Lithium carbonate alleviates colon inflammation through modulating gut microbiota and Treg cells in a GPR43-dependent manner

Background: Recent evidence suggests that neuropsychiatric stabilizers have a place in resolving gastrointestinal disorders. Lithium carbonate (LC) is one of the most commonly used drugs for bipolar disorder clinically. Here, we estimate the therapeutic function of LC against colitis and investigate the mechanism of intestinal flora and metabolism modulation. Methods: A colitis model was constructed by continuously administering 2.5% dextran sodium sulfate (DSS) solution daily for 7 days. Analysis of gut microbiota was carried out by 16S rRNA gene high-throughput sequencing. Spectrum antibiotic cocktail (ABX) and faecal microbiota transplantation (FMT) were employed to evaluate the protective effect of intestinal flora. Colonic Treg cells and related immune responses were detected by flow cytometry. Results: LC treatment significantly alleviated colon inflammation by regulating gut microbial diversity and altering flora composition. Notably, LC treatment upregulated short-chain fatty acid (SCFA)-producing bacteria, especially Akkermansia muciniphila (A. muciniphila), and transformed metabolite SCFA profiles. LC activated antiinflammatory Treg cell responses in colonic lamina propria (LP) in a G-protein coupled receptor 43 (GPR43)dependent mechanism. ABX, FMT and single bacteria gavage experiments were conducted to confirm the above mechanism. Conclusions: As an intestinal microbiome and metabolite modulator, LC alleviates colon inflammation in a GPR43-dependent manner through activating Treg cell responses. Therefore, the therapeutic strategy of the microbiome-metabolite-immune axis, as observed in the A. muciniphila-SCFA-Treg cell axis in our study, might provide a new direction for the treatment of IBD.