[www.ncbi.nlm.nih.gov]

Hormones, neurotransmitters and immunological factors released from the gut are known to send signals to the brain either directly or via autonomic neurons.

Diet alterations can have significant impact on the gut bacterial composition in as little as 24 hours.20

it is almost impossible to define a “normal” microbiome for the average human population

The dominant species and therefore enterotype results from the composition of a person’s diet.

A dysbiotic state leads to increased intestinal permeability and allows contents such as bacterial metabolites and molecules as well as bacteria themselves to leak through the submucosa and into the systemic circulation, a phenomenon aptly named leaky gut syndrome. Increased intestinal permeability leads to detrimental effects on the host immune system, which have been demonstrated in diseases such as inflammatory bowel disease (IBD), diabetes, asthma, and psychiatric disorders including depression, anxiety, and autism.2,4,10,34,35

Inflammation of the GI tract places stress on the microbiome through the release of cytokines and neurotransmitters. Coupled with the increase in intestinal permeability, these molecules then travel systemically. Elevated blood levels of cytokines TNF-a and MCP (monocyte chemoattractant protein) increase the permeability of the blood-brain barrier, enhancing the effects of rogue molecules from the permeable gut.38,39 Their release influences brain function, leading to anxiety, depression, and memory loss.39-41

Pro-inflammatory cytokines are also important stimulators of the hypothalamic-pituitary-adrenal (HPA) axis (Figure 1). The hypothalamus releases corticotropin releasing factor from the hypothalamus, stimulating the adenohypophysis to release adreno-corticotropic hormone (ACTH). In turn, ACTH stimulates the adrenal release of cortisol, a known stress hormone that acts as a negative feedback signal in the pro-inflammatory signal transduction machinery.3,41



Edited 1 time(s). Last edit at 02/08/2022 09:16PM by Panchito.