BDNF polymorphisms are linked to poorer working memory performance, reduced cerebellar and hippocampal volumes and differences in prefrontal cortex in a Swedish elderly population

Association Between Chronic Tinnitus and Brain-Derived Neurotrophic Factor Antisense RNA Polymorphisms Linked to the Val66Met Polymorphism in BDNF

Tinnitus is the sound heard in the ear or head of a person in the absence of external stimuli. Its etiopathogenesis is still not fully understood and the etiological causes responsible for tinnitus are quite variable. Brain-derived neurotrophic factor (BDNF) is one of the key neurotrophic factors in the growth, differentiation, and survival of neurons and in the developing auditory pathway, including the inner ear sensory epithelium. The regulation of BDNF gene is known to be managed by BDNF antisense (BDNF-AS) gene. BDNF-AS is located downstream of the BDNF gene and transcribes a long non-coding RNA. Inhibition of BDNF-AS upregulates BDNF mRNA, which increases protein levels and stimulates neuronal development and differentiation. Thus, BDNF and BDNF-AS both may play roles in the auditory pathway. Polymorphisms in both genes may have impact on hearing performance. A link was suggested between tinnitus and BDNF Val66Met polymorphism. However, there is no study questioning the relationship of tinnitus with BDNF-AS polymorphisms linked with BDNF Val66Met polymorphism. Therefore, this study aimed to scrutinize the role of BDNF-AS polymorphisms showing linkage with the BDNF Val66Met polymorphism in the course of tinnitus pathophysiology. Six BDNF-AS polymorphisms were analyzed on the tinnitus patients (n=85) and the control subjects (n=60) by Fluidigm Real-Time PCR using the Fluidigm Biomark microfluidic platform. When BDNF-AS polymorphisms were compared between the groups in terms of genotype and gender distribution, statistically significant differences were detected in rs925946, rs1519480, and rs10767658, polymorphisms (p<0.05). When the polymorphisms were compared by the duration of tinnitus, significant differences were found in rs925946, rs1488830, rs1519480, and rs10767658 polymorphisms (p<0.05). According to genetic inheritance model analysis, 2.33 and 1.53-fold risks were found for the rs10767658 polymorphism in the recessive and the additive models, respectively. For the rs1519480 polymorphism, a 2.25 fold risk was observed in the additive model. For the rs925946 polymorphism, 2.44 fold protective effect in dominant model, and 0.62 fold risk was found in the additive model. In conclusion, four of the polymorphisms in BDNF-AS gene (rs955946, rs1488830, rs1519480, and rs10767658) are potential gene loci that may play a role in the auditory pathway and affect auditory performance.

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.

FEASibility testing a randomized controlled trial of an exercise program to improve cognition for T2DM patients (the FEAST trial): A study protocol

While cognitive dysfunction is an important concern in persons with type 2 diabetes mellitus (T2DM), it has received little attention in the T2DM literature. Although it often remains unrecognized, cognitive dysfunction associated with T2DM can lead to severe consequences. Prior research studies have consistently shown that aerobic exercise enhances cognitive function among healthy subjects. However, very few studies have examined the effects of aerobic exercise on cognitive function in persons with T2DM. In addition, one important single-nucleotide polymorphism that influences cognition in humans is the brain-derived neurotrophic factor (BDNF) Val66Met variant. Despite strong evidence suggesting aerobic exercise has a beneficial effect on cognitive function, there is significant variability in individual response to exercise programs on cognitive outcomes among Val/Val versus Met carriers. However, the evidence on how the BDNF Val66Met variant influences cognitive outcomes following an aerobic exercise intervention among individuals with T2DM is currently lacking. Therefore, the purpose of this randomized controlled trial is to pilot-test a 3-month supervised exercise program to improve plasma BDNF levels and cognition, overall and according to genotypes of the BDNF Val66Met variant. A total of 81 patients with T2DM will be randomly assigned to either aerobic exercise group (n = 54) or attention control group (n = 27) for 3 months. Outcomes of interest include postintervention changes in plasma BDNF levels, fasting blood glucose, hemoglobin A1c, body mass index, executive function, memory, and processing speed. This study will provide further evidence on use of exercise as a non-pharmaceutical, low-cost intervention to improve cognition in this population.

Changes of BDNF exon IV DNA methylation are associated with methamphetamine dependence

Aim: We investigated DNA methylation of BDNF in methamphetamine (METH) dependence in humans and an animal model. Materials & methods: BDNF methylation at exon IV was determined by pyrosequencing of blood DNA from METH-dependent and control subjects, and from rat brain following an escalating dose of METH or vehicle. Bdnf expression was determined in rat brain. Results: BDNF methylation was increased in human METH dependence, greatest in subjects with psychosis and in prefrontal cortex of METH-administered rats; rat hippocampus showed reduced Bdnf methylation and increased gene expression. Conclusion: BDNF methylation is abnormal in human METH dependence, especially METH-dependent psychosis, and in METH-administered rats. This may influence BDNF expression and contribute to the neurotoxic effects of METH exposure.

Translational relevance of fear conditioning in rodent models of mild traumatic brain injury

Mild traumatic brain injury (mTBI) increases the risk of posttraumatic stress disorder (PTSD) in military populations. Utilizing translationally relevant animal models is imperative for establishing a platform to delineate neurobehavioral deficits common to clinical PTSD that emerge in the months to years following mTBI. Such platforms are required to facilitate preclinical development of novel therapeutics. First, this mini review provides an overview of the incidence of PTSD following mTBI in military service members. Secondly, the translational relevance of fear conditioning paradigms used in conjunction with mTBI in preclinical studies is evaluated. Next, this review addresses an important gap in the current preclinical literature; while incubation of fear has been studied in other areas of research, there are relatively few studies pertaining to the enhancement of cued and contextual fear memory over time following mTBI. Incubation of fear paradigms in conjunction with mTBI are proposed as a novel behavioral approach to advance this critical area of research. Lastly, this review discusses potential neurobiological substrates implicated in altered fear memory post mTBI.

Impact of COMT val158met on tDCS-induced cognitive enhancement in older adults

BACKGROUND

Previous studies suggest that genetic polymorphisms and aging modulate inter-individual variability in brain stimulation-induced plasticity. However, the relationship between genetic polymorphisms and behavioral modulation through transcranial direct current stimulation (tDCS) in older adults remains poorly understood.

OBJECTIVE

Link individual tDCS responsiveness, operationalized as performance difference between tDCS and sham condition, to common genetic polymorphisms in healthy older adults.

METHODS

106 healthy older participants from five tDCS-studies were re-invited to donate blood for genotyping of apoliproprotein E (APOE: ε4 carriers and ε4 non-carriers), catechol-O-methyltransferase (COMT: val/val, val/met, met/met), brain-derived neurotrophic factor (BDNF: val/val, val/met, met/met) and KIdney/BRAin encoding gene (KIBRA: C/C, C/T, T/T). Studies had assessed cognitive performance during tDCS and sham in cross-over designs. We now asked whether the tDCS responsiveness was related to the four genotypes using a linear regression models.

RESULTS

We found that tDCS responsiveness was significantly associated with COMT polymorphism; i.e., COMT val carriers (compared to met/met) showed higher tDCS responsiveness. No other significant associations emerged.

CONCLUSION

Using data from five brain stimulation studies conducted in our group, we showed that only individual variation of COMT genotypes modulated behavioral response to tDCS. These findings contribute to the understanding of inherent factors that explain inter-individual variability in functional tDCS effects in older adults, and might help to better stratify participants for future clinical trials.

Perfluoroalkyl Substance Exposure and the BDNF Pathway in the Placental Trophoblast

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants that have become globally ubiquitous in humans and the environment. In utero PFAS exposure is associated with neurodevelopmental effects; however, the mechanism is poorly understood. Brain-derived neurotrophic factor (BDNF) signaling is critical to fetal neurodevelopment during pregnancy and maintains important regulatory roles later in life. This study aims to characterize placental BDNF signaling and investigate whether PFAS exposure disrupts the signaling pathway in placental trophoblast cells.

METHODS

The expression and localization of BDNF receptors-p75^NTR and TrkB-in first trimester and term human placentas and trophoblast cells were investigated by immunofluorescence staining. To assess the effects of PFAS exposure on the BDNF pathway, BeWo cells were treated with PFAS mixtures that mimicked blood levels in a highly exposed population and major PFAS compounds in the mixture at 0.01, 0.1, 1, and 10 µM concentrations. Changes in pro-BDNF levels and phosphorylation of TrkB receptors were examined by Western blot.

RESULTS

In first trimester human placentas, TrkB and p75^NTR receptors were primarily localized to syncytiotrophoblast and cytotrophoblast cells. At term, TrkB and p75^NTR receptors were primarily observed in the placental villous stroma. TrkB receptor staining in trophoblasts was reduced at term, while p75^NTR receptor staining was negative. TrkB receptors were confined to the nuclear and perinuclear spaces, and phosphorylation occurred at the Tyr816 residue in BeWo cells. Exposure to PFOS, PFOA, PFBS, and the six-PFAS mixture did not significantly affect BDNF levels or activation (phosphorylation) of TrkB. Treating cells with 1 μM and 10 μM of PFNA resulted in increased TrkB phosphorylation compared to unexposed controls, but BDNF levels were unchanged.

CONCLUSIONS

BDNF receptors are present in different regions of human placental villi, indicating diverse functions of BDNF signaling in placental development. Our findings suggest that the BDNF pathway in placental trophoblast cells is not disrupted by exposures to PFOS, PFOA, PFBS, and a PFAS mixture, but may be affected by PFNA exposures. Further investigation is needed on how PFAS affects other critical signaling pathways during fetal neurodevelopment.

Working memory moderates the relation between the brain-derived neurotropic factor (BDNF) and psychotherapy outcome for depression

BACKGROUND

Insight into patient characteristics that predict response to treatment for major depressive disorder (MDD) may help to personalize treatment and improve outcomes. One mechanism that has been linked to the success of treatment for MDD is brain-derived neurotropic factor (BDNF). BDNF is implicated in learning and memory and may play a role in the effects of psychotherapy that involves changing cognitions and behaviors. In addition, only in individuals with low BDNF, low working memory capacity has been associated with increased symptoms of depression. However, the role of BDNF and working memory capacity in psychotherapy outcome is unclear. The aim of this study was to investigate the role of BDNF and its interaction with working memory capacity in psychotherapy outcomes for MDD.

METHOD

Adult patients with MDD were randomized to weekly or twice weekly sessions of cognitive behavioral therapy or interpersonal psychotherapy. BDNF Val66Met polymorphism (rs6265) (n = 138) was defined and serum BDNF was quantified before (n = 138) and after psychotherapy (n = 82).

RESULTS

Baseline serum BDNF and the Val66Met polymorphism were not associated with outcome and associations did not differ between treatment conditions. Working memory capacity significantly moderated the relation between baseline serum BDNF and outcome: high serum BDNF at baseline was related to less depressive symptoms following psychotherapy in the presence of high working memory capacity, but not low working memory capacity.

DISCUSSION

These findings, if replicated, might indicate that while BDNF may not be related to psychotherapy outcomes in general, they may play a role in the presence of specific learning processes such as working memory capacity.

Genetic and Neuroimaging Approaches to Understanding Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) is a highly disabling condition, increasingly recognized as both a disorder of mental health and social burden, but also as an anxiety disorder characterized by fear, stress, and negative alterations in mood. PTSD is associated with structural, metabolic, and molecular changes in several brain regions and the neural circuitry. Brain areas implicated in the traumatic stress response include the amygdala, hippocampus, and prefrontal cortex, which play an essential role in memory function. Abnormalities in these brain areas are hypothesized to underlie symptoms of PTSD and other stress-related psychiatric disorders. Conventional methods of studying PTSD have proven to be insufficient for diagnosis, measurement of treatment efficacy, and monitoring disease progression, and currently, there is no diagnostic biomarker available for PTSD. A deep understanding of cutting-edge neuroimaging genetic approaches is necessary for the development of novel therapeutics and biomarkers to better diagnose and treat the disorder. A current goal is to understand the gene pathways that are associated with PTSD, and how those genes act on the fear/stress circuitry to mediate risk vs. resilience for PTSD. This review article explains the rationale and practical utility of neuroimaging genetics in PTSD and how the resulting information can aid the diagnosis and clinical management of patients with PTSD.

Meta-analytic method reveal a significant association of theBDNF Val66Met variant with smoking persistence based on a large samples

Although numerous genetic studies have reported the link between Val66Met in BDNF gene with smoking, the findings remain controversial, mainly due to small-to-moderate sample sizes. The main aim of current investigation is to explore whether the variant of Val66Met has any genetic functions in the progress of smoking persistence. The Val-based dominant genetic model considering Val/* (namely, Val/Val + Val/Met) and Met/Met as two genotypes with comparison of the frequency of each genotype in current smokers and never smokers. There were seven genetic association articles including eight independent datasets with 10,160 participants were chosen in current meta-analytic investigation. In light of the potent effects of ethnicity on homogeneity across studies, we carried out separated meta-analyses according to the ancestry origin by using the wide-used tool of Comprehensive Meta-analysis software (V 2.0). Our meta-analyses results indicated that the Val66Met polymorphism was significantly linked with smoking persistence based on either all the chosen samples (N = 10,160; Random and fixed models: pooled OR = 1.23; 95% CI = 1.03–1.46; P value = 0.012) or Asian samples (N = 2,095; Fixed model: pooled OR = 1.25; 95% CI = 1.01–1.54; P value = 0.044; Random model: pooled OR = 1.25; 95% CI = 1.001–1.56; P value = 0.049). No significant clue of bias in publications or heterogeneity across studies was detected. Thus, we conclude that the Val66Met (rs6265) variant conveys genetic susceptibility to maintaining smoking, and smokers who carry Val/* genotypes have a higher possibility of maintaining smoking than those having Met/Met genotype.

Effects of Exercise on Cognitive Performance in Children and Adolescents with ADHD: Potential Mechanisms and Evidence-based Recommendations

Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with a complex symptomatology, and core symptoms as well as functional impairment often persist into adulthood. Recent investigations estimate the worldwide prevalence of ADHD in children and adolescents to be ~7%, which is a substantial increase compared to a decade ago. Conventional treatment most often includes pharmacotherapy with central nervous stimulants, but the number of non-responders and adverse effects call for treatment alternatives. Exercise has been suggested as a safe and low-cost adjunctive therapy for ADHD and is reported to be accompanied by positive effects on several aspects of cognitive functions in the general child population. Here we review existing evidence that exercise affects cognitive functions in children with and without ADHD and present likely neurophysiological mechanisms of action. We find well-described associations between physical activity and ADHD, as well as causal evidence in the form of small to moderate beneficial effects following acute aerobic exercise on executive functions in children with ADHD. Despite large heterogeneity, meta-analyses find small positive effects of exercise in population-based control (PBC) children, and our extracted effect sizes from long-term interventions suggest consistent positive effects in children and adolescents with ADHD. Paucity of studies probing the effect of different exercise parameters impedes finite conclusions in this regard. Large-scale clinical trials with appropriately timed exercise are needed. In summary, the existing preliminary evidence suggests that exercise can improve cognitive performance intimately linked to ADHD presentations in children with and without an ADHD diagnosis. Based on the findings from both PBC and ADHD children, we cautiously provide recommendations for parameters of exercise.

The association of BDNF gene polymorphism with cognitive impairment in insomnia patients

BACKGROUND

Reductions in BDNF activity have shown associations with depressed mood. Other evidence has demonstrated that the BDNF Val66Met polymorphism (rs6265) appears to reduce neural plasticity. A limited number of studies have investigated the influence of these genetic polymorphisms in insomnia. The present study sought to confirm the presence of associations between BDNF Val66Met polymorphism (rs6265) occurrence in normal sleepers and those with insomnia.

METHOD

The study subjects consisted of a patient group (n = 199) complaining of insomnia and a control group (n = 51). Each subject was clinically interviewed using questions taken from the Brief Insomnia Questionnaire. After the interview, the subjects were asked to complete the Insomnia Severity Index, The Hamilton Depression Rating Scale, and the Montreal Cognitive Assessment Test. An overnight polysomnography test was also administered. Blood samples were collected for genetic study.

RESULTS

The insomnia patients showed a greater prevalence of heterozygous (A/G) VAL/MET polymorphism than the normal controls (p = ≤ 0.0001). This finding confirmed that this genetic polymorphism, which impairs BDNF activity, is an important correlate of disturbed sleep. Further, the finding of significantly greater (p = ≤ 0.0001) depression scores among the insomnia group suggested that BDNF is an important factor in the development of depressive symptoms.

CLINICAL IMPLICATIONS

The results of the present study indicate that BDNF gene polymorphism plays a prominent role in the variation of symptoms among insomnia patients and, further, that this polymorphism is strongly related to the severity of depression.

The BDNF Val66Met Polymorphism Has No Effect on Encoding-Related Hippocampal Response But Influences Recall in Remitted Patients With Bipolar Disorder

Background: Cognitive impairments in bipolar disorder (BD) such as memory deficits are associated with poor functional outcomes and it has been suggested that the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism contributes to individual variability in memory function in BD. The current study investigated the relationship between the BDNF Val66Met polymorphism, neural activity during a picture-encoding task, and subsequent memory recall. Methods: A total of 70 patients with BD grouped according to genotype [ValVal or Met carriers (MetVal/MetMet)] underwent fMRI while performing a picture-encoding task. Memory for the encoded pictures was tested with a subsequent free recall memory task. Results: There was no difference between the ValVal homozygotes and Met carriers in the involvement of hypothesized memory encoding regions i.e. hippocampus and dorsal prefrontal cortex (dPFC). However, an exploratory whole-brain analysis showed greater encoding-related lateral occipital cortex activity in Met carriers. Behaviorally, Met carriers also showed better free recall of the encoded pictures. Conclusions: We found no effect of the BDNF genotype on encoding-related hippocampal and dPFC activity in BD, although Met carriers showed superior memory performance after the scan, which could be related to more efficient perceptual processing during encoding.

BDNF gene and obsessive compulsive disorder risk, symptom dimensions and treatment response

AIM

Genetic etiology of Obsessive Compulsive Disorder (OCD) has been investigated extensively, with mixed results across candidate gene studies. The dimensional subtypes of OCD are shown to better correlate with brain imaging endophenotypes and thus could potentially enhance the power of genetic association. In this study, we perform a case control analysis of association of a single nucleotide polymorphism rs6265(Val66Met) in Brain Derived Neurotrophic Factor gene, that has been previously implicated in a variety of psychiatric syndromes, and examine its association with symptom dimensions of OCD.

METHODS

Individuals diagnosed to have OCD (n=377) and controls (n=449) of South Indian origin were genotyped for polymorphism rs6265 (196G/A, Val66Met). Detailed phenotypic assessment of the cases were carried out in the cases using structured instruments. The genotypic association was tested for clinical variables such as age of onset, gender, family history, co-morbidity, treatment response, and factor analyzed OCD symptom dimensions.

RESULTS

The allele 'A' frequency was found to be significantly higher in the controls, as compared to cases suggesting a protective effect. The contamination/washing symptom dimension score was significantly lower in carriers of 'A' allele which remained significant even after testing for confounding effects on linear regression.

CONCLUSIONS

Our results support findings from previous studies on a possible protective effect of the 'Met' allele at the Val66Met locus in OCD. Its association with lower scores on the contamination/washing dimension is a novel finding of this study.

Could a blood test for PTSD and depression be on the horizon?

INTRODUCTION

Depression and posttraumatic stress disorder (PTSD) are two complex and debilitating psychiatric disorders that result in poor life and destructive behaviors against self and others. Currently, diagnosis is based on subjective rather than objective determinations leading to misdiagnose and ineffective treatments. Advances in novel neurobiological methods have allowed assessment of promising biomarkers to diagnose depression and PTSD, which offers a new means of appropriately treating patients. Areas covered: Biomarkers discovery in blood represents a fundamental tool to predict, diagnose, and monitor treatment efficacy in depression and PTSD. The potential role of altered HPA axis, epigenetics, NPY, BDNF, neurosteroid biosynthesis, the endocannabinoid system, and their function as biomarkers for mood disorders is discussed. Insofar, we propose the identification of a biomarker axis to univocally identify and discriminate disorders with large comorbidity and symptoms overlap, so as to provide a base of support for development of targeted treatments. We also weigh in on the feasibility of a future blood test for early diagnosis. Expert commentary: Potential biomarkers have already been assessed in patients' blood and need to be further validated through multisite large clinical trial stratification. Another challenge is to assess the relation among several interdependent biomarkers to form an axis that identifies a specific disorder and secures the best-individualized treatment. The future of blood-based tests for PTSD and depression is not only on the horizon but, possibly, already around the corner.

BDNF Val66Met Polymorphism and Gamma Band Disruption in Resting State Brain Functional Connectivity: A Magnetoencephalography Study in Cognitively Intact Older Females

The pathophysiological processes undermining brain functioning decades before the onset of the clinical symptoms associated with dementia are still not well understood. Several heritability studies have reported that the Brain Derived Neurotrophic Factor (BDNF) Val66Met genetic polymorphism could contribute to the acceleration of cognitive decline in aging. This mutation may affect brain functional connectivity (FC), especially in those who are carriers of the BDNF Met allele. The aim of this work was to explore the influence of the BDNF Val66Met polymorphism in whole brain eyes-closed, resting-state magnetoencephalography (MEG) FC in a sample of 36 cognitively intact (CI) older females. All of them were ε3ε3 homozygotes for the apolipoprotein E (APOE) gene and were divided into two subgroups according to the presence of the Met allele: Val/Met group (n = 16) and Val/Val group (n = 20). They did not differ in age, years of education, Mini-Mental State Examination scores, or normalized hippocampal volumes. Our results showed reduced antero-posterior gamma band FC within the Val/Met genetic risk group, which may be caused by a GABAergic network impairment. Despite the lack of cognitive decline, these results might suggest a selective brain network vulnerability due to the carriage of the BDNF Met allele, which is linked to a potential progression to dementia. This neurophysiological signature, as tracked with MEG FC, indicates that age-related brain functioning changes could be mediated by the influence of particular genetic risk factors.

Chronic Hippocampal Abnormalities and Blunted HPA Axis in an Animal Model of Repeated Unpredictable Stress

Incidence of post-traumatic stress disorder (PTSD) ranges from 3 to 30% in individuals exposed to traumatic events, with the highest prevalence in groups exposed to combat, torture, or rape. To date, only a few FDA approved drugs are available to treat PTSD, which only offer symptomatic relief and variable efficacy. There is, therefore, an urgent need to explore new concepts regarding the biological responses causing PTSD. Animal models are an appropriate platform for conducting such studies. Herein, we examined the chronic behavioral and neurobiological effects of repeated unpredictable stress (RUS) in a mouse model. 12 weeks-old C57BL/6J male mice were exposed to a 21-day RUS paradigm consisting of exposures to a predator odor (TMT) whilst under restraint, unstable social housing, inescapable footshocks and social isolation. Validity of the model was assessed by comprehensive examination of behavioral outcomes at an acute timepoint, 3 and 6 months post-RUS; and molecular profiling was also conducted on brain and plasma samples at the acute and 6 months timepoints. Stressed mice demonstrated recall of traumatic memories, passive stress coping behavior, acute anxiety, and weight gain deficits when compared to control mice. Immunoblotting of amygdala lysates showed a dysregulation in the p75NTR/ProBDNF, and glutamatergic signaling in stressed mice at the acute timepoint. At 6 months after RUS, stressed mice had lower plasma corticosterone, reduced hippocampal CA1 volume and reduced brain-derived neurotrophic factor levels. In addition, glucocorticoid regulatory protein FKBP5 was downregulated in the hypothalamus of stressed mice at the same timepoint, together implicating an impaired hypothalamus-pituitary-adrenal-axis. Our model demonstrates chronic behavioral and neurobiological outcomes consistent with those reported in human PTSD cases and thus presents a platform through which to understand the neurobiology of stress and explore new therapeutic interventions.

Task demands, tDCS intensity, and the COMT val158met polymorphism impact tDCS-linked working memory training gains

Working memory (WM) training paired with transcranial direct current stimulation (tDCS) can improve executive function in older adults. The unclear mechanism of tDCS likely depends on tDCS intensity, and task relevant genetic factors (e.g., for WM: COMT val¹⁵⁸met, DAT, BDNF val⁶⁶met). Higher tDCS intensity does not always lead to greater cognitive gains, and genetic polymorphisms may modulate tDCS-linked WM improvements. To evaluate these factors, 137 healthy older adults provided DNA samples and received Visual and Spatial WM training paired with tDCS (sham, 1, 1.5, 2 mA). After one session of tDCS, significant group differences in WM performance were predicted by COMT val¹⁵⁸met status. One month after training, there was a significant interaction of tDCS intensity, COMT genotype, and WM task. Specifically, val/val homozygotes benefited most from 1.5 mA tDCS on Visual WM and from 1 mA tDCS on Spatial WM. For met/met homozygotes, 2 mA resulted in significantly poorer performance compared to 1.5 mA on Spatial WM. While this pattern was observed with relatively small sample sizes, these data indicate that variations in COMT val¹⁵⁸met may predict the nature of WM improvement after initial and longitudinal tDCS. This contributes to our understanding of the underlying mechanism by which tDCS affects behaviour.

The Role of Working Memory for Cognitive Control in Anorexia Nervosa versus Substance Use Disorder

Prefrontal cortex executive functions, such as working memory (WM) interact with limbic processes to foster impulse control. Such an interaction is referred to in a growing body of publications by terms such as cognitive control, cognitive inhibition, affect regulation, self-regulation, top-down control, and cognitive–emotion interaction. The rising trend of research into cognitive control of impulsivity, using various related terms reflects the importance of research into impulse control, as failure to employ cognitions optimally may eventually result in mental disorder. Against this background, we take a novel approach using an impulse control spectrum model – where anorexia nervosa (AN) and substance use disorder (SUD) are at opposite extremes – to examine the role of WM for cognitive control. With this aim, we first summarize WM processes in the healthy brain in order to frame a systematic review of the neuropsychological, neural and genetic findings of AN and SUD. In our systematic review of WM/cognitive control, we found n = 15 studies of AN with a total of n = 582 AN and n = 365 HC participants; and n = 93 studies of SUD with n = 9106 SUD and n = 3028 HC participants. In particular, we consider how WM load/capacity may support the neural process of excessive epistemic foraging (cognitive sampling of the environment to test predictions about the world) in AN that reduces distraction from salient stimuli. We also consider the link between WM and cognitive control in people with SUD who are prone to ‘jumping to conclusions’ and reduced epistemic foraging. Finally, in light of our review, we consider WM training as a novel research tool and an adjunct to enhance treatment that improves cognitive control of impulsivity.

BDNF genotype is associated with hippocampal volume in mild traumatic brain injury

The negative long-term effects of mild traumatic brain injury (mTBI) have been a growing concern in recent years, with accumulating evidence suggesting that mTBI combined with additional vulnerability factors may induce neurodegenerative-type changes in the brain. However, the factors instantiating risk for neurodegenerative disease following mTBI are unknown. This study examined the link between mTBI and brain-derived neurotrophic factor (BDNF) genotype, which has previously been shown to regulate processes involved in neurodegeneration including synaptic plasticity and facilitation of neural survival through its expression. Specifically, we examined nine BDNF single-nucleotide polymorphisms (SNPs; rs908867, rs11030094, rs6265, rs10501087, rs1157659, rs1491850, rs11030107, rs7127507 and rs12273363) previously associated with brain atrophy or memory deficits in mTBI. Participants were 165 white, non-Hispanic Iraq and Afghanistan war veterans between the ages of 19 and 58, 110 of whom had at least one mTBI in their lifetime. Results showed that the BDNF SNP rs1157659 interacted with mTBI to predict hippocampal volume. Furthermore, exploratory analysis of functional resting state data showed that rs1157659 minor allele homozygotes with a history of mTBI had reduced functional connectivity in the default mode network compared to major allele homozygotes and heterozygotes. Apolipoprotein E (APOE) was not a significant predictor of hippocampal volume or functional connectivity. These results suggest that rs1157659 minor allele homozygotes may be at greater risk for neurodegeneration after exposure to mTBI and provide further evidence for a potential role for BDNF in regulating neural processes following mTBI.

Brain-Derived Neurotropic Factor Val66Met Polymorphism and Posttraumatic Stress Disorder among Survivors of the 1998 Dongting Lake Flood in China

OBJECTIVE

This study mainly aimed to explore the association between brain-derived neurotropic factor (BDNF) Val66Met polymorphism and posttraumatic stress disorder (PTSD) among flood survivors in China.

METHODS

Individuals who experienced the 1998 Dongting Lake flood in Southeast Huarong, China, were enrolled in this study. Qualified health personnel carried out face-to-face interviews with participants. PTSD was identified using PTSD Checklist-Civilian version (PCL-C). Blood samples were collected from the participants to extract DNA for genotyping.

RESULTS

A total of 175 participants were enrolled in this study. The prevalence of PTSD among flood survivors at 17-year follow-up was 16.0% (28/175). Individuals with PTSD were more likely to be female, experience at least three flood-related stressors, experience at least three postflood stressors, and carry the Met than those without PTSD. Compared with Val/Val homozygotes, Met carriers had higher scores of PCL-C (mean ± standard error: 23.60 ± 7.23 versus 27.19 ± 9.48, P < 0.05). Multivariable logistic regression analysis indicated that Met carriers (aOR = 4.76, 95% CI = 1.02-22.15, P < 0.05) were more likely to develop PTSD than Val/Val homozygotes.

CONCLUSIONS

Met carriers for BDNF rs6265 are at higher risk of developing PTSD and also exhibit more severe PTSD symptoms than Val/Val homozygotes among flood survivors in China.

The BDNF Val66Met polymorphism is associated with structural neuroanatomical differences in young children

The brain-derived neurotrophic factor (BDNF) Val⁶⁶Met single nucleotide polymorphism (SNP) has been associated with individual differences in brain structure and function, and cognition. Research on BDNF's influence on brain and cognition has largely been limited to adults, and little is known about the association of this gene, and specifically the Val⁶⁶Met polymorphism, with developing brain structure and emerging cognitive functions in children. We performed a targeted genetic association analysis on cortical thickness, surface area, and subcortical volume in 78 children (ages 6-10) who were Val homozygotes (homozygous Val/Val carriers) or Met carriers (Val/Met, Met/Met) for the Val⁶⁶Met locus using Atlas-based brain segmentation. We observed greater cortical thickness for Val homozygotes in regions supporting declarative memory systems (anterior temporal pole/entorhinal cortex), consistent with adult findings. Met carriers had greater surface area in the prefrontal and parietal cortices and greater cortical thickness in lateral occipital/parietal cortex in contrast to prior adult findings that may relate to performance on cognitive tasks supported by these regions in Met carriers. Finally, we found larger right hippocampal volume in Met carriers, although inconsistent with adult findings (generally reports larger volumes for Val homozygotes), is consistent with a recent finding in children. Gene expression levels vary across different brain regions and across development and our findings highlight the need to consider this developmental change in explorations of BDNF-brain relationships. The impact of the BDNF Val⁶⁶Met polymorphism on the structure of the developing brain therefore reflects regionally-specific developmental changes in BDNF expression and cortical maturation trajectories.

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.

The BDNF Val66Met Polymorphism Influences Reading Ability and Patterns of Neural Activation in Children

Understanding how genes impact the brain’s functional activation for learning and cognition during development remains limited. We asked whether a common genetic variant in the BDNF gene (the Val⁶⁶Met polymorphism) modulates neural activation in the young brain during a critical period for the emergence and maturation of the neural circuitry for reading. In animal models, the bdnf variation has been shown to be associated with the structure and function of the developing brain and in humans it has been associated with multiple aspects of cognition, particularly memory, which are relevant for the development of skilled reading. Yet, little is known about the impact of the Val⁶⁶Met polymorphism on functional brain activation in development, either in animal models or in humans. Here, we examined whether the BDNF Val⁶⁶Met polymorphism (dbSNP rs6265) is associated with children’s (age 6–10) neural activation patterns during a reading task (n = 81) using functional magnetic resonance imaging (fMRI), genotyping, and standardized behavioral assessments of cognitive and reading development. Children homozygous for the Val allele at the SNP rs6265 of the BDNF gene outperformed Met allele carriers on reading comprehension and phonological memory, tasks that have a strong memory component. Consistent with these behavioral findings, Met allele carriers showed greater activation in reading–related brain regions including the fusiform gyrus, the left inferior frontal gyrus and left superior temporal gyrus as well as greater activation in the hippocampus during a word and pseudoword reading task. Increased engagement of memory and spoken language regions for Met allele carriers relative to Val/Val homozygotes during reading suggests that Met carriers have to exert greater effort required to retrieve phonological codes.

BDNF DNA methylation changes as a biomarker of psychiatric disorders: literature review and open access database analysis

Brain-derived neurotrophic factor (BDNF) plays an important role in nervous system development and function and it is well established that BDNF is involved in the pathogenesis of a wide range of psychiatric disorders. Recently, numerous studies have associated the DNA methylation level of BDNF promoters with certain psychiatric phenotypes. In this review, we summarize data from current literature as well as from our own analysis with respect to the correlation of BDNF methylation changes with psychiatric disorders and address questions about whether DNA methylation related to the BDNF can be useful as biomarker for specific neuropsychiatric disorders.

Central monoaminergic systems are a site of convergence of signals conveying the experience of exercise to brain circuits involved in cognition and emotional behavior

Physical activity can enhance cognitive function and increase resistance against deleterious effects of stress on mental health. Enhanced cognitive function and stress resistance produced by exercise are conserved among vertebrates, suggesting that ubiquitous mechanisms may underlie beneficial effects of exercise. In the current review, we summarize the beneficial effects of exercise on cognitive function and stress resistance and discuss central and peripheral signaling factors that may be critical for conferring the effects of physical activity to brain circuits involved in cognitive function and stress. Additionally, it is suggested that norepinephrine and serotonin, highly conserved monoamines that are sensitive to exercise and able to modulate behavior in multiple species, could represent a convergence between peripheral and central exercise signals that mediate the beneficial effects of exercise. Finally, we offer the novel hypothesis that thermoregulation during exercise could contribute to the emotional effects of exercise by activating a subset of temperature-sensitive serotonergic neurons in the dorsal raphe nucleus that convey anxiolytic and stress-protective signals to forebrain regions. Throughout the review, we discuss limitations to current approaches and offer strategies for future research in exercise neuroscience.

Post-traumatic stress disorder risk and brain-derived neurotrophic factor Val66Met

Brain-derived neurotrophic factor (BDNF), which regulates neuronal survival, growth differentiation, and synapse formation, is known to be associated with depression and post-traumatic stress disorder (PTSD). However, the molecular mechanism for those mental disorders remains unknown. Studies have shown that BDNF is associated with PTSD risk and exaggerated startle reaction (a major arousal manifestation of PTSD) in United States military service members who were deployed during the wars in Iraq and Afghanistan. The frequency of the Met/Met in BDNF gene was greater among those with PTSD than those without PTSD. Among individuals who experienced fewer lifetime stressful events, the Met carriers have significantly higher total and startle scores on the PTSD Checklist than the Val/Val carriers. In addition, subjects with PTSD showed higher levels of BDNF in their peripheral blood plasma than the non-probable-PTSD controls. Increased BDNF levels and startle response were observed in both blood plasma and brain hippocampus by inescapable tail shock in rats. In this paper, we reviewed these data to discuss BDNF as a potential biomarker for PTSD risk and its possible roles in the onset of PTSD.

The neuroprotective effects of R-phenibut after focal cerebral ischemia

R-phenibut is a γ-aminobutyric acid (GABA)-B receptor and α₂-δ subunit of the voltage-dependent calcium channel (VDCC) ligand. The aim of the present study was to test the effects of R-phenibut on the motor, sensory and tactile functions and histological outcomes in rats following transient middle cerebral artery occlusion (MCAO). In this study, MCAO was induced by filament insertion (f-MCAO) or endothelin-1 (ET1) microinjection (ET1-MCAO) in male Wistar or CD rats, respectively. R-phenibut was administrated at doses of 10 and 50mg/kg for 14 days in the f-MCAO or 7 days in the ET1-MCAO. The vibrissae-evoked forelimb-placing and limb-placing tests were used to assess sensorimotor, tactile and proprioceptive function. Quantitative reverse transcriptase-PCR was used to detect brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF) gene expression in the damaged brain hemisphere. Both f-MCAO and ET1-MCAO resulted in statistically significant impairment of sensorimotor function and brain infarction. R-phenibut at a dose of 10mg/kg significantly improved histological outcome at day 7 in the ET1-MCAO. R-phenibut treatment at a dose of 50mg/kg significantly alleviated reduction of brain volume in damaged hemisphere in both f-MCAO and ET1-MCAO. In R-phenibut treated animals a trend of recovery of tactile and proprioceptive stimulation in the vibrissae-evoked forelimb-placing test was observed. After R-phenibut treatment at a dose of 50mg/kg statistically significant increase of BDNF and VEGF gene expression was found in damaged brain hemisphere. Taken together, obtained results provide evidence for the neuroprotective activity of R-phenibut in experimental models of stroke. These effects might be related to the modulatory effects of the drug on the GABA-B receptor and α₂-δ subunit of VDCC.

The Effects of BDNF Val66Met Gene Polymorphism on Serum BDNF and Cognitive Function in Methamphetamine-Dependent Patients and Normal Controls: A Case-Control Study

Studies suggest that a functional polymorphism of the brain-derived neurotrophic factor gene (BDNF Val66Met) may contribute to methamphetamine dependence. We hypothesized that this polymorphism had a role in cognitive deficits in methamphetamine-dependent patients and in the relationship of serum BDNF with cognitive impairments. We conducted a case-control study by assessing 194 methamphetamine-dependent patients and 378 healthy volunteers without history of drug use on the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and the presence of the BDNF Val66Met polymorphism and serum BDNF levels. We showed no significant differences in genotype and allele distributions between the methamphetamine-dependent patients and controls. Some aspects of cognitive function significantly differed in the 2 groups. The serum BDNF levels in methamphetamine-dependent patients were significantly higher than those of the healthy controls. In the patients, partial correlation analysis showed a significant positive correlation between serum BDNF and the delayed memory index score. The RBANS scores showed statistically significant BDNF level × genotype interaction. Further regression analyses showed a significant positive association between BDNF levels and the RBANS total score, immediate memory or attention index among Val homozygote patients, whereas a significant negative association of BDNF levels with the RBANS total score, visuospatial/constructional, or language index was found among Met/Val heterozygous patients. We demonstrated significant impairment on some aspects of cognitive function and increased BDNF levels in methamphetamine-dependent patients as well as genotypic differences in the relationships between BDNF levels and RBANS scores on the BDNF Val66Met polymorphism only in these patients.

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.

Is there a "metabolic-mood syndrome"? A review of the relationship between obesity and mood disorders

Obesity and mood disorders are highly prevalent and co-morbid. Epidemiological studies have highlighted the public health relevance of this association, insofar as both conditions and its co-occurrence are associated with a staggering illness-associated burden. Accumulating evidence indicates that obesity and mood disorders are intrinsically linked and share a series of clinical, neurobiological, genetic and environmental factors. The relationship of these conditions has been described as convergent and bidirectional; and some authors have attempted to describe a specific subtype of mood disorders characterized by a higher incidence of obesity and metabolic problems. However, the nature of this association remains poorly understood. There are significant inconsistencies in the studies evaluating metabolic and mood disorders; and, as a result, several questions persist about the validity and the generalizability of the findings. An important limitation in this area of research is the noteworthy phenotypic and pathophysiological heterogeneity of metabolic and mood disorders. Although clinically useful, categorical classifications in both conditions have limited heuristic value and its use hinders a more comprehensive understanding of the association between metabolic and mood disorders. A recent trend in psychiatry is to move toward a domain specific approach, wherein psychopathology constructs are agnostic to DSM-defined diagnostic categories and, instead, there is an effort to categorize domains based on pathogenic substrates, as proposed by the National Institute of Mental Health (NIMH) Research Domain Criteria Project (RDoC). Moreover, the substrates subserving psychopathology seems to be unspecific and extend into other medical illnesses that share in common brain consequences, which includes metabolic disorders. Overall, accumulating evidence indicates that there is a consistent association of multiple abnormalities in neuropsychological constructs, as well as correspondent brain abnormalities, with broad-based metabolic dysfunction, suggesting, therefore, that the existence of a "metabolic-mood syndrome" is possible. Nonetheless, empirical evidence is necessary to support and develop this concept. Future research should focus on dimensional constructs and employ integrative, multidisciplinary and multimodal approaches.

Serum brain-derived neurotrophic factor and cognitive functioning in underweight, weight-recovered and partially weight-recovered females with anorexia nervosa

Several studies support the assumption that the brain-derived neurotrophic factor (BDNF) plays an important role in the pathophysiology of eating disorders. In the present cross-sectional and longitudinal study, we investigated BDNF levels in patients with anorexia nervosa (AN) at different stages of their illness and the association with cognitive functioning. We measured serum BDNF in 72 acutely underweight female AN patients (acAN), 23 female AN patients who successfully recovered from their illness (recAN), and 52 healthy control women (HCW). Longitudinally, 30 acAN patients were reassessed after short-term weight gain. The association between BDNF levels and psychomotor speed was investigated using the Trail Making Test. BDNF serum concentrations were significantly higher in recAN participants if compared to acAN patients and increased with short-term weight gain. In acAN patients, but not HCW, BDNF levels were inversely associated with psychomotor speed. AcAN patients with higher BDNF levels also had lower life time body mass indexes. Taken together, our results indicate that serum BDNF levels in patients with AN vary with the stage of illness. Based on the pleiotropic functions of BDNF, changing levels of this neurotrophin may have different context-dependent effects, one of which may be the modulation of cognitive functioning in acutely underweight patients.

The association of the BDNF Val66Met polymorphism and the hippocampal volumes in healthy humans: a joint meta-analysis of published and new data

BACKGROUND

The brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (refSNP Cluster Report: rs6265) is a common and functionally relevant single nucleotide polymorphism (SNP). The gene itself, as well as the SNP rs6265, have been implicated in hippocampal learning and memory. However, imaging genetic studies have produced controversial results about the impact of this SNP on hippocampal volumes in healthy subjects.

METHODS

We examined the association between the rs6265 polymorphism and hippocampal volume in 643 healthy young subjects using automatic segmentation and subsequently included these data in a meta-analysis based on published studies with 5298 healthy subjects in total.

RESULTS

We found no significant association between SNP rs6265 and hippocampal volumes in our sample (g=0.05, p=0.58). The meta-analysis revealed a small, albeit significant difference in hippocampal volumes between genotype groups, such that Met-carriers had slightly smaller hippocampal volumes than Val/Val homozygotes (g=0.09, p=0.04), an association that was only evident when manual (g=0.22, p=0.01) but not automatic tracing approaches (g=0.04, p=0.38) were used. Studies using manual tracing showed evidence for publication bias and a significant decrease in effect size over the years with increasing sample sizes.

CONCLUSIONS

This study does not support the association between SNP rs6265 and hippocampal volume in healthy individuals. The weakly significant effect observed in the meta-analysis is mainly driven by studies with small sample sizes. In contrast, our original data and the meta-analysis of automatically segmented hippocampal volumes, which was based on studies with large samples sizes, revealed no significant genotype effect. Thus, meta-analyses of the association between rs6265 and hippocampal volumes should consider possible biases related to measuring technique and sample size.