Mild exercise training, cardioprotection and stress genes profile

Area of Science:

• Cardiovascular Physiology
• Exercise Science
• Molecular Biology

Background:

• Exercise training is known to confer cardioprotection, but the underlying molecular mechanisms remain incompletely understood.
• A 'second window' of protection against ischemia/reperfusion (I/R) injury has been observed hours after a conditioning stimulus.

Purpose of the Study:

• To investigate the molecular adaptations in the rat myocardium following a mild exercise training program.
• To elucidate the mechanisms responsible for exercise-induced cardioprotection against I/R injury.

Main Methods:

• Sprague-Dawley rats underwent 14 weeks of treadmill exercise (55% maximal oxygen uptake, 1 h/day, 3 days/week).
• Cardiac function and molecular markers were assessed 48 hours post-training, including biochemical assays, gene expression (real-time PCR), and protein analysis (Western blot).
• Hearts were subjected to ex vivo I/R (30 min ischemia/90 min reperfusion) to determine infarct size.

Main Results:

• Mild exercise training did not induce cardiac hypertrophy but decreased hemoglobin and increased plasma malondialdehyde and Mn-superoxide dismutase activity.
• Trained rat hearts exhibited significantly reduced infarct size following I/R compared to sedentary controls.
• Myocardial analysis revealed upregulation of growth-arrest and DNA-damage induced 153 (GADD153/CHOP), heme-oxygenase-1 (HO-1), cyclooxygenase-2 (Cox-2), and heat-shock protein 70/72 (HSP70/72).
• Conversely, heat-shock protein 60 (HSP60) and glucose-regulated protein 75 (GRP75) levels were decreased.

Conclusions:

• Mild exercise training initiates a second window of myocardial protection against I/R injury.
• This protection is mediated by the upregulation of specific genes and proteins involved in cellular defense and stress response.
• These findings highlight the potential of exercise as a non-pharmacological intervention for cardiovascular protection.