Stage-dependent BDNF serum concentrations in Alzheimer’s disease

Circadian rhythm of brain-derived neurotrophic factor in serum and plasma

The neurotrophic growth factor brain-derived neurotrophic factor (BDNF) plays a crucial role in various neurodegenerative and psychiatric diseases, such as Alzheimer's disease, schizophrenia and depression. BDNF has been proposed as a potential biomarker for diagnosis, prognosis and monitoring therapy. Understanding the factors influencing BDNF levels and whether they follow a circadian rhythm is essential for interpreting fluctuations in BDNF measurements. We aimed to investigate the circadian rhythm of BDNF by collecting multiple peripheral venous blood samples from young, healthy male participants at 12 different time points over 24 h. In addition, vital parameters, cortisol and insulin like growth factor 1 (IGF1) were measured to explore potential regulatory mechanisms, interfering variables and their correlations with BDNF concentration. The findings revealed that plasma BDNF did not exhibit any significant fluctuations over 24 h, suggesting the absence of a circadian rhythm. However, serum BDNF levels decreased during sleep. Furthermore, serum BDNF showed a positive correlation with heart rate but a negative correlation with IGF1. No significant correlation was observed between cortisol and BDNF or IGF1. Although plasma BDNF suggests steady-state conditions, the decline of serum BDNF during the nocturnal period could be attributed to physical inactivity and associated with reduced haemodynamic blood flow (heart rate reduction during sleep). The type of sample collection (peripheral venous cannula vs. blood sampling using a butterfly system) does not significantly affect the measured BDNF levels. The sample collection during the day did not significantly affect BDNF analysis, emphasizing the importance of considering activity levels rather than timing when designing standardized protocols for BDNF assessments.

Sex-dependent associations of serum BDNF, glycolipid metabolism and cognitive impairments in Parkinson's disease with depression: a comprehensive analysis

Brain-derived neurotrophic factor (BDNF) and glycolipid metabolism have been implicated in cognitive impairments and depression among Parkinson's disease (PD). However, the role of sex differences in this relationship remains elusive. This study aimed to investigate the potential sex differences in the link between serum BDNF levels, glycolipid metabolism and cognitive performance among depressive PD patients. PD patients comprising 108 individuals with depression and 108 without depression were recruited for this study. Cognitive function was assessed using the Montreal Cognitive Assessment Beijing version (MOCA-BJ). The severity of depressive symptoms was assessed using the Hamilton Depression Rating Scale (HAMD-17), while motor symptoms were evaluated using the Revised Hoehn and Yahr rating scale (H-Y) and the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III). Laboratory testing and enzyme-linked immunosorbent assay (ELISA) are used to measure serum levels of glycolipid metabolism and BDNF. Females showed superior performance in delayed recall (all p < 0.05), male PD patients exhibited higher scores in naming tasks compared to females in non-depression group. There was no sex differences in serum BDNF levels between depression and non-depression groups. Liner regression analysis indicated BDNF as an independent risk factor for language deficits in male PD patients with depression (p < 0.05), while cholesterol (CHOL) emerged as a cognitive influencing factor, particularly in delayed recall among male PD patients with depression (p < 0.05). Our study reveals extensive cognitive impairments in PD patients with depression. Moreover, BDNF and CHOL may contribute to the pathological mechanisms underlying cognitive deficits, particularly in male patients with depression.

Research Progress on the Pathogenesis, Diagnosis, and Drug Therapy of Alzheimer's Disease

As the population ages worldwide, Alzheimer's disease (AD), the most prevalent kind of neurodegenerative disorder among older people, has become a significant factor affecting quality of life, public health, and economies. However, the exact pathogenesis of Alzheimer's remains elusive, and existing highly recognized pathogenesis includes the amyloid cascade hypothesis, Tau neurofibrillary tangles hypothesis, and neuroinflammation hypothesis. The major diagnoses of Alzheimer's disease include neuroimaging positron emission computed tomography, magnetic resonance imaging, and cerebrospinal fluid molecular diagnosis. The therapy of Alzheimer's disease primarily relies on drugs, and the approved drugs on the market include acetylcholinesterase drugs, glutamate receptor antagonists, and amyloid-β monoclonal antibodies. Still, the existing drugs can only alleviate the symptoms of the disease and cannot completely reverse it. This review aims to summarize existing research results on Alzheimer's disease pathogenesis, diagnosis, and drug therapy, with the objective of facilitating future research in this area.

Improvement of spatial learning and memory deficits by intranasal administration of human olfactory ecto-mesenchymal stem cells in an Alzheimer's disease rat model

Mesenchymal stem cells therapy provides a new perspective of therapeutic approaches in the treatment of neurodegenerative diseases. The present study aimed to investigate the effects of intranasally transplanted human "olfactory ecto-mesenchymal stem cells" (OE-MSCs) in Alzheimer's disease (AD) rats. In this study, we isolated OE-MSCs from human olfactory lamina propria and phenotypically characterized them using immunocytochemistry and flow cytometry. The undifferentiated OE-MSCs were transplanted either by intranasal (IN) or intrahippocampal (IH) injection to rat models of AD, which were induced by injecting amyloid-beta (Aβ) intrahippocampally. Behavioral, histological, and molecular assessments were performed after a three-month recovery period. Based on the results, intranasal administration of OE-MSCs significantly reduced Aβ accumulation and neuronal loss, improved learning and memory impairments, and increased levels of BDNF (brain-derived neurotrophic factor) and NMDAR (N-methyl-D-Aspartate receptors) in the AD rat model. These changes were more significant in animals who received OE-MSCs by intranasal injection. The results of this study suggest that OE-MSCs have the potential to enhance cognitive function in AD, possibly mediated by BDNF and the NMDA receptors.

Blood Markers Show Neural Consequences of LongCOVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) persists throughout the world with over 65 million registered cases of survivors with post-COVID-19 sequelae, also known as LongCOVID-19 (LongC). LongC survivors exhibit various symptoms that span multiple organ systems, including the nervous system. To search for neurological markers of LongC, we investigated the soluble biomolecules present in the plasma and the proteins associated with plasma neuronal-enriched extracellular vesicles (nEVs) in 33 LongC patients with neurological impairment (nLongC), 12 COVID-19 survivors without any LongC symptoms (Cov), and 28 pre-COVID-19 healthy controls (HC). COVID-19 positive participants were infected between 2020 and 2022, not hospitalized, and were vaccinated or unvaccinated before infection. IL-1β was significantly increased in both nLongC and Cov and IL-8 was elevated in only nLongC. Both brain-derived neurotrophic factor and cortisol were significantly elevated in nLongC and Cov compared to HC. nEVs from people with nLongC had significantly elevated protein markers of neuronal dysfunction, including amyloid beta 42, pTau181 and TDP-43. This study shows chronic peripheral inflammation with increased stress after COVID-19 infection. Additionally, differentially expressed nEV neurodegenerative proteins were identified in people recovering from COVID-19 regardless of persistent symptoms.

Neurodegenerative effects of air pollutant Particles: Biological mechanisms implicated for Early-Onset Alzheimer's disease

BACKGROUND

Sporadic Alzheimer's disease (AD) occurs in 99% of all cases and can be influenced by air pollution such as diesel emissions and more recently, an iron oxide particle, magnetite, detected in the brains of AD patients. However, a mechanistic link between air pollutants and AD development remains elusive.

AIM

To study the development of AD-relevant pathological effects induced by air pollutant particle exposures and their mechanistic links, in wild-type and AD-predisposed models.

METHODS

C57BL/6 (n = 37) and APP/PS1 transgenic (n = 38) mice (age 13 weeks) were exposed to model pollutant iron-based particle (Fe0-Fe3O4, dTEM = 493 ± 133 nm), hydrocarbon-based diesel combustion particle (43 ± 9 nm) and magnetite (Fe3O4, 153 ± 43 nm) particles (66 µg/20 µL/third day) for 4 months, and were assessed for behavioural changes, neuronal cell loss, amyloid-beta (Aβ) plaque, immune response and oxidative stress-biomarkers. Neuroblastoma SHSY5Y (differentiated) cells were exposed to the particles (100 μg/ml) for 24 h, with assessments on immune response biomarkers and reactive oxygen species generation.

RESULTS

Pollutant particle-exposure led to increased anxiety and stress levels in wild-type mice and short-term memory impairment in AD-prone mice. Neuronal cell loss was shown in the hippocampal and somatosensory cortex, with increased detection of Aβ plaque, the latter only in the AD-predisposed mice, with the wild-type not genetically disposed to form the plaque. The particle exposures however, increased AD-relevant immune system responses, including inflammation, in both strains of mice. Exposures also stimulated oxidative stress, although only observed in wild-type mice. The in vitro studies complemented the immune response and oxidative stress observations.

CONCLUSIONS

This study provides insights into the mechanistic links between inflammation and oxidative stress to pollutant particle-induced AD pathologies, with magnetite apparently inducing the most pathological effects. No exacerbation of the effects was observed in the AD-predisposed model when compared to the wild-type, indicating a particle-induced neurodegeneration that is independent of disease state.

Increased brain cytokine level associated impairment of vigilance and memory in aged rats can be alleviated by alpha7 nicotinic acetylcholine receptor agonist treatment

Age-related neurocognitive disorders are common problems in developed societies. Aging not only affects memory processes, but may also disturb attention, vigilance, and other executive functions. In the present study, we aimed to investigate age-related cognitive deficits in rats and associated molecular alterations in the brain. We also aimed to test the effects of the alpha7 nicotinic acetylcholine receptor (nAChR) agonist PHA-543613 on memory as well as on the sustained attention and vigilance of aged rats. Short- and long-term spatial memories of the rats were tested using the Morris water maze (MWM) task. To measure attention and vigilance, we designed a rat version of the psychomotor vigilance task (PVT) that is frequently used in human clinical examinations. At the end of the behavioral experiments, mRNA and protein expression of alpha7 nAChRs, cytokines, and brain-derived neurotrophic factor (BDNF) were quantitatively measured in the hippocampus, frontal cortex, striatum, and cerebellum. Aged rats showed marked cognitive deficits in both the MWM and the PVT. The deficit was accompanied by increased IL-1beta and TNFalpha mRNA expression and decreased BDNF protein expression in the hippocampus. PHA-543613 significantly improved the reaction time of aged rats in the PVT, especially for unexpectedly appearing stimuli, while only slightly (non-significantly) alleviating spatial memory deficits in the MWM. These results indicate that targeting alpha7 nAChRs may be an effective strategy for the amelioration of attention and vigilance deficits in age-related neurocognitive disorders.

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 brain-derived neurotrophic factor levels as a predictor for Alzheimer disease progression

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been implicated in the pathophysiology of Alzheimer's disease (AD), and decreased peripheral levels of this protein are associated with an increased risk of developing the disease. This study focuses on whether serum BDNF levels could be used as a predictor of AD progression.

METHODS

In this longitudinal observational study, we recruited cognition normal participants (N = 98) and AD (N = 442) from the Clinic at the Taipei Veterans General Hospital. We conducted a mini-mental status exam, a 12-item memory test, a categorical verbal fluency test, and a modified 15-item Boston naming test. A Serum BDNF level and apolipoprotein E ( APOE ) allele status were measured. The AD patients were followed prospectively. Based on the difference of MMSE scores, these patients were divided into fast decliners (decline ≥ 3/y) and slow decliners (MMSE decline < 3/y). Logistic regression was conducted to examine the impact of serum BDNF levels and other factor on the likelihood of AD patients being slow decliners. Pearson's correlation was used to estimate the relationship between serum BDNF levels and the score of neuropsychological tests.

RESULTS

In a logistic regression model containing serum BDNF levels, age, sex, APOE4 carrier status, education levels, and baseline MMSE score, higher serum BDNF levels were associated with a slower rate of cognitive decline in the AD group. Serum BDNF levels positively correlated with the results of multiple neuropsychological tests.

CONCLUSION

BDNF is a protective factor against AD progression and likely plays a role in establishing a link between AD pathology and clinical manifestations.

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.

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.

Protection of high-frequency low-intensity pulsed electric fields and brain-derived neurotrophic factor for SH-SY5Y cells against hydrogen peroxide-induced cell damage

Neurodegenerative diseases (NDDs) pose a significant global health threat. In particular, Alzheimer disease, the most common type causing dementia, remains an incurable disease. Alzheimer disease is thought to be associated with an imbalance of reactive oxygen species (ROS) in neurons, and scientists considered ROS modulation as a promising strategy for novel remedies. In the study, human neural cell line SH-SY5Y was used in probing the effect of combining noninvasive high-frequency low-intensity pulsed electric field (H-LIPEF) and brain-derived neurotrophic factor (BDNF) in protection against hydrogen peroxide (H2O2)-induced neuron damage. Our result finds that the combination approach has intensified the neuroprotective effect significantly, perhaps due to H-LIPEF and BDNF synergistically increasing the expression level of the phosphorylated epidermal growth factor receptor (p-EGFR), which induces the survival-related mitogen-activated protein kinases (MAPK) proteins. The study confirmed the activation of extracellular signal-regulated kinase (ERK) and the downstream pro-survival and antioxidant proteins as the mechanism underlying neuron protection. These findings highlighted the potential of H-LIPEF combined with BDNF in the treatment of NDDs. Furthermore, BDNF-mimetic drugs combining with noninvasive H-LIPEF to patients is a promising approach worthy of further research. This points to strategies for selecting drugs to cooperate with electric fields in treating neurodegenerative disorders.

Therapeutic Strategies Aimed at Improving Neuroplasticity in Alzheimer Disease

Alzheimer disease (AD) is the most prevalent form of dementia among elderly people. Owing to its varied and multicausal etiopathology, intervention strategies have been highly diverse. Despite ongoing advances in the field, efficient therapies to mitigate AD symptoms or delay their progression are still of limited scope. Neuroplasticity, in broad terms the ability of the brain to modify its structure in response to external stimulation or damage, has received growing attention as a possible therapeutic target, since the disruption of plastic mechanisms in the brain appear to correlate with various forms of cognitive impairment present in AD patients. Several pre-clinical and clinical studies have attempted to enhance neuroplasticity via different mechanisms, for example, regulating glucose or lipid metabolism, targeting the activity of neurotransmitter systems, or addressing neuroinflammation. In this review, we first describe several structural and functional aspects of neuroplasticity. We then focus on the current status of pharmacological approaches to AD stemming from clinical trials targeting neuroplastic mechanisms in AD patients. This is followed by an analysis of analogous pharmacological interventions in animal models, according to their mechanisms of action.

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.

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.

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.

Alternative Pharmacological Strategies for the Treatment of Alzheimer's Disease: Focus on Neuromodulator Function

Alzheimer's disease (AD) is a neurodegenerative disorder, comprising 70% of dementia diagnoses worldwide and affecting 1 in 9 people over the age of 65. However, the majority of its treatments, which predominantly target the cholinergic system, remain insufficient at reversing pathology and act simply to slow the inevitable progression of the disease. The most recent neurotransmitter-targeting drug for AD was approved in 2003, strongly suggesting that targeting neurotransmitter systems alone is unlikely to be sufficient, and that research into alternate treatment avenues is urgently required. Neuromodulators are substances released by neurons which influence neurotransmitter release and signal transmission across synapses. Neuromodulators including neuropeptides, hormones, neurotrophins, ATP and metal ions display altered function in AD, which underlies aberrant neuronal activity and pathology. However, research into how the manipulation of neuromodulators may be useful in the treatment of AD is relatively understudied. Combining neuromodulator targeting with more novel methods of drug delivery, such as the use of multi-targeted directed ligands, combinatorial drugs and encapsulated nanoparticle delivery systems, may help to overcome limitations of conventional treatments. These include difficulty crossing the blood-brain-barrier and the exertion of effects on a single target only. This review aims to highlight the ways in which neuromodulator functions are altered in AD and investigate how future therapies targeting such substances, which act upstream to classical neurotransmitter systems, may be of potential therapeutic benefit in the sustained search for more effective treatments.

Association of plasma brain-derived neurotrophic factor with Alzheimer's disease and its influencing factors in Chinese elderly population

OBJECTIVE

To explore the association of plasma brain-derived neurotrophic factor (BDNF) levels with Alzheimer's disease and its influencing factors.

MATERIALS AND METHODS

A total of 1,615 participants were included in the present study. Among all subjects, 660 were cognitive normal controls (CNCs), 571 were mild cognitive impairment (MCI) patients, and 384 were dementia with Alzheimer's type (DAT) patients. BDNF in blood samples collected from these subjects was analyzed via the Luminex assay. Additionally, DNA extraction and APOE4 genotyping were performed on leukocytes using a blood genotyping DNA extraction kit. All data were processed with SPSS 20.0 software. Analysis of variance (ANOVA) or analysis of covariance (ANCOVA) was used to compare differences among groups on plasma BDNF. Pearson and Spearman correlation analysis examined the correlation between BDNF and cognitive impairment, and linear regression analysis examined the comprehensive effects of diagnosis, gender, age, education, and sample source on BDNF.

RESULTS

BDNF levels in DAT patients were higher than those in CNC and MCI patients (P < 0.01). BDNF levels were significantly correlated with CDR, MMSE, and clinical diagnosis (P < 0.001). Age, education, occupation, and sample source had significant effects on BDNF differences among the CNC, MCI, and DAT groups (P < 0.001). BDNF first decreased and then increased with cognitive impairment in the ApoE4-negative group (P < 0.05).

CONCLUSION

Plasma BDNF levels decreased in the MCI stage and increased in the dementia stage and were affected by age, education, occupation, and sample source. Unless the effects of sample heterogeneity and methodological differences can be excluded, plasma BDNF is difficult to become a biomarker for the early screening and diagnosis of AD.

Reduced plasma BDNF concentration and cognitive decline in veterans with PTSD

Post-traumatic stress disorder (PTSD) is a trauma and stress related disorder frequently associated with cognitive decline. War veterans with PTSD have a higher risk of developing dementia than healthy subjects. Brain derived neurotrophic factor (BDNF) is an important protein that modulates plasticity, memory consolidation and cognitive processes. Lower circulating BDNF levels were related to memory impairment and cognitive deterioration. The aim of this study was to evaluate cognitive deterioration and plasma BDNF concentration in 120 veterans with combat related PTSD, 120 healthy controls, 47 subjects with mild cognitive impairment (MCI) and 76 patients with Alzheimer's disease (AD), and to assess if plasma BDNF concentration might be used as biomarker of cognitive deterioration. Veterans with PTSD had significantly decreased plasma BDNF concentration and worse cognitive performances (assessed using the Mini Mental State Examination, Clock Drawing test and Montreal Cognitive Assessment scores/categories) than healthy subjects, and similarly reduced plasma BDNF and cognitive decline as MCI subjects. Reduced plasma BDNF was found in cognitively impaired subjects. These results suggest that veterans with PTSD should be closely monitored in order to early detect and predict cognitive worsening and promote interventions that might help restore blood BDNF levels and cognitive functions.

Meta-analysis of sugar-sweetened beverage intake and the risk of cognitive disorders

BACKGROUND

Previous epidemiological studies revealed inconsistent associations between sugar-sweetened beverage (SSB) consumption and cognitive disorders, but there have been no meta-analyses of the pooled results. Thus, a meta-analysis was performed to determine the association between SSB consumption and cognitive disorders.

METHODS

A systematic search of the literature prior to May 20, 2022 was performed using the PubMed and Web of Science databases. Random effects models were used to calculate and combine odds ratios (ORs) depending on the degree of heterogeneity.

RESULTS

13 studies met the inclusion criteria. A total of 242,014 participants (2752 in three cross-sectional studies and 239,262 in ten cohort studies) were included. A random effects meta-analysis, according to the comprehensive analysis of SSB consumption, was associated with a greater prevalence of cognitive disorders (OR = 1.17, 95 % CI = 1.05-1.29; I² = 90.1 %). Subgroup analyses of study design, type of SSB, or cognitive disorders outcome was performed. In subgroup analyses, we found that SSB intake was associated with a higher prevalence of cognitive disorders in cohort studies, middle-aged and elderly population, and participants with sugar-sweetened soft drinks. However, no significant association was found in other subgroups.

CONCLUSION

Our results indicate that SSB intake is positively associated with the prevalence of cognitive disorders. Therefore, attention should be paid to reducing SSB intake as an early intervention for cognitive disorders.

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.

Brain-Derived Neurotropic Factor in Neurodegenerative Disorders

Globally, neurodegenerative diseases cause a significant degree of disability and distress. Brain-derived neurotrophic factor (BDNF), primarily found in the brain, has a substantial role in the development and maintenance of various nerve roles and is associated with the family of neurotrophins, including neuronal growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5). BDNF has affinity with tropomyosin receptor kinase B (TrKB), which is found in the brain in large amounts and is expressed in several cells. Several studies have shown that decrease in BDNF causes an imbalance in neuronal functioning and survival. Moreover, BDNF has several important roles, such as improving synaptic plasticity and contributing to long-lasting memory formation. BDNF has been linked to the pathology of the most common neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease. This review aims to describe recent efforts to understand the connection between the level of BDNF and neurodegenerative diseases. Several studies have shown that a high level of BDNF is associated with a lower risk for developing a neurodegenerative disease.

Increased serum levels of brain-derived neurotrophic factor following wheelchair half marathon race in individuals with spinal cord injury

Objective: Brain-derived neurotrophic factor (BDNF) has beneficial effects on metabolism as well as the peripheral and central nervous systems. The aim of this study was to assess the response of serum BDNF concentration ([BDNF]s) to wheelchair half marathon race in individuals with spinal cord injury (SCI).Design: Prospective observational study.Setting: The 34th Oita International Wheelchair Marathon Race in Japan.Participants: Nine cervical SCIs (CSCI) and 8 thoracic and lumber SCIs (LSCI) male athletes. Interventions: Wheelchair half-Marathon Race.Outcome measures: [BDNF]s, plasma concentrations of adrenaline ([Ad]p), noradrenaline ([Nor]p), and cortisol ([Cor]p), hematocrit, and platelet count were measured the day before, immediately after, and an hour after the race.Results: [BDNF]s increased significantly immediately after the race in both groups (CSCI; P = 0.0055, LSCI; P = 0.0312) but returned to the baseline levels at one hour after the race. However, [BDNF]s immediately and one hour after the race were significantly higher in LSCI than in CSCI (immediately after the race; P = 0.0037, 1 h after the race; P = 0.0206). Hematocrit and platelet count remained unchanged throughout the study. In LSCI, [Ad]p, [Nor]p and [Cor]p increased significantly immediately after and one hour after the race, compared with the baseline values (P < 0.05). On the other hand, these variables remained unchanged throughout the study in the CSCI.Conclusions: [BDNF]_s increased significantly from the baseline in both LCSI and CSCI but was higher in LSCI than in CSCI immediately after and one hour after the race.

Exercise improves health-related quality of life sleep and fatigue domains in adult high- and low-grade glioma patients

PURPOSE

The impact of exercise on health-related quality of life (HRQOL) in patients with glioma remains unknown. We hypothesized that glioma patients with low exercise tolerance experience more distress in HRQOL sleep and fatigue domains than patients with high tolerance to exercise.

METHODS

Thirty-eight male and female patients with low- or high-grade glioma treated at a single tertiary care institution participated. Patients completed a validated telephone survey to determine their exercise habits before and following diagnosis. An unpaired t-test was run to measure the interaction between exercise tolerances on HRQOL functional and impairment domains.

RESULTS

Those with low pre-morbid physical activity levels had more distress in HRQOL sleep and fatigue domains. The effects were independent of plasma brain-derived neurotrophic factor (BDNF) levels and the degree of exercise did not appear to impact plasma BDNF in adult glioma patients.

CONCLUSIONS

The aim of this study was to examine the significance of exercise habits on perioperative functional outcomes in patients with low-grade or high-grade glioma. We found that glioma patients with low tolerance to exercise had more sleep disturbances and greater fatigue than glioma patients with high tolerance to exercise. Furthermore, exercise tolerance in the adult glioma population does not appear to impact plasma BDNF secretion.

Impact of the Age of Cecal Material Transfer Donors on Alzheimer’s Disease Pathology in 5xFAD Mice

Alzheimer’s disease is a progressive neurodegenerative disorder affecting around 30 million patients worldwide. The predominant sporadic variant remains enigmatic as the underlying cause has still not been identified. Since efficient therapeutic treatments are still lacking, the microbiome and its manipulation have been considered as a new, innovative approach. 5xFAD Alzheimer’s disease model mice were subjected to one-time fecal material transfer after antibiotics-treatment using two types of inoculation: material derived from the caecum of age-matched (young) wild type mice or from middle aged, 1 year old (old) wild type mice. Mice were profiled after transfer for physiological parameters, microbiome, behavioral tasks, and amyloid deposition. A single time transfer of cecal material from the older donor group established an aged phenotype in the recipient animals as indicated by elevated cultivatable fecal Enterobacteriaceae and Lactobacillaceae representative bacteria, a decreased Firmicutes amount as assessed by qPCR, and by increased levels of serum LPS binding protein. While behavioral deficits were not accelerated, single brain regions (prefrontal cortex and dentate gyrus) showed higher plaque load after transfer of material from older animals. We could demonstrate that the age of the donor of cecal material might affect early pathological hallmarks of Alzheimer’s disease. This could be relevant when considering new microbiome-based therapies for this devastating disorder.

Morin attenuates memory deficits in a rat model of Alzheimer's disease by ameliorating oxidative stress and neuroinflammation

This study aimed to investigate the effect of flavonoid morin on oxidative/nitrosative stress, neuroinflammation, and histological, molecular, and behavioral changes caused by amyloid-beta (Aβ)_1-42 in male Wistar rats (Alzheimer's disease model). Rats received morin (20 mg/kg, oral gavage) for 14 consecutive days after intrahippocampal injection of Aβ_1-42. Morin decreased the levels of malondialdehyde and nitric oxide, increased glutathione content, and enhanced catalase activity in the hippocampus of animals receiving Aβ_1-42. It also reduced the expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, nuclear factor-kappa B, and N-methyl-D-aspartate receptor subunits 2A and 2B and increased the expression of brain-derived neurotrophic factor and α7 nicotinic acetylcholine receptor in the hippocampus of Aβ_1-42-injected rats. Besides, morin modified neuronal loss and histological changes in the CA1 region of the hippocampus. Morin allowed Aβ_1-42-infused rats to swim more time in the target quadrant in the Morris water maze test. It is concluded that morin may be suitable for the prevention and treatment of Alzheimer's disease by strengthening the antioxidant system, inhibiting neuroinflammation, preventing neuronal death, and enhancing memory function.

Increased plasma brain-derived neurotrophic factor (BDNF) as a potential biomarker for and compensatory mechanism in mild cognitive impairment: a case-control study

Background: Previous meta-analyses examining the continuum of Alzheimer’s disease (AD) concluded significantly decreased peripheral brain-derived neurotrophic factor (BDNF) in AD. However, across different meta-analyses, there remain inconsistent findings on peripheral BDNF levels in individuals with mild cognitive impairment (MCI). This issue has been attributed to the highly heterogenous clinical and laboratory factors. Thus, BDNF’s level, discriminative accuracy for identifying all-cause MCI and its subtypes, and its associations with other biomarkers and neurocognitive domains, remain largely unknown.

Methods: To address this heterogeneity, we compared a healthy control cohort (n=56, 45 female) to an MCI cohort (n=40, 28 female), to determine whether plasma BDNF, hs-CRP, and DHEA-S can differentiate healthy from MCI individuals, including two MCI subtypes (amnestic [aMCI] and non-amnestic [non-aMCI]). The associations between BDNF with other biomarkers and neurocognitive tests were examined. Adults with cerebral palsy were included as sensitivity analyses.

Results: Compared to healthy controls, BDNF was significantly higher in all-cause MCI, aMCI, and non-aMCI. Furthermore, BDNF had good (AUC=0.84, 95% CI=0.74 to 0.95, p<0.001) and excellent discriminative accuracies (AUC=0.92, 95% CI=0.84 to 1.00, p<0.001) for all-cause MCI and non-amnestic MCI, respectively. BDNF was significantly and positively associated with plasma hs-CRP (β=0.26, 95% CI=0.02 to 0.50, p=0.038), despite attenuated association upon controlling for BMI (β=0.15, 95% CI=-0.08 to 0.38, p=0.186). Multiple inverse associations between BDNF and detailed neurocognitive tests were also detected.

Conclusions: These findings suggest BDNF is increased as a compensatory mechanism in preclinical dementia, supporting the neurotrophic and partially the inflammatory hypotheses of cognitive impairment.

Intake of Products Containing Anthocyanins, Flavanols, and Flavanones, and Cognitive Function: A Narrative Review

The purpose of this review is to examine human research studies published within the past 6 years which evaluate the role of anthocyanin, flavanol, and flavanone consumption in cognitive function, and to discuss potential mechanisms of action underlying any observed benefits. Evidence to date suggests the consumption of flavonoid-rich foods, such as berries and cocoa, may have the potential to limit, or even reverse, age-related declines in cognition. Over the last 6 years, the flavonoid subgroups of anthocyanins, flavanols, and flavanones have been shown to be beneficial in terms of conferring neuroprotection. The mechanisms by which flavonoids positively modulate cognitive function are yet to be fully elucidated. Postulated mechanisms include both direct actions such as receptor activation, neurotrophin release and intracellular signaling pathway modulation, and indirect actions such as enhancement of cerebral blood flow. Further intervention studies conducted in diverse populations with sufficient sample sizes and long durations are required to examine the effect of consumption of flavonoid groups on clinically relevant cognitive outcomes. As populations continue to focus on adopting healthy aging strategies, dietary interventions with flavonoids remains a promising avenue for future research. However, many questions are still to be answered, including identifying appropriate dosage, timeframes for intake, as well as the best form of flavonoids, before definitive conclusions can be drawn about the extent to which their consumption can protect the aging brain.

Investigation of the Molecular Role of Brain-Derived Neurotrophic Factor in Alzheimer's Disease

Brain-derived neurotrophic factor (BDNF), or abrineurin, is a member of the neurotrophin family of growth factors that acts on both the central and peripheral nervous systems. BDNF is also well known for its cardinal role in normal neural maturation. It binds to at least two receptors at the cell surface known as tyrosine kinase B (TrkB) and p75^NTR. Additional neurotrophins that are anatomically linked with BDNF include neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and nerve growth factor (NGF). It is evident that BDNF levels in patients with Alzheimer's disease (AD) are altered. AD is a progressive disorder and a form of dementia, where the mental function of an elderly person is disrupted. It is associated with a progressive decline in cognitive function, which mainly targets the thinking, memory, and behavior of the person. The degeneration of neurons occurs in the cerebral cortex region of brain. The two major sources responsible for neuronal degeneration are protein fragment amyloid-beta (Aβ), which builds up in the spaces between the nerve cells, known as plaques, disrupting the neuron signaling pathway and leading to dementia, and neurofibrillary tangles (NFTs), which are the twisted fibers of proteins that build up inside the cells. AD is highly prevalent, with recent data indicating nearly 5.8 million Americans aged 65 and older with AD in 2020, and with 80% of patients 75 and older. AD is recognized as the sixth leading cause of death in the USA, and its prevalence is predicted to increase exponentially in the coming years. As AD worsens over time, it becomes increasingly important to understand the exact pathophysiology, biomarkers, and treatment. In this article, we focus primarily on the controversial aspect of BDNF in AD, including its influence on various other proteins and enzymes and the current treatments associated with BDNF, along with future perspectives.

Association Between Components of Cognitive Reserve and Serum BDNF in Healthy Older Adults

Background: The brain-derived neurotrophic factor (BDNF) protein has been shown to have a prominent role in neuron survival, growth, and function in experimental models, and the BDNF Val66Met polymorphism which regulates its expression has been linked to resilience toward the effects of aging on cognition. Cognitively stimulating activity is linked to both increased levels of BDNF in the brain, and protection against age-related cognitive decline. The aim of this study was to investigate the associations between serum BDNF levels, the BDNF Val66Met genotype, and components of cognitive reserve in early and mid-life, measured with the Lifetime of Experiences Questionnaire (LEQ). Methods: Serum BDNF levels were measured cross-sectionally in 156 participants from the Tasmanian Healthy Brain Project (THBP) cohort, a study examining the potential benefits of older adults engaging in a university-level education intervention. Multiple linear regression was used to estimate serum BDNF's association with age, education, gender, BDNF Val66Met genotype, later-life university-level study, and cognitively stimulating activities measured by the LEQ. Results: Serum BDNF in older adults was associated with early life education and training, increasing 0.007 log(pg/ml) [95%CI 0.001, 0.012] per unit on the LEQ subscale. Conversely, education and training in mid-life were associated with a -0.007 log(pg/ml) [-0.012, -0.001] decrease per unit on the LEQ subscale. Serum BDNF decreased with age (-0.008 log(pg/ml) [-0.015, -0.001] per year), and male gender (-0.109 log(pg/ml) [-0.203, -0.015]), but mean differences between the BDNF Val66Met polymorphisms were not significant (p = 0.066). All effect sizes were small, with mid-life education and training having the largest effect size ( η p 2 = 0.044). Conclusion: Education in both early and mid-life explained small but significant amounts of variance in serum BDNF levels, more than age or gender. These effects were opposed and independent, suggesting that education at different stages of life may be associated with different cognitive and neural demands. Education at different stages of life may be important covariates when estimating associations between other exposures and serum BDNF.

Brain-derived neurotrophic factor among patients with alcoholism

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is involved in neurogenesis and in the protection against oxidative damage and neuronal apoptosis. After exercise, there is an increased expression of this myokine, especially in skeletal muscle and brain. Low BDNF levels have been described in neurodegenerative diseases. Alcoholics show both muscle atrophy and brain atrophy. Thus, this study was performed in order to analyze serum BDNF levels among alcoholics and their associations with brain atrophy and muscle strength.

METHODS

Serum BDNF values were determined to 82 male alcoholics and 27 age-matched controls, and compared with handgrip strength, with the presence of brain atrophy, assessed by computed tomography, and with the intensity of alcoholism and liver function derangement.

RESULTS

BDNF levels and handgrip strength were significantly lower among patients. Handgrip strength was correlated with BDNF values, both in the whole population and in alcoholics, especially in patients over 59 years of age. BDNF was poorly related to liver dysfunction but showed no relationship with brain atrophy or age.

CONCLUSION

Chronic alcoholics show decreased BDNF serum levels that are related to muscle function impairment rather than to age, brain atrophy, liver dysfunction, or the amount of ethanol consumed.

High fat diet and its effects on cognitive health: alterations of neuronal and vascular components of brain

It has been well recognized that intake of diets rich in saturated fats could result in development of metabolic disorders such as type 2 diabetes mellitus, obesity and cardiovascular diseases. Recent studies have suggested that intake of high fat diet (HFD) is also associated with cognitive dysfunction. Various preclinical studies have demonstrated the impact of short and long term HFD feeding on the biochemical and behavioural alterations. This review summarizes studies and the protocols used to assess the impacts of HFD feeding on cognitive performance in rodents. Further, it discuss the key mechanisms that are altered by HFD feeding, such as, insulin resistance, oxidative stress, neuro-inflammation, transcriptional dysregulation and loss of synaptic plasticity. Along with these, HFD feeding also alters the vascular components of brain such as loss of BBB integrity and reduced cerebral blood flow. It is highly possible that these factors are responsible for the development of cognitive deficits as a result of HFD feeding.

No association of both serum pro-brain-derived neurotrophic factor (proBDNF) and BDNF concentrations with depressive state in community-dwelling elderly people

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is involved in emotional and cognitive function. Low-BDNF levels occur in patients with depression, while proBDNF, a precursor of BDNF with the opposite physiological function, increases in major depression. However, it is unclear whether BDNF and proBDNF are associated with depression in the elderly. The present study aimed to investigate whether serum proBDNF and BDNF are associated with depressive state in community-dwelling elderly people.

METHODS

This was a cross-sectional study conducted in Kurogawa-cho Imari, Saga Prefecture, Japan, in people aged ≥65 years. Depressive state was assessed using the Geriatric Depression Scale-Short Form (Japanese version) (GDS). Of the 274 patients who undertook the GDS, those with a medical history affecting cognitive function were excluded, as were those with Mini-Mental State Examination score ≥ 24 or a Clinical Dementia Rating < 0.5. Further, we used delayed recall of 'logical memory A' from the Wechsler Memory Scale-Revised (LMII-DR) for memory assessment.

RESULTS

The final sample consisted of 155 individuals (mean age 75.4 ± 6.8 years; 55 men, mean age 74.8 ± 5.9 years; 100 women, mean age 76.3 ± 7.1 years). In the GDS, 139 participants showed a normal score (0-4) and 16 showed depressive tendencies or depression (score: ≥ 5). After examining confounders of the GDS, logistic regression using categorical covariates showed a negative significant difference between depressive state and serum BDNF in the low-BDNF group only, with a positive correlation in the trend test. None of the analyses showed any association between GDS and proBDNF levels.

CONCLUSION

ProBDNF and BDNF levels seemed not to be associated with depressive state in community-dwelling elderly people.

Higher Serum Brain-Derived Neurotrophic Factor Levels Are Associated With a Lower Risk of Cognitive Decline: A 2-Year Follow Up Study in Community-Dwelling Older Adults

OBJECTIVE

To assess the relationship of serum brain-derived neurotrophic factor (BDNF) levels with the subsequent short-term decline in cognitive functioning in community-dwelling older adults.

DESIGN

Two-year prospective, observational study.

SETTING AND PARTICIPANTS

The study included 405 adults aged 65-84 years, initially free of a dementia diagnosis who were living in Tokyo, Japan.

METHODS

Participants underwent health assessments at baseline (2011) and follow-up (2013). Serum BDNF levels and scores from the Montreal Cognitive Assessment-Japanese version (MoCA-J) were systematically measured. Logistic regression was used to estimate the odds of cognitive decline between baseline and follow-up assessments in the full MoCA-J scale (operationally defined as a decrease of two or more points), as well as in MoCA-J subscales (decline of one or more points in a specific subscale), as a function of serum BDNF level, adjusting for baseline demographics, prevalent chronic diseases, and baseline cognitive scores.

RESULTS

Among individuals who performed worse on the full MoCA-J at baseline (i.e., scores in the bottom quartile [≤21], which is consistent with a mild cognitive impairment status), but not among those who performed better (top 3 quartiles), those with highest baseline serum BDNF levels (top quartile) had lower odds of subsequent decline in the full MoCA-J scale than those with lowest (bottom quartile); i.e., odds ratio (OR): 0.10 (95% confidence interval [CI]: 0.02-0.62; p = 0.013). Regarding MoCA-J subscales, adjusted odds of decline in the executive function subscale, but not in the other five subscales, were substantially low among those with highest baseline serum BDNF levels (top quartile), as compared to those with the lowest (bottom quartile), i.e., OR: 0.27 (95% CI:0.13-0.60; p < 0.001).

CONCLUSION AND IMPLICATIONS

Higher serum BDNF levels were associated with a lower risk of decline in cognitive function in a sample of community-dwelling older Japanese adults. Risk varied across cognitive subdomains and according to baseline cognition. This warrants further research to evaluate the added-value of serum BDNF in health promotion initiatives directed toward cognitive decline prevention in community-dwelling older adults.

Oxidative Stress in the Pathogenesis of Alzheimer's Disease and Cerebrovascular Disease with Therapeutic Implications

The significant gain in life expectancy led to an increase in the incidence and prevalence of dementia. Although vascular risk factors have long and repeatedly been shown to increase the risk of Alzheimer's Disease (AD), translating these findings into effective preventive measures has failed. In addition, the finding that incident ischemic stroke approximately doubles the risk of a patient to develop AD has been recently reinforced. Current knowledge and pathogenetic hypotheses of AD are discussed. The implication of oxidative stress in the development of AD is reviewed, with special emphasis on its sudden burst in the setting of acute ischemic stroke and the possible link between this increase in oxidative stress and consequent cognitive impairment. Current knowledge and future directions in the prevention and treatment of AD are discussed outlining the hypothesis of a possible beneficial effect of antioxidant treatment in acute ischemic stroke in delaying the onset/progression of dementia.

Exploring the Key Genes and Identification of Potential Diagnosis Biomarkers in Alzheimer's Disease Using Bioinformatics Analysis

Background

Alzheimer’s disease (AD) is one of the major threats of the twenty-first century and lacks available therapy. Identification of novel molecular markers for diagnosis and treatment of AD is urgently demanded, and genetic biomarkers show potential prospects.

Method

We identify and intersected differentially expressed genes (DEGs) from five microarray datasets to detect consensus DEGs. Based on these DEGs, we conducted Gene Ontology (GO), performed the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, constructed a protein—protein interaction (PPI) network, and utilized Cytoscape to identify hub genes. The least absolute shrinkage and selection operator (LASSO) logistic regression was applied to identify potential diagnostic biomarkers. Gene set enrichment analysis (GSEA) was performed to investigate the biological functions of the key genes.

Result

We identified 608 consensus DEGs, several dysregulated pathways, and 18 hub genes. Sixteen hub genes dysregulated as AD progressed. The diagnostic model of 35 genes was constructed, which has a high area under the curve (AUC) value in both the validation dataset and combined dataset (AUC = 0.992 and AUC = 0.985, respectively). The model can also differentiate mild cognitive impairment and AD patients from controls in two blood datasets. Brain-derived neurotrophic factor (BDNF) and WW domain-containing transcription regulator protein 1 (WWTR1), which are associated with the Braak stage, Aβ 42 levels, and β-secretase activity, were identified as critical genes of AD.

Conclusion

Our study identified 16 hub genes correlated to the neuropathological stage and 35 potential biomarkers for the diagnosis of AD. WWTR1 were identified as candidate genes for future studies. This study deepens our understanding of the transcriptomic and functional features and provides new potential diagnostic biomarkers and therapeutic targets for AD.

Sex steroids-induced neurogenesis in adult brain: a better look at mechanisms and mediators

Adult neurogenesis is the production of new nerve cells in the adult brain. Neurogenesis is a clear example of the neuroplasticity phenomenon which can be observed in most of mammalian species, including human beings. This phenomenon occurs, at least, in two regions of the brain: the subgranular zone of the dentate gyrus in hippocampus and the ventricular zone of lateral ventricles. Numerous studies have investigated the relationship between sex steroid hormones and neurogenesis of adult brain; of which, mostly concentrated on the role of estradiol. It has been shown that estrogen plays a significant role in this process through both classic and non-classic mechanisms, including a variety of different growth factors. Therefore, the objective of this review is to investigate the role of female sex steroids with an emphasis on estradiol and also its potential implications for regulating the neurogenesis in the adult brain.

A Review of the Brain-Gut-Microbiome Axis and the Potential Role of Microbiota in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative process characterized by loss of neurons in the hippocampus and cerebral cortex, leading to progressive cognitive decline. Pathologically, the hallmark of AD is accumulation of "senile" plaques composed of amyloid-β (Aβ) protein surrounding neurons in affected regions. Despite extensive research into AD pathogenesis and therapeutic targets, there remains no breakthroughs in its management. In recent years, there has been a spark of interest in the connection between the brain and gastrointestinal tract, referred to as the brain-gut axis, and its potential implications for both metabolic and neurologic disease. Moreover, the gastrointestinal flora, referred to as the microbiome, appears to exert significant influence over the brain-gut axis. With the need for expanded horizons in understanding and treating AD, many have turned to the brain-gut-microbiome axis for answers. Here we provide a review of the brain-gut-microbiome axis and discuss the evidence supporting alterations of the axis in the pathogenesis of AD. Specifically, we highlight the role for the microbiome in disruption of Aβ metabolism/clearance, increased permeability of the blood-brain barrier and modulation of the neuroinflammatory response, and inhibition of hippocampal neurogenesis. The majority of the above described findings are the result of excellent, albeit basic and pre-clinical studies. Therefore, we conclude with a brief description of documented clinical support for brain-gut-microbiome axis alteration in AD, including potential microbiome-based therapeutics for AD. Collectively, these findings suggest that the brain-gut-microbiome axis may be a "lost link" in understanding and treating AD and call for future work.

SIRT1-Dependent Upregulation of BDNF in Human Microglia Challenged with Aβ: An Early but Transient Response Rescued by Melatonin

Microglia represent a first-line defense in the brain. However, in pathological conditions such as Alzheimer’s disease (AD), a pro-inflammatory switch may occur, leading to loss of protective functions. Using the human microglial cell line HMC3, we showed that exposure to low concentrations of β-amyloid peptide 1-42 (Aβ42; 0.2 μM) initially (6 h) upregulated anti-inflammatory markers interleukin (IL)-4, IL-13, and brain-derived neurotrophic factor (BDNF). BDNF increase was prevented by selective inhibition of SIRT1 with EX527 (2 μM). Accordingly, these early effects were accompanied by a significant Aβ42-induced increase of SIRT1 expression, nuclear localization, and activity. SIRT1 modulation involved adenosine monophosphate-regulated kinase (AMPK), which was promptly (30 min) phosphorylated by Aβ42, while the AMPK inhibitor BML-275 (2 μM) attenuated Aβ42-induced SIRT1 increase. Initially observed microglial responses appeared transient, as microglial features changed when exposure to Aβ42 was prolonged (0.2 μM for 72 h). While SIRT1 and BDNF levels were reduced, the expression of inflammatory markers IL-1β and tumor necrosis factor (TNF)-α increased. This coincided with a rise in NF-kB nuclear localization. The effects of melatonin (1 μM) on prolonged microglial exposure to Aβ42 were analyzed for their protective potential. Melatonin was able to prolong SIRT1 and BDNF upregulation, as well as to prevent NF-kB nuclear translocation and acetylation. These effects were sensitive to the melatonin receptor antagonist, luzindole (25 μM). In conclusion, our data define an early microglial defensive response to Aβ42, featuring SIRT1-mediated BDNF upregulation that can be exogenously modulated by melatonin, thus identifying an important target for neuroprotection.

A reconciling hypothesis centred on brain-derived neurotrophic factor to explain neuropsychiatric manifestations in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune chronic inflammatory disease characterized by synovitis leading to joint destruction, pain and disability. Despite efficient antirheumatic drugs, neuropsychiatric troubles including depression and cognitive dysfunction are common in RA but the underlying mechanisms are unclear. However, converging evidence strongly suggests that deficit in brain-derived neurotrophic factor (BDNF) signalling contributes to impaired cognition and depression. Therefore, this review summarizes the current knowledge on BDNF in RA, proposes possible mechanisms linking RA and brain BDNF deficiency including neuroinflammation, cerebral endothelial dysfunction and sedentary behaviour, and discusses neuromuscular electrical stimulation as an attractive therapeutic option.

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.

Therapeutic Targeting Strategies for Early- to Late-Staged Alzheimer's Disease

Alzheimer's disease (AD) is the most common cause of dementia, typically showing progressive neurodegeneration in aging brains. The key signatures of the AD progression are the deposition of amyloid-beta (Aβ) peptides, the formation of tau tangles, and the induction of detrimental neuroinflammation leading to neuronal loss. However, conventional pharmacotherapeutic options are merely relying on the alleviation of symptoms that are limited to mild to moderate AD patients. Moreover, some of these medicines discontinued to use due to either the insignificant effectiveness in improving the cognitive impairment or the adverse side effects worsening essential bodily functions. One of the reasons for the failure is the lack of knowledge on the underlying mechanisms that can accurately explain the major causes of the AD progression correlating to the severity of AD. Therefore, there is an urgent need for the better understanding of AD pathogenesis and the development of the disease-modifying treatments, particularly for severe and late-onset AD, which have not been covered thoroughly. Here, we review the underlying mechanisms of AD progression, which have been employed for the currently established therapeutic strategies. We believe this will further spur the discovery of a novel disease-modifying treatment for mild to severe, as well as early- to late-onset, AD.

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.

Assessment of BDNF serum levels as a diagnostic marker in children with autism spectrum disorder

There has been a significant increase in autism spectrum disorder (ASD) in the last decades that cannot be exclusively attributed to better diagnosis and an increase in the communication of new cases. Patients with ASD often show dysregulation of proteins associated with synaptic plasticity, notably brain-derived neurotrophic factor (BDNF). The objective of the present study was to analyze BDNF serum concentration levels in children with classic forms autism and a healthy control group to determine if there is a correlation between ASD and BDNF serum levels. Forty-nine children with severe classic form of autism, and 37 healthy children were enrolled in the study. Blood samples, from both patients and controls, were collected and BNDF levels from both groups were analyzed. The average BDNF serum concentration level was statistically higher for children with ASD (P < 0.000) compared to the control group. There is little doubt that BDNF plays a role in the pathophysiology of ASD development and evolution, but its brain levels may fluctuate depending on several known and unknown factors. The critical question is not if BDNF levels can be considered a prognostic or diagnostic marker of ASD, but to determine its role in the onset and progression of this disorder.

Effect of Daily Intake of Green Tea Catechins on Cognitive Function in Middle-Aged and Older Subjects: A Randomized, Placebo-Controlled Study

Epidemiological studies in Japan, including the Nakajima study and the Tsurugaya study, have indicated that green tea consumption may improve cognitive impairment. Catechins, which are typical polyphenols contained in green tea, have been reported to have antioxidative, anti-inflammatory, and neuroprotective effects. However, their impact on human cognitive function remains unclear. Therefore, we performed a double-blind, randomized, controlled study to investigate the effect of 336.4 mg of decaffeinated green tea catechins (GTC) on cognitive function after a single dose and after 12 weeks of daily intake. This study included Japanese adults between the ages of 50 and 69 years with a Mini-Mental State Examination Japanese version score of >24 and self-assessed cognitive decline. The Cognitrax testing battery was used to evaluate cognitive function. The incorrect response rate on the Continuous Performance Test significantly decreased after a single dose of GTC. After 12 weeks of daily GTC intake, the response time for Part 4 of the 4-part Continuous Performance Test, which is a two-back test, was shortened. These results suggest that daily intake of GTC might have beneficial effects on working memory.

Plasma BDNF Levels Following Transcranial Direct Current Stimulation Allow Prediction of Synaptic Plasticity and Memory Deficits in 3×Tg-AD Mice

Early diagnosis of Alzheimer’s disease (AD) supposedly increases the effectiveness of therapeutic interventions. However, presently available diagnostic procedures are either invasive or require complex and expensive technologies, which cannot be applied at a larger scale to screen populations at risk of AD. We were looking for a biomarker allowing to unveil a dysfunction of molecular mechanisms, which underly synaptic plasticity and memory, before the AD phenotype is manifested and investigated the effects of transcranial direct current stimulation (tDCS) in 3×Tg-AD mice, an experimental model of AD which does not exhibit any long-term potentiation (LTP) and memory deficits at the age of 3 months (3×Tg-AD-3M). Our results demonstrated that tDCS differentially affected 3×Tg-AD-3M and age-matched wild-type (WT) mice. While tDCS increased LTP at CA3-CA1 synapses and memory in WT mice, it failed to elicit these effects in 3×Tg-AD-3M mice. Remarkably, 3×Tg-AD-3M mice did not show the tDCS-dependent increases in pCREB^Ser133 and pCaMKII^Thr286, which were found in WT mice. Of relevance, tDCS induced a significant increase of plasma BDNF levels in WT mice, which was not found in 3×Tg-AD-3M mice. Collectively, our results showed that plasticity mechanisms are resistant to tDCS effects in the pre-AD stage. In particular, the lack of BDNF responsiveness to tDCS in 3×Tg-AD-3M mice suggests that combining tDCS with dosages of plasma BDNF levels may provide an easy-to-detect and low-cost biomarker of covert impairment of synaptic plasticity mechanisms underlying memory, which could be clinically applicable. Testing proposed here might be useful to identify AD in its preclinical stage, allowing timely and, hopefully, more effective disease-modifying interventions.