תזונה ותוספים Effect of glycogen availability on human skeletal muscle protein turnover during exer

[Mike Bikov]

J Appl Physiol. 2010 May 20. [Epub ahead of print]
Effect of glycogen availability on human skeletal muscle protein turnover during exercise and recovery.

Howarth KR, Phillips SM, Macdonald MJ, Richards D, Moreau NA, Gibala MJ.

1McMaster University.
Abstract

There are limited and equivocal data regarding the effect of carbohydrate (CHO) availability on protein metabolism during prolonged exercise. We aimed to examine the effect of endogenous CHO availability on whole-body and skeletal muscle protein utilization at rest, during prolonged exercise and recovery in humans. Six men cycled at ~75% VO(2peak) to exhaustion to reduce body CHO stores, and then consumed either a high (H-CHO; 71+/-3% CHO) or low (L-CHO; 11+/-1% CHO) CHO diet for 2 d prior to the trial, in random order. Following each dietary intervention, subjects received a primed constant infusion of 1-(13)C-leucine (Leu) and L-[ring-(2)H(5)]-phenylalanine (d(5)-Phe) for the measurement of whole body net protein balance (WBNB) 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 (Ex) at ~45% of kicking VO(2peak) and 1 h of recovery (Recov). Biopsy samples confirmed that muscle [glycogen] was lower in L-CHO vs H-CHO at rest, after Ex and Recov. Net leg protein balance was decreased in the L-CHO compared to rest and the H-CHO condition, which was primarily due to an increase in protein degradation (Phe Ra AUC: L-CHO 1331+/-162 vs H-CHO 786+/-51 mumol; p<0.05), but also a decrease in protein synthesis late in exercise. There were no changes during exercise in Ra compared to rest in H-CHO. Whole body Leu oxidation increased above rest in L-CHO only and was higher than H-CHO. WBNB was reduced in L-CHO, 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 rates of skeletal muscle and whole-body protein synthesis, degradation and net balance during prolonged exercise in humans.

PMID: 20489032 [PubMed - as supplied by publisher]​

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