Deranged endocannabinoid responses to hedonic eating in underweight and recently weight-restored patients with anorexia nervosa

Background: A dysregulation of reward mechanisms was suggested in the pathophysiology of anorexia nervosa (AN), but the role of the endogenous mediators of reward has been poorly investigated. Endocannabinoids, including anandamide and 2-arachidonoylglycerol, and the endocannabinoid-related compounds oleoylethanolamide and palmitoylethanolamide modulate food-related and unrelated reward. Hedonic eating, which is the consumption of food just for pleasure and not homeostatic need, is a suitable paradigm to explore food-related reward. Objective: We investigated responses of endocannabinoids and endocannabinoid-related compounds to hedonic eating in AN. Design: Peripheral concentrations of anandamide, 2-arachidonoylglycerol, oleoylethanolamide, and palmitoylethanolamide were measured in 7 underweight and 7 weight-restored AN patients after eating favorite and nonfavorite foods in the condition of no homeostatic needs, and these measurements were compared with those of previously studied healthy control subjects. Results: 1) In healthy controls, plasma 2-arachidonoylglycerol concentrations decreased after both types of meals but were significantly higher in hedonic eating; in underweight AN patients, 2-arachidonoylglycerol concentrations did not show specific time patterns after eating either favorite or nonfavorite foods, whereas in weight-restored patients, 2- arachidonoylglycerol concentrations showed similar increases with both types of meals. 2) Anandamide plasma concentrations exhibited no differences in their response patterns to hedonic eating in the groups. 3) Compared with 2-arachidonoylglycerol, palmitoylethanolamide concentrations exhibited an opposite response pattern to hedonic eating in healthy controls; this pattern was partially preserved in underweight AN patients but not in weight-restored ones. 4) Like palmitoylethanolamide, oleoylethanolamide plasma concentrations tended to be higher in non-hedonic eating than in hedonic eating in healthy controls; moreover, no difference between healthy subjects and AN patients was observed for food-intake-induced changes in oleoylethanolamide concentrations. Conclusion: These data confirm that endocannabinoids and endo-cannabinoid-related compounds are involved in food-related reward and suggest a dysregulation of their physiology in AN. This trial was registered at ISRCTN.org as ISRCTN64683774.