Effects of SCN1A and SCN2A polymorphisms on responsiveness to valproic acid monotherapy in epileptic children

Genetic and non-genetic factors influencing the therapeutic response of valproic acid in pediatric epileptic patients

AIMS

Considerable inter-individual variability in the efficacy of valproic acid (VPA) has been reported, with approximately 20-45% of patients failing to achieve satisfactory seizure control after VPA monotherapy. The aim of this study was to investigate the influence of non-genetic and genetic factors on 12-month VPA-response in a cohort of 194 pediatric patients.

MATERIALS & METHODS

Trough concentrations were determined, and a panel of 48 variants located in pharmacokinetic and pharmacodynamic gene were genotyped.

RESULTS

Aetiology was highlighted as a significant factor for the response to VPA. Specifically, patients with idiopathic epilepsy demonstrated poorer 12-month outcomes (p < 0.001). Trough VPA concentrations did not significantly affect outcomes. Marginal association was found between VPA efficacy and the following genetic variants: GABRA1 rs10068980 (p = 0.02), SLC16A1 rs7169 (p = 0.02), ABCC2 rs1885301 (p = 0.092), ACADM rs1251079 (p = 0.061) and GABRA1 rs6883877 (p = 0.085), as indicated by Fisher's exact test. A significant cumulative effect of two genetic factors (GABRA1 rs10068980 and SLC16A1 rs7169) was observed after a multiple logistic analysis, with ORs of 2.828 (1.213, 6.594) and 4.066 (1.148,14.398), respectively.

CONCLUSION

Our study indicated that GABRA1 rs10068980 and SLC16A1 rs7169 might serve as potential biomarkers for predicting the 12-month VPA treatment outcomes in pediatric patients with epilepsy.

Single-Base Gene Variants in MIR-146A and SCN1A Genes Related to the Epileptogenic Process in Drug-Responsive and Drug-Resistant Temporal Lobe Epilepsy-A Preliminary Study in a Brazilian Cohort Sample

The drug-resistant temporal lobe epilepsy (TLE) has recently been associated with single nucleotide variants (SNVs) in microRNA(miR)-146a (MIR-146A) (rs2910164) and Sodium Voltage-Gated Channel Alpha Subunit 1 (SCN1A) (rs2298771 and rs3812718) genes. Moreover, no studies have shown an association between these SNVs and susceptibility to drug-resistant and drug-responsive TLE in Brazil. Thus, deoxyribonucleic acid (DNA) samples from 120 patients with TLE (55 drug-responsive and 65 drug-resistant) were evaluated by real-time polymerase chain reaction (RT-PCR). A total of 1171 healthy blood donor individuals from the Online Archive of Brazilian Mutations (ABraOM, from Portuguese Arquivo Brasileiro On-line de Mutações), a repository containing genomic variants of the Brazilian population, were added as a control population for the studied SNVs. MIR-146A and SCN1A relative expression was performed by quantitative RT-PCR (qRT-PCR). The statistical analysis protocol was performed using an alpha error of 0.05. TLE patient samples and ABraOM control samples were in Hardy-Weinberg equilibrium for all studied SNVs. For rs2910164, the frequencies of the homozygous genotype (CC) (15.00% vs. 9.65%) and C allele (37.80% vs. 29.97%) were superior in patients with TLE compared to controls with a higher risk for TLE disease [odds ratio (OR) = 1.89 (95% confidence interval (95%CI) = 1.06-3.37); OR = 1.38 (95%CI = 1.04-1.82), respectively]. Drug-responsive patients also presented higher frequencies of the CC genotype [21.81% vs. 9.65%; OR = 2.58 (95%CI = 1.25-5.30)] and C allele [39.09% vs. 29.97%; OR = 1.50 (95%CI = 1.01-2.22)] compared to controls. For rs2298771, the frequency of the heterozygous genotype (AG) (51.67% vs. 40.40%) was superior in patients with TLE compared to controls with a higher risk for TLE disease [OR = 2.42 (95%CI = 1.08-5.41)]. Drug-resistant patients presented a higher AG frequency [56.92% vs. 40.40%; OR = 3.36 (95%CI = 1.04-17.30)] compared to the control group. For rs3812718, the prevalence of genotypes and alleles were similar in both studied groups. The MIR-146A relative expression level was lower in drug-resistant compared to drug-responsive patients for GC (1.6 vs. 0.1, p-value = 0.049) and CC (1.8 vs. 0.6, p-value = 0.039). Also, the SCN1A relative expression levels in samples from TLE patients were significantly higher in AG [2.09 vs. 1.10, p-value = 0.038] and GG (3.19 vs. 1.10, p-value < 0.001) compared to the AA genotype. In conclusion, the rs2910164-CC and rs2298771-AG genotypes are exerting significant risk influence, respectively, on responsive disease and resistant disease, probably due to an upregulated nuclear factor kappa B (NF-kB) and SCN1A loss of function.

Association between Genetic Polymorphism of SCN1A, GABRA1 and ABCB1 and Drug Responsiveness in Vietnamese Epileptic Children

Background and Objectives: Drug resistant epilepsy (DRE) is a major hurdle in epilepsy, which hinders clinical care, patients' management and treatment outcomes. DRE may partially result from genetic variants that alter proteins responsible for drug targets and drug transporters in the brain. We aimed to examine the relationship between SCN1A, GABRA1 and ABCB1 polymorphism and drug response in epilepsy children in Vietnam. Materials and Methods: In total, 213 children diagnosed with epilepsy were recruited in this study (101 were drug responsive and 112 were drug resistant). Sanger sequencing had been performed in order to detect six single nucleotide polymorphisms (SNPs) belonging to SCN1A (rs2298771, rs3812718, rs10188577), GABRA1 (rs2279020) and ABCB1 (rs1128503, rs1045642) in study group. The link between SNPs and drug response status was examined by the Chi-squared test or the Fisher's exact test. Results: Among six investigated SNPs, two SNPs showed significant difference between the responsive and the resistant group. Among those, heterozygous genotype of SCN1A rs2298771 (AG) were at higher frequency in the resistant patients compared with responsive patients, playing as risk factor of refractory epilepsy. Conversely, the heterozygous genotype of SCN1A rs3812718 (CT) was significantly lower in the resistant compared with the responsive group. No significant association was found between the remaining four SNPs and drug response. Conclusions: Our study demonstrated a significant association between the SCN1A genetic polymorphism which increased risk of drug-resistant epilepsy in Vietnamese epileptic children. This important finding further supports the underlying molecular mechanisms of SCN1A genetic variants in the pathogenesis of drug-resistant epilepsy in children.

Modeling the protein binding non-linearity in population pharmacokinetic model of valproic acid in children with epilepsy: a systematic evaluation study

Background: Several studies have investigated the population pharmacokinetics (popPK) of valproic acid (VPA) in children with epilepsy. However, the predictive performance of these models in the extrapolation to other clinical environments has not been studied. Hence, this study evaluated the predictive abilities of pediatric popPK models of VPA and identified the potential effects of protein binding modeling strategies. Methods: A dataset of 255 trough concentrations in 202 children with epilepsy was analyzed to assess the predictive performance of qualified models, following literature review. The evaluation of external predictive ability was conducted by prediction- and simulation-based diagnostics as well as Bayesian forecasting. Furthermore, five popPK models with different protein binding modeling strategies were developed to investigate the discrepancy among the one-binding site model, Langmuir equation, dose-dependent maximum effect model, linear non-saturable binding equation and the simple exponent model on model predictive ability. Results: Ten popPK models were identified in the literature. Co-medication, body weight, daily dose, and age were the four most commonly involved covariates influencing VPA clearance. The model proposed by Serrano et al. showed the best performance with a median prediction error (MDPE) of 1.40%, median absolute prediction error (MAPE) of 17.38%, and percentages of PE within 20% (F20, 55.69%) and 30% (F30, 76.47%). However, all models performed inadequately in terms of the simulation-based normalized prediction distribution error, indicating unsatisfactory normality. Bayesian forecasting enhanced predictive performance, as prior observations were available. More prior observations are needed for model predictability to reach a stable state. The linear non-saturable binding equation had a higher predictive value than other protein binding models. Conclusion: The predictive abilities of most popPK models of VPA in children with epilepsy were unsatisfactory. The linear non-saturable binding equation is more suitable for modeling non-linearity. Moreover, Bayesian forecasting with prior observations improved model fitness.

Population pharmacokinetics of oxcarbazepine active metabolite in Chinese children with epilepsy

Oxcarbazepine (OXC) is an antiepileptic drug whose efficacy is largely attributed to its monohydroxy derivative metabolite (MHD). Nevertheless, there exists significant inter-individual variability in both the pharmacokinetics and therapeutic response of this drug. The objective of this study is to explore the impact of patients' characteristics and genetic variants on MHD clearance in a population pharmacokinetic (PPK) model of Chinese pediatric patients with epilepsy. The PPK model was developed using a nonlinear mixed effects modeling method based on 231 MHD plasma concentrations obtained from 185 children with epilepsy. The one-compartment model and combined residual model were established to describe the pharmacokinetics of MHD. Forward addition and backward elimination were employed to evaluate the impact of covariates on the model parameters. The model was evaluated using goodness-of-fit, bootstrap, visual predictive checks, and normalized prediction distribution errors. In the two final PPK models, age, estimated glomerular filtration rate (eGFR), and a combined genotype of six variants (rs1045642, rs2032582, rs7668282, rs2396185, rs2304016, rs1128503) were found to significantly reduce inter-individual variability for MHD clearance. The inter-individual clearance equals to 1.38 × (Age/4.74)0.29 × (eGFR/128.66)0.25 × eθABCB-UGT-SCN-INSR for genetic variants included model and 1.30 × (Age/4.74)0.30 × (eGFR/128.66)0.23 for model without genetic variants. The precision of all parameters was deemed acceptable, and the model exhibited good predictability while remaining stable and effective.    Conclusion: Age, eGFR, and genotype may play a significant role in MHD clearance in children with epilepsy. The developed PPK models hold potential utility in facilitating oxcarbazepine dose adjustment in pediatric patients. What is Known: • The adjustment of the oxcarbazepine regimen remains difficult due to the considerable inter- and intra-individual variability of oxcarbazepine pharmacokinetics. • Body weight and co-administration with enzyme-inducing antiepileptic drugs emerge as the most influential factors contributing to the pharmacokinetics of MHD. What is New: • A positive correlation was observed between eGFR and the clearance of MHD in pediatric patients with epilepsy. • We explored the influence of genetic polymorphisms on MHD clearance and identified a combined genotype (ABCB-UGT-SCN-INSR) that exhibited a significant association with MHD concentration.

SCN1A Polymorphisms and Haplotypes Are Associated With Valproic Acid Treatment Outcomes in Chinese Children With Epilepsy

BACKGROUND

Sodium channel genes, especially SCN1A, were reported to play an important role in the treatment outcomes of antiseizure medications. The aim of this study was to explore the association of SCN1A polymorphisms with efficacy and adverse drug reactions (ADRs) related to valproic acid (VPA) among Chinese children with epilepsy.

METHODS

A total of 126 children with epilepsy treated with VPA for at least 12 months were enrolled in this study. Three single nucleotide polymorphisms (SNPs) of SCN1A including rs2298771, rs10167228, and rs3812718 were genotyped using Sequenom MassArray system. Bioinformatics tools were used to explore the potential targets and pathways of SCN1A in VPA-related ADRs.

RESULTS

The three SNPs in this study were found to be closely associated with treatment outcomes for VPA. Carriers of SCN1A rs3812718 TT genotype tended to be seizure-free with VPA treatment (P = 0.007). AA genotype of rs10167228 and TT genotype of rs2298771 might be protective factors for weight gain induced by VPA, whereas TA genotype of rs10167228 and CT genotype of rs2298771 increased the risk. TAT haplotype carriers were found to respond better to VPA treatment (P = 0.017), whereas CTC haplotype might be a risk factor for VPA-induced weight gain (P = 0.035). Bioinformatics analysis suggested that SCN1A might play a role in VPA-induced weight gain by regulating gated channel activity and GABAergic synapse pathway.

CONCLUSION

This study revealed that SCN1A rs2298771, rs10167228, and rs3812718 polymorphisms and haplotypes might affect the treatment outcomes of VPA in Chinese children with epilepsy.

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.

Identification of Novel Gene Variants in Children With Drug-Resistant Epilepsy: Expanding the Genetic Spectrum

BACKGROUND

Resistance to antiseizure drugs is an important problem in the treatment of individuals with epilepsy. Identifying the molecular etiology of drug-resistant epilepsy (DRE) is crucial for better management of epilepsy. Here, we explore the utility of whole exome sequencing (WES) in identifying causative gene variants in children with DRE.

METHODS

Forty-five children with DRE who underwent WES tests were included. Genetic examination of all patients included chromosomal analysis and clinical chromosomal microarray followed by WES. The identified variants by WES analysis were classified for pathogenicity based on the American College of Medical Genetics and Genomics guidelines and in silico protein prediction tools.

RESULTS

The overall diagnostic yield was 55.5% (25 of 45). A total of 26 variants spanning 22 genes were identified in 25 patients. Of note, only 19 of these genes were examined as novel. Ten patients (22.2%) had a pathogenic or likely pathogenic variant. There was a trend associated with a diagnostic genetic test result in girls compared with boys in DRE (P = 0.028).

CONCLUSION

Our findings expand the mutational spectrum of genes related to DRE. To form disease-specific treatment in children with DRE, the WES analysis should be included in the diagnostic algorithm because of its high diagnostic efficiency.

Overexpression of Homer1b/c induces valproic acid resistance in epilepsy

AIMS

Resistance to valproic acid (VPA) is a major challenge for epilepsy treatment. We aimed to explore the mechanism underlying this resistance.

METHODS

Pentylenetetrazol-induced chronic epileptic rats were administered VPA (250 mg/Kg) for 14 days; rats with controlled seizure stages (seizure score14th-before  ≤0) and latent time (latent time14th-before  ≥0) were considered VPA-responsive, while the others were considered nonresponsive. Differentially expressed genes (DEGs) between the VPA-responsive and nonresponsive rat hippocampus transcriptomes were identified, and their functions were evaluated. The roles of postsynaptic density (PSD) and Homer1 were also determined. Furthermore, a subtype of Homer1 (Homer1b/c) was overexpressed or silenced in HT22 cells to determine its effect on VPA efficacy. Moreover, the membrane levels of mGluR1/5 directly bound to Homer1b/c were assessed.

RESULTS

Overall, 264 DEGs commonly enriched in the PSD between VPA-responsive and nonresponsive rats. Among them, Homer1 was more highly expressed in the hippocampus of nonresponses compared to that of responses. Overexpression of Homer1b/c interrupted VPA efficacy by increasing reactive oxygen species production, lactate dehydrogenase release, and calcium content. Furthermore, it induced the overexpression of mGluR1 and mGluR5.

CONCLUSION

Overexpression of Homer1b/c influenced VPA efficacy, revealing it could be a target to improve the efficacy of this treatment.

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.

Influence of UGT2B7 and UGT1A6 polymorphisms on plasma concentration to dose ratio of valproic acid in Chinese epileptic children

We explored the potential effects of genetic variations on the concentration to dose ratio (CDR) of valproic acid (VPA) in paediatric epilepsy patients.Two hundred and twenty-nine epileptic children on VPA monotherapy were included, and the VPA trough concentrations at steady-state of all subjects were determined.Nineteen single nucleotide polymorphisms (SNPs) of seven selected genes related to the metabolising enzymes and transporters of VPA were identified, and their influences on CDR_VPA (a logarithmic transformation was performed if abnormally distributed) were evaluated.UGT2B7 rs7668258 (C>T) TT genotype was associated with a decrease in lnCDR_VPA among epileptic children receiving VPA monotherapy (β=-0.191, p = 0.036). Significantly lower lnCDR_VPA was also observed in paediatric patients with UGT1A6 rs2070959 (A>G) GG genotype compared to those AA genotype (β=-0.270, p = 0.021).This research indicated that UGT2B7 rs7668258 (C>T) and UGT1A6 rs2070959 (A>G) polymorphisms may be correlated to the normalised plasma concentrations of VPA in Chinese epileptic children. The associations could be abolished after Bonferroni's correction and our findings need to be validated in further and larger investigations.

Effects of SCN1A and SCN2A polymorphisms on responsiveness to valproic acid monotherapy in epileptic children: A protocol for systematic review and meta-analysis

BACKGROUND

: The gene mutation of coding sodium channel is one of the most important mechanisms in the pathogenesis of epilepsy. There exists a large inter-individual variation in the efficacy of valproic acid (VPA) against epilepsy. What are the genetic polymorphism influences of sodium channels on VPA response is still under discussion. In this study, a meta-analysis was used to further explore the effects of SCN1A and SCN2A gene polymorphism on VPA response in children with epilepsy.

METHODS

: The PubMed, EMBASE, Web of Science, Chinese National Knowledge Infrastructure, Chinese Science and Technique Journals Database, China Biology Medicine disc, and Wan Fang Database were searched up to April 2021 for appropriate studies regarding the association between SCN1A and SCN2A gene polymorphism on VPA response in children suffering from epilepsy. The meta-analysis was conducted by Review Manager 5.3 software.

RESULTS

: The results of this meta-analysis will be submitted to a peer-reviewed journal for publication.

CONCLUSION

: This meta-analysis will summarize the effects of SCN1A and SCN2A gene polymorphisms on VPA response in children with epilepsy.

OSF REGISTRATION NUMBER

DOI 10.17605/OSF.IO/N2786.