Association of APOE e4 and cerebrovascular pathology in traumatic brain injury

Predictors of longitudinal cognitive ageing from age 70 to 82 including APOE e4 status, early-life and lifestyle factors: the Lothian Birth Cohort 1936

Discovering why some people's cognitive abilities decline more than others is a key challenge for cognitive ageing research. The most effective strategy may be to address multiple risk factors from across the life-course simultaneously in relation to robust longitudinal cognitive data. We conducted a 12-year follow-up of 1091 (at age 70) men and women from the longitudinal Lothian Birth Cohort 1936 study. Comprehensive repeated cognitive measures of visuospatial ability, processing speed, memory, verbal ability, and a general cognitive factor were collected over five assessments (age 70, 73, 76, 79, and 82 years) and analysed using multivariate latent growth curve modelling. Fifteen life-course variables were used to predict variation in cognitive ability levels at age 70 and cognitive slopes from age 70 to 82. Only APOE e4 carrier status was found to be reliably informative of general- and domain-specific cognitive decline, despite there being many life-course correlates of cognitive level at age 70. APOE e4 carriers had significantly steeper slopes across all three fluid cognitive domains compared with non-carriers, especially for memory (β = -0.234, p < 0.001) and general cognitive function (β = -0.246, p < 0.001), denoting a widening gap in cognitive functioning with increasing age. Our findings suggest that when many other candidate predictors of cognitive ageing slope are entered en masse, their unique contributions account for relatively small proportions of variance, beyond variation in APOE e4 status. We conclude that APOE e4 status is important for identifying those at greater risk for accelerated cognitive ageing, even among ostensibly healthy individuals.

Effect of ApoE ε4 gene polymorphism on the correlation between serum uric acid and left ventricular hypertrophy remodeling in patients with coronary heart disease

Background

Hyperuricemia and dyslipidemia are associated with left ventricular hypertrophy (LVH), while the effect of ApoE gene polymorphism on the correlation between serum uric acid (UA) level and severity of LVH in patients with coronary heart disease (CHD) has not been clarified.

Methods

This was a retrospective observational study of patients with CHD. Patients were divided into groups of ε4 carriers and non-ε4 carriers based on sanger sequencing. The association of ApoE ε4 gene polymorphism, serum UA level, and LVH, determined by cardiac color Doppler ultrasound, was evaluated by multivariate analysis.

Results

A total of 989 CHD patients who underwent ApoE genotyping were enrolled and analyzed. Among them, the frequency of the ApoE ε4 genotype was 17.9% (15.7% for E3/4, 1.1% for E4/4, and 1.1% for E2/4). There were 159 patients with LVH, 262 with end-diastolic LV internal diameter (LVEDD) enlargement, 160 with left ventricular ejection fraction (LVEF) reduction, and 154 with heart failure. Multivariate analysis showed that for every increase of 10 μmol/L in serum UA level, the risk of LVH decreased in ε4 carriers (odds ratio (OR) = 0.94, 95% confidence interval (CI): 0.890-0.992, P = 0.025) and increased in non-ε4 carriers (OR = 1.03, 95% CI: 1.005-1.049, P = 0.016). The risk of LVEDD enlargement tended to decrease in ε4 carriers (OR = 0.98, 95% CI: 0.943-1.023, P = 0.391) and increased in non-ε4 carriers (OR = 1.03, 95% CI: 1.009-1.048, P = 0.003). The risk of LVEF reduction was reduced in ε4 carriers (OR = 0.996, 95% CI: 0.949-1.046, P = 0.872) and increased in non-ε4 carriers (OR = 1.02, 95% CI: 0.994-1.037, P = 0.17). The risk of LVEDD enlargement decreased in ε4 carriers (OR = 0.98, 95% CI: 0.931-1.036, P = 0.508) and increased in non-ε4 carriers (OR = 1.02, 95% CI: 0.998-1.042, P = 0.07).

Conclusion

High serum UA levels decreased the risk of LVH in ApoE ε4 carriers with CHD, while increased the risk of LVH in non-ε4 carriers.

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.

Effects of prolactin on movement disorders and APOE, GFAP, and PRL receptor gene expression following intracerebral hemorrhage in rats

OBJECTIVES

Intracerebral hemorrhage (ICH) occurs mostly in the striatum. In ICH, blood prolactin level increases 3-fold. The effects of intracerebroventricular injection (ICV) of prolactin on motor disorders will be investigated.

MATERIALS AND METHODS

This study was performed on 32 male Wistar rats in 4 groups: sham, ICH, and prolactin with 1 μg/2 μl (P1) and 2 μg/2 μl (P2) doses.

RESULTS

The weight of animals on days 1 (P˂0.01), 3, and 7 (P˂0.05) in the sham and P2 groups increased compared with the ICH group. Neurological Deficit Score (NDS) in ICH and P1 groups decreased, and increased compared with sham and ICH groups (P˂0.001), respectively. NDS in the P1 group increased compared with the P2 group on days 1 (P˂0.0 5), 3, and 7 (P˂0.001). The duration time of rotarod in ICH and P1 groups decreased and increased compared with sham and ICH groups (P˂0.001), respectively. The duration time of rotarod in the P1 group on days 3 and 7 increased compared with the P2 group (P˂0.001). Travel distance in days 1(P˂0.01), 3(P˂0.001), and 7(P˂0.01) decreased in the ICH group. Prolactin receptor (PRL receptor) expression in ICH, P1, and P2 groups increased compared with sham and ICH groups (P˂0.001). Glial fibrillary acidic protein (GFAP) expression (P˂0.001) and apolipoprotein E (APOE) (P˂0.01) expression in the ICH group increased compared with the sham group. GFAP and APOE expression in the P1 group increased compared with the ICH group (P˂0.001). APOE expression in the P1 group increased compared with the P2 group (P˂0.001).

CONCLUSION

According to the results, prolactin reduces movement disorders.

Effects of sex and genotype in human APOE-targeted replacement mice on alcohol self-administration measured with the automated IntelliCage system before and after repeated mild traumatic brain injury

BACKGROUND

Few studies have examined the association between APOE genotype and alcohol use. Although some of these studies have reported outcomes associated with a history of drinking, none have examined alcohol-seeking behavior. In addition, no preclinical studies have examined alcohol use as a function of APOE genotype with or without traumatic brain injury.

METHODS

Male and female human APOE3- and APOE4-targeted replacement (TR) mice were used to assess voluntary alcohol seeking longitudinally using a 2-bottle choice paradigm conducted within the automated IntelliCage system prior to and following repeated mild TBI (rmTBI). Following an acquisition phase in which the concentration of ethanol (EtOH) was increased to 12%, a variety of drinking paradigms that included extended alcohol access (EAA1 and EAA2), alcohol deprivation effect (ADE), limited access drinking in the dark (DID), and progressive ratio (PR) were used to assess alcohol-seeking behavior. Additional behavioral tasks were performed to measure cognitive function and anxiety-like behavior.

RESULTS

All groups readily consumed increasing concentrations of EtOH (4-12%) during the acquisition phase. During the EAA1 period (12% EtOH), there was a significant genotype effect in both males and females for EtOH preference. Following a 3-week abstinence period, mice received sham or rmTBI resulting in a genotype- and sex-independent main effect of rmTBI on the recovery of righting reflex and a main effect of rmTBI on spontaneous home-cage activity in females only. Reintroduction of 12% EtOH (EAA2) resulted in a significant effect genotype for alcohol preference in males with APOE4 mice displaying increased preference and motivation for alcohol compared with APOE3 mice independent of TBI while in females, there was a significant genotype × TBI interaction under the ADE and DID paradigms. Finally, there was a main effect of rmTBI on increased risk-seeking behavior in both sexes, but no effect on spatial learning or cognitive flexibility.

CONCLUSION

These results suggest that sex and APOE genotype play a significant role in alcohol consumption and may subsequently influence long-term recovery following traumatic brain insults.

DNA methylation under the major depression pathway predicts pediatric quality of life four-month post-pediatric mild traumatic brain injury

BACKGROUND

Major depression has been recognized as the most commonly diagnosed psychiatric complication of mild traumatic brain injury (mTBI). Moreover, major depression is associated with poor outcomes following mTBI; however, the underlying biological mechanisms of this are largely unknown. Recently, genomic and epigenetic factors have been increasingly implicated in the recovery following TBI.

RESULTS

This study leveraged DNA methylation within the major depression pathway, along with demographic and behavior measures (features used in the clinical model) to predict post-concussive symptom burden and quality of life four-month post-injury in a cohort of 110 pediatric mTBI patients and 87 age-matched healthy controls. The results demonstrated that including DNA methylation markers in the major depression pathway improved the prediction accuracy for quality of life but not persistent post-concussive symptom burden. Specifically, the prediction accuracy (i.e., the correlation between the predicted value and observed value) of quality of life was improved from 0.59 (p = 1.20 × 10^-3) (clinical model) to 0.71 (p = 3.89 × 10^-5); the identified cytosine-phosphate-guanine sites were mainly in the open sea regions and the mapped genes were related to TBI in several molecular studies. Moreover, depression symptoms were a strong predictor (with large weights) for both post-concussive symptom burden and pediatric quality of life.

CONCLUSION

This study emphasized that both molecular and behavioral manifestations of depression symptoms played a prominent role in predicting the recovery process following pediatric mTBI, suggesting the urgent need to further study TBI-caused depression symptoms for better recovery outcome.

The Human ApoE4 Variant Reduces Functional Recovery and Neuronal Sprouting After Incomplete Spinal Cord Injury in Male Mice

Spinal cord injury (SCI) is a devastating form of neurotrauma. Patients who carry one or two apolipoprotein E (ApoE)4 alleles show worse functional outcomes and longer hospital stays after SCI, but the cellular and molecular underpinnings for this genetic link remain poorly understood. Thus, there is a great need to generate animal models to accurately replicate the genetic determinants of outcomes after SCI to spur development of treatments that improve physical function. Here, we examined outcomes after a moderate contusion SCI of transgenic mice expressing human ApoE3 or ApoE4. ApoE4 mice have worse locomotor function and coordination after SCI. Histological examination revealed greater glial staining in ApoE4 mice after SCI associated with reduced levels of neuronal sprouting markers. Bulk RNA sequencing revealed that subcellular processes (SCPs), such as extracellular matrix organization and inflammatory responses, were highly ranked among upregulated genes at 7 days after SCI in ApoE4 variants. Conversely, SCPs related to neuronal action potential and neuron projection development were increased in ApoE3 mice at 21 days. In summary, our results reveal a clinically relevant SCI mouse model that recapitulates the influence of ApoE genotypes on post SCI function in individuals who carry these alleles and suggest that the mechanisms underlying worse recovery for ApoE4 animals involve glial activation and loss of sprouting and synaptic activity.

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.

Apolipoprotein E regulates the maturation of injury-induced adult-born hippocampal neurons following traumatic brain injury

Various brain injuries lead to the activation of adult neural stem/progenitor cells in the mammalian hippocampus. Subsequent injury-induced neurogenesis appears to be essential for at least some aspects of the innate recovery in cognitive function observed following traumatic brain injury (TBI). It has previously been established that Apolipoprotein E (ApoE) plays a regulatory role in adult hippocampal neurogenesis, which is of particular interest as the presence of the human ApoE isoform ApoE4 leads to significant risk for the development of late-onset Alzheimer's disease, where impaired neurogenesis has been linked with disease progression. Moreover, genetically modified mice lacking ApoE or expressing the ApoE4 human isoform have been shown to impair adult hippocampal neurogenesis under normal conditions. Here, we investigate how controlled cortical impact (CCI) injury affects dentate gyrus development using hippocampal stereotactic injections of GFP-expressing retroviruses in wild-type (WT), ApoE-deficient and humanized (ApoE3 and ApoE4) mice. Infected adult-born hippocampal neurons were morphologically analyzed once fully mature, revealing significant attenuation of dendritic complexity and spine density in mice lacking ApoE or expressing the human ApoE4 allele, which may help inform how ApoE influences neurological diseases where neurogenesis is defective.

Elucidating the Role of Apolipoprotein E Isoforms in Spinal Cord Injury-Associated Neuropathology

Spinal cord injury (SCI) is a devastating, life-altering, neurological event that affects ∼300,000 individuals in the United States. Currently, there are no effective treatments to reverse the neurological impairments caused by the lesion. Until a cure is available, there is an urgent need for strategies that can either spare injured neurons or promote neuroplasticity and functional recovery. Genetic links to outcomes after SCI may provide insights into the pathological mechanisms, and possible new avenues for drug development. In the present review, we discuss the current knowledge linking apolipoprotein E genotypes with better or worse functional outcomes after an SCI, and the possible molecular mechanisms that may contribute to this association.

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.

Predictors and Implications of Accelerated Cognitive Aging

Aging is a major risk factor for both normal and pathological cognitive decline. However, individuals vary in their rate of age-related decline. We developed an easily interpretable composite measure of cognitive age, and related both the level of cognitive age and cognitive slope to sociodemographic, genetic, and disease indicators and examine its prediction of dementia transition. Using a sample of 19,594 participants from the Health and Retirement Study, cognitive age was derived from a set of performance tests administered at each wave. Our findings reveal different conclusions as they relate to levels versus slopes of cognitive age, with more pronounced differences by sex and race/ethnicity for absolute levels of cognitive decline rather than for rates of declines. We also find that both level and slope of cognitive age are inversely related to education, as well as increased for persons with APOE ε4 and/or diabetes. Finally, results show that the slope in cognitive age predicts subsequent dementia among non-demented older adults. Overall, our study suggests that this measure is applicable to cross-sectional and longitudinal studies on cognitive aging, decline, and dementia with the goal of better understanding individual differences in cognitive decline.

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.

Antioxidants: The new frontier for translational research in cerebroprotection

It is important for the anesthesiologist to understand the etiology of free radical damage and how free-radical scavengers attenuate this, so that this knowledge can be applied to diverse neuro-pathological conditions. This review will concentrate on the role of reactive species of oxygen in the pathophysiology of organ dysfunction, specifically sub arachnoid hemorrhage (SAH), traumatic brain injury (TBI) as well as global central nervous system (CNS) hypoxic, ischemic and reperfusion states. We enumerate potential therapeutic modalities that are been currently investigated and of interest for future trials. Antioxidants are perhaps the next frontier of translational research, especially in neuro-anesthesiology.

Review: the long-term consequences of microglial activation following acute traumatic brain injury

The brain is vulnerable to a number of acute insults, with traumatic brain injury being among the commonest. Neuroinflammation is a common response to acute injury and microglial activation is a key component of the inflammatory response. In the acute and subacute phase it is likely that this response is protective and forms an important part of the normal tissue reaction. However, there is considerable literature demonstrating an association between acute traumatic brain injury to the brain and subsequent cognitive decline. This article will review the epidemiological literature relating to both single and repetitive head injury. It will focus on the neuropathological features associated with long-term complications of a single blunt force head injury, repetitive head injury and blast head injury, with particular reference to chronic traumatic encephalopathy, including dementia pugilistica. Neuroinflammation has been postulated as a key mechanism linking acute traumatic brain injury with subsequent neurodegenerative disease, and this review will consider the response to injury in the acute phase and how this may be detrimental in the longer term, and discuss potential genetic factors which may influence this cellular response. Finally, this article will consider future directions for research and potential future therapies.

Human apolipoprotein E4 worsens acute axonal pathology but not amyloid-β immunoreactivity after traumatic brain injury in 3xTG-AD mice

Apolipoprotein E4 (APOE4) genotype is a risk factor for poor outcome after traumatic brain injury (TBI), particularly in young patients, but the underlying mechanisms are not known. By analogy to effects of APOE4 on the risk of Alzheimer disease (AD), the APOE genotype may influence β-amyloid (Aβ) and tau deposition after TBI. To test this hypothesis, we crossed 3xTG-AD transgenic mice carrying 3 human familial AD mutations (PS1(M146V), tauP(301)L, and APP(SWE)) to human ApoE2-, ApoE3-, and ApoE4-targeted replacement mice. Six- to 8-month-old 3xTG-ApoE mice were assayed by quantitative immunohistochemistry for amyloid precursor protein (APP), Aβ(1-40) (Aβ40), Aβ(1-42) (Aβ42), total human tau, and phospho-serine 199 (pS199) tau at 24 hours after moderate controlled cortical impact. There were increased numbers of APP-immunoreactive axonal varicosities in 3xTG-ApoE4 mice versus the other genotypes. This finding was repeated in a separate cohort of ApoE4-targeted replacement mice without human transgenes compared with ApoE3 and ApoE2 mice. There were no differences between genotypes in the extent of intra-axonal Aβ40 and Aβ42; none of the mice had extracellular Aβ deposition. Regardless of injury status, 3xTG-ApoE4 mice had more total human tau accumulation in both somatodendritic and intra-axonal compartments than other genotypes. These results suggest that the APOE4 genotype may have a primary effect on the severity of axonal injury in acute TBI.

Prognosis in severe brain injury

BACKGROUND

The prediction of neurologic outcome is a fundamental concern in the resuscitation of patients with severe brain injury.

OBJECTIVE

To provide an evidence-based update on neurologic prognosis following traumatic brain injury and hypoxic-ischemic encephalopathy after cardiac arrest.

DATA SOURCE

Search of the PubMed database and manual review of bibliographies from selected articles to identify original data relating to prognostic methods and outcome prediction models in patients with neurologic trauma or hypoxic-ischemic encephalopathy.

DATA SYNTHESIS AND CONCLUSION

Articles were scrutinized regarding study design, population evaluated, interventions, outcomes, and limitations. Outcome prediction in severe brain injury is reliant on features of the neurologic examination, anatomical and physiological changes identified with CT and MRI, abnormalities detected with electroencephalography and evoked potentials, and physiological and biochemical derangements at both the brain and systemic levels. Use of such information in univariable association studies generally lacks specificity in classifying neurologic outcome. Furthermore, the accuracy of established prognostic classifiers may be affected by the introduction of outcome-modifying interventions, such as therapeutic hypothermia following cardiac arrest. Although greater specificity may be achieved with scoring systems derived from multivariable models, they generally fail to predict outcome with sufficient accuracy to be meaningful at the single patient level. Discriminative models which integrate knowledge of genetic determinants and biologic processes governing both injury and repair and account for the effects of resuscitative and rehabilitative care are needed.

The liver X receptor agonist GW3965 improves recovery from mild repetitive traumatic brain injury in mice partly through apolipoprotein E

Traumatic brain injury (TBI) increases Alzheimer’s disease (AD) risk and leads to the deposition of neurofibrillary tangles and amyloid deposits similar to those found in AD. Agonists of Liver X receptors (LXRs), which regulate the expression of many genes involved in lipid homeostasis and inflammation, improve cognition and reduce neuropathology in AD mice. One pathway by which LXR agonists exert their beneficial effects is through ATP-binding cassette transporter A1 (ABCA1)-mediated lipid transport onto apolipoprotein E (apoE). To test the therapeutic utility of this pathway for TBI, we subjected male wild-type (WT) and apoE−/− mice to mild repetitive traumatic brain injury (mrTBI) followed by treatment with vehicle or the LXR agonist GW3965 at 15 mg/kg/day. GW3965 treatment restored impaired novel object recognition memory in WT but not apoE−/− mice. GW3965 did not significantly enhance the spontaneous recovery of motor deficits observed in all groups. Total soluble Aβ₄₀ and Aβ₄₂ levels were significantly elevated in WT and apoE−/− mice after injury, a response that was suppressed by GW3965 in both genotypes. WT mice showed mild but significant axonal damage at 2 d post-mrTBI, which was suppressed by GW3965. In contrast, apoE−/− mice showed severe axonal damage from 2 to 14 d after mrTBI that was unresponsive to GW3965. Because our mrTBI model does not produce significant inflammation, the beneficial effects of GW3965 we observed are unlikely to be related to reduced inflammation. Rather, our results suggest that both apoE-dependent and apoE-independent pathways contribute to the ability of GW3965 to promote recovery from mrTBI.

Concussions: What a neurosurgeon should know about current scientific evidence and management strategies

BACKGROUND

There has been a tremendous amount of interest focused on the topic of concussions over the past few decades. Neurosurgeons are frequently consulted to manage patients with mild traumatic brain injuries (mTBI) that have radiographic evidence of cerebral injury. These injuries share significant overlap with concussions, injuries that typically do not reveal radiographic evidence of structural injury, in the realms of epidemiology, pathophysiology, outcomes, and management. Further, neurosurgeons often manage patients with extracranial injuries that have concomitant concussions. In these cases, neurosurgeons are often the only "concussion experts" that patients encounter.

RESULTS

The literature has been reviewed and data have been synthesized on the topic including sections on historical background, epidemiology, pathophysiology, diagnostic advances, clinical sequelae, and treatment suggestions, with neurosurgeons as the intended target audience.

CONCLUSIONS

Neurosurgeons should have a fundamental knowledge of the scientific evidence that has developed regarding concussions and be prepared to guide patients with treatment plans.

APOE genotype alters glial activation and loss of synaptic markers in mice

The ε4 allele of the Apolipoprotein E (APOE) gene is the strongest genetic risk factor for late-onset Alzheimer's disease (AD), and affects clinical outcomes of chronic and acute brain damages. The mechanisms by which apoE affect diverse diseases and disorders may involve modulation of the glial response to various types of brain damage. We examined glial activation in a mouse model where each of the human APOE alleles are expressed under the endogenous mouse APOE promoter, as well as in APOE knock-out mice. APOE4 mice displayed increased glial activation in response to intracerebroventricular lipopolysaccharide (LPS) compared to APOE2 and APOE3 mice by several measures. There were higher levels of microglia/macrophage, astrocytes, and invading T-cells after LPS injection in APOE4 mice. APOE4 mice also displayed greater and more prolonged increases of cytokines (IL-1β, IL-6, TNF-α) than APOE2 and APOE3 mice. We found that APOE4 mice had greater synaptic protein loss after LPS injection, as measured by three markers: PSD-95, drebin, and synaptophysin. In all assays, APOE knock-out mice responded similar to APOE4 mice, suggesting that the apoE4 protein may lack anti-inflammatory characteristics of apoE2 and apoE3. Together, these findings demonstrate that APOE4 predisposes to inflammation, which could contribute to its association with Alzheimer's disease and other disorders.

Genetics and outcomes after traumatic brain injury (TBI): what do we know about pediatric TBI?

Human genetic association studies in individuals with traumatic brain injury (TBI) have increased rapidly over the past few years. Recently, several review articles evaluated the association of genetics with outcomes after TBI. However, almost all of the articles discussed in these reviews focused on adult TBI. The primary objective of this review is to gain a better understanding of which genes and/or genetic polymorphisms have been evaluated in pediatric TBI. Our initial search identified 113 articles. After review of these articles only 5 genetic association studies specific to pediatric TBI were identified. All five of these studies evaluated the apolipoprotein (APOE) gene. The study design and methods of these identified papers will be discussed. An additional search was then performed to evaluate genes beyond APOE that have been evaluated in adult TBI; findings from these studies are highlighted. Larger genetic studies will need to be performed in the future to better elucidate the association of APOE and other genes with outcomes after TBI in children. There is great potential to utilized genetic information to inform prognosis and management after TBI in children; however, we have much work ahead of us to reach the goal of individualized management.

Antioxidant strategies in neurocritical care

An increase in oxidative stress and overproduction of oxidizing reactive species plays an important role in the pathophysiology of several conditions encountered in the neurocritical care setting including: ischemic and hemorrhagic strokes, traumatic brain injury, acute respiratory distress syndrome, sepsis, and organ failure. The presence of oxidative stress in these conditions is supported by a large body of pre-clinical and clinical studies, and provides a rationale to support a potential therapeutic role for antioxidants. The purpose of this article is to briefly review the basic mechanisms and molecular biology of oxidative stress, summarize its role in critically ill neurological patients, and review available data regarding the potential role of antioxidant strategies in neurocritical care and future directions.

The association between apolipoprotein E and traumatic brain injury severity and functional outcome in a rehabilitation sample

Traumatic brain injury (TBI) can result in significant disability, but outcome is variable. The impact of known predictors accounts for a limited proportion of the variance in outcomes. Apolipoprotein E (ApoE) genotype has been investigated as an additional source of variability in injury severity and outcome, with mixed findings reflecting variable methodology and generally limited sample sizes. This study aimed to examine whether possession of the ApoE ɛ4 allele was associated with greater acute injury severity and poorer long-term outcome in patients referred for rehabilitation following TBI. ApoE genotype was determined for 648 patients with TBI, who were prospectively followed up a mean of 1.9 years post-injury. Hypotheses that ɛ4 carriers would have lower Glasgow Coma Scale (GCS) scores and longer post-traumatic amnesia (PTA) duration were not supported. Prediction of worse Glasgow Outcome Scale-Extended (GOSE) scores for ɛ4 carriers was supported with greater susceptibility seen in females. These results indicate the ApoE ɛ4 allele may be associated with poorer long-term outcome, but not acute injury severity. Possible mechanisms include differential effects of the ɛ4 allele on inflammatory and cellular repair processes, and/or amyloid deposition.

Traumatic brain injury and amyloid-β pathology: a link to Alzheimer's disease?

Traumatic brain injury (TBI) has devastating acute effects and in many cases seems to initiate long-term neurodegeneration. Indeed, an epidemiological association between TBI and the development of Alzheimer's disease (AD) later in life has been demonstrated, and it has been shown that amyloid-β (Aβ) plaques — one of the hallmarks of AD — may be found in patients within hours following TBI. Here, we explore the mechanistic underpinnings of the link between TBI and AD, focusing on the hypothesis that rapid Aβ plaque formation may result from the accumulation of amyloid precursor protein in damaged axons and a disturbed balance between Aβ genesis and catabolism following TBI.

Genetic association studies in patients with traumatic brain injury

Traumatic brain injury (TBI) constitutes a major cause of mortality and disability worldwide, especially among young individuals. It is estimated that despite all the recent advances in the management of TBI, approximately half of the patients suffering head injuries still have unfavorable outcomes, which represents a substantial health care, social, and economic burden to societies.

Considerable variability exists in the clinical outcome after TBI, which is only partially explained by known factors. Accumulating evidence has implicated various genetic elements in the pathophysiology of brain trauma. The extent of brain injury after TBI seems to be modulated to some degree by genetic variants.

The authors' current review focuses on the up-to-date state of knowledge regarding genetic association studies in patients sustaining TBI, with particular emphasis on the mechanisms underlying the implication of genes in the pathophysiology of TBI.

Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.

Molecular mechanisms of traumatic brain injury in children. A review

Despite advances in molecular biology and genetics, the precise pathophysiology of traumatic brain injury (TBI) in children is unknown. In this paper the authors review what is currently known about intra- and extracellular responses to pediatric TBI and relate these factors to future investigations. Although hyperemia and vascular congestion have long been thought to be the hallmarks of pediatric TBI, on a cellular level, calcium influx as well as modulation of local neurotransmitters appears to play a major role in its onset. Recent genetic and proteomic research has identified specific neurotrophic factors as well as apoptotic and antiapoptotic genes that appear to control the progression of inflammation and neuronal damage. The search for a therapeutic target will ultimately require a thorough understanding of these factors and their interplay on a proteomic, genomic, and neuromic level.

Modulating effect of apolipoprotein E polymorphisms on secondary brain insult and outcome after childhood brain trauma

OBJECTIVE

The aim of this study was to determine the relationship between apolipoprotein E (APO E) alleles, the amount of cerebral perfusion pressure (CPP) insult and outcome in children after brain trauma.

MATERIALS AND METHODS

In a prospective two-centre case-control study, the APO E genotypes of 65 critically ill children admitted after brain trauma were correlated with age-related CPP insult quantification, conscious state at the time of discharge from intensive care and global outcome at 6 months post-injury. One hundred sixty healthy age- and sex-matched children were genotyped as controls.

RESULTS

The CPP insult level among the e4 carriers with poor outcome was significantly less than the non-e4 carriers (p=0.03). Homozygotic e3 patients with good recovery did so despite having suffered nearly 26 times more CPP insult than those who were not e3 homzygous (p=0.02).

CONCLUSION

Different APO E alleles may potentially affect cerebral ischaemic tolerance differently in children after brain trauma.

Genetic susceptibility to traumatic brain injury and apolipoprotein E gene

Traumatic brain injury (TBI) is defined as an injury caused by a blow or jolt to the head or a penetrating head injury that disrupts the normal function of the brain. It is a common emergency and severe case in neurosurgery field. Nowadays, there are more and more evidences showing that TBI, which is apparently similar in pathology and severity in the acute stage, may have different outcomes. The known prognostic factors (such as age, severity of injury and treatments, etc.) explain only part of this variability and the concept of genetic susceptibility of traumatic brain injury has already been accepted by more and more people. It is now demonstrated that genetic polymorphism may play a key role in the susceptibility to TBI, even outcome following TBI. Although there are many genes that may involved in pathophysiological processes influencing TBI, apolipoprotein E gene has become one of the most extensive studied genes in neurotrauma and neurodegenerative disease and seems to take an important part in the neural responses to TBI. In this article, we will review the current understanding of the genetic susceptibility of TBI and the advancements regarding the impact of apolipoprotein E genotype on the severity and/or outcome following TBI.

Meta-analysis of APOE4 allele and outcome after traumatic brain injury

There is conflicting evidence regarding a possible association between the apolipoprotein E4 (APOE4) allele and the consequences of traumatic brain injury (TBI). Our aim was to carry out a meta-analysis of cohort studies of sufficient rigor to determine whether the presence of the APOE4 allele contributes to initial injury severity and/or poor outcome following TBI. MEDLINE, EMBase, CBMdisc, and CNKI databases were searched for literature published from January 1993 to October 2007. Of the 100 identified studies, 14 cohort studies were selected for analysis based on comprehensive quality assessment using a standardized scale. Data from the 14 eligible cohort studies included a total of 2527 participants, 736 with and 1791 without the APOE4 allele. The APOE4 allele was not associated with initial injury severity of TBI. The pooled RR were 1.11 (95% confidence interval [CI], 0.91 to 1.35) for severe injury, 1.06 (95% CI, 0.86-1.31) for moderate injury and 0.93 (95% CI, 0.81-1.06) for mild injury. However, the APOE4 allele was significantly associated with a poor outcome of TBI at 6 months after injury (RR = 1.36; 95% CI, 1.04-1.78). The association remained significant in sensitivity tests. This meta-analysis indicates that the presence of the APOE4 allele is not associated with the initial severity of brain injury following TBI but is associated with increased risk of poor long-term outcome at 6 months after injury.

Correlation between APOE -491AA promoter in epsilon4 carriers and clinical deterioration in early stage of traumatic brain injury

The objective of this work was to investigate the relationship between apolipoprotein E (APOE) promoters (G-219T, C-427T, A-491T) polymorphisms and the clinical deterioration in early stage of traumatic brain injury (TBI) in a cohort of Chinese patients. In this study, we used the cohort of patients which has been reported previously. A total of 110 subjects with TBI (80 males and 30 females, with mean age of 43.87 years) were admitted from December 2003 to May 2004, and demographic and clinical data were collected. The clinical deterioration of patient's condition in acute stage (<7 days after TBI) was judged by either of the following criteria: decrease of Glasgow Coma Scale (GCS) score (compared with initial admission GCS), increase in hematoma volume or delayed hematoma both detected by repeated computed tomography (CT) scanning compared to that on admission. Venous blood was collected from patients with TBI on admission to determine the APOE promoter polymorphisms. The APOE genotyping was performed by means of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). chi(2) test and logistic regression analyses were done by SPSS. In 110 Chinese patients, the distributions of APOE genotypes and alleles matched Hardy-Weinberg Law, and 19 subjects presented with deteriorated clinical condition in acute stage after hospitalization. chi(2) test showed insignificant differences in association of APOE promoter polymorphisms with clinical deterioration (p>0.05). But logistic regression analyses, after adjusting patients' age, injury severity and injury mechanism etc, showed that -491AA (OR=11.681, p=0.009, 95%, CI 1.824-74.790) and APOE epsilon4 were all risk factors, with injury severity and alcohol-drinking as other risk factors. In Chinese population, as a significant but not independent risk factor, only APOE -491AA promoter in epsilon4 carriers is apt to the clinical deterioration and may contribute to the poor outcome after TBI.

Altered lipid metabolism in brain injury and disorders

Deregulated lipid metabolism may be of particular importance for CNS injuries and disorders, as this organ has the highest lipid concentration next to adipose tissue. Atherosclerosis (a risk factor for ischemic stroke) results from accumulation of LDL-derived lipids in the arterial wall. Pro-inflammatory cytokines (TNF-alpha and IL-1), secretory phospholipase A2 IIA and lipoprotein-PLA2 are implicated in vascular inflammation. These inflammatory responses promote atherosclerotic plaques, formation and release of the blood clot that can induce ischemic stroke. TNF-alpha and IL-1 alter lipid metabolism and stimulate production of eicosanoids, ceramide, and reactive oxygen species that potentiate CNS injuries and certain neurological disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Low levels of neurosteroids were related to poor outcome in many brain pathologies. Apolipoprotein E is the principal cholesterol carrier protein in the brain, and the gene encoding the variant Apolipoprotein E4 is a significant risk factor for Alzheimer's disease. Parkinson's disease is to some degree caused by lipid peroxidation due to phospholipases activation. Niemann-Pick diseases A and B are due to acidic sphingomyelinase deficiency, resulting in sphingomyelin accumulation, while Niemann-Pick disease C is due to mutations in either the NPC1 or NPC2 genes, resulting in defective cholesterol transport and cholesterol accumulation. Multiple sclerosis is an autoimmune inflammatory demyelinating condition of the CNS. Inhibiting phospholipase A2 attenuated the onset and progression of experimental autoimmune encephalomyelitis. The endocannabinoid system is hypoactive in Huntington's disease. Ethyl-eicosapetaenoate showed promise in clinical trials. Amyotrophic lateral sclerosis causes loss of motorneurons. Cyclooxygenase-2 inhibition reduced spinal neurodegeneration in amyotrophic lateral sclerosis transgenic mice. Eicosapentaenoic acid supplementation provided improvement in schizophrenia patients, while the combination of (eicosapentaenoic acid + docosahexaenoic acid) provided benefit in bipolar disorders. The ketogenic diet where >90% of calories are derived from fat is an effective treatment for epilepsy. Understanding cytokine-induced changes in lipid metabolism will promote novel concepts and steer towards bench-to-bedside transition for therapies.

Altered lipid metabolism in brain injury and disorders

Deregulated lipid metabolism may be of particular importance for CNS injuries and disorders, as this organ has the highest lipid concentration next to adipose tissue. Atherosclerosis (a risk factor for ischemic stroke) results from accumulation of LDL-derived lipids in the arterial wall. Pro-inflammatory cytokines (TNF-alpha and IL-1), secretory phospholipase A2 IIA and lipoprotein-PLA2 are implicated in vascular inflammation. These inflammatory responses promote atherosclerotic plaques, formation and release of the blood clot that can induce ischemic stroke. TNF-alpha and IL-1 alter lipid metabolism and stimulate production of eicosanoids, ceramide, and reactive oxygen species that potentiate CNS injuries and certain neurological disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Low levels of neurosteroids were related to poor outcome in many brain pathologies. Apolipoprotein E is the principal cholesterol carrier protein in the brain, and the gene encoding the variant Apolipoprotein E4 is a significant risk factor for Alzheimer's disease. Parkinson's disease is to some degree caused by lipid peroxidation due to phospholipases activation. Niemann-Pick diseases A and B are due to acidic sphingomyelinase deficiency, resulting in sphingomyelin accumulation, while Niemann-Pick disease C is due to mutations in either the NPC1 or NPC2 genes, resulting in defective cholesterol transport and cholesterol accumulation. Multiple sclerosis is an autoimmune inflammatory demyelinating condition of the CNS. Inhibiting phospholipase A2 attenuated the onset and progression of experimental autoimmune encephalomyelitis. The endocannabinoid system is hypoactive in Huntington's disease. Ethyl-eicosapetaenoate showed promise in clinical trials. Amyotrophic lateral sclerosis causes loss of motorneurons. Cyclooxygenase-2 inhibition reduced spinal neurodegeneration in amyotrophic lateral sclerosis transgenic mice. Eicosapentaenoic acid supplementation provided improvement in schizophrenia patients, while the combination of (eicosapentaenoic acid + docosahexaenoic acid) provided benefit in bipolar disorders. The ketogenic diet where >90% of calories are derived from fat is an effective treatment for epilepsy. Understanding cytokine-induced changes in lipid metabolism will promote novel concepts and steer towards bench-to-bedside transition for therapies.

Lack of association between apolipoprotein E promoters in epsilon4 carriers and worsening on computed tomography in early stage of traumatic brain injury

We investigated the relationship between apolipoprotein E (APOE) promoters (G-219T, C-427T, A-491T) polymorphisms, and worsening CT results in early stage of traumatic brain injury (TBI) in a previously reported cohort of Chinese patients. Radiographic evidence of hemorrhage extension or delayed hemorrhage in acute stage (< 7 days after TBI) was judged by serial CT scanning compared to that on admission. APOE genotyping was performed by means of PCR-RFLP. Chi2 test and logistic regression analyses were done using SPSS software. Of 110 Chinese patients, 19 presented with deteriorated clinical condition in acute stage after hospitalization. Among these 19 patients, serial CT scanning revealed 3 cases with hemorrhage extension and 2 cases with delayed hemorrhage. Chi2 test showed no statistical differences in radiographic worsening/stabilization between the APOE epsilon4(+) and APOE epsilon4(-) groups (p = 0.170 > 0.05). Furthermore, no significant correlation between intracranial bleeding based on CT scanning with genotype or with haplotype frequencies for A-491T, C-427T, or G-219T was found by chi2 test (p > 0.05). In Chinese population, our data do not support the hypothesis that genetic variations within the APOE gene are associated with CT worsening in early stage of TBI.

Role of Lipids in Brain Injury and Diseases

Lipid metabolism is of particular interest due to its high concentration in CNS. The importance of lipids in cell signaling and tissue physiology is demonstrated by many CNS disorders and injuries that involve deregulated metabolism. The long suffering lipid field is gaining reputation and respect as evidenced through the Center of Biomedical Research Excellence in Lipidomics and Pathobiology (COBRE), Lipid MAPS (Metabolites And Pathways Strategy) Consortium sponsored by NIH, European initiatives for decoding the lipids through genomic approaches, and Genomics of Lipid-associated Disorder (GOLD) project initiated by Austrian government. This review attempts to provide an overview of the lipid imbalances associated with neurological disorders (Alzheimer's, Parkinson's; Niemann-Pick; Multiple sclerosis, Huntington, amyotrophic lateral sclerosis, schizophrenia, bipolar disorders and epilepsy) and CNS injury (Stroke, traumatic brain injury; and spinal cord injury) and a few provocative thoughts. Lipidomic analyses along with RNA silencing will provide new insights into the role of lipid intermediates in cell signaling and hopefully open new avenues for prevention or treatment options.

Impact of genetic factors on outcome from brain injury

Most human phenotypic characteristics are determined by the interplay of environmental factors (whether external, or related to the internal milieu) with the unique genetic attributes of the individual. The same is true for predisposition to and outcome from most disease states, with acute brain injury being no exception. A greater understanding of this interplay is likely to allow improved risk stratification of patients, the development of new preventative and therapeutic modalities, and the possibility of 'individualizing' patient management based upon their genetic inheritance.

Genetic influences on outcome following traumatic brain injury

Several genes have been implicated as influencing the outcome following traumatic brain injury (TBI). Currently the most extensively studied gene has been APOE. APOE can influence overall and rehabilitation outcome, coma recovery, risk of posttraumatic seizures, as well as cognitive and behavioral functions following TBI. Pathologically, APOE is associated with increased amyloid deposition, amyloid angiopathy, larger intracranial hematomas and more severe contusional injury. The proposed mechanism by which APOE affects the clinicopathological consequences of TBI is multifactorial and includes amyloid deposition, disruption of cytoskeletal stability, cholinergic dysfunction, oxidative stress, neuroprotection and central nervous system plasticity in response to injury. Other putative genes have been less extensively studied and require replication of the clinical findings. The COMT and DRD2 genes may influence dopamine dependent cognitive processes such as executive/frontal lobe functions. Inflammation which is a prominent component in the pathophysiological cascade initiated by TBI, is in part is mediated by the interleukin genes, while apoptosis that occurs as a consequence of TBI may be modulated by polymorphisms of the p53 gene. The ACE gene may affect TBI outcome via mechanisms of cerebral blood flow and/or autoregulation and the CACNA1A gene may exert an influence via the calcium channel and its effect on delayed cerebral edema. Although several potential genes that may influence outcome following TBI have been identified, future investigations are needed to validate these genetic studies and identify new genes that might influence outcome following TBI.

Traumatic brain injury and Alzheimer's disease: a review

In an effort to identify the factors that are involved in the pathogenesis of Alzheimer's disease (AD), epidemiological studies have featured prominently in contemporary research. Of those epidemiological factors, accumulating evidence implicates traumatic brain injury (TBI) as a possible predisposing factor in AD development. Exactly how TBI triggers the neurodegenerative cascade of events in AD remains controversial. There has been extensive research directed towards understanding the potential relationship between TBI and AD and the putative influence that apolipoprotein E (APOE) genotype has on this relationship. The aim of the current paper is to provide a critical summary of the experimental and human studies regarding the association between TBI, AD and APOE genotype. It will be shown that despite significant discrepancies in the literature, there still appears to be an increasing trend to support the hypothesis that TBI is a potential risk factor for AD. Furthermore, although it is known that APOE genotype plays an important role in AD, its link to a deleterious outcome following TBI remains inconclusive and ambiguous.

Interventions for heart disease and their effects on Alzheimer's disease

OBJECTIVES

To review the contributions of cardiovascular disease to Alzheimer's disease and vascular dementia.

METHODS

Review of the literature.

RESULTS

Alzheimer's disease and vascular dementia both share significant risk attributable to cardiovascular risk factors. Hypertension and hypercholesterolemia at midlife are significant risk factors for both subsequent dementia. Diabetes and obesity are also risk factors for dementia. Stressful medical procedures, such as coronary artery bypass and graft operations also appear to contribute to the risk of Alzheimer's disease. Apolipoprotein E is the major risk factor for Alzheimer's disease. Apolipoprotein E does not appear to contribute to Alzheimer's disease by increasing serum cholesterol, but it might contribute to the disease through a mechanism involving both Abeta and an increase in neuronal vulnerability to stress.

DISCUSSION

The strong association of cardiovascular risk factors with Alzheimer's disease and vascular dementia suggest that these diseases share some biologic pathways in common. The contribution of cardiovascular disease to Alzheimer's disease and vascular dementia suggest that cardiovascular therapies might prove useful in treating or preventing dementia. Antihypertensive medications appear to be beneficial in preventing vascular dementia. Statins might be beneficial in preventing the progression of dementia in subjects with Alzheimer's disease.

Apolipoprotein E4 and traumatic brain injury

Apolipoprotein E plays a critical part in the maintenance, repair and growth of neurones, and seems to have an important part in the neural response to brain injury

Effect of APOE polymorphisms on early responses to traumatic brain injury

To investigate the relationship between apolipoprotein E (APOE) polymorphisms and the severity of traumatic brain injury (TBI) in acute stage in the cohort of mainland Chinese patients. We prospectively identified admissions to the two neurosurgical departments for head injury. A total of 110 subjects with TBI (80 males and 30 females, with mean age of 43.87 years) were enrolled from December 2003 to May 2004, and demographic and clinical data were collected. Venous blood was collected from patients with TBI on admission to determine the APOE genotype polymorphisms. The APOE genotyping was performed by means of PCR-RFLP. The deterioration of patients' condition in acute stage (<7 days after TBI) was judged by either of following criteria: decrease of GCS, increase in hematoma volume or delayed hematoma both detected by repeated CT scanning. Chi2-test and logistic regression analyses were done by SPSS. The distributions of APOE genotypes and alleles matched Hardy-Weinberg law. In 110 Chinese patients, 19 subjects presented with deteriorated clinical condition after hospitalization, and seven of 17 patients with APOE epsilon4 (41.2%) had a deteriorated condition which was significantly different from those without APOE epsilon4 (12 of 93 patients, 12.9%, P=0.01). However, neither the presence of epsilon2 nor of epsilon3 was significantly different from those absent of it (P>0.05). Logistic regression analyses showed that APOE epsilon4 was a risk factor (OR=4.836, P=0.011, 95% CI 1.443-16.208) to predispose to clinical deterioration after adjusting for patient age, sex, smoking or not, alcohol-drinking or not, injury severity, injury mechanisms, treatments, and pattern of TBI. This finding suggests that the patients with APOE epsilon4 predispose to clinical deterioration in acute phase after TBI and APOE polymorphisms play a role in early responses to TBI.