Evaluation of sweet taste receptors, glucose transporters, glucose absorption and gastrointestinal hormones in obesity and after bariatric surgery.
Dr. Nam Nguyen
90 participants
Jan 12, 2012
Interventional
Conditions
Summary
The purpose of this study is to explore the importance of gut sweet taste sensors in the regulation of sugar control, appetite and body weight during health, obesity and after bariatric surgery. The findings of the current study may provide further insights into the mechanisms underlying the development of obesity and diabetes mellitus, which, in turn, can have a great potential therapeutic implication. Hypothesis: We hypothesise that the number of these sweet taste receptors will be markedly reduced in the small intestine of morbidly obese patients but will be increased after bariatric surgery, leading to increased incretin responses and subsequently, better glucose control and body weight (via high GLP-1). We further hypothesise that the greater release of GLP- 1 (thus, release of insulin) after RYGB over LAGB is related to the higher expression of small intestinal sweet taste receptors, leading to better glucose control and weight loss in these patients. This study, therefore, aims to evaluate the expression of small intestinal sweet taste receptors before and after a sugar ‘meal’ and its relationship to GLP-1 concentration, glucose control and body weight in morbidly obese subjects and patients who undergo RYGB and LAGB.
Eligibility
Inclusion Criteria3
- Obese patients - BMI > 40kg/m2
- Bariatric patients - RYGB or LAGB surgery > 12 months ago
- Healthy volunteers - BMI < 40kg/m2
Exclusion Criteria5
- History of severe respiratory, cardiovascular, hepatic and/or renal disease, chronic alcohol abuse or epilepsy (excluded by history)
- Medication that may influence gastrointestinal function
- History of surgery to the gastrointestinal tract apart from the RYGB or LAGB
- Female patients not using appropriate contraceptive method (ie oral contraceptive pill, diaphragm, Depo-Provera hormonal contraceptive injection, intrauterine device, Norplant method)
- Pregnant and/or breastfeeding mothers
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Interventions
Arm 1 - Patients who have previously had bariatric surgery After inserting a thin endoscope through the nose to the duodenum, 3 biopsies will be taken. A glucose solution (30g glucose and 3g #-OMG) will then be infused into the duodenum for 30 minutes. We will collect another 3 biopsies at the end of the infusion. After 30 minutes of glucose infusion, the endoscope will be removed. Blood samples will be taken at various timepoints throughout the study to measure levels of glucose, 3-OMG, and hormones produced in response to glucose. Arm 2 Obese patients will undergo the same procedure as those in Arm 1, but will have the procedure done twice, once before and once after a two week Optifast diet (Taking one satchet of Optifast dietary supplemement (different flavoured shakes) 3x daily for two weeks) Apart from two cups of low starch vegetables daily and calorie free fluids, this will be all they will consume for the two week period. Optifast products are classified as very low calorie diets (also known as VLEDs or very low energy diets) have been shown to be very effective in the treatment of obesity, with weekly weight losses averaging approximately 2.0kg in the first 4-6 weeks, providing greater initial weight loss than other forms of calorie restriction. Each 54g satchet of Optifast dietary supplement contains: Skimmed Milk Powder, Calcium Caseinate, Sodium Caseinate, Inulin, Maltodextrin (Corn), Vegetable Oils (Canola, Sunflower), Fructose, Sugar, Coffee Extract, Minerals (Potassium Citrate, Magnesium Carbonate, Potassium Phosphate, Sodium Chloride, Ferric Pyrophosphate, Zinc Sulphate, Copper Gluconate,Tricalcium Phosphate, Manganese Sulphate, Sodium Fluoride, Chromium Chloride, Sodium Selenite, Sodium Molybdate, Potassium Iodide), Glucose Syrup (Corn, Wheat Or Potato), Medium Chain Triglycerides, Flavour, Fish Oil, Corn Starch, Vegetable Gum (414), Sweeteners (Aspartame, Acesulfame Potassium), Emulsifiers (Soy Lecithin, 472c, 471), Vitamins (Ascorbic Acid, Vitamin E Acetate, Nicotinamide, Calcium Pantothenate, Pyridoxine Hydrochloride, Thiamin Hydrochloride, Riboflavin, Vitamin A Acetate, Folic Acid, Biotin, Phytonadione, Cholecalciferol, Cyanocobalamin), Antioxidants (304, 307). Contains Milk, Soy, Wheat and Fish. Contains Phenylalanine. Made on equipment that also processes products containing Egg and Celery. To Monitor adherance to the diet a weekly phone call is made to see how they are progressing with their diet, and also weight is measured before and after the two weeks to monitor weight loss. Arm 3/Healthy control In the healthy volunteers, the same procedure is performaed as the other arms. After inserting a thin endoscope through the nose to the duodenum, 3 biopsies will be taken. A glucose solution (30g glucose and 3g #-OMG) will then be infused into the duodenum for 30 minutes. We will collect another 3 biopsies at the end of the infusion. After 30 minutes of glucose infusion, the endoscope will be removed. Blood samples will be taken at various timepoints throughout the study to measure levels of glucose, 3-OMG, and hormones produced in response to glucose.
Locations(1)
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ACTRN12613000758707