Vascular-Protective Effects of High-Density Lipoprotein Include the Downregulation of the Angiotensin II Type 1 Receptor

Increased high-density lipoprotein cholesterol in patients with type 2 diabetes and its correlates: a cross-sectional, matched case-control survey

BACKGROUND

So far, high-density lipoprotein cholesterol (HDL-C) levels and mortality were shown to have a U-shaped relationship. Additionally, high HDL-C levels increase the risk of developing a variety of diseases. However, a paucity of data exists regarding the characteristics of people with high HDL-C levels. The aim of this study was to assess the demographics and characteristics of patients with high HDL-C levels and compare their features with normal and low HDL-C groups.

METHODS

As a cross-sectional, matched case-control study, a total of 510 patients with type 2 diabetes (T2D) were enrolled in the study and categorized into three matched groups according to their HDL-C concentrations. The studied groups were matched by their age and gender. Restricted cubic spline (RCS) curves were designed to evaluate the relationship between height, blood pressure, triglyceride, and vitamin D concentrations with the probability of having high HDL-C levels. Furthermore, violin plots were conducted to illustrate the distribution of continuous variables within each group.

RESULTS

This study showed that having high HDL-C (more than 70 mg/dL) compared to having low HDL-C (less than 40 mg/dL in men and 50 mg/dL in women) was significantly associated with height (OR 0.918, 95% CI 0.866-0.974), systolic blood pressure (SBP) (0.941, 0.910-0.972), vitamin D (0.970, 0.941-0.999), and triglyceride (0.992, 0.987-0.998) serum concentrations. Further analysis investigated that having high HDL-C levels compared to desired HDL-C levels (40 ≤ HDL-C levels < 70 in men and 50 ≤ HDL-C levels < 70 in women) was inversely associated with having SPB values greater than 130 mmHg. Besides, sufficient vitamin D levels (above 20 ng/ml) could 0.349 times decrease the odds of having high HDL-C versus normal HDL-C levels.

CONCLUSION

Sufficient vitamin D levels, SPB values higher than 130 mmHg, as well as increased triglyceride levels, were inversely associated with having high HDL levels. However, higher height values were associated with a decreased likelihood of having high HDL.

Associations between long-term averages of metabolic parameters in adulthood and cardiac structure and function in later life

The effects of long-term levels of body mass index (BMI), blood pressure (BP), plasma lipids and fasting blood glucose (FBG) on the cardiac structure and function in later life in general population are to evaluate. We included adult participants without heart failure from Framingham Heart Study. The respective averages over a span of 30-36 years of seven parameters were pooled into linear regression models simultaneously to evaluate their associations with subsequent left atrial internal dimension (LAID), left ventricular mass index (LVMi), internal dimension (LVID), ejection fraction (LVEF), global longitudinal strain (GLS) and mitral inflow velocity to early diastolic mitral annular velocity (E/é). In 1838 participants (56.0% female, mean age 66.1 years), per 1-standard deviation (SD) increment of mean BMI correlated with larger LAID and LVID (β 0.05~0.17, standard error [SE] 0.01 for all), greater LVMi (β [SE], 1.49 [0.46]), worse E/é (β [SE], 0.28 [0.05]). Per 1-SD increment of mean systolic BP correlated with greater LVMi (β [SE], 4.70 [0.69]), LVEF (β [SE], 0.73 [0.24]), E/é (β [SE], 0.52 [0.08]), whereas increase of mean diastolic BP correlated with smaller LVMi (β [SE], -1.61 [0.62]), LVEF (β [SE], -0.46 [0.22]), E/é (β [SE], -0.30 [0.07]). Per 1-SD increment of mean high density lipoprotein cholesterol (HDL-c) correlated with smaller LVID (β [SE], -0.03 [0.01]) and better systolic function (LVEF, β [SE], 0.63 [0.19]; GLS, β [SE], -0.20 [0.10]). The variabilities of BMI, BP and HDL-c also correlated with certain cardiac measurements. In long-term, BMI affected the size and mass of heart chambers, systolic and diastolic BP differently influenced left ventricular mass and function, higher HDL-c linked to better systolic function. Clinical trial registration: URL: https://clinicaltrials.gov . Identifier: NCT00005121.

Angiotensin II type 1a receptor knockout ameliorates high-fat diet-induced cardiac dysfunction by regulating glucose and lipid metabolism

Obesity-related cardiovascular diseases are associated with overactivation of the renin-angiotensin system (RAS). However, the underlying mechanisms remain elusive. In this study, we investigate the role of angiotensin II (Ang II) in high-fat diet (HFD)-induced cardiac dysfunction by focusing on cardiac glucose and lipid metabolism and energy supply. Ang II plays a role in cardiovascular regulation mainly by stimulating angiotensin II type 1 receptor (AT1R), among which AT1aR is the most important subtype in regulating the function of the cardiovascular system. AT1aR gene knockout (AT1aR ‒/‒) rats and wild-type (WT) rats are randomly divided into four groups and fed with either a normal diet (ND) or a HFD for 12 weeks. The myocardial lipid content, Ang II level and cardiac function are then evaluated. The expressions of a number of genes involved in glucose and fatty acid oxidation and mitochondrial dynamics are measured by quantitative polymerase chain reaction and western blot analysis. Our results demonstrate that AT1aR knockout improves HFD-induced insulin resistance and dyslipidemia as well as lipid deposition and left ventricular dysfunction compared with WT rats fed a HFD. In addition, after feeding with HFD, AT1aR ‒/‒ rats not only show further improvement in glucose and fatty acid oxidation but also have a reverse effect on increased mitochondrial fission proteins. In conclusion, AT1aR deficiency ameliorates HFD-induced cardiac dysfunction by enhancing glucose and fatty acid oxidation, regulating mitochondrial dynamics-related protein changes, and further promoting cardiac energy supply.

The potential role of scavenger receptor B type I (SR-BI) in SARS-CoV-2 infection

Scavenger receptor type B I (SR-BI), the major receptor for high-density lipoprotein (HDL) mediates the delivery of cholesterol ester and cholesterol from HDL to the cell membrane. SR-BI is implicated as a receptor for entry of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2). SR-BI is colocalized with the angiotensin-converting enzyme 2 (ACE2) increasing the binding and affinity of SARS-CoV-2 to ACE2 with subsequent viral internalization. SR-BI regulates lymphocyte proliferation and the release of pro-inflammatory cytokines from activated macrophages and lymphocytes. SR-BI is reduced during COVID-19 due to consumption by SARS-CoV-2 infection. COVID-19-associated inflammatory changes and high angiotensin II (AngII) might be possible causes of repression of SR-BI in SARS-CoV-2 infection. In conclusion, the downregulation of SR-BI in COVID-19 could be due to direct invasion by SARS-CoV-2 or through upregulation of pro-inflammatory cytokines, inflammatory signaling pathways, and high circulating AngII. Reduction of SR-BI in COVID-19 look like ACE2 may provoke COVID-19 severity through exaggeration of the immune response. Further studies are invoked to clarify the potential role of SR-BI in the pathogenesis of COVID-19 that could be protective rather than detrimental.

Role of Oxidative Stress in Diabetic Cardiomyopathy

Type 2 diabetes is a redox disease. Oxidative stress and chronic inflammation induce a switch of metabolic homeostatic set points, leading to glucose intolerance. Several diabetes-specific mechanisms contribute to prominent oxidative distress in the heart, resulting in the development of diabetic cardiomyopathy. Mitochondrial overproduction of reactive oxygen species in diabetic subjects is not only caused by intracellular hyperglycemia in the microvasculature but is also the result of increased fatty oxidation and lipotoxicity in cardiomyocytes. Mitochondrial overproduction of superoxide anion radicals induces, via inhibition of glyceraldehyde 3-phosphate dehydrogenase, an increased polyol pathway flux, increased formation of advanced glycation end-products (AGE) and activation of the receptor for AGE (RAGE), activation of protein kinase C isoforms, and an increased hexosamine pathway flux. These pathways not only directly contribute to diabetic cardiomyopathy but are themselves a source of additional reactive oxygen species. Reactive oxygen species and oxidative distress lead to cell dysfunction and cellular injury not only via protein oxidation, lipid peroxidation, DNA damage, and oxidative changes in microRNAs but also via activation of stress-sensitive pathways and redox regulation. Investigations in animal models of diabetic cardiomyopathy have consistently demonstrated that increased expression of the primary antioxidant enzymes attenuates myocardial pathology and improves cardiac function.

Role of Oxidative Stress in Heart Failure: Insights from Gene Transfer Studies

Under physiological circumstances, there is an exquisite balance between reactive oxygen species (ROS) production and ROS degradation, resulting in low steady-state ROS levels. ROS participate in normal cellular function and in cellular homeostasis. Oxidative stress is the state of a transient or a persistent increase of steady-state ROS levels leading to disturbed signaling pathways and oxidative modification of cellular constituents. It is a key pathophysiological player in pathological hypertrophy, pathological remodeling, and the development and progression of heart failure. The heart is the metabolically most active organ and is characterized by the highest content of mitochondria of any tissue. Mitochondria are the main source of ROS in the myocardium. The causal role of oxidative stress in heart failure is highlighted by gene transfer studies of three primary antioxidant enzymes, thioredoxin, and heme oxygenase-1, and is further supported by gene therapy studies directed at correcting oxidative stress linked to metabolic risk factors. Moreover, gene transfer studies have demonstrated that redox-sensitive microRNAs constitute potential therapeutic targets for the treatment of heart failure. In conclusion, gene therapy studies have provided strong corroborative evidence for a key role of oxidative stress in pathological remodeling and in the development of heart failure.

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.

Role of the central renin‑angiotensin system in hypertension (Review)

Present in more than one billion adults, hypertension is the most significant modifiable risk factor for mortality resulting from cardiovascular disease. Although its pathogenesis is not yet fully understood, the disruption of the renin-angiotensin system (RAS), consisting of the systemic and brain RAS, has been recognized as one of the primary reasons for several types of hypertension. Therefore, acquiring sound knowledge of the basic science of RAS and the under- lying mechanisms of the signaling pathways associated with RAS may facilitate the discovery of novel therapeutic targets with which to promote the management of patients with cardiovascular and kidney disease. In total, 4 types of angiotensin II receptors have been identified (AT1R-AT4R), of which AT1R plays the most important role in vasoconstriction and has been most extensively studied. It has been found in several regions of the brain, and its distribution is highly associated with that of angiotensin-like immunoreactivity in nerve terminals. The effect of AT1R involves the activation of multiple media and signaling pathways, among which the most important signaling pathways are considered to be AT1R/JAK/STAT and Ras/Raf/MAPK pathways. In addition, the regulation of the nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) and cyclic AMP response element-binding (CREB) pathways is also closely related to the effect of ATR1. Their mechanisms of action are related to pro-inflammatory and sympathetic excitatory effects. Central AT1R is involved in almost all types of hypertension, including spontaneous hypertension, salt-sensitive hypertension, obesity-induced hypertension, renovascular hypertension, diabetic hypertension, L-NAME-induced hypertension, stress-induced hypertension, angiotensin II-induced hyper- tension and aldosterone-induced hypertension. There are 2 types of central AT1R blockade, acute blockade and chronic blockade. The latter can be achieved by chemical blockade or genetic engineering. The present review article aimed to high- light the prevalence, functions, interactions and modulation means of central AT-1R in an effort to assist in the treatment of several pathological conditions. The identification of angiotensin-derived peptides and the development of AT-2R agonists may provide a wider perspective on RAS, as well as novel therapeutic strategies.

Fetal High-Density Lipoproteins: Current Knowledge on Particle Metabolism, Composition and Function in Health and Disease

Cholesterol and other lipids carried by lipoproteins play an indispensable role in fetal development. Recent evidence suggests that maternally derived high-density lipoprotein (HDL) differs from fetal HDL with respect to its proteome, size, and function. Compared to the HDL of adults, fetal HDL is the major carrier of cholesterol and has a unique composition that implies other physiological functions. Fetal HDL is enriched in apolipoprotein E, which binds with high affinity to the low-density lipoprotein receptor. Thus, it appears that a primary function of fetal HDL is the transport of cholesterol to tissues as is accomplished by low-density lipoproteins in adults. The fetal HDL-associated bioactive sphingolipid sphingosine-1-phosphate shows strong vasoprotective effects at the fetoplacental vasculature. Moreover, lipoprotein-associated phospholipase A2 carried by fetal-HDL exerts anti-oxidative and athero-protective functions on the fetoplacental endothelium. Notably, the mass and activity of HDL-associated paraoxonase 1 are about 5-fold lower in the fetus, accompanied by an attenuation of anti-oxidative activity of fetal HDL. Cholesteryl ester transfer protein activity is reduced in fetal circulation despite similar amounts of the enzyme in maternal and fetal serum. This review summarizes the current knowledge on fetal HDL as a potential vasoprotective lipoprotein during fetal development. We also provide an overview of whether and how the protective functionalities of HDL are impaired in pregnancy-related syndromes such as pre-eclampsia or gestational diabetes mellitus.

Immunomodulation in Heart Failure with Preserved Ejection Fraction: Current State and Future Perspectives

The heart failure (HF) epidemic is growing and approximately half of the HF patients have heart failure with preserved ejection fraction (HFpEF). HFpEF is a heterogeneous syndrome, characterized by a preserved left ventricular ejection fraction (LVEF ≥ 50%) with diastolic dysfunction, and is associated with high morbidity and mortality. Underlying comorbidities of HFpEF, i.e., hypertension, type 2 diabetes mellitus, obesity, and renal failure, lead to a systemic pro-inflammatory state, thereby affecting normal cardiac function. Increased inflammatory biomarkers predict incident HFpEF and are higher in patients with HFpEF as compared with heart failure with reduced ejection fraction (HFrEF). Randomized trials in HFpEF patients using traditional HF medication failed to demonstrate a clear benefit on hard endpoints (mortality and/or HF hospitalization). Therefore, therapies targeting underlying comorbidities and systemic inflammation in early HFpEF may provide better opportunities. Here, we provide an overview of the current state and future perspectives of immunomodulatory therapies for HFpEF.

MALDI-IMS as a Tool to Determine the Myocardial Response to Syndecan-2-Selected Mesenchymal Stromal Cell Application in an Experimental Model of Diabetic Cardiomyopathy

PURPOSE

Mesenchymal stromal cells (MSC) are an attractive tool for treatment of diabetic cardiomyopathy. Syndecan-2/CD362 has been identified as a functional marker for MSC isolation. Imaging mass spectrometry (IMS) allows for the characterization of therapeutic responses in the left ventricle. This study aims to investigate whether IMS can assess the therapeutic effect of CD362+ -selected MSC on early onset experimental diabetic cardiomyopathy.

EXPERIMENTAL DESIGN

1 × 106 wild type (WT), CD362- , or CD362+ MSC are intravenously injected into db/db mice. Four weeks later, mice are hemodynamically characterized and subsequently sacrificed for IMS combined with bottom-up mass spectrometry, and isoform and phosphorylation analyses of cardiac titin.

RESULTS

Overall alterations of the cardiac proteome signatures, especially titin, are observed in db/db compared to control mice. Interestingly, only CD362+ MSC can overcome the reduced titin intensity distribution and shifts the isoform ratio toward the more compliant N2BA form. In contrast, WT and CD362- MSCs improve all-titin phosphorylation and protein kinase G activity, which is reflected in an improvement in diastolic performance.

CONCLUSIONS AND CLINICAL RELEVANCE

IMS enables the characterization of differences in titin intensity distribution following MSC application. However, further analysis of titin phosphorylation is needed to allow for the assessment of the therapeutic efficacy of MSC.

High-Density Lipoprotein-Targeted Therapies for Heart Failure

The main and common constituents of high-density lipoproteins (HDLs) are apolipoprotein A-I, cholesterol, and phospholipids. Biochemical heterogeneity of HDL particles is based on the variable presence of one or more representatives of at least 180 proteins, 200 lipid species, and 20 micro RNAs. HDLs are circulating multimolecular platforms that perform divergent functions whereby the potential of HDL-targeted interventions for treatment of heart failure can be postulated based on its pleiotropic effects. Several murine studies have shown that HDLs exert effects on the myocardium, which are completely independent of any impact on coronary arteries. Overall, HDL-targeted therapies exert a direct positive lusitropic effect on the myocardium, inhibit the development of cardiac hypertrophy, suppress interstitial and perivascular myocardial fibrosis, increase capillary density in the myocardium, and prevent the occurrence of heart failure. In four distinct murine models, HDL-targeted interventions were shown to be a successful treatment for both pre-existing heart failure with reduced ejection fraction (HFrEF) and pre-existing heart failure with preserved ejection fraction (HFrEF). Until now, the effect of HDL-targeted interventions has not been evaluated in randomized clinical trials in heart failure patients. As HFpEF represents an important unmet therapeutic need, this is likely the preferred therapeutic domain for clinical translation.

Obesity-Related Changes in High-Density Lipoprotein Metabolism and Function

In obese individuals, atherogenic dyslipidemia is a very common and important factor in the increased risk of cardiovascular disease. Adiposity-associated dyslipidemia is characterized by low high-density lipoprotein cholesterol (HDL-C) levels and an increase in triglyceride-rich lipoproteins. Several factors and mechanisms are involved in lowering HDL-C levels in the obese state and HDL quantity and quality is closely related to adiponectin levels and the bioactive lipid sphingosine-1-phosphate. Recent studies have shown that obesity profoundly alters HDL metabolism, resulting in altered HDL subclass distribution, composition, and function. Importantly, weight loss through gastric bypass surgery and Mediterranean diet, especially when enriched with virgin olive oil, is associated with increased HDL-C levels and significantly improved metrics of HDL function. A thorough understanding of the underlying mechanisms is crucial for a better understanding of the impact of obesity on lipoprotein metabolism and for the development of appropriate therapeutic approaches. The objective of this review article was to summarize the newly identified changes in the metabolism, composition, and function of HDL in obesity and to discuss possible pathophysiological consequences.

Coronary microvascular dysfunction in hypertrophy and heart failure

Left ventricular (LV) hypertrophy (LVH) is a growth in left myocardial mass mainly caused by increased cardiomyocyte size. LVH can be a physiological adaptation to physical exercise or a pathological condition either primary, i.e. genetic, or secondary to LV overload. Patients with both primary and secondary LVH have evidence of coronary microvascular dysfunction (CMD). The latter is mainly due to capillary rarefaction and adverse remodelling of intramural coronary arterioles due to medial wall thickening with an increased wall/lumen ratio. An important feature of this phenomenon is the diffuse nature of this remodelling, which generally affects the coronary microvessels in the whole of the left ventricle. Patients with LVH secondary to arterial hypertension can develop both heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF). These patients can develop HFrEF via a 'direct pathway' with an interval myocardial infarction and also in its absence. On the other hand, patients can develop HFpEF that can then progress to HFrEF with or without interval myocardial infarction. A similar evolution towards LV dysfunction and both HFpEF and HFrEF can occur in patients with hypertrophic cardiomyopathy, the most common genetic cardiomyopathy with a phenotype characterized by massive LVH. In this review article, we will discuss both the experimental and clinical studies explaining the mechanisms responsible for CMD in LVH as well as the evidence linking CMD with HFpEF and HFrEF.

Administration of apo A-I (Milano) nanoparticles reverses pathological remodelling, cardiac dysfunction, and heart failure in a murine model of HFpEF associated with hypertension

Therapeutic interventions with proven efficacy in heart failure with reduced ejection fraction (HFrEF) have been unsuccessful in heart failure with preserved ejection fraction (HFpEF). The modifiable risk factor with the greatest impact on the development of HFpEF is hypertension. The objectives of this study were to establish a murine model of HFpEF associated with hypertension and to evaluate the effect of apo A-I_Milano nanoparticles (MDCO-216) on established HFpEF in this model. Subcutaneous infusion of angiotensin II in combination with 1% NaCl in the drinking water was started at the age of 12 weeks in male C57BL/6 N mice and continued for the entire duration of the experiment. Treatment with MDCO-216 partially reversed established cardiac hypertrophy, cardiomyocyte hypertrophy, capillary rarefaction, and perivascular fibrosis in this model. Pressure-volume loop analysis was consistent with HFpEF in hypertension mice as evidenced by the preserved ejection fraction and a significant reduction of cardiac output (7.78 ± 0.56 ml/min versus 10.5 ± 0.7 ml/min; p < 0.01) and of the peak filling rate (p < 0.05). MDCO-216 completely reversed cardiac dysfunction and abolished heart failure as evidenced by the normal lung weight and normal biomarkers of heart failure. In conclusion, apo A-I_Milano nanoparticles constitute an effective treatment for established hypertension-associated HFpEF.

HDL therapy today: from atherosclerosis, to stent compatibility to heart failure

Epidemiologically, high-density lipoprotein (HDL) cholesterol levels have been inversely associated to cardiovascular (CV) events, although a Mendelian Randomisation Study had failed to establish a clear causal role. Numerous atheroprotective mechanisms have been attributed to HDL, the main being the ability to promote cholesterol efflux from arterial walls; anti-inflammatory effects related to HDL ligands such as S1P (sphingosine-1-phosphate), resolvins and others have been recently identified. Experimental studies and early clinical investigations have indicated the potential of HDL to slow progression or induce regression of atherosclerosis. More recently, the availability of different HDL formulations, with different phospholipid moieties, has allowed to test other indications for HDL therapy. Positive reports have come from studies on coronary stent biocompatibility, where the use of HDL from different sources reduced arterial cell proliferation and thrombogenicity. The observation that low HDL-C levels may be associated with an enhanced risk of heart failure (HF) has also suggested that HDL therapy may be applied to this condition. HDL infusions or apoA-I gene transfer were able to reverse heart abnormalities, reduce diastolic resistance and improve cardiac metabolism. HDL therapy may be effective not only in atherosclerosis, but also in other conditions, of relevant impact on human health.Key messagesHigh-density lipoproteins have as a major activity that of removing excess cholesterol from tissues (particularly arteries).Knowledge on the activity of high-density lipoproteins on health have however significantly widened.HDL-therapy may help to improve stent biocompatibility and to reduce peripheral arterial resistance in heart failure.

Effective Treatment of Diabetic Cardiomyopathy and Heart Failure with Reconstituted HDL (Milano) in Mice

The risk of heart failure (HF) is prominently increased in patients with type 2 diabetes mellitus. The objectives of this study were to establish a murine model of diabetic cardiomyopathy induced by feeding a high-sugar/high-fat (HSHF) diet and to evaluate the effect of reconstituted HDL_Milano administration on established HF in this model. The HSHF diet was initiated at the age of 12 weeks and continued for 16 weeks. To investigate the effect of reconstituted HDL_Milano on HF, eight intraperitoneal administrations of MDCO-216 (100 mg/kg protein concentration) or of an identical volume of control buffer were executed with a 48-h interval starting at the age of 28 weeks. The HSHF diet-induced obesity, hyperinsulinemia, and type 2 diabetes mellitus. Diabetic cardiomyopathy was present in HSHF diet mice as evidenced by cardiac hypertrophy, increased interstitial and perivascular fibrosis, and decreased myocardial capillary density. Pressure-volume loop analysis indicated the presence of both systolic and diastolic dysfunction and of decreased cardiac output in HSHF diet mice. Treatment with MDCO-216 reversed pathological remodelling and cardiac dysfunction and normalized wet lung weight, indicating effective treatment of HF. No effect of control buffer injection was observed. In conclusion, reconstituted HDL_Milano reverses HF in type 2 diabetic mice.

Higher High Density Lipoprotein 2 (HDL2) to Total HDL Cholesterol Ratio Is Associated with a Lower Risk for Incident Hypertension

BACKGROUND

Recent studies have suggested that high density lipoprotein (HDL) cholesterol is inversely associated with the development of hypertension. We aimed to determine the association between different HDL cholesterol subclasses and risk of future hypertension.

METHODS

A total of 270 Japanese Americans (130 men, 140 women) without hypertension between the ages of 34 to 75 years were enrolled. Blood pressure was measured with a mercury sphygmomanometer, and average blood pressure was calculated. Incident hypertension was determined 5 to 6 and 10 to 11 years after enrollment. HDL2, HDL3, and total HDL cholesterol were measured at baseline.

RESULTS

During 10 years of follow-up, the cumulative incidence of hypertension was 28.1% (76/270). In univariate analysis, age, diabetes, waist circumference, systolic and diastolic blood pressure, fasting glucose, insulin resistance index, total and low density lipoprotein cholesterol, and visceral adipose tissue were significant predictors for incident hypertension. Among the HDL cholesterol subclass, HDL2 cholesterol was inversely associated with hypertension incidence, but both total and HDL3 cholesterol were not. In addition, HDL2/HDL cholesterol was inversely associated with future hypertension risk. In multivariate analysis, age (odds ratio [OR], 1.71; 95% confidence interval [CI], 1.26 to 2.31; P=0.001), systolic blood pressure (OR, 1.83; 95% CI, 1.31 to 2.56; P<0.001), and HDL2/HDL cholesterol (OR, 0.71; 95% CI, 0.52 to 0.98; P=0.035), were associated with future development of hypertension.

CONCLUSION

A higher proportion of HDL2 cholesterol among total HDL cholesterol predicted a lower risk for incident hypertension. However, concentrations of total HDL, HDL2, and HDL3 cholesterol were not independent predictors of incident hypertension.

Successful treatment of established heart failure in mice with recombinant HDL (Milano)

BACKGROUND AND PURPOSE

The pleiotropic properties of HDL may exert beneficial effects on the myocardium. The effect of recombinant HDLMilano on established heart failure was evaluated in C57BL/6 mice.

EXPERIMENTAL APPROACH

Mice were subjected to transverse aortic constriction (TAC) or sham operation at the age of 14 weeks. Eight weeks later, TAC and sham mice were each randomized into three different groups. Reference groups were killed at day 56 after the operation for baseline analysis. Five i.p. injections of recombinant HDLMilano (MDCO-216), 100 mg·kg-1 , or an equivalent volume of control buffer were administered with a 48 h interval starting at day 56. Endpoint analyses in the control buffer groups and in the MDCO-216 groups were executed at day 65.

KEY RESULTS

Lung weight in MDCO-216 TAC mice was 25.3% lower than in reference TAC mice and 27.9% lower than in control buffer TAC mice and was similar in MDCO-216 sham mice. MDCO-216 significantly decreased interstitial fibrosis and increased relative vascularity compared to reference TAC mice and control buffer TAC mice. The peak rate of isovolumetric relaxation in MDCO-216 TAC mice was 30.4 and 36.3% higher than in reference TAC mice and control buffer TAC mice respectively. Nitro-oxidative stress and myocardial apoptosis were significantly reduced in MDCO-216 TAC mice compared to control buffer TAC mice.

CONCLUSIONS AND IMPLICATIONS

MDCO-216 improves diastolic function, induces regression of interstitial fibrosis and normalizes lung weight in mice with established heart failure. Recombinant HDL may emerge as a treatment modality in heart failure.

Potential pitfalls in analyzing structural uncoupling of eNOS: aging is not associated with increased enzyme monomerization

Homodimer formation is essential for the normal activity of endothelial nitric oxide synthase (eNOS). Structural uncoupling of eNOS, with generation of enzyme monomers, is thought to contribute to endothelial dysfunction in several vascular disorders, including aging. However, low-temperature SDS-PAGE of healthy arteries has revealed considerable variation between studies in the relative expression of eNOS dimers and monomers. While assessing structural uncoupling of eNOS in aging arteries, we identified methodological pitfalls that might contribute to such variation. Therefore, using human cultured aortic endothelial cells and aortas from young and aged Fischer-344 rats, we investigated optimal approaches for analyzing the expression of eNOS monomers and dimers. The results demonstrated that published differences in treatment of cell lysates can significantly impact the relative expression of several eNOS species, including denatured monomers, partially folded monomers, dimers, and higher-order oligomers. In aortas, experiments initially confirmed a large increase in eNOS monomers in aging arteries, consistent with structural uncoupling. However, these monomers were actually endogenous IgG, which, under these conditions, has mobility similar to eNOS monomers. Increased IgG levels in aged aortas likely reflect the aging-induced disruption of endothelial junctions and increased arterial penetration of IgG. After removal of the IgG signal, there were low levels of eNOS monomers in young arteries, which were not significantly different in aged arteries. Therefore, structural uncoupling of eNOS is not a prominent feature in young healthy arteries, and the process is not increased by aging. The study also identifies optimal approaches to analyze eNOS dimers and monomers. NEW & NOTEWORTHY Structural uncoupling of endothelial nitric oxide synthase (eNOS) is considered central to endothelial dysfunction. However, reported levels of eNOS dimers and monomers vary widely, even in healthy arteries. We demonstrate that sample processing can alter relative levels of eNOS species. Moreover, endothelial dysfunction in aging aortas results in IgG accumulation, which, because of similar mobility to eNOS monomers, could be misinterpreted as structural uncoupling. Indeed, enzyme monomerization is not prominent in young or aging arteries.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

Hepatocyte-Specific SR-BI Gene Transfer Corrects Cardiac Dysfunction in Scarb1 -Deficient Mice and Improves Pressure Overload-Induced Cardiomyopathy

Objective—

We investigated the hypothesis that HDL (high-density lipoprotein) dysfunction in Scarb1 −/− mice negatively affects cardiac function both in the absence and in the presence of pressure overload. Second, we evaluated whether normalization of HDL metabolism in Scarb1 −/− mice by hepatocyte-specific SR-BI (scavenger receptor class B, type I) expression after E1E3E4-deleted adenoviral AdSR-BI (E1E3E4-deleted adenoviral vector expressing SR-BI protein in hepatocytes) transfer abrogates the effects of total body SR-BI deficiency on cardiac structure and function.

Approach and Results—

Transverse aortic constriction (TAC) or sham operation was performed at the age of 14 weeks, 2 weeks after saline injection or after gene transfer with AdSR-BI or with the control vector Adnull. Mortality rate in Scarb1 −/− TAC mice was significantly increased compared with wild-type TAC mice during 8 weeks of follow-up (hazard ratio, 2.02; 95% CI, 1.14–3.61). Hepatocyte-specific SR-BI gene transfer performed 2 weeks before induction of pressure overload by TAC potently reduced mortality in Scarb1 −/− mice (hazard ratio, 0.329; 95% CI, 0.180–0.600). Hepatocyte-specific SR-BI expression abrogated increased cardiac hypertrophy and lung congestion and counteracted increased myocardial apoptosis and interstitial and perivascular fibrosis in Scarb1 −/− TAC mice. Scarb1 −/− sham mice were, notwithstanding the absence of detectable structural heart disease, characterized by systolic and diastolic dysfunction and hypotension, which were completely counteracted by AdSR-BI transfer. Furthermore, AdSR-BI transfer abrogated increased end-diastolic pressure and diastolic dysfunction in Scarb1 −/− TAC mice. Increased oxidative stress and reduced antioxidant defense systems in Scarb1 −/− mice were rescued by AdSR-BI transfer.

Conclusions—

The detrimental effects of SR-BI deficiency on cardiac structure and function are nullified by hepatocyte-specific SR-BI transfer, which restores HDL metabolism.

Innate and adaptive immunity in atherosclerosis

Atherosclerosis is a chronic inflammatory disorder of the large and medium-size arteries characterized by the subendothelial accumulation of cholesterol, immune cells, and extracellular matrix. At the early onset of atherogenesis, endothelial dysfunction takes place. Atherogenesis is further triggered by the accumulation of cholesterol-carrying low-density lipoproteins, which acquire properties of damage-associated molecular patterns and thereby trigger an inflammatory response. Following activation of the innate immune response, mainly governed by monocytes and macrophages, the adaptive immune response is started which further promotes atherosclerotic plaque formation. In this review, an overview is given describing the role of damage-associated molecular patterns, NLRP3 inflammasome activation, and innate and adaptive immune cells in the atherogenesis process.

Dysregulation of the Renin-Angiotensin System and the Vasopressinergic System Interactions in Cardiovascular Disorders

Purpose of Review

In many instances, the renin-angiotensin system (RAS) and the vasopressinergic system (VPS) are jointly activated by the same stimuli and engaged in the regulation of the same processes.

Recent Findings

Angiotensin II (Ang II) and arginine vasopressin (AVP), which are the main active compounds of the RAS and the VPS, interact at several levels. Firstly, Ang II, acting on AT1 receptors (AT1R), plays a significant role in the release of AVP from vasopressinergic neurons and AVP, stimulating V1a receptors (V1aR), regulates the release of renin in the kidney. Secondly, Ang II and AVP, acting on AT1R and V1aR, respectively, exert vasoconstriction, increase cardiac contractility, stimulate the sympathoadrenal system, and elevate blood pressure. At the same time, they act antagonistically in the regulation of blood pressure by baroreflex. Thirdly, the cooperative action of Ang II acting on AT1R and AVP stimulating both V1aR and V2 receptors in the kidney is necessary for the appropriate regulation of renal blood flow and the efficient resorption of sodium and water. Furthermore, both peptides enhance the release of aldosterone and potentiate its action in the renal tubules.

Summary

In this review, we (1) point attention to the role of the cooperative action of Ang II and AVP for the regulation of blood pressure and the water-electrolyte balance under physiological conditions, (2) present the subcellular mechanisms underlying interactions of these two peptides, and (3) provide evidence that dysregulation of the cooperative action of Ang II and AVP significantly contributes to the development of disturbances in the regulation of blood pressure and the water-electrolyte balance in cardiovascular diseases.

Epigenetic modulation of vascular diseases: Assessing the evidence and exploring the opportunities

Vascular adaptations to either physiological or pathophysiological conditions commonly require gene expression modifications in the most represented cellular elements of the vessel wall, i.e. endothelial and smooth muscle cells. In addition to transcription factors, a number of mechanisms contribute to the regulation of gene expression in these cells including noncoding RNAs, histone and DNA modifications, collectively indicated as epigenetic modifications. Here, we summarize the state of art regarding the role of epigenetic changes in major vascular diseases, and discuss the potential diagnostic and therapeutic applications of epigenetic modulation in this context.

Heart Failure with Preserved Ejection Fraction and Future Pharmacological Strategies: a Glance in the Crystal Ball

PURPOSE OF REVIEW

The current definition of heart failure is mainly based on an inappropriate measure of cardiac function, i.e., left ventricular ejection fraction (LVEF). The initial sole entity, heart failure with reduced ejection fraction (HFrEF, LVEF <40%), was complemented by the addition of heart failure with preserved ejection fraction (HFpEF, LVEF ≥50%) and most recently, heart failure with mid-range ejection fraction (HFmrEF, LVEF 40-49%). Initially, HFpEF was believed to be a purely left ventricular diastolic dysfunction. Pathophysiological concepts of HFpEF have changed considerably during the last years. In addition to intrinsic cardiac mechanisms, the heart failure pathogenesis is increasingly considered as driven by non-cardiac systemic processes including metabolic disorders, ischemic conditions, and pro-inflammatory/pro-fibrotic or immunological alterations. Presentation and pathophysiology of HFpEF is heterogeneous, and its management remains a challenge since evidence of therapeutic benefits is scarce. Up to now, there are no therapies improving survival in patients with HFpEF.

RECENT FINDINGS

Several results from clinical and preclinical interventions targeting non-cardiac mechanisms or non-pharmacological interventions including new anti-diabetic or anti-inflammatory drugs, mitochondrial-targeted anti-oxidants, anti-fibrotic strategies, microRNases incl. antagomirs, cell therapeutic options, and high-density lipoprotein-raising strategies are promising and under further investigation. This review addresses mechanisms and available data of current best clinical practice and novel approaches towards HFpEF.

Placenta-Derived Adherent Stromal Cells Improve Diabetes Mellitus-Associated Left Ventricular Diastolic Performance

Left ventricular (LV) diastolic dysfunction is among others attributed to cardiomyocyte stiffness. Mesenchymal stromal cells (MSC) have cardiac-protective properties. We explored whether intravenous (i.v.) application of PLacenta-eXpanded (PLX) MSC-like cells (PLX) improves LV diastolic relaxation in streptozotocin (STZ)-induced diabetic mice and investigated underlying mechanisms. Diabetes mellitus was induced by STZ application (50 mg/kg body weight) during five subsequent days. One week after the first STZ injection, PLX or saline were i.v. applied. Two weeks later, mice were hemodynamically characterized and sacrificed. At this early stage of diabetic cardiomyopathy with low-grade inflammation and no cardiac fibrosis, PLX reduced LV vascular cell adhesion molecule-1, transforming growth factor-β1, and interferon-γ mRNA expression, induced the percentage of circulating regulatory T cells, and decreased the splenic pro-fibrotic potential in STZ mice. STZ + PLX mice exhibited higher LV vascular endothelial growth factor mRNA expression and arteriole density versus STZ mice. In vitro, hyperglycemic PLX conditioned medium restored the hyperglycemia-impaired tube formation and adhesion capacity of human umbelical vein endothelial cells (HUVEC) via increasing nitric oxide (NO) bioavailability. PLX further induced the diabetes-downregulated activity of the NO downstream protein kinase G, as well as of protein kinase A, in STZ mice, which was associated with a raise in phosphorylation of the titin isoforms N2BA and N2B. Concomitantly, the passive force was lower in single isolated cardiomyocytes from STZ + PLX versus from STZ mice, which led to an improvement of LV diastolic relaxation. We conclude that i.v. PLX injection improves diabetes mellitus-associated diastolic performance via decreasing cardiomyocyte stiffness. Stem Cells Translational Medicine 2017;6:2135-2145.

Selective HDL-Raising Human Apo A-I Gene Therapy Counteracts Cardiac Hypertrophy, Reduces Myocardial Fibrosis, and Improves Cardiac Function in Mice with Chronic Pressure Overload

Epidemiological studies support an independent inverse association between high-density lipoprotein (HDL) cholesterol levels and heart failure incidence. The effect of selective HDL-raising adeno-associated viral serotype 8-human apolipoprotein (apo) A-I (AAV8-A-I) gene transfer on cardiac remodeling induced by transverse aortic constriction (TAC) was evaluated in C57BL/6 low-density lipoprotein receptor-deficient mice. Septal wall thickness and cardiomyocyte cross-sectional area were reduced by 16.5% (p < 0.001) and by 13.8% (p < 0.01), respectively, eight weeks after TAC in AAV8-A-I mice (n = 24) compared to control mice (n = 39). Myocardial capillary density was 1.11-fold (p < 0.05) higher and interstitial cardiac fibrosis was 45.3% (p < 0.001) lower in AAV8-A-I TAC mice than in control TAC mice. Lung weight and atrial weight were significantly increased in control TAC mice compared to control sham mice, but were not increased in AAV8-A-I TAC mice. The peak rate of isovolumetric contraction was 1.19-fold (p < 0.01) higher in AAV8-A-I TAC mice (n = 17) than in control TAC mice (n = 29). Diastolic function was also significantly enhanced in AAV8-A-I TAC mice compared to control TAC mice. Nitro-oxidative stress and apoptosis were significantly reduced in the myocardium of AAV8-A-I TAC mice compared to control TAC mice. In conclusion, selective HDL-raising human apo A-I gene transfer potently counteracts the development of pressure overload-induced cardiomyopathy.

Inflammation - Cause or Consequence of Heart Failure or Both?

PURPOSE OF REVIEW

With the intention to summarize the currently available evidence on the pathophysiological relevance of inflammation in heart failure, this review addresses the question whether inflammation is a cause or consequence of heart failure, or both.

RECENT FINDINGS

This review discusses the diversity (sterile, para-inflammation, chronic inflammation) and sources of inflammation and gives an overview of how inflammation (local versus systemic) can trigger heart failure. On the other hand, the review is outlined how heart failure-associated wall stress and signals released by stressed, malfunctioning, or dead cells (DAMPs: e.g., mitochondrial DNA, ATP, S100A8, matricellular proteins) induce cardiac sterile inflammation and how heart failure provokes inflammation in various peripheral tissues in a direct (inflammatory) and indirect (hemodynamic) manner. The crosstalk between the heart and peripheral organs (bone marrow, spleen, gut, adipose tissue) is outlined and the importance of neurohormonal mechanisms including the renin angiotensin aldosteron system and the ß-adrenergic nervous system in inflammation and heart failure is discussed. Inflammation and heart failure are strongly interconnected and mutually reinforce each other. This indicates the difficulty to counteract inflammation and heart failure once this chronic vicious circle has started and points out the need to control the inflammatory process at an early stage avoiding chronic inflammation and heart failure. The diversity of inflammation further addresses the need for a tailored characterization of inflammation enabling differentiation of inflammation and subsequent target-specific strategies. It is expected that the characterization of the systemic and/or cardiac immune profile will be part of precision medicine in the future of cardiology.

Apolipoprotein A-I gene transfer exerts immunomodulatory effects and reduces vascular inflammation and fibrosis in ob/ob mice

Background

Obesity is associated with vascular inflammation, fibrosis and reduced high-density lipoproteins (HDL)-cholesterol. We aimed to investigate whether adenoviral gene transfer with human apolipoprotein (apo) A-I (Ad.A-I), the main apo of HDL, could exert immunomodulatory effects and counteract vascular inflammation and fibrosis in ob/ob mice.

Methods

Ad.A-I transfer was performed in 8 weeks (w) old ob/ob mice, which were sacrificed 7 w later. The aorta was excised for mRNA analysis and the spleen for splenocyte isolation for subsequent flow cytometry and co-culture with murine fibroblasts. HDL was added to mononuclear cells (MNC) and fibroblasts to assess their impact on adhesion capacity and collagen deposition, respectively.

Results

Ad.A-I led to a 1.8-fold (p < 0.05) increase in HDL-cholesterol versus control ob/ob mice at the day of sacrifice, which was paralleled by a decrease in aortic TNF-α and VCAM-1 mRNA expression. Pre-culture of MNC with HDL decreased their adhesion to TNF-α-activated HAEC. Ad.A-I exerted immunomodulatory effects as evidenced by a downregulation of aortic NOD2 and NLRP3 mRNA expression and by a 12 %, 6.9 %, and 15 % decrease of the induced proliferation/activity of total splenic MNC, CD4+, and CD8+ cells in ob/ob Ad.A-I versus control ob/ob mice, respectively (p < 0.05). Ad.A-I further reduced aortic collagen I and III mRNA expression by 62 % and 66 %, respectively (p < 0.0005), and abrogated the potential of ob/ob splenocytes to induce the collagen content in murine fibroblasts upon co-culture. Finally, HDL decreased the TGF-ß1-induced collagen deposition of murine fibroblasts in vitro.

Conclusions

Apo A-I transfer counteracts vascular inflammation and fibrosis in ob/ob mice.

Electronic supplementary material

The online version of this article (doi:10.1186/s12950-016-0131-6) contains supplementary material, which is available to authorized users.

Human Endomyocardial Biopsy Specimen-Derived Stromal Cells Modulate Angiotensin II-Induced Cardiac Remodeling

: Cardiac-derived adherent proliferating cells (CardAPs) are cells derived from human endomyocardial biopsy specimens; they share several properties with mesenchymal stromal cells. The aims of this study were to evaluate whether intramyocardial injection of CardAPs modulates cardiac fibrosis and hypertrophy in a mouse model of angiotensin II (Ang II)-induced systolic heart failure and to analyze underlying mechanisms. Intramyocardial application of 200,000 CardAPs improved left ventricular function. This was paralleled by a decline in left ventricular remodeling, as indicated by a reduction in cardiac fibrosis and hypertrophy. CardAPs reduced the ratio of the left ventricle to body weight and cardiac myosin expression (heavy chain), and decreased the Ang II-induced phosphorylation state of the cardiomyocyte hypertrophy mediators Akt, extracellular-signal regulated kinase (ERK) 1, and ERK2. In accordance with the antifibrotic and antihypertrophic effects of CardAPs shown in vivo, CardAP supplementation with cardiac fibroblasts decreased the Ang II-induced reactive oxygen species production, α-SMA expression, fibroblast proliferation, and collagen production. Coculture of CardAPs with HL-1 cardiomyocytes downregulated the Ang II-induced expression of myosin in HL-1. All antifibrotic and antihypertrophic features of CardAPs were mediated in a nitric oxide- and interleukin (IL)-10-dependent manner. Moreover, CardAPs induced a systemic immunomodulation, as indicated by a decrease in the activity of splenic mononuclear cells and an increase in splenic CD4CD25FoxP3, CD4-IL-10, and CD8-IL-10 T-regulatory cells in Ang II mice. Concomitantly, splenocytes from Ang II CardAPs mice induced less collagen in fibroblasts compared with splenocytes from Ang II mice. We conclude that CardAPs improve Ang II-induced cardiac remodeling involving antifibrotic and antihypertrophic effects via paracrine actions and immunomodulatory properties.

SIGNIFICANCE

Despite effective pharmacological treatment with angiotensin II type I receptor antagonists or angiotensin II-converting enzyme inhibitors, morbidity and mortality associated with heart failure are still substantial, prompting the search of novel therapeutic strategies. There is accumulating evidence supporting the use of cell therapy for cardiac repair. This study demonstrates that cells derived from human endomyocardial biopsies, cardiac-derived adherent proliferating cells (CardAPs), have the potential to reduce angiotensin II-induced cardiac remodeling and improve left ventricular function in angiotensin II mice. The mechanism involves antifibrotic and antihypertrophic effects via paracrine actions and immunomodulatory properties. These findings support the potential of CardAPs for the treatment of heart failure.

Glucocorticoids Suppress Mitochondrial Oxidant Production via Upregulation of Uncoupling Protein 2 in Hyperglycemic Endothelial Cells

Diabetic complications are the leading cause of morbidity and mortality in diabetic patients. Elevated blood glucose contributes to the development of endothelial and vascular dysfunction, and, consequently, to diabetic micro- and macrovascular complications, because it increases the mitochondrial proton gradient and mitochondrial oxidant production. Therapeutic approaches designed to counteract glucose-induced mitochondrial reactive oxygen species (ROS) production in the vasculature are expected to show efficacy against all diabetic complications, but direct pharmacological targeting (scavenging) of mitochondrial oxidants remains challenging due to the high reactivity of some of these oxidant species. In a recent study, we have conducted a medium-throughput cell-based screening of a focused library of well-annotated pharmacologically active compounds and identified glucocorticoids as inhibitors of mitochondrial superoxide production in microvascular endothelial cells exposed to elevated extracellular glucose. The goal of the current study was to investigate the mechanism of glucocorticoids' action. Our findings show that glucocorticoids induce the expression of the mitochondrial UCP2 protein and decrease the mitochondrial potential. UCP2 silencing prevents the protective effect of the glucocorticoids on ROS production. UCP2 induction also increases the oxygen consumption and the "proton leak" in microvascular endothelial cells. Furthermore, glutamine supplementation augments the effect of glucocorticoids via further enhancing the expression of UCP2 at the translational level. We conclude that UCP2 induction represents a novel experimental therapeutic intervention in diabetic vascular complications. While direct repurposing of glucocorticoids may not be possible for the therapy of diabetic complications due to their significant side effects that develop during chronic administration, the UCP2 pathway may be therapeutically targetable by other, glucocorticoid-independent pharmacological means.

Exogenous Angiotensin I Metabolism in Aorta Isolated from Streptozotocin Treated Diabetic Rats

Purpose. Products of angiotensin (ANG) I metabolism may predispose to vascular complications of diabetes mellitus. Methods. Diabetes was induced with streptozotocin (75 mg/kg i.p.). Rat aorta fragments, isolated 4 weeks later, were pretreated with perindoprilat (3 μM), thiorphan (3 μM), or vehicle and incubated for 15 minutes with ANG I (1 μM). Products of ANG I metabolism through classical (ANG II, ANG III, and ANG IV) and alternative (ANG (1-9), ANG (1-7), and ANG (1-5)) pathways were measured in the buffer, using liquid chromatography-mass spectrometry. Results. Incubation with ANG I resulted in higher concentration of ANG II (P = 0.02, vehicle pretreatment) and lower of ANG (1-9) (P = 0.048, perindoprilat pretreatment) in diabetes. Preference for the classical pathway is suggested by higher ANG III/ANG (1-7) ratios in vehicle (P = 0.03), perindoprilat (P = 0.02), and thiorphan pretreated (P = 0.02) diabetic rat. Within the classical pathway, ratios of ANG IV/ANG II (P = 0.01) and of ANG IV/ANG III (P = 0.049), but not of ANG III/ANG II are lower in diabetes. Conclusions. Diabetes in rats led to preference toward deleterious (ANG II, ANG III) over protective (ANG IV, ANG (1-9), and ANG (1-7)) ANG I metabolites.

High-density lipoproteins reduce palmitate-induced cardiomyocyte apoptosis in an AMPK-dependent manner

Palmitate has been implicated in the induction of cardiomyocyte apoptosis via reducing the activity of 5' AMP-activated protein kinase (AMPK). We sought to evaluate whether high-density lipoproteins (HDLs), known for their cardioprotective features and their potential to increase AMPK activity, can reduce palmitate-induced cardiomyocyte apoptosis and whether this effect is AMPK-dependent. Therefore, cardiomyocytes were isolated from adult Wistar rat hearts via perfusion on a Langendorff-apparatus and cultured in free fatty acid-free BSA control medium or 0.5 mM palmitate medium in the presence or absence of HDL (5 μg protein/ml) with or without 0.1 μM of the AMPK-inhibitor compound S for the analysis of Annexin V/propidium, genes involved in apoptosis and fatty acid oxidation, and cardiomyocyte contractility. We found that HDLs decreased palmitate-induced cardiomyocyte apoptosis as indicated by a reduction in Annexin V-positive cardiomyocytes and an increase in Bcl-2 versus Bax ratio. Concomitantly, HDLs increased the palmitate-impaired expression of genes involved in fatty acid oxidation. Furthermore, HDLs improved the palmitate-impaired cardiomyocyte contractility. All effects were mediated in an AMPK-dependent manner, concluding that HDLs reduce palmitate-induced cardiomyocyte apoptosis, resulting in improved cardiomyocyte contractility through a mechanism involving AMPK.

Changes in protein and gene expression of angiotensin II receptors (AT1 and AT2) in aorta of diabetic and hypertensive rats

Diabetes and hypertension have been associated with cardiovascular diseases and stroke. Some reports have related the coexistence of hypertension and diabetes with increase in the risk of developing vascular complications. Recently some studies have shown results suggesting that in the early stages of diabetes and hypertension exist a reduced functional response to vasopressor agents like angiotensin II (Ang II), which plays an important role in blood pressure regulation mechanism through the activation of its AT1 and AT2 receptors. For that reason, the aim of this work was to study the gene and protein expression of AT1 and AT2 receptors in aorta of diabetic SHR and WKY rats. Diabetes was induced by the administration of streptozotocin (60 mg/kg i.p.). After 4 weeks of the onset of diabetes, the protein expression was obtained by western blot and the mRNA expression by RT-PCR. Our results showed that the hypertensive rats have a higher mRNA and protein expression of AT1 receptors than normotensive rats while the AT2 expression remained unchanged. On the other hand, the combination of diabetes and hypertension increased the mRNA and protein expression of AT1 and AT2 receptors significantly. In conclusion, our results suggest that diabetes with hypertension modifies the mRNA and protein expression of AT1 and AT2 receptors. However, the overexpression of AT2 could be associated with the reduction in the response to Ang II in the early stage of diabetes.

New insights in (inter)cellular mechanisms by heart failure with preserved ejection fraction

Recently, a new paradigm for the development of heart failure with preserved ejection fraction (HFpEF) has been proposed, which identifies a systemic pro-inflammatory state induced by comorbidities as the origin of microvascular endothelial cell inflammation and subsequent concentric cardiac remodeling and dysfunction. This review further discusses the pivotal role of the inflamed endothelium in the pathogenesis of HFpEF-specific cardiac remodeling. The potential importance of reciprocal interactions of the endothelium with cardiac fibroblasts and cardiomyocytes and with the cardiac neurohumoral response in this cardiac remodeling process is outlined.

High-density lipoproteins reduce endothelial-to-mesenchymal transition

OBJECTIVE

Endothelial-to-mesenchymal transition is an inflammation-induced process by which endothelial cells can transdifferentiate into fibroblasts. Based on the endothelial-protective and antifibrotic effects of high-density lipoproteins (HDL), we aimed to investigate whether HDL can reduce endothelial-to-mesenchymal transition.

APPROACH AND RESULTS

Therefore, human aortic endothelial cells were stimulated with the profibrotic factor transforming growth factor (TGF)-β1 in the presence or absence of HDL. Their impact on the transition of endothelial cells to mesenchymal-like cells was analyzed. Phase contrast microscopy demonstrated that HDL abrogated the TGF-β1-induced spindle-shape morphology in human aortic endothelial cells. Furthermore, HDL decreased the TGF-β1-mediated induction of α-smooth muscle actin expression and concomitant loss in endothelial cadherin expression, as shown by immunofluorescence staining and flow cytometry. In addition, HDL decreased the TGF-β1-induced collagen deposition in human aortic endothelial cells involving the scavenger receptor class B, type 1 and downstream phosphatidyl inositol-3-kinase following the findings that the HDL-mediated reduction was abrogated by scavenger receptor class B, type 1 siRNA knockdown and phosphatidyl inositol-3-kinase inhibition, respectively. The HDL-mediated reduction in endothelial-to-mesenchymal transition was associated with an induction of the inhibitory Smad, Smad 7.

CONCLUSIONS

We provide the first in vitro evidence that the endothelial-protective and antifibrotic effects of HDL include the reduction in endothelial-to-mesenchymal transition.

Therapeutic potential of HDL in cardioprotection and tissue repair

Epidemiological studies support a strong association between high-density lipoprotein (HDL) cholesterol levels and heart failure incidence. Experimental evidence from different angles supports the view that low HDL is unlikely an innocent bystander in the development of heart failure. HDL exerts direct cardioprotective effects, which are mediated via its interactions with the myocardium and more specifically with cardiomyocytes. HDL may improve cardiac function in several ways. Firstly, HDL may protect the heart against ischaemia/reperfusion injury resulting in a reduction of infarct size and thus in myocardial salvage. Secondly, HDL can improve cardiac function in the absence of ischaemic heart disease as illustrated by beneficial effects conferred by these lipoproteins in diabetic cardiomyopathy. Thirdly, HDL may improve cardiac function by reducing infarct expansion and by attenuating ventricular remodelling post-myocardial infarction. These different mechanisms are substantiated by in vitro, ex vivo, and in vivo intervention studies that applied treatment with native HDL, treatment with reconstituted HDL, or human apo A-I gene transfer. The effect of human apo A-I gene transfer on infarct expansion and ventricular remodelling post-myocardial infarction illustrates the beneficial effects of HDL on tissue repair. The role of HDL in tissue repair is further underpinned by the potent effects of these lipoproteins on endothelial progenitor cell number, function, and incorporation, which may in particular be relevant under conditions of high endothelial cell turnover. Furthermore, topical HDL therapy enhances cutaneous wound healing in different models. In conclusion, the development of HDL-targeted interventions in these strategically chosen therapeutic areas is supported by a strong clinical rationale and significant preclinical data.

HDL and endothelial protection

High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.

Renin-angiotensin system regulates neurodegeneration in a mouse model of normal tension glaucoma

Glaucoma, one of the leading causes of irreversible blindness, is characterized by progressive degeneration of optic nerves and retinal ganglion cells (RGCs). In the mammalian retina, excitatory amino acid carrier 1 (EAAC1) is expressed in neural cells, including RGCs, and the loss of EAAC1 leads to RGC degeneration without elevated intraocular pressure (IOP). In the present study, we found that expressions of angiotensin II type 1 receptor (AT1-R) and Toll-like receptor 4 (TLR4) are increased in RGCs and retinal Müller glia in EAAC1-deficient (KO) mice. The orally active AT1-R antagonist candesartan suppressed TLR4 and lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expressions in the EAAC1 KO mouse retina. Sequential in vivo retinal imaging and electrophysiological analysis revealed that treatment with candesartan was effective for RGC protection in EAAC1 KO mice without affecting IOP. In cultured Müller glia, candesartan suppressed LPS-induced iNOS production by inhibiting the TLR4-apoptosis signal-regulating kinase 1 pathway. These results suggest that the renin–angiotensin system is involved in the innate immune responses in both neural and glial cells, which accelerate neural cell death. Our findings raise intriguing possibilities for the management of glaucoma by utilizing widely prescribed drugs for the treatment of high blood pressure, in combination with conventional treatments to lower IOP.

HDL-mediated mechanisms of protection in cardiovascular disease

Low plasma levels of HDL-cholesterol (HDL-C) represent a strong and independent risk factor for cardiovascular disease. HDL particles display a wide spectrum of atheroprotective activities, which include effluxing cellular cholesterol, diminishing cellular death, decreasing vascular constriction, reducing inflammatory response, protecting from pathological oxidation, combating bacterial infection, lessening platelet activation, regulating gene expression by virtue of microRNAs, and improving glucose metabolism. It remains presently indeterminate as to whether some biological activities of HDL are more relevant for the protection of the endothelium from atherogenesis when compared with others. The multitude of such activities raises the question of a proper assay to assess HDL functionality ex vivo. Together with clear understanding of molecular mechanisms underlying atheroprotective properties of HDL, such assay will provide a basis to resolve the ultimate question of the HDL field to allow the development of efficient HDL-targeting therapies.

HDL-C: clinical equipoise and vascular endothelial function

Serum levels of HDL cholesterol represent a strong, and coherent cardiovascular risk marker seen across all populations, with higher levels of HDL cholesterol being associated with decreased incidence of coronary artery disease. The cardiovascular protective effects of HDL particles are attributed, in great part, to the ability of HDL particles to promote cellular cholesterol efflux from lipid-laden macrophages within the atherosclerotic plaque. HDL also has pleiotropic effects that protect the vascular wall, at least in vitro. These effects include potent anti-inflammatory and antioxidant properties and the modulation of vascular endothelial function. The mechanisms by which HDL exert their function on the vascular endothelium is dependent on HDL particle size, protein (proteome) and lipid (lipidome). The cooperative binding of HDL via SR-BI and G-coupled S1PR1-5 receptors mediates phosphorylation of endothelial nitric oxide synthase at residue 1177 through AKT signaling, preventing uncoupling of NADPH oxidation and nitric oxide synthesis and increasing endothelial nitric oxide synthase abundance. Furthermore, HDL can modulate the activation of NF-κB and the expression of cell adhesion molecules, an early step in endothelial dysfunction. In the present review the authors will focus on the controversies surrounding HDL, clinical treatments and vascular endothelial functions of HDL.

High density lipoproteins and endothelial functions: mechanistic insights and alterations in cardiovascular disease

Prospective population studies in the primary prevention setting have shown that reduced plasma levels of HDL cholesterol are associated with an increased risk of coronary disease and myocardial infarction. Experimental and translational studies have further revealed several potential anti-atherogenic effects of HDL, including protective effects on endothelial cell functions. HDL has been suggested to protect endothelial cell functions by prevention of oxidation of LDL and its adverse endothelial effects. Moreover, HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and anti-inflammatory, anti-apoptotic, and anti-thrombotic effects as well as endothelial repair processes. However, several recent clinical trials using HDL cholesterol-raising agents, such as torcetrapib, dalcetrapib, and niacin, did not demonstrate a significant reduction of cardiovascular events in patients with coronary disease. Of note, growing evidence suggests that the vascular effects of HDL can be highly heterogeneous and vasoprotective properties of HDL are altered in patients with coronary disease. Characterization of underlying mechanisms and understanding of the clinical relevance of this "HDL dysfunction" is currently an active field of cardiovascular research. Notably, in some recent studies no clear association of higher HDL cholesterol levels with a reduced risk of cardiovascular events was observed in patients with already established coronary disease. A greater understanding of mechanisms of action of HDL and its altered vascular effects is therefore critical within the context of HDL-targeted therapies. In this review, we will address different effects of HDL on endothelial cell functions potentially relevant to atherosclerotic vascular disease and explore molecular mechanisms leading to "dysfunctional HDL".

Nox as a target for diabetic complications

Oxidative stress has been linked to the pathogenesis of the major complications of diabetes in the kidney, the heart, the eye or the vasculature. NADPH oxidases of the Nox family are a major source of ROS (reactive oxygen species) and are critical mediators of redox signalling in cells from different organs afflicted by the diabetic milieu. In the present review, we provide an overview of the current knowledge related to the understanding of the role of Nox in the processes that control cell injury induced by hyperglycaemia and other predominant factors enhanced in diabetes, including the renin–angiotensin system, TGF-β (transforming growth factor-β) and AGEs (advanced glycation end-products). These observations support a critical role for Nox homologues in diabetic complications and indicate that NADPH oxidases are an important therapeutic target. Therefore the design and development of small-molecule inhibitors that selectively block Nox oxidases appears to be a reasonable approach to prevent or retard the complications of diabetes in target organs. The bioefficacy of these agents in experimental animal models is also discussed in the present review.

Role of lipotoxicity in endothelial dysfunction

Vascular endothelial dysfunction is determined by both genetic and environmental factors that cause decreased bioavailability of the vasodilator nitric oxide. This is a hallmark of atherosclerosis, hypertension, and coronary heart disease, which are major complications of metabolic disorders, including diabetes and obesity. Several therapeutic interventions, including changes in lifestyle as well as pharmacologic treatments, are useful for improving endothelial dysfunction in the face of lipotoxicity. This review discusses the current understanding of molecular and physiologic mechanisms underlying lipotoxicity-mediated endothelial dysfunction as well as relevant therapeutic approaches to ameliorate dyslipidemia and consequent endothelial dysfunction that have the potential to improve cardiovascular and metabolic outcomes.

Activation of peroxisome proliferator-activated receptor-β/-δ (PPARβ/δ) prevents endothelial dysfunction in type 1 diabetic rats

Endothelial dysfunction plays a key role in the pathogenesis of diabetic vascular disease. Herein, we have analyzed if the peroxisome proliferator-activated receptor-β/-δ (PPARβ/δ) agonist GW0742 exerts protective effects on endothelial function in type 1 diabetic rats. The rats were divided into 4 groups: control, control-treated (GW0742, 5 mg kg(-1)day(-1) for 5 weeks), diabetic (streptozotocin injection), and diabetic-treated. GW0742 administration in diabetic rats did not alter plasma glucose, systolic blood pressure, or heart rate, but reduced plasma triglyceride levels. The vasodilatation induced by acetylcholine was decreased in aortas from diabetic rats. GW0742 restored endothelial function, increasing eNOS phosphorylation. Superoxide production, NADPH oxidase activity, and mRNA expression of prepro endothelin-1, p22(phox), p47(phox), and NOX-1 were significantly higher in diabetic aortas, and GW0742 treatment prevented these changes. In addition, GW0742 prevented the endothelial dysfunction and the upregulation of prepro endothelin-1 and p47(phox) after the in vitro incubation of aortic rings with high glucose and these effects were prevented by the PPARβ/δ antagonist GSK0660. PPARβ/δ activation restores endothelial function in type 1 diabetic rats. This effect seems to be related to an increase in nitric oxide bioavailability as a result of reduced NADPH oxidase-driven superoxide production and downregulation of prepro endothelin-1.

Angiotensin II stimulates superoxide production in the thick ascending limb by activating NOX4

Angiotensin II (ANG II) stimulates production of superoxide (O(2)(-)) by NADPH oxidase (NOX) in medullary thick ascending limbs (TALs). There are three isoforms of the catalytic subunit (NOX1, 2, and 4) known to be expressed in the kidney. We hypothesized that NOX2 mediates ANG II-induced O(2)(-) production by TALs. To test this, we measured NOX1, 2, and 4 mRNA and protein by RT-PCR and Western blot in TAL suspensions from rats and found three catalytic subunits expressed in the TAL. We measured O(2)(-) production using a lucigenin-based assay. To assess the contribution of NOX2, we measured ANG II-induced O(2)(-) production in wild-type and NOX2 knockout mice (KO). ANG II increased O(2)(-) production by 346 relative light units (RLU)/mg protein in the wild-type mice (n = 9; P < 0.0007 vs. control). In the knockout mice, ANG II increased O(2)(-) production by 290 RLU/mg protein (n = 9; P < 0.007 vs. control). This suggests that NOX2 does not contribute to ANG II-induced O(2)(-) production (P < 0.6 WT vs. KO). To test whether NOX4 mediates the effect of ANG II, we selectively decreased NOX4 expression in rats using an adenovirus that expresses NOX4 short hairpin (sh)RNA. Six to seven days after in vivo transduction of the kidney outer medulla, NOX4 mRNA was reduced by 77%, while NOX1 and NOX2 mRNA was unaffected. In control TALs, ANG II stimulated O(2)(-) production by 96%. In TALs transduced with NOX4 shRNA, ANG II-stimulated O(2)(-) production was not significantly different from the baseline. We concluded that NOX4 is the main catalytic isoform of NADPH oxidase that contributes to ANG II-stimulated O(2)(-) production by TALs.