In a recent review published, researchers in Brazil investigated the role of gut microbiota in cognition, brain function, behavior, and neurodegenerative disease pathogenesis.
A growing body of evidence indicates that the gut microbiome plays an essential function in gastrointestinal health and in metabolic processes such as glucose processing, immune responses, inflammation, bone health, and central and peripheral neurotransmission.
The assembly and balance of gut microbiota begin in infancy through exposure to maternal microbiomes and continues to develop throughout the individual’s life, modified by factors such as diet. In addition, recent research has highlighted the involvement of gut microbiota in brain homeostasis, with studies in neurophysiology, neurochemistry, and neuropsychiatry reporting the role of gut microbiome disruption in brain disease pathogenesis.
Changes in gut microbiota composition have been associated with a range of diseases and disorders, such as asthma, diabetes, autoimmune disorders, Parkinson’s disease, depression, autism spectrum disorders, and Alzheimer’s disease. Enriched diets that modulate gut microbiota have shown positive results in obesity and diabetes patients.
Exposure to common peptides between humans and gut microbes is thought to increase the risk of neurodegenerative diseases such as Alzheimer’s in individuals with a genetic predisposition to the disease.
Microbiome and Alzheimer’s Disease
Alzheimer’s disease is characterized by the excessive production and aggregation of amyloid-beta (Aβ) peptides leading to extracellular insoluble plaque formation. Gut microbiota release by-products such as amyloids and lipopolysaccharides into the gut environment, the absorption of which could alter inflammatory cytokine signaling pathways, contributing to Alzheimer’s disease pathogenesis and Aβ accumulation.
Various studies with probiotics and dietary interventions have indicated increased cognitive function and decreased Aβ accumulation in Alzheimer’s patients. Studies have also suggested a correlation between amyloidosis, cognitive impairment, and gut microbiome-secreted pro-inflammatory cytokines. Furthermore, gut peptides such as leptin and ghrelin are thought to affect nervous functions such as memory and learning, and gut microbiome changes are seen to affect plasma ghrelin levels.
Overall, this comprehensive review discussed the role of gut microbiota in neuronal communications between the gut and the brain and reported the results from various studies that explored the association between microbiome diversity and cognitive function.
Furthermore, the authors also examined the involvement of gut microbiota in synthesizing neurotransmitters and the association between gut microbiome function and the pathogenesis of Alzheimer’s disease.