Lacto-N-triose II alleviates metabolic dysfunction-associated Steatotic liver disease via microbiota-dependent citrulline biosynthesis.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly recognized global metabolic disease with limited treatment options. Lacto-N-Triose II (LNT II) is an important member of the human milk oligosaccharides (HMOs) and exhibits various prebiotic properties beyond infant nutrition. In this study, we demonstrate that supplementation with probiotic Kluyveromyces lactis-derived LNT II significantly ameliorates the progression of high-fat diet (HFD)-induced MASLD in mice, as evidenced by reduced body weight gain, decreased blood lipid levels, attenuated inflammatory responses, and improved hepatic steatosis. Furthermore, integrated multi-omics analysis of MASLD mice reveals that LNT II treatment enhances the gut microbiota-dependent glutamine-citrulline synthesis pathway. Among them, the key metabolite citrulline is closely associated with improving insulin resistance, reducing systemic inflammation, and alleviating MASLD. The subsequent population cohort analyses of mild-severe MASLD patients revealed a significant correlation between serum citrulline levels and the progression of MASLD, thereby reinforcing its candidacy as a noninvasive diagnostic biomarker.