A Study to Determine Acute (After First Dose) and Chronic (After 28 Days) Effects of Empagliflozin (BI 10773) on Pre and Postprandial Glucose Homeostasis in Patients With Impaired Glucose Tolerance and Type 2 Diabetes Mellitus and Healthy Subjects

Inclusion criteria: 1. Male and female patients diagnosed with IGT according to the current ADA guidelines as a two-hour glucose levels of 140 to 199 mg/dl (7.8 mmol/l to 11.1 mmol/l) on the 75-g oral glucose tolerance test (OGTT), with an OGTT performed at the time of the screening visit (Visit 1), or ¿ Male and female patients diagnosed with type 2 diabetes mellitus (T2DM) prior to informed consent, on diet and exercise regimen who are drug-naïve, defined as absence of any oral antihyperglycemic therapy for 12 weeks prior starting with open-label active treatment, or 2. Male and female patients diagnosed with type 2 diabetes mellitus prior to informed consent, who are pre-treated with metformin background therapy, on a stable dose of metformin of at least 1500 mg per day, unchanged for at least 12 weeks prior starting with open-label active treatment 3. HbA1c at Visit 1 (screening) 1. for patients diagnosed of IGT and for healthy subjects: HbA1c \< 6.5% 2. for patients diagnosed of T2DM: HbA1c =6.5% and =10.5% 4. Age = 18 at Visit 1 5. BMI = 20 and = 40 Kg/m2 at Visit 1 6. For patients with antihypertensive treatment, this must be stable (with no change in dosage) within 4 weeks prior starting with open-label active treatment 7. Signed and dated written informed consent by date of Visit 1 in accordance with GCP and local legislation Inclusion criteria for healthy subjects: 8. Males or females matching the below mentioned criteria and otherwise healthy according to the investigator¿s assessment, as based on the following criteria: a complete medical history including a physical examination, vital signs (BP, PR) and clinical laboratory tests . 9. HbA1c at Visit 1 (screening): HbA1c \< 6.5% 10. Confirmed normal glucose tolerance (NGT) by OGTT 11. Age = 45 and = 55 at Visit 1. 12. BMI = 30 and = 40 Kg/m2 (Body Mass Index) at Visit 1. 13. Signed and dated written informed consent by date of Visit 1 in accordance with GCP and local legislation. Exclusion criteria: 1. Acute coronary syndrome (non-STEMI \[ST elevation myocardial infarction\], STEMI, unstable AP \[angina pectoris\]), stroke or Transient Ischemic Attack (TIA) within 6 months prior to informed consent. 2. Uncontrolled hyperglycaemia with a glucose level \> 240 mg/dl (\> 13.3 mmol/L) after an overnight fast during placebo run-in and confirmed by a second measurement (not on the same day). 3. Any other antidiabetic drug within 12 weeks prior to starting the open-label active treatment (Visit 4) except those defined as background via inclusion criterion 1c. 4. Indication of liver disease, defined by serum levels of either Alanine Aminotransferase (ALT \[SGPT\]), Aspartate Aminotransferase (AST \[SGOT\]), or alkaline phosphatase above 3 x upper limit of normal (ULN) as determined during screening and/or run-in phase. 5. Impaired renal function, defined as estimated Glomerular Filtration Rate (eGFR) \< 60 ml/min (moderate and severe renal impairment) as determined during screening and/or run-in phase. 6. Medical history of insufficient bladder emptying (i.e. neurogenic bladder disorders). 7. Patients with an Haemoglobin (Hb) \< 11.5 g/dl (for males) and Hb \< 10.5 g/dl (for females) at Visit 1. 8. Bariatric surgery within the past two years and other gastrointestinal surgeries that induce chronic malabsorption within the last 5 years. 9. Medical history of cancer (except for basal cell carcinoma) and/or treatment for cancer within the last 5 years. 10. For patients on metformin background therapy, the investigator must check for potential exclusion criteria according to local metformin label. 11. Treatment with anti-obesity drugs 3 months prior to informed consent or any other treatment at the time of screening (i.e. surgery, aggressive diet regimen, etc.) leading to unstable body weight. 12. Current treatment with systemic steroids at time of informed consent or change in dosage of thyroid hormones within 6 weeks prior to informed consent or any other uncontrolled endocrine disorder except T2DM. However, the use of inhaled steroids (e.g., for asthma, Chronic Obstructive Pulmonary Disease \[COPD\]) is not an exclusion as these do not cause systemic steroid action. 13. Alcohol or drug abuse (according to investigators judgment) within the 3 months prior to informed consent that would interfere with trial participation or any ongoing condition leading to a decreased compliance to study procedures or study drug intake. 14. Intake of an investigational drug in another trial Participation in another trial within 30 days prior to intake of study medication in this trial. 15. Pre-menopausal women (last menstruation \< = 1 year prior to informed consent) who: Are nursing or pregnant or Are of child-bearing potential and are not practicing an acceptable method of birth control, or do not plan to continue using this method throughout the study and do not agree to submit to periodic pregnancy testing during participation in the trial. 16. Any other clinical condition that would jeopardize patients safety while participating in this clinical trial.