Abstract
Aging is associated with declines in cognitive performance, which are mediated in part by neuroinflammation, characterized by astrocyte activation and higher levels of pro-inflammatory cytokines; however, the upstream drivers are unknown. We investigated the potential role of the gut microbiome–derived metabolite trimethylamine N-oxide (TMAO) in modulating neuroinflammation and cognitive function with aging. Study 1: In middle-aged and older humans (65 ± 7 years), plasma TMAO levels were inversely related to performance on NIH Toolbox Cognition Battery tests of memory and fluid cognition (both r2 = 0.07, p < 0.05). Study 2: In mice, TMAO concentrations in plasma and the brain increased in parallel with aging (r2 = 0.60), suggesting TMAO crosses the blood-brain barrier. The greater TMAO concentrations in old mice (27 months) were associated with higher brain pro-inflammatory cytokines and markers of astrocyte activation vs. young adult mice (6 months). Study 3: To determine if TMAO independently induces an “aging-like” decline in cognitive function, young mice (6 months) were supplemented with TMAO in chow for 6 months. Compared with controls, TMAO-supplemented mice performed worse on the novel object recognition test, indicating impaired memory and learning, and had increased neuroinflammation and markers of astrocyte activation. Study 4: Human astrocytes cultured with TMAO vs. control media exhibited changes in cellular morphology and protein markers consistent with astrocyte activation, indicating TMAO directly acts on these cells. Our results provide translational insight into a novel pathway that modulates neuroinflammation and cognitive function with aging, and suggest that TMAO might be a promising target for prevention of neuroinflammation and cognitive decline with aging.
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Data availability
All data will be made freely available upon reasonable request to the corresponding author.
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Acknowledgments
The authors would like to sincerely thank Brian Ziemba, James Richey, Danijel Djukovic, Lauren Cuevas, Christopher J. Angiletta, Laura E. Griffin, and Patrick K. Gonzales for their assistance with the data collection and analysis.
Funding
This work was supported by the National Institutes of Health awards R01 HL143887 (D.R.S.), F32 HL140875 (V.E.B.), and R01 NS063964 (C.D.L.); Administrative Supplement to NS063964 (T.J.L.) and Colorado CTSA UL1 TR002535; and the Hatch Program of the National Institute of Food and Agriculture, US Department of Agriculture (A.P.N.).
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V.E.B., T.J.L., C.D.L., and D.R.S. conceived and designed the experiments. V.E.B., T.J.L., A.E.B., Z.J.S., J.M-D., R.A.G.-R., and A.P.N. collected and analyzed the data. V.E.B., T.J.L., C.D.L., and D.R.S. interpreted the data. V.E.B. wrote the initial draft of the manuscript. All authors revised the manuscript critically for intellectual content, approved the final version, and agree to be accountable for all aspects of the work.
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Brunt, V.E., LaRocca, T.J., Bazzoni, A.E. et al. The gut microbiome–derived metabolite trimethylamine N-oxide modulates neuroinflammation and cognitive function with aging. GeroScience 43, 377–394 (2021). https://doi.org/10.1007/s11357-020-00257-2
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DOI: https://doi.org/10.1007/s11357-020-00257-2
Keywords
- Cognitive impairment
- Inflammation
- Astrocyte activation
- Brain
- Memory