Background and Purpose
Spermidine, a natural polyamine, is abundant in mammalian cells and is involved in cell growth, proliferation, and regeneration. Recently, oral spermidine supplements were cardioprotective in ageârelated cardiac dysfunction, through enhancing autophagic flux. However, the effect of spermidine on myocardial injury and cardiac dysfunction following myocardial infarction (MI) remains unknown.
Experimental Approach
We determined the effects of spermidine in a model of MI, SpragueâDawley rats with permanent ligation of the left anterior descending artery, and in cultured neonatal rat cardiomyocytes (NRCs) exposed to angiotensin II (Ang II). Cardiac function in vivo was assessed with echocardiography. In vivo and in vitro studies used histological and immunohistochemical techniques, along with western blots.
Key Results
Spermidine improved cardiomyocyte viability and decreased cell necrosis in NRCs treated with angiotensin II. In rats postâMI, spermidine reduced infarct size, improved cardiac function, and attenuated myocardial hypertrophy. Spermidine also suppressed the oxidative damage and inflammatory cytokines induced by MI. Moreover, spermidine enhanced autophagic flux and decreased apoptosis both in vitro and in vivo. The protective effects of spermidine on cardiomyocyte apoptosis and cardiac dysfunction were abolished by the autophagy inhibitor chloroquine, indicating that spermidine exerted cardioprotective effects at least partly through promoting autophagic flux, by activating the AMPK/mTOR signalling pathway.
Conclusions and Implications
Our findings suggest that spermidine improved MIâinduced cardiac dysfunction by promoting AMPK/mTORâmediated autophagic flux.