The aim of the study is to show that treatment with Glargine will lead to an improvement in beta cell function especially within times of maximal beta cell stress occurring after a meal. For this reason three different standardized test meals (breakfast, lunch, dinner) will be performed and the postprandial secretion of intact proinsulin levels will be measured. These measurements will be performed with patients treated in combination with metformin and insulin glargine versus metformin plus NPH insulin (within the core study) and if significant difference is observed, with a third treatment arm with metformin plus insulin detemir.