Effects of AQP4 and KCNJ10 Gene Polymorphisms on Drug Resistance and Seizure Susceptibility in Chinese Han Patients with Focal Epilepsy

Association of Voltage-Gated Potassium Channel Polymorphisms with the Risk and Prognosis of Epilepsy in the Saudi Population: A Case-Control Study

Background and Objectives: Epilepsy, known as an unprovoked seizure, arises from the human brain. Genetics plays a fundamental role in the development and progression of the disorder. This study aimed to investigate the influence of voltage-gated K+ channels on the risk of epilepsy. Materials and Methods: Several genetic variants were examined using PCR sequencing. This case-control study was conducted on 296 individuals who were diagnosed with epilepsy, in addition to 293 healthy participants. Results: This study revealed that within KCNAB1, both rs3755631 and rs4679773 are correlated with epilepsy, and the p-values = 0.04 for both allelic associations. In addition, regarding the KCNJ10 gene, we found that rs2820585, rs946420, rs1186679, rs61822012, and rs1186685 were significantly correlated with epilepsy risk (p-values = 0.034, 0.045, 0.021, 0.048, and 0.018), respectively. Conclusions: From the current study, we conclude that voltage-gated potassium channels can impact epilepsy risk and can also interfere with the prognosis of epilepsy.

Review of pharmacogenetics of antiseizure medications: focusing on genetic variants of mechanistic targets

Antiseizure medications (ASMs) play a central role in seizure management, however, unpredictability in the response to treatment persists, even among patients with similar seizure manifestations and clinical backgrounds. An objective biomarker capable of reliably predicting the response to ASMs would profoundly impact epilepsy treatment. Presently, clinicians rely on a trial-and-error approach when selecting ASMs, a time-consuming process that can result in delays in receiving alternative non-pharmacological therapies such as a ketogenetic diet, epilepsy surgery, and neuromodulation therapies. Pharmacogenetic studies investigating the correlation between ASMs and genetic variants regarding their mechanistic targets offer promise in predicting the response to treatment. Sodium channel subunit genes have been extensively studied along with other ion channels and receptors as targets, however, the results have been conflicting, possibly due to methodological disparities including inconsistent definitions of drug response, variations in ASM combinations, and diversity of genetic variants/genes studied. Nonetheless, these studies underscore the potential effect of genetic variants on the mechanism of ASMs and consequently the prediction of treatment response. Recent advances in sequencing technology have led to the generation of large genetic datasets, which may be able to enhance the predictive accuracy of the response to ASMs.

Predicted molecules and signaling pathways for regulating seizures in the hippocampus in lithium-pilocarpine induced acute epileptic rats: A proteomics study

Seizures in rodent models that are induced by lithium-pilocarpine mimic human seizures in a highly isomorphic manner. The hippocampus is a brain region that generates and spreads seizures. In order to understand the early phases of seizure events occurring in the hippocampus, global protein expression levels in the hippocampus on day 1 and day 3 were analyzed in lithium-pilocarpine induced acute epileptic rat models using a tandem mass tag-based proteomic approach. Our results showed that differentially expressed proteins were likely to be enhanced rather than prohibited in modulating seizure activity on days 1 and 3 in lithium-pilocarpine induced seizure rats. The differentially regulated proteins differed on days 1 and 3 in the seizure rats, indicating that different molecules and pathways are involved in seizure events occurring from day 1 to day 3 following lithium-pilocarpine administration. In regard to subcellular distribution, the results suggest that post-seizure cellular function in the hippocampus is possibly regulated in a differential manner on seizure progression. Gene ontology annotation results showed that, on day 1 following lithium-pilocarpine administration, it is likely necessary to regulate macromolecular complex assembly, and cell death, while on day 3, it may be necessary to modulate protein metabolic process, cytoplasm, and protein binding. Protein metabolic process rather than macromolecular complex assembly and cell death were affected on day 3 following lithium-pilocarpine administration. The extracellular matrix, receptors, and the constitution of plasma membranes were altered most strongly in the development of seizure events. In a KEGG pathway enrichment cluster analysis, the signaling pathways identified were relevant to sustained angiogenesis and evading apoptosis, and complement and coagulation cascades. On day 3, pathways relevant to Huntington’s disease, and tumor necrosis factor signaling were most prevalent. These results suggest that seizure events occurring in day 1 modulate macromolecular complex assembly and cell death, and in day 3 modulate biological protein metabolic process. In summary, our study found limited evidence for ongoing seizure events in the hippocampus of lithium-pilocarpine induced animal models; nevertheless, evaluating the global differential expression of proteins and their impacts on bio-function may offer new perspectives for studying epileptogenesis in the future.

Envisioning the role of inwardly rectifying potassium (Kir) channel in epilepsy

Epilepsy is a devastating neurological disorder characterized by recurrent seizures attributed to the disruption of the dynamic excitatory and inhibitory balance in the brain. Epilepsy has emerged as a global health concern affecting about 70 million people worldwide. Despite recent advances in pre-clinical and clinical research, its etiopathogenesis remains obscure, and there are still no treatment strategies modifying disease progression. Although the precise molecular mechanisms underlying epileptogenesis have not been clarified yet, the role of ion channels as regulators of cellular excitability has increasingly gained attention. In this regard, emerging evidence highlights the potential implication of inwardly rectifying potassium (Kir) channels in epileptogenesis. Kir channels consist of seven different subfamilies (Kir1-Kir7), and they are highly expressed in both neuronal and glial cells in the central nervous system. These channels control the cell volume and excitability. In this review, we discuss preclinical and clinical evidence on the role of the several subfamilies of Kir channels in epileptogenesis, aiming to shed more light on the pathogenesis of this disorder and pave the way for future novel therapeutic approaches.

Kcnj16 knockout produces audiogenic seizures in the Dahl salt-sensitive rat

Kir5.1 is an inwardly rectifying potassium (Kir) channel subunit abundantly expressed in the kidney and brain. We previously established the physiologic consequences of a Kcnj16 (gene encoding Kir5.1) knockout in the Dahl salt-sensitive rat (SSKcnj16-/-), which caused electrolyte/pH dysregulation and high-salt diet-induced mortality. Since Kir channel gene mutations may alter neuronal excitability and are linked to human seizure disorders, we hypothesized that SSKcnj16-/- rats would exhibit neurological phenotypes, including increased susceptibility to seizures. SSKcnj16-/- rats exhibited increased light sensitivity (fMRI) and reproducible sound-induced tonic-clonic audiogenic seizures confirmed by electroencephalography. Repeated seizure induction altered behavior, exacerbated hypokalemia, and led to approximately 38% mortality in male SSKcnj16-/- rats. Dietary potassium supplementation did not prevent audiogenic seizures but mitigated hypokalemia and prevented mortality induced by repeated seizures. These results reveal a distinct, nonredundant role for Kir5.1 channels in the brain, introduce a rat model of audiogenic seizures, and suggest that yet-to-be identified mutations in Kcnj16 may cause or contribute to seizure disorders.

Association of KCNJ10 variants and the susceptibility to clinical epilepsy

We first enrolled the available case-control studies to investigate the genetic association between three polymorphisms (rs1130183, rs1890532, and rs2486253) of KCNJ10 (the potassium voltage-gated channel subfamily J member 10) gene and the susceptibility towards clinical epilepsy. We utilized the meta-analysis, FPRP (false-positive report probability) test, and the TSA (trial sequential analysis) for the data pooling and the evaluation of statistical power. Totally, eight eligible articles were finally included. For KCNJ10 rs1130183, compared with population-based controls, a reduced epilepsy risk in cases was observed in models of allelic T vs. C, heterozygotic CT vs. CC, dominant CT + TT vs. CC, carrier T vs. C [all OR (odds ratio) <1, P < 0.05, Benjamini & Hochberg-adjusted P < 0.05, bonferroni-adjusted P < 0.05]. There were similar results in the subgroup analysis of "Caucasian". The positive conclusion was also statistically supported by the result of the FPRP test and TSA. Nevertheless, no statistically significant differences between epilepsy cases and negative controls were detected in any comparison of KCNJ101890532 and rs2486253. In summary, it is possible that the CT genotype of KCNJ10 rs1130183 is related to a reduced clinical epilepsy susceptibility, especially in Caucasians. However, more sample sizes are still required for a more robust conclusion in different populations, and more adjusted factors should be considered.

Clinical and genetic risk factors for new-onset diabetes mellitus after transplantation (NODAT) in major transplant centres in Malaysia

Background

New-onset diabetes after transplantation (NODAT) is associated with reduced patient and graft survival. This study examined the clinical and selected genetic factors associated with NODAT among renal-transplanted Malaysian patients.

Methods

This study included 168 non-diabetic patients (58% males, 69% of Chinese ethnicity) who received renal transplantation between 1st January 1994 to 31st December 2014, and were followed up in two major renal transplant centres in Malaysia. Fasting blood glucose levels were used to diagnose NODAT in patients who received renal transplantation within 1 year. Two single nucleotide polymorphisms (SNPs), namely; rs1494558 (interleukin-7 receptor, IL-7R) and rs2232365 (mannose-binding leptin-2, MBL2) were selected and genotyped using Sequenom MassArray platform. Cox proportional hazard regression analyses were used to examine the risk of developing NODAT according to the different demographics and clinical covariates, utilizing four time-points (one-month, three-months, six-months, one-year) post-transplant.

Results

Seventeen per cent of patients (n = 29, 55% males, 69% Chinese) were found to have developed NODAT within one-year of renal transplantation based on their fasting blood glucose levels. NODAT patients had renal transplantation at an older age compared to non-NODAT (39.3 ± 13.4 vs 33.9 ± 11.8 years, p = 0.03). In multivariate analysis, renal-transplanted patients who received a higher daily dose of cyclosporine (mg) were associated with increased risk of NODAT (Hazard ratio (HR) =1.01 per mg increase in dose, 95% confidence interval (CI) 1.00–1.01, p = 0.002). Other demographic (gender, ethnicities, age at transplant) and clinical factors (primary kidney disease, type of donor, place of transplant, type of calcineurin inhibitors, duration of dialysis pre-transplant, BMI, creatinine levels, and daily doses of tacrolimus and prednisolone) were not found to be significantly associated with risk of NODAT. GA genotype of rs1494558 (HR = 3.15 95% CI 1.26, 7.86) and AG genotype of rs2232365 (HR = 2.57 95% CI 1.07, 6.18) were associated with increased risk of NODAT as compared to AA genotypes.

Conclusion

The daily dose of cyclosporine and SNPs of IL-7R (rs1494558) and MBL2 (rs2232365) genes are significantly associated with the development of NODAT in the Malaysian renal transplant population.

Genetic underpinnings of cerebral edema in acute brain injury: an opportunity for pathway discovery

Cerebral edema constitutes an important contributor to secondary injury in acute brain injury. The quantification of cerebral edema in neuroimaging, a well-established biomarker of secondary brain injury, represents a useful intermediate phenotype to study edema formation. Population genetics provides powerful tools to identify novel susceptibility genes, biological pathways and therapeutic targets related to brain edema formation. Here, we provide an overview of the pathogenesis of cerebral edema, introduce relevant genetic methods to study this process, and discuss the ongoing research on the genetic underpinnings of edema formation in acute brain injury. The epsilon 2 and 4 variants within the Apolipoprotein E (APOE) gene are associated with worse outcome after traumatic brain injury and intracerebral hemorrhage, and recent studies link these polymorphisms to inflammatory processes that lead to blood-brain barrier disruption and vasogenic edema. For the Haptoglobin gene (HP), the Hp 2-2 genotype associates with worse outcome after acute brain injury, whereas the haptoglobin Hp 1-1 genotype correlates with increased edema in the early phases of intracerebral hemorrhage. Another important protein in cerebral edema is aquaporin 4, coded by the AQP4 gene. AQP4 mutations contribute to the formation of cytotoxic edema, and further genetic research is necessary to help elucidate the mediating mechanism. Findings supporting the target genes outlined above require replication in larger samples and evaluation in non-white populations. These next steps will be significantly facilitated by the rapid changes observed in the field of population genetics, including large international collaborations, open access to genetic data, and significant reductions in the cost of genotyping technologies.