Abstract

BackgroundObesity is a growing burden to health and economy worldwide. Obesity is associated with central -opioid receptor (MOR) downregulation, and the interaction between MOR and dopamine D2 receptor (D2R) system in the ventral striatum is disrupted among obese subjects. Weight loss recovers MOR function, but it remains unknown whether it also recovers aberrant opioid-dopamine interaction. Here we addressed this issue by studying subjects undergoing surgical weight loss (bariatric surgery) procedure. MethodsWe recruited 20 healthy non-obese (mean BMI 22) and 25 morbidly obese women (mean BMI 41) eligible for bariatric surgery. Brain MOR and D2R availability was measured using positron emission tomography (PET) with [11C]carfentanil and [11C]raclopride, respectively. Either Roux-en-Y gastric bypass or sleeve gastrectomy was performed to obese subjects according to standard clinical treatment. 21 obese subjects participated in the postoperative PET scanning six months after bariatric surgery. ResultsIn the control subjects, MOR and D2R availabilities were associated in the ventral striatum (r = .62) and dorsal caudate (r = .61). Preoperatively, the obese subjects had disrupted association in the ventral striatum (r = .12) but unaltered association in dorsal caudate (r = .43). The association between MOR and D2R availabilities in the ventral striatum was recovered (r = .62) among obese subjects following the surgery-induced weight loss (mean total weight loss 22 %). ConclusionsBariatric surgery and concomitant weight loss recovers the interaction between MOR and D2R in the ventral striatum in the morbidly obese. Consequently, the dysfunctional opioid-dopamine interaction in the ventral striatum is likely associated with an obese phenotype and may mediate excessive energy uptake. Striatal opioid-dopamine interaction provides a feasible target for pharmacological and behavioural interventions for treating obesity. Clinical Trials RegistrationSleevePET2, NCT01373892, http://www.clinicaltrials.gov