GCH1 haplotype determines vascular and plasma biopterin availability in coronary artery disease effects on vascular superoxide production and endothelial function.
OBJECTIVE
This study sought to determine the effects of endogenous tetrahydrobiopterin (BH4) bioavailability on endothelial nitric oxide synthase (eNOS) coupling, nitric oxide (NO) bioavailability, and vascular superoxide production in patients with coronary artery disease (CAD).


BACKGROUND
GTP-cyclohydrolase I, encoded by the GCH1 gene, is the rate-limiting enzyme in the biosynthesis of BH4, an eNOS cofactor important for maintaining enzymatic coupling. We examined the associations between haplotypes of the GCH1 gene, GCH1 expression and biopterin levels, and the effects on endothelial function and vascular superoxide production.


METHODS
Blood samples and segments of internal mammary arteries and saphenous veins were obtained from patients with CAD undergoing coronary artery bypass grafting (n = 347). The GCH1 haplotypes were defined by 3 polymorphisms: rs8007267G<A, rs3783641A<T, and rs10483639C<G (X haplotype: A, T, G; O haplotype: any other combination). Vascular superoxide (+/- the eNOS inhibitor N(G)-nitro-L-arginine methyl ester [L-NAME]) was measured by lucigenin-enhanced chemiluminescence, whereas the vasorelaxations of saphenous veins to acetylcholine were evaluated ex vivo.


RESULTS
Haplotype frequencies were OO 70.6%, XO 27.4%, and XX 2.0%. The X haplotype was associated with significantly lower vascular GCH1 messenger ribonucleic acid expression and substantial reductions in both plasma and vascular BH4 levels. In X haplotype carriers both vascular superoxide and L-NAME-inhibitable superoxide were significantly increased, and were associated with reduced vasorelaxations to acetylcholine.


CONCLUSIONS
GCH1 gene expression, modulated by a particular GCH1 haplotype, is a major determinant of BH4 bioavailability both in plasma and in the vascular wall in patients with CAD. Genetic variation in GCH1 underlies important differences in endogenous BH4 availability and is a determinant of eNOS coupling, vascular redox state, and endothelial function in human vascular disease.
Antoniades
Charalambos
C
Department of Cardiovascular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom.
Shirodaria
Cheerag
C
Van Assche
Tim
T
Cunnington
Colin
C
Tegeder
Irmgard
I
Lötsch
Jörn
J
Guzik
Tomasz J
TJ
Leeson
Paul
P
Diesch
Jonathan
J
Tousoulis
Dimitris
D
Stefanadis
Christodoulos
C
Costigan
Michael
M
Woolf
Clifford J
CJ
Alp
Nicholas J
NJ
Channon
Keith M
KM
D000368:Aged; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000097:blood; D003324:Coronary Artery Disease / Q000235:genetics / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000378:metabolism*; D005260:Female; D006136:GTP Cyclohydrolase / Q000235:genetics*; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D008297:Male; D008323:Mammary Arteries / Q000378:metabolism; D015999:Multivariate Analysis; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D012501:Saphenous Vein / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism
D013481:Superoxides; D001708:Biopterins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; D006136:GTP Cyclohydrolase; C003402:sapropterin