Effects of exercise training on myocardial polyamine metabolism in aged rats

AIM:To explore the effects of exercise training on myocardial polyamine metabolism in aged rats. METHODS:Wistar rats were divided into 3 groups:old+exercise group(Old+Ex), old group(Old) and young group(Young). High-performance liquid chromatography was used to test the content of myocardial polyamines(putrescine, spermidine and spermine). The activity of polyamine synthesis and catabolism rate-limiting enzyme ornithine decarboxylase(ODC) and spermidine/spermine acetyltransferase(SSAT) was analyzed by ¹⁴C] labeling. The level of malondialdehyde(MDA) and the activity of superoxide dismutase(SOD) in the myocardium were detected by colorimetric method. The levels of TNF-α and IL-1β were determined by enzyme-linked immunosorbent assay. The cardiac functions were measured by echocardiography. The changes of myocardial ultrastructure were observed under transmission electron microscope. RESULTS:(1) Compared with Young group, ODC activity decreased, SSAT activity increased, and the levels of spermidine, spermine and total polyamine were significantly decreased in Old group. SOD activity also decreased significantly, the content of MDA, TNF-α and IL-1β also increased dramatically in Old group. In the old rats, both left ventricular end-systolic diameter(LVESD) and end-diastolic diameter(LVEDD) increased, while left ventricular ejection fraction(LVEF) and fractional shortening(LVFS) decreased.(2) Compared with Old group, ODC activity increased, SSAT activity decreased, the levels of spermidine and total polyamine significantly increased, SOD activity increased significantly, and the content of MDA, TNF-α and IL-1β decreased dramatically in Old+Ex group. The functions of left ventricle also improved significantly in Old+Ex group.(3) Ultrastructural observations indicated that the myofilament and mitochondrial cristae were irregular and mitochondrial matrix density decreased in old rat heart. The cardiac sarcomere structure was clear, the mitochondrial matrix was dense and the mitochondrial cristae arranged in order in Old+Ex group. CONCLUSION:Exercise training promotes polyamine synthesis metabolism and inhibits polyamine catabolism in the heart of aged rats, thus fighting against aging-induced myocardial polyamine decrease. Exercise training also improves the capacity of anti-inflammatory and antioxidant processes of aged heart. Maintaining the appropriate levels of myocardial polyamines may be a new mechanism to delay cardiac aging.