Impaired Indole Acetic Acid and Reduced Indole-Producing Bacteria Contribute to Swainsonine-Induced Liver Inflammation.

Liver inflammation could be elicited by swainsonine in livestock, affecting the development of agriculture and animal husbandry. Our previous study showed an important role of bile acids (BAs) in swainsonine-induced hepatic inflammation. However, its pathogenesis, particularly the roles of a comprehensive profile of liver and serum metabolites and microbial-derived indole metabolites, has not been clarified. This study aimed to demonstrate the mechanisms linking the indole-producing bacteria and indole metabolites to swainsonine-induced hepatic inflammation by combining Targeted 500 metabolomics and quantitative analysis of indole metabolites. Swainsonine significantly disturbed the liver and serum metabolomes in mice. Genus Akkermansia alleviating inflammation and genus Lactobacillus producing indole metabolites were significantly declined. Indole acetic acid (IAA) was the only reduced aryl hydrocarbon receptor (AHR) ligand in this study. Analogously, some bacteria causing liver damage markedly increased. These findings suggested that indole-producing bacteria and indole metabolites may be potential triggers of swainsonine-induced hepatic inflammation.