Background: Understanding the function of FFA2 has been slowed by a lack of selective orthosteric ligands.Results: Residues within FFA2 that dictate the recognition and function of potent and selective orthosteric agonists are described.Conclusion: Key aspects of ligand interaction with the orthosteric binding pocket of FFA2 are defined.Significance: This work will be invaluable in future drug development at the FFA2 receptor.

The free fatty acid 1 receptor (FFA1 or GPR40), which is highly expressed on pancreatic β-cells and amplifies glucose-stimulated insulin secretion, has emerged as an attractive target for the treatment of type 2 diabetes. Several FFA1 agonists containing the para-substituted dihydrocinnamic acid moiety are known. We here present a structure-activity relationship study of this compound family suggesting that the central methyleneoxy linker is preferable for the smaller compounds, whereas the central methyleneamine linker gives higher potency to the larger compounds. The study resulted in the discovery of the potent and selective full FFA1 agonist TUG-469 (29).

The role of free fatty acid receptor 1 (FFAR1/GPR40) in glucose homeostasis is still incompletely understood. Small receptor agonists stimulating insulin secretion are undergoing investigation for the treatment of type 2 diabetes. Surprisingly, genome-wide association studies did not discover diabetes risk variants in FFAR1. We reevaluated the role of FFAR1 in insulin secretion using a specific agonist, FFAR1-knockout mice and human islets. Nondiabetic individuals were metabolically phenotyped and genotyped. In vitro experiments indicated that palmitate and a specific FFAR1 agonist, TUG-469, stimulate glucose-induced insulin secretion through FFAR1. The proapoptotic effect of chronic exposure of β-cells to palmitate was independent of FFAR1. TUG-469 was protective, whereas inhibition of FFAR1 promoted apoptosis. In accordance with the proapoptotic effect of palmitate, in vivo cross-sectional observations demonstrated a negative association between fasting free fatty acids (NEFAs) and insulin secretion. Because NEFAs stimulate secretion through FFAR1, we examined the interaction of genetic variation in FFAR1 with NEFA and insulin secretion. The inverse association of NEFA and secretion was modulated by rs1573611 and became steeper for carriers of the minor allele. In conclusion, FFAR1 agonists support β-cell function, but variation in FFAR1 influences NEFA effects on insulin secretion and therefore could affect therapeutic efficacy of FFAR1 agonists.

The free fatty acid receptor 1 (FFA1, also known as GPR40) enhances glucose-stimulated insulin secretion from pancreatic β-cells and is recognized as an interesting new target for treatment of type 2 diabetes. Several series of selective FFA1 agonists are already known. Most of these are derived from free fatty acids (FFAs) or glitazones and are relatively lipophilic. Aiming for the development of potent, selective, and less lipophilic FFA1 agonists, the terminal phenyl of a known compound series was replaced by nitrogen containing heterocycles. This resulted in the identification of 37, a selective FFA1 agonist with potent activity on recombinant human FFA1 receptors and on the rat insulinoma cell line INS-1E, optimal lipophilicity, and excellent in vitro permeability and metabolic stability.

A protocol for amide coupling by in situ formation of acyl fluorides and reaction with amines at elevated temperature has been developed and found to be efficient for coupling of sterically hindered substrates and electron deficient amines where standard methods failed.