SEID, or systemic exertion intolerance disorder, is an illness marked by endocrinological, neurological, and muscular abnormalities. Post-exertional worsening of muscle fatigue and neurological symptoms are hallmark features of the illness.
In order to investigate muscular health issues of SIED patients, muscle biopsy samples were taken and cultured from ten patients. These cultured muscle cells were compared microscopically and metabolically to those of age-matched, healthy controls; then, both cultures were subjected to electrical pulse stimulation (EPS) to simulate exercise.
Myogenin and IL-6 were measured in both SEID and control cells. Myogenin is a transcription factor involved in skeletal muscle biogenesis and repair. IL-6 is an inflammatory interleukin secreted during infection as well as after trauma and exercise. Pre-EPS, the muscle cells of patients with SEID showed increased myogenin expression but decreased IL-6 expression.
Figure 1. IL-6 levels measured in cultured SEID and control cells after EPS.
In healthy controls, glucose is released for cellular use during exercise. The researchers measured glucose uptake basally, upon insulin administration, upon EPS, and using EPS and insulin administration simultaneously.
Figure 2. Glucose uptake of cultured SEID and control muscle cells at basal levels and after exposure to combinations of EPS and insulin.
The AMP-activated protein kinase (AMPK) is an enzyme that is considered to be a central player in maintaining homeostasis, as it has a profound effect on ATP production and regulation. The AMPK system senses cellular energy status. It is activated by metabolic stresses that interfere either with ATP production, such as decreases in oxygen or glucose, or by processes that increase ATP consumption. AMPK was also examined in SEID muscle cells and it was found that AMPK did not activate in the muscle cells of SEID patients, while its content increased in control muscle cells as expected.
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