The implications of genetic research on alcohol dependence for prevention and treatment

1. The implications of genetic research on alcohol dependence for prevention and treatment Dr Adrian Carter Senior Research Fellow Monash Clinical and Imaging Neurosciences School of Psychological Sciences 22 October 2014

2. Collaborators Professor Wayne Hall Director, Centre for Youth Substance Abuse Research, University of Queensland and the Institute of Psychiatry, King’s College London Dr Coral Gartner and Kylie Morphett School of Population Health and the University of Queensland Centre for Clinical Research, University of Queensland Rebecca Mathews Foundation for Alcohol Research and Education, Australia The implications of genetic research on alcohol dependence for prevention and treatment

3. Overview • The promise of genetic research on alcoholism • Genetics of alcohol dependence (AD) • Alcohol metabolism • Cognition (addiction) • Critically review the strength of genetic research in AD • Examine the clinical use of genetic testing to: • Prevent AD (particularly in adolescence) • Personalise treatment of AD; pharmacogenetics The implications of genetic research on alcohol dependence for prevention and treatment

4. The promise of ‘personalised genomic medicine’ • Alcohol dependence (AD) is one of the largest causes of preventable disease burden • Lifetime prevalence: 8-15% (Hasin et al, 2007; AIHW, 2007) • US$180 billion per year (NIAAA, 2000) • Treatments are only moderately effective – abstinence low; relapse high • 12-month abstinence rates are 17-35% • Relapse is high: 80% of all AD patients will have a heavy drinking day during the 12 months following treatment • ‘Genetic revolution’ in AD promises to: • Prevent alcohol dependence through predictive genetic screening to identify those at increase risk of AD • Develop more effective treatments for AD tailored to the individual: pharmacogenetics The implications of genetic research on alcohol dependence for prevention and treatment

5. The heritability of alcohol dependence • Alcohol dependence (AD) “runs in families” • 4x greater risk of AD in relatives of alcohol dependent individuals • Genetic influence from twin and adoption studies • Identical twins at greater risk of AD than fraternal twins or siblings • Adopted children of AD parents have similar 4x greater risk of AD • Heritability of AD approx. 50-60% (Agrawal and Lynskey, 2008) • Using modern genetic techniques to identify specific or “candidate” genes underpinning heritability: ‘Gene hunting’ • Types of genetic studies: • Linkage studies • Genome-wide association studies The implications of genetic research on alcohol dependence for prevention and treatment

6. Physiological action of candidate genes Genes implicated in AD can be categorised in to TWO broad types. Those that influence: • Alcohol metabolism • Regulate the activity of enzymes in the liver • Specific to AD risk • Rewarding, reinforcing and other cognitive effects of alcohol (e.g. learning and memory, motivation, executive control) • “Addiction” aspects of alcohol use • Regulate neurotransmitter activity in the brain • Many appear to be involve personality traits (endophenotypes) that predispose to addiction in general (e.g. impulsivity, novelty seeking, impaired learning) The implications of genetic research on alcohol dependence for prevention and treatment

7. 1. Genes affecting alcohol metabolism • Include genes that influence enzymatic activity of: • Alcohol dehydrogenase (ADH) – ADH1-7 • Aldehyde dehydrogenase (ALDH) – ALDH1A1, ALDH2 • Alleles that increase ADH or decrease ALDH activity cause an accumulation of acetylaldehyde in the body, produces: • Mild symptoms: unpleasant facial flushing, sweating, headaches • Major symptoms: cardiovascular collapse, arrhythmias, unconsciousness and convulsions • Unpleasant; protective against AD • Most significant and reliable genetic associations in AD The implications of genetic research on alcohol dependence for prevention and treatment

8. Protective effect of ADH genes • High-activity ADH genes ADH1B*2, ADH1B*3 and ADN1C*1 • Produce higher levels of acetylaldehyde that protect against AD • ADH1B*2 and ADH1B*3 causes >30-fold increase in ADH • Protects against alcohol-related birth defects and fetal alcohol syndrome • 1 copy of ADH1B*2 reduced AD risk 4-fold; 2 copies reduced risk 5-fold • Prevalence of ADH alleles and protection varies by ethnicity: • ADH1B*2 & ADH1B*3 more prevalent in East Asian, Jewish, African and Native Americans populations • associated with a lower risk of alcoholism • ADH1B*2 & ADH1B*3 rare in Caucasians • lower protective effects in them than in Asian and African populations The implications of genetic research on alcohol dependence for prevention and treatment

9. Protective effect of ALDH genes • Variants in the ALDH1A1 and ALDH2 genes have also been shown to protect against alcoholism • Protective effects of ALDH2*2 are the strongest and most well replicated • Low ALDH2 activity prevents the conversion of toxic acetaldehyde to acetate • ALDH2*2 homozygotes produce an inactive ALDH enzyme and are 10x lower risk of AD (homozygotes rare) • Heterozygotes retain 30-50% enzyme activity; 5-fold reduction in AD risk • ALDH2*2 common in East Asians (30% prevalence) but virtually non-existent in Caucasian and African populations. • ALDH1A1*2 and ALDH1A1*3 protective against AD in African Americans • ALDH1A1*2 protective in Native Americans The implications of genetic research on alcohol dependence for prevention and treatment

10. Increased risk associated with ADH genes • Lower activity variants of ADH (e.g., ADH4, ADH5, ADH6, and ADH7) increase the risk of AD • result in lower levels of the aversive acetaldehyde • 12 ADH4 alleles associated with a greater risk for AD in European Americans, Brazilian populations and African American families The implications of genetic research on alcohol dependence for prevention and treatment

11. 2. Genes influencing cognition • The mesolimbic reward pathway is central to the cognitive processes in AD • reward and motivation • learning and memory • stress and affect regulation • executive control • A number of candidate genes have been identified that increase AD liability through their action on neurotransmission in the reward pathway • Dopamine (DRD2): reward and reinforcement • Opioid (OPRM1): euphoria, alcohol liking • GABA (GABRA2): sedation, anxiolytic • Serotonin (SLC6A4, 5-HTTLPR): affect and craving • Acetylcholine (CHRM2): cognitive • Glutamate (NMDAR): learning and memory The implications of genetic research on alcohol dependence for prevention and treatment

12. Scientific challenges to the clinical use of genetic screening Presentation title

13. Poor predictive ability for most genes • Identified risk genes for AD account for only a fraction of the heritability estimated from twin and adoption studies • Problem of “missing heritability” • e.g. height 90% heritable but 30 alleles explain < 5% • Most AD related alleles only weakly predict AD risk • Most OR~1.1-1.5 • Exception: ADH and ALDH • Many findings about specific genes have not been replicated The implications of genetic research on alcohol dependence for prevention and treatment

14. Gene interactions • Gene-environment interactions • Many alleles will only result in disease when combined with certain environmental factors • 5-HTTLPR associated with > alcohol use in presence of maltreatment or multiple negative life-events • MAOA predicts AD when associated with child maltreatment • Non-replications; false positive findings due to small sample sizes • Gene-gene interactions • Multiple alleles (from the same or different groups of genes) predict disease risk via their interactions with other genes • Gene–gene and gene–environment interactions in AD is a major obstacle to the reliability and validity of predictive screening The implications of genetic research on alcohol dependence for prevention and treatment

15. Epigenetics • Environmental events (e.g. stress, drug use) can have long-lasting effects on DNA folding that influences gene expression • Alcohol use may lead to epigenetic changes that are transferred to offspring (e.g., in utero alcohol exposure) • Does not alter genetic code • May be passed down generations • Interferes with the ability to predict AD liability • Carrying a particular risk allele may not translate in to expression of that allele or the manifestation of disease • Further research is needed to understand the impact of epigenetics on the use of genetic testing for AD The implications of genetic research on alcohol dependence for prevention and treatment

16. Preventing alcohol dependence using genetic screening Presentation title

17. Underlying assumptions of predictive genomic medicine • Genetic tests strongly predict the risk of disease • Disease burden is concentrated in a few high risk individuals • Preventive interventions available that are • Safe and effective • Cost effective and not too costly • Outperform population wide interventions • Do not cause additional unexpected harms • Feasible and politically acceptable • Providing genetic information • Motivates positive behaviour change (reduced drinking) • Does not reduce motivation (e.g. fatalism) The implications of genetic research on alcohol dependence for prevention and treatment

18. Population screening for single risk genes not feasible • Lack the specificity and sensitivity for genetic screening: • Candidate alleles have small effect sizes that only weakly predict AD risk • Failure to replicate • Involves complex gene-gene and gene-environment interactions that predict disease liability in ways that are difficult to identify • Epigenetic modifications influence AD risk • The susceptibility genes for AD identified thus far do not meet these criteria • Population screening not cost effective • Large numbers need to be screened to identify a single case The implications of genetic research on alcohol dependence for prevention and treatment

19. Genetic screening of “at-risk” populations • Could restrict genetic screening to those with family history would reduce number screened and costs of testing • 20 to 30% of people with a family history of AD will also be affected • Predictive performance of genetic tests for AD better due to shared genetic and/or environmental risk factors • Costs only justified if genetic testing improved upon family history • Evidence suggests that family screening outperforms genetic screening for complex disease (e.g. addiction, diabetes) The implications of genetic research on alcohol dependence for prevention and treatment

20. Family vs. Genetic prediction in smoking (Gartner et al, 2009) • Screening for 5 risk alleles performed better than chance, but worse than parental history of smoking • Adding genetic risk information did not improve prediction based solely upon family history Receiver operating characteristic (ROC) curve The implications of genetic research on alcohol dependence for prevention and treatment

21. Screening for 100’s of multiple AD risk genes • Predictive ability could be improved by screening for 200-400 risk alleles to produce an individual “risk score” – genetic profiling • Modelling suggests screening of 100’s of susceptibility alleles of little clinical utility AD (Janssens et al., 2006) • Most people will be at “average” genetic risk The implications of genetic research on alcohol dependence for prevention and treatment

22. Predictive genetic screening requires effective preventive interventions • Currently no effective medical preventative measures (e.g. drugs) • Education and counselling • What impact would risk information have on alcohol consumption? • May undermine a belief in their ability to reduce use; Fatalism • Would +ve tests encourage adolescents to test the hypothesis? • Limited empirical research • Would tests demonstrating absence of risk genes for AD encourage belief that individuals could drink with impunity? • Ignores harm of non-dependent alcohol use (e.g. binge drinking) • Intoxication significant cause of burden in alcohol • Will targeted messages be more effective than “drink in moderation” message for everyone? • Good advice for all irrespective of genetic risk The implications of genetic research on alcohol dependence for prevention and treatment

23. Clinical utility of ADH/ALDH screening • Best predictive evidence comes from genes that influence alcohol metabolism (e.g. ALDH2*2) • But how useful is a genetic test for these genes? • Those that carry them will be aware the first time they consume alcohol • Physical aversion more likely to dissuade drinking than genetic risk • Associated with greater risk of some forms of cancer, should they drink • Such more modest uses are probably the greatest hope for genetic testing • Participants told they were +ve for ALDH2*2 had reduced 30-day drinking (Boffetta and Hashibe, 2008) The implications of genetic research on alcohol dependence for prevention and treatment

24. Pharmacogenetics: Personalised treatment of alcohol dependence Presentation title

25. The promise of pharmacogenetics? • Treatments for AD (e.g. naltrexone , 12-step programs, motivational enhancement therapy, and CBT) are only modestly effective • Relapse is the norm • Response to medications and other therapeutic interventions vary widely • genetic variation may explain some of this variation • Pharmacogenetics: the use of genetic information to tailor specific treatments to individuals may: • increase the effectiveness • guide dosage levels and minimise side-effects • reduce relapse The implications of genetic research on alcohol dependence for prevention and treatment

26. Candidates for pharmacogenetics in AD • ASP40allele of OPRM1 gene predicts response to naltrexone (opioid antagonist) • Naltrexone only minimally effective in general population • Variants in GABA receptor genes (GABRA2/GABRA6) predicted responses to acamprosate • Small sample size; not replicated • A marker on the glutamate receptor 5 gene (GluR5) predicts side effects of AD treatment with topiramate • anticonvulsant drug that reduces alcohol craving by stimulating GABA activity and inhibiting glutamatergic activity • Genetic variants may also predict responses to psychological therapies for AD (e.g. motivational enhancement therapy) The implications of genetic research on alcohol dependence for prevention and treatment

27. Feasibility of pharmacogenetic testing • Requires highly prevalent genes that strongly predict treatment response • Asp40 allele of the OPRM1 gene is the most promising pharmacogenetic candidate • Persons with the Asp40 allele are 3x more likely to respond to naltrexone • More research is needed • One failure to replicate, in a small sample • Association found only in those receiving Ntx alone, and not when combined with behavioral management • Does effect size justify cost? • Cost effectiveness studies required to determine if test improves upon using treatment across population The implications of genetic research on alcohol dependence for prevention and treatment

28. Additional clinical and social challenges • Clinicians must understand and be willing to use these tests • Many are concerned about inadvertently misusing, misinterpreting or mis-communicating genetic test results (Shields and Lerman, 2008) • Particularly if tests also confer risk to other diseases (e.g. mental illness) • Does not prohibit use, but signals need for education • Genetic counselling critical given poor health/genetic literacy • Argued that genetic explanations of AD will reduce stigma and increase treatment seeking (Dackis and O’Brien, 2015) • Not at fault for addiction • May be seen as incurable and uncontrollable increasing discrimination (Phelan and Link) • Further research required The implications of genetic research on alcohol dependence for prevention and treatment

29. Conclusions • Genetic testing not ready for use in prediction of likelihood of developing alcohol dependence (AD) • AD complex, multifactorial, polygenic. Many genes and environmental factors involved • Genetic screening has minimal preventive use over and above standard advice: “Drink alcohol in moderation” • Pharmacogenetics may have clinical utility but early days and more research needed • Genomics research critical for unraveling pathogenesis and disease pathways • What will be the impact of genetic results on patients and the broader public? The implications of genetic research on alcohol dependence for prevention and treatment

30. Acknowledgments • Neuroethics Group, UQCCR • Wayne Hall • Sarah Yeates • Jayne Lucke • Carla Meurk • Kylie Morphett • Brad Partridge • Cynthia Forlini • Doug Fraser • Charmaine Jensen • Rebecca Mathews (past) • Monash Clinical and Imaging Neurosciences • Murat Yucel • Alex Fornito • Chao Suo • Valentina Lorenzetti • Nigel Rogasch • Ben Fulcher • George Youssef • Paul Klauser • Orwa Dandash • Ari Pinar • Michelle Lambin • Linden Parkes • Leah Braganza • Simon Baker • Amy Finlay • National Health and Medical Research Council & Australia Research Council The implications of genetic research on alcohol dependence for prevention and treatment

31. Identifying candidate genes involved in AD • Using modern genetic techniques to identify specific genes underpinning heritability or ‘Gene hunting’ • Types of genetic studies: • Linkage studies • Genome-wide association studies • Linkage studies: Use families or pedigrees to identify coinheritance of a genetic marker and the disorder of interest • Genetic markers identify chromosomal regions of interest • Genome wide-association studies (GWAS): Use a sample of unrelated people affected with a disorder compared to matched controls. Look at whole genome for alleles (alternative forms) of a gene that are associated with the disorder • Candidate gene association studies: The implications of genetic research on alcohol dependence for prevention and treatment

32. Dopamine system • Increased dopamine activity is key to most drug addictions • Alcohol (like most drugs) stimulates the release of dopamine and activates dopamine receptors. This causes rewarding effects, leading to craving for alcohol and alcohol-seeking behavior • Changes in the activity of dopamine receptors, particularly D1 and D2 receptors, are thought to increase the reward effects of alcohol and its resultant desirability and have therefore been implicated in AD • D2 is the most extensively studied although controversial due to conflicting findings and nonreplication • Persons with Taq1A polymorphism of D2 are 1.3 times more likely to have AD than those without • Taq1A may not directly map onto D2 but rather an adjacent gene (ANKK1) and may be a marker of a region of multiple co-located alleles involved in AD risk. • Association may be due to publication bias • Significance of the association varied for different population groups. The implications of genetic research on alcohol dependence for prevention and treatment

33. Opioid system • Alcohol activates various opioid receptors (e.g. mu opioid receptor) stimulates the release of endorphins (endogenous opioids) that indirectly activate dopaminergic reward system • Associated with euphoria, analgesia and withdrawal symptoms • Individual differences in mu opioid receptor activity have been associated with the rewarding effects and desirability of alcohol and therefore AD liability • OPRM1 (gene encoding mu opioid receptor) • Has been linked to AD, but Inconsistent findings and failure to replicate • Variants of OPRM1 have been associated with differnetial response to opioid antagonist treatment (Naltrexone) • Failure to replicate The implications of genetic research on alcohol dependence for prevention and treatment

34. Gamma-aminobutyric acid (GABA) system • GABA is the brain’s main inhibitory neurotransmitter mediated by a family of two receptors: GABA-A and GABA-B • Alcohol activates the GABA system, inhibiting the activity of related neural circuits. • Studies suggest that GABRA2 is a risk locus for AD • GABRA2 encodes a subunit of the GABA-A receptor • GABA-A mediates several important effects of alcohol (sedation, anxiolysis, impairment of motor coordination, and withdrawal symptoms) • The association between AD and GABRA2 has been replicated with three different populations • GABRA2 has also been associated with subjective response to alcohol in healthy controls The implications of genetic research on alcohol dependence for prevention and treatment

35. Serotonin (5-HT) system • Serotonergic activity regulated by the serotonin transporter (5-HTT) through the reuptake of serotonin from the synapse • 5-HTTLPR allele (gene associated with serotonin transporter) have been linked to compulsive craving, AD and relapse • Non-replication and gene-environment interactions implicated • Meta-analysis of 22 case-controlled studies found an association between short allele of 5-HTTLPR gene and AD • Poor sample size and publication bias The implications of genetic research on alcohol dependence for prevention and treatment

36. Prediction of Type 2 Diabetes risk from genotype and phenotype (Janssens & Khoury, 2010) Receiver operating characteristic (ROC) curve The implications of genetic research on alcohol dependence for prevention and treatment