Insulin Resistance and Central Nervous System (CNS) Function in Type 2 Diabetes

Study Overview
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Brief Summary
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The purpose of this study is to examine the effects of treating insulin resistance on memory and attention, brain glucose utilization, and proteins in spinal fluid.

Detailed Description
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Insulin resistant conditions such as impaired glucose tolerance, type 2 diabetes mellitus, and hyperinsulinemia have been associated with an increased risk for memory decline and for Alzheimer's disease. The main study will determine whether treatment with pioglitazone or nateglinide will improve verbal memory and selective attention for older adults with impaired glucose tolerance or mild type 2 diabetes. The main study will also characterize changes in blood concentrations of insulin, inflammatory markers, and the beta-amyloid peptides that are related to Alzheimer's disease. In one sub-study, participants will undergo brain positron emission tomography (PET) imaging before and after 16 weeks of treatment with pioglitazone, nateglinide, or placebo. The purpose of this sub-study is to determine the effects of treatment on brain glucose utilization. In a second sub-study, participants will undergo a lumbar puncture procedure before and after treatment. The purpose of this sub-study is to determine the effects of treatment on spinal fluid concentrations of insulin, inflammatory markers, and beta-amyloid peptides. Together these main and sub-studies should characterize the effects of insulin resistance on cognition and suggest a mechanism by which insulin resistant conditions increase risk for memory decline and for Alzheimer's disease.

Conditions
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Insulin Resistance, Type 2 Diabetes Mellitus

Intervention / Treatment
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* Drug: pioglitazone
* Drug: nateglinide
* Drug: placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Impaired glucose tolerance OR mild type 2 diabetes mellitus OR normal blood sugar regulation Stable weight and activity level Exclusion Criteria: Medications for diabetes Dementia Medications with known effects on memory Serious neurologic disease or head trauma Serious systemic illness (e.g., renal failure or uncontrolled hypertension) Serious psychiatric illness (e.g., schizophrenia or bipolar disorder) Allergy to pioglitazone or nateglinide

Ages Eligible for Study
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Minimum Age: 55 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: Randomized
Intervention Model: Parallel Assignment
Masking: Double


Arms and Interventions

| Intervention/Treatment |
| --- |
|Drug: pioglitazone|nan|
|Drug: nateglinide|nan|
|Drug: placebo|nan|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Verbal memory (main study) |  |  | 
| Selective attention (main study) |  |  | 
| Plasma beta-amyloid levels (main study) |  |  | 
| Cerebral glucose metabolism (sub-study) |  |  | 
| Inflammatory markers in spinal fluid (sub-study) |  |  | 
| Beta-amyloid in spinal fluid (sub-study) |  |  | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Psychomotor speed |  |  | 
| Verbal fluency |  |  | 
| Blood levels of insulin, insulin degrading enzyme, cortisol and inflammatory markers |  |  | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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impaired glucose tolerance