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Reperfusion therapy after acute myocardial infarction (AMI) can effectively restore the blood supply and nutritional support of ischemic myocardium and save the dying myocardium. However, myocardial ischaemia‐reperfusion (I/R) injury has become a new threat to reperfusion therapy for AMI. Many long‐chain noncoding RNAs (lncRNAs) are dysregulated by I/R damage. Of these dysregulated lncRNAs, Gpr19 was selected as a potential gene of interest based on its high expression change. We aimed to explore the functional role and molecular mechanism of Gpr19 in I/R injury of AMI. C57BL/6 mice underwent I/R injury as in vivo models. Neonatal rat ventricular cardiomyocytes (NRCMs) exposed to an oxygen glucose deprivation/recovery (OGD/R) system were used as an in vitro model. A TUNEL assay, western blot, and oxidative stress analysis were conducted in this study to determine apoptosis and oxidative stress levels. Our results indicated that inhibition of Gpr19 improves cardiac function and reduces apoptosis and myocardial fibrosis scar formation in vivo. Suppression of Gpr19 attenuates oxidative stress and apoptosis in NRCMs exposed to OGD/R. We further demonstrated that inhibition of Gpr19 decreases oxidative stress and apoptosis in OGD/R‐induced NRCMs by regulating miR‐324‐5p and mitochondrial fission regulator 1 (Mtfr1). We elucidated the functional role and potential molecular mechanism of Gpr19 in I/R injury of AMI, provided a theoretical basis for the importance of Gpr9 in I/R injury, and provided a new perspective for the clinical treatment of I/R injury of AMI.

Efficient and robust single-atom catalysts (SACs) based on cheap and earth-abundant elements are highly desirable for electrochemical reduction of nitrogen to ammonia (NRR) under ambient conditions. Herein, for the first time, a Mn–N–C SAC consisting of isolated manganese atomic sites on ultrathin carbon nanosheets is developed via a template-free folic acid self-assembly strategy. The spontaneous molecular partial dissociation enables a facile fabrication process without being plagued by metal atom aggregation. Thanks to well-exposed atomic Mn active sites anchored on two-dimensional conductive carbon matrix, the catalyst exhibits excellent activity for NRR with high activity and selectivity, achieving a high Faradaic efficiency of 32.02% for ammonia synthesis at  − 0.45 V versus reversible hydrogen electrode. Density functional theory calculations unveil the crucial role of atomic Mn sites in promoting N2 adsorption, activation and selective reduction to NH3 by the distal mechanism. This work provides a simple synthesis process for Mn–N–C SAC and a good platform for understanding the structure-activity relationship of atomic Mn sites. Graphic Abstract

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Secreted frizzled-related protein 5 (sFRP5) is a novel adipokine that functions as an inhibitor of Wnt signaling and is involved in embryonic development, proliferation, atherosclerosis, and apoptosis. Studies have shown that sFRP1-4 is expressed in cardiomyocytes, and sFRP3 and sFRP4 are elevated during heart failure. However, it is unclear whether sFRP5 is expressed in cardiomyocytes or cardiac hypertrophy, and as regards the effects of sFRP5 in the process. Here, we report the expression and the corresponding mechanisms of sFRP5 in angiotensin II (Ang II)-induced cardiomyocyte hypertrophy. Neonatal rat ventricular myocytes were exposed to increasing concentrations of Ang II for 12-72 h. Y27632 was used to block ROCK signal. PD98059, SB203580, and SP600125 were used to inhibit ERK1/2, p38 MAPK, and JNK signaling pathways, respectively, and anisomycin was used to activate JNK pathway. RT-PCR and Western-blot determined the expressions of sFRP5. BNP, TNF-α, ROCK1, ROCK2, MYPT1, and JNK were examined through Western-blot analysis. Ang II increased sFRP5 mRNA and protein levels in a time- and dose-dependent manner. Telmisartan, Y27632 and SP600125 effectively suppressed the expression of sFRP5. sFRP5 downregulated BNP and TNF-α expressions in hypertrophic cardiomyocytes. sFRP5 is expressed in cardiomyocytes, and upregulated in Ang II-induced cardiomyocyte hypertrophy through the AT1 receptor/Rho/ROCK1/JNK signaling pathway. sFRP5 may play an important role during cardiomyocyte hypertrophy.

Aims: Chemerin is a novel adipokine that is closely associated with cardiovascular diseases and glucose homeostasis. This study aimed to investigate the effects of chemerin on insulin resistance in rat cardiomyocytes. Methods: Rat cardiomyocytes were treated with high concentrations of glucose and tumor necrosis factor-alpha (TNF-E), and chemerin and chemokine-like receptor 1 (CMKLR1) were measured by Western blot analysis. Then, the cardiomyocytes were treated with chemerin and insulin. Glucose uptake was evaluated using a fluorescence microplate reader. Western blot analysis was used to evaluate the phosphorylation of Akt, insulin receptor substrate-1, p38 mitogen-activated protein kinase (MAPK), as well as extracellular signal-regulated kinase (ERK)1/2. Results: Chemerin and CMKLR1 were found to be expressed in rat cardiomyocytes. Pretreatment with chemerin caused decreases in glucose uptake and phosphorylation of Akt in insulin-stimulated cardiomyocytes. Furthermore, chemerin activated the phosphorylation of p38 MAPK and ERK1/2 in insulin-stimulated cardiomyocytes. Inhibition of ERK partially rescued chemerin-induced insulin resistance. Conclusion: Chemerin is a novel adipokine that induces insulin resistance in rat cardiomyocytes in part through the ERK1/2 pathway. i 2014 S. Karger AG, Basel

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