Neuroendocrinological correlates of stress responsiveness and in vivo central serotonin transporter availability in obesity: A C-11-DASB PET study

1850 Objectives To relate hypothalamic-pituitary-adrenal (HPA) axis functioning as a marker for stress responsiveness and in-vivo serotonin-transporter availability (SERT) in heavily obese subjects compared to non-obese healthy controls (HC). Methods Six obese subjects (BMI 41±8 kg/m2, age 46±10 years, 5 females, Beck Depression Inventory 10±6 points) and six HC (BMI 22±2 kg/m2, age 40±6 years, 3 females) underwent C-11-DASB PET. From the PET data, parametric images of the binding potential have been calculated by using the multilinear reference tissue model (Ichise et al., 2003) and evaluated by both VOI analysis with two standardized brain atlases (AAL/Hammers) based on an individual MR coregistration, as well as by voxel-based analysis (SPM8). HPA activity was investigated by the use of the combined dexamethasone/CRH test (Then Bergh et al., 1999). Results Compared with HC, obese subjects showed significantly higher blood cortisol levels (area -under-the-curve 611.6±462.8 vs. 143.1±97.6; p=0.04) and mean curve location 72.0±50.8 vs. 21.6±7.7; p=0.04) while the blood adrenocorticotropic hormone (ACTH) measurements did not differ. No significant correlations between the regional SERT status and both the stimulated blood cortisol and blood ACTH levels were detected. Conclusions These preliminary results suggest no direct correlation between serotonergic neurotransmission and stress response in obesity. Further this study replicates the association between hypercortisolemia and obesity.