WWP1-SHARP1-C/EBPβ positive feedback loop modulates development of metabolic dysfunction-associated steatotic liver disease.

BACKGROUND & AIMS: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant global health threat. The molecular mechanisms underlying regulation of MASLD remain largely unknown. This study aimed to investigate the role of the WW domain-containing ubiquitin E3 ligase 1 (WWP1)-enhancer-of-split and hairy-related protein 1 (SHARP1)-C/EBPβ signal loop in MASLD.

METHODS

In vivo and in vitro models of MASLD were established applying high-fat diet-fed (HFD) mice and free fatty acid (FFA)-treated hepatocytes. The relationships among SHARP1, WWP1, and C/EBPβ were examined using bioinformatics, immunoprecipitation, immunofluorescence, luciferase assays, chromatin immunoprecipitation. MASLD progression was evaluated based on food intake, energy expenditure, insulin resistance, hepatic steatosis, inflammation and white fat growth.

RESULTS

SHARP1 were significantly reduced in the MASLD livers of mouse and human and in FA-treated hepatocytes. Hepatocyte-specific SHARP1 overexpression significantly inhibited MASLD development in HFD-fed mice. Wild-type SHARP1, but not deficient SHARP1 (SHARP1-K/R and SHARP1-P/A), was ubiquitinated and degraded by the E3 ligase WWP1. Wild-type SHARP1 was not ubiquitinated when WWP1 was deficient (WWP1-C886A, WWP1-C890A, WWP1-ΔWW3). Deficient SHARP1 exhibited better inhibitory activity against MASLD than the wild-type SHARP1. WWP1 overexpression reversed the suppression of MASLD induced by wild-type SHARP1 but did not affect that induced by deficient SHARP1. Deficient WWP1 did not inhibit the wild-type SHARP1-induced MASLD amelioration. Furthermore, in FA-treated hepatocytes, the interaction between SHARP1 and C/EBPβ weakened, resulting in more C/EBPβ binding to the Wwp1 promoter and subsequent WWP1 upregulation. SHARP1 overexpression or WWP1 interference partially blocked the effects of C/EBPβ on MASLD. Hesperidin was identified as a novel WWP1 inhibitor, and it significantly blocked WWP1 overexpression-induced MASLD progression.

CONCLUSION

The WWP1-SHARP1-C/EBPβ signal loop accelerates MASLD progression. This study provides novel insights into novel biomarkers and treatment approaches for MASLD.