The real-time measurements of blood nitric oxide (NO) and hydrogen peroxide (H2O2) levels under acute hyperglycemia

Vascular endothelial dysfunction is one of the earliest recognizable events under hyperglycemic conditions. It is characterized by decreased endothelium-derived nitric oxide (NO) and increased oxidative stress, such as superoxide and hydrogen peroxide (H 2 O 2 ). However, the real-time changes in blood NO and H 2 O 2  levels under acute hyperglycemia have not been evaluated. In this study, acute hyperglycemia (≥600 mg/dl) was induced by intravenous infusion of 50% D-glucose for three hours. During this time, blood NO or H 2 O 2 levels were measured by inserting calibrated NO or H 2 O 2 microsensors (100 μm diameter) into each femoral vein. In the saline control group, NO slightly decreased (~20 nM) throughout the three hours of saline infusion (n=6). By contrast, acute hyperglycemia caused an initial NO increase, followed by a continuous reduction (~104 nM) by the end of infusion (p<0.01, n=4). On the other hand, H 2 O 2  levels were reduced (~4.4 μM) following the three hours in the saline group. Moreover, there were significantly higher H 2 O 2  levels throughout the majority of time points in the acute hyperglycemia group (p<0.05, n=5) compared to controls. In summary, acute hyperglycemia can slowly reduce the release of NO in blood associated with an increased H 2 O 2  level.