The typical pharmacophore for GPR agonists
The typical pharmacophore for GPR40 agonists contains four parts: head (acid moiety), central (phenyl ring), linker and tail (aromatic carbocyclic or heterocyclic ring) . On the other hand, the chemical features that are required for the PPARγ agonists include hydrogen bond donors and acceptors (HBD and HBA), aliphatic and aromatic hydrophobic groups (Hbic), positive and negative ionizable groups (PosIon and NegIon) and aromatic planes (RingArom) . I t is worth mentioning that both GPR40 and PPARγ have very similar pharmacophoric features . Interestingly, it has been reported that some PPARγ agonists activate GPR40 . In consequence, GPR40 and PPARγ may work together as an integrated two-receptor signal transduction pathway . The aim of this current research was to obtain evidence for the development of new dual PPARγ-GPR40 agonists based on similar properties in pharmacophore structure.
Materials and methods
Discussion In this work, we have designed compounds based on two similar pharmacophoric patterns, which would be a promise against diabetes due to a proposed dual mechanism of action. We expand the idea that retaining the features of two pharmacophoric groups in the newly designed entities we can provide or keep the original biological activity which could be an interesting strategy for further investigations in multifactorial diseases . Unlike all the other single drugs, multi-target compounds can simultaneously modulate two, three or multiple pharmacological targets . The herein compounds retain the moieties such as hydrogen bond donor and acceptor (carboxylic acid), aromatic group (benzene), and hydrophobic tail (benzimidazole) , . Although the designed compounds are relatively simple structures, the fragments and size supply the sufficient stability to maintain the interactions with both Bay 11-7085 from two targets, GPR40 and PPARγ. Interestingly, the carboxylic moiety is the most important group to give interactions at least with one residue of both binding pockets and the rest of the parts give stability and show additional contacts mainly by hydrophobic contacts. Compound 1 exhibited a relevant activity in the in vitro assay, which demonstrates the highest score, displaying expression levels of PPARγ and GLUT4 increased 7-times and 2-fold the GPR40. Regarding the in vivo antihyperglycemic effect, prodrug of compound 1 did not show hypoglycemic effect in this model, in comparison with the hypoglycemic action exhibited by glibenclamide  and it was confirmed by an oral glucose test. Then, its effect allows a low insulin release and it shows an alternative pathway to a common insulin secretagogue , ,  and it could be associated with partial activation of GPR40 or possibly to potassium channel blockage due to the similarity of molecular structure between both drugs (Fig. 5): fasiglifam (GPR40 agonist) and glibenclamide (ATP-sensitive potassium channel blocker). Therefore, these new compounds might block potassium channels too. On the other hand, although the compound 2 did not show GPR40 expression, it has the potential to become a GPR40 ligand because it induces insulin secretion and increases the calcium concentration. However, it is necessary to raise the affinity and the interactions through the enhancement of the molecular structure. Despite the increment of insulin secretion and calcium mobilization, there exists the possibility of an alternative mechanism owing their similarity to glibenclamide that also increases the expression of GPR40 (a new pharmacological finding associated with glibenclamide, Fig. 1C). Based on these findings and an excellent pharmacological profile, glibenclamide may serve as a lead structure for the development of new dual PPARγ-GPR40 ligands because it shares fragments with the typical pharmacophore for GPR40 and PPARγ agonists , . Compound 3 (prodrug of 1) showed a good in vivo antihyperglycemic effect due to insulin secretion through calcium mobilization. We decided to give an orally administered prodrug, because they achieve increased lipophilicity, increased duration of pharmacological effects, increased site-specificity or decreased toxicity and adverse reactions , . Last, according to the docking models, compound 1 may bind to the active site of both receptors in the same mode due to a similar pharmacophore structure. The activity profile exhibited for this compound makes a suitable pattern in the development of single entities with properties of dual PPARγ-GPR40 agonists.