Abstract
BackgroundIn myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), altered membrane excitability often occurs in exercising muscles demonstrating muscle dysfunction regardless of any psychiatric disorder. Increased oxidative stress is also present in many ME/CFS patients and could affect the membrane excitability of resting muscles.MethodsSeventy-two patients were examined at rest, during an incremental cycling exercise and during a 10-min post-exercise recovery period. All patients had at least four criteria leading to a diagnosis of ME/CFS. To explore muscle membrane excitability, M-waves were recorded during exercise (rectus femoris (RF) muscle) and at rest (flexor digitorum longus (FDL) muscle). Two plasma markers of oxidative stress (thiobarbituric acid reactive substance (TBARS) and oxidation–reduction potential (ORP)) were measured. Plasma potassium (K+) concentration was also measured at rest and at the end of exercise to explore K+ outflow.ResultsThirty-nine patients had marked M-wave alterations in both the RF and FDL muscles during and after exercise while the resting values of plasma TBARS and ORP were increased and exercise-induced K+ outflow was decreased. In contrast, 33 other patients with a diagnosis of ME/CFS had no M-wave alterations and had lower baseline levels of TBARS and ORP. M-wave changes were inversely proportional to TBARS and ORP levels.ConclusionsResting muscles of ME/CFS patients have altered muscle membrane excitability. However, our data reveal heterogeneity in some major biomarkers in ME/CFS patients. Measurement of ORP may help to improve the diagnosis of ME/CFS.Trial registration Ethics Committee “Ouest II” of Angers (May 17, 2019) RCB ID: number 2019-A00611-56
Highlights
In myalgic encephalomyelitis/chronic fatigue syndrome (ME/Chronic fatigue syndrome (CFS)), altered membrane excitability often occurs in exercising muscles demonstrating muscle dysfunction regardless of any psychiatric disorder
Adult patients with chronic fatigue may be suffering from chronic fatigue syndrome, known as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
In group 2, 15 patients suffered from other diseases (obstructive sleep apnoea (n = 4), ankylosing spondylitis (n = 2), sequelae of poliomyelitis (n = 1), Lyme disease (n = 4), Ehlers Danlos syndrome (n = 2) or a psychiatric disorder (n = 2))
Summary
In myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), altered membrane excitability often occurs in exercising muscles demonstrating muscle dysfunction regardless of any psychiatric disorder. Increased oxidative stress is present in many ME/CFS patients and could affect the membrane excitability of resting muscles. ME/CFS often occurs in the absence of any disease that could be responsible for body fatigue and is characterized. Several body systems including the muscular and nervous systems are affected in ME/CFS [3,4,5]. Potential causes of muscle dysfunction in ME/CFS patients may include oxidative stress with reduced heat-shock protein production. M-wave alterations show impaired muscle membrane excitability and begin early in the exercising muscles before culminating during the 10-min recovery period [6,7,8]. No data are available on altered excitability in the resting muscles of ME/CFS patients
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