title: GPR40 (FFAR1) - Combined Gs and Gq signaling in vitro is associated with robust incretin secretagogue action ex vivo and in vivo.
abstract: OBJECTIVE
  GPR40 (FFAR1), a clinically proven anti-diabetes target, is a Gq-coupled receptor for long chain fatty acids (LCFA) stimulating insulin secretion directly and mediating a major part of the dietary triglyceride-induced secretion of the incretins GLP-1 and GIP. In phase-II studies the GPR40 agonist TAK-875 decreased blood glucose but surprisingly without stimulating incretins.
  
  
  RESULTS
  Here we find that GPR40 can signal through not only Gq and IP3 but also Gs and cAMP when stimulated with certain agonists such as AM-1638 and AM-5262 in contrast to the endogenous LCFA ligands and agonists such as TAK-875 and AM-837, which only signal through Gq. In competition binding against [3H]AM-1638 and [3H]L358 the Gq + Gs and the Gq-only agonists either competed for or showed positive cooperativity by increasing the binding of the two different radio-ligands, in opposite ways. Nevertheless, both the Gq-only and the Gq + Gs agonists all docked surprisingly well into the binding site for TAK-875 in the X-ray structure of GPR40. In murine intestinal primary cell-cultures the endogenous LCFAs and the Gq-only agonists stimulated GLP-1 secretion with rather poor efficacy as compared with the high efficacy Gq + Gs GPR40 agonists and a prototype GPR119 agonist. Similarly, in fasting both male and female mice the Gq + Gs agonists showed significantly higher efficacy than the Gq-only agonists in respect of increasing plasma GLP-1 and plasma GIP in a GPR40-dependent manner.
  
  
  CONCLUSIONS
  It is concluded that stimulation of GPR40 by endogenous LCFAs or by Gq-only synthetic agonists result in a rather limited incretin response, whereas Gq + Gs GPR40 agonists stimulate incretin secretion robustly.
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark.
authors: Maria
authors: M
authors: Hauge
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark.
authors: Marie A
authors: MA
authors: Vestmar
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Anna S
authors: AS
authors: Husted
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Jeppe P
authors: JP
authors: Ekberg
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Michael J
authors: MJ
authors: Wright
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Jerry
authors: J
authors: Di Salvo
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Adam B
authors: AB
authors: Weinglass
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Maja S
authors: MS
authors: Engelstoft
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Andreas N
authors: AN
authors: Madsen
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Michael
authors: M
authors: Lückmann
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Michael W
authors: MW
authors: Miller
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Maria E
authors: ME
authors: Trujillo
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark.
authors: Thomas M
authors: TM
authors: Frimurer
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark.
authors: Birgitte
authors: B
authors: Holst
authors: Merck Research Laboratories, Kenilworth, NJ, 07033, USA.
authors: Andrew D
authors: AD
authors: Howard
authors: Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen, 2200 Copenhagen N, Denmark ; Department of Neuroscience and Pharmacology, University of Copenhagen, DK-2200, Copenhagen, Denmark.
authors: Thue W
authors: TW
authors: Schwartz
keywords: Ago-allosteric agonist; Biased signaling; G protein-coupled receptor; Glucagon like peptide 1 (GLP-1); Long chain fatty acids (LCFAs)