Epidemiological investigation of the UGT2B17 polymorphism in doping control urine samples and its correlation to T/E ratios

The deletion polymorphism of the enzyme UGT2B17 is known to correlate with the level of the testosterone to epitestosterone (T/E) ratio in urine specimen. Due to the importance of the T/E ratio to detect testosterone abuse in doping analysis, a PCR‐ELISA system (Genotype® UGT test, AmplexDiagnostics) was established to identify the UGT2B17 phenotype in urine samples. Epidemiological investigations in a set of 674 routine doping controls (in‐ and out‐of‐competition) resulted in 22.8% homozygote gene‐deleted and 74.5% UGT2B17‐positive athletes. The validated test system has shown to be robust and sensitive: in only 18 cases (2.7%) isolation of cell material from urine failed. Following hydrolysis of glucuronidated conjugates, steroids were analyzed as bis‐TMS derivatives by gas chromatography‐mass spectrometry (GC‐MS), for example, testosterone (T) and epitestosterone (E). Additionally, isotope ration mass spectrometry (IRMS) analysis and luteinizing hormone (LH) measurement were applied. Mean T/E ratios significantly correlated with the UGT2B17 phenotype (del: T/E 0.9; pos: 1.7), however the values did not differ as distinctive as reported in previous studies. Additionally, the T/E ratios in the gene‐deleted group did not show a normal curve of distribution (median of T/E 0.5). Obviously, beside the UGT2B17 deletion further influences have to be taken into account, for example, polymorphisms or induction of other metabolizing enzymes. Our results indicate that the UGT2B17 polymorphism might be insufficient when utilized solely as a crucial parameter for individual interpretation of T/E in urine. Nevertheless, the detection of the UGT2B17‐gene deletion in urine samples would provide additional information important for gathering evidence in analysis of steroids in doping control. Copyright © 2011 John Wiley & Sons, Ltd.     

S-Naproxen and desmethylnaproxen glucuronidation by human liver microsomes and recombinant human UDP-glucuronosyltransferases (UGT): role of UGT2B7 in the elimination of naproxen

AIMS: To characterize the kinetics of S-naproxen ('naproxen') acyl glucuronidation and desmethylnaproxen acyl and phenolic glucuronidation by human liver microsomes and identify the human UGT isoform(s) catalysing these reactions. METHODS: Naproxen and desmethylnaproxen glucuronidation were investigated using microsomes from six and five livers, respectively. Human recombinant UGTs were screened for activity towards naproxen and desmethylnaproxen. Where significant activity was observed, kinetic parameters were determined. Naproxen and desmethylnaproxen glucuronides were measured by separate high-performance liquid chromatography methods. RESULTS: Naproxen acyl glucuronidation by human liver microsomes followed biphasic kinetics. Mean apparent K(m) values (+/-SD, with 95% confidence interval in parentheses) for the high- and low-affinity components were 29 +/- 13 microm (16, 43) and 473 +/- 108 microm (359, 587), respectively. UGT 1A1, 1A3, 1A6, 1A7, 1A8, 1A9, 1A10 and 2B7 glucuronidated naproxen. UGT2B7 exhibited an apparent K(m) (72 microm) of the same order as the high-affinity human liver microsomal activity, which was inhibited by the UGT2B7 selective 'probe' fluconazole. Although data for desmethylnaproxen phenolic glucuronidation by human liver microsomes were generally adequately fitted to either the single- or two-enzyme Michaelis-Menten equation, model fitting was inconclusive for desmethylnaproxen acyl glucuronidation. UGT 1A1, 1A7, 1A9 and 1A10 catalysed both the phenolic and acyl glucuronidation of desmethylnaproxen, while UGT 1A3, 1A6 and 2B7 formed only the acyl glucuronide. Atypical glucuronidation kinetics were variably observed for naproxen and desmethylnaproxen glucuronidation by the recombinant UGTs. CONCLUSION: UGT2B7 is responsible for human hepatic naproxen acyl glucuronidation, which is the primary elimination pathway for this drug.     

焦磷酸测序技术检测UGT1A3和UGT2B7在中国汉族人群中的基因多态性

目的建立焦磷酸测序技术(pyrosequencing)研究二相代谢酶UGT1A3和UGT2B7基因多态性在中国汉族人群中的分布。方法应用带生物素标记扩增引物并经PCR扩增和Beads分离,制备UGT1A3和UGT2B7焦磷酸测序单倍摸板。在PYroMarkID焦磷酸测序上进行焦磷酸测序,检测233血样的DNA标本的17个SNP位点,以确定血样DNA标本的的基因型。结果 233例血样的DNA标本中,UGT1A3等位基因有9种表型,分别为UGT1A3*1*1、UGT1A3*1*2、UGT1A3*1*3、UGT1A3*1*4、UGT1A3*1*5、UGT1A3*2*3、UGT1A3*2*4、UGT1A3*3*3和UGT1A3*3*5。UGT2B7-1和UGT2B7-2各有3种基因型,分别为G/G型、G/T型、T/T和C/C型、C/T型、T/T型。结论我国汉族人群中UGT1A3和UGT2B7基因突变较高。     

Methadone inhibits CYP2D6 and UGT2B7/2B4 in vivo: a study using codeine in methadone- and buprenorphine-maintained subjects

AIMS

To compare the O-demethylation (CYP2D6-mediated), N-demethylation (CYP3A4-mediated) and 6-glucuronidation (UGT2B4/7-mediated) metabolism of codeine between methadone- and buprenorphine-maintained CYP2D6 extensive metabolizer subjects.

METHODS

Ten methadone- and eight buprenorphine-maintained subjects received a single 60 mg dose of codeine phosphate. Blood was collected at 3 h and urine over 6 h and assayed for codeine, norcodeine, morphine, morphine-3- and -6-glucuronides and codeine-6-glucuronide.

RESULTS

The urinary metabolic ratio for O-demethylation was significantly higher (P = 0.0044) in the subjects taking methadone (mean ± SD, 2.8 ± 3.1) compared with those taking buprenorphine (0.60 ± 0.43), likewise for 6-glucuronide formation (0.31 ± 0.24 vs. 0.053 ± 0.027; P < 0.0002), but there was no significant difference (P = 0.36) in N-demethylation. Similar changes in plasma metabolic ratios were also found. In plasma, compared with those maintained on buprenorphine, the methadone-maintained subjects had increased codeine and norcodeine concentrations (P < 0.004), similar morphine (P = 0.72) and lower morphine-3- and -6- and codeine-6-glucuronide concentrations (P < 0.008).

CONCLUSION

Methadone is associated with inhibition of CYP2D6 and UGTs 2B4 and 2B7 reactions in vivo, even though it is not a substrate for these enzymes. Plasma morphine was not altered, owing to the opposing effects of inhibition of both formation and elimination; however, morphine-6-glucuronide (analgesically active) concentrations were substantially reduced. Drug interactions with methadone are likely to include drugs metabolized by various UGTs and CYP2D6.     

Hepatic CYP2B6 is altered by genetic,physiologic, and environmental factors but plays little role in nicotine metabolism

1. Human cytochrome P4502B6 (CYP2B6) is predominantly expressed in the liver and it plays a major role in the metabolism of several therapeutically important drugs and environmental toxicants.

2. The objective was twofold: (1) to determine the role of genetic, physiological, and environmental factors in predicting hepatic CYP2B6 protein expression; and (2) to investigate the role of CYP2B6 in nicotine C-oxidation.

3. Human livers (n?=?40) were assessed for CYP2B6 protein and genotype.

4. Linear regression analyses indicated that CYP2B6 genotype (10%), gender (14%), and exposure to inducers (21%), but not age, were predictors of CYP2B6 protein amounts. Livers with at least one CYP2B6*5 or *6 allele were associated with lower CYP2B6. Female livers and livers exposed to inducers (phenobarbital and/or dexamethasone) were associated with higher CYP2B6.

5. A weak correlation between CYP2B6 and nicotine C-oxidation activity was observed, which was abrogated when controlling for CYP2A6 protein levels. CYP2B6*6 was not associated with different nicotine kinetics.

6. In summary, CYP2B6 protein expression was associated with genotype, gender, and exposure to inducers, but not with nicotine C-oxidation activity.

     

CYP2B6 983T>C polymorphism is prevalent in West Africa but absent in Papua New Guinea: implications for HIV/AIDS treatment

AIMS: To determine the prevalence of the novel CYP2B6 functional polymorphism 983T>C in Papua New Guinea where HIV/AIDS poses a significant health problem. METHOD: We genotyped Papua New Guineans (PNG, n = 174), West Africans (WA, n = 170), and North Americans (NA, n = 361). RESULTS: The polymorphism was absent in PNG, while its overall frequency was 4.7% in WA. Among NA, the polymorphism was present in African-Americans (7.5%) and Hispanic-Americans (1.1%) but not in Caucasian-Americans and Asian-Americans. Haplotype analysis indicated that 983T>C was present alone as the CYP2B6*18 allele in WA and African-Americans. CONCLUSIONS: Significant interethnic differences occur at the CYP2B6 locus, which may influence treatment outcomes with efavirenz.     

EGCG-meditated cyto- and genotoxicity in HaCat keratinocytes is impaired by cell-mediated clearance of auto-oxidation-derived H2O2: an algorithm for experimental setting correction

Several lines of evidence suggest that besides antioxidant also prooxidant properties are crucially involved in cytotoxic and protective activities of the major green tea catechin epigallocatechin-3-gallate (EGCG) in vitro (Elbling et al., 2011). Furthermore recent data suggest that EGCG induces oxidative stress also in vivo (Li et al., 2010). Here we set out to identify factors modulating cellular effects of EGCG in vitro. Using the HaCat keratinocytes model, we demonstrate that the cytotoxic, genotoxic and signal-activating effects of EGCG are significantly dependent on the ratio of cell number to working volume. Treatment with identical EGCG concentrations at altered experimental settings resulted in IC₅₀ values differing up to orders of magnitude and could even exert contradictory effects. This effect was based on cell-mediated clearance of autooxidation-derived H₂O₂ from the supernatant. In order to estimate EGCG/H₂O₂ concentrations equally effective under different settings, we have rationally derived and experimentally verified a simple algorithm relating concentration, working volume, cell number and - indirectly - exposure time. Algorithm application resulted in similar H₂O₂ clearance curves from cell supernatants as well as comparable EGCG/H₂O₂ effects at different settings. Our results demonstrate the importance of standardized experimental settings when investigating cytotoxic and/or beneficial effects of autooxidizing compounds.