Cholesterol-rich diet exacerbates steatohepatitis in the STAM mouse model.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a widespread chronic liver disorder spanning simple steatosis to metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis. Suitable animal models are crucial for therapeutic development, yet many fail to reproduce progression to fibrosing MASH. Here, we employed the STAM model in male C57BL/6J mice to simulate MASLD and investigated whether a high-fat, high-cholesterol (HFHC) diet would intensify disease progression compared with a standard high-fat (HF) diet. HFHC feeding in the STAM model accelerated hepatic lipid accumulation, crown-like structure formation, inflammation, and fibrosis, as demonstrated by histological analyses. Transcriptomic profiling and pathway enrichment confirmed activation of lipid and cholesterol metabolism, regulation of TNF production, and inflammatory signaling. Reactome analysis further indicated alterations in extracellular matrix formation and immune system pathways, consistent with advanced fibrotic progression. In summary, integration of HFHC feeding with the STAM model produced a more severe liver phenotype that better mirrors the pathological spectrum of MASLD. This optimized model offers a valuable platform for preclinical testing of therapeutic candidates targeting MASH and fibrosis, with potential to accelerate drug development and to improve treatment strategies for MASLD.