The effects of resistance exercise on fiber‐type specific GLUT4 and insulin‐like growth factor‐I receptor expression in human skeletal muscle

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There has been little research on the effects of resistance exercise on fiber‐type specific gene expression of glucose transporter 4 (GLUT4) and insulin‐like growth factor‐I receptor (IGFIR) expression. Thus, the purpose of this investigation was to measure the effects of an acute bout of resistance exercise (RE) on GLUT4 and IGFIR expression in human skeletal muscle. Six college‐aged males performed a bout of knee‐extensor RE. Individual fibers were isolated from muscle biopsy samples obtained from the vastus lateralis muscle prior to and 4‐hours following RE. Myosin heavy chain analysis was performed on 1/3 of each fiber and 2/3 of the fiber was directly placed in individual tubes containing buffer for the reverse transcription (RT) step of a two‐step RT‐PCR kit (Invitrogen). After RT, the cDNA of all slow‐ (MHC I, N=20 per subject) and fast‐ (MHC IIa and IIa/x, N=30 per subject) twitch fibers were combined for each subject. PCR reactions for GLUT4, IGFIR, and GAPDH (housekeeping gene) were then performed on the samples. ΔΔCT analysis revealed that there were no differences in GLUT4 (slow‐twitch = 0.81, fast‐twitch = 0.72) or IGFIR (slow‐twitch = 0.49, fast‐twitch = −0.11) expression between the pre‐RE and 4‐hour post RE time‐points. These data show that GLUT4 and IGFIR gene expression are not elevated four hours after resistance exercise; however, these genes may be elevated at other times post‐exercise.