Sibutramine promotes amygdala activity under fasting conditions in obese women

Rationale: Sibutramine, a centrally-acting selective monoamine reuptake inhibitor, has been used as an appetite suppressant drug in obesity. Objectives: To gain insight into the central nervous actions of sibutramine, brain responses to pictures of food items after sibutramine vs placebo application were assessed by functional magnetic resonance imaging (fMRI) in obese women. Methods: In a randomized double-blind crossover design, 10 healthy obese women (BMI 31.8-39.9 kg/m ²) received 15 mg/d of sibutramine vs placebo for 14 d. Obese participants, and a group of 10 age-matched normal weight controls, viewed pictures of food items and control objects in hungry and satiated states while lying in the MR scanner. The paradigm followed a block design. In obese participants, fMRI measurements were conducted prior and after two weeks of daily sibutramine or placebo administration, whereas control participants were scanned only at one point in time. Results: Upon food item presentation, obese participants showed increased brain activity in areas related to emotional and reward processing, perceptual processing, and cognitive control as compared to normal weight controls. Sibutramine exerted a divergent satiety-dependent effect on amygdala activity in obese participants, increasing activity in the hungry state while decreasing it under conditions of satiation. Conclusions: Our results demonstrate a modulatory influence of sibutramine on amygdala activity in obese women which may underlie the appetite suppressant effects of the drug.