Gut-brain axis

Question 1

Why is the gut-brain axis important?

Answer 1

• Absence of micobial colonisation is associated to an altered expresson and turnover of NTs in NS
• Compared to colonised mice, GF mice showed exaggerated HPA restrain stress reaction, impaired social behaviour etc
• Anomalies are restored after animal colonisation in bacterial species-specific manner

Question 2

What are the communication routes for Gut brain axis?

Answer 2

• Biderectional communication between the central and the enteric nervous system
• Linking emotional and cognitive centers of the brain with peripheral intestinal functions
• Includes both brain and spinal cord, the ANS, Enteric NS and HPA axis

Question 3

What is the enteric NS?

Answer 3

• Part of the PNS that controls GIT
• There is bidirecctional communication between central and enteric NS

Question 4

Explain the communication routes

Answer 4

• AN system with Symp and parasymp limbs, drives both afferent signals, arising from lumen and transmitted through enteric, spinal and vagal pathways to CNS
• Efferent signals from CNS to intestinal wall

Question 5

What are the Mechanisms for communication routes?

Answer 5

• Immune activation
• Intestinal permeability
• Enteric reflex
• Enero-endocrine signalling

Question 6

What are gut microbiota linked to?

Answer 6

• Neuroinflammatory
• Psychiatric disorders
• Brain development
• Dysbiosis linked to central NS disorders

Question 7

What is the microbiome composed of?

Answer 7

• Bacteria, Viruses, Fungi, Yeasts and Bacteriophages
• Diet and antibiotic exposure are main 2 factors that potentially influence brain function through shaping gut microbiome

Question 8

How does the GBA link with NTs?

Answer 8

• More than 90% of serotonin is synthsised in the gut
• Gut bacteria are able to produce a whole range of NTs

Question 9

What is Gut-Brain communication?

Answer 9

• Environmental stress can activate this system that, through secretion of corticotropin-releasing factor from the hypothalamus
• stimulates adrenocorticotropic hormone secretion from pituitary gland
• That release cortisol from adrenal glands
• Both neuronal and hormonal lines of communication combine to allow brain to influence activities of intestinal functional effector cells
  1. E.g. immune ells, epithelial cels, enteric neurons etc

Question 10

What impacts the GBA?

Answer 10

• Initial microbiota is acquired at birth and is shaped by a variety of intrinsic and environmental factors
• Although microbiota stability peaks in adulthood, it maintains flexibility to adjust to environmental or dietary changes

Question 11

What evidence is there for Gut microbiota on brain physiology?

Answer 11

• Mostly rom studying germ free animals, which show alterations in various aspects of neurophysiology

Question 12

What determines density and diversity of microbial species?

Answer 12

• Gradients of pH, oxygen, antimicrobial peptides and bile salts

Question 13

What do metabolites do?

Answer 13

• Can either activate enteroendocrine cells to release gut hormones
• Or be absorbed across the epithelial cell layer and taken up into bloodstream to activate Vagus nerve.
• A combo of location of microbiota within GI tract and chemicals produced is likely to determine outcomes

Question 14

What are pro and prebiotics?

Answer 14

• Probiotics -Yoghurt, sourdough, kimchi, pickled veg
• Prebiotics - Bananas, oatmeal, aspargus etc