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

Brain-derived neurotrophic factor is associated with age-related decline in hippocampal volume

Hippocampal volume shrinks in late adulthood, but the neuromolecular factors that trigger hippocampal decay in aging humans remains a matter of speculation. In rodents, brain-derived neurotrophic factor (BDNF) promotes the growth and proliferation of cells in the hippocampus and is important in long-term potentiation and memory formation. In humans, circulating levels of BDNF decline with advancing age, and a genetic polymorphism for BDNF has been related to gray matter volume loss in old age. In this study, we tested whether age-related reductions in serum levels of BDNF would be related to shrinkage of the hippocampus and memory deficits in older adults. Hippocampal volume was acquired by automated segmentation of magnetic resonance images in 142 older adults without dementia. The caudate nucleus was also segmented and examined in relation to levels of serum BDNF. Spatial memory was tested using a paradigm in which memory load was parametrically increased. We found that increasing age was associated with smaller hippocampal volumes, reduced levels of serum BDNF, and poorer memory performance. Lower levels of BDNF were associated with smaller hippocampi and poorer memory, even when controlling for the variation related to age. In an exploratory mediation analysis, hippocampal volume mediated the age-related decline in spatial memory and BDNF mediated the age-related decline in hippocampal volume. Caudate nucleus volume was unrelated to BDNF levels or spatial memory performance. Our results identify serum BDNF as a significant factor related to hippocampal shrinkage and memory decline in late adulthood.

Circulating brain-derived neurotrophic factor and indices of metabolic and cardiovascular health: data from the Baltimore Longitudinal Study of Aging

BACKGROUND

Besides its well-established role in nerve cell survival and adaptive plasticity, brain-derived neurotrophic factor (BDNF) is also involved in energy homeostasis and cardiovascular regulation. Although BDNF is present in the systemic circulation, it is unknown whether plasma BDNF correlates with circulating markers of dysregulated metabolism and an adverse cardiovascular profile.

METHODOLOGY/PRINCIPAL FINDINGS

To determine whether circulating BDNF correlates with indices of metabolic and cardiovascular health, we measured plasma BDNF levels in 496 middle-age and elderly subjects (mean age approximately 70), in the Baltimore Longitudinal Study of Aging. Linear regression analysis revealed that plasma BDNF is associated with risk factors for cardiovascular disease and metabolic syndrome, regardless of age. In females, BDNF was positively correlated with BMI, fat mass, diastolic blood pressure, total cholesterol, and LDL-cholesterol, and inversely correlated with folate. In males, BDNF was positively correlated with diastolic blood pressure, triglycerides, free thiiodo-thyronine (FT3), and bioavailable testosterone, and inversely correlated with sex-hormone binding globulin, and adiponectin.

CONCLUSION/SIGNIFICANCE

Plasma BDNF significantly correlates with multiple risk factors for metabolic syndrome and cardiovascular dysfunction. Whether BDNF contributes to the pathogenesis of these disorders or functions in adaptive responses to cellular stress (as occurs in the brain) remains to be determined.

Varenicline does not increase serum BDNF levels in patients with nicotine dependence

Varenicline, alpha4beta2 nicotinic acetylcholine receptor (nAChR) partial agonist, is a new class of medications for treating nicotine dependence. As an alpha4beta2 nAChR partial agonist, varenicline serves to reduce nicotine withdrawal symptoms, while high-affinity binding of the agonist mitigates the reinforcing effects of smoking. In the present study, we compared serum brain-derived neurotrophic factor (BDNF) levels of nicotine dependence and nonsmokers, and we investigated changes in serum BDNF levels after 8 weeks of treatment with varenicline. Patients met the DSM-IV criteria for nicotine dependence. Both the Fagerström test for nicotine dependence (FTND) and the Tobacco Dependence Screener (TDS) were used. Serum BDNF levels and breath carbon monoxide (CO) levels were measured before and 8 weeks after varenicline treatment. Fourteen of 16 subjects (87.5%) stopped smoking within 12 weeks of varenicline treatment. Thirteen healthy nonsmokers who never had previously smoked were randomly selected as a control group. Serum BDNF levels of patients before treatment (4.8 +/- 3.8 ng/ml) were significantly lower than those in the control group (12.4 +/- 6.13 ng/ml). Serum BDNF levels had not increased from baseline (4.8 +/- 3.8 ng/ml) to 8 weeks after varenicline treatment (3.0 +/- 1.1 ng/ml) of patients. These results suggest that smoking might decrease serum BDNF levels and that treatment with varenicline for 8 weeks, combined with 12 weeks of not smoking, does not increase serum BDNF levels in smokers.

Acute exercise ameliorates reduced brain-derived neurotrophic factor in patients with panic disorder

The neurotrophin brain-derived neurotrophic factor (BDNF) has been implicated in depression and anxiety. Antidepressants and exercise increase BDNF expression, and both have an antidepressant and anxiolytic activity. To further characterize the association of anxiety, BDNF and exercise, we studied panic disorder patients (n=12) and individually matched healthy control subjects (n=12) in a standardized exercise paradigm. Serum samples for BDNF analyses were taken before and after 30min of exercise (70 VO(2max)) or quiet rest. The two conditions were separated by 1 week and the order was randomized. Non-parametric statistical analyses were performed. There was a negative correlation of BDNF concentrations and subjective arousal at baseline (r=-0.42, p=0.006). Compared to healthy control subjects, patients with panic disorder had significantly reduced BDNF concentrations at baseline and 30min of exercise significantly increased BDNF concentrations only in these patients. Our results suggest that acute exercise ameliorates reduced BDNF concentrations in panic disorder patients and raise the question whether this is also found after long-term exercise training and if it is related to the therapeutic outcome.

Adding a low dose atypical antipsychotic drug to an antidepressant induced a rapid increase of plasma brain-derived neurotrophic factor levels in patients with treatment-resistant depression

Only two-thirds of depressive patients respond to antidepressant treatment. Recently, addition of an atypical antipsychotic drug to ongoing treatment with an antidepressant has been considered effective and well-tolerated. In the present study, we examined the effects of various atypical antipsychotic drugs as adjuvant to antidepressants, including selective serotonin reuptake inhibitors (SSRIs), serotonin noradrenaline reuptake inhibitors, tricyclic antidepressants and mood stabilizers, on plasma BDNF levels in refractory depressed patients. Forty-five patients who met the DSM-IV criteria for major depressive disorder (n=31) or bipolar disorder (10 with bipolar I, 4 with bipolar II) were enrolled in the study. Twenty-one were male and 24 were female, and their ages ranged from 28 to 71 (mean+/-SD=49+/-12) years. Plasma BDNF levels were measured using a sandwich ELISA. The plasma BDNF levels in responders (those showing a decline in HAM-D scores of 50% or more) were significantly increased 4weeks after the administration of each atypical antipsychotic drug, while the levels in non-responders were not changed. Furthermore, there was a significant correlation between the changes in HAM-D scores and the changes in plasma BDNF levels. These results suggest that adding an atypical antipsychotic drug to ongoing treatment with an antidepressant or mood stabilizer is useful and well-tolerated for refractory depressed patients, and the efficacy of atypical antipsychotics as an adjuvant might involve an increase of plasma BDNF levels.

Reduced serum BDNF levels in patients with chronic schizophrenic disorder in relapse, who were treated with typical or atypical antipsychotics

Brain-derived neurotrophic factor signals and dopaminergic function in the brain are strongly associated, and research on BDNF in schizophrenia may enhance our insights on the pathophysiological mechanisms of this disease. In the present study we aimed to investigate the possible association between serum BDNF levels and schizophrenic relapses and the possible differential effects of treatment with typical and atypical antipsychotics on serum BDNF levels in the same group of patients. We measured serum BDNF levels in 47 patients with schizophrenia during a relapse and again 6 weeks after administration of antipsychotic treatment (14 on risperidone, 18 on haloperidol, 10 on olanzapine and five on amisulpride) and in 44 healthy volunteers. Patients with schizophrenia showed reduced serum BDNF levels in relation to healthy volunteers at study entry. No significant differences were revealed in BDNF serum levels after 6 weeks of antipsychotic treatment in the patients compared to their own levels at study entry. However, serum BDNF was significantly increased in the subgroup receiving olanzapine compared to the other antipsychotics. Our findings may indicate a differential effect of olanzapine on BDNF levels compared to haloperidol, risperidone, and amisulpride.

The effect of depression, BDNF gene val66met polymorphism and gender on serum BDNF levels

OBJECTIVE

To determine the effect of BDNF gene val66met polymorphism on serum BDNF levels in drug-free patients with major depressive disorder (MDD) and healthy subjects, that differ by gender.

METHODS

Sixty-six drug-free patients (19 males+47 females) with non-psychotic MDD and fifty-six healthy controls (18 males+38 females) were recruited. Three-way ANOVA was employed to analyze the effect of mental health status, met-carriage and gender on Hamilton Depression Rating Scale (HDRS) scores and serum BDNF levels, by using the MIXED Procedure (SAS).

RESULTS

Patients had a lower serum BDNF level than healthy subjects (22.47 vs. 27.49; p<0.0001). Met-carrier patients had a higher HDRS score than Val homozygote's (25.99 vs. 22.99, p<0.02). Serum BDNF level for met-carrier subjects (patients+controls) was lower than Val homozygote subjects (23.08 vs. 26.87; p<0.002). However, there were no effects of two-way interactions of met-carriage and mental health status on HDRS scores and serum BDNF levels. There was no gender effect on HDRS scores in the patients. Overall, male subjects (patients+controls) had a higher serum BDNF level than female subjects (26.87 vs. 23.08; p<0.002). However, there were no effects of two-way interactions of gender with mental health status and met-carriage on serum BDNF levels.

CONCLUSIONS

We replicated the previous findings of lower serum BDNF levels during depression and in females. In addition, we found that met-carriage had an effect in reducing serum BDNF levels, regardless of gender and depression. Further animal and human studies with a larger sample size should investigate whether BDNF val66met polymorphism could alter brain and serum BDNF levels.

Blood levels of catecholamine metabolites and brain-derived neurotrophic factor in a case of Sydenham's chorea

We report a case of Sydenham's chorea with neuropsychiatric symptoms who was successfully treated with low-dose risperidone. We also longitudinally investigated serum BDNF levels and plasma levels of catecholamine metabolite in the patient. Serum BDNF levels were increased and plasma levels of HVA and MHPG were decreased according to the recovery from the active phase of the disease. These results suggest that dysfunctions of catecholaminergic neurons and neurotrophic factors might exist in Sydenham's chorea, and the decreasing catecholamine activities in response to risperidone might be associated with the improvement of the disease.

Reduced peripheral brain-derived neurotrophic factor mRNA levels are normalized by antidepressant treatment

Consistent data coming from biochemical studies have evidenced a brain-derived neurotrophic factor (BDNF) serum reduction in depressed patients compared to controls and a restoration following antidepressant treatment. However, to date, no study has evaluated whether BDNF synthesis in leukocytes could contribute to such modulation. Therefore, in this study, we analysed BDNF mRNA levels in leukocytes from 21 depressed patients prior to and during escitalopram treatment and from 23 control subjects showing that BDNF mRNA levels were decreased in drug-free depressed patients and that 12 wk escitalopram treatment was able to reverse this deficit. Interestingly, changes in BDNF mRNA levels paralleled BDNF serum increase during antidepressant treatment, and were correlated with symptoms improvement. Our results indicate that BDNF serum modulation observed in depressed patients is associated with BDNF synthesis alteration in leukocytes and suggest that these peripheral cells might play an active role in the mechanisms of action of antidepressants.

Endurance training enhances BDNF release from the human brain

The circulating level of brain-derived neurotrophic factor (BDNF) is reduced in patients with major depression and type-2 diabetes. Because acute exercise increases BDNF production in the hippocampus and cerebral cortex, we hypothesized that endurance training would enhance the release of BDNF from the human brain as detected from arterial and internal jugular venous blood samples. In a randomized controlled study, 12 healthy sedentary males carried out 3 mo of endurance training ( n = 7) or served as controls ( n = 5). Before and after the intervention, blood samples were obtained at rest and during exercise. At baseline, the training group (58 ± 106 ng·100 g−1·min−1, means ± SD) and the control group (12 ± 17 ng·100 g−1·min−1) had a similar release of BDNF from the brain at rest. Three months of endurance training enhanced the resting release of BDNF to 206 ± 108 ng·100 g−1·min−1 ( P < 0.05), with no significant change in the control subjects, but there was no training-induced increase in the release of BDNF during exercise. Additionally, eight mice completed a 5-wk treadmill running training protocol that increased the BDNF mRNA expression in the hippocampus (4.5 ± 1.6 vs. 1.4 ± 1.1 mRNA/ssDNA; P < 0.05), but not in the cerebral cortex (4.0 ± 1.4 vs. 4.6 ± 1.4 mRNA/ssDNA) compared with untrained mice. The increased BDNF expression in the hippocampus and the enhanced release of BDNF from the human brain following training suggest that endurance training promotes brain health.

Brain-derived neurotrophic factor in patients with normal-tension glaucoma

PURPOSE

The aim of this study was to detect and measure brain-derived neurotrophic factor (BDNF) in the tears of normal subjects and patients with normal-tension glaucoma (NTG).

MATERIALS AND METHODS

Twenty patients with NTG as the case group and 20 normal subjects with the same age range as the control group were tested. The control group consisted of 16 men and 4 women, ranging in age from 40 to 75, without any apparent ocular or systemic disease. The case group consisted of 15 men and 5 women, ranging in age from 45 to 74. BDNF levels in tears were determined by enzyme-linked immunosorbent assay using monoclonal antibodies specific for BDNF (R&D Systems, Minneapolis, Minnesota).

RESULTS

The mean level of BDNF detected in the tears of the normal subjects was 77.09 +/- 4.84 ng/mL and the BDNF levels in the tears of case group were 24.33 +/- 1.48 ng/mL (P < 0.001).

CONCLUSION

We suggest that BDNF in the tears might be a useful biochemical marker for early detection of normal-tension glaucoma (NTG).

Chronic stress affects the expression of brain-derived neurotrophic factor in rat salivary glands

Plasma brain-derived neurotrophic factor (BDNF) levels are associated with several neural disorders. Previously, we reported that BDNF is produced from salivary glands under acute immobilization stress. Additionally, salivary glands are the origin of plasma BDNF during stress; however, the association between the expression of BDNF by the salivary glands under chronic stress conditions is not known. In the present study, we investigated whether plasma BDNF levels in chronic stress depend on the salivary glands. Expression of BDNF mRNA and protein were identified in the submandibular glands when male rats were exposed to chronic restraint stress (12 h daily for 22 days). Chronic stress significantly increased plasma BDNF concentration, as well as adrenocorticotropic hormone and corticosterone levels, but was not altered under chronic stress in bilaterally sialoadenectomized rats. Since chronic stress increases plasma BDNF levels in the sialoadenectomized rat model, the plasma BDNF level was not dependent on BDNF from the salivary glands. Although the salivary glands were the source of plasma BDNF in acute stress conditions in our previous study, it seems that that the increased BDNF expression in the salivary glands in chronic stress does not contribute importantly to the increased circulating BDNF level. The increased plasma BDNF levels may play important roles in homeostasis under stress conditions.

Electroconvulsive therapy increases glial cell-line derived neurotrophic factor (GDNF) serum levels in patients with drug-resistant depression

Electroconvulsive therapy (ECT) can be effective in patients with depression resistant to pharmacologic medication. We report that serum levels of glial cell-line derived neurotrophic factor (GDNF) were increased following ECT of patients with drug-resistant depression. When patients were sub-classified into ECT responders and non-responders, serum GDNF levels were significantly increased (58%) in responsive patients following ECT. No significant increase was seen in non-responders. These results suggest that successful ECT may be associated with elevated serum GDNF levels.

Decreased serum brain-derived neurotrophic factor levels in elderly korean with dementia

OBJECTIVE

The primary purpose of this study was to investigate the differences in the serum brain-derived neurotrophic factor (BDNF) level between elderly Korean people over 65 years with and without dementia.

METHODS

171 individuals over 65 years were enrolled in this study. Screening for cognitive impairments was carried out using the Mini-Mental Status Examination-Korean version (MMSE-KC). One hundred thirty-two subjects scored below 1.5 standard deviations (SD) of the mean MMSE-KC score, and these were evaluated using the Consortium to Establish a Registry for Alzheimer's Disease, Korean version (CERAD-K) and the Geriatric Depression Scale (GDS). The Clinical Dementia Rating Scale (CDRS) and the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) diagnostic criteria were used for further evaluation. Subjects with a CDRS score of 1 or higher were classified as having Alzheimer's disease (AD), and subjects with a CDRS score of 0.5 were classified as having a mild cognitive impairment (MCI). Subjects with a CDRS score of 0 were classified as having aging-associated cognitive decline (AACD). Serum BDNF levels were analyzed using the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The serum BDNF levels were significantly lower in the subjects with MCI and AD compared with the healthy controls (p<0.01). A significant correlation was found between the total MMSE-KC score and serum BDNF level (r=0.295; p<0.01). However, no significant correlation was observed between the severity of MMSE-KC and the total GDS score. A significant difference was found in the total score of GDS between the AACD group and subjects with AD (p<0.05).

CONCLUSION

This study suggested that BDNF might be involved in the pathophysiology of cognitive decline in elderly people.

Brain-derived neurotrophic factor and initial antidepressant response to an N-methyl-D-aspartate antagonist

OBJECTIVE

A model has been proposed to explain the pathophysiology of mood disorders based on decreased neurotrophin levels during mood episodes; treatment with antidepressants and mood stabilizers is associated with clinical improvement. This study investigated whether changes in brain-derived neurotrophic factor (BDNF) levels are associated with the initial antidepressant effects of ketamine, a high-affinity N-methyl-D-aspartate (NMDA) antagonist.

METHOD

Twenty-three subjects aged 18 to 65 years with DSM-IV major depressive disorder (treatment resistant) participated in this study, which was conducted between October 2006 and May 2008. The subjects were given an open-label intravenous infusion of ketamine hydrochloride (0.5 mg/kg) and rated using various depression scales at baseline and at 40, 80, 120, and 230 minutes postinfusion. The primary outcome measure was the Montgomery-Asberg Depression Rating Scale score. BDNF levels were obtained at the same time points as depression rating scale scores.

RESULTS

Despite a significant (P <. 001) improvement in MADRS scores after subjects received ketamine treatment, no changes in BDNF levels were observed in subjects after they received ketamine compared to baseline. Also, no association was found between antidepressant response and BDNF levels.

CONCLUSIONS

This study demonstrates that ketamine's rapid initial antidepressant effects are not mediated by BDNF. Further studies are necessary to shed light on the neurobiological basis of these effects.

TRIAL REGISTRATION

clinicaltrials.gov Identifiers: NCT00024635 and NCT00088699.

Decreased levels of serum brain-derived neurotrophic factor in drug-naïve first-episode schizophrenia: relationship to clinical phenotypes

OBJECTIVE

There is accumulating evidence that brain-derived neurotrophic factor (BDNF) may be involved in the pathophysiology of patients with schizophrenia. Clinical studies show reductions in BDNF in schizophrenic patients treated with first generation antipsychotics or second generation antipsychotics. However, there have been few systematic studies to examine the relationship between BDNF levels and psychopathology in first-episode and drug-naïve patients with schizophrenia.

MATERIALS AND METHODS

Serum BDNF levels were determined using enzyme-linked-immunosorbent assay (ELISA) in the serum of 88 never-medicated first-episode and 90 healthy controls subjects matched for age and gender. The schizophrenia symptomatology and the depressive symptoms were assessed by the positive and negative syndrome scale (PANSS) and the Hamilton rating (HAMD) scale for depression.

RESULTS

The results showed that BDNF levels were significantly lower in first-episode patients with schizophrenia than in healthy control subjects (9.0 +/- 4.2 ng/ml vs 12.1 +/- 2.2 ng/ml; F = 37.6; df = 1, 176; p < 0.0001). A significant positive correlation between BDNF levels and PANSS positive subscore was observed (r = 0.29; df = 88; p = 0.008). Furthermore, higher BDNF levels were observed in patients with paranoid subtype of schizophrenia. However, no significant correlation between BDNF and HAMD total score was found.

CONCLUSION

Low BDNF levels at the onset of psychosis suggest that it may contribute to the pathogenesis of schizophrenia and perhaps, could be a candidate biological marker for positive symptoms.

Decreased serum BDNF levels in chronic institutionalized schizophrenia on long-term treatment with typical and atypical antipsychotics

Accumulating evidence showed that brain-derived neurotrophic factor (BDNF) may be involved in the pathophysiology of schizophrenia. Decreased BDNF levels have been found in the serum of schizophrenic patients with mixed results. In the present study, we assessed serum BDNF levels in a large group of 364 schizophrenic patients (157 on clozapine, 89 on risperidone and 118 on typical antipsychotics), compared to 323 healthy control subjects matched for age and gender. The schizophrenia symptomatology was assessed by the Positive and Negative Syndrome Scale (PANSS), and serum BDNF levels were measured by sandwich ELISA. The results showed that BDNF levels were significantly lower in chronic patients with schizophrenia than in healthy control subjects (9.9+/-2.0 ng/ml vs.11.9+/-2.3 ng/ml, p<0.0001). Lower BDNF levels were observed in patients treated with risperidone (9.3+/-2.3 ng/ml) compared to those with clozapine (10.2+/-2.0 ng/ml, p<0.001) and typical antipsychotics (10.0+/-2.1 ng/ml, p<0.01). Furthermore, a stepwise multiple regression analysis identified types of antipsychotic drugs (beta=-0.37, t=-3.15, p=0.001) and BDNF levels (beta=-0.26, t=-2.51, p=0.014) as the influencing factor for the positive symptom subscore of PANSS. In addition, there was a sex difference in BDNF levels in patients with schizophrenia (9.7+/-1.9 ng/ml for males vs.10.4+/-2.1 ng/ml for female, p<0.005), but not in normal controls. Our findings indicated decreased BDNF serum levels in chronic patients with schizophrenia, which may be related to clinical phenotypes, including gender, antipsychotic treatment and the severity of psychotic symptoms.

Stress-mediated decreases in brain-derived neurotrophic factor as potential confounding factor for acute tryptophan depletion-induced neurochemical effects

Acute tryptophan depletion (ATD) is extensively used to investigate the implication of serotonin (5-hydroxytryptamine; 5-HT) in the onset and treatment of depression and cognitive disorders. Brain-derived neurotrophic factor (BDNF) is strongly linked to the 5-HT system and plays an essential role in mood and memory processes. The present study investigated the effects of ATD upon BDNF in serum, hippocampus and prefrontal cortex in the rat to further explore the underlying mechanism of ATD. ATD significantly decreased peripheral tryptophan (TRP) levels and moderately interrupted 5-HT metabolism 4h after administration of the nutritional mixture. Although no direct effects of ATD upon serum or brain BDNF concentrations were found, a stress-mediated, decrease in BDNF was observed in the prefrontal cortex. Moreover, brain TRP levels correlated positively with BDNF in both the prefrontal cortex and hippocampus. Thus, BDNF-mediated mechanisms due to ATD and/or its application stress might underlie ATD-induced neurochemical and behavioural alterations.

Plasma BDNF is reduced among middle-aged and elderly women with impaired insulin function: evidence of a compensatory mechanism

Brain-derived neurotrophic factor (BDNF) plays a regulatory role in neuronal differentiation and synaptic plasticity and has been linked to glucose regulation and cognition. Associations among plasma BDNF, cognition, and insulin function were explored. Forty-one participants with impaired insulin function (IIF), ranging from insulin resistance to type 2 diabetes mellitus (T2DM), were matched with 41 healthy controls on gender, age, education, and IQ. Participants received complete medical, neurological, psychiatric, and neuropsychological evaluations. IIF individuals had significantly lower plasma BDNF levels than controls, particularly females, and higher BDNF levels were associated with poorer explicit memory in IIF females, suggesting that higher levels within this group may reflect the body's efforts to respond to damage. After accounting for age, education, and HbA1c, BDNF significantly predicted 13.1-23.5% of the variance in explicit memory in IIF women. These findings suggest that BDNF elevations within diseased groups may not always be a marker of health.

When top-down meets bottom-up: auditory training enhances verbal memory in schizophrenia

A critical research priority for our field is to develop treatments that enhance cognitive functioning in schizophrenia and thereby attenuate the functional losses associated with the illness. In this article, we describe such a treatment method that is grounded in emerging research on the widespread sensory processing impairments of schizophrenia, as described elsewhere in this special issue. We first present the rationale for this treatment approach, which consists of cognitive training exercises that make use of principles derived from the past 2 decades of basic science research in learning-induced neuroplasticity; these exercises explicitly target not only the higher order or "top-down" processes of cognition but also the content building blocks of accurate and efficient sensory representations to simultaneously achieve "bottom-up" remediation. We then summarize our experience to date and briefly review our behavioral and serum biomarker findings from a randomized controlled trial of this method in outpatients with long-term symptoms of schizophrenia. Finally, we present promising early psychophysiological evidence that supports the hypothesis that this cognitive training method induces changes in aspects of impaired bottom-up sensory processing in schizophrenia. We conclude with the observation that neuroplasticity-based cognitive training brings patients closer to physiological patterns seen in healthy participants, suggesting that it changes the brain in an adaptive manner in schizophrenia.

The acute response of plasma brain-derived neurotrophic factor as a result of exercise in major depressive disorder

Brain-derived neurotrophic factor (BDNF) and other neurotrophins are believed to play an important role in affective disorders. In this study we investigated plasma-BDNF response during an incremental exercise test in 18 patients suffering from moderate major depressive disorder (MDD) and 18 controls. The patients were not treated with antidepressants or neuroleptics. Possible associations between plasma plasma-BDNF levels, dexamethasone suppression test cortisol levels and Montgomery-Asberg Depression Rating Scale (MADRS) scores were also tested. No difference in basal BDNF levels between patients and controls was found. BDNF increased significantly during exercise in both male and female patients as well as in male controls, with no significant differences between the groups. BDNF levels declined after exercise, but after 60 min of rest BDNF levels showed tendencies to increase again in male patients. No correlation between BDNF and cortisol or MADRS scores was found. We conclude that unmedicated patients with moderate depression and normal activity of the hypothalamic-pituitary-adrenal axis do not have a disturbed peripheral BDNF release during exercise. The BDNF increase 60 min after interruption of exercise in male patients might indicate up-regulated BDNF synthesis, but this needs to be further investigated in future studies.

Alterations of behavioral and endocrinological reactivity induced by 3 brief social defeats in rats: relevance to human psychopathology

In the realm of animal models of psychopathology, social stress based procedures rely on robust theoretical prerequisites to meet construct validity criteria for the target syndromes. In order to further assess the relevance for human psychopathology of a social defeat based model in rats, known to elicit consistent behavioral and hormonal changes, we expanded its characterization on the basis of both behavioral parameters and peripheral biomarkers thought to be pertinent for clinical symptoms. Rats were subjected to 3 daily social defeat experiences that shortly thereafter led to the insurgence of defensive behaviors, anhedonia, and body weight loss. HPA axis showed an activated response when rats were sampled as early as after the first social defeat experience, while none of the peripheral immune, metabolic, and neurotrophic factors examined were concurrently affected. With the aim of determining the long-term bio-behavioral sequelae of the social defeat experience, rats were assessed also 3 weeks after the social defeats. At this time, behavioral changes were still observed, including decreased general activity and sociality in a social avoidance test, increased immobility and decreased escape responses in a forced swim test. These alterations were not paralleled by alterations in anhedonia nor HPA axis responses from controls, nor where evident changes in the humoral component of the immune response nor in brain derived neurotrophic factor levels, whereas a substantial increase in leptin levels was observed in previously socially defeated rats compared to control. Overall these data depict a very complex set of alterations induced both acutely and long-term by social stress in endocrinological and behavioral reactivity of rats.

State-dependent decrease in levels of brain-derived neurotrophic factor in bipolar disorder: a meta-analytic study

Evidence has suggested a role of brain-derived neurotrophic factor (BDNF) in the pathogenesis of bipolar disorder (BD). Recent studies have examined BDNF levels in BD patients, but showed inconsistent results. In current study, meta-analyses by random-effects model were performed to compare blood BDNF levels between BD patients and healthy controls, and examine patients based on different affective status (manic, depressed, or euthymic state). Fifteen studies from 10 citations were included into the analysis. Pooling of results from all studies indicated that, overall, patients with BD had a lower level of BDNF than healthy controls (p=1x10(-4)). But when separating these studies based on different affective status, it showed that the significance existed only when comparing patients in manic (p=0.0008) or depressed (p=0.02) state with controls, but not in euthymic state (p=0.25). In addition, BDNF level was significantly increased after pharmacological treatment of manic state (p=0.01). These findings indicate that BDNF levels are abnormally reduced in manic and depressed states of BD, and the reduced level in manic state increases after treatment. They suggest a role of blood BDNF level as a state-dependent biomarker of bipolar disorder.

Understanding the blood-brain barrier using gene and protein expression profiling technologies

The blood-brain barrier (BBB) contributes to the brain homeostasis by regulating the passage of endogenous and exogenous compounds. This function is in part due to well-known proteins such as tight junction proteins, plasma membrane transporters and metabolic barrier proteins. Over the last decade, genomics and proteomics have emerged as supplementary tools for BBB research. The development of genomic and proteomic technologies has provided several means to extend the BBB knowledge and to investigate additional routes for the bypass of this barrier. These profiling technologies have been used on BBB models to decipher the physiological characteristics and, under stress conditions, to understand the molecular mechanisms of brain diseases. In this review, we will report and discuss the genomic and proteomic studies recently carried out to enhance the understanding of BBB features.

Decreased brain-derived neurotrophic factor in medicated and drug-free bipolar patients

Bipolar disorder (BD) has been associated with abnormalities in neuroplasticity and previous studies suggest an important role for BDNF in the pathophysiology of BD. The confounding effect of the use of medication in these studies has been considered a limitation. Thus, studies with both drug-free and medicated patients are necessary to assess the role of medication in serum BDNF levels. Twenty-two manic and depressed drug-free and 22 medicated BD type I patients were matched to 22 controls according to sex and age in a cross-sectional study. BDNF serum levels were assessed using sandwich-ELISA. Serum BDNF levels in drug-free (0.23+/-0.09), and medicated (0.29+/-0.19) BD patients were decreased when compared to controls (0.40+/-0.12) - drug-free/medicated vs. control p<0.001. The BDNF levels did not differ between medicated and drug-free BD patients. When analyzing patients according to mood states, serum BDNF levels were lower in BD patients during both manic (0.28+/-0.11) and depressive episodes (0.22+/-0.17), as compared with healthy controls (0.40+/-0.12) - manic/depressed patients vs. controls p<0.001. Results suggest that the association of lower serum BDNF and BD mood episodes is kept even in medicated patients, which strengthens the notion that BDNF serum levels may be considered a biomarker of mood episodes in BD.

Cessation of blood-to-brain influx of interleukin-15 during development of EAE

Regulatory changes in cytokine permeation across the blood-brain barrier (BBB) may have crucial roles in central nervous system (CNS) autoimmune disease. Accordingly, we examined the interactions of interleukin (IL)-15 with the cerebral vasculature after induction of experimental autoimmune encephalomyelitis (EAE). In contrast to the influx of (125)I-IL15 from blood to the CNS in normal mice and the persistence of IL15 influx in the spinal cord of EAE mice, influx was reduced in the EAE brain. Analyses of disappearance kinetics, FITC (fluorescein isothiocyanate)-albumin space, and delivery of IL15 by in situ perfusion, all indicate that the changes were not caused by BBB disruption but by the rapid availability (high volume of distribution) of IL15 and albumin. Although there was no significant change in the BBB permeation of IL15 in either direction in EAE mice, there was an upregulation of its specific receptor, IL15Ralpha, and an increased in situ production of IL15 mRNA that showed regional variation in both basal and EAE states. Overall, for IL15, its increased cerebral vascular space in the brain was equally as important as its persistent influx across the blood-spinal cord barrier, indicating that it is fully capable of activating the upregulated IL15Ralpha in the brain along with the intrinsic CNS source of IL15 in EAE mice.

Physical activity and memory functions: an interventional study

Previous studies have suggested beneficial effects of physical activity on cognition. Here, we asked in an interventional approach if physical activity performed at different intensity levels would differentially affect episodic memory function. Additionally, we tried to identify mechanisms mediating these changes. Sixty-two healthy elderly individuals were assessed for level of physical activity, aerobic fitness, episodic memory score, neurotrophin and catecholamine levels, and received a magnetic resonance image of the brain at baseline and after a six months intervention of medium or low-intensity physical activity or control. Increase in total physical activity was positively associated with increase in memory score over the entire cohort, without significant differences between intensity groups. It was also positively associated with increases in local gray matter volume in prefrontal and cingulate cortex, and BDNF levels (trend). In conclusion, we showed that physical activity conveys the beneficial effects on memory function independently of its intensity, possibly mediated by local gray matter volume and neurotrophic factors. Our findings may carry significant implications for prevention of cognitive decline in the elderly.

Evidence for a release of brain-derived neurotrophic factor from the brain during exercise

Brain-derived neurotrophic factor (BDNF) has an important role in regulating maintenance, growth and survival of neurons. However, the main source of circulating BDNF in response to exercise is unknown. To identify whether the brain is a source of BDNF during exercise, eight volunteers rowed for 4 h while simultaneous blood samples were obtained from the radial artery and the internal jugular vein. To further identify putative cerebral region(s) responsible for BDNF release, mouse brains were dissected and analysed for BDNF mRNA expression following treadmill exercise. In humans, a BDNF release from the brain was observed at rest (P < 0.05), and increased two- to threefold during exercise (P < 0.05). Both at rest and during exercise, the brain contributed 70-80% of circulating BDNF, while that contribution decreased following 1 h of recovery. In mice, exercise induced a three- to fivefold increase in BDNF mRNA expression in the hippocampus and cortex, peaking 2 h after the termination of exercise. These results suggest that the brain is a major but not the sole contributor to circulating BDNF. Moreover, the importance of the cortex and hippocampus as a source for plasma BDNF becomes even more prominent in response to exercise.

Lack of association between BDNF Val66Met gene polymorphism and late-onset depression in a Chinese Han population

BACKGROUND

Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene has been suggested to be associated with major depressive disorder (MDD). There were a few reports of the relationship between the variant and late-onset depression (LOD) in Chinese Han population.

OBJECTIVE

To investigate the relationship among BDNF Val66Met gene variants, BDNF plasma level and LOD.

METHODS

Chinese Han patients with LOD (n = 99) and control subjects (n = 110) were assessed for BDNF Val66Met gene polymorphism. BDNF plasma level was tested only in LOD.

RESULTS

There were no significant differences in genotypes and allele frequencies between cases and controls (p = 0.744 and p = 0.845, respectively). Plasma BDNF level also did not show significant differences in three genotypes in LOD (p = 0.860).

CONCLUSION

The Val66Met polymorphism in BDNF gene may not confer susceptibility to LOD in Chinese Han population.

Reduced platelet BDNF level in patients with major depression

Serum and plasma brain-derived neurotrophic factor (BDNF) levels as well as brain BDNF have previously been shown to be decreased in patients with major depressive disorder (MDD). We explored whether platelet BDNF levels, circulating stored BDNF, would be lower in MDD patients than in normal controls. BDNF levels were examined in platelet-rich plasma (PRP) and platelet-poor plasma (PPP) in 20 hospitalized non-suicidal MDD patients, 20 recent-suicidal MDD patients, and 20 normal controls. Platelet BDNF content was calculated by subtracting PPP BDNF level from PRP BDNF level, and dividing the result by the total platelet count, and it was expressed as pg/10(6) platelets. Individuals were evaluated using a Structured Clinical Interview for DSM-IV and a Hamilton Depression Rating Scale. Platelet BDNF contents were significantly lower in non-suicidal patients (3.09+/-2.53 pg/10(6) platelets) and recent-suicidal MDD patients (3.16+/-1.99 pg/10(6) platelets) than in healthy controls (6.17+/-2.64 pg/10(6) platelets) (p<0.01). However, platelet BDNF contents had no significant differences between non-suicidal and recent-suicidal patients. PRP BDNF levels were also significantly lower in non-suicidal and suicidal MDD patients than in healthy controls (p=0.029), while PPP BDNF had no significant difference between 3 groups (p=0.971). Our findings suggest that there is a decrease in the platelet BDNF of patients with major depression. Reduced platelet BDNF contents as circulating stored BDNF could be associated with lower serum BDNF level in patients with major depression.

Relation between plasma brain-derived neurotrophic factor and nerve growth factor in the male patients with alcohol dependence

Brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) are thought to be related to neuroprotection in cell culture and animal studies. Our aim was to verify the changes in human plasma BDNF and NGF concentrations induced by chronic alcohol use. Forty-one male patients with alcohol dependence were sampled the next morning of admission and compared with 41 healthy male subjects. Plasma BDNF and NGF were assayed using an enzyme-linked immunosorbent assay (ELISA). Mean plasma BDNF level was significantly higher in the patients with alcohol dependence (3502.21+/-1726.9 pg/mL) compared with the healthy subjects (861.75+/-478.9 pg/mL) (P=.000). Mean plasma NGF level was also significantly higher in patients with alcohol dependence (137.64+/-32.7 pg/mL) than in healthy subjects (112.61+/-90.2 pg/mL) (P=.012). Plasma BDNF and NGF levels showed significant negative correlation in alcohol dependence group (r=-0.388, P=.012). Increased plasma BDNF and NGF with negative correlation in alcohol-dependent patients may have some role in the regeneration of damage done by chronic alcohol use.

Brain-derived neurotrophic factor (BDNF) and set-shifting in currently ill and recovered anorexia nervosa (AN) patients

BACKGROUND

Studies of patients with anorexia nervosa (AN) have shown that they do not perform well in set-shifting tasks but little is known about the neurobiological correlates of this aspect of executive function. The aim of this study was to measure serum brain-derived neurotrophic factor (BDNF) and to establish whether set-shifting difficulties are present in people with current AN and in those recovered from AN, and whether serum BDNF concentrations are correlated with set-shifting ability.

METHOD

Serum BDNF concentrations were measured in 29 women with current AN (AN group), 18 women who had recovered from AN (ANRec group) and 28 age-matched healthy controls (HC group). Set-shifting was measured using the Wisconsin Card Sorting Test (WCST). Eating-related psychopathology and depressive, anxiety and obsessive-compulsive symptomatology were evaluated using the Eating Disorder Examination Questionnaire (EDEQ), the Hospital Anxiety and Depression Scale (HADS), and the Maudsley Obsessive-Compulsive Inventory (MOCI) respectively.

RESULTS

Serum BDNF concentrations (mean+/-s.d.) were significantly lower in the AN group (11.7+/-4.9 ng/ml) compared to the HC group (15.1+/-5.5 ng/ml, p=0.04) and also compared to the ANRec group (17.6+/-4.8 ng/ml, p=0.001). The AN group made significantly more errors (total and perseverative) in the WCST relative to the HC group. There was no significant correlation between serum BDNF concentrations and performance on the WCST.

CONCLUSIONS

Serum BDNF may be a biological marker for eating-related psychopathology and of recovery in AN. Longitudinal studies are needed to explore possible associations between serum BDNF concentrations, illness and recovery and neuropsychological traits.

Brain-derived neurotrophic factor in infants <32 weeks gestational age: correlation with antenatal factors and postnatal outcomes

Neurotrophins (NTs) play important roles in brain growth and development. Cord blood (CB) brain-derived neurotrophic factor (BDNF) concentrations increase with gestational age but data regarding postnatal changes are limited. We measured BDNF concentrations after birth in 33 preterm infants <32-wk gestation. Serum was collected at birth (CB), at day 2, between day 6 and 10 (D6), at day 30 (D30), and at day 60 (D60). BDNF concentrations fell on D2 (p = 0.03), recovered by D6 (p = 0.10), and continued to rise thereafter at D30 (p = 0.06) and D60 (p = 0.01) compared with CB. CB BDNF concentrations positively correlated with duration of rupture of membranes (r = 0.43, p = 0.04). Antenatal steroids (ANS, p = 0.02), postnatal steroids (PNS, p = 0.04), and retinopathy of prematurity (ROP, p = 0.02) were identified as significant factors in multivariate analyses. The median (25-75th interquartile range) CB BDNF concentrations were higher in infants who received a complete course ANS compared with those who received a partial course [1461 (553-2064) versus 281 (171-536) pg/mL, p = 0.04]. BDNF concentrations negatively correlated with the use of PNS at D30 (r = -0.53, p = 0.002) and at D60 (r = -0.55, p = 0.009). PNS use was associated with reduced concentrations of BDNF at D30 [733 (101-1983) versus 2224 (1677- 4400) pg/mL, p = 0.004] and at D60 [1149 (288-2270) versus 2560 (1337-5166) pg/mL, p = 0.01]. BDNF concentrations on D60 in infants who developed ROP (n = 16) were lower than those who did not develop ROP (n = 7) [1417 (553-2540) versus 3593 (2620-7433) pg/mL, respectively, p = 0.005]. Our data suggests that BDNF concentrations rise beyond the first week of age. BDNF concentrations correlate with factors that influence neurodevelopment outcomes.

Increased serum neurotrophin-4/5 levels in bipolar disorder

Neurotrophins are central to several aspects of central nervous system function, and emerging evidence links these growth factors to mood disorders. The purpose of this study was to investigate serum neurotrophin-4/5 (NT-4/5) levels in patients with bipolar disorder, both within mood episodes and in euthymia. Patients with bipolar I disorder (n=154) and controls (n=30) had their NT-4/5 serum levels assayed using an ELISA. Levels of NT-4/5 levels were significantly higher in bipolar disorder patients than in controls; NT-4/5 levels were increased in mania, depression and euthymia, but not significantly different between BD mood states. As far as are aware, this is the first study showing NT-4/5 immunocontent alterations in bipolar disorder. A tentative explanation would be that NT-4/5 increases is compensating for ongoing oxidative damage in dopaminergic neurons.

Early life stress as a risk factor for mental health: role of neurotrophins from rodents to non-human primates

Early adverse events can enhance stress responsiveness and lead to greater susceptibility for psychopathology at adulthood. The epigenetic factors involved in transducing specific features of the rearing environment into stable changes in brain and behavioural plasticity have only begun to be elucidated. Neurotrophic factors, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), are affected by stress and play a major role in brain development and in the trophism of specific neuronal networks involved in cognitive function and in mood disorders. In addition to the central nervous system, these effectors are produced by peripheral tissues, thus being in a position to integrate the response to external challenges. In this paper we will review data, obtained from animal models, indicating that early maternal deprivation stress can affect neurotrophin levels. Maladaptive or repeated activation of NGF and BDNF, early during postnatal life, may influence stress sensitivity at adulthood and increase vulnerability for stress-related psychopathology.

Effects of fluoxetine and venlafaxine on serum brain derived neurotrophic factor levels in depressed patients

BACKGROUND

Several studies demonstrated that depressed patients had low serum BDNF levels which correlated with the severity of their depression, and antidepressant treatment increases levels of serum BDNF in depressed patients. It was speculated that agents acting on both noradrenergic and serotonergic transporters might have a greater influence on BDNF levels. The aim of our study was to determine effects of venlafaxine vs. fluoxetine on serum BDNF levels in depressive patients.

METHODS

Forty-three patients diagnosed as major depressive disorder according to DSM-IV are included in the study. Forty-three patients were randomized to take fluoxetine (22 cases) or venlafaxine (21 cases). Serum levels of BDNF were measured by ELISA at baseline and 6 weeks after the start of treatment.

RESULTS

Baseline levels of BDNF were not significantly different between the patient group and the controls. But male patients and the male controls showed statistical differences with respect to baseline BDNF levels. BDNF levels of the patient group did not change with treatment. Yet, the increase of BDNF levels was close to statistically significant in the fluoxetine group, whereas not significant in the venlafaxine group. There were no significant differences in baseline and 6th week BDNF levels between the responders and the non-responders.

CONCLUSION

Further studies controlling for a wide variety of confounding variables are needed, which may help to reach a clear conclusion about the potential of BDNF as a biomarker for depression or as a predictor of antidepressant efficacy.

Low serum BDNF and food intake regulation: a possible new explanation of the pathophysiology of eating disorders

BACKGROUND

Several lines of evidence suggest that brain-derived neurotrophic factor (BDNF) plays an important role in weight regulation and eating behavior, and poorly balanced diets lead to a decrease in blood BDNF levels. However, studies regarding BDNF blood levels in eating disorders (ED) have yielded inconsistent results. We measured serum concentrations of BDNF and assessed behavior and cognition related to eating in ED patients and control subjects.

METHODS

Forty female drug-free patients [19 with anorexia nervosa (AN), 21 with bulimia nervosa (BN)], who did not meet the diagnostic criteria for depressive disorder, and 24 age-matched normal control subjects were enrolled in the current study. We evaluated eating-related psychopathology and depressive symptoms using the Eating Disorder Inventory-2 (EDI-2), Eating Attitude Test-26 (EAT-26) and the Hamilton Depression Rating Scale (HDRS), and measured serum BDNF levels by an enzyme-linked immunosorbent assay.

RESULTS

Compared to normal controls, serum levels of BDNF were significantly reduced in AN, but not in BN. There was a significant positive correlation between serum BDNF levels and BMI in both AN patients (r=.649, p=.003) and BN patients (r=.626, p=.002). However, no correlation between serum BDNF levels and BMI was detected in the controls. Furthermore, there was a significant negative correlation between serum BDNF levels and the oral control subscale scores of EAT in both AN patients (r=-.506, p=.027) and BN patients (r=-.511, p=.018); whereas, no correlation was detected in normal controls.

CONCLUSION

Our study demonstrated that individuals showing more extreme food intake regulation were those with lower serum BDNF levels. This finding is contrary to that in mice where mice with reduced BDNF levels showed aberrant eating behavior. This result suggests that BDNF is no longer functioning appropriately in ED patients, which could be an important factor in the pathophysiological of ED.

Preliminary evidence of cannabinoid effects on brain-derived neurotrophic factor (BDNF) levels in humans

BACKGROUND

Acute and chronic exposure to cannabinoids has been associated with cognitive deficits, a higher risk for schizophrenia and other drug abuse. However, the precise mechanism underlying such effects is not known. Preclinical studies suggest that cannabinoids modulate brain-derived neurotrophic factor (BDNF). Accordingly, we hypothesized that Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the principal active component of cannabis, would alter BDNF levels in humans.

MATERIALS AND METHODS

Healthy control subjects (n = 14) and light users of cannabis (n = 9) received intravenous administration of (0.0286 mg/kg) Delta(9)-THC in a double-blind, fixed order, placebo-controlled, laboratory study. Serum sampled at baseline, after placebo administration, and after Delta(9)-THC administration was assayed for BDNF using ELISA.

RESULTS

Delta(9)-THC increased serum BDNF levels in healthy controls but not light users of cannabis. Further, light users of cannabis had lower basal BDNF levels. Delta(9)-THC produced psychotomimetic effects, perceptual alterations, and "high" and spatial memory impairments.

IMPLICATIONS

The effects of socially relevant doses of cannabinoids on BDNF suggest a possible mechanism underlying the consequences of exposure to cannabis. This may be of particular importance for the developing brain and also in disorders believed to involve altered neurodevelopment such as schizophrenia. Larger studies to investigate the effects of cannabinoids on BDNF and other neurotrophins are warranted.

Changes in plasma levels of BDNF and NGF reveal a gender-selective vulnerability to early adversity in rhesus macaques

Early stressful events can increase vulnerability for psychopathology, although knowledge on the effectors is still limited. Here we tested the hypothesis that peripheral levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), which are involved in the response to stress and in the pathophysiology of anxiety and depression, might be affected in a non-human primate model of adverse rearing. Males and females rhesus macaques reared with their mothers (MR) or in peer-only groups (PR) were used as experimental subjects. BDNF, NGF, adrenocorticotropic hormone (ACTH), cortisol and growth hormone (GH) were determined at baseline on postnatal days (PND) 14, 30 and 60 by means of specific ELISA and RIA procedures. In addition, behavior was assessed on PND 7, 14, 21, 30 (Brazelton test) and 60 (home cage observation). Data indicate gender differences in basal levels of BDNF throughout development. Peer-rearing increased significantly BDNF levels only in females. In addition, while all peer-reared subjects showed high levels of stereotypies and self-directed behaviors, behavioral passivity was selectively increased in females. By contrast, NGF levels were increased in response to peer-rearing only in males, and correlated positively with other "classic" endocrine responses to stress, such as cortisol and GH. Our data identify BDNF and NGF as neuroendocrine markers underlying differential responses to maternal deprivation in males and females rhesus macaques. The selective changes in BDNF levels in females could help explain the greater vulnerability to mood disorders of this gender reported in humans.

Caloric restriction improves memory in elderly humans

Animal studies suggest that diets low in calories and rich in unsaturated fatty acids (UFA) are beneficial for cognitive function in age. Here, we tested in a prospective interventional design whether the same effects can be induced in humans. Fifty healthy, normal- to overweight elderly subjects (29 females, mean age 60.5 years, mean body mass index 28 kg/m(2)) were stratified into 3 groups: (i) caloric restriction (30% reduction), (ii) relative increased intake of UFAs (20% increase, unchanged total fat), and (iii) control. Before and after 3 months of intervention, memory performance was assessed under standardized conditions. We found a significant increase in verbal memory scores after caloric restriction (mean increase 20%; P < 0.001), which was correlated with decreases in fasting plasma levels of insulin and high sensitive C-reactive protein, most pronounced in subjects with best adherence to the diet (all r values < -0.8; all P values <0.05). Levels of brain-derived neurotrophic factor remained unchanged. No significant memory changes were observed in the other 2 groups. This interventional trial demonstrates beneficial effects of caloric restriction on memory performance in healthy elderly subjects. Mechanisms underlying this improvement might include higher synaptic plasticity and stimulation of neurofacilitatory pathways in the brain because of improved insulin sensitivity and reduced inflammatory activity. Our study may help to generate novel prevention strategies to maintain cognitive functions into old age.

Delivery of peptide and protein drugs over the blood-brain barrier

Peptide and protein (P/P) drugs have been identified as showing great promises for the treatment of various neurodegenerative diseases. A major challenge in this regard, however, is the delivery of P/P drugs over the blood-brain barrier (BBB). Intense research over the last 25 years has enabled a better understanding of the cellular and molecular transport mechanisms at the BBB, and several strategies for enhanced P/P drug delivery over the BBB have been developed and tested in preclinical and clinical-experimental research. Among them, technology-based approaches (comprising functionalized nanocarriers and liposomes) and pharmacological strategies (such as the use of carrier systems and chimeric peptide technology) appear to be the most promising ones. This review combines a comprehensive overview on the current understanding of the transport mechanisms at the BBB with promising selected strategies published so far that can be applied to facilitate enhanced P/P drug delivery over the BBB.

Cardio-respiratory fitness, habitual physical activity and serum brain derived neurotrophic factor (BDNF) in men and women

Short episodes of high intensity exercise transiently increase serum levels of BDNF in humans, but serum levels of BDNF at rest appear to be lower in more physically active humans with greater levels of energy expenditure. The relationship between serum BDNF concentration, cardio-respiratory fitness (Astrand-Rhyming test estimated VO2 max) and volume of long-term, regular exercise and sporting activity (Baecke Habitual Physical Activity Index) was investigated in 44 men and women between the age range of 18-57 years. In this group an inverse relationship between resting serum BDNF concentration and measures of both estimated VO2 max (r=-0.352; P<0.05) and long-term sporting activity (r=-0.428, P<0.01) was found. These results indicate that increased levels of cardio-respiratory fitness and habitual exercise are associated with lower resting levels of serum BDNF in healthy humans. This is the first study to demonstrate an inverse relationship between a physiological estimate of cardio-respiratory fitness and serum BDNF.

Increased levels of plasma brain-derived neurotrophic factor (BDNF) in children with attention deficit-hyperactivity disorder (ADHD)

BACKGROUND

Recent reports have suggested a pathophysiological role of brain-derived neurotrophic factor (BDNF) in attention deficit-hyperactivity disorder (ADHD). We evaluated the plasma levels of BDNF in patients with ADHD.

METHODS

Plasma BDNF levels were measured in 41 drug naive ADHD patients and 107 normal controls. The severity of ADHD symptoms was determined by patient scores on the ADHD rating scale (ARS) and the computerized ADHD diagnostic system (ADS).

RESULTS

ANCOVA with age and gender as covariates showed that the mean plasma BDNF levels were significantly higher in ADHD patients than in normal controls (F=16.968, p<0.001). There were also significant differences in plasma BDNF levels of ADHD patients and those of normal controls for males and females (Mann-Whitney U-test, p=0.001 and 0.041, respectively). We also found a significant correlation between plasma BDNF levels and omission errors in ADS outcome-variable T-scores (p<0.001).

CONCLUSIONS

Our study suggests that there is an increase of plasma BDNF levels in untreated ADHD patients, and that plasma BDNF levels had a significant positive correlation with the severity of inattention symptoms. Further studies are required to elucidate the source and role of circulating BDNF in ADHD.

Continuous decrease in serum brain-derived neurotrophic factor (BDNF) levels in a neuropsychiatric syndrome of systemic lupus erythematosus patient with organic brain changes

In the present study, the authors reported on a case in neuropsychiatric syndromes of systemic lupus erythematosus (NPSLE) with irreversible organic brain changes. The authors also longitudinally investigated serum brain-derived neurotrophic factor (BDNF) levels in the patient. We found that serum BDNF levels in the NPSLE patient with irreversible organic brain change were consistently low, independent of the severity of psychiatric symptoms. Thus, the longitudinal measurement of serum BDNF levels might be useful in predicting the prognosis of NPSLE.

A systematic review and meta-analysis of clinical studies on major depression and BDNF levels: implications for the role of neuroplasticity in depression

Several clinical studies on major depressive disorder (MDD) have shown that blood brain-derived neurotrophic factor (BDNF) - a factor used to index neuroplasticity - is associated with depression response; however, the results are mixed. The purpose of our study was to evaluate whether BDNF levels are correlated with improvement of depression. We performed a systematic review and meta-analysis of the literature, searching Medline, Cochrane Central, SciELO databases and reference lists from retrieved articles for clinical studies comparing mean BDNF blood levels in depressed patients pre- and post-antidepressant treatments or comparing depressed patients with healthy controls. Two reviewers independently searched for eligible studies and extracted outcome data using a structured form previously elaborated. Twenty articles, including 1504 subjects, met our inclusion criteria. The results showed that BDNF levels increased significantly after antidepressant treatment (effect size 0.62, 95% CI 0.36-0.88, random effects model). In addition, there was a significant correlation between changes in BDNF level and depression scores changes (p=0.02). Moreover, the results were robust according to the sensitivity analysis and Begg's funnel plot results did not suggest publication bias. Finally, there was a difference between pre-treatment patients and healthy controls (effect size 0.91, 95% CI 0.70-1.11) and a small but significant difference between treated patients and healthy controls (effect size 0.34, 95% CI 0.02-0.66). Our results show that BDNF levels are associated with clinical changes in depression; supporting the notion that depression improvement is associated with neuroplastic changes.