Genome-wide association study on pharmacological outcomes of musculoskeletal pain in UK Biobank.

The pharmacological management of musculoskeletal pain starts with NSAIDs, followed by weak or strong opioids until the pain is under control. However, the treatment outcome is usually unsatisfying due to inter-individual differences. To investigate the genetic component of treatment outcome differences, we performed a genome-wide association study (GWAS) in ~23,000 participants with musculoskeletal pain from the UK Biobank. NSAID vs. opioid users were compared as a reflection of the treatment outcome of NSAIDs. We identified one genome-wide significant hit in chromosome 4 (rs549224715, P = 3.88 × 10-8). Suggestive significant (P < 1 × 10-6) loci were functionally annotated to 18 target genes, including four genes linked to neuropathic pain processes or musculoskeletal development. Pathway and network analyses identified immunity-related processes and a (putative) central role of EGFR. However, this study should be viewed as a first step to elucidate the genetic background of musculoskeletal pain treatment.

miRNAs as biomarkers of musculoskeletal pain in long-distance runners: the MiMuS study protocol.

miRNAs are involved in the generation and progression of musculoskeletal pain, a condition that causes significant clinical, economic and social burden. In runners, the presence of musculoskeletal pain related to an inflammatory state or ongoing underlying tissue damage may result in poor training ability and performance. This study aims to evaluate the association between circulating and salivary miRNAs and pain in runners with and without musculoskeletal pain and to observe whether dysregulated miRNAs can distinguish between responders and nonresponders to a kinesiological intervention. The possible correlation between these miRNAs and inflammatory molecules, stress parameters and individual or behavioral characteristics will be evaluated. Finally, in silico analysis will be used to characterize miRNAs function. Ethics approval was obtained.

Hippocampal volume, FKBP5 genetic risk alleles, and childhood trauma interact to increase vulnerability to chronic multisite musculoskeletal pain.

Chronic multisite musculoskeletal pain (CMP) is common and highly morbid. However, vulnerability factors for CMP are poorly understood. Previous studies have independently shown that both small hippocampal brain volume and genetic risk alleles in a key stress system gene, FKBP5, increase vulnerability for chronic pain. However, little is known regarding the relationship between these factors and CMP. Here we tested the hypothesis that both small hippocampal brain volume and FKBP5 genetic risk, assessed using the tagging risk variant, FKBP5rs3800373, increase vulnerability for CMP. We used participant data from 36,822 individuals with available genetic, neuroimaging, and chronic pain data in the UK Biobank study. Although no main effects were observed, the interaction between FKBP5 genetic risk and right hippocampal volume was associated with CMP severity (ß = -0.020, praw = 0.002, padj = 0.01). In secondary analyses, severity of childhood trauma further moderated the relationship between FKBP5 genetic risk, right hippocampal brain volume, and CMP (ß = -0.081, p = 0.016). This study provides novel evidence that both FKBP5 genetic risk and childhood trauma moderate the relationship between right hippocampal brain volume and CMP. The data increases our understanding of vulnerability factors for CMP and builds a foundation for further work assessing causal relationships that might drive CMP development.

Heritability of musculoskeletal pain and pain sensitivity phenotypes: 2 generations of the Raine Study.

ABSTRACT: There is a need to better understand biological factors that increase the risk of persistent musculoskeletal (MSK) pain and heightened pain sensitivity. Knowing the heritability (how genes account for differences in people's traits) can enhance the understanding of genetic vs environmental influences of pain and pain sensitivity. However, there are gaps in current knowledge, including the need for intergenerational studies to broaden our understanding of the genetic basis of pain. Data from Gen1 and Gen2 of the Raine Study were used to investigate the heritability of MSK pain and pressure and cold pain sensitivity. Participants included parents (Gen1, n = 1092) and their offspring (Gen2, n = 688) who underwent a battery of testing and questionnaires including pressure and cold pain threshold testing and assessments of physical activity, sleep, MSK pain, mental health, and adiposity. Heritability estimates were derived using the Sequential Oligogenic Linkage Analysis Routines software. Heritability estimates for MSK pain and pressure pain sensitivity were significant, accounting for between 0.190 and 0.289 of the variation in the phenotype. By contrast, heritability of cold pain sensitivity was not significant. This is the largest intergenerational study to date to comprehensively investigate the heritability of both MSK pain and pain sensitivity, using robust statistical analysis. This study provides support for the heritability of MSK pain and pain sensitivity to pressure, suggesting the need for further convergence of genetic and environmental factors in models for the development or maintenance of these pain disorders.

Genome-wide association study identifies RNF123 locus as associated with chronic widespread musculoskeletal pain.

BACKGROUND AND OBJECTIVES: Chronic widespread musculoskeletal pain (CWP) is a symptom of fibromyalgia and a complex trait with poorly understood pathogenesis. CWP is heritable (48%-54%), but its genetic architecture is unknown and candidate gene studies have produced inconsistent results. We conducted a genome-wide association study to get insight into the genetic background of CWP. METHODS: Northern Europeans from UK Biobank comprising 6914 cases reporting pain all over the body lasting >3 months and 242 929 controls were studied. Replication of three independent genome-wide significant single nucleotide polymorphisms was attempted in six independent European cohorts (n=43 080; cases=14 177). Genetic correlations with risk factors, tissue specificity and colocalisation were examined. RESULTS: Three genome-wide significant loci were identified (rs1491985, rs10490825, rs165599) residing within the genes Ring Finger Protein 123 (RNF123), ATPase secretory pathway Ca2+transporting 1 (ATP2C1) and catechol-O-methyltransferase (COMT). The RNF123 locus was replicated (meta-analysis p=0.0002), the ATP2C1 locus showed suggestive association (p=0.0227) and the COMT locus was not replicated. Partial genetic correlation between CWP and depressive symptoms, body mass index, age of first birth and years of schooling were identified. Tissue specificity and colocalisation analysis highlight the relevance of skeletal muscle in CWP. CONCLUSIONS: We report a novel association of RNF123 locus and a suggestive association of ATP2C1 locus with CWP. Both loci are consistent with a role of calcium regulation in CWP. The association with COMT, one of the most studied genes in chronic pain field, was not confirmed in the replication analysis.

Enrichment of genomic pathways based on differential DNA methylation profiles associated with chronic musculoskeletal pain in older adults: An exploratory study.

Our study aimed to identify differentially methylated CpGs/regions and their enriched genomic pathways associated with underlying chronic musculoskeletal pain in older individuals. We recruited cognitively healthy older adults with (n = 20) and without (n = 9) self-reported musculoskeletal pain and collected DNA from peripheral blood that was analyzed using MethylationEPIC arrays. We identified 31,739 hypermethylated CpG and 10,811 hypomethylated CpG probes (ps ≤ 0.05). All CpG probes were clustered into 5966 regions, among which 600 regions were differentially methylated at p ≤ 0.05 level, including 294 hypermethylated regions and 306 hypomethylated regions (differentially methylated regions). Ingenuity pathway enrichment analysis revealed that the pain-related differentially methylated regions were enriched across multiple pathways. The top 10 canonical pathways were linked to cellular signaling processes related to immune responses (i.e. antigen presentation, programed cell death 1 receptor/PD-1 ligand 1, interleukin-4, OX40 signaling, T cell exhaustion, and apoptosis) and gamma-aminobutyric acid receptor signaling. Further, Weighted Gene Correlation Network Analysis revealed a comethylation network module in the pain group that was not preserved in the control group, where the hub gene was the cyclic adenosine monophosphate-dependent transcription factor ATF-2. Our preliminary findings provide new epigenetic insights into the role of aberrant immune signaling in musculoskeletal pain in older adults while further supporting involvement of dysfunctional GABAergic signaling mechanisms in chronic pain. Our findings need to be urgently replicated in larger cohorts as they may serve as a basis for developing and targeting future interventions.

Vitamin D insufficiency increases risk of chronic pain among African Americans experiencing motor vehicle collision.

African Americans experience an increased burden of motor vehicle collision (MVC), post-MVC musculoskeletal pain, and vitamin D insufficiency. In this prospective multicenter study, we tested the hypothesis that African Americans (n = 133) presenting to the emergency department after MVC with low peritraumatic vitamin D levels would have worse chronic musculoskeletal pain outcomes compared to individuals with sufficient vitamin D. Vitamin D levels were assessed in the early aftermath of MVC through enzyme-linked immunosorbent assay, and pain severity was assessed using the 0 to 10 numeric rating scale at 6 weeks, 6 months, and 1 year. In repeated-measures analysis, African American MVC survivors with vitamin D insufficiency experienced more severe chronic pain (ß = 1.18, P = 0.031). In secondary analyses, we assessed for evidence that the effect of vitamin D on post-MVC pain outcomes is mediated, at least in part, by the influence of vitamin D on genetic variants in genes involved in immune system regulation (IL-10 and NLRP3). Genotyping was performed using a genome-wide microarray using collected DNA samples. Secondary analyses suggest that the effect of vitamin D on post-MVC pain outcomes may be influenced by genetic variation in IL-10 and NLRP3. Further studies are needed to assess the impact of vitamin D insufficiency on pain outcomes in African Americans experiencing MVC and other common trauma exposures, to assess factors affecting this relationship, and to assess the efficacy of administering vitamin D in the immediate aftermath of MVC to prevent chronic pain. Such low-cost, nonopioid interventions are urgently needed to address chronic pain development after MVC.

Genetic Underpinnings of Musculoskeletal Pain During Treatment With Aromatase Inhibitors for Breast Cancer: A Biological Pathway Analysis.

BACKGROUND: Musculoskeletal pain (MSKP) is the most reported symptom during treatment with aromatase inhibitors (AIs) for breast cancer. The mechanisms underlying MSKP are multidimensional and not well understood. The goals of this biological pathway analysis were to (1) gain an understanding of the genetic variation and biological mechanisms underlying MSKP with AI therapy and (2) identify plausible biological pathways and candidate genes for future investigation. METHOD: Genes associated with MSKP during AI therapy or genes involved in drug metabolism of and response to AIs were identified from the literature. Studies published through February 2019 were queried in PubMed®. The genes identified from the literature were entered into QIAGEN's Ingenuity® Pathway Analysis (IPA) software to generate canonical pathways, upstream regulators, and networks through a core analysis. RESULTS: The 17 genes identified were ABCB1, ABCG1, CYP17A1, CYP19A1, CYP27B1, CYP2A6, CYP3A4, CYP3A5, ESR1, OATP1B1, OPG, RANKL, SLCO3A1, TCL1A, UGT2A1, UGT2B17, and VDR. These genes are involved in encoding bone-remodeling regulators, drug-metabolizing enzymes (cytochrome P450 family, UDP-glucuronosyltransferases family), or drug transporters (ATP-binding cassette transporters, organic anion transporters). Multiple plausible biological pathways (e.g., nicotine degradation, melatonin degradation) and candidate genes (e.g., NFKB, HSP90, AKT, ERK1/2, FOXA2) are proposed for future investigation based on the IPA results. CONCLUSION: Multiple genes and molecular-level etiologies may contribute to MSKP with AI therapy in women with breast cancer. Our innovative combination of gene identification from the literature plus biological pathway analysis allowed for the emergence of novel candidate genes and biological pathways for future investigations.

Interleukin 6 decreases nociceptor expression of the potassium channel KV1.4 in a rat model of hand-arm vibration syndrome.

Chronic muscle pain is a prominent symptom of the hand-arm vibration syndrome (HAVS), an occupational disease induced by exposure to vibrating power tools, but the underlying mechanism remains unknown. We evaluated the hypothesis that vibration induces an interleukin 6 (IL-6)-mediated downregulation of the potassium voltage-gated channel subfamily A member 4 (KV1.4) in nociceptors leading to muscle pain. Adult male rats were submitted to a protocol of mechanical vibration of the right hind limb. Twenty-four hours after vibration, muscle hyperalgesia was observed, concomitant to increased levels of IL-6 in the gastrocnemius muscle and decreased expression of KV1.4 in the dorsal root ganglia. Local injection of neutralizing antibodies against IL-6 attenuated the muscle hyperalgesia induced by vibration, whereas antisense knockdown of this channel in the dorsal root ganglia mimicked the muscle hyperalgesia observed in the model of HAVS. Finally, knockdown of the IL-6 receptor signaling subunit glycoprotein 130 (gp130) attenuated both vibration-induced muscle hyperalgesia and downregulation of KV1.4. These results support the hypothesis that IL-6 plays a central role in the induction of muscle pain in HAVS. This likely occurs through intracellular signaling downstream to the IL-6 receptor subunit gp130, which decreases the expression of KV1.4 in nociceptors.

Dysbiotic salivary microbiota in dry mouth and primary Sjögren's syndrome patients.

OBJECTIVES: Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by reduced lacrimal and salivary secretion. Sicca symptoms together with fatigue and musculoskeletal pain can significantly reduce the patients' quality of life. Furthermore, low salivary secretion may disrupt the oral microbial homeostasis. The aim of this study was to compare the salivary microbiota from pSS patients with patients with sicca symptoms not fulfilling the classification criteria for pSS (non-SS), and with healthy controls without sicca complaints. METHODS: Pellets from centrifuged chewing-stimulated whole saliva from pSS patients (n = 15), non-SS sicca patients (n = 15) and healthy controls (n = 15) were prepared. DNA was extracted and analyzed by 16S rRNA gene sequencing. The acquired sequencing data were performed using the human oral microbiome database (HOMD). RESULTS: We detected 42, 45, and 34 bacterial genera in saliva samples from pSS patients, non-SS sicca patients, and healthy controls, respectively. The most abundant genera in all samples were Prevotella, Veillonella, Streptococcus, and Haemophilus. At species level Streptococcus intermedius, Prevotella intermedia, Fusobacterium nucleatum subsp. vincentii, Porphyromonas endodontalis, Prevotella nancensis, Tannerella spp., and Treponema spp. were detected in the samples from pSS and non-SS only, while Porphyromonas pasteri was mostly found among the healthy controls. CONCLUSION: Our study indicated dysbiosis in the salivary microbiota from pSS and non-SS patients compared to healthy controls. Additionally, the results showed that the salivary microbiome in the pSS group differed significantly from the non-SS group.

Genes known to escape X chromosome inactivation predict co-morbid chronic musculoskeletal pain and posttraumatic stress symptom development in women following trauma exposure.

Co-morbid chronic musculoskeletal pain (CMSP) and posttraumatic stress symptoms (PTSS) are frequent sequelae of motor vehicle collision, are associated with greater disability than either outcome alone, and are more prevalent in women than men. In the current study we assessed for evidence that gene transcripts originating from the X chromosome contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision. Nested samples were drawn from a longitudinal study of African American individuals, and CMSP (0-10 numeric rating scale) and PTSS (impact of events scale, revised) outcomes were assessed 6 months following motor vehicle collision. Blood RNA were sequenced (n = 101) and the relationship between X chromosome mRNA expression levels and co-morbid CMSP and PTSS outcomes was evaluated using logistic regression analyses. A disproportionate number of peritraumatic X chromosome mRNA predicting CMSP and PTSS in women were genes previously found to escape X chromosome inactivation (11/40, z = -2.9, p = .004). Secondary analyses assessing gene ontology relationships between these genes identified an enrichment in genes known to influence neuronal plasticity. Further, the relationship of expression of two critical regulators of X chromosome inactivation, X-inactive specific transcript (XIST) and Yin Yang 1 (YY1), was different in women developing CMSP and PTSS. Together, these data suggest that X chromosome genes that escape inactivation may contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision.

Familial episodic limb pain in kindreds with novel Nav1.9 mutations.

We previously performed genetic analysis in six unrelated families with infantile limb pain episodes, characterized by cold-induced deterioration and mitigation in adolescence, and reported two new mutations p.R222H/S in SCN11A responsible for these episodes. As no term described this syndrome (familial episodic pain: FEP) in Japanese, we named it as"". In the current study, we recruited an additional 42 new unrelated Japanese FEP families, between March 2016 and March 2018, and identified a total of 11 mutations in SCN11A: p.R222H in seven families, and p.R225C, p.F814C, p.F1146S, or p.V1184A, in independent families. A founder mutation, SCN11A p.R222H was confirmed to be frequently observed in patients with FEP in the Tohoku region of Japan. We also identified two novel missense variants of SCN11A, p.F814C and p.F1146S. To evaluate the effects of these latter two mutations, we generated knock-in mouse models harboring p.F802C (F802C) and p.F1125S (F1125S), orthologues of the human p.F814C and p.F1146S, respectively. We then performed electrophysiological investigations using dorsal root ganglion neurons dissected from the 6-8 week-old mice. Dissected neurons of F802C and F1125S mice showed increased resting membrane potentials and firing frequency of the action potentials (APs) by high input-current stimulus compared with WT mice. Furthermore, the firing probability of evoked APs increased in low stimulus input in F1125S mice, whereas several AP parameters and current threshold did not differ significantly between either of the mutations and WT mice. These results suggest a higher level of excitability in the F802C or F1125S mice than in WT, and indicate that these novel mutations are gain of function mutations. It can be expected that a considerable number of potential patients with FEP may be the result of gain of function SCN11A mutations.

A Functional riboSNitch in the 3' Untranslated Region of FKBP5 Alters MicroRNA-320a Binding Efficiency and Mediates Vulnerability to Chronic Post-Traumatic Pain.

Previous studies have shown that common variants of the gene coding for FK506-binding protein 51 (FKBP5), a critical regulator of glucocorticoid sensitivity, affect vulnerability to stress-related disorders. In a previous report, FKBP5 rs1360780 was identified as a functional variant because of its effect on gene methylation. Here we report evidence for a novel functional FKBP5 allele, rs3800373. This study assessed the association between rs3800373 and post-traumatic chronic pain in 1607 women and men from two ethnically diverse human cohorts. The molecular mechanism through which rs3800373 affects adverse outcomes was established via in silico, in vivo, and in vitro analyses. The rs3800373 minor allele predicted worse adverse outcomes after trauma exposure, such that individuals with the minor (risk) allele developed more severe post-traumatic chronic musculoskeletal pain. Among these individuals, peritraumatic circulating FKBP5 expression levels increased as cortisol and glucocorticoid receptor (NR3C1) mRNA levels increased, consistent with increased glucocorticoid resistance. Bioinformatic, in vitro, and mutational analyses indicate that the rs3800373 minor allele reduces the binding of a stress- and pain-associated microRNA, miR-320a, to FKBP5 via altering the FKBP5 mRNA 3'UTR secondary structure (i.e., is a riboSNitch). This results in relatively greater FKBP5 translation, unchecked by miR-320a. Overall, these results identify an important gene-miRNA interaction influencing chronic pain risk in vulnerable individuals and suggest that exogenous methods to achieve targeted reduction in poststress FKBP5 mRNA expression may constitute useful therapeutic strategies.SIGNIFICANCE STATEMENTFKBP5 is a critical regulator of the stress response. Previous studies have shown that dysregulation of the expression of this gene plays a role in the pathogenesis of chronic pain development as well as a number of comorbid neuropsychiatric disorders. In the current study, we identified a functional allele (rs3800373) in the 3'UTR of FKBP5 that influences vulnerability to chronic post-traumatic pain in two ethnic cohorts. Using multiple complementary experimental approaches, we show that the FKBP5 rs3800373 minor allele alters the secondary structure of FKBP5 mRNA, decreasing the binding of a stress- and pain-associated microRNA, miR-320a. This results in relatively greater FKBP5 translation, unchecked by miR-320a, increasing glucocorticoid resistance and increasing vulnerability to post-traumatic pain.

Multi-OMICS analyses of frailty and chronic widespread musculoskeletal pain suggest involvement of shared neurological pathways.

Chronic widespread musculoskeletal pain (CWP) and frailty are prevalent conditions in older people. We have shown previously that interindividual variation in frailty and CWP is genetically determined. We also reported an association of frailty and CWP caused by shared genetic and common environmental factors. The aim of this study was to use omic approaches to identify molecular genetic factors underlying the heritability of frailty and its genetic correlation with CWP. Frailty was quantified through the Rockwood Frailty Index (FI) as a proportion of deficits from 33 binary health deficit questions in 3626 female twins. Common widespread pain was assessed using a screening questionnaire. OMICS analysis included 305 metabolites and whole-genome (>2.5 × 10 SNPs) and epigenome (∼1 × 10 MeDIP-seq regions) assessments performed on fasting blood samples. Using family-based statistical analyses, including path analysis, we examined how FI scores were related to molecular genetic factors and to CWP, taking into account known risk factors such as fat mass and smoking. Frailty Index was significantly correlated with 51 metabolites after correction for multiple testing, with 20 metabolites having P-values between 2.1 × 10 and 4.0 × 10. Three metabolites (uridine, C-glycosyl tryptophan, and N-acetyl glycine) were statistically independent and thought to exert a direct effect on FI. Epiandrosterone sulphate, previously shown to be highly inversely associated with CWP, was found to exert an indirect influence on FI. Bioinformatics analysis of genome-wide association study and EWAS showed that FI and its covariation with CWP was through genomic regions involved in neurological pathways. Neurological pathway involvement accounts for the associated conditions of aging CWP and FI.

Genetic Factors Explain the Association Between Pain Catastrophizing and Chronic Widespread Pain.

This study aimed to clarify whether there are shared genetic and/or environmental factors explaining the strong link between pain catastrophizing (PC) and chronic widespread pain (CWP). Data were available for N = 1,109 female twins from TwinsUK. Information on self-reported CWP and PC was subject to variance component twin analysis. Heritabilities were 40% for PC and 77% for CWP. The genetic correlation between PC and CWP was .40%, whereas no evidence of an environmental correlation could be detected (.0). According to the best-fitting additive genetic, non-shared environmental (AE) Cholesky model, an additive genetic factor loading on PC as well as CWP, as well as an additive genetic factor loading on CWP alone was found. In terms of environmental influences, 2 individual environmental factors could be identified, loading separately on PC and CWP. Overall, the results add to the knowledge on the nature of CWP and the basis of its close relationship with PC by suggesting a shared genetic etiological structure. The findings highlight a potential avenue for future research and may provide useful insight for the clinical management of pain and pain coping. PERSPECTIVE: Results suggest a shared genetic etiological structure between CWP and PC with no shared influence of environmental factors. Clinicians should be aware of this biological link within the context of clinical management of pain and pain coping.

Genome-wide methylation analysis of a large population sample shows neurological pathways involvement in chronic widespread musculoskeletal pain.

Chronic widespread musculoskeletal pain (CWP), has a considerable heritable component, which remains to be explained. Epigenetic factors may contribute to and account for some of the heritability estimate. We analysed epigenome-wide methylation using MeDIPseq in whole blood DNA from 1708 monozygotic and dizygotic Caucasian twins having CWP prevalence of 19.9%. Longitudinally stable methylation bins (lsBINs), were established by testing repeated measurements conducted ≥3 years apart, n = 292. DNA methylation variation at lsBINs was tested for association with CWP in a discovery set of 50 monozygotic twin pairs discordant for CWP, and in an independent dataset (n = 1608 twins), and the results from the 2 samples were combined using Fisher method. Functional interpretation of the most associated signals was based on functional genomic annotations, gene ontology, and pathway analyses. Of 723,029 signals identified as lsBINs, 26,399 lsBINs demonstrated the same direction of association in both discovery and replication datasets at nominal significance (P ≤ 0.05). In the combined analysis across 1708 individuals, whereas no lsBINs showed genome-wide significance (P < 10-8), 24 signals reached p≤9E-5, and these included association signals mapping in or near to IL17A, ADIPOR2, and TNFRSF13B. Bioinformatics analyses of the associated methylation bins showed enrichment for neurological pathways in CWP. We estimate that the variance explained by epigenetic factors in CWP is 6%. This, the largest study to date of DNA methylation in CWP, points towards epigenetic modification of neurological pathways in CWP and provides proof of principle of this method in teasing apart the complex risk factors for CWP.

Genetic variant rs3750625 in the 3'UTR of ADRA2A affects stress-dependent acute pain severity after trauma and alters a microRNA-34a regulatory site.

α2A adrenergic receptor (α2A-AR) activation has been shown in animal models to play an important role in regulating the balance of acute pain inhibition vs facilitation after both physical and psychological stress. To our knowledge, the influence of genetic variants in the gene encoding α2A-AR, ADRA2A, on acute pain outcomes in humans experiencing traumatic stress has not been assessed. In this study, we tested whether a genetic variant in the 3'UTR of ADRA2A, rs3750625, is associated with acute musculoskeletal pain (MSP) severity following motor vehicle collision (MVC, n = 948) and sexual assault (n = 84), and whether this influence was affected by stress severity. We evaluated rs3750625 because it is located in the seed binding region of miR-34a, a microRNA (miRNA) known to regulate pain and stress responses. In both cohorts, the minor allele at rs3750625 was associated with increased musculoskeletal pain in distressed individuals (stress*rs3750625 P = 0.043 for MVC cohort and P = 0.007 for sexual assault cohort). We further found that (1) miR-34a binds the 3'UTR of ADRA2A, (2) the amount of repression is greater when the minor (risk) allele is present, (3) miR-34a in the IMR-32 adrenergic neuroblastoma cell line affects ADRA2A expression, (4) miR-34a and ADRA2A are expressed in tissues known to play a role in pain and stress, (5) following forced swim stress exposure, rat peripheral nerve tissue expression changes are consistent with miR-34a regulation of ADRA2A. Together, these results suggest that ADRA2A rs3750625 contributes to poststress musculoskeletal pain severity by modulating miR-34a regulation.

Are Epigenetic Factors Implicated in Chronic Widespread Pain?

BACKGROUND: Chronic widespread musculoskeletal pain (CWP) is the cardinal symptom of fibromyalgia and affects about 12% of the general population. Familial aggregation of CWP has been repeatedly demonstrated with estimated heritabilities of around 50%, indicating a genetic susceptibility. The objective of the study was to explore genome-wide disease-differentially methylated positions (DMPs) for chronic widespread pain (CWP) in a sample of unrelated individuals and a subsample of discordant monozygotic (MZ) twins. METHODOLOGY/PRINCIPLE FINDINGS: A total of N = 281 twin individuals from the TwinsUK registry, including N = 33 MZ twins discordant for self-reported CWP, were part of the discovery sample. The replication sample included 729 men and 756 women from a subsample of the KORA S4 survey-an independent population-based cohort from Southern Germany. Epigenome-wide analysis of DNA methylation was conducted using the Illumina Infinium HumanMethylation 450 DNA BeadChip in both the discovery and replication sample. Of our 40 main loci that were carried forward for replication, three CPGs reached significant p-values in the replication sample, including malate dehydrogenase 2 (MDH2; p-value 0.017), tetranectin (CLEC3B; p-value 0.039), and heat shock protein beta-6 (HSPB6; p-value 0.016). The associations between the collagen type I, alpha 2 chain (COL1A2) and monoamine oxidase B (MAOB) observed in the discovery sample-both of which have been previously reported to be biological candidates for pain-could not be replicated. CONCLUSION/SIGNIFICANCE: Our results may serve as a starting point to encourage further investigation in large and independent population-based cohorts of DNA methylation and other epigenetic changes as possible disease mechanisms in CWP. Ultimately, understanding the key mechanisms underlying CWP may lead to new treatments and inform clinical practice.

Genetic variant in the osteoprotegerin gene is associated with aromatase inhibitor-related musculoskeletal toxicity in breast cancer patients.

BACKGROUND: Aromatase inhibitor (AI) therapy is associated with musculoskeletal (MS) toxicity, which adversely affects quality of life and therapy adherence. Our objective was to evaluate whether genetic variants may predict endocrine therapy-related MS pain and hot flashes in a prospective observational cohort study. PATIENTS & METHODS: 254 early breast cancer patients starting AI (n = 159) or tamoxifen therapy (n = 95) were included in this genetic biomarker study. MS and vasomotor symptoms were assessed at baseline and after 3, 6 and 12 months of therapy. AI-induced MS pain was defined as an increase in arthralgia or myalgia relative to baseline. Single nucleotide polymorphisms (SNP) in candidate genes involved in oestrogen signalling or previously associated with AI-related MS pain or oestrogen levels were selected. RESULTS: Overall, 13 SNPs in CYP19, CYP17, osteoprotegerin (OPG) and oestrogen receptor 1 exhibited an allele frequency >0.05 and were included in the analysis. Patients carrying the G allele of rs2073618 in OPG experienced significantly more AI-induced MS toxicity compared to the wildtype allele, after correction for multiple testing (P = 0.046). Furthermore, this SNP was associated with severity of pain (P = 0.018). No association was found with regard to the other SNPs, both in AI and tamoxifen-treated patients. Neither could an association with vasomotor symptoms be demonstrated. CONCLUSION: The SNP rs2073618 in OPG is associated with an increased risk of MS symptoms and pain with AI therapy, which has not been reported previously. Validation of this finding in larger cohorts and further functional studies are required.

CRHBP polymorphisms predict chronic pain development following motor vehicle collision.

Musculoskeletal pain (MSP) is a common sequela of traumatic stress exposure. While biological factors contributing to chronic MSP after motor vehicle collision (MVC) have traditionally focused on tissue injury, increasing evidence suggests that neuro/stress/immune processes mediated by stress system activation may play a more dominant role. In a previous study, we found that genetic variants in the hypothalamic-pituitary-adrenal (HPA) axis-related gene FKBP5 influence vulnerability to persistent MSP 6 weeks after MVC. In the present cohort study (n = 855), we evaluated whether genetic variants in several other important HPA axis-related genes, including the glucocorticoid receptor (NR3C1), corticotropin-releasing hormone receptor R1 (CRHR1), and corticotropin-releasing hormone-binding protein (CRHBP), influence risk of chronic MSP over time after MVC. Genetic polymorphism rs7718461 in the CRHBP gene showed significant association (P = 0.0012) with overall pain severity during the year after MVC in regression models controlling for multiple comparisons. Two additional CRHBP alleles in high linkage disequilibrium with rs7718461 also showed trend-level significance. In secondary analyses, a significant interaction between this CRHBP locus (minor allele frequency = 0.33) and time was observed (P = 0.015), with increasing effect observed over time following trauma. A significant CRHBP × FKBP5 interaction was also observed, with substantially increased MSP after MVC in those with a risk allele in both genes compared with either gene alone. The results of this study indicate that genetic variants in 2 different HPA axis genes predict chronic MSP severity following MVC and support the hypothesis that the HPA axis is involved in chronic post-MVC MSP pathogenesis.