R-spondin 2 suppresses hepatic steatosis via activation of AMPK-ACC signaling

Metabolic dysfunction-associated steatotic liver disease (MASLD) primarily results from dysregulated lipid metabolism in hepatocytes. However, the mechanisms governing hepatic lipid metabolism remain incompletely understood. Our preliminary experiments demonstrated elevated expression of R-spondin 2 (RSPO2), a matricellular protein, in steatotic livers. Therefore, we investigated the role of RSPO2 in MASLD and potential underlying mechanisms.

Comprehensive in vivo and in vitro studies were performed to investigate the role of RSPO2 in steatosis. Unbiased transcriptomic analyses of hepatic RNA samples were conducted to identify RSPO2-regulated signaling pathways. To examine the in vivo role of Rspo2, both hepatocyte-specific Rspo2-deficient mice and AAV-mediated Rspo2 overexpression were utilized.

RSPO2 expression was significantly increased in steatotic livers of high-fat diet-fed wild-type (p <0.01) and Western diet-fed Apoe ^-/- mice (p <0.001). Similar results were observed with human steatotic liver tissues (p <0.01). Hepatocyte-specific deletion of Rspo2 in floxed mice, achieved either via postnatal TBG-Cre-AAV injection or embryonic Alb-Cre breeding, exacerbated diet-induced hepatic steatosis and fibrosis, suggesting that RSPO2 has protective effects against MASLD. Conversely, AAV-mediated Rspo2 overexpression in mice reduced hepatic lipid deposition (p <0.01) and decreased hepatic triglyceride and non-esterified fatty acid levels after high-rich diet feeding. Furthermore, Rspo2 overexpression suppressed hepatic fibrosis (p <0.01) and macrophage accumulation. Mechanistic studies using RNA sequencing and other techniques revealed improved lipid metabolism, increased AMPK-ACC signaling, reduced inflammation, and attenuated apoptosis in the liver with Rspo2 overexpression. In vitro experiments further demonstrated the anti-steatotic effects of recombinant RSPO2 treatment in hepatocytes.

These findings identify RSPO2 as a key suppressor of hepatic steatosis and fibrosis, and highlight its potential as a therapeutic target for MASLD.

Given the hepatic/extrahepatic complications associated with MASLD (metabolic dysfunction-associated steatotic liver disease) and its high prevalence, it is crucial to decipher the precise molecular mechanisms regulating its pathogenesis to identify novel druggable targets. In this study, we demonstrate for the first time that hepatocyte RSPO2 plays a protective role against hepatic steatosis, fibrosis, and inflammation. Rspo2 overexpression improves lipid metabolism, enhances AMPK-ACC signaling, and reduces hepatocyte apoptosis. Therefore, targeting RSPO2 in hepatocytes may represent a promising strategy to suppress MASLD.