Differential effects of exercise on insulin-signaling gene expression in human skeletal muscle

Skeletal muscle insulin sensitivity is enhanced after acute exercise and sh ort-term endurance training. We investigated the impact of exercise on the gene expression of key insulin-signaling proteins in humans. Seven untraine d subjects (4 women and 3 men) completed 9 days of cycling at 63 +/- 2% of peak O-2 uptake for 60 min/day. Muscle biopsies were taken before, immediat ely alter, and 3 h after the exercise bouts ton days 1 and 9). The gene exp ression of insulin receptor substrate-2 and the p85 alpha subunit of phosph atidylinositol 3-kinase was significantly higher 3 h after a single exercis e bout, although short-term training ameliorated this effect. Gene expressi on of insulin receptor and insulin receptor substrate-1 was not significant ly altered at any time point. These results suggest that exercise may have a transitory impact on the expression of insulin receptor substrate-2 and p hosphatidylinositol 3-kinase; however, the predominant actions of exercise on insulin sensitivity appear not to reside in the transcriptional activati on of the genes encoding major insulin-signaling proteins.