Blood Brain-Derived Neurotrophic Factor (BDNF) and Major Depression: Do We Have a Translational Perspective?

Brain-derived neurotrophic factor modulation in response to oxidative stress and corticosterone: Role of scopolamine and mirtazapine

Major Depressive Disorder (MDD) is a very complex disease, challenging to study and manage. The complexities of MDD require extensive research of its mechanisms to develop more effective therapeutic approaches. Crucial in the context of this disease is the role of brain-derived neurotrophic factor (BDNF) signaling pathway.

AIM

This manuscript aims to explore the complex relationship between MDD and BDNF signaling pathway, focusing on how BDNF is modulated in response to oxidative stress and corticosterone, known to be altered in MDD and contributing to the pathology of the disorder, when treated with scopolamine and mirtazapine.

METHODS

To assess BDNF levels after the different treatment conditions, rat hippocampal slices and mice primary hippocampus and cortical cell culture were analyzed by immunofluorescence and Western blot.

KEY FINDINGS

Both mirtazapine and scopolamine under stress conditions induced by hydrogen peroxide (H2O2) and corticosterone, had a significant impact on BDNF levels, and this was distinct in different neuronal models. Mirtazapine, especially when combined with H2O2, altered BDNF expression. Scopolamine when combined with both stressors also altered BDNF levels. However, its effects varied depending on the specific neuronal model and stress condition. In accordance with BDNF results, phosphorylated tropomyosin receptor kinase B (pTrkB) presented increased activation when neuronal cells subjected to stress were treated with mirtazapine or scopolamine.

SIGNIFICANCE

Collectively, this study highlights the complex connection between these compounds, stress conditions, and BDNF/TrkB modulation, supporting the potential therapeutic effects of scopolamine and mirtazapine in modulating BDNF levels, even in stressful conditions.

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.

Late-onset major depressive disorder: exploring the therapeutic potential of enhancing cerebral brain-derived neurotrophic factor expression through targeted microRNA delivery

Major depressive disorder (MDD) is a severe psychiatric condition that significantly impacts the overall quality of life. Although MDD can occur across all age groups, it is notably prevalent among older individuals, with the aggravating circumstance that the clinical condition is frequently overlooked and undertreated. Furthermore, older adults often encounter resistance to standard treatments, experience adverse events, and face challenges associated with polypharmacy. Given that late-life MDD is associated with heightened rates of disability and mortality, as well as imposing a significant economic and logistical burden on healthcare systems, it becomes imperative to explore novel therapeutic approaches. These could serve as either supplements to standard guidelines or alternatives for non-responsive patients, potentially enhancing the management of geriatric MDD patients. This review aims to delve into the potential of microRNAs targeting Brain-Derived Neurotrophic Factor (BDNF). In MDD, a significant decrease in both central and peripheral BDNF has been well-documented, raising implications for therapy response. Notably, BDNF appears to be a key player in the intricate interplay between microRNA-induced neuroplasticity deficits and neuroinflammation, both processes deeply implicated in the onset and progression of the disease. Special emphasis is placed on delivery methods, with a comprehensive comparison of the strengths and weaknesses of each proposed approach. Our hypothesis proposes that employing multiple microRNAs concurrently, with the ability to directly influence BDNF and activate closely associated pathways, may represent the most promising strategy. Regarding vehicles, although the perfect nanoparticle remains elusive, considering the trade-offs, liposomes emerge as the most suitable option.

Pharmacotherapeutic value of inflammatory and neurotrophic biomarkers in bipolar disorder: A systematic review

BACKGROUND

The various pharmacological interventions, ranging from mood stabilizers and antipsychotics to antidepressants, reflect the diff/iculty of treating depressive/manic symptomatology of bipolar disorder (BD). Among a broad range of mechanisms implicated, immune dysregulation may contribute to the increased inflammation that influences the course of BD. Inflammatory, neurotrophic and oxidative stress factors may be identified as promising peripheral biomarkers in brain functioning, perhaps serving as predictors of an effective response to treatment for BD. The present systematic review aimed to examine the evidence supporting the pharmacotherapeutic value of inflammatory and neurotrophic biomarkers in BD.

METHODS

PubMed, PsychINFO, Scopus and Web of Science were searched from inception to May 2024 by two independent reviewers. A total of 40 studies with 3371 patients with diagnosis and intervention of BD were selected.

RESULTS

Inconsistencies in the effects of pharmacological treatments on the connection between the expected anti-inflammatory response and symptomatologic improvement were identified. Mood stabilizers (lithium), antipsychotics (quetiapine), antidepressants (ketamine) or their combination were described to increase both pro-inflammatory (TNFα, IL-6) and anti-inflammatory (IL-4, IL-8) factors. Other medications, such as memantine and dextromethorphan, autoimmune (infliximab) non-steroidal anti-inflammatory (aspirin, celecoxib) drugs, antidiabetics (pioglitazone), and even dietary supplementation (omega-3), or their combination, clearly decrease inflammatory factors (TNFα, IL-6, IL-1β, C-reactive protein) and/or increase the neurotrophic factor BDNF in BD patients.

CONCLUSION

Inflammation in BD requires further investigation to understand the underlying immunologic mechanism, to identify predictors of treatment response, and to make informed decisions about the use and development of more effective pharmacological interventions for BD.

Deciphering Depression: Epigenetic Mechanisms and Treatment Strategies

Depression, a significant mental health disorder, is under intense research scrutiny to uncover its molecular foundations. Epigenetics, which focuses on controlling gene expression without altering DNA sequences, offers promising avenues for innovative treatment. This review explores the pivotal role of epigenetics in depression, emphasizing two key aspects: (I) identifying epigenetic targets for new antidepressants and (II) using personalized medicine based on distinct epigenetic profiles, highlighting potential epigenetic focal points such as DNA methylation, histone structure alterations, and non-coding RNA molecules such as miRNAs. Variations in DNA methylation in individuals with depression provide opportunities to target genes that are associated with neuroplasticity and synaptic activity. Aberrant histone acetylation may indicate that antidepressant strategies involve enzyme modifications. Modulating miRNA levels can reshape depression-linked gene expression. The second section discusses personalized medicine based on epigenetic profiles. Analyzing these patterns could identify biomarkers associated with treatment response and susceptibility to depression, facilitating tailored treatments and proactive mental health care. Addressing ethical concerns regarding epigenetic information, such as privacy and stigmatization, is crucial in understanding the biological basis of depression. Therefore, researchers must consider these issues when examining the role of epigenetics in mental health disorders. The importance of epigenetics in depression is a critical aspect of modern medical research. These findings hold great potential for novel antidepressant medications and personalized treatments, which would significantly improve patient outcomes, and transform psychiatry. As research progresses, it is expected to uncover more complex aspects of epigenetic processes associated with depression, enhance our comprehension, and increase the effectiveness of therapies.

Omega-3 Polyunsaturated Fatty Acids in Depression

Omega-3 polyunsaturated fatty acids have received considerable attention in the field of mental health, in particular regarding the treatment of depression. This review presents an overview of current research on the role of omega-3 fatty acids in the prevention and treatment of depressive disorders. The existing body of evidence demonstrates that omega-3 fatty acids, in particular eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have antidepressant effects that can be attributed to their modulation of neuroinflammation, neurotransmitter function, and neuroplasticity. Nevertheless, clinical trials of omega-3 supplementation have yielded inconsistent results. Some studies have demonstrated significant reductions in depressive symptoms following omega-3 treatment, whereas others have shown minimal to no beneficial impact. A range of factors, encompassing dosage, the ratio of EPA to DHA, and baseline nutritional status, have been identified as having a potential impact on the noted results. Furthermore, it has been suggested that omega-3 fatty acids may act as an adjunctive treatment for those undergoing antidepressant treatment. Notwithstanding these encouraging findings, discrepancies in study designs and variability in individual responses underscore the necessity of further research in order to establish uniform, standardized guidelines for the use of omega-3 fatty acids in the management of depressive disorders.

Luteolin promotes neuronogenesis in hippocampus of chronic unpredictable mild stress rats and primary hippocampus of fetal rats

OBJECTIVE

To investigate the effects of luteolin on chronic unpredictable mild stress (CUMS)-induced depressive rats and corticosterone (CORT)-induced depressive primary hippocampal neurons, and to elucidate the mechanism behind the action.

METHODS

The antidepressant mechanism of luteolin was studied by using CUMS rat model and primary hippocampal neurons in fetal rats. In vivo, novelty suppressed feeding, open-field and sucrose preference tests as well as Morris water maze were evaluated. The content of brain derived neurotrophic factor (BDNF), 5-hydroxytryptamine (5-HT), norepinephrine (NE), and dopamine (DA) in serum were detected by enzyme-linked immunosorbent assay. The mechanisms of luteolin were explored based on neurotrophin and hippocampal neurogenesis, and proliferation. Survival of the septo-temporal axis in hippocampus was assayed using the 5-bromo-2-deoxyuridine (BrdU), the expression of BDNF, neurotrophin-3 (NT-3), and nerve growth factor (NGF) in hippocampus dentate gyrus region were measured by Western-blotting. In vitro, BDNF, NT-3, tropomyosin receptor kinase B (TrkB), and phosphorylated cyclic adenosine monophosphate responsive element binding protein (p-CREB) were detected through the high content analysis (HCA) to investigate neurotrophin and apoptosis.

RESULTS

Induction of CUMS in rats induced depressive symptoms, while luteolin significantly enhanced sucrose consumption, decreased feeding latency, increased locomotor activity, escape latency, distance of target quadrant and regulated the content of depressive-like biomarkers. Histology analysis revealed that luteolin increased the abundance of new born neurons that had been labeled with BrdU, BrdU + neuronal nuclear antigen, and BrdU + doublecortin in septo-temporal axis of S2 (mid-septal) and T3 (mid-temporal). Moreover, expression of BDNF, NT-3, and NGF increased significantly in the septo-temporal axis of S2 and T3. HCA showed increased expression of BDNF, NT-3, TrkB and p-CREB in primary hippocampal neurons.

CONCLUSION

The results provided direct evidence that luteolin has an antidepressant effect and could effectively promote the regeneration of the septotemporal axis nerve and hippocampal neuronutrition, which suggested that the antidepressant effect of luteolin may be related to hippocampal neurogenesis.

Positive Allosteric Modulators of Trk Receptors for the Treatment of Alzheimer's Disease

Neurotrophins are important regulators of neuronal and non-neuronal functions. As such, the neurotrophins and their receptors, the tropomyosin receptor kinase (Trk) family of receptor tyrosine kinases, has attracted intense research interest and their role in multiple diseases including Alzheimer's disease has been described. Attempts to administer neurotrophins to patients have been reported, but the clinical trials have so far have been hampered by side effects or a lack of clear efficacy. Thus, much of the focus during recent years has been on identifying small molecules acting as agonists or positive allosteric modulators (PAMs) of Trk receptors. Two examples of successful discovery and development of PAMs are the TrkA-PAM E2511 and the pan-Trk PAM ACD856. E2511 has been reported to have disease-modifying effects in preclinical models, whereas ACD856 demonstrates both a symptomatic and a disease-modifying effect in preclinical models. Both molecules have reached the stage of clinical development and were reported to be safe and well tolerated in clinical phase 1 studies, albeit with different pharmacokinetic profiles. These two emerging small molecules are interesting examples of possible novel symptomatic and disease-modifying treatments that could complement the existing anti-amyloid monoclonal antibodies for the treatment of Alzheimer's disease. This review aims to present the concept of positive allosteric modulators of the Trk receptors as a novel future treatment option for Alzheimer's disease and other neurodegenerative and cognitive disorders, and the current preclinical and clinical data supporting this new concept. Preclinical data indicate dual mechanisms, not only as cognitive enhancers, but also a tentative neurorestorative function.

Unraveling the molecular basis of cannabidiolic acid methyl Ester's anti-depressive effects in a rat model of treatment-resistant depression

Major depressive disorder (MDD) stands as a significant cause of disability globally. Cannabidiolic Acid-Methyl Ester (CBDA-ME) (EPM-301, HU-580), a derivative of Cannabidiol, demonstrates immediate antidepressant-like effects, yet it has undergone only minimal evaluation in psychopharmacology. Our goal was to investigate the behavioral and potential molecular mechanisms associated with the chronic oral administration of this compound in the Wistar Kyoto (WKY) genetic model of treatment-resistant depression. Male WKY rats were subjected to behavioral assessments before and after receiving chronic (14-day) oral doses of CBDA-ME (0.5 mg/kg), 15 mg/kg of imipramine or vehicle. At the end of the study, plasma corticosterone levels and mRNA expression of various genes in the medial Prefrontal Cortex and Hippocampus were measured. Behavioral outcomes from CBDA-ME treatment indicated an antidepressant-like effect similar to imipramine, as oral ingestion reduced immobility and increased swimming duration in the Forced Swim Test. Neither treatment influenced locomotion in the Open Field Test nor preference in the Saccharin Preference Test. The behavioral impact in WKY rats coincided with reduced corticosterone serum levels, upregulated mRNA expression of Cannabinoid receptor 1, Fatty Acid Amide Hydrolase, and Corticotropin-Releasing Hormone Receptor 1, alongside downregulation of the Serotonin Transporter in the hippocampus. Additionally, there was an upregulation of CB1 mRNA expression and downregulation of Brain-Derived Neurotrophic Factor in the mPFC. These findings contribute to our limited understanding of the antidepressant effects of CBDA-ME and shed light on its potential psychopharmacological mechanisms. This discovery opens up possibilities for utilizing cannabinoids in the treatment of major depressive disorder and related conditions.

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.

Potential Plausible Role of Stem Cell for Treating Depressive Disorder: a Retrospective Review

Depression poses a significant threat to global physical and mental health, impacting around 3.8% of the population with a rising incidence. Current treatment options primarily involve medication and psychological support, yet their effectiveness remains limited, contributing to high relapse rates. There is an urgent need for innovative and more efficacious treatment modalities. Stem cell therapy, a promising avenue in regenerative medicine for a spectrum of neurodegenerative conditions, has recently garnered attention for its potential application in depression. While much of this work remains preclinical, it has demonstrated considerable promise. Identified mechanisms underlying the antidepressant effects of stem cell therapy encompass the stimulation of neurotrophic factors, immune function modulation, and augmented monoamine levels. Nonetheless, these pathways and other undiscovered mechanisms necessitate further investigation. Depression fundamentally manifests as a neurodegenerative disorder. Given stem cell therapy's success in addressing a range of neurodegenerative pathologies, it opens the door to explore its application in depression treatment. This exploration may include repairing damaged nerves directly or indirectly and inhibiting neurotoxicity. Nevertheless, significant challenges must be overcome before stem cell therapies can be applied clinically. Successful resolution of these issues will ultimately determine the feasibility of incorporating stem cell therapies into the clinical landscape. This narrative review provides insights into the progress of research, potential avenues for exploration, and the prevailing challenges in the implementation of stem cell therapy for treatment of depression.

Investigating the role of TGF-β and BDNF in cancer-related depression: a primary cross-sectional study

BACKGROUND

Cancer-related depression is a well-documented condition that significantly impacts long-term quality of life. Brain-derived neurotrophic factor (BDNF), a neurotrophin essential for neurogenesis and neuronal plasticity, has been implicated in various neuropsychological disorders including depression associated with cancer. Cytokines, on the other hand, play a crucial role in regulating depression, potentially by influencing BDNF expression. Transforming growth factor-β (TGF-β), a key immune regulator within the tumor microenvironment, has been found to elevate BDNF levels, establishing a link between peripheral immune responses and depression. The study aims to investigate the correlation of TGF-β and BDNF in cancer-related depression.

METHODS

This study involved a cohort of 153 gynecological patients, including 61 patients with gynecological cancer and 92 patients without cancer. Depression levels were assessed using the subscale of Hospital Anxiety and Depression Scale (HADS-D), and TGF-β and BDNF plasma levels were measured using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The study revealed elevated plasma TGF-β levels in patients with cancer (32.24 ± 22.93 ng/ml) compared to those without cancer (25.24 ± 19.72 ng/ml) (P = 0.046). Additionally, reduced levels of BDNF were observed in patients presenting depression symptoms (44.96 ± 41.06 pg/ml) compared to those without depression (133.5 ± 176.7 pg/ml) (P = 0.036). Importantly, a significant correlation between TGF-β and BDNF was found in patients without cancer but with depression (correlation coefficient = 0.893, **P < 0.01). Interestingly, cancer appeared to influence the association between TGF-β and BDNF in patients with depression, as evidenced by a significant difference in the correlation of TGF-β and BDNF between cancer and non-cancer groups (P = 0.041).

CONCLUSIONS

These findings underscore the active involvement of TGF-β and BDNF crosstalk in the context of cancer-related depression.

Curcumin Improves Neurogenesis in Alzheimer's Disease Mice via the Upregulation of Wnt/β-Catenin and BDNF

Adult neurogenesis in the dentate gyrus (DG) is impaired during Alzheimer's disease (AD) progression. Curcumin has been reported to reduce cell apoptosis and stimulate neurogenesis. This study aimed to investigate the influence of curcumin on adult neurogenesis in AD mice and its potential mechanism. Two-month-old male C57BL/6J mice were injected with soluble β-amyloid (Aβ1-42) using lateral ventricle stereolocalization to establish AD models. An immunofluorescence assay, including bromodeoxyuridine (BrdU), doublecortin (DCX), and neuron-specific nuclear antigen (NeuN), was used to detect hippocampal neurogenesis. Western blot and an enzyme-linked immunosorbent assay (ELISA) were used to test the expression of related proteins and the secretion of brain-derived neurotrophic factor (BDNF). A Morris water maze was used to detect the cognitive function of the mice. Our results showed that curcumin administration (100 mg/kg) rescued the impaired neurogenesis of Aβ1-42 mice, shown as enhanced BrdU+/DCX+ and BrdU+/NeuN+ cells in DG. In addition, curcumin regulated the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) -mediated glycogen synthase kinase-3β (GSK3β) /Wingless/Integrated (Wnt)/β-catenin pathway and cyclic adenosine monophosphate response element-binding protein (CREB)/BDNF in Aβ1-42 mice. Inhibiting Wnt/β-catenin and depriving BDNF could reverse both the upregulated neurogenesis and cognitive function of curcumin-treated Aβ1-42 mice. In conclusion, our study indicates that curcumin, through targeting PI3K/Akt, regulates GSK3β/Wnt/β-catenin and CREB/BDNF pathways, improving the adult neurogenesis of AD mice.

Cisplatin induces BDNF downregulation in middle-aged female rat model while BDNF enhancement attenuates cisplatin neurotoxicity

Cancer-related cognitive impairments (CRCI) are neurological complications associated with cancer treatment, and greatly affect cancer survivors' quality of life. Brain-derived neurotrophic factor (BDNF) plays an essential role in neurogenesis, learning and memory. The reduction of BDNF is associated with the decrease in cognitive function in various neurological disorders. Few pre-clinical studies have reported on the effects of chemotherapy and medical stress on BDNF levels and cognition. The present study aimed to compare the effects of medical stress and cisplatin on serum BDNF levels and cognitive function in 9-month-old female Sprague Dawley rats to age-matched controls. Serum BDNF levels were collected longitudinally during cisplatin treatment, and cognitive function was assessed by novel object recognition (NOR) 14 weeks post-cisplatin initiation. Terminal BDNF levels were collected 24 weeks after cisplatin initiation. In cultured hippocampal neurons, we screened three neuroprotective agents, riluzole (an approved treatment for amyotrophic lateral sclerosis), as well as the ampakines CX546 and CX1739. We assessed dendritic arborization by Sholl analysis and dendritic spine density by quantifying postsynaptic density-95 (PSD-95) puncta. Cisplatin and exposure to medical stress reduced serum BDNF levels and impaired object discrimination in NOR compared to age-matched controls. Pharmacological BDNF augmentation protected neurons against cisplatin-induced reductions in dendritic branching and PSD-95. Ampakines (CX546 and CX1739) and riluzole did not affect the antitumor efficacy of cisplatin in vitro. In conclusion, we established the first middle-aged rat model of cisplatin-induced CRCI, assessing the contribution of medical stress and longitudinal changes in BDNF levels on cognitive function, although future studies are warranted to assess the efficacy of BDNF enhancement in vivo on synaptic plasticity. Collectively, our results indicate that cancer treatment exerts long-lasting changes in BDNF levels, and support BDNF enhancement as a potential preventative approach to target CRCI with therapeutics that are FDA approved and/or in clinical study for other indications.

Repurposing of dextromethorphan as an adjunct therapy in patients with major depressive disorder: a randomised, group sequential adaptive design, controlled clinical trial protocol

BACKGROUND

Therapeutic latency, lack of efficacy and adverse drug reactions are the major concerns in current antidepressant therapies. To overcome these treatment hurdles, add-on therapy to conventional antidepressant medications may lead to better therapeutic outcomes. The present randomised controlled trial has been planned to evaluate the efficacy and safety of add-on dextromethorphan to selective serotonin reuptake inhibitors (SSRIs) in major depressive disorder (MDD).

METHODS AND ANALYSIS

A randomised, double-blind, add-on, placebo-controlled, group sequential design clinical trial will be conducted on patients with MDD who will be randomly assigned to the control and the test group in a 1:1 ratio. Patients in the test group will get dextromethorphan 30 mg once daily, whereas patients in the control group will receive a placebo once daily as an add-on to ongoing SSRI treatment for 8 weeks. All patients will be evaluated for the primary outcome (change in the Montgomery-Åsberg Depression Rating Scale score) and secondary outcomes (treatment response rate, remission rate, Clinical Global Impression, serum brain-derived neurotrophic factor, serum dextromethorphan and treatment-emergent adverse events) over the period of 8 weeks. Intention-to-treat analysis will be done for all parameters using suitable statistical tools.

ETHICS AND DISSEMINATION

This study was approved by the Institutional Ethics Committee of All India Institute of Medical Sciences, Bhubaneswar, India, and the study conformed to the provisions of the Declaration of Helsinki and ICMR's ethical guidelines for biomedical research on human subjects (2017). Written informed consent will be obtained from the participants before recruitment. The results of this study will be published in peer-reviewed publications.

TRIAL REGISTRATION NUMBER

NCT05181527.

Not Just a Mood Disorder─Is Depression a Neurodevelopmental, Cognitive Disorder? Focus on Prefronto-Thalamic Circuits

Depression is one of the most burdensome psychiatric disorders, affecting hundreds of millions of people worldwide. The disease is characterized not only by severe emotional and affective impairments, but also by disturbed vegetative and cognitive functions. Although many candidate mechanisms have been proposed to cause the disease, the pathophysiology of cognitive impairments in depression remains unclear. In this article, we aim to assess the link between cognitive alterations in depression and possible developmental changes in neuronal circuit wiring during critical periods of susceptibility. We review the existing literature and propose a role of serotonin signaling during development in shaping the functional states of prefrontal neuronal circuits and prefronto-thalamic loops. We discuss how early life insults affecting the serotonergic system could be important in the alterations of these local and long-range circuits, thus favoring the emergence of neurodevelopmental disorders, such as depression.

Biomarkers of Depression among Adolescent Girls: BDNF and Epigenetics

Alterations in brain-derived neurotrophic factor (BDNF) expression have been suggested to mediate the influence of environmental factors on the emergence of depression through epigenetic modifications. However, research on this subject in the developmental population is lacking and the pathophysiology of adolescent depression remains unclear. We aimed to investigate the alterations in BDNF expression and global DNA methylation in depression among adolescent girls. Thirty female inpatients with the initial diagnosis of depression were assessed before and after the period of antidepressant treatment and compared with thirty age-matched healthy controls. The assessment involved BDNF and proBDNF serum levels, the BDNF gene exon IV promoter methylation, and global DNA methylation. The methylation level in the BDNF gene exon IV promoter was significantly lower in the studied group compared with the control and correlated negatively with the severity of depression. The test distinguished the studied group from the controls with a sensitivity of 37% and specificity of 90%. The differences were no longer present after the period of antidepressant treatment. No differences in the global DNA methylation, BDNF, and proBDNF levels were found. We concluded that decreased methylation in the BDNF exon IV promoter could be considered as a biomarker of a depression state among adolescent girls.

Prevalence of sarcopenia and depressive symptoms among older adults: a scoping review

Sarcopenia causes a loss of skeletal muscle mass and decreases muscle strength and function. Depressive symptoms are a common cause of distress among geriatrics, significantly affecting the quality of life of older adults. Recently, studies have shown that a correlation exists between sarcopenia and depression. To determine the prevalence of sarcopenia and depressive symptoms and identify the factors associated with sarcopenia, we systematically searched the SCOPUS, Science Direct, and PubMed databases for papers on sarcopenia and depressive symptoms published from 2012 to 2022. We reviewed the literature on sarcopenia, depressive symptom prevalence, the prevalence of subjects with both sarcopenia and depressive symptoms, and the factors associated with sarcopenia. Only cross-sectional studies were included. Nineteen articles met the inclusion criteria for review, with overall sarcopenia prevalence ranging from 3.9% to 41.7%. The prevalence of depressive symptoms was reported in seven studies, ranging from 8.09% to 40%. The most commonly used tools to diagnose sarcopenia and depressive symptoms were the European Working Group on Sarcopenia in Older People consensus and the Geriatric Depression Scale, respectively. Being aged, malnourished, obese, having comorbidities (hypertension and diabetes), having impaired cognitive function, and having polypharmacy were found to be the factors associated with sarcopenia. Sarcopenia and depressive symptoms have been found to cause adverse health outcomes among older people. Appropriate nutritional assessments and interventions should be taken to manage these two geriatric conditions. Further studies should be planned, considering multidomain intervention strategies to improve sarcopenia and older people's mental health.

MTK, Orlowski SK. Effects of Environmental Enrichments on Welfare and Hepatic Metabolic Regulation of Broiler Chickens

The aims of this study were to find suitable environmental enrichment (EE) and evaluate the combined effect of two EEs, variable light intensity (VL) lighting program and EH, on mental health and hepatic metabolic regulation in commercial broilers. To find the advantageous EEs for broilers, three different EEs (board, hut, and ramp) were tested in trial 1. EEs were placed and the engagement of birds to EEs, dustbathing behavior, and daily physical activity were observed. Birds treated with huts showed higher engagement than the board- or ramp-treated birds (p < 0.05). The results of dustbathing behavior and daily physical activity indicated that the environmental hut (EH) is the most favorable enrichment for broilers. In the second trial, to test the effect of EHs on mental health and hepatic metabolic conditions, the brain and liver were sampled from the four treatment birds (20 lx_Con, 20 lx_Hut, VL_Con and VL_Hut) on day 42. The lower expression of TPH2 (tryptophan hydroxylase 2) of VL_Hut birds than those of VL_Con and 20 lx_Hut treated birds suggests the combining effect of EHs with the VL lighting program on the central serotonergic homeostasis of broilers. Reduced expressions of TH (tyrosine hydroxylase), GR (glucocorticoid receptor), BDNF (brain-derived neurotrophic factor) of VL_Hut treated birds compared to those of VL_Con and 20 lx_Hut birds suggest lower stress, stress susceptibility, and chronic social stress in VL_Hut treated birds. The expression of CPT1A (carnitine palmitoyl transferase 1) increased over three-fold in the liver of VL_Con birds compared to 20 lx_Con birds (p < 0.05). EHs treatment in VL birds (VL_Hut) significantly decreased CPT1A but not in 20 lx birds (20 lx_Hut). The expression of ACCα (acetyl-CoA carboxylase alpha) was significantly decreased in VL_Con birds compared to 20 lx_Con birds. There was no significant difference in the hepatic FBPase (fructose-1,6-bisphosphatase), GR, and 11β-HSD1 (11 β-hydroxysteroid dehydrogenease-1) expression between 20 lx_Con and VL_Con birds, but EHs significantly stimulated GR in 20 lx_Hut birds, and stimulated FBPase and 11β-HSD1 expression in the VL_Hut birds compared to 20 lx_Con birds, suggesting that the VL lighting program reduced fatty acid synthesis and increased fatty acid β-oxidation in the broilers' liver and VL_Hut improved the hepatic de novo glucose production. Taken together, the results suggest that the stimulated voluntary activity by EHs in the light-enriched broiler house improved mental health and hepatic metabolic function of broilers and may indicate that the improved hepatic metabolic function contributes to efficient nutritional support for broilers.

Interaction of Brain-derived Neurotrophic Factor, Exercise, and Fear Extinction: Implications for Post-traumatic Stress Disorder

Brain-Derived Neurotrophic Factor (BDNF) plays an important role in brain development, neural plasticity, and learning and memory. The Val66Met single-nucleotide polymorphism is a common genetic variant that results in deficient activity-dependent release of BDNF. This polymorphism and its impact on fear conditioning and extinction, as well as on symptoms of post-traumatic stress disorder (PTSD), have been of increasing research interest over the last two decades. More recently, it has been demonstrated that regular physical activity may ameliorate impairments in fear extinction and alleviate symptoms in individuals with PTSD via an action on BDNF levels and that there are differential responses to exercise between the Val66Met genotypes. This narrative literature review first describes the theoretical underpinnings of the development and persistence of intrusive and hypervigilance symptoms commonly seen in PTSD and their treatment. It then discusses recent literature on the involvement of BDNF and the Val66Met polymorphism in fear conditioning and extinction and its involvement in PTSD diagnosis and severity. Finally, it investigates research on the impact of physical activity on BDNF secretion, the differences between the Val66Met genotypes, and the effect on fear extinction learning and memory and symptoms of PTSD.

Home-based high-intensity interval training for people with Parkinson's: Protocol for the HIIT-Home4Parkinson's randomized, controlled feasibility study

Background

High-intensity interval training (HIIT) is feasible and beneficial for some people with Parkinson's (PwP), although adherence to extended programs may be problematic. PwP face barriers to exercise such as lack of time, expense, and difficulty with travel logistics due to motor symptoms. HIIT based in the home setting if practical, could therefore be apposite for PwP by overcoming these barriers. However, until now, no home-based HIIT program for PwP has been developed. Cocreated by PwP, clinicians, and family members, the HIIT-Home4Parkinson's (HH4P) program is an innovative, 12-week home-based HIIT program for PwP. This protocol describes a feasibility study designed to assess the feasibility and safety of the HH4P program, explore outcomes that may be sensitive to change, and inform the implementation of a potential full trial.

Methods/design

Using a randomized controlled parallel group design, 24 independently mobile people with Parkinson's of mild to moderate disease severity will be randomized 1:1 to either the HH4P program plus usual care, or usual care alone. Both groups will be assessed at baseline, and upon the completion of the program. Outcomes will include feasibility and safety factors such as recruitment, completion, adverse events, and intervention fidelity with qualitative evaluation along with mechanistic, physiological, and clinical outcomes.

Discussion

Results of this study will inform the rationale and methodological considerations for a full trial with long-term follow-up. Ultimately, further establishing the practicality and utility of home-based HIIT could provide an important exercise option for PwP, potentially leading to extended participation and increased health and well-being for this population.

Microglial stimulation triggered by intranasal lipopolysaccharide administration produces antidepressant-like effect through ERK1/2-mediated BDNF synthesis in the hippocampus

We recently reported that reversing the chronic stress-induced decline of microglia in the dentate gyrus (DG) of the hippocampus by intraperitoneal injection of a low dose of lipopolysaccharide (LPS) ameliorated depression-like behavior in chronically stressed mice. In this study, we found that a single intranasal administration of LPS dose-dependently improved depression-like behavior in mice treated with chronic unpredictable stress (CUS), as evidenced by the reduction of immobility time in the tail suspension test (TST) and forced swimming test (FST) and by the increase of sucrose uptake in the sucrose preference test (SPT). The antidepressant effects of intranasal administration of LPS could be abolished by inhibition of brain-derived neurotrophic factor (BDNF) signaling by infusion of an anti-BDNF antibody, by knock-in of the mutant BDNF Val68Met allele, or by the BDNF receptor antagonist K252a. In addition, intranasal administration of LPS was found to exert antidepressant effects in a BDNF-dependent manner via promotion of BDNF synthesis mediated by extracellular signal-regulated kinase 1/2 (ERK1/2) signaling but not protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling in DG. Inhibition of microglia by minocycline or depletion of microglia by PLX3397 was able to abolish the reversal effect of intranasal LPS administration on CUS-induced depression-like behaviors as well as the CUS-induced decrease in phospho-ERK1/2 and BDNF protein levels in DG. These results demonstrate that stimulation of hippocampal microglia by intranasal LPS administration can induce antidepressant effects via ERK1/2-dependent synthesis of BDNF protein, providing hope for the development of new strategies for the treatment of depression.

Effect of modernized collaborative care for depression on brain-derived neurotrophic factor (BDNF) and depressive symptom clusters: Data from the eIMPACT trial

Brain-derived neurotrophic factor (BDNF) levels are lower in people with depression and are normalized following pharmacological treatment. However, it is unknown if psychological treatments for depression improve BDNF and if change in BDNF is a mediator of intervention effects on depressive symptoms. Therefore, using data from the eIMPACT trial, we sought to determine the effect of modernized collaborative care for depression on 12-month changes in BDNF and cognitive/affective and somatic depressive symptom clusters and to examine whether BDNF changes mediate intervention effects on depressive symptoms. 216 primary care patients with depression from a safety net healthcare system were randomized to 12 months of the eIMPACT intervention (internet cognitive-behavioral therapy [CBT], telephonic CBT, and select antidepressant medications) or usual primary care. Plasma BDNF was measured with commercially available kits, and depressive symptom clusters were assessed by the Patient Health Questionnaire-9. The intervention did not influence BDNF but did improve both the cognitive/affective and somatic clusters over 12 months. Changes in BDNF did not mediate the intervention effect on either cluster. Our findings suggest that modernized collaborative care is an effective treatment for both the cognitive/affective and somatic symptoms of depression and that the mechanism of action is not improvements in BDNF. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02458690.

Effect of probiotic supplementation on cognition and depressive symptoms in patients with depression: A systematic review and meta-analysis

BACKGROUND

Depression affects millions globally and often coexists with cognitive deficits. This study explored the potential of probiotics in enhancing cognition and ameliorating depressive symptoms in major depressive disorder patients.

METHODS

Utilizing the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol and the Population, Intervention, Comparator, Outcome, and Study design framework, we systematically reviewed randomized controlled trials examining probiotic effects on cognition and depressive symptoms. Searches spanned 7 databases from January 2010 to May 2022. Risk of bias was assessed using Revised Cochrane Risk of Bias 2.0, and meta-analysis was conducted with RevMan 5.4.1. Publication bias was evaluated via Egger test.

RESULTS

In a systematic review on the effects of probiotic supplementation on cognition and depressive symptoms in depression patients, 635 records were initially identified, with 4 studies ultimately included. These randomized controlled trials were conducted across diverse regions, primarily involving females, with assessment periods ranging from 1 to 2 months. Concerning cognitive outcomes, a statistically significant moderate improvement was found with probiotic supplementation, based on the mean difference and its 95% confidence interval. However, for depressive symptoms, the overall effect was negligible and not statistically significant. A heterogeneity test indicated consistent findings across studies for both cognitive and depressive outcomes (I² = 0% for both). The potential for publication bias was evaluated using the Egger linear regression test, suggesting no significant bias, though caution is advised due to the limited number of studies.

CONCLUSION

Probiotics may enhance cognitive domains and mitigate depressive symptoms, emphasizing the gut-brain axis role. However, methodological variations and brief intervention durations call for more standardized, extensive research.

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.

BDNF Unveiled: Exploring Its Role in Major Depression Disorder Serotonergic Imbalance and Associated Stress Conditions

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays a significant role in the survival and development of neurons, being involved in several diseases such as Alzheimer's disease and major depression disorder. The association between BDNF and major depressive disorder is the subject of extensive research. Indeed, numerous studies indicate that decreased levels of BDNF are linked to an increased occurrence of depressive symptoms, neuronal loss, and cortical atrophy. Moreover, it has been observed that antidepressive therapy can help restore BDNF levels. In this review, we will focus on the role of BDNF in major depression disorder serotonergic imbalance and associated stress conditions, particularly hypothalamic-pituitary-adrenal (HPA) axis dysregulation and oxidative stress. All of these features are highly connected to BDNF signaling pathways in the context of this disease, and exploring this topic will aim to advance our understanding of the disorder, improve diagnostic and treatment approaches, and potentially identify new therapeutic targets to alleviate the heavy burden of depression on society.

Variation of Circulating Brain-Derived Neurotrophic Factor (BDNF) in Depression: Relationships with Inflammatory Indices, Metabolic Status and Patients' Clinical Features

This study seeks to offer a contribution to the method of subtyping major depressed patients by exploring the possible relationships between circulating brain-derived neurotrophic factor (BDNF), different peripheral inflammatory/metabolic markers in the blood and clinical characteristics. Thirty-nine patients, thoroughly diagnosed according to the DSM-5 criteria, underwent a comprehensive set of evaluations encompassing structured interviews, rating scales and a panel of blood tests. Correlation and comparison analyses were carried out by means of non-parametric statistical tests. Concurrently, a principal component analysis was performed to explain biochemical variance. The findings of our research unveiled that leukocyte counts, their ratios and other inflammatory parameters are positively correlated with depression scores. Moreover, we found variations within the BDNF pools of depressed patients. Specifically, higher levels of platelet-poor plasma BDNF (PPP-BDNF) were correlated with augmented inflammatory markers in patients showing specific episode characteristics, whereas reduced platelet BDNF (PLT-BDNF) provided a better indication of the changes that were linked to a diagnosis of long-term depression. Our findings suggest that PPP-BDNF and PLT-BDNF might differentiate depression conditions. They also imply usefulness in appraising peripheral biomarker profiles in patients for a deeper characterization of major depressive episodes. At the same time, it is plausible that they might constitute novel avenues for developing more tailored therapeutic strategies for patients with MDs.

Gene co-expression network and differential expression analyses of subcutaneous white adipose tissue reveal novel insights into the pathological mechanisms underlying ketosis in dairy cows

Ketosis is a common nutritional metabolic disease during the perinatal period in dairy cows. Although various risk factors have been identified, the molecular mechanism underlying ketosis remains elusive. In this study, subcutaneous white adipose tissue (sWAT) was biopsied for transcriptome sequencing on 10 Holstein cows with type II ketosis [blood β-hydroxybutyric acid (BHB) >1.4 mmol/L; Ket group] and another 10 cows without type II ketosis (BHB ≤1.4 mmol/L; Nket group) at d 10 after calving. Serum concentrations of nonesterified fatty acids (NEFA) and BHB, as indicators of excessive fat mobilization and circulating ketone bodies, respectively, were significantly higher in the Ket group than in the Nket group. Aspartate transaminase (AST) and total bilirubin (TBIL), as indicators of liver damage, were higher in the Ket group than in the Nket group. Weighted gene co-expression network analysis (WGCNA) of the sWAT transcriptome revealed modules significantly correlated with serum BHB, NEFA, AST, TBIL, and total cholesterol. The genes in these modules were enriched in the regulation of the lipid biosynthesis process. Neurotrophic tyrosine kinase receptor type 2 (NTRK2) was identified as the key hub gene by intramodular connectivity, gene significance, and module membership. Quantitative reverse transcription PCR analyses for these samples, as well as a set of independent samples, validated the downregulation of NTRK2 expression in the sWAT of dairy cows with type II ketosis. NTRK2 encodes tyrosine protein kinase receptor B (TrkB), which is a high-affinity receptor for brain-derived neurotrophic factor, suggesting that abnormal lipid mobilization in cows with type II ketosis might be associated with impaired central nervous system regulation of adipose tissue metabolism, providing a novel insight into the pathogenesis underlying type II ketosis in dairy cows.

The Brain-Gut-Microbiota Interplay in Depression: a key to design innovative therapeutic approaches

Depression is the most prevalent mental disorder in the world associated with huge socio-economic consequences. While depressive-related symptoms are well known, the molecular mechanisms underlying disease pathophysiology and progression remain largely unknown. The gut microbiota (GM) is emerging as a key regulator of the central nervous system homeostasis by exerting fundamental immune and metabolic functions. In turn, the brain influences the intestinal microbial composition through neuroendocrine signals, within the so-called gut microbiota-brain axis. The balance of this bidirectional crosstalk is important to ensure neurogenesis, preserve the integrity of the blood-brain barrier and avoid neuroinflammation. Conversely, dysbiosis and gut permeability negatively affect brain development, behavior, and cognition. Furthermore, although not fully defined yet, changes in the GM composition in depressed patients are reported to influence the pharmacokinetics of common antidepressants by affecting their absorption, metabolism, and activity. Similarly, neuropsychiatric drugs may shape in turn the GM with an impact on the efficacy and toxicity of the pharmacological intervention itself. Consequently, strategies aimed at re-establishing the correct homeostatic gut balance (i.e., prebiotics, probiotics, fecal microbiota transplantation, and dietary interventions) represent an innovative approach to improve the pharmacotherapy of depression. Among these, probiotics and the Mediterranean diet, alone or in combination with the standard of care, hold promise for clinical application. Therefore, the disclosure of the intricate network between GM and depression will give precious insights for innovative diagnostic and therapeutic approaches towards depression, with profound implications for drug development and clinical practice.

Clinical Improvement in Depression and Cognitive Deficit Following Electroconvulsive Therapy

Electroconvulsive therapy (ECT) is a long-standing treatment choice for disorders such as depression when pharmacological treatments have failed. However, a major drawback of ECT is its cognitive side effects. While numerous studies have investigated the therapeutic effects of ECT and its mechanism, much less research has been conducted regarding the mechanism behind the cognitive side effects of ECT. As both clinical remission and cognitive deficits occur after ECT, it is possible that both may share a common mechanism. This review highlights studies related to ECT as well as those investigating the mechanism of its outcomes. The process underlying these effects may lie within BDNF and NMDA signaling. Edema in the astrocytes may also be responsible for the adverse cognitive effects and is mediated by metabotropic glutamate receptor 5 and the protein Homer1a.

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.

Neurotrophic basis to the pathogenesis of depression and phytotherapy

Depression is a major neuropsychiatric disease that considerably impacts individuals’ psychosocial function and life quality. Neurotrophic factors are now connected to the pathogenesis of depression, while the definitive neurotrophic basis remains elusive. Besides, phytotherapy is alternative to conventional antidepressants that may minimize undesirable adverse reactions. Thus, further research into the interaction between neurotrophic factors and depression and phytochemicals that repair neurotrophic factors deficit is highly required. This review highlighted the implication of neurotrophic factors in depression, with a focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF), and detailed the antidepressant activities of various phytochemicals targeting neurotrophic factors. Additionally, we presented future opportunities for novel diagnostic and therapeutic strategies for depression and provided solutions to challenges in this area to accelerate the clinical translation of neurotrophic factors for the treatment of depression.

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.

Serum brain-derived neurotrophic factor as diagnosis clue for Alzheimer's disease: A cross-sectional observational study in the elderly

Objective

Brain-derived neurotrophic factor (BDNF) has not been validated as a diagnostic marker for Alzheimer's disease (AD). To provide a different perspective, this study aimed to evaluate the relationship between serum levels of mature BDNF (mBDNF) and precursor BDNF (proBDNF) in AD and to investigate whether serum BDNF levels or the ratio of mBDNF levels to proBDNF levels (M/P) could be a valuable biomarker for determining the risk of AD in elderly individuals.

Method

A total of 126 subjects who met the inclusion criteria were assigned to either the AD group (n = 62) or the healthy control group (HC, n = 64) in this cross-sectional observationl study. Serum levels of mBDNF and proBDNF were measured using enzyme immunoassay kits. We analyzed the Mini-Mental State Examination (MMSE) scores from the two groups and examined the associations between AD and BDNF metabolism.

Results

The serum concentration of proBDNF was significantly higher in ADs (4140.937 pg/ml) than in HCs (2606.943 pg/ml; p &lt; 0.01). The MMSE significantly correlated with proBDNF (p &lt; 0.01, r = −0.686) and M/P (p &lt; 0.01, r = 0.595) in all subjects. To determine the risk for AD, the area under the receiver operating characteristic curve was calculated, which was 0.896 (95% confidence interval 0.844–0.949) for proBDNF and 0.901 (95% 0.850–0.953) for proBDNF and M/P combined.

Conclusion

We observed a correlation between low serum proBDNF levels and higher MMSE scores in AD. The most effective diagnostic strategy was the combination of proBDNF and M/P, whereas mBDNF levels performed poorly when we evaluated the predictive model.

Effects of a variable light intensity lighting program on the welfare and performance of commercial broiler chickens

Our previous variable-light intensity lighting program studies indicate the light intensity preference behavior of broilers for their daily activity including eating and resting. To evaluate the effects of variable-light intensity lighting program on performance and welfare of broilers, four commercial trials were conducted for looking at behaviors, mortality, leg-health, performance, and brain welfare indicator genes including tryptophan hydroxylase 2 and tyrosine hydroxylase (TH), glucocorticoid receptor (GR), brain-derived neurotropic factor (BDNF), and melanopsin (Opn4) gene expression. One-day-old broilers were housed in four commercial broiler houses. Each quadrant (section) of the house was placed with 4,800 chicks. A total of four lighting programs began on day 7 with 5 lux (lx), 20 lx, natural light (NL, 480 lx), and variable light (2-5/40 lx) using LED lights on a 16L:8D photoperiod. In the variable-light house, the number of dustbathing holes was significantly higher than that in natural-light houses and 5-lx and 20-lx houses. Daily physical activities, footpad condition, fear response to novel objects, body weight, feed conversion ratio, and the number of leg-problem induced culled birds were affected by the variable-light intensity lighting program. Expression of tryptophan hydroxylase 2 in the DRN and VTA of variable-light treated birds was lower than that of 5-lx- and 20-lx-treated birds on day 42 (p < 0.05). Higher expression of VTA-TH in 5-lx-treated birds than that in 20-lx-, NL-, and variable-light-treated birds suggests the high stress-susceptibility of 5-lx treated birds. Lower VTA-GR expression in 20-lx- and variable-light-treated birds indicates lower stress than that in NL- and 5-lx-treated birds (p < 0.05). The VTA-BDNF expression of NL-treated birds was 2.5 fold higher than that of 5-lx-, 20-lx-, and variable-light-treated birds (p < 0.05), and variable-light-treated birds showed the lowest level of BDNF expression (p < 0.05), suggesting the chronic social defeat stress in NL-treated birds. The result of VTA-Opn4 expression on day 42 suggests the possible role of VTA-Opn4 in broiler welfare through central light perception. Taken together, the variable-light intensity lighting program increased volunteer natural behaviors and physical activity, which may improve footpad condition and leg health of birds, consequently. Performance data including the increased daily weight gain and the lowered feed conversion ratio and results of brain welfare indicator gene expression showed the beneficial effect of the variable-light intensity lighting program on the performance and welfare of commercial broilers.

The Role of Brain-Derived Neurotrophic Factor (BDNF) in Diagnosis and Treatment of Epilepsy, Depression, Schizophrenia, Anorexia Nervosa and Alzheimer's Disease as Highly Drug-Resistant Diseases: A Narrative Review

Brain-derived neurotrophic factor (BDNF) belongs to the family of neurotrophins, which are growth factors with trophic effects on neurons. BDNF is the most widely distributed neurotrophin in the central nervous system (CNS) and is highly expressed in the prefrontal cortex (PFC) and hippocampus. Its distribution outside the CNS has also been demonstrated, but most studies have focused on its effects in neuropsychiatric disorders. Despite the advances in medicine in recent decades, neurological and psychiatric diseases are still characterized by high drug resistance. This review focuses on the use of BDNF in the developmental assessment, treatment monitoring, and pharmacotherapy of selected diseases, with a particular emphasis on epilepsy, depression, anorexia, obesity, schizophrenia, and Alzheimer's disease. The limitations of using a molecule with such a wide distribution range and inconsistent method of determination are also highlighted.

Neurotrophins in the Neuropathophysiology, Course, and Complications of Obstructive Sleep Apnea-A Narrative Review

Obstructive sleep apnea (OSA) is a disorder characterized by chronic intermittent hypoxia and sleep fragmentation due to recurring airway collapse during sleep. It is highly prevalent in modern societies, and due to its pleiotropic influence on the organism and numerous sequelae, it burdens patients and physicians. Neurotrophins (NTs), proteins that modulate the functioning and development of the central nervous system, such as brain-derived neurotrophic factor (BDNF), have been associated with OSA, primarily due to their probable involvement in offsetting the decline in cognitive functions which accompanies OSA. However, NTs influence multiple aspects of biological functioning, such as immunity. Thus, extensive evaluation of their role in OSA might enlighten the mechanism behind some of its elusive features, such as the increased risk of developing an immune-mediated disease or the association of OSA with cardiovascular diseases. In this review, we examine the interactions between NTs and OSA and discuss their contribution to OSA pathophysiology, complications, as well as comorbidities.

Effects of a Single Bout of Endurance Exercise on Brain-Derived Neurotrophic Factor in Humans: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

We aimed to investigate the impact of a single bout of endurance exercise on the brain-derived neurotrophic factor (BDNF) in humans and analyze how a single bout of endurance exercise impacts the peripheral BDNF types by age group. We performed a systematic literature review by searching PubMed, Elsevier, and Web of Science for studies that included a single bout of endurance exercise in the experimental group and other exercise types in the control group. Eight interventions were included in the study. Overall, a single bout of endurance exercise significantly increased BDNF expression (SMD = 0.30; 95% CI = [0.08, 0.52]; p = 0.001), which was confirmed in the serum BDNF (SMD = 0.30; 95% CI = [0.04, 0.55]; p < 0.001). A non-significant trend was observed in the plasma BDNF (SMD = 0.31; 95% CI = [−0.13, 0.76]; p = 0.017). The serum and plasma BDNF levels significantly increased regardless of age (SMD = 0.35; 95% CI = [0.11, 0.58]; p = 0.004; I2 = 0%). In conclusion, a single bout of endurance exercise significantly elevates BDNF levels in humans without neurological disorders, regardless of age. The serum BDNF is a more sensitive index than the plasma BDNF in evaluating the impact of a single bout of endurance exercise on the BDNF.

Effects of a variable light intensity lighting program on the welfare and performance of commercial broiler chickens

Our previous variable-light intensity lighting program studies indicate the light intensity preference behavior of broilers for their daily activity including eating and resting. To evaluate the effects of variable-light intensity lighting program on performance and welfare of broilers, four commercial trials were conducted for looking at behaviors, mortality, leg-health, performance, and brain welfare indicator genes including tryptophan hydroxylase 2 and tyrosine hydroxylase (TH), glucocorticoid receptor (GR), brain-derived neurotropic factor (BDNF), and melanopsin (Opn4) gene expression. One-day-old broilers were housed in four commercial broiler houses. Each quadrant (section) of the house was placed with 4,800 chicks. A total of four lighting programs began on day 7 with 5 lux (lx), 20 lx, natural light (NL, 480 lx), and variable light (2-5/40 lx) using LED lights on a 16L:8D photoperiod. In the variable-light house, the number of dustbathing holes was significantly higher than that in natural-light houses and 5-lx and 20-lx houses. Daily physical activities, footpad condition, fear response to novel objects, body weight, feed conversion ratio, and the number of leg-problem induced culled birds were affected by the variable-light intensity lighting program. Expression of tryptophan hydroxylase 2 in the DRN and VTA of variable-light treated birds was lower than that of 5-lx- and 20-lx-treated birds on day 42 (p < 0.05). Higher expression of VTA-TH in 5-lx-treated birds than that in 20-lx-, NL-, and variable-light-treated birds suggests the high stress-susceptibility of 5-lx treated birds. Lower VTA-GR expression in 20-lx- and variable-light-treated birds indicates lower stress than that in NL- and 5-lx-treated birds (p < 0.05). The VTA-BDNF expression of NL-treated birds was 2.5 fold higher than that of 5-lx-, 20-lx-, and variable-light-treated birds (p < 0.05), and variable-light-treated birds showed the lowest level of BDNF expression (p < 0.05), suggesting the chronic social defeat stress in NL-treated birds. The result of VTA-Opn4 expression on day 42 suggests the possible role of VTA-Opn4 in broiler welfare through central light perception. Taken together, the variable-light intensity lighting program increased volunteer natural behaviors and physical activity, which may improve footpad condition and leg health of birds, consequently. Performance data including the increased daily weight gain and the lowered feed conversion ratio and results of brain welfare indicator gene expression showed the beneficial effect of the variable-light intensity lighting program on the performance and welfare of commercial broilers.

Hyperactive neuronal autophagy depletes BDNF and impairs adult hippocampal neurogenesis in a corticosterone-induced mouse model of depression

Background: Depression is a mental disorder that poses a serious threat to human health. Adult hippocampal neurogenesis (AHN) is closely associated with the efficacy of antidepressants. Chronic treatment with corticosterone (CORT), a well-validated pharmacological stressor, induces depressive-like behaviors and suppresses AHN in experimental animals. However, the possible mechanisms of chronic CORT action remain elusive. Methods: A chronic CORT treatment (0.1 mg/mL, drinking water for 4 weeks) was applied to prepare a mouse model of depression. Immunofluorescence was performed to analyze the hippocampal neurogenesis lineage, and immunoblotting, immunofluorescence, electron microscopy, and adeno-associated virus (AAV) expressing a pH-sensitive tandemly tagged light chain 3 (LC3) protein were used to analyze neuronal autophagy. AAV-hSyn-miR30-shRNA was used to knock down autophagy-related gene 5 (Atg5) expression in the neurons. Results: Chronic CORT induces depressive-like behaviors and decreases the expression of neuronal brain-derived neurotrophic factor (BDNF) in the dentate gyrus (DG) of the hippocampus in mice. Moreover, it markedly diminishes the proliferation of neural stem cells (NSCs), neural progenitor cells, and neuroblasts and impairs the survival and migration of newborn immature and mature neurons in the DG, which may be attributed to changes in the cell cycle kinetics and induction of NSCs apoptosis. Furthermore, chronic CORT induces hyperactive neuronal autophagy in the DG, possibly by increasing the expression of ATG5 and causing excess lysosomal degradation of BDNF in neurons. Notably, inhibiting hyperactive neuronal autophagy in the DG of mice by knocking down Atg5 in neurons using RNA interference reverses the decrease of neuronal BDNF expression, rescues AHN, and exerts antidepressant effects. Conclusion: Our findings reveal a neuronal autophagy-dependent mechanism that links chronic CORT to reduced neuronal BDNF levels, AHN suppression and depressive-like behavior in mice. In addition, our results provide insights for treating depression by targeting neuronal autophagy in the DG of the hippocampus.

Effect of short-term, high-dose probiotic supplementation on cognition, related brain functions and BDNF in patients with depression: a secondary analysis of a randomized controlled trial

BACKGROUND

In major depressive disorder (MDD), cognitive dysfunctions strongly contribute to functional impairments but are barely addressed in current therapies. Novel treatment strategies addressing cognitive symptoms in depression are needed. As the gut microbiota-brain axis is linked to depression and cognition, we investigated the effect of a 4-week high-dose probiotic supplementation on cognitive symptoms in depression.

METHODS

This randomized controlled trial included 60 patients with MDD, of whom 43 entered modified intention-to-treat analysis. A probiotic supplement or indistinguishable placebo containing maltose was administered over 31 days in addition to treatment as usual for depression. Participant scores on the Verbal Learning Memory Test (VLMT), Corsi Block Tapping Test, and both Trail Making Test versions as well as brain-derived neurotrophic factor levels were assessed at 3 different time points: before, immediately after and 4 weeks after intervention. Additionally, brain activation changes during working memory processing were investigated before and immediately after intervention.

RESULTS

We found a significantly improved immediate recall in the VLMT in the probiotic group immediately after intervention, and a trend for a time × group interaction considering all time points. Furthermore, we found a time × group interaction in hippocampus activation during working memory processing, revealing a remediated hippocampus function in the probiotic group. Other measures did not reveal significant changes.

LIMITATIONS

The modest sample size resulting from our exclusion of low-compliant cases should be considered.

CONCLUSION

Additional probiotic supplementation enhances verbal episodic memory and affects neural mechanisms underlying impaired cognition in MDD. The present findings support the importance of the gut microbiota-brain axis in MDD and emphasize the potential of microbiota-related regimens to treat cognitive symptoms in depression.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov identifier NCT02957591.

Polygonatum sibiricum ameliorated cognitive impairment of naturally aging rats through BDNF-TrkB signaling pathway

Cognitive dysfunction is high in the elderly population and seriously affects the quality of life. Brain-derived neurotrophic factor (BDNF) is one of the key neurotrophic proteins, and activation of BDNF-TrkB is considered an effective strategy to improve cognitive dysfunction during aging. In this study, administration of polygonatum sibiricum (PS) for 5 months effectively ameliorates the cognitive function, improving the Nissl body state in cortex and hippocampus in aging rats. In addition, PS can improve the synaptic structure and increase the number of synapses. Furthermore, PS reverses the reduction of synaptic plasticity-related proteins postsynaptic density protein 95 (PSD-95) and synaptophysin during aging and up-regulates the expression of BDNF-TrkB. In conclusion, PS improves cognitive dysfunction and enhances synaptic plasticity in naturally aged rats by regulating the BDNF-TrkB signaling pathway. PS has the potential to be developed as a novel and promising functional health food for the elderly. PRACTICAL APPLICATIONS: Polygonatum sibiricum (PS) is a traditional Chinese medicine, which has been included in the homologous plant of medicine and food. PS has been widely used to treat lung diseases, diabetes and antiaging in clinical. Studies have confirmed that PS can accelerate the repair and regeneration of damaged neurons, reverse the changes in synaptic structure, and improve the ability of learning and memory. Our study confirmed that PS significantly improved the cognitive function in aging rats. PS has great potential to be developed as a functional food for improving neurological function and anti-aging.

ERK1/2-dependent BDNF synthesis and signaling is required for the antidepressant effect of microglia stimulation

Depressed mice have lower numbers of microglia in the dentate gyrus (DG). Reversal of this decline by a single low dose of lipopolysaccharide (LPS) may have antidepressant effects, but there is little information on the molecular mechanisms underlying this effect. It is known that impairment of brain-derived neurotrophic factor (BDNF) signaling is involved in the development of depression. Here, we used a combination of neutralizing antibodies, mutant mice, and pharmacological approaches to test the role of BDNF-tyrosine kinase receptor B (TrkB) signaling in the DG in the effect of microglial stimulation. Our results suggest that inhibition of BDNF signaling by infusion of an anti-BDNF antibody, the BDNF receptor antagonist K252a, or knock-in of the mutant BDNF Val68Met allele abolished the antidepressant effect of LPS in chronically stressed mice. Increased BDNF synthesis in DG, mediated by extracellular signal-regulated kinase1/2 (ERK1/2) signaling but not protein kinase B (Akt)-mammalian target of rapamycin (mTOR) signaling, was essential for the antidepressant effect of microglial stimulation. These results suggest that increased BDNF synthesis through activation of ERK1/2 caused by a single LPS injection and subsequent TrkB signaling are required for the antidepressant effect of hippocampal microglial stimulation.

Association between plasma levels of BDNF and GDNF and the diagnosis, treatment response in first-episode MDD

INTRODUCTION

The aims of our study are: i) to explore whether plasma levels of BDNF/GDNF are valuable in the diagnosis of first-episode depression; ii) to discuss whether there is an association between peripheral plasma levels of BDNF/GDNF and patients' depression severity and cognitive dysfunction; iii) to explore the association between plasma levels of BDNF/GDNF and the effectiveness of antidepressant treatment.

METHODS

Ninety patients with first-episode unmedicated MDD and healthy controls were recruited. MDD patients were treated with antidepressant medication for 8 weeks. Patients were assessed for clinical symptoms using HDRS-17 and HAMA-14. Social and neurocognitive functioning of all subjects was assessed at baseline using the Functional Assessment Test Short Form (FAST) and the MATRICS Consensus Cognitive Battery (MCCB). At the same time, peripheral venous blood was drawn from all subjects for BDNF/GDNF peripheral plasma level analysis at baseline and after 8 weeks of treatment.

RESULTS

The baseline BDNF/GDNF levels in MDD patients were significantly lower than that in healthy controls. The area under ROC curve (AUC) of baseline plasma BDNF and GDNF levels predicting MDD was 0.776 (95 % CI: 0.705-0.846, p < 0.001) and 0.864 (95 % CI: 0.808-0.920, p < 0.001), respectively. The baseline GDNF level (beta = 0.425, p = 0.001), the autonomy score of FAST (beta = -0.247, p = 0.037) and BACS-SC score of MCCB (beta = 0.323, p = 0.039) were predictors of HDRS-17 reduction rate after 8 weeks' antidepressant treatment.

LIMITATIONS

A longer follow-up period than 8 weeks may make the results more convincing, and the sample size of this study is still insufficient.

CONCLUSION

The decreased plasma levels of BDNF and GDNF are strong indicators for predicting the occurrence of MDD. This preliminary finding highlighted the value of GDNF plasma concentrations in the diagnosis of MDD and the prognosis of antidepressant treatment.

Depression in Adolescence and Brain-Derived Neurotrophic Factor

The incidence of depression among adolescents has been rapidly increasing in recent years. Environmental and genetic factors have been identified as important risk factors for adolescent depression. However, the mechanisms underlying the development of adolescent depression that are triggered by these risk factors are not well understood. Clinical and preclinical studies have focused more on adult depression, and differences in depressive symptoms between adolescents and adults make it difficult to adequately diagnose and treat adolescent depression. Brain-derived neurotrophic factor (BDNF) is known to play a critical role in the pathophysiology of many psychiatric disorders, including depression. However, there are still few studies on adolescent depression. Therefore, in this review paper, the causes and treatment of adolescent depression and the function of BDNF are investigated.

Brain-derived neurotrophic factor in war veterans with or without a history of suicide attempt

BACKGROUND

Brain-derived neurotrophic factor (BDNF) plays a central role in brain development and plasticity and has been demonstrated to be altered in neuropsychiatric diseases and suicidal behavior. We examined whether there is a difference with regard to plasma BDNF levels between veterans who made or did not make a suicide attempt post-deployment.

METHODS

Combat veterans who made or did not make post-deployment suicide attempts were interviewed using Mini-International Neuropsychiatric Interview, the Montgomery-Åsberg Depression Rating Scale, the Barratt Impulsivity Scale (BIS) and the Scale for Suicidal Ideation (SSI). Reaction to the most recent suicide attempt was evaluated using item 16 of the Suicide Intent Scale. Plasma BDNF levels were determined by the BDNF ELISA kit.

RESULTS

Controlling for age and body-mass index (BMI), BDNF levels were higher among suicide attempters than non-attempters. We observed a positive correlation between BDNF levels and SSI scores among non-attempters but not among attempters. BDNF levels positively correlated with BIS scores among suicide attempters but not among non-attempters. Suicide attempters who regretted that they made a suicide attempt had significantly higher BDNF levels in comparison to attempters who did not regret their attempts, controlling or not controlling for age and BMI.

LIMITATIONS

A modest sample size is a shortcoming of our study.

CONCLUSIONS

Our study demonstrates that BDNF may be involved in the pathophysiology of suicidal behavior in combat veterans. Given the relative ease of measuring plasma BDNF levels, it may be appropriate to consider adding such assessments to studies of suicidal behavior.

Clinical Value of Inflammatory and Neurotrophic Biomarkers in Bipolar Disorder: A Systematic Review and Meta-Analysis

Bipolar disorder (BD) is a multifactorial chronic psychiatric disease highly defined by genetic, clinical, environmental and social risk factors. The present systematic review and meta-analysis aimed to examine the relationship between inflammatory and neurotrophic factors and clinical, social and environmental factors involved in the development and the characterization of BD. Web of Science, PubMed, PsycINFO, Scopus and Science Direct were searched by two independent reviewers. The systematic review was registered in PROSPERO (CRD42020180626). A total of 51 studies with 4547 patients with a diagnosis of BD were selected for systematic review. Among them, 18 articles were included for meta-analysis. The study found some evidence of associations between BDNF and/or inflammatory factors and different stressors and functional and cognitive impairment, but limitations prevented firm conclusions. The main finding of the meta-analysis was a negative correlation between circulating levels of BDNF and depression severity score (standardized mean difference = −0.22, Confidence Interval 95% = −0.38, −0.05, p = 0.01). Evidence indicates that BDNF has a role in the depressive component of BD. However, the poor consistency found for other inflammatory mediators clearly indicates that highly controlled studies are needed to identity precise biomarkers of this disorder.