Glucose "peak" and glucose "spike": Impact on endothelial function and oxidative stress

Aim: Data suggest that 2 h hyperglycaemia during an OGTT is less predictive for cardiovascular disease of the glucose "spike" (the difference between the baseline glucose level and the "peak" hyperglycaemia during the test). Methods: A euinsulinemic hyperglycaemic clamp at 10 and 15 mmol/l glucose, with or without vitamin C, was given in increasing steps in diabetic and nor-Mal subjects. Moreover, a hyperglycaemic clamp, 10 mmol/l, was performed in two groups of diabetic patients with different levels of fasting glycaemia. in both the experiments flow mediated dilation and nitrotyrosine were measured. Results: Glucose at 10 and 15 mmol/l resulted in a concentration-dependent induction of endothelial dysfunction and oxidative stress. Vitamin C counterbalanced this effect. The increase of glycaemia to 10 mmol/l induced a significant endothelial dysfunction and increased nitrotyrosine in both the groups of diabetics with different fasting glycaemia. However, when the delta (the difference between the basal value and the peak value) for endothelial function and nitrotyrosine was evaluated, patients with lower basal values showed a worse outcome. Conclusions: Our data suggest that at the same level of hyperglycaemia the grading of the endothelial dysfunction is almost super imposable, but clearly worse in terms of delta from fasting glycaemia. (C) 2008 Elsevier Ireland Ltd. All rights reserved.