Effect of glycogen availability on human skeletal muscle protein turnover during exercise and recovery

Abstract

We examined the effect of carbohydrate (CHO) availability on whole body and skeletal muscle protein utilization at rest, during exercise, and during recovery in humans. Six men cycled at approximately 75% peak O(2) uptake (Vo(2peak)) to exhaustion to reduce body CHO stores and then consumed either a high-CHO (H-CHO; 71 + or - 3% CHO) or low-CHO (L-CHO; 11 + or - 1% CHO) diet for 2 days before the trial in random order. After each dietary intervention, subjects received a primed constant infusion of [1-(13)C]leucine and l-[ring-(2)H(5)]phenylalanine for measurements of the whole body net protein balance and skeletal muscle protein turnover. Muscle, breath, and arterial and venous blood samples were obtained at rest, during 2 h of two-legged kicking exercise at approximately 45% of kicking Vo(2peak), and during 1 h of recovery. Biopsy samples confirmed that the muscle glycogen concentration was lower in the L-CHO group versus the H-CHO group at rest, after exercise, and after recovery. The net leg protein balance was decreased in the L-CHO group compared with at rest and compared with the H-CHO condition, which was primarily due to an increase in protein degradation (area under the curve of the phenylalanine rate of appearance: 1,331 + or - 162 micromol in the L-CHO group vs. 786 + or - 51 micromol in the H-CHO group, P < 0.05) but also due to a decrease in protein synthesis late in exercise. There were no changes during exercise in the rate of appearance compared with rest in the H-CHO group. Whole body leucine oxidation increased above rest in the L-CHO group only and was higher than in the H-CHO group. The whole body net protein balance was reduced in the L-CHO group, largely due to a decrease in whole body protein synthesis. These data extend previous findings by others and demonstrate, using contemporary stable isotope methodology, that CHO availability influences the rates of skeletal muscle and whole body protein synthesis, degradation, and net balance during prolonged exercise in humans.

Measurement and Physiological Relevance of the Maximal Lipid Oxidation Rate During Exercise (LIPOXmax)

“…A mechanism that may play a role in this protective effect of LI is glycogen sparing. It has been shown that CHO availability influences the rates of skeletal muscle and whole body protein synthesis, degradation and net balance during prolonged exercise in humans (Howarth et al, 2010). On the whole, although more investigation is required, LIPOXmax training is an efficient way to maintain or even to improve fat-free mass by increasing the mass of metabolically active muscle.…”

The effect of short-term heat stress on protein synthesis signaling in isolated rat skeletal muscle

“…A previous study demonstrated that a decreased rate of protein synthesis, during muscle contraction, is associated with ATP and phosphocreatine levels 30) as well as glycogen availability 31) . The energy depletion triggers an activation of a cellular energy sensor AMPK.…”

Nutritional Recommendations for Water Polo

“…Easy postgame access to foods and fluids providing carbohydrates and protein will initiate refueling of muscle glycogen stores and simultaneously enhance protein synthesis (Breen et al, 2011;Howarth et al, 2010). The recovery process will be further enhanced by a nutritious meal scheduled 2-3 hr after the game, also allowing for social interaction among players and staff.…”