Hyperinsulinemic-euglycemic clamps
All subjects were admitted to the study site one day prior to the start of the clamp test and fasted overnight after receiving a standard meal before 8:00 p.m. On the morning of the test day, with all subjects in fasting condition and supine position, intravenous blood collection and infusion channels were established by means of an indwelling catheter inserted At the start of the test, short-acting human insulin (human insulin) was injected using a syringe pump through the median cubital vein at a rate of 2.0 mU/kg/min for the first 10 minutes, and 1.0 mU/kg/min for the next 590 minutes simultaneously with 20% glucose solution being infused.Plasma glucose levels were measured for blood samples obtained every 10 minutes through the forearm’s superficial venous access. The infusion rate of glucose, 20% (w/v), was adjusted, based on measured blood glucose levels, to maintain blood glucose at ±10% of the target value. The target blood glucose value during this clamp test was equal to the baseline glucose value subtracting 0.28 mmol/L (5 mg/dL), of which the baseline glucose value was the average of three plasma glucose values measured by intravenous blood sampling at 10-minute intervals after the subject arm was placed in the heated box for 15 minutes.After confirming that GIR was stable, investigators gave either the study drug (oral insulin N11005, 300 IU, p.o.) or the reference drug (Novolin R, 0.1 IU/kg, i.h. in the abdomen).