Relation Of P450 2C9 Genetic Polymorphisms To Pharmacokinetics Of Sulfonylurea Hypoglycemic Agent In Chinese Healthy Volunteers

P450 2C9 is one of the most important drug metabolizing enzymes in human beings and the key enzymes for the metabolism of drugs, pesticides, environmental pollutants and carcinogens. Multiple single-base pair substitution polymorphisms have been identified in gene encoding for P450 2C9 protein. 6 alleles of P450 2C9 including the wild type P450 2C9*1 and the mutants P450 2C9*2(430C-T), P450 2C9*3(1075A-C), P450 2C9*4(1076T-C), P450 2C9*5(1080C-G) and P450 2C9*6(818delA) have been found. P450 2C9*l/*3 individuals showed significant alterations in pharmacokinetics of drugs compared with *1/*1 individuals. In this study, P450 2C9 genotype was determined by oligonucleotide microarray. The relationship of P450 2C9 genetic polymorphisms and the pharmacokinetics of glimepiride and tolbutamide in Chinese were studied.1. Research of the P450 2C9 genetic polymorphisms in Chinese utilizing oligonucleotide microarrayThe gene chip to P450 2C9*2, *3, *4, *5 was prepared and P450 2C9 genotype was determined by the chip. Part of the genotyping results was confirmed by direct sequencing. 9 heterozygous alleles of P4502 C9*l/*3 and 1 homozygous mutant alleles were found in 169 subjects. No mutant alleles of P4502 C9*2, P4502 C9*4 and P4502 C9*5 were detected. The P450 2C9*3 allele frequency was 0.03 in Chinese. The results of oligonucleotide microarray were same to the direct sequencing. Oligonucleotide microarray was reliable for determination of P4502C9 genetic polymorphisms.2. Relationship of the P4502C9 genetic polymorphisms in Chinese and the pharmacokinetic of tolbutamideUsing tolbutamide as a probe of P4502C9 activity, we evaluated P4502C9 phenotype in 63 healthy individuals expressing the P4502 C9*l/*l(n=53)^*l/*3(n=9) and *3/*3(n=l) genotypes. Subjects received 500 mg of tolbutamide pill, with plasma and urine collected over a 24-hour period. The tolbutamide and its metabolites concentrations in human plasma and urine through solid-phase extraction were determined by HPLC. Serum glucose concentrations were determined in hospital. Pharmacokinetic parameters of tolbutamide were estimated by noncompartmental methods through DAS?V1.0. Tolbutamide AUCo—?> significantly increased 20% and 116% and T1/2 increased 60% and 813%, respectively, in subjects expressing the P4502C9*l/*3 and *3/*3 genotypes compared with *1/*1 subjects. Significant reductions in tolbutamide oral clearance (68% and 11%) and formation clearance (39% and 3%) were detected in the *l/*3 and *3/*3 individuals, respectively, compared with "7*1 subjects. Metabolism ration in 0-24h (MR0-24) was reduced in P450 2C9*l/*3 (42%) and P450 2C9*3/*3 (12%) compared to *1/*1. Amount of 4-hydroxytolbutamide and carboxytolbutamide were varied in different P450 2C9*3 alleles. In conclusion, P4502C9 activity was significantly reduced in * 1 heterozygotes compared with *1 homozygotes, and metabolism was more severely impaired in *3/*3 individuals compared with those expressing *l/*3. Using tolbutamide as P450 2C9 probe, P450 2C9 genotype was the major determinant of P450 2C9 phenotype.3. Effects of P450 2C9 genetic polymorphisms on pharmacokinetics of glimepiride and glucose response in Chinese healthy volunteers(1) Relationship of P450 2C9 genetic polymorphisms and the pharmacokinetics of glimepiride after single administration orally in Chinese healthy volunteersWe evaluated P450 2C9 phenotype in 19 healthy individuals expressing the P4502 C9*l/*1 (n=9), *l/*3 (n=9) and *3/*3 (n=l) genotypes. Subjects received 4mg of glimepiride, with plasma and urine collected over a 48-hour period. Glimepiride concentrations in plasma and carboxyglimepiride and hydroxyglimepiride in urinary concentrations were determined by HPLC method. Serum glucose concentrations were determined in hospital. Pharmacokinetic parameters of glimepiride were estimated by noncompartmental methods through DAS?V1.0. Glimepiride AUC0-oo significantly increased 28% and 54% and T1/2 increased 63% and 235%, respectively, in subjects expressing the P4502C9*l/*3 and *3/*3 genotypes compared with *1/*1 subjects. Significant reductions in glimepiride oral clearance (78% and 62%) and formation clearance (68% and 91%) were detected in the *l/*3 and *3/*3 individuals, respectively, compared with *1/*1 subjects. Blood glucose responses to glimepiride were not significantly affected by P450 2C9 genotype. P450 2C9*l/*3 AUC0.t significantly increased 28% and 45%, Tm increased 163% and 198% and amount of hydroxyglimepiride(Ml) and carboxyglimepiride (M2) reduced 89% and 48% compared *1/*1 subjects after administration of tolbutamide and glimepiride. In conclusion, there are significant alterations in glimepiride pharmacokinetics across P450 2C9*l/*3 subjects. P450 2C9 activity was significantly reduced in P450 2C9*l/*3 subjects compared with *1 homozygotes. P450 2C9*3 was more important to glimepiride than tolbutamide. (2) Relationship of P450 2C9 genetic polymorphisms and the pharmacokinetics of glimepiride after multi-administration orally in Chinese healthy volunteersP450 2C9 phenotype were evaluated in 19 healthy individuals expressing the P4502 C9*l/*1 (n=9), *l/*3 (n=9) and *3/*3 (n=l) genotypes. Subjects received 4 mg/d of glimepiride once a day for 6 days with plasma and urine collected. Plasma glimepiride and urinary carboxyglimepiride and hydroxyglimepiride concentrations were determined by HPLC method. Serum glucose concentrations were determined in hospital. Pharmacokinetic parameters of glimepiride were estimated by noncompartmental methods through DAS?V1.0. Glimepiride AUCo-^t significantly increased 28%, MRT increased 63% and T]/2 increased 124%, respectively, in subjects expressing the P4502C9*l/*3 compared with *1/*1 subjects. Significant reductions in glimepiride oral clearance (74%) in the *l/*3 individuals, compared with *1/*1subjects. Amount of hydroxyglimepiride and carboxyglimepiride were decreased in P450 2C9*3 alleles. Blood glucose responses to glimepiride were not significantly enhanced in P450 2C9*l/*3. The Decremental AUC0-2 and Decremental AUC0-10 of serum glucose concentrations of P450 2C9*l/*3 were significantly lower than that of the wild type after multi-administration glimepiride orally. After multi-administration, the Ti/2and Cmax were increased in P450 2C9*l/*3 alleles than single administration and there is accumulation in vivo for 6 days. There are significant alterations in glimepiride pharmacokinetics and pharmacodynamics across P450 2C9*l/*3 subjects after multi-administration.In conclusion, there are significant alterations in tolbutamide and glimepiride pharmacokinetics across P450 2C9*l/*3 subjects. Pharmacodynamics of glimepiride was alter in P450 2C9*3 allele in multi-administration.