Tannic acid decreased the synthesis and secretion of sIgA in the small intestine of Brandt's voles (Lasiopodomys brandtii) by modifying gut microbiota.

Tannic acid (TA), a representative plant secondary metabolite, impairs intestinal immune function and alters intestinal microbiota abundance of Brandt's voles. Whether TA reduces intestinal immune function by modifying the gut microbiota remains unknown. In this study, Brandt's voles were divided into three groups for microbiota transplantation (FMT): normal saline (Ab), microbiota from normal saline administration (R-Con), and microbiota from TA administration (R-TA). Then, the intestinal morphology, immune indices, gut flora, and microbiota metabolites were measured after FMT. The findings showed that the sIgA content of small intestine of voles in the R-TA group were lower than in the R-con group. Additionally, the voles in the R-con group exhibited higher mRNA levels of PIgR, J-chain, BAFF, and APRIL than in the R-TA group. The ANOSIM results showed significant structural differentiation, reflecting that the β-diversity of the cecal microbiome was altered. Moreover, the voles in the R-con group had a higher concentration of butyric acid in the cecum compared to both the Ab and R-TA groups. In the experiment 2, the sIgA content in the duodenum and ileum of Brandt's voles in the TBA group (1200 mg•kg-1d-1 TA + butyrate) was significantly higher than that in the TNS group (1200 mg•kg-1d-1 TA + normal saline). To summarize, the "TA microbiota" decreased the slgA secretion and synthesis in the small intestine by reducing butyric acid content, thus lowering the intestinal immune capacity of Brandt's voles. The findings provide the experimental basis to prove the critical role of gut microorganisms in controlling animal physiological processes.