Do levels of brain-derived neurotrophic factor (BDNF) in plasma correlate with psychopathology in healthy subjects?

An Exploration of Blood Marker×Environment Interaction Effects on Pain Severity and Interference Scores in People With Acute Musculoskeletal Trauma

OBJECTIVES

Explore the moderating effects of psychological or social variables on associations between biomarkers of inflammation/stress and clinical reports of pain.

METHODS

This is a cross-sectional exploratory study. Data were drawn from the Systematic Merging of Biology, Mental Health and Environment (SYMBIOME) longitudinal study (clinicaltrials.gov ID no. NCT02711085). Eligible participants were adults who presented to an Urgent Care Centre in Ontario, Canada within 3 weeks of a noncatastrophic musculoskeletal trauma (no surgery or hospitalization). A questionnaire package was given that included the Brief Pain Inventory (capturing pain severity and pain interference) and relevant person-level variables. Blood samples were also drawn for serum analysis of 8 target biomarkers (brain-derived neurotrophic factor, transforming growth factor beta 1 [TGF-β1], c-reactive protein, tumor necrosis factor-α, interleukin [IL]-1β, IL-6, IL-10, and cortisol).

RESULTS

Employment before trauma (employed for pay/not employed for pay) fully moderated the association between tumor necrosis factor-α and pain severity (∆R2=4.4%). Pre-existing psychopathology (yes/no) fully moderated the association between TGF-β1 and pain severity (∆R2=8.0%). Sex (male/female) fully moderated the association between c-reactive protein and pain severity (∆R2=6.3%). A pre-existing pain condition (yes/no) was significantly associated with worse pain interference (R2=7.2%), and partially moderated the effect of IL-1β on pain interference (∆R2=6.9%). Higher peritraumatic life stress significantly explained 8.9% of variance in pain interference alone, and partially moderated the effect of TGF-β1 on interference (∆R2=4.4%).

DISCUSSION

Simple bivariate associations between blood-based markers and clinical symptoms are unlikely to reveal meaningful relationships. However, when stratified by existing person-level or "metadata" variables, an association may exist for at least 1 clinically relevant subgroup.

Assessment of Brain Derived Neurotrophic Factor in hair to study stress responses: A pilot investigation

To study pathogenic stress-effects in health and disease, it is paramount to define easy access parameters for non-invasive analysis of biological change in response to stress. Hair samples successfully provide this access for the study of hypothalamus-pituitary-adrenal axis (HPA) changes. In this study, we assess the hair expression and corresponding epigenetic changes of a neurotrophin essential for autonomic nervous system function and mental health: brain derived neurotrophic factor (BDNF). In three independent studies in healthy academic volunteers (study I: German students, N=36; study II, German academic population sample, N=28; study III: Mexican students, N=115), BDNF protein expression or BDNF gene (BDNF) histone acetylation was determined. Simultaneously, mental distress and distress-associated somatic complaints were assessed by self-report. In study I, we found a negative correlation between hair-BDNF protein level and hair-cortisol as well as between hair-BDNF and somatic complaints, while hair-cortisol correlated positively with mental distress. In study II, we found a negative correlation between H4 histone acetylation at the BDNF gene P4-promoter and somatic complaints. Regression analysis confirmed confounder stability of associations in both studies. In study III, we confirmed study I and found lower hair-BDNF protein level in volunteers with high somatic complaints, who also reported higher mental distress during the end of term exams. The results indicate that BDNF protein levels can be detected in clipped hair and are associated with somatic complaints and stress in life. In addition, we concluded that plucked hair can provide material for the study of epigenetic changes in stress-affected tissues. These tools can prove valuable for future studies on distress, both under experimental and field conditions.

Stress regulation in drug-resistant epilepsy

The prevalence of psychological distress, especially depressive and anxiety disorders, is higher in epilepsy than in other chronic health conditions. These comorbid conditions contribute even more than epileptic seizures themselves to impaired quality of life in patients with epilepsy (PWE). The link between these comorbidities and epilepsy appears to have a neurobiological basis, which is at least partly mediated by stress through psychological and pathophysiological pathways. The impact of stress in PWE is also particularly important because it is the most frequently reported seizure trigger. It is therefore crucial for clinicians to take stress-related conditions and psychiatric comorbidities into account when managing PWE and to propose clinical support to enhance self-control of stress. Screening tools have been specially designed and validated in PWE for depressive disorders and anxiety disorders (e.g. NDDI-E, GAD-7). Other instruments are useful for measuring stress-related variables (e.g. SRRS, PSS, SCS, MHLCS, DSR-15, ERP-R, QOLIE-31) in order to help characterize the individual "stress profile" and thus orientate patients towards the most appropriate treatment. Management includes both pharmacological treatment and nonpharmacological methods for enhancing self-management of stress (e.g. mindfulness-based therapies, yoga, cognitive-behavioral therapies, biofeedback), which may not only protect against psychiatric comorbidities but also reduce seizure frequency.

Plasma Brain-Derived Neurotrophic Factor and Psychopathology in Attempted Suicide

BACKGROUND/AIMS

Increasing evidence suggests a link between brain-derived neurotrophic factor (BDNF) and suicidal behaviour (SB). Furthermore, decreased peripheral BDNF levels have been associated with clinical symptoms in various psychiatric disorders as well as with personality dimensions in healthy individuals. However, the relationship between BDNF and psychopathology is poorly investigated regarding SB.

METHODS

Plasma BDNF concentrations were analysed in 61 recent suicide attempters. Clinical symptoms were evaluated using the Comprehensive Psychopathological Rating Scale. Personality dimensions were assessed using the Marke-Nyman Temperament Scale.

RESULTS

Plasma BDNF correlated positively and significantly with the personality dimension Solidity but not with the other personality dimensions or with clinical symptoms.

CONCLUSION

BDNF plays an important role in the regulation of neuroplasticity and neurogenesis in humans. Our results indicate that lower BDNF concentrations are associated with higher levels of impulsiveness and changeability (low scores on the Solidity scale). Furthermore, low plasma BDNF levels may be proposed as a trait marker rather than a state marker for attempted suicide.

Plasma BDNF levels following weight recovery in anorexia nervosa

OBJECTIVE

Preclinical studies have implicated brain-derived neurotrophic factor (BDNF) in the regulation of eating behavior and body weight. As reviewed in this report, prior studies of BDNF levels in anorexia nervosa have yielded variable results, perhaps reflecting effects of malnutrition and psychiatric comorbidity. The goal of the current report was to assess plasma BDNF as a biomarker in weight-recovered individuals with a history of anorexia nervosa (ANWR).

METHODS

Study groups included women meeting criteria for ANWR and healthy female controls. Participants were in a normal weight range, free of current major psychiatric disorder, and free of medication. Self-ratings included eating disorder symptoms, depression and anxiety. Plasma BDNF levels were measured by enzyme linked immunoassay.

RESULTS

Plasma BDNF levels were not significantly different for ANWR and control groups. Plasma BDNF levels were inversely correlated with anxiety ratings in controls (p<0.02) but not in the ANWR group.

DISCUSSION

This report provides new evidence that circulating BDNF concentrations do not differ in healthy controls and ANWR free of psychiatric comorbidity. Additionally, the data provide new information on the relationship between plasma BDNF and anxiety in these two study groups.

Role of Hypoxia-Induced Brain Derived Neurotrophic Factor in Human Pulmonary Artery Smooth Muscle

Background

Hypoxia effects on pulmonary artery structure and function are key to diseases such as pulmonary hypertension. Recent studies suggest that growth factors called neurotrophins, particularly brain-derived neurotrophic factor (BDNF), can influence lung structure and function, and their role in the pulmonary artery warrants further investigation. In this study, we examined the effect of hypoxia on BDNF in humans, and the influence of hypoxia-enhanced BDNF expression and signaling in human pulmonary artery smooth muscle cells (PASMCs).

Methods and Results

48h of 1% hypoxia enhanced BDNF and TrkB expression, as well as release of BDNF. In arteries of patients with pulmonary hypertension, BDNF expression and release was higher at baseline. In isolated PASMCs, hypoxia-induced BDNF increased intracellular Ca²⁺ responses to serotonin: an effect altered by HIF1α inhibition or by neutralization of extracellular BDNF via chimeric TrkB-Fc. Enhanced BDNF/TrkB signaling increased PASMC survival and proliferation, and decreased apoptosis following hypoxia.

Conclusions

Enhanced expression and signaling of the BDNF-TrkB system in PASMCs is a potential mechanism by which hypoxia can promote changes in pulmonary artery structure and function. Accordingly, the BDNF-TrkB system could be a key player in the pathogenesis of hypoxia-induced pulmonary vascular diseases, and thus a potential target for therapy.

Serum brain-derived neurotrophic factor level in elderly women depression: a community-based study

OBJECTIVES

Serum levels of brain-derived neurotrophic factor (BDNF) have been shown to be lower in patients with major depressive disorder (MDD) than in healthy persons. Although several studies have examined the associations between serum BDNF levels and broader categories of depression identified by psychiatrists or depressive symptoms measured with depression scales among nonpatient populations, some of these studies did not consider possible confounders and included mostly young or middle-aged subjects and nonrepresentative control subjects, such as volunteers and patients' relatives. Therefore, it remains unclear that whether MDD, broader categories of depression, or depressive symptoms in the elderly are associated with BDNF. The present study examined these associations in a community sample and controlled for confounders.

METHODS

The subjects were 538 women aged 78 to 88 years who had participated in a follow-up survey of a cohort and had scored 24 or more on the Mini-Mental State Examination. Two depression scales were administered, and, using the Structured Clinical Interview for DSM-IV, psychiatrists identified 53 persons having any mood disorder (AMD) - 8 with MDD and 45 with other types of depression according to the DSM-IV or its research criteria - and 106 healthy controls.

RESULTS

Subjects with MDD had serum BDNF levels lower than did controls but subjects with AMD did not. The severity of depressive symptoms assessed with either of the 2 depression scales was negatively correlated with serum BDNF levels in all subjects and in subjects remaining after persons with MDD or AMD were excluded. These associations were significant after controlling for possible confounders.

CONCLUSION

We have found an association between MDD and serum BDNF levels in old-old women, as has previously been found in younger patients. Although serum BDNF levels were not found to be associated with the broader category of depression, they were associated with depressive symptoms among subjects without clinical depression.

Biological correlates of tinnitus-related distress: an exploratory study

During the process of tinnitus diagnostics, various psychometric instruments are used to measure tinnitus-related distress. The aim of present work was to explore whether candidates for biological correlates of the tinnitus-related distress could be found in peripheral blood of patients and if so, whether there was association between them and psychometric scores that reflect tinnitus-related distress. The concentrations of interleukin-1β (IL1β), interleukin-6 (IL6), tumor necrosis factor-α (TNFα) and a brain-derived neutrotrophic factor (BDNF) were measured in serum of 30 patients diagnosed with chronic tinnitus and tested for correlation with psychometric scores collected on the same day. Spearman's correlation analyses detected significant positive association between the concentrations of tumor necrosis factor α and tinnitus loudness, total perceived stress, tension and depression and a negative association between tumor necrosis factor α and a psychometric score "joy". Concentrations of interleukin-1β correlated with the awareness grade of tinnitus. The correlation between visual analogue scale (VAS) "loudness" and tumor necrosis factor α as well as between "joy" and tumor necrosis factor α retained their significance (p < 0.00167) after the application of Bonferroni correction for multiple testing. Partial correlations removing the effects of age, hearing loss and the duration of tinnitus verified the results obtained using Spearman correlation. We conclude that measuring the concentrations of selected circulating cytokines could possibly become an additional objective element of tinnitus diagnostics in the future.

How cigarette smoking may increase the risk of anxiety symptoms and anxiety disorders: a critical review of biological pathways

Multiple studies have demonstrated an association between cigarette smoking and increased anxiety symptoms or disorders, with early life exposures potentially predisposing to enhanced anxiety responses in later life. Explanatory models support a potential role for neurotransmitter systems, inflammation, oxidative and nitrosative stress, mitochondrial dysfunction, neurotrophins and neurogenesis, and epigenetic effects, in anxiety pathogenesis. All of these pathways are affected by exposure to cigarette smoke components, including nicotine and free radicals. This review critically examines and summarizes the literature exploring the role of these systems in increased anxiety and how exposure to cigarette smoke may contribute to this pathology at a biological level. Further, this review explores the effects of cigarette smoke on normal neurodevelopment and anxiety control, suggesting how exposure in early life (prenatal, infancy, and adolescence) may predispose to higher anxiety in later life. A large heterogenous literature was reviewed that detailed the association between cigarette smoking and anxiety symptoms and disorders with structural brain changes, inflammation, and cell-mediated immune markers, markers of oxidative and nitrosative stress, mitochondrial function, neurotransmitter systems, neurotrophins and neurogenesis. Some preliminary data were found for potential epigenetic effects. The literature provides some support for a potential interaction between cigarette smoking, anxiety symptoms and disorders, and the above pathways; however, limitations exist particularly in delineating causative effects. The literature also provides insight into potential effects of cigarette smoke, in particular nicotine, on neurodevelopment. The potential treatment implications of these findings are discussed in regards to future therapeutic targets for anxiety. The aforementioned pathways may help mediate increased anxiety seen in people who smoke. Further research into the specific actions of nicotine and other cigarette components on these pathways, and how these pathways interact, may provide insights that lead to new treatment for anxiety and a greater understanding of anxiety pathogenesis.

Exercising the worry away: how inflammation, oxidative and nitrogen stress mediates the beneficial effect of physical activity on anxiety disorder symptoms and behaviours

Regular physical activity exerts positive effects on anxiety disorder symptoms, although the biological mechanisms underpinning this effect are incompletely understood. Numerous lines of evidence support inflammation and oxidative and nitrogen stress (O&NS) as important in the pathogenesis of mood and anxiety disorders, and physical activity is known to influence these same pathways. This paper reviews the inter-relationships between anxiety disorders, physical activity and inflammation and O&NS, to explore whether modulation of inflammation and O&NS may in part underpin the positive effect of physical activity on anxiety disorders. Numerous studies support the notion that physical activity operates as an anti-inflammatory and anti-O&NS agent which potentially exerts positive effects on neuroplasticity, the expression of neurotrophins and normal neuronal functions. These effects may therefore influence the expression and evolution of anxiety disorders. Further exploration of this area may elicit a deeper understanding of the pathogenesis of anxiety disorders, and inform the development of integrated programmes including PA specifically suited to the treatment and prevention of anxiety disorders and symptoms.