APOE epsilon4 is associated with postictal confusion in patients with medically refractory temporal lobe epilepsy

The association between APOE gene polymorphisms and the risk, characteristics, and prognosis of epilepsy: A systematic review and meta-analysis

OBJECTIVE

Epilepsy is one of the most common neurological diseases. Current evidence suggests that the apolipoprotein E (APOE) gene may be related to epilepsy. The purpose was to explore whether the APOE gene is associated with the risk, characteristics, and prognosis of epilepsy.

METHODS

The study was a systematic review and meta-analysis. We searched WANFANG, VIP, CNKI, Embase, CENTRAL, and Medline for relevant studies published in English and Chinese inception up to December 27, 2023. Studies containing both APOE genotypes or at least one type of APOE allele and epilepsy were included.

RESULTS

A total of 46 studies were included. Fourteen studies reported APOE genotypes and epilepsy risk (2539 patients and 2847 controls). The meta-analyses showed that the APOE 4 was higher in epilepsy (OR [95 % CI] = 1.32 [1.07, 1.62], I2 = 30 %), the APOE 2 was lower in epilepsy (OR [95 % CI] = 0.73 [0.62, 0.87], I2 = 0 %), and the APOE 3 didn't differ between epilepsy and controls (OR [95 % CI] = 1.01 [0.86, 1.19], I2 = 29 %). Our findings highlight that the risk of epilepsy is different depending on the subtype, with the APOE gene being more associated with temporal lobe epilepsy, drug-refractory epilepsy, and late-onset epilepsy. Patients with the ɛ4 allele have an earlier onset, worse cognition, and are more likely to have a history of febrile convulsion. No association between the ɛ4 allele and psychiatric symptoms and seizure-free after surgery.

INTERPRETATION

These findings will help inform the provision of epilepsy services, including clinical management an important option for epilepsy patients with cognitive impairment, temporal lobe epilepsy, late-onset epilepsy, and drug-refractory epilepsy. However, whether APOE gene testing should be used as a routine test in people with epilepsy remains to be determined.

Genetic Landscape of Common Epilepsies: Advancing towards Precision in Treatment

Epilepsy, a neurological disease characterized by recurrent seizures, is highly heterogeneous in nature. Based on the prevalence, epilepsy is classified into two types: common and rare epilepsies. Common epilepsies affecting nearly 95% people with epilepsy, comprise generalized epilepsy which encompass idiopathic generalized epilepsy like childhood absence epilepsy, juvenile myoclonic epilepsy, juvenile absence epilepsy and epilepsy with generalized tonic-clonic seizure on awakening and focal epilepsy like temporal lobe epilepsy and cryptogenic focal epilepsy. In 70% of the epilepsy cases, genetic factors are responsible either as single genetic variant in rare epilepsies or multiple genetic variants acting along with different environmental factors as in common epilepsies. Genetic testing and precision treatment have been developed for a few rare epilepsies and is lacking for common epilepsies due to their complex nature of inheritance. Precision medicine for common epilepsies require a panoramic approach that incorporates polygenic background and other non-genetic factors like microbiome, diet, age at disease onset, optimal time for treatment and other lifestyle factors which influence seizure threshold. This review aims to comprehensively present a state-of-art review of all the genes and their genetic variants that are associated with all common epilepsy subtypes. It also encompasses the basis of these genes in the epileptogenesis. Here, we discussed the current status of the common epilepsy genetics and address the clinical application so far on evidence-based markers in prognosis, diagnosis, and treatment management. In addition, we assessed the diagnostic predictability of a few genetic markers used for disease risk prediction in individuals. A combination of deeper endo-phenotyping including pharmaco-response data, electro-clinical imaging, and other clinical measurements along with genetics may be used to diagnose common epilepsies and this marks a step ahead in precision medicine in common epilepsies management.

Reconstruction and Analysis of Gene Networks of Human Neurotransmitter Systems Reveal Genes with Contentious Manifestation for Anxiety, Depression, and Intellectual Disabilities

Background: The study of the biological basis of anxiety, depression, and intellectual disabilities in humans is one of the most actual problems of modern neurophysiology. Of particular interest is the study of complex interactions between molecular genetic factors, electrophysiological properties of the nervous system, and the behavioral characteristics of people. The neurobiological understanding of neuropsychiatric disorders requires not only the identification of genes that play a role in the molecular mechanisms of the occurrence and course of diseases, but also the understanding of complex interactions that occur between these genes. A systematic study of such interactions obviously contributes to the development of new methods of diagnosis, prevention, and treatment of disorders, as the orientation to allele variants of individual loci is not reliable enough, because the literature describes a number of genes, the same alleles of which can be associated with different, sometimes extremely different variants of phenotypic traits, depending on the genetic background, of their carriers, habitat, and other factors. Results: In our study, we have reconstructed a series of gene networks (in the form of protein–protein interactions networks, as well as networks of transcription regulation) to build a model of the influence of complex interactions of environmental factors and genetic risk factors for intellectual disability, depression, and other disorders in human behavior. Conclusion: A list of candidate genes whose expression is presumably associated with environmental factors and has potentially contentious manifestation for behavioral and neurological traits is identified for further experimental verification.

Neurodegeneration and Pathology in Epilepsy: Clinical and Basic Perspectives

Epilepsy is commonly associated with a number of neurodegenerative and pathological alterations in those areas of the brain that are involved in repeated electrographic seizures. These most prominently include neuron loss and an increase in astrocyte number and size but may also include enhanced blood-brain barrier permeability, the formation of new capillaries, axonal sprouting, and central inflammation. In animal models in which seizures are either repeatedly elicited or are self-generated, a similar set of neurodegenerative and pathological alterations in brain anatomy are observed. The primary causal agent responsible for these alterations may be the cascade of events that follow a seizure and lead to an hypoperfusion/hypoxic episode. While epilepsy has long and correctly been considered an electrical disorder, the vascular system likely plays an important causal role in the neurodegeneration and pathology that occur as a consequence of repeated seizures.

Apolipoprotein E ε4 Allele was Associated With Nonlesional Mesial Temporal Lobe Epilepsy in Han Chinese Population

Apolipoprotein E (APOE) gene has been implicated as one of the genes susceptible to temporal lobe epilepsy (TLE), but the association is inconsistent. We carried out a study to investigate the association of APOEε4 allele with a subtype of TLE-nonlesional mesial temporal lobe epilepsy (NLMTLE) in Han Chinese people.T he study consisted of total 308 NLMTLE patients and 302 controls in Han Chinese. The APOE polymorphisms were genotyped using polymerase chain reaction (PCR) DNA sequencing. We compared the frequency of APOEε4 allele and carrying status between NLMTLE patients and control subjects to test for the association of APOEε4 allele with NLMTLE clinical status. Carrying status of APOEε4 allele was significantly associated with the risk of NLMTLE. No effect of APOEε4 allele was found on the age of onset, duration of epilepsy, or frequency of seizure. Moreover, there was no association between APOEε4 allele and hippocampal sclerosis (HS) or febrile convulsion (FC) history.O ur study provided an evidence that APOEε4 allele was a possible risk factor for NLMTLE, and further study with a larger sample is needed to warrant this finding.

Evidence that an APOE ε4 'double whammy' increases risk for Alzheimer's disease

Temporal lobe epilepsy (TLE) is associated with some of the same neuropathological features as those reported for early stages of typical Alzheimer's disease (AD). The APOE ε4 allele is associated with a gene-dose-dependent increase in AD risk and in the severity of amyloid-β (Aβ) pathology. In a study published in the current BMC Medicine, Sue Griffin and colleagues studied markers of brain resilience in the amputated temporal lobes of TLE patients. They discovered compelling evidence that the APOE ε3 isoform in TLE patients is apparently more neuroprotective from Aβ toxicity than is the APOE ε4 isoform, as shown by the reduced levels of neuronal damage, glial activation, and expression of IL-1α in the APOE ε3/ε3 brains. This result points to a new property of APOE isoforms: not only are APOE ε4 alleles associated with increased brain amyloid plaque burden, but these alleles are also apparently inferior to APOE ε3 alleles in conveying resistance to Aβ neurotoxicity. This 'double whammy' result opens up a new direction for studies aimed at elucidating the relevant neurobiological activities of APOE isoforms in the pathogenesis of AD.

Genetics of temporal lobe epilepsy: a review

Temporal lobe epilepsy (TLE) is usually regarded as a polygenic and complex disorder. To understand its genetic component, numerous linkage analyses of familial forms and association studies of cases versus controls have been conducted since the middle of the nineties. The present paper lists genetic findings for TLE from the initial segregation analysis to the most recent results published in May 2011. To date, no genes have been clearly related to TLE despite many efforts to do so. However, it is vital to continue replication studies and collaborative attempts to find significant results and thus determine which gene variant combination plays a definitive role in the aetiology of TLE.

Association of apolipoprotein E polymorphisms with temporal lobe epilepsy in a Chinese Han population

Apolipoprotein E (ApoE) has been implicated as one of the susceptibility genes for temporal lobe epilepsy (TLE). Previous studies indicate that ApoE ɛ4 is associated with several disease-related traits including the increased risk of late posttraumatic seizures, earlier onset of TLE, refractory complex partial seizures, and postictal confusion. Contradictory data were also reported regarding the association between ApoE polymorphisms and TLE. The present study was designed to investigate whether ApoE ɛ4 is a risk factor for TLE and the above clinical variables, as well as to determine whether -491A/T polymorphism may independently alter the risk for TLE in a Chinese Han population. The ApoE and -491A/T polymorphisms were genotyped in 558 controls and 735 patients including 560 TLE patients using polymerase chain reaction-restriction fragment length polymorphism. A significant association was detected between prior trauma and the ApoE ɛ4 allele in TLE patients. However, no significant differences were observed in the genotype and haplotype distributions and allele frequencies of these two polymorphisms between cases and controls. Furthermore, there were no significant associations between these two polymorphisms and the other clinical variables examined. The study illustrates that the ApoE ɛ4 allele may be involved in the development of TLE in those patients with prior trauma in the Chinese Han population.

ApoE epsilon4 genotype and the age at onset of temporal lobe epilepsy: a case-control study and meta-analysis

In order to investigate the role of ApoE epsilon4 as a modifier of the age at onset of temporal lobe epilepsy (TLE), we performed a molecular epidemiology study in 78 patients with mesial temporal lobe epilepsy and hippocampal sclerosis. Genotyping was done by a PCR-RFLP assay. In order to better estimate the role of this variant as a modifier of the age at onset, we also performed a systematic review of the literature. We included our results into a meta-analysis along with data available from seven published studies with 728 patients that looked into the role of ApoE epsilon4 in TLE. We found that ApoE epsilon4 carriers in our population had a non-significant earlier age of epilepsy onset than non-carriers. The meta-analysis confirmed this finding, showing that ApoE epsilon4 carriers had epilepsy onset almost 4 years earlier than non-carriers (mean difference 5.15 years; CI 95% 2.08-6.22; p=0.001). In conclusion, the ApoE epsilon4 isoform is a genetic factor that might influence the age at onset of TLE.

Exploring Candidate Genes for Epilepsy by Computational Disease-Gene Identification Strategy

Epilepsy is a complex disease with a strong genetic component. So far, studies have focused on experimental validation or genome-wide linkage scans for epilepsy susceptibility genes in multiple populations. We have used four bioinformatic tools (SNPs3D, PROSPECTR and SUSPECTS, GenWanderer, PosMed) to analyze 16 susceptibility loci selected from a literature search. Pathways and regulatory network analyses were performed using the Ingenuity Pathways Analysis (IPA) software. We identified a subset of 48 candidate epilepsy susceptibility genes. Five significant canonical pathways, in four typical networks, were identified: GABA receptor signaling, interleukin-6 (IL-6) signaling, G-protein coupled receptor signaling, type 2 diabetes mellitus signaling and airway inflammation in asthma. We concluded that online analytical tools provide a powerful way to reveal candidate genes which can greatly reduce experimental time. Our study contributes to further experimental tests for epilepsy susceptibility genes.

ApoE epsilon4 is not associated with posictal confusion in patients with mesial temporal lobe epilepsy with hippocampal sclerosis

A previous report found an association between ApoE isoforms and postictal confusion in medically intractable temporal lobe epilepsy (TLE). We performed a molecular epidemiology study in an independent sample of 77 TLE patients. We failed to replicate the original allelic association between ApoE epsilon4 allele and postictal confusion in our population (chi(2)=1.67; d.f.=1; p=0.2). Thus, the association between ApoE epsilon4 allele and postictal confusion still needs to be fully investigated in different and independent populations.