Exercise induces isoform-specific increase in 5 ' AMP-activated protein kinase activity in human skeletal muscle

The 5'AMP-activated protein kinase (AMPK) is stimulated by contractile acti vity in rat skeletal muscle. AMPK has emerged as an important signaling int ermediary in the regulation of cell metabolism being linked to exercise-ind uced changes in muscle glucose and fatty acid metabolism. In the present st udy, we determined the effects of exercise on isoform-specific AMPK activit y (alpha 1 and alpha 2) in human skeletal muscle. Needle biopsies of vastus lateralis muscle were obtained from seven healthy subjects at rest, after 20 and 60 min of cycle ergometer exercise at 70% of VO(2)max, and 30 min fo llowing the 60 min exercise bout. In comparison to the resting state, AMPK alpha 2 activity significantly increased at 20 and 60 min of exercise, and remained at a higher level with 30 min of recovery. AMPK al activity tended to slightly decrease with 20 min of exercise at 70%VO(2)max; however, the change was not statistically significant. AMPK alpha 1 activities were at b asal levels at 60 min of exercise and 30 min of recovery. On a separate day , the same subjects exercised for 20 min at 50% of VO(2)max. Exercise at th is intensity did not change alpha 2 activity, and similar to exercise at 70 % of VO(2)max, there was no significant change in alpha 1 activity. In conc lusion, exercise at a higher intensity for only 20 min leads to increases i n AMPK alpha 2 activity but not alpha 1 activity. These results suggest tha t the alpha 2-containing AMPK complex, rather than al, may be involved in t he metabolic responses to exercise in human skeletal muscle. (C) 2000 Acade mic Press.