Targeting the microbiota-gut-brain axis in neurodegeneration: Zebrafish-based investigations

The microbiota-gut-brain axis (MGBA) is a bidirectional signaling pathway regulated by the gut microbiome and the central nervous system (CNS). Moreover, MGBA is crucial for normal growth, development, and physiology of the brain and gut of the host; dysfunction in MGBA has been closely linked with the development of neurological disorders. Gut dysbiosis and its metabolites modulate barrier permeability and cause gastrointestinal tract (GIT) inflammation, which is followed by an increase in pro-inflammatory cytokines, immune cell infiltration into the brain, and vagus nerve dysfunction, resulting in neuroinflammation and neuronal defects in the brain, as well as some other behavioral defects. In this review, we will discuss the molecular and neurobehavioral properties of Zebrafish as a research model to study MGBA, as well as current discoveries in humans, highlighting the vital role of MGBA in neuropathological conditions. Using Zebrafish as a genetic model in combination with in vivo imaging technology may suggest some novel mechanisms for the interaction between gut microbiota and CNS, particularly in the case of neurological disorders including Alzheimer's disease (AD), Parkinson's disease (PD) and autism spectrum disorder (ASD). A comprehensive literature search was conducted using electronic databases including PubMed, Scopus, Web of Science, and Google Scholar.