Nicotine withdrawal sensitivity, linkage to chr6q26, and association of OPRM1 SNPs in the SMOking in FAMilies (SMOFAM) sample

Converging findings from linkage and association analyses on susceptibility genes for smoking and other addictions

Experimental approaches to genetic studies of complex traits evolve with technological advances. How do discoveries using different approaches advance our knowledge of the genetic architecture underlying complex diseases/traits? Do most of the findings of newer techniques, such as genome-wide association study (GWAS), provide more information than older ones, for example, genome-wide linkage study? In this review, we address these issues by developing a nicotine dependence (ND) genetic susceptibility map based on the results obtained by the approaches commonly used in recent years, namely, genome-wide linkage, candidate gene association, GWAS and targeted sequencing. Converging and diverging results from these empirical approaches have elucidated a preliminary genetic architecture of this intractable psychiatric disorder and yielded new hypotheses on ND etiology. The insights we obtained by putting together results from diverse approaches can be applied to other complex diseases/traits. In sum, developing a genetic susceptibility map and keeping it updated are effective ways to keep track of what we know about a disease/trait and what the next steps may be with new approaches.

Association of the OPRM1 Variant rs1799971 (A118G) with Non-Specific Liability to Substance Dependence in a Collaborative de novo Meta-Analysis of European-Ancestry Cohorts

The mu1 opioid receptor gene, OPRM1, has long been a high-priority candidate for human genetic studies of addiction. Because of its potential functional significance, the non-synonymous variant rs1799971 (A118G, Asn40Asp) in OPRM1 has been extensively studied, yet its role in addiction has remained unclear, with conflicting association findings. To resolve the question of what effect, if any, rs1799971 has on substance dependence risk, we conducted collaborative meta-analyses of 25 datasets with over 28,000 European-ancestry subjects. We investigated non-specific risk for "general" substance dependence, comparing cases dependent on any substance to controls who were non-dependent on all assessed substances. We also examined five specific substance dependence diagnoses: DSM-IV alcohol, opioid, cannabis, and cocaine dependence, and nicotine dependence defined by the proxy of heavy/light smoking (cigarettes-per-day >20 vs. ≤ 10). The G allele showed a modest protective effect on general substance dependence (OR = 0.90, 95% C.I. [0.83-0.97], p value = 0.0095, N = 16,908). We observed similar effects for each individual substance, although these were not statistically significant, likely because of reduced sample sizes. We conclude that rs1799971 contributes to mechanisms of addiction liability that are shared across different addictive substances. This project highlights the benefits of examining addictive behaviors collectively and the power of collaborative data sharing and meta-analyses.

To quit or not: Vulnerability of women to smoking tobacco

Tobacco smoking is currently on the rise among women, and can pose a greater health risk. In order to understand the nature of the increase in smoking prevalence among women, we focused on the vulnerability of women to smoking behaviors--smoking cessation or tobacco addiction--and performed a systematic review of the socioeconomic and intrinsic factors as well as tobacco ingredients that affect women's susceptibility to smoking tobacco. We observed that nicotine and other tobacco components including cocoa-relatives, licorice products, and menthol aggravate tobacco addiction in women rather than in men. Various genetic and epigenetic alterations in dopamine pathway and the pharmaco-kinetics and -dynamic factors of nicotine also showed potential evidences for high susceptibility to tobacco addiction in women. Therefore, we suggest systemic approaches to prevent tobacco smoking-related health risks, considering gene-environment-gender interaction.

Relationship Between Patients' Perceptions of Care Quality and Health Care Errors in 11 Countries: A Secondary Data Analysis

Patients may be the most reliable reporters of some aspects of the health care process; their perspectives should be considered when pursuing changes to improve patient safety. The authors evaluated the association between patients' perceived health care quality and self-reported medical, medication, and laboratory errors in a multinational sample. The analysis was conducted using the 2010 Commonwealth Fund International Health Policy Survey, a multinational consumer survey conducted in 11 countries. Quality of care was measured by a multifaceted construct developed using Rasch techniques. After adjusting for potentially important confounding variables, an increase in respondents' perceptions of care coordination decreased the odds of self-reporting medical errors, medication errors, and laboratory errors (P < .001). As health care stakeholders continue to search for initiatives that improve care experiences and outcomes, this study's results emphasize the importance of guaranteeing integrated care.

A systematic review of the A118G (Asn40Asp) variant of OPRM1 in relation to smoking initiation, nicotine dependence and smoking cessation

Candidate gene studies on smoking behaviors mainly focused on dopaminergic and serotonergic genes, but genes within the µ-opioid system might also be involved. The A118G variant within the OPRM1 gene has been most often examined in relation to smoking, yielding inconsistent findings. It is largely unknown which of the alleles increases susceptibility for smoking behaviors. The aim of this review was to merge findings of OPRM1 gene studies in relation to smoking behaviors and to elaborate on the underlying biological mechanism of the A118G variant. It appeared that A118 was more likely to increase susceptibility to smoking behaviors than 118G, especially with regard to nicotine dependence, but less with smoking initiation and cessation. The proposed functioning of the OPRM1 gene is further explained.

Pharmacogenomics of the human µ-opioid receptor

The µ-opioid receptor is a primary target for clinically important opioid analgesics, including morphine, fentanyl and methadone. Many genetic variations have been identified in the human µ-opioid receptor MOP gene (OPRM1), and their implications have been reported in the effects of opioid drugs and susceptibility to drug dependence. Interestingly, agonistic and antagonistic opioid effects are inversely associated with the A118G polymorphism genotype. The A118G polymorphism may also be associated with substance dependence and susceptibility to other disorders, including epilepsy and schizophrenia. The IVS1+A21573G, IVS1-T17286C, and TAA+A5359G polymorphisms in the OPRM1 gene may be associated with alcohol, opioid and tobacco dependence, respectively. However, some studies have failed to confirm the correlations between the polymorphisms and opioid effects and substance dependence. Further studies are needed to elucidate the molecular mechanisms underlying the effects of OPRM1 polymorphisms.

Human Mu Opioid Receptor (OPRM1 A118G) polymorphism is associated with brain mu-opioid receptor binding potential in smokers

Evidence points to the endogenous opioid system, and the mu-opioid receptor (MOR) in particular, in mediating the rewarding effects of drugs of abuse, including nicotine. A single nucleotide polymorphism (SNP) in the human MOR gene (OPRM1 A118G) has been shown to alter receptor protein level in preclinical models and smoking behavior in humans. To clarify the underlying mechanisms for these associations, we conducted an in vivo investigation of the effects of OPRM1 A118G genotype on MOR binding potential (BP(ND) or receptor availability). Twenty-two smokers prescreened for genotype (12 A/A, 10 */G) completed two [(11)C]carfentanil positron emission tomography (PET) imaging sessions following overnight abstinence and exposure to a nicotine-containing cigarette and a denicotinized cigarette. Independent of session, smokers homozygous for the wild-type OPRM1 A allele exhibited significantly higher levels of MOR BP(ND) than smokers carrying the G allele in bilateral amygdala, left thalamus, and left anterior cingulate cortex. Among G allele carriers, the extent of subjective reward difference (denicotinized versus nicotine cigarette) was associated significantly with MOR BP(ND) difference in right amygdala, caudate, anterior cingulate cortex, and thalamus. Future translational investigations can elucidate the role of MORs in nicotine addiction, which may lead to development of novel therapeutics.

Proactive recruitment of cancer patients' social networks into a smoking cessation trial

BACKGROUND

This report describes the characteristics associated with successful enrollment of smokers in the social networks (i.e., family and close friends) of patients with lung cancer into a smoking cessation intervention.

METHODS

Lung cancer patients from four clinical sites were asked to complete a survey enumerating their family members and close friends who smoke, and provide permission to contact these potential participants. Family members and close friends identified as smokers were interviewed and offered participation in a smoking cessation intervention. Repeated measures logistic regression model examined characteristics associated with enrollment.

RESULTS

A total of 1062 eligible lung cancer patients were identified and 516 patients consented and completed the survey. These patients identified 1325 potentially eligible family and close friends. Of these, 496 consented and enrolled in the smoking cessation program. Network enrollment was highest among patients who were white and had late-stage disease. Social network members enrolled were most likely to be female, a birth family, immediate family, or close friend, and live in close geographic proximity to the patient.

CONCLUSIONS

Proactive recruitment of smokers in the social networks of lung cancer patients is challenging. In this study, the majority of family members and friends declined to participate. Enlisting immediate female family members and friends, who live close to the patient as agents to proactively recruit other network members into smoking cessation trials could be used to extend reach of cessation interventions to patients' social networks. Moreover, further consideration should be given to the appropriate timing of approaching network smokers to consider cessation.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Refining the tobacco dependence phenotype using the Wisconsin Inventory of Smoking Dependence Motives: II. Evidence from a laboratory self-administration assay

Prior analyses of the Wisconsin Inventory of Smoking Dependence Motives (Piper et al., 2004) implicated 4 subscales as primary dependence motives (PDM) indexing the core features of tobacco dependence, with the remaining subscales reflecting secondary dependence motives (SDM; Piper et al., 2008). The current study extended this work by examining the correlates of PDM, SDM, their subscales, and other indicators of dependence in an operant self-administration paradigm. Smokers (N = 58) worked for cigarette puffs under differing fixed ratio schedules. Analyses focused on predicting self-administration under conditions of minimal constraint on tobacco access and on withdrawal and craving under conditions of severe constraint. Results support a 2-factor model of dependence, with the PDM factor showing relatively stronger relations with tobacco self-administration and the SDM factor showing relatively stronger relations with withdrawal symptomatology and distress-related craving. The PDM appears to index core features of tobacco dependence, but susceptibility to deprivation-contingent distress and craving may be better indexed by SDM.