Exploring the association between BDNF Val66Met polymorphism and suicidal behavior: Meta-analysis and systematic review

BDNF: New Views of an Old Player in Traumatic Brain Injury

Traumatic brain injury is a common health problem affecting millions of people each year. BDNF has been investigated in the context of traumatic brain injury due to its crucial role in maintaining brain homeostasis. Val66Met is a functional single-nucleotide polymorphism that results in a valine-to-methionine amino acid substitution at codon 66 in the BDNF prodomain, which ultimately reduces secretion of BDNF. Here, we review experimental animal models as well as clinical studies investigating the role of the Val66Met single-nucleotide polymorphism in traumatic brain injury outcomes, including cognitive function, motor function, neuropsychiatric symptoms, and nociception. We also review studies investigating the role of BDNF on traumatic brain injury pathophysiology as well as circulating BDNF as a biomarker of traumatic brain injury.

The Role of Central and Peripheral Brain-Derived Neurotrophic Factor (BDNF) as a Biomarker of Anorexia Nervosa Reconceptualized as a Metabo-Psychiatric Disorder

Neurotrophic factors play pivotal roles in shaping brain development and function, with brain-derived neurotrophic factor (BDNF) emerging as a key regulator in various physiological processes. This review explores the intricate relationship between BDNF and anorexia nervosa (AN), a complex psychiatric disorder characterized by disordered eating behaviors and severe medical consequences. Beginning with an overview of BDNF's fundamental functions in neurodevelopment and synaptic plasticity, the review delves into recent clinical and preclinical evidence implicating BDNF in the pathophysiology of AN. Specifically, it examines the impact of BDNF polymorphisms, such as the Val66Met variant, on AN susceptibility, prognosis, and treatment response. Furthermore, the review discusses the interplay between BDNF and stress-related mood disorders, shedding light on the mechanisms underlying AN vulnerability to stress events. Additionally, it explores the involvement of BDNF in metabolic regulation, highlighting its potential implications for understanding the metabolic disturbances observed in AN. Through a comprehensive analysis of clinical data and animal studies, the review elucidates the nuanced role of BDNF in AN etiology and prognosis, emphasizing its potential as a diagnostic and prognostic biomarker. Finally, the review discusses limitations and future directions in BDNF research, underscoring the need for further investigations to elucidate the complex interplay between BDNF signaling and AN pathology.

Val/Met BDNF as a genetic risk for a false sense of security in post-discharge suicide risk

BACKGROUND

The time after discharge from psychiatric inpatient care is one of the most dangerous periods in terms of suicide risk. Predicting who is at higher risk could help with resource allocation to assure patients at high risk of suicide attempts are most closely followed. We previously showed that inpatients who improve their suicide ideation levels faster while in inpatient treatment are the ones with highest rates of post-discharge suicide. Here, we studied the possible genetic underpinnings associated with such risk.

METHOD

We recorded the slope of suicide ideation recovery of 710 psychiatric inpatients from which we studied two genetic variants likely associated with suicide risk: The serotonin transporter variant 5-HTTLPR, and the BDNF gene variant Val66Met.

RESULTS

We found that inpatients carrying the BDNF Met variant (hypothesized as conferring higher suicide risk) improved their suicide ideation scores faster than Val/Val carrying inpatients. No significant association was found for 5-HTTLPR.

LIMITATIONS

The present sample was genetically homogenous, and future research should replicate these findings on a more diverse sample.

CONCLUSIONS

In conclusion, we found a paradoxical result: Carrying the BDNF Met variant allows inpatients to improve faster, which was shown to confer higher risk at the post-discharge period. This may explain some inconsistencies in the literature in terms of the role of BDNF in suicide ideation and attempts.

Genetic signatures of suicide attempt behavior: insights and applications

INTRODUCTION

Every year about 800,000 complete suicide events occur. The identification of biologic markers to identify subjects at risk would be helpful in targeting specific support treatments.

AREA COVERED

A narrative review defines the meta-analytic level of current evidence about the biologic markers of suicide behavior (SB). The meta-analytic evidence gathered so far indicates that the hypothesis-driven research largely failed to identify the biologic markers of suicide. The most consistent and replicated result was reported for: 1) 5-HTR2A T102C, associated with SB in patients with schizophrenia (OR = 1.73 (1.11-2.69)) and 2) BDNF Val66Met (rs6265), with the Met-Val + Val-Val carriers found to be at risk for suicide in the Caucasian population (OR: 1.96 (1.58-2.43)), while Val-Val vs. Val-Met + Met carriers found to be at risk for suicide in the Asian populations (OR: 1.36 (1.04-1.78)). GWAS-based meta-analyses indicate some positive replicated findings regarding the DRD2, Neuroligin gene, estrogen-related genes, and genes involved in gene expression.

EXPERT OPINION

Most consistent results were obtained when analyzing sub-samples of patients. Some promising results come from the implementation of the polygenic risk score. There is no current consensus about an implementable biomarker for SB.

BDNF rs962369 Is Associated with Major Depressive Disorder

This study enrolled 291 patients diagnosed with depression and schizophrenia (F32, F33, and F20 according to ICD-10) and 227 ethnicity-matched control subjects. We analyzed the distribution of BDNF rs6265 and BDNF rs962369 genotypes, finding no significant associations between these and schizophrenia. We revealed a significant increase in the risk of single-episode major depression disorder (MDD) for rs962369 minor allele homozygotes (CC vs. TT+TC), an association that persisted after adjusting for age and sex (OR 3.47; 95% CI 1.36-8.85; p = 0.009). Furthermore, rs962369 genotype was significantly associated with an increased risk of recurrent MDD in a log-additive model (OR per C-allele 1.65; 95% CI 1.11-2.45; p = 0.013). A comparative analysis between MDD subtypes and between MDD subtypes and schizophrenia showed no significant differences for BDNF rs6265. Notably, the frequency of minor allele C of BDNF rs962369 varied across subgroups, with the highest frequency in patients with recurrent MDD (0.32) and the lowest in schizophrenia patients (0.20). The presence of genotypes with at least one minor allele C was significantly higher in the recurrent MDD patient group compared to the schizophrenia group. In conclusion, the BDNF rs962369 variant was associated with MDD but not with schizophrenia.

BDNF and stress/mood-related interactions on emotional disorder symptoms, executive functioning, and deliberate self-harm

Some prior research has suggested that the brain-derived neurotrophic factor (BDNF) gene may amplify responses related to life stress (e.g., depression and anxiety) or associated with negative moods (e.g., self-harm and diminished cognitive functioning). The purpose of this study was to investigate whether stress/mood-related associations with depressive and anxiety symptoms, deliberate self-harm, and executive functioning (EF) are moderated by genotypic variations in BDNF rs10835210 (a relatively understudied BDNF polymorphism) in a nonclinical sample. As part of a larger study, European American social drinkers (N = 132; 43.9% female; M age = 26.0, SD = 7.6) were genotyped for BDNF rs10835210 and were administered self-report measures of subjective life stress, depressive and anxiety symptoms, and history of non-suicidal self-injury (NSSI) and behavioral measures of EF and deliberate self-harm. Results indicated that BDNF significantly moderated the life stress associations with depressive symptoms and NSSI, the anxious mood association with EF, and the depressed mood association with deliberate self-harm behavior. Each of these BDNF × stress/mood interactions were characterized by stress/mood associations that were stronger in individuals with the AA genotype (homozygous for the minor allele) than in individuals possessing a genotype that included the major allele (AC or CC). The main limitations of the present study were use of a cross-sectional design, modest sample size, and investigating only one BDNF polymorphism. Despite these limitations and though preliminary, current findings suggest that variations in BDNF may confer vulnerability to stress or mood, which may result in more adverse emotional, cognitive, or behavioral outcomes.

The association of brain-derived neurotrophic factor with the diagnosis and treatment response in depression

INTRODUCTION

Recent evidence from the studies evaluating the association between brain derived neurotrophic factor (BDNF) concentration/levels, BDNF Val66Met (rs6265) polymorphism and major depressive disorders, referred as depression, and the association between BDNF levels and/or BDNF Val66Met with the treatment response in depression, is presented.

AREAS COVERED

This mini review focuses on the changes in the peripheral BDNF levels in blood (serum, plasma, platelets) in patients with depression before or after treatment with antidepressant drugs or different therapeutic strategies. In addition, this review describes the recent data on the possible association between different antidepressants/therapeutic strategies and the particular BDNF Val66Met genotypes, evaluating the risk alleles associated with the response in patients with depression.

EXPERT OPINION

BDNF has an important role in the pathophysiology and treatment response in depression. Most data reveal that peripheral BDNF levels are lower before than after antidepressant treatment and might be used as potential biomarkers of therapeutic response. Novel therapeutic strategies should target restoring/increasing BDNF levels.

Association of HTTLPR, BDNF, and FTO Genetic Variants with Completed Suicide in Slovakia

Since suicide and suicidal behavior are considered highly heritable phenotypes, the identification of genetic markers that can predict suicide risk is a clinically important topic. Several genes studied for possible associations between genetic polymorphisms and suicidal behaviors had mostly inconsistent and contradictory findings. The aim of this case-control study was to evaluate the associations between completed suicide and polymorphisms in genes BDNF (rs6265, rs962369), SLC6A4 (5-HTTLPR), and FTO (rs9939609) in relation to sex and BMI. We genotyped 119 completed suicide victims and 137 control subjects that were age, sex, and ethnicity matched. A significant association with completed suicide was found for BDNF rs962369. This variant could play a role in completed suicide, as individuals with the CC genotype were more often found among suicides than in control subjects. After sex stratification, the association remained significant only in males. A nominally significant association between the gene variant and BMI was observed for BDNF rs962369 under the overdominant model. Heterozygotes with the TC genotype showed a lower average BMI than homozygotes with TT or CC genotypes. FTO polymorphism (rs9939609) did not affect BMI in the group of Slovak suicide completers, but our findings follow an inverse association between BMI and completed suicide.

Risk and Protective Factors for Childhood Physical Abuse and Suicidal Ideation: The Effect of Brain-Derived Neurotrophic Factor Polymorphism and Social Support

OBJECTIVE

This study aimed to explore the relationship between childhood physical abuse and suicidal ideation considering the effects of genetic and environmental factors in patients with post-traumatic stress disorder (PTSD) by focusing on brain-derived neurotrophic factor (BDNF) polymorphism and social support, respectively.

METHODS

One-hundred fourteen patients with PTSD and 94 healthy controls (HCs) were genotyped with respect to BDNF Val66Met polymorphism. All participants underwent psychological assessments. The hierarchical regression analysis and the simple slope analysis were conducted.

RESULTS

As for patients with PTSD, the moderation effect of BDNF polymorphism was significant but not for social support. Specifically, the BDNF Val/Val genotype worked as a risk factor and strengthens the relationship between childhood physical abuse and suicidal ideation. As for the HCs, the significant moderation effect was found only in social support, but not for BDNF polymorphism. The relationship between childhood physical abuse and suicidal ideation was weakened for the HCs with high social support.

CONCLUSION

This study demonstrated a significant BDNF genetic vulnerability for suicide in patients with PTSD who experienced childhood physical abuse. Our results suggested that social support provided a mitigating effect on the relationship between childhood physical abuse and suicidal ideation only in the HCs.

Suicide and Changes in Expression of Neuronal miRNA Predicted by an Algorithm Search through miRNA Databases

Suicide is multifactorial and polygenic phenotype, affected by environmental and genetic factors. Among epigenetic mechanisms, miRNAs have been studied, but so far no very concise results exist. To overcome limitations of candidate miRNA and whole genome sequencing approaches, we created an in silico analysis algorithm that would help select the best suitable miRNAs that target the most interesting genes associated with suicidality. We used databases/web algorithms DIANA microT, miRDB, miRmap, miRWalk, and TargetScan and candidate genes SLC6A4, HTR1A, BDNF, NR3C1, ZNF714, and NRIP3. Based on a prediction algorithm, we have chosen miRNAs that are targeting regulation of the genes listed, and are at the same time being expressed in the brain. The highest ranking scores were obtained for hsa-miR-4516, hsa-miR-3135b, hsa-miR-124-3p, hsa-miR-129-5p, hsa-miR-27b-3p, hsa-miR-381-3p, hsa-miR-4286. Expression of these miRNAs was tested in the brain tissue of 40 suicide completers and controls, and hsa-miR-4516 and hsa-miR-381-3p showed a trend for statistical significance. We also checked the expression of the target genes of these miRNAs, and for NR3C1 expression was lower in suicide completers compared to controls, which is in accordance with the available literature results. To determine the miRNAs that are most suitable for further suicidality research, more studies, combining in silico analysis and wet lab experiments, should be performed.

The Influence of 5-HTTLPR, BDNF Rs6265 and COMT Rs4680 Polymorphisms on Impulsivity in Bipolar Disorder: The Role of Gender

Impulsivity has been proposed as an endophenotype for bipolar disorder (BD); moreover, impulsivity levels have been shown to carry prognostic significance and to be quality-of-life predictors. To date, reports about the genetic determinants of impulsivity in mood disorders are limited, with no studies on BD individuals. Individuals with BD and healthy controls (HC) were recruited in the context of an observational, multisite study (GECOBIP). Subjects were genotyped for three candidate single-nucleotide polymorphisms (SNPs) (5-HTTLPR, COMT rs4680, BDNF rs6265); impulsivity was measured through the Italian version of the Barratt Impulsiveness Scale (BIS-11). A mixed-effects regression model was built, with BIS scores as dependent variables, genotypes of the three polymorphisms as fixed effects, and centers of enrollment as random effect. Compared to HC, scores for all BIS factors were higher among subjects with euthymic BD (adjusted β for Total BIS score: 5.35, p < 0.001). No significant interaction effect was evident between disease status (HC vs. BD) and SNP status for any polymorphism. Considering the whole sample, BDNF Met/Met homozygosis was associated with lower BIS scores across all three factors (adjusted β for Total BIS score: −10.2, p < 0.001). A significant 5-HTTLPR x gender interaction was found for the SS genotype, associated with higher BIS scores in females only (adjusted β for Total BIS score: 12.0, p = 0.001). Finally, COMT polymorphism status was not significantly associated with BIS scores. In conclusion, BD diagnosis did not influence the effect on impulsivity scores for any of the three SNPs considered. Only one SNP—the BDNF rs6265 Met/Met homozygosis—was independently associated with lower impulsivity scores. The 5-HTTLPR SS genotype was associated with higher impulsivity scores in females only. Further studies adopting genome-wide screening in larger samples are needed to define the genetic basis of impulsivity in BD.

Peripheral BDNF levels in psychiatric patients with and without a history of suicide attempt: A systematic review and meta-analysis

OBJECTIVE

Psychiatric patients are at increased risk of attempting suicide. Several potential biomarkers of suicide risk have been proposed with inconsistent findings. The present paper aimed to evaluate differences in peripheral BDNF levels between psychiatric patients with and without a history of suicide attempts.

METHODS

We conducted a systematic review and meta-analysis following the PRISMA guidelines. Relevant papers published up to January 5, 2021 were identified searching the electronic databases Web of Knowledge^SM and PsycINFO. A random-effect meta-analysis was conducted using Stata 16.

RESULTS

Thirteen studies met inclusion criteria. Overall, no significant differences in BDNF levels between the two groups were found (13 studies, n = 1340, Hedge's g = -0.21, 95% CI -0.44 to 0.02). Heterogeneity was substantial (I² = 72.91%). Subgroup analyses revealed that BDNF levels were significantly reduced in plasma with medium effect size (5 studies, n = 363, Hedge's g = -0.44, 95% CI -0.86 to -0.02), but not in serum (8 studies, n = 977, Hedge's g = -0.09, 95% CI -0.33 to 0.15). No significant differences were found according to the type of diagnosis (major depressive disorder vs. other diagnoses) or the period of suicide attempt (lifetime vs. recent).

CONCLUSION

The utility of BDNF as a biomarker of suicide attempts in psychiatric patients appears limited to its plasma concentration. Although caution interpretation is needed, our findings may represent a starting point for the design of rigorous case-control studies exploring the association between neurotrophins and suicidal behaviors.

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.

Effect of brain-derived neurotrophic factor gene polymorphisms on motor performance and motor learning: A systematic review and meta-analysis

Brain-derived neurotrophic factor (BDNF) gene polymorphisms may modulate neurotransmitter efficiency, thereby influencing motor performance and motor learning. However, studies to date have provided no consensus regarding the genetic influence of BDNF genotypes (i.e., Val/Val, Val/Met, or Met/Met type). This study aimed to investigate the effect of BDNF genotype on motor performance and motor learning in healthy human adults via a systematic review and meta-analysis. A total of 19 relevant studies were identified using PubMed and Web of Science search for articles published between 2000 and 2021 with motor performance or motor learning as the primary outcome measures. The results of our systematic review suggest that the BDNF genotype is unlikely to contribute to motor performance and motor learning abilities because only 2/32 datasets (6.3%) from 16 studies on motor performance and 3/19 datasets (17.6%) from 13 studies on motor learning indicated a significant genetic effect. Moreover, a meta-analysis of motor learning publications involving 17 datasets from 11 studies revealed that there was no significant difference in the learning score normalized using baseline data between Val/Val and Met carriers (Val/Met + Met/Met or Val/Met; standardized mean differences = 0.08, P = 0.37) with zero heterogeneity (I² = 0) and a relatively low risk of publication bias. Taken together, the BDNF genotype may have only a minor impact on individual motor performance and motor learning abilities.

Association of Serum Biomarker Levels and BDNF Gene Polymorphism with Response to Selective Serotonin Reuptake Inhibitors in Indian Patients with Major Depressive Disorder

INTRODUCTION

Depression is a major public health problem. Response to selective serotonin reuptake inhibitor (SSRI) treatment varies considerably between patients. In the context of polygenic diseases like depression, measurement of a panel of biomarkers involved in the pathophysiology of depression might help predict outcome to treatment with SSRIs.

OBJECTIVE

The objective was to establish the relationship between serum biomarker levels and the brain-derived neurotrophic factor (BDNF) val66met polymorphism and response to SSRIs in patients with major depressive disorder.

METHODS

50 patients with moderate to severe depression were recruited from the Department of Psychiatry, Sri Ra-machandra Institute of Higher Education and Research. Blood samples were collected, and Hamilton Depression Rating Scale scoring was done at baseline and after 8 weeks of treatment with SSRIs. Baseline and post-treatment levels of high-sensitivity C-reactive protein (hsCRP), BDNF and neuregulin 1β1 (NRG1β1) were analysed using commercially available ELISA kits. Genotyping of the BDNF Val66Met polymorphism was performed using a PCR-RFLP method.

RESULTS

Following treatment, there was a significant decrease in the mean hsCRP and NRG1β1 levels and a significant increase in the mean BDNF level. Responders had significantly lower baseline hsCRP and higher baseline BDNF levels when compared to non-responders. Response rates were significantly higher in the Val/Val group when compared to the Val/Met group.

CONCLUSIONS

Baseline serum levels of hsCRP and BDNF predicted response to SSRIs in major depressive disorder, and Val/Val patients responded better when compared to patients carrying the Met allele.

Suicide prevention in childhood and adolescence: a narrative review of current knowledge on risk and protective factors and effectiveness of interventions

INTRODUCTION

Suicide is a global mental health problem for people of all ages. While rates of suicide in children and adolescents are reported as lower than those in older populations worldwide, they represent the third leading cause of death in 15-19-year-olds. The rates are higher among boys than girls worldwide, though the death rates for girls exceed those for boys in Bangladesh, China, India, and Nepal. There has been a general decrease in adolescent suicide rates over recent decades. However, increases are reported in South East Asia as well as South America over the same time period.

METHODS

A narrative review method has been used to summarize current knowledge about risk and protective factors for suicide among children and adolescents and to discuss evidence-based strategy for suicide prevention in this age group.

RESULTS

Identified suicide risk and protective factors for children and adolescents largely overlap with those for adults. Nevertheless, developmental characteristics may strengthen the impact of some factors, such as decision-making style, coping strategies, family and peer relationships, and victimization. The implementation of evidence-based suicide preventive strategies is needed. Restricting access to lethal means, school-based awareness and skill training programs, and interventions delivered in clinical and community settings have been proven effective. The effectiveness of gatekeeper training and screening programs in reducing suicidal ideation and behavior is unproven but widely examined in selected settings.

DISCUSSION

Since most studies have been conducted in western countries, future research should assess the effectiveness of these promising strategies in different cultural contexts. The use of more rigorous study designs, the use of both short- and long-term follow-up evaluations, the larger inclusion of individuals belonging to vulnerable groups, the evaluation of online intervention, and the analysis of programs' cost-effectiveness are also required.

Moderators of gene-outcome associations following traumatic brain injury

The field of genomics is the principal avenue in the ongoing development of precision/personalised medicine for a variety of health conditions. However, relating genes to outcomes is notoriously complex, especially when considering that other variables can change, or moderate, gene-outcome associations. Here, we comprehensively discuss moderation of gene-outcome associations in the context of traumatic brain injury (TBI), a common, chronically debilitating, and costly neurological condition that is under complex polygenic influence. We focus our narrative review on single nucleotide polymorphisms (SNPs) of three of the most studied genes (apolipoprotein E, brain-derived neurotrophic factor, and catechol-O-methyltransferase) and on three demographic variables believed to moderate associations between these SNPs and TBI outcomes (age, biological sex, and ethnicity). We speculate on the mechanisms which may underlie these moderating effects, drawing widely from biomolecular and behavioural research (n = 175 scientific reports) within the TBI population (n = 72) and other neurological, healthy, ageing, and psychiatric populations (n = 103). We conclude with methodological recommendations for improved exploration of moderators in future genetics research in TBI and other populations.

Influence of FKBP5 Variants and Childhood Trauma on Brain Volume in Non-clinical Individuals

The present study aimed to investigate the possible influence of childhood trauma and its interaction effect with 10 single-nucleotide polymorphisms (SNPs) of the FK506-binding protein 51 (FKBP5) gene on brain volume in non-clinical individuals. One hundred forty-four non-clinical volunteers (44 men and 100 women) were genotyped with respect to 10 variants (rs9296158, rs3800373, rs1360780, rs9470080, rs4713916, rs4713919, rs6902321, rs56311918, rs3798345, and rs9380528) of FKBP5. Participants underwent magnetic resonance imaging (MRI) scan and psychological assessments such as the childhood Trauma Questionnaire (CTQ), Hospital Anxiety and Depression Scale, rumination response scale, and quality of life assessment instrument. Individuals with the high CTQ score showed enlarged volume of the left orbitofrontal cortex (OFC) if they have childhood trauma-susceptible genotype of FKBP5 rs3800373, rs1360780, rs4713916, rs4713919, rs6902321, and rs3798345 and enlarged volume of the left middle temporal gyrus (MTG) if they have childhood trauma-susceptible genotype of FKBP5 rs3800373, rs1360780, rs4713916, and rs3798345. Among those with the childhood trauma-susceptible genotype, the left OFC and left MTG showed significant negative correlations with positive feelings about life, and the left OFC showed significant positive correlations with negative cognition. This is one of the few studies to identify the volume alteration of the left OFC and the left MTG for the FKBP5 gene–childhood trauma interaction in non-clinical individuals.

Association of PICK1 and BDNF variations with increased risk of methamphetamine dependence among Iranian population: a case-control study

BACKGROUND

Genetic factors play an important role in susceptibility to methamphetamine dependency. In this line, protein that interact with C-kinase-1 (PICK1) and brain-derived neurotrophic factor (BDNF) genes are linked to methamphetamine dependence (substance use disorder). Thus, in a case-control study, we investigated the association between polymorphisms of PICK1 and BDNF genes and methamphetamine dependence in an Iranian population.

METHODS

Total of 235 cases and 204 controls were recruited in a period between 2015 to 2018. The PICK1-rs713729, -rs2076369 and BDNF-rs6265 genotypes were determined via ARMS-PCR assay. Statistical analysis was performed, using SPSS 20.0, PHASE 2.1.1 program as well as SNP Analyzer 2.0.

RESULTS

In the present study, two polymorphisms including PICK1-rs713729 (OR 1.38 (CI 1.08-1.52; P-value 0.004) in multiplicative and dominant models, and PICK1-rs2076369 (OR 1.31 (CI 1.10-1.56; P-value 0.002) in multiplicative, dominant and co-dominant models were associated with the risk of methamphetamine abuse. Moreover, haplotype analysis showed a significant association of haplotype AG (OR 2.50 (CI 1.50-4.16; P-value 0.0002) in dominant, recessive and co-dominant models, and haplotype TT (OR 0.67 (CI 0.50-0.91; P-value 0.009) in dominant and co-dominant models with the risk of methamphetamine abuse. None of the polymorphisms in this study had a high level of linkage disequilibrium.

CONCLUSION

Our findings indicate that the PICK1 gene polymorphism might affect the risk of methamphetamine dependency in our population.

Clustering suicidal phenotypes and genetic associations with brain-derived neurotrophic factor in patients with substance use disorders

Suicide attempts (SA), especially recurrent SA or serious SA, are common in substance use disorders (SUD). However, the genetic component of SA in SUD samples remains unclear. Brain-derived neurotrophic factor (BDNF) alleles and levels have been repeatedly involved in stress-related psychopathology. This investigation uses a within-cases study of BDNF and associated factors in three suicidal phenotypes ('any', 'recurrent', and 'serious') of outpatients seeking treatment for opiate and/or cocaine use disorder. Phenotypic characterization was ascertained using a semi-structured interview. After thorough quality control, 98 SNPs of BDNF and associated factors (the BDNF pathway) were extracted from whole-genome data, leaving 411 patients of Caucasian ancestry, who had reliable data regarding their SA history. Binary and multinomial regression with the three suicidal phenotypes were further performed to adjust for possible confounders, along with hierarchical clustering and compared to controls (N = 2504). Bayesian analyses were conducted to detect pleiotropy across the suicidal phenotypes. Among 154 (37%) ever suicide attempters, 104 (68%) reported at least one serious SA and 96 (57%) two SA or more. The median number of non-tobacco SUDs was three. The BDNF gene remained associated with lifetime SA in SNP-based (rs7934165, rs10835210) and gene-based tests within the clinical sample. rs10835210 clustered with serious SA. Bayesian analysis identified genetic correlation between 'any' and 'serious' SA regarding rs7934165. Despite limitations, 'serious' SA was shown to share both clinical and genetic risk factors of SA-not otherwise specified, suggesting a shared BDNF-related pathophysiology of SA in this population with multiple SUDs.

Does the Brain-Derived Neurotrophic Factor Val66Met Polymorphism Modulate the Effects of Physical Activity and Exercise on Cognition?

The Val66Met is a polymorphism of the brain-derived neurotrophic factor (BDNF) gene that encodes a substitution of a valine (Val) to methionine (Met) amino acid. Carrying this polymorphism reduces the activity-dependent secretion of the BDNF protein, which can potentially affect brain plasticity and cognition. We reviewed the biology of Val66Met and surveyed 26 studies (11,417 participants) that examined the role of this polymorphism in moderating the cognitive response to physical activity (PA) and exercise. Nine observational studies confirmed a moderating effect of Val66Met on the cognitive response to PA but differences between Val and Met carriers were inconsistent and only significant in some cognitive domains. Only five interventional studies found a moderating effect of Val66Met on the cognitive response to exercise, which was also inconsistent in its direction. Two studies showed a superior cognitive response in Val carriers and three studies showed a better response in Met carriers. These results do not support a general and consistent effect of Val66Met in moderating the cognitive response to PA or exercise. Both Val and Met carriers can improve specific aspects of cognition by increasing PA and engaging in exercise. Causes for discrepancies among studies, effect moderators, and future directions are discussed.

Epigenetic marks and their relationship with BDNF in the brain of suicide victims

Background

Suicide is a common phenomenon affecting people of all ages. There is a strong relationship between suicidal ideation and depressive disorders. Increasing number of studies suggest that epigenetic modifications in certain brain areas are the main mechanism through which environmental and genetic factors interact with each other contributing to the development of mental disorders. To verify this hypothesis, some epigenetic marks: H3K9/14ac, HDAC2/3, H3K27me2 and Sin3a, as well as p-S421-MeCP2/MeCP2 were examined. On the other hand, BDNF protein level were studied.

Materials and methods

Western blot analysis were performed in the frontal cortex (FCx) and hippocampus (HP) of suicide victims (n = 14) and non-suicidal controls (n = 8). The differences between groups and correlations between selected proteins were evaluated using Mann-Whitney U-test and Spearman’s rank correlation.

Results

Statistically significant decrease in H3K9/14ac (FCx:↓~23%;HP:↓~33%) combined with increase in HDAC3 (FCx:↑~103%;HP:↑~85% in HP) protein levels in suicides compared to the controls was shown. These alterations were accompanied by an increase in H3K27me2 (FCx:↑45%;HP:↑~59%) and Sin3a (HP:↑50%) levels and decrease in p-S421-MeCP2/MeCP2 protein ratio (HP:↓~55%;FCx:↓~27%). Moreover, reduced BDNF protein level (FCx:↓~43%;HP:↓~28%) in suicides was observed. On the other hand, some significant correlations (e.g. between H3K9/14ac and HDAC2 or between BDNF and p-S421-MeCP2/MeCP2) were demonstrated.

Conclusions

Our findings confirm the role of epigenetic component and BDNF protein in suicidal behavior. Lowered BDNF protein level in suicides is probably due to decrease in histone acetylation and increased level of factors related with deacetylation and methylation processes, including MeCP2 factor, which may operate bidirectionally (an activator or inhibitor of transcription).

Identification of key pathways and genes responsible for aggressive behavior

Aggression is a complex behavior, underpinned by cross talk between several biomolecules. To date a composite molecular network of the behavioral disorder has not been constructed. The present study aims to develop the same from the system network analyses recruiting genes with empirical evidence demonstrating their role in the incidence and progression of aggression. In short, 327 genes were recruited in the study after extensive literature survey and subsequent shortlisting by sieving out the comorbidities like cancer and other pathological and physiological ailments, other languages and repeated citations. Subsequent String network analysis coalesces 275 genes in a network with 2223 edges. The developed network was then subjected to delineate modules using MCODE which via gene clustering on the basis of gene ontology segregate all genes into 14 modules. Of these, as expected top 5 modules involved entailing of neuronal signaling pathways with redundant repetitions. Finally, 10 genes (known) were picked randomly, accounting average module size, and subjected to the network analysis with 100,000 bootstrap replicates. This results in the detection of certain novel genes that lacks empirical evidence for their association with the aggression. Amongst those, most notable are genes involved in protein turnover regulation like UBC, UBA, mitogenic proteins such as Rho and Myc, transcription factors like Tp53. The findings in turn fill caveats in the molecular resolution of cross talk that underscore the development of aggressive behavior and may then be exploited as screening biomarker and/or therapeutic intervention for aggression.

The BDNF Val66Met Polymorphism Moderates the Relationship Between Posttraumatic Stress Disorder and Trauma Script-evoked Attentional Bias to Cocaine Cues Among Patients with Cocaine Dependence

There is extensive variability in cocaine-related attentional bias (AB) following trauma script exposure among cocaine-dependent (CD) patients with posttraumatic stress disorder (PTSD). Therefore, research is needed to identify the specific PTSD-CD patients most likely to exhibit an AB to cocaine cues. A common polymorphism in brain-derived neurotrophic factor (BDNF), Val66met, is associated with risk for stimulant addiction, and thus, was examined as a moderator of the association between PTSD and cocaine-related AB following trauma script exposure in this study. Adult CD patients with (n = 17) and without (n = 28) PTSD were exposed to a personalized trauma script, followed by a visual dot-probe task assessing cocaine-related AB. Task response times were used to examine traditionally calculated AB scores, as well as trial level bias scores (TL-BS) that more accurately model the temporal dynamics of AB. PTSD-CD patients homozygous for the BDNF Val/Val genotype exhibited greater bias for attending to cocaine-related stimuli following trauma script exposure than those carrying the Met allele. The PTSD by BDNF interaction did not predict response time variability on trials for which only neutral stimuli were presented, thus increasing confidence that the observed effect is specific to cocaine-related stimuli. PTSD-CD patients homozygous for the BDNF Val/Val genotype may be at particularly high risk for negative clinical outcomes (e.g., relapse, treatment dropout) as a function of prolonged attentional engagement with cocaine cues when exposed to trauma reminders.

The rs6265 Polymorphism of the BDNF Gene Is Related to Higher-Lethality Suicide Attempts in the Korean Population

OBJECTIVE

Since the risk of suicide cannot be predicted by clinical symptoms alone, and suicide is known to have a genetic component, the discovery of genetic markers that can predict the lethality of suicide attempts is a clinically important topic. There have been many studies aiming to determine whether the rs6265 polymorphism of the BDNF gene is associated with suicidality; however, the results have been mixed, and there have been few studies investigating the relationship between this polymorphism and suicide attempt lethality.

METHODS

We assessed suicide lethality in 258 individuals who had attempted suicide using the relative risk ratio (RRR) scale and by genotyping the rs6265 polymorphism of the BDNF gene.

RESULTS

The RRR score for suicide attempts was higher in subjects with Met/Val and Val/Val genotypes than in that with a Met/Met genotype (p=0.015). The RRR score for suicide attempts was also higher in Val allele carriers (Met/Val+Val/Val) than in Met/Met homozygotes (p=0.006).

CONCLUSION

This study demonstrates the possibility that the rs6265 polymorphism of the BDNF gene could be used as a genetic marker to predict the lethality of suicide attempts, but more replication studies are needed for the application of this result in clinical practice.

SLC1A3 C3590T but not BDNF G196A is a predisposition factor for stress as well as depression, in an adolescent eastern Indian population

Background

Adolescence is a distinctive stage of various changes and is noted as peak age for onset of many psychiatric disorders, especially linked to stress and depression. Several genetic variations are being increasingly known to be linked with stress and depression. The polymorphisms in two such genes, the BDNF and SLC1A3, have been reported to be linked with either depression/stress or with suicidal behaviour. These genes have not been validated in Indian population, and therefore there is a need to investigate these genes in Indian population. The present study was undertaken to test whether the known polymorphisms SLC1A3 C3590T, SLC1A3 C869G and BDNF G196A are associated or not with stress or depression in an eastern Indian population.

Methods

A case-control association study was performed with 108 cases having variable levels of stress and depression and 205 matched controls. Detection of stress and depression was done by using standard instruments as PSS and CES-D, respectively and demographic profile was obtained for each individual on the basis of personal data sheet. Genotyping for the selected polymorphisms was performed by PCR followed by restriction digestion.

Results

The SNP SLC1A3 C3590T was found to be associated with stress and depression (p = 0.0042, OR = 2.072). Therefore, the T allele increases the risk by more than two folds for stress and depression in the present population. The other allele of SLC1A3, G869C, as well as BDNF G196A were not associated with stress or depression in the population studied.

Conclusion

SLC1A3 C3590T is a predisposition factor for stress and depression in an eastern Indian population, whereas SLC1A3 G869C and BDNF G196A were not found to be a risk factor. Therefore, presence of T allele of SLC1A3 C3590T, may predict the development of stress and depression in an individual. This may also help in the understanding of pathophysiology of the disease. However, these findings warrant a wider study in Indian populations and would be of significance in understanding the predisposition of stress and depression in this population.

Evaluation of leptin levels in serum as a biomarker for suicide behavior: systematic review and meta-analysis

Objective: We conducted a meta-analysis of case-control studies to determine whether leptin levels in serum contribute to the pathogenesis of suicide behavior.Methods: PubMed, EBSCO and Science Direct databases were used to search for relevant articles published before January 2020. The systematic review included nine case-control studies that measured leptin levels. The standardized mean difference (d) and 95% confidence intervals were calculated in a fixed-effects model and a random-effects model when appropriate.Results: The results of our meta-analysis indicated that individuals with suicide behavior presented reduced levels of leptin (d: -1.80, 95% CI: -2.21 to -01.38 ng/ml, I² = 0, p(Q) = 0.59). Sensitivity and publication bias analyses confirmed these results.Conclusions: The current meta-analysis suggests that leptin levels might be associated with an increased risk of suicide behavior. However, more studies including larger sample sizes are needed to reach conclusive result.

Association Between BDNF Gene Variant Rs6265 and the Severity of Depression in Antidepressant Treatment-Free Depressed Patients

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal plasticity, and its dysregulation has been associated with the pathogenesis of mood and anxiety disorders. Prolactin (PRL) is a pituitary hormone which is also produced as a cytokine by immune cells and could be a neurotrophic factor regulating the functional activity of stress-related mechanisms.

AIM

To investigate the possible relationship between depressive state and BDNF and PRL genotypes or levels with special reference to severity of depression.

METHODS

Participants of 18-70 years with a clinical diagnosis of depressive disorder of at least moderate severity were included. These patients had not been treated with antidepressant drugs before admission to hospital during the preceding period of the last 6 months, and 54.5% had never been treated with antidepressant drugs during their entire life. The DNA was genotyped for rs1341239 within the prolactin and for rs6265, rs7124442, and rs11030104 within the BDNF gene. Rs11030104 violated the Hardy-Weinberg equilibrium distribution and was excluded from further analyses. BDNF and prolactin concentration was measured in serum by MAGPIX multiplex analyzer (Luminex, USA) using MILLIPLEX^® MAP kit (Merck, Germany). Genetic associations were determined by sequentially regressing prolactin, BDNF, 17-items Hamilton's Depression (HAMD-17) and Clinical Global Impression scale, Severity (CGI-S) ratings, and depression (absent/present) on the available SNPs. Genetic associations were evaluated assuming an additive model.

RESULTS

A total of 186 depressed patients (of which 169 were women) and 94 healthy controls (67 women) were genotyped. After excluding subjects without genetic information on all three study SNPs, 217 remained of whom 138 suffered from depression. Within depressed patients we observed an association of rs6265 with HAMD-17: mean difference (MD) 2.33 (95%CI 0.49; 4.16; p = 0.014) and CGI-S: MD 0.38 (95%CI 0.09; 0.66; p = 0.011). No significant association was observed between the prolactin SNP rs1341239 and prolactin levels. Similarly the mean differences of BDNF SNPs did not show an association with BDNF: rs6265 -0.042 ln(pg/ml) (95%CI -0.198; 0.113), and rs7124442 0.006 ln(pg/ml) (95%CI -0.117; 0.130). No other association reached statistical significance.

CONCLUSION

We observed a significant association between BDNF gene variant rs6265 and the severity of depression in newly admitted, antidepressant treatment-free, depressed patients. Actual PRL and BDNF levels were not elevated sufficiently in depressed patients to reach statistical significance and were not associated with the studied genotypes.

Biomarkers of suicidal behaviors: A comprehensive critical review

Suicide is a relevant worldwide public health problem. Many studies have shown that different demographic and clinical factors are potentially associated with suicidal behavior. Other studies have reported data about the role of biomarkers in the onset of suicidal behaviors. Specifically, researchers have found that suicidal risk may be increased by abnormalities in serotonergic system, hypothalamic-pituitary-adrenal axis, lipid metabolism, immune system and neuronal plasticity. The identification of specific biological parameters associated with self-harm may be helpful to implement prevention strategies and also to detect new therapeutic strategies. In this review, we summarize and analyze the results of main studies about neurobiological mechanisms related to suicidal behavior, also exploring the possible interconnection between the different biological systems.

Transcranial Direct Current Stimulation to Improve the Dysfunction of Descending Pain Modulatory System Related to Opioids in Chronic Non-cancer Pain: An Integrative Review of Neurobiology and Meta-Analysis

Background: Opioid long-term therapy can produce tolerance, opioid-induced hyperalgesia (OIH), and it induces dysfunction in pain descending pain inhibitory system (DPIS). Objectives: This integrative review with meta-analysis aimed: (i) To discuss the potential mechanisms involved in analgesic tolerance and opioid-induced hyperalgesia (OIH). (ii) To examine how the opioid can affect the function of DPIS. (ii) To show evidence about the tDCS as an approach to treat acute and chronic pain. (iii) To discuss the effect of tDCS on DPIS and how it can counter-regulate the OIH. (iv) To draw perspectives for the future about the tDCS effects as an approach to improve the dysfunction in the DPIS in chronic non-cancer pain. Methods: Relevant published randomized clinical trials (RCT) comparing active (irrespective of the stimulation protocol) to sham tDCS for treating chronic non-cancer pain were identified, and risk of bias was assessed. We searched trials in PubMed, EMBASE and Cochrane trials databases. tDCS protocols accepted were application in areas of the primary motor cortex (M1), dorsolateral prefrontal cortex (DLPFC), or occipital area. Results: Fifty-nine studies were fully reviewed, and 24 with moderate to the high-quality methodology were included. tDCS improved chronic pain with a moderate effect size [pooled standardized mean difference; -0.66; 95% confidence interval (CI) -0.91 to -0.41]. On average, active protocols led to 27.26% less pain at the end of treatment compared to sham [95% CI; 15.89-32.90%]. Protocol varied in terms of anodal or cathodal stimulation, areas of stimulation (M1 and DLPFC the most common), number of sessions (from 5 to 20) and current intensity (from 1 to 2 mA). The time of application was 20 min in 92% of protocols. Conclusion: In comparison with sham stimulation, tDCS demonstrated a superior effect in reducing chronic pain conditions. They give perspectives that the top-down neuromodulator effects of tDCS are a promising approach to improve management in refractory chronic not-cancer related pain and to enhance dysfunctional neuronal circuitries involved in the DPIS and other pain dimensions and improve pain control with a therapeutic opioid-free. However, further studies are needed to determine individualized protocols according to a biopsychosocial perspective.

Antisuicidal effect, BDNF Val66Met polymorphism, and low-dose ketamine infusion: Reanalysis of adjunctive ketamine study of Taiwanese patients with treatment-resistant depression (AKSTP-TRD)

BACKGROUND

Growing evidence suggests a rapid antisuicidal effect of low-dose ketamine infusion in Caucasian patients with treatment-resistant depression (TRD). However, the antisuicidal effects of ketamine on Taiwanese patients with TRD remains unknown.

METHODS

Seventy-one patients with TRD were randomly classified into three treatment groups: 0.5 mg/kg ketamine, 0.2 mg/kg ketamine, or normal saline (placebo) infusion. The Hamilton Depression Rating Scale (HAMD) and Montgomery-Åsberg Depression Rating Scale (MADRS) were applied prior to initiation of test infusions, at 40, 80, 120, and 240 min postinfusion, and sequentially on Days 2, 3, 4, 5, 6, 7, and 14 after ketamine or placebo infusion. Item 3 (suicide) of the HAMD and item 10 (suicidal thoughts) of the MADRS were extracted for generalized estimating equation (GEE) model analyses to investigate the antisuicidal effects of ketamine infusion. Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism was genotyped.

RESULTS

The GEE model revealed significant group (p = 0.007) and time (p = 0.004) effects on suicidal symptoms over times (prior to infusion to day 14 postinfusion). The group that received 0.5 mg/kg ketamine infusion exhibited a significantly lower score in item 3 of the HAMD and item 10 of the MADRS compared with the groups that received 0.2 mg/kg ketamine or placebo infusion. Among those carrying any Val allele of BDNF, both 0.5 and 0.2 mg/kg ketamine infusions were effective in reducing suicidal thoughts; however, among those with Met/Met of BDNF, only 0.5 mg/kg ketamine infusion was effective in reducing suicidal thoughts.

DISCUSSION

A single low-dose ketamine infusion was effective in reducing suicidal ideation among Taiwanese patients with TRD. BDNF Val66Met polymorphism may play a crucial role in the antisuicidal effects of ketamine infusion.

Critical Issues in BDNF Val66Met Genetic Studies of Neuropsychiatric Disorders

Neurotrophins have been implicated in the pathophysiology of many neuropsychiatric diseases. Brain-derived neurotrophic factor (BDNF) is the most abundant and widely distributed neurotrophin in the brain. Its Val66Met polymorphism (refSNP Cluster Report: rs6265) is a common and functional single-nucleotide polymorphism (SNP) affecting the activity-dependent release of BDNF. BDNF Val66Met transgenic mice have been generated, which may provide further insight into the functional impact of this polymorphism in the brain. Considering the important role of BDNF in brain function, more than 1,100 genetic studies have investigated this polymorphism in the past 15 years. Although these studies have reported some encouraging positive findings initially, most of the findings cannot be replicated in following studies. These inconsistencies in BDNF Val66Met genetic studies may be attributed to many factors such as age, sex, environmental factors, ethnicity, genetic model used for analysis, and gene–gene interaction, which are discussed in this review. We also discuss the results of recent studies that have reported the novel functions of this polymorphism. Because many BDNF polymorphisms and non-genetic factors have been implicated in the complex traits of neuropsychiatric diseases, the conventional genetic association-based method is limited to address these complex interactions. Future studies should apply data mining and machine learning techniques to determine the genetic role of BDNF in neuropsychiatric diseases.