Endurance exercise induces mRNA expression of oxidative enzymes in human skeletal muscle late in recovery.

Exercise-induced adaptations in skeletal muscle oxidative enzymes are suggested to result from the cumulative effects of transient changes in gene expression after each single exercise session. However, for several oxidative enzymes, no changes in mRNA expression are detected up to 8 h after exercise. To test the hypothesis that mRNA expression of many oxidative enzymes is up-regulated late in recovery (10-24 h) after exercise, male subjects (n=8) performed a 90-min cycling exercise (70% VO(2-max)), with muscle biopsies obtained before exercise (pre), and after 10, 18 and 24 h of recovery. The mRNA expression of carnitine-palmitoyltransferase (CPT)I, CD36, 3-hydroxyacyl-CoA-dehydrogenase (HAD), cytochrome (Cyt)c, aminolevulinate-delta-synthase (ALAS)1 and GLUT4 was 100-200% higher at 10-24 h of recovery from exercise than in a control trial. Exercise induced a 100-300% increase in peroxisome proliferator-activated receptor gamma co-activator (PGC)-1alpha, citrate synthase (CS), CPTI, CD36, HAD and ALAS1 mRNA contents at 10-24 h of recovery relative to before exercise. No protein changes were detected in Cytc, ALAS1 or GLUT4. This shows that mRNA expression of several training-responsive oxidative enzymes is up-regulated in human skeletal muscle at 10-24 h of recovery, supporting that exercise-induced adaptations of these oxidative enzymes can be the result of the cumulative effects of transient changes in mRNA expression.