Comparison of Exenatide vs. Biphasic Insulin Aspart 30 on Glucose Variability in Type 2 Diabetes

Inclusion Criteria: * Provision of informed consent prior to any study specific procedures. * Men and women (non-pregnant and using a medically approved birth-control method) aged between 18 and 70 years at screening. * Confirmed type 2 diabetes with history of at least half a year. * Treatment with stable, maximum tolerated doses of metformin (≧1500mg/d, ≧3 months). * HbA1c ≥ 7.5% and ≤ 10.0% at screening or within 4 weeks prior to screening (by local laboratory). * Body mass index: 21-35 kg/m\^2. Exclusion Criteria: * Women who are pregnant, intending to become pregnant during the study period, currently lactating females, or women of child-bearing potential not using highly effective, medically approved birth control methods. * Diagnosis or history of: 1. Type 1 diabetes mellitus, diabetes resulting from pancreatic injury or secondary forms of diabetes, e.g., acromegaly or Cushing's syndrome. 2. Acute metabolic diabetic complications such as ketoacidosis or hyperosmolar coma within the past 6 months. * Previous treatment with any dipeptide peptidase-4 (DPP4) inhibitor or glucagon-like peptide-1 (GLP-1) receptor agonists within the past one year. * History of hypersensitivity reaction (e.g., anaphylaxis, angioedema, exfoliative skin conditions) to dipeptide peptidase-4 inhibitor (DPP4) or Acarbose. * Treatment with any anti-diabetic medication for more than 7 consecutive days other than metformin in the last 3months prior to screening. * Treatment with systemic glucocorticoids (oral, intravenous) for more than consecutive 7 days within the past 6 months. * Triglycerides (fasting) \> 4.5 mmol/L (\> 400 mg/dL) at screening or within 4 weeks prior to screening (by local laboratory). * Patients with clinically apparent liver disease characterized by either one of the following: 1. Alanine transaminase (ALT) or aspartate aminotransferase (AST) \> 3x upper limit of normal (ULN) confirmed on two consecutive measurements (by local laboratory) within 4 weeks prior to screening period 2. Impaired excretory (e.g. hyperbilirubinemia) and/or synthetic function, or other conditions of decompensated liver disease such as coagulopathy, hepatic encephalopathy, hypoalbuminemia, ascites and bleeding from oesophageal varices. 3. Acute viral or active autoimmune, alcoholic, or other types of hepatitis. * Patients with moderate /severe renal impairment or end-stage renal disease (estimated Glomerular Filtration Rate ≤ 60 mL/min calculated by using the abbreviated equation developed by the Modification of Diet in Renal Disease (MDRD) study with modification for the Chinese population) at screening or within 4 weeks prior to screening (by local laboratory) * Congestive heart failure defined as New York Heart Association (NYHA) class III or IV. * Significant cardiovascular history within the past 3 months prior to screening defined as: myocardial infarction, coronary angioplasty or bypass graft(s), valvular disease or repair, unstable angina pectoris, transient ischemic attack, or cerebrovascular accident. * History of chronic pancreatitis or idiopathic acute pancreatitis. * History of gastrointestinal disease including gastroenterostomy, enterectomy, Roemheld Syndrome, severe hernia, intestinal obstruction, intestinal ulcer. * History of genetic galactose intolerance, Lapp lactase deficiency and glucose-galactose malabsorption. * History of medullary thyroid carcinoma. * Diagnosed and/or treated malignancy (except for basal cell skin cancer, in situ carcinoma of the cervix, or in situ prostate cancer) within the past 5 years. * History of organ transplant or acquired immunodeficiency syndrome (AIDS). * History of alcohol abuse or illegal drug abuse within the past 12 months. * Potentially unreliable patients and those judged by the Investigator to be unsuitable for the study.