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

Delayed effects of alcohol consumption on the association between serum BDNF levels and post-traumatic stress disorder development over two-years

BACKGROUNDS

This study aimed to examine the individual and combined effects of serum BDNF (sBDNF) levels and alcohol consumption status, assessed shortly after a physical injury, on the development of post-traumatic stress disorder (PTSD) over two years.

METHODS

Participants were consecutively recruited from a trauma center and followed prospectively for two years. At baseline, sBDNF levels and alcohol consumption history were assessed. A range of socio-demographic and clinical covariates were also collected. PTSD diagnosis during follow-up (3, 6, 12, and 24 months post-injury) was established using the Clinician-Administered PTSD Scale for DSM-5. Binary and multinomial logistic regression analyses were employed to investigate the relationships between sBDNF levels, alcohol consumption status, and PTSD onset.

RESULTS

Out of 923 participants analyzed, 112 (12.1%) developed PTSD at some point during the study, with prevalence rates of 8.8% at 3 months, 7.6% at 6 months, 4.8% at 12 months, and 3.7% at 24 months. The study found no individual associations between sBDNF levels or alcohol consumption status and PTSD development. However, lower sBDNF levels significantly predicted PTSD in individuals who consumed alcohol, a relationship not observed in non-drinkers, with significant interaction terms. This pattern was consistent at later follow-up points from 12 to 24 months, but not at earlier assessments at 3 and 6 months.

LIMITATIONS

The study's reliance on participants from a single trauma center with moderate to severe injuries may limit the generalizability of the findings.

CONCLUSIONS

A significant interaction between sBDNF levels and alcohol consumption in relation to PTSD development was observed, particularly in the long term. These findings highlight the necessity of considering both sBDNF levels and alcohol consumption in strategies aimed at preventing PTSD among individuals with physical injuries, underscoring the need for tailored approaches based on these factors.

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.

The researcher's guide to selecting biomarkers in mental health studies

Clinical mental health researchers may understandably struggle with how to incorporate biological assessments in clinical research. The options are numerous and are described in a vast and complex body of literature. Here we provide guidelines to assist mental health researchers seeking to include biological measures in their studies. Apart from a focus on behavioral outcomes as measured via interviews or questionnaires, we advocate for a focus on biological pathways in clinical trials and epidemiological studies that may help clarify pathophysiology and mechanisms of action, delineate biological subgroups of participants, mediate treatment effects, and inform personalized treatment strategies. With this paper we aim to bridge the gap between clinical and biological mental health research by (1) discussing the clinical relevance, measurement reliability, and feasibility of relevant peripheral biomarkers; (2) addressing five types of biological tissues, namely blood, saliva, urine, stool and hair; and (3) providing information on how to control sources of measurement variability.

Antidepressant effect of PT-31, an α₂-adrenoceptor agonist, on lipopolysaccharide-induced depressive-like behavior in mice

Increasing evidence indicates that neuroinflammation, oxidative stress, and neurotrophic factors play a key role in the pathophysiology of major depressive disorder (MDD). In addition, the attenuation of inflammatory response has been considered a putative mechanism for MDD treatment. PT-31 is an imidazolidine derivative and a putative α₂-adrenoceptor agonist that has previously demonstrated antinociceptive activity. The present study aimed to investigate the effect of PT-31 on depressive-like behavior and lipopolysaccharide-induced neurochemical changes. To this end, mice received intraperitoneally saline or lipopolysaccharide (600 µg/kg), and 5 h postinjection animals were orally treated with saline, PT-31 (3, 10, and 30 mg/kg), or fluoxetine (30 mg/kg). Mice were subjected to the open field test (OFT) 6 and 24 h after lipopolysaccharide administration and to the tail suspension test (TST) 24 h postlipopolysaccharide. Subsequently, animals were euthanized, and brains were dissected for neurochemical analyses. The administration of lipopolysaccharide-induced sickness- and depressive-like behaviors, besides promoting an increase in myeloperoxidase activity and a reduction in brain-derived neurotrophic factor (BDNF) levels. Noteworthy, PT-31 3 mg/kg attenuated lipopolysaccharide-induced decreased locomotor activity 6 h after lipopolysaccharide in the OFT. All tested doses of PT-31 significantly reduced the immobility time of animals in the TST and attenuated lipopolysaccharide-induced increased myeloperoxidase activity in the cortex of mice. Our results demonstrate that PT-31 ameliorates behavioral changes promoted by lipopolysaccharide in OFT and TST, which is possibly mediated by attenuation of the inflammatory response.

The relationship between BDNF and physical activity on depression

BACKGROUND/OBJECTIVE

Major depressive disorder (MDD) is one of the leading causes of disease burden and disability worldwide. Brain-derived neurotrophic factor (BDNF) seems to have an important role in the molecular mechanisms underlying MDD aetiology, given its implication in regulating neuronal plasticity. There is evidence that physical activity (PA) improves depressive symptoms, with a key role of BDNF in this effect. We aim to perform a systematic review examining the relationship between the BDNF Val66Met polymorphism and the BDNF protein, PA and MDD.

METHODS

Both observational and experimental design original articles or systematic reviews were selected, according to the PRISMA statement.

RESULTS

Six studies evaluated the Val66Met polymorphism, suggesting a greater impact of physical activity on depression depending on the Val66Met genotype. More discordant findings were observed among the 13 studies assessing BDNF levels with acute or chronic exercise interventions, mainly due to the high heterogeneity found among intervention designs, limited sample size, and potential bias.

CONCLUSIONS

Overall, there is cumulative evidence supporting the potential role of BDNF in the interaction between PA and MDD. However, this review highlights the need for further research with more homogeneous and standardised criteria, and pinpoints important confounding factors that must be considered in future studies to provide robust conclusions.

Association between reduced plasma BDNF concentration and MMSE scores in both chronic schizophrenia and mild cognitive impairment

Reduced brain derived neurotrophic factor (BDNF) concentration is reported to be associated with a cognitive decline in schizophrenia, depending on the stage of the disease. Aim of the study was to examine the possible association between plasma BDNF and cognitive decline in chronic stable schizophrenia and mild cognitive impairment (MCI). The study included 123 inpatients of both sexes with schizophrenia, 123 patients with MCI and 208 healthy control subjects. Cognitive abilities were assessed using mini mental state examination (MMSE), Clock Drawing test (CDT) and cognitive subscale of the Positive and Negative Syndrome Scale (PANSS). Plasma BDNF concentration was determined using ELISA. BDNF concentration was lower in patients with schizophrenia and MCI compared to age-matched healthy controls and was similar in carriers of different BDNF Val/66Met genotypes. The MMSE and CDT scores were lower in patients with schizophrenia compared to healthy controls and subjects with MCI. Reduced plasma BDNF was significantly associated with lower MMSE scores in all subjects. BDNF concentration in patients with schizophrenia was not affected by clinical and demographic factors. BDNF Val66Met polymorphism was not associated with the MMSE scores in all participants. Further studies should include longitudinal follow-up and other cognitive scales to confirm these results and offer cognition-improving strategies to prevent cognitive decline in chronic schizophrenia.

Investigation of the relationship between neuroplasticity and grapheme-color synesthesia

Grapheme-color synesthesia is a normal and healthy variation of human perception. It is characterized by the association of letters or numbers with color perceptions. The etiology of synesthesia is not yet fully understood. Theories include hyperconnectivity in the brain, cross-activation of adjacent or functionally proximate sensory areas of the brain, or various models of lack of inhibitory function in the brain. The growth factor brain-derived neurotrophic (BDNF) plays an important role in the development of neurons, neuronal pathways, and synapses, as well as in the protection of existing neurons in both the central and peripheral nervous systems. ELISA methods were used to compare BDNF serum concentrations between healthy test subjects with and without grapheme-color synesthesia to establish a connection between concentration and the occurrence of synesthesia. The results showed that grapheme-color synesthetes had an increased BDNF serum level compared to the matched control group. Increased levels of BDNF can enhance the brain's ability to adapt to changing environmental conditions, injuries, or experiences, resulting in positive effects. It is discussed whether the integration of sensory information is associated with or results from increased neuroplasticity. The parallels between neurodegeneration and brain regeneration lead to the conclusion that synesthesia, in the sense of an advanced state of consciousness, is in some cases a more differentiated development of the brain rather than a relic of early childhood.

BDNF, proBDNF and proBDNF/BDNF ratio with electroencephalographic abnormalities in children with attention deficit hyperactivity disorder: Possible relations to cognition and severity

Attention deficit hyperactivity disorder (ADHD) with and without subclinical epileptogenic discharges (SED) have been suggested to negatively affect cognitive abilities of children with ADHD. The role of brain-derived neurotrophic factor (BDNF) and its precursor proBDNF in ADHD is in need of being investigated. The aims were to evaluate the levels of serum BDNF, proBDNF and the proBDNF/BDNF ratio in addition to the potential impacts of SED on the children's cognitive abilities and the severity of ADHD. The included participants with ADHD were 30 children with normal electroencephalogram (EEG) (G1) and 30 children with SED (G2), together with 30 healthy children (G3). The cognitive abilities and severity of the disorder were evaluated. The biochemical measures were determined by ELISA. The presence of coexisting SED and nocturnal enuresis has led to a deleterious effect on cognitive processes but not on the severity. The focal epileptogenic discharge was the most common among children in G2. The levels of BDNF in Groups 1 and 2 were less than those in G3. The higher proBDNF/BDNF ratio could be related to the low BDNF levels rather than high proBDNF levels. The findings of this study highlight the importance of investigating the presence of SED and nocturnal enuresis in children with ADHD. Targeting strengthening of cognitive abilities in children with coexisting ADHD and SED is advised. The role of proBDNF in the pathophysiology of ADHD needs further investigation.

The association between levels of brain-derived neurotrophic factor and comorbid depression in patients with cardiovascular disease: The Framingham Heart Study

AIM

The current study aims to investigate the association of serum brain-derived neurotrophic factor (BDNF) levels with symptoms of depression in adults with and without prevalent cardiovascular disease (CVD), an often burdensome comorbidity.

METHODS

This cross-sectional study included participants from FHS (Framingham Heart Study) who had available serum BDNF levels. Depressive symptoms were assessed using the Center for Epidemiological Studies-Depression Scale (CES-D) with a score ≥16 indicating mild to moderate and ≥21 severe depression. Participants taking antidepressant medications were excluded from the study.

RESULTS

Altogether 3716 FHS participants were included in the final analysis (mean age, 64.3 ± 11.5 years; 55% women). After adjusting for potential confounders, greater BDNF levels were associated with reduced severe depression risk (odds ratio [OR], 0.78 [95% CI, 0.64-0.96]; P = 0.016). Among participants with CVD, greater BDNF levels were related to lower risk of depressive symptoms (CES-D ≥ 16 OR, 0.63 [95% CI, 0.45-0.89], P = 0.008; CES-D ≥ 21 OR, 0.49 [95% CI, 0.31-0.76], P = 0.002). The inverse relationship between BDNF and depressive symptom risk was present in women with CVD (CES-D ≥ 16 OR, 0.63 [95% CI, 0.40-0.99], P = 0.047; CES-D ≥ 21 OR, 0.38 [95% CI, 0.21-0.70], P = 0.002) but not in men.

CONCLUSION

Lower serum BDNF levels are associated with a higher risk of depressive symptoms in CVD, particularly among women. These findings implicate BDNF in the complex biological mechanisms that underlie prior associations observed between CVD and depression. To reduce the burden of depression in the large proportion of midlife and older adults with CVD, a better understanding of how BDNF may modify these pathways is merited.

Levels of brain-derived neurotrophic factor (BDNF) among patients with COVID-19: a systematic review and meta-analysis

Many individuals have been suffering from consistent neurological and neuropsychiatric manifestations even after the remission of coronavirus disease (COVID-19). Brain-derived neurotrophic factor (BDNF) is a protein involved in the regulation of several processes, including neuroplasticity, neurogenesis, and neuronal differentiation, and has been linked to a range of neurological and psychiatric disorders. In this study, we aimed to synthesize the available evidence on the profile of BDNF in COVID-19. A comprehensive search was done in the Web of Science core collection, Scopus, and MEDLINE (PubMed), and Embase to identify relevant studies reporting the level of BDNF in patients with COVID-19 or those suffering from long COVID. We used the NEWCASTLE-OTTAWA tool for quality assessment. We pooled the effect sizes of individual studies using the random effect model for our meta-analysis. Fifteen articles were included in the systematic review. The sample sizes ranged from 16 to 183 participants. Six studies compared the level of BDNF in COVID-19 patients with healthy controls. The pooled estimate of the standardized mean difference in BDNF level between patients with COVID-19 and healthy individuals was - 0.84 (95% CI - 1.49 to - 0.18, p = 0.01, I2 = 81%) indicating a significantly lower BDNF level in patients with COVID-19. Seven studies assessed BDNF in different severity statuses of patients with COVID-19. The pooled estimate of the standardized mean difference in BDNF level was - 0.53 (95% CI - 0.85 to - 0.21, p = 0.001, I2 = 46%), indicating a significantly lower BDNF level in patients with more severe COVID-19. Three studies evaluated BDNF levels in COVID-19 patients through different follow-up periods. Only one study assessed the BDNF levels in long COVID patients. Sensitivity analyses did not alter the significance of the association. In this study, we showed a significant dysregulation of BDNF following COVID-19 infection. These findings may support the pathogenesis behind the long-lasting effects of this disease among infected patients. PROSPERO: CRD42023413536.

Acute Effects of High-Intensity Resistance Exercise on Recognition of Relational Memory, Lactate, and Serum and Plasma Brain-Derived Neurotrophic Factor

ABSTRACT

Baumgartner, NW, Belbis, MD, Kargl, C, Holmes, MJ, Gavin, TP, Hirai, DM, and Kao, S-C. Acute effects of high-intensity resistance exercise on recognition of relational memory, lactate, and serum and plasma brain-derived neurotrophic factor. J Strength Cond Res XX(X): 000-000, 2024-Acute aerobic exercise improves memory, but this phenomenon is understudied in response to resistance exercise (RE) despite evidence that RE-induced increases in lactate and brain-derived neurotrophic factor (BDNF) play mechanistic roles in memory performance. To determine the acute effect of RE on lactate, BDNF, and their associations with object and relational memory, blood lactate, and serum and plasma BDNF were taken from 36 adults (average age 23.64 ± 3.89 years; 18 woman) before and immediately after 42 minutes of high-intensity RE and a rest condition on counterbalanced days. Subjects then immediately studied a series of paired objects and completed object and relational recognition tasks. Results revealed a condition by trial interaction, previously studied objects were remembered less accurately following RE (d = 0.66) but recognition occurred faster (d = 0.28), indicating a speed-accuracy tradeoff following RE. There was no effect of either intervention on relational recognition performance. Lactate (d = 3.68) and serum BDNF (d = 0.74) increased following RE, whereas there was no time-related change in lactate and serum BDNF following rest. However, changes in lactate and BDNF did not predict any measures of object (rs < 0.25, ps > 0.16) or relation recognition (rs < 0.28, ps > 0.13). Collectively, these findings suggest that acute high-intensity RE selectively improves the processing speed of recognizing objects at the cost of less accurate recognition of previously studied objects. Furthermore, changes in object and relational memory performance are unlikely driven by acute increases in lactate or BDNF following high-intensity RE.

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.

Relationship Between Serum Brain-Derived Neurotrophic Factor and Neurotrophin-3 Levels and Hearing Thresholds in Patients With Age-Related Hearing Loss

BACKGROUND

Age-related hearing loss (ARHL) is a general term used to describe the sensorineural type of hearing loss occurring in both ears in older adults. Neurotrophins are the most promising candidates for supporting the auditory nerve by increasing neuronal survival. This study aimed to help elucidate the pathophysiology of ARHL by determining whether any relationship exists between brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) levels in serum samples from patients diagnosed with ARHL.

MATERIALS AND METHOD

Seventy-seven individuals, a study group of 41 patients diagnosed with ARHL, and a control group of 36 participants without hearing loss were evaluated. Serum samples were collected and used to measure serum BDNF and NT-3 levels with the new Nepenthe enzyme-linked immunosorbent assay method.

RESULTS

Median pure-tone average results in the 2000, 4000, and 6000 Hz ranges were 52.5 (44.3-67.3) dB HL in the ARHL group and 13.5 (11.1-17.1) dB HL in the control group. The difference was statistically significant (p = .001). Although NT-3 and BDNF levels were both lower in ARHL patients than in participants without hearing loss, only the BDNF levels were significantly (p = .002) lower. Mean left and right ear word recognition scores were also lower in ARHL patients than in control groups. The ARHL group was further divided into two subgroups based on word recognition scores to evaluate significant differences in BDNF and NT-3 levels. No statistically significant difference was observed in BDNF and NT-3 levels between these subgroups. However, there was a significant difference in word recognition scores.

CONCLUSIONS

Low BDNF levels in the ARHL group suggest that BDNF may play a role in the pathogenesis of ARHL. Patients with low (ARHL1) and high (ARHL2) word recognition scores were compared for the first time in the literature in terms of BDNF and NT-3 levels. However, the results were not statistically significant. This article is a preliminary study and was written to provide guidance for our next comprehensive project.

Distinct roles of Bdnf I and Bdnf IV transcript variant expression in hippocampal neurons

Brain-derived neurotrophic factor (Bdnf) plays a critical role in brain development, dendritic growth, synaptic plasticity, as well as learning and memory. The rodent Bdnf gene contains nine 5' non-coding exons (I-IXa), which are spliced to a common 3' coding exon (IX). Transcription of individual Bdnf variants, which all encode the same BDNF protein, is initiated at unique promoters upstream of each non-coding exon, enabling precise spatiotemporal and activity-dependent regulation of Bdnf expression. Although prior evidence suggests that Bdnf transcripts containing exon I (Bdnf I) or exon IV (Bdnf IV) are uniquely regulated by neuronal activity, the functional significance of different Bdnf transcript variants remains unclear. To investigate functional roles of activity-dependent Bdnf I and IV transcripts, we used a CRISPR activation system in which catalytically dead Cas9 fused to a transcriptional activator (VPR) is targeted to individual Bdnf promoters with single guide RNAs, resulting in transcript-specific Bdnf upregulation. Bdnf I upregulation is associated with gene expression changes linked to dendritic growth, while Bdnf IV upregulation is associated with genes that regulate protein catabolism. Upregulation of Bdnf I, but not Bdnf IV, increased mushroom spine density, volume, length, and head diameter, and also produced more complex dendritic arbors in cultured rat hippocampal neurons. In contrast, upregulation of Bdnf IV, but not Bdnf I, in the rat hippocampus attenuated contextual fear expression. Our data suggest that while Bdnf I and IV are both activity-dependent, BDNF produced from these promoters may serve unique cellular, synaptic, and behavioral functions.

Brain-Derived Neurotrophic Factor, Nociception, and Pain

This article examines the involvement of the brain-derived neurotrophic factor (BDNF) in the control of nociception and pain. BDNF, a neurotrophin known for its essential role in neuronal survival and plasticity, has garnered significant attention for its potential implications as a modulator of synaptic transmission. This comprehensive review aims to provide insights into the multifaceted interactions between BDNF and pain pathways, encompassing both physiological and pathological pain conditions. I delve into the molecular mechanisms underlying BDNF's involvement in pain processing and discuss potential therapeutic applications of BDNF and its mimetics in managing pain. Furthermore, I highlight recent advancements and challenges in translating BDNF-related research into clinical practice.

Serum BDNF Levels Among Patients with Alcohol Dependence, Depression and Alcohol Dependence with Comorbid Depression - A Comparative Study

The study aimed to assess and compare the serum brain derived neurotrophic factor (BDNF) levels in patients with alcohol dependence, depression and alcohol dependence with comorbid depression. Three groups each of 30 alcohol-dependent, depressive and alcohol-dependent with comorbid depressive patients seeking treatment were included. BDNF levels were estimated, and scales were administered to assess severity of alcohol dependence (using severity of alcohol dependence questionnaire, SADQ) and depressive symptoms (using Hamilton depression rating scale, HDRS). The mean BDNF value in ADS, depression and ADS with comorbid depression group was 16.4 ng/mL, 14.4 ng/mL and 12.29 ng/mL respectively, and the differences were statistically significant. In ADS group and ADS with comorbid depression groups significant negative association existed between BDNF and SADQ scores (r = -0.371, p = .043 and r = -0.0474, p = .008 respectively). There were significant negative association between BDNF and HDRS scores in depression and comorbid ADS and depression group (r = -0.400, p = .029 and r = -0.408, p = .025 respectively). The BDNF level was significantly lower in the ADS with comorbid depression group and was associated with severity of dependence and depression across the groups.

Plasma and Platelet Brain-Derived Neurotrophic Factor (BDNF) Levels in Bipolar Disorder Patients with Post-Traumatic Stress Disorder (PTSD) or in a Major Depressive Episode Compared to Healthy Controls

Post-traumatic stress disorder (PTSD) is a highly disabling mental disorder arising after traumatism exposure, often revealing critical and complex courses when comorbidity with bipolar disorder (BD) occurs. To search for PTSD or depression biomarkers that would help clinicians define BD presentations, this study aimed at preliminarily evaluating circulating brain-derived-neurotrophic factor (BDNF) levels in BD subjects with PTSD or experiencing a major depressive episode versus controls. Two bloodstream BDNF components were specifically investigated, the storage (intraplatelet) and the released (plasma) ones, both as adaptogenic/repair signals during neuroendocrine stress response dynamics. Bipolar patients with PTSD (n = 20) or in a major depressive episode (n = 20) were rigorously recruited together with unrelated healthy controls (n = 24) and subsequently examined by psychiatric questionnaires and blood samplings. Platelet-poor plasma (PPP) and intraplatelet (PLT) BDNF were measured by ELISA assays. The results showed markedly higher intraplatelet vs. plasma BDNF, confirming platelets' role in neurotrophin transport/storage. No between-group PPP-BDNF difference was reported, whereas PLT-BDNF was significantly reduced in depressed BD patients. PLT-BDNF negatively correlated with mood scores but not with PTSD items like PPP-BDNF, which instead displayed opposite correlation trends with depression and manic severity. Present findings highlight PLT-BDNF as more reliable at detecting depression than PTSD in BD, encouraging further study into BDNF variability contextually with immune-inflammatory parameters in wider cohorts of differentially symptomatic bipolar patients.

Baseline serum brain-derived neurotrophic factor association with future cognition in community-dwelling older adults undergoing annual memory screening

OBJECTIVES

It has been shown that peripheral measures of brain-derived neurotrophic factor (BNDF), an important neurotrophin instrumental to the biology of learning, may contribute to predicting cognitive decline. However, the two primary forms of BDNF, mature (mBDNF) and pro (proBDNF), and how they contribute to cognition longitudinally has not been well studied.

METHODS

Eighty-two older adults (average age 72.2 ± 6.4 years) provided blood samples at two time points separated on average by 4.2 years while participating in an annual memory screening that included the MoCA (Montreal Cognitive Assessment) and GDS (Geriatric Depression Scale). Both mBDNF and proBDNF from serum were quantified at each time point. Whole blood samples were genotyped for APOE and BDNF Val66Met.

RESULTS

Using logistic regression analysis controlling for age, sex, baseline MoCA score, APOE, and BDNF, higher baseline mBDNF was associated with subjects whose screening score was near maximum or maximum (as defined by MoCA score of 29 or 30) at the second collection visit. APOE was a significant contributing factor; however, BDNF Val66Met was not. Using a similar logistic regression analysis, baseline proBDNF was not found to be associated with future cognition.

DISCUSSION

This study further supports that mBDNF measured in the serum of older adults may reflect a protective role while proBDNF requires further investigation.

Formulated Palmitoylethanolamide Supplementation Improves Parameters of Cognitive Function and BDNF Levels in Young, Healthy Adults: A Randomised Cross-Over Trial

BACKGROUND

Palmitoylethanolamide (PEA) is an endocannabinoid-like lipid mediator which is naturally produced in the body and found in certain foods. The aim of this study was to assess the effect of a bioavailable formulated form of PEA (Levagen+®) on serum BDNF levels and parameters of cognitive function in healthy adults.

METHODS

A randomised double-blinded placebo-controlled cross-over trial was implemented to measure the effects of a 6-week 700 mg/day course of formulated PEA supplementation versus a placebo. Participants (n = 39) completed pre- and post-assessments of a lab-based cognitive test. Serum samples were collected to measure BDNF concentrations using an immunoassay.

RESULTS

A significant increase in serum BDNF levels was found following PEA supplementation compared with the placebo (p = 0. 0057, d = 0.62). The cognition test battery demonstrated improved memory with PEA supplementation through better first success (p = 0.142, d = 0.54) and fewer errors (p = 0.0287; d = -0.47) on the Paired Associates Learning test.

CONCLUSION

This was the first study to report a direct beneficial effect of Levagen+® PEA supplementation on memory improvement as well as corresponding increases in circulating neurotrophic marker levels. This suggests that formulated PEA holds promise as an innovative and practical intervention for cognitive health enhancement.

Isolation and Identification of the High-Affinity DNA Aptamer Target to the Brain-Derived Neurotrophic Factor (BDNF)

Aptamers are functional oligonucleotide ligands used for the molecular recognition of various targets. The natural characteristics of aptamers make them an excellent alternative to antibodies in diagnostics, therapeutics, and biosensing. DNA aptamers are mainly single-stranded oligonucleotides (ssDNA) that possess a definite binding to targets. However, the application of aptamers to the fields of brain health and neurodegenerative diseases has been limited to date. Herein, a DNA aptamer against the brain-derived neurotrophic factor (BDNF) protein was obtained by in vitro selection. BDNF is a potential biomarker of brain health and neurodegenerative diseases and has functions in the synaptic plasticity and survival of neurons. We identified eight aptamers that have binding affinity for BDNF from a 50-nucleotide library. Among these aptamers, NV_B12 showed the highest sensitivity and selectivity for detecting BDNF. In an aptamer-linked immobilized sorbent assay (ALISA), the NV_B12 aptamer strongly bound to BDNF protein, in a dose-dependent manner. The dissociation constant (Kd) for NV_B12 was 0.5 nM (95% CI: 0.4-0.6 nM). These findings suggest that BDNF-specific aptamers could be used as an alternative to antibodies in diagnostic and detection assays for BDNF.

Prediction and Validation of Hub Genes Related to Major Depressive Disorder Based on Co-expression Network Analysis

Major depressive disorder (MDD) is generally among the most prevalent psychiatric illnesses. Significant advances have occurred in comprehension of the MDD biology. However, it is still essential to recognize new biomarkers for potential targeted treatment of patients with MDD. The present work deals with in-depth comparative computational analyses to obtain new insights, such as gene ontology and pathway enrichment analyses and weighted gene co-expression network analysis (WGCNA) through gene expression dataset. The expression of selected hub-genes was validated in MDD patients using quantitative real-time PCR (RT-qPCR). We found that MDD progression includes the turquoise module genes (p-value = 1e-18, r = 0.97). According to gene enrichment analysis, the cytokine-mediated signaling pathway mostly involves genes in this module. By selection of four candidate hub-genes (IL6, NRG1, TNF, and BDNF), RT-qPCR validation was performed. A significant NRG1 downregulation was revealed by the RT-qPCR outcomes in MDD. In MDD patients, TNF and IL6 expression were considerably higher, and no considerable differences were found in the BDNF expression. Ultimately, based on ROC analyses, IL6, NRG1, and TNF had a higher MDD diagnostic performance. Therefore, our study presents information on the intricate association between MDD development and cytokine-mediated signaling, thus providing new rationales to develop new therapeutic approaches.

Neural Correlates of Balance Skill Learning in Young and Older Individuals: A Systematic Review and Meta-analysis

BACKGROUND

Despite the increasing number of research studies examining the effects of age on the control of posture, the number of annual fall-related injuries and deaths continues to increase. A better understanding of how old age affects the neural mechanisms of postural control and how countermeasures such as balance training could improve the neural control of posture to reduce falls in older individuals is therefore necessary. The aim of this review is to determine the effects of age on the neural correlates of balance skill learning measured during static (standing) and dynamic (walking) balance tasks in healthy individuals.

METHODS

We determined the effects of acute (1-3 sessions) and chronic (> 3 sessions) balance skill training on balance in the trained and in untrained, transfer balance tasks through a systematic review and quantified these effects by robust variance estimation meta-analysis in combination with meta-regression. We systematically searched PubMed, Web of Science, and Cochrane databases. Balance performance and neural plasticity outcomes were extracted and included in the systematic synthesis and meta-analysis.

RESULTS

Forty-two studies (n = 622 young, n = 699 older individuals) were included in the systematic synthesis. Seventeen studies with 508 in-analysis participants were eligible for a meta-analysis. The overall analysis revealed that acute and chronic balance training had a large effect on the neural correlates of balance skill learning in the two age groups combined (g = 0.79, p < 0.01). Both age groups similarly improved balance skill performance in 1-3 training sessions and showed little further improvements with additional sessions. Improvements in balance performance mainly occurred in the trained and less so in the non-trained (i.e., transfer) balance tasks. The systematic synthesis and meta-analysis suggested little correspondence between improved balance skills and changes in spinal, cortical, and corticospinal excitability measures in the two age groups and between the time courses of changes in balance skills and neural correlates.

CONCLUSIONS

Balance skill learning and the accompanying neural adaptations occur rapidly and independently of age with little to no training dose-dependence or correspondence between behavioral and neural adaptations. Of the five types of neural correlates examined, changes in only spinal excitability seemed to differ between age groups. However, age or training dose in terms of duration did not moderate the effects of balance training on the changes in any of the neural correlates. The behavioral and neural mechanisms of strong task-specificity and the time course of skill retention remain unclear and require further studies in young and older individuals.

REGISTRATION

PROSPERO registration number: CRD42022349573.

The Role of the Brain-Derived Neurotrophic Factor in Chronic Pain: Links to Central Sensitization and Neuroinflammation

Chronic pain is sustained, in part, through the intricate process of central sensitization (CS), marked by maladaptive neuroplasticity and neuronal hyperexcitability within central pain pathways. Accumulating evidence suggests that CS is also driven by neuroinflammation in the peripheral and central nervous system. In any chronic disease, the search for perpetuating factors is crucial in identifying therapeutic targets and developing primary preventive strategies. The brain-derived neurotrophic factor (BDNF) emerges as a critical regulator of synaptic plasticity, serving as both a neurotransmitter and neuromodulator. Mounting evidence supports BDNF's pro-nociceptive role, spanning from its pain-sensitizing capacity across multiple levels of nociceptive pathways to its intricate involvement in CS and neuroinflammation. Moreover, consistently elevated BDNF levels are observed in various chronic pain disorders. To comprehensively understand the profound impact of BDNF in chronic pain, we delve into its key characteristics, focusing on its role in underlying molecular mechanisms contributing to chronic pain. Additionally, we also explore the potential utility of BDNF as an objective biomarker for chronic pain. This discussion encompasses emerging therapeutic approaches aimed at modulating BDNF expression, offering insights into addressing the intricate complexities of chronic pain.

The MindMoves Trial: Cross-Sectional Analyses of Baseline Vascular Risk and Cognition in Older Women with Cardiovascular Disease

Background

Vascular diseases, including atherosclerotic cardiovascular disease (ASCVD) and stroke, increase the risk of Alzheimer's disease and cognitive impairment. Serum biomarkers, such as brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and insulin-like growth factor 1 (IGF-1), may be indicators of cognitive health.

Objective

We examined whether vascular risk was associated with levels of cognition and serum biomarkers in older women with cardiovascular disease (CVD).

Methods

Baseline data from a lifestyle trial in older women (n = 253) with CVD (NCT04556305) were analyzed. Vascular risk scores were calculated for ASCVD (ASCVD risk estimator) and stroke (CHA2DS2-VASc) based on published criteria. Cognition-related serum biomarkers included BDNF, VEGF, and IGF-1. Cognition was based on a battery of neuropsychological tests that assessed episodic memory, semantic memory, working memory, and executive function. A series of separate linear regression models were used to evaluate associations of vascular risk scores with outcomes of cognition and serum biomarkers. All models were adjusted for age, education level, and racial and ethnic background.

Results

In separate linear regression models, both ASCVD and CHA2DS2-VASc scores were inversely associated with semantic memory (β= -0.22, p = 0.007 and β= -0.15, p = 0.022, respectively), with no significant findings for the other cognitive domains. There were no significant associations between vascular risk scores and serum biomarkers.

Conclusions

Future studies should prospectively examine associations between vascular risk and cognition in other populations and additionally consider other serum biomarkers that may be related to vascular risk and cognition.

Brain-Heart Axis: Brain-Derived Neurotrophic Factor and Cardiovascular Disease-A Review of Systematic Reviews

BACKGROUND

The brain-heart axis is an intra- and bidirectional complex that links central nervous system dysfunction and cardiac dysfunction. In recent decades, brain-derived neurotrophic factor (BDNF) has emerged as a strategic molecule involved in both brain and cardiovascular disease (CVD). This systematic review of systematic reviews aimed to (1) identify and summarize the evidence for the BDNF genotype and BDNF concentration in CVD risk assessment, (2) evaluate the evidence for the use of BDNF as a biomarker of CVD recovery, and (3) evaluate rehabilitation approaches that can restore BDNF concentration.

METHODS

A comprehensive search strategy was developed using PRISMA. The risk of bias was assessed via ROBIS.

RESULTS

Seven studies were identified, most of which aimed to evaluate the role of BDNF in stroke patients. Only two systematic reviews examined the association of BDNF concentration and polymorphism in CVDs other than stroke.

CONCLUSIONS

The overall evidence showed that BDNF plays a fundamental role in assessing the risk of CVD occurrence, because lower BDNF concentrations and rs6265 polymorphism are often associated with CVD. Nevertheless, much work remains to be carried out in current research to investigate how BDNF is modulated in different cardiovascular diseases and in different populations.

Increased academic stress is associated with decreased plasma BDNF in Chilean college students

Introduction

Academic stress (AS) is a prevalent challenge faced by university students, potentially affecting molecular indicators such as brain-derived neurotrophic factor (BDNF) and global DNA methylation (G-DNA-M). These indicators could illuminate the physiological ramifications of academic stress.

Study Design and Methods

This research followed a quantitative, non-experimental, longitudinal panel design spanning two academic semesters, observing phenomena in their natural context. Students from the Medical Technology program at Universidad de Concepción, Chile were involved, with assessments at the beginning and during heightened academic stress periods.

Sample

Of the total participants, 63.0% were females, with an average age of 21.14 years at baseline, and 36.92% were males, averaging 21.36 years. By the study's conclusion, female participants averaged 21.95 years, and males 22.13 years.

Results

Significant differences were observed between initial and final assessments for the SISCO-II Inventory of Academic Stress and Beck Depression Inventory-II, notably in stressor scores, and physical, and psychological reactions. Gender differences emerged in the final physical and psychological reactions. No significant changes were detected between the two assessments in plasma BDNF or G-DNA-M values. A refined predictive model showcased that, on average, there was a 3.56% decrease in females' plasma BDNF at the final assessment and a 17.14% decrease in males. In the sample, the G-DNA-M percentage at the final assessment increased by 15.06% from the baseline for females and 18.96% for males.

Conclusions

The study underscores the physiological impact of academic stress on university students, evidenced by changes in markers like BDNF and G-DNA-M. These findings offer an in-depth understanding of the intricate mechanisms regulating academic stress responses and highlight the need for interventions tailored to mitigate its physiological and psychological effects.

Effect of alcohol on Brain-Derived Neurotrophic Factor (BDNF) blood levels: a systematic review and meta-analysis

Brain-Derived Neurotrophic Factor (BDNF) is a vital protein involved in neuronal development, survival, and plasticity. Alcohol consumption has been implicated in various neurocognitive deficits and neurodegenerative disorders. However, the impact of alcohol on BDNF blood levels remains unclear. This systematic review and meta-analysis aimed to investigate the effect of alcohol consumption on BDNF blood levels. A comprehensive search of electronic databases was conducted to identify relevant studies. Eligible studies were selected based on predefined inclusion criteria. Data extraction was performed, and methodological quality was assessed using appropriate tools. A meta-analysis was conducted to estimate the overall effect size of alcohol consumption on BDNF levels. A total of 25 studies met the inclusion criteria and were included in the final analysis. Alcohol use and BDNF blood levels were significantly correlated, according to the meta-analysis (p = 0.008). Overall, it was discovered that drinking alcohol significantly decreased BDNF levels (SMD: - 0.39; 95% CI: - 0.68 to - 0.10; I2: 93%). There was a non-significant trend suggesting that alcohol withdrawal might increase BDNF levels, with an SMD of 0.26 (95% CI: - 0.09 to 0.62; I2: 86%; p = 0.14). Subgroup analysis based on the source of BDNF demonstrated significant differences between the subgroups (p = 0.0008). No significant publication bias was observed. This study showed that alcohol consumption is associated with a significant decrease in BDNF blood levels. The findings suggest a negative impact of alcohol on BDNF levels regardless of alcohol dosage. Further studies are needed to strengthen the evidence and elucidate the underlying mechanisms.

Folic acid supplementation improved nicotine withdrawal-induced of memory loss via affecting oxidative status, inflammatory response, cholinergic activity, BDNF and amyloid-B in adolescent male rat

BACKGROUND

The present study aimed to assess whether folic acid (FA) have potential to prevent memory impairment caused by nicotine (Nico) withdrawal in adolescent male rats.

METHODS AND MATERIALS

The experiments were divided into 7 groups: 1) vehicle, 2) Nico (Nico 2 mg/kg injection from 21 to 42 days of ages), 3-5) Nico FA5/10/15 mg/kg (received Nico from 21 to 42 days of ages and received FA at three doses 5, 10 and 15 mg/kg 43-63 days of ages), and 6) received normal saline from 21 to 42 days of age after that received FA 15 mg/kg by oral gavage from 43 to 63 days of age. At 64-69 days of ages, behavioral tests related to memory including Morris Water Maze (MWM) and Object Recognition Test (ORT) were performed and related biochemical analysis including the hippocampal levels of oxidative stress markers, inflammatory indices, brain-derived neurotrophic factor (BDNF), nitrite, amyloid-B and acetylcholinesterase [1] were measured.

RESULTS

Results showed that nicotine exposure in adolescence followed by withdrawal dramatically impaired learning and memory performance along with affecting a variety of biochemical markers in the hippocampal tissues. In addition, it was observed that administration of FA significantly ameliorated Nico withdrawal-induced adverse effects through restoration of the mentioned biochemical disturbances.

CONCLUSION

The present study and other relevant researches demonstrated that FA as a well-known, inexpensive, and safe supplement has strong potential to either prevent or ameliorate the detrimental effect of Nico withdrawal. However, further investigation is required to be more elucidated the precise mechanisms underlying memory impairment-induced by Nico withdrawal.

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.

Polyphenols' Impact on Selected Biomarkers of Brain Aging in Healthy Middle-Aged and Elderly Subjects: A Review of Clinical Trials

With a constantly growing elderly population, incidences of neurodegenerative diseases are also rising and are expected to further increase over the next years, while costing health systems across the world trillions of dollars. Therefore, biomarkers to detect manifestations of brain aging early and interventions to slow down its pace are of great interest. In the last years, the importance of the neurotrophins brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the context of cognitive function and the aging brain has increased, besides the already well-established amyloid-beta (Aβ) and tau plaques. Due to their wide range of beneficial health effects as well as their antioxidant and anti-inflammatory properties, a class of secondary plant-metabolites, the so-called polyphenols, gained increasing attention. In this review, we discuss the roles of BDNF, Aβ, NGF, and tau proteins as biomarkers of brain aging and the effect of dietary polyphenol interventions on these biomarkers, assessed via blood analysis, magnetic resonance imaging (MRI), and positron emission tomography (PET).

Development and Validation of an Endometriosis Diagnostic Method Based on Serum Biomarkers and Clinical Variables

Endometriosis affects more than 10% of women of reproductive age, significantly impacting their quality of life. Diagnosis typically takes 4 to 11 years from symptom onset. The gold standard for diagnosing this disease, laparoscopy, is invasive, contributing to this delay in diagnosis. Two studies were conducted to develop a diagnostic test based on the combination of serum biomarkers and clinical variables. Study 1, the development study, aimed to: (i) confirm the ability of CA125, BDNF and clinical variables to differentiate between cases and controls, and (ii) develop a diagnostic algorithm based on these results. Study 2 validated the clinical performance of the developed in vitro diagnostic (IVD) test in diagnosing endometriosis. Serum samples and clinical variables extracted from psychometric questionnaires were obtained from the Oxford Endometriosis CaRe Centre biobank (UK). Case/control classification was performed based on laparoscopy and histological verification of the excised lesions. Studies 1 and 2 included n = 204 and n = 79 patients, respectively. Study 1 found a statistically significant difference between cases and controls for levels of both biomarkers. Of the assessed clinical variables from the patients' medical histories, six were found to be significantly different between endometriosis cases and controls. CA125, BDNF and these six clinical variables were combined into a multivariable prediction model. In Study 2, the IVD test demonstrated sensitivity and specificity values of 46.2% (25.5-66.8%) and 100% (86.7-100%), respectively. Due to its high specificity, this IVD test is a simple and accurate rule-in test for early disease identification, even in the presence of non-specific symptoms.

BDNF and KISS-1 Levels in Maternal Serum, Umbilical Cord, and Placenta: The Potential Role of Maternal Levels as Effect Biomarker

Brain-derived neurotrophic factor (BDNF) and kisspeptin-1 (KISS-1) regulate placental development and fetal growth. The predictive value of maternal serum BDNF and KISS-1 concentrations for placental and umbilical cord levels has not yet been explored. The influence of prenatal lead (Pb) and cadmium (Cd) exposure and maternal iron status on BDNF and KISS-1 levels is also unclarified and of concern. In a pilot cross-sectional study with 65 mother-newborn pairs, we analyzed maternal and cord serum levels of pro-BDNF, mature BDNF, and KISS-1, BDNF, and KISS-1 gene expression in placenta, Pb and Cd in maternal and umbilical cord blood (erythrocytes), and placenta. We conducted a series of in vitro experiments using human primary trophoblast cells (hTCs) and BeWo cells to verify main findings of the epidemiological analysis. Strong and consistent correlations were observed between maternal serum levels of pro-BDNF, mature BDNF, and KISS-1 and corresponding levels in umbilical serum and placental tissue. Maternal red blood cell Pb levels were inversely correlated with serum and placental KISS-1 levels. Lower expression and release of KISS-1 was also observed in Pb-exposed BeWo cells. In vitro Pb exposure also reduced cellular BDNF levels. Cd-treated BeWo cells showed increased pro-BDNF levels. Low maternal iron status was positively associated with low BDNF levels. Iron-deficient hTCs and BeWo cells showed a consistent decrease in the release of mature BDNF. The correlations between maternal BDNF and KISS-1 levels, placental gene expression, and umbilical cord serum levels, respectively, indicate the strong potential of maternal serum as predictive matrix for BDNF and KISS-1 levels in placentas and fetal sera. Pb exposure and iron status modulate BDNF and KISS-1 levels, but a clear direction of modulations was not evident. The associations need to be confirmed in a larger sample and validated in terms of placental and neurodevelopmental function.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-023-00565-w.

Brain-derived neurotrophic factor measurements in mouse serum and plasma using a sensitive and specific enzyme-linked immunosorbent assay

This study is about the quantification and validation of BDNF levels in mouse serum and plasma using a sensitive immunoassay. While BDNF levels are readily detectable in human serum, the functional implications of these measurements are unclear as BDNF released from human blood platelets is the main contributor to the serum levels of BDNF. As mouse platelets do not contain BDNF, this confounding factor is absent in the mouse. Accordingly, BDNF levels in mouse serum and plasma were found to be indistinguishable at 9.92 ± 1.97 pg/mL for serum and 10.58 ± 2.43 pg/mL for plasma (p = 0.473). These levels are approximately a thousand times lower than those measured in human serum and pre-adsorption with anti-BDNF, but not with anti-NGF or anti-NT3 monoclonal antibodies, markedly reduced the BDNF signal. These results open the possibility to explore the relevance of BDNF levels as a biomarker in accessible body fluids using existing mouse models mimicking human pathological conditions.

Effect of acupuncture in the acute phase of intracerebral hemorrhage on the prognosis and serum BDNF: a randomized controlled trial

Background

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease, with a high rate of disability. In the literature on Chinese traditional medicine, there is increasing evidence that acupuncture can help hematoma absorption and improve neurological deficits after cerebral hemorrhage. Brain-derived neurotrophic factor (BDNF), one of the most studied neurotrophic factors, is involved in a variety of neurological functions and plays an important role in brain injury recovery. We investigated the effect of acupuncture intervention in the acute phase of ICH on the prognosis and serum BDNF levels of several patient groups.

Objective

To investigate the influence of acupuncture on the prognosis and brain-derived neurotrophic factor (BDNF) levels in patients in the acute phase of ICH.

Methods

From November 2021 to May 2022, 109 subjects were consecutively enrolled, including patients with ICH, who were randomized into the acupuncture group (AG) and sham acupuncture group (SAG), and a control group (CG). The CG received the same acupuncture intervention as the AG, and the SAG received sham acupuncture, with 14 interventions in each group. The level of consciousness of patients with ICH was assessed and serum BDNF levels were measured in all three groups before the intervention and at 3 weeks after onset, and the level of consciousness and outcomes were assessed at 12 weeks after onset.

Results

After the intervention, the level of consciousness of the AG improved significantly (P < 0.05); the BDNF level of only the AG increased significantly (P < 0.05); the changes in Glasgow Coma Scale (GCS) score and BDNF level were significantly greater in the AG than in the SAG (P < 0.05), especially for locomotion (P < 0.05). At 12 weeks post-onset, the AG showed better outcomes and recovery of consciousness than the SAG (P < 0.05).

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

INTRODUCTION

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

AREAS COVERED

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

EXPERT OPINION

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

The role of BDNF in major depressive disorder, related clinical features, and antidepressant treatment: insight from meta-analyses

The brain-derived neurotrophic factor (BDNF) has received considerable attention as a potential biomarker of major depressive disorder (MDD) and antidepressant response. We conducted an overview of meta-analyses investigating the relationship of BDNF with MDD, related clinical features, and antidepressant treatment. Based on a systematic screening on main electronic databases, 11 systematic reviews with meta-analyses were included. Available evidence suggests that people with MDD have peripheral and central BDNF levels lower than non-depressed individuals. A negative correlation between blood BDNF and symptom severity emerged, while no association with suicidality was detected. Moreover, an increase in blood BDNF levels after antidepressant treatment, proportional to symptom improvement, was reported. BDNF levels seem to be increased in both treatment responders and remitters, remaining stable in non-responders. Conversely, no variations of BDNF concentrations after non-pharmacological interventions (electroconvulsive therapy, repetitive transcranial magnetic stimulation, and physical activity) were found. The findings of this overview appear consistent with the neurotrophic hypothesis of depression, suggesting that BDNF may play a role in both MDD pathophysiology and pharmacological treatment response.

Increased BDNF and hippocampal dendritic spine density are associated with the rapid antidepressant-like effect of iron-citalopram and iron-imipramine combinations in mice

Iron supplementation previously demonstrated antidepressant-like effects in post-partum rats. The present study evaluates the possible synergistic antidepressant effect of sub-therapeutic dose of iron co-administered with citalopram or imipramine in female Institute of Cancer Research mice. Depression-like symptoms were induced in the forced swim (FST), tail suspension (TST), and open space swim (OSST) tests while open field test (OFT) was used to assess locomotor activity. Mice (n=8) received iron (0.8- 7.2 mg/kg), citalopram (3-30 mg/kg), imipramine (3-30 mg/kg), desferrioxamine (50 mg/kg) or saline in the single treatment phase of each model and subsequently a sub-therapeutic dose of iron co-administered with citalopram or imipramine. Assessment of serum BDNF and dendritic spine density was done using ELISA and Golgi staining techniques respectively. Iron, citalopram and imipramine, unlike desferrioxamine, reduced immobility score in the TST, FST and OSST without affecting locomotor activity, suggesting antidepressant-like effect. Sub-therapeutic dose of iron in combination with citalopram or imipramine further enhanced the antidepressant-like effect, producing a more rapid effect when compared to the iron, citalopram or imipramine alone. Iron, citalopram and imipramine or their combinations increased serum BDNF concentration, hippocampal neuronal count and dendritic spine densities. Our study provides experimental evidence that iron has antidepressant-like effect and sub-therapeutic dose of iron combined with citalopram or imipramine produces more rapid antidepressant-like effect. We further show that iron alone or its combination with citalopram or imipramine attenuates the neuronal loss associated with depressive conditions, increases dendritic spines density and BDNF levels. These finding suggest iron-induced neuronal plasticity in the mice brain.

Environmental Enrichment Engages Vesicular Zinc Signaling to Enhance Hippocampal Neurogenesis

Zinc is highly concentrated in synaptic vesicles throughout the mammalian telencephalon and, in particular, the hippocampal dentate gyrus. A role for zinc in modulating synaptic plasticity has been inferred, but whether zinc has a particular role in experience-dependent plasticity has yet to be determined. The aim of the current study was to determine whether vesicular zinc is important for modulating adult hippocampal neurogenesis in an experience-dependent manner and, consequently, hippocampal-dependent behaviour. We assessed the role of vesicular zinc in modulating hippocampal neurogenesis and behaviour by comparing ZnT3 knockout (KO) mice, which lack vesicular zinc, to wild-type (WT) littermates exposed to either standard housing conditions (SH) or an enriched environment (EE). We found that vesicular zinc is necessary for a cascade of changes in hippocampal plasticity following EE, such as increases in hippocampal neurogenesis and elevations in mature brain-derived neurotrophic factor (mBDNF), but was otherwise dispensable under SH conditions. Using the Spatial Object Recognition task and the Morris Water task we show that, unlike WT mice, ZnT3 KO mice showed no improvements in spatial memory following EE. These experiments demonstrate that vesicular zinc is essential for the enhancement of adult hippocampal neurogenesis and behaviour following enrichment, supporting a role for zincergic neurons in contributing to experience-dependent plasticity in the hippocampus.

BDNF as a biomarker for neuropathic pain: Consideration of mechanisms of action and associated measurement challenges

INTRODUCTION

The primary objective of this paper is to (1) provide a summary of human studies that have used brain derived neurotrophic factor (BDNF) as a biomarker, (2) review animal studies that help to elucidate the mechanistic involvement of BDNF in the development and maintenance of neuropathic pain (NP), and (3) provide a critique of the existing measurement techniques to highlight the limitations of the methods utilized to quantify BDNF in different biofluids in the blood (i.e., serum and plasma) with the intention of presenting a case for the most reliable and valid technique. Lastly, this review also explores potential moderators that can influence the measurement of BDNF and provides recommendations to standardize its quantification to reduce the inconsistencies across studies.

METHODS

In this manuscript we examined the literature on BDNF, focusing on its role as a biomarker, its mechanism of action in NP, and critically analyzed its measurement in serum and plasma to identify factors that contribute to the discrepancy in results between plasma and serum BDNF values.

RESULTS

A large heterogenous literature was reviewed that detailed BDNF's utility as a potential biomarker in healthy volunteers, patients with chronic pain, and patients with neuropsychiatric disorders but demonstrated inconsistent findings. The literature provides insight into the mechanism of action of BDNF at different levels of the central nervous system using animal studies. We identified multiple factors that influence the measurement of BDNF in serum and plasma and based on current evidence, we recommend assessing serum BDNF levels to quantify peripheral BDNF as they are more stable and sensitive to changes than plasma BDNF.

CONCLUSION

Although mechanistic studies clearly explain the role of BDNF, results from human studies are inconsistent. More studies are needed to evaluate the methodological challenges in using serum BDNF as a biomarker in NP.

Bacopa monnieri supplementation has no effect on serum brain-derived neurotrophic factor levels but beneficially modulates nuclear factor kappa B and cyclic AMP response element-binding protein levels in healthy elderly subjects

Background and Aim

Bacopa monnieri is an Ayurvedic herb that has been used for multiple conditions, most notably to augment cognition, particularly memory and attention. Multiple mechanisms, including raising brain-derived neurotrophic factor (BDNF), have been proposed and investigated in animal models that require translational studies in humans.

Methods

Bacopa was administered in an open-labeled study to cognitively healthy controls over a 3-month period. Cognition and mood were assessed using the Montreal Cognitive Assessment (MoCA) and geriatric depression scale (GDS) at the baseline and 3-month visit. Laboratories were assessed for safety and serum levels of mature (mBDNF) and proBDNF were quantified. In a subset of subjects, intracellular signaling processes were assessed using western blot analysis.

Results

Bacopa was provided to 35 subjects and was well-tolerated except for 4 (11%) subjects who early terminated due to known, reversible, and gastrointestinal side effects (i.e., nausea, diarrhea). Over the 3 months, the GDS and the total MoCA did not significantly change; however, the delayed-recall subscale significantly improved (baseline: 3.8 ± 1.2, 3-months: 4.3 ± 0.9; P = 0.032). Serum mBDNF and proBDNF levels did not significantly change. Cyclic AMP response element-binding protein (CREB) phosphorylation significantly increased (P = 0.028) and p65 nuclear factor kappa B (NF-κB) phosphorylation significantly decreased (P = 0.030).

Conclusion

These results suggest that Bacopa may exert an anti-inflammatory effect through NF-κB and improve intracellular signaling processes associated with synaptogenesis (CREB). The future placebo-controlled studies are recommended.

Relevance for Patients

B. monnieri will require larger, blinded trials to better understand potential mechanisms, interactions, and utilization.

Increasing Effect of Citrus natsudaidai on Brain-Derived Neurotrophic Factor

The increase in brain-derived neurotrophic factor (BDNF) in the brain is beneficial for the treatment of depression, Alzheimer's disease (AD), and Parkinson's disease (PD); BDNF can cross the blood-brain barrier. Therefore, foods that elevate BDNF concentration in peripheral tissues may increase BDNF in the brain and thereby induce preventive and therapeutic effects against depression, AD, and PD. In this study, we aimed to determine whether Citrus natsudaidai extracts can increase BDNF concentration using the human kidney adenocarcinoma cell line ACHN, which has BDNF-producing and -secreting abilities. As test samples, methanol extracts of C. natsudaidai peel and pulp, and their n-hexane, ethyl acetate, n-butanol, and water fractions were prepared. The BDNF concentrations in culture medium of ACHN cells were assayed after 24 h cultivation in the presence of test samples. Compared with that of control (non-treated) cells, the BDNF concentration increased in the culture medium of ACHN cells treated with the methanol extract of C. natsudaidai peel and its hexane, butanol, and water fractions, as well as the butanol and water fractions of the pulp extract. Quantitative reverse transcription-polymerase chain reaction analysis revealed that ACHN cells treated with the butanol fractions of the peel and pulp extracts showed elevated levels of BDNF mRNA compared with those of non-treated cells. C. natsudaidai may increase BDNF concentration by acting on peripheral tissues and could be a medication for the prevention and treatment of depression, AD, and PD.

Development and validation of brain-derived neurotrophic factor measurement in human urine samples as a non-invasive effect biomarker

Background

Brain-derived neurotrophic factor (BDNF), a neurotrophic growth factor mainly expressed in the brain, has been proposed as a potential effect biomarker; that is, as a measurable biomarker whose values could be associated with several diseases, including neurological impairments. The European Human Biomonitoring Initiative (HBM4EU) has also recognized effect biomarkers as a useful tool for establishing link between exposure to environmental pollutants and human health. Despite the well-establish protocol for measuring serum BDNF, there is a need to validate its assessment in urine, a non-invasive sample that can be easily repeated over time. The aim of this study was to develop, standardize and validate a methodology to quantify BDNF protein levels in urine samples before its implementation in biomonitoring studies.

Methods

Different experimental conditions and non-competitive commercial enzyme-linked immunosorbent assay (ELISA) kits were tested to determine the optimal analytical procedure, trying to minimize the shortcomings of ELISA kits. The fine-tune protocol was validated in a pilot study using both upon awakening (n = 150) and prior to sleeping (n = 106) urine samples from the same Spanish adolescent males in a well-characterized study population (the Spanish INMA-Granada cohort).

Results

The best results were obtained in 0.6 ml of urine after the acidification and extraction (pre-concentration) of samples. The highest reproducibility was obtained with the ELISA kit from Raybiotech. Urinary BDNF concentrations of adolescent males were within the previously reported range (morning = 0.047-6.801 ng/ml and night = 0.047-7.404 ng/ml). Urinary BDNF levels in the awakening and pre-sleep samples did not follow a normal distribution and were not correlated.

Conclusion

The developed methodology offers good sensitivity and reproducibility. Having reliable markers in urine may facilitate both diagnosis and monitoring possible diseases (and treatment). Further studies are needed to implement urinary BDNF in biomonitoring studies to further elucidate its usefulness and biological significance for neurological impairments.

Peripheral brain-derived neurotrophic factor (BDNF) and salivary cortisol levels in college students with different levels of academic stress. Study protocol

INTRODUCTION

Brain-derived neurotrophic factor (BDNF) is essential for brain physiological processes influencing memory and learning. BDNF levels can be affected by many factors, including stress. Stress increase serum and salivary cortisol levels. Academic stress is of the chronic type. BDNF levels can be measure from serum, plasma or platelets, and there is still no standard methodology, which is relevant to ensure reproducibility and comparability between studies.

HYPOTHESIS

(i) BDNF concentrations in serum show greater variability than in plasma. (ii) In college students with academic stress, peripheral BDNF decreases and salivary cortisol increases.

GENERAL OBJECTIVE

To standardize plasma and serum collection for BDNF levels and to determine whether academic stress affects peripheral BDNF and salivary cortisol levels.

DESIGN

Quantitative research, with a non-experimental cross-sectional descriptive design.

PARTICIPANTS

Student volunteers. Under convenience sampling, 20 individuals will be included for standardization of plasma and serum collection and between 70 and 80 individuals to determine the effect of academic stress on BDNF and salivary cortisol.

PERIPHERAL BLOOD AND SALIVARY CORTISOL SAMPLING, MEASUREMENTS

12 mL of peripheral blood (with and without anticoagulant) will be drawn per participant, separated from plasma or serum and cryopreserved at -80°C. Additionally, they will be instructed in the collection of 1 mL of saliva samples, which will be centrifuged. Val66Met polymorphism will be performed by allele-specific PCR, while BDNF and salivary cortisol levels will be determined by ELISA.

STATISTICAL ANALYSIS

(i) descriptive analysis of the variables, through measures of central tendency and dispersion, and the categorical variables through their frequency and percentage. (ii) Then a bivariate analysis will be performed comparing groups using each variable separately.

EXPECTED RESULTS

We expect to (i) determine the analytical factors that allow a better reproducibility in the measurement of peripheral BDNF, and (ii) the effect of academic stress on BDNF and salivary cortisol levels.

Brain Derived Neurotrophic Factor Interacts with White Matter Hyperintensities to Influence Processing Speed and Hippocampal Volume in Older Adults

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays an important role in regulating synaptic activity and plasticity.

OBJECTIVE

Given that type-2 diabetes (T2DM) increases the risk of cognitive decline, and studies have suggested lower BDNF levels may be a risk factor of diabetic neurovascular complications, we sought to investigate total white matter hyperintensities (WMH) as a moderator of the effect of BDNF on hippocampal volume and cognition.

METHODS

Older adults without dementia from the Alzheimer's Disease Neuroimaging Initiative (N = 454 including 49 with T2DM and 405 without diabetes) underwent neuropsychological evaluation, magnetic resonance imaging to quantify hippocampal and WMH volumes, and blood draw to assess BDNF.

RESULTS

Adjusting for age, sex, and APOE ɛ4 carrier status, there was a significant interaction between total WMH and BDNF on bilateral hippocampal volume in the non-T2DM group (t = 2.63, p = 0.009). Examination of main effect models with a dichotomous high/low BNDF group revealed a significant main effect for low BDNF (t = -4.98, p < 0.001), such that as WMH increased, bilateral hippocampal volume decreased. There was also a significant interaction between total WMH and BDNF on processing speed in the non-T2DM group (t = 2.91, p = 0.004). There was a significant main effect for low BDNF (t = -3.55, p < 0.001) such that as WMH increased, processing speed decreased. The interactions were not significant in the T2DM group.

CONCLUSION

These results further elucidate the protective role that BDNF plays on cognition, as well as the cognitive effects of WMH.

Ketamine and Zinc: Treatment of Anorexia Nervosa Via Dual NMDA Receptor Modulation

Anorexia nervosa is a disorder associated with serious adverse health outcomes, for which there is currently considerable treatment ineffectiveness. Characterised by restrictive eating behaviours, distorted body image perceptions and excessive physical activity, there is growing recognition anorexia nervosa is associated with underlying dysfunction in excitatory and inhibitory neurometabolite metabolism and signalling. This narrative review critically explores the role of N-methyl-D-aspartate receptor-mediated excitatory and inhibitory neurometabolite dysfunction in anorexia nervosa and its associated biomarkers. The existing magnetic resonance spectroscopy literature in anorexia nervosa is reviewed and we outline the brain region-specific neurometabolite changes that have been reported and their connection to anorexia nervosa psychopathology. Considering the proposed role of dysfunctional neurotransmission in anorexia nervosa, the potential utility of zinc supplementation and sub-anaesthetic doses of ketamine in normalising this is discussed with reference to previous research in anorexia nervosa and other neuropsychiatric conditions. The rationale for future research to investigate the combined use of low-dose ketamine and zinc supplementation to potentially extend the therapeutic benefits in anorexia nervosa is subsequently explored and promising biological markers for assessing and potentially predicting treatment response are outlined.

Assessing the expression of two post-transcriptional BDNF regulators, TTP and miR-16 in the peripheral blood of patients with Schizophrenia

Schizophrenia (SCZ) is a severe mental disorder with an unknown pathophysiology. Brain-Derived Neurotrophic Factor (BDNF) is a neurotrophin that has been associated with synapse plasticity, learning, and memory, as well as neurodevelopment and neuroprotection. The importance of neurodevelopmental and neurotoxicity-related components in the pathophysiology of SCZ has been highlighted in research on the neurobiology of this disease. The purpose of this research is to investigate the significant expression of two variables, tristetraprolin (TTP) and miR-16, which are known to be regulators of BDNF expression. Fifty Iranian Azeri SCZ patients were enrolled, and fifty healthy volunteers were age- and gender-matched as controls. A quantitative polymerase chain reaction measured the expression levels of the TTP and miR-16 in the peripheral blood (PB) of SCZ patients and healthy people. TTP expression levels in patients were higher than in controls, regardless of gender or age (posterior beta = 1.532, adjusted P-value = 0.012). TTP and miR-16 expression levels were found to be significantly correlated in both SCZ patients and healthy controls (r = 0.701, P < 0.001 and r = 0.777, P < 0.001, respectively). Due to the increased expression of TTP in SCZ and the existence of a significant correlation between TTP and miR-16, which helps to act on target mRNAs with AU-rich elements, this mechanism can be considered an influencing factor in SCZ.

Converging Evidence Points to BDNF as Biomarker of Depressive Symptoms in Schizophrenia-Spectrum Disorders

Brain-derived neurotrophic factor (BDNF) is a key modulator of neuroplasticity and has an important role in determining the susceptibility to severe psychiatric disorder with a significant neurodevelopmental component such as major psychoses. Indeed, a potential association between BDNF serum levels and schizophrenia (SCZ) and schizoaffective disorder (SAD) has been tested in diverse studies and a considerable amount of them found reduced BDNF levels in these disorders. Here, we aimed at testing the association of BDNF serum levels with several demographic, clinical, and psychometric measures in 105 patients with SCZ and SAD, assessing the moderating effect of genetic variants within the BDNF gene. We also verified whether peripheral BDNF levels differed between patients with SCZ and SAD. Our findings revealed that BDNF serum levels are significantly lower in patients affected by SCZ and SAD presenting more severe depressive symptomatology. This finding awaits replication in future independent studies and points to BDNF as a possible prognostic indicator in major psychoses.

Early time-restricted eating may favorably impact cognitive acuity in university students: a randomized pilot study

Cognitive acuity is important for academic success. The preliminary efficacy of early time-restricted eating (eTRE) on cognitive acuity was examined in a sample of university students attending a large southwestern university. It was hypothesized that adherence to eTRE would result in improved cognitive acuity as assessed by the Trail Making Tests (i.e., TMT-A and TMT-B) and the Stroop Color and Word Test. Participants were randomized to an intervention group (eTRE) with a daily 6-hour eating window or a control group (CON) with a daily 16-hour eating window; 24 participants initiated the study (13 eTRE and 11 CON). Blood ketones (i.e., β-hydroxybutyrate [BHB]) and brain-derived neurotrophic factor were also assessed. The 8-week intervention was forestalled by COVID-19 laboratory closures beginning in March 2020, and only data obtained at week 0 (baseline) and week 4 were viable for statistical analyses. Study attrition was high (50% for eTRE and 23% for CON). At week 4, there was a 27% and 6% decrease in TMT-B response time for the eTRE and CON groups, respectively (P = .02). TMT-B response time was inversely correlated to plasma BHB among participants (r = -0.633; P = .008). Considering the inverse relationship between TMT-B response time and plasma BHB, these preliminary data suggest that eTRE may improve some aspects of cognitive acuity in this population. Future investigations are needed to confirm these findings and should accommodate individual preferences regarding the initiation time of the eating window while also considering the impact on social influences and exercise engagement.

Acute submaximal exercise does not impact aspects of cognition and BDNF in people with spinal cord injury: A pilot study

Objective

To investigate the effect of acute submaximal exercise, based on the spinal cord injury (SCI) Exercise Guidelines, on cognition and brain-derived neurotrophic factor (BDNF) in people with SCI.

Design

Eight adults (7 males) with traumatic SCI volunteered in this pre-registered pilot study. In randomized order, participants completed submaximal intensity arm cycling (60% of measured peak-power output at 55–60 rpm) for 30 min or time-matched quiet rest (control condition) on separate days. Blood-borne BDNF was measured in serum and plasma at pre-intervention, 0 min and 90 min post-intervention. Cognition was assessed using the Stroop Test and Task-Switching Test on an electronic tablet pre- and 10 min post-intervention.

Results

Submaximal exercise had no effect on plasma [F(2,12) = 1.09; P = 0.365; η² = 0.069] or serum BDNF [F(2,12) = 0.507; P = 0.614; η² = 0.024] at either 0 min or 90 min post-intervention. Similarly, there was no impact of exercise on either Stroop [F(1,7) = 2.05; P = 0.195; η² = 0.065] or Task-Switching performance [F(1,7) = 0.016; P = 0.903; η² &lt; 0.001] compared to the control condition. Interestingly, there was a positive correlation between years since injury and resting levels of both plasma (r = 0.831; P = 0.011) and serum BDNF (r = 0.799; P = 0.023). However, there was not relationship between years since injury and the BDNF response to exercise.

Conclusions

Acute guideline-based exercise did not increase BDNF or improve aspects of cognition in persons with SCI. This work establishes a foundation for continued investigations of exercise as a therapeutic approach to promoting brain health among persons with SCI.

Brain-Derived Neurotrophic Factor (BDNF) as a biomarker of treatment response in patients with Treatment Resistant Depression (TRD): A systematic review & meta-analysis

Multiple lines of evidence have implicated brain-derived neurotrophic factor (BDNF) in treatment-resistant depression (TRD). The aim of this synthesis was to determine the impact of TRD treatments on peripheral BDNF levels, and ascertain whether these changes are associated with antidepressant effects. Thirty-six articles involving 1198 patients with TRD were included herein. Electroconvulsive therapy (ECT), ketamine, and repetitive transcranial magnetic stimulation (rTMS) were the most common TRD treatments investigated. Serum BDNF levels significantly increased in six, two, four and one studies following ECT, ketamine, rTMS and atypical antipsychotics, respectively. The estimated mean baseline serum BDNF concentration in TRD patients ± 95% CI was 15.5 ± 4.34 ng/mL. Peripheral BDNF levels significantly increased overall (Hedges' g ± 95% CI = 0.336 ± 0.302; p < 0.05), but no association with depressive symptoms was found (p ≥ 0.05). These results demonstrate that peripheral measurements of total BDNF (i.e., mature and percursor forms of BDNF) are inadequate predictors of treatment response in TRD patients, and other considerations suggest that this would still apply to separable measurements of mature BDNF and its precursor.