2. A hyperglycemic clamp will be performed to measure pancreatic β-cell function. Intravenous catheters are placed within each arm (one for infusion, and one for blood collection). After a baseline period of 30 minutes, the blood glucose level is increased with a loading dose of dextrose followed by a continuous infusion to achieve a steady state condition. Blood samples are collected every 5 minutes, and glucose levels are measured. Insulin levels are measured at 0, 2.5, 5.0, 7.5, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180 minutes after the infusion. The 1st-phase insulin release is the sum of the plasma insulin concentrations at 2.5, 5.0, 7.5 and 10 minutes. The 2nd-phase is the average plasma insulin concentration during the final hour.