Establishment of The Effective and Safe Anticoagulation Therapy for Japanese Patients

为探讨白种人和日本人细胞色素P450(CYP)2C9代谢活性的群体差异，以S-华法林的非结合口服清除(CLPO，u)为活体探针，对90名日本人和47名高加索人维持性华法林治疗进行了研究。采用手性高效液相色谱结合超滤技术测定了(S)-华法林的稳态血浆游离浓度。测定了(S)-华法林的CLPO，u和(S)-7-羟基华法林的形成清除量(CLM)。用聚合酶链式反应方法对6个不同等位基因(CYP2C9^*1、CYP2C9^*2、CYP2C9^*3、CYP2C9^*4、CYP2C9^*5和内含子2的T/C转换)进行了基因分型，发现日本人的华法林(S)-华法林的CLPO，u频率分布比高加索人的频率偏高。日本人5个变异体的等位基因频率低于高加索人。当人口间比较…时携带野生型纯合子的日本人(n=85)的CLPO、u和CLm的中位数分别为10.4mlvs4.25mlmin/kg和0.015 vs0.010 mlmin/kg，差异有统计学意义(P<0.01)。此外，携带CYP2C9^*3杂合子的日本人(n=4)与携带纯合子的日本人相比，(S)-华法林的CLPO，u降低了63%(P<0.05)。然而，在高加索人群中，携带纯合子和杂合子的高加索人的上述参数并无显著差异。这些结果表明，已知的CYP2C9变异等位基因频率的群体间差异只是不同人群体内观察到的CYP2C9活性差异的部分原因。此外，在日本人中，有缺陷的CYP2C9等位基因对体内的CYP2C9活性有明显的基因剂量效应，而在高加索人中则不然。需要进一步的研究来确定隐藏因素(S)(例如，转录调控)对CYP2C9活性在种群内和种群间的巨大变异性负责。较少

To investigate the population differences in the metabolic activity of cytochrome P450 (CYP) 2C9 between genotypically-matched Caucasians and Japanese using the unbound oral clearance (CLpo,u) of (S)-warfarin as an in vivo probe.Ninety Japanese and 47 Caucasian patients on maintenance warfarin therapy were studied. Steady-state plasma unbound concentrations (Cu) of (S)-warfarin were measured by a chiral HPLC method coupled with ultrafiltration techniques. CLpo,u for (S)-warfarin and the formation clearance (CLm) of (S)-7-hydroxywarfarin were determined. Genotyping of CYP2C9 was performed with a polymerase chain reaction method for 6 distinct alleles (CYP2C9^*1, CYP2C9^*2, CYP2C9^*3, CYP2C9^*4, CYP2C9^*5 and a T/C transition in intron 2).The frequency distribution of CLpo,u for (S)-warfarin obtained from Japanese was shifted towards higher values as compared to that in Caucasians. Japanese had lower allelic frequencies for the 5 variants than Caucasians. When inter-population comparison … More s of CYP2C9 activity were made for genotype-matched subjects, Japanese with the homozygous CYP2C9^*1 (wild-type) genotype (n = 85) had significantly (p<0.01) greater median values for CLpo,u and CLm than the Caucasians with the corresponding genotype (n = 26) : 10.4 vs 4.25 ml/min/kg and 0.015 vs 0.010 ml/min/kg, respectively. In addition, heterozygous Japanese for the CYP2C9^*3 genotype (n = 4) showed a significantly (p<0.05) reduced CLpo,u for (S)-warfarin by 63 % as compared with Japanese possessing the homozygous CYP2C9^*1 genotype. By contrast, no significant differences were observed in this parameter among the Caucasian with the homozygous CYP2C9^*1 genotype and those with heterozygous CYP2C9^*2 or CYP2C9^*3 genotypes.These findings indicate that inter-population differences in the frequencies of known variant CYP2C9 alleles account only in part for the variability observed in in vivo CYP2C9 activity in different populations. Additionally, a gene-dose effect of defective CYP2C9 alleles on the in vivo CYP2C9 activity is evident in Japanese but not in Caucasians. Further studies are required to identify concealed factor(s) (e.g., transcriptional regulation) responsible for the large intra- and inter-population variability in CYP2C9 activity. Less