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Rapid exercise-induced changes in PGC-1 mRNA and protein in human skeletal muscle

Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada

Submitted 7 August 2007 ; accepted in final form 15 July 2008

The mRNA of the nuclear coactivator peroxisome proliferator-activated receptor- coactivator-1 (PGC-1) increases during prolonged exercise and is influenced by carbohydrate availability. It is unknown if the increases in mRNA reflect the PGC-1 protein or if glycogen stores are an important regulator. Seven male subjects [23 ± 1.3 yr old, maximum oxygen uptake (O_{2 max}) 48.4 ± 0.8 ml·kg^–1·min^–1] exercised to exhaustion (2 h) at 65% O_{2 max} followed by ingestion of either a high-carbohydrate (HC) or low-carbohydrate (LC) diet (7 or 2.9 g·kg^–1·day^–1, respectively) for 52 h of recovery. Glycogen remained depressed in LC (P < 0.05) while returning to resting levels by 24 h in HC. PGC-1 mRNA increased both at exhaustion (3-fold) and 2 h later (6.2-fold) (P < 0.05) but returned to rest levels by 24 h. PGC-1 protein increased (P < 0.05) 23% at exhaustion and remained elevated for at least 24 h (P < 0.05). While there was no direct treatment effect (HC vs. LC) for PGC-1 mRNA or protein, there was a linear relationship between the changes in glycogen and those in PGC-1 protein during exercise and recovery (r = –0.68, P < 0.05). In contrast, PGC-1β did not increase with exercise but rather decreased (P < 0.05) below rest level at 24 and 52 h, and the decrease was greater (P < 0.05) in LC. PGC-1 protein content increased in prolonged exercise and remained upregulated for 24 h, but this could not have been predicted by the changes in mRNA. The β-isoform declined rather than increasing, and this was greater when glycogen was not resynthesized to rest levels.

carbohydrate; gene expression; glucose; insulin; training signals; metabolism