At present, surgery has become one of the treatments for type 2 diabetes, but it is still unclear about the therapeutic mechanism. Many experiments has proved that the anatomical and physiological structure has been altered leading to significant changes related to the secretion of gastrointestinal hormones and neuropeptides. These molecular are related to the metabolism of glucose, functions of islet cells and sensitivity of insulin. Intensive studies of glucagon-like peptide-1 (GLP-1) play an important role in the surgical treatment of diabetes and now it has gained increasing recognition. However, GLP-1 must be combined with GLP-1 receptor (GLP-1R) to execute its function. In this paper we reviewed the role of GLP-1 and its receptor in the mechanism of metabolic surgery.
Diabetes Mellitus, Type 2 ; surgery ; Glucagon-Like Peptide 1 ; Glucagon-Like Peptide-1 Receptor ; Humans ; Receptors, Glucagon

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

BACKGROUND: The characteristic feature of pancreatic beta cells is highly developed endoplasmic reticulum (ER) due to a heavy engagement in insulin secretion. The ER serves several important function, including post-translational modification, folding, and assembly of newly synthesized secretory proteins, and its proper function is essential to cell survival. Various stress conditions can interfere with ER function. Pancreatic beta cells may be particularly vulnerable to ER stress that causes to impair insulin biosynthesis and beta cell survival through apoptosis. Glucagon like peptide-1 (GLP-1) is a new drug for treatment of type 2 diabetes and has effects on stimulation of insulin secretion and beta cell preservation. Also, it may have an antiapoptotic effect on beta cells, but detailed mechanisms are not proven. Therefore, we investigated the protective mechanism of GLP-1 in beta cells through ER stress response induced by 2-deoxy-D-glucose (2DG). METHODS: For induction of the ER stress, HIT-T15 cells (hamster beta cell line) were treated with 2DG (10 mM). Apoptosis was evaluated with MTT assay, hoechst 33342 staining and Annexin/PI flow cytometry. Expression of ER stress-related molecules was determined by real-time PCR or western blot. For blocking ER stress, we pretreated HIT-T15 cells with exendin-4 (Ex-4; GLP-1 receptor agonist) for 1 hour before stress induction. RESULTS: After induction with ER stress (2DG), beta cells were lost by apoptosis. We found that Ex-4 had a protective effect through ER stress related molecules (GRP78, GRP94, XBP-1, eIF2alpha, CHOP) modulation. Also, Ex-4 recovered the expression of insulin2 mRNA in beta cells. CONCLUSION: These results suggest that GLP-1 may protect beta cells apoptosis through ER stress modulation.
Apoptosis ; Benzimidazoles ; Blotting, Western ; Cell Survival ; Deoxyglucose ; Endoplasmic Reticulum ; Flow Cytometry ; Glucagon ; Glucagon-Like Peptide 1 ; Glucagon-Like Peptide-1 Receptor ; HSP70 Heat-Shock Proteins ; Insulin ; Insulin-Secreting Cells ; Membrane Proteins ; Peptides ; Protein Processing, Post-Translational ; Proteins ; Real-Time Polymerase Chain Reaction ; Receptors, Glucagon ; RNA, Messenger ; Venoms

Diabetes Mellitus is a metabolic disease caused by impaired insulin secretion of pancreatic beta cells and increased insulin resistance of peripheral tissues. In Asian T2DM, progressive loss of beta cells mass and concomitant reduction of insulin secretion are more fundamental problems than peripheral insulin resistance. To solve this problem, research fields about investigation how stimulated islet cell growth and block the islet cell death is getting more important. Recently introduced drug, Glucagon like peptide-1 (GLP-1) has many beneficial roles in treatment of diabetes. GLP-1 stimulated glucose dependent insulin secretion and also can preserve beta cell mass through stimulation of beta cell growth and differentiation and protection of beta cell death from hyperglycemic stress. After treatment of GLP-1 or Exendin-4 (GLP-1 receptor agonist), beta cell mass is increased in animal models. This can be achieved through beta cell proliferation in islet or differentiation from intrapancreatic progenitor cells like ductal epithelium. The mechanism of beta cell proliferation is mediated by the PKA-CREB pathway. After activation of GLP-1 receptor, intracellular cAMP is elevated and then it activates PKA and CREB phosphorylation. Translocation of CREB into the nucleus up-regulates PDX-1 andIRS-2. Another pathway for beta cell proliferation is trans-activation of EGFR via c-Src after GLP-1 receptor activated. The notch pathway, major determinant of pancreas development in the embryonic stage, can be participate beta mass preservation through activation of gamma secretase in the beta cell membrane. Cleaved intracellular part of the notch translocates to the nucleus and binds to the pdx-1 promoter region. In hyperglycemia, oxidative and endoplasmic reticulum (ER) stress can be caused by apoptosis of the beta cell. Protection of apoptosis is another tool for beta cell mass preservation. After treatment of GLP-1 or exendin-4, beta cell apoptosis induced by oxidative and ER stress can be protected. GLP-1 can modulate JNK and GSK 3beta activation and ER chaperone and ER stress response. In treatment of diabetes, GLP-1 increases insulin secretion with glucose dependent manner and also preserves beta cell mass against progressive beta cell loss
Amyloid Precursor Protein Secretases ; Apoptosis ; Asian Continental Ancestry Group ; Cell Death ; Cell Membrane ; Cell Proliferation ; Diabetes Mellitus ; Endoplasmic Reticulum ; Epithelium ; Glucagon ; Glucagon-Like Peptide 1 ; Glucose ; Humans ; Hyperglycemia ; Insulin ; Insulin Resistance ; Insulin-Secreting Cells ; Islets of Langerhans ; Metabolic Diseases ; Models, Animal ; Pancreas ; Peptides ; Phosphorylation ; Promoter Regions, Genetic ; Receptors, Glucagon ; Stem Cells ; Venoms ; Glucagon-Like Peptide-1 Receptor

Type 2 diabetes has been identified as a risk factor for Alzheimer's disease (AD) and Parkinson's disease (PD). In the brains of patients with AD and PD, insulin signaling is impaired. This finding has motivated new research that showed good effects using drugs that initially had been developed to treat diabetes. Preclinical studies showed good neuroprotective effects applying insulin or long lasting analogues of incretin peptides. In transgenic animal models of AD or PD, analogues of the incretin GLP-1 prevented neurodegenerative processes and improved neuronal and synaptic functionality and reduced the symptoms of the diseases. Amyloid plaque load and synaptic loss as well as cognitive impairment had been prevented in transgenic AD mouse models, and dopaminergic loss of transmission and motor function has been reversed in animal models of PD. On the basis of these promising findings, several clinical trials are being conducted with the first encouraging clinical results already published. In several pilot studies in AD patients, the nasal application of insulin showed encouraging effects on cognition and biomarkers. A pilot study in PD patients testing a GLP-1 receptor agonist that is currently on the market as a treatment for type 2 diabetes (exendin-4, Byetta) also showed encouraging effects. Several other clinical trials are currently ongoing in AD patients, testing another GLP-1 analogue that is on the market (liraglutide, Victoza). Recently, a third GLP-1 receptor agonist has been brought to the market in Europe (Lixisenatide, Lyxumia), which also shows very promising neuroprotective effects. This review will summarise the range of these protective effects that those drugs have demonstrated. GLP-1 analogues show promise in providing novel treatments that may be protective or even regenerative in AD and PD, something that no current drug does.
Alzheimer Disease ; drug therapy ; Animals ; Diabetes Mellitus, Type 2 ; drug therapy ; Disease Models, Animal ; Glucagon-Like Peptide 1 ; analogs & derivatives ; pharmacology ; Glucagon-Like Peptide-1 Receptor ; Humans ; Liraglutide ; Mice ; Mice, Transgenic ; Neuroprotective Agents ; pharmacology ; Parkinson Disease ; drug therapy ; Peptides ; pharmacology ; Receptors, Glucagon ; agonists ; Venoms ; pharmacology

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

New therapeutics for type 2 diabetes using incretin hormone were introduced recently. Incretin-based therapies consist of two types: GLP-1 agonists mainly acting on the GLP-1 receptor and dipeptidyl peptidase 4 inhibitors (DPP-4 inhibitors). The former is resistant to DPP-4 and injectable. The latter is oral medications raising endogenous GLP-1 by inhibiting the degrading enzyme DPP-4. The incretin based therapies are promising and more commonly used due to their action and safety profile. Stimulation of insulin secretion by these drugs occurs in a glucose-dependent manner. Incretin based therapies have low risk for hypoglycemia. The subsequent review outlines evidence from selected clinical trials of the currently available GLP-1 agonists, exenatide and liraglutide, and DPP-4 inhibitors, sitagliptin and vildagliptin.
Adamantane ; Dipeptidyl-Peptidase IV Inhibitors ; Glucagon-Like Peptide 1 ; Hypoglycemia ; Incretins ; Insulin ; Nitriles ; Peptides ; Pyrazines ; Pyrrolidines ; Receptors, Glucagon ; Triazoles ; Venoms ; Glucagon-Like Peptide-1 Receptor ; Liraglutide ; Sitagliptin Phosphate

BACKGROUNDA number of studies have shown that oxidative stress and mitochondrial involvement are major triggering factors in the development of neurodegenerative diseases. Cobalt chloride (CoCl(2))-induced cell death in PC12 cells may serve a simple and convenient in vitro model of hypoxia-induced neuronal cytotoxicity. To explore the effect of geniposide on CoCl(2) which induced cytotoxicity and mitochondrial function in rat pheochromocytoma PC12 cells, we analyzed the influence of geniposide on the expression of apoptosis-related proteins.

METHODSPC12 cells and RNAi PC12 cells were treated with 0, 12.5, 25, 50, 100 micromol/L geniposide for 12 hours and then exposure to 400 micromol/L CoCl(2) for 12 hours. Cell viability, cell morphology, and expression of Bcl-2, Bax, P53 and caspase-9 were determined using Western blotting.

RESULTSPretreatment with geniposide markedly improved the cells viability and morphology, decreased the expression of Bax, P53 and caspase-9, and increased the expression of Bcl-2 in PC12 cells challenged by CoCl(2)2. However, in the RNAi PC12 cells, geniposide had no significant effect on the expression of these proteins.

CONCLUSIONGeniposide protects PC12 cells from CoCl(2) involved in mitochondrial mediated apoptosis, and GLP-1R might play a critical role in the neuroprotection of geniposide in PC12 cells.

Animals ; Apoptosis ; drug effects ; Cobalt ; toxicity ; Glucagon-Like Peptide-1 Receptor ; Iridoids ; pharmacology ; Mitochondria ; physiology ; Neuroprotective Agents ; pharmacology ; PC12 Cells ; Proto-Oncogene Proteins c-bcl-2 ; physiology ; Rats ; Receptors, Glucagon ; drug effects ; physiology ; Signal Transduction ; bcl-2-Associated X Protein ; physiology

It is well known that both insulin resistance and decreased insulin secretory capacity are important factors in the pathogenesis of type 2 diabetes mellitus (T2DM). In addition to genetic factors, obesity and lipotoxicity can increase the risk of T2DM. Glucagon-like peptide 1 (GLP-1) receptor agonists are novel antidiabetic drugs with multiple effects. They can stimulate glucose-dependent insulin secretion, inhibit postprandial glucagon release, delay gastric emptying, and induce pancreatic β-cell proliferation. They can also reduce the weight of patients with T2DM and relieve lipotoxicity at the cellular level. Many intracellular targets of GLP-1 have been found, but more remain to be identified. Elucidating these targets could be a basis for developing new potential drugs. My colleagues and I have investigated new targets of GLP-1, with a particular focus on pancreatic β-cell lines and hepatic cell lines. Herein, I summarize the recent work from my laboratory, with profound gratitude for receiving the prestigious 2016 Namgok Award.
Awards and Prizes ; Diabetes Mellitus ; Diabetes Mellitus, Type 2 ; Gastric Emptying ; Glucagon ; Glucagon-Like Peptide 1* ; Glucagon-Like Peptide-1 Receptor ; Hepatocytes* ; Humans ; Hypoglycemic Agents ; Insulin ; Insulin Resistance ; Obesity

Adult ; Calcium-Transporting ATPases ; metabolism ; Erythrocyte Membrane ; metabolism ; Female ; Humans ; Hydrocarbons ; adverse effects ; Lipid Peroxidation ; Male ; Middle Aged ; Occupational Exposure ; Sodium-Potassium-Exchanging ATPase ; metabolism ; Young Adult