The role of the microbiota-gut-brain axis in neuropsychiatric disorders

Abstract

The microbiota-gut-brain axis is a bidirectional signaling mechanism between the gastrointestinal tract and the central nervous system. The complexity of the intestinal ecosystem is extraordinary; it comprises more than 100 trillion microbial cells that inhabit the small and large intestine, and this interaction between microbiota and intestinal epithelium can cause physiological changes in the brain and influence mood and behavior. Currently, there has been an emphasis on how such interactions affect mental health. Evidence indicates that intestinal microbiota are involved in neurological and psychiatric disorders. This review covers evidence for the influence of gut microbiota on the brain and behavior in Alzheimer disease, dementia, anxiety, autism spectrum disorder, bipolar disorder, major depressive disorder, Parkinson’s disease, and schizophrenia. The primary focus is on the pathways involved in intestinal metabolites of microbial origin, including short-chain fatty acids, tryptophan metabolites, and bacterial components that can activate the host’s immune system. We also list clinical evidence regarding prebiotics, probiotics, and fecal microbiota transplantation as adjuvant therapies for neuropsychiatric disorders.

Exploring the Role of Nutraceuticals in Major Depressive Disorder (MDD): Rationale, State of the Art and Future Prospects

“…Environmental factors like diet, stress or antibiotics and other pharmaceuticals, make direct effects on this MGB axis, leading to these kinds of alterations in health and disease [ 109 ]. Targeting gut microbiota has been suggested for the last decade, i.e., keeping or restoring the eubiosis status of microbiota as therapy or prevention for mental disorders [ 110 ]. In this context, recent evidence alleges that vitamin D is crucial for gut homeostasis, in fact, the vitamin metabolites act synergistically with microbiota metabolites as part of its role in the immunoregulation [ 111 ].…”

Exploring the Potential Role of the Gut Microbiome in Chemotherapy-Induced Neurocognitive Disorders and Cardiovascular Toxicity

“…Probiotic metabolites such as SCFA play a role in maintaining the BBB integrity through the increased expression of claudin and occludin in the membrane. Moreover, the production of tryptophan metabolites might block proinflammatory NFk-B and VEGF-B, the activation of astrocytes, and microglial cells within the brain [ 169 ]. According to the findings from mouse models, long-term probiotic administration reduced anxiety and depression, normalized the immune response, caused changes in GABA production, diminished oxidative stress markers in the brain, enhanced the activities of antioxidant enzymes, preserved neuronal synaptic plasticity, and restored basal noradrenaline levels in the brainstem [ 170 , 171 , 172 , 173 ].…”

Alzheimer's disease: An evolving understanding of noradrenergic involvement and the promising future of electroceutical therapies

“…[210][211][212] There has been some evidence to indicate that there is a link between the gut microbiota and the Aβ signaling pathway. [212][213][214] The vagus nerve provides extensive innervation to the visceral organs and is a key bi-directional mediator of inflammation in both the central nervous system and peripheral tissue. 210,211,214,215 The extent of the role of the enteric neurotransmitter system, and NE in particular, is poorly understood in relation to cognitive function, but is of significant interest due to the role stimulation of the vagus nerve plays in regulation of the peripheral immune system.…”