The brain-derived neurotrophic factor (BDNF) polymorphism Val66Met is associated with neither serum BDNF level nor response to selective serotonin reuptake inhibitors in depressed Japanese patients

The effect of antidepressant treatment on blood BDNF levels in depressed patients: A review and methodological recommendations for assessment of BDNF in blood

Major depressive disorder (MDD) is a highly prevalent psychiatric disorder and a leading cause of disability worldwide. Brain-derived neurotrophic factor (BDNF), a signaling protein responsible for promoting neuroplasticity, is highly expressed in the central nervous system but can also be found in the blood. Since impaired brain plasticity is considered a cornerstone in the pathophysiology of MDD, measurement of BDNF in blood has been proposed as a potential biomarker in MDD. The aim of our study is to systematically review the literature for the effects of antidepressant treatments on blood BDNF levels in MDD and the suitability of blood BDNF as a biomarker for depression severity and antidepressant response. We searched Pubmed® and Cochrane library up to March 2024 in a systematic manner using Medical Subject Headings (MeSH). The search resulted in a total of 42 papers, of which 30 were included in this systematic review. Generally, we found that patients with untreated MDD have a lower blood BDNF level than healthy controls. Antidepressant treatments increase blood BDNF levels, and more evidently after pharmacological than non-pharmacological treatment. Neither baseline nor change in the blood BDNF level correlates with depression severity or treatment outcome, which undermines its use as a biomarker in MDD. Our review also highlights the importance of considering factors influencing the accuracy and reproducibility of BDNF measurements. We summarize considerations to help obtain more robust blood BDNF values and compile a list of recommendations to help streamline assessment of blood BDNF levels in future studies.

Interaction effect of crocin and citalopram on memory and locomotor activity in rats: an insight into BDNF and synaptophysin levels in the hippocampus

Selective serotonin reuptake inhibitors (SSRIs) are widely used drugs for the treatment of depression. Citalopram is one of the most prescribed SSRIs that is useful for the treatment of depression, obsessive-compulsive disorder, and anxiety disorders. On the other hand, crocin (active constitute of saffron) has pro-cognitive and mood enhancer effects. Also, both citalopram and crocin affect the function and expression of brain-derived neurotrophic factor (BDNF) and synaptophysin, two molecular factors that are involved in cognitive functions and mood. In the present study, we aim to investigate the interaction effect of citalopram and crocin on rats' performance in the open field test (locomotor activity and anxiety-like behavior) and the shuttle box (passive avoidance memory). Citalopram was injected at the doses of 10, 30, and 50 mg/kg, and crocin was injected at the dose of 50 mg/kg; all administrations were intraperitoneal. Real-time PCR was used to assess the expression level of BDNF and synaptophysin in the hippocampus. The results showed that citalopram (30 and 50 mg/kg) impaired passive avoidance memory and decreased BDNF and synaptophysin expression in the hippocampus, while crocin reversed memory impairment, and BDNF and synaptophysin expression in the hippocampus of rats received citalopram 30 mg/kg. Also, crocin partially showed these effects in rats that received citalopram 50 mg/kg. The results of the open field test were unchanged. In conclusion, we suggested that BDNF and synaptophysin may be involved in the effects of both citalopram and crocin.

The relevance of BDNF for neuroprotection and neuroplasticity in multiple sclerosis

Background

Neuroplasticity as a mechanism to overcome central nervous system injury resulting from different neurological diseases has gained increasing attention in recent years. However, deficiency of these repair mechanisms leads to the accumulation of neuronal damage and therefore long-term disability. To date, the mechanisms by which remyelination occurs and why the extent of remyelination differs interindividually between multiple sclerosis patients regardless of the disease course are unclear. A member of the neurotrophins family, the brain-derived neurotrophic factor (BDNF) has received particular attention in this context as it is thought to play a central role in remyelination and thus neuroplasticity, neuroprotection, and memory.

Objective

To analyse the current literature regarding BDNF in different areas of multiple sclerosis and to provide an overview of the current state of knowledge in this field.

Conclusion

To date, studies assessing the role of BDNF in patients with multiple sclerosis remain inconclusive. However, there is emerging evidence for a beneficial effect of BDNF in multiple sclerosis, as studies reporting positive effects on clinical as well as MRI characteristics outweighed studies assuming detrimental effects of BDNF. Furthermore, studies regarding the Val66Met polymorphism have not conclusively determined whether this is a protective or harmful factor in multiple sclerosis, but again most studies hypothesized a protective effect through modulation of BDNF secretion and anti-inflammatory effects with different effects in healthy controls and patients with multiple sclerosis, possibly due to the pro-inflammatory milieu in patients with multiple sclerosis. Further studies with larger cohorts and longitudinal follow-ups are needed to improve our understanding of the effects of BDNF in the central nervous system, especially in the context of multiple sclerosis.

Serum brain-derived neurotrophic factor, Val66Met polymorphism and open-label SSRI treatment response in Major Depressive Disorder

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been implicated in the therapeutic action of antidepressants and possibly in the pathophysiology of Major Depressive Disorder (MDD). Clinical studies of peripheral blood levels of BDNF in MDD have provided conflicting results, and there are also conflicting reports regarding the predictive value of peripheral BDNF levels for antidepressant treatment response. The present study investigated the association between serum BDNF levels, the BDNF Val66Met polymorphism (rs6265), clinical characteristics and SSRI treatment response.

METHODS

This open-label clinical trial included 99 physically healthy, unmedicated MDD participants and 70 healthy controls. Following a baseline assessment, 53 of the MDD participants completed an eight-week, open-label course of SSRI antidepressant treatment. Serum BDNF levels and Hamilton Rating Scale for Depression (HDRS) ratings were examined at baseline and after eight weeks of treatment. Antidepressant response was defined as a decrease in HDRS ratings of > 50% from baseline to the end-of-treatment. Finally, serum BDNF levels and SSRI treatment response were compared between MDD participants who were heterozygous or homozygous for the Met allele ("Met-carriers") and individuals homozygous for the Val allele.

RESULTS

Serum BDNF levels at baseline were significantly higher in the unmedicated MDD participants compared to healthy controls (15.90 ng/ml vs 13.75 ng/ml, t (167) = -2.041, p = 0.043). In a post-hoc analysis, this difference was seen in the female but not male participants (16.85 ng/ml vs 14.06 ng/ml, t (91) = -2.067, p = 0.042; 14.86 ng/ml vs 13.31 ng/ml, t (74) = -0.923, p = 0.359). Baseline serum BDNF levels were not associated with treatment responder status or with absolute change in depression ratings over the course of 8-week SSRI treatment (p = 0.599). In both Responders and Non-responders, no significant changes in serum BDNF levels were found over the 8-week period of SSRI-treatment (16.32 ng/ml vs 16.23 ng/ml, t (18) = 0.060, p = 0.953; 16.04 ng/ml vs 15.61 ng/ml, t (29) = 0.438, p = 0.665, respectively). Further, no differences were found in serum BDNF levels prior to treatment between MDD Met-carriers and MDD Val/Val homozygotes (15.32 ng/ml vs 16.36 ng/ml, t (85) = 0.747, p = 0.457), and no differences were found in post-treatment serum BDNF (F1,42= 0.031, p = 0.862). However, MDD Val/Val homozygotes showed significantly greater antidepressant responses at week 8 than did MDD Met-carriers (F1,46 = 4.366, p = 0.043).

CONCLUSION

Our results do not support sufficient reliability of using peripheral BDNF to characterize depression or to predict antidepressant response in clinical use. The role of sex in moderating BDNF differences in depression, and the role of BDNF gene polymorphisms in predicting antidepressant response, remain to be further investigated. We conclude that, while central nervous system BDNF is likely involved in antidepressant efficacy and in aspects of MDD pathophysiology, its reflection in serum BDNF levels is of limited diagnostic or prognostic utility.

Comparing the effect of fluoxetine, escitalopram, and sertraline, on the level of BDNF and depression in preclinical and clinical studies: a systematic review

Brain-derived neurotrophic factor (BDNF) dysfunction is one of the most important mechanisms underlying depression. It seems that selective serotonin reuptake inhibitors (SSRIs) improve depression via affecting BDNF level. In this systematic review, for the first time, we aimed to review the effect of three SSRIs including fluoxetine, escitalopram, and sertraline, on both depression and BDNF level in preclinical and clinical studies. PubMed electronic database was searched, and 193 articles were included in this study. After reviewing all manuscripts, only one important difference was found: subjects. We found that SSRIs induce different effects in animals vs. humans. Preclinical studies showed many controversial effects, while human studies showed only two effects: improvement of depression, with or without the improvement of BDNF. However, most studies used chronic SSRIs treatment, while acute SSRIs were not effectively used and evaluated. In conclusion, it seems that SSRIs are reliable antidepressants, and the improvement effect of SSRIs on depression is not dependent to BDNF level (at least in human studies).

The BDNF Val66Met Polymorphism is a Relevant, But not Determinant, Risk Factor in the Etiology of Neuropsychiatric Disorders - Current Advances in Human Studies: A Systematic Review

Brain-derived neurotrophic factor (BDNF) is the brain's most-produced neurotrophin during the lifespan, essentially involved in multiple mechanisms of nervous system development and function. The production/release of BDNF requires multi-stage processing that appears to be regulated at various stages in which the presence of a polymorphism "Val66Met" can exert a critical influence.

Aim

To synthesize the knowledge on the BDNF Val66Met polymorphism on intracellular processing and function of BDNF.

Methods

We performed a systematic review and collected all available studies on the post-translation processes of BDNF, regarding the Val66Met polymorphism. Searches were performed up to 21st March 2021.

Results

Out of 129 eligible papers, 18 studies addressed or had findings relating to BDNF post-translation processes and were included in this review.

Discussion

Compilation of experimental findings reveals that the Val66Met polymorphism affects BDNF function by slightly altering the processing, distribution, and regulated release of BDNF. Regarding the critical role of pro-BDNF as a pro-apoptotic factor, such alteration might represent a risk for the development of neuropsychiatric disorders.

Sublingual buprenorphine/naloxone treatment is not affected by OPRM1 A118G and BDNF Va66Met polymorphisms, but alters the plasma beta-endorphin and BDNF levels in individuals with opioid use disorder

The study aimed to examine the genetic contribution to buprenorphine (BUP) treatment in individuals with opioid use disorder (OUD), with a specific focus on BDNF and OPRM1 genes. A total of 113 controls and 111 OUD patients receiving sublingual BUP/naloxone were enrolled. OPRM1 A118G and BDNF Val66Met polymorphisms were investigated by PCR-FRLP. Plasma BDNF and beta-endorphin levels were assessed by ELISA kits in both groups. Blood BUP levels were measured by LC-MS/MS and normalized with daily BUP dose (BUP/D). OPRM1 A118G and BDNF Val66Met polymorphisms didn't have an effect on plasma beta-endorphin and BDNF levels in OUD patients, respectively. Interestingly, OUD patients had significantly higher plasma BDNF and lower beta-endorphin levels compared to the controls (p < 0.001). A negative and significant correlation between plasma BUP/D and BDNF levels was found. Age onset of first use was associated with OPRM1 A118G polymorphism. The findings indicated that sublingual BUP/naloxone may increase plasma BDNF levels, but may decrease beta-endorphin levels in individuals with OUD. Plasma BDNF level seemed to be decreased in a BUP/D concentration-dependent manner.

A Brief Overview on BDNF-Trk Pathway in the Nervous System: A Potential Biomarker or Possible Target in Treatment of Multiple Sclerosis?

The growing incidence of neurodegenerative disorders in our populations is leading the research to identify potential biomarkers and targets for facilitating their early management and treatments. Biomarkers represent the crucial indicators of both physiological and pathological processes. Specific changes in molecular and cellular mechanisms of physiological processes result in biochemical alterations at systemic level, which can give us comprehensive information regarding the nature of any disease. In addition, any disease biomarker should be specific and reliable, able to consent of distinguishing the physiological condition of a tissue, organ, or system from disease, and be diverse among the various diseases, or subgroups or phenotypes of them. Accordingly, biomarkers can predict chances for diseases, facilitate their early diagnosis, and set guidelines for the development of new therapies for treating diseases and disease-making process. Here, we focus our attention on brain neurotrophic factor (BDNF)–tropomyosin receptor kinase (Trk) pathway, describing its multiple roles in the maintenance of central nervous system (CNS) health, as well as its implication in the pathogenesis of multiple sclerosis (MS). In addition, we also evidence the features of such pathway, which make of it a potential MS biomarker and therapeutic target.

The Val66 and Met66 Alleles-Specific Expression of BDNF in Human Muscle and Their Metabolic Responsivity

Brain-derived neurotrophic factor (BDNF) plays an essential role in nervous system formation and functioning, including metabolism. Present only in humans, the “Val66Met” polymorphism of the BDNF gene (BDNF) is suggested to have a negative influence on the etiology of neurological diseases. However, this polymorphism has only been addressed, at the molecular level, in nonhuman models. Knowledge about Val66- and Met66-variant differences, to date, has been achieved at the protein level using either cell culture or animal models. Thus, the purpose of our study was to analyze the impact of the Val66Met polymorphism on BDNF expression in healthy humans and compare the allele-specific responses to metabolic stress. Muscle biopsies from 13 male recreational athletes (34 ± 9 years, 1.80 ± 0.08 m, 76.4 ± 10.5 kg) were obtained before and immediately following a VO₂max test. Allele-specific BDNF mRNA concentrations were quantified by droplet digital PCR (ddPCR) in heterozygous and homozygous subjects. The results indicated that BDNF expression levels were influenced by the genotype according to the presence of the polymorphism. BDNF expression from the Met66-coding alleles, in heterozygotes, was 1.3-fold lower than that from the Val66-coding alleles. Total BDNF mRNA levels in these heterozygotes remained below the whole sample’s mean. A partial dominance was detected for the Val66-coding variant on the Met66-coding’s. BDNF expression levels decreased by an average of 1.8-fold following the VO₂max test, independent of the individual’s genotype. The results of this study indicate that metabolic stress downregulates BDNF expression but not plasma BDNF concentrations. No correlation between expression level and plasma BDNF concentrations was found.

Plasma brain-derived neurotrophic factor (BDNF) concentration and the BDNF Val66Met polymorphism in suicide: a prospective study in patients with depressive disorder

Purpose

The relationship was investigated between brain-derived neurotrophic factor (BDNF) concentrations, a BDNF polymorphism (196G>A), and the response to selective serotonin reuptake inhibitors (SSRIs) among Chinese patients with major depressive disorder (MDD).

Patients and methods

A total of 125 patients and 91 healthy controls were enrolled. The disease progression and treatment responses were evaluated using the Hamilton depression rating scale (HAMD24), the Hamilton anxiety scale, the Beck depression index, and BDNF concentrations at the baseline, 4, 8, and 12 weeks after treatment. Responders were defined as patients with at least a 50% decrease in the HAMD24.

Results

The BDNF concentrations were significantly lower in MDD (947±297 vs 1187±236 pg/mL, p=0.019), in MDD with attempted suicide than those without (779±231 vs 993±298, p=0.024) at the baseline. The BDNF concentrations remarkably increased in response to SSRI treatment. Significant correlations were noted between the BDNF concentrations and suicide ideation or attempted suicide (p<0.01), but not with HAMD24 or depression. BDNF 196G>A correlated with neither suicide ideation nor treatment responses.

Conclusion

BDNF concentrations were significantly lower in patients with attempted suicide/ideation. BDNF concentrations could serve as a response marker for antidepressant treatment in MDD.

Genetic variants in major depressive disorder: From pathophysiology to therapy

In spite of promising preclinical results there is a decreasing number of new registered medications in major depression. The main reason behind this fact is the lack of confirmation in clinical studies for the assumed, and in animals confirmed, therapeutic results. This suggests low predictive value of animal studies for central nervous system disorders. One solution for identifying new possible targets is the application of genetics and genomics, which may pinpoint new targets based on the effect of genetic variants in humans. The present review summarizes such research focusing on depression and its therapy. The inconsistency between most genetic studies in depression suggests, first of all, a significant role of environmental stress. Furthermore, effect of individual genes and polymorphisms is weak, therefore gene x gene interactions or complete biochemical pathways should be analyzed. Even genes encoding target proteins of currently used antidepressants remain non-significant in genome-wide case control investigations suggesting no main effect in depression, but rather an interaction with stress. The few significant genes in GWASs are related to neurogenesis, neuronal synapse, cell contact and DNA transcription and as being nonspecific for depression are difficult to harvest pharmacologically. Most candidate genes in replicable gene x environment interactions, on the other hand, are connected to the regulation of stress and the HPA axis and thus could serve as drug targets for depression subgroups characterized by stress-sensitivity and anxiety while other risk polymorphisms such as those related to prominent cognitive symptoms in depression may help to identify additional subgroups and their distinct treatment. Until these new targets find their way into therapy, the optimization of current medications can be approached by pharmacogenomics, where metabolizing enzyme polymorphisms remain prominent determinants of therapeutic success.

Progress in Elucidating Biomarkers of Antidepressant Pharmacological Treatment Response: A Systematic Review and Meta-analysis of the Last 15 Years

BACKGROUND

Antidepressant drugs are widely prescribed, but response rates after 3 months are only around one-third, explaining the importance of the search of objectively measurable markers predicting positive treatment response. These markers are being developed in different fields, with different techniques, sample sizes, costs, and efficiency. It is therefore difficult to know which ones are the most promising.

OBJECTIVE

Our purpose was to compute comparable (i.e., standardized) effect sizes, at study level but also at marker level, in order to conclude on the efficacy of each technique used and all analyzed markers.

METHODS

We conducted a systematic search on the PubMed database to gather all articles published since 2000 using objectively measurable markers to predict antidepressant response from five domains, namely cognition, electrophysiology, imaging, genetics, and transcriptomics/proteomics/epigenetics. A manual screening of the abstracts and the reference lists of these articles completed the search process.

RESULTS

Executive functioning, theta activity in the rostral Anterior Cingular Cortex (rACC), and polysomnographic sleep measures could be considered as belonging to the best objectively measured markers, with a combined d around 1 and at least four positive studies. For inter-category comparisons, the approaches that showed the highest effect sizes are, in descending order, imaging (combined d between 0.703 and 1.353), electrophysiology (0.294-1.138), cognition (0.929-1.022), proteins/nucleotides (0.520-1.18), and genetics (0.021-0.515).

CONCLUSION

Markers of antidepressant treatment outcome are numerous, but with a discrepant level of accuracy. Many biomarkers and cognitions have sufficient predictive value (d ≥ 1) to be potentially useful for clinicians to predict outcome and personalize antidepressant treatment.

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 Polymorphism: A Review of Its Diagnostic and Clinical Relevance in Neurodegenerative Disorders

Brain-derived neurotrophic factor (BDNF) has a unique role in the neuronal development, differentiation, and survival in the developing and adult nervous system. A common single-nucleotide polymorphism in the pro-region of the human BDNF gene, resulting in a valine to methionine substitution (Val66Met), has been associated with the susceptibility, incidence, and clinical features of several neurodegenerative disorders. Much research has been dedicated to evaluating the effects of polymorphism in the past decade, and functional effects of this genetic variation. A better understanding of how this naturally occurring polymorphism associates with or influences physiology, anatomy, and cognition in both healthy and diseased adults in neurodegenerative conditions will help understand neurochemical mechanisms and definable clinical outcomes in humans. Here we review the role and relevance of the BDNF Val66Met polymorphism in neurodegenerative diseases, with particular emphasis on glaucoma, multiple sclerosis (MS), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Several controversies and unresolved issues, including small effect sizes, possible ethnicity, gender, and age effects of the BDNF Val66Met are also discussed with respect to future research.

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

Background

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

Methods

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

Results

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

Conclusions

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

Serum Brain-Derived Neurotrophic Factor, and Plasma Catecholamine Metabolites in People with Major Depression: Preliminary Cross-Sectional Study

BACKGROUND

There are complicated interactions between catecholaminergic neurons and brain-derived neurotrophic factor (BDNF) in the brain. However, no reports have addressed the relationship among 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid (HVA), and BDNF in the blood.

OBJECTIVE

This paper sought to investigate correlations between serum BDNF and plasma levels of MHPG and HVA in people with major depression (MD).

MATERIALS AND METHODS

A total of 148 patients (male/female 65/83, age 49.5 ± 12.1 years old) who satisfied criteria for MD based on the Diagnostic and Statistical Manual of Mental Disorders IV were enrolled in the present study. Plasma levels of MHPG and HVA were analyzed using high-performance liquid chromatography, and serum BDNF was measured using ELISA.

RESULTS

No interactions were observed between plasma HVA levels (mean ± SD = 4.5 ± 1.5 ng/mL) and age, sex, HAMD scores, or serum BDNF levels (mean ± SD = 9.8 ± 2.9 ng/mL). No correlations were not also observed between plasma MHPG levels (mean ± SD = 5.9 ± 2.1 ng/mL) and age, sex, the HAMD17 scores (mean ± SD = 22.2 ± 2.9 ng/mL), or serum BDNF levels. Serum BDNF levels were negatively associated with HAMD17 scores.

CONCLUSION

The results suggest that there are no significant correlations between catecholamine metabolites and BDNF in the blood for MDD patients.

Association analysis between mitogen-activated protein/extracellular signal-regulated kinase (MEK) gene polymorphisms and depressive disorder in the Han Chinese population

BACKGROUND

Recent research findings suggest that BDNF and BDNF signaling pathways participate in the development of major depressive disorder. Mitogen-activated extracellular signal-regulated kinase (MEK) is the most important kinase in the extracellular signal-regulated kinase pathway, and the extracellular signal-regulated kinase pathway is the key signaling pathway of BDNF, so it may play a role in development of depressive disorder. The aim of this study is to investigate the association between polymorphisms of the MAP2K1 (also known as MEK) gene and depressive disorder.

RESULTS

Three single nucleotide polymorphisms (SNPs), were significantly associated with depressive disorder: rs1549854 (p = 0.006), rs1432441 (p = 0.025), and rs7182853 (p = 0.039). When subdividing the sample by gender, two of the SNPs remained statistically associated with depressive disorder in females: rs1549854 (p = 0.013) and rs1432441 (p = 0.04).

CONCLUSION

The rs1549854 and rs1432441 polymorphisms of the MAP2K1 gene may be associated with major depressive disorder, especially in females. This study is the first to report that the MAP2K1 gene may be a genetic marker for depressive disorder.

Val66Met functional polymorphism and serum protein level of brain-derived neurotrophic factor (BDNF) in acute episode of schizophrenia and depression

BACKGROUND

Brain-derived neurotrophic factor (BDNF) influences neuron differentiation during development as well as the synaptic plasticity and neuron survival in adulthood. BDNF has been implicated in the pathogenesis of schizophrenia and depression. Val66Met polymorphism and BDNF serum level are potential biomarkers in neuropsychiatric disorders. The aim of this study was to determine the effect of BDNF gene Val66Met functional polymorphism on serum BDNF concentration in patients with schizophrenia, during depression episode and in healthy control group.

METHODS

183 participants were recruited (61 patients with depressive episode, 56 females with schizophrenia, 66 healthy controls) from Polish population. Serum BDNF levels were measured using ELISA method. Val66Met polymorphism was genotyped using PCR- RFLP method.

RESULTS

Serum BDNF levels were not associated with Val66Met polymorphism in either of the groups. A significant increase of BDNF level in schizophrenia (p = 0.0005) and depression (p = 0.026) comparing to the control group has been observed.

CONCLUSIONS

Our results suggest that the functional Val66Met BDNF polymorphism is not associated with BDNF serum levels, which is in line with previous findings. Replication studies on larger groups are needed.

Determinants of Blood Brain-Derived Neurotrophic Factor Blood Levels in Patients with Alcohol Use Disorder

BACKGROUND

Blood brain-derived neurotrophic factor (BDNF) levels are influenced by both addiction and mood disorders, as well as somatic conditions, gender, and genetic polymorphisms, leading to widely varying results. Depressive symptoms and episodes are frequently observed in patients with alcohol use disorder, and vary widely over time, making it a challenge to determine which aspects are specifically involved in variations of serum BDNF levels in this population.

METHODS

We assessed 227 patients with alcohol dependence involved in a detoxification program, at baseline and after a follow-up of 6 months, for the Alcohol Use Disorders Identification Test score, the length of alcohol dependence, and the number of past detoxification programs. The Beck Depression Inventory and information on current tobacco and alcohol use, suicidal ideation, body mass index, age, gender, and psychotropic treatments were also collected. Serum BDNF (ELISA) and 2 genetic polymorphisms of the BDNF gene (Val33Met and rs962369) were analyzed.

RESULTS

The presence of the Met allele, 2 markers of the history of alcohol dependence (gamma glutamyl transferase and the number of past treatments in detoxification programs), and the presence of a depressive episode (but not depressive score) were significantly associated with the 2 blood levels of BDNF at baseline and after 6 months. After controlling for baseline BDNF levels, the presence of the Met allele and an ongoing depressive episode were the only variables associated with changes in BNDF levels after 6 months.

CONCLUSIONS

Low serum BDNF levels are associated with characteristics related to alcohol consumption and mood disorders, and variants of the BDNF gene in alcohol use disorder patients. The factors that most strongly influenced changes in serum BDNF levels following treatment in an alcohol detoxification program were variants of the BDNF gene and ongoing depression.

Influence of Genetic Polymorphisms and Concomitant Anxiolytic Doses on Antidepressant Maintenance Doses in Japanese Patients with Depression

To prevent recurrent depression, patients should ideally continue treatment for >6 months with the antidepressant dose that effectively suppressed acute depressive symptoms. However, there are inter-individual differences in the antidepressant doses required to achieve response and maintenance. Therefore, this study was conducted to examine the role of clinical features, including genetic polymorphisms, on the antidepressant dose required for maintenance therapy in 82 Japanese patients with depression. We calculated the antidepressant dose using the imipramine equivalent scale and the dose of concomitant anxiolytics and hypnotics using the diazepam equivalent scale. The 82 participants were classified into two groups based on the median imipramine equivalent dose, and we examined the influence of patient characteristics and the presence of genetic polymorphisms of brain-derived neurotropic factor (BDNF; rs6265) and cyclic adenosine monophosphate responsive element-binding protein 1 (CREB1; rs2253306, rs4675690, rs769963) on the antidepressant maintenance dose. Using a multivariate logistic regression analysis, we found that the concomitant diazepam equivalent dose and presence of the CREB1 rs4675690 polymorphism were significantly associated with the antidepressant maintenance dose. We concluded that these factors influenced the antidepressant dose in maintenance therapy among Japanese patients with depression. However, further research is required in large cohorts.

Brain derived neurotrophic factor in newly diagnosed diabetes and prediabetes

Brain derived neurotrophic factor (BDNF) is thought to play an important role in glucose metabolism, but the exact mechanism has not been elucidated. The aim was to assess differences in serum BDNF levels across individuals with varying levels of glucose tolerance, and the association of serum BDNF levels with genetic variants and DNA methylation. Participants were selected from an ongoing population-based cohort study in rural China. In a randomly selected subsample of healthy participants (n = 33 males, n = 52 female), we assessed serum BDNF and in n = 50 of these, also DNA methylation. In a second subsample (all women; n = 28 with diabetes, n = 104 with prediabetes, and n = 105 age- and body mass index (BMI)-matched controls), we assessed serum BDNF and genetic variants. In a third subsample (all with diabetes; n = 7 normal BMI + low insulin level, n = 9 normal BMI + high insulin level, n = 9 obese + high insulin level), we assessed DNA methylation. Compared to age- and BMI-matched controls (24.71 (IQR, 20.44, 29.80) ng/ml), serum BDNF was higher in participants with prediabetes (27.38 (IQR, 20.64, 34.29) ng/ml), but lower in those with diabetes (23.40 (IQR, 18.12, 30.34) ng/ml) (P < 0.05). Two genetic variants near BDNF (rs4074134 and rs6265) were confirmed to be associated with BMI. BDNF CpG-6 methylation was positively associated with waist-to-hip ratio (P < 0.05). Furthermore, hyper-methylation in this site was found in participants with diabetes and high fasting insulin levels compared to those with diabetes and low fasting insulin levels, regardless of BMI status (P < 0.001 and P = 0.001, respectively). Observed differences in serum BDNF levels, genetic variants, and DNA methylation patterns across different glucose metabolic state suggest that BDNF may be involved in the pathophysiological process of insulin resistance and type 2 diabetes.

A method for reproducible measurements of serum BDNF: comparison of the performance of six commercial assays

Brain-Derived Neurotrophic Factor (BDNF) has attracted increasing interest as potential biomarker to support the diagnosis or monitor the efficacy of therapies in brain disorders. Circulating BDNF can be measured in serum, plasma or whole blood. However, the use of BDNF as biomarker is limited by the poor reproducibility of results, likely due to the variety of methods used for sample collection and BDNF analysis. To overcome these limitations, using sera from 40 healthy adults, we compared the performance of five ELISA kits (Aviscera-Bioscience, Biosensis, Millipore-ChemiKine^TM, Promega-Emax^®, R&D-System-Quantikine^®) and one multiplexing assay (Millipore-Milliplex^®). All kits showed 100% sample recovery and comparable range. However, they exhibited very different inter-assay variations from 5% to 20%. Inter-assay variations were higher than those declared by the manufacturers with only one exception which also had the best overall performance. Dot-blot analysis revealed that two kits selectively recognize mature BDNF, while the others reacted with both pro-BDNF and mature BDNF. In conclusion, we identified two assays to obtain reliable measurements of human serum BDNF, suitable for future clinical applications.

Neurotrophic factors in depression in response to treatment

BACKGROUND

Brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor A (VEGF) have been suggested to play a role in the pathophysiology of depression. The neurotrophic model of depression hypothesises that the serum level of e.g. BDNF is decreased during depression and increased in response to treatment. The aim of the present study was to investigate BDNF and VEGF as potential predictors of response to antidepressant treatment.

METHODS

We investigated the longitudinal associations between depression scores and serum levels of these neurotrophic factors during antidepressant treatment in 90 individuals with depression of at least moderate severity. Serum levels were measured at baseline and after 8 and 12 weeks of treatment with nortriptyline or escitalopram.

RESULTS

No baseline or longitudinal correlations between depression scores and serum levels of BDNF and VEGF were found, and the baseline serum levels did not predict the MADRS depression score after 12 weeks of treatment or the improvement in depression scores. Interestingly, we observed a significant baseline and longitudinal correlation between serum levels of BDNF and VEGF. The two classes of antidepressant treatment did not affect the results differently.

LIMITATIONS

Information on potential factors influencing the serum levels is missing.

CONCLUSION

Our results do not support the neurotrophic model of depression, since a significant decrease in serum BDNF and VEGF levels after 12 weeks of antidepressant treatment was observed. Our study encourages future studies with large sample sizes, more observations and a longer follow-up period.

The BDNF gene Val66Met polymorphism as a modifier of psychiatric disorder susceptibility: progress and controversy

Brain-derived neurotrophic factor (BDNF) has a primary role in neuronal development, differentiation and plasticity in both the developing and adult brain. A single-nucleotide polymorphism in the proregion of BDNF, termed the Val66Met polymorphism, results in deficient subcellular translocation and activity-dependent secretion of BDNF, and has been associated with impaired neurocognitive function in healthy adults and in the incidence and clinical features of several psychiatric disorders. Research investigating the Val66Met polymorphism has increased markedly in the past decade, and a gap in integration exists between and within academic subfields interested in the effects of this variant. Here we comprehensively review the role and relevance of the Val66Met polymorphism in psychiatric disorders, with emphasis on suicidal behavior and anxiety, eating, mood and psychotic disorders. The cognitive and molecular neuroscience of the Val66Met polymorphism is also concisely reviewed to illustrate the effects of this genetic variant in healthy controls, and is complemented by a commentary on the behavioral neuroscience of BDNF and the Val66Met polymorphism where relevant to specific disorders. Lastly, a number of controversies and unresolved issues, including small effect sizes, sampling of allele inheritance but not genotype and putative ethnicity-specific effects of the Val66Met polymorphism, are also discussed to direct future research.

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.

Serotonin transporter gene: a new polymorphism may affect response to antidepressant treatments in major depressive disorder

BACKGROUND AND OBJECTIVES

Several gene variants have been related to major depressive disorder (MDD) treatment outcomes; however, few studies have investigated a possible different effect on pharmacotherapy and brief psychotherapy response.

METHODS

A total of 137 MDD patients were randomized to either interpersonal counseling (IPC; n = 40) or antidepressant pharmacological treatment (n = 97). Outcomes were remission, response, and symptom improvement at week 8. Five genetic variants were investigated (5HTR2A rs6314, BDNF rs6265, SLC6A4 rs8076005, CREB1 rs2253206, and TPH2 rs11179023) as possible modulators of outcomes.

RESULTS

The LC6A4 rs8076005 AA genotype and A allele were associated with response rate in the antidepressant group (p = 0.015 and 0.005, respectively) and in the whole sample (p = 0.03 and 0.02, respectively). In the IPC group a non-significant trend in the same direction was observed. The TPH2 rs11179023 A allele showed a marginal association with symptom improvement in the IPC group only. Other gene variants did not impact on outcomes in any treatment group.

CONCLUSION

Our study suggests that rs8076005 in the SLC6A4 gene may be a modulator of antidepressant response, especially when pharmacological treatment is used.

Association of 2 neurotrophic factor polymorphisms with efficacy of paroxetine in patients with major depressive disorder in a Chinese population

BACKGROUND

To evaluate the influence of the single nucleotide polymorphism (SNP) rs 6265 in the brain-derived neurotrophic factor (BDNF) gene and 21 SNPs of the glial cell line-derived neurotrophic factor (GDNF) gene on the efficacy of paroxetine in patients with major depressive disorder (MDD).

METHODS

Genotyping for BDNF and GDNF polymorphisms was performed in 298 patients with MDD who started 20 mg paroxetine per day and had their plasma concentrations measured after 6 weeks. The SNPs were selected from the HapMap Chinese ethnic group and literature reports. Changes in the severity of MDD were assessed with the Hamilton Depression Rating Scale (HAM-D) at baseline and at a 6-week follow-up. Paroxetine plasma concentration was measured using high-performance liquid chromatography with fluorescence detection. The Sequenom MassArray system was used for genotyping.

RESULTS

At the 6-week follow-up, 219 of the 298 patients (73.5%) were responders and 79 patients (26.5%) were nonresponders to paroxetine treatment. The lower threshold concentration of paroxetine for response was 50 ng/mL, and a linear relationship was found between paroxetine plasma concentration and clinical response. The allele types for the SNPs rs 6265 (P < 0.001), rs 2973049 (P = 0.005), and rs 2216711 (P = 0.006) demonstrated significant associations with paroxetine treatment remission at week 6.

CONCLUSIONS

Genetic variants in the BDNF and GDNF regions may be indicators of treatment response to paroxetine in patients with MDD.

Brain-derived neurotrophic factor Val66Met polymorphism and 6-month antidepressant remission in depressed Caucasian patients

BACKGROUND

Whether the Brain Derived Neurotrophic Factor (BDNF) Val66Met polymorphism can predict antidepressant drug efficacy in depressed patients remains unclear, suggesting that it may depend on antidepressant classes. We assessed the impact of Val66Met polymorphism on antidepressant response and remission depending on antidepressant classes.

METHODS

In a 6-month prospective, real-world setting, treatment study, 345 Caucasian depressed patients requiring a new or different drug treatment with a selective serotonin reuptake inhibitor (SSRI), a serotonin and noradrenalin reuptake inhibitor (SNRI) or a tricyclic antidepressant (TCA), were genotyped and assessed for response and remission.

RESULTS

231 (67%) patients were homozygous for the Val66 allele (Val/Val) and 114 (33%) were carriers of Met allele (Met). 152 (44.1%) patients were treated with SSRI, the others with SNRI/TCA. Both response and remission were explained by interactions between the Val66Met polymorphism and antidepressant drug classes (multivariate models adjusted for propensity-scores: p=0.02 and p=0.03 respectively). With SSRI, Val/Val patients had a higher response rate 3 months post-treatment than Met patients (68.1% versus 44%; adjusted-OR: 3.04, IC95% [1.05; 9.37], p=0.04). With SNRI/TCA, Val/Val patients had a lower remission rate 6 months post-treatment than Met patients (33.3% versus 60.9%, adjusted-OR: 0.27, IC95% [0.09; 0.76], p=0.02).

LIMITATIONS

Limited sample size.

CONCLUSIONS

This study argues for a personalized prescription of antidepressants in Caucasian patients with major depressive disorder, based on the BDNF Val66Met polymorphism: SSRI should be preferred for Val/Val patients and SNRI/TCA for Met patients. Further studies are required to confirm these data.

The BDNF Val(66)Met polymorphism is associated with escitalopram response in depressed patients

BACKGROUND

The brain-derived neurotrophic factor (BDNF) gene is a candidate gene in therapeutic responses to antidepressants. The aim of the study was to determine the effects of BDNF allelic variability on responses to escitalopram treatment at 3 weeks after treatment initiation and at a 6-week endpoint.

METHODS

We included 187 Caucasian subjects with depression; 153 completed the 6-week study. Clinical evaluation was performed using the Montgomery and Asberg Depression Rating Scale (MADRS) before and after 3-6 weeks of treatment.

RESULTS

After 3 weeks of treatment, we saw significantly better treatment responses in the Met carriers and greater antidepressant resistance among the Val/Val homozygotes. Relative to Val/Val homozygous (59.78 %), a significantly greater proportion of subjects Met-carriers (77.94 %) responded to escitalopram treatment (χ (2) = 5.88, p = 0.015). After 6 weeks, we found the same pattern of results but this effect did not reach statistical significance (χ (2) = 2.07, p = 0.15).

CONCLUSION

These findings highlight a significant association between the BDNF valine to methionine substitution (Val(66)Met) polymorphism and the treatment response to escitalopram in a Caucasian population of severely depressed inpatients.

Relationships between brain-derived neurotrophic factor, clinical symptoms, and decision-making in chronic schizophrenia: data from the Iowa Gambling Task

The levels of brain-derived neurotrophic factor (BDNF) are significantly decreased in patients with schizophrenia and correlate with impairments in cognitive function. However, no study has investigated the relationship between the serum BDNF levels and decision-making. We compared patients with schizophrenia to healthy controls with respect to their decision-making ability and serum BDNF levels. Eighty-six chronic schizophrenia patients and 51 healthy controls participated in this study. We controlled for gender, age, and estimated intelligence quotient (IQ), and we investigated the differences in decision-making performance on the Iowa Gambling Task (IGT) between the schizophrenia patient and control groups. We also compared the IGT scores, the serum BDNF levels, and the clinical symptoms between the groups. The IGT scores of the schizophrenia patients were lower than those of the controls. A negative correlation was detected between the mean net scores on the trials in the final two blocks and the serum BDNF levels (p < 0.05). Multiple regression analysis revealed that depressive symptoms and the serum BDNF levels were significantly associated with the mean net scores on the trials in the final two blocks. Based on these results, impaired sensitivity to both reward and punishment is associated with depressive symptoms and reduced serum BDNF levels in chronic schizophrenia patients and may be related to their poor performance on the IGT.

Mechanisms of extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway in depressive disorder

The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor signal transduction pathway plays an important role in the mechanism of action of antidepressant drugs and has dominated recent studies on the pathogenesis of depression. In the present review we summarize the known roles of extracellular signal-regulated kinase, cAMP response element-binding protein and brain-derived neurotrophic factor in the pathogenesis of depression and in the mechanism of action of antidepressant medicines. The extracellular signal-regulated kinase/cAMP response element-binding protein/brain-derived neurotrophic factor pathway has potential to be used as a biological index to help diagnose depression, and as such it is considered as an important new target in the treatment of depression.

Brain-derived neurotrophic factor Val66Met polymorphism association with antidepressant efficacy: a systematic review and meta-analysis

INTRODUCTION

Previous studies of the association of the brain-derived neurotrophic factor (BDNF) Val66Met polymorphism with antidepressant efficacy are inconsistent. Thus, we conducted a systematic review and meta-analysis.

METHODS

We searched MEDLINE, PubMed, EMBASE, and Chinese Databases (Biomedical Literature Database, National Knowledge Infrastructure, Weipu, and WanFang) up to March 2013 for relevant studies (584 retrieved, 16 met inclusion criteria). We conducted six comparisons for both response and remission rates for three genotypes in Caucasians and Asians (4 weeks or ≥6 weeks; selective serotonin reuptake inhibitors [SSRIs], serotonin-noradrenaline reuptake inhibitors, or mixed antidepressants).

RESULTS

Met carriers had a better response rate than Val/Val. In Asians, the Met carrier was positively associated with response rate (odds ratio; 95% confidence interval: 1.48; 1.02-2.14) in the SSRI group (1.81; 1.10-2.97) and with treatments ≥6 weeks. Met/Val showed a positive association with the response rate versus homozygotes (1.60; 1.20-2.13) and for ≥6 weeks (mixed antidepressant, 1.36; 1.04-1.77; SSRI, 1.55; 1.11-2.17). There was a weak effect of Met/Val versus Val/Val in response to SSRIs (mixed time, 2.07; 1.48-2.89; ≥6 weeks, 2.25; 1.53-3.32). For remission, Met/Val was better than the homozygotes (1.71; 1.09-2.68, Asians, SSRIs only).

DISCUSSION

Our meta-analysis confirms the effects of the BDNF polymorphism on SSRI response in Asians. This effect may be dependent on ethnic origin because BDNF had a lesser influence on response in mixed race studies. Antidepressants were more effective in groups with a treatment duration ≥6 weeks. Thus, future investigators should carefully consider their outcome observation end point.

Serum BDNF concentrations as peripheral manifestations of depression: evidence from a systematic review and meta-analyses on 179 associations (N=9484)

Meta-analyses, published in 2008-2010, have confirmed abnormally low serum brain-derived neurotrophic factor (BDNF) concentrations in depressed patients and normalization of this by antidepressant treatment. These findings are believed to reflect peripheral manifestations of the neurotrophin hypothesis, which states that depression is secondary to an altered expression of BDNF in the brain. Since the publication of these meta-analyses, the field has seen a huge increase in studies on these topics. This motivated us to update the evidence on the aforementioned associations and, in addition, to compile the data on serum BDNF concentrations in relation to the symptom severity of depression. Using a manifold of data as compared with earlier meta-analyses, we find low serum BDNF concentrations in 2384 antidepressant-free depressed patients relative to 2982 healthy controls and to 1249 antidepressant-treated depressed patients (Cohen's d=-0.71 and -0.56, P-values <0.0000001). When publication bias is accounted for, these effect-sizes become substantially smaller (d=-0.47 and -0.34, respectively, P-values<0.0001). We detect between-study heterogeneity in outcomes for which only year of publication and sample size are significant moderators, with more recent papers and larger samples sizes in general being associated with smaller between-group differences. Finally, the aggregated data negate consistent associations between serum BDNF concentrations and the symptom severity of depression. Our findings corroborate the claim that altered serum BDNF concentrations are peripheral manifestations of depression. However, here we highlight that the evidence for this claim is slimmer as was initially thought and amidst a lot of noise.

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.

Serum proBDNF/BDNF and response to fluvoxamine in drug-naïve first-episode major depressive disorder patients

BACKGROUND

We investigated the association between serum proBDNF, a precursor of brain-derived neurotrophic factor (BDNF), and response to fluvoxamine in patients with major depressive disorder (MDD) using the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR): physically healthy and free of current alcohol or drug abuse, comorbid anxiety, or personality disorders.

METHODS

Fifty-one patients with MDD (M/F, 19:32; age, 38 ± 19 years) and 51 healthy controls (M/F, 22:29; age, 34 ± 17 years) were studied using DSM-IV-TR: physically healthy and free of current alcohol or drug abuse, comorbid anxiety, or personality disorders. Serum levels of proBDNF and MDNF were measured by sandwich enzyme-linked immunosorbent assay (ELISA).

RESULTS

Serum mature BDNF levels in the MDD patients were significantly lower than those in the healthy controls (t = 3.046, p = 0.0018). On the other hand, no difference was found in serum proBDNF between the MDD patients and the healthy controls (t = -0.979, p = 0.833). A trend of negative correlation was found between baseline serum BDNF and baseline scores of the 17 items of the Hamilton Rating Scale for Depression (HAMD17) (r = -0.183, p = 0.071). No correlation was however found between HAMD17 scores and proBDNF at baseline (r = 0.092, p = 0.421). Furthermore, no correlation was observed between baseline HAMD17 scores and baseline proBDNF/BDNF (r = -0.130, p = 0.190). No changes were observed in serum levels of proBDNF and BDNF during the treatment periods.

CONCLUSIONS

These results suggest that there is no association between serum proBDNF/BDNF and fluvoxamine response in MDD patients at least within 4 weeks of the treatment.

Genetics of serum BDNF: meta-analysis of the Val66Met and genome-wide association study

OBJECTIVES

Lower levels of serum brain derived neurotrophic factor (BDNF) is one of the best known biomarkers of depression. To identify genetic variants associated with serum BDNF, we tested the Val66Met (rs6265) functional variant and conducted a genome-wide association scan (GWAS).

METHODS

In a community-based sample (N = 2054; aged 19-101, M = 51, SD = 15) from Sardinia, Italy, we measured serum BDNF concentration and conducted a GWAS.

RESULTS

We estimated the heritability of serum BDNF to be 0.48 from sib-pairs. There was no association between serum BDNF and Val66Met in the SardiNIA sample and in a meta-analysis of published studies (k = 13 studies, total n = 4727, P = 0.92). Although no genome-wide significant associations were identified, some evidence of association was found in the BDNF gene (rs11030102, P = 0.001) and at two loci (rs7170215, P = 4.8 × 10⁻⁵ and rs11073742 P = 1.2 × 10⁻⁵) near and within NTRK3 gene, a neurotrophic tyrosine kinase receptor.

CONCLUSIONS

Our study and meta-analysis of the literature indicate that the BDNF Val66Met variant is not associated with serum BDNF, but other variants in the BDNF and NTRK3 genes might regulate the level of serum BDNF.

Are variations in whole blood BDNF level associated with the BDNF Val66Met polymorphism in patients with first episode depression?

Brain derived neurotrophic factor (BDNF) seems to play an important role in the pathophysiology of affective disorders. The current study investigated whether blood level BDNF is correlated with the severity of depressive symptoms and recent (six months prior to onset of depression) experience of stressful life events (SLE) in a cohort of patients with a first depressive episode. 262 patients with first episode depression (females 174, males 88, age range 18-70, mean age 41) participated and control sample of 84 participants was included (females 52, males 32, age range 22-70, mean age 42). Symptomatology was rated using Hamilton Rating Scale for Depression (HAMD-17) and Becks Depression Inventory (BDI 21). No differences in whole blood BDNF was seen in relation to the BDNF Val66Met polymorphism and no significant correlations between whole blood BDNF and HAMD-17 or BDI 21 scores were found. No significant associations between the experiences of SLE before onset of depression and BDNF level were observed. Finally, peripheral BDNF differentiated between patients and healthy control persons. In the current sample of first episode depressed patients, the Val66Met polymorphism was not associated with whole blood BDNF and whole blood BNDF level was not associated with the experience of recent SLE.

BDNF Val 66 Met and 5-HTTLPR genotype moderate the impact of early psychosocial adversity on plasma brain-derived neurotrophic factor and depressive symptoms: a prospective study

Recent studies have emphasized an important role for neurotrophins, such as brain-derived neurotrophic factor (BDNF), in regulating the plasticity of neural circuits involved in the pathophysiology of stress-related diseases. The aim of the present study was to examine the interplay of the BDNF Val⁶⁶Met and the serotonin transporter promoter (5-HTTLPR) polymorphisms in moderating the impact of early-life adversity on BDNF plasma concentration and depressive symptoms. Participants were taken from an epidemiological cohort study following the long-term outcome of early risk factors from birth into young adulthood. In 259 individuals (119 males, 140 females), genotyped for the BDNF Val⁶⁶Met and the 5-HTTLPR polymorphisms, plasma BDNF was assessed at the age of 19 years. In addition, participants completed the Beck Depression Inventory (BDI). Early adversity was determined according to a family adversity index assessed at 3 months of age. Results indicated that individuals homozygous for both the BDNF Val and the 5-HTTLPR L allele showed significantly reduced BDNF levels following exposure to high adversity. In contrast, BDNF levels appeared to be unaffected by early psychosocial adversity in carriers of the BDNF Met or the 5-HTTLPR S allele. While the former group appeared to be most susceptible to depressive symptoms, the impact of early adversity was less pronounced in the latter group. This is the first preliminary evidence indicating that early-life adverse experiences may have lasting sequelae for plasma BDNF levels in humans, highlighting that the susceptibility to this effect is moderated by BDNF Val⁶⁶Met and 5-HTTLPR genotype.

Pharmacogenetics in major depression: a comprehensive meta-analysis

A number of candidate gene studies focused on major depression (MD) and antidepressant (AD) efficacy have been carried out, but results mainly remain inconclusive. We performed a comprehensive meta-analysis of published candidate gene studies focused on AD efficacy in MD to evaluate the cumulative evidence. A random-effect model was applied to study the polymorphisms with genotypic counts available from at least three independent studies. On the base of previous evidence, the analysis was stratified by ethnicity (Caucasian, Asian, and other/mixed), and AD class (SSRIs and mixed/other ADs). Genotypic data were available for 16 polymorphisms in 11 genes. After the exclusion of 5-HTTLPR in SLC6A4 included in another recent meta-analysis, 15 polymorphisms in 11 genes were included in the present meta-analysis (BDNF rs6265, SLC6A4 STin2, HTR1A rs6295, HTR2A rs6311, rs6313 and rs7997012, HTR6 rs1805054, TPH1 rs1800532, SLC6A2 rs5569, COMT rs4680, GNB3 rs5443, FKBP5 rs1360780 and rs3800373, and ABCB1 rs1045642 and rs2032582). Our results suggested that BDNF rs6265 (Val66Met) heterozygous genotype was associated with better SSRIs response compared to the homozygous genotypes, particularly in Asians (OR=1.53, 95%CI 1.12-2.07, p=0.007). SLC6A4 STin2, HTR2A rs6311 and rs7997012, GNB3 rs5443, FKBP5 rs1360780 and rs3800373, and ABCB1 rs2032582 showed associations with AD efficacy, but these results were highly dependent on one or two single studies. In conclusion, our findings suggested the BDNF Val66Met as the best single candidate involved in AD response, with a selective effect on SSRI treatment. Our overall results supported no major effect of any single gene variant on AD efficacy.

MicroRNA-132 may play a role in coexistence of depression and cardiovascular disease: a hypothesis

Different individuals have different degrees of neuroplasticity due to their different experiences. Neuroplasticity may play a role in individual differences among neuropsychiatric disease treatment efficacy. Since the nervous system monitors and coordinates internal organ function, neuroplasticity may be associated with other diseases. Cardiovascular disease (CVD) is associated with depression, which is a disorder of disrupted neuroplasticity. MicroRNA-132 (miR-132) has a roles in neuroplasticity and cardiovascular function. Thus, we hypothesize that miR-132 may play a role in coexistence of depression and CVD.

BDNF Val66Met homozygosity does not influence plasma BDNF levels in healthy human subjects

A putative pathway by which the BDNF Val66Met polymorphism (rs6265) leads to aberrant phenotypes is its influence on plasma BDNF. Research into the impact of rs6265 on plasma BDNF has given rise to conflicting results. Moreover, most such studies have compared Met-carriers with Val-homozygous subjects. We therefore genotyped subjects from a population-based cohort (the Utrecht Health Project, N=2743) and assessed whether plasma BDNF differs between rs6265 homozygous groups. We maximized the number of Met-homozygous subjects in whom we measured plasma BDNF, resulting in plasma BDNF being available for 19 Met-homozygous and 42 matched Val-homozygous subjects. Mean concentrations (S.D.) were 1963.1 (750.1) and 2133.2 pg/ml (1164.3) for the Val/Val and Met/Met groups, respectively. Using ANOVA, no differences in plasma BDNF between the two groups were detected. In conclusion, these results add to a growing body of evidence indicating that allelic variation at rs6265 does not have medium to large effects on plasma BDNF concentrations.

Increased neuroplasticity may protect against cardiovascular disease

Neuroplasticity refers to the capacity of the nervous system to modify its organization such that the brain can be shaped by environmental input. Individuals exhibit different degrees of neuroplasticity because of their different courses of growth. Neuroplasticity may thus play a role in individual differences in the treatment of neuropsychiatric diseases. The nervous system monitors and coordinates internal organ function. Thus neuroplasticity may also be associated with the pathogenesis and the treatment of some other diseases besides neuropsychiatric diseases. The cardiovascular system is controlled by the nervous system, mainly by the autonomic nervous system. Stress may lead to depression and cardiovascular disease (CVD). CVD is associated with depression, which is a disorder of decreased neuroplasticity. And the mechanisms of depression and CVD are related. So we conclude that decreased neuroplasticity causes the coexistence of depression with CVD, and increased neuroplasticity may be beneficial against the development of CVD. This theory provides another angle that can explain some of the reported phenomena related to CVD and neuropsychiatry and provide a potential treatment to protect against CVD.

The Role of Neurotrophins in Major Depressive Disorder

Neurotrophins and other growth factors have been advanced as critical modulators of depressive behavior. Support for this model is based on analyses of knockout and transgenic mouse models, human genetic studies, and screens for gene products that are regulated by depressive behavior and/or antidepressants. Even subtle alteration in the regulated secretion of brain-derived neurotrophic factor (BDNF), for example, due to a single nucleotide polymorphism (SNP)-encoded Val-Met substitution in proBDNF that affects processing and sorting, impacts behavior and cognition. Alterations in growth factor expression result in changes in neurogenesis as well as structural changes in neuronal cytoarchitecture, including effects on dendritic length and spine density, in the hippocampus, nucleus accumbens, and prefrontal cortex. These changes have the potential to impact the plasticity and stability of synapses in the CNS, and the complex brain circuitry that regulates behavior. Here we review the role that neurotrophins play in the modulation of depressive behavior, and the downstream signaling targets they regulate that potentially mediate these behavioral pro-depressant and antidepressant effects.