Methylglyoxal induces cardiac dysfunction through mechanisms involving altered intracellular calcium handling in the rat heart

Methylglyoxal (MGO) is an endogenous, highly reactive dicarbonyl metabolite generated under hyperglycaemic conditions. MGO plays a role in developing pathophysiological conditions, including diabetic cardiomyopathy. However, the mechanisms involved and the molecular targets of MGO in the heart have not been elucidated. In this work, we studied the exposure-related effects of MGO on cardiac function in an isolated perfused rat heart ex vivo model. The effect of MGO on calcium homeostasis in cardiomyocytes was studied in vitro by the fluorescence indicator of intracellular calcium Fluo-4. We demonstrated that MGO induced cardiac dysfunction, both in contractility and diastolic function. In rat heart, the effects of MGO treatment were significantly limited by aminoguanidine, a scavenger of MGO, ruthenium red, a general cation channel blocker, and verapamil, an L-type voltage-dependent calcium channel blocker, demonstrating that this dysfunction involved alteration of calcium regulation. MGO induced a significant concentration-dependent increase of intracellular calcium in neonatal rat cardiomyocytes, which was limited by aminoguanidine and verapamil. These results suggest that the functionality of various calcium channels is altered by MGO, particularly the L-type calcium channel, thus explaining its cardiac toxicity. Therefore, MGO could participate in the development of diabetic cardiomyopathy through its impact on calcium homeostasis in cardiac cells.

Diabetes Promotes Myocardial Fibrosis via AMPK/EZH2/PPAR-γ Signaling Pathway

Background

Diabetes-induced cardiac fibrosis is one of the main mechanisms of diabetic cardiomyopathy. As a common histone methyltransferase, enhancer of zeste homolog 2 (EZH2) has been implicated in fibrosis progression in multiple organs. However, the mechanism of EZH2 in diabetic myocardial fibrosis has not been clarified.

Methods

In the current study, rat and mouse diabetic model were established, the left ventricular function of rat and mouse were evaluated by echocardiography and the fibrosis of rat ventricle was evaluated by Masson staining. Primary rat ventricular fibroblasts were cultured and stimulated with high glucose (HG) in vitro. The expression of histone H3 lysine 27 (H3K27) trimethylation, EZH2, and myocardial fibrosis proteins were assayed.

Results

In STZ-induced diabetic ventricular tissues and HG-induced primary ventricular fibroblasts in vitro, H3K27 trimethylation was increased and the phosphorylation of EZH2 was reduced. Inhibition of EZH2 with GSK126 suppressed the activation, differentiation, and migration of cardiac fibroblasts as well as the overexpression of the fibrotic proteins induced by HG. Mechanical study demonstrated that HG reduced phosphorylation of EZH2 on Thr311 by inactivating AMP-activated protein kinase (AMPK), which transcriptionally inhibited peroxisome proliferator-activated receptor γ (PPAR-γ) expression to promote the fibroblasts activation and differentiation.

Conclusion

Our data revealed an AMPK/EZH2/PPAR-γ signal pathway is involved in HG-induced cardiac fibrosis.

Primordial Drivers of Diabetes Heart Disease: Comprehensive Insights into Insulin Resistance

Insulin resistance has been regarded as a hallmark of diabetes heart disease (DHD). Numerous studies have shown that insulin resistance can affect blood circulation and myocardium, which indirectly cause cardiac hypertrophy and ventricular remodeling, participating in the pathogenesis of DHD. Meanwhile, hyperinsulinemia, hyperglycemia, and hyperlipidemia associated with insulin resistance can directly impair the metabolism and function of the heart. Targeting insulin resistance is a potential therapeutic strategy for the prevention of DHD. Currently, the role of insulin resistance in the pathogenic development of DHD is still under active research, as the pathological roles involved are complex and not yet fully understood, and the related therapeutic approaches are not well developed. In this review, we describe insulin resistance and add recent advances in the major pathological and physiological changes and underlying mechanisms by which insulin resistance leads to myocardial remodeling and dysfunction in the diabetic heart, including exosomal dysfunction, ferroptosis, and epigenetic factors. In addition, we discuss potential therapeutic approaches to improve insulin resistance and accelerate the development of cardiovascular protection drugs.

Pharmacologic Activation of Angiotensin-Converting Enzyme II Alleviates Diabetic Cardiomyopathy in db/db Mice by Reducing Reactive Oxidative Stress

BACKGRUOUND

Diabetes mellitus is one of the most common chronic diseases worldwide, and cardiovascular disease is the leading cause of morbidity and mortality in diabetic patients. Diabetic cardiomyopathy (DCM) is a phenomenon characterized by a deterioration in cardiac function and structure, independent of vascular complications. Among many possible causes, the renin-angiotensin-aldosterone system and angiotensin II have been proposed as major drivers of DCM development. In the current study, we aimed to investigate the effects of pharmacological activation of angiotensin-converting enzyme 2 (ACE2) on DCM.

METHODS

The ACE2 activator diminazene aceturate (DIZE) was administered intraperitoneally to male db/db mice (8 weeks old) for 8 weeks. Transthoracic echocardiography was used to assess cardiac mass and function in mice. Cardiac structure and fibrotic changes were examined using histology and immunohistochemistry. Gene and protein expression levels were examined using quantitative reverse transcription polymerase chain reaction and Western blotting, respectively. Additionally, RNA sequencing was performed to investigate the underlying mechanisms of the effects of DIZE and identify novel potential therapeutic targets for DCM.

RESULTS

Echocardiography revealed that in DCM, the administration of DIZE significantly improved cardiac function as well as reduced cardiac hypertrophy and fibrosis. Transcriptome analysis revealed that DIZE treatment suppresses oxidative stress and several pathways related to cardiac hypertrophy.

CONCLUSION

DIZE prevented the diabetes mellitus-mediated structural and functional deterioration of mouse hearts. Our findings suggest that the pharmacological activation of ACE2 could be a novel treatment strategy for DCM.

Pyruvate Dehydrogenase Complex and Glucose Oxidation as a Therapeutic Target in Diabetic Heart Disease

Diabetic cardiomyopathy was originally described as the presence of ventricular dysfunction in the absence of coronary artery disease and/or hypertension. It is characterized by diastolic dysfunction and is more prevalent in people with diabetes than originally realized, leading to the suggestion in the field that it simply be referred to as diabetic heart disease. While there are currently no approved therapies for diabetic heart disease, a multitude of studies clearly demonstrate that it is characterized by several disturbances in myocardial energy metabolism. One of the most prominent changes in myocardial energy metabolism in diabetes is a robust impairment in glucose oxidation. Herein we will describe the mechanisms responsible for the diabetes-induced decline in myocardial glucose oxidation, and the pharmacological approaches that have been pursued to correct this metabolic disorder. With surmounting evidence that stimulating myocardial glucose oxidation can alleviate diastolic dysfunction and other pathologies associated with diabetic heart disease, this may also represent a novel strategy for decreasing the prevalence of heart failure with preserved ejection fraction in the diabetic population.

Independent and combined effects of liraglutide and aerobic interval training on glycemic control and cardiac protection in diabetic cardiomyopathy rats

OBJECTIVE

This study intended to explore the hypoglycemic and cardioprotective effects of 8-week aerobic interval training combined with liraglutide and elucidate the underlying mechanisms.

METHOD

Male Wistar rats were randomly divided into 5 groups - normal control group (CON), diabetic cardiomyopathy group (DCM), high-dose liraglutide group (DH), low-dose liraglutide group (DL), and aerobic interval training combined with liraglutide group (DLE). High-fat diet and streptozotocin (STZ) were used to induce the DCM model, and both the liraglutide administration group and combination therapy group allocated to 8 weeks of either liraglutide or liraglutide and exercise intervention. Cardiac functions were analyzed by electrocardiography. Blood biochemical parameters were measured to judge glycemic control conditions. Hematoxylin and eosin (HE) staining and Sirus red staining was used to identify cardiac morphology and collagen accumulation, respectively. Advanced glycation end products (AGEs) were determined by enzymatic methods. The mRNA expression of myocardial remodeling genes (BNP, GSK3β, α-MHC, β-MHC and PPARα) and the protein expression of GLP-1, GLP-1R were analyzed.

RESULTS

DCM rats developed hyperglycemia, impaired cardiac function with accumulation of AGEs and collagen (P < 0.05). The development of hyperglycemia and cardiac dysfunction was significantly attenuated with all interventions, as reduced cardiac fibrosis and improved cardiac function (P < 0.05). Cardiac remodeling genes were normalized after all interventions, these positive modifications were due to increased GLP-1 and GLP-1R expression in DCM heart (P < 0.05). Liraglutide combined with AIT significantly increased the diameters of cardiomyocytes, increased the α-MHC expressionx, reduced PPARαexpression and reduced the fluctuation of blood glucose level, which showed the safety and effective of medicine combined with exercise.

CONCLUSION

Liraglutide combined with AIT intervention normalized blood glucose alleviates myocardial fibrosis and improves cardiac contractile function in DCM rats, supporting the efficacy and safety of the combination therapy.

Pyrroloquinoline quinone ameliorates diabetic cardiomyopathy by inhibiting the pyroptosis signaling pathway in C57BL/6 mice and AC16 cells

Purpose

Diabetic cardiomyopathy (DCM), a common complication of diabetes mellitus and is characterized by myocardial hypertrophy and myocardial fibrosis. Pyrroloquinoline quinone (PQQ), a natural nutrient, exerts strong protection against various myocardial diseases. Pyroptosis, a type of inflammation-related programmed cell death, is vital to the development of DCM. However, the protective effects of PQQ against DCM and the associated mechanisms are not clear. This study aimed to investigate whether PQQ protected against DCM and to determine the underlying molecular mechanism.

Methods

Diabetes was induced in mice by intraperitoneal injection of streptozotocin, after which the mice were administered PQQ orally (10, 20, or 40 mg/kg body weight/day) for 12 weeks. AC16 human myocardial cells were divided into the following groups and treated accordingly: control (5.5 mmol/L glucose), high glucose (35 mmol/L glucose), and HG + PQQ groups (1 and 10 nmol/L PQQ). Cells were treated for 24 h.

Results

PQQ reduced myocardial hypertrophy and the area of myocardial fibrosis, which was accompanied by an increase in antioxidant function and a decrease in inflammatory cytokine levels. Moreover, myocardial hypertrophy—(ANP and BNP), myocardial fibrosis—(collagen I and TGF-β1), and pyroptosis-related protein levels decreased in the PQQ treatment groups. Furthermore, PQQ abolished mitochondrial dysfunction and the activation of NF-κB/IκB, and decreased NLRP3 inflammation-mediated pyroptosis in AC16 cells under high-glucose conditions.

Conclusion

PQQ improved DCM in diabetic mice by inhibiting NF-κB/NLRP3 inflammasome-mediated cell pyroptosis. Long-term dietary supplementation with PQQ may be greatly beneficial for the treatment of DCM.

Graphical abstract

Diagram of the underlying mechanism of the effects of PQQ on DCM. PQQ inhibits ROS generation and NF-κB activation, which stimulates activation of the NLRP3 inflammasome and regulates the expression of caspase-1, IL-1β, and IL-18. The up-regulated inflammatory cytokines trigger myocardial hypertrophy and cardiac fibrosis and promote the pathological process of DCM.

Role of Autophagy in Granulocyte-Colony Stimulating Factor Induced Anti-Apoptotic Effects in Diabetic Cardiomyopathy

BACKGROUND

We previously, reported that granulocyte-colony stimulating factor (G-CSF) reduces cardiomyocyte apoptosis in diabetic cardiomyopathy. However, the underlying mechanisms are not yet fully understood. Therefore, we investigated whether the mechanisms underlying of the anti-apoptotic effects of G-CSF were associated with autophagy using a rat model of diabetic cardiomyopathy.

METHODS

Diabetic cardiomyopathy was induced in rats through a high-fat diet combined with low-dose streptozotocin and the rats were then treated with G-CSF for 5 days. Rat H9c2 cardiac cells were cultured under high glucose conditions as an in vitro model of diabetic cardiomyopathy. The extent of apoptosis and protein levels related to autophagy (Beclin-1, microtubule-binding protein light chain 3 [LC3]-II/LC3-I ratio, and P62) were determined for both models. Autophagy determination was performed using an Autophagy Detection kit.

RESULTS

G-CSF significantly reduced cardiomyocyte apoptosis in the diabetic myocardium in vivo and led to an increase in Beclin-1 level and the LC3-II/LC3-I ratio, and decreased P62 level. Similarly, G-CSF suppressed apoptosis, increased Beclin-1 level and LC3-II/LC3-I ratio, and decreased P62 level in high glucose-induced H9c2 cardiac cells in vitro. These effects of G-CSF were abrogated by 3-methyladenine, an autophagy inhibitor. In addition, G-CSF significantly increased autophagic flux in vitro.

CONCLUSION

Our results suggest that the anti-apoptotic effect of G-CSF might be significantly associated with the up-regulation of autophagy in diabetic cardiomyopathy.

Epidemiology, Pathophysiology, Diagnosis and Treatment of Heart Failure in Diabetes

The cardiovascular disease continuum begins with risk factors such as diabetes mellitus (DM), progresses to vasculopathy and myocardial dysfunction, and finally ends with cardiovascular death. Diabetes is associated with a 2- to 4-fold increased risk for heart failure (HF). Moreover, HF patients with DM have a worse prognosis than those without DM. Diabetes can cause myocardial ischemia via micro- and macrovasculopathy and can directly exert deleterious effects on the myocardium. Hyperglycemia, hyperinsulinemia, and insulin resistance can cause alterations in vascular homeostasis. Then, reduced nitric oxide and increased reactive oxygen species levels favor inflammation leading to atherothrombotic progression and myocardial dysfunction. The classification, diagnosis, and treatment of HF for a patient with and without DM remain the same. Until now, drugs targeting neurohumoral and metabolic pathways improved mortality and morbidity in HF with reduced ejection fraction (HFrEF). Therefore, all HFrEF patients should receive guideline-directed medical therapy. By contrast, drugs modulating neurohumoral activity did not improve survival in HF with preserved ejection fraction (HFpEF) patients. Trials investigating whether sodium-glucose cotransporter-2 inhibitors are effective in HFpEF are on-going. This review will summarize the epidemiology, pathophysiology, and treatment of HF in diabetes.

The role of insulin resistance in the relation of visceral, abdominal subcutaneous and total body fat to cardiovascular function

BACKGROUND AND AIMS

The separate cardiovascular effects of type 2 diabetes and adiposity remain to be examined. This study aimed to investigate the role of insulin resistance in the relations of visceral (VAT), abdominal subcutaneous (aSAT) adipose tissue and total body fat (TBF) to cardiovascular remodeling.

METHODS AND RESULTS

In this cross-sectional analysis of the population-based Netherlands Epidemiology of Obesity study, 914 middle-aged individuals (46% men) were included. Participants underwent magnetic resonance imaging. Standardized linear regression coefficients (95%CI) were calculated, adjusted for potential confounding factors. All fat depots and insulin resistance (HOMA-IR), separate from VAT and TBF, were associated with lower mitral early and late peak filling rate ratios (E/A): -0.04 (-0.09;0.01) per SD (54 cm²) VAT; -0.05 (-0.10;0.00) per SD (94 cm²) aSAT; -0.09 (-0.16;-0.02) per SD (8%) TBF; -0.11 (-0.17;-0.05) per 10-fold increase in HOMA-IR, whereas VAT and TBF were differently associated with left ventricular (LV) end-diastolic volume: -8.9 (-11.7;-6.1) mL per SD VAT; +5.4 (1.1;9.7) mL per SD TBF. After adding HOMA-IR to the model to evaluate the mediating role of insulin resistance, change in E/A was -0.02 (-0.07;0.04) per SD VAT; -0.03 (-0.08;0.02) per SD aSAT; -0.06 (-0.13;0.01) per SD TBF, and change in LV end-diastolic volume was -7.0 (-9.7;-4.3) mL per SD VAT. In women, adiposity but not HOMA-IR was related to higher aortic arch pulse wave velocity.

CONCLUSION

Insulin resistance was associated with reduced diastolic function, separately from VAT and TBF, and partly mediated the associations between adiposity depots and lower diastolic function.

Effect of adenosine monophosphate-activated protein kinase-p53-Krüppel-like factor 2a pathway in hyperglycemia-induced cardiac remodeling in adult zebrafish

Aims/Introduction

Diabetic cardiomyopathy is a type of myocardial disease. It causes left ventricular hypertrophy, followed by diastolic and systolic dysfunction, eventually leading to congestive heart failure. However, the underlying mechanism still requires further elucidation.

Materials and Methods

A high‐glucose zebrafish model was constructed by administering streptozocin intraperitoneally to enhance the development of cardiomyopathy and then treated with adenosine monophosphate‐activated protein kinase (AMPK) activator. Cardiac structure and function, and protein and gene expression were then analyzed. Cardiomyocytes (CMs) culture in vitro using lentivirus were used for detection of AMPK, p53 and Krüppel‐like factor 2a (klf2a) gene expression.

Results

In the hyperglycemia group, electrocardiogram findings showed arrhythmia, echocardiography results showed heart enlargement and dysfunction, and many differences, such as increased apoptosis and myocardial fiber loss, were observed. The phospho‐AMPK and klf2a expression were downregulated, and p53 expression was upregulated. Activation of phospho‐AMPK reduced p53 and increased klf2a expression, alleviated apoptosis in CMs and improved cardiac function in the hyperglycemic zebrafish. In vitro knockdown system of AMPK, p53 and klf2a using lentivirus illustrated an increased p53 expression and decreased klf2a expression in CMs by inhibiting AMPK. Repression of p53 and upregulation of klf2a expression were observed, but no changes in the expression of AMPK and its phosphorylated type.

Conclusions

In the model of streptozocin‐induced hyperglycemia zebrafish, the reduction of phosphorylated AMPK increased p53, which led to KLF2a decrease to facilitate apoptosis of CMs, inducing the cardiac remodeling and cardiac dysfunction. These results can be reversed by AMPK activator, which means the AMPK–p53–klf2a pathway might be a potential target for diabetic cardiomyopathy intervention.

Association between Non-Alcoholic Steatohepatitis and Left Ventricular Diastolic Dysfunction in Type 2 Diabetes Mellitus

BACKGROUND

Impaired diastolic heart function has been observed in persons with non-alcoholic fatty liver disease (NAFLD) and/or with type 2 diabetes mellitus (T2DM). However, it is unclear whether NAFLD fibrotic progression, i.e., non-alcoholic steatohepatitis, poses an independent risk for diastolic dysfunction in T2DM. We investigated the association between liver fibrosis and left ventricular (LV) diastolic dysfunction in T2DM.

METHODS

We analyzed 606 patients with T2DM, aged ≥50 years, who had undergone liver ultrasonography and pulsed-wave Doppler echocardiography. Insulin sensitivity was measured by short insulin tolerance test. Presence of NAFLD and/or advanced liver fibrosis was determined by abdominal ultrasonography and NAFLD fibrosis score (NFS). LV diastolic dysfunction was defined according to transmitral peak early to late ventricular filling (E/A) ratio and deceleration time, using echocardiography.

RESULTS

LV diastolic dysfunction was significantly more prevalent in the NAFLD versus non-NAFLD group (59.7% vs. 49.0%, P=0.011). When NAFLD was stratified by NFS, subjects with advanced liver fibrosis exhibited a higher prevalence of diastolic dysfunction (49.0%, 50.7%, 61.8%; none, simple steatosis, advanced fibrosis, respectively; P for trend=0.003). In multivariable logistic regression, liver fibrosis was independently associated with diastolic dysfunction (odds ratio [OR], 1.58; 95% confidence interval [CI], 1.07 to 2.34; P=0.022) after adjusting for insulin resistance and cardiometabolic risk factors. This association remained significant in patients without insulin resistance (OR, 4.32; 95% CI, 1.73 to 11.51; P=0.002).

CONCLUSIONS

Liver fibrosis was associated with LV diastolic dysfunction in patients with T2DM and may be an independent risk factor for diastolic dysfunction, especially in patients without systemic insulin resistance.

Mitochondrial Mechanisms in Diabetic Cardiomyopathy

Mitochondrial medicine is increasingly discussed as a promising therapeutic approach, given that mitochondrial defects are thought to contribute to many prevalent diseases and their complications. In individuals with diabetes mellitus (DM), defects in mitochondrial structure and function occur in many organs throughout the body, contributing both to the pathogenesis of DM and complications of DM. Diabetic cardiomyopathy (DbCM) is increasingly recognized as an underlying cause of increased heart failure in DM, and several mitochondrial mechanisms have been proposed to contribute to the development of DbCM. Well established mechanisms include myocardial energy depletion due to impaired adenosine triphosphate (ATP) synthesis and mitochondrial uncoupling, and increased mitochondrial oxidative stress. A variety of upstream mechanisms of impaired ATP regeneration and increased mitochondrial reactive oxygen species have been proposed, and recent studies now also suggest alterations in mitochondrial dynamics and autophagy, impaired mitochondrial Ca²⁺ uptake, decreased cardiac adiponectin action, increased O-GlcNAcylation, and impaired activity of sirtuins to contribute to mitochondrial defects in DbCM, among others. In the current review, we present and discuss the evidence that underlies both established and recently proposed mechanisms that are thought to contribute to mitochondrial dysfunction in DbCM.

Role of MicroRNA-34a in Anti-Apoptotic Effects of Granulocyte-Colony Stimulating Factor in Diabetic Cardiomyopathy

BACKGROUND

Recent studies have shown that microRNAs (miRNAs) are involved in the process of cardiomyocyte apoptosis. We have previously reported that granulocyte-colony stimulating factor (G-CSF) ameliorated diastolic dysfunction and attenuated cardiomyocyte apoptosis in a rat model of diabetic cardiomyopathy. In this study, we hypothesized a regulatory role of cardiac miRNAs in the mechanism of the anti-apoptotic effect of G-CSF in a diabetic cardiomyopathy rat model.

METHODS

Rats were given a high-fat diet and low-dose streptozotocin injection and then randomly allocated to receive treatment with either G-CSF or saline. H9c2 rat cardiomyocytes were cultured under a high glucose (HG) condition to induce diabetic cardiomyopathy in vitro. We examined the extent of apoptosis, miRNA expression, and miRNA target genes in the myocardium and H9c2 cells.

RESULTS

G-CSF treatment significantly decreased apoptosis and reduced miR-34a expression in diabetic myocardium and H9c2 cells under the HG condition. G-CSF treatment also significantly increased B-cell lymphoma 2 (Bcl-2) protein expression as a target for miR-34a. In addition, transfection with an miR-34a mimic significantly increased apoptosis and decreased Bcl-2 luciferase activity in H9c2 cells.

CONCLUSION

Our results indicate that G-CSF might have an anti-apoptotic effect through down-regulation of miR-34a in a diabetic cardiomyopathy rat model.

[Impact and related mechanism on the improvement of hyperglycemia-induced pyroptosis in H9c2 cells by mircoRNA-214]

Objective: To investigate whether microRNA(miR)-214 can improve hyperglycemia induced pyroptosis in H9c2 cells through targeting caspase-1. Methods: H9c2 cells of rats those in good growth condition were selected and incubated into the T25 culture bottle after digestion and passage. Cells were cultured in an incubator at 37 ℃ with 5%CO(2), repeat passage was made after cell density reached about 80%, The 5(th) to 8(th) generations of cells were selected for the subsequent experiments. To observe the effect of overexpression of miR-214 on pyroptosis and caspase-1 expression in H9c2 cells induced by hyperglycemia, the cells were divided into 4 groups: Control group(H9c2 cells cultured normally), Hyperglycemia group (HG group, 50 mmol/L glucose was used to intervene H9c2 cells for 24 hours), miR-214 mimics+hyperglycosis group (mimics+HG group, H9c2 cells were transfected with miR-214 mimics for 24 hours and then treated with 50 mmol/L hyperglycosis for 24 hours), miR-214 mimic-negative control+hyperglycaemic group(MNC+HG group, H9c2 cells were transfected with miR-214 mimic-negative control for 24 hours and then treated with 50 mmol/L hyperglycaemic for 24 hours). In order to further verify the anti-pyroptosis effect of miR-214 was mediated by targeted inhibition on caspase-1, cells overexpressing caspase-1 were used in the rescue experiment. The cells overexpressing caspase-1 were divided into 4 groups: Hyperglycemia group (HG group, 50 mmol/L glucose was used to intervene H9c2 cells for 24 hours), miR-214 mimics+hyperglycosis group (mimics+HG group, H9c2 cells were transfected with miR-214 mimics for 24 hours and then treated with 50 mmol/L hyperglycosis for 24 hours), miR-214 mimics+hyperglycosis+recombinant adenovirus (Ad-caspase-1-EGFP) group with caspase-1 gene and EGFP green fluorescent protein expression (mimics+HG+Ad-caspase-1-EGFP group, H9c2 cells were transfected with caspase-1-green fluorescent protein-carrying adenovirus for 48 hours, followed by transfection of miR-214 mimics for 24 hours, and then treated with 50 mmol/L hyperglycaemia for 24 hours), miR-214 mimics+HG+Ad-EGFP empty virus group (mimics+HG+Ad-EGFP group, H9c2 cells were transfected with empty adenovirus containing green fluorescent protein for 48 hours, followed by transfection with miR-214 mimics for 24 hours, and then treated with 50 mmol/L hyperglycosis for 24 hours). The mRNA expression levels of miRNA-214 and caspase-1 in cells were detected by real-time quantitative PCR. The expression and localization of caspase-1 protein were detected by immunofluorescence assay. Western blot was used to detect protein expression levels of procaspase-1, cleaved caspase-1, NLRP3 and ACS with β-actin as internal reference. The secretion of IL-1β and IL-18 in cell culture medium was detected by ELISA. The correlation between miR-214 and caspase-1 was detected by double luciferase reporter gene. Results: (1) The mRNA expression levels of miR-214 and caspase-1 in each group: the mRNA expressions of miR-214 in HG group and MNC+HG group were significantly lower than that in control group(P<0.05). The mRNA expression of miR-214 in mimics+HG group was significantly higher than that in control group (P<0.05). The mRNA expression levels of caspase-1 in HG group and MNC+HG group were significantly higher than that in control group(P<0.05). The mRNA expression level of caspase-1 in mimics+HG group was lower than that in control group(P<0.05). (2) The expression of caspase-1 in each group: the green fluorescence intensity in the control group was weak, which was strong in the HG group and MNC+HG group. The green fluorescence expression was weaker in mimics+HG group than in HG group. (3) ASC and NLRP3 protein expression levels in each group: ASC and NLRP3 protein expression levels in HG group and MNC+HG group were higher than those in control group(P<0.05). ASC and NLRP3 protein expression levels were significantly lower in mimics+HG group than in mimics+HG group (P<0.05). (4) The secretion of IL-1β and IL-18 in the cell culture medium of each group: the content of IL-1β and IL-18 in the cell culture medium of HG group and MNC+HG group was significantly higher than that of control group (P<0.05). The content of IL-1β and IL-18 in the cell culture medium of mimics+HG group was significantly lower than that of the HG group (P<0.05). (5) Correlation between miR-214 and caspase-1: miR-214 specifically binds to caspase-1 3 'UTR. Meanwhile, Western blot results showed that cleaved caspase-1 protein expression levels were significantly higher in both HG group and MNC+HG group than in control group (P<0.05). The levels of cleaved caspase-1 were significantly lower in mimics+HG group than in HG group (P<0.05). There was no significant difference in procaspase-1 expression among groups (P>0.05). (6) The expression levels of procaspase-1, cleaved caspase-1, ASC and NLRP3 in each group in rescue experiment: there was no significant difference in the expression of procaspase-1 in each group (P>0.05). Cleaved caspase-1, ASC and NLRP3 protein expressions were significantly lower in mimics+HG group than in HG group (P<0.05). However, cleaved caspase-1, ASC and NLRP3 protein expressions were significantly higher in mimics+HG+ Ad-caspase-1-EGFP group than in mimics+HG group (P<0.05). (7) The expression of IL-1β and IL-18 in rescue experiment: the secretions of IL-1β and IL-18 in the cell culture medium of the mimics+HG group were significantly lower than that of HG group (P<0.05), which were significantly higher in mimics+HG+Ad-caspase-1-EGFP group than in mimics+HG group (P<0.05). Conclusion: miR-214 can improve the hyperglycemia induced pyroptosis in H9c2 cells by targeted inhibition of the caspase-1.

Phenotyping diabetic cardiomyopathy in Europeans and South Asians

Background

The pathogenesis and cardiovascular impact of type 2 diabetes (T2D) may be different in South Asians compared with other ethnic groups. The phenotypic characterization of diabetic cardiomyopathy remains debated and little is known regarding differences in T2D-related cardiovascular remodeling across ethnicities. We aimed to characterize the differences in left ventricular (LV) diastolic and systolic function, LV structure, myocardial tissue characteristics and aortic stiffness between T2D patients and controls and to assess the differences in T2D-related cardiovascular remodeling between South Asians and Europeans.

Methods

T2D patients and controls of South Asian and European descent underwent 3 Tesla cardiovascular magnetic resonance imaging (CMR) and cardiac proton-magnetic resonance spectroscopy (¹H-MRS). Differences in cardiovascular parameters between T2D patients and controls were examined using ANCOVA and were reported as mean (95% CI). Ethnic group comparisons in the association of T2D with cardiovascular remodeling were made by adding the interaction term between ethnicity and diabetes status to the model.

Results

A total of 131 individuals were included (54 South Asians [50.1 ± 8.7 years, 33% men, 33 patients vs. 21 controls) and 77 Europeans (58.8 ± 7.0 years, 56% men, 48 patients vs. 29 controls)]. The ratio of the transmitral early and late peak filling rate (E/A) was lower in T2D patients compared with controls, in South Asians [− 0.20 (− 0.36; − 0.03), P = 0.021] and Europeans [− 0.20 (− 0.36; − 0.04), P = 0.017], whereas global longitudinal strain and aortic pulse wave velocity were similar. South Asian T2D patients had a higher LV mass [+ 22 g (15; 30), P < 0.001] (P for interaction by ethnicity = 0.005) with a lower extracellular volume fraction [− 1.9% (− 3.4; − 0.4), P = 0.013] (P for interaction = 0.114), whilst European T2D patients had a higher myocardial triglyceride content [+ 0.59% (0.35; 0.84), P = 0.001] (P for interaction = 0.002) than their control group.

Conclusions

Diabetic cardiomyopathy was characterized by impaired LV diastolic function in South Asians and Europeans. Increased LV mass was solely observed among South Asian T2D patients, whereas differences in myocardial triglyceride content between T2D patients and controls were only present in the European cohort. The diabetic cardiomyopathy phenotype may differ between subsets of T2D patients, for example across ethnicities, and tailored strategies for T2D management may be required.

[Therapeutic effect of combined use of FGF1-loaded nano-liposomes and ultrasound-targeted microbubble destruction technique on treating rats with experimental diabetic cardiomyopathy]

Objective: The therapeutic effect of acid fibroblast growth factor 1(FGF1) on rats with diabetic cardiomyopathy (DCM) was evaluated by using nano-liposomes combined with ultrasound-targeted microbubble destruction technique (UTMD). Methods: The FGF1-loaded nano-liposomes were prepared by water-in-water emulsion method combined with lyophilization technique.TypeⅠdiabetes model was induced by intraperitoneal injection of streptozotocin (STZ, 70 mg/kg) in 60 male SD rats.Sixteen weeks later, diabetic rats were randomly divided into: placebo group (saline treatment), FGF1 group, FGF1-loaded nano-liposomes group, and FGF1-loaded nano-liposomes plus UTMD group (n=15 each). After two weeks of intervention followed by 2 weeks intervention stop, all rats underwent cardiac catheterization, and the left ventricular end-systolic pressure (LVESP), left ventricular end-diastolic pressure (LVEDP) and the maximal increase/decrease rate of left ventricular pressure (LV±dp/dtmax) were measured.Then, the rats were sacrificed and myocardial tissue were obtained for Masson trichrome staining, TUNEL apoptotic staining and CD31 immunohistochemistry staining to quantify myocardial collagen fraction (CVF), cardiac myocyte apoptotic index and myocardial microvascular density (MVD). Results: (1)Scanning electron microscope results revealed good morphology and FGF1 encapsulation efficiency (84.3±2.8)% with high stability and dispensability of FGF1 loaded nano-liposomes.(2)The hemodynamic evaluation showed that LVESP, LV + dp/dt(max) and LV -dp/dt(max) were all significantly higher, while LVEDP was significantly lower in the FGF1-loaded nano-liposome+ UTMD group than in DCM group, FGF1 solution group, and FGF1 nano-liposome group(all P<0.05). (3)The Masson trichrome staining demonstrated that CVF was significantly higher in all DCM groups than in control group and was significantly lower in the FGF1-loaded nano-liposome+ UTMD group than in DCM group, FGF1 solution group, and FGF1 nano-liposome group (all P<0.05). (4)The CD31 immunohistochemical staining results showed that MVD was significantly lower in all DCM groups than in control group and was significantly higher in the FGF1-loaded nano-liposome+ UTMD group than in DCM group, FGF1 solution group, and FGF1 nano-liposome group (all P<0.05). (5)The TUNEL results showed that apoptotic index was significantly higher in all DCM groups than in control group and was significantly lower in the FGF1-loaded nano-liposome + UTMD group than in DCM group, FGF1 solution group, and FGF1 nano-liposome group (all P<0.05). Conclusion: FGF1 nano-liposomes combining with UTMD technique can significantly improve cardiac functions and attenuate myocardial CVF and apoptosis and enhance myocardial MVD in DCM rats.

Diabetes-Related Cardiac Dysfunction

The proposal that diabetes plays a role in the development of heart failure is supported by the increased risk associated with this disease, even after correcting for all other known risk factors. However, the precise mechanisms contributing to the condition referred to as diabetic cardiomyopathy have remained elusive, as does defining the disease itself. Decades of study have defined numerous potential factors that each contribute to disease susceptibility, progression, and severity. Many recent detailed reviews have been published on mechanisms involving insulin resistance, dysregulation of microRNAs, and increased reactive oxygen species, as well as causes including both modifiable and non-modifiable risk factors. As such, the focus of the current review is to highlight aspects of each of these topics and to provide specific examples of recent advances in each area.

Diabetic cardiomyopathy: where we are and where we are going

The global burden of diabetes mellitus and its related complications are currently increasing. Diabetes mellitus affects the heart through various mechanisms including microvascular impairment, metabolic disturbance, subcellular component abnormalities, cardiac autonomic dysfunction, and a maladaptive immune response. Eventually, diabetes mellitus can cause functional and structural changes in the myocardium without coronary artery disease, a disorder known as diabetic cardiomyopathy (DCM). There are many diagnostic tools and management options for DCM, although it is difficult to detect its development and effectively prevent its progression. In this review, we summarize the current research regarding the pathophysiology and pathogenesis of DCM. Moreover, we discuss emerging diagnostic evaluation methods and treatment strategies for DCM, which may help our understanding of its underlying mechanisms and facilitate the identification of possible new therapeutic targets.

Diabetic Cardiomyopathy; Summary of 41 Years

Patients with diabetes have an increased risk for development of cardiomyopathy, even in the absence of well known risk factors like coronary artery disease and hypertension. Diabetic cardiomyopathy was first recognized approximately four decades ago. To date, several pathophysiological mechanisms thought to be responsible for this new entity have also been recognized. In the presence of hyperglycemia, non-enzymatic glycosylation of several proteins, reactive oxygen species formation, and fibrosis lead to impairment of cardiac contractile functions. Impaired calcium handling, increased fatty acid oxidation, and increased neurohormonal activation also contribute to this process. Demonstration of left ventricular hypertrophy, early diastolic and late systolic dysfunction by sensitive techniques, help us to diagnose diabetic cardiomyopathy. Traditional treatment of heart failure is beneficial in diabetic cardiomyopathy, but specific strategies for prevention or treatment of cardiac dysfunction in diabetic patients has not been clarified yet. In this review we will discuss clinical and experimental studies focused on pathophysiology of diabetic cardiomyopathy, and summarize diagnostic and therapeutic approaches developed towards this entity.

Diabetic cardiomyopathy and its prevention by nrf2: current status

Diabetic cardiomyopathy (DCM), as one of the major cardiac complications in diabetic patients, is known to related with oxidative stress that is due to a severe imbalance between reactive oxygen species (ROS) and/or reactive nitrogen species (RNS) generation and their clearance by antioxidant defense systems. Transcription factor nuclear factor NF-E2-related factor 2 (Nrf2) plays an important role in maintaining the oxidative homeostasis by regulating multiple downstream antioxidants. Diabetes may up-regulate several antioxidants in the heart as a compensative mechanism at early stage, but at late stage, diabetes not only generates extra ROS and/or RNS but also impairs antioxidant capacity in the heart, including Nrf2. In an early study, we have established that Nrf2 protect the cardiac cells and heart from high level of glucose in vitro and hyperglycemia in vivo, and in the following study demonstrated the significant down-regulation of cardiac Nrf2 expression in diabetic animals and patients. Using Nrf2-KO mice or Nrf2 inducers, blooming evidence has indicated the important protection by Nrf2 from cardiac pathogenesis in the diabetes. Therefore, this brief review summarizes the status of studies on Nrf2's role in preventing DCM and even other complications, the need for new and safe Nrf2 inducer screening and the precaution for the undesirable side of Nrf2 under certain conditions.

A six-month exercise intervention in subclinical diabetic heart disease: effects on exercise capacity, autonomic and myocardial function

OBJECTIVE

Autonomic dysfunction may contribute to the etiology and exercise intolerance of subclinical diabetic heart disease. This study sought the efficacy of exercise training for improvement of peak oxygen uptake (VO₂(peak)) and cardiac autonomic function in type 2 diabetic patients with non-ischemic subclinical left-ventricular (LV) dysfunction.

MATERIALS/METHODS

Forty-nine type 2 diabetic patients with early diastolic tissue Doppler velocity >1 standard deviation below the age-based mean entered an exercise intervention (n=24) or usual care (n=25) for 6-months (controlled, pre-/post- design). Co-primary endpoints were treadmill VO₂(peak) and 5-min heart-rate variability (by the coefficient of variation of normal RR intervals [CVNN]). Autonomic function was additionally assessed by resting heart-rate (for sympathovagal balance estimation), baroreflex sensitivity, cardiac reflexes, and exercise/recovery heart-rate profiles. Echocardiography was performed for LV function (systolic/diastolic tissue velocities, myocardial deformation) and myocardial fibrosis (calibrated integrated backscatter).

RESULTS

VO₂(peak) increased by 11% during the exercise intervention (p=0.001 vs. -1% in controls), but CVNN did not change (p=0.23). Reduction of resting heart-rate in the intervention group (p<0.05) was associated with an improvement in the secondary endpoint of heart-rate variability total spectral power (p<0.05). However, baroreflex sensitivity, cardiac reflexes, and exercise/recovery heart-rate profiles showed no significant benefit. No effects on LV function were observed despite favorable reduction of calibrated integrated backscatter in the intervention group (p<0.05).

CONCLUSIONS

The exercise intolerance of subclinical diabetic heart disease was amenable to improvement by exercise training. Despite a reduction in resting heart-rate and potential attenuation of myocardial fibrosis, no other cardiac autonomic or LV functional adaptations were detected.

Subclinical diastolic dysfunction in young adults with Type 2 diabetes mellitus: a multiparametric contrast-enhanced cardiovascular magnetic resonance pilot study assessing potential mechanisms

AIMS

To assess the cardiac, vascular, anthropometric, and biochemical determinants of subclinical diastolic dysfunction in younger adults with Type 2 diabetes mellitus (T2DM) using multiparametric contrast-enhanced cardiovascular magnetic resonance (CMR) imaging.

METHODS AND RESULTS

Twenty adults <40 years with T2DM [mean age 31.8(6.6) years, T2DM duration 4.7(4.0) years] and 20 age and sex-matched controls [10 obese non-diabetic controls and 10 lean controls (LC)] were studied. Cardiac volumes and function, circumferential strain and peak early diastolic strain rate (PEDSR), myocardial perfusion reserve, aortic stiffness (distensibility, pulse-wave velocity), focal fibrosis on late gadolinium enhancement, and pre- and post-contrast T1 mapping for contrast agent partition coefficient (subset, n = 26) were determined by CMR. In the T2DM cohort, mean aortic distensibility correlated with PEDSR (r = 0.564, P = 0.023) and diabetes duration correlated inversely with PEDSR (r = -0.534, P = 0.015) on univariate analysis. There was a close association between PEDSR and peak systolic strain (r = -0.580, P = 0.007).

CONCLUSION

In young adults with T2DM, diabetes duration and aortic distensibility were associated with diastolic dysfunction. Interventional studies are required to assess whether cardiac dysfunction can be reversed in this phenotype of patients.

Evaluation of cardiac functions with tissue Doppler imaging in prediabetic subjects

Background and Objectives

The aim of the present study was to evaluate left ventricle systolic and diastolic function, using tissue Doppler echocardiography (TDE), in relation to blood glucose status in prediabetic patients who had no evidence of heart disease by conventional echocardiography (CE).

Subjects and Methods

We included 60 patients (30 female, 30 male) and 20 healthy controls (10 male, 10 female). All participants were randomised into four groups according to their oral glucose tolerance test. Group-I consisted of those patients who had only impaired fasting glucose (IFG). group-II consisted of patients who had only impaired glucose tolerance (IGT) and group-III consisted of patients who had both IFG and IGT, that is so-called combined glucose intolerance. Group-IV included the healthy controls. All subjects underwent both CE and TDE.

Results

No significant differences were found among the four groups in terms of CE. There was no significant difference between group-IV and group-I with respect to the early peak diastolic velocity (Ea) of medial mitral annulus (11.65±0.66 vs. 9.72±1.58, p>0.05), whereas a statistically significant difference was found between group-IV and group-II (11.65±0.66 vs. 9.06±1.07, p<0.001) and between group-IV and group-III (11.65±0.66 vs. 9.74±1.09, p<0.05).

Conclusion

Diastolic myocardial dysfunction in prediabetic patients may be identified by quantitative TDE before the appearance of CE indices of myocardial dysfunction.