NPAS2 promotes MASLD and hepatocarcinogenesis through SIRT1-mediated PPARγ suppression

Abstract

Emerging evidence links circadian disruption to metabolic dysfunction-associated steatotic liver disease (MASLD), but the underlying mechanisms remain elusive. NPAS2, a core circadian regulator, has an undefined role in the pathogenesis of MASLD and its progression to hepatocellular carcinoma (HCC). This study aimed to elucidate the functional contribution of NPAS2 in these processes. In clinical liver biopsies and high-fat diet (HFD)-fed murine models, NPAS2 expression was consistently upregulated at both mRNA and protein levels. In vitro, NPAS2 knockdown in free fatty acid (FFA)-treated hepatocytes attenuated lipid accumulation and inflammatory responses, whereas NPAS2 overexpression exacerbated steatotic phenotypes. Hepatocyte-specific NPAS2 knockout mice on HFD exhibited comprehensive metabolic improvements, including reduced hepatic steatosis, enhanced insulin sensitivity, attenuated endoplasmic reticulum stress, and suppressed pro-fibrotic signaling. Mechanistically, NPAS2 transcriptionally activated SIRT1 by directly binding to an E-box motif in its promoter region. SIRT1 subsequently deacetylated PPARγ, leading to its destabilization and functional suppression. Furthermore, in a diethylnitrosamine (DEN)-induced HCC model combined with HFD feeding, NPAS2 deficiency conferred marked protection against tumor development, whereas NPAS2 overexpression accelerated hepatocarcinogenesis. The clinical relevance of this axis was supported by strong correlations between NPAS2 expression and SIRT1 (positive) and PPARγ (negative) in human MASLD-HCC specimens. Critically, pharmacological PPARγ activation with pioglitazone rescued NPAS2-driven metabolic dysfunction in vitro. Collectively, this study identifies NPAS2 as a critical link between circadian dysfunction and MASLD-HCC progression, and establishes the NPAS2–SIRT1–PPARγ axis as a therapeutic target. These findings support chronotherapeutic strategies aimed at disrupting this pathogenic cascade to combat MASLD-related complications.