Brain-Gut Interactions in Overweight and Normal Weight Patients With Chronic Abdominal Pain

The objective of this natural history study is to assess the specific gastrointestinal (GI) symptoms and pathophysiology of chronic abdominal pain of unknown origin at the molecular level. This research will test the hypothesis that chronic abdominal pain of unknown etiology has an inflammatory mechanism. Although increased body weight may be associated with increased inflammation, it is unclear that increased body weight is associated with chronic abdominal pain. Accordingly both overweight and normal weight subjects with and without chronic abdominal pain of unknown origin will be included in this study. The study design is a longitudinal natural history. The purpose is to test the relationship between abdominal pain symptoms and intestinal inflammation in two groups (overweight and normal weight patients with chronic abdominal pain of unknown origin). After obtaining informed consent, an initial screening history and physical exam to ensure eligibility will be performed. The participants abdominal pain, psychological distress, quality of life, socio-demographic, and co-morbidities will be assessed via questionnaires. Anthropometry, vital signs, and fasting blood work will be drawn at both of the two visits to the Clinical Center of the National Institutes of Health for clinical screening labs and research purposes. There are three measures of intestinal inflammation including fecal calprotectin, intestinal permeability, and serum cytokine IL-6 levels. A stool sample will be collected to measure fecal calprotectin. Intestinal permeability will be measured with the administration of a sugar based test solution which will be given orally to participants after an overnight fast on their second visit. Excreted urine sugar ratios, expressed per m2 of body surface area, will measure gastrointestinal permeability. Body mass and body fat analysis (plethysmography), intra-abdominal and liver ultrasound, and Fibroscan measures will also be collected on visit two. On either Day 1 or Day 2 of the study, patients will sip, swish and spit additional sweet taste solutions and complete questionnaires about their sweetness preferences related to these tastings.