Fig. 1.

Schematic representation of the role of microbiota-gut-brain axis in Alzheimer’s disease. Good bacteria probiotics are capable to stabilize digestive pH, reduce inflammation, and increase neuroprotective molecules, such as brain-derived neurotrophic factor (BDNF). These effects lead to improved cognition and reduced Aβ plaque formation in AD animal models. In contrast, impaired microbiota dysbiosis can induce neuroinflammation and reduce the expression of BDNF and NMDA receptor, leading to cognitive impairment, mood disorders, and higher levels of Aβ₄₂. Antibiotics, by affecting gut microbiota composition, interact with this circuit and produce different effects, depending on their microbiome target