Positive feedback loop of miR-320 and CD36 regulates the hyperglycemic memory-induced diabetic diastolic cardiac dysfunction

SREBP1 induction mediates long-term statins therapy related myocardial lipid peroxidation and lipid deposition in TIIDM mice

Statins therapy is efficacious in diminishing the risk of major cardiovascular events in diabetic patients. However, our research has uncovered a correlation between the prolonged administration of statins and an elevated risk of myocardial dysfunction in patients with type II diabetes mellitus (TIIDM). Here, we report the induction of sterol regulatory element-binding protein 1 (SREBP1) activation, associated lipid peroxidation, and the consequent diabetic myocardial dysfunction after statin treatment and explored the underlying mechanisms. In db/db mice, we observed that 40 weeks atorvastatin (5 and 10 mg/kg) and rosuvastatin (20 mg/kg) administration exacerbated diabetic myocardial dysfunction by echocardiography and cardiomyocyte contractility assay, increased myocardial inflammation and fibrosis as shown by CD68, IL-1β, Masson's staining and Collagen1A1 immunohistochemistry (IHC) staining, increased respiratory exchange ratio (RER) by metabolic cage system assessment, exacerbated mitochondrial structural pathological changes by transmission electron microscopy (TEM) examination, increased deposition of lipid and glycogen by TEM, Oil-red and periodic acid-schiff stain (PAS) staining, which were corresponded with augmented levels of myocardial SREBP1 protein and lipid peroxidation marked by 4-hydroxynonenal (4-HNE) staining. Comparable myocardial fibrosis was also observed in KK-ay and low-dose streptozotocin (STZ)-induced TIIDM mice. Elevated SREBP1 levels were observed in the heart tissues from diabetic patients, which was positively correlated with their myocardial dysfunction. To elucidate the role of statin induced SREBP1 in lipid peroxidation and lipid deposition and related mechanism, we cultured neonatal mouse primary cardiomyocytes (NMPCs) and treated them with atorvastatin (10 μM, 24 h), tracing with [U-13C]-glucose and evaluating for SREBP1 expression and localization. We found that statin treatment elevated de novo lipogenesis (DNL) and the levels of SREBP1 cleavage-activating protein (SCAP), reduced the interaction of SCAP with insulin-induced gene 1 (Insig1), and enhance SCAP/SREBP1 translocation to the Golgi, which facilitate SREBP1 cleavage leading to its nuclear trans-localization and activation in NMPCs. Ultimately, SREBP1 knockdown or l-carnitine mitigated long-term statins therapy induced lipid peroxidation and myocardial fibrosis in low-dose STZ treated SREBP1+/- mice and l-carnitine treated db/db mice. In conclusion, we demonstrated that statin therapy may augment DNL by activating SREBP1, resulting in myocardial lipid peroxidation and lipid deposition.

Subcellular mass spectrometric detection unveils hyperglycemic memory in the diabetic heart

BACKGROUND

Intensive glycemic control is insufficient to reduce the risk of heart failure in patients with diabetes mellitus. While the hyperglycemic memory in the diabetic cardiomyopathy has been well documented, its underlying mechanisms are not fully understood. The present study tried to investigate whether the dysregulated proteins/biological pathways, which persistently altered in diabetic hearts during normoglycemia, participate in the hyperglycemic memory.

METHODS

Hearts of streptozotocin-induced diabetic mice, with or without intensive glycemic control using slow-release insulin implants, were collected. Proteins from total heart samples and subcellular fractions were assessed by mass spectrometry, Western blotting, and KEGG pathway enrichment analysis. mRNA sequencing was used to determine whether the persistently altered proteins were regulated at the transcriptional or post-transcriptional level.

RESULTS

Western blot validation of several proteins with high pathophysiological importance, including MYH7, HMGCS2, PDK4, and BDH1, indicated that mass spectrometry was able to qualitatively, but not quantitatively, reflect the fold changes of certain proteins in diabetes. Pathway analysis revealed that the peroxisome, PPAR pathway, and fatty acid metabolism could be efficiently rescued by glycemic control. However, dysregulation of oxidative phosphorylation and reactive oxygen species persisted even after normalization of hyperglycemia. Notably, mRNA sequencing revealed that dysregulated proteins in the oxidative phosphorylation pathway were not accompanied by coordinated changes in mRNA levels, indicating post-transcriptional regulation. Moreover, literature review and bioinformatics analysis suggested that hyperglycemia-induced persistent alterations of miRNAs targeted genes from the persistently dysregulated oxidative phosphorylation pathway, whereas, oxidative phosphorylation dysfunction-induced ROS regulated miRNA expression, which thereby might sustained the dysregulation of miRNAs.

CONCLUSIONS

Glycemic control cannot rescue hyperglycemia-induced alterations of subcellular proteins in the diabetic heart, and persistently altered proteins are involved in multiple functional pathways, including oxidative phosphorylation. These findings might provide novel insights into hyperglycemic memory in diabetic cardiomyopathy.

An update on chronic complications of diabetes mellitus: from molecular mechanisms to therapeutic strategies with a focus on metabolic memory

Diabetes mellitus, a chronic metabolic disease, often leads to numerous chronic complications, significantly contributing to global morbidity and mortality rates. High glucose levels trigger epigenetic modifications linked to pathophysiological processes like inflammation, immunity, oxidative stress, mitochondrial dysfunction, senescence and various kinds of cell death. Despite glycemic control, transient hyperglycemia can persistently harm organs, tissues, and cells, a latent effect termed "metabolic memory" that contributes to chronic diabetic complications. Understanding metabolic memory's mechanisms could offer a new approach to mitigating these complications. However, key molecules and networks underlying metabolic memory remain incompletely understood. This review traces the history of metabolic memory research, highlights its key features, discusses recent molecules involved in its mechanisms, and summarizes confirmed and potential therapeutic compounds. Additionally, we outline in vitro and in vivo models of metabolic memory. We hope this work will inform future research on metabolic memory's regulatory mechanisms and facilitate the development of effective therapeutic compounds to prevent diabetic complications.

Nuclear AGO2 promotes myocardial remodeling by activating ANKRD1 transcription in failing hearts

Heart failure (HF) is manifested by transcriptional and posttranscriptional reprogramming of critical genes. Multiple studies have revealed that microRNAs could translocate into subcellular organelles such as the nucleus to modify gene expression. However, the functional property of subcellular Argonaute2 (AGO2), the core member of the microRNA machinery, has remained elusive in HF. AGO2 was found to be localized in both the cytoplasm and nucleus of cardiomyocytes, and robustly increased in the failing hearts of patients and animal models. We demonstrated that nuclear AGO2 rather than cytosolic AGO2 overexpression by recombinant adeno-associated virus (serotype 9) with cardiomyocyte-specific troponin T promoter exacerbated the cardiac dysfunction in transverse aortic constriction (TAC)-operated mice. Mechanistically, nuclear AGO2 activates the transcription of ANKRD1, encoding ankyrin repeat domain-containing protein 1 (ANKRD1), which also has a dual function in the cytoplasm as part of the I-band of the sarcomere and in the nucleus as a transcriptional cofactor. Overexpression of nuclear ANKRD1 recaptured some key features of cardiac remodeling by inducing pathological MYH7 activation, whereas cytosolic ANKRD1 seemed cardioprotective. For clinical practice, we found ivermectin, an antiparasite drug, and ANPep, an ANKRD1 nuclear location signal mimetic peptide, were able to prevent ANKRD1 nuclear import, resulting in the improvement of cardiac performance in TAC-induced HF.

AGO2 Protects Against Diabetic Cardiomyopathy by Activating Mitochondrial Gene Translation

BACKGROUND

Diabetes is associated with cardiovascular complications. microRNAs translocate into subcellular organelles to modify genes involved in diabetic cardiomyopathy. However, functional properties of subcellular AGO2 (Argonaute2), a core member of miRNA machinery, remain elusive.

METHODS

We elucidated the function and mechanism of subcellular localized AGO2 on mouse models for diabetes and diabetic cardiomyopathy. Recombinant adeno-associated virus type 9 was used to deliver AGO2 to mice through the tail vein. Cardiac structure and functions were assessed by echocardiography and catheter manometer system.

RESULTS

AGO2 was decreased in mitochondria of diabetic cardiomyocytes. Overexpression of mitochondrial AGO2 attenuated diabetes-induced cardiac dysfunction. AGO2 recruited TUFM, a mitochondria translation elongation factor, to activate translation of electron transport chain subunits and decrease reactive oxygen species. Malonylation, a posttranslational modification of AGO2, reduced the importing of AGO2 into mitochondria in diabetic cardiomyopathy. AGO2 malonylation was regulated by a cytoplasmic-localized short isoform of SIRT3 through a previously unknown demalonylase function.

CONCLUSIONS

Our findings reveal that the SIRT3-AGO2-CYTB axis links glucotoxicity to cardiac electron transport chain imbalance, providing new mechanistic insights and the basis to develop mitochondria targeting therapies for diabetic cardiomyopathy.

Icariin alleviates diabetic renal interstitial fibrosis aggravation by inhibiting miR-320a-3p targeting BMP6

Diabetic nephropathy is a common complication of diabetes, accumulating evidence underscores the pivotal role of tubulointerstitial fibrosis in the progression of diabetic nephropathy. However, the underlying mechanisms remain incompletely understood. Although the mechanisms in diabetic nephropathy fibrosis have been the focus of many studies, only limited information is currently available concerning microRNA regulation in tubulointerstitial fibrosis. In this study, we aimed to investigate the roles of miR-320a-3p and bone morphogenetic protein-6 (BMP6) in tubulointerstitial fibrosis. After inducing fibrosis with high glucose in HK-2 cells, we found that miR-320a-3p is significantly up-regulated, whereas BMP6 is markedly down-regulated. These changes suggest close link between miR-320a-3p and BMP6 in tubulointerstitial fibrosis. To elucidate this phenomenon, miR-320a-3p mimic, inhibitor and siBMP6 were employed. We observed in miR-320a-3p mimic group the fibrosis marker include alpha smooth muscle actin and type I collagen was significantly up-regulated, whereas BMP6 exhibited the opposite trend. Additionally, we found icariin could alleviate tubulointerstitial fibrosis by downregulation the miR-320a-3p expression. In conclusion, miR-320a-3p promotes tubulointerstitial fibrosis during the development of DN by suppressing BMP signal pathway activity via inhibiting BMP6 expression. Suggesting that miR-320a-3p represents a potential therapeutic target for tubulointerstitial fibrosis induced by diabetic nephropathy.

The mechanisms and therapeutic potential of clopidogrel in mitigating diabetic cardiomyopathy in db/db mice

Clopidogrel has been shown to play a protective role against diabetic nephropathy. However, whether clopidogrel exerts a protective effect against diabetic cardiomyopathy (DCM) is unknown. Three-month-old male db/db mice were administered clopidogrel daily at doses of 5, 10, and 20 mg/kg by gavage for 5 months. Here, we showed that clopidogrel effectively attenuated diabetes-induced cardiac hypertrophy and cardiac dysfunction by inhibiting cardiac fibrosis, inflammatory responses, and oxidative stress damage in db/db mice. Diabetes-induced cardiac fibrosis was inhibited by clopidogrel treatment via blockade of the TGF-β1/Smad3/P2RY12 pathway and inhibition of macrophage infiltration in db/db mice. The protective effects of clopidogrel against oxidative damage were mediated by the induction of the Nrf2 signaling pathway. Taken together, our findings provide strong evidence that clopidogrel is a promising effective agent for the treatment of DCM by alleviating diabetes-induced cardiac hypertrophy and dysfunction. P2RY12 might be an effective target for the treatment of DCM.

Cis-Cardio: A comprehensive analysis platform for cardiovascular-relavant cis-regulation in human and mouse

Cis-regulatory elements are important molecular switches in controlling gene expression and are regarded as determinant hubs in the transcriptional regulatory network. Collection and processing of large-scale cis-regulatory data are urgent to decipher the potential mechanisms of cardiovascular diseases from a cis-regulatory element aspect. Here, we developed a novel web server, Cis-Cardio, which aims to document a large number of available cardiovascular-related cis-regulatory data and to provide analysis for unveiling the comprehensive mechanisms at a cis-regulation level. The current version of Cis-Cardio catalogs a total of 45,382,361 genomic regions from 1,013 human and mouse epigenetic datasets, including ATAC-seq, DNase-seq, Histone ChIP-seq, TF/TcoF ChIP-seq, RNA polymerase ChIP-seq, and Cohesin ChIP-seq. Importantly, Cis-Cardio provides six analysis tools, including region overlap analysis, element upstream/downstream analysis, transcription regulator enrichment analysis, variant interpretation, and protein-protein interaction-based co-regulatory analysis. Additionally, Cis-Cardio provides detailed and abundant (epi-) genetic annotations in cis-regulatory regions, such as super-enhancers, enhancers, transcription factor binding sites (TFBSs), methylation sites, common SNPs, risk SNPs, expression quantitative trait loci (eQTLs), motifs, DNase I hypersensitive sites (DHSs), and 3D chromatin interactions. In summary, Cis-Cardio is a valuable resource for elucidating and analyzing regulatory cues of cardiovascular-specific cis-regulatory elements. The platform is freely available at http://www.licpathway.net/Cis-Cardio/index.html.