IDO1 and metabolic dysfunction-associated steatohepatitis: Similarly, YCH exerts therapeutic effects via decreasing Bacteroides_vulgatus abundance and Palmitoleic acid[41]. Critically, our study reveals that YCHZX not only restores Lachnospiraceae_NK4A136_group—a genus commonly depleted in human and experimental NASH [42, 43]—but also functionally couples this enrichment to the suppression of colonic IDO1, thereby redirecting tryptophan metabolism from the kynurenine pathway toward ILA generation.