There is growing evidence that NADPH oxidase 4 (Nox4) in hepatocytes contributes to liver inflammation and fibrosis during the development of metabolic dysfunction-associated steatohepatitis (MASH). However, how Nox4 is regulated and leads to liver pathogenesis is unclear. Our previous studies showed that the cytosolic protein SH3 domain-containing Ysc84-like 1 (SH3YL1) regulates Nox4 activity. Here, we asked whether SH3YL1 also participates in liver inflammation and fibrosis during MASH development. We generated that whole body SH3YL1 knockout (SH3YL1