A118G Single Nucleotide Polymorphism Research Articles

Allele frequency and genotype distribution of the opioid receptor μ-1 (OPRM1) A118G polymorphism in the Western Saudi population.

The single nucleotide polymorphism (SNP) A118G (rs1799971) in the Mu Opioid Receptor 1 (OPRM1) gene is associated with significant variations in analgesic doses and adverse effects of opioids. The A118G OPRM1 allele distributions vary significantly between different populations worldwide. The study aimed to assess the allele frequency and genotype distribution of OPRM1 A118G SNP in Saudis. This cross-sectional study included 124 healthy Saudis (62 males and 62 females) visiting the King Abdulaziz University Hospital in Jeddah, Saudi Arabia. The Oragene®-DISCOVER (OGR-600) kits were used to collect saliva samples from the participants. Polymerase chain reaction-restriction fragment length polymorphism was utilized to assess the SNP. Among the tested population, 79.03% (95% C.I. 70.81-85.82) were homozygous wild-type A118A, 16.13% (95% C.I. 10.14-23.80) were heterozygous A118G, and 4.84% (95% C.I. 1.80-10.23) were homozygous mutant G118G. OPRM1 A118G polymorphism allele frequencies were 87% (95% C.I. 79.89-92.44) and 13% (95% C.I. 7.56-20.11) for the 118A and 118G alleles, respectively. A higher frequency of the OPRM1 118G allele was present in females, 21% (95% C.I. 11.66-33.17) compared to males, 5% (95% C.I. 1.01-13.50). Relative to other Asian countries, the Saudi population showed a low prevalence of the OPRM1 A118G polymorphism, with a higher frequency of the 118G allele in females. Our research will contribute to the existing knowledge on the prevalence of OPRM1 A118G polymorphism, which could be considered for the personalized prescribing of opioid analgesics.

The A118G single-nucleotide polymorphism in OPRM1 is a risk factor for asthma severity

BackgroundAlthough population studies have implicated emotional burden in asthma severity, the underlying genetic risk factors are not completely understood. We aimed to evaluate the genetic influence of a functional single-nucleotide polymorphism (SNP) in the stress-related μ-opioid receptor gene (OPRM1; A118G SNP, rs1799971) on asthma severity. MethodsWe initially assessed disease severity in asthmatic outpatients carrying A118G. Using an ovalbumin-induced experimental asthma rodent model harboring the functionally equivalent SNP, we investigated the mechanism by which this SNP influences the allergic immune response. ResultsAmong 292 outpatients, 168 underwent airway hyperresponsiveness (AHR) to methacholine testing. Compared with patients carrying the AA and AG genotypes, those carrying the GG genotype exhibited enhanced AHR. The stress levels were presumed to be moderate among patients and were comparable among genotypes. Compared with Oprm1 AA mice, GG mice demonstrated aggravated asthma-related features and increased pulmonary interleukin-4+CD4+ effector and effector memory T cells under everyday life stress conditions. Intraperitoneal naloxone methiodide injection reduced effector CD4+ T cell elevation associated with increased eosinophil numbers in bronchoalveolar lavage fluid of GG mice to the levels in AA mice, suggesting that elevated Th2 cell generation in the bronchial lymph node (BLN) of GG mice induces enhanced eosinophilic inflammation. ConclusionsWithout forced stress exposure, patients with asthma carrying the OPRM1 GG genotype exhibit enhanced AHR, attributable to enhanced Th2 cell differentiation in the regional lymph node. Further research is necessary to elucidate the role of the OPRM1 A118G genotype in the Th2 cell differentiation pathway in the BLN.

Variation of the human mu-opioid receptor (OPRM1) gene predicts vulnerability to frustration

Understanding the emotional reaction to loss, or frustration, is a critical problem for the field of mental health. Animal models of loss have pointed to the opioid system as a nexus of frustration, physical pain, and substance abuse. However, few attempts have been made to connect the results of animal models of loss to human behavior. Allelic differences in the human mu opioid receptor gene, notably the A118G single nucleotide polymorphism, have been linked to individual differences in pain sensitivity, depressive symptoms, and reward processing. The present study explored the relationship between A118G and behavior in two frustrating tasks in humans. Results showed that carriers of the mutant G-allele were slower to recover behavior following a reward downshift and abandoned a frustrating task earlier than those without the mutation. Additionally, G-carriers were more sensitive to physical pain. These results highlight the overlap between frustration and pain, and suggest that genetic variation in opioid tone may contribute to individual differences in vulnerability and resilience following emotional disturbances.

A review of the existing literature on buprenorphine pharmacogenomics.

Buprenorphine is an effective treatment for opioid dependence; however, it demonstrates individual variability in efficacy. Pharmacogenomics may explain this drug response variability and could allow for tailored therapy on an individual basis. The Food and Drug Administration and the Clinical Pharmacogenomics Implementation Consortium have guidelines on pharmacogenomic testing for some opioids (e.g., codeine); however, no guidelines exist for the partial opioid agonist buprenorphine. Pharmacogenomic testing targets for buprenorphine include pharmacodynamic genes like the mu-opioid receptor (MOP receptor) and catechol-O-methyltransferase (COMT), as well as the pharmacokinetic genes like the CYP enzymes. In this review we identified genotypes in patients with opioid addiction receiving buprenorphine that may result in altered therapeutic dosing and increased rate of relapse. The OPRM1 A118G single nucleotide polymorphism (SNP rs1799971) gene variant encoding the N40D MOP receptor has been associated with variable efficacy and response to treatment in both adult and neonatal patients receiving buprenorphine for treatment of opioid withdrawal. An SNP associated with rs678849 of OPRD1, coding for the delta opioid receptor, was associated with opioid relapse as indicated by opioid positive urine drug screens; there was also sex specific SNP identified at rs581111 and rs529520 in the European American population. COMT variability, particularly in rs4680, has been associated with length of stay and need for opioid treatment in patients with neonatal abstinence syndrome. Variations of the pharmacokinetic gene for CYP3A4 showed that the ultrarapid metabolizer phenotype required higher doses of buprenorphine. Genotyping of patients may allow us to appropriately tailor buprenorphine therapy to individual patients and lead to improved patient outcomes; however, further research on the pharmacogenomics of buprenorphine is needed.

Relapse-like behavior in a mouse model of the OPRM1 (mu-opioid receptor) A118G polymorphism: Examination with intravenous oxycodone self-administration

The widely abused prescription opioid oxycodone is a mu-opioid receptor (MOP-r) agonist and addiction to such opioids is a relapsing disorder. The human MOP-r gene (OPRM1) has an important functional single nucleotide polymorphism (SNP), A118G, which affects risk of severe opioid use disorders. A112G (G/G) knock-in mice are models of human A118G carriers. We examined oxycodone self-administration (SA) in male and female G/G versus wild type (A/A) mice in SA sessions and in relapse-like behavior. Adult male and female G/G and A/A mice self-administered oxycodone (0.25 mg/kg/infusion, FR1) for 10 consecutive days. Following 10-day home cage drug free withdrawal, the mice were re-exposed to oxycodone SA for a further 10 days. MOP-r receptor mRNA in various brain regions were examined immediately after the last re-exposure session.We found that G/G mice had greater oxycodone SA than A/A mice in the initial and in re-exposure sessions. Mice of both genotypes had greater oxycodone intake during the re-exposure period than during the initial exposure. We also detected differences in MOP-r gene expression due to genotype, sex and oxycodone SA history in the dorsal striatum, hippocampus, and prefrontal cortex. These studies may improve our understanding of MOP-r-agonist self-exposure and relapse in human carriers of the A118G SNP.

Recovery profiles from reward downshift are correlated with operant licking maintained by alcohol, but not with genetic variation in the mu opioid receptor

After ten 5-min sessions of access to 32% sucrose, a reward downshift (RD) to 2% sucrose induces a transient rejection of the reward. Animals were segregated according to the speed of recovery from RD into Fast-recovery and Slow-recovery subgroups. Animals were subsequently trained in an operant licking (OL) task in which licking at an empty tube provided 10 s of access to a second tube containing 66% alcohol. Licking on the first tube was subjected to a progressive ratio (PR) schedule with a step of 4 licks. Fast-recovery animals (both males and females) licked to a higher ratio than Slow-recovery animals. Animals were also exposed to a well-lit open field (OF) for 20 min. Fast- and Slow-recovery males and females exhibited equal levels of activity in the OF. Tissue samples from tails were assessed for two well-known allelic variations of the human opioid receptor gene, OPRM1, known to affect mu opioid sensitivity: The C17T and A118G single nucleotide polymorphisms. There was no evidence of a relationship between genotype and behavior, suggesting that these genetic mechanisms in humans do not account for the individual differences in recovery from RD and OL for alcohol in rats.

Differential sensitivity of human neurons carrying μ opioid receptor (MOR) N40D variants in response to ethanol.

The acute and chronic effects of alcohol on the brain and behavior are linked to alterations in inhibitory synaptic transmission. Alcohol's most consistent effect at the synaptic level is probably a facilitation of γ-aminobutyric acid (GABA) release, as seen from several rodent studies. The impact of alcohol on GABAergic neurotransmission in human neurons is unknown, due to a lack of a suitable experimental model. Human neurons can also be used to model effects of genetic variants linked with alcohol use disorders (AUDs). The A118G single nucleotide polymorphism (SNP rs1799971) of the OPRM1 gene encoding the N40D (D40 minor allele) mu-opioid receptor (MOR) variant has been linked with individuals who have an AUD. However, while N40D is clearly associated with other drugs of abuse, involvement with AUDs is controversial. In this study, we employed Ascl1-and Dlx2-induced inhibitory neuronal cells (AD-iNs) generated from human iPS cell lines carrying N40D variants, and investigated the impact of ethanol acutely and chronically on GABAergic synaptic transmission. We found that N40 AD-iNs display a stronger facilitation (versus D40) of spontaneous and miniature inhibitory postsynaptic current frequency in response to acute ethanol application. Quantitative immunocytochemistry of Synapsin 1+ synaptic puncta revealed a similar synapse number between N40 and D40 iNs, suggesting an ethanol modulation of presynaptic GABA release without affecting synapse density. Interestingly, D40 iNs exposed to chronic intermittent ethanol application caused a significant increase in mIPSC frequency, with only a modest enhancement observed in N40 iNs. These data suggest that the MOR genotype may confer differential sensitivity to synaptic output, which depends on ethanol exposure time and concentration for AD-iNs and may help explain alcohol dependence in individuals who carry the MOR D40 SNPs. Furthermore, this study supports the use of human neuronal cells carrying risk-associated genetic variants linked to disease, as invitro models to assay the synaptic actions of alcohol on human neuronal cells.

The μ-opioid receptor gene A118G polymorphism is associated with insecure attachment in children with disruptive mood regulation disorder and their mothers.

BackgroundThe A118G single nucleotide polymorphism (SNP) of the μ‐opioid receptor gene, with high expression of the A allele and low expression of the G allele, has been associated with emotional/behavioral dysregulation and depressive disorders and is recognized as a mediator of affiliative behavior. No study has thus far investigated this SNP in school‐age children with disruptive mood regulation disorder (DMDD). This study compared a sample of healthy children and their mothers with a sample of children with DMDD and their mothers, evaluating whether insecure attachment and psychopathological symptoms are associated with A allele‐ or G allele‐carrying mothers and children and whether caregiving capacities are associated with A allele‐ or G allele‐carrying mothers.MethodsFor evaluation of their psychopathological symptoms and attachment styles, mothers filled out the CBCL/6‐18, the SCL‐90‐R, and the ECR. To evaluate the types of relationship children were experiencing with their mothers, children filled out the ECR‐revised child version and the PBI. Genotypic analyses were conducted on DNA samples obtained by buccal swabbing from children and mothers.ResultsAn insecure attachment style was more frequent in mothers and children carrying the G allele (G/G + A/G genotypes). In the clinical sample, G allele‐carrying children scored higher than homozygous A/A ones on the subscales of Withdrawal and Conduct Problems. G‐carrying mothers showed higher interpersonal sensitivity, depression, hostility, and paranoid ideation and provided less care than A/A mothers.ConclusionsThis study offers new insights into the associations between the A118G SNP of the μ‐opioid receptor gene and emotional/behavioral functioning, attachment style in children, and psychopathology and caregiving ability in mothers.

Mu-Opioid Receptor Polymorphisms and Breast Cancer Recurrence in Adult Korean Women Undergoing Breast Cancer Surgery: A Retrospective Study.

Background: Genetic variations of mu-opioid receptors are well known to contribute to growth and progression of tumors. The most common single-nucleotide polymorphism (SNP) in the mu-opioid receptor 1 gene (OPRM1) is the A118G mutation. We examined the association between the recurrent breast cancer and genotypes of OPRM1 A118G SNP (AA vs. AG vs. GG) in Korean women population.Methods: We analysed medical records and genetic data of 200 patients aged more than 20 who underwent primary breast cancer surgery from June 2012 to June 2014 and diagnosed recurrent breast cancer from June 2012 to September 2019.Results: The incidence of recurrent breast cancer was 6.1%, 8.2%, and 4.8% in genotype AA, AG and GG, respectively (p=0.780). The incidence of recurrent breast cancer in volatile anaesthesia group was 7.0% and 7.1% in total intravenous anaesthesia (TIVA) group (RR = 0.984, 95% CI = 0.328 - 2.951; p = 0.978).Conclusion: OPRM1 A118G SNP had no influence on breast cancer recurrence in Korean women. Anaesthesia technique did not show significant effect on the incidence of recurrent breast cancer.

Addiction associated N40D mu-opioid receptor variant modulates synaptic function in human neurons.

The OPRM1 A118G single nucleotide polymorphism (SNP rs1799971) gene variant encoding the N40D ¼-opioid receptor (MOR) has been associated with dependence on opiates and other drugs of abuse but its mechanism is unknown. The frequency of G-allele carriers is ~40% in Asians, ~16% in Europeans, and ~3% in African-Americans. With opioid abuse-related deaths rising at unprecedented rates, understanding these mechanisms may provide a path to therapy. Here we generated homozygous N40D subject-specific induced inhibitory neuronal cells (iNs) from seven human induced pluripotent stem (iPS) cell lines from subjects of European descent (both male and female) and probed the impact of N40D MOR regulation on synaptic transmission. We found that D40 iNs exhibit consistently stronger suppression (versus N40) of spontaneous inhibitory postsynaptic currents (sIPSCs) across multiple subjects. To mitigate the confounding effects of background genetic variation on neuronal function, the regulatory effects of MORs on synaptic transmission were recapitulated in two sets of independently engineered isogenic N40D iNs. In addition, we employed biochemical analysis and observed differential N-linked glycosylation of human MOR N40D. This study identifies neurophysiological and molecular differences between human MOR variants that may predict altered opioid responsivity and/or dependence in this subset of individuals.

Synaptic Regulation by OPRM1 Variants in Reward Neurocircuitry.

Mu-opioid receptors (MORs) are the primary site of action of opioid drugs, both licit and illicit. Susceptibility to opioid addiction is associated with variants in the gene encoding the MOR, OPRM1 Varying with ethnicity, ∼25% of humans carry a single nucleotide polymorphism (SNP) in OPRM1 (A118G). This SNP produces a nonsynonymous amino acid substitution, replacing asparagine (N40) with aspartate (D40), and has been linked with an increased risk for drug addiction. While a murine model of human OPRM1 A118G (A112G in mouse) recapitulates most of the phenotypes reported in humans, the neuronal mechanisms underlying these phenotypes remain elusive. Here, we investigated the impact of A118G on opioid regulation of synaptic transmission in mesolimbic VTA dopaminergic neurons. Using electrophysiology, we showed that both inhibitory and excitatory inputs to VTA dopaminergic neurons projecting to the NAc medial shell were suppressed by the MOR agonists DAMGO and morphine, which caused a shift in the excitatory/inhibitory balance and an increased action potential firing rate. Mice carrying the 112G/G allele exhibited lower sensitivity to DAMGO and morphine compared with major allele carriers (112A/A). Paradoxically, DAMGO produced facilitatory effects on mEPSCs, which were mediated by presynaptic GABAB receptors. However, this was only prominent in homozygous major allele carriers, which could explain a stronger shift in action potential firing in 112A/A mice. This study provides a better understanding on the neurobiological mechanisms that may underlie risk of addiction development in carriers of the A118G SNP in OPRM1SIGNIFICANCE STATEMENT The pandemic of opioid drug abuse is associated with many socioeconomic burdens. The primary brain target of opioid drugs is the μ-opioid receptor (MOR), encoded by the OPRM1 gene, which is highly polymorphic in humans. Using a mouse model of the human OPRM1 A118G single nucleotide polymorphism (SNP) (A112G in mice), we demonstrated that MOR and GABAB signaling coordinate in regulating mesolimbic dopamine neuronal firing via presynaptic regulation. The A118G SNP affects MOR-mediated suppression of GABA and glutamate release, showing weaker efficacy of synaptic regulation by MORs. These results may shed light on whether MOR SNPs need to be considered for devising effective therapeutic interventions.

Pain polymorphisms and opioids: An evidence based review.

Despite the various different candidate genetic polymorphisms of potential clinical relevance, there is not enough understanding of the inter-individual variability in analgesic administration. The cytochrome P450 2D6 (CYP2D6) genotype is thought to be one of the most studied. The aim of the present evidence-based review was to determine if there is now sufficient evidence to make clinical recommendations based on a specific genomic profile. The data sources utilized were as follows: PubMed (NLM) database, Evidence Based Medicine Guidelines and Google. Research on clinical guidance standards, systematic reviews, meta-analyses and clinical trials, published prior to January 2018, were evaluated in English, using the MeSH terms ‘cancer pain’, ‘polymorphism’, ‘genetic’ and ‘gene polymorphism’. To assess the level of evidence, the Strength of Recommendation Taxonomy of the American Family Physician was applied. From the initial search, 12 systematic reviews and/or meta-analyses, 5 clinical trials and 10 guidelines were selected. The results indicated that genetic variation of µ-opioid receptor 1 (OPRM1) may contribute to inter-individual differences in morphine consumption with recommendation grade A for OPRM A118G single nucleotide polymorphism (rs1799971). Polymorphisms associated with the metabolization process of morphine and other opioid drugs are very relevant in opioid titration and ethnic subgroup differences which have to be taken into account (particularly, for the recommendation grade A for the CYP2D6 polymorphism). In human studies, the catechol-O-methyl transferase (COMT) genotype affects the efficacy of opioids in acute and chronic pain under different settings, with recommendation grade B to the COMT single nucleotide polymorphism rs4680 (Val/Met). Finally, polymorphisms of the ATP-binding cassette family of efflux transporters were highlighted. Consistent data on pain polymorphisms is now widely available; however, these results have had very little impact on clinical guidelines and daily oncologist practice. Persisting pain, side effects of grade 3 (NCI-CTCAE v4.0) and breakthrough pain with more than 4 episodes/day should be considered the criteria for pain multidisciplinary team discussions and for polymorphism screening.

OPRM1 A118G and serum β-endorphin interact with sex and digit ratio (2D:4D) to influence risk and course of alcohol dependence

Activation of mesolimbic mu-opioid receptors by their endogenous ligand, β-endorphin, can mediate the rewarding effects of alcohol. However, there is conflicting evidence on the relationship between the mu-opioid receptor (OPRM1) A118G single nucleotide polymorphism (SNP) and alcohol dependence risk. Preclinical evidence suggests that sex and sex hormone-dependent prenatal brain organization may interact with the opioid system to influence alcohol drinking behavior. We genotyped 200 alcohol-dependent patients and 240 healthy individuals for the OPRM1 A118G SNP and measured serum β-endorphin level at recruitment and after acute withdrawal. We then determined the association between these factors and alcohol dependence risk and 24-month outcome in the context of both sex and second-to-fourth digit lengths ratio (2D:4D) – a biomarker of prenatal sex hormone levels. The OPRM1 A118G AA genotype associated with elevated risk of alcohol-related hospital readmission, more readmissions, and fewer days until first readmission in male patients only. After normalizing patient 2D:4D against control 2D:4D, we found that normalized 2D:4D ratios were lower in male 118G patients than male AA patients, suggesting prenatal androgens interact with OPRM1 to influence alcohol dependence risk. In addition, β-endorphin levels after acute withdrawal correlated negatively with withdrawal severity in females but not in males, which may indicate β-endorphin protects against withdrawal-induced stress in a sex-specific manner.

Nicotine-Use/Smoking Is Associated with the Efficacy of Naltrexone in the Treatment of Alcohol Dependence.

The opioid antagonist naltrexone is not efficacious for every alcohol treatment seeker. However, various individual factors, such as genetic differences and nicotine-use/smoking status, have been suggested as predictors of naltrexone response. In a randomized clinical trial, we previously reported that nicotine-use/smoking status might be a stronger predictor of naltrexone efficacy than OPRM1 A118G single nucleotide polymorphism (SNP) genotype. In this report, we further characterize the nicotine-users in that trial, examine other drinking outcomes, examine the influence of smoking change on naltrexone effects on drinking, and validate the result in smokers with disialo carbohydrate-deficient transferrin (%dCDT) change as an independent biomarker of response. Individuals (n=146) meeting DSM-IV criteria for alcohol dependence who were genotyped for the OPRM1 A118G SNP and who did, or did not, use nicotine/cigarettes were randomized, in a balanced fashion, to naltrexone (50mg/d) or placebo and provided medical management (MM) over a 16-week clinical trial. Alcohol use and smoking during the trial were assessed and analyzed. Nicotine-use/smoking status significantly interacted with medication in reducing percent heavy drinking days (PHDD) during the trial (p=0.003), such that nicotine-users/smokers showed significantly lower PHDD on naltrexone versus placebo (p=0.0001, Cohen's d=0.89), while nonusers showed no significant difference between naltrexone and placebo (p=0.95, Cohen's d=0.02). Similar effects were shown for drinks per day and percent days drinking. The superiority of naltrexone over placebo on PHDD reduction in nicotine-users/smokers was confirmed with %dCDT (Cohen's d range 0.3 to 0.9 over the study). Naltrexone did not significantly change cigarette use in smokers, and change in use did not influence naltrexone's effect on PHDD. These data confirm past findings that naltrexone is more efficacious in those who use nicotine/cigarettes. Compared to previous work on the OPRM1 A118G SNP, it appears that nicotine-use might be a more salient predictor of naltrexone treatment response. While naltrexone did not change cigarette use during the study, and smoking change was not related to alcohol reduction, it should be noted that participants were not seeking smoking cessation and MM did not address this issue.

Opioid Receptors Gene Polymorphism and Heroin Dependence in Iran.

Introduction:Genes often have multiple polymorphisms that interact with each other and the environment in different individuals. Variability in the opioid receptors can influence opiate withdrawal and dependence. In humans, A118G Single Nucleotide Polymorphisms (SNP) on μ-Opioid Receptor (MOR), 36 G>T in κ-Opioid Receptor (KOR), and T921C in the δ-Opioid Receptor (DOR) have been found to associate with substance dependence.Methods:To investigate the association between opioid receptors gene polymorphism and heroin addiction, 100 control subjects with no history of opioid use, and 100 heroin addicts (50% males and 50% females) in Tehran (capital of Iran), were evaluated. A118G, 36 G>T, and T921C SNPs on the MOR, KOR, DOR genes, respectively, were genotyped by sequencing.Results:We found no differences in either allele or genotype frequency for MOR, KOR and DOR genes SNPs between controls and subjects addicted to heroin.Conclusion:The relationships among polymorphisms may be important in determining the risk profile for complex diseases such as addiction, but opioid addiction is a multifactorial syndrome which is partially hereditary and partially affected by the environment.

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.

Neural response to alcohol taste cues in youth: effects of the OPRM1 gene.

Genetic variations in the mu-opioid receptor (OPRM1) gene have been related to high sensitivity to rewarding effects of alcohol. The current study focuses on the neural circuitry underlying this phenomenon using an alcohol versus water taste-cue reactivity paradigm in a young sample at relatively early stages of alcohol use, thus limiting the confound of variations in duration of alcohol use. Drinkers (17-21 years old) were selected on genotype carrying the AA-(n = 20) or the AG-(n = 16) variant of the A118G single nucleotide polymorphism (SNP) of the OPRM1 gene (rs1799971), and underwent functional magnetic resonance imaging (fMRI). Magnitude of the neural activity and frontostriatal functional connectivity in response to alcohol versus water were investigated. The AG-group demonstrated reduced activation in prefrontal and parietal regions, including the inferior and middle frontal gyrus, superior and inferior parietal lobule, compared with the AA-group. No activation differences were observed in the mesolimbic pathway. Connectivity from the ventral-striatum to frontal regions for alcohol > water trials was higher in the AG than the AA group. For the dorsal-striatum seed region, the AG group showed increased connectivity to non-PFC regions. These results indicate that adolescents carrying the G-allele may be more vulnerable for the alcohol to hijack the reward system in the absence of frontal control to regulate craving. This implies that findings of hyperactivation in the mesolimbic structures of G-allele carriers in earlier studies might result from both genetic susceptibility and heavy drinking.

Opioid Antagonists and the A118G Polymorphism in the μ-Opioid Receptor Gene: Effects of GSK1521498 and Naltrexone in Healthy Drinkers Stratified by OPRM1 Genotype.

The A118G single-nucleotide polymorphism (SNP rs1799971) in the μ-opioid receptor gene, OPRM1, has been much studied in relation to alcohol use disorders. The reported effects of allelic variation at this SNP on alcohol-related behaviors, and on opioid receptor antagonist treatments, have been inconsistent. We investigated the pharmacogenetic interaction between A118G variation and the effects of two μ-opioid receptor antagonists in a clinical lab setting. Fifty-six overweight and moderate–heavy drinkers were prospectively stratified by genotype (29 AA homozygotes, 27 carriers of at least 1 G allele) in a double-blind placebo-controlled, three-period crossover design with naltrexone (NTX; 25 mg OD for 2 days, then 50 mg OD for 3 days) and GSK1521498 (10 mg OD for 5 days). The primary end point was regional brain activation by the contrast between alcohol and neutral tastes measured using functional magnetic resonance imaging (fMRI). Secondary end points included other fMRI contrasts, subjective responses to intravenous alcohol challenge, and food intake. GSK1521498 (but not NTX) significantly attenuated fMRI activation by appetitive tastes in the midbrain and amygdala. GSK1521498 (and NTX to a lesser extent) significantly affected self-reported responses to alcohol infusion. Both drugs reduced food intake. Across all end points, there was less robust evidence for significant effects of OPRM1 allelic variation, or for pharmacogenetic interactions between genotype and drug treatment. These results do not support strong modulatory effects of OPRM1 genetic variation on opioid receptor antagonist attenuation of alcohol- and food-related behaviors. However, they do support further investigation of GSK1521498 as a potential therapeutic for alcohol use and eating disorders.

Mu-Opioid Receptor Polymorphisms and Breast Cancer in a Korean Female Adult Population: A Retrospective Study.

Distribution of A118G single nucleotide polymorphism (SNP) in the mu-opioid receptor 1 gene (OPRM1) differs with ethnicity. We assessed the distribution of this SNP in Korean women with breast cancer and compared it with that in women of other ethnicities with breast cancer. Distribution of SNP genotypes was as follows: 49.8% for AG genotype, 40.6% for AA genotype, and 9.6% for GG genotype. Logistic regression analysis showed a negative association between the presence of the G allele at position 118 of OPRM1 and breast cancer in the studied population (odds ratios [OR], 0.635; p=0.002). However, the AG and GG genotypes were not associated with breast cancer in the studied population (OR, 0.719; p=0.130). The proportions of the AG and GG genotypes of the OPRM1 SNP were higher in Korean women with breast cancer than in those of other ethnicities.

μ-Opioid Receptor Gene (OPRM1) Polymorphisms A118G and C17T in Alcohol Dependence: A Turkish Sample

Previous investigations on opioid system genetics have identified polymorphisms of the OPRM1 gene expressing μ-opioid receptors to be significantly associated with some features of alcohol dependence (AD). In the present study, we evaluated the relationship between single nucleotide polymorphisms (SNP) in the OPRM1 gene, A118G (rs1799971, Asn40Asp) and C17T (rs1799972, Arg6Val), and AD diagnosis, level of alcohol consumption, and AD severity in a Turkish sample. 121 AD patients and 117 healthy male subjects were included in the study. OPRM1 A118G (N40D) and C17T (A6V) polymorphisms were evaluated using PCR - RFLP (polymerase chain reaction - restriction fragment length polymorphism) method. We evaluated the association between the presence of SNPs and AD diagnosis, family history of AD, AD severity evaluated via the Michigan Alcoholism Screening Test (MAST), the daily average and maximum quantity of alcohol consumed. There was no significant difference in OPRM1 A118G genotype frequencies between the AD and control groups. T allele frequency for the OPRM1 C17T SNP was very low (0.006) in the sample population. OPRM1 A118G SNP G118 allele carriers showed significantly higher levels of AD severity as indicated by the MAST. The OPRM1 G118 allele was significantly associated with more severe AD in the Turkish population. Similar to other European populations, the frequency of the OPRM1 T17 allele was very low.