ABSTRACT
@#Objective To investigate the effect of caloric restriction(CR)on myocardial ischemia/reperfusion injury(MI/RI)in mice and its mechanism.Methods C57 mice were randomly divided into normal diet group(AL group,free feeding)and CR group(diet decreased by 10% every 2 weeks)for 8 weeks and monitored for weight changes.Each group was divided into sham operation group and MI/RI group,total 4 groups,AL + Sham group,AL + I/R group,CR + Sham group and CR + I/R group).The left anterior descending coronary artery was ligated for 30 minutes and then reperfused for 24 hours in mice of MI/RI group and mice in Sham group were only threaded but not ligated.The mice were determined for myocardial ischemia and infarct size by Evans blue/TTC staining,observed for the pathology of myocardium by HE staining,determined for the activities of lactate dehydrogenase(LDH),superoxide dismutase(SOD)and the contents of creatine kinase-MB(CK-MB)and malondialdehvde(MDA)in myocardium by the corresponding kits,determined for serum levels of IL-1β and IL-18 by ELISA and detected for the expression of pyroptosis-associated proteins in myocardium by Western blot.Results After 8weeks,the weights of mice in CR group[(24.54 ± 0.41)g]were significantly lower than those in AL group[(31.46 ±0.25)g](t = 14.34,P<0.05).Compared with those in AL + I/R group,the area of myocardial ischemia in CR + I/R group showed no significant difference(t = 0.783 0,P>0.05),while the area of myocardial infarction decreased significantly(t = 7.250,P<0.01);The myocardial arrangement was relatively neat,and the degree of pathological changes was obviously reduced;LDH activity,CK-MB and MDA contents decreased significantly(t = 4.331,2.875 and 5.343 respectively,each P<0.05),while SOD activity increased significantly(t = 4.211,P<0.05);Serum levels of IL-1β and IL-18 decreased significantly(t = 3.375 and 4.266 respectively,each P<0.05);The expression levels of nod-like receptor protein 3(NLRP3),gasdermin D(GSDMD),apoptosis-associated speckle-like protein(ASC)and caspase-1 significantly decreased(t = 3.412,3.420,3.480 and 2.585 respectively,each P<0.05).Conclusion CR alleviated MI/RI in mice,and its mechanism was related to the inhibition of cardiac pyroptosis.
ABSTRACT
Mammalian target of rapamycin (mTOR) and a ribosomal protein S6 kinase (p70S6K) mediate tissue fibrosis and negatively regulate autophagy. This study aims to investigate whether glucagon-like peptide-1 (GLP-1) analog liraglutide protects the heart against aortic banding-induced cardiac fibrosis and dysfunction through inhibiting mTOR/p70S6K signaling and promoting autophagy activity. Male SD rats were randomly divided into four groups (n = 6/each group): sham operated control; abdominal aortic constriction (AAC); liraglutide treatment during AAC (0.3 mg/kg, injected subcutaneously twice daily); rapamycin treatment during AAC (0.2 mg/kg/day, administered by gastric gavage). Relative to the animals with AAC on week 16, liraglutide treatment significantly reduced heart/body weight ratio, inhibited cardiomyocyte hypertrophy, and augmented plasma GLP-1 level and tissue GLP-1 receptor expression. Phosphorylation of mTOR/p70S6K, populations of myofibroblasts and synthesis of collagen I/III in the myocardium were simultaneously inhibited. Furthermore, autophagy regulating proteins: LC3-II/LC3-I ratio and Beclin-1 were upregulated, and p62 was downregulated by liraglutide. Compared with liraglutide group, treatment with rapamycin, a specific inhibitor of mTOR, compatibly augmented GLP-1 receptor level, inhibited phosphorylation of mTOR/p70S6K and expression of p62 as well as increased level of LC3-II/LC3-I ratio and Beclin-1, suggesting that there is an interaction between GLP-1 and mTOR/p70S6K signaling in the regulation of autophagy. In line with these modifications, treatment with liraglutide and rapamycin significantly reduced perivascular/interstitial fibrosis, and preserved systolic/diastolic function. These results suggest that the inhibitory effects of liraglutide on cardiac fibrosis and dysfunction are potentially mediated by inhibiting mTOR/p70S6K signaling and enhancing autophagy activity.
