Effects of Morbid Obesity and Bariatric Surgery on Brain Inflammation, Insulin Resistance and Central Reward System

Study Overview
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Brief Summary
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Background: Morbid obesity is associated with decreased brain µ-opioid receptor availability, possibly resulting in higher food intake needed to gain pleasure from eating. This decrease seems to normalize already 6 months after bariatric surgery, but the longer-term effects have not been studied. Obesity and insulin resistance result in significantly increased brain insulin-stimulated glucose uptake, whereas in every other tissue glucose uptake is lower. One possible explanation to this could be central inflammation and activation of brain glial cells, which has been shown to occur in animal models of obesity. Obesity has also been shown to associate with increased risk of Alzheimer's disease and cognitive decline in several studies. Aims: The first objective of this study is to both study the effects of bariatric surgery as well as compare the effects of gastric bypass and sleeve gastrectomy on food-associated pleasure, extending the follow-up period to 2 years postoperatively. The second aim is to investigate the effect of morbid obesity and weight loss on brain inflammation and gliosis and its association with increased brain insulin-stimulated glucose uptake. Furthermore, association of obesity, insulin resistance, central inflammation and neurocognitive dysfunction are evaluated.

Detailed Description
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Methods: A total of 60 morbidly obese subjects, 30 assigned for Roux-en-Y gastric bypass and 30 for sleeve gastrectomy according to routine treatment protocols will be recruited for this study. A control group of 30 healthy subjects will also be recruited. We will perform 1) structural MRI and MRS, 2) functional MRI during tasting and visual food cues, 3) PET imaging of µ-opioid receptor availability using [11C]-carfentanil, 4) PET imaging of cerebral inflammation and astrocyte activation using [11C]-PK11195, 5) measurement of whole-body and tissue insulin sensitivity by combining hyperinsulinemic, euglycemic clamp with [18F]-FDG-PET, 6) neuropsychological testing. The control group will only be studied once, whereas study procedures will be repeated for the morbidly obese before very-low calorie diet and 6, 12 and 24 months postoperatively.

Official Title
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Effects of Morbid Obesity and Bariatric Surgery on Brain Inflammation, Insulin Resistance and Activation of Central Reward System Studied Using PET- and MRI-imaging

Conditions
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Obesity, Morbid, Insulin Resistance

Intervention / Treatment
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* Procedure: Bariatric surgery


Participation Criteria
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Eligibility Criteria
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Inclusion criteria: Morbidly obese group BMI 35.0-45.0 kg/m2, or BMI 32.0-45.0 kg/m2 and diagnosed diabetes Age 18-60 years Eligible to bariatric surgery evaluated according to normal treatment paradigm Non-obese controls BMI 18-27 kg/m2 Age 18-60 years Fasting plasma glucose ≤6.1 mmol/L Normal values in 2-hour oral glucose tolerance test Exclusion criteria: Morbidly obese group Metal objects in the body (including pacemakers, metallic artificial valve prostheses, inner ear implants, surgical clipses, braces, foreign fragments) Previous participation in PET studies Pregnancy Poor compliance, alcohol or drug abuse Weight over 150 kg or waist circumference over 150 cm Diabetes with fasting glucose levels ≥7.0 mmol/L, or treatment with insulin Any chronic disease, medication or condition that could create a hazard to subject safety, endanger study procedures or interfere with the interpretation of results. Non-obese controls Metal objects in the body (including pacemakers, metallic artificial valve prostheses, inner ear implants, surgical clipses, braces, foreign fragments) Previous participation in PET studies Pregnancy Poor compliance, alcohol or drug abuse Smoking History of eating disorders, drastic weight-gain or weight-loss History of psychiatric disorders Any chronic disease, medication or condition that could create a hazard to subject safety, endanger study procedures or interfere with the interpretation of results

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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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Interventional Model Description: 60 subjects undergoing bariatric surgery (either Roux-en-Y gastric bypass or Sleeve gastrectomy) and 30 healthy controls
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Morbidly obese subjects<br>Bariatric surgery (Roux-en-Y gastric bypass or sleeve gastrectomy) | Procedure: Bariatric surgery<br>* Roux-en-Y gastric bypass or sleeve gastrectomy, chosen based on routine evaluation process<br>* Other names: Sleeve gastrectomy;|
| No Intervention: Control subjects<br>Non-obese controls are only studied at baseline | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in central inflammation | Assessment of brain glial cell activation using [11C]-PK11195 tracer and positron emission tomography | Controls: 0 months; Morbidly obese: preoperatively, 6 months postoperatively | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Changes in central reward system using fMRI imaging | Assessment of brain reward system activation after visual/taste cues using functional MRI | Controls: 0 months; Morbidly obese: preoperatively, 6 months, 12 months, 24 months postoperatively | 
| Changes in brain μ-opioid receptor availability using PET imaging | Assessment of brain μ-opioid receptor availability using [11C]-carfentanil tracer and positron emission tomography | Controls: 0 months; Morbidly obese: preoperatively, 6 months, 12 months postoperatively | 
| Changes in cognitive function studied with testing | Neuropsychological testing focusing on memory, decision-making and inhibition | Controls: 0 months; Morbidly obese: preoperatively, 6 months, 12 months, 24 months postoperatively | 
| Changes in whole-body insulin sensitivity usign FDG-PET imaging | Assessment of whole-body insulin sensitivity using hyperinsulinemic, euglycemic clamp | Controls: 0 months; Morbidly obese: preoperatively, 6 months postoperatively | 
| Changes in tissue-specific insulin sensitivity using FDG-PET imaging | Assessment of insulin-stimulated glucose uptake in the brain, liver, skeletal muscle and adipose tissue by performing positron emission tomography with [18F]-fluorodeoxyglucose tracer during hyperinsulinemic, euglycemic clamp | Controls: 0 months; Morbidly obese: preoperatively | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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obesity, insulin resistance, central nervous system inflammation, bariatric surgery