Rationale: Diabetes mellitus is often associated with cardiovascular complications, which is the leading cause of morbidity and mortality among patients with diabetes mellitus, but little is known about the mechanism that connects diabetes mellitus to the development of cardiovascular dysfunction. Objective: We aim to elucidate the mechanism underlying hyperglycemia-induced cardiac dysfunction on a well-established db/db mouse model for diabetes mellitus and diabetic complications that lead to heart failure. Methods and Results: We first profiled the expression of microRNAs (miRNAs) by microarray and quantitative reverse transcription polymerase chain reaction on db/db mice and identified miR-320 as a key miRNA associated with the disease phenotype. We next established the clinical relevance of this finding by showing the upregulation of the same miRNA in the failing heart of patients with diabetes mellitus. We demonstrated the causal role of miR-320 in inducing diabetic cardiomyopathy, showing that miR-320 overexpression exacerbated while its inhibition improved the cardiac phenotype in db/db mice. Unexpectedly, we found that miR-320 acts as a small activating RNA in the nucleus at the level of transcription. By chromatin immunoprecipitation sequencing and chromatin immunoprecipitation quantitive polymerase chain reaction analysis of Ago2 (argonaute RISC catalytic component 2) and RNA polymerase II in response to miR-320 induction, we identified CD36 (fatty acid translocase) as a key target gene for this miRNA and showed that the induced expression of CD36 is responsible for increased fatty acid uptake, thereby causing lipotoxicity in the heart. Conclusions: These findings uncover a novel mechanism for diabetes mellitus–triggered cardiac dysfunction, provide an endogenous case for small activating RNA that has been demonstrated to date only with synthetic RNAs in transfected cells, and suggest a potential strategy to develop a miRNA-based therapy to treat diabetes mellitus–associated cardiovascular complications.
Rationale: Previously, we identified the human cardiac long non-coding RNAs (lncRNAs) profile in dilated cardiomyopathy (DCM) patients, among which ZNF593-AS, also named as RP11-96L14.7 and ENST00000448923.2, showed good conservation among species. Objective: We aim to elucidate the mechanism underlying lncRNA in DCM and DCM that lead to heart failure, which might provide new insights into the mechanisms of DCM and possible treatment strategies in the future. Methods and Results: lncRNA expression was measured by real-time PCR and in situ hybridization assays. Coding potential was verified by bioinformatic and biologic assays. Recombinant adeno-associated virus with cardiac specific promoter was used to deliver lncRNA in vivo, while cardiac structure and functions were assessed by echocardiography and catheter. Sarcomere shortening, calcium imaging, gene expression profiling, and pull-down assays were performed to investigate the underlying mechanisms. ZNF593-AS, which mainly localized in the cytoplasm of cardiomyocytes, was robustly decreased in the failing heart of DCM patients, as well as in phenylephrine-treated human cardiomyocytes. Overexpression of mmu-ZNF593-AS significantly improved transverse aortic constriction (TAC)-induced cardiac dysfunction in mice. Moreover, ZNF593-AS overexpression restored the aberrant Ca 2+ handling and contractility of cardiomyocytes from TAC-treated mice. Further, we found that ZNF593-AS acted as a guide RNA scaffold and recruited HNRNPC to ryanodine receptor type 2 (RYR2) mRNA, which in turn facilitated RYR2 mRNA stability, contributed to the improvement of cardiac Ca 2+ handling and contractile function in DCM. Conclusions: Our findings suggested that lncRNA-based therapeutics may protect against DCM.
MicroRNAs (miRNAs) are aberrantly expressed in the pathophysiologic process of heart failure (HF). However, the functions of a certain miRNA in different cardiac cell types during HF are scarcely reported, which might be covered by the globe effects of it on the heart. In the current study, Langendorff system was applied to isolate cardiomyocytes (CMs) and cardiac fibroblasts (CFs) from transverse aortic constriction (TAC)-induced mice. Slight increase of miR-320 expression was observed in the whole heart tissue of TAC mice. Interestingly, miR-320 was significantly elevated in CMs but decreased in CFs from TAC mice at different time points. Then, recombinant adeno-associated virus 9 with cell-type-specific promoters were used to manipulate miR-320 expressions in vivo. Both in vitro and in vivo experiments showed the miR-320 overexpression in CMs exacerbated cardiac dysfunction, whereas overexpression of miR-320 in CFs alleviated cardiac fibrosis and hypertrophy. Mechanically, downstream signaling pathway analyses revealed that miR-320 might induce various effects via targeting PLEKHM3 and IFITM1 in CMs and CFs, respectively. Moreover, miR-320 mediated effects could be abolished by PLEKHM3 re-expression in CMs or IFITM1 re-expression in CFs. Interestingly, miR-320 treated CFs were able to indirectly affect CMs function, but not vice versa. Meanwhile, upstream signaling pathway analyses showed that miR-320 expression and decay rate were rigorously manipulated by Ago2, which was regulated by a cluster of cell-type-specific TFs distinctively expressed in CMs and CFs, respectively. Together, we demonstrated that miR-320 functioned differently in various cell types of the heart during the progression of HF.
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