Recombinant Ostreolysin Promotes the Browning of Preadipocytes by Inhibiting the Expression of Genes Associated With the Hedgehog Signaling Pathway in <i>db/db</i> Mice

Nonalcoholic steatohepatitis (NASH), a highly prevalent metabolic-related fatty liver disease, has become a major global health issue with limited therapeutic options. Recent studies indicated that ostreolysin (Oly), a protein derived from oyster mushrooms, could be a potential therapeutic agent for NASH. In this study, recombinant Oly (rOly) was expressed in E. coli BL21 (DE3) and purified using Q Sepharose and TOYOPEARL chromatography, with its identity confirmed by SDS-PAGE and mass spectrometry. Indb/db mice, subcutaneous injection of rOly at 0.5 and 1 mg/kg every 2 days for 30 days significantly reduced body weight by 14.1% in the high-dose group (p < 0.01), improved insulin resistance (insulin resistance index decreased by 35%, p < 0.05), and alleviated hepatic steatosis as shown by HE and Oil Red O staining.In vitro, rOly induced browning of 3T3-L1 preadipocytes, evidenced by 1.8-fold upregulation of UCP1 (p < 0.05) and 2.3-fold upregulation of ATGL (p < 0.01). Mechanistic studies revealed that rOly inhibited Hedgehog signaling pathway genes Gli1 and Ptch1 by 70% and 65% (p < 0.0001), respectively, promoting beige adipocyte differentiation. These findings demonstrate that rOly enhances energy metabolism by promoting preadipocyte browning via Hedgehog pathway inhibition, providing a promising basis for treating obesity and metabolic diseases.