β-Sitosterol ameliorates metabolic dysfunction-associated steatohepatitis by targeting the RAC1/mTOR/TFEB axis thus...

Area of Science:

• Hepatology and metabolic diseases
• Cellular biology and signaling pathways
• Natural product pharmacology

Background:

• Metabolic dysfunction-associated steatohepatitis (MASH) is a severe liver condition driven by inflammation and lipid accumulation.
• Dysfunctional lipophagy, the process of degrading lipid droplets via lysosomes, is a key factor in MASH progression.
• Targeting the lipophagy-lysosomal pathway presents a promising therapeutic avenue for MASH.

Purpose of the Study:

• To investigate the therapeutic potential of β-Sitosterol (β-SIT) in treating MASH.
• To elucidate the underlying molecular mechanisms of β-SIT's action on the lipophagy-lysosomal pathway in MASH.
• To explore β-SIT's effects on the RAC1-mTOR-TFEB signaling axis.

Main Methods:

• Established MASH mouse models using choline-deficient, L-amino acid-defined high-fat diet (CDAHFD) or high-fat diet (HFD).
• Utilized in vitro models with FFA-stimulated AML-12 cells to mimic lipid overload.
• Employed techniques including transmission electron microscopy, multi-SIM imaging, bioinformatics, molecular dynamics, CETSA, co-immunoprecipitation, and biochemical analyses.

Main Results:

• β-SIT treatment dose-dependently alleviated MASH symptoms in vivo and in vitro by enhancing lipophagy and lysosomal function.
• β-SIT activated autophagic flux, promoted lysosomal biogenesis, and improved lysosome-lipid droplet interactions in FFA-treated cells.
• β-SIT inhibited mTOR pathway activation by directly targeting RAC1, promoting TFEB nuclear translocation and restoring lipophagy.

Conclusions:

• β-SIT demonstrates significant therapeutic potential for MASH by enhancing the lipophagy-lysosomal pathway.
• The novel mechanism involves β-SIT targeting the RAC1-mTOR-TFEB axis to repair lipophagy-lysosomal defects.
• β-SIT emerges as a promising natural compound candidate for MASH treatment.