Decreased cerebral opioid receptors availability related to hormonal and psychometric profile in restrictive-type anorexia nervosa.

Purpose: The opioid system role in anorexia nervosa (AN) pathophysiology is still unclear since conflicting results were reported on peripheral and cerebrospinal fluid opioids levels. The study main aim was to evaluate cerebral AN opiate receptor availability by using [C] diprenorphine, a ligand with non-selective binding.

Methods: In vivo [C]diprenorphine cerebral non-displaceable binding potential (BP) evaluated by PET imaging was compared between three groups : 17 undernourished restrictive-type AN patients (LeanAN), 15 AN patients having regained normal weight (RecAN) and 15 controls. A lower BP may account for an increased opioid tone and vice versa. Serum hormones and endogenous opioids levels, eating-related and unspecific psychological traits were also evaluated.

Results: Compared to controls, LeanAN and RecAN patients had decreased [C]diprenorphine BP in middle frontal gyrus, temporo-parietal cortices, anterior cingulate cortex and in left accumbens nucleus. Hypothalamo-pituitary (H-P), left amygdala and insula BP was found decreased only in LeanAN and that of putamen only in RecAN. LeanAN presented higher dynorphin A and enkephalin serum levels than in controls or RecAN. Inverse correlations were found in total group between : 24 h mean serum cortisol levels and anterior cingulate gyrus or insula BP; eating concern score and left amygdala BP. Positive correlation were found between leptin and hypothamus BP; LH and pituitary BP.

Conclusions: Low opiate receptor availability may be interpreted as an increased opioid tone in areas associated with both reward/aversive system in both AN groups. The relationship between the opioid receptors activity and hypercorticism or specific psychometric scores in some of these regions suggests adaptive mechanisms facing anxiety but also may play a role in the disease perpetuation.