No support for a role for BDNF gene polymorphisms rs11030101 and rs61888800 in major depressive disorder or antidepressant response in patients of Finnish origin

Associations of BDNF/BDNF-AS SNPs with Depression, Schizophrenia, and Bipolar Disorder

Brain-Derived Neurotrophic Factor (BDNF) is crucial for various aspects of neuronal development and function, including synaptic plasticity, neurotransmitter release, and supporting neuronal differentiation, growth, and survival. It is involved in the formation and preservation of dopaminergic, serotonergic, GABAergic, and cholinergic neurons, facilitating efficient stimulus transmission within the synaptic system and contributing to learning, memory, and overall cognition. Furthermore, BDNF demonstrates involvement in neuroinflammation and showcases neuroprotective effects. In contrast, BDNF antisense RNA (BDNF-AS) is linked to the regulation and control of BDNF, facilitating its suppression and contributing to neurotoxicity, apoptosis, and decreased cell viability. This review article aims to comprehensively overview the significance of single nucleotide polymorphisms (SNPs) in BDNF/BDNF-AS genes within psychiatric conditions, with a specific focus on their associations with depression, schizophrenia, and bipolar disorder. The independent influence of each BDNF/BDNF-AS gene variation, as well as the interplay between SNPs and their linkage disequilibrium, environmental factors, including early-life experiences, and interactions with other genes, lead to alterations in brain architecture and function, shaping vulnerability to mental health disorders. The potential translational applications of BDNF/BDNF-AS polymorphism knowledge can revolutionize personalized medicine, predict disease susceptibility, treatment outcomes, and guide the selection of interventions tailored to individual patients.

BDNF-related mutations in major depressive disorder: a systematic review

OBJECTIVE

A better understanding of the genetic, molecular and cellular mechanisms of brain-derived neurotrophic factor (BDNF) and its association with neuroplasticity could play a pivotal role in finding future therapeutic targets for novel drugs in major depressive disorder (MDD). Because there are conflicting results regarding the exact role of BDNF polymorphisms in MDD still, we set out to systematically review the current evidence regarding BDNF-related mutations in MDD.

METHODS

We conducted a keyword-guided search of the PubMed and Embase databases, using 'BDNF' or 'brain-derived neurotrophic factor' and 'major depressive disorder' and 'single-nucleotide polymorphism'. We included all publications in line with our exclusion and inclusion criteria that focused on BDNF-related mutations in the context of MDD.

RESULTS

Our search yielded 427 records in total. After screening and application of our eligibility criteria, 71 studies were included in final analysis. According to present overall scientific data, there is a possibly major pathophysiological role for BDNF neurotrophic systems to play in MDD. However, on the one hand, the synthesis of evidence makes clear that likely no overall association of BDNF-related mutations with MDD exists. On the other hand, it can be appreciated that solidifying evidence emerged on specific significant sub-conditions and stratifications based on various demographic, clinico-phenotypical and neuromorphological variables.

CONCLUSIONS

Further research should elucidate specific BDNF-MDD associations based on demographic, clinico-phenotypical and neuromorphological variables. Furthermore, biomarker approaches, specifically combinatory ones, involving BDNF should be further investigated.

Interaction between the BDNF rs11030101 genotype and job stress on cognitive empathy

BACKGROUND

Empathy refers to an individual's ability to experience the emotional and cognitive processes of another person during social interactions. Although many studies have examined the effects of genetic variation on emotional empathy, little is currently known about whether genetic factors may influence cognitive empathy. This study investigated the relationship between BDNF rs11030101 genotype, job stress, and empathy, especially cognitive empathy, in a Chinese Han population.

METHODS

A cross-sectional design was used and 340 participants were recruited from a university in Beijing. Interpersonal Reactivity Index (IRI) was used to measure empathy. Job stress was measured using House and Rizzo's Job Stress Scale. The BDNF rs11030101 was genotyped in all participants.

RESULTS

Gender and age were associated with various IRI subscales (p < 0.001). After controlling for gender, age and education level, BDNF rs11030101 genotype had no main effect on all empathy subscales (p > 0.05). Job stress was negatively associated with Perspective Taking (p = 0.006) and positively associated with Personal Distress (p < 0.001). In addition, the BDNF rs11030101 genotype modulated the relationship between job stress and Fantasy (p = 0.013), indicating that T allele carriers had higher Fantasy scores at higher job stress and lower Fantasy scores at lower job stress than AA homozygotes. This interaction was only present in women.

LIMITATIONS

The sample size and single-nucleotide polymorphism are limited, and the cross-sectional design should be improved.

CONCLUSIONS

Female university faculty with the BDNF rs11030101 T allele may utilize higher emotional job demands, thereby fostering their cognitive empathy.

The impact of antidepressant treatment on brain-derived neurotrophic factor level: An evidence-based approach through systematic review and meta-analysis

OBJECTIVES:

Antidepressant treatment alters brain-derived neurotrophic factor (BDNF) levels, but it is not well established whether BDNF can be used as a marker to prove the efficacy of antidepressant treatment. The present systematic review and meta-analysis aim at assessing the influence of antidepressant treatment on BDNF level and the Hamilton Depression Rating Scale (HDRS) score, thereby to establish the rationale of utilizing BDNF as a predictive biomarker and HDRS score as an indicator for antidepressant treatment efficacy.

MATERIALS AND METHODS:

Search was conducted in PubMed, Science Direct, and Cochrane databases using the key words “BDNF” and “Depression” and “Antidepressants.” On the basis of the inclusion and exclusion criteria, studies were filtered and finally 6 randomized controlled trials were shortlisted.

RESULTS:

Comparison of serum BDNF level before and after antidepressant treatment was performed and the result showed that antidepressant treatment does not significantly affect the BDNF levels (confidence interval [CI]: −0.483 to 0.959; standard mean difference [SMD]: 0.238, P = 0.518). Egger's regression test (P = 0.455) and heterogeneity test (I² = 88.909%) were done. Similarly, comparison of HDRS scores before and after antidepressant treatment indicated improvement in HDRS score suggesting positive outcome (CI: 1.719 to 3.707; SMD: 2.713, P < 0.001). Egger's regression test (P = 0.1417) and heterogeneity test (I² = 89.843%) were performed. Publication bias was observed by funnel plot.

CONCLUSION:

Changes in BDNF levels do not occur uniformly for all the antidepressants. Hence, to use BDNF as a biomarker, it needs to be seen whether the same is true for all antidepressants.

BDNF and NRG1 polymorphisms and temperament in selective serotonin reuptake inhibitor-treated patients with major depression

OBJECTIVE

We investigated the separate effects of and possible interactions between the functional polymorphisms of brain-derived neurotrophic factor (BDNF) rs11030101, BDNF rs61888800, and neuregulin-1 (NRG1) rs3924999 and NRG1 rs6994992 on change of temperament scores in a clinical sample of subjects with major depression (MDD), who received selective serotonin reuptake inhibitor treatment for a period of 6 weeks.

METHODS

The study population consisted of 98 Finnish individuals with MDD. They were assessed by the 107-item Temperament and Character Inventory temperament questionnaire (version IX) and the Montgomery-Åsberg Depression Rating Scale (MADRS). In general linear univariate models (GLM) for novelty seeking (NS) or reward dependence (RD) change age, gender, MADRS score change and BDNF and NRG1 genotypes were used as explaining explanatory variables.

RESULTS

Mean comparisons between corresponding temperament dimensions and genotypes showed significant differences between NS change and BDNF rs61888800 T-carrying status (mean difference: GG 0.30, GT/TT 2.47, p=0.022, t-test) and between RD change and NRG1 rs3924999 A-carrying status (mean difference: GG 1.21, GA/AA -0.33, p=0.003). In GLM models for NS change the significant predictors comprised BDNF rs61888800 T-carrying status, age and MADRS score change (model 1), and additionally NRG1 rs6994992 T-carrying status (model 2). For RD change the predictors included NRG1 rs3924999 A-carrying status, age and MADRS score change (model 1) and additionally gender (model 2).

CONCLUSION

According to the current results both BDNF and NRG1 are associated with temperament traits during depression. These results warrant further studies regarding the impact of this association on depression recovery.

Pharmacogenetics and Imaging-Pharmacogenetics of Antidepressant Response: Towards Translational Strategies

Genetic variation underlies both the response to antidepressant treatment and the occurrence of side effects. Over the past two decades, a number of pharmacogenetic variants, among these the SCL6A4, BDNF, FKBP5, GNB3, GRIK4, and ABCB1 genes, have come to the forefront in this regard. However, small effects sizes, mixed results in independent samples, and conflicting meta-analyses results led to inherent difficulties in the field of pharmacogenetics translating these findings into clinical practice. Nearly all antidepressant pharmacogenetic variants have potentially pleiotropic effects in which they are associated with major depressive disorder, intermediate phenotypes involved in emotional processes, and brain areas affected by antidepressant treatment. The purpose of this article is to provide a comprehensive review of the advances made in the field of pharmacogenetics of antidepressant efficacy and side effects, imaging findings of antidepressant response, and the latest results in the expanding field of imaging-pharmacogenetics studies. We suggest there is mounting evidence that genetic factors exert their impact on treatment response by influencing brain structural and functional changes during antidepressant treatment, and combining neuroimaging and genetic methods may be a more powerful way to detect biological mechanisms of response than either method alone. The most promising imaging-pharmacogenetics findings exist for the SCL6A4 gene, with converging associations with antidepressant response, frontolimbic predictors of affective symptoms, and normalization of frontolimbic activity following antidepressant treatment. More research is required before imaging-pharmacogenetics informed personalized medicine can be applied to antidepressant treatment; nevertheless, inroads have been made towards assessing genetic and neuroanatomical liability and potential clinical application.

Genetic polymorphisms and the adequacy of brain stimulation: state of the art

INTRODUCTION

Heterogeneity of therapeutic response to brain stimulation techniques has inspired scientists to uncover the secrets to success or failure of these projects. Genetic polymorphisms are one of the major causes of this heterogeneity.

AREAS COVERED

More than twenty genetic variants within more than ten genes (e.g. BDNF, COMT, DRD2, TRPV1, 5-HT1A, 5-HHT, P2RX7, VEGF, TPH1, TPH2, ACE, APOE, GNB3, NET, NMDA receptors, and RGS4) have been investigated, among which the BDNF gene and its polymorphism, Val66Met, is the best documented variant. We review the genotypic combinations, which are reported to interact with the work of brain stimulation, of which the DRD2 C957T polymorphism is the most prominent type. Finally, implications of transcranial magnetic stimulation in deciphering the interaction between genetic background (e.g. SCN1A and 5-HTT) and drugs (e.g. carbamazepine and citalopram) at the cortical excitability level is explained. Expert commentary: Studies are ongoing to find missing factors responsible for heterogeneity of response to brain stimulation techniques. Further knowledge about genetic factors affecting the therapeutic response to brain stimulation techniques might provide helpful guidelines for choosing ideal candidates for treatment.

Genetic Moderators of the Impact of Physical Activity on Depressive Symptoms

BACKGROUND

Converging evidence suggests that physical activity is an effective intervention for both clinical depression and sub-threshold depressive symptoms; however, findings are not always consistent. These mixed results might reflect heterogeneity in response to physical activity, with some subgroups of individuals responding positively, but not others.

OBJECTIVES

1) To examine the impact of genetic variation and sex on changes in depressive symptoms in older adults after a physical activity (PA) intervention, and 2) to determine if PA differentially improves particular symptom dimensions of depression.

DESIGN

Randomized controlled trial.

SETTING

Four field centers (Cooper Institute, Stanford University, University of Pittsburgh, and Wake Forest University).

PARTICIPANTS

396 community-dwelling adults aged 70-89 years who participated in the Lifestyle Interventions and Independence for Elders Pilot Study (LIFE-P).

INTERVENTION

12-month PA intervention compared to an education control.

MEASUREMENTS

Polymorphisms in the serotonin transporter (5-HTT), brain-derived neurotrophic factor (BDNF), and apolipoprotein E (APOE) genes; 12-month change in the Center for Epidemiologic Studies Depression Scale total score, as well as scores on the depressed affect, somatic symptoms, and lack of positive affect subscales.

RESULTS

Men randomized to the PA arm showed the greatest decreases in somatic symptoms, with a preferential benefit in male carriers of the BDNF Met allele. Symptoms of lack of positive affect decreased more in men compared to women, particularly in those possessing the 5-HTT L allele, but the effect did not differ by intervention arm. APOE status did not affect change in depressive symptoms.

CONCLUSIONS

Results of this study suggest that the impact of PA on depressive symptoms varies by genotype and sex, and that PA may mitigate somatic symptoms of depression more than other symptoms. The results suggest that a targeted approach to recommending PA therapy for treatment of depression is viable.

BDNF/TRKB/P75NTR polymorphisms and their consequences on antidepressant efficacy in depressed patients

We propose an extensive review of the literature about BDNF/TRKB/P75NTR polymorphisms and their consequences on antidepressant efficacy in depressed patients. Five genome-wide association studies and 30 association studies were included. Twenty seven studies focused on the Val66Met polymorphism (rs6265), the Met allele being associated with a higher antidepressant efficacy only in Asian patients. Other BDNF/TRKB/P75NTR polymorphisms (BDNF: rs7103411, rs7124442, rs908867, rs2049046, rs61888800, rs10501087, rs1491850; TRKB: rs10868223, rs11140778, rs1565445, rs1659412; P75NTR: rs2072446) were reported to be associated with antidepressant efficacy but these results were not replicated. Finally, there are 15 positive studies among 30 studies regarding BDNF/TRKB/P75NTR polymorphisms. The only SNP which benefits of at least three positive studies is the BDNF Val66Met polymorphism (rs6265). Consequently, with a lack of good and consistent studies, the clinical utility of BDNF in treatment selection is far from clear. We propose several recommendations for further studies.

The role of brain-derived neurotrophic factor (BDNF) Val66Met genetic polymorphism in bipolar disorder: a case-control study, comorbidities, and meta-analysis of 16,786 subjects

OBJECTIVES

The aim of this study was to evaluate the association of Val66Met brain-derived neurotrophic factor (BDNF) polymorphism with bipolar disorder in (i) a meta-analysis and (ii) a case-control study in a Mexican population. We also investigated the possible association of this polymorphism with clinical features.

METHODS

We performed a keyword search of the PubMed and Web of Science databases. A total of 22 studies that have investigated the association of Val66Met (rs6265) with bipolar disorder were selected for inclusion and combined with random effects meta-analysis, using allelic, additive, dominant, and recessive models. Finally, the single nucleotide polymorphism (rs6265) Val66Met in the BDNF gene was genotyped and compared between 139 patients with bipolar disorder and 141 healthy volunteers in a Mexican population.

RESULTS

The pooled results from the meta-analysis (9,349 cases and 7,437 controls) did not show a significant association in any of the models. The same results were obtained in our case-control study when analyzing the distribution of the genotypic frequencies of the Val66Met polymorphism in patients with bipolar disorder. However, when we analyzed the association between rs6265 and lifetime history of suicidal behavior, we found an association between genotype Val-Val and suicide attempt (p = 0.02).

CONCLUSIONS

Although the present study has some limitations, the results indicate a lack of association between the Val66Met polymorphism and bipolar disorder. However, in our case-control study in a Mexican population, the Val66Met polymorphism was associated with suicidal behavior in patients with bipolar disorder. Nevertheless, it is important to consider potential interactions of the BDNF gene, the environment, and different inheritance patterns, when carrying out future genetic studies with larger samples.

Advances in biomarkers of major depressive disorder

Major depressive disorder (MDD) is characterized by mood, vegetative, cognitive, and even psychotic symptoms and signs that can cause substantial impairments in quality of life and functioning. Biomarkers are measurable indicators that could help diagnosing MDD or predicting treatment response. In this chapter, lipid profiles, immune/inflammation, and neurotrophic factor pathways that have long been implicated in the pathogenesis of MDD are discussed. Then, pharmacogenetics and epigenetics of serotonin transport and its metabolism pathway, brain-derived neurotrophic factor, and abnormality of hypothalamo-pituitary-adrenocortical axis also revealed new biomarkers. Lastly, new techniques, such as proteomics and metabolomics, which allow researchers to approach the studying of MDD with new directions and make new discoveries are addressed. In the future, more data are needed regarding pathophysiology of MDD, including protein levels, single nucleotide polymorphism, epigenetic regulation, and clinical data in order to better identify reliable and consistent biomarkers for diagnosis, treatment choice, and outcome prediction.

Are there meaningful biomarkers of treatment response for depression?

During the past decades, the prevalence of affective disorders has been on the rise globally, with only one out of three patients achieving remission in acute treatment with antidepressants. The identification of physiological markers that predict treatment course proves useful in increasing therapeutic success. On the basis of well-documented, recent findings in depression research, we highlight and discuss the most promising biomarkers for antidepressant therapy response. These include genetic variants and gene expression profiles, proteomic and metabolomic markers, neuroendocrine function tests, electrophysiology and imaging techniques. Ultimately, this review proposes an integrative use of biomarkers for antidepressant treatment outcome.

Antidepressant pharmacogenetics

PURPOSE OF REVIEW

This article reviews recent literature published over the period March 2012-August 2013 on antidepressant pharmacogenetics, with a focus on clinical translation and methodological challenges.

RECENT FINDINGS

Recently, various polymorphisms associated with differential antidepressant efficacy, tolerability, and safety have emerged in association studies, but mixed findings, limited effect sizes, and poor control of confounders have prevented findings translating to practice. Although promising steps have been made, empirically robust clinically translatable pharmacogenetic tests are not yet established. The complex neurobiology of major depressive disorder (MDD) together with the evolving understanding of genetic processes present research challenges for clinical translation.

SUMMARY

Early reports of clinical utility are published. The current evidence base for antidepressant pharmacogenetics is, however, not yet empirically robust enough to inform routine prescribing guidelines. Over the coming years, genetically guided versus unguided trials will help determine if antidepressant pharmacogenetics merits more widespread application.