The effects of intermittent and constant high glucose in the formation of nitrotyrosine and 8-hydroxydeoxyguanosine (markers of oxidative stress), as well as the possible linkage between oxidative stress and apoptosis in endothelial cells, have been evaluated. Stable high glucose increased nitrotyrosine, 8-hydroxydeoxyguanosine (8-OHdG), and apoptosis levels. However, these effects were more pronounced in intermittent high glucose. Protein kinase C (PKC) was elevated in both such conditions, particularly in intermittent glucose. The adding of the PKC inhibitors bisindolylmaleimide-I and LY379196, a specific inhibitor of PKC-␤ isoforms, normalized nitrotyrosine and reduced 8-OHdG concentration and cell apoptosis in both stable and intermittent high glucose. Similar results were obtained with the MnSOD mimetic Mn(III)tetrakis(4-benzoic acid)porphyrin chloride that normalized nitrotyrosine, 8-OHdG, and apoptosis and inhibited PKC activation. NAD(P)H oxidase was also measured. NAD(P)H oxidase components p47phox, p67phox, and p22phox was overexpressed during both stable and intermittent high glucose. PKC inhibition and MnSOD mimetic normalized this phenomenon. In conclusion, our study shows that the exposure of endothelial cells to both stable and intermittent high glucose stimulates reactive oxygen species overproduction also through PKC-dependent activation of NAD(P)H oxidase, leading to increased cellular apoptosis. Our data suggest that glucose fluctuations may also be involved in the development of vascular injury in diabetes. Diabetes 52:2795-2804, 2003

Adhesion molecules, particularly intracellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, and E-selectin, have been associated with cardiovascular disease. Elevated levels of these molecules have been reported in diabetic patients. Postprandial hypertriglyceridemia and hyperglycemia are considered risk factors for cardiovascular disease, and evidence suggests that postprandial hypertriglyceridemia and hyperglycemia may induce an increase in circulating adhesion molecules. However, the distinct role of these two factors is a matter of debate. Thirty type 2 diabetic patients and 20 normal subjects ate three different meals: a high-fat meal, 75 g of glucose alone, and a high-fat meal plus glucose. Glycemia, triglyceridemia, plasma nitrotyrosine, ICAM-1, VCAM-1, and Eselectin were assayed during the tests. Subsequently, diabetic subjects took simvastatin 40 mg/day or placebo for 12 weeks. The three tests were performed again at baseline, between 3 and 6 days after starting the study, and at the end of each study. High-fat load and glucose alone produced an increase of nitrotyrosine, ICAM-1, VCAM-1, and E-selectin plasma levels in normal and diabetic subjects. These effects were more pronounced when high fat and glucose were combined. Short-term simvastatin treatment had no effect on lipid parameters, but reduced the effect on adhesion molecules and nitrotyrosine, which was observed during every different test. Long-term simvastatin treatment was accompanied by a lower increase in postprandial triglycerides, which was followed by smaller variations in ICAM-1, VCAM-1, E-selectin, and nitrotyrosine during the tests. This study shows an independent and cumulative effect of postprandial hypertriglyceridemia and hyperglycemia on ICAM-1, VCAM-1, and E-selectin plasma levels, suggesting oxidative stress as a common mediator of such effects. Simvastatin shows a beneficial effect on oxidative stress and the plasma levels of adhesion molecules, which may be ascribed to a direct effect in addition to the lipid-lowering action of the drug. Diabetes 53: [701][702][703][704][705][706][707][708][709][710] 2004

Background-Postprandial hypertriglyceridemia and hyperglycemia are considered risk factors for cardiovascular disease.Evidence suggests that postprandial hypertriglyceridemia and hyperglycemia induce endothelial dysfunction and inflammation through oxidative stress. Statins and angiotensin type 1 receptor blockers have been shown to reduce oxidative stress and inflammation, improving endothelial function. Methods and Results-Twenty type 2 diabetic patients ate 3 different test meals: a high-fat meal, 75 g glucose alone, and a high-fat meal plus glucose. Glycemia, triglyceridemia, endothelial function, nitrotyrosine, C-reactive protein, intercellular adhesion molecule-1, and interleukin-6 were assayed during the tests. Subsequently, diabetics took atorvastatin 40 mg/d, irbesartan 300 mg/d, both, or placebo for 1 week. The 3 tests were performed again between 5 and 7 days after the start of each treatment. High-fat load and glucose alone produced a decrease in endothelial function and increases in nitrotyrosine, C-reactive protein, intercellular adhesion molecule-1, and interleukin-6. These effects were more pronounced when high-fat load and glucose were combined. Short-term atorvastatin and irbesartan treatments significantly counterbalanced these phenomena, and their combination was more effective than either therapy alone. Conclusions-This study confirms an independent and cumulative effect of postprandial hypertriglyceridemia and hyperglycemia on endothelial function and inflammation, suggesting oxidative stress as a common mediator of such an effect. Short-term treatment with atorvastatin and irbesartan may counterbalance this phenomenon; the combination of the 2 compounds is most effective.

Background It has been previously shown that hyperglycemia enhances free radical production, inducing oxidative damage, which in its turn activates the death pathways implicated in cell apoptosis and necrosis. But the possible involvement of this pathway in the hyperglycemia-induced apoptosis of endothelial cells has not yet been reported.

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