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Trichinella spiralis is recognized for its ability to regulate host immune responses. The serine protease inhibitor of T. spiralis (Ts-SPI) participates in T. spiralis-mediated immunoregulatory effects. Studies have shown that helminth therapy exhibits therapeutic effects on metabolic diseases. In addition, we previously found that T. spiralis-derived crude antigens could alleviate diet-induced obesity. Thus, Ts-SPI was hypothesized to alleviate non-alcoholic fatty liver disease (NAFLD). Herein, recombinant Ts-SPI (rTs-SPI) was prepared from the muscle larvae T. spiralis. The relative molecular mass of rTs-SPI was approximately 35,000 Da, and western blot analysis indicated good immunoreactivity. rTs-SPI ameliorated hepatic steatosis, inflammation, and pyroptosis in NAFLD mice, which validated the hypothesis. rTs-SPI also reduced macrophage infiltration, significantly expanded Foxp3+ Treg population, and inactivated TLR4/NF-κB/NLRP3 signaling in the liver. Furthermore, rTs-SPI treatment significantly shifted the gut microbiome structure, with a remarkable increase in beneficial bacteria and reduction in harmful bacteria to improve gut barrier integrity. Finally, Abx-treated mice and FMT confirmed that gut-liver crosstalk contributed to NAFLD improvement after rTs-SPI treatment. Taken together, Taken together, these findings suggest that rTs-SPI exerts therapeutic effects in NAFLD via anti-inflammatory activity and gut–liver crosstalk.

Enzyme-assisted ultrasonic extraction (EAUE) was utilized and optimized for extracting polysaccharides from Schizochytrium limacinum meal (SLMPs) via the response surface methodology. The optimal EAUE conditions were determined as follows: enzyme concentration at 5.18%, ultrasonic temperature at 53 °C, ultrasonic duration of 40 min, ultrasonic power at 60 W, and a liquid-to-material ratio of 34 mL/g, achieving a polysaccharide extraction yield of 11.86 ± 0.61%. The purified polysaccharide component, SLMP1-1, isolated using DEAE Sepharose Fast Flow and Sephadex G-100 columns, exhibited potent antioxidant activity. SLMP1-1, with a molecular weight of 25.5 kDa, comprises glucose, mannose, arabinose, and galactose in a molar ratio of 16.39:14.75:1:693.03. 1H NMR analysis revealed the α configuration of SLMP1-1. Antioxidant assessments, including DPPH, ABTS, and ferric ion reduction assays, were detected with inhibitory values at 21.82–82.98%, 38.21–98.46%, and 3.30–20.30% at 0.2–1.0 mg/mL. This confirmed the effective antioxidant capacity of SLMP1-1, which is notably enhanced post oral and gastric digestion. The findings suggest that polysaccharides extracted from Schizochytrium limacinum meal hold significant promise as natural antioxidants.