Hyperglycemia Increases Muscle Blood Flow and Alters Endothelial Function in Adolescents with Type 1 Diabetes

Alterations of blood flow and endothelial function precede development of complications in type 1 diabetes. The effects of hyperglycemia on vascular function in early type 1 diabetes are poorly understood. To investigate the effect of hyperglycemia on forearm vascular resistance (FVR) and endothelial function in adolescents with type 1 diabetes, FVR was measured before and after 5 minutes of upper arm arterial occlusion using venous occlusion plethysmography in (1) fasted state, (2) euglycemic state (~90 mg/dL; using 40 mU/m2/min insulin infusion), and (3) hyperglycemic state (~200 mg/dL) in 11 adolescents with type 1 diabetes. Endothelial function was assessed by the change in FVR following occlusion. Seven subjects returned for a repeat study with hyperglycemia replaced by euglycemia. Preocclusion FVR decreased from euglycemia to hyperglycemia (=0.003). Postocclusion fall in FVR during hyperglycemia was less than during euglycemia (=0.002). These findings were not reproduced when hyperglycemia was replaced with a second euglycemia. These results demonstrate that acute hyperglycemia causes vasodilation and alters endothelial function in adolescents with type 1 diabetes. In addition they have implications for future studies of endothelial function in type 1 diabetes and provide insight into the etiology of macrovascular and microvascular complications of type 1 diabetes.