Microbiota-gut –brain axis in neuropsychiatric disorders

Background and Objectives: Human intestine hosts a microbial community of between ۱, ۰۰۰ and ۱, ۵۰۰ bacterial species called "microbiota." The relationship between the microbiota and the host system is symbiotic and beneficial. There is also a complex and bidirectional signaling mechanism between this microbial community in the gastrointestinal tract and the central nervous system called the “microbiota-gut-brain axis (MGBA)”. Neuropsychiatric disorders such as cognitive impairment, Alzheimer's disease, Parkinson's disease, ADHD and depression can be caused by microbiota imbalance. So, it’s essential to understand how MGBA works and how it can cause neuropsychiatric disorders. Materials & Methods: A precise search was performed on PubMed and Google Scholar databases from ۲۰۱۹ up to ۲۰۲۳. Articles were identified by using the Key words. Findings: Based on a study, gut dysbiosis can be related to depression through different mechanisms, such as abnormal stress response, reduced neurogenesis, and neuroinflammation in the host. Other studies suggest that dysregulation of the gut microbiota can culminate in dysbiosis, decrease in SCFAs, and increase in the proinflammatory cytokines, mainly IL-۶ and IFN-γ. This inflammatory status can induce gut permeability and lead to the exit of bacteria. Brain–blood barrier can be affected by inflammatory cytokines. Inflammation in the brain, stimulates microglial activation and astrocyte atrophy lead to mood disorders such as depression. In some other studies, microbiota can influence brain by modulating the availability of circulating tryptophan, serotonin, kynurenine, and short-chain fatty acids, as well as blood-brain barrier permeability and activation of peripheral immune cells and brain glial cells. As a result, any change in the type or population of microbiota is associated with behavioral disorders. Pursuant to reviewed studies, probiotics are considered as a possible therapy for neuropsychiatric disorders. Bacteria from Bifidobacterium and Lactobacillus families are the most effective probiotics in enhancing central nervous system function. Conclusions: MGBA is increasingly recognized as an important issue in the pathophysiology and treatment of neuropsychiatric disorders through different pathways, for instance, the immune system, microbial metabolites such as SCFAs and inflammatory factors, mainly IFN-γ and IL-۶. However, the relationship between microbiota and brain disorders requires further investigation.

کلیدواژه ها:

gut microbiome ، gut–brain axis ، neuropsychiatric disorders ، brain disorders