The role of diet and gut microbiota in the pathophysiology of neurodegenerative diseases,
such as Alzheimer's, has recently come under intense investigation. Studies suggest that human gut microbiota
may contribute to the modulation of several neurochemical and neurometabolic pathways,
through complex systems that interact and interconnect with the central nervous system. The brain and
intestine form a bidirectional communication axis, or vice versa, they form an axis through bi-directional
communication between endocrine and complex immune systems, involving neurotransmitters and hormones.
Above all, studies suggest that dysbiotic and poorly diversified microbiota may interfere with the
synthesis and secretion of neurotrophic factors, such as brain-derived neurotrophic factor, gammaaminobutyric
acid and N-methyl D-Aspartate receptors, widely associated with cognitive decline and
dementia. In this context, the present article provides a review of the literature on the role of the gutbrain
axis in Alzheimer's disease.