Transport of brain-derived neurotrophic factor across the blood-brain barrier

Neuro-developmental outcome and brain-derived neurotrophic factor level in relation to feeding practice in early infancy

This study was designed to assess brain-derived neurotrophic factor (BDNF) as a possible candidate for enhanced cognition in breastfed infants. The study was conducted on 42 infants, 4-6 months old, who were classified according to their feeding pattern into breastfed group, formula-fed group and mixed-feeding group. Each infant was subjected to history taking, clinical examination, estimation of the level of BDNF by Enzyme-Linked Immunosorbent Assay (ELISA) technique and assessment by Bayley scale of infant development-second edition (BSID-II). The current study revealed that breastfed group had higher BSID-II scores followed by mixed-fed group then formula-fed one, yet these results reached statistical significance only in total behaviour rating scale (TBRS) and Motor Quality Percentile rank values. Additionally, breastfed infants had significantly higher values of BDNF when compared to those receiving formula milk. Negative correlations between BDNF and both weight for age and weight for length scores were detected. Furthermore, significant positive correlation was detected between BDNF and TBRS. Regression analysis studies revealed that breastfeeding is the most determinant factor for BDNF, TBRS and Motor Quality Percentile rank values. Serum BDNF levels are significantly higher in breastfed infants and shows positive correlations with the results of BSID-II. Given that simultaneous increase in brain BDNF occurs due to onsite production, transport from the periphery or both, it is prudent to hypothesize that BDNF could be one of the factors responsible for the enhanced cognition detected in breastfed infants.

Low serum BDNF may indicate the development of PSD in patients with acute ischemic stroke

OBJECTIVE

This study was to test whether serum BDNF or tissue plasminogen activator (tPA) is correlated with the development of depression at the acute stage of stroke.

METHODS

Hundred ischemic stroke patients admitted to the hospital within the first 24 h of stroke onset were consecutively recruited and followed up for 14 days. The 17-item HDRS and MADRS were used to assess the severity of major depressive symptoms on day 3, day 7, and day 14 after admission. The diagnoses of depression were made in accordance with DSM-IV criteria for post-stroke depression (PSD). Serum BDNF and tPA of all the patients were determined by ELISA both on day 1 and day 7 after admission. Meanwhile, 50 healthy control subjects were also recruited and underwent measurement of serum BDNF and tPA once.

RESULTS

We found that 37 patients (37.0%) were diagnosed of major depression at the end of the follow-up. Serum BDNF on day 1 was significantly higher in non-PSD stroke patients than in normal controls, while PSD patients had significantly lower BDNF than non-PSD patients. There was a significant negative correlation between serum BDNF and tPA on day 1 only in PSD patients (r = -0.440, p = 0.006). Serum BDNF < 5.86 ng/ml on day 1 was independently associated with incident PSD at the acute stage of stroke (OR = 28.992; 95% CI, 8.014-104.891; p < 0.001 after adjustment).

CONCLUSION

There was a significant elevation of BDNF early after ischemic stroke. Serum BDNF on day 1 after admission may predict the risk of subsequent PSD. Moreover, tPA may be involved in the change of BDNF.

Chronic ketamine use increases serum levels of brain-derived neurotrophic factor

RATIONALE

Ketamine is a non-competitive N-methyl-D: -aspartate (NMDA) receptor antagonist which interferes with the action of excitatory amino acids (EAAs) including glutamate and aspartate. The use of ketamine at subanaesthetic doses has increased because of its psychotomimetic properties. However, long-term ketamine abuse may interfere with memory processes and inhibit the induction of long-term potentiation (LTP) in the hippocampus, an effect probably mediated by its NMDA antagonist action. Neurotrophins such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) serve as survival factors for selected populations of central nervous system neurons, including cholinergic and dopaminergic neurons. In addition, neurotrophins, particularly BDNF, may regulate LTP in the hippocampus and influence synaptic plasticity.

OBJECTIVES

The purpose of this study was to test the hypothesis that ketamine use in humans is associated with altered serum levels of neurotrophins.

METHODS

We measured by enzyme-linked immunosorbent assay the NGF and BDNF serum levels in two groups of subjects: frequent ketamine users and healthy subjects.

RESULTS

Our data show that BDNF serum levels were increased in chronic ketamine users as compared to healthy subjects, while NGF levels were not affected by ketamine use.

CONCLUSION

These findings suggest that chronic ketamine intake is associated with increases in BDNF serum levels in humans. Other studies are needed to explore the pharmacological and molecular mechanism by which ketamine, and/or other NMDA antagonists, may induce modification in the production and utilization of BDNF and alter normal brain function.

Brain-derived neurotrophic factor plasma variation during the different phases of the menstrual cycle in women with premenstrual syndrome

Premenstrual syndrome (PMS) is characterized by a cluster of psychological and somatic symptoms that begin during the late luteal phase of the menstrual cycle and disappear after the onset of menses. Since PMS might be caused by an alteration in the cyclical hormonal modifications and ovarian steroids are directly involved in the regulation of mood, affective and cognitive functions and influence neurotrophins expression, in particular the brain-derived neurotrophic factor (BDNF), we aimed to evaluate whether plasma BDNF levels in women with PMS differ from those of normally menstruating women without PMS. Sixty-two women were divided into two groups: one group of women (n=35) with PMS and one group (n=27) composed by normally menstruating women. Plasma samples were collected at day 7 (follicular phase) and day 21 (luteal phase) of the menstrual cycle. Plasma BDNF of the control group significantly increased (p<0.001) from the follicular phase (402.90±74.41pg/ml) to the luteal phase (1098.79±146.49pg/ml). On the other hand, in the PMS group plasma BDNF levels significantly decreased (p<0.001) from the follicular phase (412.45±78.35pg/ml) to the luteal phase (233.03±75.46pg/ml) Luteal BDNF levels of the PMS women were significantly lower than those of the control group (p<0.001). In women with PMS, plasma BDNF followed a decreasing trend during the ovarian cycle, in opposition to the increasing trend observed in women without PMS. The lower luteal BDNF levels of the PMS women might be a consequence of an altered hormonal response and might play a role in the onset of the symptoms PMS related.

Circulating levels of brain-derived neurotrophic factor: correlation with mood, cognition and motor function

Brain-derived neurotrophic factor (BDNF) is the most widely distributed neurotrophin in the CNS, where it plays several pivotal roles in synaptic plasticity and neuronal survival. As a consequence, BDNF has become a key target in the physiopathology of several neurological and psychiatric diseases. Recent studies have consistently reported altered levels of BDNF in the circulation (i.e., serum or plasma) of patients with major depression, bipolar disorder, Alzheimer's disease, Huntington's disease and Parkinson's disease. Correlations between serum BDNF levels and affective, cognitive and motor symptoms have also been described. BDNF appears to be an unspecific biomarker of neuropsychiatric disorders characterized by neurodegenerative changes.

Alterations of brain-derived neurotrophic factor serum levels in patients with alcohol dependence

BACKGROUND

Alcohol dependence is a chronic relapsing disorder characterized by repetitive alcohol drinking patterns and a loss of control over alcohol consumption. Recent studies have hypothesized that dysregulations in brain neurotrophic support regulated by neurotrophins may be involved in the vulnerability to dependence and in the brain damage caused by chronic alcohol consumption. The neurotrophin brain-derived neurotrophic factor (BDNF) plays a pivotal role in neurodevelopment and in the maintenance of adult brain homeostasis through the regulation of neurogenesis and neuronal plasticity. The role of BDNF and its signaling in the mechanisms of alcohol dependence has been well documented in studies of animal models, but a few studies have been conducted in human peripheral tissues. On the basis of this rationale, we compared BDNF levels in both serum and plasma in alcohol-dependent patients and healthy volunteers.

METHODS

Thirty-seven patients with a principal diagnosis of alcohol dependence were recruited. In parallel, a control group of 37 unrelated volunteers matched for gender and age was enrolled. Serum and plasma BDNF levels were measured by ELISA.

RESULTS

A significant reduction in BDNF serum levels was observed in the patient group compared to healthy subjects (p = 0.028). On the contrary, no difference in BDNF plasma levels was evident between patients and controls.

CONCLUSIONS

In conclusion, our data show an alteration of BDNF peripheral content in patients with alcohol dependence, suggesting the involvement of this neurotrophin in this psychopathology.

Higher BDNF serum levels predict slower cognitive decline in Alzheimer's disease patients

The neurotrophin brain-derived neurotrophic factor (BDNF) plays a critical role in neuronal survival, synaptic plasticity, and memory. Several recent studies have demonstrated altered BDNF serum levels in Alzheimer's disease (AD) patients. However, the association of BDNF serum levels with the rate of cognitive decline in AD patients is still unclear. We demonstrate that BDNF serum levels are significantly decreased in AD patients with fast cognitive decline [decrease of Mini-Mental State Examination (MMSE) score >4/yr; n=12] compared to AD patients with slow cognitive decline (decrease of MMSE score ≤4/yr, n=28) and show a significant correlation with the rate of cognitive decline during 1 yr follow-up. These results suggest that higher BDNF serum levels are associated with a slower rate of cognitive decline in AD patients. Further longitudinal studies are necessary to elucidate the kinetics and the potential role of serum BDNF as a surrogate marker of disease progression in AD patients.

Blood BDNF concentrations reflect brain-tissue BDNF levels across species

Brain-derived neurotrophic factor (BDNF) is involved in synaptic plasticity, neuronal differentiation and survival of neurons. Observations of decreased serum BDNF levels in patients with neuropsychiatric disorders have highlighted the potential of BDNF as a biomarker, but so far there have been no studies directly comparing blood BDNF levels to brain BDNF levels in different species. We examined blood, serum, plasma and brain-tissue BDNF levels in three different mammalian species: rat, pig, and mouse, using an ELISA method. As a control, we included an analysis of blood and brain tissue from conditional BDNF knockout mice and their wild-type littermates. Whereas BDNF could readily be measured in rat blood, plasma and brain tissue, it was undetectable in mouse blood. In pigs, whole-blood levels of BDNF could not be measured with a commercially available ELISA kit, but pig plasma BDNF levels (mean 994±186 pg/ml) were comparable to previously reported values in humans. We demonstrated positive correlations between whole-blood BDNF levels and hippocampal BDNF levels in rats (r2=0.44, p=0.025) and between plasma BDNF and hippocampal BDNF in pigs (r2=0.41, p=0.025). Moreover, we found a significant positive correlation between frontal cortex and hippocampal BDNF levels in mice (r2=0.81, p=0.0139). Our data support the view that measures of blood and plasma BDNF levels reflect brain-tissue BDNF levels.

The early non-increase of serum BDNF predicts failure of antidepressant treatment in patients with major depression: a pilot study

In the treatment of patients with major depressive disorder (MDD), early non-improvement of symptoms after initiation of antidepressant treatment is a highly sensitive and specific marker for final treatment failure. On the other hand, meta-analyses of clinical studies investigating serum BDNF (sBDNF) concentration before and after antidepressant treatment showed an increase of sBDNF during treatment, which was correlated with amelioration of depressive symptoms. No study has yet investigated the predictive value of early changes of sBDNF for final treatment outcome of the individual patient. The aim of this study was to investigate in patients with MDD, whether i) the non-increase of sBDNF in the early course of treatment is a specific and sensitive marker for final treatment failure, ii) whether the sensitivity and specificity of early non-improvement for treatment failure can be increased by combining it with the marker "early non-increase of sBDNF". For this purpose, we performed a pilot study with 41 inpatients with MDD according to DSM-IV, who were treated in a naturalistic setting. Depression severity and sBDNF were measured in weekly intervals from baseline to week six with the 21-item Hamilton Depression Rating Scale (HAMD-21) and ELISA, respectively. The individual markers sBDNF non-increase and HAMD-21 non-improvement from baseline to day 7 or 14 predicted later non-response and non-remission with moderate to high specificity. The combined marker sBDNF non-increase plus HAMD-21 non-improvement at day 14 increased the specificity for non-response and non-remission to 100%. Our data provide the first evidence that the absence of an early increase of sBDNF in conjunction with early non-improvement might be a highly specific peripheral marker predictive for treatment failure in patients with MDD. If replicated, this combined marker could be considered useful for prospective confirmatory trials in patients with MDD.

Influence of citalopram and environmental temperature on exercise-induced changes in BDNF

PURPOSE

Serum brain-derived neurotrophic factor (BDNF) is known to increase with exercise. This increase is believed to originate from the brain and it is suggested that monoamines are involved in BDNF regulation. Heat exposure could influence the supposed BDNF output from the brain. Therefore, we hypothesized that administration of a selective serotonin reuptake inhibitor could influence the exercise-induced increase in BDNF, and that peripheral BDNF will be higher when exercise is performed in the heat.

METHODS

Eleven well-trained males performed 4 experimental trials on a cycle ergometer with citalopram or placebo treatment (20 mg in 12 h) in an environmental temperature of 18°C or 30°C. Blood samples (BDNF and cortisol) were taken at 4 time points: at rest, after 60 min at 55% W(max), after a time trial of 30 min at 75% W(max) and following 15 min of recovery. Heart rate and core temperature were measured.

RESULTS

Performance on the time trial was 20% worse in 30°C compared to 18°C (p<0.01), without influence of citalopram. Serum BDNF was found to be lower under citalopram treatment, while basal cortisol levels were increased (p<0.05). Exercise triggered an increase in both BDNF and cortisol (p<0.001). BDNF followed the same pattern as core temperature during exercise, with higher levels of both variables in 30°C. Cortisol was also increased in 30°C compared to temperate conditions (p<0.01).

CONCLUSION

Exercise caused a rise in serum BDNF and cortisol. This increase was enhanced with exercise in the heat. Since permeability of the blood-brain barrier increases with exercise in the heat, the hypothesis was raised that this causes a higher cerebral output of BDNF. Serotonergic stimulation did not increase peripheral BDNF, which was even lower with citalopram administration. Future research should focus on mechanisms behind BDNF increase with exercise.

The impact of childhood abuse and recent stress on serum brain-derived neurotrophic factor and the moderating role of BDNF Val66Met

RATIONALE

Recent findings show lowered brain-derived neurotrophic factor (BDNF) levels in major depressive disorder (MDD). Exposure to stressful life events may (partly) underlie these BDNF reductions, but little is known about the effects of early or recent life stress on BDNF levels. Moreover, the effects of stressful events on BDNF levels may in part be conditional upon a common variant on the BDNF gene (Val(66)Met; RS6265), with the Met allele being associated with a decrease in activity-dependent secretion of BDNF compared to the Val allele.

METHODS

We investigated cross-sectionally in 1,435 individuals with lifetime MDD the impact of childhood abuse (CA) and recent life events on serum BDNF levels and assessed whether the impact of these events was moderated by the BDNF Val(66)Met polymorphism.

RESULTS

Overall, BDNF Met carriers had reduced serum BDNF levels when exposed to CA in a dose-dependent way. Moreover, exposure to recent life events was also associated with decreases in BDNF levels, but this was independent of BDNF Val(66)Met. Moreover, when not exposed to CA, Met carriers had higher BDNF levels than the Val/Val individuals, who did not show decreases in BDNF associated with CA. Finally, these findings were only apparent in the MDD group without comorbid anxiety.

CONCLUSIONS

These gene-environment interactions on serum BDNF levels suggest that Met carriers are particularly sensitive to (early) stressful life events, which extends previous findings on the moderating role of the BDNF Val(66)Met polymorphism in the face of stressful life events.

Depressive symptoms following interferon-α therapy: mediated by immune-induced reductions in brain-derived neurotrophic factor?

Interferon-α (IFN-α) therapy for the treatment of hepatitis C is known to induce depressive symptoms and major depression in a substantial proportion of patients. While immune activation and disturbances in peripheral tryptophan catabolism have been implicated, the exact underlying mechanism remains unknown. A role for brain-derived neurotrophic factor (BDNF) in the pathophysiology of mood disorders has recently emerged. This study examined whether depressive symptoms over time are associated with changes in serum BDNF concentration in hepatitis C patients treated with IFN-α, and whether BDNF mediates the effects of IFN-α-induced immune activation on depressive symptoms. For this purpose, 17 hepatitis C patients received IFN-α treatment with ribavirin. Patients were assessed before and at 1, 2, 4, 8, 12 and 24 wk after start of treatment. Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale (MADRS). In addition, cytokine concentrations and serum BDNF levels were measured at all time-points. Serum levels of BDNF decreased during the course of treatment, and were significantly and inversely associated with total MADRS score. Furthermore, pro-inflammatory cytokine levels predicted lower subsequent BDNF levels, whereas low BDNF levels, as well as increased cytokine levels, were independently associated with the development of depressive symptoms during IFN-α treatment. These findings suggest that the effect of IFN-α-induced immune activation on depression may be explained in part by alterations in neuroprotective capacity, reflected by decreases in serum BDNF following IFN-α treatment.

[Molecular biological aspects of neuroplasticity: approaches for treating tinnitus and hearing disorders]

Peripheral and central structures are involved in the onset of tinnitus. Neuronal plasticity is of special importance for the occurrence of central tinnitus and its persistent form. Neuronal plasticity is the ability of the brain to adapt its own structure (synapses, nerve cells, or even whole areas of the brain) and its organization to modified biological requirements. Neuroplasticity is an ongoing dynamic process. Generally speaking, there are two types of plasticity: synaptic and cortical. Cortical plasticity involves activity-dependent changes in size, connectivity, or in the activation pattern of cortical networks. Synaptic plasticity refers to the activity-dependent change in the strength of synaptic transmission and can affect both the morphology and physiology of the synapse. The stimulation of afferent fibers leads to long-lasting changes in synaptic transmission. This phenomenon is called long-term potentiation (LTP) or long-term depression (LTD). From the perspective of molecular biology, synaptic plasticity is of particular importance for the development of tinnitus and its persistence. Ultimately, the damage to the hair cells, auditory nerve, and excitotoxicity results in an imbalance between LTP and LTD and thus in changes of synaptic plasticity. After excessive acoustic stimulation, LTP can be induced by the increase of afferent inputs, whereas decreased afferent inputs generate LTD. The imbalance between LTP and LTD leads to changes in gene expression and involves changes in neurotransmission, in the expression of the receptors, ion channels, regulatory enzymes, and in direct changes on the synapses. This causes an increase of activity on the cellular level. As a result, the imbalance can lead to hyperactivity in the dorsal cochlear nucleus, inferior colliculus, and in the auditory cortex and, later on, to changes in cortical plasticity leading to tinnitus.

Aerobic physical exercise as a possible treatment for neurocognitive dysfunction in bipolar disorder

BACKGROUND

Neurocognitive dysfunction associated with bipolar disorder (BD) is pervasive, persistent across illness phases, and is demonstrated to predispose and portend psychosocial impairment. Moreover, no approved therapies for various phases of BD have been shown to reliably improve any dimension of neurocognitive performance. In this article, we emphasize that aerobic physical exercise is a viable neurocognitive-enhancing adjunctive treatment for patients with BD. The overarching aim of this review is to emphasize that aerobic physical exercise is a viable neurocognitive-enhancing adjunctive treatment for patients with BD.

METHODS

We conducted PubMed and Google Scholar searches of all English-language articles published between January 1966 and February 2010 using the search terms bipolar disorder, major depressive disorder, depression, exercise, and physical activity cross-referenced with each other and the following terms: cognition, executive function, learning, memory, attention, emotion, and behavior. Articles selected for review were based on adequacy of sample size, use of standardized experimental procedures, validated assessment measures, and overall quality.

RESULTS

Available studies have documented an array of persisting neurocognitive deficits across disparate bipolar populations. Abnormalities in verbal working memory are highly replicated; deficits in executive function, learning, attention, and processing speed are also a consistent abnormality. The effect sizes of neurocognitive deficits in BD are intermediate between those reported in schizophrenia and major depressive disorder. Several original reports and reviews have documented the neurocognitive-enhancing effects of aerobic exercise in the general population as well as across diverse medical populations and ages. Proposed mechanisms involve nonexclusive effects on neurogenesis, neurotrophism, immunoinflammatory systems, insulin sensitivity, and neurotransmitter systems. Each of these effector systems are implicated in both normal and abnormal neurocognitive processes in BD.

CONCLUSION

Available evidence provides a rationale for empirically evaluating the neurocognitive benefits of aerobic exercise in BD.

Determinants of serum brain-derived neurotrophic factor

BACKGROUND

Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family of growth factors and affects the survival and plasticity of neurons in the adult central nervous system. The high correlation between cortical and serum BDNF levels has led to many human studies on BDNF levels in various populations, however knowledge about determinants that influence BDNF is lacking.

AIMS

To gain insight into the factors that influence BDNF levels in humans.

METHODS

In 1168 people aged 18 through 65, free of antidepressants and current psychiatric disease, from the Netherlands study of depression and anxiety four categories of determinants (sampling, sociodemographics, lifestyle indicators and diseases) were measured as well as BDNF level. We used univariate analyses as well as multivariate linear regression analyses in particular to determine which of the possible determinants significantly influenced serum BDNF levels.

RESULTS

The mean BDNF level was 8.98ng/ml (SD 3.1ng/ml) with a range from 1.56ng/ml through 18.50ng/ml. Our final multivariate regression analysis revealed that a non-fasting state of blood draw (β=-.067; p=.019), later measurement (β=-.065; p=.022), longer sample storage (β=-.082; p=.004) and being a binge drinker (β=-.063; p=.035) all resulted in attenuated BDNF levels. This was in contrast to smoking (β=.098; p=.001) and living in an urban area (β=.109; p<.001), which resulted in increased BDNF levels. Moreover we found that older subjects also had higher BDNF levels, but this only applied to women (β=.226; p<.001).

CONCLUSIONS

Future studies on serum levels of BDNF in humans should correct for the time of blood withdrawal, storage, urbanicity, age, sex, smoking status and food and alcohol intake.

Responses of serum neurotrophic factors to exercise in pregnant and postpartum women

It was recently shown in humans that exercise affects the neurotrophic factors known to function as neurogenesis regulators. No data related to exercise and pregnancy, however, is yet available. Thus, we investigated the effects of acute exercise on pregnant women during late pregnancy and women postpartum, on the serum concentration of the brain-derived neurotrophic factor (BDNF), the insulin-like growth factor 1 (IGF-1), the vascular endothelial growth factor (VEGF), prolactin (PRL) and cortisol (COR). Twenty women with uncomplicated pregnancies underwent a graded submaximal exercise test during pregnancy (weeks 32-36 of gestation; T(1)) and postpartum (10-12 weeks after childbirth; T(2)). On two of these test days the women carried out an intensifying exercise test (25 W steps) on a cycle ergometer until a heart rate of 150 bpm was reached. Blood samples were taken in the rest period before beginning the exercise, immediately at the end of the exercise and after recovery periods of 5 and 10 min, respectively. Basal maternal IGF-1, PRL and COR were found to be higher during T(1) (p<.01), while the BDNF was higher during T(2) (p=.00). VEGF was not detectable in the serum of the pregnant women. During T(2), VEGF, which was found to be within the normal range before exercise, was at a higher level after exercise (p<.01). Exercise increased the BDNF and IGF-1 during T(1) and T(2) (p<.01). This study also shows that exercise increases the serum concentrations of IGF-1 and BDNF during pregnancy and postpartum as well as VEGF postpartum. Thus, exercise might be a beneficial lifestyle factor with therapeutic/public health implications i.e. with regard to maternal mood and cognitive performance.

Pharmacotherapy for treatment-resistant schizophrenia

Schizophrenia is a disabling mental illness with a lifetime prevalence of 0.7% worldwide and significant, often devastating, consequences on social and occupational functioning. A range of antipsychotic medications are available; however, suboptimal therapeutic response in terms of psychotic symptoms is common and affects up to one-third of people with schizophrenia. Negative symptoms are generally less amenable to treatment. Because of the consequences of inadequate symptom control, effective treatment strategies are required for people with treatment-resistant schizophrenia. Clozapine has been shown to be more effective than other antipsychotics in treatment-resistant populations in several studies; however, the occurrence of adverse effects, some of which are potentially life-threatening, are important limitations. In addition to those who are intolerant to clozapine, only 30% to 50% experience clinically significant symptom improvement. This review describes the recent evidence for treatment strategies for people not responding to nonclozapine antipsychotic agents and people not responding or only partially responding to clozapine.

Is serum brain-derived neurotrophic factor related to craving for or use of alcohol, cocaine, or methamphetamine?

BACKGROUND

Data suggests that brain-derived neurotropic factor (BDNF) plays a neuroadaptive role in addiction. Whether serum BDNF levels are different in alcohol or psychostimulants as a function of craving is unknown. Here, we examined craving and serum BDNF levels in persons with alcohol versus psychostimulant dependence. Our goals were to explore BDNF as an objective biomarker for 1) craving 2) abstinence, and 3) years of chronic substance use.

METHODS

An exploratory, cross-sectional study was designed. Men and women between 20-65 years old with alcohol, cocaine, or methamphetamine dependence were eligible. A craving questionnaire was used to measure alcohol, cocaine and methamphetamine cravings. Serum levels of BDNF were measured using enzyme linked immunoassay. Analysis of variance, chi-square, and correlations were performed using a 95% confidence interval and a significance level of P < 0.05.

RESULTS

We found a significant difference in the mean craving score among alcohol, cocaine and methamphetamine dependent subjects. There were no significant influences of race, gender, psychiatric disorder or psychotropic medication on serum BDNF levels. We found that among psychostimulant users BDNF levels were significantly higher in men than in women when the number of abstinent days was statistically controlled. Further, a significant correlation between serum BDNF levels and the number of abstinent days since last psychostimulant use was found.

CONCLUSION

These data suggest that BDNF may be a biomarker of abstinence in psychostimulant dependent subjects and inform clinicians about treatment initiatives. The results are interpreted with caution due to small sample size and lack of a control group.

Neuroplasticity signaling pathways linked to the pathophysiology of schizophrenia

Schizophrenia is a severe mental illness that afflicts nearly 1% of the world's population. One of the cardinal pathological features of schizophrenia is perturbation in synaptic connectivity. Although the etiology of schizophrenia is unknown, it appears to be a developmental disorder involving the interaction of a potentially large number of risk genes, with no one gene producing a strong effect except rare, highly penetrant copy number variants. The purpose of this review is to detail how putative schizophrenia risk genes (DISC-1, neuregulin/ErbB4, dysbindin, Akt1, BDNF, and the NMDA receptor) are involved in regulating neuroplasticity and how alterations in their expression may contribute to the disconnectivity observed in schizophrenia. Moreover, this review highlights how many of these risk genes converge to regulate common neurotransmitter systems and signaling pathways. Future studies aimed at elucidating the functions of these risk genes will provide new insights into the pathophysiology of schizophrenia and will likely lead to the nomination of novel therapeutic targets for restoring proper synaptic connectivity in the brain in schizophrenia and related disorders.

Expression and Role of the BDNF Receptor-TrkB in Rat Adrenal Gland under Acute Immobilization Stress

We reported that plasma brain-derived neurotrophic factor (BDNF) was maximally elevated following a 60-min period of acute immobilization stress and that salivary glands were the main source of plasma BDNF under this stress condition. However, the expression pattern of the BDNF receptor, Tyrosine receptor kinase B (TrkB), under this condition has yet to be determined. We therefore investigated the effect of this stress on the expression level of TrkB in various rat organs using real-time PCR. No significant differences were found between controls and 60 min-stressed rats with respect to TrkB level in various organs. Only adrenal glands showed significantly increased TrkB mRNA levels after 60 min of stress. TrkB mRNA and protein were observed to localize in chromaffin cells. In addition, we investigated whether BDNF-TrkB interaction influences the release of stress hormones from PC12 cells, derived from chromaffin cells. Truncated receptor, TrkB-T1, was identified in PC12 cells using RT-PCR. Exposure of PC12 cells to BDNF induced the release of catecholamine. This BDNF-evoked release was totally blocked by administration of the K252a in which an inhibitor of Trk receptors. Thus, BDNF-TrkB interactions may modulate catecholamine release from adrenal chromaffin cells under acute stress conditions.

Changes of Serum Brain-Derived Neurotrophic Factor in Children with Obstructive Sleep Apnoea–Hypopnoea Syndrome following Adenotonsillectomy

Children with obstructive sleep apnoea syndrome (OSAS) have substantial cognitive functional morbidity. Brain-derived neurotrophic factor (BDNF) is a key mediator of memory and cognition, but its regulation in OSAS is unknown. Circulating BDNF, transforming growth factor-β1 and 5-hydroxytryptamine levels, cognitive ability and overnight polysomnography were evaluated in 44 children with newly-diagnosed OSAS and in 26 healthy children. All parameters were monitored pre-operatively and at 3, 6 and 12 months after adenotonsillectomy. Pre-operative cognitive ability and sleep parameters were significantly poorer in children with OSAS compared with controls, but BDNF levels were similar. At 3 months post-operation, serum BDNF concentrations decreased, but cognitive ability and sleep parameters remained deficient. At 6 months post-operation, serum BDNF levels, sleep parameters and cognitive ability had improved and, by 12 months, there were no differences between the two groups. It is concluded that adenotonsillectomy can rapidly normalize sleep parameters and improve the cognitive ability of children with OSAS, by regulating the circulating level of BDNF.

Effect of antidepressants on brain-derived neurotrophic factor (BDNF) release from platelets in the rats

Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family, and enhances the growth and maintenance of several neuronal systems. In addition, BDNF may promote neurogenesis and protect against hippocampal volume loss in depressive disorders. Although first detected in brain, BDNF also exists in peripheral tissues and is mainly stored in platelets and circulates in blood. Recent reports indicate that serum BDNF levels in depressive patients are lower than in control subjects, and antidepressant treatment increases serum BDNF levels in responders. A single report suggests that decreased serum BDNF in major depression is related to mechanisms of platelet BDNF release; however, the mechanisms of changes in BDNF blood levels are still poorly understood. In the present study, we investigated the direct influence of antidepressants on BDNF release from platelets and their effects on serum levels. We used samples of washed platelets prepared from rat blood, and investigated the platelet BDNF release and serum BDNF concentration changes in response to adding antidepressants. We found that BDNF was dose-dependently released from platelets by direct treatment with various kinds of antidepressants in vitro, and serum BDNF concentration was also increased by intravenous antidepressant treatment. These results confirm that BDNF release from platelets is affected by antidepressants, which may relate to the circulating BDNF level change in peripheral blood. The response of BDNF release differs depending on the type and amount of antidepressants, making BDNF a serious candidate as a predictor of antidepressant treatment response.

The roles of BDNF in the pathophysiology of major depression and in antidepressant treatment

Neurotrophic factors are critical regulators of the formation and plasticity of neuronal networks. Brain-derived neurotrophic factor (BDNF) is abundant in the brain and periphery, and is found in both human serum and plasma. Animal studies have demonstrated that stress reduces BDNF expression or activity in the hippocampus and that this reduction can be prevented by treatment with antidepressant drugs. A similar change in BDNF activity occurs in the brain of patients with major depression disorder (MDD). Recently, clinical studies have indicated that serum or plasma BDNF levels are decreased in untreated MDD patients. Antidepressant treatment for at least four weeks can restore the decreased BDNF function up to the normal value. Therefore, MDD is associated with impaired neuronal plasticity. Suicidal behavior can be a consequence of severe impaired neuronal plasticity in the brain. Antidepressant treatment promotes increased BDNF activity as well as several forms of neuronal plasticity, including neurogenesis, synaptogenesis and neuronal maturation. BDNF could also play an important role in the modulation of neuronal networks. Such a neuronal plastic change can positively influence mood or recover depressed mood. These alterations of BDNF levels or neuronal plasticity in MDD patients before and after antidepressant treatment can be measured through the examination of serum or plasma BDNF concentrations. BDNF levels can therefore be useful markers for clinical response or improvement of depressive symptoms, but they are not diagnostic markers of major depression.

Lactate infusion at rest increases BDNF blood concentration in humans

Studies in humans use blood lactate to determine the degree of the exercise intensity, suggesting that exercise with elevated blood lactate concentrations results in increased BDNF plasma concentrations. However, it is not clear if lactate per se or rather other mechanisms are responsible for changes in blood BDNF concentrations. The lactate clamp method at rest is an appropriate method to examine physiological responses of lactate on the human organism without the effects of exercise. Eight male sport students placed in a sitting position received intravenous infusions with a 4 molar sodium-lactate solution in an incremental design starting with an infusion rate of 0.01ml/kgBW/min for the first three minutes, which was increased every three minutes by 0.01ml/kgBW/min up to 0.08ml/kg/min in the 24th minute. All together each subject received 4.2mmol of infusion. Venous blood samples were taken before and immediately after the infusion as well as in the 24th and the 60th min after the infusion period and analysed for BDNF. Blood gases and capillary blood lactate (La) were analysed before the test, every three minutes directly before increasing the infusion rate, at the end of the infusion and in the post infusions period until the 12th min and after 24 and 60min. BDNF and La increased significantly after the infusion and reached baseline values at the end of the experiment (p<0.05, p<0.01, respectively). pH and hydrogen ions increased from the beginning until the end of the infusion period (p<0.01). This data suggest that blood lactate is involved in the regulation of BDNF blood concentrations.

Peripheral BDNF produces antidepressant-like effects in cellular and behavioral models

Recent clinical studies demonstrate that serum levels of brain-derived neurotrophic factor (BDNF) are significantly decreased in patients with major depressive disorder (MDD) and that antidepressant treatments reverse this effect, indicating that serum BDNF is a biomarker of MDD. These findings raise the possibility that serum BDNF may also have effects on neuronal activity and behavior, but the functional significance of altered serum BDNF is unknown. To address this issue, we determined the influence of peripheral BDNF administration on depression- and anxiety-like behavior, including the forced swim test (FST), chronic unpredictable stress (CUS)/anhedonia, novelty-induced hypophagia (NIH) test, and elevated-plus maze (EPM). Furthermore, we examined adult hippocampal neurogenesis as well as hippocampal and striatal expression of BDNF, extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB), in order to determine whether peripherally administered BDNF produces antidepressant-like cellular responses in the brain. Peripheral BDNF administration increased mobility in the FST, attenuated the effects of CUS on sucrose consumption, decreased latency in the NIH test, and increased time spent in the open arms of an EPM. Moreover, adult hippocampal neurogenesis was increased after chronic, peripheral BDNF administration. We also found that BDNF levels as well as expression of pCREB and pERK were elevated in the hippocampus of adult mice receiving peripheral BDNF. Taken together, these results indicate that peripheral/serum BDNF may not only represent a biomarker of MDD, but also have functional consequences on molecular signaling substrates, neurogenesis, and behavior.

Decreased serum BDNF levels in patients with epileptic and psychogenic nonepileptic seizures

OBJECTIVE

Neurotrophins promote neurogenesis and help regulate synaptic reorganization. Their dysregulation has been implicated in a number of neurologic and psychiatric disorders. Previous studies have shown decreased levels of brain-derived neurotrophic factor (BDNF) in the serum of patients with psychiatric disorders such as major depressive disorder (MDD) and conversion disorder (CD). In human patients with temporal lobe epilepsy, there is an increase in both BDNF mRNA and protein levels in surgically resected hippocampi compared to controls. One study of children with epilepsy has found normal to increased serum BDNF levels compared to controls. Plasma [corrected] BDNF levels have not been investigated in adult patients with epileptic seizures (ES). We hypothesized that BDNF would differentiate between ES and psychogenic nonepileptic seizures (PNES).

METHODS

We assessed plasma [corrected] BDNF immunoreactivity in 15 patients with ES, 12 patients with PNES, and 17 healthy volunteers. Plasma [corrected] BDNF levels were measured using an enzyme-linked immunoassay.

RESULTS

Healthy controls showed higher BDNF levels (4,289 ± 1,810 pg/mL) compared to patients with PNES (1,033 ± 435 pg/mL) (p < 0.001). However, unexpectedly, healthy controls also showed higher levels of BDNF compared to patients with ES without comorbid MDD (977 ± 565 pg/mL) (p < 0.001).

CONCLUSIONS

Unlike children, adults with epilepsy appear to have decreased levels of plasma [corrected] BDNF. Reduced plasma [corrected] BDNF levels can be used to differentiate adult patients with ES or PNES from healthy controls. Further human studies are needed to better understand the pathophysiology explaining the decreased plasma [corrected] BDNF levels found in epilepsy and in PNES.

Nicotine dependence and serum BDNF levels in male patients with schizophrenia

OBJECTIVE

Schizophrenia is associated with a significantly high prevalence of smoking. Upregulation of neurotrophins by nicotine is well established. Accumulating evidence shows that brain-derived neurotrophic factor (BDNF) may be involved in the pathophysiology of schizophrenia. The purposes of this study were to compare BDNF levels in smokers to nonsmokers with schizophrenia and examine the association between BDNF levels and psychopathological symptoms.

MATERIALS AND METHODS

Serum BDNF levels were measured in 139 male inpatients with DSM-IV schizophrenia: 102 smokers and 37 nonsmokers. Symptoms were assessed with the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The positive PANSS symptoms were lower in smokers than in nonsmokers, while the negative symptoms were lower in those who smoked more cigarettes. BDNF levels were significantly higher in smokers than in nonsmokers (p < 0.05). Higher BDNF levels correlated with fewer negative symptoms and with smoking more cigarettes.

CONCLUSION

The fewer positive symptoms in smokers and fewer negative symptoms in those who smoked more cigarettes may be associated with nicotine-induced upregulation of BDNF.

Association among basal serum BDNF, cardiorespiratory fitness and cardiovascular disease risk factors in untrained healthy Korean men

Evidence suggests that serum brain-derived neurotrophic factor (serum BDNF) can be affected by cardiorespiratory fitness (CRF), but this relationship is far from clear. Recent reports show an inverse relationship between serum BDNF and CRF in healthy individuals, and other studies suggest a possible association between serum BDNF and cardiovascular disease. However, the possible interaction between serum BDNF, CRF, and cardiovascular disease risk has not been studied. The purpose of this study was to examine the association among serum BDNF, CRF, and cardiovascular disease risk factors in healthy men. The investigation involved a large sample of men (n = 995, age range: 20-76 years) who live in the central area of South Korea and were recruited into the Preventive Health Study. Our study showed a significant inverse relationship between serum BDNF and relative VO(2)max (r = -0.412, p < 0.0001) and heart rate reserve (r = -0.194, p < 0.0001). Serum BDNF was positively correlated with body mass index (r = 0.80, p < 0.0001), total cholesterol (r = 0.185, p < 0.0001), and triglyceride (r = 0.320, p < 0.0001). Our data suggest that serum BDNF may be associated with effects of increased CRF on cardiovascular disease. However, more research is clearly needed before a determination of whether, and to what extent, serum BDNF may be responsible for some of the health benefits associated with CRF.

Effect of brain-derived neurotrophic factor Val66Met polymorphism and serum levels on the progression of mild cognitive impairment

OBJECTIVES

Abnormalities in neurotrophic systems have been reported in Alzheimer's disease (AD), as shown by decreased serum brain-derived neurotrophic factor (BDNF) levels and association with BDNF genetic polymorphisms. In this study, we investigate whether these findings can be detected in patients with mild cognitive impairment (MCI), which is recognized as a high risk condition for AD. We also address the impact of these variables on the progression of cognitive deficits within the MCI-AD continuum.

METHODS

One hundred and sixty older adults with varying degrees of cognitive impairment (30 patients with AD, 71 with MCI, and 59 healthy controls) were longitudinally assessed for up to 60 months. Baseline serum BDNF levels were determined by sandwich ELISA, and the presence of polymorphisms of BDNF and apolipoprotein E (Val66Met and APOE*E4, respectively) was determined by allelic discrimination analysis on real time PCR. Modifications of cognitive state were ascertained for non-demented subjects.

RESULTS

Mean serum BDNF levels were reduced in patients with MCI and AD, as compared to controls (509.2+/-210.5; 581.9+/-379.4; and 777.5+/-467.8 pg/l respectively; P<0.001). Baseline serum BDNF levels were not associated with the progression of cognitive impairment upon follow-up in patients with MCI (progressive MCI, 750.8+/-463.0; stable MCI, 724.0+/-343.4; P=0.8), nor with the conversion to AD. Although Val66Met polymorphisms were not associated with the cross-sectional diagnoses of MCI or AD, the presence of Met-BDNF allele was associated with a higher risk of disease-progression in patients with MCI (OR=3.0 CI(95%) [1.2-7.8], P=0.02). We also found a significant interaction between the APOE*E4 and Met-BDNF allele increasing the risk of progression of cognitive impairment in MCI patients (OR=4.4 CI(95%) [1.6-12.1], P=0.004).

CONCLUSION

Decreased neurotrophic support, as indicated by a reduced systemic availability of BDNF, may play role in the neurodegenerative processes that underlie the continuum from MCI to AD. The presence of Met-BDNF allele, particularly in association with APOE*E4, may predict a worse cognitive outcome in patients with MCI.

BDNF mRNA expression of peripheral blood mononuclear cells was decreased in depressive patients who had or had not recently attempted suicide

BACKGROUND

Recent reports have suggested a pathophysiological role for brain-derived neurotrophic factor (BDNF) in major depression and suicide. We evaluate BDNF mRNA in peripheral blood mononuclear cells (PBMCs) of patients with major depression who had or had not recently attempted suicide.

METHODS

BDNF mRNA expression was examined in PBMCs of 30 major depressed patients without recent suicide attempts, 30 major depressed patients with recent suicide attempts, and 30 healthy controls. All patients were diagnosed with major depressive disorder (MDD) and they were either medication-naïve or medication-free. BDNF mRNA expression was measured using real-time quantitative PCR.

RESULTS

BDNF mRNA expression was significantly decreased in PBMCs of MDD patients, with or without a history of suicide attempts, when compared with healthy controls (Z=-5.233, p<0.001). Suicidal MDD patients had more decrease in BDNF mRNA expression (chi(2)=45.881, df=2, p<0.001).

LIMITATIONS

The sample size of the present study was relatively small. Although suicidal MDD patients had higher HDRS scores than non-suicidal patients, the comparison of BDNF mRNA between them could not be adjusted for HDRS score.

CONCLUSIONS

Our study suggests that the BDNF mRNA expression is reduced in PBMCs of patients with major depression. This alteration of BDNF mRNA expression was noteworthy in recent suicide attempters. Such a decrease in BDNF mRNA might be associated with BDNF decrease in serum or plasma, and might also correspond to a BDNF decline in the brains of MDD patients.

Serum and plasma BDNF levels in major depression: a replication study and meta-analyses

OBJECTIVES

Alterations of BDNF signalling in major depression (MD) are supported by studies demonstrating decreased levels of the neurotrophin serum and plasma content in MD patients. We conducted a replication study and we performed two meta-analyses on studies analysing serum and plasma BDNF levels in MD patients.

METHODS

The samples were composed by 489 patients/483 controls for the meta-analysis on serum and by 161 patients/211 controls for that on plasma levels. We performed also subgroup analyses to examine whether the decrease in BDNF levels in MD was influenced by gender.

RESULTS

In the replication study we found decreased serum BDNF levels in MD patients (P<0.01) and we demonstrated that is down-regulated the mature form of the neurotrophin (mBDNF). No significant difference was evidenced for plasma BDNF levels. The meta-analyses showed a reduction of both BDNF serum (P<0.0001) and plasma levels (P=0.02) in MD. No difference in the effect size on serum BDNF was observed between males and females (P=0.18).

CONCLUSIONS

In conclusion, our results provide evidence of peripheral BDNF alteration in MD and support the rationale for further investigation aiming to the identification of biomarkers for differential diagnosis and personalization of therapies in this disorder.

Peripheral BDNF produces antidepressant-like effects in cellular and behavioral models

Recent clinical studies demonstrate that serum levels of brain-derived neurotrophic factor (BDNF) are significantly decreased in patients with major depressive disorder (MDD) and that antidepressant treatments reverse this effect, indicating that serum BDNF is a biomarker of MDD. These findings raise the possibility that serum BDNF may also have effects on neuronal activity and behavior, but the functional significance of altered serum BDNF is unknown. To address this issue, we determined the influence of peripheral BDNF administration on depression- and anxiety-like behavior, including the forced swim test (FST), chronic unpredictable stress (CUS)/anhedonia, novelty-induced hypophagia (NIH) test, and elevated-plus maze (EPM). Furthermore, we examined adult hippocampal neurogenesis as well as hippocampal and striatal expression of BDNF, extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB), in order to determine whether peripherally administered BDNF produces antidepressant-like cellular responses in the brain. Peripheral BDNF administration increased mobility in the FST, attenuated the effects of CUS on sucrose consumption, decreased latency in the NIH test, and increased time spent in the open arms of an EPM. Moreover, adult hippocampal neurogenesis was increased after chronic, peripheral BDNF administration. We also found that BDNF levels as well as expression of pCREB and pERK were elevated in the hippocampus of adult mice receiving peripheral BDNF. Taken together, these results indicate that peripheral/serum BDNF may not only represent a biomarker of MDD, but also have functional consequences on molecular signaling substrates, neurogenesis, and behavior.

Brain-derived neurotrophic factor as a biomarker for mood disorders: an historical overview and future directions

Mood disorders, such as major depressive disorder (MDD) and bipolar disorder (BPD), are the most prevalent psychiatric conditions, and are also among the most severe and debilitating. However, the precise neurobiology underlying these disorders is currently unknown. One way to combat these disorders is to discover novel biomarkers for them. The development of such biomarkers will aid both in the diagnosis of mood disorders and in the development of effective psychiatric medications to treat them. A number of preclinical studies have suggested that the brain-derived neurotrophic factor (BDNF) plays an important role in the pathophysiology of MDD. In 2003, we reported that serum levels of BDNF in antidepressant-naive patients with MDD were significantly lower than those of patients medicated with antidepressants and normal controls, and that serum BDNF levels were negatively correlated with the severity of depression. Additionally, we found that decreased serum levels of BDNF in antidepressant-naive patients recovered to normal levels associated with the recovery of depression after treatment with antidepressant medication. This review article will provide an historical overview of the role played by BDNF in the pathophysiology of mood disorders and in the mechanism of action of therapeutic agents. Particular focus will be given to the potential use of BDNF as a biomarker for mood disorders. BDNF is initially synthesized as a precursor protein proBDNF, and then proBDNF is proteolytically cleaved to the mature BDNF. Finally, future perspectives on the use of proBDNF as a novel biomarker for mood disorders will be discussed.

Altered production of brain-derived neurotrophic factor by peripheral blood immune cells in multiple sclerosis

Background: Within multiple sclerosis lesions, brain-derived neurotrophic factor is detected in neurons and immunocytes.

Objective: To clarify brain-derived neurotrophic factor production by peripheral blood immunocytes and its relationship with clinical parameters in multiple sclerosis.

Methods: Serum brain-derived neurotrophic factor levels were measured by conventional enzyme-linked immunosorbent assay while brain-derived neurotrophic factor production by immunocytes was determined by an in situ enzyme-linked immunosorbent assay in 74 multiple sclerosis patients, 32 healthy controls, and 86 patients with other neurological diseases. The tyrosine kinase receptor TrkB expression level in peripheral blood mononuclear cells was measured by real-time polymerase chain reaction.

Results: Multiple sclerosis patients showed significantly higher serum brain-derived neurotrophic factor levels than healthy controls and patients with other neurological diseases. Multiple sclerosis patients with high brain-derived neurotrophic factor levels were younger, and showed fewer relapse numbers than those with low brain-derived neurotrophic factor levels. Brain-derived neurotrophic factor production by T cells increased with age in healthy controls, but not in multiple sclerosis patients. Interferon beta induced a significant increase in serum brain-derived neurotrophic factor levels. Brain-derived neurotrophic factor production from T cells and TrkB expression levels in peripheral blood mononuclear cells were significantly enhanced in interferon beta-treated multiple sclerosis patients compared with untreated ones. Conclusions: A high brain-derived neurotrophic factor level is related to early mild disease in young multiple sclerosis patients. Interferon beta potentiates brain-derived neurotrophic factor production and brain-derived neurotrophic factor receptor expression in peripheral blood mononuclear cells, which may act beneficially.

Effects of maternal smoking and exposure to methylmercury on brain-derived neurotrophic factor concentrations in umbilical cord serum

Brain-derived neurotrophic factor (BDNF) is a neurotrophin essential for neuronal survival and differentiation. We examined the concentration of BDNF in cord serum from newborns exposed to methylmercury (MeHg) and polychlorinated biphenyls (PCB) in utero by maternal consumption of whale meat. The cohort consisted of 395 singleton births (206 boys and 189 girls), gestational age ranging from 38 to 42 weeks. Serum BDNF was measured by sandwich ELISA. Maternal smoking habits and other relevant factors were obtained by interviewing the mothers. The exposure to MeHg was estimated from Hg concentrations in cord blood, whereas exposure to PCB was estimated based on maternal serum concentrations. Only MeHg exposure affected the serum BDNF, which decreased in a concentration-dependent manner in girls born to nonsmoking mothers. Maternal smoking significantly increased BNDF in girls but not in boys. For further statistical analyses, we used the serum BDNF concentration as a continuous outcome variable in supervised regression models. Serum BDNF concentration increased with gestational age, increased by maternal smoking, decreased slightly with MeHg exposure, and maternal smoking enhanced the decrease in serum BDNF induced by MeHg exposure. Cord blood BDNF has been reported to increase in association with perinatal brain injuries and has been proposed as a possible predictive marker of neurodevelopmental outcomes. The negative effect that MeHg seems to exert on cord blood BDNF concentration could endanger compensatory responses to an adverse impact and therefore deserves attention.

Increase in brain-derived neurotrophic factor in first episode psychotic patients after treatment with atypical antipsychotics

Some preclinical and postmortem studies suggest that the effects of atypical antipsychotics could be mediated by brain-derived neurotrophic factor (BDNF). Olanzapine is an atypical antipsychotic with shown efficacy in psychosis treatment. The aim of this study was to compare plasma BDNF levels at baseline and after 1 year of olanzapine treatment in 18 drug-naive patients who experienced a first psychotic episode with those of 18 healthy control participants matched by age, sex, and socioeconomic level. Plasma BDNF levels were measured in patients at the index episode and at 1, 6, and 12 months of follow-up using an enzyme-linked immunosorbent assay. Symptoms and functioning of patients and controls were assessed with the Positive and Negative Symptom Scale and Global Assessment of Function Scale. BDNF levels of patients at onset were significantly lower than controls but increased toward control values during olanzapine treatment. There was a significant positive correlation between BDNF levels and functioning (Global Assessment of Function Scale). BDNF levels were also negatively correlated with positive symptoms, but not with negative symptoms or general psychopathology. Results suggest that olanzapine can offset the low BDNF levels at the onset of first psychotic episodes, and improving psychotic symptoms. The increase in BDNF levels may be its mechanism of action in improving positive symptoms.

Plasma BDNF concentration, Val66Met genetic variant and depression-related personality traits

Brain-derived neurotrophic factor (BDNF) regulates synaptic plasticity and neurogenesis, and BDNF plasma and serum levels have been associated with depression, Alzheimer's disease, and other psychiatric and neurodegenerative disorders. In a relatively large community sample, drawn from the Baltimore Longitudinal Study of Aging (BLSA), we examine whether BDNF plasma concentration is associated with the Val66Met functional polymorphism of the BDNF gene (n = 335) and with depression-related personality traits assessed with the NEO-PI-R (n = 391). Plasma concentration of BDNF was not associated with the Val66Met variant in either men or women. However, in men, but not in women, BDNF plasma level was associated with personality traits linked to depression. Contrary to the notion that low BDNF is associated with negative outcomes, we found lower plasma levels in men who score lower on depression and vulnerability to stress (two facets of Neuroticism) and higher on Conscientiousness and Extraversion. These findings challenge the prevailing hypothesis that lower peripheral levels of BDNF are a marker of depression.

Peptides derived from the solvent-exposed loops 3 and 4 of BDNF bind TrkB and p75(NTR) receptors and stimulate neurite outgrowth and survival

Brain-derived neurotrophic factor (BDNF) is critically involved in modeling the developing nervous system and is an important regulator of a variety of crucial functions in the mature CNS. BDNF exerts its action through interactions with two transmembrane receptors, either separately or in concert. BDNF has been implicated in several neurological disorders, and irregularities in BDNF function may have severe consequences. Administration of BDNF as a drug has thus far yielded few practicable results, and the potential side effects when using a multifunctional protein are substantial. In an effort to produce more specific compounds without side effects, small peptides mimicking protein function have been developed. The present study characterized two mimetic peptides, Betrofin 3 and Betrofin 4, derived from the BDNF sequence. Both Betrofins bound the cognate BDNF receptors, TrkB and p75(NTR), and induced neurite outgrowth and enhanced neuronal survival, probably by inducing signaling through tha Akt and MAPK pathways. Distinct, charged residues within the Betrofin sequences were identified as important for generating the neuritogenic response, which was also inhibited when BDNF was added together with either Betrofin, indicating partial agonistic effects of the peptides. Thus, two peptides derived from BDNF induced neurite outgrowth and enhanced neuronal survival, probably through binding to BDNF receptors.

Neurotrophic growth factors for the treatment of amyotrophic lateral sclerosis: where do we stand?

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease that results in progressive loss of motoneurons, motor weakness and death within 3–5 years after disease onset. Therapeutic options remain limited despite substantial number of approaches that have been tested clinically. Many neurotrophic growth factors are known to promote the survival of neurons and foster regeneration in the central nervous system. Various neurotrophic factors have been investigated pre-clinically and clinically for the treatment of ALS. Although pre-clinical data appeared promising, no neurotrophic factors succeeded yet in a clinical phase III trial. In this review we discuss the rationale behind those factors, possible reasons for clinical failures, and argue for a renewal of hope in this powerful class of drugs for the treatment of ALS.

Inverse correlation of brain and blood BDNF levels in a genetic rat model of depression

There is accumulating evidence that brain-derived neurotrophic factor (BDNF) plays a critical role in the pathophysiology of depression. Decreased serum levels have been reported in major depression, and a correlation between BDNF reduction and the severity of the disease was found. Moreover, in post-mortem hippocampal tissue, increased levels of BDNF immunoreactivity have been reported in subjects treated with antidepressants compared to untreated subjects. These findings indicate parallel changes in brain and serum BDNF levels during depression. BDNF has been measured in selected brain areas in several animal models. In investigations between Flinders Sensitive Line (FSL) and Flinders Resistant Line (FRL) rats, a genetic rat model of depression, no differences were found in BDNF levels in the frontal cortex and hippocampus, areas believed to be core brain regions in depression. However, to our knowledge brain and serum BDNF levels have never been reported in parallel for any psychiatric disease model. Therefore, we examined the levels of BDNF in whole blood, serum, cerebrospinal fluid (CSF), hippocampus, and frontal cortex in male FSL and FRL rats. BDNF levels in serum and whole blood of FSL rats were significantly increased compared to FRL rats. In contrast, in the hippocampus the BDNF level was significantly decreased in FSL compared to FRL rats while no differences were found in the frontal cortex and CSF. The differential regulation of the BDNF levels in hippocampus, serum, and whole blood in FSL/FRL rats adds to the hypothesis that neurotrophic factors are related to the pathophysiology of depression.

Exercise-induced normalization of decreased BDNF serum concentration in elderly women with remitted major depression

Major depression (MD) has been associated with decreased brain-derived neurotrophic factor (BDNF) serum levels, while antidepressant drugs were found to increase these decreased BDNF levels. We investigated if this is also caused by a single exercise session in elderly women with remitted MD. In our study 35 elderly women with a (partially) remitted depressive episode of unipolar depression according to DSM-IV criteria within the last year and 20 age-matched healthy female controls were included. Depression severity was assessed by HAMD. Serum levels of BDNF were measured by ELISA. Blood samples were taken during the rest period before beginning the exercise including spiroergometry, at the end of the exercise and after a 30-min recovery period. At baseline MD patients showed significantly decreased BDNF serum levels compared to healthy female controls. After a single 30-min exercise period, we found a significant increase of BDNF serum levels in MD patients towards values comparable with the baseline levels of the healthy controls, followed by a significant decrease after 30 min rest, while the healthy controls showed only a mild but non-significant increase. In conclusion, a single exercise session leads to a significant up-regulation and transient normalization of BDNF serum levels in elderly women with remitted MD. This mechanism may contribute to the beneficial therapeutic and relapse-preventing effects of physical activity on MD.

Decreased BDNF in patients with antipsychotic naïve first episode schizophrenia

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) is a key factor known to mediate neuronal proliferation, differentiation, survival and response to stress. Decreases in BDNF levels have been reported in schizophrenia, but studies in treatment naïve patients are few. Herein we report on serum BDNF levels in a series of patients with first-episode treatment naïve psychoses in comparison to age matched healthy controls.

METHOD

Fasting serum BDNF levels were measured in 41 patients with treatment naive first episode psychosis (24 with schizophrenia, schizoaffective disorder or schizophreniform disorder, and 17 with non-schizophrenia psychotic disorders) and 41 age-matched healthy controls.

RESULTS

A three group analyses of covariance (ANCOVA) showed a diagnosis effect (p=.038) in which patients with schizophrenia had lesser serum BDNF levels than patient with non-schizophrenia psychosis, who in turn had lesser BDNF levels than matched healthy controls. Planned two-group ANCOVAs suggested that patients with schizophrenia had lower serum BDNF level than matched controls (p=.016), whereas patients with non-schizophrenia psychosis did not differ from controls. There were no age effects on BDNF, but there was a trend (p=.08) for a gender by group interaction with greater reductions in female patients with schizophrenia. The BDNF levels did not correlate with magnitude of smoking, body mass index, severity of positive and negative symptoms or overall functioning.

CONCLUSIONS

Serum BDNF may be reduced at the onset of psychosis but its role in the pathogenesis of schizophrenia remains unclear. Elucidating the role of BDNF in schizophrenia and related psychotic disorders may provide an important therapeutic target. Further studies are also needed to examine if patients with schizophrenia have more pronounced reductions in BDNF than those with affective psychosis.

Brain-derived neurotrophic factor gene and protein expression in pediatric and adult depressed subjects

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a member of a neurotrophin family and is involved in many physiological functions, including cell proliferation, migration, and differentiation, and neuron survival in the human nervous system. Abnormalities of BDNF have been implicated in the pathophysiology of depression based on observations that antidepressant drugs cause increases in the levels of BDNF in rat brains and its abnormalities have appeared in the serum of depressed patients and in postmortem brains of suicide victims.

METHODS

We examined the gene expression of BDNF in the lymphocytes and protein expression in the platelets of adult and pediatric depressed patients during a drug-free period. We determined BDNF gene expression using a quantitative RT-PCR method and protein expression using the ELISA method.

RESULTS

We observed that the gene expression of BDNF was significantly decreased in the lymphocytes of adult and pediatric depressed patients compared with normal control subjects. Similarly, the protein expression of BDNF was significantly decreased in the platelets of adult and pediatric depressed patients compared with normal control subjects.

CONCLUSIONS

To our knowledge, this is the first study that reports a decrease in BDNF gene expression in the peripheral cells of depressed patients. Because of the bidirectional movement of BDNF between the periphery and the CNS, the reduced gene expression in the lymphocytes and the protein expression in the platelets may be an index of similar abnormalities in the brain and could be a target for antidepressant drugs.

Salivary glands as the source of plasma brain-derived neurotrophic factor in stressed rats engaged in biting behavior

Brain-derived neurotrophic factor (BDNF) is crucial for the survival and differentiation of the central and peripheral nervous systems. Recently, BDNF has been reported to exert broader biological activity on non-neural cells. A previous study examined the effect of immobilization stress on BDNF and its receptor tyrosine receptor kinase B in male rat submandibular glands. In the present study, we found that the rat submandibular gland is the major source of plasma BDNF during acute immobilization stress. Biting modulates the mRNA and protein levels of BDNF in the rat hippocampus, so we also investigated whether the plasma BDNF concentration is influenced by biting. Two hours of acute immobilization stress significantly increased the amount of BDNF mRNA within the rat submandibular glands. Moreover, allowing biting behavior for the second half of the 2-h stress exposure significantly increased the amount of salivary gland BDNF mRNA relative to stress alone. Similar results were found with plasma BDNF concentrations under the same conditions. We confirmed that biting during stress attenuates the increases in plasma adrenocorticotropic hormone and corticosterone concentrations, but this was not dependent on the submandibular glands. Increased BDNF, mRNA and protein expressions were observed in salivary duct cells as a result of immobilization stress and biting behavior, as demonstrated by real-time polymerase chain reaction, immunohistochemistry, western blotting, and enzyme-linked immunosorbent assay. Taken together, the findings indicate that the submandibular glands evidently contribute to the increase in plasma BDNF upon biting.