Microbiome, Gut-Brain-Axis, and Implications for Brain Health

Abstract

As Antonio Damasio highlighted back in 1994, Descartes' division of mind and body slowed the full realization of the connectedness of the brain and the body by centuries. The simple fact that homeostasis in the brain was fully interconnected with the body has eluded researchers and clinicians even after the connection was well established. Recent studies reporting the central role in dysfunction of mental systems as a result of inflammation in the gut and the autonomic nervous system (ANS) was yet one more reminder that the entire system is connected and interdependent. Central to this discovery and its application to mental function has been the growing field of study of the microbiome. This article is an attempt to situate those who are active in the variety of ways and means of treating the brain in the essential role that is likely being played by a vast community of bacteria living in the bowels of the human being and influencing all of the higher and most “sophisticated” aspects of human interchange and thought. It is the authors hope that this brief introduction will remind and inform researchers and clinicians that the organism is more interconnected and more complex than we have tended to think and that disorders of the mind are likely also, often disorders of the gut.

Microbiota-gut-liver-brain axis and hepatic encephalopathy

“…Additionally, these aromatic amines can directly enter the brain when liver function is impaired, and generate pseudo-neurotransmitters including phenylethanolamine and β-hydroxytyramine. These pseudo-neurotransmitters cannot transmit nerve impulses [ 49 , 50 ] and, therefore, may cause brain dysfunction and liver coma. Research on the influence of gut microbiota-derived metabolites on the pathophysiological mechanisms of HE found that hyperammonemia plays an important role in the progression of HE.…”

Investigating the pivotal role of gut microbiota in cognitive disorders

“…It has been shown to have positive effects on conditions such as depression, schizophrenia, addiction, and various neurological diseases (22). Stress and anxiety in rats have been observed to alter the composition of intestinal microbiota and decrease the production of neurogenesis factors derived from the brain (23).…”

“…The intestinal microbiota also has the ability to regulate hormone release through the hypothalamus-pituitary-adrenal axis, which is involved in the body's response to stress. Additionally, corticosteroid hormones released by the hypothalamus-pituitary-adrenal axis can influence the composition of the intestinal microbiota (24). The colonization of Bifidobacterium infantis in the gut has been shown to improve behavioral and stress-related brain deficits.…”

Evolving Concepts of Food Safety: The Need for Understanding Mechanisms of Food Toxicology for Public Policy

“…However, with populations, that have established a stable homeostatic symbiosis with beneficial microbiome, now eating foods that challenge the established microbiome, are creating new gut microenvironments for new microbiome populations that might not be compatible for normal tissue health [82][83][84][85]. The consequences of these new microbiome secreted toxins might have all kinds of health effects along the gut/brain axis [86]. With the trillions of various populations of microbes in the gut, confronting all kinds of foods, grown and processed differently, together with medications, pollutants and supplements, it seems that the chemical sequelae of the signaling from this metabolism on the physiological responses of all the organs affected would be unpredictable.…”