Genetic variation in GCH1, encoding GTP-cyclohydrolase 1, regulates biopterin levels and endothelial function in atherosclerosis - Van, A; Antoniades, C; Shirodaria, C; Guzik, T; Pillai, R; Ratnatunga, C; Tousoulis, D; Stefanadis, C; Tegeder, I; Channon, K (2008)