APOE and Alzheimer disease: Of note, as the most prevalent genetic risk gene for AD, apolipoprotein E (ApoE)‐mediated neuroinflammation is involved in tau‐mediated neurodegeneration, and ApoE genotype is associated with differences in the abundance of several gut bacterial taxa, particularly the butyrate‐producing gut microbiota, which may drive differences in the metabolite levels of the gut microbiota.173, 174