Non-diabetic Hearts Research Articles

Time dependent deterioration of mitochondrial oxidative capacity in heart transplantat recipients with type 2 diabetes mellitus

Abstract Background Diabetic cardiomyopathy is defined as Heart failure in patients with Type 2 Diabetes (T2DM) in absence of traditional risk factors. Following HTX, a substantial number of recipients develop insulin resistance or T2DM, associated with cardiac allograft vasculopathy and with increased mortality. Recently we have shown that endomyocardial biopsies of heart transplant (HTX) recipients with T2DM express reduced mitochondrial respiration. Purpose The current study analyses time depended impact of T2DM on myocardial mitochondrial respiration of a priorly non-diabetic heart. We hypothesized that myocardial mitochondrial oxidative phosphorylation capacity declines in patients with T2DM compared to glucose tolerant heart transplant recipients and that reduced mitochondrial respiration leads to impairment of cardiac function. Methods We included 101 HTX recipients who underwent routine endomyocardial biopsy. Patients with T1DM or a Donor with DM were excluded. Patients were classified according to criteria of the American Diabetes Association as non-diabetic (n=23), prediabetic (n=38) or T2DM (n=40), by either Fasting Plasma Glucose, 2h Plasma Glucose, HbA1c or intake of antidiabetic medication. We performed ex vivo high resolution respirometry on permeabilized fibres to assess myocardial mitochondrial respiration. Left ventricular ejection fraction (LV-EF) was assessed by cardiac-MRI or Echocardiography. Results Groups were of comparable age (p=0.06), sex (p=0.25) and time since HTX (p=0.91). Mean time since HTX was 29 months. Current rejection episodes (p=0.37) or corticoid pulse therapy (p=0.46) did not significantly differ between groups. Linear regression in T2DM patients revealed an inverse relationship between time since HTX and mitochondrial respiration at state III conditions supported by the substrates octanoyl-carnitine and ADP (R2=0.16, F(1,38)=6.97, p=0.01). Regression analyses for non-DM group and Prediabetes group revealed no significant relationship between time since HTX and mitochondrial function (non-DM: R2=0.04, F(1,21)=0.9, p=0.35; Prediabetes: R2=0.01, F(1,36)=0.27, p=0.61). Exclusion of patients with cellular allograft rejection (ISHLT ≥1) or of patients with recent corticoid pulse therapy did not alter these results. Linear correlation revealed a significant relationship (r=0.33, p=0.04) between declining mitochondrial state III respiration and left ventricular ejection fraction (n=39), suggesting associated functional consequences. Conclusions Our results suggest a T2DM associated decline of mitochondrial oxidative capacity in HTX recipients. Reduced mitochondrial respiration is associated to lower LV-EF. Targeting mitochondrial respiration might be a promising novel therapeutic approach to address T2DM associated mortality. Funding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Research Counsil

Sodium-glucose co-transporter-2 inhibitors in the non-diabetic heart failure patient.

Heart failure (HF) with reduced ejection fraction (HFrEF) is a global cause of morbidity and mortality with over 60 million estimated cases worldwide. The burden of HF care is expected to increase with an ageing population as evidenced by the fact that 80% of HF-related hospitalizations occur in those aged above 65. Given the significant morbidity and mortality associated with HFrEF, there is a need for new prognostic therapies that have an impact on morbidity and mortality. In February of 2021, the National institute for Health and Care Excellence (NICE) released new guidance on the utility of Dapagliflozin for the management of heart failure with reduced ejection fraction (HFrEF). NICE advocated that dapagliflozin is a viable treatment option in symptomatic HFrEF patients on optimal medical management. The current list price of dapagliflozin is around £36.59 per 28-tablet pack with an estimated annual cost of £476.98 equating to £6939 per quality-adjusted life year. The guidance was mainly based on evidence produced from the 2019 DAPA-HF trial. This demonstrated that in HFrEF population, the use of dapagliflozin led to a significant reduction in worsening HF events, cardiovascular, and all-cause death. In this article, we summarize the evidence base for sodium-glucose co-transporter-2 inhibitors in the non-diabetic heart failure patient.

Sodium-Glucose Cotransporter-2 Inhibitor–Associated Euglycemic Diabetic Ketoacidosis After Orthotopic Heart Transplant in a Prediabetic Patient: A Case Report

Postoperative euglycemic diabetic ketoacidosis (euDKA) associated with sodium-glucose cotransporter-2 (SGLT2) inhibitor use has been well-documented and carries a Food and Drug Administration recommendation to hold SGLT2 inhibitors 3 to 4 days before a planned surgical procedure. Unfortunately, many surgical procedures, such as orthotopic heart transplant (OHT), are unplanned and unpredictable. With the increasing use of SGLT2 inhibitors in diabetic and non-diabetic heart failure patients, new challenges in patient management and perioperative risk have arisen. We report a case in which SGLT2 inhibitor-associated euDKA complicated the postoperative course of a prediabetic patient who had undergone OHT.

Abstract P405: Cardioprotective Actions Of Nitroxyl Donor Angeli's Salt Are Preserved In The Diabetic Heart And Vasculature In The Face Of Nitric Oxide Resistance

Introduction: The risk of fatal cardiovascular events is increased in patients with type 2 diabetes mellitus (T2DM). A major contributor to poor prognosis is impaired nitric oxide (NO•) signalling at the level of tissue responsiveness, termed NO• resistance. Nitroxyl (HNO) induces positive inotropic and lusitropic effects in healthy and failing hearts. Hypothesis: We hypothesised that in a rodent model, T2DM will promote, and HNO will circumvent, NO• resistance in the myocardium and coronary vasculature. Methods: At 8 weeks of age, male Sprague-Dawley rats commenced a high-fat diet. After two weeks, the rats received low-dose streptozotocin (two intraperitoneal injections, 35 mg/kg, over two consecutive days), and continued the diet. Twelve weeks later, hearts were Langendorff-perfused to assess responses to the NO• donor diethylamine NONOate (DEA/NO) and the HNO donor Angeli’s salt. Results: Inotropic, lusitropic and coronary vasodilator responses to DEA/NO were impaired, and responses to Angeli’s salt were preserved or enhanced, in T2DM hearts compared with non-diabetic hearts. Conclusions: This is the first evidence that inotropic and lusitropic responses are preserved, and NO• resistance in the coronary vasculature is circumvented, by the HNO donor Angeli’s salt in T2DM. These findings highlight the cardiovascular therapeutic potential of HNO donors, especially in cardiac emergencies such as acute ischaemia or heart failure. Figure 1. Dose-response curves and maximal responses to DEA/NO or Angeli's salt in diabetic or non-diabetic hearts. (A-C) LV+dP/dt, (D-F) LV-dP/dt and (G-I) coronary flow rate. Data expressed as change from baseline (denoted by Δ), mean ± SEM. Data analysed by two-way RM ANOVA with Sidak's post-hoc test. *P<0.05 vs. non-diabetic. LV, left ventricular; LV+dP/dt, maximal rate of rise in LV pressure; LV-dP/dt, maximal rate of fall in LV pressure.

Overview of Sodium-Glucose Co-transporter 2 (SGLT2) Inhibitors for the Treatment of Non-diabetic Heart Failure Patients.

Heart failure (HF) is a clinical syndrome that results from any structural or functional impairment of ventricular filling or ejection of blood, and results in low life quality and expectancy, creating a significant burden on the healthcare system. The pharmacological HF management has remained unchanged for a decade, however, several randomized clinical trials have demonstrated the potential clinical benefits of sodium-glucose cotransporter-2 inhibitors, an antidiabetic agent, by reducing the rate of hospitalizations for HF, cardiovascular death, and all-cause death. The cardioprotective effects are characterized by reduction of inflammatory, metabolic and ionic dyshomeostasis despite the diabetic status. Since the United States Food and Drug Administration (FDA) approval in May 2020, SGLT2 inhibitors have been used mostly in heart failure with reduced ejection fraction (HFrEF). In this review article, we provide a comprehensive overview of the potential benefits, effectiveness, and safety profile of SGLT2 inhibitors used in HF patients with no history of diabetes mellitus.

Quality and utility of [123I]I-metaiodobenzylguanidine cardiac SPECT imaging in nondiabetic postinfarction heart failure patients qualified for implantable cardioverter defibrillator

ObjectiveImpaired cardiac adrenergic activity has been demonstrated in heart failure (HF) and in diabetes mellitus (DM). [123I]I-metaiodobenzylguanidine (MIBG) enables assessment of the cardiac adrenergic nervous system. Tomographic imaging of the heart is expected to be superior to planar imaging. This study aimed to determine the quality and utility of MIBG SPECT in the assessment of cardiac innervation in postinfarction HF patients without DM, qualified for implantable cardioverter defibrillator (ICD) in primary prevention of sudden cardiac death.MethodsConsecutive patients receiving an ICD on the basis of contemporary guidelines were prospectively included. Planar MIBG studies were followed by SPECT. The essential analysis was based on visual assessment of the quality of SPECT images (“high”, “low” or “unacceptable”). The variables used in the further analysis were late summed defect score for SPECT images and heart-to-mediastinum rate for planar images. MIBG images were assessed independently by two experienced readers.ResultsFifty postinfarction nondiabetic HF subjects were enrolled. In 13 patients (26%), the assessment of SPECT studies was impossible. In addition, in 13 of 37 patients who underwent semiquantitative SPECT evaluation, the assessment was equivocal. Altogether, in 26/50 patients (52%, 95% confidence interval 38–65%), the quality of SPECT images was unacceptable or low and was limited by low MIBG cardiac uptake and by comparatively high, interfering MIBG uptake in the neighboring structures (primarily, in the lungs).ConclusionsThe utility of MIBG SPECT imaging, at least with conventional imaging protocols, in the qualification of postinfarction HF patients for ICD, is limited. In approximately half of the postinfarction HF patients, SPECT assessment of cardiac innervation can be impossible or equivocal, even without additional damage from diabetic cardiac neuropathy. The criteria predisposing the patient to good-quality MIBG SPECT are: high values of LVEF from the range characterizing the patients qualified to ICD (i.e., close to 35%) and left lung uptake intensity in planar images comparable to or lower than heart uptake.

Expression of the SARS-CoV-2 receptorACE2 in human heart is associated with uncontrolled diabetes, obesity, and activation of the renin angiotensin system

BackgroundDiabetic and obese patients are at higher risk of severe disease and cardiac injury in corona virus 2 (SARS-CoV-2) infections. Cellular entry of SARS-CoV-2 is mainly via the angiotensin-converting enzyme 2 (ACE2) receptor, which is highly expressed in normal hearts. There is a disagreement regarding the effect of factors such as obesity and diabetes on ACE2 expression in the human heart and whether treatment with renin–angiotensin system inhibitors or anti-diabetic medications increases ACE2 expression and subsequently the susceptibility to infection. We designed this study to elucidate factors that control ACE2 expression in human serum, human heart biopsies, and mice.MethodsRight atrial appendage biopsies were collected from 79 patients that underwent coronary artery bypass graft (CABG) surgery. We investigated the alteration in ACE2 mRNA and protein expression in heart tissue and serum. ACE2 expression was compared with clinical risk factors: diabetes, obesity and different anti-hypertensive or anti-diabetic therapies. WT or db/db mice were infused with Angiotensin II (ATII), treated with different anti-diabetic drugs (Metformin, GLP1A and SGLT2i) were also tested.ResultsACE2 gene expression was increased in diabetic hearts compared to non-diabetic hearts and was positively correlated with glycosylated hemoglobin (HbA1c), body mass index (BMI), and activation of the renin angiotensin system (RAS), and negatively correlated with ejection fraction. ACE2 was not differentially expressed in patients who were on angiotensin converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) prior to the operation. We found no correlation between plasma free ACE2 and cardiac tissue ACE2 expression. Transmembrane serine protease 2 (TMPRSS2), metalloprotease ADAM10 and ADAM17 that facilitate viral-ACE2 complex entry and degradation were increased in diabetic hearts. ACE2 expression in mice was increased with ATII infusion and attenuated following anti-diabetic drugs treatment.ConclusionPatients with uncontrolled diabetes or obesity with RAS activation have higher ACE2 expressions therefore are at higher risk for severe infection. Since ACEi or ARBs show no effect on ACE2 expression in the heart further support their safety.

Should SGLT2i be used prior to transcatheter edge-to-edge repair for secondary mitral regurgitation?

Should SGLT2i be used prior to transcatheter edge-to-edge repair for secondary mitral regurgitation?

Aldose Reductase: An Emerging Target for Development of Interventions for Diabetic Cardiovascular Complications.

Diabetes is a leading cause of cardiovascular morbidity and mortality. Despite numerous treatments for cardiovascular disease (CVD), for patients with diabetes, these therapies provide less benefit for protection from CVD. These considerations spur the concept that diabetes-specific, disease-modifying therapies are essential to identify especially as the diabetes epidemic continues to expand. In this context, high levels of blood glucose stimulate the flux via aldose reductase (AR) pathway leading to metabolic and signaling changes in cells of the cardiovascular system. In animal models flux via AR in hearts is increased by diabetes and ischemia and its inhibition protects diabetic and non-diabetic hearts from ischemia-reperfusion injury. In mouse models of diabetic atherosclerosis, human AR expression accelerates progression and impairs regression of atherosclerotic plaques. Genetic studies have revealed that single nucleotide polymorphisms (SNPs) of the ALD2 (human AR gene) is associated with diabetic complications, including cardiorenal complications. This Review presents current knowledge regarding the roles for AR in the causes and consequences of diabetic cardiovascular disease and the status of AR inhibitors in clinical trials. Studies from both human subjects and animal models are presented to highlight the breadth of evidence linking AR to the cardiovascular consequences of diabetes.

Remote liver ischemic preconditioning attenuates myocardial ischemia/reperfusion injury in streptozotocin-induced diabetic rats

Diabetes mellitus (DM) exhibits a higher sensitivity to myocardial ischemia/reperfusion (I/R) injury and may compromise the effectiveness of cardioprotective interventions, including ischemic preconditioning. We previously found that liver ischemic preconditioning (RLIPC) could limit infarct size post I/R in non-diabetic rat hearts and further exerted anti-arrhythmic effects in diabetic or non-diabetic rats after myocardial I/R, however, little is known regarding the effect of RLIPC on infarct-sparing in diabetic hearts. In this study, we evaluated the protective effects of RLIPC on I/R injury in streptozotocin-induced type 1 diabetic rats. Type 1 diabetes mellitus was induced by one-time intraperitoneal injection of streptozotocin in Sprague–Dawley rats. Rats were exposed to 45 min of left anterior descend in (LAD) coronary artery occlusion, followed by 3 h of reperfusion. For liver ischemic preconditioning, four cycles of 5 min of liver I/R stimuli were performed before LAD occlusion. The cardioprotective effect of RLIPC was determined in diabetic rats. Compared to non-RLIPC treated DM rats, RLIPC treatment significantly reduced infarct size and cardiac tissue damage, inhibited apoptosis in diabetic hearts post I/R. RLIPC also improved cardiac functions including LVESP, LVEDP, dp/dtmax, and − dp/dtmax. In addition, RLIPC preserved cardiac morphology by reducing the pathological score post I/R in diabetic hearts. Finally, Westernblotting showed that RLIPC stimulated phosphorylation of ventricular GSK-3β and STAT-5, which are key components of RISK and SAFE signaling pathways. Our study showed that liver ischemic preconditioning retains strong cardioprotective properties in diabetic hearts against myocardial I/R injury via GSK-3β/STAT5 signaling pathway.

Effect of transient elevation of glucose on contractile properties in non-diabetic rat cardiac muscle.

In non-diabetic patients with severe disease, such as acute myocardial infarction or acute heart failure, admission blood glucose level is associated with their short-term and long-term mortality. We examined whether transient elevation of glucose affects contractile properties in non-diabetic hearts. Force, intracellular Ca2+ ([Ca2+]i), and sarcomere length were measured in trabeculae from rat hearts. To assess contractile properties, maximum velocity of contraction (Max dF/dt) and minimum velocity of relaxation (Min dF/dt) were calculated. The ratio of phosphorylated troponin I (P-TnI) to troponin I (TnI) was measured. One hour after elevation of glucose from 150 to 400mg/dL, developed force, Max dF/dt, and Min dF/dt were reduced without changes in [Ca2+]i transients at 2.5Hz stimulation and 2.0mM [Ca2+]o,while developed force and [Ca2+]i transients showed no changes at 0.5Hz stimulation and 0.7mM [Ca2+]o. In the presence of 1μM KN-93, a Ca2+/calmodulin-dependent protein kinaseII (CaMKII) inhibitor, or 50μM diazo-5-oxonorleucine, a L-glutamine-D-fructose-6-phosphate amidotransferase inhibitor, the reduction of contractile properties after elevation of glucose was suppressed. Furthermore, 1 h after elevation of glucose to 400mg/dL at 2.0mM [Ca2+]o, the ratio of P-TnI to TnI was increased. These results suggest that in non-diabetic hearts under higher Ca2+-load, transient elevation of glucose for 1 h reduces contractile properties probably by activating CaMKII through O-GlcNAcylation. Thus, in the patients with severe disease, transient elevation of blood glucose, such as due to stress, may worsen cardiac function and thereby affect their mortality without known diabetes.

Abstract 15671: Adipocyte-derived Exosomal Lncrna Nbr2 Promotes Diabetic Myocardial Fibrosis Through Regulating the Ikba/nf-kb Pathway

Introduction: The activation of NF-κB is the dominant process that correlates with the pathogenesis of diabetic cardiomyopathy (DCM). Recently, accumulating evidence shows that long noncoding RNAs (lncRNAs) play crucial roles in sustaining the NF-κB pathway. However, the underlying mechanisms remain unclear. In this study, we identified the upregulated expressed lncRNA NBR2 in adipocyte-derived exosomes (AdEXO) and investigated its regulatory role in diabetic myocardial fibrosis. Hypothesis: We hypothesized that AdEXO-NBR2 promotes diabetic myocardial fibrosis through regulating the IκBα/NF-κB pathway. Methods: We examined the effect of exosomes from diabetic (db/db) mice-derived adipocytes on ANG-II-induced cardiac fibrosis and function in non-diabetic (C57BL/6J mice). In the invitro study, HG (33mmol/L)-stimulated AdEXO were cultured with adult human cardiac fibroblasts (aHCFs). Differentially expressed lncRNAs in AdEXO were screened using lncRNA sequencing. Results: Intramyocardial injection of diabetic AdEXO in the non-diabetic heart significantly exacerbated myocardial fibrosis, as evidenced by poorer cardiac function and enhancer collagen deposition. Whereas administration of a exosomes biogenesis inhibitor mitigated cardiac fibrosis in diabetic mice. We found lncRNA-NBR2 is a common molecule significantly increased in diabetic AdEXO and HG-stimulated non-diabetic AdEXO. After four weeks of ANG II infusion, EXO-db/dbWT-injected mice displayed fibrosis in the heart. However, interestingly, mice receiving NBR2-deficient db/db-EXO showed a decrease in cardiac fibrosis. Similarly, AdEXO-NBR2 promoted aHCFs proliferation and transformation capabilities in vitro. Mechanistically, NBR2 was loaded to AdEXO by directly interacting with heterogeneous nuclear ribonucleoprotein K (hnRNPK). Subsequently, AdEXO-NBR2 was internalized by aHCFs and epigenetically downregulated IκBα expression by recruitment of hnRNPK/SETDB1 and increasing the H3K9 trimethylation level in the IκBα promoter, ultimately activating the NF-κB pathway. Conclusions: Our findings highlight a novel epigenetic mechanism of AdEXO lncRNA-mediated diabetic cardiac fibrosis and identify NBR2 as a therapeutic target of DCM.

Empagliflozin Ameliorates Diastolic Dysfunction and Left Ventricular Fibrosis/Stiffness in Nondiabetic Heart Failure: A Multimodality Study

ObjectivesThe purpose of this study was to investigate the effect of empagliflozin on diastolic function in a nondiabetic heart failure with reduced ejection fraction (HFrEF) scenario and on the pathways causing diastolic dysfunction. BackgroundThis group demonstrated that empagliflozin ameliorates adverse cardiac remodeling, enhances myocardial energetics, and improves left ventricular systolic function in a nondiabetic porcine model of HF. Whether empagliflozin also improves diastolic function remains unknown. Hypothetically, empagliflozin would improve diastolic function in HF mediated both by a reduction in interstitial myocardial fibrosis and an improvement in cardiomyocyte stiffness (titin phosphorylation). MethodsHF was induced in nondiabetic pigs by 2-h balloon occlusion of proximal left anterior descending artery. Animals were randomized to empagliflozin or placebo for 2 months. Cardiac function was evaluated with cardiac magnetic resonance (CMR), 3-dimensional echocardiography, and invasive hemodynamics. In vitro relaxation of cardiomyocytes was studied in primary culture. Myocardial samples were obtained for histological and molecular evaluation. Myocardial metabolite consumption was analyzed by simultaneous blood sampling from coronary artery and coronary sinus. ResultsDespite similar initial ischemic myocardial injury, the empagliflozin group showed significantly improved diastolic function at 2 months, assessed by conventional echocardiography (higher e′ and color M-mode propagation velocity, lower E/e′ ratio, myocardial performance Tei index, isovolumic relaxation time, and left atrial size), echocardiography-derived strain imaging (strain imaging diastolic index, strain rate at isovolumic relaxation time and during early diastole, and untwisting), and CMR (higher peak filling rate, larger first filling volume). Invasive hemodynamics confirmed improved diastolic function with empagliflozin (better peak LV pressure rate of decay (–dP/dt), shorter Tau, lower end-diastolic pressure-volume relationship (EDPVR), and reduced filling pressures). Empagliflozin reduced interstitial myocardial fibrosis at the imaging, histological and molecular level. Empagliflozin improved nitric oxide signaling (endothelial nitric oxide synthetase [eNOS] activity, nitric oxide [NO] availability, cyclic guanosine monophosphate (cGMP) content, protein kinase G [PKG] signaling) and enhanced titin phosphorylation (which is responsible for cardiomyocyte stiffness). Indeed, isolated cardiomyocytes exhibited better relaxation in empagliflozin-treated animals. Myocardial consumption of glucose and ketone bodies negatively and positively correlated with diastolic function, respectively. ConclusionsEmpagliflozin ameliorates diastolic function in a nondiabetic HF porcine model, mitigates histological and molecular remodeling, and reduces both left ventricle and cardiomyocyte stiffness.

Cardioprotective effect of succinate dehydrogenase inhibition in rat hearts and human myocardium with and without diabetes mellitus

Ischemia reperfusion (IR) injury may be attenuated through succinate dehydrogenase (SDH) inhibition by dimethyl malonate (DiMAL). Whether SDH inhibition yields protection in diabetic individuals and translates into human cardiac tissue remain unknown. In isolated perfused hearts from 24 weeks old male Zucker diabetic fatty (ZDF) and age matched non-diabetic control rats and atrial trabeculae from patients with and without diabetes, we compared infarct size, contractile force recovery and mitochondrial function. The cardioprotective effect of a 10 minutes DiMAL administration prior to global ischemia and ischemic preconditioning (IPC) was evaluated. In non-diabetic hearts exposed to IR, DiMAL 0.1 mM reduced infarct size compared to IR (55 ± 7% vs. 69 ± 6%, p < 0.05). Mitochondrial respiration was reduced by DiMAL 0.6 mM compared to sham and DiMAL 0.1 mM (p < 0.05). In diabetic hearts an increased concentration of DiMAL (0.6 mM) was required for protection compared to IR (64 ± 13% vs. 79 ± 8%, p < 0.05). Mitochondrial function remained unchanged. In trabeculae from humans without diabetes, IPC and DiMAL improved contractile force recovery compared to IR (43 ± 12% and 43 ± 13% vs. 23 ± 13%, p < 0.05) but in patients with diabetes only IPC provided protection compared to IR (51 ± 15% vs. 21 ± 8%, p < 0.05). Neither IPC nor DiMAL modulated mitochondrial respiration in patients. Cardioprotection by SDH inhibition is possible in human tissue, but depends on diabetes status. The narrow therapeutic range and discrepancy in respiration between experimental and human studies may limit clinical translation.

Nanotoxicology of Dendrimers in the Mammalian Heart: ex vivo and in vivo Administration of G6 PAMAM Nanoparticles Impairs Recovery of Cardiac Function Following Ischemia-Reperfusion Injury.

AimThe effects of polyamidoamine (PAMAM) dendrimers on the mammalian heart are not completely understood. In this study, we have investigated the effects of a sixth-generation cationic dendrimer (G6 PAMAM) on cardiac function in control and diabetic rat hearts following ischemia-reperfusion (I/R) injury.MethodsIsolated hearts from healthy non-diabetic (Ctr) male Wistar rats were subjected to ischemia and reperfusion (I/R). LV contractility and hemodynamics data were computed digitally whereas cardiac damage following I/R injury was assessed by measuring cardiac enzymes. For ex vivo acute exposure experiments, G6 PAMAM was administered during the first 10 mins of reperfusion in Ctr animals. In chronic in vivo studies, nondiabetic rats (Ctr) received either vehicle or daily i.p. injections of G6 PAMAM (40 mg/kg) for 4 weeks. Diabetic (D) animals received either vehicle or daily i.p. injections of G6 PAMAM (10, 20 or 40 mg/kg) for 4 weeks. The impact of G6 PAMAM on pacing-postconditioning (PPC) was also studied in Ctr and D rats.ResultsIn ex vivo studies, acute administration of G6 PAMAM to isolated Ctr hearts during reperfusion dose-dependently impaired recovery of cardiac hemodynamics and vascular dynamics parameters following I/R injury. Chronic daily i.p. injections of G6 PAMAM significantly (P<0.01) impaired recovery of cardiac function following I/R injury in nondiabetic animals but this was not generally observed in diabetic animals except for CF which was impaired by about 50%. G6 PAMAM treatment completely blocked the protective effects of PPC in the Ctr animals.ConclusionAcute ex vivo or chronic in vivo treatment with naked G6 PAMAM dendrimer can significantly compromise recovery of non-diabetic hearts from I/R injury and can further negate the beneficial effects of PPC. Our findings are therefore extremely important in the nanotoxicological evaluation of G6 PAMAM dendrimers for potential clinical applications in physiological and pathological settings.

An evaluation of empagliflozin and it’s applicability to hypertension as a therapeutic option

ABSTRACT Introduction Sodium-glucose cotransporter 2 (SGLT2) inhibitors such as Empagliflozin are novel antihyperglycemic drugs approved for the treatment of type 2 diabetes (T2D). In addition to its glucose-lowering effects, Empagliflozin promotes weight loss, blood pressure reduction, and other beneficial metabolic benefits. Areas covered This review outlines the pharmacokinetics, pharmacodynamics, safety, and tolerability of Empagliflozin and discusses its role in diabetes-associated hypertension. Expert opinion Empagliflozin was the first in class to not only demonstrate safety of SGLT2 inhibition but also cardio- and reno-protective effects in an adequately powered cardiovascular outcome trial. The EMPA-REG study showed significant reductions in mortality from cardiovascular causes, hospitalization for heart failure, and progression of diabetic kidney disease. These benefits cannot be attributed to glycemic control alone, suggesting the involvement of other SGLT2 inhibition-mediated mechanisms. Recent data suggests the potential utility of SGLT2 inhibition in other conditions including type 1 diabetes (T1D) and non-diabetic heart failure patients with clinical trials currently being conducted. In concert with ongoing pre-clinical investigations to unravel the mechanisms contributing to cardiorenal protection, the full therapeutic potential of SGLT2 inhibition will become apparent over the next few years and promises to be one of the major success stories in clinical medicine. Abbreviations T1D: type 1 diabetes; T2D: type 2 diabetes; SGLT2: sodium-glucose cotransporter 2; CVD: cardiovascular disease; SBP: systolic blood pressure; DBP: diastolic blood pressure; SNS: sympathetic nervous system; BP: blood pressure; CV: cardiovascular; ZDF: Zucker diabetic fatty; CKD: chronic kidney disease; FDA: Food and Drug Administration

Role of the Renal Nerves in Regulating SGLT2 inhibitor‐induced Diuresis and Natriuresis in rats with Heart Failure

Sodium‐glucose cotransporter 2 (SGLT2) inhibitors promoting glucose excretion are widely used to treat type 2 diabetes. Recently, the clinical trial in both diabetic and non‐diabetic heart failure (HF) patients with reduced ejection fraction demonstrated that SGLT2 inhibitor prevents worsening HF. However, the underlying mechanisms have not been fully elucidated. The present study was conducted to assess whether the effects of SGLT2 inhibitor on urine flow, sodium and glucose excretions are changed in HF. To address the underlying mechanisms the mRNA and protein levels of renal SGLT2 are investigated. HF was induced in rats by left coronary artery ligation. Further, to assess the contribution of renal nerves in the regulation of renal SGLT2, four weeks after ligation surgery, surgical bilateral renal denervation (RDN) was performed. Acute experiments were performed one week after RDN (five weeks after coronary ligation). Urine flow, sodium and glucose excretion responses to SGLT2 inhibitor dapagliflozin (0.5 mg/kg, i.v.) were greater in HF than Sham (Urine flow 15.8 ± 1.8 vs. 8.3 ± 1.1 μl/min/gkw, Sodium excretion 2.23 ± 0.35 vs. 1.13 ± 0.18 μEq/min/gkw, Glucose excretion 0.84 ± 0.06 vs. 0.52 ± 0.08 mg/min/gkw at 120 min, P&lt;0.05, n=5–7). RDN significantly attenuated these responses to dapagliflozin in HF (Urine flow 9.8 ± 1.2 vs. 15.8 ± 1.8 μl/min/gkw, Sodium excretion 1.31 ± 0.17 vs. 2.23 ± 0.35 μEq/min/gkw, Glucose excretion 0.66 ± 0.04 vs. 0.84 ± 0.06 mg/min/gkw at 120 min, P&lt;0.05, n=5–7). Western blot analysis indicated that SGLT2 protein expressions in the renal cortex were higher in HF than Sham (SGLT2/GAPDH 0.83 ± 0.06 vs. 0.58 ± 0.05, P&lt;0.05, n=6). RDN significantly reduced enhanced protein levels of SGLT2 in the renal cortex of rats with HF (SGLT2/GAPDH 0.60 ± 0.07 vs. 0.83 ± 0.06, P&lt;0.05, n=6). In contrast, RT‐PCR analysis indicated that RDN increased mRNA levels of SGLT2 in the renal cortex of rats with HF (SGLT2/18sRNA 1.08 ± 0.28 vs. 0.23 ± 0.06, P&lt;0.05, n=6), possibly a compensatory change to SGLT2 protein expressions. Immunohistochemistry of renal sections confirmed the enhanced staining for SGLT2 in HF. These findings suggest that increases in urine flow, sodium and glucose excretion responses to SGLT2 inhibitor are enhanced in HF due to the upregulation of renal SGLT2. Renal sympathoexcitation in HF might enhance the expression and functional activity of renal SGLT2, thereby contribute to subsequent pathophysiology of renal sodium and water retention associated with HF.Support or Funding InformationSupported by Japan Heart Foundation and NIH grants DK 114663 and HL62222.

Transient Elevation of Glucose Increases Arrhythmia Susceptibility in Non-Diabetic Rat Trabeculae With Non-Uniform Contraction.

In non-diabetic patients with acute coronary syndrome, stress hyperglycemia occasionally occurs and is related to their mortality. Whether transient elevation of glucose affects arrhythmia susceptibility in non-diabetic hearts with non-uniform contraction was examined.Methods and Results:Force, intracellular Ca2+([Ca2+]i), and membrane potential were measured in trabeculae from rat hearts. Non-uniform contraction was produced by a jet of paralyzing solution. Ca2+waves and arrhythmias were induced by electrical stimulation (2.0 mmol/L [Ca2+]o). The activity of Ca2+/calmodulin-dependent protein kinaseII (CaMKII) was measured. An elevation of glucose from 150 to 400 mg/dL increased the velocity of Ca2+waves and the number of spontaneous action potentials triggered by electrical stimulation. Besides, the elevation of glucose increased the CaMKII activity. In the presence of 1 μmol/L KN-93, the elevation of glucose did not increase the velocity of Ca2+waves and the number of triggered action potentials. In addition, in the presence of 1 μmol/L autocamtide-2 related inhibitory peptide or 50 μmol/L diazo-5-oxonorleucine, the elevation of glucose did not increase the number of triggered action potentials. Furthermore, the elevation of glucose by adding L-glucose did not increase their number. In non-diabetic hearts with non-uniform contraction, transient elevation of glucose increases the velocity of Ca2+waves by activating CaMKII,probably through glycosylation with O-linked β-N-acetylglucosamine, thereby increasing arrhythmia susceptibility.

Small Extracellular Microvesicles Mediated Pathological Communications Between Dysfunctional Adipocytes and Cardiomyocytes as a Novel Mechanism Exacerbating Ischemia/Reperfusion Injury in Diabetic Mice.

Diabetes mellitus exacerbates myocardial ischemia/reperfusion (MI/R) injury by incompletely understood mechanisms. Adipocyte dysfunction contributes to remote organ injury. However, the molecular mechanisms linking dysfunctional adipocytes to increased MI/R injury remain unidentified. The current study attempted to clarify whether and how small extracellular vesicles (sEV) may mediate pathological communication between diabetic adipocytes and cardiomyocytes, exacerbating MI/R injury. Adult male mice were fed a normal or a high-fat diet for 12 weeks. sEV (from diabetic serum, diabetic adipocytes, or high glucose/high lipid-challenged nondiabetic adipocytes) were injected intramyocardially distal of coronary ligation. Animals were subjected to MI/R 48 hours after injection. Intramyocardial injection of diabetic serum sEV in the nondiabetic heart significantly exacerbated MI/R injury, as evidenced by poorer cardiac function recovery, larger infarct size, and greater cardiomyocyte apoptosis. Similarly, intramyocardial or systemic administration of diabetic adipocyte sEV or high glucose/high lipid-challenged nondiabetic adipocyte sEV significantly exacerbated MI/R injury. Diabetic epididymal fat transplantation significantly increased MI/R injury in nondiabetic mice, whereas administration of a sEV biogenesis inhibitor significantly mitigated MI/R injury in diabetic mice. A mechanistic investigation identified that miR-130b-3p is a common molecule significantly increased in diabetic serum sEV, diabetic adipocyte sEV, and high glucose/high lipid-challenged nondiabetic adipocyte sEV. Mature (but not primary) miR-130b-3p was significantly increased in the diabetic and nondiabetic heart subjected to diabetic sEV injection. Whereas intramyocardial injection of a miR-130b-3p mimic significantly exacerbated MI/R injury in nondiabetic mice, miR-130b-3p inhibitors significantly attenuated MI/R injury in diabetic mice. Molecular studies identified AMPKα1/α2, Birc6, and Ucp3 as direct downstream targets of miR-130b-3p. Overexpression of these molecules (particularly AMPKα2) reversed miR-130b-3p induced proapoptotic/cardiac harmful effect. Finally, miR-130b-3p levels were significantly increased in plasma sEV from patients with type 2 diabetes mellitus. Incubation of cardiomyocytes with diabetic patient sEV significantly exacerbated ischemic injury, an effect blocked by miR-130b-3p inhibitor. We demonstrate for the first time that miR-130b-3p enrichment in dysfunctional adipocyte-derived sEV, and its suppression of multiple antiapoptotic/cardioprotective molecules in cardiomyocytes, is a novel mechanism exacerbating MI/R injury in the diabetic heart. Targeting miR-130b-3p mediated pathological communication between dysfunctional adipocytes and cardiomyocytes may be a novel strategy attenuating diabetic exacerbation of MI/R injury.

Serum angiostatin levels in diabetic patients with heart failure taking oral antidiabetic therapy or basal insulin and its clinical significance

Diabetes mellitus is a metabolic disorder with an increasing incidence all over the world leading to high sequelae and high mortality rates behind other microvascular and macrovascular complications. The deterioration in angiogenesis in particular is known to cause deterioration of vascular complications of diabetes. After the discovery of a natural angiogenesis inhibitor, angiostatin in the ethiopathogenesis of retinopathy and nephropathy, which are frequent complications of diabetes, several successful clinical trials have been made. However, the most lethal complication of diabetes, diabetic heart failure, lacks any trial about effectiveness of angiostatin. In this study, the levels and the clinical significance of angiostatin were investigated in oral antidiabetic or Insulin treated diabetic patients with heart failure. The patient group consisted of 31 patients with a diagnosis of diabetes mellitus and heart failure and the control group included 30 patients with heart failure without diabetes mellitus. Serum levels of angiostatin were studied. A total of 61 subjects were enrolled in the study. The patient group consisted of 31 patients; between the age of 56-88 (73.06 ± 8.7) years, of which 16 (51.6%) were female and 15 (48.4%) were male. The control group included 30 patients; 15 (% 50) women and 15 (50%) of were male, between the ages of 57 to 85 (74.23 ± 8.27). In the case group, the average angiostatin levels were 133.25 ± 78.46 and in the control group it was found to be 121.7 ± 71.81. The average angiostatin levels were similar in diabetic and non-diabetic heart failure groups (p=0.55). The average serum angiostatin levels showed a significant negative correlation with the level of fasting blood glucose. In our study, diabetic patients with heart failure, when compared with non-diabetic patients with heart failure, showed no significant difference in the levels of angiostatin. Levels of angiostatin are not affected by the level of HbA1c. Fasting blood glucose level has a negative correlation with the level of angiostatin. In order to be used in determining the prognosis in diabetic patients with heart failure, further studies are needed on angiostatin levels.