Antiallergic drug Mebhydrolin ameliorates glucose homeostasis in type 2 diabetic mice by functioning as a selective FXR antagonist.

INTRODUCTION Type 2 diabetes mellitus (T2DM) is a chronic disease with hallmarks of hyperglycemia and hyperlipidemia. Long-term hyperglycemia damages the functions of multiple tissues and organs leading to a series of complications and disability or even death. Nuclear receptor farnesoid X receptor (FXR) antagonism has been recently discovered to exhibit beneficial effect on glucose metabolism in T2DM mice, although the underlying mechanisms remain unclear. Here, we performed the study on the discovery of new FXR antagonist and investigated the mechanism underlying the amelioration of FXR antagonism on glucose homeostasis in T2DM mice by using the determined FXR antagonist as a probe. METHODS FXR antagonist Mebhydrolin was discovered by screening against the lab in-house FDA approved drug library through surface plasmon resonance (SPR), microscale thermophoresis (MST), Alphascreen, mammalian one-hybrid and transactivation assays. Activity of Mebhydrolin in improving glucose homeostasis was evaluated in db/db and HFD/STZ-induced T2DM mice, and the mechanisms governing the regulation of Mebhydrolin were investigated by assays of immunostaining, western blot, ELISA, RT-PCR against liver tissues of both T2DM mice and the T2DM mice with liver-specific FXR knockdown injected via adeno-associated-virus AAV-FXR-RNAi and mouse primary hepatocytes. Finally, molecular docking and molecular dynamics (MD) technology-based study was performed to investigate the structural basis for the antagonistic regulation of Mebhydrolin against FXR at an atomic level. FINDINGS Mebhydrolin ameliorated blood glucose homeostasis in T2DM mice by both suppressing hepatic gluconeogenesis via FXR/miR-22-3p/PI3K/AKT/FoxO1 pathway and promoting glycogen synthesis through FXR/miR-22-3p/PI3K/AKT/GSK3β pathway. Structurally, residues L291, M332 and Y373 of FXR were required for Mebhydrolin binding to FXR-LBD, and Mebhydrolin induced H2 and H6 shifting of FXR potently affecting the regulation of the downstream target genes. CONCLUSIONS Our work has revealed a novel mode for the regulation of FXR against glucose metabolism in T2DM mice and highlighted the potential of Mebhydrolin in the treatment of T2DM.