Association between two mu-opioid receptor gene (OPRM1) haplotype blocks and drug or alcohol dependence

Pain Intensity in Patients with Opioid Use Disorder on Extended-Release Naltrexone or Opioid Agonists; The Role of COMT rs4680 and OPRM1 rs1799971: An Exploratory Study

Purpose

To examine whether reported pain intensity over time is related to the single nucleotide polymorphisms of the catechol-O-methyltransferase (COMT rs4680) and mu-opioid receptor (OPRM1 rs1799971) in patients with opioid use disorder (OUD) choosing treatment with extended-release naltrexone (XR-NTX) or opioid agonist treatment (OAT).

Patients and Methods

This exploratory study was part of a 24-week, open-label clinical prospective trial of patients with OUD who chose intramuscular XR-NTX, and patients receiving OAT. Men and women aged 18 to 65 years with OUD per the Diagnostic and Statistical Manual of Mental Disorders, fifth edition were included. Pain intensity was measured at baseline and at 24-week follow-up using the Numerical Pain Rating Scale-11 and genotyping was performed by TaqMan technology. Data were analyzed with ordinal logistic regression.

Results

Of 317 participants included at baseline, 210 samples were obtained and analyzed. In the OAT group, there was a negative significant association between pain intensity and having the Val/Val allele of COMT rs4680 (wild-type = most common type) and the rare allele G of OPRM1 rs1799971 at 24-week follow-up. No such effects were seen in the XR-NTX group.

Conclusion

The wild-type allele Val/Val of COMT rs4680 and the rare allele G of OPRM1 rs1799971 may have a possible protective effect regarding pain intensity in patients with OUD receiving OAT. Given relatively low sample size, particularly low number of female participants in the XR-NTX group and other possible confounders, our findings should be interpreted with caution.

Chronic intermittent ethanol exposure-induced m6A modifications around mRNA stop codons of opioid receptor genes

Chronic alcohol consumption may alter mRNA methylation and expression levels of genes related to addiction and reward in the brain, potentially contributing to alcohol tolerance and dependence. Neuron-like (SH-SY5Y) and non-neuronal (SW620) cells were utilized as models to examine chronic intermittent ethanol (CIE) exposure-induced global m6A RNA methylation changes, as well as m6A mRNA methylation changes around the stop codon of three opioid receptor genes (OPRM1, OPRD1, and OPRK1), which are known to regulate pain, reward, and addiction behaviours. CIE exposure for three weeks significantly increased global RNA methylation levels in both SH-SY5Y (t = 3.98, P = 0.007) and SW620 (t = 2.24, P = 0.067) cells. However, a 3-week CIE exposure resulted in hypomethylation around mRNA stop codon regions of OPRM1 and OPRD1 in both cell lines [OPRM1(SH-SY5Y): t = -5.05, P = 0.0005; OPRM1(SW620): t = -3.19, P = 0.013; OPRD1(SH-SY5Y): t = -13.43, P < 0.00001; OPRD1(SW620): t = -4.00, P = 0.003]. Additionally, mRNA expression levels of OPRM1, OPRD1, and OPRK1 were downregulated (corresponding to mRNA hypomethylation) in both SH-SY5Y and SW620 cells after a 3-week CIE exposure. The present study demonstrated that chronic ethanol exposure altered global RNA methylation levels, as well as mRNA methylation and expression levels of opioid receptor genes in both neuron-like and non-neuronal cells. Our findings suggest a potential epitranscriptomic mechanism by which chronic alcohol consumption remodels the expression of reward-related and alcohol responsive genes in the brain, thus increasing the risk of alcohol use disorder development.Abbreviations: OPRM1: the μ-opioid receptor; OPRD1: the δ-opioid receptor; OPRK1: the κ-opioid receptor; CIE: chronic intermittent ethanol exposure; CIE+WD: chronic intermittent ethanol exposure followed by a 24-hr withdrawal; SH-SY5Y: human neuroblastoma cell Line; SW620: human colon carcinoma cell line; RT-qPCR: reverse transcription followed by quantitative polymerase reaction; MazF-RT-qPCR: MazF digestion followed by RT-qPCR.

Candidate gene-environment interactions in substance abuse: A systematic review

BACKGROUND

The abuse of psychogenic drugs can lead to multiple health-related problems. Genetic and environmental vulnerabilities are factors in the emergence of substance use disorders. Empirical evidence regarding the gene-environment interaction in substance use is mixed. Summaries of the latest findings from a candidate gene approach will be useful for revealing the significance of particular gene contributions. Thus, we aim to identify different gene-environment interactions in patterns of substance use and investigate whether any effects trend notably across different genders and races.

METHODS

We reviewed published studies, until March 1, 2022, on substance use for candidate gene-environment interaction. Basic demographics of the included studies, target genes, environmental factors, main findings, patterns of gene-environment interaction, and other relevant information were collected and summarized.

RESULTS

Among a total of 44 studies, 38 demonstrated at least one significant interaction effect. About 61.5% of studies on the 5-HTTLPR gene, 100% on the MAOA gene, 42.9% on the DRD2 gene, 50% on the DRD4 gene, 50% on the DAT gene, 80% on the CRHR1 gene, 100% on the OPRM1 gene, 100% on the GABRA1 gene, and 50% on the CHRNA gene had a significant gene-environment interaction effect. The diathesis-stress model represents a dominant interaction pattern (89.5%) in the studies with a significant interaction effect; the remaining significant effect on substance use is found in the differential susceptibility model. The social push and swing model were not reported in the included studies.

CONCLUSION

The gene-environment interaction research on substance use behavior is methodologically multidimensional, which causes difficulty in conducting pooled analysis, or stated differently-making it hard to identify single sources of significant influence over maladaptive patterns of drug taking. In decreasing the heterogeneity and facilitating future pooled analysis, researchers must (1) replicate the existing studies with consistent study designs and measures, (2) conduct power calculations to report gene-environment correlations, (3) control for covariates, and (4) generate theory-based hypotheses with factorial based experiments when designing future studies.

Association between opioid and dopamine receptor gene polymorphisms OPRM1 rs1799971, DAT VNTR 9-10 repeat allele, DRD1 rs4532 and DRD2 rs1799732 and alcohol dependence: an ethnicity oriented meta-analysis

OBJECTIVE

We carried out a meta-analysis of four opioid and dopamine candidate gene polymorphisms having conflicting results in prior literature, namely OPRM1 rs1799971, DAT VNTR 9-10 repeat, DRD1 rs4532 and DRD2 rs1799732, to clarify their association with alcohol dependence and further stratified results by ethnicity to analyze possible ethnicity-mediated effects.

METHODS

Inclusion criteria: case-control studies assessing the association between OPRM1 rs1799971, DAT VNTR 9/10 repeat allele, DRD1 rs4532 and DRD2 rs1799732 with alcohol dependence, with sufficient data available to calculate the odds ratio (OR) within a 95% confidence interval. Exclusion criteria: studies of quantitative measures of alcohol consumption, response to medications or analyses of other markers in the candidate genes, studies without controls, animal studies and lack of genotyping data. Information sources were PubMed, Google Scholar and ScienceDirect databases, all of which were searched for articles published till 2021. Heterogeneity between studies and publication bias, subgroup analyses and sensitivity analyses were carried out.

RESULTS

A total of 41 published studies were included in the current meta-analysis. For the OPRM1 gene, there was a statistically significant association in the Asian population with a pooled OR of 1.707 (95% CI, 1.32-2.20 P  < 0.0001) and 1.618 (95% CI, 1.16-2.26 P  = 0.005) in the additive and dominant genetic models. For DAT VNTR 9/10 repeat, a statistically significant association of the risk vs. common allele was observed in AD with a pooled OR of 1.104 (95% CI, 1.00-1.21 P  = 0.046) in the allele model and the additive genetic model in the Caucasian population with pooled OR of 1.152 (95% CI, 1.01-1.31 P  = 0.034).

CONCLUSION

Results indicate that some of the effects may be ethnicity-specific.

OTHER

The meta-analysis has been registered in the CRD PROSPERO (CRD42023411576).

Multi-trait genome-wide association study of opioid addiction: OPRM1 and beyond

Opioid addiction (OA) is moderately heritable, yet only rs1799971, the A118G variant in OPRM1, has been identified as a genome-wide significant association with OA and independently replicated. We applied genomic structural equation modeling to conduct a GWAS of the new Genetics of Opioid Addiction Consortium (GENOA) data together with published studies (Psychiatric Genomics Consortium, Million Veteran Program, and Partners Health), comprising 23,367 cases and effective sample size of 88,114 individuals of European ancestry. Genetic correlations among the various OA phenotypes were uniformly high (rg > 0.9). We observed the strongest evidence to date for OPRM1: lead SNP rs9478500 (p = 2.56 × 10-9). Gene-based analyses identified novel genome-wide significant associations with PPP6C and FURIN. Variants within these loci appear to be pleiotropic for addiction and related traits.

Cross-ancestry meta-analysis of opioid use disorder uncovers novel loci with predominant effects in brain regions associated with addiction

Despite an estimated heritability of ~50%, genome-wide association studies of opioid use disorder (OUD) have revealed few genome-wide significant loci. We conducted a cross-ancestry meta-analysis of OUD in the Million Veteran Program (N = 425,944). In addition to known exonic variants in OPRM1 and FURIN, we identified intronic variants in RABEPK, FBXW4, NCAM1 and KCNN1. A meta-analysis including other datasets identified a locus in TSNARE1. In total, we identified 14 loci for OUD, 12 of which are novel. Significant genetic correlations were identified for 127 traits, including psychiatric disorders and other substance use-related traits. The only significantly enriched cell-type group was CNS, with gene expression enrichment in brain regions previously associated with substance use disorders. These findings increase our understanding of the biological basis of OUD and provide further evidence that it is a brain disease, which may help to reduce stigma and inform efforts to address the opioid epidemic.

Genome-wide association study in individuals of European and African ancestry and multi-trait analysis of opioid use disorder identifies 19 independent genome-wide significant risk loci

Despite the large toll of opioid use disorder (OUD), genome-wide association studies (GWAS) of OUD to date have yielded few susceptibility loci. We performed a large-scale GWAS of OUD in individuals of European (EUR) and African (AFR) ancestry, optimizing genetic informativeness by performing MTAG (Multi-trait analysis of GWAS) with genetically correlated substance use disorders (SUDs). Meta-analysis included seven cohorts: the Million Veteran Program, Psychiatric Genomics Consortium, iPSYCH, FinnGen, Partners Biobank, BioVU, and Yale-Penn 3, resulting in a total N = 639,063 (Ncases = 20,686;Neffective = 77,026) across ancestries. OUD cases were defined as having a lifetime OUD diagnosis, and controls as anyone not known to meet OUD criteria. We estimated SNP-heritability (h2SNP) and genetic correlations (rg). Based on genetic correlation, we performed MTAG on OUD, alcohol use disorder (AUD), and cannabis use disorder (CanUD). A leave-one-out polygenic risk score (PRS) analysis was performed to compare OUD and OUD-MTAG PRS as predictors of OUD case status in Yale-Penn 3. The EUR meta-analysis identified three genome-wide significant (GWS; p ≤ 5 × 10-8) lead SNPs-one at FURIN (rs11372849; p = 9.54 × 10-10) and two OPRM1 variants (rs1799971, p = 4.92 × 10-09; rs79704991, p = 1.11 × 10-08; r2 = 0.02). Rs1799971 (p = 4.91 × 10-08) and another OPRM1 variant (rs9478500; p = 1.95 × 10-08; r2 = 0.03) were identified in the cross-ancestry meta-analysis. Estimated h2SNP was 12.75%, with strong rg with CanUD (rg = 0.82; p = 1.14 × 10-47) and AUD (rg = 0.77; p = 6.36 × 10-78). The OUD-MTAG resulted in a GWAS Nequivalent = 128,748 and 18 independent GWS loci, some mapping to genes or gene regions that have previously been associated with psychiatric or addiction phenotypes. The OUD-MTAG PRS accounted for 3.81% of OUD variance (beta = 0.61;s.e. = 0.066; p = 2.00 × 10-16) compared to 2.41% (beta = 0.45; s.e. = 0.058; p = 2.90 × 10-13) explained by the OUD PRS. The current study identified OUD variant associations at OPRM1, single variant associations with FURIN, and 18 GWS associations in the OUD-MTAG. The genetic architecture of OUD is likely influenced by both OUD-specific loci and loci shared across SUDs.

Hypermethylation of the OPRM1 and ALDH2 promoter regions in Chinese Han males with alcohol use disorder in Yunnan Province

BACKGROUND

Alcohol use disorder (AUD) is one of the most serious public health problems worldwide. The OPRM1 and ALDH2 genes are important factors in the reward and alcohol metabolism pathways, and their DNA methylation patterns are closely related to AUD and are population-specific. Chinese Han people are the most populous ethnic group in the world, and this group experiences severe AUD. No epigenetic study on OPRM1 and ALDH2 has been performed in Chinese Han patients with AUD.

OBJECTIVES

To investigate whether methylation patterns of OPRM1 and ALDH2 are associated with susceptibility to AUD in Chinese Han males.

METHODS

DNA methylation of the OPRM1 and ALDH2 promoters was studied in Chinese Han males with AUD in Yunnan Province (N = 50 controls, N = 90 individuals with AUD) using the bisulfite pyrosequencing method.

RESULTS

In the AUD group, compared with the control group, OPRM1 was hypermethylated(p < .01) but there was no significant difference in the methylation level of ALDH2 (p > .05). 9 CpG sites of OPRM1 (p < .05) and 2 CpG sites of ALDH2 (p > .01) were hypermethylated. Smoking promoted AUD-mediated hypermethylation of OPRM1, in which 3 CpG sites showed significant hypermethylation (p < .01). Age had no significant effect on the DNA methylation levels of these two genes.

CONCLUSIONS

Our study demonstrates that DNA hypermethylation of the OPRM1 and ALDH2 promoter regions is associated with an increased risk of AUD, which may help to explain the pathogenesis and progression of AUD.

Population-specific genetic background for the OPRM1 variant rs1799971 (118A>G): implications for genomic medicine and functional analysis

The mu-opioid receptor (MOR, OPRM1) has important roles in diverse functions including reward, addiction, and response to pain treatment. SNP rs1799971 (118A > G, N40D) which occur at a high frequency (40-60%) in Asia and moderate frequency (15%) in samples of European ancestry, is the only common coding variant in the canonical transcript, in non-African populations. Despite extensive studies, the molecular consequences of this variation remained unresolved. The aim of this study was to determine the genetic background of the OPRM1 region of 118G in four representative populations and to assess its potential modulatory effect. Seven common haplotypes with distinct population distribution were identified based on seven SNPs. Three haplotypes carry the 118G and additional highly linked regulatory SNPs (e.g., rs9383689) that could modulate the effect of 118G. Extended analysis in the 1000 Genomes database (n = 2504) revealed a common East Asian-specific haplotype with a different genetic background in which there are no variant alleles for an upstream LD block tagged by the eQTL rs9397171. The major European haplotype specifically includes the eQTL intronic SNP rs62436463 that must have arisen after the split between European and Asian populations. Differentiating between the effect of 118G and these SNPs requires specific experimental approaches. The analysis also revealed a significant increase in two 118A haplotypes with eQTL SNPs associated with drug addiction (rs510769) and obesity (rs9478496) in populations with native Mexican ancestry. Future studies are required to assess the clinical implication of these findings.

Significant association of mu-opioid receptor 1 haplotype with tobacco smoking in healthy control subjects but not in patients with schizophrenia and alcohol dependence

Tobacco smoking is highly prevalent in patients with schizophrenia and alcohol dependence. The underlying neurobiology of nicotine addiction is complex. Rewarding effects of nicotine from cigarettes are associated, among others, with mu-opioid receptors encoded by the OPRM1 gene. The aim of the study was to evaluate the association between two OPRM1 gene polymorphisms, rs1799971 and rs510769, and tobacco smoking in Caucasian patients with schizophrenia, alcohol dependence, and healthy control subjects. The study included 1058 Caucasians (277 patients with schizophrenia, 359 patients with alcohol dependence, and 422 healthy control subjects), subdivided according to the nicotine dependence into smokers (i.e. current smokers) and non-smokers. A significant association was found between the GC haplotype (OPRM1 rs1799971 and rs510769) and smoking in healthy controls, but not in patients with schizophrenia and alcohol dependence. A nominal association was detected in all cases/controls, but this significance did not survive the correction for the multiple testing. This is the first study to reveal that nicotine dependence is associated with the GC haplotype of the OPRM1 rs1799971 and rs510769 in all subjects or specifically in healthy controls. These results did not confirm the strong connection between OPRM1 polymorphisms and nicotine dependence in schizophrenia or alcohol dependence.

Cannabinoids as an Alternative Option for Conventional Analgesics in Cancer Pain Management: A Pharmacogenomics Perspective

The global cancer burden is significantly increasing at an alarming rate affecting patients, relatives, communities, and health-care system. Cancer patients require adequate pain relief and palliative care throughout the life course, especially in terminal illness. Although opioid treatment is successful in majority of patients, around 40% do not achieve enough analgesia or are prone to serious side effects and toxicity. The treatment of medical conditions with cannabis and cannabinoid compounds is constantly expanding. This review organizes the current knowledge in the context of SNPs associated with opioids and nonopioids and its clinical consequences in pain management and pharmacogenetic targets of cannabinoids, for use in clinical practice.

The Effect of OPRM1 rs648893 Gene Polymorphism on Opioid Addiction in an Iranian population in Zabol: A Case-Control Study

Introduction: Opioid addiction (OA) is a neurologically life-threatening challenge associated with socioeconomic and health concerns for individuals and society. The addictive drugs trigger neuromodulators and neurotransmitters through the opioid receptors and corresponding endogenous peptide ligands. In addition, drug addiction is reportedly related to the mu-opioid receptor (OPRM1) encoding gene and its variants. According to the role of the rs648893 polymorphism of the OPRM1 gene in numerous disorders, it has been suggested as a candidate associated with drug addiction. The present case-control study was conducted to evaluate the role of OPRM1 rs648893 polymorphism in the OA risk. Methods: To this end, the rs648893 polymorphism was genotyped by tetra amplification refractory mutation system-polymerase chain reaction among 160 Iranian subjects consisting of 105 OA cases and 155 controls. Results: According to our findings, there was no significant association between OA and the OPRM1 rs648893 gene polymorphism. Moreover, a marginally insignificant difference was found between OA cases and controls in accordance with the allelic frequencies (P=0.05) Conclusion: In general, our results reported no association between OPRM1 rs648893 gene polymorphism and OA although further research among various ethnicities with larger sample sizes is needed to draw a definite conclusion on the association of rs648893 polymorphism and other OPRM1 intronic variants with opioid and other addictions.

Haplotype-Based Association and In Silico Studies of OPRM1 Gene Variants with Susceptibility to Opioid Dependence Among Addicted Iranians Undergoing Methadone Treatment

The associations of OPRM1 gene variants with opioid dependence have been demonstrated. This study investigated the association of rs495491, rs1799971 (A118G), rs589046, and rs10457090 variants of OPRM1 gene with opium dependence and their haplotypes among addicted individuals undergoing methadone treatment. Moreover, we investigated whether any of these variants were associated with libido dysfunction or insomnia among addicted people. A total of 404 individuals were genotyped by amplification refractory mutation system (ARMS) PCR. In silico studies were designed through homology modeling of A118G structures (N40 and D40) and docked with 41 FDA-approved drugs of OPRM1 protein by SWISS-MODEL, COACH, MolProbity, ProSA, Errat, Glide XP, and Autodock 4. Results revealed that rs495491, A118G, rs589046, and rs10457090 were significantly associated with opium dependence under recessive (P = 6.66E-10), dominant (P = 0.017), co-dominant (P = 0.001), and recessive (P = 9.28E-6) models of inheritance, respectively. Further analyses indicated three significant haplotypes including A-A-A-C (P-permutation < 1E-9), G-G-A-C (P-permutation = 0.04), and G-A-G-C (P-permutation = 8.69E-4). Genotype-phenotype associations of OPRM1 variants with insomnia and libido dysfunction showed no significant association. Docking showed the higher binding affinity of N40 rather than D40 model; however, methadone and morphine were bonded with D40 structure more powerful. Consequently, rs495491, A118G, rs589046, and rs10457090 were associated with opioid dependence among Iranians; also, A118G might be the most remarkable marker of OPRM1 owing to its vital structural roles.

OPRM1 A118G Polymorphisms and Its Role in Opioid Addiction: Implication on Severity and Treatment Approaches

The epidemic of opioid addiction is shaping up as the most serious clinical issues of current times. Opioids have the greatest propensity to develop addiction after first exposure. Molecular, genetic variations, epigenetic alterations, and environmental factors are also implicated in the development of opioid addiction. Genetic and epigenetic variations in candidate genes have been identified for their associations with opioid addiction. OPRM1 nonsynonymous single nucleotide polymorphism rs1799971 (A118G) is the most prominent candidate due to its significant association with onset and treatment of opioid addiction. Marked inter-individual variability in response to available maintenance pharmacotherapies is the common feature observed in individuals with opioid addiction. Several therapies are only effective among subgroups of opioid individuals which indicate that ethnic, environmental factors and genetic polymorphism including rs1799971 may be responsible for the response to treatment. Pharmacogenetics has the potential to enhance our understanding around the underlying genetic, epigenetic and molecular mechanisms responsible for the heterogeneous response of maintenance pharmacotherapies in opioid addiction. A more detailed understanding of molecular, epigenetic and genetic variants especially the implication of OPRM1 A118G polymorphism in an individual may serve as the way forward to address the opioid epidemic. Personalized medicine, which involves developing targeted pharmacotherapies in accordance with individual genetic and epigenetic makeup, are required to develop safe and effective treatments for opioid addiction.

Assessing the contribution of opioid- and dopamine-related genetic polymorphisms to the abuse liability of oxycodone

BACKGROUND

Attempts to identify opioid users at increased risk of escalating to opioid use disorder have had limited success. Data from a variety of sources suggest that genetic variation may mediate the subjective response to opioid drugs, and therefore contribute to their abuse potential. The goal of the current study was to observe the relationship between select genetic polymorphisms and the subjective effects of oxycodone under controlled clinical laboratory conditions.

METHODS

Non-dependent, volunteers with some history of prescription opioid exposure (N = 36) provided a blood sample for analyses of variations in the genes that encode for the μ-, κ- and δ-opioid receptors, and the dopamine metabolizing enzyme, catechol-O-methyltransferase (COMT). Participants then completed a single laboratory test session to evaluate the subjective and analgesic effects of oral oxycodone (0, 10, and 20 mg, cumulative dose = 30 mg).

RESULTS

Oxycodone produced typical μ-opioid receptor agonist effects, such as miosis, and decreased pain perception. Oxycodone also produced dose-dependent increases in positive subjective responses such as: drug "Liking" and "Good Effect." Genetic variants in the μ- (rs6848893) and δ-opioid receptor (rs581111) influenced the responses to oxycodone administration. Additionally, self-reported "Stimulated" effects of oxycodone varied significantly as a function of COMT rs4680 genotype.

DISCUSSION

The current study shows that the euphoric and stimulating effects of oxycodone can vary as a function of genetic variation. Though the relationship between the stimulating effects of opioids and their abuse liability is not well established, we know that the ability of opioids to provide intense feelings of pleasure is a significant motivator for continued use. If replicated, specific genetic variants may be useful in predicting who is at increased risk of developing maladaptive patterns of use following medical exposure to opioid analgesics.

Opening up new horizons for psychiatric genetics in the Russian Federation: moving toward a national consortium

We provide an overview of the recent achievements in psychiatric genetics research in the Russian Federation and present genotype-phenotype, population, epigenetic, cytogenetic, functional, ENIGMA, and pharmacogenetic studies, with an emphasis on genome-wide association studies. The genetic backgrounds of mental illnesses in the polyethnic and multicultural population of the Russian Federation are still understudied. Furthermore, genetic, genomic, and pharmacogenetic data from the Russian Federation are not adequately represented in the international scientific literature, are currently not available for meta-analyses and have never been compared with data from other populations. Most of these problems cannot be solved by individual centers working in isolation but warrant a truly collaborative effort that brings together all the major psychiatric genetic research centers in the Russian Federation in a national consortium. For this reason, we have established the Russian National Consortium for Psychiatric Genetics (RNCPG) with the aim to strengthen the power and rigor of psychiatric genetics research in the Russian Federation and enhance the international compatibility of this research.The consortium is set up as an open organization that will facilitate collaborations on complex biomedical research projects in human mental health in the Russian Federation and abroad. These projects will include genotyping, sequencing, transcriptome and epigenome analysis, metabolomics, and a wide array of other state-of-the-art analyses. Here, we discuss the challenges we face and the approaches we will take to unlock the huge potential that the Russian Federation holds for the worldwide psychiatric genetics community.

Association of opioid receptor gene polymorphisms with drinking severity and impulsivity related to alcohol use disorder in a Korean population

Aims

Recent evidence suggests that the opioid system is implicated in the pathophysiology of alcohol use disorder (AUD). We aimed to examine the genetic influence of opioid receptors on susceptibility to AUD and its clinical and psychological characteristics including harmful drinking behavior and various aspects of impulsivity in AUD patients.

Methods

Three μ‐opioid receptor gene (OPRM1) variants and two κ‐opioid receptor gene (OPRK1) variants were examined in 314 male patients with AUD and 324 male controls. We applied the Alcohol Use Disorders Identification Test (AUDIT), Obsessive Compulsive Drinking Scale (OCDS), and Alcohol Dependence Scale. AUD patients also completed the stop‐signal task, delay discounting task, balloon analogue risk task, and the Barratt Impulsiveness Scale version 11 (BIS‐11).

Results

No significant differences in genotype distributions or haplotype frequencies were found between AUD patients and controls. However, OPRK1 SNP rs6473797 was significantly related to the severity of alcohol‐related symptoms as measured by AUDIT and OCDS and a haplotype containing rs6473797 was also related to OCDS scores in AUD patients. For other psychological traits, OPRM1 SNP rs495491 was significantly associated with scores on the motor subfactor of the BIS‐11.

Conclusion

Genetic variations in opioid receptors may contribute to symptom severity and impulsivity in AUD patients.

Alcohol Interaction with Cocaine, Methamphetamine, Opioids, Nicotine, Cannabis, and γ-Hydroxybutyric Acid

Millions of people around the world drink alcoholic beverages to cope with the stress of modern lifestyle. Although moderate alcohol drinking may have some relaxing and euphoric effects, uncontrolled drinking exacerbates the problems associated with alcohol abuse that are exploding in quantity and intensity in the United States and around the world. Recently, mixing of alcohol with other drugs of abuse (such as opioids, cocaine, methamphetamine, nicotine, cannabis, and γ-hydroxybutyric acid) and medications has become an emerging trend, exacerbating the public health concerns. Mixing of alcohol with other drugs may additively or synergistically augment the seriousness of the adverse effects such as the withdrawal symptoms, cardiovascular disorders, liver damage, reproductive abnormalities, and behavioral abnormalities. Despite the seriousness of the situation, possible mechanisms underlying the interactions is not yet understood. This has been one of the key hindrances in developing effective treatments. Therefore, the aim of this article is to review the consequences of alcohol's interaction with other drugs and decipher the underlying mechanisms.

Lack of Association between Opioid-Receptor Genotypes and Smoking Cessation Outcomes in a Randomized, Controlled Naltrexone Trial

AIMS

The present study examined how variation in mu- (OPRM1), kappa- (OPRK), and delta- (OPRD) opioid receptor genes may influence the efficacy of naltrexone in the context of a smoking cessation trial.

METHODS

The study's primary objective was to examine the association of the Asn40Asp OPRM1 single nucleotide polymorphism (SNP) with naltrexone's effects on smoking quit rate, weight gain, and heavy drinking behavior during a double-blind, randomized clinical trial in 280 adult DSM-IV nicotine-dependent participants. The secondary goal of the study was to examine the relationship of 20 additional SNPs of OPRM1, OPRK, and OPRD with the aforementioned outcomes.

RESULTS

Results indicated a null association between any opioid-receptor gene SNP and naltrexone's effects on smoking quit rate, weight gain, and heavy drinking behavior in this sample of nicotine dependent participants.

CONCLUSIONS

In sum, these results do not suggest that genetic variation in opioid-receptors is related to treatment responses to naltrexone in a smoking cessation trial.

Molecular Imaging of Opioid and Dopamine Systems: Insights Into the Pharmacogenetics of Opioid Use Disorders

Opioid use in the United States has steadily risen since the 1990s, along with staggering increases in addiction and overdose fatalities. With this surge in prescription and illicit opioid abuse, it is paramount to understand the genetic risk factors and neuropsychological effects of opioid use disorder (OUD). Polymorphisms disrupting the opioid and dopamine systems have been associated with increased risk for developing substance use disorders. Molecular imaging studies have revealed how these polymorphisms impact the brain and contribute to cognitive and behavioral differences across individuals. Here, we review the current molecular imaging literature to assess how genetic variations in the opioid and dopamine systems affect function in the brain's reward, cognition, and stress pathways, potentially resulting in vulnerabilities to OUD. Continued research of the functional consequences of genetic variants and corresponding alterations in neural mechanisms will inform prevention and treatment of OUD.

Implication of OPRM1 A118G Polymorphism in Opioids Addicts in Pakistan: In vitro and In silico Analysis

Single nucleotide polymorphism in OPRM1 gene is associated with hedonic and reinforcing consequences of opioids. Risk and protective alleles may vary in different populations. One hundred healthy controls and 100 opioids (predominantly heroin) addicts from Pakistani origin were genotyped for A118G (N40D) polymorphism in OPRM1. Structural and functional impact of the polymorphism on encoded protein was predicted by in silico analysis. Results show significant association between homozygous GG genotype and opioid addiction in Pakistani population (p value = 0.016). In silico analysis by SIFT (TI = 0.61), PolyPhen (PISC = 0.227), PANTHER (subPSEC = -1.7171), and SNP effect predicted this SNP benign for encoded protein. Superimposing wild-type and mutated proteins by MODELLER shows no change (RMSD = 0.1) in extracellular ligand binding domain of μ-opioid receptor. However, Haploreg and RegulomeDB predicted OPRM1 gene repression by chromatin condensation and increased binding affinity of RXRA transcription factor that may reduce protein translation and hence the number of available receptors to bind with drugs, which may trigger underlying mechanisms for opioids addiction. Thus, this study outlines causal relationship between opioids addiction and genetic predisposition in Pakistani population.

Influence of maternal and own genotype at tanning dependence-related SNPs on sun exposure in childhood

Background

Research suggests there may be a genetic influence on the likelihood of becoming tanning dependent (TD). The way in which mothers regulate their children’s sun exposure may be affected by being TD. We investigated the associations between single nucleotide polymorphisms (SNPs) related to being TD and early sun exposure.

Methods

Data from the Avon Longitudinal Study of Parents and Children (ALSPAC) were used. Associations between 17 TD related SNPs in children and their mothers and 10 sun exposure variables in children (assessed via questionnaire at age 8) were analyzed in logistic and ordinal logistic regressions. Analyses were adjusted for principal components of population structure and age (at time of questionnaire response). Models with additional adjustment for maternal or offspring genotypes were also tested. Secondary analyses included adjustment for sex and skin pigmentation.

Results

Among ALSPAC children, the rs29132 SNP in the Vesicle-associated membrane protein-associated protein A (VAPA) gene was associated with five sun exposure variables whilst the rs650662 SNP in the Opioid Receptor Mu 1 (OPRM1) gene was associated with three. The remaining SNPs did not show associations beyond what was expected by chance. After Bonferroni correction one SNP in the children was associated with an increased likelihood of using sun cream whilst in the sun at 8 years old (rs60050811 in the Spermatogenesis and Centriole Associated 1 (SPATC1) gene, OR per C allele = 1.34, 95% CI 1.11–1.62, p = .003). In the mothers, rs650662 in OPRM1 was associated with the use of a lower factor of sun cream in their children, (OR per A allele = 0.89, 95% CI 0.82–0.96, p = .002). Whilst rs2073478 in the Aldehyde Dehydrogenase 1 Family Member B1 (ALDH1B1) gene was associated with a reduced odds of their child using a sun block or cream with a 4 star rating (OR per T allele = 0.68, 95% CI 0.53–0.88, p = .003). Similar but weaker associations were observed for the main findings in the secondary analyses.

Conclusions

We found weak evidence to suggest that genes previously associated with TD are associated with sun exposure in children of European ancestry from southwest England.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0575-z) contains supplementary material, which is available to authorized users.

Increased ethanol drinking in "humanized" mice expressing the mu opioid receptor A118G polymorphism are mediated through sex-specific mechanisms

The A118G single nucleotide polymorphism (SNP) of the mu-opioid receptor gene (Oprm1) has been implicated in mediating the rewarding effects of alcohol. Clinical and preclinical studies suggest that the G allele may confer a genetic vulnerability to alcohol dependence, though it remains unknown whether these effects are sex-specific. We used male and female mice homozygous for the "humanized" 118AA or 118GG alleles to determine whether the A118G SNP potentiates ethanol consumption in a sex-specific manner in both the two-bottle choice and drinking-in-the-dark (DID) paradigms. Mice were also assessed for differences in naltrexone sensitivity, ethanol reward assessed via conditioned place preference (CPP), and sensitivity to the sedative/ataxic effects of ethanol using the rota-rod and loss of righting reflex (LORR) assays. We found that male and female 118GG mice drank significantly more ethanol than 118AA littermates using a continuous access, two-bottle choice paradigm. In the limited-access DID drinking model, (i) female (but not male) 118GG mice consumed more ethanol than 118AA mice and (ii) naltrexone pretreatment was equally efficacious at attenuating ethanol intake in both 118AA and 118GG female mice while having no effect in males. Male and female 118GG and female 118AA mice developed a robust conditioned place preference (CPP) for ethanol. Female 118GG mice displayed less sensitivity to the sedative/ataxic effects of ethanol compared to female 118AA mice on both the rota-rod and the LORR assays while male mice did not differ in their responses on either assay. Our findings suggest that increased ethanol consumption in male 118GG mice may be due to increased ethanol reward, while increased drinking in female 118GG mice might be due to decreased sensitivity to the sedative/ataxic effects of ethanol. Collectively, these data might be used to help identify sex-specific pharmacotherapies to combat alcohol use disorders.

The frequency of DRD2 rs1076560 and OPRM1 rs1799971 in substance use disorder patients from the United Arab Emirates

BACKGROUND

Dopaminergic and opioid systems are involved in mediating drug reward and reinforcement of various types of substances including psychoactive compounds. Genes of both systems have been candidate for investigation for associations with substance use disorder (SUD) in various populations. This study is the first study to determine the allele frequency and the genetic association of the DRD2 rs1076560 SNP and OPRM1 rs1799971 SNP variants in clinically diagnosed patients with SUD from the United Arab Emirates (UAE).

METHODS

A cross-sectional case-control cohort that consisted of 512 male subjects was studied. Two hundred and fifty patients with SUD receiving treatment at the UAE National Rehabilitation Center were compared to 262 controls with no prior history of mental health and SUD. DNA from each subject was extracted and genotyped using the TaqMan ^® SNP genotyping assay.

RESULTS

There were no significant associations observed for DRD2 rs1076560 SNP, OPRM1 rs1799971 SNP, and combined genotypes of both SNPs in the SUD group.

CONCLUSION

Further research is required with refinements to the criteria of the clinical phenotypes. Genetic studies have to be expanded to include other variants of the gene, the interaction with other genes, and possible epigenetic relationships.

Bivariate genome-wide association analyses identified genetic pleiotropic effects for bone mineral density and alcohol drinking in Caucasians

Several studies indicated bone mineral density (BMD) and alcohol intake might share common genetic factors. The study aimed to explore potential SNPs/genes related to both phenotypes in US Caucasians at the genome-wide level. A bivariate genome-wide association study (GWAS) was performed in 2069 unrelated participants. Regular drinking was graded as 1, 2, 3, 4, 5, or 6, representing drinking alcohol never, less than once, once or twice, three to six times, seven to ten times, or more than ten times per week respectively. Hip, spine, and whole body BMDs were measured. The bivariate GWAS was conducted on the basis of a bivariate linear regression model. Sex-stratified association analyses were performed in the male and female subgroups. In males, the most significant association signal was detected in SNP rs685395 in DYNC2H1 with bivariate spine BMD and alcohol drinking (P = 1.94 × 10-8). SNP rs685395 and five other SNPs, rs657752, rs614902, rs682851, rs626330, and rs689295, located in the same haplotype block in DYNC2H1 were the top ten most significant SNPs in the bivariate GWAS in males. Additionally, two SNPs in GRIK4 in males and three SNPs in OPRM1 in females were suggestively associated with BMDs (of the hip, spine, and whole body) and alcohol drinking. Nine SNPs in IL1RN were only suggestively associated with female whole body BMD and alcohol drinking. Our study indicated that DYNC2H1 may contribute to the genetic mechanisms of both spine BMD and alcohol drinking in male Caucasians. Moreover, our study suggested potential pleiotropic roles of OPRM1 and IL1RN in females and GRIK4 in males underlying variation of both BMD and alcohol drinking.

Lack of associations of the opioid receptor mu 1 (OPRM1) A118G polymorphism (rs1799971) with alcohol dependence: review and meta-analysis of retrospective controlled studies

Background

Studies have sought associations of the opioid receptor mu 1 (OPRM1) A118G polymorphism (rs1799971) with alcohol-dependence, but findings are inconsistent. We summarize the information as to associations of rs1799971 (A > G) and the alcohol-dependence.

Methods

Systematically, we reviewed related literatures using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Embase, PubMed, Web of Knowledge, and Chinese National Knowledge Infrastructure (CNKI) databases were searched using select medical subject heading (MeSH) terms to identify all researches focusing on the present topic up to September 2016. Odds ratios (ORs) along with the 95% confidence interval (95% CI) were estimated in allele model, homozygote model, heterozygote model, dominant model and recessive model. Ethnicity-specific subgroup-analysis, sensitivity analysis, heterogeneity description, and publication-bias assessment were also analyzed.

Results

There were 17 studies, including 9613 patients in the present meta-analysis. The ORs in the 5 genetic-models were 1.037 (95% CI: 0.890, 1.210; p = 0.64), 1.074 (95% CI: 0.831, 1.387; p = 0.586), 1.155 (95% CI: 0.935, 1.427; p = 0.181), 1.261 (95% CI: 1.008, 1.578; p = 0.042), 0.968 (95% CI: 0.758, 1.236; p = 0.793), respectively. An association is significant in the dominant model, but there is no statistical significance upon ethnicity-specific subgroup analysis.

Conclusion

The rs1799971 (A > G) is not strongly associated with alcohol-dependence. However, there are study heterogeneities and limited sample sizes.

Convergent Balancing Selection on the Mu-Opioid Receptor in Primates

The mu opioid receptor is involved in many natural processes including stress response, pleasure, and pain. Mutations in the gene also have been associated with opiate and alcohol addictions as well as with responsivity to medication targeting these disorders. Two common and mutually exclusive polymorphisms have been identified in humans, A118G (N40D), found commonly in non-African populations, and C17T (V6A), found almost exclusively in African populations. Although A118G has been studied extensively for associations and in functional assays, C17T is much less well understood. In addition to a parallel polymorphism previously identified in rhesus macaques (Macaca mulatta), C77G (P26R), resequencing in additional non-human primate species identifies further common variation: C140T (P47L) in cynomolgus macaques (Macaca fascicularis), G55C (D19H) in vervet monkeys (Chlorocebus aethiops sabeus), A111T (L37F) in marmosets (Callithrix jacchus), and C55T (P19S) in squirrel monkeys (Saimiri boliviensis peruviensis). Functional effects on downstream signaling are observed for each of these variants following treatment with the endogenous agonist β-endorphin and the exogenous agonists morphine, DAMGO ([d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin), and fentanyl. In addition to demonstrating the importance of functional equivalency in reference to population variation for minority health, this also shows how common evolutionary pressures have produced similar phenotypes across species, suggesting a shared response to environmental needs and perhaps elucidating the mechanism by which these organism-environment interactions are mediated physiologically and molecularly. These studies set the stage for future investigations of shared functional polymorphisms across species as a new genetic tool for translational research.

A cis-eQTL in OPRM1 is Associated with Subjective Response to Alcohol and Alcohol Use

BACKGROUND

A functional polymorphism within the μ-opioid receptor (OPRM1) gene, rs1799971 (A118G), previously has been associated with measures of alcohol use and sensitivity to its effects, but findings have been inconclusive. A recent study suggested that a second nearby variant within OPRM1, rs3778150, is robustly associated with heroin dependence and fully explained a smaller observed association with rs1799971. Given evidence that the rs3778150-C allele is associated with decreased OPRM1 expression levels in the human brain, the current study sought to test the hypothesis that rs3778150 represents a causal variant within OPRM1 that increases risk for a variety of alcohol use phenotypes.

METHODS

Participants with genotype and phenotype data from a larger experimental study (N = 152) were assessed on measures of subjective response to alcohol and alcohol use. Measures included (i) the Self-Rating of the Effects of Alcohol and the Alcohol Sensitivity Questionnaire, (ii) the Biphasic Alcohol Effects Scale (BAES) and ratings of subjective intoxication, and (iii) average number of drinks per week in the past month.

RESULTS

Compared to rs3778150-T homozygous individuals, carriers of the rs3778150-C allele exhibited significantly lower retrospective self-report levels of alcohol sensitivity. Carriers of the rs3778150-C allele also exhibited lower levels of BAES alcohol-related stimulation during an alcohol challenge and reported higher levels of drinking in the last 30 days. With the exception of lower levels of BAES alcohol-related sedation, the rs1799971 variant did not show consistent significant association with any of the alcohol phenotypes in the presence of rs3778150.

CONCLUSIONS

Results suggest that rs3778150 may be causally related to alcohol use phenotypes, and could potentially account for previously observed associations of rs1799971 with substance use phenotypes. Future studies may investigate potential causal relations among genetic variants in OPRM1, subjective response to alcohol, and drinking phenotypes to further delineate the effects of rs3778150.

Genome-wide association study of therapeutic opioid dosing identifies a novel locus upstream of OPRM1

Opioids are very effective analgesics, but they are also highly addictive. Methadone is used to treat opioid dependence (OD), acting as a selective agonist at the μ-opioid receptor encoded by the gene OPRM1. Determining the optimal methadone maintenance dose is time consuming; currently, no biomarkers are available to guide treatment. In methadone-treated OD subjects drawn from a case and control sample, we conducted a genome-wide association study of usual daily methadone dose. In African-American (AA) OD subjects (n=383), we identified a genome-wide significant association between therapeutic methadone dose (mean=68.0 mg, s.d.=30.1 mg) and rs73568641 (P=2.8 × 10-8), the nearest gene (306 kilobases) being OPRM1. Each minor (C) allele corresponded to an additional ~20 mg day-1 of oral methadone, an effect specific to AAs. In European-Americans (EAs) (n=1027), no genome-wide significant associations with methadone dose (mean=77.8 mg, s.d.=33.9 mg) were observed. In an independent set of opioid-naive AA children being treated for surgical pain, rs73568641-C was associated with a higher required dose of morphine (n=241, P=3.9 × 10-2). Similarly, independent genomic loci previously shown to associate with higher opioid analgesic dose were associated with higher methadone dose in the OD sample (AA and EA: n=1410, genetic score P=1.3 × 10-3). The present results in AAs indicate that genetic variants influencing opioid sensitivity across different clinical settings could contribute to precision pharmacotherapy for pain and addiction.

Genetics of alcoholism

Multiple lines of evidence strongly indicate that genetic factors contribute to the risk for alcohol use disorders (AUD). There is substantial heterogeneity in AUD, which complicates studies seeking to identify specific genetic factors. To identify these genetic effects, several different alcohol-related phenotypes have been analyzed, including diagnosis and quantitative measures related to AUDs. Study designs have used candidate gene analyses, genetic linkage studies, genomewide association studies (GWAS), and analyses of rare variants. Two genes that encode enzymes of alcohol metabolism have the strongest effect on AUD: aldehyde dehydrogenase 2 and alcohol dehydrogenase 1B each has strongly protective variants that reduce risk, with odds ratios approximately 0.2-0.4. A number of other genes important in AUD have been identified and replicated, including GABRA2 and alcohol dehydrogenases 1B and 4. GWAS have identified additional candidates. Rare variants are likely also to play a role; studies of these are just beginning. A multifaceted approach to gene identification, targeting both rare and common variations and assembling much larger datasets for meta-analyses, is critical for identifying the key genes and pathways important in AUD.

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.

Parent and peer influences on emerging adult substance use disorder: A genetically informed study

The present study utilizes longitudinal data from a high-risk community sample to examine the unique effects of genetic risk, parental knowledge about the daily activities of adolescents, and peer substance use on emerging adult substance use disorders (SUDs). These effects are examined over and above a polygenic risk score. In addition, this polygenic risk score is used to examine gene-environment correlation and interaction. The results show that during older adolescence, higher adolescent genetic risk for SUDs predicts less parental knowledge, but this relation is nonsignificant in younger adolescence. Parental knowledge (using mother report) mediates the effects of parental alcohol use disorder (AUD) and adolescent genetic risk on risk for SUD, and peer substance use mediates the effect of parent AUD on offspring SUD. Finally, there are significant gene-environment interactions such that, for those at the highest levels of genetic risk, less parental knowledge and more peer substance use confers greater risk for SUDs. However, for those at medium and low genetic risk, these effects are attenuated. These findings suggest that the evocative effects of adolescent genetic risk on parenting increase with age across adolescence. They also suggest that some of the most important environmental risk factors for SUDs exert effects that vary across level of genetic propensity.

Searching for evidence of genetic mediation of opioid withdrawal by opioid receptor gene polymorphisms

BACKGROUND

Previous research has identified many genetic polymorphisms that appear to mediate the effects of opioid drugs. However, the relationship between genetic polymorphisms and the severity of opioid withdrawal has not yet been characterized.

METHODS

Data were collected from 48 daily heroin users who previously completed a standardized abstinence-induced or naloxone-precipitated withdrawal procedure to assess opioid dependence. The total withdrawal severity score (based on the COWS) from this procedure was correlated with genotype information for variants of OPRM1 (rs1799971; rs6848893), OPRD1 (rs10753331; rs2234918; rs581111; rs678849; rs1042114), and OPRK1 (rs6473797; rs963549). Genotype and other participant variables (age, race, sex, duration of drug use, concomitant drug use, route of opioid use) were used as predictors.

RESULTS

Of these variables, those individually correlated with a p < .2 were entered into a multivariate regression in order to identify the most predictive model. Three polymorphisms were significantly associated with severity of abstinence-induced withdrawal (n = 19) in the bivariate analysis (R): OPRM1 rs6848893 (.45), OPRD1 rs10753331 (.03), and rs678849 (.08), but only the OPRM1 rs6848893 was retained in the multivariate model (p < .001). For participants who underwent naloxone-precipitated withdrawal (n = 29) only OPRK1 rs6473797 (-.23) was significant in the bivariate analysis, though not retained in the final model.

CONCLUSIONS

These data provide evidence for genetic modulation of opioid withdrawal severity, and suggest there may be qualitative differences between withdrawal resulting from abstinence and antagonist-precipitated withdrawal.

SCIENTIFIC SIGNIFICANCE

This study demonstrates the importance and feasibility of incorporating genetic information into clinical addiction research.

Dimensionality and Genetic Correlates of Problem Behavior in Low-Income African American Adolescents

Researchers have long observed that problem behaviors tend to cluster together, particularly among adolescents. Epidemiological studies have suggested that this covariation is due, in part, to common genetic influences, and a number of plausible candidates have emerged as targets for investigation. To date, however, genetic association studies of these behaviors have focused mostly on unidimensional models of individual phenotypes within European American samples. Herein, we compared a series of confirmatory factor models to best characterize the structure of problem behavior (alcohol and marijuana use, sexual behavior, and disruptive behavior) within a representative community-based sample of 592 low-income African American adolescents (50.3% female), ages 13 to 18. We further explored the extent to which 3 genes previously implicated for their role in similar behavioral dimensions (CHRM2, GABRA2, and OPRM1) independently accounted for variance within factors specified in the best-fitting model. Supplementary analyses were conducted to derive comparative estimates for the predictive utility of these genes in more traditional unidimensional models. Findings provide initial evidence for a bifactor structure of problem behavior among African American adolescents and highlight novel genetic correlates of specific behavioral dimensions otherwise undetected in an orthogonal syndromal factor. Implications of this approach include increased precision in the assessment of problem behavior, with corresponding increases in the reliability and validity of identified genetic associations. As a corollary, the comparison of primary and supplementary association analyses illustrates the potential for overlooking and/or overinterpreting meaningful genetic effects when failing to adequately account for phenotypic complexity.

Cis-Expression Quantitative Trait Loci Mapping Reveals Replicable Associations with Heroin Addiction in OPRM1

BACKGROUND

No opioid receptor, mu 1 (OPRM1) gene polymorphisms, including the functional single nucleotide polymorphism (SNP) rs1799971, have been conclusively associated with heroin/other opioid addiction, despite their biological plausibility. We used evidence of polymorphisms altering OPRM1 expression in normal human brain tissue to nominate and then test associations with heroin addiction.

METHODS

We tested 103 OPRM1 SNPs for association with OPRM1 messenger RNA expression in prefrontal cortex from 224 European Americans and African Americans of the BrainCloud cohort. We then tested the 16 putative cis-expression quantitative trait loci (cis-eQTL) SNPs for association with heroin addiction in the Urban Health Study and two replication cohorts, totaling 16,729 European Americans, African Americans, and Australians of European ancestry.

RESULTS

Four putative cis-eQTL SNPs were significantly associated with heroin addiction in the Urban Health Study (smallest p = 8.9 × 10(-5)): rs9478495, rs3778150, rs9384169, and rs562859. Rs3778150, located in OPRM1 intron 1, was significantly replicated (p = 6.3 × 10(-5)). Meta-analysis across all case-control cohorts resulted in p = 4.3 × 10(-8): the rs3778150-C allele (frequency = 16%-19%) being associated with increased heroin addiction risk. Importantly, the functional SNP allele rs1799971-A was associated with heroin addiction only in the presence of rs3778150-C (p = 1.48 × 10(-6) for rs1799971-A/rs3778150-C and p = .79 for rs1799971-A/rs3778150-T haplotypes). Lastly, replication was observed for six other intron 1 SNPs that had prior suggestive associations with heroin addiction (smallest p = 2.7 × 10(-8) for rs3823010).

CONCLUSIONS

Our findings show that common OPRM1 intron 1 SNPs have replicable associations with heroin addiction. The haplotype structure of rs3778150 and nearby SNPs may underlie the inconsistent associations between rs1799971 and heroin addiction.

A heroin addiction severity-associated intronic single nucleotide polymorphism modulates alternative pre-mRNA splicing of the μ opioid receptor gene OPRM1 via hnRNPH interactions

Single nucleotide polymorphisms (SNPs) in the OPRM1 gene have been associated with vulnerability to opioid dependence. The current study identifies an association of an intronic SNP (rs9479757) with the severity of heroin addiction among Han-Chinese male heroin addicts. Individual SNP analysis and haplotype-based analysis with additional SNPs in the OPRM1 locus showed that mild heroin addiction was associated with the AG genotype, whereas severe heroin addiction was associated with the GG genotype. In vitro studies such as electrophoretic mobility shift assay, minigene, siRNA, and antisense morpholino oligonucleotide studies have identified heterogeneous nuclear ribonucleoprotein H (hnRNPH) as the major binding partner for the G-containing SNP site. The G-to-A transition weakens hnRNPH binding and facilitates exon 2 skipping, leading to altered expressions of OPRM1 splice-variant mRNAs and hMOR-1 proteins. Similar changes in splicing and hMOR-1 proteins were observed in human postmortem prefrontal cortex with the AG genotype of this SNP when compared with the GG genotype. Interestingly, the altered splicing led to an increase in hMOR-1 protein levels despite decreased hMOR-1 mRNA levels, which is likely contributed by a concurrent increase in single transmembrane domain variants that have a chaperone-like function on MOR-1 protein stability. Our studies delineate the role of this SNP as a modifier of OPRM1 alternative splicing via hnRNPH interactions, and suggest a functional link between an SNP-containing splicing modifier and the severity of heroin addiction.

Association between single nucleotide polymorphisms in the OPRM1 gene and intraoperative remifentanil consumption in northern Chinese women

BACKGROUND

Recent studies have suggested that some single nucleotide polymorphisms (SNPs) in the human µ-opioid receptor gene (OPRM1) affect the postoperative analgesic efficacy of opioids and their side effects. In this study, we assessed the association between SNPs in the OPRM1 gene and intraoperative remifentanil consumption as well as perioperative side effects during gynecological hysteroscopic surgery in women from Northern China.

METHODS

We analyzed 178 women undergoing gynecological hysteroscopic surgery. SNP genotyping was performed using the SNaPshot method. The state anxiety index (SAI) and pressure pain threshold (PPT) of all patients were assessed preoperatively. Monitored anesthesia care was maintained by the intravenous infusion of remifentanil. Intraoperative remifentanil usage and perioperative side effects were recorded. Statistical analyses were performed using SPSS software.

RESULTS

Patients carrying one or two copies of the minor allele (G allele) of rs558025 required significantly more intraoperative remifentanil than patients without the minor allele (p = 0.001, corrected p = 0.006). There were no significant associations between the six SNPs and various clinical characteristics. No significant associations between the six SNPs and PPT or SAI were found in our study.

CONCLUSIONS

SNP rs558025 in the OPRM1 gene was associated with intraoperative remifentanil consumption during gynecological hysteroscopic surgery in our subjects.

A psycho-genetic study of hedonic responsiveness in relation to "food addiction"

While food addiction has no formally-recognized definition, it is typically operationalized according to the diagnostic principles established by the Yale Food Addiction Scale-an inventory based on the symptom criteria for substance dependence in the DSM-IV. Currently, there is little biologically-based research investigating the risk factors for food addiction. What does exist has focused almost exclusively on dopaminergic reward pathways in the brain. While brain opioid signaling has also been strongly implicated in the control of food intake, there is no research examining this neural circuitry in the association with food addiction. The purpose of the study was therefore to test a model predicting that a stronger activation potential of opioid circuitry-as indicated by the functional A118G marker of the mu-opioid receptor gene-would serve as an indirect risk factor for food addiction via a heightened hedonic responsiveness to palatable food. Results confirmed these relationships. In addition, our findings that the food-addiction group had significantly higher levels of hedonic responsiveness to food suggests that this bio-behavioral trait may foster a proneness to overeating, to episodes of binge eating, and ultimately to a compulsive and addictive pattern of food intake.

Therapygenetics in mindfulness-based cognitive therapy: do genes have an impact on therapy-induced change in real-life positive affective experiences?

Positive affect (PA) has an important role in resilience against depression and has been shown to increase with mindfulness-based cognitive therapy (MBCT). To elucidate the underlying mechanisms of change in PA as well as develop insights that may benefit personalized medicine, the current study examined the contribution of genetic variation to individual differences in change in PA in response to MBCT. Individuals (n=126) with residual depressive symptoms were randomized to either an MBCT group or treatment as usual. PA was assessed using experience sampling methodology (ESM). Single-nucleotide polymorphisms (SNPs) in genes known to be involved in reward functioning were selected. SNPs in the genes for brain-derived neurotrophic factor (BDNF), the muscarinic acetylcholine receptor M2 (CHRM2), the dopamine receptor D4 (DRD4) and the μ1 opioid receptor (OPRM1) significantly moderated the impact of treatment condition over time on PA. Genetic variation in the genes for CHRM2 and OPRM1 specifically had an impact on the level of PA following MBCT. The current study shows that variation in response to MBCT may be contingent on genetic factors associated with the regulation of PA. These findings contribute to our understanding of the processes moderating response to treatment and prediction of treatment outcome.

OPRM1 rs1799971 polymorphism and opioid dependence: evidence from a meta-analysis

The OPRM1 gene encodes the µ-opioid receptor, which is the primary site of action of most opioids. Several studies and three meta-analyses have examined a possible link between the exonic OPRM1 A118G (rs1799971) polymorphism and opioid dependence; however, results have been inconclusive. Therefore, a systematic review and meta-analysis have been carried out to examine whether this polymorphism is associated with opioid dependence. Thirteen studies (n = 9385), comprising 4601 opioid dependents and 4784 controls, which evaluated association of the OPRM1 rs1799971 polymorphism with susceptibility to opioids, were included in this study. Our meta-analysis showed significant association between this polymorphism and susceptibility to opioid dependence in overall studies under a codominant model, as well as susceptibility to opioid dependence or heroin dependence in Asians under an autosomal dominant model. The nonsynonymous OPRM1 rs1799971 might be a risk factor for addiction to opioids or heroin in an Asian population.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Neurogenetics of aggressive behavior: studies in primates

Aggressive behavior can have adaptive value in certain environmental contexts, but when extreme or executed inappropriately, can also lead to maladaptive outcomes. Neurogenetic studies performed in nonhuman primates have shown that genetic variation that impacts reward sensitivity, impulsivity, and anxiety can contribute to individual differences in aggressive behavior. Genetic polymorphisms in the coding or promoter regions of the Mu-Opioid Receptor (OPRM1), Corticotropin Releasing Hormone (CRH), Monoamine Oxidase A (MAOA), Dopamine D4 Receptor (DRD4), and Serotonin Transporter (SLC6A4) genes have been shown to be functionally similar in humans and rhesus macaques and have been demonstrated to contribute to individual differences in aggression. This body of literature suggests mechanisms by which genetic variation that promotes aggressivity could simultaneously increase evolutionary success while making modern humans more vulnerable to psychopathology.

Association of OPRD1 polymorphisms with heroin dependence in a large case-control series

Genes encoding the opioid receptors (OPRM1, OPRD1 and OPRK1) are obvious candidates for involvement in risk for heroin dependence. Prior association studies commonly had samples of modest size, included limited single nucleotide polymorphism (SNP) coverage of these genes and yielded inconsistent results. Participants for the current investigation included 1459 heroin-dependent cases ascertained from maintenance clinics in New South Wales, Australia, 1495 unrelated individuals selected from an Australian sample of twins and siblings as not meeting DSM-IV criteria for lifetime alcohol or illicit drug dependence (non-dependent controls) and 531 controls ascertained from economically disadvantaged neighborhoods in proximity to the maintenance clinics. A total of 136 OPRM1, OPRD1 and OPRK1 SNPs were genotyped in this sample. After controlling for admixture with principal components analysis, our comparison of cases to non-dependent controls found four OPRD1 SNPs in fairly high linkage disequilibrium for which adjusted P values remained significant (e.g. rs2236857; OR 1.25; P=2.95×10(-4) ) replicating a previously reported association. A post hoc analysis revealed that the two SNP (rs2236857 and rs581111) GA haplotype in OPRD1 is associated with greater risk (OR 1.68; P=1.41×10(-5) ). No OPRM1 or OPRK1 SNPs reached more than nominal significance. Comparisons of cases to neighborhood controls reached only nominal significance. Our results replicate a prior report providing strong evidence implicating OPRD1 SNPs and, in particular, the two SNP (rs2236857 and rs581111) GA haplotype in liability for heroin dependence. Support was not found for similar association involving either OPRM1 or OPRK1 SNPs.

Pharmacogenetics of OPRM1

Pharmacogenetic research has the potential to explain the variation in treatment efficacy within patient populations. Understanding the interaction between genetic variation and medications may provide a method for matching patients to the most effective therapeutic options and improving overall patient outcomes. The OPRM1 gene has been a target of interest in a large number of pharmacogenetic studies due to its genetic and structural variation, as well as the role of opioid receptors in a variety of disorders. The mu-opioid receptor (MOR), encoded by OPRM1, naturally regulates the analgesic response to pain and also controls the rewarding effects of many drugs of abuse, including opioids, nicotine, and alcohol. Genetic variants in OPRM1, particularly the non-synonymous polymorphism A118G, have been repeatedly associated with the efficacy of treatments for pain and various types of dependence. This review focuses on the current understanding of the pharmacogenetic impact of OPRM1, primarily with regard to the treatment of pain and addiction.

Case-control association study of WLS variants in opioid and cocaine addicted populations

The opioid receptor family is involved in the development and maintenance of drug addiction. The mu-opioid receptor (MOR) mediates the rewarding effects of multiple drugs, including opiates and cocaine. A number of proteins interact with MOR, potentially modulating MOR function and altering the physiological consequences of drug use. These mu-opioid receptor interacting proteins (MORIPs) are potential therapeutic targets for the treatment of addiction. The Wntless (WLS) protein was recently identified as a MORIP in a yeast two-hybrid screen. In this study, we conducted a case-control association analysis of 16 WLS genetic variants in opioid and cocaine addicted individuals of both African-American (opioid n=336, cocaine n=908) and European-American (opioid n=335, cocaine n=336) ancestry. Of the analyzed SNPs, three were nominally associated with opioid addiction and four were nominally associated with cocaine addiction. None of these associations were significant following multiple testing correction. These data suggest that the common variants of WLS analyzed in this study are not associated with opioid or cocaine addiction. However, this study does not exclude the possibilities that rare variants in WLS may affect susceptibility to drug addiction, or that common variants with small effect size may fall below the detection level of our analysis.

RGS17: an emerging therapeutic target for lung and prostate cancers

Ligands for G-protein-coupled receptors (GPCRs) represent approximately 50% of currently marketed drugs. RGS proteins modulate heterotrimeric G proteins and, thus, GPCR signaling, by accelerating the intrinsic GTPase activity of the Gα subunit. Given the prevalence of GPCR targeted therapeutics and the role RGS proteins play in G protein signaling, some RGS proteins are emerging as targets in their own right. One such RGS protein is RGS17. Increased RGS17 expression in some prostate and lung cancers has been demonstrated to support cancer progression, while reduced expression of RGS17 can lead to development of chemotherapeutic resistance in ovarian cancer. High-throughput screening is a powerful tool for lead compound identification, and utilization of high-throughput technologies has led to the discovery of several RGS inhibitors, thus far. As screening technologies advance, the identification of novel lead compounds the subsequent development of targeted therapeutics appears promising.

μ-Opioid receptor gene (OPRM1) polymorphism A118G: lack of association in Finnish populations with alcohol dependence or alcohol consumption

Aims: The molecular epidemiological studies on the association of the opioid receptor µ-1 (OPRM1) polymorphism A118G (Asn40Asp, rs1799971) and alcohol use disorders have given conflicting results. The aim of this study was to test the possible association of A118G polymorphism and alcohol use disorders and alcohol consumption in three large cohort-based study samples. Methods: The association between the OPRM1 A118G (Asn40Asp, rs1799971) polymorphism and alcohol use disorders and alcohol consumption was analyzed using three different population-based samples: (a) a Finnish cohort study, Health 2000, with 503 participants having a DSM-IV diagnosis for alcohol dependence and/or alcohol abuse and 506 age- and sex-matched controls; (b) a Finnish cohort study, FINRISK (n = 2360) and (c) the Helsinki Birth Cohort Study (n = 1384). The latter two populations lacked diagnosis-based phenotypes, but included detailed information on alcohol consumption. Results: We found no statistically significant differences in genotypic or allelic distribution between controls and subjects with alcohol dependence or abuse diagnoses. Likewise no significant effects were observed between the A118G genotype and alcohol consumption. Conclusion: These results suggest that A118G (Asn40Asp) polymorphism may not have a major effect on the development of alcohol use disorders at least in the Finnish population.