Inflammatory bowel disease (IBD) is a chronic, inflammatory, and autoimmune disorder. The pathogenesis of IBD is not yet clear. Studies have shown that the imbalance between T helper 17 (Th17) and regulatory T (Treg) cells, which differentiate from CD4 ⁺ T cells, contributes to IBD. Th17 cells promote tissue inflammation, and Treg cells suppress autoimmunity in IBD. Therefore, Th17/Treg cell balance is crucial. Some regulatory factors affecting the production and maintenance of these cells are also important for the proper regulation of the Th17/Treg balance; these factors include T cell receptor (TCR) signaling, costimulatory signals, cytokine signaling, bile acid metabolites, and the intestinal microbiota. This article focuses on our understanding of the function and role of the balance between Th17/Treg cells in IBD and these regulatory factors and their clinical significance in IBD.

Gut microbiota (GM) dysbiosis and bile acid (BA) metabolism disorder play an important role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Probiotics had a beneficial effect on NAFLD, but further study is needed to explore probiotics as a potential therapeutic agent to NAFLD. The aim of this study was to investigate the regulatory effect of probiotics on gut microbiota in NAFLD rats and to explore the possible mechanism of probiotics regulating the bile acid receptor farnesoid X receptor/growth factor 15 (FXR/FGF15) signaling pathway in rats. We established a rat model of NAFLD fed with a high-fat diet (HFD) for 14 weeks, which was given different interventions (312mg/kg/day probiotics or 10mg/kg/day atorvastatin) from the 7^th week. Serum lipids and total bile acids (TBA) were biochemically determined; hepatic steatosis and lipid accumulation were evaluated with HE staining. The expression levels of FXR, FGF15 mRNA, and protein in rat liver were detected. 16S rDNA was used to detect the changes of gut microbiota in rats. Compared with the HFD group, probiotics and atorvastatin significantly reduced serum lipids and TBA levels. And probiotics increased dramatically the expression of FXR, FGF15 mRNA, and protein in the liver. But there were no significant changes in the atorvastatin group. Probiotics and atorvastatin can upregulate the diversity of gut microbiota and downregulate the abundance of pathogenic bacteria in NAFLD model rats. In summary, probiotics alleviated NAFLD in HFD rats via the gut microbiota/FXR/FGF15 signaling pathway.

Our previous studies found that Pure total flavnoids from citrus (PTFC) can effectively improve non-alcoholic steatohepatitis (NASH) in mice. Here, we discuss on the mechanism of PTFC in treating NASH with focus on the regulation of the gut microbiota and bile acid metabolism. C57BL/6 J mice were randomly divided into three groups: normal diet group (Normal), high-fat diet group (HFD) and high-fat + PTFC treatment group (PTFC). Mice in the Normal group were fed chow diet, while the other groups were fed high fat diet (HFD) for 16 weeks. In the 5th week, the mice in the PTFC group were treated with 50 mg/kg/day PTFC for an additional twelve weeks. After sacrifice, histopathology of the liver was assessed, and the gut microbial composition was analyzed by 16S rDNA gene sequencing. Bile Acid profiles in serum were determined by ultraperformance liquid chromatography (UPLC-MS/MS). PTFC intervention significantly attenuated HFD-induced NASH symptoms compared with the HFD group in mice. 16S rDNA sequencing showed that PTFC treatment increased the phylogenetic diversity of the HFD-induced microbiota dysbiosis. PTFC intervention significantly increased the relative abundances of Bacteroidaceae and Christensenellaceae. Furthermore, PTFC reduced the content of toxic bile acids, such as TDCA, DCA, TCA, CA and increased the ratio of secondary to primary bile acids. FXR and TGR5 deficiency were significantly alleviated. PTFC can improve NASH via the the gut microbiota and bile acid metabolism.

Shenqi pill (SQP), a famous traditional Chinese medicine (TCM) herbal formula derived from Jinguiyaolue (Synopsis of Prescriptions of the Golden Chamber), has long been used to treat kidney yang deficiency syndrome. According to the TCM treatment principle that the liver and kidney are homologies, the clinical use of SQP in the treatment of nonalcoholic steatohepatitis (NASH) has achieved a good effect. However, the active targeted genes and underlying mechanism remain unclear. In this study, we aimed to explore the treatment mechanism of SQP in NASH rats, which may further contribute to the in-depth exploration of SQP in clinical applications. Network pharmacology analysis was used to screen the target genes of SQP for NASH treatment based on public databases. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and proteinprotein interaction (PPI) analysis were used to search for crucial target genes and mechanisms. UPLCMS/MS was used to verify the active compounds of the SQP screened. The hepatic pathology and biochemical indicators of rats were used to judge the modeling results and the curative effect of SQP. Western blotting and qRTPCR were used to verify the expression of crucial target genes at the protein and RNA levels, respectively. Network pharmacology analysis and bioinformatics analysis showed that PTGS2, JUN, MYC, and CDKN1A might be crucial target genes in the primary mechanism of SQP in treating NASH and improving the inflammatory response. The UPLCMS/MS results confirmed that the hub active compound, quercetin, screened out through the TCMSP database, is indeed present in SQP. Hepatic injury and lipid metabolism indicators of NASH rats were significantly improved after SQP treatment. The results of WB and qRTPCR showed that the expression of PTGS2, JUN, MYC, and CDKN1A was higher in NASH rats than in normal rats and decreased after SQP treatment. The expression of inflammatory cytokines (IL-1β, IL-6, TNF-α) was reduced after SQP treatment, which confirmed that SQP could improve hepatic inflammation in rats. These results suggested that SQP could ameliorate NASH in rats, and that quercetin may be the critical active compound that exerts the therapeutic effect.