BDNF serum and CSF concentrations in Alzheimer's disease, normal pressure hydrocephalus and healthy controls

Brain-Derived neurotrophic factor and inflammatory biomarkers are unaffected by acute and chronic intermittent hypoxic-hyperoxic exposure in geriatric patients: a randomized controlled trial

BACKGROUND

Animal and human studies have shown that exposure to hypoxia can increase brain-derived neurotrophic factor (BDNF) protein transcription and reduce systematic inflammatory cytokine response. Therefore, the aim of this study was to investigate the acute and chronic effects of intermittent hypoxic-hyperoxic exposure (IHHE) prior to aerobic exercise on BDNF, interleukin-6 (IL-6), and C-reactive protein (CRP) blood levels in geriatric patients.

PATIENTS AND METHODS

Twenty-five geriatric patients (83.1 ± 5.0 yrs, 71.1 ± 10.0 kg, 1.8 ± 0.9 m) participated in a placebo-controlled, single-blinded trial and were randomly assigned to either an intervention (IG) or control group (CG) performing an aerobic cycling training (17 sessions, 20 min·session-1, 3 sessions·week-1). Prior to aerobic cycling exercise, the IG was additionally exposed to IHHE for 30 min, whereas the CG received continuous normoxic air. Blood samples were taken immediately before (pre-exercise) and 10 min (post-exercise) after the first session as well as 48 h (post-training) after the last session to determine serum (BDNFS) and plasma BDNF (BDNFP), IL-6, and CRP levels. Intervention effects were analyzed using a 2 x 2 analysis of covariance with repeated measures. Results were interpreted based on effect sizes with a medium effect considered as meaningful (ηp2 ≥ 0.06, d ≥ 0.5).

RESULTS

CRP was moderately higher (d = 0.51) in the CG compared to the IG at baseline. IHHE had no acute effect on BDNFS (ηp2 = 0.01), BDNFP (ηp2 < 0.01), BDNF serum/plasma-ratio (ηp2 < 0.01), IL-6 (ηp2 < 0.01), or CRP (ηp2 = 0.04). After the 6-week intervention, an interaction was found for BDNF serum/plasma-ratio (ηp2 = 0.06) but not for BDNFS (ηp2 = 0.04), BDNFP (ηp2 < 0.01), IL-6 (ηp2 < 0.01), or CRP (ηp2 < 0.01). BDNF serum/plasma-ratio increased from pre-exercise to post-training (d = 0.67) in the CG compared to the IG (d = 0.51). A main effect of time was found for BDNFP (ηp2 = 0.09) but not for BDNFS (ηp2 = 0.02). Within-group post-hoc analyses revealed a training-related reduction in BDNFP in the IG and CG by 46.1% (d = 0.73) and 24.7% (d = 0.57), respectively.

CONCLUSION

The addition of 30 min IHHE prior to 20 min aerobic cycling seems not to be effective to increase BDNFS and BDNFP or to reduce IL-6 and CRP levels in geriatric patients after a 6-week intervention.The study was retrospectively registered at drks.de (DRKS-ID: DRKS00025130).

A review of the application of exercise intervention on improving cognition in patients with Alzheimer's disease: mechanisms and clinical studies

Alzheimer's disease (AD) is the most common form of dementia, leading to sustained cognitive decline. An increasing number of studies suggest that exercise is an effective strategy to promote the improvement of cognition in AD. Mechanisms of the benefits of exercise intervention on cognitive function may include modulation of vascular factors by affecting cardiovascular risk factors, regulating cardiorespiratory health, and enhancing cerebral blood flow. Exercise also promotes neurogenesis by stimulating neurotrophic factors, affecting neuroplasticity in the brain. Additionally, regular exercise improves the neuropathological characteristics of AD by improving mitochondrial function, and the brain redox status. More and more attention has been paid to the effect of Aβ and tau pathology as well as sleep disorders on cognitive function in persons diagnosed with AD. Besides, there are various forms of exercise intervention in cognitive improvement in patients with AD, including aerobic exercise, resistance exercise, and multi-component exercise. Consequently, the purpose of this review is to summarize the findings of the mechanisms of exercise intervention on cognitive function in patients with AD, and also discuss the application of different exercise interventions in cognitive impairment in AD to provide a theoretical basis and reference for the selection of exercise intervention in cognitive rehabilitation in AD.

A Review of Cerebrospinal Fluid Circulation and the Pathogenesis of Congenital Hydrocephalus

The brain's ventricles are filled with a colorless fluid known as cerebrospinal fluid (CSF). When there is an excessive accumulation of CSF in the ventricles, it can result in high intracranial pressure, ventricular enlargement, and compression of the surrounding brain tissue, leading to potential damage. This condition is referred to as hydrocephalus. Hydrocephalus is classified into two categories: congenital and acquired. Congenital hydrocephalus (CH) poses significant challenges for affected children and their families, particularly in resource-poor countries. Recognizing the psychological and economic impacts is crucial for developing interventions and support systems that can help alleviate the distress and burden faced by these families. As our understanding of CSF production and circulation improves, we are gaining clearer insights into the causes of CH. In this article, we will summarize the current knowledge regarding CSF circulation pathways and the underlying causes of CH. The main causes of CH include abnormalities in the FoxJ1 pathway of ventricular cilia, dysfunctions in the choroid plexus transporter Na+-K+-2Cl- contransporter isoform 1, developmental abnormalities in the cerebral cortex, and structural abnormalities within the brain. Understanding the causes of CH is indeed crucial for advancing research and developing effective treatment strategies. In this review, we will summarize the findings from existing studies on the causes of CH and propose potential research directions to further our understanding of this condition.

Normal-Tension Glaucoma and Potential Clinical Links to Alzheimer's Disease

Glaucoma is a group of optic neuropathies and the world's leading cause of irreversible blindness. Normal-tension glaucoma (NTG) is a subtype of glaucoma that is characterized by a typical pattern of peripheral retinal loss, in which the patient's intraocular pressure (IOP) is considered within the normal range (<21 mmHg). Currently, the only targetable risk factor for glaucoma is lowering IOP, and patients with NTG continue to experience visual field loss after IOP-lowering treatments. This demonstrates the need for a better understanding of the pathogenesis of NTG and underlying mechanisms leading to neurodegeneration. Recent studies have found significant connections between NTG and cerebral manifestations, suggesting NTG as a neurodegenerative disease beyond the eye. Gaining a better understanding of NTG can potentially provide new Alzheimer's Disease diagnostics capabilities. This review identifies the epidemiology, current biomarkers, altered fluid dynamics, and cerebral and ocular manifestations to examine connections and discrepancies between the mechanisms of NTG and Alzheimer's Disease.

Dentate Gyrus Granule Cells Show Stability of BDNF Protein Expression in Mossy Fiber Axons with Age, and Resistance to Alzheimer's Disease Neuropathology in a Mouse Model

Brain-derived neurotrophic factor (BDNF) is important in the development and maintenance of neurons and their plasticity. Hippocampal BDNF has been implicated in Alzheimer's disease (AD) because hippocampal levels in AD patients and AD animal models are often downregulated, suggesting that reduced BDNF contributes to AD. However, the location where hippocampal BDNF protein is most highly expressed, the mossy fiber (MF) axons of dentate gyrus granule cells (GCs), has been understudied, and not in controlled conditions. Therefore, we evaluated MF BDNF protein in the Tg2576 mouse model of AD. Tg2576 and wild-type (WT) mice of both sexes were examined at 2-3 months of age, when amyloid-β (Aβ) is present in neurons but plaques are absent, and 11-20 months of age, after plaque accumulation. As shown previously, WT mice exhibited high levels of MF BDNF protein. Interestingly, there was no significant decline with age in either the genotype or sex. Notably, MF BDNF protein was correlated with GC ΔFosB, a transcription factor that increases after 1-2 weeks of elevated neuronal activity. We also report the novel finding that Aβ in GCs or the GC layer was minimal even at old ages. The results indicate that MF BDNF is stable in the Tg2576 mouse, and MF BDNF may remain unchanged due to increased GC neuronal activity, since BDNF expression is well known to be activity dependent. The resistance of GCs to long-term Aβ accumulation provides an opportunity to understand how to protect vulnerable neurons from increased Aβ levels and therefore has translational implications.

Noradrenergic signaling controls Alzheimer's disease pathology via activation of microglial β2 adrenergic receptors

Norepinephrine (NE) is a potent anti-inflammatory agent in the brain. In Alzheimer's disease (AD), the loss of NE signaling heightens neuroinflammation and exacerbates amyloid pathology. NE inhibits surveillance activity of microglia, the brain's resident immune cells, via their β2 adrenergic receptors (β2ARs). Here, we investigate the role of microglial β2AR signaling in AD pathology in the 5xFAD mouse model of AD. We found that loss of cortical NE projections preceded the degeneration of NE-producing neurons and that microglia in 5xFAD mice, especially those microglia that were associated with plaques, significantly downregulated β2AR gene expression early in amyloid pathology. Importantly, dampening microglial β2AR signaling worsened plaque load and the associated neuritic damage, while stimulating microglial β2AR signaling attenuated amyloid pathology. Our results suggest that microglial β2AR could be explored as a potential therapeutic target to modify AD pathology.

Salivary Brain-Derived Neurotrophic Factor and Cortisol Associated with Psychological Alterations in University Students

INTRODUCTION

Recent evidence reported mental health issues in university students such as anxiety and depressive symptoms and poor sleep quality. Decreased plasma brain-derived neurotrophic factor (BDNF) levels have been proposed as a biomarker of depressive symptoms, whereas cortisol levels are an index of energy mobilization and stress and have been linked to sleep quality. Given that salivary biomarkers represent an interesting new field of research, the aim of this cross-sectional study was to evaluate salivary BDNF and cortisol levels in university students to assess whether they have associations with psychological disturbances such as anxiety and depressive symptoms, sleep quality, and stress level.

METHODS

Salivary BDNF and cortisol levels were measured by specific immunoassays in 70 students whose mental health was also evaluated on the same day through the evaluation of anxiety and depression symptoms (Goldberg scale), sleep quality (Pittsburg Sleep Quality Index and Athens Insomnia Scale), and stress (self-perceived stress scale) and healthy lifestyle habits (alcohol consumption, smoking, regular exercise, and body mass index) were also measured. Multivariate regression analyses were performed in order to identify the strengths of associations between psychological alterations and the concentrations of BDNF, cortisol, and other variables.

RESULTS

Salivary BDNF levels were significantly higher in students with more depressive symptoms, whereas no significant differences were found for cortisol levels. When performing the binary logistic regression model, BDNF levels are included as a predictor variable for a high-depressive-symptoms burden (p < 0.05). Students with worse sleep quality on the Pittsburg Scale had higher cortisol levels (p < 0.05). The subdomains of sleep latency and sleep medication were those significantly associated with salivary cortisol levels in logistic regression analyses (OR = 15.150, p = 0.028). Sleep medication only appeared to be related to cortisol levels (OR = 185.142, p = 0.019). Perceived stress levels and anxiety symptoms were not associated with BDNF or cortisol levels.

CONCLUSIONS

BDNF could play a key role in the pathophysiology of mood-related disorders, and elevation of its peripheral levels could contribute to protecting neurons from the development of mental illness. Higher salivary cortisol levels measured in the morning are accompanied by poorer sleep quality. More research is needed, focusing on salivary biomarkers of disorders related to depressive symptoms and poor sleep quality as a potential tool for the diagnosis and prevention of mental illness.

Isolation and Identification of the High-Affinity DNA Aptamer Target to the Brain-Derived Neurotrophic Factor (BDNF)

Aptamers are functional oligonucleotide ligands used for the molecular recognition of various targets. The natural characteristics of aptamers make them an excellent alternative to antibodies in diagnostics, therapeutics, and biosensing. DNA aptamers are mainly single-stranded oligonucleotides (ssDNA) that possess a definite binding to targets. However, the application of aptamers to the fields of brain health and neurodegenerative diseases has been limited to date. Herein, a DNA aptamer against the brain-derived neurotrophic factor (BDNF) protein was obtained by in vitro selection. BDNF is a potential biomarker of brain health and neurodegenerative diseases and has functions in the synaptic plasticity and survival of neurons. We identified eight aptamers that have binding affinity for BDNF from a 50-nucleotide library. Among these aptamers, NV_B12 showed the highest sensitivity and selectivity for detecting BDNF. In an aptamer-linked immobilized sorbent assay (ALISA), the NV_B12 aptamer strongly bound to BDNF protein, in a dose-dependent manner. The dissociation constant (Kd) for NV_B12 was 0.5 nM (95% CI: 0.4-0.6 nM). These findings suggest that BDNF-specific aptamers could be used as an alternative to antibodies in diagnostic and detection assays for BDNF.

Aniracetam: An Evidence-Based Model for Preventing the Accumulation of Amyloid-β Plaques in Alzheimer's Disease

 Alzheimer's disease is the leading cause of dementia in the world. It affects 6 million people in the United States and 50 million people worldwide. Alzheimer's disease is characterized by the accumulation of amyloid-β plaques (Aβ), an increase in tau protein neurofibrillary tangles, and a loss of synapses. Since the 1990s, removing and reducing Aβ has been the focus of Alzheimer's treatment and prevention research. The accumulation of Aβ can lead to oxidative stress, inflammation, neurotoxicity, and eventually apoptosis. These insults impair signaling systems in the brain, potentially leading to memory loss and cognitive decline. Aniracetam is a safe, effective, cognitive-enhancing drug that improves memory in both human and animal studies. Aniracetam may prevent the production and accumulation of Aβ by increasing α-secretase activity through two distinct pathways: 1) increasing brain derived neurotrophic factor expression and 2) positively modulating metabotropic glutamate receptors. This is the first paper to propose an evidence-based model for aniracetam reducing the accumulation and production of Aβ.

Noradrenergic signaling controls Alzheimer's disease pathology via activation of microglial β2 adrenergic receptors

In Alzheimer's disease (AD) pathophysiology, plaque and tangle accumulation trigger an inflammatory response that mounts positive feed-back loops between inflammation and protein aggregation, aggravating neurite damage and neuronal death. One of the earliest brain regions to undergo neurodegeneration is the locus coeruleus (LC), the predominant site of norepinephrine (NE) production in the central nervous system (CNS). In animal models of AD, dampening the impact of noradrenergic signaling pathways, either through administration of beta blockers or pharmacological ablation of the LC, heightened neuroinflammation through increased levels of pro-inflammatory mediators. Since microglia are the resident immune cells of the CNS, it is reasonable to postulate that they are responsible for translating the loss of NE tone into exacerbated disease pathology. Recent findings from our lab demonstrated that noradrenergic signaling inhibits microglia dynamics via β2 adrenergic receptors (β2ARs), suggesting a potential anti-inflammatory role for microglial β2AR signaling. Thus, we hypothesize that microglial β2 adrenergic signaling is progressively impaired during AD progression, which leads to the chronic immune vigilant state of microglia that worsens disease pathology. First, we characterized changes in microglial β2AR signaling as a function of amyloid pathology. We found that LC neurons and their projections degenerate early and progressively in the 5xFAD mouse model of AD; accompanied by mild decrease in the levels of norepinephrine and its metabolite normetanephrine. Interestingly, while 5xFAD microglia, especially plaque-associated microglia, significant downregulated β2AR gene expression early in amyloid pathology, they did not lose their responsiveness to β2AR stimulation. Most importantly, we demonstrated that specific microglial β2AR deletion worsened disease pathology while chronic β2AR stimulation resulted in attenuation of amyloid pathology and associated neuritic damage, suggesting microglial β2AR might be used as potential therapeutic target to modify AD pathology.

Brain-derived neurotrophic factor interplay with oxidative stress: neuropathology approach in potential biomarker of Alzheimer's disease

The aging population poses a serious challenge concerning an increased prevalence of Alzheimer's disease (AD) and its impact on global burden, morbidity, and mortality. Oxidative stress, as a molecular hallmark that causes susceptibility in AD, interplays to other AD-related neuropathology cascades and decreases the expression of central and circulation brain-derived neurotrophic factor (BDNF), an essential neurotrophin that serves as nerve development and survival, and synaptic plasticity in AD. By its significant correlation with the molecular and clinical progression of AD, BDNF can potentially be used as an objectively accurate biomarker for AD diagnosis and progressivity follow-up in future clinical practice. This comprehensive review highlights the oxidative stress interplay with BDNF in AD neuropathology and its potential use as an AD biomarker.

Serum PAI-1/BDNF Ratio Is Increased in Alzheimer's Disease and Correlates with Disease Severity

We previously demonstrated that serum levels of plasminogen activator inhibitor-1 (PAI-1), which inhibits both the tissue plasminogen activator (tPA) and plasmin activity, are increased in patients with Alzheimer's disease. tPA/plasmin not only prevents the accumulation of β-amyloid in the brain but also is involved in the synthesis of the brain-derived neurotrophic factor (BDNF), a neurotrophin whose levels are reduced in Alzheimer. In the present study, we compared BDNF serum levels in Alzheimer patients with dementia to those in Alzheimer patients with amnestic mild cognitive impairment and to cognitively healthy controls. Moreover, we examined whether the PAI-1/BDNF ratio correlates with disease severity, as measured by Mini-Mental State Examination. Our results showed that BDNF serum levels are lower (13.7% less) and PAI-1 levels are higher in Alzheimer patients with dementia than in Alzheimer patients with amnestic mild cognitive impairment patients (23% more) or controls (36% more). Furthermore, the PAI-1/BDNF ratio was significantly increased in Alzheimer patients as compared to amnestic mild cognitive impairment (36.4% more) and controls (40% more). Lastly, the PAI-1/BDNF ratio negatively correlated with the Mini-Mental score. Our results suggest that increased PAI-1 levels in Alzheimer, by impairing the production of the BDNF, are implicated in disease progression. They also indicate that the PAI-1/BDNF ratio could be used as a marker of Alzheimer. In support of this hypothesis, a strong negative correlation between the PAI-1/BDNF ratio and the Mini-Mental score was observed.

Comparative assessment of Alzheimer's disease-related biomarkers in plasma and neuron-derived extracellular vesicles: a nested case-control study

Introduction: Alzheimer's disease (AD) is currently defined according to biomarkers reflecting the core underlying neuropathological processes: Aβ deposition, Tau, and neurodegeneration (ATN). The soluble phase of plasma and plasma neuron-derived extracellular vesicles (NDEVs) are increasingly being investigated as sources of biomarkers. The aim of this study was to examine the comparative biomarker potential of these two biofluids, as well as the association between respective biomarkers. Methods: We retrospectively identified three distinct diagnostic groups of 44 individuals who provided samples at baseline and at a mean of 3.1 years later; 14 were cognitively unimpaired at baseline and remained so (NRM-NRM), 13 had amnestic MCI that progressed to AD dementia (MCI-DEM) and 17 had AD dementia at both timepoints (DEM-DEM). Plasma NDEVs were isolated by immunoaffinity capture targeting the neuronal markers L1CAM, GAP43, and NLGN3. In both plasma and NDEVs, we assessed ATN biomarkers (Aβ42, Aβ40, total Tau, P181-Tau) alongside several other exploratory markers. Results: The Aβ42/Aβ40 ratio in plasma and NDEVs was lower in MCI-DEM than NRM-NRM at baseline and its levels in NDEVs decreased over time in all three groups. Similarly, plasma and NDEV-associated Aβ42 was lower in MCI-DEM compared to NRM-NRM at baseline and its levels in plasma decreased over time in DEM-DEM. For NDEV-associated proBDNF, compared to NRM-NRM, its levels were lower in MCI-DEM and DEM-DEM at baseline, and they decreased over time in the latter group. No group differences were found for other exploratory markers. NDEV-associated Aβ42/Aβ40 ratio and proBDNF achieved the highest areas under the curve (AUCs) for discriminating between diagnostic groups, while proBDNF was positively associated with Mini-Mental State Examination (MMSE) score. No associations were found between the two biofluids for any assessed marker. Discussion: The soluble phase of plasma and plasma NDEVs demonstrate distinct biomarker profiles both at a single time point and longitudinally. The lack of association between plasma and NDEV measures indicates that the two types of biofluids demonstrate distinct biomarker signatures that may be attributable to being derived through different biological processes. NDEV-associated proBDNF may be a useful biomarker for AD diagnosis and monitoring.

Beyond the amyloid hypothesis: how current research implicates autoimmunity in Alzheimer's disease pathogenesis

The amyloid hypothesis has so far been at the forefront of explaining the pathogenesis of Alzheimer's Disease (AD), a progressive neurodegenerative disorder that leads to cognitive decline and eventual death. Recent evidence, however, points to additional factors that contribute to the pathogenesis of this disease. These include the neurovascular hypothesis, the mitochondrial cascade hypothesis, the inflammatory hypothesis, the prion hypothesis, the mutational accumulation hypothesis, and the autoimmunity hypothesis. The purpose of this review was to briefly discuss the factors that are associated with autoimmunity in humans, including sex, the gut and lung microbiomes, age, genetics, and environmental factors. Subsequently, it was to examine the rise of autoimmune phenomena in AD, which can be instigated by a blood-brain barrier breakdown, pathogen infections, and dysfunction of the glymphatic system. Lastly, it was to discuss the various ways by which immune system dysregulation leads to AD, immunomodulating therapies, and future directions in the field of autoimmunity and neurodegeneration. A comprehensive account of the recent research done in the field was extracted from PubMed on 31 January 2022, with the keywords "Alzheimer's disease" and "autoantibodies" for the first search input, and "Alzheimer's disease" with "IgG" for the second. From the first search, 19 papers were selected, because they contained recent research on the autoantibodies found in the biofluids of patients with AD. From the second search, four papers were selected. The analysis of the literature has led to support the autoimmune hypothesis in AD. Autoantibodies were found in biofluids (serum/plasma, cerebrospinal fluid) of patients with AD with multiple methods, including ELISA, Mass Spectrometry, and microarray analysis. Through continuous research, the understanding of the synergistic effects of the various components that lead to AD will pave the way for better therapeutic methods and a deeper understanding of the disease.

CSF Biomarkers in the Early Diagnosis of Mild Cognitive Impairment and Alzheimer's Disease

Alzheimer's disease (AD) is a rapidly growing disease that affects millions of people worldwide, therefore there is an urgent need for its early diagnosis and treatment. A huge amount of research studies are performed on possible accurate and reliable diagnostic biomarkers of AD. Due to its direct contact with extracellular space of the brain, cerebrospinal fluid (CSF) is the most useful biological fluid reflecting molecular events in the brain. Proteins and molecules that reflect the pathogenesis of the disease, e.g., neurodegeneration, accumulation of Abeta, hyperphosphorylation of tau protein and apoptosis may be used as biomarkers. The aim of the current manuscript is to present the most commonly used CSF biomarkers for AD as well as novel biomarkers. Three CSF biomarkers, namely total tau, phospho-tau and Abeta42, are believed to have the highest diagnostic accuracy for early AD diagnosis and the ability to predict AD development in mild cognitive impairment (MCI) patients. Moreover, other biomarkers such as soluble amyloid precursor protein (APP), apoptotic proteins, secretases and inflammatory and oxidation markers are believed to have increased future prospects.

Brain-derived neurotrophic factor measurements in mouse serum and plasma using a sensitive and specific enzyme-linked immunosorbent assay

This study is about the quantification and validation of BDNF levels in mouse serum and plasma using a sensitive immunoassay. While BDNF levels are readily detectable in human serum, the functional implications of these measurements are unclear as BDNF released from human blood platelets is the main contributor to the serum levels of BDNF. As mouse platelets do not contain BDNF, this confounding factor is absent in the mouse. Accordingly, BDNF levels in mouse serum and plasma were found to be indistinguishable at 9.92 ± 1.97 pg/mL for serum and 10.58 ± 2.43 pg/mL for plasma (p = 0.473). These levels are approximately a thousand times lower than those measured in human serum and pre-adsorption with anti-BDNF, but not with anti-NGF or anti-NT3 monoclonal antibodies, markedly reduced the BDNF signal. These results open the possibility to explore the relevance of BDNF levels as a biomarker in accessible body fluids using existing mouse models mimicking human pathological conditions.

Stability of dentate gyrus granule cell mossy fiber BDNF protein expression with age and resistance of granule cells to Alzheimer's disease neuropathology in a mouse model

The neurotrophin brain-derived neurotrophic factor (BDNF) is important in development and maintenance of neurons and their plasticity. Hippocampal BDNF has been implicated Alzheimer's disease (AD) because hippocampal levels in AD patients and AD animal models are consistently downregulated, suggesting that reduced BDNF contributes to AD. However, the location where hippocampal BDNF protein is most highly expressed, the mossy fiber (MF) axons of dentate gyrus (DG) granule cells (GCs), has been understudied, and never in controlled in vivo conditions. We examined MF BDNF protein in the Tg2576 mouse model of AD. Tg2576 and wild type (WT) mice of both sexes were examined at 2-3 months of age, when amyloid-β (Aβ) is present in neurons but plaques are absent, and 11-20 months of age, after plaque accumulation. As shown previously, WT mice exhibited high levels of MF BDNF protein. Interestingly, there was no significant decline with age in either genotype or sex. Notably, we found a correlation between MF BDNF protein and GC ΔFosB, a transcription factor that increases after 1-2 weeks of elevated neuronal activity. Remarkably, there was relatively little evidence of Aβ in GCs or the GC layer even at old ages. Results indicate MF BDNF is stable in the Tg2576 mouse, and MF BDNF may remain unchanged due to increased GC neuronal activity, since BDNF expression is well known to be activity-dependent. The resistance of GCs to long-term Aβ accumulation provides an opportunity to understand how to protect other vulnerable neurons from increased Aβ levels and therefore has translational implications.

The Role of BDNF as a Biomarker in Cognitive and Sensory Neurodegeneration

Brain-derived neurotrophic factor (BDNF) has a crucial function in the central nervous system and in sensory structures including olfactory and auditory systems. Many studies have highlighted the protective effects of BDNF in the brain, showing how it can promote neuronal growth and survival and modulate synaptic plasticity. On the other hand, conflicting data about BDNF expression and functions in the cochlear and in olfactory structures have been reported. Several clinical and experimental research studies showed alterations in BDNF levels in neurodegenerative diseases affecting the central and peripheral nervous system, suggesting that BDNF can be a promising biomarker in most neurodegenerative conditions, including Alzheimer's disease, shearing loss, or olfactory impairment. Here, we summarize current research concerning BDNF functions in brain and in sensory domains (olfaction and hearing), focusing on the effects of the BDNF/TrkB signalling pathway activation in both physiological and pathological conditions. Finally, we review significant studies highlighting the possibility to target BDNF as a biomarker in early diagnosis of sensory and cognitive neurodegeneration, opening new opportunities to develop effective therapeutic strategies aimed to counteract neurodegeneration.

Relationship between Brain-Derived Neurotrophic Factor and Cognitive Decline in Patients with Mild Cognitive Impairment and Dementia

In the last decade, increasing evidence has emerged linking alterations in the brain-derived neurotrophic factor (BDNF) expression with the development of Alzheimer's disease (AD). Because of the important role of BDNF in cognition and its association with AD pathogenesis, the aim of this study was to evaluate the potential difference in plasma BDNF concentrations between subjects with mild cognitive impairment (MCI; N = 209) and AD patients (N = 295) and to determine the possible association between BDNF plasma levels and the degree of cognitive decline in these individuals. The results showed a significantly higher (p < 0.001) concentration of plasma BDNF in subjects with AD (1.16; 0.13-21.34) compared with individuals with MCI (0.68; 0.02-19.14). The results of the present study additionally indicated a negative correlation between cognitive functions and BDNF plasma concentrations, suggesting higher BDNF levels in subjects with more pronounced cognitive decline. The correlation analysis revealed a significant negative correlation between BDNF plasma levels and both Mini-Mental State Examination (p < 0.001) and Clock Drawing test (p < 0.001) scores. In conclusion, the results of our study point towards elevated plasma BDNF levels in AD patients compared with MCI subjects, which may be due to the body's attempt to counteract the early and middle stages of neurodegeneration.

Serum brain-derived neurotrophic factor as diagnosis clue for Alzheimer's disease: A cross-sectional observational study in the elderly

Objective

Brain-derived neurotrophic factor (BDNF) has not been validated as a diagnostic marker for Alzheimer's disease (AD). To provide a different perspective, this study aimed to evaluate the relationship between serum levels of mature BDNF (mBDNF) and precursor BDNF (proBDNF) in AD and to investigate whether serum BDNF levels or the ratio of mBDNF levels to proBDNF levels (M/P) could be a valuable biomarker for determining the risk of AD in elderly individuals.

Method

A total of 126 subjects who met the inclusion criteria were assigned to either the AD group (n = 62) or the healthy control group (HC, n = 64) in this cross-sectional observationl study. Serum levels of mBDNF and proBDNF were measured using enzyme immunoassay kits. We analyzed the Mini-Mental State Examination (MMSE) scores from the two groups and examined the associations between AD and BDNF metabolism.

Results

The serum concentration of proBDNF was significantly higher in ADs (4140.937 pg/ml) than in HCs (2606.943 pg/ml; p &lt; 0.01). The MMSE significantly correlated with proBDNF (p &lt; 0.01, r = −0.686) and M/P (p &lt; 0.01, r = 0.595) in all subjects. To determine the risk for AD, the area under the receiver operating characteristic curve was calculated, which was 0.896 (95% confidence interval 0.844–0.949) for proBDNF and 0.901 (95% 0.850–0.953) for proBDNF and M/P combined.

Conclusion

We observed a correlation between low serum proBDNF levels and higher MMSE scores in AD. The most effective diagnostic strategy was the combination of proBDNF and M/P, whereas mBDNF levels performed poorly when we evaluated the predictive model.

Association of plasma BDNF levels with different stages of Alzheimer's disease: a cross-sectional study

BACKGROUND

Growing evidence shows that the expression of brain-derived neurotrophic factor (BDNF) is altered in the peripheral blood of participants with Alzheimer's disease (AD). It is unclear, however, whether altered BDNF expression is also observed in the early stages of AD.

METHODS

In the present study, 138 normal controls (NC), 57 participants with subjective cognitive decline (SCD), and 37 participants with amnestic mild cognitive impairment (aMCI) and AD were included. Plasma BDNF protein levels were assessed using a commercial multiplex Luminex-based kit. Patient samples were also probed for the presence of BDNF gene variant rs6265.

RESULTS

Pairwise comparisons between the groups showed that there was not a significant difference in BDNF levels when comparing SCD with NC and when comparing SCD with aMCI/AD, but BDNF levels in aMCI/AD samples were increased when compared with NC samples. For models differentiating clinical groups, discriminant analysis was performed by including education, APOE genotype, and BDNF levels in the model. This approach distinguishes participants with SCD (AUC = 0.630) and aMCI/AD (AUC = 0.665) from NC.

CONCLUSION

Our results suggest that expression of BDNF in plasma is altered at the clinical stage of AD.

Serum and cerebrospinal fluid BDNF concentrations are associated with neurological and cognitive improvement in multiple sclerosis: A pilot study

BACKGROUND

Biomarkers of disease activity have been intensively studied in multiple sclerosis (MS) but knowledge on predictors of disability improvement is limited. The aim of this pilot study was to explore whether increased brain-derived neurotrophic factor concentrations in serum and CSF (sBDNF/cBDNF) precede neurological and cognitive improvement in MS.

METHODS

In this pilot, monocentric prospective cohort study we collected serum/CSF samples at baseline together with EDSS (n = 36) and cognitive testing (n = 34) in patients with relapsing-remitting/primary progressive MS or clinically isolated syndrome. BDNF was assessed in serum and CSF with a single molecule array (SIMOA) HD-1 analyser (Quanterix). Twelve months later EDSS and cognitive testing were repeated. BDNF concentrations of patients with vs. without disability or cognitive improvement (disability improvement: decrease in EDSS ≥ 0.5; cognitive improvement: average z-score increase in neuropsychological performance ≥ 0.5) were compared using univariate ANOVAs adjusting for covariates.

RESULTS

Compared to subjects without, patients with disability improvement had higher sBDNF at baseline (q = 0.04). Subjects with cognitive improvement had higher cBDNF at baseline than those without cognitive improvement (q = 0.004). Secondary analysis demonstrated significant correlations between sBDNF and EDSS change (q = 0.036), cBDNF and average z-score change (q = 0.04) and cBDNF and number of cognitive tests with improvement (q = 0.04), while controlling for covariates.

CONCLUSIONS

Our findings suggest a possible role for BDNF in neurological and cognitive improvement in MS. These findings have to be confirmed in a larger sample but they already highlight the potential of BDNF as a biomarker for disability improvement and neuroplasticity in MS.

Difference in Methylation and Expression of Brain-Derived Neurotrophic Factor in Alzheimer's Disease and Mild Cognitive Impairment

Due to the increasing number of progressive dementias in the population, numerous studies are being conducted that seek to determine risk factors, biomarkers and pathological mechanisms that could help to differentiate between normal symptoms of aging, mild cognitive impairment (MCI) and dementia. The aim of this study was to investigate the possible association of levels of BDNF and COMT gene expression and methylation in peripheral blood cells with the development of Alzheimer's disease (AD). Our results revealed higher expression levels of BDNF (p < 0.001) in MCI subjects compared to individuals diagnosed with AD. However, no difference in COMT gene expression (p = 0.366) was detected. DNA methylation of the CpG islands and other sequences with potential effects on gene expression regulation revealed just one region (BDNF_9) in the BDNF gene (p = 0.078) with marginally lower levels of methylation in the AD compared to MCI subjects. Here, we show that the level of BDNF expression in the periphery is decreased in subjects with AD compared to individuals with MCI. The combined results from the gene expression analysis and DNA methylation analysis point to the potential of BDNF as a marker that could help distinguish between MCI and AD patients.

Exploring the Causality Between Plasma Brain-Derived Neurotrophic Factor and Neurological Diseases: A Mendelian Randomization Study

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a protein synthesized in the brain and widely expressed in the nervous system. Previous studies have demonstrated a controversial role of BDNF in neurological diseases.

OBJECTIVE

In this study, we aimed to assess the association between BDNF levels and the risk of neurological diseases by Mendelian randomization analysis.

METHODS

From a genome-wide association analysis of plasma proteins comprising 3,301 European participants, we isolated 25 genetic variations as instrumental variables for BDNF levels. Summary statistics data on six common neurological diseases as outcome variables. Two-sample Mendelian randomization (MR) analysis was used to assess whether plasma BDNF is causally related to neurological diseases. We also performed sensitivity analysis to ensure the robustness of the results and reverse MR to exclude potential reverse causality.

RESULTS

We confirmed the significant causal relationship between BDNF levels and the risk of Alzheimer's disease (AD) (OR, 0.92; 95% CI, 0.85, 0.98; p = 0.013). Other methods have also shown similar results. We infer that BDNF also reduces the risk of epilepsy (OR, 0.94; 95% CI, 0.90, 0.98; p = 0.004). In reverse MR analysis, we also found that AD can affect the level of BDNF.

CONCLUSIONS

Our study suggests higher plasma BDNF was associated with the reduced risk of AD. Moreover, higher plasma BDNF is a protective factor on AD and focal epilepsy. The results provide credence to the idea that BDNF may play a significant role in the development of focal epilepsy and AD.

Biomarkers in the diagnosis of neurodegenerative diseases

Biomarkers are molecules that behave as of biological states. Ideally, they should have high sensitivity, specificity, and accuracy in reflecting the total disease burden. The review discusses the current status of biomarkers used in neurological disorders. Neurodegenerative diseases are a heterogeneous group disorders characterized by progressive loss of structure and function of the central nervous system or peripheral nervous system. The review discusses the main biomarkers that have predictive value for describing clinical etiology, pathophysiology, and intervention strategies. Preciseness and reliability are one of important requirement for good biomarker. As a result of the analysis of literature data, it was revealed that beta-amyloid, total tau protein and its phosphorylated forms are the first biochemical biomarkers of neurodegenerative diseases measured in cerebrospinal fluid, but these markers are dependent upon invasive lumbar puncture and therefore it’s a cumbersome process for patients. Among the various biomarkers of neurodegenerative diseases, special attention is paid to miRNAs. MicroRNAs, important biomarkers in many disease states, including neurodegenerative disorders, make them promising candidates that may lead to identify new therapeutic targets. Conclusions. Biomarkers of neurological disease are present optimal amount in the cerebrospinal fluid but they are also present in blood at low levels. The data obtained reveal the predictive value of molecular diagnostics of neurodegenerative disorders and the need for its wider use.

New Insights into lncRNAs in Aβ Cascade Hypothesis of Alzheimer's Disease

Alzheimer's disease (AD) is the most common type of dementia, but its pathogenesis is not fully understood, and effective drugs to treat or reverse the progression of the disease are lacking. Long noncoding RNAs (lncRNAs) are abnormally expressed and deregulated in AD and are closely related to the occurrence and development of AD. In addition, the high tissue specificity and spatiotemporal specificity make lncRNAs particularly attractive as diagnostic biomarkers and specific therapeutic targets. Therefore, an in-depth understanding of the regulatory mechanisms of lncRNAs in AD is essential for developing new treatment strategies. In this review, we discuss the unique regulatory functions of lncRNAs in AD, ranging from Aβ production to clearance, with a focus on their interaction with critical molecules. Additionally, we highlight the advantages and challenges of using lncRNAs as biomarkers for diagnosis or therapeutic targets in AD and present future perspectives in clinical practice.

New Frontiers in Neurodegeneration and Regeneration Associated with Brain-Derived Neurotrophic Factor and the rs6265 Single Nucleotide Polymorphism

Brain-derived neurotrophic factor is an extensively studied neurotrophin implicated in the pathology of multiple neurodegenerative and psychiatric disorders including, but not limited to, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, traumatic brain injury, major de-pressive disorder, and schizophrenia. Here we provide a brief summary of current knowledge on the role of BDNF and the common human single nucleotide polymorphism, rs6265, in driving the pathogenesis and rehabilitation in these disorders, as well as the status of BDNF-targeted therapies. A common trend has emerged correlating low BDNF levels, either detected within the central nervous system or peripherally, to disease states, suggesting that BDNF replacement therapies may hold clinical promise. In addition, we introduce evidence for a distinct role of the BDNF pro-peptide as a biologically active ligand and the need for continuing studies on its neurological function outside of that as a molecular chaperone. Finally, we highlight the latest research describing the role of rs6265 expression in mechanisms of neurodegeneration as well as paradoxical advances in the understanding of this genetic variant in neuroregeneration. All of this is discussed in the context of personalized medicine, acknowledging there is no “one size fits all” therapy for neurodegenerative or psychiatric disorders and that continued study of the multiple BDNF isoforms and genetic variants represents an avenue for discovery ripe with therapeutic potential.

Increased Serum NSE and S100B Indicate Neuronal and Glial Alterations in Subjects Under 71 Years With Mild Neurocognitive Disorder/Mild Cognitive Impairment

Background

Mild cognitive impairment (MCI) is considered a pre-stage of different dementia syndromes. Despite diagnostic criteria refined by DSM-5 and a new term for MCI – “mild neurocognitive disorder” (mild NCD) – this diagnosis is still based on clinical criteria.

Methods

To link mild NCD to the underlying pathophysiology we assessed the degree of white matter hyperintensities (WMH) in the brain and peripheral biomarkers for neuronal integrity (neuron-specific enolase, NSE), plasticity (brain-derived neurotrophic factor, BDNF), and glial function (S100B) in 158 community-dwelling subjects with mild NCD and 82 healthy controls. All participants (63–79 years old) were selected from the Leipzig-population-based study of adults (LIFE).

Results

Serum S100B levels were increased in mild NCD in comparison to controls (p = 0.007). Serum NSE levels were also increased but remained non-significant after Bonferroni-Holm correction (p = 0.04). Furthermore, age by group interaction was significant for S100B. In an age-stratified sub-analysis, NSE and S100B were higher in younger subjects with mild NCD below 71 years of age. Some effects were inconsistent after controlling for potentially confounding factors. The discriminatory power of the two biomarkers NSE and S100B was insufficient to establish a pathologic threshold for mild NCD. In subjects with mild NCD, WMH load correlated with serum NSE levels (r = 0.20, p = 0.01), independently of age.

Conclusion

Our findings might indicate the presence of neuronal (NSE) and glial (S100B) injury in mild NCD. Future studies need to investigate whether younger subjects with mild NCD with increased biomarker levels are at risk of developing major NCD.

Human Borna disease virus 1 encephalitis shows marked pro-inflammatory biomarker and tissue immunoactivation during the course of disease

Human Borna disease virus 1 (BoDV-1) encephalitis is a severe emerging disease with a very high case-fatality rate. While the clinical disease, case definitions, diagnostic algorithms and neuropathology have been described, very little is known about the immunological processes of human BoDV-1 encephalitis. Here, we analyzed serum and cerebrospinal fluid (CSF) samples from 10 patients with fatal BoDV-1 encephalitis for changes of different cytokines, chemokines, growth factors and other biomarkers over time. From one of these individuals, also autoptic formalin-fixed brain tissue was analyzed for the expression of inflammatory biomarkers by mRNA levels and immunostaining; in a further patient, only formalin-fixed brain tissue was available and examined in addition. A marked and increasing immune activation from the initial phase to the last phase of acute BoDV-1 encephalitis is shown in serum and CSF, characterized by cytokine concentration changes (IFNγ, IL-5, IL-6, IL-9, IL-10, IL-12p40, IL-13, IL-18, TGF-β1) with a predominantly pro-inflammatory pattern over time. IFNγ production was demonstrated in endothelial cells, astrocytes and microglia, IL-6 in activated microglia, and TGF-β1 in endothelial cells, activated astrocytes and microglia. This was paralleled by an increase of chemokines (CCL-2, CCL-5, CXCL-10, IL-8) to attract immune cells to the site of infection, contributing to inflammation and tissue damage. Pathologically low growth factor levels (BDNF, β-NGF, PDGF) were seen. Changed levels of arginase and sTREM further fostered the pro-inflammatory state. This dysbalanced, pro-inflammatory state likely contributes importantly to the fatal outcome of human BoDV-1 encephalitis, and might be a key target for possible treatment attempts.

Recent Advances on the Role of Brain-Derived Neurotrophic Factor (BDNF) in Neurodegenerative Diseases

Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are essential for neuronal survival and growth. The signaling cascades initiated by BDNF and its receptor are the key regulators of synaptic plasticity, which plays important role in learning and memory formation. Changes in BDNF levels and signaling pathways have been identified in several neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Huntington's disease, and have been linked with the symptoms and course of these diseases. This review summarizes the current understanding of the role of BDNF in several neurodegenerative diseases, as well as the underlying molecular mechanism. The therapeutic potential of BDNF treatment is also discussed, in the hope of discovering new avenues for the treatment of neurodegenerative diseases.

Improving Control of Gene Therapy-Based Neurotrophin Delivery for Inner Ear Applications

Background: Survival and integrity of the spiral ganglion is vital for hearing in background noise and for optimal functioning of cochlear implants. Numerous studies have demonstrated that supplementation of supraphysiologic levels of the neurotrophins BDNF and NT-3 by pumps or gene therapy strategies supports spiral ganglion survival. The endogenous physiological levels of growth factors within the inner ear, although difficult to determine, are likely extremely low within the normal inner ear. Thus, novel approaches for the long-term low-level delivery of neurotrophins may be advantageous.

Objectives: This study aimed to evaluate the long-term effects of gene therapy-based low-level neurotrophin supplementation on spiral ganglion survival. Using an adenovirus serotype 28-derived adenovector delivery system, the herpes latency promoter, a weak, long expressing promoter system, has been used to deliver the BDNF or NTF3 genes to the inner ear after neomycin-induced ototoxic injury in mice.

Results: Treatment of the adult mouse inner ear with neomycin resulted in acute and chronic changes in endogenous neurotrophic factor gene expression and led to a degeneration of spiral ganglion cells. Increased survival of spiral ganglion cells after adenoviral delivery of BDNF or NTF3 to the inner ear was observed. Expression of BDNF and NT-3 could be demonstrated in the damaged organ of Corti after gene delivery. Hearing loss due to overexpression of neurotrophins in the normal hearing ear was avoided when using this novel vector–promoter combination.

Conclusion: Combining supporting cell-specific gene delivery via the adenovirus serotype 28 vector with a low-strength long expressing promoter potentially can provide long-term neurotrophin delivery to the damaged inner ear.

Immediate effect of high-intensity exercise on brain-derived neurotrophic factor in healthy young adults: A systematic review and meta-analysis

BACKGROUND

Although brain-derived neurotrophic factor (BDNF) has been identified as a molecular biomarker of the neurophysiological effects induced by exercise, the acute effects of high-intensity exercise (HIE) on BDNF levels are inconclusive. This study aims to estimate the immediate effects of HIE on BDNF levels in healthy young adults.

METHODS

A systematic search was conducted in the MEDLINE, Scopus, Cochrane CENTRAL, and SPORTDiscuss databases up to December 2020. Randomized controlled trials (RCTs) and non-RCTs reporting pre-post changes in serum or plasma BDNF after an acute intervention of HIE compared to a control condition were included. Pooled effect sizes (p-ESs) and 95% confidence intervals (95%CIs) were calculated for RCTs using a random effects model with Stata/SE (Version 15.0; StataCorp., College Station, TX, USA). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. PROPERO registration number: CRD42020221047.

RESULTS

A total of 22 studies with 552 individuals (age range: 20-31 years; 59.1% male) were included. The meta-analysis included 10 RCTs that reported valid outcome data. Higher BDNF levels were observed when HIE interventions were compared with non-exercise (p-ES = 0.55, 95%CI: 0.12-0.98; I2 = 25.7%; n = 4 studies) and light-intensity exercise (p-ES = 0.78, 95%CI: 0.15-1.40; I2 = 52.4%; n = 3 studies) but not moderate-intensity exercise (p-ES = 0.93, 95%CI: -0.16 to 2.02; I2 = 88.5%; n = 4 studies) conditions.

CONCLUSION

In comparison to non-exercise or light-intensity exercises, an immediate increase in BDNF levels may occur when young adults perform HIE. Given the benefits obtained maximizing circulating BDNF when performing HIE and its potential effects on brain health, our findings suggest that HIE could be recommended by clinicians as a useful exercise strategy to healthy adults.

Brain-derived neurotrophic factor in Alzheimer's disease and its pharmaceutical potential

Synaptic abnormalities are a cardinal feature of Alzheimer's disease (AD) that are known to arise as the disease progresses. A growing body of evidence suggests that pathological alterations to neuronal circuits and synapses may provide a mechanistic link between amyloid β (Aβ) and tau pathology and thus may serve as an obligatory relay of the cognitive impairment in AD. Brain-derived neurotrophic factors (BDNFs) play an important role in maintaining synaptic plasticity in learning and memory. Considering AD as a synaptic disorder, BDNF has attracted increasing attention as a potential diagnostic biomarker and a therapeutical molecule for AD. Although depletion of BDNF has been linked with Aβ accumulation, tau phosphorylation, neuroinflammation and neuronal apoptosis, the exact mechanisms underlying the effect of impaired BDNF signaling on AD are still unknown. Here, we present an overview of how BDNF genomic structure is connected to factors that regulate BDNF signaling. We then discuss the role of BDNF in AD and the potential of BDNF-targeting therapeutics for AD.

Neurodegenerative Disorders of Alzheimer, Parkinsonism, Amyotrophic Lateral Sclerosis and Multiple Sclerosis: An Early Diagnostic Approach for Precision Treatment

Neurodegenerative diseases (NDs) are characterised by progressive dysfunction of synapses, neurons, glial cells and their networks. Neurodegenerative diseases can be classified according to primary clinical features (e.g., dementia, parkinsonism, or motor neuron disease), anatomic distribution of neurodegeneration (e.g., frontotemporal degenerations, extrapyramidal disorders, or spinocerebellar degenerations), or principal molecular abnormalities. The most common neurodegenerative disorders are amyloidosis, tauopathies, a-synucleinopathy, and TAR DNA-binding protein 43 (TDP-43) proteopathy. The protein abnormalities in these disorders have abnormal conformational properties along with altered cellular mechanisms, and they exhibit motor deficit, mitochondrial malfunction, dysfunctions in autophagic-lysosomal pathways, synaptic toxicity, and more emerging mechanisms such as the roles of stress granule pathways and liquid-phase transitions. Finally, for each ND, microglial cells have been reported to be implicated in neurodegeneration, in particular, because the microglial responses can shift from neuroprotective to a deleterious role. Growing experimental evidence suggests that abnormal protein conformers act as seed material for oligomerization, spreading from cell to cell through anatomically connected neuronal pathways, which may in part explain the specific anatomical patterns observed in brain autopsy sample. In this review, we mention the human pathology of select neurodegenerative disorders, focusing on how neurodegenerative disorders (i.e., Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis) represent a great healthcare problem worldwide and are becoming prevalent because of the increasing aged population. Despite many studies have focused on their etiopathology, the exact cause of these diseases is still largely unknown and until now with the only available option of symptomatic treatments. In this review, we aim to report the systematic and clinically correlated potential biomarker candidates. Although future studies are necessary for their use in early detection and progression in humans affected by NDs, the promising results obtained by several groups leads us to this idea that biomarkers could be used to design a potential therapeutic approach and preclinical clinical trials for the treatments of NDs.

Brain-derived neurotrophic factor in patients with epilepsy: A systematic review and meta-analysis

INTRODUCTION

Epilepsy affects almost 1% of people and is characterized by sudden seizures. To date, no reliable biomarker has been found to diagnose or predict the outcomes of epilepsy. Brain-derived neurotrophic factor (BDNF) levels have recently been shown to differ between patients with certain neurologic disorders and normal population, and it is unknown whether this is the case for epilepsy. In this study, we mainly aim to answer this question.

METHODS

We searched three databases for studies comparing BDNF levels between patients with epilepsy and controls. Quality assessment of included studies was performed using the Newcastle-Ottawa scale and statistical analyses were carried out in STATA software version 16.

RESULTS

Final analyses included 10 studies involving 403 patients with epilepsy. BDNF levels were statistically similar between patients and controls (standardized mean difference (SMD) = - 0.30, 95% CI = - 1.32 to 0.71, p = 0.56). When categorized by epilepsy subtype, patients with partial epilepsy showed lower BDNF measures than controls (95% CI = - 1.42 to - 0.32, p < 0.01), while the difference was not significant in patients with generalized epilepsy (95% CI = - 2.81 to 1.65, p = 0.61). Subgroup analyses indicated that BDNF was lower in patients than controls when age or sex matching was not present. Patient samples acquired in the morning also showed significantly lower BDNF levels than controls, unlike afternoon samples. Meta-regression identified no predictor for the difference in BDNF levels.

CONCLUSION

Generally, patients with epilepsy had BDNF levels similar to general population, although patients with partial epilepsy showed lower BDNF levels. Taking into account the sub-group analyses, further studies with higher qualities are required to evaluate the role and utility of BDNF in epilepsy.

Family and Community Support, Brain-Derived Neurotrophic Factor, and Cognitive Performance in Older Adults: Findings From the Health, Wellbeing and Aging Study Population-Based Cohort

Background: Social networks can modulate physiological responses, protects against the detrimental consequences of prolonged stress, and enhance health outcomes. Family ties represent an essential source of social networks among older adults. However, the impact of family support on cognitive performance and the biological factors influencing that relationship is still unclear. We aimed to determine the relationship between family support, cognitive performance and BDNF levels. Methods: Cross-sectional data from three-hundred, eight-six individuals aged on average 60 years enrolled in the Health, Wellbeing and Aging Study (SABE), a population-cohort study, were assessed for family support, community support and cognitive performance. Structural and functional family support was evaluated based on family size and interactions allied to scores in the Family APGAR questionnaire. Community assistance (received or provided) assessed the community support. Cognitive performance was determined using the Mini-Mental State Examination (MMSE), verbal fluency (animals per minute) and backward digital span. Blood samples were obtained to determine BDNF levels. Results: Multivariate analysis showed that functional family support, but not structural, was associated with higher MMSE, verbal fluency and digit span scores, even controlling for potential cofounders (p < 0.001). Providing support to the community, rather than receiving support from others, was associated with better cognitive performance (p < 0.001). BDNF concentration was not associated with community support, family function, or cognitive performance. Conclusion: These findings suggest that emotional components of functional family and community support (e.g., loving and empathic relationship) may be more significant to cognitive health than size and frequency of social interactions.

Stimulating Memory: Reviewing Interventions Using Repetitive Transcranial Magnetic Stimulation to Enhance or Restore Memory Abilities

Human memory systems are imperfect recording devices that are affected by age and disease, but recent findings suggest that the functionality of these systems may be modifiable through interventions using non-invasive brain stimulation such as repetitive transcranial magnetic stimulation (rTMS). The translational potential of these rTMS interventions is clear: memory problems are the most common cognitive complaint associated with healthy aging, while pathological conditions such as Alzheimer's disease are often associated with severe deficits in memory. Therapies to improve memory or treat memory loss could enhance independence while reducing costs for public health systems. Despite this promise, several important factors limit the generalizability and translational potential of rTMS interventions for memory. Heterogeneity of protocol design, rTMS parameters, and outcome measures present significant challenges to interpretation and reproducibility. However, recent advances in cognitive neuroscience, including rTMS approaches and recent insights regarding functional brain networks, may offer methodological tools necessary to design new interventional studies with enhanced experimental rigor, improved reproducibility, and greater likelihood of successful translation to clinical settings. In this review, we first discuss the current state of the literature on memory modulation with rTMS, then offer a commentary on developments in cognitive neuroscience that are relevant to rTMS interventions, and finally close by offering several recommendations for the design of future investigations using rTMS to modulate human memory performance.

A proposal: How to study pro-myelinating proteins in MS

Multiple sclerosis (MS) is an inflammatory and degenerative disease of the CNS. An unmet need in MS is repair i.e.,promoting endogenous regeneration and remyelination after demyelinating inflammatory injury. Remyelination is critical in neuronal preservation and the prevention of clinical progression. There is a good deal of evidence for histological repair and remyelination in MS patients. Repair is driven by several prominent endogenous pro-myelinating proteinsincluding neural cellular adhesion molecule (N-CAM) and brain derived neurotrophic factor (BDNF) among others. To follow changes during acute re-myelination in vivo in MS subjects, non conventional MRI techniques are necessary such as quantitative susceptibility mapping (QSM) that detects the release of Fe from dying oligodendroglial cells and myelin water imaging (MWI) that detects water captured within newly formed myelin. The best time to monitor changes in pro-myelinating proteins and link those changes to imaging evolution is immediately after the acute inflammatory response in MS lesions (gadolinium enhancement [Gd+]) during an intense period of remyelination. We can monitor MS subjects with new Gd + lesions with periodic imaging along with sampling of blood and CSF and determine if myelin formation is linked with increases in pro-myelinating proteins. This would lead to potential therapeutic manipulation with directly administered proteins to promote CNS re-myelination in animal models and in early clinical trials.

Cardiovascular, Cellular, and Neural Adaptations to Hot Yoga versus Normal-Temperature Yoga

CONTEXT

Chronic heat exposure promotes cardiovascular and cellular adaptations, improving an organism's ability to tolerate subsequent stressors. Heat exposure may also promote neural adaptations and alter the neural-hormonal stress response. Hot-temperature yoga (HY) combines mind-body exercise with heat exposure. The added heat component in HY may induce cardiovascular and cellular changes, along with neural benefits and modulation of stress hormones.

AIMS

The purpose of the present study is to compare the cardiovascular, cellular heat shock protein 70 (HSP70), neural, and hormonal adaptations of HY versus normal-temperature yoga (NY).

SETTINGS AND DESIGN

Twenty-two subjects (males = 11 and females = 11, 26 ± 6 years) completed 4 weeks of NY (n = 11) or HY (n = 11, 41°C, 40% humidity). Yoga sessions were performed 3 times/week following a modified Bikram protocol.

SUBJECTS AND METHODS

Pre- and posttesting included (1) hemodynamic measures during a heat tolerance test and maximal aerobic fitness test; (2) neural and hormonal adaptations using serum brain-derived neurotrophic factor (BDNF) and adrenocorticotropic hormone (ACTH), along with a mental stress questionnaire; and (3) cellular adaptations (HSP70) in peripheral blood mononuclear cells (PBMCs).

STATISTICAL ANALYSIS

Within- and between-group Student's t-test analyses were conducted to compare pre- and post-VO2 max, perceived stress, BDNF, HSP70, and ACTH in HY and NY groups.

RESULTS

Maximal aerobic fitness increased in the HY group only. No evidence of heat acclimation or change in mental stress was observed. Serum BDNF significantly increased in yoga groups combined. Analysis of HSP70 suggested higher expression of HSP70 in the HY group only.

CONCLUSIONS

Twelve sessions of HY promoted cardiovascular fitness and cellular thermotolerance adaptations. Serum BDNF increased in response to yoga (NY + HY) and appeared to not be temperature dependent.

Effects of acupuncture versus cognitive behavioral therapy on brain-derived neurotrophic factor in cancer survivors with insomnia: an exploratory analysis

INTRODUCTION

Decreased brain-derived neurotrophic factor (BDNF) is associated with poor sleep. This study examined the effects of acupuncture versus cognitive behavioral therapy for insomnia (CBT-I) on serum BDNF and sleep outcomes in cancer survivors with insomnia.

METHODS

This was an exploratory analysis of a randomized clinical trial (n = 160) comparing acupuncture versus CBT-I for cancer survivors with insomnia. Interventions were delivered over 8 weeks. Outcomes were assessed at baseline and week 8. Serum BDNF was evaluated with enzyme-linked immunosorbent assay (ELISA). Sleep was evaluated with the insomnia severity index and consensus sleep diary. Pearson correlations between BDNF and sleep outcomes were calculated. Data analysis was limited to 87 survivors who provided serum samples.

RESULTS

Among 87 survivors, the mean age was 61.9 (SD: 11.4) years, 51.7% were women, and 24.1% were non-White. Mean serum BDNF did not significantly increase in acupuncture (n = 50) or CBT-I (n = 37) groups. When analysis was restricted to patients with low baseline BDNF (i.e. levels below the sample median of 47.1 ng/mL), the acupuncture group (n = 22) demonstrated a significant 7.2 ng/mL increase in mean serum BDNF (P = 0.03), whereas the CBT-I group (n = 21) demonstrated a non-significant 2.9 ng/mL increase (P = 0.28). Serum BDNF was not significantly correlated with sleep outcomes (all P > 0.05).

CONCLUSION

Among cancer survivors with insomnia and low baseline BDNF, acupuncture significantly increased serum BDNF levels; however, the clinical significance of this finding requires further investigation.Trial registration no. NCT02356575 (ClinicalTrials.gov).

Serum level of brain-derived neurotrophic factor in patients with relapsing–remitting multiple sclerosis: a potential biomarker for disease activity

Background

Brain-derived neurotrophic factor (BDNF) is secreted by immune cells in response to neuroimmune and inflammatory cascades as an act to prevent axonal and neuronal damage after various pathological insults. The serum level of BDNF is altered in a diversity of neurological diseases. The aim of this work was to investigate the serum level of BDNF in patients with relapsing–remitting multiple sclerosis and the relation between BDNF and disease activity and severity.

Methods

A case–control study was conducted on 90 subjects: 60 patients with relapsing–remitting multiple sclerosis (30 in relapse and 30 in remission) on different lines of medical treatment and 30 healthy volunteers as a control. Clinical, functional, and radiological evaluation was done for the patients, and all the patients and controls were subjected to assessment of the serum level of BDNF by sandwich-ELISA technique.

Results

The BDNF level was significantly higher in MS patients in relapse than in patients in remission (P value = 0.006). In the remission group, there was no significant linear correlation between different MS patients’ characteristics and BDNF level, while in the relapse group, a positive linear correlation was found between the number of T2 infratentorial lesions and BDNF level (r = 0.402, P = 0.028). There was no statistically significant difference between the BDNF level in patients administered different drugs for MS in both remission and relapse groups (P value > 0.05).

Conclusion

BDNF was significantly higher in relapsing–remitting multiple sclerosis patients in the relapse phase. Attention should be paid to the link between serum BDNF level as a neuroprotective factor and multiple sclerosis; it can be a biomarker for MS activity in the near future.

Systemic brain derived neurotrophic factor but not intestinal barrier integrity is associated with cognitive decline and incident Alzheimer's disease

The inflammatory hypothesis posits that sustained neuroinflammation is sufficient to induce neurodegeneration and the development of Alzheimer's disease (AD) and Alzheimer's dementia. One potential source of inflammation is the intestine which harbors pro-inflammatory microorganisms capable of promoting neuroinflammation. Systemic inflammation is robustly associated with neuroinflammation as well as low levels of brain derived neurotrophic factor (BDNF) in the systemic circulation and brain. Thus, in this pilot study, we tested the hypothesis that intestinal barrier dysfunction precedes risk of death, incident AD dementia and MCI, cognitive impairment and neuropathology. Serum BDNF was associated with changes in global cognition, working memory, and perceptual speed but not risk of death, incident AD dementia, incident MCI, or neuropathology. Neither of the markers of intestinal barrier integrity examined, including lipopolysaccharide binding protein (LBP) nor intestinal fatty acid binding protein (IFABP), were associated with risk of death, incident AD dementia, incident mild cognitive impairment (MCI), change in cognition (global or domains), or neuropathology. Taken together, the data in this pilot study suggest that intestinal barrier dysfunction does not precede diagnosis of AD or MCI, changes in cognition, or brain pathology. However, since MCI and AD are related to global cognition, the findings with BDNF and the contiguous cognitive measures suggest low power with the trichotomous cognitive status measures. Future studies with larger sample sizes are necessary to further investigate the results from this pilot study.

Brain-derived neurotrophic factor in cerebrospinal fluid and plasma is not a biomarker for Huntington's disease

Brain-derived neurotrophic factor (BDNF) is implicated in the survival of striatal neurons. BDNF function is reduced in Huntington's disease (HD), possibly because mutant huntingtin impairs its cortico-striatal transport, contributing to striatal neurodegeneration. The BDNF trophic pathway is a therapeutic target, and blood BDNF has been suggested as a potential biomarker for HD, but BDNF has not been quantified in cerebrospinal fluid (CSF) in HD. We quantified BDNF in CSF and plasma in the HD-CSF cohort (20 pre-manifest and 40 manifest HD mutation carriers and 20 age and gender-matched controls) using conventional ELISAs and an ultra-sensitive immunoassay. BDNF concentration was below the limit of detection of the conventional ELISAs, raising doubt about previous CSF reports in neurodegeneration. Using the ultra-sensitive method, BDNF concentration was quantifiable in all samples but did not differ between controls and HD mutation carriers in CSF or plasma, was not associated with clinical scores or MRI brain volumetric measures, and had poor ability to discriminate controls from HD mutation carriers, and premanifest from manifest HD. We conclude that BDNF in CSF and plasma is unlikely to be a biomarker of HD progression and urge caution in interpreting studies where conventional ELISA was used to quantify CSF BDNF.

Plasma Brain-Derived Neurotropic Factor Levels Are Associated with Aging and Smoking But Not with Future Dementia in the Rotterdam Study

BACKGROUND

Brain-derived neurotropic factor (BDNF) plays a vital role in neuronal survival and plasticity and facilitates long-term potentiation, essential for memory. Alterations in BDNF signaling have been associated with cognitive impairment, dementia, and Alzheimer's disease. Although peripheral BDNF levels are reduced in dementia patients, it is unclear whether changes in BDNF levels precede or follow dementia onset.

OBJECTIVE

In the present study, we examined the association between BDNF plasma levels and dementia risk over a follow-up period of up to 16 years.

METHODS

Plasma BDNF levels were assessed in 758 participants of the Rotterdam Study. Dementia was assessed from baseline (1997-1999) to follow-up until January 2016. Associations of plasma BDNF and incident dementia were assessed with Cox proportional hazards models, adjusted for age and sex. Associations between plasma BDNF and lifestyle and metabolic factors are investigated using linear regression.

RESULTS

During a follow up of 3,286 person-years, 131 participants developed dementia, of whom 104 had Alzheimer's disease. We did not find an association between plasma BDNF and risk of dementia (adjusted hazard ratio 0.99; 95%CI 0.84-1.16). BDNF levels were positively associated with age (B = 0.003, SD = 0.001, p = 0.002), smoking (B = 0.08, SE = 0.01, p = < 0.001), and female sex (B = 0.03, SE = 0.01, p = 0.03), but not with physical activity level (B = -0.01, SE = 0.01, p = 0.06).

CONCLUSION

The findings suggest that peripheral BDNF levels are not associated with an increased risk of dementia.

Influence of BDNF Genetic Polymorphisms in the Pathophysiology of Aging-related Diseases

For the first time in history, most of the population has a life expectancy equal or greater than 60 years. By the year 2050, it is expected that the world population in that age range will reach 2000 million, an increase of 900 million with respect to 2015, which poses new challenges for health systems. In this way, it is relevant to analyze the most common diseases associated with the aging process, namely Alzheimer´s disease, Parkinson Disease and Type II Diabetes, some of which may have a common genetic component that can be detected before manifesting, in order to delay their progress. Genetic inheritance and epigenetics are factors that could be linked in the development of these pathologies. Some researchers indicate that the BDNF gene is a common factor of these diseases, and apparently some of its polymorphisms favor the progression of them. In this regard, alterations in the level of BDNF expression and secretion, due to polymorphisms, could be linked to the development and/or progression of neurodegenerative and metabolic disorders. In this review we will deepen on the different polymorphisms in the BDNF gene and their possible association with age-related pathologies, to open the possibilities of potential therapeutic targets.

Dynamics of Internalization and Intracellular Interaction of Tau Antibodies and Human Pathological Tau Protein in a Human Neuron-Like Model

We and others have shown in various in vivo, ex vivo and cell culture models that several tau antibodies interact with pathological tau within neurons. To further clarify this interaction in a dynamic human model, we differentiated SH-SY5Y cells with retinoic acid and BDNF to create a neuron-like model. Therein, tau antibodies were primarily taken up by receptor-mediated endocytosis, and prevented toxicity of human brain-derived paired helical filament-enriched tau (PHF). Subsequently, we monitored in real-time the interaction of antibodies and PHF within endocytic cellular compartments. Cells were pre-treated with fluorescently-tagged PHF and then incubated with tau antibodies, 4E6, 6B2, or non-specific isotype control IgG1 labeled with a pH sensitive dye. The uptake and binding of the efficacious antibody, 4E6, to PHF occurred mainly within the soma, whereas the ineffective antibody, 6B2, and ineffective control IgG1, were visualized via the processes and showed limited colocalization with PHF within this period. In summary, we have developed a neuron-like model that clarifies the early intracellular dynamics of the interaction of tau antibodies with pathological tau, and identifies features associated with efficacy. Since the model is entirely human, it is suitable to verify the therapeutic potential of humanized antibodies prior to extensive clinical trials.

Beyond Haemostasis and Thrombosis: Platelets in Depression and Its Co-Morbidities

Alongside their function in primary haemostasis and thrombo-inflammation, platelets are increasingly considered a bridge between mental, immunological and coagulation-related disorders. This review focuses on the link between platelets and the pathophysiology of major depressive disorder (MDD) and its most frequent comorbidities. Platelet- and neuron-shared proteins involved in MDD are functionally described. Platelet-related studies performed in the context of MDD, cardiovascular disease, and major neurodegenerative, neuropsychiatric and neurodevelopmental disorders are transversally presented from an epidemiological, genetic and functional point of view. To provide a complete scenario, we report the analysis of original data on the epidemiological link between platelets and depression symptoms suggesting moderating and interactive effects of sex on this association. Epidemiological and genetic studies discussed suggest that blood platelets might also be relevant biomarkers of MDD prediction and occurrence in the context of MDD comorbidities. Finally, this review has the ambition to formulate some directives and perspectives for future research on this topic.

Do serum GDNF levels correlate with severity of Alzheimer's disease?

INTRODUCTION

A growing body of evidence that glial cell line-derived neurotrophic factor (GDNF) levels are probably involved in pathogenesis and disease course of Alzheimer's disease (AD) suggested that its blood levels could potentially be used as a biomarker of AD. The aim of this study was to compare serum GDNF levels in patients with AD and age-matched controls.

METHODS

Serum concentrations of GDNF were compared in 25 AD patients and 25 healthy volunteers using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA). Severity of the disease in AD patients was assessed using Functional Assessment Staging (FAST). Cognitive assessment of the patients was done using the Mini-Mental State Examination (MMSE).

RESULTS

Mean GDNF levels were found to be 2.45 ± 0.93 ng/ml in AD patients and 4.61 ± 3.39 ng/ml in age-matched controls. There was a statistically significant difference in GDNF serum levels in patients with AD compared to age-matched controls (p = 0.001). Moreover, GDNF serum levels were significantly correlated with disease severity (p < 0.001) and cognitive impairment (p < 0.001).

CONCLUSION

This study showed that serum levels of GDNF are significantly decreased in AD patients in comparison with age-matched controls, thus suggesting a potential role of GDNF as a disease biomarker. However, a comprehensive study of changes in serum levels of multiple neurotrophic factors reflective of different neurobiological pathways in large-scale population studies is recommended.

Neuroprotective Biomarkers and Cognitive Function in a Long-Term Prospective Population-based Study of Aging US Adults

BACKGROUND

Relationships between brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF-1), aldosterone, and cognition in aging were evaluated in the population-based Epidemiology of Hearing Loss Study (1993 to present).

METHODS

Beginning in 1998 to 2000, cognitive impairment was assessed by report of physician diagnoses and the Mini-Mental State Examination. In 2009 to 2010 and 2013 to 2016, information was collected on diagnosis of mild cognitive impairment/dementia. Decline in cognitive function was assessed by principal component analysis from additional tests administered during 2009 to 2010 and 2013 to 2016. BDNF, IGF-1, and aldosterone were measured in serum collected in 1998 to 2000.

RESULTS

There were 1970 participants (mean age=66.9 y; 59.1% female) without cognitive impairment at baseline. Among women, low BDNF was associated with 16-year incident cognitive impairment [hazard ratio=1.76; 95% confidence interval (CI)=1.04, 2.98]. Among men, increasing IGF-1 was associated with decreased risk [per SD: relative risk (RR)=0.57; 95% CI=0.35, 0.92], whereas increasing aldosterone levels were associated with increased risk (per SD: RR=1.28; 95% CI=1.01, 1.62) for 5-year incident mild cognitive impairment/dementia. Overall, low BDNF was associated with increased risk (RR=1.52; 95% CI=1.02, 2.26) for 5-year cognitive decline.

CONCLUSION

Low levels of serum BDNF and IGF-1 were associated with poorer cognition during aging. There may be differential biomarker effects by sex.

Levels of brain-derived neurotrophic factor in patients with multiple sclerosis

Objective

To determine the levels of brain‐derived neurotrophic factor (BDNF) in the serum of patients suffering from multiple sclerosis (MS) to evaluate the potential of serum BDNF as a biomarker for MS.

Methods

Using a recently validated enzyme‐linked immunoassay (ELISA) we measured BDNF in patients with MS (pwMS), diagnosed according to the 2001 McDonald criteria and aged between 18 and 70 years, participating in a long‐term cohort study with annual clinical visits, including blood sampling, neuropsychological testing, and brain magnetic resonance imaging (MRI). The results were compared with an age‐ and sex‐matched cohort of healthy controls (HC). Correlations between BDNF levels and a range of clinical and magnetic resonance imaging variables were assessed using an adjusted linear model.

Results

In total, 259 pwMS and 259 HC were included, with a mean age of 44.42 ± 11.06 and 44.31 ± 11.26 years respectively. Eleven had a clinically isolated syndrome (CIS), 178 relapsing remitting MS (RRMS), 56 secondary progressive MS (SPMS), and 14 primary progressive MS (PPMS). Compared with controls, mean BDNF levels were lower by 8 % (p˂0.001) in pwMS. The level of BDNF in patients with SPMS was lower than in RRMS (p = 0.004).

Interpretation

We conclude that while the use of comparatively large cohorts enables the detection of a significant difference in BDNF levels between pwMS and HC, the difference is small and unlikely to usefully inform decision‐making processes at an individual patient level.