Muscle Glucose Metabolism following Exercise in the Rat
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Overview
Controlled laboratory study demonstrates enhanced insulin sensitivity and glucose transport in exercised rat muscle, indicating glycogen depletion primes fiber-specific metabolic recovery.
Key Points
- To investigate the mechanisms driving rapid muscle glycogen repletion and altered glucose utilization during the recovery period following exercise.
- Untrained male rats ran for 45 minutes on a motor-driven treadmill, after which glucose utilization was evaluated during isolated hindquarter perfusion.
- Perfusion was performed with or without insulin (30 to 40,000 µU/ml) to assess glucose uptake, 2-deoxyglucose uptake, and [14C]glucose incorporation into glycogen across different fiber types.
- Prior exercise reduced the half-maximal insulin concentration required to stimulate glucose utilization from 480 µU/ml in controls to 150 µU/ml, persisting for 4 hours post-exercise but resolving by 24 hours.
- At 75 µU/ml insulin, glycogen synthesis increased eightfold more in glycogen-depleted fast-twitch red fibers of exercised rats than in controls, with minimal effect in non-depleted fast-twitch white fibers.
- Enhanced glucose utilization was rate-limited by cell membrane glucose transport rather than intracellular phosphorylation, while glycogen synthase D-to-I conversion remained unaltered.
Cite This Study
Richter et al. (1982) studied this question.