Diosgenin inhibits necroptosis to alleviate NAFLD by blocking the RIPK1/RIPK3/MLKL pathway.

Nonalcoholic fatty liver disease (NAFLD) is currently the most common chronic liver disease worldwide. Necroptosis is a controlled, programmed form of cell death, with its core comprising a highly conserved signaling pathway that primarily involves key proteins, including Receptor-interacting protein kinase-1 (RIPK1), RIPK3, and Mixed lineage kinase domain-like protein (MLKL). Diosgenin (DG), classified as a steroidal saponin, exhibits anti-inflammatory, immune-regulating, and lipid-lowering properties, demonstrating efficacy in ameliorating dyslipidemia across multiple metabolic pathologies. However, the exact signaling pathways involved in improving NAFLD and preventing liver damage remain unclear. In our study, the data showed that the administration of diosgenin effectively mitigated hepatic damage and excessive lipid deposition in the high-fat diet (HFD)-induced rat model. Meanwhile, it also significantly downregulates Tumor necrosis factor-α (TNF-α), Tumor necrosis factor receptor-1 (TNFR1), and Tumor necrosis factor receptor-associated death domain protein (TRADD), inhibits upstream signaling of the necroptosis pathway, and suppresses necroptosis by reducing RIPK1, RIPK3, and MLKL phosphorylation. DG decreases cell damage and inhibits the expression of necroptosis-related genes in free fatty acids (FFAs)-induced HepG2 cells, which is consistent with the results of in vivo experiments. We inhibited and overexpressed RIPK1 in vitro for further research. Inhibition of RIPK1 enhances the effect of DG on NAFLD, while overexpression of RIPK1 partially reverses its beneficial effect. In addition, to test whether DG acts independently of upstream TNF-α, we introduced exogenous recombinant TNF-α to amplify upstream signals. In conclusion, DG has a favorable reduction effect on NAFLD through the RIPK1-dependent necroptosis signaling pathway. Also, this study offers further data and a theoretical basis for the use of natural medicines to improve NAFLD.