Metformin is a widely used antidiabetic drug for type 2 diabetes that can play a cardioprotective role through multiple pathways. It is a recognized agonist of AMP-activated protein kinase (AMPK) that blocks mitochondrial complex I. The NLRP3 inflammasome has been demonstrated to be activated in diabetic cardiomyopathy (DCM). However, the role of metformin in regulating the NLRP3 signaling pathway in DCM remains unclear. It has been reported that AMPK can inhibit NLRP3 by activating autophagy. The aim of this study was to investigate whether metformin can inhibit the NLRP3 inflammasome by activating the AMPK/mTOR pathway in DCM. In this study, streptozotocin-induced C57BL/6 mice and high glucose-treated primary cardiomyocytes from neonatal mice were treated with metformin or an AMPK inhibitor compound C. Echocardiography, hematoxylin-eosin and Masson staining showed that the function and morphology of the diabetic hearts were improved after metformin treatment, whereas these parameters deteriorated after intervention with an AMPK inhibitor. Immunohistochemical staining, immunofluorescence staining and western blot assays indicated that the expression levels of mTOR, NLRP3, caspase-1, IL-1β and GSDMD-N were decreased in the diabetic model treated with metformin and were reversed after the administration of an AMPK inhibitor in vivo and in vitro . Mechanistically, our results demonstrated that metformin can activate AMPK, thus improving autophagy via inhibiting the mTOR pathway and alleviating pyroptosis in DCM. Thus, we provide novel information for the treatment of DCM.

Diabetes cardiomyopathy (DCM) is a critical complication of long-term chronic diabetes mellitus and is characterized by myocardial fibrosis and myocardial hypertrophy. It has been suggested that DCM is related to pyroptosis, a programmed cell death associated with inflammation. The long non-coding RNA Kcnq1ot1 is involved in different pathophysiological mechanisms of multiple diseases, including acute myocardial damage and arrhythmia. Our previous study found that Kcnq1ot1 was elevated in left ventricular tissue of diabetic mice. However, whether Kcnq1ot1 is capable of regulating pyroptosis and fibrosis in high glucose-treated cardiac fibroblasts remains unknown. The aim of the study was to investigate the mechanisms of Kcnq1ot1 in DCM. Our study revealed that silencing Kcnq1ot1 by a lentivirus-shRNA improved cardiac function and fibrosis, ameliorated pyroptosis, and inhibited TGF-β1/smads pathway in C57BL/6 mice. In vitro, experiments revealed that Kcnq1ot1 and pyroptosis were activated in cardiac fibroblasts treated with 30 mmol/l glucose. Furthermore, Kcnq1ot1 knockdown by a small interfering RNA decreased caspase-1 expression. Bioinformatic prediction and luciferase assays showed that Kcnq1ot1 functioned as a competing endogenous RNA to regulate the expression of caspase-1 by sponging miR-214-3p. In addition, silencing Kcnq1ot1 promoted gasdermin D cleavage and the secretion of IL-1β, thus repressing the TGF-β1/smads pathway in high glucose-treated cardiac fibroblasts through miR-214-3p and caspase-1. Therefore, Kcnq1ot1/miR-214-3p/caspase-1/TGF-β1 signal pathway presents a new mechanism of DCM progression and could potentially be a novel therapeutic target.

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N6-methyladenosine (m6A) is the most abundant internal modification in mammalian mRNAs. Despite its functional importance in various physiological events, the role of m6A in chemical carcinogenesis remains largely unknown. Here we profiled the dynamic m6A mRNA modification during cellular transformation induced by chemical carcinogens and identified a subset of cell transformation-related, concordantly modulated m6A sites. Notably, the increased m6A in 3′-UTR mRNA of oncogene CDCP1 was found in malignant transformed cells. Mechanistically, the m6A methyltransferase METTL3 and demethylases ALKBH5 mediate the m6A modification in 3′-UTR of CDCP1 mRNA. METTL3 and m6A reader YTHDF1 preferentially recognize m6A residues on CPCP1 3′-UTR and promote CDCP1 translation. We further showed that METTL3 and CDCP1 are upregulated in the bladder cancer patient samples and the expression of METTL3 and CDCP1 is correlated with the progression status of the bladder cancers. Inhibition of the METTL3-m6A-CDCP1 axis resulted in decreased growth and progression of chemical-transformed cells and bladder cancer cells. Most importantly, METTL3-m6A-CDCP1 axis has synergistic effect with chemical carcinogens in promoting malignant transformation of uroepithelial cells and bladder cancer tumorigenesis in vitro and in vivo. Taken together, our results identify dynamic m6A modification in chemical-induced malignant transformation and provide insight into critical roles of the METTL3-m6A-CDCP1 axis in chemical carcinogenesis.

Bone marrow mesenchymal stem cells (MSCs) have improved cardiac performance when administered after acute myocardial infarction (MI) in both large-animal models and in patients.1,2 However, the results from randomized controlled clinical trials have been less impressive; the authors of one meta-analysis concluded that left ventricular ejection fractions (LVEFs) increased by just 2.92% in response to cell therapy.