Polymorphisms of ABAT, SCN2A and ALDH5A1 may affect valproic acid responses in the treatment of epilepsy in Chinese

Consensus guidelines for the diagnosis and management of succinic semialdehyde dehydrogenase deficiency

Succinic semialdehyde dehydrogenase deficiency (SSADHD) (OMIM #271980) is a rare autosomal recessive metabolic disorder caused by pathogenic variants of ALDH5A1. Deficiency of SSADH results in accumulation of γ-aminobutyric acid (GABA) and other GABA-related metabolites. The clinical phenotype of SSADHD includes a broad spectrum of non-pathognomonic symptoms such as cognitive disabilities, communication and language deficits, movement disorders, epilepsy, sleep disturbances, attention problems, anxiety, and obsessive-compulsive traits. Current treatment options for SSADHD remain supportive, but there are ongoing attempts to develop targeted genetic therapies. This study aimed to create consensus guidelines for the diagnosis and management of SSADHD. Thirty relevant statements were initially addressed by a systematic literature review, resulting in different evidence levels of strength according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria. The highest level of evidence (level A), based on randomized controlled trials, was unavailable for any of the statements. Based on cohort studies, Level B evidence was available for 12 (40%) of the statements. Thereupon, through a process following the Delphi Method and directed by the Appraisal of Guidelines for Research and Evaluation (AGREE II) criteria, expert opinion was sought, and members of an SSADHD Consensus Group evaluated all the statements. The group consisted of neurologists, epileptologists, neuropsychologists, neurophysiologists, metabolic disease specialists, clinical and biochemical geneticists, and laboratory scientists affiliated with 19 institutions from 11 countries who have clinical experience with SSADHD patients and have studied the disorder. Representatives from parent groups were also included in the Consensus Group. An analysis of the survey's results yielded 25 (83%) strong and 5 (17%) weak agreement strengths. These first-of-their-kind consensus guidelines intend to consolidate and unify the optimal care that can be provided to individuals with SSADHD.

Association of ABCB1 Polymorphisms with Efficacy and Adverse Drug Reactions of Valproic Acid in Children with Epilepsy

Genetic polymorphisms in ATP-binding cassette subfamily B member 1 (ABCB1, also known as MDR1) have been reported to be possibly associated with the regulation of response to antiseizure medications. The aim of this study was to investigate the association of ABCB1 polymorphisms with the efficacy of and adverse drug reactions to valproic acid among Chinese children with epilepsy. A total of 170 children from southern China with epilepsy treated with valproic acid for more than one year were recruited, including 61 patients with persistent seizures and 109 patients who were seizure-free. Two single nucleotide polymorphisms of ABCB1, rs1128503 and rs3789243, were genotyped using the Sequenom MassArray system. The two single nucleotide polymorphisms of ABCB1 were found to be significantly associated with treatment outcomes of valproic acid in children with epilepsy. Carriers with the TT genotype of ABCB1 rs1128503 were more inclined to exhibit persistent seizures after treatment with valproic acid (p = 0.013). The CC genotype of rs3789243 was observed to be a potential protective factor for valproic acid-induced gastrointestinal adverse drug reactions (p = 0.018), but possibly increased the risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). In contrast, the CT genotype of rs3789243 was associated with a lower risk of valproic acid-induced cutaneous adverse drug reactions (p = 0.011). Haplotype analysis showed that CC haplotype carriers tended to respond better to valproic acid treatment (p = 0.009). Additionally, no significant association was found between ABCB1 polymorphisms and serum concentrations of valproic acid. This study revealed that the polymorphisms and haplotypes of the ABCB1 gene might be associated with the treatment outcomes of valproic acid in Chinese children with epilepsy.

Structural variation of the coding and non-coding human pharmacogenome

Genetic variants in drug targets and genes encoding factors involved in drug absorption, distribution, metabolism and excretion (ADME) can have pronounced impacts on drug pharmacokinetics, response, and toxicity. While the landscape of genetic variability at the level of single nucleotide variants (SNVs) has been extensively studied in these pharmacogenetic loci, their structural variation is only poorly understood. Thus, we systematically analyzed the genetic structural variability across 908 pharmacogenes (344 ADME genes and 564 drug targets) based on publicly available whole genome sequencing data from 10,847 unrelated individuals. Overall, we extracted 14,984 distinct structural variants (SVs) ranging in size from 50 bp to 106 Mb. Each individual harbored on average 10.3 and 1.5 SVs with putative functional effects that affected the coding regions of ADME genes and drug targets, respectively. In addition, by cross-referencing pharmacogenomic SVs with experimentally determined binding data of 224 transcription factors across 130 cell types, we identified 1276 non-coding SVs that overlapped with gene regulatory elements. Based on these data, we estimate that non-coding structural variants account for 22% of the genetically encoded pharmacogenomic variability. Combined, these analyses provide the first comprehensive map of structural variability across pharmacogenes, derive estimates for the functional impact of non-coding SVs and incentivize the incorporation of structural genomic data into personalized drug response predictions.

Effects of UGT1A, CYP2C9/19 and ABAT polymorphisms on plasma concentration of valproic acid in Chinese epilepsy patients

Aim: To evaluate the association between genetic polymorphisms and plasma concentration-to-dose ratio of valproic acid (CDRV) in Chinese epileptic patients. Methods: A total of 46 epileptic patients treated with valproic acid therapy were enrolled. 18 SNPs in nine genes related to valproic acid were directly sequenced with Sanger methods. Results: Patients carrying UGT1A6 heterozygous genotypes had significantly lower CDRV than those carrying the wild-type genotypes. In contrast, patients with the homozygote genotypes of CYP2C9 and ABAT had higher CDRV than those with the wild-type genotypes and patients with the heterozygous genotypes of CYP2C19 had higher CDRV. Conclusion: Detection of genetic polymorphism in these genes might facilitate an appropriate dose of valproic acid for epileptic patients. Further studies with larger cohorts are necessary to underpin these observations.

Pharmacogenetics-based population pharmacokinetic analysis and dose optimization of valproic acid in Chinese southern children with epilepsy: Effect of ABCB1 gene polymorphism

Objective: The aim of this study was to establish a population pharmacokinetic (PPK) model of valproic acid (VPA) in pediatric patients with epilepsy in southern China, and provide guidance for individualized medication of VPA therapy. Methods: A total of 376 VPA steady-state trough concentrations were collected from 103 epileptic pediatric patients. The PPK parameter values for VPA were calculated by using the nonlinear mixed-effects modeling (NONMEM) method, and a one-compartment model with first-order absorption and elimination processes was applied. Covariates included demographic information, concomitant medications and selected gene polymorphisms. Goodness-of-fit (GOF), bootstrap analysis, and visual predictive check (VPC) were used for model evaluation. In addition, we used Monte Carlo simulations to propose dose recommendations for different subgroup patients. Results: A significant effect of the patient age and ABCB1 genotypes was observed on the VPA oral clearance (CL/F) in the final PPK model. Compared with patients with the ABCB1 rs3789243 AA genotype, CL/F in patients with GG and AG genotypes was increased by 8% and reduced by 4.7%, respectively. The GOF plots indicated the satisfactory predictive performance of the final model, and the evaluation by bootstrap and VPC showed that a stable model had been developed. A table of individualized dosing regimens involving age and ABCB1 genotype was constructed based on the final PPK model. Conclusion: This study quantitatively investigated the effects of patient age and ABCB1 rs3789243 variants on the pharmacokinetic variability of VPA. The PPK models could be beneficial to individual dose optimization in epileptic children on VPA therapy.

Genetic Analysis of Sodium Channel Genes in Pediatric Epilepsy Patients of Pakistan

Epilepsy affects millions of people worldwide. Although antiepileptic drugs work for the majority of epileptic patients, these drugs do not work for some of the patients, subjecting them to drug-resistant epilepsy (DRE). Voltage-gated sodium channels act as targets for a number of antiepileptic drugs, and the genes encoding these channels can play a crucial role in developing drug-resistant epilepsy. This case-control (100 control: 101patients) study evaluated the association of sodium channel genes SCN1A and SCN2A with drug-resistant epilepsy. The cases were further accounted in two categories, drug-resistant and drug-responsive epileptic patients. The polymorphic sites rs794726754, rs1057518252, rs121918809, rs12191792, rs121917932, c.730 G > T, c.735 G > T, c.736 A > T, rs10167228, and rs2298771 of the SCN1A gene and rs17183814 of SCN2A gene were selected for mutational analysis. The DNA was isolated, amplified by PCR, and then, was run through 1% agarose gel. The sequencing was performed, and the sequences were observed through BioEdit software for any change in DNA sequence. In our study, no polymorphism was observed in the studied SNPs except for rs2298771. For rs2298771, a significant difference existed in the distribution of genotypic and allelic frequencies (p < 0.01) among the case and control group. Furthermore, the genotypic and allelic frequencies of the two categories of cases (drug responder drug resistant) were calculated. The genotypic and allelic frequencies of drug-responsive and drug-resistant epileptic patients did not differ significantly (p > 0.01). Our study indicated that the rs2298771 polymorphism of SCN1A may not be associated with chance of developing DRE in the Pakistani population.

Association Between SCN1A rs2298771, SCN1A rs10188577, SCN2A rs17183814, and SCN2A rs2304016 Polymorphisms and Responsiveness to Antiepileptic Drugs: A Meta-Analysis

Background:SCN1A and SCN2A genes have been reported to be associated with the efficacy of single and combined antiepileptic therapy, but the results remain contradictory. Previous meta-analyses on this topic mainly focused on the SCN1A rs3812718 polymorphism. However, meta-analyses focused on SCN1A rs2298771, SCN1A rs10188577, SCN2A rs17183814, or SCN2A rs2304016 polymorphisms are scarce or non-existent.

Objective: We aimed to conduct a meta-analysis to determine the effects of SCN1A rs2298771, SCN1A rs10188577, SCN2A rs17183814, and SCN2A rs2304016 polymorphisms on resistance to antiepileptic drugs (AEDs).

Methods: We searched the PubMed, Embase, Cochrane Library, WANFANG, and CNKI databases up to June 2020 to collect studies on the association of SCN1A and SCN2A polymorphisms with reactivity to AEDs. We calculated the pooled odds ratios (ORs) under the allelic, homozygous, heterozygous, dominant, and recessive genetic models to identify the association between the four single-nucleotide polymorphisms (SNPs) and resistance to AEDs.

Results: Our meta-analysis included 19 eligible studies. The results showed that the SCN1A rs2298771 polymorphism was related to AED resistance in the allelic, homozygous, and recessive genetic models (G vs. A: OR = 1.20, 95% CI: 1.012–1.424; GG vs. AA: OR = 1.567, 95% CI: 1.147–2.142; GG vs. AA + AG: OR = 1.408, 95% CI: 1.053–1.882). The homozygous model remained significant after Bonferroni correction (P < 0.0125). Further subgroup analyses demonstrated the significance of the correlation in the dominant model in Caucasians (South Asians) after Bonferroni correction (GG + GA vs. AA: OR = 1.620, 95% CI: 1.165–2.252). However, no association between SCN1A rs2298771 polymorphism and resistance to AEDs was found in Asians or Caucasians (non-South Asians). For SCN1A rs10188577, SCN2A rs17183814, and SCN2A rs2304016 polymorphisms, the correlations with responsiveness to AEDs were not significant in the overall population nor in any subgroup after conducting the Bonferroni correction. The results for SCN1A rs2298771, SCN1A rs10188577, and SCN2A rs2304016 polymorphisms were stable and reliable according to sensitivity analysis and Begg and Egger tests. However, the results for SCN2A rs17183814 polymorphism have to be treated cautiously owing to the significant publication bias revealed by Begg and Egger tests.

Conclusions: The present meta-analysis indicated that SCN1A rs2298771 polymorphism significantly affects resistance to AEDs in the overall population and Caucasians (South Asians). There were no significant correlations between SCN1A rs10188577, SCN2A rs17183814, and SCN2A rs2304016 polymorphisms and resistance to AEDs.

Polymorphic Genetic Markers of the GABA Catabolism Pathway in Alzheimer's Disease

BACKGROUND

The compilation of a list of genetic modifiers in Alzheimer's disease (AD) is an open research field. The GABAergic system is affected in several neurological disorders but its role in AD is largely understudied.

OBJECTIVE/METHODS

As an explorative study, we considered variants in genes of GABA catabolism (ABAT, ALDH5A1, AKR7A2), and APOE in 300 Italian patients and 299 controls. We introduce a recent multivariate method to take into account the individual APOE genotype, thus controlling for the effect of the discrepant allele distributions in cases versus controls. We add a genotype-phenotype analysis based on age at onset and the Mini-Mental State Evaluation score.

RESULTS

On the background of strongly divergent APOE allele distributions in AD versus controls, two genotypic interactions that represented a subtle but significant peculiarity of the AD cohort emerged. The first is between ABAT and APOE, and the second between some ALDH5A1 genotypes and APOE. Decreased SSADH activity is predicted in AD carriers of APOEɛ4, representing an additional suggestion for increased oxidative damage.

CONCLUSION

We identified a difference between AD and controls, not in a shift of the allele frequencies at genes of the GABA catabolism pathway, but rather in gene interactions peculiar of the AD cohort. The emerging view is that of a multifactorial contribution to the disease, with a main risk factor (APOE), and additional contributions by the variants here considered. We consider genes of the GABA degradation pathway good candidates as modifiers of AD, contributing to energy impairment in AD brain.

Potential pharmacogenomic targets in bipolar disorder: considerations for current testing and the development of decision support tools to individualize treatment selection

Background

Treatment in bipolar disorder (BD) is commonly applied as a multimodal therapy based on decision algorithms that lack an integrative understanding of molecular mechanisms or a biomarker associated clinical outcome measure. Pharmacogenetics/genomics study the individual genetic variation associated with drug response. This selective review of pharmacogenomics and pharmacogenomic testing (PGT) in BD will focus on candidate genes and genome wide association studies of pharmacokinetic drug metabolism and pharmacodynamic drug response/adverse event, and the potential role of decision support tools that incorporate multiple genotype/phenotype drug recommendations.

Main body

We searched PubMed from January 2013 to May 2019, to identify studies reporting on BD and pharmacogenetics, pharmacogenomics and PGT. Studies were selected considering their contribution to the field. We summarize our findings in: targeted candidate genes of pharmacokinetic and pharmacodynamic pathways, genome-wide association studies and, PGT platforms, related to BD treatment. This field has grown from studies of metabolizing enzymes (i.e., pharmacokinetics) and drug transporters (i.e., pharmacodynamics), to untargeted investigations across the entire genome with the potential to merge genomic data with additional biological information.

Conclusions

The complexity of BD genetics and, the heterogeneity in BD drug-related phenotypes, are important considerations for the design and interpretation of BD PGT. The clinical applicability of PGT in psychiatry is in its infancy and is far from reaching the robust impact it has in other medical disciplines. Nonetheless, promising findings are discovered with increasing frequency with remarkable relevance in neuroscience, pharmacology and biology.

Gene polymorphisms in VEGFA and COL2A1 are associated with response to inhaled corticosteroids in children with asthma

Aim: The purpose of this study was to investigate the involvement of single-nucleotide polymorphisms in VEGFA, TBX21 and COL2A1 in the response to inhaled corticosteroids in asthmatic children. Subjects & methods: Children with mild-to-moderate asthma were enrolled in the study. The SEQUENOM MassARRAY method was used to sequence 27 SNP genotypes. By ranking the data from smallest to largest, we could infer whether the change in distribution of forced expiratory volume in one second/forced vital capcacity (FEV₁/FVC) and fractional exhaled nitric oxide differed between genotype groups. Results: VEGFA rs3025039 T allele carriers had a smaller change in FEV₁ than CC carriers (p = 0.040), and in COL2A1 rs3809324, the frequency of T allele carriers was lower than that of GG carriers (p = 0.048). rs3025039 was also associated with changes in FEV₁/FVC (p = 0.016). Conclusion: VEGFA and COL2A1 polymorphisms are significantly associated with the response to inhaled corticosteroids in asthmatic children.

Pharmacogenomics of Cognitive Dysfunction and Neuropsychiatric Disorders in Dementia

Symptomatic interventions for patients with dementia involve anti-dementia drugs to improve cognition, psychotropic drugs for the treatment of behavioral disorders (BDs), and different categories of drugs for concomitant disorders. Demented patients may take >6-10 drugs/day with the consequent risk for drug-drug interactions and adverse drug reactions (ADRs >80%) which accelerate cognitive decline. The pharmacoepigenetic machinery is integrated by pathogenic, mechanistic, metabolic, transporter, and pleiotropic genes redundantly and promiscuously regulated by epigenetic mechanisms. CYP2D6, CYP2C9, CYP2C19, and CYP3A4/5 geno-phenotypes are involved in the metabolism of over 90% of drugs currently used in patients with dementia, and only 20% of the population is an extensive metabolizer for this tetragenic cluster. ADRs associated with anti-dementia drugs, antipsychotics, antidepressants, anxiolytics, hypnotics, sedatives, and antiepileptic drugs can be minimized by means of pharmacogenetic screening prior to treatment. These drugs are substrates, inhibitors, or inducers of 58, 37, and 42 enzyme/protein gene products, respectively, and are transported by 40 different protein transporters. APOE is the reference gene in most pharmacogenetic studies. APOE-3 carriers are the best responders and APOE-4 carriers are the worst responders; likewise, CYP2D6-normal metabolizers are the best responders and CYP2D6-poor metabolizers are the worst responders. The incorporation of pharmacogenomic strategies for a personalized treatment in dementia is an effective option to optimize limited therapeutic resources and to reduce unwanted side-effects.

Genetic 3'UTR variations and clinical factors significantly contribute to survival prediction and clinical response in breast cancer patients

The study describes a relationship between the 3′UTR variants, clinicopathological parameters and response to chemotherapy. We analyzed 33 germline polymorphisms in 3′UTRs of ADME genes in 305 breast cancer women treated with FAC regime. Clinical endpoints of this study were: overall survival (OS), progression-free survival (PFS), recurrence-free survival (RFS) and overall response defined as treatment failure-free survival (TFFS). The shortened OS was connected with the presence of NR1/2 rs3732359 AA, SLC22A16 rs7756222 CC, as well as SLC22A16 rs9487402 allele G and clinical factors belonging to TNM classification: tumor size >1 cm, nodal involvement and presence of metastases. PFS was related to two polymorphisms PGR rs1824125 GG, PGR rs12224560 CC and SLC22A16 rs7756222 CC as well as preexisting metastases. The RFS was shortened due to the DPYD rs291593 CC, AKR1C3 rs3209896 AG and negative expression of PGR. The presence of ALDH5A1 rs1054899 allele A, lack of pre-chemotherapy surgery and negative status of PGR correlated with worse treatment response. The germline variants commonly present in the population are important factors determining the response to treatment. We observed the effect of the accumulation of genetic and clinical factors on poor survival prognosis and overall treatment response.

Genetic variations associated with pharmacoresistant epilepsy (Review)

Epilepsy is a common, serious neurological disorder worldwide. Although this disease can be successfully treated in most cases, not all patients respond favorably to medical treatments, which can lead to pharmacoresistant epilepsy. Drug-resistant epilepsy can be caused by a number of mechanisms that may involve environmental and genetic factors, as well as disease- and drug-related factors. In recent years, numerous studies have demonstrated that genetic variation is involved in the drug resistance of epilepsy, especially genetic variations found in drug resistance-related genes, including the voltage-dependent sodium and potassium channels genes, and the metabolizer of endogenous and xenobiotic substances genes. The present review aimed to highlight the genetic variants that are involved in the regulation of drug resistance in epilepsy; a comprehensive understanding of the role of genetic variation in drug resistance will help us develop improved strategies to regulate drug resistance efficiently and determine the pathophysiological processes that underlie this common human neurological disease.

Lack of association of SCN2A rs17183814 polymorphism with the efficacy of lamotrigine monotherapy in patients with focal epilepsy from Herzegovina area, Bosnia and Herzegovina

OBJECTIVE

We assessed the influence of the SCN2A gene polymorphism c.56 G > A rs17183814 on the response to lamotrigine monotherapy in patients with focal epilepsy in Herzegovina area, Bosnia and Herzegovina.

MATERIAL AND METHODS

For SCN2A polymorphism c.56 G > A rs17183814, one hundred patients with epilepsy who were receiving lamotrigine in monotherapy and seventy-one age and sex matched healthy controls were genotyped using TaqMan assay. All patients were Caucasians from the region of Herzegovina, Bosnia and Herzegovina. Genotyping was conducted using a polymerase chain reaction in real time. Patients were divided into two groups: responders and non-responders.

RESULTS

Of all patients with epilepsy, 33% were non-responders, and 67% were responders. The mean age of non-responders was 38.8 vs. group of responders in which it was 35.2. Mean age of onset of seizures in epilepsy patients was 26.7 for non-responders and 25.4 for responders. In patients with epilepsy, the mean age of seizure onset was 26.7 for non-responders and 25.4 for responders. For SCN2A c.56 G > A gene polymorphism, we did not observe any significant differences in genotypic or allelic frequency between patients with epilepsy and healthy controls. Genotype or allelic frequencies of SCN2A c.56 G > A gene polymorphism did not significantly differ for AG or GG genotypes in the non-responders vs. responders.

CONCLUSION

There was no significant association in patients with focal epilepsy between studied genotypes and response to lamotrigine monotherapy in Herzegovina patients with focal epilepsy. However, we need studies in a bigger cohort of patients with epilepsy to be assessed in the future.

Resurgent and Gating Pore Currents Induced by De Novo SCN2A Epilepsy Mutations

Over 150 mutations in the SCN2A gene, which encodes the neuronal Nav1.2 protein, have been implicated in human epilepsy cases. Of these, R1882Q and R853Q are two of the most commonly reported mutations. This study utilized voltage-clamp electrophysiology to characterize the biophysical effects of the R1882Q and R853Q mutations on the hNav1.2 channel, including their effects on resurgent current and gating pore current, which are not typically investigated in the study of Nav1.2 channel mutations. HEK cells transiently transfected with DNA encoding either wild-type (WT) or mutant hNav1.2 revealed that the R1882Q mutation induced a gain-of-function phenotype, including slowed fast inactivation, depolarization of the voltage dependence of inactivation, and increased persistent current. In this model system, the R853Q mutation primarily produced loss-of-function effects, including reduced transient current amplitude and density, hyperpolarization of the voltage dependence of inactivation, and decreased persistent current. The presence of a Navβ4 peptide (KKLITFILKKTREK-OH) in the pipette solution induced resurgent currents, which were increased by the R1882Q mutation and decreased by the R853Q mutation. Further study of the R853Q mutation in Xenopus oocytes indicated a reduced surface expression and revealed a robust gating pore current at negative membrane potentials, a function absent in the WT channel. This not only shows that different epileptogenic point mutations in hNav1.2 have distinct biophysical effects on the channel, but also illustrates that individual mutations can have complex consequences that are difficult to identify using conventional analyses. Distinct mutations may, therefore, require tailored pharmacotherapies in order to eliminate seizures.

Effects of GRM4, SCN2A and SCN3B polymorphisms on antiepileptic drugs responsiveness and epilepsy susceptibility

BACKGROUND

Pharmacotherapy of epilepsy including antiepileptic drugs (AEDs) is one of the main treatment approaches. As a biological target, sodium channels (Nav channels) and glutamate receptor genes are playing a major role in the etiology and treatment of epilepsy.

OBJECTIVE

This study aims to investigate the genetic associations of certain genetic polymorphisms with increased risk of epilepsy susceptibility and variability in response to AEDs treatment in a Jordanian Arab population.

METHOD

A pharmacogenetics and case-control study on 296 unrelated epileptic Jordanian patients recruited from the pediatric neurology clinic at the Queen Rania Al-Abdullah Hospital (QRAH) in Amman, Jordan and 299 healthy individuals was conducted. Children up to 15 years old which receiving AEDs for at least three months were scanned for genetic association of 7 single nucleotide polymorphisms (SNPs) within three candidate genes (SCN2A, SCN3B and GRM4) with epilepsy susceptibility.

RESULTS

SCN2A rs2304016 (P = 0.04) and GRM4 rs2499697 (P = 0.031) were statistically significant with generalized epilepsy. Haplotype of CAACG GRM4 was genetically associated with epilepsy and partial epilepsy (P = 0.036; P = 0.024, respectively). This study also found that TGTAA genetic haplotype formed within GRM4 gene was associated with generalized epilepsy susceptibility (P = 0.006). While, no significant linkage of SCN3B rs3851100 to either disease susceptibility or drug responsiveness was found.

CONCLUSION

This study identified no significant associations of allelic or genotypic SNPs with the susceptibility of epilepsy and medication response with an exception of rs2304016 and rs2499697 SNPs that were associated with the generalized type of epilepsy among Jordanian population. Further studies are required in different populations to confirm our results and identify genetic factors that involved in susceptibility and treatment response.

2-Pyrrolidinone and Succinimide as Clinical Screening Biomarkers for GABA-Transaminase Deficiency: Anti-seizure Medications Impact Accurate Diagnosis

Broad-scale untargeted biochemical phenotyping is a technology that supplements widely accepted assays, such as organic acid, amino acid, and acylcarnitine analyses typically utilized for the diagnosis of inborn errors of metabolism. In this study, we investigate the analyte changes associated with 4-aminobutyrate aminotransferase (ABAT, GABA transaminase) deficiency and treatments that affect GABA metabolism. GABA-transaminase deficiency is a rare neurodevelopmental and neurometabolic disorder caused by mutations in ABAT and resulting in accumulation of GABA in the cerebrospinal fluid (CSF). For that reason, measurement of GABA in CSF is currently the primary approach to diagnosis. GABA-transaminase deficiency results in severe developmental delay with intellectual disability, seizures, and movement disorder, and is often associated with death in childhood. Using an untargeted metabolomics platform, we analyzed EDTA plasma, urine, and CSF specimens from four individuals with GABA-transaminase deficiency to identify biomarkers by comparing the biochemical profile of individual patient samples to a pediatric-centric population cohort. Metabolomic analyses of over 1,000 clinical plasma samples revealed a rich source of biochemical information. Three out of four patients showed significantly elevated levels of the molecule 2-pyrrolidinone (Z-score ≥2) in plasma, and whole exome sequencing revealed variants of uncertain significance in ABAT. Additionally, these same patients also had elevated levels of succinimide in plasma, urine, and CSF and/or homocarnosine in urine and CSF. In the analysis of clinical EDTA plasma samples, the levels of succinimide and 2-pyrrolidinone showed a high level of correlation (R = 0.73), indicating impairment in GABA metabolism and further supporting the association with GABA-transaminase deficiency and the pathogenicity of the ABAT variants. Further analysis of metabolomic data across our patient population revealed the association of elevated levels of 2-pyrrolidinone with administration of vigabatrin, a commonly used anti-seizure medication and a known inhibitor of GABA-transaminase. These data indicate that anti-seizure medications may alter the biochemical and metabolomic data, potentially impacting the interpretation and diagnosis for the patient. Further, these data demonstrate the power of combining broad scale genotyping and phenotyping technologies to diagnose inherited neurometabolic disorders and support the use of metabolic phenotyping of plasma to screen for GABA-transaminase deficiency.

SCN1A and SCN2A polymorphisms are associated with response to valproic acid in Chinese epilepsy patients

PURPOSE

There is a large inter-individual variation in the efficacy of valproic acid (VPA) against epilepsy. The genetic polymorphism influence of sodium channels on VPA response remains a matter of debate. The aim of the study was to explore the effect of SCN1A and SCN2A gene polymorphisms on VPA response in the treatment of epilepsy among Chinese patients.

METHODS

A total of 354 epileptic patients with VPA treatment were genotyped for five single nucleotide polymorphisms (SNP), including SCN1A rs10188577 T>C, rs2298771 T>C, rs3812718 G>A, and SCN2A rs2304016 A>G, rs17183814 G>A. A binary logistic regression analysis was performed to evaluate the association of genotype with VPA antiepileptic effects, adjusting the influence of confounding factors.

RESULTS

Genotype distributions of all selected SNPs were consistent with the Hardy-Weinberg equilibrium in epilepsy patients. SCN1A rs3812718 and SCN2A rs2304016 were found to be significantly associated with VPA response, both in monotherapy and in VPA-based polytherapy. Patients with the rs3812718 A allele were more frequently seen in the VPA-responsive group (P < 0.05), and the rs2304016 G allele was related to an increased risk of resistance to VPA therapy (P < 0.05).

CONCLUSIONS

Our study revealed that SCN1A rs3812718 and SCN2A rs2304016 polymorphisms might be markers of VPA response in Chinese epilepsy patients.

TRIAL REGISTRATION

ChiCTR-1800016477.

Correlation of MCT1 and ABCC2 gene polymorphisms with valproic acid resistance in patients with epilepsy on valproic acid monotherapy

Valproic acid (VPA) is used as one of the first-line antiepileptic drugs to control seizure in epilepsy patients. However, one third of patients do not respond to VPA. This study is to investigate the influence of single nucleotide polymorphisms (SNPs) in multidrug transporters on VPA responses in Han Chinese epilepsy patients on VPA monotherapy. Twelve SNPs involved in VPA transport pathways, including ABCC2, ABCC4, ABCG2, MCT1, MCT2 and OATP2B1 were genotyped in 153 Han Chinese epilepsy patients. We found that among all the patients, MCT1 rs60844753 CC carriers have higher incidence of VPA-resistance than CG carriers (P = 0.05), and in subgroup of generalized seizure, ABCC2 rs3740066 CC carriers had higher frequency of VPA resistance than TC + TT carriers (P = 0.03). Although other SNPs were not correlated with VPA resistance, significant ethnic difference was found in minor allele frequency of these SNPs, indicating that the influence of these SNPs on VPA efficacy should be broadly investigated in other ethnic populations. This study provides nominal evidence that SNPs of genes involved in the transport of VPA contribute to interpatient variation in VPA response. Although the associations were abolished after Bonferroni correction, the results provide an incentive for further research in sufficiently large samples.

NR3C1 gene polymorphisms are associated with steroid resistance in patients with primary nephrotic syndrome

Aim: The aim of this study was to investigate the role of SNPs of genes involved in the glucocorticoid pathway in the development of steroid resistance in patients with primary nephrotic syndrome. Methods: Sequenom MassARRAY method was used to sequence 25 SNP genotypes in 154 patients. The frequency distribution of the genotypes was compared between patients with steroid-sensitive nephrotic syndrome and those with steroid-resistant nephrotic syndrome. Results: NR3C1 rs6196 G allele carriers had a decreased risk of steroid resistance compared with that of the A allele carriers. The presence of rs10052957 and rs258751 A alleles could reduce the incidence of steroid resistance compared with that with G allele. Haplotype analysis showed AAG and GGA haplotypes that contain NR3C1 rs10052957, rs258751 and rs6196 were associated with steroid resistance. Conclusion: NR3C1 gene polymorphisms are significantly associated with the response to glucocorticoids in patients with primary nephrotic syndrome.

The pharmacogenomics of valproic acid

Valproic acid is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder. Adverse effects of valproic acid are rare, but hepatotoxicity is severe in particular in those younger than 2 years old and polytherapy. During valproic acid treatment, it is difficult for prescribers to predict its individual response. Recent advances in the field of pharmacogenomics have indicated variants of candidate genes that affect valproic acid efficacy and safety. In this review, a large number of candidate genes that influence valproic acid pharmacokinetics and pharmacodynamics are discussed, including metabolic enzymes, drug transporters, neurotransmitters and drug targets. Furthermore, pharmacogenomics is an important tool not only in further understanding of interindividual variability but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization.