INS and type 2 diabetes mellitus: In spite of insulin therapy in addition to dietary/exercise therapy or concomitant oral drug therapy other than DPP-4 inhibitors over ≥12 weeks, the T2D patients had high glucose levels than the healthy volunteers (HbA1c, 8.3 ± 0.2% vs. 5.4 ± 0.2%; FBG, 189 ± 24 mg/dL vs. 93 ± 2 mg/dL), and the duration of T2D was 19 ± 6 years.