Endocrine Abstracts

Introduction: Patient’s nutrition is generally considered to be the main cause of the accumulation of excess body weight. However, this accumulation can be mitigated by treatment involving drugs with a central mechanism of action. By using functional Magnetic Resonance Imaging (fMRI) we can meliorate our understanding of the organization of neuronal networks responsible for eating behavior, and see how they respond to the mechanisms of action of sibutramine in the treatment of the obesity.

Purpose: To assess changes in eating behavior by fMRI in obesity patients, who took sibutramine for 3 months.

Methods: The study included 30 patients (87% women) with obesity having BMI of ≥30 kg/m² with mean age of 32.6 years, mean body weight (BW) – 110.0 kg, mean waist circumference – 109.8 cm. All patients were right-handed. The control group included 23 people with normal BMI of comparable gender and age. All participants underwent initial fMRI-mapping focused on the dominant hemisphere of the brain. The obesity cohort was treated with sibutramine (Reduxine) at a dose of 10 or 15 mg per day for 3 months. After treatment patients with obesity underwent a second fMRI mapping to assess changes against the initial mapping.

Results: According to fMRI in the group with obesity (before treatment), there was a lower activation of the upper and lower parietal lobes in both hemispheres as well as a lower activation the lateral right frontal cortex compared to the healthy control group. Furthermore, in the obese group there was also a pronounced activation in regions 45, 46, and 9 in the DorsoLateral PreFrontal Cortex (DLPFC) of Broadman fields on the left. Activation of the Supplemental Motor Area (SMA) and DLPFC on the right in patients with obesity was absent, compared to the control group. After 3 months of treatment with sibutramine 80% of patients lose ≥5% of BW. After treatment in obese individuals there was a decrease in activation of the visual cortex, DLPFC and the appearance of activation in area 8 of the Broadman field on the left.

Conclusion: DLPFC and SMA are essential parts of the control neural network related to eating behavior. According to fMRI observations in this study, obese patients treated with sibutramine for 3 months, had a decrease in activation in the projection of the left DLPFC what was regarded as a change in disordered patterns of eating and may indicate increased appetite control due to the treatment.