OBJECTIVETo investigate the effects of activation of the GLP-1 receptor on the p38MAPK signaling pathway in hepatic stellate cells (HSCs).

METHODSHSCs were isolated and identified according to morphological features; the levels of GLP-1R protein were determined by western blotting.The HSCs were randomly divided into a control grouP (normal saline treatment) and experimental grouP(liraglutide treatment); after 120 hours, the expression of p38MAPK mRNA was examined by RT-PCR and of phosphorylated (p)-p38MAPK protein was detected by western blotting.

RESULTSGLP-1R proteins were detected in the HSCs. Compared with the control group, the experimental group showed significantly decreased p38MAPK mRNA and p-p38MAPK protein (both P < 0.01).

CONCLUSIONThe p38MAPK signaling pathway could be down-regulated when GLP-1R is activated in HSCs.

Cells, Cultured ; Glucagon-Like Peptide 1 ; analogs & derivatives ; pharmacology ; Glucagon-Like Peptide-1 Receptor ; Hepatic Stellate Cells ; metabolism ; Humans ; Liraglutide ; MAP Kinase Signaling System ; RNA, Messenger ; Receptors, Glucagon ; metabolism ; p38 Mitogen-Activated Protein Kinases ; metabolism

There is a close correlation between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD) in the course of pathophysiological processes. The neuroprotective action of glucagon-like peptide 1 (GLP-1), a latest drug for clinical treatment of T2DM, is being more deeply investigated at present, and a novel therapeutic strategy for AD with GLP-1 has been proposed boldly. This review mainly discussed the correlation of pathogenesis between T2DM and AD, the synthesis and secretion of GLP-1, the distribution and physiological effects of GLP-1 receptor in the brain, and the progresses on the study of GLP-1 in the treatment of AD.
Alzheimer Disease ; drug therapy ; physiopathology ; Amyloid beta-Peptides ; drug effects ; metabolism ; Animals ; Brain ; metabolism ; Diabetes Mellitus, Type 2 ; physiopathology ; Glucagon-Like Peptide 1 ; pharmacology ; therapeutic use ; Glucagon-Like Peptide-1 Receptor ; Humans ; Neuroprotective Agents ; pharmacology ; therapeutic use ; Receptors, Glucagon ; metabolism

Through phage display, we tried to find out whether the N-terminal fragment of glucogan-like peptide 1 receptor (nGLP-1R) still had binding activity to Exendin-4 after missing one or two gene segments. By error-prone PCR, We constructed a randomly mutated phage display peptide library with different length of the N-terminal (21-145 residues) extracellular domain of glucogan-like peptide 1 receptor (GLP-1R) from rat lung. A mutant named EP16 without binding activity was found by ELISA. Through sequence alignment we found that EP16 missed the first 20 and last 10 amino acids and the 52nd tryptophan was mutated to arginine. In order to determine why Ep16 did not show its binding ability to Exendin-4, a wild type EP16 without the first 20 and last 10 amino acids and nGLP-1R(W52R) was constructed in which the 52nd tryptophan was mutated to arginine. The contrastive analysis showed that the substitution of W52R led to a markedly reduced binding ability of EP16. The mutation of the conserved W52 could change the biologic activity of the protein. The lack of the first 20 and last 10 amino acids had no effect on its biologic activity. Therefore, the mutation of a single amino acid residue of the key sequence could change the biologic activity of the nGLP-1R.
Amino Acid Sequence ; Amino Acid Substitution ; Animals ; Binding Sites ; Glucagon-Like Peptide-1 Receptor ; Molecular Sequence Data ; Mutagenesis, Site-Directed ; Mutation ; Peptide Fragments ; chemistry ; genetics ; metabolism ; Peptides ; metabolism ; Protein Binding ; Rats ; Receptors, Glucagon ; chemistry ; genetics ; metabolism ; Venoms ; metabolism

Animals ; Animals, Newborn ; Cells, Cultured ; Cyclic AMP ; metabolism ; Glucagon-Like Peptide 1 ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; secretion ; Peptide Fragments ; pharmacology ; RNA, Messenger ; genetics ; Rats

AIM: To identify the glucose lowering ability and chronic treatment effects of a novel coumarin-glucagon-like peptide-1 (GLP-1) conjugate HJ07. METHOD: A receptor activation experiment was performed in HEK 293 cells and the glucose lowering ability was evaluated with hypoglycemic duration and glucose stabilizing tests. Chronic treatment was performed by daily injection of exendin-4, saline, and HJ07. Body weight and HbA1c were measured every week, and an intraperitoneal glucose tolerance test was performed before treatment and after treatment. RESULTS: HJ07 showed well-preserved receptor activation efficacy. The hypoglycemic duration test showed that HJ07 possessed a long-acting, glucose-lowering effect and the glucose stabilizing test showed that the antihyperglycemic activity of HJ07 was still evident at a predetermined time (12 h) prior to the glucose challenge (0 h). The long time glucose-lowering effect of HJ07 was better than native GLP-1 and exendin-4. Furthermore, once daily injection of HJ07 to db/db mice achieved long-term beneficial effects on HbA1c lowering and glucose tolerance. CONCLUSION The biological activity results of HJ07 suggest that HJ07 is a potential long-acting agent for the treatment of type 2 diabetes.
Animals ; Blood Glucose ; metabolism ; Coumarins ; pharmacology ; Diabetes Mellitus ; blood ; drug therapy ; Diabetes Mellitus, Type 2 ; drug therapy ; Exenatide ; Glucagon-Like Peptide 1 ; analogs & derivatives ; pharmacology ; therapeutic use ; Glucagon-Like Peptide-1 Receptor ; Glucose Tolerance Test ; Glycated Hemoglobin A ; metabolism ; HEK293 Cells ; Humans ; Hypoglycemic Agents ; pharmacology ; therapeutic use ; Male ; Mice, Inbred C57BL ; Mice, Knockout ; Peptides ; pharmacology ; Receptors, Glucagon ; metabolism ; Venoms ; pharmacology

Though bile acids have been well known as digestive juice, recent studies have demonstrated that bile acids bind to their endogenous receptors, including Farnesoid X receptor (FXR) and G protein-coupled bile acid receptor 1 (GPBAR1; TGR5) and serve as hormone to control various biological processes, including cholesterol/bile acid metabolism, glucose/lipid metabolism, immune responses, and energy metabolism. Deficiency of those bile acid receptors has been reported to induce diverse metabolic syndromes such as obesity, hyperlipidemia, hyperglycemia, and insulin resistance. As consistent, numerous studies have reported alteration of bile acid signaling pathways in type II diabetes patients. Interestingly, bile acids have shown to activate TGR5 in intestinal L cells and enhance secretion of glucagon-like peptide 1 (GLP-1) to potentiate insulin secretion in response to glucose. Moreover, FXR has been shown to crosstalk with TGR5 to control GLP-1 secretion. Altogether, bile acid receptors, FXR and TGR5 are potent therapeutic targets for the treatment of metabolic diseases, including type II diabetes.
Bile ; Bile Acids and Salts ; Biological Processes ; Energy Metabolism ; Enteroendocrine Cells ; Glucagon-Like Peptide 1* ; Glucose ; Homeostasis* ; Humans ; Hyperglycemia ; Hyperlipidemias ; Insulin ; Insulin Resistance ; Metabolic Diseases ; Metabolism ; Obesity

Dipeptidyl peptidase-4 (DPP-4) inhibitors are promising new antidiabetic drugs. It had been proposed that DPP-4 inhibitors exert their antidiabetic effect by inhibiting the degradation of glucagon-like peptide 1(GLP-1) . However, new evidence has shown that the increase of GLP-1 is not notable after the use of these drugs in patients with type 2 diabetes. Therefore, the specific mechanisms via which DPP-4 inhibitors in controlling blood glucose has became questionable. In recent years, studies have revealed many possible mechanisms through which DPP-4 inhibitors regulate glycemia: DPP-4 inhibitors may selectively reduce DPP-4 activity in the intestine, causing the increase of portal plasma GLP-1 level and thus promoting the release of insulin via nerve reflex;also, they may decrease the cleavage product of GLP-1 and reduce the degradation of other bioactive peptides.
Blood Glucose ; metabolism ; Diabetes Mellitus, Type 2 ; drug therapy ; Dipeptidyl-Peptidase IV Inhibitors ; pharmacology ; Glucagon-Like Peptide 1 ; drug effects ; metabolism ; Humans ; Hypoglycemic Agents ; pharmacology

Child ; Diabetes Mellitus, Type 2 ; drug therapy ; metabolism ; physiopathology ; Glucagon-Like Peptide 1 ; metabolism ; therapeutic use ; Humans ; Incretins ; therapeutic use ; Treatment Outcome

OBJECTIVETo observe the effect of glucagon-like peptide-1 (GLP-1) on hypoxia-reoxygenation (H/R) induced injury in neonatal rat cardiomyocytes.

METHODSCultured neonatal rat cardiomyocytes were randomly divided into seven groups: normal control group, H/R group, GLP-1 + H/R group, GLP-1 + H/R + UO126 group, GLP-1 + H/R + LY294002 group, H/R + UO126 group, H/R + LY294002 group. LDH activity, apoptosis rate of cardiomyocytes, Caspase-3 activity were detected.

RESULTSCompared with normal control group, the activity of LDH, cardiomyocyte apoptosis rate, Caspase-3 activity were all significantly increased in H/R group (all P < 0.01). However, compared with H/R group, these changes were significantly attenuated in GLP-1 + H/R group [the activity of LDH (128.47 +/- 7.96) U/L vs. (223.96 +/- 22.10) U/L, P < 0.01, and cardiomyocyte apoptosis rate (2.84 +/- 2.56)% vs. (12.58 +/- 6.69)%, P < 0.01, and Caspase-3 activity (36,809 +/- 4750) RLU vs. (57,602 +/- 9161) RLU, P < 0.01], while LY294002 (PI3K inhibitor) and UO126 (MAPK inhibitor) could block the effects of GLP-1 in cardiomyocytes underwent H/R injury.

CONCLUSIONSGLP-1 could protect H/R injury mainly by inhibiting cardiomyocytes apoptosis via activating PI3K/Akt and MAPK signaling pathway.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Cell Hypoxia ; Cells, Cultured ; Glucagon ; metabolism ; Glucagon-Like Peptide 1 ; pharmacology ; Myocardial Reperfusion Injury ; metabolism ; Myocytes, Cardiac ; drug effects ; Rats ; Rats, Wistar

New insights in the complex metabolic pathways and its control mechanism for energy homeostasis have refined our understanding of the pathophysiology of obesity. It is now recognized that there are several additional regulatory mechanism such as peripheral signals including leptin, ghrelin, GLP-1 and PYY and cellular signals including uncoupling proteins and beta Adrenergic receptors, which contribute to the regulation of food intake and energy expenditure, respectively. In addition, the function of adipocyte as an endocrine organ in energy homeostasis has been recently emphasized. Recent findings suggest that elevated levels of adipokines, such as leptin, adiponectin, resistin and TNF-alpha, in addition to increased free fatty acid level could be related to the pathophysiology of insulin resistance in obesity. For effective treatments and prevention of obesity, further studies on the circuits of neural and endocrine interactions in the regulation of energy homeostasis are needed.
Adipocytes ; Adipokines ; Adiponectin ; Eating ; Energy Metabolism ; Ghrelin ; Glucagon-Like Peptide 1 ; Homeostasis* ; Insulin Resistance ; Leptin ; Metabolic Networks and Pathways ; Obesity* ; Receptors, Adrenergic, beta ; Resistin ; Tumor Necrosis Factor-alpha