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1
Bloodworth, Melissa Harintho, Jian Zhang, Anne L. Hotard, Martin L. Moore, Tina V. Hartert, Kevin D. Niswender, and R. Stokes Peebles. "Glucagon-like peptide-1 receptor signaling attenuates RSV-induced type 2 responses and immunopathology." Journal of Immunology 198, no. 1_Supplement (May 1, 2017): 153.5. http://dx.doi.org/10.4049/jimmunol.198.supp.153.5.
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Abstract Glucagon-like peptide-1 receptor (GLP-1R) agonists are a well-accepted and safe treatment for Type II diabetes. Although GLP-1R agonists mainly act to potentiate insulin and suppress glucagon secretion, recent evidence suggests that GLP-1R signaling also has anti-inflammatory effects. Severe RSV-associated illness is partially caused by type 2-associated immunopathology. We hypothesized that GLP-1R signaling inhibits type 2-mediated immunopathology during infection with RSV 12/12-6, a strain of RSV that was isolated from a hospitalized infant with severe lower respiratory tract infection and bronchiolitis. We show here that GLP-1R agonist treatment decreased airway inflammation, airway reactivity, and airway mucus production in RSV 12/12-6-infected mice. GLP-1R agonist treatment decreased total lung IL-13 and IL-33 levels, with concurrent decreases in lung IL-13-producing group 2 innate lymphoid cell (ILC2), CD4+ Th2 cell, and basophil numbers as well as IL-33-producing epithelial cells. The GLP-1R agonist prevented airway inflammation, and did not impact viral load, anti-viral interferon and antibody production during secondary RSV infection. Relative to the respective mock-infected groups, RSV-infected GLP-1R agonist treated mice did not have increased weight loss compared to vehicle treated mice. A phenome-wide association study (PheWAS) identified a link between GLP-1R signaling and acute bronchitis and bronchiolitis in humans. These studies demonstrate that GLP-1R signaling protects against type 2-mediated immunopathology during RSV infection. GLP-1R agonists are the first known FDA-approved agents to inhibit IL-33 and may represent a novel treatment strategy for RSV bronchiolitis.
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Viby, Niels-Erik, Marie S. Isidor, Katrine B. Buggeskov, Steen S. Poulsen, Jacob B. Hansen, and Hannelouise Kissow. "Glucagon-Like Peptide-1 (GLP-1) Reduces Mortality and Improves Lung Function in a Model of Experimental Obstructive Lung Disease in Female Mice." Endocrinology 154, no. 12 (December 1, 2013): 4503–11. http://dx.doi.org/10.1210/en.2013-1666.
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The incretin hormone glucagon-like peptide-1 (GLP-1) is an important insulin secretagogue and GLP-1 analogs are used for the treatment of type 2 diabetes. GLP-1 displays antiinflammatory and surfactant-releasing effects. Thus, we hypothesize that treatment with GLP-1 analogs will improve pulmonary function in a mouse model of obstructive lung disease. Female mice were sensitized with injected ovalbumin and treated with GLP-1 receptor (GLP-1R) agonists. Exacerbation was induced with inhalations of ovalbumin and lipopolysaccharide. Lung function was evaluated with a measurement of enhanced pause in a whole-body plethysmograph. mRNA levels of GLP-1R, surfactants (SFTPs), and a number of inflammatory markers were measured. GLP-1R was highly expressed in lung tissue. Mice treated with GLP-1R agonists had a noticeably better clinical appearance than the control group. Enhanced pause increased dramatically at day 17 in all control mice, but the increase was significantly less in the groups of GLP-1R agonist-treated mice (P < .001). Survival proportions were significantly increased in GLP-1R agonist-treated mice (P < .01). SFTPB and SFTPA were down-regulated and the expression of inflammatory cytokines were increased in mice with obstructive lung disease, but levels were largely unaffected by GLP-1R agonist treatment. These results show that GLP-1R agonists have potential therapeutic potential in the treatment of obstructive pulmonary diseases, such as chronic obstructive pulmonary disease, by decreasing the severity of acute exacerbations. The mechanism of action does not seem to be the modulation of inflammation and SFTP expression.
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Al-Zamel, Noura, Suleiman Al-Sabah, Yunus Luqmani, Lobna Adi, Siby Chacko, Tom Dario Schneider, and Cornelius Krasel. "A Dual GLP-1/GIP Receptor Agonist Does Not Antagonize Glucagon at Its Receptor but May Act as a Biased Agonist at the GLP-1 Receptor." International Journal of Molecular Sciences 20, no. 14 (July 19, 2019): 3532. http://dx.doi.org/10.3390/ijms20143532.
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Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are important regulators of metabolism, making their receptors (GLP-1R and GIPR) attractive targets in the treatment of type 2 diabetes mellitus (T2DM). GLP-1R agonists are used clinically to treat T2DM but the use of GIPR agonists remains controversial. Recent studies suggest that simultaneous activation of GLP-1R and GIPR with a single peptide provides superior glycemic control with fewer adverse effects than activation of GLP-1R alone. We investigated the signaling properties of a recently reported dual-incretin receptor agonist (P18). GLP-1R, GIPR, and the closely related glucagon receptor (GCGR) were expressed in HEK-293 cells. Activation of adenylate cyclase via Gαs was monitored using a luciferase-linked reporter gene (CRE-Luc) assay. Arrestin recruitment was monitored using a bioluminescence resonance energy transfer (BRET) assay. GLP-1, GIP, and glucagon displayed exquisite selectivity for their receptors in the CRE-Luc assay. P18 activated GLP-1R with similar potency to GLP-1 and GIPR with higher potency than GIP. Interestingly, P18 was less effective than GLP-1 at recruiting arrestin to GLP-1R and was inactive at GCGR. These data suggest that P18 can act as both a dual-incretin receptor agonist, and as a G protein-biased agonist at GLP-1R.
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McKay, Naomi J., Scott E. Kanoski, Matthew R. Hayes, and Derek Daniels. "Glucagon-like peptide-1 receptor agonists suppress water intake independent of effects on food intake." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 301, no. 6 (December 2011): R1755—R1764. http://dx.doi.org/10.1152/ajpregu.00472.2011.
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Glucagon-like peptide-1 (GLP-1) is produced by and released from the small intestine following ingestion of nutrients. GLP-1 receptor (GLP-1R) agonists applied peripherally or centrally decrease food intake and increase glucose-stimulated insulin secretion. These effects make the GLP-1 system an attractive target for the treatment of type 2 diabetes mellitus and obesity. In addition to these more frequently studied effects of GLP-1R stimulation, previous reports indicate that GLP-1R agonists suppress water intake. The present experiments were designed to provide greater temporal resolution and site specificity for the effect of GLP-1 and the long-acting GLP-1R agonists, exendin-4 and liraglutide, on unstimulated water intake when food was and was not available. All three GLP-1R ligands suppressed water intake after peripheral intraperitoneal administration, both in the presence of and the absence of food; however, the magnitude and time frame of water intake suppression varied by drug. GLP-1 had an immediate, but transient, hypodipsic effect when administered peripherally, whereas the water intake suppression by IP exendin-4 and liraglutide was much more persistent. Additionally, intracerebroventricular administration of GLP-1R agonists suppressed water intake when food was absent, but the suppression of intake showed modest differences depending on whether the drug was administered to the lateral or fourth ventricle. To the best of our knowledge, this is the first demonstration of GLP-1 receptor agonists affecting unstimulated, overnight intake in the absence of food, the first test for antidipsogenic effects of hindbrain application of GLP-1 receptor agonists, and the first test of a central effect (forebrain or hindbrain) of liraglutide on water intake. Overall, these results show that GLP-1R agonists have a hypodipsic effect that is independent of GLP-1R-mediated effects on food intake, and this occurs, in part, through central nervous system GLP-1R activation.
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Maida, Adriano, Julie A. Lovshin, Laurie L. Baggio, and Daniel J. Drucker. "The Glucagon-Like Peptide-1 Receptor Agonist Oxyntomodulin Enhances β-Cell Function but Does Not Inhibit Gastric Emptying in Mice." Endocrinology 149, no. 11 (July 31, 2008): 5670–78. http://dx.doi.org/10.1210/en.2008-0336.
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The proglucagon gene gives rise to multiple peptides that play diverse roles in the control of energy intake, gut motility, and nutrient disposal. Glucagon-like peptide-1 (GLP-1), a 30-amino-acid peptide regulates glucose homeostasis via control of insulin and glucagon secretion and by inhibition of gastric emptying and food intake. Oxyntomodulin (OXM) a 37-amino-acid peptide also derived from the proglucagon gene, binds to both the glucagon and GLP-1 receptor (GLP-1R); however, a separate OXM receptor has not yet been identified. Here we show that OXM, like other GLP-1R agonists, stimulates cAMP formation and lowers blood glucose after both oral and ip glucose administration, actions that require a functional GLP-1R. OXM also directly stimulates insulin secretion from murine islets and INS-1 cells in a glucose- and GLP-1R-dependent manner. Moreover, OXM ameliorates hyperglycemia and significantly reduces apoptosis in murine β-cells after streptozotocin administration and directly reduces apoptosis in thapsigargin-treated INS-1 cells. Unexpectedly, OXM, but not the GLP-1R agonist exendin-4, increased plasma levels of insulin after oral glucose administration. Moreover, OXM administered at doses that potently lower blood glucose had no effect on inhibition of gastric emptying but reduced food intake in WT mice. Taken together, these findings illustrate that although structurally distinct proglucagon-derived peptides such as GLP-1 and OXM engage the GLP-1R, OXM mimics some but not all of the actions of GLP-1R agonists in vivo. These findings may have implications for therapeutic efforts using OXM as a long-acting GLP-1R agonist for the treatment of metabolic disorders.
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Kanoski, Scott E., Samantha M. Fortin, Myrtha Arnold, Harvey J. Grill, and Matthew R. Hayes. "Peripheral and Central GLP-1 Receptor Populations Mediate the Anorectic Effects of Peripherally Administered GLP-1 Receptor Agonists, Liraglutide and Exendin-4." Endocrinology 152, no. 8 (June 21, 2011): 3103–12. http://dx.doi.org/10.1210/en.2011-0174.
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The long-acting glucagon-like peptide-1 receptor (GLP-1R) agonists, exendin-4 and liraglutide, suppress food intake and body weight. The mediating site(s) of action for the anorectic effects produced by peripheral administration of these GLP-1R agonists are not known. Experiments addressed whether food intake suppression after ip delivery of exendin-4 and liraglutide is mediated exclusively by peripheral GLP-1R or also involves direct central nervous system (CNS) GLP-1R activation. Results showed that CNS delivery [third intracerebroventricular (3rd ICV)] of the GLP-1R antagonist exendin-(9–39) (100 μg), attenuated the intake suppression by ip liraglutide (10 μg) and exendin-4 (3 μg), particularly at 6 h and 24 h. Control experiments show that these findings appear to be based neither on the GLP-1R antagonist acting as a nonspecific competing orexigenic signal nor on blockade of peripheral GLP-1R via efflux of exendin-(9–39) to the periphery. To assess the contribution of GLP-1R expressed on subdiaphragmatic vagal afferents to the anorectic effects of liraglutide and exendin-4, food intake was compared in rats with complete subdiaphragmatic vagal deafferentation and surgical controls after ip delivery of the agonists. Both liraglutide and exendin-4 suppressed food intake at 3 h, 6 h, and 24 h for controls; for subdiaphragmatic vagal deafferentation rats higher doses of the GLP-1R agonists were needed for significant food intake suppression, which was observed at 6 h and 24 h after liraglutide and at 24 h after exendin-4. Conclusion: Food intake suppression after peripheral administration of exendin-4 and liraglutide is mediated by activation of GLP-1R expressed on vagal afferents as well as direct CNS GLP-1R activation.
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Burcelin, Rémy, Pierre Gourdy, and Stéphane Dalle. "GLP-1-Based Strategies: A Physiological Analysis of Differential Mode of Action." Physiology 29, no. 2 (March 2014): 108–21. http://dx.doi.org/10.1152/physiol.00009.2013.
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DPP4 inhibitors and GLP-1 receptor agonists used in incretin-based strategies treat Type 2 diabetes with different modes of action. The pharmacological blood GLP-1R agonist concentration targets pancreatic and some extrapancreatic GLP-1R, whereas DPP4i favors the physiological activation of the gut-brain-periphery axis that could allow clinicians to adapt the management of Type 2 diabetes, according to the patient's pathophysiological characteristics.
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Malbert, Charles-Henri, Alain Chauvin, Michael Horowitz, and Karen L. Jones. "Pancreatic GLP-1r binding potential is reduced in insulin-resistant pigs." BMJ Open Diabetes Research & Care 8, no. 2 (November 2020): e001540. http://dx.doi.org/10.1136/bmjdrc-2020-001540.
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IntroductionThe insulinotropic capacity of exogenous glucagon like peptide-1 (GLP-1) is reduced in type 2 diabetes and the insulin-resistant obese. We have tested the hypothesis that this response is the consequence of a reduced pancreatic GLP-1 receptor (GLP-1r) density in insulin-resistant obese animals.Research design and methodsGLP-1r density was measured in lean and insulin-resistant adult miniature pigs after the administration of a 68Ga-labeled GLP-1r agonist. The effect of hyperinsulinemia on GLP-1r was assessed using sequential positron emission tomography (PET), both in the fasted state and during a clamp. The impact of tissue perfusion, which could account for changes in GLP-1r agonist uptake, was also investigated using 68Ga-DOTA imaging.ResultsGLP-1r binding potential in the obese pancreas was reduced by 75% compared with lean animals. Similar reductions were evident for fat tissue, but not for the duodenum. In the lean group, induced hyperinsulinemia reduced pancreatic GLP-1r density to a level comparable with that of the obese group. The reduction in blood to tissue transfer of the GLP-1r ligand paralleled that of tissue perfusion estimated using 68Ga-DOTA.ConclusionsThese observations establish that a reduction in abdominal tissue perfusion and a lower GLP-1r density account for the diminished insulinotropic effect of GLP-1 agonists in type 2 diabetes.
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Nahmias, Avital, Priska Stahel, Lili Tian, Changting Xiao, and Gary F. Lewis. "GLP-1 (Glucagon-Like Peptide-1) Is Physiologically Relevant for Chylomicron Secretion Beyond Its Known Pharmacological Role." Arteriosclerosis, Thrombosis, and Vascular Biology 41, no. 6 (June 2021): 1893–900. http://dx.doi.org/10.1161/atvbaha.121.316311.
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Objective: GLP-1R (glucagon-like peptide-1 receptor) agonists are increasingly used for the treatment of hyperglycemia in type 2 diabetes, with additional body weight reducing effects. Long-term administration of GLP-1R agonists has demonstrated cardioprotective effects, but the mechanism of cardiovascular protection is not currently known. Several studies in humans and animal models have shown suppression of intestinal CM (chylomicron) secretion and plasma TG (triglyceride) levels by pharmacological doses of GLP-1R agonists. The objective of this study was to assess the physiological role of endogenously secreted GLP-1 on CM secretion in rats. Approach and Results: Lymph flow, TG concentration, and TG output were assessed in mesenteric lymph duct-cannulated rats in response to an intraduodenal lipid bolus, preceded by an intraperitoneal injection of GLP-1R antagonist Ex (9–39; exendin 9–39) or vehicle. TG output was significantly enhanced in the presence of Ex (9–39) compared with vehicle over a 4-hour period post-lipid bolus ( P =0.007). Total lymph volume ( P =0.005) and TG mass ( P <0.0001) cumulatively collected by the end of the 4-hour period were significantly increased by GLP-1R antagonist. Conclusions: GLP-1R antagonism enhanced intestinal TG output in rats through stimulation of lymph flow and increased lymph TG concentration. Endogenously secreted GLP-1 after a lipid bolus is sufficient to modulate CM secretion in the rat, with GLP-1 physiologically restraining CM secretion through the GLP-1R. It remains to be determined whether the lipid lowering actions of GLP-1R agonists play a role in the cardiovascular protective effects of these therapeutic agents.
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Rode, Anna K. O., Terkild Brink Buus, Veronika Mraz, Fatima Abdul Hassan Al-Jaberi, Daniel Villalba Lopez, Shayne L. Ford, Stephanie Hennen, et al. "Induced Human Regulatory T Cells Express the Glucagon-like Peptide-1 Receptor." Cells 11, no. 16 (August 19, 2022): 2587. http://dx.doi.org/10.3390/cells11162587.
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The glucagon-like peptide-1 receptor (GLP-1R) plays a key role in metabolism and is an important therapeutic target in diabetes and obesity. Recent studies in experimental animals have shown that certain subsets of T cells express functional GLP-1R, indicating an immune regulatory role of GLP-1. In contrast, less is known about the expression and function of the GLP-1R in human T cells. Here, we provide evidence that activated human T cells express GLP-1R. The expressed GLP-1R was functional, as stimulation with a GLP-1R agonist triggered an increase in intracellular cAMP, which was abrogated by a GLP-1R antagonist. Analysis of CD4+ T cells activated under T helper (Th) 1, Th2, Th17 and regulatory T (Treg) cell differentiation conditions indicated that GLP-1R expression was most pronounced in induced Treg (iTreg) cells. Through multimodal single-cell CITE- and TCR-sequencing, we detected GLP-1R expression in 29–34% of the FoxP3+CD25+CD127- iTreg cells. GLP-1R+ cells showed no difference in their TCR-gene usage nor CDR3 lengths. Finally, we demonstrated the presence of GLP-1R+CD4+ T cells in skin from patients with allergic contact dermatitis. Taken together, the present data demonstrate that T cell activation triggers the expression of functional GLP-1R in human CD4+ T cells. Given the high induction of GLP-1R in human iTreg cells, we hypothesize that GLP-1R+ iTreg cells play a key role in the anti-inflammatory effects ascribed to GLP-1R agonists in humans.
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Chang, Rulue, Xin Zhang, Anna Qiao, Antao Dai, Matthew J. Belousoff, Qiuxiang Tan, Lijun Shao, et al. "Cryo-electron microscopy structure of the glucagon receptor with a dual-agonist peptide." Journal of Biological Chemistry 295, no. 28 (May 5, 2020): 9313–25. http://dx.doi.org/10.1074/jbc.ra120.013793.
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Unimolecular dual agonists of the glucagon (GCG) receptor (GCGR) and glucagon-like peptide-1 receptor (GLP-1R) are a new class of drugs that are potentially superior to GLP-1R–specific agonists for the management of metabolic disease. The dual-agonist, peptide 15 (P15), is a glutamic acid 16 analog of GCG with GLP-1 peptide substitutions between amino acids 17 and 24 that has potency equivalent to those of the cognate peptide agonists at the GCGR and GLP-1R. Here, we have used cryo-EM to solve the structure of an active P15-GCGR-Gs complex and compared this structure to our recently published structure of the GCGR-Gs complex bound to GCG. This comparison revealed that P15 has a reduced interaction with the first extracellular loop (ECL1) and the top of transmembrane segment 1 (TM1) such that there is increased mobility of the GCGR extracellular domain and at the C terminus of the peptide compared with the GCG-bound receptor. We also observed a distinct conformation of ECL3 and could infer increased mobility of the far N-terminal His-1 residue in the P15-bound structure. These regions of conformational variance in the two peptide-bound GCGR structures were also regions that were distinct between GCGR structures and previously published peptide-bound structures of the GLP-1R, suggesting that greater conformational dynamics may contribute to the increased efficacy of P15 in activation of the GLP-1R compared with GCG. The variable domains in this receptor have previously been implicated in biased agonism at the GLP-1R and could result in altered signaling of P15 at the GCGR compared with GCG.
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Morris, Lindsey C., Emily L. Days, Maxine Turney, Dehui Mi, Craig W. Lindsley, C. David Weaver, and Kevin D. Niswender. "A Duplexed High-Throughput Screen to Identify Allosteric Modulators of the Glucagon-Like Peptide 1 and Glucagon Receptors." Journal of Biomolecular Screening 19, no. 6 (February 13, 2014): 847–58. http://dx.doi.org/10.1177/1087057114520971.
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Injectable, degradation-resistant peptide agonists for the glucagon-like peptide 1 (GLP-1) receptor (GLP-1R), such as exenatide and liraglutide, activate the GLP-1R via a complex orthosteric-binding site and are effective therapeutics for glycemic control in type 2 diabetes. Orally bioavailable orthosteric small-molecule agonists are unlikely to be developed, whereas positive allosteric modulators (PAMs) may offer an improved therapeutic profile. We hypothesize that allosteric modulators of the GLP-1R would increase the potency and efficacy of native GLP-1 in a spatial and temporally preserved manner and/or may improve efficacy or side effects of injectable analogs. We report the design, optimization, and initial results of a duplexed high-throughput screen in which cell lines overexpressing either the GLP-1R or the glucagon receptor were coplated, loaded with a calcium-sensitive dye, and probed in a three-phase assay to identify agonists, antagonists, and potentiators of GLP-1, and potentiators of glucagon. 175,000 compounds were initially screened, and progression through secondary assays yielded 98 compounds with a variety of activities at the GLP-1R. Here, we describe five compounds possessing different patterns of modulation of the GLP-1R. These data uncover PAMs that may offer a drug-development pathway to enhancing in vivo efficacy of both endogenous GLP-1 and peptide analogs.
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Kawai, Takahiro, Bingfa Sun, Hitoshi Yoshino, Dan Feng, Yoshiyuki Suzuki, Masanori Fukazawa, Shunsuke Nagao, et al. "Structural basis for GLP-1 receptor activation by LY3502970, an orally active nonpeptide agonist." Proceedings of the National Academy of Sciences 117, no. 47 (November 11, 2020): 29959–67. http://dx.doi.org/10.1073/pnas.2014879117.
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Glucagon-like peptide-1 receptor (GLP-1R) agonists are efficacious antidiabetic medications that work by enhancing glucose-dependent insulin secretion and improving energy balance. Currently approved GLP-1R agonists are peptide based, and it has proven difficult to obtain small-molecule activators possessing optimal pharmaceutical properties. We report the discovery and mechanism of action of LY3502970 (OWL833), a nonpeptide GLP-1R agonist. LY3502970 is a partial agonist, biased toward G protein activation over β-arrestin recruitment at the GLP-1R. The molecule is highly potent and selective against other class B G protein–coupled receptors (GPCRs) with a pharmacokinetic profile favorable for oral administration. A high-resolution structure of LY3502970 in complex with active-state GLP-1R revealed a unique binding pocket in the upper helical bundle where the compound is bound by the extracellular domain (ECD), extracellular loop 2, and transmembrane helices 1, 2, 3, and 7. This mechanism creates a distinct receptor conformation that may explain the partial agonism and biased signaling of the compound. Further, interaction between LY3502970 and the primate-specific Trp33 of the ECD informs species selective activity for the molecule. In efficacy studies, oral administration of LY3502970 resulted in glucose lowering in humanized GLP-1R transgenic mice and insulinotropic and hypophagic effects in nonhuman primates, demonstrating an effect size in both models comparable to injectable exenatide. Together, this work determined the molecular basis for the activity of an oral agent being developed for the treatment of type 2 diabetes mellitus, offering insights into the activation of class B GPCRs by nonpeptide ligands.
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Yang, Fan, Xinshang Wang, Jingyu Qi, Kun Zhang, Yongli Jiang, Ban Feng, Tao Lv, et al. "Glucagon-like Peptide 1 Receptor Activation Inhibits Microglial Pyroptosis via Promoting Mitophagy to Alleviate Depression-like Behaviors in Diabetic Mice." Nutrients 15, no. 1 (December 21, 2022): 38. http://dx.doi.org/10.3390/nu15010038.
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Depression is a frequent and serious comorbidity associated with diabetes which adversely affects prognosis and quality of life. Glucagon-like peptide-1 receptor (GLP-1R) agonists, widely used in the treatment of diabetes, are reported to exert neuroprotective effects in the central nervous system. Thus, we aim to evaluate whether GLP-1R agonist exendin-4 (EX-4) could alleviate depression-like behaviors in diabetic mice and to explore its underlying mechanism. The antidepressant effects of EX-4 were evaluated using behavioral tests in db/db mice. The effects of EX-4 on microglial pyroptosis and neuroinflammation were assessed in N9 microglial cells. EX-4 administration alleviated depression-like behaviors in diabetic db/db mice. GLP-1R activation by EX-4 significantly suppressed microglial pyroptosis and neuroinflammation by downregulation of gasdermin D (GSDMD) and interleukin (IL)-1β in diabetic mice and lipopolysaccharide (LPS)-primed N9 microglia. Mechanistically, GLP-1R activation improved mitochondrial function and promoted mitophagy by decreasing the accumulation of mitochondrial reactive oxygen species (mtROS) and intracellular ROS production. EX-4 exhibits antidepressant effects in depression associated with diabetes in diabetic mice, which may be mediated by inhibiting microglial pyroptisis via promoting mitophagy. It is supposed that GLP-1R agonists may be a promising therapy in depression associated with diabetes.
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Quarta, Carmelo, Kerstin Stemmer, Aaron Novikoff, Bin Yang, Felix Klingelhuber, Alex Harger, Mostafa Bakhti, et al. "GLP-1-mediated delivery of tesaglitazar improves obesity and glucose metabolism in male mice." Nature Metabolism 4, no. 8 (August 22, 2022): 1071–83. http://dx.doi.org/10.1038/s42255-022-00617-6.
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AbstractDual agonists activating the peroxisome proliferator-activated receptors alpha and gamma (PPARɑ/ɣ) have beneficial effects on glucose and lipid metabolism in patients with type 2 diabetes, but their development was discontinued due to potential adverse effects. Here we report the design and preclinical evaluation of a molecule that covalently links the PPARɑ/ɣ dual-agonist tesaglitazar to a GLP-1 receptor agonist (GLP-1RA) to allow for GLP-1R-dependent cellular delivery of tesaglitazar. GLP-1RA/tesaglitazar does not differ from the pharmacokinetically matched GLP-1RA in GLP-1R signalling, but shows GLP-1R-dependent PPARɣ-retinoic acid receptor heterodimerization and enhanced improvements of body weight, food intake and glucose metabolism relative to the GLP-1RA or tesaglitazar alone in obese male mice. The conjugate fails to affect body weight and glucose metabolism in GLP-1R knockout mice and shows preserved effects in obese mice at subthreshold doses for the GLP-1RA and tesaglitazar. Liquid chromatography–mass spectrometry-based proteomics identified PPAR regulated proteins in the hypothalamus that are acutely upregulated by GLP-1RA/tesaglitazar. Our data show that GLP-1RA/tesaglitazar improves glucose control with superior efficacy to the GLP-1RA or tesaglitazar alone and suggest that this conjugate might hold therapeutic value to acutely treat hyperglycaemia and insulin resistance.
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Zhong, Xia, Zhu Chen, Qiong Chen, Wei Zhao, and Zhi Chen. "Novel Site-Specific Fatty Chain-Modified GLP-1 Receptor Agonist with Potent Antidiabetic Effects." Molecules 24, no. 4 (February 21, 2019): 779. http://dx.doi.org/10.3390/molecules24040779.
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Glucagon-like peptide-1 receptor (GLP-1R) agonists have emerged as treatment options for type 2 diabetes mellitus (T2DM). Here, we designed a high-throughput GLP-1R extracellular domain (ECD)-based system that enabled the screening of high-potency receptor-biased GLP-1R agonists demonstrating new pharmacological virtues. Firstly, six 12-mer peptides (termed PEP01–06), screened from a large phage displayed peptide library were fused to the N-terminus of Exendin-4 (29–39) to generate PEP07–12. By the use of four lysine-altered PEP07 (PEP13–16) as the starting point, a series of fatty chain conjugates (PEP17–20) were synthesized and evaluated by in vitro GLP-1R-based cell assays. In addition, the acute and long-term in vivo effects on diet-induced obesity (DIO) mice were further evaluated. All four conjugates showed good receptor activation efficacy, and PEP20 was selected to undergo further assessment. Preclinical experiments in DIO mice demonstrated that PEP20 had significant insulinotropic activities and glucose-lowering abilities. Moreover, a prolonged antidiabetic effect of PEP20 was also observed by the hypoglycemic test in DIO mice. Furthermore, long-term treatment with PEP20 achieved beneficial effects on the food intake, weight gain, hemoglobin A1C (HbA1C) lowering activity, and glucose tolerance compared with the control and was similar to the Liraglutide. In conclusion, PEP20, a GLP-1R ECD-biased agonist, may provide a novel therapeutic approach to T2DM.
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Madsen, Lars Wichmann, Jeffrey A. Knauf, Carsten Gotfredsen, Andrew Pilling, Ingrid Sjögren, Søren Andersen, Lene Andersen, et al. "GLP-1 Receptor Agonists and the Thyroid: C-Cell Effects in Mice Are Mediated via the GLP-1 Receptor and not Associated with RET Activation." Endocrinology 153, no. 3 (March 1, 2012): 1538–47. http://dx.doi.org/10.1210/en.2011-1864.
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Liraglutide and exenatide are glucagon-like peptide receptor (GLP-1R) agonists used in the treatment of type 2 diabetes. Both molecules have been associated with the development of thyroid C-cell tumors after lifetime exposure in rodents. Previously, it has been reported that these tumors are preceded by increased plasma calcitonin and C-cell hyperplasia. We can now document that the murine C-cell effects are mediated via GLP-1R. Thus, 13 wk of continuous exposure to GLP-1R agonists was associated with marked increases in plasma calcitonin and in the incidence of C-cell hyperplasia in wild-type mice. In contrast, similar effects were not seen in GLP-1R knockout mice. Human C-cell cancer is often caused by activating mutations in the rearranged-during-transfection (RET) protooncogene. We developed an immunohistochemical method to assess RET activation in tissues. Liraglutide dosing to mice was not found to activate RET. Further evaluation of the signaling pathways demonstrated that liraglutide increased ribosomal S6, but not MAPK kinase, phosphorylation. These observations are consistent with effects of GLP-1R agonists on rodent C cells being mediated via mammalian target of rapamycin activation in a RET- and MAPK-independent manner.
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Vikulova, O. K., Z. T. Zuraeva, O. V. Michaleva, L. V. Nikankina, M. Sh Shamkhalova, M. V. Shestakova, and I. I. Dedov. "Renal effects of glucagon-like peptide receptor agonists in patients with type 1 diabetes mellitus." Terapevticheskii arkhiv 90, no. 6 (June 15, 2018): 59–64. http://dx.doi.org/10.26442/terarkh201890659-64.
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The purpose of our study is to assess the effects of glucagon-like peptide-1 receptor agonists (GLP-1R agonists) on early markers of kidney damage in patients with type 1 diabetes mellitus (DM). Materials and methods. The study included 27 patients with type 1 diabetes with normo- (n=16) and microalbuminuria (n=11) on intensive insulin injection regimen with insulin analogs. Patients were divided into two groups: 15 patients continued insulin therapy throughout the follow-up period, 12 patients were given 1.2 mg GLP-1R agonist (Liraglutide) once a day in addition to the insulin therapy for 6 months. HbA1c, lipid profile, classic markers of kidney damage (albuminuria, creatinine, glomerular filtration rate); plazma (neutrophilic gelatinase-associated lipoxalin - NGAL, molecule renal damage of type 1 - KIM-1, cystatin C, osteopontin) and urinary kidney biomarkers (nephrin, podocyne, uromodulin, NGAL, KIM-1, collagen type IV, cystatin C) were evaluated prior and in dynamics at 6 months. Kidney biomarkers levels were assessed by the enzyme-linked immunosorbent assay (ELISA). Results. We observed a significant decrease in the urinary excretion of type IV collagen, cystatin C, increased uromodulin excretion and decrease in the plasma levels of osteopontin, NGAL and cystatin C in the group of combined insulin and GLP-1R agonist therapy. Conclusions. Changes in the level of sensitive kidney biomarkers indicate a possible renoprotective effect of GLP-1R agonist therapy in patients with type 1 diabetes at an early stages of kidney damage.
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Liao, Hui-Jun, and Jason T. C. Tzen. "Investigating Potential GLP-1 Receptor Agonists in Cyclopeptides from Pseudostellaria heterophylla, Linum usitatissimum, and Drymaria diandra, and Peptides Derived from Heterophyllin B for the Treatment of Type 2 Diabetes: An In Silico Study." Metabolites 12, no. 6 (June 15, 2022): 549. http://dx.doi.org/10.3390/metabo12060549.
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GLP-1 receptor agonists stimulate GLP-1R to promote insulin secretion, whereas DPP4 inhibitors slow GLP-1 degradation. Both approaches are incretin-based therapies for T2D. In addition to GLP-1 analogs, small nonpeptide GLP-1RAs such as LY3502970, TT-OAD2, and PF-06882961 have been considered as possible therapeutic alternatives. Pseudostellaria heterophylla, Linum usitatissimum, and Drymaria diandra are plants rich in cyclopeptides with hypoglycemic effects. Our previous study demonstrated the potential of their cyclopeptides for DPP4 inhibition. Reports of cyclic setmelanotide as an MC4R (GPCR) agonist and cyclic α-conotoxin chimeras as GLP-1RAs led to docking studies of these cyclopeptides with GLP-1R. Heterophyllin B, Pseudostellarin B, Cyclolinopeptide B, Cyclolinopeptide C, Drymarin A, and Diandrine C are abundant in these plants, with binding affinities of −9.5, −10.4, −10.3, −10.6, −11.2, and −11.9 kcal/mol, respectively. The configuration they demonstrated established multiple hydrogen bonds with the transmembrane region of GLP-1R. DdC:(cyclo)-GGPYWP showed the most promising docking score. The results suggest that, in addition to DPP4, GLP-1R may be a hypoglycemic target of these cyclopeptides. This may bring about more discussion of plant cyclopeptides as GLP-1RAs. Moreover, peptides derived from the HB precursor (IFGGLPPP), including IFGGWPPP, IFPGWPPP, IFGGYWPPP, and IFGYGWPPPP, exhibited diverse interactions with GLP-1R and displayed backbones available for further research.
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Mietlicki-Baase, Elizabeth G., Pavel I. Ortinski, Laura E. Rupprecht, Diana R. Olivos, Amber L. Alhadeff, R. Christopher Pierce, and Matthew R. Hayes. "The food intake-suppressive effects of glucagon-like peptide-1 receptor signaling in the ventral tegmental area are mediated by AMPA/kainate receptors." American Journal of Physiology-Endocrinology and Metabolism 305, no. 11 (December 1, 2013): E1367—E1374. http://dx.doi.org/10.1152/ajpendo.00413.2013.
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Glucagon-like peptide-1 receptor (GLP-1R) activation in the ventral tegmental area (VTA) is physiologically relevant for the control of palatable food intake. Here, we tested whether the food intake-suppressive effects of VTA GLP-1R activation are mediated by glutamatergic signaling within the VTA. Intra-VTA injections of the GLP-1R agonist exendin-4 (Ex-4) reduced palatable high-fat food intake in rats primarily by reducing meal size; these effects were mediated in part via glutamatergic AMPA/kainate but not NMDA receptor signaling. Additional behavioral data indicated that GLP-1R expressed specifically within the VTA can partially mediate the intake- and body weight-suppressive effects of systemically administered Ex-4, offering the intriguing possibility that this receptor population may be clinically relevant for food intake control. Intra-VTA Ex-4 rapidly increased tyrosine hydroxylase levels within the VTA, suggesting that GLP-1R activation modulates VTA dopaminergic signaling. Further evidence for this hypothesis was provided by electrophysiological data showing that Ex-4 increased the frequency of AMPA-mediated currents and reduced the paired/pulse ratio in VTA dopamine neurons. Together, these data provide novel mechanisms by which GLP-1R agonists in the mesolimbic reward system control for palatable food intake.
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Sun, Lei, Zhi-Ming Zheng, Chang-Sheng Shao, Zhi-Yong Zhang, Ming-Wei Li, Li Wang, Han Wang, Gen-Hai Zhao, and Peng Wang. "Rational Design by Structural Biology of Industrializable, Long-Acting Antihyperglycemic GLP-1 Receptor Agonists." Pharmaceuticals 15, no. 6 (June 13, 2022): 740. http://dx.doi.org/10.3390/ph15060740.
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Glucagon-like peptide-1 (GLP-1) is easily degraded by dipeptidyl peptidase-4 (DPP-4) in the human body, limiting its therapeutic effect on type II diabetes. Therefore, improving GLP-1 receptor agonist (GLP-1RA) stability is a major obstacle for drug development. We analyzed human GLP-1, DPP-4, and GLP-1 receptor structures and designed three GLP-1RAs, which were introduced into fusion protein fragments and changed in the overall conformation. This modification effectively prevented GLP-1RAs from entering the DPP-4 active center without affecting GLP-1RAs’ ability to bind to GLP-1R, the new GLP-1RA hypoglycemic effect lasting for >24 h. Through molecular modeling, molecular dynamics calculation, and simulation, possible tertiary structure models of GLP-1RAs were obtained; molecular docking with DPP-4 and GLP-1R showed access to the fusion protein. The overall conformational change of GLP-1RAs prevented DPP-4 binding, without affecting GLP-1RAs’ affinity to GLP-1R. This study provides important drug design ideas for GLP-1RA development and a new example for application of structural biology-based protein design in drug development.
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Le, Thao D. V., Dianxin Liu, Sheila Collins, and Julio E. Ayala. "The Glucagon-Like Peptide 1 Receptor Agonist Liraglutide Stimulates Mechanistic Target of Rapamycin (mTOR) Signaling via PKA And Akt." Journal of the Endocrine Society 5, Supplement_1 (May 1, 2021): A510—A511. http://dx.doi.org/10.1210/jendso/bvab048.1044.
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Abstract Glucagon-like peptide 1 receptor (GLP-1R) agonists enhance glucose-stimulated insulin secretion and act on several regions of the brain to reduce food intake and body weight, making the GLP-1R a major therapeutic target for the treatment of type 2 diabetes and obesity. Surprisingly, little is known about the signaling mechanisms mediating the food intake-lowering effects of GLP-1R agonists. We have previously shown that inhibiting the mechanistic Target of Rapamycin (mTOR) in the ventromedial hypothalamus blocks anorexia induced by GLP-1R activation in this brain nucleus (1). Therefore, the goal of the present studies is to elucidate the mechanisms by which GLP-1R activation stimulates mTOR signaling. To accomplish this, we treated Chinese Hamster Ovary cells stably expressing the human GLP-1R with the GLP-1R agonist liraglutide (Lira) in combination with inhibitors of various signaling molecules. Since PKA is a canonical target of GLP-1R signaling, and PKA phosphorylates mTOR and its regulating protein Raptor following β-adrenergic stimulation (2), we used the PKA inhibitors H89 and KT 5720 to examine whether PKA is required for the stimulation of mTOR activity by Lira. We expressed myc-tagged mTOR or Raptor in GLP-1R stably expressing CHO cells, treated them with Lira, immunoprecipitated myc-mTOR or myc-Raptor, and immunoblotted for the PKA substrate RRXS/T motif. We found that Lira significantly increased PKA-substrate motif phosphorylation of myc-Raptor but not myc-mTOR, and this was blocked by pre-treatment with H89. Lira also failed to stimulate phosphorylation of a Ser791Ala Raptor mutant that cannot be phosphorylated by PKA (2). To test whether Akt, a well-known regulator of mTOR activity, contributes to the activation of mTOR signaling by Lira, we pre-treated GLP-1R stably expressing CHO cells with either of the Akt inhibitors Akt-i 1/2 and MK-2206 followed by treatment with Lira or forskolin (Fsk), a cAMP inducer and PKA activator. Pre-treatment with either Akt-i 1/2 or MK-2206 blocked mTOR activation by both Lira and Fsk. This suggests that the contribution of Akt to Lira-induced mTOR activation is likely downstream of cAMP production. Taken together, our results suggest a novel two-pronged, PKA-dependent mechanism for the stimulation of mTOR signaling following GLP-1R activation – directly via phosphorylation of Raptor and indirectly via stimulation of Akt. Future studies will assess the respective contributions and temporal dynamics of each of these pathways. Reference: (1) Burmeister et al., Am J Physiol Endocrinol Metab. 2017 Aug;313: E651–E662. (2) Liu et al., J Clin Invest. 2016;126(5):1704-1716.
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Kim, Dong Seok, Ho-Il Choi, Yun Wang, Yu Luo, Barry J. Hoffer, and Nigel H. Greig. "A New Treatment Strategy for Parkinson's Disease through the Gut–Brain Axis." Cell Transplantation 26, no. 9 (September 2017): 1560–71. http://dx.doi.org/10.1177/0963689717721234.
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Molecular communications in the gut–brain axis, between the central nervous system and the gastrointestinal tract, are critical for maintaining healthy brain function, particularly in aging. Epidemiological analyses indicate type 2 diabetes mellitus (T2DM) is a risk factor for neurodegenerative disorders including Alzheimer's disease (AD) and Parkinson's diseases (PD) for which aging shows a major correlative association. Common pathophysiological features exist between T2DM, AD, and PD, including oxidative stress, inflammation, insulin resistance, abnormal protein processing, and cognitive decline, and suggest that effective drugs for T2DM that positively impact the gut–brain axis could provide an effective treatment option for neurodegenerative diseases. Glucagon-like peptide-1 (GLP-1)-based antidiabetic drugs have drawn particular attention as an effectual new strategy to not only regulate blood glucose but also decrease body weight by reducing appetite, which implies that GLP-1 could affect the gut–brain axis in normal and pathological conditions. The neurotrophic and neuroprotective effects of GLP-1 receptor (R) stimulation have been characterized in numerous in vitro and in vivo preclinical studies using GLP-1R agonists and dipeptidyl peptidase-4 inhibitors. Recently, the first open label clinical study of exenatide, a long-acting GLP-1 agonist, in the treatment of PD showed long-lasting improvements in motor and cognitive function. Several double-blind clinical trials of GLP-1R agonists including exenatide in PD and other neurodegenerative diseases are already underway or are about to be initiated. Herein, we review the physiological role of the GLP-1R pathway in the gut–brain axis and the therapeutic strategy of GLP-1R stimulation for the treatment of neurodegenerative diseases focused on PD, for which age is the major risk factor.
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Hou, Yanan, Stephen A. Ernst, Kaeli Heidenreich, and John A. Williams. "Glucagon-like peptide-1 receptor is present in pancreatic acinar cells and regulates amylase secretion through cAMP." American Journal of Physiology-Gastrointestinal and Liver Physiology 310, no. 1 (January 1, 2016): G26—G33. http://dx.doi.org/10.1152/ajpgi.00293.2015.
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Glucagon-like peptide-1 (GLP-1) is a glucoincretin hormone that can act through its receptor (GLP-1R) on pancreatic β-cells and increase insulin secretion and production. GLP-1R agonists are used clinically to treat type 2 diabetes. GLP-1 may also regulate the exocrine pancreas at multiple levels, including inhibition through the central nervous system, stimulation indirectly through insulin, and stimulation directly on acinar cells. However, it has been unclear whether GLP-1R is present in pancreatic acini and what physiological functions these receptors regulate. In the current study we utilized GLP-1R knockout (KO) mice to study the role of GLP-1R in acinar cells. RNA expression of GLP-1R was detected in acutely isolated pancreatic acini. Acinar cell morphology and expression of digestive enzymes were not affected by loss of GLP-1R. GLP-1 induced amylase secretion in wild-type (WT) acini. In GLP-1R KO mice, this effect was abolished, whereas vasoactive intestinal peptide-induced amylase release in KO acini showed a pattern similar to that in WT acini. GLP-1 stimulated cAMP production and increased protein kinase A-mediated protein phosphorylation in WT acini, and these effects were absent in KO acini. These data show that GLP-1R is present in pancreatic acinar cells and that GLP-1 can regulate secretion through its receptor and cAMP signaling pathway.
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Sang, Peng, Zhihong Zhou, Yan Shi, Candy Lee, Zaid Amso, David Huang, Timothy Odom, Vân T. B. Nguyen-Tran, Weijun Shen, and Jianfeng Cai. "The activity of sulfono-γ-AApeptide helical foldamers that mimic GLP-1." Science Advances 6, no. 20 (May 2020): eaaz4988. http://dx.doi.org/10.1126/sciadv.aaz4988.
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Existing long α-helix mimicking necessitates the retention of most natural amino acid residues to maintain their biological activity. Here, we report the exploration of helical sulfono-γ-AApeptides with entire unnatural backbones for their ability to structurally and functionally mimic glucagon-like peptide 1 (GLP-1). Our findings suggest that efficient construction of novel GLP-1 receptor (GLP-1R) agonists could be achieved with nanomolar potencies. In addition, the resulting sulfono-γ-AApeptides were also proved to display remarkable stability against enzymatic degradation compared to GLP-1, augmenting their biological potential. This alternative strategy of α-helix mimicking, as a proof of concept, could provide a new paradigm to prepare GLP-1R agonists.
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Burmeister, Melissa A., Jacob D. Brown, Jennifer E. Ayala, Doris A. Stoffers, Darleen A. Sandoval, Randy J. Seeley, and Julio E. Ayala. "The glucagon-like peptide-1 receptor in the ventromedial hypothalamus reduces short-term food intake in male mice by regulating nutrient sensor activity." American Journal of Physiology-Endocrinology and Metabolism 313, no. 6 (December 1, 2017): E651—E662. http://dx.doi.org/10.1152/ajpendo.00113.2017.
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Pharmacological activation of the glucagon-like peptide-1 receptor (GLP-1R) in the ventromedial hypothalamus (VMH) reduces food intake. Here, we assessed whether suppression of food intake by GLP-1R agonists (GLP-1RA) in this region is dependent on AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR). We found that pharmacological inhibition of glycolysis, and thus activation of AMPK, in the VMH attenuates the anorectic effect of the GLP-1R agonist exendin-4 (Ex4), indicating that glucose metabolism and inhibition of AMPK are both required for this effect. Furthermore, we found that Ex4-mediated anorexia in the VMH involved mTOR but not acetyl-CoA carboxylase, two downstream targets of AMPK. We support this by showing that Ex4 activates mTOR signaling in the VMH and Chinese hamster ovary (CHO)-K1 cells. In contrast to the clear acute pharmacological impact of the these receptors on food intake, knockdown of the VMH Glp1r conferred no changes in energy balance in either chow- or high-fat-diet-fed mice, and the acute anorectic and glucose tolerance effects of peripherally dosed GLP-1RA were preserved. These results show that the VMH GLP-1R regulates food intake by engaging key nutrient sensors but is dispensable for the effects of GLP-1RA on nutrient homeostasis.
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Martins, Flavia L., Matthew A. Bailey, and Adriana C. C. Girardi. "Endogenous Activation of Glucagon-Like Peptide-1 Receptor Contributes to Blood Pressure Control." Hypertension 76, no. 3 (September 2020): 839–48. http://dx.doi.org/10.1161/hypertensionaha.120.14868.
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The pharmacological administration of GLP-1R (glucagon-like peptide-1 receptor) agonists reduces blood pressure (BP) in type 2 diabetes mellitus and nondiabetic patients. This study tested the hypothesis that endogenous GLP-1R signaling influences the regulation of BP. To this end, SHRs (spontaneously hypertensive rats) and Wistar rats were treated with the GLP-1R antagonist Ex9 (exendin-9) or vehicle for 4 weeks. Rats receiving the GLP-1R agonist Ex4 (exenatide) were used as an additional control. We found that blockade of baseline GLP-1R signaling by Ex9 increased systolic BP in both SHR and Wistar rats, compared with vehicle-treated animals, while Ex4 only reduced systolic BP in SHR. Higher systolic BP induced by Ex9 was accompanied by reduced lithium clearance and lower levels of NHE3 (Na + /H + exchanger isoform 3) phosphorylation at the serine 552, indicative of increased proximal tubule sodium reabsorption. Additionally, urinary AGT (angiotensinogen) and renal cortical concentration of Ang II (angiotensin II) were enhanced by Ex9. Conversely, Ex4 decreased both urinary AGT and cortical Ang II but exclusively in SHRs. Moreover, both SHR and Wistar rats treated with Ex9 displayed hyperinsulinemia as compared with vehicle-treated rats, whereas Ex4 reduced fasting insulin concentration in SHR. Collectively, these results suggest that endogenous GLP-1R signaling exerts a physiologically relevant effect on BP control, which may be attributable, in part, to its tonic actions on the proximal tubule NHE3-mediated sodium reabsorption, intrarenal renin-angiotensin system, and insulin sensitivity. The possible role of impaired GLP-1R signaling in the pathogenesis of hypertension warrants further investigation.
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Yusta, Bernardo, Laurie L. Baggio, Jacqueline Koehler, Dianne Holland, Xiemin Cao, Lee J. Pinnell, Kathene C. Johnson-Henry, et al. "GLP-1R Agonists Modulate Enteric Immune Responses Through the Intestinal Intraepithelial Lymphocyte GLP-1R." Diabetes 64, no. 7 (March 3, 2015): 2537–49. http://dx.doi.org/10.2337/db14-1577.
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Naylor, Jacqueline, Arthur T. Suckow, Asha Seth, David J. Baker, Isabelle Sermadiras, Peter Ravn, Rob Howes, et al. "Use of CRISPR/Cas9-engineered INS-1 pancreatic β cells to define the pharmacology of dual GIPR/GLP-1R agonists." Biochemical Journal 473, no. 18 (September 12, 2016): 2881–91. http://dx.doi.org/10.1042/bcj20160476.
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Dual-agonist molecules combining glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) activity represent an exciting therapeutic strategy for diabetes treatment. Although challenging due to shared downstream signalling pathways, determining the relative activity of dual agonists at each receptor is essential when developing potential novel therapeutics. The challenge is exacerbated in physiologically relevant cell systems expressing both receptors. To this end, either GIP receptors (GIPR) or GLP-1 receptors (GLP-1R) were ablated via RNA-guided clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 endonucleases in the INS-1 pancreatic β-cell line. Multiple clonal cell lines harbouring gene disruptions for each receptor were isolated and assayed for receptor activity to identify functional knockouts (KOs). cAMP production in response to GIPR or GLP-1R activation was abolished and GIP- or GLP-1-induced potentiation of glucose-stimulated insulin secretion (GSIS) was attenuated in the cognate KO cell lines. The contributions of individual receptors derived from cAMP and GSIS assays were confirmed in vivo using GLP-1R KO mice in combination with a monoclonal antibody antagonist of GIPR. We have successfully applied CRISPR/Cas9-engineered cell lines to determining selectivity and relative potency contributions of dual-agonist molecules targeting receptors with overlapping native expression profiles and downstream signalling pathways. Specifically, we have characterised molecules as biased towards GIPR or GLP-1R, or with relatively balanced potency in a physiologically relevant β-cell system. This demonstrates the broad utility of CRISPR/Cas9 when applied to native expression systems for the development of drugs that target multiple receptors, particularly where the balance of receptor activity is critical.
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Trevaskis, James L., Peter S. Griffin, Carrie Wittmer, Brent A. Neuschwander-Tetri, Elizabeth M. Brunt, Carrie S. Dolman, Mary R. Erickson, James Napora, David G. Parkes, and Jonathan D. Roth. "Glucagon-like peptide-1 receptor agonism improves metabolic, biochemical, and histopathological indices of nonalcoholic steatohepatitis in mice." American Journal of Physiology-Gastrointestinal and Liver Physiology 302, no. 8 (April 15, 2012): G762—G772. http://dx.doi.org/10.1152/ajpgi.00476.2011.
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These preclinical studies aimed to 1) increase our understanding the dietary induction of nonalcoholic steatohepatitis (NASH), and, 2) further explore the utility and mechanisms of glucagon-like peptide-1 receptor (GLP-1R) agonism in NASH. We compared the effects of a high trans-fat (HTF) or high lard fat (HLF) diet on key facets of nonalcoholic fatty liver disease (NAFLD)/NASH in Lep ob /Lep ob and C57BL6J (B6) mice. Although HLF-fed mice experienced overall greater gains in weight and adiposity, the addition of trans-fat better mirrored pathophysiological features of NASH (e.g., hepatomegaly, hepatic lipid, and fibrosis). Administration of AC3174, an exenatide analog, and GLP-1R agonist to Lep ob /Lep ob and B6 ameliorated hepatic endpoints in both dietary models. Next, we assessed whether AC3174-mediated improvements in diet-induced NASH were solely due to weight loss in HTF-fed mice. AC3174-treatment significantly reduced body weight (8.3%), liver mass (14.2%), liver lipid (12.9%), plasma alanine aminotransferase, and triglycerides, whereas a calorie-restricted, weight-matched group demonstrated only modest nonsignificant reductions in liver mass (9%) and liver lipid (5.1%) relative to controls. Treatment of GLP-1R-deficient (GLP-1RKO) mice with AC3174 had no effect on body weight, adiposity, liver or plasma indices pointing to the GLP-1R-dependence of AC3174's effects. Interestingly, the role of endogenous GLP-1Rs in NASH merits further exploration as the GLP-1RKO model was protected from the deleterious hepatic effects of HTF. Our pharmacological data further support the clinical evaluation of the utility of GLP-1R agonists for treatment of NASH.
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Shaghouli, Amna Ali, Razan Ballani, and Naglaa Mesbah. "Management of Late Dumping Syndrome Induced Hypoglycemia With GLP-1R Agonist." Journal of the Endocrine Society 5, Supplement_1 (May 1, 2021): A416. http://dx.doi.org/10.1210/jendso/bvab048.849.
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Abstract Background: Late dumping syndrome is a prominent post-bariatric surgery side effect. Glucose-dependenthyperinsulinemia, induced by elevated gastric inhibitory polypeptide (GIP) and glucagon-likepeptide-1 (GLP-1) levels, leading to 2–3 hours post-prandial hypoglycemia. In literature, several managements are available: dietary changes, glucosidase inhibitor, andsomatostatin analogues. In case of failure of those strategies, partial or total pancreatectomy isindicated. Recently, management using GLP-1R agonists showed promising effect inmanagement of late dumping syndrome induced post-prandial hypoglycemia. (1)AimThe aim of this study was to investigate the effect of using GLP-1R agonists w/o low glycemicindex diet for treating dumping syndromes induced post-prandial hypoglycemia in post bariatricsurgery patients. Methods: A sample of 27 cases (25 females, 2 males) mean age 44.64, SD 10.2 of post-bariatric surgerywere managed using GLP-1R w/o low-glycemic index diet after being diagnosed with the latedumping syndrome induced post-prandial hypoglycemia for duration 1–3 years post-surgery. The27 were sent a survey of 13 questions related to their experience pre-and post-management plan. Results: Out of the 27 patients, 15 responded to the survey. The results showed 100% of the participantsdeveloped episodes of severe symptomatic late dumping syndrome with hypoglycemiasymptoms diagnosed after one and half years of their symptoms. 87% of them experiencedhypoglycemia post meals 2–3 hours.70 % of the participants got hypoglycemia more than 5episodes per week (less than 4.0 mmol/l) which was confirmed by blood glucose monitoring. After starting treatment with GLP-1R agonists with or without low-glycemic index diet, 87% ofthe participants reported that the hypoglycemia episodes were reduced. Out of those 87%participants 46% did not get any hypoglycemia episode and 54% of them experienced 1–2 timeshypoglycemia episodes. Conclusion: The results of the survey showed the successful reduction or prevention of late dumpinghypoglycemia episodes frequency post-bariatric surgery by GLP 1R agonist with or without lowglycemicindex diet. References: Non, A.N.H.W.H. and Black, H., 2012. Scope of the Problem. Am J Prev Med, 42, pp.563–70.Chiappetta, S. and Stier, C., 2017. A case report: Liraglutide as a novel treatment option in late dumping syndrome. Medicine, 96(12).
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Diz-Chaves, Yolanda, Manuel Gil-Lozano, Laura Toba, Juan Fandiño, Hugo Ogando, Lucas C. González-Matías, and Federico Mallo. "Stressing diabetes? The hidden links between insulinotropic peptides and the HPA axis." Journal of Endocrinology 230, no. 2 (August 2016): R77—R94. http://dx.doi.org/10.1530/joe-16-0118.
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Diabetes mellitus exerts metabolic stress on cells and it provokes a chronic increase in the long-term activity of the hypothalamus–pituitary–adrenocortical (HPA) axis, perhaps thereby contributing to insulin resistance. GLP-1 receptor (GLP-1R) agonists are pleiotropic hormones that not only affect glycaemic and metabolic control, but they also produce many other effects including activation of the HPA axis. In fact, several of the most relevant effects of GLP-1 might involve, at least in part, the modulation of the HPA axis. Thus, the anorectic activity of GLP-1 could be mediated by increasing CRF at the hypothalamic level, while its lipolytic effects could imply a local increase in glucocorticoids and glucocorticoid receptor (GC-R) expression in adipose tissue. Indeed, the potent activation of the HPA axis by GLP-1R agonists occurs within the range of therapeutic doses and with a short latency. Interestingly, the interactions of GLP-1 with the HPA axis may underlie most of the effects of GLP-1 on food intake control, glycaemic metabolism, adipose tissue biology and the responses to stress. Moreover, such activity has been observed in animal models (mice and rats), as well as in normal humans and in type I or type II diabetic patients. Accordingly, better understanding of how GLP-1R agonists modulate the activity of the HPA axis in diabetic subjects, especially obese individuals, will be crucial to design new and more efficient therapies for these patients.
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Renner, Éva, Fanni Dóra, Erzsébet Oszwald, Árpád Dobolyi, and Miklós Palkovits. "Elevated Glucagon-like Peptide-1 Receptor Level in the Paraventricular Hypothalamic Nucleus of Type 2 Diabetes Mellitus Patients." International Journal of Molecular Sciences 23, no. 24 (December 15, 2022): 15945. http://dx.doi.org/10.3390/ijms232415945.
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Glucagon-like peptide-1 (GLP-1) receptor (GLP-1R) agonists have been approved for the treatment of type 2 diabetes mellitus (T2DM); however, the brain actions of these drugs are not properly established. We used post mortem microdissected human hypothalamic samples for RT-qPCR and Western blotting. For in situ hybridization histochemistry and immunolabelling, parallel cryosections were prepared from the hypothalamus. We developed in situ hybridization probes for human GLP-1R and oxytocin. In addition, GLP-1 and oxytocin were visualized by immunohistochemistry. Radioactive in situ hybridization histochemistry revealed abundant GLP-1R labelling in the human paraventricular hypothalamic nucleus (PVN), particularly in its magnocellular subdivision (PVNmc). Quantitative analysis of the mRNA signal demonstrated increased GLP-1R expression in the PVNmc in post mortem hypothalamic samples from T2DM subjects as compared to controls, while there was no difference in the expression level of GLP-1R in the other subdivisions of the PVN, the hypothalamic dorsomedial and infundibular nuclei. Our results in the PVN were confirmed by RT-qPCR. Furthermore, we demonstrated by Western blot technique that the GLP-1R protein level was also elevated in the PVN of T2DM patients. GLP-1 fibre terminals were also observed in the PVNmc closely apposing oxytocin neurons using immunohistochemistry. The data suggest that GLP-1 activates GLP-1Rs in the PVNmc and that GLP-1R is elevated in T2DM patients, which may be related to the dysregulation of feeding behaviour and glucose homeostasis in T2DM.
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Cantini, Giulia, Martina Trabucco, Alessandra Di Franco, Edoardo Mannucci, and Michaela Luconi. "Glucagon modulates proliferation and differentiation of human adipose precursors." Journal of Molecular Endocrinology 63, no. 4 (November 2019): 249–60. http://dx.doi.org/10.1530/jme-19-0095.
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Glucagon-like peptide 1 receptor agonists (GLP-1RAs), which are currently used for the treatment of type 2 diabetes, have recently been proposed as anti-obesity drugs, due to their relevant effects on weight loss. Furthermore, dual agonists for both GLP-1R and glucagon receptor (GCGR) are under investigation for their promising action on adiposity, although underlying mechanisms still need to be clarified. We have recently demonstrated that GLP-1 and liraglutide interfere with the proliferation and differentiation of human adipose precursors, supporting the hypothesis of a peripheral action of GLP-1RA on weight. Here, we investigated glucagon activity in an in vitro model of primary human adipose-derived stem cells (ASCs). Glucagon significantly inhibited ASC proliferation in a dose- and time-dependent manner, as evaluated by cell count and thymidine incorporation. When added during in vitro-induced adipogenesis, glucagon significantly reduced adipocyte differentiation, as demonstrated by the evaluation of intracellular fat content and quantitative expression of early and mature adipocyte markers (PPARγ and FABP4, HSL). Notably, the inhibitory effect of glucagon on cell proliferation and adipogenesis was reversed by specific GLP-1R (exendin-9) and GCGR (des-His1-Glu9-glucagon(1–29)) antagonists. The presence of both receptors was demonstrated by Western blot, immunofluorescence and cytofluorimetric analysis of ASCs. In conclusion, we demonstrated a direct inhibitory action of glucagon on the proliferation and differentiation of human adipose precursors, which seems to involve both GLP-1R and GCGR. These findings suggest that the adipose stem compartment is a novel target of glucagon, possibly contributing to the weight loss obtained in vivo with dual GLP-1R/glucagon agonists.
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Greco, Eulalia, Giuseppina Russo, Annalisa Giandalia, Francesca Viazzi, Roberto Pontremoli, and Salvatore De Cosmo. "GLP-1 Receptor Agonists and Kidney Protection." Medicina 55, no. 6 (May 31, 2019): 233. http://dx.doi.org/10.3390/medicina55060233.
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Type 2 diabetes mellitus (T2DM) is the leading cause of chronic kidney disease (CKD). Diabetic nephropathy (DN) is determined by specific pathological structural and functional alterations of the kidneys in patients with diabetes, and its clinical manifestations are albuminuria and decline of glomerular filtration rate (GFR). Apart from renin–angiotensin–aldosterone system (RAAS) inhibitors, no other drugs are currently available as therapy for diabetic kidney disease (DKD). Glucagon-like peptide-1 receptor (GLP-1R) agonists are a new class of anti-hyperglycemic drugs which have been demonstrated to prevent the onset of macroalbuminuria and reduce the decline of GFR in diabetic patients. These drugs may exert their beneficial actions on the kidneys through blood glucose- and blood pressure (BP)-lowering effects, reduction of insulin levels and weight loss. Clinical benefits of GLP-1R agonists were acknowledged due to data from large randomized phase III clinical trials conducted to assess their cardiovascular(CV) safety. These drugs improved renal biomarkers in placebo-controlled clinical studies, with effects supposed to be independent of the actions on glycemic control. In this review, we will focus on the actions of GLP-1R agonists on glucose metabolism and kidney physiology, and evaluate direct and indirect mechanisms through which these drugs may confer renal protection.
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Xiao, Q., W. Jeng, and MB Wheeler. "Characterization of glucagon-like peptide-1 receptor-binding determinants." Journal of Molecular Endocrinology 25, no. 3 (December 1, 2000): 321–35. http://dx.doi.org/10.1677/jme.0.0250321.
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Glucagon-like peptide 1 (GLP-1) is a potent insulinotropic hormone currently under study as a therapeutic agent for type 2 diabetes. Since an understanding of the molecular mechanisms leading to high-affinity receptor (R) binding and activation may facilitate the development of more potent GLP-1R agonists, we have localized specific regions of GLP-1R required for binding. The purified N-terminal fragment (hereafter referred to as NT) of the GLP-1R produced in either insect (Sf9) or mammalian (COS-7) cells was shown to bind GLP-1. The physical interaction of NT with GLP-1 was first demonstrated by cross-linking ((125)I-GLP-1/NT complex band at approximately 28 kDa) and secondly by attachment to Ni(2+)-NTA beads. The GLP-1R NT protein attached to beads bound GLP-1, but with lower affinity (inhibitory concentration (IC(50)): 4.5 x 10(-7) M) than wild-type (WT) GLP-1R (IC(50): 5.2 x 10(-9)M). The low affinity of GLP-1R NT suggested that other receptor domains may contribute to GLP-1 binding. This was supported by studies using chimeric glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptors. GIP(1-151)/GLP-1R, but not GIP(1-222)/GLP-1R, exhibited specific GLP-1 binding and GLP-1-induced cAMP production, suggesting that the region encompassing transmembrane (TM) domain 1 through to TM3 was required for binding. Since it was hypothesized that certain charged or polar amino acids in this region might be involved in binding, these residues (TM2-TM3) were analyzed by substitution mutagenesis. Five mutants (K197A, D198A, K202A, D215A, R227A) displayed remarkably reduced binding affinity. These studies indicate that the NT domain of the GLP-1R is able to bind GLP-1, but charged residues concentrated at the distal TM2/extracellular loop-1 (EC1) interface (K197, D198, K202) and in EC1 (D215 and R227) probably contribute to the binding determinants of the GLP-1R.
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Yokomori, Hiroaki, and Wataru Ando. "Spatial expression of glucagon-like peptide 1 receptor and caveolin-1 in hepatocytes with macrovesicular steatosis in non-alcoholic steatohepatitis." BMJ Open Gastroenterology 7, no. 1 (May 2020): e000370. http://dx.doi.org/10.1136/bmjgast-2019-000370.
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ObjectiveNon-alcoholic steatohepatitis (NASH) can progress to fibrosis, cirrhosis and end-stage liver disease. Glucagon-like peptide 1 receptor (GLP-1R) mediates β cell function. Its receptor agonists, currently used to treat type 2 diabetes mellitus, might be effective against NASH. GLP-1R, a G protein-coupled receptor family member, preferentially localises to caveolae. Therefore, we ascertained the cellular localisation of GLP-1R and caveolin (CAV)-1 in NASH liver.MethodsLiver biopsies were obtained from three patients with NASH and were compared with those of four normal patients. Immunohistochemistry (IHC) and immunoelectron microscopy (IEM) were used to compare GLP-1R and CAV-1 expression in the livers of patients with metastatic liver cancer and normal patients.ResultsIHC showed that GLP-1R localised to basolateral membranes of hepatocytes with macrovesicular steatosis and was expressed in monocytes infiltrating hepatic sinusoids. CAV-1 was minimally associated with low-electron density lipid droplets (LDs) in hepatocytes. IEM showed small clusters of GLP-1R molecules on the peripheral rims of LDs and on cytoplasmic leaflets of endoplasmic reticulum membranes and vesicles, whereas CAV-1 molecules were found in LD caveolae.ConclusionsGLP-1R is present in the lipid microdomains of hepatocytes with macrovesicular steatosis. These results may help inform future studies about the liver-specific mechanisms of GLP-1 modulation in NASH therapy.
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Zhao, He-jun, Xia Jiang, Li-juan Hu, Lei Yang, Lian-dong Deng, Ya-ping Wang, and Zhi-peng Ren. "Activation of GLP-1 receptor enhances the chemosensitivity of pancreatic cancer cells." Journal of Molecular Endocrinology 64, no. 2 (February 2020): 103–13. http://dx.doi.org/10.1530/jme-19-0186.
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This study aimed to determine whether and how the glucagon-like peptide 1 receptor (GLP-1R) agonist liraglutide affects the chemoresistance and chemosensitivity of pancreatic cancer cells to gemcitabine in vitro and in vivo. The GLP-1R and protein kinase A (PKA) levels were compared between the human pancreatic cancer cell line PANC-1 and the gemcitabine-resistant cell line PANC-GR. The in vitro effects of liraglutide on the cell proliferation and apoptosis as well as the nuclear factor-kappa B NF-κB expression levels of PANC-GR cells were evaluated. In addition, a mouse xenograft model of human pancreatic cancer was established by s.c. injection of PANC-1 cells, and the effects of liraglutide on the chemosensitivity were evaluated in vitro and in vivo. In contrast to PANC-1 cells, PANC-GR cells exhibited lower expression levels of GLP-1R and PKA. Incubation with liraglutide dose dependently inhibited the growth, promoted the apoptosis, and increased the expression of GLP-1R and PKA of PANC-GR cells. Similar effects of liraglutide were observed in another human pancreatic cancer cell line MiaPaCa-2/MiaPaCa-2-GR. Either the GLP-1R antagonist Ex-9, the PKA inhibitor H89, or the NF-κB activator lipopolysaccharide (LPS) could abolish the antiproliferative and proapoptotic activities of liraglutide. Additionally, each of these agents could reverse the expression of NF-κB and ABCG2, which was decreased by liraglutide treatment. Furthermore, liraglutide treatment increased the chemosensitivity of pancreatic cancer cells to gemcitabine, as evidenced by in vitro and in vivo experiments. Thus, GLP-1R agonists are safe and beneficial for patients complicated with pancreatic cancer and diabetes, especially for gemcitabine-resistant pancreatic cancer.
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Tsai, Shang-Feng, and Cheng-Hsu Chen. "Management of Diabetes Mellitus in Normal Renal Function, Renal Dysfunction and Renal Transplant Recipients, Focusing on Glucagon-Like Peptide-1 Agonist: A Review Based upon Current Evidence." International Journal of Molecular Sciences 20, no. 13 (June 28, 2019): 3152. http://dx.doi.org/10.3390/ijms20133152.
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Diabetes Mellitus (DM) is a leading cause of both Cardiovascular Disease (CVD) and End-stage Renal Disease (ESRD). After 2008, there has been much evidence presented, and recently the guidelines for sugar control have changed to focus on being more disease orientated. GLP-1 Receptor Agonists (GLP-1R) and sodium glucose cotransporter-2 inhibitors are suggested as the first line towards fighting all DM, CVD and ESRD. However, the benefits of GLP-1R in organ transplantation recipients remain very limited. No clinical trials have been designed for this particular population. GLP-1R, a gastrointestinal hormone of the incretin family, possesses antidiabetic, antihypertensive, anti-inflammatory, anti-apoptotic and immunomodulatory actions. There are few drug–drug interactions, with delayed gastric emptying being the major concern. The trough level of tacrolimus may not be significant but should still be closely monitored. There are some reasons which support GLP-1R in recipients seeking glycemic control. Post-transplant DM is due to an impaired β-cell function and glucose-induced glucagon suppression during hyperglycemia, which can be reversed by GLP-1R. GLP-1R infusion tends to relieve immunosuppressant related toxicity. Until now, in some cases, glycemic control and body weight reduction can be anticipated with GLP-1R. Additional renal benefits have also been reported. Side effects of hypoglycemia and gastrointestinal discomfort were rarely reported. In conclusion, GLP-1R could be implemented for recipients while closely monitoring their tacrolimus levels and any potential side effects. Any added benefits, in addition to sugar level control, still require more well-designed studies to prove their existence.
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Mori, Yusaku, Takanori Matsui, Tsutomu Hirano, and Sho-ichi Yamagishi. "GIP as a Potential Therapeutic Target for Atherosclerotic Cardiovascular Disease–A Systematic Review." International Journal of Molecular Sciences 21, no. 4 (February 22, 2020): 1509. http://dx.doi.org/10.3390/ijms21041509.
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Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that are secreted from enteroendocrine L cells and K cells in response to digested nutrients, respectively. They are also referred to incretin for their ability to stimulate insulin secretion from pancreatic beta cells in a glucose-dependent manner. Furthermore, GLP-1 exerts anorexic effects via its actions in the central nervous system. Since native incretin is rapidly inactivated by dipeptidyl peptidase-4 (DPP-4), DPP-resistant GLP-1 receptor agonists (GLP-1RAs), and DPP-4 inhibitors are currently used for the treatment of type 2 diabetes as incretin-based therapy. These new-class agents have superiority to classical oral hypoglycemic agents such as sulfonylureas because of their low risks for hypoglycemia and body weight gain. In addition, a number of preclinical studies have shown the cardioprotective properties of incretin-based therapy, whose findings are further supported by several randomized clinical trials. Indeed, GLP-1RA has been significantly shown to reduce the risk of cardiovascular and renal events in patients with type 2 diabetes. However, the role of GIP in cardiovascular disease remains to be elucidated. Recently, pharmacological doses of GIP receptor agonists (GIPRAs) have been found to exert anti-obesity effects in animal models. These observations suggest that combination therapy of GLP-1R and GIPR may induce superior metabolic and anti-diabetic effects compared with each agonist individually. Clinical trials with GLP-1R/GIPR dual agonists are ongoing in diabetic patients. Therefore, in this review, we summarize the cardiovascular effects of GIP and GIPRAs in cell culture systems, animal models, and humans.
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Yang, Zixin, Zhengkun Kuang, Rui Wang, Ni Pi, Xiyao Cheng, Yongqi Huang, and Zhengding Su. "Rational Design of Small Molecular GLP-1R Agonists." Biophysical Journal 120, no. 3 (February 2021): 27a. http://dx.doi.org/10.1016/j.bpj.2020.11.422.
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Koch, Linda. "GLP-1R agonists—the new weapon against obesity?" Nature Reviews Endocrinology 8, no. 4 (January 31, 2012): 196. http://dx.doi.org/10.1038/nrendo.2012.13.
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Zhou, Bilan, Anlin Peng, Hao Gong, and Kun Huang. "GLP-1R agonists therapy for type 2 diabetes." Wuhan University Journal of Natural Sciences 19, no. 1 (January 8, 2014): 27–33. http://dx.doi.org/10.1007/s11859-014-0974-8.
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Manell, Elin, Emmi Puuvuori, Anna Svensson, Irina Velikyan, Gry Hulsart-Billström, Patricia Hedenqvist, Jens Juul Holst, Marianne Jensen Waern, and Olof Eriksson. "Exploring the GLP-1–GLP-1R axis in porcine pancreas and gastrointestinal tract in vivo by ex vivo autoradiography." BMJ Open Diabetes Research & Care 9, no. 1 (April 2021): e002083. http://dx.doi.org/10.1136/bmjdrc-2020-002083.
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IntroductionGlucagon-like peptide-1 (GLP-1) increases insulin secretion from pancreatic beta-cells and GLP-1 receptor (GLP-1R) agonists are widely used as treatment for type 2 diabetes mellitus. Studying occupancy of the GLP-1R in various tissues is challenging due to lack of quantitative, repeatable assessments of GLP-1R density. The present study aimed to describe the quantitative distribution of GLP-1Rs and occupancy by endogenous GLP-1 during oral glucose tolerance test (OGTT) in pigs, a species that is used in biomedical research to model humans.Research design and methodsGLP-1R distribution and occupancy were measured in pancreas and gastrointestinal tract by ex vivo autoradiography using the GLP-1R-specific radioligand 177Lu-exendin-4 in two groups of pigs, control or bottle-fed an oral glucose load. Positron emission tomography (PET) data from pigs injected with 68Ga-exendin-4 in a previous study were used to retrieve data on biodistribution of GLP-1R in the gastrointestinal tract.ResultsHigh homogenous uptake of 177Lu-exendin-4 was found in pancreas, and even higher uptake in areas of duodenum. Low uptake of 177Lu-exendin-4 was found in stomach, jejunum, ileum and colon. During OGTT, there was no increase in plasma GLP-1 concentrations and occupancy of GLP-1Rs was low. The ex vivo autoradiography results were highly consistent with to the biodistribution of 68Ga-exendin-4 in pigs scanned by PET.ConclusionWe identified areas with similarities as well as important differences regarding GLP-1R distribution and occupancy in pigs compared with humans. First, there was strong ligand binding in the exocrine pancreas in islets. Second, GLP-1 secretion during OGTT is minimal and GLP-1 might not be an important incretin in pigs under physiological conditions. These findings offer new insights on the relevance of porcine diabetes models.
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Angeli, Franca S., and Richard P. Shannon. "Incretin-based therapies: can we achieve glycemic control and cardioprotection?" Journal of Endocrinology 221, no. 1 (August 7, 2013): T17—T30. http://dx.doi.org/10.1530/joe-13-0195.
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Glucagon-like (GLP-1) is a peptide hormone secreted from the small intestine in response to nutrient ingestion. GLP-1 stimulates insulin secretion in a glucose-dependent manner, inhibits glucagon secretion and gastric emptying, and reduces appetite. Because of the short circulating half-life of the native GLP-1, novel GLP-1 receptor (GLP-1R) agonists and analogs and dipeptidyl peptidase 4 (DPP-4) inhibitors have been developed to facilitate clinical use. Emerging evidence indicates that GLP-1-based therapies are safe and may provide cardiovascular (CV) benefits beyond glycemic control. Preclinical and clinical studies are providing increasing evidence that GLP-1 therapies may positively affect CV function and metabolism by salutary effects on CV risk factors as well as via direct cardioprotective actions. However, the mechanisms whereby the various classes of incretin-based therapies exert CV effects may be mechanistically distinct and may not necessarily lead to similar CV outcomes. In this review, we will discuss the potential mechanisms and current understanding of CV benefits of native GLP-1, GLP-1R agonists and analogs, and of DPP-4 inhibitor therapies as a means to compare their putative CV benefits.
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Yaribeygi, Habib, Farin Rashid Farrokhi, Mohammed Altigani Abdalla, Thozhukat Sathyapalan, Maciej Banach, Tannaz Jamialahmadi, and Amirhossein Sahebkar. "The Effects of Glucagon-Like Peptide-1 Receptor Agonists and Dipeptydilpeptidase-4 Inhibitors on Blood Pressure and Cardiovascular Complications in Diabetes." Journal of Diabetes Research 2021 (June 30, 2021): 1–10. http://dx.doi.org/10.1155/2021/6518221.
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Glucagon-like peptide-1 receptor (GLP-1R) agonists are a class of newly introduced antidiabetic medications that potentially lower blood glucose by several molecular pathways. DPP-4 inhibitors are the other type of novel antidiabetic medications which act by preventing GLP-1 inactivation and thereby increasing the activity levels of GLP-1, leading to more glucose-induced insulin release from islet β-cells and suppression of glucagon release. Most patients with diabetes have concurrent hypertension and cardiovascular disorder. If antihyperglycemic agents can attenuate the risk of hypertension and cardiovascular disease, they will amplify their overall beneficial effects. There is conflicting evidence on the cardiovascular benefits of GLP-1R induction in laboratory studies and clinical trials. In this study, we have reviewed the main molecular mechanisms by which GLP-1R induction may modulate the cardiovascular function and the results of cardiovascular outcome clinical trials.
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Elabi, Osama F., Jeffrey S. Davies, and Emma L. Lane. "L-dopa-Dependent Effects of GLP-1R Agonists on the Survival of Dopaminergic Cells Transplanted into a Rat Model of Parkinson Disease." International Journal of Molecular Sciences 22, no. 22 (November 16, 2021): 12346. http://dx.doi.org/10.3390/ijms222212346.
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Cell therapy is a promising treatment for Parkinson’s disease (PD), however clinical trials to date have shown relatively low survival and significant patient-to-patient variability. Glucagon Like Peptide-1 receptor (GLP-1R) agonists have potential neuroprotective effects on endogenous dopaminergic neurons. This study explores whether these agents could similarly support the growth and survival of newly transplanted neurons. 6-OHDA lesioned Sprague Dawley rats received intra-striatal grafts of dopaminergic ventral mesencephalic cells from embryonic day 14 Wistar rat embryos. Transplanted rats then received either saline or L-dopa (12 mg/kg) administered every 48 h prior to, and following cell transplantation. Peripheral GLP-1R agonist administration (exendin-4, 0.5 μg/kg twice daily or liraglutide, 100 μg/kg once daily) commenced immediately after cell transplantation and was maintained throughout the study. Graft survival increased under administration of exendin-4, with motor function improving significantly following treatment with both exendin-4 and liraglutide. However, this effect was not observed in rats administered with L-dopa. In contrast, L-dopa treatment with liraglutide increased graft volume, with parallel increases in motor function. However, this improvement was accompanied by an increase in leukocyte infiltration around the graft. The co-administration of L-dopa and exendin-4 also led to indicators of insulin resistance not seen with liraglutide, which may underpin the differential effects observed between the two GLP1-R agonists. Overall, there may be some benefit to the supplementation of grafted patients with GLP-1R agonists but the potential interaction with other pharmacological treatments needs to be considered in more depth.
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Hviid, Aleksander Vauvert R., and Charlotte M. Sørensen. "Glucagon-like peptide-1 receptors in the kidney: impact on renal autoregulation." American Journal of Physiology-Renal Physiology 318, no. 2 (February 1, 2020): F443—F454. http://dx.doi.org/10.1152/ajprenal.00280.2019.
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Glucagon-like peptide-1 (GLP-1) and strategies based on this blood sugar-reducing and appetite-suppressing hormone are used to treat obesity and type 2 diabetes. However, the GLP-1 receptor (GLP-1R) is also present in the kidney, where it influences renal function. The effect of GLP-1 on the kidney varies between humans and rodents. The effect of GLP-1 on kidney function also seems to vary depending on its concentration and the physiological or pathological state of the kidney. In studies with rodents or humans, acute infusion of pharmacological doses of GLP-1 stimulates natriuresis and diuresis. However, the effect on the renal vasculature is less clear. In rodents, GLP-1 infusion increases renal plasma flow and glomerular filtration rate, suggesting renal vasodilation. In humans, only a subset of the study participants exhibits increased renal plasma flow and glomerular filtration rate. Differential status of kidney function and changes in renal vascular resistance of the preglomerular arterioles may account for the different responses of the human study participants. Because renal function in patients with type 2 diabetes is already at risk or compromised, understanding the effects of GLP-1R activation on kidney function in these patients is particularly important. This review examines the distribution of GLP-1R in the kidney and the effects elicited by GLP-1 or GLP-1R agonists. By integrating results from acute and chronic studies in healthy individuals and patients with type 2 diabetes along with those from rodent studies, we provide insight into how GLP-1R activation affects renal function and autoregulation.
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Chung, Sungjin, and Gheun-Ho Kim. "Use of Anti-Diabetic Agents in Non-Diabetic Kidney Disease: From Bench to Bedside." Life 11, no. 5 (April 25, 2021): 389. http://dx.doi.org/10.3390/life11050389.
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New drugs were recently developed to treat hyperglycemia in patients with type 2 diabetes mellitus (T2D). However, metformin remains the first-line anti-diabetic agent because of its cost-effectiveness. It has pleiotropic action that produces cardiovascular benefits, and it can be useful in diabetic nephropathy, although metformin-associated lactic acidosis is a hindrance to its use in patients with kidney failure. New anti-diabetic agents, including glucagon-like peptide-1 receptor (GLP-1R) agonists, dipeptidyl peptidase-4 (DPP-4) inhibitors, and sodium-glucose transporter-2 (SGLT-2) inhibitors, also produce cardiovascular or renal benefits in T2D patients. Their glucose-independent beneficial actions can lead to cardiorenal protection via hemodynamic stabilization and inflammatory modulation. Systemic hypertension is relieved by natriuresis and improved vascular dysfunction. Enhanced tubuloglomerular feedback can be restored by SGLT-2 inhibition, reducing glomerular hypertension. Patients with non-diabetic kidney disease might also benefit from those drugs because hypertension, proteinuria, oxidative stress, and inflammation are common factors in the progression of kidney disease, irrespective of the presence of diabetes. In various animal models of non-diabetic kidney disease, metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors were favorable to kidney morphology and function. They strikingly attenuated biomarkers of oxidative stress and inflammatory responses in diseased kidneys. However, whether those animal results translate to patients with non-diabetic kidney disease has yet to be evaluated. Considering the paucity of new agents to treat kidney disease and the minimal adverse effects of metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors, these anti-diabetic agents could be used in patients with non-diabetic kidney disease. This paper provides a rationale for clinical trials that apply metformin, GLP-1R agonists, DPP-4 inhibitors, and SGLT-2 inhibitors to non-diabetic kidney disease.
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Fortin, Samantha M., Rachele K. Lipsky, Rinzin Lhamo, Jack Chen, Eun Kim, Tito Borner, Heath D. Schmidt, and Matthew R. Hayes. "GABA neurons in the nucleus tractus solitarius express GLP-1 receptors and mediate anorectic effects of liraglutide in rats." Science Translational Medicine 12, no. 533 (March 4, 2020): eaay8071. http://dx.doi.org/10.1126/scitranslmed.aay8071.
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The glucagon-like peptide-1 receptor (GLP-1R) agonist liraglutide is approved for the treatment of obesity; however, there is still much to be learned regarding the neuronal sites of action that underlie its suppressive effects on food intake and body weight. Peripherally administered liraglutide in rats acts in part through central GLP-1Rs in both the hypothalamus and the hindbrain. Here, we extend findings supporting a role for hindbrain GLP-1Rs in mediating the anorectic effects of liraglutide in male rats. To dissociate the contribution of GLP-1Rs in the area postrema (AP) and the nucleus tractus solitarius (NTS), we examined the effects of liraglutide in both NTS AAV-shRNA–driven Glp1r knockdown and AP-lesioned animals. Knockdown of NTS GLP-1Rs, but not surgical lesioning of the AP, attenuated the anorectic and body weight–reducing effects of acutely delivered liraglutide. In addition, NTS c-Fos responses were maintained in AP-lesioned animals. Moreover, NTS Glp1r knockdown was sufficient to attenuate the intake- and body weight–reducing effects of chronic daily administered liraglutide over 3 weeks. Development of improved obesity pharmacotherapies requires an understanding of the cellular phenotypes targeted by GLP-1R agonists. Fluorescence in situ hybridization identified Glp1r transcripts in NTS GABAergic neurons, which when inhibited using chemogenetics, attenuated the food intake– and body weight–reducing effects of liraglutide. This work demonstrates the contribution of NTS GLP-1Rs to the anorectic potential of liraglutide and highlights a phenotypically distinct (GABAergic) population of neurons within the NTS that express the GLP-1R and are involved in the mediation of liraglutide signaling.