Increased brain type 1 cannabinoid receptor availability in patients with anorexia and bulimia nervosa.

Objectives The endocannabinoid system is a possible target in eating disorder treatment. We used [¹⁸F]MK-9470 PET to test whether in vivo binding of this type 1 cannabinoid receptor (CB1R) ligand is altered in bulimic and anorectic patients compared to healthy volunteers.

Methods We investigated 16 female bulimia nervosa patients (BN;mean age=23.8±7.1;range 17-45y) and 14 anorexia nervosa patients (AN;mean age=20.5±3.6;range 17-30y) using [¹⁸F]MK-9470 PET. The control group consisted of 19 women (mean age=25.2±8.5;range 18-45y).Parametric modified standardized uptake value (mSUV) images reflecting receptor availability were calculated. For regional analysis, mSUV values were normalized on individual lobal grey matter mSUV.Statistical parametric mapping (SPM2;p_FWE<0.05) and volume-of-interest (VOI;unpaired t-tests,p<0.05) analyses were performed.

Results CB1R availability was increased in cortical and subcortical brain areas in AN patients,not in BN patients,compared to healthy controls (+24.5%,p=0.0003). Regionally, CB1R availability was most increased in the insula in AN and BN patients (p=0.01 and p=0.0004) and in inferior frontal and inferior temporal areas in AN patients (p=0.02). Between AN and BN patients no differences in regional CB1R availability were found.

Conclusions Global CB1R upregulation in AN patients is a possible compensatory mechanism in line with the hypothesis of an underactive endocannabinoid system. Our results also point to regional similarities of CB1R dysregulation in AN and BN in the insular cortex, a region important in integration of interoceptive information including primary gustatory information.

Research Support Research Council KU Leuven (OT/05/58).