Association between apolipoprotein E4 and rehabilitation outcome in hospitalized ischemic stroke patients

Influences of genetic variants on stroke recovery: a meta-analysis of the 31,895 cases

Background

The influences of genetic variants on functional clinical outcomes following stroke are unclear. In order to reliably quantify these influences, we undertook a comprehensive meta-analysis of outcomes after acute intracerebral haemorrhage (ICH) or ischaemic stroke (AIS) in relation to different genetic variants.

Methods

PubMed, PsycInfo, Embase and Medline electronic databases were searched up to January 2019. Outcomes, defined as favourable or poor, were assessed by validated scales (Barthel index, modified Rankin scale, Glasgow outcome scale and National Institutes of Health stroke scale).

Results

Ninety-two publications comprising 31,895 cases met our inclusion criteria. Poor outcome was observed in patients with ICH who possessed the APOE4 allele: OR =2.60 (95% CI = 1.25–5.41, p = 0.01) and in AIS patients with the GA or AA variant at the BDNF-196 locus: OR = 2.60 (95% CI = 1.25–5.41, p = 0.01) or a loss of function allele of CYP2C19: OR = 2.36 (95% CI = 1.56–3.55, p < 0.0001). Poor outcome was not associated with APOE4: OR = 1.02 (95% CI = 0.81–1.27, p = 0.90) or IL6-174 G/C: OR = 2.21 (95% CI = 0.55–8.86, p = 0.26) in patients with AIS.

Conclusions

We demonstrate that recovery of AIS was unfavourably associated with variants of BDNF and CYP2C19 genes whilst recovery of ICH was unfavourably associated with APOE4 gene.

Electronic supplementary material

The online version of this article (10.1007/s10072-019-04024-w) contains supplementary material, which is available to authorized users.

ApoE and Neurodegenerative Diseases in Aging

Age and apolipoprotein E (ApoE) are the mightiest risk factors for dementia and cardiovascular diseases, but the underlying mechanisms remain unclear. In human, ApoE has three isoforms, ApoE2, ApoE3, and ApoE4, which are expressed by the polymorphic alleles: ɛ2, ɛ3, and ɛ4. Among the three polymorphic alleles, apoE ε4 is the most risk gene. ApoE is the main ligand for the low-density lipoprotein (LDL) receptor and the LDL receptor-related protein (LRP), functioning as the component of plasma lipoproteins in the transportation of lipids. Physiologically, ApoE is a multifunctional protein with central roles in lipid metabolism; it transports lipids, including cholesterol, through the cerebrospinal fluid (CSF) and plasma. ApoE expression regulation and apoE gene polymorphism have an important connection with neurological or neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's disease (PD), ischemic stroke, and other diseases.

Linking genes to neurological clinical practice: the genomic basis for neurorehabilitation

Large-scale genomics projects such as the Human Genome Project and the International HapMap Project promise significant advances in the ability to diagnose and treat many conditions, including those with a neurological basis. A major focus of research has emerged in the neurological sciences to elucidate the molecular and genetic basis of various neurological diseases. Indeed, genetic factors are implicated in susceptibility for many neurological disorders, with family history studies providing strong evidence of familial risk for conditions such as stroke, Parkinson's, Alzheimer's, and Huntington's diseases. Heritability studies also suggest a strong genetic contribution to the risk for neurological diseases. Genome-wide association studies are also uncovering novel genetic variants associated with neurological disorders. Whole-genome and exome sequencing are likely to provide novel insights into the genetic basis of neurological disorders. Genetic factors are similarly associated with clinical phenotypes such as symptom severity and progression as well as response to treatment. Specifically, disease progression and functional restoration depend, in part, on the capacity for neural plasticity within residual neural tissues. Furthermore, such plasticity may be influenced in part by the presence of polymorphisms in several genes known to orchestrate neural plasticity including brain-derived neurotrophic factor (BDNF) and Apolipoprotein E. (APOE). It is important for neurorehabilitation therapist practicing in the "genomic era" to be aware of the potential influence of genetic factors during clinical encounters, as advances in molecular sciences are revealing information of critical relevance to the clinical rehabilitation management of individuals with neurological conditions. Video Abstract available (See Video, Supplemental Digital Content 1, http://links.lww.com/JNPT/A88) for more insights from the authors.

Role of apolipoprotein E in neurodegenerative diseases

Apolipoprotein E (APOE) is a lipid-transport protein abundantly expressed in most neurons in the central nervous system. APOE-dependent alterations of the endocytic pathway can affect different functions. APOE binds to cell-surface receptors to deliver lipids and to the hydrophobic amyloid-β peptide, regulating amyloid-β aggregations and clearances in the brain. Several APOE isoforms with major structural differences were discovered and shown to influence the brain lipid transport, glucose metabolism, neuronal signaling, neuroinflammation, and mitochondrial function. This review will summarize the updated research progress on APOE functions and its role in Alzheimer's disease, Parkinson's disease, cardiovascular diseases, multiple sclerosis, type 2 diabetes mellitus, Type III hyperlipoproteinemia, vascular dementia, and ischemic stroke. Understanding the mutations in APOE, their structural properties, and their isoforms is important to determine its role in various diseases and to advance the development of therapeutic strategies. Targeting APOE may be a potential approach for diagnosis, risk assessment, prevention, and treatment of various neurodegenerative and cardiovascular diseases in humans.

Genomic, transcriptomic, and epigenomic approaches to recovery after acquired brain injury

Genomics and its related fields have expanded rapidly, primarily because of the potential utility for clinical decision making and improving our understanding of the pathophysiology of complex conditions. The state of the science and technology associated with this field is such that current and future health care providers, when consulting with new patients about their acquired brain injury and options for rehabilitation, will use genetic information as a routine part of the process, which may include information received from a laboratory report that uses transcriptomic data, informs regarding patient prognosis, and makes recommendations for individualized therapeutic approaches to optimize recovery. This may sound like science fiction, but, in the field of oncology, it is the norm for breast cancer and, more recently, for colon cancer, with expansion to other types of cancer on the horizon as research data continue to contribute to the understanding of the pathophysiology of these conditions. Something similar for rehabilitation after acquired brain injury is much further off on the horizon. However, it is a possibility that will never be realized if the community of scientists and health care providers who work with these patients do not have the knowledge or expertise to embrace genomics and related approaches. This article discusses these approaches, some practical considerations for using such approaches, and what is currently published in this area with regard to brain injury.

Impact of COX-2 rs5275 and rs20417 and GPIIIa rs5918 polymorphisms on 90-day ischemic stroke functional outcome: a novel finding

We hypothesized that polymorphisms in 5 genes related to thrombolytic and inflammation pathways will independently influence occurrence, severity, and 3-month functional outcome in patients with ischemic stroke. This was a case-control design with ischemic stroke patients recruited from 4 public hospitals (n = 640) and community controls (n = 627). Baseline clinical data were collected, and follow-up telephone interviews were conducted with 520 patients at 90 days postevent to determine stroke outcome using the Barthel Index (BI), Modified Rankin Scale (mRS) and Glasgow Outcome Scale (GOS). Blood samples were collected and genotyped for polymorphisms in platelet glycoprotein Ibα (GPIbα) rs224309 and rs6065, glycoprotein IIIa (GPIIIa) rs5918, tissue plasminogen activator (tPA) rs63020761, plasminogen activating inhibitor (PAI-1) rs72578597, and cyclooxygenase-2 (COX-2) rs5275 and rs20417. COX-2 polymorphism rs5275 demonstrated a significant association with poststroke mRS, with a dominant genetic model demonstrating the best fit (CC + TC) (adjusted odds ratio [aOR] = 1.61; P = .026). The COX-2 rs20417 C allele showed an association with GOS (aOR = 1.95; P = .012), and again a dominant genetic model demonstrated the best fit (CC + GC). GPIIIa rs5918 (A1A2) was associated with poststroke BI, with a dominant model demonstrating the best fit (A1A2 + A2A2) (aOR = 0.56; P = .014). There was a significant association between stroke severity and tPA rs63020761 TT allele (aOR = 1.96; 95% CI = 1.03-3.72; P = .040). This is the first study to demonstrate associations between stroke functional outcome and 2 COX-2 variants (rs20417 and rs5275) and a GPIIIa variant (rs5918).

Effects of apolipoprotein E genotype on outcome after ischaemic stroke, intracerebral haemorrhage and subarachnoid haemorrhage

BACKGROUND

Rodent models of acute ischaemic stroke and head injury suggest that apolipoprotein E (APOE) genotype influences neuronal repair, regeneration and survival after brain injury. Possession of an APOE epsilon4 allele is associated with poor outcome after head injury in clinical studies. APOE might therefore influence outcome after acute stroke in humans.

OBJECTIVE AND METHODS

To comprehensively search, identify, assess and carry out meta-analyses of studies reporting on the association between APOE and the combined outcome of death or dependency, or death alone, several months after ischaemic stroke, intracerebral haemorrhage (ICH) or subarachnoid haemorrhage (SAH).

RESULTS

Main analyses included data from nine studies on 2262 patients (1453 with ischaemic stroke, 199 with ICH and 610 with SAH). Overall, epsilon4+ genotypes were not significantly associated with risk of death or dependency several months after stroke. However, there was significant heterogeneity between studies, and between the three pathological types of stroke. Epsilon4+ genotypes were associated with increased death or dependency after SAH (relative risk (RR) 1.40, 95% confidence interval (CI) 1.06 to 1.84), with a trend towards a similar association with ICH (RR 1.38, 95% CI 0.99 to 1.92), but not with ischaemic stroke (RR 0.98, 95% CI 0.85 to 1.12). Results were similar for death alone.

CONCLUSIONS

APOE may differentially affect outcome after the three main pathological types of stroke. Further, large studies are needed to confirm or refute these findings, and to assess the possibility of an interaction between the effects of APOE and age.

Genetic influences on outcome following acute neurological insults

PURPOSE OF REVIEW

To examine the evidence for a genetic influence on clinical outcome after a variety of acute neurologic events.

RECENT FINDINGS

Clinical outcome after brain injury is variable and cannot easily be predicted. It has been proposed that genetic polymorphisms may have an important role in determining outcome from a number of conditions, including acute neurologic events. Apolipoprotein E, an important mediator of cholesterol and lipid transport in the brain, is coded by a polymorphic gene (APOE). The APOE epsilon4 allele has been associated with unfavorable outcome after traumatic brain injury (TBI), hemorrhagic stroke and subarachnoid hemorrhage (SAH). Genes involved in other pathophysiological processes, such as cytokine genes in neuroinflammation, are now being implicated. For example interleukin-6 (IL-6) promoter polymorphisms are a risk factor for poor outcome after ischemic stroke, and may have an effect after traumatic brain injury. The emerging importance of a number of other gene polymorphisms is outlined in the review.

SUMMARY

There is evidence demonstrating the epsilon4 allele of APOE predisposes to poor outcome after TBI, hemorrhagic stroke and SAH, but not ischemic stroke. The reason for this difference is unclear but it suggests there may be differences in the key mechanisms underlying the response to different types of insult. The role of other gene polymorphisms is being increasingly explored but there is still a need for larger prospective studies looking at larger panels of gene polymorphisms.

Clinically Translated Ischemic Stroke Genomics

Cohort studies show that having a positive family history of stroke increases the odds of having a stroke by approximately 30%. The heritability of stroke appears to be heterogeneous across ischemic stroke subtypes, with cardioembolic stroke being least heritable. The relative influence of stroke risk attenuates with age, but genetics does not cease to be relevant in later adulthood. Recent family history and twin studies suggest that genetic factors remain relevant even beyond the seventh decade of life. One of the challenges of gene discovery in stroke relates to the complexities of phenotype. The complexities of phenotype can be addressed by focusing on individual ischemic stroke subtypes or by studying intermediate phenotypes like leukaraiosis, which has a heritability of approximately 70%. Although most stroke genetics research has focused on the identification of risk factor genes, an independent set of genes likely influences poststroke outcomes (for example, apolipoprotein E) and response to drug therapies (example, alpha-adducin and diuretic therapy).