Oral glucose loading acutely attenuates endothelium-dependent vasodilationin healthy adults without diabetes: An effect prevented by vitamins C and E

OBJECTIVES The goal of this study was to determine whether postprandial hyp erglycemia, induced by oral glucose loading, attenuates endothelial functio n in healthy subjects without diabetes and whether coadministration of vita mins C and E could prevent these postprandial changes. BACKGROUND Epidemiologic evidence suggests that postprandial hyperglycemia, below diabetic levels, is a risk factor for cardiovascular disease. Postpr andial hyperglycemia may promote atherosclerosis through endothelial dysfun ction and oxidative stress. METHODS We evaluated the acute effects of oral glucose loading (75 g), alon e and with vitamins C (2 g) and E (800 IU), on endothelium-dependent flow-m ediated dilation (FMD) of the brachial artery, in a randomized, double-blin d, placebo-controlled, crossover study of 10 healthy volunteers. Changes in the levels of markers of oxidative stress (plasma malondialdehyde and eryt hrocyte glutathione, glutathione peroxidase and superoxide dismutase) were also assessed. RESULTS Increases in plasma glucose and insulin after glucose loading were unaffected by vitamin coadministration. With glucose loading alone, FMD fel l from 6.5 +/- 2.2 at baseline to 5.4 +/- 1.7, 3.7 +/- 2.1*, 4.1 +/- 3.5* a nd 5.7 +/- 1.9% at 1, 2, 3 and 4 h (*p < 0.05 vs. 0 h). In contrast, FMD di d not change significantly after glucose plus vitamins (6.4 +/- 1.3, 7.6 +/ - 1.8, 7.9 +/- 2.7, 6.9 +/- 2.3, 6.9 +/- 1.9% at 0, 1, 2, 3 and 4 h). By tw o-way repeated measures analysis of variance we found a significant interac tion between vitamin treatment and time (p = 0.0003), indicating that vitam ins prevented the glucose-induced attenuation of FMD. Oxidative stress mark ers did not significantly change with glucose loading alone or with vitamin s. CONCLUSIONS Oral glucose loading causes an acute, transient decrease of FMD in healthy subjects without diabetes, which is prevented by vitamins C and E. (C) 2000 by the American College of Cardiology.