MAPT and Alzheimer disease: Accumulation of Ab plaques outside neurons of AD subjects has been shown to stimulate the release of inflammatory mediators by the microglia and astrocytes, thus generating neuroinflammation [46]. Moreover, it has been reported that trimethylamine N-oxide (TNMO), a microbiota-derived metabolite found in higher concentrations in the cerebrospinal fluid of MCI and AD patients, promotes the assembly of hyperphosphorylated tau, a protein that makes up the neurofibrillary tangles inside the neurons of AD subjects [47].