Effect of Exenatide, Sitagliptin or Glimepiride on Functional ß -Cell Mass

1. Male and female patients age 18 to 70 years.

2. Ability to provide written informed consent

3. Mentally stable and able to comply with the procedures of the study protocol

4. Clinical history compatible with impaired fasting glucose or early T2D as defined by a plasma glucose concentration between 110-159 mg/dl following a 12 hour overnight fast performed off any anti-diabetogenic agent for at least 2 weeks (6 weeks for thiazolidinediones)

5. Stable body weight (+ 5%) for at least 2 weeks

6. Female Patients: Agree to use adequate contraception if reproductively capable. Adequate contraception includes either a hormonal or barrier method, or surgical sterilization.

1. Diagnosis of type 1 diabetes

2. Receiving insulin, exenatide (Byetta®), or sitagliptin (Januvia®) treatment or taking > 2 oral anti-diabetogenic agents for the treatment of diabetes

3. BMI > 44 kg/m2

4. Allergy to any sulfa-containing compounds

5. Uncontrolled hypertension (Systolic Blood Pressure >160 or Diastolic Blood Pressure > 100 mmHg)

6. Uncontrolled hyperlipidemia (triglycerides > 500 or LDL > 160 mg/dl)

7. Elevation of liver function tests > 2 times the upper limit of normal

8. Estimated Glomerular Filtration Rate (GFR) < 55 ml/min/1.73m2 (46)

9. Hyperkalemia (serum potassium > 5.5 mmol/L)

10. Moderate anemia (hemoglobin concentration < 12 g/dl in men and < 11 g/dl in women)

11. Female patients: pregnant or lactating

12. Hepatic cirrhosis

13. Known active alcohol or substance abuse

14. Active cardiovascular disease

15. Use of any investigational agent within 6 weeks of the baseline visit

16. Any medical condition that, in the opinion of the investigator, will interfere with the safe completion of the trial