Inhibition of MEF2A prevents hyperglycemia-induced extracellular matrix accumulation by blocking Akt and TGF-β1/Smad activation in cardiac fibroblasts

Effect of strontium on transcription factors identified by transcriptome analyses of bovine ruminal epithelial cells

BACKGROUND

Strontium (Sr) has similar physicochemical properties as calcium (Ca) and is often used to evaluate the absorption of this mineral. Because the major route of Ca absorption in the bovine occurs in the rumen, it is essential to understand whether Sr impacts the ruminal epithelial cells and to what extent.

RESULTS

In the present study, RNA sequencing and assembled transcriptome assembly were used to identify transcription factors (TFs), screening and bioinformatics analysis in bovine ruminal epithelial cells treated with Sr. A total of 1405 TFs were identified and classified into 64 families based on an alignment of conserved domains. A total of 174 differently expressed TFs (DE-TFs) were increased and 52 DE-TFs were decreased; the biological process-epithelial cell differentiation was inhibited according to the GSEA-GO analysis of TFs; The GO analysis of DE-TFs was enriched in the DNA binding. Protein-protein interaction network (PPI) found 12 hubs, including SMAD4, SMAD2, SMAD3, SP1, GATA2, NR3C1, PPARG, FOXO1, MEF2A, NCOA2, LEF1, and ETS1, which verified genes expression levels by real-time PCR.

CONCLUSIONS

In this study, SMAD2, PPARG, LEF1, ETS1, GATA2, MEF2A, and NCOA2 are potential candidates that could be targeted by Sr to mediate cell proliferation and differentiation, as well as lipid metabolism. Hence, these results enhance the comprehension of Sr in the regulation of transcription factors and provide new insight into the study of Sr biological function in ruminant animals.

Calorie restriction modulates the transcription of genes related to stress response and longevity in human muscle: The CALERIE study

The lifespan extension induced by 40% caloric restriction (CR) in rodents is accompanied by postponement of disease, preservation of function, and increased stress resistance. Whether CR elicits the same physiological and molecular responses in humans remains mostly unexplored. In the CALERIE study, 12% CR for 2 years in healthy humans induced minor losses of muscle mass (leg lean mass) without changes of muscle strength, but mechanisms for muscle quality preservation remained unclear. We performed high-depth RNA-Seq (387-618 million paired reads) on human vastus lateralis muscle biopsies collected from the CALERIE participants at baseline, 12- and 24-month follow-up from the 90 CALERIE participants randomized to CR and "ad libitum" control. Using linear mixed effect model, we identified protein-coding genes and splicing variants whose expression was significantly changed in the CR group compared to controls, including genes related to proteostasis, circadian rhythm regulation, DNA repair, mitochondrial biogenesis, mRNA processing/splicing, FOXO3 metabolism, apoptosis, and inflammation. Changes in some of these biological pathways mediated part of the positive effect of CR on muscle quality. Differentially expressed splicing variants were associated with change in pathways shown to be affected by CR in model organisms. Two years of sustained CR in humans positively affected skeletal muscle quality, and impacted gene expression and splicing profiles of biological pathways affected by CR in model organisms, suggesting that attainable levels of CR in a lifestyle intervention can benefit muscle health in humans.

Transcriptome Profiling Based at Different Time Points after Hatching Deepened Our Understanding on Larval Growth and Development of Amphioctopus fangsiao

As the quality of life improves, there is an increasing demand for nutrition-rich marine organisms like fish, shellfish, and cephalopods. To address this, artificial cultivation of these organisms is being explored along with ongoing research on their growth and development. A case in point is Amphioctopus fangsiao, a highly valued cephalopod known for its tasty meat, nutrient richness, and rapid growth rate. Despite its significance, there is a dearth of studies on the A. fangsiao growth mechanism, particularly of its larvae. In this study, we collected A. fangsiao larvae at 0, 4, 12, and 24 h post-hatching and conducted transcriptome profiling. Our analysis identified 4467, 5099, and 4181 differentially expressed genes (DEGs) at respective intervals, compared to the 0 h sample. We further analyzed the expression trends of these DEGs, noting a predominant trend of continuous upregulation. Functional exploration of this trend entailed GO and KEGG functional enrichment along with protein-protein interaction network analyses. We identified GLDC, DUSP14, DPF2, GNAI1, and ZNF271 as core genes, based on their high upregulation rate, implicated in larval growth and development. Similarly, CLTC, MEF2A, PPP1CB, PPP1R12A, and TJP1, marked by high protein interaction numbers, were identified as hub genes and the gene expression levels identified via RNA-seq analysis were validated through qRT-PCR. By analyzing the functions of key and core genes, we found that the ability of A. fangsiao larvae to metabolize carbohydrates, lipids, and other energy substances during early growth may significantly improve with the growth of the larvae. At the same time, muscle related cells in A. fangsiao larvae may develop rapidly, promoting the growth and development of larvae. Our findings provide preliminary insights into the growth and developmental mechanism of A. fangsiao, setting the stage for more comprehensive understanding and broader research into cephalopod growth and development mechanisms.

Single-Dose Treatment with Rapamycin Preserves Post-Ischemic Cardiac Function through Attenuation of Fibrosis and Inflammation in Diabetic Rabbit

Robust activation of mTOR (mammalian target of rapamycin) signaling in diabetes exacerbates myocardial injury following lethal ischemia due to accelerated cardiomyocyte death with cardiac remodeling and inflammatory responses. We examined the effect of rapamycin (RAPA, mTOR inhibitor) on cardiac remodeling and inflammation following myocardial ischemia/reperfusion (I/R) injury in diabetic rabbits. Diabetic rabbits (DM) were subjected to 45 min of ischemia and 10 days of reperfusion by inflating/deflating a previously implanted hydraulic balloon occluder. RAPA (0.25 mg/kg, i.v.) or DMSO (vehicle) was infused 5 min before the onset of reperfusion. Post-I/R left ventricular (LV) function was assessed by echocardiography and fibrosis was evaluated by picrosirius red staining. Treatment with RAPA preserved LV ejection fraction and reduced fibrosis. Immunoblot and real-time PCR revealed that RAPA treatment inhibited several fibrosis markers (TGF-β, Galectin-3, MYH, p-SMAD). Furthermore, immunofluorescence staining revealed the attenuation of post-I/R NLRP3-inflammasome formation with RAPA treatment as shown by reduced aggregation of apoptosis speck-like protein with a caspase recruitment domain and active-form of caspase-1 in cardiomyocytes. In conclusion, our study suggests that acute reperfusion therapy with RAPA may be a viable strategy to preserve cardiac function with the alleviation of adverse post-infarct myocardial remodeling and inflammation in diabetic patients.

Unveiling the Vital Role of Long Non-Coding RNAs in Cardiac Oxidative Stress, Cell Death, and Fibrosis in Diabetic Cardiomyopathy

Diabetes mellitus is a burdensome public health problem. Diabetic cardiomyopathy (DCM) is a major cause of mortality and morbidity in diabetes patients. The pathogenesis of DCM is multifactorial and involves metabolic abnormalities, the accumulation of advanced glycation end products, myocardial cell death, oxidative stress, inflammation, microangiopathy, and cardiac fibrosis. Evidence suggests that various types of cardiomyocyte death act simultaneously as terminal pathways in DCM. Long non-coding RNAs (lncRNAs) are a class of RNA transcripts with lengths greater than 200 nucleotides and no apparent coding potential. Emerging studies have shown the critical role of lncRNAs in the pathogenesis of DCM, along with the development of molecular biology technologies. Therefore, we summarize specific lncRNAs that mainly regulate multiple modes of cardiomyopathy death, oxidative stress, and cardiac fibrosis and provide valuable insights into diagnostic and therapeutic biomarkers and strategies for DCM.

Myostatin deficiency decreases cardiac extracellular matrix in pigs

Myostatin (MSTN), a member of the TGF-β superfamily, negatively regulates muscle growth. MSTN inhibition has been known to cause a double-muscled phenotype in skeletal muscle and fibrosis reduction in the heart. However, the role of MSTN in the cardiac extracellular matrix (ECM) needs more studies in various species of animal models to draw more objective conclusions. The main objective of the present study was to investigate whether loss of MSTN affects the cardiac extracellular matrix in pigs. Three MSTN knockouts (MSTN-/-) and three wild type (WT) male pigs were generated by crossing MSTN ± heterozygous gilts and boars. Cardiac ECM and underlying mechanisms were determined post-mortem. The role of MSTN on collagen expression was investigated by treating cardiac fibroblasts with active MSTN protein in vitro. MSTN protein was detected in WT hearts, while no expression was detected in MSTN-/- hearts. The heart-to-body weight ratio was significantly decreased in MSTN-/- pigs. The morphometric analyses, including picrosirius red staining, immunofluorescent staining, and ultra-structural thickness examination of the endomysium, revealed a significant reduction of connective tissue content in MSTN-/- hearts compared to WT. Hydroxyproline, type I collagen (Col1A), and p-Smad3/Smad3 levels were significantly lower in MSTN-/- hearts in vivo. On the contrary, cardiac fibroblasts treated with exogenous MSTN protein overexpressed Col1A and activated Smad and AKT signaling pathways in vitro. The present study suggests that inhibition of MSTN decreases cardiac extracellular matrix.

Intrauterine hyperglycemia impairs endometrial receptivity via up-regulating SGK1 in diabetes

Diabetes is a complex metabolic disorder which can adversely affect reproductive function. SGK1 is found to be up-regulated in multiple tissues of diabetic patients. However, the effects of diabetes on endometrial SGK1 expression and endometrial receptivity remain unknown. In this study, we established a streptozotocin-induced diabetic mouse model and observed reduced implantation sites, retarded development of pinopodes, increased SGK1, and aberrant expression of LIF and MUC1 in the endometrial epithelium. We injected the uterine lumen of normal mice with high-glucose solution and cultured endometrial cells in high-glucose medium to mimic intrauterine hyperglycemia. Both studies provided compelling evidence that hyperglycemia could lead to diminished embryo implantation and dysregulated SGK1, LIF and MUC1. Additionally, through over-expression of SGK1 in vivo and in vitro, we found that enhanced SGK1 also decreased LIF expression, increased MUC1 expression, and attenuated embryo implantation rate. We further identified that hyperglycemia-activated SMAD2/3 might be responsible for the enhancement of SGK1 and verified directly the interaction between SMAD3 and corresponding SMAD binding elements within SGK1 promoter. Taken together, our study confirmed the association between diabetes-related hyperglycemia and endometrial receptivity defects. Hyperglycemia-induced SGK1 has a tremendous role in this pathological process, rendering it as an attractive therapeutic target for diabetes-related reproductive disorders.

Roflumilast-Mediated Phosphodiesterase 4D Inhibition Reverses Diabetes-Associated Cardiac Dysfunction and Remodeling: Effects Beyond Glucose Lowering

Patients with type 2 diabetes have a substantial risk of developing cardiovascular disease. Phosphodiesterase 4 (PDE4) dysregulation is of pathophysiological importance in metabolic disorders. For determination of the role of PDE4 in diabetic cardiac dysfunction, mice fed with a high-fat diet (HFD) were treated by pharmacological inhibition of PDE4 or cardiac specific knocking down of PDE4D. Mice on HFD developed diabetes and cardiac dysfunction with increased cardiac PDE4D5 expression. PDE4 inhibitor roflumilast can reverse hyperglycemia and cardiac dysfunction, accompanied by the decrease of PDE4D expression and increase of muscle specific miRNA miR-1 level in hearts. Either cardiac specific PDE4D knockdown or miR-1 overexpression significantly reversed cardiac dysfunction in HFD mice, despite persistence of hyperglycemia. Findings of gain- and loss-of-function studies of PDE4D in cardiomyocytes indicated that inhibition of insulin-induced PDE4D protected cardiac hypertrophy by preserving miR-1 expression in cardiomyocytes through promoting cAMP-CREB-Sirt1 signaling-induced SERCA2a expression. We further revealed that insulin also induced PDE4D expression in cardiac fibroblasts, which causes cardiac fibrosis through TGF-β1 signaling-mediated miR-1 reduction. Importantly, the expression of PDE4D5 was increased in human failing hearts of individuals with diabetes. These studies elucidate a novel mechanism by which hyperinsulinemia-induced cardiac PDE4D expression contributes to diabetic cardiac remodeling through reducing the expression of miR-1 and upregulation of miR-1 target hypertrophy and fibrosis-associated genes. Our study suggests a therapeutic potential of PDE4 inhibitor roflumilast in preventing or treating cardiac dysfunction in diabetes in addition to lowering glucose.

Emerging Role of LncRNA Regulation for NLRP3 Inflammasome in Diabetes Complications

Diabetes is a widespread metabolic disease with various complications, including diabetic nephropathy, retinopathy, cardiomyopathy, and other cardiovascular or cerebrovascular diseases. As the prevalence of diabetes increases in all age groups worldwide, diabetes and its complications cause an emerging public health burden. NLRP3 inflammasome is a complex of several proteins that play a critical role in inflammatory response and various diseases, including diabetes and its complications. Accumulating evidences indicate that NLRP3 inflammasome contributes to the development of diabetes and diabetic complications and that NLRP3 inflammation inactivation is beneficial in treating these illnesses. Emerging evidences suggest the critical role of long non-coding RNAs (lncRNAs) in regulating NLRP3 inflammasome activity in various diseases. LncRNAs are non-coding RNAs exceeding 200 nucleotides in length. Its dysregulation has been linked to the development of diseases, including diabetes. Recently, growing evidences hint that regulating lncRNAs on NLRP3 inflammasome is critical in developing and progressing diabetes and diabetic complications. Here, we discuss the role of lncRNAs in regulating NLRP3 inflammasome as well as its participation in diabetes and diabetic complications, providing novel insights into developing future therapeutic approaches for diabetes.

Quercetin alleviates diastolic dysfunction and suppresses adverse pro-hypertrophic signaling in diabetic rats

INTRODUCTION

Quercetin (Que) is a potent anti-inflammatory and antioxidant flavonoid with cardioprotective potential. However, very little is known about the signaling pathways and gene regulatory proteins Que may interfere with, especially in diabetic cardiomyopathy. Therefore, we aimed to study the potential cardioprotective effects of Que on the cardiac phenotype of type 2 diabetes mellitus (T2DM) accompanied by obesity.

METHODS

For this experiment, we used Zucker Diabetic Fatty rats (fa/fa) and their age-matched lean controls (fa/+) that were treated with either vehicle or 20 mg/kg/day of Que for 6 weeks. Animals underwent echocardiographic (echo) examination before the first administration of Que and after 6 weeks.

RESULTS

After the initial echo examination, the diabetic rats showed increased E/A ratio, a marker of left ventricular (LV) diastolic dysfunction, in comparison to the control group which was selectively reversed by Que. Following the echo analysis, Que reduced LV wall thickness and exhibited an opposite effect on LV luminal area. In support of these results, the total collagen content measured by hydroxyproline assay was decreased in the LVs of diabetic rats treated with Que. The follow-up immunoblot analysis of proteins conveying cardiac remodeling pathways revealed that Que was able to interfere with cardiac pro-hypertrophic signaling. In fact, Que reduced relative protein expression of pro-hypertrophic transcriptional factor MEF2 and its counter-regulator HDAC4 along with pSer²⁴⁶-HDAC4. Furthermore, Que showed potency to decrease GATA4 transcription factor, NFAT3 and calcineurin, as well as upstream extracellular signal-regulated kinase Erk5 which orchestrates several pro-hypertrophic pathways.

DISCUSSION

In summary, we showed for the first time that Que ameliorated pro-hypertrophic signaling on the level of epigenetic regulation and targeted specific upstream pathways which provoked inhibition of pro-hypertrophic signals in ZDF rats. Moreover, Que mitigated T2DM and obesity-induced diastolic dysfunction, therefore, might represent an interesting target for future research on novel cardioprotective agents.

Fufang Xueshuantong Improves Diabetic Cardiomyopathy by Regulating the Wnt/β-Catenin Pathway

Diabetic cardiomyopathy (DCM) is one of the main complications of diabetic patients and the major reason for the high prevalence of heart failure in diabetic patients. Fufang Xueshuantong (FXST) is a traditional Chinese medicine formula commonly used in the treatment of diabetic retinopathy and stable angina pectoris. However, the role of FXST in DCM has not yet been clarified. This study was conducted to investigate the effects of FXST on diabetic myocardial lesions and reveal its molecular mechanism. The rats were intraperitoneally injected with 65 mg/kg streptozotocin (STZ) to induce diabetes mellitus (DM). DM rats were given saline or FXST. The rats in the control group were intraperitoneally injected with an equal amount of sodium citrate buffer and gavaged with saline. After 12 weeks, echocardiography, heart weight index (HWI), and myocardial pathological changes were determined. The expression of transforming growth factor-beta1 (TGF-β1), collagen I, and collagen III was examined using immunofluorescence staining and western blot. The expressions of Wnt/β-catenin signaling pathway-related proteins and mRNA were detected by western blot and real-time PCR. The results showed that FXST significantly improved cardiac function, ameliorated histopathological changes, and decreased HWI in the DM rats. FXST significantly inhibited the expression of myocardial TGF-β1, collagen I, and collagen III in DM rats. Furthermore, FXST significantly inhibited the Wnt/β-catenin pathway. Taken together, FXST has a protective effect on DCM, which might be mediated by suppressing the Wnt/β-catenin pathway.

Inhibition of miR-218-5p reduces myocardial ischemia-reperfusion injury in a Sprague-Dawley rat model by reducing oxidative stress and inflammation through MEF2C/NF-κB pathway

Following myocardial ischemia, myocardial reperfusion injury causes oxidative stress (OS) and inflammation, leading to myocardial cell apoptosis and necrosis. Recently, emerging studies have shown that microRNAs (miRNAs) contribute to the pathophysiology associated with myocardial ischemia-reperfusion (I/R). In this study, we conducted both in-vitro and in-vivo experiments to explore the role of miR-218-5p in ischemia-reperfusion (I/R)- or oxygen and glucose deprivation/reperfusion (OGD/R)-mediated cardiomyocyte injury. A total 44 Sprague-Dawley (SD) rats were used, and randomly divided into four groups, control group (n = 11), miR-218-5p-in group (n = 11), I/R group (n = 11), I/R + miR-218-5p-in group (n = 11). Our data showed that miR-218-5p was overexpressed in H9C2 cardiomyocytes under OGD/R treatment. miR-218-5p inhibition reduced the lactate dehydrogenase (LDH) activity and the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD), as well as the expression of tumor necrosis factor alpha (TNF-α), interleukin (IL-1β), and IL-6. Oppositely, miR-218-5p overexpression aggravated OGD/R-mediated damage on H9C2 cells, whereas nuclear factor kappa B (NF-κB) pathway inhibition or myocyte enhancer factor 2C (MEF2C) upregulation reversed miR-218-5p mimics-mediated effects. Bioinformatics analysis predicted that miR-218-5p targeted and dampened its expression, which was testified by the dual-luciferase reporter assay and RNA pull-down assay. In vivo, inhibiting miR-218-5p declined LDH activities and ROS, MDA and SOD levels in rat myocardial tissues under I/R injury, alleviated myocardial fibrosis and inflammatory reactions, and reduced myocardial infarction area. Overall, inhibition of miR-218-5p choked oxidative stress and inflammation in myocardial I/R injury via targeting MEF2C/NF-κB axis, thus relieving the disease progression.

Changes in N6-Methyladenosine Modification Modulate Diabetic Cardiomyopathy by Reducing Myocardial Fibrosis and Myocyte Hypertrophy

In this study, we aimed to systematically profile global RNA N6-methyladenosine (m⁶A) modification patterns in a mouse model of diabetic cardiomyopathy (DCM). Patterns of m⁶A in DCM and normal hearts were analyzed via m⁶A-specific methylated RNA immunoprecipitation followed by high-throughput sequencing (MeRIP-seq) and RNA sequencing (RNA-seq). m⁶A-related mRNAs were validated by quantitative real-time PCR analysis of input and m⁶A immunoprecipitated RNA samples from DCM and normal hearts. A total of 973 new m⁶A peaks were detected in DCM samples and 984 differentially methylated sites were selected for further study, including 295 hypermethylated and 689 hypomethylated m⁶A sites (fold change (FC) > 1.5, P < 0.05). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway analyses indicated that unique m⁶A-modified transcripts in DCM were closely linked to cardiac fibrosis, myocardial hypertrophy, and myocardial energy metabolism. Total m⁶A levels were higher in DCM, while levels of the fat mass and obesity-associated (FTO) protein were downregulated. Overexpression of FTO in DCM model mice improved cardiac function by reducing myocardial fibrosis and myocyte hypertrophy. Overall, m⁶A modification patterns were altered in DCM, and modification of epitranscriptomic processes, such as m⁶A, is a potentially interesting therapeutic approach.

Epigenetic Alterations Are Associated With Gastric Emptying Disturbances in Diabetes Mellitus

Epigenetic modifications have been implicated to mediate several complications of diabetes mellitus (DM), especially nephropathy and retinopathy. Our aim was to ascertain whether epigenetic alterations in whole blood discriminate among patients with DM with normal, delayed, and rapid gastric emptying (GE).

Myocyte enhancer factor 2A delays vascular endothelial cell senescence by activating the PI3K/p-Akt/SIRT1 pathway

Myocyte enhancer factor 2A (MEF2A) dysfunction is closely related to the occurrence of senile diseases such as cardiocerebrovascular diseases, but the underlying molecular mechanism is unclear. Here, we studied the effects of MEF2A on the senescent phenotype of vascular endothelial cells (VEC) and downstream signaling pathway, and the association between plasma MEF2A levels and coronary artery disease (CAD). Results showed that MEF2A silencing promoted cell senescence and down-regulated PI3K/p-AKT/Sirtuin 1 (SIRT1) expression. MEF2A overexpression delayed cell senescence and up-regulated PI3K/p-AKT/SIRT1. Hydrogen peroxide (H₂O₂) treatment induced cellular senescence and down-regulated the expression of MEF2A and PI3K/p-AKT/SIRT1. MEF2A overexpression inhibited cellular senescence and the down-regulation of PI3K/p-AKT/SIRT1 induced by H₂O₂. Further study revealed that MEF2A directly up-regulated the expression of PIK3CA and PIK3CG through MEF2 binding sites in the promoter region. Pearson correlation and logistic regression analysis showed that the plasma level of MEF2A was negatively correlated with CAD, and with age in the controls. These results suggested that MEF2A can directly up-regulate PI3K gene expression, and one of the molecular mechanisms of delaying effect of MEF2A on VEC cell senescence was SIRT1-expression activation through the PI3K/p-Akt pathway. Moreover, the plasma MEF2A levels may be a potential biomarker for CAD risk prediction.

Melatonin alleviates cardiac fibrosis via inhibiting lncRNA MALAT1/miR-141-mediated NLRP3 inflammasome and TGF-β1/Smads signaling in diabetic cardiomyopathy

Melatonin is a hormone produced by the pineal gland, and it has extensive beneficial effects on various tissue and organs; however, whether melatonin has any effect on cardiac fibrosis in the pathogenesis of diabetic cardiomyopathy (DCM) is still unknown. Herein, we found that melatonin administration significantly ameliorated cardiac dysfunction and reduced collagen production by inhibiting TGF-β1/Smads signaling and NLRP3 inflammasome activation, as manifested by downregulating the expression of TGF-β1, p-Smad2, p-Smad3, NLRP3, ASC, cleaved caspase-1, mature IL-1β, and IL-18 in the heart of melatonin-treated mice with diabetes mellitus (DM). Similar beneficial effects of melatonin were consistently observed in high glucose (HG)-treated cardiac fibroblasts (CFs). Moreover, we also found that lncRNA MALAT1 (lncR-MALAT1) was increased along with concomitant decrease in microRNA-141 (miR-141) in DM mice and HG-treated CFs. Furthermore, we established NLRP3 and TGF-β1 as target genes of miR-141 and lncR-MALAT1 as an endogenous sponge or ceRNA to limit the functional availability of miR-141. Finally, we observed that knockdown of miR-141 abrogated anti-fibrosis action of melatonin in HG-treated CFs. Our findings indicate that melatonin produces an antifibrotic effect via inhibiting lncR-MALAT1/miR-141-mediated NLRP3 inflammasome activation and TGF-β1/Smads signaling, and it might be considered a potential agent for the treatment of DCM.

The Diabetic Cardiac Fibroblast: Mechanisms Underlying Phenotype and Function

Diabetic cardiomyopathy involves remodeling of the heart in response to diabetes that includes microvascular damage, cardiomyocyte hypertrophy, and cardiac fibrosis. Cardiac fibrosis is a major contributor to diastolic dysfunction that can ultimately result in heart failure with preserved ejection fraction. Cardiac fibroblasts are the final effector cell in the process of cardiac fibrosis. This review article aims to describe the cardiac fibroblast phenotype in response to high-glucose conditions that mimic the diabetic state, as well as to explain the pathways underlying this phenotype. As such, this review focuses on studies conducted on isolated cardiac fibroblasts. We also describe molecules that appear to oppose the pro-fibrotic actions of high glucose on cardiac fibroblasts. This represents a major gap in knowledge in the field that needs to be addressed.

MiR-32-5p influences high glucose-induced cardiac fibroblast proliferation and phenotypic alteration by inhibiting DUSP1

Background

The current study aimed to investigate the effects of miR-32-5p on cardiac fibroblasts (CFs) that were induced with high levels of glucose; we also aimed to identify the potential mechanisms involved in the regulation of DUSP1 expression.

Methods

Human CFs were transfected with a miR-32-5p inhibitor or mimic and were treated with a normal concentration or a high concentration of glucose. Flow cytometry analysis was performed to identify cardiac fibroblasts by examining vimentin, fibronectin (FN) and α-actin expression in human CFs. qRT-PCR and western blot assays were performed to confirm the expression of miR-32-5p, DUSP1 and cardiac fibrosis relevant proteins. The proliferation of CFs was assessed by using MTT assay. An immunocytofluorescent staining assay was performed to determine the protein level of α-SMA and to investigate the degree of phenotypic changes in human CFs. The specific relationship between miR-32-5p and DUSP1 was investigated by a dual luciferase reporter assay. Cell apoptosis rates were measured with flow cytometry and the annexin V-FITC and propidine iodide (PI) staining method.

Results

A luciferase reporter assay indicated that miR-32-5p could directly target DUSP1. High glucose levels resulted in the overexpression of miR-32-5p, which downregulated DUSP1 expression. Both the upregulation of miR-32-5p and the downregulation of DUSP1 promoted cell apoptosis, proliferation and phenotypic changes in human CFs.

Conclusions

All findings in this study provide further evidence for the positive effects of miR-32-5p on cell proliferation and the phenotypic changes in CFs by inhibiting DUSP1 expression, and reveal that miR-32-5p could serve as prognostic diagnostic target for cardiac fibrosis.

Electronic supplementary material

The online version of this article (10.1186/s12867-019-0135-x) contains supplementary material, which is available to authorized users.

MEF-2 isoforms' (A-D) roles in development and tumorigenesis

Myocyte enhancer factor (MEF)-2 plays a critical role in proliferation, differentiation, and development of various cell types in a tissue specific manner. Four isoforms of MEF-2 (A-D) differentially participate in controlling the cell fate during the developmental phases of cardiac, muscle, vascular, immune and skeletal systems. Through their associations with various cellular factors MEF-2 isoforms can trigger alterations in complex protein networks and modulate various stages of cellular differentiation, proliferation, survival and apoptosis. The role of the MEF-2 family of transcription factors in the development has been investigated in various cell types, and the evolving alterations in this family of transcription factors have resulted in a diverse and wide spectrum of disease phenotypes, ranging from cancer to infection. This review provides a comprehensive account on MEF-2 isoforms (A-D) from their respective localization, signaling, role in development and tumorigenesis as well as their association with histone deacetylases (HDACs), which can be exploited for therapeutic intervention.

Overexpression of microRNA-202-3p protects against myocardial ischemia-reperfusion injury through activation of TGF-β1/Smads signaling pathway by targeting TRPM6

MicroRNAs (miRNAs) have been found to act as key regulators in the pathogenesis of myocardial ischemic-reperfusion (I/R) injury. In this study, we explore the role and mechanism of microRNA-202-3p (miR-202-3p) in regulating cardiomyocyte apoptosis, in respective of the TGF-β1/Smads signaling pathway by targeting the transient receptor potential cation channel, subfamily M, member 6 (TRPM6). The targeting relationship between miR-202-3p and TRPM6 was verified by a dual-luciferase reporter gene assay. Sprague-Dawley rat models of myocardial I/R injury were initially established and treated with different mimics, inhibitors and siRNAs to test the effects of miR-202-3p and TRPM6 on myocardial I/R injury. The levels of inflammatory factors; IL-1β, IL-6, TNF-α as well as the degree of myocardial fibrosis and cardiomyocyte apoptosis were determined in rats transfected with different plasmids. TRPM6 was found to be the target of miR-202-3p. Up-regulated miR-202-3p or knockdown of TRPM-6 alleviated oxidative stress and inflammatory response, reduced ventricular mass, altered cardiac hemodynamics, suppressed myocardial infarction, attenuated cell apoptosis, and inhibited myocardial fibrosis. MiR-202-3p overexpression activates the TGF-β1/Smads signaling pathway by negatively regulating TRPM6 expression. Taken together, these findings suggest that miR-202-3p offers protection against ventricular remodeling after myocardial I/R injury via activation of the TGF-β1/Smads signaling pathway.

Silymarin ameliorates diabetic cardiomyopathy via inhibiting TGF-β1/Smad signaling

Diabetic cardiomyopathy (DCM) is the leading cause of morbidity and mortality in diabetes mellitus (DM) patients. Previous studies have shown that the transforming growth factor-beta 1 (TGF-β1)/Smad signaling pathway plays a key role in the development of myocardial fibrosis in DCM. Silymarin (SMN) is used clinically to treat liver disorders and acts by influencing TGF-β1. However, the possible effects of silymarin on DCM remain to be elucidated. In our study, the DM animal model was induced by streptozotocin (STZ) injection. Fasting blood glucose level was measured, and the structure and function of the heart were measured by hematoxylin and eosin (H&E) and Masson staining, echocardiography, and transmission electron microscopy (TEM). Western blot was used to detect the expression of TGF-β1, Smad2/3, phosphorylation Smad2/3(p-Smad2/3), and Smad7. Our results showed that silymarin downregulated blood glucose level and significantly improved cardiac fibrosis and collagen deposition in DM rats detected by H&E, Masson staining, and TEM assays. The echocardiography results showed that silymarin administration attenuated cardiac dysfunction in DM rats. Additionally, compared with untreated DM rats, levels of TGF-β1 and p-Smad2/3 were decreased, whereas Smad7 was increased following silymarin administration. These data demonstrate that silymarin ameliorates DCM through the inhibition of TGF-β1/Smad signaling, suggesting that silymarin may be a potential target for DCM treatment.

Oxymatrine Inhibits Transforming Growth Factor β1 (TGF-β1)-Induced Cardiac Fibroblast-to-Myofibroblast Transformation (FMT) by Mediating the Notch Signaling Pathway In Vitro

Background

Oxymatrine, a component extracted from the traditional Chinese herb Sophora japonica (Sophora flavescens Ait.), has various pharmacological effects, especially on the cardiovascular system. However, its cardiac protection effects and the underlying mechanism are still poorly understood. In the present study, we investigated the inhibitory effect and mechanism of oxymatrine on cardiac fibrosis induced by TGF-β1.

Material/Methods

Cardiac fibroblasts were isolated and purified from neonatal rats. Immunocytochemical staining was used to identify the cells. MTT assay and immunofluorescence staining were used to assess cardiac fibroblasts proliferation and myofibroblasts transformation. Hematoxylin-eosin staining was performed to evaluate morphological changes of cardiac fibroblasts. The secretion of type I and III collagen was assessed by staining with picrosirius red and the hydroxyproline content was determined by colorimetric assay. Cardiac fibroblast migration was examined by scratch assay and DNA content was detected to analyze cell cycle distribution using flow cytometry. Western blot analysis was used to detect the protein expressions of Notch pathway-associated protein in cardiac fibroblasts.

Results

Oxymatrine and Notch signaling pathway inhibitor DAPT could attenuated TGF-β1 induced the capacity of proliferation and migration increased in cardiac fibroblasts, as well as the secretion of collagen and hydroxyproline colorimetric content in medium. TGF-β1 induced the biomarker α-SMA of fibroblast-to-myofibroblast transformation (FMT), which was inhibited by oxymatrine and DAPT. Western blotting confirmed that oxymatrine blocked the activation of Notch induced by TGF-β1.

Conclusions

Oxymatrine is a potential inhibitor FMT induced by TGF-β1, which is at least in part mediated via inhibition of Notch signaling.

MicroRNA-495 inhibits the high glucose-induced inflammation, differentiation and extracellular matrix accumulation of cardiac fibroblasts through downregulation of NOD1

Background

MicroRNAs (miRNAs) have physiological and pathophysiological functions that are involved in the regulation of cardiac fibrosis. This study aimed to investigate the effects of miR-495 on high glucose-induced cardiac fibrosis in human cardiac fibroblasts (CFs) and to establish the mechanism underlying these effects.

Methods

Human CFs were transfected with an miR-495 inhibitor or mimic and incubated with high glucose. The levels of NOD1 and miR-495 were then determined via quantitative RT-PCR. Pro-inflammatory cytokine levels, cell differentiation and extracellular matrix accumulation were respectively detected using ELISA, quantitative RT-PCR and western blot assays. The luciferase reporter assay, quantitative RT-PCR and western blot were used to explore whether NOD1 was a target of miR-495. The effects of miR-495 on the NF-κB and TGF-β1/Smad signaling pathways were also detected via western blot.

Results

Our results show that high glucose can significantly increase the expression of NOD1 in a time-dependent manner. Upregulation of miR-495 significantly alleviated the high glucose-induced increases in cell differentiation and collagen accumulation of CFs. Moreover, the bioinformatics analysis predicted that NOD1 was a potential target gene for miR-495. The luciferase reporter assay showed that miR-495 can directly target NOD1. The introduction of miR-495 could significantly inhibit the high glucose-activated NF-κB and TGF-β1/Smad signaling pathways.

Conclusion

Upregulation of miR-495 ameliorates the high glucose-induced inflammatory, cell differentiation and extracellular matrix accumulation of human CFs by modulating both the NF-κB and TGF-β1/Smad signaling pathways through downregulation of NOD1 expression. These results provide further evidence for the protective effect of miR-495 overexpression in cases of high glucose-induced cardiac fibrosis.

Myocyte enhancer factor 2A promotes proliferation and its inhibition attenuates myogenic differentiation via myozenin 2 in bovine skeletal muscle myoblast

Myocyte enhancer factor 2A (MEF2A) is widely distributed in various tissues or organs and plays crucial roles in multiple biological processes. To examine the potential effects of MEF2A on skeletal muscle myoblast, the functional role of MFE2A in myoblast proliferation and differentiation was investigated. In this study, we found that the mRNA expression level of Mef2a was dramatically increased during the myogenesis of bovine skeletal muscle primary myoblast. Overexpression of MEF2A significantly promoted myoblast proliferation, while knockdown of MEF2A inhibited the proliferation and differentiation of myoblast. RT-PCR and western blot analysis revealed that this positive effect of MEF2A on the proliferation of myoblast was carried out by triggering cell cycle progression by activating CDK2 protein expression. Besides, MEF2A was found to be an important transcription factor that bound to the myozenin 2 (MyoZ2) proximal promoter and performed upstream of MyoZ2 during myoblast differentiation. This study provides the first experimental evidence that MEF2A is a positive regulator in skeletal muscle myoblast proliferation and suggests that MEF2A regulates myoblast differentiation via regulating MyoZ2.

Extracellular Vesicles as Protagonists of Diabetic Cardiovascular Pathology

Extracellular vesicles (EVs) represent an emerging mechanism of cell–cell communication in the cardiovascular system. Recent data suggest that EVs are produced and taken up by multiple cardiovascular cell types, influencing target cells through signaling or transfer of cargo (including proteins, lipids, messenger RNA, and non-coding RNA). The concentration and contents of circulating EVs are altered in several diseases and represent explicit signatures of cellular activation, making them of particular interest as circulating biomarkers. EVs also actively contribute to the progression of various cardiovascular diseases, including diabetes-related vascular disease. Understanding the relationships between circulating EVs, diabetes, and cardiovascular disease is of importance as diabetic patients are at elevated risk for developing several debilitating cardiovascular pathologies, including diabetic cardiomyopathy (DCM), a disease that remains an enigma at the molecular level. Enhancing and exploiting our understanding of EV biology could facilitate the development of effective non-invasive diagnostics, prognostics, and therapeutics. This review will focus on EV biology in diabetic cardiovascular diseases, including atherosclerosis and DCM. We will review EV biogenesis and functional properties, as well as provide insight into their emerging role in cell–cell communication. Finally, we will address the utility of EVs as clinical biomarkers and outline their impact as a biomedical tool in the development of therapeutics.

miR-155 regulates high glucose-induced cardiac fibrosis via the TGF-β signaling pathway

Cardiac fibrosis, as a pathological process, plays an important role in various cardiac diseases. microRNA-155 (miR-155) is one of the most important miRNAs, and previous studies have shown that it is a regulatory factor in various fibrotic diseases. However, the mechanism by which miR-155 affects myocardial fibrosis remains unclear. In this study, we aim to establish the biological function of miR-155 in myocardial fibrosis induced by diabetes in mice. We used normal C57BL/6 wild type (WT) and miR-155 knockout (KO) mice to establish the diabetic model by intraperitoneal injection of streptozotocin, and we utilized echocardiography to evaluate the cardiac function at 30 and 60 days post-modeling. Hematoxylin-eosin (HE) and sirius-red (SR) staining were used to evaluate the degree of myocardial lesions. Furthermore, we extracted cardiac fibroblasts (CFs) from the WT mice and transfected them with miR-155 inhibitors, mimics and negative control siRNAs to analyze the specific mechanism involved in the development of myocardial fibrosis. The results showed that miR-155 deficiency could prevent cardiac fibrosis induced by diabetes in mice and also that attenuated collagen synthesis is induced by high glucose (HG) in CFs. We found that miR-155 regulated cardiac fibrosis via the TGF-β1-Smad 2 signaling pathway. These findings suggest that miR-155 may be a therapeutic target for preventing cardiac fibrosis induced by diabetes.

Transcription Factor CREM Mediates High Glucose Response in Cardiomyocytes and in a Male Mouse Model of Prolonged Hyperglycemia

This study aims at investigating the epigenetic landscape of cardiomyocytes exposed to elevated glucose levels. High glucose (30 mM) for 72 hours determined some epigenetic changes in mouse HL-1 and rat differentiated H9C2 cardiomyocytes including upregulation of class I and III histone deacetylase protein levels and activity, inhibition of histone acetylase p300 activity, increase in histone H3 lysine 27 trimethylation, and reduction in H3 lysine 9 acetylation. Gene expression analysis focused on cardiotoxicity revealed that high glucose induced markers associated with tissue damage, fibrosis, and cardiac remodeling such as Nexilin (NEXN), versican, cyclic adenosine 5'-monophosphate-responsive element modulator (CREM), and adrenoceptor α2A (ADRA2). Notably, the transcription factor CREM was found to be important in the regulation of cardiotoxicity-associated genes as assessed by specific small interfering RNA and chromatin immunoprecipitation experiments. In CD1 mice, made hyperglycemic by streptozotoicin (STZ) injection, cardiac structural alterations were evident at 6 months after STZ treatment and were associated with a significant increase of H3 lysine 27 trimethylation and reduction of H3 lysine 9 acetylation. Consistently, NEXN, CREM, and ADRA2 expression was significantly induced at the RNA and protein levels. Confocal microscopy analysis of NEXN localization showed this protein irregularly distributed along the sarcomeres in the heart of hyperglycemic mice. This evidence suggested a structural alteration of cardiac Z-disk with potential consequences on contractility. In conclusion, high glucose may alter the epigenetic landscape of cardiac cells. Sildenafil, restoring guanosine 3', 5'-cyclic monophosphate levels, counteracted the increase of CREM and NEXN, providing a protective effect in the presence of hyperglycemia.

MicroRNA-9 inhibits high glucose-induced proliferation, differentiation and collagen accumulation of cardiac fibroblasts by down-regulation of TGFBR2

To investigate the effects of miR-9 on high glucose (HG)-induced cardiac fibrosis in human cardiac fibroblasts (HCFs), and to establish the mechanism underlying these effects. HCFs were transfected with miR-9 inhibitor or mimic, and then treated with normal or HG. Cell viability and proliferation were detected by using the Cell Counting Kit-8 (CCK-8) assay and Brdu-ELISA assay. Cell differentiation and collagen accumulation of HCFs were detected by qRT-PCR and Western blot assays respectively. The mRNA and protein expressions of transforming growth factor-β receptor type II (TGFBR2) were determined by qRT-PCR and Western blotting. Up-regulation of miR-9 dramatically improved HG-induced increases in cell proliferation, differentiation and collagen accumulation of HCFs. Moreover, bioinformatics analysis predicted that the TGFBR2 was a potential target gene of miR-9 Luciferase reporter assay demonstrated that miR-9 could directly target TGFBR2. Inhibition of TGFBR2 had the similar effect as miR-9 overexpression. Down-regulation of TGFBR2 in HCFs transfected with miR-9 inhibitor partially reversed the protective effect of miR-9 overexpression on HG-induced cardiac fibrosis in HCFs. Up-regulation of miR-9 ameliorates HG-induced proliferation, differentiation and collagen accumulation of HCFs by down-regulation of TGFBR2. These results provide further evidence for protective effect of miR-9 overexpression on HG-induced cardiac fibrosis.

Evolving lessons on nanomaterial-coated viral vectors for local and systemic gene therapy

Viral vectors are promising gene carriers for cancer therapy. However, virus-mediated gene therapies have demonstrated insufficient therapeutic efficacy in clinical trials due to rapid dissemination to nontarget tissues and to the immunogenicity of viral vectors, resulting in poor retention at the disease locus and induction of adverse inflammatory responses in patients. Further, the limited tropism of viral vectors prevents efficient gene delivery to target tissues. In this regard, modification of the viral surface with nanomaterials is a promising strategy to augment vector accumulation at the target tissue, circumvent the host immune response, and avoid nonspecific interactions with the reticuloendothelial system or serum complement. In the present review, we discuss various chemical modification strategies to enhance the therapeutic efficacy of viral vectors delivered either locally or systemically. We conclude by highlighting the salient features of various nanomaterial-coated viral vectors and their prospects and directions for future research.