Costunolide Ameliorates Hepatic Steatosis and Insulin Resistance in a Diet-Induced Mouse Model of Metabolic Dysfunction-Associated Steatotic Liver Disease by Activating the AMPK/ACC1 Signalling Pathway

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects over a quarter of the global adult population and is the primary cause of liver diseases worldwide. Costunolide (COS) is a sesquiterpene lactone that exhibits a range of biological activities and has significant hepatoprotective effects. However, the regulatory effects of COS on hepatic lipid metabolism and its potential molecular mechanisms remain poorly understood. This study aimed to examine the effects of COS on MASLD and to elucidate the underlying molecular mechanisms. The therapeutic effects of COS were assessed using a mouse model, fed a high-fat/high-fructose/high-cholesterol diet (HFHFrC) and primary hepatocytes treated with palmitic acid (PA) and oleic acid (OA). RNA Sequencing (RNA-seq), quantitative PCR and western blotting were performed to explore the molecular mechanisms by which COS modulates hepatic lipid metabolism. Our findings indicated that COS effectively reduced lipid accumulation in the livers of mice fed a HFHFrC diet and lowered triglyceride (TG) content in hepatocytes induced by PA/OA. RNA-seq analysis, along with in vitro and in vivo experiments, demonstrated that COS activated ACC1 phosphorylation by promoting AMPK phosphorylation and inhibiting the expression of genes related to lipid synthesis. Co-treatment with the AMPK Inhibitor, compound C abolished the lipid-lowering effect of COS. COS reduced the expression of genes related to lipid synthesis through the AMPK/ACC1 signalling pathway, thereby improving liver function, alleviating excessive lipid accumulation and ameliorating MASLD in both in vitro and in vivo models.