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pubmed:abstractText |
Numerous human in vivo studies on skeletal muscle gene expression have investigated the effects of given interventions. These have been founded on the assumption that presampling can be regarded as a representative control for postintervention sampling. However, many genes are responsive to the metabolic status, which varies during the day, so that observed differences in gene expression between the pre- and post-sample may therefore be a result of the daily variations rather than an intervention. Furthermore, the sampling itself can cause a local stress response, which may also influence the expression of some genes in later samples from the same localized area. To test this, we performed a short-term human endurance exercise study in which muscle biopsies were obtained from healthy untrained individuals (n=14) before and in the hours after exercise to measure the expression of mRNA for previously reported exercise-related genes (e.g., PPARgamma coactivator-1alpha (PGC-1alpha), pyruvate dehydrogenase kinase 4 (PDK4), MyoD, p21, (heat shock protein 72 (HSP72), lipoprotein lipase (LPL), citrate synthase (CS), and glucose transporter 4 (GLUT4)). To test for changes unrelated to exercise, one half of the subjects did not exercise. As suspected, several presumed exercise-induced genes were induced even without the exercise. Our data demonstrate that presampling is not always a representative control for postintervention sampling, illustrating that use of presampling can cause erroneous interpretations of the underlying induction signals.
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