in vivo molecular imaging of the brain type 1 cannabinoid receptor in eating disorders

Nathalie Gérard - MIRC seminar 1

In vivo molecular imaging of the Brain Type 1 Cannabinoid Receptor in Eating Disorders

25/06/2009

Nathalie GérardDivision of Nuclear Medicine

UZ Leuven – KU LeuvenPromotor : Prof. Dr. Koen Van Laere

work in progress seminar

Nathalie Gérard - MIRC seminar 225/06/2009

Outline

1. Introduction• Anorexia nervosa / Bulimia nervosa• Activity-based anorexia rat model• The endocannabinoid system• CB1 receptor imaging

2. Hypothesis and aims

3. CB1 receptor characterization in an animal model for anorexia nervosa• Cross-sectional design• Longitudinal design• Pharmacological intervention

4. CB1 receptor characterization in anorexia nervosa and bulimia nervosa patients

5. Additional and future work


Introduction

Anorexia nervosa Bulimia nervosa

• refusal to maintain normal body weight• intense fear of gaining weight• distorted body perception• amenorrhea• excessive physical activity

• restrictive / binge - purge

• 0.7% in young women• 47% full recovery• 5 to 10% mortality rate

• binge eating with loss of control• inappropriate compensatory behaviour• excessive emphasis on body shape / weight• twice a week for min. 3 months

• purging / (non-purging)

• 2% in young women• 50% full recovery over 10 years• 0 to 3% mortality rate

Fairburn, Lancet 2003 ; Keel, Am J Psychiatry 1997


Introduction

Routtenberg, J Comp Physiol Psychol 1968

activity-based anorexia model : well-characterized and validated model for anorexia nervosa in the rat

limited feeding period (1.5h / day)

running wheel+

induction of hyperactivity and spontaneous food restriction


Introductionthe endocannabinoid system : important in brain neuromodulation

Guzman Nature Reviews 2003


Introductionthe role of the endocannabinoid system in eating behaviour

Van den Eynde Child Adolesc Psychiatric Clin N Am 2008

homeostatic hedonic

somatic metabolic wanting liking

dopamine neurotransmission

opiates

cannabinoid system


Introductionthe role of the endocannabinoid system in eating behaviour

• Cannabinoid agonists stimulate food intake

e.g. - cannabis-induced hunger (Abel Behav Biol 1975)

- agonist therapy in AIDS-related anorexia (Beal et al. J Pain Symptom Manage 1997) ;

however one trial with ∆⁹-THC in AN patients failed (Gross et al. J Clin Psychopharmacol 1983)

- orexigenic effect in animals (Arias Horcajadas Mol Neurobiol 2007)

Cannabinoid inverse agonists / antagonists as anti-obesity medication (Rimonabant, Taranabant) (Pi-Sunyer et al. JAMA 2006, Addy et al. Cell Metabolism 2008)

• Different CB1R alleles associated with Anorexia Nervosa-restrictive and Anorexia Nervosa-bingeing purging subtypes (Siegfried et al. Am J Med Genet 2004)

• Endocannabinoid anandamide increased in plasma of AN patients, not in BN (Monteleone et al. Neuropsychopharmacology 2005)


IntroductionImaging of the type 1 cannabinoid receptor

[18F]MK-9470 High-affinity, highly selective CB1 receptor tracer Preclinical validation / clinical application

Burns et al. PNAS 2007

Receptor Ki (nM)

hCB1 0.7

hCB2 44


Hypothesis and aims

• PET characterization of in vivo cerebral CB1R availability in activity-based anorexia rats / female patients with anorexia or bulimia nervosa compared to controls

Is the endocannabinoid system hypoactive in anorectic conditions ?

• Endocannabinoid augmenting therapy in ABA


ANIMAL RESEARCHCB1R microPET in the activity-based anorexia model


Cross-sectional designCB1R

microPET

ABA, n = 14

CONTROL , n = 10

DIET, n = 10

WHEEL , n = 10n = 44

time (days)

arrival

randomisation IN ABA model


Longitudinal design

randomisation IN ABA model OUT ABA model

c recovery

CB1R microPET CB1R microPET CB1R microPET

time (days)

arrivalbody weight


Methods

• microPET : 500 µCi 18F-MK9470 20’ 1 hour post injection

• image processing : • spatial normalization on 18F-MK9470 binding

template oriented in standardized Paxinos space

mSUV = Activity conc * ((body weight + 250 g) / 2)

Injected dose

• parametric images based on mSUV quantification


Resultsrelative mean body weight

mean food intake

CS LG

ABADIETWHEELCON

0 2 4 6 8 1060

70

80

90

100

110

120

130

days

%

1 2 3 4 5 6 7 8 9 1060

70

80

90

100

110

120

days

%

0 2 4 6 8 100

5

10

15

20

25

30

days

g

2 3 4 5 6 7 8 9 100

5

10

15

20

25

30

35

days

g


Resultswheel rotations

weight during recovery

CS LG

1 2 3 4 5 695

100

105

110

115

120

125

130

days

%

ABADIETWHEELCON

2 3 4 5 6 7 8 9 100

100020003000400050006000700080009000

10000

days

rot /

24h

0 2 4 6 8 100

100020003000400050006000700080009000

10000

days

rot /

24h

Nathalie Gérard - MIRC seminar 16mSUV

*** p < 0,001

mea

n CB

1R b

indi

ng (m

SUV)

+ 51%

+ 53%

25/06/2009

Results : cross-sectional CB1R

ABA DIET WHEEL CON


Results : longitudinal CB1R

BASELINE CHRONIC RECOVERY

ABA

CONmSUV

0.7

2.3

med

ian

CB1R

bin

ding

(mSU

V)

** p < 0,01


Results : regional CB1R binding in ABA

Cross-sectional Longitudinal

% P-value % P-value

Hippocampus + 4,6 P < 0,0003 + 2,1 P < 0,004

ABA > control

Most pronounced regional increase in CB1R binding was consistently found in the hippocampus

stress

ECS

+

_HPA axis Hypercortisolism,

Affects especially hippocampal neurons due to large amounts of glucocorticoid receptors

↓

Hillebrand et al. Peptides 2005


Conclusions

Global significant increase in CB1R binding in ABA ; confirmed in a follow-up experiment

CB1R upregulation suggests a reversible compensation mechanism for a hypoactive ECS

CB1R upregulation in ABA normalizes with recovery

Could endocannabinoid augmenting therapy be beneficial in ABA?


EC augmenting therapy in ABA

4x 7 ABA rats, 1 week i.p. injection twice a day with :

• Exogenous CB1R agonist : WIN 55,212-2 ; low dose 0.25 mg/kg or higher dose 1 mg/kg

• Fatty acid amide hydrolase inhibitor : URB-597 ; 0.3 mg/kg

• Vehicle : 1% Tween-80 in aqua


Preliminary results∆

food

inta

ke (g

)

WIN L URBVEH

WIN H

∆ bo

dy w

eigh

t (g)

WIN L URBVEH

WIN H

∆ ru

nnin

g ac

tivity

(km

)

WIN L URBVEH

WIN H

mean

mean ± SE

min-max


Conclusions

No significant differences between groups in changes of body weight, food intake and running activity after therapy compared to before therapy

CAVE suboptimal low dosage vs. more rapid tolerance with higher dosage?

Effect of endogenous 2-AG increase with monoamine glycerol lipase inhibitors?


HUMAN RESEARCHCB1R PET in anorexia and bulimia nervosa

25/06/2009 24Nathalie Gérard - MIRC seminar

Study aim

To characterize the in vivo cerebral CB1R availability in female patients with anorexia and bulimia nervosa compared to

healthy women

Is the in vivo cerebral CB1R availability correlated with eating disorder-related symptoms in AN or BN?

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Subjects

Parameter AN BN Controls

N 14 F (7 AN-BP/7 AN-R) 16 F (16 BN-P) 19 F

Age (yrs) 20.5 ± 3.6 23.8 ± 7.1 25.2 ± 8.5

Weight (kg) 42.5 ± 6.2 * # 61.2 ± 10.3 * 66.4 ± 13.1 #

BMI (kg/m²) 15.5 ± 1.3 * # 21.8 ± 2.5 * 23.1 ± 4.3 #

Disease dur. (yrs) 4.2 ± 4.5 6.3 ± 6.3 -

Handedness (L/AMB/R)

2/0/12 2/0/14 0/2/17

EDES 36.7 ± 9.5 # 37.4 ± 9.5 § 69.5 ± 6.2 # §

EDI 87.3 ± 19.4 # 83.4 ± 30.1 § 13.7 ± 9.6 # §

p < 0.05 : * AN vs. BN, # AN vs. controls, § BN vs. controls

EDES : eating disorder evaluation scale (Vandereycken 1993)

EDI : eating disorder inventory (Garner 2007)

Nathalie Gérard - MIRC seminar25/06/2009


Methods (1)

[18F]MK-9470~ 306 MBq

90 min.

30 min.

…

Modified Standard Uptake Values

PET scan

25/06/2009


Methods (2)

mSUV = activity concentration x (body mass +70)/2 injected dose

0 0.5 1 1.5 2 2.5 3 3.50

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04 AN_001_ADJ

AN_002_LEM1

AN_002_LEM2

AN_004_VPE

AN_005_WYF

BN_001_MOE

BN_002_STS

BN_004_DPA

BN_005_STB

BN_007_KRS

BN_008_BRJ

mSUV

Ki

quantification of [18F]MK-9470 PET

Sanabria et al. 2009 (submitted)

• based on the macroparameter mSUV as index of CB1R availability

• mSUV is correlated with irreversible uptake rate constant Ki which is a measure for VT, in healthy subjects and AN/BN patients, and is independent of blood flow

• no arterial sampling -> better clinical feasibility


Methods (3)

PET – MRI coregistration

Normalization on CB1R binding template

- Voxel-by-voxel : Statistical Parametric Mapping (SPM2)

- Volumes-of-interest (Pmod)

Statistical analyses

25/06/2009

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Results (1)

Global cerebral increase of CB1R binding in AN patients :

compared to BN patients on average + 14.7 % ; p < 0.05

compared to controls on average + 24.5 % ; p < 0.001


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Results (2)Regional increases of CB1R binding in AN and BN patients compared to controls(mSUV normalized on global cerebral uptake)

p height < 0.001 ; p cluster < 0.05 :

AN > CON

Insular cortex Inferior frontal cortex Inferior temporal cortex


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Results (3)Regional increases of CB1R binding in AN and BN patients compared to controls(mSUV normalized on global cerebral uptake)


BN > CON

Insular cortex

No significant differences between AN and BN patientsNo significant differences between AN subtypes



Results (4)

Positive correlation in the superior temporal brain area with the EDI subscale

‘drive for thinness’

Regional CB1R binding correlates with disease parameters in AN, not in BN patients



Discussion (1)

• Global cerebral increase of in vivo CB1R availability in AN, not in BN

- Reducing the endocannabinoid tone in anorectic conditions could reduce appetite and motivation to eat (Fride et al. Exp Biol Med 2005)

- CB1R upregulation as a compensatory response ?

BN : overeating (Klein et al. Physiol Behav 2004)

hormonal effects : e.g. FAAH inhibition by estrogen absent in AN patients (due to amenorrhea), anandamide ↓ (Waleh et al. Gene 2002)


Discussion (2)

• Common feature in AN and in BN : increased insular CB1R availability- Insula serves an integrative function for brain processes relevant to eating disorders : hunger and food intake, reward and emotion processing, interoceptive awareness

-Insular dysfunction in eating disorders :

• µ-opioid receptor decrease in BN (Bencherif et al J Nucl Med 2005)

• altered activity with symptom provocation or taste stimuli (fMRI) (e.g. Oberndorfer et al Biol Psychiatry 2008)


Conclusion

ECS seems to be a relevant player in AN, to a lesser

extent in BN

Importance of insular dysfunction in AN / BN

Trait- or state- related changes?

Follow-up study in subgroup fulfilling

criteria indicating recovery


ADDITIONAL AND FUTURE WORK


Results : metabolic imaging in AN and BN

AN < HV BN < HV

• parietal cortex

• cingulate brain area

• central brain area

Common metabolic signatures in anorectics and bulimics :


AN > HV BN > HV

• occipital cortex

• orbitofrontal cortex

• mesiotemporal cortex

Results : metabolic imaging in AN and BN


Human studies : ongoing

CB1R PET in eating disorders : repeat study in

recovering anorectics and bulimics

CB1R PET in obesity : what about the opposite

site of the eating disorder spectrum?

40

Acknowledgements

• All study participants

• University Hospitals Leuven :

• Laboratory for Experimental and Functional Neurosurgery

• Merck & Co, Inc. for the tracer precursor

• Research Council K.U. Leuven (OT/05/58)

Nuclear Medicine team

Centre for Eating Disorders

PET Radiopharmacy team


in vivo molecular imaging of the brain type 1 cannabinoid receptor in eating disorders

Documents

anorexia nervosarestrictive

anorexia nervosabingeing

activitybased anorexia

cannabinoid receptor18fmk

eating disorders

endocannabinoid anandamide

receptor ki nmhcb10

brain type