Roles of Activin A and Gpnmb in Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD).

Metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as nonalcoholic fatty liver disease [NAFLD]) and metabolic dysfunction-associated steatohepatitis (MASH, formerly known as nonalcoholic steatohepatitis [NASH]) are leading chronic liver diseases, driving cirrhosis, hepatocellular carcinoma, and mortality. MASLD/MASH is associated with increased senescence proteins, including Activin A, and senolytics have been proposed as a therapeutic approach. To test the role of Activin A, we induced hepatic expression of Activin A in a murine MASLD/MASH model. Surprisingly, overexpression of hepatic Activin A dramatically mitigated MASLD, reducing liver steatosis and inflammation as well as systemic fat accumulation, while improving insulin sensitivity. Further studies identified a dramatic decrease in the lipid-associated macrophages marker glycoprotein NMB (Gpnmb) by Activin A, and Gpnmb knockdown in the same model produced similar benefits and transcriptional changes to Activin A expression. These studies reveal a surprising protective role for Activin A in MASLD and the potential for SASP proteins to have context-specific beneficial effects. Moreover, they implicate both Activin A and Gpnmb as potential therapeutic targets for this condition. Article Highlights: Cellular senescence may promote metabolic dysfunction-associated steatotic liver disease/ metabolic dysfunction-associated steatohepatitis (MASLD/MASH), leading to chronic liver diseases associated with obesity and metabolic disease with no approved medical treatment. Circulating Activin A, a senescence-associated secretory phenotype (SASP) protein, increases in MASLD/MASH patients. Surprisingly, hepatic Activin A overexpression or Gpnmb knockdown dramatically mitigated MASLD phenotypes and fat accumulation, SASP gene expression, and dysglycemia, underscoring the need for nuanced understanding of SASP biology. Hepatic Activin A overexpression dramatically decreased liver Gpnmb, a lipid-associated macrophage upregulated in MASLD, and Gpnmb knockdown produced similar benefits and transcriptional changes to Activin A overexpression, identifying Gpnmb as a tractable potential therapeutic target. [ABSTRACT FROM AUTHOR]