Interleukin-6 production in contracting human skeletal muscle is influenced by pre-exercise muscle glycogen content.
Level 3 - non-randomized controlled study
Within-subject controlled physiological study using a contralateral limb model
PubMed 11731593 · doi:10.1111/j.1469-7793.2001.00633.x
What was done
Seven men performed 5 hours of continuous two-legged knee-extensor exercise with one leg having normal (control) and the contralateral leg having reduced (depleted) pre-exercise muscle glycogen content. Muscle biopsies were collected from both legs before exercise, immediately after exercise, and 3 hours into recovery. Catheters were inserted in one femoral artery and both femoral veins to measure net IL-6 flux before exercise, hourly during exercise, and during recovery.
What was found
Pre-exercise glycogen content was lower in the depleted leg than in the control leg. Exercise increased intramuscular IL-6 mRNA levels in both legs, with an augmented increase at the end of exercise in the leg with the lowest glycogen content. Arterial plasma IL-6 rose from 0.6 ± 0.1 ng·L⁻¹ pre-exercise to 21.7 ± 5.6 ng·L⁻¹ at the end of exercise. The glycogen-depleted leg demonstrated significant IL-6 release by 1 hour (4.38 ± 2.80 ng·min⁻¹, P < 0.05) compared to no significant release in the control leg (0.36 ± 0.14 ng·min⁻¹); significant net IL-6 release in the control leg was delayed until 2 hours.
Why it matters
This study provides direct evidence that cytokine release from contracting skeletal muscle is sensitive to intramuscular energy stores, supporting a role for IL-6 as an energy-sensing myokine.
Limits
The sample size is very small (n = 7) and consists entirely of male participants. The abstract does not state whether the depleted leg was randomized, nor does it provide absolute numerical values for muscle glycogen levels or IL-6 mRNA fold changes.
Cited by
- supports The post-exercise spike in IL-6 is particularly pronounced when skeletal muscle glycogen stores are depleted.