Ed TBARS increase and positively correlated with CD26-expression while the pain component of SF-36 was negatively correlated with CD26-expression; (4) the TBARS increase and the M-wave decrease were the highest, and the CD26-expression level the lowest in patients who had been submitted to infectious stressors. Conclusion: In ME/CFS patients, severe alterations of the muscle excitability, the redox status, as well as the CD26expression level are correlated with a marked impairment of the quality-of-life. They are particularly significant when infectious stressors are reported in the medical history. Keywords: Myalgic encephalomyelitis/chronic fatigue syndrome, CD26, Muscle excitability, Quality of life, Oxidative stress*Correspondence: [email protected] 1 DS-ACI UMR MD2, Faculty of Medicine, Aix-Marseille University, Bd. Pierre Dramard, 13916 Marseille Cedex 20, France Full list of author information is available at the end of the article?2016 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide PubMed ID:https://www.ncbi.nlm.nih.gov/pubmed/28893839 a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Fenouillet et al. J Transl Med (2016) 14:Page 2 ofBackground As primarily defined by Fukuda [1], and in broad agreement with the latest case definition published in 2015 by the Institute of Medicine [2], the myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is currently described as a debilitating disorder characterized by an intense fatigue that is not improved by rest, and that is worsened by physical/mental activity. This clinical picture is usually associated with a marked loss of quality of life [1]. The definitions of ME/CFS do not use biological markers. Several body systems such as the muscular and nervous systems are affected in a context of neuroimmune alterations and chronic low-grade inflammation [3?]. The etiology of ME/CFS is unknown, and its pathogenesis appears to be multifactorial, various stressors being repeatedly reported in the medical history of these patients, notably an intense sport practice, severe infections, and/or emotional stress [7, 8]. Whereas sport practice induces a moderate oxidative stress in healthy subjects [9], a strong exercise-induced production of reactive oxygen species (ROS) is found in ME/CFS patients [10?4]. The antioxidant response is also altered at rest, as shown by an increased level of the thiobarbituric acid reactive substances (TBARS: a marker of lipid peroxidation) and a decreased concentration of the reduced ascorbic acid marker (RAA: an endogenous antioxidant) [10, 13, 14]. Because the increased ROS production affects the muscle excitability [15, 16], the increased redox stress in ME/CFS may participate to the muscle fatigue as evidenced via an alteration of the compound evoked muscle action potential (M-wave) [10]. The significant dysregulation of the immune system found in ME/CFS patients combined increased levels of pro-inflammatory cytokines (e.g. interleukin-1, tumor necrosis factor-), a natural killer cell cytokine production and purchase CEP-37440 mitogen-acti.
