Endurance training induces muscle-specific changes in mitochondrial function in skinned muscle fibers

Area of Science:

• Exercise Physiology
• Mitochondrial Biology
• Skeletal Muscle Metabolism

Background:

• Exercise training improves the integration of ATP supply and demand in skeletal muscle.
• The creatine kinase (CK) system plays a crucial role in cellular energy homeostasis.
• Understanding adaptations in mitochondrial function and CK coupling is key to explaining training effects.

Purpose of the Study:

• To investigate how exercise training alters the apparent K(m) for ADP (adenosine diphosphate).
• To examine changes in creatine kinase (CK) system efficiency after training.
• To determine the role of these factors in the tighter integration of ATP supply and demand.

Main Methods:

• Mitochondrial function was assessed in saponin-skinned muscle fibers from soleus and red gastrocnemius.
• Rats were subjected to a 4-week treadmill running program (trained group) or served as controls.
• Key parameters measured included V(max) (maximal velocity), apparent K(m) for ADP, and CK efficiency.

Main Results:

• In soleus muscle, training increased V(max) for ADP but did not alter K(m) for ADP or CK efficiency.
• In red gastrocnemius, training significantly decreased the apparent K(m) for ADP (increased sensitivity) without affecting V(max) or CK efficiency.
• These findings indicate muscle-specific adaptations in mitochondrial response to training.

Conclusions:

• Exercise training induces muscle-specific adaptations in mitochondrial function.
• A training-induced increase in mitochondrial sensitivity to ADP may partly explain enhanced ATP supply-demand coupling.
• Changes in the apparent K(m) for ADP are a key factor in the tighter integration of energy metabolism post-training.