• Change in AUC for Glucose During a Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Insulin Sensitivity Index as Measured by M-value. [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Insulin AUC in the First Stage From Baseline to Endpoint. [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Insulin iAUC From Baseline to Endpoint. [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Ratio (Value at Endpoint Divided by Value at Baseline) of AUC for Insulin During a Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in AUC for C-peptide During a Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Incremental for Postprandial Glucose During a Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Incremental for Postprandial Insulin During Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Incremental for Postprandial C-peptide During Meal Challenge Test (MCT). [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in HbA1c [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting Serum Glucose Concentration. [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting C-peptide [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting Insulin [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting Proinsulin [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Body Weight [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting Total Cholesterol. [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting HDL Cholesterol [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting LDL Cholesterol [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Fasting Triglycerides [ Time Frame: Week 20 ] [ Designated as safety issue: No ]
• Change in Percent Body Fat During a Meal Challenge Test (MCT) [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Change in Body Fat Mass During a Meal Challenge Test (MCT) [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Change in Lean Body Mass During a Meal Challenge Test (MCT) [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Change in Waist Circumference [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Change in Hip Circumference [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Change in Waist-to-hip Ratio [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Incidence of Hypoglycemia Events [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Hypoglycemia Rate Per 30 Days Per Patient [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]
• Pedal Edema Score [ Time Frame: 20 weeks ] [ Designated as safety issue: No ]

• *Compare the effects of exenatide, rosiglitazone, and a combination of exenatide and rosiglitazone in subjects with type 2 diabetes treated with metformin on various pharmacodynamic measurements and safety and tolerability.
• *Compare total insulin secretion between the exenatide group, rosiglitazone group, and the exenatide plus rosiglitazone group.

This protocol is designed to evaluate the metabolic effects of adding exenatide, rosiglitazone, or both to an existing regimen of metformin in subjects with inadequate glycemic control.

• Drug: exenatide
• Drug: rosiglitazone

Inclusion Criteria:

• HbA1c of 6.8% to 10.0%, inclusive.
• Body mass index (BMI) of 25 kg/m^2 to 40 kg/m^2, inclusive.

Exclusion Criteria:

• Have participated in this study previously, or have received exenatide, pramlintide acetate, GLP-1 analogs, or dipeptidyl peptidase-IV (DPP-IV) inhibitors
• Have participated in an interventional, medical, surgical, or pharmaceutical study (a study in which an experimental, drug, medical, or surgical treatment was given) within 30 days of study start. This criterion includes drugs that have not received regulatory approval for any indication at the time of study start.

• Treated with any of the following medications:

  • Thiazolidinedione within 5 months of screening;
  • Sulfonylurea within 3 months of screening;
  • Metformin/sulfonylurea combination therapy within 3 months of screening;
  • Alpha-glucosidase inhibitor within 3 months of screening;
  • Meglitinide within 3 months of screening;
  • Insulin for more than 1 week within the 3 months prior to screening.
  • Symlin (pramlintide acetate) injection or Byetta (exenatide) injection at any time
  • Chronic (more than 2 weeks) or recent (within 4 weeks of study start) use of a drug that directly affects gastrointestinal motility
  • Are receiving chronic (lasting longer than 2 weeks) systemic glucocorticoid therapy (excluding topical and inhaled preparations) or have received such therapy within the 4 weeks immediately preceding study start
  • Regular use of a medication with addictive potential such as an opiate, narcotic, or tranquilizer
  • Systemic antineoplastic agent
  • Systemic transplantation medication
  • Drugs for weight loss, including over-the-counter medications, within the 4 months prior to study start