Effects of Intranasal Insulin Administration on Tissue Specific Insulin Sensitivity

Subjects administer 2 intranasal sprays into each nostril every minute for 4 minutes, a total of 16 sprays or 160 IU of fast-acting human insulin (Actrapid, Novo Nordisk A/S, Bagsvaerd, Denmark). The glass spray flasks are produced by AeroPump GmBH, Germany and give 0,1 ml of fluid per spray.

Subjects administer 2 intranasal sprays into each nostril every minute for 4 minutes, a total of 16 sprays. Sprays contain Insulin Diluting Medium for Novorapid and Levemir (Novo Nordisk A/S, Bagsvaerd, Denmark). The glass spray flasks are produced by AeroPump GmBH, Germany and give 0,1 ml of fluid per spray. To account for the small amount of insulin absorbed into circulation after the insulin nasal sprays, on the placebo day subjects will be administered 2.5 mU/kg of additional intravenous insulin (Actrapid, Novo Nordisk A/S, Bagsvaerd, Denmark) over 15 minutes.

All subjects will undergo two positron emission tomography (PET) studies. On both visits they are injected with 185 MBq \[18F\]-fluorodeoxyglucose and scanned with a combined PET and computed tomography scanner.

All subjects will undergo two hyperinsulinemic euglycemic clamp studies. The insulin infusion will be administered intravenously at a steady rate of 0.25 mU/kg/min for approximately 170 minutes. Glucose will be administered intravenously as a 200 mg/ml fluid to at varying rate to maintain euglycemia.