Glucose Fluctuations Aggravate Cardiac Susceptibility to Ischemia/Reperfusion Injury by Modulating MicroRNAs Expression

SGLT1: A Potential Drug Target for Cardiovascular Disease

SGLT1 and SGLT2 are the two main members of the sodium-glucose cotransporters (SGLTs), which are mainly responsible for glucose reabsorption in the body. In recent years, many large clinical trials have shown that SGLT2 inhibitors have cardiovascular protection for diabetic and non-diabetic patients independent of lowering blood glucose. However, SGLT2 was barely detected in the hearts of humans and animals, while SGLT1 was highly expressed in myocardium. As SGLT2 inhibitors also have a moderate inhibitory effect on SGLT1, the cardiovascular protection of SGLT2 inhibitors may be due to SGLT1 inhibition. SGLT1 expression is associated with pathological processes such as cardiac oxidative stress, inflammation, fibrosis, and cell apoptosis, as well as mitochondrial dysfunction. The purpose of this review is to summarize the protective effects of SGLT1 inhibition on hearts in various cell types, including cardiomyocytes, endothelial cells, and fibroblasts in preclinical studies, and to highlight the underlying molecular mechanisms of protection against cardiovascular diseases. Selective SGLT1 inhibitors could be considered a class of drugs for cardiac-specific therapy in the future.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Deciphering the Role of miR-200c-3p in Type 1 Diabetes (Subclinical Cardiovascular Disease) and Its Correlation with Inflammation and Vascular Health

Uncomplicated type 1 diabetes (T1DM) displays all features of subclinical cardiovascular disease (CVD) as is associated with inflammation, endothelial dysfunction and low endothelial progenitor cells. MiR-200c-3p has been shown in animal tissues to be pro-atherogenic. We aimed to explore the role of miR-200c-3p in T1DM, a model of subclinical CVD. 19 samples from T1DM patients and 20 from matched controls (HC) were analyzed. MiR-200c in plasma and peripheral blood mononuclear cells (PBMCs) was measured by real-time quantitative polymerase chain reaction. The results were compared with the following indices of vascular health: circulating endothelial progenitor cells, (CD45dimCD34+VEGFR-2+ or CD45dimCD34+CD133+) and proangiogenic cells (PACs). MiR-200c-3p was significantly downregulated in PBMCs but not in plasma in T1DM. There was a significant negative correlation between the expression of miR-200c-3p and HbA1c, interleukin-7 (IL-7), vascular endothelial growth factor-C (VEGF-C), and soluble vascular cell adhesion molecule-1, and a positive correlation with CD45dimCD34+VEGFR-2+, CD45dimCD34+CD133+ and PACs. Receiver operating curve analyses showed miR-200c-3p as a biomarker for T1DM with significant downregulation of miR-200c-3p, possibly defining subclinical CVD at HbA1c > 44.8 mmol/mol (6.2%). In conclusion, downregulated miR-200c-3p in T1DM correlated with diabetic control, VEGF signaling, inflammation, vascular health and targeting VEGF signaling, and may define subclinical CVD. Further prospective studies are necessary to validate our findings in a larger group of patients.

Mitochondrial quality control mechanisms as molecular targets in diabetic heart

Mitochondrial dysfunction has been regarded as a hallmark of diabetic cardiomyopathy. In addition to their canonical metabolic actions, mitochondria influence various other aspects of cardiomyocyte function, including oxidative stress, iron regulation, metabolic reprogramming, intracellular signaling transduction and cell death. These effects depend on the mitochondrial quality control (MQC) system, which includes mitochondrial dynamics, mitophagy and mitochondrial biogenesis. Mitochondria are not static entities, but dynamic units that undergo fission and fusion cycles to maintain their structural integrity. Increased mitochondrial fission elevates the number of mitochondria within cardiomyocytes, a necessary step for cardiomyocyte metabolism. Enhanced mitochondrial fusion promotes communication and cooperation between pairs of mitochondria, thus facilitating mitochondrial genomic repair and maintenance. On the contrary, erroneous fission or reduced fusion promotes the formation of mitochondrial fragments that contain damaged mitochondrial DNA and exhibit impaired oxidative phosphorylation. Under normal/physiological conditions, injured mitochondria can undergo mitophagy, a degradative process that delivers poorly structured mitochondria to lysosomes. However, defective mitophagy promotes the accumulation of nonfunctional mitochondria, which may induce cardiomyocyte death. A decline in the mitochondrial population due to mitophagy can stimulate mitochondrial biogenesis), which generates new mitochondrial offspring to maintain an adequate mitochondrial number. Energy crises or ATP deficiency also increase mitochondrial biogenesis, because mitochondrial DNA encodes 13 subunits of the electron transport chain (ETC) complexes. Disrupted mitochondrial biogenesis diminishes the mitochondrial mass, accelerates mitochondrial senescence and promotes mitochondrial dysfunction. In this review, we describe the involvement of MQC in the pathogenesis of diabetic cardiomyopathy. Besides, the potential targeted therapies that could be applied to improve MQC during diabetic cardiomyopathy are also discussed and accelerate the development of cardioprotective drugs for diabetic patients.

Research progress on ncRNAs regulation of mitochondrial dynamics in diabetes

Diabetes mellitus and its complications are major health concerns worldwide that should be routinely monitored for evaluating disease progression. And there is currently much evidence to suggest a critical role for mitochondria in the common pathogenesis of diabetes and its complications. Mitochondrial dynamics are involved in the development of diabetes through mediating insulin signaling and insulin resistance, and in the development of diabetes and its complications through mediating endothelial impairment and other closely related pathophysiological mechanisms of diabetic cardiomyopathy (DCM). noncoding RNAs (ncRNAs) are closely linked to mitochondrial dynamics by regulating the expression of mitochondrial dynamic-associated proteins, or by regulating key proteins in related signaling pathways. Therefore, this review summarizes the research progress on the regulation of Mitochondrial Dynamics by ncRNAs in diabetes and its complications, which is a promising area for future antibodies or targeted drug development.

Glucose Fluctuations Aggravate Myocardial Fibrosis via the Nuclear Factor-κB-Mediated Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3 Inflammasome Activation

Background

Glucose fluctuations may be associated with myocardial fibrosis. This study aimed to investigate the underlying mechanisms of glucose fluctuation-related myocardial fibrosis.

Methods

Streptozotocin (STZ)-injected type 1 diabetic rats were randomized to five groups: the controlled blood glucose (CBG) group, uncontrolled blood glucose (UBG) group, fluctuated blood glucose (FBG) group, FBG rats injected with 0.9% sodium chloride (NaCl) (FBG + NaCl) group, and FBG rats injected with MCC950 (FBG + MCC950) group. Eight weeks later, left ventricular function was evaluated by echocardiography and myocardial fibrosis was observed by Masson trichrome staining. The primary neonatal rat cardiac fibroblasts were cultured with different concentrations of glucose in vitro.

Results

The left ventricular function was impaired and myocardial fibrosis was aggravated most significantly in the FBG group compared with the CBG and UBG groups. The levels of interleukin (IL)-1β, IL-18, transforming growth factor-β1 (TGF-β1), collagen type 1 (collagen I), nuclear factor (NF)-κB, and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome were significantly increased in the FBG group. In vitro, the inhibition of NF-κB and inflammasome reversed these effects. In vivo, NLRP3 inhibition with MCC950 reversed left ventricular systolic dysfunction and myocardial fibrosis induced by glucose fluctuations.

Conclusion

Glucose fluctuations promote diabetic myocardial fibrosis by the NF-κB-mediated inflammasome activation.

Glucose fluctuation accelerates cardiac injury of diabetic mice via sodium-dependent glucose cotransporter 1 (SGLT1)

Recent studies have shown that blood glucose fluctuation is associated with complications of diabetes mellitus (DM). SGLT1 (sodium-dependent glucose cotransporter 1), is highly expressed in pathological conditions of heart, and is expressed in cardiomyocytes induced by high glucose. Herein, we constructed a diabetic mouse model with glucose fluctuation to investigate whether SGLT1 is involved in glucose fluctuation-induced cardiac injury. Echocardiography, histology examination, and TUNEL staining were performed to evaluate cardiac dysfunction and damage. To assess glucose fluctuation-induced oxidative stress, reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) levels were measured. To assess mitochondrial dysfunction, mitochondrial membrane potential (MMP), ATP content, mitochondrial respiratory chain complex activity, and expression of mitochondrial fusion and fission proteins were determined. The results indicated that diabetic mice with glucose fluctuation showed elevation of cardiac SGLT1 expression, left ventricular dysfunction, oxidative stress and mitochondrial dysfunction. Knockdown of SGLT1 could abrogate the effects of glucose fluctuation on cardiac injury. Thus, our study highlighted that SGLT1 plays an important role in glucose fluctuation induced cardiac injury through oxidative stress and mitochondrial dysfunction.

Glucose Variability: How Does It Work?

A growing body of evidence points to the role of glucose variability (GV) in the development of the microvascular and macrovascular complications of diabetes. In this review, we summarize data on GV-induced biochemical, cellular and molecular events involved in the pathogenesis of diabetic complications. Current data indicate that the deteriorating effect of GV on target organs can be realized through oxidative stress, glycation, chronic low-grade inflammation, endothelial dysfunction, platelet activation, impaired angiogenesis and renal fibrosis. The effects of GV on oxidative stress, inflammation, endothelial dysfunction and hypercoagulability could be aggravated by hypoglycemia, associated with high GV. Oscillating hyperglycemia contributes to beta cell dysfunction, which leads to a further increase in GV and completes the vicious circle. In cells, the GV-induced cytotoxic effect includes mitochondrial dysfunction, endoplasmic reticulum stress and disturbances in autophagic flux, which are accompanied by reduced viability, activation of apoptosis and abnormalities in cell proliferation. These effects are realized through the up- and down-regulation of a large number of genes and the activity of signaling pathways such as PI3K/Akt, NF-κB, MAPK (ERK), JNK and TGF-β/Smad. Epigenetic modifications mediate the postponed effects of glucose fluctuations. The multiple deteriorative effects of GV provide further support for considering it as a therapeutic target in diabetes.

Insulin Crystals Grown in Short-Peptide Supramolecular Hydrogels Show Enhanced Thermal Stability and Slower Release Profile

Protein therapeutics have a major role in medicine in that they are used to treat diverse pathologies. Their three-dimensional structures not only offer higher specificity and lower toxicity than small organic compounds but also make them less stable, limiting their in vivo half-life. Protein analogues obtained by recombinant DNA technology or by chemical modification and/or the use of drug delivery vehicles has been adopted to improve or modulate the in vivo pharmacological activity of proteins. Nevertheless, strategies to improve the shelf-life of protein pharmaceuticals have been less explored, which has challenged the preservation of their activity. Herein, we present a methodology that simultaneously increases the stability of proteins and modulates the release profile, and implement it with human insulin as a proof of concept. Two novel thermally stable insulin composite crystal formulations intended for the therapeutic treatment of diabetes are reported. These composite crystals have been obtained by crystallizing insulin in agarose and fluorenylmethoxycarbonyl-dialanine (Fmoc-AA) hydrogels. This process affords composite crystals, in which hydrogel fibers are occluded. The insulin in both crystalline formulations remains unaltered at 50 °C for 7 days. Differential scanning calorimetry, high-performance liquid chromatography, mass spectrometry, and in vivo studies have shown that insulin does not degrade after the heat treatment. The nature of the hydrogel modifies the physicochemical properties of the crystals. Crystals grown in Fmoc-AA hydrogel are more stable and have a slower dissolution rate than crystals grown in agarose. This methodology paves the way for the development of more stable protein pharmaceuticals overcoming some of the existing limitations.

Endothelium-dependent remote signaling in ischemia and reperfusion: Alterations in the cardiometabolic continuum

Intact endothelial function plays a fundamental role for the maintenance of cardiovascular (CV) health. The endothelium is also involved in remote signaling pathway-mediated protection against ischemia/reperfusion (I/R) injury. However, the transfer of these protective signals into clinical practice has been hampered by the complex metabolic alterations frequently observed in the cardiometabolic continuum, which affect redox balance and inflammatory pathways. Despite recent advances in determining the distinct roles of hyperglycemia, insulin resistance (InR), hyperinsulinemia, and ultimately diabetes mellitus (DM), which define the cardiometabolic continuum, our understanding of how these conditions modulate endothelial signaling remains challenging. It is widely accepted that endothelial cells (ECs) undergo functional changes within the cardiometabolic continuum. Beyond vascular tone and platelet-endothelium interaction, endothelial dysfunction may have profound negative effects on outcome during I/R. In this review, we summarize the current knowledge of the influence of hyperglycemia, InR, hyperinsulinemia, and DM on endothelial function and redox balance, their influence on remote protective signaling pathways, and their impact on potential therapeutic strategies to optimize protective heterocellular signaling.

Effect of hyperglycaemia and diabetes on acute myocardial ischaemia-reperfusion injury and cardioprotection by ischaemic conditioning protocols

Diabetic patients are at increased risk of developing coronary artery disease and experience worse clinical outcomes following acute myocardial infarction. Novel therapeutic strategies are required to protect the myocardium against the effects of acute ischaemia-reperfusion injury (IRI). These include one or more brief cycles of non-lethal ischaemia and reperfusion prior to the ischaemic event (ischaemic preconditioning [IPC]) or at the onset of reperfusion (ischaemic postconditioning [IPost]) either to the heart or to extracardiac organs (remote ischaemic conditioning [RIC]). Studies suggest that the diabetic heart is resistant to cardioprotective strategies, although clinical evidence is lacking. We overview the available animal models of diabetes, investigating acute myocardial IRI and cardioprotection, experiments investigating the effects of hyperglycaemia on susceptibility to acute myocardial IRI, the response of the diabetic heart to cardioprotective strategies e.g. IPC, IPost and RIC. Finally we highlight the effects of anti-hyperglycaemic agents on susceptibility to acute myocardial IRI and cardioprotection. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Bioinformatic Reconstruction and Analysis of Gene Networks Related to Glucose Variability in Diabetes and Its Complications

Glucose variability (GV) has been recognized recently as a promoter of complications and therapeutic targets in diabetes. The aim of this study was to reconstruct and analyze gene networks related to GV in diabetes and its complications. For network analysis, we used the ANDSystem that provides automatic network reconstruction and analysis based on text mining. The network of GV consisted of 37 genes/proteins associated with both hyperglycemia and hypoglycemia. Cardiovascular system, pancreas, adipose and muscle tissues, gastrointestinal tract, and kidney were recognized as the loci with the highest expression of GV-related genes. According to Gene Ontology enrichment analysis, these genes are associated with insulin secretion, glucose metabolism, glycogen biosynthesis, gluconeogenesis, MAPK and JAK-STAT cascades, protein kinase B signaling, cell proliferation, nitric oxide biosynthesis, etc. GV-related genes were found to occupy central positions in the networks of diabetes complications (cardiovascular disease, diabetic nephropathy, retinopathy, and neuropathy) and were associated with response to hypoxia. Gene prioritization analysis identified new gene candidates (THBS1, FN1, HSP90AA1, EGFR, MAPK1, STAT3, TP53, EGF, GSK3B, and PTEN) potentially involved in GV. The results expand the understanding of the molecular mechanisms of the GV phenomenon in diabetes and provide molecular markers and therapeutic targets for future research.

Potential Risk of Hypoglycemia in Patients with Heart Failure

The properties of glucose changes in patients with chronic heart failure remain elusive. In the present study, we investigated the sequential changes of interstitial glucose concentrations in patients with chronic heart failure and heart disease who were not undergoing antidiabetic therapy.A glucose monitoring device (FreeStyle Libre Pro) was attached to the backside of an upper arm and the interstitial glucose concentration was monitored every 15 minutes for 1 week. Eleven patients with chronic heart failure (Heart failure (+) ) and 7 patients with chronic heart diseases but not with heart failure (Heart failure (-) ) were enrolled. The average level and peak value of interstitial glucose concentrations, and the duration of hyperglycemia (≥ 140 mg/dL) were not significantly different between Heart failure (+) and Heart failure (-). The duration of hypoglycemia (< 80 mg/dL) was significantly longer and the trough value was significantly lower in Heart failure (+) compared with Heart failure (-). Most of the patients in Heart failure (+) were exposed to a long duration of hypoglycemia from midnight to morning. Importantly, none of the patients who showed hypoglycemia complained of any subjective symptoms during hypoglycemia. Malabsorption may be one of the mechanisms of hypoglycemia.In summary, patients with chronic heart failure are at risk of developing hypoglycemia even if they do not undergo any antidiabetic therapy.

Cardiac miRNA Expression and their mRNA Targets in a Rat Model of Prediabetes

Little is known about the mechanism of prediabetes-induced cardiac dysfunction. Therefore, we aimed to explore key molecular changes with transcriptomic and bioinformatics approaches in a prediabetes model showing heart failure with preserved ejection fraction phenotype. To induce prediabetes, Long-Evans rats were fed a high-fat diet for 21 weeks and treated with a single low-dose streptozotocin at week 4. Small RNA-sequencing, in silico microRNA (miRNA)-mRNA target prediction, Gene Ontology analysis, and target validation with qRT-PCR were performed in left ventricle samples. From the miRBase-annotated 752 mature miRNA sequences expression of 356 miRNAs was detectable. We identified two upregulated and three downregulated miRNAs in the prediabetic group. We predicted 445 mRNA targets of the five differentially expressed miRNAs and selected 11 mRNAs targeted by three differentially expressed miRNAs, out of which five mRNAs were selected for validation. Out of these five targets, downregulation of three mRNAs i.e., Juxtaposed with another zinc finger protein 1 (Jazf1); RAP2C, member of RAS oncogene family (Rap2c); and Zinc finger with KRAB and SCAN domains 1 (Zkscan1) were validated. This is the first demonstration that prediabetes alters cardiac miRNA expression profile. Predicted targets of differentially expressed miRNAs include Jazf1, Zkscan1, and Rap2c mRNAs. These transcriptomic changes may contribute to the diastolic dysfunction and may serve as drug targets.

Hyponatraemia aggravates cardiac susceptibility to ischaemia/reperfusion injury

Hyponatraemia is defined as a serum sodium concentration of <135 mEql/L and is the most common electrolyte disturbance in patients with chronic heart failure. We hypothesize that hyponatraemia may induce Ca²⁺ overload and enhance reactive oxygen species (ROS) production, which will exacerbate myocardial injury more than normonatraemia. We investigated the effect of hyponatraemia on the ability of the heart to recover from ischaemia/reperfusion episodes. Cardiomyocytes were obtained from 1- to 3-day-old Sprague Dawley rats. After isolation, cardiomyocytes were placed in Dulbecco's modified Eagle's medium (DMEM) containing low sodium concentration (110, 120, or 130 mEq/L) or normal sodium concentration (140 mEq/L) for 72 hours. Exposure of cardiomyocytes to each of the low-sodium medium significantly increased both ROS and intracellular Ca²⁺ levels compared with the exposure to the normal-sodium medium. In vivo, 8-week-old male Sprague Dawley rats were divided into four groups: control group (Con), furosemide group (Fur), low-sodium diet group (Lsd) and both furosemide and low-sodium diet group (Fur + Lsd). The hearts subjected to global ischaemia exhibited considerable decrease in left ventricular developed pressure during reperfusion, and the size of infarcts induced by ischaemia/reperfusion significantly increased in the Fur, Lsd and Fur + Lsd compared with that in the Con. Hyponatraemia aggravates cardiac susceptibility to ischaemia/reperfusion injury by Ca²⁺ overload and increasing in ROS levels.

Overexpression of miR‑200a‑3p promoted inflammation in sepsis‑induced brain injury through ROS‑induced NLRP3

Sepsis, a systemic inflammatory response syndrome induced by infection, is a common complication of trauma, burns, postoperative infection and critical disease, and is characterized by an acute onset and high fatality rate. The aim of the present study was to explore the possible molecular mechanisms of microRNA-200a-3p (miRNA-200a-3p) on inflammation during sepsis. Reverse transcription-quantitative PCR and gene microarray were used to measure the expression of miRNA-200a-3p. Tumor necrosis factor-α, interleukin (IL)-1β, IL-6 and IL-18 were searched by ELISA. The related proteins expression was measured using western blotting. The expression of miRNA-200a-3p was markedly higher in the sepsis model when compared with the normal control group. In addition, the expression of miRNA-200a-3p was upregulated by the miRNA-200a-3p plasmid in human brain microvascular endothelial cells treated with lipopolysaccharide, which further induced inflammation via the induction of NLR family pyrin domain containing 3 (NLRP3) and suppression of Kelch like ECH associated protein (Keap)-1/nuclear factor erythroid 2 like 2 (Nrf2)/heme oxygenase (HO)-1. The inhibition of Keap1/Nrf2/HO-1 attenuated the effects of anti-miRNA-200a-3p on inflammation. However, the inhibition of NLRP3 attenuated the effects of miRNA-200a-3p on inflammation. In conclusion, to the best of our knowledge, the results of the present study demonstrated for the first time that overexpression of miRNA-200a-3p promoted inflammation in sepsis-induced brain injury through reactive oxygen species-induced NLRP3.

Functional Screening Identifies MicroRNAs as Multi-Cellular Regulators of Heart Failure

Heart failure (HF) is the leading cause of death in the Western world. Pathophysiological processes underlying HF development, including cardiac hypertrophy, fibrosis and inflammation, are controlled by specific microRNAs (miRNAs). Whereas most studies investigate miRNA function in one particular cardiac cell type, their multicellular function is poorly investigated. The present study probed 194 miRNAs –differentially expressed in cardiac inflammatory disease – for regulating cardiomyocyte size, cardiac fibroblasts collagen content, and macrophage polarization. Of the tested miRNAs, 13%, 26%, and 41% modulated cardiomyocyte size, fibroblast collagen production, and macrophage polarization, respectively. Seventeen miRNAs affected all three cellular processes, including miRNAs with established (miR-210) and unknown roles in cardiac pathophysiology (miR-145-3p). These miRNAs with a multi-cellular function commonly target various genes. In-depth analysis in vitro of previously unstudied miRNAs revealed that the observed phenotypical alterations concurred with changes in transcript and protein levels of hypertrophy-, fibrosis- and inflammation-related genes. MiR-145-3p and miR-891a-3p were identified to regulate the fibrotic response, whereas miR-223-3p, miR-486-3p, and miR-488-5p modulated macrophage activation and polarisation. In conclusion, miRNAs are multi-cellular regulators of different cellular processes underlying cardiac disease. We identified previously undescribed roles of miRNAs in hypertrophy, fibrosis, and inflammation, and attribute new cellular effects to various well-known miRNAs.

MicroRNAs as Potential Pharmaco-targets in Ischemia-Reperfusion Injury Compounded by Diabetes

BACKGROUND

Ischemia-Reperfusion (I/R) injury is the tissue damage that results from re-oxygenation of ischemic tissues. There are many players that contribute to I/R injury. One of these factors is the family of microRNAs (miRNAs), which are currently being heavily studied. This review aims to critically summarize the latest papers that attributed roles of certain miRNAs in I/R injury, particularly in diabetic conditions and dissect their potential as novel pharmacologic targets in the treatment and management of diabetes.

METHODS

PubMed was searched for publications containing microRNA and I/R, in the absence or presence of diabetes. All papers that provided sufficient evidence linking miRNA with I/R, especially in the context of diabetes, were selected. Several miRNAs are found to be either pro-apoptotic, as in the case of miR-34a, miR-144, miR-155, and miR-200, or anti-apoptotic, as in the case of miR-210, miR-21, and miR-146a. Here, we further dissect the evidence that shows diverse cell-context dependent effects of these miRNAs, particularly in cardiomyocytes, endothelial, or leukocytes. We also provide insight into cases where the possibility of having two miRNAs working together to intensify a given response is noted.

CONCLUSIONS

This review arrives at the conclusion that the utilization of miRNAs as translational agents or pharmaco-targets in treating I/R injury in diabetic patients is promising and becoming increasingly clearer.

Down-regulation of miR-200c attenuates AngII-induced cardiac hypertrophy via targeting the MLCK-mediated pathway

Background

MicroRNAs (miRNAs) have been shown to commonly contribute to cardiac hypertrophy (CH). The aim of this study was to test the hypothesis that miR‐200c plays an important role in the progression of CH by targeting myosin light chain kinase (MLCK/MYLK).

Methods and results

Cardiac hypertrophy was induced by aortic banding (AB) in rats. Cellular hypertrophy in neonatal rat cardiomyocytes (NCMs) was induced by AngII treatment. Echocardiography, histology and molecular measurements were used to assess the results of the experiments. The levels of apoptosis and reactive oxygen species (ROS) were also measured. Quantitative real‐time PCR (qRT‐PCR) and Western blotting were used to measure mRNA and protein levels respectively. The present results showed that miR‐200c expression was increased in response to CH both in vivo and in vitro. The down‐regulation of miRNA‐200c by a specific inhibitor markedly ameliorated CH resulting from AngII treatment, and the mRNA levels of atrial natriuretic peptide, brain natriuretic peptide and β‐myosin heavy chain were simultaneously decreased. Notably, minimal apoptosis and ROS accumulation were identified in AngII‐induced hypertrophic cardiomyocytes. Conversely, the up‐regulation of miR‐200c using specific mimics reversed these effects. Mechanistic investigations demonstrated that the MLCK gene is a direct target of miR‐200c; an increase in miR‐200c levels led to a decrease in the expression of MLCK and its downstream effector, p‐MLC2, while miR‐200c inhibition increased the expression of these proteins. Furthermore, inhibiting MLCK impaired the anti‐hypertrophic effects contributions produced by the knockdown of miR‐200c.

Conclusion

Our studies suggest that miR‐200c may serve as a potential therapeutic target that could delay hypertrophy. We have also uncovered a relationship between miR‐200c and MLCK, identifying MLCK as a direct mediator of miR‐200c.

Molecular Mechanisms of Glucose Fluctuations on Diabetic Complications

Accumulating evidence indicates the occurrence and development of diabetic complications relates to not only constant high plasma glucose, but also glucose fluctuations which affect various kinds of molecular mechanisms in various target cells and tissues. In this review, we detail reactive oxygen species and their potentially damaging effects upon glucose fluctuations and resultant downstream regulation of protein signaling pathways, including protein kinase C, protein kinase B, nuclear factor-κB, and the mitogen-activated protein kinase signaling pathway. A deeper understanding of glucose-fluctuation-related molecular mechanisms in the development of diabetic complications may enable more potential target therapies in future.

Redox Regulation and Noncoding RNAs

SIGNIFICANCE

RNA is a heterogeneous class of molecules with the minority being protein coding. Noncoding RNAs (ncRNAs) are involved in translation and epigenetic control mechanisms of gene expression. Recent Advances: In recent years, the number of identified ncRNAs has dramatically increased and it is now clear that ncRNAs provide a complex layer of differential gene expression control.

CRITICAL ISSUES

NcRNAs exhibit interplay with redox regulation. Redox regulation alters the expression of ncRNAs; conversely, ncRNAs alter the expression of generator and effector systems of redox regulation in a complex manner, which will be the focus of this review article.

FUTURE DIRECTIONS

Understanding the role of ncRNA in redox control will lead to the development of new strategies to alter redox programs. Given that many ncRNAs (particularly microRNAs [miRNAs]) change large gene sets, these molecules are attractive drug candidates; already, now miRNAs can be targeted in patients. Therefore, the development of ncRNA therapies focusing on these molecules is an attractive future strategy. Antioxid. Redox Signal. 29, 793-812.

Impact of glycemic variability on myocardial infarct size in patients with ST-segment elevation myocardial infarction: quantitative assessment of left ventricular wall motion severity

Glycemic variability (GV) is relevant to impaired myocardial salvage in acute ST-elevation myocardial infarction (STEMI). Severity of hypokinesis at the infarct site as assessed from contrast left ventriculography can reportedly predict infarct size in STEMI. We prospectively studied 58 consecutive patients (mean age, 63 ± 11 years) with anterior or inferior STEMI who underwent successful reperfusion therapy. Mean amplitude of glucose excursion (MAGE) was obtained from continuous glucose monitoring system. Patients were divided into the upper tertile of MAGE as Group H, and the other two-thirds as Group L. Serial regional wall motion severity at the infarct site was computed postprocedure and at follow-up using a quantitative left ventricular analysis system. Impaired myocardial salvage was defined as severity recovery ratio < 20%. Significantly shorter onset-to-balloon time (196.9 vs. 279.0 min, p = 0.033) and relatively lower postprocedural wall motion severity (2.4 vs. 2.9, p = 0.096) were observed in Group H, but absolute severity recovery was significantly smaller in Group H (0.5 vs. 1.3, p = 0.017). Multivariate analysis showed higher MAGE as predictive of impaired myocardial salvage (OR, 406.10; 95% CI, 4.41-37,366.60; p = 0.009). Recovery of reginal wall motion severity at the infarct site was compromised in STEMI patients with higher MAGE. Our results suggest that final infarct size is potentially larger than expected in STEMI patients with higher GV.

Dioscin protects against coronary heart disease by reducing oxidative stress and inflammation via Sirt1/Nrf2 and p38 MAPK pathways

Cardiovascular diseases are common diseases in Sweden as in most countries. In 2016, 25,700 persons suffered from coronary heart disease (CHD) and 25% of these died within 28 days. The present study investigated whether dioscin may exert protective effects against CHD‑induced heart apoptosis, oxidative stress and inflammation in a pig model and the potential underlying mechanisms. Adult pigs were used to establish a CHD model group and 80 mg/kg dioscin was administered for 4 weeks. Histological analysis and measurement of serum levels of heart injury markers demonstrated that 80 mg/kg dioscin markedly alleviated CHD, while left ventricular ejection fraction and left ventricular systolic internal diameter measurements indicated that 80 mg/kg dioscin also increased heart function in the CHD pig model. Furthermore, western blotting demonstrated that 80 mg/kg dioscin significantly reduced protein levels of apoptosis markers in the heart of CHD model pigs, including Bcl‑2‑associated X and caspase‑3, potentially via the suppression of poly (ADP‑ribose) polymerase 1 (PARP)/p53 expression. Additionally, the results of ELISA and western blotting demonstrated that 80 mg/kg dioscin may reduce oxidative stress and inflammation in CHD model pigs through the promotion of sirtuin 1 (Sirt1)/nuclear factor erythroid 2‑related factor 2 (Nrf2) protein expression and the suppression of PARP/p53 and p38 mitogen‑activated protein kinase (MAPK) expression. The results of the current study indicate that dioscin may protect against CHD by regulating oxidative stress and inflammation via Sirt1/Nrf2 and p38 MAPK pathways.

Function of microRNA‑141 in human breast cancer through cytotoxic CD4+ T cells regulated by MAP4K4 expression

The present study investigated the anti‑cancer effect of microRNA (miRNA)‑141 on apoptosis rate of breast cancer cells and the possible underlying mechanism. In patients with breast cancer, the expression of miRNA‑141 was downregulated. Overexpression of miRNA‑141 reduced breast cancer cell growth, inhibited the expression of cyclooxygenase‑2 (COX‑2), prostaglandin E2 (PGE2) and tumor necrosis factor (TNF)‑α, and increased the expression levels of interleukin (IL)‑10. However, downregulation of miRNA‑141 resulted in upregulation of COX‑2, PGE2 and TNF‑α expression levels, and an inhibition of IL‑10. Overexpression of miRNA‑141 suppressed mitogen‑activated protein kinase kinase kinase kinase 4 (MAP4K4) protein expression. Downregulation of miRNA‑141 markedly upregulated MAP4K4 protein expression in MCF‑7 cells. Promotion of MAP4K4 protein expression reduced the effects of miRNA‑141 on the toxicity of CD4+ T cells on breast cancer cells. The results of the present study indicated that miRNA‑141 may cause anti‑tumor effects in human breast cancer cells via cytotoxic CD4+ T cells.

Effects of hypoglycemia on myocardial susceptibility to ischemia-reperfusion injury and preconditioning in hearts from rats with and without type 2 diabetes

BACKGROUND

Hypoglycemia is associated with increased mortality rate in patients with diabetes. The underlying mechanisms may involve reduced myocardial tolerance to ischemia and reperfusion (IR) or reduced capacity for ischemic preconditioning (IPC). As IPC is associated with increased myocardial glucose uptake (MGU) during reperfusion, cardioprotection is linked to glucose metabolism possibly by O-linked β-N-acetylglucosamine (O-GlcNAc). We aimed to investigate the impact of hypoglycemia in hearts from animals with diabetes on myocardial IR tolerance, on the efficacy of IPC and whether modulations of MGU and O-GlcNAc levels are involved in the underlying mechanisms.

METHODS

In a Langendorff model using diabetic ZDF (fa/fa) and non-diabetic (fa/+) rats (n = 6-7 in each group) infarct size (IS) was evaluated after 40 min of global ischemia and 120 min reperfusion during hypoglycemia [(glucose) = 3 mmol/l] and normoglycemia [(glucose) = 11 mmol/l]. Myocardial glucose uptake and O-GlcNAc levels were evaluated during reperfusion. IPC was induced by 2 × 5 min of global ischemia prior to index ischemia.

RESULTS

IS increased in hearts from animals with (p < 0.01) and without (p < 0.01) diabetes during hypoglycemia compared to normoglycemia. IPC reduced IS during normoglycemia in both animals with (p < 0.01) and without (p < 0.01) diabetes. During hypoglycemia, however, IPC only reduced IS in hearts from animals with diabetes (p < 0.05). IPC increased MGU during reperfusion and O-GlcNAc levels in animals with diabetes during hypo- (MGU: p < 0.05, O-GlcNAc: p < 0.05) and normoglycemia (MGU: p < 0.01, O-GlcNAc: p < 0.05) and in animals without diabetes only during normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01).

CONCLUSIONS

Hypoglycemia increases myocardial susceptibility to IR injury in hearts from animals with and without diabetes. In contrast to hearts from animals without diabetes, the hearts from animals with diabetes are amenable to cardioprotection during hypoglycemia. In parallel with IPC induced cardioprotection, MGU and O-GlcNAc levels increase suggesting that increased MGU and O-GlcNAc levels are involved in the mechanisms of IPC.

Regulating microRNA expression: at the heart of diabetes mellitus and the mitochondrion

Type 2 diabetes mellitus is a major risk factor for cardiovascular disease and mortality. Uncontrolled type 2 diabetes mellitus results in a systemic milieu of increased circulating glucose and fatty acids. The development of insulin resistance in cardiac tissue decreases cellular glucose import and enhances mitochondrial fatty acid uptake. While triacylglycerol and cytotoxic lipid species begin to accumulate in the cardiomyocyte, the energy substrate utilization ratio of free fatty acids to glucose changes to almost entirely free fatty acids. Accumulating evidence suggests a role of miRNA in mediating this metabolic transition. Energy substrate metabolism, apoptosis, and the production and response to excess reactive oxygen species are regulated by miRNA expression. The current momentum for understanding the dynamics of miRNA expression is limited by a lack of understanding of how miRNA expression is controlled. While miRNAs are important regulators in both normal and pathological states, an additional layer of complexity is added when regulation of miRNA regulators is considered. miRNA expression is known to be regulated through a number of mechanisms, which include, but are not limited to, epigenetics, exosomal transport, processing, and posttranscriptional sequestration. The purpose of this review is to outline how mitochondrial processes are regulated by miRNAs in the diabetic heart. Furthermore, we will highlight the regulatory mechanisms, such as epigenetics, exosomal transport, miRNA processing, and posttranslational sequestration, that participate as regulators of miRNA expression. Additionally, current and future treatment strategies targeting dysfunctional mitochondrial processes in the diseased myocardium, as well as emerging miRNA-based therapies, will be summarized.

GYY4137, a Hydrogen Sulfide Donor Modulates miR194-Dependent Collagen Realignment in Diabetic Kidney

The relationship between hydrogen sulfide (H₂S), microRNAs (miRs), matrix metalloproteinases (MMPs) and poly-ADP-ribose-polymerase-1 (PARP-1) in diabetic kidney remodeling remains mostly obscured. We aimed at investigating whether alteration of miR-194-dependent MMPs and PARP-1 causes renal fibrosis in diabetes kidney, and whether H₂S ameliorates fibrosis. Wild type, diabetic Akita mice as well as mouse glomerular endothelial cells (MGECs) were used as experimental models, and GYY4137 as H₂S donor. In diabetic mice, plasma H₂S levels were decreased while ROS and expression of its modulator (ROMO1) were increased. In addition, alteration of MMPs-9, −13 and −14 expression, PARP-1, HIF1α, and increased collagen biosynthesis as well as collagen cross-linking protein, P4HA1 and PLOD2 were observed along with diminished vascular density in diabetic kidney. These changes were ameliorated by GYY4137. Further, downregulated miRNA-194 was normalized by GYY4137 in diabetic kidney. Similar results were obtained in in vitro condition. Interestingly, miR-194 mimic also diminished ROS production, and normalized ROMO1, MMPs-9, −13 and −14, and PARP-1 along with collagen biosynthesis and cross-linking protein in HG condition. We conclude that decrease H₂S diminishes miR-194, induces collagen deposition and realignment leading to fibrosis and renovascular constriction in diabetes. GYY4137 mitigates renal fibrosis in diabetes through miR-194-dependent pathway.

Relationship Between Glucose Fluctuations and ST-Segment Resolution in Patients With ST-Elevation Acute Myocardial Infarction

This study was conducted to assess whether any relationships exist between glucose fluctuations and electrocardiographic surrogate markers of reperfusion injury in patients with ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PCI).We prospectively studied 63 consecutive patients with STEMI undergoing primary PCI. Patients had either diabetes (n = 30), impaired glucose tolerance (n = 26), impaired fasting glucose (n = 1), or normal glucose tolerance (n = 6). STsegment resolution (STR, %) was measured using electrocardiograms recorded 60 minutes after PCI. STR was categorized as ≥ 30% and < 30%. Glucose fluctuations were assessed by the following parameters obtained from a continuous glucose monitoring system: mean amplitude of glucose excursion (MAGE, mg/dL); and area under curve with reference to mean blood glucose (AUC_MBG, mg/ dL/day).Both MAGE and AUC_MBG were significantly higher in STR < 30%. In univariate analysis, MAGE ≥ 70 mg/dL (OR = 17.0; 95%CI, 1.93-150.12; P < 0.01), AUC_MBG ≥ 20 mg/dL/day (OR = 10.9; 95%CI, 1.92-61.77; P < 0.01), and reperfusion arrhythmias (OR = 7.6; 95%CI, 1.32-44.29; P < 0.05) were significantly associated with suboptimal STR. Multiple logistic regression analysis showed only MAGE ≥ 70 mg/dL was predictive of suboptimal STR (OR = 22.5; 95%CI, 2.43-208.66, P < 0.01).Parameters of glucose fluctuations correlated with electrocardiographic surrogate markers of impaired myocardial salvage in STEMI after reperfusion therapy. Our results suggest that glucose fluctuations may represent a potential therapeutic target to reduce myocardial reperfusion injury in STEMI.

miRNAs: Nanomachines That Micromanage the Pathophysiology of Diabetes Mellitus

Diabetes mellitus (DM) refers to a combination of heterogeneous complex metabolic disorders that are associated with episodes of hyperglycemia and glucose intolerance occurring as a result of defects in insulin secretion, action, or both. The prevalence of DM is increasing at an alarming rate, and there exists a need to develop better therapeutics and prognostic markers for earlier detection and diagnosis. In this review, after giving a brief introduction of diabetes mellitus and microRNA (miRNA) biogenesis pathway, we first describe various in vitro and animal model systems that have been developed to study diabetes. Further, we elaborate on the significant roles played by miRNAs as regulators of gene expression in the context of development of diabetes and its secondary complications. The different approaches to quantify miRNAs and their potential to be used as therapeutic targets for alleviation of diabetes have also been discussed.

Specific MicroRNAs comparisons in hypoxia and morphine preconditioning against hypoxia-reoxgenation injury with and without heart failure

AIMS

Ischemia reperfusion (I/R) injury is an inevitable event arising during the cardiovascular diseases development and the process of potent surgical treatments. microRNAs (miRNAs) are critical regulators of multiple cell processes including I/R injury. The present study aims to quantify miRNA alterations and regulated genes upon hypoxia-reoxygenation (H/R) injury in a rat heart failure model comparing with normal cardiomyocytes.

MAIN METHODS

Chronic heart failure was established by injecting doxorubicin (2mg/kg/week) for 6weeks, then H/R was performed on primary cultured cardiomyocytes isolated from normal and failed heart. Cellular injury was evaluated by detecting LDH release levels, cell variability and apoptotic rate. Dysregulated miRNAs in control, hypoxia preconditioning (HPC) and morphine preconditioning (MPC) groups under two conditions were quantified by microarray analysis. Fas protein expression was analyzed using Western Blotting analysis.

KEY FINDINGS

Chronic heart failure was confirmed with lower ejection fraction (EF), and significant cellular injury. HPC could reverse the injury induced by H/R in normal heart rather than failed heart, otherwise, MPC significantly attenuated cellular injury dose dependently in both conditions. There was 12 miRNAs significantly altered after doxorubicin injection, 7 downregulated and 5 upregulated. miR-133b-5p, miR-6216, miR-664-1-5p and let7e-5p were differentially expressed after HPC and MPC treatments. The direct interaction between miR-133b-5p and target gene Fas were established. The Fas protein expression was manipulated by MPC not HPC affording protective effect against H/R injury.

SIGNIFICANCE

We investigated that miR-133b-5p might play a particularly important role in the cardioprotective effect of MPC by regulating the target gene Fas.

miR-1273g-3p participates in acute glucose fluctuation-induced autophagy, dysfunction, and proliferation attenuation in human umbilical vein endothelial cells

Acute glucose fluctuations (AGF) often cause high mortality among critically ill patients, but the mechanisms induced by AGF are not clear. Recent studies suggest that endothelial dysfunction is a key factor that leads to high mortality among critically ill patients. Our goal is to evaluate the phenomenon and mechanisms of endothelial dysfunction induced by AGF. In this study, the functions of human umbilical vein endothelial cells (HUVECs) were compared after treatment with sustained high glucose (SHG), AGF in two groups (AGF1 fluctuations between 5 and 16 mM and AGF2 fluctuations between 5 and 25 mM), and normal glucose levels as a control group (CTR). The medium of the groups was changed every 4 h. The influence of AGF on wound healing was also tested on C57BL/6 mice. The results show that cell proliferation, angiogenesis, and migration functions were injured in the SHG and both AGF groups. AGF2 group shows the worse condition in vitro. In vivo, the wound healing was delayed after the AGF treatment. Furthermore, the markers of apoptosis and autophagy were analyzed. We observed that the autophagy changed in all treatment groups, but apoptosis showed no change. To get to know the mechanism of dysfunction and autophagy, we performed the microRNA chip assay and real-time PCR and found miR-1273g-3p remarkably changed in AGF2 group. After the mimic and inhibitor of miR-1273g-3p were transfected during the AGF2 treatment, we found that the dysfunction and autophagy were partially enhanced by miR-1273g-3p mimic and reversed by miR-1273g-3p inhibitor in AGF2 group. Thus, we conclude that AGF can induce more dysfunction and autophagy, and miR-1273g-3p is also an important factor that leads to the injury.