Impaired HDL antioxidant and anti-inflammatory functions are linked to increased mortality in acute heart failure patients

AIMS

Acute heart failure (AHF) is typified by inflammatory and oxidative stress responses, which are associated with unfavorable patient outcomes. Given the anti-inflammatory and antioxidant properties of high-density lipoprotein (HDL), this study sought to examine the relationship between impaired HDL function and mortality in AHF patients. The complex interplay between various HDL-related biomarkers and clinical outcomes remains poorly understood.

METHODS

HDL subclass distribution was quantified by nuclear magnetic resonance spectroscopy. Lecithin-cholesterol acyltransferase (LCAT) activity, cholesterol ester transfer protein (CETP) activity, and paraoxonase (PON-1) activity were assessed using fluorometric assays. HDL-cholesterol efflux capacity (CEC) was assessed in a validated assay using [3H]-cholesterol-labeled J774 macrophages.

RESULTS

Among the study participants, 74 (23.5 %) out of 315 died within three months after hospitalization due to AHF. These patients exhibited lower activities of the anti-oxidant enzymes PON1 and LCAT, impaired CEC, and lower concentration of small HDL subclasses, which remained significant after accounting for potential confounding factors. Smaller HDL particles, particularly HDL3 and HDL4, exhibited a strong association with CEC, PON1 activity, and LCAT activity.

CONCLUSIONS

In patients with AHF, impaired HDL CEC, HDL antioxidant and anti-inflammatory function, and impaired HDL metabolism are associated with increased mortality. Assessment of HDL function and subclass distribution could provide valuable clinical information and help identify patients at high risk.

Low LCAT activity is linked to acute decompensated heart failure and mortality in patients with CKD

Chronic kidney disease (CKD) is often associated with decreased activity of lecithin-cholesterol acyltransferase (LCAT), an enzyme essential for HDL maturation. This reduction in LCAT activity may potentially contribute to an increased risk of cardiovascular mortality in patients with CKD. The objective of this study was to investigate the association between LCAT activity in patients with CKD and the risk of adverse outcomes. We measured serum LCAT activity and characterized lipoprotein profiles using nuclear magnetic resonance spectroscopy in 453 non-dialysis CKD patients from the CARE FOR HOMe study. LCAT activity correlated directly with smaller HDL particle size, a type of HDL potentially linked to greater cardiovascular protection. Over a mean follow-up of 5.0 ± 2.2 years, baseline LCAT activity was inversely associated with risk of death (standardized HR 0.62, 95% CI 0.50-0.76; P < 0.001) and acute decompensated heart failure (ADHF) (standardized HR 0.67, 95% CI 0.52-0.85; P = 0.001). These associations remained significant even after adjusting for other risk factors. Interestingly, LCAT activity was not associated with the incidence of atherosclerotic cardiovascular events or kidney function decline during the follow-up. To conclude, our findings demonstrate that low LCAT activity is independently associated with all-cause mortality and ADHF in patients with CKD, and is directly linked to smaller, potentially more protective HDL subclasses.

Isthmin-1 Improves Aging-Related Cardiac Dysfunction in Mice through Enhancing Glycolysis and SIRT1 Deacetylase Activity

Aging-related cardiac dysfunction poses a major risk factor of mortality for elderly populations, however, efficient treatment for aging-related cardiac dysfunction is far from being known. Isthmin-1 (ISM1) is a novel adipokine that promotes glucose uptake and acts indispensable roles in restraining inflammatory and fibrosis. The present study aims to investigate the potential role and molecular mechanism of ISM1 in aging-related cardiac dysfunction. Aged and matched young mice were overexpressed or silenced with ISM1 to investigate the role of ISM1 in aging-related cardiac dysfunction. Moreover, H9C2 cells were stimulated with D-galactose (D-gal) to examine the role of ISM1 in vitro. Herein, we found that cardiac-specific overexpression of ISM1 significantly mitigated insulin resistance by promoting glucose uptake in aging mice. ISM1 overexpression alleviated while ISM1 silencing deteriorated cellular senescence, cardiac inflammation, and dysfunction in natural and accelerated cardiac aging. Mechanistically, ISM1 promoted glycolysis and activated Sirtuin-1 (SIRT1) through increasing glucose uptake. ISM1 increased glucose uptake via translocating GLUT4 to the surface, thereby enhancing glycolytic flux and hexosamine biosynthetic pathway (HBP) flux, ultimately leading to increased SIRT1 activity through O-GlcNAc modification. ISM1 may serve as a novel potential therapeutic target for preventing aging-related cardiac disease in elderly populations. ISM1 prevents aging-related cardiac dysfunction by promoting glycolysis and enhancing SIRT1 deacetylase activity, making it a promising therapeutic target for aging-related cardiac disease.

High-Density Lipoproteins at the Interface between the NLRP3 Inflammasome and Myocardial Infarction

Despite significant therapeutic advancements, morbidity and mortality following myocardial infarction (MI) remain unacceptably high. This clinical challenge is primarily attributed to two significant factors: delayed reperfusion and the myocardial injury resulting from coronary reperfusion. Following reperfusion, there is a rapid intracellular pH shift, disruption of ionic balance, heightened oxidative stress, increased activity of proteolytic enzymes, initiation of inflammatory responses, and activation of several cell death pathways, encompassing apoptosis, necroptosis, and pyroptosis. The inflammatory cell death or pyroptosis encompasses the activation of the intracellular multiprotein complex known as the NLRP3 inflammasome. High-density lipoproteins (HDL) are endogenous particles whose components can either promote or mitigate the activation of the NLRP3 inflammasome. In this comprehensive review, we explore the role of inflammasome activation in the context of MI and provide a detailed analysis of how HDL can modulate this process.

Hypoxia-inducible factor-1: Regulatory mechanisms and drug therapy in myocardial infarction

Myocardial infarction (MI), an acute cardiovascular disease characterized by coronary artery blockage, inadequate blood supply, and subsequent ischemic necrosis of the myocardium, is one of the leading causes of death. The cellular, physiological, and pathological responses following MI are complex, involving multiple intertwined pathological mechanisms. Hypoxia-inducible factor-1 (HIF-1), a crucial regulator of hypoxia, plays a significant role in of the development of MI by modulating the behavior of various cells such as cardiomyocytes, endothelial cells, macrophages, and fibroblasts under hypoxic conditions. HIF-1 regulates various post-MI adaptive reactions to acute ischemia and hypoxia through various mechanisms. These mechanisms include angiogenesis, energy metabolism, oxidative stress, inflammatory response, and ventricular remodeling. With its crucial role in MI, HIF-1 is expected to significantly influence the treatment of MI. However, the drugs available for the treatment of MI targeting HIF-1 are currently limited, and most contain natural compounds. The development of precision-targeted drugs modulating HIF-1 has therapeutic potential for advancing MI treatment research and development. This study aimed to summarize the regulatory role of HIF-1 in the pathological responses of various cells following MI, the diverse mechanisms of action of HIF-1 in MI, and the potential drugs targeting HIF-1 for treating MI, thus providing the theoretical foundations for potential clinical therapeutic targets.

Association of per- and polyfluoroalkyl substances with hepatic steatosis and metabolic dysfunction-associated fatty liver disease among patients with acute coronary syndrome

Etiology of hepatic steatosis and metabolic dysfunction-associated fatty liver disease (MAFLD) among acute coronary syndrome (ACS) remains unclear. Existing studies suggested the potential role of per- and polyfluoroalkyl substances (PFAS) in comorbidity of hepatic steatosis among ACS patients. Therefore, we conducted a cross-sectional study based on the ACS inpatients to assess the associations of plasma PFAS congeners and mixtures with hepatic steatosis and MAFLD. This study included 546 newly diagnosed ACS patients. Twelve PFAS were quantified using ultra-high-performance liquid chromatography-tandem mass spectrometry. Hepatic steatosis was defined by hepatic steatosis index (HSI). MAFLD was defined as the combination of hepatic steatosis based on the risk factor calculation with metabolic abnormalities. Generalized linear model was used to examine the associations of PFAS congeners with HSI and MAFLD. Adaptive elastic net (AENET) was further used for PFAS congeners selection. Mixture effects were also assessed with Bayesian kernel machine regression model (BKMR). Congeners analysis observed significant greater percent change of HSI for each doubling in PFOS (1.82%, 95% CI: 0.87%, 2.77%), PFHxS (1.17%, 95% CI: 0.46%, 1.89%) and total PFAS (1.84%, 95% CI: 0.56%, 3.14%). Moreover, each doubling in PFOS (OR=1.42, 95% CI: 1.13, 1.81), PFHxS (OR=1.31, 95% CI: 1.09, 1.59) and total PFAS (OR=1.43, 95% CI: 1.06, 1.94) was associated with increased risk of MAFLD. In AENET regression, only PFOS presented significant positive associations with HSI. Mixture analysis indicated significant positive associations between PFAS mixtures and HSI. This is the first study to demonstrate associations of PFAS congeners and mixtures with hepatic steatosis and MAFLD among ACS patients, which provides hypothesis into the mechanisms behind comorbidity of hepatic steatosis among ACS patients, as well as tertiary prevention of ACS.

Understanding Myeloperoxidase-Induced Damage to HDL Structure and Function in the Vessel Wall: Implications for HDL-Based Therapies

Atherosclerosis is a disease of increased oxidative stress characterized by protein and lipid modifications in the vessel wall. One important oxidative pathway involves reactive intermediates generated by myeloperoxidase (MPO), an enzyme present mainly in neutrophils and monocytes. Tandem MS analysis identified MPO as a component of lesion derived high-density lipoprotein (HDL), showing that the two interact in the arterial wall. MPO modifies apolipoprotein A1 (apoA-I), paraoxonase 1 and certain HDL-associated phospholipids in human atheroma. HDL isolated from atherosclerotic plaques depicts extensive MPO mediated posttranslational modifications, including oxidation of tryptophan, tyrosine and methionine residues, and carbamylation of lysine residues. In addition, HDL associated plasmalogens are targeted by MPO, generating 2-chlorohexadecanal, a pro-inflammatory and endothelial barrier disrupting lipid that suppresses endothelial nitric oxide formation. Lesion derived HDL is predominantly lipid-depleted and cross-linked and exhibits a nearly 90% reduction in lecithin-cholesterol acyltransferase activity and cholesterol efflux capacity. Here we provide a current update of the pathophysiological consequences of MPO-induced changes in the structure and function of HDL and discuss possible therapeutic implications and options. Preclinical studies with a fully functional apoA-I variant with pronounced resistance to oxidative inactivation by MPO-generated oxidants are currently ongoing. Understanding the relationships between pathophysiological processes that affect the molecular composition and function of HDL and associated diseases is central to the future use of HDL in diagnostics, therapy, and ultimately disease management.

Mitochondrial Metabolism in Myocardial Remodeling and Mechanical Unloading: Implications for Ischemic Heart Disease

Ischemic heart disease refers to myocardial degeneration, necrosis, and fibrosis caused by coronary artery disease. It can lead to severe left ventricular dysfunction (LVEF ≤ 35–40%) and is a major cause of heart failure (HF). In each contraction, myocardium is subjected to a variety of mechanical forces, such as stretch, afterload, and shear stress, and these mechanical stresses are clinically associated with myocardial remodeling and, eventually, cardiac outcomes. Mitochondria produce 90% of ATP in the heart and participate in metabolic pathways that regulate the balance of glucose and fatty acid oxidative phosphorylation. However, altered energetics and metabolic reprogramming are proved to aggravate HF development and progression by disturbing substrate utilization. This review briefly summarizes the current insights into the adaptations of cardiomyocytes to mechanical stimuli and underlying mechanisms in ischemic heart disease, with focusing on mitochondrial metabolism. We also discuss how mechanical circulatory support (MCS) alters myocardial energy metabolism and affects the detrimental metabolic adaptations of the dysfunctional myocardium.

Glycolysis Inhibition Alleviates Cardiac Fibrosis After Myocardial Infarction by Suppressing Cardiac Fibroblast Activation

Objective: To explore the role of glycolysis in cardiac fibroblast (CF) activation and cardiac fibrosis after myocardial infarction (MI).

Method:In vivo: 2-Deoxy-D-glucose (2-DG), a glycolysis inhibitor, was injected into the abdominal cavity of the MI or sham mice every day. On the 28th day, cardiac function was measured by ultrasonic cardiography, and the hearts were harvested. Masson staining and immunofluorescence (IF) were used to evaluate the fibrosis area, and western blot was used to identify the glycolytic level. In vitro, we isolated the CF from the sham, MI and MI with 2-DG treatment mice, and we also activated normal CF with transforming growth factor-β1 (TGF-β1) and block glycolysis with 2-DG. We then detected the glycolytic proteins, fibrotic proteins, and the concentrations of lactate and glucose in the culture medium. At last, we further detected the fibrotic and glycolytic markers in human fibrotic and non-fibrotic heart tissues with masson staining, IF and western blot.

Result: More collagen and glycolytic protein expressions were observed in the MI mice hearts. The mortality increased when mice were treated with 2-DG (100 mg/kg/d) after the MI surgery (Log-rank test, P < 0.05). When the dosage of 2-DG declined to 50 mg/kg/d, and the treatment was started on the 4th day after MI, no statistical difference of mortality between the two groups was observed (Log-rank test, P = 0.98). The collagen volume fraction was smaller and the fluorescence signal of α-smooth muscle actin (α-SMA) was weaker in mice treated with 2-DG than PBS. In vitro, 2-DG could significantly inhibit the increased expression of both the glycolytic and fibrotic proteins in the activated CF.

Conclusion: Cardiac fibrosis is along with the enhancement of CF activation and glycolysis. Glycolysis inhibition can alleviate cardiac fibroblast activation and cardiac fibrosis after myocardial infarction.

Role of high-density lipoproteins in cardioprotection and in reverse remodeling: Therapeutic implications

Cardioprotection includes all mechanisms that contribute to preservation of the heart by reducing or even preventing myocardial damage. High-density lipoproteins (HDLs) are circulating multimolecular platforms that exert a multitude of effects on cardiomyocytes and nonmyocyte cells in the myocardium leading to preservation of cardiac structure and function. Animal intervention studies applying HDL-targeted therapies have provided consistent evidence that HDLs protect against ischemia-reperfusion injury, leading to smaller myocardial infarctions, and that HDLs attenuate infarct expansion and cardiac remodeling post-myocardial infarction. These beneficial effects of HDLs are not restricted to prevention of development of ischemic cardiomyopathy but also apply to prevention of pathological hypertrophy and adverse remodeling in the presence of diabetes or in the presence of pressure overload. Moreover, HDLs can induce reverse remodeling characterized by a reduction of cardiac hypertrophy, a decrease of myocardial fibrosis, a regression of capillary rarefaction, and a restoration of cardiac function. HDL-targeted interventions are an effective treatment for heart failure in animal models. In conclusion, whereas protective effects of HDLs on coronary arteries remain essentially unproven till now, the potential for clinical translation of HDL-targeted interventions in prevention of cardiomyopathy and in treatment of heart failure is supported by consistent evidence from animal intervention studies.

MEDI6012: Recombinant Human Lecithin Cholesterol Acyltransferase, High-Density Lipoprotein, and Low-Density Lipoprotein Receptor-Mediated Reverse Cholesterol Transport

Background MEDI6012 is recombinant human lecithin cholesterol acyltransferase, the rate-limiting enzyme in reverse cholesterol transport. Infusions of lecithin cholesterol acyltransferase have the potential to enhance reverse cholesterol transport and benefit patients with coronary heart disease. The purpose of this study was to test the safety, pharmacokinetic, and pharmacodynamic profile of MEDI6012. Methods and Results This phase 2a double-blind study randomized 48 subjects with stable coronary heart disease on a statin to a single dose of MEDI6012 or placebo (6:2) (NCT02601560) with ascending doses administered intravenously (24, 80, 240, and 800 mg) and subcutaneously (80 and 600 mg). MEDI6012 demonstrated rates of treatment-emergent adverse events that were similar to those of placebo. Dose-dependent increases in high-density lipoprotein cholesterol were observed with area under the concentration-time curves from 0 to 96 hours of 728, 1640, 3035, and 5318 should be: mg·h/mL in the intravenous dose groups and 422 and 2845 mg·h/mL in the subcutaneous dose groups. Peak mean high-density lipoprotein cholesterol percent change was 31.4%, 71.4%, 125%, and 177.8% in the intravenous dose groups and 18.3% and 111.2% in the subcutaneous dose groups, and was accompanied by increases in endogenous apoA1 (apolipoprotein A1) and non-ATP-binding cassette transporter A1 cholesterol efflux capacity. Decreases in apoB (apolipoprotein B) were observed across all dose levels and decreases in atherogenic small low-density lipoprotein particles by 41%, 88%, and 79% at the 80-, 240-, and 800-mg IV doses, respectively. Conclusions MEDI6012 demonstrated an acceptable safety profile and increased high-density lipoprotein cholesterol, endogenous apoA1, and non-ATP-binding cassette transporter A1 cholesterol efflux capacity while reducing the number of atherogenic low-density lipoprotein particles. These findings are supportive of enhanced reverse cholesterol transport and a functional high-density lipoprotein phenotype. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02601560.

High Density Lipoproteins and Diabetes

Epidemiological studies have established that a high plasma high density lipoprotein cholesterol (HDL-C) level is associated with reduced cardiovascular risk. However, recent randomised clinical trials of interventions that increase HDL-C levels have failed to establish a causal basis for this relationship. This has led to a shift in HDL research efforts towards developing strategies that improve the cardioprotective functions of HDLs, rather than simply increasing HDL-C levels. These efforts are also leading to the discovery of novel HDL functions that are unrelated to cardiovascular disease. One of the most recently identified functions of HDLs is their potent antidiabetic properties. The antidiabetic functions of HDLs, and recent key advances in this area are the subject of this review. Given that all forms of diabetes are increasing at an alarming rate globally, there is a clear unmet need to identify and develop new approaches that will complement existing therapies and reduce disease progression as well as reverse established disease. Exploration of a potential role for HDLs and their constituent lipids and apolipoproteins in this area is clearly warranted. This review highlights focus areas that have yet to be investigated and potential strategies for exploiting the antidiabetic functions of HDLs.

HIF-1/AKT Signaling-Activated PFKFB2 Alleviates Cardiac Dysfunction and Cardiomyocyte Apoptosis in Response to Hypoxia

Myocardial infarction (MI) is the most prevalent disease with severe mortality, and hypoxia-induced cardiac injury and cardiomyocyte apoptosis are the significant and harmful consequences of this disease. The cross talk between hypoxia signaling and glycolysis energy flux plays a critical role in modulating MI-related heart disorder. However, the underlying mechanism remains unclear. Here, we aimed to explore the effect of a key glycolytic enzyme of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 2 (PFKFB2) on cardiac dysfunction and apoptosis in response to hypoxia. Our data demonstrated that the mRNA and protein expression of PFKFB2 were significantly elevated in the MI mice. The MI treatment promoted the activation of PFKFB2 in vivo, as presented by the remarkably increased phosphorylation levels of PFKFB2. PFKFB2 depletion enhanced MI-induced cardiac dysfunction and cardiomyocyte apoptosis in the MI mouse model. Moreover, hypoxia treatment dramatically upregulated the expression and activation of PFKFB2 in a time-dependent manner in cardiomyocytes. Hypoxia-stimulated PFKFB2 relieved hypoxia-induced cardiomyocyte apoptosis in vitro. PFKFB2 activated the fructose-2, 6-bisphosphate (Fru-2, 6-p2) /PFK/anaerobic adenosine triphosphate (ATP) glycolysis energy flux in response to hypoxia in cardiomyocytes. Mechanically, hypoxia-activated PFKFB2 by stimulating the hypoxia-inducible factor 1 (HIF-1) /ATK signaling. Thus, we conclude that HIF-1/AKT axis-activated PFKFB2 alleviates cardiac dysfunction and cardiomyocyte apoptosis in response to hypoxia. Our finding presents a new insight into the mechanism by which HIF-1/AKT/PFKFB2 signaling modulates MI-related heart disorder under the hypoxia condition, providing potential therapeutic targets and strategy for hypoxia-related myocardial injury.

Cardiometabolism as an Interlocking Puzzle between the Healthy and Diseased Heart: New Frontiers in Therapeutic Applications

Cardiac metabolism represents a crucial and essential connecting bridge between the healthy and diseased heart. The cardiac muscle, which may be considered an omnivore organ with regard to the energy substrate utilization, under physiological conditions mainly draws energy by fatty acids oxidation. Within cardiomyocytes and their mitochondria, through well-concerted enzymatic reactions, substrates converge on the production of ATP, the basic chemical energy that cardiac muscle converts into mechanical energy, i.e., contraction. When a perturbation of homeostasis occurs, such as an ischemic event, the heart is forced to switch its fatty acid-based metabolism to the carbohydrate utilization as a protective mechanism that allows the maintenance of its key role within the whole organism. Consequently, the flexibility of the cardiac metabolic networks deeply influences the ability of the heart to respond, by adapting to pathophysiological changes. The aim of the present review is to summarize the main metabolic changes detectable in the heart under acute and chronic cardiac pathologies, analyzing possible therapeutic targets to be used. On this basis, cardiometabolism can be described as a crucial mechanism in keeping the physiological structure and function of the heart; furthermore, it can be considered a promising goal for future pharmacological agents able to appropriately modulate the rate-limiting steps of heart metabolic pathways.

Apo AI Nanoparticles Delivered Post Myocardial Infarction Moderate Inflammation

RATIONALE

Decades of research have examined immune-modulatory strategies to protect the heart after an acute myocardial infarction and prevent progression to heart failure but have failed to translate to clinical benefit.

OBJECTIVE

To determine anti-inflammatory actions of n-apo AI (Apo AI nanoparticles) that contribute to cardiac tissue recovery after myocardial infarction.

METHODS AND RESULTS

Using a preclinical mouse model of myocardial infarction, we demonstrate that a single intravenous bolus of n-apo AI (CSL111, 80 mg/kg) delivered immediately after reperfusion reduced the systemic and cardiac inflammatory response. N-apo AI treatment lowered the number of circulating leukocytes by 30±7% and their recruitment into the ischemic heart by 25±10% (all P<5.0×10^-2). This was associated with a reduction in plasma levels of the clinical biomarker of cardiac injury, cardiac troponin-I, by 52±17% (P=1.01×10^-2). N-apo AI reduced the cardiac expression of chemokines that attract neutrophils and monocytes by 60% to 80% and lowered surface expression of integrin CD11b on monocytes by 20±5% (all P<5.0×10^-2). Fluorescently labeled n-apo AI entered the infarct and peri-infarct regions and colocalized with cardiomyocytes undergoing apoptosis and with leukocytes. We further demonstrate that n-apo AI binds to neutrophils and monocytes, with preferential binding to the proinflammatory monocyte subtype and partially via SR-BI (scavenger receptor BI). In patients with type 2 diabetes, we also observed that intravenous infusion of the same n-apo AI (CSL111, 80 mg/kg) similarly reduced the level of circulating leukocytes by 12±5% (all P<5.0×10^-2).

CONCLUSIONS

A single intravenous bolus of n-apo AI delivered immediately post-myocardial infarction reduced the systemic and cardiac inflammatory response through direct actions on both the ischemic myocardium and leukocytes. These data highlight the anti-inflammatory effects of n-apo AI and provide preclinical support for investigation of its use for management of acute coronary syndromes in the setting of primary percutaneous coronary interventions.

PFKFB3-mediated glycolysis rescues myopathic outcomes in the ischemic limb

Compromised muscle mitochondrial metabolism is a hallmark of peripheral arterial disease, especially in patients with the most severe clinical manifestation - critical limb ischemia (CLI). We asked whether inflexibility in metabolism is critical for the development of myopathy in ischemic limb muscles. Using Polg mtDNA mutator (D257A) mice, we reveal remarkable protection from hind limb ischemia (HLI) due to a unique and beneficial adaptive enhancement of glycolytic metabolism and elevated ischemic muscle PFKFB3. Similar to the relationship between mitochondria from CLI and claudicating patient muscles, BALB/c muscle mitochondria are uniquely dysfunctional after HLI onset as compared with the C57BL/6 (BL6) parental strain. AAV-mediated overexpression of PFKFB3 in BALB/c limb muscles improved muscle contractile function and limb blood flow following HLI. Enrichment analysis of RNA sequencing data on muscle from CLI patients revealed a unique deficit in the glucose metabolism Reactome. Muscles from these patients express lower PFKFB3 protein, and their muscle progenitor cells possess decreased glycolytic flux capacity in vitro. Here, we show supplementary glycolytic flux as sufficient to protect against ischemic myopathy in instances where reduced blood flow-related mitochondrial function is compromised preclinically. Additionally, our data reveal reduced glycolytic flux as a common characteristic of the failing CLI patient limb skeletal muscle.

Cardiac metabolism as a driver and therapeutic target of myocardial infarction

Reducing infarct size during a cardiac ischaemic-reperfusion episode is still of paramount importance, because the extension of myocardial necrosis is an important risk factor for developing heart failure. Cardiac ischaemia-reperfusion injury (IRI) is in principle a metabolic pathology as it is caused by abruptly halted metabolism during the ischaemic episode and exacerbated by sudden restart of specific metabolic pathways at reperfusion. It should therefore not come as a surprise that therapy directed at metabolic pathways can modulate IRI. Here, we summarize the current knowledge of important metabolic pathways as therapeutic targets to combat cardiac IRI. Activating metabolic pathways such as glycolysis (eg AMPK activators), glucose oxidation (activating pyruvate dehydrogenase complex), ketone oxidation (increasing ketone plasma levels), hexosamine biosynthesis pathway (O-GlcNAcylation; administration of glucosamine/glutamine) and deacetylation (activating sirtuins 1 or 3; administration of NAD+ -boosting compounds) all seem to hold promise to reduce acute IRI. In contrast, some metabolic pathways may offer protection through diminished activity. These pathways comprise the malate-aspartate shuttle (in need of novel specific reversible inhibitors), mitochondrial oxygen consumption, fatty acid oxidation (CD36 inhibitors, malonyl-CoA decarboxylase inhibitors) and mitochondrial succinate metabolism (malonate). Additionally, protecting the cristae structure of the mitochondria during IR, by maintaining the association of hexokinase II or creatine kinase with mitochondria, or inhibiting destabilization of FO F1 -ATPase dimers, prevents mitochondrial damage and thereby reduces cardiac IRI. Currently, the most promising and druggable metabolic therapy against cardiac IRI seems to be the singular or combined targeting of glycolysis, O-GlcNAcylation and metabolism of ketones, fatty acids and succinate.

The Apolipoprotein A-I Mimetic L-4F Attenuates Monocyte Activation and Adverse Cardiac Remodeling after Myocardial Infarction

Excessive inflammation after myocardial infarction (MI) can promote infarct expansion and adverse left ventricular (LV) remodeling. L-4F, a mimetic peptide of apolipoprotein A-I (apoA-I), exhibits anti-inflammatory and anti-atherogenic properties; however, whether L-4F imparts beneficial effects after myocardial infarction (MI) is unknown. Here we demonstrate that L-4F suppresses the expansion of blood, splenic, and myocardial pro-inflammatory monocytes and macrophages in a mouse model of reperfused MI. Changes in immune cell profiles were accompanied by alleviation of post-MI LV remodeling and dysfunction. In vitro, L-4F also inhibited pro-inflammatory and glycolytic gene expression in macrophages. In summary, L-4F treatment prevents prolonged and excessive inflammation after MI, in part through modulation of pro-inflammatory monocytes and macrophages, and improves post-MI LV remodeling. These data suggest that L-4F could be a used as a therapeutic adjunct in humans with MI to limit inflammation and alleviate the progression to heart failure.

High-density lipoprotein-mediated cardioprotection in heart failure

The prevalence of heart failure (HF), including reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF), has increased significantly worldwide. However, the prognosis and treatment of HF are still not good. Recent studies have demonstrated that high-density lipoprotein (HDL) plays an important role in cardiac repair during HF. The exact role and mechanism of HDL in the regulation of HF remain unexplained. Here, we discuss recent findings regarding HDL in the progression of HF, such as the regulation of excitation-contraction coupling, energy homeostasis, inflammation, neurohormone activation, and microvascular dysfunction. The effects of HDL on the regulation of cardiac-related cells, such as endothelial cells (ECs), cardiomyocytes (CMs), and on cardiac resident immune cell dysfunction in HF are also explained. An in-depth understanding of HDL function in the heart may provide new strategies for the prevention and treatment of HF.

Hyperlipidaemia and cardioprotection: Animal models for translational studies

Hyperlipidaemia is a well-established risk factor for cardiovascular diseases and therefore, many animal model have been developed to mimic the human abnormal elevation of blood lipid levels. In parallel, extensive research for the alleviation of ischaemia/reperfusion injury has revealed that hyperlipidaemia is a major co-morbidity that attenuates the cardioprotective effect of conditioning strategies (preconditioning, postconditioning and remote conditioning) and that of pharmacological interventions by interfering with cardioprotective signalling pathways. In the present review article, we summarize the existing data on animal models of hypercholesterolaemia (total, low density and HDL abnormalities) and hypertriglyceridaemia used in ischaemia/reperfusion injury and protection from it. We also provide recommendations on preclinical animal models to be used for translations of the cardioprotective strategies into clinical practice. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Myocardial subcellular glycogen distribution and sarcoplasmic reticulum Ca2+ handling: effects of ischaemia, reperfusion and ischaemic preconditioning

Ischaemic preconditioning (IPC) protects against myocardial ischaemia-reperfusion injury. The metabolic and ionic effects of IPC remain to be clarified in detail. We aimed to investigate the effect of IPC (2 times 5 min ischaemia) on the subcellular distribution of glycogen and Ca²⁺-uptake and leakiness by the sarcoplasmic reticulum (SR) in response to ischaemia-reperfusion in cardiomyocytes of isolated perfused rat hearts (Wistar rats, 335 ± 25 g). As estimated by quantitative transmission electron microscopy, the pre-ischaemic contribution [%, mean (95% CI)] of three sub-fractions of glycogen relative to total glycogen was 50 (39:61) as subsarcolemmal, 41 (31:50) as intermyofibrillar, and 9 (5:13) as intramyofibrillar glycogen. After 25 min of ischaemia, the relative contribution (%) of subsarcolemmal glycogen decreased to 39 (32:47) in control hearts (Con) and to 38 (31:45) in IPC. After 15 min reperfusion the contribution of subsarcolemmal glycogen was restored to pre-ischaemic levels in IPC hearts, but not in Con hearts. IPC increased the left ventricular developed pressure following ischaemia-reperfusion compared with Con. In saponin-skinned cardiomyocyte bundles, ischaemia reduced the SR Ca²⁺-uptake rate, with no effect of IPC. However, IPC reduced a SR Ca²⁺-leakage at pre-ischaemia, after ischaemia and during reperfusion. In conclusion, subsarcolemmal glycogen was preferentially utilised during sustained myocardial ischaemia. IPC improved left ventricular function reflecting reduced ischaemia-reperfusion injury, mediated a re-distribution of glycogen towards a preferential storage within the subsarcolemmal space during reperfusion, and lowered SR Ca²⁺-leakage. Under the present conditions, we found no temporal associations between alterations in glycogen localisation and SR Ca²⁺ kinetics.

Analysis of Cell Type-Specific Effects of MicroRNA-92a Provides Novel Insights Into Target Regulation and Mechanism of Action

BACKGROUND

MicroRNAs (miRs) regulate nearly all biological pathways. Because the dysregulation of miRs can lead to disease progression, they are being explored as novel therapeutic targets. However, the cell type-specific effects of miRs in the heart are poorly understood. Thus, we assessed miR target regulation using miR-92a-3p as an example. Inhibition of miR-92a is known to improve endothelial cell function and recovery after acute myocardial infarction.

METHODS

miR-92a-3p was inhibited by locked nucleic acid (LNA)-based antimiR (LNA-92a) in mice after myocardial infarction. Expression of regulated genes was evaluated 3 days after myocardial infarction by RNA sequencing of isolated endothelial cells, cardiomyocytes, fibroblasts, and CD45⁺ hematopoietic cells.

RESULTS

LNA-92a depleted miR-92a-3p expression in all cell types and derepressed predicted miR-92a-3p targets in a cell type-specific manner. RNAseq showed endothelial cell-specific regulation of autophagy-related genes. Imaging confirmed increased endothelial cell autophagy in LNA-92a treated relative to control animals. In vitro inhibition of miR-92a-3p augmented EC autophagy, derepressed autophagy-related gene 4a, and increased luciferase activity in autophagy-related gene 4a 3'UTR containing reporters, whereas miR-92a-3p overexpression had the opposite effect. In cardiomyocytes, LNA-92a derepressed metabolism-related genes, notably, the high-density lipoprotein transporter Abca8b. LNA-92a further increased fatty acid uptake and mitochondrial function in cardiomyocytes in vitro.

CONCLUSIONS

Our data show that miRs have cell type-specific effects in vivo. Analysis of miR targets in cell subsets disclosed a novel function of miR-92a-3p in endothelial cell autophagy and cardiomyocyte metabolism. Because autophagy is upregulated during ischemia to supply nutrients and cardiomyocyte metabolic-switching improves available substrate utilization, these prosurvival mechanisms may diminish tissue damage.

Reciprocal Multifaceted Interaction Between HDL (High-Density Lipoprotein) and Myocardial Infarction

Despite decades of therapeutic advances, myocardial infarction remains a leading cause of death worldwide. Recent studies have identified HDLs (high-density lipoproteins) as a potential candidate for mitigating coronary ischemia/reperfusion injury via a broad spectrum of signaling pathways. HDL ligands, such as S1P (sphingosine-1-phosphate), Apo (apolipoprotein) A-I, clusterin, and miRNA, may influence the opening of the mitochondrial channel, insulin sensitivity, and production of vascular autacoids, such as NO, prostacyclin, and endothelin-1. In parallel, antioxidant activity and sequestration of oxidized molecules provided by HDL can attenuate the oxidative stress that triggers ischemia/reperfusion. Nevertheless, during myocardial infarction, oxidation and the capture of oxidized and proinflammatory molecules generate large phenotypic and functional changes in HDL, potentially limiting its beneficial properties. In this review, new findings from cellular and animal models, as well as from clinical studies, will be discussed to describe the cardioprotective benefits of HDL on myocardial infarction. Furthermore, mechanisms by which HDL modulates cardiac function and potential strategies to mitigate postmyocardial infarction risk damage by HDL will be detailed throughout the review.

ApoAI-derived peptide increases glucose tolerance and prevents formation of atherosclerosis in mice

AIMS/HYPOTHESIS

Finding new treatment alternatives for individuals with diabetes with severe insulin resistance is highly desired. To identify novel mechanisms that improve glucose uptake in skeletal muscle, independently from insulin levels and signalling, we have explored the therapeutic potential of a short peptide sequence, RG54, derived from apolipoprotein A-I (ApoA-I).

METHODS

INS-1E rat clonal beta cells, C2C12 rat muscle myotubes and J774 mouse macrophages were used to study the impact of RG54 peptide on glucose-stimulated insulin secretion, glucose uptake and cholesterol efflux, respectively. GTTs were carried out on diet-induced insulin-resistant and Lepr^db diabetic mouse models treated with RG54 peptide, and the impact of RG54 peptide on atherosclerosis was evaluated in Apoe^-/- mice. Control mice received ApoA-I protein, liraglutide or NaCl.

RESULTS

The synthetic RG54 peptide induced glucose uptake in cultured muscle myotubes by a similar amount as insulin, and also primed pancreatic beta cells for improved glucose-stimulated insulin secretion. The findings were verified in diet-induced insulin-resistant and Lepr^db diabetic mice, jointly confirming the physiological effect. The RG54 peptide also efficiently catalysed cholesterol efflux from macrophages and prevented the formation of atherosclerotic plaques in Apoe^-/- mice.

CONCLUSIONS/INTERPRETATION

The RG54 peptide exhibits good prospects for providing glucose control and reducing the risk of cardiovascular disease in individuals with severe insulin resistance.

Cardiac ischemia-reperfusion injury under insulin-resistant conditions: SGLT1 but not SGLT2 plays a compensatory protective role in diet-induced obesity

BACKGROUND

Recent large-scale clinical trials have shown that SGLT2-inhibitors reduce cardiovascular events in diabetic patients. However, the regulation and functional role of cardiac sodium-glucose cotransporter (SGLT1 is the dominant isoform) compared with those of other glucose transporters (insulin-dependent GLUT4 is the major isoform) remain incompletely understood. Given that glucose is an important preferential substrate for myocardial energy metabolism under conditions of ischemia-reperfusion injury (IRI), we hypothesized that SGLT1 contributes to cardioprotection during the acute phase of IRI via enhanced glucose transport, particularly in insulin-resistant phenotypes.

METHODS AND RESULTS

The hearts from mice fed a high-fat diet (HFD) for 12 weeks or a normal-fat diet (NFD) were perfused with either the non-selective SGLT-inhibitor phlorizin or selective SGLT2-inhibitors (tofogliflozin, ipragliflozin, canagliflozin) during IRI using Langendorff model. After ischemia-reperfusion, HFD impaired left ventricular developed pressure (LVDP) recovery compared with the findings in NFD. Although phlorizin-perfusion impaired LVDP recovery in NFD, a further impaired LVDP recovery and a dramatically increased infarct size were observed in HFD with phlorizin-perfusion. Meanwhile, none of the SGLT2-inhibitors significantly affected cardiac function or myocardial injury after ischemia-reperfusion under either diet condition. The plasma membrane expression of GLUT4 was significantly increased after IRI in NFD but was substantially attenuated in HFD, the latter of which was associated with a significant reduction in myocardial glucose uptake. In contrast, SGLT1 expression at the plasma membrane remained constant during IRI, regardless of the diet condition, whereas SGLT2 was not detected in the hearts of any mice. Of note, phlorizin considerably reduced myocardial glucose uptake after IRI, particularly in HFD.

CONCLUSIONS

Cardiac SGLT1 but not SGLT2 plays a compensatory protective role during the acute phase of IRI via enhanced glucose uptake, particularly under insulin-resistant conditions, in which IRI-induced GLUT4 upregulation is compromised.

Rethinking good cholesterol: a clinicians' guide to understanding HDL

Low HDL cholesterol dyslipidaemia affects about half of people with type 2 diabetes and represents a major independent risk factor for atherosclerotic cardiovascular disease. The "good cholesterol" label was coined decades ago on the basis of a presumed causal role of HDL cholesterol in atherosclerotic cardiovascular disease. However, this view has been challenged by the negative results of several studies of HDL cholesterol-raising drugs, creating a paradox for clinicians regarding the value of HDL cholesterol as a risk biomarker and therapeutic target, and seemingly contradicting decades of evidence substantiating an inverse relation between HDL cholesterol and cardiovascular disease risk. We seek to resolve this issue by revisiting the history of the HDL hypothesis, chronicling how this paradox is ultimately rooted in the progressive erroneous blurring of the distinction between HDL and HDL cholesterol. We describe the compositional complexity of HDL particles beyond their cholesterol cargo and focus on their role in lipid transport. We discuss the evidence regarding novel HDL functions, including effects on glucose metabolism, and speculate on the implications for type 2 diabetes. HDL cholesterol is an imperfect biomarker of a highly complex and multifunctional lipid transport system, and we should now consider how new HDL markers more causally linked to cardiovascular complications could be adapted for clinical use. In the absence of a superior alternative, HDL cholesterol generally has value as a component of primary cardiovascular disease risk prediction models, including in people with type 2 diabetes. However, to avoid prognostic overgeneralisations, it is high time that the good cholesterol label is dropped.

Loss of GCN5L1 in cardiac cells disrupts glucose metabolism and promotes cell death via reduced Akt/mTORC2 signaling

GCN5L1 regulates protein acetylation and mitochondrial energy metabolism in diverse cell types. In the heart, loss of GCN5L1 sensitizes the myocardium to injury from exposure to nutritional excess and ischemia/reperfusion injury. This phenotype is associated with the reduced acetylation of metabolic enzymes and elevated mitochondrial reactive oxygen species (ROS) generation, although the direct molecular targets of GCN5L1 remain largely unknown. In this study, we sought to determine the mechanism by which GCN5L1 impacts energy substrate utilization and mitochondrial health. We find that hypoxia and reoxygenation (H/R) leads to a reduction in cell viability and Akt phosphorylation in GCN5L1 knockdown AC16 cardiomyocytes, in parallel with elevated glucose utilization and impaired fatty acid use. We demonstrate that glycolysis is uncoupled from glucose oxidation under normoxic conditions in GCN5L1-depleted cells. We show that GCN5L1 directly binds to the Akt-activating mTORC2 component Rictor, and that loss of Rictor acetylation is evident in GCN5L1 knockdown cells. Finally, we show that restoring Rictor acetylation in GCN5L1-depleted cells reduces mitochondrial ROS generation and increases cell survival in response to H/R. These studies suggest that GCN5L1 may play a central role in energy substrate metabolism and cell survival via the regulation of Akt/mTORC2 signaling.

Non-invasive ECG recording and QT interval correction assessment in anesthetized rats and mice

ABSTRACT: Rats and mice are the most common species used in experimental cardiac electrophysiology studies. Electrocardiogram (ECG) recording shows paramount importance for monitoring arrhythmias and cardiac function in several disease models, including QT syndrome. However, the lack of standardized reference values and QT correction formula for different animal species and lineages represent a challenge for ECG interpretation. The aim of this study is to provide an improved method for ECG recording, establishing reference range values and determine the QT formulas with higher correlation to heart rate (HR). A total of 10 Wistar rats, 10 Swiss mice, 10 C57BL/6 mice and 10 FVB/NJ mice were used in the study. Animals were submitted to anesthesia with isoflurane and ECG recording was performed using a six-channel non-invasive electrocardiograph. QT was corrected using the following formulas: Bazzett, Fridericia, Mitchell, Hodges, Van der Water and Framingham. Normal range values for ECG parameters were established in all animals studied. Pearsons’ correlation defined Hodges formula as the most suitable for QT correction. This study demonstrated an improved method of ECG recording with reference values for Swiss, FVB/NJ, C57BL/6 mice, and Wistar rats. Hodges’ formula was the most effective formula for QT correction in rodents, whereas Bazett’s and Friderica formulas were ineffective for such animals. The present work contributes to arrhythmias investigation in experimental cardiology and may reduce misinterpretations in rodents’ ECG.

Cardiovascular organ damage in type 2 diabetes mellitus: the role of lipids and inflammation

BACKGROUND

The relationship between dyslipidemia, inflammation and CV organ damage in type 2 diabetes mellitus (T2DM) is complex. Insulin resistance and inflammatory cytokines interleukins (ILs) increase plasma triglycerides (TG). ILs also up-regulate expression of matrix-metalloproteinases (MMPs) that, together with TG, decrease high density lipoprotein cholesterol (HDL) levels. High TG, low HDL, increased ILs and MMPs trigger structural and functional changes in different parts of cardiovascular (CV) system. To understand better the role of lipids and inflammation in CV organ damage, the present study investigated the inter-relationships between lipids, ILs and MMPs, as well as the associations of lipids, ILs and MMPs with various CV measures, both in diabetic and non-diabetic population (nonT2DM).

METHODS

In T2DM patients (N = 191) and nonT2DM subjects (N = 94) were assessed carotid intima-media thickness (cIMT) and inter-adventitial diameter (IADiam), carotid wave speed (ccaWS), carotid-femoral pulse wave velocity (cfPWV), left ventricular (LV) mass, LV systolic (s') and early diastolic (e') longitudinal velocities of mitral annulus, together with glycemic control, lipid profile, IL-6, IL-18 and MMP-12.

RESULTS

T2DM patients, as compared to nonT2DM subjects, had significantly higher plasma levels of IL-6, IL-18, MMP-12 and lower HDL (P < 0.05-0.0001). They had also higher cIMT, IADiam, ccaWS, cfPWV and LV mass, and lower e' velocity (P < 0.005-0.0001). Both in T2DM patients and nonT2DM subjects, MMP-12 increased with IL-6 (r = 0.43 and 0.39; P < 0.0001) and IL-18 (r = 0.32 and 0.42; P < 0.0001), and HDL decreased with MMP-12 (r = - 0.29 and - 0.42; P < 0.0001). In both populations, MMP-12 was directly associated with IADiam, ccaWS, cfPWV and LV mass (r = 0.42, 0.32, 0.26 and 0.29; P < 0.0001 in T2DM patients, and r = 0.39, 0.28, 0.32 and 0.27; P < 0.01-0.0001 in nonT2DM subjects). In multivariate analysis, MMP-12 remained independently related to IADiam, ccaWS, cfPWV and LV mass in T2DM patients, and to IADiam only in nonT2DM subjects.

CONCLUSIONS

This cross-sectional study demonstrated a direct association between ILs and MMP-12, as well as an inverse association between MMP-12 and HDL, both in T2DM patients and in nonT2DM subjects. In T2DM patients, who had higher levels of ILs and MMP-12, the latter was independently related to several structural and functional markers of preclinical CV organ damage.

PEDF increases GLUT4-mediated glucose uptake in rat ischemic myocardium via PI3K/AKT pathway in a PEDFR-dependent manner

BACKGROUND

Targeted increase in glucose uptake of ischemic myocardium is a potential therapeutic strategy for myocardial ischemia. PEDF presents a profound moderating effect on glucose metabolism of cells, but its role is still controversial. Here, we try to demonstrate the direct effect of PEDF on glucose uptake in ischemic myocyte and to elucidate its underlying mechanism.

METHODS AND RESULTS

Lentivirus vectors carrying PEDF gene were delivered into the myocardium to locally overexpress PEDF in a myocardial ischemia/reperfusion rat model. PET imaging showed that PEDF local overexpression increased [¹⁸F]-FDG uptake of ischemic myocardium. In vitro, PEDF directly increased the glucose uptake in hypoxic cardiomyocytes. The expression of glucose transporter 4 (GLUT4) on plasma membrane of hypoxic cardiomyocytes was significantly upregulated by PEDF, but its total amount was not changed. The increased glucose uptake and cardioprotective effects induced by PEDF were blocked by the GLUT4 inhibitor indinavir. PEDF-mediated GLUT4 translocation and glucose uptake increase in hypoxic cardiomyocytes were prevented by phosphatidyl-inositol-3 kinase (PI3K) inhibitor or AKT inhibitor. The PEDF-mediated glucose uptake was also diminished when PEDF receptor (PEDFR) was downregulated or potent phospholipase A2 enzymatic activity was inhibited.

CONCLUSIONS

PEDF can increase glucose uptake in ischemic myocardium through a PEDFR-dependent mechanism, involving PI3K/AKT signaling and GLUT4 translocation.

Site-specific glycations of apolipoprotein A-I lead to differentiated functional effects on lipid-binding and on glucose metabolism

Prolonged hyperglycemia in poorly controlled diabetes leads to an increase in reactive glucose metabolites that covalently modify proteins by non-enzymatic glycation reactions. Apolipoprotein A-I (apoA-I) of high-density lipoprotein (HDL) is one of the proteins that becomes glycated in hyperglycemia. The impact of glycation on apoA-I protein structure and function in lipid and glucose metabolism were investigated. ApoA-I was chemically glycated by two different glucose metabolites (methylglyoxal and glycolaldehyde). Synchrotron radiation and conventional circular dichroism spectroscopy were used to study apoA-I structure and stability. The ability to bind lipids was measured by lipid-clearance assay and native gel analysis, and cholesterol efflux was measured by using lipid-laden J774 macrophages. Diet induced obese mice with established insulin resistance, L6 rat and C2C12 mouse myocytes, as well as INS-1E rat insulinoma cells, were used to determine in vivo and in vitro glucose uptake and insulin secretion. Site-specific, covalent modifications of apoA-I (lysines or arginines) led to altered protein structure, reduced lipid binding capability and a reduced ability to catalyze cholesterol efflux from macrophages, partly in a modification-specific manner. The stimulatory effects of apoA-I on the in vivo glucose clearance were negatively affected when apoA-I was modified with methylglyoxal, but not with glycolaldehyde. The in vitro data showed that both glucose uptake in muscle cells and insulin secretion from beta cells were affected. Taken together, glycation modifications impair the apoA-I protein functionality in lipid and glucose metabolism, which is expected to have implications for diabetes patients with poorly controlled blood glucose.

Chymase released from hypoxia-activated cardiac mast cells cleaves human apoA-I at Tyr192 and compromises its cardioprotective activity

ApoA-I, the main structural and functional protein of HDL particles, is cardioprotective, but also highly sensitive to proteolytic cleavage. Here, we investigated the effect of cardiac mast cell activation and ensuing chymase secretion on apoA-I degradation using isolated rat hearts in the Langendorff perfusion system. Cardiac mast cells were activated by injection of compound 48/80 into the coronary circulation or by low-flow myocardial ischemia, after which lipid-free apoA-I was injected and collected in the coronary effluent for cleavage analysis. Mast cell activation by 48/80 resulted in apoA-I cleavage at sites Tyr¹⁹² and Phe²²⁹, but hypoxic activation at Tyr¹⁹² only. In vitro, the proteolytic end-product of apoA-I with either rat or human chymase was the Tyr¹⁹²-truncated fragment. This fragment, when compared with intact apoA-I, showed reduced ability to promote migration of cultured human coronary artery endothelial cells in a wound-healing assay. We propose that C-terminal truncation of apoA-I by chymase released from cardiac mast cells during ischemia impairs the ability of apoA-I to heal damaged endothelium in the ischemic myocardium.

High-density lipoprotein (HDL) promotes angiogenesis via S1P3-dependent VEGFR2 activation

High-density lipoprotein (HDL) has previously been shown to promote angiogenesis. However, the mechanisms by which HDL enhances the formation of blood vessels remain to be defined. To address this, the effects of HDL on the proliferation, transwell migration and tube formation of human umbilical vein endothelial cells were investigated. By examining the abundance and phosphorylation (i.e., activation) of the vascular endothelial growth factor receptor VEGFR2 and modulating the activity of the sphingosine-1 phosphate receptors S1P1-3 and VEGFR2, we characterized mechanisms controlling angiogenic responses in response to HDL exposure. Here, we report that HDL dose-dependently increased endothelial proliferation, migration and tube formation. These events were in association with increased VEGFR2 abundance and rapid VEGFR2 phosphorylation at Tyr1054/Tyr1059 and Tyr1175 residues in response to HDL. Blockade of VEGFR2 activation by the VEGFR2 inhibitor SU1498 markedly abrogated the pro-angiogenic capacity of HDL. Moreover, the S1P3 inhibitor suramin prevented VEGFR2 expression and abolished endothelial migration and tube formation, while the S1P1 agonist CYM-5442 and the S1P2 inhibitor JTE-013 had no effect. Last, the role of S1P3 was further confirmed in regulation of S1P-induced endothelial proliferation, migration and tube formation via up-regulation and activation of VEGFR2. Together, these findings argue that HDL promotes angiogenesis via S1P3-dependent up-regulation and activation of VEGFR2 and also suggest that the S1P-S1P3-VEGFR2 signaling cascades as a novel target for HDL-modulating therapy implicated in vascular remodeling and functional recovery in atherosclerotic diseases such as myocardial infarction and ischemic stroke.

Thrombosis and Vascular Inflammation in Diabetes: Mechanisms and Potential Therapeutic Targets

Cardiovascular disease remains the main cause of morbidity and mortality in patients with diabetes. The risk of vascular ischemia is increased in this population and outcome following an event is inferior compared to individuals with normal glucose metabolism. The reasons for the adverse vascular profile in diabetes are related to a combination of more extensive atherosclerotic disease coupled with an enhanced thrombotic environment. Long-term measures to halt the accelerated atherosclerotic process in diabetes have only partially addressed vascular pathology, while long-term antithrombotic management remains largely similar to individuals without diabetes. We address in this review the pathophysiological mechanisms responsible for atherosclerosis with special emphasis on diabetes-related pathways. We also cover the enhanced thrombotic milieu, characterized by increased platelet activation, raised activity of procoagulant proteins together with compromised function of the fibrinolytic system. Potential new therapeutic targets to reduce the risk of atherothrombosis in diabetes are explored, including alternative use of existing therapies. Special emphasis is placed on diabetes-specific therapeutic targets that have the potential to reduce vascular risk while keeping an acceptable clinical side effect profile. It is now generally acknowledged that diabetes is not a single clinical entity but a continuum of various stages of the condition with each having a different vascular risk. Therefore, we propose that future therapies aiming to reduce vascular risk in diabetes require a stratified approach with each group having a "stage-specific" vascular management strategy. This "individualized care" in diabetes may prove to be essential to improve vascular outcome in this high risk population.

Papers of note in Science Translational Medicine (411)

This week’s articles describe ways to potentially prevent heart failure after myocardial infarction and treat the autoimmune disease plaque psoriasis.