scholarly journals Refinement of Glucagon-like Peptide 1 Docking to Its Intact Receptor Using Mid-region Photolabile Probes and Molecular Modeling

2011 ◽  
Vol 286 (18) ◽  
pp. 15895-15907 ◽  
Author(s):  
Laurence J. Miller ◽  
Quan Chen ◽  
Polo C.-H. Lam ◽  
Delia I. Pinon ◽  
Patrick M. Sexton ◽  
...  
Keyword(s):  
Family Members ◽  
Receptor Site ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Amino Terminal ◽  
Single Receptor ◽  
Loop Region ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Amino Terminal Domain

The glucagon-like peptide 1 (GLP1) receptor is an important drug target within the B family of G protein-coupled receptors. Its natural agonist ligand, GLP1, has incretin-like actions and the receptor is a recognized target for management of type 2 diabetes mellitus. Despite recent solution of the structure of the amino terminus of the GLP1 receptor and several close family members, the molecular basis for GLP1 binding to and activation of the intact receptor remains unclear. We previously demonstrated molecular approximations between amino- and carboxyl-terminal residues of GLP1 and its receptor. In this work, we study spatial approximations with the mid-region of this peptide to gain insights into the orientation of the intact receptor and the ligand-receptor complex. We have prepared two new photolabile probes incorporating a p-benzoyl-l-phenylalanine into positions 16 and 20 of GLP1(7–36). Both probes bound to the GLP1 receptor specifically and with high affinity. These were each fully efficacious agonists, stimulating cAMP accumulation in receptor-bearing CHO cells in a concentration-dependent manner. Each probe specifically labeled a single receptor site. Protease cleavage and radiochemical sequencing identified receptor residue Leu141 above transmembrane segment one as its site of labeling for the position 16 probe, whereas the position 20 probe labeled receptor residue Trp297 within the second extracellular loop. Establishing ligand residue approximation with this loop region is unique among family members and may help to orient the receptor amino-terminal domain relative to its helical bundle region.

scholarly journals Actions of glucagon-like peptide-1 on KATP channel-dependent and -independent effects of glucose, sulphonylureas and nateglinide

2006 ◽  
Vol 190 (3) ◽  
pp. 889-896 ◽  
Author(s):  
Neville H McClenaghan ◽  
Peter R Flatt ◽  
Andrew J Ball
Keyword(s):  
Insulin Secretion ◽  
Protein Kinase ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Channel Dependent ◽  
Releasing Effect ◽  
Independent Effects

This study examined the effects of glucagon-like peptide-1 (GLP-1) on insulin secretion alone and in combination with sulphonylureas or nateglinide, with particular attention to KATP channel-independent insulin secretion. In depolarised cells, GLP-1 significantly augmented glucose-induced KATP channel-independent insulin secretion in a glucose concentration-dependent manner. GLP-1 similarly augmented the KATP channel-independent insulin-releasing effects of tolbutamide, glibenclamide or nateglinide. Downregulation of protein kinase A (PKA)- or protein kinase C (PKC)-signalling pathways in culture revealed that the KATP channel-independent effects of sulphonylureas or nateglinide were critically dependent upon intact PKA and PKC signalling. In contrast, GLP-1 exhibited a reduced but still significant insulin-releasing effect following PKA and PKC downregulation, indicating that GLP-1 can modulate KATP channel-independent insulin secretion by protein kinase-dependent and -independent mechanisms. The synergistic insulin-releasing effects of combinatorial GLP-1 and sulphonylurea/nateglinide were lost following PKA- or PKC-desensitisation, despite GLP-1 retaining an insulin-releasing effect, demonstrating that GLP-1 can induce insulin release under conditions where sulphonylureas and nateglinide are no longer effective. Our results provide new insights into the mechanisms of action of GLP-1, and further highlight the promise of GLP-1 or similarly acting analogues alone or in combination with sulphonylureas or meglitinide drugs in type 2 diabetes therapy.

Binding specificity and signal transduction of receptors for glucagon-like peptide-1(7–36)amide and gastric inhibitory polypeptide on RINm5F insulinoma cells

1993 ◽  
Vol 10 (3) ◽  
pp. 259-268 ◽  
Author(s):  
B Gallwitz ◽  
M Witt ◽  
U R Fölsch ◽  
W Creutzfeldt ◽  
W E Schmidt
Keyword(s):  
Cyclic Amp ◽  
Gastric Inhibitory Polypeptide ◽  
Dependent Manner ◽  
Binding Studies ◽  
Concentration Dependent Manner ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Insulinoma Cells

ABSTRACT Glucagon-like peptide-1(7–36)amide (GLP-1(7–36) amide) and gastric inhibitory polypeptide (GIP), peptides of the glucagon family, stimulate insulin secretion in vitro and in vivo. They possess high N-terminal sequence homology. Binding studies with 125I-labelled GIP and 125I-labelled GLP-1(7– 36)amide were performed in RINm5F insulinoma cells to investigate receptor specificity and to compare both receptors directly. Both binding sites were highly ligand-specific: GIP did not bind to the GLP-1(7–36)amide receptor and vice versa. Both peptides increased intracellular cyclic AMP levels; GLP-1(7– 36)amide was 100-fold more potent in stimulating cyclic AMP production when compared with GIP. At ranges of 1–10 nmol GLP-1(7–36)amide/1 and 0·1–10 GIP/1, corresponding to submaximal binding concentrations, the hormones showed an additive effect on cyclic AMP production. The N-terminal portion of GIP was important for binding, as GIP(1–30) showed almost full binding and biological activity. GIP(17–42) bound in a concentration-dependent manner with approximately 500-fold lower potency than GIP. At concentrations of up to 10 μmol GIP(17–42)/1 no stimulation of cyclic AMP was observed.

scholarly journals A selective small molecule glucagon-like peptide-1 secretagogue acting via depolarization-coupled Ca2+ influx

2009 ◽  
Vol 201 (3) ◽  
pp. 361-367 ◽  
Author(s):  
Jun-ichi Eiki ◽  
Kaori Saeki ◽  
Norihiro Nagano ◽  
Tomoharu Iino ◽  
Mari Yonemoto ◽  
...  
Keyword(s):  
Small Molecule ◽  
Underlying Mechanism ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Compound A ◽  
Fetal Rat ◽  
Small Molecule Compound ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that potentiates insulin secretion in a glucose-dependent manner. Selective GLP-1 secretagogue would be one of the potential therapeutic targets for type 2 diabetes. Here, we describe a newly identified small molecule compound (compound A) that stimulates secretion of GLP-1 in murine enteroendocrine cell lines, STC-1 and GLUTag cells, and in primary cultured fetal rat intestinal cells (FRIC). The underlying mechanism by which compound A stimulated GLP-1 secretion was also examined. Compound A stimulated GLP-1 secretion from STC-1 cells in a concentration-dependent manner, and also from GLUTag cells and FRIC. The action of compound A was selective against other tested endocrine functions such as secretion of insulin from rat islets, growth hormone from rat pituitary gland cells, and norepinephrine from rat PC-12 cells. In STC-1 cells, the compound A-stimulated GLP-1 secretion was neither due to cyclic AMP production nor to Ca2+ release from intracellular stores, but to extracellular Ca2+ influx. The response was inhibited by the presence of either L-type Ca2+ channel blockers or K+ ionophore. Perforated-patch clamp study revealed that compound A induces membrane depolarization. These results suggest that neither Gαs- nor Gαq-coupled signaling account for the mechanism of action, but depolarization-coupled Ca2+ influx from extracellular space is the primary cause for the GLP-1 secretion stimulated by compound A. Identifying a specific target molecule for compound A will reveal a selective regulatory pathway that leads to depolarization-mediated GLP-1 secretion.

Receptors for glucagon-like peptide-1(7–36) amide on rat insulinoma-derived cells

1988 ◽  
Vol 116 (3) ◽  
pp. 357-362 ◽  
Author(s):  
R. Göke ◽  
J. M. Conlon
Keyword(s):  
Specific Binding ◽  
Maximal Response ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Single Class ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Dose Dependent Increase ◽  
Dose Dependent ◽  
Rat Insulinoma

ABSTRACT Specific binding of 125I-labelled glucagon-like peptide-1(7–36)amide (GLP-1(7–36)amide) to rat insulinoma-derived RINm5F cells was dependent upon time and temperature and was proportional to cell concentration. Binding of radioactivity was inhibited in a concentration-dependent manner by GLP-1(7–36) amide consistent with the presence of a single class of binding site with a dissociation constant (Kd) of 204± 8 pmol/l (mean ± s.e.m.). Binding of the peptide resulted in a dose-dependent increase in cyclic AMP concentrations (half maximal response at 250 ± 20 pmol/l). GLP-1(1–36)amide was approximately 200 times less potent than GLP-1(7–36)amide in inhibiting the binding of 125I-labelled GLP-1(7–36)amide to the cells (Kd of 45±6 nmol/l). Binding sites for GLP-1 (7–36)amide were not present on dispersed enterocytes from porcine small intestine. J. Endocr. (1988) 116, 357–362

Central glucagon-like peptide 1 receptor-induced anorexia requires glucose metabolism-mediated suppression of AMPK and is impaired by central fructose

2013 ◽  
Vol 304 (7) ◽  
pp. E677-E685 ◽  
Author(s):  
Melissa A. Burmeister ◽  
Jennifer Ayala ◽  
Daniel J. Drucker ◽  
Julio E. Ayala
Keyword(s):  
Food Intake ◽  
Glucose Metabolism ◽  
Dependent Manner ◽  
Anorectic Effect ◽  
Dependent Inhibition ◽  
Glycolytic Inhibitor ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Amp Activated Protein Kinase ◽  
Mediated Reduction

Glucagon-like peptide-1 (GLP-1) suppresses food intake via activation of a central (i.e., brain) GLP-1 receptor (GLP-1R). Central AMP-activated protein kinase (AMPK) is a nutrient-sensitive regulator of food intake that is inhibited by anorectic signals. The anorectic effect elicited by hindbrain GLP-1R activation is attenuated by the AMPK stimulator AICAR. This suggests that central GLP-1R activation suppresses food intake via inhibition of central AMPK. The present studies examined the mechanism(s) by which central GLP-1R activation inhibits AMPK. Supporting previous findings, AICAR attenuated the anorectic effect elicited by intracerebroventricular (icv) administration of the GLP-1R agonist exendin-4 (Ex-4). We demonstrate that Ex-4 stimulates glycolysis and suppresses AMPK phosphorylation in a glucose-dependent manner in hypothalamic GT1-7 cells. This suggests that inhibition of AMPK and food intake by Ex-4 requires central glucose metabolism. Supporting this, the glycolytic inhibitor 2-deoxyglucose (2-DG) attenuated the anorectic effect of Ex-4. However, icv glucose did not enhance the suppression of food intake by Ex-4. AICAR had no effect on Ex-4-mediated reduction in locomotor activity. We also tested whether other carbohydrates affect the anorectic response to Ex-4. Intracerebroventricular pretreatment with the sucrose metabolite fructose, an AMPK activator, attenuated the anorectic effect of Ex-4. This potentially explains the increased food intake observed in sucrose-fed mice. In summary, we propose a model whereby activation of the central GLP-1R reduces food intake via glucose metabolism-dependent inhibition of central AMPK. We also suggest that fructose stimulates food intake by impairing central GLP-1R action. This has significant implications given the correlation between sugar consumption and obesity.

scholarly journals Exogenous glucagon-like peptide 1 reduces contractions in human colon circular muscle

2014 ◽  
Vol 221 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Antonella Amato ◽  
Sara Baldassano ◽  
Rosa Liotta ◽  
Rosa Serio ◽  
Flavia Mulè
Keyword(s):  
Colonic Motility ◽  
Circular Muscle ◽  
Human Colon ◽  
Inhibitory Effect ◽  
Mechanical Activity ◽  
Organ Bath ◽  
Dependent Manner ◽  
Double Labeling ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Glucagon-like peptide 1 (GLP1) is a naturally occurring peptide secreted by intestinal L-cells. Though its primary function is to serve as an incretin, GLP1 reduces gastrointestinal motility. However, only a handful of animal studies have specifically evaluated the influence of GLP1 on colonic motility. Consequently, the aims of this study were to investigate the effects induced by exogenous GLP1, to analyze the mechanism of action, and to verify the presence of GLP1 receptors (GLP1Rs) in human colon circular muscular strips. Organ bath technique, RT-PCR, western blotting, and immunofluorescence were used. In human colon, exogenous GLP1 reduced, in a concentration-dependent manner, the amplitude of the spontaneous contractions without affecting the frequency and the resting basal tone. This inhibitory effect was significantly reduced by exendin (9–39), a GLP1R antagonist, which per se significantly increased the spontaneous mechanical activity. Moreover, it was abolished by tetrodotoxin, a neural blocker, or Nω-nitro-l-arginine – a blocker of neuronal nitric oxide synthase (nNOS). The biomolecular analysis revealed a genic and protein expression of the GLP1R in the human colon. The double-labeling experiments with anti-neurofilament or anti-nNOS showed, for the first time, that immunoreactivity for the GLP1R was expressed in nitrergic neurons of the myenteric plexus. In conclusion, the results of this study suggest that GLP1R is expressed in the human colon and, once activated by exogenous GLP1, mediates an inhibitory effect on large intestine motility through NO neural release.

scholarly journals Glucagon-Like Peptide-1 Mediates the Protective Effect of the Dipeptidyl Peptidase IV Inhibitor on Renal Fibrosis via Reducing the Phenotypic Conversion of Renal Microvascular Cells in Monocrotaline-Treated Rats

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jian Xu ◽  
Jingjing Wang ◽  
Yusheng Cheng ◽  
Xiang Li ◽  
Mengyu He ◽  
...  
Keyword(s):  
Protective Effect ◽  
Renal Fibrosis ◽  
Kidney Diseases ◽  
Dipeptidyl Peptidase ◽  
Dependent Manner ◽  
Mesenchymal Transition ◽  
Matrix Deposition ◽  
Renal Microcirculation ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Chronic kidney diseases are characterized by renal fibrosis with excessive matrix deposition, leading to a progressive loss of functional renal parenchyma and, eventually, renal failure. Renal microcirculation lesions, including the phenotypic conversion of vascular cells, contribute to renal fibrosis. Here, renal microcirculation lesions were established with monocrotaline (MCT, 60 mg/kg). Sitagliptin (40 mg/kg/d), a classical dipeptidyl peptidase-4 (DPP-4) inhibitor, attenuated the renal microcirculation lesions by inhibiting glomerular tuft hypertrophy, glomerular mesangial expansion, and microvascular thrombosis. These effects of sitagliptin were mediated by glucagon-like peptide-1 receptor (GLP-1R), since they were blocked by the GLP-1R antagonist exendin-3 (Ex-3, 40 ug/kg/d). The GLP-1R agonist liraglutide showed a similar renal protective effect in a dose-independent manner. In addition, sitagliptin, as well as liraglutide, alleviated the MCT-induced apoptosis of renal cells by increasing the expression of survival factor glucose-regulated protein 78 (GRP78), which was abolished by the GLP-1R antagonist Ex-3. Sitagliptin and liraglutide also effectively ameliorated the conversion of vascular smooth muscle cells (SMCs) from a synthetic phenotype to contractile phenotype. Moreover, sitagliptin and liraglutide inhibited endothelial-mesenchymal transition (EndMT) via downregulating transforming growth factor-β1 (TGF-β1). Collectively, these findings suggest that DPP-4 inhibition can reduce microcirculation lesion-induced renal fibrosis in a GLP-1-dependent manner.

Activation of glucagon-like peptide-1 receptor inhibits growth and promotes apoptosis of human pancreatic cancer cells in a cAMP-dependent manner

2014 ◽  
Vol 306 (12) ◽  
pp. E1431-E1441 ◽  
Author(s):  
Hejun Zhao ◽  
Rui Wei ◽  
Liang Wang ◽  
Qing Tian ◽  
Ming Tao ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Cells ◽  
Human Pancreatic Cancer ◽  
Dependent Manner ◽  
Pancreatic Cancer Cells ◽  
Tumor Tissues ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1

Glucagon-like peptide-1 (GLP-1) promotes pancreatic β-cell regeneration through GLP-1 receptor (GLP-1R) activation. However, whether it promotes exocrine pancreas growth and thereby increases the risk of pancreatic cancer has been a topic of debate in recent years. Clinical data and animal studies published so far have been controversial. In the present study, we report that GLP-1R activation with liraglutide inhibited growth and promoted apoptosis in human pancreatic cancer cell lines in vitro and attenuated pancreatic tumor growth in a mouse xenograft model in vivo. These effects of liraglutide were mediated through activation of cAMP production and consequent inhibition of Akt and ERK1/2 signaling pathways in a GLP-1R-dependent manner. Moreover, we examined GLP-1R expression in human pancreatic cancer tissues and found that 43.3% of tumor tissues were GLP-1R-null. In the GLP-1R-positive tumor tissues (56.7%), the level of GLP-1R was lower compared with that in tumor-adjacent normal pancreatic tissues. Furthermore, the GLP-1R-positive tumors were significantly smaller than the GLP-1R-null tumors. Our study shows for the first time that GLP-1R activation has a cytoreductive effect on human pancreatic cancer cells in vitro and in vivo, which may help address safety concerns of GLP-1-based therapies in the context of human pancreatic cancer.

scholarly journals Dipeptidyl-Peptidase IV Converts Intact B-Type Natriuretic Peptide into Its des-SerPro Form

2006 ◽  
Vol 52 (1) ◽  
pp. 82-87 ◽  
Author(s):  
Inger Brandt ◽  
Anne-Marie Lambeir ◽  
Jean-Marie Ketelslegers ◽  
Marc Vanderheyden ◽  
Simon Scharpé ◽  
...  
Keyword(s):  
Natriuretic Peptide ◽  
Ex Vivo ◽  
Dipeptidyl Peptidase ◽  
Dipeptidyl Peptidase Iv ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Amino Terminal ◽  
Dpp Iv

Abstract Background: Analysis of plasma B-type natriuretic peptide (BNP) has suggested the in vivo formation of a truncated form, BNP (3–32), also called des-SerPro-BNP. The objectives of this study were to investigate (a) whether BNP and other natriuretic peptides are truncated by dipeptidyl-peptidase IV (DPP IV/CD26; EC 3.4.14.5) and (b) whether this truncation affects the susceptibility to cleavage by neutral endopeptidase (NEP; EC 3.4.24.11). Methods: Human BNP (1–32), A-type natriuretic peptide 1–28 (ANP 1–28), and related peptides were incubated with purified DPP IV and with human plasma. In addition, BNP (1–32), BNP (3–32), and ANP (1–28) were subjected to hydrolysis by NEP. Cleavage products were analyzed by mass spectrometry. Results: BNP (1–32) was cleaved by purified DPP IV with a specificity constant of 0.37 × 106 L · mol−1 · s−1. The DPP IV activity in EDTA-plasma was able to truncate BNP (1–32) ex vivo. Addition of Vildagliptin, a specific DPP IV inhibitor, prevented this truncation in a concentration-dependent manner. Under in vitro circumstances in which ANP was hydrolyzed extensively, BNP (1–32) and BNP (3–32) were very resistant to NEP-mediated cleavage. Conclusions: DPP IV cleaves BNP (1–32) with an efficiency higher than or comparable to several known in vivo substrates of the enzyme. Even after loss of the amino-terminal dipeptide, BNP remains highly resistant to cleavage by NEP.

scholarly journals Ingestion of coffee polyphenols increases postprandial release of the active glucagon-like peptide-1 (GLP-1(7–36)) amide in C57BL/6J mice

2015 ◽  
Vol 4 ◽  
Author(s):  
Yoshie Fujii ◽  
Noriko Osaki ◽  
Tadashi Hase ◽  
Akira Shimotoyodome
Keyword(s):  
Insulin Secretion ◽  
Human Subjects ◽  
Coffee Consumption ◽  
Epidemiological Studies ◽  
Diabetes Risk ◽  
Dependent Manner ◽  
Diabetes In Animals ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Dose Dependent

AbstractThe widespread prevalence of diabetes, caused by impaired insulin secretion and insulin resistance, is now a worldwide health problem. Glucagon-like peptide 1 (GLP-1) is a major intestinal hormone that stimulates glucose-induced insulin secretion from β cells. Prolonged activation of the GLP-1 signal has been shown to attenuate diabetes in animals and human subjects. Therefore, GLP-1 secretagogues are attractive targets for the treatment of diabetes. Recent epidemiological studies have reported that an increase in daily coffee consumption lowers diabetes risk. The present study examined the hypothesis that the reduction in diabetes risk associated with coffee consumption may be mediated by the stimulation of GLP-1 release by coffee polyphenol extract (CPE). GLP-1 secretion by human enteroendocrine NCI-H716 cells was augmented in a dose-dependent manner by the addition of CPE, and was compatible with the increase in observed active GLP-1(7–36) amide levels in the portal blood after administration with CPE alone in mice. CPE increased intracellular cyclic AMP (cAMP) levels in a dose-dependent manner, but this was not mediated by G protein-coupled receptor 119 (GPR119). The oral administration of CPE increased diet (starch and glyceryl trioleate)-induced active GLP-1 secretion and decreased glucose-dependent insulinotropic polypeptide release. Although CPE administration did not affect diet-induced insulin secretion, it decreased postprandial hyperglycaemia, which indicates that higher GLP-1 levels after the ingestion of CPE may improve insulin sensitivity. We conclude that dietary coffee polyphenols augment gut-derived active GLP-1 secretion via the cAMP-dependent pathway, which may contribute to the reduced risk of type 2 diabetes associated with daily coffee consumption.

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