Glucagon-like peptide-1 (GLP-1; Insulinotropin) is an intestinally-derived blood glucose-lowering hormone that stimulates pancreatic insulin secretion and which is now under investigation for use as a therapeutic agent in treatment of type-2 diabetes mellitus. The Central Hypothesis presented here is that the beneficial insulinotropic action of GLP-1 at the islets of Langerhans results, in part, from an ability of GLP-1 to stimulate metabolism of D-glucose by the pancreatic beta- cells. Studies are presented demonstrating that GLP-1 augments the glucose-dependent production of ATP in beta-cells, as imaged by single photon counting of mitochondrially-targeted luciferase reporters. The action of GLP-1 is preceded by an increase of [Ca2+]i that reflects mobilization of Ca2+ from endoplasmic reticulum Ca2+ stores, and which is proposed to facilitate the enzymatic activity of mitochondrial dehydrogenases, thereby increasing [ATP]i. Subsequent inhibition of ATP-sensitive K+ channels (K-ATP) produces depolarization, oscillatory Ca2+ influx, and pulsatile exocytosis of insulin. To test our hypothesis, and to validate this model of GLP-1 signal transduction in human beta-cells, luminescence-based measurements of [ATP]i will be combined with fura-2 determinations of [Ca2+]i while monitoring K-ATP using the patch clamp technique. It will be determined: 1) if GLP-1 increases the potency and efficacy of glucose to stimulate production of ATP, 2) if stimulatory effects of GLP-1 on [Ca2+]i and [ATP]i explain how this hormone inhibits K-ATP, and 3) which second messengers and protein kinases mediate stimulatory effects of GLP-1 on beta-cell glucose metabolism. Our goal is to elucidate the complex cellular signal transduction properties of GLP-1 that explain its effectiveness for use in treatment of diabetes mellitus.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK045817-07
Application #
6517250
Study Section
Metabolism Study Section (MET)
Program Officer
Laughlin, Maren R
Project Start
1993-01-01
Project End
2004-06-30
Budget Start
2002-07-01
Budget End
2003-06-30
Support Year
7
Fiscal Year
2002
Total Cost
$328,732
Indirect Cost
Name
New York University
Department
Physiology
Type
Schools of Medicine
DUNS #
City
New York
State
NY
Country
United States
Zip Code
10016
Nadkarni, Prashant; Chepurny, Oleg G; Holz, George G (2014) Regulation of glucose homeostasis by GLP-1. Prog Mol Biol Transl Sci 121:23-65
Smrcka, Alan V; Brown, Joan Heller; Holz, George G (2012) Role of phospholipase Cýý in physiological phosphoinositide signaling networks. Cell Signal 24:1333-43
Leech, Colin A; Dzhura, Igor; Chepurny, Oleg G et al. (2011) Molecular physiology of glucagon-like peptide-1 insulin secretagogue action in pancreatic ? cells. Prog Biophys Mol Biol 107:236-47
Dzhura, Igor; Chepurny, Oleg G; Leech, Colin A et al. (2011) Phospholipase C-? links Epac2 activation to the potentiation of glucose-stimulated insulin secretion from mouse islets of Langerhans. Islets 3:121-8
Leech, Colin A; Dzhura, Igor; Chepurny, Oleg G et al. (2010) Facilitation of ß-cell K(ATP) channel sulfonylurea sensitivity by a cAMP analog selective for the cAMP-regulated guanine nucleotide exchange factor Epac. Islets 2:72-81
Chepurny, Oleg G; Kelley, Grant G; Dzhura, Igor et al. (2010) PKA-dependent potentiation of glucose-stimulated insulin secretion by Epac activator 8-pCPT-2'-O-Me-cAMP-AM in human islets of Langerhans. Am J Physiol Endocrinol Metab 298:E622-33
Leech, Colin A; Chepurny, Oleg G; Holz, George G (2010) Epac2-dependent rap1 activation and the control of islet insulin secretion by glucagon-like peptide-1. Vitam Horm 84:279-302
Dzhura, Igor; Chepurny, Oleg G; Kelley, Grant G et al. (2010) Epac2-dependent mobilization of intracellular Ca²+ by glucagon-like peptide-1 receptor agonist exendin-4 is disrupted in ?-cells of phospholipase C-? knockout mice. J Physiol 588:4871-89
Chepurny, Oleg G; Leech, Colin A; Kelley, Grant G et al. (2009) Enhanced Rap1 activation and insulin secretagogue properties of an acetoxymethyl ester of an Epac-selective cyclic AMP analog in rat INS-1 cells: studies with 8-pCPT-2'-O-Me-cAMP-AM. J Biol Chem 284:10728-36
Peyot, Marie-Line; Gray, Joshua P; Lamontagne, Julien et al. (2009) Glucagon-like peptide-1 induced signaling and insulin secretion do not drive fuel and energy metabolism in primary rodent pancreatic beta-cells. PLoS One 4:e6221

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