OPRM1 Research Articles

Opioid Addiction and Opioid Receptor Dimerization: Structural Modeling of the OPRD1 and OPRM1 Heterodimer and Its Signaling Pathways.

Opioid addiction is a complex phenomenon with genetic, social, and other components. Due to such complexity, it is difficult to interpret the outcome of clinical studies, and thus, mutations found in individuals with these addictions are still not indisputably classified as opioid addiction-causing variants. Here, we computationally investigated two such mutations, A6V and N40D, found in the mu opioid receptor gene OPRM1. The mutations are located in the extracellular domain of the corresponding protein, which is important to the hetero-dimerization of OPRM1 with the delta opioid receptor protein (OPRD1). The hetero-dimerization of OPRD1–OPRM1 affects the signaling pathways activated by opioids and natural peptides and, thus, could be considered a factor contributing to addiction. In this study, we built four 3D structures of molecular pathways, including the G-protein signaling pathway and the β-arrestin signaling pathway of the heterodimer of OPRD1–OPRM1. We also analyzed the effect of mutations of A6V and N40D on the stability of individual OPRM1/OPRD1 molecules and the OPRD1–OPRM1 heterodimer with the goal of inferring their plausible linkage with opioid addiction. It was found that both mutations slightly destabilize OPRM1/OPRD1 monomers and weaken their association. Since hetero-dimerization is a key step for signaling processes, it is anticipated that both mutations may be causing increased addiction risk.

Ketogenic Diet Decreases Alcohol Intake in Adult Male Mice.

The classic ketogenic diet is a diet high in fat, low in carbohydrates, and well-adjusted proteins. The reduction in glucose levels induces changes in the body’s metabolism, since the main energy source happens to be ketone bodies. Recent studies have suggested that nutritional interventions may modulate drug addiction. The present work aimed to study the potential effects of a classic ketogenic diet in modulating alcohol consumption and its rewarding effects. Two groups of adult male mice were employed in this study, one exposed to a standard diet (SD, n = 15) and the other to a ketogenic diet (KD, n = 16). When a ketotic state was stable for 7 days, animals were exposed to the oral self-administration paradigm to evaluate the reinforcing and motivating effects of ethanol. Rt-PCR analyses were performed evaluating dopamine, adenosine, CB1, and Oprm gene expression. Our results showed that animals in a ketotic state displayed an overall decrease in ethanol consumption without changes in their motivation to drink. Gene expression analyses point to several alterations in the dopamine, adenosine, and cannabinoid systems. Our results suggest that nutritional interventions may be a useful complementary tool in treating alcohol-use disorders.

Association of Mu-Opioid Receptor(MOR) Expression and Opioids Requirement With Survival in Patients With Stage I-III Pancreatic Ductal Adenocarcinoma.

BackgroundThe use of opioids in patients with metastatic pancreatic ductal adenocarcinoma (PDAC) is associated with shorter survival and not dependent on the expression of the mu-opioid receptor (MOR). The role of opioid use and MOR expression in stage I-III PDAC has not been investigated.MethodsWe conducted retrospective study in patients with stage I-III PDAC. MOR expression and OPRM1 gene expression in tumour tissue and non-tumour tissue was measured. Primary endpoints were overall survival (OS) and disease-free survival (DFS). Secondary endpoints included perineural invasion, intraoperative sufentanil consumption, and length of stay. We performed a subgroup group analysis to evaluate the interaction between levels of MOR expression, amount of opioids use (high versus low) and its association with survival.ResultsA total of 236 patients were enrolled in this study.There were no significantly difference in OS rates in patients with high versus low levels of MOR (1-year OS: 65.2% versus 70.6%, P=0.064; 3-year: 31.4% versus 35.8%, P=0.071; 5-year: 19.4% versus. 16.2%, P=0.153, respectively) in the tumours. The DFS rates between the groups were no significantly difference. Of note, a high expression of MOR combined with high opioid consumption was associated with poor prognosis in stage I-III PDAC patients. Tumor expressing high levels of MOR show higher rates of perineural invasion.ConclusionMOR is not an independent predictor of poor survival in stage I-III PDAC but associated with perineural invasion. Patients requiring high amounts of opioids intraoperatively show worse outcome if they are expressing high levels of MOR.

Association of OPRM1, MIR23B, and MIR107 genetic variability with acute and chronic pain after postoperative tramadol treatment in breast cancer.

e24052 Background: Tramadol is an opioid analgesic often used for pain management after axillary lymph node dissection in breast cancer. It exerts its analgesic activity through activation of the G protein-coupled µ-opioid receptor, encoded by the OPRM1 gene. Genetic factors that may modify activity or expression of OPRM1 could thus affect the efficacy of tramadol treatment. This study investigated the association of genetic variability of OPRM1 and genes coding for miRNAs regulating OPRM1 expression with pain management in breast cancer patients treated with tramadol after surgery. Methods: The study included 113 breast cancer patients treated with either 75 or 37.5 mg of tramadol for pain relief after breast cancer surgery within the randomized clinical trial KCT 04/2015-DORETAonko/si at Institute of Oncology Ljubljana. All patients were genotyped for OPRM1 rs1799971 and rs677830, MIR23B rs1011784 and MIR107 rs2296616 using competitive allele-specific PCR. The association of genetic factors with acute and chronic pain was evaluated using logistic regression, Fisher’s exact test and Mann-Whitney test. Results: The investigated OPRM1 related genetic factors were not associated with acute pain measured using VAS scale within four weeks after surgery, even after adjustment for tramadol dose (all P > 0.05). One year after surgery, 21 (21.1%) patients experienced chronic pain and 25 (25.3%) experienced neuropathic pain. In carriers of two polymorphic MIR107 rs2296616 alleles, chronic pain was significantly more common compared to carriers of two wild-type alleles (35.3% compared to 0% of patients, P = 0.004). Carriers of at least one polymorphic MIR23B rs1011784 allele experienced more neuropathic pain compared to carriers of two wild-type alleles after adjustment for tramadol dose (OR = 2.85, 95% CI = 1.07-7.59, P = 0.036). Conclusions: Genetic variability of miRNAs that could affect OPRM1 expression may be associated with chronic pain in breast cancer patients treated with postoperative tramadol.

Negative symptoms in schizophrenia: correlation with clinical and genetic factors.

Aim: Explore the possible association between clinical factors and genetic variants of the dopamine pathways and negative symptoms. Materials & methods: Negative symptoms were assessed in 206 patients with schizophrenia using the Arabic version of the self-evaluation of negative symptoms scale and the Positive and Negative Syndrome Scale. Genotyping for COMT, DRD2, MTHFR and OPRM1 genes was performed. Results: Multivariable analysis showed that higher self-evaluation of negative symptoms scale scores were significantly associated with higher age, higher chlorpromazine-equivalent daily dose for typical antipsychotics and in married patients. Higher negative Positive and Negative Syndrome Scale scores were significantly associated with women and having the CT genotype for MTHFR c.677C>T (β=4.25; p=0.008) compared with CC patients. Conclusion: Understanding both clinical/genetic factors could help improve the treatment of patients.

Genetic Factors Associated With Pain Severity, Daily Opioid Dose Requirement, and Pain Response Among Advanced Cancer Patients Receiving Supportive Care

BackgroundCurrent understanding of genetic factors associated with pain severity, and improvement of pain with opioids in advanced cancer patients (AC) is inadequate for delivery of personalized pain therapy (PPT). Therefore, the aim of this study was to determine the genetic factors associated with pain severity, daily opioid dose, and pain response in AC patients receiving supportive care. MethodsIn this prospective study, AC patients were eligible if they had cancer pain ≥4/10 on Edmonton Symptom Assessment Scale (ESAS) - Pain Item and needed opioid rotation for pain control by specialist at the outpatient supportive care center. Association of genetic factors with pain phenotype was assessed using logistic regression models and SKATO (Gene-block) analysis. ResultsAbout 174/178 (98%) patient samples were analyzed. After adjustment for demographic and clinical variables, pain severity was negatively associated with intron variant alleles in OPRM1 rs9322446, P = 0.02; rs2270459, P = 0.038; rs62052210, P = 0.038. Opioid daily dose was positively associated NFKBIA rs2233419, P = 0.008; rs2233417, P = 0.007; rs3138054, P = 0.008; rs1050851, P = 0.015; ORPM1 rs9479759, P = 0.046; rs2003185, P = 0.047; rs636433, P = 0.044; COMT (rs9306234, P = 0.014; rs165728, P = 0.014; rs2020917, P = 0.036; rs165728, P = 0.034); ARRB2 (rs1045280, P = 0.045); and pain response to opioids was negatively associated OPRM1 rs1319339, P = 0.024; rs34427887, P = 0.048; and COMT rs4646316, P = 0.03; rs35478083, P = 0.028, respectively. SKATO analysis showed association between pain severity and CXCL8 (P = 0.0056), and STAT6 (P = 0.0297) genes respectively, and pain response with IL-6 (P = 0.00499). ConclusionsThis study identified that SNPs of OPRM1, COMT, NFKBIA, CXCL8, IL-6, STAT6, and ARRB2 genes were associated with pain severity, opioid daily dose, and pain response in AC receiving supportive care. Additional studies are needed to validate our findings for PPT.

The administration of sertraline plus naltrexone reduces ethanol consumption and motivation in a long-lasting animal model of post-traumatic stress disorder

This study was aimed to evaluate the effects of sertraline (STR) and/or naltrexone (NTX) on ethanol consumption and motivation in an animal model of post-traumatic stress disorder (PTSD) and alcohol use disorder (AUD).Male C57BL/6J mice were submitted to an intermittent and progressively increasing stressful stimuli simulating PTSD behavioural features. Behavioural alterations were explored by the fear conditioning (FC), novelty suppressed feeding test (NSFT) and acoustic startle response (ASR) paradigms. Afterwards, mice were evaluated in the voluntary ethanol consumption (VC) and the oral ethanol self-administration (OEA) paradigms. The effects of STR (10 mg/kg) and/or NTX (0.7 mg/kg) on ethanol consumption and motivation were analysed in the OEA. Furthermore, relative gene expression analyses of tyrosine hydroxylase (Th), mu-opioid receptor (Oprm1) and 5-hydroxitryptamine transporter (Slc6a4) were performed in the ventral tegmental area (VTA), nucleus accumbens (NAcc) and dorsal raphe nucleus (DR), respectively.PTSD-like mice presented increased fear-related memory, anxiety-like behaviours, and startle response, as well as enhanced ethanol consumption and motivation in the VC and OEA paradigms. Interestingly, STR plus NTX combination significantly reduced ethanol intake and motivation in the OEA. Gene expression analyses revealed reduced Th and Oprm1 whereas Slc6a4 gene expression increased in PTSD-like mice. STR and/or NTX modulated Th and Slc6a4 gene expression changes in PTSD-like mice. Furthermore, NTX increased Oprm1 gene expression revealing a synergistic action when combined with STR.These results provide evidence about the efficacy of the STR plus NTX to attenuate ethanol reinforcement and motivation in an animal model of PTSD and AUD dual pathology.

Hedonic Hunger Is Associated with Intake of Certain High-Fat Food Types and BMI in 20- to 40-Year-Old Adults

Hedonic hunger occurs in response to a desire to consume food for pleasure. The μ-opioid system regulates the hedonic impact of food and the opioid receptor mu 1 gene (OPRM1) polymorphism has been associated with fat intake. The aim of this study was to determine whether the intake of high-fat food is associated with hedonic hunger and the OPRM1 polymorphism and whether these variables are related to BMI. Participants were 20- to 40-y-old women and men enrolled in Poznań, Poland in 2016-2018. The frequency of consumption of high-fat food was measured using a validated application for mobile devices. Hedonic hunger was assessed with the use of the Power of Food Scale (PFS). PFS1, PFS2, and PFS3 scores were generated for food available, food present, and food tasted, respectively. Genotyping of rs1799971 in the OPRM1 gene was performed using TaqMan probes. The associations were analyzed using linear regression or logistic regression, as appropriate. Hedonic hunger scores were not associated with total high-fat food intake. Total PFS was associated with snack intake (β: 0.16, P=0.0066). PFS1 was positively associated with healthy high-fat food intake (β: 0.27, P=0.0001) and PFS2 with sweet high-fat food and fast-food intake (β: 0.27, P=0.0030). OPRM1 genotype and hedonic hunger interacted on fast-food intake (β: -0.17; P<0.0154). Total PFS and PFS2 increased the chance of having a BMI≥25kg/m2 (OR: 1.43; 95% CI: 1.03, 2.01; P=0.0335 and OR: 1.89; 95% CI: 1.37, 2.61; P=0.0001, respectively), whereas PFS3 decreased it (OR: 0.61; 95% CI: 0.41, 0.87; P=0.0082). Hedonic hunger is associated with the intake of selected types of high-fat food, but not with its total intake, in people aged 20-40 y. Associations between hedonic hunger and fast-food intake can be modified by OPRM1 genotype. Hedonic hunger is associated with BMI.

Association of the OPRM1 A118G polymorphism and Pavlovian-to-instrumental transfer: Clinical relevance for alcohol dependence.

Background:Pavlovian-to-instrumental transfer (PIT) quantifies the extent to which a stimulus that has been associated with reward or punishment alters operant behaviour. In alcohol dependence (AD), the PIT effect serves as a paradigmatic model of cue-induced relapse. Preclinical studies have suggested a critical role of the opioid system in modulating Pavlovian–instrumental interactions. The A118G polymorphism of the OPRM1 gene affects opioid receptor availability and function. Furthermore, this polymorphism interacts with cue-induced approach behaviour and is a potential biomarker for pharmacological treatment response in AD. In this study, we tested whether the OPRM1 polymorphism is associated with the PIT effect and relapse in AD.Methods:Using a PIT task, we examined three independent samples: young healthy subjects (N = 161), detoxified alcohol-dependent patients (N = 186) and age-matched healthy controls (N = 105). We used data from a larger study designed to assess the role of learning mechanisms in the development and maintenance of AD. Subjects were genotyped for the A118G (rs1799971) polymorphism of the OPRM1 gene. Relapse was assessed after three months.Results:In all three samples, participants with the minor OPRM1 G-Allele (G+ carriers) showed increased expression of the PIT effect in the absence of learning differences. Relapse was not associated with the OPRM1 polymorphism. Instead, G+ carriers displaying increased PIT effects were particularly prone to relapse.Conclusion:These results support a role for the opioid system in incentive salience motivation. Furthermore, they inform a mechanistic model of aberrant salience processing and are in line with the pharmacological potential of opioid receptor targets in the treatment of AD.

Association between polymorphisms in catechol-O-methyl transferase, opioid receptor Mu 1 and serotonin receptor genes with postoperative pain following root canal treatment.

To evaluate the effect of single nucleotide polymorphisms in the COMT, OPRM1, 5HT1A, 5HT2A and 5HTR3B genes on the intensity of postoperative pain following root canal treatment. Ninety-five patients with mandibular and maxillary molar teeth diagnosed with symptomatic apical periodontitis and a level of preoperative pain greater than 50 on a 100mm visual analogue scale (VAS) were included. Salivary DNA was collected from the participants and stored in Eppendorf tubes at -80°C. Preoperative percussion pain values were recorded before the root canal treatment procedures. After completion of root canal treatment, the participants were given instructions to record their postoperative pain intensity levels at 24, 48 and 72h, 5days and 1week after treatment, using the VAS. A second visit for the patients after seven days was planned to record their intensity levels of percussion pain on VAS. The percussion test was performed by tapping on the occlusal surface of the tooth with a blunt instrument. A QIAamp DNA Mini Kit was used to isolate DNA from saliva, and SNP Genotyping Analysis software version 1 was used to analyse the genotypes by calculating FAM and HEX signals. The Kruskal-Wallis and Mann-Whitney U-tests were used to evaluate pain intensity values amongst the genotypes, alleles, haplotypes and allele combinations. Nominal data (gender, intake and tooth number) were analysed using a Chi-square test. Bonferroni correction was performed. Thus, the significance level was set at 1.6% (P=0.016), 2.5% (P=0.025) and 1.25% (P=0.0125) for genotype, allele and haplotype comparisons, respectively. There was no significant difference amongst the genotypes and alleles in terms of pre- and postoperative pain intensity. There was no significant difference amongst the haplotypes formed for the COMT gene in terms of pain intensity. Additionally, there was no significant association between the allelic combination formed for 5HT1A+5HT2A genes and the intensity of postoperative pain. The findings indicate that none of the evaluated SNPs for COMT, OPRM1, 5HT1A, 5HT2A and 5HTR3B genes were associated with the intensity of postoperative pain.

Clinical and Genetic Factors Associated With the Breast Cancer-Related Sleep Disorders: The “CAGE-Sleep” Study–A Cross-Sectional Study

ContextDespite being among the most reported concerns in breast cancer patients, sleep disturbances are still poorly assessed and managed in routine clinical practice. Correctly evaluating these symptoms and understanding the underlying clinical and genetic factors would help medical teams develop an adequate treatment strategy for each patient. Objectives1) To explore the severity of insomnia as well as sleep quality in a sample of Lebanese women with breast cancer undergoing chemotherapy; 2) To examine the correlation between sociodemographic, clinical, psychiatric (anxiety and depression), genetic factors, and alterations in sleep patterns. MethodsA cross-sectional study was carried out using the Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI) (December 2017–June 2019; Ethical reference number: CEHDF1016). All patients gave their written consent and were genotyped for several polymorphisms in CLOCK, CRY2, PER2, COMT, DRD2, OPRM1, and ABCB1 genes using Lightcycler® (Roche). ResultsOur sample included a total of 112 women. Almost half of the patients reported insomnia problems (with 20.5% moderate insomnia and 7.1% severe insomnia). Multivariable analyses taking the PSQI score as the dependent variable, showed that higher depression score and dyslipidemia (yes versus no) were significantly associated with higher PSQI scores (worse sleep quality), whereas having the DRD2 CT genotype versus CC and a higher chemotherapy cycle number were significantly associated with lower PSQI scores (better sleep quality). Depression was also significantly associated with higher ISI scores. When forcing all the genes in each model, the results remained the same except for depression that has been replaced by anxiety in the multivariable analysis. ConclusionOur study confirms the relationship between anxiety/depression, cycle number, dyslipidemia and DRD2 polymorphism with insomnia and highlights the importance of treating all associated factors to improve the overall QOL of patients.

Genetic susceptibility of opioid receptor genes polymorphism to drug addiction: A candidate-gene association study

BackgroundLike other complex diseases including drug addiction, genetic factors can interfere with the disease. In this study, three opioid genes (OPRM1, OPRD1, and OPRK1) were examined for an association with drug addiction among Jordanian males.MethodsThe study involved 498 addicts, in addition to 496 healthy controls and all from Arab descent.ResultsThe findings in this study showed that rs1799971 of the OPRM1 gene was in association with drug addiction for both alleles and genotypes with P-values = 0.002 and 0.01, respectively. In addition, a significant association between the dominant model (A/A vs G/A-G/G) of rs1799971 (OPRM1) and drug addiction (P-value = 0.003, OR = 1.59 (1.17–2.15)) was detected. Moreover, a genetic haplotype (AGGGCGACCCC) of theOPRM1 gene revealed a significant association with drug addiction (P-value = 0.01, OR = 1.56 (1.15–2.12)). We also found that the age of addicts, smoking, and marital status with genetic variants within OPRM1, OPRD1, and OPRK1 genes may be implicated in drug addiction risk.ConclusionWe propose that rs1799971 of the OPRM1gene is a genetic risk factor for drug addiction among Jordanian males.

Analgesic effects of piritramide in acute postoperative pain - comparison of intramuscular administration with patient-controlled intravenous analgesia and impact of OPRM1 and ABCB1 polymorphisms.

The aim of this study was to compare the efficacy, consumption and safety after piritramide administered either intramuscularly (IM) on demand or via patient-controlled intravenous analgesia (PCA) and to examine the impact of OPRM1 and ABCB1 gene polymorphisms on the drug efficacy/safety in both regimens. One hundred and four patients scheduled for elective inguinal hernioplasty received piritramide with PCA or IM for postoperative pain management. We evaluated piritramide consumption, pain intensity using visual analogue scale (VAS) and adverse effects. Median (IQR) piritramide consumption was 18.5 (13.5-31.2) and 15.0 (15.0-15.0) mg in the PCA and IM groups, respectively (P=0.0092). The respective values of area under the VAS2-16-time curve were 40 and 280 mm.h (P=0.0027). Opioid-induced adverse effects were more frequent in the PCA than in the IM group. Variant OPRM1 allele was associated with decreased pain relief, increased opioid consumption and increased incidence of adverse effects, while ABCB1 polymorphisms showed no impact on the observed parameters. We observed higher piritramide consumption, better pain relief and slightly worse safety profile in the PCA group compared with IM administration. Variant OPRM1 118G allele carriers required higher opioid dosing and suffered from more adverse effects, however, the differences between genotypes have been less pronounced in the PCA patients likely due to improved pain management via PCA.

Resistin Gene Polymorphism Is an Influencing Factor of Postoperative Pain for Chinese Patients

Background Gene polymorphism is an important factor affecting the efficacy and dosage of opioids. A recent study showed RETN rs3745367 was associated with postoperative pain intensity. OPRM1 gene was confirmed to affect the postoperative analgesic consumption of morphine and other opioids. Objective In this study, we investigated the association between single nucleotide polymorphisms (SNPs) in the RETN, OPRM1 gene and postoperative pain intensity, analgesics consumption, and ADR. The haplotype analysis focus on OPRM1 was also implemented. Study design This was a prospective, observational study. Setting Patients undergoing spinal fusion and correction operation were recruited. Genotypes of rs3745367, rs1799971, rs2075572, and rs9322447 were tested. Pain assessment was performed to measure postoperative pain intensity, postoperative fentanyl and pethidine consumption was recorded to calculate analgesics consumption, and adverse reactions were recorded. Method We recruited 142 patients undergoing spinal correction and fusion. Genotyping was performed by using a real-time polymerase chain reactions (PCRs) system and validated with allelic discrimination assays. The pain was assessed using a numerical rating scale (NRS). Statistical analyses were performed using SPSS software. LD test and the construction and analysis of haplotype were using Haploview software. Results Rs3745367 demonstrated a significant association with postoperative average pain intensity in 24h (P = 0.015) and 48h (P = 0.001) after surgery. Rs2075572 and rs9322447 influenced postoperative maximal pain intensity in 48h after surgery (P = 0.042, 0.033, respectively). No correlation was found between OPRM1 SNPs and analgesics consumption and adverse reaction. According to the results of this study, a strong LD was observed between rs1799971 and rs9322447 (Block 1, LD parameters: D' = 0.82, r2 = 0.14), rs2075572 and rs9322447 (Block 2, LD parameters: D' = 0.92, r2 = 0.51). Limitations The association between rs3745367 with serum resistin levels was not investigated in this research, serum resistin levels of the incision part should be investigated in future studies. Conclusion RETN rs3745367 was associated with postoperative average pain intensity, OPRM1 rs2075572 and rs9322447 may influence postoperative maximal pain intensity.

Polymorphisms of the μ-opioid receptor gene influence cerebral pain processing in fibromyalgia.

BackgroundDysregulation of the μ‐opioid receptor has been reported in fibromyalgia (FM) and was linked to pain severity. Here, we investigated the effect of the functional genetic polymorphism of the μ‐opioid receptor gene (OPRM1) (rs1799971) on symptom severity, pain sensitivity and cerebral pain processing in FM subjects and healthy controls (HC).MethodsSymptom severity and pressure pain sensitivity was assessed in FM subjects (n = 70) and HC (n = 35). Cerebral pain‐related activation was assessed by functional magnetic resonance imaging during individually calibrated painful pressure stimuli.ResultsFibromyalgia subjects were more pain sensitive but no significant differences in pain sensitivity or pain ratings were observed between OPRM1 genotypes. A significant difference was found in cerebral pain processing, with carriers of at least one G‐allele showing increased activation in posterior cingulate cortex (PCC) extending to precentral gyrus, compared to AA homozygotes. This effect was significant in FM subjects but not in healthy participants, however, between‐group comparisons did not yield significant results. Seed‐based functional connectivity analysis was performed with the seed based on differences in PCC/precentral gyrus activation between OPRM1 genotypes during evoked pain across groups. G‐allele carriers displayed decreased functional connectivity between PCC/precentral gyrus and prefrontal cortex.ConclusionsG‐allele carriers showed increased activation in PCC/precentral gyrus but decreased functional connectivity with the frontal control network during pressure stimulation, suggesting different pain modulatory processes between OPRM1 genotypes involving altered fronto‐parietal network involvement. Furthermore, our results suggest that the overall effects of the OPRM1 G‐allele may be driven by FM subjects.SignificanceWe show that the functional polymorphism of the μ‐opioid receptor gene OPRM1 was associated with alterations in the fronto‐parietal network as well as with increased activation of posterior cingulum during evoked pain in FM. Thus, the OPRM1 polymorphism affects cerebral processing in brain regions implicated in salience, attention, and the default mode network. This finding is discussed in the light of pain and the opioid system, providing further evidence for a functional role of OPRM1 in cerebral pain processing.

Alternative Splicing of Opioid Receptor Genes Shows a Conserved Pattern for 6TM Receptor Variants

The opioid receptor (OPR) family comprises the mu-, delta-, and kappa-opioid, and nociceptin receptors that belong to the superfamily of 7-transmembrane spanning G protein-coupled receptors (GPCRs). The mu-opioid receptor is the main target for clinically used opioid analgesics, and its biology has been extensively studied. The N-terminally truncated 6TM receptors isoform produced through alternative splicing of the OPRM1 gene displays unique signaling and analgesic properties, but it is unclear if other OPRs have the same ability. In this study, we have built a comprehensive map of alternative splicing events that produce 6TM receptor variants in all the OPRs and demonstrated their evolutionary conservation. We then obtained evidence for their translation through ribosomal footprint analysis. We discovered that N-terminally truncated 6TM GPCRs are rare in the human genome and OPRs are overrepresented in this group. Finally, we also observed a significant enrichment of 6TM GPCR genes among genes associated with pain, psychiatric disorders, and addiction. Understanding the biology of 6TM receptors and leveraging this knowledge for drug development should pave the way for novel therapies.

GENETICS OF GENERALIZED ANXIETY DISORDER

The essential feature of generalized anxiety disorder (GAD) is excessive anxiety and worry about various spheres of own life. Its prevalence ranges from 0,4% to 3,6%. The genetic share of GAD is about 32%. The rest is an influence of environmental factors, of which the most significant are childhood adversities and parental overprotection. In consequence of such features the genetic study of GAD is very difficult.To reveal candidate genes for GAD the genetic study of brain neurotransmitters is dominated. Now there are proposed over 20 genes, which has been associated with GAD.First candidate gene was proposed by D.C. Rowe with colleagues in 1998. It was the dopamine transporter gene (DAT1; modern gene symbol is SLC6A3; 5p15.33). The disorder symptoms are increased with a greater number of 10 tandem repeats of a 40 bp fragment in the 3’UT region of DAT1 gene. In following year K. Ohara with colleagues obtained a significant similar result for the serotonin transporter gene (5-HTT; modern gene symbol is SLC6A4; 17q11.2). In this study tandem repeats of 17 bp have been identified in the second intron of the gene. The 5-HTT gene variants are associated also with over 80 different diseases. Later A. Tadic with colleagues found a significant association between GAD and single nucleotide polymorphism (SNP) T941G (rs6323) in exon 8 of the monoamine oxidase A gene (MAOA; Xp11.3). In the MAOA gene uVNTR promoter J. Samochowiec with colleagues discovered an association between GAD and an increase of tandem repeats of 30 bp number over 3. In the study of J.S. You with colleagues there was showed the significant involvement of short alleles of the 5-HTT gene (allase SLC6A4) in GAD, but there is not confirmed the involvement of variable number tandem repeats in this gene, as shown by Japanese authors. Short allele of 5-HTT contains 14 tandem repeats of a 22 bp vs normal 16 in the 5-HTTLPR intron region near the promoter.In addition, the J.M. Hettema’s group of American psychiatrists proposed three GAD candidate genes – the GAD1 (Glutamate Decarboxylase 1; 2q31.1), the HTR1A (Serotonin Receptor 1A; 5q12.3) and the COMT (Catechol-O-methyltransferase; 22q11.21). Several SNPs were related to GAD: three SNPs (rs2241165, rs2058725 and rs3791850) were localized in the GAD1 gene introns, one (rs6295) – in the HTR1A gene promoter and two in the COMT gene (rs4680 – in exon and rs165599 – in the 3’UTR).A study dedicated to assessing the effects of exposure to the 2004 Florida hurricane reported increased risk of GAD in relation to SNP in the 3’UTR (rs4606) of the RGS2 gene (Regulator of G-Protein Signaling 2; 1q31.2) and SNP in the promoter region (rs16147) of the NPY gene (Neuropeptide Y; 7p15.3).A. J. Cooper with colleagues suggested some more two candidate genes for GAD: the hypophysis activating hormone (PACAP; allase ADCYAP1; 18p11.32) and the opioid receptor 1(OPRM1; allase MOR1; 6q25.2). In the PACAP gene SNP Asp54Gly (rs2856966) was involved in GAD. It was located in exon 2 of the gene. There was also showed a small correlation between SNP A118G (rs1799971; Asn40Asp) in exon 1 of the OPRM1 gene and GAD.All these results should be taken quite critically. First, the study was carried out on a statistically small samples of a few hundred people. Second, the results of these studies was not confirmed by other authors for samples of a few thousand people. GAD problems remains relevant and requires further intense research efforts.

Increased mu-opioid receptor expression is associated with reduced disease-free and overall survival in laryngeal squamous cell carcinoma

BackgroundExpression of the mu-opioid receptor (MOR) is associated with poor long-term outcomes in various types of cancer. The association between MOR expression and clinical outcomes in laryngeal squamous cell carcinoma (LSCC) is not clear. MethodsThis retrospective study included patients who underwent laryngectomy for LSCC. The expression pattern of the MOR protein and OPRM1 gene in tumours and corresponding adjacent non-carcinoma specimens was measured. Propensity score matching was used to minimise bias. The primary endpoints were overall survival (OS) and disease-free survival (DFS). The secondary endpoints were intraoperative sufentanil consumption, grade of surgical complications according to the Clavien-Dindo classification, and hospital length of stay. ResultsA total of 207 LSCC patients were enrolled. After propensity score matching, there was a significant difference in DFS between groups at 1, 3, and 5 yr (60.2% vs 81.2%, P=0.019; 39.4% vs 50.2%, P=0.026; 37.5% vs 42.5%, P=0.023, respectively) in patients with high MOR expression. The OS rates at 1, 3, and 5 yr were significantly lower in the high MOR expression group (81.2% vs 93.2%, P=0.027; 57.7% vs 78.3%, P<0.001; 42.5% vs 60.3%, P<0.001, respectively). The multivariate analysis indicated that high MOR expression was associated with worse DFS and OS (hazard ratio: 1.52, 95% confidence interval: 1.07, 2.25, P=0.034; hazard ratio: 1.42, 95% confidence interval: 1.17, 2.34, P=0.032). ConclusionHigh MOR expression may be associated with poor prognosis in patients with LSCC, suggesting that MOR could be used as a valuable molecular biomarker to predict prognosis of LSCC patients.

The μ-opioid receptor gene polymorphism 118A>G weakens the pharmacological action of buprenorphine.

Opioids are commonly used analgesics for moderate to severe pain, but levels of drug effect vary among individuals. As for the mechanisms underlying these individual differences, there have been reports suggesting effects of polymorphisms in the gene encoding μ-opioid receptor (OPRM1). However, whether these polymorphisms affect the actions of μ-opioid receptor partial agonists has yet to be determined. This study aimed to assess differences in the pharmacological actions of buprenorphine, a μ-opioid receptor partial agonist, due to a polymorphism (A118G, rs1799971) in the OPRM1 gene in humans. Ten healthy adult men (5 with OPRM1 c.118AA and 5 with OPRM1 c.118GG) received a single intravenous dose of buprenorphine hydrochloride at 0.001 mg/kg. Blood samples were collected up to 360 minutes after drug administration to assess the pharmacokinetics of buprenorphine. Nociceptive thresholds (temperature), digital symbol substitution test (DSST), and visual analog self-rating scale (VAS) for subjective symptoms were also evaluated over time to assess the pharmacodynamics. Nociceptive thresholds were significantly increased in the AA as compared to the GG group after buprenorphine administration (p = 0.025), while the DSST scores were significantly lower in the AA group (p < 0.001). The VAS scores for drowsiness (p < 0.001), malaise (p < 0.001), nausea (p < 0.001), and euphoria (p = 0.004) were higher in the AA than in the GG group. Levels of pharmacological actions of a μ-opioid receptor partial agonist vary in accordance with a polymorphism in the OPRM1 gene (A118G).

A118G polymorphism of OPRM1 gene caused different morphine consumption in female patients after total knee replacement

BackgroundWe intended to clarify the effect of gender and A118G polymorphism of Opioid Receptor μ1 (OPRM1) on the required morphine for patients to maintain Visual Analogue Scale ≦ 3 for post-operative pain control after total knee replacement (TKR). MethodsWith approval from Institutional Review Board (IRB) and obtainment of informed consents, 111 patients undergoing primary TKR were enrolled without violating the exclusion criteria, including previous history of allergy to morphine, alcohol or substance abuse, use of psychotropic medications, morbid obesity of body mass index (BMI) > 40 kg/m2, chronic pain with evidence of central sensitization, and uncooperative use of patient controlled analgesia (PCA) device. The amount of PCA-delivered morphine for pain control and the ‘demand’ (the count of button pushing for requiring pain medication from PCA) were recorded at 3, 6, 12, 24, 36, 48 and 72 h after the operation. One-way ANOVA with post-hoc test by Scheffe's method was adopted for statistical analysis of each variant (AA, AG, GG). The side-effects (nausea, vomiting and sedation) from morphine were recorded. P < 0.05 was considered to be statistically significant. ResultsWith sequencing by ABI PRISM 310 Genetic Analyser, we disclosed that the allele frequency was 75.5% for the A allele (female: 77.5%, male: 69.6%) and 24.5% for the G allele (female: 22.5%, male: 30.4%). The frequency of genotype occurrence was 61.3% for AA, 24.3% for AG and 14.4% for GG. Female patients of homozygous G118G of OPRMI required more morphine from PCA device for post-operative pain control than patients of AA and AG genotypes. No significant difference in morphine consumption for post-operative pain control was disclosed among three genotypes for male patients. ConclusionsThe impact caused by G118G polymorphism of OPRM1 on requirement of morphine consumption for post-operative pain control is potentially gender-linked.