LP(a): Structure, Genetics, Associated Cardiovascular Risk, and Emerging Therapeutics.

Lipoprotein(a) [Lp(a)] is a molecule bound to apolipoprotein(a) with some similarity to low-density lipoprotein cholesterol (LDL-C), which has been found to be a risk factor for cardiovascular disease (CVD). Lp(a) appears to induce inflammation, atherogenesis, and thrombosis. Approximately 20% of the world's population has increased Lp(a) levels, determined predominantly by genetics. Current clinical practices for the management of dyslipidemia are ineffective in lowering Lp(a) levels. Evolving RNA-based therapeutics, such as the antisense oligonucleotide pelacarsen and small interfering RNA olpasiran, have shown promising results in reducing Lp(a) levels. Phase III pivotal cardiovascular outcome trials [Lp(a)HORIZON and OCEAN(a)] are ongoing to evaluate their efficacy in secondary prevention of major cardiovascular events in patients with elevated Lp(a). The future of cardiovascular residual risk reduction may transition to a personalized approach where further lowering of either LDL-C, triglycerides, or Lp(a) is selected after high-intensity statin therapy based on the individual risk profile and preferences of each patient.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part one: Pleiotropic pro-atherosclerotic effects of PCSK9.

BACKGROUND: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily recognized for its role in lipid metabolism, but recent evidence suggests that it may have broader implications due to its diverse tissue expression. OBJECTIVE: This review aims to explore the multifaceted functions of PCSK9, highlighting its pro-atherosclerotic effects, including its impact on circulating lipoprotein variables, non-low-density lipoprotein receptors, and various cell types involved in atherosclerotic plaque development. CONCLUSIONS: PCSK9 exhibits diverse roles beyond lipid metabolism, potentially contributing to atherosclerosis through multiple pathways. Understanding these mechanisms could offer new insights into therapeutic strategies targeting PCSK9 for cardiovascular disease management.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part two: Current and emerging concepts in the clinical use of PCSK9 inhibition.

BACKGROUND: Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have emerged as a novel class of drugs with cardioprotective effects through their lipid-lowering effects. OBJECTIVE: This review aims to discuss existing and novel strategies of PCSK9 inhibition, providing an overview of established randomized controlled trials and ongoing outcome trials that assess the efficacy and long-term safety of PCSK9 inhibitors. It also explores the evolving role of PCSK9 beyond lipid metabolism and outlines the pleiotropic actions of PCSK9 inhibition in various disorders and future directions including novel strategies to target PCSK9. CONCLUSION: PCSK9 inhibition shows promise not only in lipid metabolism but also in other disease processes, including atherosclerotic plaque remodeling, acute coronary syndrome, stroke, inflammation, and immune response.

Peroxisome Proliferator-Activated Receptor Gamma Regulates Interleukin-6-Induced Lipoprotein (a) Gene Expression in Human HepG2 Cells.

Lipoprotein(a) [Lp(a)] is a risk factor for coronary disease. Although levels are primarily genetically determined, data from patients with inflammatory diseases indicate that the inflammatory milieu is associated with increased Lp(a) levels. Lp(a) is synthesized in the liver and the LPA gene promoter contains an interleukin-6 (IL-6) responsive binding site, but the regulatory steps linking inflammation with hepatic Lp(a) synthesis are not well clarified. We explored the interplay between IL-6, peroxisome proliferator-activated receptor gamma (PPARγ), and Lp(a) synthesis in HepG2 cells. Through genetic mapping, a regulatory variant within the LPA promoter overlapping with a PPARγ binding site was identified. In in vitro experiments, IL-6-mediated LPA gene transcription was heightened with PPARγ knock-down and suppressed with pioglitazone, a PPARγ agonist. These results demonstrate an important role of PPARγ as a negative regulator of IL-6 induced hepatic Lp(a) production and may represent a new therapeutic target for patients with inflammatory conditions characterized by elevated Lp(a).

Is it time for a paradigm shift? Inclusion of APOE on genetic dyslipidemia panels.

APOE codes for apolipoprotein E (ApoE), which plays an important role in lipid and lipoprotein metabolism and homeostasis of tissue lipid content. Several variants in APOE have been associated with inherited dyslipidemias, and a subsequent increased risk of developing premature coronary artery disease (CAD). However, these variants and their impact on risk can be thought of on a spectrum, with some being more monogenic in nature, and others contributing in a polygenic/multifactorial manner. Despite these known associations, there is often hesitancy around ordering APOE genetic testing due to the association with Alzheimer's disease. This paper aims to catalyze discussion around APOE testing and counseling strategies, highlight the nuances around this topic, and advocate for inclusion of APOE testing on dyslipidemia panels when an inherited dyslipidemia is suspected.

Coronary artery endothelial function and aging in people with HIV and HIV-negative individuals.

Coronary artery disease (CAD) is a common comorbidity in people with human immunodeficiency virus (HIV) (PWH) and impaired coronary endothelial function (CEF) plays a central role in the pathogenesis of CAD. Age-related impaired CEF among PWH, however, is not well characterized. We investigated the association between CEF and age in males and females with and without HIV using 3-T magnetic resonance imaging (MRI). We measured the changes in coronary cross-sectional area (CSA) and coronary blood flow during isometric handgrip exercise (IHE), an established endothelial-dependent stressor with smaller increases in CSA and coronary blood flow indicative of impaired CEF. We included 106 PWH and 82 individuals without HIV. Differences in demographic and clinical characteristics between PWH and individuals without HIV were explored using Pearson's χ2 test for categorical variables and Welch's t test for continuous variables. Linear regression models were used to examine the association between CEF and age. CEF was significantly lower in PWH as compared with individuals without HIV. Coronary endothelial dysfunction was also present at younger ages in PWH than in the individuals without HIV and there were significant differences in CEF between the PWH and individuals without HIV across age groups. Among the individuals without HIV, the percent changes in CSA were inversely related to age in unadjusted and adjusted models. There was no significant association between CEF and age in PWH. To the best of our knowledge, this is the first study to examine the relationship between age and CEF in PWH, and our results suggest that factors other than age significantly impair CEF in PWH across the life span.NEW & NOTEWORTHY This is the first study to examine the relationship between age and coronary endothelial function (CEF) in people with human immunodeficiency virus (HIV) (PWH). CEF was assessed using magnetic resonance imaging (MRI) in people with and without HIV. Although age and CEF were significantly inversely related in individuals without HIV, there was no association between age and CEF in PWH.

Hypoxia Triggers SENP1 (Sentrin-Specific Protease 1) Modulation of KLF15 (Kruppel-Like Factor 15) and Transcriptional Regulation of Arg2 (Arginase 2) in Pulmonary Endothelium.

OBJECTIVE: KLF15 (Kruppel-like factor 15) has recently been shown to suppress activation of proinflammatory processes that contribute to atherogenesis in vascular smooth muscle, however, the role of KLF15 in vascular endothelial function is unknown. Arginase mediates inflammatory vasculopathy and vascular injury in pulmonary hypertension. Here, we tested the hypothesis that KLF15 is a critical regulator of hypoxia-induced Arg2 (arginase 2) transcription in human pulmonary microvascular endothelial cells (HPMEC). APPROACH AND RESULTS: Quiescent HPMEC express ample amounts of full-length KLF15. HPMECs exposed to 24 hours of hypoxia exhibited a marked decrease in KLF15 protein levels and a reciprocal increase in Arg2 protein and mRNA. Chromatin immunoprecipitation indicated direct binding of KLF15 to the Arg2 promoter, which was relieved with HPMEC exposure to hypoxia. Furthermore, overexpression of KLF15 in HPMEC reversed hypoxia-induced augmentation of Arg2 abundance and arginase activity and rescued nitric oxide (NO) production. Ectopic KLF15 also reversed hypoxia-induced endothelium-mediated vasodilatation in isolated rat pulmonary artery rings. Mechanisms by which hypoxia regulates KLF15 abundance, stability, and compartmentalization to the nucleus in HPMEC were then investigated. Hypoxia triggered deSUMOylation of KLF15 by SENP1 (sentrin-specific protease 1), and translocation of KLF15 from nucleus to cytoplasm. CONCLUSIONS: KLF15 is a critical regulator of pulmonary endothelial homeostasis via repression of endothelial Arg2 expression. KLF15 abundance and nuclear compartmentalization are regulated by SUMOylation/deSUMOylation-a hypoxia-sensitive process that is controlled by SENP1. Strategies including overexpression of KLF15 or inhibition of SENP1 may represent novel therapeutic targets for pulmonary hypertension.

Cystathionine γ-lyase protects vascular endothelium: a role for inhibition of histone deacetylase 6.

Endothelial cystathionine γ-lyase (CSEγ) contributes to cardiovascular homeostasis, mainly through production of H2S. However, the molecular mechanisms that control CSEγ gene expression in the endothelium during cardiovascular diseases are unclear. The aim of the current study is to determine the role of specific histone deacetylases (HDACs) in the regulation of endothelial CSEγ. Reduced CSEγ mRNA expression and protein abundance were observed in human aortic endothelial cells (HAEC) exposed to oxidized LDL (OxLDL) and in aortas from atherogenic apolipoprotein E knockout (ApoE-/-) mice fed a high-fat diet compared with controls. Intact murine aortic rings exposed to OxLDL (50 µg/ml) for 24 h exhibited impaired endothelium-dependent vasorelaxation that was blocked by CSEγ overexpression or the H2S donor NaHS. CSEγ expression was upregulated by pan-HDAC inhibitors and by class II-specific HDAC inhibitors, but not by other class-specific inhibitors. The HDAC6 selective inhibitor tubacin and HDAC6-specific siRNA increased CSEγ expression and blocked OxLDL-mediated reductions in endothelial CSEγ expression and CSEγ promoter activity, indicating that HDAC6 is a specific regulator of CSEγ expression. Consistent with this finding, HDAC6 mRNA, protein expression, and activity were upregulated in OxLDL-exposed HAEC, but not in human aortic smooth muscle cells. HDAC6 protein levels in aortas from high-fat diet-fed ApoE-/- mice were comparable to those in controls, whereas HDAC6 activity was robustly upregulated. Together, our findings indicate that HDAC6 is upregulated by atherogenic stimuli via posttranslational modifications and is a critical regulator of CSEγ expression in vascular endothelium. Inhibition of HDAC6 activity may improve endothelial function and prevent or reverse the development of atherosclerosis.NEW & NOTEWORTHY Oxidative injury to endothelial cells by oxidized LDL reduced cystathionine γ-lyase (CSEγ) expression and H2S production, leading to endothelial dysfunction, which was prevented by histone deacetylase 6 (HDAC6) inhibition. Our data suggest HDAC6 as a novel therapeutic target to prevent the development of atherosclerosis.

Transcatheter aortic valve replacement: a novel abdominal transaortic approach.

Transcatheter aortic valve replacement (TAVR) via the transfemoral (TF), transapical (TA), or even the transaortic (TAO) approach in high-risk or inoperable patients is quickly becoming a safe and effective modality for the treatment of symptomatic severe aortic stenosis (AS). However, in this selected group of patients, those with anatomical or physiologic constraints preventing TF, TA, and conventional TAO TAVR, alternative sites of access must be explored. Here, we report a successful TAVR in an inoperable patient with severe AS using a distal abdominal TAO approach via a synthetic graft-conduit.

Neurocardiac Axis Physiology and Clinical Applications.

The neurocardiac axis constitutes the neuronal circuits between the arteries, heart, brain, and immune organs (including thymus, spleen, lymph nodes, and mucosal associated lymphoid tissue) that together form the cardiovascular brain circuit. This network allows the individual to maintain homeostasis in a variety of environmental situations. However, in dysfunctional states, such as exposure to environments with chronic stressors and sympathetic activation, this axis can also contribute to the development of atherosclerotic vascular disease as well as other cardiovascular pathologies and it is increasingly being recognized as an integral part of the pathogenesis of cardiovascular disease. This review article focuses on 1) the normal functioning of the neurocardiac axis; 2) pathophysiology of the neurocardiac axis; 3) clinical implications of this axis in hypertension, atherosclerotic disease, and heart failure with an update on treatments under investigation; and 4) quantification methods in research and clinical practice to measure components of the axis and future research areas.

Intra-individual variability in lipoprotein(a): the value of a repeat measure for reclassifying individuals at intermediate risk.

Aims: Lipoprotein(a) [Lp(a)] levels are predominantly genetically determined and repeat measurements are generally considered unlikely to be clinically useful. However, the temporal variation of Lp(a) is not well characterized. Our aim was to determine the intra-individual variability of Lp(a) and whether a repeated measure reclassified Lp(a)-specific cardiovascular risk using the European Atherosclerosis Society (EAS) consensus statement risk categories. Methods and results: This retrospective cohort study analysed initial and repeated serum Lp(a) levels measured using the same methodology from 609 individuals in the Nashville Biosciences database, a de-identified electronic medical records database. Baseline and follow-up paired values were significantly different (P < 0.05), with an absolute change of ≥10 mg/dL in 38.1% [95% CI 34.2-42%] and a >25% change in 40.5% [95% CI 36.6-44.3%] of individuals. Although the categories of those whose values were in the EAS low-risk and high-risk categories did not change, 53% of those in the intermediate 'grey-zone' category transitioned to either the low-risk (20%) or high-risk (33%) category. Black individuals exhibited greater variability than White individuals and women exhibited greater variability than men. There was a positive correlation between the baseline Lp(a) levels and the absolute changes in Lp(a), (r = 0.59, P < 0.01). Conclusion: Temporal-related changes in Lp(a) variability were present in many individuals. A repeat Lp(a) measure may allow more precise Lp(a)-specific cardiovascular risk prediction for individuals whose initial value is in the EAS-defined intermediate 'grey-zone' category. Lp(a) variability should be included in calculating the expected effect sizes in future clinical research studies targeting Lp(a).

Early Initiation of PCSK9 Inhibitor Therapy Versus Placebo in Patients With Acute Coronary Syndrome: A Systematic Review and Meta-Analysis.

In patients with stable atherosclerotic cardiovascular disease, proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9is) have shown a 50% to 60% reduction in low-density lipoprotein cholesterol (LDL-C) from baseline when added to high-intensity statin therapy. However, less is known about the impact of PCSK9is in the setting of an acute coronary syndrome (ACS). Therefore, we performed a systematic review and meta-analysis comparing PCSK9is with placebo in the setting of ACS added to guideline-directed high-intensity or maximally tolerated statin therapy. We included randomized controlled trials with initiation of a PCSK9i or placebo within 1 week of presentation or percutaneous coronary intervention for ACS. PubMed, EMBASE, and Cochrane Central were searched. This study followed the Cochrane and Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) recommendations. A total of 6 randomized controlled trials were included, with a total of 996 patients, of whom 503 (50.5%) received PCSK9is. The mean follow-up ranged from 4 to 52 weeks. The LDL-C (mean difference [MD] -44.0 mg/100 ml, CI -54.3 to -33.8, p <0.001) and lipoprotein (a) levels (MD -24.0 nmol/L, confidence interval [CI] -43.0 to -4.9, p = 0.01) were significantly lower at follow-up with PCSK9is. Similarly, the total cholesterol (MD -49.2 mg/100 ml, CI -59.0 to -39.3), triglycerides (MD -19.0 mg/100 ml, CI -29.9 to -8.2), and apolipoprotein B (MD -33.3 mg/100 ml, CI -44.4 to -22.1) were significantly reduced with PCSK9is. In conclusion, in patients with ACS, early initiation of PCSK9i added to statin significantly reduces LDL-C and lipoprotein (a) levels compared with placebo. Whether the differences in these atherogenic lipoproteins translate into a reduction in clinical end points is yet to be determined.

Expanded genetic testing in familial hypercholesterolemia-A single center's experience.

Objective: Assess the yield of genetic testing for pathogenic variants in ABCG5, ABCG8, LIPA, and APOE in individuals with personal and family histories suggestive of familial hypercholesterolemia. Methods: Retrospective review of patients seen in the Advanced Lipid Disorders Clinic at Johns Hopkins. Results: In the lipid clinic at a single center during the years 2015-2023, 607 patients underwent genetic testing for familial hypercholesterolemia, of which 263 underwent the expanded genetic testing for sitosterolemia. Eighty-eight patients had genetic testing which included APOE, and 22 patients had testing which included LIPA. Among these, one patient was identified to have a pathogenic variant in APOE and another patient with a pathogenic variant in ABCG5 (0.7 % yield). The frequency of a positive result was double that of a variant of uncertain significance. Conclusion: These data suggest in rare cases expanded testing can provide answers for patients and families with a minimal likelihood of a variant of uncertain significance.

Homocysteine modifies the association of coronary stenosis and HIV infection in an inner city African American population.

BACKGROUND AND AIMS: People with HIV (PWH) whose disease is controlled on anti-retroviral regimens remain at an increased risk for coronary artery disease (CAD). Traditional cardiovascular risk factors do not fully explain the residual risk in PWH suggesting contributions from nontraditional factors. Homocysteine (Hcy) may be one of these as prior work in adults without HIV demonstrate that Hcy may impair endothelial function by decreasing the availability of nitric oxide, promoting the development of atherosclerosis. In addition, plasma Hcy levels are higher in PWH than in individuals living without HIV. The aim of this study was to investigate whether Hcy levels influence the association between HIV and coronary stenosis in an inner city African American population. METHODS: African Americans from the Heart Study in Baltimore, with and without HIV, recruited from inner-city Baltimore between June 2004 and February 2015, were included in this analysis. Participants underwent coronary CT angiography to evaluate the presence of coronary stenosis, defined as luminal stenosis >10%. Hcy was measured from stored serum samples. RESULTS: In this analysis, the median [IQR] age of the 664 participants was 56 [50-66] years; 68.1% were living with HIV and 43.1% were women. Elevated Hcy (>15 µmol/L) was more prevalent in those with coronary stenosis (23.3%, 95% CI: 18.4%-28.2%) than in those without coronary stenosis (13.1%, 95% CI: 9.7%-16.5%) (p = 0.0007), and HIV was associated with coronary stenosis in those participants with an elevated Hcy (Prevalence Ratio: 1.94, 95% CI: 1.04-3.64, p = 0.0038) and not in those with a Hcy ≤15 µmol/L (Prevalence Ratio: 1.02, 95% CI: 0.83-1.25, p = 0.87). CONCLUSIONS: Our data suggest an association between elevated Hcy levels (>15 µmol/L) and the prevalence of coronary stenosis in PWH from this inner city African American population.

VERICIGUAT RESCUES CYCLIC GUANOSINE MONOPHOSPHATE PRODUCTION IN HUMAN AORTIC VASCULAR SMOOTH MUSCLE CELLS AND AUGMENTS VASORELAXATION IN AORTIC RINGS EXPOSED TO HIGH GLUCOSE.

Background: Normal endothelial cell dependent vascular smooth muscle cell function is mediated by nitric oxide (NO), which stimulates soluble guanylyl cyclase (sGC) production of the second messenger, cyclic guanosine monophosphate (cGMP) leading to increased protein kinase G (PKG) activity and vascular smooth muscle relaxation. NO bioavailability is impaired in inflammatory settings, such as high glucose (HG). We examined whether the direct sGC sensitizer/stimulator vericiguat, augments cGMP production in human vascular smooth muscle cells (HVSMC) exposed to high glucose and explored its effect on vasorelaxation. Methods: Aortic HVSMCs were exposed to HG for 24h. In the treatment group, cells also received 1uM vericiguat for 24h. After incubation, cGMP and PKG activity were measured. Additionally, thoracic murine aortas were exposed to HG or to normal glucose (NG) control. The rings were then placed in an organ chamber bath and dose response curves to increasing doses of acetylcholine (Ach) and sodium nitroprusside were constructed for three groups: control (normal glucose), HG alone, and HG + vericiguat. Results: HVSMCs exposed to HG produced significantly less cGMP than those exposed to NG. cGMP production in the presence of HG was rescued when treated with 1uM vericiguat. Additionally, PKG activity was impaired in the presence of HG and enzyme activity was restored with vericiguat. In isolated mouse aortic rings, ACh mediated relaxation was impaired following treatment with HG, but was improved when a HG group was treated with vericiguat. Conclusions: The sGC sensitizer/stimulator vericiguat restored cGMP production and PKG activity in the setting of HG. Vericiguat enhanced ACh-mediated vasorelaxation in the setting of HG. The findings suggest clinical studies are warranted to investigate the potential of sGC sensitization/stimulation as a therapeutic intervention to improve vascular endothelial-dependent function that is impaired in pro-inflammatory settings that are associated with the development of atherosclerotic disease.

A Case-Based Approach to the Management of Patients with Chronic Coronary Disease: Updates from the 2023 AHA/ACC Guidelines.

The 2023 American Heart Association (AHA)/American College of Cardiology (ACC) Multisociety Guideline for the Management of Patients with Chronic Coronary Disease presents important updates to the care of patients with chronic coronary disease (1). The recommendations of these guidelines inform the care for patients with (1) asymptomatic coronary artery disease, (2) stable angina or equivalent symptoms (e.g., dyspnea upon exertion), (3) symptomatic nonobstructive coronary disease including coronary microvascular dysfunction and vasospasm, and (4) left ventricular (LV) systolic dysfunction with known coronary artery disease. In this review, we aim to demonstrate key recommendations in the 2023 guideline using the following four hypothetical cases.

Recent advances in cardiovascular risk assessment: The added value of non-invasive anatomic imaging.

In 2022, multiple original research studies were conducted highlighting the utility of coronary artery calcium (CAC) imaging in young individuals and provided further evidence for the role of CAC to improve atherosclerotic cardiovascular disease (ASCVD) risk assessment. Mean calcium density was shown to be a more reliable predictor than peak density in risk assessment. Additionally, in light of the ACC/AHA/Multispecialty Chest Pain Guideline's recent elevation of coronary computed tomography angiography (CCTA) to a Class I (level of evidence A) recommendation as an index diagnostic test for acute or stable chest pain, several studies support the utility of CCTA and guided future directions. This review summarizes recent studies that highlight the role of non-invasive imaging in enhancing ASCVD risk assessment across different populations.

COVID-19 in the Initiation and Progression of Atherosclerosis: Pathophysiology During and Beyond the Acute Phase.

The incidence of atherosclerotic cardiovascular disease is increasing globally, especially in low- and middle-income countries, despite significant efforts to reduce traditional risk factors. Premature subclinical atherosclerosis has been documented in association with several viral infections. The magnitude of the recent COVID-19 pandemic has highlighted the need to understand the association between SARS-CoV-2 and atherosclerosis. This review examines various pathophysiological mechanisms, including endothelial dysfunction, platelet activation, and inflammatory and immune hyperactivation triggered by SARS-CoV-2 infection, with specific attention on their roles in initiating and promoting the progression of atherosclerotic lesions. Additionally, it addresses the various pathogenic mechanisms by which COVID-19 in the post-acute phase may contribute to the development of vascular disease. Understanding the overlap of these syndromes may enable novel therapeutic strategies. We further explore the need for guidelines for closer follow-up for the often-overlooked evidence of atherosclerotic cardiovascular disease among patients with recent COVID-19, particularly those with cardiometabolic risk factors.