Fig. 1
From: The gut microbiome in Alzheimer’s disease: what we know and what remains to be explored
Theory of GMB involvement in AD. Environmental factors, such as diet, sleep, and exercise and the development of AD due to genetics contribute to an inflammatory environment in the gut microbiota, which leads to changes in composition and diversity over time. Changes in the gut microbiota influence gut microbiome-derived metabolites and peripheral immunity by altering peripheral immune cell gene expression and cytokine release. Changes in peripheral immunity, possibly gut-derived metabolites directly, and vagus nerve trafficked gut-derived hormones can then alter phenotype of the blood brain barrier and central nervous system cell types (microglia, astrocytes, neurons), which can then modulate amyloidosis, tauopathy, and neurodegeneration and contribute to disease pathogenesis