The association between APOE ε4, age and outcome after head injury: a prospective cohort study

Prospective memory performance in veterans with and without histories of mild traumatic brain injury: effect of the apolipoprotein E (APOE) ε4 genotype

OBJECTIVE

Identifying factors that moderate cognitive outcomes following mild traumatic brain injury (mTBI) is crucial. Prospective memory (PM) is a cognitive domain of interest in mTBI recovery as it may be especially sensitive to TBI-related changes. Since studies show that genetic status - particularly possession of the apolipoprotein E (APOE) ε4 allele - can modify PM performance, we investigated associations between mTBI status and APOE-ε4 genotype on PM performance in a well-characterized sample of Veterans with neurotrauma histories.

METHODS

59 Veterans (mTBI = 33, Military Controls [MCs] = 26; age range: 24-50; average years post-injury = 10.41) underwent a structured clinical interview, neuropsychological assessment, and genotyping. The Memory for Intentions Test (MIST) measured PM across multiple subscales. ANCOVAs, adjusting for age and posttraumatic stress symptoms, tested the effects of mTBI status (mTBI vs. MC) and ε4 status (ε4+ vs. ε4-) on MIST scores.

RESULTS

Veterans with mTBI history performed more poorly compared to MCs on the MIST 15-min delay (p=.002, ηp2 =.160), Time Cue (p = .003, ηp2 =.157), and PM Total (p = .016, ηp2 =.102). Those with at least one copy of the ε4 allele performed more poorly compared to ε4- Veterans on the MIST 15-min delay (p = .011, ηp2 =.113) and PM Total (p = .048, ηp2 = .071). No significant interactions were observed between mTBI and APOE-ε4 status on MIST outcomes (ps>.25). Within the mTBI group, APOE-ε4+ Veterans performed worse than APOE-ε4- Veterans on the MIST 15-min delay subscale (p = .031, ηp2 = .150).

CONCLUSIONS

mTBI history and APOE-ε4 genotype status were independently associated with worse PM performance compared to those without head injury histories or possession of the APOE-e4 genotype. Performance on the MIST 15-min delay was worse in Veterans with both risk factors (mTBI history and APOE-ε4 positivity). Findings suggest that genetic status may modify outcomes even in relatively young Veterans with mTBI histories. Future research examining longitudinal associations and links to neuroimaging and biomarker data are needed.

Apolipoprotein E in lipid metabolism and neurodegenerative disease

Dysregulation of lipid metabolism has emerged as a central component of many neurodegenerative diseases. Variants of the lipid transport protein, apolipoprotein E (APOE), modulate risk and resilience in several neurodegenerative diseases including late-onset Alzheimer's disease (LOAD). Allelic variants of the gene, APOE, alter the lipid metabolism of cells and tissues and have been broadly associated with several other cellular and systemic phenotypes. Targeting APOE-associated metabolic pathways may offer opportunities to alter disease-related phenotypes and consequently, attenuate disease risk and impart resilience to multiple neurodegenerative diseases. We review the molecular, cellular, and tissue-level alterations to lipid metabolism that arise from different APOE isoforms. These changes in lipid metabolism could help to elucidate disease mechanisms and tune neurodegenerative disease risk and resilience.

Blood proteome of acute intracranial hemorrhage in infant victims of abusive head trauma

Abusive head trauma (AHT) is a leading cause of mortality and morbidity in infants. While the reported incidence is close to 40 cases per 100'000 births/year, misdiagnoses are commonly observed in cases with atypical, subacute, or chronic presentation. Currently, standard clinical evaluation of inflicted intracranial hemorrhagic injury (ICH) in infants urgently requires a screening test able to identify infants who need additional investigations. Blood biomarkers characteristic of AHT may assist in detecting these infants, improving prognosis through early medical care. To date, the application of innovative omics technologies in retrospective studies of AHT in infants is rare, due also to the blood serum and cerebrospinal fluid of AHT cases being scarce and not systematically accessible. Here, we explored the circulating blood proteomes of infants with severe AHT and their atraumatic controls. We discovered 165 circulating serum proteins that display differential changes in AHT cases compared with atraumatic controls. The peripheral blood proteomes of pediatric AHT commonly reflect: (i) potentially secreted proteome from injured brain, and (ii) proteome dysregulated in the system's circulation by successive biological events following acute ICH. This study opens up a novel opportunity for research efforts in clinical screening of AHT cases.

APOE ε4-dependent effects on the early amyloid pathology in induced neurons of patients with Alzheimer's disease

Background

The ε4 allele of apolipoprotein E (APOE ε4) is the strongest known genetic risk factor for late-onset Alzheimer’s disease (AD), associated with amyloid pathogenesis. However, it is not clear how APOE ε4 accelerates amyloid-beta (Aβ) deposition during the seeding stage of amyloid development in AD patient neurons.

Methods

AD patient induced neurons (iNs) with an APOE ε4 inducible system were prepared from skin fibroblasts of AD patients. Transcriptome analysis was performed using RNA isolated from the AD patient iNs expressing APOE ε4 at amyloid-seeding and amyloid-aggregation stages. Knockdown of IGFBP3 was applied in the iNs to investigate the role of IGFBP3 in the APOE ε4-mediated amyloidosis.

Results

We optimized amyloid seeding stage in the iNs of AD patients that transiently expressed APOE ε4. Remarkably, we demonstrated that Aβ  pathology was aggravated by the induction of APOE ε4 gene expression at the amyloid early-seeding stage in the iNs of AD patients. Moreover, transcriptome analysis in the early-seeding stage revealed that IGFBP3 was functionally important in the molecular pathology of APOE ε4-associated AD.

Conclusions

Our findings suggest that the presence of APOE ε4 at the early Aβ-seeding stage in patient iNs is critical for aggravation of sporadic AD pathology. These results provide insights into the importance of APOE ε4 expression for the progression and pathogenesis of sporadic AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40035-022-00319-9.

The Emergence of Model Systems to Investigate the Link Between Traumatic Brain Injury and Alzheimer's Disease

Numerous epidemiological studies have demonstrated that individuals who have sustained a traumatic brain injury (TBI) have an elevated risk for developing Alzheimer's disease and Alzheimer's-related dementias (AD/ADRD). Despite these connections, the underlying mechanisms by which TBI induces AD-related pathology, neuronal dysfunction, and cognitive decline have yet to be elucidated. In this review, we will discuss the various in vivo and in vitro models that are being employed to provide more definite mechanistic relationships between TBI-induced mechanical injury and AD-related phenotypes. In particular, we will highlight the strengths and weaknesses of each of these model systems as it relates to advancing the understanding of the mechanisms that lead to TBI-induced AD onset and progression as well as providing platforms to evaluate potential therapies. Finally, we will discuss how emerging methods including the use of human induced pluripotent stem cell (hiPSC)-derived cultures and genome engineering technologies can be employed to generate better models of TBI-induced AD.

Moderators of gene-outcome associations following traumatic brain injury

The field of genomics is the principal avenue in the ongoing development of precision/personalised medicine for a variety of health conditions. However, relating genes to outcomes is notoriously complex, especially when considering that other variables can change, or moderate, gene-outcome associations. Here, we comprehensively discuss moderation of gene-outcome associations in the context of traumatic brain injury (TBI), a common, chronically debilitating, and costly neurological condition that is under complex polygenic influence. We focus our narrative review on single nucleotide polymorphisms (SNPs) of three of the most studied genes (apolipoprotein E, brain-derived neurotrophic factor, and catechol-O-methyltransferase) and on three demographic variables believed to moderate associations between these SNPs and TBI outcomes (age, biological sex, and ethnicity). We speculate on the mechanisms which may underlie these moderating effects, drawing widely from biomolecular and behavioural research (n = 175 scientific reports) within the TBI population (n = 72) and other neurological, healthy, ageing, and psychiatric populations (n = 103). We conclude with methodological recommendations for improved exploration of moderators in future genetics research in TBI and other populations.

Apolipoprotein E e4 is associated with worse self-reported neurobehavioral symptoms following uncomplicated mild traumatic brain injury in U.S. military service members

Past research has found a relationship between the apolipoprotein E (APOE) e4 allele and worse neurobehavioral functioning following mild traumatic brain injury (MTBI) in civilian populations. The purpose of this study was to examine this relationship in service members and veterans (SMVs) following MTBI. Participants were 151 SMVs (103 uncomplicated MTBI; 48 Injured Controls [IC]) prospectively enrolled in the DVBIC-TBICoE 15-Year Longitudinal TBI Study. Participants completed a battery of self-reported neurobehavioral symptom measures on average 76.2 months post-injury (SD = 31.8). APOE genotyping was undertaken using non-fasting blood samples. Participants were classified into four subgroups based on injury (MTBI vs. IC) and APOE e4 allele status (e4 present/absent). In the IC group, there were no significant differences across APOE e4 status subgroups for all measures. In the MTBI group, participants with the APOE e4 allele had significantly worse scores on measures of depression, pain, anxiety, grief, positive well-being, social participation, and resilience compared to those without the e4 allele (d = .44 to d = .69). When comparing the number of 'clinically elevated' neurobehavioral measures simultaneously, the MTBI/e4 present subgroup consistently had a higher number of elevated measures compared to the MTBI/e4 absent, IC/e4 present, and IC/e4 absent subgroups. The APOE e4 allele was associated with poorer neurobehavioral outcome in SMVs in the chronic phase of recovery following MTBI. APOE e4 could be incorporated into screening tools to predict SMVs at risk for poor long-term neurobehavioral outcome in an effort to provide early intervention to improve long-term clinical outcome.

Apolipoprotein E4 Polymorphism and Outcomes from Traumatic Brain Injury: A Living Systematic Review and Meta-Analysis

The mortality of traumatic brain injury (TBI) has been largely static despite advances in monitoring and imaging techniques. Substantial variance exists in outcome, not fully accounted for by baseline characteristics or injury severity, and genetic factors likely play a role in this variance. The aims of this systematic review were to examine the evidence for a link between the apolipoprotein E4 (APOE4) polymorphism and TBI outcomes and where possible, to quantify the effect size via meta-analysis. We searched EMBASE, MEDLINE, CINAHL, and gray literature in December 2017. We included studies of APOE genotype in relation to functional adult TBI outcomes. Methodological quality was assessed using the Quality in Prognostic Studies Risk of Bias Assessment Instrument and the prognostic studies adaptation of the Grading of Recommendations Assessment, Development and Evaluation tool. In addition, we contacted investigators and included an additional 160 patients whose data had not been made available for previous analyses, giving a total sample size of 2593 patients. Meta-analysis demonstrated higher odds of a favorable outcome following TBI in those not possessing an ApoE ɛ4 allele compared with ɛ4 carriers and homozygotes (odds ratio 1.39, 95% confidence interval 1.05 to 1.84; p = 0.02). The influence of APOE4 on neuropsychological functioning following TBI remained uncertain, with multiple conflicting studies. We conclude that the ApoE ɛ4 allele confers a small risk of poor outcome following TBI, with analysis by TBI severity not possible based on the currently available published data. Further research into the long-term neuropsychological impact and risk of dementia is warranted.

Using Oculomotor Features to Predict Changes in Optic Nerve Sheath Diameter and ImPACT Scores From Contact-Sport Athletes

There is mounting evidence linking the cumulative effects of repetitive head impacts to neuro-degenerative conditions. Robust clinical assessment tools to identify mild traumatic brain injuries are needed to assist with timely diagnosis for return-to-field decisions and appropriately guide rehabilitation. The focus of the present study is to investigate the potential for oculomotor features to complement existing diagnostic tools, such as measurements of Optic Nerve Sheath Diameter (ONSD) and Immediate Post-concussion Assessment and Cognitive Testing (ImPACT). Thirty-one high school American football and soccer athletes were tracked through the course of a sports season. Given the high risk of repetitive head impacts associated with both soccer and football, our hypotheses were that (1) ONSD and ImPACT scores would worsen through the season and (2) oculomotor features would effectively capture both neurophysiological changes reflected by ONSD and neuro-functional status assessed via ImPACT. Oculomotor features were used as input to Linear Mixed-Effects Regression models to predict ONSD and ImPACT scores as outcomes. Prediction accuracy was evaluated to identify explicit relationships between eye movements, ONSD, and ImPACT scores. Significant Pearson correlations were observed between predicted and actual outcomes for ONSD (Raw = 0.70; Normalized = 0.45) and for ImPACT (Raw = 0.86; Normalized = 0.71), demonstrating the capability of oculomotor features to capture neurological changes detected by both ONSD and ImPACT. The most predictive features were found to relate to motor control and visual-motor processing. In future work, oculomotor models, linking neural structures to oculomotor function, can be built to gain extended mechanistic insights into neurophysiological changes observed through seasons of participation in contact sports.

The genetic basis of inter-individual variation in recovery from traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of death among young people, and is increasingly prevalent in the aging population. Survivors of TBI face a spectrum of outcomes from short-term non-incapacitating injuries to long-lasting serious and deteriorating sequelae. TBI is a highly complex condition to treat; many variables can account for the observed heterogeneity in patient outcome. The limited success of neuroprotection strategies in the clinic has led to a new emphasis on neurorestorative approaches. In TBI, it is well recognized clinically that patients with similar lesions, age, and health status often display differences in recovery of function after injury. Despite this heterogeneity of outcomes in TBI, restorative treatment has remained generic. There is now a new emphasis on developing a personalized medicine approach in TBI, and this will require an improved understanding of how genetics impacts on long-term outcomes. Studies in animal model systems indicate clearly that the genetic background plays a role in determining the extent of recovery following an insult. A candidate gene approach in human studies has led to the identification of factors that can influence recovery. Here we review studies of the genetic basis for individual differences in functional recovery in the CNS in animals and man. The application of in vitro modeling with human cells and organoid cultures, along with whole-organism studies, will help to identify genes and networks that account for individual variation in recovery from brain injury, and will point the way towards the development of new therapeutic approaches.

[APOΕ gene polymorphism and markers of brain damage in the outcomes of severe traumatic brain injury in children]

OBJECTIVE

To compare apolipoprotein E (APOE) genotypes with outcomes and levels of neuromarkers in children with severe traumatic brain injury (TBI).

MATERIAL AND METHODS

APOE polymorphisms were genotyped in 69 children with severe TBI. The following markers of brain damage were identified: neuron-specific enolase (NSE), glial protein S100b, content of autoantibodies (aAB) to glutamate receptors (to the NR2 subunit of NMDA receptors), aAB to S100b and brain-derived neurotrophic factor (BDNF).

RESULTS AND CONCLUSION

There was no association between APOE 3/3, 3/4, 3/2 genotypes and outcomes assessed by the Glasgow Outcome Scale (GOS). The greatest number of favorable outcomes was noted in the group of APOE 3/3 genotype carriers (60%). The ratio of favorable outcomes to unfavorable outcomes was equal (50%:50%) in groups with APOE 3/4 and APOE 3/2 genotypes. An association between APOE polymorphism and BDNF was found: there were normal BDNF levels in the APOE 3/3 group and reduced levels in the APOE 3/2 group. The correlation between neuromarkers and GOS scores was shown for BDNF and aAB to S100b. In children with favorable TBI outcomes, normal BDNF levels and a lower level of aAB to S100b were observed. Regardless of APOE genotypes, almost all children with severe TBI (95%) showed a significant increase in aAB to glutamate receptors in the remote period and most children had an increase in aAB to S100b in the blood. This fact can be explained by the presence of cerebral hypoxia, activation of autoimmune processes and increased BBB permeability, which may be enhanced by increased NO content and intensification of oxidative processes in children with severe TBI.

Putative Survival Advantages in Young Apolipoprotein ɛ4 Carriers are Associated with Increased Neural Stress

Inheritance of a single copy of the apolipoprotein E (APOE) ɛ4 allele increases risk of Alzheimer’s disease (AD) by 3-4-fold, with homozygosity associated with a 12-16-fold increase in risk, relative to ɛ3 allele homozygosity. There is a decreased risk associated with the APOE ɛ2 allele. The pathological consequence of APOE genotype has led to intense efforts to understand the mechanistic basis of the interplay between APOE status and loss of synapses. Numerous ɛ4 allele-related associations have been reported with the potential relevance of these associations to the pathogenesis of AD unknown at this time. In primarily young subjects, we have reviewed a representative body of literature on ɛ4 allele-associations related to the following: cardiovascular responses; impacts on reproduction and fetal development; co-morbidities; resistance to infectious disease; responses to head injury; biochemical differences possibly related to neural stress; and brain structure-function differences. In addition, the literature on the association between the ɛ4 allele and cognitive performance has been reviewed comprehensively. The weight-of-the-evidence supports the hypothesis that possession of the ancestral ɛ4 allele in youth is associated with improved fitness during fetal development, infancy, and youth relative to the more recently appearing ɛ3 allele, at the expense of decreased fitness in old age, which is substantially improved by the ɛ3 allele. However, possession of the ɛ4 allele is also associated with higher levels of synaptic macromolecular turnover, which likely stresses basic cellular neuroplasticity mechanisms. Clinical trials of potential AD therapeutics should consider APOE status as an enrollment criterion.

Factors influencing recovery from mild traumatic brain injury

PRIMARY OBJECTIVE

This study determined whether initial GCS score, head CT results, cognitive performance on IMPACT testing, or APOE genotype most effectively predicted 1-month functional outcome after mild traumatic brain injury (mTBI). This study tested the hypotheses that participants with poor performance on initial cognitive testing and those with an APOEe4 genotype would exhibit a poorer 1-month recovery after mTBI.

RESEARCH DESIGN

Regression analysis determined which independent variables were most effective in predicting 1-month GOS-E or DRS score. Independent t-test procedures determined whether cognitive recovery varied across APOEe4 carriers.

METHODS AND PROCEDURES

49 participants admitted to the hospital with mTBI received cognitive evaluation within 48 hours after injury and again one month later. DNA analysis provided participant APOE genotype.

MAIN OUTCOMES AND RESULTS

Results showed that no study variables significantly predicted GOS-E or DRS scores, however, differences were identified when APOE groups were compared. Participants who were noncarriers of APOEe4 had significantly slower reaction times compared to APOEe4 carriers. Participants who were homozygous APOEe4 carriers had significantly lower instances of impulsivity than noncarriers.

CONCLUSIONS

Further research is needed to understand how APOE allele status and performance on initial cognitive testing may influence short-term recovery after mTBI.

Impact of Apolipoprotein E gene polymorphism during normal and pathological conditions of the brain across the lifespan

The central nervous system (CNS) is the cellular substrate for the integration of complex, dynamic, constant, and simultaneous interactions among endogenous and exogenous stimuli across the entire human lifespan. Numerous studies on aging-related brain diseases show that some genes identified as risk factors for some of the most common neurodegenerative diseases - such as the allele 4 of APOE gene (APOE4) for Alzheimer's disease (AD) - have a much earlier neuro-anatomical and neuro-physiological impact. The impact of APOE polymorphism appears in fact to start as early as youth and early-adult life. Intriguingly, though, those same genes associated with aging-related brain diseases seem to influence different aspects of the brain functioning much earlier actually, that is, even from the neonatal periods and earlier. The APOE4, an allele classically associated with later-life neurodegenerative disorders as AD, seems in fact to exert a series of very early effects on phenomena of neuroplasticity and synaptogenesis that begin from the earliest periods of life such as the fetal ones.We reviewed some of the findings supporting the hypothesis that APOE polymorphism is an early modifier of various neurobiological aspects across the entire human lifespan - from the in-utero to the centenarian life - during both normal and pathological conditions of the brain.

Brain injury-induced dysfunction of the blood brain barrier as a risk for dementia

The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

The association between dual-task walking and counting responses and cognitive function and disability after severe head injury: A preliminary study

Adverse outcomes after severe head injury (SHI) can be difficult to detect in primary care and other settings where there is not specialist expertise for interpretation. Walking and counting dual-task (DT) measures are strongly associated with cognitive impairment and dementia and this preliminary study investigates whether performance on DT walking and counting tasks are associated with cognitive function and disability in 125 participants who sustained a SHI on average 26 years before. Single Task (ST) walking (speed over 6 metres) and ST counting (Serial 3s) and DT performance of concurrent walking and Serial 3s were compared with neuropsychological, wellbeing and disability tests for strength of association. The strongest correlations were between ST Correct Cognitive Responses (CCRs) and MMSE (rho = 0.435), DT CCRs and Short-term Memory Binding Tests (STMBT) binding accuracy (rho = 0,409) and DT CCRs and STROOP (rho = 0.420), but associations were less strong with disability. Developing this test, as a cost-efficient screening tool for triage to onward referral for neuropsychological assessment, holds promise, but requires further research.

Blast-Related Traumatic Brain Injury: Current Concepts and Research Considerations

Traumatic brain injury (TBI) is a well-known consequence of participation in activities such as military combat or collision sports. But the wide variability in eliciting circumstances and injury severities makes the study of TBI as a uniform disease state impossible. Military Service members are under additional, unique threats such as exposure to explosive blast and its unique effects on the body. This review is aimed toward TBI researchers, as it covers important concepts and considerations for studying blast-induced head trauma. These include the comparability of blast-induced head trauma to other mechanisms of TBI, whether blast overpressure induces measureable biomarkers, and whether a biodosimeter can link blast exposure to health outcomes, using acute radiation exposure as a corollary. This examination is contextualized by the understanding of concussive events and their psychological effects throughout the past century's wars, as well as the variables that predict sustaining a TBI and those that precipitate or exacerbate psychological conditions. Disclaimer: The views expressed in this article are solely the views of the authors and not those of the Department of Defense Blast Injury Research Coordinating Office, US Army Medical Research and Development Command, US Army Futures Command, US Army, or the Department of Defense.

In vivo detection of cerebral tau pathology in long-term survivors of traumatic brain injury

Traumatic brain injury (TBI) can trigger progressive neurodegeneration, with tau pathology seen years after a single moderate-severe TBI. Identifying this type of posttraumatic pathology in vivo might help to understand the role of tau pathology in TBI pathophysiology. We used flortaucipir positron emission tomography (PET) to investigate whether tau pathology is present many years after a single TBI in humans. We examined PET data in relation to markers of neurodegeneration in the cerebrospinal fluid (CSF), structural magnetic resonance imaging measures, and cognitive performance. Cerebral flortaucipir binding was variable, with many participants with TBI showing increases in cortical and white matter regions. At the group level, flortaucipir binding was increased in the right occipital cortex in TBI when compared to healthy controls. Flortaucipir binding was associated with increased total tau, phosphorylated tau, and ubiquitin carboxyl-terminal hydrolase L1 CSF concentrations, as well as with reduced fractional anisotropy and white matter tissue density in TBI. Apolipoprotein E (APOE) ε4 genotype affected the relationship between flortaucipir binding and time since injury, CSF β amyloid 1–42 (Aβ42) concentration, white matter tissue density, and longitudinal Mini-Mental State Examination scores in TBI. The results demonstrate that tau PET is a promising approach to investigating progressive neurodegeneration associated with tauopathy after TBI.

Elevated cerebrospinal fluid total tau in former professional athletes with multiple concussions

OBJECTIVE

To identify CSF biomarkers that are related to decreased white matter (WM) integrity and poor cognitive performance in former professional athletes with a history of multiple concussions.

METHODS

Concentrations of phosphorylated tau181, total tau (t-tau), and β-amyloid in the CSF were measured in 3 groups: 22 former professional athletes with multiple concussions (mean ± SD age 55.9 ± 12.2 years), 5 healthy controls (age 57.4 ± 5.2 years), and 12 participants (age 60.0 ± 6.6 years) diagnosed with Alzheimer disease (AD). All participants in the former athletes group underwent diffusion tensor imaging to determine WM tract integrity and completed neuropsychological testing. We divided the former athletes group into those with normal (<300 pg/mL) and high (>300 pg/mL) CSF t-tau.

RESULTS

CSF t-tau in the former athletes group was significantly higher than in the healthy control group (349.3 ± 182.6 vs 188.8 ± 39.9 pg/mL, p = 0.003) and significantly lower than in the patients with AD (349.3 ± 182.6 vs 857.0 ± 449.3 pg/mL, p = 0.007). Fractional anisotropy values across all the tracts were significantly lower in the high CSF t-tau group compared to the normal CSF t-tau group (p = 0.036). Participants in the high CSF t-tau group scored significantly lower on the Trail Making Test (TMT) Part B compared to the normal CSF t-tau group (t scores 45.6 ± 18.8 vs 62.3 ± 10.1, p = 0.017).

CONCLUSION

Our findings indicate that former athletes with multiple concussions are at increased risk of elevated levels of CSF t-tau and that high CSF t-tau is associated with reduced WM integrity and worse scores on the TMT Part B.

Apolipoprotein E Epsilon 4 Genotype, Mild Traumatic Brain Injury, and the Development of Chronic Traumatic Encephalopathy

The annual incidence of mild traumatic brain injury (MTBI) is 3.8 million in the USA with 10⁻15% experiencing persistent morbidity beyond one year. Chronic traumatic encephalopathy (CTE), a neurodegenerative disease characterized by accumulation of hyperphosphorylated tau, can occur with repetitive MTBI. Risk factors for CTE are challenging to identify because injury mechanisms of MTBI are heterogeneous, clinical manifestations and management vary, and CTE is a postmortem diagnosis, making prospective studies difficult. There is growing interest in the genetic influence on head trauma and development of CTE. Apolipoprotein epsilon 4 (APOE-ε4) associates with many neurologic diseases, and consensus on the ε4 allele as a risk factor is lacking. This review investigates the influence of APOE-ε4 on MTBI and CTE. A comprehensive PubMed literature search (1966 to 12 June 2018) identified 24 unique reports on the topic (19 MTBI studies: 8 athletic, 5 military, 6 population-based; 5 CTE studies: 4 athletic and military, 1 leucotomy group). APOE-ε4 genotype is found to associate with outcomes in 4/8 athletic reports, 3/5 military reports, and 5/6 population-based reports following MTBI. Evidence on the association between APOE-ε4 and CTE from case series is equivocal. Refining modalities to aid CTE diagnosis in larger samples is needed in MTBI.

Intelligence across the seventh decade in patients with brain injuries acquired in young adulthood

In this longitudinal study, we examined intelligence in a group of Vietnam veterans in their 60 s who suffered combat-related penetrating traumatic brain injuries (pTBI) in their 20 s (n = 120), as well as matched veterans with no brain damage (n = 33). Intelligence was evaluated using the Armed Forces Qualification Test (AFQT) administered before the injury occurred and then again at three points in time over the following 45 years. We tested for potential predictors and correlates of late midlife intelligence score, as well as the recent change in score over the seventh decade. The pTBI group had lower intelligence scores than the control group when currently evaluated. Pre-injury intelligence and the presence of a pTBI were the most consistent predictors of current intelligence scores. While exacerbated intellectual decline occurs following a young-adulthood pTBI and affects everyday life, no evidence for late midlife accelerated cognitive decline or dementia was found.

Catechol-O-Methyltransferase Genotypes and Parenting Influence on Long-Term Executive Functioning After Moderate to Severe Early Childhood Traumatic Brain Injury: An Exploratory Study

OBJECTIVES

To examine catechol-O-methyltransferase (COMT) rs4680 genotypes as moderators of the effects of parenting style on postinjury changes in parent behavior ratings of executive dysfunction following moderate to severe early childhood traumatic brain injury.

SETTING

Research was conducted in an outpatient setting.

PARTICIPANTS

Participants included children admitted to hospital with moderate to severe traumatic brain injury (n = 55) or orthopedic injuries (n = 70) between ages 3 and 7 years.

DESIGN

Prospective cohort followed over 7 years postinjury.

MAIN MEASURES

Parenting Practices Questionnaire and the Behavior Rating Inventory of Executive Functioning obtained at baseline, 6, 12, and 18 months, and 3.5 and 6.8 years postinjury. DNA was collected from saliva samples, purified using the Oragene (DNA Genotek, Ottawa, Ontario, Canada) OG-500 self-collection tubes, and analyzed using TaqMan (Applied Biosystems, Thermo Fisher Scientific, Waltham, Massachusetts) assay protocols to identify the COMT rs4680 polymorphism.

RESULTS

Linear mixed models revealed a significant genotype × parenting style × time interaction (F = 5.72, P = .02), which suggested that the adverse effects of authoritarian parenting on postinjury development of executive functioning were buffered by the presence of the COMT AA genotype (lower enzyme activity, higher dopamine levels). There were no significant associations of executive functioning with the interaction between genotype and authoritative or permissive parenting ratings.

CONCLUSION

The lower activity COMT rs4680 genotype may buffer the negative effect of authoritarian parenting on long-term executive functioning following injury in early childhood. The findings provide preliminary evidence for associations of parenting style with executive dysfunction in children and for a complex interplay of genetic and environmental factors as contributors to decreases in these problems after traumatic injuries in children. Further investigation is warranted to understand the interplay among genetic and environmental factors related to recovery after traumatic brain injury in children.

The Effect of the Relationship of APOE Polymorphisms and Cerebral Vasospasm on Functional Outcomes in Children With Traumatic Brain Injury

BACKGROUND

Pediatric traumatic brain injury (TBI) is a leading cause of death and disability. Polymorphisms in the apolipoprotein E ( APOE) gene have been linked to cerebral vasospasm (CV) and poor outcomes in adults with TBI, yet these associations remain poorly defined in children.

OBJECTIVE

We examined the effect of the relationship between APOE polymorphisms and CV on functional outcomes in children with a TBI.

METHOD

This prospective, descriptive study examined 60 children (aged 10 days to 15 years) with a TBI. Data included demographic information, genetic sampling for the APOE gene and single-nucleotide polymorphisms (SNPs; rs405509, rs429358, rs7412), and daily transcranial Doppler ultrasounds to evaluate for CV. We examined Glasgow Outcome Scale-Extended Pediatrics (GOS-E Peds) scores at the time of discharge and 4-6 weeks after discharge.

RESULTS

More than half (56.7%) of the 60 children ( M_age = 5.9 years) were male. Twenty-six participants (43.3%) experienced an occurrence of CV. There were significant differences in injury mechanism (unadjusted p = .048) and age (unadjusted p = .02) between those with and without CV. Also, the noncoding promoter SNP rs405509 T/T, when considered with injury severity, appeared to modify the relationship of APOE genotype to CV. The relationship between APOE and CV had no significant effect on GOS-E Peds scores.

CONCLUSION

Injury severity and the APOE noncoding promoter SNP rs405509 may modify the relationship between APOE and CV in children with TBI. More studies are needed to understand the role of APOE polymorphisms in outcomes in children with TBI.

Polymorphism and plasma levels of apolipoprotein E and the risk of aneurysmal subarachnoid hemorrhage in a Chinese population: a case-control study

Background

Aneurysmal subarachnoid hemorrhage (aSAH) is the most common types of subarachnoid hemorrhage, which is a critical clinical problem with high morbidity, mortality, and economic impact. Recent studies have shown that APOE was a genetic risk factor of aSAH, however, the studies lack consistent conclusions and the evidence from Chinese Han population is rare.

Objective

To determine the relationship between APOE polymorphism and the incidence of aSAH in Chinese Fujian Han population and explore the possible mechanism of ApoE in the pathogenesis of aSAH.

Methods

A total of 131 patients newly diagnosed with aSAH were selected as aSAH group and 137 healthy subjects were selected as the control group. All the samples were analyzed for blood lipids and serum ApoE levels, and ApoE genotype was determined by a commercial chip and further confirmed with Sanger sequencing. An adjusted multivariate logistic regression analysis was carried out to estimate the effects of APOE polymorphism on the risk of aSAH.

Results

Compared with the controls, the serum TC, HDL-C and ApoA1 levels in aSAH were significantly lower: TC (4.52 ± 1.38 vs. 5.11 ± 0.86 mmol/L, P < 0.001), HDL-C (1.23 ± 0.46 vs. 1.44 ± 0.32 mmol/L, P < 0.001) and ApoA1 (1.20 ± 0.32 vs. 1.38 ± 0.25 g/L, P < 0.001). The distribution of ε2/ε3 genotype (19.08% vs. 9.49%, P = 0.038) and ε2 allele frequency (11.07% vs. 5.84%, P = 0.039) was significantly higher in aSAH than the healthy controls. The multivariate logistic regression identified that ApoE ε2 allele was independently associated with aSAH (OR = 2.083; and 95% CI = 1.045-4.153, P = 0.037). The serum ApoE in aSAH were significantly higher than controls (53.03 ± 24.64 vs. 45.06 ± 12.84 mg/L, P = 0.010).

Conclusion

APOE polymorphism might be associated with the incidence of aSAH in Chinese Fujian Han population. ApoE ε2 may be a risk factor for the incidence of aSAH, which may be related with the impacts of ApoE genotypes for the serum lipids, especially for the plasma levels of ApoE.

The Inflammatory Continuum of Traumatic Brain Injury and Alzheimer's Disease

The post-injury inflammatory response is a key mediator in long-term recovery from traumatic brain injury (TBI). Moreover, the immune response to TBI, mediated by microglia and macrophages, is influenced by existing brain pathology and by secondary immune challenges. For example, recent evidence shows that the presence of beta-amyloid and phosphorylated tau protein, two hallmark features of AD that increase during normal aging, substantially alter the macrophage response to TBI. Additional data demonstrate that post-injury microglia are “primed” and become hyper-reactive following a subsequent acute immune challenge thereby worsening recovery. These alterations may increase the incidence of neuropsychiatric complications after TBI and may also increase the frequency of neurodegenerative pathology. Therefore, the purpose of this review is to summarize experimental studies examining the relationship between TBI and development of AD-like pathology with an emphasis on the acute and chronic microglial and macrophage response following injury. Furthermore, studies will be highlighted that examine the degree to which beta-amyloid and tau accumulation as well as pre- and post-injury immune stressors influence outcome after TBI. Collectively, the studies described in this review suggest that the brain’s immune response to injury is a key mediator in recovery, and if compromised by previous, coincident, or subsequent immune stressors, post-injury pathology and behavioral recovery will be altered.

Apolipoprotein E polymorphism and the risk of aneurysmal subarachnoid hemorrhage in a South Indian population

Background

The rupture of a brain aneurysm causes bleeding in the subarachnoid space. This is known as aneurysmal subarachnoid hemorrhage (aSAH). We evaluated the association of apolipoprotein E (APOE) polymorphism and the risk of aSAH in a South Indian population.

Methods

The study was performed on 200 subjects with aSAH and 253 healthy control subjects. Blood samples (5 ml) were used to isolate DNA and genotyping was performed for rs7412 and rs429358 using a Taqman allelic discrimination assay. Statistical software R.3.0.11 was used to statistically analyze the data and a p value < 0.05 was considered as statistically significant.

Results

We found a significant association with the risk of aSAH in ε3/ ε4 genetic model (OR = 1.91, 95% CI = 1.16-3.14, p = 0.01). However, in the other genetic models and allele frequency, there was no significant association with the risk of aSAH. In subtyping, we found a significant association of ε2 allele frequency with posterior communicating artery (PCOM) aneurysm (OR = 3.59, 95% CI = 1.11-11.64, p = 0.03).

Conclusion

Our results suggest that APOE polymorphism has an influence on the risk of aSAH in this South Indian population, specifically in the PCOM subtype.

Effects of apolipoprotein E gene polymorphism on the intracellular Ca2+ concentration of astrocytes in the early stages post injury

The present study aimed to investigate the correlation between apolipoprotein E (APOE) polymorphisms and the intracellular concentration of Ca²⁺ in astrocytes in the early stages after an injury. The chondroitin sulfate region of three APOE alleles (ε2, ε3 and ε4) was obtained by reverse transcription-polymerase chain reaction (RT-PCR). A recombinant plasmid, pEGFP-N1-APOE, was constructed and identified by sequencing, while astrocytes were isolated from APOE gene-knockout mice and examined using immunocytochemistry. The recombinant plasmid was transfected into the astrocytes using the liposome-mediated method and cell injury models were constructed by a scratch assay. Laser confocal scanning microscopy (LCSM) was used to detect dynamic alterations in intracellular Ca²⁺ concentration at 12, 24, 48 and 72 h after injury. Compared with the control group, cells transfected with any of the three alleles demonstrated significant increases in the fluorescence intensity of Ca²⁺ (P<0.05). The fluorescence intensity of Ca²⁺ was weak at 12 h after injury, with no statistically significant difference detected between any two groups at this time point (P>0.05). However, the fluorescence intensity increased in a time-dependent manner and at 24, 48 and 72 h post injury, the fluorescence intensity of the ε4 allele-containing cells was significantly higher when compared with that of cells harboring the other two alleles (P<0.05). These results indicate that intracellular Ca²⁺ overloading may contribute to the deterioration of brain cells and poor outcome subsequent to traumatic brain injury in APOE ε4 carriers.

The Impact of Traumatic Brain Injury on Later Life: Effects on Normal Aging and Neurodegenerative Diseases

The acute and chronic effects of traumatic brain injury (TBI) have been widely described; however, there is limited knowledge on how a TBI sustained during early adulthood or mid-adulthood will influence aging. Epidemiological studies have explored whether TBI poses a risk for dementia and other neurodegenerative diseases associated with aging. We will discuss the influence of TBI and resulting medical comorbidities such as endocrine, sleep, and inflammatory disturbances on age-related gray and white matter changes and cognitive decline. Post mortem studies examining amyloid, tau, and other proteins will be discussed within the context of neurodegenerative diseases and chronic traumatic encephalopathy. The data support the suggestion that pathological changes triggered by an earlier TBI will have an influence on normal aging processes and will interact with neurodegenerative disease processes rather than the development of a specific disease, such as Alzheimer's or Parkinson's. Chronic neurophysiologic change after TBI may have detrimental effects on neurodegenerative disease.

Genetic polymorphisms associated with the risk of concussion in 1056 college athletes: a multicentre prospective cohort study

BACKGROUND/AIM

To evaluate the association of genetic polymorphisms APOE, APOE G-219T promoter, microtubule associated protein(MAPT)/tau exon 6 Ser⁵³Pro, MAPT/tau Hist⁴⁷Tyr, IL-6572 G/C and IL-6R^Asp358^Ala with the risk of concussion in college athletes.

METHODS

A 23-centre prospective cohort study of 1056 college athletes with genotyping was completed between August 2003 and December 2012. All athletes completed baseline medical and concussion questionnaires, and post-concussion data were collected for athletes with a documented concussion.

RESULTS

The study cohort consisted of 1056 athletes of mean±SD age 19.7±1.5 years, 89.3% male, 59.4% Caucasian, 35.0% African-American, 5.6% other race. The athletes participated in American football, soccer, basketball, softball, men's wrestling and club rugby. A total of 133 (12.1% prevalence) concussions occurred during an average surveillance of 3 years per athlete. We observed a significant positive association between IL-6R CC (p=0.001) and a negative association between APOE4 (p=0.03) and the risk of concussion. Unadjusted and adjusted logistic regression analysis showed a significant association between IL-6R CC and concussion (OR 3.48; 95% CI 1.58 to 7.65; p=0.002) and between the APOE4 allele and concussion (OR 0.61; 95% CI 0.38 to 0.96; p=0.04), which persisted after adjustment for confounders.

CONCLUSIONS

IL-6R CC was associated with a three times greater concussion risk and APOE4 with a 40% lower risk.

Apolipoprotein E epsilon 4 (APOE-ε4) genotype is associated with decreased 6-month verbal memory performance after mild traumatic brain injury

INTRODUCTION

The apolipoprotein E (APOE) ε4 allele associates with memory impairment in neurodegenerative diseases. Its association with memory after mild traumatic brain injury (mTBI) is unclear.

METHODS

mTBI patients (Glasgow Coma Scale score 13-15, no neurosurgical intervention, extracranial Abbreviated Injury Scale score ≤1) aged ≥18 years with APOE genotyping results were extracted from the Transforming Research and Clinical Knowledge in Traumatic Brain Injury Pilot (TRACK-TBI Pilot) study. Cohorts determined by APOE-ε4(+/-) were assessed for associations with 6-month verbal memory, measured by California Verbal Learning Test, Second Edition (CVLT-II) subscales: Immediate Recall Trials 1-5 (IRT), Short-Delay Free Recall (SDFR), Short-Delay Cued Recall (SDCR), Long-Delay Free Recall (LDFR), and Long-Delay Cued Recall (LDCR). Multivariable regression controlled for demographic factors, seizure history, loss of consciousness, posttraumatic amnesia, and acute intracranial pathology on computed tomography (CT).

RESULTS

In 114 mTBI patients (APOE-ε4(-)=79; APOE-ε4(+)=35), ApoE-ε4(+) was associated with long-delay verbal memory deficits (LDFR: B = -1.17 points, 95% CI [-2.33, -0.01], p = .049; LDCR: B = -1.58 [-2.63, -0.52], p = .004), and a marginal decrease on SDCR (B = -1.02 [-2.05, 0.00], p = .050). CT pathology was the strongest predictor of decreased verbal memory (IRT: B = -8.49, SDFR: B = -2.50, SDCR: B = -1.85, LDFR: B = -2.61, LDCR: B = -2.60; p < .001). Seizure history was associated with decreased short-term memory (SDFR: B = -1.32, p = .037; SDCR: B = -1.44, p = .038).

CONCLUSION

The APOE-ε4 allele may confer an increased risk of impairment of 6-month verbal memory for patients suffering mTBI, with implications for heightened surveillance and targeted therapies. Acute intracranial pathology remains the driver of decreased verbal memory performance at 6 months after mTBI.

What is the Relationship of Traumatic Brain Injury to Dementia?

There is a long history linking traumatic brain injury (TBI) with the development of dementia. Despite significant reservations, such as recall bias or concluding causality for TBI, a summary of recent research points to several conclusions on the TBI-dementia relationship. 1) Increasing severity of a single moderate-to-severe TBI increases the risk of subsequent Alzheimer's disease (AD), the most common type of dementia. 2) Repetitive, often subconcussive, mild TBIs increases the risk for chronic traumatic encephalopathy (CTE), a degenerative neuropathology. 3) TBI may be a risk factor for other neurodegenerative disorders that can be associated with dementia. 4) TBI appears to lower the age of onset of TBI-related neurocognitive syndromes, potentially adding "TBI cognitive-behavioral features". The literature further indicates several specific risk factors for TBI-associated dementia: 5) any blast or blunt physical force to the head as long as there is violent head displacement; 6) decreased cognitive and/or neuronal reserve and the related variable of older age at TBI; and 7) the presence of apolipoprotein E ɛ4 alleles, a genetic risk factor for AD. Finally, there are neuropathological features relating TBI with neurocognitive syndromes: 8) acute TBI results in amyloid pathology and other neurodegenerative proteinopathies; 9) CTE shares features with neurodegenerative dementias; and 10) TBI results in white matter tract and neural network disruptions. Although further research is needed, these ten findings suggest that dose-dependent effects of violent head displacement in vulnerable brains predispose to dementia; among several potential mechanisms is the propagation of abnormal proteins along damaged white matter networks.

Applying Systems Biology Methodology To Identify Genetic Factors Possibly Associated with Recovery after Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality worldwide. It is linked with a number of medical, neurological, cognitive, and behavioral sequelae. The influence of genetic factors on the biology and related recovery after TBI is poorly understood. Studies that seek to elucidate the impact of genetic influences on neurorecovery after TBI will lead to better individualization of prognosis and inform development of novel treatments, which are considerably lacking. Current genetic studies related to TBI have focused on specific candidate genes. The objectives of this study were to use a system biology-based approach to identify biologic processes over-represented with genetic variants previously implicated in clinical outcomes after TBI and identify unique genes potentially related to recovery after TBI. After performing a systematic review to identify genes in the literature associated with clinical outcomes, we used the genes identified to perform a systems biology-based integrative computational analysis to ascertain the interactions between molecular components and to develop models for regulation and function of genes involved in TBI recovery. The analysis identified over-representation of genetic variants primarily in two biologic processes: response to injury (cell proliferation, cell death, inflammatory response, and cellular metabolism) and neurocognitive and behavioral reserve (brain development, cognition, and behavior). Overall, this study demonstrates the use of a systems biology-based approach to identify unique/novel genes or sets of genes important to the recovery process. Findings from this systems biology-based approach provide additional insight into the potential impact of genetic variants on the underlying complex biological processes important to TBI recovery and may inform the development of empirical genetic-related studies for TBI. Future studies that combine systems biology methodology and genomic, proteomic, and epigenetic approaches are needed in TBI.

Genetic findings in sport-related concussions: potential for individualized medicine?

Concussion is a traumatic transient disturbance of the brain. In sport, the initial time and severity of concussion is known giving an opportunity for subsequent analysis. Variability in susceptibility and recovery between individual athletes depends, among other parameters, on genetic factors. The genes-encoding polypeptides that determine incidence, severity and prognosis for concussion are the primary candidates for genetic analysis. Genetic polymorphisms in the genes contributing to plasticity and repair (APOE), synaptic connectivity (GRIN2A), calcium influx (CACNA1E), uptake and deposit of glutamate (SLC17A7) are potential biomarkers of concussion incidence and recovery rate. With catalogued genetic variants, prospective genotyping of athletes at the beginning of their career will allow medical professionals to improve concussion management and return-to-play decisions.

Does Apolipoprotein e4 Status Moderate the Association of Family Environment with Long-Term Child Functioning following Early Moderate to Severe Traumatic Brain Injury? A Preliminary Study

OBJECTIVES

To examine whether apolipoprotein e4 (APOE) status moderates the association of family environment with child functioning following early traumatic brain injury (TBI).

METHODS

Sixty-five children with moderate to severe TBI and 70 children with orthopedic injury (OI) completed assessments 6, 12, 18 months, and 3.5 and 6.8 years post injury. DNA was extracted from saliva samples and genotyped for APOE e4 status. Linear mixed models examined moderating effects of APOE e4 status on associations between two family environment factors (parenting style, home environment) and three child outcomes (executive functioning, behavioral adjustment, adaptive functioning).

RESULTS

Children with TBI who were carriers of the e4 allele showed poorer adaptive functioning relative to non-carriers with TBI and children with OI in the context of low authoritarianism. At high levels of authoritarianism, non-carriers with TBI showed the poorest adaptive functioning among groups. There were no main effects or interactions involving APOE and executive functioning or behavioral adjustment.

CONCLUSIONS

The APOE e4 allele was detrimental for long-term adaptive functioning in the context of positive parenting, whereas in less optimal parenting contexts, being a non-carrier was detrimental. We provide preliminary evidence for an interaction of APOE e4 status and parenting style in predicting long-term outcomes following early TBI. (JINS, 2016, 22, 859-864).

Chapter 6 state of the science of pediatric traumatic brain injury: biomarkers and gene association studies

OBJECTIVES

Our objective is to review the most widely used biomarkers and gene studies reported in pediatric traumatic brain injury (TBI) literature, to describe their findings, and to discuss the discoveries and gaps that advance the understanding of brain injury and its associated outcomes. Ultimately, we aim to inform the science for future research priorities.

DATA SOURCES

We searched PubMed, MEDLINE, CINAHL, and the Cochrane Database of Systematic Reviews for published English language studies conducted in the last 10 years to identify reviews and completed studies of biomarkers and gene associations in pediatric TBI. Of the 131 biomarker articles, only 16 were specific to pediatric TBI patients, whereas of the gene association studies in children with TBI, only four were included in this review.

CONCLUSION

Biomarker and gene attributes are grossly understudied in pediatric TBI in comparison to adults. Although recent advances recognize the importance of biomarkers in the study of brain injury, the limited number of studies and genomic associations in the injured brain has shown the need for common data elements, larger sample sizes, heterogeneity, and common collection methods that allow for greater understanding of the injured pediatric brain. By building on to the consortium of interprofessional scientists, continued research priorities would lead to improved outcome prediction and treatment strategies for children who experience a TBI.

IMPLICATIONS FOR NURSING RESEARCH

Understanding recent advances in biomarker and genomic studies in pediatric TBI is important because these advances may guide future research, collaborations, and interventions. It is also important to ensure that nursing is a part of this evolving science to promote improved outcomes in children with TBIs.

Polymorphisms of apolipoprotein E and aneurysmal subarachnoid haemorrhage: A meta-analysis

Subarachnoid haemorrhage (SAH) is characterised by bleeding in the subarachnoid space in the brain. There are various polymorphisms in genes which are associated with this disease. We performed a systematic meta- analysis to investigate the relationship of APOE polymorphism on aSAH. A comprehensive literature search was done in the Pubmed database, Science Direct, Cochrane library and Google Scholar. The OR and 95% CI were evaluated for the gene and aSAH association using fixed and random effect models. Publication bias was assessed using Begg's funnel plot and Egger's regression test. All statistical evaluations were done using the software Review Manager 5.0 and Comprehensive Meta Analysis v2.2.023. A total of 9 studies were assessed on APOE polymorphism (1100 Cases, 2732 Control). Meta analysis results showed significant association in ε2/ ε2 versus ε3/ε3, ε2 versus ε3 genetic models and ε2 allele frequency. In subgroup analysis statistically significant association was observed in Asians in the genetic models ε2/ ε2 versus ε3/ε3, ε2/ε3 versus ε3/ε3, ε2 versus ε3 and also in ε2 allele frequency. However, in Caucasian population only ε2/ε2 versus ε3/ε3 genetic model showed significant association between APOE and risk of aSAH. In this meta-analysis study, the ε2/ε2 genotype is associated with increased risk of aSAH.

Protein profile changes in the frontotemporal lobes in human severe traumatic brain injury

Severe traumatic brain injury (sTBI) is a serious public health issue with high morbidity and mortality rates. Previous proteomic studies on sTBI have mainly focused on human cerebrospinal fluid and serum, as well as on brain protein changes in murine models. However, human proteomic data in sTBI brain is still scarce. We used proteomic and bioinformatic strategies to investigate variations in protein expression levels in human brains after sTBI, using samples from the Department of Neurosurgery, Affiliated Hospital of Hebei University (Hebei, China). Our proteomic data identified 4031 proteins, of which 160 proteins were overexpressed and 5 proteins were downregulated. Bioinformatics analysis showed significant changes in biological pathways including glial cell differentiation, complement activation and apolipoprotein catalysis in the statin pathway. Western blot verification of protein changes in a subset of the available tissue samples showed results that were consistent with the proteomic data. This study is one of the first to investigate the whole proteome of human sTBI brains, and provide a characteristic signature and overall landscape of the sTBI brain proteome.

Association of the APOE-ε4 allele with outcome of traumatic brain injury in children and youth: a meta-analysis and meta-regression

OBJECTIVE

To disentangle the temporal relationship between the APOE-ε4 allele and outcomes of paediatric traumatic brain injury (TBI).

METHODS

PubMed, EMBASE, Web of Science, MEDLINE, PsychINFO and HuGE Navigator Genopedia databases were searched from their inception up to January 2015 without language limitations. Included studies were analysed under a dominant genetic model to assess the association between the APOE-ε4 allele and poor outcomes of paediatric TBI at 6 months. Meta-regression was used to assess trends over time.

RESULTS

Of the 325 initially identified records, 6 studies were selected and analysed based on inclusion/exclusion criteria. A total of 358 cases of paediatric TBI were included. 2 studies assessed outcomes at multiple time points ranging from 3 to 36 months; 4 studies assessed outcomes at a single time point (either 6 or 12 months). At 6 months, there is 2.36 (95% CI 1.26 to 4.42; p=0.007) times higher odds of poor outcome following TBI in children with at least one APOE-ε4 allele, compared with the children without. Further, the adjusted odds suggested an increasing trend of 7% per month (95% CI -9 to 25; p=0.359).

CONCLUSIONS

This meta-analysis provides cumulative evidence that the APOE-ε4 allele is important to the prognosis of paediatric TBI, but may have a different effect compared with adult TBI; moreover, this effect may be time dependent.

Exploring the effect of the apolipoprotein E (APOE) gene on executive function, working memory, and processing speed during the early recovery period following traumatic brain injury

INTRODUCTION

There is evidence that the e4 allele of the apolipoprotein E (APOE) gene is detrimental to cognitive function, but results from traumatic brain injury (TBI) populations are mixed. A possible explanation is that APOEe2 carriers have routinely been incorporated into APOEe4 and non-e4 groups, despite APOEe2 being proposed to have an ameliorative effect. Our primary aim was to investigate the influence of APOEe4 on cognitive impairment during early recovery following TBI, excluding the potential confound of APOEe2 possession. A secondary objective was to explore whether APOEe4 displays more pronounced effects in moderate to severe TBI and to consider the potential postinjury protective influence of the APOEe2 allele.

METHOD

Participants who recently sustained a TBI (posttraumatic amnesia > 5 minutes) were assessed on measures of information processing speed, executive function, and working memory upon remission of posttraumatic amnesia. APOE genotype was determined by buccal saliva DNA extraction (APOEe4 n = 37, APOEe3 n = 92, APOEe2 n = 13).

RESULTS

Stepwise multiple regressions were performed to compare APOEe4 carriers to APOEe3 homozygotes, with injury severity, age, and estimated premorbid IQ included in the first step. This model was found to significantly predict performance on all tasks, accounting for 17.3-24.3% of the variance. When APOEe4 status was added for the second step, there were no significant changes on any tasks (additional variance <1%). The effect of APOEe4 in moderate to severe TBI and the effect of APOEe2 were explored by analysis of covariance (ANCOVA), with no significant effects revealed.

CONCLUSIONS

It is unlikely that APOE genotype influences cognitive function in the initial recovery period following TBI, regardless of injury severity. However, a more nuanced and long-term exploration of the effect of APOE genotype in the TBI population is warranted.

Cerebral amyloid-β accumulation and deposition following traumatic brain injury--A narrative review and meta-analysis of animal studies

Traumatic brain injury (TBI) increases the risk of neurodegenerative disorders many years post-injury. However, molecular mechanisms underlying the relationship between TBI and neurodegenerative diseases, such as Alzheimer's disease (AD), remain to be elucidated. Nevertheless, previous studies have demonstrated a link between TBI and increased amyloid-β (Aβ), a protein involved in AD pathogenesis. Here, we review animal studies that measured Aβ levels following TBI. In addition, from a pool of initially identified 1209 published papers, we examined data from 19 eligible animal model studies using a meta-analytic approach. We found an acute increase in cerebral Aβ levels ranging from 24h to one month following TBI (overall log OR=2.97 ± 0.40, p<0.001). These findings may contribute to further understanding the relationship between TBI and future dementia risk. The methodological inconsistencies of the studies discussed in this review suggest the need for improved and more standardised data collection and study design, in order to properly elucidate the role of TBI in the expression and accumulation of Aβ.

Chronic Traumatic Encephalopathy: The Neuropathological Legacy of Traumatic Brain Injury

Almost a century ago, the first clinical account of the punch-drunk syndrome emerged, describing chronic neurological and neuropsychiatric sequelae occurring in former boxers. Thereafter, throughout the twentieth century, further reports added to our understanding of the neuropathological consequences of a career in boxing, leading to descriptions of a distinct neurodegenerative pathology, termed dementia pugilistica. During the past decade, growing recognition of this pathology in autopsy studies of nonboxers who were exposed to repetitive, mild traumatic brain injury, or to a single, moderate or severe traumatic brain injury, has led to an awareness that it is exposure to traumatic brain injury that carries with it a risk of this neurodegenerative disease, not the sport or the circumstance in which the injury is sustained. Furthermore, the neuropathology of the neurodegeneration that occurs after traumatic brain injury, now termed chronic traumatic encephalopathy, is acknowledged as being a complex, mixed, but distinctive pathology, the detail of which is reviewed in this article.

Apolipoprotein E (APOE) ϵ4 Allele Is Associated with Increased Symptom Reporting Following Sports Concussion

Exploring the relationship between genetic factors and outcome following brain injury has received increased attention in recent years. However, few studies have evaluated the influence of genes on specific sequelae of concussion. The purpose of this study was to determine how the ϵ4 allele of the apolipoprotein E (APOE) gene influences symptom expression following sports-related concussion. Participants included 42 collegiate athletes who underwent neuropsychological testing, including completion of the Post-Concussion Symptom Scale (PCSS), within 3 months after sustaining a concussion (73.8% were evaluated within 1 week). Athletes provided buccal samples that were analyzed to determine the make-up of their APOE genotype. Dependent variables included a total symptom score and four symptom clusters derived from the PCSS. Mann-Whitney U tests showed higher scores reported by athletes with the ϵ4 allele compared to those without it on the total symptom score and the physical and cognitive symptom clusters. Furthermore, logistic regression showed that the ϵ4 allele independently predicted those athletes who reported physical and cognitive symptoms following concussion. These findings illustrate that ϵ4+ athletes report greater symptomatology post-concussion than ϵ4- athletes, suggesting that the ϵ4 genotype may confer risk for poorer post-concussion outcome. (JINS, 2016, 22, 89-94).

Role of apolipoprotein E polymorphism as a prognostic marker in traumatic brain injury and neurodegenerative disease: a critical review

OBJECT

The difference in course and outcome of several neurodegenerative conditions and traumatic injuries of the nervous system points toward a possible role of genetic and environmental factors as prognostic markers. Apolipoprotein E (Apo-E), a key player in lipid metabolism, is recognized as one of the most powerful genetic risk factors for dementia and other neurodegenerative diseases. In this article, the current understanding of APOE polymorphism in various neurological disorders is discussed.

METHODS

The English literature was searched for various studies describing the role of APOE polymorphism as a prognostic marker in neurodegenerative diseases and traumatic brain injury. The wide ethnic distribution of APOE polymorphism was discussed, and the recent meta-analyses of role of APOE polymorphism in multiple diseases were analyzed and summarized in tabular form.

RESULTS

Results from the review of literature revealed that the distribution of APOE is varied in different ethnic populations. APOE polymorphism plays a significant role in pathogenesis of neurodegeneration, particularly in Alzheimer’s disease. APOE ε4 is considered a marker for poor prognosis in various diseases, but APOE ε2 rather than APOE ε4 has been associated with cerebral amyloid angiopathy-related bleeding and sporadic Parkinson’s disease. The role of APOE polymorphism in various neurological diseases has not been conclusively elucidated.

CONCLUSIONS

Apo-E is a biomarker for various neurological and systemic diseases. Therefore, while analyzing the role of APOE polymorphism in neurological diseases, the interpretation should be done after adjusting all the confounding factors. A continuous quest to look for associations with various neurological diseases and wide knowledge of available literature are required to improve the understanding of the role of APOE polymorphism in these conditions and identify potential therapeutic targets.