Liver B Cells Promotes MASLD Progression via the Apelin/APLNR System

<b>Aims:</b> Investigate the role of the apelin/APLNR axis in metabolic dysfunction-associated steatotic liver disease (MASLD), focusing on the progression from metabolic dysfunction-associated simple steatotic liver (MASS) to metabolic dysfunction-associated steatohepatitis (MASH) and fibrosis, with emphasis on liver B cells. <b>Methods:</b> Serum samples from MASLD patients and liver tissues from hepatocellular carcinoma patients were collected to measure apelin and APLNR protein expression. C57BL/6J mouse models of varying MASLD stages were developed using a high-fat diet and CCl₄. RNA sequencing was used to study the apelin/APLNR axis's regulatory functions in the Raji B cell line. <b>Results:</b> Bioinformatic and clinical analyses show that apelin and APLNR are up-regulated in MASLD, correlating with disease severity. Animal models demonstrate that apelin and ML221 injections affect liver steatosis, inflammation, and fibrosis. Sequencing and RT-PCR in Raji cells indicate that the apelin/APLNR axis promotes the expression of inflammatory cytokines and extracellular matrix molecules. <b>Conclusion:</b> The apelin/APLNR axis is crucial in MASLD progression. Targeting this axis may offer therapeutic potential to modulate B cell function and mitigate MASLD advancement.