Eph/ephrin targeting with a small molecule improves glucose tolerance in healthy and insulin-resistant mice

Introduction: The Eph/ephrin system is expressed on β-cells and EphA5 and ephrin-A5 are the most representative members on these cells. Inhibition of EphA forward signaling or activation of ephrin-A reverse signaling were shown to regulate glucose-stimulated insulin secretion (GSIS) occurring in the pancreatic islets. In particular, pharmacological blockade of EphA receptors by means of a kinase inhibitor resulted in increased GSIS. Here we tested the in vitro and in vivo efficacy of UniPR500, a new protein-protein-interaction inhibitor targeting Eph-ephrin interaction, as GSIS enhancer.. Method: The potency of UniPR500 as Eph-ephrin-interaction inhibitor was determined through ELISA binding assays and surface plasmon resonance studies (SPR). The efficacy of the compound as GSIS enhancer was assessed in vitro on EndoC-βH1 cells and its selectivity towards Eph/ephrin system was evaluated on a panel of well-known molecular targets responsible for the regulation of glucose homeostasis. Since the compound was orally bioavailable, UniPR500 was tested in vivo as hypoglycemic agent in healthy mice, in a non-genetic mouse model of insulin resistance (IR) induced by diet and in a non-genetic mouse model of type 1 diabetes (T1D) induced by diet and streptozotocin. Results: UniPR500 is a pan-Eph/ephrin-interaction antagonist inhibiting EphA5/ephrin-A5 interaction in ELISA binding assays with a Ki of 1.7microM. SPR studies further confirmed these data. Micromolar concentrations of the compound significantly increased insulin release from EndoC-βH1 cells after glucose stimulation when compared to stimulated untreated cells. When the selectivity of the compound was tested on a panel of targets responsible for metabolism regulation, including TGR5, GLP1, PPAR-γ,PTP1B, DPP IV and KATP channel, UniPR500 did not show any activity. In vivo studies showed UniPR500 30mg/kg/day os significantly improved glucose tolerance in healthy and insulin-resistant mice whereas it was inactive on a non-genetic mouse model of type 1 diabetes, where pancreatic function was severely compromised. Conclusions: Eph targeting could be a novel pharmacological strategy in the search of new hypoglycemic agents, useful in pre-diabetes conditions. Toxicological studies are warranted to complete the characterization of UniPR500.