Elena García-Martín

Glutathione S-transferase m1 and t1 null genotypes increase susceptibility to idiosyncratic drug-induced liver injury.

Individual vulnerability to drug‐induced liver injury (DILI) might result from deficiencies in the detoxification process, which determines the level of exposure to the reactive metabolite. We evaluated whether a genetically determined reduction in the ability to detoxify electrophilic compounds, such as that expected among individuals with glutathione S‐transferase (GST) null genotypes, might play a role in determining the risk for DILI and its clinical expression. Genomic DNA from 154 patients (74 men, 80 women; mean age, 53 years) with a diagnosis of DILI as assessed with the Council for International Organizations of Medical Science scale and 250 sex‐ and age‐matched healthy controls were analyzed. A multiplex polymerase chain reaction–based method was used to detect GSTM1 and GSTT1 gene deletions. Carriers of double GSTT1‐M1 null genotypes had a 2.70‐fold increased risk of developing DILI compared with noncarriers (odds ratio 2.70, 95% confidence interval 1.45‐5.03; P = 0.003). The odds ratio for DILI patients receiving antibacterials, and NSAIDs were 3.52 (P = 0.002), and 5.61 (P = 0.001), respectively. Patients with amoxicillin‐clavulanate hepatotoxicity (n = 32) had a 2.81‐fold increased risk (P = 0.037). Patients classified by the combined GSTT1 and GSTM1 null genotypes did not differ with regard to the type of injury, clinical presentation, or outcome, except for the predominance of women in the combined null genotype (P < 0.001). Conclusion: The double‐null genotype for GSTT1 and GSTM1 might play a role in determining the susceptibility to develop DILI, as a general mechanism that occurs regardless of the type of drug involved, and predominantly in women. (HEPATOLOGY 2008;48:588–596.)

Interindividual variability in ibuprofen pharmacokinetics is related to interaction of cytochrome P450 2C8 and 2C9 amino acid polymorphisms

Our objective was to identify genetic factors related to interindividual variability in the pharmacokinetics of ibuprofen and its enantiomers.

Interethnic and Intraethnic Variability of CYP2C8 and CYP2C9 Polymorphisms in Healthy Individuals

Cytochrome P450 (CYP) superfamily members CYP2C8 and CYP2C9 are polymorphically expressed enzymes that are involved in the metabolic inactivation of several drugs, including, among others, antiepileptics, NSAIDs, oral hypoglycemics, and anticoagulants. Many of these drugs have a narrow therapeutic index, and growing evidence indicates a prominent role of CYP2C8 and CYP2C9 polymorphisms in the therapeutic efficacy and in the development of adverse effects among patients treated with drugs that are CYP2C8 or CYP2C9 substrates.In this review, we summarize present knowledge on human variability in the frequency of variant CYP2C8 and CYP2C9 alleles. Besides an expected interethnic variability in allele frequencies, a large intraethnic variability exists. Among Asian subjects, for example, statistically significant differences (p < 0.0001) in CYP2C9*3 allele frequencies between Chinese and Japanese individuals have been reported. In addition, individuals from East Asia present different allele frequencies for CYP2C9*2 and CYP2C9*3 compared with South Asian subjects (p < 0.0001). Among Caucasian Europeans, statistically significant differences for the frequency of CYP2C8*3, CYP2C9*2, and CYP2C9*3 exist (p < 0.0001). This indicates that Asian individuals or Caucasian European individuals cannot be considered as homogeneous groups regarding CYP2C8 or CYP2C9 allele frequencies. Caucasian American subjects also show a large variability in allele frequencies, which is likely to be related to ethnic ancestry. A higher frequency of variant CYP2C8 and CYP2C9 alleles is expected among Caucasian Americans with South European ancestry than in individuals with North European ancestry.The findings summarized in this review suggest that among individuals with Asian or European ancestry, intraethnic differences in the risk of developing adverse effects with drugs that are CYP2C8 or CYP2C9 substrates are to be expected. In addition, the observed intraethnic variability reinforces the need for proper selection of control subjects and points against the use of surrogate control groups for studies involving association of CYP2C8 or CYP2C9 alleles with adverse drug reactions or spontaneous diseases.

CYP3A4 variant alleles in white individuals with low CYP3A4 enzyme activity

Our objective was to evaluate the presence of CYP3A4 gene variants in white individualswith low CYP3A4 enzyme activity.

Genetic predisposition to acute gastrointestinal bleeding after NSAIDs use

Impaired drug metabolism is a major cause of adverse drug reactions, and it is often caused by mutations at genes coding for drug‐metabolising enzymes. Two amino‐acid polymorphisms of cytochrome P4502C9 (CYP2C9), an enzyme involved in the metabolism of several nonsteroidal anti‐inflammatory drugs (NSAIDs), were studied in 94 individuals with acute bleeding after NSAIDs use and 124 individuals receiving NSAIDs with no adverse effects. The frequency of CYP2C9 variant alleles was increased in overall bleeding patients, with a significant trend to higher risk with increasing number of variant alleles (P=0.02). The odds ratio for bleeding patients receiving CYP2C9 substrates (n=33) was 2.5 for heterozygous and 3.7 for homozygous carriers of mutations (P<0.015), suggesting that the inherited impairment of CYP2C9 activity increases the risk for severe adverse drug reactions after NSAIDs use.

Interethnic and Intraethnic Variability of NAT2 Single Nucleotide Polymorphisms

Genetic polymorphisms of human arylamine N-acetyltransferase 2 (NAT2) are responsible for interindividual variation in the acetylation of numerous drugs and in the transformation of aromatic and heterocyclic amines into carcinogenic intermediates. Although large interethnic variability in the frequency for NAT2 variant alleles has been reported, comparison of allele frequencies is hampered by differences in the criteria for the assignment of allelic variants. To avoid such sources of bias, in this review we analyze the occurrence of both interethnic and intraethnic variability for the seven commonest single nucleotide polymorphisms (SNP) in the NAT2 gene by using raw SNP data instead of inferred haplotypes. Besides the large interethnic variability observed for all SNPs except C282T, intraethnic variability for NAT2 SNPs was identified for the SNPs G191A among Caucasians (p<0.0001), T341C among Oriental (p<0.001) or African individuals (p<0.012), C481T among Oriental (p<0.001) or African individuals (p<0.001), and G590A among Oriental individuals (p<0.001). In contrast, no major intraethnic differences were identified for the SNPs C282T, A806G or G857A. Intraethnic variability may have relevant clinical implications. For instance, case-control NAT2 studies should not be extrapolated from one Oriental population to another. Nonsynonymous SNPs occur in 32% of alleles in Japanese individuals and in 47% of alleles in Chinese individuals, therefore the frequency of adverse effects and cancer related to slow acetylation is expected to be higher in individuals with Chinese descent than in those with Japanese descent. Intraethnic variability reinforces the need for proper selection of control subjects and points against the use of surrogate control groups for studies involving association of NAT2 alleles with adverse drug effects or spontaneous diseases.

High frequency of mutations related to impaired CYP2C9 metabolism in a Caucasian population.

Abstract. Objective: To search for ethnic variability in the impact of cytochrome P450 2C9 (CYP2C9) polymorphism. Methods: CYP2C9 allelic variants related to impaired CYP2C9 metabolism were analysed in genomic DNA from 157 Spanish healthy subjects using amplification–restriction and sequencing procedures. Results: The frequency for CYP2C9 mutated alleles is higher among the Spanish subjects analysed than that reported for other Caucasian individuals: CYP2C9*2, 0.143 and CYP2C9*3, 0.162 (P=0.0001). Nearly 10% of the individuals studied are expected to metabolise deficiently CYP2C9 substrates. Conclusion: In some Caucasian populations the impact of the CYP2C9 polymorphism may be much higher than that estimated from genotyping studies published to date.

Retinal thickness measured with optical coherence tomography and risk of disability worsening in multiple sclerosis: a cohort study

BACKGROUND Most patients with multiple sclerosis without previous optic neuritis have thinner retinal layers than healthy controls. We assessed the role of peripapillary retinal nerve fibre layer (pRNFL) thickness and macular volume in eyes with no history of optic neuritis as a biomarker of disability worsening in a cohort of patients with multiple sclerosis who had at least one eye without optic neuritis available. METHODS In this multicentre, cohort study, we collected data about patients (age ≥16 years old) with clinically isolated syndrome, relapsing-remitting multiple sclerosis, and progressive multiple sclerosis. Patients were recruited from centres in Spain, Italy, France, Germany, Czech Republic, Netherlands, Canada, and the USA, with the first cohort starting in 2008 and the latest cohort starting in 2013. We assessed disability worsening using the Expanded Disability Status Scale (EDSS). The pRNFL thickness and macular volume were assessed once at study entry (baseline) by optical coherence tomography (OCT) and was calculated as the mean value of both eyes without optic neuritis for patients without a history of optic neuritis or the value of the non-optic neuritis eye for patients with previous unilateral optic neuritis. Researchers who did the OCT at baseline were masked to EDSS results and the researchers assessing disability with EDSS were masked to OCT results. We estimated the association of pRNFL thickness or macular volume at baseline in eyes without optic neuritis with the risk of subsequent disability worsening by use of proportional hazards models that included OCT metrics and age, disease duration, disability, presence of previous unilateral optic neuritis, and use of disease-modifying therapies as covariates. FINDINGS 879 patients with clinically isolated syndrome (n=74), relapsing-remitting multiple sclerosis (n=664), or progressive multiple sclerosis (n=141) were included in the primary analyses. Disability worsening occurred in 252 (29%) of 879 patients with multiple sclerosis after a median follow-up of 2·0 years (range 0·5-5 years). Patients with a pRNFL of less than or equal to 87 μm or less than or equal to 88 μm (measured with Spectralis or Cirrus OCT devices) had double the risk of disability worsening at any time after the first and up to the third years of follow-up (hazard ratio 2·06, 95% CI 1·36-3·11; p=0·001), and the risk was increased by nearly four times after the third and up to the fifth years of follow-up (3·81, 1·63-8·91; p=0·002). We did not identify meaningful associations for macular volume. INTERPRETATION Our results provide evidence of the usefulness of monitoring pRNFL thickness by OCT for prediction of the risk of disability worsening with time in patients with multiple sclerosis. FUNDING Instituto de Salud Carlos III.

Mitochondrial superoxide dismutase and glutathione peroxidase in idiosyncratic drug‐induced liver injury

Drug‐induced liver injury (DILI) susceptibility has a potential genetic basis. We have evaluated possible associations between the risk of developing DILI and common genetic variants of the manganese superoxide dismutase (SOD2 Val16Ala) and glutathione peroxidase (GPX1 Pro200Leu) genes, which are involved in mitochondrial oxidative stress management. Genomic DNA from 185 DILI patients assessed by the Council for International Organizations of Medical Science scale and 270 sex‐ and age‐matched controls were analyzed. The SOD2 and GPX1 genotyping was performed using polymerase chain reaction restriction fragment length polymorphism and TaqMan probed quantitative polymerase chain reaction, respectively. The statistical power to detect the effect of variant alleles with the observed odds ratio (OR) was 98.2% and 99.7% for bilateral association of SOD2 and GPX1, respectively. The SOD2 Ala/Ala genotype was associated with cholestatic/mixed damage (OR = 2.3; 95% confidence interval [CI] = 1.4‐3.8; corrected P [Pc] = 0.0058), whereas the GPX1 Leu/Leu genotype was associated with cholestatic injury (OR = 5.1; 95%CI = 1.6‐16.0; Pc = 0.0112). The presence of two or more combined risk alleles (SOD2 Ala and GPX1 Leu) was more frequent in DILI patients (OR = 2.1; 95%CI = 1.4‐3.0; Pc = 0.0006). Patients with cholestatic/mixed injury induced by mitochondria hazardous drugs were more prone to have the SOD2 Ala/Ala genotype (OR = 3.6; 95%CI = 1.4‐9.3; Pc = 0.02). This genotype was also more frequent in cholestatic/mixed DILI induced by pharmaceuticals producing quinone‐like or epoxide metabolites (OR = 3.0; 95%CI = 1.7‐5.5; Pc = 0.0008) and S‐oxides, diazines, nitroanion radicals, or iminium ions (OR = 16.0; 95%CI = 1.8‐146.1; Pc = 0.009). Conclusion: Patients homozygous for the SOD2 Ala allele and the GPX1 Leu allele are at higher risk of developing cholestatic DILI. SOD2 Ala homozygotes may be more prone to suffer DILI from drugs that are mitochondria hazardous or produce reactive intermediates. (HEPATOLOGY 2010)

Ability and reproducibility of Fourier-domain optical coherence tomography to detect retinal nerve fiber layer atrophy in Parkinson's disease.

PURPOSE To evaluate and compare the ability of 3 protocols of Fourier-domain optical coherence tomography (OCT) to detect retinal thinning and retinal nerve fiber layer (RNFL) atrophy in patients with Parkinsons disease (PD) compared with healthy subjects. To test the intrasession reproducibility of RNFL thickness measurements in patients with PD and healthy subjects using the Cirrus (Carl Zeiss Meditec Inc., Dublin, CA) and Spectralis (Heidelberg Engineering, Inc., Heidelberg, Germany) OCT devices. DESIGN Observational, cross-sectional study. PARTICIPANTS Patients with PD (n = 75) and age-matched healthy subjects (n = 75) were enrolled. METHODS All subjects underwent three 360-degree circular scans centered on the optic disc by the same experienced examiner using the Cirrus OCT instrument, the classic glaucoma application, and the new Nsite Axonal Analytics of the Spectralis OCT instrument. MAIN OUTCOME MEASURES Differences between the eyes of healthy subjects and the eyes of patients with PD were compared using the 3 protocols. The relationship between measurements provided by each OCT protocol was evaluated. Repeatability was studied by intraclass correlation coefficients and coefficients of variation. RESULTS Retinal nerve fiber layer atrophy was detected in eyes of patients with PD (P = 0.025, P=0.042, and P < 0.001) with the 3 protocols used, but the Nsite Axonal Analytics of the Spectralis OCT device was the most sensitive for detecting subclinical defects. In eyes of patients with PD, RNFL thickness measurements determined by the OCT devices were correlated, but they were significantly different between the Cirrus and Spectralis devices (P = 0.038). Reproducibility was good with all 3 protocols but better using the Glaucoma application of the Spectralis OCT device. CONCLUSIONS Fourier-domain OCT can be considered a valid and reproducible device for detecting subclinical RNFL atrophy in patients with PD, especially the Nsite Axonal Analytics of the Spectralis device. Retinal nerve fiber layer thickness measurements differed significantly between the Cirrus and Spectralis devices despite a high correlation of the measurements between the 2 instruments.