FAM83A acts as an amplifier for lipogenic signaling to facilitate the pathogenesis of metabolic dysfunction-associated steatohepatitis.

Abstract

BACKGROUND & AIMS: Metabolic dysfunction-associated fatty liver disease (MAFLD) and its more severe manifestation, metabolic-associated steatohepatitis (MASH), are intimately linked to disturbances in lipid metabolism. Although downstream signaling pathways of epidermal growth factor receptor (EGFR), including extracellular signal-regulated kinase (ERK) and proto-oncogene serine/threonine kinase (RAF1), exhibited heightened activation during MASH progression, their specific roles and underlying mechanisms in driving MASH pathogenesis remain inadequately elucidated. METHODS: A comprehensive transcriptomic analysis was performed to indentify key genes involved in MAFLD development. Murine models with hepatocyte-specific depletion or overexpression of FAM83A were subjected to either a high-fat diet (HFD) for 8 or 14 weeks to simulate simple steatosis (MAFL) and MASH, respectively, or a choline-deficient high-fat diet (CDAHFD) to accelerate MASH progression. RESULTS: FAM83A, recognized as a downstream effector of EGFR that activates the ERK signaling pathway, was predominantly expressed in hepatoctyes and upregulated during MASH pathogenesis in both animal models and clinical patients. Hepatocyte-specific FAM83A knockout delayed MASH progression and mitigated hepatic inflammation and fibrosis. Conversely, overexpression of FAM83A exacerbated MASH pathology, evidence by increased lipid accumulation, inflammation and fibrosis. Mechanistically, insulin induces transcriptional expression of FAM83A, which physically bound to RAF1, enhancing its phosphorylation and subsequent ERK signaling activation. Furthermore, FAM83A-mediated upregulatation of lipogenic gene expression and lipogenesis was significantly inhibited by the treatment of RAF1 inhibitor sorafenib or ERK inhibitor PD98059. CONCLUSIONS: FAM83A promotes MASH pathogenesis by interacting with RAF1 to activate ERK signaling, thereby stimulating fatty acid and cholesterol biosynthesis. Targeting this axis may offer therapeutic potential for MASH and metabolic dyslipidemia.