Brain-derived neurotrophic factor gene polymorphisms, neurotransmitter levels, and depressive symptoms in an elderly population

A Potential Role for MAGI-1 in the Bi-Directional Relationship Between Major Depressive Disorder and Cardiovascular Disease

PURPOSE OF REVIEW

Major Depressive Disorder (MDD) is characterized by persistent symptoms such as fatigue, loss of interest in activities, feelings of sadness and worthlessness. MDD often coexist with cardiovascular disease (CVD), yet the precise link between these conditions remains unclear. This review explores factors underlying the development of MDD and CVD, including genetic, epigenetic, platelet activation, inflammation, hypothalamic-pituitary-adrenal (HPA) axis activation, endothelial cell (EC) dysfunction, and blood-brain barrier (BBB) disruption.

RECENT FINDINGS

Single nucleotide polymorphisms (SNPs) in the membrane-associated guanylate kinase WW and PDZ domain-containing protein 1 (MAGI-1) are associated with neuroticism and psychiatric disorders including MDD. SNPs in MAGI-1 are also linked to chronic inflammatory disorders such as spontaneous glomerulosclerosis, celiac disease, ulcerative colitis, and Crohn's disease. Increased MAGI-1 expression has been observed in colonic epithelial samples from Crohn's disease and ulcerative colitis patients. MAGI-1 also plays a role in regulating EC activation and atherogenesis in mice and is essential for Influenza A virus (IAV) infection, endoplasmic reticulum stress-induced EC apoptosis, and thrombin-induced EC permeability. Despite being understudied in human disease; evidence suggests that MAGI-1 may play a role in linking CVD and MDD. Therefore, further investigation of MAG-1 could be warranted to elucidate its potential involvement in these conditions.

Multi-frequency electromagnetic radiation induces anxiety in mice via inflammation in the cerebral cortex

Modern life is filled with radiofrequency electromagnetic radiation (RF-EMR) in various frequency bands, while the health risks are not clear. In this study, mice were whole-body exposed to 0.9/1.5/2.65 GHz radiofrequency radiation at 4 W/kg for 2 h per day for 4 weeks to investigate the emotional effects. It was found that the mice showed anxiety but no severe depression. The ELISA results showed a significant decrease in amino acid neurotransmitters (GABA, DA, 5-HT), although acetylcholine (ACH) levels were not significantly altered. Furthermore, Western blot results showed that BDNF, TrkB, and CREB levels were increased in the cerebral cortex, while NF-κB levels were decreased. In addition, pro-inflammatory factors (IL-6, IL-1β, TNF-α) were significantly elevated, and anti-inflammatory factors (IL-4, IL-10) tended to decrease. In conclusion, multi-frequency electromagnetic radiation induces an inflammatory response through the CREB-BDNF-TrkB and NF-κB pathways in the cerebral cortex and causes a decrease in excitatory neurotransmitters, which ultimately causes anxiety in mice.

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

BACKGROUND

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

METHODS

A systematic search strategy was developed using PRISMA guidelines.

RESULTS

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

CONCLUSIONS

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

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.

Brain-derived neurotrophic factor rs6265 (Val66Met) single nucleotide polymorphism as a master modifier of human pathophysiology

Brain-derived neurotrophic factor is the most prevalent member of the nerve growth factor family. Since its discovery in 1978, this enigmatic molecule has spawned more than 27,000 publications, most of which are focused on neurological disorders. Brain-derived neurotrophic factor is indispensable during embryogenesis and postnatally for the normal development and function of both the central and peripheral nervous systems. It is becoming increasingly clear, however, that brain-derived neurotrophic factor likewise plays crucial roles in a variety of other biological functions independently of sympathetic or parasympathetic involvement. Brain-derived neurotrophic factor is also increasingly recognized as a sophisticated environmental sensor and master coordinator of whole organismal physiology. To that point, we recently found that a common nonsynonymous (Val66→Met) single nucleotide polymorphism in the brain-derived neurotrophic factor gene (rs6265) not only substantially alters basal cardiac transcriptomics in mice but subtly influences heart gene expression and function differentially in males and females. In addition to a short description of recent results from associative neuropsychiatric studies, this review provides an eclectic assortment of research reports that support a modulatory role for rs6265 including and beyond the central nervous system.

The relationship between job stress and job burnout moderated by BDNF rs6265 polymorphism

RATIONALE

Job stress can lead to job burnout, and BDNF polymorphism has been found to be involved in its psychopathological mechanism. Research needs a better understanding of the important role of gene × environment (i.e., BDNF polymorphism × job stress) interaction on job burnout.

OBJECTIVE

This study aimed to explore how BDNF rs6265 polymorphism may moderate the relationship between job stress and job burnout.

METHODS

Three hundred forty-one healthy participants (187 males and 154 females) from a Chinese university were included. The present study used a standardized questionnaire including demographic characteristics, job stress assessed by the House and Rizzo's Work Stress Scale, and job burnout assessed by the Maslach Burnout Inventory-General Survey. The BDNF rs6265 polymorphism was genotyped.

RESULTS

Job stress showed a positive correlation with emotional exhaustion (p < 0.001), cynicism (p < 0.001), and reduced personal accomplishment (p < 0.01). The main effects of BDNF rs6265 polymorphism on emotional exhaustion and cynicism were significant [F_(1,333) = 5.136, p = 0.024; F_(1,333) = 4.175, p = 0.042, respectively]. The interaction between job stress and BDNF rs6265 on cynicism was significant (△ R² = 0.013, p = 0.014) after controlling for age, sex, education, and position, indicating that individuals with BDNF rs6265 TT genotype showed higher level of cynicism when in high job stress.

CONCLUSIONS

The results provided evidence for the association of BDNF gene rs6265 polymorphism, job stress, and their interaction with job burnout. Individuals with TT genotype in BDNF rs6265 might be susceptible to stressful situations, which would lead to cynicism.

Dysregulation of the SNARE-binding protein Munc18-1 impairs BDNF secretion and synaptic neurotransmission: a novel interventional target to protect the aging brain

Brain-derived neurotrophic factor (BDNF) has a central role in maintaining and strengthening neuronal connections and to stimulate neurogenesis in the adult brain. Decreased levels of BDNF in the aging brain are thought to usher cognitive impairment. BDNF is stored in dense core vesicles and released through exocytosis from the neurites. The exact mechanism for the regulation of BDNF secretion is not well understood. Munc18-1 (STXBP1) was found to be essential for the exocytosis of synaptic vesicles, but its involvement in BDNF secretion is not known. Interestingly, neurons lacking munc18-1 undergo severe degeneration in knock-out mice. Here, we report the effects of BDNF treatment on the presynaptic terminal using munc18-1-deficient neurons. Reduced expression of munc18-1 in heterozygous (+/-) neurons diminishes synaptic transmitter release, as tested here on individual synaptic connections with FM1-43 fluorescence imaging. Transduction of cultured neurons with BDNF markedly increased BDNF secretion in wild-type but was less effective in munc18-1 +/- cells. In turn, BDNF enhanced synaptic functions and restored the severe synaptic dysfunction induced by munc18-1 deficiency. The role of munc18-1 in the synaptic effect of BDNF is highlighted by the finding that BDNF upregulated the expression of munc18-1 in neurons, consistent with enhanced synaptic functions. Accordingly, this is the first evidence showing the functional effect of BDNF in munc18-1 deficient synapses and about the direct role of munc18-1 in the regulation of BDNF secretion. We propose a molecular model of BDNF secretion and discuss its potential as therapeutic target to prevent cognitive decline in the elderly.

The role of neurotrophins in psychopathology and cardiovascular diseases: psychosomatic connections

Cardiovascular (CV) diseases and mood disorders are common public health problems worldwide. Their connections are widely studied, and the role of neurotrophins (NTs) is already supposed in both conditions. However, data in the literature of clinical aspects are sometimes controversial and no reviews are available describing possible associations between CV risk and mood disorders based on NTs. The mostly studied NT is brain-derived neurotrophic factor (BDNF). Decreased level of BDNF is observed in depression and its connection to hypertension has also been demonstrated with affecting the arterial baroreceptors, renin–angiotensin system and endothelial nitric oxide synthase. BDNF was also found to be the predictor of CV outcome in different patient populations. Other types of human NT-s, such as nerve growth factor, neurotrophin 3 and neurotrophin 4 also seem to have both psychopathological and CV connections. Our aim was to overview the present knowledge in this area, demonstrating a new aspect of the associations between mood disorders and CV diseases through the mediation of NTs. These findings might enlighten new psychosomatic connections and suggest new therapeutic targets that are beneficial both in respect of mood disorders and CV pathology.

GSK-3β and BDNF genes may not be associated with venlafaxine treatment response in Chinese of Han ethnicity

PURPOSE

Venlafaxine is one of the commonly prescribed antidepressants for major depressive disorder (MDD). Accumulated evidence revealed the involvement of glutamatergic system in the pathophysiology of MDD and antidepressant treatment.

METHODS

We recruited 193 MDD patients who have been taking venlafaxine for 6 weeks, and investigated whether single nucleotide polymorphisms (SNPs) in GSK-3β and BDNF were associated with treatment response. Nine SNPs were selected randomly depending on association studies. Efficacy of treatment was determined by 17-item Hamilton Rating Scale. Allele and genotype frequencies were compared between responders and nonresponders.

RESULTS

After adjusting the false discovery rate, no significant difference was observed between response and nonresponse groups in allele or genotype distributions after venlafaxine treatment for 6 weeks.

CONCLUSION

Our results indicated that genetic variants in the GSK-3β and BDNF may not be associated with treatment response in MDD patients treated with venlafaxine.

Interaction between job stress and the BDNF Val66Met polymorphism affects depressive symptoms in Chinese healthcare workers

BACKGROUND

Chronic exposure to job-related stress can lead to depression and BDNF polymorphism may play an important role in this process. The role of the stress × BDNF Val66Met interaction in depression has been studied widely using childhood stress, but few studies have utilized chronic stress in adulthood as a moderator. This study was to examine the chronic stress × BDNF Val66Met interaction in job-related depression in the healthcare workers in a Chinese Han population, which has not been reported yet.

METHODS

Using a cross-sectional design, 243 doctors and nurses were recruited from a general hospital in Beijing, and were assessed for depression with Self-rating Depression Scale (SDS), and the stress using the House and Rizzo's Work Stress Scale. The BDNF Val66Met polymorphism was genotyped.

RESULTS

There was a significant positive association between job stress and depressive scores (p < 0.001). No significant main effect of the BDNF Val66Met genotype on depressive symptoms was observed (p > 0.05). A statistically significant interaction between BDNF Val66Met and job stress on depressive symptoms was found (p < 0.05); individuals with Val/Val genotype showed a higher SDS score than Met allele carriers only in the low-stress group, without significant differences in SDS score between the BDNF Val66Met subgroups in medium- or high-stress group.

LIMITATIONS

Limitations include cross-sectional study design, the small sample size only in healthcare workers and only one polymorphism in BDNF gene was analyzed.

CONCLUSIONS

Our results suggest a close relationship between job-related stress and depression, and the interaction of the BDNF Val66Met polymorphism and chronic stress in adulthood may impact the depressive symptoms.

Sperm count and motility are quantitatively affected by functional polymorphisms of HTR2A, MAOA and SLC18A

Spermatozoa and neurones share similar membrane characteristics and features. Associations of multiple polymorphisms traditionally related to neurotransmission were investigated. Infertile men were grouped into controls with normospermia (n = 182) and idiopathic infertile men with asthenozoospermia (n = 103), and analysed as a case-control study and as a quantitative association of each genotype. Ten neurotransmission-associated genetic variants were mapped by SNP analysis using quantitative polymerase chain reaction with TaqMan probes. Men with HTR2A rs6313 had a higher risk of asthenozoospermia (OR = 2.14; P = 0.04). MAOA rs3788862 G carriers displayed an increased risk of asthenozoospermia (OR = 2.29; P = 0.02). The SLC18A1 rs1390938 G allele was more frequent among such cases (0.75 versus 0.87; P < 0.01 and P < 0.01 for Armitage trend test); for SLC18A1 rs2270641 P = 0.02 (case-control frequency) and P = 0.01 (Armitage trend test). MAOA rs3788862 was correlated with sperm motility (Spearman ρ = 0.14; P = 0.02); SLC18A1 rs1390938 was correlated with sperm count and motility (Spearman ρ = 0.20; P < 0.01). Gene polymorphisms of HTR2A, MAOA and SLC18A1, related to neurotransmission, are individually associated with asthenozoospermia through variation in sperm count and motility, without detectable allelic or genotype interaction.

Effects of the BDNF Val66Met Polymorphism on Gray Matter Volume in Typically Developing Children and Adolescents

The Val66Met polymorphism of brain-derived neurotrophic factor (BDNF) is associated with psychiatric disorders and regional gray matter volume (rGMV) in adults. However, the relationship between BDNF and rGMV in children has not been clarified. In this 3-year cross-sectional/longitudinal (2 time points) study, we investigated the effects of BDNF genotypes on rGMV in 185 healthy Japanese children aged 5.7-18.4 using magnetic resonance imaging (MRI) and voxel-based morphometry (VBM) analyses. We found that the volume of the right cuneus in Met homozygotes (Met/Met) was greater than in Val homozygotes (Val/Val) in both exams, and the left insula and left ventromedial prefrontal cortex volumes were greater in Val homozygotes versus Met homozygotes in Exam l. In addition, Met homozygous subjects exhibited higher processing speed in intelligence indices than Val homozygotes and Val/Met heterozygotes at both time points. Longitudinal analysis showed that the left temporoparietal junction volume of Val/Met heterozygotes increased more substantially over the 3-year study period than in Val homozygotes, and age-related changes were observed for the Val/Met genotype. Our findings suggest that the presence of 2 Met alleles may have a positive effect on rGMV at the developmental stages analyzed in this study.

Single nucleotide polymorphisms in the BDNF gene and suicide in the Slovenian sample

In recent years, brain-derived neurotrophic factor (BDNF) and sequence variations within and near the BDNF gene have been studied for associations with various psychiatric disorders, including suicidal behavior. Since our previous work on completed suicide in Slavic population showed an association of the functional single nucleotide polymorphism (SNP) rs6265 in the BDNF gene, we decided to extend the investigation and test additional SNPs in the BDNF gene, rs7124442, rs10767664, rs962369, rs12273363, rs908867, rs1491850, and rs1491851, for association with completed suicide. Our study subjects were Caucasians, and included 486 suicide completers and 289 controls. The case/control comparisons of allele, genotype and haplotype frequency distributions were performed by means of Pearson's X(2) tests. Analyses of allele and genotype frequency distributions of the sudied SNPs did not reveal any significant differences between the controls and suicide completers. Haplotype analysis (rs7124442-rs10767664-rs962369-rs12273363-rs908867) showed an association of the haplotype C-A-T-C-C (p(corr)=0.038) with completed suicide, indicating that these SNPs on a haplotype level may play a role in completed suicide phenotype in our study sample.

Blood BDNF level is gender specific in severe depression

Though the role of brain derived neurotrophic factor (BDNF) as a marker for major depressive disorder (MDD) and antidepressant efficacy has been widely studied, the role of BDNF in distinct groups of patients remains unclear. We evaluated the diagnostic value of BDNF as a marker of disease severity measured by HAM-D scores and antidepressants efficacy among MDD patients. Fifty-one patients who met DSM-IV criteria for MDD and were prescribed antidepressants and 38 controls participated in this study. BDNF in serum was measured at baseline, 1st, 2nd and 8th treatment weeks. Depression severity was evaluated using the Hamilton Rating Scale for Depression (HAM-D). BDNF polymorphism rs6265 (val66met) was genotyped. We found a positive correlation between blood BDNF levels and severity of depression only among untreated women with severe MDD (HAM-D>24). Serum BDNF levels were lower in untreated MDD patients compared to control group. Antidepressants increased serum BDNF levels and reduced between-group differences after two weeks of treatment. No correlations were observed between BDNF polymorphism, depression severity, duration of illness, age and BDNF serum levels. Further supporting the role of BDNF in the pathology and treatment of MDD, we suggest that it should not be used as a universal biomarker for diagnosis of MDD in the general population. However, it has diagnostic value for the assessment of disease progression and treatment efficacy in individual patients.

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.

No influence of brain-derived neurotrophic factor (BDNF) polymorphisms on treatment response in a naturalistic sample of patients with major depression

The role of the brain-derived neurotrophic factor (BDNF) in the pathophysiology of major depressive disorder (MDD) remains to be elucidated. Recent post hoc analyses indicated a potential association of three polymorphisms in the BDNF gene with worse treatment outcome in patients with the subtype of melancholic depression. We aimed at replicating these findings in a German naturalistic multicenter follow-up. Three polymorphisms in the BDNF gene (rs7103411, rs6265 (Val66Met) and rs7124442) were genotyped in 324 patients with MDD and 470 healthy controls. We applied univariate tests and logistic regression models stratifying for depression subtype and gender. The three polymorphisms were not associated with MDD as diagnosis. Further, no associations were found in univariate tests. With logistic regression, we only found a tendency towards an association of the rs6265 (Val66Met) polymorphism with overall response to treatment (response rates: GG (val/val) < GA (val/met) < AA (met/met); p = 0.0129) and some gender differences for the rs6265 (Val66Met) and rs7103411 polymorphisms. Treatment outcome stratified for subtypes of depression did not differ significantly between the investigated polymorphisms or using haplotype analyses. However, results showed a tendency towards significance. At this stage, we cannot support an influence of these three polymorphisms. Further studies in larger patient samples to increase sample sizes of subgroups are warranted.

Brain-derived neurotrophic factor (BDNF) Val66Met and adulthood chronic stress interact to affect depressive symptoms

BACKGROUND

BDNF Val66Met by chronic stress interaction has been studied using childhood stress as a moderator, but has not been widely studied using chronic stress in adulthood.

METHODS

Two independent samples were used: Duke-CG (238 Caucasians) and MESA (5524 Caucasians, African Americans and Hispanics). Chronic stress in Duke-CG was operationalized as having primary caregiving responsibility for a spouse or relative with diagnosed Alzheimer's disease or other major dementia; chronic stress in MESA was defined using chronic burden score constructed from self-reported problems of health (self and someone close), job, finance and relationships. CES-D scale was the measure of depression in both samples. The BDNF Val66Met by adulthood chronic stress interaction predicting CES-D was examined using linear regression, adjusted for covariates.

RESULTS

The main effect of BDNF Val66Met genotype on CES-D scores was non-significant (ps > 0.607) but the adulthood chronic stress indicator was significant (ps < 0.001) in both samples. The BDNF Val66Met genotype by adulthood chronic stress interaction was also significant (ps < 0.039) in both samples. The impact of chronic stress in adulthood on CES-D scores was significantly larger in Val/Val genotype individuals than Met carriers.

CONCLUSION

We found in two independent samples that depression levels increased significantly more as a function of adulthood chronic stress Val/Val genotype carriers than Met carriers. Individuals with the Val/Val genotype and chronic stress exposure could be targeted for interventions designed to reduce risk of depression if this finding is confirmed in future studies.

The brain-derived neurotrophic-factor (BDNF) val66met polymorphism is associated with geriatric depression: a meta-analysis

Depression has been associated with reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. Genetic association studies of the BDNF Val66Met polymorphism (rs6265) in geriatric depression have produced inconsistent results. A meta-analysis of studies was conducted to compare the frequency of the BDNF Val66Met variant between cases with geriatric depression and age-matched controls. A total of five studies involving 523 cases with geriatric depression and 1,220 psychiatrically healthy controls was included. Met allele carriers had an increased risk for geriatric depression when compared to Val/Val homozygotes (P = 0.004, OR = 1.48, 95% CI = 1.13-1.93). Our findings suggest the BDNF Met allele may confer increased risk for depression as individual age.