Anti-PCSK9 antibodies inhibit pro-atherogenic mechanisms in APOE*3Leiden.CETP mice

Genetically Predicted Apolipoprotein E Levels with the Risk of Panvascular Diseases: A Mendelian Randomization Study

The aim of this study was to comprehensively assess the causal relationship between the overall genetic effect of circulating ApoE levels and panvascular lesions using newer genome-wide association data and two-sample bidirectional Mendelian randomization (MR) analysis. Two-way MR using single-nucleotide polymorphisms of circulating ApoE as instrumental variables was performed using the highest-priority Genome-wide association study (GWAS) data, with factor-adjusted and data-corrected statistics, to estimate causal associations between circulating ApoE levels and 10 pan-vascular diseases in > 500,000 UK Biobank participants, > 400,000 participants of Finnish ancestry, and numerous participants in a consortium of predominantly European ancestry. Meta-analysis was conducted to assess positive results. After correcting for statistical results, elevated circulating ApoE levels were shown to have a significant protective effect against Cerebral ischemia (CI) [IVW odds ratio (OR) 0.888, 95% Confidence Interval (CI): 0.823-0.958, p = 2.3 × 10-3], Coronary heart disease [IVW OR 0.950,95% CI: 0.924-0.976, p = 2.0 × 10-4] had a significant protective effect and potentially suggestive protective causality against Angina pectoris [IVW odds ratio (OR) 0.961, 95%CI: 0.931-0.991, p = 1.1 × 10-2]. There was a potential causal effect for increased risk of Heart failure (HF) [IVW ratio (OR) 1.040, 95%CI: 1.006-1.060, p = 1.8 × 10-2]. (Bonferroni threshold p < 0.0026, PFDR < 0.05) Reverse MR analysis did not reveal significant evidence of a causal effect of PVD on changes in circulating ApoE levels. Meta-analysis increases reliability of results. Elevated circulating ApoE levels were particularly associated with an increased risk of heart failure. Elevated ApoE levels reduce the risk of cerebral ischemia, coronary heart disease, and angina pectoris, reflecting a protective effect. The possible pathophysiological role of circulating ApoE levels in the development of panvascular disease is emphasized.

PCSK9 regulates myofibroblast transformation through the JAK2/STAT3 pathway to regulate fibrosis after myocardial infarction

Cardiac fibrosis is pivotal in the progression of numerous cardiovascular diseases. This phenomenon is hallmarked by an excessive deposition of ECM protein secreted by myofibroblasts, leading to increased myocardial stiffness. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that belongs to the proprotein-converting enzyme family. It has emerged as a viable therapeutic target for reducing plasma low-density lipoprotein cholesterol. However, the exact mechanism via which PCSK9 impacts cardiac fibrosis remains unclear. In the present research, an increase in circulating PCSK9 protein levels was observed in individuals with myocardial infarction and rat models of myocardial infarction. Moreover, the inhibition of circulating PCSK9 in rats was found to reduce post-infarction fibrosis. In vitro experiments further demonstrated that overexpression of PCSK9 or stimulation by extracellular PCSK9 recombinant protein enhanced the transformation of cardiac fibroblasts to myofibroblasts. This process also elevated collagen Ⅰ, and Ⅲ, as well as α-SMA protein levels. However, these effects were countered when co-incubated with the STAT3 inhibitor S3I-201. This study suggests that PCSK9 may function as a novel regulator of myocardial fibrosis, primarily via the JAK2/STAT3 pathway.

Real-world effectiveness and safety of evolocumab in very high-risk atherosclerotic cardiovascular disease patients with acute ischemic stroke

BACKGROUND

We investigated evolocumab's real-world effectiveness and safety on a background of statin therapy in the acute phase of ischemic stroke (IS) patients with a very high-risk of atherosclerotic cardiovascular disease (ASCVD).

METHODS

A real-world, single-center, retrospective study was conducted in the neurology department at Tianjin Huanhu Hospital in China. Patients were divided into two groups: evolocumab treatment (140 mg every two weeks) or the standard of care (SOC) group. The primary efficacy outcome of the study was the achievement of a targeted lipid control rate and the incidence of major adverse cardiovascular events (MACE) by the end of the follow-up. MACE was defined as a composite of various cardiovascular events, cerebrovascular events such as stroke or TIA, and event-related deaths. Propensity score matching (PSM) analysis was utilized to account for confounding factors between groups. Survival analyses were performed using the Kaplan-Meier method and COX regression modeling.

RESULTS

1080 AIS patients with very high-risk ASCVD were recruited. After PSM, there were 528 individuals, with 206 in the evolocumab group and 322 in the SOC group. At 12 months of follow-up, the proportion of LDL-C < 1.4mmol/L and ≥ 50% reduction was 44.91% in the evolocumab group, compared with only 3.12% of SOC-treated patients (p < 0.01). The median follow-up time for clinical events was 15 months. The evolocumab group was associated with a lower risk of cerebrovascular events compared to the SOC group (HR, 0.45; 95% CI, 0.23-0.89; p = 0.02).

CONCLUSIONS

This real-world study suggested that evolocumab on a background of statin reduced the LDL-C levels significantly and lowered the incidence of recurrent cerebrovascular events in the very high-risk ASCVD patients with AIS in China.

Targeting PCSK9 to tackle cardiovascular disease

Lowering blood cholesterol levels efficiently reduces the risk of developing atherosclerotic cardiovascular disease (ASCVD), including coronary artery disease (CAD), which is the main cause of death worldwide. CAD is caused by plaque formation, comprising cholesterol deposits in the coronary arteries. Proprotein convertase subtilisin kexin/type 9 (PCSK9) was discovered in the early 2000s and later identified as a key regulator of cholesterol metabolism. PCSK9 induces lysosomal degradation of the low-density lipoprotein (LDL) receptor in the liver, which is responsible for clearing LDL-cholesterol (LDL-C) from the circulation. Accordingly, gain-of-function PCSK9 mutations are causative of familial hypercholesterolemia, a severe condition with extremely high plasma cholesterol levels and increased ASCVD risk, whereas loss-of-function PCSK9 mutations are associated with very low LDL-C levels and protection against CAD. Since the discovery of PCSK9, extensive investigations in developing PCSK9 targeting therapies have been performed. The combined delineation of clear biology, genetic risk variants, and PCSK9 crystal structures have been major drivers in developing antagonistic molecules. Today, two antibody-based PCSK9 inhibitors have successfully progressed to clinical application and shown to be effective in reducing cholesterol levels and mitigating the risk of ASCVD events, including myocardial infarction, stroke, and death, without any major adverse effects. A third siRNA-based inhibitor has been FDA-approved but awaits cardiovascular outcome data. In this review, we outline the PCSK9 biology, focusing on the structure and nonsynonymous mutations reported in the PCSK9 gene and elaborate on PCSK9-lowering strategies under development. Finally, we discuss future perspectives with PCSK9 inhibition in other severe disorders beyond cardiovascular disease.

The Anti-Thrombotic Effects of PCSK9 Inhibitors

Atherosclerosis is the primary process that underlies cardiovascular disease. The connection between LDL cholesterol and the formation of atherosclerotic plaques is established by solid evidence. PCSK9 inhibitors have proven to be a valuable and practical resource for lowering the LDL cholesterol of many patients in recent years. Their inhibitory effect on atherosclerosis progression seems to be driven not just by lipid metabolism modification but also by LDL-independent mechanisms. We review the effect of PCSK9 inhibitors on various mechanisms involving platelet activation, inflammation, endothelial dysfunction, and the resultant clot formation. The main effectors of PCSK9 activation of platelets are CD36 receptors, lipoprotein(a), oxidised LDL particles, tissue factor, and factor VIII. Many more molecules are under investigation, and this area of research is growing rapidly.

Intravascular imaging assessment of pharmacotherapies targeting atherosclerosis: advantages and limitations in predicting their prognostic implications

Intravascular imaging has been often used over the recent years to examine the efficacy of emerging therapies targeting plaque evolution. Serial intravascular ultrasound, optical coherence tomography, or near-infrared spectroscopy-intravascular ultrasound studies have allowed us to evaluate the effects of different therapies on plaque burden and morphology, providing unique mechanistic insights about the mode of action of these treatments. Plaque burden reduction, a decrease in necrotic core component or macrophage accumulation-which has been associated with inflammation-and an increase in fibrous cap thickness over fibroatheromas have been used as surrogate endpoints to assess the value of several drugs in inhibiting plaque evolution and improving clinical outcomes. However, some reports have demonstrated weak associations between the effects of novel treatments on coronary atheroma and composition and their prognostic implications. This review examines the value of invasive imaging in assessing pharmacotherapies targeting atherosclerosis. It summarizes the findings of serial intravascular imaging studies assessing the effects of different drugs on atheroma burden and morphology and compares them with the results of large-scale trials evaluating their impact on clinical outcome. Furthermore, it highlights the limited efficacy of established intravascular imaging surrogate endpoints in predicting the prognostic value of these pharmacotherapies and introduces alternative imaging endpoints based on multimodality/hybrid intravascular imaging that may enable more accurate assessment of the athero-protective and prognostic effects of emerging therapies.

Aggregation-induced emission fluorescent probes for lipid droplets-specific bioimaging of cells and atherosclerosis plaques

Visualizing lipid droplets (LDs) using fluorescence imaging is highly desirable for the diagnosis and treatment of atherosclerotic heart diseases. However, the imaging performance of the current commercial lipid probes is unsatisfactory. In this study, we prepared two probes (TTM and MeO-TTM) with aggregation-induced emission (AIE) properties for LD imaging with efficiency. Interestingly, TTM and MeO-TTM showed low emissions in H₂O but their emissions were significantly increased in oil. Moreover, TTM and MeO-TTM showed great biocompatibility and intracellular LDs would be specifically illuminated by these probes with good resistance to photobleaching. In addition, TTM and MeO-TTM also exhibited great imaging performance in studying the spatial distribution of LDs in mouse atherosclerotic plaques. This work not only provides a simple tool for studying atherosclerosis but also hopes to enhance the development of fluorescent probes for LDs-specific imaging applications.

PCSK9 Inhibition During the Inflammatory Stage of SARS-CoV-2 Infection

BACKGROUND

The intensity of inflammation during COVID-19 is related to adverse outcomes. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is involved in low-density lipoprotein receptor homeostasis, with potential influence on vascular inflammation and on COVID-19 inflammatory response.

OBJECTIVES

The goal of this study was to investigate the impact of PCSK9 inhibition vs placebo on clinical and laboratory outcomes in patients with severe COVID-19.

METHODS

In this double-blind, placebo-controlled, multicenter pilot trial, 60 patients hospitalized for severe COVID-19, with ground-glass opacity pneumonia and arterial partial oxygen pressure to fraction of inspired oxygen ratio ≤300 mm Hg, were randomized 1:1 to receive a single 140-mg subcutaneous injection of evolocumab or placebo. The primary endpoint was death or need for intubation at 30 days. The main secondary endpoint was change in circulating interleukin (IL)-6 at 7 and 30 days from baseline.

RESULTS

Patients randomized to receive the PCSK9 inhibitor had lower rates of death or need for intubation within 30 days vs placebo (23.3% vs 53.3%, risk difference: -30%; 95% CI: -53.40% to -6.59%). Serum IL-6 across time was lower with the PCSK9 inhibitor than with placebo (30-day decline: -56% vs -21%). Patients with baseline IL-6 above the median had lower mortality with PCSK9 inhibition vs placebo (risk difference: -37.50%; 95% CI: -68.20% to -6.70%).

CONCLUSIONS

PCSK9 inhibition compared with placebo reduced the primary endpoint of death or need for intubation and IL-6 levels in severe COVID-19. Patients with more intense inflammation at randomization had better survival with PCSK9 inhibition vs placebo, indicating that inflammatory intensity may drive therapeutic benefits. (Impact of PCSK9 Inhibition on Clinical Outcome in Patients During the Inflammatory Stage of the COVID-19 [IMPACT-SIRIO 5]; NCT04941105).

Interactions between PCSK9 and NLRP3 inflammasome signaling in atherosclerosis

Atherosclerosis is an early pathological basis of numerous cardiovascular events that result in death or disability. Recent studies have described PCSK9 as a novel target for the treatment of atherosclerosis; PCSK9 is capable of degrading LDLR on the surface of hepatocytes through the regulation of lipid metabolism, and it can function as a novel inflammatory modulator in atherosclerosis. Inflammasomes are important intracellular multiprotein complexes that promote the inflammatory response in atherosclerosis. Among inflammasomes, the NLRP3 inflammasome is particularly notable because of its important role in the development of atherosclerotic disease. After activation, NLRP3 forms a complex with ASC and pro-caspase-1, converting pro-caspase-1 into activated caspase-1, which may trigger the release of IL-1β and IL-18 and contribute to the inflammatory response. Several recent studies have indicated that there may be interactions between PCSK9 and the NLRP3 inflammasome, which may contribute to the inflammatory response that drives atherosclerosis development and progression. On the one hand, the NLRP3 inflammasome plays an important role via IL-1β in regulating PCSK9 secretion. On the other hand, PCSK9 regulates caspase-1-dependent pyroptosis by initiating mtDNA damage and activating NLRP3 inflammasome signaling. This paper reviews the mechanisms underlying PCSK9 and NLRP3 inflammasome activation in the context of atherosclerosis. Furthermore, we describe the current understanding of the specific molecular mechanism underlying the interactions between PCSK9 and NLRP3 inflammasome signaling as well as the drug repositioning events that influence vascular cells and exert beneficial antiatherosclerotic effects. This review may provide a new therapeutic direction for the effective prevention and treatment of atherosclerosis in the clinic.

PCSK9 inhibitors for anti-inflammation in atherosclerosis: protocol for a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Atherosclerosis is the leading cause of cardiovascular disease (CVD), which is one of the most common causes of morbidity and mortality worldwide. Lipid accumulation and inflammation play a crucial role in the pathogenesis of atherosclerosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are an emerging lipid-lowering agent reported as a potential anti-inflammation effect in the prevention of CVD. However, the anti-inflammatory effect is still elusive. Therefore, a systematic review and meta-analysis is needed to analyse the anti-inflammatory effect of PCSK9 inhibitors on atherosclerosis in practice.

METHODS AND ANALYSIS

This protocol was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols. We will include double-blind, randomised controlled trials that reported changes in the levels of inflammatory markers, with an intervention arm of PCSK9 inhibitors and a treatment duration of more than 2 weeks. The following databases will be mainly searched from 1 January 2003 to the formal search date: PubMed, Embase, Web of Science and the Cochrane Central Register of Controlled Trials. The primary aim is to assess the effect of PCSK9 inhibitors on inflammatory markers, including circulating inflammatory markers such as C-reactive protein, high-sensitivity C-reactive protein, white cell counts, IL-1β, IL-6 and TNF-α and local inflammatory markers such as the most diseased segment target-to-background ratio of the index vessel in adult patients with atherosclerosis. We will assess the quality of evidence, heterogeneity and report bias following the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions.

ETHICS AND DISSEMINATION

Due to the systematic review being based on published studies, no ethics approval is required. The study results will be presented at international conferences and published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022297710.

Effects of Lipid Lowering Therapy Optimization by PCSK9 Inhibitors on Circulating CD34+ Cells and Pulse Wave Velocity in Familial Hypercholesterolemia Subjects without Atherosclerotic Cardiovascular Disease: Real-World Data from Two Lipid Units

Background: Circulating CD34+ progenitor cells (CD34+CPCs) are characterized by pronounced tissue regeneration activity. Dyslipidemic subjects seemed to have reduced CD34+CPCs, and statin therapy appeared to restore their levels. We aimed to evaluate the effects of PCSK9 inhibitors (PCSK9-i) on CD34+CPCs and pulse wave velocity (PWV) in a cohort of heterozygous familial hypercholesterolemia (HeFH) subjects. Methods: We determined CD34+ cell count and its change after PCSK9-i in 30 selected HeFH subjects and 30 healthy controls. Lipid profile and PWV were evaluated at baseline (T0), 6 months after intensive lipid lowering strategy (statin plus ezetimibe, T1), and after 6 months of optimized therapy with PCSK9-i (T2); CD34+ cell count was reported at T1 and T2. Results: At T1, the median value of CD34+ cells was not significantly different between HeFH subjects and controls, and the same result was obtained at T2. PWV was significantly reduced at T1 (ΔPWV − 14.8%, p < 0.001 vs. T0) and T2 (ΔPWV − 10.96%, p < 0.001 vs. T1). Dividing HeFH subjects into two groups of high- and low-CD34+ cell count, CD34+CPCs appeared to be polarized with a significant difference between the two groups (1.2 (0.46) vs. 4.74 (1.92), p < 0.001), also with respect to controls (both p < 0.001). This polarization was no longer observed at T2, and neither with respect to controls. ΔCD34+ was +67.4% in the low-CD34+ group and −39.24% in the high-CD34+ group (p < 0.001). Lastly, we found a significant correlation between ΔCD34+ cell number and ΔPWV in HeFH subjects (rho = −0.365, p < 0.05), particularly in the low-CD34+ group (rho = −0.681, p < 0.001). Conclusion: PCSK9-i exhibited favorable effects on CD34 + CPCs as was on PWV values in a cohort of FH subjects. Our preliminary findings suggest a possible positive role of this novel lipid-lowering strategy on vascular homeostasis.

Association of genetic polymorphisms of PCSK9 with type 2 diabetes in Uygur Chinese population

Background

PCSK9 gene expression is associated with biological processes such as lipid metabolism, glucose metabolism, and inflammation. In the present study, our primary objective was to assess the association between the single-nucleotide polymorphisms in the PCSK9 gene and type 2 diabetes in Uygur subjects, in Xinjiang, China.

Methods

We designed a case–control study including 662 patients diagnosed with T2DM and 1220 control subjects. Four single-nucleotide polymorphisms (rs11583680, rs2483205, rs2495477 and rs562556) of PCSK9 gene were genotyped using the improved multiplex ligation detection reaction technique.

Results

For rs2483205, the distribution of genotypes, dominant model (CC vs CT + TT), overdominant model (CC + TT vs CT) showed significant differences between T2DM patients and the controls (P = 0.011 and P = 0.041 respectively). For rs2495477, the distribution of genotypes, the dominant model (AA vs GA + GG) showed significant differences between T2DM patients and the controls (P = 0.024). Logistic regression analysis suggested after adjustment of other confounders, the differences remained significant between the two groups [for rs2483205 CC vs CT + TT: odds ratio (OR) = 1.321, 95% confidence interval (CI) 1.078–1.617, P = 0.007; CC + TT vs CT: OR = 1.255, 95% CI 1.021–1.542, P = 0.03; for rs2495477 AA vs GA + GG: OR = 1.297, 95% CI 1.060–1.588, P = 0.012].

Conclusion

The present study indicated that CT + TT genotype and CT genotype of rs2483205, as well as GA + GG genotype of rs2495477 in PCSK9 gene were associated with an increased risk of type 2 diabetes in the Uygur population in Xinjiang.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-022-02710-w.

Novel Nongenetic Murine Model of Hyperglycemia and Hyperlipidemia-Associated Aggravated Atherosclerosis

Objective

Atherosclerosis, the main pathology underlying cardiovascular diseases is accelerated in diabetic patients. Genetic mouse models require breeding efforts which are time-consuming and costly. Our aim was to establish a new nongenetic model of inducible metabolic risk factors that mimics hyperlipidemia, hyperglycemia, or both and allows the detection of phenotypic differences dependent on the metabolic stressor(s).

Methods and Results

Wild-type mice were injected with gain-of-function PCSK9^D377Y (proprotein convertase subtilisin/kexin type 9) mutant adeno-associated viral particles (AAV) and streptozotocin and fed either a high-fat diet (HFD) for 12 or 20 weeks or a high-cholesterol/high-fat diet (Paigen diet, PD) for 8 weeks. To evaluate atherosclerosis, two different vascular sites (aortic sinus and the truncus of the brachiocephalic artery) were examined in the mice. Combined hyperlipidemic and hyperglycemic (HGHCi) mice fed a HFD or PD displayed characteristic features of aggravated atherosclerosis when compared to hyperlipidemia (HCi HFD or PD) mice alone. Atherosclerotic plaques of HGHCi HFD animals were larger, showed a less stable phenotype (measured by the increased necrotic core area, reduced fibrous cap thickness, and less α-SMA-positive area) and had more inflammation (increased plasma IL-1β level, aortic pro-inflammatory gene expression, and MOMA-2-positive cells in the BCA) after 20 weeks of HFD. Differences between the HGHCi and HCi HFD models were confirmed using RNA-seq analysis of aortic tissue, revealing that significantly more genes were dysregulated in mice with combined hyperlipidemia and hyperglycemia than in the hyperlipidemia-only group. The HGHCi-associated genes were related to pathways regulating inflammation (increased Cd68, iNos, and Tnfa expression) and extracellular matrix degradation (Adamts4 and Mmp14). When comparing HFD with PD, the PD aggravated atherosclerosis to a greater extent in mice and showed plaque formation after 8 weeks. Hyperlipidemic and hyperglycemic mice fed a PD (HGHCi PD) showed less collagen (Sirius red) and increased inflammation (CD68-positive cells) within aortic plaques than hyperlipidemic mice (HCi PD). HGHCi-PD mice represent a directly inducible hyperglycemic atherosclerosis model compared with HFD-fed mice, in which atherosclerosis is severe by 8 weeks.

Conclusion

We established a nongenetically inducible mouse model allowing comparative analyses of atherosclerosis in HCi and HGHCi conditions and its modification by diet, allowing analyses of multiple metabolic hits in mice.

Pleiotropic Effects of PCSK9: Focus on Thrombosis and Haemostasis

The proprotein convertase subtilisin/keying 9 (PCSK9) is a serine protease that has gained importance in recent years as a drug target, mainly due to its effect on cholesterol metabolism in promoting the degradation of the low-density lipoprotein receptor (LDLR). However, this protease may also play an important role in lipid-independent reactions, including the process of thrombogenesis. Considering this, we reviewed the effects and implications of PCSK9 on platelet function and blood coagulation. PCSK9 knockout mice exhibited reduced platelet activity and developed less agonist-induced arterial thrombi compared to the respective control animals. This is in line with known research that elevated blood levels of PCSK9 are associated with an increased platelet reactivity and total number of circulating platelets in humans. Moreover, PCSK9 also has an effect on crucial factors of the coagulation cascade, such as increasing factor VIII plasma levels, since the degradation of this blood clotting factor is promoted by the LDLR. The aforementioned pleiotropic effects of the PCSK9 are important to take into account when evaluating the clinical benefit of PCSK9 inhibitors.

Downregulation of low-density lipoprotein receptor mRNA in lymphatic endothelial cells impairs lymphatic function through changes in intracellular lipids

Rationale: Impairment in lymphatic transport is associated with the onset and progression of atherosclerosis in animal models. The downregulation of low-density-lipoprotein receptor (LDLR) expression, rather than increased circulating cholesterol level per se, is involved in early atherosclerosis-related lymphatic dysfunction. Enhancing lymphatic function in Ldlr-/- mice with a mutant form of VEGF-C (VEGF-C 152s), a selective VEGFR-3 agonist, successfully delayed atherosclerotic plaque onset when mice were subsequently fed a high-fat diet. However, the specific mechanisms by which LDLR protects against lymphatic function impairment is unknown. Methods and results: We have thus injected wild-type and Pcsk9-/- mice with an adeno-associated virus type 1 expressing a shRNA for silencing Ldlr in vivo. We herein report that lymphatic contractility is reduced upon Ldlr dowregulation in wild-type mice only. Our in vitro experiments reveal that a decrease in LDLR expression at the mRNA level reduces the chromosome duplication phase and the protein expression of VEGFR-3, a membrane-bound key lymphatic marker. Furthermore, it also significantly reduced the levels of 18 lipid subclasses, including key constituents of lipid rafts as well as the transcription of several genes involved in cholesterol biosynthesis and cellular and metabolic processes. Exogenous PCSK9 only reduces lymphatic endothelial-LDLR at the protein level and does not affect lymphatic endothelial cell integrity. This puts forward that PCSK9 may act upon lymphatic muscle cells to mediate its effect on lymphatic contraction capacity in vivo. Conclusion: Our results suggest that treatments that specifically palliate the down regulation of LDLR mRNA in lymphatic endothelial cells preserve the integrity of the lymphatic endothelium and sustain lymphatic function, a prerequisite player in atherosclerosis.

The Reciprocal Relationship between LDL Metabolism and Type 2 Diabetes Mellitus

Type 2 diabetes mellitus and insulin resistance feature substantial modifications of the lipoprotein profile, including a higher proportion of smaller and denser low-density lipoprotein (LDL) particles. In addition, qualitative changes occur in the composition and structure of LDL, including changes in electrophoretic mobility, enrichment of LDL with triglycerides and ceramides, prolonged retention of modified LDL in plasma, increased uptake by macrophages, and the formation of foam cells. These modifications affect LDL functions and favor an increased risk of cardiovascular disease in diabetic individuals. In this review, we discuss the main findings regarding the structural and functional changes in LDL particles in diabetes pathophysiology and therapeutic strategies targeting LDL in patients with diabetes.

Endogenous PCSK9 may influence circulating CD45neg/CD34bright and CD45neg/CD34bright/CD146neg cells in patients with type 2 diabetes mellitus

Protease proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of LDL cholesterol clearance and has been associated with cardiovascular risk. PCSK9 inhibitors increase in vivo circulating endothelial progenitor cells (EPCs), a subtype of immature cells involved in ongoing endothelial repair. We hypothesized that the effect of PCSK9 on vascular homeostasis may be mediated by EPCs in patients with or without type 2 diabetes mellitus (T2DM). Eighty-two patients (45 with, 37 without T2DM) at high cardiovascular risk were enrolled in this observational study. Statin treatment was associated with higher circulating levels of PCSK9 in patients with and without T2DM (p < 0.001 and p = 0.036) and with reduced CD45neg/CD34bright (total EPC compartment) (p = 0.016) and CD45neg/CD34bright/CD146neg (early EPC) (p = 0.040) only among patients with T2DM. In the whole group of patients, statin treatment was the only independent predictor of low number of CD45neg/CD34bright (β = - 0.230; p = 0.038, adjusted R2 = 0.041). Among T2DM patients, PCSK9 circulating levels were inversely related and predicted both the number of CD45neg/CD34bright (β = - 0.438; p = 0.003, adjusted R2 = 0.173), and CD45neg/CD34bright/CD146neg (β = - 0.458; p = 0.002, adjusted R2 = 0.191) independently of age, gender, BMI and statin treatment. In high-risk T2DM patients, high endogenous levels of PCSK9 may have a detrimental effect on EPCs by reducing the endothelial repair and worsening the progression of atherothrombosis.

CARotid plaqUe StabilizatiOn and regression with evolocumab: Rationale and design of the CARUSO study

BACKGROUND

While the experience with PCSK9i in patients with coronary artery disease has been wide, and coronary plaque regression has been documented, little is known regarding the role of these drugs on carotid plaque regression. The CARotid plaqUe StabilizatiOn and regression with evolocumab (CARUSO) study is a randomized, single-center, investigator-initiated trial aiming at evaluating carotid plaque morphological stabilization and regression following, respectively, 6 and 12 months of therapy with evolocumab.

METHODS

Asymptomatic patients with uni- or bilateral de novo carotid artery stenosis ≥50% and LDL-C values ≥100 mg/dl despite maximum tolerated lipid lowering therapy (LLT) will be randomized to evolocumab 140 mg s.c. every 2 weeks on top of ongoing LLT, or no additional treatment. 100 patients (50 in each arm) will be enrolled. Serial carotid duplex ultra-sonography will be performed to monitor the carotid plaque morphology and stenosis over time.

RESULTS

The primary end point of the study is, (a) carotid plaque morphological stabilization at 6 months, defined as defined as the disappearance of ulcerations and fluffy components and the achievement of a regular plaque morphology with prevalence of fibrous atheroma and/or (b) carotid plaque regression at 12 months, defined as reduction of the entity of the stenosis and/or peak systolic velocity by at least 5%, as compared with baseline.

CONCLUSION

The CARUSO trial will test the superiority of evolocumab on top of ongoing LLT versus ongoing LLT alone regarding carotid plaque morphological stabilization and regression. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

PCSK9 Functions in Atherosclerosis Are Not Limited to Plasmatic LDL-Cholesterol Regulation

The relevance of PCSK9 in atherosclerosis progression is demonstrated by the benefits observed in patients that have followed PCSK9-targeted therapies. The impact of these therapies is attributed to the plasma lipid-lowering effect induced when LDLR hepatic expression levels are recovered after the suppression of soluble PCSK9. Different studies show that PCSK9 is involved in other mechanisms that take place at different stages during atherosclerosis development. Indeed, PCSK9 regulates the expression of key receptors expressed in macrophages that contribute to lipid-loading, foam cell formation and atherosclerotic plaque formation. PCSK9 is also a regulator of vascular inflammation and its expression correlates with pro-inflammatory cytokines release, inflammatory cell recruitment and plaque destabilization. Furthermore, anti-PCSK9 approaches have demonstrated that by inhibiting PCSK9 activity, the progression of atherosclerotic disease is diminished. PCSK9 also modulates thrombosis by modifying platelets steady-state, leukocyte recruitment and clot formation. In this review we evaluate recent findings on PCSK9 functions in cardiovascular diseases beyond LDL-cholesterol plasma levels regulation.

Inadvertent nucleotide sequence alterations during mutagenesis: highlighting the vulnerabilities in mouse transgenic technology

In the last three decades, researchers have utilized genome engineering to alter the DNA sequence in the living cells of a plethora of organisms, ranging from plants, fishes, mice, to even humans. This has been conventionally achieved by using methodologies such as single nucleotide insertion/deletion in coding sequences, exon(s) deletion, mutations in the promoter region, introducing stop codon for protein truncation, and addition of foreign DNA for functional elucidation of genes. However, recent years have witnessed the advent of novel techniques that use programmable site-specific nucleases like CRISPR/Cas9, TALENs, ZFNs, Cre/loxP system, and gene trapping. These have revolutionized the field of experimental transgenesis as well as contributed to the existing knowledge base of classical genetics and gene mapping. Yet there are certain experimental/technological barriers that we have been unable to cross while creating genetically modified organisms. Firstly, while interfering with coding strands, we inadvertently change introns, antisense strands, and other non-coding elements of the gene and genome that play integral roles in the determination of cellular phenotype. These unintended modifications become critical because introns and other non-coding elements, although traditionally regarded as “junk DNA,” have been found to play a major regulatory role in genetic pathways of several crucial cellular processes, development, homeostasis, and diseases. Secondly, post-insertion of transgene, non-coding RNAs are generated by host organism against the inserted foreign DNA or from the inserted transgene/construct against the host genes. The potential contribution of these non-coding RNAs to the resulting phenotype has not been considered. We aim to draw attention to these inherent flaws in the transgenic technology being employed to generate mutant mice and other model organisms. By overlooking these aspects of the whole gene and genetic makeup, perhaps our current understanding of gene function remains incomplete. Thus, it becomes important that, while using genetic engineering techniques to generate a mutant organism for a particular gene, we should carefully consider all the possible elements that may play a potential role in the resulting phenotype. This perspective highlights the commonly used mouse strains and the most probable associated complexities that have not been considered previously, resulting in possible limitations in the currently utilized transgenic technology. This work also warrants the use of already established mouse lines in further research.

The Effect of Proprotein Convertase Subtilisin Kexin Type 9 Inhibitors on Circulating Endothelial Progenitor Cells in Patients with Cardiovascular Disease

PURPOSE

Circulating endothelial progenitor cells (cEPCs) are vital to vascular repair by re-endothelialization. We aimed to explore the effect of proprotein convertase subtilisin kexin type 9 inhibitors (PCSK9i) on cEPCs hypothesizing a possible pleiotropic effect.

METHODS

Patients with cardiovascular disease (CVD) were sampled for cEPCs at baseline and following the initiation of PCSK9i. cEPCs were assessed using flow cytometry by the expression of CD34⁽⁺⁾/CD133⁽⁺⁾ and vascular endothelial growth factor receptor (VEGFR)-2⁽⁺⁾, and by the formation of colony-forming units (CFUs) and production of VEGF.

RESULTS

Our cohort included 26 patients (median age 68 (IQR 63, 73) years; 69% male). Following 3 months of treatment with PCSK9i and a decline in low-density lipoprotein cholesterol levels (153 (IQR 116, 176) to 56 (IQR 28, 72) mg/dl), p < 0.001), there was an increase in CD34⁽⁺⁾/CD133⁽⁺⁾ and VEGFR-2⁽⁺⁾ cell levels (0.98% (IQR 0.37, 1.55) to 1.43% (IQR 0.90, 4.51), p = 0.002 and 0.66% (IQR 0.22, 0.99) to 1.53% (IQR 0.73, 2.70), p = 0.05, respectively). Functionally, increase in EPCs-CFUs was microscopically evident following treatment with PCSK9i (1 CFUs (IQR 0.0, 1.0) to 2.5 (IQR 1.5, 3), p < 0.001) with a concomitant increase in EPC's viability as demonstrated by an MTT assay (0.15 (IQR 0.11, 0.19) to 0.21 (IQR 0.18, 0.23), p < 0.001). VEGF levels increased following PCSK9i treatment (57 (IQR 18, 24) to 105 (IQR 43, 245), p = 0.006).

CONCLUSIONS

Patients with CVD treated with PCSK9i demonstrate higher levels of active cEPCs, reflecting the promotion of endothelial repair. These findings may represent a novel mechanism of action of PCSK9i.

PCSK9 Inhibition: Insights From Clinical Trials and Future Prospects

In 2003, clinical observations led to the discovery of the involvement of proprotein convertase subtilisin/kexin type 9 (PCSK9) in lipid metabolism. Functional studies demonstrated that PCSK9 binds to the low-density lipoprotein (LDL) receptor directing it to its lysosomal degradation. Therefore, carriers of gain-of-function mutations in PCSK9 exhibit decreased expression of LDL receptors on the hepatocyte surface and have higher LDL cholesterol (LDL-C) levels. On the contrary, loss-of-function mutations in PCSK9 are associated with low LDL-C concentrations and significantly reduced lifetime risk of cardiovascular disease. These insights motivated the search for strategies to pharmacologically inhibit PCSK9. In an exemplary rapid development, fully human monoclonal antibodies against PCSK9 were developed and found to effectively reduce LDL-C. Administered subcutaneously every 2–4 weeks, the PCSK9 antibodies evolocumab and alirocumab reduce LDL-C by up to 60% in a broad range of populations either as monotherapy or in addition to statins. Two large cardiovascular outcome trials involving a total of ∼46,000 cardiovascular high-risk patients on guideline-recommended lipid-lowering therapy showed that treatment with evolocumab and alirocumab led to a relative reduction of cardiovascular risk by 15% after 2.2 and 2.8 years of treatment, respectively. These findings expanded the armamentarium of pharmacological approaches to address residual cardiovascular risk associated with LDL-C. Furthermore, the unprecedented low LDL-C concentrations achieved (e.g., 30 mg/dL in the FOURIER study) suggest that the relationship between LDL-C and cardiovascular risk is without a lower threshold, and without associated adverse events during the timeframe of the studies. The side effect profile of PCSK9 antibodies is favorable with few patients exhibiting injection-site reactions. Currently, the access to PCSK9 antibodies is limited by high treatment costs. The development of novel approaches to inhibit PCSK9 such as the use of small interfering RNA to inhibit PCSK9 synthesis seems promising and may soon become available.

No effects of PCSK9-inhibitor treatment on spatial learning, locomotor activity, and novel object recognition in mice

Monoclonal anti-proprotein convertase subtilisin/kexin type 9 (PSCK9) neutralizing antibodies effectively lower plasma cholesterol levels and decrease cardiovascular events but also raised some concern that cognitive function could worsen as a side effect. Here, we performed experiments in mice to characterize the effect of anti-PCSK9 antibodies on behavior and cognitive function in detail. APOE*3Leiden.CETP mice and B6129SF1/J wildtype mice were fed a Western type diet and treated with the fully human anti-PCSK9 antibody CmAb1 (PL-45134; 10mg*kg^-1 s.c.) or vehicle for 6 weeks. Locomotor activity, anxiety levels, recognition memory, and spatial learning were investigated using the open field, novel object recognition test, and Morris water maze, respectively. Serum cholesterol levels in APOE*3Leiden.CETP mice after treatment with anti-PCSK9 antibody were significantly lower compared to controls whereas cholesterol levels in B6129SF1/J wildtype mice remained unchanged at low levels. No apparent differences were found regarding locomotor activity, anxiety, recognition memory, and spatial learning between animals treated with anti-PCSK9 antibody or vehicle in APOE*3Leiden.CETP and B6129SF1/J wildtype mice. In this study, we found no evidence that treatment with anti-PCSK9 antibodies lead to differences in behavior or changes of cognition in mice.

Small rodent models of atherosclerosis

The ease of breeding, low cost of maintenance, and relatively short period for developing atherosclerosis make rodents ideal for atherosclerosis research. However, none of the current models accurately model human lipoprotein profile or atherosclerosis progression since each has its advantages and disadvantages. The advent of transgenic technologies much supports animal models' establishment. Notably, two classic transgenic mouse models, apoE-/- and Ldlr-/-, constitute the primary platforms for studying underlying mechanisms and development of pharmaceutical approaches. However, there exist crucial differences between mice and humans, such as the unhumanized lipoprotein profile, and the different plaque progression and characteristics. Among rodents, hamsters and guinea pigs might be the more realistic models in atherosclerosis research based on the similarities in lipoprotein metabolism to humans. Studies involving rat models, a rodent with natural resistance to atherosclerosis, have revealed evidence of atherosclerotic plaques under dietary induction and genetic manipulation by novel technologies, notably CRISPR-Cas9. Ldlr-/- hamster models were established in recent years with severe hyperlipidemia and atherosclerotic lesion formation, which could offer an alternative to classic transgenic mouse models. In this review, we provide an overview of classic and innovative small rodent models in atherosclerosis researches, including mice, rats, hamsters, and guinea pigs, focusing on their lipoprotein metabolism and histopathological changes.