Submitted on October 24, 2007
Accepted on February 16, 2008
Training at high exercise intensity promotes qualitative adaptations of mitochondrial function in human skeletal muscle
Frederic Nicolas Daussin1, Joffrey Zoll2*, Elodie Ponsot1, Stephane P. Dufour3, Stephane Doutreleau1, Evelyne Lonsdorfer4, Renee Ventura-Clapier5, Bertrand Mettauer6, Francois Piquard7, Bernard Geny8, and Ruddy Richard9
1 Physiology and Functional Explorations, University Louis Pasteur, France, Strasbourg, France
2 Physiology and Functional Explorations Department, University Louis Pasteur, Strasbourg, France
3 Hopital Civil et Universite Louis Pasteur, Service de Physiologie et d'Explorations Fonctionnelles and Institut de Physiologie, Strasbourg, France
4 Physiology and Functional Explorations, University Louis Pasteur, Strasbourg, France
5 Faculte de Pharmacie, Universite Paris-Sud, U-769 Inserm; IFR-141, Chatenay-Malabry, France
6 Hopitaux Civils, Service de Cardiologie, Colmar, France
7 Facule de Medecine, Instut de physiologie, Strasbourg Cedex, France
8 EA 3072, Institut de Physiologie, STRASBOURG, France
9 Cardio-circulatoires et de l'exercice, Service des explorations fonctionnelles respiratoires, Strasbourg, France
* To whom correspondence should be addressed. E-mail: zolljoffrey{at}yahoo.com.
This study explored mitochondrial capacities to oxidize carbohydrate and fatty acids and functional optimization of mitochondrial respiratory chain complexes in athletes who regularly train at high exercise intensity (ATH, n=7) in comparison with sedentary (SED, n=7). Peak O2 uptake (VO2max) was measured and muscle biopsies of vastus lateralis were collected. Maximal O2 uptake of saponin-skinned myofibers was evaluated with several metabolic substrates (glutamate-malate (VGM), pyruvate (VPyr), palmitoyl carnitine (VPC)) and the activity of mitochondrial respiratory complexes II and IV were assessed using succinate (Vs) and TMPD (VTMPD) respectively. VO2max was higher in ATH than in SED (57.8±2.2 vs. 31.4±1.3 mL·min-1·kg-1, respectively, p<0.001). VGM was higher in ATH than in SED (8.6±0.5 vs. 3.3±0.3 µmol O2·min-1·g-1 dry weight, respectively, p<0.001). VPyr was higher in ATH than in SED (8.7±1.0 vs. 5.5±0.2 µmol O2·min-1·g-1 dry weight respectively, p<0.05) whereas VPC was not significantly different (5.3±0.9 vs. 4.4±0.5 µmol O2·min-1·g-1 dry weight, respectively). VS was higher in ATH than in SED (11.0±0.6 vs. 6.0±0.3 µmol O2·min-1·g-1 dry weight, respectively, p<0.001). VTMPD was also higher in ATH than in SED (20.1±1.0 vs. 16.2±3.4 µmol O2·min-1·g-1 dry weight, respectively, p<0.05). The ratio VS/VGM (1.3±0.1 vs. 2.0±0.1, p<0.001) and VTMPD/VGM (2.4±1.0 vs. 5.2±1.8, p<0.01) were lower in ATH than in SED. In conclusion, comparison of ATH vs SED subjects suggested that regular endurance training at high intensity favor enhancement of maximal mitochondrial capacities to oxidize carbohydrate rather than fatty acid and induce specific adaptations of the mitochondrial respiratory chain at the level of complex I.
