PCSK9 Plasma Concentrations Are Independent of GFR and Do Not Predict Cardiovascular Events in Patients with Decreased GFR

PCSK9 and Cardiovascular Disease in Individuals with Moderately Decreased Kidney Function

Background and objectives: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of lipid homeostasis. Studies investigating the association between PCSK9 and cardiovascular disease in large cohorts of CKD patients are limited. Design, setting, participants, and measurements: The association of PCSK9 concentrations with prevalent and incident cardiovascular disease was investigated in 5,138 Caucasians of the German Chronic Kidney Disease study with a median follow-up of 6.5 years. Inclusion criteria were eGFR of 30-60 mL/min/1.73 m² or an eGFR>60 mL/min/1.73m² in the presence of overt proteinuria (urine albumin-creatinine ratio >300mg/g or equivalent). Prevalent cardiovascular disease was defined as history of non-fatal myocardial infarction, coronary artery bypass grafting, percutaneous transluminal coronary angioplasty, carotid arteries interventions and stroke. Incident major adverse cardiovascular disease events included death from cardiovascular causes, acute non-fatal myocardial infarction and non-fatal stroke. Results: Median PCSK9 concentration in the cohort was 285 ng/mL (interquartile range 231-346 ng/mL). There was no association between PCSK9 concentrations and baseline eGFR and albuminuria. With each 100 ng/ml increment of PCSK9, the odds for prevalent cardiovascular disease (n=1,284) was 1.22-fold (95%CI 1.12-1.34, p<0.001) higher in a model with extended adjustment for major confounders. This association was stronger in non-statin than statin-users (p-value for interaction=0.009). During follow-up 474 individuals experienced a major adverse cardiovascular disease event and participants in PCSK9 quartiles 2 to 4 had a 32%-47% higher risk compared to quartile 1 (p<0.05). Subgroup analysis revealed this association was restricted to those participants who already had cardiovascular disease at baseline (all HR>1.75, p<0.05). In addition, PCSK9 showed a valuable gain in classification accuracy both for prevalent cardiovascular disease (NRI=0.27, 95%CI:0.20-0.33) and incident major adverse cardiovascular disease events during follow-up (NRI=0.10, 95%CI:0.008-0.21) when added to an extended adjustment model. Conclusions: Our findings reveal no relation of PCSK9 with baseline eGFR and albuminuria, but a significant association between higher PCSK9 concentrations and risk of cardiovascular disease independent of traditional risk factors including LDL-cholesterol levels.

The Emerging Roles of Intracellular PCSK9 and Their Implications in Endoplasmic Reticulum Stress and Metabolic Diseases

The importance of the proprotein convertase subtilisin/kexin type-9 (PCSK9) gene was quickly recognized by the scientific community as the third locus for familial hypercholesterolemia. By promoting the degradation of the low-density lipoprotein receptor (LDLR), secreted PCSK9 protein plays a vital role in the regulation of circulating cholesterol levels and cardiovascular disease risk. For this reason, the majority of published works have focused on the secreted form of PCSK9 since its initial characterization in 2003. In recent years, however, PCSK9 has been shown to play roles in a variety of cellular pathways and disease contexts in LDLR-dependent and -independent manners. This article examines the current body of literature that uncovers the intracellular and LDLR-independent roles of PCSK9 and also explores the many downstream implications in metabolic diseases.

Meta-GWAS of PCSK9 levels detects two novel loci at APOB and TM6SF2

Background

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key player in lipid metabolism, as it degrades low-density lipoprotein (LDL) receptors from hepatic cell membranes. So far, only variants of the PCSK9 gene locus were found to be associated with PCSK9 levels. Here we aimed to identify novel genetic loci that regulate PCSK9 levels and how they relate to other lipid traits. Additionally, we investigated to what extend the causal effect of PCSK9 on coronary artery disease (CAD) is mediated by low-density lipoprotein–cholesterol (LDL–C).

Methods and Results

We performed a genome-wide association study meta-analysis of PCSK9 levels in up to 12 721 samples of European ancestry. The estimated heritability was 10.3%, which increased to 12.6% using only samples from patients without statin treatment. We successfully replicated the known PCSK9 hit consisting of three independent signals. Interestingly, in a study of 300 African Americans, we confirmed the locus with a different PCSK9 variant. Beyond PCSK9, our meta-analysis detected three novel loci with genome-wide significance. Co-localization analysis with cis-eQTLs and lipid traits revealed biologically plausible candidate genes at two of them: APOB and TM6SF2. In a bivariate Mendelian Randomization analysis, we detected a strong effect of PCSK9 on LDL-C, but not vice versa. LDL-C mediated 63% of the total causal effect of PCSK9 on CAD.

Conclusion

Our study identified novel genetic loci with plausible candidate genes affecting PCSK9 levels. Ethnic heterogeneity was observed at the PCSK9 locus itself. Although the causal effect of PCSK9 on CAD is mainly mediated by LDL-C, an independent direct effect also occurs.

Circulating Proprotein Convertase Subtilisin/Kexin Type 9 Levels Predict Future Cardiovascular Event Risks in Hemodialyzed Black African Patients

CONTEXT AND OBJECTIVE

Cardiovascular diseases are the leading cause of mortality in patients. In this context, proprotein convertase subtilisin/kexin type 9 (PCSK9) appears to be the new biomarker identified as interfering in lipid homeostasis. This study aimed to investigate the association between PCSK9, dyslipidemia, and future risk of cardiovascular events in a population of black Africans.

METHODS

A cross-sectional study was conducted between August 2016 and July 2020 in six hemodialysis centers in the city of Kinshasa, Democratic Republic of the Congo. Serum PCSK9 was measured by ELISA; lipid levels of 251 chronic kidney disease grade 5 (CKD G5) hemodialysis patients and the Framingham predictive instrument were used for predicting cardiac events.

RESULTS

Total cholesterol (TC), low-density lipoprotein cholesterol (LDL-c), and triglycerides (TG) were significantly increased in the tertile with the highest PCSK9. By contrast, high-density lipoprotein cholesterol (HDL-c) was significantly decreased in the same tertile. A strong positive and significant correlation was found between PCSK9 and TC, TG, and LDL-c. Negative and significant correlation was observed between PCSK9 and HDL-c. The levels of PCSK9, smoking, overweight, and atherogenic dyslipidemia were associated with future risks for cardiovascular events in univariate analysis. After adjustment, all these variables persisted as independent determinants of future risk for cardiovascular events. The probability of having a cardiovascular event in this population was independently associated with PCSK9 levels. Compared to the patients in the lowest PCSK9 tertile, patients with PCSK9 levels in the middle (aOR 5.9, 95% CI 2.06-17.3, P<0.001) and highest tertiles (aOR 8.9, 95% CI 3.02-25.08, P<0.001) presented a greater risk of cardiac event.

CONCLUSION

Increased PCSK9 serum levels are associated with higher levels of TC, LDL-c, and TG and lower levels of HDL-c in black African hemodialysis patients. Serum PCSK9 levels in these patients predict increased risk of cardiovascular events, independent of traditional potential confounders.

Association between PCSK9 Levels and Markers of Inflammation, Oxidative Stress, and Endothelial Dysfunction in a Population of Nondialysis Chronic Kidney Disease Patients

Proprotein convertase subtilisin/kexin 9 (PCSK9) plays an important role in lipid metabolism while available literature regarding its involvement in the pathogenesis of atherosclerosis and in the expression of genes associated with apoptosis and inflammation is constantly increasing. Patients with chronic kidney disease (CKD) experience disproportionately increased cardiovascular morbidity and mortality due to dyslipidemia, accelerated atherosclerosis, inflammation, oxidative stress, and other risk factors. In the present cross-sectional study, we investigated the possible association of serum PCSK9 levels with markers of inflammation, oxidative stress, and endothelial damage in patients with CKD. Patients and Methods. Ninety-two patients with CKD stages II-ΙV (eGFR CKD-EPI 47.3 ± 25.7 ml/min/1.73 m², mean age 66 years, 51 men) were included in the study. Plasma PCSK9 levels were correlated with comorbidities (arterial hypertension, diabetes mellitus, and history of cardiovascular disease), renal function indices (eGFR, proteinuria–UPR/24 h), lipid parameters (LDL-cholesterol, HDL-cholesterol, triglycerides, Lp(a), APO-A1, and APO-B), and soluble biomarkers of inflammation, oxidative stress, and endothelial damage (hs-CRP, fibrinogen, 8-epiPGF2a, ox-LDL, IL-6, TNF-α, sICAM-1, and sVCAM-1). Results. The mean plasma value of PCSK9 was 278.1 ng/ml. PCSK9 levels showed direct correlation with serum triglycerides (p = 0.03), Lp(a) (p = 0.01), and sICAM-1 levels (p = 0.03). There was no significant correlation between PCSK9 levels and indices of the renal function, other lipid profile parameters, inflammatory markers, or comorbidities. Multiple regression analysis showed a significant effect of Lp(a) on PCSK9 levels, and for each unit of higher Lp(a), an increase by 3.082 is expected (95% CI: 0.935-5.228, p = 0.006). At the same time, patients receiving statins are expected to have on average 63.8 ng/ml higher PCSK9 values compared to patients not receiving statins (95% CI: 14.6-113.5, p = 0.012). Conclusion. Plasma levels of PCSK9 in nondialysis CKD patients are correlated with endothelial dysfunction and lipid metabolism parameters. Statin intake increases PCSK9 levels significantly in this patient population. PCSK9 levels are not correlated with the severity of kidney disease. Major prospective studies are necessary to investigate the role of PCSK9 in the atherosclerotic cardiovascular outcome in CKD.

Evaluation of cardiovascular events and progression to end-stage renal disease in patients with dyslipidemia and chronic kidney disease from the North-Eastern area of Romania

PURPOSE

The aim of this prospective cohort study was: to identify the association between different biomarkers [proprotein convertase subtilisin/kexin 9-PCSK9, lipoprotein(a)-Lp(a) and high-sensitivity C-reactive protein-hsCRP] and the cardiovascular events; to evaluate the relationship between the 3 biomarkers mentioned above and the renal outcomes that contributed to end-stage renal disease (ESRD).

METHODS

We studied 110 patients with chronic kidney disease (CKD) stages 2 to 4. The identification of the new cardiovascular events and the renal outcomes were performed by clinical and paraclinical explorations.

RESULTS

350 patients were examined and 110 (31.4%) were included in this study. The mean age was 55.6 ± 10.9 years, with a higher number of men compared to women. The CKD patients with de novo cardiovascular events and new renal outcome during the study, had significantly increased values of total cholesterol (TC), low density cholesterol lipoprotein (LDL-C) at 6 and 12 months and higher levels of Lp(a), PCSK9, hsCRP and low ankle-brachial index (ABI) and ejection fraction (EF) values compared to patients without cardiovascular and renal events. In CKD patients, PCSK9 > 220 ng/mL was a predictor of cardiovascular events, while the EF < 50% was a predictor for renal outcomes. For CKD patients with PCSK9 > 220 ng/mL and hsCRP > 3 mg/L levels, the time-interval for the new cardiovascular and renal events occurrence were significantly decreased compared to patients displaying low values of these biomarkers.

CONCLUSION

The results of this study show that PCSK9 > 220 ng/mL was predictor for cardiovascular events, while EF < 50% was predictor for CKD progression to ESRD. PCSK9 > 220 ng/mL and hsCRP > 3 mg/L were associated with the occurrence of renal and cardiovascular events earlier.

Molecular Genetic Approach and Evaluation of Cardiovascular Events in Patients with Clinical Familial Hypercholesterolemia Phenotype from Romania

This study identifies the genetic background of familial hypercholesterolemia (FH) patients in Romania and evaluates the association between mutations and cardiovascular events. We performed a prospective observational study of 61 patients with a clinical diagnosis of FH selected based on Dutch Lipid Clinic Network (DLCN) and Simon Broome score between 2017 and 2020. Two techniques were used to identify mutations: multiplex ligation-dependent probe amplification (MLPA) and Sanger sequencing. The mutation rate was 37.7%, i.e., 23 patients with mutations were identified, of which 7 subjects had pathogenic mutations and 16 had polymorphisms. Moreover, 10 variants of the low-density lipoprotein receptor (LDLR) gene were identified in 22 patients, i.e., one variant of the proprotein convertase subtilisin/kexin type 9 (PCSK9) gene in six patients, and one variant of the apolipoprotein B (APOB) gene in three patients. Of the LDLR gene variants, four were LDLR pathogenic mutations (c.81C > G, c.502G > A, c.1618G > A mutations in exon 2, exon 4, exon 11, and exon 13–15 duplication). The PCSK9 and APOB gene variants were benign mutations. The pathogenic LDLR mutations were significant predictors of the new cardiovascular events, and the time interval for new cardiovascular events occurrence was significantly decreased, compared to FH patients without mutations. In total, 12 variants were identified, with four pathogenic variants identified in the LDLR gene, whereas 62.3% of the study population displayed no pathological mutations.

Association Between Circulating Proprotein Convertase Subtilisin/Kexin Type 9 and Major Adverse Cardiovascular Events, Stroke, and All-Cause Mortality: Systemic Review and Meta-Analysis

Background: Proprotein convertase subtilisin/kexin type 9 (PCSK9), a pivotal protein in low-density lipoprotein cholesterol metabolism, has been validated to be an established target for cardiovascular (CV) risk reduction. Nevertheless, prospective studies concerning the associations between circulating PCSK9 and the risk of CV events and mortality have yielded, so far, inconsistent results. Herein, we conducted a meta-analysis to evaluate the association systemically. Methods: Pertinent studies were identified from PubMed, EMBASE, and Cochrane Library database through July 2020. Longitudinal studies investigating the value of circulating PCSK9 for predicting major adverse cardiovascular events (MACEs) or stroke or all-cause mortally with risk estimates and 95% confidence intervals (CI) were included in the analyses. Dose-response meta-analysis was also applied to evaluate circulating PCSK9 and risk of MACEs in this study. Results: A total of 22 eligible cohorts comprising 28,319 participants from 20 eligible articles were finally included in the study. The pooled relative risk (RR) of MACEs for one standard deviation increase in baseline PCSK9 was 1.120 (95% CI, 1.056-1.189). When categorizing subjects into tertiles, the pooled RR for the highest tertile of baseline PCSK9 was 1.252 (95% CI, 1.104-1.420) compared with the lowest category. This positive association between PCSK9 level and risk of MACEs persisted in sensitivity and most of the subgroup analyses. Twelve studies were included in dose-response meta-analysis, and a linear association between PCSK9 concentration and risk of MACEs was observed (x2 test for non-linearity = 0.31, P non-linearity = 0.575). No significant correlation was found either on stroke or all-cause mortality. Conclusion: This meta-analysis added further evidence that high circulating PCSK9 concentration significantly associated with increased risk of MACEs, and a linear dose-response association was observed. However, available data did not suggest significant association either on stroke or all-cause mortality. Additional well-designed studies are warranted to further investigate the correlations between PCSK9 concentration and stroke and mortality.

The systemic implication of novel non-statin therapies in cardiovascular diabetology: PCSK9 as a case model

PCSK9, like other novel non-statin drugs were primarily developed to help patients achieve low-density lipoprotein cholesterol targets, especially in patients with dyslipidemia not achieving lipid goals with statins due to poor tolerance or inadequate response. PCSK9 inhibitors, in addition to modulating lipid metabolism, improve mortality outcomes in cardiovascular disease. These benefits are markedly pronounced in patients with type 2 diabetes mellitus. However, these benefits do not come without associated risk. Multiple trials, studies, and case reports have attempted to explain observed outcomes with PCSK9 expression and administration of PCSK9 inhibitors from multiple perspectives, such as their effects on insulin sensitivity and glucose tolerance, changes in renal physiology, thyroid physiology, vascular tone, intestinal regulation of lipids, and improved cardiovascular function. These agents represent an opportunity for physicians to exercise prudence by using appropriate clinical judgement when managing comorbidities in the hyperglycemic patient, a concept that extends to other novel non-statin drugs.

Arylesterase activity but not PCSK9 levels is associated with chronic kidney disease in type 2 diabetes

PURPOSE

Oxidative stress and dyslipidemia have been found to be associated with the progression of chronic kidney disease (CKD) in type 2 diabetes mellitus (T2DM) patients. Paraoxonase 1 (PON-1) activity, and proprotein convertase subtilisin kexin type 9 (PCSK9) levels play an important role regarding anti-oxidants, and lipid metabolism, respectively. The aim of this study was to investigate the association of PON-1 activity, and PCSK9 levels with CKD in T2DM.

METHODS

A total of 180 T2DM (87 CKD, and 93 non-CKD) with age-, and gender-matched subjects were recruited in this study. PON-1 activity was measured with two kinds of substrate: paraoxon for paraoxonase (PONase) activity and phenylacetate for arylesterase (AREase) activity. PCSK9 levels were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

AREase activity was significantly lower in CKD compared with non-CKD (225.53 ± 108.73 vs. 257.45 ± 106.12 kU/L, p = 0.044) in T2DM, whereas there was no significant difference in PONase activity and PCSK9 levels between CKD and non-CKD groups. In addition, multivariate logistic regression analysis showed that the lowest tertile of AREase increased the risk for CKD in T2DM (OR 3.251; 95% CI 1.333-7.926, p = 0.010), whereas PONase activity and PCSK9 levels were not associated with CKD in T2DM.

CONCLUSION

Reduced AREase activity can increase the risk for CKD in T2DM patients. AREase activity, but not PONase activity and PCSK9 levels, may be used as the biomarker for predicting the progression of CKD in T2DM.

Comparison of Serum PCSK9 Levels in Subjects with Normoglycemia, Impaired Fasting Glucose, and Impaired Glucose Tolerance

We investigated proprotein convertase subtilisin/kexin type 9 (PCSK9) concentrations in individuals with normoglycemia, impaired fasting glucose (IFG), and impaired glucose tolerance (IGT). This was a pilot, cross-sectional study including 92 individuals who had not been diagnosed with or treated for diabetes. We measured PCSK9 levels in three groups of subjects; namely, normoglycemia (n=57), IFG (n=21), and IGT (n=14). Individuals with IFG and IGT showed higher PCSK9 concentrations than those in the normoglycemic group, with the highest serum PCSK9 concentrations found in individuals with IGT (55.25±15.29 ng/mL for normoglycemia, 63.47±17.78 ng/mL for IFG, 72.22±15.46 ng/mL for IGT, analysis of variance P=0.001). There were no significant differences in high- or low-density lipoprotein cholesterol among groups. Serum PCSK9 levels are increased in patients with prediabetes compared to subjects with normoglycemia.

Lipid management in patients with chronic kidney disease

An increased risk of cardiovascular disease, independent of conventional risk factors, is present even at minor levels of renal impairment and is highest in patients with end-stage renal disease (ESRD) requiring dialysis. Renal dysfunction changes the level, composition and quality of blood lipids in favour of a more atherogenic profile. Patients with advanced chronic kidney disease (CKD) or ESRD have a characteristic lipid pattern of hypertriglyceridaemia and low HDL cholesterol levels but normal LDL cholesterol levels. In the general population, a clear relationship exists between LDL cholesterol and major atherosclerotic events. However, in patients with ESRD, LDL cholesterol shows a negative association with these outcomes at below average LDL cholesterol levels and a flat or weakly positive association with mortality at higher LDL cholesterol levels. Overall, the available data suggest that lowering of LDL cholesterol is beneficial for prevention of major atherosclerotic events in patients with CKD and in kidney transplant recipients but is not beneficial in patients requiring dialysis. The 2013 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for Lipid Management in CKD provides simple recommendations for the management of dyslipidaemia in patients with CKD and ESRD. However, emerging data and novel lipid-lowering therapies warrant some reappraisal of these recommendations.

Endothelin Receptor Antagonism Improves Lipid Profiles and Lowers PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) in Patients With Chronic Kidney Disease

Dyslipidemia is common in chronic kidney disease (CKD). Despite statins, many patients fail to adequately lower lipids and remain at increased risk of cardiovascular disease. Selective ET_A (endothelin-A) receptor antagonists reduce cardiovascular disease risk factors. Preclinical data suggest that ET_A antagonism has beneficial effects on circulating lipids. We assessed the effects of selective ET_A antagonism on circulating lipids and PCSK9 (proprotein convertase subtilisin/kexin type 9) in CKD. This was a secondary analysis of a fully randomized, double-blind, 3-phase crossover study. Twenty-seven subjects with predialysis CKD on optimal cardio- and renoprotective treatment were randomly assigned to receive 6 weeks dosing with placebo, the selective ET_A receptor antagonist, sitaxentan, or long-acting nifedipine. We measured circulating lipids and PCSK9 at baseline and then after 3 and 6 weeks. Baseline lipids and PCSK9 did not differ before each study phase. Whereas placebo and nifedipine had no effect on lipids, 6 weeks of ET_A antagonism significantly reduced total (-11±1%) and low-density lipoprotein-associated (-20±3%) cholesterol, lipoprotein (a) (-16±2%) and triglycerides (-20±4%); high-density lipoprotein-associated cholesterol increased (+14±2%), P<0.05 versus baseline for all. Additionally, ET_A receptor antagonism, but neither placebo nor nifedipine, reduced circulating PCSK9 (-19±2%; P<0.001 versus baseline; P<0.05 versus nifedipine and placebo). These effects were independent of statin use and changes in blood pressure or proteinuria. Selective ET_A antagonism improves lipid profiles in optimally-managed patients with CKD, effects that may occur through a reduction in circulating PCSK9. ET_A receptor antagonism offers a potentially novel strategy to reduce cardiovascular disease risk in CKD. Clinical Trial Registration- URL: http://www.clinicaltrials.gov . Unique identifier: NCT00810732.

Proprotein convertase subtilisin/kexin type 9 and mortality in patients starting hemodialysis

BACKGROUND

Cardiovascular events are the leading cause of death in end stage renal disease (ESRD), but traditional markers of dyslipidemia are not clearly associated with cardiovascular risk in this population. Proprotein Convertase Subtilsin/Kexin type 9 (PCSK-9) could be of interest as a novel cardiovascular risk marker in ESRD due to the emergence of lipid lowering therapy based on PCSK-9 inhibition. The aim of the present study was to investigate if the convertase PCSK-9 is a potential risk marker for mortality among patients starting haemodialysis treatment.

MATERIALS AND METHODS

This is a cohort study of 265 patients starting haemodialysis between 1991-2009, with 3 years follow-up. The association between baseline PCSK-9 levels and mortality was assessed using Cox proportional hazards- and quantile regression models, with adjustment for potential confounders.

RESULTS

PCSK-9 levels at initiation of haemodialysis were associated to mortality in multivariable adjusted analysis. PCSK-9 levels exhibited an U-shaped association to mortality. Inclusion of the quadratic term of PCSK-9 in regression modelling optimized model performance. At baseline, PCSK-9 levels had positive correlations to Davies comorbidity score, haemoglobin and C-reactive protein while negative correlations were found for high-density lipoprotein and total cholesterol. PCSK-9 levels were higher in statin users and patients with a history of cardiovascular disease.

CONCLUSIONS

This study shows, for the first time, that the level of PCSK-9 is associated with all-cause mortality in haemodialysis patients, independently of a number of potential confounders.

Apolipoproteins A and B and PCSK9: Nontraditional Cardiovascular Risk Factors in Chronic Kidney Disease and in End-Stage Renal Disease

PURPOSE

Nontraditional cardiovascular risk factors as apolipoprotein A (ApoA), apolipoprotein B (ApoB), and the proprotein convertase subtilisin/kexin type 9 (PCSK9) increase the prevalence of cardiovascular mortality in chronic kidney disease (CKD) or in end-stage renal disease (ESRD) through quantitative alterations. This review is aimed at establishing the biomarker (ApoA, ApoB, and PCSK9) level variations in uremic patients, to identify the studies showing the association between these biomarkers and the development of cardiovascular events and to depict the therapeutic options to reduce cardiovascular risk in CKD and ESRD patients.

METHODS

We searched the electronic database of PubMed, Scopus, EBSCO, and Cochrane CENTRAL for studies evaluating apolipoproteins and PCSK9 in CKD and ESRD. Randomized controlled trials, observational studies (including case-control, prospective or retrospective cohort), and reviews/meta-analysis were included if reference was made to those keys and cardiovascular outcomes in CKD/ESRD.

RESULTS

18 studies met inclusion criteria. Serum ApoA-I has been significantly associated with the development of new cardiovascular event and with cardiovascular mortality in ESRD patients. ApoA-IV level was independently associated with maximum carotid intima-media thickness (cIMT) and was a predictor for sudden cardiac death. The ApoB/ApoA-I ratio represents a strong predictor for coronary artery calcifications, cardiovascular mortality, and myocardial infarction in CKD/ESRD. Plasma levels of PCSK9 were not associated with cardiovascular events in CKD patients.

CONCLUSIONS

Although the "dyslipidemic status" in CKD/ESRD is not clearly depicted, due to different research findings, ApoA-I, ApoA-IV, and ApoB/ApoA-I ratio could be predictors of cardiovascular risk. Serum PCSK9 levels were not associated with the cardiovascular events in patients with CKD/ESRD. Probably in the future, the treatment of dyslipidemia in CKD/ESRD will be aimed at discovering new effective therapies on the action of these biomarkers.

Inhibiting PCSK9 - biology beyond LDL control

Clinical trials have unequivocally shown that inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) efficaciously and safely prevents cardiovascular events by lowering levels of LDL cholesterol. PCSK9 in the circulation is derived mainly from the liver, but the protein is also expressed in the pancreas, the kidney, the intestine and the central nervous system. Although PCSK9 modulates cholesterol metabolism by regulating LDL receptor expression in the liver, in vitro and in vivo studies have suggested that PCSK9 is involved in various other physiological processes. Although therapeutic PCSK9 inhibition could theoretically have undesired effects by interfering with these non-cholesterol-related processes, studies of individuals with genetically determined reduced PCSK9 function and clinical trials of PCSK9 inhibitors have not revealed clinically meaningful adverse consequences of almost completely eradicating PCSK9 from the circulation. The clinical implications of PCSK9 functions beyond lipid metabolism in terms of wanted or unwanted effects of therapeutic PCSK9 inhibition therefore appear to be limited. The objective of this Review is to describe the physiological role of PCSK9 beyond the LDL receptor to provide a rational basis for monitoring the effects of PCSK9 inhibition as these drugs gain traction in the clinic.

Association between circulating proprotein convertase subtilisin/kexin type 9 levels and prognosis in patients with severe chronic kidney disease

Background

Chronic kidney disease is a risk factor for premature development of coronary atherosclerosis and mortality. A high level of proprotein convertase subtilisin/kexin type 9 (PCSK9) is a recently recognized cardiovascular risk factor and has become the target of effective inhibitory treatment. In 167 kidney transplantation candidates, we aimed to: (i) compare levels of PCSK9 with those of healthy controls, (ii) examine the association between levels of PCSK9 and low-density lipoprotein cholesterol (LDL-c) and the degree of coronary artery disease (CAD) and (iii) evaluate if levels of PCSK9 predict major adverse cardiac events (MACE) and mortality.

Methods

Kidney transplant candidates (n = 167) underwent coronary computed tomography angiography (CCTA) and invasive coronary angiography (ICA) before transplantation. MACE and mortality data were extracted from the Western Denmark Heart Registry, a review of patient records and patient interviews. A group of 79 healthy subjects were used as controls.

Results

Mean PCSK9 levels did not differ between healthy controls and kidney transplant candidates. In patients not receiving lipid-lowering therapy, PCSK9 correlated positively with LDL-c (rho = 0.24, P &lt; 0.05). Mean PCSK9 was similar in patients with and without obstructive CAD at both CCTA and ICA. In a multiple regression analysis, PCSK9 was associated with neither LDL-c (β=−6.45, P = 0.44) nor coronary artery calcium score (β=2.17, P = 0.84). During a follow-up of 3.7 years, PCSK9 levels were not associated with either MACE or mortality.

Conclusions

The ability of PCSK9 levels to predict cardiovascular disease and prognosis does not seem to apply to a cohort of kidney transplant candidates.

Relationship between Plasma Proprotein Convertase Subtilisin/Kexin Type 9 and Estimated Glomerular Filtration Rate in the General Chinese Population

BACKGROUND

Elevated levels of proprotein convertase subtilisin/kexin type 9 (PCSK9) have been reported to be related to dyslipidemia, including patients with kidney dysfunction. However, its association with estimated glomerular filtration rate (eGFR) in individuals with normal serum creatinine (SCr) has not been determined.

METHODS

A total of 2,089 subjects with normal SCr and without lipid-lowering treatment were consecutively enrolled in this study. Plasma PCSK9 levels were measured by ELISA kit and eGFR was evaluated by the Chronic Kidney Disease Epidemiology Collaboration equation. Subjects were divided into a normal eGFR group (n = 1,205, ≥90 mL/min/1.73 m2) and a decreased eGFR group (n = 884, < 90 mL/min/1.73 m2). Baseline characteristics and laboratory findings were compared between the two groups. Spearman's correlation and linear regression were performed to determine the association between PCSK9 and eGFR.

RESULTS

No significant difference in PCSK9 levels was found between the normal eGFR group and the decreased eGFR group (236.84 ± 67.87 vs. 239.98 ± 68.72 ng/mL, p = 0.303). In Spearman's correlation and multivariable linear regression analysis, no association of PCSK9 levels with eGFR was detected in the total cohort (r = -0.039, p = 0.079; adjusted β = -0.013, p = 0.630). This result remained the same in the subgroups of normal eGFR (r = -0.038, p = 0.190; adjusted β = -0.031, p = 0.367) and decreased eGFR (r = -0.054, p = 0.109; adjusted β = -0.034, p = 0.319).

CONCLUSION

In this single-center study with moderate sample size, the data showed no relationship of PCSK9 levels with normal or decreased eGFR in untreated patients with normal SCr, suggesting that further studies may be needed to understand the relationship between PCSK9 and lipid disorder in different stage of kidney dysfunction.

Pleiotropic effects of proprotein convertase subtilisin/kexin type 9 inhibitors?

PURPOSE OF REVIEW

Current data suggest that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors may affect many metabolic pathways beyond lowering LDL cholesterol. The aim of the present manuscript is to present these so-called pleiotropic effects of PCSK9 inhibitors.

RECENT FINDINGS

PCSK9 may affect the activity of other receptors beyond LDL receptors (LDLR), such as cluster of differentiation 36 (CD36), very-low-density-lipoprotein (VLDL) receptors, apolipoprotein (Apo) E receptors, LDLR-related protein 1 (LRP-1) and ATP-Binding Cassette Transporter (ABCA1). Thus, a role of PCSK9 in the development of atherosclerosis, in vascular wall inflammation and in platelet function has been suggested. Additionally, PCSK9 inhibitors may affect lipid variables beyond LDL cholesterol, carbohydrate variables, as well as they may affect brain and kidney function. Additionally, a controversial role of PCSK9 in sepsis, hepatitis C infection and Alzheimer's disease has been suggested.

SUMMARY

These possible pleiotropic effects of PCSK9 inhibitors need further research, as they may affect cardiovascular risk and provide further insights in the development of atherosclerosis and other diseases such as Alzheimer's disease or chronic viral infection and sepsis.

Disorders of Lipid Metabolism in Chronic Kidney Disease

Cardiovascular disease (CVD) is the leading cause of death in chronic kidney disease (CKD). One of the most important pathophysiological mechanisms for CVD in patients with CKD is the widespread and possibly accelerated formation of atherosclerotic plaques due to hyperlipidemia, uremic toxins, inflammation, oxidative stress, and endothelial dysfunction. Recent studies showed that the level of oxidized low-density lipoprotein cholesterol increases, and that high-­density lipoprotein cholesterol dysfunction occurs as kidney function declines and inflammation becomes more prevalent. In this review, we aimed to discuss the effect of kidney dysfunction, oxidative stress, and inflammation on lipid ­profile.

Plasma proprotein-convertase-subtilisin/kexin type 9 (PCSK9) and cardiovascular events in type 2 diabetes

AIM

To investigate whether plasma concentrations of proprotein-convertase-subtilisin/kexin type 9 (PCSK9) were associated with cardiovascular (CV) events in two cohorts of patients with type 2 diabetes mellitus.

METHODS

We considered patients from the DIABHYCAR (n = 3137) and the SURDIAGENE (n = 1468) studies. Baseline plasma PCSK9 concentration was measured using an immunofluorescence assay. In post hoc, but preplanned, analyses we assessed the relationship between PCSK9 and the following endpoints: (1) a combined endpoint of major CV events: CV death, non-fatal myocardial infarction (MI), stroke and heart failure-related hospital admission; (2) a composite of all CV events: MI, stroke, heart failure-related hospital admission, coronary/peripheral angioplasty or bypass, CV death; (3) MI; (4) stroke/transient ischaemic attack (TIA); and (5) CV death.

RESULTS

In the DIABHYCAR study, plasma PCSK9 tertiles were associated with the incidence of MI, all CV events and stroke/TIA (P for trend <.05). In adjusted Cox analysis, plasma PCSK9 was associated, independently of classic risk factors, with the incidence of major CV events (hazard ratio [HR] for 1-unit increase of log[PCSK9] 1.28 [95% confidence interval {CI} 1.06-1.55]), the incidence of MI (HR 1.66 [95% CI 1.05-2.63]), and the incidence of all CV events (HR 1.22 [95% CI 1.04-1.44]), but not with CV death. Plasma PCSK9 was not associated with the incidence of CV disease in the participants of the SURDIAGENE study with high CV risk treated with statins and insulin.

CONCLUSIONS

We found that PCSK9 was inconsistently associated with CV events in populations with type 2 diabetes. The association may depend on the level of CV risk and the background treatment.

High circulating proprotein convertase subtilisin/Kexin type 9 concentration associates with cardiovascular risk: A meta-analysis of cohort studies

Whether the baseline circulating proprotein convertase subtilisin/Kexin type 9 (PCSK9) concentration associates with cardiovascular risk remains uncertain. This study aimed to investigate the predictive value of circulating PCSK9 in cardiovascular risk prediction.Relevant studies were searched through the MEDLINE, EMBASE, and Cochrane Library databases. The relative risk (RR) and 95% confidence interval (CI) were pooled to evaluate the association between the circulating PCSK9 concentration and cardiovascular risk. Dose-response meta-analysis was also performed in this study.A total of 11 cohort studies with 13,761 participants were included. The RR for cardiovascular risk was 1.25 (95% CI: 1.14-1.38, P < .001, I = 25%) while compared highest to lowest PCSK9 concentration. Subgroup meta-analysis, which sorted by ethnicity, base risk characteristic, and follow-up time, presented consistent results that there was a pronounced association between highest PCSK9 concentration and cardiovascular risk, such relationship was not significant in the statin-taking subjects. Seven studies were included in dose-response meta-analysis, and a nonlinear association between PCSK9 concentration and cardiovascular risk was observed [(χ test for nonlinearity = 6.7, (df = 2), P = .036].This study suggests that high circulating PCSK9 concentration associates with significantly increased cardiovascular risk, and demonstrates for the first time that it is a nonlinear dose-response association between circulating PCSK9 concentration and cardiovascular risk. These results provide the evidence that PCSK9 is an independent risk factor beyond the traditional cardiovascular risk factors and indicates a potential role of PCSK9 measurement for medical decisions. The clinical value of PCSK9 measurement and the identification of risk threshold should be confirmed in appropriately designed clinical trials.

High Serum PCSK9 Is Associated With Increased Risk of New-Onset Diabetes After Transplantation in Renal Transplant Recipients

OBJECTIVE

New-onset diabetes after transplantation (NODAT) is a major complication in renal transplant recipients (RTRs). Cholesterol metabolism has been linked to diabetes development. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is crucial in LDL receptor regulation. Its association with NODAT is unknown. We prospectively determined the association between serum PCSK9 levels and NODAT development and then with all-cause mortality, cardiovascular mortality, and renal graft failure.

RESEARCH DESIGN AND METHODS

In a university setting, nondiabetic RTRs recruited between 2001 and 2003 with a functional graft for ≥1 year were eligible. Serum PCSK9 was measured by ELISA. Cox proportional hazards analysis was used to assess the association of PCSK9 with the development of NODAT, all-cause mortality, cardiovascular mortality, and graft failure.

RESULTS

In 453 RTRs (age 51 ± 12 years, 56% male; 6.1 [2.7-11.7] years after transplantation), serum PCSK9 was 107.1 ± 43.4 μg/L. During a median follow-up of 10 years, 70 RTRs developed NODAT, 123 died, and 59 developed graft failure. NODAT occurred more frequently in the upper PCSK9 tertile (23%) versus the lowest two PCSK9 tertiles (12%; P < 0.001). In crude Cox regression analyses, PCSK9 was significantly associated with development of NODAT (hazard ratio 1.34 [95% CI 1.10-1.63]) per SD change (P = 0.004). This association remained independent of adjustment for potential confounders, including statin use. PCSK9 was not associated with all-cause mortality, cardiovascular mortality, or graft failure.

CONCLUSIONS

Circulating PCSK9 is associated with NODAT in RTRs. The PCSK9 pathway may contribute to the pathogenesis of NODAT.

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.

PCSK9 in chronic kidney disease

PURPOSE

Chronic kidney disease (CKD) is accompanied by a number of secondary metabolic dysregulations, such as lipid abnormalities, presenting with unique characteristics. Proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors have been introduced as the new era in the management of dyslipidemia with promising results in groups with refractory lipid abnormalities. Increasing number of studies investigate the possible association of PCSK9 levels with kidney function, especially with nephrotic range proteinuria, as well as its role as a prognostic cardiovascular risk marker in CKD. In this review, we discuss the existing evidence for PCSK9 levels in patient groups with nephrotic syndrome, non-dialysis CKD, end-stage renal disease and kidney transplantation.

METHODS

Online research was conducted in MEDLINE database to identify articles investigating PCSK9 in all different aspects of CKD. References from relevant studies were screened for supplementary articles.

RESULTS

Four cross-sectional studies, one secondary analysis, one publication from two independent cohort studies and one multicentre prospective cohort study assessed PCSK9 plasma levels in different subgroups of CKD patients. PCSK9 levels increase in nephrotic syndrome and have a positive correlation with proteinuria. In CKD patients, no correlation was found between PCSK9 levels and estimated GFR. Peritoneal dialysis patients have higher PCSK9 levels compared with hemodialysis and renal transplant patients as well as general population.

CONCLUSION

Accumulative evidence focuses on the possible association of PCSK9 levels with kidney function. No data are available for the administration of PCSK9 inhibitors in CKD patients. Further research will optimize knowledge on the role of PCSK9 levels and PCSK9 inhibitors in CKD.

Circulating proprotein convertase subtilisin-kexin type 9, all-cause mortality, and cardiovascular mortality: The Ludwigshafen Risk and Cardiovascular Health study

Background It is unclear whether proprotein convertase subtilisin-kexin type 9 (PCSK9) concentrations may be useful for cardiovascular risk stratification. Design The LUdwigshafen RIsk and Cardiovascular health (LURIC) study is a prospective observational registry of patients who were referred for coronary angiography. Methods Circulating PCSK9 was measured in 2139 participants of the LURIC study. There was a follow-up for all-cause and cardiovascular mortality with a median (interquartile range) duration of 10.1 (8.1-10.8) years. Results The mean (standard deviation) age of the participants (1470 males and 669 females) was 62.6 (10.8) years, body mass index 27.3 (4.0) kg/m², and low density lipoprotein cholesterol 114 (33) mg/dl. The mean (standard deviation) PCSK9 concentration was 220 (82) ng/ml. Of the participants, 1035 (48.4%) were on statins. Use of statins was associated with significantly lower low density lipoprotein cholesterol (106 vs 121 mg/dl, p < 0.001) but significantly higher circulating PCSK9 (244 vs 197 ng/ml, p < 0.001). A total of 674 (31.5%) study participants died from any cause and 431 (20.1%) from cardiovascular diseases. In the entire cohort, the third vs first tertile of PCSK9 was not associated with the risk of death from any cause (hazard ratio = 1.09, p = 0.367) and from cardiovascular diseases (hazard ratio = 1.09, p = 0.476). In participants without statins, the third vs first PCSK9 tertile was modestly associated with increased all cause mortality (hazard ratio = 1.34, p = 0.029) but not with cardiovascular mortality (hazard ratio = 1.25, p = 0.194). Conclusions Circulating PCSK9 may be upregulated by statin use and does not appear to be useful for cardiovascular risk stratification.

Association of PCSK9 with platelet reactivity in patients with acute coronary syndrome treated with prasugrel or ticagrelor: The PCSK9-REACT study

BACKGROUND

Circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme might be associated with increased activation of platelets. We aimed to assess the relationship between PCSK9 levels, platelet reactivity and ischemic outcomes.

METHODS

Consecutive ACS patients receiving prasugrel or ticagrelor and undergoing percutaneous coronary intervention (PCI) were enrolled in a prospective, observational study. Adenosine diphosphate (ADP)-induced platelet aggregation was determined by Multiplate Analyzer in the maintenance phase of treatment with prasugrel or ticagrelor. Major adverse cardiovascular events (MACEs) defined as composite of cardiovascular death, myocardial infarction, unstable angina, stent thrombosis, repeat revascularization, ischemic stroke were evaluated at 12months.

RESULTS

A direct association was found between increased PCSK9 serum levels and platelet reactivity (r=0.30; p=0.004). When assessed according to tertile values of PCSK9, there was a significant increase in platelet reactivity in the upper vs lower tertile (p=0.02). Clinical outcome was available at follow-up in 178 subjects. In the upper PCSK9 tertile 13/59 (22.03%) patients experienced a clinical MACE at one year, vs 2/59 (3.39%) patients in the lower PCSK9 tertile. At one-year follow-up, PCSK9 was independently associated with increased ischemic MACEs: hazard ratio for upper vs lower PCSK9-level tertile was 2.62 (95% confidence interval 1.24-5.52; p=0.01).

CONCLUSIONS

These findings suggest that increased PCSK9 levels are associated with higher platelet reactivity and are a possible predictor of ischemic events in ACS patients undergoing PCI.

Plasma PCSK9 concentrations during the course of nondiabetic chronic kidney disease: Relationship with glomerular filtration rate and lipid metabolism

BACKGROUND

The association between proprotein convertase subtilisin/kexin type 9 (PCSK9), a critical regulator of low-density lipoprotein (LDL) metabolism, and kidney function is a matter of debate.

OBJECTIVE

We aimed to assess the association of circulating PCSK9 concentrations with both glomerular filtration rate (eGFR) and serum lipid parameters in nondiabetic patients with chronic kidney disease (CKD).

METHODS

Fasting plasma PCSK9 concentrations were measured by ELISA in 94 nondiabetic nondialysis CKD (ND-CKD) patients not receiving statins, at different stages of CKD.

RESULTS

Plasma PCSK9 levels were associated neither to eGFR (P = .770) nor to proteinuria (P = .888) at several stages of CKD. In addition, plasma PCSK9 levels did not vary significantly between the different CKD stages. Plasma PCSK9 concentrations were positively correlated with apolipoprotein B (r = 0.221; P = .03) and triglycerides (r = 0.211; P = .04) but not with total cholesterol, calculated LDL-cholesterol, HDL cholesterol, lipoprotein(a), or CRP.

CONCLUSION

In a homogeneous population of nondiabetic subjects without lipid-lowering therapy, plasma PCSK9 concentrations are not associated to eGFR at several stages of CKD. These data suggest that kidney function per se does not impact significantly PCSK9 metabolism.

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.