BDNF Val66Met polymorphism and brain-derived neurotrophic factor levels across the female life span: implications for the sex bias in affective disorders

Brain-derived neurotrophic factor Val(66)Met genotype and ovarian steroids interactively modulate working memory-related hippocampal function in women: a multimodal neuroimaging study

Preclinical evidence suggests that the actions of ovarian steroid hormones and brain-derived neurotrophic factor (BDNF) are highly convergent on brain function. Studies in humanized mice document an interaction between estrus cycle-related changes in estradiol secretion and BDNF Val⁶⁶Met genotype on measures of hippocampal function and anxiety-like behavior. We believe our multimodal imaging data provide the first demonstration in women that the effects of the BDNF Val/Met polymorphism on hippocampal function are selectively modulated by estradiol. In a 6-month pharmacological hormone manipulation protocol, healthy, regularly menstruating, asymptomatic women completed positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) scans while performing the n-back working memory task during three hormone conditions: ovarian suppression induced by the gonadotropin-releasing hormone agonist, leuprolide acetate; leuprolide plus estradiol; and leuprolide plus progesterone. For each of the three hormone conditions, a discovery data set was obtained with oxygen-15 water regional cerebral blood flow PET in 39 healthy women genotyped for BDNF Val⁶⁶Met, and a confirmatory data set was obtained with fMRI in 27 women. Our results, in close agreement across the two imaging platforms, demonstrate an ovarian hormone-by-BDNF interaction on working memory-related hippocampal function (PET: F_2,37=9.11, P=0.00026 uncorrected, P=0.05, familywise error corrected with small volume correction; fMRI: F_2,25=5.43, P=0.01, uncorrected) that reflects differential hippocampal recruitment in Met carriers but only in the presence of estradiol. These findings have clinical relevance for understanding the neurobiological basis of individual differences in the cognitive and behavioral effects of ovarian steroids in women, and may provide a neurogenetic framework for understanding neuropsychiatric disorders related to reproductive hormones as well as illnesses with sex differences in disease expression and course.

Do obsessive-compulsive disorder and Tourette syndrome share a common susceptibility gene? An association study of the BDNF Val66Met polymorphism in the Chinese Han population

OBJECTIVES

We explored the association between the BDNF Val66Met polymorphism and susceptibility to both obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) in the Chinese Han population.

METHODS

Genotyping for the BDNF Val66Met polymorphism was performed in 321 OCD patients and 426 healthy control subjects and case-control association study data were analysed. Additionally, we evaluated the genetic contribution of this variant in 331 TS patients (including 267 TS trios) and 519 controls using the transmission disequilibrium test (TDT) and case-control study.

RESULTS

A statistically significant difference was found in the genetic contribution of the BDNF Val66Met polymorphism between both the OCD (χ(2) = 7.50, P = 0.023 by genotype; χ(2) = 6.67, P = 0.01 by allele) and TS (χ(2) = 6.76, P = 0.03 by genotype; χ(2) = 4.27, P = 0.04 by allele), and control groups. TDT and GHRR analysis for TS trios also showed a significant transform disequilibrium of this polymorphism (TDT: χ(2) = 3.96, P = 0.05; HHRR: χ(2) = 4.33 P = 0.04; GHRR: χ(2) = 5.74, P = 0.02; χ(2) = 0.98, P = 0.37). There was also a significant gender trend between patients and controls in female cases for OCD and in male cases for TS.

CONCLUSIONS

Our study supports the involvement of the BDNF Val66Met polymorphism as a common genetic susceptibility for OCD and TS in the Chinese Han population, showing specific gender trends.

Inflammation, neurotrophism and oxidative stress and childhood psychopathology in a large community sample

OBJECTIVE

To investigate the association between peripheral biomarkers and child psychopathology in a large community sample.

METHOD

A total of 625 aged 6- to 13-year old subjects were recruited from a community school-based study. Psychopathology was assessed using the Child Behaviour Checklist (CBCL). Psychiatric diagnosis was evaluated using the Development and Well-Being Assessment. The following biomarkers were examined in peripheral blood: brain-derived neurotrophic factor, cytokines (IL-2, IL-4, IL-6, IL-10, IL-17, IFN-g, and TNF-α), chemokines (eotaxin/CCL11, IP-10, MCP-1), cytokine receptors (sTNFR1 and sTNFR2), and the oxidative stress marker TBARS.

RESULTS

We found significant associations between sTNFR2, eotaxin/CCL11 and CBCL total score, as well as with specific dimensions of psychopathology. There were different patterns of association between these biomarkers and psychological and behavioural symptoms in children with and without a mental disorder. TBARS, IL-6 and MCP-1 were more specific to some clusters of symptoms in children with a psychiatric diagnosis.

CONCLUSION

Our data support the potential use of biomarkers, especially those involved in immune-inflammatory pathways, in investigating neurodevelopmental psychopathology. Their association with different dimensions of symptoms might be of useful when analyzing illness severity and clusters of symptoms within specific disorders.

Emotional fronto-cingulate cortex activation and brain derived neurotrophic factor polymorphism in premenstrual dysphoric disorder

Premenstrual dysphoric disorder (PMDD) is the prototypical sex‐specific disorder in which symptom onset and offset require a particular hormonal milieu and for which there is moderate heritability. The present study investigated brain emotion processing in PMDD and healthy controls, as well as functional polymorphisms in two candidate genes for PMDD, the serotonin transporter (5‐HTT) and brain derived neurotrophic factor (BDNF). The 5‐HTT linked polymorphic region (5‐HTTLPR) and BDNF Val66Met polymorphisms were genotyped in 31 patients with PMDD and 31 healthy controls. A subset of 16 patients and 15 controls participated in two functional magnetic resonance imaging‐sessions performing an emotion processing task; once in the mid‐follicular, and once in the late luteal phase which corresponds with maximum severity of mood symptoms. Genotypes were not directly associated with PMDD. A main effect of group was found in the whole brain analysis, with patients having lower activation of the pre‐genual anterior cingulate and ventro‐medial prefrontal cortex, independent of menstrual cycle phase. Post‐hoc functional ROI analyses in the fronto‐cingulate cluster showed no effect of 5‐HTTLPR genotype but a genotype‐by‐group‐by‐phase interaction effect of BDNF Val66Met. Women with PMDD who were carriers of the Met‐allele had lower fronto‐cingulate cortex activation in the luteal phase compared to Met‐allele carrying controls. The results provide suggestive evidence of impaired emotion‐induced fronto‐cingulate cortex activation in PMDD patients. Although limited by a small sample, the potential influence of BDNF Val66Met in PMDD is in line with preclinical findings. Hum Brain Mapp 35:4450–4458, 2014. © 2014 The Authors. Human Brain Mapping Published by Wiley Periodicals, Inc.

Menopause effects on verbal memory: findings from a longitudinal community cohort

CONTEXT

Although cognitive complaints are common among menopausal women, it is debatable whether there is an objective decline in cognition with menopause that exceeds what is expected with normal aging.

OBJECTIVE

The objective of the study was to determine whether reproductive senescence is associated with an age-independent decline in verbal memory.

DESIGN AND SETTING

The study was a 14-year, longitudinal, population-based cohort study of women who underwent yearly endocrine, behavioral, and cognitive assessments from pre- to postmenopause.

PARTICIPANTS

Caucasian and African American premenopausal women (n = 403), who were enrolled in the Penn Ovarian Aging Study, participated in the study.

MAIN OUTCOME MEASURES

Buschke Selective Reminding Test (immediate and delayed verbal recall), the digit symbol substitution task, and the symbol copy task were used to measure outcomes.

RESULTS

A total of 3958 assessments were conducted in this sample of 403 women. In models that were adjusted for age and important cofactors, immediate (P = .03) and delayed (P = .03) recall on the Buschke Selective Reminding Test declined from the pre- to postmenopausal stages. Further evaluation identified a significant decline (P < .002) in delayed recall early in the transition and immediate recall (P = .04) late in the transition. Race was a significant factor in performance on all tasks (all P < .0001) except the delayed verbal recall task (P = .06) in adjusted models. Endocrine measures were significantly associated with cognitive performance in unadjusted models.

CONCLUSIONS

Certain cognitive domains are sensitive to the physiological changes of reproductive senescence independent of age. The differences in cognitive performance between African American and Caucasian women were not explained by factors examined in this study but are of important public health concern that warrants further investigation.

Views and opinion on BDNF as a target for diabetic cognitive dysfunction

Type 2 diabetes mellitus (T2DM) is a known cause of cognitive dysfunction and involves increased risk of dementia. Brain-derived neurotrophic factor (BDNF) is a member of neurotrophic family of nerve growth factors, a key protein in promoting memory, growth and survival of neurons. BDNF is recognized as a metabotrophic factor, a molecule that is involved in Alzheimer's disease (AD) as well as in other neurological disorders. It provides cellular and local regulatory mechanisms for mediating synaptic plasticity. Impaired BDNF signaling can compromise many aspects of brain functions. Studies investigating the relationship between diabetes and BDNF in adults demonstrate that BDNF levels are decreased in T2DM and are regulated in response to plasma levels of glucose. BDNF could serve as biomarker in predicting the development of obesity and T2DM. Thirty-two cavities were predicted to locate the active sites of BDNF for the ligands to bind. The shape of the site was identified by extracting the cavity volume surfaces enclosing regions with highest probability. Different ligands can be chosen for interaction of active sites of BDNF and can be targeted for drug discovery. This review focuses on computational exploitation selectively to deliver BDNF as a drug to appropriate hypothalamic neurons, which can serve as a novel approach in diabetic encephalopathy treatment.

Central nervous system effects of prenatal selective serotonin reuptake inhibitors: sensing the signal through the noise

RATIONALE

Women are increasingly prescribed selective serotonin reuptake inhibitors (SSRIs) during pregnancy, with potential implications for neurodevelopment. Whether prenatal SSRI exposure has an effect on neurodevelopment and behavior in the offspring is an important area of investigation.

OBJECTIVES

The aim of this paper was to review the existing preclinical and clinical literature of prenatal SSRI exposure on serotonin-related behaviors and markers in the offspring. The goal is to determine if there is a signal in the literature that could guide clinical care and/or inform research.

RESULTS

Preclinical studies (n = 4) showed SSRI exposure during development enhanced depression-like behavior. Half of rodent studies examining anxiety-like behavior (n = 13) noted adverse effects with SSRI exposure. A majority of studies of social behavior (n = 4) noted a decrease in sociability in SSRI exposed offspring. Human studies (n = 4) examining anxiety in the offspring showed no adverse effects of prenatal SSRI exposure. The outcome of one study suggested that children with autism were more likely to have a mother who was prescribed an SSRI during pregnancy.

CONCLUSIONS

Preclinical findings in rodents exposed to SSRIs during development point to an increase in depression- and anxiety-like behavior and alteration in social behaviors in the offspring, though both the methods used and the findings were not uniform. These data are not robust enough to discourage use of SSRIs during human pregnancy, particularly given the known adverse effects of maternal mental illness on pregnancy outcomes and infant neurodevelopment. Future research should focus on consistent animal models and prospective human studies with larger samples.

Sex differences in anxiety and emotional behavior

Research has elucidated causal links between stress exposure and the development of anxiety disorders, but due to the limited use of female or sex-comparative animal models, little is known about the mechanisms underlying sex differences in those disorders. This is despite an overwhelming wealth of evidence from the clinical literature that the prevalence of anxiety disorders is about twice as high in women compared to men, in addition to gender differences in severity and treatment efficacy. We here review human gender differences in generalized anxiety disorder, panic disorder, posttraumatic stress disorder and anxiety-relevant biological functions, discuss the limitations of classic conflict anxiety tests to measure naturally occurring sex differences in anxiety-like behaviors, describe sex-dependent manifestation of anxiety states after gestational, neonatal, or adolescent stressors, and present animal models of chronic anxiety states induced by acute or chronic stressors during adulthood. Potential mechanisms underlying sex differences in stress-related anxiety states include emerging evidence supporting the existence of two anatomically and functionally distinct serotonergic circuits that are related to the modulation of conflict anxiety and panic-like anxiety, respectively. We discuss how these serotonergic circuits may be controlled by reproductive steroid hormone-dependent modulation of crfr1 and crfr2 expression in the midbrain dorsal raphe nucleus and by estrous stage-dependent alterations of γ-aminobutyric acid (GABAergic) neurotransmission in the periaqueductal gray, ultimately leading to sex differences in emotional behavior.

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.

Contemporary Genetics for Gender Researchers

Over the past century, much of genetics was deterministic, and feminist researchers framed justified criticisms of genetics research. However, over the past two decades, genetics research has evolved remarkably and has moved far from earlier deterministic approaches. Our article provides a brief primer on modern genetics, emphasizing contemporary evidence for the complex interplay between genes and environment. We focus particularly on the role of gene–environment interactions for gender-imbalanced disorders such as depression. We review research on epigenetics, which is one mechanism by which environment influences gene expression. Modern genetics is not based on a model of genetic determinism; instead, it recognizes the complexity of genetic influences and the nuanced interplay between genes and environment across life span development. Even with the modern genetics approaches, of course, there is still room for criticism and input from gender researchers. We outline methodological and conceptual issues more generally and from a gender researcher’s perspective. We argue that, with interdisciplinary collaborations, modern genetics can be integrated into gender research and vice versa in ways that will create progress in both fields.