Oxyberberine Inhibits Hepatic Gluconeogenesis via AMPK-Mediated Suppression of FoxO1 and CRTC2 Signaling Axes.

Abstract

Oxyberberine (OBB), a natural metabolite of berberine, has been shown to exhibit inhibitory effects on gluconeogenesis in our previous work. This work was designed to investigate the potential effects and underlying mechanisms of OBB on hepatic gluconeogenesis. Our work found that OBB significantly inhibited the expressions of glucose 6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK), and decreased the glucose production in palmitic acid-induced HepG2 cells. Then, AMPK/Akt/FoxO1 and AMPK/CRTC2 signaling pathways were confirmed by transcriptomics and network pharmacology analyses. It was shown that AMPK activation may phosphorylate and promote nuclear exclusion of FoxO1 and CRTC2, two key regulators of hepatic gluconeogenesis transcriptional pathways, resulting in the inhibition of gluconeogenesis under OBB administration. Afterwards, AMPK/Akt/FoxO1, AMPK/CRTC2 signaling pathways were evidenced by western blot, immunoprecipitation and confocal immunofluorescence, and the targeted inhibitor (Compound C) and siRNA of AMPK were applied for further mechanism verification. Moreover, it was found that OBB treatment activated AMPK/Akt/FoxO1 and AMPK/CRTC2 signaling pathways to decrease hepatic gluconeogenesis in db/db mice. Similarly, the in vivo inhibitory effects of OBB on gluconeogenesis were also diminished by AMPK inhibition. Our work demonstrated that OBB can inhibit hepatic gluconeogenesis in vitro and in vivo, and its underlying mechanisms were associated with AMPK-mediated suppression of FoxO1 and CRTC2 signaling axes.