This study investigated the effects of melatonin on diabetic cardiomyopathy (DCM) and determined the underlying mechanisms. Echocardiography indicated that melatonin notably mitigated the adverse left ventricle remodeling and alleviated cardiac dysfunction in DCM. The mechanisms were attributed to increased autophagy, reduced apoptosis, and alleviated mitochondrial dysfunction. Furthermore, melatonin inhibited Mst1 phosphorylation and promoted Sirt3 expression in DCM. These results indicated that melatonin may exert its effects through Mst1/Sirt3 signaling. To verify this hypothesis, a DCM model using Mst1 transgenic (Mst1 Tg) and Mst1 knockout (Mst1 ) mice was constructed. As expected, melatonin increased autophagy, reduced apoptosis and improved mitochondrial biogenesis in Mst1 Tg mice subjected to DCM injury, while it had no effects on Mst1 mice. In addition, cultured neonatal mouse cardiomyocytes were subjected to simulated diabetes to probe the mechanisms involved. Melatonin administration promoted autophagic flux as demonstrated by elevated LC3-II and lowered p62 expression in the presence of bafilomycin A1. The results suggest that melatonin alleviates cardiac remodeling and dysfunction in DCM by upregulating autophagy, limiting apoptosis, and modulating mitochondrial integrity and biogenesis. The mechanisms are associated with Mst1/Sirt3 signaling.

Aims/hypothesis Diabetic cardiomyopathy (DCM) is associated with suppressed autophagy and augmented apoptosis in the heart although the interplay between the two remains elusive. The ability of mammalian sterile 20-like kinase 1 to regulate both autophagy and apoptosis prompted us to investigate it as a possible candidate in the progression of DCM. Methods Wild-type, Mst1 (also known as Stk4) transgenic and Mst1-knockout mice were challenged with streptozotocin to induce experimental diabetes. In addition, cultured neonatal mouse cardiomyocytes were subjected to simulated diabetes to probe mechanisms. Results Mst1 knockout alleviated while Mst1 overexpression aggravated cardiac dysfunction in diabetes. Diabetic Mst1 transgenic mice exhibited decreased LC3 expression and enhanced protein aggregation. In contrast, typical autophagosomes were observed in diabetic Mst1-knockout mice with increased LC3 expression and reduced protein aggregation. Mst1 downregulation promoted autophagic flux as demonstrated by increased LC3-II and decreased p62 expression in the presence of bafilomycin A1. Furthermore, Mst1 overexpression increased, while Mst1 knockout decreased, cardiomyocyte apoptosis both in vivo and in vitro. Coimmunoprecipitation assays showed that Mst1 overexpression promoted Beclin1 binding to B cell lymphoma 2 (Bcl-2) and induced dissociation of Bcl-2 from Bax in diabetic mice. Conversely, Mst1 knockout disrupted the Beclin1-Bcl-2 complex and enhanced the interaction between Bcl-2 and Bax. Conclusions/interpretation Mst1 knockout restores autophagy and protects against apoptosis in cardiomyocytes, en route to the rescue against DCM.

Melatonin reportedly protects against several cardiovascular diseases including ischemia/reperfusion (I/R), atherosclerosis, and hypertension. The present study investigated the effects and mechanisms of melatonin on cardiomyocyte autophagy, apoptosis, and mitochondrial injury in the context of myocardial infarction (MI). We demonstrated that melatonin significantly alleviated cardiac dysfunction after MI. Four weeks after MI, echocardiography and Masson staining indicated that melatonin notably mitigated adverse left ventricle remodeling. The mechanism may be associated with increased autophagy, reduced apoptosis, and alleviated mitochondrial dysfunction. Furthermore, melatonin significantly inhibited Mst1 phosphorylation while promoting Sirt1 expression after MI, which indicates that Mst1/Sirt1 signaling may serve as the downstream target of melatonin. We thus constructed a MI model using Mst1 transgenic (Mst1 Tg) and Mst1 knockout (Mst1 ) mice. The absence of Mst1 abolished the favorable effects of melatonin on cardiac injury after MI. Consistently, melatonin administration did not further increase autophagy, decrease apoptosis, or alleviate mitochondrial integrity and biogenesis in Mst1 knockout mice subjected to MI injury. These results suggest that melatonin alleviates postinfarction cardiac remodeling and dysfunction by upregulating autophagy, decreasing apoptosis, and modulating mitochondrial integrity and biogenesis. The attributed mechanism involved, at least in part, Mst1/Sirt1 signaling.

Myocardial infarction (MI), which is characterized by chamber dilation and LV dysfunction, is associated with substantially higher mortality. We investigated the effects and underlying mechanisms of Luteolin on post‐infarction cardiac dysfunction. Myocardial infarction was constructed by left anterior descending coronary artery ligation. In vitro, cultured neonatal cardiomyocytes subjected to simulated MI were used to probe mechanism. Luteolin significantly improved cardiac function, decreased cardiac enzyme and inflammatory cytokines release after MI. Enhanced autophagic flux as indicated by more autophagosomes puncta, less accumulation of aggresomes and P62 in the neonatal cardiomyocytes after hypoxia was observed in the Luteolin pre‐treatment group. Western blot analysis also demonstrated that Luteolin up‐regulated autophagy in the cardiomyocytes subjected to simulated MI injury. Furthermore, Luteolin increased mitochondrial membrane potential, adenosine triphosphate content, citrate synthase activity and complexes I/II/III/IV/V activities in the cardiomyocytes subjected to simulated MI injury. Interestingly, mammalian sterile 20‐like kinase 1 (Mst1) knockout abolished the protective effects of Luteolin administration. Luteolin enhances cardiac function, reduces cardiac enzyme and inflammatory markers release after MI. The protective effects of Luteolin are associated with up‐regulation of autophagy and improvement of mitochondrial biogenesis through Mst1 inhibition.

Myocardial infarction (MI), which is characterized by chamber dilation and left ventricular (LV) dysfunction, represents a major cause of morbidity and mortality worldwide. Polydatin (PD), a monocrystalline and polyphenolic drug isolated from a traditional Chinese herb (Polygonum cuspidatum), alleviates mitochondrial dysfunction. We investigated the effects and underlying mechanisms of PD in post-MI cardiac dysfunction. We constructed an MI model by left anterior descending (LAD) coronary artery ligation using wild-type (WT) and Sirt3 knockout (Sirt3) mice. Cardiac function, cardiomyocytes autophagy levels, apoptosis and mitochondria biogenesis in mice that underwent cardiac MI injury were compared between groups. PD significantly improved cardiac function, increased autophagy levels and decreased cardiomyocytes apoptosis after MI. Furthermore, PD improved mitochondrial biogenesis, which is evidenced by increased ATP content, citrate synthase (CS) activity and complexes I/II/III/IV/V activities in the cardiomyocytes subjected to MI injury. Interestingly, Sirt3 knockout abolished the protective effects of PD administration. PD inhibited apoptosis in cultured neonatal mouse ventricular myocytes subjected to hypoxia for 6h to simulate MI injury. PD increased GFP-LC3 puncta, and reduced the accumulation of protein aggresomes and p62 in cardiomyocytes after hypoxia. Interestingly, the knock-down of Sirt3 nullified the PD-induced beneficial effects. Thus, the protective effects of PD are associated with the up-regulation of autophagy and improvement of mitochondrial biogenesis through Sirt3 activity.

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The incidence and prevalence of heart failure (HF) in the world are rapidly rising possibly attributed to the worsened HF following myocardial infarction (MI) in recent years. Here we examined the effects of oncostatin M (OSM) on postinfarction cardiac remodeling and the underlying mechanisms involved. MI model was induced using left anterior descending coronary artery (LAD) ligation. In addition, cultured neonatal mouse cardiomyocytes were subjected to simulated MI. Our results revealed that OSM alleviated left ventricular remodeling, promoted cardiac function, restored mitochondrial cristae density and architecture disorders after 4weeks of MI. Enhanced autophagic flux was indicated in cardiomyocytes transduced with Ad-GFP -LC3 in the OSM treated group as compared with the MI group. OSM receptor Oβ knockout blocked the beneficial effects of OSM in postinfarction cardiac remodeling and cardiomyocytes autophagy. OSM pretreatment significantly alleviated left ventricular remodeling and dysfunction in Mst1 transgenic mice, while it failed to reverse further the postinfarction left ventricular dilatation and cardiac function in the Mst1 knockout mice. Our data revealed that OSM alleviated postinfarction cardiac remodeling and dysfunction by enhancing cardiomyocyte autophagy. OSM holds promise as a therapeutic target in treating HF after MI through Oβ receptor by inhibiting Mst1 phosphorylation.

Cardiovascular complications account for a substantial proportion of morbidity and mortality in diabetic patients. Abnormalities of cardiac microvascular endothelial cells (CMECs) lead to impaired cardiac microvascular vessel integrity and subsequent cardiac dysfunction, underlining the importance of coronary microvascular dysfunction. In this study, experimental diabetes models were constructed using Mst1 transgenic, Mst1 knockout and sirt1 knockout mice. Diabetic Mst1 transgenic mice exhibited impaired cardiac microvessel integrity and decreased cardiac function. Mst1 overexpression deceased CMECs autophagy as evidenced by decreased LC3 expression and enhanced protein aggregation when subjected to high glucose culture. Mst1 knockout improved cardiac microvessel integrity and enhanced cardiac functions in diabetic mice. Mst1 knockdown up-regulated autophagy as indicated by more typical autophagosomes and increased LC3 expression in CMECs subjected to high glucose cultures. Mst1 knockdown also promoted autophagic flux in the presence of bafilomycin A1. Mst1 overexpression increased CMECs apoptosis, whereas Mst1 knockout decreased CMECs apoptosis. Sirt1 knockout abolished the effects of Mst1 overexpression in cardiac microvascular injury and cardiac dysfunction. In conclusion, Mst1 knockout preserved cardiac microvessel integrity and improved cardiac functions in diabetic mice. Mst1 decreased sirt1 activity, inhibited autophagy and enhanced apoptosis in CMECs, thus participating in the pathogenesis of diabetic coronary microvascular dysfunction.The prevalence of diabetes has reached 12.3% of the adult population in the USA with an increasing 1.7 million new diagnosed diabetic patients per year. The economic cost of diabetes and prediabetes was estimated to be US$322 billion in 2012 1 . Cardiovascular complications are major public health issues that account for a substantial proportion of morbidity and mortality in diabetic patients 2 . Our previous studies demonstrated that coronary microvascular dysfunction occurred in the early stages of diabetes as manifested by impaired microvascular barrier dysfunction, increased oxidative stress and apoptosis in CMECs 3,4 . However, little is known about the mechanisms underlying coronary microvascular damage associated with diabetes. Thus, to better manage diabetic patients and to prevent coronary microvascular damage, we sought to elucidate the pathogenesis of this dysfunction.As the barrier between blood glucose and cardiomyocytes, the endothelium is believed to play a major role in the pathogenesis of diabetes-associated cardiovascular diseases (CVDs) 5 . Interestingly, autophagy has recently emerged as a potential novel target for the treatment of cardiovascular diseases. In particular, Lenoir and colleagues demonstrated that endothelial cell and podocyte autophagy synergistically protected patients from diabetes-induced glomerulosclerosis 6 . Nevertheless, no data exists on the role of CMECs autophagy in diabetes.