Ovarian tumor domain-containing protein 1 deficiency attenuates metabolic dysfunction-associated steatotic liver disease by promoting the ubiquitination of HSP90α in hepatocytes.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is the most prevalent chronic liver disease worldwide, yet approved pharmacotherapies remain limited. The ovarian tumor domain-containing protein 1 (OTUD1) has been implicated in metabolic regulation, but its role in MASLD remains unclear. OTUD1 expression was significantly elevated in liver samples from patients with MASLD and in high-fat diet (HFD)-fed mice, a finding further supported by two independent Gene Expression Omnibus (GEO) cohorts (GSE24807 and GSE126848). Studies using systemic Otud1-knockout mice showed that Otud1 deficiency markedly alleviated insulin resistance and inflammation under HFD and high-fat, methionine-restricted, choline-deficient (HFMCD) diet conditions. To assess the hepatocyte-specific and therapeutic relevance of OTUD1, Otud1 was silenced in hepatocytes using AAV8-TBG-shOtud1, which significantly ameliorated HFMCD-induced steatohepatitis. Mechanistically, integrated interactome analyses identified heat shock protein 90α (HSP90α) as a direct substrate of OTUD1. OTUD1 bound to HSP90α and removed its K48-linked polyubiquitin chains at K283, thereby preventing its proteasomal degradation and enhancing its stability. This effect was required for OTUD1-driven lipid accumulation in hepatocytes, as the catalytically inactive OTUD1-C320S mutant failed to stabilize HSP90α or promote lipid deposition. Transcriptomic profiling further revealed that OTUD1 overexpression activated lipid metabolism and inflammatory pathways in OA/PA-treated LO2 cells. Together, these findings identify OTUD1 as a previously unrecognized driver of MASLD progression through the OTUD1-HSP90α axis and suggest that OTUD1 may serve as a potential therapeutic target for metabolic liver disease.