Alcohol Consumption in Healthy OPRM1 G Allele Carriers and Its Association with Impulsive Behavior

Prefrontal and striatal dopamine D2/D3 receptors correlate with fMRI BOLD activation during stopping

D2-like dopamine receptors in animals and humans have been shown to be linked to impulsive behaviors that are highly relevant for several psychiatric disorders. Here, we investigate the relationship between the fronto-striatal D2/D3 dopamine receptor availability and response inhibition in a selected population of healthy OPRM1 G-allele carriers. Twenty-two participants successively underwent blood-oxygen level dependent functional magnetic resonance imaging (fMRI) while performing a stop-signal task and a separate positron emission tomography (PET) scan. Striatal and extrastriatal D2/D3 dopamine receptor availability was measured using the radiotracer [18F]fallypride. Caudate D2/D3 dopamine receptor availability positively correlated with stopping-related fronto-striatal fMRI activation. In addition, right prefrontal D2/D3 dopamine receptor availability correlated positively with stopping-related striatal fMRI BOLD signal. Our study partially replicates previous findings on correlations between striatal D2/D3 dopamine receptor availability and response inhibition in a population selected for its genetic determination of dopamine response to alcohol and as a modulator of impulse control via the endogenous opioid system. We confirm the important role of D2/D3 dopamine receptor availability in the fronto-striatal neural circuit for response inhibition. Moreover, we extend previous findings suggesting that dopamine receptor availability in the right inferior frontal cortex, a crucial region of the stopping network, is also strongly associated with stopping-related striatal fMRI activity in healthy OPRM1 G-allele carriers.

Genetic Vulnerability to Opioid Addiction

Opioid addiction, also referred to as opioid use disorder, continues to be a devastating problem throughout the world. Familial relation and twin studies have revealed opioid addiction, like other addictive diseases, to be profoundly influenced by genetics. Genetics studies of opioid addiction have affirmed the importance of genetics contributors in susceptibility to develop opioid addiction, and also have important implications on treatment for opioid addiction. But the complexity of the interactions of multiple genetic variants across diverse genes, as well as substantial differences in allelic frequencies across populations, thus far limits the predictive value of individual genetics variants.

Alcohol in Psoriasis-From Bench to Bedside

Alcohol affects the symptoms, compliance and comorbidities as well as the safety and efficacy of treatments in psoriatic patients. In this review, we aim to summarize and link clinical observations with a molecular background, such as signaling pathways at the cellular level and genetic variations, and to provide an overview of how this knowledge could influence our treatment selection and patient management.

Recent advances in genetic studies of alcohol use disorders

PURPOSE OF REVIEW

Alcohol use disorder (AUD) is a complex genetic disorder with very high heritability. This polygenic disorder not only results in increased morbidity and mortality, it is also a substantial social and economic burden on families and the nation. For past three decades, several genetic studies were conducted to identify genes and pathways associated with AUD. This review aims to summarize past efforts and recent advances in genetic association studies of AUD and related traits.

RECENT FINDINGS

Initial genetic association studies achieved a limted success and suffered from low power due to small sample sizes. AUD is a polygenic trait and data from several thousands individuals was required to identify the genetic factors of small effect sizes. The scenario changed recently with technological advances and significant reduction in cost of the genome wide association analyses (GWAS). This enabled researchers to generate genomic data on mega biobanks and cohorts with access to extensive clinical and non-clinical phenotypes. Public access to data from biobanks and collaborative efforts of researchers lead to identification of several novel loci associated with AUDs and related traits. Efforts are now underway to identify the causal variants under the GWAS loci to identify target genes and biological mechanisms underpining AUDs. Many GWAS variants occur in promoter or enhancer regions of the genes and are involved in regulation of gene expression of causal genes. This, large amounts of "omics" data from projects such as "ENCODE", RoadMap and GTEx is also helping researchers to integrate "multi-omics" data to interpret functional significance of GWAS variants.

SUMMARY

With current review, we aim to present the recent advances in genetic and molecular studies of AUDs. Recent successes in genetic studies of AUDs will definetely motivate researchers and lead to better therapeutic interventions for this complex disorder.

Associations among the opioid receptor gene (OPRM1) A118G polymorphism, psychiatric symptoms, and quantitative EEG in Korean males with gambling disorder: A pilot study

BACKGROUND AND AIMS

A single nucleotide polymorphism of A118G (SNP; rs1799971) in the opioid receptor μ-1 (OPRM1) gene is a missense variant that influences the affinity of μ-opioid receptors. This study aimed to investigate the associations among the A118G polymorphism in the OPRM1 gene, psychiatric symptoms, and quantitative electroencephalography (qEEG) findings in patients with gambling disorder.

METHODS

Fifty-five male patients with gambling disorder aged between 18 and 65 years old participated in the study. The A118G polymorphism was genotyped into the AA, GA, and GG groups by the polymerase chain reaction/restriction fragment length polymorphism method. Resting-state qEEG was recorded with the eyes closed, and the absolute power of the delta (1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), and beta (12-30 Hz) frequency bands was analyzed. Psychiatric symptoms, including depression, anxiety, impulsivity and severity of gambling, were assessed by a self-rating scale.

RESULTS

There were no significant differences in psychiatric symptoms among the three genotype groups (AA, GA, and GG). However, the frequency band power of qEEG showed significant differences among the three genotype groups. The absolute power of the beta and theta bands in the frontal lobe was higher in G allele carriers.

DISCUSSION AND CONCLUSION

Based on the findings of this study, the polymorphism in the OPRM1 gene might affect the neurophysiological process in patients with gambling disorder.

Four single nucleotide polymorphisms in genes involved in neuronal signaling are associated with Opioid Use Disorder in West Virginia

Objective

Pilot study to assess utility in opioid use disorder (OUD) of a panel of single nucleotide polymorphisms in genes previously related to substance use disorder (SUD) and/or phenotypes that predispose individuals to OUD/SUD.

Design

Genetic association study.

Setting

West Virginia University's Chestnut Ridge Center Comprehensive Opioid Abuse Treatment (COAT) clinic for individuals diagnosed with OUD.

Patients

Sixty patients 18 years of age or older with OUD undergoing medication (buprenorphine/naloxone)-assisted treatment (MAT); all sixty patients recruited contributed samples for genetic analysis.

Outcome Measures

Minor allele frequencies for single nucleotide polymorphisms.

Results

Four of the fourteen single nucleotide polymorphisms examined were present at frequencies that are statistically significantly different than in a demographically-matched general population.

Conclusions

For the purposes of testing WV individuals via genetic means for predisposition to OUD, at least four single nucleotide polymorphisms in three genes are likely to have utility in predicting susceptibility. Additional studies with larger populations will need to be conducted to confirm these results before use in a clinical setting.

The prevalence of ADH1B and OPRM1 alleles predisposing for alcohol consumption are increased in the Hungarian psoriasis population

Alcohol intake affects in great the symptoms and life of  psoriasis patients, although the association of SNPs related to increased alcohol consumption with psoriasis has not been elucidated. Therefore, to investigate the association of psoriasis with established alcohol consumption and dependence-related gene variants we conducted a population-based case-control study including 3743 subjects (776 psoriasis cases and 2967 controls from the general Hungarian population). Genotyping of 23 SNPs at ADH1B, ADH1C, ALDH1A1, ALDH2, SLC6A3, DDC, GABRA2, GABRG1, HTR1B, MAOA, TPH2, CHRM2, GRIN2A, POMC, OPRM1, OPRK1 and BDNF were determined and differences in genotype and allele distributions were investigated. Multiple logistic regression analyses were implemented. Analysis revealed association between C allele of the rs1229984 polymorphism (ADH1B gene) and psoriasis risk (OR_additive = 1.58, 95% CI 1.23-2.03, p < 0.001, OR_recessive = 1.58, 95% CI 1.22-2.04, p = 0.001). Furthermore, the G allele of rs1799971 polymorphism (OPRM1 gene) increased the risk of familial aggregation (OR_additive = 1.99, 95% CI 1.36-2.91, p < 0.001 OR_dominant = 2.01, 95% CI 1.35-3.01, p < 0.001). In subgroups of psoriatic patients with history of early onset and familial aggregation effect allele 'C' of rs1229984 showed association in the additive and recessive models (OR_additive = 2.41, 95% CI 1.26-4.61, p < 0.01, OR_recessive = 2.42, 95% CI 1.26-4.68, p < 0.01). While effect allele 'G' of rs1799971 (OPRM1) also associated with increased risk of early onset and familial aggregation of psoriasis in the additive and dominant models (OR_additive = 1.75, 95% CI 1.27-2.43, p = 0.001, OR_dominant = 1.82, 95% CI 1.26-2.63, p = 0.001). Our results suggest that genetically defined high-risk individuals for alcohol consumption are more common in the psoriasis population.

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.

Genetic analysis of impulsive personality traits: Examination of a priori candidates and genome-wide variation

Impulsive personality traits are heritable risk factors and putative endophenotypes for addiction and other psychiatric disorders involving disinhibition. This study examined the genetic basis of impulsive personality traits, defined as scores on the Barratt Impulsiveness Scale (BIS-11) and the UPPS-P Impulsive Behavior Scale (UPPS-P). In 983 healthy young adults of European ancestry, the study examined genetic variation in relation to a combined phenotype of seven subscales based on high phenotypic intercorrelations. The study first tested 14 a priori loci that have previously been associated impulsive personality traits or closely related constructs. Second, the study included an exploratory genome-wide scan (i.e., GWAS), acknowledging that only relatively large effects would be detectable in a sample size of ~ 1000. A priori SNP analyses revealed a significant association between the combined impulsivity phenotype and two SNPs within the 5-HT2a receptor gene (HTR2A; rs6313 and rs6311). Follow-up analyses suggested that the effects were specific to the Motor and Non-planning subscales on the BIS-11, and also that the two loci were in linkage disequilibrium. The GWAS yielded no statistically significant findings. This study further implicates loci within HTR2A with certain forms of self-reported impulsivity and identifies candidates for future investigation from the genome-wide analyses.

Acute effect of intravenously applied alcohol in the human striatal and extrastriatal D2 /D3 dopamine system

Investigations on the acute effects of alcohol in the human mesolimbic dopamine D₂ /D₃ receptor system have yielded conflicting results. With respect to the effects of alcohol on extrastriatal D₂ /D₃ dopamine receptors no investigations have been reported yet. Therefore we applied PET imaging using the postsynaptic dopamine D₂ /D₃ receptor ligand [¹⁸ F]fallypride addressing the question, whether intravenously applied alcohol stimulates the extrastriatal and striatal dopamine system. We measured subjective effects of alcohol and made correlation analyses with the striatal and extrastriatal D₂ /D₃ binding potential. Twenty-four healthy male μ-opioid receptor (OPRM1)118G allele carriers underwent a standardized intravenous and placebo alcohol administration. The subjective effects of alcohol were measured with a visual analogue scale. For the evaluation of the dopamine response we calculated the binding potential (BP_ND ) by using the simplified reference tissue model (SRTM). In addition, we calculated distribution volumes (target and reference regions) in 10 subjects for which metabolite corrected arterial samples were available. In the alcohol condition no significant dopamine response in terms of a reduction of BP_ND was observed in striatal and extrastriatal brain regions. We found a positive correlation for 'liking' alcohol and the BP_ND in extrastriatal brain regions (Inferior frontal cortex (IFC) (r = 0.533, p = 0.007), orbitofrontal cortex (OFC) (r = 0.416, p = 0.043) and prefrontal cortex (PFC) (r = 0.625, p = 0.001)). The acute alcohol effects on the D₂ /D₃ dopamine receptor binding potential of the striatal and extrastriatal system in our experiment were insignificant. A positive correlation of the subjective effect of 'liking' alcohol with cortical D₂ /D₃ receptors may hint at an addiction relevant trait.

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.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.