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

Abstract

Aims/hypothesis Activation of the G protein-coupled receptor (GPR)40 by long-chain fatty acids potentiates glucosestimulated 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 Gα q/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 Gpr40islets. Exogenous DAG potentiates GSIS in both WT and Gpr40 −/− islets. Oleate induces PKD phosphorylation atElectronic supplementary material The online version of this article

Isocitrate-to-SENP1 signaling amplifies insulin secretion and rescues dysfunctional β cells

“…Adenoviruses expressing GFP (Ad-GFP), Cre-IRES-GFP (Ad-Cre), and GFP-SENP1 (Ad-GFP-SENP1) were from Welgen Inc. Intact and dissociated islets were infected with recombinant viruses as previously described (66).…”

The Pancreatic β-Cell: A Bioenergetic Perspective

“…El-Azzouny et al (144) performed an exhaustive study of the bioenergetic and metabolic consequences of acute fatty acid exposure of INS-1 cells, including the use of a GPR40 antagonist, but again used a high 6:1 molar ratio. Ferdaoussi et al (152) compared islets from wild-type and Gpr40Ϫ/Ϫ mice, concluding that GPR40 was responsible for ϳ50% of the oleatemediated enhancement of second phase secretion (FIGURE 8B), but utilized a 5:1 molar ratio. It is possible that some of the uncertainty as to the mechanism mediated by the receptor results from the use of supraphysiological unbound fatty acid concentrations.…”

β-Arrestin Recruitment and Biased Agonism at Free Fatty Acid Receptor 1

“…To date, the predominant view holds that GPR40 signals primarily via the heterotrimeric G protein G q/11 and that its biological effects are mediated by downstream second messenger molecules, namely diacylglycerol and inositol 1,4,5-trisphosphate as well as Ca 2ϩ mobilization (9,10). Additionally, coupling of GPR40 to the G s /PKA/cAMP pathway has also been reported (11,12).…”