NPAS2 Promotes MASLD and Hepatocarcinogenesis through SIRT1-Mediated PPARγ Suppression

Abstract Emerging evidence suggests a link between circadian disruption and metabolic dysfunction-associated steatotic liver disease (MASLD), although the precise mechanisms are not yet fully understood. As a central circadian regulator, the role of NPAS2 in the pathogenesis and progression of MASLD to hepatocellular carcinoma (HCC) is not well characterized. This study aimed to clarify the functional and mechanistic contributions of NPAS2 to the development of MASLD and the progression to HCC. Analysis of clinical liver biopsies and high-fat diet (HFD)-fed murine models consistently demonstrated significant upregulation of NPAS2 in MASLD, at both mRNA and protein levels. In vitro, free fatty acid (FFA)-treated LO2 hepatocytes with NPAS2 knockdown showed attenuated lipid accumulation and inflammatory responses, whereas NPAS2 overexpression exacerbated steatotic phenotypes. In hepatocyte-specific NPAS2 knockout mice subjected to HFD, we observed comprehensive metabolic improvement including reduced hepatic steatosis, improved insulin sensitivity, attenuated endoplasmic reticulum stress, and suppressed pro-fibrotic signaling. Mechanistically, NPAS2 was found to transcriptionally activate SIRT1 by directly binding to an E-box motif in its promoter region. SIRT1 subsequently deacetylated PPARγ, leading to its destabilization and functional suppression. The clinical relevance of this axis was underscored by strong correlations between NPAS2 expression and both SIRT1 (positive) and PPARγ (negative) in human MASLD specimens. Furthermore, in a diethylnitrosamine (DEN)-induced HCC model coupled with HFD feeding, NPAS2 deficiency conferred remarkable protection against tumor development. Conversely, NPAS2 overexpression accelerated hepatocarcinogenesis. Critically, pharmacological PPARγ activation by pioglitazone rescued NPAS2-driven metabolic dysfunction in vitro.Our study reveals NPAS2 as a critical node connecting circadian dysfunction to MASLD-HCC progression and identifies the NPAS2-SIRT1-PPARγ axis as a therapeutic target. These findings provide a rationale for chronotherapeutic strategies to disrupt this pathogenic cascade, offering new hope for combating MASLD-related complications.