Association of serum brain derived neurotropic factor with duration of drug-naive period and positive-negative symptom scores in drug naive schizophrenia

Brain-derived neurotrophic factor (BDNF): an effect biomarker of neurodevelopment in human biomonitoring programs

The present narrative review summarizes recent findings focusing on the role of brain-derived neurotrophic factor (BDNF) as a biomarker of effect for neurodevelopmental alterations during adolescence, based on health effects of exposure to environmental chemical pollutants. To this end, information was gathered from the PubMed database and the results obtained in the European project Human Biomonitoring for Europe (HBM4EU), in which BDNF was measured at two levels of biological organization: total BDNF protein (serum) and BDNF gene DNA methylation (whole blood) levels. The obtained information is organized as follows. First, human biomonitoring, biomarkers of effect and the current state of the art on neurodevelopmental alterations in the population are presented. Second, BDNF secretion and mechanisms of action are briefly explained. Third, previous studies using BDNF as an effect biomarker were consulted in PubMed database and summarized. Finally, the impact of bisphenol A (BPA), metals, and non-persistent pesticide metabolites on BDNF secretion patterns and its mediation role with behavioral outcomes are addressed and discussed. These findings were obtained from three pilot studies conducted in HBM4EU project. Published findings suggested that exposure to some chemical pollutants such as fine particle matter (PM), PFAS, heavy metals, bisphenols, and non-persistent pesticides may alter circulating BDNF levels in healthy population. Therefore, BDNF could be used as a valuable effect biomarker to investigate developmental neurotoxicity of some chemical pollutants.

Serum total cholesterol levels associated with immediate memory performance in patients with chronic schizophrenia

Cognitive impairments are common in patients with schizophrenia. Changes in total cholesterol (TC) may be involved in the development of schizophrenia and associated with cognitive function. This study aimed to investigate differences in serum TC level and cognitive function between schizophrenia patients and healthy controls and explore the relationship between serum TC level and cognitive function in patients with schizophrenia. A total of 105 schizophrenia patients and 105 healthy controls were recruited. Results showed that patients with schizophrenia had significantly lower scores on the overall RBANS scale and subscales (i.e., immediate memory, language, attention, and delayed memory) than those of healthy controls. Pearson's correlation analyses showed that in patients with schizophrenia, serum TC levels were positively associated with RBANS subscale scores of immediate memory and language. Furthermore, multivariate regression analyses showed that serum TC level was positively associated with the immediate memory index in patients with schizophrenia. However, no significant association was found between serum TC level and RBANS score in the healthy control group. Our results suggest that elevated serum TC level may be related to improved cognitive function in patients with schizophrenia, especially that of immediate memory.

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.

BDNF, proBDNF and IGF-1 serum levels in naïve and medicated subjects with autism

Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1) promote the development and maintenance of neural circuits. Alterations in these factors might contribute to autism spectrum disorder (ASD). We asked whether serum BDNF, proBDNF, and IGF-1 levels are altered in an ASD population compared to controls. We measured serum BDNF, proBDNF, and IGF-1 immunoreactive protein in boys and girls aged 5–15 years old with mild to moderate ASD and non-autistic controls by ELISA. IGF-1 was increased in ASD serum compared to controls and was correlated with age and with CARS scores. Serum BDNF levels did not differ between groups, however, proBDNF serum levels were decreased in subjects with ASD compared to non-autistic controls. Medicated, but not unmedicated, ASD subjects exhibited lower serum proBDNF levels compared to controls, while neither IGF-1 nor BDNF levels differed between treatment groups. These data support the involvement of proBDNF and IGF-1 in the pathogenesis and treatment of autism.

The mediating effect of brain-derived neurotrophic factor levels on childhood trauma and psychiatric symptoms in patients with first-episode schizophrenia

BACKGROUND

Previous studies have implicated childhood trauma and abnormal brain-derived neurotrophic factor in the pathogenesis of schizophrenia. Here, we explored whether brain-derived neurotrophic factor levels mediated the relationship between childhood trauma and psychopathological symptoms in patients with first-episode schizophrenia.

METHODS

Patients with first-episode schizophrenia (n = 192) and healthy controls (n = 136) were enrolled. Childhood traumatic experiences and psychopathology were assessed by Childhood Trauma Questionnaire and Positive and Negative Syndrome Scale, respectively. Enzyme-linked immunosorbent assay was used to quantify brain-derived neurotrophic factor levels.

RESULTS

The patients with first-episode schizophrenia experienced more severe childhood trauma and had lower serum brain-derived neurotrophic factor levels than healthy controls. Emotional abuse and Childhood Trauma Questionnaire total score showed positive correlation with Positive and Negative Syndrome Scale positive, general psychopathological subscore and total score. Emotional neglect showed positive correlation with Positive and Negative Syndrome Scale positive subscore. Physical neglect was positively associated with Positive and Negative Syndrome Scale negative subscore. Emotional neglect and Childhood Trauma Questionnaire total score were negatively correlated with serum brain-derived neurotrophic factor levels. The serum brain-derived neurotrophic factor levels mediated the relationship between both Childhood Trauma Questionnaire total score and Positive and Negative Syndrome Scale total score and negative symptoms in the patients. The brain-derived neurotrophic factor levels also mediated the relationship between emotional neglect and Positive and Negative Syndrome Scale total score in the patients.

CONCLUSION

Childhood trauma might contribute to the clinical symptoms of schizophrenia by affecting brain-derived neurotrophic factor levels. Perhaps we can prevent schizophrenia by reducing childhood traumatic experiences.

The role of BDNF and NGF plasma levels in first-episode schizophrenia: A longitudinal study

Neurotrophins have been proposed to be involved in biological mechanisms which might underlie different clinical outcomes in schizophrenia. The aims of the present study were to examine the BDNF/NGF plasma levels in a cohort of first-episode schizophrenia (FES) patients in remission as potential biological predictors of relapse; to study the associations between these neurotrophins and the symptomatology severity through different stages after a FES in two independent cohorts. 2EPs-Cohort: 69 first-episode in clinical remission were included. BDNF/NGF plasma levels and symptom severity were measured at enrollment and at 3-year or at the time of the second episode/relapse. FLAMM-PEPs-Cohort: 65 first-episodes were also included. BDNF/NGF and symptom severity were obtained at enrollment and 2-year follow-up. Symptomatology was assessed with the Marder-PANSS-Factor scores. Plasma neurotrophins did not differ significantly over time and neither BDNF/NGF were predictors of relapse. Besides, in remission stages, baseline BDNF levels showed significant correlations with both positive and negative symptoms (p<0.05); NGF, with negative symptomatology (p<0.01). Similarly, in the FLAMM-PEPs-Cohort, baseline BDNF/NGF levels showed significant correlations with negative symptoms (and not positive symptomatology) at follow-up (p<0.05). In both cohorts, lower levels correlated with higher symptom severity. Findings did not support a role for BDNF/NGF plasma levels as biomarkers of relapse in FES patients. Nevertheless, baseline BDNF/NGF may lead to be considered potentially useful biomarkers of long-term severity in schizophrenia and of the underlying illness traits, specially of negative symptomatology severity. More longitudinal studies in FES samples and adding a control group are warranted to replicate these findings.

Peripheral Blood Levels of Brain-Derived Neurotrophic Factor in Patients with First Episode Psychosis: A Systematic Review and Meta-Analysis

Background: Peripheral blood level of brain-derived neurotrophic factor (BDNF) may be used as a diagnostic and/or prognostic marker for schizophrenia. Previous studies were inconsistent. A systematic review was conducted to examine whether BDNF level is different in patients with first episode psychosis (FEP) compared to health controls (HC) and whether it changes after treatment. Methods: Literature search was done in PubMed, Web of Science, and Google Scholar following standard procedures. Hedges’ g was used as the measure of effect size (ES), which was pooled with random effects model. Publication bias and moderator effects were examined. Results: Search yielded 29 studies with a total sample size of 2912. First meta-analysis included 27 studies with FEP vs. HC comparison. Pooled ES was −0.63, p < 0.001, indicating that BDNF level was lower in FEP than in HC. Studies were heterogeneous, and moderator analysis showed that studies of younger patient, higher symptom severity, and more drug naïve had larger ES. Second meta-analysis examined change in BDNF levels before and after antipsychotic treatment in eight studies. A pooled ES of −0.003 (p = 0.96) showed no change in peripheral BDNF level after treatment. Conclusion: Peripheral BDNF level was decreased in FEP compared to HC, but it did not change after treatment.

Association of BDNF and MMP-9 single-nucleotide polymorphisms with the clinical phenotype of schizophrenia

OBJECTIVE

Schizophrenia is a highly polygenic psychiatric disorder; however, the complex genetic architecture underlying the pathogenesis remains elusive. Brain-derived neurotrophic factor (BDNF), a neurotrophin, and matrix metalloproteinase 9 (MMP-9), a gelatinase B, are the promising candidate genes for schizophrenia. To shed new light on the relationship between the single-nucleotide polymorphisms (SNPs) of BDNF and MMP-9 and the clinical variability of schizophrenia phenotype, this study aims to evaluate the relationship, and provide more definitive evidence for the relationship with various clinical features of schizophrenia.

METHODS

A case-control association study was performed, and one hundred and five subjects of Chinese Han population were enrolled, including 55 schizophrenia patients (SP) and 50 healthy controls (HC). The BDNF rs6265 196 G > A and MMP-9 rs3918242 -1562C > T SNPs were genotyped using PCR-RFLP assay. The Positive and Negative Syndrome Scale (PANSS) was used to assess the clinical symptoms of patients with schizophrenia.

RESULTS

Compared with HC, the frequency of SP carrying BDNF rs6265 GG/GA genotype was significantly higher than HC, and the frequency of SP carrying BDNF rs6265 AA genotype was significantly lower than HC (p < 0.01). With regards to MMP-9 rs3918242 -1562C > T SNP, no significant difference was observed between the control and SP. BDNF GG genotype showed significantly higher PANSS and positive symptoms score than GA and AA genotypes (P < 0.01). MMP-9 CC genotype showed significantly higher PANSS and general score than CT and TT genotypes (P < 0.05).

CONCLUSION

BDNF rs6265 196 G > A and MMP-9 rs3918242-1562C > T SNPs are related to the clinical features of schizophrenia and could be a useful biomarker for the changes, remission or deterioration of clinical status of schizophrenia.

Association of Glial Cell-Line Derived Neurotrophic Factor and Nerve Growth Factor with Duration of Untreated Psychosis and Clinical Symptoms in Drug-Naive Schizophrenia

Background

The neurodevelopmental hypothesis is one of the most-emphasized hypotheses in the etiology of schizophrenia. Nerve growth factor (NGF) and glial cell-line derived neurotropic factor (GDNF) are neurotrophic factors that provide growth, differentiation, and survival in nerve cells in the development process. In this study, we aimed to compare the GDNF and NGF levels of schizophrenia patients with healthy controls and to analyze the relationship between the Positive and Negative Syndrome Scale (PANSS) scores, serum GDNF and NGF levels and the duration of untreated psychosis (DUP) of the patients.

Methods

The study involved 45 patients with a diagnosis of schizophrenia, who had never used any antipsychotic drug, and 45 age- and sex-matched healthy participants. The participants filled a sociodemographic data form. The PANSS was applied to evaluate the clinical conditions. Before the initiation of the treatment, serum samples were collected from the patients.

Results

The difference between the GDNF and NGF levels of the patient group and control group was statistically significant. The serum GDNF and NGF levels in schizophrenia patients were lower than healthy controls. No correlation was found between the DUP and serum GDNF and NGF levels. There was a positive correlation between general psychopathology and negative scores of PANSS and the DUP of patients.

Conclusion

GDNF and NGF levels seem to be indicators of schizophrenia and its progress; nevertheless, we still do not have sufficient information about these neurotrophic factors. The results of our study indicate that the neurodevelopmental changes occurring at the early stages of the illness prominently affect the progress of disease, highlighting the importance of treatment in the early stages of disease.

BDNF in antipsychotic naive first episode psychosis: Effects of risperidone and the immune-inflammatory response system

Brain-derived neurotrophic factor (BDNF) and the immune-inflammatory response system (IRS) have been implicated in the pathophysiology of schizophrenia. However, no research examined the associations between BDNF and immune activation both before and after treatment in antipsychotic-naïve first episode psychosis (AN-FEP). This study aims to examine serum BDNF levels and their association with IRS and the compensatory immune-regulatory reflex system (CIRS) in AN-FEP before and after risperidone treatment. We included 31 AN-FEP and 22 healthy controls. AN-FEP showed reduced levels of BDNF as compared to controls, and BDNF levels normalized after treatment with risperidone. BDNF levels were inversely correlated with a greater IRS response. Higher levels of IRS/CIRS biomarkers were associated with lower levels of BDNF including M1 macrophage, T-helper (Th)-1, Th-2, and Th-17, and T-regulatory (Treg) cell responses. Our findings indicate that AN-FEP is characterized by decreased levels of BDNF, which are normalized after treatment with risperidone. BDNF levels were inversely associated with activated immune-inflammatory pathways. The findings support the hypothesis that, increased IRS is linked to neurotoxicity, and that a decrease in BDNF may be part of the IRS/CIRS responses in FEP and, thus, be involved in the development of psychosis.

The Role of the Second Extracellular Loop of Norepinephrine Transporter, Neurotrophin-3 and Tropomyosin Receptor Kinase C in T Cells: A Peripheral Biomarker in the Etiology of Schizophrenia

The neurobiology of schizophrenia is multifactorial, comprising the dysregulation of several biochemical pathways and molecules. This research proposes a peripheral biomarker for schizophrenia that involves the second extracellular loop of norepinephrine transporter (NEText), the tropomyosin receptor kinase C (TrkC), and the neurotrophin-3 (NT-3) in T cells. The study of NEText, NT-3, and TrkC was performed in T cells and plasma extracted from peripheral blood of 54 patients with schizophrenia and 54 healthy controls. Levels of NT-3, TrkC, and NET were significantly lower in plasma and T cells of patients compared to healthy controls. Co-immunoprecipitation (co-IPs) showed protein interactions with Co-IP NEText–NT-3 and Co-IP NEText–TrkC. Computational modelling of protein–peptide docking by CABS-dock provided a medium–high accuracy model for NT-3–NEText (4.6935 Å) and TrkC–NEText (2.1365 Å). In summary, immunocomplexes reached statistical relevance in the T cells of the control group contrary to the results obtained with schizophrenia. The reduced expression of NT-3, TrkC, and NET, and the lack of molecular complexes in T cells of patients with schizophrenia may lead to a peripheral dysregulation of intracellular signaling pathways and an abnormal reuptake of norepinephrine (NE) by NET. This peripheral molecular biomarker underlying schizophrenia reinforces the role of neurotrophins, and noradrenergic and immune systems in the pathophysiology of schizophrenia.

Association of circulating BDNF levels with BDNF rs6265 polymorphism in schizophrenia

Schizophrenia is a severe neuropsychiatric disorder affecting 1% of the world population. Disturbances in neuronal development and synaptic connections are important factors in the pathogenesis of schizophrenia. Brain derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays a critical role in the development of neurons. Among several polymorphisms reported in BDNF, the rs6265 polymorphism is known to be associated with many neuropsychiatric diseases. This study was aimed to determine the effect of BDNF rs6265 functional polymorphism on serum BDNF concentration in patients with schizophrenia. In total, 50 schizophrenia patients and 50 controls were recruited after obtaining written informed consent. Serum BDNF levels were estimated using the ELISA method and BDNF rs6265 polymorphism was genotyped using T-ARMS PCR. Serum BDNF levels were decreased significantly in schizophrenia patients when compared to the healthy controls (p < 0.0001). Further, the rs6265 polymorphism was also not associated with the schizophrenia (p = 0.41). Intragroup analysis between different genotypes revealed no association between the serum BDNF levels and rs6265 polymorphism. Our results suggest that the functional polymorphism rs6265 is not associated with serum BDNF levels, which is in line with previous findings, which indicates that serum BDNF levels depend more on diagnostic effect than genetic effect. Replication studies on a larger study population are needed.

MicroRNA Alterations in Induced Pluripotent Stem Cell-Derived Neurons from Bipolar Disorder Patients: Pathways Involved in Neuronal Differentiation, Axon Guidance, and Plasticity

Bipolar disorder (BP) is a complex psychiatric condition characterized by severe fluctuations in mood for which underlying pathological mechanisms remain unclear. Family and twin studies have identified a hereditary component to the disorder, but a single causative gene (or set of genes) has not been identified. MicroRNAs (miRNAs) are small, noncoding RNAs ∼20 nucleotides in length, that are responsible for the posttranslational regulation of multiple genes. They have been shown to play important roles in neural development as well as in the adult brain, and several miRNAs have been reported to be dysregulated in postmortem brain tissue isolated from bipolar patients. Because there are no viable cellular models to study BP, we have taken advantage of the recent discovery that somatic cells can be reprogrammed to pluripotency then directed to form the full complement of neural cells. Analysis of RNAs extracted from Control and BP patient-derived neurons identified 58 miRNAs that were differentially expressed between the two groups. Using quantitative polymerase chain reaction we validated six miRNAs that were elevated and two miRNAs that were expressed at lower levels in BP-derived neurons. Analysis of the targets of the miRNAs indicate that they may regulate a number of cellular pathways, including axon guidance, Mapk, Ras, Hippo, Neurotrophin, and Wnt signaling. Many are involved in processes previously implicated in BP, such as cell migration, axon guidance, dendrite and synapse development, and function. We have validated targets of several different miRNAs, including AXIN2, BDNF, RELN, and ANK3 as direct targets of differentially expressed miRNAs using luciferase assays. Identification of pathways altered in patient-derived neurons suggests that disruption of these regulatory networks that may contribute to the complex phenotypes in BP.

Elevated brain-derived neurotrophic factor (BDNF) serum levels in an acute episode of schizophrenia in polish women: Correlation with clinical and metabolic parameters

Brain-derived neurotrophic factor (BDNF) has been implicated in the pathogenesis of psychiatric disorders. Schizophrenia is associated with metabolic abnormalities and BDNF regulates energy homeostasis and glucose metabolism in peripheral tissues. The aim of this study was to examine serum levels of BDNF in schizophrenic women during 8 weeks of treatment and control group, and its correlation with clinical and metabolic parameters. The study was performed on a group of 96 women: 55 diagnosed with paranoid schizophrenia according to DSM-IV criteria, and 41 healthy controls. Positive and Negative Syndrome Scale (PANSS) was used to assess the severity of schizophrenia. BDNF serum levels and metabolic parameters: fasting serum glucose, total cholesterol, triglyceride (TG), high-density lipoprotein (HDL-C), low-density lipoprotein (LDL-C) were measured at baseline and week 8 of treatment. BDNF serum levels were significantly elevated in medicated patients with schizophrenia comparing to controls. After 8 weeks of antipsychotic treatment, BDNF levels did not significantly change. Increase in TG and TG/HDL-C ratio and a decrease in HDL-C was detected in medicated patients. Correlation between BDNF and lipid profile as well as symptoms severity was found. In our study we detected abnormalities in BDNF levels and lipid profile in medicated schizophrenic women in Polish population.

The neurobiological hypothesis of neurotrophins in the pathophysiology of schizophrenia: A meta-analysis

BACKGROUND

Schizophrenia is associated with patterns of aberrant neurobiological circuitry. The disease complexity is mirrored by multiple biological interactions known to contribute to the disease pathology. One potential contributor is the family of neurotrophins which are proteins involved in multiple functional processes in the nervous system, with crucial roles in neurodevelopment, synaptogenesis and neuroplasticity. With these roles in mind, abnormal neurotrophin profiles have been hypothesized to contribute to the pathology of schizophrenia.

METHODS

We performed a systematic review and a meta-analysis to scrutinize the neurobiological hypothesis of neurotrophins in schizophrenia, examining the correlation between peripheral levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin 4/5 (NT-4/5) associated with schizophrenia.

RESULTS

Fifty-two studies were reviewed and twenty-two studies were included in this meta-analysis. Using a random effects model, we confirmed that decreased levels of neurotrophins (BDNF, NGF and NT-4/5) were associated with schizophrenia (Hedges's g = -0.846; SE = 0.058; 95% confidence interval: -0.960 to -0.733; Z-value = -14.632; p-value = 0.000). Subgroup analysis indicated that neurotrophin levels are significantly decreased in both medicated and drug-näive patients. Meta-regression of continuous variables such as mean age, duration of illness and PANSS total score did not show significant effects (p > 0.05) in relation to neurotrophins levels.

DISCUSSION

We confirm that decreased peripheral neurotrophin levels are significantly associated with schizophrenia, thereby confirming the neurobiological hypothesis of neurotrophins in schizophrenia. Low levels of neurotrophins in peripheral blood of patients with schizophrenia may explain, in part, the pathophysiology of schizophrenia.