Association between Val66Met brain-derived neurotrophic factor (BDNF) gene polymorphism and post-treatment relapse in alcohol dependence

Association of Brain-derived Neurotrophic Factor Polymorphisms With Alcohol Use Disorder: An Updated Meta-Analysis of Genetic Association Studies

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been proposed to play a role in chronic alcohol consumption. However, studies investigating the association of single nucleotide polymorphisms (SNPs) in the BDNF gene with alcohol use disorder (AUD), including alcohol dependence, have obtained inconsistent results. This meta-analysis aims to examine the role of BDNF SNPs (rs6265, rs16917204, rs7103411, and rs11030104) in the risk of AUD.

MATERIALS AND METHODS

A multidatabase search identified 17 articles (20 studies) for inclusion. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to estimate associations using standard genetic models (homozygous, recessive, dominant, and codominant). Significant associations were defined as those with a p-value ≤ 0.05 after applying the Bonferroni correction (pBC). Subgroup analysis was conducted based on ethnicity (Caucasian and Asian populations). Sources of heterogeneity were investigated through outlier treatment and meta-regression analysis. Only significant outcomes were further subjected to sensitivity analysis and assessment of publication bias.

RESULTS

This meta-analysis generated four significant pooled ORs, representing the core outcomes, all of which indicated reduced risks. Overall, the results indicated a significant association between the BDNF polymorphism and the risk of AUD in homozygous (OR = 0.72, 95% CIs = 0.60-0.85, pBC = 0.0038) and codominant (OR = 0.84, 95% CIs = 0.78-0.91, pBC = 0.0019) model. In subgroup analysis by ethnicity, homozygous (OR = 0.59, 95% CIs = 0.44-0.78, pBC = 0.0057) and recessive (OR = 0.61, 95% CIs = 0.46-0.81, pBC = 0.0133) models of BDNF polymorphisms were significantly associated with a reduced risk of AUD in Caucasians. However, no significant associations were found in Asians. Meta-regression analysis did not identify any covariates that significantly contributed to the observed heterogeneity. The core significant associations were robust and showed no evidence of publication bias.

CONCLUSION

The current meta-analysis suggests that the examined BDNF SNPs have a protective effect in the overall analysis (homozygous and codominant) and in the Caucasians subgroup (homozygous and recessive) while the Asians exhibited no effects of BDNF SNPs on AUD. BDNF polymorphisms might serve as a protective factor against the risk of AUD and could be useful markers in the clinical genetics of AUD.

Analysis of the BDNF Gene rs6265 Polymorphism in a Group of Women with Alcohol Use Disorder, Taking into Account Personality Traits

It seems that BDNF has a direct influence on the brain pathways and is typically engaged during the processing of rewards. A surge in BDNF levels in the ventral tegmental area (the region from which the dopaminergic neurons of the mesocorticolimbic dopamine system originate and extend to the dorsolateral and ventromedial striatum) triggers a state of reward similar to that produced by opiates in animal studies. The aims of the study were (1) to analyze the association of the BDNF gene rs6265 polymorphism with AUD (alcohol use disorder) in women, (2) analyze personality and anxiety in alcohol-dependent and control woman, and (3) conduct an interaction analysis of rs6265 on personality, anxiety, and alcohol dependence. Our study found a notable interaction between the anxiety (trait and state), neuroticism, rs6265, and AUD. The alcohol AUD G/A genotype carriers revealed higher level of the anxiety trait (p < 0.0001) and neuroticism (p < 0.0001) compared to the control group with G/A and G/G genotypes. The alcohol use disorder subjects with the G/A genotype displayed higher levels of an anxiety state than the control group with G/A (p < 0.0001) and G/G (p = 0.0014) genotypes. Additionally, the alcohol use disorder subjects with the G/G genotype obtained lower levels of agreeability compared to the controls with G/A (p < 0.0001) and G/G (p < 0.0001) genotypes. Our study indicates that anxiety (trait and state) and neuroticism are interacting with the BDNF gene rs6265 polymorphism in alcohol-dependent women. Characteristics like anxiety (both as a trait and a state) and neuroticism could have a significant impact on the mechanism of substance dependency, particularly in females who are genetically susceptible. This is regardless of the reward system that is implicated in the emotional disruptions accompanying anxiety and depression.

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.

BDNF CpG methylation and serum levels covary during alcohol withdrawal in patients with alcohol use disorder: A pilot study

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) levels vary in various conditions including alcohol use disorder (AUD). We aimed to identify drivers of these variations.

METHODS

Twelve patients with AUD were assessed at hospitalisation for alcohol withdrawal and four months later. We looked for associations between the change in serum BDNF levels and (1) length of abstinence, (2) anxiety (Hamilton Anxiety Scale) and depression (Beck-Depression Inventory), (3) one functional BDNF genotype (rs6265) and (4) methylation levels of 12 CpG sites within the BDNF gene (located in exons I, IV and IX).

RESULTS

While abstinence remained, serum BDNF level increased. This increase correlated with the variation of methylation levels of the BDNF gene, and more specifically of exon I. We found no significant effect of length of abstinence, rs6265, depression or anxiety on serum BDNF level.

CONCLUSIONS

Epigenetic regulation of the BDNF gene may be involved in variations of BDNF blood level associated with alcohol abstinence.

Stress and Susceptibility: A Systematic Review of Prenatal Epigenetic Risks for Developing Post-Traumatic Stress Disorder

This review aims to systematically assess the current literature about prenatal epigenetic markers that lead to post-traumatic stress disorder susceptibility across the lifespan. Studies included in this review met several research criteria: Studies included (1) participants with a PTSD diagnosis according to the DSM-5, (2) prenatal epigenetic marker data that could be analyzed, and (3) explicit references to postnatal PTSD susceptibility. Our study sample fit within a timeframe of 2002 (the earliest recorded studies of prenatal susceptibility to post-traumatic stress disorder in the databases used) and February 2021 when the literature search for this review was terminated. Studies for this review were collated from PubMed, MEDLINE, Science Direct, and Boston College School of Social Work Library databases. A systematic search was conducted in these databases using basic keyword terms, such as "PSTD resilience" and "PTSD vulnerability," and then adding clarifying terms to refine specific searches, such as "epigenetics," "genetics," "epigenetic markers," "haplotypes," and "mRNA methylation." Based on these criteria and research methods, 33 studies remained for inclusion in the review sample. This review suggests that BDNF Val66-Met, a polymorphism of FKBP5, and an altered messenger ribonucleic acid methylation marker in NR3C1 present most often in cases of PTSD. These epigenetic markers might be implicated in central neurological processes related to post-traumatic stress disorder symptomatology.

Brain-derived neurotrophic factor Val66Met polymorphism moderates the relationship between impulsivity, negative emotions, and binge drinking intensity in university students

Studies on the genetic factors involved in binge drinking (BD) and its associated traits are very rare. The aim of this cross-sectional study was to investigate differences in the association between impulsivity, emotion regulation and BD in a sample of young adults according to the rs6265/Val66Met variant in the brain-derived neurotrophic factor (BDNF) gene, a well-known candidate gene in alcohol use disorders. We recruited 226 university students (112 women), aged between 18 and 25 years old, from two centers in France. The participants completed measures related to alcohol consumption, depression severity, state anxiety levels, impulsivity (UPPS-P), and difficulties in emotion regulation [Difficulty in Emotion Regulation Scale (DERS)]. The relationship between the BD score and the clinical characteristics in the BDNF genotype groups was assessed by partial correlation analyses and moderation analyses. The partial correlation analyses showed that, in the Val/Val genotype group, the BD score was positively related to UPPS-P Lack of Premeditation and Sensation Seeking scores. In the Met carriers group, the BD score was positively related to UPPS-P Positive Urgency, lack of Premeditation, lack of Perseverance and Sensation Seeking scores and to Clarity score of the DERS. Moreover, the BD score was positively associated with depression severity and state anxiety scores. The moderation analyses revealed that BDNF Val/Met genotype moderated the relationship between several clinical variables and BD. The results of the present study support the hypothesis of common and specific vulnerability factors regarding impulsivity and emotion regulation difficulties associated with BD according to this BDNF rs6265 polymorphism.

A Rat Model of the Brain-Derived Neurotrophic Factor Val66Met Polymorphism Shows Attenuated Motivation for Alcohol Self-Administration and Diminished Propensity for Cue-Induced Relapse in Females

Brain-derived neurotrophic factor (BDNF) has been implicated in alcohol use disorder. The Val66Met polymorphism is a common variant of the BDNF gene (rs6265) which reduces activity-dependent BDNF release, and has been suggested as a risk factor for psychiatric disorders and substance use. Using an operant self-administration paradigm, this study aimed to investigate ethanol preference and ethanol seeking in a novel rat model of the BDNF Val66Met polymorphism, Val68Met rats. Male and female BDNF Val68Met rats of three genotypes (Val/Val, Val/Met and Met/Met) were trained to lever press for a 10% ethanol solution. There was no effect of Val68Met genotype on acquisition of stable response to ethanol or its extinction. Met/Met rats of both sexes had a slight, but significantly lower breakpoint during progressive ratio sessions while female rats with the Met/Met genotype demonstrated a lower propensity for reinstatement of responding to cues. There were no effects of Val68Met genotype on anxiety-like behaviour or locomotor activity. In conclusion, Met/Met rats showed lower motivation to continue to press for a reward, and also a decreased propensity to relapse, suggesting a possible protective effect of the Met/Met genotype against alcohol use disorder, at least in females.

The BDNF Val68Met polymorphism causes a sex specific alcohol preference over social interaction and also acute tolerance to the anxiolytic effects of alcohol, a phenotype driven by malfunction of BDNF in the ventral hippocampus of male mice

BACKGROUND

The brain-derived neurotrophic factor (BDNF) Valine 66 to Methionine human polymorphism results in impaired activity-dependent BDNF release and has been linked to psychiatric disorders including depression and anxiety. We previously showed that male knock-in mice carrying the mouse Methionine homolog (Met68BDNF) exhibit excessive and compulsive alcohol drinking behaviors as compared to the wild-type Val68BDNF mice.

OBJECTIVE

Here, we set out to determine the potential mechanism for the heightened and compulsive alcohol drinking phenotypes detected in Met68BDNF mice.

RESULTS

We found that male, but not female Met68BDNF mice exhibit social anxiety-like behaviors. We further show that male Met68BDNF mice exhibit a preference for alcohol over social interaction. In contrast, alcohol place preference without an alternative social reward, is similar in male Met68BDNF and Val68BDNF mice. Since the Met68BDNF mice show social anxiety phenotypes, we tested whether alcohol reliefs anxiety similarly in Met68BDNF and Val68BDNF mice and found that male, but not female Met68BDNF mice are insensitive to the acute anxiolytic action of alcohol. Finally, we show that this acute tolerance to alcohol-dependent anxiolysis can be restored by overexpressing wild-type Val68BDNF in the ventral hippocampus (vHC) of Met68BDNF mice.

CONCLUSIONS

Together, our results suggest that excessive alcohol drinking in the Met68BDNF may be attributed, in part, to heighted social anxiety and a lack of alcohol-dependent anxiolysis, a phenotype that is associated with malfunction of BDNF signaling in the vHC of male Met68BDNF mice.

A Genome-Wide Association Study Reveals a BDNF-Centered Molecular Network Associated with Alcohol Dependence and Related Clinical Measures

At least 50% of factors predisposing to alcohol dependence (AD) are genetic and women affected with this disorder present with more psychiatric comorbidities, probably indicating different genetic factors involved. We aimed to run a genome-wide association study (GWAS) followed by a bioinformatic functional annotation of associated genomic regions in patients with AD and eight related clinical measures. A genome-wide significant association of rs220677 with AD (p-value = 1.33 × 10^-8 calculated with the Yates-corrected χ² test under the assumption of dominant inheritance) was discovered in female patients. Associations of AD and related clinical measures with seven other single nucleotide polymorphisms listed in previous GWASs of psychiatric and addiction traits were differently replicated in male and female patients. The bioinformatic analysis showed that regulatory elements in the eight associated linkage disequilibrium blocks define the expression of 80 protein-coding genes. Nearly 68% of these and of 120 previously published coding genes associated with alcohol phenotypes directly interact in a single network, where BDNF is the most significant hub gene. This study indicates that several genes behind the pathogenesis of AD are different in male and female patients, but implicated molecular mechanisms are functionally connected. The study also reveals a central role of BDNF in the pathogenesis of AD.

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.

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.

The Influence of 5-HTTLPR, BDNF Rs6265 and COMT Rs4680 Polymorphisms on Impulsivity in Bipolar Disorder: The Role of Gender

Impulsivity has been proposed as an endophenotype for bipolar disorder (BD); moreover, impulsivity levels have been shown to carry prognostic significance and to be quality-of-life predictors. To date, reports about the genetic determinants of impulsivity in mood disorders are limited, with no studies on BD individuals. Individuals with BD and healthy controls (HC) were recruited in the context of an observational, multisite study (GECOBIP). Subjects were genotyped for three candidate single-nucleotide polymorphisms (SNPs) (5-HTTLPR, COMT rs4680, BDNF rs6265); impulsivity was measured through the Italian version of the Barratt Impulsiveness Scale (BIS-11). A mixed-effects regression model was built, with BIS scores as dependent variables, genotypes of the three polymorphisms as fixed effects, and centers of enrollment as random effect. Compared to HC, scores for all BIS factors were higher among subjects with euthymic BD (adjusted β for Total BIS score: 5.35, p < 0.001). No significant interaction effect was evident between disease status (HC vs. BD) and SNP status for any polymorphism. Considering the whole sample, BDNF Met/Met homozygosis was associated with lower BIS scores across all three factors (adjusted β for Total BIS score: −10.2, p < 0.001). A significant 5-HTTLPR x gender interaction was found for the SS genotype, associated with higher BIS scores in females only (adjusted β for Total BIS score: 12.0, p = 0.001). Finally, COMT polymorphism status was not significantly associated with BIS scores. In conclusion, BD diagnosis did not influence the effect on impulsivity scores for any of the three SNPs considered. Only one SNP—the BDNF rs6265 Met/Met homozygosis—was independently associated with lower impulsivity scores. The 5-HTTLPR SS genotype was associated with higher impulsivity scores in females only. Further studies adopting genome-wide screening in larger samples are needed to define the genetic basis of impulsivity in BD.

Consequences of the rs6265 (Val66Met) polymorphism in the BDNF gene in selected mental disorders and sport

Introduction: Brain-derived neurotrophic factor (BDNF) is a polypeptide of 247 amino acid residues and is widely distributed throughout the central nervous system of the CNS. It plays an important role in the survival, differentiation, growth, and development of neurons in the central nervous system. The human BDNF gene is located on chromosome 11 in the p13-14 region and covers approximately 70 kb. The gene has a complex structure as it consists of 11 exons (I-IX, plus Vh and VIIIh) and nine functional promoters. BDNF expression in the brain is relatively low but it is found in most major regions of the brain.

Material and methods: The gene encoding the brain-derived neurotrophic factor BDNF has many polymorphisms, but one of them mainly attracts the attention of researchers. This is a common, non-conservative polymorphism - rs6265 - a single nucleotide SNP polymorphism that results in an amino acid change – valine (Val) to methionine (Met) - at codon 66.

Results: Polymorphism rs6265 is associated with many neuropsychiatric disorders, including depression or a higher risk of addiction, but it also determines other features, such as e.g. sports performance. Few studies are investigating the relationship between rs6265 polymorphism and predisposition to play sports.

Conclusions: The results on the effect of rs6265 BDNF polymorphic variants on the risk of depression and addition are inconsistent, indicating a significant association in some studies and none in others. Therefore, more studies are needed to determine how rs6265 affects gene expression and function.

Data-driven study on resting-state functional magnetic resonance imaging during early abstinence of alcohol dependence in male patients and its predictive value for relapse

BACKGROUND

Alcohol dependence is a mental disorder with a high relapse rate. However, specific neuroimaging biomarkers have not been determined for alcohol dependence and its relapse. We conducted data-driven research to investigate resting-state functional magnetic resonance imaging (rs-fMRI) during early abstinence from alcohol dependence and its potential ability to predict relapse.

METHODS

Participants included 68 alcohol-dependent patients and 68 healthy controls (HCs). The regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuations (fALFF) were compared between the alcohol dependence group and the HCs and between the relapse group and the nonrelapse group. The brain regions that presented significantly different ReHo and/or fALFF between the alcohol-dependent patients and HCs and/or between the relapsed and nonrelapsed patients were selected as the seeds to calculate the functional connectivities (FCs).

RESULTS

During a 6-month follow-up period, 52.24% of alcohol-dependent patients relapsed. A regression model for differentiating alcohol-dependent patients and HCs showed that reductions in ReHo in the left postcentral region, fALFF in the right fusiform region, and FC in the right fusiform region to the right middle cingulum were independently associated with alcohol dependence, with an area under the receiver operating characteristic curve (AUC) of 0.841. The baseline FC of the left precentral to the left cerebellum of the relapse group was significantly lower than that of the nonrelapse group. The AUC of this FC to predict relapse was 0.774.

CONCLUSIONS

Our findings contribute to advancing research on the neurobiological etiology and predictive biomarkers for relapse associated with alcohol dependence.

Trophic factors as potential therapies for treatment of major mental disorders

Notwithstanding major advances in psychotherapeutics, their efficacy and specificity remain limited. The slow onset of beneficial outcomes and numerous adverse effects of widely used medications remain of chief concern, warranting in-depth studies. The majority of frontline therapies are thought to enhance the endogenous monoaminergic drive, to initiate a cascade of molecular events leading to lasting functional and structural plasticity. They also involve alterations in trophic factor signalling, including brain-derived neurotrophic factor (BDNF), VGF (non-acronymic), vascular endothelial growth factor (VEGF), fibroblast growth factor 2 (FGF2), glial cell-derived neurotrophic factor (GDNF), and others. In several major mental disorders, emerging data suggest protective and restorative effects of trophic factors in preclinical models, when applied on their own. Antidepressant outcomes of VGF and FGF2, for instance, were shown in experimental animals, while BDNF and GDNF prove useful in the treatment of addiction, schizophrenia, and autism spectrum disorders. The main challenge with the effective translation of these and other findings in the clinic is the knowledge gap in action mechanisms with potential risks, as well as the lack of effective platforms for validation under clinical settings. Herein, we review the state-of-the-art and advances in the therapeutic use of trophic factors in several major neuropsychiatric disorders.

A systematic review of gene-by-intervention studies of alcohol and other substance use

Alcohol and other substance use problems are common, and the efficacy of current prevention and intervention programs is limited. Genetics may contribute to differential effectiveness of psychosocial prevention and intervention programs. This paper reviews gene-by-intervention (G×I) studies of alcohol and other substance use, and implications for integrating genetics into prevention science. Systematic review yielded 17 studies for inclusion. Most studies focused on youth substance prevention, alcohol was the most common outcome, and measures of genotype were heterogeneous. All studies reported at least one significant G×I interaction. We discuss these findings in the context of the history and current state of genetics, and provide recommendations for future G×I research. These include the integration of genome-wide polygenic scores into prevention studies, broad outcome measurement, recruitment of underrepresented populations, testing mediators of G×I effects, and addressing ethical implications. Integrating genetic research into prevention science, and training researchers to work fluidly across these fields, will enhance our ability to determine the best intervention for each individual across development. With growing public interest in obtaining personalized genetic information, we anticipate that the integration of genetics and prevention science will become increasingly important as we move into the era of precision medicine.

Differential correlation of serum BDNF and microRNA content in rats with rapid or late onset of heavy alcohol use

Heavy alcohol use reduces the levels of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex of rodents through the upregulation of microRNAs (miRs) targeting BDNF mRNA. In humans, an inverse correlation exists between circulating blood levels of BDNF and the severity of psychiatric disorders including alcohol abuse. Here, we set out to determine whether a history of heavy alcohol use produces comparable alterations in the blood of rats. We used an intermittent access to 20% alcohol using the two-bottle choice paradigm (IA20%2BC) and measured circulating levels of BDNF protein and miRs targeting BDNF in the serum of Long-Evans rats before and after 8 weeks of excessive alcohol intake. We observed that the drinking profile of heavy alcohol users is not unified, whereas 70% of the rats gradually escalate their alcohol intake (late onset), and 30% of alcohol users exhibit a very rapid onset of drinking (rapid onset). We found that serum BDNF levels are negatively correlated with alcohol intake in both rapid onset and late onset rats. In contrast, increased expression of the miRs targeting BDNF, miR30a-5p, miR-195-5p, miR191-5p and miR206-3p, was detected only in the rapid onset rats. Finally, we report that the alcohol-dependent molecular changes are not due to alterations in platelet number. Together, these data suggest that rats exhibit both late and rapid onset of alcohol intake. We further show that heavy alcohol use produces comparable changes in BDNF protein levels in both groups. However, circulating microRNAs are responsive to alcohol only in the rapid onset rats.

Dimensions of Craving Interact with COMT Genotype to Predict Relapse in Individuals with Alcohol Use Disorder Six Months after Treatment

(1) Background: Alcohol use disorder (AUD) is associated with poor medical, psychological, and psychosocial outcomes and approximately 60% of individuals with AUD relapse six months after treatment. Craving is a core aspect of AUD and associated with high risk of relapse. One promising avenue to improve outcomes may be in understanding the relationship between COMT genotype, craving, and treatment outcomes. (2) Methods: To this end, we assessed craving, recent drinking history, and impulsivity in 70 individuals with AUD undergoing a standard course of treatment at a regional Veteran Affairs (VA) medical center. Saliva samples were collected to determine COMT genotype. In this prospective observational study, participants were followed for six months to determine who went on to relapse after treatment. (3) Results: Results revealed a significant interaction between craving and catechol-O-methyltransferse (COMT) genotype in predicting relapse. Post hoc exploratory analyses indicated that Met/Met homozygotes reported the highest levels of craving, and craving was associated with recent drinking history. Among Val/Val homozygotes, who had higher rates of relapse, craving was associated with impulsivity. (4) Conclusions: These associations highlight that specific profiles of psychological and biological factors may be important in understanding which individuals are at highest risk of relapse following treatment. Future studies that build on these findings are warranted.

Functional Connectivity of Nucleus Accumbens and Medial Prefrontal Cortex With Other Brain Regions During Early-Abstinence Is Associated With Alcohol Dependence and Relapse: A Resting-Functional Magnetic Resonance Imaging Study

Background: Alcohol dependence (AD) is a chronic recurrent brain disease that causes a heavy disease burden worldwide, partly due to high relapse rates after detoxification. Verified biomarkers are not available for AD and its relapse, although the nucleus accumbens (NAc) and medial prefrontal cortex (mPFC) may play important roles in the mechanism of addiction. This study investigated AD- and relapse-associated functional connectivity (FC) of the NAc and mPFC with other brain regions during early abstinence. Methods: Sixty-eight hospitalized early-abstinence AD male patients and 68 age- and education-matched healthy controls (HCs) underwent resting-functional magnetic resonance imaging (r-fMRI). Using the NAc and mPFC as seeds, we calculated changes in FC between the seeds and other brain regions. Over a follow-up period of 6 months, patients were measured with the Alcohol Use Disorder Identification Test (AUDIT) scale to identify relapse outcomes (AUDIT ≥ 8). Results: Thirty-five (52.24%) of the AD patients relapsed during the follow-up period. AD displayed lower FC of the left fusiform, bilateral temporal superior and right postcentral regions with the NAc and lower FC of the right temporal inferior, bilateral temporal superior, and left cingulate anterior regions with the mPFC compared to controls. Among these FC changes, lower FC between the NAc and left fusiform, lower FC between the mPFC and left cingulate anterior cortex, and smoking status were independently associated with AD. Subjects in relapse exhibited lower FC of the right cingulate anterior cortex with NAc and of the left calcarine sulcus with mPFC compared to non-relapsed subjects; both of these reductions in FC independently predicted relapse. Additionally, FC between the mPFC and right frontal superior gyrus, as well as years of education, independently predicted relapse severity. Conclusion: This study found that values of FC between selected seeds (i.e., the NAc and the mPFC) and some other reward- and/or impulse-control-related brain regions were associated with AD and relapse; these FC values could be potential biomarkers of AD or for prediction of relapse. These findings may help to guide further research on the neurobiology of AD and other addictive disorders.

Brain-Derived neurotrophic factor Val66Met induces female-specific changes in impulsive behaviour and alcohol self-administration in mice

Substance use disorders are a debilitating neuropsychiatric condition, however it remains unclear why some individuals are at greater risk of substance use disorders than others and what genetic factors determine such individual differences. Impulsivity appears a promising candidate endophenotype to bridge the gap between genetic risk and addiction. Brain-derived neurotrophic factor (BDNF), and in particular the BDNF^Val66Met polymorphism, has been suggested to be involved in both impulsivity and substance use disorders, however results so far have been inconsistent. To investigate the role of BDNF, and more specifically the BDNF^Val66Met polymorphism, in both impulsivity and operant alcohol self-administration using the same animal model. Separate cohorts of humanized Val66Met transgenic mice were assessed for either trait impulsivity in the 5-choice serial reaction time (5-CSRT) touchscreen task, or propensity towards obtaining ethanol in an operant paradigm. It was found that female hBDNF^Val/Val mice exhibited both greater impulsivity compared to hBDNF^Met/Met mice of the same sex as shown by a higher number of premature responses at one of three increased inter-trial intervals tested in the 5-CSRT task, and a greater propensity toward stable ethanol self-administration relative to male mice of the same genotype in the operant paradigm. By contrast, male mice showed no difference between genotypes in impulsivity or stable ethanol self-administration. The hBDNF^Met/Met genotype appears to sex-specifically alter aspects of both impulsive behaviour and addiction propensity. These results suggest that impulse behaviour may be a possible predictor of addiction risk.

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.

Investigating the link between serum concentrations of brain-derived neurotrophic factor and behavioral measures in anxious alcohol-dependent individuals

Brain-derived neurotrophic factor (BDNF) plays a role in different neurophysiological processes, including those involved in alcohol- and anxiety-related behaviors. Preclinical and clinical studies indicate that chronic excessive alcohol use leads to a downregulation of BDNF production in the periphery and in the brain. In addition, a decrease in BDNF concentrations in the blood has been reported to be associated with increased anxiety levels. Non-treatment-seeking alcohol-dependent individuals with high trait anxiety were studied to assess whether serum BDNF concentrations may be linked to self-reported levels of alcohol drinking, anxiety, and other behavioral measures. Participants had a current diagnosis of alcohol dependence, high trait anxiety score, and were not seeking treatment for alcohol dependence or anxiety. A fasting blood sample was collected from each participant and serum BDNF was measured using an enzyme-linked immunosorbent assay (ELISA). Behavioral data were collected on the same day, including measures of alcohol drinking, craving, dependence severity, and anxiety. Bivariate correlations were run between BDNF levels and behavioral measures. Serum BDNF concentrations were negatively correlated with average drinks per drinking days (r = -0.41, p = 0.02) and positively correlated with obsessive-compulsive drinking scale (r = 0.48, p = 0.007) and state-trait anxiety inventory (r = 0.52, p = 0.003) scores. These findings shed light on the possible role of the BDNF system in the neurobiology of alcohol- and anxiety-related behaviors.

The IMAGEN study: a decade of imaging genetics in adolescents

Imaging genetics offers the possibility of detecting associations between genotype and brain structure as well as function, with effect sizes potentially exceeding correlations between genotype and behavior. However, study results are often limited due to small sample sizes and methodological differences, thus reducing the reliability of findings. The IMAGEN cohort with 2000 young adolescents assessed from the age of 14 onwards tries to eliminate some of these limitations by offering a longitudinal approach and sufficient sample size for analyzing gene-environment interactions on brain structure and function. Here, we give a systematic review of IMAGEN publications since the start of the consortium. We then focus on the specific phenotype 'drug use' to illustrate the potential of the IMAGEN approach. We describe findings with respect to frontocortical, limbic and striatal brain volume, functional activation elicited by reward anticipation, behavioral inhibition, and affective faces, and their respective associations with drug intake. In addition to describing its strengths, we also discuss limitations of the IMAGEN study. Because of the longitudinal design and related attrition, analyses are underpowered for (epi-) genome-wide approaches due to the limited sample size. Estimating the generalizability of results requires replications in independent samples. However, such densely phenotyped longitudinal studies are still rare and alternative internal cross-validation methods (e.g., leave-one out, split-half) are also warranted. In conclusion, the IMAGEN cohort is a unique, very well characterized longitudinal sample, which helped to elucidate neurobiological mechanisms involved in complex behavior and offers the possibility to further disentangle genotype × phenotype interactions.

Receptor Tyrosine Kinases as Therapeutic Targets for Alcohol Use Disorder

The receptor tyrosine kinases (RTKs) are a large family of proteins that transduce extracellular signals to the inside of the cell to ultimately affect important cellular functions such as cell proliferation, survival, apoptosis, differentiation, and migration. They are expressed in the nervous system and can regulate behavior through modulation of neuronal and glial function. As a result, RTKs are implicated in neurodegenerative and psychiatric disorders such as depression and addiction. Evidence has emerged that 5 RTKs (tropomyosin-related kinase B (TrkB), RET proto-oncogene (RET), anaplastic lymphoma kinase (ALK), fibroblast growth factor receptor (FGFR), and epidermal growth factor receptor (EGFR)) modulate alcohol drinking and other behaviors related to alcohol addiction. RTKs are considered highly "druggable" targets and small-molecule inhibitors of RTKs have been developed for the treatment of various conditions, particularly cancer. These kinases are therefore attractive targets for the development of new pharmacotherapies to treat alcohol use disorder (AUD). This review will examine the preclinical evidence describing TrkB, RET, ALK, FGFR, and EGFR modulation of alcohol drinking and other behaviors relevant to alcohol abuse.

Association Between Brain-Derived Neurotrophic Factor Val66Met Polymorphism and Methamphetamine Use Disorder: A Meta-Analysis

Background: Several studies had examined the association between brain-derived neurotrophic factor (BDNF) Val66Met polymorphism and methamphetamine (METH) use disorder, whereas the results were conflicting. The aim of this study was to conduct a meta-analysis to achieve a pooled effect size of the association between BDNF Val66Met polymorphism and METH use disorder. Methods: Literature searches were conducted in PubMed, EMBASE, and Cochrane Library up to July, 2020. All relevant studies on the relationship of BDNF Val66Met polymorphism and METH addiction were retrieved. Pooled odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated in the dominant, recessive, co-dominant, and allele model to appraise the association. Results: Seven case-control studies with a total of 2,204 subjects (956 METH-dependent cases and 1,248 healthy controls) were included in this meta-analysis. The results showed a significant correlation between BDNF Val66Met polymorphism and METH dependence in overall population under different genetic models. However, subgroup analysis indicated that the association only existed in Han Chinese but not in other Asian populations. Conclusion: Although the current data indicate that BDNF Val66Met polymorphism might be a potential genetic factor for METH use disorder, more researches are needed to prove its role in different populations.

Comorbid HIV infection and alcohol use disorders: Converging glutamatergic and dopaminergic mechanisms underlying neurocognitive dysfunction

Alcohol use disorders (AUDs) are highly comorbid with human immunodeficiency virus (HIV) infection, occurring at nearly twice the rate in HIV positive individuals as in the general population. Individuals with HIV who consume alcohol show worse long-term prognoses and may be at elevated risk for the development of HIV-associated neurocognitive disorders. The direction of this relationship is unclear, and likely multifactorial. Chronic alcohol exposure and HIV infection independently promote cognitive dysfunction and further may interact to exacerbate neurocognitive deficits through effects on common targets, including corticostriatal glutamate and dopamine neurotransmission. Additionally, drug and alcohol use is likely to reduce treatment adherence, potentially resulting in accelerated disease progression and subsequent neurocognitive impairment. The development of neurocognitive impairments may further reduce cognitive control over behavior, resulting in escalating alcohol use. This review will examine the complex relationship between HIV infection and alcohol use, highlighting impacts on dopamine and glutamate systems by which alcohol use and HIV act independently and in tandem to alter corticostriatal circuit structure and function to dysregulate cognitive function.

A real-world study on clinical predictors of relapse after hospitalized detoxification in a Chinese cohort with alcohol dependence

BACKGROUND

The relapse rate of alcohol dependence (AD) after detoxification is high, but few studies have investigated the clinical predictors of relapse after hospitalized detoxification in real-world clinical practice, especially among Chinese patients.

METHODS

This longitudinal cohort study followed up 122 AD patients who were discharged from January 1, 2016 to January 30, 2018 from their most recent hospitalization for detoxification. These patients were interviewed by telephone from May 20, 2017, to June 30, 2018, at least 6 months after discharge. During the interview, the relapse were assessed by using a revised Chinese version of the Alcohol Use Disorder Identification Test. Candidate predictors, such as therapeutic modalities during hospitalization and at discharge, medical history data related to alcohol use, and demographic information, were obtained from the medical records in the hospital information system.

RESULTS

During the 6-24 months (with a median of 9 months) follow-up period, the relapse rate was 53.3%. Individuals with a college education level and those who had not been treated with the brief comprehensive cognitive-motivational-behavioural intervention (CCMBI) were more likely than their counterparts to relapse after hospitalized detoxification, and their adjusted HRs (95% CIs) were 1.85 (1.09, 3.16) and 2.00 (1.16, 3.46), respectively. The CCMBI use predicted a reduction in the relapse rate by approximately one-fifth.

CONCLUSION

Undergoing the CCMBI during detoxification hospitalization and having less than a college-level education could predict a reduced risk of AD relapse. These findings provide useful information both for further clinical research and for real-world practice.

Alcohol use disorder relapse factors: A systematic review

A relapsing-remitting course is very common in patients with an Alcohol Use Disorder (AUD). Understanding the determinants associated with alcohol resumption remains a formidable task. This paper examines relapse determinants based on a systematic review of recent alcohol literature (2000-2019). Relevant databases were consulted for articles that contained information about specific relapse determinants and reported statistical significance of each relapse determinant in predicting relapse. Relapse was broadly defined based on the characterization in the included articles. From the initial identified 4613 papers, a total of 321 articles were included. Results encompass multiple relapse determinants, which were ordered according to biopsychosocial and spiritual categories, and presented, using a descriptive methodology. Psychiatric co-morbidity, AUD severity, craving, use of other substances, health and social factors were consistently significantly associated with AUD relapse. Conversely, supportive social network factors, self efficacy, and factors related to purpose and meaning in life, were protective against AUD relapse. Despite heterogeneity in different methods, measures, and sample characteristics, these findings may contribute to a better therapeutic understanding in which specific factors are associated with relapse and those that prevent relapse. Such factors may have a role in a personalized medicine framework to improve patient outcomes.

Crossed Eye/Hand Laterality and Left-Eyedness Predict a Positive 24-Month Outcome in Alcohol-Dependent Patients

BACKGROUND

Available predictors of hospital readmission following withdrawal in alcohol-dependent patients are limited. However, such parameters are needed to optimize individualized treatment strategies. This study investigated whether crossed eye/hand laterality, eyedness, and handedness may predict outcomes in alcohol dependence.

METHODS

The prospective study included 200 early-abstinent alcohol-dependent inpatients (n[males] = 113, n[females] = 87) and 240 control subjects (n[males] = 133, n[females] = 107). We assessed eyedness and handedness using the hole-in-the-card and Shimizu tests and documented alcohol-related readmissions over 12 and 24 months.

RESULTS

Crossed eye/hand laterality and left-eyedness were associated with a reduced risk for alcohol-related readmission (12-month: odds ratios [OR] = 0.41, p = 0.008, OR = 0.42, p = 0.004; 24-month: OR = 0.57, p = 0.097, OR = 0.47, p = 0.016), fewer median readmissions (12-month: 0 vs. 1, p = 0.005, 0 vs. 1, p = 0.005; 24-month: 1 vs. 2, p = 0.014, 1 vs. 2, p = 0.006), and more mean days to the first readmission (12-month: 270 vs. 209, p = 0.007, 269 vs. 207, p = 0.003; 24-month: 462 vs. 335, p = 0.039, 461 vs. 323, p = 0.005). They also interacted with treatment and alcohol drinking history to predict the outcome. In sex-specific analyses, most of these effects remained significant in males but not in females. Handedness alone did not significantly predict outcome. Moreover, the laterality markers did not significantly differ between alcohol-dependent patients and control subjects.

CONCLUSIONS

Determining crossed eye/hand laterality and eyedness may help to individualize relapse prevention in the future. Both are easily accessible predictors of alcohol-related readmission following inpatient withdrawal treatment.

Cognitive Control as a 5-HT1A-Based Domain That Is Disrupted in Major Depressive Disorder

Heterogeneity within Major Depressive Disorder (MDD) has hampered identification of biological markers (e.g., intermediate phenotypes, IPs) that might increase risk for the disorder or reflect closer links to the genes underlying the disease process. The newer characterizations of dimensions of MDD within Research Domain Criteria (RDoC) domains may align well with the goal of defining IPs. We compare a sample of 25 individuals with MDD compared to 29 age and education matched controls in multimodal assessment. The multimodal RDoC assessment included the primary IP biomarker, positron emission tomography (PET) with a selective radiotracer for 5-HT1A [(11C)WAY-100635], as well as event-related functional MRI with a Go/No-go task targeting the Cognitive Control network, neuropsychological assessment of affective perception, negative memory bias and Cognitive Control domains. There was also an exploratory genetic analysis with the serotonin transporter (5-HTTLPR) and monamine oxidase A (MAO-A) genes. In regression analyses, lower 5-HT1A binding potential (BP) in the MDD group was related to diminished engagement of the Cognitive Control network, slowed resolution of interfering cognitive stimuli, one element of Cognitive Control. In contrast, higher/normative levels of 5-HT1A BP in MDD (only) was related to a substantial memory bias toward negative information, but intact resolution of interfering cognitive stimuli and greater engagement of Cognitive Control circuitry. The serotonin transporter risk allele was associated with lower 1a BP and the corresponding imaging and cognitive IPs in MDD. Lowered 5HT 1a BP was present in half of the MDD group relative to the control group. Lowered 5HT 1a BP may represent a subtype including decreased engagement of Cognitive Control network and impaired resolution of interfering cognitive stimuli. Future investigations might link lowered 1a BP to neurobiological pathways and markers, as well as probing subtype-specific treatment targets.

Body mass index and craving predict 24-month hospital readmissions of alcohol-dependent in-patients following withdrawal

OBJECTIVE

Addictive alcohol drinking, craving, and overeating share common etiopathological mechanisms. We investigated whether body mass index (BMI) and craving predict outcome of alcohol-dependent in-patients.

METHOD

The prospective study included 101 male and 72 female early-abstinent alcohol-dependent in-patients. Craving was quantified by Obsessive-Compulsive Drinking Scale (OCDS) scores. We documented alcohol-related readmissions over 24 months.

RESULTS

In males, a higher BMI was associated with alcohol-related hospital readmission (median 26.1 vs. 23.1 kg/m², P = .007) and correlated with more (ρ = 0.286, P = .004) and earlier readmissions (ρ = -0.256, P = .010). These associations were stronger in the subgroup of active smokers (n = 79; median 25.9 vs. 22.3 kg/m², P = .005; ρ = 0.350, P = .002; ρ = -0.340, P = .002). BMI did not significantly predict outcome in females. Males with at least one readmission reported higher OCDS scores than those without (OCDS-total, OCDS-obsessive, OCDS-compulsive, P < .040), and the OCDS scores correlated with more readmissions (males: OCDS-total, OCDS-obsessive, OCDS-compulsive, ρ > 0.244, P < .014; females: OCDS-compulsive, ρ = 0.341, P = .003) and fewer days to first readmission (males: OCDS-total, OCDS-compulsive, ρ < -0.195, P < .050; females: OCDS-compulsive, ρ = -0.335, P = .004). The OCDS scores explained 9 to 19% of the relationship between BMI and outcome in males.

CONCLUSION

BMI and craving are easily accessible outcome predictors of alcohol-related readmission following in-patient withdrawal treatment. They might be used to individualize relapse prevention in the future.

Increasing Brain-Derived Neurotrophic Factor (BDNF) in medial prefrontal cortex selectively reduces excessive drinking in ethanol dependent mice

The neurotrophin Brain-Derived Neurotrophic Factor (BDNF) has been implicated in a number of neuropsychiatric disorders, including alcohol use disorder. Studies have shown that BDNF activity in cortical regions, such as the medial prefrontal cortex (mPFC) mediates various ethanol-related behaviors. We previously reported a significant down-regulation in Bdnf mRNA in mPFC following chronic ethanol exposure compared to control mice. The present study was conducted to extend these findings by examining whether chronic ethanol treatment reduces BDNF protein expression in mPFC and whether reversing this deficit via direct injection of BDNF or viral-mediated overexpression of BDNF in mPFC alters voluntary ethanol consumption in dependent and nondependent mice. Repeated cycles of chronic intermittent ethanol (CIE) exposure was employed to model ethanol dependence, which produces robust escalation of ethanol intake. Results indicated that CIE treatment significantly increased ethanol intake and this was accompanied by a significant decrease in BDNF protein in mPFC that lasted at least 72 h after CIE exposure. In a separate study, once dependence-related increased drinking was established, bilateral infusion of BDNF (0, 0.25, 0.50 μg) into mPFC significantly decreased ethanol intake in a dose-related manner in dependent mice but did not affect moderate drinking in nondependent mice. In a third study, viral-mediated overexpression of BDNF in mPFC prevented escalation of drinking in dependent mice but did not alter intake in nondependent mice. Collectively, these results provide evidence that adaptations in cortical (mPFC) BDNF activity resulting from chronic ethanol exposure play a role in mediating excessive ethanol drinking associated with dependence.

TPH2 polymorphisms across the spectrum of psychiatric morbidity: A systematic review and meta-analysis

Tryptophan hydroxylase 2 (TPH2) is the rate-limiting enzyme in brain serotonin synthesis. The TPH2 gene has frequently been investigated in relation to psychiatric morbidity. The aim of the present review is to integrate results from association studies between TPH2 single nucleotide polymorphisms (SNPs) and various psychiatric disorders, which we furthermore quantified with meta-analysis. We reviewed 166 studies investigating 69 TPH2 SNPs in a broad range of psychiatric disorders, including over 30,000 patients. According to our meta-analysis, TPH2 polymorphisms show strongest associations with mood disorders, suicide (attempt) and schizophrenia. Despite small effect sizes, we conclude that TPH2 SNPs in the coding and non-coding areas (rs4570625, rs11178997, rs11178998, rs10748185, rs1843809, rs4290270, rs17110747) are each associated with one or more psychopathological conditions. Our findings highlight the possible common serotonergic mechanisms of the investigated psychiatric disorders. Yet, the functional relevance of most TPH2 polymorphisms is unclear. Characterizing how exactly the different TPH2 variants influence the serotonergic neurotransmission is a next necessary step in understanding the psychiatric disorders where serotonin is implicated.

Differential COMT expression and behavioral effects of COMT inhibition in male and female Wistar and alcohol preferring rats

Polymorphisms of the catechol-O-methyl transferase (COMT) gene have been associated with alcoholism, suggesting that alterations in the metabolism of catecholamines may be a critical component of the neuropathology of alcoholism. In the current experiments, the COMT inhibitor tolcapone was utilized in an operant behavioral model of reinforcer-seeking and drinking to determine if this compound was capable of remediating the excessive seeking and drinking phenotype of the alcohol-preferring P rat. Tolcapone was administered to male and female alcohol-reinforced P and Wistar rats. Additionally, tolcapone was administered to male sucrose-reinforced P and Wistar rats to determine if its effects also extended to a natural reinforcer. Animals were trained to make an operant response that resulted in 20 min uninterrupted access to the reinforcer solutions. Tolcapone had no effect in female rats on either seeking or consumption of ethanol. However, reductions of both reinforcer seeking and consumption were observed in male P rats, but only of seeking in Wistars. In separate experiments, using reinforcer naïve male and female animals, COMT expression was assessed via Western Blot analysis. Sex differences in COMT expression were also observed, where male P rats exhibited a marked reduction in protein expression relative to females in the PFC. Sex differences were not observed for Wistars or in the striatum and hippocampus. These data complement our previous findings in which tolcapone reduced cue-evoked responses in P rats and further suggest clinical utility of COMT inhibitors in the treatment of addiction disorders, specifically in male high drinkers.

Transcriptional Regulators as Targets for Alcohol Pharmacotherapies

Alcohol use disorder (AUD) is a chronic relapsing brain disease that currently afflicts over 15 million adults in the United States. Despite its prevalence, there are only three FDA-approved medications for AUD treatment, all of which show limited efficacy. Because of their ability to alter expression of a large number of genes, often with great cell-type and brain-region specificity, transcription factors and epigenetic modifiers serve as promising new targets for the development of AUD treatments aimed at the neural circuitry that underlies chronic alcohol abuse. In this chapter, we will discuss transcriptional regulators that can be targeted pharmacologically and have shown some efficacy in attenuating alcohol consumption when targeted. Specifically, the transcription factors cyclic AMP-responsive element binding protein (CREB), peroxisome proliferator-activated receptors (PPARs), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and glucocorticoid receptor (GR), as well as the epigenetic enzymes, the DNA methyltransferases (DNMTs) and histone deacetylases (HDACs), will be discussed.

Targeting the intracellular signaling "STOP" and "GO" pathways for the treatment of alcohol use disorders

In recent years, research has identified the molecular and neural substrates underlying the transition of moderate "social" consumption of alcohol to the characteristic alcohol use disorder (AUD) phenotypes including excessive and compulsive alcohol use which we define in the review as the GO signaling pathways. In addition, growing evidence points to the existence of molecular mechanisms that keep alcohol consumption in check and that confer resilience for the development of AUD which we define herein as the STOP signaling pathways. In this review, we focus on examples of the GO and the STOP intracellular signaling pathways and discuss our current knowledge of how manipulations of these pathways may be used for the treatment of AUD.

COMT and BDNF Gene Variants Help to Predict Alcohol Consumption in Alcohol-dependent Patients

BACKGROUND

The neurobiology of alcohol dependence (AD) involves alterations in neurotransmitters and the stress response. We hypothesized that an interaction between functional variants of dopaminergic and neurotrophic genes may influence drinking in AD.

METHODS

The relationship between alcohol consumption and single-nucleotide polymorphisms, Val66Met in the brain-derived neurotrophic factor (BDNF), and Val158Met in the catechol-O-methyltransferase (COMT), was analyzed among 281 alcohol-dependent individuals.

RESULTS

Individuals carrying both the COMT Met158Met genotype and the BDNF Val66Val genotype drank more than those with other variants of these genes (P = 0.039). Those who had a family history of AD also drank more than those without a family history (P = 0.048). Patients with both Met/Met genotype in the COMT Val158Met polymorphism and Val/Val genotype in the BDNF Val66Met polymorphism suffered from more health problems than those carrying other variants (P = 0.030) and had lower motivation to change drinking patterns (P = 0.031).

CONCLUSIONS

Patients carrying both the BDNF Val66Val and COMT Met158Met variants had higher alcohol consumption. These effects may be influenced by the effects of BDNF and COMT on dopamine responses to alcohol. Motivation-enhancing strategies might benefit the group of patients identified by genotyping in this study, and also treatment aimed at reducing alcohol consumption.

Effect of single-nucleotide polymorphisms in ADH1B, ADH4, ADH1C, OPRM1, DRD2, BDNF, and ALDH2 genes on alcohol dependence in a Caucasian population

Alcohol is a frequently used addictive substance worldwide. Aim of this study is to determine the frequency distribution of SNPs within ADH1B,ADH4,ADH1C,ALDH2, BDNF,OPRM1, and DRD2 genes in a southeastern European Caucasian population from Greece. For this purpose samples of 1276 volunteers were analyzed after deidentification and anonymization. The allele distribution of the examined polymorphisms in the present Greek population cohort was as follows: rs1229984 (ADH1B): GG(wt) = 64.14%, GA = 29.86%, AA = 4.00%; rs1693482 (ADH1C): CC(wt) = 57.45%, CT = 36.76%, TT = 5.80%; rs1799971 (OPRM1): AA(wt) = 72.43%, AG = 28.72%, GG = 1.89%; rs1800497 (DRD2): CC(wt) = 70.84%, CT = 27.18%, TT = 1.98%; rs1800759 (ADH4): CC(wt) = 34.25%, CA = 48.12%, AA = 17.63%; rs6265 (BDNF): GG(wt) = 65.99%, GA = 31.02%, AA = 2.99%; and rs671 (ALDH2): GG(wt) = 99.84% GA = 0.16%, AA = 0.00%. Mutant rs1229984 allele A was ~6.5× more frequent in the Greek than in the European population. Mutant rs1693482 allele T was ~1.7× more frequent in the European than in the Greek population. Mutant alleles for polymorphisms rs1800759 and rs1799971 show similar frequencies in both northern and southern Europeans. One rs671 mutant A allele was detected in the Greek population (0.08%). The mutant rs1800497 allele T was ~1.2× more frequent in the European than in the Greek population and the mutant rs6265 allele A was ~1.1× more frequent in the European than in the Greek population. An alcohol addiction‐specific algorithm was generated (TGS) that may predict alcohol addiction prevalence in a population. According to our findings, the analyzed Southeastern population may differ genetically from north Europeans due to influences from neighboring Asian and African populations and a calculated TGS score >50 indicates individuals with low susceptibility to develop alcohol addiction.

Standardized Passiflora incarnata L. Extract Reverts the Analgesia Induced by Alcohol Withdrawal in Rats

Passiflora incarnata L. (Passifloraceae) has been traditionally used for treatment of anxiety, insomnia, drug addiction, mild infections, and pain. The aim of this study was to investigate the effect of a commercial extract of P. incarnata in the analgesia induced by alcohol withdrawal syndrome in rats. In addition, brain-derived neurotrophic factor and interleukin-10 levels were evaluated in prefrontal cortex, brainstem, and hippocampus. Male adult rats received by oral gavage: (1: water group) water for 19 days, 1 day interval and water (8 days); (2: P. incarnata group) water for 19 days, 1 day interval and P. incarnata 200 mg/kg (8 days); (3: alcohol withdrawal group) alcohol for 19 days, 1 day interval and water (8 days); and (4: P. incarnata in alcohol withdrawal) alcohol for 19 days, 1 day interval and P. incarnata 200 mg/kg (8 days). The tail-flick and hot plate tests were used as nociceptive response measures. Confirming previous study of our group, it was showed that alcohol-treated groups presented an increase in the nociceptive thresholds after alcohol withdrawal, which was reverted by P. incarnata, measured by the hot plate test. Besides, alcohol treatment increased brain-derived neurotrophic factor and interleukin-10 levels in prefrontal cortex, which was not reverted by P. incarnata. Considering these results, the P. incarnata treatment might be a potential therapy in the alcohol withdrawal syndrome. Copyright © 2017 John Wiley & Sons, Ltd.

Determinants of Blood Brain-Derived Neurotrophic Factor Blood Levels in Patients with Alcohol Use Disorder

BACKGROUND

Blood brain-derived neurotrophic factor (BDNF) levels are influenced by both addiction and mood disorders, as well as somatic conditions, gender, and genetic polymorphisms, leading to widely varying results. Depressive symptoms and episodes are frequently observed in patients with alcohol use disorder, and vary widely over time, making it a challenge to determine which aspects are specifically involved in variations of serum BDNF levels in this population.

METHODS

We assessed 227 patients with alcohol dependence involved in a detoxification program, at baseline and after a follow-up of 6 months, for the Alcohol Use Disorders Identification Test score, the length of alcohol dependence, and the number of past detoxification programs. The Beck Depression Inventory and information on current tobacco and alcohol use, suicidal ideation, body mass index, age, gender, and psychotropic treatments were also collected. Serum BDNF (ELISA) and 2 genetic polymorphisms of the BDNF gene (Val33Met and rs962369) were analyzed.

RESULTS

The presence of the Met allele, 2 markers of the history of alcohol dependence (gamma glutamyl transferase and the number of past treatments in detoxification programs), and the presence of a depressive episode (but not depressive score) were significantly associated with the 2 blood levels of BDNF at baseline and after 6 months. After controlling for baseline BDNF levels, the presence of the Met allele and an ongoing depressive episode were the only variables associated with changes in BNDF levels after 6 months.

CONCLUSIONS

Low serum BDNF levels are associated with characteristics related to alcohol consumption and mood disorders, and variants of the BDNF gene in alcohol use disorder patients. The factors that most strongly influenced changes in serum BDNF levels following treatment in an alcohol detoxification program were variants of the BDNF gene and ongoing depression.

The Neurotrophic Factor Receptor p75 in the Rat Dorsolateral Striatum Drives Excessive Alcohol Drinking

Brain-derived neurotrophic factor (BDNF) signaling in the dorsolateral striatum (DLS) keeps alcohol intake in moderation. For example, activation of the BDNF receptor tropomyosin receptor kinase B (TrkB) in the DLS reduces intake in rats that consume moderate amounts of alcohol. Here, we tested whether long-term excessive consumption of alcohol produces neuroadaptations in BDNF signaling in the rat DLS. We found that BDNF was no longer able to gate alcohol self-administration after a history of repeated cycles of binge alcohol drinking and withdrawal. We then elucidated the possible neuroadaptations that could block the ability of BDNF to keep consumption of alcohol in moderation. We report that intermittent access to 20% alcohol in a two-bottle choice paradigm that models excessive alcohol drinking produces a mobilization of DLS p75 neurotrophin receptor (p75NTR), whose activities oppose those of the Trk receptors, including TrkB. These neuroadaptations were not observed in the DLS of rats exposed to continuous access to 10% alcohol or in rats consuming sucrose. Furthermore, short hairpin RNA (shRNA)-mediated knockdown of the p75NTR gene in the DLS, as well as intra-DLS infusion or systemic administration of the p75NTR modulator, LM11A-31, significantly reduced binge drinking of alcohol. Together, our results suggest that excessive alcohol consumption produces a change in BDNF signaling in the DLS, which is mediated by the recruitment of p75NTR. Our data also imply that modulators of p75NTR signaling could be developed as medications for alcohol abuse disorders.

SIGNIFICANCE STATEMENT

Neuroadaptations gate or drive excessive, compulsive alcohol drinking. We previously showed that brain-derived neurotrophic factor and its receptor, TrkB, in the dorsolateral striatum (DLS), are part of an endogenous system that keeps alcohol drinking in moderation. Here, we show that a history of excessive alcohol intake produces neuroadaptations in the DLS that preclude BDNF's ability to gate alcohol self-administration in rats by the recruitment of the low-affinity neurotrophin receptor, p75NTR, whose activities opposes those of the Trk receptors. Finally, we show that the administration of the p75NTR modulator, LM11A-31, significantly reduces excessive alcohol intake suggesting that the drug may be developed as a new treatment for alcohol abuse disorders.

Association of Brain-Derived Neurotrophic Factor G196A and Attempted Suicide: A Case-Control Study in Rural China

BACKGROUND

Suicide is an important public problem, the mechanism of which has not been clarified. Many studies have focused on the molecular, biological and genetic mechanisms of suicide. Brain-derived neurotrophic factor (BDNF) G196A is one of the most leading loci in recent studies, but the results are inconsistent.

METHODS

We conducted a 1:1 age- and sex-matched case-control study in rural areas of Shandong Province, China. A total of 365 pairs of cases and controls were finally recruited into our study. The adjusted odds ratios (AORs) of BDNF 196G/G and their 95% confidence intervals (CIs) were calculated by multivariate conditional logistic regression models.

RESULTS

No association between BDNF polymorphisms and attempted suicide was found in the overall population. However, the BDNF 196G/G genotype was significantly related to attempted suicide in the elderly population (AOR = 7.85, 95% CI: 1.12-54.90, p = 0.038), while the associations were not significant in young and middle-aged groups.

CONCLUSION

Our study suggests that the BDNF 196G/G genotype increases the risk of attempted suicide in elderly people.

Molecular mechanisms underlying alcohol-drinking behaviours

The main characteristic of alcohol use disorder is the consumption of large quantities of alcohol despite the negative consequences. The transition from the moderate use of alcohol to excessive, uncontrolled alcohol consumption results from neuroadaptations that cause aberrant motivational learning and memory processes. Here, we examine studies that have combined molecular and behavioural approaches in rodents to elucidate the molecular mechanisms that keep the social intake of alcohol in check, which we term 'stop pathways', and the neuroadaptations that underlie the transition from moderate to uncontrolled, excessive alcohol intake, which we term 'go pathways'. We also discuss post-transcriptional, genetic and epigenetic alterations that underlie both types of pathways.

The BDNF Val66Met polymorphism enhances glutamatergic transmission but diminishes activity-dependent synaptic plasticity in the dorsolateral striatum

The Val66Met polymorphism in the brain-derived neurotrophic factor (BDNF) gene disrupts the activity-dependent release of BDNF, which might underlie its involvement in several neuropsychiatric disorders. Consistent with the potential role of regulated release of BDNF in synaptic functions, earlier studies have demonstrated that the BDNF Val66Met polymorphism impairs NMDA receptor-mediated synaptic transmission and plasticity in the hippocampus, the medial prefrontal cortex and the central amygdala. However, it is unknown whether the BDNF Val66Met polymorphism affects synapses in the dorsal striatum, which depends on cortical afferents for BDNF. Electrophysiological experiments revealed an enhanced glutamatergic transmission in the dorsolateral striatum (DLS) of knock-in mice containing the variant polymorphism (BDNF^Met/Met) compared to the wild-type (BDNF^Val/Val) mice. This increase in glutamatergic transmission is mediated by a potentiation in glutamate release and NMDA receptor transmission in the medium spiny neurons without any alterations in non-NMDA receptor-mediated transmission. We also observed an impairment of synaptic plasticity, both long-term potentiation and depression in the DLS neurons, in BDNF^Met/Met mice. Thus, the BDNF Val66Met polymorphism exerts an increase in glutamatergic transmission but impairs synaptic plasticity in the dorsal striatum, which might play a role in its effect on neuropsychiatric symptoms. This article is part of the Special Issue entitled 'Ionotropic glutamate receptors'.

Dommages liés à l’alcool : et si agir sur l’environnement était aussi la clé ?

Il apparaît évident aujourd’hui de la nécessité, dans une perspective de santé publique, d’aider à réduire les dommages liés à l’alcool. Les leviers d’action sont nombreux et doivent tenir compte de l’environnement. Nous souhaitons l’illustrer par quelques exemples. Le premier concerne l’âge. L’enjeu du trouble de l’usage d’alcool chez la personne âgée n’est pas tant la dépendance mais les dommages associés en lien avec la fréquence à cet âge des comorbidités, des modifications physiologiques, la polymédication , et enfin les représentations des soignants plus enclins à penser derniers plaisirs à conserver plutôt que gain en qualité de vie. Le deuxième exemple pour illustrer l’importance de l’environnement concerne la place de la culture dans les comportements d’usage d’alcool notamment chez les femmes en Afrique du Sud, où la province du CAP a une des plus fortes prévalences du syndrome d’alcoolisme fœtal (SAF) dans le monde. Parmi les facteurs associés les plus significatifs, se situe le contexte culturel marqué par le Dop System inventé au 17e siècle, qui consistait à un mode de paiement des ouvriers agricoles par du pain, du vin et du tabac favorisant l’alcoolisme . L’influence de l’environnement passe aussi par les gènes ; ainsi le troisième exemple concerne l’alcooldéshydrogénase (ADH), enzyme dont l’allèle ADH1B*1 serait associé à un risque trois fois supérieur d’alcoolodépendance comparé à l’allèle ADH1B*2 inexistant ou rare chez les caucasiens et les africains mais majoritaires chez les asiatiques . Enfin, un dernier exemple est constitué par le brain-derived neurotrophic factor (BDNF), neurotrophine qui a un rôle essentiel dans la synaptogenèse, qui semble important dans les mécanismes de dépendance, et dont le polymorphisme Val66Met retrouvé dans 20 à 30 % de la population en Europe, Amérique, ou Asie semble associé à la vulnérabilité à la dépendance alcoolique .

The Molecular Neurobiology of Twelve Steps Program & Fellowship: Connecting the Dots for Recovery

There are some who suggest that alcoholism and drug abuse are not diseases at all and that they are not consequences of a brain disorder as espoused recently by the American Society of Addiction Medicine (ASAM). Some would argue that addicts can quit on their own and moderate their alcohol and drug intake. When they present to a treatment program or enter the 12 Step Program & Fellowship, many addicts finally achieve complete abstinence. However, when controlled drinking fails, there may be successful alternatives that fit particular groups of individuals. In this expert opinion, we attempt to identify personal differences in recovery, by clarifying the molecular neurobiological basis of each step of the 12 Step Program. We explore the impact that the molecular neurobiological basis of the 12 steps can have on Reward Deficiency Syndrome (RDS) despite addiction risk gene polymorphisms. This exploration has already been accomplished in part by Blum and others in a 2013 Springer Neuroscience Brief. The purpose of this expert opinion is to briefly, outline the molecular neurobiological and genetic links, especially as they relate to the role of epigenetic changes that are possible in individuals who regularly attend AA meetings. It begs the question as to whether "12 steps programs and fellowship" does induce neuroplasticity and continued dopamine D2 receptor proliferation despite carrying hypodopaminergic type polymorphisms such as DRD2 A1 allele. "Like-minded" doctors of ASAM are cognizant that patients in treatment without the "psycho-social-spiritual trio," may not be obtaining the important benefits afforded by adopting 12-step doctrines. Are we better off with coupling medical assisted treatment (MAT) that favors combining dopamine agonist modalities (DAM) as possible histone-deacetylase activators with the 12 steps followed by a program that embraces either one or the other? While there are many unanswered questions, at least we have reached a time when "science meets recovery," and in doing so, can further redeem joy in recovery.