Interactions between BDNF Val66Met polymorphism and early life stress predict brain and arousal pathways to syndromal depression and anxiety

Depressive Emotionality Moderates the Influence of the BDNF Val66Met Polymorphism on Executive Functions and on Unconscious Semantic Priming

Automatic semantic processing can be assessed using semantic priming paradigms. Individual differences in semantic priming have been associated with differences in executive functions. The brain-derived neurotrophic factor (BDNF) Val66Met (substitution of valine (Val) to methionine (Met) at codon 66) polymorphism has been shown to be associated with executive functions as well as depression. Depression-associated variables such as depressed mood also moderated the relationship between BDNF Val66Met and executive functions in previous work. In this study, we therefore aimed at investigating whether BDNF Val66Met genotype modulates masked and unmasked semantic priming as well as executive functions and whether sadness is a moderator of these associations. We collected data of N = 155 participants measuring reaction times (RTs) as well as error rates (ERs) in masked and unmasked semantic priming paradigms using a lexical decision task. We assessed the primary emotion of SADNESS using the Affective Neuroscience Personality Scale (ANPS) and working memory using digit span forward and backward tasks. Met+ carriers showed reduced RT priming and increased ER priming in the masked priming paradigm. Even though there was no direct association between BDNF Val66Met and executive functions, SADNESS significantly moderated the association between BDNF Val66Met and executive functions as well as masked RT priming. We suggest that Met+ individuals with low depressive tendencies have not only superior EF, but also a faster and more superficial processing style, compared with Val/Val homozygotes. However, in Met+ individuals, cognitive functioning exhibits a greater vulnerability to depressed emotionality compared with Val/Val homozygotes. Our study thus demonstrates how emotional and molecular genetic factors exert an interacting influence on higher-level cognition.

Effects of BDNF Val66Met polymorphisms on brain structures and behaviors in adolescents with conduct disorder

Accumulating evidence suggests that neural abnormalities in conduct disorder (CD) may be subject to genetic influences, but few imaging studies have taken genetic variants into consideration. The Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) has emerged as a high-interest genetic variant due to its importance in cortical maturation, and several studies have implicated its involvement in neurodevelopmental disorders. Thus, it is unclear how this polymorphism may influence brain anatomy and aberrant behaviors in CD. A total of 65 male adolescents with CD and 69 gender-, IQ- and socioeconomic status-matched healthy controls (HCs) (age range 13-17 years) were enrolled in this study. Analyses of variance (ANOVAs) were used to assess the main effects of CD diagnosis, BDNF genotype, and diagnosis-genotype interactions on brain anatomy and behaviors. We detected a significant main effect of BDNF genotype on temporal gyrification and antisocial behaviors, but not on CD symptoms. Diagnosis-genotype interactive effects were found for cortical thickness of the superior temporal and adjacent areas. These results suggest that the BDNF Val66Met polymorphism may exert its influence both on neural alterations and delinquent behaviors in CD patients. This initial evidence highlights the importance of elucidating potentially different pathways between BDNF genotype and cortical alterations or delinquent behaviors in CD patients.

Anger and Depression in Middle-Aged Men: Implications for a Clinical Diagnosis of Chronic Traumatic Encephalopathy

OBJECTIVE

In recent years, it has been proposed that problems with anger control and depression define clinical features of chronic traumatic encephalopathy (CTE). The authors examined anger problems and depression in middle-aged men from the general population and related those findings to the proposed clinical criteria for CTE.

METHODS

A sample of 166 community-dwelling men ages 40-60 was extracted from the normative database of the National Institutes of Health Toolbox. All participants denied prior head injury or traumatic brain injury (TBI). Participants completed scales assessing anger, hostility, aggression, anxiety, and depression.

RESULTS

In response to the item "I felt angry," 21.1% of men reported "sometimes," and 4.8% reported "often." When asked "If I am provoked enough I may hit another person," 11.4% endorsed the statement as true. There were moderate correlations between anger and anxiety (Spearman's ρ=0.61) and between depression and affective anger (ρ=0.51), hostility (ρ=0.56), and perceived hostility (ρ=0.35). Participants were dichotomized into a possible depression group (N=49) and a no-depression group (N=117) on the basis of the question "I feel depressed," specific to the past 7 days. The possible depression group reported higher anxiety (p<0.001, Cohen's d=1.51), anger (p<0.001, Cohen's d=0.96), and hostility (p<0.001, Cohen's d=0.95).

CONCLUSIONS

Some degree of anger and aggression are reported by a sizable minority of middle-aged men in the general population with no known history of TBI. Anger and hostility are correlated with depression and anxiety, indicating that all tend to co-occur. The base rates and comorbidity of affective dysregulation in men in the general population is important to consider when conceptualizing CTE phenotypes.

Natural Psychoplastogens As Antidepressant Agents

Increasing prevalence and burden of major depressive disorder presents an unavoidable problem for psychiatry. Existing antidepressants exert their effect only after several weeks of continuous treatment. In addition, their serious side effects and ineffectiveness in one-third of patients call for urgent action. Recent advances have given rise to the concept of psychoplastogens. These compounds are capable of fast structural and functional rearrangement of neural networks by targeting mechanisms previously implicated in the development of depression. Furthermore, evidence shows that they exert a potent acute and long-term positive effects, reaching beyond the treatment of psychiatric diseases. Several of them are naturally occurring compounds, such as psilocybin, N,N-dimethyltryptamine, and 7,8-dihydroxyflavone. Their pharmacology and effects in animal and human studies were discussed in this article.

Genetics of resilience: Implications from genome-wide association studies and candidate genes of the stress response system in posttraumatic stress disorder and depression

Resilience is the ability to cope with critical situations through the use of personal and socially mediated resources. Since a lack of resilience increases the risk of developing stress-related psychiatric disorders such as posttraumatic stress disorder (PTSD) and major depressive disorder (MDD), a better understanding of the biological background is of great value to provide better prevention and treatment options. Resilience is undeniably influenced by genetic factors, but very little is known about the exact underlying mechanisms. A recently published genome-wide association study (GWAS) on resilience has identified three new susceptibility loci, DCLK2, KLHL36, and SLC15A5. Further interesting results can be found in association analyses of gene variants of the stress response system, which is closely related to resilience, and PTSD and MDD. Several promising genes, such as the COMT (catechol-O-methyltransferase) gene, the serotonin transporter gene (SLC6A4), and neuropeptide Y (NPY) suggest gene × environment interaction between genetic variants, childhood adversity, and the occurrence of PTSD and MDD, indicating an impact of these genes on resilience. GWAS on PTSD and MDD provide another approach to identifying new disease-associated loci and, although the functional significance for disease development for most of these risk genes is still unknown, they are potential candidates due to the overlap of stress-related psychiatric disorders and resilience. In the future, it will be important for genetic studies to focus more on resilience than on pathological phenotypes, to develop reasonable concepts for measuring resilience, and to establish international cooperations to generate sufficiently large samples.

Neurotrophic mechanisms underlying the rapid and sustained antidepressant actions of ketamine

Clinical and preclinical studies have demonstrated that depression, one of the most common psychiatric illnesses, is associated with reduced levels of neurotrophic factors, including brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), contributing to neuronal atrophy in the prefrontal cortex (PFC) and hippocampus, and reduced hippocampal adult neurogenesis. Conventional monoaminergic antidepressants can block/reverse, at least partially, these deficits in part via induction of BDNF and/or VEGF, although these drugs have significant limitations, notably a time lag for therapeutic response and low response rates. Recent studies reveal that ketamine, an N-methyl-d-aspartate receptor antagonist produces rapid (within hours) and sustained (up to a week) antidepressant actions in both patients with treatment-resistant depression and rodent models of depression. Rodent studies also demonstrate that ketamine rapidly increases BDNF and VEGF release and/or expression in the medial PFC (mPFC) and hippocampus, leading to increase in the number and function of spine synapses in the mPFC and enhancement of hippocampal neurogenesis. These neurotrophic effects of ketamine are associated with the antidepressant effects of this drug. Together, these findings provide evidence for a neurotrophic mechanism underlying the rapid and sustained antidepressant actions of ketamine and pave the way for the development of rapid and more effective antidepressants with fewer side effects than ketamine.

The Devastating Clinical Consequences of Child Abuse and Neglect: Increased Disease Vulnerability and Poor Treatment Response in Mood Disorders

A large body of evidence has demonstrated that exposure to childhood maltreatment at any stage of development can have long-lasting consequences. It is associated with a marked increase in risk for psychiatric and medical disorders. This review summarizes the literature investigating the effects of childhood maltreatment on disease vulnerability for mood disorders, specifically summarizing cross-sectional and more recent longitudinal studies demonstrating that childhood maltreatment is more prevalent and is associated with increased risk for first mood episode, episode recurrence, greater comorbidities, and increased risk for suicidal ideation and attempts in individuals with mood disorders. It summarizes the persistent alterations associated with childhood maltreatment, including alterations in the hypothalamic-pituitary-adrenal axis and inflammatory cytokines, which may contribute to disease vulnerability and a more pernicious disease course. The authors discuss several candidate genes and environmental factors (for example, substance use) that may alter disease vulnerability and illness course and neurobiological associations that may mediate these relationships following childhood maltreatment. Studies provide insight into modifiable mechanisms and provide direction to improve both treatment and prevention strategies.

Role of BDNF in the pathophysiology and treatment of depression: Activity-dependent effects distinguish rapid-acting antidepressants

The pathophysiology and treatment of depression have been the focus of intense research and while there is much that remains unknown, modern neurobiological approaches are making progress. This work demonstrates that stress and depression are associated with atrophy of neurons and reduced synaptic connectivity in brain regions such as the hippocampus and prefrontal cortex that contribute to depressive behaviors, and conversely that antidepressant treatment can reverse these deficits. The role of neurotrophic factors, particularly brain-derived neurotrophic factor (BDNF), has been of particular interest as these factors play a key role in activity-dependent regulation of synaptic plasticity. Here, we review the literature demonstrating that exposure to stress and depression decreases BDNF expression in the hippocampus and PFC and conversely that antidepressant treatment can up-regulate BDNF in the adult brain and reverse the effects of stress. We then focus on rapid-acting antidepressants, particularly the NMDA receptor antagonist ketamine, which produces rapid synaptic and antidepressant behavioral actions that are dependent on activity-dependent release of BDNF. This rapid release of BDNF differs from typical monoaminergic agents that require chronic administration to produce a slow induction of BDNF expression, consistent with the time lag for the therapeutic action of these agents. We review evidence that other classes of rapid-acting agents also require BDNF release, demonstrating that this is a common, convergent downstream mechanism. Finally, we discuss evidence that the actions of ketamine are also dependent on another growth factor, vascular endothelial growth factor (VEGF) and its complex interplay with BDNF.

Association between fecal microbiota and generalized anxiety disorder: Severity and early treatment response

BACKGROUND

Associations between abnormal gut microbiome compositions and anxiety-like behaviors are well established. However, it is unknown whether the gut microbiome composition is associated with the severity of generalized anxiety disorder (GAD) and relief from clinical symptoms in patients.

METHODS

Stool samples from 36 patients with active GAD (A-GAD group) and 24 matched healthy control subjects (HC group) were analyzed by 16S rRNA gene sequencing. Anxiety was assessed with the Hamilton Anxiety Rating Scale and the Self-rating Anxiety Scale, and global assessments of functioning were performed at baseline and 1 month after drug treatment.

RESULTS

Gut microbiome compositions were altered in A-GAD patients, with fewer operational taxonomic units and lower fecal bacterial α-diversity. Specifically, Firmicutes and Tenericutes abundances were lower in A-GAD patients, and several genera were differentially represented in the A-GAD and HC groups. The abundances of Eubacterium_coprostanoligenes_group, Ruminococcaceae_UCG-014, and Prevotella_9 correlated negatively with the anxiety severity and positively with anxiety reduction, whereas the abundances of Bacteroides and Escherichia-Shigella were positively associated with anxiety severity. Sex, smoking, and alcohol intake influenced the gut microbiome composition.

LIMITATIONS

The sample sizes were small and the stool samples were collected only at baseline; therefore, a causal association between changes in intestinal flora and disease remission was not established. Moreover, the effects of different drugs on gut microbiome composition were not investigated.

CONCLUSIONS

Altered gut microbiome composition may contribute to GAD pathogenesis and remission.

Adverse Childhood Experiences and Amygdalar Reduction: High-Resolution Segmentation Reveals Associations With Subnuclei and Psychiatric Outcomes

The aim of the present study was 2-fold: (1) to utilize improved amygdala segmentation and exploratory factor analysis to characterize the latent volumetric structure among amygdala nuclei and (2) to assess the effect of adverse childhood experiences (ACEs) on amygdalar morphometry and current psychiatric symptoms. To investigate these aims, structural (T1) MRI and self-report data were obtained from 119 emerging adults. Regression analysis showed that higher ACE scores were related to reduced volume of the right, but not the left, amygdalar segments. Further, exploratory factor analysis yielded a two-factor structure, basolateral and central-medial nuclei of the right amygdala. Stractual equation modeling analyses revealed that higher ACE scores were significantly related to a reduced volume of the right basolateral and central-medial segments. Furthermore, reduction in the right basolateral amygdala was associated with increased anxiety, depressive symptoms, and alcohol use. This association supports an indirect effect between early adversity and psychiatric problems via reduced right basolateral amygdalar volume. The high-resolution segmentation results reveal a latent structure among amygdalar nuclei, which is consistent with prior work conducted in nonhuman mammals. These findings extend previous reports linking early adversity, right amygdala volume, and psychopathology.

Self-Reported Mild Traumatic Brain Injuries in Relation to Rumination and Depressive Symptoms: Moderating Role of Sex Differences and a Brain-Derived Neurotrophic Factor Gene Polymorphism

OBJECTIVE

Mild traumatic brain injuries (mTBIs) have frequently been associated with the emergence and persistence of depressive symptoms. However, the factors which contribute to the increased risk for depression after these head injuries remain unclear. Accordingly, we examined the relationship between frequency of self-reported mTBIs and current symptoms of depression and the mediating role of rumination and cognitive flexibility. We also examined whether these relations were moderated by sex differences and the presence of the Val66Met polymorphism in a gene coding for brain-derived neurotrophic factor (BDNF).

DESIGN

Retrospective, cross-sectional.

SETTING

Carleton University.

PARTICIPANTS

Two hundred nineteen Carleton University undergraduate students.

MAIN OUTCOME MEASURES

Cognitive flexibility as assessed by the Wisconsin Card Sorting Task (WCST); subtypes of rumination (Ruminative Response Scale; Treynor, Gonzalez, and Nolen-Hoeksema, 2003); depressive symptoms (Beck Depression Inventory; Beck, Ward, and Mendelson, 1961).

RESULTS

Greater frequency of self-reported mTBIs was associated with more frequent depressive rumination among women, but not men, which was accompanied by elevated current depressive symptoms. In addition, among Met allele carriers of the BDNF polymorphism, but not those who were Val homozygotes, greater frequency of mTBIs was related to higher levels of brooding, which was accompanied by heightened depressive symptoms. Brain-derived neurotrophic factor genotype also moderated the relationship between self-reported mTBIs and cognitive flexibility in that more frequent mTBIs were associated with more perseverative errors on the WCST among Met carriers, but not Val homozygotes.

CONCLUSIONS

The present findings raise the possibility that the evolution of depression after mTBIs may be dependant on a BDNF polymorphism and sex differences.

Early-life adversity and neurological disease: age-old questions and novel answers

Neurological illnesses, including cognitive impairment, memory decline and dementia, affect over 50 million people worldwide, imposing a substantial burden on individuals and society. These disorders arise from a combination of genetic, environmental and experiential factors, with the latter two factors having the greatest impact during sensitive periods in development. In this Review, we focus on the contribution of adverse early-life experiences to aberrant brain maturation, which might underlie vulnerability to cognitive brain disorders. Specifically, we draw on recent robust discoveries from diverse disciplines, encompassing human studies and experimental models. These discoveries suggest that early-life adversity, especially in the perinatal period, influences the maturation of brain circuits involved in cognition. Importantly, new findings suggest that fragmented and unpredictable environmental and parental signals comprise a novel potent type of adversity, which contributes to subsequent vulnerabilities to cognitive illnesses via mechanisms involving disordered maturation of brain 'wiring'.

Promising Neuroimaging Biomarkers in Depression

The neuroimaging has been applied in the study of pathophysiology in major depressive disorder (MDD). In this review article, several kinds of methodologies of neuroimaging would be discussed to summarize the promising biomarkers in MDD. For the magnetic resonance imaging (MRI) and magnetoencephalography field, the literature review showed the potentially promising roles of frontal lobes, such as anterior cingulate cortex (ACC), dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC). In addition, the limbic regions, such as hippocampus and amygdala, might be the potentially promising biomarkers for MDD. The structures and functions of ACC, DLPFC, OFC, amygdala and hippocampus might be confirmed as the biomarkers for the prediction of antidepressant treatment responses and for the pathophysiology of MDD. The functions of cognitive control and emotion regulation of these regions might be crucial for the establishment of biomarkers. The near-infrared spectroscopy studies demonstrated that blood flow in the frontal lobe, such as the DLPFC and OFC, might be the biomarkers for the field of near-infrared spectroscopy. The electroencephalography also supported the promising role of frontal regions, such as the ACC, DLPFC and OFC in the biomarker exploration, especially for the sleep electroencephalogram to detect biomarkers in MDD. The positron emission tomography (PET) and single-photon emission computed tomography (SPECT) in MDD demonstrated the promising biomarkers for the frontal and limbic regions, such as ACC, DLPFC and amygdala. However, additional findings in brainstem and midbrain were also found in PET and SPECT. The promising neuroimaging biomarkers of MDD seemed focused in the fronto-limbic regions.

Parenting Interacts With Plasticity Genes in Predicting Behavioral Outcomes in Preschoolers

BACKGROUND

Public health and pediatric nurses typically focus on supporting parenting to reduce the likelihood of children's behavioral problems. Studies have identified interactions between early exposures to stress in caregiving and child genotype in predicting children's behavioral problems, such that certain genotypes connote greater differential susceptibility or plasticity to environmental stressors. We sought to uncover the interaction between observational measures of parent-child relationship quality and genotype in predicting early-onset behavioral problems in 24-month-olds, using prospective methods.

METHODS

We conducted a secondary analysis of data collected on a subsample of 176 women and their infants enrolled during pregnancy in the ongoing Alberta Pregnancy Outcomes and Nutrition (APrON) cohort study. Inclusion criteria required mothers to be ≥18 years of age, English speaking and ≤22 weeks gestational age at enrollment. Genetic data were obtained from blood leukocytes and buccal epithelial cell samples, collected from infants at three months of age. For each child, the presence of plasticity alleles was determined for BDNF, CNR1, DRD2/ANKK1, DRD4, DAT1, 5-HTTLPR, and MAOA and an overall index was calculated to summarize the number of plasticity alleles present. Observational assessments of parent-child relationship quality (sensitivity, controlling, and unresponsiveness) were conducted at six months of age. Children's internalizing (e.g., emotionally reactive, anxious/depressed, somatic complaint, withdrawn) and externalizing (e.g., aggression, inattention) behaviors were assessed at 24 months of age. After extracting genetic data, a maximum likelihood method for regressions was employed with Akaike Information Criterion (AIC) for model selection.

RESULTS

When parents were less responsive and children possessed more plasticity alleles, children were more likely to be emotionally reactive, anxious/depressed, report somatic complaints, and withdrawn, while when parents were less responsive and children possessed fewer plasticity alleles, children were less likely to display these internalizing behaviors, in a differentially susceptible manner. Furthermore, when parents were more responsive, and children possessed more plasticity alleles, children were less likely to display internalizing behaviors (P = 0.034). Similarly, children who possessed either the CNR1-A plasticity allele (P = 0.010) or DAT1 9-repeat plasticity allele (P = 0.036) and experienced more/less parental control displayed more/fewer externalizing problems, respectively, in a differentially susceptible manner.

CONCLUSIONS

The plasticity index score interacted with parental unresponsiveness in predicting anxiety and depressive behavioral problems in children, while individual genetic variants interacted with parental controlling behavior in predicting aggression and inattention in children, suggestive of differential susceptibility to caregiving. Especially in the context of nursing interventions designed to support childrearing and children's development, nurses need to be aware of the interactions between child genotype and parenting in understanding how well interventions will work in promoting optimal child behavior.

Early Life Stress, Physiology, and Genetics: A Review

Early life stress (ELS) is a widely studied concept due to both its prevalent nature and its (presumed) detrimental consequences. In this review, we discuss the relationship between ELS and its underlying physiology spanning the sympathetic nervous system, hypothalamic-pituitary-adrenal axis, and markers of inflammation related to immune function in both human and animal literature. We also consider the potential role of genetic and epigenetic factors on the ELS-health outcome relationship. We conclude with recommendations to overcome identified shortcomings in a field that seeks to address the health consequences of ELS.

Future considerations for pediatric cancer survivorship: Translational perspectives from developmental neuroscience

Breakthroughs in modern medicine have increased pediatric cancer survival rates throughout the last several decades. Despite enhanced cure rates, a subset of pediatric cancer survivors exhibit life-long psychological side effects. A large body of work has addressed potential mechanisms for secondary symptoms of anxiety, post-traumatic stress, impaired emotion regulation and cognitive deficits in adults. Yet, absent from many studies are the ways in which cancer treatment can impact the developing brain. Additionally, it remains less known whether typical neurobiological changes during adolescence and early adulthood may potentially buffer or exacerbate some of the known negative cancer survivorship outcomes. This review highlights genetic, animal, and human neuroimaging research across development. We focus on the neural circuitry associated with aversive learning, which matures throughout childhood, adolescence and early adulthood. We argue that along with other individual differences, the precise timing of oncological treatment insults on such neural circuitry may expose particular vulnerabilities for pediatric cancer patients. We also explore other moderators of treatment outcomes, including genetic polymorphisms and neural mechanisms underlying memory and cognitive control. We discuss how neural maturation extending into young adulthood may also provide a sensitive period for intervention to improve psychological and cognitive outcomes in pediatric cancer survivors.

Stress, psychiatric disorders, molecular targets, and more

Mental health is central to normal health outcomes. A widely accepted theory is that chronic persistent stress during adulthood as well as during early life triggers onset of neuropsychiatric ailments. However, questions related to how that occurs, and why are some individuals resistant to stress while others are not, remain unanswered. An integrated, multisystemic stress response involving neuroinflammatory, neuroendocrine, epigenetic and metabolic cascades have been suggested to have causative links. Several theories have been proposed over the years to conceptualize this link including the cytokine hypothesis, the endocrine hypothesis, the oxidative stress hypothesis and the oxido-neuroinflammation hypothesis. The data discussed in this review describes potential biochemical basis of the link between stress, and stress-induced neuronal, behavioral and emotional deficits, providing insights into potentially novel drug targets.

Preventing epigenetic traces of caregiver maltreatment: A role for HDAC inhibition

Reorganization of the brain's epigenetic landscape occurs alongside early adversity in both human and non-human animals. Whether this reorganization is simply incidental to or is a causal mechanism of the behavioral abnormalities that result from early adversity is important to understand. Using the scarcity-adversity model of low nesting resources in Long Evans rats, our lab has previously reported specific epigenetic and behavioral trajectories occurring in response to early disruption of the caregiving environment. To further probe that relationship, the current work investigates the ability of the epigenome-modifying drug sodium butyrate to prevent maltreatment-induced methylation changes when administered alongside maltreatment. Following exposure to the scarcity-adversity model, during which drug was administered prior to each caregiving session, methylation of Brain-derived Neurotrophic Factor (Bdnf) IX DNA was examined in the Prefrontal Cortex (PFC) of male and female pups at postnatal day (PN) 8. As our previous work reports, increased methylation at this exon of Bdnf in the PFC is a stable epigenetic change across the lifespan that occurs in response to early maltreatment, thus giving us a suitable starting point to investigate pharmacological prevention of maltreatment-induced epigenetic marks. Here we also examined off-target effects of sodium butyrate by assessing methylation in another region of Bdnf (exon IV) not affected in the infant brain as well as global levels of methylation in the brain region of interest. Results indicate that a 400 mg/kg (but not 300 mg/kg) dose of sodium butyrate is effective in preventing the maltreatment-induced rise in methylation at Bdnf exon IX in the PFC of male (but not female) infant pups. Administration of sodium butyrate did not affect the methylation status of Bdnf IV or overall levels of global methylation in the PFC, suggesting potential specificity of this drug. These data provide us an avenue forward for investigating whether the relationship between adversity-induced epigenetic outcomes in our model can be manipulated to improve behavioral outcomes.

Limited effects of early life manipulations on sex-specific gene expression and behavior in adulthood

Exposure to childhood adversity is associated with increased vulnerability to stress-related disorders in adulthood which has been replicated in rodent stress models, whereas environmental enrichment has been suggested to have beneficial effects. However, the exact neurobiological mechanisms underlying these environment influences on adult brain and behavior are not well understood. Therefore, we investigated the long-term effects of maternal separation (MS) or environmental enrichment (EE) in male and female CD1 mice. We found clear sex-specific effects, but limited influence of environmental manipulations, on adult behavior, fecal corticosterone metabolite (FCM) levels and stress- and plasticity related gene expression in discrete brain regions. In detail, adult females displayed higher locomotor activity and FCM levels compared to males and EE resulted in attenuation in both measures, but only in females. There were no sex- or postnatal manipulation-dependent differences in anxiety-related behaviors in either sex. Gene expression analyses revealed that adult males showed higher Fkbp5 mRNA levels in hippocampus, hypothalamus and raphe nuclei, and higher hippocampal Nos1 levels. Interestingly, MS elevated Nos1 levels in hippocampus but reduced Fkbp5 expression in hypothalamus of males. Finally, we also found higher Maoa expression in the hypothalamus of adult females, however no differences were observed in the expression levels of Bdnf, Crhr1, Nr3c1 and Htr1a. Our findings further contribute to sex-dependent differences in behavior, corticosterone and gene expression and reveal that the effects of postnatal manipulations on these parameters in outbred CD1 mice are limited.

Interactive effects of genetic polymorphisms and childhood adversity on brain morphologic changes in depression

The etiology of depression is characterized by the interplay of genetic and environmental factors and brain structural alteration. Childhood adversity is a major contributing factor in the development of depression. Interactions between childhood adversity and candidate genes for depression could affect brain morphology via the modulation of neurotrophic factors, serotonergic neurotransmission, or the hypothalamus-pituitary-adrenal (HPA) axis, and this pathway may explain the subsequent onset of depression. Childhood adversity is associated with structural changes in the hippocampus, amygdala, anterior cingulate cortex (ACC), and prefrontal cortex (PFC), as well as white matter tracts such as the corpus callosum, cingulum, and uncinate fasciculus. Childhood adversity showed an interaction with the brain-derived neurotrophic factor (BDNF) gene Val66Met polymorphism, serotonin transporter-linked promoter region (5-HTTLPR), and FK506 binding protein 51 (FKBP5) gene rs1360780 in brain morphologic changes in patients with depression and in a non-clinical population. Individuals with the Met allele of BDNF Val66Met and a history of childhood adversity had reduced volume in the hippocampus and its subfields, amygdala, and PFC and thinner rostral ACC in a study of depressed patients and healthy controls. The S allele of 5-HTTLPR combined with exposure to childhood adversity or a poorer parenting environment was associated with a smaller hippocampal volume and subsequent onset of depression. The FKBP5 gene rs160780 had a significant interaction with childhood adversity in the white matter integrity of brain regions involved in emotion processing. This review identified that imaging genetic studies on childhood adversity may deepen our understanding on the neurobiological background of depression by scrutinizing complicated pathways of genetic factors, early psychosocial environments, and the accompanying morphologic changes in emotion-processing neural circuitry.

Altered Connectivity in Depression: GABA and Glutamate Neurotransmitter Deficits and Reversal by Novel Treatments

The mechanisms underlying the pathophysiology and treatment of depression and stress-related disorders remain unclear, but studies in depressed patients and rodent models are beginning to yield promising insights. These studies demonstrate that depression and chronic stress exposure cause atrophy of neurons in cortical and limbic brain regions implicated in depression, and brain imaging studies demonstrate altered connectivity and network function in the brains of depressed patients. Studies of the neurobiological basis of the these alterations have focused on both the principle, excitatory glutamate neurons, as well as inhibitory GABA interneurons. They demonstrate structural, functional, and neurochemical deficits in both major neuronal types that could lead to degradation of signal integrity in cortical and hippocampal regions. The molecular mechanisms underlying these changes have not been identified but are thought to be related to stress induced excitotoxic effects in combination with elevated adrenal glucocorticoids and inflammatory cytokines as well as other environmental factors. Transcriptomic studies are beginning to demonstrate important sex differences and, together with genomic studies, are starting to reveal mechanistic domains of overlap and uniqueness with regards to risk and pathophysiological mechanisms with schizophrenia and bipolar disorder. These studies also implicate GABA and glutamate dysfunction as well as immunologic mechanisms. While current antidepressants have significant time lag and efficacy limitations, new rapid-acting agents that target the glutamate and GABA systems address these issues and offer superior therapeutic interventions for this widespread and debilitating disorder.

Validation of hippocampal biomarkers of cumulative affective experience

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Recent knowledge on hippocampal structural plasticity is reviewed.

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This knowledge is harnessed to develop biomarkers of cumulative experience.

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Hippocampal plasticity is shown to have construct, content and criterion validity in mammals.

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The biomarkers require further validation to be used in birds and fish.

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We discuss some practical considerations to implement the biomarkers.

Progress in improving the welfare of captive animals has been hindered by a lack of objective indicators to assess the quality of lifetime experience, often called cumulative affective experience. Recent developments in stress biology and psychiatry have shed new light on the role of the mammalian hippocampus in affective processes. Here we review these findings and argue that structural hippocampal biomarkers demonstrate criterion, construct and content validity as indicators of cumulative affective experience in mammals. We also briefly review emerging findings in birds and fish, which have promising implications for applying the hippocampal approach to these taxa, but require further validation. We hope that this review will motivate welfare researchers and neuroscientists to explore the potential of hippocampal biomarkers of cumulative affective experience.

Interactive effect of 5-HTTLPR and BDNF polymorphisms on amygdala intrinsic functional connectivity and anxiety

The serotonin transporter (5-HTTLPR) and brain-derived neurotrophic factor (BDNF) gene polymorphisms have been associated with risk for affective disorders and functional variability of the amygdala. We examined whether the two genotypes interactively influence intrinsic functional connectivity (FC) of the amygdala and whether FC mediates the genetic association with anxiety. Eighty genotyped healthy adults underwent resting state fMRI and completed the self-reported State-Trait Anxiety Inventory. Interactive genetic association with anxiety was observed such that effects of 5-HTTLPR depended on the BDNF Val66Met polymorphism (rs6265 variant), with higher anxiety scores in short and Met carriers compared to the other allelic groups. Voxel-wise FC with left and right amygdala seeds identified regions that were sensitive to variability in anxiety scores. A significant moderated mediation model demonstrated that the effect of 5-HTTLPR genotype on anxiety, moderated by BDNF Val66Met genotype, was fully mediated by FC between the left amygdala and the right dorsolateral prefrontal cortex, a cognitive control-related region, during a task-free state. FC was highest in carriers of the 5-HTTLPR short allele and BDNF Met allele. These findings establish intrinsic amygdala-prefrontal functional connectivity as a potential intermediate phenotype for anxiety, an important step toward identification of causal pathways for vulnerability to affective disorders.

The Role of Dendritic Brain-Derived Neurotrophic Factor Transcripts on Altered Inhibitory Circuitry in Depression

BACKGROUND

A parallel downregulation of brain-derived neurotrophic factor (BDNF) and somatostatin (SST), a marker of inhibitory gamma-aminobutyric acid interneurons that target pyramidal cell dendrites, has been reported in several brain areas of subjects with major depressive disorder (MDD). Rodent genetic studies suggest that they are linked and that both contribute to the illness. However, the mechanism by which they contribute to the pathophysiology of the illness has remained elusive.

METHODS

With quantitative polymerase chain reaction, we determined the expression level of BDNF transcript variants and synaptic markers in the prefrontal cortex of patients with MDD and matched control subjects (n = 19/group) and of C57BL/6J mice exposed to chronic stress or control conditions (n = 12/group). We next suppressed Bdnf transcripts with long 3' untranslated region (L-3'-UTR) using short hairpin RNA and investigated changes in cell morphology, gene expression, and behavior.

RESULTS

L-3'-UTRs containing BDNF messenger RNAs, which migrate to distal dendrites of pyramidal neurons, are selectively reduced, and their expression was highly correlated with SST expression in the prefrontal cortex of subjects with MDD. A similar downregulation occurs in mice submitted to chronic stress. We next show that Bdnf L-3'-UTR knockdown is sufficient to induce 1) dendritic shrinkage in cortical neurons, 2) cell-specific MDD-like gene changes (including Sst downregulation), and 3) depressive- and anxiety-like behaviors. The translational validity of the Bdnf L-3'-UTR short hairpin RNA-treated mice was confirmed by significant cross-species correlation of changes in MDD-associated gene expression.

CONCLUSIONS

These findings provide evidence for a novel MDD-related pathological mechanism linking local neurotrophic support, pyramidal cell structure, dendritic inhibition, and mood regulation.

Vagal Tone as a Putative Mechanism for Pragmatic Competence: An Investigation of Carriers of the FMR1 Premutation

Pragmatic language skills exist across a continuum in typical and clinical populations, and are impaired in many neurodevelopmental disorders, most notably autism. The mechanisms underlying pragmatic impairment are poorly understood, although theory suggests dampened vagal tone plays a role. This study investigated the FMR1 premutation as a genetic model that may lend insight into the relationship between vagal function and pragmatic ability. Participants included 38 women with the FMR1 premutation and 23 controls. Vagal tone accounted for significant variance in pragmatics across both groups and statistically mediated the effect of FMR1 premutation status on pragmatic ability. Results support vagal tone as a biophysiological correlate of pragmatic ability, which informs potential mechanistic underpinnings and could have implications for targeted treatment.

The ERK Pathway: Molecular Mechanisms and Treatment of Depression

Major depressive disorder is a chronic debilitating mental illness. Its pathophysiology at cellular and molecular levels is incompletely understood. Increasing evidence supports a pivotal role of the mitogen-activated protein kinase (MAPK), in particular the extracellular signal-regulated kinase (ERK) subclass of MAPKs, in the pathogenesis, symptomatology, and treatment of depression. In humans and various chronic animal models of depression, the ERK signaling was significantly downregulated in the prefrontal cortex and hippocampus, two core areas implicated in depression. Inhibiting the ERK pathway in these areas caused depression-like behavior. A variety of antidepressants produced their behavioral effects in part via normalizing the downregulated ERK activity. In addition to ERK, the brain-derived neurotrophic factor (BDNF), an immediate upstream regulator of ERK, the cAMP response element-binding protein (CREB), a transcription factor downstream to ERK, and the MAPK phosphatase (MKP) are equally vulnerable to depression. While BDNF and CREB were reduced in their activity in the prefrontal cortex and hippocampus of depressed animals, MKP activity was enhanced in parallel. Chronic antidepressant treatment readily reversed these neurochemical changes. Thus, ERK signaling in the depression-implicated brain regions was disrupted during the development of depression, which contributes to the long-lasting and transcription-dependent neuroadaptations critical for enduring depression-like behavior and the therapeutic effect of antidepressants.

Early life stress impairs fear memory and synaptic plasticity; a potential role for GluN2B

Programming of the brain by early life stress has been associated with alterations in structure and function of the dorsal hippocampus. Yet, the underlying molecular mechanisms remain largely elusive. In this study, we examined the effects of early life stress (ELS) - by housing mouse dams with limited nesting and bedding material from postnatal days 2-9 and examined in 6 month old offspring; 1) auditory fear conditioning, 2) expression of the hippocampal N-methyl-d-aspartate receptor (NMDA-R) subunits 2A and 2B (GluN2A, GluN2B), and expression of PSD-95 and synaptophysin, and 3) short- and long-term (LTP) synaptic plasticity. Given its critical role in NMDA receptor function and synaptic plasticity, we further examined the role of GluN2B in effects of ELS on synaptic plasticity and fear memory formation. We demonstrate that ELS impaired fear memory in 6 month old mice and decreased hippocampal LTP as well as the paired-pulse ratio (PPR). ELS also reduced hippocampal GluN2B expression. Interestingly, pharmacological blockade of GluN2B with the selective antagonist Ro25 6981 was less effective to reduce synaptic plasticity in ELS mice, and was also ineffective to impair memory retrieval in ELS mice. These studies suggest that ELS reduces hippocampal synaptic plasticity and fear memory formation and hampers GluN2B receptor function. As such, GluN2B may provide an important target for future strategies to prevent lasting ELS effects on cognition.

The roles of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in predicting treatment remission in a Chinese Han population with generalized anxiety disorder

Neurotrophic factors, particularly brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF), are involved in neuroplasticity in the nervous system. To explore the characteristics of BDNF and GDNF and their roles in predicting treatment remission in a Chinese Han population with generalized anxiety disorder (GAD), 85 GAD patients were treated with escitalopram or venlafaxine randomly for 8 weeks. The serum BDNF/GDNF levels were detected, while Hamilton Anxiety Rating Scale (HAMA) scores were measured at baseline and after 8 weeks of treatment. The differences in serum BDNF/GDNF levels between GAD patients (n = 85) and healthy controls (n = 73) and between remission and nonremission were then compared. The serum BDNF levels were lower in GAD patients (1197.24 ± 367.41 µg/L) than in healthy controls (1378.09 ± 382.46 µg/L) (P < 0.05). The serum GDNF levels were also lower in GAD patients (10.19 ± 9.86 µg/L) than in healthy controls (13.73 ± 9.44 µg/L) (P < 0.05). The BDNF level was negatively correlated with baseline HAMA score (P < 0.05). The GDNF level was negatively correlated with baseline HAMA score (P < 0.05). The BDNF level was positively correlated with GDNF level (P < 0.05). Both baseline BDNF/GDNF levels in remission and nonremission showed no statistically significant differences. No significant correlation was found between baseline BDNF level and the HAMA reduction rate or between baseline GDNF levels and the HAMA reduction rate. Both serum BDNF and GDNF were demonstrated to be potential biomarkers of GAD, it seems that serum BDNF and GDNF levels can be used to assess the baseline anxiety severity of GAD but cannot serve as a factor to predict treatment remission.

Advance in Stress for Depressive Disorder

Stress is an adaptive response to environment aversive stimuli and a common life experience of one's daily life. Chronic or excessive stress especially that happened in early life is found to be deleterious to individual's physical and mental health, which is highly related to depressive disorders onset. Stressful life events are consistently considered to be the high-risk factors of environment for predisposing depressive disorders. In linking stressful life events with depressive disorder onset, dysregulated HPA axis activity is supposed to play an important role in mediating aversive impacts of life stress on brain structure and function. Increasing evidence have indicated the strong association of stress, especially the chronic stress and early life stress, with depressive disorders development, while the association of stress with depression is moderated by genetic risk factors, including polymorphism of SERT, BDNF, GR, FKBP5, MR, and CRHR1. Meanwhile, stressful life experience particularly early life stress will exert epigenetic modification in these risk genes via DNA methylation and miRNA regulation to generate long-lasting effects on these genes expression, which in turn cause brain structural and functional alteration, and finally increase the vulnerability to depressive disorders. Therefore, the interaction of environment with gene, in which stressful life exposure interplay with genetic risk factors and epigenetic modification, is essential in predicting depressive disorders development. As the mediator of environmental risk factors, stress will function together with genetic and epigenetic mechanism to influence brain structure and function, physiology and psychology, and finally the vulnerability to depressive disorders.

Changes in neuroplasticity following early-life social adversities: the possible role of brain-derived neurotrophic factor

Social adversities experienced in childhood can have a profound impact on the developing brain, leading to the emergence of psychopathologies in adulthood. Despite the burden this places on both the individual and society, the neurobiological aspects mediating this transition remain unclear. Recent advances in preclinical and clinical research have begun examining neuroplasticity-the nervous system's ability to form adaptive changes in response to new experience-in the context of early-life vulnerability to social adversities and plasticity-related alterations following such traumatic events. A key mediator of plasticity-related molecular processes is the brain-derived neurotrophic factor (BDNF), which has also been implicated in various psychiatric disorders related to childhood social adversities. Preclinical and clinical data suggest early-life social adversities (ELSA) might be associated with accelerated maturation of social network circuitry, a possible ontogenic adaptation to the adverse environment. Neural plasticity decreases by adulthood, lessening the efficacy of treatment in ELSA-related psychiatric disorders. However, literature data suggest that by increasing BDNF/TrkB signalling through antidepressant treatment a juvenile-like plasticity state can be induced, which allows for reorganization of the social circuitry when guided by psychotherapy and surrounded by a safe and positive environment.

Imaging Genetics Towards a Refined Diagnosis of Schizophrenia

Current diagnoses of schizophrenia and related psychiatric disorders are classified by phenomenological principles and clinical descriptions while ruling out other symptoms and conditions. Specific biomarkers are needed to assist the current diagnostic system. However, complicated gene and environment interactions induce great disease heterogeneity. This unclear etiology and heterogeneity raise difficulties in distinguishing schizophrenia-related effects. Simultaneously, the overlap in symptoms, genetic variations, and brain alterations in schizophrenia and related psychiatric disorders raises similar difficulties in determining disease-specific effects. Imaging genetics is a unique methodology to assess the impact of genetic factors on both brain structure and function. More importantly, imaging genetics builds a bridge to understand the behavioral and clinical implications of genetics and neuroimaging. By characterizing and quantifying the brain measures affected in psychiatric disorders, imaging genetics is contributing to identifying potential biomarkers for schizophrenia and related disorders. To date, candidate gene analysis, genome-wide association studies, polygenetic risk score analysis, and large-scale collaborative studies have made contributions to the understanding of schizophrenia with the potential to serve as biomarkers. Despite limitations, imaging genetics remains promising as more aggregative, clustering methods and imaging genetics-compatible clinical assessments are employed in future studies. We review imaging genetics' contribution to our understanding of the heterogeneity within schizophrenia and the commonalities across schizophrenia and other diagnostic borders, and we will discuss whether imaging genetics is ready to form its own diagnostic system.

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.

Adverse early life environment induces anxiety-like behavior and increases expression of FKBP5 mRNA splice variants in mouse brain

Adverse early life environment (AELE) predisposes adult offspring toward anxiety disorders. Anxiety disorders are associated with prenatal injuries in key regions of the brain including prefrontal cortex (PFC), hippocampus (HP), and hypothalamus (HT). Injuries in these brain regions result in an impaired hypothalamus-pituitary-adrenal axis (HPA axis) and stress response. An important regulator of the stress response is FK506-binding protein 5 (FKBP5). FKBP5 is a cochaperone of the glucocorticoid receptor (GR) and inhibits GR-mediated regulatory feed-back on the HPA axis in response to stress. Human studies have shown that polymorphisms of FKBP5 are associated with higher FKBP5 levels. Increased FKBP5 leads to GR resistance and impaired negative feedback, which is associated with anxiety disorders. FKBP5 and its mRNA splice variants in the aforementioned brain regions have not been reported. We hypothesized that AELE will increase expression of FKBP5 and its mRNA splice variants in PFC, HP, and HT as well as increase anxiety in adult mice. AELE increased expression of FKBP5 and its mRNA variants in PFC, HP and HT at postnatal day 21. Additionally, AELE caused anxiety and increased GR abundance in association with these changes in FKBP5 expression. We speculate that these changes in FKBP5 mRNA variants affect HPA axis function and contributes to subsequent anxiety-like behavior later in life in AELE mice.

Ondansetron ameliorates depression associated with obesity in high-fat diet fed experimental mice: An investigation-based on the behavioral, biochemical, and molecular approach

INTRODUCTION:

Obesity is an important risk factor for depression as more than half of the obese population is susceptible for depression at double rate. Our earlier studies reported the antidepressant potential of 5-HT₃ receptor antagonist, ondansetron (OND) in depression associated obesity using behavioral tasks. The present research work is aimed to evaluate the effect of OND on depression associated with obesity with special emphasis on biochemical and molecular mechanisms such as hippocampal brain-derived neurotrophic factor (BDNF), cyclic adenosine monophosphate (cAMP), 5-hydroxytryptamine (5-HT), hippocampal histological examination and immunohistochemical expression of p53 proteins.

MATERIALS AND METHODS:

Mice were fed with high-fat diet (HFD) for 14 weeks, followed by treatment schedule for 28 days with vehicle/OND (0.5 and 1 mg/kg, p.o.)/reference antidepressant escitalopram (10 mg/kg, p.o.). Subsequently, animals were screened in the behavioral tests of depression such as forced swim test (FST) and sucrose preference test (SPT), biochemical estimations including hippocampal cAMP, BDNF and 5-HT, and molecular assays mainly histology and p53 expression of dentate gyrus (DG).

RESULTS:

HFD-fed mice showed increased immobility time in FST, reduced sucrose consumption in SPT, decreased level of signal transduction factor cAMP, neuronal growth factor BDNF and neurotransmitter 5-HT in the hippocampus, and raised and p53 expression neuronal damage in the DG region of mice fed with HFD in comparison to the mice fed with normal pellet diet. Chronic treatment with OND (0.5 and 1 mg/kg, p.o.) significantly inhibited the behavioral, biochemical and molecular modifications in HFD-fed mice.

CONCLUSION:

In the preliminary study, OND attenuated depression associated with obesity in mice fed with HFD using various assays procedures, at least in part by the modulation of serotonergic transmission.

Early scars are forever: Childhood abuse in patients with adult-onset PTSD is associated with increased prevalence and severity of psychiatric comorbidity

Childhood abuse and PTSD are independently associated with severe psychiatric comorbidity. We hypothesized that among patients with adult-onset PTSD, a history of child abuse was associated with increased prevalence and severity of comorbid mental disorders. Participants were 109 adult treatment-seeking patients, 23.9% of whom had a history of childhood sexual, physical or emotional abuse. The socio-demographic characteristics and comorbidity profile of PTSD patients with and without history of child abuse were compared using the two-tailed t-test and the chi-square test. PTSD patients with a history of child abuse had significantly higher average PCL-C hyperarousal [21.8 (SD = 3.6) vs 19.8 (SD = 3.5)] and BDI [35.7 (SD = 9.2) vs 29.1 (SD = 13.9)] scores, a significantly increased average number of lifetime [4.85 (SD = 1.43) vs 3.93 (SD = 1.33)] and current [4.46 (SD = 1.24) vs 3.75 (SD = 1.32)] comorbid disorders, and a greater prevalence of lifetime (73.1% vs 44.6%) and current (79.2% vs 46.7%) panic disorder/agoraphobia and of psychotic symptoms (73.1% vs 30.1%). All effect sizes were in the medium to large range. Adult-onset PTSD patients with a history of child abuse may represent a subgroup with a more severe form of the disorder that is associated with a more serious clinical course, treatment resistance and poorer outcome.

Interaction between job stress and the BDNF Val66Met polymorphism affects depressive symptoms in Chinese healthcare workers

BACKGROUND

Chronic exposure to job-related stress can lead to depression and BDNF polymorphism may play an important role in this process. The role of the stress × BDNF Val66Met interaction in depression has been studied widely using childhood stress, but few studies have utilized chronic stress in adulthood as a moderator. This study was to examine the chronic stress × BDNF Val66Met interaction in job-related depression in the healthcare workers in a Chinese Han population, which has not been reported yet.

METHODS

Using a cross-sectional design, 243 doctors and nurses were recruited from a general hospital in Beijing, and were assessed for depression with Self-rating Depression Scale (SDS), and the stress using the House and Rizzo's Work Stress Scale. The BDNF Val66Met polymorphism was genotyped.

RESULTS

There was a significant positive association between job stress and depressive scores (p < 0.001). No significant main effect of the BDNF Val66Met genotype on depressive symptoms was observed (p > 0.05). A statistically significant interaction between BDNF Val66Met and job stress on depressive symptoms was found (p < 0.05); individuals with Val/Val genotype showed a higher SDS score than Met allele carriers only in the low-stress group, without significant differences in SDS score between the BDNF Val66Met subgroups in medium- or high-stress group.

LIMITATIONS

Limitations include cross-sectional study design, the small sample size only in healthcare workers and only one polymorphism in BDNF gene was analyzed.

CONCLUSIONS

Our results suggest a close relationship between job-related stress and depression, and the interaction of the BDNF Val66Met polymorphism and chronic stress in adulthood may impact the depressive symptoms.

The interaction of BDNF Val66Met, PTSD, and child abuse on psychophysiological reactivity and HPA axis function in a sample of Gulf War Veterans

INTRODUCTION

While the BDNF Val66Met polymorphism has been linked to various psychological disorders, limited focus has been on its relationship to posttraumatic stress disorder (PTSD) and early traumas such as child abuse. Therefore, we assessed whether Val66Met was associated with fear potentiated psychophysiological response and HPA axis dysfunction and whether PTSD status or child abuse history moderated these outcomes in a sample of Veterans.

METHODS

226 and 173 participants engaged in a fear potentiated acoustic startle paradigm and a dexamethasone suppression test (DST) respectively. Fear conditions included no, ambiguous, and high threat conditions. Psychophysiological response measures included electromyogram (EMG), skin conductance response (SCR), and heart rate. The Clinician Administered PTSD Scale (CAPS) and the Trauma History Questionnaire (THQ) were used to assess PTSD status and child abuse history respectively.

RESULTS

Met allele carriers exhibited greater SCR magnitudes in the no and ambiguous threat conditions (p < 0.01 and p < 0.05 respectively). Met carriers with PTSD exhibited greater physiological response magnitudes in the ambiguous (SCR, p < 0.001) and high threat conditions (SCR and heart rate, both p ≤ 0.005). Met carrier survivors of child abuse exhibited blunted heart rate magnitudes in the high threat condition (p < 0.01). Met allele carries with PTSD also exhibited greater percent cortisol suppression (p < 0.005).

LIMITATIONS

Limitations included small sample size and the cross-sectional nature of the data.

CONCLUSIONS

The Val66met may impact PTSD susceptibility differentially via enhanced threat sensitivity and HPA axis dysregulation. Child abuse may moderate Val66Met's impact on threat reactivity. Future research should explore how neuronal mechanisms might mediate this risk.

Neurobiology of depression: A neurodevelopmental approach

OBJECTIVES

The main aims of this paper are to review and evaluate the neurobiology of the depressive syndrome from a neurodevelopmental perspective.

METHODS

An English language literature search was performed using PubMed.

RESULTS

Depression is a complex syndrome that involves anatomical and functional changes that have an early origin in brain development. In subjects with genetic risk for depression, early stress factors are able to mediate not only the genetic risk but also gene expression. There is evidence that endocrine and immune interactions have an important impact on monoamine function and that the altered monoamine signalling observed in the depressive syndrome has a neuro-endocrino-immunological origin early in the development.

CONCLUSIONS

Neurodevelopment is a key aspect to understand the whole neurobiology of depression.

The Need to Separate Chronic Traumatic Encephalopathy Neuropathology from Clinical Features

There is tremendous recent interest in chronic traumatic encephalopathy (CTE) in former collision sport athletes, civilians, and military veterans. This critical review places important recent research results into a historical context. In 2015, preliminary consensus criteria were developed for defining the neuropathology of CTE, which substantially narrowed the pathology previously reported to be characteristic. There are no agreed upon clinical criteria for diagnosis, although sets of criteria have been proposed for research purposes. A prevailing theory is that CTE is an inexorably progressive neurodegenerative disease within the molecular classification of the tauopathies. However, historical and recent evidence suggests that CTE, as it is presented in the literature, might not be pathologically or clinically progressive in a substantial percentage of people. At present, it is not known whether the emergence, course, or severity of clinical symptoms can be predicted by specific combinations of neuropathologies, thresholds for accumulation of pathology, or regional distributions of pathologies. More research is needed to determine the extent to which the neuropathology ascribed to long-term effects of neurotrauma is static, progressive, or both. Disambiguating the pathology from the broad array of clinical features that have been reported in recent studies might facilitate and accelerate research- and improve understanding of CTE.

Neurogenetic Approaches to Stress and Fear in Humans as Pathophysiological Mechanisms for Posttraumatic Stress Disorder

In this review article, genetic variation associated with brain responses related to acute and chronic stress reactivity and fear learning in humans is presented as an important mechanism underlying posttraumatic stress disorder. We report that genes related to the regulation of the hypothalamic-pituitary-adrenal axis, as well as genes that modulate serotonergic, dopaminergic, and neuropeptidergic functions or plasticity, play a role in this context. The strong overlap of the genetic targets involved in stress and fear learning suggests that a dimensional and mechanistic model of the development of posttraumatic stress disorder based on these constructs is promising. Genome-wide genetic analyses on fear and stress mechanisms are scarce. So far, reliable replication is still lacking for most of the molecular genetic findings, and the proportion of explained variance is rather small. Further analysis of neurogenetic stress and fear learning needs to integrate data from animal and human studies.

Cerebellar BDNF Promotes Exploration and Seeking for Novelty

Background

Approach system considered a motivational system that activates reward-seeking behavior is associated with exploration/impulsivity, whereas avoidance system considered an attentional system that promotes inhibition of appetitive responses is associated with active overt withdrawal. Approach and avoidance dispositions are modulated by distinct neurochemical profiles and synaptic patterns. However, the precise working of neurons and trafficking of molecules in the brain activity predisposing to approach and avoidance are yet unclear.

Methods

In 3 phenotypes of inbred mice, avoiding, balancing, and approaching mice, selected by using the Approach/Avoidance Y-maze, we analyzed endogenous brain levels of brain derived neurotrophic factor, one of the main secretory proteins with pleiotropic action. To verify the effects of the acute increase of brain derived neurotrophic factor, balancing and avoiding mice were bilaterally brain derived neurotrophic factor-infused in the cortical cerebellar regions.

Results

Approaching animals showed high levels of explorative behavior and response to novelty and exhibited higher brain derived neurotrophic factor levels in the cerebellar structures in comparison to the other 2 phenotypes of mice. Interestingly, brain derived neurotrophic factor-infused balancing and avoiding mice significantly increased their explorative behavior and response to novelty.

Conclusions

Cerebellar brain derived neurotrophic factor may play a role in explorative and novelty-seeking responses that sustain the approach predisposition.

Translational profiling of stress-induced neuroplasticity in the CA3 pyramidal neurons of BDNF Val66Met mice

Genetic susceptibility and environmental factors (such as stress) can interact to affect the likelihood of developing a mood disorder. Stress-induced changes in the hippocampus have been implicated in mood disorders, and mutations in several genes have now been associated with increased risk, such as brain-derived neurotrophic factor (BDNF). The hippocampus has important anatomical subdivisions, and pyramidal neurons of the vulnerable CA3 region show significant remodeling after chronic stress, but the mechanisms underlying their unique plasticity remain unknown. This study characterizes stress-induced changes in the in vivo translating mRNA of this cell population using a CA3-specific enhanced green fluorescent protein (EGFP) reporter fused to the L10a large ribosomal subunit (EGFPL10a). RNA-sequencing after isolation of polysome-bound mRNAs allows for cell-type-specific, genome-wide characterization of translational changes after stress. The data demonstrate that acute and chronic stress produce unique translational profiles and that the stress history of the animal can alter future reactivity of CA3 neurons. CA3-specific EGFPL10a mice were then crossed to the stress-susceptible BDNF Val66Met mouse line to characterize how a known genetic susceptibility alters both baseline translational profiles and the reactivity of CA3 neurons to stress. Not only do Met allele carriers exhibit distinct levels of baseline translation in genes implicated in ion channel function and cytoskeletal regulation, but they also activate a stress response profile that is highly dissimilar from wild-type mice. Closer examination of genes implicated in the mechanisms of neuroplasticity, such as the NMDA and AMPA subunits and the BDNF pathway, reveal how wild-type mice upregulate many of these genes in response to stress, but Met allele carriers fail to do so. These profiles provide a roadmap of stress-induced changes in a genetically homogenous population of hippocampal neurons and illustrate the profound effects of gene-environment interactions on the translational profile of these cells.

Stress Response Modulation Underlying the Psychobiology of Resilience

PURPOSE OF REVIEW

This review focuses on the relationship between resilience and the ability to effectively modulate the stress response. Neurobiological and behavioral responses to stress are highly variable. Exposure to a similar stressor can lead to heterogeneous outcomes-manifesting psychopathology in one individual, but having minimal effect, or even enhancing resilience, in another. We highlight aspects of stress response modulation related to early life development and epigenetics, selected neurobiological and neurochemical systems, and a number of emotional, cognitive, psychosocial, and behavioral factors important in resilience. We also briefly discuss interventions with potential to build and promote resilience.

RECENT FINDINGS

Throughout this review, we include evidence from recent preclinical and clinical studies relevant to the psychobiology of resilient stress response modulation. Effective modulation of the stress response is an essential component of resilience and is dependent on a complex interplay of neurobiological and behavioral factors.

Biomarkers as Common Data Elements for Symptom and Self-Management Science

PURPOSE

Biomarkers as common data elements (CDEs) are important for the characterization of biobehavioral symptoms given that once a biologic moderator or mediator is identified, biologically based strategies can be investigated for treatment efforts. Just as a symptom inventory reflects a symptom experience, a biomarker is an indicator of the symptom, though not the symptom per se. The purposes of this position paper are to (a) identify a "minimum set" of biomarkers for consideration as CDEs in symptom and self-management science, specifically biochemical biomarkers; (b) evaluate the benefits and limitations of such a limited array of biomarkers with implications for symptom science; (c) propose a strategy for the collection of the endorsed minimum set of biologic samples to be employed as CDEs for symptom science; and (d) conceptualize this minimum set of biomarkers consistent with National Institute of Nursing Research (NINR) symptoms of fatigue, depression, cognition, pain, and sleep disturbance.

DESIGN AND METHODS

From May 2016 through January 2017, a working group consisting of a subset of the Directors of the NINR Centers of Excellence funded by P20 or P30 mechanisms and NINR staff met bimonthly via telephone to develop this position paper suggesting the addition of biomarkers as CDEs. The full group of Directors reviewed drafts, provided critiques and suggestions, recommended the minimum set of biomarkers, and approved the completed document. Best practices for selecting, identifying, and using biological CDEs as well as challenges to the use of biological CDEs for symptom and self-management science are described. Current platforms for sample outcome sharing are presented. Finally, biological CDEs for symptom and self-management science are proposed along with implications for future research and use of CDEs in these areas.

FINDINGS

The recommended minimum set of biomarker CDEs include pro- and anti-inflammatory cytokines, a hypothalamic-pituitary-adrenal axis marker, cortisol, the neuropeptide brain-derived neurotrophic factor, and DNA polymorphisms.

CONCLUSIONS

It is anticipated that this minimum set of biomarker CDEs will be refined as knowledge regarding biologic mechanisms underlying symptom and self-management science further develop. The incorporation of biological CDEs may provide insights into mechanisms of symptoms, effectiveness of proposed interventions, and applicability of chosen theoretical frameworks. Similarly, as for the previously suggested NINR CDEs for behavioral symptoms and self-management of chronic conditions, biological CDEs offer the potential for collaborative efforts that will strengthen symptom and self-management science.

CLINICAL RELEVANCE

The use of biomarker CDEs in biobehavioral symptoms research will facilitate the reproducibility and generalizability of research findings and benefit symptom and self-management science.

The BDNF gene val66met polymorphism and behavioral inhibition in early childhood

Stably elevated behavioural inhibition (BI) is an established risk factor for internalizing disorders. This stability may be related to genetic factors, including a valine-to-methionine substitution on codon 66 (val66met) of the brain-derived neurotrophic factor (BDNF) gene. Past work on the BDNF met variant has inconsistently linked it to vulnerability to internalizing problems; some of this inconsistency may stem from the failure to consider gene-trait interactions in shaping the course of early BI. Toward elucidating early pathways to anxiety vulnerability, we examined gene-by-trait interactions in predicting the course of BI over time in 476 children, assessed for BI using standardized laboratory methods. We found that children with the met allele showed lower stability of BI between ages 3 and 6 than those without this allele. While the mechanisms that underlie this effect are unclear, our findings are consistent with the notion that the met variant, in the context of early BI, influences the stability of this trait in early development.

Association of BDNF Val66Met Polymorphism and Brain BDNF Levels with Major Depression and Suicide

BACKGROUND

Brain-derived neurotrophic factor is implicated in the pathophysiology of major depressive disorder and suicide. Both are partly caused by early life adversity, which reduces brain-derived neurotrophic factor protein levels. This study examines the association of brain-derived neurotrophic factor Val66Met polymorphism and brain brain-derived neurotrophic factor levels with depression and suicide. We hypothesized that both major depressive disorder and early life adversity would be associated with the Met allele and lower brain brain-derived neurotrophic factor levels. Such an association would be consistent with low brain-derived neurotrophic factor mediating the effect of early life adversity on adulthood suicide and major depressive disorder.

METHODS

Brain-derived neurotrophic factor Val66Met polymorphism was genotyped in postmortem brains of 37 suicide decedents and 53 nonsuicides. Additionally, brain-derived neurotrophic factor protein levels were determined by Western blot in dorsolateral prefrontal cortex (Brodmann area 9), anterior cingulate cortex (Brodmann area 24), caudal brainstem, and rostral brainstem. The relationships between these measures and major depressive disorder, death by suicide, and reported early life adversity were examined.

RESULTS

Subjects with the Met allele had an increased risk for depression. Depressed patients also have lower brain-derived neurotrophic factor levels in anterior cingulate cortex and caudal brainstem compared with nondepressed subjects. No effect of history of suicide death or early life adversity was observed with genotype, but lower brain-derived neurotrophic factor levels in the anterior cingulate cortex were found in subjects who had been exposed to early life adversity and/or died by suicide compared with nonsuicide decedents and no reported early life adversity.

CONCLUSIONS

This study provides further evidence implicating low brain brain-derived neurotrophic factor and the brain-derived neurotrophic factor Met allele in major depression risk. Future studies should seek to determine how altered brain-derived neurotrophic factor expression contributes to depression and suicide.

BDNF Val66Met polymorphism, life stress and depression: A meta-analysis of gene-environment interaction

BACKGROUND

Depression is thought to be multifactorial in etiology, including genetic and environmental components. While a number of gene-environment interaction studies have been carried out, meta-analyses are scarce. The present meta-analysis aimed to quantify evidence on the interaction between brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and stress in depression.

METHODS

Included were 31 peer-reviewed with a pooled total of 21060 participants published before October 2016 and literature searches were conducted using PubMed, Wolters Kluwer, Web of Science, EBSCO, Elsevier Science Direct and Baidu Scholar databases.

RESULTS

The results indicated that the Met allele of BDNF Val66Met polymorphism significantly moderated the relationship between stress and depression (Z=2.666, p = 0.003). The results of subgroup analysis concluded that stressful life events and childhood adversity separately interacted with the Met allele of BDNF Val66Met polymorphism in depression (Z = 2.552, p = 0.005; Z = 1.775, p = 0.03).

LIMITATIONS

The results could be affected by errors or bias in primary studies which had small sample sizes with relatively lower statistic power. We could not estimate how strong the interaction effect between gene and environment was.

CONCLUSIONS

We found evidence that supported the hypothesis that BDNF Val66Met polymorphism moderated the relationship between stress and depression, despite the fact that many included individual studies did not show this effect.