Research Progress on the Association Between Trimethylamine/Trimethylamine-N-Oxide and Neurological Disorders
- Lizheng Xie, Li Pan, Baiyun Liu, et al.
- 2023
Why this matters for your gut health
TMAO is a gut microbiota-derived metabolite produced when bacteria break down dietary choline, carnitine, and betaine (found in red meat, eggs, and fish). It crosses the blood–brain barrier and has been linked to neurological damage through neuroinflammation and oxidative stress — directly connecting gut bacterial activity to brain disease risk. This research underpins gut-targeted interventions (diet, probiotics, enzyme inhibitors) as potential treatments for conditions like Alzheimer’s, Parkinson’s, and depression.
Summary
TMAO is formed when gut microbiota metabolize dietary choline and related nutrients into TMA, which the liver converts to TMAO via FMO1/FMO3 enzymes. Originally studied for cardiovascular disease, TMAO is now recognized as a multi-system actor operating through the microbiota–gut–brain axis. This review surveys evidence linking TMA/TMAO to traumatic brain injury, Parkinson’s disease, Alzheimer’s disease, epilepsy, intracerebral hemorrhage, ALS, depression, and PTSD, while identifying new therapeutic targets.
Key findings
- Neuroinflammation pathway: Elevated plasma TMAO levels are associated with increased expression of inflammatory markers TNF-α, IL-6, and C-reactive protein, forming a basis for neurological disease development.
- Parkinson’s Disease: TMAO crosses the blood–brain barrier, promotes α-synuclein aggregation, induces oxidative stress, and damages dopaminergic neurons. Higher baseline TMAO levels correlated with faster motor and cognitive decline in PD patients.
- Alzheimer’s Disease: Rising TMAO levels with age promote neuroinflammation, activate astrocytes, increase β-secretase production, and are directly correlated with AD pathological features in cerebrospinal fluid.
- Stroke / Intracerebral Hemorrhage: Each 1 µmol/L increase in TMAO raises ischemic stroke risk by 22%. The CutC gene (driving TMAO synthesis) significantly increases cerebral infarction size in animal models.
- Depression: TMAO levels are positively correlated with depression severity, particularly in patients with carbohydrate malabsorption. Elevated TMAO is also associated with susceptibility to PTSD following myocardial infarction.
- Therapeutic potential: Small molecules like 3,3-dimethyl-1-butanol and berberine can reduce TMAO production by modulating gut microbiota, improving cognitive outcomes and reducing neurodegeneration in animal models.
Read the full paper
Citation
Xie L, Pan L, Liu B, Cheng H, Mao X. Research progress on the association between trimethylamine/trimethylamine-N-oxide and neurological disorders. Postgraduate Medical Journal. 2024;100(1183):283–288.