Using FDG-PET functional neuroimaging to investigate regional brain responses to food ingestion in normal weight, obesity and after Roux-en-Y gastric bypass (RYGB) and the role of gut peptides after RYGB

Student thesis: Doctoral ThesisDoctor of Medicine by Research


Roux-en-Y gastric bypass (RYGB) causes reduced food intake and sustained weight loss. The nature of differences in gut-to-brain communication and the associated differences in brain responses to food ingestion after RYGB that translate into reduced food intake are not yet elucidated. One theory is exaggerated postprandial satiety hormone responses. 
I conducted a cross-sectional study in twelve normal weight (NW, BMI 22.3±1.4kg/m2), 21 obese (Ob, BMI 34.1±2.6kg/m2) and 9 post-RYGB (RYGB, 18±12 months post-surgery, BMI 34.0±3.3kg/m2) subjects. Subjects underwent [18F]-fluorodeoxyglucose positron emission tomography (FDG-PET) neuroimaging after overnight fasting: once FED (400 kcal mixed meal), once FASTED (water only) in random order. RYGB subjects were also studied FED and FASTED with somatostatin (to inhibit pancreatic and gut peptide secretion) with basal insulin replacement. I compared regional brain FDG uptake, a neuronal activation marker, using Statistical Parametric Mapping. Subjects underwent a post-scan ad libitum meal; fullness, hunger, anticipated pleasantness of eating, nausea and relaxedness were assessed using visual analogue scales (VAS); and pancreatic and gut peptides were measured. 
This thesis presents: 
• Development of a new functional neuroimaging protocol using FDG-PET to image the regional brain responses to food ingestion 
• Regional brain responses to food ingestion across all subjects 
• Differences in regional brain responses to food ingestion between normal weight, obese and post-RYGB subjects 
• Correlations between food-evoked signal change and ad libitum food consumption and appetitive sensations 
• Investigation of the role of exaggerated postprandial gut peptide responses in post-RYGB subjects.
Date of Award1 Jan 2019
Original languageEnglish
Awarding Institution
  • King's College London
SupervisorStephanie Amiel (Supervisor) & Paul Marsden (Supervisor)

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