Correlations between the enantio- and regio-selective metabolisms of warfarin.

AIM: To clarify whether the activities of multiple CYPs associated with warfarin metabolism would be correlated with each other. METHODS: Oral clearances (CLpo) of warfarin enantiomers were estimated in 378 Chinese, Caucasians and African-Americans. The partial metabolic clearances (CLm) for 7-hydroxywarfarin enantiomers were also measured. In addition, CLpo and CLm were determined in a patient on warfarin and rifampicin. RESULTS: Correlations between CLpo for warfarin enantiomers existed across the three populations. In addition, there was a significant correlation between the CLm for 7-hydroxylation of warfarin enantiomers. Under induced conditions by rifampicin, there were significant correlations between the enantio- and regio-selective metabolisms of warfarin. CONCLUSION: Metabolic activities of CYP2C9, CYP1A2 and CYP3A4 may be regulated by common transcriptional mechanism(s).

Biological definition of multiple chemical sensitivity from redox state and cytokine profiling and not from polymorphisms of xenobiotic-metabolizing enzymes.

BACKGROUND: Multiple chemical sensitivity (MCS) is a poorly clinically and biologically defined environment-associated syndrome. Although dysfunctions of phase I/phase II metabolizing enzymes and redox imbalance have been hypothesized, corresponding genetic and metabolic parameters in MCS have not been systematically examined. OBJECTIVES: We sought for genetic, immunological, and metabolic markers in MCS. METHODS: We genotyped patients with diagnosis of MCS, suspected MCS and Italian healthy controls for allelic variants of cytochrome P450 isoforms (CYP2C9, CYP2C19, CYP2D6, and CYP3A5), UDP-glucuronosyl transferase (UGT1A1), and glutathione S-transferases (GSTP1, GSTM1, and GSTT1). Erythrocyte membrane fatty acids, antioxidant (catalase, superoxide dismutase (SOD)) and glutathione metabolizing (GST, glutathione peroxidase (Gpx)) enzymes, whole blood chemiluminescence, total antioxidant capacity, levels of nitrites/nitrates, glutathione, HNE-protein adducts, and a wide spectrum of cytokines in the plasma were determined. RESULTS: Allele and genotype frequencies of CYPs, UGT, GSTM, GSTT, and GSTP were similar in the Italian MCS patients and in the control populations. The activities of erythrocyte catalase and GST were lower, whereas Gpx was higher than normal. Both reduced and oxidised glutathione were decreased, whereas nitrites/nitrates were increased in the MCS groups. The MCS fatty acid profile was shifted to saturated compartment and IFNgamma, IL-8, IL-10, MCP-1, PDGFbb, and VEGF were increased. CONCLUSIONS: Altered redox and cytokine patterns suggest inhibition of expression/activity of metabolizing and antioxidant enzymes in MCS. Metabolic parameters indicating accelerated lipid oxidation, increased nitric oxide production and glutathione depletion in combination with increased plasma inflammatory cytokines should be considered in biological definition and diagnosis of MCS.

Flavin-containing monooxygenase 3 polymorphisms in 13 ethnic populations from Europe, East Asia and sub-Saharan Africa: frequency and linkage analysis.

AIMS: To investigate intra- and inter-ethnic differences in three widespread (E158K, V257M and E308G) and two African-specific (D132H and L360P) flavin-containing monooxygenase 3 (FMO3) polymorphisms. MATERIALS & METHODS: Allele frequencies were determined by TaqMan allelic discrimination assay in 2152 healthy volunteers from Europe (Swedes, Italians and Turks), East Asia (Japanese) and sub-Saharan Africa (nine ethnic groups covering eastern, southern and western regions), followed by haplotype and linkage analysis. RESULTS: Significant subpopulation differences (p < 0.001) in allele frequencies were found for E158K, V257M and E308G in Europeans and regional differences (p < 0.01) for D132H among Africans. No carrier of P360 was identified. Cis-linkage between G308 and K158 was confirmed with the compound variant (K158/G308) being found in a high proportion (12.0-38.3%) of non-African subjects, but rarely (1.3%) among Africans. CONCLUSIONS: Distribution of functionally relevant FMO3 polymorphisms varies not only between ethnicities but also within. The K158/G308 variant may have potential clinical importance primarily in non-African populations due to its low prevalence in Africa.

Different contributions of polymorphisms in VKORC1 and CYP2C9 to intra- and inter-population differences in maintenance dose of warfarin in Japanese, Caucasians and African-Americans.

OBJECTIVE: To investigate pharmacokinetic and pharmacodynamic factors associated with population differences in warfarin doses needed to achieve anticoagulation, in particular the possible involvement of genetic variability in vitamin K epoxide reductase (VKOR) and CYP2C9. METHODS: Warfarin maintenance dose, unbound plasma S-warfarin concentration [Cu(S)] and INR were determined in 157 Caucasians, 172 Japanese, and 36 African-Americans stably anticoagulated patients. In a subset (n = 166), fully carboxylated plasma normal prothrombin levels (NPT) were also measured. Genotyping for seven CYP2C9 (CYP2C9*1 through 6 and *11) and seven VKORC1 variants were performed in 115 Caucasians and 64 Japanese patients and 66 healthy African-Americans. Multivariate analysis was performed to identify covariates associated with warfarin requirement. RESULTS: The relationship between NPT and Cu(S) indicated Japanese are more susceptible to inhibition of NPT production by S-warfarin than the other two populations. VKORC1 1173 C > T had a greater frequency in Japanese (89.1%) than Caucasians (42.2%) and African-Americans (8.6%). CYP2C9 variants with reduced metabolizing ability were less frequent in Japanese compared to the other two populations. The median warfarin dose was significantly higher in Caucasians than Japanese patients (5.5 versus 3.5 mg/day), however, when matched for CYP2C9*1 homozygosity, no difference in dose was observed between VKORC1 genotype-matched groups. Furthermore, VKORC1 1173C > T and CYP2C9 (*2/*3/*11) genotypes, age and weight were identified as independent covariates contributing to interpatient variability in warfarin dosage. CONCLUSIONS: Both VKORC1 and CYP2C9 polymorphisms contribute to inter-population difference in warfarin doses among the three populations, but their contribution to intra-population variability may differ within each population.

Influence of CYP2C9, 2C19 and 2D6 genetic polymorphisms on the steady-state plasma concentrations of the enantiomers of fluoxetine and norfluoxetine.

The antidepressant fluoxetine is administered as racemic mixture of two enantiomers (S- and R-fluoxetine). While S- and R-fluoxetine are equipotent in blocking serotonin reuptake, the enantiomers of the demethylated metabolite, norfluoxetine, show marked differences in pharmacological activity, S-norfluoxetine being about 20 times as potent as R- norfluoxetine as a serotonin reuptake inhibitor. In vitro and in vivo data suggest that the metabolism of fluoxetine to norfluoxetine is stereoselective and mediated, at least in part, by the polymorphic cytochrome P450 (CYP) isoenzymes CYP2D6, CYP2C9 and CYP2C19. In the present study, the influence of CYP2D6, CYP2C9 and CYP2C19 polymorphisms on the steady-state plasma concentrations of fluoxetine and norfluoxetine enantiomers was evaluated in 78 patients receiving chronic fluoxetine treatment (10-60 mg/day). The plasma concentrations of fluoxetine and norfluoxetine enantiomers were measured and CYP2D6, CYP2C9 and CYP2C19 genotypes were analyzed. No statistically significant relationship was identified between CYP2D6 or CYP2C19 genotypes and the dose normalised plasma concentrations of any of the enantiomers or the active moiety (i.e. the sum of S-fluoxetine, R-fluoxetine and S-norfluoxetine). However, the plasma concentration of S-norfluoxetine was very low in the only CYP2D6 poor metaboliser. Furthermore, the median S-norfluoxetine/S-fluoxetine ratios were higher in homozygous than in heterozygous extensive metabolisers (P<0.05). Among homozygous extensive metabolizers for CYP2D6, patients homozygous for CYP2C9*1 had lower dose-normalized R-fluoxetine concentrations and lower active moiety levels compared with those carrying detrimental CYP2C9 alleles (P<0.05). These results suggest that CYP2D6 and CYP2C9 polymorphisms contribute to the interindividual variability in fluoxetine pharmacokinetics at steady-state.