Teneligliptin on the Progressive Left Ventricular Diastolic Dysfunction With Type 2 Diabetes Mellitus Study

Inclusion Criteria: * Asians aged from 20 to 85 years old at baseline * Patients with type 2 diabetes mellitus and including either A) or B) criteria. A) Patients necessary to start the treatment using anti-diabetic agent(s) or to change the anti-diabetic agent(s). B) Patients possible to change the anti-diabetic agent(s). * Patients with left ventricular ejection fraction more than 40% * Patients with written informed consent Exclusion Criteria: * Patients with type 1 diabetes mellitus * Patients with slowly progressive type 1 diabetes mellitus positive for pancreatic islets related autoimmune antibody as GAD antibody or IA-2 antibody or ICA antibody * Patients with diabetes mellitus caused by evident genetic factors * Patients with diabetes mellitus caused by secondary factors as endocrine disease or liver disease * Patients with diabetic ketoacidosis or hyperosmolar hyperglycemic syndrome * Patients with any severe infectious diseases or planed any surgical treatments or suffered any severe traumas * Patients with severe liver dysfunction * Patients with hypophyseoprivic or adrenal insufficiency * Patients under malnutrition or starved state or irregular caloric intake or calorie insufficiency or hyposthenia * Patients judged to be unsuitable for the study as they are planning to exercise intensively * Patients judged to be unsuitable for the study as they may drink excessively or abuse drugs * Patients showing QT prolongation in the electrocardiogram * Patients with any past histories of heart failure showing NYHA classification grade more than 3 at baseline * Patients with any past histories of acute coronary syndrome or coronary intervention or cardiac surgery developed within 6 months * Patients with any surgical past histories of mitral valve replacement or mitral valve repair or severe calcification of mitral valve * Patients already treated with Teneligliptin * Women with breast-feeding * Pregnant women or patients who have possibilities of pregnancy * Patients expected to live less than 3 years * Patients with any past histories of drug hypersensitivity against Teneligliptin * Patients already involved in any other interventional clinical trials or planned to be involved * Patients judged to be inappropriate for the study by the doctors in charge