Host-derived chitinase orchestrates gut-liver dialogue to improve growth and immunity in dark sleeper (Odontobutis potamophila)

Exogenous chitinase has potential to improve growth performance and health in aquatic species, but the underlying mechanisms remain incompletely understood. This study investigated the effects of graded doses of recombinant Odontobutis potamophila chitinase (OpCht) in O. potamophila fed a high-chitin diet for 8 weeks. Results demonstrated dose-dependent improvements in growth performance and hepatointestinal health. Gut metagenomics showed enrichment of orders Chitinophagales and Flavobacteriales and increased abundance of chitin-related CAZyme families (e.g., GH18 and GH19), together with functional shifts involving lipid metabolism and immune-related pathways. Liver transcriptomics revealed that medium/high-dose OpCht significantly enhanced lipid transport genes ( fxr , angptl4 , apoa ) and immune effectors ( c3 , il-10r ). Crucially, correlation analyses identified significant correlations between specific microbiota and host genes: Flavobacteriales abundance positively correlated with the hepatic lipid regulator angptl4 , while Chitinophagales abundance correlated with the bile acid receptor fxr . These findings suggest that OpCht may both facilitate dietary chitin breakdown and remodel gut microbiome functionality, which is associated with enhanced chitin utilization and metabolite generation, thereby supporting a putative gut-liver axis contributing to improved host physiological functions. • OpCht altered gut microbiota structure, enriching GH18 and GH19 families. • OpCht activated key lipid and immune pathways in the liver. • OpCht improved hepatointestinal health through the gut-liver axis.