Stage-dependent BDNF serum concentrations in Alzheimer’s disease

Effect of Daily Intake of Green Tea Catechins on Cognitive Function in Middle-Aged and Older Subjects: A Randomized, Placebo-Controlled Study

Epidemiological studies in Japan, including the Nakajima study and the Tsurugaya study, have indicated that green tea consumption may improve cognitive impairment. Catechins, which are typical polyphenols contained in green tea, have been reported to have antioxidative, anti-inflammatory, and neuroprotective effects. However, their impact on human cognitive function remains unclear. Therefore, we performed a double-blind, randomized, controlled study to investigate the effect of 336.4 mg of decaffeinated green tea catechins (GTC) on cognitive function after a single dose and after 12 weeks of daily intake. This study included Japanese adults between the ages of 50 and 69 years with a Mini-Mental State Examination Japanese version score of >24 and self-assessed cognitive decline. The Cognitrax testing battery was used to evaluate cognitive function. The incorrect response rate on the Continuous Performance Test significantly decreased after a single dose of GTC. After 12 weeks of daily GTC intake, the response time for Part 4 of the 4-part Continuous Performance Test, which is a two-back test, was shortened. These results suggest that daily intake of GTC might have beneficial effects on working memory.

Plasma BDNF Levels Following Transcranial Direct Current Stimulation Allow Prediction of Synaptic Plasticity and Memory Deficits in 3×Tg-AD Mice

Early diagnosis of Alzheimer’s disease (AD) supposedly increases the effectiveness of therapeutic interventions. However, presently available diagnostic procedures are either invasive or require complex and expensive technologies, which cannot be applied at a larger scale to screen populations at risk of AD. We were looking for a biomarker allowing to unveil a dysfunction of molecular mechanisms, which underly synaptic plasticity and memory, before the AD phenotype is manifested and investigated the effects of transcranial direct current stimulation (tDCS) in 3×Tg-AD mice, an experimental model of AD which does not exhibit any long-term potentiation (LTP) and memory deficits at the age of 3 months (3×Tg-AD-3M). Our results demonstrated that tDCS differentially affected 3×Tg-AD-3M and age-matched wild-type (WT) mice. While tDCS increased LTP at CA3-CA1 synapses and memory in WT mice, it failed to elicit these effects in 3×Tg-AD-3M mice. Remarkably, 3×Tg-AD-3M mice did not show the tDCS-dependent increases in pCREB^Ser133 and pCaMKII^Thr286, which were found in WT mice. Of relevance, tDCS induced a significant increase of plasma BDNF levels in WT mice, which was not found in 3×Tg-AD-3M mice. Collectively, our results showed that plasticity mechanisms are resistant to tDCS effects in the pre-AD stage. In particular, the lack of BDNF responsiveness to tDCS in 3×Tg-AD-3M mice suggests that combining tDCS with dosages of plasma BDNF levels may provide an easy-to-detect and low-cost biomarker of covert impairment of synaptic plasticity mechanisms underlying memory, which could be clinically applicable. Testing proposed here might be useful to identify AD in its preclinical stage, allowing timely and, hopefully, more effective disease-modifying interventions.

The role of CREB and BDNF in neurobiology and treatment of Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia worldwide. β-amyloid peptide (Aβ) is currently assumed to be the main cause of synaptic dysfunction and cognitive impairments in AD, but the molecular signaling pathways underlying its neurotoxic consequences have not yet been completely explored. Additional investigations regarding these pathways will contribute to development of new therapeutic targets. In context, developing evidence suggest that Aβ decreases brain-derived neurotrophic factor (BDNF) mostly by lowering phosphorylated cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) protein. In fact, it has been observed that brain or serum levels of BDNF appear to be beneficial markers for cognitive condition. In addition, the participation of transcription mediated by CREB has been widely analyzed in the memory process and AD development. Designing pharmacologic or genetic therapeutic approaches based on the targeting of CREB-BDNF signaling could be a promising treatment potential for AD. In this review, we summarize data demonstrating the role of CREB-BDNF signaling pathway in cognitive status and mediation of Aβ toxicity in AD. Finally, we also focus on the developing intervention methods for improvement of cognitive decline in AD based on targeting of CREB-BDNF pathway.

A narrative review of brain-derived neurotrophic factor (BDNF) on cognitive performance in Alzheimer's disease

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that is highly expressed in the brain. It influences neuronal survival, growth and acts as a control centre for neurotransmitters. It also plays a crucial role in learning and memory. Current evidence indicates that BDNF may be a possible neurotrophic factor that controls cognitive functions under normal and neuropathological conditions. Recent findings indicate a reduction in cognitive performance in individuals with Alzheimer's disease (AD). This relationship between cognitive performance and AD is important for investigating both the time they overlap and the pathophysiological mechanism in each case. Therefore, this study reviewed the existing knowledge about BDNF and cognitive performance in the AD population. The findings support the idea that this tropic factor may be a potential biomarker for evaluating the changes in cognitive performance in AD.

Muscle BDNF improves synaptic and contractile muscle strength in Kennedy's disease mice in a muscle-type specific manner

KEY POINTS

Muscle-derived neurotrophic factors may offer therapeutic promise for treating neuromuscular diseases. We report that a muscle-derived neurotrophic factor, BDNF, rescues synaptic and muscle function in a muscle-type specific manner in mice modelling Kennedy's disease (KD). We also find that BDNF rescues select molecular mechanisms in slow and fast muscle that may underlie the improved cellular function. We also report for the first time that expression of BDNF, but not other members of the neurotrophin family, is perturbed in muscle from patients with KD. Given that muscle BDNF had divergent therapeutic effects that depended on muscle type, a combination of neurotrophic factors may optimally rescue neuromuscular function via effects on both pre- and postsynaptic function, in the face of disease.

ABSTRACT

Deficits in muscle brain-derived neurotrophic factor (BDNF) correlate with neuromuscular deficits in mouse models of Kennedy's disease (KD), suggesting that restoring muscle BDNF might restore function. To test this possibility, transgenic mice expressing human BDNF in skeletal muscle were crossed with '97Q' KD mice. We found that muscle BDNF slowed disease, doubling the time between symptom onset and endstage. BDNF also improved expression of genes in muscle known to play key roles in neuromuscular function, including counteracting the expression of neonatal isoforms induced by disease. Intriguingly, BDNF's ameliorative effects differed between muscle types: synaptic strength was rescued only in slow-twitch muscle, while contractile strength was improved only in fast-twitch muscle. In sum, muscle BDNF slows disease progression, rescuing select cellular and molecular mechanisms that depend on fibre type. Muscle BDNF expression was also affected in KD patients, reinforcing its translational and therapeutic potential for treating this disorder.

Is Blood Brain-Derived Neurotrophic Factor a Useful Biomarker to Monitor Mild Cognitive Impairment Patients?

Availability of reliable prognostic biomarkers that are also able to monitor preventive/therapeutic interventions in patients with mild cognitive impairment (MCI) is crucial. Cerebral brain-derived neurotrophic factor (BDNF) alterations were evidenced in Alzheimer's disease, but the value of blood BDNF in MCI is unclear, especially because of the incomplete/incorrect management of the numerous confounding factors unrelated to the disease. This study, applying a multidisciplinary methodological approach, aimed at clarifying whether blood BDNF can really mirror the cognitive symptoms of MCI, thus supporting the evaluation of clinical protocols' effectiveness as well as the definition of the conversion rate to dementia. Healthy elderly subjects (HE) and MCI patients were assessed for sociodemographic, neuropsychological, pharmacological, and lifestyle data, and plasma BDNF was measured (baseline); then, in the MCI cohort, the biomarker was tested in a comprehensive cognitive stimulation intervention (CS) as well as in a 2-year follow-up period. Plasma BDNF, cleansed from all the interfering factors, (1) did not discriminate HE and MCI patients; (2) in MCI patients reflected mood, social engagement, and subjective memory complaints but not cognition; (3) changed due to CS, although with no correlations to cognitive performances; and (4) predicted no functional deterioration. Our data indicate that the possible biased use of plasma BDNF in MCI is critically risky.

Serum pro-BDNF levels correlate with phospho-tau staining in Alzheimer's disease

Disruption of brain-derived neurotrophic factor (BDNF) biosynthesis and/or signaling has been implicated in the pathogenesis of Alzheimer's disease (AD). We used postmortem brain and fluid samples from 20 patients with variable severity of AD and 11 controls to investigate whether BDNF levels in serum and brain tissue correlated with hippocampal pathology. Total BDNF, precursor BDNF (pro-BDNF), and mature BDNF were measured in cerebrospinal fluid, serum, and 3 postmortem brain regions. Histological markers for AD pathology, the BDNF cognate receptor (TrkB), and glia were measured in the hippocampus (HIP). Lower pro-BDNF levels were observed in the entorhinal and frontal cortices in AD cases compared with controls. AD cases also exhibited significantly lower staining densities of the cognate BDNF receptor TrkB in the HIP compared with controls, and TrkB staining was inversely correlated with both Amylo-Glo and pTau staining in the same region, suggesting a relationship between the density of the cognate BDNF receptor and accumulation of AD pathology. In addition, higher serum pro-BDNF levels correlated with lower HIP pro-BDNF levels and higher pTau staining in the HIP. Total BDNF levels in cortical regions were also negatively correlated with Amylo-Glo staining in the HIP suggesting that reduced BDNF cortical levels might influence hippocampal amyloid accumulation. These results strongly suggest that altered BDNF and TrkB receptors are involved in AD pathology and therefore warrant investigations into therapies involving the BDNF pathway.

Phenotypes of Sarcopenic Obesity: Exploring the Effects on Peri-Muscular Fat, the Obesity Paradox, Hormone-Related Responses and the Clinical Implications

Sarcopenic obesity combines the words sarcopenia and obesity. This definition of obesity should be better differentiated between visceral and subcutaneous fat phenotypes. For this reason, this review lays the foundation for defining the subcutaneous and the visceral fat into the context of sarcopenia. Thus, the review aims to explore the missing links on pathogenesis of visceral fat and its relationship on age: defining the peri-muscular fat as a new entity and the subcutaneous fat as a first factor that leads to the obesity paradox. Last but not least, this review underlines and motivates the mechanisms of the hormonal responses and anti-inflammatory adipokines responsible for the clinical implications of sarcopenic visceral obesity, describing factor by factor the multiple axis between the visceral fat-sarcopenia and all mortality outcomes linked to cancer, diabetes, cardiovascular diseases, cirrhosis, polycystic ovary, disability and postoperative complications.

Gut Microbiota in Neurological Disorders

The incidence of neurological disorders such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD) is increasing throughout the world, but their pathogenesis remains unclear and successful treatment remains elusive. Bidirectional communications between the central nervous system and gut microbiota may play some role in the pathogenesis of the above disorders. Up to a thousand bacterial species reside in human intestine; they colonize the gut shortly after birth and remain for life. Numerous studies point to the role of microbiota composition in the development, course and treatment of MS, AD and PD.

Ratio of plasma BDNF to leptin levels are associated with treatment response in major depressive disorder but not in panic disorder: A 12-week follow-up study

BACKGROUND

A link between brain-derived neurotrophic factor (BDNF) expression and the mood regulatory effect of leptin has been suggested in the pathophysiology of major depressive disorder (MDD). We investigated treatment response and pre-treatment leptin and BDNF in patients with MDD and with panic disorder (PD).

METHODS

We recruited 41 patients with MDD, 52 patients with PD, and 59 matched healthy controls. All subjects completed five visits (at baseline, 2, 4, 8, and 12 weeks), and both MDD and PD patients were treated with standard pharmacotherapy for 12 weeks. Plasma BDNF (pBDNF) and blood leptin levels were obtained along with a 17-item Hamilton Depression Scale rating (HDRS-17) score at every visit.

RESULTS

The ratio of pre-treatment pBDNF to leptin was significantly lower in patients with MDD and PD compared to healthy controls (p = 0.024), but was not associated with severity of depressive or anxiety symptoms. Pre-treatment pBDNF:leptin ratio was significantly higher in treatment responders than in non-responders (p = 0.012) in MDD but not in PD. This difference was larger in MDD patients with appetite loss (p = 0.034). In multivariate analysis, pre-treatment pBDNF:leptin ratio was significantly associated with treatment responsiveness (Adjusted Odds Ration [AOR] = 2.50, 95% CI 1.02-6.14) in MDD.

LIMITATION

small sample size; limited information on detailed pharmacological effects.

CONCLUSIONS

A relatively higher ratio of pre-treatment pBDNF to leptin was associated with greater treatment response in MDD but not in PD. Further research should focus on exploration of a link between BDNF and leptin underlying neuronal plasticity in depression.

Recent Issues on Body Composition Imaging for Sarcopenia Evaluation

Recently, sarcopenia has garnered renewed interest. Sarcopenia is a disease characterized by decreased skeletal muscle mass and strength/function, which can impair the quality of life and increase physical disability, adverse metabolic effects, and mortality. Imaging tools for evaluating and diagnosing sarcopenia have developed rapidly. Radiologists should be aware of sarcopenia and its clinical implications. We review current knowledge about sarcopenia, its pathophysiological impact, and advantages and disadvantages of methods for evaluation of sarcopenia focusing on body composition imaging modalities such as whole-body dual-energy X-ray absorptiometry, CT, and MRI. Controversial issues are discussed, including the lack of consensus and standardization of the disease definition, imaging modality, measurement methods, and diagnostic cutoff points.

Accelerated Ovarian Failure as a Unique Model to Study Peri-Menopause Influence on Alzheimer's Disease

Despite decades of extensive research efforts, efficacious therapies for Alzheimer's disease (AD) are lacking. The multi-factorial nature of AD neuropathology and symptomatology has taught us that a single therapeutic approach will most likely not fit all. Women constitute ~70% of the affected AD population, and pathology and rate of symptoms progression are 2-3 times higher in women than men. Epidemiological data suggest that menopausal estrogen loss may be causative of the more severe symptoms observed in AD women, however, results from clinical trials employing estrogen replacement therapy are inconsistent. AD pathological hallmarks-amyloid β (Aβ), neurofibrillary tangles (NFTs), and chronic gliosis-are laid down during a 20-year prodromal period before clinical symptoms appear, which coincides with the menopause transition (peri-menopause) in women (~45-54-years-old). Peri-menopause is marked by widely fluctuating estrogen levels resulting in periods of irregular hormone-receptor interactions. Recent studies showed that peri-menopausal women have increased indicators of AD phenotype (brain Aβ deposition and hypometabolism), and peri-menopausal women who used hormone replacement therapy (HRT) had a reduced AD risk. This suggests that neuroendocrine changes during peri-menopause may be a trigger that increases risk of AD in women. Studies on sex differences have been performed in several AD rodent models over the years. However, it has been challenging to study the menopause influence on AD due to lack of optimal models that mimic the human process. Recently, the rodent model of accelerated ovarian failure (AOF) was developed, which uniquely recapitulates human menopause, including a transitional peri-AOF period with irregular estrogen fluctuations and a post-AOF stage with low estrogen levels. This model has proven useful in hypertension and cognition studies with wild type animals. This review article will highlight the molecular mechanisms by which peri-menopause may influence the female brain vulnerability to AD and AD risk factors, such as hypertension and apolipoprotein E (APOE) genotype. Studies on these biological mechanisms together with the use of the AOF model have the potential to shed light on key molecular pathways underlying AD pathogenesis for the development of precision medicine approaches that take sex and hormonal status into account.

Plasma brain-derived neurotrophic factor (pBDNF) and executive dysfunctions in patients with major depressive disorder

Objectives: Executive dysfunctions are frequently seen in patients with major depressive disorder (MDD) and normalise in many cases during effective antidepressant therapy. This study investigated whether a normalisation of executive dysfunctions during antidepressant treatment correlates with or can be predicted by clinical parameters or levels of brain-derived neurotrophic factor (BDNF).Methods: In 110 MDD patients with executive dysfunctions (percentile <16), executive functions and plasma BDNF levels were analysed at baseline, and days 14 and 56 of an antidepressant treatment. BDNF exon IV and P11 methylation status was studied at baseline.Results: Eighty patients (73%) experienced a normalisation of executive dysfunctions, while 30 (27%) suffered from persistent dysfunctions until day 56. Patients with persistent dysfunctions had significantly higher HAMD scores at days 14 and 56, and lower plasma BDNF levels at each time point than patients with a normalisation of dysfunctions (F₁= 10.18; P = 0.002). This was seen for verbal fluency, but not processing speed. BDNF exon IV and p11 promoter methylation was not associated with test performance.Conclusions: Our results corroborate a concomitant amelioration of executive dysfunctions with successful antidepressant therapy and support a role of BDNF in the neural mechanisms underlying the normalisation of executive dysfunctions in MDD.ClinicalTrials.gov number: NCT00974155; EudraCT: 2008-008280-96.

Brain-Derived Neurotrophic Factor: A Key Molecule for Memory in the Healthy and the Pathological Brain

Brain Derived Neurotrophic Factor (BDNF) is a key molecule involved in plastic changes related to learning and memory. The expression of BDNF is highly regulated, and can lead to great variability in BDNF levels in healthy subjects. Changes in BDNF expression are associated with both normal and pathological aging and also psychiatric disease, in particular in structures important for memory processes such as the hippocampus and parahippocampal areas. Some interventions like exercise or antidepressant administration enhance the expression of BDNF in normal and pathological conditions. In this review, we will describe studies from rodents and humans to bring together research on how BDNF expression is regulated, how this expression changes in the pathological brain and also exciting work on how interventions known to enhance this neurotrophin could have clinical relevance. We propose that, although BDNF may not be a valid biomarker for neurodegenerative/neuropsychiatric diseases because of its disregulation common to many pathological conditions, it could be thought of as a marker that specifically relates to the occurrence and/or progression of the mnemonic symptoms that are common to many pathological conditions.

Habitual sugar intake and cognitive impairment among multi-ethnic Malaysian older adults

Background: Sugar is widely consumed in Malaysia, and the excessive intake of sugar has been associated with cognitive functions. However, the association between sugar intake and cognitive impairment among Malaysian older adults is yet to be determined.

Purpose: The objective of this study was to evaluate the associations between types and sources of sugar intake and cognitive functions and to identify their risk in predicting cognitive impairment (MMSE score <24).

Subjects and methods: A total of 1,209 subjects aged ≥60 years were recruited through multi-stage random sampling from selected states in Malaysia. Dietary intake was derived using a 7-day dietary history questionnaire and supplemented with a quantitative food frequency questionnaire for added sugar intake.

Results: The prevalence of cognitive impairment as defined by Mini-Mental State Examination (MMSE) less than 24 was 31.9%, while the prevalence of mild cognitive impairment was 13.1%. The median (IQR) for total sugar intake was 44.60 g/day (26.21–68.81) or 8 tsp, and free sugar intake was 33.08 g/day (17.48–57.26) or 6 tsp. The higher intake of total sugars, free sugars, sucrose, lactose, sugar-sweetened beverages, sugar-sweetened cakes, and dessert was found to be significantly associated with a lower MMSE score, after adjusting for covariates. On the other hand, the consumption of cooked dishes and fruits was significantly associated with a better MMSE score. The adjusted OR for risk of cognitive impairment (MMSE score <24) was 3.30 (95% CI 2.15–5.08) for total sugars and 3.58 (95% CI 2.32–5.52) for free sugars, comparing the highest with the lowest intake percentiles.

Conclusion: Excessive sugar consumption among older adults showed a notable association with poor cognitive functions, but longitudinal studies and clinical trials are further needed to clarify the direction of causality and to investigate the underlying mechanism.

Impact of Acute Physical Activity on Children's Divergent and Convergent Thinking: The Mediating Role of a Low Body Mass Index

While prior studies have examined the positive influence of physical activity (PA) programs on children's creative potential, they have not explored the mediating roles of psychological and physiological variables. In this study, we investigated the impact of a single dance session as a form of PA on two indicators of creative potential-divergent and convergent thinking, each of which adopts a different cognitive pathway. We also investigated the influence of a physiological condition, low body mass index (BMI), on the relation between PA and creative potential. This was a randomized controlled experiment involving 34 school children randomly assigned to either the dance intervention or a sedentary group based on their BMI profile. We measured the children's divergent and convergent thinking at pre- and post-intervention time points. Following this single PA session, we found a significant difference between divergent and convergent thinking abilities in treatment group participants with normal BMI levels and participants in the control group, but there was no difference between low BMI level treatment group participants and those in the control group. This study supported hypothesized boundary conditions for executive function improvements from PA and suggests a need for a holistic approach (involving both proper nourishment and PA) in order to facilitate improved creativity in children.

Is Brain-Derived Neurotrophic Factor: A Common Link Between Neurodegenerative Disorders and Cancer?

BACKGROUND

Cancer is a common disease caused by the excessive proliferation of cells, and neurodegenerative diseases are the disorders caused due to the degeneration of neurons. Both can be considered as diseases caused by the dysregulation of cell cycle events. A recent data suggests that there is a strong inverse association between cancer and neurodegenerative disorders. There is indirect evidence to postulate Brain-derived Neurotrophic Factor (BDNF) as a potential molecular link in this association.

DISCUSSION

The BDNF levels are found to be downregulated in many neurodegenerative disorders and are found to be upregulated in various kinds of cancers. The lower level of BDNF in Alzheimer's and Parkinson's disease has been found to be related to cognitive and other neuropsychological impairments, whereas, its higher levels are associated with the tumour growth and metastasis and poor survival rate in the cancer patients.

CONCLUSION

In this review, we propose that variance in BDNF levels is critical in determining the course of cellular pathophysiology and the development of cancer or neurodegenerative disorder. We further propose that an alternative therapeutic strategy that can modulate BDNF expression, can rescue or prevent above said pathophysiological course. Larger studies that examine this link through animal studies are imperative to understand the putative biochemical and molecular link to wellness and disease.

An investigation into the relationship between cardiorespiratory fitness, cognition and BDNF in young healthy males

BACKGROUND

Recent investigations demonstrate that cardiorespiratory fitness may benefit brain health and plasticity with concurrent enhancements in cognitive performance; possibly via a brain-derived neurotrophic factor (BDNF)-regulated mechanism. While a number of studies have demonstrated an increase in BDNF concentration post exercise the relationship between BDNF, cardiorespiratory fitness and cognitive function requires further investigation.

OBJECTIVE

The present cross-sectional study assessed the association between cardiorespiratory fitness (VO₂max), cognitive performance and circulating BDNF concentration.

METHODS

Thirty-nine healthy male volunteers (mean age 21.7 ± 0.5 years) participated. Cognitive performance was measured by reaction time on a standard detection task and accuracy in a n-back and Continuous Paired Associative Learning (CPAL) task. Cardiorespiratory fitness was assessed using a standardised graded exercise test. Plasma and serum BDNF concentrations were assayed by ELISA.

RESULTS

A significant negative correlation between VO₂max and reaction time was demonstrated (p < 0.05). However VO₂max was not associated with circulating BDNF concentration, or performance in the n-back and CPAL tasks (p > 0.05).

CONCLUSIONS

Enhanced psychomotor speed was associated with higher cardiorespiratory fitness. In contrast to previous research no significant association between cardiorespiratory fitness and BDNF concentration was observed.

Efficacy and Safety of Lactobacillus Plantarum C29-Fermented Soybean (DW2009) in Individuals with Mild Cognitive Impairment: A 12-Week, Multi-Center, Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Early intervention using dietary supplements may be effective in alleviating cognitive impairment among individuals with mild cognitive impairment (MCI). This study investigated the efficacy and safety of Lactobacillus plantarum C29-fermented soybean (DW2009) as a nutritional supplement for cognitive enhancement. One hundred individuals with MCI were randomly assigned to take DW2009 (800 mg/day, n = 50) or placebo (800 mg/day, n = 50) for 12 weeks. The primary outcome measure was change in the composite score of cognitive functions related to memory and attention, measured by computerized neurocognitive function tests. Associations between changes in serum brain-derived neurotrophic factor (BDNF) levels and cognitive performance for each treatment group were evaluated. Compared to the placebo group, the DW2009 group showed greater improvements in the combined cognitive functions (z = 2.36, p for interaction = 0.02), especially in the attention domain (z = 2.34, p for interaction = 0.02). Cognitive improvement was associated with increased serum BDNF levels after consumption of DW2009 (t = 2.83, p = 0.007). The results of this clinical trial suggest that DW2009 can be safely administered to enhance cognitive function in individuals with MCI. Increased serum BDNF levels after administering DW2009 may provide preliminary insight into the underlying effects of cognitive improvement, which suggests the importance of the gut-brain axis in ameliorating cognitive deficits in MCI.

Decreased Serum Brain-Derived Neurotrophic Factor (BDNF) Levels in Patients with Alzheimer's Disease (AD): A Systematic Review and Meta-Analysis

Findings from previous studies reporting the levels of serum brain-derived neurotrophic factor (BDNF) in patients with Alzheimer's disease (AD) and individuals with mild cognitive impairment (MCI) have been conflicting. Hence, we performed a meta-analysis to examine the aggregate levels of serum BDNF in patients with AD and individuals with MCI, in comparison with healthy controls. Fifteen studies were included for the comparison between AD and healthy control (HC) (n = 2067). Serum BDNF levels were significantly lower in patients with AD (SMD: -0.282; 95% confidence interval [CI]: -0.535 to -0.028; significant heterogeneity: I² = 83.962). Meta-regression identified age (p < 0.001) and MMSE scores (p < 0.001) to be the significant moderators that could explain the heterogeneity in findings in these studies. Additionally, there were no significant differences in serum BDNF levels between patients with AD and MCI (eight studies, n = 906) and between MCI and HC (nine studies, n = 5090). In all, patients with AD, but not MCI, have significantly lower serum BDNF levels compared to healthy controls. This meta-analysis confirmed the direction of change in serum BDNF levels in dementia. This finding suggests that a significant change in peripheral BDNF levels can only be detected at the late stage of the dementia spectrum. Molecular mechanisms, implications on interventional trials, and future directions for studies examining BDNF in dementia were discussed.

Evaluating the effect of BDNF Val66Met polymorphism on complex formation with HAP1 and Sortilin1 via structural modeling

Brain derived neurotrophic factor (BDNF) has a critical role in the neurogenesis, differentiation, survival of the neurons, regulation of the appetite, and energy homeostasis. Two key proteins, Huntingtin associated protein-1 (HAP1) and sortilin1, regulate the intracellular trafficking and stabilization of the precursor proBDNF through interaction with its prodomain region and mark it for secretion. Evidence suggests that the most frequent single nucleotide polymorphism (SNP) of BDNF gene (rs6265) has been associated with different psychiatric, neurodegenerative and eating disorders. In this study, structural bioinformatics and molecular dynamics (MD) simulations were applied, in order to get precise insights into the impact of Val66Met polymorphism on the proBDNF structure and its interaction with HAP1 and Sortilin1. Homology modeling, structure validation, refinement and also protein-protein docking were performed using appropriate servers. The stability, the fluctuations and the compactness of protein complexes were measured by MD simulation parameters including root mean square deviation (RMSD), root mean square fluctuation (RMSF) and Radius of gyration (Rg), respectively. The mutant proBDNF complexes with HAP1 and Sortilin1 revealed higher RMSD and RMSF values and also variable R_g over time compared with wild-type proBDNF. These computational results indicated that, wild-type proBDNF possessed more stable structure in binding with HAP1 and Sortilin1 compared with its mutant form. Therefore, Val66Met SNP could be deleterious due to making structural changes. It may cause a decrease in proBDNF secretion, which could possibly lead to different psychiatric, neurodegenerative and eating disorders. Further experimental lab studies are required for a more accurate conclusion.

Mammalian Target of Rapamycin at the Crossroad Between Alzheimer's Disease and Diabetes

Accumulating evidence suggests that Alzheimer's disease may manifest as a metabolic disorder with pathology and/or dysfunction in numerous tissues. Adults with Alzheimer's disease suffer with significantly more comorbidities than demographically matched Medicare beneficiaries (Zhao et al, BMC Health Serv Res 8:108, 2008b). Reciprocally, comorbid health conditions increase the risk of developing Alzheimer's disease (Haaksma et al, PLoS One 12(5):e0177044, 2017). Type 2 diabetes mellitus is especially notable as the disease shares many overlapping pathologies observed in patients with Alzheimer's disease, including hyperglycemia, hyperinsulinemia, insulin resistance, glucose intolerance, dyslipidemia, inflammation, and cognitive dysfunction, as described in Chap. 8 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al, Neurology 53(9):1937-1942, 1999; Voisin et al, Rev Med Interne 24(Suppl 3):288s-291s, 2003; Janson et al. Diabetes 53(2):474-481, 2004; Ristow M, J Mol Med (Berl) 82(8):510-529, 2004; Whitmer et al, BMJ 330(7504):1360, 2005, Curr Alzheimer Res 4(2):103-109, 2007; Ohara et al, Neurology 77(12):1126-1134, 2011). Although nondiabetic older adults also experience age-related cognitive decline, diabetes is uniquely associated with a twofold increased risk of Alzheimer's disease, as described in Chap. 2 of this book (Yoshitake et al, Neurology 45(6):1161-1168, 1995; Leibson et al, Am J Epidemiol 145(4):301-308, 1997; Ott et al. Neurology 53(9):1937-1942, 1999; Ohara et al, Neurology 77(12):1126-1134, 2011). Good glycemic control has been shown to improve cognitive status (Cukierman-et al, Diabetes Care 32(2):221-226, 2009), and the use of insulin sensitizers is correlated with a lower rate of cognitive decline in older adults (Morris JK, Burns JM, Curr Neurol Neurosci Rep 12(5):520-527, 2012). At the molecular level, the mechanistic/mammalian target of rapamycin (mTOR) plays a key role in maintaining energy homeostasis. Nutrient availability and cellular stress information, both extracellular and intracellular, are integrated and transduced through mTOR signaling pathways. Aberrant regulation of mTOR occurs in the brains of patients with Alzheimer's disease and in numerous tissues of individuals with type 2 diabetes (Mannaa et al, J Mol Med (Berl) 91(10):1167-1175, 2013). Moreover, modulating mTOR activity with a pharmacological inhibitor, rapamycin, provides wide-ranging health benefits, including healthy life span extension in numerous model organisms (Vellai et al, Nature 426(6967):620, 2003; Jia et al, Development 131(16):3897-3906, 2004; Kapahi et al, Curr Biol 14(10):885-890, 2004; Kaeberlein et al, Science 310(5751):1193-1196, 2005; Powers et al, Genes Dev 20(2):174-184, 2006; Harrison et al, Nature 460(7253):392-395, 2009; Selman et al, Science 326(5949):140-144, 2009; Sharp ZD, Strong R, J Gerontol A Biol Sci Med Sci 65(6):580-589, 2010), which underscores its importance to overall organismal health and longevity. In this chapter, we discuss the physiological role of mTOR signaling and the consequences of mTOR dysregulation in the brain and peripheral tissues, with emphasis on its relevance to the development of Alzheimer's disease and link to type 2 diabetes.

Association of intraoperative changes in brain-derived neurotrophic factor and postoperative delirium in older adults

Background

Delirium is common after surgery, although the aetiology is poorly defined. Brain-derived neurotrophic factor (BDNF) is a neurotrophin important in neurotransmission and neuroplasticity. Decreased levels of BDNF have been associated with poor cognitive outcomes, but few studies have characterized the role of BDNF perioperatively. We hypothesized that intraoperative decreases in BDNF levels are associated with postoperative delirium.

Methods

Patients undergoing spine surgery were enrolled in a prospective cohort study. Plasma BDNF was collected at baseline and at least hourly intraoperatively. Delirium was assessed using rigorous methods, including the Confusion Assessment Method (CAM) and CAM for the intensive care unit. Associations of changes in BDNF and delirium were examined using regression models.

Results

Postoperative delirium developed in 32 of 77 (42%) patients. The median baseline BDNF level was 7.6 ng ml -1 [interquartile range (IQR) 3.0-11.2] and generally declined intraoperatively [median decline 61% (IQR 31-80)]. There was no difference in baseline BDNF levels by delirium status. However, the percent decline in BDNF was greater in patients who developed delirium [median 74% (IQR 51-82)] vs in those who did not develop delirium [median 50% (IQR 14-79); P =0.03]. Each 1% decline in BDNF was associated with increased odds of delirium in unadjusted {odds ratio [OR] 1.02 [95% confidence interval (CI) 1.00-1.04]; P =0.01}, multivariable-adjusted [OR 1.02 (95% CI 1.00-1.03); P =0.03], and propensity score-adjusted models [OR 1.02 (95% CI 1.00-1.04); P =0.03].

Conclusions

We observed an association between intraoperative decline in plasma BDNF and delirium. These preliminary results need to be confirmed but suggest that plasma BDNF levels may be a biomarker for postoperative delirium.

Serum Levels of Brain-Derived Neurotrophic Factor and Insulin-Like Growth Factor 1 Are Associated With Autonomic Dysfunction and Impaired Cerebral Autoregulation in Patients With Epilepsy

Background: Brain-derived neurotrophic factor (BDNF) and insulin-like growth factor 1 (IGF-1) may regulate the autonomic nervous system (ANS) in epilepsy. The present study investigated the role of IGF-1 and BDNF in the regulation of autonomic functions and cerebral autoregulation in patients with epilepsy. Methods: A total of 57 patients with focal epilepsy and 35 healthy controls were evaluated and their sudomotor, cardiovagal, and adrenergic functions were assessed using a battery of ANS function tests, including the deep breathing, Valsalva maneuver, head-up tilting, and Q-sweat tests. Cerebral autoregulation was measured by transcranial doppler during the breath-holding test and the Valsalva maneuver. Interictal serum levels of BDNF and IGF-1 were measured with enzyme-linked immunosorbent assay kits. Results: During interictal period, reduced serum levels of BDNF and IGF-1, impaired autonomic functions, and decreased cerebral autoregulation were noted in patients with epilepsy compared with healthy controls. Reduced serum levels of BDNF correlated with age, adrenergic and sudomotor function, overall autonomic dysfunction, and the autoregulation index calculated in Phase II of the Valsalva maneuver, and showed associations with focal to bilateral tonic-clonic seizures. Reduced serum levels of IGF-1 were found to correlate with age and cardiovagal function, a parameter of cerebral autoregulation (the breath-hold index). Patients with a longer history of epilepsy, higher seizure frequency, and temporal lobe epilepsy had lower serum levels of IGF-1. Conclusions: Long-term epilepsy and severe epilepsy, particularly temporal lobe epilepsy, may perturb BDNF and IGF-1 signaling in the central autonomic system, contributing to the autonomic dysfunction and impaired cerebral autoregulation observed in patients with focal epilepsy.

Amyloid beta soluble forms and plasminogen activation system in Alzheimer's disease: Consequences on extracellular maturation of brain-derived neurotrophic factor and therapeutic implications

Soluble oligomeric forms of amyloid beta (Aβ) play an important role in causing the cognitive deficits in Alzheimer’s disease (AD) by targeting and disrupting synaptic pathways. Thus, the present research is directed toward identifying the neuronal pathways targeted by soluble forms and, accordingly, develops alternative therapeutic strategies. The neurotrophin brain‐derived neurotrophic factor (BDNF) is synthesized as a precursor (pro‐BDNF) which is cleaved extracellularly by plasmin to release the mature form. The conversion from pro‐BDNF to BDNF is an important process that regulates neuronal activity and memory processes. Plasmin‐dependent maturation of BDNF in the brain is regulated by plasminogen activator inhibitor‐1 (PAI‐1), the natural inhibitor of tissue‐type plasminogen activator (tPA). Therefore, tPA/PAI‐1 system represents an important regulator of extracellular BDNF/pro‐BDNF ratio. In this review, we summarize the data on the components of the plasminogen activation system and on BDNF in AD. Moreover, we will hypothesize a possible pathogenic mechanism caused by soluble Aβ forms based on the effects on tPA/PAI‐1 system and on the consequence of an altered conversion from pro‐BDNF to the mature BDNF in the brain of AD patients. Translation into clinic may include a better characterization of the disease stage and future direction on therapeutic targets.

The protective effect of betulinic acid on microvascular responsivity and protein expression in alzheimer disease induced by cerebral micro-injection of beta-amyloid and streptozotocin

OBJECTIVE

Alzheimer's disease (AD) is mainly caused by accumulation of β-amyloid (Aβ) in vessels or parenchyma of the brain. Accordingly, natural compounds such as betulinic acid (BA) might improve the AD signs by increase in blood flow and through reduction in amyloid plaques.

METHODS

Intra-hippocampal injection of BA (0.2 and 0.4 μmol/L /10 μL DMSO /rat) was done at intervals of 180 and 10 min before co-microinjection of 0.1 μmol/L Aβ dissolved in PBS (5 μL/rat, hippocampi) and 1.5 mg/kg Streptozotocin dissolved in aCSF (10 μL/rat, lateral ventricles). Cerebro-vascular responsivity tested by Laser Doppler, BBB leakage, Elisa assays of cytokines (TNF-α and IL-10), and Western blot analysis of proteins (BDNF and AchE) in the hippocampus were assessed 1 month after the injections.

RESULTS

Microvascular reaction and BBB function were significantly impaired in AD rats, which were improved via BA pretreatment. BA could increase BDNF expression and decrease cytokine levels in the hippocampus of AD rats (especially 0.1 μmol/L Aβ: 0.4 μmol/L BA); however, no significant changes were detected in the blotting of AchE among the groups.

CONCLUSIONS

Betulinic acid could have a role in AD through protecting microcirculation, alleviating inflammation, and up-regulating BDNF expression which is clearer toward 1:4 molar ratios of Aβ to BA.

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.

Measurement of Cerebral Biomarkers Proving Traumatic Brain Injuries in Post-Mortem Body Fluids

Until now, it is impossible to identify a fatal traumatic brain injury (TBI) before post-mortem radiological investigations or an autopsy take place. It would be preferable to have an additional diagnostic tool such as post-mortem biochemistry to get greater insight into the pathological pathways and survival times after sustaining TBI. Cerebrospinal fluid (CSF) and serum samples of 84 autopsy cases were collected from forensic autopsies with post-mortem intervals (PMI) of up to 148 h. The cases were categorized into a fatal TBI case group (n = 42) and non-TBI controls (n = 42). The values of glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF), and neutrophil gelatinase-associated lipocalin (NGAL) were analyzed by means of quantitative chemiluminescent multiplex immunoassays. The main results indicate that the usage of liquid samples with good macroscopic quality is more relevant for meaningful biomarker analyses than the length of the PMI. All three proteins were shown to differentiate TBI fatalities from the controls in CSF. In serum, only GFAP could be shown to be able to identify TBI cases. This study is the first approach to measure the three proteins together in CSF and serum in autopsy cases. Determined threshold values may differentiate between fatal TBI and control cases. The presented results emphasize the possible use of post-mortem biochemistry as a supplemental tool in everyday forensic routine.

Precision medicine and drug development in Alzheimer's disease: the importance of sexual dimorphism and patient stratification

Neurodegenerative diseases (ND) are among the leading causes of disability and mortality. Considerable sex differences exist in the occurrence of the various manifestations leading to cognitive decline. Alzheimer's disease (AD) exhibits substantial sexual dimorphisms and disproportionately affects women. Women have a higher life expectancy compared to men and, consequently, have more lifespan to develop AD. The emerging precision medicine and pharmacology concepts - taking into account the individual genetic and biological variability relevant for disease risk, prevention, detection, diagnosis, and treatment - are expected to substantially enhance our knowledge and management of AD. Stratifying the affected individuals by sex and gender is an important basic step towards personalization of scientific research, drug development, and care. We hypothesize that sex and gender differences, extending from genetic to psychosocial domains, are highly relevant for the understanding of AD pathophysiology, and for the conceptualization of basic/translational research and for clinical therapy trial design.

Modeling the neuron as a nanocommunication system to identify spatiotemporal molecular events in neurodegenerative disease

AIM

In tauopathies such as Alzheimer's disease (AD), molecular changes spanning multiple subcellular compartments of the neuron contribute to neurodegeneration and altered axonal signaling. Computational modeling of end-to-end linked events benefit mechanistic analysis and can be informative to understand disease progression and accelerate development of effective therapies. In the calcium-amyloid beta model of AD, calcium ions that are an important regulator of neuronal function undergo dysregulated homeostasis that disrupts cargo loading for neurotrophic signaling along axonal microtubules (MTs). The aim of the present study was to develop a computational model of the neuron using a layered architecture simulation that enables us to evaluate the functionalities of several interlinked components in the calcium-amyloid beta model.

METHODS

The elevation of intracellular calcium levels is modeled upon binding of amyloid beta oligomers (AβOs) to calcium channels or as a result of membrane insertion of oligomeric Aβ1-42 to form pores/channels. The resulting subsequent Ca2+ disruption of dense core vesicle (DCV)-kinesin cargo loading and transport of brain-derived neurotrophic factor (BDNF) on axonal MTs are then evaluated. Our model applies published experimental data on calcium channel manipulation of DCV-BDNF and incorporates organizational complexity of the axon as bundled polar and discontinuous MTs. The interoperability simulation is based on the Institute of Electrical and Electronics Engineers standard association P1906.1 framework for nanoscale and molecular communication.

RESULTS

Our analysis provides new spatiotemporal insights into the end-to-end signaling events linking calcium dysregulation and BDNF transport and by simulation compares the relative impact of dysregulation of calcium levels by AβO-channel interactions, oligomeric Aβ1-42 pores/channel formation, and release of calcium by internal stores. The flexible platform of our model allows continued expansion of molecular details including mechanistic and morphological parameters of axonal cytoskeleton networks as they become available to test disease and treatment predictions.

CONCLUSION

The present model will benefit future drug studies on calcium homeostasis and dysregulation linked to measurable neural functional outcomes. The algorithms used can also link to other multiscale multi-cellular modeling platforms to fill in molecular gaps that we believe will assist in broadening and refining multiscale computational maps of neurodegeneration.

The contribution of microglia to early synaptic compensatory responses that precede β-amyloid-induced neuronal death

Glial-neuronal cross-talk has a critical role in the development of neurodegenerative conditions, including Alzheimer's Disease, where it affects neuronal responses to β-amyloid peptide (Aβ)-induced toxicity. We set out to identify factors regulating synaptic responses to Aβ, dissecting the specific role of glial signaling. A low concentration of aggregated Aβ42 induced selective up-regulation of mature brain-derived neurotrophic factor (BDNF) expression and release in rat organotypic hippocampal cultures as well as in cortical pure microglia. Conditioned media from resting (CMC) or Aβ42-treated (CMA) microglia were tested for their effects on synaptophysin expression in SH-SY5Y neuronal-like cells during challenge with Aβ42. Both CMC and CMA prevented Aβ-induced synaptophysin loss. In the presence of Aβ + CMA, synaptophysin was over-expressed, although it appeared partly clumped in cell bodies. Synaptophysin over-expression was not directly dependent on BDNF signaling on neuronal-like cells, but relied on autocrine BDNF action on microglia. FM1-43 labeling experiments revealed compromised synaptic vesicle recycling in Aβ42-treated neuronal-like cells, rescued by microglial conditioned medium. In these conditions, significant and prolonged neuroprotection was observed. Our results point to microglia as a target for early intervention, given its positive role in supporting neuronal compensatory responses to Aβ synaptotoxicity, which potentially lead to their extended survival.

Mechanisms of Risk Reduction in the Clinical Practice of Alzheimer's Disease Prevention

Alzheimer’s disease (AD) is a neurodegenerative dementia that affects nearly 50 million people worldwide and is a major source of morbidity, mortality, and healthcare expenditure. While there have been many attempts to develop disease-modifying therapies for late-onset AD, none have so far shown efficacy in humans. However, the long latency between the initial neuronal changes and onset of symptoms, the ability to identify patients at risk based on family history and genetic markers, and the emergence of AD biomarkers for preclinical disease suggests that early risk-reducing interventions may be able to decrease the incidence of, delay or prevent AD. In this review, we discuss six mechanisms—dysregulation of glucose metabolism, inflammation, oxidative stress, trophic factor release, amyloid burden, and calcium toxicity—involved in AD pathogenesis that offer promising targets for risk-reducing interventions. In addition, we offer a blueprint for a multi-modality AD risk reduction program that can be clinically implemented with the current state of knowledge. Focused risk reduction aimed at particular pathological factors may transform AD to a preventable disorder in select cases.

Measuring and Validating the Levels of Brain-Derived Neurotrophic Factor in Human Serum

Brain-derived neurotrophic factor (BDNF) secreted by neurons is a significant component of synaptic plasticity. In humans, it is also present in blood platelets where it accumulates following its biosynthesis in megakaryocytes. BDNF levels are thus readily detectable in human serum and it has been abundantly speculated that they may somehow serve as an indicator of brain function. However, there is a great deal of uncertainty with regard to the range of BDNF levels that can be considered normal, how stable these values are over time and even whether BDNF levels can be reliably measured in serum. Using monoclonal antibodies and a sandwich ELISA, this study reports on BDNF levels in the serum of 259 volunteers with a mean value of 32.69 ± 8.33 ng/ml (SD). The mean value for the same cohort after 12 months was not significantly different (N = 226, 32.97 ± 8.36 ng/ml SD, p = 0.19). Power analysis of these values indicates that relatively large cohorts are necessary to identify significant differences, requiring a group size of 60 to detect a 20% change. The levels determined by ELISA could be validated by Western blot analyses using a BDNF monoclonal antibody. While no association was observed with gender, a weak, positive correlation was found with age. The overall conclusions are that BDNF levels can be reliably measured in human serum, that these levels are quite stable over one year, and that comparisons between two populations may only be meaningful if cohorts of sufficient sizes are assembled.

Effect of a Comprehensive Intervention on Plasma BDNF in Patients with Alzheimer's Disease

A comprehensive intervention (CI) on patients with Alzheimer’s disease was assessed by measuring plasmabrain-derived neurotrophic factor (pBDNF) and ADAS-Cog score (ADAS-Cog_score) before, immediately after (FU1), and 6 (FU2) and 24 months (FU3) after the CI. Baseline pBDNF was higher in patients with moderate AD (but not mild AD) than in healthy controls. At FU1, pBDNF and ADAS-Cog_score decreased significantly. At FU2 and FU3, patients’ cognitive status worsened and pBDNF further increased versus baseline, suggesting that CI interruption may be a stress event that prevents return to homeostasis. CI exerted positive short-term effects, but more information is needed on long-term consequences.

Acute Down-regulation of BDNF Signaling Does Not Replicate Exacerbated Amyloid-β Levels and Cognitive Impairment Induced by Cholinergic Basal Forebrain Lesion

Degeneration of basal forebrain cholinergic neurons (BFCNs) precedes hippocampal degeneration and pathological amyloid-beta (Aβ) accumulation, and underpins the development of cognitive dysfunction in sporadic Alzheimer’s disease (AD). We hypothesized that degeneration of BFCNs causes a decrease in neurotrophin levels in innervated brain areas, which in turn promotes the development of Aβ pathology and cognitive impairment. Here we show that lesion of septo-hippocampal BFCNs in a pre-symptomatic transgenic amyloid AD mouse model (APP/PS1 mice) increases soluble Aβ levels in the hippocampus, and induces cognitive deficits in a spatial memory task that are not seen in either unlesioned APP/PS1 or non-transgenic littermate control mice. Furthermore, the BFCN lesion results in decreased levels of brain-derived neurotrophic factor (BDNF). However, viral knockdown of neuronal BDNF in the hippocampus of APP/PS1 mice (in the absence of BFCN loss) neither increased the level of Aβ nor caused cognitive deficits. These results suggest that the cognitive decline and Aβ pathology induced by BFCN loss occur independent of dysfunctional neuronal BDNF signaling, and may therefore be directly underpinned by reduced cholinergic neurotransmission.

Changes in Plasma β-NGF and Its Receptors Expression on Peripheral Blood Monocytes During Alzheimer's Disease Progression

Alzheimer's disease (AD), the most common cause of dementia, is characterized by the deposition of extracellular amyloid-β (Aβ) plaques and intracellular neurofibrillary tangles, and by neuroinflammation. During the pathogenesis of AD, monocyte-macrophage lineage cells become increasingly ineffective in clearing Aβ deposits, less able to differentiate, and shift toward pro-inflammatory processes. Beta-nerve growth factor (β-NGF) and its receptors, TrKA and p75NTR, produce several biological responses, including cell apoptosis and survival, and inflammation. In the central nervous system, the involvement of these receptors in several critical hallmarks of AD is well known, but their role in circulating monocytes during the progression of dementia is unclear. We investigated the relationship between plasma β-NGF concentration and TrkA/p75NTR receptor expression in monocytes of patients with mild cognitive impairment (MCI), mild AD, and severe AD. We observed that plasma β-NGF concentration was increased with a higher expression of TrKA, but not of p75NTR, in monocytes from patients with MCI and mild AD, whereas β-NGF concentration and TrKA expression were decreased and p75NTR expression was increased, associated with caspase 3-mediated apoptosis, in patients with severe AD. In our study, we show evidence of variation in plasmatic β-NGF and monocytic TrkA/p75NTR receptor expression during the progression of dementia. These novel findings add evidence to support the hypothesis for the involvement of β-NGF and its receptors on monocytes during AD progression.

Caloric restriction ameliorates acrolein-induced neurotoxicity in rats

OBJECTIVE

Acrolein, a highly reactive unsaturated aldehyde, is a ubiquitous environmental pollutant and oxidative damage induced by acrolein is hypothesized to involve in the etiology of Alzheimer's disease (AD). Calorie restriction (CR) is the only non-genetic intervention that has consistently been verified to retard aging by ameliorating oxidative stress. Therefore, we investigated the effects of CR on acrolein-induced neurotoxicity in Sprague-Dawley (SD) rats.

METHODS

A total of 45 weaned and specific-pathogen-free SD rats (male, weighing 180-220 g) were gavage-fed with acrolein (2.5 mg/kg/day) and fed ab libitum of 10 g/day or 7 g/day (representing 30% CR regimen), or gavage-fed with same volume of tap water and fed al libitum as vehicle control for 12 weeks. After behavioral test conducted by Morris Water Maze, SD rats were sacrificed and brain tissues were prepared for histochemical evaluation and Western blotting to detect alterations in oxidative stress, BDNF/TrkB pathway and key enzymes involved in amyloid precursor protein (APP) metabolism.

RESULTS

Treatment with 30% CR in SD rats significantly attenuated acrolein-induced cognitive impairment. Oxidative damage including deletion of glutathione and superoxide dismutase and sharp rise in malondialdehyde were notably improved by 30% CR. Further study suggested that 30% CR showed protective effects against acrolein by modulating BDNF/TrkB signaling pathways. Moreover, 30% CR restored acrolein-induced changes of APP, β-secretase, α-secretase and receptor for advanced glycation end products.

CONCLUSION

These findings suggest that CR may provide a promising approach for the treatment of AD, targeting acrolein.

Differential Peripheral Inflammatory Factors Associated with Cognitive Function in Patients with Heart Failure

OBJECTIVE

Cognitive deficits are common in patients with heart failure (HF), and can negatively affect self-care, predict rehospitalizations, and increase mortality rates 5-fold. Inflammation can produce vascular pathology, reducing cerebral blood flow to brain regions necessary for optimal cognitive function. The purpose of the investigation was to identify a pattern of peripheral blood inflammation-related biomarkers associated with cognitive impairment in patients with HF.

METHODS

Forty-five outpatients (median age = 67 years, SD = 9.9) were recruited from University of California, San Diego (UCSD) and Veterans Affairs San Diego Healthcare Systems (VASDHS), diagnosed with New York Heart Association Stages I-III HF. Participants were administered the Montreal Cognitive Assessment (MoCA) as a measure of global cognitive impairment, and blood was analyzed for plasma biomarkers, interferon-γ, tumor necrosis factor-α (TNFα), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), brain-derived neurotrophic factor (BDNF), interleukin-8 (IL-8), matrix metallopeptidase-9 (MMP-9), IL-6, C-reactive protein (CRP), and serum amyloid-A (SAA).

RESULTS

Almost half the patients scored below the threshold on the MoCA, indicating at least mild cognitive impairment. A factor analysis produced three biomarker factors: vascular inflammatory factor-1: TNFα, sICAM1, sVCAM1; neuroinflammatory factor-2: BDNF, MMP-9, IL-8; peripheral inflammatory factor-3: IL-6, CRP, SAA. Only vascular inflammatory factor-1 was significantly associated with cognitive function (MoCA) (ΔR2 = 0.214, beta = -0.468, p = 0.008).

CONCLUSIONS

In this cohort with HF, vascular inflammation appears related to poorer cognitive function. This could indicate targets for treatment to reduce cognitive deficits in HF. However, this is a preliminary study, and further research is needed.

Computerized cognitive training and brain derived neurotrophic factor during bed rest: mechanisms to protect individual during acute stress

Acute stress, as bed rest, was shown to increase plasma level of the neurotrophin brain-derived neurotrophic factor (BDNF) in older, but not in young adults. This increase might represent a protective mechanism towards acute insults in aging subjects. Since computerized cognitive training (CCT) is known to protect brain, herein we evaluated the effect of CCT during bed rest on BDNF, muscle mass, neuromuscular function and metabolic parameters. The subjects that underwent CCT did not show an increase of BDNF after bed rest, and showed an anti-insular modification pattern in metabolism. Neuromuscular function parameters, already shown to beneficiate from CCT, negatively correlated with BDNF in research participants undergoing CCT, while positively correlated in the control group. In conclusion, BDNF increase can be interpreted as a standardized protective mechanism taking place whenever an insult occurs; it gives low, but consistent preservation of neuromuscular function. CCT, acting as an external protective mechanism, seems to modify this standardized response, avoiding BDNF increase or possibly modifying its time course. Our results suggest the possibility of differential neuroprotective mechanisms among ill and healthy individuals, and the importance of timing in determining the effects of protective mechanisms.

Head-out immersion in hot water increases serum BDNF in healthy males

PURPOSE

Brain-derived neurotrophic factor (BDNF) is an important neurotrophin. The present study investigated the effects of head-out water immersion (HOI) on serum BDNF concentrations.

METHODS

Eight healthy men performed 20 min head-out water immersion at 42 °C (hot-HOI) and 35 °C (neutral-HOI). These experimental trials were administered in a randomised order separated by at least 7 days. Venous blood samples were withdrawn at rest, immediately after the 20-min HOI, as well as at 15 and 30 min after the end of the HOI. Serum BDNF and S100β, plasma cortisol, platelet and monocyte counts, and core body temperature (T_cb) were measured.

RESULTS

T_cb was higher at the end of the hot-HOI and 15 min after hot-HOI (p < 0.01), but recovered to pre-HOI level at 30 min after hot-HOI. No change in T_cb was recorded during neutral-HOI. BDNF level was higher (p < 0.05) at the end of the hot-HOI and at 15 min after the end of hot-HOI, and returned to the baseline at 30 min after hot-HOI. S100β, platelet count and monocyte count remained stable throughout the study. Cortisol level was lower at the end of the hot-HOI and returned to pre-HOI level during the recovery period. BDNF and S100β, cortisol, and platelet and monocyte counts did not change throughout the neutral-HOI study.

CONCLUSIONS

The present findings suggested that the increase in BDNF during 20-min hot-HOI was induced by hyperthermia through enhanced production, rather than by changes in permeability of the blood-brain barrier (BBB), platelet clotting mechanisms or secretion from monocytes.

Sex Differences in Risk for Alzheimer's Disease Related to Neurotrophin Gene Polymorphisms: The Cache County Memory Study

Neurotrophins, including nerve-growth factor and brain-derived neurotrophic factor, have been implicated in Alzheimer's disease (AD). Associations between AD and neurotrophin signaling genes have been inconsistent, with few studies examining sex differences in risk. We examined four single-nucleotide polymorphisms (SNPs) involved in neurotrophin signaling (rs6265, rs56164415, rs2289656, rs2072446) and risk for AD by sex in a population-based sample of older adults. Three thousand four hundred and ninety-nine individuals without dementia at baseline [mean (standard deviation) age = 74.64 (6.84), 58% female] underwent dementia screening and assessment over four triennial waves. Cox regression was used to examine time to AD or right censoring for each SNP. Female carriers of the minor T allele for rs2072446 and rs56164415 had a 60% (hazard ratio [HR] = 1.60, 95% confidence interval [CI] = 1.02-2.51) and 93% (HR = 1.93, 95% CI = 1.30-2.84) higher hazard for AD, respectively, than male noncarriers of the T allele. Furthermore, male carriers of the T allele of rs2072446 had a 61% lower hazard (HR = 0.39, 95% CI = 0.14-1.06) than male noncarriers at trend-level significance (p = .07). The association between certain neurotrophin gene polymorphisms and AD differs by sex and may explain inconsistent findings in the literature.

New insights about the putative role of myokines in the context of cardiac rehabilitation and secondary cardiovascular prevention

Exercise training prevents the onset and the development of many chronic diseases, acting as an effective tool both for primary and for secondary prevention. Various mechanisms that may be the effectors of these beneficial effects have been proposed during the past decades: some of these are well recognized, others less. Muscular myokines, released during and after muscular contraction, have been proposed as key mediators of the systemic effects of the exercise. Nevertheless the availability of an impressive amount of evidence regarding the systemic effects of muscle-derived factors, few studies have examined key issues: (I) if skeletal muscle cells themselves are the main source of cytokine during exercise; (II) if the release of myokines into the systemic circulation reach an adequate concentration to provide significant effects in tissues far from skeletal muscle; (III) what may be the role carried out by muscular cytokine regarding the well-known benefits induced by regular exercise, first of all the anti-inflammatory effect of exercise. Furthermore, a greater part of our knowledge regarding myokines derives from the muscle of healthy subjects. This knowledge may not necessarily be transferred per se to subjects with chronic diseases implicating a direct or indirect muscular dysfunction and/or a chronic state of inflammation with persistent immune-inflammatory activation (and therefore increased circulating levels of some cytokines): cachexia, sarcopenia due to multiple factors, disability caused by neurological damage, chronic congestive heart failure (CHF) or coronary artery disease (CAD). A key point of future studies is to ascertain how is modified the muscular release of myokines in different categories of unhealthy subjects, both at baseline and after rehabilitation. The purpose of this review is to discuss the main findings on the role of myokines as putative mediators of the therapeutic benefits obtained through regular exercise in the context of secondary cardiovascular prevention.

Treadmill exercise ameliorates the regulation of energy metabolism in skeletal muscle of NSE/PS2mtransgenic mice with Alzheimer's disease

[Purpose]

Alzheimer’s disease (AD) is classified as a progressive neurological disorder, which not only causes cognitive impairment but also abnormal weight loss, with a reduction of muscle mass related to the accumulation of amyloid-β (Aβ) in skeletal muscle. Thus, we investigated the effect of treadmill exercise on Aβ deposition, and p-AMPK, p-ACC, BDNF, and GLUT4 protein levels the regulation of muscle energy metabolism using an AD mouse.

[Methods]

At 13 months of age, NSE/PS2m mice (Tg) and control mice (non-Tg) were assigned to non-exercise control (Con) and exercise groups (Exe). The four groups were as follows: non-Tg Con, non-Tg Exe, Tg Con, and Tg Exe. The treadmill exercise was carried out for 12 weeks.

[Results]

The highest levels of Aβ expression in the skeletal muscle were in the Tg Con group. Aβ expression was significantly reduced in the Tg Exe group, compared to the Tg Con group. Congo red staining showed remarkable diffuse red amyloid deposition in the Tg Con group, while Aβ-deposition in the skeletal was reduced with muscle exercise in the Tg Exe group. Exercise also increased AMPK and ACC phosphorylation and BDNF and GLUT4 expression in the skeletal muscle of non-Tg and Tg mice.

[Conclusion]

Treadmill exercise reduces Aβ-deposition in the skeletal muscle and improves the regulation of energy metabolism. Thus, collectively, these results suggest that exercise could be a positive therapeutic strategy for skeletal muscle dysfunction in AD patients.

Cytokines, Hepatic Fibrosis, and Antiretroviral Therapy Role in Neurocognitive Disorders HIV Related

The HIV may trigger a process of neuronal loss and axonal degeneration throughout the brain, which is carried on by the immune system releasing of proinflammatory cytokines, so that chronic inflammation associated with dysregulated innate immune response, glial cell dysfunction, and adverse antiretroviral therapy (ART) effect play an important role causing milder HIV-associated neurocognitive disorders or asymptomatic neurocognitive impairment. All patients have been tested for neurocognitive functioning through a comprehensive, five-domain neuropsychological battery performed in the study. Human cytokine (interleukin [IL]-6, IL-8, IL-18, and tumor necrosis factor [TNF]-α) and brain-derived neurotrophic factor serum levels were quantified using ELISAs, and the hepatic fibrosis was estimated using the noninvasive Fibrosis 4 (FIB-4) score. The study showed a group of 40 HIV-infected individuals and it was observed that almost 40% of HIV⁺ individuals, even if clinically asymptomatic, displayed some degree of neurocognitive dysfunction, compared to normative performance standards, at least in two cognitive areas. The functions affected the most were memory, attention, executive function, and psychomotor processing speed. Three cytokines (IL-6, IL-8, and IL-18) to be significantly linked to test results in specific neurocognitive domain were found. Treatments with nucleoside reverse transcriptase inhibitor plus non-nucleoside reverse transcriptase inhibitor alone were instead associated with poor neurocognitive outcome, especially in verbal fluency, fine motility, and Zung Depression Scale. Elevated value of FIB-4 score showed an opposite connection with cognitive performance as well, underlining the direct association between hepatic steatosis and neurocognitive deficit. The cytokine panel and the FIB-4 score can predict presence or worsening of neurocognitive functions in HIV-infected individuals. An ART switch can be suggested according to the neurocognitive domain involved the most, advising a therapy with protease inhibitors or/and integrase inhibitors to improve fluency, executive functions, and to prevent depression.