MAPT and early-onset autosomal dominant Alzheimer disease: Moreover, microbiota-derived metabolic molecule trimethylamine N-oxide (TMAO, a small molecule produced by the metabolism of dietary choline) were detected in the cerebrospinal fluid of people with Alzheimer’s disease and associated with biomarkers of Alzheimer’s pathology (i.e., phosphorylated tau and phosphorylated tau/Aβ42) (Vogt et al., 2018).