Chronic fatigue syndrome (CFS) is a disabling condition characterized by unexplained chronic fatigue that impairs normal activities. Although immunological and psychological aspects are present, symptoms related to skeletal muscles, such as muscle soreness, fatigability and increased lactate accumulation, are prominent in CFS patients.
In this case-control study, the phenotype of the same biopsy samples was analyzed by determining:
1. Fiber-type proportion using myosin isoforms as fiber type molecular marker and gel electrophoresis as a tool to separate and quantify myosin isoforms, and
2. Contractile properties of manually dissected, chemically made permeable and calcium-activated single muscle fibers.
The results showed that fiber-type proportion was significantly altered in CFS samples, which showed a shift from the slow- to the fast-twitch phenotype.
Cross sectional area, force, maximum shortening velocity and calcium sensitivity were not significantly changed in single muscle fibers from CSF samples.
Thus, the contractile properties of muscle fibers were preserved but their proportion was changed, with an increase in the more fatigue-prone, energetically expensive fast fiber type.
Taken together, these results support the view that muscle tissue is directly involved in the pathogenesis of CSF and it might contribute to the early onset of fatigue typical of the skeletal muscles of CFS patients.
Source: International Journal of Immunopathology and Pharmacology, Apr-Jun 2009;22(2):427-436. PMID: 19505395, by Pietrangelo T, Toniolo L, Paoli A, Fulle S, Puglielli C, Fan X00f2 G, Reggiani C. Dept of Basic and Applied Medical Sciences, Center for Excellence on Ageing, University - G. dAnnunzio- Chieti-Pescara, Chieti, Italy.