Gene Polymorphism Of CYP450 2C9 And VKORC1 And Their Relationship With Warfarin Maintaining Dose

Objective: Warfarin is an effective drug for the treatment and prevention of thromboembolic diseases. However, this drug has a narrow therapeutic range and shows the risk of complications, patients because of excessive anticoagulation caused by the fatal bleeding incidence of 4.4 to 9.3 percent. Also this drug shows a large interindividual and intraindividual variability in dose requirement, which necessitates frequent monitoring of the anticoagulant effect and dosage adjustments. Known factors contributing to this variability are age, drug–drug interactions, ingestion of varying quantities of vitamin K, heart failure, infections, impairment of liver function, and polymorphisms of the CYP2C9 gene, which encodes for the main metabolizing enzyme of the warfarin. Warfarin is a metabolic conformation selective, and S-warfarin and R-warfarin, respectively, through different enzymes at different sites and identification of the carboxyl group and the formation of different metabolites. Has been confirmed in the liver, anticoagulation stronger role in the S-enantiomer more than 85% by CYP2C9 no metabolic activity into the 6 - and 7 - hydroxylation products. At present, the impact of warfarin metabolism of CYP2C9 gene concentrated in the hot spots. The presence of polymorphisms in the VKORC1 gene has been recently identified as another source of variability in the response to warfarin. The enzyme vitamin K epoxide reductase (VKORC) reduces vitamin K 2,3-epoxide to the biologically active vitamin K hydroquinone, which catalyzes the production of the blood-clotting proteins II, VII, IX, and X by carboxylation of glutamic acid residues. Warfarin interferes with this carboxylation by inhibiting VKORC through their recently identified target protein vitamin K reductase complex subunit 1 (VKORC1), which is encoded by the homonymous gene VKORC1. At present, warfarin mechanism of gene research on the hot VKORC. Using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) to analyze the frequency distribution of CYP2C9*3 +1075C/A and VKORC1 -1639 A/G genotypes and alleles in the normal cases and stable patients of Hebei. And this study investigated the contribution of age, CYP2C9 and VKORC1 genotype, and body size to warfarin-dose requirements.Methods: 1 487 normal individuals for annual health examination were randomly recruited from the Second Hospital of Hebei Medical University. 2 A blood sample (2 mL) was taken for CYP 2C9*3+1075C/A and VKORC1 -1639A/G genotyping by the way of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). 3 One hundred and one patients from the Second Affiliated Hospital of Hebei Medical University, with stable anticoagulation with warfarin for a target international normalized ratio (INR) of 2.0 to 3.0 were enrolled for studying the relationship between the gene polymorphism and warfarin maintaining dose. 4 A blood sample (2mL) was taken for venous INR measurement, CYP 2C9*3+1075C/A and VKORC1 -1639A/G genotyping by the way of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Demographics of sex, age, weight, and height, as well as indications for warfarin therapy, additional medical problems, and concurrent medications were also recorded during the clinic visit. Stepwise regression was used to identify factors contributing to the warfarin stable dose followed by linear regression to obtain P values for the nonselected factors.Results: 1 Allele frequencies of 487 normal cases: CYP450 2C9*3+1075C/A allen frequencies were: AA 449 cases (92.2%), AC 36 cases (7.4%) and CC 2 cases (0.4%), respectively. VKORC1 -1639A/G allen frequencies were: AA 415 cases (85.2%), GA 72 cases (14.8%), and GG 0 case (0.0%), respectively. Allele frequencies of both genotypes were in Hardy–Weinberg equilibrium (P> 0.05). 2 Allele frequencies of 101 patients who were taking warfarin: CYP450 2C9 * 3 +1075C/A: AA, 93 cases (92.08%); AC, 8 cases (7.92%); and CC, 0 cases (0.00%), respectively. VKORC1 -1639A/G: AA, 87 cases (86.14%); GA, 14 cases (13.96%); and GG, 0 case (0.00%), respectively. Allele frequencies of both genotypes were in Hardy–Weinberg equilibrium (P > 0.05). 3 Allele frequencies in the normal group and patients taking warfarin were not statistically significantly different, both for CYP450 2C9*3 +1075C/A (P = 0.926) and VKORC1 -1639A/G (P = 0.812). 4 There are no significant differences in the allele frequencies of CYP4502C9* 3 +1075C/A in the Han population in Hebei, Han population in Beijing, China's Guangdong crowd, South Korean and Japanese population, but there were statistically difference between this population and those in China's Xinjiang Uygur population, Americans, Russians, Italians, Swiss and Turks (all P < 0.05). There are no significant differences in the allele frequencies for VKORC1 -1639A/G in the Han population in Hebe and Han Chinese in Xinjiang, China's Taiwan crowd, the Japanese, and Singaporeans, while there were statistically difference between this population and those in Malaysian, Spanish (all P <0.05), and there were remarkably difference between this population and those in Indians, Americans, British, French, and the Caucasus (all P <0.01). 5 The warfarin daily maintaining dose was 3.11±0.76 mg/d in CYP2C9 homozygous wild-type (P450 2C9*1/*1) patients, which was significantly higher than that in P450 2C9*1/*3 patients (2.21±0.60 mg/d) (P= 0.002). The warfarin daily maintaing dose was 3.86±0.95 mg/d in patients with the VKORC1 -1639GA genotype, which was significantly higher than that in the VKORC1 -1639AA genotype patients (2.91±0.67 mg/d) (P = 0.000). 6 Linear stepwise regression analysis was used to identify factors contributing to warfarin stable does. The final equation was: ln(D) = 0.346 + 0.017(weight) - 0.376(CYP450 2C9*3+1075C/A) + 0.148 (VKORC1 -1639A/G ) - 0.002(age), R=0.827,R2adj = 0.671.Conclusions: 1 There are significant differences in the allele frequencies of CYP450 2C9*3+1075C/A and VKORC1 -1639A/G in the Han population and the European and other ethnic population. 2 Gene polymorphisms of CYP450 2C9*3+1075C/A and VKORC1 -1639A/G significantly affect the maintaing dose of warfarin in Chinese.