## 4 Discussion
Next, control group, model group and combination group were selected to investigate the effect of intestinal microbial diversity and composition on liver damage reduction. Liver health was closely associated with the homeostasis of gut microbiota [20]. We speculated that 21 days of continuous oral administration of EGCG and LPP101 could regulate gut microbiota beforehand and allow the mice to cope with liver damage caused by CCl4 better. As a result, the unweighted pair-group method with arithmetic means (UPGMA) and principal coordinates analysis (PCoA) showed that the microbial composition was altered in the combination group and deviated from the control group and model group (Figure 4A-B). A previous study indicated that CCl4 (twice a week for six weeks) induced liver fibrosis, as well as disruption of the gut microbiota in mice [21]. In this study, an acute injection of CCl4 did not induce strong gut microbiological changes (Figures 4-6), possibly due to the short exposure time. Although there were differences in gut microbiota between the control and model group or between the control and combination group, the differences were far less than that between the model and combination group (Figure 5), indicating the effect of EGCG and LPP101 in regulating gut microbiota. Similarly, tea and probiotics play a role in regulating gut microbiota in a previous study [22; 23]. Specifically, at the phylum level, the relative abundance of Bacteroidetes was decreased, while firmicutes and proteobacteria increased in the combination group (Figure 4C-D). Similar to our results, in [PERSON] et al. 's study [24], _Lactiplantiobacillus plantarum_ TW1-1 increased the abundance of firmicutes and alleviated testicular damage of mice. LEFSe (Figure 5) was used to show the specific bacteria with statistical differences between groups. The combination of EGCG and LPP101 were given in advance, which mainly increased the abundance of _Akkermansia_ at the phylum of Verrucomicrobia, and _Desulfovibrionaceae_ at the phylum of Proteobacteria. _Akkermansia_ is a typical probiotic, and its reduction is positively correlated with intestinal inflammation and liver disease [25]. Studies have found that _Desulfovibrionaceae_ produces acetic acid and regulates metabolic diseases [26]. Furthermore, we listed some species that changed significantly, associated with the pathogenesis (Figure 6A). _Alloprerotella_, _Prevotellaceae UCG-001_ and _Bacteroides_ was associated with irritable bowel syndrome and promote inflammation [27; 28; 29]. _Alistipes_ is an opportunistic pathogen, and _uncultured bacterium Muribaculaceae_ was associated with liver failure [30; 31; 32]. EGCG combined with L.P.P101 reduced the abundance of these bacteria as shown in Figure 5A. _Blautia_, _Ruminicostridium 9_ and _Roseburia_, which produce butyrate and benefit human health [33; 34], were decreased in the model group, while their relative abundance in the combination group was even higher than that in the control group (Figure 6A). [PERSON] et al. found that butyrate reduced ROS-mediated hepatocyte apoptosis [35]. There was no significant difference in the relative abundance of _Lactohacillus_ and _Akkermansia_ between the control group and the model group, but the combination of EGCG and LPP101 significantly increased the abundance of these two probiotics (Figure 6A). Correspondingly, [PERSON]'s correlation analysis also showed that the liver health was associated with gut microbiota (Figure 6C). [PERSON] et al. [36] demonstrated that non-extractable and indigestible dietary polyphenol were fermented into small molecules by colon microbiota. These small molecules of nutrients could persist in circulation, and had effects of antioxidant and anti-inflammatory. Similarly, _Ruminococcus_ and _Faecalibacterium_ fermented non-digestible carbohydrates to produce short-chain fatty acids, and then inhibited the activation of _NF-kb_ and reduced inflammatory damage [37], which was similar to our study.