To confirm the hypothesis that aged microbiota may have an impact on AF development, they performed FMT between old and young rats and observed that the aged microbiota transplantation enhanced intestinal permeability and increased circulating LPS, triggering atrial TLR4/NF-κB signaling and NLRP3 inflammasome assembly in atrial tissues of young individuals. This evidence concerns the gene TLR4 and atrial fibrillation.