Dietary PhIP Exposure Induces Intestinal Barrier Injury in Zebrafish Involving Proteobacteria-Associated Dysbiosis and Metabolic Remodeling

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a major heat-induced contaminant in protein-rich foods, yet its effects on intestinal barrier homeostasis and luminal microecology remain insufficiently defined. In this study, adult zebrafish were exposed to dietary PhIP for 90 days at estimated intake doses of 0.006, 0.4, and 7.2 mg/kg bw/day to evaluate intestinal injury, microbial dysbiosis, and metabolic remodeling. PhIP exposure impaired growth-related indices and induced progressive intestinal lesions, accompanied by mucus barrier depletion, reduced goblet cell abundance, and downregulation of muc2. Tight junction integrity was disrupted, as indicated by decreased zo-1, occludin, and claudin1 expression, weakened ZO-1 and Claudin-1 immunofluorescence signals, and reduced tight junction-related protein levels. Serum LPS and intestinal pro-inflammatory cytokines were markedly elevated, whereas il-10 expression was suppressed, indicating increased endotoxin burden and inflammatory activation. 16S rRNA gene sequencing revealed Proteobacteria-enriched dysbiosis and exposure-associated shifts in candidate genera, including Chitinilyticum, Shewanella, Aeromonas, Acinetobacter, Microbacterium, and Reyranella. Untargeted metabolomics further identified luminal metabolic remodeling involving lipid-related compounds, organic acids, amino acid metabolism, arachidonic acid metabolism, the citrate cycle, and pathways related to choline and glycerophospholipid metabolism. Association analysis linked genus-level microbial variation and core pathway-related metabolites with LPS, inflammatory cytokines, and tight junction markers. These findings indicate that dietary PhIP exposure disrupts intestinal barrier homeostasis in parallel with Proteobacteria-related dysbiosis and luminal metabolic remodeling, providing an integrated microbiota-metabolite-barrier association framework for evaluating intestinal risks of heat-induced food contaminants.