The role of apolipoprotein E in Alzheimer's disease, acute brain injury and cerebrovascular disease: evidence of common mechanisms and utility of animal models

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.

Genome-wide association study of traumatic brain injury in U.S. military veterans enrolled in the VA million veteran program

Large-scale genetic studies of traumatic brain injury (TBI) are lacking; thus, our understanding of the influence of genetic factors on TBI risk and recovery is incomplete. This study aimed to conduct a genome-wide association study (GWAS) of TBI in VA Million Veteran Program (MVP) enrollees. Participants included a multi-ancestry cohort (European, African, and Hispanic ancestries; N = 304,485; 111,494 TBI cases, 192,991 controls). TBI was assessed using MVP survey data and International Classification of Diseases (ICD) codes from the Veterans Health Administration's electronic health record. GWAS was performed using logistic regression in PLINK, and meta-analyzed in METAL. FUMA was used for post-GWAS analysis. Genomic structural equation modeling (gSEM) was conducted to investigate underlying genetic associations with TBI, and bivariate MiXeR was used to estimate phenotype specific and shared polygenicity. SNP-based heritability was 0.060 (SE = 0.004, p = 7.83×10-66). GWAS analysis identified 15 genome-wide significant (GWS) loci at p < 5×10-8. Gene-based analyses revealed 14 gene-wide significant genes; top genes included NCAM1, APOE, FTO, and FOXP2. Gene tissue expression analysis identified the brain as significantly enriched, particularly in the frontal cortex, anterior cingulate cortex, and nucleus accumbens. Genetic correlations with TBI were significant for risk-taking behaviors and psychiatric disorders, but generally not significant for the neurocognitive variables investigated. gSEM analysis revealed stronger associations with risk-taking traits than with psychiatric traits. Finally, the genetic architecture of TBI was similar to polygenic psychiatric disorders. Neurodegenerative disorders including Alzheimer's and Parkinson's disease showed much less polygenicity, however, the proportion of shared variance with TBI was high. This first well-powered GWAS of TBI identified 15 loci including genes relevant to TBI biology, and showed that TBI is a heritable trait with comparable genetic architecture and high genetic correlation with psychiatric traits. Our findings set the stage for future TBI GWASs that focus on injury severity and diversity and chronicity of symptom sequelae.

Novel small molecules inhibit proteotoxicity and inflammation: Mechanistic and therapeutic implications for Alzheimer's Disease, healthspan and lifespan- Aging as a consequence of glycolysis

Inflammation drives many age-related, especially neurological, diseases, and likely mediates age-related proteotoxicity. For example, dementia due to Alzheimer's Disease (AD), cerebral vascular disease, many other neurodegenerative conditions is increasingly among the most devastating burdens on the American (and world) health system and threatens to bankrupt the American health system as the population ages unless effective treatments are developed. Dementia due to either AD or cerebral vascular disease, and plausibly many other neurodegenerative and even psychiatric conditions, is driven by increased age-related inflammation, which in turn appears to mediate Abeta and related proteotoxic processes. The functional significance of inflammation during aging is also supported by the fact that Humira, which is simply an antibody to the pro-inflammatory cytokine TNF-a, is the best-selling drug in the world by revenue. These observations led us to develop parallel high-throughput screens to discover small molecules which inhibit age-related Abeta proteotoxicity in a C. elegans model of AD AND LPS-induced microglial TNF-a. In the initial screen of 2560 compounds (Microsource Spectrum library) to delay Abeta proteotoxicity, the most protective compounds were, in order, phenylbutyrate, methicillin, and quetiapine, which belong to drug classes (HDAC inhibitors, beta lactam antibiotics, and tricyclic antipsychotics, respectably) already robustly implicated as promising to protect in neurodegenerative diseases, especially AD. RNAi and chemical screens indicated that the protective effects of HDAC inhibitors to reduce Abeta proteotoxicity are mediated by inhibition of HDAC2, also implicated in human AD, dependent on the HAT Creb binding protein (Cbp), which is also required for the protective effects of both dietary restriction and the daf-2 mutation (inactivation of IGF-1 signaling) during aging. In addition to methicillin, several other beta lactam antibiotics also delayed Abeta proteotoxicity and reduced microglial TNF-a. In addition to quetiapine, several other tricyclic antipsychotic drugs also delayed age-related Abeta proteotoxicity and increased microglial TNF-a, leading to the synthesis of a novel congener, GM310, which delays Abeta as well as Huntingtin proteotoxicity, inhibits LPS-induced mouse and human microglial and monocyte TNF-a, is highly concentrated in brain after oral delivery with no apparent toxicity, increases lifespan, and produces molecular responses highly similar to those produced by dietary restriction, including induction of Cbp inhibition of inhibitors of Cbp, and genes promoting a shift away from glycolysis and toward metabolism of alternate (e.g., lipid) substrates. GM310, as well as FDA-approved tricyclic congeners, prevented functional impairments and associated increase in TNF-a in a mouse model of stroke. Robust reduction of glycolysis by GM310 was functionally corroborated by flux analysis, and the glycolytic inhibitor 2-DG inhibited microglial TNF-a and other markers of inflammation, delayed Abeta proteotoxicity, and increased lifespan. These results support the value of phenotypic screens to discover drugs to treat age-related, especially neurological and even psychiatric diseases, including AD and stroke, and to clarify novel mechanisms driving neurodegeneration (e.g., increased microglial glycolysis drives neuroinflammation and subsequent neurotoxicity) suggesting novel treatments (selective inhibitors of microglial glycolysis).

Prediction of early prognosis after traumatic brain injury by multifactor model

AIMS

To design a model to predict the early prognosis of patients with traumatic brain injury (TBI) based on parameters that can be quickly obtained in emergency conditions from medical history, physical examination, and supplementary examinations.

METHODS

The medical records of TBI patients who were hospitalized in two medical institutions between June 2015 and June 2021 were collected and analyzed. Patients were divided into the training set, validation set, and testing set. The possible predictive indicators were screened after analyzing the data of patients in the training set. Then prediction models were found based on the possible predictive indicators in the training set. Data of patients in the validation set and the testing set was provided to validate the predictive values of the models.

RESULTS

Age, Glasgow coma scale score, Apolipoprotein E genotype, damage area, serum C-reactive protein, and interleukin-8 (IL-8) levels, and Marshall computed tomography score were found associated with early prognosis of TBI patients. The accuracy of the early prognosis prediction model (EPPM) was 80%, and the sensitivity and specificity of the EPPM were 78.8% and 80.8% in the training set. The accuracy of the EPPM was 79%, and the sensitivity and specificity of the EPPM were 66.7% and 86.2% in the validation set. The accuracy of the early EPPM was 69.1%, and the sensitivity and specificity of the EPPM were 67.9% and 77.8% in the testing set.

CONCLUSION

Prediction models integrating general information, clinical manifestations, and auxiliary examination results may provide a reliable and rapid method to evaluate and predict the early prognosis of TBI patients.

APOE ε4 and late-life cognition: mediation by structural brain imaging markers

The apolipoprotein E allele 4 (APOE-ε4) is established as a major genetic risk factor for cognitive decline and late-onset Alzheimer's disease. Accumulating evidence has linked ε4 carriership to abnormal structural brain changes across the adult lifespan. To better understand the underlying causal mechanisms, we investigated the extent to which the effect of the ε4 allele on cognition is mediated by structural brain imaging markers in the population-based Age, Gene/Environment Susceptibility-Reykjavik Study (AGES-Reykjavik). This study included 4527 participants (aged 76.3 ± 5.4 at baseline) who underwent the brain magnetic resonance imaging assessment (of brain tissue volumes, white matter lesion volume, subcortical and cortical infarcts, and cerebral microbleeds) and a battery of neuropsychological tests at baseline. Causal mediation analysis was used to quantify the mediation of the ε4 effect on cognition by these MRI markers, both individually and jointly. We observed that about 9% of the total effect of ε4 carriership on cognition was mediated by white matter lesion volume. This proportion increased to 25% when total brain tissue volume was jointly considered with white matter lesion volume. In analyses separating ε4 homozygotes from ε4 heterozygotes, the effect on global cognition of specifically ε4 homozygosity appeared to be partially mediated by cerebral microbleeds, particularly lobar microbleeds. There was no evidence of mediation of the ε4 effect by cortical or subcortical infarcts. This study shows that the ε4 effect on cognition is partly mediated by white matter lesion volume and total brain tissue volume. These findings suggest the joint role of cerebral small vessel disease and neurodegeneration in the ε4-cognition relationship.

Combined homocysteine and apoE rs429358 and rs7412 polymorphism in association with serum lipid levels and cognition in Chinese community-dwelling older adults

BACKGROUND

ApoE gene polymorphism and serum total homocysteine (tHcy) has been reportedly associated with cognition. In this study, we assessed the association of combined ApoE gene polymorphism and tHcy with cognition in Chinese elder adults.

METHODS

A cross- sectional study was carried out by recruiting 1458 community-dwelling people aged 55+ and above in Beijing in 2009. All participants were interviewed using a standard questionnaire and underwent a physical examination. The mini-mental scale examination (MMSE) score was used in assessing cognitive function. Fasting venous blood samples were taken for ApoE rs429358, rs7412 genotyping, tHcy and other serum lipid measurements.

RESULTS

Participants with high serum tHcy level showed a relatively lower orientation, attention abilities as well as the total MMSE score than the group with normal tHcy after adjusting confounding factors. ApoE rs429358 and rs7412 variants were observed to have the highest serum TC and TG level in the subjects with high serum tHcy level (p <  0.05). Cognition of the subjects was found to be significantly associated with high serum tHcy level and ApoE genetic polymorphism (p <  0.05). Independent of age, BMI, education levels, smoking and alcohol drinking, the worst cognitive ability were detected in the high serum tHcy level subjects with ApoE rs429358C/T and rs7412 C/T as compare with other groups, especially orientation function, memory and delayed recall ability and attention ability.

CONCLUSION

High serum tHcy level in combination with ApoE rs429358 and rs7412 variants might be linked with serum lipid levels and cognition, particularly for orientation function and memory and delayed recall ability in old Chinese adults.

APOE-ε4 Is Associated With Reduced Verbal Memory Performance and Higher Emotional, Cognitive, and Everyday Executive Function Symptoms Two Months After Mild Traumatic Brain Injury

Background

Substantial variance exists in outcomes after mild traumatic brain injury (MTBI), and these differences are not fully explained by injury characteristics or severity. Genetic factors are likely to play a role in this variance.

Objectives

The aim of this study was to examine associations between the apolipoprotein (APOE)-ε4 allele and memory measures at two months post-MTBI and to evaluate whether subjective cognitive and affective symptoms were associated with APOE-ε4 status. Based on previous research, it was hypothesized that APOE-ε4 carriers would show poorer verbal memory performance compared to APOE-ε4 non-carriers.

Methods

Neuropsychological data at two months post-injury and blood samples that could be used to assess APOE genotype were available for 134 patients with MTBI (mean age 39.2 years, 62% males, 37% APOE-ε4 carriers). All patients underwent computed tomography at hospital admission and magnetic resonance imaging four weeks post-injury.

Results

The APOE-ε4 + status was associated with decreased immediate memory recall (p = 0.036; β = −0.10, 95% CI [−0.19, −0.01]). Emotional, cognitive, and everyday executive function symptoms at two months post-injury were significantly higher in APOE-ε4 carriers compared to non-carriers.

Conclusion

The APOE-ε4+ allele has a negative effect on verbal memory and symptom burden two months after MTBI.

Association between Apolipoprotein E Polymorphism and Clinical Outcome after Ischemic Stroke, Intracerebral Hemorrhage, and Subarachnoid Hemorrhage

BACKGROUNDS

Previous studies reported inconsistent results regarding associations between apolipoprotein E (APOE) polymorphism and clinical outcomes after ischemic stroke (IS), intracerebral hemorrhage (ICH), or subarachnoid hemorrhage (SAH). Thus, the study was designed to make a systematic review and meta-analysis regarding the association between APOE polymorphism and clinical outcome after IS, ICH, and SAH.

METHODS

To identify studies eligible for this meta-analysis, we searched for articles published before August 2021 in the databases (PubMed, Web of Science, and Google Scholar). We used STATA 12.0 software to compute hazard ratios (HRs) and their 95% confidence intervals (CIs) regarding APOE polymorphism and clinical outcome after IS, ICH, and SAH.

RESULTS

Meta-analysis showed no significant association between APOE polymorphism and functional outcome after IS with fixed effects models (ε4 carrier vs. non-ε4 carrier: HR, 1.00; 95% CI: 0.83-1.21, I2 = 29.4%, p = 0.183; ε2 carrier vs. non-ε2 carrier: HR, 0.92; 95% CI: 0.72-1.16, I2 = 15.6%, p = 0.307). Meta-analysis showed that ICH patients carrying ε4 allele have increased risk of poor outcome in Caucasian population with fixed effects models (ε4 carrier vs. non-ε4 carrier: HR, 1.75; 95% CI: 1.19-2.57, I2 = 0.0%, p = 0.543). Meta-analysis showed no significant association between APOE polymorphism and functional outcomes after SAH with random effects models (ε4 carrier vs. non-ε4 carrier: HR, 1.51; 95% CI: 0.80-2.84, I2 = 57.1%, p = 0.022).

CONCLUSIONS

In conclusion, the present study demonstrated APOE ε4 carriers show worse functional outcomes after ICH, but not after IS or SAH. More large-scale studies were critical to explore the association between APOE polymorphism and clinical outcome after IS, ICH, and SAH.

Apolipoprotein e (APOE) ε4 genotype influences memory performance following remote traumatic brain injury in U.S. military service members and veterans

The purpose of this study was to examine the association between the apolipoprotein E (APOE) ε4 allele and neurocognitive functioning following traumatic brain injury (TBI) in military service members and veterans (SMVs). Participants included 176 SMVs with a history of remote TBI (≥1 year post-injury), categorized into mild (n = 100), moderate (n = 40), and severe (n = 36) TBI groups. Participants completed a neuropsychological assessment and APOE genotyping (n = 46 ε4+, n = 130 ε4-). Neurocognitive composite scores representing memory, executive functioning, and visual processing speed were computed. ANCOVAs adjusting for race, education, combat exposure, and PTSD symptom severity showed a significant main effect of ε4 on the memory composite, such that ε4+ SMVs exhibited poorer memory performance than ε4- SMVs. When ε2 allele carriers were removed from the analyses, associations with memory were strengthened, demonstrating a possible protective effect of the ε2 allele. No main effect of TBI group was identified on any cognitive composite, nor were there any significant TBI group × ε4 status interactions for any cognitive composite. Future studies with larger samples are needed to verify these findings, but our results suggest an important relationship between ε4 status and memory functioning following remote TBI of all severities.

Effects of Apolipoprotein Ε ε4 allele on early postoperative cognitive dysfunction after anesthesia

BACKGROUND

Postoperative cognitive dysfunction (POCD) is one of the main causes of morbidity after noncardiac surgery; however, the pathogenic mechanisms of POCD have remained unclear until now. In this study, we performed a pilot study to investigate the association between apolipoprotein E (ApoE) ε4 and POCD in older patients undergoing intravenous anesthesia (IVA) and inhalation anesthesia (IAA).

METHODS

In total, 180 patients from Shenzhen People's Hospital were recruited and randomly divided into an IVA group and an IAA group. The IVA group and IAA group received propofol and sevoflurane treatment, respectively. Within 7 days after surgery, the mini-mental state examination (MMSE) was used daily to assess the cognitive function of both groups of patients. The genotypes of the ApoE gene were detected using the restriction fragment length polymorphism technique. In addition, the serum levels of (soluble protein-100β) S‑100β and (Interleukin- 6) L‑6 were also analyzed.

RESULTS

Compared to the preoperative and IVA groups, the MMSE score in the IAA group significantly decreased at 3 days after surgery. Furthermore, the IAA group had a higher percentage of patients who scored less than 25 points than the IVA group at 3 days after surgery. The decrease in the MMSE score was closely related to the ApoE ε4 allele in the IAA group, but this correlation was not observed in the IVA group. The levels of S‑100β and IL‑6 were increased sharply in patients with the ε4/ε4 genotype who received IAA compared with IVA at 1 day after surgery.

CONCLUSION

The results of the study indicated that the ApoΕ ε4/ε4 genotype was a risk factor for early POCD in older patients undergoing sevoflurane anesthesia.

Postoperative cognitive dysfunction: an acute approach for the development of novel treatments for neuroinflammation

Inflammation within the central nervous system (CNS; neuroinflammation) is a major contributor to lasting symptoms of traumatic brain injury and stroke, and likely has a casual role Alzheimer's disease (AD) and other neurodegenerative conditions. Therapeutic modulation of the immune processes that initiate and maintain neuroinflammation is of growing scientific interest but neuroinflammatory drug development is hampered by limited reliability and availability of neuroimaging or other biomarkers in humans. Better means of establishing drug efficacy on human neuroinflammation would have great value in accelerating the development of neuroinflammatory compounds for many clinical indications. Here, we discuss the use of postoperative cognitive decline (POCD), which is hypothesised to have a neuroinflammatory basis, as an acute indication to demonstrate the efficacy of novel neuroinflammatory drugs.

Association of APOE ε4 with progressive hemorrhagic injury in patients with traumatic intracerebral hemorrhage

OBJECTIVE

The intracranial hematoma volume in patients with traumatic brain injury is a key parameter for the determination of the management approach and outcome. Apolipoprotein E (APOE) ε4 is reported to be a risk factor for larger hematoma volume, which might contribute to a poor outcome. However, whether APOE ε4 is related to progressive hemorrhagic injury (PHI), a common occurrence in the clinical setting, remains unclear. In this study, the authors aimed to investigate the association between the APOE genotype and occurrence of PHI.

METHODS

This prospective study included a cohort of 123 patients with traumatic intracerebral hemorrhage who initially underwent conservative treatment. These patients were assigned to the PHI or non-PHI group according to the follow-up CT scan. A polymerase chain reaction and sequencing method were carried out to determine the APOE genotype. Multivariate logistic regression analysis was applied to identify predictors of PHI.

RESULTS

The overall frequency of the alleles was as follows: E2/2, 0%; E2/3, 14.6%; E3/3, 57.8%; E2/4, 2.4%; E3/4, 22.8%; and E4/4, 2.4%. Thirty-four patients carried at least one allele of ε4. In this study 60 patients (48.8%) experienced PHI, and the distribution of the alleles was as follows: E2/2, 0%; E2/3, 5.7%; E3/3, 22.8%; E2/4, 2.4%; E3/4, 16.3%; and E4/4, 1.6%, which was significantly different from that in the non-PHI group (p = 0.008). Additionally, the late operation rate in the PHI group was significantly higher than that in the non-PHI group (24.4% vs 11.4%, p = 0.002). Multivariate logistic regression identified APOE ε4 (OR 5.14, 95% CI 2.40-11.62), an elevated international normalized ratio (OR 3.57, 95% CI 1.61-8.26), and higher glucose level (≥ 10 mmol/L) (OR 3.88, 95% CI 1.54-10.77) as independent risk factors for PHI. Moreover, APOE ε4 was not a risk factor for the coagulopathy and outcome of the patients with traumatic intracerebral hemorrhage.

CONCLUSIONS

The presence of APOE ε4, an elevated international normalized ratio, and a higher glucose level (≥ 10 mmol/L) are predictors of PHI. Additionally, APOE ε4 is not associated with traumatic coagulopathy and patient outcome.

Association between (GT)n Promoter Polymorphism and Recovery from Concussion: A Pilot Study

Variability in recovery among concussed athletes can be attributed to several risk factors. One risk factor not definitively explored is genetic variation. Genetic variations such as variable number tandem repeats (VNTR) in the promotor region are normal in the population, and can lead to disparities in the amount of protein produced, which could be associated with neuronal recovery. Little research has been conducted to investigate promoter VNTRs within genes responsible for recovery following a concussion. The authors implemented a prospective cohort design using a standardized concussion protocol to diagnose and follow 93 athletes to full recovery at three different sites to determine the association between promotor GT(n) VNTR polymorphisms and recovery time within concussed athletes. The GT(n) VNTR within the promoter region of glutamate ionotropic receptor N-methyl-d-aspartate (NMDA) type subunit 2A (GRIN2A), potassium voltage-gated channel subfamily H member 2 (KCNH2), glutamate ionotropic receptor kainate type subunit 1 (GRIK1), and neurofilament light (NEFL) were genotyped using capillary electrophoresis. GT(n) VNTR promotor polymorphisms were dichotomized into long (L) and short (s) alleles. Using adjusted negative binomial regression models we found that athletes carrying the LL GRIN2A GT(n) VNTR within the promoter region were more likely to experience a prolonged concussion recovery, which resulted in their not being able to return to play for ∼60 days. Additionally, there was a trend toward significance, in which the ss NEFL GT(n) Caucasian athletes had prolonged concussion recovery. This could presumably be attributed to altered proteins or protein levels that disrupt neuronal recovery. This pilot study suggests that these VNTRs are associated with prolonged concussion recovery. In future studies, we plan to measure the extent to which the L or s alleles alter the level and the activity of the GluNR2a and NEFL proteins that GRIN2A and NEFL produce, respectively.

APOE-ε4 Genotype is Associated with Elevated Post-Concussion Symptoms in Military Veterans with a Remote History of Mild Traumatic Brain Injury

OBJECTIVE

We evaluated the influence of the APOE-ε4 allele on post-concussive symptoms in military Veterans with a remote history of mild traumatic brain injury (mTBI).

METHOD

Participants (N = 77) were administered neuropsychiatric measures, on average, approximately 5 years following their most recent mTBI and provided a DNA sample for APOE genotyping. Veterans were divided into two groups based on their ε4 status (n = 14 ε4+, n = 63 ε4-). The Neurobehavioral Symptom Inventory (NSI) was the primary outcome measure, from which a total score was derived, as well as three symptom clusters (somatic, cognitive, and affective).

RESULTS

ANCOVAs showed a significant main effect of ε4 genotype on the NSI total score and somatic symptom cluster after adjusting for posttraumatic stress symptoms and mTBI history (p = .019-.028, ηp2 = .064-.073), such that ε4+ Veterans endorsed significantly greater symptoms than ε4- Veterans.

CONCLUSIONS

Our findings suggest that genetic risk may help to explain the poorer long-term outcomes often observed in this population.

Close-Range Blast Exposure Is Associated with Altered White Matter Integrity in Apolipoprotein ɛ4 Carriers

Evidence suggests that blast exposure has profound negative consequences for the health of the human brain, and that it may confer risk for the development of neurodegenerative diseases such as chronic traumatic encephalopathy and Alzheimer's disease (AD). Although the molecular mechanisms linking blast exposure to subsequent neurodegeneration is an active focus of research, recent studies suggest that genetic risk for AD may elevate the risk of neurodegeneration following traumatic brain injury (TBI). However, it is currently unknown if blast exposure also interacts with AD risk to promote neurodegeneration. In this study we examined whether apolipoprotein (APOE) ɛ4, a well-known genetic risk factor for AD, influenced the relationship between blast exposure and white matter integrity in a cohort of 200 Iraq and Afghanistan war veterans. Analyses revealed a significant interaction between close-range blast exposure (CBE) (close range being within 10 m) and APOE ɛ4 carrier status in predicting white matter abnormalities, measured by a voxelwise cluster-based method that captures spatial heterogeneity in white matter disruptions. This interaction remained significant after controlling for TBI, pointing to the specificity of CBE and APOE in white matter disruptions. Further, among veteran ɛ4 carriers exposed to close-range blast, we observed a positive association between the number of CBEs and the number of white matter abnormalities. These results raise the possibility that CBE interacts with AD genetic influences on neuropathological processes such as the degradation of white matter integrity.

Executive functions

Executive functions (EFs) include high-order cognitive abilities such as working memory, inhibitory control, cognitive flexibility, planning, reasoning, and problem solving. EFs enable humans to achieve goals, adapt to novel everyday life situations, and manage social interactions. Traditionally EFs have been associated with frontal lobe functioning. More recent evidence shows that posterior and subcortical regions also play a crucial role in EF processing, especially in the integration of sensory information and emotion. This chapter reviews the variety of EFs and their neural underpinning, based on lesion mapping and neuroimaging studies, as well as the evidence for rehabilitation interventions, neuropsychological assessment based on standard and ecologically valid tests, development, and genetic predisposition for recovery of executive functions after brain injury. Taken together, the EFs are critical for unique human abilities and more careful analyses of their subcomponents may help the development of targeted translational interventions to improve them.

Rehabilitation Needs of the Elder with Traumatic Brain Injury

The incidence of traumatic brain injury (TBI) in older adults is increasing. As the expected life expectancy increases, there is a heightened need for comprehensive rehabilitation for this population. Elderly patients with TBI benefit from rehabilitation interventions at all stages of injury and can achieve functional gains during acute inpatient rehabilitation. Clinicians should be vigilant of unique characteristics of this population during inpatient rehabilitation, including vulnerability to polypharmacy, posttraumatic hydrocephalus, neuropsychiatric sequelae, sleep disturbances, and sensory deficits. Long-term care should include fall prevention, assessment of cognitive deficits, aerobic activity, community reintegration, and caretaker support. Life expectancy is reduced after TBI.

The Role of Neuroinflammation in Postoperative Cognitive Dysfunction: Moving From Hypothesis to Treatment

Postoperative cognitive dysfunction (POCD) is a common complication of the surgical experience and is common in the elderly and patients with preexisting neurocognitive disorders. Animal and human studies suggest that neuroinflammation from either surgery or anesthesia is a major contributor to the development of POCD. Moreover, a large and growing body of literature has focused on identifying potential risk factors for the development of POCD, as well as identifying candidate treatments based on the neuroinflammatory hypothesis. However, variability in animal models and clinical cohorts makes it difficult to interpret the results of such studies, and represents a barrier for the development of treatment options for POCD. Here, we present a broad topical review of the literature supporting the role of neuroinflammation in POCD. We provide an overview of the cellular and molecular mechanisms underlying the pathogenesis of POCD from pre-clinical and human studies. We offer a brief discussion of the ongoing debate on the root cause of POCD. We conclude with a list of current and hypothesized treatments for POCD, with a focus on recent and current human randomized clinical trials.

Blood-based metabolic signatures in Alzheimer's disease

Introduction

Identification of blood-based metabolic changes might provide early and easy-to-obtain biomarkers.

Methods

We included 127 Alzheimer's disease (AD) patients and 121 control subjects with cerebrospinal fluid biomarker-confirmed diagnosis (cutoff tau/amyloid β peptide 42: 0.52). Mass spectrometry platforms determined the concentrations of 53 amine compounds, 22 organic acid compounds, 120 lipid compounds, and 40 oxidative stress compounds. Multiple signatures were assessed: differential expression (nested linear models), classification (logistic regression), and regulatory (network extraction).

Results

Twenty-six metabolites were differentially expressed. Metabolites improved the classification performance of clinical variables from 74% to 79%. Network models identified five hubs of metabolic dysregulation: tyrosine, glycylglycine, glutamine, lysophosphatic acid C18:2, and platelet-activating factor C16:0. The metabolite network for apolipoprotein E (APOE) ε4 negative AD patients was less cohesive compared with the network for APOE ε4 positive AD patients.

Discussion

Multiple signatures point to various promising peripheral markers for further validation. The network differences in AD patients according to APOE genotype may reflect different pathways to AD.

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Multiple metabolic signatures point to peripheral AD markers for future validation.

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AD may be described by changes in the metabolism of amines and oxidative stressors.

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APOE ε4-driven AD and non- APOE ε4-driven AD represent different biochemical pathways.

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Network analyses of metabolomics data enable the study of metabolic changes in AD.

Making Stem Cell Lines Suitable for Transplantation

Human stem cells, progenitor cells, and cell lines have been derived from embryonic, fetal, and adult sources in the search for graft tissue suitable for the treatment of CNS disorders. An increasing number of experimental studies have shown that grafts from several sources survive, differentiate into distinct cell types, and exert positive functional effects in experimental animal models, but little attention has been given to developing cells under conditions of good manufacturing practice (GMP) that can be scaled up for mass treatment. The capacity for continued division of stem cells in culture offers the opportunity to expand their production to meet the widespread clinical demands posed by neurodegenerative diseases. However, maintaining stem cell division in culture long term, while ensuring differentiation after transplantation, requires genetic and/or oncogenetic manipulations, which may affect the genetic stability and in vivo survival of cells. This review outlines the stages, selection criteria, problems, and ultimately the successes arising in the development of conditionally immortal clinical grade stem cell lines, which divide in vitro, differentiate in vivo, and exert positive functional effects. These processes are specifically exemplified by the murine MHP36 cell line, conditionally immortalized by a temperature-sensitive mutant of the SV40 large T antigen, and cell lines transfected with the c-myc protein fused with a mutated estrogen receptor (c-mycERTAM), regulated by a tamoxifen metabolite, but the issues raised are common to all routes for the development of effective clinical grade cells.

ApoE ε4 Is Associated With Cognition, Brain Integrity, and Atrophy in HIV Over Age 60

BACKGROUND

There are contradicting reports on the associations between Apolipoprotein E4 (ApoE ε4) and brain outcomes in HIV with some evidence that relationships may be greatest in older age groups.

METHODS

We assessed cognition in 76 clinically stable HIV-infected participants over age 60 and genotyped ApoE. Sixty-one of these subjects underwent structural brain magnetic resonance imaging and diffusion tensor imaging.

RESULTS

The median age of the participants was 64 years (range: 60-84) and the median estimated duration of HIV infection was 22 years. Apo ε4 carriers (n = 19) were similar to noncarriers (n = 57) in sex (95% vs. 96% male), and education (16.0 vs. 16.2 years) ApoE ε4 carriers demonstrated greater deficits in cognitive performance in the executive domain (P = 0.045) and had reduced fractional anisotropy and increased mean diffusivity throughout large white matter tracts within the brain compared with noncarriers. Tensor-based morphometry analyses revealed ventricular expansion and atrophy in the posterior corpus callosum, thalamus, and brainstem among HIV-infected ApoE ε4 carriers compared with ε4 noncarriers.

CONCLUSIONS

In this sample of older HIV-infected individuals, having at least 1 ApoE ε4 allele was associated with decreased cognitive performance in the executive functioning domain, reduced brain white matter integrity, and brain atrophy. Brain atrophy was most prominent in the posterior corpus callosum, thalamus, and brainstem. This pattern of cognitive deficit, atrophy, and damage to white matter integrity was similar to that described in HIV, suggesting an exacerbation of HIV-related pathology; although emergence of other age-associated neurodegenerative disorders cannot be excluded.

Viral and host factors associated with outcomes of hepatitis C virus infection (Review)

Hepatitis C virus (HCV) infection is a major health issue globally. Owing to the progress made in host genetics and HCV molecular virology, emerging data have suggested that the natural course and treatment response in patients with HCV infection are largely determined by complex host‑viral interactions. HCV genotype is the most important viral factor predicting the response to pegylated interferon‑α plus ribavirin therapy. The subtype of HCV genotype 1 is the key viral factor that predicts the efficacy of direct‑acting antiviral therapy. HCV genome heterogeneity and baseline viral load are additionally associated with the treatment response. Multiple host genetic variants localized in genes associated with the immune response have been identified as predictors of spontaneous disease course and therapy outcome in chronic HCV. However, most findings from candidate gene association studies have not been proven universal for all investigated populations and independent studies. Previous findings in independent large genome wide association studies confirmed that interferon‑λ3 gene polymorphisms are associated with spontaneous clearance and treatment responsiveness. A polymorphism of the inosine triphosphatase gene has been identified as a protective factor against ribavirin‑induced anemia and dose reductions. Another genetic variant in the patatin‑like phospholipase domain containing 3 genes is associated with hepatic steatosis and fibrosis in patients with HCV. The present review focused on the identified viral and host factors associated with outcomes of patients with HCV, and assessed the involvement of viral and host genetics in the natural history and treatment outcomes of HCV infection. This will provide novel ideas concerning personalized prevention and individualized clinical management.

Apolipoprotein E4 causes early olfactory network abnormalities and short-term olfactory memory impairments

While apolipoprotein (Apo) E4 is linked to increased incidence of Alzheimer's disease (AD), there is growing evidence that it plays a role in functional brain irregularities that are independent of AD pathology. However, ApoE4-driven functional differences within olfactory processing regions have yet to be examined. Utilizing knock-in mice humanized to ApoE4 versus the more common ApoE3, we examined a simple olfactory perceptual memory that relies on the transfer of information from the olfactory bulb (OB) to the piriform cortex (PCX), the primary cortical region involved in higher order olfaction. In addition, we have recorded in vivo resting and odor-evoked local field potentials (LPF) from both brain regions and measured corresponding odor response magnitudes in anesthetized young (6-month-old) and middle-aged (12-month-old) ApoE mice. Young ApoE4 compared to ApoE3 mice exhibited a behavioral olfactory deficit coinciding with hyperactive odor-evoked response magnitudes within the OB that were not observed in older ApoE4 mice. Meanwhile, middle-aged ApoE4 compared to ApoE3 mice exhibited heightened response magnitudes in the PCX without a corresponding olfactory deficit, suggesting a shift with aging in ApoE4-driven effects from OB to PCX. Interestingly, the increased ApoE4-specific response in the PCX at middle-age was primarily due to a dampening of baseline spontaneous activity rather than an increase in evoked response power. Our findings indicate that early ApoE4-driven olfactory memory impairments and OB network abnormalities may be a precursor to later network dysfunction in the PCX, a region that not only is targeted early in AD, but may be selectively vulnerable to ApoE4 genotype.

Olfactory Dysfunction in ApoE ɛ4/4 Homozygotes with Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory impairment and the presence of amyloid plaques and neurofibrillary tangles. The associated neuropathology originates in brain areas responsible for olfaction, which makes olfactory tasks potentially useful for assessing AD. The strongest genetic risk factor for AD is the apolipoprotein E (ApoE) ɛ4 allele that has been associated with increased cognitive and olfactory deficits. While individuals carrying one ɛ4 allele of the ApoE gene are at increased risk for AD relative to non-carriers, those with two copies of the ɛ4 allele demonstrate an even higher risk for developing AD. Furthermore, homozygous ApoE ɛ4/4 individuals diagnosed with AD are known to have heightened amyloid burden and a more rapid rate of cognitive decline relative to heterozygous ɛ3/4 ApoE carriers. All of these factors suggest there are differences in severity and progression of AD as a function of possessing one versus two ɛ4 alleles. The current study investigated olfactory functioning in homozygous ɛ4/4 older adults diagnosed with probable AD. Compared to demographically matched ɛ3/3 and ɛ3/4 individuals, ɛ4/4 individuals showed deficits in odor identification and remote odor memory as measured by odor familiarity ratings. The current findings suggest that these particular domains of olfactory functioning may be more impaired in AD ɛ4/4 homozygotes compared to ɛ3/4 heterozygotes and ɛ3/3 homozygotes. These deficits give insight into how the presence of two ɛ4 alleles may differentially affect the progression of AD and suggest the usefulness of odor tasks in detecting those at risk for AD.

Plasma Lipidomic Profiling in a Military Population of Mild Traumatic Brain Injury and Post-Traumatic Stress Disorder with Apolipoprotein E ɛ4-Dependent Effect

In the military population, there is high comorbidity between mild traumatic brain injury (mTBI) and post-traumatic stress disorder (PTSD) due to the inherent risk of psychological trauma associated with combat. These disorders present with long-term neurological dysfunction and remain difficult to diagnose due to their comorbidity and overlapping clinical presentation. Therefore, we performed cross-sectional analysis of blood samples from demographically matched soldiers (total, n = 120) with mTBI, PTSD, and mTBI+PTSD and those who were considered cognitively and psychologically normal. Soldiers were genotyped for apolipoprotein E (APOE) ɛ4, and phospholipids (PL) were examined using liquid chromatography/mass spectrometry analysis. We observed significantly lower levels of several major PL classes in TBI, PTSD, and TBI+PTSD, compared with controls. PTSD severity analysis revealed that significant PL decreases were primarily restricted to the moderate-to-severe PTSD group. An examination of the degree of unsaturation showed that monounsaturated fatty acid-containing phosphatidylcholine (PC) and phosphatidylinositol (PI) species were lower in the TBI and TBI+PTSD groups. However, these PLs were unaltered among PTSD subjects, compared with controls. Similarly, ether PC (ePC) levels were lower in PTSD and TBI+PTSD subjects, relative to controls. Ratios of arachidonic acid (AA) to docosahexaenoic acid (DHA)-containing species were significantly decreased within PC and phosphatidylethanolamine (PE) classes. APOE ɛ4 (+) subjects exhibited higher PL levels than their APOE ɛ4 (-) counterparts within the same diagnostic groups. These findings suggest that PL profiles, together with APOE genotyping, could potentially aid to differentiate diagnosis of mTBI and PTSD and warrant further validation. In conclusion, PL profiling may facilitate clinical diagnosis of mTBI and PTSD currently hindered by comorbid pathology and overlapping symptomology of these two conditions.

Common variants of APOE are associated with anti-epileptic drugs resistance in Han Chinese patients

Purpose/aim of the study: Apolipoprotein E (APOE) has been implicated as one of the susceptibility genes for some subtypes of epilepsy and may be related to anti-epileptic drugs resistance. The purpose of this study was to investigate the possible association between APOE variants and the anti-epileptic drugs resistance in Chinese population.

MATERIALS AND METHODS

APOE gene rs429358 and rs7412 variants were genotyped for ϵ2, ϵ3, ϵ4 alleles using amplification refractory mutation system in 480 subjects including 207 anti-epileptic drugs-resistant patients and 273 drug-responsive patients.

RESULTS

We found that the frequency of APOE gene rs429358 C allele in the drug resistant patients is higher than that in the drug-responsive patients (14.98% vs. 10.1%, OR = 1.25[1.02 - 1.52], p = 0.017). Moreover, according to the two variants, we analyzed the distributions of -ϵ4 and +ϵ4 alleles of APOE gene and found that there were higher frequencies of +ϵ4 allele in drug-resistant epileptic patients than that in drug-responsive patients (31.8% vs. 13.2%, OR = 1.15[1.05 - 1.25], p = 0.002).

CONCLUSIONS

Our study demonstrated that APOE rs429358 variant C allele and ϵ4 allele were associated with the anti-epileptic drugs resistance in Han Chinese patients.

Effect of 10 different polymorphisms on preoperative volumetric characteristics of glioblastoma multiforme

There is a distinct diversity between the appearance of every glioblastoma multiforme (GBM) on pretreatment magnetic resonance imaging (MRI) with a potential impact on clinical outcome and survival of the patients. The object of this study was to determine the impact of 10 different single nucleotide polymorphisms (SNPs) on various volumetric parameters in patients harboring a GBM. We prospectively analyzed 20 steroid-naïve adult patients who had been treated for newly diagnosed GBM. The volumetry was performed using MRI with the help of a semiautomated quantitative software measuring contrast enhancing tumor volume including necrosis, central necrosis alone and peritumoral edema (PTE). We calculated ratios between the tumor volume and edema (ETR), respectively necrosis (NTR). SNP analysis was done using genomic DNA extracted from peripheral blood genotyped via PCR and sequencing. There was a strong correlation between tumor volume and PTE (p < 0.001), necrosis (p < 0.001) and NTR (p = 0.003). Age and sex had no influence on volumetric data. The Aquaporin 4-31G > A SNP had a significant influence on the ETR (p = 0.042) by decreasing the measured edema compared with the tumor volume. The Interleukin 8-251A > T SNP was significantly correlated with an increased tumor (p = 0.048), PTE (p = 0.033) and necrosis volume (p = 0.028). We found two SNPs with a distinct impact on pretreatment tumor characteristics, presenting a potential explanation for the individual diversity of GBM appearance on MRI and influence on survival.

Genetic Variation of ApoE Gene in Ethnic Kashmiri Population and Its Association with Outcome After Traumatic Brain Injury

The outcome from traumatic brain injury (TBI) is variable and only partly explained by known prognostic factors. Genetic factors may influence the brain's susceptibility to injury or capacity for repair and regeneration. ApoE has been implicated in modifying neurological outcome after TBI, although the mechanisms by which this occurs remain poorly defined. Apolipoprotein E is an apparently multifunctional protein involved in the response of the brain to injury and in subsequent repair processes. Several studies have shown that patients with APOE e4 have a poorer outcome after TBI. This study was aimed to analyse the genotypes of ApoE in Kashmiri population and to examine the association of APOE genotype with outcome after TBI. A total of 450 subjects (300 healthy controls and 150 TBI patients) were recruited for the study. Genotyping was done by PCR-restriction fragment length polymorphism (RFLP).Our study indicated Apoe3/e3 to be the most common genotype in this study group. The allele frequency of the Apo E gene in these study subjects was observed to be 0.07 for the e2 allele, 0.82 for the e3 allele and 0.11 for the e4 allele. However, no association between the presence of APOe4 allele and outcome after head injury was observed in this study [p = 0.92]. Thus, genotype containing the e4 allele (e4/e3 and e4/e4) was not associated with unfavourable outcome after TBI in Kashmiri population.

Homozygosity in the ApoE 4 polymorphism is associated with dysphagic symptoms in older adults

Apolipoprotein E (ApoE) is the most well-described genetic risk factor for Alzheimer's disease and nonpathological cognitive decline. While possession of the E2 allele may have protective properties, substantial research evidence suggests the E4 allele increases the risk of cognitive degeneration. As neurodegenerative processes are implicated in swallowing dysfunction, we hypothesized that the presence of ApoE 4 would be predictive of dysphagia symptoms in older adults. Eight hundred members of a genetically well characterized community dwelling elderly cohort received the Sydney oropharyngeal dysphagia questionnaire via mail. Cognitive function was also measured using the modified Telephone Interview of Cognitive Status (TiCS-m) and depression with the Geriatric Depression Score (GDS). ApoE allele was genotyped on blood samples from all subjects and data analyzed using standard statistical software (SPSS version 16). Completed questionnaire response rate was 79% (23.5% men, 76.5% women; mean age 81 ± 5 years; range 69-98 years). Possession of one or more of the ApoE 4 and 2 alleles was found in 23.5% and 16%, respectively. Swallowing score was significantly related to GDS (rho 0.133, P < 0.001**) and age (rho 0.107, P < 0.007**) but not general cognitive function as measured by TICS-m. Self-reported swallowing function was not significantly associated with heterozygosity of any allele or homozygosity for E2 or E3 alleles. Although infrequent (1.1% of all subjects) ApoE E4 homozygosity was significantly associated with higher swallowing scores compared to all other allele combinations (P = 0.033) and while attenuated, was still predicted in multivariate regression modeling (B = 0.812; SE = 0.323; P = 0.012). We report the association between ApoE 4 homozygous genotype and self-reported oropharyngeal dysphagia symptoms in community-dwelling older adults. As this association is weakened by the multivariate analysis and the population frequency of ApoE 4 allele homozygosity is low, this finding while intriguing requires replication in larger independent cohorts.

Molecular regulation of synaptogenesis during associative learning and memory

Synaptogenesis plays a central role in associative learning and memory. The biochemical pathways that underlie synaptogenesis are complex and incompletely understood. Nevertheless, research has so far identified three conceptually distinct routes to synaptogenesis: cell-cell contact mediated by adhesion proteins, cell-cell biochemical signaling from astrocytes and other cells, and neuronal signaling through classical ion channels and cell surface receptors. The cell adhesion pathways provide the physical substrate to the new synaptic connection, while cell-cell signaling may provide a global or regional signal, and the activity-dependent pathways provide the neuronal specificity that is required for the new synapses to produce functional neuronal networks capable of storing associative memories. These three aspects of synaptogenesis require activation of a variety of interacting biochemical pathways that converge on the actin cytoskeleton and strengthen the synapse in an information-dependent manner. This article is part of a Special Issue titled SI: Brain and Memory.

The dark sides of amyloid in Alzheimer's disease pathogenesis

Although widely explored, the pathogenesis of Alzheimer's disease (AD) has yet to be cleared. Over the past twenty years the so call amyloid cascade hypothesis represented the main research paradigm in AD pathogenesis. In spite of its large consensus, the proposed role of β-amyloid (Aβ) remain to be elucidated. Many evidences are starting to cast doubt on Aβ as the primary causative factor in AD. For instance, Aβ is deposited in the brain following many different kinds of injury. Also, concentration of Aβ needed to induce toxicity in vitro are never reached in vivo. In this review we propose an amyloid-independent interpretation of several AD pathogenic features, such as synaptic plasticity, endo-lysosomal trafficking, cell cycle regulation and neuronal survival.

Apolipoprotein E gene polymorphism, alcohol use, and their interactions in combat-related posttraumatic stress disorder

BACKGROUND

The symptomatology of posttraumatic stress disorder (PTSD) is related not only to the intensity of the causative trauma, but also to alcohol use and genetic factors. Among the many candidate genes, the apolipoprotein E gene (APOE) is thought to be associated with stress reactivity.

METHODS

Korean veterans of the Vietnam War with (n = 128) or without (n = 128) PTSD participated in this study. The Clinician-Administered PTSD Scale and Combat Exposure Scale were administered, and the severity of alcohol use was assessed among these veterans. The APOE polymorphism and clinical variables of the subjects were compared, and associations between PTSD and potential explanatory variables were tested using logistic regression analysis.

RESULTS

Higher frequencies of APOE ε2 alleles and a greater number of individuals with the ε2 allele were found in the PTSD group. Among patients with PTSD, ε2-allele noncarriers consumed alcohol in greater amounts and more frequently than did ε2-allele carriers. Regression analysis revealed a significant interactional effect between harmful drinking and the absence of the ε2 allele associated with PTSD risk.

CONCLUSIONS

These results suggest that the APOE ε2 allele operates as a susceptibility gene for combat-related PTSD, with the relationship between alcohol use and PTSD differing according to the ε2-allele status. Future studies should determine the role of the APOE in adaptation to extreme stress, the development of PTSD, and comorbid alcohol-related disorders.

Increased CSF levels of phosphorylated neurofilament heavy protein following bout in amateur boxers

Introduction

Diagnosis of mild TBI is hampered by the lack of imaging or biochemical measurements for identifying or quantifying mild TBI in a clinical setting. We have previously shown increased biomarker levels of protein reflecting axonal (neurofilament light protein and tau) and glial (GFAP and S-100B) damage in cerebrospinal fluid (CSF) after a boxing bout. The aims of this study were to find other biomarkers of mild TBI, which may help clinicians diagnose and monitor mild TBI, and to calculate the role of APOE ε4 allele genotype which has been associated with poor outcome after TBI.

Materials and Methods

Thirty amateur boxers with a minimum of 45 bouts and 25 non-boxing matched controls were included in a prospective cohort study. CSF and blood were collected at one occasion between 1 and 6 days after a bout, and after a rest period for at least 14 days (follow up). The controls were tested once. CSF levels of neurofilament heavy (pNFH), amyloid precursor proteins (sAPPα and sAPPβ), ApoE and ApoA1 were analyzed. In blood, plasma levels of Aβ42 and ApoE genotype were analyzed.

Results

CSF levels of pNFH were significantly increased between 1 and 6 days after boxing as compared with controls (p<0.001). The concentrations decreased at follow up but were still significantly increased compared to controls (p = 0.018). CSF pNFH concentrations correlated with NFL (r =  0.57 after bout and 0.64 at follow up, p<0.001). No significant change was found in the other biomarkers, as compared to controls. Boxers carrying the APOE ε4 allele had similar biomarker concentrations as non-carriers.

Conclusions

Subconcussive repetitive trauma in amateur boxing causes a mild TBI that may be diagnosed by CSF analysis of pNFH, even without unconsciousness or concussion symptoms. Possession of the APOE ε4 allele was not found to influence biomarker levels after acute TBI.

Role of peripheral inflammatory markers in postoperative cognitive dysfunction (POCD): a meta-analysis

Background

Postoperative cognitive dysfunction (POCD) is common following cardiac and non-cardiac surgery, but the pathogenic mechanisms remain unknown. Many studies suggest that an inflammatory response is a key contributor to POCD. The current meta-analysis shows that the levels of peripheral inflammatory markers are associated with POCD.

Methods

An online search was performed to identify peer-reviewed studies without language restriction that measured peripheral inflammatory markers of patients with and without POCD, using PubMed, ScienceDirect, SinoMed and the National Knowledge Infrastructure database. Extracted data were analyzed with STATA (version 12).The standardized mean difference (SMD) and the 95% confidence interval (95%CI) were calculated for each outcome using a random effect model. Tests of heterogeneity assessment of bias, and meta-regression were performed in the meta-analysis.

Results

A total of 13 studies that measured the concentrations of peripheral inflammatory markers were included. The current meta-analysis found significantly higher concentrations of S-100β(SMD[95%CI]) (1.377 [0.423, 2.331], p-value < 0.001, N [POCD/non-POCD] =178/391, 7 studies), and interleukin(IL)-6 (SMD[95%CI]) (1.614 [0.603,2.624], p-value < 0.001, N[POCD/non-POCD] = 91/99, 5 studies), but not of neuron specific enolase, interleukin-1β, or tumor necrosis factor-α , in POCD compared with patients without POCD. In meta-regression analyses, a significant positive association was found between the SMD and the preoperative interleukin-6 peripheral blood concentration in patients with POCD (Coef.= 0.0587, p-value=0.038, 5 studies).

Conclusions

This study shows that POCD is indeed correlated with the concentrations of peripheral inflammatory markers, particularly interleukin-6 and S-100β.

The neuropathology and neurobiology of traumatic brain injury

The acute and long-term consequences of traumatic brain injury (TBI) have received increased attention in recent years. In this Review, we discuss the neuropathology and neural mechanisms associated with TBI, drawing on findings from sports-induced TBI in athletes, in whom acute TBI damages axons and elicits both regenerative and degenerative tissue responses in the brain and in whom repeated concussions may initiate a long-term neurodegenerative process called dementia pugilistica or chronic traumatic encephalopathy (CTE). We also consider how the neuropathology and neurobiology of CTE in many ways resembles other neurodegenerative illnesses such as Alzheimer's disease, particularly with respect to mismetabolism and aggregation of tau, β-amyloid, and TDP-43. Finally, we explore how translational research in animal models of acceleration/deceleration types of injury relevant for concussion together with clinical studies employing imaging and biochemical markers may further elucidate the neurobiology of TBI and CTE.

The influence of cerebral small vessel disease on default mode network deactivation in mild cognitive impairment

Introduction

Cerebral small vessel disease (CSVD) is thought to contribute to cognitive dysfunction in patients with mild cognitive impairment (MCI). The underlying mechanisms, and more specifically, the effects of CSVD on brain functioning in MCI are incompletely understood. The objective of the present study was to examine the effects of CSVD on brain functioning, activation and deactivation, in patients with MCI using task-related functional MRI (fMRI).

Methods

We included 16 MCI patients with CSVD, 26 MCI patients without CSVD and 25 controls. All participants underwent a physical and neurological examination, neuropsychological testing, structural MRI, and fMRI during a graded working memory paradigm.

Results

MCI patients with and without CSVD had a similar neuropsychological profile and task performance during fMRI, but differed with respect to underlying (de)activation patterns. MCI patients with CSVD showed impaired deactivation in the precuneus/posterior cingulate cortex, a region known to be involved in the default mode network. In MCI patients without CSVD, brain activation depended on working memory load, as they showed relative ‘hyperactivation’ during vigilance, and ‘hypoactivation’ at a high working memory load condition in working memory related brain regions.

Conclusions

We present evidence that the potential underlying mechanism of CSVD affecting cognition in MCI is through network interference. The observed differences in brain activation and deactivation between MCI patients with and without CSVD, who had a similar ‘clinical phenotype’, support the view that, in patients with MCI, different types of pathology can contribute to cognitive impairment through different pathways.

Does Apolipoprotein E Play a Role in Outcome After Severe Traumatic Brain Injury?

There is mixed evidence linking adverse outcomes after traumatic brain injury to the presence of the ε4 allele of the apolipoprotein gene (APOE). Further, there has been limited investigation of the role of APOE in populations who have sustained severe brain injuries. In this study, 100 individuals aged 16 to 65 years with a severe to extremely severe traumatic brain injury were recruited prospectively from an inpatient rehabilitation unit. APOE genotypes were determined, and demographic and clinical data were collected by blind assessors at 6 months postinjury. Sixty-nine participants who were divided into an acute (less than 12 months postinjury) and chronic (greater than 12 months) groups also completed neuropsychological assessments testing various domains of memory, attention and problem-solving at follow-up. No significant differences in injury severity, cognitive or functional outcome were found between individuals with the ε4 allele and those without at either time postinjury. This finding is consistent with other recent data that has questioned the role of APOE status as a factor in recovery from TBI.

Proteomic analysis of mitochondria in APOE transgenic mice and in response to an ischemic challenge

Apolipoprotein E (APOE)-ɛ4 is associated with a deleterious outcome after ischemic brain injury, which may involve abnormal regulation of mitochondrial function. We have assessed the mitochondrial proteomic response of APOE-ɛ3 and APOE-ɛ4 transgenic mice to transient global ischemic injury in the hippocampus. A genotype-dependent increase in ApoE levels in mitochondria was observed after ischemia, with APOE-ɛ4 mice showing significantly greater increases than APOE-ɛ3 mice. Quantitative analysis of the mitochondria-enriched fractions was performed using liquid-chromatography mass spectrometry coupled to label-free analysis. Of the 1,067 identified proteins, 274 were mitochondria associated. Mitochondrial protein expression was significantly different between genotypes under basal conditions as well as in response to global ischemia. A total of 12 mitochondrial proteins (including respiratory chain proteins NDUFA11, NDUFS3, NDUF5B, ATP5J, as well as ETFA, CYB5B, ATP6V1A, HSPA1B, OXR1, GLUL, IARS2, and PHYHIPL) were significantly altered with respect to genotype, global ischemia, or their interaction (P<0.01). A compelling interactome, created using proteins found to be significantly modulated by global ischemia (P<0.05), involved proteins that regulate energy production and oxidative stress. Thus, APOE genotype has a differential effect on the mitochondrial protein expression in the absence and presence of an injury, which may underlie the differing genotype susceptibility.

Peripheral markers in neurodegenerative patients and their first-degree relatives

We have determined various biomarkers in the peripheral blood of Alzheimer, Parkinson and vascular dementia patients by comparing the samples with those of first-degree relatives and control subjects. Our results, together with correlation studies using data from the Mini-Mental State Examination (MMSE), suggest that the clinical evaluation of the nitrite (NOx) concentration in Alzheimer patients should be complemented by assays of protein carbonyls (PCs) levels, the ratio of reduced to oxidized glutathione (GSH/GSSG) in plasma, PCs in erythrocytes and PCs and calcium content in leukocytes. For Parkinson patients it would be useful to determine NOx, thiobarbituric-acid reactive substances (TBARS) and PCs in erythrocytes, and NOx and TBARS en leukocytes. For vascular-demented (VD) patients, determination of NOx, Cu, and GSH/GSSG in plasma and TBARS, and PCs in erythrocytes together with PCs in leukocytes should be assayed. Relatives of Alzheimer patients showed alterations in plasma Se and Zn concentrations, catalase (CAT) activity in erythrocytes and calcium content in leukocytes as possible predictive markers of the disease. Relatives of Parkinson patients showed elevated levels of NOx in leukocytes. In the case of vascular-demented patients we suggest NOx, GSH/GSSG and α-tocopherol in plasma, the CAT/superoxide dismutase ratio in erythrocytes and TBARS, GSSG and glutathione reductase in leukocytes as predictive markers. Large-scale longitudinal population-based studies using these suggested biomarkers are necessary in order to assess their level of reliability and specificity in clinical practice.

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.

Association between APOE genotype, neuropathology and dementia in the older population of England and Wales

AIMS

Apolipoprotein E (APOE) genotype is the major genetic risk factor for sporadic Alzheimer's disease (AD) but it is unclear how this is mediated. Most studies of APOE genotype have used case-control design to compare groups differing by two variables: i.e. dementia and AD pathology, so it is unclear to which of these variables APOE genotype is more strongly related. The prospective Medical Research Council Cognitive Function and Ageing Study neuropathology cohort is population-based sample in which donations are unbiased by dementia status.

METHODS

We investigated the association between APOE genotypes and neuropathological and cognitive data in this cohort (n = 310).

RESULTS

APOEε4 was associated with an increased risk of diffuse plaques, neuritic plaques, tangles and cerebral amyloid angiopathy. APOEε4 was not associated with infarcts, lacunes, haemorrhages or small vessel disease. APOEε2 appeared to have a protective effect on AD pathology and also on the risk of cortical atrophy. APOE genotype had a non-significant effect on the presence of dementia after adjusting for AD pathology.

CONCLUSIONS

APOE genotype is associated with each of the key features of AD pathology but not with cerebrovascular disease other than cerebral amyloid angiopathy. The excess risk of dementia in those with an APOEε4 allele is explained by the pathological features of AD. However, it remains unclear to what extent cognitive dysfunction is caused by these specific pathological features or more directly by closely related APOE-associated mechanisms.

ApoE isoform-specific regulation of regeneration in the peripheral nervous system

Apolipoprotein E (apoE) is a 34 kDa glycoprotein with three distinct isoforms in the human population (apoE2, apoE3 and apoE4) known to play a major role in differentially influencing risk to, as well as outcome from, disease and injury in the central nervous system. In general, the apoE4 allele is associated with poorer outcomes after disease or injury, whereas apoE3 is associated with better responses. The extent to which different apoE isoforms influence degenerative and regenerative events in the peripheral nervous system (PNS) is still to be established, and the mechanisms through which apoE exerts its isoform-specific effects remain unclear. Here, we have investigated isoform-specific effects of human apoE on the mouse PNS. Experiments in mice ubiquitously expressing human apoE3 or human apoE4 on a null mouse apoE background revealed that apoE4 expression significantly disrupted peripheral nerve regeneration and subsequent neuromuscular junction re-innervation following nerve injury compared with apoE3, with no observable effects on normal development, maturation or Wallerian degeneration. Proteomic isobaric tag for relative and absolute quantitation (iTRAQ) screens comparing healthy and regenerating peripheral nerves from mice expressing apoE3 or apoE4 revealed significant differences in networks of proteins regulating cellular outgrowth and regeneration (myosin/actin proteins), as well as differences in expression levels of proteins involved in regulating the blood-nerve barrier (including orosomucoid 1). Taken together, these findings have identified isoform-specific roles for apoE in determining the protein composition of peripheral nerve as well as regulating nerve regeneration pathways in vivo.

Long-term post-operative cognitive decline in the elderly: the effects of anesthesia type, apolipoprotein E genotype, and clinical antecedents

Cognitive dysfunction in the elderly commonly observed following anesthesia has been attributed to age-related neuronal changes exacerbated by pharmacotoxic effects. However, the extent to which these changes may persist following recovery from surgery is still largely unknown. This study investigates the long-term effects of anesthesia on cognitive functioning after orthopedic surgery in 270 elderly patients over the age of 65 who completed a computerized cognitive battery before and 8 days, 4 and 13 months after surgery. Their performance was compared to those of 310 elderly controls who completed the same neuropsychiatric evaluation at baseline and one-year interval. Multivariate analyses adjusted for socio-demographic variables, depressive symptomatology, vascular pathology as well as baseline cognitive performance. We found early and transient post-operative decline in reaction time and constructional praxis. With regard to long-term changes we observed improvement compared to controls in most verbal tasks (probably due to learning effects). On the other hand, a clear dissociation effect was observed for several areas of visuospatial functioning which persisted up to the 13-month follow-up. This specific pattern of visuospatial deficit was found to be independent of apolipoprotein E genotype and closely resembles what has recently been termed vascular mild cognitive impairment, in turn associated with subtle sub-cortical vascular changes. The observation of only minor differences between persons operated by general and regional anesthesia makes it difficult to attribute these changes directly to the anesthetic agents themselves, suggesting that cognitive dysfunction may be attributable at least in part to peri-operative conditions, notably stress and glucocorticoid exposure.

Viral hepatitis: human genes that limit infection

Treatment response and susceptibility to chronic viral hepatitis C and B may be modified by host genetic factors. The majority of genetic variants that confer a significant risk have been localized in genes involved in immune response. However, many findings could not be replicated and almost none of the identified risk factors had a noticeable impact on clinical decisions. In contrast, recent findings in independent large genome wide association studies confirmed genetic variants in the interferon gamma gene locus as strong predictors of outcome with outstanding clinical relevance. This review gives an overview on significant genetic susceptibility factors for susceptibility and treatment outcome in chronic viral hepatitis C and B that have been identified by the classical candidate gene approach and genome wide studies and also highlights some recent findings on genetic factors for common adverse drug reactions.

Cognitive impairment and the role of the ApoE epsilon4-allele after stroke--a 13 months follow-up study

OBJECTIVE

To examine the relationship between the ApoE epsilon4 allele and cognitive impairment 13 months after stroke.

METHODS

One hundred four stroke rehabilitation patients were cognitively tested on average 18 days after hospital admission and again 13 months later with the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The following potential risk factors for post-stroke cognitive impairment (defined by a RBANS total index score below 77.5 points) at 13 months follow-up were analyzed in bivariate and logistic regression analyses: ApoE-genotype, socio-demographic variables, pre-stroke cognitive reduction (The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE)), vascular factors, lesion characteristics, and neurological impairment (The National Institute of Health Stroke Scale (NIHSS)). Differences in general cognitive performance (pre-stroke, baseline, and follow-up) across patients with different ApoE-genotypes were analyzed, and lastly differences between epsilon4-carriers and non-carriers for changes in performance in various cognitive domains over the 13 months period were examined.

RESULTS

Significant risk factors for cognitive impairment at 13 months were ApoE epsilon4, pre-stroke cognitive reduction (IQCODE 3.44+), previous stroke, and neurological impairment (NIHSS Total Score >5). A significant dose-dependent effect of the ApoE-genotype in relation to overall post-stroke cognitive functioning was found at baseline and follow-up, but not pre-stroke. The epsilon4 carriers showed a significant decline in tests related to verbal learning and memory compared to the non-carriers.

CONCLUSIONS

The ApoE epsilon4-allele constitutes an independent risk factor for cognitive impairment at 13 months post-stroke, and is associated with progression of cognitive decline in tasks related to verbal learning and memory.

Genetic determinants of cerebral vasospasm, delayed cerebral ischemia, and outcome after aneurysmal subarachnoid hemorrhage

Despite extensive effort to elucidate the cellular and molecular bases for delayed cerebral injury after aneurysmal subarachnoid hemorrhage (aSAH), the pathophysiology of these events remains poorly understood. Recently, much work has focused on evaluating the genetic underpinnings of various diseases in an effort to delineate the contribution of specific molecular pathways as well as to uncover novel mechanisms. The majority of subarachnoid hemorrhage genetic research has focused on gene expression and linkage studies of these markers as they relate to the development of intracranial aneurysms and their subsequent rupture. Far less work has centered on the genetic determinants of cerebral vasospasm, the predisposition to delayed cerebral injury, and the determinants of ensuing functional outcome after aSAH. The suspected genes are diverse and encompass multiple functional systems including fibrinolysis, inflammation, vascular reactivity, and neuronal repair. To this end, we present a systematic review of 21 studies suggesting a genetic basis for clinical outcome after aSAH, with a special emphasis on the pathogenesis of cerebral vasospasm and delayed cerebral ischemia. In addition, we highlight potential pitfalls in the interpretation of genetic association studies, and call for uniformity of design of larger multicenter studies in the future.