Semaglutide attenuates pathological electrophysiological remodeling in diabetic cardiomyopathy via restoring Cx43 expression.

BACKGROUND: Semaglutide is a relatively new anti-hyperglycemic agent that was shown to carry cardioprotective potentials. However, the exact effects of semaglutide on diabetic cardiomyopathy (DCM) and their underlining mechanism remain unclear. This study aimed to evaluate the effects of semaglutide on myocardium injury and cardiac function in DCM mice and its potential mechanisms, with emphasis on its effects on Cx43 and electrophysiological remodeling. METHODS: C57BL/6 mice were randomly divided into four groups: control group, semaglutide group, diabetes group, and diabetes + semaglutide treatment group. Type 1 diabetes were induced by intraperitoneal injection of streptozotocin. Mice in the semaglutide intervention group were injected subcutaneously with semaglutide (0.15 mg/kg) every week for 8 weeks. The blood glucose, cardiac function, oxidative stress markers, apoptosis, expression of Sirt1, AMPK, Cx43, and electrocardiogram of mice in each group were evaluated. RESULTS: Treatment with semaglutide alleviated glucose metabolism disorders and improved cardiac dysfunction in diabetic mice. In addition, semaglutide ameliorated the increase in oxidative stress and apoptosis in diabetic heart. Sirt1/AMPK pathway was activated after semaglutide treatment. Furthermore, diabetic mice showed reduced expression of Cx43 in the myocardium, accompanied by changes in electrocardiogram, including significantly prolonged RR, QRS, QT and QTc interval. Semaglutide treatment restored Cx43 expression and reversed the above-mentioned ECG abnormalities. CONCLUSIONS: Our research results showed that semaglutide protected against oxidative stress and apoptosis in diabetic heart, thereby improving cardiac function and electrophysiological remodelling in DCM mice, which may attribute to activation of Sirt1/AMPK pathway and restore of Cx43 expression.

Systemic immune inflammation index and system inflammation response index are potential biomarkers of atrial fibrillation among the patients presenting with ischemic stroke.

BACKGROUND: Chronic inflammatory disorders in atrial fibrillation (AF) contribute to the onset of ischemic stroke. Systemic immune inflammation index (SIII) and system inflammation response index (SIRI) are the two novel and convenient measurements that are positively associated with body inflammation. However, little is known regarding the association between SIII/SIRI with the presence of AF among the patients with ischemic stroke. METHODS: A total of 526 ischemic stroke patients (173 with AF and 353 without AF) were consecutively enrolled in our study from January 2017 to June 2019. SIII and SIRI were measured in both groups. Logistic regression analysis was used to analyse the potential association between SIII/SIRI and the presence of AF. Finally, the correlation between hospitalization expenses, changes in the National Institutes of Health Stroke Scale (NIHSS) scores and SIII/SIRI values were measured. RESULTS: In patients with ischemic stroke, SIII and SIRI values were significantly higher in AF patients than in non-AF patients (all p < 0.001). Moreover, with increasing quartiles of SIII and SIRI in all patients, the proportion of patients with AF was higher than that of non-AF patients gradually. Logistic regression analyses demonstrated that log-transformed SIII and log-transformed SIRI were independently associated with the presence of AF in patients with ischemic stroke (log-transformed SIII: odds ratio [OR]: 1.047, 95% confidence interval CI = 0.322-1.105, p = 0.047; log-transformed SIRI: OR: 6.197, 95% CI = 2.196-17.484, p = 0.001). Finally, a positive correlation between hospitalization expenses, changes in the NIHSS scores and SIII/SIRI were found, which were more significant in patients with AF (all p < 0.05). CONCLUSIONS: Our study suggests SIII and SIRI are convenient and effective measurements for predicting the presence of AF in patients with ischemic stroke. Moreover, they were correlated with increased financial burden and poor short-term prognosis in AF patients presenting with ischemic stroke.

Impaired Left Atrial Performance Resulting From Age-Related Arial Fibrillation Is Associated With Increased Fibrosis Burden: Insights From a Clinical Study Combining With an in vivo Experiment.

Background: Atrial fibrillation (AF) is increasingly considered an age-related degenerative disease, whose process is associated with the development of impaired left atrial (LA) performance. However, the subtle dynamic changes of LA performance in AF during aging have yet to be fully elucidated. Atrial fibrosis is a key substrate for the development of AF, but the progression of fibrosis during aging and its relationship with LA dysfunction need to be further explored. Methods: A total of 132 control individuals and 117 persistent AF patients were prospectively studied. Subjects were further stratified into three age groups (age group 1: younger than 65 years, age group 2: between 65 and 79 years old, and age group 3: older than 80 years). The two-dimensional speckle tracking imaging was carried out for analyzing the alterations in LA function underlying LA remodeling, whereas electroanatomic mapping was performed to investigate LA fibrosis burden. In animal study, aged mice and young mice served as research subjects. Echocardiography and histological staining were used to assess LA performance and fibrosis burden, respectively. Results: Echocardiography showed progressive increases in LA dimension and LA stiffness index, and progressive decreases in LA global longitudinal strain and LA strain rates with advancing age in both AF and control cohorts, which was more prominent in AF cohort. Electroanatomic mapping showed progressive decrease in mean LA voltage and progressive increases in LA surface area, low-voltage area %, and LA volume with advancing age, whereas more significant alterations were observed in AF patients. Moreover, left atrial global longitudinal strain was positively correlated with mean LA voltage, whereas LA stiffness index was negatively related to mean LA voltage. In animal experiment, increased LA size and pulmonary artery dimension as well as longer P-wave duration and more prominent LA fibrosis were found in aged mice. Conclusions: This study provides new evidence of subtle changes in structure and performance of left atrium and their association with atrial fibrosis in both AF and non-AF subjects during physiological aging. In addition, our study also provides normal values for LA structure and performance in both AF and non-AF conditions during aging. These measurements may provide an early marker for onset of AF and LA adverse remodeling.

Glucose impairs angiogenesis and promotes ventricular remodelling following myocardial infarction via upregulation of microRNA-17.

Hyperglycaemia is known to impair angiogenesis, which may contribute to the poor prognosis of diabetic patients following myocardial infarction (MI). miR-17 has been reported to be involved in the proliferation, migration, and angiogenesis of a variety of vascular endothelial cells. However, how miR-17 regulates angiogenesis under hyperglycaemic conditions has not been reported. Thus, the aim of this study was to investigate the role of miR-17 in the impairment of angiogenesis induced by high glucose. In vitro, human umbilical vein endothelial cells (HUVECs) transfected with miR-17 mimics or inhibitors were incubated with normal-glucose or high-glucose (HG) medium. In vivo, miR-17 or negative control antagomirs were administered by tail vein injection in an MI model of streptozotocin (STZ)-induced diabetic mice. MiR-17 was upregulated, while VEGFA was downregulated in MI mice with diabetes and in HUVECs exposed to HG. The luciferase reporter gene assay confirmed that VEGFA is a target gene of miR-17. Moreover, inhibition of miR-17 prevented HG-induced VEGFA downregulation and impaired the capacity for migration and tube formation in HUVECs. Administration of miR-17 antagomirs significantly improved LV function and reduced infarct size in diabetic post-MI mice. Furthermore, the effects of diabetes-induced decreases in angiogenesis and VEGFA expression were abrogated by miR-17 antagomirs treatment in diabetic infarcted myocardium. These findings suggest that inhibition of miR-17 prevents HG-induced impairment of angiogenesis and improves cardiac function after MI by targeting VEGFA in diabetic mice.

Cardiac-Specific Overexpression of Silent Information Regulator 1 Protects Against Heart and Kidney Deterioration in Cardiorenal Syndrome via Inhibition of Endoplasmic Reticulum Stress.

BACKGROUND/AIMS: Increased endoplasmic reticulum (ER) stress contributes to development of cardiorenal syndrome (CRS), and Silent Information Regulator 1 (SIRT1), a class III histone deacetylase, may have protective effects on heart and renal disease, by reducing ER stress. We aimed to determine if SIRT1 alleviates CRS through ER stress reduction. METHODS: Wild type mice (n=37), mice with cardiac-specific SIRT1 knockout (n=29), or overexpression (n=29), and corresponding controls, were randomized into four groups: sham MI (myocardial infarction) +sham STNx (subtotal nephrectomy); MI+sham STNx; sham MI+STNx; and MI+STNx. To establish the CRS model, subtotal nephrectomy (5/6 nephrectomy, SNTx) and myocardial infarction (MI) (induced by ligation of the left anterior descending (LAD) coronary artery) were performed successively to establish CRS model. At week 8, the mice were sacrificed after sequential echocardiographic and hemodynamic studies, and then pathology and Western-blot analysis were performed. RESULTS: Neither MI nor STNx alone significantly influenced the other healthy organ. However, in MI groups, STNx led to more severe cardiac structural and functional deterioration, with increased remodeling, increased BNP levels, and decreased EF, Max +dp/dt, and Max -dp/dt values than in sham MI +STNx groups. Conversely, in STNx groups, MI led to renal structural and functional deterioration, with more severe morphologic changes, augmented desmin and decreased nephrin expression, and increased BUN, SCr and UCAR levels. In MI+STNx groups, SIRT1 knockout led to more severe cardiac structural and functional deterioration, with higher Masson-staining score and BNP levels, and lower EF, FS, Max +dp/dt, and Max -dp/dt values; while SIRT1 overexpression had the opposite attenuating effects. In kidney, SIRT1 knockout resulted in greater structural and functional deterioration, as evidenced by more severe morphologic changes, higher levels of UACR, BUN and SCr, and increased desmin and TGF-ß expression, while SIRT1 overexpression resulted in less severe morphologic changes and increased nephrin expression without significant influence on BUN or SCr levels. The SIRT1 knockout but not overexpression resulted in increased myocardial expression of CHOP and GRP78. Cardiac-specific SIRT1 knockout or overexpression resulted in increased or decreased renal expression of CHOP, Bax, and p53 respectively. CONCLUSIONS: Myocardial SIRT1 activation appears protective to both heart and kidney in CRS models, probably through modulation of ER stress.

Uric Acid Induces Cardiomyocyte Apoptosis via Activation of Calpain-1 and Endoplasmic Reticulum Stress.

BACKGROUND/AIMS: Hyperuricemia is associated with an increased risk for multiple cardiovascular diseases, but the underlying mechanisms remain largely elusive. Calpain-1 is a protease that is implicated in several pathological conditions that affect the heart. The aim of this current study was to test the effects of uric acid (UA) on cardiomyocyte survival and cardiac function and to investigate the role of calpain-1 in the UA-induced effects in the heart and their underlying mechanisms. METHODS: In vivo, hyperuricemia was induced by oxonic acid (OA) administration in Sprague-Dawley rats for 16 weeks; TUNEL staining was used to identify apoptotic cells. Left ventricular (LV) sections were stained with Sirius Red to evaluate interstitial fibrosis. Cardiac catheterization was performed to evaluate cardiac function. In vitro, cultured H9c2 cells were incubated with different UA concentrations. MTT assays and flow cytometry were used to evaluate cell viability and apoptosis. All related gene expression levels were analyzed by quantitative real-time PCR (qRT-PCR), and all protein expression levels were analyzed by western blotting. RESULTS: Hyperuricemia induction in vivo resulted in cellular apoptosis, interstitial fibrosis and diastolic dysfunction in the rat hearts, as well as increased activation of calpain-1 and endoplasmic reticulum (ER) stress, while allopurinol treatment mitigated the above changes. UA administration in vitro increased apoptosis and decreased H9c2 cell viability in a dose-dependent manner. Increased activation of calpain-1 and ER stress was also observed in the groups with high UA levels. Calpain-1 siRNA and the calpain inhibitor CI-III alleviated UA-induced ER stress and apoptosis, while inhibiting ER stress by tauroursodeoxycholic acid (TUDCA) mitigated UA-induced apoptosis without affecting calpain-1 expression or activity. CONCLUSIONS: These findings suggest that UA induces cardiomyocyte apoptosis through activation of calpain-1 and ER stress. These results may provide new insights into the mechanisms of hyperuricemia-associated cardiovascular risks and hopefully identify new treatment targets.

Insulin upregulates GRIM-19 and protects cardiac mitochondrial morphology in type 1 diabetic rats partly through PI3K/AKT signaling pathway.

Insulin is involved in the development of diabetic heart disease and is important in the activities of mitochondrial complex I. However, the effect of insulin on cardiac mitochondrial nicotinamide adenine dinucleotide dehydrogenase (ubiquinone) 1 subunit of retinoic-interferon-induced mortality 19 (GRIM-19) has not been characterized. The aim of this study was to investigate the effect of insulin on the mitochondrial GRIM-19 in the hearts of rats with streptozotocin (STZ)-induced type 1 diabetes. Protein changes of GRIM-19 were evaluated by western blotting and reverse transcription-quantitative polymerase chain reaction. Furthermore, the effects of insulin on mitochondrial complex I were detected in HeLa cells and H9C2 cardiac myocytes. During the development of diabetic heart disease, the cardiac function did not change within the 8 weeks, but the mitochondrial morphology was altered. The hearts from the rats with STZ-induced diabetes exhibited reduced expression of GRIM-19. Prior to the overt cardiac dilatation, mitochondrial alterations were already present. Following subcutaneous insulin injection, it was demonstrated that GRIM-19 protein was altered, as well as the mitochondrial morphology. The phosphoinositide 3-kinase inhibitor LY294002 had an effect on insulin signaling in H9C2 cardiacmyocytes, and decreased the level of GRIM-19 by half compared with that in the insulin group. The results indicate that insulin is essential for the control of cardiac mitochondrial morphology and the GRIM-19 expression partly via PI3K/AKT signaling pathways.

Intermedin1­53 enhances angiogenesis and attenuates adverse remodeling following myocardial infarction by activating AMP­activated protein kinase.

Adverse ventricular remodeling is a maladaptive response to acute loss of myocardium and an important risk factor for heart failure following myocardial infarction (MI). Intermedin (IMD) is a novel member of the calcitonin/calcitonin gene­related peptide family, which may possess potent cardioprotective properties. The aim of the present study was to determine whether IMD1­53, a mature bioactive form of IMD, may promote therapeutic angiogenesis within the infarcted myocardium, therefore attenuating adverse ventricular remodeling post­MI. The present study observed that treatment with IMD1­53 promoted proliferation, migration and tube formation of primary cultured myocardial microvascular endothelial cells (MMVECs). In a rat model of MI, chronic administration of IMD1­53 increased capillary density in the peri­infarct zone, attenuated ventricular remodeling and improved cardiac performance post­MI. Treatment with IMD1­53 also significantly increased the expression levels of phosphorylated­AMP­activated protein kinase (AMPK) and the subsequent activation of endothelial nitric oxide synthase in MMVECs and post­MI rat myocardium, without a significant influence on the expression of vascular endothelial growth factor. Notably, the in vitro effects of IMD1­53 on angiogenesis and the in vivo effects of IMD1­53 on post­MI ventricular remodeling were largely abrogated by the co­administration of compound C, an AMPK inhibitor. In conclusion, the present study demonstrated that IMD1­53 could attenuate adverse ventricular remodeling post­MI via the promotion of therapeutic angiogenesis, possibly through the activation of AMPK signaling.

Combination of remote ischemic perconditioning and remote ischemic postconditioning fails to increase protection against myocardial ischemia/reperfusion injury, compared with either alone.

Remote ischemic perconditioning (RIPerC) and remote ischemic postconditioning (RIPostC) have been previously demonstrated to protect the myocardium against ischemia/reperfusion (IR) injury. However, their combined effects remain to be fully elucidated. In order to investigate this, the present study used an in vivo rat model to assess whether synergistic effects are produced when RIPerC is combined with RIPostC. The rats were randomly assigned to the following groups: Sham, IR, RIPerC, RIPostC and RIPerC + RIPostC groups. The IR model was established by performing 40 min of left coronary artery occlusion, followed by 2 h of reperfusion. RIPerC and RIPostC were induced via four cycles of 5 min occlusion and 5 min reperfusion of the hindlimbs, either during or subsequent to myocardial ischemia. On measurement of infarct sizes, compared with the IR group (49.45±6.59%), the infarct sizes were significantly reduced in the RIPerC (34.36±5.87%) and RIPostC (36.04±6.16%) groups (P<0.05). However, no further reduction in infarct size was observed in the RIPerC + RIPostC group (31.43±5.43%; P>0.05), compared with the groups treated with either RIPerC or RIPostC alone. Activation of the reperfusion injury salvage kinase (RISK) Akt, extracellular signal­regulated kinase 1/2 and glycogen synthase kinase­3ß, and survivor activating factor enhancement (SAFE) signal transducer and activator of transcription­3 pathways were enhanced in the RIPerC, RIPostC and the RIPerC + RIPostC groups, compared with the IR group, with no difference among the three groups. Therefore, whereas RIPerC and RIPostC were equally effective in providing protection against myocardial IR injury, the combination of RIPerC and RIPostC failed to provide further protection than treatment with either alone. The cardioprotective effects were found to be associated with increased activation of the RISK and SAFE pathways.

Apelin-13 stimulates angiogenesis by promoting cross­talk between AMP-activated protein kinase and Akt signaling in myocardial microvascular endothelial cells.

Currently, there is major interest in the functions of apelin-13, an endogenous ligand for the orphan G-protein coupled receptor APJ, a receptor that closely resembles the angiotensin receptor AT1. In the present study, the role of apelin-13 in angiogenesis and its mechanism as a novel angiogenic factor in myocardial microvascular endothelial cells (MMVECs) was investigated. It was revealed that apelin-13 can promote proliferation, migration and tube formation in MMVECs. In addition, apelin-13 dose dependently stimulated the phosphorylation of AMP-activated protein kinase (AMPK) and endothelial nitric oxide synthase (eNOS) at Thr-172 and Ser-1179, respectively. The treatment with the AMPK (compound C) and protein kinase Akt/protein kinase B (Akt; LY294002) inhibitor significantly suppressed the apelin­13-induced AMPK, Akt and eNOS phosphorylation. They also inhibited the apelin13­stimulated endothelial cell migration and tube formation. Therefore, we hypothesize that apelin-13 promotes angiogenesis through the modulation of AMPK and Akt signaling in MMVECs.

Naturally and externally pulsed electrospray.

The current studies on pulsation phenomena in electrospray ionization, and pulsed electrospray ionization (ESI) under external electrical control are reviewed. A number of investigations have shown that two types of pulsation processes exist: low-frequency fluctuation and high-frequency droplet-formation. The low-frequency pulsation is induced by an imbalance between the flow rate of the input sample to the Taylor cone and the feed rate of the output solution to the liquid filament. The high-frequency pulsation mainly results from the initial droplet formation process, and is modulated by the low-frequency pulsation. The fundamental and experimental sections of these two pulsations are discussed. Experimental results also show that low and high pulsations can both be controlled electrically to create a pulsed ESI so that high sensitivity and an enhanced S/N ratio can be achieved. However, the co-ordination of the synchronization between a natural pulsation and a pulsed ESI, as well as its application to mass spectrometer (MS) analysis, demands further research.