Asiatic Acid Alleviates Ulcerative Colitis Through a Gut Microbiota-Driven cAMP/PKA/NF-κB Pathway: γ-Glutamyltyrosine Is a Crucial Player.

Abstract

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon, characterized by recurrent flare-ups and limited effectiveness of available drug therapies. Asiatic acid (AA), a triterpenoid compound extracted from Centella asiatica, has shown promising pharmacological activities and therapeutic potential in several inflammation-related diseases. However, AA's efficacy in treating UC and its precise mechanisms of action remain to be fully explored. This study aimed to provide a comprehensive assessment of AA's therapeutic effects on UC and to investigate its underlying mechanisms, with a focus on gut microbiota interactions. In our study, a dextran sulfate sodium-induced UC mouse model was used to evaluate AA's therapeutic potential and explore its impact on gut microbiota composition and function. We further used an antibiotic cocktail and fecal microbiota transplantation assays to substantiate the role of gut microbiota in AA's mechanisms of action. A metabolomic analysis was also conducted to identify key metabolic pathways and gut microbiota-derived metabolites involved in AA's effects. Our findings demonstrated that AA significantly alleviates symptoms of UC, including reducing weight loss, slowing disease progression, mitigating colonic inflammation, and restoring immune balance. Mechanistically, the beneficial effects of AA were strongly linked to alterations in the gut microbiota and its metabolites, particularly γ-glutamyltyrosine. This metabolite was found to regulate the cyclic adenosine monophosphate/protein kinase A/nuclear factor kappa-B signaling pathway, which plays a crucial role in inflammatory responses. Overall, these findings strongly suggest that AA holds promise as a therapeutic agent for UC by modulating the gut microbiota and influencing critical inflammatory pathways.