The Effect of Fentanyl Abuse on the Gut Microbiota Pattern, Inflammation, and Metabolic Alterations in a Fentanyl Dependance Rat Model

<b>Introduction:</b> This study examines the effects of fentanyl misuse on gut microbiota, inflammation, and metabolic pathways using a rat model. As the opioid crisis, driven by synthetic opioids like fentanyl, escalates, identifying new biomarkers, and therapeutic strategies becomes crucial to mitigate its negative impacts and rising overdose cases. <b>Methods:</b> This study was done using species-specific 16S rRNA gene profiling through absolute real-time PCR techniques, alongside relative real-time PCR analysis for inflammatory and metabolic markers and liquid chromatography-mass spectrometry (LC-MS) for metabolite quantification. To visualize the correlations between microbial abundance and inflammatory/metabolic markers, Spearman/Pearson correlation analyses were performed. <b>Results:</b> Fentanyl treatment increased <i>Clostridium sensu stricto</i> (<i>p</i>=0.69) and <i>Bacteroides fragilis</i> (<i>p</i>=0.04), while <i>Faecalibacterium prausnitzii</i> (<i>p</i>=0.14) and <i>Lacticaseibacillus rhamnosus</i> (<i>p</i>=0.14) showed a tendency to decrease. Additionally, fentanyl-treated rats exhibited heightened levels of pro-inflammatory cytokines (<i>IL-1β</i>, <i>p</i>=0.01; <i>TNF-α</i>, <i>p</i>=0.083; <i>IL-6</i>, <i>p</i>=0.17) and increased expression of toll-like receptors (<i>TLR-2</i>, <i>p</i>=0.005; <i>TLR-4</i>, <i>p</i>=0.001), indicating intestinal inflammation. Metabolic pathway analysis revealed significant alterations, including increased <i>BCoAT</i> expression (<i>p</i> < 0.001) and decreased <i>tph1</i> expression (<i>p</i> < 0.001) in fentanyl-treated rats. LC-MS analysis indicated a significant reduction in butyrate levels (45.49 ± 7.82; 73.52 ± 5.4 µM; <i>p</i> < 0.001), suggesting impaired short-chain fatty acid production and potential gut barrier integrity issues. Tryptophan levels were also significantly lower (14.96 ± 1.3; 22.38 ± 2.1 µM; <i>p</i> < 0.001), indicating possible disruptions in serotonin synthesis, while deoxycholic acid levels increased (106.1 ± 7.3; 77.35 ± 3.5 µM; <i>p</i> < 0.001), suggesting altered bile acid metabolism contributing to gut inflammation. Leucine levels (31.8 ± 1.5; 30.67 ± 1.6 µM; <i>p</i>=0.15) remained comparable between groups. <b>Conclusion:</b> This study reveals complex relationships between fentanyl consumption, gut microbiota alterations, gut inflammation, and metabolic functions. The identified changes in specific bacterial species and inflammatory markers suggest a potential mechanism by which fentanyl may exacerbate gut inflammation and disrupt metabolic pathways, highlighting the importance of these dynamics in understanding the microbiota importance and opioid dependance.