Gut-brain axis and immunoneuroendocrine modulation in neurological and psychiatric disorders: A systematic review

Abstract

The present study aimed to explore the influence of the gut-brain axis on neuroendocrine and immunological modulation in neurological and psychiatric disorders. This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyzes (PRISMA) guidelines, and searches were conducted in the electronic databases PubMed and SciELO using combinations of descriptors “Gastrointestinal Microbiome”, “Neurosecretory Systems”, “Immune Response”, “Nervous System Diseases” e “Mental Disorders”. From the 144 studies generated by crossing the descriptors, 32 of them were excluded because they were duplicated in the databases, 13 because they were not related to the objectives of the review, and another 29 because they were not on eligibility criteria. Therefore, 70 studies were included in the present review. Communication between the GI tract and the CNS occurs via the neuronal, endocrine, and immunological pathways through a) the production of neurotransmitters, b) the tryptophan metabolism, c) the modulation of the immunological activity in the CNS and the SNE, d) production of short chain fatty acids, e) the production of intestinal hormones, and f) the production of branched chain amino acids.

Branched-chain amino acids govern the high learning ability phenotype in Tokai high avoider (THA) rats

“…One of the observed mechanisms for maintaining high levels of serum and hippocampal BCAA in THA rats was the increased expression of amino acid transporter B 0 AT1 in the small intestine. Recently, studies have explored the gut-brain axis in an attempt to explain interactions between the CNS and gastrointestinal hormones, which are closely associated with the bidirectional relationship of cognitive disorders with metabolic diseases 44 , 45 . The vagal efferent nerves, which send signals from the brain to the gut, account for approximately 10–20% of all nerve fibers.…”

Effect of Gut Brain Axis on Neurologic Diseases and Psychiatric Disorders

“…[2][3][4] Neurologic and psychiatric diseases represent a huge health burden, as they impact many individuals worldwide irrespective of social class or age. Indeed, evidence suggests that these disorders represent approximately 12% of diseases globally [5], Lami, Oliveira, de and Batista 2021 , et al Research shows a bidirectional intestine-brain communication happens via the neural, endocrine, and immunological pathways ; thus, it has been hypothesized that this communication's imbalances might affect these diseases' development. Researchers have used human and animal models to assess the impact of the gutbrain axis (GBA) communication pathways in the disorders' multi-causal perspective.…”