Falk W. Lohoff

Overview of the Genetics of Alcohol Use Disorder

AIMS Alcohol Use Disorder (AUD) is a chronic psychiatric illness characterized by harmful drinking patterns leading to negative emotional, physical, and social ramifications. While the underlying pathophysiology of AUD is poorly understood, there is substantial evidence for a genetic component; however, identification of universal genetic risk variants for AUD has been difficult. Recent efforts in the search for AUD susceptibility genes will be reviewed in this article. METHODS In this review, we provide an overview of genetic studies on AUD, including twin studies, linkage studies, candidate gene studies, and genome-wide association studies (GWAS). RESULTS Several potential genetic susceptibility factors for AUD have been identified, but the genes of alcohol metabolism, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), have been found to be protective against the development of AUD. GWAS have also identified a heterogeneous list of SNPs associated with AUD and alcohol-related phenotypes, emphasizing the complexity and heterogeneity of the disorder. In addition, many of these findings have small effect sizes when compared to alcohol metabolism genes, and biological relevance is often unknown. CONCLUSIONS Although studies spanning multiple approaches have suggested a genetic basis for AUD, identification of the genetic risk variants has been challenging. Some promising results are emerging from GWAS studies; however, larger sample sizes are needed to improve GWAS results and resolution. As the field of genetics is rapidly developing, whole genome sequencing could soon become the new standard of interrogation of the genes and neurobiological pathways which contribute to the complex phenotype of AUD. SHORT SUMMARY This review examines the genetic underpinnings of Alcohol Use Disorder (AUD), with an emphasis on GWAS approaches for identifying genetic risk variants. The most promising results associated with AUD and alcohol-related phenotypes have included SNPs of the alcohol metabolism genes ADH and ALDH.

Pharmacogenetics of alcohol use disorders and comorbid psychiatric disorders.

Alcohol use disorders (AUDs) represent a significant health burden worldwide. Currently, there are three medications approved by the U.S. Food and Drug Administration for the treatment of AUDs, and other drugs are being prescribed off-label for this purpose. However, response rates for pharmacologic treatment are low, and extant research suggests that treatment effects may partially depend on genetic factors. Personalized medicine, or using a patients genetics and/or personal history to determine efficacy of treatment prior to prescription, is an emerging tool that will help clinicians treat their patients more effectively and safely. This review systematically discusses current findings from AUD pharmacotherapy trials examining disulfiram, acamprosate, naltrexone, the injectable naltrexone, and topiramate. Furthermore, it presents pharmacogenetics findings associated with these medications in an attempt to further the field of personalized medicine. Research from trials examining AUDs and comorbid major depressive disorder and anxiety disorders is also presented, and pharmacogenetic findings for these treatments are discussed. Lastly, the authors comment on the present and future states of the field of personalized medicine for AUD.

Resting-state functional connectivity and presynaptic monoamine signaling in Alcohol Dependence

Alcohol Dependence (AD) is a chronic relapsing disorder with high degrees of morbidity and mortality. While multiple neurotransmitter systems are involved in the complex symptomatology of AD, monoamine dysregulation and subsequent neuroadaptations have been long postulated to play an important role. Presynaptic monoamine transporters, such as the vesicular monoamine transporter 1 (VMAT1), are likely critical as they represent a key common entry point for monoamine regulation and may represent a shared pathway for susceptibility to AD. Excessive monoaminergic signaling as mediated by genetic variation in VMAT1 might affect functional brain connectivity in particular in alcoholics compared to controls. We conducted resting‐state fMRI functional connectivity (FC) analysis using the independent component analysis (ICA) approach in 68 AD subjects and 72 controls. All subjects were genotyped for the Thr136Ile (rs1390938) variant in VMAT1. Functional connectivity analyses showed a significant increase of resting‐state FC in 4 networks in alcoholics compared to controls (P < 0.05, corrected). The FC was significantly positively correlated with Alcohol Dependence Scale (ADS). The hyperfunction allele 136Ile was associated with a significantly decreased FC in the Default Mode Network, Prefrontal Cortex Network, and Executive Control Network in alcohol dependent participants (P < 0.05, corrected), but not in controls. Our data suggest that increased FC might represent a neuroadaptive mechanism relevant to AD that is furthermore mediated by genetic variation in VMAT1. The hyperfunction allele Thr136Ile might have a protective effect that is, in particular, relevant in AD by mechanism of increased monoamine transport into presynaptic storage vesicles. Hum Brain Mapp 36:4808–4818, 2015. Published 2015. This article is a U.S. Government work and is in the public domain in the USA

Human neutrophils can mimic myeloid-derived suppressor cells (PMN-MDSC) and suppress microbead or lectin-induced T cell proliferation through artefactual mechanisms

We report that human conventional CD15+ neutrophils can be isolated in the peripheral blood mononuclear cell (PBMC) layer during Ficoll gradient separation, and that they can impair T cell proliferation in vitro without concomitant neutrophil activation and killing. This effect was observed in a total of 92 patients with organ transplants, lung cancer or anxiety/depression, and in 18 healthy donors. Although such features are typically associated in the literature with the presence of certain myeloid-derived suppressor cell (PMN-MDSC) populations, we found that commercial centrifuge tubes that contained membranes or gels for PBMC isolation led to up to 70% PBMC contamination by CD15+ neutrophils, with subsequent suppressive effects in certain cellular assays. In particular, the suppressive activity of human MDSC should not be evaluated using lectin or microbead stimulation, whereas assays involving soluble or plate-bound antibodies or MLR are unaffected. We conclude that CD15+ neutrophil contamination, and associated effects on suppressor assays, can lead to significant artefacts in studies of human PMN-MDSC.

DNA methylation age is accelerated in alcohol dependence

Alcohol dependence (ALC) is a chronic, relapsing disorder that increases the burden of chronic disease and significantly contributes to numerous premature deaths each year. Previous research suggests that chronic, heavy alcohol consumption is associated with differential DNA methylation patterns. In addition, DNA methylation levels at certain CpG sites have been correlated with age. We used an epigenetic clock to investigate the potential role of excessive alcohol consumption in epigenetic aging. We explored this question in five independent cohorts, including DNA methylation data derived from datasets from blood (n = 129, n = 329), liver (n = 92, n = 49), and postmortem prefrontal cortex (n = 46). One blood dataset and one liver tissue dataset of individuals with ALC exhibited positive age acceleration (p < 0.0001 and p = 0.0069, respectively), whereas the other blood and liver tissue datasets both exhibited trends of positive age acceleration that were not significant (p = 0.83 and p = 0.57, respectively). Prefrontal cortex tissue exhibited a trend of negative age acceleration (p = 0.19). These results suggest that excessive alcohol consumption may be associated with epigenetic aging in a tissue-specific manner and warrants further investigation using multiple tissue samples from the same individuals.

Random Forest Based Classification of Alcohol Dependence Patients and Healthy Controls Using Resting State MRI

Currently, classification of alcohol use disorder (AUD) is made on clinical grounds; however, robust evidence shows that chronic alcohol use leads to neurochemical and neurocircuitry adaptations. Identifications of the neuronal networks that are affected by alcohol would provide a more systematic way of diagnosis and provide novel insights into the pathophysiology of AUD. In this study, we identified network-level brain features of AUD, and further quantified resting-state within-network, and between-network connectivity features in a multivariate fashion that are classifying AUD, thus providing additional information about how each network contributes to alcoholism. Resting-state fMRI were collected from 92 individuals (46 controls and 46 AUDs). Probabilistic Independent Component Analysis (PICA) was used to extract brain functional networks and their corresponding time-course for AUD and controls. Both within-network connectivity for each network and between-network connectivity for each pair of networks were used as features. Random forest was applied for pattern classification. The results showed that within-networks features were able to identify AUD and control with 87.0% accuracy and 90.5% precision, respectively. Networks that were most informative included Executive Control Networks (ECN), and Reward Network (RN). The between-network features achieved 67.4% accuracy and 70.0% precision. The between-network connectivity between RN-Default Mode Network (DMN) and RN-ECN contribute the most to the prediction. In conclusion, within-network functional connectivity offered maximal information for AUD classification, when compared with between-network connectivity. Further, our results suggest that connectivity within the ECN and RN are informative in classifying AUD. Our findings suggest that machine-learning algorithms provide an alternative technique to quantify large-scale network differences and offer new insights into the identification of potential biomarkers for the clinical diagnosis of AUD.

The major depressive disorder GWAS-supported variant rs10514299 in TMEM161B-MEF2C predicts putamen activation during reward processing in alcohol dependence

Alcohol dependence (AD) frequently co-occurs with major depressive disorder (MDD). While this comorbidity is associated with an increase in disease burden, worse treatment outcomes, and greater economic costs, the underlying neurobiology remains poorly understood. A recent large-scale GWAS of MDD has identified a locus in the TMEM161B-MEF2C region (rs10514299) as a novel risk variant; however, the biological relevance of this variant has not yet been studied. Given previous reports of disrupted reward processing in both AD and MDD, we hypothesized that rs10514299 would be associated with differences in striatal BOLD responses during reward/loss anticipation in AD. DNA samples from 45 recently detoxified patients with AD and 45 healthy controls (HC) were genotyped for rs10514299. Participants performed the Monetary Incentive Delay task in a 3-Tesla MRI scanner. Effects of rs10514299 on striatal activation during anticipation of high/low reward/loss were investigated. Furthermore, we examined associations between rs10514299 and lifetime AD diagnosis in two independent clinical samples [NIAAA: n = 1858 (1123 cases, 735 controls); SAGE: n = 3838 (1848 cases, 1990 controls)], as well as its association with depression severity in a subsample of individuals with a lifetime AD diagnosis (n = 953). Patients carrying the T allele showed significantly greater putamen activation during anticipation of high reward (p = 0.014), low reward (at trend-level; p = 0.081), high loss (p = 0.024), and low loss (p = 0.046) compared to HCs. Association analyses in the NIAAA sample showed a trend-level relationship between rs10514299 and a lifetime AD diagnosis in the European American subgroup (odds ratio = 0.82, p = 0.09). This finding was not replicated in the SAGE sample. In the NIAAA sample, the T allele was significantly associated with greater depression symptom severity in individuals with a lifetime AD diagnosis (β = 1.25, p = 0.02); this association was driven by the African American ancestry subgroup (β = 2.11, p = 0.008). We show for the first time that the previously identified MDD risk variant rs10514299 in TMEM161B-MEF2C predicts neuronal correlates of reward processing in an AD phenotype, possibly explaining part of the shared pathophysiology and comorbidity between the disorders.

Association Analysis Between Genetic Variation in GATA Binding Protein 4 (GATA4) and Alcohol Use Disorder

Aims Previous genetic association studies have shown that variation in the GATA4 gene encoding the GATA binding protein 4, a binding protein that binds to the ANA sequence GATA, increase susceptibility for alcohol use disorder (AUD). In this study, we aimed to replicate those findings in an independent sample and analyze their association with anxiety. Methods Overall, 1044 individuals with AUD [534 European American (EA), 510 African Americans (AA)] and 645 controls [413 EA, 232 AA] were genotyped using 34 markers. Genotype and allele frequencies were compared between cases and controls using chi-square analysis. Other phenotype data were analyzed for possible associations with GATA4 single-nucleotide polymorphisms (SNPs) in individuals with AUD. Results Rs6601604 was nominally significantly associated with AUD in EA, and 3 SNPs (rs6990313, rs11250159 and rs17153694) showed trend-level significance (P < 0.10) in AA. However, none of the SNPs were significant after correcting for multiple testing. Haplotype analysis of the 34 SNPs did not find a significant association between haplotype blocks and AUD diagnosis after correcting for multiple testing. From the phenotype analysis, anxiety was associated with GATA4 SNP rs10112596 among the AA group with AUD after a correction for multiple testing. Conclusions Although previous studies have shown a relationship between variants of the GATA4 gene and a diagnosis of AUD, we did not replicate these findings in our sample. Additional studies of variation in this gene are needed to elucidate whether polymorphisms of the GATA4 gene are associated with AUD and other alcohol-related phenotypes. Short Summary GATA4 variants were not associated with AUD in either the European ancestry or African ancestry groups after correcting for multiple comparisons. Rs10112596 demonstrated a significant relationship with an anxiety measure among the African ancestry group with AUD.

Imaging resilience and recovery in alcohol dependence

BACKGROUND AND AIMS Resilience and recovery are of increasing importance in the field of alcohol dependence (AD). This paper describes how imaging studies in man can be used to assess the neurobiological correlates of resilience and, if longitudinal, of disease trajectories, progression rates and markers for recovery to inform treatment and prevention options. METHODS Original papers on recovery and resilience in alcohol addiction and its neurobiological correlates were identified from PubMed and have been analyzed and condensed within a systematic literature review. RESULTS Findings deriving from functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) studies have identified links between increased resilience and less task-elicited neural activation within the basal ganglia, and benefits of heightened neural pre-frontal cortex (PFC) engagement regarding resilience in a broader sense; namely, resilience against relapse in early abstinence of AD. Furthermore, findings consistently propose at least partial recovery of brain glucose metabolism and executive and general cognitive functioning, as well as structural plasticity effects throughout the brain of alcohol-dependent patients during the course of short-, medium- and long-term abstinence, even when patients only lowered their alcohol consumption to a moderate level. Additionally, specific factors were found that appear to influence these observed brain recovery processes in AD, e.g. genotype-dependent neuronal (re)growth, gender-specific neural recovery effects, critical interfering effects of psychiatric comorbidities, additional smoking or marijuana influences or adolescent alcohol abuse. CONCLUSIONS Neuroimaging research has uncovered neurobiological markers that appear to be linked to resilience and improved recovery capacities that are furthermore influenced by various factors such as gender or genetics. Consequently, future system-oriented approaches may help to establish a broad neuroscience-based research framework for alcohol dependence.