GCH1 Haplotype Determines Vascular and Plasma Biopterin Availability in Coronary Artery Disease

Abstract

Objectives 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 NG-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.

Differential effects of eNOS uncoupling on conduit and small arteries in GTP-cyclohydrolase I-deficient hph-1 mice

“…Previous studies (6,19,42) also demonstrated that genetic deficiency of GTPCH I in hph-1 mice is associated with significantly enhanced eNOS-derived production of superoxide anions. Consistent with observations in genetically modified mice, genetic variants of GCH gene in humans are also associated with increased levels of vascular superoxide production and endothelial dysfunction (2,48). In the present study, we confirmed that both enzymatic activity of GTPCH I and BH 4 biosynthesis were significantly reduced in both the aortas and the mesenteric arteries of hph-1 mice aortas.…”

Experimental Intrauterine Growth Restriction Induces Alterations in DNA Methylation and Gene Expression in Pancreatic Islets of Rats

“…29 and associated Gene Expression Omnibus (GEO) dataset GSE3544). Gch1 is a crucial (rate-limiting) component of the tetrahydrobiopterin synthetic pathway and has been directly implicated in diabetes-associated endothelial dysfunction through its critical role in nitric oxide (NO) synthesis (30,31). Interestingly, folate supplementation of protein-restricted dams, known to buffer against changes in DNA methylation (32), prevented the development of hypertension and reduced NO synthesis and endothelial dysfunction that was otherwise observed in male offspring (33,34).…”

Tetrahydrobiopterin in Cardiovascular Health and Disease

“…Studies of a haplotype defined by three single nucleotide polymorphisms (SNP) have shown that the X haplotype is associated with lower vascular levels of GCH1 mRNA and decreased levels of BH4 in plasma and the vasculature. This attenuation of BH4 is associated with increased vascular O 2 -production and reduced endothelial dependent vasodilatation in arterial and venous segments from coronary artery disease patients (7).…”