Inflammatory biomarkers for neurobehavioral dysregulation in former American football players: findings from the DIAGNOSE CTE Research Project.

BACKGROUND: Traumatic encephalopathy syndrome (TES) is defined as the clinical manifestation of the neuropathological entity chronic traumatic encephalopathy (CTE). A core feature of TES is neurobehavioral dysregulation (NBD), a neuropsychiatric syndrome in repetitive head impact (RHI)-exposed individuals, characterized by a poor regulation of emotions/behavior. To discover biological correlates for NBD, we investigated the association between biomarkers of inflammation (interleukin (IL)-1ß, IL-6, IL-8, IL-10, C-reactive protein (CRP), tumor necrosis factor (TNF)-α) in cerebrospinal fluid (CSF) and NBD symptoms in former American football players and unexposed individuals. METHODS: Our cohort consisted of former American football players, with (n = 104) or without (n = 76) NBD diagnosis, as well as asymptomatic unexposed individuals (n = 55) from the DIAGNOSE CTE Research Project. Specific measures for NBD were derived (i.e., explosivity, emotional dyscontrol, impulsivity, affective lability, and a total NBD score) from a factor analysis of multiple self-report neuropsychiatric measures. Analyses of covariance tested differences in biomarker concentrations between the three groups. Within former football players, multivariable linear regression models assessed relationships among log-transformed inflammatory biomarkers, proxies for RHI exposure (total years of football, cumulative head impact index), and NBD factor scores, adjusted for relevant confounding variables. Sensitivity analyses tested (1) differences in age subgroups (< 60, ≥ 60 years); (2) whether associations could be identified with plasma inflammatory biomarkers; (3) associations between neurodegeneration and NBD, using plasma neurofilament light (NfL) chain protein; and (4) associations between biomarkers and cognitive performance to explore broader clinical symptoms related to TES. RESULTS: CSF IL-6 was higher in former American football players with NBD diagnosis compared to players without NBD. Furthermore, elevated levels of CSF IL-6 were significantly associated with higher emotional dyscontrol, affective lability, impulsivity, and total NBD scores. In older football players, plasma NfL was associated with higher emotional dyscontrol and impulsivity, but also with worse executive function and processing speed. Proxies for RHI exposure were not significantly associated with biomarker concentrations. CONCLUSION: Specific NBD symptoms in former American football players may result from multiple factors, including neuroinflammation and neurodegeneration. Future studies need to unravel the exact link between NBD and RHI exposure, including the role of other pathophysiological pathways.

Flortaucipir tau PET findings from former professional and college American football players in the DIAGNOSE CTE research project.

INTRODUCTION: Tau is a key pathology in chronic traumatic encephalopathy (CTE). Here, we report our findings in tau positron emission tomography (PET) measurements from the DIAGNOSE CTE Research Project. METHOD: We compare flortaucipir PET measures from 104 former professional players (PRO), 58 former college football players (COL), and 56 same-age men without exposure to repetitive head impacts (RHI) or traumatic brain injury (unexposed [UE]); characterize their associations with RHI exposure; and compare players who did or did not meet diagnostic criteria for traumatic encephalopathy syndrome (TES). RESULTS: Significantly elevated flortaucipir uptake was observed in former football players (PRO+COL) in prespecified regions (p < 0.05). Association between regional flortaucipir uptake and estimated cumulative head impact exposure was only observed in the superior frontal region in former players over 60 years old. Flortaucipir PET was not able to differentiate TES groups. DISCUSSION: Additional studies are needed to further understand tau pathology in CTE and other individuals with a history of RHI.

Randomized controlled pilot trial of prazosin for prophylaxis of posttraumatic headaches in active-duty service members and veterans.

OBJECTIVE: Evaluate the efficacy and tolerability of prazosin for prophylaxis of headaches following mild traumatic brain injury in active-duty service members and military veterans. BACKGROUND: Prazosin is an alpha-1 adrenoreceptor antagonist that reduces noradrenergic signaling. An open-label trial in which prazosin reduced headache frequency in veterans following mild traumatic brain injury provided the rationale for this pilot study. METHODS: A 22-week parallel-group randomized controlled trial  which included 48 military veterans and active-duty service members with mild traumatic brain injury-related headaches was performed. The study design was based on International Headache Society consensus guidelines for randomized controlled trials for chronic migraine. Following a pre-treatment baseline phase, participants with at least eight qualifying headache days per 4 weeks were randomized 2:1 to prazosin or placebo. After a 5-week titration to a maximum possible dose of 5 mg (morning) and 20 mg (evening), participants were maintained on the achieved dose for 12 weeks. Outcome measures were evaluated in 4-week blocks during the maintenance dose phase. The primary outcome measure was change in 4-week frequency of qualifying headache days. Secondary outcome measures were percent participants achieving at least 50% reduction in qualifying headache days and change in Headache Impact Test-6 scores. RESULTS: Intent-to-treat analysis of randomized study participants (prazosin N = 32; placebo N = 16) demonstrated greater benefit over time in the prazosin group for all three outcome measures. In prazosin versus placebo participants, reductions from baseline to the final rating period for 4-week headache frequency were -11.9 ± 1.0 (mean ± standard error) versus -6.7 ± 1.5, a prazosin minus placebo difference of -5.2 (-8.8, -1.6 [95% confidence interval]), p = 0.005 and for Headache Impact Test-6 scores were -6.0 ± 1.3 versus +0.6 ± 1.8, a difference of -6.6 (-11.0, -2.2), p = 0.004. The mean predicted percent of participants at 12 weeks with ≥50% reduction in headache days/4 weeks, baseline to final rating, was 70 ± 8% for prazosin (21/30) versus 29 ± 12% for placebo (4/14), odds ratio 5.8 (1.44, 23.6), p = 0.013. The trial completion rate of 94% in the prazosin group (30/32) and 88% in the placebo group (14/16) indicated that prazosin was generally well tolerated at the administered dose regimen. Morning drowsiness/lethargy was the only adverse effect that differed significantly between groups, affecting 69% of the prazosin group (22/32) versus 19% of the placebo group (3/16), p = 0.002. CONCLUSIONS: This pilot study provides a clinically meaningful efficacy signal for prazosin prophylaxis of posttraumatic headaches. A larger randomized controlled trial is needed to confirm and extend these promising results.

The dynorphin/kappa opioid receptor mediates adverse immunological and behavioral outcomes induced by repetitive blast trauma.

BACKGROUND: Adverse pathophysiological and behavioral outcomes related to mild traumatic brain injury (mTBI), posttraumatic stress disorder (PTSD), and chronic pain are common following blast exposure and contribute to decreased quality of life, but underlying mechanisms and prophylactic/treatment options remain limited. The dynorphin/kappa opioid receptor (KOR) system helps regulate behavioral and inflammatory responses to stress and injury; however, it has yet to be investigated as a potential mechanism in either humans or animals exposed to blast. We hypothesized that blast-induced KOR activation mediates adverse outcomes related to inflammation and affective behavioral response. METHODS: C57Bl/6 adult male mice were singly or repeatedly exposed to either sham (anesthesia only) or blast delivered by a pneumatic shock tube. The selective KOR antagonist norBNI or vehicle (saline) was administered 72 h prior to repetitive blast or sham exposure. Serum and brain were collected 10 min or 4 h post-exposure for dynorphin A-like immunoreactivity and cytokine measurements, respectively. At 1-month post-exposure, mice were tested in a series of behavioral assays related to adverse outcomes reported by humans with blast trauma. RESULTS: Repetitive but not single blast exposure resulted in increased brain dynorphin A-like immunoreactivity. norBNI pretreatment blocked or significantly reduced blast-induced increase in serum and brain cytokines, including IL-6, at 4 h post exposure and aversive/anxiety-like behavioral dysfunction at 1-month post-exposure. CONCLUSIONS: Our findings demonstrate a previously unreported role for the dynorphin/KOR system as a mediator of biochemical and behavioral dysfunction following repetitive blast exposure and highlight this system as a potential prophylactic/therapeutic treatment target.

Blood extracellular vesicles carrying synaptic function- and brain-related proteins as potential biomarkers for Alzheimer's disease.

INTRODUCTION: Objective and accessible markers for Alzheimer's disease (AD) and other dementias are critically needed. METHODS: We identified NMDAR2A, a protein related to synaptic function, as a novel marker of central nervous system (CNS)-derived plasma extracellular vesicles (EVs) and developed a flow cytometry-based technology for detecting such plasma EVs readily. The assay was initially tested in our local cross-sectional study to distinguish AD patients from healthy controls (HCs) or from Parkinson's disease (PD) patients, followed by a validation study using an independent cohort collected from multiple medical centers (the Alzheimer's Disease Neuroimaging Initiative). Cerebrospinal fluid AD molecular signature was used to confirm diagnoses of all AD participants. RESULTS: Likely CNS-derived EVs in plasma were significantly reduced in AD compared to HCs in both cohorts. Integrative models including CNS-derived EV markers and AD markers present on EVs reached area under the curve of 0.915 in discovery cohort and 0.810 in validation cohort. DISCUSSION: This study demonstrated that robust and rapid analysis of individual neuron-derived synaptic function-related EVs in peripheral blood may serve as a helpful marker of synaptic dysfunction in AD and dementia.

Trial of Prazosin for Post-Traumatic Stress Disorder in Military Veterans.

BACKGROUND: In randomized trials, prazosin, an α1-adrenoreceptor antagonist, has been effective in alleviating nightmares associated with post-traumatic stress disorder (PTSD) in military veterans. METHODS: We recruited veterans from 13 Department of Veterans Affairs medical centers who had chronic PTSD and reported frequent nightmares. Participants were randomly assigned to receive prazosin or placebo for 26 weeks; the drug or placebo was administered in escalating divided doses over the course of 5 weeks to a daily maximum of 20 mg in men and 12 mg in women. After week 10, participants continued to receive prazosin or placebo in a double-blind fashion for an additional 16 weeks. The three primary outcome measures were the change in score from baseline to 10 weeks on the Clinician-Administered PTSD Scale (CAPS) item B2 ("recurrent distressing dreams"; scores range from 0 to 8, with higher scores indicating more frequent and more distressing dreams); the change in score from baseline to 10 weeks on the Pittsburgh Sleep Quality Index (PSQI; scores range from 0 to 21, with higher scores indicating worse sleep quality); and the Clinical Global Impression of Change (CGIC) score at 10 weeks (scores range from 1 to 7, with lower scores indicating greater improvement and a score of 4 indicating no change). RESULTS: A total of 304 participants underwent randomization; 152 were assigned to prazosin, and 152 to placebo. At 10 weeks, there were no significant differences between the prazosin group and the placebo group in the mean change from baseline in the CAPS item B2 score (between-group difference, 0.2; 95% confidence interval [CI], -0.3 to 0.8; P=0.38), in the mean change in PSQI score (between-group difference, 0.1; 95% CI, -0.9 to 1.1; P=0.80), or in the CGIC score (between-group difference, 0; 95% CI, -0.3 to 0.3; P=0.96). There were no significant differences in these measures at 26 weeks (a secondary outcome) or in other secondary outcomes. At 10 weeks, the mean difference between the prazosin group and the placebo group in the change from baseline in supine systolic blood pressure was a decrease of 6.7 mm Hg. The adverse event of new or worsening suicidal ideation occurred in 8% of the participants assigned to prazosin versus 15% of those assigned to placebo. CONCLUSIONS: In this trial involving military veterans who had chronic PTSD, prazosin did not alleviate distressing dreams or improve sleep quality. (Funded by the Department of Veterans Affairs Cooperative Studies Program; PACT ClinicalTrials.gov number, NCT00532493 .).

Repetitive blast mild traumatic brain injury increases ethanol sensitivity in male mice and risky drinking behavior in male combat veterans.

BACKGROUND: Mild traumatic brain injury (mTBI) is common in civilians and highly prevalent among military service members. mTBI can increase health risk behaviors (e.g., sensation seeking, impulsivity) and addiction risk (e.g., for alcohol use disorder (AUD)), but how mTBI and substance use might interact to promote addiction risk remains poorly understood. Likewise, potential differences in single vs. repetitive mTBI in relation to alcohol use/abuse have not been previously examined. METHODS: Here, we examined how a history of single (1×) or repetitive (3×) blast exposure (blast-mTBI) affects ethanol (EtOH)-induced behavioral and physiological outcomes using an established mouse model of blast-mTBI. To investigate potential translational relevance, we also examined self-report responses to the Alcohol Use Disorders Identification Test-Consumption questions (AUDIT-C), a widely used measure to identify potential hazardous drinking and AUD, and used a novel unsupervised machine learning approach to investigate whether a history of blast-mTBI affected drinking behaviors in Iraq/Afghanistan Veterans. RESULTS: Both single and repetitive blast-mTBI in mice increased the sedative properties of EtOH (with no change in tolerance or metabolism), but only repetitive blast potentiated EtOH-induced locomotor stimulation and shifted EtOH intake patterns. Specifically, mice exposed to repetitive blasts showed increased consumption "front-loading" (e.g., a higher rate of consumption during an initial 2-h acute phase of a 24-h alcohol access period and decreased total daily intake) during an intermittent 2-bottle choice condition. Examination of AUDIT-C scores in Iraq/Afghanistan Veterans revealed an optimal 3-cluster solution: "low" (low intake and low frequency), "frequent" (low intake and high frequency), and "risky" (high intake and high frequency), where Veterans with a history of blast-mTBI displayed a shift in cluster assignment from "frequent" to "risky," as compared to Veterans who were deployed to Iraq/Afghanistan but had no lifetime history of TBI. CONCLUSIONS: Together, these results offer new insight into how blast-mTBI may give increase AUD risk and highlight the increased potential for adverse health risk behaviors following repetitive blast-mTBI.

Sex differences in the genetic predictors of Alzheimer's pathology.

Autopsy measures of Alzheimer's disease neuropathology have been leveraged as endophenotypes in previous genome-wide association studies (GWAS). However, despite evidence of sex differences in Alzheimer's disease risk, sex-stratified models have not been incorporated into previous GWAS analyses. We looked for sex-specific genetic associations with Alzheimer's disease endophenotypes from six brain bank data repositories. The pooled dataset included 2701 males and 3275 females, the majority of whom were diagnosed with Alzheimer's disease at autopsy (70%). Sex-stratified GWAS were performed within each dataset and then meta-analysed. Loci that reached genome-wide significance (P < 5 × 10-8) in stratified models were further assessed for sex interactions. Additional analyses were performed in independent datasets leveraging cognitive, neuroimaging and CSF endophenotypes, along with age-at-onset data. Outside of the APOE region, one locus on chromosome 7 (rs34331204) showed a sex-specific association with neurofibrillary tangles among males (P = 2.5 × 10-8) but not females (P = 0.85, sex-interaction P = 2.9 × 10-4). In follow-up analyses, rs34331204 was also associated with hippocampal volume, executive function, and age-at-onset only among males. These results implicate a novel locus that confers male-specific protection from tau pathology and highlight the value of assessing genetic associations in a sex-specific manner.

Effect of dietary palmitic and stearic acids on sucrose motivation and hypothalamic and striatal cell signals in the rat.

We have reported that motivation for sucrose is increased in rats fed a moderate (31%) mixed-fat diet for 4-6 wk. In this study, rats were fed diets containing 32% stearic (STEAR) or palmitic (PALM) acid, and behavior, metabolic profile, and cell signals were compared with those of rats fed a matched low-fat diet (LF; 11% fat) diet. Rats fed STEAR or PALM increased sucrose motivation relative to LF rats (one-way ANOVA for lever presses; P = 0.03). Diet did not change fasting glucose, insulin, total cholesterol, triglycerides, intravenous glucose tolerance test glucose profile, percent body fat, or total kilocalories, although kilocalories as fat were increased (ANOVA, P < 0.05). Cell signals were assessed in rats ranked from high to low sucrose motivation. Diet did not alter Thr and Ser phosphorylation of Akt in the medial hypothalamus (HYP) and striatum (STR). However, Ser phosphorylation of GSK3Β was decreased in HYP and STR from both high- and low-performer tertiles of STEAR and PALM rats (ANOVA within each brain region, P < 0.05). Two histone 3 (H3) modifications were also assessed. Although there was no effect of diet on the transcription-repressive H3 modification, H3K27me3, the transcription-permissive H3 modification, H3K4me3, was significantly decreased in the HYP of high performers fed PALM or STEAR (ANOVA, P = 0.013). There was no effect of diet on H3K4me3 levels in HYP of low performers, or in STR. Our findings suggest signal-specific and brain region-specific effects of PALM or STEAR diets and may link downstream signaling effects of GSK3Β activity and H3 modifications with enhanced motivational behavior.

Sex-specific genetic predictors of Alzheimer's disease biomarkers.

Cerebrospinal fluid (CSF) levels of amyloid-ß 42 (Aß42) and tau have been evaluated as endophenotypes in Alzheimer's disease (AD) genetic studies. Although there are sex differences in AD risk, sex differences have not been evaluated in genetic studies of AD endophenotypes. We performed sex-stratified and sex interaction genetic analyses of CSF biomarkers to identify sex-specific associations. Data came from a previous genome-wide association study (GWAS) of CSF Aß42 and tau (1527 males, 1509 females). We evaluated sex interactions at previous loci, performed sex-stratified GWAS to identify sex-specific associations, and evaluated sex interactions at sex-specific GWAS loci. We then evaluated sex-specific associations between prefrontal cortex (PFC) gene expression at relevant loci and autopsy measures of plaques and tangles using data from the Religious Orders Study and Rush Memory and Aging Project. In Aß42, we observed sex interactions at one previous and one novel locus: rs316341 within SERPINB1 (p = 0.04) and rs13115400 near LINC00290 (p = 0.002). These loci showed stronger associations among females (ß = - 0.03, p = 4.25 × 10-8; ß = 0.03, p = 3.97 × 10-8) than males (ß = - 0.02, p = 0.009; ß = 0.01, p = 0.20). Higher levels of expression of SERPINB1, SERPINB6, and SERPINB9 in PFC was associated with higher levels of amyloidosis among females (corrected p values < 0.02) but not males (p > 0.38). In total tau, we observed a sex interaction at a previous locus, rs1393060 proximal to GMNC (p = 0.004), driven by a stronger association among females (ß = 0.05, p = 4.57 × 10-10) compared to males (ß = 0.02, p = 0.03). There was also a sex-specific association between rs1393060 and tangle density at autopsy (pfemale = 0.047; pmale = 0.96), and higher levels of expression of two genes within this locus were associated with lower tangle density among females (OSTN p = 0.006; CLDN16 p = 0.002) but not males (p ≥ 0.32). Results suggest a female-specific role for SERPINB1 in amyloidosis and for OSTN and CLDN16 in tau pathology. Sex-specific genetic analyses may improve understanding of AD's genetic architecture.

Retrospective and Prospective Memory Among OEF/OIF/OND Veterans With a Self-Reported History of Blast-Related mTBI.

OBJECTIVES: To evaluate prospective and retrospective memory abilities in Operation Enduring Freedom (OEF), Operation Iraqi Freedom (OIF), and Operation New Dawn (OND) Veterans with and without a self-reported history of blast-related mild traumatic brain injury (mTBI). METHODS: Sixty-one OEF/OIF/OND Veterans, including Veterans with a self-reported history of blast-related mTBI (mTBI group; n=42) and Veterans without a self-reported history of TBI (control group; n=19) completed the Memory for Intentions Test, a measure of prospective memory (PM), and two measures of retrospective memory (RM), the California Verbal Learning Test-II and the Brief Visuospatial Memory Test-Revised. RESULTS: Veterans in the mTBI group exhibited significantly lower PM performance than the control group, but the groups did not differ in their performance on RM measures. Further analysis revealed that Veterans in the mTBI group with current PTSD (mTBI/PTSD+) demonstrated significantly lower performance on the PM measure than Veterans in the control group. PM performance by Veterans in the mTBI group without current PTSD (mTBI/PTSD-) was intermediate between the mTBI/PTSD+ and control groups, and results for the mTBI/PTSD- group were not significantly different from either of the other two groups. CONCLUSIONS: Results suggest that PM performance may be a sensitive marker of cognitive dysfunction among OEF/OIF/OND Veterans with a history of self-reported blast-related mTBI and comorbid PTSD. Reduced PM may account, in part, for complaints of cognitive difficulties in this Veteran cohort, even years post-injury. (JINS, 2018, 24, 324-334).

Associations between CSF cortisol and CSF norepinephrine in cognitively normal controls and patients with amnestic MCI and AD dementia.

OBJECTIVE: This study evaluated the effects of Alzheimer disease (AD) on the relationship between the brain noradrenergic system and hypothalamic pituitary adrenocortical axis (HPA). Specifically, relationships between cerebrospinal fluid (CSF) norepinephrine (NE) and CSF cortisol were examined in cognitively normal participants and participants with AD dementia and amnestic mild cognitive impairment (aMCI). We hypothesized that there would a positive association between these 2 measures in cognitively normal controls and that this association would be altered in AD. METHODS: Four hundred twenty-one CSF samples were assayed for NE and cortisol in controls (n = 305), participants with aMCI (n = 22), and AD dementia (n = 94). Linear regression was used to examine the association between CSF cortisol and NE, adjusting for age, sex, education, and body mass index. RESULTS: Contrary to our hypothesis, CSF cortisol and NE levels were not significantly associated in controls. However, higher cortisol levels were associated with higher NE levels in AD and aMCI participants. Regression coefficients ± standard errors for the change in cortisol per 100-pg/mL increase in NE are as follows: controls 0.0 ± 0.2, P = 1.0; MCI, 1.4 ± 0.7, P = .14; and AD 1.1 ± 0.4, P = .032. Analysis with MCI and AD participants combined strengthened statistical significance (1.2 ± 0.3, P = .007). CONCLUSIONS: Enhanced responsiveness of the HPA axis to noradrenergic stimulatory regulation in AD and disruption of the blood brain barrier may contribute to these findings. Because brainstem noradrenergic stimulatory regulation of the HPA axis is substantially increased by both acute and chronic stress, these findings are also consistent with AD participants experiencing higher levels of acute and chronic stress.

Mass-Spectrometry-Based Method To Quantify in Parallel Tau and Amyloid ß 1-42 in CSF for the Diagnosis of Alzheimer's Disease.

Alzheimer's disease (AD), the most common form of dementia, afflicts about 50 million people worldwide. Currently, AD diagnosis is primarily based on psychological evaluation and can only be confirmed post-mortem. Reliable and objective biomarkers for prognosis and diagnosis have been sought for years. Together, tau and amyloid ß 1-42 (Aß42) in cerebrospinal fluid (CSF) have been shown to provide good diagnostic sensitivity and specificity. Additionally, phosphorylated forms of tau, such as tau pS181, have also shown promising results. However, the measurement of such markers currently relies on antibody-based immunoassays that have shown variability, leading to discrepant results across laboratories. To date, mass spectrometry methods developed to evaluate CSF tau and Aß42 are not compatible. We present in this article the development of a mass-spectrometry-based method of quantification for CSF tau and Aß42 in parallel. The absolute concentrations of tau and Aß42 we measured are on average 50 ng/mL (7-130 ng/mL) and 7.1 ng/mL (3-13 ng/mL), respectively. Analyses of CSF tau and Aß42, in a cohort of patients with AD, mild cognitive impairment, and healthy controls (30 subjects), provide significant group differences evaluated with ROC curves (AUC(control-AD) and AUC(control-MCI) = 1, AUC(MCI-AD) = 0.76), with at least equivalent diagnostic utility to immunoassay measurements in the same sample set. Finally, a significant and negative correlation was found between the tau and Aß peptides ratio and the disease severity.

Seed-competent high-molecular-weight tau species accumulates in the cerebrospinal fluid of Alzheimer's disease mouse model and human patients.

OBJECTIVE: Cerebrospinal fluid (CSF) tau is an excellent surrogate marker for assessing neuropathological changes that occur in Alzheimer's disease (AD) patients. However, whether the elevated tau in AD CSF is just a marker of neurodegeneration or, in fact, a part of the disease process is uncertain. Moreover, it is unknown how CSF tau relates to the recently described soluble high-molecular-weight (HMW) species that is found in the postmortem AD brain and can be taken up by neurons and seed aggregates. METHODS: We have examined seeding and uptake properties of brain extracellular tau from various sources, including interstitial fluid (ISF) and CSF from an AD transgenic mouse model and postmortem ventricular and antemortem lumbar CSF from AD patients. RESULTS: We found that brain ISF and CSF tau from the AD mouse model can be taken up by cells and induce intracellular aggregates. Ventricular CSF from AD patients contained a rare HMW tau species that exerted a higher seeding activity. Notably, the HMW tau species was also detected in lumbar CSF from AD patients, and its levels were significantly elevated compared to control subjects. HMW tau derived from CSF of AD patients was seed competent in vitro. INTERPRETATION: These findings suggest that CSF from an AD brain contains potentially bioactive HMW tau species, giving new insights into the role of CSF tau and biomarker development for AD. Ann Neurol 2016;80:355-367.

Genome-wide, high-content siRNA screening identifies the Alzheimer's genetic risk factor FERMT2 as a major modulator of APP metabolism.

Genome-wide association studies (GWASs) have identified 19 susceptibility loci for Alzheimer's disease (AD). However, understanding how these genes are involved in the pathophysiology of AD is one of the main challenges of the "post-GWAS" era. At least 123 genes are located within the 19 susceptibility loci; hence, a conventional approach (studying the genes one by one) would not be time- and cost-effective. We therefore developed a genome-wide, high-content siRNA screening approach and used it to assess the functional impact of gene under-expression on APP metabolism. We found that 832 genes modulated APP metabolism. Eight of these genes were located within AD susceptibility loci. Only FERMT2 (a ß3-integrin co-activator) was also significantly associated with a variation in cerebrospinal fluid Aß peptide levels in 2886 AD cases. Lastly, we showed that the under-expression of FERMT2 increases Aß peptide production by raising levels of mature APP at the cell surface and facilitating its recycling. Taken as a whole, our data suggest that FERMT2 modulates the AD risk by regulating APP metabolism and Aß peptide production.

Genome-wide association study identifies four novel loci associated with Alzheimer's endophenotypes and disease modifiers.

More than 20 genetic loci have been associated with risk for Alzheimer's disease (AD), but reported genome-wide significant loci do not account for all the estimated heritability and provide little information about underlying biological mechanisms. Genetic studies using intermediate quantitative traits such as biomarkers, or endophenotypes, benefit from increased statistical power to identify variants that may not pass the stringent multiple test correction in case-control studies. Endophenotypes also contain additional information helpful for identifying variants and genes associated with other aspects of disease, such as rate of progression or onset, and provide context to interpret the results from genome-wide association studies (GWAS). We conducted GWAS of amyloid beta (Aß42), tau, and phosphorylated tau (ptau181) levels in cerebrospinal fluid (CSF) from 3146 participants across nine studies to identify novel variants associated with AD. Five genome-wide significant loci (two novel) were associated with ptau181, including loci that have also been associated with AD risk or brain-related phenotypes. Two novel loci associated with Aß42 near GLIS1 on 1p32.3 (ß = -0.059, P = 2.08 × 10-8) and within SERPINB1 on 6p25 (ß = -0.025, P = 1.72 × 10-8) were also associated with AD risk (GLIS1: OR = 1.105, P = 3.43 × 10-2), disease progression (GLIS1: ß = 0.277, P = 1.92 × 10-2), and age at onset (SERPINB1: ß = 0.043, P = 4.62 × 10-3). Bioinformatics indicate that the intronic SERPINB1 variant (rs316341) affects expression of SERPINB1 in various tissues, including the hippocampus, suggesting that SERPINB1 influences AD through an Aß-associated mechanism. Analyses of known AD risk loci suggest CLU and FERMT2 may influence CSF Aß42 (P = 0.001 and P = 0.009, respectively) and the INPP5D locus may affect ptau181 levels (P = 0.009); larger studies are necessary to verify these results. Together the findings from this study can be used to inform future AD studies.

The ageing systemic milieu negatively regulates neurogenesis and cognitive function.

In the central nervous system, ageing results in a precipitous decline in adult neural stem/progenitor cells and neurogenesis, with concomitant impairments in cognitive functions. Interestingly, such impairments can be ameliorated through systemic perturbations such as exercise. Here, using heterochronic parabiosis we show that blood-borne factors present in the systemic milieu can inhibit or promote adult neurogenesis in an age-dependent fashion in mice. Accordingly, exposing a young mouse to an old systemic environment or to plasma from old mice decreased synaptic plasticity, and impaired contextual fear conditioning and spatial learning and memory. We identify chemokines--including CCL11 (also known as eotaxin)--the plasma levels of which correlate with reduced neurogenesis in heterochronic parabionts and aged mice, and the levels of which are increased in the plasma and cerebrospinal fluid of healthy ageing humans. Lastly, increasing peripheral CCL11 chemokine levels in vivo in young mice decreased adult neurogenesis and impaired learning and memory. Together our data indicate that the decline in neurogenesis and cognitive impairments observed during ageing can be in part attributed to changes in blood-borne factors.

Cerebrospinal fluid peptides as potential Parkinson disease biomarkers: a staged pipeline for discovery and validation.

Finding robust biomarkers for Parkinson disease (PD) is currently hampered by inherent technical limitations associated with imaging or antibody-based protein assays. To circumvent the challenges, we adapted a staged pipeline, starting from our previous proteomic profiling followed by high-throughput targeted mass spectrometry (MS), to identify peptides in human cerebrospinal fluid (CSF) for PD diagnosis and disease severity correlation. In this multicenter study consisting of training and validation sets, a total of 178 subjects were randomly selected from a retrospective cohort, matching age and sex between PD patients, healthy controls, and neurological controls with Alzheimer disease (AD). From ∼14,000 unique peptides displaying differences between PD and healthy control in proteomic investigations, 126 peptides were selected based on relevance and observability in CSF using bioinformatic analysis and MS screening, and then quantified by highly accurate and sensitive selected reaction monitoring (SRM) in the CSF of 30 PD patients versus 30 healthy controls (training set), followed by diagnostic (receiver operating characteristics) and disease severity correlation analyses. The most promising candidates were further tested in an independent cohort of 40 PD patients, 38 AD patients, and 40 healthy controls (validation set). A panel of five peptides (derived from SPP1, LRP1, CSF1R, EPHA4, and TIMP1) was identified to provide an area under curve (AUC) of 0.873 (sensitivity = 76.7%, specificity = 80.0%) for PD versus healthy controls in the training set. The performance was essentially confirmed in the validation set (AUC = 0.853, sensitivity = 82.5%, specificity = 82.5%). Additionally, this panel could also differentiate the PD and AD groups (AUC = 0.990, sensitivity = 95.0%, specificity = 97.4%). Furthermore, a combination of two peptides belonging to proteins TIMP1 and APLP1 significantly correlated with disease severity as determined by the Unified Parkinson's Disease Rating Scale motor scores in both the training (r = 0.381, p = 0.038)j and the validation (r = 0.339, p = 0.032) sets. The novel panel of CSF peptides, if validated in independent cohorts, could be used to assist in clinical diagnosis of PD and has the potential to help monitoring or predicting disease progression.

Biofluid biomarkers of traumatic brain injury.

PRIMARY OBJECTIVE: The purpose of this paper is to review the clinical and research utility and applications of blood, cerebrospinal fluid (CSF), and cerebral microdialysis biomarkers in traumatic brain injury (TBI). RESEARCH DESIGN: Not applicable. METHODS AND PROCEDURES: A selective review was performed on these biofluid biomarkers in TBI. MAIN OUTCOME AND RESULTS: Neurofilament heavy chain protein (NF-H), glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase-L1 (UCHL1), neuron-specific enolase (NSE), myelin basic protein (MBP), tau, and s100ß blood biomarkers are elevated during the acute phase of severe head trauma but have key limitations in their research and clinical applications to mild TBI (mTBI). CSF biomarkers currently provide the best reflection of the central nervous system (CNS) pathobiological processes in TBI. Both animal and human studies of TBI have demonstrated the importance of serial sampling of biofluids and suggest that CSF biomarkers may be better equipped to characterize both TBI severity and temporal profiles. CONCLUSIONS: The identification of biofluid biomarkers could play a vital role in identifying, diagnosing, and treating the underlying individual pathobiological changes of TBI. CNS-derived exosomes analyzed by ultra-high sensitivity detection methods have the potential to identify blood biomarkers for the range of TBI severity and time course.