Consensus paper of the WFSBP Task Force on Biological Markers: biological markers in depression

Exercise affects symptom severity but not biological measures in depression and somatization - results on IL-6, neopterin, tryptophan, kynurenine and 5-HIAA

Exercise leads to symptom reduction in affective disorders and functional somatic syndromes. Biological hypotheses of underlying mechanisms include serotonergic and immunological pathways. We aimed to investigate biological features in persons with major depression and somatoform syndromes, and to analyze effects of short-term graded exercise on these parameters. Baseline values for depressive and somatoform symptoms, tryptophan, kynurenine, 5-hydroxyindoleacetic acid, neopterin and interleukin-6 were compared with those after one week of increased and one week of reduced physical activity. Thirty-eight persons with major depression, 27 persons with a minimum of 6-8 somatoform symptoms, and 48 healthy controls participated in the study. Depressive and somatoform symptoms were reduced after the active week, and an interaction pointed towards group-specific reduction of psychopathology. Participants with major depression had lower levels of kynurenine compared to controls, with intermediate concentrations in somatoform patients. There were no systematic associations of symptom improvement with biological changes. A possible limitation of the design is that a control condition with low physical activity, but no placebo condition was included. People with multiple somatoform symptoms and major depression benefit from a short and low-graded exercise intervention. These effects do not seem to be mediated by changes in serotonergic and inflammatory parameters.

Genetics of serum BDNF: meta-analysis of the Val66Met and genome-wide association study

OBJECTIVES

Lower levels of serum brain derived neurotrophic factor (BDNF) is one of the best known biomarkers of depression. To identify genetic variants associated with serum BDNF, we tested the Val66Met (rs6265) functional variant and conducted a genome-wide association scan (GWAS).

METHODS

In a community-based sample (N = 2054; aged 19-101, M = 51, SD = 15) from Sardinia, Italy, we measured serum BDNF concentration and conducted a GWAS.

RESULTS

We estimated the heritability of serum BDNF to be 0.48 from sib-pairs. There was no association between serum BDNF and Val66Met in the SardiNIA sample and in a meta-analysis of published studies (k = 13 studies, total n = 4727, P = 0.92). Although no genome-wide significant associations were identified, some evidence of association was found in the BDNF gene (rs11030102, P = 0.001) and at two loci (rs7170215, P = 4.8 × 10⁻⁵ and rs11073742 P = 1.2 × 10⁻⁵) near and within NTRK3 gene, a neurotrophic tyrosine kinase receptor.

CONCLUSIONS

Our study and meta-analysis of the literature indicate that the BDNF Val66Met variant is not associated with serum BDNF, but other variants in the BDNF and NTRK3 genes might regulate the level of serum BDNF.

Multivariate classification of blood oxygen level-dependent FMRI data with diagnostic intention: a clinical perspective

SUMMARY

There has been a recent upsurge of reports about applications of pattern-recognition techniques from the field of machine learning to functional MR imaging data as a diagnostic tool for systemic brain disease or psychiatric disorders. Entities studied include depression, schizophrenia, attention deficit hyperactivity disorder, and neurodegenerative disorders like Alzheimer dementia. We review these recent studies which-despite the optimism from some articles-predominantly constitute explorative efforts at the proof-of-concept level. There is some evidence that, in particular, support vector machines seem to be promising. However, the field is still far from real clinical application, and much work has to be done regarding data preprocessing, model optimization, and validation. Reporting standards are proposed to facilitate future meta-analyses or systematic reviews.

Lower CSF interleukin-6 predicts future depression in a population-based sample of older women followed for 17 years

OBJECTIVE

The literature regarding cerebrospinal fluid (CSF) cytokines in geriatric depression is sparse. The aim of this study was to examine associations between CSF interleukin-6 (IL-6) and related proinflammatory cytokines and current and future depression in a population-based sample of older women who were followed for 17 years.

METHODS

83 non-demented women aged 70-84 years who participated in the Prospective Population Study of Women in Gothenburg, Sweden took part in a lumbar puncture in 1992-3. CSF- IL-6, interleukin-1β (IL-1β), interleukin- 8 (IL-8) and tumor necrosis factor-α (TNF-α) were measured. Psychiatric symptoms were rated with the Comprehensive Psychopathological Rating Scale at baseline and at three subsequent face-to-face examinations. Depression (major or minor) was diagnosed in accordance with DSM-IV/DSM-IV research criteria.

RESULTS

At baseline, women with ongoing depression had lower levels of IL-6 (p<0.04), IL-8 (p<0.05) and TNF-α (p<0.05) compared with those without depression. In women without depression at baseline, lower CSF IL-6 levels predicted depression at one or more follow-up examination (p<0.03). Results from the generalized linear mixed logistic model using all baseline and follow-up data on depression status and Mini Mental State Examination score showed a significant relationship between IL-6 and depression (p=0.005 OR 0.370 CI [0.184-0.744]).

CONCLUSION

Lower levels of CSF IL-6 were associated with current depression and with future depression during a follow-up of almost two decades. Our findings suggest that lower levels of CSF IL-6 may be related to depression vulnerability in later life.

The DEX/CRH test for major depression: a potentially useful diagnostic test

The dexamethasone/corticotropin-releasing hormone (DEX/CRH) test has been proposed as a potential diagnostic test for major depressive disorder (MDD). A previously proposed four-step approach assesses the stage of development for a biological finding into a clinically useful diagnostic test. Using this approach, we evaluated the progress of the DEX/CRH test using meta-analysis as a part of step 1. A literature review identified 15 studies of the DEX/CRH test in patients with MDD and healthy controls. Meta-analysis estimated the effect size, heterogeneity, and confidence intervals using random effects models. Studies consistent with any step of the four-step approach were identified, and their characteristics were presented. Eleven studies reported significantly higher cortisol levels with the DEX/CRH test in patients with MDD, compared with the healthy controls (step 1). Eight eligible studies were included in meta-analysis, and had an effect size of 1.34 (95% confidence interval: 0.70-1.97). Most studies were step-1 studies (comparison of patients and healthy controls), and no step-4 studies (multicenter trials) were found. This review emphasizes that despite appearing as a promising test, the DEX/CRH has not been adequately studied for the required stages of development into a clinically useful laboratory test. Particularly, additional step-3 and step-4 studies are necessary.

Analysis of oxysterols and cholesterol in prefrontal cortex of suicides

Brain oxysterol levels, which are enzymatic oxidation products of cholesterol (Chl), have been proposed to reflect the dynamic process of physiological synapse maintenance and repair of nerve terminals within the central nervous system (CNS), due to the turnover of membrane Chl. Modifications of oxysterols have important implications in neurological conditions, especially in neurodegenerative and psychiatric disorders in which alterations of synaptic plasticity or cell signalling are implicated, such as depression. Oxysterols can diffuse across the blood-brain barrier and have been hypothesized to provide a mechanism by which the brain can eliminate excess Chl to maintain a steady state. Relations of 24-hydroxycholesterol (24OH) and 27-hydroxycholesterol (27OH) specifically may provide a depiction of CNS Chl homeostasis. Thus, the objective of this study was to integrate oxysterol measures and gene expression measures in an effort to identify how they may relate to depression and suicide. Using post-mortem human prefrontal cortex tissue, quantification of metabolites by GC-MS and gene expression by qRT-PCR were performed with the aim to provide a characterization of enzymatic oxidative Chl homeostasis. Results show a significant increase in 24OH, which suggests a higher turnover of Chl to 24OH in the prefrontal cortex of suicide cases. An increase in 24OH may, in combination with liver-X receptor activation, explain the observed reduction of low central and peripheral Chl in suicide and would have implications for synapse maintenance and loss in the neuropathology of depression and suicide.

[The effects of hormone replacement therapy on mind and brain]

Hormonal fluctuations during the perimenopausal transition lead to physical discomfort but are also frequently accompanied by mood swings, depressive symptoms, anxiety and sleeping disorders. The important role of the neurotransmitter serotonin in the pathogenesis of anxiety disorders and major depression is unquestioned, but only little is known about the influence of sex hormones on the serotonergic system. This review provides an overview of potential risk factors for the occurrence of affective disorders in the menopausal transition and discusses possible therapeutic options. Current research findings from longitudinal studies testing the efficacy of hormone replacement therapy and antidepressants with effects on the serotonergic neurotransmission on physical and mental discomforts during menopause are presented. Furthermore, studies using positron emission tomography and genetic methods that explore the effects of sex steroids on different components of the serotonergic system are shown. The interactions between estrogen, progesterone and the serotonergic system are described, and possible neurobiological and endocrinological mechanisms underlying depressive symptoms in the perimenopause are elucidated.

Monitoring dendritic cell and cytokine biomarkers during remission prior to relapse in patients with FLT3-ITD acute myeloid leukemia

Relapse occurs frequently after treatment of acute myeloid leukemia (AML) patients with the FMS-like tyrosine kinase 3-internal tandem duplication (ITD) mutation. The availability of immunologic biomarkers to predict patients at high risk could allow clinicians to accelerate alternative treatments such as stem cell transplantation, immunotherapy, or novel drugs. We have previously reported that first diagnostic (FD) ITD(+) AML showed immunophenotypic and functional characteristics of arrested dendritic cell (DC) precursors. In this study, we show that the high frequency of precursor DCs in 16 FD ITD(+) AML samples (Lin(-)/HLA-DR(+)/CD11c(+)/CD123(+)) was associated with a lack of terminal DCs (myeloid DCs: BDCA-1(+) or BDCA-3(+); plasmacytoid DC: BDCA-2(+)). We further evaluated prospectively the peripheral blood complete remission (CR) samples obtained from 11 ITD(+) AML patients after chemotherapy regarding the frequency of DCs and their pattern of cytokine production. Whereas the aberrant frequencies of precursor and terminal plasmacytoid DCs resolved during remission, the myeloid DC compartment did not fully recover. For an available cohort of patients (n = 4) who could be monitored over a period of >15 months after FD, we identified IL-10, TNF-α, IL-6, and IL-1β as cytokines produced by the CR samples at high levels a few months prior to relapse. Cell-free supernatant of an FD ITD(+) AML sample stimulated monocytes obtained from two healthy donors to secrete IL-10, TNF-α, IL-6, and IL-1β. Thus, we hypothesize that ITD(+) AML minimal residual disease can act directly as dysfunctional antigen-presenting cells or indirectly by production of factors that convert monocytes into myeloid-derived suppressor cells secreting cytokines that promote immune evasion. Monitoring these immunologic biomarkers could improve prediction of relapse.

Cytokine targets in the brain: impact on neurotransmitters and neurocircuits

Increasing attention has been paid to the role of inflammation in a host of illnesses including neuropsychiatric disorders such as depression and anxiety. Activation of the inflammatory response leads to release of inflammatory cytokines and mobilization of immune cells both of which have been shown to access the brain and alter behavior. The mechanisms of the effects of inflammation on the brain have become an area of intensive study. Data indicate that cytokines and their signaling pathways including p38 mitogen-activated protein kinase have significant effects on the metabolism of multiple neurotransmitters such as serotonin, dopamine, and glutamate through impact on their synthesis, release, and reuptake. Cytokines also activate the kynurenine pathway, which not only depletes tryptophan, the primary amino acid precursor of serotonin, but also generates neuroactive metabolites that can significantly influence the regulation of dopamine and glutamate. Through their effects on neurotransmitter systems, cytokines impact neurocircuits in the brain including the basal ganglia and anterior cingulate cortex, leading to significant changes in motor activity and motivation as well as anxiety, arousal, and alarm. In the context of environmental challenge from the microbial world, these effects of inflammatory cytokines on the brain represent an orchestrated suite of behavioral and immune responses that subserve evolutionary priorities to shunt metabolic resources away from environmental exploration to fighting infection and wound healing, while also maintaining vigilance against attack, injury, and further pathogen exposure. Chronic activation of this innate behavioral and immune response may lead to depression and anxiety disorders in vulnerable individuals.

Assessment of a multi-assay, serum-based biological diagnostic test for major depressive disorder: a pilot and replication study

Despite decades of intensive research, the development of a diagnostic test for major depressive disorder (MDD) had proven to be a formidable and elusive task, with all individual marker-based approaches yielding insufficient sensitivity and specificity for clinical use. In the present work, we examined the diagnostic performance of a multi-assay, serum-based test in two independent samples of patients with MDD. Serum levels of nine biomarkers (alpha1 antitrypsin, apolipoprotein CIII, brain-derived neurotrophic factor, cortisol, epidermal growth factor, myeloperoxidase, prolactin, resistin and soluble tumor necrosis factor alpha receptor type II) in peripheral blood were measured in two samples of MDD patients, and one of the non-depressed control subjects. Biomarkers measured were agreed upon a priori, and were selected on the basis of previous exploratory analyses in separate patient/control samples. Individual assay values were combined mathematically to yield an MDDScore. A 'positive' test, (consistent with the presence of MDD) was defined as an MDDScore of 50 or greater. For the Pilot Study, 36 MDD patients were recruited along with 43 non-depressed subjects. In this sample, the test demonstrated a sensitivity and specificity of 91.7% and 81.3%, respectively, in differentiating between the two groups. The Replication Study involved 34 MDD subjects, and yielded nearly identical sensitivity and specificity (91.1% and 81%, respectively). The results of the present study suggest that this test can differentiate MDD subjects from non-depressed controls with adequate sensitivity and specificity. Further research is needed to confirm the performance of the test across various age and ethnic groups, and in different clinical settings.

Selected cytokine profiles during remission in bipolar patients

OBJECTIVES

The aim of the study was to examine the cytokine status in bipolar patients during immediate remission after acute episodes of mania or depression and in patients with sustained (≥6 months) remission, compared with healthy controls.

METHODS

The study was performed on 121 bipolar patients, of whom 35 were in immediate remission after mania, 41 were in immediate remission after depression, and 45 were in >6-month remission on lithium monotherapy or lithium combined with other drugs. The control group consisted of 78 healthy individuals without any history of psychiatric or immunological illnesses. Serum concentrations of IL-1β, IL-2, IL-6, IL-10, TNF-α and IFN-γ were determined using the Human Th1/Th2 Cytometric Bead Array method.

RESULTS

The concentration of IL-10 was higher in patients in remission after mania and the concentration of IFN-γ was higher in those in remission after depression than in healthy controls. On the other hand, cytokine concentrations in patients with sustained remission were not different from those of healthy subjects.

CONCLUSIONS

The results obtained in this study show that sustained remission in bipolar patients achieved mostly by lithium maintenance brings the cytokine status to a level similar to healthy control subjects.

Towards automated detection of depression from brain structural magnetic resonance images

INTRODUCTION

Depression is a major issue worldwide and is seen as a significant health problem. Stigma and patient denial, clinical experience, time limitations, and reliability of psychometrics are barriers to the clinical diagnoses of depression. Thus, the establishment of an automated system that could detect such abnormalities would assist medical experts in their decision-making process. This paper reviews existing methods for the automated detection of depression from brain structural magnetic resonance images (sMRI).

METHODS

Relevant sources were identified from various databases and online sites using a combination of keywords and terms including depression, major depressive disorder, detection, classification, and MRI databases. Reference lists of chosen articles were further reviewed for associated publications.

RESULTS

The paper introduces a generic structure for representing and describing the methods developed for the detection of depression from sMRI of the brain. It consists of a number of components including acquisition and preprocessing, feature extraction, feature selection, and classification.

CONCLUSION

Automated sMRI-based detection methods have the potential to provide an objective measure of depression, hence improving the confidence level in the diagnosis and prognosis of depression.

Are neuroticism and extraversion associated with the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS)? An exploratory 4-week trial

Several randomized, controlled trials have found high frequency repetitive transcranial magnetic stimulation (HF-rTMS) to be effective for treating major depressive disorder (MDD), but its antidepressant mechanisms have yet to be firmly understood. In this context, pre-treatment personality traits and subsequent changes in personality concomitant to treatment may be relevant for our understanding of these mechanisms. To investigate this issue we conducted a naturalistic trial in which 14 subjects with moderate to severe depression were treated with daily HF-rTMS over the left dorsolateral prefrontal cortex for 4 weeks. Objective depressive symptoms (as assessed by the HAM-D(21)) and the major personality dimensions of neuroticism and extraversion were measured pre-post HF-rTMS. Pre-rTMS levels of extraversion predicted subsequent decrease in depressive symptoms. Also, HF-rTMS treatment resulted in a decrease in neuroticism scores, and this relative decrease was associated with the relative decrease in depression. Our results suggest that HF-rTMS may positively affect the personality dimension of neuroticism. Also, pre-treatment levels of extraversion may predict the subsequent antidepressant response to HF-rTMS. However, further studies with larger samples and controlled designs are needed to better clarify these preliminary findings.

Evidence for sustained elevation of IL-6 in the CNS as a key contributor of depressive-like phenotypes

There is compelling clinical literature implicating a role for cytokines in the pathophysiology of major depressive disorder (MDD). Interleukin-6 (IL-6) and interleukin-1β (IL-1β) are pleiotropic inflammatory cytokines that have been reported to be elevated in patients with MDD. The present studies were undertaken to investigate the relationship between IL-6 and IL-1β in animal models of depressive-like behavior. Analysis of brain tissue homogenates in the cortex of rats subjected to chronic stress paradigms revealed elevated levels of IL-6 protein in the absence of elevations in IL-1β. Central administration of recombinant mouse IL-6 produced depressive-like phenotypes in mice, which were not accompanied by IL-1β-induced increases in the brain tissue or IL-1β-related sickness behavior typical of a general central nervous system inflammatory response. Systemic administration of fluoxetine in the presence of centrally administered IL-6 failed to produce the expected antidepressant-like response in mice relative to sham-infused controls. Further, administration of fluoxetine to mice with endogenous overexpression of brain IL-6 (MRL/MpJ-Fas(LPR/LPR) (LPR mice)) failed to produce the expected antidepressant-like effect relative to fluoxetine-treated control mice (MRL/MpJ(+/+)). Interestingly, blockade of IL-6 trans-signaling by coadministration of a gp130/Fc monomer or an anti-mouse IL-6 antibody with IL-6 prevented the IL-6-induced increases in immobility time as well as attenuated IL-6-induced increases of protein in the cortex. Taken together, these data indicate that elevations in IL-6 may have a pathophysiological role underlying depression and more specifically resistance to current classes of antidepressant medications and suggest that modulation of the IL-6 signaling pathway may have therapeutic potential for treatment-resistant depression.

Genetic biomarkers of depression

Depression is a term that has been used to describe a variety of ailments, ranging from minor to incapacitating. Clinically significant depression, termed as major depression, is a serious condition characterized not only by depressed mood but also by a cluster of somatic, cognitive, and motivational symptoms. Significant research efforts are aimed to understand the neurobiological as well as psychiatric disorders, and the evaluation of treatment of these disorders is still based solely on the assessment of symptoms. In order to identify the biological markers for depression, we have focused on gathering information on different factors responsible for depression including stress, genetic variations, neurotransmitters, and cytokines and chemokines previously suggested to be involved in the pathophysiology of depression. The present review illustrates the potential of biomarker profiling for psychiatric disorders, when conducted in large collections. The review highlighted the biomarker signatures for depression, warranting further investigation.

Association study between functional polymorphisms in the TNF-alpha gene and obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a prevalent psychiatric disorder of unknown etiology. However, there is some evidence that the immune system may play an important role in its pathogenesis. In the present study, two polymorphisms (rs1800795 and rs361525) in the promoter region of the cytokine tumor necrosis factor-alpha (TNFA) gene were genotyped in 183 OCD patients and in 249 healthy controls. The statistical tests were performed using the PLINK(®) software. We found that the A allele of the TNFA rs361525 polymorphism was significantly associated with OCD subjects, according to the allelic χ(2) association test (p=0.007). The presence of genetic markers, such as inflammatory cytokines genes linked to OCD, may represent additional evidence supporting the role of the immune system in its pathogenesis.

Bridging the gap between the immune and glutamate hypotheses of schizophrenia and major depression: Potential role of glial NMDA receptor modulators and impaired blood-brain barrier integrity

OBJECTIVES

Previous studies have suggested that the pathogenesis of schizophrenia and major depression involves an altered peripheral immune system. It is not clear, however, whether such changes are associated with corresponding neuroinflammatory responses and disturbances of neurotransmission.

METHODS

This paper reviews the current state of knowledge about the involvement of immune alterations in schizophrenia and major depression and a possible link to disturbances of glutamatergic transmission.

RESULTS

Inflammatory endogenous modulators of the NMDA receptor, the kynurenine pathway metabolites, are potential candidates for such a link. Studies of the blood and cerebrospinal fluid have suggested a schizophrenia-related upregulation of the NMDA receptor antagonist kynurenic acid in astrocytes, analogous to the ketamine psychosis model. Conversely, it has been proposed that there is depression-related microglial synthesis of the NMDA receptor agonist quinolinic acid, which is consistent with the observation that ketamine has therapeutic effects in major depression. Few publications have studied NMDA receptor modulating kynurenines in the brain, however.

CONCLUSIONS

Future research on the cerebral cell-type specific distribution of kynurenine metabolites and their brain-regional concentration imbalances will be required to connect peripheral immune changes, the hypotheses of blood-brain barrier dysfunction and glial pathology with concepts of altered neurotransmission in schizophrenia and major depression.

Neuroplastic changes in depression: a role for the immune system

Accumulating evidence suggests that there is a rich cross-talk between the neuroimmune system and neuroplasticity mechanisms under both physiological conditions and pathophysiological conditions in depression. Anti-neuroplastic changes which occur in depression include a decrease in proliferation of neural stem cells (NSCs), decreased survival of neuroblasts and immature neurons, impaired neurocircuitry (cortical-striatal-limbic circuits), reduced levels of neurotrophins, reduced spine density and dendritic retraction. Since both humoral and cellular immune factors have been implicated in neuroplastic processes, in this review we present a model suggesting that neuroplastic processes in depression are mediated through various neuroimmune mechanisms. The review puts forward a model in that both humoral and cellular neuroimmune factors are involved with impairing neuroplasticity under pathophysiological conditions such as depression. Specifically, neuroimmune factors including interleukin (IL)-1, IL-6, tumour necrosis factor (TNF)-α, CD4⁺CD25⁺T regulatory cells (T reg), self-specific CD4⁺T cells, monocyte-derived macrophages, microglia and astrocytes are shown to be vital to processes of neuroplasticity such as long-term potentiation (LTP), NSC survival, synaptic branching, neurotrophin regulation and neurogenesis. In rodent models of depression, IL-1, IL-6 and TNF are associated with reduced hippocampal neurogenesis; mechanisms which are associated with this include the stress-activated protein kinase (SAPK)/Janus Kinase (JNK) pathway, hypoxia-inducible factors (HIF)-1α, JAK-Signal Transducer and Activator of Transcription (STAT) pathway, mitogen-activated protein kinase (MAPK)/cAMP responsive element binding protein (CREB) pathway, Ras-MAPK, PI-3 kinase, IKK/nuclear factor (NF)-κB and TGFβ activated kinase-1 (TAK-1). Neuroimmunological mechanisms have an active role in the neuroplastic changes associated with depression. Since therapies in depression, including antidepressants (AD), omega-3 polyunsaturated fatty acids (PUFAs) and physical activity exert neuroplasticity-enhancing effects potentially mediated by neuroimmune mechanisms, the immune system might serve as a promising target for interventions in depression.

Long-term course of brain-derived neurotrophic factor serum levels in a patient treated with deep brain stimulation of the lateral habenula

INTRODUCTION

According to the neurotrophin hypothesis, a brain-derived neurotrophic factor (BDNF) decrease has been postulated as a pivotal pathomechanism in affective disorder, and the treatment-associated increase in peripheral BDNF has been linked to therapeutic efficacy of antidepressant drugs and electroconvulsive therapy. However, in deep brain stimulation (DBS), a still experimental antidepressant treatment approach, this issue has not yet been investigated.

METHODS

We examine the long-term course of serum BDNF levels in a 64-year-old woman who is being treated with DBS of the lateral habenula for severe major depressive disorder.

RESULTS

Our main findings are a significant increase in BDNF serum levels following DBS of the lateral habenula and an inverse U-shaped correlation of depression scores and BDNF levels.

DISCUSSION

The data indicate that DBS, like other effective antidepressant treatments, may contribute to an increase in peripheral BDNF levels, which are thought to reflect central nervous DBS-induced neuroplastic changes. Moreover, our observations underscore the complex nature of disease-associated BDNF alterations. Their identification as either state or trait marker remains controversial and requires larger-scale longitudinal studies.

Psychological stress is associated with high levels of IL-6 in HIV-1 infected individuals on effective combined antiretroviral treatment

This study explores the role of psychological stress in the circulating levels of interleukin-6 (IL-6) in a group of HIV-1 infected individuals on effective cART. We developed a cross-sectional study with 50 individuals with confirmed diagnosis of HIV-1 infection ≥1 and ≤8 years, on continuous cART for >1 and <8 years and with plasma viral load <50 copies/mL for at least 1 year. Clinical, behavioral and psychological variables were collected to control their possible indirect contribution in the relationship between psychological stress and IL-6. Pearson correlation and univariate/multivariate logistic regressions were performed. Eighty-eight percent of the subjects were male: median (IQR) age: 39.0 (32.7-42.2), years since HIV-1 infection: 3.4 (2.1-7.0), years on cART: 2.5 (1.6-5.7), CD4 cell count: 709.0 (573.5-881.0) cell/mm(3), plasma levels of IL-6: 7.0 (0-12.2) pg/ml. A strong correlation between IL-6 and psychological stress was found (r=.81). Psychological stress (coef: 0.49; SD: 0.05), anxiety/depression (0.37; 0.08) and unhealthy diet (2.94; 1.38) were associated with higher levels of IL-6. In the multivariate model psychological stress remained strongly associated with IL-6 (R(2): 59%). In conclusion, individuals with psychological stress presented high levels of IL-6 and psychological stress was the only variable which remained strongly associated with IL-6. This strong relationship suggests evidence for a mechanism through which psychological stress might contribute to the health's impairment of HIV-infected individuals on effective cART.

Cognitive functions and serum levels of brain-derived neurotrophic factor in patients with major depressive disorder

OBJECTIVE

We assessed major cognitive domains in major depressive disorder (MDD) compared to a healthy control group using neurocognitive tests. We hypothesized that lower serum brain-derived neurotrophic factor (BDNF) levels would be associated with poorer neurocognitive performance in patients with major depression and that these associations would be shown in healthy controls as well.

METHOD

Executive functions, sustaining and focusing of attention, memory functions, and verbal fluency were assessed in this study using the Trail-Making Test (TMT), Stroop Color Word Interference Test-TBAG Form (SCWT), Wisconsin Card Sorting Test (WCST), Test of Variables of Attention (TOVA), Auditory Consonant Trigram test (ACTT), Digit Span subtest of the Wechsler Memory Scale (DST), Rey Auditory Verbal Learning Test (RAVLT), and Controlled Oral Word Association Test (COWAT).

RESULTS

The MDD group showed significantly poorer performance than the control group in cognitive functions; they also had lower levels of BDNF than the control group. However, there was no correlation between cognitive performances and BDNF levels except in the TMT, Part B.

CONCLUSIONS

The current understanding of the importance of neurocognitive assessment and related biological markers in depression is improving. Further studies with larger sample sizes evaluating neurocognitive functions with molecular analyses of BDNF levels may reveal a novel marker for predicting and monitoring neurocognitive deficits in depression.

Circulating cytokine signatures in healthy medical students exposed to academic examination stress

Stress-induced production of proinflammatory cytokines in the brain and periphery is associated with mental distress. In this study, we measured changes in levels of salivary cortisol and 50 circulating immune mediators in 28 4th-grade medical students (19 males and 9 females) 7 weeks before, 1 day before, immediately after, and 1 week after an authorized nationwide examination for promotion. Repeated measures ANOVA with multiple testing correction and post hoc tests revealed that the examination significantly increased levels of proinflammatory cytokines (granulocyte colony-stimulating factor, interferon-γ, interleukin (IL)-1β, and tumor necrosis factor-α), Th2 cytokines (IL-4, IL-5, and IL-13), and β-nerve growth factor in association with significant decreases in salivary cortisol levels and anxiety after the examination. These mediators may have a negative impact on the mental state of healthy young adults exposed to naturalistic stressors.

Interleukin-1β: a new regulator of the kynurenine pathway affecting human hippocampal neurogenesis

Increased inflammation and reduced neurogenesis have been associated with the pathophysiology of major depression. Here, we show for the first time how IL-1β, a pro-inflammatory cytokine shown to be increased in depressed patients, decreases neurogenesis in human hippocampal progenitor cells. IL-1β was detrimental to neurogenesis, as shown by a decrease in the number of doublecortin-positive neuroblasts (-28%), and mature, microtubule-associated protein-2-positive neurons (-36%). Analysis of the enzymes that regulate the kynurenine pathway showed that IL-1β induced an upregulation of transcripts for indolamine-2,3-dioxygenase (IDO), kynurenine 3-monooxygenase (KMO), and kynureninase (42-, 12- and 30-fold increase, respectively, under differentiating conditions), the enzymes involved in the neurotoxic arm of the kynurenine pathway. Moreover, treatment with IL-1β resulted in an increase in kynurenine, the catabolic product of IDO-induced tryptophan metabolism. Interestingly, co-treatment with the KMO inhibitor Ro 61-8048 reversed the detrimental effects of IL-1β on neurogenesis. These observations indicate that IL-1β has a critical role in regulating neurogenesis whereas affecting the availability of tryptophan and the production of enzymes conducive to toxic metabolites. Our results suggest that inhibition of the kynurenine pathway may provide a new therapy to revert inflammatory-induced reduction in neurogenesis.

Serotonin transporter clustering in blood lymphocytes as a putative biomarker of therapeutic efficacy in major depressive disorder

BACKGROUND

Serotonin transporter (SERT) binding is decreased in lymphocytes of depression patients and this decrease is partially reversed by antidepressant medication. However, recent evidence has shown that clustering of SERT on cell membranes is very important for receptor functionality. Alteration in SERT clustering on peripheral lymphocytes does not affect symptoms severity. At the most it is associated or predicts responsivity to treatment.

METHODS

We collected blood samples from 38 untreated and newly diagnosed depression patients at the time of diagnosis and after 8weeks of pharmacological treatment and of 38 control subjects. We used the Hamilton Scale to quantify the level of depression in patients both before and after pharmacological treatment. We then used immunocytochemistry to assess SERT protein clusters in lymphocyte blood samples.

RESULTS

We found an increase in SERT cluster size, but not the number of SERT clusters, in naïve depression patients compared to control subjects. Based on the distribution of SERT cluster size we differentiated the naïve depression patients into two groups (D-I and D-II). Naïve D-I and D-II patients initially showed similar Hamilton scores. However, after pharmacological treatment the D-II patients showed a greater decrease in Hamilton scores than did the D-I patients, and they had an increase in the number of SERT clusters.

LIMITATIONS

The data should be replicated in a larger cohort of patients and with a proper clinical trial.

CONCLUSIONS

We propose that SERT clustering in blood lymphocytes may be a putative biomarker for antidepressant efficacy in major depressive disorder.

[Can we identify biomarkers in bipolar depression? From imaging to biology]

Biomarkers can be used to describe and quantify a biological process related to pathology or to the effect of a treatment. In bipolar depression, progresses in the fields of structural and functional imaging, but also in biological research help to identify such biomarkers. Results in structural imaging are heterogeneous. Using functional imaging, in bipolar depression we can identify an hyperactivity of limbic and striatal regions with a specific implication of the lateral part of the orbito-frontal cortex. Bipolar depression is also associated with a modification of neurotrophic factors and of factors involved in the inflammatory process. Modifications in circadian rhythms have also be described but their level of specificity have to be demonstrated. The identification of biomarkers for bipolar depression seems to be an interesting field, but it still remains in the domain of research.

Serum brain-derived neurotrophic factor: determinants and relationship with depressive symptoms in a community population of middle-aged and elderly people

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) is involved in major depressive disorder and neurodegenerative diseases. Clinical studies, showing decreased serum BDNF levels, are difficult to interpret due to limited knowledge of potential confounders and mixed results for age and sex effects. We explored potential determinants of serum BDNF levels in a community sample of 1230 subjects.

METHODS

Multiple linear regression analyses with serum BDNF level as the dependent variable were conducted to explore the effect of four categories of potential BDNF determinants (sampling characteristics, sociodemographic variables, lifestyle factors and somatic diseases) and of self-reported depressive symptoms (Beck's Depression Inventory (BDI).

RESULTS

Our results show that BDNF levels decline with age in women, whereas in men levels remain stable. Moreover, after controlling for age and gender, the assays still showed lower serum BDNF levels with higher BDI sum scores. Effects remained significant after correction for two main confounders (time of sampling and smoking), suggesting that they serve as molecular trait factors independent of lifestyle factors.

CONCLUSIONS

Given the age-sex interaction on serum BDNF levels and the known association between BDNF and gonadal hormones, research is warranted to delineate the effects of the latter interaction on the risk of psychiatric and neurodegenerative diseases.

A neuroimmunological perspective on anxiety disorders

OBJECTIVE

Research into psychoneuroimmunology has led to substantial advances in our understanding of the reciprocal interactions between the central nervous system and the immune system in neuropsychiatric disorders. To date, the presence of inflammatory responses and the crucial role of cytokines in major depression have been addressed in numerous studies. However, neuroinflammatory hypotheses in anxiety disorders have been studied less extensively than in major depression. There is a high research need for better understanding of both the heterogeneous role of specific cytokines in the control of anxious states and in different anxiety disorders and of the immunomodulating effects of antidepressants on anxiety.

METHODS

Relevant literature was identified through a search of MEDLINE via PubMed. We discuss recent research on neuroimmunology in anxiety and make methodological recommendations for future investigation of neuroinflammatory hypotheses in anxiety disorders.

RESULTS

Some accumulating evidence has indicated modulatory effects of cytokines on neuronal communication and anxiety; however, research has not revealed consistent reproducible findings.

CONCLUSIONS

The availability of inflammatory biomarkers may provide an opportunity to identify patients via specific pathophysiological processes and to monitor therapeutic responses within relevant pathways. Further understanding of the neuroimmunological mechanisms to untangle the reciprocal associations between inflammation and anxiety is warranted.

Functional biomarkers of depression: diagnosis, treatment, and pathophysiology

Major depressive disorder (MDD) is a heterogeneous illness for which there are currently no effective methods to objectively assess severity, endophenotypes, or response to treatment. Increasing evidence suggests that circulating levels of peripheral/serum growth factors and cytokines are altered in patients with MDD, and that antidepressant treatments reverse or normalize these effects. Furthermore, there is a large body of literature demonstrating that MDD is associated with changes in endocrine and metabolic factors. Here we provide a brief overview of the evidence that peripheral growth factors, pro-inflammatory cytokines, endocrine factors, and metabolic markers contribute to the pathophysiology of MDD and antidepressant response. Recent preclinical studies demonstrating that peripheral growth factors and cytokines influence brain function and behavior are also discussed along with their implications for diagnosing and treating patients with MDD. Together, these studies highlight the need to develop a biomarker panel for depression that aims to profile diverse peripheral factors that together provide a biological signature of MDD subtypes as well as treatment response.

The genetic blueprint of major depressive disorder: contributions of imaging genetics studies

OBJECTIVES

To review neuroimaging intermediate phenotypes of MDD and their relation to genetic risk variants.

METHODS

A systematic literature search of peer-reviewed English language articels using PubMed ( www.pubmed.org ) was performed.

RESULTS

Comprehensive evidence on the influence of serotonergic genes (SLC6A4, HTR1A, MAOA, TPH2) and BDNF on the following neural intermediate phenotypes is displayed: amygdala reactivity, coupling of amygdala-anterior cingulate cortex (ACC) activity, ACC volume, hippocampal volume and serotonin receptor 1A (5-HT1A) binding potential (BP).

CONCLUSIONS

Intermediate phenotypes may bridge the gap between genotype and phenotype by reducing the impreciseness of psychiatric phenotypes and yield more insights into the underlying biology.

Constant darkness induces IL-6-dependent depression-like behavior through the NF-κB signaling pathway

Substantial experimental evidence indicates a major role for the circadian system in mood disorders. Additionally, proinflammatory cytokines have been proposed to be involved in the pathogenesis of depression. However, the molecular elements determining the functional interplay between these two systems in depression have not been described as yet. Here we investigate whether long-term light deprivation in the constant darkness (DD) paradigm affects depression-like behavior in mice and concomitantly modulates the levels of proinflammatory cytokines. We find that after 4 weeks of DD, mice display depression-like behavior, which is paralleled by reduced hippocampal cell proliferation. This chronobiologically induced depressive state is associated with elevated levels of plasma IL-6 (interleukin-6) and IL-6 and Il1-R1 (interleukin 1 receptor, type I) protein levels in the hippocampus and also alters hippocampal protein levels of the clock genes per2 and npas2. Using pharmacological blockers of the NF-κB pathway, we provide evidence that the effects of DD on depression-like behavior, on hippocampal cell proliferation, on altered expressional levels of brain and plasma IL-6, and on the modulation of clock gene expression are mediated through NF-κB signaling. Moreover, NF-κB activity is enhanced in hippocampal tissue of DD mice. Mice with a deletion of IL-6, one of the target genes of NF-κB, are resistant to DD-induced depression-like behavior, which suggests a pivotal role for this cytokine in the constant darkness mouse model of depression. We here first describe some of the molecular elements bridging chronobiological and inflammatory processes in the constant darkness mouse model of depression.

DNA methylation profiles of the brain-derived neurotrophic factor (BDNF) gene as a potent diagnostic biomarker in major depression

Major depression, because of its recurring and life-threatening nature, is one of the top 10 diseases for global disease burden. Major depression is still diagnosed on the basis of clinical symptoms in patients. The search for specific biological markers is of great importance to advance the method of diagnosis for depression. We examined the methylation profile of 2 CpG islands (I and IV) at the promoters of the brain-derived neurotrophic factor (BDNF) gene, which is well known to be involved in the pathophysiology of depression. We analyzed genomic DNA from peripheral blood of 20 Japanese patients with major depression and 18 healthy controls to identify an appropriate epigenetic biomarker to aid in the establishment of an objective system for the diagnosis of depression. Methylation rates at each CpG unit was measured using a MassArray® system (SEQUENOM), and 2-dimensional hierarchical clustering analyses were undertaken to determine the validity of these methylation profiles as a diagnostic biomarker. Analyses of the dendrogram from methylation profiles of CpG I, but not IV, demonstrated that classification of healthy controls and patients at the first branch completely matched the clinical diagnosis. Despite the small number of subjects, our results indicate that classification based on the DNA methylation profiles of CpG I of the BDNF gene may be a valuable diagnostic biomarker for major depression.

Biomarkers for major depression and its delineation from neurodegenerative disorders

Major depressive disorders (MDD) are among the most debilitating diseases worldwide and occur with a high prevalence in elderly individuals. Neurodegenerative diseases (in particular Alzheimer's disease, AD) do also show a strong age-dependent increase in incidence and prevalence among the elderly population. A high number of geriatric patients with MDD show cognitive deficits and a very high proportion of AD patients present co-morbid MDD, which poses difficult diagnostic and prognostic questions. Especially in prodromal and in very early stages of AD, it is almost impossible to differentiate between pure MDD and MDD with underlying AD. Here, we give a comprehensive review of the literature on the current state of candidate biomarkers for MDD ("positive MDD markers") and briefly refer to established and validated diagnostic AD biomarkers in order to rule out underlying AD pathophysiology in elderly MDD subjects with cognitive impairments ("negative MDD biomarkers"). In summary, to date there is no evidence for positive diagnostic MDD biomarkers and the only way to delineate MDD from AD is to use "negative MDD" biomarkers. Because of this highly unsatisfactory current state of MDD biomarker research, we propose a research strategy targeting to detect and validate positive MDD biomarkers, which is based on a complex (genetic, molecular and neurophysiological) biological model that incorporates current state of the art knowledge on the pathobiology of MDD. This model delineates common pathways and the intersection between AD and MDD. Applying these concepts to MDD gives hope that positive MDD biomarkers can be successfully identified in the near future.

Cytokines mediated inflammation and decreased neurogenesis in animal models of depression

In patients with major depression or in animal models of depression, significantly increases in the concentrations of pro-inflammatory cytokines have been consistently reported. Proinflammatory cytokines can stimulate the hypothalamic-pituitary-adrenal (HPA) axis to release stress hormone, glucocorticoids. As a consequence of excessive inflammatory response triggered by pro-inflammatory cytokines in the periphery, free radicals, oxidants and glucocorticoids are over-produced, which can affect glial cell functions and damage neurons in the brain. Indeed, decreased neurogenesis and the dysfunction of neurotrophic system (up- or down-regulations of neurotrophins and their receptors) have been recently found. Effective treatments for depressive symptoms, such as antidepressants and omega-3 fatty acids can increase or modulate neurotrophic system and enhance neurogenesis. However, the relationship between glial cells; microglia (mostly involved in neuroinflammation) and astrocytes (producing neurotrophins), and the contribution of inflammation to decreased neurogenesis and dysfunction of neurotrophic system are almost unknown. This review first introduces changes in behavior, neurotransmitter, cytokine and neurogenesis aspects in depressed patients and several animal models of depression, secondly explores the possible relationship between pro- and anti-inflammatory cytokines and neurogenesis in these models, then discusses the effects of current treatments on inflammation, neurotrophic system and neurogenesis, and finally pointes out the limitations and future research directions.

The Utility of Animal Models in Understanding Links between Psychosocial Processes and Cardiovascular Health

A bidirectional association between mood disorders and cardiovascular disease has been described; however, the neurobiological mechanisms that underlie this link have not been fully elucidated. The purpose of this review is first to describe some of the important behavioral neurobiological processes that are common to both mood and cardiovascular disorders. Second, this review focuses on the value of conducting research with animal models (primarily rodents) to investigate potential behavioral, physiological, and neural processes involved in the association of mood disorders and cardiovascular disease. In combination with findings from human research, the study of mechanisms underlying mood and cardiovascular regulation using animal models will enhance our understanding of the association of depression and cardiovascular disease, and can promote the development of novel interventions for individuals with these comorbid conditions.

The possibility of evidence-based psychiatry: depression as a case

Considering psychiatry as a medical discipline, a diagnosis identifying a disorder should lead to an effective therapy. Such presumed causality is the basis of evidence-based psychiatry. We examined the strengths and weaknesses of research onto the causality of relationship between diagnosis and therapy of major depressive disorder and suggest what could be done to strengthen eventual claims on causality. Four obstacles for a rational evidence-based psychiatry were recognised. First, current classification systems are scientifically nonfalsifiable. Second, cerebral processes are-at least to some extent-nondeterministic, i.e. they are random, stochastic and/or chaotic. Third, the vague or lack of relationship between therapeutic regimens and suspected pathogenesis. Fourth, the inadequacy of tools to diagnose and delineate a functional disorder. We suggest a strategy to identify diagnostic prototypes that are characterised by a limited number of parameters (symptoms, markers and other characteristics). A prototypical diagnosis that may either support or reject particular elements of current diagnostic systems. Nevertheless, one faces the possibility that psychiatry will remain a relatively weak evidence-based medical discipline.

Determinants of serum brain-derived neurotrophic factor

BACKGROUND

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Peripheral blood and neuropsychological markers for the onset of action of antidepressant drugs in patients with Major Depressive Disorder

BACKGROUND

In Major Depressive Disorder (MDD), treatment outcomes with currently available strategies are often disappointing. Therefore, it is sensible to develop new strategies to increase remission rates in acutely depressed patients. Many studies reported that true drug response can be observed within 14 days (early improvement) of antidepressant treatment. The identical time course of symptom amelioration after early improvement in patients treated with antidepressants of all classes or with placebo strongly suggests a common biological mechanism, which is not specific for a particular antidepressant medication. However, the biology underlying early improvement and final treatment response is not understood and there is no established biological marker as yet, which can predict treatment response for the individual patient before initiation or during the course of antidepressant treatment. Peripheral blood markers and executive functions are particularly promising candidates as markers for the onset of action and thus the prediction of final treatment outcome in MDD.

METHODS/DESIGN

The present paper presents the rationales, objectives and methods of a multi-centre study applying close-meshed repetitive measurements of peripheral blood and neuropsychological parameters in patients with MDD and healthy controls during a study period of eight weeks for the identification of biomarkers for the onset of antidepressants' action in patients with MDD. Peripheral blood parameters and depression severity are assessed in weekly intervals from baseline to week 8, executive performance in bi-weekly intervals. Patients are participating in a randomized controlled multi-level clinical trial, healthy controls are matched according to mean age, sex and general intelligence.

DISCUSSION

This investigation will help to identify a biomarker or a set of biomarkers with decision-making quality in the treatment of MDD in order to increase the currently disappointing remission rates of antidepressant treatment.

A biological pathway linking inflammation and depression: activation of indoleamine 2,3-dioxygenase

This article highlights the evidence linking depression to increased inflammatory drive and explores putative mechanisms for the association by reviewing both preclinical and clinical literature. The enzyme indoleamine 2,3-dioxygenase is induced by proinflammatory cytokines and may form a link between immune functioning and altered neurotransmission, which results in depression. Increased indoleamine 2,3-dioxygenase activity may cause both tryptophan depletion and increased neurotoxic metabolites of the kynurenine pathway, two alterations which have been hypothesized to cause depression. The tryptophan-kynurenine pathway is comprehensively described with a focus on the evidence linking metabolite alterations to depression. The use of immune-activated groups at high risk of depression have been used to explore these hypotheses; we focus on the studies involving chronic hepatitis C patients receiving interferon-alpha, an immune activating cytokine. Findings from this work have led to novel strategies for the future development of antidepressants including inhibition of indoleamine 2,3-dioxygenase, moderating the cytokines which activate it, or addressing other targets in the kynurenine pathway.

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

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

Is there a personalized medicine for mood disorders?

Major Depressive Disorder (MDD) and antidepressant therapy response are largely based on behavioral criteria, which are known to correlate at best modestly with biological measures. Therefore, it is not surprising that the search for peripheral biological markers (biomarkers) being assessed in distant biological systems such as body fluids has not yet resulted in clinically convincing measures for MDD diagnostics or treatment evaluation. Imaging genetics studies, however, have been successful in the search for intermediate imaging phenotypes of MDD and treatment response that are directly related to the neurobiological underpinnings of MDD, but are not suitable for a broad clinical use today. Hence, we argue that intermediate phenotypes derived from imaging genetics studies should be utilized as substitutes of behaviorally assessed psychiatric diagnoses or therapy response in the search for easily accessible peripheral biomarkers. This article will further cover the current state of peripheral and neural biomarker research.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Early-life stress and antidepressants modulate peripheral biomarkers in a gene-environment rat model of depression

BACKGROUND

Availability of peripheral biomarkers for depression could aid diagnosis and help to predict treatment response. The objective of this work was to analyse the peripheral biomarker response in a gene-environment interaction model of depression. Genetically selected Flinders Sensitive Line (FSL) rats were subjected to maternal separation (MS), since early-life trauma is an important antecedent of depression. An open-ended approach based on a proteomic analysis of serum was combined with the evaluation of depression-associated proteins.

METHODS

Rats experienced MS and chronically received escitalopram (ESC) or nortryptiline (NOR). Serum proteins were compared by two-dimensional gel electrophoresis. Corticosterone, cytokines, BDNF and C-reactive protein (CRP) were measured by immunoassays.

RESULTS

Comparing FSL with the control Flinders Resistant Line (FRL), Apo-AI and Apo-AIV, alpha1-macroglobulin, glutathione peroxidase and complement-C3 were significantly modulated. Significant increases were detected in leptin, interleukin (IL) 1alpha and BDNF. CRP levels were significantly reduced. The impact of early-life stress was assessed by comparing FSL+MS versus FSL. Apo-E, alpha1-macroglobulin, complement-C3, transferrin and hemopexin were significantly modulated. The effect of stress in antidepressant response was then evaluated. In the comparison FSL+ESC+MS versus FSL+ESC, albumin, alpha1-macroglobulin, glutathione peroxidase and complement-C3 were modulated and significant reductions were detected in IL4, IL6, IL10, CRP and BDNF. By comparing FSL+NOR+MS versus FSL+NOR proteins like Apo-AIV, pyruvate dehydrogenase, alpha1-macroglobulin, transferrin and complement-C3 showed different levels.

CONCLUSIONS

Lipid metabolism and immunity proteins were differently expressed in FSL in comparison with FRL. Exposure to MS induced changes in inflammation and transport proteins which became apparent in response to antidepressant treatments. Modulated proteins could suggest biomarker studies in humans.

The association of infectious agents and schizophrenia

OBJECTIVES

The influence of infectious agents on the pathogenesis of psychiatric disorders has been discussed for decades. Pre- and postnatal infections are risk factors for schizophrenia. This may be explained by chronic infections or an altered immune status. However most of the studies have only focused on one single pathogen and not on the impact of different infectious agents. We investigated the association between schizophrenia and various neurotophic infectious agents.

METHODS

A total of 31 schizophrenic patients and 30 healthy matched individuals were included. Antibody titres of cytomegalovirus, herpes simplex virus, Epstein-Barr virus, mycoplasma, chlamydia and toxoplasma were evaluated. For statistical analysis we used Fisher's exact and Wilcoxon test.

RESULTS

Significantly elevated positive antibody titres within schizophrenic patients were found only for Chlamydia trachomatis (P=0.005) and a trend to significance for herpes simplex virus (P=0.055). Combining the different agents, schizophrenics had a significantly higher rate of positive titres to infectious agents as compared to controls (P=0.04).

CONCLUSIONS

The higher prevalence of antibodies within schizophrenic patients emphasizes a possible role of infectious agents in the pathogenesis of schizophrenia. Our data indicates that not one specific agent might be responsible for schizophrenic symptoms but the resulting immune response in the central nervous system.

Differences and similarities in the serotonergic diathesis for suicide attempts and mood disorders: a 22-year longitudinal gene-environment study

To investigate similarities and differences in the serotonergic diathesis for mood disorders and suicide attempts, we conducted a study in a cohort followed longitudinally for 22 years. A total of 1255 members of this cohort, which is representative of the French-speaking population of Quebec, were investigated. Main outcome measures included (1) mood disorders (bipolar disorder and major depression) and suicide attempts by early adulthood; (2) odds ratios and probabilities associated with 143 single nucleotide polymorphisms in 11 serotonergic genes, acting directly or as moderators in gene-environment interactions with childhood sexual or childhood physical abuse (CPA), and in gene-gene interactions; (3) regression coefficients for putative endophenotypes for mood disorders (childhood anxiousness) and suicide attempts (childhood disruptiveness). Five genes showed significant adjusted effects (HTR2A, TPH1, HTR5A, SLC6A4 and HTR1A). Of these, HTR2A variation influenced both suicide attempts and mood disorders, although through different mechanisms. In suicide attempts, HTR2A variants (rs6561333, rs7997012 and rs1885884) were involved through interactions with histories of sexual and physical abuse whereas in mood disorders through one main effect (rs9316235). In terms of phenotype-specific contributions, TPH1 variation (rs10488683) was relevant only in the diathesis for suicide attempts. Three genes contributed exclusively to mood disorders, one through a main effect (HTR5A (rs1657268)) and two through gene-environment interactions with CPA (HTR1A (rs878567) and SLC6A4 (rs3794808)). Childhood anxiousness did not mediate the effects of HTR2A and HTR5A on mood disorders, nor did childhood disruptiveness mediate the effects of TPH1 on suicide attempts. Of the serotonergic genes implicated in mood disorders and suicidal behaviors, four exhibited phenotype-specific effects, suggesting that despite their high concordance and common genetic determinants, suicide attempts and mood disorders may also have partially independent etiological pathways. To identify where these pathways diverge, we need to understand the differential, phenotype-specific gene-environment interactions such as the ones observed in the present study, using suitably powered samples.

Evolving refractory major depressive disorder diagnostic and treatment paradigms: toward closed-loop therapeutics

Current antidepressant therapies do not effectively control or cure depressive symptoms. Pharmaceutical therapies altogether fail to address an estimated 4 million Americans who suffer from a recurrent and severe treatment-resistant form of depression known as refractory major depressive disorder. Subjective diagnostic schemes, differing manifestations of the disorder, and antidepressant treatments with limited theoretical bases each contribute to the general lack of therapeutic efficacy and differing levels of treatment resistance in the refractory population. Stimulation-based therapies, such as vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation, are promising treatment alternatives for this treatment-resistant subset of patients, but are plagued with inconsistent reports of efficacy and variable side effects. Many of these problems stem from the unknown mechanisms of depressive disorder pathogenesis, which prevents the development of treatments that target the specific underlying causes of the disorder. Other problems likely arise due to the non-specific stimulation of various limbic and paralimbic structures in an open-loop configuration. This review critically assesses current literature on depressive disorder diagnostic methodologies, treatment schemes, and pathogenesis in order to emphasize the need for more stringent depressive disorder classifications, quantifiable biological markers that are suitable for objective diagnoses, and alternative closed-loop treatment options tailored to well-defined forms of the disorder. A closed-loop neurostimulation device design framework is proposed, utilizing symptom-linked biomarker abnormalities as control points for initiating and terminating a corrective electrical stimulus which is autonomously optimized for correcting the magnitude and direction of observed biomarker abnormality.

Serotonin transporter clustering in blood lymphocytes of reeler mice

Serotonin transporter clustering is an important feature for regulation of this transporter activity. We used immunocytochemistry to analyze alterations in serotonin transporter clustering in blood lymphocytes of reeler mice. Serotonin transporter immunolabelling is observed mostly as a patchy staining in lymphocytes membranes. Comparison of the number and size of serotonin transporter clusters in wild-type mice, heterozygous reeler mice, and homozygous reeler mice showed an increase in the number and size of clusters in heterozygous reeler mice, but only an increase in clusters size in homozygous reeler mice. Reelin is down-regulated in the brain of schizophrenia, autism, and mood disorders, and is also expressed in blood plasma. There is the possibility therefore that alterations in serotonin transporter clustering in blood lymphocytes associated with a decrease in reelin expression may be operative in some cardiovascular or immune system alterations showing comorbidity with these mental disorders.

Altered cardiovascular adaptability in depressed patients without heart disease

OBJECTIVES

Despite its clinical importance and relevance for health care policy, the pathways between depression and stress regulation remain poorly understood. The objective of our study was to compare cardiovascular and autonomic responses to brief psychosocial stress in a group of severely depressed subjects without heart disease and a non-depressed control-group.

METHODS

We recorded cardiovascular and autonomic reactions to two different stress tasks including anger recall and mental arithmetic in a sample of 25 severely depressed and 25 non-depressed subjects. Aggregated data were compared with repeated-measures MANOVA. We used contrasts to evaluate different response patterns concerning cardiovascular and autonomic reactivity vs. recovery.

RESULTS

Depressed subjects showed overall reduced high-frequency heart rate variability and an altered cardiovascular adaptability concerning heart rate, blood pressure, cardiac output, and, on a trend level, peripheral resistance. With few exceptions, we found no differences between reactivity vs. recovery response patterns.

CONCLUSIONS

Our results provide further evidence for altered cardiovascular reactivity and impaired cardiac autonomic functioning in depression. Further research is needed on psychophysiological response to either more disease-oriented or more personality-oriented stressors.