Dietary Isorhamnetin Alleviates Alcoholic Liver Injury in Mice by Regulating Gut Microbiota via the Gut-Liver Axis

Background: Alcoholic liver disease (ALD) refers to a progressive liver injury syndrome induced by chronic excessive alcohol intake. Current treatment options are mainly limited to symptom management, and there are safety risks associated with long-term use. Hence, there is an urgent demand to discover new therapeutic targets and investigate natural active substances. Isorhamnetin (IS) is an O-methylated flavonoid, and its specific structure confers unique biological activities and relatively good oral bioavailability, making it a potential natural candidate for the prevention of metabolic liver diseases. However, few studies have explored the application and action mechanism of IS in the intervention of alcoholic liver injury and intestinal flora imbalance. Methods: This work established a mouse model of chronic alcoholic liver injury to evaluate the beneficial effects of IS on hepatic injury, oxidative stress, and intestinal flora disturbance. Results: The results showed that IS intervention therapy can alleviate the symptoms of increased liver index, ALT, AST, TC, and TG levels due to alcohol intake. Furthermore, IS can alleviate liver oxidative stress caused by alcohol consumption, thereby protecting the liver of mice. Intestinal analysis in mice revealed that IS elevated the expression of tight junction proteins ZO-1 and Claudin-1, thereby attenuating alcohol-induced intestinal hyperpermeability and LPS translocation. This further suppressed the activation of the hepatic LPS/TLR4 signaling pathway and decreased the production of TNF-α and IL-1β. Meanwhile, IS significantly improved the intestinal flora disorder induced by alcohol in a dose-dependent manner. Compared with the EtOH group, IS treatment, particularly at the high dose (EISH), significantly increased the Ace, Chao1, Shannon, and Simpson indices. Conclusions: Consistently, NMDS analysis based on the OTU level showed that the IS-treated groups clustered away from the EtOH group and shifted toward the Control group, indicating a partial restoration of the overall microbial community structure toward that of healthy controls. In terms of species composition, IS treatment enriched beneficial microbial communities and inhibited the proliferation of pathogenic bacteria, efficiently restoring intestinal flora homeostasis. Collectively, these findings suggested that the hepatoprotective effects of IS were closely associated with the amelioration of gut microbiota dysbiosis and intestinal barrier function, pointing to a potential involvement of the gut-liver axis, although its causal contribution remains to be confirmed by further mechanistic studies (e.g., microbiota depletion or fecal microbiota transplantation). The findings not only provide new scientific evidence for the hepatoprotective effects of isorhamnetin but also offer a preliminary theoretical basis for the development of natural products potentially targeting the gut-liver axis.