Coronary endothelial dysfunction in the insulin-resistant state is linked to abnormal pteridine metabolism and vascular oxidative stress.
OBJECTIVE
We investigated whether abnormal pteridine metabolism is related to coronary endothelial dysfunction in insulin-resistant subjects.


BACKGROUND
Depletion of tetrahydrobiopterin (BH(4)) and elevation of the 7,8-dihydrobiopterin (BH(2)) (activating and inactivating cofactors of nitric oxide synthase [NOS], respectively) contribute to impairment of NO-dependent vasodilation through reduction of NOS activity as well as increased superoxide anion generation in insulin-resistant rats.


METHODS
Thirty-six consecutive nondiabetic, normotensive and nonobese subjects with angiographically normal coronary vessels were studied. Traditional coronary risk factors, plasma pteridine levels, activities of erythrocyte dihydropteridine reductase (DHPR), the recycling enzyme that converts BH(2) to BH(4) and lipid peroxide (LPO) levels were measured and coronary endothelial function was assessed with graded infusions of acetylcholine (ACh).


RESULTS
When we divided patients into tertiles based on insulin sensitivity, we observed stepwise decreases in the maximal ACh-induced vasodilation and plasma BH(4)/7,8-BH(2) ratio, and increases in coronary LPO production as insulin sensitivity decreased. The ACh-induced vasodilation was positively correlated with insulin sensitivity, BH(4)/7,8-BH(2) ratio and DHPR activity. Furthermore, BH(4)/7,8-BH(2) was inversely correlated with DHPR activity and insulin sensitivity. In multiple stepwise regression analysis, BH(4)/BH(2) was independently related to ACh-induced vasodilation and accounted for 39% of the variance. However, no significant correlation existed between other traditional risk factors and BH(4)/7,8-BH(2).


CONCLUSIONS
These results indicate that both abnormal pteridine metabolism and vascular oxidative stress are linked to coronary endothelial dysfunction in the insulin-resistant subjects.
Shinozaki
K
K
Department of Pharmacology, Shiga University of Medical Science, Seta, Otsu, Shiga, Japan.
Hirayama
A
A
Nishio
Y
Y
Yoshida
Y
Y
Ohtani
T
T
Okamura
T
T
Masada
M
M
Kikkawa
R
R
Kodama
K
K
Kashiwagi
A
A
D000109:Acetylcholine; D000368:Aged; D001708:Biopterins / Q000031:analogs & derivatives* / Q000097:blood*; D003326:Coronary Circulation / Q000502:physiology*; D003327:Coronary Disease / Q000503:physiopathology*; D004093:Dihydropteridine Reductase / Q000097:blood; D004730:Endothelium, Vascular / Q000503:physiopathology*; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008054:Lipid Peroxides / Q000097:blood; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000502:physiology; D018384:Oxidative Stress; D012016:Reference Values; D012307:Risk Factors
D008054:Lipid Peroxides; D001708:Biopterins; D009569:Nitric Oxide; C017226:7,8-dihydrobiopterin; D004093:Dihydropteridine Reductase; C003402:sapropterin; D000109:Acetylcholine