Endocrinological and Neuronal Aspects of Bariatric Surgery

Change in Functional magnetic resonance imaging following intravenous glucose infusion.

Change in responsivity of the hypothalamus (extracted as percent signal change) as the core region of homeostatic control will be assessed after an intravenous glucose infusion (by calculating the area under the curve of hypothalamic responsivity) before and after bariatric surgery or dietary intervention.

Time frame: 2 weeks before surgery or start of dietary intervention and 2 weeks after surgery or start of dietary intervention.

Experimental functional magnetic resonance imaging task (gustatory stimulation).

Neuronal gustatory processing of food stimuli will be assessed (ingestion of sweet liquids using a gustometer) using a general linear model (comparing brain activation during ingestion of sweet liquids with brain activation during the ingestion of water) and within as well as between groups analyses. Changes in neural gustatory processing of food stimuli will be assessed before and after bariatric surgery or dietary intervention.

Time frame: 2 weeks before surgery or start of dietary intervention and 2 weeks after surgery or start of dietary intervention.

Assessment of glucose-induced changes in peripheral ghrelin using blood samples.

Blood is collected to measure the concentration of peripheral ghrelin as an indicator of hormonal satiety signaling. Blood samples are collected at the beginning and end of each experimental session to assess the influence of intravenuous infusion of glucose on ghrelin signaling. Blood samples will be analysed using using commercially available kits (enzyme-linked immunosorbent assay).

Time frame: 15 minutes before and 15 minutes after functional magnetic resonance imaging