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

Addition of risperidone to sertraline improves sertraline-resistant refractory depression without influencing plasma concentrations of sertraline and desmethylsertraline

In the present study, we examined the efficacy of risperidone addition on sertraline-resistant depressed patients and the effects of risperidone on the metabolism of sertraline. Ten patients (M/F: 4/6, age: 54 +/- 10 years) met the DSM-IV criteria for major depressive disorder enrolled the study. Hamilton Dating Scale for Depression (HAM-D) scores (mean +/- SD) in all 10 patients significantly decreased from 19 +/- 4 (before risperidone addition) to 11 +/- 3 (4 weeks after risperidone addition). Plasma levels of sertraline and desmethylsertraline did not change after risperidone addition. Serum BDNF levels in responders to risperidone addition were changed from 8.1 +/- 2.7 ng/ml (before risperidone addition) to 11.5 +/- 0.9 ng/ml (4 weeks after risperidone addition); in contrast, those in nonresponders changed from 7.8 +/- 2.2 ng/ml (before risperidone addition) to 7.9 +/- 2.4 ng/ml (4 weeks after risperidone addition). These results suggest that the addition of risperidone to sertraline is effective and well tolerated for sertraline-resistant depressive patients, which is accompanied with the increase in serum BDNF levels in responders to the risperidone addition, and the addition of risperidone to sertraline does not seem to influence sertraline metabolism.

Reduced serum concentrations of nerve growth factor, but not brain-derived neurotrophic factor, in chronic cannabis abusers

Chronic cannabis use produces effects within the central nervous system (CNS) which include deficits in learning and attention tasks and decreased brain volume. Neurotrophins, in particular nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are proteins that serve as survival factors for CNS neurons. Deficits in the production and utilization of these proteins can lead to CNS dysfunctions including those associated with cannabis abuse. In this study we measured by enzyme-linked immunosorbent assay (ELISA) the NGF and BDNF serum levels in two groups of subjects: cannabis-dependent patients and healthy subjects. We found that NGF serum levels were significantly reduced in cannabis abusers as compared to healthy subjects. These findings indicate that NGF may have a role in the central action of cannabis and potentially in the neurotoxicity induced by this drug. These data also suggest that chronic cannabis consumption may be a risk factor for developing psychosis among drug users.

A longitudinal observation of brain-derived neurotrophic factor mRNA levels in patients with relapsing-remitting multiple sclerosis

This report is part of a 2-year study assessing the functional effect of Brain-Derived Neurotrophic Factor (BDNF) and its Val66Met polymorphism on a selected population of Relapsing-Remitting Multiple Sclerosis (RRMS) patients from Southern Italy. For this purpose, we measured the peripheral BDNF expression in RRMS patients compared to healthy controls. The influence of concomitant IFNbeta therapy was also evaluated. Thirty-six inactive RRMS patients and 37 healthy controls were genotyped for BDNF Val66Met, and total RNA was extracted at time-points 0-24 months. The BDNF level was quantified by ABI Prism 7900 HT Sequence Detection System, and its relative expression was calculated by the comparative method of 2(-DeltaDeltaCt). At baseline and after 24 months, the BDNF levels of RRMS patients resulted significantly higher than controls (p=0.001), independently of the concomitant IFNbeta treatment; no correlations were found with the investigated clinical and MRI features of MS. Otherwise, carriers of the Met-allele showed significantly higher levels of BDNF in RRMS patients than healthy controls (p=0.005). These data was replicated after a 24-month interval. The present study confirms the increased levels of peripheral BDNF levels in RRMS, even during the inactive phase of the disease. Although with caution due to the small sample size, it also underscores the potential role of the Val66Met polymorphism on the peripheral BDNF expression in RRMS. Functional studies are needed to better clarify this issue.

Brain-derived neurotrophic factor gene expression in pediatric bipolar disorder: effects of treatment and clinical response

OBJECTIVE

Pediatric bipolar disorder (PBD) is a major public health concern; however, little is known about the cellular and genetic factors that are involved in the pathophysiology of this illness. The observed structural abnormality in the brains of patients with mood disorders has been related to abnormal brain-derived neurotrophic factor (BDNF) function, suggesting an important role for BDNF in these disorders.

METHOD

We determined the gene expression of BDNF in lymphocytes obtained from 26 PBD subjects during a drug-free baseline period and during the eighth week of treatment (n = 19) and from 21 medication-free normal control subjects. We also determined the protein levels of BDNF in platelets of patients with PBD and normal control subjects. Subjects were diagnosed according to DSM-IV diagnostic criteria using the Washington University at St. Louis Schedule for Affective Disorders and Schizophrenia.

RESULTS

The mRNA levels of BDNF in lymphocytes of PBD subjects were significantly decreased compared with those of normal control subjects and were significantly higher in 19 subjects after 8 weeks of treatment than the pretreatment drug-free baseline levels and similar to those of normal controls. Similarly, protein levels of BDNF were decreased in platelets of patients with PBD.

CONCLUSIONS

These studies suggest that BDNF levels may be a potential biomarker for PBD. BDNF levels may also serve as a potential treatment predictor and prognostic indicator in PBD.

BDNF levels and genotype are associated with antipsychotic-induced weight gain in patients with chronic schizophrenia

Recent evidence suggests that centrally released brain-derived neurotrophic factor (BDNF) modulates eating behavior and metabolism that is responsible for body weight fluctuation. BDNF also may play an important role in the therapeutic action of antipsychotic medications. We investigated whether the Val66Met polymorphism of the BDNF gene affected weight gain after long-term antipsychotic treatment in schizophrenia. The polymorphism was genotyped in 196 Chinese patients with schizophrenia on long-term antipsychotic medication. Serum BDNF was measured in all patients and 50 normal controls. Mean body mass index (BMI) change was evaluated retrospectively by means of clinical records. The results showed that there was a significant relationship between the three BDNF Val/Met genotypes and mean BMI gain, with genotype having a strong effect on BMI gain in male but not female patients. BDNF levels were significantly lower in patients than normal controls, and negatively correlated with BMI gain in female but not male patients. Our results suggest that variation in the BDNF gene may be a risk factor for weight gain in male patients with schizophrenia on long-term antipsychotic treatment, and decreased BDNF levels may be associated with weight gain in females.

Blood levels of brain-derived neurotrophic factor correlate with several psychopathological symptoms in anorexia nervosa patients

BACKGROUND

Evidence of a role of brain-derived neurotrophic factor (BDNF) in the pathophysiology of eating disorders (ED) has been provided by association studies and by murine models. BDNF plasma levels have been found altered in ED and in psychiatric disorders that show comorbidity with ED.

AIMS

Since the role of BDNF levels in ED-related psychopathological symptoms has not been tested, we investigated the correlation of BDNF plasma levels with the Symptom Checklist 90 Revised (SCL-90R) questionnaire in a total of 78 ED patients.

METHODS

BDNF levels, measured by the enzyme-linked immunoassay system, and SCL-90R questionnaire, were assessed in a total of 78 ED patients. The relationship between BDNF levels and SCL-90R scales was calculated using a general linear model.

RESULTS

BDNF plasma levels correlated with the Global Severity Index and the Positive Symptom Distress Index global scales and five of the nine subscales in the anorexia nervosa patients. BDNF plasma levels were able to explain, in the case of the Psychoticism subscale, up to 17% of the variability (p = 0.006).

CONCLUSION

Our data suggest that BDNF levels could be involved in the severity of the disease through the modulation of psychopathological traits that are associated with the ED phenotype.

Efficacy of electroconvulsive therapy is associated with changing blood levels of homovanillic acid and brain-derived neurotrophic factor (BDNF) in refractory depressed patients: a pilot study

Electroconvulsive therapy (ECT) is effective for patients with antidepressant medication-resistant depression. However, the mechanisms of ECT's effectiveness for treating depression are not fully understood. We therefore investigated ECT's effects on blood levels of brain-derived neurotrophic factor (BDNF), catecholamine metabolites, and nitric oxide (NO) in 18 treatment-refractory depressed patients. Serum BDNF levels increased significantly following ECT in responders to ECT (before ECT: 8.0+/-9.7 ng/mL; five weeks after start of ECT: 15.1+/-11.1 ng/mL), whereas BDNF levels in non-responders were unchanged (before ECT: 11.5+/-11.0 ng/mL; five weeks after start of ECT: 9.4+/-7.5 ng/mL). Furthermore, the plasma HVA levels, but not MHPG levels, were significantly reduced after ECT (before ECT: 8.5+/-1.9 ng/mL; five weeks after start of ECT: 5.8+/-2.2 ng/mL). This latter finding occurred in parallel with the improvement of depressive symptoms in all patients. These results suggest that the mechanisms underlying ECT's effect on refractory depression may be related to dopaminergic neurons and BDNF.

Investigation of serum BDNF levels in drug-naive patients with schizophrenia

The role of brain-derived neurotrophic factor (BDNF) is to promote and modulate the neuronal responses across neurotransmitter systems in the brain. Therefore, abnormal BDNF signaling may be associated with the pathophysiology of schizophrenia. Decreased BDNF levels in the brain and the serum of patients with psychotic disorders have been reported. In the present study, we assessed serum BDNF levels in a group of 14 drug-naive first-episode patients with schizophrenia (FEP), compared to 15 healthy controls. The serum BDNF levels in the sample of FEP patients was significantly reduced compared to normal controls (23.92+/-5.99 ng/ml vs. 30.0+/-8.43 ng/ml, F=5.01, df=1, p=.034). Negative correlations were shown between serum BDNF levels of the patients and the PANSS Positive and Negative subscale scores. Our findings indicate that BDNF levels at the onset of schizophrenia may reflect associated pathophysiological processes as well as the severity of positive and negative psychotic symptoms.

Permeation of blood-borne IL15 across the blood-brain barrier and the effect of LPS

Interleukin15 (IL 15) is a proinflammatory cytokine with elevated concentrations in autoimmune diseases involving the periphery (e.g. rheumatoid arthritis) and CNS (e.g. multiple sclerosis). Its interactions with the blood-brain barrier (BBB) were studied in normal and lipopolysaccharide (LPS)-treated mice. (125)I-IL15 remained intact for at least 10 min after i.v. injection and reached CNS parenchyma with regional differences between brain and spinal cord. Both in vivo and in situ brain perfusion of (125)I-IL15 showed that its permeation of the BBB was non-saturable. LPS induced a significant increase of IL15 uptake by the brain and spinal cord, partly related to a higher general permeability of the BBB. The results suggest that the BBB is an interface for blood-borne IL15 to interact with the CNS in the basal state and during inflammation.

Serum brain-derived neurotrophic factor levels in patients with major depression: effects of antidepressants

This study tried to investigate the relationships between serum brain-derived neurotrophic factor (BDNF) protein levels and major depressive patients and discuss the effects of antidepressants on the serum BDNF protein levels. A total of 218 participants, including 111 patients with major depression (91 women) and 107 healthy controls (65 women), were recruited in this study. Serum BDNF protein levels were measured using an ELISA kit. Psychiatric diagnoses were made according to DSM-IV criteria. Severity of major depression was assessed by the 17-item Hamilton Depression Rating Scale. Using analysis of covariance with age adjustment, there were significantly low serum BDNF protein levels in depressive patients than healthy controls in women (F=7.530, p=0.007), but not in men. Additionally, changes in serum BDNF protein levels were significantly increased in 79 patients taking antidepressants during a period of 4 weeks (t=2.116, p=0.038), especially in 61 women (t=2.542, p=0.014). Age-adjusted ANCOVA revealed no significant differences in serum BDNF protein levels between 58 responders and 21 non-responders (F=0.008, P=0.928). In responders, there were significantly increased changes in serum BDNF protein levels in 44 women (t=2.501, p=0.016), but not in 14 men (t=-0.767, p=0.457). These analytical results suggest that low serum BDNF may play an important role in depressive women and antidepressant treatment significantly increase serum BDNF. However, further studies of larger populations are necessary to confirm these results and further elucidate the effects of different classes of antidepressants on serum BDNF protein levels.

Blood level of brain-derived neurotrophic factor mRNA is progressively reduced in rodent models of Huntington's disease: restoration by the neuroprotective compound CEP-1347

Huntington's disease (HD) is an age-related neurodegenerative disorder that is currently untreatable. A prominent feature of HD pathology is the reduction of the pro-survival neurotrophin Brain-Derived Neurotrophic Factor (BDNF). Both mRNA and protein levels of BDNF are decreased in the brains of several HD rodent models and in human HD patients. We now report for the first time that this molecular event is mirrored in blood from HD rodent models. While protein levels of BDNF are undetectable in mouse blood, mRNA levels are measurable and diminish during HD progression in transgenic mouse (R6/2) and rat models of HD. Among the eight different BDNF transcripts, only BDNF exon III is transcribed in mouse blood and its expression is progressively compromised in R6/2 mice with respect to age-matched wild-types. Assessment of BDNF mRNA in HD rat blood shows a similar result, which is reinforced by evidence that protein levels of the neurotrophin are also significantly reduced at a symptomatic stage. Finally, we demonstrate that acute and chronic treatment of R6/2 mice with CEP-1347, a mixed lineage kinase (MLK) inhibitor with neuroprotective and neurotrophic effects, leads to increased total BDNF mRNA in blood when compared to untreated R6/2 mice. Our results indicate that alterations in BDNF mRNA levels in peripheral blood are a readily accessible measurement of disease progression and drug efficacy in HD rodent models.

Effect of treatment on serum glial cell line-derived neurotrophic factor in depressed patients

Post-mortem studies have demonstrated a decreased number of glia, reduced glial density, and a decreased glia/neuron ratio in different brain areas of patients diagnosed with a major depressive disorder (MDD). Researchers have therefore suggested that neurotrophic growth factor systems might be involved in the aetiology of MDD. This study aimed to test whether glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor beta family, in serum was associated with MDD. Serum concentrations were measured in MDD patients before treatment (n=76), after 8 weeks of antidepressant treatment (n=39), and in control subjects (n=50) using a sandwich ELISA method. Serum GDNF was significantly lower in MDD patients before treatment than in control subjects (P<0.001). From baseline to remission after 8 weeks of treatment, the increase in serum GDNF was statistically significant (P<0.001). The present study suggests that lower serum GDNF might be involved in the pathophysiology of MDD and antidepressant treatment increases the GDNF in MDD.

Low serum levels of brain-derived neurotrophic factor and epidermal growth factor in patients with chronic schizophrenia

Neurotrophic factors (NFs) play a pivotal role in the development of the central nervous system. They are thus also suspected of being involved in the etiology of schizophrenia. Previous studies reported a decreased level of serum brain-derived neurotrophic factor (BDNF) in schizophrenia, whereas the association of epidermal growth factor (EGF) with this illness remains controversial. Using a two-site enzyme immunoassay, we conducted the simultaneous measurement of serum BDNF and EGF levels in a group of patients with chronic schizophrenia (N=74) and a group of normal controls matched in age, body mass index, smoking habit and sex (N=87). We found that, compared to normal controls, patients with chronic schizophrenia exhibited lower serum levels of both BDNF and EGF across all ages examined (21-59 years). The serum levels of BDNF and EGF were negatively correlated in the controls (r=-0.387, P=0.0002) but not in the patients. Clinical parameters such as duration of illness and psychiatric rating scale also showed no robust correlations with the NF levels. Collectively, these results suggest that pervasive, abnormal signaling of NFs underlies the pathophysiology of chronic schizophrenia.

Stress at work alters serum brain-derived neurotrophic factor (BDNF) levels and plasma 3-methoxy-4-hydroxyphenylglycol (MHPG) levels in healthy volunteers: BDNF and MHPG as possible biological markers of mental stress?

There is growing evidence that blood levels of brain-derived neurotrophic factor (BDNF) and catecholamine, and cytokines are related to not only to depressive, suicidal, and anxious states but also to depression-associated personality traits. Psychological job stress is well known to lead to symptoms of depression and anxiety. In the present study, we examined effects of psychological job stress on serum levels of BDNF and plasma levels of catecholamine metabolites, and cytokines in healthy volunteers (n=106, male/female=42/64, age=36+/-12 yr) working in a hospital setting. The values (mean+/-SD) of scores for stress items in the Stress and Arousal Check List (s-SACL), plasma MHPG levels, and, serum BDNF levels in all participants were 7.2+/-3.3, 5.2+/-3.4 ng/mL, and 23.3+/-14.7 ng/mL, respectively. A negative correlation was found between scores for s-SACL and serum BDNF levels (rho=-0.211, p=0.022). A positive correlation was also found between scores on the s-SACL and plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) (rho=0.416, p=0.01), but not homovanillic acid (HVA). No relationship was found between s-SACL scores and plasma levels of interleukin-6 (IL-6) or tumor necrosis factor alpha (TNFalpha). These results suggest that serum BDNF levels and plasma MHPG levels might be biological markers reflective of psychological job stress in hospital employees.

Impact of exercise on neuroplasticity-related proteins in spinal cord injured humans

The present study investigated the effects of exercise on the serum concentrations of brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), prolactin (PRL) and cortisol (COR) in 11 chronically spinal cord-injured athletes. In these subjects BDNF concentration at rest was sixfold higher compared with the concentrations reported earlier in able-bodied persons, while IGF-1, PRL and COR were within normal range. Ten minutes of moderate intensity handbiking (54% of the maximal heart rate) during a warm-up period (W) induced an increase (P<0.05) of BDNF of approximately 1.5-fold from basal level at rest, while a decrease to basal level was found after an immediately succeeding handbiking time trial (89% of the maximal heart rate) over the marathon distance of 42 km (M). An increase (P<0.01) of serum IGF-1 was found after W and this levels remained elevated (P<0.01) until the end of M. W had no significant effects on the serum PRL and COR, however, M induced an increase (P<0.01) of both hormones. This is the first study showing elevated BDNF concentrations at rest in spinal cord-injured athletes. Furthermore, short moderate intensity handbiking but not immediately following long lasting high intensity handbiking further increases serum BDNF concentrations. IGF-1 response to exercise differs to BDNF response as this neuroplasticity-related protein remains elevated during the long lasting physical demand with high intensity. The augmented PRL concentration suggests that a possible mechanism by which exercise promotes neuroplasticity might be the activation of neural serotonergic pathways as 5-HT is the main PRL releasing factor. Elevated COR concentrations after M are unlikely to be deleterious to neuroplasticity as COR concentrations remain within the physiological range. The present study suggests that exercise might be beneficial to enhance neuroprotection and neuroplasticity, thereby improving recovery after spinal cord injury.

Increase of BDNF serum concentration during donepezil treatment of patients with early Alzheimer's disease

Alzheimer's disease (AD) can be treated with inhibitors of the enzyme acetylcholinesterase (AChE). Recent pre-clinical and clinical studies gave evidence that AChE-inhibitors have neuroprotective effects and thereby a disease-modifying potential. The mechanism of this action is still discussed. In an animal model oral administration of an AChE-inhibitor lead to an increase of brain derived neurotrophic factor (BDNF) in hippocampus and cortex. Recent studies have found a decrease of BDNF in the serum and brain of AD patients with potentially consecutive lack of neurotrophic support and contribution to progressive neurodegeneration. BDNF serum concentrations were assessed by ELISA in 19 AD patients and 20 age-matched healthy controls at baseline and in the AD patients after 15 months of treatment with donepezil 10 mg per day (one patient received just 5 mg). Before treatment with donepezil we found in AD significantly decreased BDNF serum concentrations (19.2 +/- 3.7 ng/ml) as compared to healthy controls (23.2 +/- 6.0 ng/ml, P = 0.015). After 15 months of treatment the BDNF serum concentration increased significantly in the AD patients (23.6 +/- 7.0 ng/ml, P = 0.001) showing no more difference to the healthy controls (P = 0.882). The results of the present study confirm data of prior investigations that a down-regulation of BDNF in serum and brain of AD patients seems to begin with the first clinical symptoms and to be persistent. A treatment with the AChE-inhibitor donepezil is accompanied with an increase of BDNF serum concentration in AD patients reaching the level of healthy controls. Thus, up-regulation of BDNF might be part of a neuroprotective effect of AChE-inhibitors. The molecular mechanism of this potentially disease-modifying mechanism of action of donepezil should be clarified.

Developmental changes of leptin receptors in cerebral microvessels: unexpected relation to leptin transport

The adipokine leptin participates not only in the regulation of feeding and obesity in adults but also in neonatal development. It crosses the blood-brain barrier (BBB) by receptor-mediated transport. Leptin concentrations in blood differ between neonates and adults. We determined the developmental changes of leptin receptor subtypes in the cerebral microvessels composing the BBB and examined their expected correlation with leptin transport across the BBB. Total RNA was extracted from enriched cerebral microvessels of mice 1, 7, 14, and 60 d of age for real-time RT-PCR analysis of leptin receptor subtypes. In cerebral microvessels from neonates, ObRa, ObRb, ObRc, and ObRe mRNA were all higher than in adults, but ObRd was not detectable. Hypothalamus showed similar age-related changes except for ObRb, which was higher in adults. The homologous receptor gp130 did not show significant age-related changes in either region. Despite the increase of leptin receptors, leptin permeation across the BBB after iv injection was less in the neonates. In situ brain perfusion with blood-free buffer showed no significant difference in the brain uptake of leptin between neonates and adults, indicating an antagonistic role of leptin-binding proteins in the circulation, especially the soluble receptor ObRe. The results are consistent with our previous finding that ObRe antagonizes leptin endocytosis in cultured endothelia and transport from blood to brain in mice. Overall, the developmental changes observed for leptin receptors unexpectedly failed to correlate with the entry of leptin into brain, and this may indicate different functions of the receptors in neonates and adults.

Peripheral Blood Leukocyte Production of BDNF following Mitogen Stimulation in Early Onset and Regressive Autism

Brain-derived neurotrophic factor (BDNF) is critical for neuronal differentiation and synaptic development. BDNF is also implicated in the development of psychological disorders including depression, bipolar disorder and schizophrenia. Previously, elevated BDNF levels were observed in neonatal blood samples from infants who were later diagnosed with autism when compared with children who developed normally, suggesting that BDNF may be involved in the development of autism. BDNF is produced by activated brain microglial cells, a cellular phenotype that shares several features with peripheral macrophages, suggesting an important role for the immune system in BDNF production. We hypothesized that under mitogenic stimulation, peripheral blood mononuclear cells obtained from children with autism may have altered BDNF production compared with age-matched typically developing control subjects. In addition, we examined the differences between the production of BDNF in classic/early-onset autism and children who had a regressive form of autism. We show here that plasma levels of BDNF levels are increased in children with autism, especially in early onset autism subjects. Furthermore, under mitogenic stimulation with PHA and LPS, BDNF production is significantly increased in children with autism compared with typically developing subjects. However, stimulation with tetanus toxoid results in a decreased response in children with autism. This data suggest that immune cell-derived production of BDNF could be an important source for the increased BDNF that is detected in some subjects with autism. As a neurotrophic factor produced by immune cells, BDNF could help elucidate the role of the immune system in neurodevelopment and neuronal maintenance, which may be dysregulated in autism.

Decreased levels of serum brain-derived neurotrophic factor in both depressed and euthymic patients with unipolar depression and in euthymic patients with bipolar I and II disorders

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) has been proposed as a candidate molecule in the pathophysiology of major depressive disorder (MDD) and bipolar disorders (BD). Reduced levels of peripheral BDNF have been found in drug-free MDD patients, in drug-treated depressed or manic patients with BD type I (BD-I), but not in drug-treated euthymic BD-I individuals. No study has been done in patients with BD type II (BD-II). Moreover, the influence of Axis I psychiatric comorbidity on circulating BDNF in affective patients has never been evaluated. Therefore, in the present study, we aimed: (i) to confirm previous findings on peripheral BDNF in MDD and BD-I patients; (ii) to assess whether changes in circulating BDNF occur also in patients with BD-II; and (iii) to exclude the possibility that comorbid psychiatric disorders exerted an effect on BDNF levels in affective patients.

METHODS

We measured serum BDNF concentrations by an enzyme-linked immunosorbent assay method in 85 subjects, including 24 euthymic patients with unipolar depression (UD), 17 euthymic patients with BD-I, 11 euthymic patients with BD-II, 11 UD patients with a current major depressive episode and 22 drug-free healthy controls. At the time of the study, 15 patients were drug-treated; the remaining ones were drug-free for at least four weeks.

RESULTS

Compared to healthy controls, serum BDNF concentrations were significantly reduced in all the patient groups (F(4,80) = 3.840, p = 0.006) with no significant difference among them. Drug treatments and comorbid psychiatric disorders had no effect on lowered circulating BDNF levels in affective patients.

CONCLUSIONS

Present results confirm previous independent findings of reduced circulating BDNF in patients with MDD and report, for the first time, decreased serum BDNF levels in euthymic patients with UD, BD-I and BD-II, independently from drug treatment status and concomitant Axis I psychiatric disorders.

Neurobiological factors linking personality traits and major depression

OBJECTIVE

To examine the neurobiological basis of personality and depression.

METHOD

We examined preclinical and clinical studies related to neuroanatomy, neuroendocrine, molecular, and genetic alterations in depressed patients. We considered whether common neurobiological factors might be shared between personality and depression.

RESULTS

Preclinical studies provide insights into the neurobiological mechanisms underlying the pathophysiology of depression including neuroendocrine alterations in hypothalamic-pituitary-adrenal (HPA) function, neuroanatomical alterations in key brain regions, and alterations in neurotrophin and serotonergic signalling systems. Clinical studies show similar alterations in depressed patients. Evidence suggests that neuroendocrine alterations in HPA function may contribute to personality traits. Brain regions implicated in depression, including the hippocampus and the anterior cingulate cortex, might play a role in personality. Key molecules implicated in depression have been extensively studied with reference to personality traits, particularly neuroticism. To date, physiological measures (serum and positron emission tomography) provide the strongest evidence implicating brain-derived neurotrophic factor and serotonin in personality, while genetic evidence is less convincing.

CONCLUSIONS

A neurobiological link exists between personality and depression; however, more work is needed to provide an understanding of the nature of this relation and to link this work with clinical studies examining the influence of personality factors on depression.

Blood-brain barrier and feeding: regulatory roles of saturable transport systems for ingestive peptides

The two main ways for peptides in the peripheral body to enter the brain are by either saturable transport or passive diffusion across the blood-brain barrier (BBB). Saturable transport systems have the advantage of being responsive to physiological and pathological stimuli. Since saturable systems can regulate peptide entry into the brain, they have the potential to play controlling roles in feeding behavior. For therapeutic applications, however, saturable systems have the disadvantage of functioning as a threshold to limit access of large amounts of peptides into the brain. This pharmacological problem presumably would not be encountered for peptides crossing the BBB by passive diffusion, a process dependent on physicochemical properties. Thus, the gatekeeper function of the BBB can be expanded to a primary governing role, especially for entry of ingestive peptides subject to their respective saturable transport systems.

Chronic heroin and cocaine abuse is associated with decreased serum concentrations of the nerve growth factor and brain-derived neurotrophic factor

Chronic cocaine and heroin users display a variety of central nervous system (CNS) dysfunctions including impaired attention, learning, memory, reaction time, cognitive flexibility, impulse control and selective processing. These findings suggest that these drugs may alter normal brain functions and possibly cause neurotoxicity. Neurotrophins are a class of proteins that serve as survival factors for CNS neurons. In particular, nerve growth factor (NGF) plays an important role in the survival and function of cholinergic neurons while brain-derived neurotrophic factor (BDNF) is involved in synaptic plasticity and in the maintenance of midbrain dopaminergic and cholinergic neurons. In the present study, we measured by enzyme-linked immunosorbent assay (ELISA) the NGF and BDNF levels in serum of three groups of subjects: heroin-dependent patients, cocaine-dependent patients and healthy volunteers. Our goal was to identify possible change in serum neurotrophins in heroin and cocaine users. BDNF was decreased in heroin users whereas NGF was decreased in both heroin and cocaine users. These findings indicate that NGF and BDNF may play a role in the neurotoxicity and addiction induced by these drugs. In view of the neurotrophin hypothesis of schizophrenia the data also suggest that reduced level of neurotrophins may increase the risk of developing psychosis in drug users.

Altered brain-derived neurotrophic factor blood levels and gene variability are associated with anorexia and bulimia

Murine models and association studies in eating disorder (ED) patients have shown a role for the brain-derived neurotrophic factor (BDNF) in eating behavior. Some studies have shown association of BDNF -270C/T single-nucleotide polymorphism (SNP) with bulimia nervosa (BN), while BDNF Val66Met variant has been shown to be associated with both BN and anorexia nervosa (AN). To further test the role of this neurotrophin in humans, we screened 36 SNPs in the BDNF gene and tested for their association with ED and plasma BDNF levels as a quantitative trait. We performed a family-based association study in 106 ED nuclear families and analyzed BDNF blood levels in 110 ED patients and in 50 sib pairs discordant for ED. The rs7124442T/rs11030102C/rs11030119G haplotype was found associated with high BDNF levels (mean BDNF TCG haplotype carriers = 43.6 ng/ml vs. mean others 23.0 ng/ml, P = 0.016) and BN (Z = 2.64; P recessive = 0.008), and the rs7934165A/270T haplotype was associated with AN (Z =-2.64; P additive = 0.008). The comparison of BDNF levels in 50 ED discordant sib pairs showed elevated plasma BDNF levels for the ED group (mean controls = 41.0 vs. mean ED = 52.7; P = 0.004). Our data strongly suggest that altered BDNF levels modulated by BDNF gene variability are associated with the susceptibility to ED, providing physiological evidence that BDNF plays a role in the development of AN and BN, and strongly arguing for its involvement in eating behavior and body weight regulation.

Serum brain-derived neurotrophic factor levels in conversion disorder: Comparative study with depression

The aim of the present study was to compare serum brain-derived neurotrophic factor (BDNF) levels of patients with major depressive disorder (MDD) and conversion disorder (CD). Serum BDNF levels were measured in the following three groups: 15 CD patients without any comorbid diagnosis of psychiatric disorder, 24 patients with MDD, and 26 healthy subjects without any psychiatric diagnosis or psychiatric treatment. The serum BDNF level of the healthy control group (31.4 +/- 8.8 ng/mL) was statistically higher than the level of the MDD group (21.2 +/- 11.3 ng/mL) and the CD group (24.3 +/- 9.0 ng/mL; P = 0.008). This suggests that BDNF level may play a similar role in the pathophysiology of MDD and CD.

Increased BDNF serum concentration in fibromyalgia with or without depression or antidepressants

Fibromyalgia (FM) is still often viewed as a psychosomatic disorder. However, the increased pain sensitivity to stimuli in FM patients is not an "imagined" histrionic phenomena. Pain, which is consistently felt in the musculature, is related to specific abnormalities in the CNS pain matrix. Brain-derived neurotrophic factor (BDNF) is an endogenous protein involved in neuronal survival and synaptic plasticity of the central and peripheral nervous system (CNS and PNS). Several lines of evidence converged to indicate that BDNF also participates in structural and functional plasticity of nociceptive pathways in the CNS and within the dorsal root ganglia and spinal cord. In the latter, release of BDNF appears to modulate or even mediate nociceptive sensory inputs and pain hypersensitivity. We were interested, if BDNF serum concentration may be altered in FM. The present pilot study assessed to our knowledge for the first time BDNF serum concentrations in 41 FM patients in comparison to 45 age-matched healthy controls. Mean serum levels of BDNF in FM patients (19.6 ng/ml; SD 3.1) were significantly increased as compared to healthy controls (16.8 ng/ml; SD 2.7; p<0.0001). In addition, BDNF serum concentrations in FM patients were independent from age, gender, illness duration, preexisting recurrent major depression and antidepressive medication in low doses. In conclusion, the results from our study indicate that BDNF may be involved in the pathophysiology of pain in FM. Nevertheless, how BDNF increases susceptibility to pain is still not known.

Genetic engineering, expression, and activity of a fusion protein of a human neurotrophin and a molecular Trojan horse for delivery across the human blood-brain barrier

Neurotrophins, such as brain derived neurotrophic factor (BDNF), do not cross the blood-brain barrier (BBB). Certain monoclonal antibodies (MAb) to the human insulin receptor (HIR) do cross the BBB via receptor-mediated transport, and can act as a molecular Trojan horse to ferry across the BBB an attached drug. A genetically engineered fusion protein was produced whereby the amino terminus of human BDNF is fused to the carboxyl terminus of the heavy chain of a chimeric HIRMAb. The HIRMAb-BDNF fusion protein reacted equally with antibodies to human IgG and BDNF. The bi-functionality of the fusion protein was retained as the affinity of the fusion protein for the HIR was identical to that of the chimeric HIRMAb, and the affinity of the fusion protein for the trkB receptor was identical to that of BDNF. The fusion protein was equi-potent with BDNF in a neuroprotection assay in human neural cells. The pharmacokinetics (PK) of the fusion protein was examined in the adult Rhesus monkey. The mean residence time (MRT) of the fusion protein in blood was >100-fold longer than the MRT of BDNF. Therapeutic levels of BDNF were produced in primate brain following the intravenous administration of the fusion protein. A fusion protein tandem vector was engineered that allowed for isolation of a CHO cell line that produced the fusion protein at high levels in serum free medium. Neurotrophins, such as BDNF, can be re-formulated to enable these molecules to cross the human BBB, and such fusion proteins represent a new class of human neurotherapeutics.

Serum neurotrophins—A study on the time course and influencing factors in a large old age sample

The neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are important mediators of brain and neuronal development, the maintenance of homeostatic conditions in the adult nervous system, and the complex interplay of central and peripheral physiological and pathophysiological factors. To date there are few studies examining blood concentrations of neurotrophic factors in large samples of healthy and diseased individuals and no published study specifically addresses peripheral BDNF and NGF levels in late life. Using improved highly sensitive and specific fluorometric two-site enzyme-linked immunosorbent assays we examined BDNF (n=465) and NGF (n=175) serum levels in a large cohort of elderly individuals (age range: 70-103 years). Neither BDNF nor NGF serum levels proved to be normally distributed, indicating that previously published studies with small sample sizes using parametric testing may be misleading. A significant correlation was found between BDNF and platelet count (r=0.344, p<0.01), age and BDNF protein (r=-0.101, p=0.029) and BDNF and NGF serum levels (r=0.152, p=0.04). No other major influencing factors were found including gender, depression, and dementia.

Decreased levels of plasma glutamate in patients with first-episode schizophrenia and bipolar disorder

A variety of studies have suggested that glutamatergic neurotransmission is altered in schizophrenia and bipolar disorder. Here, we tested if plasma glutamate levels are altered in 56 patients diagnosed with schizophrenia, bipolar disorder or non-specified psychosis at the first psychotic episode and at various stages during one-year follow-up. A decrease in the levels of plasma glutamate was observed in all groups of patients at the first psychotic episode. Furthermore, plasma glutamate levels were restored after treatment in all instances. Decreased plasma glutamate levels at first psychotic episodes may reflect impaired glutamate signaling during the initial stages of schizophrenia and bipolar disorder.

Correlation between serum brain-derived neurotrophic factor level and an in vivo marker of cortical integrity

BACKGROUND

Brain-derived neurotrophic factor (BDNF) signaling at synapses improves synaptic strengthening associated with learning and memory. In the present study we hypothesized that serum BDNF concentration is associated with in vivo level of cerebral N-acetylaspartate (NAA), a well established marker of neuronal integrity.

METHODS

In 36 healthy subjects BDNF serum concentration and absolute concentration of NAA together with other metabolites were measured by proton magnetic resonance spectroscopy (1H-MRS) in regions with high BDNF levels (anterior cingulate cortex [ACC], left hippocampus). Relationship between BDNF concentration and brain metabolites was studied in linear regression analysis with BDNF concentration as dependent variable and metabolite concentrations, age, and gender as predictor variables.

RESULTS

The BDNF serum concentrations were positively associated with the concentrations of NAA (T = 2.193, p = .037) and total choline (T = 1.997, p = .055; trend) but not total creatine or glutamate in the ACC. No significant association was observed between BDNF serum concentration and absolute metabolite concentrations in the hippocampus.

CONCLUSIONS

The preliminary data might indicate that BDNF serum concentration reflects some aspects of neuronal plasticity as indicated by its association with NAA level in the cerebral cortex. The results would be in line with the notion that BDNF plays a central role in the regulation of neuronal survival and differentiation in the human brain.

Brain derived neurotrophic factor circulating levels in patients undergoing IVF

PURPOSE

The aim of the study was to measure circulating BDNF levels, a neurotrophin recently identified in the ovary, in parallel with estradiol, to verify if assessing this factor could add any predictive value to the outcome of in vitro fertilization.

METHODS

Blood sampling for BDNF and estradiol was performed in 23 subjects undergoing IVF on day 1 (D1), day 8 (D8), day of HCG administration (DHCG) and day of oocyte retrieval.(DOR).

RESULTS

There was a positive correlation between BDNF and estradiol throughout the stimulation cycle in all subjects. In both pregnant and nonpregnant patients, the values of BDNF grew significantly only between D8 and DHCG and remained constant until DOR. Between-group comparisons showed no statistically significant differences in both BDNF and estradiol values throughout the IVF cycle.

CONCLUSION

Although BDNF plasma concentrations are not seemingly predictive of IVF outcome, this neurotrophin is highly correlated to estradiol levels and seems to be an important factor especially in the periovulatory period.

Brain-derived neurotrophic factor and its receptor tropomyosin-related kinase B in the mechanism of action of antidepressant therapies

The focus of this review is to critically examine and review the literature on the role of brain-derived neurotrophic factor (BDNF) and its primary receptor, tropomyosin-related kinase B (TrkB), in the actions of pharmacologically diverse antidepressant treatments for depression. This will include a review of the studies on the regulation of BDNF and TrkB by different types of antidepressant drug treatments and animal in models of depression, as well as altered levels of BDNF and TrkB in the blood and postmortem brain of patients with depression. Results from clinical and basic studies have demonstrated that stress and depression decrease BDNF expression and neurogenesis and antidepressant treatment reverses or blocks these effects, leading to the neurotrophic hypothesis of depression. Clinical studies demonstrate an association between BDNF levels and several disorders, including depression, epilepsy, bipolar disorder, Parkinson's and Alzheimer's diseases. Physical activity and diet exert neurotrophic effects and positively modulate BDNF levels. A common single nucleotide polymorphism (SNP) in the BDNF gene, a methionine substitution for valine, is associated with alterations in brain anatomy and memory, but what role it has in clinical disorders is unclear. Findings suggest that early childhood events and adult stress produce neurodegenerative alterations in the brain that can eventually cause breakdown of information processing in the neuronal networks regulating mood. Antidepressant treatments elevate activity-dependent neuronal plasticity by activating BDNF, thereby gradually restoring network function and ultimately mood.

BDNF serum and CSF concentrations in Alzheimer's disease, normal pressure hydrocephalus and healthy controls

Alzheimer's disease (AD) and normal pressure hydrocephalus (NPH) are common forms of dementia in the elderly. Recent findings have suggested an involvement of brain-derived neurotrophic factor (BDNF) in the pathogenesis of AD. BDNF is an endogenous protein involved in the maintenance of neuronal function, synaptic plasticity and structural integrity in the adult brain. BDNF serum and cerebrospinal fluid (CSF) concentrations were assessed by a sensitive ELISA in 27 AD patients in comparison to 9 NPH patients and 28 age-matched healthy controls (10 CSF samples). We found a significant decrease of BDNF serum concentration in AD (18.6ng/ml) and NPH patients (18.1ng/ml) as compared to healthy controls (21.3ng/ml; p=0.041/p=0.017). BDNF serum concentrations did not correlate with CSF levels, age or MMSE scores both in AD and NPH patients. In unconcentrated CSF samples, BDNF could be detected in AD patients in 8/27 cases (29.6%; mean of 4.6pg/ml), in NPH patients in 1/9 cases (11.1%; mean of 6.4pg/ml) and in the control subjects in 5/10 cases (50%; mean of 1.6pg/ml) with no significant differences as regards mean concentration and frequency of detectable BDNF in CSF. The decrease of BDNF serum levels in AD and NPH may reflect a lack of trophic support and thus contribute to progressive degeneration in both diseases. In contrast to serum, CSF seems to be no useful source to determine BDNF in AD or NPH because of too low concentrations. Further examinations have to follow to elucidate the potential sources and the meaning of reduced BDNF levels in the blood in AD and NPH.

Decreased plasma BDNF level in depressive patients

BACKGROUND

Recent reports have suggested a pathophysiological role for brain-derived neurotrophic factor (BDNF) in major depressive disorder (MDD). We evaluated plasma levels of BDNF in patients with MDD.

METHODS

Plasma BDNF levels were measured in 77 MDD patients and 95 normal controls. The severity of psychiatric symptoms was measured with the Hamilton Depression Rating Scale and the Brief Psychiatric Rating Scale.

RESULTS

Plasma BDNF levels were significantly lower in MDD patients than in normal control subjects (p<0.001). Plasma BDNF levels were significantly lower in MDD patients with recurrent episodes than in MDD patients with the first episode or normal controls (p<0.001). Plasma BDNF levels were significantly lower in non-psychotic MDD patients than in psychotic MDD patients or normal controls (p<0.001). Plasma BDNF in suicidal MDD patients were significantly lower than those in non-suicidal MDD patients (p<0.001).

LIMITATIONS

We measured only plasma levels of BDNF. However, the cellular sources of BDNF in human plasma are not yet clearly defined.

CONCLUSIONS

Our study suggests that there is a decrease in plasma BDNF levels in untreated MDD patients. However, relapsed or recurrent episodes, suicidal behavior, and psychotic features could also affect the plasma levels of BDNF. Further studies are required to understand the source and role of the circulating BDNF in depression.

Serum brain-derived neurotrophic factor level in dysthymia: a comparative study with major depressive disorder

In this present work, it is aimed to demonstrate BDNF serum concentrations in patients with dysthymia and to compare them with BDNF serum concentrations in patients with major depressive disorder and healthy subjects. The study was carried out in Celal Bayar University Hospital, Manisa, Turkey. Seventeen patients with dysthymia, 24 patients with major depressive disorder and 26 subjects without any psychiatric diagnosis and any psychiatric treatment were included in the study. The severity of depression was assessed with 17-item HAM-D. All subjects were asked to give their written consent. Blood samples were collected at baseline. Serum BDNF was kept at -70 degrees C before testing, and assayed with an ELISA Kit (Promega; Madison, WI, USA), after dilution with the Block and Sample solution provided with the kit. The data were subjected to the analysis of variance. The BDNF serum concentrations of the dysthymia group (mean=28.9+/-9.2 ng/ml) were significantly higher than that of the major depressive disorder group (21.2+/-11.3 ng/ml) (p=0.002), and it was not different from the level of the control group (31.4+/-8.8 ng/ml). BDNF serum concentrations and HAM-D score did not have any significant correlation in the dysthymia and major depression groups (r=-0.276, p=0.086). The low level of BDNF in patients with dysthymic disorder seems to point out that BDNF changes in mood disorders are state-dependent and vary according to the severity of depressive episodes.

Treatment with risperidone for 4 weeks increased plasma 3-methoxy-4-hydroxypnenylglycol (MHPG) levels, but did not alter plasma brain-derived neurotrophic factor (BDNF) levels in schizophrenic patients

In the present study, we investigated the effects of risperidone treatment for 4 weeks on plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) and brain-derived neurotrophic factor (BDNF) in 89 schizophrenic patients. We also compared the plasma levels of BDNF and MHPG between the schizophrenic group and 103 sex-and age-matched normal controls. In addition, we investigated the effects of two SNPs of the noradrenaline transporter (NAT) gene on plasma levels of MHPG, BDNF, and clinical improvement. The mean dose of risperidone was 3.8+/-1.4 mg/day. We demonstrated that treatment with risperidone increased plasma MHPG levels, and this increase was associated with an improvement of the negative symptoms of schizophrenia. In contrast, plasma BDNF did not change after 4 weeks of risperidone treatment, and the two SNPs in NAT did not influence the response to risperidone treatment or plasma MHPG and BDNF levels. These results suggest that the enhancement of noradrenergic neurons by risperidone, which occurs independently of the two SNPs of NAT, plays a role in the clinical efficacy of the drug.

Low brain-derived neurotrophic factor (BDNF) levels in serum of Huntington's disease patients

Huntington's disease (HD) is a neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms and by a progressive degeneration of neurons in basal ganglia and in brain cortex. Brain-derived neurotrophic factor (BDNF) is a pro-survival factor for striatal neurons. Some evidence implicates a brain BDNF deficiency, related to mutated huntingtin expression, in the selective vulnerability of striatal neurons in HD. We compared BDNF serum levels in 42 patients with HD (range 28-72 years, mean age 51.9 +/- 11.5), and 42 age-matched healthy subjects (range 25-68 years, mean age 48.2 +/- 12.5). We evaluated the potential relationship between BDNF serum levels, CAG repeat number (range 40-54, mean 44.8 +/- 3.4) and duration of illness (range 6-228 months, mean 103.6 +/- 62.1). Serum BDNF levels were significantly lower in patients than in age-matched healthy subjects. Lower BDNF levels were associated with a longer CAG repeat length and a longer duration of illness. Severity of the illness, as assessed by the Unified Huntington's Disease Rating Scale (UHDRS) motor and cognitive scores, was negatively related to serum BDNF levels. These results in vivo confirm that the huntingtin mutation causes BDNF production to decline and show that the BDNF deficiency is detectable in HD patients' sera. Further studies on a larger sample size should confirm whether BDNF concentrations in patients' serum could be a useful clinical marker related to the patients' disease phenotype.

Toluene inhalation induced neuronal damage in the spinal cord and changes of neurotrophic factors in rat

We investigated the effects of toluene inhalation on neurons and neurotrophic factors in the spinal cord and the relationship between them. Male Wistar rats were exposed to toluene (1500ppm for 4h per day) for 7 days. To observe damage of the neurons in spinal cord with the toluene, expression of microtubule associated protein 2 (MAP2) and 70kDa heat shock protein (HSP70) in spinal cord were performed by immunohistochemistry. MAP2 was degraded and HSP70-immunoreactivity was enhanced in nerve cell bodies of the gray matter in toluene inhalation group. Immunoreactivity of glial fibrillary acidic protein (GFAP), a marker of astrocytes, was enhanced in the toluene-treated group. Furthermore, glial cell line-derived neurotrophic factor (GDNF)- and brain-derived neurotrophic factor (BDNF)-immunoreactivity in spinal cord were slightly decreased in the treated group. In addition, the concentrations of GDNF and BDNF in the spinal cord were determined using enzyme linked immunosorbent assay (ELISA). Concentration of GDNF was reduced significantly by toluene exposure. BDNF also reduced, but not significantly. The toluene inhalation caused the damage of the neuron in the spinal cord, which was accompanied by the decrease in the neurotrophic factors, such as BDNF and GDNF.

Measurements of brain-derived neurotrophic factor: methodological aspects and demographical data

Although numerous studies have dealt with changes in blood brain-derived neurotrophic factor (BDNF), methodological issues about BDNF measurements have only been incompletely resolved. We validated BDNF ELISA with respect to accuracy, reproducibility and the effect of storage and repeated freezing cycles on BDNF concentrations. Additionally, the effect of demographic characteristics in healthy subjects on BDNF was verified. Whole blood and serum was collected from 206 healthy subjects and a subgroup was genotyped for BDNF Val66Met polymorphism. The effect of age, gender, BDNF genotype and thrombocyte count on whole blood BDNF was assessed. The BDNF ELISA measurement was accurate, 91.6+/-3.0%, and showed high reproducibility, whereas inter-assay and intra-subject variations were modest, 8.4+/-5.2% and 17.5+/-14.1%, respectively. Storage of whole blood samples at 4 degrees C significantly decreased BDNF concentration, while repeated freezing cycles and storage at -20 degrees C was without any effect. Storage at -20 degrees C of serum, but not whole blood, was associated with a significant decrease in BDNF concentration. Women had significantly higher whole blood BDNF concentrations than men (18.6+/-1.3 ng/ml versus 16.5+/-1.4 ng/ml), and showed a right-skewed BDNF concentration distribution. No association between whole blood BDNF concentrations and thrombocyte count, age, or BDNF genotype was found. In conclusion, the BDNF ELISA assay determines whole blood BDNF accurately and with high reproducibility. Female gender is associated with higher whole blood BDNF concentrations whereas age, thrombocyte count and BDNF Val66Met polymorphism were un-associated.

The Effect of Acute Exercise on Serum Brain-Derived Neurotrophic Factor Levels and Cognitive Function

Brain-derived neurotrophic factor (BDNF) is one of a family of neurotrophic factors that participates in neuronal transmission, modulation and plasticity. Previous studies using animals have demonstrated that acute and chronic exercise leads to increases in BDNF in various brain regions.

PURPOSE

To determine the effects of acute exercise on serum BDNF levels in humans, and to determine the relationship between exercise intensity and BDNF responses. Additionally, the relationship between changes in BDNF and cognitive function was examined.

METHODS

Fifteen subjects (25.4 +/- 1.01 yr; 11 male, 4 female) performed a graded exercise test (GXT) for the determination of VO2max and ventilatory threshold (VTh) on a cycle ergometer. On separate days, two subsequent 30-min endurance rides were performed at 20% below the VTh (VTh - 20) and at 10% above the VTh (VTh + 10). Serum BDNF and cognitive function were determined before and after the GXT and endurance rides with an enzyme-linked immunosorbent assay (ELISA) and the Stroop tests, respectively.

RESULTS

The mean VO2max was 2805.8 +/- 164.3 mL x min(-1) (104.2 +/- 7.0% pred). BDNF values (pg x mL(-1)) increased from baseline (P<0.05) after exercise at the VTh + 10 (13%) and the GXT (30%). There was no significant change in BDNF from baseline after the VTh - 20. Changes in BDNF did not correlate with VO2max during the GXT, but they did correlate with changes in lactate (r=0.57; P<0.05). Cognitive function scores improved after all exercise conditions, but they did not correlate with BDNF changes.

CONCLUSION

BDNF levels in humans are significantly elevated in response to exercise, and the magnitude of increase is exercise intensity dependent. Given that BDNF can transit the blood-brain barrier in both directions, the intensity-dependent findings may aid in designing exercise prescriptions for maintaining or improving neurological health.

Brain-derived neurotrophic factor (BDNF) and type 2 diabetes

AIMS/HYPOTHESIS

Decreased levels of brain-derived neurotrophic factor (BDNF) have been implicated in the pathogenesis of Alzheimer's disease and depression. These disorders are associated with type 2 diabetes, and animal models suggest that BDNF plays a role in insulin resistance. We therefore explored whether BDNF plays a role in human glucose metabolism.

SUBJECTS AND METHODS

We included (Study 1) 233 humans divided into four groups depending on presence or absence of type 2 diabetes and presence or absence of obesity; and (Study 2) seven healthy volunteers who underwent both a hyperglycaemic and a hyperinsulinaemic-euglycaemic clamp.

RESULTS

Plasma levels of BDNF in Study 1 were decreased in humans with type 2 diabetes independently of obesity. Plasma BDNF was inversely associated with fasting plasma glucose, but not with insulin. No association was found between the BDNF G196A (Val66Met) polymorphism and diabetes or obesity. In Study 2 an output of BDNF from the human brain was detected at basal conditions. This output was inhibited when blood glucose levels were elevated. In contrast, when plasma insulin was increased while maintaining normal blood glucose, the cerebral output of BDNF was not inhibited, indicating that high levels of glucose, but not insulin, inhibit the output of BDNF from the human brain.

CONCLUSIONS/INTERPRETATION

Low levels of BDNF accompany impaired glucose metabolism. Decreased BDNF may be a pathogenetic factor involved not only in dementia and depression, but also in type 2 diabetes, potentially explaining the clustering of these conditions in epidemiological studies.

Low plasma BDNF is associated with suicidal behavior in major depression

Brain-derived neurotrophic factor (BDNF), the most abundant neurotrophin in the brain, has a known association with the pathophysiology of anxiety and depression. However, the role of BDNF in suicide has not been well investigated to date. This study examined plasma BDNF levels in 32 major depressive disorder (MDD) patients who had recently attempted suicide, 32 non-suicidal MDD patients, and 30 normal controls. The lethality of the suicide attempt was measured using the Risk-Rescue Rating (RRR) and Lethality Suicide Attempt Rating Scale (LSARS). The severity of depression was measured with the Hamilton Depression Rating Scale (HDRS). Plasma BDNF levels were measured by enzyme linked immunosorbent assay. BDNF levels were significantly lower in suicidal MDD patients (430.5+/-397.0 pg/ml) than non-suicidal MDD patients (875.80+/-663.02 pg/ml) or normal controls (889.4+/-611.3 pg/ml) (F=6.682, p=0.002). The most suitable cut-off point of BDNF level between suicidal depression and non-suicidal depression groups was 444.58 pg/ml. At this cut-off point, the sensitivity=68.7%, specificity=78.1%, positive predictive value=75.9%, and negative predictive value=71.4%. However, there was no significant difference in BDNF levels between the depressive control and normal control groups (p=0.996). LSARS and RRR did not reveal any significant correlations with BDNF levels in suicidal patients. In addition, BDNF levels were not different between fatal and non-fatal suicide attempts. These results suggest that reduction of plasma BDNF level is related to suicidal behavior in major depression and that BDNF level may be a biological marker of suicidal depression.

Production of brain-derived neurotrophic factor by mononuclear cells of patients with multiple sclerosis treated with glatiramer acetate, interferon-beta 1a, and high doses of immunoglobulins

Sixty, relapsing remitting (RR) multiple sclerosis (MS) patients, who underwent treatment with glatiramer acetate (GA), interferon (IFN)-beta 1a, and immunoglobulins (Igs) (20 per treatment group), were assessed for levels of brain-derived neurotrophic factor (BDNF) in the supernatants of unstimulated and stimulated peripheral blood mononuclear cells (PBMCs) in the first year of treatment. Phytohemagglutinin (PHA), anti-OKT3 antibody, myelin basic protein (MPB) and GA were used as stimuli. Cytokine responses by ELISPOT and lymphoproliferative responses were also assessed. The GA-treated MS patient group showed a progressive increase in BDNF levels, from baseline to month three; thereafter, the levels remained stable and significantly greater compared with baseline and controls (ANOVA=P<0.001). IFN-beta 1a had no effect on BDNF production, whereas Igs induced a slight decrease (ANOVA=P<0.04). ELISPOT analysis revealed a significant decrease of IFN-gamma, an increase of interleukin (IL)-4 and IL-5 in GA-treated MS patients, and an increase of IL-10 in patients treated with IFN-beta 1a and GA. No significant correlation was found between BDNF secretion in the supernatants of PBMCs and cytokine response, lesional load, and measures of atrophy. Increased BDNF production related to GA treatment can have implications for understanding the mechanism of action of this immunomodulatory agent, in light of evidence suggesting its effects in promoting neuroprotective immunity in MS patients; however, a clinically measurable effect, especially in terms of an impact on actual disease progression, remains to be established.

Influence of endogenous and exogenous sex hormones on plasma brain-derived neurotrophic factor

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a mediator of neuronal plasticity and influences learning, memory and cognitive behaviour. The aim of this study is to assess plasma BDNF variations according to hormonal status.

METHODS

A total of 60 subjects were included: 20 fertile ovulatory women, 15 amenorrhoeic women and 25 postmenopausal women. Blood samples were collected after overnight fasting. For 5 out of the 20 fertile women, samples were collected every 2 days throughout the whole menstrual cycle. Following basal evaluation, 10 out of 25 postmenopausal women were administered a hormone replacement therapy (HRT) and reevaluated after 6 months of treatment. Plasma BDNF concentrations were measured by enzyme-linked immunosorbent assay. In fertile women, estradiol (E(2)), progesterone and gonadotrophins were also assessed.

RESULTS

In fertile women, luteal phase levels of plasma BDNF were significantly higher than follicular phase levels (P < 0.001). BDNF increased from early follicular phase up to Day 14 of the cycle, reaching a pre-ovulatory peak, similar to E(2). A second rise took place during mid-luteal phase, with a peak on Day 24. Amenorrhoeic subjects, as well as postmenopausal women, showed significantly lower plasma BDNF levels compared with fertile females (P < 0.001). BDNF was positively correlated with E(2) and progesterone and negatively correlated with menopausal age. HRT restored BDNF levels to those present in fertile women during the follicular phase.

CONCLUSIONS

Plasma BDNF levels are influenced by hormonal status. Modifications in BDNF circulating levels during the menstrual cycle suggest a potential role for gonadal sex hormones (E(2) and progesterone) in regulating neurotrophin expression.