Sodium-Glucose Cotransporter-2 Inhibition Normalizes Metabolic Derangements in the Ischemic Myocardium.

INTRODUCTION: Sodium-glucose cotransporter-2 inhibitors (SGLT2i) have shown efficacy in the context of heart failure but have not been well-studied in ischemic heart disease. We employed a large animal model of chronic coronary artery disease and metabolic syndrome (MS) to investigate the hemodynamic and metabolic consequences of SGLT2i administration. METHODS: Thirty-eight Yorkshire swine were divided into two groups, with half (n = 21) receiving a high fat diet to induce MS, and the other half fed a standard diet (n = 17). All animals underwent thoracotomy for ameroid constrictor placement over the left circumflex coronary artery. Treatment with SGLT2i was then initiated, generating four groups: regular diet placebo (CON, n = 9), regular diet canagliflozin (n = 8), high-fat control (n = 11), and high-fat canagliflozin (n = 10). After 5 wks, all animals underwent terminal myocardial harvest with pressure-volume loop acquisition, perfusion studies, and tissue resection for molecular analysis. RESULTS: SGLT2i improved multiple measures of myocardial performance, including a nearly 1.5-fold increase in both cardiac output and ejection fraction; these changes were associated with augmented capillary density and a twofold increase perfusion to the ischemic myocardium. These augmentations were blunted; however, in the presence of MS, and associated with modulated myocardial expression of multiple major metabolic enzymes. CONCLUSIONS: SGLT2i significantly improved cardiac function in our large animal model of coronary artery disease, with metabolic modulation of the myocardial tissue serving as a candidate account of these changes. The blunting seen with MS underscores the dependence of clinical translatability on faithful representation of the biochemical environment of human disease.

Intramyocardial injection of hypoxia-conditioned extracellular vesicles increases myocardial perfusion in a swine model of chronic coronary disease.

Objective: Coronary artery disease remains a leading cause of morbidity and mortality worldwide. Patients with advanced coronary artery disease who are not eligible for endovascular or surgical revascularization have limited options. Extracellular vesicles have shown potential to improve myocardial function in preclinical models. Extracellular vesicles can be conditioned to modify their components. Hypoxia-conditioned extracellular vesicles have demonstrated the ability to reduce infarct size and apoptosis in small animals. Our objective is to assess the potential benefits of hypoxia-conditioned extracellular vesicles in a large animal model of coronary artery disease. Methods: Coronary artery disease was induced in 14 Yorkshire swine by ameroid constriction of the left circumflex coronary artery. Two weeks postsurgery, swine underwent a repeat left thoracotomy for injections of hypoxia-conditioned extracellular vesicles (n = 7) or saline (control, n = 7). Five weeks later, all animals underwent terminal harvest for perfusion measurements and myocardial sectioning. Results: Myocardial perfusion analysis demonstrated a trend toward increase at rest and a significant increase during rapid pacing (P = .09, P < .001). There were significant increases in activated phosphorylated endothelial nitric oxide synthase, endothelial nitric oxide synthase, phosphatidylinositol 3-kinase, phosphorylated protein kinase B, and the phosphorylated protein kinase B/protein kinase B ratio in the hypoxia-conditioned extracellular vesicles group compared with the control group (all P < .05). Additionally, there was a significant decrease in the antiangiogenic proteins collagen 18 and angiostatin (P = .01, P = .01) in the hypoxia-conditioned extracellular vesicles group. Conclusions: Intramyocardial injection of hypoxia-conditioned extracellular vesicles results in increased myocardial perfusion without a corresponding change in vessel density. Therefore, this improvement in perfusion is possibly due to changes in nitric oxide signaling. Hypoxia-conditioned extracellular vesicles represent a potential therapeutic strategy to increase myocardial perfusion in patients with advanced coronary artery disease.

Assessing informal caregiver burden as well as knowledge on positioning and feeding of stroke patients in a tertiary hospital in Kelantan, Malaysia.

A significant proportion of stroke patients in Malaysia are supported by informal caregivers who often lack sufficient training. This lack of preparation contributes to an escalation in caregiver burden. A cross-sectional study was conducted using Caregiving Knowledge Questionnaire (CKQ-my) and Zarit Burden Interview (ZBI) with convenient sampling. The findings revealed that caregivers had limited knowledge regarding proper positioning, and most of them reported experiencing mild burden. Multiple logistic regression analysis showed that informal caregivers who were also the primary caregivers for severe stroke patients experienced a higher burden. Recognising and understanding the factors that contribute to caregiver burden in stroke cases is essential for developing effective programs to improve the quality of life for both stroke survivors and their informal caregivers.

Identifying vulnerabilities in essential health services: Analysing the effects of system shocks on childhood vaccination delivery in Lebanon.

Shocks effects are under-theorised in the growing literature on health system resilience. Existing work has focused on the effects of single shocks on discrete elements within the health system, typically at national level. Using qualitative system dynamics, we explored how effects of multiple shocks interacted across system levels and combined with existing vulnerabilities to produce effects on essential health services delivery, through the prism of a case study on childhood vaccination in Lebanon. Lebanon has experienced a series of shocks in recent years, including large-scale refugee arrivals from neighbouring Syria, the COVID-19 pandemic and a political-economic crisis. We developed a causal loop diagram (CLD) to explore the effects of each shock individually, and in combination. The CLD was developed and validated using qualitative data from interviews with 38 stakeholders working in Lebanon's vaccination delivery system, in roles ranging from national level policy to facility-level service delivery, conducted between February 2020 and January 2022. We found that each of the shocks had different effects on service demand- and supply-side dynamics. These effects cascaded from national through to local levels. Both Syrian refugee movement and the COVID-19 pandemic primarily exposed vulnerabilities in service demand, mainly through slowly emerging knock-on effects on vaccination uptake behaviour among host communities, and fear of contracting infection in crowded health facilities respectively. The economic crisis exposed wider system vulnerabilities, including demand for vaccination as household income collapsed, and supply-side effects such as reduced clinic time for vaccination, declining workforce retention, and reduced availability of viable vaccine doses, among others. Finally, important pathways of interaction between shocks were identified, particularly affecting the balance between demand for vaccination through publicly supported facilities and private clinics. Future research should incorporate dynamic approaches to identifying within-system vulnerabilities and their potential impacts under different scenarios, as a precursor to improved resilience measurement, system preparedness, and intervention targeting.

A Single-Surgeon Experience Transitioning to Total Arterial Revascularization.

Background: Coronary artery bypass grafting remains the standard of care for advanced and multifocal coronary artery disease; however, for patients that are surgical candidates, total arterial revascularization (TAR) remains underutilized due to concerns such as sternal wound infections and the learning curve. We present the results of a large cohort of mid-career surgeons transitioning to TAR, focusing on short-term outcomes and the learning curve. Methods: The surgeons transitioned to using TAR as the preferred revascularization technique in August of 2017. The Society of Thoracic Surgeons database was reviewed to identify all patients who underwent isolated non-emergent CABG performed by a single surgeon from January 2014 through January 2022. Patients were divided into two groups-those who had TAR and those who had traditional CABG using one internal mammary artery and vein grafts (IMA-SVG). Results: Eight hundred ninety-eight patients meet inclusion criteria (458 IMA-SVG and 440 TAR). The TAR group had slightly longer cardiopulmonary bypass time, cross clamp times, and operative times (all p < 0.05); however, ICU stay was shorter and 30-day readmission rate was lower for TAR compared to IMA-SVG (all p < 0.05). The TAR group also required fewer postoperative transfusions (p = 0.005). There was no difference in prolonged intubation, stroke, length of stay, mortality, or sternal wound complications between groups (all p > 0.05). The average TAR was 30 min longer; however, learning curves, stratified by number of grafts placed, showed no significant learning curve associated with TAR. Conclusions: An experienced surgeon transitioning from IMA-SVG to TAR slightly increases operative time, but decreases ICU stay, readmissions, and postoperative transfusions with no significant difference in rates of immediate post-operative complications or 30-day mortality, with a minimal learning curve.

Antineutrophil Cytoplasmic Antibody Vasculitis after Coronary Artery Bypass Grafting.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a group of rare autoimmune disorders associated with the presence of ANCA autoantibodies. We present the first reported case of acute ANCA-associated vasculitis following coronary artery bypass grafting in a 74-year-old male presenting on postoperative day 13 with shortness of breath, orthopnea, and acute kidney injury. Renal biopsy ultimately showed focal necrotizing and crescentic glomerulonephritis, and the patient was successfully managed with corticosteroids and outpatient rituximab. This rare case highlights the importance of having an expanded differential for uncommon causes of cardiovascular disease and unexpected outcomes after coronary artery bypass grafting.

Comparative effects of canagliflozin and sitagliptin in chronically ischemic myocardium.

Aim: Recent studies demonstrate that sodium-glucose cotransporter 2 inhibitors (SGLT2i) and dipeptidyl peptidase-4 inhibitors (DPP4i), two classes of antidiabetic drugs, are cardioprotective. However, the mechanisms of these benefits and their comparative efficacy remain unclear. We aimed to compare the effects of these antidiabetic agents on cardiac function, perfusion, and microvascular density using a swine model of chronic myocardial ischemia. Methods: Chronic myocardial ischemia was induced in Yorkshire swine by ameroid constrictor placement to the left circumflex artery. Two weeks later, pigs were administered vehicle ("CON", 8 pigs), 300 mg SGLT2i canagliflozin, ("CANA", 8 pigs), or 100 mg DPP4i sitagliptin ("SIT", 5 pigs) daily. Five weeks later, pigs were euthanized. Cardiac function, perfusion, collateralization, and protein expression were determined by pressure-volume catheter, microsphere analysis, immunofluorescence, and immunoblotting, respectively. Results: Compared with SIT, CANA was associated with improved stroke volume and cardiac output, with a trend towards reduced left ventricular stiffness. Both CANA and SIT trended towards improved perfusion compared to CON, but there were no differences between the two treatment groups. SIT was associated with improved capillary density with a trend towards improved arteriolar density compared to CANA. Both CANA and SIT were associated with increased expression of vascular endothelial cadherin compared to CON, without differences in treatment groups. SIT pigs had decreased 5' adenosine monophosphate-activated protein kinase activation compared to CON and CANA. There was a trend towards increased endothelial nitric oxide synthase activation in the SIT group compared to CON. There were no differences in activation of extracellular signal-regulated kinase 1/2 across groups. Conclusions: In the setting of chronic myocardial ischemia, canagliflozin is associated with improved cardiac function compared to sitagliptin, with similar effects on perfusion despite differences in microvascular collateralization.

Correction: Community interventions for pandemic preparedness: A scoping review of pandemic preparedness lessons from HIV, COVID-19, and other public health emergencies of international concern.

[This corrects the article DOI: 10.1371/journal.pgph.0002758.].

Dipeptidyl peptidase 4 inhibitor sitagliptin decreases myocardial fibrosis and modulates myocardial insulin signaling in a swine model of chronic myocardial ischemia.

Although both clinical data and animal models suggest cardiovascular benefits following administration of Dipeptidyl Peptidase 4 (DPP-4) inhibitors, the underlying mechanisms remain unclear. We therefore sought to evaluate the effect of the DPP-4 inhibitor sitagliptin on myocardial fibrosis, and insulin signaling in chronic myocardial ischemia using a swine model. An ameroid constrictor placement on the left coronary circumflex artery of thirteen Yorkshire swine to model chronic myocardial ischemia. After two weeks of recovery, swine were assigned to one of two groups: control (CON, n = 8), or sitagliptin 100mg daily (SIT, n = 5). After 5 weeks of treatment, the swine underwent terminal harvest with collection of myocardial tissue. Fibrosis was quantified using Masson's trichrome. Protein expression was quantified by Immunoblotting. Trichrome stain demonstrated a significant decrease in perivascular and interstitial fibrosis in the SIT group relative to CON (all p<0.05). Immunoblot showed a reduction in Jak2, the pSTAT3 to STAT 3 Ratio, pSMAD 2/3, and SMAD 2/3, and an increase in STAT 3 in the SIT group relative to CON (all p<0.05). SIT treatment was associated with increased expression of insulin receptor one and decreased expression of makers for insulin resistance, including phospho-PKC- alpha, RBP-4, SIRT1, and PI3K (p<0.05). Sitagliptin results in a reduction in perivascular and interstitial fibrosis and increased insulin sensitivity in chronically ischemic swine myocardium. This likely contributes to the improved cardiovascular outcomes seen with DPP-4 inhibitors.

Metformin Preconditioning Augments Cardiac Perfusion and Performance in a Large Animal Model of Chronic Coronary Artery Disease.

OBJECTIVE: To test the efficacy of metformin (MET) during the induction of coronary ischemia on myocardial performance in a large animal model of coronary artery disease (CAD) and metabolic syndrome (MS), with or without concomitant extracellular vesicular (EV) therapy. BACKGROUND: Although surgical and endovascular revascularization are durably efficacious for many patients with CAD, up to one-third are poor candidates for standard therapies. For these patients, many of whom have comorbid MS, adjunctive strategies are needed. EV therapy has shown promise in this context, but its efficacy is attenuated by MS. We investigated whether MET pretreatment could ameliorate therapeutic decrements associated with MS. METHODS: Yorkshire swine (n = 29) were provided a high-fat diet to induce MS, whereupon an ameroid constrictor was placed to induce CAD. Animals were initiated on 1000 mg oral MET or placebo; all then underwent repeat thoracotomy for intramyocardial injection of EVs or saline. Swine were maintained for 5 weeks before the acquisition of functional and perfusion data immediately before terminal myocardial harvest. Immunoblotting and immunofluorescence were performed on the most ischemic tissue from all groups. RESULTS: Regardless of EV administration, animals that received MET exhibited significantly improved ejection fraction, cardiac index, and contractility at rest and during rapid myocardial pacing, improved perfusion to the most ischemic myocardial region at rest and during pacing, and markedly reduced apoptosis. CONCLUSIONS: MET administration reduced apoptotic cell death, improved perfusion, and augmented both intrinsic and load-dependent myocardial performance in a highly translatable large animal model of chronic myocardial ischemia and MS.

"Filler-Associated Acute Stroke Syndrome": Classification, Predictive Modelling of Hyaluronidase Efficacy, and Updated Case Review on Neurological and Visual Complications.

INTRODUCTION: The rising use of soft tissue fillers for aesthetic procedures has seen an increase in complications, including vascular occlusions and neurological symptoms that resemble stroke. This study synthesizes information on central nervous system (CNS) complications post-filler injections and evaluates the effectiveness of hyaluronidase (HYAL) treatment. METHODS: A thorough search of multiple databases, including PubMed, EMBASE, Scopus, Web of Science, Google Scholar, and Cochrane, focused on publications from January 2014 to January 2024. Criteria for inclusion covered reviews and case reports that documented CNS complications related to soft tissue fillers. Advanced statistical and computational techniques, including logistic regression, machine learning, and Bayesian analysis, were utilized to dissect the factors influencing therapeutic outcomes. RESULTS: The analysis integrated findings from 20 reviews and systematic analyses, with 379 cases reported since 2018. Hyaluronic acid (HA) was the most commonly used filler, particularly in nasal region injections. The average age of patients was 38, with a notable increase in case reports in 2020. Initial presentation data revealed that 60.9% of patients experienced no light perception, while ptosis and ophthalmoplegia were present in 54.3 and 42.7% of cases, respectively. The statistical and machine learning analyses did not establish a significant linkage between the HYAL dosage and patient recovery; however, the injection site emerged as a critical determinant. CONCLUSION: The study concludes that HYAL treatment, while vital for managing complications, varies in effectiveness based on the injection site and the timing of administration. The non-Newtonian characteristics of HA fillers may also affect the incidence of complications. The findings advocate for tailored treatment strategies incorporating individual patient variables, emphasizing prompt and precise intervention to mitigate the adverse effects of soft tissue fillers. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Effects of diet-induced metabolic syndrome on cardiac function and angiogenesis in response to the sodium-glucose cotransporter-2 inhibitor canagliflozin.

INTRODUCTION: Sodium-glucose cotransporter-2 inhibitors are antidiabetic medications that have been shown to decrease cardiovascular events and heart failure-related mortality in clinical studies. We attempt to examine the complex interplay between metabolic syndrome and the sodium-glucose cotransporter-2 inhibitor canagliflozin (CAN) in a clinically relevant model of chronic myocardial ischemia. METHODS: Twenty-one Yorkshire swine were fed a high-fat diet starting at 6 weeks of age to induce metabolic syndrome. At 11 weeks, all underwent placement of an ameroid constrictor around the left circumflex coronary artery to induce chronic myocardial ischemia. After 2 weeks, swine received either control (CON) (n = 11) or CAN 300 mg by mouth daily (n = 10) for 5 weeks, whereupon all underwent terminal harvest. RESULTS: There was a significant increase in cardiac output and heart rate with a decrease in pulse pressure in the CAN group compared with CON (all P values < .05). The CAN group had a significant increase in capillary density (P = .02). There was no change in myocardial perfusion or arteriolar density. CAN induced a significant increase in markers of angiogenesis, including Phospho-endothelial nitric oxide synthase, Endothelial nitric oxide synthase, vascular endothelial growth factor receptor-1, heat shock protein 70, and extracellular signal-regulated kinases (all P values < .05), plausibly resulting in capillary angiogenesis. CONCLUSIONS: CAN treatment leads to a significant increase in capillary density and augmented cardiac function in a swine model of chronic myocardial ischemia in the setting of metabolic syndrome. This work further elucidates the mechanism of sodium-glucose cotransporter-2 inhibitors in patients with cardiac disease; however, more studies are needed to determine if this increase in capillary density plays a role in the improvements seen in clinical studies.

Cardioprotection in cardiovascular surgery.

Since the invention of cardiopulmonary bypass, cardioprotective strategies have been investigated to mitigate ischemic injury to the heart during aortic cross-clamping and reperfusion injury with cross-clamp release. With advances in cardiac surgical and percutaneous techniques and post-operative management strategies including mechanical circulatory support, cardiac surgeons are able to operate on more complex patients. Therefore, there is a growing need for improved cardioprotective strategies to optimize outcomes in these patients. This review provides an overview of the basic principles of cardioprotection in the setting of cardiac surgery, including mechanisms of cardiac injury in the context of cardiopulmonary bypass, followed by a discussion of the specific approaches to optimizing cardioprotection in cardiac surgery, including refinements in cardiopulmonary bypass and cardioplegia, ischemic conditioning, use of specific anesthetic and pharmaceutical agents, and novel mechanical circulatory support technologies. Finally, translational strategies that investigate cardioprotection in the setting of cardiac surgery will be reviewed, with a focus on promising research in the areas of cell-based and gene therapy. Advances in this area will help cardiologists and cardiac surgeons mitigate myocardial ischemic injury, improve functional post-operative recovery, and optimize clinical outcomes in patients undergoing cardiac surgery.

Patients with uncontrolled hypertension subjected to cardiopulmonary bypass have altered coronary vasomotor responses to serotonin.

BACKGROUND: We previously found that cardioplegic arrest and cardiopulmonary bypass are associated with altered coronary arteriolar response to serotonin in patients undergoing cardiac surgery. In this study, we investigated the effects of hypertension on coronary microvascular vasomotor tone in response to serotonin and alterations in serotonin receptor protein expression in the setting of cardioplegic arrest and cardiopulmonary bypass. METHODS: Coronary arterioles were dissected from harvested pre- and post-cardioplegic arrest and cardiopulmonary bypass right atrial tissue samples of patients undergoing cardiac surgery with normotension, well-controlled hypertension, and uncontrolled hypertension. Vasomotor tone was assessed by video-myography, and protein expression was measured with immunoblotting. RESULTS: Pre-cardioplegic arrest and cardiopulmonary bypass, serotonin induced moderate relaxation responses of coronary arterioles in normotension and well-controlled hypertension patients, whereas serotonin caused moderate contractile responses in uncontrolled hypertension patients. Post-cardioplegic arrest and cardiopulmonary bypass, serotonin caused contractile responses of coronary arterioles in all 3 groups. The post-cardioplegic arrest and cardiopulmonary bypass contractile response to serotonin was significantly higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups (P < .05). Pre-cardioplegic arrest and cardiopulmonary bypass, expression of the serotonin 1A receptor was significantly lower in the uncontrolled hypertension group compared with the well-controlled hypertension and normotension groups (P = .01 and P < .001). Serotonin 1B receptor expression was higher in the uncontrolled hypertension group compared with the normotension or well-controlled hypertension groups post-cardioplegic arrest and cardiopulmonary bypass (P = .03 and P = .046). CONCLUSION: Uncontrolled hypertension is associated with an increased coronary contractile response of coronary microvessels to serotonin and altered serotonin receptor protein expression after cardioplegic arrest and cardiopulmonary bypass. These findings may contribute to a worse postoperative coronary spasm and worsened recovery of coronary perfusion in patients with uncontrolled hypertension after cardioplegic arrest and cardiopulmonary bypass and cardiac surgery.

Community interventions for pandemic preparedness: A scoping review of pandemic preparedness lessons from HIV, COVID-19, and other public health emergencies of international concern.

Community action is broadly recognised as central to comprehensive and effective system responses to pandemics. However, there is uncertainty about how and where communities can be best supported to bolster long-term resilience and preparedness. We applied a typology of community interventions (Community Informing, Consulting, Involving, Collaborating or Empowering-or CICICE) to cover the diverse range of interventions identified across the literature and used this to structure a scoping review addressing three linked topics: (i) how CICICE interventions have been understood and applied in the literature on epidemic and pandemic preparedness; (ii) the spectrum of interventions that have been implemented to strengthen CICICE and (iii) what evidence is available on their effectiveness in influencing preparedness for current and future emergencies. We drew on peer-reviewed and grey literature from the HIV (from 2000) and COVID-19 pandemics and recent public health emergencies of international concern (from 2008), identified through systematic searches in MEDLINE, Scopus, the Cochrane Collaboration database, supplemented by keyword-structured searches in GoogleScholar and websites of relevant global health organisations. Following screening and extraction, key themes were identified using a combined inductive/deductive approach. 130 papers met the criteria for inclusion. Interventions for preparedness were identified across the spectrum of CICICE. Most work on COVID-19 focused on informing and consulting rather than capacity building and empowerment. The literature on HIV was more likely to report interventions emphasising human rights perspectives and empowerment. There was little robust evidence on the role of CICICE interventions in building preparedness. Evidence of effect was most robust for multi-component interventions for HIV prevention and control. Much of the reporting focused on intermediate outcomes, including measures of health service utilisation. We put forward a series of recommendations to help address evidence shortfalls, including clarifying definitions, organising and stratifying interventions by several parameters and strengthening evaluation methods for CICICE.

Proteomic Profiling of SGLT-2 Inhibitor Canagliflozin in a Swine Model of Chronic Myocardial Ischemia.

BACKGROUND: Sodium-glucose cotransporter-2 (SGLT2) inhibitors are known to be cardioprotective independent of glucose control, but the mechanisms of these benefits are unclear. We previously demonstrated improved cardiac function and decreased fibrosis in a swine model of chronic myocardial ischemia. The goal of this study is to use high-sensitivity proteomic analyses to characterize specific molecular pathways affected by SGLT-2 inhibitor canagliflozin (CAN) therapy in a swine model of chronic myocardial ischemia. METHODS: Chronic myocardial ischemia was induced in sixteen Yorkshire swine via the placement of an ameroid constrictor to the left circumflex coronary artery. After two weeks of recovery, swine received either 300 mg of CAN daily (n = 8) or a control (n = 8). After five weeks of therapy, the group of swine were euthanized, and left ventricular tissue was harvested and sent for proteomic analysis. RESULTS: Total proteomic analysis identified a total of 3256 proteins between the CAN and control groups. Three hundred and five proteins were statistically different. This included 55 proteins that were downregulated (p < 0.05, fold change <0.5) and 250 that were upregulated (p < 0.05, fold change >2) with CAN treatment. Pathway analysis demonstrated the upregulation of several proteins involved in metabolism and redox activity in the CAN-treated group. The CAN group also exhibited a downregulation of proteins involved in motor activity and cytoskeletal structure. CONCLUSIONS: In our swine model of chronic myocardial ischemia, CAN therapy alters several proteins involved in critical molecular pathways, including redox regulation and metabolism. These findings provide additional mechanistic insights into the cardioprotective effects of canagliflozin.

DPP-4 inhibitor sitagliptin treatment results in altered myocardial metabolic proteome and oxidative phosphorylation in a swine model of chronic myocardial ischemia.

Small animal models have shown improved cardiac function with DPP-4 inhibition, but many human studies have shown worse outcomes or no benefit. We seek to bridge the gap by studying the DPP-4 inhibitor sitagliptin in a swine model of chronic myocardial ischemia using proteomic analysis. Thirteen Yorkshire swine underwent the placement of an ameroid constrictor on the left coronary circumflex artery to model chronic myocardial ischemia. Two weeks post-op, swine received either sitagliptin 100 mg daily (SIT, n = 5) or no drug (CON, n = 8). After 5 weeks of treatment, swine underwent functional measurements and tissue harvest. In the SIT group compared to CON, there was a trend towards decreased cardiac index (p = 0.06). The non-ischemic and ischemic myocardium had 396 and 166 significantly decreased proteins, respectively, in the SIT group compared to CON (all p < 0.01). This included proteins involved in fatty acid oxidation (FAO), myocardial contraction, and oxidative phosphorylation (OXPHOS). Sitagliptin treatment resulted in a trend towards decreased cardiac index and decreased expression of proteins involved in OXPHOS, FAO, and myocardial contraction in both ischemic and non-ischemic swine myocardium. These metabolic and functional changes may provide some mechanistic evidence for outcomes seen in clinical studies.

Intramyocardial Injection of Hypoxia-Conditioned Extracellular Vesicles Modulates Response to Oxidative Stress in the Chronically Ischemic Myocardium.

INTRODUCTION: Patients with advanced coronary artery disease (CAD) who are not eligible for stenting or surgical bypass procedures have limited treatment options. Extracellular vesicles (EVs) have emerged as a potential therapeutic target for the treatment of advanced CAD. These EVs can be conditioned to modify their contents. In our previous research, we demonstrated increased perfusion, decreased inflammation, and reduced apoptosis with intramyocardial injection of hypoxia-conditioned EVs (HEVs). The goal of this study is to further understand the function of HEVs by examining their impact on oxidative stress using our clinically relevant and extensively validated swine model of chronic myocardial ischemia. METHODS: Fourteen Yorkshire swine underwent a left thoracotomy for the placement of an ameroid constrictor on the left circumflex coronary artery to model chronic myocardial ischemia. After two weeks of recovery, the swine underwent a redo thoracotomy with injection of either HEVs (n = 7) or a saline control (CON, n = 7) into the ischemic myocardium. Five weeks after injection, the swine were subjected to terminal harvest. Protein expression was measured using immunoblotting. OxyBlot analysis and 3-nitrotyrosine staining were used to quantify total oxidative stress. RESULTS: There was a significant increase in myocardial expression of the antioxidants SOD 2, GPX-1, HSF-1, UCP-2, catalase, and HO-1 (all p ≤ 0.05) in the HEV group when compared to control animals. The HEVs also exhibited a significant increase in pro-oxidant NADPH oxidase (NOX) 1, NOX 3, p47phox, and p67phox (all p ≤ 0.05). However, no change was observed in the expression of NFkB, KEAP 1, and PRDX1 (all p > 0.05) between the HEV and CON groups. There were no significant differences in total oxidative stress as determined by OxyBlot and 3-nitrotyrosine staining (p = 0.64, p = 0.32) between the groups. CONCLUSIONS: Administration of HEVs in ischemic myocardium induces a significant increase in pro- and antioxidant proteins without a net change in total oxidative stress. These findings suggest that HEV-induced changes in redox signaling pathways may play a role in increased perfusion, decreased inflammation, and reduced apoptosis in ischemic myocardium. Further studies are required to determine if HEVs alter the net oxidative stress in ischemic myocardium at an earlier time point of HEV administration.

Crafting a Rigorous, Clinically Relevant Large Animal Model of Chronic Myocardial Ischemia: What Have We Learned in 20 Years?

The past several decades have borne witness to several breakthroughs and paradigm shifts within the field of cardiovascular medicine, but one component that has remained constant throughout this time is the need for accurate animal models for the refinement and elaboration of the hypotheses and therapies crucial to our capacity to combat human disease. Numerous sophisticated and high-throughput molecular strategies have emerged, including rational drug design and the multi-omics approaches that allow extensive characterization of the host response to disease states and their prospective resolutions, but these technologies all require grounding within a faithful representation of their clinical context. Over this period, our lab has exhaustively tested, progressively refined, and extensively contributed to cardiovascular discovery on the basis of one such faithful representation. It is the purpose of this paper to review our porcine model of chronic myocardial ischemia using ameroid constriction and the subsequent myriad of physiological and molecular-biological insights it has allowed our lab to attain and describe. We hope that, by depicting our methods and the insight they have yielded clearly and completely-drawing for this purpose on comprehensive videographic illustration-other research teams will be empowered to carry our work forward, drawing on our experience to refine their own investigations into the pathogenesis and eradication of cardiovascular disease.