Genetic influences on the dynamics of pain and affect in fibromyalgia

Pharmacogenetic Approach to Tramadol Use in the Arab Population

Tramdol is one of most popular opioids used for postoperative analgesia worldwide. Among Arabic countries, there are reports that its dosage is not appropriate due to cultural background. To provide theoretical background of the proper usage of tramadol, this study analyzed the association between several genetic polymorphisms (CYP2D6/OPRM1) and the effect of tramadol. A total of 39 patients who took tramadol for postoperative analgesia were recruited, samples were obtained, and their DNA was extracted for polymerase chain reaction products analysis followed by allelic variations of CYP2D6 and OPRM A118G determination. Numerical pain scales were measured before and 1 h after taking tramadol. The effect of tramadol was defined by the difference between these scales. We concluded that CYP2D6 and OPRM1 A118G single nucleotide polymorphisms may serve as crucial determinants in predicting tramadol efficacy and susceptibility to post-surgical pain. Further validation of personalized prescription practices based on these genetic polymorphisms could provide valuable insights for the development of clinical guidelines tailored to post-surgical tramadol use in the Arabic population.

Central sensitization in opioid use disorder: a novel application of the American College of Rheumatology Fibromyalgia Survey Criteria

Central sensitization may be an underlying mechanism linking chronic pain and opioid use disorder associated with opioid use disorder onset, maintenance, escalation, treatment delay, and relapse.

Introduction:

Central sensitization (CS) involves dysfunctional central nervous system pain modulation resulting in heightened pain perception. Central sensitization is not commonly assessed among patients with opioid use disorder (OUD), despite the fact that pain has been implicated in the development, maintenance, and relapse of OUD and chronic opioid use may produce opioid-induced hyperalgesia. Central sensitization is a plausibly important mechanism underlying the complex relationship between OUD and chronic pain. However, this premise is largely untested.

Methods:

Participants with OUD (n = 141) were recruited from an academic addiction treatment center in Columbus, Ohio. An established surrogate measure of CS, the American College of Rheumatology 2011 Fibromyalgia Survey Criteria, was administered using electronic survey. Participants also responded to questions about pain interference (Brief Pain Inventory), quality of life (RAND-36), and items regarding pain beliefs and expectations of pain and addiction treatment. Descriptive analyses, Spearman rho correlations, and Mann–Whitney U tests were performed.

Results:

Hypothesized relationships were confirmed between degree of CS, pain interference, and health-related quality of life. Degree of CS was also positively correlated with greater endorsement of pain as a reason for the onset, maintenance, and escalation of OUD; treatment delay; and OUD relapse. Participants with the American College of Rheumatology 2011 Fibromyalgia Survey Criteria ≥13 had significantly greater endorsement of pain as a reason for delaying OUD treatment, continuing and increasing opioid use, and precipitating OUD relapse.

Conclusions:

This study provides early evidence CS may underlie previously observed connections between clinically salient features of chronic pain and OUD, potentially informing future mechanistic research and precision treatment.

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.

The role of affect in chronic pain: A systematic review of within-person symptom dynamics

OBJECTIVE

Chronic pain is conceptualized as a biopsychosocial phenomenon that involves both physical and emotional processes. The vast majority of research regarding these facets of chronic pain characterizes differences between individuals. In this review, we describe problems with assuming that differences between persons accurately characterize within-person processes. We also provide a systematic review of studies that have examined within-person relationships between pain and affect among individuals with chronic pain.

METHOD

Articles published by December 2020 that pertained to within-person assessment of pain and emotion, affect, or mood were identified. Data regarding study design, adherence, and concurrent and prospective relationships among pain and affect variables were extracted and summarized.

RESULTS

Of 611 abstracts, 55 studies met inclusion criteria. Results suggest that individuals with chronic pain tend to experience increased negative affect and decreased positive affect when experiencing more severe pain (r_pooled = .18 and - .19, respectively). However, the size of these effects appeared smaller than between-person associations, and there was evidence of significant variability between individuals. Examination of predictive relationships between pain and affect largely suggested the tendency of symptoms to predict themselves, rather than pain predicting affect or vice versa.

CONCLUSIONS

Consistent with group-level relationships, experiencing more severe pain relative to an individual's average seems to be associated with more negative affect and less positive affect. However, individuals vary in the size and even direction of these effects. More research is necessary to understand the implications of such variability for the assessment and treatment of chronic pain.

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.

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

Background

Dysregulation of the μ‐opioid receptor has been reported in fibromyalgia (FM) and was linked to pain severity. Here, we investigated the effect of the functional genetic polymorphism of the μ‐opioid receptor gene (OPRM1) (rs1799971) on symptom severity, pain sensitivity and cerebral pain processing in FM subjects and healthy controls (HC).

Methods

Symptom severity and pressure pain sensitivity was assessed in FM subjects (n = 70) and HC (n = 35). Cerebral pain‐related activation was assessed by functional magnetic resonance imaging during individually calibrated painful pressure stimuli.

Results

Fibromyalgia subjects were more pain sensitive but no significant differences in pain sensitivity or pain ratings were observed between OPRM1 genotypes. A significant difference was found in cerebral pain processing, with carriers of at least one G‐allele showing increased activation in posterior cingulate cortex (PCC) extending to precentral gyrus, compared to AA homozygotes. This effect was significant in FM subjects but not in healthy participants, however, between‐group comparisons did not yield significant results. Seed‐based functional connectivity analysis was performed with the seed based on differences in PCC/precentral gyrus activation between OPRM1 genotypes during evoked pain across groups. G‐allele carriers displayed decreased functional connectivity between PCC/precentral gyrus and prefrontal cortex.

Conclusions

G‐allele carriers showed increased activation in PCC/precentral gyrus but decreased functional connectivity with the frontal control network during pressure stimulation, suggesting different pain modulatory processes between OPRM1 genotypes involving altered fronto‐parietal network involvement. Furthermore, our results suggest that the overall effects of the OPRM1 G‐allele may be driven by FM subjects.

Significance

We show that the functional polymorphism of the μ‐opioid receptor gene OPRM1 was associated with alterations in the fronto‐parietal network as well as with increased activation of posterior cingulum during evoked pain in FM. Thus, the OPRM1 polymorphism affects cerebral processing in brain regions implicated in salience, attention, and the default mode network. This finding is discussed in the light of pain and the opioid system, providing further evidence for a functional role of OPRM1 in cerebral pain processing.

Plasma Concentrations of Select Inflammatory Cytokines Predicts Pain Intensity 48 Hours Post-Shoulder Muscle Injury

OBJECTIVES

The relationship between elevated inflammatory cytokine levels and peak pain intensity following acute musculoskeletal injury has not been fully elucidated in high risk subgroups. Identifying the role that these cytokines have on pain responses may help with developing tailored therapeutic approaches.

METHODS

Data were collected from 54 participants who were vulnerable to a robust pain response and delayed recovery following musculoskeletal injury. Participants completed baseline active and resting pain measurements and a blood draw before an exercised induced shoulder muscle injury. Participants returned at 24 and 48 hours postinjury for follow-up pain measurements and blood draws. Blood plasma was analyzed for interleukin (IL)-1β, IL-6, IL-8, IL-10, and tumor necrosis factor α. Pearson bivariate correlations were performed between cytokines and pain measurements to identify candidate variables for stepwise multiple linear regression predicting pain intensity reports.

RESULTS

Pearson bivariate correlation identified 13/45 correlations between inflammatory cytokines and resting pain intensity and 9/45 between inflammatory cytokines and active pain (P<0.05, r≥0.3 or r≤-0.3). This led to 5 stepwise multiple linear regression models, of which 4 met the statistical criterion (P<0.0167); including IL-10 baseline plasma concentrations predicting active pain (r=0.19) and resting pain (r=0.15) intensity 48 hours postinjury. IL-6 and IL-10 plasma concentrations at 48 hours were respectively associated with active and resting pain at 48 hours.

DISCUSSION

These findings suggest that elevated concentrations of inflammatory cytokines, specifically IL-10 (at baseline and 48 h) and IL-6 (at 48 h), may play a role in heightened pain responses following exercise-induced muscle injury.

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.

Towards a science and practice of resilience in the face of pain

The primary objective of this paper is to discuss how a resilience approach to (chronic) pain may advance our current understanding of (mal)adaptation to pain. Different resilience perspectives are described, and future challenges for research, prevention and treatment of (chronic) pain are discussed. Literature searches were performed in Web of Science and PubMed to identify relevant literature on risk and resilience in the context of pain. Resilience can be best defined as the ability to restore and sustain living a fulfilling life in the presence of pain. The Psychological Flexibility Model, the Broaden-and-Build Theory, and Self-Determination Theory are described as theories that may provide insight into resilience within the context of (chronic) pain. We describe how a resilience paradigm shifts the outcomes to pursue in pain research and intervention and argue the need for including positive outcomes in addition to negative outcomes. Psychological flexibility, positive affect and basic psychological needs satisfaction are described as potentially important resilience mechanisms with the potential to target both sustainability and recovery from pain. A resilience approach to chronic pain may have important implications for the prevention and treatment of chronic pain problems, as it may give specific indications on how to empower patients to continue living a fulfilling life (in the presence of pain).

SIGNIFICANCE

The resilience approach put forward in this review spotlights sustainability of positive outcomes (e.g. engagement in meaningful activities) in the presence of pain as an outcome to pursue beyond recovery of negative outcomes. We illuminate the evidence-base and practical application of promising resilience mechanisms (positive emotions, psychological flexibility, needs satisfaction). For this article, a commentary is available at the Wiley Online Library.

An observational study of the impact of genetic testing for pain perception in the clinical management of chronic non-cancer pain

OBJECTIVE

Pain levels are a key metric in clinical care. However, the assessment of pain is limited to basic questionnaires and physician interpretation, which yield subjective data. Genetic markers of pain sensitivity, such as single nucleotide polymorphisms in the catechol-O-methyltransferase gene, have been shown to be associated with pain perception and have been used to provide objective information about a patient's pain. The goal of this study was to determine if physician treatment adjustments based on genetic tests of pain perception resulted in improved outcomes for patients.

MATERIAL AND METHODS

A prospective, longitudinal study was conducted with 134 chronic non-cancer pain patients genotyped for pain perception-related catechol-O-methyltransferase haplotypes. Physicians were provided with patients' results and asked to document 1) their assessment of benefit of the genetic test; 2) treatment changes made based on the genetic test; and 3) patient clinical responses to changes implemented.

RESULTS

Based on genetic testing results, physicians adjusted treatment plans for 40% of patients. When medication changes were made based on genetic testing results, 72% of patients showed improvement in clinical status. When non-pharmacological actions were performed, 69% of physicians felt their patients' clinical status improved. Moreover, physicians believed the genetic test results were consistent with patient pain levels in 85% of cases.

CONCLUSIONS

These results demonstrate that providing personalized medicine with genetic information related to pain perception affected physician clinical decision-making for a substantial proportion of patients in this study, and that the availability and utilization of this information was a contributing factor in clinical improvement.

Fibromyalgia: A Critical and Comprehensive Review

Fibromyalgia is a disorder that is part of a spectrum of syndromes that lack precise classification. It is often considered as part of the global overview of functional somatic syndromes that are otherwise medically unexplained or part of a somatization disorder. Patients with fibromyalgia share symptoms with other functional somatic problems, including issues of myalgias, arthralgias, fatigue and sleep disturbances. Indeed, there is often diagnostic and classification overlap for the case definitions of a variety of somatization disorders. Fibromyalgia, however, is a critically important syndrome for physicians and scientists to be aware of. Patients should be taken very seriously and provided optimal care. Although inflammatory, infectious, and autoimmune disorders have all been ascribed to be etiological events in the development of fibromyalgia, there is very little data to support such a thesis. Many of these disorders are associated with depression and anxiety and may even be part of what has been sometimes called affected spectrum disorders. There is no evidence that physical trauma, i.e., automobile accidents, is associated with the development or exacerbation of fibromyalgia. Treatment should be placed on education, patient support, physical therapy, nutrition, and exercise, including the use of drugs that are approved for the treatment of fibromyalgia. Treatment should not include opiates and patients should not become poly pharmacies in which the treatment itself can lead to significant morbidities. Patients with fibromyalgia are living and not dying of this disorder and positive outlooks and family support are key elements in the management of patients.

Symptoms of Depression and Risk of New Episodes of Low Back Pain: A Systematic Review and Meta-Analysis

OBJECTIVE

To investigate the contribution of symptoms of depression to future episodes of low back pain (LBP).

METHODS

A search was conducted of AMED, CINAHL, Embase, Health and Society (H&S), LILACS, MEDLINE, PsycINFO, Scopus, and Web of Science databases. We included cohort studies investigating the effect of symptoms of depression on the development of new episodes of LBP, either lifetime incidence or a recurrent episode, in a population free of LBP at baseline. We accepted the original study's definition for a new episode of LBP, and for classifying patients as LBP-free at study entry. Two independent investigators extracted data and assessed methodological quality. Meta-analyses with random effects were used to pool risk estimates.

RESULTS

We included 19 studies, with 11 incorporated in the meta-analyses. Overall pooled results showed that symptoms of depression increased the risk of developing LBP (odds ratio [OR] 1.59, 95% confidence interval [95% CI] 1.26-2.01). The risk was similar in studies that used the diagnostic interview method (OR 1.66, 95% CI 1.14-2.42) and in studies using self-report screening questionnaires (OR 1.68, 95% CI 1.05-2.70). No statistically significant relationship was observed when we pooled studies that employed nonspecific screening questionnaires (OR 1.17, 95% CI 0.48-2.87). Three studies provided results in incremental categories of symptoms of depression and the pooled OR for the most severe level of depression (OR 2.51, 95% CI 1.58-3.99) was higher than for the lowest level (OR 1.51, 95% CI 0.89-2.56).

CONCLUSION

Individuals with symptoms of depression have an increased risk of developing an episode of LBP in the future, with the risk being higher in patients with more severe levels of depression.

COMT and OPRM1 Genotype Associations with Daily Knee Pain Variability and Activity Induced Pain

BACKGROUND

Osteoarthritis (OA) of the knee is a common and increasingly prevalent condition that is one of the primary causes of chronic pain. Staying physically active protects against disability from knee OA but is also very challenging. A critical but unexamined question is whether patients at greatest risk for becoming less active are those with a genetic predisposition for greater sensitivity to daily pain.

AIMS

We examined day-to-day variability in knee OA pain for patients with different variants of catechol-O-methyltransferase (COMT) and mu-opioid receptor (OPRM1) single nucleotide polymorphisms (SNPs), and whether patients with a specific genotype experience more pain following daily physical activity. We predicted that patients having one or more copies of the Met158 allele of COMT rs4680 (A-A or A-G) and one or more copies of the Asp40 allele of OPRM1 rs1799971 (A-G or G-G) would show greater pain variability. We expected to see the same pattern for these SNPs with regard to moderation (i.e., exacerbation) of the activity-pain association.

METHODS

A total of 120 knee OA patients reported on their pain 3 times per day over 22 days using handheld computers, and wore an accelerometer to capture daily physical activity. Multilevel modeling was used to examine the magnitude of within-person variability in pain by genetic group. We also examined whether lagged, within-patient associations between level of activity in the afternoon (i.e., minutes of moderate intensity activity, and number of steps) and knee pain at the end-of-day were moderated by between-patient differences in genotype.

RESULTS

Regarding OPRM1 rs1799971 (Asn40Asp), patients with two copies of the Asn40 allele showed the greatest day-to-day pain variability. Regarding COMT rs4680 (Val158Met), patients with the Val/Val genotype showed the greatest pain variability and also experienced the greatest increase in pain as a result of physical activity. A similar pattern of findings across bi-directional temporal lags was consistent with a negative feedback loop between daily physical activity and pain according to genotype. Consistent with some previous studies, there were no significant between-person differences in daily pain when comparing patients according to COMT rs4680, or OPRM1 rs1799971.

CONCLUSION

This study provides preliminary evidence that patients with certain genotypes for COMT rs4680 and OPRM1 rs1799971 (G-G and A-A, respectively) experience more variability in their day-to-day pain and exacerbation of pain after daily physical activity compared to patients with other genotypes. Our findings should be replicated in larger study populations.

IMPLICATIONS

Previous clinical research has focused primarily on differences in average level of pain between patients with and without a specific genotype. Assessment of within-person variability through repeated measurements in daily life enhances the reliability, power, and ecological validity of phenotypic measurement.

The role of positive affect in pain and its treatment

OBJECTIVE

This narrative review summarizes and integrates the available literature on positive affect (PA) and pain to: (1) provide a brief overview of PA and summarize the key findings that have emerged in the study of PA and pain; (2) provide a theoretical foundation from which to understand how PA operates in the context of chronic pain (CP); and (3) highlight how the prevailing psychosocial treatments for CP address PA in the therapeutic context, and offer suggestions for how future treatment development research can maximize the benefit of PA for patients with CP.

RESULTS

In experimental studies, the evidence suggests PA is analgesic. In clinical studies, the association of PA and pain is dynamic, time variant, and may be best considered in context of its interacting role with negative affect.

DISCUSSION

We offer an "upward spiral" model of PA, resilience and pain self-management, which makes specific predictions that PA will buffer maladaptive cognitive and affective responses to pain, and promote active engagement in valued goals that enhance CP self-management.

Genetic contribution of catechol-O-methyltransferase in hippocampal structural and functional changes of female migraine sufferers

Physiological and emotional stressors are associated with or provoke each migraine attack and cause structural and functional changes in the central nervous system. The hippocampus, a limbic structure important in anxiety-related behavior, is vulnerable to long-term stress. Given that catechol-O-methyltransferase (COMT) is widely distributed in the hippocampus and its genetic variation is thought to contribute to the interindividual variability in pain perception and anxiety regulation, whether or not migraine and COMT val(158) met genotype have an interactive effect in the key brain area related to maladaptive stress, the hippocampus, is still poorly understood. Using T1-weighted and resting functional MRI, we evaluated the effect of COMT genetic variations on migraine and possible interactions between COMT and the disease in brain structure and function in 135 females with migraine without aura (MWoA) and 111 matched health controls (HC). Optimized voxel-based morphometry (VBM) and functional connectivity (FC) analyses were applied. From the whole brain VBM analysis, we found a significant disease × genotype interaction in the hippocampus, which overlapped with disease-related increase of gray matter (GM) in val homozygote migraineurs. In our results, increased GM in the hippocampus was only found in val homozygote MWoA compared to val homozygote HC. Moreover, FC between the hippocampus and the medial prefrontal cortex was significantly decreased in val homozygotes, and it was negatively correlated with self-rating anxiety scale values.Our results indicated that brain structure and function of the hippocampus are differentially affected by migraine in val homozygotes compared with met carriers.

Proinflammatory cytokines and DHEA-S in women with fibromyalgia: impact of psychological distress and menopausal status

Though fibromyalgia is not traditionally considered an inflammatory disorder, evidence for elevated inflammatory processes has been noted in this disorder in multiple studies. Support for inflammatory markers in fibromyalgia has been somewhat equivocal to date, potentially due to inattention to salient patient characteristics that may affect inflammation, such as psychiatric distress and aging milestones like menopause. The current study examined the relationships between proinflammatory cytokines and hormone levels, pain intensity, and psychological distress in a sample of 34 premenopausal and postmenopausal women with fibromyalgia. Our results indicated significant relationships between interleukin-8 and ratings of pain catastrophizing (r=0.555, P<0.05), pain anxiety (r=0.559, P<0.05), and depression (r=0.551, P<0.05) for postmenopausal women but not premenopausal women (r,0.20 in all cases). Consistent with previous studies, ratios of interleukin-6 to interleukin-10 were significantly lower in individuals with greater levels of depressive symptoms (r=−0.239, P<0.05). Contrary to previous research, however, dehydroepiandrosterone sulfate did not correlate with pain intensity or psychological or biological variables. The results of the current study highlight the importance of psychological functioning and milestones of aging in the examination of inflammatory processes in fibromyalgia.

Biological pathways, candidate genes, and molecular markers associated with quality-of-life domains: an update

BACKGROUND

There is compelling evidence of a genetic foundation of patient-reported quality of life (QOL). Given the rapid development of substantial scientific advances in this area of research, the current paper updates and extends reviews published in 2010.

OBJECTIVES

The objective was to provide an updated overview of the biological pathways, candidate genes, and molecular markers involved in fatigue, pain, negative (depressed mood) and positive (well-being/happiness) emotional functioning, social functioning, and overall QOL.

METHODS

We followed a purposeful search algorithm of existing literature to capture empirical papers investigating the relationship between biological pathways and molecular markers and the identified QOL domains.

RESULTS

Multiple major pathways are involved in each QOL domain. The inflammatory pathway has the strongest evidence as a controlling mechanism underlying fatigue. Inflammation and neurotransmission are key processes involved in pain perception, and the catechol-O-methyltransferase (COMT) gene is associated with multiple sorts of pain. The neurotransmitter and neuroplasticity theories have the strongest evidence for their relationship with depression. Oxytocin-related genes and genes involved in the serotonergic and dopaminergic pathways play a role in social functioning. Inflammatory pathways, via cytokines, also play an important role in overall QOL.

CONCLUSIONS

Whereas the current findings need future experiments and replication efforts, they will provide researchers supportive background information when embarking on studies relating candidate genes and/or molecular markers to QOL domains. The ultimate goal of this area of research is to enhance patients' QOL.

Pharmacogenetics of OPRM1

Pharmacogenetic research has the potential to explain the variation in treatment efficacy within patient populations. Understanding the interaction between genetic variation and medications may provide a method for matching patients to the most effective therapeutic options and improving overall patient outcomes. The OPRM1 gene has been a target of interest in a large number of pharmacogenetic studies due to its genetic and structural variation, as well as the role of opioid receptors in a variety of disorders. The mu-opioid receptor (MOR), encoded by OPRM1, naturally regulates the analgesic response to pain and also controls the rewarding effects of many drugs of abuse, including opioids, nicotine, and alcohol. Genetic variants in OPRM1, particularly the non-synonymous polymorphism A118G, have been repeatedly associated with the efficacy of treatments for pain and various types of dependence. This review focuses on the current understanding of the pharmacogenetic impact of OPRM1, primarily with regard to the treatment of pain and addiction.

Pharmacogenetics of chronic pain and its treatment

This paper reviews the impact of genetic variability of drug metabolizing enzymes, transporters, receptors, and pathways involved in chronic pain perception on the efficacy and safety of analgesics and other drugs used for chronic pain treatment. Several candidate genes have been identified in the literature, while there is usually only limited clinical evidence substantiating for the penetration of the testing for these candidate biomarkers into the clinical practice. Further, the pain-perception regulation and modulation are still not fully understood, and thus more complex knowledge of genetic and epigenetic background for analgesia will be needed prior to the clinical use of the candidate genetic biomarkers.

Gene expression profiles of fatigued fibromyalgia patients with different categories of pain and catastrophizing: a preliminary report

BACKGROUND

Fibromyalgia (FM) is a chronic condition characterized by diffused musculoskeletal pain and overwhelming fatigue.

PURPOSE

To compare the gene expression profiles of fatigued FM women with different levels of pain and catastrophizing.

METHODS

Nine women with FM enrolled in an active Medstar Research Institute protocol were included in the gene expression analyses of peripheral blood RNA via Affymetrix GeneChip Human Genome U133 Plus 2.0 array (Santa Clara, CA). Scores from Brief Pain Inventory, Pain Catastrophizing Scale, and Multidimensional Fatigue Inventory categorized the nine participants into pain (high, n = 3; low, n = 6) and catastrophizing groups (high, n = 5; low, n = 4).

DISCUSSION

Differential expression of 107 genes between the high and low pain groups and 139 genes between the high and low catastrophizing groups (over 2.0-fold change, p < .05) were observed. Network analyses showed interferon signaling and interferon regulatory activation factor pathways distinguished between the pain groups whereas dendritic cell maturation delineated between the catastrophizing groups.

CONCLUSION

Findings provide preliminary evidence that specific physiological pathways may possibly delineate pain and catastrophizing mechanisms. Further investigation via the use of a larger and more homogenous sample is warranted.

Nature and nurture of human pain

Humans are very different when it comes to pain. Some get painful piercings and tattoos; others can not stand even a flu shot. Interindividual variability is one of the main characteristics of human pain on every level including the processing of nociceptive impulses at the periphery, modification of pain signal in the central nervous system, perception of pain, and response to analgesic strategies. As for many other complex behaviors, the sources of this variability come from both nurture (environment) and nature (genes). Here, I will discuss how these factors contribute to human pain separately and via interplay and how epigenetic mechanisms add to the complexity of their effects.

The phenotypic and genetic signatures of common musculoskeletal pain conditions

Musculoskeletal pain conditions, such as fibromyalgia and low back pain, tend to coexist in affected individuals and are characterized by a report of pain greater than expected based on the results of a standard physical evaluation. The pathophysiology of these conditions is largely unknown, we lack biological markers for accurate diagnosis, and conventional therapeutics have limited effectiveness. Growing evidence suggests that chronic pain conditions are associated with both physical and psychological triggers, which initiate pain amplification and psychological distress; thus, susceptibility is dictated by complex interactions between genetic and environmental factors. Herein, we review phenotypic and genetic markers of common musculoskeletal pain conditions, selected based on their association with musculoskeletal pain in previous research. The phenotypic markers of greatest interest include measures of pain amplification and 'psychological' measures (such as emotional distress, somatic awareness, psychosocial stress and catastrophizing). Genetic polymorphisms reproducibly linked with musculoskeletal pain are found in genes contributing to serotonergic and adrenergic pathways. Elucidation of the biological mechanisms by which these markers contribute to the perception of pain in these patients will enable the development of novel effective drugs and methodologies that permit better diagnoses and approaches to personalized medicine.

Catechol-O-methyltransferase gene polymorphism and chronic human pain: a systematic review and meta-analysis

In human studies, low COMT (catechol-O-methyltransferase) activity has been associated with increased sensitivity to acute clinical preoperative or postoperative pain. We explored the association between the COMT genotype and three chronic pain conditions: migrainous headache, fibromyalgia, or chronic widespread pain and chronic musculoskeletal pain. Furthermore, we evaluated whether COMT genotype affects the efficacy of opioids in chronic pain. After a systematic literature review, we carried out meta-analyses on the three chronic pain conditions. The efficacy of opioids was evaluated using a systematic review only. The meta-analyses showed that fibromyalgia or chronic widespread pain is the only type of chronic pain that could be associated with the COMT single nucleotide polymorphism rs4680 (Val158Met). Met158, which results in the low-activity variant of COMT, is the risk allele. In chronic clinical pain, the effect of the COMT polymorphism depends on the pain condition. Low COMT activity is not associated with migrainous headache or chronic musculoskeletal pain conditions, but it may increase the risk for fibromyalgia or chronic widespread pain. Low COMT activity increases opioid receptors and enhances opioid analgesia and adverse effects in some cancer pains. Findings from animal studies that have utilized COMT inhibitors elucidate the mechanism behind these findings. In rodent pain models, COMT inhibitors are pronociceptive, except for neuropathic pain models, where nitecapone was found to be antiallodynic. The complex interplay between enhanced adrenergic and dopaminergic activity in different parts of the nociceptive system probably explains the complicated actions of low COMT activity.

Overlap between functional GI disorders and other functional syndromes: what are the underlying mechanisms?

BACKGROUND

Irritable bowel syndrome and other gastrointestinal (GI) and non-GI disorders such as functional dyspepsia, fibromyalgia, temporomandibular joint disorder, interstitial cystitis/painful bladder syndrome, and chronic fatigue syndrome are known as functional pain syndromes. They commonly coexist within the same individual. The pathophysiologic mechanisms of these disorders are not well understood, but it has been hypothesized that they share a common pathogenesis.

PURPOSE

The objective of this review is to discuss the proposed pathophysiologic mechanisms, which have been similarly studied in these conditions. These mechanisms include enhanced pain perception, altered regional brain activation, infectious etiologies, dysregulations in immune and neuroendocrine function, and genetic susceptibility. Studies suggest that these functional disorders are multifactorial, but factors which increase the vulnerability of developing these conditions are shared.

Somatoform pain: a developmental theory and translational research review

Somatoform pain is a highly prevalent, debilitating condition and a tremendous public health problem. Effective treatments for somatoform pain are urgently needed. The etiology of this condition is, however, still unknown. On the basis of a review of recent basic and clinical research, we propose one potential mechanism of symptom formation in somatoform pain and a developmental theory of its pathogenesis. Emerging evidence from animal and human studies in developmental neurobiology, cognitive-affective neuroscience, psychoneuroimmunology, genetics, and epigenetics, as well as that from clinical and treatment studies on somatoform pain, points to the existence of a shared neural system that underlies physical and social pain. Research findings also show that nonoptimal early experiences interact with genetic predispositions to influence the development of this shared system and the ability to regulate it effectively. Interpersonal affect regulation between infant and caregiver is crucial for the optimal development of these brain circuits. The aberrant development of this shared neural system during infancy, childhood, and adolescence may therefore ultimately lead to an increased sensitivity to physical and social pain and to problems with their regulation in adulthood. The authors critically review translational research findings that support this theory and discuss its clinical and research implications. Specifically, the proposed theory and research review suggest that psychotherapeutic and/or pharmacological interventions that foster the development of affect regulation capacities in an interpersonal context will also serve to more effectively modulate aberrantly activated neural pain circuits and thus be of particular benefit for the treatment of somatoform pain.

The comorbidity of insomnia, chronic pain, and depression: dopamine as a putative mechanism

Epidemiological, cross-sectional, and prospective studies suggest that insomnia, chronic pain, and depression frequently co-occur and are mutually interacting conditions. However, the mechanisms underlying these comorbid disorders have yet to be elucidated. Overlapping mechanisms in the central nervous system suggest a common neurobiological substrate(s) may underlie the development and interplay of these disorders. We propose that the mesolimbic dopamine system is an underappreciated and attractive venue for the examination of neurobiological processes involved in the interactions, development, exacerbation, and maintenance of this symptom complex. In the present article, studies from multiple disciplines are reviewed to highlight the role of altered dopaminergic function in the promotion of arousal, pain sensitivity, and mood disturbance. We argue that studies aiming to elucidate common factors accounting for the comorbidity of insomnia, chronic pain, and depression should evaluate functioning within the mesolimbic dopaminergic system and its effect on common processes known to be dysregulated in all three disorders.

Ambulatory monitoring in the genetics of psychosomatic medicine

Psychosomatic disorders are composed of an array of psychological, biologic, and environmental features. The existing evidence points to a role for genetic factors in explaining individual differences in the development and maintenance of a variety of disorders, but studies to date have not shown consistent and replicable effects. As such, the attempt to uncover individual differences in the expression of psychosomatic disorders as a function of genetic architecture requires careful attention to their phenotypic architecture or the various intermediate phenotypes that make up a heterogeneous disorder. Ambulatory monitoring offers a novel approach to measuring time-variant and situation-dependent intermediate phenotypes. Recent examples of the use of ambulatory monitoring in genetic studies of stress reactivity, chronic pain, alcohol use disorders, and psychosocial resilience are reviewed in an effort to highlight the benefits of ambulatory monitoring for genetic study designs.

Recent advances in the understanding of genetic susceptibility to chronic pain and somatic symptoms

Regional (e.g., low back) and widespread chronic pain disorders are common in the general population and are known to be heritable. Recent research suggests that genetic factors increase the risk of developing chronic pain independent of the site of pain. Candidate gene studies have been conducted on key pathways to elucidate susceptibility genes that are likely to be involved in both the sensory and affective components of pain. Findings have been largely equivocal, predominantly due to small sample size, but larger studies of pain in general population samples are being conducted. Interesting candidate genes from animal models and monogenic pain disorders are beginning to emerge. Recent advances in genetics research have yet to make an impact in the pain field but provide considerable scope for future research efforts.

Catecholamines and heart rate in female fibromyalgia patients

BACKGROUND

Fibromyalgia syndrome is a disease of unknown pathogenesis characterised by widespread chronic musculoskeletal pain. Fibromyalgia has been associated with dysregulation of the stress systems, but results are inconsistent.

PURPOSE

To investigate autonomic nervous system activity (urinary noradrenaline, adrenaline, dopamine, and heart rate) of fibromyalgia patients and healthy controls.

METHODS

Urinary catecholamines and heart rate were assessed for a 24-hour period in a controlled hospital setting (including relaxation, a test with prolonged mental stress, and sleep), and during daily activity in 29 female fibromyalgia patients and 29 age-matched female healthy controls.

RESULTS

With repeated measures ANOVAs, catecholamine levels were lower in patients than controls (P=.035 for noradrenaline; P=.005 for adrenaline; P=.001 for dopamine). One-way ANOVAs for the single periods showed that patients compared to controls had significantly lower adrenaline levels during the night (P=.010) and the second day (P=.010), significantly lower dopamine levels during the first day (P=.008), the night (P=.001), and the second day (P=.004). However, single time point noradrenaline levels were not significantly different between the groups. Overall, heart rate was significantly higher in patients than controls (P=.014). Specifically, significant differences emerged during relaxation (P=.016) and sleep (P=.011), but not during stress provocation or daily activities.

CONCLUSIONS

The results indicate an altered regulation of the autonomic nervous system in fibromyalgia patients, with attenuated activity of both the sympathetic (adrenal medulla component) and the parasympathetic branch.

COMT moderates the relation of daily maladaptive coping and pain in fibromyalgia

Forty-five women with fibromyalgia (FM) engaged in a 30-day electronic diary assessment, recording daily ratings of pain and 2 forms of maladaptive coping: pain catastrophizing and pain attention. Participants were genotyped for the val(158)met single nucleotide polymorphism (rs4680) in the catechol-O-methyltransferase (COMT) gene. COMT genotype moderated the daily relations of both maladaptive coping processes and pain. FM women with the homozygous met/met genotype evidenced more pain on days when pain catastrophizing was elevated relative to heterozygous and homozygous val(158) carriers. FM women with the homozygous met/met genotype evidenced more pain on days when pain attention was elevated relative to those with the homozygous val/val genotype. Evidence is presented to suggest that these are independent effects. The findings provide multimeasure and multimethod support for genetic moderation of a maladaptive coping and pain process, which has been previously characterized in a sample of postoperative shoulder pain patients. Further, the findings advance our understanding of the role of COMT in FM, suggesting that genetic variation in the val(158)met polymorphism may affect FM pain through pathways of pain-related cognition. This study examined 2 forms of maladaptive coping: pain catastrophizing and pain attention. The findings provide multimeasure and multimethod support for genetic moderation of a maladaptive coping and pain process and suggest that genetic variation in the val(158)met polymorphism may affect fibromyalgia pain through pathways of pain-related cognition.

Fibromyalgia and fatigue: central processing, widespread dysfunction

Biological and psychological bases for the covariation of pain and fatigue in fibromyalgia (FM) are reviewed. FM is characterized as a disorder of central sensitization, with pain and fatigue as the most prominent symptoms. The roles of sleep disturbance and affective dysregulation as both precipitants and consequences of pain and fatigue in FM are discussed. It is argued that a positive affective disturbance may uniquely characterize pain and fatigue symptoms in FM. Finally, pharmacological and nonpharmacological treatments for FM are highlighted, with an emphasis on the efficacy of these treatments in alleviating pain and fatigue symptoms.

Does Exercise Benefit Fibromyalgia?

This review discusses evidence-based perspectives on the potential benefits of exercise for fibromyalgia. Future directions for inquiry and clinical management also are addressed.