Quantitative Sensory Testing in Fibromyalgia Syndrome: A Scoping Review

Background/Objectives: Quantitative sensory testing (QST) is one of the most reliable methods for assessing Fibromyalgia Syndrome (FMS). Despite its importance, there are still controversies regarding the correct interpretation of evoked responses, as they may vary depending on the protocol, individual characteristics, disease severity, and other factors. This study aims to examine how QST has been applied as an outcome measure in FMS. Methods: We considered three databases (Medline, Embase, and Web of Science) until June 2024. From a total of 2512 studies, 126 (39 RCTs and 87 non-RCTs) were selected for full reading after assessment for risk of bias and eligibility criteria. These criteria included at least one type of QST and a clear diagnosis of fibromyalgia (FMS). Results: The results highlighted a lack of standardization in QST, as no reported protocols were followed and there was no specific number of tender points tested for FMS. Additionally, there was inconsistency in the selection of sites and types of tests conducted. Conclusions: This heterogeneity in methodology may affect the comparability and interpretation of results, underscoring the urgent need for standardized guidelines for conducting QST in fibromyalgia studies. A clear understanding of how QST has been measured could prompt a reevaluation of current approaches to FMS assessment, leading to more accurate interpretations and, ultimately, improved management of this complex condition.

Analgesic therapy failure in a COMT HPS/HPS diplotype carrier heterozygous for the CYP2D6 *4 allele with fibromyalgia-a case report

Introduction

The cytochrome P450 enzyme 2D6 (CYP2D6) and the catechol-O-methyltransferase (COMT) enzyme are involved in catecholamine metabolism, potentially influencing pain modulation. Catechol-O-methyltransferase has 3 major haplotypes related to pain sensitivity: low (LPS), average (APS), and high (HPS). However, the reliability of these haplotypes in predicting clinical outcomes is not well investigated. We present a 40-year-old female patient with fibromyalgia. Despite extensive pharmacotherapy with 120 mg/d duloxetine, 150 mg/d pregabalin, 80 mg/d oxycodone, 2 g/d paracetamol, and 1.6 g/d ibuprofen, she suffered from severe pain.

Objectives

We aim to investigate the patient's susceptibility to analgesic therapy failure (TF) and pain sensitivity with pharmacogenotyping.

Methods

PGx panel testing, including CYP2D6 and COMT rs4680, was conducted by a commercial provider. Additional genotyping of COMT rs6269, rs4633 and rs4818 was performed applying PCR, restriction fragment length polymorphism assay and sanger sequencing.

Results

The patient was identified as COMT HPS/HPS diplotype carrier and CYP2D6 intermediate metabolizer. CYP2D6 is mainly responsible for the bioactivation of oxycodone into oxymorphone. Reduced CYP2D6 activity may result in a lower oxycodone activation. Considering the coadministration of duloxetine (a moderate CYP2D6 inhibitor), the TF of oxycodone could also be the result of a drug-drug-gene interaction. No other medications were affected by her genetic profile.

Conclusion

We hypothesize that the broad TF of pain medications and associated high pain sensitivity could be related to the patient's genetic predisposition in CYP2D6 and COMT, warranting further investigation in a larger patient sample.

Weathering the Pain: Ambient Temperature's Role in Chronic Pain Syndromes

PURPOSE OF REVIEW

Chronic pain is highly prevalent and involves a complex interaction of sensory, emotional, and cognitive processes, significantly influenced by ambient temperature. Despite advances in pain management, many patients continue to experience inadequate pain relief. This review aims to consolidate and critically evaluate the current evidence on the impact of ambient temperature on chronic pain conditions such as fibromyalgia (FM), multiple sclerosis (MS), complex regional pain syndrome (CRPS), and osteoarthritis (OA).

RECENT FINDINGS

Patients with FM often report pain exacerbations due to temperature changes, with studies showing lower thresholds for heat and cold-induced pain compared to healthy controls. In MS, the Uhthoff phenomenon, characterized by temperature-induced neurological deterioration, underscores the significance of ambient temperature in pain management. CRPS patients exhibit heightened pain sensitivity to temperature changes, with both warm and cold stimuli potentially aggravating symptoms. OA patients frequently report increased pain and rigidity associated with lower temperatures and higher humidity. Understanding the mechanisms through which temperature influences pain can enhance pain management strategies. This review highlights the need for further research to elucidate these mechanisms and develop targeted interventions, ultimately improving the quality of life for individuals with chronic pain conditions.

Early diagnostics of fibromyalgia: an overview of the challenges and opportunities

INTRODUCTION

Fibromyalgia is a common pain disorder with features of widespread musculoskeletal pain, fatigue, disrupted sleep, cognitive dysfunction, autonomic dysfunction, and mood disorders. Despite its high prevalence and significant impact on quality of life, the diagnosis and management of fibromyalgia remain challenging. Advancements in classification and diagnostics in broad areas have improved our understanding and treatment approach for this condition. We culminate with a discussion of future directions for research into early diagnostics in fibromyalgia.

AREAS COVERED

This perspective examines the current landscape of fibromyalgia biomarker discovery, highlighting challenges that must be addressed and opportunities that are presented as the field evolves.

EXPERT OPINION

Advances in fibromyalgia diagnostics provide an opportunity to dramatically reduce the cost burden placed on health resources for fibromyalgia once we have discovered a reliable reproducible biomarker that is widely accepted among practitioners and patients. Promising results in a number of fields may lead to point of care technologies that will be applicable in the office or bedside without the need for transport to specialized centers. Future research should focus on integrating these various diagnostic approaches to develop a comprehensive, multi-modal diagnostic tool for fibromyalgia.

Epigenetic Control in Schizophrenia

Schizophrenia is a severe and complex psychiatric condition ranking among the top 15 leading causes of disability worldwide. Despite the well-established heritability component, a complex interplay between genetic and environmental risk factors plays a key role in the development of schizophrenia and psychotic disorders in general. This chapter covers all the clinical evidence showing how the analysis of the epigenetic modulation in schizophrenia might be relevant to understand the pathogenesis of schizophrenia as well as potentially useful to develop new pharmacotherapies.

The polymorphism Val158Met in the COMT gene: disrupted dopamine system in fibromyalgia patients?

ABSTRACT

The single-nucleotide polymorphism (SNP) rs4680 in the catechol-O-methyltransferase gene ( COMT ) is a missense variant (Val158Met) associated with altered activity of the COMT enzyme and suggested as a predictive feature for developing some chronic pain conditions. However, there are controversial results on its role in fibromyalgia (FM). Here, the SNP Val158Met was analyzed in 294 FM patients (without comorbidities) and 209 healthy controls (without chronic pain). The concurrent impact of Val158Met genotypes and FM comorbid disorders (depression and sleep impairment) on FM risk were tested. In addition, the genotypic distribution of FM patients in relation to pain intensity was evaluated. The G allele (Val) resulted in being more represented in the FM group (57.8%) compared with the control group (48.8%; P = 0.037). Logistic regression highlighted that having the G/G (Val/Val) homozygous genotype was associated with 2 times higher risk of having FM compared with the A/A (Met/Met) carriers ( P = 0.038), whereas depression and sleep impairment increased FM risk by 12 and 8 times, respectively ( P < 0.001). However, considering only the FM patient group, the A/A homozygous genotype was significantly associated with severe pain intensity ( P = 0.007). This study highlighted associations between the SNP Val158Met and both FM and pain intensity, suggesting a link between dopaminergic dysfunction and vulnerability to chronic pain. Further studies should explore this SNP in FM patients in conjunction with COMT enzymatic activity and other symptoms connected with the dopaminergic system such as depression or sleep impairment.

Association of OPRM1 rs1799971, HTR1B rs6296 and COMT rs4680 polymorphisms with clinical phenotype among women with fibromyalgia

To investigate the association between three selected pain polymorphisms and clinical, functional, sensory-related, psychophysical, psychological or cognitive variables in a sample of women with fibromyalgia (FMS). One hundred twenty-three (n = 123) women with FMS completed demographic (age, height, weight), clinical (years with pain, intensity of pain at rest and during daily living activities), functional (quality of life, physical function), sensory-related (sensitization-associated and neuropathic-associated symptoms), psychophysical (pressure pain thresholds), psychological (sleep quality, depressive and anxiety level) and cognitive (pain catastrophizing, kinesiophobia) variables. Those three genotypes of the OPRM1 rs1799971, HTR1B rs6296 and COMT rs4680 single nucleotide polymorphisms were obtained by polymerase chain reactions from no-stimulated whole saliva collection. No significant differences in demographic, clinical, functional, sensory-related, psychophysical, psychological and cognitive variables according to OPRM1 rs1799971, HTR1B rs6296 or COMT rs4680 genotype were identified in our sample of women with FMS. A multilevel analysis did not either reveal any significant gene-to-gene interaction between OPRM1 rs1799971 x HTR1B rs6296, OPRM1 rs1799971 x COMT rs4680 and HTR1B rs6296 x COMT rs4680 for any of the investigated outcomes. This study revealed that three single nucleotide polymorphisms, OPRM1 rs1799971, HTR1B rs6296 or COMT rs4680, mostly associated with chronic pain were not involved in phenotyping features of FMS. Potential gene-to-gene interaction and their association with clinical phenotype in women with FMS should be further investigated in future studies including large sample sizes.

Distinctive Patterns of 5-Methylcytosine and 5-Hydroxymethylcytosine in Schizophrenia

Schizophrenia is a highly heritable neuropsychiatric disorder characterized by cognitive and social dysfunction. Genetic, epigenetic, and environmental factors are together implicated in the pathogenesis and development of schizophrenia. DNA methylation, 5-methycytosine (5mC) and 5-hydroxylcytosine (5hmC) have been recognized as key epigenetic elements in neurodevelopment, ageing, and neurodegenerative diseases. Recently, distinctive 5mC and 5hmC pattern and expression changes of related genes have been discovered in schizophrenia. Antipsychotic drugs that affect 5mC status can alleviate symptoms in patients with schizophrenia, suggesting a critical role for DNA methylation in the pathogenesis of schizophrenia. Further exploring the signatures of 5mC and 5hmC in schizophrenia and developing precision-targeted epigenetic drugs based on this will provide new insights into the diagnosis and treatment of schizophrenia.

DNMT1 SNPs (rs2114724 and rs2228611) associated with positive symptoms in Chinese patients with schizophrenia

OBJECTIVE

Schizophrenia is a serious mental disorder with complex clinical manifestations, while its pathophysiological mechanism is not fully understood. Accumulated evidence suggested the alteration in epigenetic pathway was associated with clinical features and brain dysfunctions in schizophrenia. DNA methyltransferases (DNMTs), a key enzyme for DNA methylation, are related to the development of schizophrenia, whereas the current research evidence is not sufficient. The aim of study was to explore the effects of gene polymorphisms of DNMTs on the susceptibility and symptoms of schizophrenia.

METHODS

The study was case-control study that designed and employed the Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) as the diagnostic standard. 134 hospitalized patients with schizophrenia in the Third People's Hospital of Zhongshan City from January 2018 to April 2020 (Case group) as well as 64 healthy controls (Control group) from the same region were involved. Single nucleotide polymorphisms (SNPs) of DNMT1 genes (r s2114724 and rs 2228611) and DNMT3B genes (rs 2424932, rs 1569686, rs 6119954 and rs 2424908) were determined with massARRAY. Linkage disequilibrium analysis and haplotype analysis were performed, and genotype and allele frequencies were compared. The Hardy-Weinberg equilibrium was tested by the Chi-square test in SPSS software (version 20.0, SPSS Inc., USA). The severity of clinical symptoms was assessed by the Positive and Negative Syndrome Scale (PANSS). The correlation between DNMT1 genes (rs 2114724 and rs 2228611) and DNMT3B genes (rs2424932, rs1569686, rs6119954 and rs2424908) and clinical features was analyzed.

RESULTS

There were no significant differences in genotype, allele frequency and haplotype of DNMT1 genes (rs 2114724 and rs 2228611) and DNMT3B genes (rs 2424932, rs 1569686, rs 6119954 and rs 2424908) between the case and healthy control group. There were significant differences in the PANSS total positive symptom scores, P3 (hallucinatory behavior), P6 (suspicious/persecution), G7 (motor retardation), and G15 (preoccupation) in patients with different DNMT1 gene rs 2114724 and rs 2228611 genotypes. The linkage disequilibrium analysis of gene polymorphic loci revealed that rs 2114724-rs 2228611 was complete linkage disequilibrium, and rs 1569686-rs 2424908, rs 2424932-rs 1569696 and rs 2424932-rs 2424908 were strongly linkage disequilibrium.

CONCLUSION

The polymorphisms alteration in genetic pathway may be associated with development of specific clinical features in schizophrenia.

A Comprehensive Review of the Genetic and Epigenetic Contributions to the Development of Fibromyalgia

This narrative review summarizes the current knowledge of the genetic and epigenetic contributions to the development of fibromyalgia (FM). Although there is no single gene that results in the development of FM, this study reveals that certain polymorphisms in genes involved in the catecholaminergic pathway, the serotonergic pathway, pain processing, oxidative stress, and inflammation may influence susceptibility to FM and the severity of its symptoms. Furthermore, epigenetic changes at the DNA level may lead to the development of FM. Likewise, microRNAs may impact the expression of certain proteins that lead to the worsening of FM-associated symptoms.

Point-of-Care Testing of Enzyme Polymorphisms for Predicting Hypnotizability and Postoperative Pain

Hypnotizability is a stable trait that moderates the benefit of hypnosis for treating pain, but limited availability of hypnotizability testing deters widespread use of hypnosis. Inexpensive genotyping of four single-nucleotide polymorphisms in the catechol-o-methyltransferase (COMT) gene was performed using giant magnetoresistive biosensors to determine if hypnotizable individuals can be identified for targeted hypnosis referrals. For individuals with the proposed optimal COMT diplotypes, 89.5% score highly on the Hypnotic Induction Profile (odds ratio, 6.12; 95% CI, 1.26-28.75), which identified 40.5% of the treatable population. Mean hypnotizability scores of the optimal group were significantly higher than the total population (P = 0.015; effect size = 0.60), an effect that was present in women (P = 0.0015; effect size = 0.83), but not in men (P = 0.28). In an exploratory cohort, optimal individuals also reported significantly higher postoperative pain scores (P = 0.00030; effect size = 1.93), indicating a greater need for treatment.

How Deepbics Quantifies Intensities of Transcription Factor-DNA Binding and Facilitates Prediction of Single Nucleotide Variant Pathogenicity With a Deep Learning Model Trained On ChIP-Seq Data Sets

The binding of DNA sequences to cell type-specific transcription factors is essential for regulating gene expression in all organisms. Many variants occurring in these binding regions play crucial roles in human disease by disrupting the cis-regulation of gene expression. We first implemented a sequence-based deep learning model called deepBICS to quantify the intensity of transcription factors-DNA binding. The experimental results not only showed the superiority of deepBICS on ChIP-seq data sets but also suggested deepBICS as a language model could help the classification of disease-related and neutral variants. We then built a language model-based method called deepBICS4SNV to predict the pathogenicity of single nucleotide variants. The good performance of deepBICS4SNV on 2 tests related to Mendelian disorders and viral diseases shows the sequence contextual information derived from language models can improve prediction accuracy and generalization capability.

Working memory dysfunction in fibromyalgia is associated with genotypes of the catechol- O-methyltransferase gene: an event-related potential study

Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic-pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioral responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioral outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient's strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.

Polymorphisms in COMT and OPRM1 Collectively Contribute to Chronic Shoulder Pain and Disability in South African Breast Cancer Survivors'

Chronic shoulder pain and disability is a common adverse effect experienced by >40% of breast cancer survivors (BCS). Pain management protocols for acute and chronic pain include the use of opioids and opioid derivatives. Furthermore, pain-modulating genes, such as COMT and OPRM1, have been linked to the aetiology of chronic pain. This study aimed to investigate the association between genetic variants of major pain modulator genes and chronic pain/disability in BCS. Assessment of pain, disability and combined (pain and disability) symptoms were determined using the Shoulder Pain and Disability Index (SPADI). Participants were grouped according to their scores such as no-low (<30%) and moderate-high (≥30%) groups of pain, disability and combined (pain and disability). Genotyping of the COMT rs6269 (A > G), rs4633 (C > T), rs4818 (C > G) and the functional rs4680(G > A) SNPs within the BCS (N = 252) cohort were conducted using TaqMan^® SNP assays. Genotype, allele, haplotype, and allele-allele combination frequencies were evaluated. Statistical analysis was applied, with significance accepted at p < 0.05. The COMT rs4680:A/A genotype was significantly associated with moderate-high pain (p = 0.024, OR: 3.23, 95% CI: 1.33-7.81) and combined (pain and disability) (p = 0.015, OR: 3.81, 95% CI: 1.47-9.85). The rs4680:A allele was also significantly associated with moderate-high pain (p = 0.035, OR: 1.58, 95% CI: 1.03-2.43) and combined (pain and disability) (p = 0.017, OR: 1.71, 95% CI: 1.07-2.71). For the inferred COMT (rs6269 A > G-rs4680 G > A) haplotype analyses, the G-G (p = 0.026, OR: 0.67, 95% CI: 0.38-1.18) and A-A (p = 0.007, OR: 2.09, 95% CI: 0.89-4.88) haplotypes were significantly associated with reduced and increased likelihoods of reporting moderate-high pain, respectively. The inferred A-A (p = 0.003, OR: 2.18, 95% CI: 0.92-5.17) haplotype was also significantly associated with combined (pain and disability). Gene-gene interaction analyses further showed allele-allele combinations for COMT (rs4680 G > A)-OPRM1 (rs1799971 A > G) and COMT (rs4680 G > A)-OPRM1(rs540825 T > A) were associated with reporting pain and combined (pain and disability) symptoms, p < 0.05. The findings of this study suggest that COMT and OPRM1 SNPs play a role in the development of chronic shoulder pain/disability in BCS in a unique South African cohort from the Western Cape.

No Association between Genetic Variants of the COMT and OPRM1 Genes and Pain Perception among Patients Undergoing Total Hip or Knee Arthroplasty for Primary Osteoarthritis

Each year approximately 1 million total hip replacements are performed worldwide. The most common indications to choose this procedure are rest pain and pain after activity as well as functional limitations influencing daily activities. Experimental pain is highly variable by individuals, which is partly due to genetics. The aim of the study was to investigate a possible association of the catechol-O-methyltransferase (COMT) and μ-opioid receptor (OPRM1) genotypes with pain perception in patients undergoing total hip replacement and total knee replacement taking into account aspects such as age, sex and diabetes. The study included 207 patients (119 females, 88 males, median age 65 years, range 33−77) that qualified for surgical treatment (total hip replacement and knee arthroplasty) due to osteoarthritis. Pain sensitivity measurement was performed using a standard algometer. The genomic DNA was extracted from the buccal cells.. Single locus analysis was conducted using a general linear model. In the study group, we did not find statistically significant genetic associations between variants of COMT and OPRM1 and pain thresholds/pain tolerance. The analysis of subjective pain perception using the visual analog scale did not show any relationship between the OPRM1 rs1799971A>G variant and COMT rs4680, rs4633, rs4818 and rs6269.

In Silico Molecular Docking Analysis of Karanjin against Alzheimer's and Parkinson's Diseases as a Potential Natural Lead Molecule for New Drug Design, Development and Therapy

Parkinson's disease (PD) and Alzheimer's disease (AD) are neurodegenerative disorders that have emerged as among the serious health problems of the 21st century. The medications currently available to treat AD and PD have limited efficacy and are associated with side effects. Natural products are one of the most vital and conservative sources of medicines for treating neurological problems. Karanjin is a furanoflavonoid, isolated mainly from Pongamia pinnata with several medicinal plants, and has been reported for numerous health benefits. However, the effect of karanjin on AD and PD has not yet been systematically investigated. To evaluate the neuroprotective effect of karanjin, extensive in silico studies starting with molecular docking against five putative targets for AD and four targets for PD were conducted. The findings were compared with three standard drugs using Auto Dock 4.1 and Molegro Virtual Docker software. Additionally, the physiochemical properties (Lipinski rule of five), drug-likeness and parameters including absorption, distribution, metabolism, elimination and toxicity (ADMET) profiles of karanjin were also studied. The molecular dynamics (MD) simulations were performed with two selective karanjin docking complexes to analyze the dynamic behaviors and binding free energy at 100 ns time scale. In addition, frontier molecular orbitals (FMOs) and density-functional theory (DFT) were also investigated from computational quantum mechanism perspectives using the Avogadro-ORCA 1.2.0 platform. Karanjin complies with all five of Lipinski's drug-likeness rules with suitable ADMET profiles for therapeutic use. The docking scores (kcal/mol) showed comparatively higher potency against AD and PD associated targets than currently used standard drugs. Overall, the potential binding affinity from molecular docking, static thermodynamics feature from MD-simulation and other multiparametric drug-ability profiles suggest that karanjin could be considered as a suitable therapeutic lead for AD and PD treatment. Furthermore, the present results were strongly correlated with the earlier study on karanjin in an Alzheimer's animal model. However, necessary in vivo studies, clinical trials, bioavailability, permeability and safe dose administration, etc. must be required to use karanjin as a potential drug against AD and PD treatment, where the in silico results are more helpful to accelerate the drug development.

Multi-Site Observational Study to Assess Biomarkers for Susceptibility or Resilience to Chronic Pain: The Acute to Chronic Pain Signatures (A2CPS) Study Protocol

Chronic pain has become a global health problem contributing to years lived with disability and reduced quality of life. Advances in the clinical management of chronic pain have been limited due to incomplete understanding of the multiple risk factors and molecular mechanisms that contribute to the development of chronic pain. The Acute to Chronic Pain Signatures (A2CPS) Program aims to characterize the predictive nature of biomarkers (brain imaging, high-throughput molecular screening techniques, or "omics," quantitative sensory testing, patient-reported outcome assessments and functional assessments) to identify individuals who will develop chronic pain following surgical intervention. The A2CPS is a multisite observational study investigating biomarkers and collective biosignatures (a combination of several individual biomarkers) that predict susceptibility or resilience to the development of chronic pain following knee arthroplasty and thoracic surgery. This manuscript provides an overview of data collection methods and procedures designed to standardize data collection across multiple clinical sites and institutions. Pain-related biomarkers are evaluated before surgery and up to 3 months after surgery for use as predictors of patient reported outcomes 6 months after surgery. The dataset from this prospective observational study will be available for researchers internal and external to the A2CPS Consortium to advance understanding of the transition from acute to chronic postsurgical pain.

Polymorphisms in the HTR2A and HTR3A Genes Contribute to Pain in TMD Myalgia

Background: The aim of this study was to investigate if single nucleotide polymorphisms (SNPs) related to monoaminergic neurotransmission, in particular the serotonergic pathway, contribute to pain perception in patients with temporomandibular disorder (TMD) myalgia and if there is a correlation to jaw function as well as psychosocial factors such as stress, anxiety and depression.

Materials and Methods: One hundred and seventeen individuals with TMD myalgia were included. A venous blood or saliva sample was taken for genetic analyses and genotyped regarding HTR2A (rs9316233) HTR3A (rs1062613), HTR3B (rs1176744), SERT (5-HTTLPR) and COMT (rs4680). A clinical examination according to Diagnostic Criteria for TMD (DC/TMD) was performed and axis II data (psychosocial factors) were compared between participants with different genotypes for each gene using Kruskall–Wallis test. The characteristic pain intensity (CPI) was tested for correlations to scores for the Perceived Stress Scale, Generalized Anxiety Disorder, and Patient Health Questionnaires using Spearman's rank correlation test with Bonferroni correction for multiple testing. To further explore data factor analysis was performed to identify latent factors associated to the outcome variables.

Results: Participants carrying at least one copy of the rare allele of the HTR2A (rs9316233) and HTR3A (rs1062613) had higher CPI compared with the participants with the homozygous common genotype (P = 0.042 and P = 0.024, respectively). Correlation analyses showed several significant positive correlations between CPI on one hand, and self-reported psychosocial distress and jaw function on the other hand for several genotypes that mostly were weak to moderate. The factor analysis identified two latent variables. One was positively correlated to the HTR3B gene, jaw function and self-reported parafunctions, and the other was positively correlated to psychological distress and negatively correlated to SERT.

Conclusion: Taken together, the polymorphism rs1062613 in the HTR3A gene contributes to pain intensity in TMD myalgia. This together with positive interactions between pain variables and psychological factors in genotypes strengthens that pain and psychological distress are related. Further research is needed to explore this as well as the influence of gene-to-gene interactions on pain and psychological distress.

UNRAVELING THE CLINICO-GENETIC ASSOCIATION OF CATECHOL-O-METHYLTRANSFERASE-RS4680 G>A GENE POLYMORPHISM IN WOMEN WITH FIBROMYALGIA SYNDROME

OBJECTIVE

The aim: To determine the clinical and the genetic association of the COMT rs4680 SNP in women with FMS.

PATIENTS AND METHODS

Materials and methods: Extracted DNA from peripheral blood samples were utilized as template for the PCR and RFLP analysis.

RESULTS

Results: A significant difference was found in the distribution of the COMT genotype between FMS patients and controls (P<0.05). The frequency of GG, AG, AA genotypes were 12%, 72%, 21% in FMS patients and 32%, 62%, 11% in controls. The clinical features of FMS reveal that FIQR and the severity of pain measured by VAS were significantly associated with the COMT rs4680 SNP (P=0.042; P=0.016). The co-dominant model for GG verse v. AG genotype (P=0.004) and AG v. AA genotype (P=0.002) has shown to be high risk for FMS. An increased risk of FMS in the dominant model for (AG+AA) v. GG genotype (P=0.001) and no significant difference was found between (GG+AG) v. AA genotype (P=0.08) in the recessive model. The result indicated that A allele considerably increase the risk of FMS (P=0.004) in comparison to the G allele.

CONCLUSION

Conclusions: AA genotype and A allele of the COMT rs4680 SNP were significantly associated with severity in FMS patients and also plays a significant role in the clinical manifestation of this disease.

Tactile Detection in Fibromyalgia: A Systematic Review and a Meta-Analysis

Fibromyalgia is a chronic pain syndrome characterized by sensorimotor deficits and distortions of body representation, that could both be caused by alterations in sensory processing. Several studies suggest a hypersensitivity to various sensory stimulations in fibromyalgia but results on detection of both noxious and non-noxious tactile stimulation, which are particularly relevant for body representation and motor control, remain conflicting. Therefore, the aim of this study is to systematically review and quantify the detection thresholds to noxious and non-noxious tactile stimuli in individuals with fibromyalgia compared to pain-free controls. A systematic review and a meta-analysis were performed in the MEDLINE, EMBASE, CINAHL, Cochrane, PsycInfo and Web of Science databases using keywords related to fibromyalgia, tactile pain detection threshold, tactile detection threshold and quantitative sensory testing. Nineteen studies were included in the review, with 12 in the meta-analysis. Despite the heterogeneity of the results, the data from both the review and from the meta-analysis suggest a trend toward hyperalgesia and no difference of sensitivity to non-noxious tactile stimuli in participants with fibromyalgia compared to healthy controls. This contradicts the hypothesis of a general increase in responsiveness of the central nervous system to noxious and non-noxious stimulations in fibromyalgia. This study shows no alteration of the sensitivity to non-noxious tactile stimulation in fibromyalgia, suggesting that an altered unimodal processing is not sufficient to explain symptoms such as sensorimotor impairments and body representation distortions. Future research should investigate whether alterations in multisensory integration could contribute to these symptoms.

Influence of Catechol-O-Methyltransferase Gene Polymorphism on the Correlation between Alexithymia and Hypervigilance to Pain

The psychological characteristic of having difficulty expressing emotions, known as alexithymia, is associated with hypervigilance to pain and is considered one of the risk factors for chronic pain. The correlation between alexithymia and hypervigilance to pain can be observed even in healthy individuals. However, the factors influencing this correlation remain unknown. We explored the dopamine system, which is known to be involved in emotion and pain. The dopamine-degrading enzyme catechol-O-methyltransferase (COMT) has a genetic polymorphism known to influence dopamine metabolism in the prefrontal cortex. COMT polymorphism reportedly affects various aspects of pain and increases pain sensitivity in Met allele carriers. Therefore, we investigated whether the correlation between alexithymia and hypervigilance to pain is influenced by COMT polymorphism in healthy individuals. The results revealed a significant positive correlation between the "difficulty describing feelings" of the 20-item Toronto Alexithymia Scale and the "attention to changes in pain" of the pain vigilance and awareness questionnaire in COMT Met carriers but not in Val/Val individuals. This finding suggests that the correlation between alexithymia and hypervigilance to pain is influenced by COMT polymorphism.

Interplay between genetics and lifestyle on pain susceptibility in women with fibromyalgia: The al-Ándalus project

Objectives

It is widely acknowledged that the experience of pain is promoted by both genetic susceptibility and environmental factors such as engaging in physical activity (PA), and that pain-related cognitions are also important. Thus, the purpose of the present study was to test the association of 64 polymorphisms (34 candidate genes) and the gene–gene, gene–PA and gene–sedentary behaviour interactions with pain and pain-related cognitions in women with FM.

Methods

Saliva samples from 274 women with FM [mean (s.d.) age 51.7 (7.7) years] were collected for extracting DNA. We measured PA and sedentary behaviour by accelerometers for a week, pain with algometry and questionnaires, and pain-related cognitions with questionnaires. To assess the robustness of the results, a meta-analysis was also performed.

Results

The rs6311 and rs6313 polymorphisms (5-hydroxytryptamine receptor 2A, HTR2A) were individually related to algometer scores. The interaction of rs4818 (catechol-O-methyltransferase, COMT) and rs1799971 (opioid receptor μ gene, OPRM1) was related to pain catastrophizing. Five gene–behaviour interactions were significant: the interactions of sedentary behaviour with rs1383914 (adrenoceptor alpha 1A, ADRA1A), rs6860 (charged multivesicular body protein 1A, CHMP1A), rs4680 (COMT), rs165599 (COMT) and rs12994338 (SCN9A) on bodily pain subscale of the Short Form 36. Furthermore, the meta-analysis showed an association between rs4680 (COMT) and severity of FM symptoms (codominant model, P-value 0.032).

Conclusion

The HTR2A gene (individually), COMT and OPRM1 gene–gene interaction, and the interactions of sedentary behaviour with ADRA1A, CHMP1A, COMT and SCN9A genes were associated with pain-related outcomes. Collectively, findings from the present study indicate a modest contribution of genetics and gene–sedentary behaviour interaction to pain and pain catastrophizing in women with FM. Future research should examine whether reducing sedentary behaviour is particularly beneficial for reducing pain in women with genetic susceptibility to pain.

Genetic variation in catechol-O-methyltransferase is associated with individual differences in conditioned pain modulation in healthy subjects

BACKGROUND

Genetic variation in the catechol-O-methyltransferase (COMT) gene is associated with sensitivity to both acute experimental pain and chronic pain conditions. Four single nucleotide polymorphisms (SNPs) have traditionally been used to infer three common haplotypes designated as low, average and high pain sensitivity and are reported to affect both COMT enzymatic activity and pain sensitivity. One mechanism that may partly explain individual differences in sensitivity to pain is conditioned pain modulation (CPM). We hypothesized that variation in CPM may have a genetic basis.

METHODS

We evaluated CPM in 77 healthy pain-free Caucasian subjects by applying repeated mechanical stimuli to the dominant forearm using 26-g von Frey filament as the test stimulus with immersion of the non-dominant hand in hot water as the conditioning stimulus. We assayed COMT SNP genotypes by the TaqMan method using DNA extracted from saliva.

RESULTS

SNP rs4680 (val¹⁵⁸ met) was not associated with individual differences in CPM. However, CPM was associated with COMT low pain sensitivity haplotypes under an additive model (p = 0.004) and the effect was independent of gender.

CONCLUSIONS

We show that, although four SNPs are used to infer COMT haplotypes, the low pain sensitivity haplotype is determined by SNP rs6269 (located in the 5' regulatory region of COMT), suggesting that inherited variation in gene expression may underlie individual differences in pain modulation. Analysis of 13 global populations revealed that the COMT low pain sensitivity haplotype varies in frequency from 13% to 44% and showed that two SNPs are sufficient to distinguish all COMT haplotypes in most populations.

DNA Methylation and Schizophrenia: Current Literature and Future Perspective

Schizophrenia is a neuropsychiatric disorder characterized by dissociation of thoughts, idea, identity, and emotions. It has no central pathophysiological mechanism and precise diagnostic markers. Despite its high heritability, there are also environmental factors implicated in the development of schizophrenia. Epigenetic factors are thought to mediate the effects of environmental factors in the development of the disorder. Epigenetic modifications like DNA methylation are a risk factor for schizophrenia. Targeted gene approach studies attempted to find candidate gene methylation, but the results are contradictory. Genome-wide methylation studies are insufficient in literature and the available data do not cover different populations like the African populations. The current genome-wide studies have limitations related to the sample and methods used. Studies are required to control for these limitations. Integration of DNA methylation, gene expression, and their effects are important in the understanding of the development of schizophrenia and search for biomarkers. There are currently no precise and functional biomarkers for the disorder. Several epigenetic markers have been reported to be common in functional and peripheral tissue. This makes the peripheral tissue epigenetic changes a surrogate of functional tissue, suggesting common epigenetic alteration can be used as biomarkers of schizophrenia in peripheral tissue.

Polymorphisms of Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 genes in trigeminal neuralgia

SUBJECTS

Trigeminal neuralgia is a neuropathic pain characterized by episodes of severe shock-like pain within the distribution of one or more divisions of the trigeminal nerve. Pain can be influenced by ethnicity, environment, gender, psychological traits, and genetics. Molecules Nav1.6 sodium channel, Brain-derived Neurotrophic Factor, Catechol-O-methyltransferase and Guanosine Triphosphate Cyclohydrolase 1 have been involved in mechanisms that underlie pain and neurological conditions.

OBJECTIVE

The aim of this case-control study was to investigate the occurrence of genetic polymorphisms in Nav1.6 sodium channel (SCN8A/rs303810), Brain-derived Neurotrophic Factor (BDNF/rs6265/Val66Met), Catechol-O-methyltransferase (COMT/rs4680/Val158Met), and Guanosine Triphosphate Cyclohydrolase 1 (GCH1/rs8007267) genes in trigeminal neuralgia patients.

METHODS

Ninety-six subjects were divided into two groups: 48 with trigeminal neuralgia diagnosis and 48 controls. Pain was evaluated by visual analog scale and genomic DNA was obtained from oral swabs and analyzed by real-time polymerase chain reaction.

RESULTS

No association was observed among SCN8A, BDNF, COMT or GCH1 polymorphisms and the presence of trigeminal neuralgia. Genotype distribution and allele frequencies did not correlate to pain severity.

CONCLUSIONS

Although no association of evaluated polymorphisms and trigeminal neuralgia or pain was observed, our data contributes to the knowledge of genetic susceptibility to trigeminal neuralgia, which is very scarce. Further studies may focus on other polymorphisms and mutations, as well as on epigenetics and transcriptional regulation of these genes, in order to clarify or definitively exclude the role of Nav1.6, BDNF, COMT or GCH1 in trigeminal neuralgia susceptibility and pathophysiology.

Fear of pain moderates the relationship between self-reported fatigue and methionine allele of catechol-O-methyltransferase gene in patients with fibromyalgia

Previous research has shown a consistent association among genetic factors, psychological symptoms and pain associated with fibromyalgia. However, how these symptoms interact to moderate genetic factors in fibromyalgia has rarely been studied to date. The present research investigates whether psychological symptoms can moderate the effects of catechol-O-methyltransferase on pain and fatigue. A total of 108 women diagnosed with fibromyalgia and 77 healthy control participants took part in the study. Pain, fatigue, and psychological symptoms (anxiety, depression, pain catastrophizing, fear of pain and fear of movement) were measured by self-report questionnaires. Two types of statistical analyses were performed; the first was undertaken to explore the influences of COMT genotypes on clinical symptoms by comparing patients with fibromyalgia and healthy controls. In the second analysis, moderation analyses to explore the role of psychological symptoms as potential factors that moderate the relationship between pain/fatigue and COMT genotypes were performed. The main results indicated that patients carrying the Met/Met genotype reported significantly higher levels of fatigue than heterozygote carriers (i.e., Met/Val genotype) and higher levels of fatigue, but not significantly different, than Val homozygote carriers. Among patients with fibromyalgia carrying methionine alleles (i.e., Met/Met + Met/Val carriers), only those who scored high on medical fear of pain, experienced an intensified feeling of fatigue. Thus, the present research suggests that fear of pain, as a psychological symptom frequently described in fibromyalgia may act as a moderating factor in the relationship between the Met allele of the COMT gene and the increase or decrease in self-reported fatigue. Although further research with wider patient samples is needed to confirm the present findings, these results point out that the use of psychological interventions focused on affective symptomatology might be a useful tool to reduce the severity of fibromyalgia.

A Pilot Study Investigating the Role of Gender in the Intergenerational Relationships between Gene Expression, Chronic Pain, and Adverse Childhood Experiences in a Clinical Sample of Youth with Chronic Pain

Chronic pain is a highly prevalent and costly issue that often emerges during childhood or adolescence and persists into adulthood. Adverse childhood experiences (ACEs) increase risk for several adverse health conditions, including chronic pain. Recent evidence suggests that parental trauma (ACEs, post-traumatic stress disorder (PTSD) symptoms) confers risk of poor health outcomes in their children. Intergenerational relationships between parental trauma and child chronic pain may be mediated by epigenetic mechanisms. A clinical sample of youth with chronic pain and their parents completed psychometrically sound questionnaires assessing ACEs, PTSD symptoms, and chronic pain, and provided a saliva sample. These were used to investigate the intergenerational relationships between four epigenetic biomarkers (COMT, DRD2, GR, and SERT), trauma, and chronic pain. The results indicated that the significant biomarkers were dependent upon the gender of the child, wherein parental ACEs significantly correlated with changes in DRD2 expression in female children and altered COMT expression in the parents of male children. Additionally, the nature of the ACE (maltreatment vs. household dysfunction) was associated with the specific epigenetic changes. There may be different pathways through which parental ACEs confer risk for poor outcomes for males and females, highlighting the importance of child gender in future investigations.

Fibromyalgia: Pathogenesis, Mechanisms, Diagnosis and Treatment Options Update

Fibromyalgia is a syndrome characterized by chronic and widespread musculoskeletal pain, often accompanied by other symptoms, such as fatigue, intestinal disorders and alterations in sleep and mood. It is estimated that two to eight percent of the world population is affected by fibromyalgia. From a medical point of view, this pathology still presents inexplicable aspects. It is known that fibromyalgia is caused by a central sensitization phenomenon characterized by the dysfunction of neuro-circuits, which involves the perception, transmission and processing of afferent nociceptive stimuli, with the prevalent manifestation of pain at the level of the locomotor system. In recent years, the pathogenesis of fibromyalgia has also been linked to other factors, such as inflammatory, immune, endocrine, genetic and psychosocial factors. A rheumatologist typically makes a diagnosis of fibromyalgia when the patient describes a history of pain spreading in all quadrants of the body for at least three months and when pain is caused by digital pressure in at least 11 out of 18 allogenic points, called tender points. Fibromyalgia does not involve organic damage, and several diagnostic approaches have been developed in recent years, including the analysis of genetic, epigenetic and serological biomarkers. Symptoms often begin after physical or emotional trauma, but in many cases, there appears to be no obvious trigger. Women are more prone to developing the disease than men. Unfortunately, the conventional medical therapies that target this pathology produce limited benefits. They remain largely pharmacological in nature and tend to treat the symptomatic aspects of various disorders reported by the patient. The statistics, however, highlight the fact that 90% of people with fibromyalgia also turn to complementary medicine to manage their symptoms.

The association between selected genetic variants and individual differences in experimental pain

OBJECTIVES

The underlying mechanisms for individual differences in experimental pain are not fully understood, but genetic susceptibility is hypothesized to explain some of these differences. In the present study we focus on three genetic variants important for modulating experimental pain related to serotonin (SLC6A4 5-HTTLPR/rs25531 A>G), catecholamine (COMT rs4680 Val158Met) and opioid (OPRM1 rs1799971 A118G) signaling. We aimed to investigate associations between each of the selected genetic variants and individual differences in experimental pain.

METHODS

In total 356 subjects (232 low back pain patients and 124 healthy volunteers) were genotyped and assessed with tests of heat pain threshold, pressure pain thresholds, heat pain tolerance, conditioned pain modulation (CPM), offset analgesia, temporal summation and secondary hyperalgesia. Low back pain patients and healthy volunteers did not differ in regards to experimental test results or allelic frequencies, and were therefore analyzed as one group. The associations were tested using analysis of variance and the Kruskal-Wallis test.

RESULTS

No significant associations were observed between the genetic variants (SLC6A4 5-HTTLPR/rs25531 A>G, COMT rs4680 Val158Met and OPRM1 rs1799971 A118G) and individual differences in experimental pain (heat pain threshold, pressure pain threshold, heat pain tolerance, CPM, offset analgesia, temporal summation and secondary hyperalgesia).

CONCLUSIONS

The selected pain-associated genetic variants were not associated with individual differences in experimental pain. Genetic variants well known for playing central roles in pain perception failed to explain individual differences in experimental pain in 356 subjects. The finding is an important contribution to the literature, which often consists of studies with lower sample size and one or few experimental pain assessments.

Effects of COMT Genotypes on Working Memory Performance in Fibromyalgia Patients

Growing research has reported the presence of a clear impairment of working memory functioning in fibromyalgia. Although different genetic factors involving dopamine availability (i.e, the COMT gene) have been associated with the more severe presentation of key symptoms in fibromyalgia, scientific evidence regarding the influence of COMT genotypes on cognitive impairment in these patients is still lacking. To this end, 167 participants took part in the present investigation. Working memory performance was assessed by the application of the SST (Spatial Span Test) and LNST (Letter and Number Sequence Test) belonging to the Weschler Memory Scale III. Significant working memory impairment was shown by the fibromyalgia patients. Remarkably, our results suggest that performance according to different working memory measures might be influenced by different genotypes of the COMT gene. Specifically, fibromyalgia patients carrying the Val/Val genotype exhibited significantly worse outcomes for the span of SST backward, SST backward score, SST total score and the Working Memory Index (WMI) than the Val/Val healthy carriers. Furthermore, the Val/Val patients performed worse on the SST backward and SST score than heterozygotes. Our findings are the first to show a link between the COMT gene and working memory dysfunction in fibromyalgia, supporting the idea that higher COMT enzyme activity would contribute to more severe working memory impairment in fibromyalgia.

Age-Related Changes in Pain Perception Are Associated With Altered Functional Connectivity During Resting State

Aging affects pain experience and brain functioning. However, how aging leads to changes in pain perception and brain functional connectivity has not yet been completely understood. To investigate resting-state and pain perception changes in old and young participants, this study employed region of interest (ROI) to ROI resting-state functional connectivity (rsFC) analysis of imaging data by using regions implicated in sensory and affective dimensions of pain, descending pain modulation, and the default-mode networks (DMNs). Thirty-seven older (66.86 ± 4.04 years; 16 males) and 38 younger healthy participants (20.74 ± 4.15 years; 19 males) underwent 10 min’ eyes-closed resting-state scanning. We examined the relationship between rsFC parameters with pressure pain thresholds. Older participants showed higher pain thresholds than younger. Regarding rsFC, older adults displayed increased connectivity of pain-related sensory brain regions in comparison to younger participants: increased rsFC between bilateral primary somatosensory area (SI) and anterior cingulate cortex (ACC), and between SI(L) and secondary somatosensory area (SII)-(R) and dorsolateral prefrontal cortex (PFC). Moreover, decreased connectivity in the older compared to the younger group was found among descending pain modulatory regions: between the amygdala(R) and bilateral insula(R), thalamus(R), ACC, and amygdala(L); between the amygdala(L) and insula(R) and bilateral thalamus; between ACC and bilateral insula, and between periaqueductal gray (PAG) and bilateral thalamus. Regarding the DMN, the posterior parietal cortex and lateral parietal (LP; R) were more strongly connected in the older group than in the younger group. Correlational analyses also showed that SI(L)-SII(R) rsFC was positively associated with pressure pain thresholds in older participants. In conclusion, these findings suggest a compensatory mechanism for the sensory changes that typically accompanies aging. Furthermore, older participants showed reduced functional connectivity between key nodes of the descending pain inhibitory pathway.

Association of catechol-O-methyltranferase 472G>A (Val158Met) polymorphism with susceptibility to fibromyalgia syndrome

Background

Several lines of research have suggested that the 472G > A (Val158Met) polymorphism at Catechol-O-methyltranferase (COMT) gene is implicated in the pathophysiology of FMS. Here, we have evaluated the association of COMT 472G > A polymorphism with risk of FMS.

Methods

In this study 250 patients with FMS and 250 healthy controls were evaluated for COMT 472G > A polymorphism by RFLP-PCR assay.

Results

There were no significant differences in the allele and genotype frequencies of COMT 472G > A polymorphism between FMS cases and healthy controls.

Conclusions

Our results suggested that the COMT 472G > A polymorphism may not be risk factor for development of FMS.

Associations Between Catecholaminergic and Serotonergic Genes and Persistent Arm Pain Severity Following Breast Cancer Surgery

Persistent arm pain is a common problem after breast cancer surgery. Little is known about genetic factors that contribute to this type of postsurgical pain. Study purpose was to explore associations between persistent arm pain phenotypes and genetic polymorphisms among 15 genes involved in catecholaminergic and serotonergic neurotransmission. Women (n = 398) rated the presence and intensity of arm pain monthly for 6 months after breast cancer surgery. Three distinct latent classes of patients were identified (ie, no arm pain [41.6%], mild arm pain (23.6%), and moderate arm pain (34.8%). Logistic regression analyses were used to evaluate for differences between genotype or haplotype frequencies and the persistent arm pain classes. Compared with the no arm pain class, 3 single nucleotide polymorphisms and 1 haplotype, in 4 genes, were associated with membership in the mild arm pain class: COMT rs4633, HTR2A haplotype B02 (composed of rs1923886 and rs7330636), HTR3A rs1985242, and TH rs2070762. Compared with the no arm pain class, 4 single nucleotide polymorphisms in 3 genes were associated with membership in the moderate arm pain class: COMT rs165656, HTR2A rs2770298 and rs9534511, and HTR3A rs1985242. Findings suggest that variations in catecholaminergic and serotonergic genes play a role in the development of persistent arm pain. PERSPECTIVE: Limited information is available on genetic factors that contribute to persistent arm pain after breast cancer surgery. Genetic polymorphisms in genes involved in catecholaminergic and serotonergic neurotransmission were associated with 2 persistent arm pain phenotypes. Findings may be used to identify patients are higher risk for this common pain condition.

Pharmacogenomics in chronic pain therapy: from disease to treatment and challenges for clinical practice

Pharmacogenomics (PGx) has emerged as an encouraging tool in chronic pain therapy. Genetic variations associated with drug effectiveness or adverse reactions (amitriptyline/nortriptyline/codeine/oxycodone/tramadol-CYP2D6, amitriptyline-CYP2C19, carbamazepine-HLA-A, carbamazepine/oxcarbazepine-HLA-B) can be used to guide chronic pain management. Despite this evidence, many obstacles still need to be overcome for the effective clinical implementation of PGx. To translate the pharmacogenetic testing into actionable clinical decisions, the Clinical Pharmacogenetics Implementation Consortium has been developing guidelines for several drug–gene pairs. This review will show the applicability of PGx in chronic pain from disease to treatment; report the drug–gene pairs with strongest evidences in the clinic; and the challenges for the clinical implementation of PGx.

Catechol-O-methyltransferase polymorphism Val158Met is associated with distal neuropathic pain in HIV-associated sensory neuropathy

BACKGROUND

Many of those aging with HIV suffer from distal neuropathic pain (DNP) due to HIV-associated sensory neuropathy (HIV-SN). Prior studies have linked chronic pain conditions to a variant of the catechol-O-methyltransferase (COMT), ValMet. This variant confers reduced enzymatic activity and results in higher synaptic dopamine levels. Here we examined the role of ValMet as a predictor of DNP in HIV-SN.

METHODS

In 1044 HIV-infected individuals enrolled in CNS HIV Antiretroviral Therapy Effects Research, an observational study across six US institutions, we characterized the relationship between ValMet and DNP in HIV-SN. Participants underwent neurologic examination and genotyping. Stratification into genetic ancestry groups was employed to eliminate bias due to genetic background.

FINDINGS

Of 590 participants with HIV-SN, 38% endorsed DNP, 24% reported nonpainful symptoms of neuropathy (paresthesia and numbness), and 38% were asymptomatic. Compared with asymptomatic HIV-SN, ValMet was associated with 2.3 higher odds of DNP. There were no increased odds of nonpainful symptoms. The association remained significant after controlling for other risk factors for DNP: lifetime diagnosis of depression, older age, ancestry, cumulative exposure to dideoxynucleoside antiretrovirals, diabetes, and nadir CD4. Stratified by genetic ancestry, the association between ValMet and DNP was significant in European and African genetic ancestry.

INTERPRETATION

ValMet may be a genetic marker for susceptibility to DNP in HIV-SN. Our findings support the notion that differences in pain processing mediated by COMT-related dopamine signaling play a role in susceptibility to DNP in HIV-SN. Because prior studies suggest that the COMT allele may influence dose-response relationships with opioid treatment, knowing COMT genotype could influence management.

Catechol-O-Methyltransferase Val158Met Polymorphism Is Associated with Anxiety, Depression, and Widespread Pressure Pain Sensitivity in Women with Chronic, but Not Episodic, Migraine

OBJECTIVES

To analyze the association between the rs4680 catechol-O-methyltransferase Val158Met polymorphism and to determine the association of this polymorphism with clinical, psychological, and pain sensitivity variables in women with episodic or chronic migraine.

METHODS

Fifty women with episodic migraine, 50 with chronic migraine, and 50 matched healthy women participated. After amplifying the Val158Met polymorphism by polymerase chain reaction, we assessed genotype frequencies and allele distributions. Participants were classified according to the Val158Met polymorphism genotype into Val/Val, Val/Met, or Met/Met. A headache diary was used for collecting migraine pain features. Disability was assessed with the Migraine Disability Assessment Scale, trait/state anxiety levels with the State-Trait Anxiety Inventory, and depression/anxiety with the Hospital Anxiety and Depression Scale. Pressure pain thresholds (PPTs) were bilaterally assessed over the temporalis, the upper trapezius, the second metacarpal, and the tibialis anterior.

RESULTS

The distribution of the rs4680 Val158Met genotype was not significantly different between women with and without migraine (P = 0.157). No differences in migraine features were found to be dependent on the Val158Met genotype. Women with the Met/Met genotype showed higher migraine-related disability than those with the Val/Val or Val/Met genotype in both migraine groups (P < 0.01). Women with chronic, but not episodic, migraine with the Met/Met genotype exhibited higher depressive and anxiety levels and lower PPTs than those with the Val/Val or Val/Met genotype.

CONCLUSIONS

The Val158Met rs4680 polymorphism does not appear to be involved in predisposition to suffer from migraine; however, this genetic factor may be involved in the phenotypic expression of chronic migraine, as anxiety, depression, and widespread pressure pain sensitivity were greater in those women with chronic, but not episodic, migraine with the Met/Met genotype.

Catechol-O-Methyltransferase (COMT) rs4680 Val158Met Polymorphism is Associated With Widespread Pressure Pain Sensitivity and Depression in Women With Chronic, but not Episodic, Tension-Type Headache

OBJECTIVES

The aims of this study were: (1) to investigate the association between the rs4680 Val158Met polymorphism in frequent episodic tension-type headache (FETTH) and chronic tension-type headache (CTTH); and (2) to analyze the association between the rs4680 Val158Met polymorphism with clinical, psychological, or psychophysical variables.

METHODS

In total, 50 women with FETTH, 50 with CTTH, and 50 matched headache-free women participated. After amplifying Val158Met polymorphism by polymerase chain reaction, the genotype frequencies and allele distributions based on restriction fragment length polymorphism were assessed. Participants were classified according to the Val158Met polymorphism rs4680 genotype (Val/Val, Val/Met, or Met/Met). A headache diary collected clinical features. Disability (Headache Disability Inventory), sleep quality (Pittsburgh Sleep Quality Index), and depression/anxiety levels (Hospital Anxiety and Depression Scale) were also assessed. Pressure pain thresholds were assessed bilaterally over the temporalis, upper trapezius, second metacarpal, and tibialis anterior by a blinded assessor.

RESULTS

The distribution of rs4680 Val158Met genotype was not significantly different between women with/without headache (P=0.796). No differences in headache features, disability, anxiety, or sleep quality were observed depending on the rs4680 Val158Met genotype. Women with CTTH, but not FETTH, carrying the Met/Met genotype had lower widespread pressure pain thresholds and higher depressive symptoms than those with Val/Val or Val/Met genotype (P<0.05).

CONCLUSIONS

The Val158Met polymorphism (rs4680) does not appear to be involved in predisposition to tension-type headache; however, this genetic factor may be involved in the pathogenesis expression of CTTH, as greater pressure pain sensitivity and higher depressive levels were found in CTTH carrying the Met/Met genotype.

Association of COMT gene variability with pain intensity in patients after total hip replacement

Pain is one of the most interdisciplinary clinical symptoms of a disease. The aim of the study was to evaluate the association of COMT gene polymorphism with pain perception in patients after total hip replacement (THR). The study included 195 patients qualified for surgical treatment (THR) due to osteoarthritis. Patients previously undergoing hip replacement subsequently underwent multimodal pain management therapy, in accordance with the recommendations for treating postoperative pain. The intensity of pain was measured three times at pre-defined time intervals: 1.5, 6 and 12 months after hip replacement, using the visual analogue scale. Single nucleotide polymorphism (SNP) in the COMT gene rs4680: A>G (Val158Met), rs6269: A>G (promoter region), rs4633: C>T (His62His) and rs4818: C>G (Leu136Leu) was genotyped. COMT SNP frequency distribution was analysed. For rs6269 and rs4818, the minor allele was the G allele (38.7 and 38.5%, respectively). It was also observed that rs4633 (T) allele frequency (50%) equalled that of the rs4680 (A) allele (50%). We assessed COMT haplotype frequency in the patients studied. The most frequent haplotype was haplotype M (ATCA) (50%), the rarest haplotype was haplotype R (ATGG), with a frequency of 0.3%. The most frequent diplotype was H/M, which was found in 37.95% of the patients. The frequency of other diplotypes was: M/M-24.10%, H/H-15.90% and L/M-13.33%. The study showed a significant association of rs4818 G allele and equivalent COMT H haplotype with lower sensitivity to pain after hip replacement.

Psychological and Genetic Predictors of Pain Tolerance

Previous studies have shown associations between genetic polymorphisms and pain tolerance, but psychological evaluations are seldom measured. The objective of this study was to determine the independent effects of demographic, psychological, and genetic predictors of cold noxious pain tolerance. Healthy subjects (n = 89) completed the Pain Catastrophizing Scale (PCS) and Fear of Pain Questionnaire (FPQ‐III), underwent genotyping for candidate single nucleotide polymorphisms (SNPs), and completed a cold‐pressor test in a 1–2°C water bath for a maximum of 3 minutes. The primary outcome measure was pain tolerance, defined as the maximum duration of time subjects left their nondominant hand in the cold‐water bath. Cox proportional hazards regression indicated that female sex, Asian race, and increasing PCS and FPQ‐III scores were associated with lower pain tolerance. No candidate SNP was significantly associated with pain tolerance. Future genetic studies should include demographic and psychological variables as confounders in experimental pain models.

Computational Studies Applied to Flavonoids against Alzheimer's and Parkinson's Diseases

Neurodegenerative diseases, such as Parkinson's and Alzheimer's, are understood as occurring through genetic, cellular, and multifactor pathophysiological mechanisms. Several natural products such as flavonoids have been reported in the literature for having the capacity to cross the blood-brain barrier and slow the progression of such diseases. The present article reports on in silico enzymatic target studies and natural products as inhibitors for the treatment of Parkinson's and Alzheimer's diseases. In this study we evaluated 39 flavonoids using prediction of molecular properties and in silico docking studies, while comparing against 7 standard reference compounds: 4 for Parkinson's and 3 for Alzheimer's. Osiris analysis revealed that most of the flavonoids presented no toxicity and good absorption parameters. The Parkinson's docking results using selected flavonoids as compared to the standards with four proteins revealed similar binding energies, indicating that the compounds 8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, capensinidin, and rosinidin are potential leads with the necessary pharmacological and structural properties to be drug candidates. The Alzheimer's docking results suggested that seven of the 39 flavonoids studied, being those with the best molecular docking results, presenting no toxicity risks, and having good absorption rates (8-prenylnaringenin, europinidin, epicatechin gallate, homoeriodictyol, aspalathin, butin, and norartocarpetin) for the targets analyzed, are the flavonoids which possess the most adequate pharmacological profiles.

Association of Catechol-O-methyltransferase single nucleotide polymorphisms, ethnicity, and sex in a large cohort of fibromyalgia patients

Background

Fibromyalgia (FM) is a complex, centralized pain condition that is often difficult to diagnose and treat. FM is considered to have a genetic background due to its familial aggregation and due to findings from multiple candidate-gene studies implicating catecholaminergic and serotonergic neurotransmitter systems in chronic pain. However, a multi-factorial analysis of both genetic and environmental risk factors is lacking. A better characterization of the interplay of risk factors may assist in understanding the pathophysiology of FM, its clinical course, and assist in early diagnosis and treatment of the disorder.

Methods

This retrospective study included 60,367 total participants from 237 clinics across the USA. Of those, 2713 had been diagnosed with fibromyalgia, as indicated by ICD code. Logistic regression was used to test for associations of diagnosed FM in study subjects with COMT SNPs and COMT haplotypes, which were previously found to be linked with pain sensitivity, as well as demographics such as age, sex, and ethnicity. The minor allele frequencies of COMT SNPs in the FM population were compared with 1000 Genomes data using a χ2 test to determine significant deviations from the estimated population allelic frequencies.

Results

FM diagnosis was strongly associated with sex, age, and ethnicity. Females, those between 49 and 63 years, and non-Caucasians were at higher risk of FM. Females had 1.72 increased odds of FM (p = 1.17 × 10^− 30). African-Americans were 1.52 times more likely to have a diagnosis of FM compared to Caucasians (p = 3.11 × 10^− 12). Hispanics were less likely to have a diagnosis of FM compared to Caucasians (p = 3.95 × 10^− 7). After adjusting for sex and ethnicity, those in the low age group and mid age group had 1.29 (p = 1.02 × 10^− 5) and 1.60 (p = 1.93 × 10^− 18) increased odds of FM, respectively, compared to the high age group, where age was categorized by tertile (low (< 49), mid (49–63), and high (> 63)). The COMT haplotypes associated with pain sensitivity were not associated with FM, but African-Americans were 11.3 times more likely to have a high pain sensitivity COMT diplotype, regardless of FM diagnosis. However, the minor alleles of COMT SNPs rs4680, rs4818, rs4633 and rs6269 were overrepresented in the FM population overall, and varied when compared with ethnically-similar populations from 1000 Genomes.

Conclusions

This is the largest study, to date, that examines demographic and genetic associations of FM in a diverse population. While pain sensitivity-associated COMT haplotypes were not found to be directly associated with FM diagnosis, the minor alleles that make up the COMT haplotypes were overrepresented in the FM population, suggesting a role of COMT in FM. Future studies are needed to elucidate the exact role of COMT variation in widespread pain conditions, such as FM. Clinically, this information can be used to provide insight into the pathways underlying FM and to identify those at greater risk of developing FM.

Electronic supplementary material

The online version of this article (10.1186/s41927-018-0045-4) contains supplementary material, which is available to authorized users.

Association between brain-derived neurotrophic factor gene polymorphisms and fibromyalgia in a Korean population: a multicenter study

Background

Several lines of evidence imply that brain-derived neurotrophic factor (BDNF) is involved in the pathophysiology of fibromyalgia (FM); in this regard, patients with FM have altered blood and cerebrospinal fluid levels of BDNF. In this study, we explored the association between BDNF gene polymorphisms and FM susceptibility and the severity of symptoms.

Methods

In total, 409 patients with FM and 423 healthy controls in 10 medical centers were enrolled from the Korean nationwide FM survey. The alleles and genotypes at 10 positions in the BDNF gene were genotyped.

Results

The allele and genotype frequencies of BDNF rs11030104 differed significantly between the patients with FM and the controls (P = 0.031). The GG genotype of rs11030104 had a protective effect against FM (P = 0.016), and the G allele of rs11030104 was negatively associated with the presence of FM compared with the A allele (P = 0.013). In comparison, although the allele and genotype frequencies of BDNF rs12273539 did not differ between the two groups, the TT genotype of BDNF rs12273539 was associated with susceptibility to FM (P = 0.038). Haplotype analyses implied that some BDNF haplotypes have a protective effect against FM. Finally, several genotypes and haplotypes of the BDNF gene contributed to specific symptoms of FM.

Conclusions

This study is the first to evaluate the associations between BDNF gene polymorphisms and FM. Our results imply that some BDNF single-nucleotide polymorphisms and haplotypes are associated with susceptibility to, and contribute to the symptoms of, FM.

The Role of Genetic Polymorphisms in Chronic Pain Patients

It is estimated that the total annual financial cost for pain management in the U.S. exceeds 100 billion dollars. However, when indirect costs are included, such as functional disability and reduction in working hours, the cost can reach more than 300 billion dollars. In chronic pain patients, the role of pharmacogenetics is determined by genetic effects on various pain types, as well as the genetic effect on drug safety and efficacy. In this review article, we discuss genetic polymorphisms present in different types of chronic pain, such as fibromyalgia, low back pain, migraine, painful peripheral diabetic neuropathy and trigeminal neuralgia. Furthermore, we discuss the role of CYP450 enzymes involved in metabolism of drugs, which have been used for treatment of chronic pain (amitriptyline, duloxetine, opioids, etc.). We also discuss how pharmacogenetics can be applied towards improving drug efficacy, shortening the time required to achieve therapeutic outcomes, reducing risks of side effects, and reducing medical costs and reliance upon polypharmacy.

COMT genotype and non-recovery after a whiplash injury in a Northern European population

Background

The COMT (Catechol-O-Methyl Transferase) gene may influence a person’s vulnerability to develop long-term pain and some COMT single nucleotide polymorphisms (SNPs) may associate with patterns of acute or chronic pain. Many patients with whiplash-associated disorders (WADs) suffer from long-term pain and other related symptoms, but it is less known if genetic factors play a role in the recovery process. The primary aim of this study was to evaluate whether self-reported non-recovery, including pain, was related to COMT genotype in patients with WAD. The secondary aim was to investigate whether or not background factors, including mental health, were related to genotype and non-recovery.

Methods

A total of 133 patients with neck pain after a whiplash trauma were included. Background factors were collected and blood samples were taken during the acute phase after the accident. DNA was isolated from blood and used to genotype the SNPs rs6269, rs4633, rs4818 and rs4680 in the COMT gene; additionally haplotypes were estimated and haplogenotypes inferred. The patients were followed up after 12 months and asked to rate their recovery including pain, mental health and quality of life.

Results

The overall reported non-recovery rate at 12 months was 44% with no significant differences in distribution of the COMT haplotypes. High levels of self-reported pain (OR 7.2) and anxiety (OR 4.4) after the accident were associated with non-recovery, but not related to the haplotypes. None of the other background factors were related to the haplotypes or non-recovery.

Conclusion

No association between self-reported non-recovery or pain levels and COMT haplotypes in patients with acute whiplash injuries could be detected. Independent replications are necessary to discard the hypothesis that COMT haplotypes do not influence non-recovery or pain levels in patients with acute whiplash injuries. High levels of initial pain and anxiety were associated with non-recovery, thereby confirming previously published reports.

New insights into the genetics of fibromyalgia

Although debate on the concept of fibromyalgia (FM) has been vigorous ever since the classification criteria were first published, FM is now better understood and has become recognized as a disorder. Recently, FM has come to be considered a major health problem, affecting 1% to 5% of the general population. As familial aggregations have been observed among some FM patients, genetic research on FM is logical. In fact, genome-wide association studies and linkage analysis, and studies on candidate genes, have uncovered associations between certain genetic factors and FM. Genetic susceptibility is now considered to influence the etiology of FM. At the same time, novel genetic techniques, such as microRNA analysis, have been used in attempts to improve our understanding of the genetic predisposition to FM. In this article, we review recent advances in, and continuing challenges to, the identification of genes contributing to the development of, and symptom severity in, FM.

Comorbidity of Alcohol Use Disorder and Chronic Pain: Genetic Influences on Brain Reward and Stress Systems

Alcohol use disorder (AUD) is highly comorbid with chronic pain (CP). Evidence has suggested that neuroadaptive processes characterized by reward deficit and stress surfeit are involved in the development of AUD and pain chronification. Neurological data suggest that shared genetic architecture associated with the reward and stress systems may contribute to the comorbidity of AUD and CP. This monograph first delineates the prevailing theories of the development of AUD and pain chronification focusing on the reward and stress systems. It then provides a brief summary of relevant neurological findings followed by an evaluation of evidence documented by molecular genetic studies. Candidate gene association studies have provided some initial support for the genetic overlap between AUD and CP; however, these results must be interpreted with caution until studies with sufficient statistical power are conducted and replications obtained. Genomewide association studies have suggested a number of genes (e.g., TBX19, HTR7, and ADRA1A) that are either directly or indirectly related to the reward and stress systems in the AUD and CP literature. Evidence reviewed in this monograph suggests that shared genetic liability underlying the comorbidity between AUD and CP, if present, is likely to be complex. As the advancement in molecular genetic methods continues, future studies may show broader central nervous system involvement in AUD-CP comorbidity.

Affection of Comt1 genetype on anxiety and nociceptive sensitivity: an Ego-network analysis approach

Purpose

The aim of this study was to predict key genes and their relationships for anxiety and nociceptive sensitivity related to Comt1 genetype.

Methods

The raw data of E-GEOD-20160 related to anxiety and nociceptive sensitivity were obtained. Pearson correlation coefficient of interaction in protein–protein interaction was calculated. Topological analysis was processed for protein–protein interaction network, and genes in this network were ranked based on their degrees. Ego genes were identified, and models were searched and refined. A total of 1000 randomized tests were processed for ego networks. The classification accuracy of each ego network was obtained in this process.

Results

The interactions with genes in gene expression profiles were extracted, and protein–protein interaction was constructed. The protein–protein interaction included 4639 genes and 43,837 relationships. Differential co-expression network was constructed, and 74 ego genes were obtained. Thereinto, top five ego genes were ADCY2, GRM8, S1PR3, ADCY6, and ANXA1. After module searching and refinement, a total of 11 candidate modules were obtained, including module 14, module 51, and module 9. In addition, these 11 modules were confirmed to be with significance. Module 14 contained 10 genes, such as HRH3, DRD2, and CXCR3. Similarly, module 51 included six genes, such as HELZ2, NCOA3, and MED30.

Conclusions

Ego network analysis was a useful and comprehensive method for biomarkers screening. Several modules such as module 3 and module 36 were important subnetworks. Potential genes in these modules including ADCYs, GNAI1, DRD2, PNOC, CCR2, DRD2, and LPAR1 might be important genes in the research of anxiety and nociceptive sensitivity.