Select microbial metabolites promote tau aggregation in a murine tauopathy model.

The gut microbiome is emerging as a modifier of risk for neurodegenerative diseases, but underlying mechanisms remain poorly understood. Here, we show that the hTau.P301S mouse model for progressive tauopathy develops alterations in the composition and function of the gut microbiome that are not recapitulated in amyloid-based 5xFAD or 3xTg models for Alzheimer's disease. Disrupting the gut microbiome via chronic antibiotic treatment exacerbates cognitive deficits and tau pathology in hTau.P301S mice, demonstrating a causal influence of the microbiome on tau-driven disease progression. This corresponds with widespread alterations in microbiome-dependent metabolites in the sera and brains of hTau.P301S mice, including subsets that correlate with the severity of tau pathology. By screening against tau biosensor cells, we identify select microbial metabolites-trimethylamine-N-oxide, 3-indoxyl sulfate, phenol sulfate, thymidine, and 2'deoxyuridine-that promote tau seeding and aggregation. Systemic administration of these metabolites worsens cognitive impairment and tau pathology in hTau.P301S mice. These findings establish a mechanistic link between the gut microbiome, serum and brain metabolites, as well as tau aggregation, suggesting that select microbial metabolites could potentially serve as therapeutic targets for tau-driven diseases.