De ‘microbiota-gut-brain

axis’Tussen hype en revolutie?

• Prof. Dr. Lukas Van Oudenhove

• Laboratory for Brain-Gut Axis Studies (LaBGAS)

• Translational Research Center for Gastrointestinal

Disorders (TARGID)

• KU Leuven

Introductionanatomy & physiology of the ‘brain-gut axis’

Gastrointestinal Tract

Gastrointestinal Tractan extremely complex organ system

• surface ~ 300 m²

o absorption

• nervous organ

o 100 million nerve cells

• “intrinsic”

• “extrinsic”

o most complex interaction with the brain

• hormonal organ

o largest hormone production (> 30 hormones)

• immune organ

o 60-70% of our immune cells

• 1014 bacteria

Gastrointestinal Tract

Slide 6

Enteric Nervous System (ENS)

Brain

Nervous Systems

Emotional Brain

• Brainstem

o PAG, periaqueductal gray

o LC, locus coeruleus

• Subcortical

o NA, nucleus accumbens

o AMG, amygdala

• Cortical

o ACC, anterior cingulate

cortex

o OFC, orbitofrontal cortex

Gut-Brain Axis

HUMORALGUT-BRAIN

gastrointestinal hormones

inflammatory mediators

BRAIN-GUT

Hypothalamo-Pituitary-

Adrenal Axis

NEURALAutonomic

Nervous System

Vagus nerve

InsulaLinking sensory & emotional information

Hypothalamo-Pituitary-Adrenal (HPA) axis

1. The link between psychological &

gastrointestinal symptoms

‘stress-related’ gastrointestinal symptomsnormality to functional gastrointestinal disorders

• normality

o gastrointestinal symptoms during stress

• stomach problems

• diarrhea

o “butterflies in the stomach”

• “functional gastrointestinal disorders”

o irritable bowel syndrome, functional dyspepsia,…

o symptom-based diagnosis, no organic cause

o associated with stress, fear/anxiety, depression,…

irritable bowel syndrome (IBS)Rome IV definition

irritable bowel syndrome

world prevalence

functional gastrointestinal disordersbiopsychosocial model

symptom reporting

visceral perception

sensorimotornetwork

GI motor (dys)function

mechanoreceptors

afferent nerves

dorsalhorn

mechanicalGI stimulation

autonomicnetwork

affective cognitive networks Brain

modulatory pathways

descendingmodulatory pathways

HPA-axisANS

spinal(ortho-

sympathic)

GI immune & barrier functiongut microbiota

CRF

CRF

CRF

Brain modulatory pathways

Functional Gastrointestinal Disordersdisorders of gut-brain interactions

symptom reporting

visceral perception

sensorimotornetwork

GI motor (dys)function

mechanoreceptors

afferent nerves

dorsalhorn

mechanicalGI stimulation

autonomicnetwork

affective cognitive networks Brain

modulatory pathways

descendingmodulatory pathways

HPA-axisANS

spinal(ortho-

sympathic)

GI immune & barrier functiongut microbiota

CRF

CRF

CRF

Brain modulatory pathways

Psychological impact on GI symptomsoverview

HPA-axis & gastrointestinal responses to CRH injection in IBS

Kano, …, Van Oudenhove, …, Fukudo, Sci Rep 2017

Increased ACTH response to CRH injection in IBS

Kano, …, Van Oudenhove, …, Fukudo, Sci Rep 2017

Increased colonic motility response to CRH injection in male IBS patients

Kano, …, Van Oudenhove, …, Fukudo, Sci Rep 2017

symptom reporting

visceral perception

sensorimotornetwork

GI motor (dys)function

mechanoreceptors

afferent nerves

dorsalhorn

mechanicalGI stimulation

autonomicnetwork

affective cognitive networks Brain

modulatory pathways

descendingmodulatory pathways

HPA-axisANS

spinal(ortho-

sympathic)

GI immune & barrier functiongut microbiota

CRF

CRF

CRF

Brain modulatory pathways

Psychological impact on GI symptomsoverview

Basal Speech Shock0

5

10

15

20 ***

Saliv

ary

Cort

isol (

ng/m

l)

Psychosocial stress increases small intestinal permeability in healthy subjects

Vanuytsel et al, Gut 2013Basal Speech Shock0

20

40

60 ******#

ST

AI s

core

Basal Speech Shock0.00

0.02

0.04

0.06

**

LM

R

mixed models + Bonferroni:

** P<0.01 vs. basal

*** P<0.001 vs. basal

# P<0.05 vs. speech

salivary cortisolanxiety

small intestinal

permeability

stressor LMR

cortisol

p=0.22p=0.01

symptom reporting

visceral perception

sensorimotornetwork

GI motor (dys)function

mechanoreceptors

afferent nerves

dorsalhorn

mechanicalGI stimulation

autonomicnetwork

affective cognitive networks Brain

modulatory pathways

descendingmodulatory pathways

HPA-axisANS

spinal(ortho-

sympathic)

GI immune & barrier functiongut microbiota

CRF

CRF

CRF

Brain modulatory pathways

Psychological impact on GI symptomsoverview

gastrointestinal sensitivitytesting

gastrointestinal hypersensitivity

Emotional modulation of visceral painparadigm

Weltens, Schaub, Aziz, Tack, Van Oudenhove* & Coen*, submitted

stop emotion induction

start emotion induction

ES ES ES ES ES ES ES ES ES ES

VASSAM

“Emotional pain modulation period”“Emotion induction period”

SAM

Emotion induction Validated classical music

Velten mood induction

statements

IAPS pictures

“time 0” “time 1” “time 2”

Emotional modulation of visceral painsad emotion induction

Emotional modulation of visceral paineffect on esophageal pain ratings

Weltens, Schaub, Aziz, Tack, Van Oudenhove* & Coen*, submitted

0

20

40

60

80

Pa

in in

ten

sit

y (

0 -

100)

Negative Neutral Positive

*** ***

***

0 1 2 3 4 5 6 7 8 9 10

40

45

50

55

60

65

70Negative

β=-0.064; p=1

Neutral

β=-0.48; p=0.0026

Positive

β=-0.72; p=0.0001

Stimulus number

Pa

in in

ten

sit

y (

0 -

100)

Negative Positive-50

-25

0

25

50

% Δ

in p

ain

in

ten

sit

y

Emotion, cognition & pain

Bushnell et al, Nature Reviews Neuroscience 2013

Emotion, cognition & pain

PAG: periaqueductal gray

PB: parabrachial nucleus

AMY: amygdala

BG: basal ganglia

S1, S2: somatosensory cortex

ACC: anterior cingulatecortex

PFC: prefrontal cortex

Bushnell et al, Nature Reviews Neuroscience 2013

Emotion, cognition & pain

PAG: periaqueductal gray

PB: parabrachial nucleus

AMY: amygdala

BG: basal ganglia

S1, S2: somatosensory cortex

ACC: anterior cingulatecortex

PFC: prefrontal cortex

SPL: superior parietal lobule

Bushnell et al, Nature Reviews Neuroscience 2013

EMOTION

ATTENTION

descending pain modulatory pathways

3. impact of the gut microbiota on

psychological & brain function

Microbiota-Gut-Brain AxisThe hype of the day?

Gut microbiota

collection of micro-organisms in our gastrointestinal tract

bacteria 1014 in the colon (~ 10 x human cells in the entire body)

> 1000 species (but ~ 200 in each individual)

3 x 106 genes (~ 100 x human genes)

1 – 2 kg weight

variability between individuals host genetics

birth mode (caesarian section versus vaginal delivery)

breastfed versus bottle-fed

antibiotics

diet, diet, diet!

stress

age

Gut microbiota

Gut microbiota

Microbiota-Gut-Brain AxisWhat?

Microbiota-gut-brain axisMechanisms

Microbiota-gut-brain axisHow to study?

Microbiota-gut-brain axisdefinitions

• probiotics

o “live microorganisms which, when administered in

adequate amounts, confer a health benefit on the host”

• prebiotics

o “a substrate that is selectively utilized by host micro-

organisms conferring a health benefit”

• “psychobiotics”

o either of the above conferring a health benefit in patients

with psychiatric illness

Microbiota-gut-brain axisfecal microbiota transplantation

How to test anxious behaviour in mice?elevated plus maze test

How to test anxious behaviour in mice?open field test

How to test depressive behaviour in mice?forced swim test

Bravo, Forsythe et al, Proceedings of the National Academy of Sciences USA 2011

stress-induced hyperthermia

elevated plus maze

forced swim test

response to forced swim test

L. Rhamnosus & central GABA receptors

Bravo, Forsythe et al, Proceedings of the National Academy of Sciences USA 2011

cingulate gyrus prelimbic cortex infralimbic cortex

basolateral amygdala central amygdala locus coeruleus

hippocampus: dentate hippocampus: CA3 hippocampus: CA1

Bruce-Keller et al, Biol Psychiatry 2015

elevated plus maze

open field test overall locomotor activity

How to measure emotional responses in humans?Affect labeling/matching task

Prebiotic B-GOS alters cortisol awakeningresponse and emotional bias in health

Schmidt et al, Psychopharmacology 2015

no differences on

• 2 other emotion tasks• facial expression recognition• emotional categorization &

memory

• self-report questionnaires• anxiety• stress

NEGATIVE

POSITIVE

Probiotic intake alters resting state brain function in healthy humans

Tillisch,..., Mayer, Gastroenterology 2013

How to measure emotional brain response in humans?Affect labeling/matching task

Probiotic intake alters brain responses to emotional attention task in healthy humans

Tillisch,..., Mayer, Gastroenterology 2013

How to measure emotional brain response in humans?Backward masking paradigm

Probiotic treatment decreases depressivesymptoms & emotional brain responses in IBS

Pinto Sanchez et al, Gastroenterology 2017

Altered microbiota composition in major depressive disorder

Zheng et al, Mol Psychiatry 2016

Microbiota from depressed patients inducedepressive & anxious behaviour in germ-free mice

Zheng et al, Mol Psychiatry 2016

forced swim test

tail suspension test

open field testoverall locomotor

activity

Microbiota from anxious IBS patients induceanxious behaviour in germ-free mice

De Palma et al, Sci Transl Med 2017

Take home messages

There is intimate bidirectional communication between the gastrointestinal tract and the brain

This constitutes the biological basis of the link betweenpsychological and gastrointestinal symptoms

The gut microbiota have recently been identified as a keynew player in this communication

Therefore, the microbiota could have a strong impact on ourpsychological and brain function, but translation fromanimals to humans has only just started