3d - MICROBIOTA-GUT BRAIN AXIS IN PSYCHIATRIC DISORDERS

Question 1

Core concept

Answer 1

• Microbiota-Gut-Brain (MGB) axis = bidirectional communication system involving CNS, enteric nervous
  system (ENS) & gastrointestinal microbiota
• Plays crucial role in regulating mood, cognition, stress responses & behavior
• Dysregulation of axis increasingly implicated in psychiatric disorders, including depression, anxiety,
  schizophrenia & autism spectrum disorder (ASD)

Question 2

Mechanisms of communication in MGB axis

Answer 2

Table

Question 3

Key microbiota contributions to mental health

Answer 3

• Tryptophan metabolism: Gut microbes regulate conversion of tryptophan to serotonin or kynurenine—
  imbalances linked to depression
• Neurotransmitter production: Gut microbes can produce GABA, dopamine, serotonin, acetylcholine
• SCFAs (butyrate, propionate): Have anti-inflammatory & neuroprotective effects
• Gut permeability (“leaky gut”): Leads to systemic inflammation → activates microglia in brain

Question 4

Psychiatric disorders linked to MGB axis dysfunction

Answer 4

Table

Question 5

Clinical & therapeutic implications:
- diagnostic considerations
- therapeutic interventions

Answer 5

Diagnostic Considerations
- Microbiota profiling may help assess risk or subtype psychiatric disorders
- Markers: Zonulin (for gut permeability), cytokines (inflammatory status), SCFA levels

Therapeutic Interventions
- Probiotics (“psychobiotics”)ex: Lactobacillus and Bifidobacterium => promise in mood & stress regulation
- Prebiotics: Fibers that stimulate beneficial gut bacteria
- Fecal Microbiota Transplantation (FMT): Experimental use in depression and ASD
- Dietary interventions: Mediterranean diet, ketogenic diet, high-fiber diets
- Antibiotics: May reduce microbial diversity—linked to depression and cognitive dysfunction