ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The efficacy of the immunosuppressants azathioprine and 6-mercaptopurine has been well established in the therapy of inflammatory bowel diseases (IBD). However, its use has been complicated by a high incidence of serious adverse drug reactions such as hematotoxicity, hepatotoxicity, pancreatitis and gastrointestinal disturbances. Whereas azathioprine-related pancytopenia has been clearly linked to thiopurineS-methyltransferase (TPMT) polymorphism limited data are available to explain gastrointestinal side effects. In a retrospective analysis of 93 adults with IBD and azathioprine therapy both phenotyping and genotyping was used to explore systematically the relationship between TPMT and azathioprine-related adverse reactions. At time of inclusion, 69 patients were still receiving azathioprine therapy and had never experienced side effects. Azathioprine had been withdrawn in 10 patients for non-medical reasons or lack of response and 14 patients (15%) had stopped medication or were on reduced dose due to severe azathioprine-related side effects. Nine of these 14 patients had developed gastrointestinal side effects (hepatotoxicity,n= 3; pancreatitis,n= 3; others,n= 3), but their normal red blood cell TPMT activities were in accordance toTPMTwild-type. TPMT deficiency in one patient had led to pancytopenia whereas only two of the remaining four patients with hematotoxicity displayed an intermediate phenotype of TPMT. This study demonstrates that azathioprine-related gastrointestinal side effects are independent of the TPMT polymorphism. Nevertheless pharmacogenetic testing for TPMT prior to commencing thiopurine therapy should become routine practice in order to avoid severe hematotoxicity in TPMT deficient patients and lowering the incidence of hematological side effects in individuals heterozygous for TPMT.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The MDR1 multidrug transporter plays a key role in determining drug bioavailability, and differences in drug response exist amongst different ethnic groups. Numerous studies have identified an association between theMDR1 single nucleotide polymorphism (SNP) exon 26 3435C>T and differences in MDR1 function. We performed a haplotype analysis of theMDR1 gene in three major ethnic groups (Chinese, Malays and Indians) by examining 10 intragenic SNPs. Four were polymorphic in all three ethnic groups: one occurring in the non-coding region and three occurring in coding exons. All three coding SNPs (exon 12 1236C>T, exon 21 2677G>T/A and exon 26 3435C>T) were present in high frequency in each ethnic group, and the derived haplotype profiles exhibited distinct differences between the groups. Fewer haplotypes were observed in the Malays (n= 6) compared to the Chinese (n= 10) and Indians (n= 9). Three major haplotypes (>10% frequency) were observed in the Malays and Chinese; of these, two were observed in the Indians. Strong linkage disequilibrium (LD) was detected between the three SNPs in all three ethnic groups. The strongest LD was present in the Chinese, followed by Indians and Malays, with the corresponding LD blocks estimated to be approximately 80 kb, 60 kb and 40 kb, respectively. These data strongly support the hypothesis that strong LD between the neutral SNP exon 26 3435C>T and a nearby unobserved causal SNP underlies the observed associations between the neutral SNP and MDR1 functional differences. Furthermore, strong LD between exon 26 3435T and different unobserved causal SNPs in different study populations may provide a plausible explanation for conflicting reports associating the same exon 26 3435T allele with different MDR1 functional changes.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The bioavailability of structurally unrelated drugs is limited by active secretion via the multidrug resistance gene (MDR1) product P-glycoprotein (Pgp) from enterocyte into lumen as well as intestinal metabolism by cytochrome P450 IIIA4 (CYP3A4). In the present study, we analyzed whether genetic polymorphism of theMDR1had some influence on the intestinal expression levels of Pgp and CYP3A4 and the tacrolimus concentration/dose ratio over the first postoperative days in recipients of living-donor liver transplantation (LDLT). Genotyping assays were performed for the major 10 polymorphisms in theMDR1gene by the polymerase chain reaction–restriction enzyme length polymorphism method. The allele frequencies of variations at five positions were almost comparable with those in the former studies in Caucasians and Japanese, but there was no variation at the other five positions. Although no polymorphism correlated with the intestinal expression of MDR1 mRNA or the tacrolimus concentration/dose ratio in the LDLT recipients, the C3435T polymorphism significantly affected the intestinal expression level of CYP3A4 mRNA as follows; 3435C/C>3435C/T (P<0.05 vs. 3435C/C)>3435T/T (P<0.01 vs. 3435C/C). Therefore, the identified polymorphisms including C3435T in theMDR1gene were indicated to have no influence on the intestinal expression level of Pgp or the tacrolimus concentration/dose ratio in the recipients of LDLT. On the other hand, the C3435T polymorphism ofMDR1was suggested to correlate with the enterocyte expression of CYP3A4 rather than Pgp linking unknown genetic variation inCYP3A4gene.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

High-throughput genotyping technology of multiple genes based on large samples of cases and controls are likely to be important in identifying common genes which have a moderate effect on the development of specific diseases. We present here a comprehensive list of 313 known experimentally confirmed polymorphisms in 54 genes which are particularly relevant for metabolism of drugs, alcohol, tobacco, and other potential carcinogens. We have compiled a catalog with a standardized format that summarizes the genetic and biochemical properties of the selected polymorphisms. We have also confirmed or redesigned experimental conditions for simplex or multiplex PCR amplification of a subset of 168 SNPs of particular interest, which will provide the basis for the design of assays compatible with high-throughput genotyping.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The β1selective beta-blocker metoprolol is metabolized predominantly but not exclusively by CYP2D6. Due to the polymorphism of theCYP2D6gene, CYP2D6 activity varies markedly between individuals. Consequently, after short-term administration metoprolol plasma concentrations were found to be several fold higher in poor metabolizers than in extensive metabolizers. However, it is currently not known, whether the impact of theCYP2D6polymorphism persists during long-term therapy, since alternate mechanisms of elimination or metabolism could be effective in this setting. The study comprised 91 Caucasian patients on long-term treatment with metoprolol (median duration of treatment 12.6 months; median daily drug dose: 47.5 mg/day). Metoprolol and α-OH-metoprolol plasma concentrations were assessed by HPLC. Genotyping detected the null alleles (*0): *3, *4, *5, *6, *7, *8, *12, *14, *15, the alleles *9, *10 and *41 associated with reduced enzymatic activity as well as the fully functional alleles *1 and *2. Genotype and allele frequencies were in accordance with published frequencies for the German population. The plasma metabolic ratio of metoprolol/α-OH-metoprolol was markedly affected by the genotype (P<0.0001). In accordance, median adjusted metoprolol plasma concentrations were 6.2- and 3.9-fold higher in patients with *0/*0 genotypes (n= 8) and intermediate genotypes (n= 10), respectively, as compared to those with two fully functional alleles (n= 31;P<0.01). In summary, the pronounced effect of theCYP2D6genotype persists during long-term therapy, affecting both metabolic ratio and metoprolol plasma concentration.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

This study investigated the role of genetic factors (CYP1A2) in caffeine metabolism. The CYP1A2 activity was determined in 378 Danish twins following oral intake of a single dose of 200 mg caffeine and subsequent determination of the caffeine ratio (AFMU+1MU+1MX)/17DMU in a 6-h urine sample. The mean (± SD) caffeine ratio was 5.9 ± 3.4. The caffeine ratio was statistically significantly higher in men compared to women, in smoking men and women compared to non-smoking persons of the same gender and in women not taking oral contraceptives compared with women on oral contraceptives. Thus, we confirmed that CYP1A2 is more active in men than in women, that it is induced by smoking and inhibited by oral contraceptives. In the subsequent analysis of heritability, we included 49 monozygotic twin pairs and 34 same gender dizygotic twin pairs concordant for non-smoking and non-use of oral contraceptives. The intraclass correlation coefficient was 0.798 (95% confidence interval, 0.696–0.900) and 0.394 (95% confidence interval, 0.109–0.680) in the monozygotic and dizygotic twins, respectively. The correlation was statistically significantly higher (P= 0.0015) in the former compared with the latter. A biometrical model for the caffeine ratio including only additive genetic factors and unique environmental factors was the overall best fitting model. Estimates based on this model gave a heritability estimate of 0.725 (95% confidence interval 0.577–0.822). Unique environmental effects seem to account for the remainder 0.275 (95% confidence interval, 0.178–0.423). Our study shows that the CYP1A2 activity is mainly governed by genetic factors.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Three alleles of the human reduced nicotinamide adenine dinucleotide phosphate:quinone oxidoreductase-1 (NQO1) gene are known; wild-type, 609C>T variant, and 465C>T variant; designated as NQO1*1 and NQO1*2, and NQO1*3, respectively. Previously, we found NQO1*3 in one allele of HCT-116 cells, and in both alleles of the mitomycin C-resistant subline, HCT-116R30A. The NQO1 protein content of HCT-116R30A is 5% that of HCT-116. RT–PCR revealed an exon-4-deleted NQO1 mRNA in both cell lines indicating alternative splicing. However, the cause of the lower expression of NQO1 in HCT-116R30A is unknown. Current data show that HCT-116R30A cells are able to express NQO1 protein from transfected cDNA constructs when RNA splicing is omitted. The ratio of full-length to exon-4-deleted mRNA measured by semiquantitative PCR shows that HCT-116 and HCT-116R30A have ratios of 64 : 36 and 34 : 66, respectively. All other cell lines tested have a ratio of 90 : 10, including HT-29, NIH-125 and NCI-H1688 (homozygous NQO1*1); MCF-7 and HL-60 (heterozygous NQO1*1/*2); and MDA-MB231 (homozygous NQO1*2/*2). Alternative splicing of NQO1 at the 5′-splice site of intron-4 increased in cells with NQO1*3. The 465C>T single nucleotide polymorphism (SNP) disrupts the consensus sequence at the 5′-splice site, which is required for binding by U1 small nuclear RNA (U1 snRNA) in spliceosomes. This defective RNA splicing was partially corrected by transfecting HCT-116R30A cells with U1 snRNA constructs, containing base changes to compensate for the 465 SNP. NQO1 protein and enzymatic activity increased with corrected splicing. The 465 SNP was the major cause of increased alternative splicing and decreased expression of NQO1 protein in HCT-116R30A cells.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Hypertension is associated with enhanced peripheral vascular resistance, which may be mediated by enhanced vasoconstriction. The impact of the recently detected G-protein β3-subunit gene C825T polymorphism on the response to the major pressor mediators has been studiedin vivoin the human microcirculation. We assessed the effects of endothelin-1 (ET-1), angiotensin II (AT), endothelin-antagonists (BQ-123 and BQ-788) and noradrenaline (NA, each 10−16–10−8mol) on vasoconstriction in the human skin microcirculationin vivoin 25 healthy male volunteers (13 with CC genotype, 12 TC/TT genotype) using laser Doppler flowmetry. The effects of endothelium-derived vasodilation on NA-induced effects were studied using the NO-synthase inhibitor l-nitro-monomethyl-arginine (L-NMMA) and the α2-adrenoceptor-antagonist yohimbine (YO). ET-1, AT and NA caused a dose-dependent vasoconstriction (P<0.001). In carriers of the 825T allele the response to ET-1, AT and NA was significantly enhanced leading to a shift to the left of the dose–response curve of up to two log units (ET-1:P<0.001 vs. CC; AT:P<0.01 vs. CC; NA:P<0.05 vs. CC). After pretreatment with L-NMMA or YO, NA induced vasoconstriction was no longer different between subjects with the CC- and CT/TT genotypes. However, following combined pretreatment with both L-NMMA and YO, vasoconstriction to NA was significantly potentiated in carriers of the T-allele. Vasodilatation to an ETA-antagonist (BQ-123) was more pronounced in the CT/TT genotype, while ETB-antagonism (BQ-788) led to a more pronounced vasoconstriction in the CT/TT genotype (not significant vs. CC). Healthy, normotensive carriers of the 825T-allele have enhanced vasoconstriction to ET-1, AT and NA in the skin microcirculation. This enhanced vasoconstriction appears to be partially antagonized by an enhanced release of endothelium derived vasodilators mediated by the stimulation of endothelial α2-adrenoceptors. The GNB3 C825T polymorphism is potentially an attractive pharmacogenetic marker to predict hormone-mediated responses in humans.

ISSN:0960-314X    

出版商:OVID    

年代:2002

数据来源: OVID