trans-Cinnamic acid alleviates high-fat diet induced hepatic steatosis by activating AMPK-mTOR pathway

trans-Cinnamic acid (CA), a bioactive compound from cinnamon bark, exhibits well-known pharmacological properties; however, its effects and underlying mechanisms in hepatic steatosis (HS) remain elusive. Therefore, this study aims to evaluate the protective efficacy of CA and elucidate the molecular pathways by which it alleviates HS. To achieve this, a combination of in vitro cellular assays and in vivo zebrafish models was employed. Comprehensive methodologies, including histological analysis, RNA-sequencing, western blotting, targeted metabolomics, molecular docking, cellular thermal shift assays, and microscale thermophoresis, were utilized to explore how CA influences lipid metabolism. Phenotypic evaluations revealed that CA treatment significantly reduced lipid accumulation in the liver and aorta of juvenile zebrafish, while simultaneously alleviating hepatic lipid deposition, tissue damage, and fibrosis in adult models. Mechanistically, CA suppressed the expression and activity of key lipogenic genes, including SREBP1, PPARg, and FAS. Furthermore, CA reprogrammed energy metabolism to drive futile thermogenesis via the activation of the AMPK signaling pathway. Additionally, the administration of CA promoted lipid droplet (LD) autophagy through the modulation of the AMPK-mTOR signaling axis. Crucially, biophysical analyses identified the AMPKα as a direct cellular target of CA, with specific binding occurring at the Arg133 and His134 residues within its kinase domain. Subsequent inhibition of AMPK pathway using Compound C successfully abolished the protective effects conferred by CA. Collectively, these findings demonstrate that CA alleviates HS by directly targeting and activating AMPKα and modulating the AMPK-mTOR-regulated lipophagy and energy metabolism pathways, highlighting its potential as a therapeutic candidate for HS.