Fig. 6.

Three-stage hyperglycaemic clamp. *Glucose infusion aiming at blood glucose = 5.4 mmol/l above basal. T = time. The hyperglycaemic clamp is used to evaluate beta-cell function. Participants will meet fasting in the laboratory in the morning. After placement of an antecubital venous catheter in both arms, a tracer prime dose (concentration calculated from fasting glucose and body weight) will be injected and infusion of tracers will commence at T = − 120 min. Tracer infusion will continue for 2 h to reach saturation in the circulation. During the 2-h tracer loading period, the muscle and adipose tissue biopsies will be collected. At baseline (time 0), the glucose infusion will be initiated aiming to reach blood glucose concentration at 5.4 mM above fasting. Simultaneously, the tracer infusion rate will be adjusted accordingly. Blood glucose will be measured every 5th minute throughout the remaining clamp and glucose infusion rate (GIR) will be adjusted according to the algorithm. At T = 120 min, the GLP-1 infusion is added. After another hour (T = 180), the arginine bolus is administered, and blood samples are taken continuously for 10 min before ending the clamp