Apolipoprotein E DNA methylation and posttraumatic stress disorder are associated with plasma ApoE level: A preliminary study

Research on the Potential Biomarkers of Mild Traumatic Brain Injury: a Systematic Review and Bibliometric Analysis

Reliable diagnostic methods for mild traumatic brain injury (mTBI) are lacking, and many researchers continue to search for objective biomarkers that can both define and detect mTBI. Although much research has been conducted in this field, there have not been many bibliometric studies. In this study, we aim to analyze the development over the last two decades in scientific output relating to the diagnosis of mTBI. To do this, we extracted documents from Web of Science, PubMed, and Embase and performed descriptive analysis (number of publications, primary journals, authors, and countries/regions), trend topics analysis, and citation analysis for papers across the globe, with a particular focus on molecular markers. One thousand twenty-three publications spanning 390 journals were identified on Web of Science, PubMed, and Embase for the period from 2000 to 2022. The number of publications increased every year (from 2 in 2000 to 137 in 2022). Of all the publications we analyzed, 58.7% had authors from the USA. Our analysis shows that molecular markers are the most studied markers in the field of mTBI diagnostics, accounting for 28.4% of all publications, and that the number of studies focused on this specific aspect has increased sharply in the past 5 years, indicating that molecular markers may become a research trend in the future.

Insulin Resistance in Peripheral Tissues and the Brain: A Tale of Two Sites

The concept of insulin resistance has been around since a few decades after the discovery of insulin itself. To allude to the classic Charles Dicken's novel published 62 years before the discovery of insulin, in some ways, this is the best of times, as the concept of insulin resistance has expanded to include the brain, with the realization that insulin has a life beyond the regulation of glucose. In other ways, it is the worst of times as insulin resistance is implicated in devastating diseases, including diabetes mellitus, obesity, and Alzheimer's disease (AD) that affect the brain. Peripheral insulin resistance affects nearly a quarter of the United States population in adults over age 20. More recently, it has been implicated in AD, with the degree of brain insulin resistance correlating with cognitive decline. This has led to the investigation of brain or central nervous system (CNS) insulin resistance and the question of the relation between CNS and peripheral insulin resistance. While both may involve dysregulated insulin signaling, the two conditions are not identical and not always interlinked. In this review, we compare and contrast the similarities and differences between peripheral and CNS insulin resistance. We also discuss how an apolipoprotein involved in insulin signaling and related to AD, apolipoprotein E (apoE), has distinct pools in the periphery and CNS and can indirectly affect each system. As these systems are both separated but also linked via the blood-brain barrier (BBB), we discuss the role of the BBB in mediating some of the connections between insulin resistance in the brain and in the peripheral tissues.

Apolipoprotein E Isoform-specific changes related to stress and trauma exposure

Post-Traumatic Stress Disorder (PTSD) is a highly prevalent mental health disorder. Due to the high level of variability in susceptibility and severity, PTSD therapies are still insufficient. In addition to environmental exposures, genetic risks play a prominent role and one such factor is apolipoprotein E. The protein (apoE) is functionally involved in cholesterol transport and metabolism and exists as 3 major isoforms in humans: E2, E3, and E4. To model the role of apolipoprotein E isoform in stress-related changes in behavior and cognition, female and male mice (3-5 months of age) expressing E2, E3, or E4 were used. Mice were either placed into control groups or exposed to chronic variable stress (CVS), which has been shown to induce PTSD-like behavioral and neuroendocrine changes. E2 mice showed a unique response to CVS compared to E3 and E4 mice that included impaired spatial learning and memory, increased adrenal gland weight, and no increase in glucocorticoid receptor protein levels (normalized to apoE levels). In addition, the cholesterol metabolite 7-ketocholesterol was elevated in the cortex after CVS in E3 and E4, but not E2 female mice. E2 confers unique changes in behavioral, cognitive, and biomarker profiles after stress exposure and identify 7-ketocholesterol as a possible novel biomarker of the traumatic stress response. We further explored the relationship between E2 and PTSD in an understudied population by genotyping 102 patients of Cambodian and Vietnamese ethnicity. E2 carriers demonstrated a higher odds ratio of having a PTSD diagnosis compared to E3/E3 carriers, supporting that the E2 genotype is associated with PTSD diagnosis after trauma exposure in this population.

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.

Post-traumatic stress disorder and its association with stroke and stroke risk factors: A literature review

Stroke is a major cause of mortality and disability globally that has multiple risk factors. A risk factor that has recently gained more attention is post-traumatic stress disorder (PTSD). Literature searches were carried out for updated PTSD information and for the relationship between PTSD and stroke. The review was divided into two sections, one exploring PTSD as an independent risk factor for stroke, with a second concentrating on PTSD's influence on stroke risk factors. The study presents accumulating evidence that shows traumatic stress predicts stroke and is also linked to many major stroke risk factors. The review contributes knowledge to stroke aetiology and acts as a reference for understanding the relationship between PTSD and stroke. The information presented indicates that screening and identification of traumatic experience would be beneficial for directing stroke patients to appropriate psychological and lifestyle interventions. In doing so, the burden of stroke may be reduced worldwide.

Shared genetic etiology underlying late-onset Alzheimer's disease and posttraumatic stress syndrome

INTRODUCTION

Late-onset Alzheimer's disease (LOAD) manifests comorbid neuropsychiatric symptoms and posttraumatic stress disorder (PTSD) is associated with an increased risk for dementia in late life, suggesting the two disorders may share genetic etiologies.

METHODS

We performed genetic pleiotropy analysis using LOAD and PTSD genome-wide association study (GWAS) datasets from white and African-American populations, followed by functional-genomic analyses.

RESULTS

We found an enrichment for LOAD across increasingly stringent levels of significance with the PTSD GWAS association (LOAD|PTSD) in the discovery and replication cohorts and a modest enrichment for the reverse conditional association (PTSD|LOAD). LOAD|PTSD association analysis identified and replicated the MS4A genes region. These genes showed similar expression pattern in brain regions affected in LOAD, and across-brain-tissue analysis identified a significant association for MS4A6A. The African-American samples showed moderate enrichment; however, no false discovery rate-significant associations.

DISCUSSION

We demonstrated common genetic signatures for LOAD and PTSD and suggested immune response as a common pathway for these diseases.

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

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