Streptozotocin-induced Diabetic Rat Model Research Articles

ANTI-HYPERGLYCEMIC EFFECT OF TERMINALIA CATAPPA FRUIT EXTRACT IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

Objective: To explore the anti-hyperglycemic effect of fruit extract of Terminalia catappa (Indian almond), a potential medicine from plant origin in a diabetic rat model.Methods: Streptozotocin-induced chronic diabetic rat model was utilized in the study. Three doses of test drug, hydro-alcoholic fruit extract of Terminalia catappa in 20 mg/kg, 30 mg/kg and 40 mg/kg and a standard anti-diabetic drug, glibenclamide (10 mg/kg) was used. The study had a total of nine groups with eight animals in each group. Drugs were given orally every day for 12 w. Blood glucose, body weight and urine volume were measured weekly, glycosylated hemoglobin (HbA1c) was estimated at 12th week in all groups. Data for all parameters were analyzed using one-way ANOVA repeated measures followed by Mann-Whitney test.Results: Hydro-alcoholic fruit extract of T. catappa significantly decreased blood glucose, urine volume and increased body weight in a dose-dependent manner in diabetic rats. At 12th week, blood glucose level in control, diabetic control, glibenclamide, T. catappa (40 mg/kg) group was 96.25±2.05 mg/dl, 599.75±0.25 mg/dl, 248.25±11.45 mg/dl, 115.00±3.78 mg/dl respectively. Effect of T. catappa in 30 mg/kg and 40 mg/kg dose was significantly more than glibenclamide. At 12th week, HbA1c level in control, diabetic control, glibenclamide, T. catappa (40 mg/kg) was 2.94±0.33 mmol/l, 4.94±0.49 mmol/l, 3.61±0.28 mmol/l, 3.21±0.27 mmol/l. Treatment with T. catappa 30 mg/kg, 40 mg/kg and glibenclamide brought back the level of HbA1c to normal levels. The addition of glibenclamide to T. catappa (40 mg/kg) did not produce any additional effect on blood glucose and HbA1c levels compared to the effect of T. catappa (40 mg/kg) in diabetic rats.Conclusion: Terminalia catappa fruit extract exhibited a significant anti-hyperglycemic effect in diabetic rats and has a great potential to be used in diabetes.

Diabetes alters myelin lipid profile in rat cerebral cortex: Protective effects of dihydroprogesterone

Due to the emerging association of diabetes with several psychiatric and neurodegenerative events, the evaluation of the effects of this pathology on the brain function has now a high priority in biomedical research. In particular, the effects of diabetes on myelin compartment have been poorly taken into consideration. To this purpose, we performed a deep lipidomic analysis of cortical myelin in the streptozotocin-induced diabetic rat model. In male rats three months of diabetes induced an extensive alterations in levels of phosphatidylcholines and phosphatidylethanolamines (the main species present in myelin membranes), plasmalogens as well as phosphatidylinositols and phosphatidylserines. In addition, the levels of cholesterol and myelin basic protein were also decreased. Because these lipids exert important functional and structural roles in the myelin compartment, our data indicate that cerebral cortex myelin is severely compromised in diabetic status. Treatment for one-month with a metabolite of progesterone, dihydroprogesterone, restored the lipid and protein myelin profiles to the levels observed in non-diabetic animals. These data suggest the potential of therapeutic efficacy of DHP to restore myelin in the diabetic brain.

Potential of CeCl3@mSiO2 nanoparticles in alleviating diabetic cataract development and progression

Cataract is a major cause of visual impairment for diabetic patients. It is imperative to develop efficient therapeutic agents against diabetic cataract (DC) because diabetes confers higher risk for complications after cataract surgery. We have previously reported the role of CeCl3 loaded mesoporous silica (CeCl3@mSiO2) nanoparticles in reducing the oxidative stress of lens epithelial cells. However, the potential of CeCl3@mSiO2 in preventing diabetic cataract development remains unclear. In this study, we applied CeCl3@mSiO2 nanoparticles with a size of 87.6±8.9nm to streptozotocin-induced diabetic cataract rat model by intraperitoneal injection. Our results showed that CeCl3@mSiO2 efficiently ameliorated the progression of DC. Consistent with antioxidant effect of CeCl3@mSiO2in vitro, administration of CeCl3@mSiO2 significantly abrogated hyperglycemia-mediated upregulation of advanced glycation end products, lipid peroxidation and protein carbonylation in animal lens. Taken together, our study provides a potential nanodrug to manage the development of DC.

Liraglutide prevents cognitive decline in a rat model of streptozotocin-induced diabetes independently from its peripheral metabolic effects

Diabetes has been identified as a risk factor for cognitive dysfunctions. Glucagone like peptide 1 (GLP-1) receptor agonists have neuroprotective effects in preclinical animal models. We evaluated the effects of GLP-1 receptor agonist, liraglutide (LIR), on cognitive decline associated with diabetes. Furthermore, we studied LIR effects against hippocampal neurodegeneration induced by streptozotocin (STZ), a well-validated animal model of diabetes and neurodegeneration associated with cognitive decline. Diabetes and/or cognitive decline were induced in Wistar rats by intraperitoneal or intracerebroventricular injection of STZ and then rats were treated with LIR (300μg/kg daily subcutaneously) for 6 weeks. Rats underwent behavioral tests: Morris water maze, passive avoidance, forced swimming (FST), open field, elevated plus maze, rotarod tests. Furthermore, LIR effects on hippocampal neurodegeneration and mTOR pathway (AKT, AMPK, ERK and p70S6K) were assessed. LIR improved learning and memory only in STZ-treated animals. Anxiolytic effects were observed in all LIR-treated groups but pro-depressant effects in CTRL rats were observed. At a cellular/molecular level, intracerebroventricular STZ induced hippocampal neurodegeneration accompanied by decreased phosphorylation of AMPK, AKT, ERK and p70S6K. LIR reduced hippocampal neuronal death and prevented the decreased phosphorylation of AKT and p70S6K; AMPK was hyper-phosphorylated in comparison to CTRL group, while LIR had no effects on ERK. LIR reduced animal endurance in the rotarod test and this effect might be also linked to a reduction in locomotor activity during only the last two minutes of the FST. LIR had protective effects on cognitive functions in addition to its effects on blood glucose levels. LIR effects in the brain also comprised anxiolytic and pro-depressant actions (although influenced by reduced endurance). Finally, LIR protected from diabetes-dependent hippocampal neurodegeneration likely through an effect on mTOR pathway.

Antioxidative and Anti-Inflammatory Activities of Galloyl Derivatives and Antidiabetic Activities of Acer ginnala.

Chromatographic isolation of the 80% MeOH extract of Acer ginnala (AG) yielded seven galloyl derivatives: gallic acid (1), ginnalin B (2), acertannin (3), maplexin D (4), maplexin E (5), quercetin-3-O-(2′′-galloyl)-α-L-rhamnopyranoside (6), and kaempferol-3-O-(2′′-galloyl)-α-L-rhamnopyranoside (7). This is the first study to report the isolation of compounds 4 and 5 from AG. Galloyl derivatives 3–7 exhibited potent radical scavenging activities, with 5 and 7 showing particularly strong inhibitory activities against nitric oxide production in lipopolysaccharides- (LPS-) stimulated RAW264.7 cells. In addition, oral administration of AG extract (500 mg/kg b.w.) improved symptoms of hyperglycemia and blunted the increases in serum GOT/GPT levels in a rat model of streptozotocin-induced diabetes. These results suggest that galloyl derivatives (1–7) are antioxidant and anti-inflammatory agents and that AG extract has potential as a functional material or novel herbal medicine for treating diabetes mellitus.

Electrospun Nanofibers Loaded with Quercetin Promote the Recovery of Focal Entrapment Neuropathy in a Rat Model of Streptozotocin-Induced Diabetes.

In this study, quercetin-loaded zein-based nanofibers were developed using electrospinning technique. The therapeutic effect of these quercetin-loaded nanofibers on neuropathy in streptozotocin- (STZ-) induced diabetes in rats was assessed. Diabetic condition was induced in male Wistar rats by STZ, after which a crush injury of the right sciatic nerve was performed to induce mononeuropathy. Functional recovery was assessed using walking track analysis, measurements of foot withdrawal reflex, nerve conduction velocity, and morphological analysis. The oxidative stress status and the ratio of phosphorylated extracellular recognition kinase (pERK)/extracellular recognition kinase (ERK) expression in the nerve lesion were also assessed in order to elucidate the potential mechanisms involved. Results showed that quercetin-loaded zein-based nanofibers slightly enhanced functional recovery from neuropathy in STZ-diabetic rats. The potential mechanism might partially involve improvements in oxidative stress status and the ratio of pERK/ERK expression in the nerve lesion.

Extract of Bauhinia vahlii Shows Antihyperglycemic Activity, Reverses Oxidative Stress, and Protects against Liver Damage in Streptozotocin-induced Diabetic Rats.

Background:Several studies have affirmed the effectiveness of some Bauhinia plants as antihyperglycemic agents.Objective:We investigated the possible effect of Bauhinia vahlii leaves extract in reducing hyperglycemia and reversing signs of organ damage associated with diabetes in streptozotocin (STZ) rat model.Materials and Methods:Both polar fraction of the B. vahlii leaves (defatted ethanolic extract [DEE]) and nonpolar fraction (n-hexane extract) were evaluated in vitro for α-glucosidase inhibition and 2,2-diphenyl-1-picrylhydrazyl radical scavenging potential. DEE was selected for further in vivo studies and was administered at two doses, i.e., 150 or 300 mg/kg to STZ-diabetic rats for 4 weeks.Results:Only DEE exhibited in vitro antioxidant and antihyperglycemic activities and its oral administration at both dose levels resulted in significant reduction in fasting blood glucose and glycated hemoglobin. Furthermore, signs of oxidative stress as indicated by hepatic reduced glutathione, nitric oxide, and malondialdehyde levels were completely reversed. In addition, histopathological examination and measurement of serum aspartate transaminase and alanine transaminase levels showed that DEE protected the liver from signs of liver pathogenesis when compared to diabetic untreated animals and those treated with metformin. Phytochemical analysis of DEE showed high flavonoids content with quercitrin as the major constituent along with other quercetin glycosides.Conclusion:This study strongly highlights the possible beneficial effect of B. vahlii leaves extract in relieving hyperglycemia and liver damage in STZ-diabetic rats and recommends further investigation of the value of quercetin derivatives in controlling diabetes and ameliorating liver damage associated with it.SUMMARY The polar fraction of the Bauhinia vahlii leaves (defatted ethanolic extract [DEE]) exhibited both in vitro antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl scavenging assay and strong α-glucosidase inhibition while the nonpolar fraction (n-hexane extract) failed to show any activity in both assays. DEE was further investigated in streptozotocin-induced diabetic rat model where oral administration of DEE at 2 doses (150 and 300 mg/kg) for 4 weeks resulted in significant reduction in fasting blood glucose and glycated hemoglobin and reversal of oxidative stress signs as indicated by measurement of hepatic reduced glutathione, nitric oxide, and malondialdehyde levels. In addition, histopathological examination and measurement of serum aspartate transaminase and alanine transaminase levels showed that DEE protected the liver from signs of pathogenesis observed in diabetic untreated rats. Phytochemical analysis of DEE showed high flavonoid content with quercitrin as the major constituent (62.9 ± 0.18 mg/mg). Abbreviations used: ALT: Alanine transaminase, AST: Aspartate transaminase, DEE: Defatted ethanol extract, DPPH: 2,2-diphenyl-1-picrylhydrazyl, FBG: Fasting blood glucose, GAE: Gallic acid equivalent, GSH: Reduced glutathione, Hb1Ac: Glycated hemoglobin, HE: Hexane extract MDA: Malondialdehyde, QE: Quercetin equivalent, STZ: Streptozotocin, TAC: Total antioxidant capacity.

Parenchymal and Stromal Cells Contribute to Pro-Inflammatory Myocardial Environment at Early Stages of Diabetes: Protective Role of Resveratrol.

Background: Little information is currently available concerning the relative contribution of cardiac parenchymal and stromal cells in the activation of the pro-inflammatory signal cascade, at the initial stages of diabetes. Similarly, the effects of early resveratrol (RSV) treatment on the negative impact of diabetes on the different myocardial cell compartments remain to be defined. Methods: In vitro challenge of neonatal cardiomyocytes and fibroblasts to high glucose and in vivo/ex vivo experiments on a rat model of Streptozotocin-induced diabetes were used to specifically address these issues. Results: In vitro data indicated that, besides cardiomyocytes, neonatal fibroblasts contribute to generating initial changes in the myocardial environment, in terms of pro-inflammatory cytokine expression. These findings were mostly confirmed at the myocardial tissue level in diabetic rats, after three weeks of hyperglycemia. Specifically, monocyte chemoattractant protein-1 and Fractalkine were up-regulated and initial abnormalities in cardiomyocyte contractility occurred. At later stages of diabetes, a selective enhancement of pro-inflammatory macrophage M1 phenotype and a parallel reduction of anti-inflammatory macrophage M2 phenotype were associated with a marked disorganization of cardiomyocyte ultrastructural properties. RSV treatment inhibited pro-inflammatory cytokine production, leading to a recovery of cardiomyocyte contractile efficiency and a reduced inflammatory cell recruitment. Conclusion: Early RSV administration could inhibit the pro-inflammatory diabetic milieu sustained by different cardiac cell types.

Efficacy of zinc oxide nanoparticles in attenuating pancreatic damage in a rat model of streptozotocin-induced diabetes

ABSTRACTZinc oxide nanoparticles (ZnO NPs) therapy is a promising strategy for treatment of several diseases. We aimed to investigate the therapeutic potential of ZnO NPs in ameliorating the histopathological and functional alterations in the pancreas of a rat model of streptozotocin-induced diabetes. Rats were randomized into control, diabetic and ZnO NPs-treated diabetic groups. Biochemical assays of blood glucose and serum insulin were performed. Pancreas specimens were processed for light and electron microscope examinations. ZnO NPs effectively reversed diabetes-induced pancreatic injury, as evidenced by the structural and ultrastructural improvement and confirmed by biochemical normalization of blood glucose and serum insulin.

Antioxidant-Rich Extract from Plantaginis Semen Ameliorates Diabetic Retinal Injury in a Streptozotocin-Induced Diabetic Rat Model

Plantaginis semen, the dried ripe seed of Plantago asiatica L. or Plantago depressa Willd. (Plantaginaceae), has been traditionally used to treat blurred vision in Asia. The aim of this work was to investigate the effect of plantaginis semen ethanol extract (PSEE) on the amelioration of diabetic retinopathy (DR) in streptozotocin (STZ)-diabetic rats. PSEE has abundant polyphenols with strong antioxidant activity. PSEE (100, 200 or 300 mg/kg) was oral administrated to the diabetic rats once daily consecutively for 8 weeks. Oral administration of PSEE resulted in significant reduction of hyperglycemia, the diameter of the retinal vessels, and retinal vascular permeability and leukostasis in diabetic rats. In addition, PSEE administration increased the activities of superoxidase dismutase (SOD) and catalase (CAT), and glutathione peroxidase (GSH) level in diabetic retinae. PSEE treatment inhibited the expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) and the phosphorylation of Akt without altering the Akt protein expression in diabetic retinae. PSEE not only down-regulated the gene expression of hypoxia-inducible factor-1α (TNF-α) and interleukin-1β (IL-1β), but also reduced ICAM-1 and VCAM-1 expression in diabetic retinae. Moreover, PSEE reduced the nuclear factor-κB (NF-κB) activation and corrected imbalance between histone deacetylases (HDAC) and histone acetyltransferases (HAT) activities in diabetic retinae. In conclusion, phenolic antioxidants extract from plantaginis semen has potential benefits in the prevention and/or progression of DR.

Pharmacological and toxicological assessment of innovative self-assembled polymeric micelles as powders for insulin pulmonary delivery.

Explore the use of polymeric micelles in the development of powders intended for pulmonary delivery of biopharmaceuticals, using insulin as a model protein. Formulations were assessed in vitro for aerosolization properties and in vivo for efficacy and safety using a streptozotocin-induced diabetic rat model. Powders presented good aerosolization properties like fine particle fraction superior to 40% and a mass median aerodynamic diameter inferior of 6 μm. Endotracheally instilled powders have shown a faster onset of action than subcutaneous administration of insulin at a dose of 10 IU/kg, with pharmacological availabilities up to 32.5% of those achieved by subcutaneous route. Additionally, micelles improved the hypoglycemic effect of insulin. Bronchoalveolar lavage screening for toxicity markers (e.g., lactate dehydrogenase, cytokines) revealed no signs of lung inflammation and cytotoxicity 14 days postadministration. Developed powders showed promising safety and efficacy characteristics for the systemic delivery of insulin by pulmonary administration.

The effects of gliclazide, methylcobalamin, and gliclazide + methylcobalamin combination therapy on diabetic peripheral neuropathy in rats

AimsThis study investigated the efficacies of gliclazide (GLZ), methylcobalamin (MCA), and GLZ+MCA combination therapy on DPN by evaluating the treatment-related changes in peripheral nerve function, the polyol pathway, and oxidative stress in the sciatic nerve of streptozotocin-induced diabetic rats. Materials and methodsThe rat model of streptozotocin-induced diabetes was orally given GLZ (25mg/kg/day), MCA (175μg/kg/day), and GLZ+MCA (25mg/kg/day+175μg/kg/day) combination therapy for 8weeks, in order to observe its effects on the motor nerve conduction velocity (MNCV), on the activities of Na+, K+-ATPase, aldose reductase(AR), AR mRNA expression, on the polyol contents, antioxidative enzyme activities and peroxidation products in the sciatic never tissue. Key findingsMost of the indicators of DPN, such as delayed MNCV, altered/damaged nerve structure, inhibited Na+,K+-ATPase activity, enhanced AR activity and AR mRNA expression, increased polyol contents, altered Cu,Zn-superoxide dismutase, catalase, and glutathione-peroxidase activities, and elevated malondialdehyde level in the sciatic nerves of the diabetic rats, were significantly ameliorated by treatment with either GLZ or MCA. Moreover, the combination of GLZ and MCA was found to enhance the curative effect on DPN in parts of above-mentioned parameters as compared to monotherapy. SignificanceMonotherapy with GLZ or MCA, and especially the combined application of GLZ and MCA, could be efficient therapeutic strategies for combating experimental DPN in diabetic rats.

Antidiabetic effect of Polyherbal Formulation “Kathakakhadiradi Kashyam” in Streptozotocin induced Diabetic rats

Aim: The aim of the present study was to evaluate the antidiabetic potential of “kathakakhadiradi kashyam” (KKS) an indigenious polyherbal ayurvedic formulation in streptozotocin induced diabetes rat model. Methodology: Initially a single day oral glucose tolerance test was conducted and the effective dose (1.08 ml/kg) found in this study was taken for further evaluation in the 28 day continues administration study. The effects were compared with diabetic control and standard control groups. Result and Conclusion: The ratio of percentage reduction observed between standard drug treated group (Glibenclamide) and KKS treated group from the 7 th day to 14 th , 21 st and 28 th day are 43.99:35.54, 46.53:44.4, 53.88:43.5 respectively. When compared with all other groups KKS treated group shows more similar glucose lowering activities. The study also correlates food, water intake and body weight changes in different groups throughout the study. The results shows that KSS posses promising antidiabetic activity. More detailed molecular level studies and toxicological evaluations are necessary to conform the safety and efficacy of KKS for clinical practice. Key words: Kathakakhadiradi kashyam, Polyherbal, Antidiabetic activity, Oral glucose tolerance test.

The efficacy of Aesculus hippocastanum seeds on diabetic nephropathy in a streptozotocin-induced diabetic rat model.

Cytokines, such as transforming growth factor (TGF)-ß1, and increased oxidative stress are considered to be responsible for the development of diabetic nephropathy. We hypothesized that Aesculus hippocastanum (AH) seeds may have preventive effects on oxidative stress and TGF-β-related diabetic nephropathy in streptozotocin (STZ)-induced diabetic nephropathy in rats. Twenty-one male Sprague-Dawley albino rats were divided into three groups (n=7). Except for the control group, they all had diabetic nephropathy induced by an intraperitoneal injection of STZ. While the diabetes group did not receive any medication, the diabetes+AH group was given the medication for 4 weeks. After the experiment, analyses were performed to evaluate the glomerular area, severity of sclerosis, and fibronectin immunoexpression, as well as levels of malondialdehyde (MDA), TGF-β, blood urea nitrogen (BUN), blood glucose, creatinine, and proteinuria. It was found that glomerular area, severity of sclerosis, fibronectin immunoexpression, and levels of MDA, TGF-β, BUN, creatinine, and proteinuria were decreased in the diabetes+AH group. It is known that diabetic nephropathy is induced, to a large extent, by hyperglycemia. In the present study, AH extract ameliorated diabetic nephropathy without decrease in blood glucose levels. In the study, AH seeds showed beneficial effects on the functional properties of the kidney and microscopic improvements in diabetic nephropathy.

Berberine regulates glycemia via local inhibition of intestinal dipeptidyl peptidase-Ⅳ

Objective: To investigate the effect of berberine on glycemia regulation in rats with diabetes and the related mechanisms. Methods: Diabetic-like rat model was successfully induced by intraperitoneal injection of streptozotocin in 50 out of 60 male SD rats, which were then randomly divided into 5 groups with 10 rats in each:control group (received vehicle only), positive drug control group (sitagliptin 10 mg·kg-1·d-1), low-dose berberine group (30 mg·kg-1·d-1), moderate-dose berberine group (60 mg·kg-1·d-1), and high-dose berberine group (120 mg·kg-1·d-1). All animals were fed for 3 d, and fasting blood sampling was performed on day 3 of administration. Rats were given glucose (2 g/kg) by gavage 30 min after the last dose. Blood and intestinal samples were obtained 2 h after glucose loading. Fasting blood glucose (FBG) and 2-h postprandial plasma glucose (2h-PPG) were detected by using biochemical analyzer, and insulin, glucagon-like peptide-1 (GLP-1) and dipeptidyl peptidase-Ⅳ(DPP-Ⅳ) were measured by using ELISA kit. Results: No significant difference in FBG and serum DPP-Ⅳ level were found between berberine groups and control group (all P>0.05). Compared with control group, serum levels of GLP-1 and insulin were increased in high-and moderate-dose berberine groups, while 2h-PPG was decreased (all P<0.05); GLP-1 levels in the intestinal samples were increased, while DPP-Ⅳ levels were decreased in all berberine groups (all P<0.05). Conclusions: Short-term berberine administration can decrease 2h-PPG level in streptozotocin-induced diabetic rat model through local inhibition of intestinal DPP-Ⅳ. The efficacy of DPP-Ⅳ inhibitor may be associated with its intestinal pharmacokinetics.

Berberine alleviates the cerebrovascular contractility in streptozotocin-induced diabetic rats through modulation of intracellular Ca²⁺ handling in smooth muscle cells.

BackgroundVascular dysfunction is a distinctive phenotype in diabetes mellitus. Current treatments mostly focus on the tight glycemic control and few of these treatments have been designed to directly recover the vascular dysfunction in diabetes. As a classical natural medicine, berberine has been explored as a possible therapy for DM. In addition, it is reported that berberine has an extra-protective effect in diabetic vascular dysfunction. However, little is known whether the berberine treatment could ameliorate the smooth muscle contractility independent of a functional endothelium under hyperglycemia. Furthermore, it remains unknown whether berberine affects the arterial contractility by regulating the intracellular Ca2+ handling in vascular smooth cells (VSMCs) under hyperglycemia.MethodsSprague–Dawley rats were used to establish the diabetic model with a high-fat diet plus injections of streptozotocin (STZ). Berberine (50, 100, and 200 mg/kg/day) were intragastrically administered to control and diabetic rats for 8 weeks since the injection of STZ. The intracellular Ca2+ handling of isolated cerebral VSMCs was investigated by recording the whole-cell L-type Ca2+ channel (CaL) currents, assessing the protein expressions of CaL channel, and measuring the intracellular Ca2+ in response to caffeine. Our results showed that chronic administration of 100 mg/kg/day berberine not only reduced glucose levels, but also inhibited the augmented contractile function of cerebral artery to KCl and 5-hydroxytryptamine (5-HT) in diabetic rats. Furthermore, chronic administration of 100 mg/kg/day berberine significantly inhibited the CaL channel current densities, reduced the α1C-subunit expressions of CaL channel, decreased the resting intracellular Ca2+ ([Ca2+]i) level, and suppressed the Ca2+ releases from RyRs in cerebral VSMCs isolated from diabetic rats. Correspondingly, acute application of 10 μM berberine could directly inhibit the hyperglycemia-induced CaL currents and suppress the hyperglycemia-induced Ca2+ releases from RyRs in cerebral VSMCs isolated from normal control rats.ConclusionsOur study indicated that berberine alleviated the cerebral arterial contractility in the rat model of streptozotocin-induced diabetes via regulating the intracellular Ca2+ handling of smooth muscle cells.

Ameliorative effect of melatonin against increased intestinal permeability in diabetic rats: possible involvement of MLCK-dependent MLC phosphorylation.

The increased intestinal permeability and functional impairment play an important role in type 2 diabetes (T2D), and melatonin may possess enteroprotection properties. Therefore, we used streptozotocin-induced diabetic rat model to investigate the regulation of intestinal permeability by melatonin. Rats were randomly divided into three groups, including control, diabetes mellitus (DM), and DM rats treated with melatonin. Melatonin was administered (10mg/kg/day) by gavage for 24weeks. The DM rats significantly increased the serum fasting blood glucose and lipid levels, which were alleviated by melatonin treatment. Importantly, the intestinal epithelial permeability was significantly increased in DM rats but was ameliorated following treatment with melatonin. These findings also indicated the expression of myosin light chain kinase (MLCK) and phosphorylation of MLC targeting subunit (MYPT) induced myosin light chain (MLC) phosphorylation level was markedly elevated in hyperglycemic and hyperlipidemic status. They were partly associated with down-regulated membrane type 1 and 2 (MT1 and MT2) expression, and up-regulated Rho-associated protein kinase (ROCK) expression and increased extracellular signal-regulated kinase (ERK) phosphorylation. However, the changes in target protein expression were reversed by melatonin. In conclusion, our results show melatonin beneficial effects on impaired intestinal epithelial permeability in T2D by suppressing ERK/MLCK- and ROCK/MCLP-dependent MLC phosphorylation.

Recombinant fibromodulin has therapeutic effects on diabetic nephropathy by down-regulating transforming growth factor-β1 in streptozotocin-induced diabetic rat model.

Diabetic nephropathy is an important long-term complication of diabetes mellitus which appears to be partially mediated by an increase in secretion of transforming growth factor-β (TGF-β). Fibromodulin, the small leucine-rich proteoglycan, has been proposed to be the potent TGFβ1 modulator. In this study, the therapeutic effects of recombinant adenoviral vectors expressing fibromodulin on TGF-β1 expression on diabetic nephropathy were assessed. Forty-eight Sprague-Dawley rats were divided into 4 groups: STZ-induced diabetic rats (diabetic-control), fibromodulin adenovirus vector treated STZ rats (Ad- fibromodulin), and Ad-lacZ-treated STZ rats (Ad-lacZ), and vehicle control (PBS-control). At 10 weeks after STZ treatment, we measured urinary albumin excretion (UAE), urine creatinine was measured by Jaffe method. We also measured kidney TGF-β1 levels by reverse transcription polymerase chain reaction and Real-time PCR. Urine albumin to creatinine ratio or UAE level were listed in four groups. UAE difference between healthy and diabetic rats in all three groups were significant (P≤0.005) and between the control group and treated groups were not significant. Our results indicated that TGF-β1gene expression in diabetic rats were increased and difference between normal group and diabetic group were significant (P≤0.001). Fibromodulin gene transfection mediated by a recombinant adenovirus decreased TGF-β1 level in STZ-induced diabetic rats and TGF-β1 mRNA in diabetic kidney were reduced 2 weeks after Ad-fibromodulin injection. Intraperitoneal injection of adenoviral vectors expressing fibromodulin reduced TGF-β1 level in diabetic rat models. The molecular mechanisms involved in this process require further study.

Inhibitory effect of curcumin on angiogenesis in a streptozotocin-induced diabetic rat model: An aortic ring assay

BackgroundCurcumin (diferuloylmethane) has been associated with the inhibition of angiogenesis, as well as the prevention of cancers and inflammatory processes. The aim of this study was to assess the efficacy of curcumin in suppressing angiogenesis in the cultured endothelial cells of rat aortic rings. MethodsEight-week-old male Wistar rats were randomized into five groups each with a different treatment and cell culturing paradigm: controls cultured in the absence of VEGF (vascular endothelial growth factor) (C), controls cultured in the presence of VEGF (C-V), controls treated with curcumin and then cultured in media lacking VEGF (C-TC), diabetics cultured in media supplemented with VEGF (D-V) and diabetics treated with curcumin and then cultured in media supplemented with VEGF (D-V-TC). Each group consisted of 8 animals. Diabetes was induced in by streptozotocin (STZ; 60 mg/kg body weight, IV). After 8 weeks, animals were sacrificed and their aortas were excised. Ring-shaped explants were embedded in a 96-well culture plate. Angiogenesis response was measured by counting the number of primary microtubules in each well. ResultsOptic microscopy revealed that the D-V group had the highest number of microvessels, while angiogenesis was not observed in the C or C-TC groups. The number of primary microtubules was significantly lower in the D-V-TC group compared to the D-V group (P < 0.05). The D-V-TC group had a significantly higher number of microvessels compared to the C-TC group (P < 0.05). ConclusionCurcumin attenuates angiogenesis response in stertozotocin-induced diabetic rats.

Resveratrol Ameliorates the Components of Hepatic Inflammation and Apoptosis in a Rat Model of Streptozotocin-Induced Diabetes.

Preclinical Research Trans-resveratrol has a wide range of biological effects that reflect its antioxidant, anti-inflammatory, anticarcinogenic and cardioprotective properties. This study was conducted to elucidate the potential role of resveratrol on hepatic inflammation and the apoptotic pathway components Bcl-2, Bax and p53 in a streptozotocin (STZ)-induced rat model of diabetes mellitus. Inflammatory and apoptotic biomarkers indicated a reduction in hepatic erythropoietin (1.26-fold) and increased asymmetric dimethylarginine (3.9-fold), visfatin (1.6-fold), inflammatory interleukins and TNF-α contents (approximately twofold each) in the diabetic animals. Induction of inducible nitric oxide synthase gene (2.04-fold) and protein expression (1.24-fold) was also observed. Immunohistochemical studies showed enhancement of the apoptotic biomarkers Bax and p53 in diabetic animals. STZ-induced diabetic male Wistar rats were treated with resveratrol (20 mg/kg/day i.p.). Resveratrol succeeded to recover most of these inflammatory and apoptotic elements. Therefore, inflammatory and apoptotic pathways were proved to be affected by STZ-induced diabetes in several aspects and resveratrol might contribute hepatoprotective effects as evidenced from this study.