Impaired glucose tolerance: its relevance to early endothelial dysfunction.
We studied the effects of acute glycemia on plasma nitric oxide (NO; nitrite plus nitrate) levels, Cu-Zn Superoxide dismutase (Cu-Zn SOD) activity and thiobarbituric acid-reactive substances (TBARS) levels in age-matched female subjects before and two hours after glucose loading. According to the results of glucose loading, subjects were divided in the three groups as normal (n = 13, NGT), impaired (n = 11, IGT) and diabetic glucose tolerance (n = 10, DGT). Plasma NO levels were significantly higher in subjects with DGT than in subjects with NGT (p< 0.001) and IGT (p< 0.05) at baseline. Two hours after glucose loading, plasma NO levels were significantly decreased in subjects with IGT and DGT (p< 0.001 and p< 0.001). Although plasma TBARS levels in subject with NGT did not change from the baseline levels after glucose loading, TBARS levels were significantly elevated in subjects with DGT and IGT (p< 0.001 and p< 0.001). Plasma Cu-Zn SOD activities were within a similar range in all subjects at baseline. Cu-Zn SOD activities were significantly increased in subjects with NGT, and were significantly decreased in subjects with IGT and DGT (p< 0.001 and p< 0.001) after glucose loading. There was a positive correlation between NO and glucose in subjects with NGT (r = 0.34, p< 0.01) and a negative correlation between NO and TBARS in IGT sum DGT during glucose tolerance (r= -0.38, p< 0.01). We suggest that NO availability was decreased when the blood glucose levels were only moderately elevated above normal levels. This might be related with the enhanced oxidative stress.
Konukoglu
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D
Department of Biochemistry, Cerrahpasa Medical Faculty, Istanbul University, Turkey. dkonuk@yahoo.com
Dogan
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E
Turhan
M S
MS
Husrev Hatemi
H
H
D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D003920:Diabetes Mellitus / Q000503:physiopathology; D004730:Endothelium, Vascular / Q000503:physiopathology*; D005260:Female; D018149:Glucose Intolerance / Q000503:physiopathology*; D005951:Glucose Tolerance Test; D006801:Humans; D008875:Middle Aged; D009569:Nitric Oxide / Q000097:blood; D013482:Superoxide Dismutase / Q000097:blood; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis
D001786:Blood Glucose; D017392:Thiobarbituric Acid Reactive Substances; D009569:Nitric Oxide; D013482:Superoxide Dismutase