Bariatric Surgeries and Glucose Homeostasis During a Mixed Meal Test

Study Overview
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Brief Summary
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Bariatric surgery can lead to improvement or even resolution of type 2 diabetes Mellitus (T2DM) with the spectrum of responses depending also on operation procedures. However, many mechanisms of metabolic action of different surgical techniques still are unclear. The aim of this study is to provide a better understanding of the effects of three types of bariatric surgery (lap banding, gastric bypass and sleeve gastrectomy) on beta-cell function and incretin secretion. A mixed meal tolerance (MMT) test will be performed before and 1 and 12 months after surgery to assess beta cell adequacy and glucagon-like-peptide-1 (GLP1)/glucose-dependent insulinotropic polypeptide (GIP) bioavailability.

Detailed Description
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The effects of different kind of bariatric surgery on glucose homeostasis and its primary determinants (insulin sensitivity and secretion) may differ from one procedure to another. In spite being able to promote improvement/resolution of T2DM, many mechanisms of metabolic action of weight-loss surgery are still unclear. It has been hypothesized that changing the nutrient route through the gut may be a key factor in changing beta cell function and/or insulin sensitivity. In this study a mixed meal test will be used to assess changes in glucose regulation, beta cell function and incretin bioavailability brought about by different bariatric surgeries in obese patients. All participants will ingest a standardized mixed meal (163 Kcal; 57% carbohydrate, 33% fat, 22% prot) and will be monitored for 300 minutes thereafter. Baseline (-20', -10', 0') blood samples will be collected to measure plasma glucose, insulin, C-peptide, incretins and the 13-Carbon-glucose/12-Carbon-glucose (13C-/12C-glucose) ratio (the last one by isotope ratio mass spectrometry). At time 0', subjects will ingest a standardized mixed meal containing 30 g corn flour and 20 g cheese (parmesan) over 20 minutes. Plasma glucose, insulin, C-peptide, GLP1/GIP and the 13C-/12C-glucose ratio will be assessed at +10', +20', +30', +45', +60', +75', +90', +105', +120', +140', +160', +180', +200', +220', +240', +270', +300'. Blood samples will be quickly spun at 1500 g at +4°C, plasma/serum will be collected and stored at -80°C. The 13-Carbon content of maize starch is higher than most of non maize derived sugars. Thus, in individuals on maize and cane sugar free diets, the 13-Carbon/12-Carbon (13C/12C) maize starch ratio is higher (about 10:1000) than the 13C/12C ratio of endogenous glucose derived from glycogenolysis/gluconeogenesis. When these individuals ingest maize starch, the glucose molecules appearing in the systemic circulation which are derived from maize starch will display a 13C-/12C ratio which is identical to maize starch and higher than endogenous glucose. Thus, by measuring the time course of plasma 13C-/12C-glucose ratio, it will be possible to distinguish meal derived glucose from endogenous glucose output (glycogenolysis and gluconeogenesis). This mixed meal test will be performed before and 1 and 12 months after bariatric surgery. The same tests with the same timing will be performed in a control group of obese patients not undergoing bariatric surgery, being treated with diet only.

Official Title
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Effects of Bariatric Surgeries on Glucose Homeostasis and Its Determinants During a Mixed Meal Tolerance Test

Conditions
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Obesity

Intervention / Treatment
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* Procedure: Roux-en-Y-gastric bypass
* Procedure: laparoscopic adjustable gastric banding
* Procedure: laparoscopic sleeve gastrectomy
* Other: diet treatment


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI > 40 kg/m2. BMI ≥ 35 kg/m2 and comorbidities. No major organ disease unrelated to excess body weight. Mentally able to understand the study and willingness to participate in the study Exclusion Criteria: BMI< 35 kg/m2. pregnancy/lactation. prior bariatric or gastrointestinal surgery. Malignancies; mental incapacity; unwillingness or language barriers precluding adequate understanding or cooperation

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Roux-en-Y-gastric bypass<br>morbidly obese subjects undergoing gastric bypass surgery | Procedure: Roux-en-Y-gastric bypass<br>* Gastric bypass consisted of creation of a 15-20 ml gastric pouch, a 150 cm Roux limb, and a 50 cm biliopancreatic limb<br>* Other names: RYGB;|
| gastric banding<br>morbidly obese subjects undergoing laparoscopic adjustable gastric banding | Procedure: laparoscopic adjustable gastric banding<br>* Gastric banding functions by limiting food intake after the placement of an inflatable tube around the stomach just below the gastroesophageal junction, which allows for adjustment of the size of the outlet via the addition or removal of saline through a subcutaneous port.<br>* Other names: LAGB;|
| sleeve gastrectomy<br>morbidly obese subjects undergoing laparoscopic sleeve gastrectomy | Procedure: laparoscopic sleeve gastrectomy<br>* Sleeve gastrectomy involved a gastric reduction of 75 to 80% by resecting the stomach alongside a 30-French endoscope beginning 3 cm from pylorus and ending at the angle of His<br>* Other names: SG;|
| control group<br>morbidly obese subjects not undergoing bariatric surgery, on diet treatment | Other: diet treatment<br>* Hypocaloric diet providing a 1000 Kcal/d deficit from total energy expenditure assessed by indirect calorimetry and physical activity determination<br>* Other names: diet;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in glucose response (pAUC) to mixed meal test between baseline and 1 month after undergoing bariatric surgery or being put on low calorie diet | Blood samples will be taken at basal (-20',-10' and 0'), and after the ingestion of a standardized mixed meal (+10', +20', +30',+45', +60', +75', +90', +105', +120', +140', +160', +180', +200', +220', +240', +270', +300'). | 1 month | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| change in glucose response (pAUC) to mixed meal test between baseline and 12 months after undergoing bariatric surgery or being put on low calorie diet | Blood samples will be taken at basal(-20',-10' and 0'), and after the ingestion of a standardized mixed meal (+10', +20', +30',+45', +60', +75', +90', +105', +120', +140', +160', +180', +200', +220', +240', +270', +300'). | 12 months | 
| changes in β-cell response mixed meal test between baseline and 1 and 12 months after undergoing bariatric surgery or being put on low calorie diet | Beta-cell function will be assessed by a state of art mathematical model applied to glucose and C-peptide curves during a standardized mixed meal. Two main metrics of beta cell function will be derived from modeling: 1) derivative or dynamic control of beta cell function, and 2) proportional or static control of beta cell function. | 1 month and 12 months | 
| changes in active GLP1 systemic bioavailability during a mixed meal test between baseline and 1 or 12 months after undergoing bariatric surgery or being put on low calorie diet. | Blood samples will be taken at basal(-20',-10' and 0'), and after the ingestion of a standardized mixed meal (+10', +20', +30',+45', +60', +75', +90', +105', +120', +140', +160', +180', +200', +220', +240', +270', +300'). | 1 month and 12 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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bariatric surgery, gastric bypass, gastric banding, sleeve gastrectomy, weight loss, Type 2 Diabetes mellitus, GLP1, obesity, mixed meal test