Impaired nerve growth factor homeostasis in patients with bipolar disorder

Neurotrophic factor levels and executive functions in children of parents with bipolar disorder: A case controlled study

BACKGROUND

In the current study, it was aimed to evaluate neurotrophic factor levels and their relationship with executive functions in high-risk children and adolescents (high-risk group) whose parents were diagnosed with bipolar disorder (BD) but not affected by any psychiatric disease,and in order to determine possible vulnerability factors related to the disease.

METHODS

The study sample consisted of 32 high-risk group and 34 healthy controls. The Schedule for Affective Disorders and Schizophrenia for School-Age Children-Present and Lifetime Version-Turkish Adaptation (KSADS-PL-T), Stroop Test, Serial Digit Learning Test (SDLT) and Cancellation Test to evaluate executive functions were administered to all participants by the clinician.Serum levels of neurotrophic factors were measured using commercial enzyme linked immunosorbent assay kits.

RESULTS

Serum BDNF, NT-3, NT-4 levels and SDLT scores were significantly lower in the high-risk group for BD compared to the healthy control group. A moderate negative correlation was found between BDNF levels and the Cancellation Test scores in the high-risk group. In addition to these results, the odds ratios of age, NT-4, SDLT scores for being in the risky group in terms of BD diagnosis were 1.26, 0.99 and 0.86 respectively.

LIMITATIONS

This was a cross-sectional study. Causality between study results is therefore difficult to establish. The relatively small sample size of the study is another limitation.

CONCLUSION

The results of the present study suggest that BDNF, NT-3, NT-4 may play a role in the physiopathology of BD and may be associated with impaired executive function areas such as attention and response inhibition in the high-risk group.

Imipramine Can Be Effective on Depressive-Like Behaviors, but Not on Neurotrophic Factor Levels in an Animal Model for Bipolar Disorder Induced by Ouabain

INTRODUCTION

Despite possible risks of mania switching with the long-term use of antidepressants in patients with bipolar disorder (BD), these drugs may help in depressive episodes. Alterations in neurotrophic factor levels seem to be involved in the pathophysiology of BD. The present study aimed to evaluate the effect of acute treatment of imipramine on behavior and neurotrophic levels in rats submitted to the animal model for BD induced by ouabain.

METHODS

Wistar rats received a single intracerebroventricular (ICV) injection of artificial cerebrospinal fluid or ouabain (10^-3 M). Following the ICV administration, the rats were treated for 14 days with saline (NaCl 0.9%, i.p.), lithium (47.5 mg/kg, i.p.), or valproate (200 mg/kg, i.p.). On the 13^th and 14^th days of treatment, the animals received an additional injection of saline or imipramine (10 mg/kg, i.p.). Behavior tests were evaluated 7 and 14 days after ICV injection. Adrenal gland weight and concentrations of ACTH were evaluated. Levels of neurotrophins BDNF, NGF, NT-3, and GDNF were measured in the frontal cortex and hippocampus by ELISA test.

RESULTS

The administration of ouabain induced mania- and depressive-like behavior in the animals 7 and 14 days after ICV, respectively. The treatment with lithium and valproate reversed the mania-like behavior. All treatments were able to reverse most of the depressive-like behaviors induced by ouabain. Moreover, ouabain increased HPA-axis parameters in serum and decreased the neurotrophin levels in the frontal cortex and hippocampus. All treatments, except imipramine, reversed these alterations.

CONCLUSION

It can be suggested that acute administration of imipramine alone can be effective on depressive-like symptoms but not on neurotrophic factor alterations present in BD.

Serum levels of glial cell line-derived neurotrophic factor as a biomarker for mood disorders and lithium response

Glial cell line-derived neurotrophic factor (GDNF) plays an important role in the pathophysiology of neuropsychiatric disorders. We examined serum GDNF levels in bipolar disorder (BD) patients and major depressive disorder (MDD) patients and their association with response to lithium therapy. We used a multicenter (six sites), exploratory, cross-sectional case-control design and recruited 448 subjects: 143 BD patients, 116 MDD patients, and 158 healthy controls (HCs). We evaluated the patients' clinical severity using the Clinical Global Impression (CGI), and responses to lithium therapy using the Alda scale. The serum GDNF levels were significantly decreased in the BD and MDD groups compared to the HCs, with no significant difference between the BD and MDD groups. After adjustment, the serum GDNF levels in the BD and MDD patients in remission or depressive states were decreased compared to the HC values. Lower serum GDNF levels in BD patients were associated with higher CGI and Alda scores (i.e., severe illness and good response to lithium therapy, respectively). Our findings suggest that the serum GDNF level may be a biomarker for both BD and MDD in remission or depressive states. The serum GDNF level may be associated with the lithium response of BD patients.

Neurobiology of bipolar disorders: a review of genetic components, signaling pathways, biochemical changes, and neuroimaging findings

Bipolar disorder (BD) is a chronic mental illness characterized by changes in mood that alternate between mania and hypomania or between depression and mixed states, often associated with functional impairment. Although effective pharmacological and non-pharmacological treatments are available, several patients with BD remain symptomatic. The advance in the understanding of the neurobiology underlying BD could help in the identification of new therapeutic targets as well as biomarkers for early detection, prognosis, and response to treatment in BD. In this review, we discuss genetic, epigenetic, molecular, physiological and neuroimaging findings associated with the neurobiology of BD. Despite the advances in the pathophysiological knowledge of BD, the diagnosis and management of the disease are still essentially clinical. Given the complexity of the brain and the close relationship between environmental exposure and brain function, initiatives that incorporate genetic, epigenetic, molecular, physiological, clinical, environmental data, and brain imaging are necessary to produce information that can be translated into prevention and better outcomes for patients with BD.

NRG1, PIP4K2A, and HTR2C as Potential Candidate Biomarker Genes for Several Clinical Subphenotypes of Depression and Bipolar Disorder

GSK3B, BDNF, NGF, NRG1, HTR2C, and PIP4K2A play important roles in molecular mechanisms of psychiatric disorders. GSK3B occupies a central position in these molecular mechanisms and is also modulated by psychotropic drugs. BDNF regulates a number of key aspects in neurodevelopment and synaptic plasticity. NGF exerts a trophic action and is implicated in cerebral alterations associated with psychiatric disorders. NRG1 is active in neural development, synaptic plasticity, and neurotransmission. HTR2C is another important psychopharmacological target. PIP4K2A catalyzes the phosphorylation of PI5P to form PIP2, the latter being implicated in various aspects of neuronal signal transduction. In the present study, the six genes were sequenced in a cohort of 19 patients with bipolar affective disorder, 41 patients with recurrent depressive disorder, and 55 patients with depressive episode. The study revealed a number of genetic variants associated with antidepressant treatment response, time to recurrence of episodes, and depression severity. Namely, alleles of rs35641374 and rs10508649 (NRG1 and PIP4K2A) may be prognostic biomarkers of time to recurrence of depressive and manic/mixed episodes among patients with bipolar affective disorder. Alleles of NC_000008.11:g.32614509_32614510del, rs61731109, and rs10508649 (also NRG1 and PIP4K2A) seem to be predictive biomarkers of response to pharmacological antidepressant treatment on the 28th day assessed by the HDRS-17 or CGI-I scale. In particular, the allele G of rs10508649 (PIP4K2A) may increase resistance to antidepressant treatment and be at the same time protective against recurrent manic/mixed episodes. These results support previous data indicating a biological link between resistance to antidepressant treatment and mania. Bioinformatic functional annotation of associated variants revealed possible impact for transcriptional regulation of PIP4K2A. In addition, the allele A of rs2248440 (HTR2C) may be a prognostic biomarker of depression severity. This allele decreases expression of the neighboring immune system gene IL13RA2 in the putamen according to the GTEx portal. The variant rs2248440 is near rs6318 (previously associated with depression and effects of psychotropic drugs) that is an eQTL for the same gene and tissue. Finally, the study points to several protein interactions relevant in the pathogenesis of mood disorders. Functional studies using cellular or animal models are warranted to support these results.

Neurotrophic factors in bipolar disorders patients with manic episode

Background/aim

Neurotrophins are one of the most important molecule groups affecting cerebral neuroplasticity. The amount of evidence about the role of changes in neuroplasticity in the pathophysiology of bipolar disease is growing.

Materials and methods

We measured serum levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), glial cell-line derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), insulin-like growth factor-1 (IGF-1), fibroblast growth factor (FGF)-2, neuritin 1 (Nrn 1) in bipolar 1 manic episode patients (n = 45) and healthy control group.

Results

When controlled for age, BMI and cortisol, it was found that the serum levels of BDNF, NGF, NT-3, VEGF and FGF-2 of bipolar manic episode patients were not statistically different compared to those of the control group. GDNF level and Nrn 1 levels were significantly lower (P = 0.003 and P = 0.025 respectively) while IGF-1 levels were significantly higher than the control group (P = 0.0001). ROC analysis was performed and the area under the the curve was calculated as 0.737, 0.766 for GDNF, IGF-1 respectively.

Conclusion

The changes in the levels of GDNF, IGF-1 and Nrn 1 might be involved in pathopysiology of bipolar disorder, and GDNF, IGF-1 may be considered as state markers in bipolar manic episode.

Role of gut microbiota in the GBR12909 model of mania-like behavior in mice

Growing evidence suggests a role for brain-gut-microbiota axis in affective disorders including major depression and bipolar disorder (BD). Herein, we aim to explore, by employing germ-free (GF) mice, the effect of the indigenous microbiota in the development of mania-like behavior. Conventional and GF mice were evaluated for the hyperlocomotion induced by the dopamine transporter inhibitor GBR12909 (15 mg/Kg), a validated model for mania-like behavior. Inflammatory mediators and neurotrophic factors were quantified in the prefrontal cortex, hippocampus and striatum. Mice lacking indigenous microbiota were less susceptible to the mania-like behavior induced by GBR12909. This effect was associated with decreased levels of inflammatory cytokines such as IL-6 and TNF-α, along with increased concentrations of anti- inflammatory cytokines (IL-10) and of neurotrophins (BDNF and NGF). We provided the first evidence that gut-microbiota-brain axis participates in the development of mania-like behavior in rodents, possibly through neuroimmunepathways.

Effects of lithium and valproate on behavioral parameters and neurotrophic factor levels in an animal model of mania induced by paradoxical sleep deprivation

The present study aimed to evaluate the effects of treatment with lithium (Li) and valproate (VPA) on behaviors and brain BDNF, NGF, NT-3, NT-4 and GDNF levels in mice submitted to paradoxical sleep deprivation (PSD), which induces an animal model of mania. Male C57BL/6J mice received an intraperitoneal (i.p.) injection of saline solution (NaCl 0.09%, 1 ml/kg), Li (47.3 mg/kg, 1 ml/kg) or VPA (200 mg/kg, 1 ml/kg) once a day for seven days. Animals were randomly distributed into six groups (n = 10 per group): (1) Control + Sal; (2) Control + Li; (3) Control + VPA; (4) PSD + Sal; (5) PSD + Li; or (6) PSD + VPA. Animals were submitted to 36 h of PSD, and then, they were submitted to the open field test. The frontal cortex and hippocampus were dissected from the brain. The manic-like behaviors in the mice were analyzed. Treatment with Li and VPA reversed the behavioral alterations induced by PSD. PSD decreased BDNF, NGF, and GDNF levels in the frontal cortex and hippocampus of mice. The administration of Li and VPA protected the brain against the damage induced by PSD. However, PSD and the administration of Li and VPA did not affect the levels of NT-3 and NT-4 in either brain structure evaluated. In conclusion, the PSD protocol induced manic-like behavior in rats and induced alterations in neurotrophic factor levels. It seems that neurotrophic factors and sleep are essential targets to treat BD.

Serum level of nerve growth factor is a potential biomarker of conversion to bipolar disorder in women with major depressive disorder

AIM

The aim of this study was to identify biomarkers associated with major depressive disorder (MDD) and conversion from MDD to bipolar disorder (BD) in an outpatient sample of women.

METHODS

This was a longitudinal study including women diagnosed with MDD and aged 18 to 60 years. The follow-up was 3 years. The diagnosis was performed using the Mini International Neuropsychiatric Interview Plus. Blood collection was just performed in the first phase. Serum interleukin-6, tumor necrosis factor-α, brain-derived neurotrophic factor, glial cell-derived neurotrophic factor, and nerve growth factor (NGF) levels were measured using a commercial immunoassay kit.

RESULTS

We included 156 women. The conversion rate from MDD to BD was 15.4% (n = 24). NGF serum levels were increased in patients who converted to BD compared to the remitted MDD group and current MDD group (P = 0.013). The Bonferroni post-hoc test for multiple comparisons revealed significant differences for higher NGF levels in patients who converted to BD compared to patients with current MDD (P = 0.037). Interleukin-6, tumor necrosis factor-α, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor serum levels did not differ among the groups.

CONCLUSION

Our results suggest that NGF might be a useful biomarker associated with early detection of conversion to BD, helping clinicians in the clinical diagnosis.

The role of neurotrophic factors in manic-, anxious- and depressive-like behaviors induced by amphetamine sensitization: Implications to the animal model of bipolar disorder

BACKGROUND

Bipolar disorder (BD) and substance use disorders share common symptoms, such as behavioral sensitization. Amphetamine-induced behavioral sensitization can serve as an animal model of BD. Neurotrophic factors have an important role in BD pathophysiology. This study evaluated the effects of amphetamine sensitization on behavior and neurotrophic factor levels in the brains of rats.

METHODS

Wistar rats received daily intraperitoneal (i.p) injections of dextroamphetamine (d-AMPH) 2 mg/kg or saline for 14 days. After seven days of withdrawal, the animals were challenged with d-AMPH (0.5 mg/kg, i.p) and locomotor behavior was assessed. In a second protocol, rats were similarly treated with d-AMPH (2 mg/kg, i.p) for 14 days. After withdrawal, without d-AMPH challenge, depressive- and anxiety-like behaviors were evaluated through forced swimming test and elevated plus maze. Levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin 3 (NT-3), neurotrophin 4/5 (NT-4/5) and glial-derived neurotrophic factor (GDNF) were evaluated in the frontal cortex, hippocampus, and striatum.

RESULTS

D-AMPH for 14 days augmented locomotor sensitization to a lower dose of d-AMPH (0.5 mg/kg) after the withdrawal. d-AMPH withdrawal induced depressive- and anxious-like behaviors. BDNF, NGF, and GDNF levels were decreased, while NT-3 and NT-4 levels were increased in brains after d-AMPH sensitization.

LIMITATIONS

Although d-AMPH induces manic-like behavior, the mechanisms underlying these effects can also be related to phenotypes of drug abuse.

CONCLUSIONS

Together, vulnerability to mania-like behavior following d-AMPH challenge and extensive neurotrophic alterations, suggest amphetamine-induced behavioral sensitization is a good model of BD pathophysiology.

Proteomic Studies of Psychiatric Disorders

Many diseases result from programming effects in utero. This chapter describes recent advances in proteomic studies which have improved our understanding of the underlying pathophysiological pathways in the major psychiatric disorders, resulting in the development of potential novel biomarker tests. Such tests should be based on measurement of blood-based proteins given the ease of accessibility of this medium and the known connections between the periphery and the central nervous system. Most importantly, emerging biomarker tests should be developed on lab-on-a-chip and other handheld devices to enable point-of-care use. This should help to identify individuals with psychiatric disorders much sooner than ever before, which will allow more rapid treatment options for the best possible patient outcomes.

Pathophysiology in the comorbidity of Bipolar Disorder and Alzheimer's Disease: pharmacological and stem cell approaches

Neuropsychiatric disorders involve various pathological mechanisms, resulting in neurodegeneration and brain atrophy. Neurodevelopmental processes have shown to be critical for the progression of those disorders, which are based on genetic and epigenetic mechanisms as well as on extrinsic factors. We review here common mechanisms underlying the comorbidity of Bipolar Disorders and Alzheimer's Disease, such as aberrant neurogenesis and neurotoxicity, reporting current therapeutic approaches. The understanding of these mechanisms precedes stem cell-based strategies as a new therapeutic possibility for treatment and prevention of Bipolar and Alzheimer's Disease progression. Taking into account the difficulty of studying the molecular basis of disease progression directly in patients, we also discuss the importance of stem cells for effective drug screening, modeling and treating psychiatric diseases, once in vitro differentiation of patient-induced pluripotent stem cells provides relevant information about embryonic origins, intracellular pathways and molecular mechanisms.

Brief psychoeducation for bipolar disorder: Evaluation of trophic factors serum levels in young adults

The aim of this study was to evaluate the impact of psychoeducation in serum levels of BDNF, NGF and GDNF in young adults presenting bipolar disorder (BD). This is a randomized clinical trial including 39 young adults (18-29 years) diagnosed with BD through the Structured Clinical Interview for DSM-IV (SCID-CV). Participants were randomized in two treatment groups: usual treatment (medication) and combined intervention (medication plus psychoeducation). Depressive symptoms were assessed using the Hamilton Depression Rating Scale (HDRS) and severity of manic and hypomanic symptoms was evaluated through the Young Mania Rating Scale (YMRS). The serum levels of trophic factors were measured with an ELISA kit. In both intervention groups, there was an improvement in depressive symptoms significantly between baseline and post-intervention. In the combined intervention, GDNF serum levels increased significantly from baseline to post-intervention. However, there were no differences in BDNF and NGF serum levels. In the usual treatment group, no changes were observed in serum levels of GDNF, BDNF, and NGF the post-intervention in individuals. Our data suggests that only combined intervention was effective in improving depressive symptoms and increasing GDNF levels in a sample of young adults with bipolar disorder.

Regulatory role of NGFs in neurocognitive functions

Nerve growth factors (NGFs), especially the prototype NGF and brain-derived neurotrophic factor (BDNF), have a diverse array of functions in the central nervous system through their peculiar set of receptors and intricate signaling. They are implicated not only in the development of the nervous system but also in regulation of neurocognitive functions like learning, memory, synaptic transmission, and plasticity. Evidence even suggests their role in continued neurogenesis and experience-dependent neural network remodeling in adult brain. They have also been associated extensively with brain disorders characterized by neurocognitive dysfunction. In the present article, we aimed to make an exhaustive review of literature to get a comprehensive view on the role of NGFs in neurocognitive functions in health and disease. Starting with historical perspective, distribution in adult brain, implied molecular mechanisms, and developmental basis, this article further provides a detailed account of NGFs’ role in specified neurocognitive functions. Furthermore, it discusses plausible NGF-based homeostatic and adaptation mechanisms operating in the pathogenesis of neurocognitive disorders and has presents a survey of such disorders. Finally, it elaborates on current evidence and future possibilities in therapeutic applications of NGFs with an emphasis on recent research updates in drug delivery mechanisms. Conclusive remarks of the article make a strong case for plausible role of NGFs in comprehensive regulation of the neurocognitive functions and pathogenesis of related disorders and advocate that future research should be directed to explore use of NGF-based mechanisms in the prevention of implicated diseases as well as to target these molecules pharmacologically.

Peripheral blood nerve growth factor levels in major psychiatric disorders

Nerve growth factor (NGF) plays crucial roles in promoting neural growth and survival, and mediating synaptic and morphological plasticity. Several studies investigated the correlation between peripheral NGF levels and major psychiatric disorders, including schizophrenia (SCZ), major depressive disorder (MDD) and bipolar disorder (BPD); however, the findings were inconsistent. This meta-analysis sought to investigate blood NGF levels in patients with psychiatric disorders compared with healthy subjects and examined potential effects of blood fraction, medication and disease status. A total of 21 eligible studies, encompassing 1342 patients suffering from psychiatric disorders and 1225 healthy subjects, were enrolled in the present meta-analysis. No obvious publication bias was observed either for SCZ, MDD or BPD by the Begg's test (P > 0.05). Random-effects meta-analysis showed that SCZ (Z = 2.14, P = 0.033, SMD = -1.08, 95% CI = -2.07 to -0.09) and MDD (Z = 2.57, P = 0.010, SMD = -0.61, 95% CI = -1.08 to -0.14) patients had significantly reduced NGF levels, compared with healthy controls. Notably, this decrease was enhanced in un-medicated patients of SCZ (P = 0.004) and medicated or chronic patients of MDD (P < 0.001). No significant difference of NGF levels was observed between BPD patients and controls (P > 0.05). These results supported an association between the reduction of NGF levels and psychiatric disorders. It remains unclear whether the change of NGF levels is a prerequisite for its function in psychiatric disorders development or merely an epiphenomenon unrelated to the pathophysiologic mechanisms.

Biological hypotheses and biomarkers of bipolar disorder

The most common mood disorders are major depressive disorders and bipolar disorders (BD). The pathophysiology of BD is complex, multifactorial, and not fully understood. Creation of new hypotheses in the field gives impetus for studies and for finding new biomarkers for BD. Conversely, new biomarkers facilitate not only diagnosis of a disorder and monitoring of biological effects of treatment, but also formulation of new hypotheses about the causes and pathophysiology of the BD. BD is characterized by multiple associations between disturbed brain development, neuroplasticity, and chronobiology, caused by: genetic and environmental factors; defects in apoptotic, immune-inflammatory, neurotransmitter, neurotrophin, and calcium-signaling pathways; oxidative and nitrosative stress; cellular bioenergetics; and membrane or vesicular transport. Current biological hypotheses of BD are summarized, including related pathophysiological processes and key biomarkers, which have been associated with changes in genetics, systems of neurotransmitter and neurotrophic factors, neuroinflammation, autoimmunity, cytokines, stress axis activity, chronobiology, oxidative stress, and mitochondrial dysfunctions. Here we also discuss the therapeutic hypotheses and mechanisms of the switch between depressive and manic state.

Update on bipolar disorder biomarker candidates

INTRODUCTION

Bipolar disorder is a chronic and disabling mood disorder with a complex pathophysiological basis. A significant percentage of patients do not receive correct diagnosis which directly influences therapeutic response, rendering recovery troublesome. There is a long-standing need for proper non-clinically based tools for diagnosis, treatment selection and follow-up of such patients. Areas covered: In the past decade, the scientific community has shown a great interest in biomarker development. Here, we highlight the different potential biomarkers and we discuss their feasibility and their possible clinical relevance. Expert commentary: To date, despite the major ongoing trials and consortia with promising future perspectives, no reliable biomarker of bipolar disorder has been fully defined.

Is there Progress? An Overview of Selecting Biomarker Candidates for Major Depressive Disorder

Major depressive disorder (MDD) contributes to a significant worldwide disease burden, expected to be second only to heart disease by 2050. However, accurate diagnosis has been a historical weakness in clinical psychiatry. As a result, there is a demand for diagnostic modalities with greater objectivity that could improve on current psychiatric practice that relies mainly on self-reporting of symptoms and clinical interviews. Over the past two decades, literature on a growing number of putative biomarkers for MDD increasingly suggests that MDD patients have significantly different biological profiles compared to healthy controls. However, difficulty in elucidating their exact relationships within depression pathology renders individual markers inconsistent diagnostic tools. Consequently, further biomarker research could potentially improve our understanding of MDD pathophysiology as well as aid in interpreting response to treatment, narrow differential diagnoses, and help refine current MDD criteria. Representative of this, multiplex assays using multiple sources of biomarkers are reported to be more accurate options in comparison to individual markers that exhibit lower specificity and sensitivity, and are more prone to confounding factors. In the future, more sophisticated multiplex assays may hold promise for use in screening and diagnosing depression and determining clinical severity as an advance over relying solely on current subjective diagnostic criteria. A pervasive limitation in existing research is heterogeneity inherent in MDD studies, which impacts the validity of biomarker data. Additionally, small sample sizes of most studies limit statistical power. Yet, as the RDoC project evolves to decrease these limitations, and stronger studies with more generalizable data are developed, significant advances in the next decade are expected to yield important information in the development of MDD biomarkers for use in clinical settings.

Correlations between amygdala volumes and serum levels of BDNF and NGF as a neurobiological markerin adolescents with bipolar disorder

BACKGROUND

The amygdala is repeatedly implicated as a critical component of the neurocircuitry regulating emotional valence. Studies have frequently reported reduced amygdala volumes in children and adolescents with bipolar disorder (BD). Brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF) play critical roles in growth, differentiation, maintenance, and synaptic plasticity of neuronal systems in adolescent brain development. The aim of the present study was to assess amygdala volumesand its correlation with serum levels of NGF and BDNF in euthymic adolescents with BD and healthy controls.

METHODS

Using structural MRI, we compared the amygdala volumes of 30 euthymic subjects with BD with 23 healthy control subjects aged between 13 and 19 years during a naturalistic clinical follow-up. The boundaries of the amygdala were outlined manually. Serum BDNF and NGF levels were measured using sandwich-ELISA and compared between the study groups.

RESULTS

The right or left amygdala volume did not differ between the study groups.The right and left amygdala volumes were highly correlated with levels of BDNF in the combined BD group and the valproate-treated group.Both R and L amygdala volumes were correlated with BDNF levels in healthy controls. The left amygdala volumes were correlated with BDNF levels in the lithium-treated group.

LIMITATIONS

This cross-sectional study cannot inform longitudinal changes in brain structure. Further studies with larger sample sizes are needed to improve reliability.

CONCLUSIONS

The correlations between amygdala volumes and BDNF levels might be an early neuromarker for diagnosis and/or treatment response in adolescents with BD.

Neurotrophic factors in tension-type headache

Neurotrophic factors (NF) are involved in pain regulation and a few studies have suggested that they may play a pathophysiological role in primary headaches. The aim of this study was to investigate NF levels in patients with tension type headache (TTH). We carried out a cross sectional study including 48 TTH patients and 48 age and gender matched controls. Beck Depression and Anxiety Inventories, and Headache Impact Test were recorded. Serum levels of NF were determined by ELISA. There were not significant differences between NF levels between TTH patients and controls. Patients with chronic and episodic TTH had not significant differences in NF levels. The presence of headache at the time of evaluation did not significantly alter the levels of NF. Depression and anxiety scores as well as headache impact did not correlate with NF levels. Our study suggest that the serum levels of NF are not altered in TTH.

Neurotrophic Effects of Mu Bie Zi (Momordica cochinchinensis) Seed Elucidated by High-Throughput Screening of Natural Products for NGF Mimetic Effects in PC-12 Cells

Post-mitotic central nervous system (CNS) neurons have limited capacity for regeneration, creating a challenge in the development of effective therapeutics for spinal cord injury or neurodegenerative diseases. Furthermore, therapeutic use of human neurotrophic agents such as nerve growth factor (NGF) are limited due to hampered transport across the blood brain barrier (BBB) and a large number of peripheral side effects (e.g. neuro-inflammatory pain/tissue degeneration etc.). Therefore, there is a continued need for discovery of small molecule NGF mimetics that can penetrate the BBB and initiate CNS neuronal outgrowth/regeneration. In the current study, we conduct an exploratory high-through-put (HTP) screening of 1144 predominantly natural/herb products (947 natural herbs/plants/spices, 29 polyphenolics and 168 synthetic drugs) for ability to induce neurite outgrowth in PC12 dopaminergic cells grown on rat tail collagen, over 7 days. The data indicate a remarkably rare event-low hit ratio with only 1/1144 tested substances (<111.25 µg/mL) being capable of inducing neurite outgrowth in a dose dependent manner, identified as; Mu Bie Zi, Momordica cochinchinensis seed extract (MCS). To quantify the neurotrophic effects of MCS, 36 images (n = 6) (average of 340 cells per image), were numerically assessed for neurite length, neurite count/cell and min/max neurite length in microns (µm) using Image J software. The data show neurite elongation from 0.07 ± 0.02 µm (controls) to 5.5 ± 0.62 µm (NGF 0.5 μg/mL) and 3.39 ± 0.45 µm (138 μg/mL) in MCS, where the average maximum length per group extended from 3.58 ± 0.42 µm (controls) to 41.93 ± 3.14 µm (NGF) and 40.20 ± 2.72 µm (MCS). Imaging analysis using immunocytochemistry (ICC) confirmed that NGF and MCS had similar influence on 3-D orientation/expression of 160/200 kD neurofilament, tubulin and F-actin. These latent changes were associated with early rise in phosphorylated extracellular signal-regulated kinase (ERK) p-Erk1 (T202/Y204)/p-Erk2 (T185/Y187) at 60 min with mild changes in pAKT peaking at 5 min, and no indication of pMEK involvement. These findings demonstrate a remarkable infrequency of natural products or polyphenolic constituents to exert neurotrophic effects at low concentrations, and elucidate a unique property of MCS extract to do so. Future research will be required to delineate in depth mechanism of action of MCS, constituents responsible and potential for therapeutic application in CNS degenerative disease or injury.

Sodium butyrate and mood stabilizers block ouabain-induced hyperlocomotion and increase BDNF, NGF and GDNF levels in brain of Wistar rats

Bipolar Disorder (BD) is one of the most severe psychiatric disorders. Despite adequate treatment, patients continue to have recurrent mood episodes, residual symptoms, and functional impairment. Some preclinical studies have shown that histone deacetylase inhibitors may act on manic-like behaviors. Neurotrophins have been considered important mediators in the pathophysiology of BD. The present study aims to investigate the effects of lithium (Li), valproate (VPA), and sodium butyrate (SB), an HDAC inhibitor, on BDNF, NGF and GDNF in the brain of rats subjected to an animal model of mania induced by ouabain. Wistar rats received a single ICV injection of ouabain or artificial cerebrospinal fluid. From the day following ICV injection, the rats were treated for 6 days with intraperitoneal injections of saline, Li, VPA or SB twice a day. In the 7th day after ouabain injection, locomotor activity was measured using the open-field test. The BDNF, NGF and GDNF levels were measured in the hippocampus and frontal cortex by sandwich-ELISA. Li, VPA or SB treatments reversed ouabain-related manic-like behavior. Ouabain decreased BDNF, NGF and GDNF levels in hippocampus and frontal cortex of rats. The treatment with Li, VPA or SB reversed these impairment induced by ouabain. In addition, Li, VPA and SB per se increased NGF and GDNF levels in hippocampus of rats. Our data support the notion that neurotrophic factors play a role in BD and in the mechanisms of the action of Li, VPA and SB.

The role of neurotrophins in bipolar disorder

Bipolar disorder (BD) is a chronic psychiatric illness of which the pathophysiology remains partially unknown. Abnormalities of neurotrophins and other trophic factors orchestrate important alterations which could be implicated in the etiology of BD. Therefore, the main objective of this review is to examine the recent findings and critically evaluate the potential role of neurotrophins that may allow us to substantially improve the development of novel treatments. The most recently published findings highlight that brain-derived neurotrophic factor (BDNF), insulin-like growth factor (IGF-1) and vascular endothelial growth factor (VEGF) present distinct patterns in the different stages of BD, suggesting their potential in the identification of the BD subgroups and may ultimately advance treatment strategies.

Significantly lower nerve growth factor levels in patients with major depressive disorder than in healthy subjects: a meta-analysis and systematic review

INTRODUCTION

Since its discovery several decades ago, nerve growth factor (NGF) has been found to play roles in different areas, such as neurology, endocrinology, and immunology. There is some evidence linking NGF and psychiatry, including the role of NGF in subjects' response to stress, the alteration of NGF in different emotional states, and the penetration of NGF across the blood-brain barrier under specific conditions. There are many inconsistent findings regarding the differences in NGF in patients with major depressive disorder (MDD) at the present time. The aim of our study was to clarify whether NGF levels are different in MDD compared with healthy controls (HCs).

METHODS

We conducted a thorough literature search and compared peripheral NGF levels between MDD and HC through meta-analysis, and investigated possible confounding variables through meta-regression.

RESULTS

Seven studies were brought into the current meta-analysis comparing peripheral NGF in MDD and HCs. The main result was that the NGF levels were significantly lower in MDD than in HCs and that this had an inverse correlation with mean age and disease severity. In addition, meta-analysis of four articles found that the peripheral NGF levels did not change significantly before and after treatment.

CONCLUSION

Our study highlights the significant differences in peripheral NGF levels in patients with MDD. However, further exploration of the dynamic changes in peripheral NGF along with the disease course, and specific studies investigating the correlation of NGF in the peripheral and CNS environments are still needed.

Applications of blood-based protein biomarker strategies in the study of psychiatric disorders

Major psychiatric disorders such as schizophrenia, major depressive and bipolar disorders are severe, chronic and debilitating, and are associated with high disease burden and healthcare costs. Currently, diagnoses of these disorders rely on interview-based assessments of subjective self-reported symptoms. Early diagnosis is difficult, misdiagnosis is a frequent occurrence and there are no objective tests that aid in the prediction of individual responses to treatment. Consequently, validated biomarkers are urgently needed to help address these unmet clinical needs. Historically, psychiatric disorders are viewed as brain disorders and consequently only a few researchers have as yet evaluated systemic changes in psychiatric patients. However, promising research has begun to challenge this concept and there is an increasing awareness that disease-related changes can be traced in the peripheral system which may even be involved in the precipitation of disease onset and course. Converging evidence from molecular profiling analysis of blood serum/plasma have revealed robust molecular changes in psychiatric patients, suggesting that these disorders may be detectable in other systems of the body such as the circulating blood. In this review, we discuss the current clinical needs in psychiatry, highlight the importance of biomarkers in the field, and review a representative selection of biomarker studies to highlight opportunities for the implementation of personalized medicine approaches in the field of psychiatry. It is anticipated that the implementation of validated biomarker tests will not only improve the diagnosis and more effective treatment of psychiatric patients, but also improve prognosis and disease outcome.

Elevated serum levels of FGF-2, NGF and IGF-1 in patients with manic episode of bipolar disorder

Multiple neurotrophic and/or growth factors, recently nominated as "angioneurins", play the key roles in mood modulation and neuroplasticity, and their dysfunction might be involved in the pathophysiology and treatment of mood disorders. We examined serum levels of vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF)-2, nerve growth factor (NGF) and insulin-like growth factor (IGF)-1 in 70 drug-naïve or drug-free patients with manic episode of bipolar disorder and 50 healthy controls, using the enzyme-linked immunosorbent assay (ELISA) method. The results showed that mean serum levels of VEGF, FGF-2, NGF and IGF-1 were 168.13±225.61pg/ml, 279.09±378.62pg/ml, 61.38±171.67pg/ml and 162.01±72.00ng/ml in patients, and 140.80±143.71pg/ml, 275.46±235.29pg/ml, 36.34±15.14pg/ml and 138.90±80.11ng/ml in healthy controls, respectively. Serum levels of FGF-2, NGF and IGF-1 in patients were significantly higher than those in healthy controls, though there was no statistical difference in serum VEGF level between two groups. Moreover, serum NGF level in patients was significantly correlated with duration of disorder and times of previous manic episodes. We conclude that the increase of serum FGF-2, NGF and IGF-1 levels in manic state of bipolar disorder may be associated with their compensatory roles of neuroprotection and angiogenesis, and these angioneurins may be involved in the pathophysiology of bipolar disorder.

Neurotrophic factors, clinical features and gender differences in depression

Recent studies have evaluated the role of brain-derived neurotrophic factor (BDNF) in mood disorders; however, little is known about alterations in nerve growth factor (NGF) and glial cell line-derived neurotrophic factor (GDNF). The aim of this study was to evaluate differences among serum neurotrophic factors (BDNF, NGF and GDNF) in depressed patients and healthy controls and to verify the association between serum neurotrophic levels and clinical characteristics in a young, depressed population stratified by gender. This is a cross-sectional study with depressed patients and population controls 18-29 years of age. The concentrations of neurotrophic factors were determined by the ELISA method. The diagnosis of depression and the duration of the disease were assessed by the Structured Clinical Interview according to the diagnostic and statistical manual of mental disorders. Depression severity was measured with the 17-item Hamilton Rating Scale for Depression, and the severity of anxiety symptoms was measured using the Hamilton Anxiety Rating Scale. Serum BDNF and GDNF were lower in major depressive disorder (MDD) patients compared to controls (p ≤ 0.001). Serum NGF levels were higher in MDD patients versus controls (p ≤ 0.001). BDNF was associated with the duration of disease only in women (p = 0.005). GDNF was not associated with clinical characteristics in either gender. In women, NGF was associated with the severity of depressive symptoms (p = 0.009), anxiety (p = 0.011) and disease duration (p = 0.005). NGF was associated with disease duration in men (p = 0.026). Our results demonstrated that significant neurochemical differences in NGF and BDNF, but not in GDNF, were associated with the clinical features of MDD when patients were stratified by gender.

Nerve growth factor variations in patients with mood disorders: no changes in eight weeks of clinical treatment

BACKGROUND

Nerve growth factor (NGF) has received much attention for its role in mood disorders. The primary objective of the present study was to examine serum NGF levels in Chinese inpatients with depressive or manic episodes in the acute phase and to explore the changes in NGF levels after effective clinical treatments.

METHODS

One hundred and seven consecutive inpatients and outpatients with mood disorders (30 with unipolar depression, 23 with bipolar depression, and 54 with bipolar mania), and 50 healthy controls were recruited. The serum NGF levels were detected by enzyme-linked immunosorbent assay.

RESULTS

Patients with bipolar mania presented higher serum NGF levels compared to those of healthy controls. After 8 weeks of medical treatment, there were significant improvements in symptoms in patients, but no significant changes in NGF levels.

CONCLUSION

The present findings may help to strengthen and expand the understanding of the role of NGF in the acute stages of mood disorders.

Serum nerve growth factor (NGF) levels in children with attention deficit/hyperactivity disorder (ADHD)

Attention deficit/hyperactivity disorder (ADHD) is the most commonly diagnosed neurobehavioral disorder of childhood. The etiopathogeny of ADHD has not been totally defined. Recent reports have suggested a pathophysiological role of neurotrophins in ADHD. In this study, we evaluated serum levels of nerve growth factor (NGF) in patients with ADHD. The sample population consisted of 44 child or adolescent patients diagnosed with ADHD according to DSM-IV criteria; 36 healthy subjects were included in the study as controls. Venous blood samples were collected, and NGF levels were measured. The mean serum NGF levels of the ADHD patients were significantly higher than those of the controls. Age and gender of the patients were not correlated with serum NGF levels. There were no significant differences in NGF levels among the combined and predominantly inattentive subtypes of ADHD. Our study suggests that there are higher levels of serum NGF in drug naive ADHD patients, and that increased levels of NGF might have an important role in the pathophysiology of ADHD.

High insulin-like growth factor-1 in patients with bipolar I disorder: a trait marker?

OBJECTIVES

Neurotrophic factors exert substantial effects on the central nervous system. The present study investigates the roles of insulin-like growth factor-1 (IGF-1), β-nerve growth factor (β-NGF), and brain-derived neurotrophic factor (BDNF) in bipolar disorder.

METHODS

Baseline levels of culture-stimulated IGF-1, β-NGF, and BDNF were compared in 116 patients with bipolar I disorder and 123 healthy controls. Neurotrophic factors were also compared in patients before and after 6 weeks of pharmacotherapy. A multivariate logistic regression analysis was used to investigate the influence of the neurotrophic factors analyzed in quartile form, in relation to confounding variables, such as age, sex, and body mass index.

RESULTS

IGF-1 was significantly higher in patients (mean=514.57, SD=259.78) than in healthy controls (mean=316.82, SD=270.00, p<0.0001) at baseline. Furthermore, higher levels of IGF-1 substantially increased the risk for bipolar I disorder. IGF-1 level was not significantly changed at 6-weeks (mean=506.41, SD=313.66). No changes in BDNF or β-NGF-1 levels were found following the 6-week treatment period. IGF-1 and β-NGF were negatively correlated in healthy controls, but not in patients. Severity of manic symptoms was not associated with any of the neurotrophic factors.

LIMITATIONS

We did not measure cortisol, growth hormone, or IGF-1 receptors. This study is cross-sectional in design.

CONCLUSIONS

Elevated IGF-1 levels may be a trait marker for bipolar disorder. Further studies are needed to thoroughly investigate the role of IGF-1 in relation to other neuroendocrine factors and biological markers for bipolar disorder.

Serum neurotrophic factors in adolescent depression: gender difference and correlation with clinical severity

BACKGROUND

Brain derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3) and glial cell line derived neurotrophic factor (GDNF) play critical role in growth, differentiation, maintenance and synaptic plasticity in neuronal systems which is more relevant in adolescence. The present study was undertaken to verify the 'neurotrophin hypothesis' in adolescent depression by (i) comparing serum concentrations of neurotrophic factors in depression patients and healthy control, and (ii) analyzing correlations between clinical severity and serum neurotrophin levels.

METHODS

Eighty four adolescent (aged 13-18 years) depressed patients (56 males; 60 medication free/naive) and 64 healthy controls (39 males) were recruited. Severity of depression was measured by Beck's depression inventory, and anxiety by state-trait anxiety inventory. Measurement of serum neurotrophins was done by ELISA.

RESULTS

Adolescents with depression had significantly lower levels of BDNF: mean diff. (95% C.I.): 2093.9 (1074.0, 3113.9), NGF: 813.3 (343.1, 1283.6) and GDNF: 158.8 (77.2, 240.4) compared to controls. On gender based analysis female controls had significantly increased trait anxiety scores [-1.1 (-1.8, -0.1)], as compared to control males. In the patient group, female patients had far lower level of NGF: 919.6 (210.9, 1628.3) and NT-3: 1288.8 (145.4, 2432.3) compared to male. BDI-II score showed a statistically significant (p<0.01) negative correlation with all four neurotrophins in male patients while in female patients such negative correlation was observed only with NGF and GDNF (p<0.01).

LIMITATIONS

The study is cross-sectional from a tertiary care hospital.

CONCLUSION

The novelty of the study lies in its large number of exclusively adolescent depression patients showing significant reduction of BDNF, NGF and GDNF serum levels as compared to controls. A gender bias with much reduction in female has also been recorded.

Cytokine alterations in bipolar disorder: a meta-analysis of 30 studies

BACKGROUND

We conducted a meta-analysis of studies comparing cytokine concentrations between patients with bipolar disorder (BD) and healthy control subjects (HCs).

METHODS

We searched ISI Web of Science, MEDLINE, BIOSIS Previews, Scopus, Current Contents Connect, and Biological Abstracts for relevant studies. Based on heterogeneity status, we used fixed-effect or restricted maximal likelihood model to perform meta-analysis.

RESULTS

Thirty studies with a total of 2599 participants (1351 BD and 1248 HCs) were eligible for the analysis. Concentrations of interleukin (IL)-4 (p = .008), IL-6 (p = .073), IL-10 (p = .013), soluble IL-2 receptor (sIL-2R; p < .001), sIL-6R (p = .021), tumor necrosis factor (TNF)-α (p = .010), soluble TNF receptor-1 (sTNFR1; p < .001), and IL-1 receptor antagonist (p value in mania < .001 and euthymia = .021) were significantly elevated in patients compared with HCs. Moreover, IL-1β (p = .059), and IL-6 (p = .073) tended to show higher values in patients. Levels of IL-2 (p = .156), interferon (INF)-γ (p = .741), C-C motif ligand 2 (p = .624), and IL-8 (p = .952) did not significantly differ between patients and HCs. Subgroup analysis based on mitogen stimulation status partially or completely resolved heterogeneity for most of the cytokines. Concentrations of IL-2, IL-4, sIL-6R, and INF-γ were unrelated to medication status. Phasic difference was present for TNF-α, sTNFR1, sIL-2R, IL-6, and IL-1RA, whereas it was absent for IL-4 and IL-10.

CONCLUSIONS

This meta-analysis provides evidence for significant elevation of proinflammatory, anti-inflammatory, and regulatory cytokines in BD.

Refinement of chromosome 3p22.3 region and identification of a susceptibility gene for bipolar affective disorder

Genome-wide association studies and meta-analysis, as well as our own previous family-based association results, have pointed to chromosome (ch) 3p22.3 and 3p21.1 as candidate regions to contain a susceptibility gene for bipolar affective disorder (BPAD). In the present study, we further refined the region of interest on ch 3p22.3. We genotyped 94 SNPs within the candidate region in 74 families and performed family-based association analysis using a transmission disequilibrium test. One single SNP (rs166508) was associated with the BPAD phenotype (P = 0.0187). This SNP is located within intron 15 of the integrin alpha 9 (ITGA9) gene. ITGA9 encodes the α9 subunit of the α9β1 integrin, a membrane glycoprotein receptor for neurotrophins, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Quantification of ITGA9 transcripts in the peripheral blood of patients with BPAD and controls showed an upregulation of ITGA9 (Kruskal-Wallis P = 0.0339) in patients with the disease-associated genotype (rs166508*A/A), compared to those with rs166508*G/G and rs166508*G/A genotypes. Sequencing of the ITGA9 cDNA revealed a sequence variant (r.1689_1839del) in rs166508*A carriers, which leads to loss of the entire exon 16. In silico analysis revealed that the deleted region contains three putative microRNA binding sites, which may be involved in the negative regulation of ITGA9. In conclusion, our results confirm previous evidence pointing to a candidate region for BPAD on ch 3p.22.3. In addition, we suggest a molecular substrate that could explain the increase of ITGA9 mRNA levels in probands with BPAD, proposing a new mechanism that could be involved in the genetic susceptibility to the disease.

Does lithium prevent Alzheimer's disease?

Lithium salts have a well-established role in the treatment of major affective disorders. More recently, experimental and clinical studies have provided evidence that lithium may also exert neuroprotective effects. In animal and cell culture models, lithium has been shown to increase neuronal viability through a combination of mechanisms that includes the inhibition of apoptosis, regulation of autophagy, increased mitochondrial function, and synthesis of neurotrophic factors. In humans, lithium treatment has been associated with humoral and structural evidence of neuroprotection, such as increased expression of anti-apoptotic genes, inhibition of cellular oxidative stress, synthesis of brain-derived neurotrophic factor (BDNF), cortical thickening, increased grey matter density, and hippocampal enlargement. Recent studies addressing the inhibition of glycogen synthase kinase-3 beta (GSK3B) by lithium have further suggested the modification of biological cascades that pertain to the pathophysiology of Alzheimer's disease (AD). A recent placebo-controlled clinical trial in patients with amnestic mild cognitive impairment (MCI) showed that long-term lithium treatment may actually slow the progression of cognitive and functional deficits, and also attenuate Tau hyperphosphorylation in the MCI-AD continuum. Therefore, lithium treatment may yield disease-modifying effects in AD, both by the specific modification of its pathophysiology via inhibition of overactive GSK3B, and by the unspecific provision of neurotrophic and neuroprotective support. Although the clinical evidence available so far is promising, further experimentation and replication of the evidence in large scale clinical trials is still required to assess the benefit of lithium in the treatment or prevention of cognitive decline in the elderly.

Novel therapeutic targets in depression: minocycline as a candidate treatment

Mood disorders are marked by high rates of non-recovery, recurrence, and chronicity, which are insufficiently addressed by current therapies. Several patho-etiological models have been proposed that are not mutually exclusive and include but are not limited to the monoamine, inflammatory, neurotrophic, gliotrophic, excitatory, and oxidative stress systems. A derivative of these observations is that treatment(s) which target one or more of these mechanistic steps may be capable of mitigating, or preventing, disparate psychopathological features. Minocycline is an agent with pleiotropic properties that targets multiple proteins and cellular processes implicated in the patho-etiology of mood disorders. Moreover, preclinical and preliminary clinical evidence suggests that minocycline possesses antidepressant properties. Herein, we provide the rationale for conducting a randomized, controlled trial to test the antidepressant properties of minocycline.

Olanzapine plus fluoxetine treatment increases Nt-3 protein levels in the rat prefrontal cortex

Evidence is emerging for a role for neurotrophins in the treatment of mood disorders. In this study, we evaluated the effects of chronic administration of fluoxetine, olanzapine and the combination of fluoxetine/olanzapine on the brain-derived-neurotrophic factor (BDNF), nerve growth factor (NGF), and neurotrophin-3 (NT-3) in the rat brain. Wistar rats received daily injections of olanzapine (3 or 6 mg/kg) and/or fluoxetine (12.5 or 25mg/kg) for 28 days, and we evaluated for BDNF, NGF and NT-3 protein levels in the prefrontal cortex, hippocampus and amygdala. Our results showed that treatment with fluoxetine and olanzapine alone or in combination did not alter BDNF in the prefrontal cortex (p=0.37), hippocampus (p=0.98) and amygdala (p=0.57) or NGF protein levels in the prefrontal cortex (p=0.72), hippocampus (p=0.23) and amygdala (p=0.64), but NT-3 protein levels were increased by olanzapine 6 mg/kg/fluoxetine 25mg/kg combination in the prefrontal cortex (p=0.03), in the hippocampus (p=0.83) and amygdala (p=0.88) NT-3 protein levels did not alter. Finally, these findings further support the hypothesis that NT-3 could be involved in the effect of treatment with antipsychotic and antidepressant combination in mood disorders.