Ascorbic acid blocks hyperglycemic impairment of endothelial function in adolescents with type 1 diabetes

Objective: To determine whether acute ascorbic acid infusions alter the effect of hyperglycemia on endothelial function in adolescents with type 1 diabetes. Research design and methods: The forearm blood flow (FBF) reactive hyperemic response to 5min of upper arm occlusion was studied in eight adolescents with type 1 diabetes during euglycemic and hyperglycemic insulin clamp (40mU/m2/min) with and without ascorbic acid infusion (3mg/min). Results: The ratio of post- to preocclusion FBF decreased during hyperglycemia without ascorbic acid (p=0.013), but did not change during hyperglycemia with ascorbic acid. The changes during hyperglycemia were different between the two studies (p=0.038). Similar results were found when the percent change in forearm vascular resistance following occlusion was assessed. Conclusions: These results indicate that antioxidant treatment with ascorbic acid blocks acute hyperglycemic impairment of endothelial function in adolescents with type 1 diabetes.