BDNF Val66Met polymorphism is associated with higher anticipatory cortisol stress response, anxiety, and alcohol consumption in healthy adults

Emerging treatment mechanisms for depression: focus on glutamate and synaptic plasticity

Major depression is a chronic and debilitating illness that effects approximately 1 in 5 people, but currently available treatments are limited by low rates of efficacy, therapeutic time lag, and undesirable side effects. Recent efforts have been directed towards investigating rapid-acting agents that reverse the behavioral and neuronal deficits of chronic stress and depression, notably the glutamate NMDA receptor antagonist ketamine. The cellular mechanisms underlying the rapid antidepressant actions of ketamine and related agents are discussed, as well as novel, selective glutamatergic receptor targets that are safer and have fewer side effects.

Neuromodulation of Aerobic Exercise-A Review

Running, and aerobic exercise in general, is a physical activity that increasingly many people engage in but that also has become popular as a topic for scientific research. Here we review the available studies investigating whether and to which degree aerobic exercise modulates hormones, amino acids, and neurotransmitters levels. In general, it seems that factors such as genes, gender, training status, and hormonal status need to be taken into account to gain a better understanding of the neuromodular underpinnings of aerobic exercise. More research using longitudinal studies and considering individual differences is necessary to determine actual benefits. We suggest that, in order to succeed, aerobic exercise programs should include optimal periodization, prevent overtraining and be tailored to interindividual differences, including neuro-developmental and genetically-based factors.

Allelic Variation of Risk for Anxiety Symptoms Moderates the Relation Between Adolescent Safety Behaviors and Social Anxiety Symptoms

Social anxiety often develops in adolescence, and precedes the onset of depression and substance use disorders. The link between social anxiety and use of behaviors to minimize distress in social situations (i.e., safety behaviors) is strong and for some patients, this link poses difficulty for engaging in, and benefiting from, exposure-based treatment. Yet, little is known about whether individual differences may moderate links between social anxiety and safety behaviors, namely variations in genetic alleles germane to anxiety. We examined the relation between adolescent social anxiety and expressions of safety behaviors, and whether allelic variation for anxiety moderates this relation. Adolescents (n=75; ages 14-17) were recruited from two larger studies investigating measurement of family relationships or adolescent social anxiety. Adolescents completed self-report measures about social anxiety symptoms and use of safety behaviors. They also provided saliva samples to assess allelic variations for anxiety from two genetic polymorphisms (BDNF rs6265; TAQ1A rs1800497). Controlling for adolescent age and gender, we observed a significant interaction between social anxiety symptoms and allelic variation (β=0.37, t=2.41, p=.02). Specifically, adolescents carrying allelic variations for anxiety evidenced a statistically significant and relatively strong positive relation between social anxiety symptoms and safety behaviors (β=0.73), whereas adolescents not carrying allelic variation evidenced a statistically non-significant and relatively weak relation (β=0.22). These findings have important implications for treating adolescent social anxiety, in that we identified an individual difference variable that can be used to identify people who evidence a particularly strong link between use of safety behaviors and expressing social anxiety.

Predicting change in symptoms of depression during the transition to university: the roles of BDNF and working memory capacity

Studies on depression risk emphasize the importance of both cognitive and genetic vulnerability factors. The present study has provided the first examination of whether working memory capacity, the BDNF Val66Met polymorphism, and their interaction predict changes in symptoms of depression during the transition to university. Early in the semester, students completed a self-report measure of depressive symptoms and a modified version of the reading span task to assess working memory capacity in the presence of both neutral and negative distractors. Whole blood was genotyped for the BDNF Val66Met polymorphism. Students returned at the end of the semester to complete additional self-report questionnaires. Neither working memory capacity nor the BDNF Val66Met polymorphism predicted change in depressive symptoms either independently or in interaction with self-reported semester difficulty. The BDNF Val66Met polymorphism, however, moderated the association between working memory capacity and symptom change. Among met carriers, lower working memory capacity in the presence of negative-but not neutral-distractors was associated with increased symptoms of depression over the semester. For the val/val group, working memory capacity did not predict symptom change. These findings contribute directly to biological and cognitive models of depression and highlight the importance of examining Gene × Cognition interactions when investigating risk for depression.

Cortisol response and psychological distress predict susceptibility to false memories for a trauma film

For eyewitness testimony to be considered reliable, it is important to ensure memory remains accurate following the event. As many testimonies involve traumatic, as opposed to neutral, events, it is important to consider the role of distress in susceptibility to false memories. The aim of this study was to investigate whether cortisol response following a stressor would be associated with susceptibility to false memories. Psychological distress responses were also investigated, specifically, dissociation, intrusions, and avoidance. Participants were allocated to one of three conditions: those who viewed a neutral film (N = 35), those who viewed a real trauma film (N = 35), and a trauma "reappraisal" group where participants were told the film was not real (N = 35). All received misinformation about the film in the form of a narrative. Participants provided saliva samples (to assess cortisol) and completed distress and memory questionnaires. Cortisol response was a significant predictor of the misinformation effect. Dissociation and avoidance were related to confabulations. In conclusion, following a stressor an individual may differ with regard to their psychological response to the event, and also whether they experience a cortisol increase. This may affect whether they are more distressed later on, and also whether they remember the event accurately.

BDNF promoter methylation and genetic variation in late-life depression

The regulation of the brain-derived neurotrophic factor (BDNF) is important for depression pathophysiology and epigenetic regulation of the BDNF gene may be involved. This study investigated whether BDNF methylation is a marker of depression. One thousand and twenty-four participants were recruited as part of a longitudinal study of psychiatric disorders in general population elderly (age ⩾ 65). Clinical levels of depression were assessed using the Mini International Neuropsychiatric Interview for the diagnosis of major depressive disorder according to the Diagnostic and Statistical Manual of Mental Disorder IV criteria, and the Centre for Epidemiologic Studies Depression Scale (CES-D) for assessment of moderate to severe depressive symptoms. Buccal DNA methylation at the two most widely studied BDNF promoters, I and IV, was investigated using the Sequenom MassARRAY platform that allows high-throughput investigation of methylation at individual CpG sites within defined genomic regions. In multivariate linear regression analyses adjusted for a range of participant characteristics including antidepressant use, depression at baseline, as well as chronic late-life depression over the 12-year follow-up, were associated with overall higher BDNF methylation levels, with two sites showing significant associations (promoter I, Δ mean = 0.4%, P = 0.0002; promoter IV, Δ mean = 5.4%, P = 0.021). Three single-nucleotide polymorphisms (rs6265, rs7103411 and rs908867) were also found to modify the association between depression and promoter I methylation. As one of the largest epigenetic studies of depression, and the first investigating BDNF methylation in buccal tissue, our findings highlight the potential for buccal BDNF methylation to be a biomarker of depression.

Effects of the BDNF Val66Met Polymorphism on Anxiety-Like Behavior Following Nicotine Withdrawal in Mice

INTRODUCTION

Nicotine withdrawal is characterized by both affective and cognitive symptoms. Identifying genetic polymorphisms that could affect the symptoms associated with nicotine withdrawal are important in predicting withdrawal sensitivity and identifying personalized cessation therapies. In the current study we used a mouse model of a non-synonymous single nucleotide polymorphism in the translated region of the brain-derived neurotrophic factor (BDNF) gene that substitutes a valine (Val) for a methionine (Met) amino acid (Val66Met) to examine the relationship between the Val66Met single nucleotide polymorphism and nicotine dependence.

METHODS

This study measured proBDNF and the BDNF prodomain levels following nicotine and nicotine withdrawal and examined a mouse model of a common polymorphism in this protein (BDNF(Met/Met)) in three behavioral paradigms: novelty-induced hypophagia, marble burying, and the open-field test.

RESULTS

Using the BDNF knock-in mouse containing the BDNF Val66Met polymorphism we found: (1) blunted anxiety-like behavior in BDNF(Met/Met) mice following withdrawal in three behavioral paradigms: novelty-induced hypophagia, marble burying, and the open-field test; (2) the anxiolytic effects of chronic nicotine are absent in BDNF(Met/Met) mice; and (3) an increase in BDNF prodomain in BDNF(Met/Met) mice following nicotine withdrawal.

CONCLUSIONS

Our study is the first to examine the effect of the BDNF Val66Met polymorphism on the affective symptoms of withdrawal from nicotine in mice. In these mice, a single-nucleotide polymorphism in the translated region of the BDNF gene can result in a blunted withdrawal, as measured by decreased anxiety-like behavior. The significant increase in the BDNF prodomain in BDNF(Met/Met) mice following nicotine cessation suggests a possible role of this ligand in the circuitry remodeling after withdrawal.

Genotypes do not confer risk for delinquency but rather alter susceptibility to positive and negative environmental factors: gene-environmentinteractions of BDNF Val66Met, 5-HTTLPR, and MAOA-uVNTR [corrected]

BACKGROUND

Previous evidence of gene-by-environment interactions associated with emotional and behavioral disorders is contradictory. Differences in findings may result from variation in valence and dose of the environmental factor, and/or failure to take account of gene-by-gene interactions. The present study investigated interactions between the brain-derived neurotrophic factor gene (BDNF Val66Met), the serotonin transporter gene-linked polymorphic region (5-HTTLPR), the monoamine oxidase A (MAOA-uVNTR) polymorphisms, family conflict, sexual abuse, the quality of the child-parent relationship, and teenage delinquency.

METHODS

In 2006, as part of the Survey of Adolescent Life in Västmanland, Sweden, 1 337 high-school students, aged 17-18 years, anonymously completed questionnaires and provided saliva samples for DNA analyses.

RESULTS

Teenage delinquency was associated with two-, three-, and four-way interactions of each of the genotypes and the three environmental factors. Significant four-way interactions were found for BDNF Val66Met × 5-HTTLPR×MAOA-uVNTR × family conflicts and for BDNF Val66Met × 5-HTTLPR×MAOA-uVNTR × sexual abuse. Further, the two genotype combinations that differed the most in expression levels (BDNF Val66Met Val, 5-HTTLPR LL, MAOA-uVNTR LL [girls] and L [boys] vs BDNF Val66Met Val/Met, 5-HTTLPR S/LS, MAOA-uVNTR S/SS/LS) in interaction with family conflict and sexual abuse were associated with the highest delinquency scores. The genetic variants previously shown to confer vulnerability for delinquency (BDNF Val66Met Val/Met × 5-HTTLPR S × MAOA-uVNTR S) were associated with the lowest delinquency scores in interaction with a positive child-parent relationship.

CONCLUSIONS

Functional variants of the MAOA-uVNTR, 5-HTTLPR, and BDNF Val66Met, either alone or in interaction with each other, may be best conceptualized as modifying sensitivity to environmental factors that confer either risk or protection for teenage delinquency.

Association between smoking, nicotine dependence, and BDNF Val66Met polymorphism with BDNF concentrations in serum

INTRODUCTION

Nicotine use is associated with the upregulation of brain-derived neurotrophic factor (BDNF) in serum. An association between smoking and the BDNF Val(66)Met polymorphism has also been found. The aim of this study is to examine the levels of serum BDNF in never-smokers, former smokers, and current smokers-with and without nicotine dependence-and to examine the interaction of the polymorphism and smoking status with serum BDNF.

METHODS

We used baseline serum and gene data of BDNF on 2,088 participants from the Netherlands Study of Depression and Anxiety (NESDA) to investigate smoking-BDNF association while controlling for potential confounding variables. Nicotine dependence was assessed with the Fagerstrom Test for Nicotine Dependence (FTND).

RESULTS

Smokers with and without nicotine dependence had higher levels of serum BDNF than former and never-smokers. Nicotine dependence and number of cigarettes smoked per day did not add to the prediction of serum BDNF; however, total number of smoking years was a significant predictor of serum BDNF. There was no association of BDNF Val(66)Met, nor an interaction of this polymorphism and smoking status, with serum BDNF.

CONCLUSIONS

Current smoking and higher number of smoking years are associated with higher levels of serum BDNF, and this is independent of the BDNF genotype. Nicotine dependence itself is not associated with a further increase or decrease of serum BDNF. Longitudinal investigations that address changes in serum BDNF in incident smokers and/or in quitters may be useful to understand the association of smoking with BDNF.

Effect of variation in BDNF Val(66)Met polymorphism, smoking, and nicotine dependence on symptom severity of depressive and anxiety disorders

BACKGROUND

Smoking, especially nicotine dependence is associated with more severe symptoms of depression and anxiety disorders. However, the mechanisms underlying this association are unclear. We investigated the effect of brain-derived neurotrophic factor (BDNF) Val(66)Met polymorphism on the severity of depressive and anxiety symptoms in never-smokers, former smokers, non-dependent, and nicotine-dependent smokers with a current diagnosis of depression and/or anxiety.

METHODS

Patients with depressive or anxiety disorders and with available BDNF Val(66)Met polymorphism data (N=1271) were selected from Netherlands Study of Depression and Anxiety (NESDA). Dependent variables were severity of symptoms. Independent variables were smoking status and BDNF genotype. Age, sex, education, recent negative life events, alcohol use, body mass index, and physical activity were treated as covariates.

RESULTS

After controlling for covariates, nicotine-dependent smokers had more severe depressive symptoms than non-dependent smokers, former and never-smokers. The latter three groups did not differ in severity of depression. In Val(66)Val carriers, nicotine-dependent smokers had more severe symptoms of depression and anxiety than the other three groups, which were comparable in symptom severity. In Met(66) carriers, there were no group differences on severity of depression and anxiety. Nicotine dependence was the strongest predictor of severity of symptoms only in Val(66)Val carriers.

CONCLUSIONS

In patients with a current diagnosis of depression or anxiety, the relationship between nicotine dependence and symptom severity may be moderated by BDNF Val(66)Met. These results suggest that inherent genetic differences may be crucial for the worse behavioral outcome of nicotine, and that Val(66)Val carriers may benefit most in mental health from smoking cessation.

BDNF Val66Met and reward-related brain function in adolescents: role for early alcohol consumption

Changes in reward processing have been identified as one important pathogenetic mechanism in alcohol addiction. The nonsynonymous single nucleotide polymorphism in the brain-derived neurotrophic factor (BDNF) gene (rs6265/Val66Met) modulates the central nervous system activity of neurotransmitters involved in reward processing such as serotonin, dopamine, and glutamate. It was identified as crucial for alcohol consumption in healthy adults and, in rats, specifically related to the function in the striatum, a region that is commonly involved in reward processing. However, studies in humans on the association of BDNF Val66Met and reward-related brain functions and its role for alcohol consumption, a significant predictor of later alcohol addiction, are missing. Based on an intermediate phenotype approach, we assessed the early orientation toward alcohol and alcohol consumption in 530 healthy adolescents that underwent a monetary incentive delay task during functional magnetic resonance imaging. We found a significantly lower response in the putamen to reward anticipation in adolescent Met carriers with high versus low levels of alcohol consumption. During reward feedback, Met carriers with low putamen reactivity were significantly more likely to orient toward alcohol and to drink alcohol 2 years later. This study indicates a possible effect of BDNF Val66Met on alcohol addiction-related phenotypes in adolescence.

Preliminary study of anxiety symptoms, family dysfunction, and the brain-derived neurotrophic factor (BDNF) Val66Met genotype in offspring of parents with bipolar disorder

Several genetic and environmental factors place youth offspring of parents with bipolar disorder (BD) at high risk for developing mood and anxiety disorders. Recent studies suggest that anxiety symptoms, even at subclinical levels, have been associated with an increased risk for developing BD. The brain-derived neurotrophic factor (BDNF) gene has been implicated in the pathophysiology of both BD and anxiety disorders. We aimed to explore whether anxiety in BD offspring was associated with the BDNF Val66Met polymorphism. 64 BD offspring (mean age: 13.73 (S.D. 3.45) M = 30, F = 34) and 51 HC (mean age: 13.68 (S.D. 2.68) M = 23, F = 28) were compared on presence of the met allele and on scores from the Multidimensional Anxiety Scale for Children (MASC). To assess family function, we used the Family Adaptability and Cohesion Evaluation Scales (FACES-IV). The Baron & Kenny method was the statistical approach used to examine the moderating effects between variables. BD offspring showed higher levels of overall anxiety than did the HC group. BD offspring with the val/val genotype showed higher levels of anxiety than BD offspring with other genotypes. No significant levels of anxiety or its association with BDNF genotype were found in the HC group. BD offspring group showed significantly more family dysfunction when compared with the HC group and the family dysfunction moderated the association between the BDNF genotype and anxiety symptoms. This study demonstrated the potential interplay of three factors: BD offspring, anxiety symptoms and family dysfunction.

Brain derived neurotrophic factor gene (BDNF) and personality traits: the modifying effect of season of birth and sex

Personality traits are complex phenotypes influenced by interactions of multiple genetic variants of small effect and environmental factors. It has been suggested that the brain derived neurotrophic factor gene (BDNF) is involved in personality traits. Season of birth (SOB) has also been shown to affect personality traits due to its influences on brain development during prenatal and early postnatal periods. The present study aimed to investigate the effects of BDNF on personality traits; and the modifying effects of SOB and sex on associations between BDNF and personality traits. A sample of 1018 young adults (68% women; age range 17-25years) of Caucasian origin from the Russian Federation was assessed on personality traits (Novelty Seeking, Harm Avoidance, Reward Dependence, Persistence, Self-directedness, Cooperativeness, Self-transcendence) with the Temperament and Character Inventory-125 (TCI-125). Associations between personality traits and 12 BDNF SNPs were tested using linear regression models. The present study demonstrated the effect of rs11030102 on Persistence in females only (PFDR=0.043; r(2)=1.3%). There were significant interaction effects between Val66Met (rs6265) and SOB (PFDR=0.048, r(2)=1.4%), and between rs2030323 and SOB (PFDR=0.042, r(2)=1.3%), on Harm Avoidance. Our findings provide evidence for the modifying effect of SOB on the association between BDNF and Harm Avoidance, and for the modifying effect of sex on the association between BDNF and Persistence.

A functional polymorphism in the HTR2C gene associated with stress responses: a validation study

Previously we have shown that a functional nonsynonymous single nucleotide polymorphism (SNP), rs6318 on the HTR2C gene located on the X-chromosome, is associated with hypothalamic-pituitary-adrenal axis response to a laboratory stress recall task. The present paper reports a validation of the cortisol response to stress in a second, independent sample. The study population consisted of 60 adult participants (73.3% males). Consistent with our prior findings, compared to Cys23 G allele carriers, persons homozygous for the Ser23C allele had a significantly greater average cortisol response (p=0.007) and area under the curve (p=0.021) over the course of an emotional stress recall protocol. Also parallel to our prior report, the change in cortisol from baseline to the average during the stress protocol was roughly twice as large among Ser23C homozygotes than among persons with Cys23 G. These findings validate our initial observation of association between rs6318 and cortisol response to an acute stressor, and extend the results to include females.

Influence of the BDNF Val66Met polymorphism on coping response to stress in patients with advanced gastric cancer

OBJECTIVE

Coping with cancer is an important determinant of psychological morbidity, quality of life, and treatment adherence in cancer patients. The aim of this study was to elucidate the association between the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and coping response to stress in patients diagnosed with advanced gastric cancer.

METHODS

Ninety-one subjects (60 males, 31 females) recently diagnosed with advanced gastric cancer were recruited. Coping style and distress level were examined using the Mini-Mental Adjustment to Cancer (Mini-MAC) scale and Hospital Anxiety and Depression Scale, and genotyping was evaluated. To examine the temporal stability of the Mini-MAC scores, a 6-week follow-up evaluation was conducted in 72 patients, after completion of two chemotherapy cycles.

RESULTS

Coping style to cancer significantly differed between the Met carriers of BDNF Val66Met and the Val/Val homozygotes. The Met carriers were significantly more anxious than the Val/Val homozygotes.

CONCLUSION

The present findings suggest that the BDNF Val66Met polymorphism may be involved in individual coping responses to cancer. The Met allele of BDNF Val66Met may be predictive of an anxious coping style in patients with advanced cancer.

Translational findings on brain-derived neurotrophic factor and anxiety: contributions from basic research to clinical practice

BACKGROUND/AIMS

Anxious responses are evolutionarily adaptive, but excessive fear can become disabling and lead to anxiety disorders. Translational models of anxiety might be useful sources for understanding the neurobiology of fear and anxiety and can contribute to future proposals of therapeutic intervention for the disorders studied. Brain-derived neurotrophic factor (BDNF), which is known for its importance on neuroplasticity and contextual memory, has emerged as a relevant element for emotional memory. Recent studies show that the Val(66)Met BDNF polymorphism correlates with various psychiatric disorders, including anxiety, but there are several differences between experimental and clinical studies.

METHODS

In this work, we review the literature focused on the BDNF Val(66)Met polymorphism and anxiety, and discuss biological findings from animal models to clinical studies.

RESULTS

As occurs with other psychiatric disorders, anxiety correlates with anatomical, behavioral and physiological changes related to the BDNF polymorphism. In animal studies, it has been shown that a significant decrease in regulated secretion from both BDNFVal/Met and BDNFMet/Met neurons represented a significant decrease in available BDNF.

CONCLUSION

These studies suggest that developing pharmacological strategies facilitating the release of BDNF from synapses or prolongation of the half-life of secreted BDNF may improve the therapeutic responses of humans expressing the BDNF polymorphism.

Valence-specific effects of BDNF Val66Met polymorphism on dopaminergic stress and reward processing in humans

Brain-derived neurotrophic factor (BDNF) levels in dopaminergic (DA) cells within the ventral tegmental area (VTA)/nucleus accumbens (NAc) circuitry appear to be a candidate mechanism for the neuroadaptive changes that follow stress and reward responses in animal models. However, the role of the BDNF gene variants in responses to salient cues through DA neurotransmission in humans remains unexplored. Here, we studied the effect of the common functional BDNF Val(66)Met (rs6265) polymorphism on rewarding experiences in the striatum and DA-mediated responses to stress. Seventy-two healthy controls were genotyped for the BDNF Val(66)Met polymorphism and underwent the monetary incentive delay task during an functional magnetic resonance imaging (fMRI) session. Forty-nine of them also underwent a sustained pain challenge with and without placebo administration with potential analgesic properties during PET measures of DA D2/3-receptor-mediated neurotransmission. Neuroimaging results revealed a significant effect of BDNF (Met(66) carriers > Val/Val) on brain responses during the anticipation of monetary losses, baseline D2/3 receptor availability, and pain-stress-induced DA release in the NAc. Conversely, BDNF Met(66) carriers showed no activation in response to monetary gains and a blunted DA response to the analgesic placebo in the NAc. These results provide initial human evidence regarding the effect of the BDNF Val(66)Met polymorphism on DA-mediated responses to stress, its cognitive regulation by positive expectations, and the anticipatory responses to monetary gains and losses in the VTA-NAc pathway. Our results are of relevance to the neurobiology of stress and reward interactions and the pathophysiology of stress-related disorders.

Neuropeptide S and BDNF gene expression in the amygdala are influenced by social decision-making under stress

In a newly developed conceptual model of stressful social decision-making, the Stress-Alternatives Model (SAM; used for the 1st time in mice) elicits two types of response: escape or remain submissively. Daily (4d) aggressive social interaction in a neutral arena between a C57BL6/N test mouse and a larger, novel aggressive CD1 mouse, begin after an audible tone (conditioned stimulus; CS). Although escape holes (only large enough for smaller test animals) are available, and the aggressor is unremittingly antagonistic, only half of the mice tested utilize the possibility of escape. During training, for mice that choose to leave the arena and social interaction, latency to escape dramatically decreases over time; this is also true for control C57BL6/N mice which experienced no aggression. Therefore, the open field of the SAM apparatus is intrinsically anxiogenic. It also means that submission to the aggressor is chosen despite this anxiety and the high intensity of the aggressive attacks and defeat. While both groups that received aggression displayed stress responsiveness, corticosterone levels were significantly higher in animals that chose submissive coexistence. Although both escaping and non-escaping groups of animals experienced aggression and defeat, submissive animals also exhibited classic fear conditioning, freezing in response to the CS alone, while escaping animals did not. In the basolateral amygdala (BLA), gene expression of brain-derived neurotrophic factor (BDNF) was diminished, at the same time neuropeptide S (NPS) expression was significantly elevated, but only in submissive animals. This increase in submission-evoked NPS mRNA expression was greatest in the central amygdala (CeA), which coincided with decreased BDNF expression. Reduced expression of BDNF was only found in submissive animals that also exhibit elevated NPS expression, despite elevated corticosterone in all socially interacting animals. The results suggest an interwoven relationship, linked by social context, between amygdalar BDNF, NPS and plasma corticosterone.

Gene Effects and G × E Interactions in the Differential Prediction of Three Aspects of Impulsiveness

Several polymorphisms relevant to dopamine and serotonin have been identified as potential contributors to individual differences in impulsivity versus self-control. Because impulsivity is a multifaceted construct, a need remains to examine more closely how various genes relate to different aspects of impulsivity. We examined four dopamine-related polymorphisms and the serotonin transporter as predictors of three aspects of impulsivity, two bearing on impulsive reactions to emotions and one on difficulty in completing intended actions. Early adversity was also examined as a potentiator of genetic effects. Undergraduates completed measures of impulsivity and early adversity and were genotyped. COMT, BDNF, DRD4, and 5HTTLPR (the latter two in interaction with early adversity) made independent contributions to prediction of Pervasive Influence of Feelings. BDNF made a contribution to Lack of Follow-Through. ANKK1 and 5HTTLPR (both in interaction with early adversity) made independent contributions to Feelings Trigger Action. Thus, five polymorphisms contributed to predicting impulsivity, but different polymorphisms related to different aspects.

The Association Between Peer and own Aggression is Moderated by the BDNF Val-met Polymorphism

Peer antisocial behavior robustly predicts adolescents' own behavior but not all adolescents are equally vulnerable to their peers' influence and genetic factors may confer vulnerability. This study used data of n = 3081 adolescents from the Avon Longitudinal Study of Parents and Children (ALSPAC) to examine whether BDNF, a polymorphism that affects psychological functioning, moderates the association between affiliation with aggressive peers at age 10 and own aggression at age 15. A significant gene-environment interaction was found, where those who affiliated with aggressive peers in childhood showed increased risk for being aggressive in adolescence if they carried the BDNF met-met variant compared to val-val carriers. Our findings underline the importance of both biological and social factors for adolescent development.

Reversal of deficits in dendritic spines, BDNF and Arc expression in the amygdala during alcohol dependence by HDAC inhibitor treatment

Development of anxiety-like behaviours during ethanol withdrawal has been correlated with increased histone deacetylase (HDAC) activity and decreased brain-derived neurotrophic factor (BDNF) and activity-regulated cytoskeleton-associated protein (Arc) gene expression in the amygdala. Furthermore, HDAC-mediated histone modifications play a role in synaptic plasticity. In this study we used the HDAC inhibitor trichostatin A (TSA) to determine whether HDAC inhibition could prevent ethanol withdrawal-induced deficits in dendritic spine density (DSD), BDNF or Arc expression in the amygdala of rats. It was found that decreased BDNF and Arc expression in the central (CeA) and medial nucleus of amygdala (MeA), observed during withdrawal after chronic ethanol exposure, were normalized following acute TSA treatment. TSA treatment was also able to attenuate anxiety-like behaviours during ethanol withdrawal and correct the observed decrease in DSD in the CeA and MeA of ethanol-withdrawn rats. Taken together, these findings demonstrate that correcting the deficits in histone acetylation through TSA treatment also amends downstream synaptic plasticity-related deficits such as BDNF and Arc expression, and DSD in the CeA and MeA as well as attenuates anxiety-like behaviours in rats during withdrawal after chronic ethanol exposure.

Transcriptome profiling analysis of the mechanisms underlying the BDNF Val66Met polymorphism induced dysfunctions of the central nervous system

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism affects postnatal behaviors and is associated with a variety of neuropsychiatric disorders. However, the mechanisms underlying the BDNF(Met) variant induced dysfunctions of the central nervous system remain obscure. In order to identify the candidate genes and pathways responsible for the dysfunctions associated with this BDNF variation, we analyzed the expression of genes in the hippocampus, prefrontal cortex, and amygdala of the BDNF(Met) variant mice in comparison with the wild-type mice using Illumina bead microarray. Transcriptome profiling analysis revealed region-distinctive and gene-dose dependent changes of gene expression associated with the BDNF(Met) variant. BDNF(Met) variant mice exhibited altered expression of genes associated with translational machinery, neuronal plasticity and mitochondrial function based on the gene ontology (GO) annotation. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that the chemokine, cell adhesion, ubiquitin-proteosome and wnt signaling pathways were altered in the BDNF(Met) variant mice brain. Finally, the CX3CL1/CX3CR1 signaling was identified to be impaired in the hippocampus and microinjection of CX3CL1 into the hippocampus could rescue the hippocampal dependent memory deficits in BDNF(Met/Met) mice, indicating that CX3CL1 may be an effective treatment option for memory disorders in humans with this genetic BDNF variation. These findings will help us further understanding the molecular mechanisms involved in the BDNF(Met) associated behavior and neuroanatomy alternations.

Gender-specific effects of brain-derived neurotrophic factor Val66Met polymorphism and childhood maltreatment on anxiety

BACKGROUND

Although the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is thought to play an important role in the pathophysiology of anxiety, studies on the association between the BDNF polymorphism and anxiety have reported inconsistent results. As possible confounders in determining anxiety, childhood maltreatment and gender as well as their interactions with BDNF polymorphism have been suggested. This study examined the effect of BDNF genotype, childhood maltreatment, and their interaction on anxiety levels by gender.

METHODS

A total of 206 unrelated Korean healthy young adults (108 were male and the mean age was 23.1 ± 3.2 years) were genotyped for the BDNFVal66Met polymorphism. Measures for anxiety and childhood maltreatment were completed. The main and interaction effects of BDNF polymorphism and childhood maltreatment on anxiety were analyzed by general linear models in all subjects and then in gender-stratified groups.

RESULTS

Gender-specific analyses revealed that the interaction effect was significant only in males (p = 0.014). Interestingly, male subjects with the Val/Met genotype tended to be resilient against the increased anxiety after childhood maltreatment. In females, the main effects of both BDNF genotype and childhood maltreatment were significant (p = 0.024 and p = 0.009, respectively) and post-hoc analysis revealed that the Val/Val genotype was associated with a higher anxiety than the Met/Met genotype (p = 0.004).

CONCLUSIONS

Our results support the interaction effect between the BDNFVal66Met polymorphism and childhood maltreatment in determining anxiety and further emphasize the possible moderating role of gender in this gene-environment interaction.

Estrogen and the prefrontal cortex: towards a new understanding of estrogen's effects on executive functions in the menopause transition

Midlife decline in cognition, specifically in areas of executive functioning, is a frequent concern for which menopausal women seek clinical intervention. The dependence of executive processes on prefrontal cortex function suggests estrogen effects on this brain region may be key in identifying the sources of this decline. Recent evidence from rodent, nonhuman primate, and human subject studies indicates the importance of considering interactions of estrogen with neurotransmitter systems, stress, genotype, and individual life events when determining the cognitive effects of menopause and estrogen therapy.

On the biology of technostress

Despite the fact that human society has greatly benefited from the availability of information and communication technologies (ICT), both the use and ubiquity of ICT may also have a "dark side." Direct human interaction with ICT, as well as perceptions, emotions, and thoughts regarding the implementation of ICT in organizations and its pervasiveness in society in general, may lead to notable stress perceptions--a type of stress referred to as technostress. Analysis of the information systems (IS) literature reveals that technostress has hardly been addressed from a biological perspective. This is problematic, because biology not only provides objective measurements, but also, to a notable degree, determines human behavior toward ICT. Most important, biological measures (e.g., stress hormone levels, cardiovascular activity) are crucial predictors of human health, making them an indispensable complement to self-reports on stress perceptions. Against this background, the present article reviews the technostress research based on biological approaches that has been published in various disciplines such as human-computer interaction, medicine, biological psychology, and ergonomics. With the goal of developing a "big-picture" view of technostress and biology, this article integrates a body of highly fragmented work. The review reveals significant negative biological effects that develop from human interaction with ICT (e.g., increased activity of the cardiovascular system, or elevated levels of stress hormones such as adrenaline and cortisol). However, the review also indicates that countermeasures, which may positively affect biological parameters (e.g., reduced levels of stress hormones), do exist. Drawing on the literature review, this article also specifies a research agenda for future technostress research. The agenda is organized along three themes (theory and methods, design science and engineering, health and coping strategies), and proposes fifteen research questions (topics) that can be addressed in future investigations.

Associations between parenting behavior and anxiety in a rodent model and a clinical sample: relationship to peripheral BDNF levels

Adverse early-life environment is associated with anxiety-like behaviors and disorders. Brain-derived neurotrophic factor (BDNF) is sensitive to this environment and could be a marker of underlying brain changes. We aimed at evaluating the development of anxiety-like behaviors in a rat model of early adversity, as well as the possible association with BDNF levels. Similar associations were investigated in a sample of adolescent humans. For the rat study, Wistar rat litters were divided into: early-life stress (ELS, limited access to nesting material) and control groups. Maternal behavior was observed from days 1 to 9 of life and, as adults, rats were subjected to behavioral testing and BDNF measurements in plasma, hippocampus, amygdala and periaqueductal gray. For the human study, 129 adolescents were evaluated for anxiety symptoms and perceived parental care. Serum BDNF levels and the Val66Met polymorphism of the BDNF gene were investigated. We found that ELS dams showed more pure contact, that is, contact with low care and high control, toward pups, and their adult offspring demonstrated higher anxiety-like behaviors and plasma BDNF. Also the pure contact correlated positively with adult peripheral BDNF. Similarly in humans, there was a positive correlation between maternal overprotection and serum BDNF only in Met carriers. We also found negative correlations between maternal warmth and separation anxiety, social phobia and school phobia. Finally, our translational approach revealed that ELS, mediated through variations in maternal care, is associated with anxiety in both rats and humans and increased peripheral BDNF may be marking these phenomena.

Epigenetic alterations related to early-life stressful events

Objective: Early stress events severely impact brain and behaviour. From a neurobiological point of view early stress influences neuroanatomical structures and is associated with a dysregulation of the hypothalamic-pituitary-adrenal axis. The objective of this article is to review the epigenetic alterations implicated in brain adaptation to early stress events.

Method: A review of empirical research of epigenetic alterations associated to early stress events was performed.

Results: Neuroanatomic and epigenetic alterations have been observed after early stress events. Epigenetics alterations include DNA methylation, histones modifications and microRNA (miRNA) expression. The most studied is largely the former, affecting genes involved in neuroendocrine, neurotransmission and neuroplasticity regulation after early stress exposition. It includes glucocorticoid receptor, FK506-binding protein 5, arginine vasopressin, oestrogen receptor alpha, 5-hydroxy-tryptamine transporter and brain-derived neurotrophic factor.

Conclusion: Epigenetic regulation is critical in the interplay between nature and nurture. Alterations in the DNA methylation as well as histones modifications and miRNA expression patterns could explain abnormal behaviours secondary to early stress events.

Children under stress - COMT genotype and stressful life events predict cortisol increase in an acute social stress paradigm

Dopamine and norepinephrine are key regulators of cognitive and affective processes. The enzyme catechol-O-methyltransferase (COMT) catabolizes catecholamines and the COMT Val158Met polymorphism has been linked to several neuropsychiatric variables. Additionally, stressful life events (SLEs) contribute substantially to affective processes. We used the stress-induced activation of the hypothalamic-pituitary-adrenal axis to investigate the effects of COMT and SLEs on the cortisol response in 119 healthy children (8-12 yr). Saliva cortisol was measured during and after the Trier Social Stress Test for Children. SLEs were assessed with a standardized interview with one of the children's parents. Linear regression analysis revealed a significant effect for COMT, with Met allele carriers showing a higher cortisol response (β=0.300, p=0.001). In turn, more SLEs lead to a less pronounced cortisol increase (β=-0.192, p=0.029) probably indicating increased resilience. Our results further underscore the essential and differential role of genetic variation and environmental factors on stress responsivity.

Alterations in grooming activity and syntax in heterozygous SERT and BDNF knockout mice: the utility of behavior-recognition tools to characterize mutant mouse phenotypes

Serotonin transporter (SERT) and brain-derived neurotrophic factor (BDNF) are key modulators of molecular signaling, cognition and behavior. Although SERT and BDNF mutant mouse phenotypes have been extensively characterized, little is known about their self-grooming behavior. Grooming represents an important behavioral domain sensitive to environmental stimuli and is increasingly used as a model for repetitive behavioral syndromes, such as autism and attention deficit/hyperactivity disorder. The present study used heterozygous ((+/-)) SERT and BDNF male mutant mice on a C57BL/6J background and assessed their spontaneous self-grooming behavior applying both manual and automated techniques. Overall, SERT(+/-) mice displayed a general increase in grooming behavior, as indicated by more grooming bouts and more transitions between specific grooming stages. SERT(+/-) mice also aborted more grooming bouts, but showed generally unaltered activity levels in the observation chamber. In contrast, BDNF(+/-) mice displayed a global reduction in grooming activity, with fewer bouts and transitions between specific grooming stages, altered grooming syntax, as well as hypolocomotion and increased turning behavior. Finally, grooming data collected by manual and automated methods (HomeCageScan) significantly correlated in our experiments, confirming the utility of automated high-throughput quantification of grooming behaviors in various genetic mouse models with increased or decreased grooming phenotypes. Taken together, these findings indicate that mouse self-grooming behavior is a reliable behavioral biomarker of genetic deficits in SERT and BDNF pathways, and can be reliably measured using automated behavior-recognition technology.

Possible involvement of brain-derived neurotrophic factor in eating disorders

Eating disorders (EDs) manifest as abnormal patterns of eating behavior and weight regulation driven by low self-esteem due to weight preoccupation and perceptions toward body weight and shape. Two major groups of such disorders are anorexia nervosa (AN) and bulimia nervosa (BN). The etiology of EDs is complex and evidence indicates that both biological/genetic and psychosocial factors are involved. Several lines of evidence indicate that brain-derived neurotrophic factor (BDNF) plays a critical role in regulating eating behaviors and cognitive impairments in the EDs. BDNF is involved in neuronal proliferation, differentiation, and survival during development. BDNF and its tyrosine kinase receptor (TrkB) are expressed in hypothalamic nuclei associated with eating behaviors. A series of studies using BDNF knockout mice and the human BDNF gene indicate an association of BDNF and EDs with predisposition and vulnerability. In the previous studies, serum BDNF levels in subjects with EDs are reduced significantly compared with healthy controls, hence, we proposed that levels of serum BDNF would be a useful diagnostic indicator for EDs.

Contrasting hippocampal and amygdalar expression of genes related to neural plasticity during escape from social aggression

Social subjugation has widespread consequences affecting behavior and underlying neural systems. We hypothesized that individual differences in stress responsiveness were associated with differential expression of neurotrophin associated genes within the hippocampus and amygdala. To do this we examined the brains of hamsters placed in resident/intruder interactions, modified by the opportunity to escape from aggression. In the amygdala, aggressive social interaction stimulated increased BDNF receptor TrK(B) mRNA levels regardless of the ability to escape the aggressor. In contrast, the availability of escape limited the elevation of GluR(1) AMPA subunit mRNA. In the hippocampal CA(1), the glucocorticoid stress hormone, cortisol, was negatively correlated with BDNF and TrK(B) gene expression, but showed a positive correlation with BDNF expression in the DG. Latency to escape the aggressor was also negatively correlated with CA(1) BDNF expression. In contrast, the relationship between amygdalar TrK(B) and GluR(1) was positive with respect to escape latency. These results suggest that an interplay of stress and neurotrophic systems influences learned escape behavior. Animals which escape faster seem to have a more robust neurotrophic profile in the hippocampus, with the opposite of this pattern in the amygdala. We propose that changes in the equilibrium of hippocampal and amygdalar learning result in differing behavioral stress coping choices.

Enhanced extinction of cocaine seeking in brain-derived neurotrophic factor Val66Met knock-in mice

The Val66Met polymorphism in the brain-derived neurotropic factor (BDNF) gene results in alterations in fear extinction behavior in both human populations and mouse models. However, it is not clear whether this polymorphism plays a similar role in extinction of appetitive behaviors. Therefore, we examined operant learning and extinction of both food and cocaine self-administration behavior in an inbred genetic knock-in mouse strain expressing the variant Bdnf. These mice provide a unique opportunity to relate alterations in aversive and appetitive extinction learning as well as provide insight into how human genetic variation can lead to differences in behavior. BDNF(Met/Met) mice exhibited a severe deficit in operant learning as demonstrated by an inability to learn the food self-administration task. Therefore, extinction experiments were performed comparing wildtype (BDNF(Val/Val) ) animals to mice heterozygous for the Met allele (BDNF(Val/Met) ), which did not differ in food or cocaine self-administration behavior. In contrast to the deficit in fear extinction previously demonstrated in these mice, we found that BDNF(Val/Met) mice exhibited more rapid extinction of cocaine responding compared to wildtype mice. No differences were found between the genotypes in the extinction of food self-administration behavior or the reinstatement of cocaine seeking, indicating that the effect is specific to extinction of cocaine responding. These results suggest that the molecular mechanisms underlying aversive and appetitive extinction are distinct from one another and BDNF may play opposing roles in the two phenomena.

Stress and the HPA axis: role of glucocorticoids in alcohol dependence

Stress has long been suggested to be an important correlate of uncontrolled drinking and relapse. An important hormonal response system to stress-the hypothalamic-pituitary-adrenal (HPA) axis-may be involved in this process, particularly stress hormones known as glucocorticoids and primarily cortisol. The actions of this hormone system normally are tightly regulated to ensure that the body can respond quickly to stressful events and return to a normal state just as rapidly. The main determinants of HPA axis activity are genetic background, early-life environment, and current life stress. Alterations in HPA axis regulation are associated with problematic alcohol use and dependence; however, the nature of this dysregulation appears to vary with respect to stage of alcohol dependence. Much of this research has focused specifically on the role of cortisol in the risk for, development of, and relapse to chronic alcohol use. These studies found that cortisol can interact with the brain's reward system, which may contribute to alcohol's reinforcing effects. Cortisol also can influence a person's cognitive processes, promoting habit-based learning, which may contribute to habit formation and risk of relapse. Finally, cortisol levels during abstinence may be useful clinical indicators of relapse vulnerability in alcohol-dependent people.

Genetic Modulation of Training and Transfer in Older Adults: BDNF ValMet Polymorphism is Associated with Wider Useful Field of View

Western society has an increasing proportion of older adults. Increasing age is associated with a general decrease in the control over task-relevant mental processes. In the present study we investigated the possibility that successful transfer of game-based cognitive improvements to untrained tasks in elderly people is modulated by preexisting neuro-developmental factors as genetic variability related to levels of the brain-derived neurotrophic factor (BDNF), an important neuromodulator underlying cognitive processes. We trained participants, genotyped for the BDNF Val⁶⁶Met polymorphism, on cognitive tasks developed to improve dynamic attention. Pre-training (baseline) and post-training measures of attentional processes (divided and selective attention) were acquired by means of the useful field of view task. As expected, Val/Val homozygous individuals showed larger beneficial transfer effects than Met/-carriers. Our findings support the idea that genetic predisposition modulates transfer effects.

The contribution of imaging genetics to the development of predictive markers for addictions

A key challenge for intervention and prevention of addictions is the identification of genetic, neurobiological and cognitive risk profiles that can predict which adolescents are at risk for addiction. Abnormalities in reinforcement behaviour have been linked to addiction vulnerability and imaging genetic studies have begun to elucidate the mechanisms by which genetic and environmental factors influence brain function underlying individual variability in reinforcement behaviour. Most studies have examined associations between a few well-characterised candidate polymorphisms and task-related brain activation differences in individual regions of interest. Here we propose that integrating the imaging genetic strategy with biological network approaches and longitudinal adolescent designs in large multi-centre samples may offer promising opportunities to identify risk markers for early diagnosis, progression and prediction of addictions.