摘要:

Central dopaminergic reward pathways give rise to dependence and are activated by nicotine. Allelic variants in genes involved in dopamine metabolism may therefore influence the amount of tobacco consumed by smokers. We developed assays for polymorphisms in dopamine β-hydroxylase (DBH), monoamine oxidase (MAO) and catechol O-methyl transferase (COMT) using the polymerase chain reaction with sequence specific primers (PCR-SSP). We then typed 225 cigarette smokers to assess whether genotype was related to the number of cigarettes smoked a day. Smokers with DBH 1368 GG genotype smoked fewer cigarettes than those with GA/AA [mean difference−2.9 cigarettes, 95% confidence interval (CI)−5.5,−0.4;P= 0.022]. The effect reached statistical significance in women (−3.8, 95% CI−6.4,−1.0,P= 0.007) but not in men (−1.5, 95% CI−6.0, 3.0,P= 0.498). Overall, the effect was greater when analysis was confined to Caucasians (−3.8, 95% CI−6.6,−1.1,P= 0.007). Smokers withMAO-A 1460 TT/TO smoked more cigarettes than those with CC/CT/CO (2.9, 95% CI 0.6, 5.1,P= 0.013). Within each sex group, the trend was similar but not statistically significant (difference for men 2.9, 95% CI−1.0, 6.7; for women 2.0, 95% CI−0.7, 4.8). The effect of the allele was greater in smokers with a high body mass index (>26) (difference 5.1, 95% CI 1.4, 8.8,P= 0.008). More heavy smokers (>20 a day) had theDBH1368A allele when compared to light smokers (<10 a day). (Relative risk 2.3, 95% CI 1.1, 5.0,P= 0.024.) The trend for increasing prevalence of theDBHA allele in heavy smokers was greater when analysis was restricted to Caucasians (relative risk 3.2, 95% CI 1.3, 8.2,P= 0.004). Conversely, heavy smokers were less likely to have theMAO-A 1460C allele (relative risk 0.3, 95% CI 0.1, 0.7,P= 0.012). Variations inDBHandMAOpredict whether a person is a heavy smoker and how many cigarettes they consume. Our results support the view that these enzymes help to determine a smoker's requirement for nicotine and may explain why some people are predisposed to tobacco addiction and why some find it very difficult to stop smoking. This finding has important implications for smoking prevention and offers potential for developing patient-specific therapy for smoking cessation.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Quantitative aspects of the in-vitro interferon (IFN)-γ-induced nitric oxide (NO) production by peritoneal macrophages of eight inbred strains of mice were investigated. Animals employed in the study can be assorted into three phenotype categories: high, moderate, and low NO-responders. Concentration of nitrites in the 24-h supernatants of cells stimulated with recombinant murine IFN-γ (25 U/ml) reached the following values (mean±SEM; in μm): C57BL/10 (33.7±1.88) = C57BL/6 (32.1±2.10)>SJL (24.0±1.55)>CBA/J (18.1±1.79) = C3H/HeN (18.0±1.10)>DBA/2 (11.4±1.16) = DBA/1 (11.0±1.20) = Balb/c (11.0±1.16). Approximately 80% of the total variation was found to be controlled by genetic factors. No association between the extent of NO formation and variation in the constitutive expression of macrophage IFN-γ receptor was observed. Similar magnitude of inter-strain differences was sustained after enhanced NO-stimulation of the cells with IFN-γ + tumour necrosis factor (TNF)-α, but only high (strains BL/10, BL/6, SJL, CBA/J, C3H/HeN) and low (DBA/1, DBA/2, Balb/c) NO-responder phenotypes were detected after the triple cytokine cocktail composed of IFN-γ + TNF-α + interleukin (IL)-10. The strain differences remained unchanged after the supplementation of culture medium withl-arginine or tetrahydrobipopterin. Genetically governed differences in IFN-γ-induced NO production have been found to be tightly associated with differential expression of inducible nitric oxide synthase mRNA. Possible implications of the findings for various fields of NO biomedical research are discussed.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Progress towards construction of a dense map of di-allelic markers across the human genome has generated considerable enthusiasm for pharmacogenomic applications. To date, however, nearly all of the effort on single nucleotide polymorphism (SNP) projects has been focused on marker identification and screening, not on how the SNP genotype data actually can be used in clinical trials to advance medical practice. Here, we explore how different properties of SNPs impact the size, scope and design of clinical trials using a simple trial design. We evaluate the clinical trial sampling requirements under different allele frequencies, gene action, gene effect size and number of markers in a genome screen. Power and sample size calculations suggest that allele frequency and type of gene action can have a dramatic impact on trial sample sizes, in that under some conditions the required sample sizes are too large to be applicable in a costly clinical trial setting. In other situations, however, pharmacogenomic clinical trials can yield significant sampling/cost savings over traditional trials. These properties are discussed with regard to the general usage of genetic information in clinical trial settings.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The mechanism by which diclofenac-induced hepatotoxicity occurs is unclear, even though covalent modification of proteins by diclofenac metabolites appears to be important in pathogenesis, either by altering protein function or by eliciting an immune response. Adduct formation may be due to metabolism of diclofenac via an alternative pathway rather than via its major 4′-hydroxylation pathway mediated by the cytochrome P450 CYP2C9. We hypothesized that possession of variant CYP2C9 alleles might be a risk factor for diclofenac-induced hepatotoxicity, since the allelic variantsCYP2C9*2andCYP2C9*3may be associated with impaired metabolism compared to the wild-type (CYP2C9*1). To investigate in more detail the effects of the polymorphisms on diclofenac metabolism in human liver, the kinetics of diclofenac 4-hydroxylation by human liver microsomes of knownCYP2C9>genotype were examined. An overall difference inVmaxandVmax/Kmbetween samples homozygous forCYP2C9*1and heterozygous forCYP2C9*2orCYP2C9*3was detected (P= 0.044). However, on subgroup analysis, there was no significant difference between samples homozygous forCYP2C9*1and heterozygous forCYP2C9*2, although there was a borderline difference between the samples homozygous forCYP2C9*1and those heterozygous forCYP2C9*3(P= 0.057). The relationship betweenCYP2C9genotype and susceptibility to diclofenac-induced hepatotoxicity was further examined by genotyping 24 patients with diclofenac-induced hepatotoxicity together with 100 healthy controls for theCYP2C9*2andCYP2C9*3alleles.CYP2C9genotype frequencies forCYP2C9*2andCYP2C9*3were similar in patients and controls. To assess whether diclofenac-induced hepatotoxicity was due to rare CYP2C9 mutations, the upstream sequence (−1 to−1000) and all exons and exon–intron boundaries ofCYP2C9from four subjects who had suffered severe hepatotoxicity was determined. However, no new polymorphisms were detected. We therefore found no evidence that polymorphism inCYP2C9is a determinant of diclofenac-induced hepatotoxicity.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Steroid hydroxylation specificities were determined for the wild-type and the two allelic variants of the polymorphic human cytochrome P450 1A1 (CYP1A1) that were associated with amino acid exchanges near the active site of the enzyme. All three variants were expressed in insect cells using recombinant baculoviruses. Each variant protein was spectrally and enzymatically active, as judged by the ability of the prepared microsomes to catalyseO-dealkylation of ethoxyresorufin and pentoxyresorufin in cumene hydroperoxide-mediated reactions. With progesterone and testosterone as substrate, all variants of CYP1A1 exhibited high, but different steroid hydroxylation activities (8–40 pmol hydroxysteroid/min/pmol CYP1A1, i.e. approximately 800–4000 pmol/min/mg microsomal protein). All three variants exclusively catalysed 6β-hydroxylation of both steroids. In addition, towards progesterone as substrate, all variants also catalysed 16α-hydroxylations with approximately half of the rate of 6β-hydroxylation activity. With progesterone as substrate for hydroxylation in 6β position, CYP1A1 T461N had the lowest catalytic efficiency (Vmax/Km) followed by the CYP1A1 I462V variant and the wild-type enzyme. For 16α-hydroxylation of progesterone, the catalytic efficiencies of the three variants are not statistically significantly different. With testosterone as substrate the CYP1A1 I462V variant catalysed 6β-hydroxylation with an efficiency considered not significantly different compared to the wild-type, although both the apparentKmandVmaxwere significantly decreased. In contrast, the CYP1A1 T461N variant exhibited significantly decreased catalytic efficiencies compared to both the I462V variant and the wild-type enzyme. These results indicate that all three naturally occurring allelic variants of human CYP1A1 hydroxylate steroid hormones with varying efficiencies in a stereo- and regioselective manner, whereby the CYP1A1 T461N variant exhibited the lowest catalytic efficiency.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The purpose of this study was to establish the frequencies ofCYP2D6,CYP1A1,GSTM1andp53polymorphic genotypes in Tundra Nentsi, which comprises the small group of indigenous people belonging to Northern Mongoloids and Caucasians of Western Siberia. A total number of 102 Tundra Nentsi individuals and 96 Caucasians of Western Siberia were genotyped by means of polymerase chain reaction-based assays. Mutated alleles comprisingCYP2D6*4,CYP1A1Val,GSTM1*0andp53Prowere analysed along with the wild-type alleles. The results showed the intermedial position ofCYP2D6*4allele frequency in Tundra Nentsi, compared to Caucasians and Orientals (0.07 versus 0.2,P= 0.0003; 0.07 versus 0.003,P= 1×10−6, respectively). Thus, our data indicate that the intermedial position of Tundra Nentsi between Orientals and Caucasians most likely shows the Caucasian ancestral origin ofCYP2D6*4allele. Comparative analysis ofp53Proallele frequency showed the pronounced ethnic differences with geographic gradient. Though the frequency ofp53Proallele ranged from 0.17 in Tundra Nentsi up to 0.3 in Caucasians of Western Siberia (P= 0.002), which is in agreement with the previously reported radial distribution of the known genetic markers. No differences were found in theCYP1A1Valallele distribution among Caucasians of Western Siberia and Caucasoid populations presented in other studies, whereas the frequency ofValallele in Nentsi was 1.5-fold higher (P= 0.076) compared to the Japanese group. It was found that the frequency ofGSTM1null genotype in Tundra Nentsi was only 39.8%. The frequency ofGSTM1null genotype in females was higher than in males (0.27 and 0.50, respectively) but that difference was not statistically significant. Comparative analyses of the distribution of putative markers towards cancer susceptibility,CYP1A1Val,GSTM1*0andp53Proalleles, have shown that the healthy Tundra Nentsi population (Northern Mongoloids) have a low number ofp53Proalleles andGSTM1*0/*0genotypes and a high level ofCYP1A1Valalleles. Further investigations of gene polymorphisms in isolated Northern native populations would be valuable in clarifying the origin of Northern natives. All this is important for comparative analyses of pharmacogenetic data in Mongoloid populations.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The activity of uridine-diphosphoglucuronosyl transferase 1 (UGT1) may influence the concentration of serum bilirubin. Because UGT1 is too labile to be measured with classical biochemical methods, we analysed the wholeUGT1A1gene in 290 healthy Taiwanese adults by using the polymerase chain reaction method, and investigated the relationship betweenUGT1A1genotypes and serum bilirubin levels. The results showed that slightly more than 50% of the subjects had one or more variant sites inUGT1A1gene. The most common variant was A(TA)6TAA/A(TA)7TAA (6/7) in the promoter area, followed by heterozygous variation within the coding region, compound heterozygous and homozygous variations. Among the four variant sites within the coding region, 211 G to A was the predominate one, 1091 C to T was a novel variation, and 686 C to A was associated with 6/7. Subjects with 6/7 or heterozygous variation within the coding region or compound heterozygous (plus one homozygous) variation had significantly higher bilirubin levels than those with wildUGT1A1gene. When the 290 subjects were stratified into six groups according to their serum bilirubin concentrations, the bilirubin levels were correlated well to the frequencies of variantUGT1A1gene. Our results show that there is a strong association betweenUGT1A1gene and bilirubin levels in healthy Taiwanese adults. The occurrence of A(TA)7TAA allele was relatively rare and the variation rate within the coding region was much higher in Taiwanese compared to that in Caucasians.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

We previously described associations between basal cell carcinoma (BCC) numbers and allelic variants at loci that mediate host response to ultraviolet radiation (UV). These associations were largely exerted in cases with the multiple presentation phenotype (MPP). This phenotype describes patients who present at their first or a later presentation with a cluster of BCC (2–10 new BCC). Remaining BCC cases have the single presentation phenotype (SPP) and may develop more than one BCC but only have single new lesions at any presentation. We proposed that the MPP cases comprise a high-risk group as they suffer significantly more lesions than SPP cases. We are attempting to determine, in the total BCC case group and subgroups, how many genes influence BCC numbers and their relative importance. In this study, we assessed the influence of two further candidates, glutathioneS-transferaseGSTP1and cyclin D1 (CCND1), on tumour numbers in a total group of 457 patients comprising MPP and SPP cases. The relative importance of these genes in comparison with occupational UV exposure and host response (skin type) was also considered. We found that the frequencies ofGSTP1genotypes based on the Ile105and Val105-expressing alleles andCCND1 AA,AG,GGgenotypes were similar in MPP and SPP cases and that there were no significant associations betweenGSTP1orCCND1genotypes and BCC numbers in the total or SPP groups. However, in the MPP cases,GSTP1Val105/Val105was associated with more tumours (P= 0.05, referenceGSTP1Ile105/Ile105). Inclusion of skin type and indoor/outdoor occupation in the negative binomial regression models did not alter the associations of these genotypes with tumour numbers. DNA from 258 cases was analysed to identifyGSTP1*A(Ile105-Ala114),GSTP1*B(Val105-Ala114),GSTP1*C(Val105-Val114) andGSTP1*D(Ile105-Val114). In SPP cases, there was no association between BCC numbers andGSTP1 BB, though the association withGSTP1 BCapproached significance (P= 0.09). In MPP cases,GSTP1 BCwas associated with BCC numbers (P= 0.03). We also found that the interaction term,GSTP1Val105/Val105withCCND1 AA, was associated with BCC numbers in the total (P= 0.001) and MPP (P= 0.006) but not SPP (P= 0.68) groups. In a stepwise model includingGSTP1Val105/Val105,CCND1 AAand their interaction terms as well asGSTM1,GSTT1andCYP2D6genotypes, skin type 1 and gender, the combination of genotypes was the best predictor of BCC numbers. These data suggest that study of further genes involved in cell-cycle control and protection from oxidative stress will be useful, particularly in high-risk subgroups.

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

GlutathioneS-transferase theta enzyme activity involved in the metabolism of toxic compounds is absent in approximately 20% of Caucasians due to a homozygous deletion ofGSTT1(*0/0). Because the exact manner of theGSTT1deletion was unknown, current genotyping ofGSTT1was limited to detect the presence versus complete absence of the gene by aGSTT1-specific polymerase chain reaction (PCR). Thus, heterozygous (*A/0) and homozygous (*A/A) samples could not be discriminated. We have characterized the boundaries of the deletion of the human glutathioneS-transferase theta (GSTT1) gene: PCR mapping and sequencing revealed a 54251 bp fragment includingGSTT1to be deleted from chromosome 22, most likely by a homologous recombination event between two highly homologous sequence stretches that flankGSTT1. Based on the knowledge of theGSTT1*0region, a PCR assay was devised for unambiguous discrimination of homozygously deleted (*0/0), heterozygously (*A/0) and homozygouslyGSTT1carrying (*A/A) individuals. Genotyping of 180 samples of a Caucasian population revealed that the deletion consists of one defined allele, whose distribution in the population fits the Hardy–Weinberg equilibrium with observed 20%*0/0, 46%*A/0and 34%*A/Aindividuals. The number ofGSTT1*Aalleles detected by this procedure correlated highly significant with the enzyme activity in erythrocytes. Genotype–phenotype comparisons demonstrated a codominant type of inheritance by a gene–dose effect: samples with two active alleles expressed a statistically significant higher enzymatic activity compared to those with one null allele (P< 0.0001, ANOVA).

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0960-314X    

出版商:OVID    

年代:2000

数据来源: OVID