Time course of myogenic and metabolic gene expression in response to acute exercise in human skeletal muscle.
Level 3 - non-randomized controlled study
Non-randomized comparative physiological study
PubMed 15618316 · doi:10.1152/japplphysiol.01185.2004
What was done
Twelve subjects (6 resistance exercise [RE], 6 running [Run]) underwent an acute exercise bout. Eight sequential muscle biopsies were collected before, immediately after, and at 1, 2, 4, 8, 12, and 24 hours post-exercise (vastus lateralis for RE, gastrocnemius for Run) to examine the mRNA time course of select myogenic (MRF4, Myf5, MyoD, myogenin) and metabolic (CD36, CPT1, HKII, PDK4) genes.
What was found
RE increased mRNA of MRF4 (3.7- to 4.5-fold at 2-4 h post), MyoD (5.8-fold at 8 h post), myogenin (2.6- and 3.5-fold at 8-12 h post), HKII (3.6- to 10.5-fold at 2-12 h post), and PDK4 (14- to 26-fold at 2-8 h post), with no differences in Myf5, CD36, or CPT1. Run increased mRNA of MyoD (5.0- to 8.0-fold), HKII (12- to 16-fold), and PDK4 (32- to 52-fold) at 8-12 h post-exercise, with no differences in MRF4, Myf5, myogenin, CD36, or CPT1. Gene induction generally peaked 4-8 h post-exercise and returned to levels not significantly different from pre-exercise baseline by 24 h.
Why it matters
This study defines the acute temporal window of myogenic and metabolic transcriptional responses in human muscle, demonstrating that biopsy timing between 4 and 8 hours post-exercise is optimal to capture peak gene expression changes.
Limits
The sample size is very small (n = 6 per group). Biopsies were taken from different muscle groups (vastus lateralis vs. gastrocnemius), confounding the comparison between exercise modes with anatomical differences. Only mRNA was quantified; downstream protein expression and functional adaptations were not measured.
Cited by
- supports Post-exercise gene expression related to muscle anabolism typically peaks between 3 and 6 hours following a workout.