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

Epigenetic aging in major depressive disorder: Clocks, mechanisms and therapeutic perspectives

Depression, a chronic mental disorder characterized by persistent sadness, loss of interest, and difficulty in daily tasks, impacts millions globally with varying treatment options. Antidepressants, despite their long half-life and minimal effectiveness, leave half of patients undertreated, highlighting the need for new therapies to enhance well-being. Epigenetics, which studies genetic changes in gene expression or cellular phenotype without altering the underlying Deoxyribonucleic Acid (DNA) sequence, is explored in this article. This article delves into the intricate relationship between epigenetic mechanisms and depression, shedding light on how environmental stressors, early-life adversity, and genetic predispositions shape gene expression patterns associated with depression. We have also discussed Histone Deacetylase (HDAC) inhibitors, which enhance cognitive function and mood regulation in depression. Non-coding RNAs, (ncRNAs) such as Long Non-Coding RNAs (lncRNAs) and micro RNA (miRNAs), are highlighted as potential biomarkers for detecting and monitoring major depressive disorder (MDD). This article also emphasizes the reversible nature of epigenetic modifications and their influence on neuronal growth processes, underscoring the dynamic interplay between genetics, environment, and epigenetics in depression development. It explores the therapeutic potential of targeting epigenetic pathways in treating clinical depression. Additionally, it examines clinical findings related to epigenetic clocks and their role in studying depression and biological aging.

A Secondary Analysis of the Complex Interplay between Psychopathology, Cognitive Functions, Brain Derived Neurotrophic Factor Levels, and Suicide in Psychotic Disorders: Data from a 2-Year Longitudinal Study

Identifying phenotypes at high risk of suicidal behaviour is a relevant objective of clinical and translational research and can facilitate the identification of possible candidate biomarkers. We probed the potential association and eventual stability of neuropsychological profiles and serum BDNF concentrations with lifetime suicide ideation and attempts (LSI and LSA, respectively) in individuals with schizophrenia (SCZ) and schizoaffective disorder (SCA) in a 2-year follow-up study. A secondary analysis was conducted on a convenience sample of previously recruited subjects from a single outpatient clinic. Retrospectively assessed LSI and LSA were recorded by analysing the available longitudinal clinical health records. LSI + LSA subjects consistently exhibited lower PANSS-defined negative symptoms and better performance in the BACS-letter fluency subtask. There was no significant association between BDNF levels and either LSI or LSA. We found a relatively stable pattern of lower negative symptoms over two years among patients with LSI and LSA. No significant difference in serum BDNF concentrations was detected. The translational viability of using neuropsychological profiles as a possible avenue for the identification of populations at risk for suicide behaviours rather than the categorical diagnosis represents a promising option but requires further confirmation.

Advances in development of biomarkers for brain damage and ischemia

Acquired brain injury is an urgent situation that requires rapid diagnosis and treatment. Magnetic resonance imaging (MRI) and computed tomography (CT) are required for accurate diagnosis. However, these methods are costly and require substantial infrastructure and specialized staff. Circulatory biomarkers of acute brain injury may help in the management of patients with acute cerebrovascular events and prevent poor outcome and mortality. The purpose of this review is to provide an overview of the development of potential biomarkers of brain damage to increase diagnostic possibilities. For this purpose, we searched the PubMed database of studies on the diagnostic potential of brain injury biomarkers. We also accessed information from Clinicaltrials.gov to identify any clinical trials of biomarker measurements for the diagnosis of brain damage. In total, we present 41 proteins, enzymes and hormones that have been considered as biomarkers for brain injury, of which 20 have been studied in clinical trials. Several microRNAs have also emerged as potential clinical biomarkers for early diagnosis. Combining multiple biomarkers in a panel, along with other parameters, is yielding promising outcomes.

Health risks of Bisphenol-A exposure: From Wnt signaling perspective

Human beings are routinely exposed to chronic and low dose of Bisphenols (BPs) due to their widely pervasiveness in the environment. BPs hold similar chemical structures to 17β-estradiol (E2) and thyroid hormone, thus posing threats to human health by rendering the endocrine system dysfunctional. Among BPs, Bisphenol-A (BPA) is the best-known and extensively studied endocrine disrupting compound (EDC). BPA possesses multisystem toxicity, including reproductive toxicity, neurotoxicity, hepatoxicity and nephrotoxicity. Particularly, the central nervous system (CNS), especially the developing one, is vulnerable to BPA exposure. This review describes our current knowledge of BPA toxicity and the related molecular mechanisms, with an emphasis on the role of Wnt signaling in the related processes. We also discuss the role of oxidative stress, endocrine signaling and epigenetics in the regulation of Wnt signaling by BPA exposure. In summary, dysfunction of Wnt signaling plays a key role in BPA toxicity and thus can be a potential target to alleviate EDCs induced damage to organisms.

Changes in BDNF methylation patterns after cognitive remediation therapy in schizophrenia: A randomized and controlled trial

Although cognitive remediation therapy (CRT) produces cognitive benefits in schizophrenia, we do not yet understand whether molecular changes are associated with this cognitive improvement. A gene central to synaptic plasticity, the BDNF, has been proposed as one potential route. This study assesses whether BDNF methylation changes following CRT-produced cognitive improvement are detected. A randomized and controlled trial was performed with two groups (CRT, n = 40; TAU: Treatment as Usual, n = 20) on a sample of participants with schizophrenia. CRT was delivered by trained therapists using a web-based computerized program. Mixed Models, where the interaction of treatment (CRT, TAU) by time (T0: 0 weeks, T1: 16 weeks) was the main effect were used. Then, we tested the association between the treatment and methylation changes in three CpG islands of the BDNF gene. CRT group showed significant improvements in some cognitive domains. Between-groups differential changes in 5 CpG units over time were found, 4 in island 1 (CpG1.2, CpG1.7, CpG1.10, CpG1.17) and 1 in island 3 (CpG3.2). CRT group showed increases in methylation in CpG1.2, CpG1.7 and decreases in pG1.10, CpG1.17, and CpG3.2. Differences in the degree of methylation were associated with changes in Speed of Processing, Working Memory, and Verbal Learning within the CRT group. Those findings provide new data on the relationship between cognitive improvement and changes in peripheral methylation levels of BDNF gene, a key factor involved in neuroplasticity regulation. Trial Registration: NCT04278027.

Acupressure bladder meridian alleviates anxiety disorder via HMGB1

The aim of this study was to investigate the effects of acupressure bladder meridian (ABM) on anxiety in rats with chronic stress.

METHODS

The sugar water preference (SPF), tail suspension time (TST) and forced swimming time (FST) of rats were measured. The levels of reactive oxygen species (ROS), myeloperoxidase (MPO) in hippocampus tissue, oxidative stress parameters and inflammatory cytokines were detected. Underlying mechanisms of ABM on anxiety were detected. lipopolysaccharide (LPS) stimulated PC12 cells were adopted in vitro. HMGB1 knockdown were used in PC12 cells, and related signaling was further detected.

RESULTS

ABM significantly increased SPF, decreased TST and FST. ABM decreased ROS, MPO levels, decreased the levels of inflammatory cytokines. Furthermore, ABM decreased the levels of oxidative stress index. ABM reduced the expression of inflammation-related proteins mediated by HMGB1, increased nuclear factor erythroid2-related factor 2 (Nrf-2) and hemeoxygenase-1 (HO-1). In vitro PC12 cells, Rat serum (RS-ABM) treated with ABM significantly decreased LPS induced inflammation-related proteins and increased Nrf-2/HO-1 pathway. HMGB1 knockdown inhibited LPS-induced PC12 cell inflammatory signaling pathway and increased Nrf-2/HO-1 pathway.

CONCLUSION

Our results demonstrated that ROS-dependent HMGB1 plays an important role in anxiety, and ABM exhibits inhibited inflammation in anxiety.

In silico and in vivo analysis of the relationship between ADHD and social isolation in pups rat model: Implication of redox mechanisms, and the neuroprotective impact of Punicalagin

Attention deficit hyperactivity disorder (ADHD) has high incidence rate among children which may be due to excessive monosodium glutamate (MSG) consumption and social isolation (SI).

AIM

We aimed to explore the relationships between MSG, SI, and ADHD development and to evaluate the neuroprotective potential of Punicalagin (PUN).

METHODS

Eighty male rat pups randomly distributed into eight groups. Group I is the control, and Group II is socially engaged rats treated with PUN. Groups III to VII were exposed to ADHD-inducing factors: Group III to SI, Group IV to MSG, and Group V to both SI and MSG. Furthermore, Groups VI to VIII were the same Groups III to V but additionally received PUN treatment.

KEY FINDINGS

Exposure to MSG and/or SI led to pronounced behavioral anomalies, histological changes and indicative of ADHD-like symptoms in rat pups which is accompanied by inhibition of the nuclear factor erythroid 2-related factor 2 (Nrf2)/Heme-oxygenase 1 (HO-1)/Glutathione (GSH) pathway, decline of the brain-derived neurotrophic factor (BDNF) expression and activation of the Toll-like receptor 4 (TLR4)/Nuclear factor kappa B (NF-kB)/NLR Family Pyrin Domain Containing 3 (NLRP3) pathway. This resulted in elevated inflammatory biomarker levels, neuronal apoptosis, and disrupted neurotransmitter equilibrium. Meanwhile, pretreatment with PUN protected against all the previous alterations.

SIGNIFICANCE

We established compelling associations between MSG consumption, SI, and ADHD progression. Moreover, we proved that PUN is a promising neuroprotective agent against all risk factors of ADHD.

Stress-related cellular pathophysiology as a crosstalk risk factor for neurocognitive and psychiatric disorders

In this narrative review, we examine biological processes linking psychological stress and cognition, with a focus on how psychological stress can activate multiple neurobiological mechanisms that drive cognitive decline and behavioral change. First, we describe the general neurobiology of the stress response to define neurocognitive stress reactivity. Second, we review aspects of epigenetic regulation, synaptic transmission, sex hormones, photoperiodic plasticity, and psychoneuroimmunological processes that can contribute to cognitive decline and neuropsychiatric conditions. Third, we explain mechanistic processes linking the stress response and neuropathology. Fourth, we discuss molecular nuances such as an interplay between kinases and proteins, as well as differential role of sex hormones, that can increase vulnerability to cognitive and emotional dysregulation following stress. Finally, we explicate several testable hypotheses for stress, neurocognitive, and neuropsychiatric research. Together, this work highlights how stress processes alter neurophysiology on multiple levels to increase individuals' risk for neurocognitive and psychiatric disorders, and points toward novel therapeutic targets for mitigating these effects. The resulting models can thus advance dementia and mental health research, and translational neuroscience, with an eye toward clinical application in cognitive and behavioral neurology, and psychiatry.

The Role of Brain-Derived Neurotrophic Factor (BDNF) in Depression and Cardiovascular Disease: A Systematic Review

BACKGROUND

Several studies have been conducted to prove the bidirectional relationship between cardiovascular disease (CVD) and depression. These two major illnesses share several common risk factors such that the development of either condition may increase the risk of the occurrence of the other. Brain-derived neurotrophic factor (BDNF) has been suggested as a reliable biomarker for depression and a strong predictor of CVD because it plays an important role in neuron survival and growth, serves as a neurotransmitter modulator, and promotes neuronal plasticity. The aim of this systematic review was to examine the bidirectional relationship between CVD and depression, focusing on the potential role of low serum BDNF levels in the development of either disease in the presence of the other.

METHODS

A systematic search strategy was developed using PRISMA guidelines.

RESULTS

Six studies (comprising 1251 patients) were identified, all of which examined the association between CVD and depression.

CONCLUSIONS

It was found that there may be a strong association between low serum BDNF levels and the risk of post-stroke depression. However, the studies on the role of altered serum BDNF levels and other types of CVD are few. Therefore, the inverse association between depression and CVD cannot be proven.

Chronic Ethanol Consumption by Rats before Mating Affects Working Memory in the Offspring

Parameters of non-spatial and spatial memory were evaluated in sexually mature offspring of outbred rats (females and males F0) consuming a 10% ethanol solution for 30 weeks before mating. We found a significant increase in the recognition index in F1 males and its decrease in F1 females in the novel object recognition test. During the first days of the experiment in T-maze, a decrease in spatial memory was revealed in F1 males, which remained at the trend level until the end of testing; no significant deviations were detected in F1 females. Memory impairment in F1 females was accompanied by a decrease in BDNF level in the hippocampus, but not in the prefrontal cortex. Thus, ethanol consumption by F0 rats before mating led to impairment of long-term working memory only in female F1 offspring.

Environmental Enrichment Increased Bdnf Transcripts in the Prefrontal Cortex: Implications for an Epigenetically Controlled Mechanism

Environmental enrichment (EE) is a condition characterized by its complexity regarding social contact, exposure to novelty, tactile stimuli and voluntary exercise, also is considered as a eustress model. The impact of EE on brain physiology and behavioral outcomes may be at least partly underpinned by mechanisms involving the modulation of the brain-derived neurotrophic factor (BDNF), but the connection between specific Bdnf exon expression and their epigenetic regulation remain poorly understood. This study aimed to dissect the transcriptional and epigenetic regulatory effect of 54-day exposure to EE on BDNF by analysing individual BDNF exons mRNA expression and the DNA methylation profile of a key transcriptional regulator of the Bdnf gene, exon IV, in the prefrontal cortex (PFC) of C57BL/6 male mice (sample size = 33). Bdnf exons II, IV, VI and IX mRNA expression were upregulated and methylation levels at two CpG sites of exon IV were reduced in the PFC of EE mice. As deficit in exon IV expression has also been causally implicated in stress-related psychopathologies, we also assessed anxiety-like behavior and plasma corticosterone levels in these mice to determine any potential correlation. However, no changes were observed in EE mice. The findings may suggest an EE-induced epigenetic control of BDNF exon expression via a mechanism involving exon IV methylation. The findings of this study contribute to the current literature by dissecting the Bdnf gene topology in the PFC where transcriptional and epigenetic regulatory effect of EE takes place.

Perceived Parental Support and Psychological Control, DNA Methylation, and Loneliness: Longitudinal Associations Across Early Adolescence

A broad range of factors have been associated with the development of adolescent loneliness. In the family context, a lack of parental support and high levels of parental psychological control have systematically been linked to loneliness. On the biological level, DNA methylation (which is an epigenetic process that suppresses gene expression) is believed to play a role in the development of loneliness. Specifically, high levels of DNA methylation in genes that play an important role in the functioning of the human stress response system are believed to elevate the risk of loneliness. Moreover, DNA methylation levels in these stress-related genes can be influenced by stressful environmental factors, suggesting a potential mediating role of DNA methylation in the association between parenting behaviors and loneliness. The current 3-year longitudinal study is the first study to examine the potential bidirectional longitudinal associations between loneliness, DNA methylation in stress-related genes, and both perceived parental support and psychological control. Furthermore, we explored the potential mediating role of DNA methylation in stress-related genes in the associations between perceived parenting and loneliness. The sample comprised 622 early adolescents (55% girls, M_{age T1} = 10.77 years, SD_{age T1} = 0.48) who were followed from Grade 5 to 7. Parental support, psychological control, and loneliness were assessed annually by adolescent self-report questionnaires and DNA methylation was determined from saliva samples. Cross-Lagged Panel Models (CLPM) revealed that higher levels of loneliness predicted lower perceived parental support and higher perceived psychological control over time, as well as higher DNA methylation in some stress-related genes, that is, the glucocorticoid receptor gene (NR3C1) and the brain-derived neurotrophic factor (BDNF). In addition, higher NR3C1 methylation was predictive of lower perceived parental support and higher psychological control over time. No evidence was found for a mediating role of DNA methylation. Overall, our longitudinal findings challenge the current focus on DNA methylation and parenting behaviors as risk factors for adolescent loneliness. Instead, they suggest that the less considered direction of effects, which implies that loneliness predicts DNA methylation and aspects of parenting such as support and psychological control, should receive greater attention in future research.

The influence of the BDNF Val66Met genotype on emotional recognition memory in post-traumatic stress disorder

Dysregulated consolidation of emotional memories is a core feature of posttraumatic stress disorder (PTSD). Brain Derived Neurotrophic Factor (BDNF) influences synaptic plasticity and emotional memory consolidation. The BDNF Val66Met polymorphism has been associated with PTSD risk and memory deficits respectively, although findings have been inconsistent, potentially due to a failure to control for important confounds such as sex, ethnicity, and the timing/extent of previous trauma experiences. Furthermore, very little research has examined the impact of BDNF genotypes on emotional memory in PTSD populations. This study investigated the interaction effects of Val66Met and PTSD symptomatology in an emotional recognition memory task in 234 participants divided into healthy control (n = 85), trauma exposed (TE: n = 105) and PTSD (n = 44) groups. Key findings revealed impaired negative recognition memory in PTSD compared to control and TE groups and in participants with the Val/Met compared to the Val/Val genotype. There was a group × genotype interaction showing no Met effect in the TE group despite significant effects in PTSD and controls. Results suggest that people previously exposed to trauma who do not develop PTSD may be protected from the BDNF Met effect, however more research is needed to replicate findings and to explore the epigenetic and neural processes involved.

Methylation of BDNF gene in association with episodic memory in women

Brain-derived neurotrophic factor (BDNF) gene regulation plays an important role in long-term memory formation, and the DNA methylation (DNAm) level of BDNF promoters has been associated with episodic memory deficits. Our aim was to explore the association between DNAm levels in BDNF promoter IV with verbal learning and memory performance in healthy women. We conducted a cross-sectional study by recruiting 53 individuals. Episodic memory was assessed by using the Rey Auditory Verbal Learning Test (RAVLT). Clinical interviews, RAVLT, and blood sample collection were assessed in all participants. DNAm was measured on DNA from whole peripheral blood using pyrosequencing. According to generalized linear model (GzLM) analyses, cytosine guanine dinucleotide (CpG) site 5 showed significant associations between learning capacity (LC, p < 0.035), that is, every 1% of DNA methylation at CpG site 5 results in a 0.068 reduction in verbal learning performance. To the best of our knowledge, the current study is the first to show that BDNF DNAm plays an important role in episodic memory.

Brain-derived neurotrophic factor (BDNF) in perinatal depression: Side show or pivotal factor?

Perinatal depression is the most common psychiatric complication of pregnancy, with its detrimental effects on maternal and infant health widely underrated. There is a pressing need for specific molecular biomarkers, with pregnancy-related decline in brain-derived neurotrophic factor (BDNF) in the blood and downregulation of TrkB receptor in the brain reported in clinical and preclinical studies. In this review, we explore the emerging role of BDNF in reproductive biology and discuss evidence suggesting its deficiency as a risk factor for perinatal depression. With the increasing evidence for restoration of serum BDNF levels by antidepressant therapy, the strengthening association of perinatal depression with deficiency of BDNF supports its potential as a surrogate endpoint for preclinical and clinical studies.

Association of BDNF gene missense polymorphism rs6265 (Val66Met) with three quantitative traits, namely, intelligence quotient, body mass index, and blood pressure: A genetic association analysis from North India

Background

Brain-derived neurotrophic factor (BDNF), a neurotransmitter modulator, plays a significant role in neuronal survival and growth and participates in neuronal plasticity, thus being essential for learning, memory, and the development of cognition. Additionally, it is crucial for appetite, weight, and metabolic control and plays a pivotal role in the cardiovascular system. The Val66Met polymorphism (rs6265) of the BDNF gene causes a decrease in BDNF secretion and plays a role in impairments in cognition, energy homeostasis, and cardiovascular events. The present study aimed to evaluate the association of polymorphism (rs6265) of the BDNF gene with three quantitative traits simultaneously, namely, intelligence quotient (IQ), body mass index (BMI), and blood pressure (BP).

Methods

Psychometric, morphometric, and physiometric data of the total participants (N = 246) were collected. WASI-II^INDIA was used to measure cognitive ability. Genotyping was carried out using allele-specific PCR for the rs6265 polymorphism (C196T), and genotypes were determined. Statistical analyses were performed at p < 0.05 significance level using MS-Excel and SigmaPlot. The odds ratio models with a 95% confidence interval were used to test the associations. The used models are co-dominant, recessive, dominant, over-dominant, and additive.

Results

The allelic frequencies of alleles C and T were 72 and 28%, respectively. Under the dominant genetic model, a significant susceptible association of minor allele T was observed with a lower average verbal comprehensive index (OR = 2.216, p = 0.003, CI (95%) =1.33-3.69), a lower average performance reasoning index (OR = 2.634, p < 0.001, CI (95%) = 1.573-4.41), and a lower average full-scale IQ-4 (OR = 3.159, p < 0.001, CI (95%) = 1.873-5.328). Carriers of Met-alleles were found to have an increased body mass index (OR = 2.538, p < 0.001, CI (95%) = 1.507-4.275), decreased systolic blood pressure (OR = 2.051, p = 0.012, CI (95%) = 1.202-3.502), and decreased diastolic blood pressure (OR = 2.162, p = 0.006, CI (95%) = 1.278-3.657). Under the recessive genetic model, several folds decrease in IQ and BP and an increase in BMI with the presence of the T allele was also detected.

Conclusion

This novel study may improve our understanding of genetic alterations to the traits and hence be helpful for clinicians and researchers to investigate the diagnostic and prognostic value of this neurotrophic factor.

Childhood adverse events and BDNF promoter methylation in later-life

Studies have shown that the effects of early-life stress and trauma can be enduring, with long-term negative effects on health. Epigenetics, including DNA methylation, have been implicated as a potential mechanism for these effects. Brain-derived neurotropic factor (BDNF) is a neurotransmitter involved in learning and memory, and altered BDNF promoter methylation measured in peripheral tissue has been found with early-life stress. However, whether such methylation differences remain stable into later life, is unknown. This study aimed to investigate the association between childhood adversity and BDNF promoter methylation in adults aged 65 years and over. Data came from a large study of older community-dwelling individuals in France (ESPRIT). Information on three major childhood adverse events, namely abuse/maltreatment, war/natural disaster, and financial difficulties/poverty, was obtained by retrospective reporting from participants of ESPRIT study. BDNF promoter I and IV methylation was assessed in blood and buccal tissue. Linear regression analysis was performed, adjusting for age, sex, education, depression, and morbidity. Among 927 participants, there was no strong evidence that childhood abuse/maltreatment or financial difficulties/poverty were associated with BDNF methylation in older individuals. For war/natural disaster, differential methylation at four of twenty-nine CpG sites was observed, however, these would not have remained significant after correction for multiple testing. Together, these findings do not support a long-term association between adverse childhood events and BDNF methylation in older age, but further large prospective studies are needed, which do not target specific genes, but consider DNA methylation across the genome.

BDNF exon IV promoter methylation and antidepressant action: a complex interplay

BACKGROUND

BDNF exon IV promoter methylation is a potential biomarker for treatment response to antidepressants in MDD. We have previously shown CpG-87 methylation as a successful biomarker for the prediction of non-response to monoaminergic antidepressants like the SSRI Fluoxetine or the SNRI Venlafaxine. This study aimed to dissect the biological evidence and mechanisms for the functionality of CpG-87 methylation in a cell culture model.

RESULTS

We observed a significant interaction between methylation and antidepressant-mediated transcriptional activity in BDNF exon IV promoter. In addition, antidepressant treatment increased the promoter methylation in a concentration-dependent manner. Further single CpG methylation of -87 did not change the promoter activity, but methylation of CREB domain CpG-39 increased the transcriptional activity in an antidepressant-dependent manner. Interestingly, DNMT3a overexpression also increases the BDNF exon IV transcription and more so in Venlafaxine-treated cells.

CONCLUSIONS

The study strengthens the previously reported association between antidepressant treatment and BDNF exon IV promoter methylation as well as hints toward the mechanism of action. We argue that potential CpG methylation biomarkers display a complex synergy with the molecular changes at the neighboring CpG positions, thus highlighting the importance of epiallele analyses.

The stress-vulnerability model on the path to schizophrenia: Interaction between BDNF methylation and schizotypy on the resting-state brain network

The interplay between schizophrenia liability and environmental influences has been considered to be responsible for the development of schizophrenia. Recent neuroimaging studies have linked aberrant functional connectivity (FC) between the default-mode network (DMN) and the frontoparietal network (FPN) in the resting-state to the underlying neural mechanism of schizophrenia. By using schizotypy as the proxy for genetic-based liability to schizophrenia and methylation of brain-derived neurotrophic factor (BDNF) to represent environmental exposure, this study investigated the impact of the interaction between vulnerability and the environment on the neurobiological substrates of schizophrenia. Participants in this study included 101 healthy adults (HC) and 46 individuals with ultra-high risk for psychosis (UHR). All participants were tested at resting-state by functional magnetic resonance imaging, and group-independent component analysis was used to identify the DMN and the FPN. The Perceptual Aberration Scale (PAS) was used to evaluate the schizotypy level. The methylation status of BDNF was measured by pyrosequencing. For moderation analysis, the final sample consisted of 83 HC and 32 UHR individuals. UHR individuals showed reduced DMN-FPN network FC compared to healthy controls. PAS scores significantly moderated the relationship between the percentage of BDNF methylation and DMN-FPN network FC. The strength of the positive relationship between BDNF methylation and the network FC was reduced when the schizotypy level increased. These findings support the moderating role of schizotypy on the neurobiological mechanism of schizophrenia in conjunction with epigenetic changes.

Regulation of DNA Methylation by Cannabidiol and Its Implications for Psychiatry: New Insights from In Vivo and In Silico Models

Cannabidiol (CBD) is a non-psychotomimetic compound present in cannabis sativa. Many recent studies have indicated that CBD has a promising therapeutic profile for stress-related psychiatric disorders, such as anxiety, schizophrenia and depression. Such a diverse profile has been associated with its complex pharmacology, since CBD can target different neurotransmitter receptors, enzymes, transporters and ion channels. However, the precise contribution of each of those mechanisms for CBD effects is still not yet completely understood. Considering that epigenetic changes make the bridge between gene expression and environment interactions, we review and discuss herein how CBD affects one of the main epigenetic mechanisms associated with the development of stress-related psychiatric disorders: DNA methylation (DNAm). Evidence from in vivo and in silico studies indicate that CBD can regulate the activity of the enzymes responsible for DNAm, due to directly binding to the enzymes and/or by indirectly regulating their activities as a consequence of neurotransmitter-mediated signaling. The implications of this new potential pharmacological target for CBD are discussed in light of its therapeutic and neurodevelopmental effects.

Post hoc power is not informative

Post hoc power estimates are often requested by reviewers and/or performed by researchers after a study has been conducted. The purpose of this commentary is to provide a heuristic explanation of why post hoc power should not be used. To illustrate our point, we provide a detailed simulation study of two essentially identical research experiments hypothetically conducted in parallel at two separate universities. The simulation demonstrates that post hoc power calculations are misleading and simply not informative for data interpretation. As such, we encourage authors and peer-reviewers to avoid using or requesting post hoc power calculations.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Neuroinflammation in HIV-associated depression: evidence and future perspectives

People living with HIV face a high risk of mental illness, especially depression. We do not yet know the precise neurobiological mechanisms underlying HIV-associated depression. Depression severity in the general population has been linked to acute and chronic markers of systemic inflammation. Given the associations between depression and peripheral inflammation, and since HIV infection in the brain elicits a neuroinflammatory response, it is possible that neuroinflammation contributes to the high prevalence of depression amongst people living with HIV. The purpose of this review was to synthesise existing evidence for associations between inflammation, depression, and HIV. While there is strong evidence for independent associations between these three conditions, few preclinical or clinical studies have attempted to characterise their interrelationship, representing a major gap in the literature. This review identifies key areas of debate in the field and offers perspectives for future investigations of the pathophysiology of HIV-associated depression. Reproducing findings across diverse populations will be crucial in obtaining robust and generalisable results to elucidate the precise role of neuroinflammation in this pathophysiology.

Pathophysiology of Depression: Stingless Bee Honey Promising as an Antidepressant

Depression is a debilitating psychiatric disorder impacting an individual’s quality of life. It is the most prevalent mental illness across all age categories, incurring huge socio-economic impacts. Most depression treatments currently focus on the elevation of neurotransmitters according to the monoamine hypothesis. Conventional treatments include tricyclic antidepressants (TCAs), norepinephrine–dopamine reuptake inhibitors (NDRIs), monoamine oxidase inhibitors (MAOIs), and serotonin reuptake inhibitors (SSRIs). Despite numerous pharmacological strategies utilising conventional drugs, the discovery of alternative medicines from natural products is a must for safer and beneficial brain supplement. About 30% of patients have been reported to show resistance to drug treatments coupled with functional impairment, poor quality of life, and suicidal ideation with a high relapse rate. Hence, there is an urgency for novel discoveries of safer and highly effective depression treatments. Stingless bee honey (SBH) has been proven to contain a high level of antioxidants compared to other types of honey. This is a comprehensive review of the potential use of SBH as a new candidate for antidepressants from the perspective of the monoamine, inflammatory and neurotrophin hypotheses.

Interactive effects of the BDNF Val66Met polymorphism and posttraumatic stress disorder on cognition in U.S. military veterans

Posttraumatic stress disorder (PTSD) is associated with mild-to-moderate deficits in cognition. The Met allele of the brain-derived neurotrophic factor (BDNF) Val66Met gene may also be associated with deficits in cognition. However, findings are inconsistent and may be sensitive to moderating variables such as psychopathology. While emerging research suggests that PTSD and the Met allele may interact, few studies have replicated this effect or examined the interactive effect of PTSD and the Met allele on subjective cognition. To address this gap, the current study analyzed data from European-American (EA) U.S. military veterans (n = 1244) who participated in the National Health and Resilience in Veterans Study (NHRVS) to examine the main and interactive effects of BDNF Val66Met genotype and probable PTSD on objective and subjective cognition. Results revealed significant (p's < 0.001) interactions between Met allele carrier status and probable PTSD in objective and subjective cognition. Among individuals with probable PTSD (n = 131), the Met allele was associated with poorer objective (p < .001, d = 0.62) and subjective cognition (p = .001, d = 0.53). Among individuals without PTSD (n = 1113), the Met allele was not significantly associated with objective or subjective cognition. These findings suggest that PTSD may moderate the association between Met allele carrier status and cognition. Implications of these results for the mitigation of cognitive dysfunction in older veterans are discussed.

Oxytocin receptor genes moderate BDNF epigenetic methylation by childhood trauma

OBJECTIVES

Gene-Environment (G × E) interaction is of increasing importance in understanding the pathophysiology of posttraumatic stress disorder (PTSD). This study investigated the interaction effect of childhood traumatic experience and epigenetic methylation of brain-derived neurotrophic factor (BDNF) and a possible moderating effect of oxytocin receptor (OXTR) gene rs53576.

METHODS

Ninety-nine patients with PTSD and 81 healthy controls (HCs) were recruited. Clinical assessments, including the childhood trauma questionnaire (CTQ) and posttraumatic stress disorder Checklist (PCL) were performed. BDNF methylation and OXTR genotyping (A vs. G allele) were conducted through blood sampling. A two-way multivariate analysis and a moderated regression analysis were conducted to investigate the moderating effect of the OXTR gene on the relationship between CTQ and BDNF methylation.

RESULTS

As for the HC group, the interaction effect of the CTQ and OXTR genotype was significant on BDNF methylation, and the moderation model showed that CTQ and OXTR group are significant predictors of BDNF methylation. In the G-OXTR type, the high CTQ group showed a greater BDNF methylation level. As for the PTSD group, no interaction or moderation effects were found.

LIMITATIONS

The present study did not control the dosage, duration of medications, and different trauma types and the assessment of childhood trauma was based on self-report.

CONCLUSIONS

These results suggested that childhood traumatic experience showed a significant impact on BDNF methylation, and OXTR genes have a moderating effect on this epigenetic mechanism in people who have experienced the childhood traumatic episodes.

BDNF as a potential mediator between childhood BPA exposure and behavioral function in adolescent boys from the INMA-Granada cohort

BACKGROUND

Bisphenol A (BPA) exposure has been linked to altered behavior in children. Within the European Human Biomonitoring Initiative (HBM4EU), an adverse outcome pathway (AOP) network was constructed supporting the mechanistic link between BPA exposure and brain-derived neurotrophic factor (BDNF).

OBJECTIVE

To test this toxicologically-based hypothesis in the prospective INMA-Granada birth cohort (Spain).

METHODS

BPA concentrations were quantified by LC-MS/MS in spot urine samples from boys aged 9-11 years, normalized by creatinine and log-2 transformed. At adolescence (15-17 years), blood and urine specimens were collected, and serum and urinary BDNF protein levels were measured using immunoassays. DNA methylation levels at 6 CpGs in Exon IV of the BDNF gene were also assessed in peripheral blood using bisulfite-pyrosequencing. Adolescent's behavior was parent-rated using the Child Behavior Checklist (CBCL/6-18) in 148 boys. Adjusted linear regression and mediation models were fit.

RESULTS

Childhood urinary BPA concentrations were longitudinally and positively associated with thought problems (β = 0.76; 95% CI: 0.02, 1.49) and somatic complaints (β = 0.80; 95% CI: -0.16, 1.75) at adolescence. BPA concentrations were positively associated with BDNF DNA methylation at CpG6 (β = 0.21; 95% CI: 0.06, 0.36) and mean CpG methylation (β = 0.10; 95% CI: 0.01, 0.18), but not with total serum or urinary BDNF protein levels. When independent variables were categorized in tertiles, positive dose-response associations were observed between BPA-thought problems (p-trend = 0.08), BPA-CpG6 (p-trend ≤ 0.01), and CpG6-thought problems (p-trend ≤ 0.01). A significant mediated effect by CpG6 DNA methylation was observed (β = 0.23; 95% CI: 0.01, 0.57), accounting for up to 34% of the BPA-thought problems association.

CONCLUSIONS

In line with toxicological studies, BPA exposure was longitudinally associated with increased BDNF DNA methylation, supporting the biological plausibility of BPA-behavior relationships previously described in the epidemiological literature. Given its novelty and preliminary nature, this effect biomarker approach should be replicated in larger birth cohorts.

Dysregulated Methylation Patterns in Exon IV of the Brain-Derived Neurotrophic Factor (BDNF) Gene in Nicotine Dependence and Changes in BDNF Plasma Levels During Smoking Cessation

INTRODUCTION

Several studies reported dysregulated protein levels of brain-derived neurotrophic factor (BDNF) in smokers and during cessation. However, the epigenetic regulation of the BDNF gene has not yet been investigated. We measured the plasma levels of BDNF and the epigenetic regulation of exon IV of the BDNF gene in smokers compared to healthy controls over a cessation period of 14 days.

METHOD

We measured BDNF plasma levels and BDNF promoter methylation in 49 smokers and 51 non-smokers at baseline, day 7, and day 14 of smoking cessation. Mean methylation levels of 11 Cytosine Guanosine dinucleotides of exon IV of the BDNF gene were determined via bisulfite sequencing.

RESULTS

BDNF plasma and methylation levels were significantly lower in healthy controls when compared with smokers across all time points. BDNF levels for smokers decreased significantly during the cessation period. Comparing the sexes, female smokers showed significantly lower plasma BDNF levels than healthy controls at baseline and over 14 days of cessation. Male and female smokers showed significantly higher mean methylation rates than non-smokers at baseline. In male smokers, mean methylation levels decreased significantly during the cessation period.

CONCLUSION

Our findings replicate the findings of previous studies that BDNF plasma levels are altered in smokers. Furthermore, BDNF expression and gene methylation are altered during the first 14 days of cessation. Our novel findings of dysregulated methylation patterns in exon IV of the BDNF gene further support the thesis that BDNF plays a role in nicotine dependence.

Is Brain-Derived Neurotropic Factor Methylation Involved in the Association Between Prenatal Stress and Maternal Postnatal Anxiety During the COVID-19 Pandemic?

BACKGROUND

The COVID-19 pandemic is a collective trauma that may expose susceptible individuals to high levels of stress. Pregnant women represent a high-risk population, considering that pregnancy is a period of heightened neuroplasticity and susceptibility to stress through epigenetic mechanisms. Previous studies showed that the methylation status of the BDNF gene is linked with prenatal stress exposure. The goals of this study were (a) to assess the association between pandemic-related stress and postnatal anxiety and (b) to investigate the potential role of maternal BDNF methylation as a significant mediator of this association.

METHODS

In the present study, we report data on the association among pandemic-related stress during pregnancy, maternal BDNF methylation, and postnatal anxiety symptoms. Pandemic-related stress and postnatal anxiety were assessed through self-report instruments. BDNF methylation was estimated in 11 CpG sites in DNA from mothers' buccal cells. Complete data were available from 108 mothers.

RESULTS

Results showed that pandemic-related stress was associated with an increased risk of postnatal anxiety, r = 0.20, p < 0.05. CpG-specific BDNF methylation was significantly associated with both prenatal pandemic-related stress, r = 0.21, p < 0.05, and postnatal maternal anxious symptoms, r = 0.25, p = 0.01. Moreover, a complete mediation by the BDNF CpG6 methylation emerged between pandemic-related stress during pregnancy and postnatal maternal anxiety, ACME = 0.66, p < 0.05.

CONCLUSION

These findings suggest that BDNF epigenetic regulation by pandemic-related stress might contribute to increase the risk of anxiety in mothers. Policymakers should prioritize the promotion of health and wellbeing in pregnant women and mothers during the present healthcare emergency.

Aspirin ameliorates the cognition impairment in mice following benzo[a]pyrene treatment via down-regulating BDNF IV methylation

Benzo[a]pyrene (B[a]P) is neurotoxic, however, the mechanisms remain unclear and there is no effective prevention. Available evidence suggests a role of DNA methylation in B[a]P-induced neurotoxicity. This study investigated the brain-derived neurotrophic factor (BDNF) IV methylation in the development of and aspirin intervention against B[a]P's neurotoxicity in mice and HT22 cells. Mice were intraperitoneally treated with solvent or B[a]P (0.5, 2, and 10 mg/kg b.w.) for 60 days. An intervention group was treated simultaneously with B[a]P (10 mg/kg, i.p.) and aspirin (10 mg/kg, daily water-drinking). The treated mice showed a dose-dependent cognitive and behavioral impairment, and cerebral cell apoptosis, which were alleviated by aspirin co-treatment. Following B[a]P treatment, DNA methyltransferase (DNMTs) and BDNF IV hypermethylation were increased in the cerebral cortex of mice compared to controls, while significant decreases were found in BDNF IV and BDNF mRNA, and BDNF protein levels. Aspirin co-treatment rescued DNMTs activation and BDNF IV hypermethylation, and mitigated the recession in BDNF mRNA and protein induced by B[a]P treatment. Similar results were shown in HT22 cells. These findings reveal a critical role of BDNF IV methylation in the neurotoxicity of B[a]P, and demonstrate a promising prevention of aspirin against B[a]P-induced cognitive impairment via inhibiting BDNF IV hypermethylation.

BDNF methylation and mRNA expression in brain and blood of completed suicides in Slovenia

BACKGROUND

Suicide is a major public health problem. Worldwide, around 800000 people die by suicide every year. Suicide is a multifactorial disorder, with numerous environmental and genetic risk factors involved. Among the candidate genes, changes in the BDNF locus at the gene, epigenetic, mRNA, and protein expression levels have been implicated in psychiatric disorders, including suicidal behavior and completed suicides.

AIM

To investigate changes in BDNF methylation and expression of four alternative BDNF transcripts for association with completed suicide.

METHODS

This case-control study included 42 unrelated male Caucasian subjects, where 20 were control subjects who died following acute cardiac arrest, and 22 were suicide victims who died by hanging. DNA and RNA were extracted from brain tissue (Brodmann area 9 and hippocampus) and from blood. DNA methylation and mRNA expression levels were determined by targeted bisulfite next-generation sequencing and reverse-transcription quantitative PCR. Statistical analysis was done by use of two-tailed Student’s t tests for two independent samples, and the Benjamini-Hochberg procedure was implemented for correction for multiple comparisons.

RESULTS

In DNA from brain tissue, there were no significant differences in BDNF methylation between the study groups. However, data showed significantly reduced DNA methylation of the BDNF region upstream of exon I in blood samples of suicide victims compared to the controls (5.67 ± 0.57 vs 6.83 ± 0.64, P_corr = 0.01). In Brodmann area 9 of the brain of the suicide victims but not in their hippocampus, there was higher expression of BDNF transcript I-IX (NM_170731.4) compared to the controls (0.077 ± 0.024 vs 0.05 ± 0.013, P = 0.042). In blood, expression analysis for the BDNF transcripts was not feasible due to extensive RNA degradation.

CONCLUSION

Despite the limitations of the study, the obtained data further support a role for BDNF in suicidality. However, it should be noted that suicidal behavior is a multifactorial disorder with numerous environmental and genetic risk factors involved.

Multidimensional Analysis of Major Depression: Association Between BDNF Methylation, Psychosocial and Cognitive Domains

Major Depression is a complex disorder with a growing incidence worldwide and multiple variables have been associated with its etiology. Nonetheless, its diagnosis is continually changing and the need to understand it from a multidimensional perspective is clear. The purpose of this study was to identify risk factors for depression in a case-control study with 100 depressive inpatients and 87 healthy controls. A multivariate logistic regression analysis was performed including psychosocial factors, cognitive maladaptive schema domains, and specific epigenetic marks (BDNF methylation levels at five CpG sites in promoter IV). A family history of depression, the cognitive schemas of impaired autonomy/performance, impaired limits, other-directedness, and the methylation level of a specific CpG site were identified as predictors. Interestingly, we found a mediating effect of those cognitive schemas in the relationship between childhood maltreatment and depression. Also, we found that depressive patients exhibited hypomethylation in a CpG site of BDNF promoter IV, which adds to the current discussion about the role of methylation in depression. We highlight that determining the methylation of a specific region of a single gene offers the possibility of accessing a highly informative an easily measurable variable, which represents benefits for diagnosis. Following complete replication and validation on larger samples, models like ours could be applicable as additional diagnostic tools in the clinical context.

DNA methylations of brain-derived neurotrophic factor exon VI are associated with major depressive disorder and antidepressant-induced remission in females

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been suggested to play important roles in major depressive disorder (MDD) and antidepressant treatment. The main purpose of this study was to evaluate the association of DNA methylation changes in the BDNF gene with MDD and antidepressant treatment.

METHODS

A total of 291 MDD patients and 100 healthy controls were included and followed up for 6 weeks. The Hamilton Depression Rating Scale-17 (HDRS-17) was used to measure treatment improvement. The life events scales (LES) and childhood trauma questionnaire (CTQ) were used to rate recent and early life stress. DNA methylation levels of CpG sites in the BDNF gene were measured.

RESULTS

Two CpG sites in BDNF exon VI (BDNF133 and BDNF134) were demonstrated to have significantly higher methylation in MDD patients than in controls (both FDR-adjusted P = 0.001). A logistics regression model indicated that the interaction between the hypermethylation of BDNF133 and negative subscore of LES was associated to MDD (OR=0.0075, P<0.001). Methylation of BDNF140 at baseline was significantly elevated in remitters (FDR-adjusted P = 0.046) at week 6. In subgroup analyses, these findings could be replicated in females, but not in males.

LIMITATIONS

The methylation status of BDNF after 6 weeks of antidepressant treatment was not measured and the DNA methylation were detected in peripheral blood cells.

CONCLUSIONS

These findings highlight gender-specific alteration of methylation at several CpG sites in BDNF exon VI as a promising candidate indicator of MDD and antidepressant-induced remission.

Lead (Pb) and neurodevelopment: A review on exposure and biomarkers of effect (BDNF, HDL) and susceptibility

Lead (Pb) is a ubiquitous environmental pollutant and a potent toxic compound. Humans are exposed to Pb through inhalation, ingestion, and skin contact via food, water, tobacco smoke, air, dust, and soil. Pb accumulates in bones, brain, liver and kidney. Fetal exposure occurs via transplacental transmission. The most critical health effects are developmental neurotoxicity in infants and cardiovascular effects and nephrotoxicity in adults. Pb exposure has been steadily decreasing over the past decades, but there are few recent exposure data from the general European population; moreover, no safe Pb limit has been set. Sensitive biomarkers of exposure, effect and susceptibility, that reliably and timely indicate Pb-associated toxicity are required to assess human exposure-health relationships in a situation of low to moderate exposure. Therefore, a systematic literature review based on PubMed entries published before July 2019 that addressed Pb exposure and biomarkers of effect and susceptibility, neurodevelopmental toxicity, epigenetic modifications, and transcriptomics was conducted. Finally included were 58 original papers on Pb exposure and 17 studies on biomarkers. The biomarkers that are linked to Pb exposure and neurodevelopment were grouped into effect biomarkers (serum brain-derived neurotrophic factor (BDNF) and serum/saliva cortisol), susceptibility markers (epigenetic markers and gene sequence variants) and other biomarkers (serum high-density lipoprotein (HDL), maternal iron (Fe) and calcium (Ca) status). Serum BDNF and plasma HDL are potential candidates to be further validated as effect markers for routine use in HBM studies of Pb, complemented by markers of Fe and Ca status to also address nutritional interactions related to neurodevelopmental disorders. For several markers, a causal relationship with Pb-induced neurodevelopmental toxicity is likely. Results on BDNF are discussed in relation to Adverse Outcome Pathway (AOP) 13 ("Chronic binding of antagonist to N-methyl-D-aspartate receptors (NMDARs) during brain development induces impairment of learning and memory abilities") of the AOP-Wiki. Further studies are needed to validate sensitive, reliable, and timely effect biomarkers, especially for low to moderate Pb exposure scenarios.

The Influence of Psychotherapy on Peripheral Brain-Derived Neurotrophic Factor Concentration Levels and Gene Methylation Status: A Systematic Review

Psychotherapy is a well-established method of treating many mental disorders. It has been proven that psychotherapy leads to structural and functional changes in the brain; however, knowledge about the molecular and cellular mechanisms of these changes is limited. Neuroplasticity and one of its mediators, brain-derived neurotrophic factor (BDNF), are potential research targets in this field. To define the role of BDNF concentration in serum, or in plasma, and BDNF promoter gene methylation in saliva or leucocytes, in psychotherapy, an extensive literature search was conducted in the PubMed and Web of Science databases. The literature review was conducted based on papers published up until May 2021 that included pre and post psychotherapy measurements of either BDNF concentration levels or promoter gene methylation status. Ten studies were indicated as eligible for analysis: eight studies that investigated peripheral BDNF concentration levels, one study that investigated methylation status, and one study that included an evaluation of both subject matters. Patients underwent cognitive behavioral therapy or interpersonal psychotherapy. Patients were diagnosed with borderline personality disorder, major depressive disorder, anorexia nervosa, bulimia nervosa, or post-traumatic stress disorder. There were only three of the nine studies that showed statistically significant increases in BDNF concentration levels after psychotherapy. The two studies that involved BDNF gene methylation status showed a decrease in methylation after dialectical behavioral therapy of borderline patients.

BDNF in antipsychotic naive first episode psychosis: Effects of risperidone and the immune-inflammatory response system

Brain-derived neurotrophic factor (BDNF) and the immune-inflammatory response system (IRS) have been implicated in the pathophysiology of schizophrenia. However, no research examined the associations between BDNF and immune activation both before and after treatment in antipsychotic-naïve first episode psychosis (AN-FEP). This study aims to examine serum BDNF levels and their association with IRS and the compensatory immune-regulatory reflex system (CIRS) in AN-FEP before and after risperidone treatment. We included 31 AN-FEP and 22 healthy controls. AN-FEP showed reduced levels of BDNF as compared to controls, and BDNF levels normalized after treatment with risperidone. BDNF levels were inversely correlated with a greater IRS response. Higher levels of IRS/CIRS biomarkers were associated with lower levels of BDNF including M1 macrophage, T-helper (Th)-1, Th-2, and Th-17, and T-regulatory (Treg) cell responses. Our findings indicate that AN-FEP is characterized by decreased levels of BDNF, which are normalized after treatment with risperidone. BDNF levels were inversely associated with activated immune-inflammatory pathways. The findings support the hypothesis that, increased IRS is linked to neurotoxicity, and that a decrease in BDNF may be part of the IRS/CIRS responses in FEP and, thus, be involved in the development of psychosis.

Associations of age, sex, sexual abuse, and genotype with monoamine oxidase a gene methylation

Epigenome-wide studies report higher methylation among women than men with decreasing levels with age. Little is known about associations of sex and age with methylation of monoamine oxidase A (MAOA). Methylation of the first exonic and partial first intronic region of MAOA has been shown to strengthen associations of interactions of MAOA-uVNTR genotypes and adversity with aggression and substance misuse. Our study examined associations of sex and age with MAOA first exon and intron methylation levels in 252 women and 157 men aged 14–73 years. Participants included adolescents recruited at a substance misuse clinic, their siblings and parents, and healthy women. Women showed ~ 50% higher levels of exonic, and ~ 15% higher intronic, methylation than men. Methylation levels were similar between younger (M = 22.7 years) and older (M = 46.1 years) participants, and stable across age. Age modified few associations of methylation levels with sex. MAOA genotypes modified few associations of methylation with sex and age. Higher methylation levels among women were not explained by genotype, nor interaction of genotype and sexual abuse. Findings were similar after adjusting for lifetime diagnoses of substance dependence (women = 24.3%; men = 34.2%). Methylation levels were higher among women who experienced sexual abuse than women who did not. Results extend on prior studies by showing that women display higher levels of methylation than men within first intronic/exonic regions of MAOA, which did not decrease with age in either sex. Findings were not conditioned by genotype nor interactions of genotype and trauma, and indicate X-chromosome inactivation.

Interplay of Val66Met and BDNF methylation: effect on reward learning and cognitive performance in major depression

Background

There is a growing interest in the role of brain-derived neurotrophic factor (BDNF) in major depressive disorder (MDD). BDNF potentially exhibits opposite effects in the pathways linked to anhedonia and reward learning on the one hand and cognitive performance, on the other hand. However, the epigenetic mechanisms behind this remain unknown. In the present study, we aimed to investigate the interplay of DNA methylation of different BDNF exons and the common Val66Met polymorphism on anhedonia, reward learning and cognitive performance in MDD.

Methods

We recruited 80 depressed patients and 58 age- and gender-matched healthy controls. Participants underwent clinical assessment including neuropsychological testing and a probabilistic reward task to assess reward learning. Val66Met polymorphism and DNA methylation of BDNF promoters I, IV and exon IX were assessed from whole blood derived DNA, using pyrosequencing.

Results

BDNF promoter I methylation was lower in MDD patients (p = 0.042) and was negatively associated with self-reported anhedonia. In depressed patients, both Val66Met polymorphism and DNA methylation of promoter I were significantly associated with reward bias (p < 0.050 and p = 0.040, respectively), without an interaction effect. On the other hand, methylation of exon IX had a negative impact on executive functioning (p = 0.002) and mediated the effect of Val66Met on this outcome in patients with MDD.

Conclusions

Our results provide the first evidence of Val66Met susceptibility to differential epigenetic regulation of BDNF exons in reward learning and executive functioning in MDD, which needs to be further explored.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01136-z.

Methylome-wide change associated with response to electroconvulsive therapy in depressed patients

Electroconvulsive therapy (ECT) is a quick-acting and powerful antidepressant treatment considered to be effective in treating severe and pharmacotherapy-resistant forms of depression. Recent studies have suggested that epigenetic mechanisms can mediate treatment response and investigations about the relationship between the effects of ECT and DNA methylation have so far largely taken candidate approaches. In the present study, we examined the effects of ECT on the methylome associated with response in depressed patients (n = 34), testing for differentially methylated CpG sites before the first and after the last ECT treatment. We identified one differentially methylated CpG site associated with the effect of ECT response (defined as >50% decrease in Hamilton Depression Rating Scale score, HDRS), TNKS (q < 0.05; p = 7.15 × 10^-8). When defining response continuously (ΔHDRS), the top suggestive differentially methylated CpG site was in FKBP5 (p = 3.94 × 10^-7). Regional analyses identified two differentially methylated regions on chromosomes 8 (Šídák's p = 0.0031) and 20 (Šídák's p = 4.2 × 10^-5) associated with ΔHDRS. Functional pathway analysis did not identify any significant pathways. A confirmatory look at candidates previously proposed to be involved in ECT mechanisms found CpG sites associated with response only at the nominally significant level (p < 0.05). Despite the limited sample size, the present study was able to identify epigenetic change associated with ECT response suggesting that this approach, especially when involving larger samples, has the potential to inform the study of mechanisms involved in ECT and severe and treatment-resistant depression.

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

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

Folic acid ameliorates neonatal isolation-induced autistic like behaviors in rats: epigenetic modifications of BDNF and GFAP promotors

The current study investigated the role of epigenetic dysregulation of brain derived neurotrophic factor (BDNF) and glial fibrillary acidic protein (GFAP) genes and oxidative stress as possible mechanisms of autistic-like behaviors in neonatal isolation model in rats and the impact of folic acid administration on these parameters. Forty Wistar albino pups were used as follows: control, folic acid administered, isolated, and isolated folic acid treated groups. Isolated pups were separated from their mothers for 90 min daily from postnatal day (PND) 1 to 11. Pups (isolated or control) received either the vehicle or folic acid (4 mg/kg/day) orally from PND 1 to 29. Behavioral tests were done from PND 30 to 35. Oxidative stress markers and antioxidant defense in the frontal cortex homogenate were determined. DNA methylation of BDNF and GFAP genes was determined by qPCR. Histopathological examination was carried out. Neonatal isolation produced autistic-like behaviors that were associated with BDNF and GFAP hypomethylation, increased oxidative stress, increased inflammatory cell infiltration, and structural changes in the frontal cortex. Folic acid administration concurrently with isolation reduced neonatal isolation-induced autistic-like behaviors, decreased oxidative stress, regained BDNF and GFAP gene methylation, and ameliorated structural changes in the frontal cortices of isolated folic acid treated rats. Novelty: Neonatal isolation induces "autistic-like" behavior and these behaviors are reversed by folic acid supplementation. Neonatal isolation induces DNA hypomethylation of BDNF and GFAP, increased oxidative stress markers, and neuroinflammation. All of these changes were reversed by daily folic acid supplementation.

Prenatal methylmercury exposure and DNA methylation in seven-year-old children in the Seychelles Child Development Study

BACKGROUND

Methylmercury (MeHg) is present in fish and is a neurotoxicant at sufficiently high levels. One potential mechanism of MeHg toxicity early in life is epigenetic dysregulation that may affect long-term neurodevelopment. Altered DNA methylation of nervous system-related genes has been associated with adult mental health outcomes.

OBJECTIVE

To assess associations between prenatal MeHg exposure and DNA methylation (at the cytosine of CG dinucleotides, CpGs) in three nervous system-related genes, encoding brain-derived neurotropic factor (BDNF), glutamate receptor subunit NR2B (GRIN2B), and the glucocorticoid receptor (NR3C1), in children who were exposed to MeHg in utero.

METHODS

We tested 406 seven-year-old Seychellois children participating in the Seychelles Child Development Study (Nutrition Cohort 2), who were prenatally exposed to MeHg from maternal fish consumption. Total mercury in maternal hair (prenatal MeHg exposure measure) collected during pregnancy was measured using atomic absorption spectroscopy. Methylation in DNA from the children's saliva was measured by pyrosequencing. To assess associations between prenatal MeHg exposure and CpG methylation at seven years of age, we used multivariable linear regression models adjusted for covariates.

RESULTS

We identified associations with prenatal MeHg exposure for DNA methylation of one GRIN2B CpG and two NR3C1 CpGs out of 12 total CpG sites. Higher prenatal MeHg was associated with higher methylation for each CpG site. For example, NR3C1 CpG3 had an expected increase of 0.03-fold for each additional 1 ppm of prenatal MeHg (B = 0.030, 95% CI 0.001, 0.059; p = 0.047). Several CpG sites associated with MeHg are located in transcription factor binding sites and the observed methylation changes are predicted to lead to lower gene expression.

CONCLUSIONS

In a population of people who consume large amounts of fish, we showed that higher prenatal MeHg exposure was associated with differential DNA methylation at seven years of age at specific CpG sites that may influence neurodevelopment and mental health.

Effect of adverse childhood experiences and DNA methylation on male sexual orientation

The causes for male sexual orientation are complicated, which have not yet been clarified. Recent years have witnessed fruitful progress in the field of biology, while the impact of environment has received little attention. Adverse childhood experiences (ACEs), identified as a special environment in the early stage of development, can affect the individual phenotype by DNA methylation. Given the relationships among male sexual orientation, ACEs, and DNA methylation, as well as based on the existing theory, this article proposes the model "ACEs-DNA methylation-male sexual orientation"from the perspective of environment and epigenetics, aiming to provide a theoretical basis for future research.

Perfluoroalkyl Substance Exposure and the BDNF Pathway in the Placental Trophoblast

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Increases in Bdnf DNA Methylation in the Prefrontal Cortex Following Aversive Caregiving Are Reflected in Blood Tissue

Child maltreatment not only leads to epigenetic changes, but also increases the risk of related behavioral deficits and mental disorders. These issues presumably are most closely associated with epigenetic changes in the brain, but epigenetic changes in peripheral tissues like blood are often examined instead, due to their accessibility. As such, the reliability of using the peripheral epigenome as a proxy for that of the brain is imperative. Previously, our lab has found aberrant methylation at the Brain-derived neurotrophic factor (Bdnf) gene in the prefrontal cortex of rats following aversive caregiving. The current study examined whether aversive caregiving alters Bdnf DNA methylation in the blood compared to the prefrontal cortex. It was revealed that DNA methylation associated with adversity increased in both tissues, but this methylation was not correlated between tissues. These findings indicate that group trends in Bdnf methylation between blood and the brain are comparable, but variation exists among individual subjects.

Is Peripheral BDNF Promoter Methylation a Preclinical Biomarker of Dementia?

Brain-derived neurotrophic factor (BDNF) has been implicated in dementia. Preliminary evidence suggests that BDNF DNA methylation may be a diagnostic biomarker of dementia, but the potential pre-clinical utility remains unclear. Participants in the ESPRIT study were assessed for cognitive function and dementia (DSM-IV criteria) over 14 years. BDNF exon 1 promoter methylation was measured in blood at baseline (n = 769) and buccal samples during follow-up (n = 1062). Genotyping was carried out for several common BDNF SNPs, including Val66Met (rs6265) and APOE ɛ4. Multivariable logistic regression analyses determined the association between BDNF methylation and both prevalent and incident dementia. Adjustment for gender, age, education, APOEɛ4 genotype, body mass index, depression, and type 2 diabetes, as well as possible effect modification by gender and genetic variation were also investigated. Weak evidence of an association between lower blood methylation and dementia was observed at one of 11 sites investigated (Δ-0.5%, 95% CI:-0.9,-0.04, p = 0.03, p = 0.22 adjusted for multiple comparisons). Buccal methylation at two other sites was associated with 14-year incident dementia cases prior to adjustment for multiple comparisons only, and the effect sizes were small (Δ+0.3%, OR:1.57, SE:0.30, p = 0.02, p = 0.14 adjusted and Δ-1.5%, OR:0.85, SE:0.06, p = 0.03, p = 0.14 adjusted). Genetic variation in the BDNF gene did not modify these associations, and no gender-specific effects were observed. There was only a weak correlation between blood and buccal BDNF log-methylation at two sites (both r=-0.11). There was no strong evidence that blood or buccal BDNF exon 1 promoter DNA methylation is associated with prevalent or incident dementia, and reported associations would not remain after adjustment for multiple testing.

Synaptic control of DNA methylation involves activity-dependent degradation of DNMT3A1 in the nucleus

DNA methylation is a crucial epigenetic mark for activity-dependent gene expression in neurons. Very little is known about how synaptic signals impact promoter methylation in neuronal nuclei. In this study we show that protein levels of the principal de novo DNA-methyltransferase in neurons, DNMT3A1, are tightly controlled by activation of N-methyl-D-aspartate receptors (NMDAR) containing the GluN2A subunit. Interestingly, synaptic NMDARs drive degradation of the methyltransferase in a neddylation-dependent manner. Inhibition of neddylation, the conjugation of the small ubiquitin-like protein NEDD8 to lysine residues, interrupts degradation of DNMT3A1. This results in deficits in promoter methylation of activity-dependent genes, as well as synaptic plasticity and memory formation. In turn, the underlying molecular pathway is triggered by the induction of synaptic plasticity and in response to object location learning. Collectively, the data show that plasticity-relevant signals from GluN2A-containing NMDARs control activity-dependent DNA-methylation involved in memory formation.

Epigenetic perspective on the role of brain-derived neurotrophic factor in burnout

Brain-derived neurotrophic factor (BDNF) plays a potential role in the neurobiology of burnout, but there are no studies investigating the underlying genetic and epigenetic mechanisms. Our aim is to further explore the role of BDNF in burnout, by focusing on the Val66Met polymorphism and methylation patterns of the BDNF gene and serum BDNF (sBDNF) protein expression. We conducted a cross-sectional study by recruiting 129 individuals (59 with burnout and 70 healthy controls). Participants underwent a clinical interview, psychological assessment and blood sample collection. Polymorphism and DNA methylation were measured on DNA from whole blood, using pyrosequencing and sBDNF levels were measured using ELISA. We found significantly increased methylation of promoter I and IV in the burnout group, which also correlated with burnout symptoms. In addition, DNA methylation of promoter I had a significant negative effect on sBDNF. For DNA methylation of exon IX, we did not find a significant difference between the groups, nor associations with sBDNF. The Val66Met polymorphism neither differed between groups, nor was it associated with sBDNF levels. Finally, we did not observe differences in sBDNF level between the groups. Interestingly, we observed a significant negative association between depressive symptoms and sBDNF levels. The current study is the first to show that BDNF DNA methylation changes might play an important role in downregulation of the BDNF protein levels in burnout. The presence of depressive symptoms might have an additional impact on these changes.

The Influence of the BDNF Val66Met Polymorphism on the Association of Regular Physical Activity With Cognition Among Individuals With Diabetes

INTRODUCTION

Diabetes is associated with cognitive dysfunction that comes with substantial lifetime consequences, such as interference with diabetes self-management and reduced quality of life. Although regular physical activity has been consistently shown to enhance cognitive function among healthy subjects, significant interpersonal differences in exercise-induced cognitive outcomes have been reported among brain-derived neurotrophic factor (BDNF) Val/Val vs. Met carriers. However, the evidence on how the BDNF Val66Met variant influences the relationship between regular physical activity and cognition among individuals with diabetes is currently lacking.

METHODS

A total of 3,040 individuals with diabetes were included in this analysis using data from the Health and Retirement Study. Associations among moderate and vigorous physical activities (MVPA) and measures of cognitive function were evaluated using multivariable linear regression models within each stratum of the Val66Met genotypes.

RESULTS

MVPA was more strongly associated with total cognitive score, mental status, and words recall among Met/Met carriers, compared to Val/Val and Val/Met carriers.

CONCLUSIONS

This study provided preliminary findings on how BDNF variants may modulate the exercise-induced cognitive benefits among mid-aged and older adults with diabetes. Given the limitations of the current study, it is necessary for randomized controlled trials to stratify by BDNF genotypes to more conclusively determine whether Met carriers benefit more from increased physical activity. In addition, future research is needed to examine how the interplay of BDNF Val66Met variants, DNA methylation, and physical activity may have an impact on cognitive function among adults with diabetes.