Dopamine and Insulin Resistance

Not Applicable

Completed

• Conditions: Obesity
• Interventions: Radiation: PET scan; Procedure: Oral glucose tolerance test; Procedure: MRI; Behavioral: Psychological scales to assess attitudes and behaviors related to eating and quality of life; Other: Caloric Restriction

• Registration Number: NCT00802204
• Lead Sponsor: Vanderbilt University

Brief Summary

Obese individuals have fewer striatal dopamine type 2 receptors (DRD2) than normal weight individuals. Lower DRD2 levels are associated with addiction and a decreased sense of pleasure.Obesity is also associated with insulin resistance (poor insulin action).We propose that insulin resistance and low DRD2 are associated. Using PET imaging,we aim to determine DRD2 binding potential (BP) in the brain is associated with insulin resistance and neuroendocrine hormone levels. Obese participants will be compared to lean, gender and age similar participants. We also aim to determine the effect of caloric restriction on DRD2 BP in obese subjects

Detailed Description

In has been reported obese individuals have fewer striatal dopamine type 2 receptors (DRD2) compared to normal weight individuals congruent with diet induced obese rodent models and similar to models of addiction. Lower DRD2 levels are associated with addiction and a decreased sense of pleasure. Excessive weight gain also contributes to the onset of impaired insulin signaling (insulin resistance). In the brain insulin regulates monoamines and has trophic effects. We propose that the previous reports of low DRD2 in individuals with obesity will be associated with the degree of insulin resistance. Using PET imaging, we aim to determine DRD2 binding potential (BP) in the striatum and hypothesize these measurements will be associated with insulin resistance and potentially other neuroendocrine hormone levels. Obese participants will be compared to lean, sex and age similar participants. We also aim to determine the effect of caloric restriction on DRD2 BP in obese subjects. We hypothesize the caloric restriction will improve insulin resistance and that changes in DRD2 binding will be associated with changes in insulin signaling.

Study Timeline

• Study Start: 2008-12
• Study First Submitted: 2008-12-02
• Study First Submitted QC: 2008-12-03
• Study First Posted: 2008-12-04
• Primary Completion: 2011-04
• Study Completion: 2012-12
• Results First Submitted: 2016-07-14
• Status Verified: 2017-03
• Results First Submitted QC: 2017-03-29
• Last Update Submitted: 2017-03-29
• Results First Posted: 2017-05-10
• Last Update Posted: 2017-05-10

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 28

Inclusion Criteria

• Ages 18-60 yrs
• obese BMI > 30kg/m2 and Weight less than 350 lbs
• lean control BMI 18-25kg/m2

Exclusion Criteria

• Structured exercise > equivalent to 30mins 5x week of walking times a week
• History of Substance Abuse, including but exclusive to alcohol, cocaine, marijuana, heroin, nicotine
• Current psychiatric disorder or significant h/o disorder
• Use or any antidepressants or antipsychotics for last 3-6months or depot antipsychotics in the last 12 months
• Any condition felt by PI or co-investigators to interfere with ability to complete the study
• Inability to abstain from alcohol, physical exercise or > 1 cup of coffee or equivalent daily for 3 days prior to imaging studies
• Significant co-morbidities including atherosclerotic disease, metabolic disease, liver or renal insufficiency or abnormality found on MRI
• Any condition which would interfere with MRI or PET studies, e.g. claustrophobia, cochlear implant, metal fragments in eyes, cardiac pacemaker, neural stimulator, tattoos with iron pigment and metallic body inclusions or other metal implanted in the body which may interfere with MRI scanning
• Subjects on medications determined by PI, ex. sibutramine, frequent benzodiazepines or related drugs, which could affect quality of study for last 3 months.

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: SEQUENTIAL

Arm && Interventions

Group	Intervention	Description
Lean controls	MRI	Lean complete baseline outcome measures only
Lean controls	Oral glucose tolerance test	Lean complete baseline outcome measures only
Obese	PET scan	Obese completing baseline and post-VLCD outcome measures
Obese	Caloric Restriction	Obese completing baseline and post-VLCD outcome measures
Lean controls	PET scan	Lean complete baseline outcome measures only
Obese	MRI	Obese completing baseline and post-VLCD outcome measures
Obese	Psychological scales to assess attitudes and behaviors related to eating and quality of life	Obese completing baseline and post-VLCD outcome measures
Lean controls	Psychological scales to assess attitudes and behaviors related to eating and quality of life	Lean complete baseline outcome measures only
Obese	Oral glucose tolerance test	Obese completing baseline and post-VLCD outcome measures

Primary Outcome Measures

Name	Time	Method
Striatal DRD2 Receptor Binding	Baseline and after 8-10days VLCD	Region of interest compared to reference region to calculate binding potential
Leptin	Baseline to post 8-10days after VLCD
Insulin	Baseline to post 8-10days after VLCD	microU/ml
Acyl Ghrelin	Baseline to post 8-10days after VLCD
Glucose	Baseline to post 8-10days after VLCD
Insulin Sensitivity From Oral Glucose Tolerance Test (OGTT_SI)	Baseline to post 8-10days after VLCD	Insulin Sensitivity from Oral Glucose Tolerance Test was estimated using the minimal model method

Secondary Outcome Measures

Name	Time	Method
Binge Eating Score Questionnaire	Baseline	Increased scores indicate increased binge eating behaviors. Score 0-46

Trial Locations

Locations (1)

Vanderbilt University Medical Center; 🇺🇸 Nashville, Tennessee, United States