Dietary fibre combinations modulate gut microbiome composition and metabolic responses in zebrafish, with lasting effects on intestinal barrier gene expression

In adult zebrafish (Danio rerio), combining apple pectin and cellulose (APC) yields a gut microbiome composition that is less-than-additive and more pectin-like than either fibre alone.

• Why it matters: Fibre mixtures in real diets may produce non-linear host effects across microbiome, metabolites, and barrier function, but these cross-level interactions are not well defined.
• What they did: Adult male and female zebrafish were fed diets containing apple pectin (AP), cellulose (C), or their combination (APC), and gut 16S rRNA sequencing was integrated with intestinal, brain, and liver metabolomics plus targeted qPCR after a saponin challenge.
• The result: Microbial functional predictions did not match intestinal or brain SCFA concentrations, and intestinal SCFA did not mirror brain SCFAs; after fibre cessation, qPCR suggested a potentially protective intestinal barrier response.

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