Brain-derived Neurotrophic Factor Is Associated with Cognitive Impairment in Elderly Korean Individuals

The Effect of Aerobic or Strength Training in Elderly with Cognitive Decline: The Fit4Alz Project

This study aimed to examine the effects of aerobic and strength training methodologies, either combined with or without cognitive training, on mitigating cognitive decline. A total of 154 subjects were recruited (72.8 ± 6.1 years, 69% females) and were divided into four groups: i) strength plus cognitive training (STCT, n = 56); ii) strength training (ST, n = 23); iii) aerobic training (AT, n = 41); and iv) aerobic plus cognitive training (ATCT, n = 34). Subjects were previously cognitively assessed and showed cognitive decline (less than 26 points on the Montreal Cognitive Assessment, MoCA). For 12 weeks, all groups performed 3 times a week, for 60 minutes, a training program corresponding to their attributed group. The MoCA test and the Senior Fitness test were applied at the beginning and the end of the intervention. A repeated-measures ANCOVA revealed significant time-by-group interactions for physical performance measures, including the 2-minute step-in-place (p = 0.026), arm curl (p < 0.001), chair sit-and-reach (p < 0.001), back-scratch (p < 0.001), 8-foot up-and-go (p < 0.001), and 6-minute walk tests (p < 0.001). However, no significant improvements were observed for cognitive function (MoCA, p = 0.242) or lower body strength (chair stand, p = 0.411). The AT group showed greater improvements in upper body strength compared to STCT and ST (p < 0.001; d = 0.698; p = 0.004; d = 0.598), while STCT significantly improved flexibility compared to ATCT (p < 0.001; d = 1.049). ATCT had the greatest improvements in aerobic endurance compared to STCT and ST (p = 0.004; d = 0.133; p < 0.001; d = 0.350). It was demonstrated that aerobic and strength training significantly improved overall physical performance in elderly individuals. However, no significant effects were observed on cognitive performance. Although these findings suggest that both aerobic and strength exercise, with or without cognitive training, improve overall physical fitness, further research is needed to determine its impact on cognitive performance.

Serum brain-derived neurotrophic factor levels in type 2 diabetes mellitus patients and its association with cognitive impairment: A meta-analysis

OBJECTIVE

To compare the serum levels of brain-derived neurotrophic factor (BDNF) in type 2 diabetes mellitus (T2DM) patients with healthy controls (HC) and evaluate the BDNF levels in T2DM patients with/without cognitive impairment.

METHODS

PubMed, EMBASE, and the Cochrane Library databases were searched for the published English literature on BDNF in T2DM patients from inception to December 2022. The BDNF data in the T2DM and HC groups were extracted, and the study quality was evaluated using the Agency for Healthcare Research and Quality. A meta-analysis of the pooled data was conducted using Review Manager 5.3 and Stata 12.0 software.

RESULTS

A total of 18 English articles fulfilled with inclusion criteria. The standard mean difference of the serum BDNF level was significantly lower in T2DM than that in the HC group (SMD: -2.04, z = 11.19, P <0.001). Besides, T2DM cognitive impairment group had a slightly lower serum BDNF level compared to the non-cognitive impairment group (SMD: -2.59, z = 1.87, P = 0.06).

CONCLUSION

BDNF might be involved in the neuropathophysiology of cerebral damage in T2DM, especially cognitive impairment in T2DM.

The clinical features and potential mechanisms of cognitive disorders in peripheral autoimmune and inflammatory diseases

According to a study from World Health Organization's Global Burden of Disease, mental and neurological disorders have accounted for 13% of global diseases in recent years and are on the rise. Neuropsychiatric conditions or neuroinflammatory disorders are linked by the presence of an exaggerated immune response both peripherally and in the central nervous system (CNS). Cognitive dysfunction (CD) encompasses a complex group of diseases and has frequently been described in the field of autoimmune diseases, especially in multiple non-CNS-related autoimmune diseases. Recent studies have provided various hypotheses regarding the occurrence of cognitive impairment in autoimmune diseases, including that abnormally activated immune cells can disrupt the integrity of the blood-brain barrier (BBB) to trigger a central neuroinflammatory response. When the BBB is intact, autoantibodies and pro-inflammatory molecules in peripheral circulation can enter the brain to activate microglia, inducing CNS inflammation and CD. However, the mechanisms explaining the association between the immune system and neural function and their contribution to diseases are uncertain. In this review, we used clinical statistics to illustrate the correlation between CD and autoimmune diseases that do not directly affect the CNS, summarized the clinical features and mechanisms by which autoimmune diseases trigger cognitive impairment, and explored existing knowledge regarding the link between CD and autoimmune diseases from the perspective of the field of neuroimmunology.

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.

Correlation of Brain-Derived Neurotrophin Factor Levels in Epilepsy Patients Treated with Valproic Acid and Phenytoin with Cognitive Function

BACKGROUND: Epilepsy cases requiring OAE multitherapy are found in 40% of total epilepsy cases. Many epilepsy patients are referred to Dr. Kariadi Hospital Semarang because of the occurrence of intractable epilepsy. Valproic acid is one of the OAEs that are widely used in the BPJS era in Indonesia as a combination of phenytoin. Seizures increase the expression of BDNF mRNA and protein. METHODS: This study is a cross-sectional study that took place from January to May 2022. The subjects of this study were epilepsy patients who used a combination of phenytoin-valproic acid who met the inclusion criteria. Patient data were obtained from medical records and filling out questionnaires. Patients were asked to fast for ± 8−10 h. Furthermore, blood sampling (±5 ml) of BDNF was carried out at 08.00−10.00 WIB. Cognitive function assessments were performed using MoCA-Ina and the Hamilton depression rating scale at the same time. Data were analyzed by Spearman correlation test and partial correlation test. The results are said to be meaningful if p < 0.05. RESULTS: Thirty-two study subjects used a combination of phenytoin-valproic acid. The Spearman correlation test between the relationship between BDNF levels and cognitive function in epilepsy patients treated with valproic acid and phenytoin showed a significant relationship with the direction and strength of which was strongly positive (r = 0.676 and p ≤ 0.001). The partial correlation test between the relationship between BDNF levels and cognitive function after controlling for age (r = 0.692), seizure frequency (r = 0.641), duration of combination therapy (r = 0.700), and age of seizure onset (r = 0.693) remained the same, while after controlling for the level of education (r = 0.812) and the type of seizure (r = 0.747) increased. CONCLUSION: There is a strong correlation between BDNF levels and cognitive function in epilepsy patients treated with valproic acid and phenytoin. The relationship between BDNF levels and cognitive function remained the same after controlling for age, frequency of seizures, duration of combination therapy, and age of onset of epilepsy.

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.

Synapse-specific changes in Arc and BDNF in rat hippocampus following chronic temporal lobe epilepsy

Expression of immediate early genes (IEGs) in the brain is important for synaptic plasticity, and probably also in neurodegenerative conditions. To understand the cellular mechanisms of the underlying neuropathophysiological processes in epilepsy, we need to pinpoint changes in concentration of synaptic plasticity-related proteins at subsynaptic levels. In this study, we examined changes in synaptic expression of Activity-regulated cytoskeleton-associated (Arc) and Brai Derived Neurotrophic Factor (BDNF) in a rat model of kainate-induced temporal lobe epilepsy (TLE). Western blotting showed reduced concentrations of Arc and increased concentrations of BDNF in hippocampal synaptosomes in chronic TLE rats. Then, using quantitative electron microscopy, we found corresponding changes in subsynaptic regions in the hippocampus. Specifically, we detected significant reductions in the concentrations of Arc in the presynaptic terminal of Schaffer collateral glutamatergic synapses in the stratum radiatum of the CA1 area in TLE, as well as in their adjacent postsynaptic spines. In CA3, there was a significant reduction of Arc only in the presynaptic terminal cytoplasm. Conversely, in CA3, there was a significant increase in the expression of BDNF in the presynaptic terminal, but not in the postsynaptic spine. Significant increase in BDNF concentration in the CA1 postsynaptic density was also obtained. We hypothesize that the observed changes in Arc and BDNF may contribute to both cognitive impairment and increased excitotoxic vulnerability in chronic epilepsy.

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.

A comprehensive program of cognitive stimulation with digital inclusion, physical activity and social interaction can modify BDNF levels and improve cognition in adults over 50: a randomized controlled pilot study

OBJECTIVES

To analyze the effect of a comprehensive program of cognitive stimulation with digital inclusion, physical activity and social interaction, called "Oficina da Lembrança" (OL), on the cognitive status and concentration of biomarkers of neuroplasticity, neurodegeneration in adults aged 50 years and over attending a Memory Clinic.

METHODS

In this pilot randomized controlled study, 64 patients without dementia aged 45 to 79 years, seen at a University Memory Clinic in Southern Brazil, were randomly allocated to the intervention and control groups. The intervention consisted of participation in OL for 12 weeks. Serum biomarkers (brain-derived neurotrophic factor [BDNF], S100β, and neuron-specific enolase [NSE]) and cognitive status were analyzed as primary and secondary outcomes. The Wilcoxon test and Generalized Estimating Equations (GEE) were applied.

RESULTS

Of the 64 patients invited to participate in the study, 33 (intervention: 17, control: 16) completed the study with all data. Improvement of cognitive status was significant in the intervention group (22.6 to 24.5) but not in the control group (20.1 to 21.1). There was a significant reduction of BDNF in OL participants, but no significant change was observed in the neurodegenerative biomarkers S100β or NSE. The concentration of BDNF decreased significantly post-OL in the intervention group (-288.1, 95%CI -362.1 to -94.1), even after adjusting for sex, age, and educational level. Cognitive status was significantly improved in OL participants.

CONCLUSION

The OL program improved cognitive status, reduced serum BDNF levels, and empowered digitally excluded older adults. There was no effect of this intervention on S100β or NSE.

CLINICAL TRIAL REGISTRATION

This study has a Universal Trial Number (UTN) U1111-1195-2642 and was registered in the Brazilian Clinical Trials Registry (ReBEC), number RBR-38X665.

Neurotrophin Signaling Impairment by Viral Infections in the Central Nervous System

Neurotrophins, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin 3 (NT-3), NT-4, and NT-5, are proteins involved in several important functions of the central nervous system. The activation of the signaling pathways of these neurotrophins, or even by their immature form, pro-neurotrophins, starts with their recognition by cellular receptors, such as tropomyosin receptor kinase (Trk) and 75 kD NT receptors (p75NTR). The Trk receptor is considered to have a high affinity for attachment to specific neurotrophins, while the p75NTR receptor has less affinity for attachment with neurotrophins. The correct functioning of these signaling pathways contributes to proper brain development, neuronal survival, and synaptic plasticity. Unbalanced levels of neurotrophins and pro-neurotrophins have been associated with neurological disorders, illustrating the importance of these molecules in the central nervous system. Furthermore, reports have indicated that viruses can alter the normal levels of neurotrophins by interfering with their signaling pathways. This work discusses the importance of neurotrophins in the central nervous system, their signaling pathways, and how viruses can affect them.

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.

An Intense, But Ecologically Valid, Resistance Exercise Session Does Not Alter Growth Factors Associated With Cognitive Health

The purpose of this investigation was to assess the acute changes in growth factors associated with cognitive health following two ecologically valid, intense resistance exercise sessions. Twenty-nine late-middle-aged adults performed one session of either (a) moderate-load resistance exercise or (b) high-load resistance exercise. Venous blood was collected prior to warm-up, immediately following exercise and 30 min following exercise. Serum was analyzed for brain-derived neurotrophic factor, insulin-like growth factor 1, and vascular endothelial growth factor. Session intensity was determined by blood lactate concentration and session rating of perceived exertion. Postexercise blood lactate was greater following moderate-load when compared with high-load resistance exercise. Subjective session intensity was rated higher by the session rating of perceived exertion following moderate-load when compared with high-load resistance exercise. No differences were observed in serum growth factor levels between groups. Ecologically valid and intense moderate-load or high-load exercise methods do not alter serum growth factor levels in late-middle-aged adults.

Dose-dependent relationships between chronic arsenic exposure and cognitive impairment and serum brain-derived neurotrophic factor

BACKGROUND

Arsenic poisoning is a public health problem worldwide. A few studies have reported the effects of arsenic exposure on adult cognitive function, but with limitations in the subject selection and exposure markers. Moreover, information regarding the association between arsenic exposure and biomarker of cognitive impairment is scarce.

OBJECTIVES

We examined the associations between arsenic exposure and adult cognitive impairment using the Mini-Mental State Examination (MMSE) and the serum levels of brain-derived neurotrophic factor (BDNF), a potential biomarker of cognitive health status.

METHODS

We designed a cross-sectional study that recruited 693 adult (18-60 years old) subjects from the areas of low- and high‑arsenic exposure in rural Bangladesh. The subjects' arsenic exposure levels (drinking water, hair, and nail arsenic concentrations) were measured by inductively coupled plasma-mass spectroscopy. The Bangla version of the MMSE was used as a cognitive assessment tool. Serum BDNF (sBDNF) levels were assessed by immunoassay.

RESULTS

In this study, we found that average MMSE score and sBDNF level of the subjects in arsenic-endemic areas were significantly (p < 0.001 for both) lower than those of the subjects in non-endemic area. Our analyses revealed that both MMSE scores and sBDNF levels were decreased with the increasing concentrations of arsenic in drinking water, hair, and nails in a dose-dependent fashion. In regression analyses, significant associations of arsenic exposure metrics with MMSE scores and sBDNF levels were observed even after adjustment for several variables. Intriguingly, MMSE scores showed a significantly positive correlation with sBDNF levels.

CONCLUSION

Our findings demonstrate that chronic exposure to arsenic dose-dependently decreases cognitive function in adults, with a concomitant reduction of sBDNF levels. A decreased BDNF level may be part of the biochemical basis of chronic arsenic exposure-related cognitive impairment.

BDNF increases associated with constant troponin T levels and may protect against poor cognitive interference control: The SABPA prospective study

BACKGROUND

Brain-derived neurotrophic factor (BDNF) modulates brain health and cognition, which can interfere with executive cognitive function. BDNF was implicated with microcirculatory ischaemia and may reflect cardiomyocyte injury. We aimed to determine whether prospective changes (%Δ) in BDNF and cardiac troponin T (cTnT) will be associated with executive cognitive function in a bi-ethnic cohort.

DESIGN

A prospective investigation was conducted over a three-year period in a bi-ethnic sex cohort (N = 338; aged 20-65 years) from South Africa. Fasting serum samples for BDNF and cTnT were obtained. The STROOP-color-word conflict test (CWT) was applied to assess executive cognitive function at baseline.

RESULTS

In Blacks, BDNF (P < 0.001) increased over the three-year period while cTnT did not change. In contrast, in Whites, BDNF and cTnT decreased over three years. In Black men, no change in cTnT was associated with increased ΔBDNF (β = 0.25; 95% CI 0.05-0.45; P = 0.02). In the Black men, constant cTnT levels were inversely associated with executive cognitive function (β = -0.33; 95% CI -0.53 to -0.12; P = 0.003). Three-year increases in BDNF increased the likelihood for chronic lower cTnT levels at a pre-established cut-point of <4.2 ng/L [OR = 2.35 (1.12-4.94), P = 0.02]. The above associations were not found in the White sex groups.

CONCLUSIONS

Central neural control mechanisms may have upregulated BDNF in Black men as a way to protect against myocardial stress progression and to possibly improve processes related to cognitive interference control. High-sensitive cTnT levels may act as an early predictor of disturbed neural control mechanisms.

Dysregulation of the SNARE-binding protein Munc18-1 impairs BDNF secretion and synaptic neurotransmission: a novel interventional target to protect the aging brain

Brain-derived neurotrophic factor (BDNF) has a central role in maintaining and strengthening neuronal connections and to stimulate neurogenesis in the adult brain. Decreased levels of BDNF in the aging brain are thought to usher cognitive impairment. BDNF is stored in dense core vesicles and released through exocytosis from the neurites. The exact mechanism for the regulation of BDNF secretion is not well understood. Munc18-1 (STXBP1) was found to be essential for the exocytosis of synaptic vesicles, but its involvement in BDNF secretion is not known. Interestingly, neurons lacking munc18-1 undergo severe degeneration in knock-out mice. Here, we report the effects of BDNF treatment on the presynaptic terminal using munc18-1-deficient neurons. Reduced expression of munc18-1 in heterozygous (+/-) neurons diminishes synaptic transmitter release, as tested here on individual synaptic connections with FM1-43 fluorescence imaging. Transduction of cultured neurons with BDNF markedly increased BDNF secretion in wild-type but was less effective in munc18-1 +/- cells. In turn, BDNF enhanced synaptic functions and restored the severe synaptic dysfunction induced by munc18-1 deficiency. The role of munc18-1 in the synaptic effect of BDNF is highlighted by the finding that BDNF upregulated the expression of munc18-1 in neurons, consistent with enhanced synaptic functions. Accordingly, this is the first evidence showing the functional effect of BDNF in munc18-1 deficient synapses and about the direct role of munc18-1 in the regulation of BDNF secretion. We propose a molecular model of BDNF secretion and discuss its potential as therapeutic target to prevent cognitive decline in the elderly.

Decreased Serum Brain-Derived Neurotrophic Factor (BDNF) Levels in Patients with Alzheimer's Disease (AD): A Systematic Review and Meta-Analysis

Findings from previous studies reporting the levels of serum brain-derived neurotrophic factor (BDNF) in patients with Alzheimer's disease (AD) and individuals with mild cognitive impairment (MCI) have been conflicting. Hence, we performed a meta-analysis to examine the aggregate levels of serum BDNF in patients with AD and individuals with MCI, in comparison with healthy controls. Fifteen studies were included for the comparison between AD and healthy control (HC) (n = 2067). Serum BDNF levels were significantly lower in patients with AD (SMD: -0.282; 95% confidence interval [CI]: -0.535 to -0.028; significant heterogeneity: I² = 83.962). Meta-regression identified age (p < 0.001) and MMSE scores (p < 0.001) to be the significant moderators that could explain the heterogeneity in findings in these studies. Additionally, there were no significant differences in serum BDNF levels between patients with AD and MCI (eight studies, n = 906) and between MCI and HC (nine studies, n = 5090). In all, patients with AD, but not MCI, have significantly lower serum BDNF levels compared to healthy controls. This meta-analysis confirmed the direction of change in serum BDNF levels in dementia. This finding suggests that a significant change in peripheral BDNF levels can only be detected at the late stage of the dementia spectrum. Molecular mechanisms, implications on interventional trials, and future directions for studies examining BDNF in dementia were discussed.

Impact of brain-derived neurotrophic factor genetic polymorphism on cognition: A systematic review

INTRODUCTION

Brain-derived neurotrophic factor (BDNF) has an important role in the neurogenesis and neuroplasticity of the brain. This systematic review was designed to examine the association between BDNF Val66Met (rs6265) polymorphism and four cognitive domains-attention and concentration, executive function, verbal fluency, and memory, respectively.

METHODOLOGY

Primary literature search was performed using search engines such as PubMed and Scopus. Observational studies that evaluated the neurocognitive performances in relation to BDNF polymorphism within human subjects were included in this review, while animal studies, overlapping studies, and meta-analysis were excluded.

RESULTS

Forty of 82 reviewed studies (48.8%) reported an association between Val66Met polymorphism and neurocognitive domains. The proportion of the studies showing positive findings in cognitive performances between Val/Val homozygotes and Met carriers was comparable, at 30.5% and 18.3%, respectively. The highest percentage of positive association between Val66Met polymorphism and neurocognition was reported under the memory domain, with 26 of 63 studies (41.3%), followed by 18 of 47 studies (38.3%) under the executive function domain and four of 23 studies (17.4%) under the attention and concentration domain. There were no studies showing an association between Val66Met polymorphism and verbal fluency. In particular, Val/Val homozygotes performed better in tasks related to the memory domain, while Met carriers performed better in terms of executive function, in both healthy individuals and clinical populations.

CONCLUSION

While numerous studies report an association between Val66Met polymorphism and neurocognitive changes in executive function and memory domains, the effect of Met allele has not been clearly established.

The Effects of Moderate Physical Exercise on Adult Cognition: A Systematic Review

Background: Physical exercise is a systematic sequence of movements executed with a predefined purpose. This muscular activity impacts not only on circulatory adaptations, but also neuronal integration with the potential to influence cognition. The aim of this review was to determine whether the literature supports the idea that physical exercise promotes cognitive benefits in healthy adults.

Methods: A systematic search for relevant articles was performed according to the Preferred Reporting Items for Systematic Review and Meta-Analysis criteria using available databases (PubMed, LILACS, Scopus, Web of Science, The Cochrane Library, OpenGrey, Google Scholar and CENTRAL). The search terms included “humans” or “adults” or “cognition” or “awareness” or “cognitive dissonance” or “cognitive reserve” or “comprehension” or “consciousness” and “motor activity” or “exercise” or “physical fitness,” and not “aged” or “nervous system diseases,” with the purpose of finding associations between moderate physical exercise and cognition. A methodological quality and risk of bias unit assessed the eligibility of articles.

Results: A total of 7179 articles were identified. Following review and quality assessment, three articles were identified to fulfill the inclusion criteria. An association between moderate physical exercise and cognition was observed. Improvements in cognitive parameters such as reduced simple reaction time, improved response precision and working memory were identified among the included articles.

Conclusion: This systematic review found that moderate physical exercise improves cognition.

Neurotrophic factors and hippocampal activity in PTSD

Although numerous studies have investigated the neurotrophic factors and hippocampal activity in posttraumatic stress disorder (PTSD) separately each other, it is unclear whether an association between neurotrophic factors and hippocampal activity is present. The aim of this study was to evaluate the functional changes in hippocampus before and after treatment with escitalopram and to associate these changes with peptides related to neuronal growth in patients with chronic PTSD and trauma survivors without PTSD. Fifteen earthquake survivors with chronic PTSD and thirteen drug naïve trauma exposed individuals without PTSD underwent fMRI scans in a block design. Serum levels of Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF) were measured before and after 12 weeks treatment with escitalopram. Baseline median serum level of NGF was significantly lower in patients with chronic PTSD than trauma survivors; however, 12 weeks of treatment with escitalopram significantly increased it. Higher activation was found both in left and right hippocampus for chronic PTSD group than trauma survivors. Treatment with escitalopram was significantly associated with suppression of the hyperactivation in left hippocampus in patients with chronic PTSD. Bilateral hyperactivation in hippocampus and lowered NGF may associate with neurobiological disarrangements in chronic PTSD. Treatment with escitalopram was significantly associated with both improvement in the severity of PTSD symptoms and biological alterations. Patients diagnosed with PTSD may have further and complicated deteriorations in hippocampal networks and neurotransmitter systems than individuals who had not been diagnosed with PTSD following the same traumatic experience.

Cognitive impairment in rheumatoid arthritis: role of lymphocyte subsets, cytokines and neurotrophic factors

To what extent the cognitive impairment of rheumatoid arthritis (RA) is modulated by autoimmune and/or inflammatory activity is largely unknown. The aim of this study was to investigate the role of peripheral inflammation on cognitive functions of patients with active (Ac-), controlled (Co-) RA and healthy controls. In a cross-sectional study, 102 RA patients and 30 matched healthy controls were recruited. B and T cell subsets were immunophenotyped by flow cytometry. Plasma cytokines and neurotrophins were measured by flow cytometry and ELISA, respectively. Cognitive performance, depression and stress were evaluated by structured clinical interviews. Generalized linear modeling (GzLM) was used to compare differences between groups and multiple linear regression models were used to explore the predictive value of immune variables on cognitive performance. RA patients had overall cognitive impairment. Of note, the Ac-RA had the poorest performance on digit span (DST) and N-back when compared to Co-RA and control group (DST 9.9 ± 2.1, 12.9 ± 4.2, 15.5 ± 4.7, respectively; N-back 49.2 ± 8.3, 55.5 ± 11.1, 60.8 ± 9.1, respectively, all p < 0.0001). RA patients had expansions of immature B cells (Ac-RA 11.2 ± 7.1, Co-RA: 9 ± 5.7, control 5.9 ± 2.1) and plasma cells (Ac-RA 5.2 ± 2.5, Co-RA 6.9 ± 3.7, control 2.8 ± 1.7) as compared to controls, all p < 0.05. RA patients (controlled and active disease) had higher plasma levels of TNF, IL-2, IL-4, IL-6 and IL-10 than controls (all p < 0.002). RA patients had higher BDNF levels (Ac-RA 17,354.4 ± 5357.3, Co-RA 13,841.2 ± 5953.7, control 11,543.3 ± 3772), but lower GDNF levels [median (interquartile range) Ac-RA 0 pg/ml (0.0), Co-RA 0 pg/ml (4.6) and control 4.7 pg/ml (18.1)] than controls (all p < 0.05). RA patients had global cognitive impairment, which was associated with disease activity and immune changes.

Identification of Neuroprotective Factors Associated with Successful Ageing and Risk of Cognitive Impairment among Malaysia Older Adults

The increase of ageing population has raised public attention on the concept of successful ageing. Studies have shown that vitamin D, telomere length, and brain-derived neurotrophic factor (BDNF) have been associated with cognitive function. Therefore, this study aimed to identify neuroprotective factors for cognitive decline in different ageing groups. A total of 300 older adults aged 60 years and above were recruited in this population based cross-sectional study. Participants were categorized into three groups: mild cognitive impairment (MCI) (n = 100), usual ageing (UA) (n = 100), and successful ageing (SA) (n = 100). Dietary vitamin D intake was assessed through Diet History Questionnaire (DHQ). Out of the 300 participants, only 150 were subjected to fasting blood sample collection. These samples were used for serum vitamin D and plasma BDNF measurements. Whole blood telomere length was measured using RT-PCR method. The results show that the reduction of the risk of MCI was achieved by higher serum vitamin D level (OR: 0.96, 95% CI: 0.92–0.99, p < 0.05), higher plasma BDNF level (OR: 0.51, 95% CI: 0.30–0.88,  p < 0.05), and longer telomere (OR: 0.97, 95% CI: 0.95–0.99,  p < 0.001). In conclusion, participants with higher vitamin D level, higher BDNF level, and longer telomere length were more likely to age successfully.

Metabolic reprogramming by the pyruvate dehydrogenase kinase-lactic acid axis: Linking metabolism and diverse neuropathophysiologies

Emerging evidence indicates that there is a complex interplay between metabolism and chronic disorders in the nervous system. In particular, the pyruvate dehydrogenase (PDH) kinase (PDK)-lactic acid axis is a critical link that connects metabolic reprogramming and the pathophysiology of neurological disorders. PDKs, via regulation of PDH complex activity, orchestrate the conversion of pyruvate either aerobically to acetyl-CoA, or anaerobically to lactate. The kinases are also involved in neurometabolic dysregulation under pathological conditions. Lactate, an energy substrate for neurons, is also a recently acknowledged signaling molecule involved in neuronal plasticity, neuron-glia interactions, neuroimmune communication, and nociception. More recently, the PDK-lactic acid axis has been recognized to modulate neuronal and glial phenotypes and activities, contributing to the pathophysiologies of diverse neurological disorders. This review covers the recent advances that implicate the PDK-lactic acid axis as a novel linker of metabolism and diverse neuropathophysiologies. We finally explore the possibilities of employing the PDK-lactic acid axis and its downstream mediators as putative future therapeutic strategies aimed at prevention or treatment of neurological disorders.