title: Glucagon-like peptide-1 receptor signaling modulates beta cell apoptosis.
abstract: Glucagon-like peptide-1 (GLP-1) stimulates insulin secretion and augments beta cell mass via activation of beta cell proliferation and islet neogenesis. We examined whether GLP-1 receptor signaling modifies the cellular susceptibility to apoptosis. Mice administered streptozotocin (STZ), an agent known to induce beta cell apoptosis, exhibit sustained improvement in glycemic control and increased levels of plasma insulin with concomitant administration of the GLP-1 agonist exendin-4 (Ex-4). Blood glucose remained significantly lower for weeks after cessation of exendin-4. STZ induced beta cell apoptosis, which was significantly reduced by co-administration of Ex-4. Conversely, mice with a targeted disruption of the GLP-1 receptor gene exhibited increased beta cell apoptosis after STZ administration. Exendin-4 directly reduced cytokine-induced apoptosis in purified rat beta cells exposed to interleukin 1beta, tumor necrosis fator alpha, and interferon gamma in vitro. Furthermore, Ex-4-treated BHK-GLP-1R cells exhibited significantly increased cell viability, reduced caspase activity, and decreased cleavage of beta-catenin after treatment with cycloheximide in vitro. These findings demonstrate that GLP-1 receptor signaling directly modifies the susceptibility to apoptotic injury, and provides a new potential mechanism linking GLP-1 receptor activation to preservation or enhancement of beta cell mass in vivo.
authors.affiliation: Department of Medicine, Banting and Best Diabetes Centre, Toronto General Hospital, University of Toronto, Ontario M5G 2C4, Canada.
authors.forename: Yazhou
authors.initials: Y
authors.lastname: Li
authors.forename: Tanya
authors.initials: T
authors.lastname: Hansotia
authors.forename: Bernardo
authors.initials: B
authors.lastname: Yusta
authors.forename: Frederic
authors.initials: F
authors.lastname: Ris
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Drucker
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D005576:Colforsin / Q000494:pharmacology; D006224:Cricetinae; D003513:Cycloheximide / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental; D000077270:Exenatide; D005934:Glucagon / Q000819:agonists / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1; D000067757:Glucagon-Like Peptide-1 Receptor; D005951:Glucose Tolerance Test; D020287:In Situ Nick-End Labeling; D007328:Insulin / Q000097:blood; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000819:agonists / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D011498:Protein Precursors / Q000819:agonists / Q000378:metabolism*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018027:Receptors, Glucagon / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013311:Streptozocin / Q000008:administration & dosage; D015534:Trans-Activators / Q000378:metabolism; D014688:Venoms; D051176:beta Catenin
chemical_list: D001786:Blood Glucose; C495267:CTNNB1 protein, mouse; C495268:Ctnnb1 protein, rat; D016207:Cytokines; D003598:Cytoskeletal Proteins; C000593834:Glp1r protein, mouse; C000593835:Glp1r protein, rat; D000067757:Glucagon-Like Peptide-1 Receptor; D007328:Insulin; D010446:Peptide Fragments; D010455:Peptides; D011498:Protein Precursors; D011500:Protein Synthesis Inhibitors; D018027:Receptors, Glucagon; D015534:Trans-Activators; D014688:Venoms; D051176:beta Catenin; D005576:Colforsin; D013311:Streptozocin; D052216:Glucagon-Like Peptide 1; D005934:Glucagon; D003513:Cycloheximide; D000077270:Exenatide