Relative Contribution of Brain Insulin Action for Postprandial Metabolism

Subjects will undergo a 75 g OGTT (180 min) combined with a double tracer dilution. The double-tracer dilution technique will be used to quantify endogenous glucose production, glucose appearance and disappearance rate. \[6,6-2H\]glucose will be infused for a total of 300 minutes,while the infusion will start 120 minutes prior the OGTT and will last until the end of the OGTT. Intranasal insulin will be administered 15 minutes prior to the start of the OGTT. The drink consumed at time point 0 min contains 75 gram glucose, enriched with \[U-13C6\]-glucose.

Subjects will undergo a 75 g OGTT (180 min) combined with a double tracer dilution. The double-tracer dilution technique will be used to quantify endogenous glucose production, glucose appearance and disappearance rate. \[6,6-2H\]glucose will be infused for a total of 300 minutes,while the infusion will start 120 minutes prior the OGTT and will last until the end of the OGTT. Placebo spray will be administered 15 minutes prior to the start of the OGTT. The drink consumed at time point 0 min contains 75 gram glucose, enriched with \[U-13C6\]-glucose. To mimic insulin spill-over from nasal spray into systemic circulation, an i.v. insulin bolus of 3 mU × kg-1. will be administered over ten minutes starting at time point -15 minutes on the placebo spray day. On the insulin spray day a comparable amount of saline will be infused.