Background To test the effect of normoglycemia and glucagon-like peptide-1 (GLP-1), alone or in combination, on the possible normalization of endothelial function in type 1 diabetes. Methods Fifteen people with type 1 diabetes participated in three experiments: reaching and maintaining normoglycemia for 4 h; reaching and maintaining hyperglycemia plus GLP-1 infusion for 4 h; and reaching and maintaining normoglycemia for 4 h with simultaneous infusion of GLP-1. Results Both normoglycemia and GLP-1 infusion restored endothelial function and decreased and plasma 8-iso prostaglandin F2α levels. However, only the combination of normoglycemia and GLP-1 was able to normalize endothelial function. Conclusions This study confirms that long-lasting hyperglycemia in type 1 diabetes induces a permanent alteration which contributes to maintaining endothelial dysfunction even when glycemia is normalized, and that in the presence of normoglycemia, GLP-1 can contribute to normalizing endothelial function.
