucidated on the basis of extensive spectroscopic (1D-, 2D-NMR, GC-MS, FTIR) data analysis. The Component C5 was found to be the most potent hypoglycaemic in reducing blood glucose by 12.55 ± 3.55% at 4 h post-oral administration, when compared to the positive (18.07 ± 1.20%) and negative (-1.99 ± 0.43%) controls. The spectroscopic data analysis reveals that the isolated compound has a structure consistent with 11β,13-dihydrovernolide. The isolated compound is part of the hypoglycaemic components present in V. amygdalina leaves that is responsible for the anti-diabetic activities. Further research is needed in the development of this compound or its derivatives for pharmaceutical use.

Silencing of lncRNA PVT1 ameliorates streptozotocin-induced pancreatic β cell injury and enhances insulin secretory capacity by regulating miR-181a-5p

Diabetes mellitus (DM) is a type of metabolic disorder characterized by long-term hyperglycemia. Accumulating evidence shows that long noncoding RNAs (lncRNAs) play significant roles in the occurrence and development of DM. This study intended to investigate the role of lncRNA plasmacytoma variant translocation 1 (PVT1) in rat insulinoma (INS-1) cells damaged by streptozotocin (STZ) and to identify the potential mechanisms. Firstly, PVT1 expression in INS-1 cells was assessed using RT-qPCR after STZ stimulation. After PVT1-knockdown, cell apoptosis, the contents of oxidative stress related markers, and changes in insulin secretion were detected. Results indicated that PVT1 was remarkably upregulated after STZ stimulation. PVT1-knockdown inhibited STZ-induced oxidative stress and apoptosis of INS-1 cells. Moreover, the insulin secretory capacity was notably elevated following PVT1 silencing. Subsequently, a luciferase reporter assay verified that miR-181a-5p was directly targeted by PVT1. The rescue assays revealed that miR-181a-5p inhibitor dramatically abrogated the effects of PVT1 silencing on oxidative stress, apoptosis, and insulin secretion. Taken together, these findings demonstrated that PVT1-knockdown could ameliorate STZ-induced oxidative stress and apoptosis and elevate insulin secretory capacity in pancreatic β cells by regulating miR-181a-5p, suggesting a promising biomarker in DM diagnosis and treatment.

Antidiabetic Activity of Gold Nanoparticles Synthesized Using Wedelolactone in RIN-5F Cell Line

We synthesized the gold nanoparticles (AuNPs) using wedelolactone (WDL) and characterized them using UV-visible spectroscopy, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopic (SEM), transmission electron microscopic (TEM), energy dispersive X-ray diffraction, and atomic force microscopic (AFM) studies. The electronic spectrum exhibited an absorption peak at 535 nm. The FT-IR results proved that WDL was stabilized on the surface of AuNPs by acting as a capping or reducing agent. The crystalline structure was affirmed by XRD pattern and the spherical shape of WDL-AuNPs was evidenced by SEM, TEM, and AFM. The synthesized WDL-AuNPS were evaluated for anti-diabetic activity in pancreatic RIN-5F cell lines. In vitro results showed that WDL-AuNPs did not only improve the insulin secretion affected by di-(2-ethylhexyl) phthalate (DEHP), but also the cell viability in RIN5F cells. WDL-AuNPs treatment modulates the pro-apoptotic proteins and anti-apoptotic proteins expression to prevent the cells undergoing apoptosis in DEHP-exposed RIN-5F cells. The exposure of DEHP causes an increase in ROS production and lipid peroxidation levels. The free radical scavenging and antioxidant properties of WDL-AuNPs increase the deleterious effect caused by DEHP. On the other side, WDL-AuNPs increase mRNA expressions of insulin-signaling proteins in RIN-5F cells. This study concludes that WDL-AuNPs can be successfully used to regulate the expression of Bcl-2 family proteins, reduce lipid peroxidation, and to improve the secretion of antioxidants and insulin through the GLUT2 pathway in RIN-5F cell lines.

Combined effect of GABA and glucagon-like peptide-1 receptor agonist on cytokine-induced apoptosis in pancreatic β-cell line and isolated human islets

BACKGROUND

Treatment with GABA or glucagon-like peptide-1 (GLP-1) can preserve pancreatic β-cell mass and prevent diabetes. Recently, we reported that the combination of GABA and sitagliptin (a dipeptidyl peptidase-4 inhibitor that increases endogenous GLP-1) was more effective than either agent alone in reducing drug-induced β-cell damage and promoting β-cell regeneration in mice. However, in human islets, it remains unclear whether GABA and GLP-1 exert similar effects.

METHODS

To investigate GABA and GLP-1 interactions, human islets or INS-1 cells were treated with GABA and/or exendin-4, a GLP-1 receptor agonist (GLP-1RA) in clinical use, and incubated with a cytokine mixture for 24 hours. Cleaved caspase-3 and annexin V binding were measured by western blot and flow cytometry analysis, respectively, to investigate effects on cytokine-induced apoptosis.

RESULTS

Cytokine-induced apoptosis was reduced by either GABA or exendin-4 alone. This was markedly improved by combining GABA and exendin-4, resulting in a reversal of apoptosis. The combination notably increased Akt pathway signaling. Furthermore, sirtuin-1 (SIRT1) and α-Klotho, both reported to have protective effects on β-cells, were increased. Importantly, the combination ameliorated insulin secretion by human β-cells.

CONCLUSIONS

The combination of GABA and a GLP-1RA exerted additive effects on β-cell survival and function, suggesting that this combination may be superior to either drug alone in the treatment of diabetes.

Biofunctionalization of selenium nanoparticles with a polysaccharide from Rosa roxburghii fruit and their protective effect against H2O2-induced apoptosis in INS-1 cells

Defective glucose-stimulated insulin secretion (GSIS) induced by chronic exposure to reactive oxygen species (ROS) is a hallmark of type 2 diabetes mellitus (T2DM). Therefore, it is of great interest to search for biofunctional agents with antioxidant activity to protect pancreatic islet cells from oxidative damage. In the present study, selenium nanoparticles (SeNPs) functionalized with a novel polysaccharide (RTFP-3) extracted from Rosa roxburghii fruit were first prepared via a facile, single-step and green in situ synthesis method. The in vitro protective effects of RP3-SeNPs on INS-1 cells against H2O2-induced cell apoptosis were investigated. Structural characterization indicated that RTFP-3-functionalized SeNPs (RP3-SeNPs) with an average diameter of 104.5 nm were highly uniform and extremely stable in comparison with bare SeNPs. The results of bioassays revealed that RP3-SeNPs possessed much higher protective and suppressive activities against H2O2-induced apoptosis of INS-1 cells in comparison with their individual components. After treatment with an RP3-SeNPs solution (2 μg mL-1), the cell viability of INS-1 cells reached about 89.34%. Mechanistic studies demonstrated that RP3-SeNPs effectively blocked the overproduction of intracellular ROS, mitochondrial damage, and the activation of caspase-3, caspase-8, and caspase-9 in INS-1 cells, which indicated that RP3-SeNPs functioned via attenuating oxidative stress and downregulating the expression of uncoupling protein-2 (UCP-2). Our findings suggest that RP3-SeNPs can function as a promising candidate to prevent or limit the dysfunction of β-cells.

Daphnetin inhibits high glucose-induced extracellular matrix accumulation, oxidative stress and inflammation in human glomerular mesangial cells

Diabetic nephropathy (DN) is one of the most common causes of end-stage renal disease (ESRD). Oxidative stress and inflammation have been documented to play important roles in the pathogenesis of DN. Daphnetin, a natural coumarin compound, possesses antioxidant and anti-inflammatory activities. However, the role of daphnetin in DN has not yet been investigated. The aim of the present study was to explore the function of daphnetin in DN and the underlying mechanism in vitro. Our results demonstrated that daphnetin alleviated cell proliferation induced by high glucose (HG) in human mesangial cells (MCs). Daphnetin strikingly reduced reactive oxygen species (ROS) and malonaldehyde (MDA) levels, and induced the superoxide dismutase (SOD) activity in HG-stimulated MCs. Besides, the production of TNF-α, IL-1β, IL-6, fibronectin (FN) and collagen IV (Col IV) was also inhibited by daphnetin in HG-stimulated MCs. In addition, daphnetin enhanced the expression of nuclear factor-erythroid 2-related factor 2 (Nrf2) and inhibited the levels of p-Akt and p-p65 in HG-stimulated MCs. The results indicated that daphnetin inhibited HG-induced oxidative stress, inflammatory response, and ECM accumulation in human MCs. The effect is partially mediated by Nrf2/keap1 and Akt/NF-κB pathways. The findings suggested that daphnetin might be a therapeutic or preventive agent for DN.

Leptospermum flavescens Sm. protect pancreatic β cell function from streptozotocin involving apoptosis and autophagy signaling pathway in in vitro and in vivo case study

ETHNOPHARMACOLOGICAL IMPORTANCE

Leptospermum flavescens has been used traditionally in Malaysia to treat various ailments such as constipation, hypertension, diabetes and cancer.

AIM OF STUDY

To investigate the potential protective effects of L. flavescens in pancreatic β cells through inhibition of apoptosis and autophagy cell death mechanisms in in vitro and in vivo models.

MATERIALS AND METHODS

L. flavescens leaves were extracted using solvent in increasing polarities: hexane, ethyl acetate, methanol and water. All extracts were tested for INS-1 β cells viability stimulated by streptozotocin (STZ). The extract which promotes the highest cell protective activity was further evaluated for insulin secretion, apoptosis and autophagy signaling pathways. Then, the acute toxicity of extract was carried out in SD rats according to OECD 423 guideline. The active extract was tested in diabetic rats where the pancreatic β islets were evaluated for insulin, apoptosis and autophagy protein.

RESULTS

The methanolic extract of L. flavescens (MELF) was found to increase INS-1 β cells viability and insulin secretion against STZ. In addition, MELF has been shown to inhibit INS-1 β cells apoptosis and autophagy activity. Notably, there was no toxicity observed in SD rats when administered with MELF. Furthermore, MELF exhibited anti-hyperglycemic activity in diabetic rats where apoptosis and autophagy protein expression was found to be suppressed in pancreatic β islets.

CONCLUSION

MELF was found to protect pancreatic β cells function from STZ-induced apoptosis and autophagy in in vitro and in vivo.

Tangeretin inhibits streptozotocin-induced cell apoptosis via regulating NF-κB pathway in INS-1 cells

Oxidative stress is considered to play an important role in inducing the pancreatic β-cells apoptosis and promoting the development of diabetes mellitus. Tangeretin is a plant-derived flavonoid that retains antidiabetic effects. However, the role of tangeretin in streptozotocin (STZ)-induced β-cell apoptosis remains unclear. In this study, we aimed to examine the effects of tangeretin on STZ-induced cell apoptosis and the underlying mechanisms implicated in vitro. Our results showed that tangeretin improved the cell viability in STZ-induced INS-1 cells. Tangeretin reduced the increase of apoptosis ratio and revered the altered expressions of Bax and Bcl-2 caused by STZ induction. Furthermore, the impairment of insulin secretion ability as well as a reduction in messenger RNA levels of insulin 1 and 2 was significantly attenuated by tangeretin in STZ-induced INS-1 cells. Moreover, tangeretin resulted in a significant decrease in reactive oxygen species content, accompanied by an evident increase in the activities of superoxide dismutase, catalase, and glutathione peroxidase. Mechanistic studies further revealed that tangeretin inhibited the NF-κB pathway in STZ-induced INS-1 cells. These data indicated that tangeretin improved the cell apoptosis induced by STZ in INS-1 cells, which might be partly due to its antioxidant potential. Furthermore, NF-κB was found to be involved in the protective effect of tangeretin. Collectively, the results indicated that tangeretin could be used as a therapeutic approach for diabetes mellitus treatment.

Allium tuberosum: Antidiabetic and hepatoprotective activities

Allium tuberosum (AT) is traditionally used for treating nocturnal emissions, abdominal pain, diarrhea, sexual dysfunction and asthma. This study aimed at investigating the antidiabetic and hepatoprotective activities of the butyl alcohol fraction from the methanolic extract of A. tuberosum. For the antidiabetic activity, rats were induced with diabetes by intraperitoneal injection of 150mg/kg alloxan and treated for 30days with AT extract (100, 200 and 400mg/kg). Animals were sacrificed after the study and the fasting blood glucose (FBG), triglyceride (TG), total cholesterol (TC), HDL, malondialdehyde (MDA) catalase, superoxide dismutase and glutathione levels were determined. The hepatoprotective assay, mice were pretreated for seven days with AT (100, 200 and 400mg/kg) and silymarin (100mg/kg or). Thereafter 10ml/kg of 2% v/v CCl₄ was administered intraperitoneally on the 7th day to induce acute liver injury. Blood and liver samples were obtained and serum enzymes ALT, AST, ALP, SOD, GSH, CAT, MDA and pro-inflammatory mediators were assessed. AT significantly decrease FBG, serum TG, TC, MDA levels and significant increased HDL, SOD, GSH and CAT activities in the diabetic rats. In addition, AT significantly inhibited MDA, IL-1b, IL-6 and TNF-α levels and prevented the depletion of the antioxidant enzymes GSH, SOD and CAT activities in CCl₄ induced liver damage. Furthermore, AT markedly reduced AST, ALT and ALP levels in the CCl₄ treated mice groups. In conclusion, the antidiabetic and hepatoprotective effect of AT may be associated with its antioxidant and its ability to inhibit the pro-inflammatory mediators.

New Coumarinyl Ethers in Daphne oleoides Schreb. Collected from Sardinia Island

The phytochemical analysis of the ethanolic extract obtained from D. oleoides collected from Sardinia Island allowed the isolation of several new constituents for the species (3, 8, and 9) together with two new coumarinyl ethers (1 and 2) besides the chemotaxonomic markers of the Daphne genus (4 - 7 and 10) which are also known to possess interesting biological activities. The structure of the new compounds were elucidated by extensive spectroscopic and spectrometric analyses. The identification of these compounds gives an experimental evidence of the variability in the secondary metabolites pattern owned by populations growing in restricted area in respect to populations not confined by geographical barrier.