关键词: 牙龈卟啉单胞菌, 炎症性肠病, 肠道菌群, 代谢物, 苯丙氨酸

Abstract: Objective    To investigate the role of Porphyromonas gingivalis（P. gingivalis）in the onset of inflammatory bowel disease in mice and its effect on gut microbiota and metabolites. Methods    Twenty male C57BL/6 mice（6 - 8 weeks）were randomly divided into four groups（n = 5）：control group（oral gavage of PBS solution for 40 d，100 µL/d），P. gingivalis group（oral gavage of PBS suspension containing P. gingivalis for 40 d，100 µL/d），the dextran sulfate sodium（DSS）group，and P. gingivalis+DSS group. Mice in the DSS and P. gingivalis+DSS groups were administered 2% DSS in their drinking water from day 31 to day 40，following the respective treatment protocols established for the control and P. gingivalis groups. Changes in relative body weight，stool characteristics and hematochezia were monitored and the disease activity index（DAI）scores were calculated. On day 41，the mice were euthanized；colon tissues were collected for hematoxylin and eosin（HE）staining and histological activity index（HAI）evaluation. The composition, structure of gut microbiota and characteristics of metabolites in the samples of mice feces were analyzed by 16S rRNA sequencing and metabolomics techniques. Integrative multi-omics analysis was performed to assess the correlations among differential microbiota，differential metabolites，and DAI scores. Results    ①No significant phenotypic differences were observed among the groups during the initial 30 d. On day 5 of DSS treatment，mice in the P. gingivalis+DSS group developed diarrhea and hematochezia. Following DSS treatment，the relative body weight and DAI scores changed in a time-dependent manner，with significant differences observed among the groups. These inter-group differences became increasingly pronounced over time（P < 0.001）. ②Compared with the control and P. gingivalis groups，the DSS and P. gingivalis+DSS groups exhibited significantly shorter colon lengths and higher HAI scores. The HAI scores in the P. gingivalis+DSS group were significantly higher than those in the DSS group（P < 0.05）. ③Non-metric multidimensional scaling（NMDS）analysis revealed significant differences in the structure of the gut microbiota among the groups. Linear discriminant analysis effect size（LEfSe）showed that Lachnospiraceae_NK4A136_group，Muribaculaceae，and Prevotella were significantly enriched in the P. gingivalis+DSS group（P < 0.05）. Metastat heat map analysis indicated that the relative abundance of Lactobacillus was lower，whereas that of Lachnospiraceae_NK4A136_group and Muribaculaceae was higher in the P. gingivalis+DSS group（P < 0.05）. ④Untargeted metabolomics demonstrated that the relative abundances of phenylalanine，citrulline，tyrosine，histidine，and DL-aspartic acid were significantly higher in the P. gingivalis+DSS group than in the other three groups（P < 0.05）. KEGG pathway analysis revealed that amino acid metabolism was significantly enriched（P < 0.05）. ⑤Correlation analysis demonstrated that Lachnospiraceae_NK4A136_group was strongly correlated with both phenylalanine levels and DAI scores（P < 0.05）. Conclusion    The combination of P. gingivalis administration and DSS treatment alters the gut microbiota structure and metabolic profiles in mice. The concomitant increase in the relative abundances of Lachnospiraceae_NK4A136_group and phenylalanine may promote the onset and progression of inflammatory bowel disease in mice.

Key words: Porphyromonas gingivalis, inflammatory bowel disease, gut microbiota, metabolites, phenylalanines