Figure 3.

(A) Study protocol of the 2-step hyperglycemic clamp study: During step 1 of the study, plasma glucose level was acutely raised and maintained at 12 mmol/L by an initial 50% dextrose bolus followed by 20% glucose infusion. After 90 minutes, 20% glucose was withdrawn, allowing plasma glucose to return to baseline. A 75-g of oral glucose was then administered to induce incretin. Forty minutes later, step 2 of the clamp study was started by 50% dextrose bolus followed by 20% glucose infusion to raise and maintain plasma glucose level at 12mmol/L for another 90 minutes. Plasma insulin concentrations were measured at 2-minute intervals during the first 10 minutes, then at 10 minute intervals during the remaining 80 minutes of each step of the clamp. (B) The average relative insulin concentrations (baseline insulin concentrations at time of zero of clamp study were set to 100) at each time points during the 2-step clamp for both groups. Asterisks indicate time points when insulin concentrations were statistically different between the 2 groups. (C)AUC of phase 1 (0-10 minutes) and phase 2 (10-90 minutes) insulin secretion during the two-step hyperglycemic clamp study. P values of the differences between the 2 groups are indicated.