Diabetic Remodeling Research Articles

Empagliflozin improves pressure-overload-induced cardiac hypertrophy by inhibiting the canonical Wnt/β-catenin signaling pathway

BackgroundEmpagliflozin (EMPA) is an SGLT-2 inhibitor that can control hyperglycemia. Clinical trials have indicated its cardio-protective effects against cardiac remodeling in diabetes or non-diabetes patients. However, the underlying molecular mechanisms of EMPA’s cardio-protective effects remain elusive.MethodsWe evaluated whether the EMPA attenuated the pressure-overload-induced cardiac hypertrophy by inhibiting the Wnt/β-catenin pathway. Furthermore, the effects of the EMPA on a mouse model of transverse aortic constriction (TAC) induced cardiac hypertrophy was also evaluated. Mice were administrated with 0.5% CMC-Na as a vehicle or EMPA (10 mg/kg/day, daily, throughout the study) by intragastric gavage.ResultsThe in vivo echocardiography and histologic morphological analyses revealed that EMPA attenuated TAC-induced cardiac hypertrophy. Moreover, it also ameliorated TAC-induced cardiac fibrosis and decreased the cell size of the cardiomyocytes in isolated adult cardiomyocytes. Molecular mechanism analysis revealed that the EMPA reduced the TAC-induced enhanced expression of the Wnt/β-catenin pathway in vivo. For in vitro assessments, isolated neonatal rat cardiomyocytes (NRCMs) were treated with Angiotensin II (AngII) and EMPA; the results showed that in the absence of EMPA, the expression of the Wnt/β-catenin pathway was enhanced. In the trans-genetic heterozygous β-catenin deletion mice, EMPA attenuated TAC-induced cardiac remodeling by reducing the Wnt/β-catenin pathway. In addition, molecular docking analysis indicated that EMPA interacts with FZD4 to inhibit the TAC and AngII induced Wnt/β-catenin pathway in cardiomyocytes.ConclusionOur study illustrated that EMPA might directly interact with FZD4 to inhibit the TAC and AngII-induced activation of the Wnt/β-catenin pathway to attenuate the adverse cardiac remodeling.

Endurance Exercise Prevented Diabetic Cardiomyopathy through the Inhibition of Fibrosis and Hypertrophy in Rats.

Exercise training could be essential in preventing pathological cardiac remodeling in diabetes. Therefore, the effects of moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) singly or plus metformin on diabetes-induced cardiomyopathy were investigated in this study. Forty-nine Wistar rats (male) were recruited. Seven groups of animals were treated for six weeks as control, diabetes, MICT (15 m/min, 40 min/day), HIIT (20 m/min, 40 min/day), metformin (300 mg/kg), HIIT+metformin (Met-HIIT), and MICT+metformin (Met-MICT). The metformin was orally administered with an intragastrical needle, and the exercised rats were trained (5 days/week) with a motorized treadmill. Metabolic parameters, echocardiographic indices, histopathology evaluation, and assessment of gene expression connected with cardiac fibrosis, hypertrophy, mitochondrial performance, and intracellular calcium homeostasis were investigated. Our results demonstrated that all the interventions prevented weight loss and enhanced heart weight/body weight ratio and fasting plasma glucose in diabetic rats. Both types of exercise and their metformin combinations improved diabetic animals' echocardiography indices by enhancing heart rate, fractional shortening (FS), ejection fraction (EF) and reducing end-systolic and end-diastolic diameter of left ventricular (LVESD and LVEDD). Gene expression of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), transforming growth factor (TGF)- , and collagen increased in the diabetes group. In contrast, the gene expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 ), AMP-activated protein kinase (AMPK), ryanodine receptors (RyR), and ATPase pump of the sarcoplasmic reticulum (SERCA) was reduced in diabetic animals. Exercise training alone or in combination with metformin reversed these changes. Moreover, diabetes-induced cardiac fibrosis was ameliorated in treated groups. All indicators of diabetic cardiomyopathy were improved more in the Met-HIIT group than in other groups. Exercise training, notably with metformin combination, alleviated diabetes-induced cardiac complications. The beneficial effects of exercise could be related to improving pathological cardiac remodeling and enhancing cardiac function.

BAG3 promotes proliferation and migration of arterial smooth muscle cells by regulating STAT3 phosphorylation in diabetic vascular remodeling

BackgroundDiabetic vascular remodeling is the most important pathological basis of diabetic cardiovascular complications. The accumulation of advanced glycation end products (AGEs) caused by elevated blood glucose promotes the proliferation and migration of vascular smooth muscle cells (VSMCs), leading to arterial wall thickening and ultimately vascular remodeling. Therefore, the excessive proliferation and migration of VSMCs is considered as an important therapeutic target for vascular remodeling in diabetes mellitus. However, due to the lack of breakthrough in experiments, there is currently no effective treatment for the excessive proliferation and migration of VSMCs in diabetic patients. Bcl-2-associated athanogene 3 (BAG3) protein is a multifunctional protein highly expressed in skeletal muscle and myocardium. Previous research has confirmed that BAG3 can not only regulate cell survival and apoptosis, but also affect cell proliferation and migration. Since the excessive proliferation and migration of VSMCs is an important pathogenesis of vascular remodeling in diabetes, the role of BAG3 in the excessive proliferation and migration of VSMCs and its molecular mechanism deserve further investigation.MethodsIn this study, BAG3 gene was manipulated in smooth muscle to acquire SM22αCre; BAG3FL/FL mice and streptozotocin (STZ) was used to simulate diabetes. Expression of proteins and aortic thickness of mice were detected by immunofluorescence, ultrasound and hematoxylin-eosin (HE) staining. Using human aorta smooth muscle cell line (HASMC), cell viability was measured by CCK-8 and proliferation was measured by colony formation experiment. Migration was detected by transwell, scratch experiments and Phalloidin staining. Western Blot was used to detect protein expression and Co-Immunoprecipitation (Co-IP) was used to detect protein interaction.ResultsIn diabetic vascular remodeling, AGEs could promote the interaction between BAG3 and signal transducer and activator of transcription 3 (STAT3), leading to the enhanced interaction between STAT3 and Janus kinase 2 (JAK2) and reduced interaction between STAT3 and extracellular signal-regulated kinase 1/2 (ERK1/2), resulting in accumulated p-STAT3(705) and reduced p-STAT3(727). Subsequently, the expression of matrix metallopeptidase 2 (MMP2) is upregulated, thus promoting the migration of VSMCs.ConclusionsBAG3 upregulates the expression of MMP2 by increasing p-STAT3(705) and decreasing p-STAT3(727) levels, thereby promoting vascular remodeling in diabetes. This provides a new orientation for the prevention and treatment of diabetic vascular remodeling.

TALK-1-mediated alterations of β-cell mitochondrial function and insulin secretion impair glucose homeostasis on a diabetogenic diet

Mitochondrial Ca2+ ([Ca2+]m) homeostasis is critical for β-cell function and becomes disrupted during the pathogenesis of diabetes. [Ca2+]m uptake is dependent on elevations in cytoplasmic Ca2+ ([Ca2+]c) and endoplasmic reticulum Ca2+ ([Ca2+]ER) release, both of which are regulated by the two-pore domain K+ channel TALK-1. Here, utilizing a novel β-cell TALK-1-knockout (β-TALK-1-KO) mouse model, we found that TALK-1 limited β-cell [Ca2+]m accumulation and ATP production. However, following exposure to a high-fat diet (HFD), ATP-linked respiration, glucose-stimulated oxygen consumption rate, and glucose-stimulated insulin secretion (GSIS) were increased in control but not TALK1-KO mice. Although β-TALK-1-KO animals showed similar GSIS before and after HFD treatment, these mice were protected from HFD-induced glucose intolerance. Collectively, these data identify that TALK-1 channel control of β-cell function reduces [Ca2+]m and suggest that metabolic remodeling in diabetes drives dysglycemia.

Mapping the cellular and molecular landscape of cardiac non-myocytes in murine diabetic cardiomyopathy

Diabetes is associated with a significantly elevated risk of heart failure. However, despite extensive efforts to characterize the phenotype of the diabetic heart, the molecular and cellular protagonists that underpin cardiac pathological remodeling in diabetes remain unclear, with a notable paucity of data regarding the impact of diabetes on non-myocytes within the heart. Here we aimed to define key differences in cardiac non-myocytes between spontaneously type-2 diabetic (db/db) and healthy control (db/h) mouse hearts. Single-cell transcriptomic analysis revealed a concerted diabetes-induced cellular response contributing to cardiac remodeling. These included cell-specific activation of gene programs relating to fibroblast hyperplasia and cell migration, and dysregulation of pathways involving vascular homeostasis and protein folding. This work offers a new perspective for understanding the cellular mediators of diabetes-induced cardiac pathology, and pathways that may be targeted to address the cardiac complications associated with diabetes.

Retracted: RAGE Regulating Vascular Remodeling in Diabetes by Regulating Mitochondrial Dynamics with JAK2/STAT3 Pathway.

[This retracts the article DOI: 10.1155/2022/2685648.].

Identification of metabolite shifts and early serum predictors for indicators of remodelling in diabetes and nondiabetic models of cardiac hypertrophy

Background: Cardiac hypertrophy (CH) is the asymptomatic enlargement of ventricular walls witnessed in diabetes and hypertension, for which early metabolite differences and prediction are less stated previously. Aim: The aim of the study was (i) to understand the metabolic and ventricular events in diabetes and nondiabetes induced CH at the end of 2 weeks and (ii) to identify significant metabolite predictors and pathways that influence the seven metabolic and physiological responders of CH, namely, 3-hydroxybutyrate (3-HB); lactic acid; urea; and electrocardiography (ECG) waves (QRS complex, R amplitude, R-R interval, and heart rate). Methods: Diabetic rat models of CH using streptozotocin (40 mg/kg, i. p., single dose), and nondiabetic models using adrenaline (0.3 mg/kg, i. p, 2 weeks) were developed. Blood glucose levels, ECG, heart weight/body weight ratio, histopathological analysis, and serum metabolite analysis using gas chromatography mass spectrometry were performed at the end of 2 weeks. Strong metabolite predictors and pathways were identified using Pearson's correlation, multiple regression (MRA) and metabolite set enrichment (MSEA) analyses. Results: The prevalence of CH was observed through preliminary screenings at the end of 2 weeks. Galactose, leucine, erythrose, sorbitol, and valine were identified as significant (P < 0.05) predictors in SZ model, whereas isoleucine, galactose, leucine, inositol, and palmitic acid were identified in ADR model. However, galactose metabolism, branched-chain amino acid, and lactose degradation pathways were mapped as the highly influential apparent pathways during early CH remodeling in both the models. Conclusion: This study identified putative initial metabolite shifts, significant predictors pathways that can aid in forecasting, intervention, and prevention of CH.

Exosomes from human umbilical cord mesenchymal stem cells protect aortas in Db/db mice characterized by combination of metabolomics and proteomics

Diabetic cardiovascular complication is a common systemic disease with high morbidity and mortality worldwide. We hypothesise that exosomes derived from human umbilical cord mesenchymal stem cells (hUCMSCs-exos) can rescue these disorders and alleviate vascular remodeling in diabetes. Morphological, non-targeted metabolomics and 4D label-free proteomics techniques were used to analyze the aortas of db/m mice as normal control group (NCA), saline treated db/db mice (DMA), and hUCMSCs-exos treated db/db mice (DMTA), and to clarify the molecular mechanism of the protection of hUCMSCs-exos in vascular remodeling from a new point of view. The results showed that 74 metabolites were changed significantly in diabetic aortas, of which 15 were almost restored by hUCMSCs-exos. In proteomics, 30 potential targets such as Stromal cell-derived factor 2-like protein 1, Leukemia inhibitory factor receptor, Peroxisomal membrane protein and E3 ubiquitin-protein ligase MYCBP2 were detected. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway-based analysis showed that Central carbon metabolism in cancer and Galactose metabolism pathway were up-regulated to near normal by hUCMSCs-exos in metabolomics, with janus associated kinase-signal transducer and activator of transcription (JAK-STAT) pathway displayed in proteomics. According to bioinformatics and integrated analysis, these targeted molecules of hUCMSCs-exos to attenuate the vascular remodeling were mainly associated with regulation of energy metabolism, oxidative stress, inflammation, and cellular communications. This study provided a reference for the therapy of diabetes-induced cardiovascular complications.

RAGE Regulating Vascular Remodeling in Diabetes by Regulating Mitochondrial Dynamics with JAK2/STAT3 Pathway.

In this research, we will explore the role and modulation of mitochondrial dynamics in diabetes vascular remodeling. Only a few cell types express the pattern recognition receptor, also known as the AGE receptor (RAGE). However, it is triggered in almost all of the cells that have been investigated thus far by events that are known to cause inflammation. Here, Type 2 diabetes was studied in both cellular and animal models. Elevated Receptor for advanced glycation end products (RAGE), phosphorylated JAK2 (p-JAK2), phosphorylated STAT3 (p-STAT3), transient receptor potential ion channels (TRPM), and phosphorylated dynamin-related protein 1 (p-DRP1) were observed in the context of diabetes. In addition, we found that inhibition of RAGE was followed by a remarkable decrease in the expression of the above proteins. It has also been demonstrated by western blotting and immunofluorescence results in vivo and in vitro. Suppressing STAT3 and DRP1 phosphorylation produced effects similar to those of RAGE inhibition on the proliferation, cell cycle, migration, invasion, and expression of TRPM in VSMCs and vascular tissues obtained from diabetic animals. These findings indicate that RAGE regulates vascular remodeling via mitochondrial dynamics through modulating the JAK2/STAT3 axis in diabetes. The findings could be crucial in gaining a better understanding of diabetes-related vascular remodeling. It also contributes to a better cytopathological understanding of diabetic vascular disease and provides a theoretical foundation for novel targets that aid in the prevention and treatment of diabetes-related cardiovascular problems.

Exacerbated post-infarct pathological myocardial remodelling in diabetes is associated with impaired autophagy and aggravated NLRP3 inflammasome activation.

BackgroundDiabetes mellitus (DM) patients surviving myocardial infarction (MI) have substantially higher mortality due to the more frequent development of subsequent pathological myocardial remodelling and concomitant functional deterioration. This study investigates the molecular pathways underlying accelerated cardiac remodelling in a well‐established mouse model of diabetes exposed to MI.Methods and resultsMyocardial infarction in DM mice was established by ligating the left anterior descending coronary artery. Cardiac function was assessed by echocardiography. Myocardial hypertrophy and cardiac fibrosis were determined histologically 6 weeks post‐MI or sham operation. Autophagy, the NLRP3 inflammasome, and caspase‐1 were evaluated by western blotting or immunofluorescence. Echocardiographic imaging revealed significantly increased left ventricular dilation in parallel with increased mortality after MI in DM mice (53.33%) compared with control mice (26.67%, P < 0.05). Immunoblotting, electron microscopy, and immunofluorescence staining for LC3 and p62 indicated impaired autophagy in DM + MI mice compared with control mice (P < 0.05). Furthermore, defective autophagy was associated with increased NLRP3 inflammasome and caspase‐1 hyperactivation in DM + MI mouse cardiomyocytes (P < 0.05). Consistent with NLRP3 inflammasome and caspase‐I hyperactivation, cardiomyocyte death and IL‐1β and IL‐18 secretion were increased in DM + MI mice (P < 0.05). Importantly, the autophagy inducer and the NLRP3 inhibitor attenuated the cardiac remodelling of DM mice after MI.ConclusionIn summary, our results indicate that DM aggravates cardiac remodelling after MI through defective autophagy and associated exaggerated NLRP3 inflammasome activation, proinflammatory cytokine secretion, suggesting that restoring autophagy and inhibiting NLRP3 inflammasome activation may serve as novel targets for the prevention and treatment of post‐infarct remodelling in DM.

Abstract 14193: Bmp-7 Ameliorates Lipid Accumulation Induced, Hmgb1 Initiated Pyroptosis Leading To Sarcopenia, Muscle Deterioration And Adverse Muscle Remodeling In Diabetes

Introduction: Diabetic muscle myopathy involves hyperglycemia and inflammation that causes skeletal muscle dysfunction. However, the potential cellular mechanisms that occur during hyperglycemia and inflammation, which induces sarcopenia, muscle deterioration and muscle dysfunction remains unknown. Hypothesis: We hypothesize that, Bone morphogenetic protein-7 (BMP-7) ameliorates hyperlipidemia induced inflammation and pyroptosis in the development and progression of diabetic myopathy. Methods: C57BL6 mice were treated with saline, streptozotocin (STZ), or STZ+BMP-7 to generate diabetic muscle myopathy. Diabetes was established by increased fasting glucose levels and GTT. Gastrocnemius muscle and blood samples were collected. Blood was used to determine the lipid levels. Skeletal muscle was used to investigate lipid accumulation, pyroptosis, muscle deterioration, atrophy, and adverse structural remodeling using histology, immunohistochemistry, western blot, and RT-PCR. Results: We observed a significant ( p &lt;0.05) increase in blood glucose and serum lipid levels in diabetic animals. A significant ( p &lt;0.05) increase in hyperglycemia lead an increase in lipid accumulation, inflammasome formation and further an up-regulation of the downstream pyroptotic markers as well as signaling markers [TGFβ, Smad2 and Smad3] in diabetic muscle cells. Structural analysis showed the significant ( p &lt;0.05) loss of muscle weight, decreased myofibrillar area, increased muscle deterioration and fibrosis leading to muscle dysfunction. Whereas, BMP-7 attenuated hyperglycemia, hyperlipidemia, lipid accumulation, inflammation, pyroptosis, signaling markers and diabetic adverse structural modifications resulting in significantly ( p &lt;0.05) improved muscle function. Conclusion: We report for the first time that increased hyperlipidemia aggravates inflammation involved cellular pyroptosis that induces significant muscle cell loss and adverse remodeling in diabetic muscle myopathy. Targeting pyroptosis and lipid accumulation in muscle cells, with BMP-7 improves diabetic muscle pathophysiology and muscle function. These findings shows BMP-7 as a potential therapeutic option to treat diabetic myopathy.

Mechanistic insights from a multiparametric magnetic resonance imaging study regarding the role of sodium glucose co-transporter 2 inhibitors

Abstract Background Type 2 diabetes (T2D) is associated with an increased risk of heart failure (HF) and cardiovascular (CV) mortality. Sodium–glucose-co transporter-2 (SGLT2) inhibitors reduce the risk of major adverse CV events and hospitalisation for HF in T2D patients with high cardiovascular risk, despite only a modest improvement in glycemic control. Restoring cellular energy homeostasis and reversing adverse cardiac remodelling in diabetes have been speculated as a potential metabolic modulatory effect of SGLT2 inhibitors leading to their beneficial CV outcomes. Myocardial energy deficient states can be detected non-invasively by 31-phosphorus magnetic resonance spectroscopy (31P-MRS). Objectives Utilising cardiovascular magnetic resonance imaging (CMR) and 31P-MRS in a single centre longitudinal cohort study, we aimed to investigate the effects of the selective SGLT2 inhibitor empagliflozin on myocardial energetics, function, perfusion, and myocardial cellular volume in patients with T2D. Methods Eighteen consecutive T2D patients who were commenced on empagliflozin in cardiometabolic optimisation clinics underwent CMR and 31P-MRS scans before and after twelve-week empagliflozin treatment, and plasma N-terminal pro hormone B-type natriuretic peptide (NT-proBNP) levels were measured. Ten controls with no diabetes underwent an identical 31P-MRS and CMR protocol on a single visit. Results When compared to controls, patients with T2D showed: lower myocardial energetics (1.52±0.40 vs 2.20±0.5, p=0.0005), lower stress myocardial blood flow (1.60±0.50 vs 2.10±0.50, p=0.02) and lower left ventricular ejection fraction (52±13% vs 63±4%, p=0.01). Treatment with empagliflozin led to significant improvements in myocardial energetics (PCr/ATP: 1.52 to 1.76, p=0.009). This was accompanied by a relative 13% improvement in left ventricular ejection fraction (p=0.001), 3% improvement in global longitudinal strain (p=0.01), 61% reduction in NTproBNP (p=0.05), and 9% reduction in myocardial cell volume (p=0.04). No significant change in myocardial blood flow or diastolic strain was detected. Conclusions For the first time, we demonstrate that empagliflizon improves myocardial energetics and function, reduces myocardial cellular volume, and reduces NT-proBNP levels in patients with T2D. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): British Heart Foundation PCr/ATPLVEF

Bimodal Effects of P2Y12 Antagonism on Matrix Metalloproteinase–Associated Contractile Dysfunction in İnsulin-Resistant Mammalian Heart

The matrix metalloproteinases (MMPs) contribute to matrix remodeling in diabetes via tissue degradation; however, their contributions can be different depending on the pathology. For instance, MMPs are elevated in acute stress hyperglycemia, whereas they can be degraded in chronic hyperglycemia. Since studies emphasize the possible cardioprotective effect of ticagrelor (Tica) beyond its antiplatelet action, we aimed to examine whether Tica treatment can reverse the depressed heart function of metabolic syndrome (MetS) rats via affecting the expression levels of MMPs. Tica treatment of high-carbohydrate-induced MetS rats could not affect significantly the depressed contractile activity of Langendorff-perfused heart preparations. On the other hand, the Tica treatment provided a significant recovery in the reduced relaxation activity of the aortic preparations from the same animals. Histological examination of the hearts demonstrated marked damages in Mets rats, such as increases in the number of foamy cells and accumulation of collagen fiber and increases in the elastic lamellar irregularity of tunica media, while Tica treatment provided a slight improvement in the structure of left ventricle tissue. We also could not obtain a significant reverse in the high cytosolic labile Zn2+ ([Zn2+]i) with the treatment of cardiomyocytes with Tica. Furthermore, Tica treatment of MetS rats could not significantly reverse the degraded protein levels of MMP-2 and MMP-9 in the heart, as well. Overall, we demonstrated that Tica treatment of MetS rats has no significant benefits on the depressed heart function, although provide a significant beneficial impact on vascular relaxation. This action of Tica may be through its lack of action on both MMP degradation and high [Zn2+]i, which can further precipitate in cleavage of extracellular matrix in the heart.

PKCβ/NF-κB pathway in diabetic atrial remodeling.

Atrial remodeling in diabetes is partially attributed to NF-κB/TGF-β signal transduction pathway activation. We examined whether the hyperglycemia-induced increased expression of NF-κB/TGF-β was dependent upon protein kinase C-β (PKCβ) and tested the hypothesis that selective inhibition of PKCβ using ruboxistaurin (RBX) can reduce NF-κB/TGF-β expression and inhibit abnormal atrial remodeling in streptozotocin (STZ)-induced diabetic rats. The effects of PKCβ inhibition on NF-κB/TGF-β signal transduction pathway-mediated atrial remodeling were investigated in STZ-induced diabetic rats. Mouse atrial cardiomyocytes (HL-1 cells) were cultured in low- or high-glucose or mannitol conditions in the presence or absence of small interference RNA that targeted PKCβ. PKCβ inhibition using ruboxistaurin (RBX, 1mg/kg/day) decreased the expression of NF-κBp65, p-IκB, P38MARK, TNF-α, TGF-β, Cav1.2, and NCX proteins and inducibility of atrial fibrillation (AF) in STZ-induced diabetic rats. Exposure of cardiomyocytes to high-glucose condition activated PKCβ and increased NF-κB/TGF-β expression. Suppression of PKCβ expression by small interference RNA decreased high-glucose-induced NF-κB and extracellular signal-related kinase activation in HL-1 cells. Pharmacological inhibition of PKCβ is an effective method to reduce AF incidence in diabetic rat models by preventing NF-κB/TGF-β-mediated atrial remodeling.

Mitochondrial ROS Formation in the Pathogenesis of Diabetic Cardiomyopathy.

Diabetic cardiomyopathy is a result of diabetes-induced changes in the structure and function of the heart. Hyperglycemia affects multiple pathways in the diabetic heart, but excessive reactive oxygen species (ROS) generation and oxidative stress represent common denominators associated with adverse tissue remodeling. Indeed, key processes underlying cardiac remodeling in diabetes are redox sensitive, including inflammation, organelle dysfunction, alteration in ion homeostasis, cardiomyocyte hypertrophy, apoptosis, fibrosis, and contractile dysfunction. Extensive experimental evidence supports the involvement of mitochondrial ROS formation in the alterations characterizing the diabetic heart. In this review we will outline the central role of mitochondrial ROS and alterations in the redox status contributing to the development of diabetic cardiomyopathy. We will discuss the role of different sources of ROS involved in this process, with a specific emphasis on mitochondrial ROS producing enzymes within cardiomyocytes. Finally, the therapeutic potential of pharmacological inhibitors of ROS sources within the mitochondria will be discussed.

O-Glycosylation of Camkii at Serine 280 Promotes Cardiac Arrhythmias in Diabetic Hyperglycemia

Diabetic cardiomyopathy is associated with increased arrhythmia risk. However, the exact molecular details in signaling and arrhythmia mechanisms remain incompletely understood. We measured action potentials (APs) in isolated murine ventricular myocytes exposed to high glucose (30 mM) versus control (5.5 mM glucose+24.5 mM mannitol to match osmolarity). Acute hyperglycemia prolonged AP duration, increased delayed afterdepolarizations and inducibility of AP-duration alternans during tachypacing. These effects were prevented by OSMI-1, a selective inhibitor of O-GlcNAc transferase (preventing O-GlcNAcylation), and enhanced by thiamet-G, a selective O-GlcNAcase inhibitor (that should promote O-GlcNAcylation). Thus, O-GlcNAcylation is necessary and sufficient for these arrhythmogenic alterations. These effects were also prevented in CaMKIIδ-knockout myocytes and in mice in which a known O-GlcNAcylated Serine on CaMKII was mutated (S280A knock-in). In streptozotocin-induced diabetes, myocytes bathed in normal (5.5 mM) glucose exhibited prolonged AP duration, enhanced delayed afterdepolarizations and alternans, all of which were worsened by acute hyperglycemia. Premature ventricular complexes on electrocardiograms were enhanced in diabetic WT but not in CaMKIIδ-knockout animals. Moreover, the arrhythmogenic remodeling in diabetes was abolished by the CaMKII inhibitor AIP or in S280A mice. We conclude that O-GlcNAcylation of CaMKII at Serine 280 enhances cardiac arrhythmias and represents a significant, novel therapeutic target in diabetes.

Abstract WP492: Differential Effects of Iron Chelation With Deferoxamine on Post-Stroke Neurovascular Inflammation: Disease and Sex Interactions

We have shown that 1) poor recovery in diabetes is associated with greater hemorrhagic transformation and significant loss of the cerebrovasculature, and 2) iron chelation therapy with deferoxamine (DFX) improves sensorimotor and cognitive outcomes while preventing vasoregression in male diabetic animals after stroke. This study tested the hypotheses that 1) diabetes mediates pathological post-stroke neovascularization in females and 2) DFX attenuates microglial activation and pathological neurovascular remodeling in both sexes. Control and diabetic animals were subjected to embolic middle cerebral artery occlusion (MCAO). DFX (100 mg/kg) or vehicle was given 1hour after MCAO and repeated every 12h for 7 days after stroke. Functional outcomes were assessed over time. Vascular indices, microglial morphology (activation), and neurovascular integrity (IgG and unpolarized Aquaporin-4) were measured at Day 14. Male and female microvascular endothelial cells (BMVECs) treated with iron and/or DFX were tested for viability and endothelial mesenchymal transition (EndMT) markers. DFX preserved vascular volume post-stroke in diabetic males. Stroke did not cause vasoregression in diabetic female animals; however, DFX reduced vascular indices while improving sensorimotor but not cognitive outcomes in both control and diabetic females. Ischemic injury amplified microglial activation and neurovascular remodeling in diabetes while DFX treatment restored these changes to control levels in male diabetic animals but not in females (Table). Female BMVECs grown under diabetic conditions expressed α-SMA and N-cadherin while VE-cadherin was decreased, indicative of EndMT (p&lt;0.05 vs normal glucose). Data suggest that DFX treatment has sex- and disease-dependent effects on post-stroke neovascularization. Additional studies will aim to address the mechanisms by which DFX exerts these differential effects on functional outcomes and neurovascular remodeling.

Study of the diacylglycerol composition in the liver and serum of mice with prediabetes and diabetes using MeV TOF-SIMS

AimsHepatic insulin resistance, induced by fat, occurs before peripheral resistance and leads to prediabetes and diabetes. If insulin resistance is detected earlier, lifestyle changes could prevent or delay disease development. Therefore, we analysed lipids in the liver and serum of prediabetic and diabetic mice by MeV TOF-SIMS with a focus on diacylglycerols (DAGs) as the best predictor of (liver) resistance. MethodsGlucose impairment was spontaneously developed or induced by HFD in NOD/LtJ mice, and prediabetic and diabetic mice were selected according to their glucose levels. MeV TOF-SIMS was applied to image the lipid distribution in the liver and to relatively quantify lipids related to insulin resistance in both the liver and serum. ResultsThe same lipids were detected in the liver and serum but with different intensities between mice. The intensity of DAGs and fatty acids was higher in the diabetic than that in the prediabetic liver.Imaging of liver tissue showed a more compact density of prediabetic (non-fatty) than diabetic liver with DAG remodelling in diabetes. DAGs, which are greatly increased in diabetic serum, were successfully detected and quantified already in prediabetes. ConclusionMeV TOF-SIMS applied to the serum presents an excellent tool for in vivo monitoring of disease development over time.

Abstract WP152: Iron Chelation Improves Stroke Outcomes in Diabetes: Impact on Neurovascular Remodeling, Microglial Activation and Ferroptotic Endothelial Cell Death

Introduction: We have shown that 1) poor recovery in diabetes is associated with greater hemorrhagic transformation (HT) and significant loss the cerebrovasculature, and 2) iron chelation therapy with deferoxamine (DFX) improves functional outcomes while preventing vasoregression in diabetic animals after embolic stroke. However, underlying mechanisms remained unknown. Current study was designed to test the hypotheses that DFX attenuates 1) microglial activation and pathological neurovascular remodeling, and 2) ferroptosis, iron-dependent cell death, of brain microvascular endothelial cells (BMVECs). Methods: Control and type 2 diabetic animals were subjected to embolic middle cerebral artery occlusion (MCAO). DFX (100 mg/kg) or vehicle was given 1hour after MCAO and repeated every 12 h for 7 days after stroke. At Day 14, microglial activation and neurovascular integrity were evaluated by immunohistochemical analyses of Iba1 and Aquaporin-4 (AQP4) polarity, respectively. BMVECs isolated from control Wistar and diabetic Goto-Kakizaki rats were treated with iron(III)sulfate (0.1mM) in presence/absence of DFX (100μM) for 6 hours. Cell viability and ferroptotic cell death markers like IREB2, ACSL4, MDA formation and total glutathione content were measured. Results: Ischemia/reperfusion injury amplified microglial activation and neurovascular remodeling in diabetes while DFX treatment reduced these changes to control levels (Table 1). DFX treatment also prevented iron-mediated cell death and decreased the expression of ferroptotic cell death markers (Table 1). Conclusions: Mechanisms underlying DFX-mediated improvement of sensorimotor and cognitive functions after stroke in diabetes involve attenuation of neuroinflammation, pathological neurovascular remodeling and endothelial ferroptosis. Iron chelation is a potential therapeutic strategy to improve outcomes in diabetic stroke that is associated with greater HT.

Let's face the fats: palmitate restores cellular redox state in the diabetic heart.

Let's face the fats: palmitate restores cellular redox state in the diabetic heart.