Abstract-Normal insulin action in vivo involves a decrease in stiffness of large arteries (a decrease in aortic pressure augmentation). We determined whether the ability of insulin to decrease arterial stiffness is altered in uncomplicated type 1 diabetes. Nine type 1 diabetic men (age 28Ϯ2 years, body mass index 24Ϯ1 kg/m 2 ) and 9 matched normal men were studied under normoglycemic hyperinsulinemic (sequential 2-hour insulin infusions of 1 [step 1] and 2 [step 2] mU ⅐ kg Ϫ1 ⅐ min Ϫ1) conditions. Central aortic pressure waveforms were synthesized from those recorded in periphery with applanation tonometry on the radial artery and a validated reverse transfer function to construct the central aortic pressure wave every 30 minutes. This allowed the determination of aortic augmentation (the pressure difference between the first and the second systolic peaks) and the augmentation index (augmentation divided by pulse pressure), as the measure of stiffness of large arteries. Whole-body glucose uptake was 44% (step 1) and 37% (step 2) lower (PϽ0.001) in the diabetic patients than in the normal subjects. At baseline, before the insulin infusion, augmentation averaged 0Ϯ1 and 2Ϯ1 mm Hg (NS) and the augmentation index was Ϫ1.5Ϯ4.5% and 4.0Ϯ3.7% (NS) in the normal and diabetic subjects, respectively. After 1 hour of hyperinsulinemia, the augmentation index had decreased significantly (PϽ0.01) to Ϫ9.5Ϯ4.8% in the normal subjects but remained at 4.4Ϯ4.2% in the diabetic patients. A significant decrease was not observed in the diabetic patients until 150 minutes (Ϫ1.2Ϯ4.1%, PϽ0.05 versus baseline). Whole-body glucose uptake was significantly inversely correlated with the change in the augmentation index during step 1 (rϭϪ0.61, PϽ0.01). Insulin resistance in type 1 diabetes involves a defect in the ability of insulin to decrease central aortic pressure. This defect could predispose these patients to premature stiffening of large arteries.

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