The Gut Microbiome as a Component of the Gut–Brain Axis in Cognitive Health

Abstract

Introduction: The human microbiome, the microorganisms living in and on the body, plays a vital role in brain physiology and pathophysiology. The gut microbiome (GMB) has been identified as a link in the gut–brain axis moderating cognitive development and health. Objectives: The objectives of this scoping review are to discuss mechanisms of the microbiome–gut–brain axis in cognition, review the existing literature on the GMB and cognition, and discuss implications for nursing research. Methods: We searched Pubmed using the terms “gut microbiome,” “brain,” and “cognition” and the terms “gut brain axis,” “microbiome,” and “cognition”; removed duplicates, studies not published in English, and unrelated publications; and added additional articles identified through references. We retained the 85 most relevant publications for this review. Results: Common themes in the current literature include GMB components; interactions on cognitive development; effects of GMB–gut–brain interactions on cognition, mild cognitive impairment and Alzheimer’s disease; effects of GMB interactions with physiologic stress on cognition in critical care; and GMB modification for improved cognition. Review of the literature on each of these topics reveals multiple theoretical mechanisms of action for GMB–gut–brain interaction that modify cognitive development and function across the lifespan. Discussion: GMB components and dysbiosis have been implicated in many cognitive states, and specific microbiota constituents contribute to cognitive development, stability, and impairment. The study of these interactions is relevant to nursing research as it addresses the holistic human experience and microbiome constituents are modifiable, facilitating translation into the clinical setting.

Bacillus subtilis-Based Probiotic Improves Skeletal Health and Immunity in Broiler Chickens Exposed to Heat Stress

“…It can be further affected by management issues such as rearing conditions (restriction, crowding, heat, cold environments), breeding programs (selected for a special production indicator), and stress-related factors (transportation and weaning) in farm animals [ 16 , 17 , 18 , 19 ]. Impaired gut microbiota (dysbiosis), alterations in the richness and diversity of microbiota, leads to the pathophysiological processes of various diseases in humans and animals [ 20 , 21 , 22 , 23 , 24 ]. The modulation of the gut microbiota by the administration of probiotics, as well as prebiotics and synbiotics, has become a biotherapy strategy for preventing and treating many diseases, from stress-related irritable bowel syndrome to neuropsychiatric disorders [ 25 , 26 , 27 ].…”

Gut Microbiota, Probiotic Interventions, and Cognitive Function in the Elderly: A Review of Current Knowledge

“…In recent years, the number of studies that focus on explaining this mechanism has been increasing, but most of the research has been done within animal models. In a scoping review, Gao et al distinguished five main pathways through which the microbiota–gut–brain axis may modify cognitive function [ 114 ]. First, gut microbiota dysbiosis has been shown to have an impact on the function of the hypothalamic–pituitary–adrenal (HPA) axis, which regulates cognitive function.…”

“…First, gut microbiota dysbiosis has been shown to have an impact on the function of the hypothalamic–pituitary–adrenal (HPA) axis, which regulates cognitive function. The second pathway is the neuronal regulation pathway, where gut microbiota communicates with the CNS and autonomic nervous system (ANS) via vagus nerve stimulation [ 114 , 115 ]. The other pathway is based on microbiota and its metabolites that can stimulate the increased release of inflammatory markers, interacting with the blood–brain barrier.…”

In Pursuit of Healthy Aging: Effects of Nutrition on Brain Function

“…The neurotransmitters produced by the GI tract and gut microbiota can directly interact with the enteric and peripheral nervous systems or communicate with the brain via stimulation of vagal nerve innervation or the immune system, which in turn may influence the CNS. Of note, serotonin, catecholamines (dopamine, epinephrine, and norepinephrine), acetylcholine, and gamma-aminobutyric acid (GABA) (neurotransmitters known to impact several brain functions, including cognition [ 92 , 93 , 94 , 95 ]) can all be synthesized in the GI tract [ 96 , 97 ].…”