BACKGROUND: With the increasing prevalence of sedentary lifestyles and high-fat, high-sugar diets, the incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) has continued to rise. Although the natural flavonoid compound isorhamnetin (ISO) has been shown to improve dyslipidemia in MASLD mice, its mechanism of action in regulating lipid metabolism via the gut microbiota and its metabolites remains unclear.
OBJECTIVE: This study investigates whether ISO can ameliorate high-fat diet-induced MASLD in mice in a dose-dependent manner and explores the mediating role of the gut microbiota in this process.
METHODS: Physiological monitoring, biochemical markers assessment, tissue section analysis, 16S rRNA sequencing, bile acid (BA) targeted metabolomics, and molecular analysis were performed on mouse tissues. In addition, fecal microbiota transplantation (FMT) from mice fed a high-dose of ISO further validated the regulatory role of the gut microbiota in MASLD mice. Molecular dynamics simulations and in vitro assays were performed to evaluate the interaction between ISO and FXR.
RESULTS: ISO dose-dependently reduced body weight and hepatic lipid content, inhibited lipid synthesis and promoted lipid oxidation. ISO reshaped the gut microbiota, increasing the relative abundance of Lachnospiraceae, Oscillospiraceae, and Ruminococcaceae. These changes altered the BA pool composition by increasing the proportion of primary and conjugated BAs, activated the hepatic-ileal Farnesoid X Receptor (FXR) signaling axis, accelerated enterohepatic BA circulation, and reduced dietary fat absorption. Concurrently, ISO enhanced intestinal barrier integrity and alleviated hepatic inflammation. Fecal microbiota transplantation from ISO-treated mice partially reproduced these metabolic benefits. Molecular dynamics simulations and in vitro experiments further verified that ISO interacts with FXR and consequently enhances FXR signaling.
CONCLUSION: ISO alleviates MASLD by synergistically regulating gut microbiota and FXR signaling, highlighting its potential as a mild, multi-target natural therapeutic candidate for MASLD therapy.
