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Fig. 1 | Molecular Neurodegeneration

Fig. 1

From: Microbial-derived metabolites as a risk factor of age-related cognitive decline and dementia

Fig. 1

Microbial metabolites can directly and indirectly modulate the CNS through immune, neuronal and direct metabolite mediated pathways within the microbiota-gut-brain axis. In the gut lumen, dietary products can be metabolised by microbiota into neuroactive compounds, including neurotransmitters, (e.g., serotonin, dopamine), amino acids (e.g., tryptophan, tryptamine) and other microbial-derived metabolites (e.g., short-chain fatty acids, trimethylamine (TMA)). These compounds subsequently communicate with the central nervous system either directly, travelling through the portal vein, liver and crossing the blood–brain barrier, or indirectly via the production of neurotransmitters by enterochromaffin cells (ECC) or immune pathways (stimulated immune cells produce cytokines that can enter the blood or stimulate the vagus nerve)

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