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

HDL-replacement therapy: From traditional to emerging clinical applications

The unique and multifaceted properties of high-density lipoproteins (HDL)-ranging from cholesterol efflux to anti-inflammatory, anti-oxidant, and immunomodulatory effects-have prompted their direct use, particularly in cardiovascular ischemic conditions. Recent advances have extended the interest in HDL-based treatments to novel applications, from improving stent biocompatibility, to treatment of heart failure to central nervous system (CNS) disorders. Strategies to harness HDL's therapeutic potential have evolved from the direct use of isolated HDL in animal models to reconstituted HDL (rHDL) in humans. For these latter, the use of isolated apoA-I associated with different phospholipids has been the most frequent approach, also involving apparently beneficial mutants, such as the apo A-I Milano (AIM). From the initial very promising results, particularly with this mutant in coronary patients, later studies have mostly been non-confirmatory, although issues such as possible inadequate dose/response and unexpected immunological properties have come to light. Most recently a study on isolated plasma HDL in coronary patients (AEGIS-II) provided overall negative findings, but a clear fall of major cardiovascular events was recorded when restricting analysis to hypercholesterolemic patients. Emerging approaches, including gene therapy and plant-derived recombinant HDL formulations, hold promise for enhancing the accessibility and efficacy of HDL-based interventions. At this time, an improved approach to heart failure treatment also appears feasible, and a better understanding of the role played by HDL in the CNS may lead to significant improvements in the handling of some dramatic diseases at this level. While challenges persist, the evolving landscape of HDL replacement therapies offers hope for significant progress in addressing both cardiovascular and non-cardiovascular conditions.

Lipoprotection in cardiovascular diseases

Cardioprotection is a well-established term in the scientific world. It describes the protection of various mediators on the cardiovascular system. These protective effects can also be provided by certain lipids. Since lipids are a very specific and clearly definable class of substances, we define the term lipoprotection as lipid-mediated cardioprotection. In this review, we highlight high-density lipoprotein (HDL), sphingosine-1-phosphate (S1P) and omega-3 polyunsaturated fatty acids (n-3 PUFA) as the most important lipoprotective mediators and show their beneficial impact on coronary artery disease (CAD), acute myocardial infarction (AMI) and heart failure (HF).

Microarray analysis identifies human apoA-IMilano and apoA-II as determinants of the liver gene expression related to lipid and energy metabolism

The phenotype of individuals carrying the apolipoprotein A-IMilano (apoA-IM), the mutant form of human apoA-I (apoA-I), is characterized by very low concentrations of HDL and apoA-I, and hypertriglyceridemia. Paradoxically, these subjects are not found to be at increased risk of premature cardiovascular disease compared to controls. Besides, various in vitro and in vivo studies have demonstrated that apoA-IM possesses greater anti-atherosclerotic activity compared to apoA-I. The molecular mechanisms explaining the apoA-IM carrier's phenotype and the apoA-IM higher efficacy are still not fully elucidated. To investigate such mechanisms, we crossed previously generated apoA-I (A-I k-in) or apoA-IM knock-in mice (A-IM k-in) with transgenic mice expressing human apoA-II but lacking murine apoA-I (hA-II) to generate hA-II/A-I k-in, and hA-II/A-IM k-in, respectively. These genetically modified mice completely reproduced the apoA-IM carrier's phenotype, including hypoalphalipoproteinemia and hypertriglyceridemia. Furthermore, by using the microarray methodology, we investigated the intrinsic differences in hepatic gene expression among these k-in mouse lines. The expression of 871, 1,018, 1129 and 764 genes was significantly altered between 1) hA-II/A-I and hA-II/A-IM k-in; 2) A-IM and hA-II/A-IM k-in; 3) A-I and A-IM; 4) A-I and hA-II/A-I k-in liver samples, respectively. Bioinformatics analysis highlighted that the hepatic expression of two genes, Elovl6 and Gatm, related to fatty acid/lipid and energy metabolism, respectively, is influenced by the presence of the apoA-IM natural variant and/or apoA-II.

High-Density Lipoprotein and Heart Failure

The protective effect of high-density lipoprotein (HDL) on atherosclerosis is well known, and its mechanisms of action has been extensively studied. However, the impact of HDL on heart failure and its mechanisms are still controversial or unknown. The cardioprotective role of HDL may be reflected in its antioxidant, anti-inflammatory, anti-apoptotic, and endothelial function protection. In epidemiological studies, high-density lipoprotein cholesterol (HDL-C) levels have been negatively associated with heart failure (HF). The major protein component of HDL-C is apolipoprotein (Apo) A-I, while paraoxonase-1 (PON-1) is an essential mediator for many protective functions of HDL, and HDL may act through components like (Apo) A-I or PON-1 to delay heart failure progress. HDL can slow heart failure disease progression through parts like (Apo) A-I or PON-1. The potential causality between HDL and heart failure, the role of HDL in the pathogenesis of HF, and its interaction with C-reactive protein (CRP), triglycerides (TG), and monocytes in the process of heart failure have been briefly summarized and discussed in this article. HDL plays an important role in the pathogenesis, progression and treatment of HF.

HDL-apoA-II Is Strongly Associated with 1-Year Mortality in Acute Heart Failure Patients

The prognostic value of the subset of high-density lipoprotein (HDL) particles containing apolipoprotein (apo)A-II (HDL-apoA-II) in acute heart failure (AHF) remains unexplored. In this study, baseline serum levels of HDL-apoA-II (total and subfractions 1−4) were measured in 315 AHF patients using NMR spectroscopy. The mean patient age was 74.2 ± 10.5 years, 136 (43.2%) were female, 288 (91.4%) had a history of cardiomyopathy, 298 (94.6%) presented as New York Heart Association class 4, and 118 (37.5%) patients died within 1 year after hospitalization for AHF. Multivariable Cox regression analyses, adjusted for age and sex as well as other clinical and laboratory parameters associated with 1-year mortality in the univariable analyses, revealed a significant inverse association of HDL-apoA-II (hazard ratio (HR) 0.67 per 1 standard deviation (1 SD) increase, 95% confidence interval (CI) 0.47−0.94, p = 0.020), HDL2-apoA-II (HR 0.72 per 1 SD increase, 95% CI 0.54−0.95, p = 0.019), and HDL3-apoA-II (HR 0.59 per 1 SD increase, 95% CI 0.43−0.80, p < 0.001) with 1-year mortality. We conclude that low baseline HDL-apoA-II, HDL2-apoA-II, and HDL3-apoA-II serum levels are associated with increased 1-year mortality in AHF patients and may thus be of prognostic value in AHF.

Increased Remnant Lipoproteins in Apo E Deficient Mice Induce Coronary Atherosclerosis following Transverse Aortic Constriction and Aggravate the Development of Pressure Overload-Induced Cardiac Hypertrophy and Heart Failure

Murine coronary arteries are very resistant to the development of atherosclerosis, which may be related to their intramyocardial course. Blood pressure promotes atherosclerotic plaque formation by acting as a physical force that potentiates the migration of pro-atherogenic lipoproteins across the endothelium. C57BL/6N apolipoprotein (apo) E deficient mice have increased remnant lipoproteins that are a risk factor for coronary atherosclerosis. In this study, our aim was to quantify coronary atherosclerosis and artery remodeling following transverse aortic constriction (TAC) in C57BL/6N apo E−/− mice and to evaluate the impact of increased remnant lipoproteins on the development of pressure overload-induced cardiac hypertrophy and heart failure. Advanced atherosclerotic lesions were observed in the left coronary artery of C57BL/6N apo E−/− TAC mice but not in C57BL/6N TAC mice. Pressure overload resulted in markedly increased cardiac hypertrophy and more pronounced heart failure in C57BL/6N apo E−/− TAC mice in comparison to C57BL/6N TAC mice. Pathological hypertrophy, as evidenced by increased myocardial fibrosis and capillary rarefaction, was more prominent in C57BL/6N TAC apo E−/− than in C57BL/6N TAC mice and led to more marked cardiac dysfunction. In conclusion, TAC in apo E deficient mice induces coronary atherosclerosis and aggravates the development of pathological cardiac hypertrophy and heart failure.

The Role of High-Density Lipoprotein Cholesterol in 2022

PURPOSE OF THE REVIEW

High-density lipoproteins (HDL) are responsible for the transport in plasma of a large fraction of circulating lipids, in part from tissue mobilization. The evaluation of HDL-associated cholesterol (HDL-C) has provided a standard method for assessing cardiovascular (CV) risk, as supported by many contributions on the mechanism of this arterial benefit. The present review article will attempt to investigate novel findings on the role and mechanism of HDL in CV risk determination.

RECENT FINDINGS

The most recent research has been aimed to the understanding of how a raised functional capacity of HDL, rather than elevated levels per se, may be responsible for the postulated CV protection. Markedly elevated HDL-C levels appear instead to be associated to a raised coronary risk, indicative of a U-shaped relationship. While HDL-C reduction is definitely related to a raised CV risk, HDL-C elevations may be linked to non-vascular diseases, such as age-related macular disease. The description of anti-inflammatory, anti-oxidative and anti-infectious properties has indicated potential newer areas for diagnostic and therapeutic approaches. In the last two decades inconclusive data have arisen from clinical trials attempting to increase HDL-C pharmacologically or by way of recombinant protein infusions (most frequently with the mutant A-I Milano); prevention of stent occlusion or heart failure treatment have shown instead significant promise. Targeted clinical studies are still ongoing.

HDL Composition, Heart Failure, and Its Comorbidities

Although research on high-density lipoprotein (HDL) has historically focused on atherosclerotic coronary disease, there exists untapped potential of HDL biology for the treatment of heart failure. Anti-oxidant, anti-inflammatory, and endothelial protective properties of HDL could impact heart failure pathogenesis. HDL-associated proteins such as apolipoprotein A-I and M may have significant therapeutic effects on the myocardium, in part by modulating signal transduction pathways and sphingosine-1-phosphate biology. Furthermore, because heart failure is a complex syndrome characterized by multiple comorbidities, there are complex interactions between heart failure, its comorbidities, and lipoprotein homeostatic mechanisms. In this review, we will discuss the effects of heart failure and associated comorbidities on HDL, explore potential cardioprotective properties of HDL, and review novel HDL therapeutic targets in heart failure.

U-Shaped Association Between Serum Uric Acid Level and Hypertensive Heart Failure: A Genetic Matching Case-Control Study

Background: Heart failure (HF) is a global pandemic and lays an added burden on public healthcare. Previous studies indicated that high and low serum uric acid levels are associated with worse outcomes in many diseases. Reduced serum uric acid may not result in a better outcome.

Methods: A comparative, matched cross-sectional study design was implemented. The matching variables were age, sex, BMI, BP, and histories of CKD, CVD, diabetes mellitus, stroke, hyperlipidemia. We reviewed the electronic medical records to identify patients diagnosed with hypertension or hypertensive heart failure (HHF) admitted to Beijing Hospital's cardiology department.

Results: The median age of the two groups after matching are 71. There are 55.6% males in the hypertension group and 53.8% in the heart failure group. Univariate logistic regression analysis showed that UA's quadratic term is significant (OR = 1.00, 95% CI 1.00 to 1.00; P = 0.03), which indicated a u-shaped relationship between hypertension and HHF. FBS (OR = 0.22, 95% CI 0.05 to 0.95, p = 0.07) and HDL (OR = 1.23, 95% CI 1.00 to 1.54, P = 0.05) were not significant but close.

Conclusion: Our results supported that both low and high uric acid levels were predictive of hypertensive heart failure. Besides, high-density lipoprotein cholesterol and fasting blood sugar were also associated with hypertensive heart failure. Low-density lipoprotein cholesterol was not associated with hypertensive 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.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

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.

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.

Apolipoprotein A-I in mouse cerebrospinal fluid derives from the liver and intestine via plasma high-density lipoproteins assembled by ABCA1 and LCAT

Apolipoprotein (apo) A-I, the major structural protein of high-density lipoprotein (HDL), is present in human and mouse cerebrospinal fluid (CSF) despite its lack of expression in brain cells. To identify the origin of apoA-I in CSF, we generated intestine-specific and liver-specific Apoa1 knockout mice (Apoa1^ΔInt and Apoa1^Δliv mice, respectively). Lipoprotein profiles of Apoa1^ΔInt and Apoa1^ΔLiv mice resembled those of control littermates, whereas knockout of Apoa1 in both intestine and liver (Apoa1^ΔIntΔLiv ) resulted in a 60-percent decrease in HDL-cholesterol levels, thus strongly mimicking the Apoa1^-/- mice. Immunoassays revealed that mouse apoA-I was not present in the CSF of the Apoa1^ΔIntΔLiv mice. Furthermore, apoA-I levels in CSF were highly correlated with plasma spherical HDL levels, which were regulated by ABCA1 and LCAT. Collectively, these results suggest that apoA-I protein in CSF originates in liver and small intestine and is taken up from the plasma.

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.

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.

Reduced Apolipoprotein M and Adverse Outcomes Across the Spectrum of Human Heart Failure

BACKGROUND

Apo (apolipoprotein) M mediates the physical interaction between high-density lipoprotein (HDL) particles and sphingosine-1-phosphate (S1P). Apo M exerts anti-inflammatory and cardioprotective effects in animal models.

METHODS

In a subset of PHFS (Penn Heart Failure Study) participants (n=297), we measured apo M by Enzyme-Linked ImmunoSorbent Assay (ELISA). We also measured total S1P by liquid chromatography-mass spectrometry and isolated HDL particles to test the association between apo M and HDL-associated S1P. We confirmed the relationship between apo M and outcomes using modified aptamer-based apo M measurements among 2170 adults in the PHFS and 2 independent cohorts: the Washington University Heart Failure Registry (n=173) and a subset of TOPCAT (Treatment of Preserved Cardiac Function Heart Failure With an Aldosterone Antagonist Trial; n=218). Last, we examined the relationship between apo M and ≈5000 other proteins (SomaScan assay) to identify biological pathways associated with apo M in heart failure.

RESULTS

In the PHFS, apo M was inversely associated with the risk of death (standardized hazard ratio, 0.56 [95% CI, 0.51-0.61]; P<0.0001) and the composite of death/ventricular assist device implantation/heart transplantation (standardized hazard ratio, 0.62 [95% CI, 0.58-0.67]; P<0.0001). This relationship was independent of HDL cholesterol or apo AI levels. Apo M remained associated with death (hazard ratio, 0.78 [95% CI, 0.69-0.88]; P<0.0001) and the composite of death/ventricular assist device/heart transplantation (hazard ratio, 0.85 [95% CI, 0.76-0.94]; P=0.001) in models that adjusted for multiple confounders. This association was present in both heart failure with reduced and preserved ejection fraction and was replicated in the Washington University cohort and a cohort with heart failure with preserved ejection fraction only (TOPCAT). The S1P and apo M content of isolated HDL particles strongly correlated (R=0.81, P<0.0001). The top canonical pathways associated with apo M were inflammation (negative association), the coagulation system (negative association), and liver X receptor/retinoid X receptor activation (positive association). The relationship with inflammation was validated with multiple inflammatory markers measured with independent assays.

CONCLUSIONS

Reduced circulating apo M is independently associated with adverse outcomes across the spectrum of human heart failure. Further research is needed to assess whether the apo M/S1P axis is a suitable therapeutic target in heart failure.

Inborn errors of apolipoprotein A-I metabolism: implications for disease, research and development

PURPOSE OF REVIEW

We review current knowledge regarding naturally occurring mutations in the human apolipoprotein A-I (APOA1) gene with a focus on their clinical complications as well as their exploitation for the elucidation of structure-function-(disease) relationships and therapy.

RECENT FINDINGS

Bi-allelic loss-of-function mutations in APOA1 cause HDL deficiency and, in the majority of patients, premature atherosclerotic cardiovascular disease (ASCVD) and corneal opacities. Heterozygous HDL-cholesterol decreasing mutations in APOA1 were associated with increased risk of ASCVD in several but not all studies. Some missense mutations in APOA1 cause familial amyloidosis. Structure-function-reationships underlying the formation of amyloid as well as the manifestion of amyloidosis in specific tissues are better understood. Lessons may also be learnt from the progress in the treatment of amyloidoses induced by transthyretin variants. Infusion of reconstituted HDL (rHDL) containing apoA-I (Milano) did not cause regression of atherosclerosis in coronary arteries of patients with acute coronary syndrome. However, animal experiments indicate that rHDL with apoA-I (Milano) or apoA-I mimetic peptides may be useful for the treatment of heart failure of inflammatory bowel disease.

SUMMARY

Specific mutations in APOA1 are the cause of premature ASCVD or familial amyloidosis. Synthetic mimetics of apoA-I (mutants) may be useful for the treatment of several diseases beyond ASCVD.

A Compendium of the Biological Effects of Apolipoprotein A-IMilano

Obesity is a pathologic condition generated by an energy imbalance, that is, excess caloric consumption, leading to weight gain and metabolic disturbances characterized by adipose tissue inflammation and hyperglycemic conditions. In line with these observations, increasing evidence causally links inflammation, or the molecules and networks integral to inflammatory response, to the development of obesity and the complications that emerge from this pathology, such as cardiovascular, neurologic, respiratory, and metabolic illnesses, as well as sepsis and cancer. Not surprisingly, this chronic and abnormal metabolic background leads to constant derangements in innate and adaptive immunity. It is well known that high-density lipoprotein (HDL) possesses anti-inflammatory and antioxidant properties, and various studies have highlighted an emerging role of HDL in modulating immune function. The efficacy of synthetic HDL (sHDL) containing the recombinant form of apoA-IMilano (sHDL-apoA-IM), originating from the observation that carriers of this mutation have low levels of HDL cholesterol without increased atherosclerosis, has been largely proved in diverse animal models of atherosclerosis; however, the therapeutic use of sHDL-apoA-IM still needs clinical validation. One of the main limitations to the use of recombinant proteins in clinical studies lies in the unsustainable purification costs. Unpurified rice-milk-apoA-IM demonstrated anti-inflammatory and antiatherogenic properties in a mouse model, even though administrated by an unconventional way: by oral gavage. Additionally, recent data have uncovered new therapeutic applications for this sHDL-apoA-IM This review provides an overview of all potential application of sHDL-apoA-IM in some inflammatory-based diseases. SIGNIFICANCE STATEMENT: A recent study demonstrated that oral administration of rice-seed protein extracts containing the apoA-IM (i.e., the milk-apoA-IM) reduced atherosclerosis development in a mouse model. Moreover, the rice-milk-apoA-IM preserved both in vitro and in vivo anti-inflammatory properties, as observed when sHDL-apoA-IM was given by intravascular infusion. Besides, various studies suggested that sHDL-apoA-IM could positively affect other inflammatory-based diseases. Together, these data might represent a new starting point for "sHDL-apoA-IM-based therapies" in chronic degenerative disease.

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.

Inheritance of high and low HDL: mechanisms and management

PURPOSE OF REVIEW

The inverse association between plasma high-density lipoprotein cholesterol (HDL-C) concentration and the incidence of cardiovascular disease (CVD) has been unequivocally proven by many epidemiological studies. There are several genetic disorders affecting HDL-C plasma levels, either providing atheroprotection or predisposing to premature atherosclerosis. However, up to date, there has not been any pharmacological intervention modulating HDL-C levels, which has been clearly shown to prevent the progression of CVD. Thus, clarifying the exact underlying mechanisms of inheritance of these genetic disorders that affect HDL is a current goal of the research, as key roles of molecular components of HDL metabolism and function can be revealed and become targets for the discovery of novel medications for the prevention and treatment of CVD.

RECENT FINDINGS

Primary genetic disorders of HDL can be either associated with longevity or, in contrast, may lead to premature CVD, causing high morbidity and mortality to their carriers. A large body of recent research has closely examined the genetic disorders of HDL and new promising therapeutic strategies have been developed, which may be proven beneficial in patients predisposed to CVD in the near future.

SUMMARY

We have reviewed recent findings on the inheritance of genetic disorders associated with high and low HDL-C plasma levels and we have discussed their clinical features, as well as information about new promising HDL-C-targeted therapies that are under clinical trials.

Cholesterol-Lowering Gene Therapy Prevents Heart Failure with Preserved Ejection Fraction in Obese Type 2 Diabetic Mice

Hypercholesterolemia may be causally related to heart failure with preserved ejection fraction (HFpEF). We aimed to establish a HFpEF model associated with hypercholesterolemia and type 2 diabetes mellitus by feeding a high-sucrose/high-fat (HSHF) diet to C57BL/6J low-density lipoprotein receptor (LDLr)^−/− mice. Secondly, we evaluated whether cholesterol-lowering adeno-associated viral serotype 8 (AAV8)-mediated LDLr gene transfer prevents HFpEF. AAV8-LDLr gene transfer strongly (p < 0.001) decreased plasma cholesterol in standard chow (SC) mice (66.8 ± 2.5 mg/dl versus 213 ± 12 mg/dl) and in HSHF mice (84.6 ± 4.4 mg/dl versus 464 ± 25 mg/dl). The HSHF diet induced cardiac hypertrophy and pathological remodeling, which were potently counteracted by AAV8-LDLr gene transfer. Wet lung weight was 19.0% (p < 0.001) higher in AAV8-null HSHF mice than in AAV8-null SC mice, whereas lung weight was normal in AAV8-LDLr HSHF mice. Pressure–volume loop analysis was consistent with HFpEF in AAV8-null HSHF mice and showed a completely normal cardiac function in AAV8-LDLr HSHF mice. Treadmill exercise testing demonstrated reduced exercise capacity in AAV8-null HSHF mice but a normal capacity in AAV8-LDLr HSHF mice. Reduced oxidative stress and decreased levels of tumor necrosis factor-α may mediate the beneficial effects of cholesterol lowering. In conclusion, AAV8-LDLr gene therapy prevents HFpEF.

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.

Long-term testosterone deficiency modifies myofilament and calcium-handling proteins and promotes diastolic dysfunction in the aging mouse heart

The impact of long-term gonadectomy (GDX) on cardiac contractile function was explored in the setting of aging. Male mice were subjected to bilateral GDX or sham operation (4 wk) and investigated at 16-18 mo of age. Ventricular myocytes were field stimulated (2 Hz, 37°C). Peak Ca²⁺ transients (fura 2) and contractions were similar in GDX and sham-operated mice, although Ca²⁺ transients (50% decay time: 45.2 ± 2.3 vs. 55.6 ± 3.1 ms, P < 0.05) and contractions (time constant of relaxation: 39.1 ± 3.2 vs. 69.5 ± 9.3 ms, P < 0.05) were prolonged in GDX mice. Action potential duration was increased in myocytes from GDX mice, but this did not account for prolonged responses, as Ca²⁺ transient decay was slow even when cells from GDX mice were voltage clamped with simulated "sham" action potentials. Western blots of proteins involved in Ca²⁺ sequestration and efflux showed that Na⁺/Ca²⁺ exchanger and sarco(endo)plasmic reticulum Ca²⁺-ATPase type 2 protein levels were unaffected, whereas phospholamban was dramatically higher in ventricles from aging GDX mice (0.24 ± 0.02 vs. 0.86 ± 0.13, P < 0.05). Myofilament Ca²⁺ sensitivity at physiological Ca²⁺ was similar, but phosphorylation of essential myosin light chain 1 was reduced by ≈50% in ventricles from aging GDX mice. M-mode echocardiography showed no change in systolic function (e.g., ejection fraction). Critically, pulse-wave Doppler echocardiography showed that GDX slowed isovolumic relaxation time (12.9 ± 0.9 vs. 16.9 ± 1.0 ms, P < 0.05), indicative of diastolic dysfunction. Thus, dysregulation of intracellular Ca²⁺ and myofilament dysfunction contribute to deficits in contraction in hearts from testosterone-deficient aging mice. This suggests that low testosterone helps promote diastolic dysfunction in the aging heart. NEW & NOTEWORTHY The influence of long-term gonadectomy on contractile function was examined in aging male hearts. Gonadectomy slowed the decay of Ca²⁺ transients and contractions in ventricular myocytes and slowed isovolumic relaxation time, demonstrating diastolic dysfunction. Underlying mechanisms included Ca²⁺ dysregulation, elevated phospholamban protein levels, and hypophosphorylation of a myofilament protein, essential myosin light chain. Testosterone deficiency led to intracellular Ca²⁺ dysregulation and myofilament dysfunction, which may facilitate diastolic dysfunction in the setting of aging.

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.

Reconstituted HDL (Milano) Treatment Efficaciously Reverses Heart Failure with Preserved Ejection Fraction in Mice

Heart failure with preserved ejection fraction (HFpEF) represents a major unmet therapeutic need. This study investigated whether feeding coconut oil (CC diet) for 26 weeks in female C57BL/6N mice induces HFpEF and evaluated the effect of reconstituted high-density lipoprotein (HDL)_Milano (MDCO-216) administration on established HFpEF. Eight intraperitoneal injections of MDCO-216 (100 mg/kg protein concentration) or of an equivalent volume of control buffer were executed with a 48-h interval starting at 26 weeks after the initiation of the diet. Feeding the CC diet for 26 weeks induced pathological left ventricular hypertrophy characterized by a 17.1% (p < 0.0001) lower myocardial capillary density and markedly (p < 0.0001) increased interstitial fibrosis compared to standard chow (SC) diet mice. Parameters of systolic and diastolic function were significantly impaired in CC diet mice resulting in a reduced stroke volume, decreased cardiac output, and impaired ventriculo-arterial coupling. However, ejection fraction was preserved. Administration of MDCO-216 in CC diet mice reduced cardiac hypertrophy, increased capillary density (p < 0.01), and reduced interstitial fibrosis (p < 0.01). MDCO-216 treatment completely normalized cardiac function, lowered myocardial acetyl-coenzyme A carboxylase levels, and decreased myocardial transforming growth factor-β1 in CC diet mice. In conclusion, the CC diet induced HFpEF. Reconstituted HDL_Milano reversed pathological remodeling and functional cardiac abnormalities.