title: Comparison of the Levels of Pro-Inflammatory Cytokines Released in the Vastus Lateralis Muscle of Patients with Fibromyalgia and Healthy Controls during Contractions of the Quadriceps Muscle--A Microdialysis Study.
abstract: OBJECTIVE
  Fibromyalgia is associated with central hyperexcitability, but it is suggested that peripheral input is important to maintain central hyperexcitability. The primary aim was to investigate the levels of pro-inflammatory cytokines released in the vastus lateralis muscle during repetitive dynamic contractions of the quadriceps muscle in patients with fibromyalgia and healthy controls. Secondarily, to investigate if the levels of pro-inflammatory cytokines were correlated with pain or fatigue during these repetitive dynamic contractions.
  
  
  METHODS
  32 women with fibromyalgia and 32 healthy women (controls) participated in a 4 hour microdialysis session, to sample IL-1β, IL-6, IL-8, and TNF from the most painful point of the vastus lateralis muscle before, during and after 20 minutes of repeated dynamic contractions. Pain (visual analogue scale; 0-100) and fatigue Borg's Rating of Perceived Exertion Scale; 6-20) were assessed before and during the entire microdialysis session.
  
  
  RESULTS
  The repetitive dynamic contractions increased pain in the patients with fibromyalgia (P < .001) and induced fatigue in both groups (P < .001). Perceived fatigue was significantly higher among patients with fibromyalgia than controls (P < .001). The levels of IL-1β did not change during contractions in either group. The levels of TNF did not change during contractions in patients with fibromyalgia, but increased in controls (P < .001) and were significantly higher compared to patients with fibromyalgia (P = .033). The levels of IL-6 and IL-8 increased in both groups alike during and after contractions (P's < .001). There were no correlations between pain or fatigue and cytokine levels after contractions.
  
  
  CONCLUSIONS
  There were no differences between patients with fibromyalgia and controls in release of pro-inflammatory cytokines, and no correlations between levels of pro-inflammatory cytokines and pain or fatigue. Thus, this study indicates that IL-1β, IL-6, IL-8, and TNF do not seem to play an important role in maintenance of muscle pain in fibromyalgia.
authors.affiliation: Section for Orofacial Pain and Jaw Function, Department of Dental Medicine, Karolinska Institutet, and the Scandinavian Center for Orofacial Neurosciences (SCON), Huddinge, Sweden.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Christidis
authors.affiliation: Division of Community Medicine, Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Pain and Rehabilitation Center, Anaesthetics, Operations and Specialty Surgery Center, County Council of Östergötland, Linköping, Sweden.
authors.forename: Bijar
authors.initials: B
authors.lastname: Ghafouri
authors.affiliation: Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.|Centre for Person Centered Care (GPCC), University of Gothenburg, Göteborg, Sweden.
authors.forename: Anette
authors.initials: A
authors.lastname: Larsson
authors.affiliation: Section of Health and Rehabilitation/Physiotherapy, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
authors.forename: Annie
authors.initials: A
authors.lastname: Palstam
authors.affiliation: Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.|Section of Health and Rehabilitation/Physiotherapy, Institute of Neuroscience and Physiology, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.|Centre for Person Centered Care (GPCC), University of Gothenburg, Göteborg, Sweden.
authors.forename: Kaisa
authors.initials: K
authors.lastname: Mannerkorpi
authors.affiliation: Department of Clinical Sciences, Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden.
authors.forename: Indre
authors.initials: I
authors.lastname: Bileviciute-Ljungar
authors.affiliation: Department of Clinical Sciences, Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden.
authors.forename: Monika
authors.initials: M
authors.lastname: Löfgren
authors.affiliation: Department of Rheumatology and Inflammation Research, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
authors.forename: Jan
authors.initials: J
authors.lastname: Bjersing
authors.affiliation: Department of Clinical Neuroscience, Karolinska Institutet, and Stockholm Spine Center, Stockholm, Sweden.
authors.forename: Eva
authors.initials: E
authors.lastname: Kosek
authors.affiliation: Division of Community Medicine, Department of Medical and Health Sciences, Faculty of Health Sciences, Linköping University, Pain and Rehabilitation Center, Anaesthetics, Operations and Specialty Surgery Center, County Council of Östergötland, Linköping, Sweden.
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
authors.affiliation: Section for Orofacial Pain and Jaw Function, Department of Dental Medicine, Karolinska Institutet, and the Scandinavian Center for Orofacial Neurosciences (SCON), Huddinge, Sweden.
authors.forename: Malin
authors.initials: M
authors.lastname: Ernberg
mesh_terms: D016207:Cytokines / Q000032:analysis / Q000378:metabolism*; D005221:Fatigue; D005260:Female; D005356:Fibromyalgia / Q000503:physiopathology*; D006801:Humans; D007249:Inflammation; D017551:Microdialysis; D009119:Muscle Contraction; D010146:Pain; D052097:Quadriceps Muscle / Q000378:metabolism* / Q000502:physiology
chemical_list: D016207:Cytokines