Beta-Cell Function of Insulin Glargine Compared to Neutral Protamine Hagedorn (NPH) Insuline and to Insulin Detemir in Combination With Metformin

Inclusion Criteria: * Type 2 Diabetes mellitus according to the ADA criteria * HbA1c between 6.5% and 8.5% * Individually optimized combination therapy with metformin in combination with sulfonylurea in a stable dosage within the last 3 months * Age between 40 and 75 years * Fasting intact proinsulin level \> 7 pmol/Land \< 20 pmol/Lat screening Exclusion Criteria: * Type 1 Diabetes mellitus * Pre-Treatment with insulin within the last 3 months prior to screening * Pre-Treatment with PPARy-agonists (glitazones) within the last 3 months prior to screening * Major micro- or macrovascular complications as judged by the investigator * BMI \> 40 kg/m² * Hypokalemia (K \< 3.5 mmol /L) * History of drug or alcohol abuse * Anamnestic history of hypersensitivity to the study drugs or to drugs with similar chemical structures * History of severe or multiple allergies * Treatment with any other investigational drug within 3 months prior to screening * Progressive fatal disease * History of significant cardiovascular, respiratory, gastrointestinal, hepatic (ALAT and/or ASAT \> 3 times the normal reference range), renal (creatinine \> 1.3 mg/dL in women and \> 1.7 mg/dL in men), neurological, psychiatric and/or haematological disease as judged by the investigator * Pregnancy or breast feeding * Sexually active women of childbearing potential not actively and consistently practicing birth control by using a medically accepted device or therapy