OGT-enriched Hepatocyte-derived Extracellular Vesicles Promote Capillarization of Liver Sinusoidal Endothelial Cells in Metabolic Dysfunction-associated Steatotic Liver Disease.

BACKGROUND & AIMS: The global incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) has risen dramatically. The capillarization of liver sinusoidal endothelial cells (LSEC) represents a crucial target for intervention in MASLD. However, the regulatory mechanisms underlying LSEC capillarization in MASLD remain unclear. Angiopoietin-2 (Ang-2) serves as a key regulator of vascularization. METHODS: The role and molecular mechanism of lipotoxic hepatocyte-derived small extracellular vesicles (LTH-sEVs) on LSEC capillarization was assessed in both LSEC and high-fat diet (HFD)-induced MASLD mice. O-linked N-acetylglucosamine transferase (OGT) expression was assessed in serum sEV and liver samples from healthy individuals and patients with MASLD. The O-GlcNAcylation inhibitor Benzyl-α-GalNAc (BAGN) was utilized to HFD-induced MASLD mice. RESULTS: Here, we showed that LTH-sEV can upregulate the vascularization marker Ang-2 and promote LSEC capillarization in vivo and in vitro. Mechanistically, LTH-sEV may transport O-linked N-acetylglucosamine (O-GlcNAc) glycosyltransferase (OGT) to enhance the O-GlcNAc glycosylation (O-GlcNAcylation) of the hepatocyte nuclear factor 1-alpha (HNF1α) Ser471 site. This process facilitates the nuclear translocation of HNF1α and increases its transcriptional activation of Ang-2, thereby promoting the LSEC capillarization. Serum sEV derived from patients with MASLD exhibit elevated levels of OGT, which are positively correlated with alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Additionally, BAGN could dose-dependently reduce HNF1α O-GlcNAcylation, thereby alleviating LSEC capillarization and MASLD progression in HFD-induced mice. CONCLUSIONS: LTH-sEV may transport OGT to enhance HNF1α O-GlcNAcylation and activate Ang-2 expression regulated by HNF1α transcription, thus promoting LSEC capillarization. Consequently, sEV-derived OGT may serve as a novel diagnostic and therapeutic target for MASLD.