Age-associated decrease in serum glial cell line-derived neurotrophic factor levels in patients with major depressive disorder

Altered blood parameters in "major depression" patients receiving repetitive transcranial magnetic stimulation (rTMS) therapy: a randomized case-control study

Major depressive disorder (MDD) is a debilitating illness that includes depressive mood. Repetitive Transcranial Magnetic Stimulation (rTMS) is a therapy method used in the treatment of MDD. The purpose of this study was to assess neurotrophic factors, and oxidative stress levels in MDD patients and evaluate the changes in these parameters as a result of rTMS therapy. Twenty-five patients with MDD and twenty-six healthy volunteers with the same demographic characteristics were included in the study. Brain-derived neurotrophic factors were measured photometrically with commercial kits. Oxidative stress parameters were measured by the photometric method. Oxidative stress index (OSI) and disulfide (DIS) levels were calculated with mathematical formulas. In this study, total antioxidant status (TAS), total thiol (TT), and native thiol (NT) antioxidant parameters and brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and allopregnanolone (ALLO) levels were reduced in pre-rTMS with regard to the healthy control group; TOS, OSI, DIS, and S100 calcium-binding protein B (S100B) levels were increased statistically significantly (p < 0.01). Moreover, owing to TMS treatment; TAS, TT, NT, BDNF, GDNF, and ALLO levels were increased compared to pre-rTMS, while DIS, TOS, OSI, and S100B levels were decreased significantly (p < 0.01). The rTMS treatment reduces oxidative stress and restores thiol-disulfide balance in MDD patients. Additionally, rTMS modulates neurotrophic factors and neuroactive steroids, suggesting its potential as an antidepressant therapy. The changes in the biomarkers evaluated may help determine a more specific approach to treating MDD with rTMS therapy.

Glial cell line-derived neurotrophic factor (GDNF) in blood serum and lacrimal fluid of patients with a current depressive episode

BACKGROUND

Many studies indicate a significant role of GDNF in the pathogenesis of the mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD). Potentially, neurotrophic factors in lacrimal fluid (LF) could become biomarkers of various specific disorders. The aim of this study was to assess GDNF levels in LF and blood serum (BS) of patients with a current depressive episode (cDE).

METHODS

We studied the glial cell line-derived neurotrophic factor (GDNF) concentration in the LF and BS of 39 healthy controls and 137 patients with a current depressive episode (cDE) (both subgroups members were 20-49 years): BD - 46 patients, MDD - 91 patients.

RESULTS

GDNF concentration in BS of women with MDD was significantly lower than in men. In BD patients, univariate linear regression analysis revealed significant correlations between GDNF concentration in the LF and the use of anxiolytics or antidepressants. These correlations were confirmed by the multivariate linear regression analysis. A significant correlation between GDNF concentrations in the LF and BS was found in controls.

LIMITATIONS

The unequal proportion of men in the BD group did not permit adjusting GDNF concentrations for sex. The collected LF was stimulated, which could influence GDNF levels. It should also be noted that the patients included in the study were not treatment- naïve.

CONCLUSIONS

Our findings suggest that GDNF concentration in LF could be a biomarker of the cDE (both unipolar and bipolar), though the sensitivity of this potential biomarker may be lower in depressive patients with anxiety symptoms.

The Relationship between Allostasis and Mental Health Patterns in a Pre-Deployment French Military Cohort

(1) Background: While a number of studies among military personnel focus on specific pathologies such as post-traumatic stress disorder (PTSD), anxiety, and depression, they do not address the cumulative impact on mental health of stressors related to the profession. The present study aims to determine the relationship between allostatic load and mental health status in a cohort of fit-for-duty soldiers prior to their deployment to Afghanistan. The aim is to better-define the consequences of stressor adjustment. (2) Methods: A cohort of 290 soldiers was evaluated in a cross-sectional study with respect to psychopathology (PTSD, anxiety, depression), psychological functioning (stress reactivity, psychological suffering), and allostatic profile (urinary cortisol and 8-iso-PGF2α, blood cortisol and BDNF). A hierarchical cluster analysis was used to identify allostatic patterns. (3) Results: Around 10% of the cohort reported high scores for psychopathology, and biological alterations were identified. For the remainder, four allostatic profiles could be identified by their psychological functioning. (4) Conclusions: Both biological and psychological assessments are needed to characterize subthreshold symptomatology among military personnel. The psychological significance of allostatic load should be considered as a way to improve health outcomes.

Neuromuscular Junction Aging: A Role for Biomarkers and Exercise

Age-related skeletal muscle degradation known as "sarcopenia" exerts considerable strain on public health systems globally. While the pathogenesis of such atrophy is undoubtedly multifactorial, disruption at the neuromuscular junction (NMJ) has recently gained traction as a key explanatory factor. The NMJ, an essential communicatory link between nerve and muscle, undergoes profound changes with advancing age. Ascertaining whether such changes potentiate the onset of sarcopenia would be paramount in facilitating a timely implementation of targeted therapeutic strategies. Hence, there is a growing level of importance to further substantiate the effects of age on NMJs, in parallel with developing measures to attenuate such changes. As such, this review aimed to establish the current standpoint on age-related NMJ deterioration and consequences for skeletal muscle, while illuminating a role for biomarkers and exercise in ameliorating these alterations. Recent insights into the importance of key biomarkers for NMJ stability are provided, while the stimulative benefits of exercise in preserving NMJ function are demonstrated. Further elucidation of the diagnostic and prognostic relevance of biomarkers, coupled with the therapeutic benefits of regular exercise may be crucial in combating age-related NMJ and skeletal muscle degradation.

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.

Depression: Biological markers and treatment

Nowadays depression is considered as a systemic illness with different biological mechanisms involved in its etiology, including inflammatory response, hypothalamic-pituitary-adrenal (HPA) axis dysregulation and neurotransmitter and neurotrophic systems imbalance. Novel "omics" approaches, such as metabolomics and glycomics provide information about altered metabolic pathways and metabolites, as well as disturbances in glycosylation processes affected by or causing the development of depression. The clinical diagnosis of depression continues to be established based on the presence of the specific symptoms, but due to its heterogeneous underlying biological background, that differs according to the disease stage, there is an unmet need for treatment response biomarkers which would facilitate the process of appropriate treatment selection. This paper provides an overview of the role of major stress response system, the HPA axis, and its dysregulation in depression, possible involvement of neurotrophins, especially brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor and insulin-like growth factor-1, in the development of depression. Article discusses how activated inflammation processes and increased cytokine levels, as well as disturbed neurotransmitter systems can contribute to different stages of depression and could specific metabolomic and glycomic species be considered as potential biomarkers of depression. The second part of the paper includes the most recent findings about available medical treatment of depression. The described biological factors impose an optimistic conclusion that they could represent easy obtainable biomarkers potentially predicting more personalized treatment and diagnostic options.

Glial cell induced neural differentiation of bone marrow stromal cells

Background

Bone marrow stromal cells (BMSCs) have an important application prospect in the field of cell therapy for various neurodegenerative diseases, and inducing factors that regulate BMSC differentiation are proposed as a promising therapeutic strategy. In this study, we explored the effect of glial cell-derived neurotrophic factor (GDNF) on the course of BMSC differentiation.

Methods

BMSCs were isolated from rat bone marrow and induced by GDNF. The effects of GDNF on BMSC viability and proliferation were verified by cell counting kit-8, MTT, bromodeoxyuridine, and flow cytometry assays. Neuronal differentiation from BMSCs was detected by quantitative real-time polymerase chain reaction and immunofluorescence via measuring the expression of several neural specific markers.

Results

Compared to untreated BMSCs, GDNF induced the differentiation of BMSCs into neuron-like cells and enhanced the expression levels of neuronal markers including nestin and NCAM. Moreover, the expression of SCF was suppressed by GDNF stimulation.

Conclusion

GDNF could elevate the differentiation of BMSCs into neuron-like cells and could be considered as an effective candidate cell for future neuroscience research.

Gender Differences in Developing Biomarker-Based Major Depressive Disorder Diagnostics

The identification of biomarkers associated with major depressive disorder (MDD) holds great promise to develop an objective laboratory test. However, current biomarkers lack discriminative power due to the complex biological background, and not much is known about the influence of potential modifiers such as gender. We first performed a cross-sectional study on the discriminative power of biomarkers for MDD by investigating gender differences in biomarker levels. Out of 28 biomarkers, 21 biomarkers were significantly different between genders. Second, a novel statistical approach was applied to investigate the effect of gender on MDD disease classification using a panel of biomarkers. Eleven biomarkers were identified in men and eight in women, three of which were active in both genders. Gender stratification caused a (non-significant) increase of Area Under Curve (AUC) for men (AUC = 0.806) and women (AUC = 0.807) compared to non-stratification (AUC = 0.739). In conclusion, we have shown that there are differences in biomarker levels between men and women which may impact accurate disease classification of MDD when gender is not taken into account.

Reduced serum BDNF levels are associated with the increased risk for developing MDD: a case-control study with or without antidepressant therapy

Objective

We do not have any consistent markers for major depressive disorder (MDD) though various biological factors are involved in the pathophysiology. We aimed to evaluate the serum brain-derived neurotrophic factor (BDNF) levels in MDD patients with or without antidepressant therapy compared to healthy controls (HCs).

Results

We assessed serum BDNF levels among three groups: drug-naïve MDD patients (n = 41), drug-treated MDD patients (n = 44), and age-and sex-matched HCs (n = 82). Serum BDNF levels were measured by enzyme-linked immunosorbent assay (ELISA) kit. Serum levels of BDNF were detected significantly lower in drug-naïve MDD patients compared to HCs. No significant alterations of serum BDNF levels between drug-treated patients and HCs were identified. Significant negative correlations between serum BDNF levels and Hamilton depression rating (Ham-D) scores were observed in both drug-naïve and drug-treated MDD patients. Receiver operating characteristic (ROC) analysis showed good diagnostic value for serum BDNF levels in drug-naïve MDD patients with the area under the curve at 0.821. The present study suggests that low serum BDNF levels may be involved in the pathophysiology of MDD. The reduced serum BDNF levels might be used as an early risk assessment marker for major depression.

Hippocampal neurons in direct contact with astrocytes exposed to amyloid β25-35 exhibit reduced excitatory synaptic transmission

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We exposed astrocytes to Aβ _25-35 and then co-cultured them with primary hippocampal neurons.

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The Aβ_25-35-exposed astrocytes lowered excitatory postsynaptic release and the size of the readily releasable synaptic pool.

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The number of excitatory synapses was reduced by direct contact between Aβ_25-35-exposed astrocytes and hippocampal neurons.

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The dendritic branching was decreased by direct contact between Aβ_25-35-exposed astrocytes and hippocampal neurons.

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The number of excitatory synapses and dendrite branches were conserved by putting distance from Aβ_25-35-exposed astrocytes.

Amyloid β protein (Aβ) is closely related to the progression of Alzheimer's disease because senile plaques consisting of Aβ cause synaptic depression and synaptic abnormalities. In the central nervous system, astrocytes are a major glial cell type that contribute to the modulation of synaptic transmission and synaptogenesis. In this study, we examined whether astrocytes exposed to Aβ fragment 25-35 (Aβ_25-35) affect synaptic transmission. We show that synaptic transmission by hippocampal neurons was inhibited by astrocytes exposed to Aβ_25-35. The Aβ_25-35-exposed astrocytes lowered excitatory postsynaptic release and the size of the readily releasable synaptic pool. The number of excitatory synapses was also reduced. However, the number of excitatory synapses was unchanged unless there was direct contact between Aβ_25-35-exposed astrocytes and hippocampal neurons. These data indicate that direct contact between Aβ_25-35-exposed astrocytes and neurons is critical for inhibiting synaptic transmission in the progression of Alzheimer’s disease.

Decreased plasma glial cell line-derived neurotrophic factor level in major depressive disorder is associated with age and clinical severity

BACKGROUND

Glial cell line-derived neurotrophic factor (GDNF) as a neurotrophic factor closely related to depression is able to promote the growth, proliferation, differentiation, and survival of multiple neurons. Clinical features, recurrence rates and suicide rates are significant different in major depressive disorder (MDD) according to age. GDNF level changes in the peripheral blood has been reported in patients with MDD. In this study, we aimed to investigate whether GDNF levels differentiated within various age groups and its relationship with age/clinical severity.

METHOD

MDD subjects and healthy controls (HC) are divided into younger (age 13-24 years) group (yMDD n = 35, yHC n = 44) and older (age 25-45 years) group (oMDD n = 30, oHC n = 55) based on the age of brain maturity. Clinical symptom severity was evaluated by the Hamilton Depression Rating Scale (HAMD-17) and the Hamilton Anxiety Rating Scale (HAMA-17). The levels of plasma GDNF were compared within subgroups.

RESULTS

Plasma GDNF levels in yMDD patients were significantly decreased compared to yHC (yMDD 1.55 ± 0.46pg/ml, yHC 1.77 ± 0.47pg/ml, p < 0.05). Moreover, such difference was not found between oMDD group and oHC group. Our results also showed negative correlations between plasma GDNF levels and HAMD/HAMA scores (r = -0.33, p < 0.05; r = -0.39, p < 0.05).

LIMITATIONS

This study was underpowered to observe dynamic changes between age and GDNF in MDD due to the cross-sectional design of present study. We also failed to divided subjects into more age groups because of moderate sample size.

CONCLUSION

The present result showed the level of protective neurotrophic factor GDNF associated with age in MDD, suggesting a relevance between GDNF and MDD subjects abnormal brain development in adolescent and young adult period.

Tactile Stimulation on Adulthood Modifies the HPA Axis, Neurotrophic Factors, and GFAP Signaling Reverting Depression-Like Behavior in Female Rats

Depression is a common psychiatric disease which pharmacological treatment relieves symptoms, but still far from ideal. Tactile stimulation (TS) has shown beneficial influences in neuropsychiatric disorders, but the mechanism of action is not clear. Here, we evaluated the TS influence when applied on adult female rats previously exposed to a reserpine-induced depression-like animal model. Immediately after reserpine model (1 mg/kg/mL, 1×/day, for 3 days), female Wistar rats were submitted to TS (15 min, 3×/day, for 8 days) or not (unhandled). Imipramine (10 mg/kg/mL) was used as positive control. After behavioral assessments, animals were euthanized to collect plasma and prefrontal cortex (PFC). Behavioral observations in the forced swimming test, splash test, and sucrose preference confirmed the reserpine-induced depression-like behavior, which was reversed by TS. Our findings showed that reserpine increased plasma levels of adrenocorticotropic hormone and corticosterone, decreased brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B, and increased proBDNF immunoreactivity in the PFC, which were also reversed by TS. Moreover, TS reestablished glial fibrillary acidic protein and glucocorticoid receptor levels, decreased by reserpine in PFC, while glial cell line-derived neurotrophic factor was increased by TS per se. Our outcomes are showing that TS applied in adulthood exerts a beneficial influence in depression-like behaviors, modulating the HPA axis and regulating neurotrophic factors more effectively than imipramine. Based on this, our proposal is that TS, in the long term, could be considered a new therapeutic strategy for neuropsychiatric disorders improvement in adult life, which may represent an interesting contribution to conventional pharmacological treatment.

Mifepristone attenuates depression-like changes induced by chronic central administration of interleukin-1β in rats

Increased proinflammatory cytokines, such as interleukin (IL)-1β, may play an important role in the etiology of depression because they cause the hypothalamic-pituitary-adrenal axis to release glucocorticoids (GC) and induce dysfunction of serotonin and norepinephrine neurotransmission. Sustained increase in GC may activate microglia to induce neuroinflammation, and suppress astrocytes to produce neurotrophins, which lead to neuronal apoptosis. Here, we tested the hypothesis that glucocorticoid receptor (GR) antagonist mifepristone (RU486) may attenuate IL-1β-induced depression-like behavior by regulating the neuroinflammation and neurotrophin functions of microglia and astrocytes. Rats received intracerebroventricular injections of IL-1β (10 ng) and/or subcutaneous injections of RU486 for 14 days. Then animal depression-like behaviors, serum corticosterone concentration, the levels of pro-inflammatory cytokines (TNF-α, IL-6), mRNA and protein expressions of CD11b, GFAP and neurotrophins (pro-BDNF, BDNF, GDNF and their receptors TrkB, p75, GFRα-1 and GFRα-2) in the amygdala were studied. Compared to controls, significantly decreased rearing score and increased defecation in the open field test, decreases in ratio of open/closed time in the elevated plus maze and in sucrose preference, while increased level of corticosterone in the serum were found in the rats administrated with IL-1β. IL-1β administration also reduced the expressions of GFAP, BDNF, GDNF and its receptor GFR-α1, but increased the expressions of CD11b, pro-BDNF, p75 and pro-inflammatory cytokines (TNF-α, IL-6) concentrations. RU486 treatment markedly attenuated these changes induced by IL-1β, except for the expressions of GFR-α1. In conclusion, RU486 may improve depression-like changes by suppressing microglia and inflammation and promoting astrocytes to restore neurotrophin function.

Astrocytes with previous chronic exposure to amyloid β-peptide fragment 1-40 suppress excitatory synaptic transmission

Synaptic dysfunction and neuronal death are responsible for cognitive and behavioral deficits in Alzheimer's disease (AD). It is well known that such neurological abnormalities are preceded by long-term exposure of amyloid β-peptide (Aβ) and/or hyperphosphorylated tau prior. In addition to the neurological deficit, astrocytes as a major glial cell type in the brain, significantly participate in the neuropathogenic mechanisms underlying synaptic modulation. Although astrocytes play a significant key role in modulating synaptic transmission, little is known on whether astrocyte dysfunction caused by such long-term Aβ exposure affects synapse formation and function. Here, we show that synapse formation and synaptic transmission are attenuated in hippocampal-naïve neurons co-cultured with astrocytes that have previously experienced chronic Aβ_1-40 exposure. In this abnormal astrocytic condition, hippocampal neurons exhibit decrements of evoked excitatory post-synaptic currents (EPSCs) and miniature EPSC frequency. Furthermore, size of readily releasable synaptic pools and number of excitatory synapses were also significantly decreased. Contrary to these negative effects, release probability at individual synapses was significantly increased in the same astrocytic condition. Taken together, our data indicate that lower synaptic transmission caused by astrocytes previously, and chronically, exposed to Aβ1-40 is attributable to a small number of synapses with higher release probability.

Impaired Latent Inhibition in GDNF-Deficient Mice Exposed to Chronic Stress

Increased reactivity to stress is maladaptive and linked to abnormal behaviors and psychopathology. Chronic unpredictable stress (CUS) alters catecholaminergic neurotransmission and remodels neuronal circuits involved in learning, attention and decision making. Glial-derived neurotrophic factor (GDNF) is essential for the physiology and survival of dopaminergic neurons in substantia nigra and of noradrenergic neurons in the locus coeruleus. Up-regulation of GDNF expression during stress is linked to resilience; on the other hand, the inability to up-regulate GDNF in response to stress, as a result of either genetic or epigenetic modifications, induces behavioral alterations. For example, GDNF-deficient mice exposed to chronic stress exhibit alterations of executive function, such as increased temporal discounting. Here we investigated the effects of CUS on latent inhibition (LI), a measure of selective attention and learning, in GDNF-heterozygous (HET) mice and their wild-type (WT) littermate controls. No differences in LI were found between GDNF HET and WT mice under baseline experimental conditions. However, following CUS, GDNF-deficient mice failed to express LI. Moreover, stressed GDNF-HET mice, but not their WT controls, showed decreased neuronal activation (number of c-Fos positive neurons) in the nucleus accumbens shell and increased activation in the nucleus accumbens core, both key regions in the expression of LI. Our results add LI to the list of behaviors affected by chronic stress and support a role for GDNF deficits in stress-induced pathological behaviors relevant to schizophrenia and other psychiatric disorders.

Glial Cell Line-Derived Neurotrophic Factor (GDNF) serum level in women with schizophrenia and depression, correlation with clinical and metabolic parameters

AIM

Neurotrophic factors have been implicated in neuropsychiatric disorders, including schizophrenia and depression. Glial Cell Line-Derived Neurotrophic Factor (GDNF) promotes development, differentiation, and protection of dopaminergic, serotonergic, GABAergic and noradrenergic neurons as well as glial cells in different brain regions. This study examined serum levels of GDNF in schizophrenia and depression and its correlation with metabolic parameters during 8 weeks of treatment.

METHODS

Serum GDNF level, fasting serum glucose and lipid profile were measured at baseline and week 8 in 133 women: 55 with schizophrenia, 30 with a first episode depression and 48 healthy controls. The severity of the symptoms was evaluated using Positive and Negative Syndrome Scale (PANSS), 17-item Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI).

RESULTS

There was statistically significant higher GDNF level in schizophrenia at baseline when compared with week 8. Correlations of GDNF with PANSS in schizophrenia and cholesterol level in depression have also been detected.

CONCLUSIONS

To our knowledge, this is the first study which correlates GDNF levels with metabolic parameters. Our results show no differences in GDNF serum level between schizophrenia, a first depressive episode, and healthy controls. GDNF serum level did not correlate with metabolic parameters except for total cholesterol in depression.

Role of glial cell line-derived neurotrophic factor in the pathogenesis and treatment of mood disorders

Glial cell line-derived neurotrophic factor (GDNF) is widely recognized as a survival factor for dopaminergic neurons, but GDNF has also been shown to promote development, differentiation, and protection of other central nervous system neurons and was thought to play an important role in various neuropsychiatric disorders. Severe mood disorders, such as primarily major depressive disorder and bipolar affective disorder, attract particular attention. These psychopathologies are characterized by structural alterations accompanied by the dysregulation of neuroprotective and neurotrophic signaling mechanisms required for the maturation, growth, and survival of neurons and glia. The main objective of this review is to summarize the recent findings and evaluate the potential role of GDNF in the pathogenesis and treatment of mood disorders. Specifically, it describes (1) the implication of GDNF in the mechanism of depression and in the effect of antidepressant drugs and mood stabilizers and (2) the interrelation between GDNF and brain neurotransmitters, playing a key role in the pathogenesis of depression. This review provides converging lines of evidence that (1) brain GDNF contributes to the mechanism underlying depressive disorders and the effect of antidepressants and mood stabilizers and (2) there is a cross-talk between GDNF and neurotransmitters representing a feedback system: GDNF-neurotransmitters and neurotransmitters-GDNF.

Role of trophic factors GDNF, IGF-1 and VEGF in major depressive disorder: A comprehensive review of human studies

RATIONALE

The neurotrophin hypothesis of major depressive disorder (MDD) postulates that this illness results from aberrant neurogenesis in brain regions that regulates emotion and memory. Notwithstanding this theory has primarily implicated BDNF in the neurobiology of MDD. Recent evidence suggests that other trophic factors namely GDNF, VEGF and IGF-1 may also be involved.

PURPOSE

The present review aimed to critically summarize evidence regarding changes in GDNF, IGF-1 and VEGF in individuals with MDD compared to healthy controls. In addition, we also evaluated the role of these mediators as potential treatment response biomarkers for MDD.

METHODS

A comprehensive review of original studies studies measuring peripheral, central or mRNA levels of GDNF, IGF-1 or VEGF in patients with MDD was conducted. The PubMed/MEDLINE database was searched for peer-reviewed studies published in English through June 2nd, 2015.

RESULTS

Most studies reported a reduction in peripheral GDNF and its mRNA levels in MDD patients versus controls. In contrast, IGF-1 levels in MDD patients compared to controls were discrepant across studies. Finally, most studies reported high peripheral VEGF levels and mRNA expression in MDD patients compared to healthy controls.

CONCLUSIONS

GDNF, IGF-1 and VEGF levels and their mRNA expression appear to be differentially altered in MDD patients compared to healthy individuals, indicating that these molecules might play an important role in the pathophysiology of depression and antidepressant action of therapeutic interventions.

Plasma glial cell line-derived neurotrophic factor in patients with major depressive disorder: a preliminary study

BACKGROUND

Some clinical studies have reported reduced peripheral glial cell line-derived neurotrophic factor (GDNF) level in elderly patients with major depressive disorder (MDD). We verified whether a reduction in plasma GDNF level was associated with MDD.

METHOD

Plasma GDNF level was measured in 23 healthy control subjects and 23 MDD patients before and after 6 weeks of treatment.

RESULTS

Plasma GDNF level in MDD patients at baseline did not differ from that in healthy controls. Plasma GDNF in MDD patients did not differ significantly from baseline to the end of treatment. GDNF level was significantly lower in recurrent-episode MDD patients than in first-episode patients before and after treatment.

CONCLUSIONS

Our findings revealed significantly lower plasma GDNF level in recurrent-episode MDD patients, although plasma GDNF levels in MDD patients and healthy controls did not differ significantly. The discrepancy between our study and previous studies might arise from differences in the recurrence of depression or the ages of the MDD patients.

Significantly Higher Peripheral Insulin-Like Growth Factor-1 Levels in Patients With Major Depressive Disorder or Bipolar Disorder Than in Healthy Controls: A Meta-Analysis and Review Under Guideline of PRISMA

An increasing amount of research has focused on insulin-like growth factor-1 (IGF-1) because of multiple neurotrophic effects, including neurogenesis, remyelination, and synaptogenesis. In addition, IGF-1 can mediate an antidepressant effect in patients with major affective disorder, and its levels in the cerebrospinal fluid have been found to vary with antidepressant treatment. Furthermore, it has been proven to crossover the blood-brain barrier, with a reciprocal feedback loop being the central effect. However, recent studies have reported inconclusive findings about the role of IGF-1 in major affective disorder. The aim of the current study was to conduct a thorough meta-analysis of changes in peripheral IGF-1 levels in patients with major depressive disorder (MDD) or bipolar disorder (BD). We conducted a thorough literature search and compared peripheral IGF-1 levels in patients with MDD or BD and in healthy controls, and investigated clinical variables through meta-regression. Electronic research was conducted through platform of PubMed. We used inclusion criteria as clinical trials discussing comparisons of peripheral IGF-1 protein levels in patients with MDD or BD and those in healthy controls. We analyzed the cases from 9 studies with the random-effect model. The main finding was that peripheral IGF-1 levels in the patients were significantly higher than in the healthy controls (P < 0.001), with a significant inverse association with duration of illness (P = 0.03). In meta-analysis comparing peripheral IGF-1 levels in patients with BD or MDD before and after treatment, there was no significant change in peripheral IGF-1 levels after treatment (P = 0.092). The small numbers of studies and lack of correlation data with growth hormone in current studies are the main limitations of this meta-analysis. Our results indicated that peripheral IGF-1 levels may not be an indicator of disease severity, but may be a disease trait marker or an indicator of cognition. However, further investigations on the correlation between cognitive function and peripheral IGF-1 levels are needed to explore the role of IGF-1 in the pathophysiology of MDD and BD.

Increased levels of vascular endothelial growth factor in patients with major depressive disorder: A meta-analysis

The regulation of neurotrophic factors plays an important role in the pathophysiology of major depressive disorder (MDD). Vascular endothelial growth factor (VEGF) has been shown to promote neurogenesis, neuroprotection, and influence synaptic transmission. Many studies have examined the VEGF levels in patients with depression, however the results have been inconsistent. In the current meta-analysis, we compared blood VEGF levels between MDD patients and control subjects (16 articles including 872 patients and 882 control subjects). The effect sizes of individual studies were synthesized using a random effect model. We found that the blood VEGF levels in the patients with MDD were significantly higher than those in the healthy controls (p<0.001), and the difference was negatively correlated with mean age (p=0.01). Other variables including proportion of female subjects, body mass index, severity of depression, duration of illness, and age at onset were not significantly correlated with the difference. Our results highlight that elevated blood VEGF levels may be a disease marker in patients with MDD. Further studies are needed to examine the relationship between VEGF levels in central and peripheral environments, and clarify the role of VEGF in the pathophysiology of MDD.

New alterations at potentially regulated regions of the Glial Derived Neurotrophic Factor gene in bipolar disorder

INTRODUCTION

Glial Derived Neurotrophic Factor (GDNF) plays an important role in the survival and differentiation of neurons. We examined 5'upstream and 3' untranslated region of the GDNF gene by PCR amplification and direct sequencing to explore the effect of alteration in the potentially regulated part of GDNF in bipolar disorder.

MATERIALS AND METHODS

Sixty-six patients with bipolar disorder, 27 first degree relatives of these patients and 56 healthy volunteers were screened for mutations and polymorphisms in GDNF gene.

RESULTS

Seven previously reported polymorphisms and additional three novel allele variants of GDNF were detected. Association test of rs2075680 C>A SNP showed significant difference between patients and healthy subjects with higher allele frequency in healthy subjects performing Chi-square test. However, there was no significant difference after multiple test corrections between groups. There were no significant differences in association test of rs2075680 C>A SNP between first degree relatives and healthy volunteers/patients. rs142426358 T>C SNP was seen only in one patient with an early age of illness onset. New T>A alterations were found in chromosome locations 5:37812784 and 5:37812782 in two male bipolar disorder patients with age of illness onset 12 and 24 years.

LIMITATIONS

The sample size was relatively small.

DISCUSSION

Our study proposes the suggestive association between polymorphisms in the potential regulatory sites of GDNF and bipolar disorder.

Association of 2 neurotrophic factor polymorphisms with efficacy of paroxetine in patients with major depressive disorder in a Chinese population

BACKGROUND

To evaluate the influence of the single nucleotide polymorphism (SNP) rs 6265 in the brain-derived neurotrophic factor (BDNF) gene and 21 SNPs of the glial cell line-derived neurotrophic factor (GDNF) gene on the efficacy of paroxetine in patients with major depressive disorder (MDD).

METHODS

Genotyping for BDNF and GDNF polymorphisms was performed in 298 patients with MDD who started 20 mg paroxetine per day and had their plasma concentrations measured after 6 weeks. The SNPs were selected from the HapMap Chinese ethnic group and literature reports. Changes in the severity of MDD were assessed with the Hamilton Depression Rating Scale (HAM-D) at baseline and at a 6-week follow-up. Paroxetine plasma concentration was measured using high-performance liquid chromatography with fluorescence detection. The Sequenom MassArray system was used for genotyping.

RESULTS

At the 6-week follow-up, 219 of the 298 patients (73.5%) were responders and 79 patients (26.5%) were nonresponders to paroxetine treatment. The lower threshold concentration of paroxetine for response was 50 ng/mL, and a linear relationship was found between paroxetine plasma concentration and clinical response. The allele types for the SNPs rs 6265 (P < 0.001), rs 2973049 (P = 0.005), and rs 2216711 (P = 0.006) demonstrated significant associations with paroxetine treatment remission at week 6.

CONCLUSIONS

Genetic variants in the BDNF and GDNF regions may be indicators of treatment response to paroxetine in patients with MDD.

Decreased glial cell line-derived neurotrophic factor levels in patients with depression: a meta-analytic study

Glial cell-line derived neurotrophic factor (GDNF) has been shown to promote development, differentiation, and protection of CNS neurons and was thought to play an important role in various neuropsychiatric disorders. Several studies have examined the GDNF levels in patients with depression but shown inconsistent results. In this study, we compared blood GDNF levels between depressive patients and control subjects through meta-analytic method. The effect sizes (ESs) from all eligible studies were synthesized by using a random effect model. In this meta-analysis, we included 526 patients and 502 control subjects from 12 original articles. Compared to control subjects, blood GDNF levels are significantly decreased in patients with depression (ES = -0.62, p = 0.0011). However, significant heterogeneity was found among included studies. Through subgroup analysis, we found that GDNF was still decreased in studies with major depressive disorder (ES = -0.73, p = 0.0001); in studies with non-old-age depression (ES = -1.25, p = 0.0001), but not with old-age depression; and in studies using serum samples (ES = -0.86, p < 0.0001), but not in studies using plasma sample. Meta-regression did not show moderating effects of mean age of subjects, gender distribution, and age of onset of depression. Our findings support blood GDNF levels as a biomarker of depression as a whole, but the results were modulated by psychiatric diagnosis, age of included subjects, and sampling sources. With these results, future studies are required to examine whether effective antidepressant treatment is associated with an increase in serum GDNF levels.

Biomarker approaches in major depressive disorder evaluated in the context of current hypotheses

Major depressive disorder is a heterogeneous disorder, mostly diagnosed on the basis of symptomatic criteria alone. It would be of great help when specific biomarkers for various subtypes and symptom clusters of depression become available to assist in diagnosis and subtyping of depression, and to enable monitoring and prognosis of treatment response. However, currently known biomarkers do not reach sufficient sensitivity and specificity, and often the relation to underlying pathophysiology is unclear. In this review, we evaluate various biomarker approaches in terms of scientific merit and clinical applicability. Finally, we discuss how combined biomarker approaches in both preclinical and clinical studies can help to make the connection between the clinical manifestations of depression and the underlying pathophysiology.

MicroRNA regulation of central glial cell line-derived neurotrophic factor (GDNF) signalling in depression

Although multiple studies have reported that peripheral glial cell line-derived neurotrophic factor (GDNF) is reduced in depression, cerebral GDNF signalling has yet to be examined in this condition. Here, we report an isoform-specific decrease in GDNF family receptor alpha 1 (GFRA1) mRNA expression, resulting in lowered GFRα1a protein levels in basolateral amygdala (BLA) samples from depressed subjects. Downregulation of GFRα1a was associated with increased expression of microRNAs, including miR-511, predicted to bind to long 3' untranslated region (3'-UTR)-containing transcripts (GFRA1-L) coding for GFRα1a. Transfection of human neural progenitor cells (NPCs) with a miR-511 mimic was sufficient to repress GFRA1-L/GFRα1a without altering GFRα1b, and resulted in pathway-specific changes in immediate early gene activity. Unexpectedly, GFRα1a knockdown did not reduce NPC responses to GDNF. Rather, it greatly enhanced mitogen-activated protein kinase signalling. This effect appeared to be mediated by GDNF/soluble GFRα1/neural cell adhesion molecule binding, and substituting the soluble GFRα1a/GFRα1b content of miR-511-transfected NPCs with that of controls rescued signalling. In light of previous reports suggesting that GFRα1b can inhibit GFRα1a-induced neuroplasticity, we also assessed the association between GFRα1 and doublecortin (DCX; a hyperplastic marker) in human BLA. Although controls displayed coordinated expression of GFRα1a and b isoforms and these correlated positively with DCX, the only significant association observed among depressed subjects was a strongly negative correlation between GFRα1b and DCX. Taken together, these results suggest that microRNA-mediated reductions of GFRα1a in depression change the quality, rather than the quantity, of GDNF signalling. They also suggest that central GDNF signalling may represent a novel target for antidepressant treatment.

Alterations in BDNF (brain derived neurotrophic factor) and GDNF (glial cell line-derived neurotrophic factor) serum levels in bipolar disorder: The role of lithium

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) has been consistently reported to be decreased in mania or depression in bipolar disorders. Evidence suggests that Glial cell line-derived neurotrophic factor (GDNF) has a role in the pathogenesis of mood disorders. Whether GDNF and BDNF act in the same way across different episodes in bipolar disorders is unclear.

METHOD

BDNF and GDNF serum levels were measured simultaneously by enzyme-linked immunosorbent assay (ELISA) method in 96 patients diagnosed with bipolar disorder according to DSM-IV (37 euthymic, 33 manic, 26 depressed) in comparison to 61 healthy volunteers. SCID- I and SCID-non patient version were used for clinical evaluation of the patients and healthy volunteers respectively. Correlations between the two trophic factor levels, and medication dose, duration and serum levels of lithium or valproate were studied across different episodes of illness.

RESULTS

Patients had significantly lower BDNF levels during mania and depression compared to euthymic patients and healthy controls. GDNF levels were not distinctive. However GDNF/BDNF ratio was higher in manic state compared to euthymia and healthy controls. Significant negative correlation was observed between BDNF and GDNF levels in euthymic patients. While BDNF levels correlated positively, GDNF levels correlated negatively with lithium levels. Regression analysis confirmed that lithium levels predicted only GDNF levels positively in mania, and negatively in euthymia.

LIMITATIONS

Small sample size in different episodes and drug-free patients was the limitation of thestudy.

CONCLUSION

Current data suggests that lithium exerts its therapeutic action by an inverse effect on BDNF and GDNF levels, possibly by up-regulating BDNF and down-regulating GDNF to achieve euthymia.

Neurotrophic factors in women with crack cocaine dependence during early abstinence: the role of early life stress

BACKGROUND

Neurotrophic factors have been investigated in the pathophysiology of alcohol and drug dependence and have been related to early life stress driving developmental programming of neuroendocrine systems.

METHODS

We conducted a follow-up study that aimed to assess the plasma levels of glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT3) and neurotrophin-4/5 (NT4/5) in crack users during 3 weeks of early abstinence in comparison with healthy controls. We performed a comprehensive clinical assessment in female inpatients with crack cocaine dependence (separated into 2 groups: participants with (CSA+) and without (CSA-) a history of childhood sexual abuse) and a group of nonuser control participants.

RESULTS

Our sample included 104 women with crack cocaine dependence and 22 controls; of the women who used crack cocaine, 22 had a history of childhood sexual abuse and 82 did not. The GDNF plasma levels in the CSA+ group increased dramatically during 3 weeks of detoxification. In contrast, those in the CSA- group showed lower and stable levels of GDNF under the same conditions. Compared with the control group, BDNF plasma levels remained elevated and NGF levels were reduced during early abstinence. We found no differences in NT3 and NT4/5 between the patients and controls. However, within-group analyses showed that the CSA+ group exhibited higher levels of NT4/5 than the CSA- group at the end of detoxification.

LIMITATIONS

Some of the participants were using neuroleptics, mood stabilizers or antidepressants; our sample included only women; memory bias could not be controlled; and we did not investigate the possible confounding effects of other forms of stress during childhood.

CONCLUSION

This study supports the association between early life stress and peripheral neurotrophic factor levels in crack cocaine users. During early abstinence, plasmastic GDNF and NT4/5 were the only factors to show changes associated with a history of childhood sexual abuse.

Age-associated decrease in global DNA methylation in patients with major depression

BACKGROUND

Evidence has supported a role of DNA methylation in the pathophysiology of mood disorders. The purpose of the current study is to examine 5-methylcytosine (5-mc) and 5-hydroxymethylcytosine (5-hmc) levels in patients with major depressive disorder (MDD) at different disease states.

METHODS

Forty-nine patients with MDD and 25 healthy control subjects were included. The severity in the disease was assessed by using the 17-item Hamilton Rating Scale of Depression (HAM-D) (HAM-D ≥19 for severe MDD and HAM-D ≤7 for remitted MDD). The 5-mc and 5-hmc levels in leukocyte DNA were measured using an enzyme-linked immunosorbent assay-based method.

RESULTS

We found a significant decrease in 5-hmc and trends of decreasing 5-mc levels in patients with severe MDD compared to healthy controls (P=0.059 for 5-mc and P=0.013 for 5-hmc). The decrease in the level exists only in the older age group (P=0.035 for 5-mc and P=0.002 for 5-hmc) but not in the younger age group (P=0.077 for 5-mc and P=0.620 for 5-hmc). In addition, the 5-mc level was found to be inversely correlated with disease severity (P=0.011).

CONCLUSION

Our results support a decrease in global DNA methylation associated with age in patients with severe depression. Further studies are needed to clarify the role of the methylation level as a disease marker of depression and whether antidepressant treatment changes the methylation profiles.

Glial cell line-derived neurotrophic factor (GDNF) as a novel candidate gene of anxiety

Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophic factor for dopaminergic neurons with promising therapeutic potential in Parkinson's disease. A few association analyses between GDNF gene polymorphisms and psychiatric disorders such as schizophrenia, attention deficit hyperactivity disorder and drug abuse have also been published but little is known about any effects of these polymorphisms on mood characteristics such as anxiety and depression. Here we present an association study between eight (rs1981844, rs3812047, rs3096140, rs2973041, rs2910702, rs1549250, rs2973050 and rs11111) GDNF single nucleotide polymorphisms (SNPs) and anxiety and depression scores measured by the Hospital Anxiety and Depression Scale (HADS) on 708 Caucasian young adults with no psychiatric history. Results of the allele-wise single marker association analyses provided significant effects of two single nucleotide polymorphisms on anxiety scores following the Bonferroni correction for multiple testing (p = 0.00070 and p = 0.00138 for rs3812047 and rs3096140, respectively), while no such result was obtained on depression scores. Haplotype analysis confirmed the role of these SNPs; mean anxiety scores raised according to the number of risk alleles present in the haplotypes (p = 0.00029). A significant sex-gene interaction was also observed since the effect of the rs3812047 A allele as a risk factor of anxiety was more pronounced in males. In conclusion, this is the first demonstration of a significant association between the GDNF gene and mood characteristics demonstrated by the association of two SNPs of the GDNF gene (rs3812047 and rs3096140) and individual variability of anxiety using self-report data from a non-clinical sample.

Neurovascular unit dysfunction with blood-brain barrier hyperpermeability contributes to major depressive disorder: a review of clinical and experimental evidence

About one-third of people with major depressive disorder (MDD) fail at least two antidepressant drug trials at 1 year. Together with clinical and experimental evidence indicating that the pathophysiology of MDD is multifactorial, this observation underscores the importance of elucidating mechanisms beyond monoaminergic dysregulation that can contribute to the genesis and persistence of MDD. Oxidative stress and neuroinflammation are mechanistically linked to the presence of neurovascular dysfunction with blood-brain barrier (BBB) hyperpermeability in selected neurological disorders, such as stroke, epilepsy, multiple sclerosis, traumatic brain injury, and Alzheimer’s disease. In contrast to other major psychiatric disorders, MDD is frequently comorbid with such neurological disorders and constitutes an independent risk factor for morbidity and mortality in disorders characterized by vascular endothelial dysfunction (cardiovascular disease and diabetes mellitus). Oxidative stress and neuroinflammation are implicated in the neurobiology of MDD. More recent evidence links neurovascular dysfunction with BBB hyperpermeability to MDD without neurological comorbidity. We review this emerging literature and present a theoretical integration between these abnormalities to those involving oxidative stress and neuroinflammation in MDD. We discuss our hypothesis that alterations in endothelial nitric oxide levels and endothelial nitric oxide synthase uncoupling are central mechanistic links in this regard. Understanding the contribution of neurovascular dysfunction with BBB hyperpermeability to the pathophysiology of MDD may help to identify novel therapeutic and preventative approaches.

Neuroplasticity and the next wave of antidepressant strategies

Depression is a common chronic psychiatric disorder that is also often co-morbid with numerous neurological and immune diseases. Accumulating evidence indicates that disturbances of neuroplasticity occur with depression, including reductions of hippocampal neurogenesis and cortical synaptogenesis. Improper trophic support stemming from stressor-induced reductions of growth factors, most notably brain derived neurotrophic factor (BDNF), likely drives such aberrant neuroplasticity. We posit that psychological and immune stressors can interact upon a vulnerable genetic background to promote depression by disturbing BDNF and neuroplastic processes. Furthermore, the chronic and commonly relapsing nature of depression is suggested to stem from "faulty wiring" of emotional circuits driven by neuroplastic aberrations. The present review considers depression in such terms and attempts to integrate the available evidence indicating that the efficacy of current and "next wave" antidepressant treatments, whether used alone or in combination, is at least partially tied to their ability to modulate neuroplasticity. We particularly focus on the N-methyl-D-aspartate (NMDA) antagonist, ketamine, which already has well documented rapid antidepressant effects, and the trophic cytokine, erythropoietin (EPO), which we propose as a potential adjunctive antidepressant agent.

Second messenger/signal transduction pathways in major mood disorders: moving from membrane to mechanism of action, part I: major depressive disorder

The etiopathogenesis and treatment of major mood disorders have historically focused on modulation of monoaminergic (serotonin, norepinephrine, dopamine) and amino acid [γ-aminobutyric acid (GABA), glutamate] receptors at the plasma membrane. Although the activation and inhibition of these receptors acutely alter local neurotransmitter levels, their neuropsychiatric effects are not immediately observed. This time lag implicates intracellular neuroplasticity as primary in the mechanism of action of antidepressants and mood stabilizers. The modulation of intracellular second messenger/signal transduction cascades affects neurotrophic pathways that are both necessary and sufficient for monoaminergic and amino acid-based treatments. In this review, we will discuss the evidence in support of intracellular mediators in the pathophysiology and treatment of preclinical models of despair and major depressive disorder (MDD). More specifically, we will focus on the following pathways: cAMP/PKA/CREB, neurotrophin-mediated (MAPK and others), p11, Wnt/Fz/Dvl/GSK3β, and NFκB/ΔFosB. We will also discuss recent discoveries with rapidly acting antidepressants, which activate the mammalian target of rapamycin (mTOR) and release of inhibition on local translation via elongation factor stimulation. Throughout this discourse, we will highlight potential intracellular targets for therapeutic intervention. Finally, future clinical implications are discussed.