OBJECTIVE: To elucidate the effect of Huanglian-Renshen-Decoction (HRD) on ameliorating type 2 diabetes mellitus by maintaining islet β -cell identity through regulating paracrine and endocrine glucagon-like peptide-1 (GLP-1)/GLP-1 receptor (GLP-1R) in both islet and intestine. METHODS: The db/db mice were divided into the model (distilled water), low-dose HRD (LHRD, 3 g/kg), high-dose HRD (HHRD, 6 g/kg), and liraglutide (400 µ g/kg) groups using a random number table, 8 mice in each group. The db/m mice were used as the control group (n=8, distilled water). The entire treatment of mice lasted for 6 weeks. Blood insulin, glucose, and GLP-1 levels were quantified using enzyme-linked immunosorbent assay kits. The proliferation and apoptosis factors of islet cells were determined by immunohistochemistry (IHC) and immunofluorescence (IF) staining. Then, GLP-1, GLP-1R, prohormone convertase 1/3 (PC1/3), PC2, v-maf musculoaponeurotic fibrosarcoma oncogene homologue A (MafA), and pancreatic and duodenal homeobox 1 (PDX1) were detected by Western blot, IHC, IF, and real-time quantitative polymerase chain reaction, respectively. RESULTS: HRD reduced the weight and blood glucose of the db/db mice, and improved insulin sensitivity at the same time (P<0.05 or P<0.01). HRD also promoted mice to secrete more insulin and less glucagon (P<0.05 or P<0.01). Moreover, it also increased the number of islet β cell and decreased islet α cell mass (P<0.01). After HRD treatment, the levels of GLP-1, GLP-1R, PC1/3, PC2, MafA, and PDX1 in the pancreas and intestine significantly increased (P<0.05 or P<0.01). CONCLUSION HRD can maintain the normal function and identity of islet β cell, and the underlying mechanism is related to promoting the paracrine and endocrine activation of GLP-1 in pancreas and intestine.
Animals ; Glucagon-Like Peptide 1/metabolism* ; Diabetes Mellitus, Type 2/metabolism* ; Glucagon-Like Peptide-1 Receptor/metabolism* ; Insulin-Secreting Cells/pathology* ; Drugs, Chinese Herbal/pharmacology* ; Male ; Blood Glucose/metabolism* ; Insulin/blood* ; Mice ; Intestinal Mucosa/pathology* ; Apoptosis/drug effects* ; Cell Proliferation/drug effects* ; Islets of Langerhans/pathology*

This study aims to observe the effects of different doses of Astragali Radix on the expression of glucagon(GLP-1) in se-rum and glucagon receptor(GLP-1R) in cartilage tissue in rats with knee osteoarthritis(KOA), explore the effect of Astragali Radix on the inflammation and apoptosis of KOA by regulating GLP-1/GLP-1R signaling axis, and investigate the mechanism of its action in alleviating KOA. Forty-eight male SD rats were randomly divided into six groups: blank group, model group, low-, medium-, and high-dose Astragali Radix groups(3.125, 6.25, and 12.5 g·kg~(-1)), and glucosamine sulfate group(0.1 g·kg~(-1)). Except for the blank group, rats in other groups were injected with sodium iodoacetate(MIA) into the knee joint to establish KOA models. After successful modeling, the rats were continuously treated for five weeks. Enzyme-linked immunosorbent assay(ELISA) was used to detect the levels of GLP-1, tumor necrosis factor-alpha(TNF-α), and interleukin-1β(IL-1β) in rat serum. Pathological examination was utilized to observe the pathological changes in knee joint cartilage. The mRNA levels of TNF-α and MMP13 in knee joint cartilage were detected by qRT-PCR, and the protein expression levels of GLP-1R, MMP13, and caspase-8 in knee joint cartilage were detected by Western blot. The expression of GLP-1R and MMP13 in the knee joint was detected by immunohistochemistry. Tunel staining was used to observe the apoptosis of chondrocytes in the knee joint. The above experimental results showed that Astragali Radix may raise the serum levels of GLP-1, reduce serum levels of TNF-α and IL-1, and decrease the relative mRNA expression of TNF-α and MMP13 through the GLP-1/GLP-1R axis. It thus activated GLP-1R, reduced the protein expression of MMP13 and caspase-8 in cartilage, and regulated their related signaling pathways to improve inflammation and apoptosis, so as to protect cartilage and improve KOA.
Animals ; Male ; Rats, Sprague-Dawley ; Osteoarthritis, Knee/genetics* ; Rats ; Drugs, Chinese Herbal/pharmacology* ; Glucagon-Like Peptide 1/metabolism* ; Glucagon-Like Peptide-1 Receptor/metabolism* ; Astragalus propinquus/chemistry* ; Humans ; Matrix Metalloproteinase 13/metabolism* ; Signal Transduction/drug effects* ; Tumor Necrosis Factor-alpha/metabolism* ; Astragalus Plant/chemistry* ; Apoptosis/drug effects*

Peptide dual agonists toward both glucagon-like peptide 1 receptor (GLP-1R) and glucagon receptor (GCGR) are emerging as novel therapeutics for the treatment of type 2 diabetes mellitus (T2DM) patients with obesity. Our previous work identified a Xenopus GLP-1-based dual GLP-1R/GCGR agonist termed xGLP/GCG-13, which showed decent hypoglycemic and body weight lowering activity. However, the clinical utility of xGLP/GCG-13 is limited due to its short in vivo half-life. Inspired by the fact that O-GlcNAcylation of intracellular proteins leads to increased stability of secreted proteins, we rationally designed a panel of O-GlcNAcylated xGLP/GCG-13 analogs as potential long-acting GLP-1R/ GCGR dual agonists. One of the synthesized glycopeptides 1f was found to be equipotent to xGLP/GCG-13 in cell-based receptor activation assays. As expected, O-GlcNAcylation effectively improved the stability of xGLP/GCG-13 in vivo. Importantly, chronic administration of 1f potently induced body weight loss and hypoglycemic effects, improved glucose tolerance, and normalized lipid metabolism and adiposity in both db/db and diet induced obesity (DIO) mice models. These results supported the hypothesis that glycosylation is a useful strategy for improving the in vivo stability of GLP-1-based peptides and promoted the development of dual GLP-1R/GCGR agonists as antidiabetic/antiobesity drugs.
Mice ; Animals ; Glucagon-Like Peptide 1/metabolism* ; Receptors, Glucagon/therapeutic use* ; Xenopus laevis/metabolism* ; Diabetes Mellitus, Type 2/drug therapy* ; Glycopeptides/therapeutic use* ; Obesity/drug therapy* ; Hypoglycemic Agents/pharmacology* ; Peptides/pharmacology*

Lycopene is an antioxidant which has potential anti-diabetic activity, but the cellular mechanisms have not been clarified. In this study, different concentrations of lycopene were used to treat pancreatic alpha and beta cell lines, and the changes of cell growth, cell apoptosis, cell cycle, reactive oxygen species (ROS), ATP levels and expression of related cytokines were determined. The results exhibited that lycopene did not affect cell growth, cell apoptosis, cell cycle, ROS and ATP levels of alpha cells, while it promoted the growth of beta cells, increased the ratio of S phase, reduced the ROS levels and increased the ATP levels of beta cells. At the same time, lycopene treatment elevated the mRNA expression levels of tnfα, tgfβ and hif1α in beta cells. These findings suggest that lycopene plays cell-specific role and activates pancreatic beta cells, supporting its application in diabetes therapy.
Adenosine Triphosphate ; metabolism ; Apoptosis ; Carotenoids ; pharmacology ; Cell Cycle ; Cells, Cultured ; Cytokines ; metabolism ; Glucagon-Secreting Cells ; drug effects ; Humans ; Insulin-Secreting Cells ; drug effects ; Lycopene ; pharmacology ; Reactive Oxygen Species ; metabolism

OBJECTIVE: To study the effect of exendin-4(Ex-4) on the differentiation of neural stem cells(NSCs) in adult mouse subventricular zone(SVZ)and its mechanism . METHODS: NSCs in the SVZ were derived from 5-week C57BL/6J mice and the expression of nestin was detected by immunofluorescence. The cell morphology was observed after the cells treatmed with 100 nmol/L Ex-4 for 14 days.The expressions of nestin and glucagon-like peptide-1 receptor (GLP-1R) were detected by immunofluorescence. GLP-1R was knocked down by using shRNA and the study was divided into four groups: control group, Ex-4 group, GLP-1R knockdown group, GLP-1R knockdown + Ex-4 group. After treatment with 100 nmol/L Ex-4 for 14 d, β-tublin III and glial fibrillary acidic protein (GFAP) were labeled by immunofluorescence and then the proportion of β-tublin III positive cells were counted. Western blot was used to detect the activation of cAMP-response element binding protein (CREB) in NSCs. In order to further study the effects of Ex-4 on mitogen-activated protein kinase(MAPK) and phosphatidylinositol 3-hydroxy kinase (PI3K) pathways, the cells were pretreated with MAPK inhibitor U0126 at a concentration of 0.07 μmol/L for 30 min or PI3K inhibitor LY294002 at 50 μmol for 2 h, respectively. The study was divided into six groups: control group, Ex-4 group, U0126 group, U0126 + Ex-4 group, LY294002 group, LY294002 + Ex-4 group. The activation of CREB in each group was detected by Western blot. The experiment was repeated three times independently. RESULTS: NSCs were successfully extracted from SVZ of C57BL/6J mice. Immunofluorescence showed that nestin and GLP-1R were positive in NSCs. Compared with the control group, the proportion of neurons differentiated from Ex-4 group was higher. The percentage of neurons in GLP-1R knockdown + Ex-4 group was basically the same as that in control group (P＜0.01). The positive cells of beta-tublin III showed positive activation of GLP-1R and CREB. Western blot showed that CREB was significantly activated in the Ex-4 group, and knockdown of GLP-1R abolished its activation (P＜0.01). U0126 did not affect Ex-4-mediated CERB activation, and LY294002 significantly reduced Ex-4-mediated CREB activation (P＜0.01). CONCLUSION Ex-4 promotes the differentiation of NSCs into neurons in SVZ of adult mice through GLP-1R receptor, which may be achieved through PI3K/CREB pathway.
Animals ; Cell Differentiation ; Cells, Cultured ; Cyclic AMP Response Element-Binding Protein ; metabolism ; Exenatide ; pharmacology ; Gene Knockdown Techniques ; Glucagon-Like Peptide-1 Receptor ; genetics ; metabolism ; Lateral Ventricles ; cytology ; Mice ; Mice, Inbred C57BL ; Neural Stem Cells ; cytology ; Phosphatidylinositol 3-Kinases

Glucagon-like peptide-1 (GLP-1) expression is shared by both intestinal cells and neurons of brainstem, which plays anorexigenic role on food intake. However, the exact source of physiological GLP-1 influencing food intake and pertinent mechanism of GLP-1 receptor agonists (GLP-1RA) remain unelucidated. In this study, the immediate early gene product c-Fos was chosen as the specific antigen for immunohistochemistry to show the certain areas of central nervous system (CNS) activation by the GLP-1RA. Thirty normal SD rats were randomly assigned to 3 groups, which were single intraperitoneally injected with Liraglutide (200 μg/kg), Exenatide (10 μg/kg) and saline, respectively. After injection, the amount of food intake and acute glycemic variation were assessed for comparison. The results showed that acute pharmacological dosage of GLP-1RA (Liraglutide or Exenatide) could significantly influence food intake. However, glycemic change indicated that the anorexic effect was dissociated with change in blood glucose in normal rats. Moreover, c-Fos was expressed significantly higher in major critical nuclei related to food intake in GLP-1RA groups when compared with the control group, and its expression was also found in spinal cord. The results suggested that acute administration of pharmacological doses of GLP-1 influences CNS via circulation and vagal pathways, especially on the arcuate nucleus (ARC) and the nucleus of solitary tract (NTS), and GLP-1 modulates autonomic nervous activities.
Animals ; Eating ; drug effects ; Exenatide ; pharmacology ; Glucagon-Like Peptide-1 Receptor ; agonists ; Liraglutide ; pharmacology ; Random Allocation ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo investigate the effect of glucagon-like peptide 1 (GLP-1) on cognitive dysfunction in diabetic rats.

METHODSMale SD rats were randomly divided into normal control group, diabetes mellitus (DM) group, and GLP-1 treatment group. Rat models of type 2 diabetes were established by high-sugar and high-fat feeding and streptozotocin (STZ) injection, and 25 days after the onset of diabetes, GLP-1 was infused in GLP-1 treatment group at the rate of 30 pmol·kg·minvia a subcutaneous osmotic pump for 7 days. The learning and cognitive ability of the rats was assessed with Morris water maze test, and the expression of cognition-related genes in the hippocampus tissue was detected with real-time PCR, Western blotting and immunohistochemical staining.

RESULTSCompared with the normal control group, the diabetic rats showed significantly decreased learning and memory abilities (P<0.05) with increased hippocampal expressions of APP, BACE1, Arc, ERK1/2, PKA, and PKC mRNAs (P<0.05) and Arc protein. Compared with diabetic rats, GLP-1-treated rats showed significantly improvements in the learning and memory function (P<0.05) with decreased expressions of APP, BACE1, Arc, ERK1/2, and PKA mRNAs (P<0.05) and Arc protein.

CONCLUSIONGLP-1 can improve cognitive dysfunctions in diabetic rats possibly by regulating the PKC, PKA, and ERK1/2 pathways and inhibiting Arc expression in the hippocampus.

Animals ; Diabetes Mellitus, Experimental ; drug therapy ; Diabetes Mellitus, Type 2 ; drug therapy ; Glucagon-Like Peptide 1 ; pharmacology ; Hippocampus ; drug effects ; Learning ; drug effects ; Male ; Memory ; drug effects ; Rats ; Rats, Sprague-Dawley ; Real-Time Polymerase Chain Reaction ; Streptozocin

To investigate the effect of berberine on glycemia regulation in rats with diabetes and the related mechanisms.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·d), low-dose berberine group (30 mg·kg·d), moderate-dose berberine group (60 mg·kg·d), and high-dose berberine group (120 mg·kg·d). 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.No significant difference in FBG and serum DPP-Ⅳ level were found between berberine groups and control group (all>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<0.05); GLP-1 levels in the intestinal samples were increased, while DPP-Ⅳ levels were decreased in all berberine groups (all<0.05).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.
Animals ; Berberine ; pharmacokinetics ; pharmacology ; Blood Glucose ; drug effects ; Diabetes Mellitus, Experimental ; chemically induced ; drug therapy ; Dipeptidyl Peptidase 4 ; analysis ; drug effects ; pharmacokinetics ; Dipeptidyl-Peptidase IV Inhibitors ; Dose-Response Relationship, Drug ; Glucagon-Like Peptide 1 ; analysis ; blood ; Hypoglycemic Agents ; Insulin ; blood ; Intestines ; chemistry ; drug effects ; Male ; Rats ; Rats, Sprague-Dawley ; Sitagliptin Phosphate

Dipeptidyl peptidase-4 (DPP-4) inhibitors are a new class of oral antidiabetic agent for the treatment of type 2 diabetes mellitus. They increase endogenous levels of incretin hormones, which stimulate glucose-dependent insulin secretion, decrease glucagon secretion, and contribute to reducing postprandial hyperglycemia. Although DPP-4 inhibitors have similar benefits, they can be differentiated in terms of their chemical structure, pharmacology, efficacy and safety profiles, and clinical considerations. Gemigliptin (brand name: Zemiglo), developed by LG Life Sciences, is a potent, selective, competitive, and long acting DPP-4 inhibitor. Various studies have shown that gemigliptin is an optimized DPP-4 inhibitor in terms of efficacy, safety, and patient compliance for treatment of type 2 diabetes mellitus. In this review, we summarize the characteristics of gemigliptin and discuss its potential benefits in clinical practice.
Biological Science Disciplines ; Diabetes Mellitus, Type 2* ; Dipeptidyl-Peptidase IV Inhibitors ; Glucagon ; Hyperglycemia ; Incretins ; Insulin ; Patient Compliance ; Pharmacology

OBJECTIVETo investigate the role of p38MAPK signaling pathway in the mechanism by which glucagon-like peptide-1 (GLP-1) inhibits endothelial cell damage induced by AGEs.

METHODSHuman umbilical vein endothelial cells were divided into control group, AGEs group, GLP-1 group, AGEs+GLP-1 group, AGEs+inhibitor group, and AGEs+GLP-1+inhibitor group. The expressions of p-p38MAPK/p38MAPK and p-eNOS/eNOS protein were examined by Western blotting, and the cell apoptosis rates were tested by flow cytometry.

RESULTSCompared with the control group, AGEs significantly enhanced the expression of p-p38 MAPK protein (P=0.001) while GLP-1 significantly inhibited its expression (P<0.001). AGEs significantly inhibited the expression of p-eNOS protein (P=0.007), which was enhanced by GLP-1 and p38 MAPK inhibitor (SB203580) (P=0.004). Both SB203580 and GLP-1 treatment decreased the apoptosis rate of AGEs-treated cells (P<0.001).

CONCLUSIONGLP-1 can protect human umbilical vein endothelial cells against AGEs-induced apoptosis partially by inhibiting the phosphorylation of p38MAPK protein and promoting the expression of p-eNOS protein.

Apoptosis ; Cells, Cultured ; Glucagon-Like Peptide 1 ; pharmacology ; Glycation End Products, Advanced ; metabolism ; Human Umbilical Vein Endothelial Cells ; cytology ; metabolism ; Humans ; Nitric Oxide Synthase Type III ; metabolism ; Phosphorylation ; Signal Transduction ; p38 Mitogen-Activated Protein Kinases ; metabolism