Plasma concentrations but not serum concentrations of brain-derived neurotrophic factor are related to pro-inflammatory cytokines in patients undergoing major abdominal surgery

Short communication: Serum levels of brain-derived neurotrophic factor and association with pro-inflammatory cytokines in acute and recovered anorexia nervosa

Brain-derived neurotrophic factor (BDNF) is a neuroprotective molecule known to be involved in neuroplasticity, learning and memory. Additionally, it may mitigate the effects of inflammation on the brain. There is inconclusive evidence as to whether reductions in BDNF found in AN are related to features associated with the illness such as changes in inflammatory markers and comorbidities, and whether they persist after recovery. This cross-sectional study measured BDNF and 36 inflammatory markers in the serum of individuals recovered from AN (rec-AN; n = 24), with acute AN (n = 56), and healthy controls (n = 51). We (a) compared BDNF concentrations between AN, rec-AN and controls including four pre-determined covariates; (b) assessed the relationship between BDNF and body mass index, eating disorder (ED) psychopathology and depression; and (c) correlated BDNF with inflammatory markers, stratified by group. The AN group showed reductions in BDNF compared to controls and rec-AN. BDNF was negatively associated with depression and ED psychopathology in the whole sample, but not the AN sample. BDNF was positively correlated with three inflammatory markers in the control group (interleukin (IL)-8, Eotaxin-3, tumor necrosis factor (TNF)-α) and negatively correlated with one (IL-16). The only pro-inflammatory marker associated with BDNF in the AN group was TNF-α, and no pro-inflammatory markers were associated with BDNF in the rec-AN group. These results indicate that BDNF serum concentrations may be a state marker of AN. In people with acute AN, BDNF levels seem to be linked to TNF-α signalling. However, BDNF concentrations do not appear to reflect AN symptom severity.

Plasma levels of myokines and inflammatory markers are related with functional and respiratory performance in older adults with COPD and sarcopenia

This study investigated whether blood-based biomarkers were related to functional test performance and respiratory muscle strength in older adults with COPD and sarcopenia. The participants included in this cross-sectional study were from both sexes and sixty years or older. Based on clinical assessment, participants were categorized in COPD (n = 43) and non-COPD (NCOPD) (n = 43) groups. They were also assessed for body composition and muscular mass by dual-energy X-ray absorptiometry, using the relative skeletal muscle index for the diagnosis of sarcopenia. A series of functional tests, including short physical performance battery (SPPB), 6-minute walking test (6MWT), maximal inspiratory and expiratory pressures (MIP and MEP), were carried out. Plasma levels of myokines (Irisin and BDNF), and soluble TNF receptors (sTNFR1 and sTNFR2) were determined by ELISA. In the multivariate analysis, 6MWD was associated with age, COPD-related sarcopenia and BDNF (R² = 0.29; f² = 0.41). SPPB score was associated with COPD-related sarcopenia and sTNFR1 (R² = 0.25; f² = 0.33). MIP value was associated with sex, COPD-related sarcopenia, sTNFR2 and Irisin (R² = 0.24; f² = 0.31). Finally, MEP value was associated with sex COPD-related sarcopenia (R² = 0.18; f² = 0.22). Plasma levels of myokines and inflammatory markers are related with functional and respiratory performance in older adults with COPD and sarcopenia.

Effects of long-term administration of Lactobacillus reuteri DSM-17938 on circulating levels of 5-HT and BDNF in adults with functional constipation

Accumulated evidence shows that some probiotic strains ameliorate functional constipation (FC) via the modulation of specific gastrointestinal peptide pathways. The aims of this study were to investigate: (1) the effects of long-term administration of Lactobacillus reuteri (LR) DSM 17938 on the serum levels of serotonin (5-HT) and brain-derived neurotrophic factor (BDNF); (2) the possible link between 5-HT, BDNF, and specific constipation-related symptoms; (3) whether genetic variability at the 5-HTT gene-linked polymorphic region (5-HTTLPR) and BDNF Val66Met loci could be associated with serum 5-HT and BDNF variations. LR DSM 17938 was administered to 56 FC patients for 105 days in a randomised, double-blind manner. The fasting blood samples were collected during the randomisation visit (V₁), at day 15 (induction period, V₂), day 60 (intermediate evaluation, V₃), and day 105 (V₄) and the Constipaq questionnaire (the sum of Constipation Scoring System (CSS) and patient assessment constipation quality of life (PAC-QoL)) was administered. A group of healthy subjects was enrolled as controls (HC). At V1, the mean serum 5-HT level in the whole patient group was significantly higher (P=0.027) than in HC subjects, while serum BDNF did not. At the end of probiotic administration (V4), 5-HT and BDNF levels were significantly lower than the initial values (V1) (P=0.008 and P=0.015, respectively). 5-HT and BDNF serum concentration were significantly associated (r=0.355; P=0.007). Neither 5-HT nor BDNF serum levels correlated with the CSS item scores and with the PAC-QoL. Lastly, the regression analysis demonstrated that the presence of the S allele of the 5-HTTLPR accounted for the reduction in the 5-HT concentration at V4. In conclusion, the long-term administration of LR DSM 17938 demonstrated that such a probiotic strain could improve FC by affecting 5-HT and BDNF serum concentrations.

The impact of plasma brain-derived neurotrophic factor concentration and weight gain after kidney transplantation

Obesity and its related complications continue to be significant challenges for kidney transplant recipients. In previous studies, researchers have reported that brain-derived neurotrophic factor (BDNF) is closely associated with metabolic imbalance and obesity, but the role of BDNF in weight gain after kidney transplant has not been elucidated. The purpose of this pilot study was to explore the relationship between plasma BDNF levels and weight change. We examined associations between plasma BDNF levels measured at transplantation and 12 months later and measures of weight change during these 12 months in a sample of 55 kidney recipients (mean age of 48 years, 60% male, 56% African American). Of the 55 recipients, 49 had BDNF levels measured at baseline, 33 had BDNF levels measured at 12 months, and 27 had BDNF levels measured at both time points. We found that plasma BDNF levels at baseline (n = 49), but not at 12 months (n = 33), were significantly and positively correlated with the body mass index change (p = 0.037) and percentage weight change (p = 0.036). In addition, average plasma BDNF value at 12 months (307 ± 254 pg/ml) was significantly lower than at baseline (452 ± 345 pg/ml) in the 27 recipients with BDNF levels measured at both time points. Findings from this pilot work suggest that BDNF might serve as a regulator of weight change for kidney transplant related obesity.

Peripheral Blood Brain-Derived Neurotrophic Factor as a Biomarker of Alzheimer's Disease: Are There Methodological Biases?

Mounting evidence that alterations in brain-derived neurotrophic factor (BDNF) levels and signaling may be involved in the etiopathogenesis of Alzheimer's disease (AD) has suggested that its blood levels could be used as a biomarker of the disease. However, higher, lower, or unchanged circulating BDNF levels have all been described in AD patients compared to healthy controls. Although the reasons for such different findings are unclear, methodological issues are likely to be involved. The heterogeneity of participant recruitment criteria and the lack of control of variables that influence circulating BDNF levels regardless of dementia (depressive symptoms, medications, lifestyle, lack of overlap between serum and plasma, and experimental aspects) are likely to bias result and prevent study comparability. The present work reviews a broad panel of factors, whose close control could help reduce the inconsistency of study findings, and offers practical advice on their management. Research directed at elucidating the weight of each of these variables and at standardizing analytical methodologies is urgently needed.

Plasma BDNF Level in Major Depression: Biomarker of the Val66Met BDNF Polymorphism and of the Clinical Course in Met Carrier Patients

AIMS

Despite the involvement of the brain-derived neurotrophic factor (BDNF) in the physiopathology of major depressive disorder (MDD), the coherence between the components of the BDNF pathway and their link with the clinical features of MDD are insufficiently studied. We aimed to assess in Caucasian depressed patients the impact of the BDNF Val66Met polymorphism on plasma BDNF levels taking into account the clinical characteristics of MDD.

METHODS

A total of 328 Caucasian adult MDD patients with a current major depressive episode (MDE) were assessed for the BDNF Val66Met polymorphism, plasma BDNF levels and clinical characteristics of the MDD.

RESULTS

Plasma BDNF levels were linearly associated with the BDNF Val66Met genotypes (ValVal: 1,525.9 ± 1,183.3 pg/mL vs. ValMet: 1,248.7 ± 1,081.8 vs. MetMet: 1,004.9 ± 952.8; p = 0.04), Met carriers having lower BDNF levels than ValVal ones. Significant interactions between the Val66Met polymorphism and 3 clinical characteristics - age at onset (p = 0.03), MDD duration (p = 0.04), and number of previous MDE (p = 0.04) - were evidenced for plasma BDNF levels. Indeed, in Met carriers, but not in ValVal ones, plasma BDNF levels were negatively correlated with age at onset and positively correlated with MDD duration and number of previous MDE.

CONCLUSION

Our results show a measurable, coherent, and functional BDNF pathway based on the BDNF Val66Met polymorphism and plasma BDNF levels in patients with a current MDE. This pathway is related to the clinical course of major depression, plasma BDNF levels being associated with the long-term history of MDD in Met carriers. Further studies assessing central BDNF are needed to understand the underlying mechanisms of this association.

Brain-derived neurotrophic factor: a mediator of inflammation-associated neurogenesis in Alzheimer's disease

In early- or late-onset Alzheimer's disease (AD), inflammation, which is triggered by pathologic conditions, influences the progression of neurodegeneration. Brain-derived neurotrophic factor (BDNF) has emerged as a crucial mediator of neurogenesis, because it exhibits a remarkable activity-dependent regulation of expression, which suggests that it may link inflammation to neurogenesis. Emerging evidence suggests that acute and chronic inflammation in AD differentially modulates neurotrophin functions, which are related to the roles of inflammation in neuroprotection and neurodegeneration. Recent studies also indicate novel mechanisms of BDNF-mediated neuroprotection, including the modulation of autophagy. Numerous research studies have demonstrated reverse parallel alterations between proinflammatory cytokines and BDNF during neurodegeneration; thus, we hypothesize that one mechanism that underlies the negative impact of chronic inflammation on neurogenesis is the reduction of BDNF production and function by proinflammatory cytokines.

Clinical outcomes after craniotomy for unruptured intracranial aneurysm in patients with coronary artery disease

BACKGROUND

Coronary artery disease (CAD) patients receiving antiplatelet agents occasionally undergo craniotomy. We aimed to clarify clinical outcomes after craniotomy for unruptured intracranial aneurysm (UIA) in patients with CAD. We also aimed to identify the possible predictive factors for morbidity and surgical complications in patients on antiplatelet treatment.

METHODS

We retrospectively analyzed 401 consecutive patients who had undergone craniotomy for UIA at our institution between January 2006 and December 2016. Forty-three patients (10.7%) received antiplatelet agents during the perioperative period. The underlying reasons for antiplatelet treatment were CAD in 12 patients and other diseases in 31 patients.

RESULTS

Severe morbidity and intracranial hemorrhage occurred more commonly and symptomatic brain infarction occurred less frequently in patients with CAD compared to patients with other underlying diseases (16.7% versus 3.2%, 16.7% versus 9.7%, and 8.3% versus 16.1%, respectively), though differences between the two groups were not significant. Univariate analysis revealed that a low preoperative baseline platelet count was significantly correlated with the occurrence of intracranial hemorrhage (cutoff value, 16.5×10⁴/µL; odds ratio (OR), 46.67; 95% confidence interval (CI), 3.88-561.95; p=0.0005), and a high baseline platelet count tended to correlate with severe morbidity (cutoff value, 29.8×10⁴/µL; OR, 11.33; 95% CI, 0.88-145.52; p=0.0550).

CONCLUSIONS

Our results suggest that surgical complications and clinical outcomes after craniotomy may depend on the underlying reason for antiplatelet treatment. Moreover, a preoperative platelet count can be useful in predicting the occurrence of intracranial hemorrhage and severe morbidity after craniotomy in patients receiving antiplatelet agents.

Stability of BDNF in Human Samples Stored Up to 6 Months and Correlations of Serum and EDTA-Plasma Concentrations

Brain-derived neurotrophic factor (BDNF), an important neural growth factor, has gained growing interest in neuroscience, but many influencing physiological and analytical aspects still remain unclear. In this study we assessed the impact of storage time at room temperature, repeated freeze/thaw cycles, and storage at −80 °C up to 6 months on serum and ethylenediaminetetraacetic acid (EDTA)-plasma BDNF. Furthermore, we assessed correlations of serum and plasma BDNF concentrations in two independent sets of samples. Coefficients of variations (CVs) for serum BDNF concentrations were significantly lower than CVs of plasma concentrations (n = 245, p = 0.006). Mean serum and plasma concentrations at all analyzed time points remained within the acceptable change limit of the inter-assay precision as declared by the manufacturer. Serum and plasma BDNF concentrations correlated positively in both sets of samples and at all analyzed time points of the stability assessment (r = 0.455 to r_s = 0.596; p < 0.004). In summary, when considering the acceptable change limit, BDNF was stable in serum and in EDTA-plasma up to 6 months. Due to a higher reliability, we suggest favoring serum over EDTA-plasma for future experiments assessing peripheral BDNF concentrations.

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.

Are the changes in the peripheral brain-derived neurotrophic factor levels due to platelet activation?

Brain-derived neurotrophic factor (BDNF) plays an important role in central nervous system development, neurogenesis and neuronal plasticity. BDNF is also expressed in several non-neuronal tissues, and it could play an important role in other processes, such as cancer, angiogenesis, etc. Platelets are the major source of peripheral BDNF. However, platelets also contain high amounts of serotonin; they express specific surface receptors during activation, and a multitude of pro-inflammatory and immunomodulatory bioactive compounds are secreted from the granules. Until recently, there was insufficient knowledge regarding the relationship between BDNF and platelets. Recent studies showed that BDNF is present in two distinct pools in platelets, in α-granules and in the cytoplasm, and only the BDNF in the granules is secreted following stimulation, representing 30% of the total BDNF in platelets. BDNF has an important role in the pathophysiology of depression. Low levels of serum BDNF have been described in patients with major depressive disorder, and BDNF levels increased with chronic antidepressant treatment. Interestingly, there is an association between depression and platelet function. This review analyzed studies that evaluated the relationship between BDNF and platelet activation and the effect of treatments on both parameters. Only a few studies consider this possible confounding factor, and it could be very important in diseases such as depression, which show changes in both parameters.

May BDNF Be Implicated in the Exercise-Mediated Regulation of Inflammation? Critical Review and Synthesis of Evidence

Introduction:

Exercise attenuates inflammation and enhances levels of brain-derived neurotrophic factor (BDNF). Exercise also enhances parasympathetic tone, although its role in activating the cholinergic anti-inflammatory pathway is unclear. The physiological pathways of exercise’s effect on inflammation are obscure.

Aims:

To critically review the evidence on the role of BDNF in the anti-inflammatory effects of exercise and its potential involvement in the cholinergic anti-inflammatory pathway.

Methods:

Critical literature review of studies published in MEDLINE, PubMed, CINAHL, Embase, and Cochrane databases.

Results:

BDNF is critically involved in the bidirectional signaling between immune and neurosensory cells and in the regulation of parasympathetic system responses. BDNF is also intricately involved in the inflammatory response: inflammation induces BDNF production, and, in turn, BDNF exerts pro- and/or anti-inflammatory effects. Although exercise modulates BDNF and its receptors in lymphocytes, data on BDNF’s immunoregulatory/anti-inflammatory effects in relation to exercise are scarce. Moreover, BDNF increases cholinergic activity and is modulated by parasympathetic system activation. However, its involvement in the cholinergic anti-inflammatory pathway has not been investigated.

Conclusion:

Converging lines of evidence implicate BDNF in exercise-mediated regulation of inflammation; however, data are insufficient to draw concrete conclusions. We suggest that there is a need to investigate BDNF as a potential modulator/mediator of the anti-inflammatory effects of exercise and of the cholinergic anti-inflammatory pathway during exercise. Such research would have implications for a wide range of inflammatory diseases and for planning targeted exercise protocols.

Strength training reduces circulating interleukin-6 but not brain-derived neurotrophic factor in community-dwelling elderly individuals

Ageing is associated with a chronic low-grade inflammatory profile (CLIP). Physical exercise could circumvent the deleterious effects of CLIP by influencing circulating inflammatory mediators and neurotrophic growth factors. This study aimed at assessing whether 12 weeks of progressive strength training (PST) influences circulating brain-derived neurotrophic factor (BDNF), interleukin (IL)-6 and IL-10 in elderly individuals. Forty community-dwelling persons aged 62-72 years participated. Twenty participants were assigned to 12-week PST (70-80 % of maximal strength, three times per week). Matched control individuals (n = 20) maintained daily activity levels. Serum was collected for BDNF, IL-6 and IL-10 assay from all participants before and after 12 weeks (for PST subjects 24-48 h after the last training). In PST, muscle strength was significantly improved (+49 % for leg extension, p = 0.039), and basal IL-6 levels significantly reduced (p = 0.001), which remained unchanged in control (p = 0.117). No significant change in BDNF was observed in PST subjects (p = 0.147) or control (p = 0.563). IL-10 was below the detection limit in most subjects. Gender and health status did not influence the results. Our results show that after 12-week PST, muscle performance improved significantly, and basal levels of IL-6 were significantly decreased in older subjects. However, serum BDNF was not altered. The lack of an observable change in BDNF might be due to a short-lived BDNF response, occurring acutely following exercise, which might have been washed out when sampling. Furthermore, blood levels of BDNF may not reflect parallel increases that occur locally in the brain and muscle. These hypotheses need confirmation by further studies.

Depression, 5HTTLPR and BDNF Val66Met polymorphisms, and plasma BDNF levels in hemodialysis patients with chronic renal failure

OBJECTIVE

Depression is the most prevalent comorbid psychiatric disease among hemodialysis patients with end-stage renal disease. This cross-sectional study investigated whether depression in hemodialysis patients is associated with the polymorphism of the 5' flanking transcriptional region (5-HTTLPR) of the serotonin transporter gene, the valine (Val)-to-methionine (Met) substitution at codon 66 (Val66Met) polymorphism of the brain-derived neurotrophic factor (BDNF) gene, or plasma BDNF levels.

METHODS

A total of 188 participants (mean age: 58.5±14.0 years; 89 men and 99 women) receiving hemodialysis at the Chang Gung Memorial Hospital were recruited. The diagnosis of major depressive disorder (MDD) was confirmed using the Chinese version of the Mini International Neuropsychiatric Interview. The genotypes of 5-HTTLPR and BDNF Val66Met were conducted using polymerase chain reactions plus restriction fragment length polymorphism analysis. The plasma BDNF levels were measured using an enzyme-linked immunosorbent assay kit.

RESULTS

Forty-five (23.9%) patients fulfilled the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV-TR) criteria for a MDD. There were no significant effects of the 5-HTTLPR or BDNF Val66Met gene polymorphism on MDD among the hemodialysis patients. The plasma BDNF levels correlated significantly with age (P=0.003) and sex (P=0.047) but not with depression, the genotypes of 5-HTTLPR and BDNF Val66Met, the current antidepressant treatment, or the duration under hemodialysis.

CONCLUSION

Our results did not support the hypothesis of an involvement of the 5HTTLPR and BDNF Val66Met genotypes, or plasma BDNF levels in the pathogenesis of depression, in patients receiving hemodialysis. A study with a large sample size and homogenous patient group is warranted to confirm these findings.