Synthesis and Biological Evaluation of a New Dihydroceramide Desaturase Inhibitor for the Treatment of MASLD.

Ceramides and dihydroceramides are associated with obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD). Despite their pathogenic relevance, effective strategies to reduce ceramide levels remain lacking. Delta-tocotrienol (δ-TT) derivatives have been reported as weak inhibitors of dihydroceramide desaturase-1 (DEGS1), a key enzyme in ceramide biosynthesis. Here, we screened a library of δ-TT derivatives and identified GAA-4OH as a potent and irreversible inhibitor of DEGS1. In vitro, GAA-4OH exhibited nanomolar activity, surpassing existing compounds such as fenretinide. Kinetic assays and molecular docking simulations suggest that GAA-4OH may undergo oxidation to form a reactive iminoquinone that covalently blocks the enzyme catalytic cavity. In vivo, GAA-4OH administration in a mouse model of MASLD reduced ceramide-to-dihydroceramide ratios and improved steatosis, inflammation, and fibrosis. These benefits occurred without body weight loss and were correlated with reduced pro-inflammatory and pro-fibrogenic gene expression, without signs of toxicity, supporting its safety and potential as a therapeutic for MASLD.