Active duty service members who sustain a traumatic brain injury have chronically elevated peripheral concentrations of Aß40 and lower ratios of Aß42/40.

PRIMARY OBJECTIVE: Excessive accumulation of amyloid beta (Aß) and tau have been observed in older individuals with chronic neurological symptoms related to a traumatic brain injury (TBI), yet little is known about the possible role of Aß in younger active duty service members following a TBI. The purpose of the study was to determine if Aß 40 or 42 related to sustaining a TBI or to chronic neurological symptoms in a young cohort of military personnel. RESEARCH DESIGN: This was a cross-sectional study of active duty service members who reported sustaining a TBI and provided self-report of neurological and psychological symptoms and provided blood. METHODS AND PROCEDURES: An ultrasensitive single-molecule enzyme-linked immunosorbent assay was used to compare concentrations of Aß in active duty service members with (TBI+; n = 53) and without (TBI-; n = 18) a history of TBI. Self-report and medical history were used to measure TBI occurrence and approximate the number of total TBIs and the severity of TBIs sustained during deployment. MAIN OUTCOMES AND RESULTS: This study reports that TBI is associated with higher concentrations of Aß40 (F1,68 = 6.948, p = 0.009) and a lower ratio of Aß42/Aß40 (F1,62 = 5.671, p = 0.020). These differences remained significant after controlling for co-morbid symptoms of post-traumatic stress disorder and depression. CONCLUSIONS: These findings suggest that alterations in Aß relate to TBIs and may contribute to chronic neurological symptoms.

Altered gene expression of the innate immune, neuroendocrine, and nuclear factor-kappa B (NF-κB) systems is associated with posttraumatic stress disorder in military personnel.

Whole transcriptome analysis provides an unbiased examination of biological activity, and likely, unique insight into the mechanisms underlying posttraumatic stress disorder (PTSD) and comorbid depression and traumatic brain injury. This study compared gene-expression profiles in military personnel with PTSD (n=28) and matched controls without PTSD (n=27) using HG-U133 Plus 2.0 microarrays (Affymetrix), which contain 54,675 probe sets representing more than 38,500 genes. Analysis of expression profiles revealed 203 differentially expressed genes in PTSD, of which 72% were upregulated. Using Partek Genomics Suite 6.6, differentially expressed transcription clusters were filtered based on a selection criterion of ≥1.5 relative fold change at a false discovery rate of ≤5%. Ingenuity Pathway Analysis (Qiagen) of the differentially expressed genes indicated a dysregulation of genes associated with the innate immune, neuroendocrine, and NF-κB systems. These findings provide novel insights that may lead to new pharmaceutical agents for PTSD treatments and help mitigate mental and physical comorbidity risk.

Peripheral Total Tau in Military Personnel Who Sustain Traumatic Brain Injuries During Deployment.

IMPORTANCE: Approximately one-third of military personnel who deploy for combat operations sustain 1 or more traumatic brain injuries (TBIs), which increases the risk for chronic symptoms of postconcussive disorder, posttraumatic stress disorder, and depression and for the development of chronic traumatic encephalopathy. Elevated concentrations of tau are observed in blood shortly following a TBI, but, to our knowledge, the role of tau elevations in blood in the onset and maintenance of chronic symptoms after TBI has not been investigated. OBJECTIVES: To assess peripheral tau levels in military personnel exposed to TBI and to examine the relationship between chronic neurological symptoms and tau elevations. DESIGN, SETTING, AND PARTICIPANTS: Observational assessment from September 2012 to August 2014 of US military personnel at the Madigan Army Medical Center who had been deployed within the previous 18 months. Plasma total tau concentrations were measured using a novel ultrasensitive single-molecule enzyme-linked immunosorbent assay. Classification of participants with and without self-reported TBI was made using the Warrior Administered Retrospective Casualty Assessment Tool. Self-reported symptoms of postconcussive disorder, posttraumatic stress disorder, and depression were determined by the Neurobehavioral Symptom Inventory, the Posttraumatic Stress Disorder Checklist Military Version, and the Quick Inventory of Depressive Symptomatology, respectively. Group differences in tau concentrations were determined through analysis of variance models, and area under the receiver operating characteristic curve determined the sensitivity and specificity of tau concentrations in predicting TBI and chronic symptoms. Seventy participants with self-reported TBI on the Warrior Administered Retrospective Casualty Assessment Tool and 28 control participants with no TBI exposure were included. MAIN OUTCOMES AND MEASURES: Concentration of total tau in peripheral blood. RESULTS: Concentrations of plasma tau were significantly elevated in the 70 participants with self-reported TBI compared with the 28 controls (mean [SD], 1.13 [0.78] vs 0.63 [0.48] pg/mL, respectively; F1,97 = 4.97; P = .03). Within the self-reported TBI cases, plasma total tau concentrations were significantly associated with having a medical record of TBI compared with self-reported TBI only (mean [SD], 1.57 [0.92] vs 0.85 [0.52] pg/mL, respectively; F1,69 = 6.15; P = .02) as well as reporting the occurrence of 3 of more TBIs during deployment compared with fewer than 3 TBIs (mean [SD], 1.52 [0.82] vs 0.82 [0.60] pg/mL, respectively; F1,69 = 8.57; P = .008). The severity of total postconcussive symptoms correlated with total tau concentrations in the self-reported TBI group (r = 0.37; P = .003). CONCLUSIONS AND RELEVANCE: Military personnel who report multiple TBIs have long-term elevations in total tau concentration. The total tau concentration relates to symptoms of postconcussive disorder.