Issues in genetic testing for susceptibility to alcoholism: lessons from Alzheimer's disease and Huntington's disease

Moderate Alcohol Drinking and the Amygdala Proteome: Identification and Validation of Calcium/Calmodulin Dependent Kinase II and AMPA Receptor Activity as Novel Molecular Mechanisms of the Positive Reinforcing Effects of Alcohol

BACKGROUND

Despite worldwide consumption of moderate amounts of alcohol, the neural mechanisms that mediate the transition from use to abuse are not fully understood.

METHODS

Here, we conducted a high-throughput screen of the amygdala proteome in mice after moderate alcohol drinking (n = 12/group) followed by behavioral studies (n = 6-8/group) to uncover novel molecular mechanisms of the positive reinforcing properties of alcohol that strongly influence the development of addiction.

RESULTS

Two-dimensional difference in-gel electrophoresis with matrix assisted laser desorption ionization tandem time-of-flight identified 29 differentially expressed proteins in the amygdala of nondependent C57BL/6J mice following 24 days of alcohol drinking. Alcohol-sensitive proteins included calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα) and a network of functionally linked proteins that regulate neural plasticity and glutamate-mediated synaptic activity. Accordingly, alcohol drinking increased α-amino-3-hydroxy-5-methyl-4-isooxazole receptor (AMPAR) in central amygdala (CeA) and phosphorylation of AMPAR GluA1 subunit at a CaMKII locus (GluA1-Ser831) in CeA and lateral amygdala. Further, CaMKIIα-Thr286 and GluA1-Ser831 phosphorylation was increased in CeA and lateral amygdala of mice that lever-pressed for alcohol versus the nondrug reinforcer sucrose. Mechanistic studies showed that targeted pharmacologic inhibition of amygdala CaMKII or AMPAR activity specifically inhibited the positive reinforcing properties of alcohol but not sucrose.

CONCLUSIONS

Moderate alcohol drinking increases the activity and function of plasticity-linked protein networks in the amygdala that regulate the positive reinforcing effects of the drug. Given the prominence of positive reinforcement in the etiology of addiction, we propose that alcohol-induced adaptations in CaMKIIα and AMPAR signaling in the amygdala may serve as a molecular gateway from use to abuse.

Perceptions about genetic testing for the susceptibility to alcohol dependence and other multifactorial diseases

BACKGROUND

Beliefs, attitudes, and preferences about the risk and benefits of genetic testing are important determinants of willingness to undergo testing.

AIMS

The purpose of this study was to evaluate the perceived importance of genetic testing for alcohol dependence compared with other multifactorial diseases among African Americans.

METHODS

Surveys were conducted with 258 participants using the Genetic Psycho-Social Implications (GPSI) questionnaire to evaluate several areas of hypothetical genetic testing for alcohol dependence. Respondents were divided into two groups: those who perceived testing for alcohol dependence to be equally important as testing for cancer and those who did not. Using chi-square, the groups' responses were compared for nine GPSI items measuring beliefs about the severity of alcohol dependence, general benefits of genetic testing, and specific benefits of genetic testing for diabetes, hypertension, or a disease affecting a family member.

RESULTS

Nearly 86% of respondents believed that genetic testing for alcoholism was equally as important as testing for cancer. Those who reported parity of importance of alcohol dependence and cancer screening were more likely to believe that alcoholism is a deadly disease (p<0.001) and genetic testing influences health (p<0.001).

CONCLUSION

African Americans reported favorable attitudes and beliefs in possible availability of susceptibility genetic testing for alcohol dependence. The perceived importance of testing for alcohol dependence was associated with beliefs about the severity of alcoholism and certain benefits of genetic testing in general.

Perspectives on medical research involving men in schizophrenia and HIV-related protocols

Ethical issues in research on serious physical and mental illnesses have received great attention, and yet little is known about how the perspectives of clinical research participants with different diagnoses may compare. We conducted a preliminary study to examine the attitudes of men enrolled in schizophrenia-related protocols and in HIV-related protocols regarding the importance of medical research, key aspects of research participation, and the acceptability of research involvement by various groups. A total of 33 men enrolled in schizophrenia protocols and 15 men enrolled in HIV-related protocols volunteered for our study. Respondents affirmed the importance of medical research and endorsed many positive things about participation. Autonomy and altruism were identified as motivators for research involvement. Participation by diverse groups was seen as acceptable. Respondents expressed comfort and little stress with the interview process. Men in different diagnostic groups largely saw the issues the same. Our findings thus suggest that people with schizophrenia and HIV/AIDS who are enrolled in protocols may share a number of core attitudes or beliefs related to ethical aspects of research participation. Further study is needed to explore how research involvement may influence perspectives and whether differences in views exist across people with diverse physical and mental illnesses.

Genetic and environmental contributions to age of onset of alcohol dependence symptoms in male twins

AIMS

To investigate genetic and environmental influences on the development of specific alcohol dependence symptoms.

DESIGN AND PARTICIPANTS

A classical twin study of 3372 male-male twin pairs in the Vietnam Era Twin (VET) Registry based on telephone interviews about alcohol use.

MEASUREMENTS

The nine diagnostic symptoms according to the Diagnostic and Statistical Manual of Mental Disorder, version III (revised) (DSM-III-R) definition of alcohol dependence. Symptoms were grouped into those based on impaired control, biological effects and social consequences (Beresford's classification) or early versus late symptoms (Nelson's classification). Survival models with random effects were used to examine the age of onset of each symptom.

FINDINGS

Approximately 38% of the variation in age of onset of each symptom group based on Beresford's classification is due to additive genetic factors. The age of onset of late symptoms from Nelson's classification appears to be most affected by genetic factors. Estimates of genetic effects for impaired control symptoms are greatly decreased when twins with comorbid psychiatric disorders are excluded.

CONCLUSIONS

Our results support the heritability of age of onset of DSM-III-R-defined symptoms for alcohol dependence. However, no symptom group in Beresford's classification could be identified as more heritable than other symptom groups. A strong association between genetic vulnerability and co-occurring diseases for symptoms indicative of impaired control could be found. In addition, our findings show that the late symptom group could be a good candidate for subsequent genetic research.

Ethical issues in the use of genetic information

Advances in molecular genetics promise to deepen our understanding of the biological basis of human behavior and shed light on the pathophysiology of mental illness. Genetic research is likely to improve our ability to develop somatic treatments for psychiatric syndromes as well as to identify targets for environmental intervention. However, population-screening tests for disorders with multifactorial inheritance may offer little clinical benefit to outweigh their potential for misuse. Relevant legal issues surrounding the use of genetic information in psychiatry include the perceived need for laws to prevent insurance and employment discrimination, and concerns about genetic status as a possible excuse for criminal behavior. Relevant ethical issues include threats to patient privacy and confidentiality and the importance of fairly distributing the benefits and burdens of genetic advances.

Genes and geneticization? The social construction of autosomal dominant polycystic kidney disease

Critics of the new genetics argue that contemporary understandings of health and illness are becoming increasingly 'geneticized.' Salient implications of this critique are explored here within the context of Autosomal Dominant Polycystic Kidney Disease (PKD), a life-threatening genetic disease that causes fluid-filled cysts in the kidneys and progressive loss of renal function. Although PKD is very common, public awareness of the disease remains low and there is little clinical emphasis on hereditary aspects. Drawing upon qualitative interviews with 16 healthcare providers, 13 patients and 15 family members, this paper examines the social construction and clinical management of PKD. In particular, interviewees' perceptions of the role of genetics in PKD and views on presymptomatic testing are considered. Finding little impetus toward early diagnosis and/or presymptomatic identification of mutation carriers, we conclude that careful empirical study of PKD (or other neglected hereditary conditions) contributes new insights into factors mitigating geneticization.

The policy and ethical implications of genetic research on attention deficit hyperactivity disorder

OBJECTIVE

To review the policy and ethical implications of recent research on the molecular genetics of attention deficit hyperactivity disorder (ADHD).

METHOD

MEDLINE and psycINFO database searches were used to identify studies on the genetics of ADHD. The implications of replicated candidate genes are discussed.

RESULTS

The findings for most genes have been inconsistent but several studies have implicated the genes in the dopaminergic pathway in the aetiology of ADHD.

CONCLUSIONS

The current evidence on the genetics of ADHD is insufficient to justify genetic screening tests but it will provide important clues as to the aetiology of ADHD. Genetic information on susceptibility to ADHD has the potential to be abused and to stigmatize individuals. Researchers and clinicians need to be mindful of these issues in interpreting and disseminating the results of genetic studies of ADHD.

Genetics and drug use as a complex phenotype

Drug use is a complex behavior influenced by multiple biological, family, and sociocultural factors. The concurrent use/misuse of multiple drugs is often seen and drug use also co-occurs with other psychiatric conditions. Behavior and molecular genetic studies support an important posited role of genes in drug use. This posited genetic risk does not appear to be conferred by one or two major genes manifesting large effects, but rather by a number of genes manifesting smaller effects. Genetic factors explain, on average, only about half of the total variability in drug use, with the remaining variability influenced by environmental factors. Also, genetic risk may be differentially expressed in the presence vs. absence of particular environmental conditions. Thus, investigation of environmental factors and their interaction with genetic risk is a necessary component of genetic research. While the full potential of genetic investigations for the prevention of drug misuse has yet to be realized, an example of the impact of risk factor modification under various conditions of gene-environment interaction is provided, and the implications for use of genetic information in drug-misuse prevention are discussed. The multifactorial nature of drug use necessitates coordinated investigation from multiple disciplines and timely dissemination of scientific findings. In addition, this work demands adherence to the highest standards of confidentiality and ethical use of genetic information to best inform future prevention efforts.

Aggressiveness, family history of alcoholism, and the heart rate response to alcohol intoxication

Some sons of male alcoholics (SOMAs) are characterized by an increased heart rate (HR) response to alcohol intoxication, which is thought to reflect increased sensitivity to alcohol-induced reward. Such a response has also been related to increased physical aggression. However, the confounding effect of aggression in SOMAs may be obscuring the interpretation of these findings. The HR response to alcohol was therefore assessed in 4 groups: high/low aggressive SOMAs and high/low aggressive non-SOMAs. Results indicate that aggressive SOMAs had the highest intoxicated HR response and that they reported the most alcohol consumption. This suggests that in some cases the high comorbidity between alcohol misuse and aggression is related to an increased sensitivity to alcohol-induced reward.

Conducting research related to treatment of Alzheimer's disease. Ethical issues

Researchers are obligated to protect the rights of study participants. Protecting the rights of patients with Alzheimer's disease (AD) is particularly complicated because of the special needs of this patient population, and the characteristics of developing treatments and technologies. Respecting autonomy and the right to self-determination are complicated by difficulties associated with assuring competence, understanding, and voluntariness in the informed consent process. Protecting patients with AD from harm may be complicated because new treatments have subtle side effects that may be difficult to detect in patients experiencing communication difficulties. Harm to patients with AD also may occur from withholding proven treatments in placebo-controlled trials, and in the use of genetic testing. Issues of justice in the allocation of research dollars and the ability of patients with AD to participate in research are also discussed. By recognizing potential pitfalls, researchers involved in testing new treatments for patients with AD can take proper steps to assure ethical treatment of study participants.