Small Extracellular Vesicles From Brown Adipose Tissue Mediate Exercise Cardioprotection

Area of Science:

• Cardiovascular Biology
• Metabolic Physiology
• Extracellular Vesicle Biology

Background:

• Long-term exercise confers cardioprotection through incompletely understood mechanisms.
• Brown adipose tissue (BAT), traditionally viewed as thermogenic, possesses endocrine functions impacting remote organs like the heart.
• Exercise induces BAT expansion, but its role in exercise-mediated cardioprotection is unclear.

Purpose of the Study:

• To investigate if BAT-secreted small extracellular vesicles (sEVs) and their microRNAs (miRNAs) mediate cardiomyocyte survival and exercise cardioprotection against myocardial ischemia/reperfusion (MI/R) injury.
• To elucidate the mechanisms by which BAT sEVs exert cardioprotective effects.

Main Methods:

• Mice underwent 4 weeks of exercise, followed by assessment of BAT expansion and response to MI/R injury.
• BAT ablation and in situ silencing of Rab27a (a gene essential for sEV secretion) were performed to evaluate BAT's role in exercise cardioprotection.
• BAT sEVs were isolated and administered intramyocardially, and their miRNA cargo was analyzed.
• The impact of BAT sEVs and specific miRNAs on the mitogen-associated protein kinase (MAPK) pathway in cardiomyocytes was assessed.

Main Results:

• Exercise led to significant BAT expansion and improved cardiac function post-MI/R, effects blunted by BAT ablation or Rab27a silencing.
• Intramyocardial delivery of BAT sEVs ameliorated MI/R injury.
• Specific miRNAs (miR-125b-5p, miR-128-3p, miR-30d-5p) within BAT sEVs were identified as key mediators of cardioprotection.
• These miRNAs were shown to suppress the proapoptotic MAPK pathway by targeting key signaling molecules.

Conclusions:

• BAT-derived sEVs contribute to exercise-induced cardioprotection by delivering specific miRNAs to the heart.
• These findings reveal a novel mechanism of intercellular communication between BAT and the heart.
• BAT sEVs and their miRNA cargo represent potential therapeutic targets for enhancing cardiac protection.