Increased serum neurotrophin levels related to alcohol use disorder in a young population sample

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.

A Four-Week High-Fat Diet Induces Anxiolytic-like Behaviors through Mature BDNF in the mPFC of Mice

The effect of a high-fat diet (HFD) on mood is a widely debated topic, with the underlying mechanisms being poorly understood. This study explores the anxiolytic effects of a four-week HFD in C57BL/6 mice. Five-week-old mice were exposed to either an HFD (60% calories from fat) or standard chow diet (CD) for four weeks, followed by cannula implantation, virus infusion, behavioral tests, and biochemical assays. Results revealed that four weeks of an HFD induced anxiolytic-like behaviors and increased the protein levels of mature brain-derived neurotrophic factor (mBDNF) and phosphorylated tyrosine kinase receptor B (p-TrkB) in the medial prefrontal cortex (mPFC). Administration of a BDNF-neutralizing antibody to the mPFC reversed HFD-induced anxiolytic-like behaviors. Elevated BDNF levels were observed in both neurons and astrocytes in the mPFC of HFD mice. Additionally, these mice exhibited a higher number of dendritic spines in the mPFC, as well as upregulation of postsynaptic density protein 95 (PSD95). Furthermore, mRNA levels of the N6-methyladenosine (m6A) demethylase, fat mass and obesity-associated protein (FTO), and the hydrolase matrix metalloproteinase-9 (MMP9), also increased in the mPFC. These findings suggest that an HFD may induce FTO and MMP9, which could potentially regulate BDNF processing, contributing to anxiolytic-like behaviors. This study proposes potential molecular mechanisms that may underlie HFD-induced anxiolytic behaviors.

Effect of alcohol on Brain-Derived Neurotrophic Factor (BDNF) blood levels: a systematic review and meta-analysis

Brain-Derived Neurotrophic Factor (BDNF) is a vital protein involved in neuronal development, survival, and plasticity. Alcohol consumption has been implicated in various neurocognitive deficits and neurodegenerative disorders. However, the impact of alcohol on BDNF blood levels remains unclear. This systematic review and meta-analysis aimed to investigate the effect of alcohol consumption on BDNF blood levels. A comprehensive search of electronic databases was conducted to identify relevant studies. Eligible studies were selected based on predefined inclusion criteria. Data extraction was performed, and methodological quality was assessed using appropriate tools. A meta-analysis was conducted to estimate the overall effect size of alcohol consumption on BDNF levels. A total of 25 studies met the inclusion criteria and were included in the final analysis. Alcohol use and BDNF blood levels were significantly correlated, according to the meta-analysis (p = 0.008). Overall, it was discovered that drinking alcohol significantly decreased BDNF levels (SMD: - 0.39; 95% CI: - 0.68 to - 0.10; I2: 93%). There was a non-significant trend suggesting that alcohol withdrawal might increase BDNF levels, with an SMD of 0.26 (95% CI: - 0.09 to 0.62; I2: 86%; p = 0.14). Subgroup analysis based on the source of BDNF demonstrated significant differences between the subgroups (p = 0.0008). No significant publication bias was observed. This study showed that alcohol consumption is associated with a significant decrease in BDNF blood levels. The findings suggest a negative impact of alcohol on BDNF levels regardless of alcohol dosage. Further studies are needed to strengthen the evidence and elucidate the underlying mechanisms.

BDNF and its Role in the Alcohol Abuse Initiated During Early Adolescence: Evidence from Preclinical and Clinical Studies

Brain-derived neurotrophic factor (BDNF) is a crucial brain signaling protein that is integral to many signaling pathways. This neurotrophin has shown to be highly involved in brain plastic processes such as neurogenesis, synaptic plasticity, axonal growth, and neurotransmission, among others. In the first part of this review, we revise the role of BDNF in different neuroplastic processes within the central nervous system. On the other hand, its deficiency in key neural circuits is associated with the development of psychiatric disorders, including alcohol abuse disorder. Many people begin to drink alcohol during adolescence, and it seems that changes in BDNF are evident after the adolescent regularly consumes alcohol. Therefore, the second part of this manuscript addresses the involvement of BDNF during adolescent brain maturation and how this process can be negatively affected by alcohol abuse. Finally, we propose different BNDF enhancers, both behavioral and pharmacological, which should be considered in the treatment of problematic alcohol consumption initiated during the adolescence.

Glial cell line-derived neurotrophic factor contributes to alcoholic-induced liver injury by regulating the NF-κB pathway

BACKGROUND

Alcoholic liver disease (ALD) is associated with high morbidity and mortality worldwide. The pathogenesis of ALD is not completely understood. Although accumulating evidence suggests an important role of glial cell line-derived neurotrophic factor (GDNF) in several diseases, there are no data concerning its role in ALD. This study compared patients with ALD with control subjects and used a mouse model and a cell culture model to investigate the function of GDNF in ALD and its mechanism of action in hepatocyte injury.

METHODS

Serum levels of GDNF were measured in 25 patients with ALD and 25 healthy control subjects. A 4-week Lieber-DeCarli ethanol (EtOH) liquid diet combined with the Gao-Binge model was used in the mouse study. Mouse primary hepatocytes and Huh-7 cells were used for cell experiments. The parameters of liver injury, inflammatory cytokines, and lipid metabolism were measured.

RESULTS

Patients with alcoholic hepatitis had higher serum GDNF than control subjects. Expression of GDNF mRNA and protein was markedly increased in mice in the chronic-plus-binge ALD mouse model. The level of GDNF mRNA was upregulated in primary hepatic stellate cells isolated from ethanol-fed mouse liver. Ethanol induced GDNF expression in LX2 cells. The levels of inflammatory cytokines (tumor necrosis factor α, interleukin 1β, and monocyte chemotactic protein 1) were significantly increased after GDNF stimulation in primary hepatocytes and Huh-7 cells. After GDNF stimulation, levels of both p-AKT and p-NF-κB were significantly increased in primary hepatocytes and Huh-7 cells. The NF-κB activity induced by GDNF was significantly decreased by an NF-κB inhibitor, which limited hepatocyte injury and inflammation.

CONCLUSIONS

The concentration of GDNF is increased in the circulation of ALD patients. GDNF promotes alcohol-induced liver injury and inflammation via the activation of NF-κB, which mediates hepatocyte injury and inflammatory cytokine expression. Based on these findings, GDNF is a potential therapeutic target for preventing or ameliorating liver injury in ALD.

Nerve Growth Factor in Alcohol Use Disorders

The nerve growth factor (NGF) belongs to the family of neurotrophic factors. Initially discovered as a signaling molecule involved in the survival, protection, differentiation, and proliferation of sympathetic and peripheral sensory neurons, it also participates in the regulation of the immune system and endocrine system. NGF biological activity is due to the binding of two classes of receptors: the tropomyosin-related kinase A (TrkA) and the low-affinity NGF pan-neurotrophin receptor p75. Alcohol Use Disorders (AUD) are one of the most frequent mental disorders in developed countries, characterized by heavy drinking, despite the negative effects of alcohol on brain development and cognitive functions that cause individual’s work, medical, legal, educational, and social life problems. In addition, alcohol consumption during pregnancy disrupts the development of the fetal brain causing a wide range of neurobehavioral outcomes collectively known as fetal alcohol spectrum disorders (FASD). The rationale of this review is to describe crucial findings on the role of NGF in humans and animals, when exposed to prenatal, chronic alcohol consumption, and on binge drinking.

Growth Factors and Alcohol Use Disorder

Neurotrophic growth factors were originally characterized for their support in neuronal differentiation, outgrowth, and survival during development. However, it has been acknowledged that they also play a vital role in the adult brain. Abnormalities in growth factors have been implicated in a variety of neurological and psychiatric disorders, including alcohol use disorder (AUD). This work focuses on the interaction between alcohol and growth factors. We review literature suggesting that several growth factors play a unique role in the regulation of alcohol consumption, and that breakdown in these growth factor systems is linked to the development of AUD. Specifically, we focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), fibroblast growth factor 2 (FGF2), and insulin growth factor 1 (IGF-1). We also review the literature on the potential role of midkine (MDK) and pleiotrophin (PTN) and their receptor, anaplastic lymphoma kinase (ALK), in AUD. We show that alcohol alters the expression of these growth factors or their receptors in brain regions previously implicated in addiction, and that manipulations on these growth factors and their downstream signaling can affect alcohol-drinking behaviors in animal models. We conclude that there is a need for translational and clinical research to assess the therapeutic potential of new pharmacotherapies targeting these systems.

Human Plasma BDNF Is Associated With Amygdala-Prefrontal Cortex Functional Connectivity and Problem Drinking Behaviors

BACKGROUND

Preclinical studies suggest that decreased levels of brain-derived neurotrophic factor in the amygdala play a role in anxiety and alcohol use disorder. The association between brain-derived neurotrophic factor levels and amygdala function in humans with alcohol use disorder is still unclear, although neuroimaging studies have also implicated the amygdala in alcohol use disorder and suggest that alcohol use disorder is associated with disrupted functional connectivity between the amygdala and prefrontal cortex during aversive states.

METHODS

The current study investigated whether plasma brain-derived neurotrophic factor levels in individuals with and without alcohol use disorder (n = 57) were associated with individual differences in amygdala reactivity and amygdala-prefrontal cortex functional connectivity during 2 forms of aversive responding captured via functional magnetic resonance imaging: anxiety elicited by unpredictable threat of shock and fear elicited by predictable threat of shock. We also examined whether brain-derived neurotrophic factor and brain function were associated with binge drinking episodes and alcohol use disorder age of onset.

RESULTS

During anxiety, but not fear, lower levels of plasma brain-derived neurotrophic factor were associated with less connectivity between the left amygdala and the medial prefrontal cortex and the inferior frontal gyrus. In addition, within individuals with alcohol use disorder (only), lower levels of brain-derived neurotrophic factor and amygdala-medial prefrontal cortex functional connectivity during anxiety were associated with more binge episodes within the past 60 days and a lower age of alcohol use disorder onset. There were no associations between brain-derived neurotrophic factor levels and focal amygdala task reactivity.

CONCLUSIONS

Together, the results indicate that plasma brain-derived neurotrophic factor levels are related to amygdala circuit functioning in humans, particularly during anxiety, and these individual differences may relate to drinking behaviors.

Alcohol consumption alters Gdnf promoter methylation and expression in rats

Alcohol use disorder is one of the most disabling diseases worldwide. Glial-cell derived neurotrophic factor (Gdnf) shows promising results concerning the inhibition of alcohol consumption in rodent models. We investigated the epigenetic regulation of Gdnf following ethanol consumption and withdrawal in a rat model. 32 Wistar rats underwent 7 weeks of intermittent access to alcohol in a 2-bottle choice (IA2BC). Whole blood, Nucleus Accumbens (NAc) and Ventral Tegmental Area (VTA) were collected immediately after the last 24 h of an alcohol-drinking session (alcohol group, AG) or 24 h after withdrawal (withdrawal group, WG). MRNA levels were measured using real-time quantitative PCR. Bisulfite-conversion of DNA and capillary sequencing was used to determine methylation levels of the core promoter (CP) and the negative regulatory element (NRE). The CP of the AG in the NAc was significantly less methylated compared to controls (p < 0.05). In the NAc, mRNA expression was significantly higher in the WG (p < 0.05). In the WG, mRNA expression levels in the VTA were significantly lower (p < 0.05) and showed significantly less methylation in the NRE in the VTA (p < 0.001) and the NAc (p < 0.01) compared to controls. Changes in the cerebral mRNA expression correspond to alterations in DNA methylation of the Gdnf promoter in a rodent model. Our results hold clinical relevance since differences in Gdnf mRNA expression and DNA methylation could be a target for pharmacological interventions.

A review of peripheral brain-derived neurotrophic factor levels in alcohol-dependent patients: Current understanding

Brain-derived neurotrophic factor (BDNF) plays a crucial role in neuroplasticity of the brain, and its role in alcohol dependence has been explored in the recent past. Animal studies suggest that BDNF may function as a protective factor in transition from social drinking to an alcohol use disorder. However, clinical studies have not been able to establish similar findings and have shown mixed results. In order to obtain a comprehensive understanding, the current review aims to evaluate the existing literature on the role of BDNF in alcohol dependence. Articles were retrieved using search engines PubMed and Google Scholar. Original research studies focusing on human participants, published in English till October 2018 were reviewed. Studies which measured BDNF levels in serum or plasma or both were included in this study. A total of 13 studies were found which compared BDNF levels in alcohol-dependent patients with control population. The studies have mixed findings. Seven studies measured BDNF levels across the abstinence period, and most of the studies show improving BDNF levels across the abstinence. The current review supports the notion that BDNF plays an important role in the neuroplasticity of alcohol dependence. However, it is premature at this stage to draw conclusions that BDNF may be used as a biomarker, as there have been inconclusive findings when compared with control population. Future studies with longer follow-ups, larger sample size, comparing early and late periods of alcohol abstinence are required for better understanding of the role BDNF in alcohol dependence.

GDNF and alcohol use disorder

Glial cell line-derived neurotrophic factor (GDNF) has been extensively studied for its role in the development and maintenance of the midbrain dopaminergic system, although evidence suggests that GDNF also plays a role in drug and alcohol addiction. This review focuses on the unique actions of GDNF in the mechanisms that prevent the transition from recreational alcohol use to abuse. Specifically, we describe studies in rodents suggesting that alcohol acutely increases GDNF expression in the ventral tegmental area, which enables the activation of the mitogen-activated protein kinase signaling pathway and the gating of alcohol intake. We further provide evidence to suggest that GDNF acts in the ventral tegmental area via both nongenomic and genomic mechanisms to suppress alcohol consumption. In addition, we describe findings indicating that when this endogenous protective pathway becomes dysregulated, alcohol intake levels escalate. Finally, we describe the potential use of GDNF inducers as a novel therapeutic approach to treat alcohol use disorder.

Expression of brain-derived neurotrophic factors, neurotrophin-3, and neurotrophin-4 in the nucleus accumbens during heroin dependency and withdrawal

Neurotrophins, brain-derived neurotrophic factors (BDNF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4), have been implicated in the modulation of heroin dependency. This study was designed to explore the expression alterations of BDNF, NT-3, and NT-4 in the context of heroin dependence and withdrawal in the rat nucleus accumbens (NAc). Heroin dependence was induced by a progressive intraperitoneal treatment of heroin. The results showed that the expression levels of BDNF and NT-4 were significantly decreased in the NAc of rats with heroin addiction in comparison with the control group, whereas there was a significant increase in BDNF and NT-4 expressions in the groups of rats with both naloxone-induced and spontaneous withdrawal. Moreover, NT-3 expression was markedly increased in the NAc of rats with heroin addiction and spontaneous withdrawal in comparison with the control group, but decreased in the NAc of rats with naloxone-induced withdrawal. These results indicated that chronic administration of heroin results in the alterations of BDNF, NT-3, and NT-4 expressions in the rat NAc. BDNF, NT-3, and NT-4 may play a critical role in the development of heroin dependency and withdrawal.

Peripheral levels of BDNF and opiate-use disorder: literature review and update

Several neurobiological factors are related to opiate-use disorder (OUD), and among them, neurotrophins have a relevant role. Brain-derived neurotrophic factor (BDNF) is a central neurotrophin involved in many neuronal processes, and it has been related to several psychiatric diseases and addictive disorders. BDNF can be measured in plasma and serum; its levels may reflect BDNF concentrations in the central nervous system (CNS) and, indirectly, CNS processes. Hence, peripheral BDNF could be a biomarker in clinical practice. This manuscript explores the findings about peripheral BDNF and OUD in humans. Opiates induce neurotoxicity in the CNS, which may be correlated with modifications in BDNF expression. Thus, basal levels of peripheral BDNF in OUD patients may be altered, which could be modified with abstinence. Also, opiates may modify epigenetic processes that may be associated with peripheral concentrations of BDNF, and in this line, withdrawal could reflect recovering processes in the CNS. Additionally, treatment modifies the peripheral concentrations of BDNF, but the clinical implications of those changes are yet not elucidated. No specific conclusion can be performed and more investigation in this area is necessary to elucidate the real potential of peripheral BDNF as a biomarker.

Mood disorder, anxiety, and suicide risk among subjects with alcohol abuse and/or dependence: a population-based study

Objective:

To evaluate the prevalence of alcohol abuse and/or dependence in a population-based sample of young adults and assess the prevalence of comorbid mood disorders, anxiety, and suicide risk in this population.

Methods:

This cross-sectional, population-based study enrolled 1,953 young adults aged 18-35 years. The CAGE questionnaire was used to screen for alcohol abuse and/or dependence, with CAGE scores ≥ 2 considered positive. Psychiatric disorders were investigated through the structured Mini International Neuropsychiatric Interview (MINI).

Results:

Alcohol abuse and/or dependence was identified in 187 (9.60%) individuals (5.10% among women and 15.20% among men). Alcohol abuse and/or dependence were more prevalent among men than women, as well as among those who used tobacco, illicit drugs or presented with anxiety disorder, mood disorder, and suicide risk.

Conclusion:

These findings suggest that alcohol abuse and/or dependence are consistently associated with a higher prevalence of psychiatric comorbidities, could be considered important predictors of other psychiatric disorders, and deserve greater public heath attention, pointing to the need for alcohol abuse prevention programs.

Mental disorders, functional impairment, and nerve growth factor

Nerve growth factor (NGF) is an important member of the neurotrophin family and its alteration has been associated with psychiatric disorders. Functionality consists of the activities that an individual can perform, as well as their social participation, which is an important factor in analyzing the carrier living conditions of subjects with psychiatric suffering. Several studies have evaluated functionality in bipolar disorder; however, no studies have evaluated the functionality in other mental disorders. There are also few studies investigating the association between functionality and the biological bases of mental disorders. This study aimed to evaluate the serum NGF levels in psychiatric patients and to verify a possible association between the serum neurotrophic levels and functionality. This was a cross-sectional study with a convenient sample obtained from the Public Mental Health Service from the south of Brazil. The final sample was composed of 286 patients enrolled from July 2013 to October 2014. Data was collected using a sociodemographic questionnaire, and the diagnosis was confirmed using the Mini International Neuropsychiatric Interview (M.I.N.I) and a Functioning Assessment Short Test. The serum NGF levels were determined using the enzyme-linked immunosorbent assay method. Statistical analyses were performed using IBM SPSS Statistic 21.0 software. NGF serum levels were increased significantly in patients with obsessive-compulsive disorder compared with patients with no obsessive-compulsive disorder (P=0.015). An increase in serum NGF levels in generalized anxiety disorder patients was observed compared with patients with no generalized anxiety disorder (P=0.047). NGF was negatively associated with autonomy (P=0.024, r=-0.136), work (P=0.040, r=-0.124), and cognition (P=0.024, r=-0.137), thereby showing that changes in serum levels of NGF are associated with functionality in mental disorders.