Hyperinsulinemic-euglycemic Clamp Protocol

Patients arrived at the CRC at 0650 on the day of the clamp test. A primed-continuous infusion {3.6 mg/kg [(free plasma glucose in mg/dL)/90]} of D-[6,6-²H₂] glucose (99% enriched, Cambridge Isotope Laboratories) was started at 0700. At 0855, the somatostatin infusion (0.1 μg · kg BW⁻¹ · min⁻¹) was commenced, simultaneously with infusion of 20 mU · min⁻¹ · m⁻² (low-dose for 2 h, low clamp), followed by 40 mU · min⁻¹ · m⁻² (high-dose for 2 h, high clamp) of short-acting human insulin (Insuman Rapid, Sanofi-Aventis) (36 (link)). Plasma glucose was measured every 5 min and kept constant by a variable intravenous glucose infusion (20% glucose, enriched in D-[6,6-²H₂] glucose). Insulin-stimulated whole-body glucose disposal (M value: expressed as mg · kg BW⁻¹ · min⁻¹) was calculated as described (37 (link)). M/I was calculated as the HEC-derived M value adjusted for the prevailing insulin concentrations during steady-state conditions. For measuring endogenous glucose production (EGP), participants received a 20-min priming bolus [0.36 mg · kg BW⁻¹ · min⁻¹ · fasting plasma glucose (mg/dL)] of D-[6,6-²H₂] glucose (99% enriched in ²H glucose; Cambridge Isotope Laboratories) at −240 min, followed by a continuous infusion (0.036 mg · kg BW⁻¹ · min⁻¹) (25 (link)).