Effect of Adding Vildagliptin on Beta Cell Function and Cardiovascular Risk Markers in Patients With Moderate Metabolic Control During Metformin Monotherapy

Inclusion Criteria: * Diabetes mellitus type 2 * HbA1c \> 6.5%\* ≤ 9.5% \* NOTE: Patients with cardiovascular preconditions (Coronary Heart Disease or Myocard Infarction) require an HbA1c \> 7.0% ≤ 9.5% * Treatment with Metformin at maximal or maximal tolerated dosage, stable for at least 3 months with indication for treatment with an additional medication as judged by the investigator * Age 30 - 80 years * Patient consents that his/her family physician will be informed of trial participation Exclusion Criteria: * Pre-treatment with insulin, peroxisome proliferator activated receptor (PPAR) gamma agonists or other oral antidiabetic treatments (except Metformin) within the last three months * History of type-1-diabetes * Fasting blood glucose \>240mg/dl * Uncontrolled hypertension (systolic blood pressure \>160 and/or diastolic blood pressure \>90) * Anamnestic history of acute infections * Anamnestic history of epilepsy * Anamnestic history of hypersensitivity to the study drugs or to drugs with similar chemical structures * History of severe or multiple allergies * Hereditary galactose intolerance, lapp-lactase defect or glucose-galactose mal-absorption * Treatment with any other investigational drug within 3 months before trial entry * Pregnant or lactating women * Sexually active woman of childbearing age not practicing a highly effective method of birth control as defined as those which result in a low failure rate (i.e. less than 1% per year) when used consistently and correctly such as implants, injectables, combined oral contraceptives, hormonal intrauterine devices, sexual abstinence or vasectomized partner * Progressive fatal disease * History of drug or alcohol abuse in the past 2 years * State after kidney transplantation * Serum potassium \> 5.5 mmol/L * Acute myocardial infarction, open heart surgery or cerebral event (stroke/transient ischemic attack) within the previous 6 months * Any elective surgery during study participation * Have had more than one unexplained episode of severe hypoglycemia (defined as requiring assistance of another person due to disabling hypoglycemia) within 6 months prior to screening visit * History of pancreatitis * Anamnestic history of dehydration, diabetic precoma or diabetic ketoacidosis * Acute or scheduled investigation with iodine containing radiopaque material * Uncontrolled unstable angina pectoris * Anamnestic history of pericarditis, myocarditis, endocarditis, hemodynamic relevant aortic stenosis, aortic aneurysm or heart insufficiency NYHA III or IV * Anamnestic recent pulmonary embolism * History of significant cardiovascular, respiratory, gastrointestinal, hepatic (ALAT and/or ASAT \> 3 times the normal reference range), renal (GFR \< 60 ml), neurological, psychiatric and/or hematological disease as judged by the investigator * Lack of compliance or other similar reason that, according to investigator, precludes satisfactory participation in the study