Pro-protein convertase subtilisin/kexin 9 concentrations correlate with coronary artery disease atheroma burden in a Pakistani cohort with chronic chest pain

Proprotein convertase subtisilin/kexin 9 levels decline with hepatitis C virus therapy in people with HIV/hepatitis C virus and correlate with inflammation

BACKGROUND

Proprotein convertase subtisilin/kexin 9 (PCSK9) raises low-density lipoprotein cholesterol (LDL-C) levels and is associated with inflammation, which is elevated in HIV and hepatitis C virus (HCV) infection. We compared PCSK9 levels in people with co-occurring HIV and HCV (HIV/HCV) vs. HIV alone, and evaluated the impact of HCV direct-acting antiviral (DAA) therapy on PCSK9.

DESIGN

A prospective, observational cohort study.

METHODS

Thirty-five adults with HIV/HCV and 37 with HIV alone were evaluated, all with HIV virologic suppression and without documented cardiovascular disease. Circulating PCSK9 and inflammatory biomarkers were measured at baseline and following HCV treatment or at week 52 (for HIV alone) and compared using Wilcoxon tests and Spearman correlations.

RESULTS

At baseline, PCSK9 trended higher in HIV/HCV vs. HIV alone (307 vs. 284 ng/ml, P  = 0.06). Twenty-nine participants with HIV/HCV completed DAA therapy with sustained virologic response. PCSK9 declined from baseline to posttreatment 1 (median 7.3 weeks after end of therapy [EOT]) and posttreatment 2 (median 43.5 weeks after EOT), reaching levels similar to HIV alone; median within-person reduction was -60.5 ng/ml ( P  = 0.003) and -55.6 ng/ml ( P  = 0.02), respectively. Decline in PCSK9 correlated with decline in soluble (s)E-selectin and sCD163 ( r  = 0.64, P  = 0.002; r  = 0.58, P  = 0.008, respectively), but not with changes in LDL-C or other biomarkers. No significant change in PCSK9 occurred in the HIV alone group over 52 weeks.

CONCLUSION

PCSK9 declined with DAA therapy in participants with HIV/HCV, correlating with declines in several inflammatory biomarkers but not LDL-C. Elevated PCSK9 with HCV may be linked to particular HCV-associated inflammatory pathways more so than cholesterol homeostasis.

Novel Insights into the Molecular Mechanisms of Atherosclerosis

Atherosclerosis is one of the most fatal diseases in the world. The associated thickening of the arterial wall and its background and consequences make it a very composite disease entity with many mechanisms that lead to its creation. It is an active process, and scientists from various branches are engaged in research, including molecular biologists, cardiologists, and immunologists. This review summarizes the available information on the pathophysiological implications of atherosclerosis, focusing on endothelium dysfunction, inflammatory factors, aging, and uric acid, vitamin D, and miRNA expression as recent evidence of interactions of the molecular and cellular elements. Analyzing new discoveries for the underlying causes of this condition assists the general research to improve understanding of the mechanism of pathophysiology and thus prevention of cardiovascular diseases.

Proprotein Convertase Subtilisin/Kexin 9 Levels in Relation to Systemic Immune Activation and Subclinical Coronary Plaque in HIV

Background

Proprotein convertase subtilisin/kexin 9 (PCSK9) is known to mediate homeostasis of low-density lipoprotein cholesterol (LDL-c), but it may also participate in immune reactivity and atherogenesis.

Methods

We compared circulating PCSK9 levels among asymptomatic individuals with and without HIV. Further, within each group, we assessed the relationship between PCSK9 levels, traditional cardiovascular disease risk factors, immune activation, and subclinical coronary atherosclerotic plaque.

Results

PCSK9 levels were higher among HIV-infected (n = 149) vs matched non-HIV-infected subjects (n = 69; 332 [272, 412] ng/mL vs 304 [257, 375] ng/mL; P = .047). Among HIV-infected subjects, significant albeit modest positive associations were noted between PCSK9 levels and markers of systemic monocyte activation including sCD14 (rho = 0.22; P = .009) and sCD163 (rho = 0.23; P = .006). In this group, PCSK9 levels related weakly to LDL-c (rho = 0.16; P = .05) and also to Framingham Point Score but did not relate to subclinical coronary atherosclerotic plaque parameters.

Conclusions

Among HIV-infected individuals, circulating PCSK9 levels are elevated and related to systemic markers of monocyte activation but not to coronary plaque parameters. Additional studies are needed to determine the effects of PCSK9 on immune activation and atherogenesis in HIV and to assess whether PCSK9 inhibition reduces immune activation and coronary atherosclerotic plaque burden.

Clinical Trial Registration

NCT00455793.

PCSK9 inhibitors - from discovery of a single mutation to a groundbreaking therapy of lipid disorders in one decade

Hypercholesterolemia is one of the main risk factors for coronary heart disease and significantly contributes to the high mortality associated with cardiovascular diseases. Statin therapy represents the gold standard in the reduction of low-density lipoprotein cholesterol concentration. Nevertheless, many patients still cannot achieve the recommended target levels, due to either inadequate effectiveness or intolerance of these drugs. Monoclonal antibodies that inhibit proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged as a promising option in lipid-lowering treatment. After confirmation of their efficacy and safety in clinical trials, evolocumab and alirocumab received approval from the US Food and Drug Administration (FDA) and European Medicines Agency (EMA) for introduction into clinical practice. In this review, we present a history of the development and mechanisms of action, as well as the results of the most important studies concerning PCSK9 inhibitors.

Prediction of cardiovascular events with levels of proprotein convertase subtilisin/kexin type 9: A systematic review and meta-analysis

BACKGROUND AND AIMS

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) reduces atherogenic lipoproteins and could lead to reduction of cardiovascular (CV) events. However, it is unclear whether blood PCSK9 levels predict future CV events. We performed a meta-analysis of all longitudinal studies to determine the ability of PCSK9 levels to predict risk of future CV events.

METHODS

A comprehensive search of electronic databases was conducted up to February 2016. Longitudinal studies that reported events or relative risk (RR) estimates with 95% confidence intervals (CI) were included.

RESULTS

All 9 studies included (12,081 participants, mean follow-up 6.62 years) reported results on total CV events. The pooled RR of total CV events for an increase in baseline PCSK9 by 1 standard deviation (SD) was 1.098 (95% CI, 1.02-1.18), corresponding to a risk increase of 10% (Z = 2.43, p = 0.015). The pooled RR of total CV events for subjects categorized in the highest tertile of baseline PCSK9 was 1.228 (95% CI, 1.035-1.457), corresponding to a risk increase of 23% (Z = 2.35, p = 0.019). When pooled estimates were derived independently for low- and high-CV risk populations, baseline PCSK9 levels predicted total CV events only in apparently healthy subjects (RR = 1.13, 95% CI: 1.050-1.222, Z = 3.21, p = 0.001) and not in populations with established CV or renal disease (RR = 1.09, 95% CI: 0.961-1.23, Z = 1.33, p = 0.182).

CONCLUSIONS

PCSK9 levels are modestly but significantly associated with increased risk of total CV events. These results suggest a predictive role of PCSK9 levels on CV health and support the possible clinical role of PCSK9 inhibitors.

Human PCSK9 promotes hepatic lipogenesis and atherosclerosis development via apoE- and LDLR-mediated mechanisms

AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the degradation of hepatic low-density lipoprotein (LDL) receptors (LDLR), thereby, decreasing hepatocyte LDL-cholesterol (LDL-C) uptake. However, it is unknown whether PCSK9 has effects on atherogenesis that are independent of lipid changes. The present study investigated the effect of human (h) PCSK9 on plasma lipids, hepatic lipogenesis, and atherosclerotic lesion size and composition in transgenic mice expressing hPCSK9 (hPCSK9tg) on wild-type (WT), LDLR⁻/⁻, or apoE⁻/⁻ background.

METHODS AND RESULTS

hPCSK9 expression significantly increased plasma cholesterol (+91%), triglycerides (+18%), and apoB (+57%) levels only in WT mice. The increase in plasma lipids was a consequence of both decreased hepatic LDLR and increased hepatic lipid production, mediated transcriptionally and post-transcriptionally by PCSK9 and dependent on both LDLR and apoE. Despite the lack of changes in plasma lipids in mice expressing hPCSK9 and lacking LDLR (the main target for PCSK9) or apoE (a canonical ligand for the LDLR), hPCSK9 expression increased aortic lesion size in the absence of apoE (268 655 ± 97 972 µm² in hPCSK9tg/apoE⁻/⁻ vs. 189 423 ± 65 700 µm(2) in apoE⁻/⁻) but not in the absence of LDLR. Additionally, hPCSK9 accumulated in the atheroma and increased lesion Ly6C(hi) monocytes (by 21%) in apoE⁻/⁻ mice, but not in LDLR⁻/⁻ mice.

CONCLUSIONS

PCSK9 increases hepatic lipid and lipoprotein production via apoE- and LDLR-dependent mechanisms. However, hPCSK9 also accumulate in the artery wall and directly affects atherosclerosis lesion size and composition independently of such plasma lipid and lipoprotein changes. These effects of hPCSK9 are dependent on LDLR but are independent of apoE.

Promising new therapies for the treatment of hypercholesterolemia

INTRODUCTION

Statins are currently the most commonly used agents for treatment of hypercholesterolemia in patients with atherosclerotic cardiovascular disease. However, some patients on statins do not achieve their treatment goals or are intolerant to statins. Therefore, new therapies for treatment of hypercholesterolemia are under investigation.

AREAS COVERED

This article reviews the new emerging medications for the treatment of hypercholesterolemia and discusses their efficacy and safety profile based on literature searches that included human studies published on PubMed and reported clinical trials.

EXPERT OPINION

Inhibition of the PCSK9 protein by monoclonal antibodies results in a dramatic 40%-60% lowering of serum low-density lipoprotein cholesterol (LDL-C). This is in addition to LDL-C lowering achieved by statins. Multiple clinical studies have demonstrated the high selectivity of these antibodies for the PCSK9 pathway and their long-term safety and efficacy. Alirocumab and evolocumab have been approved by the FDA for the treatment of patients with heterozygous familial hypercholesterolemia and patients with clinical atherosclerotic cardiovascular disease) who do not achieve their LDL-C target on maximal tolerated statin treatment and dietary modification. In addition, evolocumab has been approved by the FDA for homozygous familial hypercholesterolemia. However, the long-term efficacy and safety of PCSK9 inhibitors are unknown.

From proprotein convertase subtilisin/kexin type 9 to its inhibition: state-of-the-art and clinical implications

Statins are recommended as first-line therapy for patients with hypercholesterolaemia. A sizable proportion of patients, however, does not reach therapeutic goals, is statin intolerant, or, despite optimal statin therapy, is at high risk of ischaemic events. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a major role in lipid metabolism and several comorbidities. Monoclonal antibodies targeting PCSK9 are a new lipid-lowering approach with the potential to improve clinical outcomes in patients with dyslipidaemia. In this review, we discuss current experimental and clinical evidence of the role of PCSK9 and its inhibition on lipid metabolism and several pathologic conditions with a focus on clinical outcomes. A state-of-the-art analysis of current clinical evidence and future directions on PCSK9 and its inhibition is provided.

New developments in atherosclerosis: clinical potential of PCSK9 inhibition

Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a secreted 692-amino acid protein that binds surface low-density lipoprotein (LDL) receptor (LDLR) and targets it toward lysosomal degradation. As a consequence, the number of LDLRs at the cell surface is decreased, and LDL-cholesterol (LDL-C) clearance is reduced, a phenomenon that is magnified by gain-of-function mutations of PCSK9. In contrast, loss-of-function mutations of PCSK9 result in increased surface LDLR and improved LDL-C clearance. This provides the rationale for targeting PCSK9 in hypercholesterolemic subjects as a means to lower LDL-C levels. Monoclonal antibodies (mAbs) against PCSK9 that block its interaction with the LDLR have been developed in the past decade. Two companies have recently received the approval for their anti-PCSK9 mAbs by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) Regeneron/Sanofi, with alirocumab (commercial name – PRALUENT^®) and, Amgen with evolocumab (commercial name – Repatha™). The introduction of anti-PCSK9 mAbs will provide an alternative therapeutic strategy to address many of the unmet needs of current lipid-lowering therapies, such as inability to achieve goal LDL-C level, or intolerance and aversion to statins. This review will focus on the kinetics of PCSK9, pharmacokinetics and pharmacodynamics of anti-PCSK9 mAbs, and recent data linking PCSK9 and anti-PCSK9 mAbs to cardiovascular events. Moreover, it will highlight the unanswered questions that still need to be addressed in order to understand the physiologic function, kinetics, and dynamics of PCSK9.