ObjectiveThe significance of the liver-microbiome axis has been increasingly recognised as a major modulator of autoimmunity. The aim of this study was to take advantage of a large well-defined corticosteroids treatment-naïve group of patients with autoimmune hepatitis (AIH) to rigorously characterise gut dysbiosis compared with healthy controls.DesignWe performed a cross-sectional study of individuals with AIH (n=91) and matched healthy controls (n=98) by 16S rRNA gene sequencing. An independent cohort of 28 patients and 34 controls was analysed to validate the results. All the patients were collected before corticosteroids therapy.ResultsThe gut microbiome of steroid treatment-naïve AIH was characterised with lower alpha-diversity (Shannon and observed operational taxonomic units, both p<0.01) and distinct overall microbial composition compared with healthy controls (p=0.002). Depletion of obligate anaerobes and expansion of potential pathobionts including Veillonella were associated with disease status. Of note, Veillonella dispar, the most strongly disease-associated taxa (p=8.85E–8), positively correlated with serum level of aspartate aminotransferase and liver inflammation. Furthermore, the combination of four patients with AIH-associated genera distinguished AIH from controls with an area under curves of approximately 0.8 in both exploration and validation cohorts. In addition, multiple predicted functional modules were altered in the AIH gut microbiome, including lipopolysaccharide biosynthesis as well as metabolism of amino acids that can be processed by bacteria to produce immunomodulatory metabolites.ConclusionOur study establishes compositional and functional alterations of gut microbiome in AIH and suggests the potential for using gut microbiota as non-invasive biomarkers to assess disease activity.

Mucosal-associated invariant T (MAIT) cells, a novel population of innate-like lymphocytes, have been involved in various inflammatory and autoimmune diseases. However, their role in the development of nonalcoholic fatty liver disease (NAFLD) remains unclear. In this study, we investigated the alterations of phenotype and immunological function of MAIT cells in NAFLD. Analysis of PBMCs in 60 patients with NAFLD and 48 healthy controls (HC) revealed that circulating MAIT cell frequency decreased in NAFLD, especially in the patients with higher serum levels of γ-glutamyl transferase or total triglyceride. Functional alterations of circulating MAIT cells were also detected in NAFLD patients, such as the increased production of IL-4 whereas the decreased production of IFN-γ and TNF-α. Furthermore, elevated expression of CXCR6 was observed in circulating MAIT cells of patients. Meanwhile, we found an increased number of MAIT cells in the livers of NAFLD, and the number was even greater in patients with higher NAFLD activity score. Moreover, activated MAIT cells induced monocytes/macrophages differentiation into M2 phenotype in vitro. Additionally, MAIT cells were enriched and displayed Th2 type cytokines profile in livers of wild type mice fed with methionine and choline deficient diet (MCD). Notably, mice deficient of MAIT cells exhibited more severe hepatic steatosis and inflammation upon MCD, accompanied with more CD11c+ proinflammatory macrophages (M1) and less CD206+ anti-inflammatory macrophages (M2) in livers. Our results indicate that MAIT cells protect against inflammation in NAFLD through producing regulatory cytokines and inducing anti-inflammatory macrophage polarization, which may provide novel therapeutic strategies for NAFLD.

ObjectiveMultiple clinical similarities exist between IgG4-related sclerosing cholangitis (IgG4-SC) and primary sclerosing cholangitis (PSC), and while gut dysbiosis has been extensively studied in PSC, the role of the gut microbiota in IgG4-SC remains unknown. Herein, we aimed to evaluate alterations of the gut microbiome and metabolome in IgG4-SC and PSC.DesignWe performed 16S rRNA gene amplicon sequencing of faecal samples from 135 subjects with IgG4-SC (n=34), PSC (n=37) and healthy controls (n=64). A subset of the samples (31 IgG4-SC, 37 PSC and 45 controls) also underwent untargeted metabolomic profiling.ResultsCompared with controls, reduced alpha-diversity and shifted microbial community were observed in IgG4-SC and PSC. These changes were accompanied by differences in stool metabolomes. Importantly, despite some common variations in the microbiota composition and metabolic activity, integrative analyses identified distinct host–microbe associations in IgG4-SC and PSC. The disease-associated genera and metabolites tended to associate with the transaminases in IgG4-SC. Notable depletion of Blautia and elevated succinic acid may underlie hepatic inflammation in IgG4-SC. In comparison, potential links between the microbial or metabolic signatures and cholestatic parameters were detected in PSC. Particularly, concordant decrease of Eubacterium and microbiota-derived metabolites, including secondary bile acids, implicated novel host–microbial metabolic pathways involving cholestasis of PSC. Interestingly, the predictive models based on metabolites were more effective in discriminating disease status than those based on microbes.ConclusionsOur data reveal that IgG4-SC and PSC possess divergent host–microbe interplays that may be involved in disease pathogenesis. These data emphasise the uniqueness of IgG4-SC.