Morphine-induced dysbiosis and metabolic remodeling of the gut microbiota is transmissible via fecal microbiota transplantation in mice.

OBJECTIVE: Opioids such as morphine are widely used analgesics but are highly addictive. Emerging evidence implicates the gut microbiota in modulating opioid-associated pathophysiology. However, the global metabolic impact of morphine on gut microbial function and the causal transmissibility of morphine-induced dysbiosis remain to be fully elucidated. METHODS: Adult C57BL/6 mice received repeated morphine administration for four consecutive days. Fecal metabolomic profiling was performed using integrated gas chromatography-mass spectrometry (GC/MS) and liquid chromatography-mass spectrometry (LC/MS) platforms. Gut microbial composition was analyzed by 16S rRNA gene sequencing and terminal restriction fragment length polymorphism (T-RFLP) profiling. To determine causality and transmissibility, fecal microbiota transplantation (FMT) was conducted from morphine-treated donor mice into antibiotic-depleted recipient mice. RESULTS: Repeated morphine administration induced a profound global reprogramming of fecal metabolic profiles, with clear separation between morphine-treated and control mice. A total of 179 fecal metabolites were annotated. Morphine significantly increased diethylene glycol, N-acetyl-L-glutamic acid, and urea, while decreasing 3-aminoisobutyric acid, 2-aminobutyric acid, and pseudouridine. Pathway enrichment analysis revealed that amino acid-centered metabolic pathways, including branched-chain amino acid biosynthesis, arginine biosynthesis, and aminoacyl-tRNA biosynthesis, were the most prominently disrupted. Morphine exposure also induced a distinct dysbiotic microbial signature characterized by expansion of Enterococcus faecalis and Alistipes indistinctus, and depletion of Prevotella melaninogenica. Importantly, FMT from morphine-treated donors into microbiota-depleted recipients successfully transferred both the dysbiotic microbial structure and metabolic phenotype. Post-transplant recipient mice exhibited microbial profiles closely resembling morphine-treated donors, demonstrating that the morphine-induced dysbiosis is transmissible in the short term in the absence of direct drug exposure. CONCLUSION: Repeated acute morphine exposure alters fecal amino acid and nitrogen metabolism and drives a transmissible dysbiotic state in the short term. These findings highlight a potential association between morphine exposure, metabolic remodeling, and gut dysbiosis, suggesting the gut microbiota may be a relevant factor in opioid-associated intestinal interactions.