DICER1 and Alzheimer disease: Before we determine the specific changes in gut microbiome and miRNA in AD mice and patients, and to feed AD mice with a specific miRNA for a long term (≥ 2 months), we knocked out Dicer1 gene that encodes the key enzyme for miRNA production in intestinal epithelial cells and investigated the effects of Dicer1 deletion on AD-associated brain pathology in AppNL−G−F knock-in mice.