Minutes that matter: time-efficient high-intensity interval training improves cardiac function with transcriptomic...

Area of Science:

• Cardiovascular Physiology
• Exercise Science
• Molecular Cardiology

Background:

• High-intensity interval training (HIIT) is known to enhance cardiovascular performance.
• The underlying mechanisms by which HIIT influences cardiac remodeling post-myocardial infarction (MI) are not fully understood.

Purpose of the Study:

• To investigate the effects of HIIT on left-ventricular (LV) remodeling and cardiac function in a mouse model of MI.
• To explore the molecular adaptations in the heart following HIIT in post-MI mice.

Main Methods:

• Adult mice underwent permanent coronary ligation (MI) or sham surgery.
• Mice were randomized into groups: Control, HIIT-only, Sham, MI-only, and MI + HIIT.
• HIIT protocol involved 15 treadmill bouts (60s high intensity, 30s rest) 3x/week for 6 weeks.
• Echocardiography assessed LV function and dimensions; fibrosis was quantified via histology; DNA synthesis was measured using EdU incorporation; gene expression was analyzed by bulk RNA sequencing.

Main Results:

• The MI + HIIT group exhibited significantly improved running capacity, LV ejection fraction, and fractional shortening compared to the MI-only group.
• HIIT led to reduced myocardial fibrosis and LV dilation in post-MI mice, indicative of physiological remodeling.
• Increased DNA synthesis was observed in hearts from both HIIT-only and MI + HIIT groups.
• RNA sequencing revealed coordinated upregulation of contractile/metabolic pathways and downregulation of apoptosis/inflammatory signaling in the MI + HIIT group.

Conclusions:

• HIIT effectively enhances exercise capacity and cardiac function following MI in mice.
• HIIT attenuates adverse cardiac remodeling, including fibrosis and dilation, post-MI.
• HIIT reprograms cardiac gene expression towards pro-contractile, anti-inflammatory, and cell-cycle-permissive states, promoting cardiac recovery.