Is atrial fibrillation in HFpEF a distinct phenotype? Insights from multiparametric MRI and circulating biomarkers.

BACKGROUND: Heart failure with preserved ejection fraction (HFpEF) and atrial fibrillation (AF) frequently co-exist. There is a limited understanding on whether this coexistence is associated with distinct alterations in myocardial remodelling and mechanics. We aimed to determine if patients with atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF) represent a distinct phenotype. METHODS: In this secondary analysis of adults with HFpEF (NCT03050593), participants were comprehensively phenotyped with stress cardiac MRI, echocardiography and plasma fibroinflammatory biomarkers, and were followed for the composite endpoint (HF hospitalisation or death) at a median of 8.5 years. Those with AF were compared to sinus rhythm (SR) and unsupervised cluster analysis was performed to explore possible phenotypes. RESULTS: 136 subjects were included (SR = 75, AF = 61). The AF group was older (76 ± 8 vs. 70 ± 10 years) with less diabetes (36% vs. 61%) compared to the SR group and had higher left atrial (LA) volumes (61 ± 30 vs. 39 ± 15 mL/m2, p < 0.001), lower LA ejection fraction (EF) (31 ± 15 vs. 51 ± 12%, p < 0.001), worse left ventricular (LV) systolic function (LVEF 63 ± 8 vs. 68 ± 8%, p = 0.002; global longitudinal strain 13.6 ± 2.9 vs. 14.7 ± 2.4%, p = 0.003) but higher LV peak early diastolic strain rates (0.73 ± 0.28 vs. 0.53 ± 0.17 1/s, p < 0.001). The AF group had higher levels of syndecan-1, matrix metalloproteinase-2, proBNP, angiopoietin-2 and pentraxin-3, but lower level of interleukin-8. No difference in clinical outcomes was observed between the groups. Three distinct clusters were identified with the poorest outcomes (Log-rank p = 0.029) in cluster 2 (hypertensive and fibroinflammatory) which had equal representation of SR and AF. CONCLUSIONS: Presence of AF in HFpEF is associated with cardiac structural and functional changes together with altered expression of several fibro-inflammatory biomarkers. Distinct phenotypes exist in HFpEF which may have differing clinical outcomes.

Transintestinal cholesterol excretion is an active metabolic process modulated by PCSK9 and statin involving ABCB1.

OBJECTIVE: Transintestinal cholesterol excretion (TICE) is an alternate pathway to hepatobiliary secretion. Our study aimed at identifying molecular mechanisms of TICE. APPROACH AND RESULTS: We studied TICE ex vivo in mouse and human intestinal explants, and in vivo after bile diversion and intestinal cannulation in mice. We provide the first evidence that both low-density lipoprotein (LDL) and high-density lipoprotein deliver cholesterol for TICE in human and mouse jejunal explants at the basolateral side. Proprotein convertase subtilisin kexin type 9 (PCSK9)(-/-) mice and intestinal explants show increased LDL-TICE, and acute injection of PCSK9 decreases TICE in vivo, suggesting that PCSK9 is a repressor of TICE. The acute repression was dependent on the LDL receptor (LDLR). Further, TICE was increased when mice were treated with lovastatin. These data point to an important role for LDLR in TICE. However, LDLR(-/-) mice showed increased intestinal LDL uptake, contrary to what is observed in the liver, and tended to have higher TICE. We interpret these data to suggest that there might be at least 2 mechanisms contributing to TICE; 1 involving LDL receptors and other unidentified mechanisms. Acute modulation of LDLR affects TICE, but chronic deficiency is compensated for most likely by the upregulation of the unknown mechanisms. Using mice deficient for apical multidrug active transporter ATP-binding cassette transporter B1 a and b, and its inhibitor, we show that these apical transporters contribute significantly to TICE. CONCLUSIONS: TICE is operative in human jejunal explants. It is a metabolically active process that can be acutely regulated, inversely related to cholesterolemia, and pharmacologically activated by statins.

Essential fatty acids deficiency promotes lipogenic gene expression and hepatic steatosis through the liver X receptor.

BACKGROUND & AIMS: Nutrients influence non-alcoholic fatty liver disease. Essential fatty acids deficiency promotes various syndromes, including hepatic steatosis, through increased de novo lipogenesis. The mechanisms underlying such increased lipogenic response remain unidentified. METHODS: We used wild type mice and mice lacking Liver X Receptors to perform a nutrigenomic study that aimed at examining the role of these transcription factors. RESULTS: We showed that, in the absence of Liver X Receptors, essential fatty acids deficiency does not promote steatosis. Consistent with this, Liver X Receptors are required for the elevated expression of genes involved in lipogenesis in response to essential fatty acids deficiency. CONCLUSIONS: This work identifies, for the first time, the central role of Liver X Receptors in steatosis induced by essential fatty acids deficiency.

PCSK9 and LDL cholesterol: unravelling the target to design the bullet.

Gain-of-function mutations within proprotein convertase subtilisin kexin type 9 (PCSK9) are linked to familial autosomal dominant hypercholesterolaemia, a disease characterized by elevated plasma concentrations of cholesterol associated with low-density lipoproteins (LDLs). Conversely, PCSK9 loss-of-function mutations result in low levels of LDL cholesterol (LDLC) and protect against coronary heart disease. Although compelling evidence indicates that PCSK9 impairs the LDLR pathway, its role in cholesterol metabolism remains incompletely defined. In the past two years, several new biochemical findings, including the PCSK9 crystal structure and the identification of several transcriptional repressors, were reported. Moreover, new clinical and epidemiological data have revealed the correlation between plasma PCSK9 concentrations and LDLC levels.

Impact of diabetes on remodelling, microvascular function and exercise capacity in aortic stenosis.

OBJECTIVE: To characterise cardiac remodelling, exercise capacity and fibroinflammatory biomarkers in patients with aortic stenosis (AS) with and without diabetes, and assess the impact of diabetes on outcomes. METHODS: Patients with moderate or severe AS with and without diabetes underwent echocardiography, stress cardiovascular magnetic resonance (CMR), cardiopulmonary exercise testing and plasma biomarker analysis. Primary endpoint for survival analysis was a composite of cardiovascular mortality, myocardial infarction, hospitalisation with heart failure, syncope or arrhythmia. Secondary endpoint was all-cause death. RESULTS: Diabetes (n=56) and non-diabetes groups (n=198) were well matched for age, sex, ethnicity, blood pressure and severity of AS. The diabetes group had higher body mass index, lower estimated glomerular filtration rate and higher rates of hypertension, hyperlipidaemia and symptoms of AS. Biventricular volumes and systolic function were similar, but the diabetes group had higher extracellular volume fraction (25.9%±3.1% vs 24.8%±2.4%, p=0.020), lower myocardial perfusion reserve (2.02±0.75 vs 2.34±0.68, p=0.046) and lower percentage predicted peak oxygen consumption (68%±21% vs 77%±17%, p=0.002) compared with the non-diabetes group. Higher levels of renin (log10renin: 3.27±0.59 vs 2.82±0.69 pg/mL, p<0.001) were found in diabetes. Multivariable Cox regression analysis showed diabetes was not associated with cardiovascular outcomes, but was independently associated with all-cause mortality (HR 2.04, 95% CI 1.05 to 4.00; p=0.037). CONCLUSIONS: In patients with moderate-to-severe AS, diabetes is associated with reduced exercise capacity, increased diffuse myocardial fibrosis and microvascular dysfunction, but not cardiovascular events despite a small increase in mortality.

Proprotein convertase subtilisin kexin type 9 null mice are protected from postprandial triglyceridemia.

OBJECTIVES: Proprotein convertase subtilisin kexin type 9 (PCSK9) is a natural inhibitor of the low-density lipoprotein receptor, and its deficiency in humans results in low plasma LDL-cholesterol and protection against cardiovascular disease. We explored whether PCSK9 expression impacts postprandial triglyceridemia, another important cardiovascular risk factor. METHODS AND RESULTS: Real-time PCR and confocal microscopy were used to show that PCSK9 is expressed throughout the entire small intestine and in human enterocytes. On olive oil gavage, PCSK9-deficient mice showed a dramatically decreased postprandial triglyceridemia compared with their wild-type littermates. Lymph analysis revealed that intestinal TG output is not quantitatively modified by PCSK9 deletion. However, PCSK9-/- mice present with a significant reduction of lymphatic apoB secretion compared to PCSK9+/+ mice. Modulating PCSK9 expression in polarized CaCo-2 cells confirmed the relationship between PCSK9 and apoB secretion; PCSK9-/- mice consistently secrete larger TG-rich lipoprotein than wild-type littermates. Finally, kinetic studies showed that PCSK9-deficient mice have an increased ability to clear chylomicrons compared to wild-type littermates. CONCLUSION: These findings indicate that in addition to its effect on LDL-cholesterol, PCSK9 deficiency might protect against cardiovascular disease by reducing postprandial triglyceridemia.

PCSK9 dominant negative mutant results in increased LDL catabolic rate and familial hypobetalipoproteinemia.

OBJECTIVE: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a central player in the regulation of cholesterol homeostasis, increasing the low-density lipoprotein (LDL) receptor degradation. Our study aimed at exploring the pathogenic consequences in vivo and in vitro of a PCSK9 prodomain mutation found in a family with hypobetalipoproteinemia (FHBL). METHODS AND RESULTS: A white 49-year-old diabetic man had profound FBHL (LDLC: 16 mg/dL) whereas his daughter and sister displayed a milder phenotype (LDLC 44 mg/dL and 57 mg/dL, respectively), all otherwise healthy with a normal liver function. A monoallelic PCSK9 double-mutant R104C/V114A cosegregated with FBHL, with no mutation found at other FHBL-causing loci. A dose-effect was also found in FBHL relatives for plasma APOB and PCSK9 (very-low to undetectable in proband, approximately 50% decreased in sister and daughter) and LDL catabolic rate (256% and 88% increased in proband and daughter). Transient transfection in hepatocytes showed severely impaired processing and secretion of the double mutant which acted as a dominant negative over secretion of wild-type PCSK9. CONCLUSIONS: These results show that heterozygous PCSK9 missense mutations may associate with profound hypobetalipoproteinemia and constitute the first direct evidence in human that decrease of plasma LDLC concentrations associated to PCSK9 LOF mutations are attributable to an increased clearance rate of LDL.

Molecular Profiling Reveals a Common Metabolic Signature of Tissue Fibrosis.

Fibrosis, or the accumulation of extracellular matrix, is a common feature of many chronic diseases. To interrogate core molecular pathways underlying fibrosis, we cross-examine human primary cells from various tissues treated with TGF-ß, as well as kidney and liver fibrosis models. Transcriptome analyses reveal that genes involved in fatty acid oxidation are significantly perturbed. Furthermore, mitochondrial dysfunction and acylcarnitine accumulation are found in fibrotic tissues. Substantial downregulation of the PGC1α gene is evident in both in vitro and in vivo fibrosis models, suggesting a common node of metabolic signature for tissue fibrosis. In order to identify suppressors of fibrosis, we carry out a compound library phenotypic screen and identify AMPK and PPAR as highly enriched targets. We further show that pharmacological treatment of MK-8722 (AMPK activator) and MK-4074 (ACC inhibitor) reduce fibrosis in vivo. Altogether, our work demonstrate that metabolic defect is integral to TGF-ß signaling and fibrosis.

PCSK9 is expressed in pancreatic delta-cells and does not alter insulin secretion.

PCSK9 (Proprotein Convertase Subtilisin Kexin type 9) is a proprotein convertase that plays a key role in cholesterol homeostasis by decreasing hepatic low-density lipoprotein receptor (LDLR) protein expression. Here, we investigated the expression and the function of PCSK9 in pancreatic islets. Immunohistochemistry analysis showed that PCSK9 co-localized specifically with somatostatin in human pancreatic delta-cells, with no expression in alpha- and beta-cells. PCSK9 seems not to be secreted by mouse isolated islets maintained in culture. Pcsk9-deficiency led to a 200% increase in LDLR protein content in mouse isolated islets, mainly in beta-cells. Conversely, incubation of islets with recombinant PCSK9 almost abolished LDLR expression. However, Pcsk9-deficiency did not alter cholesterol content nor glucose-stimulated insulin secretion in mouse islets. Finally, invivo glucose tolerance was similar in Pcsk9(+/+) and Pcsk9(-/-) mice under basal conditions and following streptozotocin treatment. These results suggest, at least in mice, that PCSK9 does not alter insulin secretion.

Activation of the farnesoid X receptor represses PCSK9 expression in human hepatocytes.

The purpose of this study was to determine whether bile acids (BAs) modulate hepatic pro-protein convertase subtilisin/kexin 9 (PCSK9) gene expression. Immortalized human hepatocytes were treated with various BAs. Chenodeoxycholic acid (CDCA) treatment specifically decreased both PCSK9 mRNA and protein contents. Moreover, activation of the BA-activated farnesoid X receptor (FXR) by its synthetic specific agonist GW4064 also decreased PCSK9 expression. Of functional relevance, coadministration of CDCA counteracted the statin-induced PCSK9 expression, leading to a potentiation of LDL receptor activity. This study suggests that a transcriptional repression of PCSK9 by CDCA or FXR agonists may potentiate the hypolipidemic effect of statins.

Galactosylated multimodular lipoplexes for specific gene transfer into primary hepatocytes.

BACKGROUND: Numerous synthetic cationic vectors have been synthesized and are successfully used for in vitro gene transfer but an excess of positive charges can lead to cytotoxicity and does not enable specific transfection. METHODS: We decided to develop alternative molecular systems consisting of neutral, colloidally stable bioassemblies equipped with ligands for specific cell targeting. Consequently, we directed our efforts toward the development of a multimodular non-viral gene delivery system consisting of a condensed core of DNA with cationic liposomes of bis(guanidinium)-tren-cholesterol and an external corona of poly(ethylene oxide) stretches harbored by the steric stabilizers used to stabilize lipoplexes colloidally. A ligand capable of cell targeting by receptor-mediated endocytosis was covalently linked at the poly(ethylene oxide) extremity of steric stabilizers. Steric stabilizers were functionalized by a one-step enzymatic galactosylation to develop new supramolecular assemblies of lipoplexes able to target asialoglycoprotein receptors located on primary hepatocytes. RESULTS: Cryo-TEM and fluorescence experiments showed that DNA was condensed within lamellar complexes whose size ranged between 100 to 300 nm in diameter. Bis(guanidinium)-tren-cholesterol-DNA lipoplexes, colloidally stabilized by galactosylated steric stabilizers at a galactosylated steric stabilizer/DNA ratio of 300, led to specific transfection of primary hepatocytes whereas ungalactosylated steric stabilizer did not transfect. CONCLUSIONS: Our findings confirm the receptor-mediated endocytosis pathway of galactosylated multimodular lipoplexes. Thus, we conclude that the fabrication of a multimodular assembly harboring a ligand without non-specific interaction with cell membranes is possible and a highly promising system to transfect other primary or cultured cells specifically through a receptor-dependent mechanism.

Retinoic acid receptor-mediated induction of ABCA1 in macrophages.

ABCA1, the mutant molecule in Tangier Disease, mediates efflux of cellular cholesterol to apoA-I and is induced by liver X receptor (LXR)/retinoid X receptor (RXR) transcription factors. Retinoic acid receptor (RAR) activators (all-trans-retinoic acid [ATRA] and TTNPB) were found to increase ATP-binding cassette transporter 1 (ABCA1) mRNA and protein in macrophages. In cellular cotransfection assays, RARgamma/RXR activated the human ABCA1 promoter, via the same direct repeat 4 (DR4) promoter element as LXR/RXR. Chromatin immunoprecipitation analysis in macrophages confirmed the binding of RARgamma/RXR to the ABCA1 promoter DR4 element in the presence of ATRA, with weaker binding of RARalpha/RXR, and no binding of RARbeta/RXR. However, in macrophages from RARgamma(-/-) mice, TTNPB still induced ABCA1, in association with marked upregulation of RARalpha, suggesting that high levels of RARalpha can compensate for the absence of RARgamma. Dose-response experiments with ATRA in mouse primary macrophages showed that other LXR target genes were weakly induced (ABCG1 and SREBP-1c) or not induced (apoE and LXRalpha). The more specific RAR activator TTNPB did not induce SREBP-1c in mouse primary macrophages or liver. These studies indicate a direct role of RARgamma/RXR in induction of macrophage ABCA1.

PCSK9: a promising therapeutic target for dyslipidemias?

PCSK9 is the third gene to be implicated in autosomal dominant hypercholesterolemia. The recent discovery of mutations in PCSK9 protein associated with low plasma low-density lipoprotein in humans, the characterization of PCSK9-deficient mice hypersensitive to statins and the severely pathological phenotype of D374Y PCSK9-mutated patients shed a new light on this gene: is it a promising therapeutic target for dyslipidemias?

Fasting induces hyperlipidemia in mice overexpressing proprotein convertase subtilisin kexin type 9: lack of modulation of very-low-density lipoprotein hepatic output by the low-density lipoprotein receptor.

Several proprotein convertase subtilisin kexin type 9 (PCSK9) mutations lead to familial hypercholesterolemia by virtue of its role as a negative modulator of the low-density lipoprotein receptor (LDLr). Here, we uncover that upon dietary challenge, the down-regulation of the LDLr is also a key mechanism by which PCSK9 modulates the hepatic production of apolipoprotein-B-containing lipoproteins. Thus, adenoviral-mediated overexpression of PCSK9 in 24-h fasted mice results in massive hyperlipidemia, due to a striking increase in very-low-density lipoprotein (VLDL) triglycerides and apolipoprotein B100 hepatic output. Similar studies in LDLr (-/-) mice demonstrate that PCSK9-mediated alteration of VLDL output in the fasted state requires the LDLr. This increased production of VLDL was associated with a concomitant reduction of intrahepatic lipid stores as well as a lack of down-regulation of peroxisome proliferator-activated receptor-alpha activity and target genes expression. Finally, we show that PCSK9 hepatic expression is inhibited by the hypotriglyceridemic peroxisome proliferator-activated receptor-alpha agonist fenofibrate. In summary, the negative modulation of LDLr expression by PCSK9, which decreases plasma LDL clearance, also promotes an overproduction of nascent VLDL in vivo upon fasting.

Apolipoprotein B100 metabolism in autosomal-dominant hypercholesterolemia related to mutations in PCSK9.

OBJECTIVE: We have reported further heterogeneity in familial autosomal-dominant hypercholesterolemia (FH) related to mutation in proprotein convertase subtilisin/kexin type 9 (PCSK9) gene previously named neural apoptosis regulated convertase 1 (Narc-1). Our aim was to define the metabolic bases of this new form of hypercholesterolemia. METHODS AND RESULTS: In vivo kinetics of apolipoprotein B100-containing lipoproteins using a 14-hour primed constant infusion of [2H3] leucine was conducted in 2 subjects carrying the mutation S127R in PCSK9, controls subjects, and FH subjects with known mutations on the low-density lipoprotein (LDL) receptor gene (LDL-R). Apo B100 production, catabolism, and transfer rates were estimated from very LDL (VLDL), intermediate-density lipoprotein (IDL), and LDL tracer enrichments by compartmental analysis. PCSK9 mutation dramatically increased the production rate of apolipoprotein B100 (3-fold) compared with controls or LDL-R mutated subjects, related to direct overproduction of VLDL (3-fold), IDL (3-fold), and LDL (5-fold). The 2 subjects also showed a decrease in VLDL and IDL conversion (10% to 30% of the controls). LDL fractional catabolic rate was slightly decreased (by 30%) compared with controls but still higher than LDL-R-mutated subjects. CONCLUSIONS: These results showed that the effect of the S127R mutation of PCSK9 on plasma cholesterol homeostasis is mainly related to an overproduction of apolipoprotein B100.

Plasma PCSK9 is a late biomarker of severity in patients with severe trauma injury.

CONTEXT: PCSK9 (proprotein convertase subtilisin kexin type 9) is a secreted protease that modulates cholesterol homeostasis by decreasing low-density lipoprotein receptor expression. Low levels of plasma lipoproteins are related to severity of illness and survival in patients of intensive care units (ICU). OBJECTIVE: The aim of the study was to investigate the regulation of plasma PCSK9 and its association with plasma lipid parameters and clinical markers of severity during critical illness. DESIGN AND PATIENTS: The plasma biobank from the previously published HYPOLYTE prospective study was used to measure PCSK9 concentrations by ELISA at days 0 and 8 in 111 patients admitted to surgical ICU for severe multiple trauma. Patients were randomly assigned to hydrocortisone therapy or placebo. RESULTS: Plasma PCSK9 levels were increased by 2-fold between days 0 and 8 (231 ± 116 vs 481 ± 227 ng/ml; P = .0001). Hydrocortisone therapy did not alter PCSK9 concentrations (451 ± 216 vs 511 ± 239 ng/ml in placebo group; P = .33). PCSK9 was positively associated with low-density lipoprotein-cholesterol (Pearson coefficient, 0.26; P = .007) at day 0, but not at day 8. At day 8, an inverse correlation was found between PCSK9 and high-density lipoprotein-cholesterol (ß = -653; P = .004). Although baseline PCSK9 concentrations were not associated to severity scores, PCSK9 values at day 8 were related to injury severity score (ß = 6.17; P = .0007), length of stay in ICU (ß = 6.14; P = .0001), and duration of both mechanical ventilation (ß = 8.26; P = .0001) and norepinephrine infusion (ß = 18.57; P = .015). CONCLUSIONS: Plasma PCSK9 appears as a late biomarker of illness severity in patients with severe multiple trauma.

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

BACKGROUND: PCSK9 (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. METHODS: We 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). FINDINGS: HF 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. CONCLUSIONS: Plasma 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.

Clinical aspects of PCSK9.

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a circulating protein that impairs LDL clearance by promoting the LDL receptor (LDLR) degradation. PCSK9 has emerged as a new pharmacological target for hypercholesterolemia, and different PCSK9 inhibitors are now evaluated in clinical trials. Here, we propose an overview of the clinical perspectives of PCSK9. First, we describe the clinical features of patients with PCSK9 mutations, and how these variations impact the cardiovascular risk. Then, we extensively discuss the potential role of circulating PCSK9 as a new biomarker of lipid metabolism. Indeed, many studies conducted in healthy and type 2 diabetic patients have tested the association of circulating PCSK9 with LDL-cholesterol as well as with multiple metabolic parameters. The overall picture of the clinical relevance of circulating PCSK9 is complicated by the effect of nutritional status and hypolipidemic drugs such as statins, fibrates, ezetimibe on plasma PCSK9 concentrations. Finally, we present a brief overview of the available therapeutic strategies to inhibit PCSK9.

Lack of association between plasma PCSK9 and LDL-apoB100 catabolism in patients with uncontrolled type 2 diabetes.

OBJECTIVE: Pro-protein convertase subtilisin/kexin type 9 (PCSK9) is a post-transcriptional inhibitor of LDL-receptor. In non-diabetic men, plasma PCSK9 levels were found to be inversely correlated with low-density lipoprotein (LDL) apolipoprotein B100 (apoB) fractional catabolic rate (FCR). Here, we aimed to determine the effect of type 2 diabetes on the association between plasma PCSK9 and FCR of LDL. METHODS: A kinetic study of LDL-apoB100, using stable isotopes, was performed in 38 individuals (20 men, 18 women) including 23 non-diabetic normolipidemic subjects and 15 patients with type 2 diabetes. RESULTS: In the non-diabetic group, plasma PCSK9 was positively correlated with LDL-C (r=0.64, p=0.001), apoB (r=0.67, p<0.001), and inversely correlated with LDL-apoB FCR (r=-0.61, p=0.002). In contrast, in type 2 diabetic patients, plasma PCSK9 was not associated with LDL-C, apoB and LDL-apoB FCR. However, the lack of association between PCSK9 and LDL-apoB FCR seemed to be limited to the patients with "uncontrolled" diabetes (HbA1c>7%) since a borderline significant negative correlation between PCSK9 and LDL FCR (r=-0.70, p=0.08) was retrieved in patients with HbA1c≤7%. In multivariate analysis, LDL-apoB FCR was independently associated with PCSK9 (p=0.001) and fasting glycaemia (log) (p=0.030) in the non-diabetic population and with PCSK9 (p=0.040) and HbA1c (p=0.029) in diabetic patients. CONCLUSION: Our data indicate that both PCSK9 and glycaemia are independent factors influencing LDL catabolism. Plasma PCSK9 influences significantly the catabolism of LDL-apoB100 in individuals without diabetes, but not in patients with uncontrolled type 2 diabetes. Thus, the influence of diabetes on LDL-apoB FCR catabolism may overwhelm the influence of PCSK9.