Spermidine-enhanced autophagic flux improves cardiac dysfunction following myocardial infarction by targeting the AMPK/mTOR signalling pathway

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 age-related 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, Sprague-Dawley 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 post-MI, 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 MI-induced cardiac dysfunction by promoting AMPK/mTOR-mediated autophagic flux.

[Changes in serum level of carboxy-terminal telopeptide of type I collagen in patients with coronary heart disease]

OBJECTIVE

To investigate the serum level of carboxy-terminal telopeptide of type I collagen (ICTP) and explore its correlation with MMP-2 and MMP-9 in patients with coronary artery disease (CHD).

METHODS

A total of 103 CHD patients treated in our hospital between October, 2013 and May, 2014 were enrolled, including 39 with stable angina pectoris (SAP), 39 with unstable angina (UA), and 25 with acute myocardial infarction (AMI), with 38 non-CHD volunteers as the control group. The serum levels of ICTP, MMP-2, and MMP-9 were detected in all the subjects using enzyme-linked immunosorbent assay (ELISA).

RESULTS

No significant difference in serum levels of MMP-2, MMP-9, or ICTP was found between the control and SAP groups or between UA and AMI groups (P>0.05), but the latter two groups had significantly higher serum levels of MMP-2, MMP-9, and ICTP than the former two groups (P<0.05). Serum ICTP level was found to negatively correlated with the fibrotic area and positively with the lipid component in the plaques (P<0.05). Regression analysis revealed significant positive correlations of serum ICTP with MMP-2 and MMP-9 (P<0.05).

CONCLUSION

An elevated serum ICTP level is indicative of the presence of unstable plaques in CHD patients. Serum ICTP is more strongly correlated with MMP-2 than with MMP-9, and can be used as a non-invasive marker for assessing vulnerable plaques in patients with acute coronary syndrome.