OBJECTIVE: To investigate the effect of complete Freund's adjuvant (CFA) on islet beta cell apoptosis in preventing diabetes in non-obese diabetic (NOD) mice, and the influence on apoptotic related-gene expression. METHODS: Four-week-old female NOD mice were randomly divided into Group CFA (n=5) and Group saline (NS) control (n=5). Mice in Group CFA were injected in the hind footpad with 50 microL CFA and mice in Group NS with 50 microL NS. Blood sugar was monitored and diabetes was diagnosed if blood sugar was higher than 11.1 mmol/L for 2 continuous days in the NOD mice. The mice were sacrificed when diagnosed as diabetes or at 30 weeks of age. Pancreatic sections were made for: evaluation of insulitis severity with HE staining; counting of apoptotic beta cells with the terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end labeling (TUNEL) method, and ABC immunohistochemical double labeling; counting of Fas, FasL and Bcl-x positive cells respectively with ABC immunohistochemical method. RESULTS: By 30 weeks of age, none of the 5 CFA-treated mice, compared with 3 of the 5 control mice, had developed diabetes. The insulitis score was lower (1.820+/-0.962 vs. 3.020+/-1.040, P<0.05), the rates of apoptotic beta cells, Fas positive cells and FasL positive cells were lower [(10.2+/-2.8)% vs. (15.9+/-6.5)%, (54.9+/-14.5)% vs. (75.7+/-12.9)%, (20.3+/-10.4)% vs. (27.9+/-12.0)%, P<0.05), and the Bcl-x positive cell rate was higher [(74.9+/-10.7)% vs. (66.0+/-18.3)%, P<0.05] in the CFA-treated group than those in the NS-treated group respectively. CONCLUSION CFA may inhibit beta cell apoptosis in NOD mice by regulating Fas, FasL and Bcl-x expression on cells within islets.
Animals ; Apoptosis ; drug effects ; Diabetes Mellitus, Type 1 ; pathology ; Fas Ligand Protein ; metabolism ; Female ; Freund's Adjuvant ; pharmacology ; Insulin-Secreting Cells ; drug effects ; pathology ; Mice ; Mice, Inbred NOD ; bcl-X Protein ; metabolism ; fas Receptor ; metabolism

OBJECTIVETo study the effects of Meilian Xiaoke capsule (a traditional Chinese medicinal preparation) combined with metformin for protecting islet cells and lowering blood glucose in diabetic rats.

METHODSRat models with type 2 diabetes, established by high-fat and high-glucose diet combined with streptozotocin (STZ) injection, were treated with a low dose of metformin, Meilian Xiaoke capsule, or both for 4 weeks by gavage. Blood glucose level was tested in the rats, and islet pathologies and changes in islet β cell number after the treatment were observed with HE staining and aldehyde fuchsin staining, respectively.

RESULTSTreatment with metformin or Meilian Xiaoke capsule alone for 2 or 4 weeks did not produce significant improvement of blood glucose in the diabetic rats. Their combined treatment for 4 weeks resulted in significantly lowered blood glucose level and improved glucose tolerance with also obviously increased islet β cell number and lessened islet pathologies.

CONCLUSIONSMeilian Xiaoke capsule and metformin show a synergistic effect to significantly enhance the therapeutic effect in rats with type 2 diabetes.

Animals ; Blood Glucose ; drug effects ; Diabetes Mellitus, Experimental ; drug therapy ; Diabetes Mellitus, Type 2 ; drug therapy ; Drug Synergism ; Drugs, Chinese Herbal ; pharmacology ; Hypoglycemic Agents ; pharmacology ; Insulin-Secreting Cells ; pathology ; Metformin ; pharmacology ; Rats ; Streptozocin

PURPOSE: Although the presence of cannabinoid type 1 (CB1) receptor in islets has been reported, the major contributor to the protective effect of rimonabant on islet morphology is unknown. We determined whether the protective effect of rimonabant on pancreatic islet morphology is valid in established diabetes and also whether any effect was independent of decreased food intake. MATERIALS AND METHODS: After diabetes was confirmed, Otsuka Long-Evans Tokushima Fatty rats, aged 32 weeks, were treated with rimonabant (30 mg/kg/d, rimonabant group) for 6 weeks. Metabolic profiles and islet morphology of rats treated with rimonabant were compared with those of controls without treatment (control group), a pair-fed control group, and rats treated with rosiglitazone (4 mg/kg/d, rosiglitazone group). RESULTS: Compared to the control group, rats treated with rimonabant exhibited reduced glycated albumin levels (p<0.001), islet fibrosis (p<0.01), and improved glucose tolerance (p<0.05), with no differences from the pair-fed control group. The retroperitoneal adipose tissue mass was lower in the rimonabant group than those of the pair-fed control and rosiglitazone groups (p<0.05). Rimonabant, pair-fed control, and rosiglitazone groups showed decreased insulin resistance and increased adiponectin, with no differences between the rimonabant and pair-fed control groups. CONCLUSION: Rimonabant had a protective effect on islet morphology in vivo even in established diabetes. However, the protective effect was also reproduced by pair-feeding. Thus, the results of this study did not support the significance of islet CB1 receptors in islet protection with rimonabant in established obesity-associated type 2 diabetes.
Adiponectin/metabolism ; Adiposity/drug effects ; Animals ; Cell Proliferation/drug effects ; Diabetes Mellitus, Type 2/diet therapy/*drug therapy ; Eating/*drug effects ; Glucose Intolerance/diet therapy/*drug therapy ; Insulin Resistance ; Insulin-Secreting Cells/*drug effects/pathology ; Male ; Piperidines/adverse effects/*therapeutic use ; Pyrazoles/adverse effects/*therapeutic use ; Rats ; Rats, Inbred OLETF ; Receptor, Cannabinoid, CB1/physiology ; Thiazolidinediones/*therapeutic use

OBJECTIVETo investigate the mechanism of beta-cell dysfunction induced by glucolipotoxicity in high fat-fed obese rats.

METHODSEighteen high-fat obese male Wistar rats were assigned into 3 groups and underwent 48-hour infusion through the jugular vein with normal saline (n=6), 20% intralipid + heparin (FFA group, n=6), or 25%glucose +20% intralipid + heparin (GS-FFA group, n=6). The plasma beta-hydroxybutyric acid (beta-HBA) was measured before and at the end of the infusion. After the infusion, the rats were sacrificed following an intravenous glucose tolerance test (IVGTT) to remove the tail of the pancreas for detection of apoptotic islet cells using TUNEL method. Immunohistochemical staining was performed to detect the expression of cytochrome c (cyt c), apoptosis-inducing factor (AIF), caspase-9 and caspase-3 in the islet cells.

RESULTSAt the end of the infusion, all the rats exhibited increased plasma beta-HBA levels, which was the highest in the GS-FFA group (P<0.05). IVGTT performed after the infusion showed a significantly lower insulinogenic index in GS-FFA group than that in NS and FFA groups. Greater number of apoptotic islet cells was found in the GS-FFA group than in the FFA and NS groups (P<0.05), and the islets had significantly higher levels of cyt c, AIF, caspase-9 and caspase-3 in the former group than in the latter two groups (P<0.05).

CONCLUSIONSHyperglycemia and high free fatty acid level synergistically impair insulin secretions to cause ketone overproduction in high fat-fed obese rats. The beta-cell dysfunction due to glucolipotoxicity is associated with increased beta-cell apoptosis and activation of mitochondrial apoptotic pathway.

3-Hydroxybutyric Acid ; blood ; Animals ; Apoptosis ; drug effects ; Fat Emulsions, Intravenous ; pharmacology ; Glucose ; pharmacology ; Glucose Tolerance Test ; Insulin-Secreting Cells ; cytology ; pathology ; Male ; Mitochondria ; drug effects ; Obesity ; physiopathology ; Rats ; Rats, Wistar

BACKGROUNDThe effects of triterpenic acid from Prunella vulgaris L. (TAP) on diabetes and its mechanism are uncertain. The aim of this study was to investigate the effects of TAP on antihyperglycemic, antioxidant, and pancreas-protective in streptozotozin (STZ)-diabetic rats.

METHODSThe diabetic model was produced by injection of 60 mg/kg STZ. Blood was drawn from the tail vein of rats after 72 hours. Rats with blood glucose ≥ 16.7 mmol/L were considered diabetic. Diabetic rats were randomly divided into four groups: (1) Diabetes rat (STZ), (2) Diabetic rats treated with 50 mg/kg of triterpenic acid from Prunella vulgaris L (STZ + TAP50), (3) Diabetic rats treated with 100 mg/kg TAP (STZ + TAP100), and (4) Diabetic rats treated with 200 mg/kg TAP (STZ + TAP200). Normal rats (n = 10) acted as the control group (NC). TAP was administered by the intragastric route once each day for six weeks. Body weight and the concentration of blood glucose (BG) were measured after three and six weeks. Fructosamine (FMN), malondialdehyde (MDA), and nitric oxide (NO), and the activities of nitric oxide synthase (NOS) and superoxide dismutase (SOD) in serum were determined after six weeks using commercially available kits following the manufacturer's instructions. Pathologic changes in pancreatic β-cells were also investigated by microscopic examination after hematoxylin-eosin (HE) staining. The level of SOD mRNA in pancreatic β-cells was measured by polymerase chain reaction (PCR).

RESULTSThe levels of BG, FMN, NO, and MDA and the activities of NOS in serum in the four diabetes groups were significantly increased compared with the control group (P < 0.01). The activity of SOD in serum and the body weight was significantly decreased compared with the control group (P < 0.01). After administration of TAP to diabetic rats for six weeks, the body weight and the levels of BG, FMN, MDA, NO and the activity of NOS in serum decreased significantly compared with the STZ group in a dose-dependent manner. The activity of SOD in serum and body weight increased significantly compared with the STZ group in a dose-dependent manner. In addition, diabetic rats showed a significant decrease in SOD mRNA expression in pancreatic β cells. However, these changes were reversed by TAP. Histopathological examination also showed the protective effect of TAP on pancreatic β cells.

CONCLUSIONSTriterpenic acid from Prunella vulgaris L. has an anti-diabetic effect, by controlling blood glucose and antioxidants, and has a protective effect on the pancreas.

Animals ; Blood Glucose ; analysis ; Diabetes Mellitus, Experimental ; drug therapy ; metabolism ; Insulin-Secreting Cells ; drug effects ; pathology ; Male ; Prunella ; chemistry ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Streptozocin ; Superoxide Dismutase ; genetics ; Triterpenes ; therapeutic use

Metformin has been reported to increase the expression of the glucagon-like peptide-1 (GLP-1) receptor in pancreatic beta cells in a peroxisome proliferator-activated receptor (PPAR)-alpha-dependent manner. We investigated whether a PPARalpha agonist, fenofibrate, exhibits an additive or synergistic effect on glucose metabolism, independent of its lipid-lowering effect, when added to metformin. Non-obese diabetic Goto-Kakizaki (GK) rats were divided into four groups and treated for 28 days with metformin, fenofibrate, metformin plus fenofibrate or vehicle. The random blood glucose levels, body weights, food intake and serum lipid profiles were not significantly different among the groups. After 4 weeks, metformin, but not fenofibrate, markedly reduced the blood glucose levels during oral glucose tolerance tests, and this effect was attenuated by adding fenofibrate. Metformin increased the expression of the GLP-1 receptor in pancreatic islets, whereas fenofibrate did not. During the intraperitoneal glucose tolerance tests with the injection of a GLP-1 analog, metformin and/or fenofibrate did not alter the insulin secretory responses. In conclusion, fenofibrate did not confer any beneficial effect on glucose homeostasis but reduced metformin's glucose-lowering activity in GK rats, thus discouraging the addition of fenofibrate to metformin to improve glycemic control.
Animals ; Blood Glucose/metabolism ; Body Weight/drug effects ; Diabetes Mellitus, Experimental/*drug therapy/*metabolism ; Drug Therapy, Combination ; Feeding Behavior/drug effects ; Fenofibrate/*pharmacology/therapeutic use ; Glucagon-Like Peptide 1/agonists/metabolism ; Glucose/*metabolism ; Glucose Tolerance Test ; Homeostasis/*drug effects ; Immunohistochemistry ; Injections, Intraperitoneal ; Insulin-Secreting Cells/drug effects/metabolism/pathology ; Lipid Metabolism/drug effects ; Male ; Metformin/*pharmacology/therapeutic use ; Peptides/administration & dosage/pharmacology ; Rats ; Receptors, Glucagon/metabolism ; Venoms/administration & dosage/pharmacology

OBJECTIVETo study the effect of Astragalus polysaccharide (APS) on pancreatic beta cell mass in type 1 diabetic mice.

METHODDiabetic mice induced by multiple low dose streptozotocin (MLD-STZ) were administered either APS (100, 200, 400 mg x kg(-1) body weight) or saline intraperitoneally daily, and sacrificed after 15 or 30 days of treatment. Streptavidin-peroxidase immunohistochemical method with counterstain was performed to determine the effect of APS on insulitis. Indirect double immunofluorescence for Insulin/Ki67 (counterstained by Hoechst33258) and Insulin/Cleaved caspase-3 was used to evaluate pancreatic cell (besides beta cell) proliferation, beta cell neogenesis, beta cell apoptosis and beta cell mass. Semi-quantitative RT-PCR was utilized to characterize pancreatic regenerating protein 1 mRNA levels, and ELISA method was performed to measure the levels of cytokine IFN-gamma and IL-4 secreted by splenocytes.

RESULTAttenuated insulitis, upregulated beta cell mass, increased number of neogenetic pancreas islets, decreased number of apoptosis beta cells and downregulation of Th1/Th2 cytokine ratio were significantly time-and dose-dependent on APS treatment, when compared to saline controls. However, no significant differences of the number of pancreatic proliferative cells or replicative cells and pancreatic regenerating protein 1 mRNA levels were demonstrated between APS (APS100, APS200 and APS400) and saline vehicle group on day 15 and 30 with APS treatment.

CONCLUSIONAPS can upregulate pancreatic beta cell mass in type 1 diabetic mice, strongly associated with improved autoimmunity.

Animals ; Apoptosis ; drug effects ; Astragalus membranaceus ; chemistry ; Carrier Proteins ; metabolism ; Diabetes Mellitus, Experimental ; chemically induced ; metabolism ; pathology ; Diabetes Mellitus, Type 1 ; chemically induced ; metabolism ; pathology ; Enzyme-Linked Immunosorbent Assay ; Insulin-Secreting Cells ; drug effects ; metabolism ; pathology ; Interferon-gamma ; metabolism ; Interleukin-4 ; metabolism ; Islets of Langerhans ; drug effects ; metabolism ; pathology ; Lithostathine ; biosynthesis ; genetics ; Male ; Mice ; Mice, Inbred C57BL ; Plants, Medicinal ; chemistry ; Polysaccharides ; isolation & purification ; pharmacology ; RNA, Messenger ; biosynthesis ; genetics ; Reverse Transcriptase Polymerase Chain Reaction ; Streptozocin ; Transcription Factors

OBJECTIVETo investigate the protective effect of losartan against angiotensin II (AngII)-induced beta cell (RIN-m) impairment and explore its mechanism.

METHODSIn vitro cultured RIN-m cells were divided into control group, 100 nmol/L AngII group and losartan pretreatment group. After cell incubation with the corresponding agents for 24 h, the amount of basal (3.3 mmol/L) and glucose-stimulated (16.7 mmol/L) insulin secretion (GSIS) was detected by radioimmunoassay, and the cellular reactive oxygen species (ROS) was assayed by flow cytometry with DCFH-DA staining; the mRNA and protein expressions of uncoupling protein 2 (UCP2) were determined by RT-PCR and Western blotting, respectively.

RESULTSThe basal insulin secretion showed no significant differences between the 3 groups (P>0.05). The GSIS in 100 nmol/L AngII group was significantly lower than that of the control group (P<0.001), but losartan pretreatment markedly restored the insulin secretion function to a level comparable to that of the control group (P<0.05). Compared with the control group, 100 nmol/L AngII significantly increased the cellular ROS level and the mRNA and protein expressions of UCP2 (P<0.05), and these changes were eliminated by losartan pretreatment.

CONCLUSIONSLosartan pretreatment offers protective effect against AngII-induced impairment of the GSIS of beta cells possibly by antagonizing the effects of AngII that causes increased ROS level and UCP2 expressions in beta-cells.

Angiotensin II ; adverse effects ; antagonists & inhibitors ; Animals ; Antihypertensive Agents ; pharmacology ; Cell Line, Tumor ; Insulin-Secreting Cells ; drug effects ; physiology ; Insulinoma ; pathology ; Ion Channels ; genetics ; metabolism ; Losartan ; pharmacology ; Mitochondrial Proteins ; genetics ; metabolism ; Protective Agents ; pharmacology ; RNA, Messenger ; genetics ; metabolism ; Rats ; Uncoupling Protein 2

This study is to investigate the effect of dexamethasone on cell apoptosis of murine MIN6 pancreatic beta-cells, and to investigate the mechanism of dexamethasone-dependent cell apoptosis. The cell apoptosis model was established by choosing the murine MIN6 pancreatic beta-cells, which was cultured in vitro and induced by dexamethasone. The morphology of the cell apoptosis was observed through fluorescence microscopic analysis after Hochest/PI staining and flow cytometric assay after Annexin-V/PI staining. The expression of caspase-3 was detected with caspase-3 activity assay kit. The expressions of Cyt-c, Bcl-2, Bax, AKT and p-AKT were observed with Western blotting. The results indicated that after exposure to dexamethasone at a concentration ranging from 50-800 nmol x L(-1) for 48 h, the percentage of cell apoptosis was significantly increased with the concentration over 100 nmol x L(-1) of dexamethasone; after exposure to dexamethasone (100 nmol x L(-1)) for 72 h, the activity of caspase-3 increased significantly; after exposure to dexamethasone at a concentration ranging from 50-800 nmol x L(-1) for 48 h, the expression of Cyt-c increased, Bcl-2 and AKT phosphorylation decreased while Bax and T-AKT remained unchanged. It could be concluded that the effect of dexamethasone on murine MIN6 pancreatic beta-cells apoptosis is significant. The mechanism of dexamethasone-dependent cell apoptosis is probably related to down regulation of the Bcl-2 expression and reduction of AKT phosphorylation.
Animals ; Antineoplastic Agents, Hormonal ; pharmacology ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Cell Line ; Cytochromes c ; metabolism ; Dexamethasone ; pharmacology ; Down-Regulation ; Insulin-Secreting Cells ; metabolism ; pathology ; Mice ; Phosphorylation ; Proto-Oncogene Proteins c-akt ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; bcl-2-Associated X Protein ; metabolism

OBJECTIVETo observe the effect of glucagon-like peptide-1 (GLP-1) on interleukin-1β (IL-1β)-induced damage in INS-1 cells and explore its possible mechanisms.

METHODSINS-1 cells were divided into normal control group, IL-1β group, and GLP-1+IL-1β group with corresponding treatments. The cell viability was determined by MTT assay, the expression of IKKβ mRNA was detected by real-time PCR, and that of the protein p65 was detected by Western blotting.

RESULTSIn comparison with the normal control group, the cells in the IL-1β group showed a significantly decreased viability by 29% (P < 0.01); compared with those in IL-1β group, the cells in GLP-1+IL-1β group exhibited an significant increase in the cell viability by 30% (P < 0.01). In comparison with the normal control group, the cells in IL-1β group showed an significantly increased expression of IKKβ mRNA (1.967 ± 0.091 vs 1 ± 0, P < 0.05); GLP-1 significantly reduced IL-1β-induced increment of IKKβ mRNA expression to 1.287 ± 0.084 (P < 0.05). IL-1β treatment significantly increased NF-κB protein expression as compared to the control level (0.814 ± 0.111 vs 0.396 ± 0.026, P < 0.01), and GLP-1 significantly inhibited such effect (0.622 ± 0.059, P < 0.05).

CONCLUSIONSGLP-1 inhibits IL-1β-induced β-cell damage probably by inhibiting the NF-κB pathway.

Cell Line ; Cell Survival ; Glucagon-Like Peptide 1 ; pharmacology ; Humans ; I-kappa B Kinase ; genetics ; metabolism ; Insulin-Secreting Cells ; cytology ; pathology ; Interleukin-1beta ; antagonists & inhibitors ; pharmacology ; NF-kappa B ; antagonists & inhibitors ; Protective Agents ; pharmacology ; RNA, Messenger ; genetics ; metabolism ; Signal Transduction ; drug effects