Val66Met BDNF polymorphism is associated with Parkinson's disease cognitive impairment

Association of the BDNF rs6265 Polymorphism with Cognitive Impairment in Multiple Sclerosis: A Case-Control Study in Mexican Patients

Cognition is a set of brain processes that allow the individual to interact with their environment. Multiple sclerosis (MS) is a chronic inflammatory disease that affects the cerebral white matter of the brain cortex and spinal cord, leading to cognitive impairment (CI) in 40-60% of the patients. Many studies have determined that CI is linked to genetic risk factors. We aimed to evaluate the association between BDNF gene rs6265 polymorphism and cognitive impairment in Mexican patients with MS by performing a case-control study. Mestizo-Mexican patients diagnosed with MS based on McDonald's criteria were enrolled. Cases were MS patients with CI (n = 31) while controls were MS patients without CI (n = 31). To measure cognitive functioning in MS patients, a neuropsychological screening battery for MS (NSB-MS) was used. Genotyping of the rs6265 gene variant was performed using quantitative real-time PCR (qPCR) with TaqMan probes. The results showed no statistically significant differences in sociodemographic and disease variables between case and control groups. qPCR analysis showed that there were 68% Val/Val wild-type homozygotes, 29% Val/Met polymorphic heterozygotes, and 3% Met/Met polymorphic homozygotes. The presence of BDNF gene rs6265 polymorphism showed an increased probability (3.6 times) of global cognitive impairment.

Brain-derived neurotrophic factor gene polymorphism affects cognitive function and neurofilament light chain level in patients with subcortical ischaemic vascular dementia

Objective

To investigate the effects of brain-derived neurotrophic factor (BDNF) gene polymorphism on cognitive function, neuroimaging and blood biological markers in patients with subcortical ischaemic vascular dementia (SIVD).

Methods

A total of 81 patients with SIVD were included. According to their BDNF gene polymorphism, the participants were divided into the Val/Val (n = 26), Val/Met (n = 35), and Met/Met (n = 20) groups. A comprehensive neuropsychological evaluation and multimodal brain MRI scan were performed. MRI markers for small vessel disease were visually rated or quantitatively analysed. Moreover, 52 patients were further evaluated with blood marker assays, including amyloid beta (Aβ), phosphorylated tau at threonine-181 (P-tau181), glial fibrillary acidic protein (GFAP), total tau (T-tau) and neurofilament light chain (NfL).

Results

There were no significant differences in demographics, disease duration or MRI markers of small vessel disease between the three groups. Compared with the Val/Val and Val/Met groups, the Met/Met group showed worse performance in the verbal fluency test and higher levels of plasma NfL.

Conclusion

The rs6265 polymorphism of the BDNF gene is associated with semantic language fluency in patients with SIVD. The Met genotype may be a risk factor for cognitive impairment and neuronal injury.

Brain-derived neurotrophic factor genetic polymorphism rs6265 and creativity

The protein brain-derived neurotrophic factor (BDNF) promotes neural plasticity of the central nervous system and plays an important role for learning and memory. A single nucleotide polymorphism (rs6265) at position 66 in the pro-region of the human BDNF gene, resulting in a substitution of the amino acid valine (val) with methionine (met), leads to attenuated BDNF secretion and has been associated with reduced neurocognitive function. Inhomogeneous results have been found regarding the effect of the BDNF genotype on behavior. We determined the BDNF genotype and performance on the Compound Remote Associate (CRA) task as a common measure of creativity in 76 healthy university students. In our main analyses, we did not find significant differences between met-carriers (n = 30) and non-met carriers (n = 46). In a secondary analysis, we found that met-carriers had a slower solution time (medium effect size) for items of medium difficulty. Our results suggest that met-carriers and non-met-carriers do not generally differ regarding their creativity, but non-met-carriers may have a certain advantage when it comes to moderately difficult problems. The wider literature suggests that both genetic variants come with advantages and disadvantages. Future research needs to sharpen our understanding of the disadvantages and, potentially, advantages met allele carriers may have.

The Role of Brain-Derived Neurotrophic Factor Signaling in Central Nervous System Disease Pathogenesis

Recent studies have found abnormal levels of brain-derived neurotrophic factor (BDNF) in a variety of central nervous system (CNS) diseases (e.g., stroke, depression, anxiety, Alzheimer’s disease, and Parkinson’s disease). This suggests that BDNF may be involved in the pathogenesis of these diseases. Moreover, regulating BDNF signaling may represent a potential treatment for such diseases. With reference to recent research papers in related fields, this article reviews the production and regulation of BDNF in CNS and the role of BDNF signaling disorders in these diseases. A brief introduction of the clinical application status of BDNF is also provided.

Recent Advances on the Role of Brain-Derived Neurotrophic Factor (BDNF) in Neurodegenerative Diseases

Neurotrophins, such as brain-derived neurotrophic factor (BDNF), are essential for neuronal survival and growth. The signaling cascades initiated by BDNF and its receptor are the key regulators of synaptic plasticity, which plays important role in learning and memory formation. Changes in BDNF levels and signaling pathways have been identified in several neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease, and have been linked with the symptoms and course of these diseases. This review summarizes the current understanding of the role of BDNF in several neurodegenerative diseases, as well as the underlying molecular mechanism. The therapeutic potential of BDNF treatment is also discussed, in the hope of discovering new avenues for the treatment of neurodegenerative diseases.

Astrocytic Calcium and cAMP in Neurodegenerative Diseases

It is commonly accepted that the role of astrocytes exceeds far beyond neuronal scaffold and energy supply. Their unique morphological and functional features have recently brough much attention as it became evident that they play a fundamental role in neurotransmission and interact with synapses. Synaptic transmission is a highly orchestrated process, which triggers local and transient elevations in intracellular Ca²⁺, a phenomenon with specific temporal and spatial properties. Presynaptic activation of Ca²⁺-dependent adenylyl cyclases represents an important mechanism of synaptic transmission modulation. This involves activation of the cAMP-PKA pathway to regulate neurotransmitter synthesis, release and storage, and to increase neuroprotection. This aspect is of paramount importance for the preservation of neuronal survival and functionality in several pathological states occurring with progressive neuronal loss. Hence, the aim of this review is to discuss mutual relationships between cAMP and Ca²⁺ signaling and emphasize those alterations at the Ca²⁺/cAMP crosstalk that have been identified in neurodegenerative disorders, such as Alzheimer's and Parkinson's disease.

BDNF Val66Met Polymorphism Is Associated With Motor Recovery After Rehabilitation in Progressive Multiple Sclerosis Patients

Background

Rehabilitation is fundamental for progressive multiple sclerosis (MS), but predictive biomarkers of motor recovery are lacking, making patient selection difficult. Motor recovery depends on synaptic plasticity, in which the Brain-Derived Neurotrophic Factor (BDNF) is a key player, through its binding to the Neurotrophic-Tyrosine Kinase-2 (NTRK2) receptor. Therefore, genetic polymorphisms in the BDNF pathway may impact motor recovery. The most well-known polymorphism in BDNF gene (rs6265) causes valine to methionine substitution (Val66Met) and it influences memory and motor learning in healthy individuals and neurodegenerative diseases. To date, no studies have explored whether polymorphisms in BDNF or NTRK2 genes may impact motor recovery in MS.

Objectives

To assess whether genetic variants in BDNF and NTRK2 genes affect motor recovery after rehabilitation in progressive MS.

Methods

The association between motor recovery after intensive neurorehabilitation and polymorphisms in BDNF (rs6265) and NTKR2 receptor (rs2289656 and rs1212171) was assessed using Six-Minutes-Walking-Test (6MWT), 10-Metres-Test (10MT) and Nine-Hole-Peg-Test (9HPT) in 100 progressive MS patients.

Results

We observed greater improvement at 6MWT after rehabilitation in carriers of the BDNF Val66Met substitution, compared to BDNF Val homozygotes (p = 0.024). No significant association was found for 10MT and 9HPT. NTRK2 polymorphisms did not affect the results of motor function tests.

Conclusion

BDNF Val66Met was associated with walking function improvement after rehabilitation in progressive MS patients. This result is in line with previous evidence showing a protective effect of Val66Met substitution on brain atrophy in MS. Larger studies are needed to explore its potential as a predictive biomarker of rehabilitation outcome.

Evaluation of neurotrophic factors and education level as predictors of cognitive decline in alcohol use disorder

Cognitive reserve (CR) is the capability of an individual to cope with a brain pathology through compensatory mechanisms developed through cognitive stimulation by mental and physical activity. Recently, it has been suggested that CR has a protective role against the initiation of substance use, substance consumption patterns and cognitive decline and can improve responses to treatment. However, CR has never been linked to cognitive function and neurotrophic factors in the context of alcohol consumption. The present cross-sectional study aims to evaluate the association between CR (evaluated by educational level), cognitive impairment (assessed using a frontal and memory loss assessment battery) and circulating levels of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) in patients with alcohol use disorder (AUD). Our results indicated that lower educational levels were accompanied by earlier onset of alcohol consumption and earlier development of alcohol dependence, as well as impaired frontal cognitive function. They also suggest that CR, NT-3 and BDNF may act as compensatory mechanisms for cognitive decline in the early stages of AUD, but not in later phases. These parameters allow the identification of patients with AUD who are at risk of cognitive deterioration and the implementation of personalized interventions to preserve cognitive function.

Association Between BDNF Val66Met Polymorphism and Mild Behavioral Impairment in Patients With Parkinson's Disease

Neuropsychiatric symptoms (NPS) are common in Parkinson's disease (PD) and have demonstrated an association with the p. Val66Met, a polymorphism in the BDNF gene. Mild behavioral impairment (MBI) is a validated syndrome describing emergent and persistent NPS in older adults as a marker of potential cognitive decline and dementia. This study investigated if PD patients with the Met allele were more likely to have MBI and whether they had impairments in specific domains of MBI using the Mild Behavioral Impairment Checklist (MBI-C) as the MBI ascertainment tool. One hundred forty-six PD patients were screened for neuropsychiatric and cognitive impairments with the MBI-C and the Montreal Cognitive Assessment (MoCA). All participants were genotyped for the BDNF p.Val66Met single-nucleotide polymorphism (SNP) using TaqMan Genotyping Assay. Statistical analysis was performed using multiple linear and logistic regression models. Met carriers had a 2 times higher likelihood of being MBI positive (MBI-C total score ≥8) than Val carriers. Met carriers had significantly higher MBI-C total scores and significantly greater impairments in the mood/anxiety and the psychotic domains of MBI-C compared to Val carriers. These findings indicate that the BDNF Met allele is associated with a higher neuropsychiatric burden in PD.

Influence of BDNF Genetic Polymorphisms in the Pathophysiology of Aging-related Diseases

For the first time in history, most of the population has a life expectancy equal or greater than 60 years. By the year 2050, it is expected that the world population in that age range will reach 2000 million, an increase of 900 million with respect to 2015, which poses new challenges for health systems. In this way, it is relevant to analyze the most common diseases associated with the aging process, namely Alzheimer´s disease, Parkinson Disease and Type II Diabetes, some of which may have a common genetic component that can be detected before manifesting, in order to delay their progress. Genetic inheritance and epigenetics are factors that could be linked in the development of these pathologies. Some researchers indicate that the BDNF gene is a common factor of these diseases, and apparently some of its polymorphisms favor the progression of them. In this regard, alterations in the level of BDNF expression and secretion, due to polymorphisms, could be linked to the development and/or progression of neurodegenerative and metabolic disorders. In this review we will deepen on the different polymorphisms in the BDNF gene and their possible association with age-related pathologies, to open the possibilities of potential therapeutic targets.

Neurotrophic Factor BDNF, Physiological Functions and Therapeutic Potential in Depression, Neurodegeneration and Brain Cancer

Brain-derived neurotrophic factor (BDNF) is one of the most distributed and extensively studied neurotrophins in the mammalian brain. BDNF signals through the tropomycin receptor kinase B (TrkB) and the low affinity p75 neurotrophin receptor (p75NTR). BDNF plays an important role in proper growth, development, and plasticity of glutamatergic and GABAergic synapses and through modulation of neuronal differentiation, it influences serotonergic and dopaminergic neurotransmission. BDNF acts as paracrine and autocrine factor, on both pre-synaptic and post-synaptic target sites. It is crucial in the transformation of synaptic activity into long-term synaptic memories. BDNF is considered an instructive mediator of functional and structural plasticity in the central nervous system (CNS), influencing dendritic spines and, at least in the hippocampus, the adult neurogenesis. Changes in the rate of adult neurogenesis and in spine density can influence several forms of learning and memory and can contribute to depression-like behaviors. The possible roles of BDNF in neuronal plasticity highlighted in this review focus on the effect of antidepressant therapies on BDNF-mediated plasticity. Moreover, we will review data that illustrate the role of BDNF as a potent protective factor that is able to confer protection against neurodegeneration, in particular in Alzheimer’s disease. Finally, we will give evidence of how the involvement of BDNF in the pathogenesis of brain glioblastoma has emerged, thus opening new avenues for the treatment of this deadly cancer.

Elucidating the Relationship Between Diabetes Mellitus and Parkinson's Disease Using 18F-FP-(+)-DTBZ, a Positron-Emission Tomography Probe for Vesicular Monoamine Transporter 2

Diabetes mellitus (DM) and Parkinson’s disease (PD) have been and will continue to be two common chronic diseases globally that are difficult to diagnose during the prodromal phase. Current molecular genetics, cell biological, and epidemiological evidences have shown the correlation between PD and DM. PD shares the same pathogenesis pathways and pathological factors with DM. In addition, β-cell reduction, which can cause hyperglycemia, is a striking feature of DM. Recent studies indicated that hyperglycemia is highly relevant to the pathologic changes in PD. However, further correlation between DM and PD remains to be investigated. Intriguingly, polycystic monoamine transporter 2 (VMAT2), which is co-expressed in dopaminergic neurons and β cells, is responsible for taking up dopamine into the presynaptic vesicles and can specifically bind to the β cells. Furthermore, we have summarized the specific molecular and diagnostic functions of VMAT2 for the two diseases reported in this review. Therefore, VMAT2 can be applied as a target probe for positron emission tomography (PET) imaging to detect β-cell and dopamine level changes, which can contribute to the diagnosis of DM and PD during the prodromal phase. Targeting VMAT2 with the molecular probe ¹⁸F-FP-(+)-DTBZ can be an entry point for the β cell mass (BCM) changes in DM at the molecular level, to clarify the potential relationship between DM and PD. VMAT2 has promising clinical significance in investigating the pathogenesis, early diagnosis, and treatment evaluation of the two diseases.

Systematic review of genetic variants associated with cognitive impairment and depressive symptoms in Parkinson's disease

OBJECTIVE

Cognitive impairment and depression are among the most prevalent and most disabling non-motor symptoms in Parkinson's disease (PD). The genetic factors that are associated with these symptoms remain uncertain. This systematic review aims to summarise the prevailing evidence from all genetic association studies investigating the genetic variants associated with cognitive impairment and depressive symptoms in people with PD.

METHOD

A systematic review using five online databases: PubMed, PsycINFO, CINAHL, EMBASE and OpenGrey (PROSPERO protocol: CRD42017067431). We completed the quality assessment using the Q-Genie tool.

RESULTS

2353 articles were screened, and 43 articles were found to be eligible to be included. A meta-analysis of studies investigating LRRK2 rs34637584 confirmed that the minor allele carriers had significantly less cognitive impairment (p = 0.015). Further meta-analyses showed that GBA variants rs76763715 (p < 0.001) and rs421016 (p = 0.001) were significantly associated with more cognitive impairment in people with PD. Minor alleles of GBA variants rs76763715, rs421016, rs387906315 and rs80356773 were associated with more depressive symptoms in PD. Moreover, APOE ε4 allele has been associated with more cognitive impairment in PD. BDNF (rs6265) and CRY1 (rs2287161) variants have been associated with more depressive symptoms in people with PD.

CONCLUSIONS

PD carriers of GBA variants are at high risk for cognitive decline and depression. Screening for these variants may facilitate early identification and effective management of these non-motor symptoms. The molecular mechanisms underlying favourable cognitive functioning in LRRK2 rs34637584 variant carriers warrant further investigation.

Association between BDNF G196A (Val66Met) polymorphism and cognitive impairment in patients with Parkinson's disease: a meta-analysis

Brain-derived neurotrophic factor (BDNF) is widely expressed in the central nervous system and prolongs the survival of dopaminergic neurons in the substantia nigra. Several studies have recently investigated the association between BDNF G196A (Val66Met), a single nucleotide polymorphism influencing cognitive processes, and cognitive impairment in Parkinson's disease (PD), but with contradictory findings. Thus, this meta-analysis was performed to clarify the possible association. Relevant studies were identified by a systematic search of PubMed, Embase, and China National Knowledge Infrastructure (CNKI) databases. The strength of the association was evaluated using crude odds ratios and 95% confidence interval. Finally, six studies involving 532 cases and 802 controls were included. Our analyses suggested the G196A (Val66Met) polymorphism was significantly associated with cognitive impairment in PD, especially in Caucasian populations. In conclusion, BDNF G196A (Val66Met) is confirmed to be a risk factor for cognitive impairment in PD.

Multiple pathways for natural product treatment of Parkinson's disease: A mini review

BACKGROUND

It is established that natural medicines for Parkinson's disease (PD) provide an antioxidant activity in preventing dopaminergic neurons from degeneration. However, the underlying and related molecular details remain poorly understood.

METHODS AND AIM

We review published in vitro and rodent studies of natural products in PD models with the aim to identify common molecular pathways contributing to the treatment efficacy. Commonly regulated genes were identified through the systemic literature search and further analyzed from a network perspective.

FINDINGS

Approximately thirty different types of natural products have been investigated for their ability to regulate protein density and gene activity in various experimental systems. Most were found to attenuate neurotoxin-induced regulations. Three common PD pathways are involved. The most studied pathway was neuronal development/anti-apoptosis consisting of Bax/Bcl-2, caspases 3/9, and MAPK signaling. Another well studied was anti-inflammation comprising iNOS, nNOS, Nrf2/ARE, cytokines, TNFα, COX2 and MAPK signaling. The third pathway referred to dopamine transmission modulation with upregulated VMAT2, DAT, NURR1 and GDNF levels. To date, HIPK2, a conserved serine/threonine kinase and transcriptional target of Nrf2 in an anti-apoptosis signaling pathway, is the first protein identified as the direct binding target of a natural product (ZMHC).

IMPLICATIONS

Natural products may utilize multiple and intercellular pathways at various steps to prevent DA neurons from degeneration. Molecular delineation of the mechanisms of actions is revealing new, perhaps combinational therapeutic approaches to stop the progression of DA degeneration.

BDNF Val66Met polymorphism and cognitive impairment in Parkinson's disease-a meta-analysis

BACKGROUND

Conflicting results identifying the association between Brain-derived neurotrophic factor (BDNF) polymorphism, Val66Met, and cognitive impairment in Parkinson's disease (PD) have been reported.

METHODS AND RESULTS

To clarify whether Val66Met is related to cognitive impairment in PD, we carried out this meta-analysis by searching literature from PubMed, Web of Science, and Embase databases regarding this polymorphism. Six eligible studies involving 1467 PD patients were included in this meta-analysis. Our results showed statistically significant association between Val66Met and risk of cognitive impairment in PD patients in additive model (Met/Met vs. Val/Val: OR 3.82, 95%CI 1.32 to 11.08, p = 0.01) and recessive model (Met/Met vs. Val-carrier: OR 3.81, 95%CI 1.38 to 10.53, p = 0.01) except for dominant model.

CONCLUSIONS

Our meta-analysis implicates Val66Met BDNF polymorphism may be associated with Parkinson's disease cognitive impairment, further well-designed studies with larger populations are required to validate these results owing to the limited research.

[The genetic predictors of cognitive impairment in Parkinson's disease]

Parkinson's disease (PD) is a common neurodegenerative disorder that can be both sporadic and familial. A number of studies are devoted to the study of non-motor symptoms in PD today. Cognitive deficits, and especially dementia, are one of the most severe and disabling non-motor symptoms of PD. More than a quarter of patients in the early stages of PD have a moderate cognitive impairment, more than half of patients with PD develop dementia within 10 years from the date of diagnosis. Using genome-wide association studies (GWAS), a number of genes associated with cognitive impairment have been identified based on a comparison of genetic and clinical phenotypes. These genes can be divided into three groups: genes that lead to the development of PD and are inherited according to the laws of Mendel (SNCA), genes that are risk factors for PD development (GBA, MAPT) and genes associated with the development of cognitive impairment, but not with PD (COMT, APOE, BDNF). This review examines the effect of genetic variants in the above-mentioned genes on cognitive functions in patients with PD. The elucidation of the genetic basis of cognitive deficits in PD could help in choice of treatment tactics and in development of new therapeutic strategies.

Replication and Meta-analysis of the Association between BDNF Val66Met Polymorphism and Cognitive Impairment in Patients Receiving Chemotherapy

Cancer-related cognitive impairment (CRCI) adversely affects cancer patients. We had previously demonstrated that the BDNF Val66Met genetic polymorphism is associated with lower odds of subjective CRCI in the multitasking and verbal ability domains among breast cancer patients receiving chemotherapy. To further assess our previous findings, we evaluated the association of BDNF Val66Met polymorphism with subjective and objective CRCI in a temporally separate cohort of patients and pooled findings from both the original (n = 145) and current (n = 193) cohorts in a meta-analysis. Subjective CRCI was assessed using FACT-Cog. Objective CRCI was evaluated using computerized neuropsychological tests. Genotyping was carried out using Sanger sequencing. The association of BDNF Val66Met genotypes and CRCI was examined with logistic regression. A fixed-effect meta-analysis was conducted using the inverse variance method. In the meta-analysis (n = 338), significantly lower odds of CRCI were associated with Met allele carriers based on the global FACT-Cog score (OR = 0.52, 95% CI 0.29–0.94). Furthermore, Met allele carriers were at lower odds of developing impairment in the domains of memory (OR = 0.34, 95% CI: 0.17–0.70), multitasking (OR = 0.33, 95% CI: 0.18–0.59), and verbal ability (OR = 0.46, 95% CI: 0.24–0.88). Consistent with the previous study, lower odds of subjective CRCI among patients with the BDNF Met allele was observed after adjusting for potential confounders in the multitasking (OR = 0.30, 95% CI: 0.14–0.67) domain. In conclusion, carriers of the BDNF Met allele were protected against global subjective CRCI, particularly in the domains of memory, multitasking, and verbal ability. Our findings further contribute to the understanding of CRCI pathophysiology.

Impact of brain-derived neurotrophic factor genetic polymorphism on cognition: A systematic review

INTRODUCTION

Brain-derived neurotrophic factor (BDNF) has an important role in the neurogenesis and neuroplasticity of the brain. This systematic review was designed to examine the association between BDNF Val66Met (rs6265) polymorphism and four cognitive domains-attention and concentration, executive function, verbal fluency, and memory, respectively.

METHODOLOGY

Primary literature search was performed using search engines such as PubMed and Scopus. Observational studies that evaluated the neurocognitive performances in relation to BDNF polymorphism within human subjects were included in this review, while animal studies, overlapping studies, and meta-analysis were excluded.

RESULTS

Forty of 82 reviewed studies (48.8%) reported an association between Val66Met polymorphism and neurocognitive domains. The proportion of the studies showing positive findings in cognitive performances between Val/Val homozygotes and Met carriers was comparable, at 30.5% and 18.3%, respectively. The highest percentage of positive association between Val66Met polymorphism and neurocognition was reported under the memory domain, with 26 of 63 studies (41.3%), followed by 18 of 47 studies (38.3%) under the executive function domain and four of 23 studies (17.4%) under the attention and concentration domain. There were no studies showing an association between Val66Met polymorphism and verbal fluency. In particular, Val/Val homozygotes performed better in tasks related to the memory domain, while Met carriers performed better in terms of executive function, in both healthy individuals and clinical populations.

CONCLUSION

While numerous studies report an association between Val66Met polymorphism and neurocognitive changes in executive function and memory domains, the effect of Met allele has not been clearly established.

Methylene blue protects dopaminergic neurons against MPTP-induced neurotoxicity by upregulating brain-derived neurotrophic factor

The relatively old, yet clinically used, drug methylene blue (MB) is known to possess neuroprotective properties by reducing aggregated proteins, augmenting the antioxidant response, and enhancing mitochondrial function and survival in various models of neurodegenerative diseases. In this study, we aimed to examine the effects of MB in Parkinson's disease (PD) in vivo and in vitro models by using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/1-methyl-4-phenylpyridinium (MPP⁺ ) with a focus on possible effects on induction of neurotrophic factors. Our results indicate that pretreatment with MB significantly attenuated MPTP-induced loss of dopaminergic neurons, glial cell activation, and depletion of dopamine. We also found that MB upregulated brain-derived neurotrophic factor (BDNF) and activated its downstream signaling pathways, suggesting that BDNF might be a contributor to MB-associated neuroprotection. Specific inhibition of the BDNF receptor or extracellular signal-regulated kinase (Erk) reversed the MB-mediated protection against MPP⁺ toxicity, thus implying a role for BDNF and the Erk pathway in the neuroprotective effects. Taken together, our data suggest that MB protects neurons from MPTP neurotoxicity via induction of BDNF. Further study to determine whether MB preserves dopaminergic neurons in the brains of PD patients is warranted.

BDNF Polymorphism: A Review of Its Diagnostic and Clinical Relevance in Neurodegenerative Disorders

Brain-derived neurotrophic factor (BDNF) has a unique role in the neuronal development, differentiation, and survival in the developing and adult nervous system. A common single-nucleotide polymorphism in the pro-region of the human BDNF gene, resulting in a valine to methionine substitution (Val66Met), has been associated with the susceptibility, incidence, and clinical features of several neurodegenerative disorders. Much research has been dedicated to evaluating the effects of polymorphism in the past decade, and functional effects of this genetic variation. A better understanding of how this naturally occurring polymorphism associates with or influences physiology, anatomy, and cognition in both healthy and diseased adults in neurodegenerative conditions will help understand neurochemical mechanisms and definable clinical outcomes in humans. Here we review the role and relevance of the BDNF Val66Met polymorphism in neurodegenerative diseases, with particular emphasis on glaucoma, multiple sclerosis (MS), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Several controversies and unresolved issues, including small effect sizes, possible ethnicity, gender, and age effects of the BDNF Val66Met are also discussed with respect to future research.

De novo tetrahydrobiopterin biosynthesis is impaired in the inflammed striatum of parkin(-/-) mice

Parkinson's disease (PD), the second-most prevalent neurodegenerative disease, is primarily characterized by neurodegeneration in the substantia nigra pars compacta, resulting in motor impairment. Loss-of-function mutations in parkin are the major cause of the early onset familial form of the disease. Although rodents deficient in parkin (parkin(-/-) ) have some dopaminergic system dysfunction associated with central oxidative stress and energy metabolism deficiencies, these animals only display nigrostriatal pathway degeneration under inflammatory conditions. This study investigated the impact of the inflammatory stimulus induced by lypopolisaccharide (LPS) on tetrahydrobiopterin (BH4) synthesizing enzymes (de novo and salvage pathways), since this cofactor is essential for dopamine synthesis. The mitochondrial content and architecture was investigated in the striatum of LPS-exposed parkin(-/-) mice. As expected, the LPS (0.33 mg/kg; i.p.) challenge compromised spontaneous locomotion and social interaction with juvenile parkin(-/-) and WT mice. Moreover, the genotype impacted the kinetics of the investigation of the juvenile. The inflammatory scenario did not induce apparent changes in mitochondrial ultrastructure; however, it increased the quantity of mitochondria, which were of smaller size, and provoked the perinuclear distribution of the organelle. Furthermore, the BH4 de novo biosynthetic pathway failed to be up-regulated in the LPS challenge, a well-known stimulus for its activation. The LPS treatment increased sepiapterin reductase (SPR) expression, suggesting compensation by the salvage pathway. This might indicate that dopamine synthesis is compromised in parkin(-/-) mice under inflammatory conditions. Finally, this scenario impaired the striatal expression of the transcription factor BDNF, possibly favoring cell death.

Significant association of BDNF rs6265 G>A polymorphism with susceptibility to epilepsy: a meta-analysis

INTRODUCTION

Previously published articles have suggested that BDNF rs6265 G>A polymorphism is a potential risk factor for epilepsy. However, the results were not consistent.

METHODS

We conducted a meta-analysis to explore the association between BDNF rs6265 G>A polymorphism and epilepsy risk. Four online databases were searched, and related studies were reviewed from their inception up to June 20, 2017. ORs and corresponding 95% CIs were used to calculate the associations of each genetic model. Overall, 10 case-control publications involving 9,512 subjects were included in this meta-analysis.

RESULTS

Significant associations were found between BDNF rs6265 G>A polymorphism and epilepsy (A vs G: OR=0.88, 95% CI=0.83-0.94, P<0.01, I²=0%; GA vs GG: OR=0.88, 95% CI=0.79-0.97, P=0.01, I²=0%; AA vs GG: OR=0.79, 95% CI=0.70-0.90, P<0.01, I²=0%; GA+AA vs GG: OR=0.85, 95% CI=0.77-0.94, P<0.01, I²=0%; AA vs GG+GA: OR=0.85, 95% CI=0.76-0.95, P=0.01, I²=0%). Subgroup analysis also showed similar results in an Asian population.

CONCLUSION

Our meta-analysis indicated that BDNF rs6265 G>A polymorphism might be involved in epilepsy susceptibility, especially in the Asian population.

Childhood trauma, BDNF Val66Met and subclinical psychotic experiences. Attempt at replication in two independent samples

Childhood trauma exposure is a robust environmental risk factor for psychosis. However, not all exposed individuals develop psychotic symptoms later in life. The Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism (rs6265) has been suggested to moderate the psychosis-inducing effects of childhood trauma in clinical and nonclinical samples. Our study aimed to explore the interaction effect between childhood trauma and the BDNF Val66Met polymorphism on subclinical psychotic experiences (PEs). This was explored in two nonclinical independent samples: an undergraduate and technical-training school student sample (n = 808, sample 1) and a female twin sample (n = 621, sample 2). Results showed that childhood trauma was strongly associated with positive and negative PEs in nonclinical individuals. A BDNF Val66Met x childhood trauma effect on positive PEs was observed in both samples. These results were discordant in terms of risk allele: while in sample 1 Val allele carriers, especially males, were more vulnerable to the effects of childhood trauma regarding PEs, in sample 2 Met carriers presented higher PEs scores when exposed to childhood trauma, compared with Val carriers. Moreover, in sample 2, a significant interaction was also found in relation to negative PEs. Our study partially replicates previous findings and suggests that some individuals are more prone to develop PEs following childhood trauma because of a complex combination of multiple factors. Further studies including genetic, environmental and epigenetic factors may provide insights in this field.