Glycyrrhizic acid mitigates hepatocyte steatosis and inflammation through ACE2 stabilization via dual modulation of AMPK activation and MDM2 inhibition

As a hepatoprotective phytochemical derived from Glycyrrhiza species, glycyrrhizic acid (GA) exhibits unique dual-target therapeutic efficacy against metabolic-driven hepatic steatosis and inflammation. Building upon our previous finding that GA-mediated amelioration of murine steatohepatitis is closely associated with restoration of hepatic ACE2/Ang (1–7)/Mas axis signaling, this study was designed to identify the role of hepatocyte ACE2 both in vitro and in vivo, and mechanistically decipher how GA reprograms ACE2 signaling. We found that GA treatment mitigated steatosis and inflammation in LPS/free fatty acid-stimulated hepatocytes. GA reversed the downregulation of ACE2 and Mas protein expression, while it suppressed the overexpression of Ang II and sterol regulatory element-binding protein 1c proteins. Notably, the ACE2 gene silencing abolished the beneficial effects. Furthermore, GA not only reversed the downregulation of ACE2 Y781 and phosphorylated AMPKα protein levels, but also inhibited the overexpression of total and phosphorylated MDM2 proteins in both the livers of LPS/D-galactosamine-induced steatohepatitic mice and in LPS/free fatty acid-stimulated hepatocytes. The GA-induced recovery of downregulated ACE2 protein expression in hepatocytes was abolished by either the AMPKα gene silencing or MDM2 overexpression. Therefore, this study first identifies GA as an agent that ameliorates hepatocyte steatosis and inflammation through the ACE2-dependent pathway. Further, our results demonstrate that GA regulates ACE2 by targeting AMPK and MDM2. We propose that GA stabilizes ACE2 via both AMPK-mediated phosphorylation and MDM2-mediated ubiquitination. Our findings offer new insights into the molecular mechanisms underlying the hepatoprotective effects of GA.