Association between BDNF val66 met genotype and episodic memory

Atrial Fibrillation and Older Age Predict Serum Brain-Derived Neurotrophic Factor Levels Among Patients With Heart Failure

BACKGROUND

Predictors have not been determined of serum brain-derived neurotrophic factor (BDNF) levels among patients with heart failure (HF).

OBJECTIVE

The primary purpose was to evaluate history of atrial fibrillation, age, gender, and left ventricular ejection fraction as predictors of serum BDNF levels at baseline, 10 weeks, and 4 and 8 months after baseline among patients with HF.

METHODS

This study was a retrospective cohort analyses of 241 patients with HF. Data were retrieved from the patients' health records (coded history of atrial fibrillation, left ventricular ejection fraction), self-report (age, gender), and serum BDNF. Linear multiple regression analyses were conducted.

RESULTS

One hundred three patients (42.7%) had a history of atrial fibrillation. History of atrial fibrillation was a significant predictor of serum BDNF levels at baseline (β = -0.16, P = .016), 4 months (β = -0.21, P = .005), and 8 months (β = -0.19, P = .015). Older age was a significant predictor at 10 weeks (β = -0.17, P = .017) and 4 months (β = -0.15, P = .046).

CONCLUSIONS

Prospective studies are needed to validate these results. Clinicians need to assess patients with HF for atrial fibrillation and include treatment of it in management plans.

In silico analysis of the Val66Met mutation in BDNF protein: implications for psychological stress

The brain-derived neurotrophic factor (BDNF) involves stress regulation and psychiatric disorders. The Val66Met polymorphism in the BDNF gene has been linked to altered protein function and susceptibility to stress-related conditions. This in silico analysis aimed to predict and analyze the consequences of the Val66Met mutation in the BDNF gene of stressed individuals. Computational techniques, including ab initio, comparative, and I-TASSER modeling, were used to evaluate the functional and stability effects of the Val66Met mutation in BDNF. The accuracy and reliability of the models were validated. Sequence alignment and secondary structure analysis compared amino acid residues and structural components. The phylogenetic analysis assessed the conservation of the mutation site. Functional and stability prediction analyses provided mixed results, suggesting potential effects on protein function and stability. Structural models revealed the importance of BDNF in key biological processes. Sequence alignment analysis showed the conservation of amino acid residues across species. Secondary structure analysis indicated minor differences between the wild-type and mutant forms. Phylogenetic analysis supported the evolutionary conservation of the mutation site. This computational study suggests that the Val66Met mutation in BDNF may have implications for protein stability, structural conformation, and function. Further experimental validation is needed to confirm these findings and elucidate the precise effects of this mutation on stress-related disorders.

BDNF gene Val66Met polymorphisms as a predictor for clinical presentation in schizophrenia - recent findings

Schizophrenia is a highly heritable, severe psychiatric disorder that involves dysfunctions in thinking, emotions, and behavior, with a profound impact on a person's ability to function normally in their daily life. Research efforts continue to focus on elucidating possible genetic underlying mechanisms of the disorder. Although the genetic loci identified to date to be significantly associated with schizophrenia risk do not represent disease-causing factors, each one of them could be seen as a possible incremental contributor. Considering the importance of finding new and more efficient pharmacological approaches to target the complex symptomatology of this disorder, in this scoping review, we are focusing on the most recent findings in studies aiming to elucidate the contribution of one of the genetic factors involved - the BDNF gene Val66Met polymorphisms. Here we performed a systematic search in Pubmed, Embase, and Web of Science databases with the search terms: (BDNF gene polymorphism) AND (schizophrenia) for articles published in the last 5 years. To be selected for this review, articles had to report on studies where genotyping for the BDNF Val66Met polymorphism was performed in participants diagnosed with schizophrenia (or schizophrenia spectrum disorders or first-episode psychosis). The search provided 35 results from Pubmed, 134 results from Embase, and 118 results from the Web of Science database. Twenty-two articles were selected to be included in this review, all reporting on studies where an implication of the BDNF Val66Met polymorphisms in the disorder's pathophysiology was sought to be elucidated. These studies looked at BDNF gene Val66Met polymorphism variants, their interactions with other genes of interest, and different facets of the illness. The Met/Met genotype was found to be associated with higher PANSS positive scores. Furthermore, Met/Met homozygous individuals appear to present with worse cognitive function and lower levels of serum BDNF. In the Val/Val genotype carriers, increased BDNF levels were found to correlate with weight gain under Risperidone treatment. However, due to heterogeneous results, the diversity in study populations and studies' small sample sizes, generalizations cannot be made. Our findings emphasize the need for further research dedicated to clarifying the role of gene polymorphisms in antipsychotic treatment to enhance specificity and efficacy in the treatment of schizophrenia.

Evaluating depressive symptoms, BDNF Val66Met, and APOE-ε4 as moderators of response to computerized cognitive training in heart failure

BACKGROUND

Depressive symptoms, brain-derived neurotrophic factor (BDNF) Val66Met, and apolipoprotein (APOE)-ε4 may moderate response to computerized cognitive training (CCT) interventions among patients with heart failure (HF).

OBJECTIVES

The purpose of this study was to examine moderators of intervention response to CCT over 8 months among patients with HF enrolled in a 3-arm randomized controlled trial. Outcomes were memory, serum BDNF, working memory, instrumental activities of daily living (IADLs), and health-related quality of life (HRQL).

METHODS

256 patients with HF were randomized to CCT, computerized crossword puzzles active control, and usual care control groups for 8 weeks. Data were collected at enrollment, baseline, 10 weeks, and 4 and 8 months. Mixed effects models were computed to evaluate moderators.

RESULTS

As previously reported, there were no statistically significant group by time effects in outcomes among the 3 groups over 8 months. Tests of moderation indicated that depressive symptoms and presence of BDNF Val66Met and APOE-ε4 were not statistically significant moderators of intervention response in outcomes of delayed recall memory, serum BDNF, working memory, IADLs, and HRQL. In post hoc analysis evaluating baseline global cognitive function, gender, age, and HF severity as moderators, no significant effects were found. HF severity was imbalanced among groups (P = .049) which may have influenced results.

CONCLUSIONS

Studies are needed to elucidate biological mechanisms of cognitive dysfunction in HF and test novel interventions to improve memory, serum BDNF, working memory, IADLs and HRQL. Patients may need to be stratified or randomized by HF severity within intervention trials.

BDNF Val66Met polymorphism is associated with consolidation of episodic memory during sleep

The brain-derived neurotrophic factor (BDNF) is an essential regulator of synaptic plasticity, a candidate neurobiological mechanism underlying learning and memory. A functional polymorphism in the BDNF gene, Val66Met (rs6265), has been linked to memory and cognition in healthy individuals and clinical populations. Sleep contributes to memory consolidation, yet information about the possible role of BDNF in this process is scarce. To address this question, we investigated the relationship between the BDNF Val66Met genotype and consolidation of episodic declarative and procedural (motor) non-declarative memories in healthy adults. The carriers of Met66 allele, as compared with Val66 homozygotes, showed stronger forgetting overnight (24hours after encoding), but not over shorter time (immediately or 20minutes after word list presentation). There was no effect of Val66Met genotype on motor learning. These data suggest that BDNF plays a role in neuroplasticity underlying episodic memory consolidation during sleep.

Neuronavigated Repetitive Transcranial Stimulation Improves Neurocognitive Functioning in Veterans with Schizophrenia: A Possible Role of BDNF Polymorphism

It has been reported in the previous literatures that high-frequency (HF) neuronavigated repetitive transcranial magnetic stimulation (rTMS) may improve neurocognitive functioning in patients with schizophrenia. Nonetheless, the heterogeneity of the research findings with regards to the effectiveness of HF-rTMS on the neurocognitive functioning in patients with schizophrenia greatly hinders its clinical application. The current study was designed to determine the predictive role of BDNF variants for neurocognitive improvements after rTMS administration in veterans with schizophrenia. 109 hospitalized veterans with schizophrenia were randomly allocated to active HF-rTMS (n=63) or sham stimulation (n=46) over left DLPFC for 4 consecutive weeks. Neurocognitive functions were assessed by using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) at baseline and at the end of week 4. BDNF polymorphism was genotyped by the technicians. Compared with sham stimulation sessions, the immediate memory performance was significantly increased in active sessions after neuronavigated HF-rTMS administration. In addition, patients with the CC homozygotes demonstrated greater improvement of immediate memory after rTMS treatment, while T allele carriers showed no significant improvement in immediate memory domain relative to baseline performance of immediate memory. Our findings suggest that add-on neuronavigated HF-rTMS is beneficial on immediate memory only in patients with CC homozygotes, but not in T allele carriers. This pilot study provides further evidence for BDNF as a promise biomarker in predicting the clinical response to rTMS stimulation.

Integration of GWAS and brain transcriptomic analyses in a multiethnic sample of 35,245 older adults identifies DCDC2 gene as predictor of episodic memory maintenance

Identifying genes underlying memory function will help characterize cognitively resilient and high-risk declining subpopulations contributing to precision medicine strategies. We estimated episodic memory trajectories in 35,245 ethnically diverse older adults representing eight independent cohorts. We conducted apolipoprotein E (APOE)-stratified genome-wide association study (GWAS) analyses and combined individual cohorts' results via meta-analysis. Three independent transcriptomics datasets were used to further interpret GWAS signals. We identified DCDC2 gene significantly associated with episodic memory (Pmeta = 3.3 x 10^-8 ) among non-carriers of APOE ε4 (N = 24,941). Brain transcriptomics revealed an association between episodic memory maintenance and (1) increased dorsolateral prefrontal cortex DCDC2 expression (P = 3.8 x 10^-4 ) and (2) lower burden of pathological Alzheimer's disease (AD) hallmarks (paired helical fragment tau P = .003, and amyloid beta load P = .008). Additional transcriptomics results comparing AD and cognitively healthy brain samples showed a downregulation of DCDC2 levels in superior temporal gyrus (P = .007) and inferior frontal gyrus (P = .013). Our work identified DCDC2 gene as a novel predictor of memory maintenance.

Considering medication exposure in genomic association studies of cognition in psychotic disorders

Cognitive dysfunction is a core feature of psychosis-spectrum illnesses, and the characterization of related genetic mechanisms may provide insights regarding the disease pathophysiology. Substantial efforts have been made to determine the genetic component of cognitive symptoms, without clear success. Illness-related moderators and environmental factors such as medications hinder the detection of genomic association with cognition. Polypharmacy is common in psychotic disorders, and the cumulative effects of medication regimens can confound gene-cognition associations. A review of the relative contributions of important pharmacological and genetic relationships identifies that the effects of medications on cognition in psychotic disorders may be at least, if not more, impactful than individual genes, thus underscoring the importance of accounting for medication exposure in gene-cognition association studies.

Effect of brain-derived neurotrophic factor gene polymorphisms on motor performance and motor learning: A systematic review and meta-analysis

Brain-derived neurotrophic factor (BDNF) gene polymorphisms may modulate neurotransmitter efficiency, thereby influencing motor performance and motor learning. However, studies to date have provided no consensus regarding the genetic influence of BDNF genotypes (i.e., Val/Val, Val/Met, or Met/Met type). This study aimed to investigate the effect of BDNF genotype on motor performance and motor learning in healthy human adults via a systematic review and meta-analysis. A total of 19 relevant studies were identified using PubMed and Web of Science search for articles published between 2000 and 2021 with motor performance or motor learning as the primary outcome measures. The results of our systematic review suggest that the BDNF genotype is unlikely to contribute to motor performance and motor learning abilities because only 2/32 datasets (6.3%) from 16 studies on motor performance and 3/19 datasets (17.6%) from 13 studies on motor learning indicated a significant genetic effect. Moreover, a meta-analysis of motor learning publications involving 17 datasets from 11 studies revealed that there was no significant difference in the learning score normalized using baseline data between Val/Val and Met carriers (Val/Met + Met/Met or Val/Met; standardized mean differences = 0.08, P = 0.37) with zero heterogeneity (I² = 0) and a relatively low risk of publication bias. Taken together, the BDNF genotype may have only a minor impact on individual motor performance and motor learning abilities.

Do Brain-Derived Neurotrophic Factor Genetic Polymorphisms Modulate the Efficacy of Motor Cortex Plasticity Induced by Non-invasive Brain Stimulation? A Systematic Review

Techniques of non-invasive brain stimulation (NIBS) of the human primary motor cortex (M1) are widely used in basic and clinical research to induce neural plasticity. The induction of neural plasticity in the M1 may improve motor performance ability in healthy individuals and patients with motor deficit caused by brain disorders. However, several recent studies revealed that various NIBS techniques yield high interindividual variability in the response, and that the brain-derived neurotrophic factor (BDNF) genotype (i.e., Val/Val and Met carrier types) may be a factor contributing to this variability. Here, we conducted a systematic review of all published studies that investigated the effects of the BDNF genotype on various forms of NIBS techniques applied to the human M1. The motor-evoked potential (MEP) amplitudes elicited by single-pulse transcranial magnetic stimulation (TMS), which can evaluate M1 excitability, were investigated as the main outcome. A total of 1,827 articles were identified, of which 17 (facilitatory NIBS protocol, 27 data) and 10 (inhibitory NIBS protocol, 14 data) were included in this review. More than two-thirds of the data (70.4–78.6%) on both NIBS protocols did not show a significant genotype effect of NIBS on MEP changes. Conversely, most of the remaining data revealed that the Val/Val type is likely to yield a greater MEP response after NIBS than the Met carrier type in both NIBS protocols (21.4–25.9%). Finally, to aid future investigation, we discuss the potential effect of the BDNF genotype based on mechanisms and methodological issues.

The BDNF val66met polymorphism is associated with decreased use of landmarks and decreased fMRI activity in the hippocampus during virtual navigation

People can navigate in a new environment using multiple strategies dependent on different memory systems. A series of studies have dissociated between hippocampus-dependent 'spatial' navigation and habit-based 'response' learning mediated by the caudate nucleus. The val66met polymorphism of the brain-derived neurotrophic factor (BDNF) gene leads to decreased secretion of BDNF in the brain, including the hippocampus. Here, we aim to investigate the role of the BDNF val66met polymorphism on virtual navigation behaviour and brain activity in healthy older adults. A total of 139 healthy older adult participants (mean age = 65.8 ± 4.4 years) were tested in this study. Blood samples were collected, and BDNF val66met genotyping was performed. Participants were divided into two genotype groups: val homozygotes and met carriers. Participants were tested on virtual dual-solution navigation tasks in which they could use either a hippocampus-dependent spatial strategy or a caudate nucleus-dependent response strategy to solve the task. A subset of the participants (n = 66) were then scanned in a 3T functional magnetic resonance imaging (fMRI) scanner while engaging in another dual-solution navigation task. BDNF val/val individuals and met carriers did not differ in learning performance. However, the two BDNF groups differed in learning strategy. BDNF val/val individuals relied more on landmarks to remember target locations (i.e., increased use of flexible spatial learning), while met carriers relied more on sequences and patterns to remember target locations (i.e., increased use of inflexible response learning). Additionally, BDNF val/val individuals had more fMRI activity in the hippocampus compared with BDNF met carriers during performance on the navigation task. This is the first study to show in older adults that BDNF met carriers use alternate learning strategies from val/val individuals and to identify differential brain activation of this behavioural difference between the two groups.

The Brain-Derived Neurotrophic Factor Val66Met Polymorphism Can Protect Against Cognitive Impairment in Multiple Sclerosis

Introduction: Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family, involved in neuronal survival and synaptic plasticity. The BDNF Val66Met polymorphism is known to reduce BDNF expression and secretion; its role in multiple sclerosis (MS) is poorly investigated.

Objectives and Methods: In this multicenter, retrospective study, we assessed the role of BDNF Val66Met polymorphism on cognitive and motor disability in MS patients consecutively referred to the University of Florence and the Hospital of Barletta. All patients underwent a genetic analysis for the presence of Val66Met polymorphism and a comprehensive neuropsychological examination on the Rao's Brief Repeatable Battery and the Stroop Color Word Test. Possible predictors of the Expanded Disability Status Scale (EDSS) score and number of failed neuropsychological tests were assessed through linear multivariable regression models.

Results: Ninety-eight patients were recruited. Patients with the BDNF Val66Met polymorphism (35.7%) were more frequently males (p = 0.020), more disabled (p = 0.026) and, marginally, older (p = 0.064). In the multivariable analysis, BDNF Val66Met polymorphism was associated with a better cognitive performance (B = −1.1 ± 0.5, p = 0.027). Higher EDSS score was associated with a progressive disease course (B = 3.4, p < 0.001) and, marginally, with the presence of the BDNF Val66Met polymorphism (B = 0.56, p = 0.066).

Discussion: Our results preliminarily suggest a protective role of BDNF Val66Met polymorphism against cognitive impairment in MS patients, possibly related to a detrimental effect of increased BDNF concentration in a neuroinflammatory environment.

Testing influences of APOE and BDNF genes and heart failure on cognitive function

BACKGROUND

Apolipoprotein E (APOE) ε2, ε4 and brain-derived neurotrophic factor (BDNF) Val66Met alleles have been associated with cognition. Associations of these alleles with cognition in heart failure (HF) and influences of HF across the cognitive spectrum (i.e., cognitively normal to Alzheimer's dementia [AD]) remain unexplored.

OBJECTIVES

To investigate influences of APOE ε2, ε4, BDNF Met and HF on cognition among participants across the cognitive spectrum.

METHODS

Genetic association study using national databases (N = 7,166).

RESULTS

APOE ε2 frequencies were similar across the cognitive spectrum among participants with HF. APOE ε4 frequency was lower among participants with HF and AD than non-HF participants with AD. BDNF Met frequencies did not differ across the spectrum. HF was associated with worse attention and language. In the HF subsample, ε4 was associated with worse memory.

CONCLUSION

Associations between APOE and cognition may differ in HF but need to be tested in a larger sample.

An Integrative Review of Brain-Derived Neurotrophic Factor and Serious Cardiovascular Conditions

BACKGROUND

There is emerging evidence that supports a role for brain-derived neurotrophic factor (BDNF) in the risk and presence of serious cardiovascular conditions. However, few existing literature reviews methodically describe empirical findings regarding this relationship.

OBJECTIVES

The purpose of this integrative review was to (a) evaluate BDNF (serum/plasma BDNF levels, BDNF Val66Met genotype) among humans at risk for or with serious cardiovascular conditions and (b) investigate the relationship between BDNF and risk/presence of serious cardiovascular conditions in humans.

METHODS

An integrative review was conducted. Articles in English included human subjects, a measure of BDNF levels or BDNF gene, serious cardiovascular conditions, and quantitative data analyses. The search resulted in 475 unique titles, with the final sample including 35 articles representing 30 studies. Articles that received "good" or "fair" ratings (n = 31) using the National Heart, Lung, and Blood Institute Study Quality Assessment Tools were included for synthesis.

RESULTS

The retrieved articles were largely nonexperimental, with sample sizes ranging from 20 to 5,510 participants. Overall, BDNF levels were lower in patients with chronic heart failure and stroke, but higher in patients with unstable angina and recent myocardial infarction. Lower BDNF levels were associated with higher incidence of cardiovascular events in patients with a prior history of serious cardiovascular conditions and decreased cardiovascular risk in healthy samples. For BDNF genotype, on average, 36.3% of participants had Met alleles. The frequency of the BDNF Met allele varied across race/ethnicity and cardiovascular conditions and in terms of association with serious cardiovascular condition incidence/risk.

DISCUSSION

These findings indicate an emerging area of science. Future investigation is needed on serious cardiovascular condition phenotypes in relationship to BDNF in the same study conditions. Results also suggest for use of standardized BDNF measurement across studies and additional investigation in cardiovascular inflammatory processes that affect BDNF. Moreover, within specific populations, the frequency of Met alleles may be too low to be detected in sample sizes normally found in these types of studies.

Dissociation of BDNF Val66Met polymorphism on neurocognitive functioning in military veterans with and without a history of remote mild traumatic brain injury

OBJECTIVE

Since neurocognitive functioning following mild traumatic brain injury (mTBI) may be influenced by genetic factors that mediate synaptic survival and repair, we examined the influence of a common brain-derived neurotrophic factor (BDNF) polymorphism (Val66Met) on cognition using a well-defined sample of military Veterans with and without a history of mTBI.

METHOD

Participants included 138 Veterans (mTBI = 75; military controls [MCs] = 63) who underwent neuropsychological testing, including completion of self-report measures assessing psychiatric distress, and BDNF genotyping. The mTBI group was tested roughly 66.7 months following their most recent mTBI. Veterans were divided into two groups-Met+ (Met/Met and Met/Val; n = 49) and Met- (Val/Val; n = 89) and compared on domain-specific cognitive composite scores representing memory, executive functioning, and visuospatial speed.

RESULTS

ANCOVAs adjusting for psychiatric distress, sex, years of education, and ethnicity/race revealed a significant group (mTBI vs. MC) by BDNF genotype (Met + vs. Met-) interaction for the memory (p = .024; η_p ² = .039) and executive functioning (p = .010; η_p ² = .050) composites, such that Met+ mTBI Veterans demonstrated better performance than Met- mTBI Veterans on the cognitive measures, whereas Met+ MCs demonstrated worse performance relative to Met- MCs on the cognitive measures. No significant interaction was observed for the visuospatial speed composite (p = .938; η_p ² < .001).

CONCLUSIONS

These findings offer preliminary evidence to suggest that the Met allele may be protective in the context of remote mTBI. Findings need to be replicated using larger samples, and future studies are necessary to elucidate the precise mechanisms and neural underpinnings of this interaction.

Association of the brain-derived neurotrophic factor Val66Met polymorphism with negative symptoms severity, but not cognitive function, in first-episode schizophrenia spectrum disorders

Objective

A functional polymorphism of the brain-derived neurotrophic factor gene (BDNF) Val66Met has been associated with cognitive function and symptom severity in patients with schizophrenia. It has been suggested that the Val66Met polymorphism has a role as a modulator in a range of clinical features of the illness, including symptoms severity, therapeutic responsiveness, age of onset, brain morphology and cognitive function. However, little work has been done in first-episode schizophrenia (FES) spectrum disorders. The objective of this study is to investigate the association of the BDNF Val66Met polymorphism on cognitive function and clinical symptomatology in FES patients.

Methods

Using a cross-sectional design in a cohort of 204 patients with FES or a schizophrenia spectrum disorder and 204 healthy matched controls, we performed BDNF Val66Met genotyping and tested its relationship with cognitive testing (attention, working memory, learning/verbal memory and reasoning/problem-solving) and assessment of clinical symptom severity.

Results

There was no significant influence of the BDNF allele frequency on cognitive factor scores in either patients or controls. An augmented severity of negative symptoms was found in FES patients that carried the Met allele.

Conclusions

The results of this study suggest that in patients with a first-episode of schizophrenia or a schizophrenia spectrum disorder, the BDNF Val66Met polymorphism does not exert an influence on cognitive functioning, but is associated with negative symptoms severity. BDNF may serve as suitable marker of negative symptomatology severity in FES patients within the schizophrenia spectrum.

Human Plasma BDNF Is Associated With Amygdala-Prefrontal Cortex Functional Connectivity and Problem Drinking Behaviors

BACKGROUND

Preclinical studies suggest that decreased levels of brain-derived neurotrophic factor in the amygdala play a role in anxiety and alcohol use disorder. The association between brain-derived neurotrophic factor levels and amygdala function in humans with alcohol use disorder is still unclear, although neuroimaging studies have also implicated the amygdala in alcohol use disorder and suggest that alcohol use disorder is associated with disrupted functional connectivity between the amygdala and prefrontal cortex during aversive states.

METHODS

The current study investigated whether plasma brain-derived neurotrophic factor levels in individuals with and without alcohol use disorder (n = 57) were associated with individual differences in amygdala reactivity and amygdala-prefrontal cortex functional connectivity during 2 forms of aversive responding captured via functional magnetic resonance imaging: anxiety elicited by unpredictable threat of shock and fear elicited by predictable threat of shock. We also examined whether brain-derived neurotrophic factor and brain function were associated with binge drinking episodes and alcohol use disorder age of onset.

RESULTS

During anxiety, but not fear, lower levels of plasma brain-derived neurotrophic factor were associated with less connectivity between the left amygdala and the medial prefrontal cortex and the inferior frontal gyrus. In addition, within individuals with alcohol use disorder (only), lower levels of brain-derived neurotrophic factor and amygdala-medial prefrontal cortex functional connectivity during anxiety were associated with more binge episodes within the past 60 days and a lower age of alcohol use disorder onset. There were no associations between brain-derived neurotrophic factor levels and focal amygdala task reactivity.

CONCLUSIONS

Together, the results indicate that plasma brain-derived neurotrophic factor levels are related to amygdala circuit functioning in humans, particularly during anxiety, and these individual differences may relate to drinking behaviors.

Brain-derived neurotrophic factor and schizophrenia

The brain-derived neurotrophic factor (BDNF) is a secretory growth factor that promotes neuronal proliferation and survival, synaptic plasticity and long-term potentiation in the central nervous system. Brain-derived neurotrophic factor biosynthesis and secretion are chrono-topically regulated processes at the cellular level, accounting for specific localizations and functions. Given its role in regulating brain development and activity, BDNF represents a potentially relevant gene for schizophrenia, and indeed BDNF and its non-synonymous functional variant, rs6265 (C → T, Val → Met) have been widely studied in psychiatric genetics. Human and animal studies have indicated that brain-derived neurotrophic factor is relevant for schizophrenia-related phenotypes, and that: (1) fine-tuned regulation of brain-derived neurotrophic factor secretion and activity is necessary to guarantee brain optimal development and functioning; (2) the Val → Met substitution is associated with impaired activity-dependent secretion of brain-derived neurotrophic factor; (3) disruption of brain-derived neurotrophic factor signaling is associated with altered synaptic plasticity and neurodevelopment. However, genome-wide association studies failed to associate the BDNF locus with schizophrenia, even though a sub-threshold association exists. Here, we will review studies focused on the relationship between the genetic variation of BDNF and schizophrenia, trying to fill the gap between genetic risk per se and insights from molecular biology. A deeper understanding of brain-derived neurotrophic factor biology and of the epigenetic regulation of brain-derived neurotrophic factor and its interactome during development may help clarifying the potential role of this gene in schizophrenia, thus informing development of brain-derived neurotrophic factor-based strategies of prevention and treatment of this disorder.

Design and Rationale of the Cognitive Intervention to Improve Memory in Heart Failure Patients Study

BACKGROUND

Memory loss is an independent predictor of mortality among heart failure patients. Twenty-three percent to 50% of heart failure patients have comorbid memory loss, but few interventions are available to treat the memory loss. The aims of this 3-arm randomized controlled trial were to (1) evaluate efficacy of computerized cognitive training intervention using BrainHQ to improve primary outcomes of memory and serum brain-derived neurotrophic factor levels and secondary outcomes of working memory, instrumental activities of daily living, and health-related quality of life among heart failure patients; (2) evaluate incremental cost-effectiveness of BrainHQ; and (3) examine depressive symptoms and genomic moderators of BrainHQ effect.

METHODS

A sample of 264 heart failure patients within 4 equal-sized blocks (normal/low baseline cognitive function and gender) will be randomly assigned to (1) BrainHQ, (2) active control computer-based crossword puzzles, and (3) usual care control groups. BrainHQ is an 8-week, 40-hour program individualized to each patient's performance. Data collection will be completed at baseline and at 10 weeks and 4 and 8 months. Descriptive statistics, mixed model analyses, and cost-utility analysis using intent-to-treat approach will be computed.

CONCLUSIONS

This research will provide new knowledge about the efficacy of BrainHQ to improve memory and increase serum brain-derived neurotrophic factor levels in heart failure. If efficacious, the intervention will provide a new therapeutic approach that is easy to disseminate to treat a serious comorbid condition of heart failure.

Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain

Brain Derived Neurotrophic Factor (BDNF) is a key molecule involved in plastic changes related to learning and memory. The expression of BDNF is highly regulated, and can lead to great variability in BDNF levels in healthy subjects. Changes in BDNF expression are associated with both normal and pathological aging and also psychiatric disease, in particular in structures important for memory processes such as the hippocampus and parahippocampal areas. Some interventions like exercise or antidepressant administration enhance the expression of BDNF in normal and pathological conditions. In this review, we will describe studies from rodents and humans to bring together research on how BDNF expression is regulated, how this expression changes in the pathological brain and also exciting work on how interventions known to enhance this neurotrophin could have clinical relevance. We propose that, although BDNF may not be a valid biomarker for neurodegenerative/neuropsychiatric diseases because of its disregulation common to many pathological conditions, it could be thought of as a marker that specifically relates to the occurrence and/or progression of the mnemonic symptoms that are common to many pathological conditions.

The brain-derived neurotrophic factor Val66Met genotype does not influence the grey or white matter structures underlying recognition memory

A single nucleotide polymorphism (SNP) in the gene coding for brain-derived neurotrophic factor (BDNF) has previously been associated with a reduction in recognition memory performance. While previous findings have highlighted that this SNP contributes to recognition memory, little is known about its influence on subprocesses of recognition, familiarity and recollection. Previous research has reported reduced hippocampal volume and decreased fractional anisotropy in carriers of the Met allele across a range of white matter tracts, including those networks that may support recognition memory. Here, in a sample of 61 healthy young adults, we used a source memory task to measure accuracy on each recognition subprocess, in order to determine whether the Val66Met SNP (rs6265) influences these equally. Additionally, we compared grey matter volume between these groups for structures that underpin familiarity and recollection separately. Finally, we used probabilistic tractography to reconstruct tracts that subserve each of these two recognition systems. Behaviourally, we found group differences on the familiarity measure, but not on recollection. However, we did not find any group difference on grey- or white-matter structures. Together, these results suggest a functional influence of the Val66Met SNP that is independent of coarse structural changes, and nuance previous research highlighting the relationship between BDNF, brain structure, and behaviour.

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.

The brain-derived neurotrophic factor VAL68MET polymorphism modulates how developmental ethanol exposure impacts the hippocampus

Prenatal exposure to alcohol causes a wide range of deficits known as fetal alcohol spectrum disorders (FASDs). Many factors determine vulnerability to developmental alcohol exposure including timing and pattern of exposure, nutrition and genetics. Here, we characterized how a prevalent single nucleotide polymorphism in the human brain-derived neurotrophic factor (BDNF) gene (val66met) modulates FASDs severity. This polymorphism disrupts BDNF's intracellular trafficking and activity-dependent secretion, and has been linked to increased incidence of neuropsychiatric disorders such as depression and anxiety. We hypothesized that developmental ethanol (EtOH) exposure more severely affects mice carrying this polymorphism. We used transgenic mice homozygous for either valine (BDNFval/val ) or methionine (BDNFmet/met ) in residue 68, equivalent to residue 66 in humans. To model EtOH exposure during the second and third trimesters of human pregnancy, we exposed mice to EtOH in vapor chambers during gestational days 12 to 19 and postnatal days 2 to 9. We found that EtOH exposure reduces cell layer volume in the dentate gyrus and the CA1 hippocampal regions of BDNFmet/met but not BDNFval/val mice during the juvenile period (postnatal day 15). During adulthood, EtOH exposure reduced anxiety-like behavior and disrupted trace fear conditioning in BDNFmet/met mice, with most effects observed in males. EtOH exposure reduced adult neurogenesis only in the ventral hippocampus of BDNFval/val male mice. These studies show that the BDNF val66met polymorphism modulates, in a complex manner, the effects of developmental EtOH exposure, and identify a novel genetic risk factor that may regulate FASDs severity in humans.

Effects of smoking on cognition and BDNF levels in a male Chinese population: relationship with BDNF Val66Met polymorphism

Recent studies demonstrate that brain-derived neurotrophic factor (BDNF) might be associated with nicotine addiction, and circulating BDNF is a biomarker of memory and general cognitive function. Moreover, studies suggest that a functional polymorphism of the BDNF Val66Met may mediate hippocampal-dependent cognitive functions. We aimed to explore the relationships between smoking, cognitive performance and BDNF in a normal Chinese Han population. We recruited 628 male healthy subjects, inducing 322 smokers and 306 nonsmokers, and genotyped them the BDNF Val66Met polymorphism. Of these, we assessed 114 smokers and 98 nonsmokers on the repeatable battery for the assessment of neuropsychological status (RBANS), and 103 smokers and 89 nonsmokers on serum BDNF levels. Smokers scored lower than the nonsmokers on RBANS total score (p = 0.002), immediate memory (p = 0.003) and delayed memory (p = 0.021). BDNF levels among the smokers who were Val allele carriers were correlated with the degree of cognitive impairments, especially attention, as well as with the carbon monoxide concentrations. Our findings suggest that smoking is associated with cognitive impairment in a male Chinese Han population. The association between higher BDNF levels and cognitive impairment, mainly attention in smokers appears to be dependent on the BDNF Val66Met polymorphism.

Brain-Derived Neurotrophic Factor (BDNF): Novel Insights into Regulation and Genetic Variation

Since its discovery, brain-derived neurotrophic factor (BDNF) has spawned a literature that now spans 35 years of research. While all neurotrophins share considerable overlap in sequence homology and their processing, BDNF has become the most widely studied neurotrophin because of its broad roles in brain homeostasis, health, and disease. Although research on BDNF has produced thousands of articles, there remain numerous long-standing questions on aspects of BDNF molecular biology and signaling. Here we provide a comprehensive review, including both a historical narrative and a forward-looking perspective on advances in the actions of BDNF within the brain. We specifically review BDNF’s gene structure, peptide composition (including domains, posttranslational modifications and putative motif sites), mechanisms of transport, signaling pathway recruitment, and other recent developments including the functional effects of genetic variation and the discovery of a new BDNF prodomain ligand. This body of knowledge illustrates a highly conserved and complex role for BDNF within the brain, that promotes the idea that the neurotrophin biology of BDNF is diverse and that any disease involvement is likely to be equally multifarious.

BDNF as a pharmacogenetic target for antipsychotic treatment of schizophrenia

Antipsychotic drugs remain the mainstay of pharmacotherapy for schizophrenia. As there are large individual variations in efficacy and side-effects of antipsychotic drugs, there is a strong demand for personalized medication to treat schizophrenia. Pharmacogenetic research into antipsychotic drugs has examined a number of genetic variants and only a few polymorphisms have been found which promise to be associated with the therapeutic efficacy and side-effects of antipsychotic drugs. Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays a major role in neurogenesis and neuroplasticity, and in the modulation of several neurotransmitter systems including the dopaminergic system involved in the pathophysiology of schizophrenia. This review focused on the association between the BDNF gene Val66Met polymorphism and antipsychotic drugs. The BDNF Val66Met polymorphism has been related to the pathophysiology of schizophrenia, psychotic symptomatology, cognition, efficacy and side-effects of antipsychotic drugs. The BDNF Val66Met variants could be a promising target for antipsychotic medication options or developing next generation antipsychotic drugs. However, some studies showed inconsistent results due to sample size, ethnic differences and different antipsychotic drugs. Further studies will be required in this area to confirm the effect of the BDNF Val66Met polymorphism in the pathophysiology of schizophrenia and patients' response to antipsychotic drugs, especially in a larger sample size and in different ethnic populations.

The impact of brain-derived neurotrophic factor Val66Met polymorphism on cognition and functional brain networks in patients with intractable partial epilepsy

INTRODUCTION

Medial temporal lobe epilepsy (mTLE) is the most common refractory focal epilepsy in adults. Around 30%-40% of patients have prominent memory impairment and experience significant postoperative memory and language decline after surgical treatment. BDNF Val66Met polymorphism has also been associated with cognition and variability in structural and functional hippocampal indices in healthy controls and some patient groups.

AIMS

We examined whether BDNF Val66Met variation was associated with cognitive impairment in mTLE.

METHODS

In this study, we investigated the association of Val66Met polymorphism with cognitive performance (n = 276), postoperative cognitive change (n = 126) and fMRI activation patterns during memory encoding and language paradigms in 2 groups of patients with mTLE (n = 37 and 34).

RESULTS

mTLE patients carrying the Met allele performed more poorly on memory tasks and showed reduced medial temporal lobe activation and reduced task-related deactivations within the default mode networks in both the fMRI memory and language tasks than Val/Val patients.

CONCLUSIONS

Although cognitive impairment in epilepsy is the result of a complex interaction of factors, our results suggest a role of genetic factors on cognitive impairment in mTLE.

Estrogens and the cognitive symptoms of schizophrenia: Possible neuroprotective mechanisms

Schizophrenia is a complex neuropsychiatric illness with marked sex differences. Women have later onset and lesser symptoms, which has led to the hypothesis that estrogens are protective in schizophrenia. Cognitive dysfunction is a hallmark of the disease and the symptom most correlated with functional outcome. Here we describe a number of mechanisms by which estrogens may be therapeutic in schizophrenia, with a focus on cognitive symptoms. We review the relationship between estrogens and brain derived neurotrophic factor, neuroinflammation, NMDA receptors, GABA receptors, and luteinizing hormone. Exploring these pathways may enable novel treatments for schizophrenia and a greater understanding of this devastating disease.

Effects of the Brain-Derived Neurotrophic Factor Val66Met polymorphism and resting brain functional connectivity on individual differences in tactile cognitive performance in healthy young adults

Cognitive processes involve input from multiple sensory modalities and obvious differences in the level of cognitive function can be observed between individuals. Evidence to date understanding the biological basis of tactile cognitive variability, however, is limited compared with other forms of sensory cognition. Data from auditory and visual cognition research suggest that variations in both genetics and intrinsic brain function might contribute to individual differences in tactile cognitive performance. In the present study, by using the tactual performance test (TPT), a widely used neuropsychological assessment tool, we investigated the effects of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and resting-state brain functional connectivity (FC) on interindividual variability in TPT performance in healthy, young Chinese adults. Our results showed that the BDNF genotypes and resting-state FC had significant effects on the variability in TPT performance, together accounting for 32.5% and 19.1% of the variance on TPT total score and Memory subitem score respectively. Having fewer Met alleles, stronger anticorrelations between left posterior superior temporal gyrus and somatosensory areas (right postcentral gyrus and right parietal operculum cortex), and greater positive correlation between left parietal operculum cortex and left central opercular cortex, all correspond with better performance of TPT task. And FC between left parietal operculum cortex and left central opercular cortex might be a mediator of the relationship between BDNF genotypes and Memory subitem score. These data demonstrate a novel contribution of intrinsic brain function to tactile cognitive capacity, and further confirm the genetic basis of tactile cognition. Our findings might also explain the interindividual differences in cognitive ability observed in those who are blind and/or deaf from a new perspective.

BDNF Variants May Modulate Long-Term Visual Memory Performance in a Healthy Cohort

Brain-derived neurotrophic factor (BDNF) is involved in numerous cognitive functions including learning and memory. BDNF plays an important role in synaptic plasticity in humans and rats with BDNF shown to be essential for the formation of long-term memories. We previously identified a significant association between the BDNF Val66Met polymorphism (rs6265) and long-term visual memory (p-value = 0.003) in a small cohort (n = 181) comprised of healthy individuals who had been phenotyped for various aspects of memory function. In this study, we have extended the cohort to 597 individuals and examined multiple genetic variants across both the BDNF and BDNF-AS genes for association with visual memory performance as assessed by the Wechsler Memory Scale—Fourth Edition subtests Visual Reproduction I and II (VR I and II). VR I assesses immediate visual memory, whereas VR II assesses long-term visual memory. Genetic association analyses were performed for 34 single nucleotide polymorphisms genotyped on Illumina OmniExpress BeadChip arrays with the immediate and long-term visual memory phenotypes. While none of the BDNF and BDNF-AS variants were shown to be significant for immediate visual memory, we found 10 variants (including the Val66Met polymorphism (p-value = 0.006)) that were nominally associated, and three variants (two variants in BDNF and one variant in the BDNF-AS locus) that were significantly associated with long-term visual memory. Our data therefore suggests a potential role for BDNF, and its anti-sense transcript BDNF-AS, in long-term visual memory performance.

Neurotrophins role in depressive symptoms and executive function performance: Association analysis of NRN1 gene and its interaction with BDNF gene in a non-clinical sample

BACKGROUND

Neuritin-1 is a neurotrophic factor involved in synaptic plasticity that has been associated with depressive disorders, schizophrenia and cognitive performance. The study of genotype-phenotype relationships in healthy individuals is a useful framework to investigate the etiology of brain dysfunctions. We therefore aimed to investigate in a non-clinical sample whether NRN1 gene contributes to the psychopathological profile, with a particular focus on the clinical dimensions previously related to the NRN1 gene (i.e. depressive and psychotic). Furthermore, we aimed to analyze: i) the role of NRN1 on executive functions, ii) whether the association between either NRN1-psychopathological profile or NRN1-cognitive performance is moderated by the BDNF gene.

METHODS

The sample comprised 410 non-clinical subjects who filled in the self-reported Brief Symptom Inventory (BSI) and were assessed for executive performance (Verbal Fluency, Wisconsin Card Sorting Test (WCST) and Letter-Number subscale (WAIS-III)). Genotyping included nine SNPs in NRN1 and one in BDNF.

RESULTS

i) GG homozygotes (rs1475157-NRN1) showed higher scores on BSI depressive dimension and on total scores compared to A carriers (corrected p-values: 0.0004 and 0.0003, respectively). ii) a linear trend was detected between GG genotype of rs1475157 and a worse cognitive performance in WCST total correct responses (uncorrected p-value: 0.029). iii) Interaction between rs1475157-NRN1 and Val66Met-BDNF was found to modulate depressive symptoms (p=0.001, significant after correction).

LIMITATIONS

Moderate sample size; replication in a larger sample is needed.

CONCLUSIONS

NRN1 is associated with depressive symptoms and executive function in a non-clinical sample. Our results also suggest that the role of NRN1 seems to be modulated by BDNF.

Altered Episodic Memory in Introverted Young Adults Carrying the BDNFMet Allele

While most studies have been interested in the distinct, predisposing roles of the common BDNF Val66Met variant and extraversion personality traits on episodic memory, very few studies have looked at the synergistic effects of genetic and personality factors to account for cognitive variance. This is surprising considering recent reports challenging the long-held belief that the BDNF_Met variant negatively impacts cognitive function. A total of 75 young healthy adults (26 of them carried at least one copy of the BDNF_Met allele) took part in this study consisting of genetic profiling from saliva, personality assessment using the Revised NEO Personality Inventory (NEO PI-R) and a short battery of neuropsychological tests. An ANOVA revealed that BDNF_Met carriers were significantly less extraverted than BDNF_Val carriers (F_1,73 = 9.54; p < 0.01; η_p² = 0.126). Moreover, extraversion was found to significantly moderate the relationship between the BDNF genotype and episodic memory performance (p = 0.03). Subsequent correlational analyses yielded a strong and significant correlation (r = 0.542; p < 0.005) between introversion and delayed episodic memory specific to BDNF_Met individuals. The present study suggests that introversion and the BDNF_Met variant synergistically interact to reduce episodic memory performance in healthy, young adults. These findings reaffirm that a more accurate explanation of cognitive variance can be achieved by looking at the synergistic effects of genotype and phenotype factors.

The brain-derived neurotrophic factor Val66Met polymorphism affects encoding of object locations during active navigation

The brain‐derived neurotrophic factor (BDNF) was shown to be involved in spatial memory and spatial strategy preference. A naturally occurring single nucleotide polymorphism of the BDNF gene (Val66Met) affects activity‐dependent secretion of BDNF. The current event‐related fMRI study on preselected groups of ‘Met’ carriers and homozygotes of the ‘Val’ allele investigated the role of this polymorphism on encoding and retrieval in a virtual navigation task in 37 healthy volunteers. In each trial, participants navigated toward a target object. During encoding, three positional cues (columns) with directional cues (shadows) were available. During retrieval, the invisible target had to be replaced while either two objects without shadows (objects trial) or one object with a shadow (shadow trial) were available. The experiment consisted of blocks, informing participants of which trial type would be most likely to occur during retrieval. We observed no differences between genetic groups in task performance or time to complete the navigation tasks. The imaging results show that Met carriers compared to Val homozygotes activate the left hippocampus more during successful object location memory encoding. The observed effects were independent of non‐significant performance differences or volumetric differences in the hippocampus. These results indicate that variations of the BDNF gene affect memory encoding during spatial navigation, suggesting that lower levels of BDNF in the hippocampus results in less efficient spatial memory processing.

Gender-specific Associations of the Brain-derived Neurotrophic Factor Val66Met Polymorphism with Neurocognitive and Clinical Features in Schizophrenia

Objective

To explore associations of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism with cognitive functioning and psychopathology in patients with schizophrenia.

Methods

We included 133 subjects meeting the DSM-IV criteria for schizophrenia who were in the post-acute stage of the disease. BDNF Val66Met genotypes were identified via polymerase chain reaction. The computerized neurocognitive function battery, Positive and Negative Syndrome Scale (PANSS), Calgary Depression Scale for Schizophrenia (CDSS), Social and Occupational Functioning Scale (SOFAS), and the Subjective Well-being under Neuroleptic Treatment (SWN-K) were administered. Gender-stratified sub-analysis was also conducted to identify gender-specific patterns in the findings.

Results

In male patients, no significant difference in any measure by BDNF genotype was evident. In female patients, scores on the CDSS and total PANSS and all subscales were significantly higher in valine (Val) carriers. In addition, scores on the SOFAS and SWN-K were significantly lower in Val carriers. In terms of neurocognitive measures, female patients with the Val allele had significantly poorer reaction times and fewer correct responses on the Continuous Performance Test (CPT) and the Trail Making Test (Parts A and B). After adjustment of PANSS total scores and log-transformed CDSS scores, CPT outcomes were significantly poorer in female patients with than in those without the Val allele.

Conclusion

Gender-specific associations of the Val allele with poor neurocognitive function and more severe psychopathology were evident. Further studies are required to explore the mechanisms of these differences and the potential utility of the BDNF genotype as a predictor of outcome in patients with schizophrenia.

Lack of an association of BDNF Val66Met polymorphism and plasma BDNF with hippocampal volume and memory

Brain-derived neurotrophic factor (BDNF) has been shown to be important for neuronal survival and synaptic plasticity in the hippocampus in nonhuman animals. The Val66Met polymorphism in the BDNF gene, involving a valine (Val) to methionine (Met) substitution at codon 66, has been associated with lower BDNF secretion in vitro. However, there have been mixed results regarding associations between either circulating BDNF or the BDNF Val66Met polymorphism with hippocampal volume and memory in humans. The current study examined the association of BDNF genotype and plasma BDNF with hippocampal volume and memory in two large independent cohorts of middle-aged and older adults (both cognitively normal and early-stage dementia). Sample sizes ranged from 123 to 649. Measures of the BDNF genotype, plasma BDNF, MRI-based hippocampal volume, and memory performance were obtained from the Knight Alzheimer Disease Research Center (ADRC) and the Alzheimer's Disease Neuroimaging Initiative (ADNI). There were no significant differences between BDNF Met+ and Met- groups on either hippocampal volume or memory in either cohort. In addition, plasma BDNF was not significantly associated with either hippocampal volume or memory in either cohort. Neither age, cognitive status, nor gender moderated any of the relationships. Overall, current findings suggest that BDNF genotype and plasma BDNF may not be robust predictors for variance in hippocampal volume and memory in middle age and older adult cohorts.

Brain-derived neurotrophic factor Val66met polymorphism and plasma levels in road traffic accident survivors

BACKGROUND

Alterations in brain-derived neurotrophic factor (BDNF) expression and release may play a role in the pathogenesis of post-traumatic stress disorder (PTSD).

DESIGN

This study evaluated road traffic accident (RTA) survivors to determine whether PTSD and trauma-related factors were associated with plasma BDNF levels and BDNF Val66Met carrier status following RTA exposure.

METHODS

One hundred and twenty-three RTA survivors (mean age 33.2 years, SD = 10.6 years; 56.9% male) were assessed 10 (SD = 4.9) days after RTA exposure. Acute stress disorder (ASD), as assessed with the Acute Stress Disorder Scale, was present in 50 (42.0%) of the participants. Plasma BDNF levels were measured with enzyme-linked immunosorbent assay and BDNF Val66Met genotyping was performed. PTSD, as assessed with the Clinician-Administered PTSD Scale, was present in 10 (10.8%) participants at 6 months follow-up.

RESULTS

Neither BDNF Val66Met genotype nor plasma BDNF was significantly associated with the presence or severity of ASD or PTSD. Plasma BDNF levels were, however, significantly correlated with the lifetime number of trauma exposures.

CONCLUSIONS

In RTA survivors, plasma BDNF levels increased with increasing number of prior trauma exposures. Plasma BDNF may, therefore, be a marker of trauma load.

Flow-Mediated Dilation and Neurocognition: Systematic Review and Future Directions

BACKGROUND

Previous literature indicates that flow-mediated dilation (FMD) is associated with impaired cognition among patients with stroke. The relationship between FMD and cognition in individuals without cerebrovascular disease has yet to be systematically reviewed.

METHODS

The literature was searched using MEDLINE. Exclusion criteria were as follows: focus on neurological disease (e.g., stroke), animal studies, no quantitative measure of endothelial function or cognition, newborn studies, articles with no original data, and articles that are irrelevant to the topic of interest. Neurocognitive tests were categorized in the following domains: executive function, memory (general, working, episodic/semantic, verbal, visual), global cognitive function, information processing speed, language, psychomotor speed, and visual-spatial ability.

RESULTS

The search yielded 700 articles, of which 10 articles, consisting of 2791 participants, met the criteria for inclusion. Most studies conclude that impaired FMD is associated with poorer neuropsychological functioning, particularly in executive functioning (effect sizes: r = 0.07-0.58) and working memory tasks (effect sizes: r = 0.19-0.39). No association was found between other subdomains of memory and FMD. Visual spatial tasks, information processing speed, language tasks, and global cognition were not associated with FMD overall; however fewer studies examined these domains.

CONCLUSIONS

Even in the absence of cerebrovascular disease, there are links between cognition, particularly executive tasks, and vascular function. Public health implications include the potential value of examining FMD as a predictor of cognitive decline, as well as the potential value of improving cognition through pharmacological and behavioral interventions that improve vascular function. Future studies incorporating neuroimaging measures of cerebral blood flow are warranted.

Molecular Pathways Bridging Frontotemporal Lobar Degeneration and Psychiatric Disorders

The overlap of symptoms between neurodegenerative and psychiatric diseases has been reported. Neuropsychiatric alterations are commonly observed in dementia, especially in the behavioral variant of frontotemporal dementia (bvFTD), which is the most common clinical FTD subtype. At the same time, psychiatric disorders, like schizophrenia (SCZ), can display symptoms of dementia, including features of frontal dysfunction with relative sparing of memory. In the present review, we discuss common molecular features in these pathologies with a special focus on FTD. Molecules like Brain Derived Neurotrophic Factor (BDNF) and progranulin are linked to the pathophysiology of both neurodegenerative and psychiatric diseases. In these brain-associated illnesses, the presence of disease-associated variants in BDNF and progranulin (GRN) genes cause a reduction of circulating proteins levels, through alterations in proteins expression or secretion. For these reasons, we believe that prevention and therapy of psychiatric and neurological disorders could be achieved enhancing both BDNF and progranulin levels thanks to drug discovery efforts.

Brain-derived neurotrophic factor genetic polymorphism (rs6265) is protective against chemotherapy-associated cognitive impairment in patients with early-stage breast cancer

Background

Brain-derived neurotrophic factor (BDNF), a neurotrophin that regulates neuronal function and development, is implicated in several neurodegenerative conditions. Preliminary data suggest that a reduction of BDNF concentrations may lead to postchemotherapy cognitive impairment. We hypothesized that a single nucleotide polymorphism (rs6265) of the BDNF gene may predispose patients to cognitive impairment. This study aimed to evaluate the effect of BDNF gene polymorphism on chemotherapy-associated cognitive impairment.

Methods

Overall, 145 patients receiving chemotherapy for early-stage breast cancer (mean age: 50.8 ± 8.8 y; 82.1% Chinese) were recruited. Patients' cognitive functions were assessed longitudinally using the validated Functional Assessment of Cancer Therapy–Cognitive Function (v.3) and an objective computerized tool, Headminder. Genotyping was performed using Sanger sequencing. Logistic regression was used to evaluate the association between BDNF Val66Met polymorphism and cognition after adjusting for ethnicity and clinically important covariates.

Results

Of the 145 patients, 54 (37%) reported cognitive impairment postchemotherapy. The Met/Met genotype was associated with statistically significant lower odds of developing cognitive impairment (odds ratio [OR] = 0.26; 95% CI: 0.08–0.92; P = .036). The Met carriers were less likely to experience impairment in the domains of verbal fluency (OR = 0.34; 95% CI: 0.12–0.90; P = .031) and multitasking ability (OR = 0.37; 95% CI: 0.15–0.91; P = .030) compared with the Val/Val homozygote. No associations were observed between Headminder and the BDNF Val66Met polymorphism.

Conclusions

This is the first study to provide evidence that carriers of the BDNF Met allele are protected against chemotherapy-associated cognitive impairment. Further studies are required to validate the findings.

The BDNF gene Val66Met polymorphism as a modifier of psychiatric disorder susceptibility: progress and controversy

Brain-derived neurotrophic factor (BDNF) has a primary role in neuronal development, differentiation and plasticity in both the developing and adult brain. A single-nucleotide polymorphism in the proregion of BDNF, termed the Val66Met polymorphism, results in deficient subcellular translocation and activity-dependent secretion of BDNF, and has been associated with impaired neurocognitive function in healthy adults and in the incidence and clinical features of several psychiatric disorders. Research investigating the Val66Met polymorphism has increased markedly in the past decade, and a gap in integration exists between and within academic subfields interested in the effects of this variant. Here we comprehensively review the role and relevance of the Val66Met polymorphism in psychiatric disorders, with emphasis on suicidal behavior and anxiety, eating, mood and psychotic disorders. The cognitive and molecular neuroscience of the Val66Met polymorphism is also concisely reviewed to illustrate the effects of this genetic variant in healthy controls, and is complemented by a commentary on the behavioral neuroscience of BDNF and the Val66Met polymorphism where relevant to specific disorders. Lastly, a number of controversies and unresolved issues, including small effect sizes, sampling of allele inheritance but not genotype and putative ethnicity-specific effects of the Val66Met polymorphism, are also discussed to direct future research.

Spatial learning associated with stimulus response in goldfish Carassius auratus: relationship to activation of CREB signalling

Earlier, we reported spatial learning ability in goldfish (Carassius auratus) by using spatial paradigm with food reward. Therefore, we hypothesized that goldfish may use associated cue to integrate "where" and "what" for spatial memory. To test our hypothesis, we first trained goldfish to learn to cross the gate1, which is associated with spatial task. Subsequently, they were trained to learn to enter the task chamber and to identify the food reward chamber associated with visual cue (red/green light). Red and green lights were positioned randomly for each trial but always the food reward was kept in green chamber. In addition, to elucidate the role of the signalling cascade in spatial memory associated with visual cue, nicotinamide (NAM, 1000 mg/kg, i.p), a NAD(+) precursor, was used to inhibit the Sirtuin 1 (SIRT1) cyclic AMP response element binding protein (CREB) pathway. Fishes were trained for 5 days in a maze after treating with either vehicle (VEH, DD H2O) or NAM, and then, they were individually tested for memory. We found that VEH-treated fish learned and recalled the task successfully by showing less latency and making more correct choices than NAM-treated group. Subsequent analysis showed that NAM treatment significantly down-regulated the phosphorylation of extracellular signal-regulated kinase (ERK1/2), CREB, expression of SirT1 and brain-derived neurotrophic factor (Bdnf) in telencephalon. Taken together, our results provide behavioural evidence of spatial memory associated with visual cue in C. auratus, which could be regulated by ERK1/2-CREB-SirT1-Bdnf pathway.

Genetic polymorphisms and traumatic brain injury: the contribution of individual differences to recovery

Recovery after Traumatic Brain Injury (TBI) is variable, even for patients with similar severity of brain injury. Recent research has highlighted the contribution that genetic predisposition plays in determining TBI outcome. This review considers the potential for genetic polymorphisms to influence recovery of cognitive and social processes following TBI. Limitations and considerations that researchers should make when assessing the potential impact of polymorphisms on TBI outcome are also discussed. Understanding the genetic factors that support neuroplasticity will contribute to an understanding of the variation in outcome following injury and help to identify potential targets for rehabilitation.

Nurse-Enhanced Computerized Cognitive Training Increases Serum Brain-Derived Neurotropic Factor Levels and Improves Working Memory in Heart Failure

BACKGROUND

Memory loss is common in heart failure (HF) patients, but few interventions have been tested to treat it. The objective of this study was to evaluate efficacy of a cognitive training intervention, Brain Fitness, to improve memory, serum brain-derived neurotropic factor (BDNF) levels, working memory, processing speed, executive function, instrumental activities of daily living, mobility, depressive symptoms, and health-related quality of life.

METHODS AND RESULTS

Twenty-seven HF patients were randomly assigned to Brain Fitness and health education active control interventions. Data were collected at baseline and 8 and 12 weeks. Linear mixed models analyses were completed. Patients in the Brain Fitness group were older with lower ejection fraction. At 12 weeks, a group by time interaction effect was found for serum BDNF levels (P = .011): serum BDNF levels increased among patients who completed Brain Fitness and decreased among patients who completed health education. No differences were found in memory, but a group by time interaction (P = .046) effect was found for working memory.

CONCLUSIONS

Findings support efficacy of Brain Fitness in improving working memory and serum BDNF levels as a biomarker of intervention response. A randomized controlled study is needed among a larger more diverse group of HF patients.

Blood pressure interacts with APOE ε4 to predict memory performance in a midlife sample

OBJECTIVE

Elevated blood pressure and the Apolipoprotein ε4 allele (APOE ε4) are independent risk factors for Alzheimer's disease. We sought to determine whether the combined presence of the APOE ε4 allele and elevated blood pressure is associated with lower cognitive performance in cognitively healthy middle-aged adults.

METHODS

A total of 975 participants aged 30-54 (mean age = 44.47) were genotyped for APOE. Cardiometabolic risk factors including blood pressure, lipids, and glucose were assessed and cognitive function was measured using the Trail Making Test and the Visual Reproduction and Logical Memory subtests from the Wechsler Memory Scale.

RESULTS

Multivariable regression analysis showed that the association between APOE ε4 and episodic memory performance varied as a function of systolic blood pressure (SBP), such that elevated SBP was predictive of poorer episodic memory performance only in APOE ε4 carriers (β = -.092; t = -2.614; p = .009). Notably, this association was apparent at prehypertensive levels (≥130 mmHg), even after adjusting for physical activity, depression, smoking, and other cardiometabolic risk factors.

CONCLUSIONS

The joint presence of APOE ε4 and elevated SBP, even at prehypertensive levels, is associated with lower cognitive performance in healthy, middle-aged adults. Results of this study suggest that the combination of APOE ε4 and elevated SBP may synergistically compromise memory function well before the appearance of clinically significant impairments. Interventions targeting blood pressure control in APOE ε4 carriers during midlife should be studied as a possible means to reduce the risk of cognitive decline in genetically susceptible samples.

Peripheral BDNF: a candidate biomarker of healthy neural activity during learning is disrupted in schizophrenia

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptogenesis and synaptic plasticity underlying learning. However, a relationship between circulating BDNF levels and brain activity during learning has not been demonstrated in humans. Reduced brain BDNF levels are found in schizophrenia and functional neuroimaging studies of probabilistic association learning in schizophrenia have demonstrated reduced activity in a neural network that includes the prefrontal and parietal cortices and the caudate nucleus. We predicted that brain activity would correlate positively with peripheral BDNF levels during probabilistic association learning in healthy adults and that this relationship would be altered in schizophrenia.

METHOD

Twenty-five healthy adults and 17 people with schizophrenia or schizo-affective disorder performed a probabilistic association learning test during functional magnetic resonance imaging (fMRI). Plasma BDNF levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found a positive correlation between circulating plasma BDNF levels and brain activity in the parietal cortex in healthy adults. There was no relationship between plasma BDNF levels and task-related activity in the prefrontal, parietal or caudate regions in schizophrenia. A direct comparison of these relationships between groups revealed a significant diagnostic difference.

CONCLUSIONS

This is the first study to show a relationship between peripheral BDNF levels and cortical activity during learning, suggesting that plasma BDNF levels may reflect learning-related brain activity in healthy humans. The lack of relationship between plasma BDNF and task-related brain activity in patients suggests that circulating blood BDNF may not be indicative of learning-dependent brain activity in schizophrenia.

BDNF-Val66Met-polymorphism impact on cortical plasticity in schizophrenia patients: a proof-of-concept study

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been shown to be a moderator of neuroplasticity. A frequent BDNF-polymorphism (Val66Met) is associated with impairments of cortical plasticity. In patients with schizophrenia, reduced neuroplastic responses following non-invasive brain stimulation have been reported consistently. Various studies have indicated a relationship between the BDNF-Val66Met-polymorphism and motor-cortical plasticity in healthy individuals, but schizophrenia patients have yet to be investigated. The aim of this proof-of-concept study was, therefore, to test the impact of the BDNF-Val66Met-polymorphism on inhibitory and facilitatory cortical plasticity in schizophrenia patients.

METHODS

Cortical plasticity was investigated in 22 schizophrenia patients and 35 healthy controls using anodal and cathodal transcranial direct-current stimulation (tDCS) applied to the left primary motor cortex. Animal and human research indicates that excitability shifts following anodal and cathodal tDCS are related to molecular long-term potentiation and long-term depression. To test motor-cortical excitability before and after tDCS, well-established single- and paired-pulse transcranial magnetic stimulation protocols were applied.

RESULTS

Our analysis revealed increased glutamate-mediated intracortical facilitation in met-heterozygotes compared to val-homozygotes at baseline. Following cathodal tDCS, schizophrenia met-heterozygotes had reduced gamma-amino-butyric-acid-mediated short-interval intracortical inhibition, whereas healthy met-heterozygotes displayed the opposite effect. The BDNF-Val66Met-polymorphism did not influence single-pulse motor-evoked potential amplitudes after tDCS.

CONCLUSIONS

These preliminary findings support the notion of an association of the BDNF-Val66Met-polymorphism with observable alterations in plasticity following cathodal tDCS in schizophrenia patients. This indicates a complex interaction between inhibitory intracortical interneuron-networks, cortical plasticity, and the BDNF-Val66Met-polymorphism. Further replication and validation need to be dedicated to this question to confirm this relationship.

Chemobrain: a critical review and causal hypothesis of link between cytokines and epigenetic reprogramming associated with chemotherapy

One consequence of modern cancer therapy is chemotherapy related cognitive dysfunction or "chemobrain", the subjective experience of cognitive deficits at any point during or following chemotherapy. Chemobrain, a well-established clinical syndrome, has become an increasing concern because the number of long-term cancer survivors is growing dramatically. There is strong evidence that correlates changes in peripheral cytokines with the development of chemobrain in commonly used chemotherapeutic drugs for different types of cancer. However, the mechanisms by which these cytokines elicit change in the central nervous system are still unclear. In this review, we hypothesize that the administration of chemotherapy agents initiates a cascade of biological changes, with short-lived alterations in the cytokine milieu inducing persistent epigenetic alterations. These epigenetic changes lead to changes in gene expression, alterations in metabolic activity and neuronal transmission that are responsible for generating the subjective experience of cognition. This speculative but testable hypothesis should help to gain a comprehensive understanding of the mechanism underlying cognitive dysfunction in cancer patients. Such knowledge is critical to identify pharmaceutical targets with the potential to prevent and treat cancer-treatment related cognitive dysfunction and similar disorders.