Exercise training suppresses Mst1 activation and attenuates myocardial dysfunction in mice with type 1 diabetes

Our study was to test the effects of aerobic exercise on myocardial function in mice with type 1 diabetes and investigate the underlying mechanism associated with mammalian sterile 20-like kinase 1 (Mst1). Wild-type mice and Mst1(-/-) mice were injected with streptozotocin to induce diabetes and given moderate-intensity exercise for 12 weeks. Phosphorylation of Mst1 was significantly enhanced in the left ventricles of diabetic mice, which was reversed by exercise training. Exercise training or Mst1 deficiency improved myocardial function and reduced myocardial fibrosis in diabetic mice. Exercise training or Mst1 deficiency reduced TUNEL-positive cells and caspase-3 activity in the myocardium of diabetic mice. Exercise training or Mst1 deficiency abated oxidative stress and reduced mitochondrial reactive oxygen species formation, attenuated mitochondrial swelling, and enhanced mitochondrial adenosine triphosphate formation and mitochondrial membrane potential in the myocardium of diabetic mice. Exercise training or Mst1 deficiency suppressed inflammation in the myocardium of diabetic mice. Furthermore, exercise training did not provide further protection in Mst1 knockout mice in diabetes. In conclusion, chronic exercise training attenuated myocardial dysfunction in mice with type 1 diabetes, at least in part, through suppressing Mst1 activation.

Crocin Improves Insulin Sensitivity and Ameliorates Adiposity by Regulating AMPK-CDK5-PPARγ Signaling

Crocin is a carotenoid compound which possesses multiple biological activities. Our and other laboratory's previous findings show that crocin alleviates obesity and type 2 diabetes-related complications. We have found that crocin activates AMP-activated protein kinase (AMPK) signaling and inhibition of AMPK suppresses crocin-induced protective effects. However, the causal role of AMPK activation in the biological role of crocin is still not verified. In the present study, we showed that crocin markedly inhibits the changes of glucose metabolic parameters and serum lipid profiles in wild type diabetic mice. In AMPKα KO diabetic mice, those protective effects of crocin against glucose and lipid metabolic dysfunction were abolished. These results demonstrated AMPK activation was responsible for the beneficial effects of crocin on metabolic dysfunction. Moreover, we have shown that the antiobese effect of crocin has been abolished by the deficiency of AMPKα. We also showed that crocin induced a significant decrease of CDK5 protein level in wild type diabetic mice, while this effect was abolished in AMPKα KO diabetic mice. The regulation of downstream targets of CDK5/PPARγ by crocin was abolished by the deficiency of AMPK. In conclusion, our study verified that activation of AMPK is involved in crocin-induced protective effects against glucose and lipid metabolic dysfunction. Activation of AMPK downregulates the protein level of CDK5, followed by the decrease of PPARγ phosphorylation, leading to the inhibition of adipose formation and metabolic dysfunction. Our study provides new insights into the mechanism of protective effects of crocin and interaction of AMPK and CDK5/PPARγ signaling.

Prokineticin 2 (PK2) Rescues Cardiomyocytes from High Glucose/High Palmitic Acid-Induced Damage by Regulating the AKT/GSK3β Pathway In Vitro

Prokineticin 2 (PK2) is a small 8 kDa protein that participates in many physiological processes, such as angiogenesis, inflammation, and neurogenesis. This experiment investigated the effect of PK2 on high glucose/high palmitic acid-induced oxidative stress, apoptosis, and autophagy in cardiomyocytes and the AKT/GSK3β signalling pathway. H9c2 cells were exposed to normal and high concentrations (33 mM) of glucose and palmitic acid (150 μM) with or without PK2 (10 nM) for 48 h. Reactive oxygen species were detected using the fluorescent probes DCFH-DA and DHE. Changes in apoptosis were assessed using flow cytometry, and autophagosomes were detected using Ad-GFP-LC3. Apoptotic proteins, such as Cleaved Caspase3, Bax, and Bcl-2; autophagy proteins, including Beclin-1 and LC3B; and PK2/PKR/AKT/GSK3β signals were evaluated using western blotting. Cardiomyocytes exposed to high glucose/high palmitic acid exhibited increases in intracellular ROS, apoptosis, and autophagosomes, and these increases were robustly prevented by PK2. In addition, high glucose/high palmitic acid remarkably suppressed PK2, PKR1, and PKR2 expression and p-AKT/AKT and p-GSK3β/GSK3β ratios, and these effects were significantly prevented by PK2. Moreover, an AKT1/2 kinase inhibitor (AKT inhibitor, 10 μM) blocked the effects of PK2 on the changes in cardiomyocyte exposure to high glucose/high palmitic acid. These results suggest that PK2 attenuates high glucose/high palmitic acid-induced cardiomyocyte apoptosis by inhibiting oxidative stress and autophagosome accumulation and that this protective effect is most likely mediated by the AKT-related signalling pathway.