γ-HYDROXY LACTONE BASED PPARγ NON-AGONISTS AS SAFE AND INNOVATIVE ANTI-DIABETIC AGENTS.

Peroxisome proliferator-activated receptor γ (PPARγ) represents a key target for the treatment of type 2 diabetes and metabolic syndrome. PPARγ takes part in the control of many cellular functions and pathways related to the regulation of fatty acid metabolism and glucose homeostasis. To avoid the serious adverse effects related to the PPARγ agonism profile of traditional antidiabetic drugs, a new opportunity is represented by the development of molecules acting as inhibitors of PPARγ phosphorylation by the cyclin-dependent kinase 5 (CDK5). Their mechanism of action is mediated by the stabilization of the PPARγ β-sheet containing Ser245. We performed a biological screening, through Surface Plasmon Resonance (SPR), of an in-house library of synthetic γ-hydroxy-lactone derivatives, among which 4-(4-bromophenyl)-3-hydroxy-5-(3-hydroxyphenyl)furan-2(5H)-one (1) emerged as a promising candidate. The library was screened for the ability to prevent PPARγ phosphorylation by CDK5 given the structural similarity with BLI, a natural product, isolated from Aspergillus terreus, reported in literature as both PPARγ partial agonist and CDK5 inhibitor. Compound 1, endowed with a promising Kd of 3.75 μM, showed also an effective inhibition of CDK5-mediated phosphorylation of PPARγ in vitro by a kinase assay. The agonist and antagonist activities on PPARy, and the direct inhibition on CDK5 were dismissed by assays that validated the non-agonist profile of our compound. We deeply investigated the interaction mode of 1 with PPARγ, by performing crystallographic experiments. The co-crystal structure of 1-PPARy showed that the compound occupies the canonical partial agonist hydrophobic binding region between the helix 3 (H3) and β-sheets of the PPARγ LBD (PDB: 8ADF). These data were used in the computational studies for the design of optimized derivatives of 1. Overall, this study represents the starting point for the development of novel anti-diabetic drugs based on γ-hydroxy-lactone scaffold, effective for the treatment of diabetes, but without adverse effects.