Unaltered low nerve growth factor and high brain-derived neurotrophic factor levels in plasma from patients with fibromyalgia after a 15-week progressive resistance exercise

Brain-Derived Neurotrophic Factor, Nociception, and Pain

This article examines the involvement of the brain-derived neurotrophic factor (BDNF) in the control of nociception and pain. BDNF, a neurotrophin known for its essential role in neuronal survival and plasticity, has garnered significant attention for its potential implications as a modulator of synaptic transmission. This comprehensive review aims to provide insights into the multifaceted interactions between BDNF and pain pathways, encompassing both physiological and pathological pain conditions. I delve into the molecular mechanisms underlying BDNF's involvement in pain processing and discuss potential therapeutic applications of BDNF and its mimetics in managing pain. Furthermore, I highlight recent advancements and challenges in translating BDNF-related research into clinical practice.

Effects of exercise-based interventions on inflammatory markers in patients with fibromyalgia: A systematic review and meta-analysis

OBJECTIVES

The aim of the present review was (1) to determine the effects of exercise based-interventions (EBIs) on pro-inflammatory and anti-inflammatory biomarkers in patients with fibromyalgia (FM), and (2) to determine the most effective type (acute or maintained) and modality (aerobic, resistance, etc.).

METHODS

A systematic search was conducted in various electronic databases to identify all the relevant studies: Medline (PubMed), PEDro, EBSCO and Google Scholar. Clinical trials assessing the effects of EBIs in patients with FM were selected. Methodological quality was evaluated by two independent investigators using the Cochrane Risk of Bias Tool. Qualitative analysis was based on the classification of the results into levels of evidence according to GRADE.

RESULTS

Eleven studies were included. The meta-analysis showed a statistically significant decrease in proinflammatory biomarkers by EBIs with a large clinical effect in 19 comparisons (SMD: 1.74; 95 % CI: 0.85-2.62; p < 0.05), especially for IL8. The certainty of the evidence was low. The meta-analysis showed no statistically significant increase in anti-inflammatory biomarkers (IL10) by EBIs in 6 comparisons and very low certainty of evidence. Evidence was found for acute and maintained effects of exercise, with aerobic and aquatic exercise modalities showing better improvements than resistance exercise.

CONCLUSIONS

EBIs are effective in inducing an immunomodulatory response in FM, characterized by decreased pro-inflammatory signaling. However, there was no evidence of an increase in anti-inflammatory biomarkers. These results should be interpreted with caution due to low certainty of evidence.

The Role of the Brain-Derived Neurotrophic Factor in Chronic Pain: Links to Central Sensitization and Neuroinflammation

Chronic pain is sustained, in part, through the intricate process of central sensitization (CS), marked by maladaptive neuroplasticity and neuronal hyperexcitability within central pain pathways. Accumulating evidence suggests that CS is also driven by neuroinflammation in the peripheral and central nervous system. In any chronic disease, the search for perpetuating factors is crucial in identifying therapeutic targets and developing primary preventive strategies. The brain-derived neurotrophic factor (BDNF) emerges as a critical regulator of synaptic plasticity, serving as both a neurotransmitter and neuromodulator. Mounting evidence supports BDNF's pro-nociceptive role, spanning from its pain-sensitizing capacity across multiple levels of nociceptive pathways to its intricate involvement in CS and neuroinflammation. Moreover, consistently elevated BDNF levels are observed in various chronic pain disorders. To comprehensively understand the profound impact of BDNF in chronic pain, we delve into its key characteristics, focusing on its role in underlying molecular mechanisms contributing to chronic pain. Additionally, we also explore the potential utility of BDNF as an objective biomarker for chronic pain. This discussion encompasses emerging therapeutic approaches aimed at modulating BDNF expression, offering insights into addressing the intricate complexities of chronic pain.

Transcranial direct current stimulation is more effective than pregabalin in controlling nociceptive and anxiety-like behaviors in a rat fibromyalgia-like model

OBJECTIVES

Despite the fact that fibromyalgia, a widespread disease of the musculoskeletal system, has no specific treatment, patients have shown improvement after pharmacological intervention. Pregabalin has demonstrated efficacy; however, its adverse effects may reduce treatment adherence. In this context, neuromodulatory techniques such as transcranial direct current stimulation (tDCS) may be employed as a complementary pain-relieving method. Consequently, the purpose of this study was to evaluate the effect of pregabalin and tDCS treatments on the behavioral and biomarker parameters of rats submitted to a fibromyalgia-like model.

METHODS

Forty adult male Wistar rats were divided into two groups: control and reserpine. Five days after the end of the administration of reserpine (1 mg/kg/3 days) to induce a fibromyalgia-like model, rats were randomly assigned to receive either vehicle or pregabalin (30 mg/kg) along with sham or active- tDCS treatments. The evaluated behavioral parameters included mechanical allodynia by von Frey test and anxiety-like behaviors by elevated plus-maze test (time spent in opened and closed arms, number of entries in opened and closed arms, protected head-dipping, unprotected head-dipping [NPHD], grooming, rearing, fecal boluses). The biomarker analysis (brain-derived neurotrophic factor [BDNF] and tumor necrosis factor-α [TNF-α]) was performed in brainstem and cerebral cortex and in serum.

RESULTS

tDCS reversed the reduction in the mechanical nociceptive threshold and the decrease in the serum BDNF levels induced by the model of fibromyalgia; however, there was no effect of pregabalin in the mechanical threshold. There were no effects of pregabalin or tDCS found in TNF-α levels. The pain model induced an increase in grooming time and a decrease in NPHD and rearing; while tDCS reversed the increase in grooming, pregabalin reversed the decrease in NPHD.

CONCLUSIONS

tDCS was more effective than pregabalin in controlling nociception and anxiety-like behavior in a rat model-like fibromyalgia. Considering the translational aspect, our findings suggest that tDCS could be a potential non-pharmacological treatment for fibromyalgia.

Clinical relevance of resistance training in women with fibromyalgia: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

There has been an increase in the number of papers assessing the effects of resistance training (RT) in patients with fibromyalgia. Therefore, the objective of our study was to evaluate the clinical relevance and effectiveness of RT for pain intensity, functionality and severity of the disease specifically in women with fibromyalgia through a systematic review with meta-analysis.

DATABASES AND DATA TREATMENT

Seven databases were searched. Randomized controlled trials conducted in women over 18 years of age with fibromyalgia were included. Fifteen trials were included in the systematic review and 14 of these studies were included in the three meta-analyses performed. Study quality assessment was performed using the PEDro scale. In addition, the GRADE recommendations were used.

RESULTS

The global meta-analysis revealed statistically significant differences in the RT group versus the control group on pain intensity (SMD = -0.49; 95% CI [-0.74, -0.24], p = 0.0001), functionality (SMD = -0.23; 95% CI [0.01, 0.45], p = 0.04) and on severity of the disease (SMD = -0.58; 95% CI [-0.90, -0.26], p = 0.0005). Clinically relevant improvements in the overall outcome of the three variables studied in favour of RT were obtained.

CONCLUSIONS

RT is effective to improve pain intensity, functionality and severity of the disease in women with fibromyalgia. These improvements are clinically relevant. More clinical trials of RT are needed in women with fibromyalgia to support our results due to the low strength of evidence.

SIGNIFICANCE

This systematic review with meta-analysis provides evidence that RT produces clinically relevant improvements in women with fibromyalgia. The absence of immediate benefit is often a major barrier to adherence to treatment. Our findings will help clinicians to empower patients that if they continue treatment, they will achieve improvement in their disease.

Brain-derived neurotrophic factor in fibromyalgia: A systematic review and meta-analysis of its role as a potential biomarker

BACKGROUND

Fibromyalgia (FM) is a form of chronic pain disorder accompanied by several tender points, fatigue, sleeping and mood disturbances, cognitive dysfunction, and memory problems. Brain-derived neurotrophic factor (BDNF) is also a mediator of neurotrophin for many activity-dependent processes in the brain. Despite numerous research studies investigating BDNF in FM, contradictory results have been reported. Thus, we investigated the overall effect shown by studies to find the association between peripheral BDNF concentrations and its gene polymorphisms with FM.

METHODS

A systematic search in online international databases, including PubMed, Cochrane Library, Embase, the Web of Science, and Scopus was performed. Relevant studies assessing BDNF levels or gene polymorphism in patients with FM and comparing them with controls were included. Case reports, reviews, and non-English studies were excluded. We conducted the random-effect meta-analysis to estimate the pooled standardized mean difference (SMD) or odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Twenty studies were found to be included composed of 1,206 FM patients and 1,027 controls. The meta-analysis of 15 studies indicated that the circulating BDNF levels were significantly higher in FM (SMD 0.72, 95% CI 0.12 to 1.31; p-value = 0.02). However, no difference between the rate of Val/Met carrier status at the rs6265 site was found (p-value = 0.43). Using meta-regression, the sample size and age variables accounted for 4.69% and 6.90% of the observed heterogeneity of BDNF level analysis, respectively.

CONCLUSION

Our meta-analysis demonstrated that FM is correlated with increased peripheral BDNF levels. This biomarker's diagnostic and prognostic value should be further investigated in future studies.

Effects of progressive intensity resistance training on the impact of fibromyalgia: protocol for a blinded randomized controlled trial

BACKGROUND

Fibromyalgia guidelines indicate that exercise is critical in the management of fibromyalgia, and there is evidence that patients with fibromyalgia can perform resistance training at moderate and high intensities. However, despite the biological plausibility that progression of intensity provides greater benefit to individuals, no studies have compared different intensities (progressive versus constant intensities) of the same exercise in this population.

OBJECTIVE

To compare the effect of 24 sessions of resistance training (progressive vs. constant intensity) on impact of fibromyalgia, sleep quality, anxiety, depression, pain, walking ability, and musculoskeletal capacity.

METHODS

A protocol for a blinded randomized controlled trial. The sample will be randomized into three groups: group 1 (progressive intensity, experimental), group 2 (constant intensity, control A), and group 3 (walking, control B). Group 1 will perform resistance training at moderate intensity (50% of maximum dynamic strength), previously determined by the 1 repetition maximum (1-RM) test in the proposed exercises. The strength of each individual will be reassessed every 4 weeks (by 1-RM) and the intensity of each exercise will be positively adjusted by 20% of the value observed in kg (i.e., first month 50%; second month 70%; third month 90% of the maximum dynamic strength). Group 2 will perform the same procedure, but the intensity will be maintained at 50% of the maximum dynamic strength throughout the treatment (i.e., constant intensity from the first to the third month). Group 3 will perform a 40-minute treadmill walk at low intensity, defined by a walking speed corresponding to 60-70% of the maximum heart rate, which we will control with a heart rate monitor. All groups will receive a 45-minute pain education session prior to the exercise program, covering the pathophysiologic mechanisms of chronic pain, strategies for coping with pain, avoiding hypervigilance, and deconstructing beliefs and myths about chronic pain.

DISCUSSION

The results of the present study may help health care professionals adjust the intensity of resistance training and thus plan the most effective intervention (progressive or constant intensity) to reduce the impact of fibromyalgia on patients' lives.

TRIAL REGISTRATION

Brazilian Registry of Clinical Trials (ReBEC) ID: RBR-9pbq9fg, date of registration: October 06, 2022.

The Effects of Non-Pharmacological Interventions in Fibromyalgia: A Systematic Review and Metanalysis of Predominants Outcomes

(1) Fibromyalgia (FM) is a chronic musculoskeletal condition with multiple symptoms primarily affecting women. An imbalance in cytokine levels has been observed, suggesting a chronic low-grade inflammation. The main aim of the meta-analysis was to examine the effect of multimodal rehabilitation on cytokine levels and other predominant variables in patients with FM. Furthermore, to examine which non-pharmacological tools have been used to investigate the effects that these can have on cytokines in FM patients. (2) Methods: Searches were conducted in PubMed, Scopus, Web of Science, Cochrane, and ScienceDirect databases. This systematic review and metanalysis followed the PRISMA statement protocol. The methodological quality of the studies was assessed using the PEDro scale, the risk of bias followed the Cochrane Manual 5.0.1, and the GRADE system was used for rating the certainty of evidence. (3) Results: Of 318 studies found, eight were finally selected, with a sample size of 320 women with a mean age of 57 ± 20. The proinflammatory cytokines IL-1β, IL-6, IL-8 and TNF-α were the most studied. Resistance exercise, aquatic exercise, dynamic contractions, cycling, treadmill, and infrared therapy were the main non-pharmacological tools used. (4) Conclusions: The systematic review with meta-analysis found evidence of elevated cytokine levels in patients with FM, suggesting low chronic inflammation and a possible contribution to central sensitization and chronic pain. However, the effects of physiotherapeutic interventions on cytokine levels are variable, highlighting the importance of considering different factors and the need for further research.

Mechanisms hypothesized for pain-relieving effects of exercise in fibromyalgia: a scoping review

Background

Exercise is one of the most recommended management strategies by treatment guidelines for fibromyalgia (FM); however, the mechanism through which exercise improves pain in FM is still unknown.

Objective

We aimed to summarize the hypothesized theoretical mechanisms for the pain-relieving effects of exercise in people with FM.

Eligibility Criteria

Randomized controlled trials (RCTs) in English reporting mechanisms for pain-relieving effects of exercise in the 'Introduction' and 'Discussion' sections and significant within- group or between-group effects of exercise interventions were included.

Sources of Evidence

We searched the databases Ovid MEDLINE(R), EMBASE, CINAHL, COCHRANE, Sports Discuss, and AMED with the keywords: exercise and fibromyalgia until December 2021.

Charting Methods

Two authors independently performed title/abstract, full-text review, and data abstraction using a data abstraction form. The hypothesized mechanisms from individual studies were grouped into three categories.

Results

The literature search resulted in 2147 studies, out of which 220 studies were considered for full-text review. A total of 50 RCTs proposing 29 unique mechanisms for the pain-relieving effects of exercise were included. These mechanisms were divided into three categories: physical, neuro-physiological, and psychological. The neuro-physiological category was further subdivided into exercise-induced hypoalgesia (EIH), pain sensitization, the autonomic system, the immune system, the endocrine system, and miscellaneous categories. The most frequently hypothesized mechanisms were EIH (n = 15), autonomic modulation (n = 7), improved sleep (n = 6), muscle oxygenation (n = 6), self-efficacy (n = 5), mental health (n = 4), and benefits of the aquatic environment (n = 12). While all exercise interventions involved FM patients, most of the supporting evidence for these mechanisms was cited from previous studies conducted on healthy samples. No studies performed analyses to demonstrate causal associations between the mechanisms and outcomes.

Conclusion

Multiple mechanisms were hypothesized for the positive influence of exercise in people with FM. Future studies using causal analyses, such as mediation analysis, are recommended to validate these mechanisms.

Pain Biomarkers in Fibromyalgia Syndrome: Current Understanding and Future Directions

Fibromyalgia is a complex and heterogeneous clinical syndrome, mainly characterized by the presence of widespread pain, possibly associated with a variety of other symptoms. Fibromyalgia can have an extremely negative impact on the psychological, physical and social lives of people affected, sometimes causing patients to experience dramatically impaired quality of life. Nowadays, the diagnosis of fibromyalgia is still clinical, thus favoring diagnostic uncertainties and making its clear identification challenging to establish, especially in primary care centers. These difficulties lead patients to undergo innumerable clinical visits, investigations and specialist consultations, thus increasing their stress, frustration and even dissatisfaction. Unfortunately, research over the last 25 years regarding a specific biomarker for the diagnosis of fibromyalgia has been fruitless. The discovery of a reliable biomarker for fibromyalgia syndrome would be a critical step towards the early identification of this condition, not only reducing patient healthcare utilization and diagnostic test execution but also providing early intervention with guideline-based treatments. This narrative article reviews different metabolite alterations proposed as possible biomarkers for fibromyalgia, focusing on their associations with clinical evidence of pain, and highlights some new, promising areas of research in this context. Nevertheless, none of the analyzed metabolites emerge as sufficiently reliable to be validated as a diagnostic biomarker. Given the complexity of this syndrome, in the future, a panel of biomarkers, including subtype-specific biomarkers, could be considered as an interesting alternative research area.

Can exercise-based interventions reverse gray and white matter abnormalities in patients with chronic musculoskeletal pain? A systematic review

BACKGROUND

Recent evidence has suggested that reversal of gray or white matter abnormalities could be a criterion of recovery in patients with chronic pain.

OBJECTIVE

To determine the effectiveness of exercise-based interventions in reversing gray and white matter abnormalities in patients with chronic musculoskeletal pain.

METHODS

An electronic search was performed in the MEDLINE (Via PubMed), EMBASE, Web of Science, LILACS, SPORTDiscus, CINAHL, PEDro, and CENTRAL databases for articles published up to November 2022. Randomized clinical trials (RCTs) including patients with chronic musculoskeletal pain, which assessed the change in gray and white matter abnormalities after exercise-based interventions were selected. The risk of bias was assessed using the Risk of Bias II tool.

RESULTS

Four RCTs were included (n= 386). Three studies showed reversal of abnormalities with exercise-based interventions compared to control groups. The reversal was observed in the gray matter volume in the medial orbital prefrontal cortex and in the supplementary motor area of patients with osteoarthritis, in the hippocampus, insula, amygdala and thalamus in fibromyalgia patients. Furthermore, in patients with chronic spinal pain, reversal was observed in the gray matter thickness of the frontal middle caudal cortex and in the caudate, putamen and thalamus gray matter volume.

CONCLUSIONS

There is insufficient evidence to determine the effectiveness of exercise-based interventions for reversing gray and white matter abnormalities in patients with chronic pain. Further studies are still needed in this field.

Topical review - salivary biomarkers in chronic muscle pain

BACKGROUND AND AIMS

Muscle related temporomandibular disorders (myogenous TMD), one of the most common orofacial pain conditions, is characterized by facial pain and often accompanied by jaw movement limitations. Although the underlying biological mechanisms are still unclear, a cluster of proteins and peptides is assumed to be involved in the pathophysiology. These proteins and peptides may be measured in a simple non-invasive saliva sample. This work investigated whether saliva can be used to sample algogenic substances that can serve as molecular biomarkers for TMD myalgia.

METHODS

Saliva and blood samples were collected from healthy individuals (n=69) and patients diagnosed with TMD myalgia (n=39) according to the Diagnostic Criteria for TMD. Unstimulated and stimulated whole, parotid, and sublingual saliva were analysed. The protein profiles were investigated using two-dimensional gel electrophoresis followed by identification with liquid chromatography tandem mass spectrometry. Levels of nerve growth factor (NGF), calcitonin gene-related peptide (CGRP), and brain derived neuro-tropic factor (BDNF) were determined using western blotting based technology and multiplex electro-chemiluminescence assay panel. Glutamate, serotonin, and substance p (SP) were determined using commercially available methods.

RESULTS

Different saliva collection approaches resulted in significant differences in the protein profile as well as in the expression of NGF, BDNF, CGRP, SP, and glutamate. Stimulated whole saliva showed least variability in protein concentration (35%) and was correlated to plasma levels of glutamate. Unlike SP and glutamate, NGF and BDNF expressed a rhythmic variation in salivary expression with higher levels in the morning (p<0.05). Patients with a diagnosis of TMD myalgia had significantly higher levels of salivary glutamate but lower salivary NGF and BDNF compared to controls; in addition, the lower NGF and BDNF levels correlated to psychological dysfunction. The quantitative proteomics data revealed 20 proteins that were significantly altered in patients compared to controls. The identified proteins are involved in metabolic processes, immune response, and stress response. Dissimilarities in protein profile and clinical variables were observed between TMD myalgia and myofascial pain.

CONCLUSIONS

The work highlights the importance of consistency in saliva collection approaches, including the timing of the collection. It displayed significant changes in pain specific mediators and protein profile in TMD myalgia and furthermore dissimilarities between subclasses indicating different pathophysiology. After extensive validation, potential salivary biomarkers can be combined with clinical features to better understand and diagnose TMD myalgia.

The Vastus Lateralis Muscle Interstitium Proteome Changes after an Acute Nociception in Patients with Fibromyalgia Compared to Healthy Subjects-A Microdialysis Study

Fibromyalgia (FM) is a complex disorder and a clinical challenge to diagnose and treat. Microdialysis is a valuable tool that has been used to investigate the interstitial proteins and metabolites of muscle in patients with fibromyalgia. The implantation of the catheter in the muscle causes acute tissue trauma and nociception. The aim of this study was to investigate acute proteome changes in the vastus lateralis muscle in women fibromyalgia patients (FM) and healthy subjects (CON). A further aim was to study if a 15-week resistance exercise program in FM had any influence on how chronic painful muscle responds to acute nociception. Twenty-six women patients with FM and twenty-eight CON were included in this study. A microdialysis catheter (100 kilo Dalton cut off, membrane 30 mm) was inserted in the vastus lateralis muscle, and samples were collected every 20 min. Subjects rated pain before catheter insertion, directly after, and every 20 min of sample collection. Dialysate samples from time points 0-120 were pooled and considered trauma samples due to the catheter insertion. The samples were analyzed with nano-liquid chromatography-tandem mass spectrometry (nLC-MS/MS). Advanced multivariate data analysis was used to investigate protein profile changes between the groups. Multivariate data analysis showed significant (CV-ANOVA p = 0.036) discrimination between FM and CON based on changes in 26 proteins. After the 15-week exercise intervention, the expression levels of the 15 proteins involved in muscle contraction, response to stimulus, stress, and immune system were increased to the same expression levels as in CON. In conclusion, this study shows that microdialysis, in combination with proteomics, can provide new insights into the interstitial proteome in the muscle of FM. In response to acute nociception, exercise may alter the innate reactivity in FM. Exercise may also modulate peripheral muscle proteins related to muscle contraction, stress, and immune response in patients with FM.

Effect of Different Physical Therapy Interventions on Brain-Derived Neurotrophic Factor Levels in Chronic Musculoskeletal Pain Patients: A Systematic Review

OBJECTIVE

The main objectives of this review were, firstly, to study the effect of different physiotherapy interventions on BDNF levels, and, secondly, to analyze the influence of physiotherapy on pain levels to subsequently draw conclusions about its possible relationship with BDNF.

BACKGROUND

Based on the theory that neurotrophic factors such as BDNF play a fundamental role in the initiation and/or maintenance of hyperexcitability of central neurons in pain, it was hypothesized that the levels of this neurotrophic factor may be modified by the application of therapeutic interventions, favoring a reduction in pain intensity.

METHODS

A literature search of multiple electronic databases (Pubmed, PsycINFO, Medline (Ebsco), Scopus, WOS, Embase) was conducted to identify randomized control trials (RCTs) published without language restrictions up to and including March 2022. The search strategy was based on the combination of medical terms (Mesh) and keywords relating to the following concepts: "pain", "chronic pain", "brain derived neurotrophic factor", "BDNF", "physiotherapy", and "physical therapy". A total of seven papers were included.

RESULTS

There were two studies that showed statistically significant differences in pain intensity reduction and an increase in the BDNF levels that used therapies such as rTMS and EIMS in patients with chronic myofascial pain. However, the same conclusions cannot be drawn for the other physical therapies applied.

CONCLUSIONS

rTMS and EIMS interventions achieved greater short-term reductions in pain intensity and increased BDNF over other types of interventions in chronic myofascial pain patients, as demonstrated by a moderate amount of evidence. In contrast, other types of physical therapy (PT) interventions did not appear to be more effective in decreasing pain intensity and increasing BDNF levels than placebo PT or minimal intervention, as a low amount of evidence was found.

Influence of routine exercise on the peripheral immune system to prevent and alleviate pain

Routine physical activity reduces the onset of pain and exercise is a first line treatment for individuals who develop chronic pain. In both preclinical and clinical research regular exercise (routine exercise sessions) produces pain relief through multiple mechanisms such as alterations in the central and peripheral nervous system. More recently, it has been appreciated that exercise can also alter the peripheral immune system to prevent or reduce pain. In animal models, exercise can alter the immune system at the site of injury or pain model induction, in the dorsal root ganglia, and systemically throughout the body to produce analgesia. Most notably exercise shows the ability to dampen the presence of pro-inflammatory immune cells and cytokines at these locations. Exercise decreases M1 macrophages and the cytokines IL-6, IL-1β, and TFNα, while increasing M2 macrophages and the cytokines IL-10, IL-4, and IL-1ra. In clinical research, a single bout of exercise produces an acute inflammatory response, however repeated training can lead to an anti-inflammatory immune profile leading to symptom relief. Despite the clinical and immune benefits of routine exercise, the direct effect of exercise on immune function in clinical pain populations remains unexplored. This review will discuss in more detail the preclinical and clinical research which demonstrates the numerous ways through which multiple types of exercise alter the peripheral immune system. This review closes with the clinical implications of these findings along with suggestions for future research directions.

Plasma proteins from several components of the immune system differentiate chronic widespread pain patients from healthy controls - an exploratory case-control study combining targeted and non-targeted protein identification

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain and hyperalgesia. Plasma proteins from proteomics (non-targeted) and from targeted inflammatory panels (cytokines/chemokines) differentiate CWP/FM from controls. The importance of proteins obtained from these two sources, the protein-protein association network, and the biological processes involved were investigated. Plasma proteins from women with CWP (n = 15) and CON (n = 23) were analyzed using two-dimensional gel electrophoresis analysis and a multiplex proximity extension assay for analysis of cytokines/chemokines. Associations between the proteins and group were multivarietly analyzed. The protein-protein association network and the biological processes according to the Gene Ontology were investigated. Proteins from both sources were important for group differentiation; the majority from the two-dimensional gel electrophoresis analysis. 58 proteins significantly differentiated the two groups (R2 = 0.83). A significantly enriched network was found; biological processes were acute phase response, complement activation, and innate immune response. As with other studies, this study shows that plasma proteins can differentiate CWP from healthy subjects. Focusing on cytokines/chemokines is not sufficient to grasp the peripheral biological processes that maintain CWP/FM since our results show that other components of the immune and inflammation systems are also highly significant.

Correlation Between Sleep Electroencephalogram, Brain-Derived Neurotrophic Factor, AVPR1B Gene Polymorphism, and Suicidal Behavior in Patients with Depression

The purpose of this article was to investigate the level of serum brain-derived neurotrophic factor and its relationship with suicidal symptoms and severity in mentally ill suicide attempt patients, and to explore the possible role of serum brain-derived neurotrophic factor (BDNF) in the occurrence of psychotic suicidal behavior. A retrospective analysis was performed on patients with depression in the neurology department of a hospital. General physical examination, neurological specialist examination, and cranial magnetic resonance imaging (MRI) examination were performed on any selected group. We applied the 24-item Hamilton Depression Scale, Hamilton Anxiety Scale, and Mini-Intelligence Mental State Scale, and performed polysomnography and electroencephalography (EEG) monitoring to conduct statistical analysis on sleep indicators. The amplitude of low-frequency fluctuation (ALFF) values of the right frontal gyrus, left posterior cerebellar lobe, right anterior cerebellar lobe, and right occipital lingual gyrus of the patient group were significantly lower than those of the control group. The ReHo values of the right superior parietal lobule, the left precuneus, and the right occipital lingual gyrus were significantly higher than those of the control group. The genotype and allele frequency distribution of FKBP5, AVPR1B, and CRHR2 gene SNPs had no significant difference between the case group and the control group (P > 0.05). The ReHo value of the precuneus is significantly correlated with the proportion of N3 sleep, and the dysfunction of the precuneus or default network may be related to the altered sleep structure in patients with depression. The GT and TT genotypes at rs9324924 of the NR3C1 gene are associated with suicide attempts.

Effects of resistance training on the physical symptoms and functional capacity of patients with fibromyalgia: a systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Resistance training (RT) has become an important topic for the treatment of fibromyalgia (FM); however, there are still controversies regarding its ability to significantly improve physical symptoms and a lack of adequate recommendations for evidence-based practice.

AIM

The aim of this study is to analyze the effects of RT on the physical symptoms of patients with FM through a systematic review with meta-analysis.

METHODS

We conducted a systematic review of randomized controlled trials in June 2022, according to PRISMA recommendations. The searches were carried out on the databases PubMed, Embase, Science Direct, Web of Science, PEDro, CINAHL, SciELO, and Google Scholar for gray literature, and the protocol was recorded in PROSPERO. Studies that evaluated patients with FM undergoing an RT program lasting more than 2 weeks and that analyzed physical health were selected. To carry out the meta-analysis, the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions were followed.

RESULTS

In total, 13 studies were included for qualitative analysis and nine for meta-analysis. Regarding meta-analysis, a favorable improvement was found for pain ([MD =  - 10.22 (95% CI: - 18.86 to - 1.58; I²: 64%; P for heterogeneity: 0.003)]; very low quality of evidence {QoE}), fatigue ([SMD =  - 0.39 (95% CI: - 0.61 to - 0.17; I²: 0%; P = 0.91)]; moderate QoE), and muscle strength ([SMD = 0.94 (95% CI: 0.02 to 1.85; I²: 93%; for heterogeneity: < 0.0001)]; very low QoE) and improvement in functional capacity ([MD = 18.75 (95% CI: 4.27 to 33.22; I²: 39%; P = 0.19)]; low QoE), in the general comparison.

CONCLUSION

RT was effective in reducing pain and fatigue and increasing strength and functional capacity; however, due to the quality of the evidence, more studies are needed.

On the superiority of a combination of aerobic and resistance exercise for fibromyalgia syndrome: A network meta-analysis

Background

Fibromyalgia syndrome is the second most common chronic diffuse pain disorder and can have a lasting negative impact on the quality of life, pain, and physical function of people. Exercise therapy is an important component of the treatment of fibromyalgia, but there was not a consensus understanding of the effect of various exercise programs on the quality of life, pain, and physical function of people with fibromyalgia syndrome. This study aimed to compare three exercise programs (aerobic exercise, resistance exercise, and a combination of aerobic and resistance exercise) in their effectiveness in improving quality of life, relieving muscle pain, and enhancing physical function in patients with fibromyalgia.

Methods

A comprehensive search of databases, including China National Knowledge Internet, Wan fang, The Cochrane Library, PubMed, EMBASE, and Web of Science, was conducted to identify randomized controlled trials on exercise therapy for patients with fibromyalgia syndrome with outcome indicators including at least one of Fibromyalgia Impact Questionnaire (FIQ), Tender point count (TPC), and 6-minute walk test (6MWT) from the date of database creation on 20 April 2022. The included studies were evaluated for literature quality according to Cochrane Handbook criteria, and a network meta-analysis was performed using STATA 14.0.

Result

Forty-five randomized controlled trials met all inclusion criteria and were analyzed. The network meta-analysis showed that a combination of aerobic and resistance exercise was ranked first in all three dimensions of quality of life improvement, pain alleviation, and physical function enhancement (Mean Rank = 1.6, 1.2, 5.9).

Conclusion

The current meta-analysis demonstrates that the combination of aerobic and resistance exercise may be the best type of exercise to accentuate the quality of life, pain alleviation, and physical function for people with fibromyalgia syndrome.

Altered Plasma Proteins in Myogenous Temporomandibular Disorders

The aims of this study were (1) to compare the levels and interactions of several plasma proteins in patients with myogenous temporomandibular disorders (TMDM) compared to healthy and pain-free controls, (2) to compare the levels and interactions in two TMDM subgroups, myalgia (MYA) and myofascial pain (MFP), and (3) to explore associations between the proteins and clinical data. Thirty-nine patients with TMDM (MFP, n = 25, MYA, n = 14), diagnosed according to the diagnostic criteria for TMD (DC/TMD), aged 38 years, and sex-matched pain-free controls completed an extended DC/TMD Axis II questionnaire and the plasma concentration of 87 biomarkers were analyzed. Nine proteins separated TMDM from controls (p = 0.0174) and 12 proteins separated MYA from MFP (p = 0.019). Pain duration, characteristic pain intensity, pain catastrophizing, perceived stress, and insomnia severity were significantly associated with protein markers (p < 0.001 to p < 0.022). In conclusion, several plasma proteins were upregulated in TMDM and either upregulated or downregulated in MYA compared to MFP. Some proteins in TMDM were associated with pain variables, sleep disturbance, and emotional function. These results show that systemic differences in protein expression exist in patients with TMDM and that altered levels of specific plasma proteins are associated with different clinical variables.

Comparison of the serum brain-derived neurotrophic factor (BDNF) between fibromyalgia and nociceptive pain groups; and effect of duloxetine on the BDNF level

Background

The primary objective was to compare the serum brain-derived neurotrophic factor (BDNF) level in the patients with two types of pain: fibromyalgia (FM) and non-FM nociceptive pain (non-FM NP). The secondary objective was to investigate the effect of duloxetine on serum BDNF in FM patients and assess the direction of BDNF changes’ relation to clinical parameters’ alterations.

Methods: This is a study on 73 patients (50 FM and 23 non-FM chronic non-inflammatory pain patients). Serum BDNF was first compared between both groups. Patients with FM, then prospectively, underwent standardized FM treatment with duloxetine maximized to 60 mg/day. The Revised Fibromyalgia Impact Questionnaire (FIQR), Short-Form Health Survey (SF-12), pain visualized analog scale (pain VAS), Beck Depression Inventory-II (BDI-II), polysymptomatic distress scale (PSD) and serum BDNF were measured and compared at baseline and 4 weeks after treatment in FM group.

Results

The mean of adjusted BDNF level in the FM group had no significant difference than the non-FM NP group ((5293.5 ± 2676.3 vs. 6136.3 ± 4037.6; P value = 0.77). Using linear mixed model, we showed that duloxetine reduced BDNF level significantly in FM patients, even after adjusting for depression, pain and severity of the disease (P < 0.01). The FIQR, BDI-II, PSD, and pain VAS improved significantly after duloxetine treatment.

Conclusions

Non-significant BDNF level difference between FM and non-FM nociceptive pain suggested that peripheral BDNF is not a pathophysiological feature of FM. The decreased BDNF level parallel with improvement of PSD/pain scores after duloxetine treatment indicates BDNF alteration in the pain modulation process, regardless of cause and effect.

Proteomic Investigation in Plasma from Women with Fibromyalgia in Response to a 15-wk Resistance Exercise Intervention

PURPOSE

Fibromyalgia (FM) is a complex pain condition, and exercise is considered the first option of treatment. Few studies have examined the effect of exercise on molecular mechanisms in FM. The aim of this study was to analyze the plasma proteome in women with FM and healthy controls (CON) before and after 15 wk of resistance exercise. This study further investigated whether clinical and exercises-related outcomes correlated with identified plasma proteins in FM.

METHODS

Plasma samples from 40 FM/25 CON (baseline) and 21 FM/24 CON (postexercise) were analyzed using shotgun proteomics. Clinical/background data were retrieved through questionnaires. Exercise-related variables and pressure pain thresholds were assessed using standardized instruments. Multivariate statistics were applied to analyze the proteomic profile at baseline and postexercise, and correlation with clinical/exercise-related data.

RESULTS

Fifteen weeks of resistance exercises improved clinical symptoms and muscle strength, and affected circulating proteins related to immunity, stress, mRNA stability, metabolic processes, and muscle structure development in FM. Pressure pain threshold was related to a specific protein profile, with proteins involved in metabolic and immune response. Subgroups of FM based on plasma proteins, FM duration, and improved muscle strength were identified.

CONCLUSIONS

Exercise seems to affect circulating proteins, clinical characteristics, and muscle strength in FM. This study contributes to better understanding of systemic protein changes in FM compared with CON and how resistance exercise affects such changes.

Efficacy of Whole-Body Vibration Training on Brain-Derived Neurotrophic Factor, Clinical and Functional Outcomes, and Quality of Life in Women with Fibromyalgia Syndrome: A Randomized Controlled Trial

This study aimed to investigate the efficacy of whole-body vibration training (WBVT) on blood brain-derived neurotrophic factor (BDNF) levels and determine the clinical and functional outcomes in patients with fibromyalgia syndrome (FMS). Thirty-two women with FMS were randomized into an intervention group (IG), receiving 6 weeks of WBVT, or a control group (CG) with no intervention. The outcomes at the baseline and follow-up in both groups included blood BDNF levels, sit-to-stand test (STS), 6-minute walk test (6MWT), Fibromyalgia Impact Questionnaire (FIQ), Pittsburgh Sleep Quality Index (PSQI), Beck Depression Inventory (BDI), and visual analogue scale (VAS). WBVT resulted in a group-by-time interaction effect. Thus, after the intervention time, the IG had increased blood BDNF levels (p=0.045), a higher number of repetitions on the STS test (p=0.011), and increased walking distance on the 6MWT (p=0.010), compared to CG. Moreover, there was a reduction in the scores of the FIQ (p=0.001), the PSQI (p=0.001), the BDI (p=0.017), and pain assessed using VAS (p=0.008) in IG. The results demonstrate that WBVT promotes an increase in blood BDNF levels, with concomitant improvement in lower limb muscle strength, aerobic capacity, clinical symptoms, and quality of life in women with FMS. This trial is registered with Brazilian Clinical Trials Registry (REBEC; RBR-38nbbx) (https://ensaiosclinicos.gov.br/rg/RBR-38nbbx).

Thermal Pain Thresholds Are Significantly Associated with Plasma Proteins of the Immune System in Chronic Widespread Pain-An Exploratory Pilot Study Using Multivariate and Network Analyses

Chronic widespread pain (CWP), including fibromyalgia (FM), is characterized by generalized musculoskeletal pain. An important clinical feature is widespread increased pain sensitivity such as lowered pain thresholds for different stimuli such as heat (HPT) and cold (CPT). There is a growing interest in investigating the activated neurobiological mechanisms in CWP. This explorative proteomic study investigates the multivariate correlation pattern between plasma and muscle proteins and thermal pain thresholds in CWP and in healthy controls (CON). In addition, we analysed whether the important proteins and their networks for CPT and HPT differed between CWP and CON. We used a proteomic approach and analysed plasma and muscle proteins from women with CWP (n = 15) and CON (n = 23). The associations between the proteins and CPT/HPT were analysed using orthogonal partial least square (OPLS). The protein-protein association networks for the important proteins for the two thermal pain thresholds were analysed using STRING database. CWP had lowered pain thresholds for thermal stimulus. These levels were generally not related to the included clinical variables except in CWP for HPT. Highly interacting proteins mainly from plasma showed strong significant associations with CPT and HPT both in CWP and in CON. Marked differences in the important proteins for the two thermal pain thresholds were noted between CWP and CON; more complex patterns emerged in CWP. The important proteins were part of the immune system (acute phase proteins, complement factors, and immunoglobulin factors) or known to interact with the immune system. As expected, CWP had lowered pain thresholds for thermal stimulus. Although different proteins were important in the two groups, there were similarities. For example, proteins related to the host defence/immunity such as acute phase proteins, complement factors, immunoglobulin factors, and cytokines/chemokines (although not in CON for CPT) were important habitual/tonic factors for thermal pain thresholds. The fact that peripheral proteins contribute to thermal pain thresholds does not exclude that central factors also contribute and that complex interactions between peripheral and central factors determine the registered pain thresholds in CWP.

Neuroimmune interactions in painful TMD: Mechanisms and treatment implications

The underlying mechanisms and treatment of painful temporomandibular disorders (TMDs) are important but understudied topics in craniofacial research. As a group of musculoskeletal diseases, the onset of painful TMD is proved to be a result of disturbance of multiple systems. Recently, emerging evidence has revealed the involvement of neuroimmune interactions in painful TMD. Inflammatory factors play an important role in peripheral sensitization of temporomandibular joint (TMJ), and neurogenic inflammation in turn enhances TMJs dysfunction in TMD. Furthermore, centralized neuroimmune communications contribute to neuron excitability amplification, leading to pain sensitization, and is also responsible for chronic TMD pain and other CNS symptoms. Therapeutics targeting neuroimmune interactions may shed light on new approaches for treating TMD. In this review, we will discuss the role of neuroimmune interactions in the onset of painful TMD from the peripheral and centralized perspectives, and how understanding this mechanism could provide new treatment options. Insights into the neuroimmune interactions within TMJs and painful TMD would broaden the knowledge of mechanisms and treatments of this multifactorial disease.

The Search for Biomarkers in Fibromyalgia

Fibromyalgia is the most common of the central sensitivity syndromes affecting 2–5% of the adult population in the United States. This pain amplification syndrome has enormous societal impact as measured by work absenteeism, decreased work productivity, disability and injury compensation and over-utilization of healthcare resources. Multiple studies have shown that early diagnosis of this condition can improve patient outlook and redirect valuable healthcare resources towards more appropriate targeted therapy. Efforts have been made towards improving diagnostic accuracy through updated criteria. The search for biomarkers for diagnosis and verification of Fibromyalgia is an ongoing process. Inadequacies with current diagnostic criteria for this condition have fueled these efforts for identification of a reproducible marker that can verify this disease in a highly sensitive, specific and reproducible manner. This review focuses on areas of research for biomarkers in fibromyalgia and suggests that future efforts might benefit from approaches that utilize arrays of biomarkers to identify this disorder that presents with a diverse clinical phenotype.

Regular Leisure-Time Physical Activity is Effective in Boosting Neurotrophic Factors and Alleviating Menopause Symptoms

BACKGROUND

The study investigated the effects of regular leisure-time physical activity on the parameters of cognitive function (plasma brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and cathepsin B) and menopausal symptoms (the climacterium, depression, and cognitive impairment) in obese middle-aged women.

METHODS

All subjects were middle-aged and obese women (n = 52, % body fat > 30%). The participants were divided into premenopausal (PRM) (n = 18, age = 47.56 ± 6.11 years) and postmenopausal (POM) (n = 34, age = 57.79 ± 5.68 years) groups. The participants completed a survey questionnaire related to depression and the climacterium, as well as cognitive tests. Physical activity was performed for 12 weeks. Blood samples from the forearm vein were analyzed after 12 h of fasting. Blood levels of BDNF, NGF, and cathepsin B were analyzed using an R&D kit.

RESULTS

Regular leisure-time physical activity had a positive effect on reducing the percentage of body fat in premenopausal and postmenopausal obese women. In addition, the results of the questionnaire showed that regular exercise had a positive effect on body composition caused by lifestyle change and enhanced psychological stability. The BDNF concentration was significantly lower in postmenopausal than in premenopausal obese women. In addition, regular physical activity significantly increased the cathepsin B and NGF levels in postmenopausal obese women.

CONCLUSIONS

Continuous leisure-time physical activity improved body composition and neurotrophic factors and alleviated menopausal symptoms in obese Korean women.

Evidence of Mitochondrial Dysfunction in Fibromyalgia: Deviating Muscle Energy Metabolism Detected Using Microdialysis and Magnetic Resonance

In fibromyalgia (FM) muscle metabolism, studies are sparse and conflicting associations have been found between muscle metabolism and pain aspects. This study compared alterations in metabolic substances and blood flow in erector spinae and trapezius of FM patients and healthy controls. FM patients (n = 33) and healthy controls (n = 31) underwent a clinical examination that included pressure pain thresholds and physical tests, completion of a health questionnaire, participation in microdialysis investigations of the etrapezius and erector spinae muscles, and also underwent phosphorus-31 magnetic resonance spectroscopy of the erector spinae muscle. At the baseline, FM had significantly higher levels of pyruvate in both muscles. Significantly lower concentrations of phosphocreatine (PCr) and nucleotide triphosphate (mainly adenosine triphosphate) in erector spinae were found in FM. Blood flow in erector spinae was significantly lower in FM. Significant associations between metabolic variables and pain aspects (pain intensity and pressure pain threshold PPT) were found in FM. Our results suggest that FM has mitochondrial dysfunction, although it is unclear whether inactivity, obesity, aging, and pain are causes of, the results of, or coincidental to the mitochondrial dysfunction. The significant regressions of pain intensity and PPT in FM agree with other studies reporting associations between peripheral biological factors and pain aspects.

Altered levels of salivary and plasma pain related markers in temporomandibular disorders

Background

Different pain syndromes may be characterized by different profiles of mediators reflecting pathophysiological differences, and these alterations may be measured in a simple saliva sample. The aims of the current study were to compare concentration of glutamate, serotonin (5-HT), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and substance P (SP) in saliva and plasma from a well-defined group of patients with chronic temporomandibular disorders myalgia (TMD-myalgia) with a group of pain-free controls, and further investigate the relationship between these markers and clinical characteristics.

Methods

Patients diagnosed according to the diagnostic criteria for TMD (n = 39), and matched healthy pain-free controls (n = 39) were included. Stimulated whole saliva and plasma samples were collected in the morning. Glutamate was analysed using a colorimetric assay, and 5-HT and SP were analysed by commercially available ELISA. Levels of NGF and BDNF were determined using multiplex electrochemiluminescence assay panel.

Results

Patients expressed higher salivary and plasma levels of glutamate (saliva: 40.22 ± 13.23 μmol/L; plasma: 30.31 ± 18.73 μmol/L) than controls (saliva: 33.24 ± 11.27 μmol/L; plasma: 20.41 ± 15.96 μmol/L) (p < 0.05). Salivary NGF (0.319 ± 0.261 pg/ml) and BDNF (3.57 ± 1.47 pg/ml) were lower in patients compared to controls (NGF: 0.528 ± 0.477 pg/ml; BDNF 4.62 ± 2.51 pg/ml)(p’s < 0.05). Contrary, plasma BDNF, was higher in patients (263.33 ± 245.13 pg/ml) than controls (151.81 ± 125.90 pg/ml) (p < 0.05). 5-HT was undetectable in saliva. Neither plasma 5-HT, nor SP levels differed between groups. BDNF and NGF concentrations correlated to levels of psychological distress (p < 0.0005).

Conclusion

The higher levels of salivary and plasma glutamate in patients with TMD-myalgia compared to controls strengthens its importance in the pathophysiology of TMD-myalgia. However, the lack of correlation to pain levels question its role as a putative biomarker. Patients with TMD-myalgia further had lower levels of salivary NGF and BDNF, but higher plasma BDNF. These results and their correlations to psychological distress warrant further investigations.

Plasma protein patterns are strongly correlated with pressure pain thresholds in women with chronic widespread pain and in healthy controls-an exploratory case-control study

Chronic widespread pain (CWP) is a complex pain condition characterized by generalized musculoskeletal pain and often associated with other symptoms. An important clinical feature is widespread increased pain sensitivity such as lowered pain thresholds for mechanical stimuli (pressure pain thresholds [PPT]). There is a growing interest in investigating the activated neurobiological mechanisms in CWP, which includes fibromyalgia. In CWP, strong significant correlations have been found between muscle protein patterns and PPT. This explorative proteomic study investigates the multivariate correlation pattern between plasma proteins and PPT in CWP and in healthy controls (CON). In addition, this study analyses whether the important proteins for PPT differ between the 2 groups.Using 2-dimensional gel electrophoresis, we analyzed the plasma proteome of the CWP (n = 15) and the CON (n = 23) and proteins were identified using mass spectrometry. For both the CWP and the CON, the associations between the identified proteins and PPT were analyzed using orthogonal partial least square in 2 steps.Significant associations between certain plasma proteins and PPT existed both in CWP (R = 0.95; P = .006) and in CON (R = 0.89; P < .001). For both groups of subjects, we found several proteins involved in PPT that reflect different biological processes. The plasma proteins as well as the biological processes involved in PPT differed markedly between the 2 groups of subjects.This study suggests that plasma protein patterns are associated with pain thresholds in CWP. Using the plasma proteome profile of CWP to study potential biomarker candidates could provide a snapshot of ongoing systemic mechanisms in CWP.

Nerve Growth Factor Signaling and Its Contribution to Pain

Nerve growth factor (NGF) is a neurotrophic protein essential for the growth, differentiation, and survival of sympathetic and sensory afferent neurons during development. A substantial body of evidence, based on both animal and human studies, demonstrates that NGF plays a pivotal role in modulation of nociception in adulthood. This has spurred development of a variety of novel analgesics that target the NGF signaling pathway. Here, we present a narrative review designed to summarize how NGF receptor activation and downstream signaling alters nociception through direct sensitization of nociceptors at the site of injury and changes in gene expression in the dorsal root ganglion that collectively increase nociceptive signaling from the periphery to the central nervous system. This review illustrates that NGF has a well-known and multifunctional role in nociceptive processing, although the precise signaling pathways downstream of NGF receptor activation that mediate nociception are complex and not completely understood. Additionally, much of the existing knowledge derives from studies performed in animal models and may not accurately represent the human condition. However, available data establish a role for NGF in the modulation of nociception through effects on the release of inflammatory mediators, nociceptive ion channel/receptor activity, nociceptive gene expression, and local neuronal sprouting. The role of NGF in nociception and the generation and/or maintenance of chronic pain has led to it becoming a novel and attractive target of pain therapeutics for the treatment of chronic pain conditions.