Association between Val66Met polymorphism of Brain-Derived Neurotrophic Factor (BDNF) gene and a deficiency of colour vision in alcohol-dependent male patients

Alterations in Neurotrophins in Alcohol-Addicted Patients during Alcohol Withdrawal

BACKGROUND

Alcohol use disorder (AUD) is related to mental and somatic disorders that result in alcohol withdrawal syndrome (AWS), with 30% of AWS cases leading to life-threatening delirium tremens (DTs). Currently, studies do not support using any one biomarker in DTs. Neurotrophins affect neuromodulation, playing a role in the pathogenesis of AUD, AWS, and DTs.

METHODS

This review aims to summarize experimental and clinical data related to neurotrophins and S100B in neuroplasticity, as well as neurodegeneration in the context of AUD, AWS, and DTs. This work used publications that were selected based on the protocol consistent with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement.

RESULTS

The BDNF level could be a good candidate biomarker for relapse susceptibility, as it is significantly reduced during consumption and gradually increases during abstinence. GDNF influences AUD through its integral role in the function of dopaminergic neurons and ablates the return to alcohol-drinking behavior. NGF protects neurons from ethanol-induced cytotoxic damage and affects recovery from cognitive deficits after brain damage. The NT-3 level is decreased after alcohol exposure and is involved in compensatory mechanisms for cognitive decline in AUD. NT-4 affects oxidative stress, which is associated with chronic alcohol consumption. S100B is used as a biomarker of brain damage, with elevated levels in serum in AUD, and can protect 5-HT neurons from the damage caused by alcohol.

CONCLUSIONS

BDNF, GDNF, NT-3, NT-4, NGF, and S100B may be valuable markers for withdrawal syndrome. In particular, the most relevant is their association with the development of delirium complications. However, there are few data concerning some neurotrophins in AWS and DTs, suggesting the need for further research.

Aerobic exercise as a promising nonpharmacological therapy for the treatment of substance use disorders

Despite the prevalence and public health impact of substance use disorders (SUDs), effective long-term treatments remain elusive. Aerobic exercise is a promising, nonpharmacological treatment currently under investigation as a strategy for preventing drug relapse. Aerobic exercise could be incorporated into the comprehensive treatment regimens for people with substance abuse disorders. Preclinical studies of SUD with animal models have shown that aerobic exercise diminishes drug-seeking behavior, which leads to relapse, in both male and female rats. Nevertheless, little is known regarding the effects of substance abuse-induced cellular and physiological adaptations believed to be responsible for drug-seeking behavior. Accordingly, the overall goal of this review is to provide a summary and an assessment of findings to date, highlighting evidence of the molecular and neurological effects of exercise on adaptations associated with SUD.

BDNF Therapeutic Mechanisms in Neuropsychiatric Disorders

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain and functions as both a primary neurotrophic signal and a neuromodulator. It serves essential roles in neuronal development, maintenance, transmission, and plasticity, thereby influencing aging, cognition, and behavior. Accumulating evidence associates reduced central and peripheral BDNF levels with various neuropsychiatric disorders, supporting its potential utilization as a biomarker of central pathologies. Subsequently, extensive research has been conducted to evaluate restoring, or otherwise augmenting, BDNF transmission as a potential therapeutic approach. Promising results were indeed observed for genetic BDNF upregulation or exogenous administration using a multitude of murine models of neurological and psychiatric diseases. However, varying mechanisms have been proposed to underlie the observed therapeutic effects, and many findings indicate the engagement of disease-specific and other non-specific mechanisms. This is because BDNF essentially affects all aspects of neuronal cellular function through tropomyosin receptor kinase B (TrkB) receptor signaling, the disruptions of which vary between brain regions across different pathologies leading to diversified consequences on cognition and behavior. Herein, we review the neurophysiology of BDNF transmission and signaling and classify the converging and diverging molecular mechanisms underlying its therapeutic potentials in neuropsychiatric disorders. These include neuroprotection, synaptic maintenance, immunomodulation, plasticity facilitation, secondary neuromodulation, and preservation of neurovascular unit integrity and cellular viability. Lastly, we discuss several findings suggesting BDNF as a common mediator of the therapeutic actions of centrally acting pharmacological agents used in the treatment of neurological and psychiatric illness.

Visuoperceptive Impairments in Severe Alcohol Use Disorder: A Critical Review of Behavioral Studies

The present literature review is aimed at offering a comprehensive and critical view of behavioral data collected during the past seventy years concerning visuoperception in severe alcohol use disorders (AUD). To pave the way for a renewal of research and clinical approaches in this very little understood field, this paper (1) provides a critical review of previous behavioral studies exploring visuoperceptive processing in severe AUD, (2) identifies the alcohol-related parameters and demographic factors that influence the deficits, and (3) addresses the limitations of this literature and their implications for current clinical strategies. By doing so, this review highlights the presence of visuoperceptive deficits but also shows how the lack of in-depth studies exploring the visual system in this clinical population results in the current absence of integration of these deficits in the dominant models of vision. Given the predominance of vision in everyday life, we stress the need to better delineate the extent, the specificity, and the actual implications of the deficits for severe AUD.

Association study of BDNF and DRD3 genes with alcohol use disorder in Schizophrenia

Alcohol use disorder (AUD) is a leading risk factor of disease burden in the world. It is also commonly comorbid with over 20% of schizophrenia patients. The brain-derived neurotrophic factor (BDNF) and dopamine D3 receptor (DRD3) have been implicated in alcohol drinking behaviour. Previous genetic studies of the BDNF and DRD3 genes produced mixed findings; however, only one study investigated two BDNF genetic markers with alcohol dependence in schizophrenia patients. We investigated 15 single-nucleotide polymorphisms (SNPs) in DRD3 and four SNPs in BDNF for possible association with alcohol abuse or dependence in schizophrenia patients of European ancestry (N = 195). The patients were assessed for the occurrence of alcohol abuse or alcohol dependence using the Structured Clinical Interview for DSM-IV Axis I Disorders, Patient Edition (SCID-I/P). We found the BDNF Val66Met to be associated with alcohol dependence (p = 0.004). We also found haplotypes across BDNF to be nominally associated with alcohol dependence. Analyses of DRD3 markers and haplotypes yielded mostly negative findings. Our findings support a role of the BDNF gene in alcohol dependence in schizophrenia patients. Larger samples are required to confirm our findings, particularly those of BDNF haplotypes.

From genetic studies to precision medicine in alcohol dependence

Genetic factors contribute to more than 50% of the variation in the vulnerability to alcohol dependence (AD). Although significant advances have been made in medications for AD, these medications do not work for all people. Precise tailoring of medicinal strategies for individual alcoholic patients is needed to achieve optimal outcomes. This review updates the most promising information on genetic variants in AD, which may be useful for improving diagnostic, therapeutic, and monitoring strategies. We describe genetic candidates of various neurotransmitter and enzyme systems. In addition to biological and allelic associations with AD, genetic effects on AD-related phenotypes and treatment responses have also been described. Gene-gene and gene-environment interactions have been considered. Potential applications of genomewide and epigenetic approaches for identifying genetic biomarkers of AD have been discussed. Overall, the application of genetic findings in precision medicine for AD will likely involve an integrated approach that distinguishes effect sizes of specific genetic predictors with regard to sex, pharmacotherapy, ethnicity, and AD-related aspects and considers gene-gene and gene-environment interactions. Our work may pave the way toward more precise treatment for AD that could ultimately improve clinical management and interventions.

Arachidonate 5-lipoxygenase (ALOX5) gene polymorphism is associated with Alzheimer's disease and body mass index

Dementias of old age, in particular Alzheimer's disease (AD), pose a growing threat to the longevity and quality of life of individuals as well as whole societies world-wide. The risk factors are both genetic and environmental (life-style) and there is an overlap with similar factors predisposing to cardiovascular diseases (CVD). Using a case-control genetic approach, we have identified a SNP (rs10507391) in ALOX5 gene, previously associated with an increased risk of stroke, as a novel genetic risk factor for AD. ALOX5 gene encodes a 5'-lipoxygenase (5'-LO) activating protein (FLAP), a crucial component of the arachidonic acid/leukotriene inflammatory cascade. A-allele of rs4769874 polymorphism increases the risk of AD 1.41-fold (p<0.0001), while AA genotype does so 1.79-fold (p<0.0001). In addition, GG genotype of rs4769874 polymorphism is associated with a modest increase in body mass index (BMI). We discuss potential biochemical mechanisms linking the SNP to AD and suggest possible preventive pharmacotherapies some of which are based on commonly available natural products. Finally, we set the newly identified AD risk factors into a broader context of similar CVD risk factors to generate a more comprehensive picture of interacting genetics and life-style habits potentially leading to the deteriorating mental health in the old age.

A 40-bp VNTR polymorphism in the 3'-untranslated region of DAT1/SLC6A3 is associated with ADHD but not with alcoholism

Background

ADHD and alcoholism are psychiatric diseases with pathophysiology related to dopamine system. DAT1 belongs to the SLC6 family of transporters and is involved in the regulation of extracellular dopamine levels. A 40 bp variable number tandem repeat (VNTR) polymorphism in the 3′-untranslated region of DAT1/SLC6A3 gene was previously reported to be associated with various phenotypes involving disturbed regulation of dopaminergic neurotransmission.

Methods

A total of 1312 subjects were included and genotyped for 40 bp VNTR polymorphism of DAT1/SLC6A3 gene in this study (441 alcoholics, 400 non-alcoholic controls, 218 ADHD children and 253 non ADHD children). Using miRBase software, we have performed a computer analysis of VNTR part of DAT1 gene for presence of miRNA binding sites.

Results

We have found significant relationships between ADHD and the 40 bp VNTR polymorphisms of DAT1/SLC6A3 gene (P < 0.01). The 9/9 genotype appeared to reduce the risk of ADHD about 0.4-fold (p < 0.04). We also noted an occurrence of rare genotypes in ADHD (frequency different from controls at p < 0.01). No association between alcoholism and genotype frequencies of 40 bp VNTR polymorphism of DAT1/SLC6A3 gene has been detected.

Conclusions

We have found an association between 40 bp VNTR polymorphism of DAT1/SLC6A3 gene and ADHD in the Czech population; in a broad agreement with studies in other population samples. Furthermore, we detected rare genotypes 8/10, 7/10 and 10/11 present in ADHD boys only and identified miRNAs that should be looked at as potential novel targets in the research on ADHD.

GLAST But Not Least--Distribution, Function, Genetics and Epigenetics of L-Glutamate Transport in Brain--Focus on GLAST/EAAT1

Synaptically released L-glutamate, the most important excitatory neurotransmitter in the CNS, is removed from extracellular space by fast and efficient transport mediated by several transporters; the most abundant ones are EAAT1/GLAST and EAAT2/GLT1. The review first summarizes their location, functions and basic characteristics. We then look at genetics and epigenetics of EAAT1/GLAST and EAAT2/GLT1 and perform in silico analyses of their promoter regions. There is one CpG island in SLC1A2 (EAAT2/GLT1) gene and none in SLC1A3 (EAAT1/GLAST) suggesting that DNA methylation is not the most important epigenetic mechanism regulating EAAT1/GLAST levels in brain. There are targets for specific miRNA in SLC1A2 (EAAT2/GLT1) gene. We also note that while defects in EAAT2/GLT1 have been associated with various pathological states including chronic neurodegenerative diseases, very little is known on possible contributions of defective or dysfunctional EAAT1/GLAST to any specific brain disease. Finally, we review evidence of EAAT1/GLAST involvement in mechanisms of brain response to alcoholism and present some preliminary data showing that ethanol, at concentrations which may be reached following heavy drinking, can have an effect on the distribution of EAAT1/GLAST in cultured astrocytes; the effect is blocked by baclofen, a GABA-B receptor agonist and a drug potentially useful in the treatment of alcoholism. We argue that more research effort should be focused on EAAT1/GLAST, particularly in relation to alcoholism and drug addiction.

BDNF rs6265 polymorphism and drug addiction: a systematic review and meta-analysis

A majority of studies have shown a link between the common functional rs6265 polymorphism of the BDNF gene and susceptibility to drug dependence. However, the pattern of results is inconsistent. To precisely evaluate this association, a systematic review and meta-analysis of previous case–control reports was conducted. Data from 20 studies containing 9419 participants (4665 cases and 4754 controls) conducted between 2004 and 2013 restricted to alcohol, nicotine, heroin, substance and methamphetamine dependency were meta-analyzed. Following quality control of the results, a significant association between C allele and methamphetamine dependence remained in south Asian subjects (p = 0.004). Similar results were detected in south Asian subjects for methamphetamine dependence and in Chinese subjects for heroin dependence under an autosomal codominant genotype model (TT vs CC, p = 0.005 and p = 0.0004, respectively). In conclusion, the rs6265 polymorphism may be a risk factor for methamphetamine dependence in south Asian subjects or for heroin dependence in Chinese subjects.

Brain-derived neurotrophic factor Val66Met polymorphism and alcohol-related phenotypes

Alcoholism is a chronic psychiatric disorder affecting neural pathways that regulate motivation, stress, reward and arousal. Brain-derived neurotrophic factor (BDNF) regulates mood, response to stress and interacts with neurotransmitters and stress systems involved in reward pathways and addiction. Aim of the study was to evaluate the association between a single nucleotide polymorphism (BDNF Val66Met or rs6265) and alcohol related phenotypes in Caucasian patients. In ethnically homogenous Caucasian subjects of the Croatian origin, the BDNF Val66Met genotype distribution was determined in 549 male and 126 female patients with alcohol dependence and in 655 male and 259 female healthy non-alcoholic control subjects. Based on the structured clinical interview, additional detailed clinical interview, the Brown-Goodwin Scale, the Hamilton Rating Scale for Depression and the Clinical Global Impression scores, alcoholic patients were subdivided into those with or without comorbid depression, aggression, delirium tremens, withdrawal syndrome, early/late onset of alcohol abuse, prior suicidal attempt during lifetime, current suicidal behavior, and severity of alcohol dependence. The results showed no significant association between BDNF Val66Met variants and alcohol dependence and/or any of the alcohol related phenotypes in either Caucasian women, or men, with alcohol dependence. There are few limitations of the study. The overall study sample size was large (N=1589) but not well-powered to detect differences in BDNF Val66Met genotype distribution between studied groups. Healthy control women were older than female alcoholic patients. Only one BDNF polymorphism (rs6265) was studied. In conclusion, these data do not support the view that BDNF Val66Met polymorphism correlates with the specific alcohol related phenotypes in ethnically homogenous medication-free Caucasian subjects with alcohol dependence.