Arhgap25 Promotes Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) by Driving Kupffer Cell Polarization via Activation of the AKT/mTOR Signaling Pathway

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a leading global health burden, yet the regulatory nodes linking hepatic immune dysregulation to metabolic perturbations remain incompletely understood. Methods: We integrated bulk and single-cell RNA sequencing (scRNA-seq) to identify core regulatory genes dysregulated by a high-fat diet (HFD). The functional role of the candidate gene Arhgap25, was validated using an adeno-associated virus (AAV)-mediated overexpression mouse model and an in vitro Kupffer cell (KC)-hepatocyte co-culture system. Results: Integrated transcriptomic analysis identified Arhgap25 as a key differentially expressed gene consistently upregulated in HFD-fed livers, with specific enrichment in KCs. In vivo, Arhgap25 overexpression significantly promoted macrovesicular steatosis, increased intrahepatic triglycerides and cholesterol levels, and exacerbated liver injury. Mechanistically, Arhgap25 triggered a pro-inflammatory microenvironment by promoting KC polarization toward the M1 phenotype, characterized by increased TNF-α, IL-6, and IL-1β expression and suppression of the M2 marker ARG1. In vitro co-culture assays demonstrated that Arhgap25 exacerbated hepatocellular lipid accumulation and inflammatory responses by promoting the phosphorylation of the AKT/mTOR signaling axis. AKT inhibition further confirmed this signaling dependency. Conclusion: Our findings establish Arhgap25 as a critical mediator in the hepatic immune-metabolic network. By positively regulating AKT/mTOR signaling in KCs, Arhgap25 promotes M1 polarization and subsequent metabolic dysfunction, highlighting it as a potential therapeutic target for MASLD.