Genetic profile of patients with epilepsy on first-line antiepileptic drugs and potential directions for personalized treatment

Impact of ABCB1 genetic polymorphism on carbamazepine dose requirement among Southern Indian persons with epilepsy

OBJECTIVES

Carbamazepine (CBZ) is one of the oldest, yet first line drugs for treating epilepsy. However, there is a large inter-individual difference in requirement of maintenance dose and one third of persons treated with antiepileptic drugs (AEDs) exhibit drug resistance to therapy. One of the proposed mechanisms for the drug resistance was increased expression of efflux transporter P-glycoprotein. The pharmacogenetic studies of drug transporters (ABCB1) done in combination therapies of AEDs were inconclusive. Hence, we have attempted to study the impact of ABCB1 3435C>T genetic polymorphism and CBZ monotherapy in persons with epilepsy (PWE) from South India, which is a genetically distinct population. With this background, this study was aimed to determine the dose of CBZ in ABCB1 3435C>T genotypes and to determine the distribution of ABCB1 3435C>T genotypes (which codes P-glycoprotein) between responders and non-responders to CBZ therapy.

METHODS

A cross sectional study was conducted in 200 persons with epilepsy, who were categorised as responders and non-responders according to ILAE (international league against epilepsy) criteria. Eligible participants were enrolled from the epilepsy clinic of the neurology department and five ml of blood was collected. DNA extraction and genotyping were done by phenol-chloroform method and real time polymerase chain reaction (RT-PCR), respectively.

RESULTS

The mean maintenance dose of carbamazepine was statistically significant among different genotypes (p<0.05) of ABCB1 3435C>T (526 vs. 637 mg/day in CC vs. TT genotype). There was no significant association between ABCB1 3435C>T polymorphism (p=0.827) and CBZ resistance in PWE. Duration of disease and age of onset were found to be significant in predicting the response to CBZ therapy.

CONCLUSIONS

We report that ABCB1 3435C>T polymorphism is significantly associated with an increase in dose requirement of CBZ in persons with epilepsy from South India.

Genetic Analysis of CYP2C9 with Reference to Drug Response in Epilepsy Patients of Pakistan

Epilepsy is a major global issue. Epilepsy patients are treated with AED (antiepileptic drugs). Interindividual variability in drug response has been documented in several studies. The resistance to drug response may be attributed to genetic polymorphism. The current study was undertaken to investigate the CYP2C9 gene polymorphism associated with antiepileptic drug (AED) resistance in the Pakistani population. The current study included 337 individuals including 100 control subjects, 110 drug-resistant subjects, and 127 drug responders. Genomic DNA was isolated from blood, and amplification of rs1799853 (430C > T) and rs1057910 was carried out by polymerase chain reaction. Genotypes of CYP2C9 SNPs were determined by Sanger’s sequencing. Astounding results were observed in the current study that none of the well-known reported SNPs of CYP2C9 was found in our Pakistani cohorts. However, a novel missense variant (c.374G > A) was found only in drug-resistant patients of the current study. According to the in silico analysis performed by PolyPhen-2, it was observed that this nonsynonymous substitution is likely to be pathogenic. The results of our study demonstrated that rs1799853 and rs1057910 may be involved in drug resistance in the Pakistani population. However, some other variants on CYP2C9 may play a critical role in AED resistance that needs to be explored.

ABCB1 c.3435C > T and EPHX1 c.416A > G polymorphisms influence plasma carbamazepine concentration, metabolism, and pharmacoresistance in epileptic patients

The gene polymorphisms of ABCB1, EPHX1, and SCN1A were found to influence carbamazepine (CBZ) metabolism and resistance in epilepsy patients, but the relevance remains controversial. To reveal the relationships among the gene polymorphisms of ABCB1, EPHX1, SCN1A and the metabolism and resistance of CBZ, the databases of PubMed, EMBASE, Cochrane Library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals, China Biology medicine disc and Wan Fang were retrieved for suitable studies up to April 2021. 18 studies containing 3293 epilepsy patients were included. The result revealed the gene polymorphism of ABCB1 c.3435C > T is significantly associated with altered concentration-dose ratios of CBZ (CDR_CBZ) (CC vs. CT, OR = 0.25 (95% CI: 0.08-0.42), P = 0.004), and EPHX c.416A > G gene polymorphism may also significantly adjusted the concentration-dose ratios of carbamazepine-10, 11-trans dihydrodiol (CDR_CBZD) (AA vs. GG, OR = 0.48 (95% CI: 0.01-0.96), P = 0.045; AG vs. GG, OR = 0.68 (95% CI: 0.16-1.20), P = 0.010, respectively) and the ratio of CBZD:carbamazepine-10,11-epoxide (CBZE) (CDR_CBZD:CDR_CBZE) (AG vs GG, OR = 0.83 (95% CI: 0.31-1.36), P = 0.002). Furthermore, ABCB1 c.3435C > T polymorphism was also observed to be significantly influenced CBZ resistance (CC vs TT, OR = 1.78 (95% CI: 1.17-2.72), P = 0.008; CT vs TT, OR = 1.60 (95% CI: 1.12-2.30), P = 0.01; CC + CT vs TT, OR = 1.61 (95% CI: 1.15-2.26), P = 0.006, respectively). Therefore, CBZ metabolism and resistance in patients with epilepsy may be adjusted by the gene polymorphisms of ABCB1 c.3435C > T and EPHX1 c.416A > G which provides the further scientific basis for clinical individualized therapy of epilepsy. However, larger sample size studies are still needed to provide further conclusive evidence.

A systematic review and meta-analysis of the association of ABCC2/ABCG2 polymorphisms with antiepileptic drug responses in epileptic patients

PURPOSE

Accumulating evidence indicates that genetic polymorphisms in ATP-binding cassette superfamily members, such asABCC2 and ABCG2, alter responses to antiepileptic drugs (AEDs); however, this evidence is controversial and inconclusive. To provide strong evidence of the association between common polymorphisms in ABCC2 and ABCG2 and AED responses in patients with epilepsy, we performed a systematic review and meta-analysis.

METHODS

A literature search of electronic databases (PubMed, EBSCO, Ovid and the China National Knowledge Infrastructure) was performed. To evaluate the association of genetic polymorphisms inABCC2 and ABCG2 and risk of AED treatment, we calculated pooled odds ratios (ORs) and 95 % confidence intervals (CIs) using a fixed- or random-effect model.

RESULTS

A significant association of theABCC2 rs717620 polymorphism with resistance to AEDs was found in the overall pooled populations (homozygous comparison: OR = 1.77, 95 % CI, 1.27-2.48; dominant model: OR = 1.23, 95 % CI, 1.06-1.43; recessive model: OR = 1.75, 95 % CI, 1.28-2.40) and Asians (dominant model: OR = 1.21, 95 % CI, 1.03-1.42; recessive model: OR = 1.80, 95 % CI, 1.30-2.50). Using a recessive model, a similarly significant association of ABCC2 rs3740066 with AED resistance was observed in the overall pooled populations (OR = 2.29, 95 % CI, 1.44-3.64) and Asians (OR = 2.53, 95 % CI, 1.56-4.08). However, ABCC2 rs2273697, ABCG2 rs2231137 and rs2231142 were not found to be associated with AED responsiveness.

CONCLUSION

This meta-analysis suggests thatABCC2 rs717620 and rs3740066 are risk factors that predict responses to AEDs in epileptic patients.

The association of adjusted plasma valproic acid concentration with CYP2C9 gene polymorphism in patients with epilepsy: a systematic review and meta-analysis

Background

Valproic acid (VPA) is a common antiepileptic drug used to treat both generalized and partial epilepsy. Although there is increasing evidence to suggest that CYP2C9 gene polymorphisms are associated with interindividual variability of VPA metabolism, the results are debatable. Therefore, in the present study, we conducted a meta-analysis to evaluate the correlation between CYP2C9 gene polymorphisms and adjusted plasma VPA concentration.

Methods

The EMBASE, MEDLINE, and Cochrane Library databases were searched to obtain relevant studies. Eligible articles were reviewed, and data extraction was performed. We calculated 95% confidence intervals (CIs) and mean differences (MDs) to assess the strength of the relationship of CYP2C9 gene polymorphisms with adjusted plasma VPA concentration.

Results

The meta-analysis included 6 studies involving 847 patients with epilepsy. The pooled analysis showed that the CYP2C9 A1075C (AA vs. AC) polymorphism was related to the adjusted plasma concentration of VPA (P=0.02, I²= 82%). Additionally, the AC phenotype statistically significantly increased the adjusted plasma VPA concentration in children compared with the mixed age subgroup (P=0.04, I²= 48%). A similar association was observed between the AC phenotype for Asians (P<0.00001, I²=0%) but not for Caucasians (P=0.34, I²=87%).

Discussion

Age might be a crucial covariate influencing the dosage-adjusted VPA concentration in patients with epilepsy. A reduced VPA dosage may be recommendable for children, particularly Asian children, who are CYP2C9 A1075C AC carriers. Further studies could provide high-quality evidence to confirm the correlation between VPA pharmacokinetics and CYP2C9 A1075C polymorphisms.

Associations between CYP3A4, CYP3A5 and SCN1A polymorphisms and carbamazepine metabolism in epilepsy: A meta-analysis

BACKGROUND AND OBJECTIVE

CYP3A4 (rs2242480), CYP3A5 (rs776746) and SCN1A (rs3812718 and rs2298771) gene polymorphisms were previously indicated to be associated with carbamazepine (CBZ) metabolism and resistance in epilepsy. However, previous studies regarding the effects of these polymorphisms still remain controversial. Therefore, we performed a meta-analysis to evaluate whether the four polymorphisms are associated with CBZ metabolism and resistance.

METHODS

The PubMed, EMBASE, Cochrane library, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database, China Biology Medicine disc and Wan Fang Database were searched up to January 2021 for appropriate studies regarding the association of rs2242480, rs776746, rs3812718 and rs2234922 polymorphisms with CBZ metabolism and resistance. The meta-analysis was conducted by Review Manager 5.3 software.

RESULTS

Eighteen studies involving 2546 related epilepsy patients were included. We found that the G allele of CYP3A4 rs2242480 markedly decreased the plasma CBZ concentration in epilepsy. For CYP3A5 rs776746 polymorphism, the GG genotype (homozygote codominant model: GG vs. AA) and GG + GA genotype (dominant model: GG + GA vs. AA and recessive model: GG vs. GA + AA) were respectively found to be significantly associated with increased CBZ plasma concentration. Additionally, it was also found that the SCN1A rs3812718 A allele was significantly associated with decreased CBZ plasma concentration and increased CBZ resistance. However, no association was observed between SCN1A rs2298771 polymorphism and CBZ metabolism and resistance.

CONCLUSION

The CYP3A4 rs2242480, CYP3A5 rs776746 and SCN1A rs3812718 polymorphisms may play important roles in CBZ metabolism and resistance, while SCN1A rs2298771 polymorphism is not associated with CBZ in epilepsy. These findings would improve the individualized therapy of epileptic patients in clinics.

SCN1A IVS5N+5 G>A Polymorphism and Risk of Febrile Seizure and Epilepsy: A Systematic Review and Meta-Analysis

Background: Previous studies had investigated the association between polymorphism of IVS5N+5 G>A in SCN1A and the risk of febrile seizure and epilepsy. However, the results were inconsistent. We aimed to conduct a systematic review and meta-analysis to evaluate the association between SCN1A IVS5N+5 G>A polymorphism and risk of febrile seizures and epilepsy. Methods: We searched Embase, Medline, Scopus, and CNKI for studies on the association between SCN1A IVS5N+5 G>A polymorphism and risk of febrile seizures and epilepsy up to 19 February 2020. We pooled odds ratios (ORs) and 95% confidence intervals (CIs) by different genetic models. To explore the source of heterogeneity, we performed the subgroup analysis by ethnicity and source of control. Results: We included a total of 12 studies in the meta-analysis. We found a significant negative association between G allele SCN1A IVS5N+5 G>A polymorphism, febrile seizures [G vs. A: OR (95% CI): 0.690 (0.530-0.897); GG vs. AA: 0.503 (0.279-0.908); AG vs. AA: 0.581 (0.460-0.733); GG + AG vs. AA: 0.543 (0.436-0.677); AA + GG vs. AG: 1.309 (1.061-1.615)], and epilepsy [G vs. A: 0.822 (0.750-0.902); GG vs. AA: 0.655 (0.515-0.832); AG vs. AA: 0.780 (0.705-0.862); GG vs. AG + AA: 0.769 (0.625-0.947); GG + AG vs. AA: 0.743 (0.663-0.833); AA + GG vs. AG: 1.093 (1.001-1.193)]. The subgroup analysis shows the association varied by type of disease, ethnicity, and source of control. Conclusion: The present meta-analysis suggests that G allele in SCN1A IVS5N+5 G>A polymorphism is a protective factor of febrile seizures and epilepsy. It is possible to determine the vulnerability of each individual to develop febrile seizures or epilepsy genotype by these genetic variants. Future studies with better study designs are needed to confirm the results. Study Registration: This study was registered in the International Prospective register of systematic reviews (PROSPERO, CRD42020163318).

Frequency spectrum of rare and clinically relevant markers in multiethnic Indian populations (ClinIndb): A resource for genomic medicine in India

There have been concerted efforts toward cataloging rare and deleterious variants in different world populations using high-throughput genotyping and sequencing-based methods. The Indian population is underrepresented or its information with respect to clinically relevant variants is sparse in public data sets. The aim of this study was to estimate the burden of monogenic disease-causing variants in Indian populations. Toward this, we have assessed the frequency profile of monogenic phenotype-associated ClinVar variants. The study utilized a genotype data set (global screening array, Illumina) from 2795 individuals (multiple in-house genomics cohorts) representing diverse ethnic and geographically distinct Indian populations. Of the analyzed variants from Global Screening Array, ~9% were found to be informative and were either not known earlier or underrepresented in public databases in terms of their frequencies. These variants were linked to disorders, namely inborn errors of metabolism, monogenic diabetes, hereditary cancers, and various other hereditary conditions. We have also shown that our study cohort is genetically a better representative of the Indian population than its representation in the 1000 Genome Project (South Asians). We have created a database, ClinIndb, linked to the Leiden Open Variation Database, to help clinicians and researchers in diagnosis, counseling, and development of appropriate genetic screening tools relevant to the Indian populations and Indians living abroad.

Association of SCN1A, SCN2A, and UGT2B7 Polymorphisms with Responsiveness to Valproic Acid in the Treatment of Epilepsy

Purpose

The efficacy of valproic acid (VPA) varies widely in clinical treatment of epileptic patients. Our study is aimed at exploring a potential association between polymorphisms of SCN1A, SCN2A, and UGT2B7 genetic factors and VPA responses.

Methods

In this observational study, a total of 114 epileptic patients only treated with VPA for at least 1 year were included to explore the genetic polymorphisms of drug responses (mean follow-up time: 3.68 ± 1.78 years). Thirty-one single-nucleotide polymorphisms (SNPs) in three candidate genes that related with drug-metabolizing enzymes and receptors were genotyped.

Results

Of the 31 SNPs, eight were significantly associated with VPA responses, including rs1381105, rs2162600, rs10197716, rs2119068, rs2119067, rs353116, rs353112 and rs6740895. The interaction between rs10197716 and rs2119068 was the most significantly correlated with VPA responses compared with other combinations (the highest VPA-responsive rate 0.92 versus the lowest VPA-responsive rate 0.33, p = 0.007).

Conclusion

The study indicated that eight SNPs and SNP-SNP interaction may be associated with VPA responses in Chinese Han epileptic patients. The SNPs were rs1381105 (SCN1A), rs2162600 (SCN1A), rs10197716 (SCN2A), rs2119068 (SCN2A), rs2119067 (SCN2A), rs353116 (SCN2A), rs353112 (SCN2A) and rs6740895 (SCN2A), respectively. The interaction between the three pairs of rs10197716-rs2119068, rs10197716-rs11889342 and rs7598931-rs12233719 was the most significant for VPA. This implied that these SNPs may play an important role in the pharmacogenomics mechanism of valproic acid.

Genomics of rare genetic diseases-experiences from India

Home to a culturally heterogeneous population, India is also a melting pot of genetic diversity. The population architecture characterized by multiple endogamous groups with specific marriage patterns, including the widely prevalent practice of consanguinity, not only makes the Indian population distinct from rest of the world but also provides a unique advantage and niche to understand genetic diseases. Centuries of genetic isolation of population groups have amplified the founder effects, contributing to high prevalence of recessive alleles, which translates into genetic diseases, including rare genetic diseases in India.Rare genetic diseases are becoming a public health concern in India because a large population size of close to a billion people would essentially translate to a huge disease burden for even the rarest of the rare diseases. Genomics-based approaches have been demonstrated to accelerate the diagnosis of rare genetic diseases and reduce the socio-economic burden. The Genomics for Understanding Rare Diseases: India Alliance Network (GUaRDIAN) stands for providing genomic solutions for rare diseases in India. The consortium aims to establish a unique collaborative framework in health care planning, implementation, and delivery in the specific area of rare genetic diseases. It is a nation-wide collaborative research initiative catering to rare diseases across multiple cohorts, with over 240 clinician/scientist collaborators across 70 major medical/research centers. Within the GUaRDIAN framework, clinicians refer rare disease patients, generate whole genome or exome datasets followed by computational analysis of the data for identifying the causal pathogenic variations. The outcomes of GUaRDIAN are being translated as community services through a suitable platform providing low-cost diagnostic assays in India. In addition to GUaRDIAN, several genomic investigations for diseased and healthy population are being undertaken in the country to solve the rare disease dilemma.In summary, rare diseases contribute to a significant disease burden in India. Genomics-based solutions can enable accelerated diagnosis and management of rare diseases. We discuss how a collaborative research initiative such as GUaRDIAN can provide a nation-wide framework to cater to the rare disease community of India.

Study of the allelic variants CYP2C9*2 and CYP2C9*3 in samples of the Peruvian mestizo population

Introducción.

El citocromo CYP2C9 metaboliza, aproximadamente, el 15 % de los fármacos prescritos. Su gen presenta alelos cuyas frecuencias difieren entre grupos étnicos y poblaciones. Los alelos CYP2C9*2 y CYP2C9*3 dan cuenta de una enzima con actividad disminuida cuya frecuencia no ha sido determinada en la población mestiza peruana.

Objetivo.

Caracterizar la frecuencia de las variantes *2 (rs1799853) y *3 (rs1057910) del gen CYP2C9 en muestras de población mestiza peruana provenientes de Lima, Tacna y Junín.

Materiales y métodos.

Se hizo un estudio descriptivo, observacional y prospectivo, con muestreo no probabilístico, por conveniencia e incidental. Se incluyeron 218 sujetos según los criterios de inclusión y exclusión; todos los participantes otorgaron su consentimiento informado. El ADN genómico se obtuvo mediante hisopado de mucosa oral, y la detección de los genotipos para los alelos CYP2C9*2 y CYP2C9*3 se hizo mediante reacción en cadena de la polimerasa (PCR) en tiempo real, utilizando sondas TaqMan™.

Resultados.

Las variantes de CYP2C9*2 y CYP2C9*3 están presentes en la población mestiza peruana con frecuencias de 0,046 y 0,062, respectivamente. El análisis de las frecuencias genotípicas observadas permitió predecir que la frecuencia de fenotipos metabolismo intermedio sería del 15,13 % (CYP2C9*1/*2: 5,96 %; CYP2C9*1/*3: 9,17 %), y la de fenotipos de metabolismo lento, del 3,22 % (CYP2C9*2/*2: 1,38 %; CYP2C9*3/*3: 1,38 %; CYP2C9*2/*3: 0,46 %).

Conclusiones.

Se lograron determinar las frecuencias genotípicas y alélicas para las variantes *2 y *3 del gen CYP2C9 en una muestra no probabilística de población mestiza peruana. Las frecuencias obtenidas (0,046 y 0,062, respectivamente) están entre las esperadas para una población mestiza sudamericana con ascendencia amerindia, europea, africana y asiática.

Impact of Genetic Polymorphisms on Phenytoin Pharmacokinetics and Clinical Outcomes in the Middle East and North Africa Region

BACKGROUND

Genetic polymorphisms are known to influence outcomes with phenytoin yet effects in the Middle East and North Africa region are poorly understood.

OBJECTIVES

The objective of this systematic review was to evaluate the impact of genetic polymorphisms on phenytoin pharmacokinetics and clinical outcomes in populations originating from the Middle East and North Africa region, and to characterize genotypic and allelic frequencies within the region for genetic polymorphisms assessed.

METHODS

MEDLINE (1946-3 May, 2017), EMBASE (1974-3 May, 2017), Pharmacogenomics Knowledge Base, and Public Health Genomics Knowledge Base online databases were searched. Studies were included if genotyping and analyses of phenytoin pharmacokinetics were performed in patients of the Middle East and North Africa region. Study quality was assessed using a National Institutes of Health assessment tool. A secondary search identified studies reporting genotypic and allelic frequencies of assessed genetic polymorphisms within the Middle East and North Africa region.

RESULTS

Five studies met the inclusion criteria. CYP2C9, CYP2C19, and multidrug resistance protein 1 C3435T variants were evaluated. While CYP2C9*2 and *3 variants significantly reduced phenytoin metabolism, the impacts of CYP2C19*2 and *3 variants were unclear. The multidrug resistance protein 1 CC genotype was associated with drug-resistant epilepsy, but reported impacts on phenytoin pharmacokinetics were conflicting. Appreciable variability in minor allele frequencies existed both between and within countries of the Middle East and North Africa region.

CONCLUSIONS

CYP2C9 decrease-of-function alleles altered phenytoin pharmacokinetics in patients originating from the Middle East and North Africa region. The impacts of CYP2C19 and multidrug resistance protein 1 C3435T variants on phenytoin pharmacokinetic and clinical outcomes are unclear and require further investigation. Future research should focus on the clinical outcomes associated with phenytoin therapy. PROSPERO 2017: CRD42017057850.

Pharmacogenetics of antiepileptic drug efficacy in childhood absence epilepsy

OBJECTIVE

To determine whether common polymorphisms in CACNA1G, CACNA1H, CACNA1I, and ABCB1 are associated with differential short-term seizure outcome in childhood absence epilepsy (CAE).

METHODS

Four hundred forty-six CAE children in a randomized double-blind trial of ethosuximide, lamotrigine, and valproate had short-term seizure outcome determined. Associations between polymorphisms (minor allele frequency ≥ 15%) in 4 genes and seizure outcomes were assessed. In vitro electrophysiology on transfected CACNA1H channels determined impact of 1 variant on T-type calcium channel responsiveness to ethosuximide.

RESULTS

Eighty percent (357 of 446) of subjects had informative short-term seizure status (242 seizure free, 115 not seizure free). In ethosuximide subjects, 2 polymorphisms (CACNA1H rs61734410/P640L, CACNA1I rs3747178) appeared more commonly among not-seizure-free participants (p = 0.011, odds ratio [OR] = 2.63, 95% confidence limits [CL] = 1.25-5.56; p = 0.026, OR = 2.38, 95% CL = 1.11-5.00). In lamotrigine subjects, 1 ABCB1 missense polymorphism (rs2032582/S893A; p = 0.015, OR = 2.22, 95% CL = 1.16-4.17) was more common in not-seizure-free participants, and 2 CACNA1H polymorphisms (rs2753326, rs2753325) were more common in seizure-free participants (p = 0.038, OR = 0.52, 95% CL = 0.28-0.96). In valproate subjects, no common polymorphisms were associated with seizure status. In vitro electrophysiological studies showed no effect of the P640L polymorphism on channel physiology in the absence of ethosuximide. Ethosuximide's effect on rate of decay of CaV 3.2 was significantly less for P640L channel compared to wild-type channel.

INTERPRETATION

Four T-type calcium channel variants and 1 ABCB1 transporter variant were associated with differential drug response in CAE. The in vivo P640L variant's ethosuximide effect was confirmed by in vitro electrophysiological studies. This suggests that genetic variation plays a role in differential CAE drug response. Ann Neurol 2017;81:444-453.

Synergistic association of STX1A and VAMP2 with cryptogenic epilepsy in North Indian population

INTRODUCTION

"Common epilepsies", merely explored for genetics are the most frequent, nonfamilial, sporadic cases in hospitals. Because of their much debated molecular pathology, there is a need to focus on other neuronal pathways including the existing ion channels.

METHODS

For this study, a total of 214 epilepsy cases of North Indian ethnicity comprising 59.81% generalized, 40.19% focal seizures, and based on epilepsy types, 17.29% idiopathic, 37.38% cryptogenic, and 45.33% symptomatic were enrolled. Additionally, 170 unrelated healthy individuals were also enrolled. Here, we hypothesize the involvement of epilepsy pathophysiology genes, that is, synaptic vesicle cycle, SVC genes (presynapse), ion channels and their functionally related genes (postsynapse). An interactive analysis was initially performed in SVC genes using multifactor dimensionality reduction (MDR). Further, in order to understand the influence of ion channels and their functionally related genes, their interaction analysis with SVC genes was also performed.

RESULTS

A significant interactive two-locus model of STX1A_rs4363087|VAMP2_rs2278637 (presynaptic genes) was observed among SVC variants in all epilepsy cases (P 1000-value = 0.054; CVC = 9/10; OR = 2.86, 95%CI = 1.88-4.35). Further, subgroup analysis revealed stronger interaction for the same model in cryptogenic epilepsy patients only (P 1000-value = 0.012; CVC = 10/10; OR = 4.59, 95%CI = 2.57-8.22). However, interactive analysis of presynaptic and postsynaptic genes did not show any significant association.

CONCLUSIONS

Significant synergistic interaction of SVC genes revealed the possible functional relatedness of presynapse with pathophysiology of cryptogenic epilepsy. Further, to establish the clinical utility of the results, replication in a large and similar phenotypic group of patients is warranted.

Iranian-Islamic traditional medicine: An ancient comprehensive personalized medicine

Personalized medicine (PM) is a novel term used for a medical model in which all diagnostic, prognostic, and therapeutic aspects of a disease are individualized for a patient using specific molecular testing. In Iranian-Islamic traditional medicine (IITM) an ancient paradigm for PM has been described which has been introduced in this paper. We reviewed the ancient resources of IITM and many valid recent studies on personalized medicine and described an ancient feature of personalized medicine in comparison with new ones. According to IITM scholars, every person has an individual temperament which is concluded of four basic humors combination. The individual temper is influenced by internal and external factors such as age, gender, ethnicity, season, and environment. This variability leads to different physical and mental behaviors toward a particular condition; so if we could identify the patient's temper, we would predict his/her health-related behaviors rather than predisposition and prognosis to different diseases, and select the best treatment. This holistic viewpoint of IITM to the human health and disease justifies the variable phenotypes among similar illnesses; the fact around which more advanced high-tech researches are being developed to explore all specific molecular pathways. IITM offers an ancient comprehensive PM (APM) which is more available and inexpensive compared to the modern PM (MPM). Moreover, APM focuses more on fitness than illness in comparison to MPM. It seems more attention to APM introduced by IITM could help us to promote health community. Design studies using high-tech MPM techniques would likely lead to clarification of most molecular aspects of APM.

The effect of genetic polymorphisms of cytochrome P450 CYP2C9, CYP2C19, and CYP2D6 on drug-resistant epilepsy in Turkish children

BACKGROUND AND OBJECTIVE

Despite the availability of several antiepileptic drugs, drug resistance remains one of the major challenges in epilepsy therapy. Genetic factors are known to play a significant role in the prognosis and treatment of epilepsy. The aim of this study was to determine the frequencies of alleles for CYP2C9, CYP2C19, and CYP2D6 genes in Turkish children with epilepsy, and to investigate the relationship between the genetic polymorphism of these genes with multiple drug resistance in epilepsy patients.

METHODS

We genotyped 132 epileptic patients (60 drug resistant and 72 drug responsive) and 55 healthy controls for six single nucleotide polymorphisms (SNPs) in CYP2C9, CYP2C19, and CYP2D6. Genotype, allele, and haplotype frequencies were compared between groups.

RESULTS

The frequencies of CYP2C9*3/*3 genotype and CYP2C9*3 allele, and the haplotype CCGG (CYP2C9*2 C>T, CYP2C9*3 A>C, and CYP2C19*2 G>A, CYP2C19* G>A) were significantly higher in drug-resistant versus -responsive patients.

CONCLUSION

Our results demonstrated the important role of the CYP2C9*3 allelic variant in preventing epilepsy patients from developing drug resistance. These data suggest that CYP2C9, CYP2C19, and CYP2D6 SNPs and haplotypes may affect the response to antiepileptic drugs.

Validation of a multigenic model to predict seizure control in newly treated epilepsy

A multigenic classifier based on five single nucleotide polymorphisms (SNPs) was previously reported to predict treatment response in an Australian newly-diagnosed epilepsy cohort using a k-nearest neighbour (kNN) algorithm. We assessed the validity of this classifier in predicting response to initial antiepileptic drug (AED) treatment in two UK cohorts of newly-diagnosed epilepsy and investigated the utility of these five SNPs in predicting seizure control in general. The original Australian cohort constituted the training set for the classifier and was used to predict response to the first well-tolerated AED monotherapy in independently recruited UK cohorts (Glasgow, n=281; SANAD, n=491). A "leave-one-out" cross-validation was also employed, with training sets derived internally from the UK datasets. The multigenic classifier using the Australian cohort as the training set was unable to predict treatment response in either UK cohort. In the "leave-one-out" analysis, the five SNPs collectively predicted treatment response in both Glasgow and SANAD patients prescribed either carbamazepine or valproate (Glasgow OR=3.1, 95% CI=1.4-6.6, p=0.018; SANAD OR=2.8, 95% CI=1.3-6.1, p=0.048), but not those receiving lamotrigine (Glasgow OR=1.3, 95% CI=0.6-2.8, p=1.0; SANAD OR=2.2, 95% CI=0.9-5.4, p=0.36) or other AEDs (Glasgow OR=0.6, 95% CI=0.2-2.0, p=1.0; SANAD OR=1.9, 95% CI=0.9-4.2, p=0.36). The Australian-based multigenic kNN model is not predictive of initial treatment response in UK cohorts of newly-diagnosed epilepsy. However, the five SNPs identified in the original Australian study appear to collectively have a predictive influence in UK patients prescribed either carbamazepine or valproate.

Adherence to antiepileptic drugs among children attending a tertiary health unit in a low resource setting

INTRODUCTION

Epilepsy is one of the neglected and highly stigmatised diseases, yet it is very common affecting about 70 million people worldwide. In Uganda, the estimated prevalence of epilepsy is 13% with about 156 new cases per 100,000 people per year. Adherence to antiepileptic drugs is crucial in achieving seizure control yet in Uganda; there is lack of information on adherence to antiepileptic drugs and the factors that affect this among children. This study was therefore designed to determine the level of adherence to antiepileptic drugs and the factors that are associated with non adherence.

METHODS

In a cross sectional study, 122 children who met the inclusion criteria were enrolled and interviewed using a pretested questionnaire. Assessment of adherence to antiepileptic drugs was done by self report and assay of serum drug levels of the antiepileptic drugs. Focus group discussions were held to further evaluate the factors that affect adherence.

RESULTS

Age range was 6 months - 16 years, male to female ratio 1.3:1 and majority had generalised seizures 76 (62.3%). Adherence to antiepileptic drugs by self report was 79.5% and 22.1% by drug levels. Majority of the children in both adherent and non adherent groups by self report had inadequate drug doses (95/122). Children were found to be more non-adherent if the caregiver had an occupation (p-value 0.030, 95%CI 1.18-28.78).

CONCLUSION

Majority of children had good adherence levels when estimated by self report. The caregiver having an occupation was found to increase the likelihood of non adherence in a child.

Case-control association study of polymorphisms in the voltage-gated sodium channel genes SCN1A, SCN2A, SCN3A, SCN1B, and SCN2B and epilepsy

High-frequency action potentials are mediated by voltage-gated sodium channels, composed of one large α subunit and two small β subunits, encoded mainly by SCN1A, SCN2A, SCN3A, SCN1B, and SCN2B genes in the brain. These play a key role in epilepsy, with the most commonly mutated gene in epilepsy being SCN1A. We examined whether polymorphisms in the above genes affect epilepsy risk in 1,529 epilepsy patients and 1,935 controls from four ethnicities or locations: Malay, Indian, and Chinese, all from Malaysia, and Chinese from Hong Kong. Of patients, 19 % were idiopathic, 42 % symptomatic, and 40 % cryptogenic. We genotyped 43 polymorphisms: 27 in Hong Kong, 28 in Malaysia, and 12 in both locations. The strongest association with epilepsy was rs3812718, or SCN1A IVS5N+5G>A: odds ratio (OR) = 0.85 for allele G (p = 0.0009) and 0.73 for genotype GG versus AA (p = 0.003). The OR was between 0.76 and 0.87 for all ethnicities. Meta-analysis confirmed the association (OR = 0.81 and p = 0.002 for G, and OR = 0.67 and p = 0.007 for GG versus AA), which appeared particularly strong for Indians and for febrile seizures. Allele G affects splicing and speeds recovery from inactivation. Since SCN1A is preferentially expressed in inhibitory neurons, G may decrease epilepsy risk. SCN1A rs10188577 displayed OR = 1.20 for allele C (p = 0.003); SCN2A rs12467383 had OR = 1.16 for allele A (p = 0.01), and displayed linkage disequilibrium with rs2082366 (r (2) = 0.67), whose genotypes tended toward association with SCN2A brain expression (p = 0.10). SCN1A rs2298771 was associated in Indians (OR = 0.56, p = 0.005) and SCN2B rs602594 with idiopathic epilepsy (OR = 0.62, p = 0.002). Therefore, sodium channel polymorphisms are associated with epilepsy.

Effects of polymorphisms in six candidate genes on phenytoin maintenance therapy in Han Chinese patients

AIM

The present study aimed to investigate the associations between variants in pharmacokinetic- and pharmacodynamic-related genes with the dosages, concentrations and concentration-dose ratios (CDRs) of phenytoin (PHT).

METHODS & RESULTS

Eleven genetic polymorphisms in the six candidate genes were detected in 269 epileptic patients under maintenance PHT monotherapy by real-time PCR and PCR-RFLP. Results of a bivariate analysis demonstrated that among tested polymorphisms, carriers of the variant CYP2C9*3 tended to require significantly lower maintenance PHT dosages than wild-type carriers (p < 0.0001); on the other hand, carriers of the variants CYP2C9*3 or CYP2C19*3 revealed significantly higher CDRs than wild-type carriers (p < 0.004). In a further multivariate analysis, variants in SCN1A, CYP2C9, CYP2C19 and ABCB1 genes were significantly associated with CDRs of PHT under adjustment of age, gender and epilepsy classifications (adjusted r(2) = 20.07%).

CONCLUSION

The results of present study indicated that polygenic analysis may provide useful information in PHT therapy optimization.

Genetic association analysis of transporters identifies ABCC2 loci for seizure control in women with epilepsy on first-line antiepileptic drugs

OBJECTIVE

The ATP-binding cassette (ABC) superfamily of transporters is known to efflux antiepileptic drugs (AEDs) primarily in the brain, gastrointestinal tract, liver, and kidneys. In addition, they are also known to be involved in estrogen disposition and may modulate seizure susceptibility and drug response. The objective of the present study was to investigate the role of genetic variants from ABC transporters in seizure control in epilepsy patients treated with monotherapy of first-line AEDs for 12 months.

METHODS

On the basis of gene coverage and functional significance, a total of 98 single nucleotide polymorphisms from ABCB1, ABCC1, and ABCC2 were genotyped in 400 patients from North India. Of these, 216 patients were eligible for therapeutic assessment. Genetic variants were compared between the 'no-seizures' and the 'recurrent-seizures' groups. Bonferroni corrections for multiple comparisons and adjustment for covariates were performed before assessment of associations.

RESULTS

Functionally relevant promoter polymorphisms from ABCC2: c.-1549G>A and c.-1019A>G either considered alone or in haplotype and diplotype combinations were observed for a significant association with seizure control in women (odds ratio>3.5, P<10, power>95%). Further, low protein-expressing CGT and TGT (c.-24C>T, c.1249G>A, c.3972C>T) haplotypes were always observed to be present in combination with the AG (c.-1549G>A, c.-1019A>G) haplotype that was over-represented in women with 'no seizures'.

CONCLUSION

The distribution of the associated variants supports the involvement of ABCC2 in controlling seizures in women possibly by lowering of its expression. The biological basis of this finding could be an altered interaction of ABCC2 with AEDs and estrogens. These results necessitate replication in a larger pool of patients.

Increased 2-hydroxylation of estrogen is associated with lower body fat and increased lean body mass in postmenopausal women

Menopause is associated with changes in bone, muscle and fat mass. The importance of postmenopausal estrogen metabolism in bone health has been established. However, its relationship to body composition in postmenopausal women remains undetermined. The objective of this study is to determine the association between estrogen metabolism and body composition in postmenopausal women. This is a cross sectional study of 97 postmenopausal Caucasian women, 49-80 y.o., ≥1 year from the last normal menstrual period or those who have had oophorectomy. Inactive [2-hydroxyestrone (2OHE(1))] and active [16α-hydroxyestrone (16α-OHE(1))] urinary metabolites of estrogen were measured by ELISA. The whole and regional body composition was measured by DXA. We have found that both 2OHE(1), and 2OHE(1)/16α-OHE(1) ratio were negatively correlated with % total fat, and % truncal fat but positively correlated with % total lean mass. Comparing the fat and lean parameters of body composition according to tertiles of 2OHE(1) and 2OHE(1)/16αOHE(1) ratio showed that subjects in the lowest tertiles, had the highest % total fat, and % truncal fat and the lowest % total lean mass. Multiple regression analysis also showed 2OHE(1) and calcium intake as statistically significant predictors of all body composition parameters. In conclusion, in postmenopausal women, an increase in the metabolism of estrogen towards the inactive metabolites is associated with lower body fat and higher lean mass than those with predominance of the metabolism towards the active metabolites.

A hot topic: temperature sensitive sodium channelopathies

Perturbations to body temperature affect almost all cellular processes and, within certain limits, results in minimal effects on overall physiology. Genetic mutations to ion channels, or channelopathies, can shift the fine homeostatic balance resulting in a decreased threshold to temperature induced disturbances. This review summarizes the functional consequences of currently identified voltage-gated sodium (NaV) channelopathies that lead to disorders with a temperature sensitive phenotype. A comprehensive knowledge of the relationships between genotype and environment is not only important for understanding the etiology of disease, but also for developing safe and effective treatment paradigms.

The effect of ABCB1 genetic variants on chemotherapy response in HIV and cancer treatment

Despite their clearly distinct pathophysiologies, HIV and cancer are diseases whose response to chemotherapy treatment varies substantially amongst patients, in particular for those with prior drug exposure. This has been attributed, in part, to elevated expression of the ABCB1 drug transporter in some patients, which results in reduced drug accumulation in target tissues. Many mechanisms have been identified for this elevated expression of ABCB1, including variations in the sequence of the gene coding for the transporter (ABCB1). Over 50 SNPs within ABCB1 have been identified. Associations have been made between the presence of specific ABCB1 SNPs/haplotypes and both ABCB1 expression and the efficacy or toxicity of certain chemotherapy regimens. If these associations are strong and reproducibly demonstrated, then this would greatly aid in the development of individualized therapy regimes for specific cancer or HIV patients, based on their ABCB1 genotypes. This article highlights the significant recent progress made in this direction, but cautions that the utility of ABCB1 gene variants as biomarkers of chemotherapy drug response remains unclear to date.

A thermoprotective role of the sodium channel β1 subunit is lost with the β1 (C121W) mutation

PURPOSE

A mutation in the β(1) subunit of the voltage-gated sodium (Na(V)) channel, β(1) (C121W), causes genetic epilepsy with febrile seizures plus (GEFS+), a pediatric syndrome in which febrile seizures are the predominant phenotype. Previous studies of molecular mechanisms underlying neuronal hyperexcitability caused by this mutation were conducted at room temperature. The prevalence of seizures during febrile states in patients with GEFS+, however, suggests that the phenotypic consequence of β(1) (C121W) may be exacerbated by elevated temperature. We investigated the putative mechanism underlying seizure generation by the β(1) (C121W) mutation with elevated temperature.

METHODS

Whole-cell voltage clamp experiments were performed at 22 and 34°C using Chinese Hamster Ovary (CHO) cells expressing the α subunit of neuronal Na(V) channel isoform, Na(V) 1.2. Voltage-dependent properties were recorded from CHO cells expressing either Na(V) 1.2 alone, Na(V) 1.2 plus wild-type (WT) β(1) subunit, or Na(V) 1.2 plus β(1) (C121W).

KEY FINDINGS

Our results suggest WT β(1) is protective against increased channel excitability induced by elevated temperature; protection is lost in the absence of WT β(1) or with expression of β(1) (C121W). At 34°C, Na(V) 1.2 + β(1) (C121W) channel excitability increased compared to NaV1.2 + WT β(1) by the following mechanisms: decreased use-dependent inactivation, increased persistent current and window current, and delayed onset of, and accelerated recovery from, fast inactivation.

SIGNIFICANCE

Temperature-dependent changes found in our study are consistent with increased neuronal excitability of GEFS+ patients harboring C121W. These results suggest a novel seizure-causing mechanism for β(1) (C121W): increased channel excitability at elevated temperature.

Pharmacogenomics and epilepsy: the road ahead

Epilepsy is one of the most common, serious neurological disorders, affecting an estimated 50 million people worldwide. The condition is typically treated using antiepileptic drugs of which there are 16 in widespread use. However, there are many different syndrome and seizure types within epilepsy and information guiding clinicians on the most effective drug and dose for individual patients is lacking. Further, all of the antiepileptic drugs have associated adverse reactions, some of which are severe and life-threatening. Here, we review the pharmacogenomic work to date in the context of these issues and comment on key aspects of study design that are required to speed up the identification of clinically relevant genetic factors.

Challenges and recommendations for conducting epidemiological studies in the field of epilepsy pharmacogenetics

Epilepsy is one of the most prevalent neurological disorders, afflicting approximately 50 million Indians. Owing to affordability and easy availability, use of first-generation antiepileptic drugs (AEDs) is heavily encouraged for the treatment of epilepsy in resource-limited countries such as India. Although first-generation AEDs are at par with second-generation AEDs in terms of efficacy, adverse drug reactions (ADRs) are quite common with them. This could be attributed to the inferior pharmacokinetic parameters such as nonlinear metabolism, narrow therapeutic index and formation of toxic intermediates. In addition, epilepsy patients may differ in the pharmacokinetic and pharmacodynamic profiles, with about 1/3^rd of the population failing to respond to treatment. A proportion of this interindividual variability in response may be explained by genetic heterogeneity in the activity and expression of the network of proteins such as metabolizing enzymes, transporters and targets of AEDs. Over the last two decades, a considerable effort has been made by the scientific community for unraveling this genetic basis of variable response to AEDs. However, there have been inconsistencies in such genetic association studies conducted across different territories of the world. There could be several reasons underlying the poor replicability of these studies, mainly nonuniform phenotypic definitions, poor sample size and interethnic variability. In the present review article, we provide an overview of heterogeneity in study designs for conducting pharmacogenetic studies. In addition, critical recommendations required for overcoming such challenges imposed by pharmacogenetic epidemiological studies have been briefly discussed.