Article

Diabetologia

, Volume 55, Issue 10, pp 2682-2692

First online:

G protein-coupled receptor (GPR)40-dependent potentiation of insulin secretion in mouse islets is mediated by protein kinase D1

  • M. FerdaoussiAffiliated withMontreal Diabetes Research Center, CRCHUM, Technopole AngusDepartment of Medicine, University of Montreal
  • , V. BergeronAffiliated withMontreal Diabetes Research Center, CRCHUM, Technopole AngusDepartment of Medicine, University of Montreal
  • , B. ZarroukiAffiliated withMontreal Diabetes Research Center, CRCHUM, Technopole AngusDepartment of Medicine, University of Montreal
  • , J. KolicAffiliated withDepartment of Pharmacology and the Alberta Diabetes Institute, University of Alberta
  • , J. CantleyAffiliated withGarvan Institute of Medical Research, St Vincent’s Hospital
  • , J. FielitzAffiliated withExperimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular MedicineMedical Department, Division of Cardiology, Charité University
  • , E. N. OlsonAffiliated withDepartments of Molecular Biology, Internal Medicine, and Pathology, University of Texas Southwestern Medical Center
  • , M. PrentkiAffiliated withMontreal Diabetes Research Center, CRCHUM, Technopole AngusDepartments of Nutrition and Biochemistry, University of Montreal
  • , T. BidenAffiliated withGarvan Institute of Medical Research, St Vincent’s Hospital
    • , P. E. MacDonaldAffiliated withDepartment of Pharmacology and the Alberta Diabetes Institute, University of Alberta
    • , V. PoitoutAffiliated withMontreal Diabetes Research Center, CRCHUM, Technopole AngusDepartment of Medicine, University of MontrealDepartments of Nutrition and Biochemistry, University of Montreal Email author 

Abstract

Aims/hypothesis

Activation of the G protein-coupled receptor (GPR)40 by long-chain fatty acids potentiates glucose-stimulated insulin secretion (GSIS) from pancreatic beta cells, and GPR40 agonists are in clinical development for type 2 diabetes therapy. GPR40 couples to the G protein subunit Gαq/11 but the signalling cascade activated downstream is unknown. This study aimed to determine the mechanisms of GPR40-dependent potentiation of GSIS by fatty acids.

Methods

Insulin secretion in response to glucose, oleate or diacylglycerol (DAG) was assessed in dynamic perifusions and static incubations in islets from wild-type (WT) and Gpr40 −/− mice. Depolymerisation of filamentous actin (F-actin) was visualised by phalloidin staining and epifluorescence. Pharmacological and molecular approaches were used to ascertain the roles of protein kinase D (PKD) and protein kinase C delta in GPR40-mediated potentiation of GSIS.

Results

Oleate potentiates the second phase of GSIS, and this effect is largely dependent upon GPR40. Accordingly, oleate induces rapid F-actin remodelling in WT but not in Gpr40 −/− islets. Exogenous DAG potentiates GSIS in both WT and Gpr40 −/− islets. Oleate induces PKD phosphorylation at residues Ser-744/748 and Ser-916 in WT but not Gpr40 −/− islets. Importantly, oleate-induced F-actin depolymerisation and potentiation of GSIS are lost upon pharmacological inhibition of PKD1 or deletion of Prkd1.

Conclusions/interpretation

We conclude that the signalling cascade downstream of GPR40 activation by fatty acids involves activation of PKD1, F-actin depolymerisation and potentiation of second-phase insulin secretion. These results provide important information on the mechanisms of action of GPR40, a novel drug target for type 2 diabetes.

Keywords

Diacylglycerol Filamentous actin G protein-coupled receptor GPR40 Insulin secretion Islet Protein kinase D Type 2 diabetes