Plasma Proprotein Convertase Subtilisin/kexin Type 9 Levels Research Articles

Plasma PCSK9 levels are elevated with acute myocardial infarction in two independent retrospective angiographic studies.

ObjectiveProprotein convertase subtilisin/kexin type 9 (PCSK9) is a circulating protein that promotes degradation of the low density lipoprotein (LDL) receptor. Mutations that block PCSK9 secretion reduce LDL-cholesterol and the incidence of myocardial infarction (MI). However, it remains unclear whether elevated plasma PCSK9 associates with coronary atherosclerosis (CAD) or more directly with rupture of the plaque causing MI.Methods and ResultsPlasma PCSK9 was measured by ELISA in 645 angiographically defined controls (<30% coronary stenosis) and 3,273 cases of CAD (>50% stenosis in a major coronary artery) from the Ottawa Heart Genomics Study. Because lipid lowering medications elevated plasma PCSK9, confounding association with disease, only individuals not taking a lipid lowering medication were considered (279 controls and 492 with CAD). Replication was sought in 357 controls and 465 with CAD from the Emory Cardiology Biobank study. PCSK9 levels were not associated with CAD in Ottawa, but were elevated with CAD in Emory. Plasma PCSK9 levels were elevated in 45 cases with acute MI (363.5±140.0 ng/ml) compared to 398 CAD cases without MI (302.0±91.3 ng/ml, p = 0.004) in Ottawa. This finding was replicated in the Emory study in 74 cases of acute MI (445.0±171.7 ng/ml) compared to 273 CAD cases without MI (369.9±139.1 ng/ml, p = 3.7×10−4). Since PCSK9 levels were similar in CAD patients with or without a prior (non-acute) MI, our finding suggests that plasma PCSK9 is elevated either immediately prior to or at the time of MI.ConclusionPlasma PCSK9 levels are increased with acute MI.

PCSK9 levels in abdominally obese men: Association with cardiometabolic risk profile and effects of a one-year lifestyle modification program

ObjectivesStudies performed in rodents have suggested a role for proprotein convertase subtilisin/kexin type 9 (PCSK9) in insulin resistance and impaired body fat distribution. Our objective was to examine the relationships between markers of adiposity and insulin resistance and plasma PCSK9 levels in humans. In addition, we explored the effect of a one-year lifestyle modification program on plasma PCSK9 levels in abdominally obese, dyslipidemic men. MethodsPlasma PCSK9 levels were measured by ELISA in 175 abdominally obese, dyslipidemic sedentary men. Of these abdominally obese men, 117 non-diabetic individuals completed a one-year lifestyle modification program aiming at increasing cardiorespiratory fitness levels and improving nutritional quality. ResultsWe found no association between plasma PCSK9 levels and body mass index, waist circumference, fat and fat-free mass, or visceral and subcutaneous adipose tissue measured by computed tomography. Compared to men with the lowest PCSK9 levels (bottom tertile), those with the highest PCSK9 levels (top tertile) had the most detrimental lipoprotein-lipid profile including lower LDL particle size (253.6 ± 4.0 vs. 251.6 ± 4.0 Å, p < 0.05) and higher apolipoprotein C-III levels (36.8 ± 10.6 vs. 32.3 ± 32.3, p < 0.05). These men were also characterized by higher HOMA-IR indices (6.78 ± 3.01 vs. 5.54 ± 2.91, p < 0.05). After one year, study participants lost on average 6.7 ± 4.6 kg (p < 0.0001). Plasma PCSK9 decreased by 9.2 ± 53.7 ng/ml (3.8%, p = 0.07). ConclusionsPlasma PCSK9 levels are not associated with body fat distribution indices, modestly associated with markers of insulin resistance and LDL particle size and are slightly affected by a lifestyle modification program in abdominally obese men.

Permanent alteration of PCSK9 with in vivo CRISPR-Cas9 genome editing.

Individuals with naturally occurring loss-of-function proprotein convertase subtilisin/kexin type 9 (PCSK9) mutations experience reduced low-density lipoprotein cholesterol levels and protection against cardiovascular disease. The goal of this study was to assess whether genome editing using a clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated system can efficiently introduce loss-of-function mutations into the endogenous PCSK9 gene in vivo. We used adenovirus to express CRISPR-associated 9 and a CRISPR guide RNA targeting Pcsk9 in mouse liver, where the gene is specifically expressed. We found that <3 to 4 days of administration of the virus, the mutagenesis rate of Pcsk9 in the liver was as high as >50%. This resulted in decreased plasma PCSK9 levels, increased hepatic low-density lipoprotein receptor levels, and decreased plasma cholesterol levels (by 35-40%). No off-target mutagenesis was detected in 10 selected sites. Genome editing with the CRISPR-CRISPR-associated 9 system disrupts the Pcsk9 gene in vivo with high efficiency and reduces blood cholesterol levels in mice. This approach may have therapeutic potential for the prevention of cardiovascular disease in humans.

Abstract 427: Plasma PCSK9 Levels Are Positively Correlated With LDL-Cholesterol Concentrations in Familial Hypercholesterolemia

Autosomal dominant familial hypercholesterolemia (FH) is caused by mutations in the LDL receptor (LDLR), its ligand apoB or proprotein convertase subtilisin/kexin type 9 (PCSK9) genes. PCSK9 regulates LDL-C levels by binding to LDLR, thereby enhancing its intracellular degradation. Although PCSK9 levels have been shown to be elevated in FH subjects, the extent to which PCSK9 levels correlate with LDL-C concentrations in FH has not been examined. Therefore, the objective of the present study was to assess the relationship between PCSK9 and LDL-C levels in a large cohort of genetically defined French-Canadian (FC) FH subjects. A total of 292 FH heterozygotes (heFH) carrying one of the nine FC mutations in the LDLR gene were recruited. 226 subjects were carriers of a negative receptor (NR) mutation in the LDLR gene, while the other 66 were carriers of a defective (DR) LDLR gene mutation. 56 control subjects matched for gender and body mass index (BMI) were also recruited. Fasting blood samples were collected after a 6-week period without lipid lowering medication. PCSK9 levels were significantly higher in the heFH group than in the control group (317.9 ng/ml vs 203.3 ng/ml; P&lt;0.001). In the heFH group, PCSK9 levels were positively and independently correlated with LDL-C concentrations and predicted 8.1% (P&lt;0.001) of the variability in LDL-C levels. Age, the type of LDLR mutation (NR vs DR), and BMI were also significantly associated with the variability in LDL-C levels, predicting 13.6% (P&lt;0.001), 3.9% (P&lt;0.001), and 1.8% (P=0.02) of the LDL-C variance, respectively. Interestingly, PCSK9 levels were also positively correlated with lipoprotein(a) levels in heFH (r=0.20; P&lt;0.001). These results indicate that PCSK9 levels are positively correlated with LDL-C and lipoprotein(a) concentrations in heFH.

Association of plasma PCSK9 levels with white blood cell count and its subsets in patients with stable coronary artery disease

ObjectiveRecent studies have suggested that proprotein convertase subtilisin/kexin type 9 (PCSK9) is associated with atherosclerosis and plays a potential role in inflammation. However, the correlation between PCSK9 and white blood cell count (WBCC) has not yet been assessed. The objective of the present study was to examine the association of the WBCC and its subset counts with plasma PCSK9 levels in patients with stable coronary artery disease (CAD). MethodsIn this cross-sectional study, a total of 251 consecutive, stable CAD patients who were not treated with lipid-lowering drugs were enrolled at our center between October 2012 and October 2013. The baseline clinical characteristics were collected, and the plasma PCSK9 levels were determined using ELISA. The associations of plasma PCSK9 levels with the WBCC and its subsets were investigated. ResultsIn the overall population, plasma PCSK9 levels were positively associated with the WBCC (r = 0.167, p = 0.008). Multivariable regression analysis revealed that the plasma PCSK9 levels were significantly and independently associated with the WBCC (β = 0.217, p < 0.001) and its subsets (neutrophil β = 0.152, p < 0.05; lymphocyte β = 0.241, p < 0.001). However, the relationships between PCSK9 and WBCC and its subsets remained significant in men (WBCC r = 0.234, p = 0.001; neutrophil r = 0.181, p = 0.014; lymphocyte r = 0.226, p = 0.002) but were not significant in women when the analysis was performed based on gender. ConclusionsThese data demonstrate that the plasma PCSK9 levels are independently associated with the WBCC and its subsets, suggesting a potential interaction between PCSK9 and chronic inflammation in patients with CAD.

Policosanol attenuates statin-induced increases in serum proprotein convertase subtilisin/kexin type 9 when combined with atorvastatin.

Objective. Statin treatment alone has been demonstrated to significantly increase plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels. The effect of policosanol combined with statin on PCSK9 is unknown. Methods. Protocol I: 26 patients with atherosclerosis were randomly assigned to receive either atorvastatin 20 mg/d or policosanol 20 mg/d + atorvastatin 20 mg/d for 8 weeks. Protocol II: 15 healthy volunteers were randomly assigned to either policosanol 20 mg/d or a control group for 12 weeks. Serum levels of PCSK9 were determined at day 0 and the end of each protocol. Results. Protocol I: atorvastatin 20 mg/d significantly increased serum PCSK9 level by 39.4% (256 ± 84 ng/mL versus 357 ± 101 ng/mL, P = 0.002). However, policosanol 20 mg/d + atorvastatin 20 mg/d increased serum PCSK9 level by only 17.4% without statistical significance (264 ± 60 ng/mL versus 310 ± 86 ng/mL, P = 0.184). Protocol II: there was a trend toward decreasing serum PCSK9 levels in the policosanol group (289 ± 71 ng/mL versus 235 ± 46 ng/mL, P = 0.069). Conclusion. Policosanol combined with statin attenuated the statin-induced increase in serum PCSK9 levels. This finding indicates that policosanol might have a modest effect of lowering serum PCSK9 levels.

Plasma PCSK9 in Nephrotic Syndrome and in Peritoneal Dialysis: A Cross-sectional Study

Serum total and low-density lipoprotein (LDL) cholesterol levels are elevated in patients with nephrotic syndrome and those with kidney failure treated by peritoneal dialysis (PD), who are characterized by heavy losses of protein in urine and peritoneal dialysate, respectively. Hypercholesterolemia in nephrotic syndrome is associated with and largely due to acquired LDL receptor (LDLR) deficiency. Because PCSK9 (proprotein convertase subtilisin/kexin type 9) promotes degradation of LDLR, we tested the hypothesis that elevation of LDL cholesterol levels in patients with nephrotic syndrome and PD patients may be due to increased PCSK9 levels. Cross-sectional study. Patients with nephrotic syndrome or treated by PD or hemodialysis and age- and sex-matched healthy Korean individuals (n=15 in each group). Group and serum total and LDL cholesterol levels. Plasma PCSK9 concentration. Concentrations of fasting serum PCSK9, lipids, and albumin, and urine protein excretion. Mean serum total and LDL cholesterol levels in patients with nephrotic syndrome (317.9±104.2 [SD] and 205.9±91.1mg/dL) and PD patients (200.0±27.6 and 126.7±18.5mg/dL) were significantly (P<0.05) higher than in hemodialysis patients (140.9±22.9 and 79.1±19.5mg/dL) and the control group(166.5±26.5 and 95.9±25.2mg/dL). This was associated with significantly (P<0.05) higher plasmaPCSK9 levels in patients with nephrotic syndrome (15.13±4.99ng/mL) and PD patients (13.30±1.40ng/mL) than in the control (9.19±0.60ng/mL) and hemodialysis (7.30±0.50ng/mL) groups. Plasma PCSK9 level was directly related to total and LDL cholesterol concentrations in the study population (r=0.559 [P<0.001] and r=0.497 [P<0.001], respectively). Small number of participants may limit generalizability. Nephrotic syndrome and PD are associated with higher plasma PCSK9 concentration, which can contribute to elevation of LDL levels by promoting LDLR deficiency.

Plasma proprotein convertase subtilisin kexin type 9 levels are related to markers of cholesterol synthesis in familial combined hyperlipidemia

Background and aimsTwo recent independent studies showed that patients with familial combined hyperlipidemia (FCHL) have elevated plasma levels of proprotein convertase subtilisin kexin type 9 (PCSK9) and markers of cholesterol synthesis. Both PCSK9 expression and cholesterol synthesis are downstream effects of hepatic activation of sterol regulatory element binding protein 2 (SREBP2). The present study was conducted to study the relationship between plasma PCSK9 and markers of cholesterol synthesis in FCHL. Methods and resultsMarkers of cholesterol synthesis (squalene, desmosterol, lathosterol), cholesterol absorption (campesterol, sitosterol, cholestanol) and PCSK9 were measured in plasma of FCHL patients (n = 103) and their normolipidemic relatives (NLR; n = 240). Plasma PCSK9, lathosterol and desmosterol levels were higher in FCHL patients than their NLR (p < 0.001, age and sex adjusted). Heritability calculations demonstrated that 35% of the variance in PCSK9 levels could be explained by additive genetic effects (p < 0.001). Significant age- and sex-adjusted correlations were observed for the relationship between PCSK9 and lathosterol, both unadjusted and adjusted for cholesterol, in the overall FCHL population (both p < 0.001). Multivariate regression analyses, with PCSK9 as the dependent variable, showed that the regression coefficient for FCHL status decreased by 25% (from 0.8 to 0.6) when lathosterol was included. Nevertheless, FCHL status remained an independent contributor to plasma PCSK9 (p < 0.001). ConclusionsThe present study confirms the previously reported high and heritable PCSK9 levels in FCHL patients. Furthermore, we now show that high PCSK9 levels are, in part, explained by plasma lathosterol, suggesting that SREBP2 activation partly accounts for elevated PCSK9 levels in FCHL.

Plasma PCSK9 concentrations during an oral fat load and after short term high-fat, high-fat high-protein and high-fructose diets

BackgroundPCSK9 (Proprotein Convertase Subtilisin Kexin type 9) is a circulating protein that promotes hypercholesterolemia by decreasing hepatic LDL receptor protein. Under non interventional conditions, its expression is driven by sterol response element binding protein 2 (SREBP2) and follows a diurnal rhythm synchronous with cholesterol synthesis. Plasma PCSK9 is associated to LDL-C and to a lesser extent plasma triglycerides and insulin resistance. We aimed to verify the effect on plasma PCSK9 concentrations of dietary interventions that affect these parameters.MethodsWe performed nutritional interventions in young healthy male volunteers and offspring of type 2 diabetic (OffT2D) patients that are more prone to develop insulin resistance, including: i) acute post-prandial hyperlipidemic challenge (n=10), ii) 4 days of high-fat (HF) or high-fat/high-protein (HFHP) (n=10), iii) 7 (HFruc1, n=16) or 6 (HFruc2, n=9) days of hypercaloric high-fructose diets. An acute oral fat load was also performed in two patients bearing the R104C-V114A loss-of-function (LOF) PCSK9 mutation. Plasma PCSK9 concentrations were measured by ELISA. For the HFruc1 study, intrahepatocellular (IHCL) and intramyocellular lipids were measured by 1H magnetic resonance spectroscopy. Hepatic and whole-body insulin sensitivity was assessed with a two-step hyperinsulinemic-euglycemic clamp (0.3 and 1.0 mU.kg-1.min-1).FindingsHF and HFHP short-term diets, as well as an acute hyperlipidemic oral load, did not significantly change PCSK9 concentrations. In addition, post-prandial plasma triglyceride excursion was not altered in two carriers of PCSK9 LOF mutation compared with non carriers. In contrast, hypercaloric 7-day HFruc1 diet increased plasma PCSK9 concentrations by 28% (p=0.05) in healthy volunteers and by 34% (p=0.001) in OffT2D patients. In another independent study, 6-day HFruc2 diet increased plasma PCSK9 levels by 93% (p<0.0001) in young healthy male volunteers. Spearman’s correlations revealed that plasma PCSK9 concentrations upon 7-day HFruc1 diet were positively associated with plasma triglycerides (r=0.54, p=0.01) and IHCL (r=0.56, p=0.001), and inversely correlated with hepatic (r=0.54, p=0.014) and whole-body (r=−0.59, p=0.0065) insulin sensitivity.ConclusionsPlasma PCSK9 concentrations vary minimally in response to a short term high-fat diet and they are not accompanied with changes in cholesterolemia upon high-fructose diet. Short-term high-fructose intake increased plasma PCSK9 levels, independent on cholesterol synthesis, suggesting a regulation independent of SREBP-2. Upon this diet, PCSK9 is associated with insulin resistance, hepatic steatosis and plasma triglycerides.

Plasma levels of PCSK9 and phenotypic variability in familial hypercholesterolemia

The extent of hypercholesterolemia varies considerably in patients with familial hypercholesterolemia (FH). We hypothesized that the variability of the FH phenotype might be partly explained by variation in proprotein convertase subtilisin kexin type 9 (PCSK9) activity. Individuals between 18 and 53 years of age who had been tested for a pathogenic LDLR or APOB mutation were eligible. Mutation carriers with a LDL-C level below the 75(th) percentile (called "FH low") were selected, as well as those with LDL-C above the 90(th) percentile (called "FH high"). Relatives who tested negative for the mutation were the "controls." PCSK9 plasma levels were assessed in 267 individuals who did not receive cholesterol-lowering treatment at the time of the study. Mean PCSK9 plasma levels (95% CI) were lower in the FH-low group compared with the FH-high group [152 (137-167) ng/ml vs. 186 (165-207) ng/ml, P = 0.010] and the control group [177 (164-190) ng/ml, P = 0.013]. Mean PCSK9 levels did not statistically differ between the FH-high and control groups (P = 0.50). Plasma PCSK9 levels are positively associated with LDL-C levels in FH patients and might contribute to the phenotypic severity in this disorder. Therefore, the results of pharmaceutical inhibition of PCSK9 in FH patients are eagerly awaited.

Abstract 318: Hepatic Site-1 Protease Knockdown in Mice Decreases Proprotein Convertase Subtilisin/kexin Type 9 Expression

Introduction— Site-1 protease (S1P) is a proprotein convertase involved in activation of transcription factors from their membrane-bound precursors in a process known as Regulated Intramembrane Proteolysis. These factors include Sterol Regulatory Element Binding Proteins (SREBPs) and CRE Binding Protein-H. SREBPs are the transcriptional master regulators of de novo cholesterol and fatty acid biosynthetic genes, and also positively regulate Low density lipoprotein receptor (LDLR) and Proprotein convertase subtilisin/kexin type 9 (PCSK9) expression. Inhibition of PCSK9 is a promising drug targeting strategy for treatment of dyslipidemia since the major function of PCSK9 is to degrade LDLR. Hypothesis— S1P controls PCSK9 expression and function in the liver. Results— Inducing Cre-LoxP mediated DNA recombination in the liver of S1P flox mice by three different approaches, we consistently observed that S1P knockdown significantly decreases PCSK9 mRNA expression in the liver and reduces plasma PCSK9 concentrations compared to S1P flox control mice. This effect is largely due to a decrease in PCSK9 mRNA synthesis without a change in its mRNA stability. The reduction of PCSK9 mRNA correlates with downregulation of the SREBP pathways and has a positive effect on hepatic LDLR protein levels as evident in mice after food entrainment. Also, we found that S1P differentially regulates PCSK9 and LDLR mRNA levels in a dose- and time-dependent manner. Finally a constitutively active form of SREBP, but not CREBH, almost restores PCSK9 expression in isolated hepatocytes from S1P knockdown mice to that of S1P flox control. Hence, S1P regulates PCSK9 expression through SREBPs. Conclusion— Taken together, our study reveals the physiological role of liver S1P in regulating hepatic and plasma PCSK9 levels and influencing its function. This may provide a novel strategy to inhibit PCSK9.

RETRACTED: Plasma PCSK9 Levels and Clinical Outcomes in the TNT (Treating to New Targets) Trial: A Nested Case-Control Study

The purpose of this study was to investigate whether high levels of circulating proprotein convertase subtilisin kexin type 9 (PCSK9) would increase cardiovascular risk in statin-treated patients. Statins activate low-density lipoprotein (LDL) receptor gene expression, thus lowering plasma LDL levels. But statins also activate the expression of PCSK9, a secreted inhibitor of the LDL receptor, thereby limiting their beneficial effects. We have measured the plasma PCSK9 levels of 1,613 patients with stable coronary heart disease enrolled in the Treating to New Targets study, a randomized trial that compared the efficacy of high- versus low-dose atorvastatin. After a run-in period with atorvastatin 10 mg daily, patients were randomized to either continue with 10 mg or be up-titrated to 80 mg of atorvastatin, and followed during 5 years for major cardiovascular events (MCVEs). Circulating PCSK9 levels measured at randomization were predictive of clinical outcomes in the group randomized to remain on atorvastatin 10 mg (p = 0.039), but not in the group that intensified atorvastatin treatment to 80 mg (p = 0.24). Further, PCSK9 levels measured 1 year post-randomization did not change upon increase of the statin dose. PCSK9 levels predict cardiovascular events in patients treated with low-dose atorvastatin. (A Study to Determine the Degree of Additional Reduction in CV Risk in Lowering LDL Below Minimum Target Levels [TNT]; NCT00327691).

Abstract 287: Plasma PCSK9 Concentrations in Critically Ill Patients

Objective. Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a circulating protein that impairs LDL clearance by promoting the LDL receptor (LDLR) degradation. Plasma lipid parameters (LDL-C and HDL-C) are related to severity of illness and survival in intensive care patients. Here, we aimed to determine whether circulating PCSK9 concentrations were correlated to the severity of illness in patients with multiple trauma. Methods/Results. Plasma PCSK9 were measured, at day 0 and 8 after admission, by ELISA in 111 patients hospitalized in ICU for severe trauma. Patients were included in the HIPOLYTE study and were randomly assigned to hydrocortisone therapy or placebo. Plasma PCSK9 levels were significantly increased by 161% at day 8 compared to day 0 (481 ± 227 vs 231 ± 117 ng/ml, P=0.0001). Hydrocortisone therapy did not alter PCSK9 concentrations at day 8 compared to placebo (451 ± 216 vs 511 ± 239ng/ml, P=0.33). In the whole population of the study, PCSK9 was positively associated with LDL-C (Pearson coefficient : 0.26, p=0.007) at day 0, but not with markers of severity illness. At day 8, an inverse correlation was found between PCSK9 and HDL-C (β =-653 ; P=0.004). Interestingly, PCSK9 concentrations at day 8 were related to markers of severity illness as injury severity score (β =6.17 ; P=0.0007), length of stay in ICU (β =6.14 ; P=0.0001), duration of both mechanical ventilation (β =8.26 ; P=0.0001) and cathecolamines infusion (β =18.57; P=0.015). Conclusion. PCSK9 appears as a late biomarker of severity illness in patients hospitalized for multiple trauma in ICU. These results open new perspectives for a role of PCSK9 in critical illness.

Abstract 131: PCSK9: A Biomarker Associated with the Metabolic Complications of Morbid Obesity

Objectives: Plasma pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protease that inhibits the activity of the LDL-receptor. Here, we determined the effect of bariatric surgery on plasma PCSK9 levels. Methods: Sixty-five obese patients (BMI : 46.7 ± 6.5 kg/m 2) were prospectively evaluated before and 6 months after bariatric surgery (sleeve-gastrectomy [n=53], Roux-en-Y gastric bypass [n=12], gastric banding [n=1]). Plasma PCSK9 were measured by ELISA and liver mRNA PCSK9 expression by Q-PCR. Results: Before surgery, plasma PCSK9 was positively associated with LDL-C (r=0.59, P&lt;0.0001), plasma triglycerides (TG) (r=0.48, P=0.0006) and fasting plasma glucose (FPG) (r=0.29 ; P=0.036), and negatively with BMI (r =-0.34, P=0.01). Plasma PCSK9 concentrations were increased in obese patients with metabolic syndrome (MetS) compared to those without MetS (295 ± 93 vs 210 ± 58 ng/ml, P&lt;0.0001). Bariatric surgery did not alter plasma PCSK9 concentrations at 6 months. Interestingly, circulating PCSK9 was not longer correlated with LDL-C after bariatric surgery, but remained strongly associated with TG (r=0.50 P=0.0006), FPG (r=0.40 P=0.006) and HOMA-IR (r=0.40 P=0.007). Plasma PCSK9 levels were positively associated with liver steatosis (r=0.26, P=0.05), and were higher in patients with NASH (347 ± 101 vs 228 ± 73 ng/ml, P=0.003). Surprisingly, PCSK9 hepatic mRNA expression did not correlate with plasma PCSK9 concentrations, neither with LDL-C nor TG. Conclusions: Circulating PCSK9 concentrations are associated with the metabolic complications of obesity, including insulin resistance, hyperglycaemia, hypertriglyceridemia and NASH and are not a direct reflect of its hepatic synthesis. ClinicalTrials.gov identifier : NCT00422006

Serum levels of proprotein convertase subtilisin/kexin type 9 in subjects with familial hypercholesterolemia indicate that proprotein convertase subtilisin/kexin type 9 is cleared from plasma by low-density lipoprotein receptor–independent pathways

Secreted proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the low-density lipoprotein receptor (LDLR) at the cell surface and disrupts the normal recycling of the LDLR. When human PCSK9 is injected into LDLR-deficient mice, PCSK9 is still rapidly cleared by the liver. This finding may suggest that PCSK9 is physiologically also cleared by receptors other than the LDLR. An alternative explanation could be that PCSK9 has undergone modifications during purification and is cleared by scavenger receptors on liver endothelial sinusoidal cells when injected into mice. If the only mechanism for clearing PCSK9 in humans is through the LDLR, one would expect that differences in the number of LDLRs would affect the plasma levels of low-density lipoprotein cholesterol (LDLC) and PCSK9 in a similar fashion. In this study, levels of LDLC and PCSK9 were measured in familial hypercholesterolemia (FH) homozygotes, FH heterozygotes, and normocholesterolemic subjects. The ratio between the levels of LDLC and PCSK9 was 1.7-fold higher in FH heterozygotes and 3-fold higher in FH homozygotes than in the normocholesterolemic subjects. Thus, defective LDLRs have a greater impact on the levels of LDLC than on the levels of PCSK9. By assuming that the rate of PCSK9 synthesis is similar in the 3 groups, this finding suggests that in humans, plasma PCSK9 is also cleared by LDLR-independent mechanisms.

Plasma proprotein convertase subtilisin kexin type 9 is a heritable trait of familial combined hyperlipidaemia

The aim of the present study was to investigate the relationship between circulating PCSK9 (proprotein convertase subtilisin kexin type9) and FCHL (familial combined hyperlipidaemia) and, when positive, to determine the strength of its heritability. Plasma PCSK9 levels were measured in FCHL patients (n=45), NL (normolipidaemic) relatives (n=139) and their spouses (n=72). In addition, 11 FCHL patients were treated with atorvastatin to study the response in PCSK9 levels. PCSK9 levels were higher in FCHL patients compared with NL relatives and spouses: 96.1 compared with 78.7 and 82.0ng/ml (P=0.004 and P=0.002 respectively). PCSK9 was significantly associated with both TAG (triacylglycerol) and apolipoprotein B levels (P<0.001). The latter relationship was accounted for by LDL (low-density lipoprotein)-apolipoprotein B (r=0.31, P=0.02), not by VLDL (very-low-density lipoprotein)-apolipoprotein B (r=0.09, P=0.49) in a subgroup of subjects (n=59). Heritability calculations for PCSK9 using SOLAR and FCOR software yielded estimates of 67-84% respectively (P<0.0001). PCSK9 increased from 122 to 150ng/ml in 11 FCHL patients treated with atorvastatin (40mg) once daily for 8weeks (P=0.018). In conclusion, plasma PCSK9 is a heritable trait associated with both FCHL diagnostic hallmarks. These results, combined with the significant rise in PCSK9 levels after statin therapy, warrant further studies in order to unravel the exact role of PCSK9 in the pathogenesis and treatment of this highly prevalent genetic dyslipidaemia.

Plasma proprotein convertase subtilisin kexin type 9 is not altered in subjects with impaired glucose metabolism and type 2 diabetes mellitus, but its relationship with non-HDL cholesterol and apolipoprotein B may be modified by type 2 diabetes mellitus: The CODAM study

ObjectiveType 2 diabetes mellitus (T2DM) is associated with elevated plasma apolipoprotein B and triglycerides levels, reduced HDL cholesterol and the presence of small-dense LDL particles. The present study was conducted to investigate the role of plasma proprotein convertase subtilisin kexin type 9 (PCSK9) levels, a regulator of LDL-receptor expression, in the occurrence of diabetic dyslipidemia. MethodsPlasma PCSK9 was measured in a cohort of subjects with normal glucose metabolism (NGM; n=288), impaired glucose metabolism (IGM; n=121) and type 2 diabetes mellitus (T2DM; n=139) to study whether its relation with plasma apolipoprotein B, triglycerides, total cholesterol, non-HDL cholesterol, LDL cholesterol and HDL cholesterol differed by levels of glucose metabolism status. ResultsPlasma PCSK9 levels were not different between the three groups (82, 82 and 80ng/mL in NGM, IGM and T2DM, respectively). PCSK9 was positively associated with total cholesterol, non-HDL cholesterol, LDL cholesterol, apolipoprotein B and triglycerides levels in all subgroups. The regression slopes for the associations with non-HDL cholesterol were steeper among individuals with T2DM than with NGM (β=0.016 versus β=0.009, p-interaction=0.05). Similar results were obtained for the relation with apolipoprotein B (β=0.004 versus β=0.002, p-interaction=0.09). ConclusionsAlthough glucose metabolism status per se is not associated with plasma PCSK9 levels, the presence of T2DM may modify the relation between plasma PCSK9 and non-HDL cholesterol and apolipoprotein B. These observations should be regarded as hypothesis generating for further studies aimed at elucidating the role of PCSK9 in the pathogenesis and treatment of diabetic dyslipidemia.

Fasting reduces plasma proprotein convertase, subtilisin/kexin type 9 and cholesterol biosynthesis in humans

Proprotein convertase, subtilisin/kexin type 9 (PCSK9), a key regulator of plasma LDL-cholesterol (LDL-c) and cardiovascular risk, is produced in liver and secreted into plasma where it binds hepatic LDL receptors (LDLR), leading to their degradation. PCSK9 is transcriptionally activated by sterol response element-binding protein (SREBP)-2, a transcription factor that also activates all genes for cholesterol synthesis as well as the LDLR. Here we investigated the relationship between plasma PCSK9 levels and the lathosterol-to-cholesterol ratio, a marker of cholesterol biosynthesis, in 18 healthy subjects during a 48 h fast. In all individuals, plasma PCSK9 levels declined steadily during the fasting period, reaching a nadir at 36 h that was ∼58% lower than levels measured in the fed state (P < 0.001). Similarly, the lathosterol-to-cholesterol ratio declined in parallel with plasma PCSK9 concentrations during the fast, reaching a nadir at 36 h that was ∼28% lower than that measured in the fed state (P = 0.024). In summary, fasting has a marked effect on plasma PCSK9 concentrations, which is mirrored by measures of cholesterol synthesis in humans. Inasmuch as cholesterol synthesis and PCSK9 are both regulated by SREBP-2, these results suggest that plasma PCSK9 levels may serve as a surrogate marker of hepatic SREBP-2 activity in humans.

Beyond LDL Cholesterol, a New Role for PCSK9

Elevated low-density lipoprotein cholesterol (LDLC) levels in the plasma is the most important causative factor of atherosclerosis and associated ischemic cardiovascular diseases. The LDL receptor (LDLR) is the preferential pathway through which LDLs are cleared from the circulation. LDLs bound to the LDLR are internalized into clathrin-coated pits and subsequently undergo lysosomal degradation, whereas the LDLR is recycled back to the plasma membrane. See accompanying article on page 1333 Familial hypercholesterolemia (FH) is an autosomal dominant disorder associated with elevated LDL levels and premature coronary heart disease. FH is caused primarily by mutations of the LDLR or of apolipoprotein B100 (apoB100), the protein component of LDL that interacts with the LDLR. In 2003, “gain of function” mutations on a newly identified gene, proprotein convertase subtilisin/kexin type 9 ( PCSK9), were associated with FH. In 2005, a causative association was established between “loss of function” mutations in PCSK9 and low LDLC levels in 2% of the African-American population. The coronary heart disease risk in these individuals was reduced by 88%. As a result of these landmark studies (reviewed in Reference 1), PCSK9 became the subject of intensive research to discover the underlying mechanisms. PCSK9 is a serine protease mainly expressed in the liver and the intestine. It acts by reducing the amount of LDLR in hepatocytes. This was demonstrated in vitro and in mouse models …

Association between plasma PCSK9 and gamma-glutamyl transferase levels in diabetic patients

Background Proprotein convertase subtilisin kexin type 9 (PCSK9) is a secreted proprotein convertase acting as a natural inhibitor of the low-density lipoprotein (LDL) receptor. Here, we prospectively investigated the relationship between the circulating levels of PCSK9 and metabolic parameters in 117 diabetic patients. Results Plasma PCSK9 level was significantly higher in type 2 than in type 1 diabetes ( P = 0.04), in diabetic patients under statins ( P < 10 −4) and in those with macrovascular complications ( P = 0.002). Univariable regression analysis revealed that plasma PCSK9 level correlated positively with age ( P = 0.003), body mass index ( P = 0.04), systolic blood pressure (SBP) ( P = 0.01), gamma-glutamyl transferase (GGT) levels ( P = 0.0002) and statin treatment ( P = 0.001). In a multivariable linear regression analysis, PCSK9 correlated positively with GGT level ( β = 21.91, P = 0.0019) after adjustment for gender, age, type of diabetes, statin treatment, BMI, SBP and HbA1c. Conclusion PCSK9 level was independently associated with GGT level in diabetic patients, suggesting potential interaction between PCSK9 and liver function.