Microbiome-metabolome responses of Fuzhuan brick tea crude polysaccharides with immune-protective benefit in cyclophosphamide-induced immunosuppressive mice

The present study investigated the immune-protective effect of polysaccharides from Fuzhuan brick tea (FBTPs) in cyclophosphamide (Cy)-induced immunosuppressive mice. The results showed that high-dose of FBTPs administration remarkably alleviated Cy-evoked immune damage through improving the body features, organ indices, immune responses and oxidative stress in the mice. Further microbiota analysis revealed that FBTPs obviously restored Cy-evoked microbial dysbiosis by increasing several beneficial bacteria Lactobacillus, Allo-baculum, Unclassified_f_Lachnospiraceae and norank_f_Lachnospiraceae, while reducing Bacteroides, norank_-f_Ruminococcaceae, Colidextribacter, Alloprevotella, norank_f_Desulfovibrionaceae and Helicobacter. Meanwhile, metabolomics analysis found that FBTPs significantly altered a range of microbial metabolites, including inosine, deoxyinosine, taurine, sinapic acid, maltotriose, butyric acid, lysophosphatidyl cholines (LysoPCs), lysophos-phatidic acids (LysoPAs) and choline. These altered metabolites were involved in purine metabolism, ABC transporters, sulfur metabolism, neuroactive ligand-receptor interaction, biosynthesis of phenylpropanoids, carbohydrate digestion and absorption, protein digestion and absorption, choline metabolism in cancer and glycerophospholipid metabolism pathways, which were mainly related to immune responses, antioxidant ca-pacity and energy supply of the immunosuppressive mice. Additionally, some significant correlations were observed between the specific microbiota and effective metabolites. These results provide a novel insight into the immune-protective effect of FBTPs on regulating the intestinal microbiota and metabolism, which are helpful for thoroughly understanding the nutrition of FBTPs and providing a solid basis for the deeper utilization of Fuzhuan brick tea (FBT).