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Effects of gastric inhibitory polypeptide (GIP) and related analogues on glucagon release at normo- and hyperglycaemia in Wistar rats and isolated islets

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Cassidy, Roslyn S., Irwin, Nigel and Flatt, Peter (2008) Effects of gastric inhibitory polypeptide (GIP) and related analogues on glucagon release at normo- and hyperglycaemia in Wistar rats and isolated islets. BIOLOGICAL CHEMISTRY, 389 (2). pp. 189-193. [Journal article]

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DOI: 10.1515/BC.2008.019

Abstract

Glucose-dependent insulinotropic polypeptide (GIP) is an incretin hormone secreted by endocrine K-cells in response to nutrient absorption. This study has utilised numerous well-characterised dipeptidyl peptidase IV-resistant GIP analogues to evaluate the glucagonotropic actions of GIP in Wistar rats and isolated rat islets. Intraperitoneal administration of GIP analogues (25 nmol/kg body weight) in combination with glucose had no effect on circulating glucagon concentrations compared to controls in Wistar rats. However, plasma glucose concentrations were significantly (p<0.05 to p<0.001) lowered by the GIP-receptor agonists, N-AcGIP, GIP(Lys(37)) PAL and N-AcGIP(Lys(37))PAL. The GIP antagonist, (Pro(3))GIP, caused a significant (p<0.05) reduction in glucagon levels following concurrent administration with saline in Wistar rats. In isolated rat islets native GIP induced a significant (p<0.01) enhancement of glucagon release at basal glucose concentrations, which was completely annulled by (Pro(3))GIP. Furthermore, glucagon release in the presence of GLP-1, GIP(Lys(37))PAL, N-AcGIP(Lys(37)) PAL and (Pro(3))GIP was significantly (p<0.05 to p<0.001) decreased compared to native GIP in isolated rat islets. These data indicate a modest effect of GIP on glucagon secretion from isolated rat islets, which was not observed in vivo. However, the GIP agonists N-AcGIP, GIP(Lys(37))PAL and N-AcGIP(Lys(37))PAL had no effect on glucagon release demonstrating an improved therapeutic potential for the treatment of type 2 diabetes.

Item Type:Journal article
Faculties and Schools:Faculty of Life and Health Sciences
Faculty of Life and Health Sciences > School of Biomedical Sciences
Faculty of Life and Health Sciences > School of Pharmacy and Pharmaceutical Science
Research Institutes and Groups:Biomedical Sciences Research Institute
Biomedical Sciences Research Institute > Diabetes
ID Code:2923
Deposited By:Professor Peter Flatt
Deposited On:17 Dec 2009 10:22
Last Modified:19 Nov 2012 15:54

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