The Study of Effect of antidiabetic agents on pancreatic beta-Cell REsponsiveness To glucose; comparative Evaluation of DPP-4 Inhibitors and SGLT2 inhibitor, Luseogliflozin

INTERVENTION: Luseogliflozin group: administer 2.5 mg of luseogliflozin orally before or after breakfast Teneligliptin group: administer 20 mg of teneligliptin orally before or after breakfast CONDITION: D003924 Type 2 Diabetes Mellitus ; Diabetes Mellitus, Type 2 PRIMARY OUTCOME: Change in Disposition Index((Delta Ins 0‐120 / Delta Glu 0‐120) x (Matsuda index)) from base line to week 25‐26 (after week 1‐2 of washout period) SECONDARY OUTCOME: 1.Change in Disposition Indexes other than primary outcome ((Delta Ins 0‐30 / Delta Glu 0‐30) x (Matsuda index), (AUCIns / AUCGlu) x (Matsuda index)); 2.Change in proinsulin, proinsulin/CPR ratio, and proinsulin/insulin ratio; 3.Change in HbA1c; 4.Change in oral glucose tolerance test biomarkers (plasma glucose, insulin, proinsulin, C‐peptide); 5.Change in specific blood test biomarkers (NEFA, adiponectin, MDA); 6.Change in General blood tests (plasma glucose, ketone body fraction (venous blood), lipid biomarkers (HDL‐chol, T‐chol, LDL‐chol, TG), hepatic function biomarkers (T‐Bil, AST, ALT, gamma‐GTP), blood count (red blood cell, hemoglobin, hematocrit, leukocyte, platelet), uric acid, serum creatinine; 7.Change in urine tests (urinary albumin, urinary creatinine); 8.Change in blood pressure, body weight, BMI, and body compositions; 9.Change in skin AGEs; 10.Medication adherence; 11.Frequency of adverse events, diseases or the like INCLUSION CRITERIA: Patients meeting the following criteria will be included in the study. 1.patients with type 2 diabetes mellitus whose HbA1c is 7.0% or higher and less than 9.0%, despite diet and exercise therapy alone (drug‐naive) or anti‐diabetic agent treatment other than DPP‐4 inhibitors or SGLT2 inhibitors for 12 weeks or longer in addition to diet and exercise therapy 2.patients who do not start to use anti‐diabetic agent or who do not increase the dose of anti‐diabetic agent within 12 weeks before giving their consent 3.male and female aged >= 20 years and < 80 years 4.patients whose body mass index (BMI) is 20 kg/m2 or higher 5.Patients who provide written consent form to participate in this study after full explanation of the study