Acute Effect of Exenatide on Brain Glucose Metabolism

Inclusion Criteria: 1. Males age 18-65 years old 2. Patients must have Body Mass Index (BMI) between 25 and 40 kg/m2 3. 2-hour glucose concentration above 140mg/dl after 75g glucose load, ie, having impaired glucose tolerance or newly diagnosed type 2 diabetes. 4. Patients must have BMI of 25-40 kg/m2 5. Patients must have no known severe liver or kidney disease, cancer, neurologic, psychiatric or systemic disease, ability to understand the study. 6. Only patients whose body weight has been stable (±3-4 pounds) over the three months prior to study will be included. 7. Patients must have the following laboratory values: * Hematocrit ≥ 34 vol% * Serum creatinine\* ≤ 1.5 mg/dl in males and * Aspartate aminotransferase (AST) serum glutamic oxaloacetic transaminase (SGOT): ≤ 2.5 times upper limit of normal * Alanine aminotransferase (ALT) serum glutamic pyruvic transaminase (SGPT): ≤ 2.5 times upper limit of normal * Alkaline phosphatase ≤ 2.5 times upper limit of normal * If serum creatinine is ≤ 1.5 mg/dl in males, the PI can grant an exception and not exclude the patient if the Glomerular filtration rate (GFR) is \>70 ml/min Exclusion Criteria: Patients are excluded from participation in the study if they meet any of the following criteria: 1. Patients with major chronic illness (cancer, liver, kidney, cardiovascular disease) 2. Patients with BMI over 40 and under 25 3. Patient with age below 18 yrs and over 65 yrs 4. Female subjects 5. Patients with type 1 diabetes 6. Patients treated for type 2 diabetes 7. Subjects with normal glucose tolerance (NGT)