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Study objective: This systematic review and meta-analysis aimed to assess the efficacy and safety profile of treatment with inclisiran, a drug that has been recently approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Design: A systematic literature search was conducted in order to identify randomized controlled trials (RCTs) assessing the effect on lipoproteins and the safety profile of inclisiran. Results: Data were pooled from 5 RCTs, which included 4226 subjects. Meta-analyses of data suggested that the multiple-dose regimens of inclisiran yielded a significant reduction in serum levels of proprotein convertase subtilisin/kexin type 9 (MD = −78.23%, 95%CI: −86.74, −69.71) and low-density lipoprotein cholesterol (MD = −45.48%, 95%CI: −50.36%, −40.61%) throughout the studies. Furthermore, treatment with inclisiran significantly affected total cholesterol (MD = −13.67%, 95%CI: −20.78%, −6.57%), high-density lipoprotein cholesterol (MD = 8.29%, 95%CI: 4.66%,11.93%), non-HDL cholesterol (MD = −39.45%, 95%CI: −43.6%, −35.31%), apolipoprotein B (MD = −34.58%, 95%CI: −38.78%, −30.78%) and lipoprotein(a) (MD = −20.9%, 95%CI: −25.8%, −15.99%). Multiple-dose regimens of inclisiran were associated with increased risk of injection-site reactions (any reaction: OR = 5.86, 95%CI: 3.44, 9.98; mild reactions: OR = 5.19, 95%CI: 1.68, 16.07; moderate reactions: OR = 13.37, 95%CI: 3.17, 56.46), and bronchitis (OR = 1.58, 95%CI: 1.10, 2.26), while the incidence of the pre-specified exploratory CV endpoint significantly decreased at 18 months (OR = 0.74, 95%CI: 0.58, 0.94). Conclusion and relevance: Inclisiran has favourable effects on serum lipid levels and an acceptable safety profile. Further well-designed RCTs are needed to explore its longer-term safety.

This study investigated the effects of far-infrared (FIR) irradiation on low-density lipoprotein cholesterol (LDL-C) uptake by human hepatocellular carcinoma G2 (HepG2) cells via the regulation of proprotein convertase subtilisin/kexin type 9 (PCSK9). FIR irradiation for 30 min significantly decreased PCSK9 expression (p < 0.01) in HepG2 cells. FIR irradiation substantially increased the low-density lipoprotein receptor (p < 0.0001) and LDL-C uptake (p < 0.01). Activation of transient receptor potential vanilloid (TRPV) channels mimicked the effects of FIR irradiation, significantly decreasing the protein expression of PCSK9 (p < 0.05). Conversely, inhibition of TRP channels using ruthenium red reversed the reduction in PCSK9 protein expression following FIR irradiation (p < 0.01). The specific activation of TRPV4 using 4α-PDD mimicked the effect of FIR irradiation (p < 0.01), whereas PCSK9 reduction by FIR irradiation was significantly reversed by the inhibition of TRPV4 using RN1734 (p < 0.05). These findings implied that FIR irradiation emitted from a ceramic lamp specifically increased TRPV4 activity. These findings provide insights into a novel therapeutic approach using FIR irradiation for LDL-C regulation and its implications for cardiovascular health., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: The authors declare the following competing interests. Some of content in the manuscript also appear in the patent P2023-0130 KR registered in the Republic of Korea. The patent pertains to FIR irradiation emitted from ceramic and carbon, which is linked to the data presented in this manuscript, indicating PCSK9 reduction. Ewha Womans University and the Korea Carbon Industry Promotion Agency (KCARBON) are the beneficiaries or potential beneficiaries of the patent., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background and Aims: Previous studies have not found a consistent association between circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) levels and the risk of cardiovascular events partly due to measurement methods that cannot distinguish between uncleaved and furin-cleaved forms of PCSK9., Methods: This is a prespecified sub-study of the REAL-CAD study which is a prospective, multicenter, randomized trial to compare high- versus low-dose statin in patients with stable coronary artery disease (CAD). The primary endpoint was major adverse cerebrovascular and cardiovascular events (MACCE) defined as a composite of cardiovascular death, nonfatal myocardial infarction, nonfatal ischemic stroke, or unstable angina requiring emergency hospitalization. In this case-cohort study, serum mature (uncleaved) and furin-cleaved PCSK9 levels obtained at 6 months after randomization were measured among 426 participants who developed MACCE (cases) and 1,478 randomly selected participants (sub-cohort)., Results: From 1,478 patients in sub-cohort, the Cox proportional hazards models with a pseudolikelihood method for case-cohort design revealed that the risk of the primary endpoint in patients with the highest quartile of mature PCSK9 levels was similar to that in the lowest quartile (hazard ration [HR] 0.809; 95% confidence intervals [CI], 0.541-1.209). Similarly, the HR for the highest to lowest quartiles of furin-cleaved PCSK9 was 0.948 [95% CI, 0.645-1.392] (P = 0.784). Compared to the lowest quartile, neither serum mature nor furin-cleaved PCSK9 levels predicted MACCE., Conclusions: In a large-scale secondary prevention cohort, serum mature and furin-cleaved PCSK9 levels did not provide useful information for predicting future cardiovascular events in statin-treated patients with stable CAD., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Kiyoshi Hibi reports financial support was provided by the Public Health Research Foundation. Kiyoshi Hibi reports financial support was provided by Kowa. Kiyoshi Hibi reports a relationship with Abbott Medical that includes: speaking and lecture fees. Kiyoshi Hibi reports a relationship with Daiichi Sankyo that includes: speaking and lecture fees. Kiyoshi Hibi reports a relationship with Medtronic that includes: speaking and lecture fees. Kiyoshi Hibi reports a relationship with the Research Institute for Production Development that includes: funding grants. Kiyoshi Hibi reports a relationship with Japan Medical Device Corporation that includes: funding grants. Kiyoshi Hibi reports a relationship with Abbott Medical that includes: funding grants. Kiyoshi Hibi reports a relationship with NIPRO that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Inc.)

Very few studies have investigated the interrelations between proprotein convertase subtilisin/kexin type 9 (PCSK9) metabolism, cholesterol synthesis, and cholesterol absorption. We aimed to address this issue in a large clinical trial of 245 patients with hypercholesterolemia. Serum lipids, PCSK9, lathosterol (cholesterol synthesis marker), campesterol, and sitosterol (cholesterol absorption markers) were measured before and 4–8 weeks after the start of treatment with PCSK9-antibodies (alirocumab or evolocumab). The patients had mean (standard error) LDL-cholesterol and PCSK9 concentrations of 3.87 (0.10) mmol/l and 356 (17) ng/ml, respectively. Eighty-four patients received no lipid-lowering pretreatment, 26 ezetimibe, 38 statins, and 97 ezetimibe + statins. Circulating PCSK9 increased in parallel with the potency of lipid-lowering pretreatment with circulating PCSK9 being highest in the ezetimibe + statin group (P < 0.001). Treatment with PCSK9-antibodies strongly decreased LDL-cholesterol, lathosterol, campesterol, and sitosterol (all P < 0.001) but hardly affected noncholesterol sterol to cholesterol ratios. Lipid-lowering pretreatment was not associated with the effects of PCSK9-antibodies on noncholesterol sterols (all P > 0.05). Summing up, circulating PCSK9 is increased by cholesterol synthesis and absorption inhibitors. Increased PCSK9 expression may partly explain the strong reductions of LDL-cholesterol achieved with PCSK9-antibodies after such pretreatment. On the other hand, treatment with PCSK9-antibodies does not significantly change the balance between cholesterol synthesis and absorption.

After training as a gastroenterologist in the UK, the author became interested in lipidology while he was a research fellow in the USA and switched careers after returning home. Together with Nick Myant, he introduced the use of plasma exchange to treat familial hypercholesterolemia (FH) homozygotes and undertook non-steady state studies of LDL kinetics, which showed that the fractional catabolic rate of LDL remained constant irrespective of pool size. Subsequent steady-state turnover studies showed that FH homozygotes had an almost complete lack of receptor-mediated LDL catabolism, providing in vivo confirmation of the Nobel Prize-winning discovery by Goldstein and Brown that LDL receptor dysfunction was the cause of FH. Further investigation of metabolic defects in FH revealed that a significant proportion of LDL in homozygotes and heterozygotes was produced directly via a VLDL-independent pathway. Management of heterozygous FH has been greatly facilitated by statins and proprotein convertase subtilisin/kexin type 9 inhibitors but remains dependent upon lipoprotein apheresis in homozygotes. In a recent analysis of a large cohort treated with a combination of lipid-lowering measures, survival was markedly enhanced in homozygotes in the lowest quartile of on-treatment serum cholesterol. Emerging therapies could further improve the prognosis of homozygous FH; whereas in heterozygotes, the current need is better detection.

Background and Aims: Long noncoding RNAs (lncRNAs) play important roles in the progression of atherosclerosis. In this study, we identified an uncharacterized lncRNA, Liver Expressions by PSRC1 Induced Specifically (LEPIS). This study aimed to clarify the mechanism though which LEPIS affects atherosclerosis (AS)., Methods: The expression of LEPIS and its potential target, tropomodulin 4 (TMOD4), was increased in the livers of ApoE -/- mice fed a high-fat diet (HFD). An ApoE -/- mouse model in which LEPIS or TMOD4 was overexpressed in the liver was established. The plaque load in the aorta was assessed, plasma was collected to measure blood lipid levels, and the liver was collected to study cholesterol metabolism., Results: We found that both LEPIS and TMOD4 increased the AS burden and reduced hepatic cholesterol levels. A further study revealed that LEPIS and TMOD4 affected the expression of genes related to hepatic cholesterol homeostasis, including proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR), which are closely related to hypercholesterolemia. Mechanistically, human antigen R (HuR), an RNA-binding protein (RBP), was shown to be critical for the regulation of TMOD4 by LEPIS. Furthermore, we found that verexpression of LEPIS promoted the shuttling of HuR from the nucleus to the cytoplasm, enhanced the stability of TMOD4 mRNA, and in turn promoted the expression of TMOD4. In addition, TMOD4 was found to affect intracellular cholesterol levels through PCSK9., Conclusions: These results suggest that the LEPIS-HuR-TMOD4 axis is a potential intervention target for dysregulated hepatic cholesterol homeostasis and AS and may provide the basis for further reductions in the circulating LDL-C concentration and arterial plaque burden., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: The association between serum uric acid (SUA) levels and serum PCSK9 levels has not yet been uncovered. This study aimed to explore the potential link between SUA levels and serum PCSK9 levels and quantify the mediating effect of metabolic factors and inflammation in Chinese adults. Furthermore, assessed whether gender differences modified this association., Methods: In total, 2624 participants were enrolled and categorized based on their serum UA levels as the hypouricemic (n = 432) and normouricemic group (n = 2192). Stepwise multivariable regression analysis, binary logistic regression analysis and mediation analyses were performed., Results: Participants with hyperuricemia had higher serum PCSK9 levels than those with normouricemia (73.74 ± 30.25 vs 68.55 ± 29.01 ng/ml, P < 0.05), especially in women (69.11 ± 28.84 vs 87.86 ± 27.90 ng/ml, P < 0.001). SUA levels were positively associated with serum PCSK9 levels in all participants (r = 0.06, P < 0.01) and in women (r = 0.22, P < 0.01), but not in men (r = 0.03, P = 0.18). Multiple linear regression and binary logistic regression analyses indicated that serum PCSK9 levels were significantly correlated with SUA levels and hyperuricemia in women. However, when the model was adjusted for triglyceride (TG), the associations of serum PCSK9 levels with SUA levels and hyperuricemia disappeared. In mediation analyses, TG, low-density lipoprotein cholesterol (LDL-C), body mass index(BMI), total cholesterol (TC), white blood cell count and neutrophil count explained 35.08 %, 20.58 %,19.99 %, 14.37 %, 7.10 % and 3.24 % of SUA levels association with serum PCSK9 levels, respectively., Conclusion: Serum PCSK9 levels are positively associated with SUA levels in women. Furthermore, this association is partially mediated through metabolic factors and inflammation., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest., (Copyright © 2024. Published by Elsevier Inc.)

Background: Clinical diagnostic criteria of familial hypercholesterolemia (FH) in Japan include LDL cholesterol ​≥ ​180 ​mg/dL, Achilles tendon thickness ​≥ ​9.0 ​mm, and family history. However, few data exist regarding its validation. Design and Methods: A series of 680 participants, with a mean LDL cholesterol of 175 ​mg/dL were enrolled at Kanazawa University Hospital between 2006 and 2018. All had full assessments of, LDL cholesterol, Achilles tendon X-rays, family history records, and genetic analysis of FH-associated genes (LDLR, APOB, and PCSK9). The area under the curve (AUC) of receiver operating characteristic (ROC) curve analysis predicting the presence of FH mutations by each clinical marker were assessed. Results: The optimal cutoff values predicting the presence of an FH-associated mutation were 181 ​mg/dL for LDL cholesterol and ≥7.0 ​mm for Achilles tendon thickness. AUCs predicting FH mutations were 0.827 for Achilles tendon thickness ≥9.0 ​mm, 0.889 for LDL cholesterol ≥180 ​mg/dL, and 0.906 for family history. If Achilles tendon thickness ≥7.0 ​mm was used as a clinical criterion, then 41 participants (6%) were newly diagnosed with FH and 86 (12%) were newly misclassified as FH. Conclusions: Current clinical diagnostic criteria of FH were validated in this cohort. We recommend considering a tentative diagnosis of “potential FH” if the Achilles tendon thickness is ​≥ ​7.0 ​mm and

Intestinal triglyceride (TG)-rich lipoproteins (TRLs) are important in the pathogenesis of atherosclerosis in insulin resistance (IR). We investigated the association of plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) concentrations with apoB-48-containing TRL metabolism in 148 men displaying various degrees of IR by measuring in vivo kinetics of TRL apoB-48 during a constant-fed state after a primed-constant infusion of L-[5,5,5-D3]leucine. Plasma PCSK9 concentrations positively correlated with TRL apoB-48 pool size (r = 0.31, P = 0.0002) and production rate (r = 0.24, P = 0.008) but not the fractional catabolic rate (r = −0.04, P = 0.6). Backward stepwise multiple linear regression analysis identified PCSK9 concentrations as a positive predictor of TRL apoB-48 production rate (standard β = +0.20, P = 0.007) independent of BMI, age, T2D/metformin use, dietary fat intake during the kinetic study, and fasting concentrations of TGs, insulin, glucose, LDL cholesterol, or C-reactive protein. We also assessed intestinal expression of key genes involved in chylomicron processing from duodenal samples of 71 men. Expression of PCSK9 and HMG-CoAR genes was positively associated (r = 0.43, P = 0.002). These results support PCSK9 association with intestinal secretion and plasma overaccumulation of TRL apoB-48 in men with IR.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) interacts directly with cytoplasmic apoB and prevents its degradation via the autophagosome/lysosome pathway. This process affects VLDL and LDL production and influences atherogenesis. Here, we investigated the molecular machinery by which PCSK9 modulates autophagy and affects atherogenesis. We backcrossed Pcsk9−/− mice with atherosclerosis-prone Ldlr−/−Apobec1−/− (LDb) mice to generate Ldlr−/−Apobec1−/−Pcsk9−/− (LTp) mice. Deletion of PCSK9 resulted in decreased hepatic apoB secretion, increased autophagic flux, and decreased plasma levels of IDL and LDL particles. The LDLs from LTp mice (LTp-LDLs) were less atherogenic and contained less cholesteryl ester and phospholipids than LDb-LDLs. Moreover LTp-LDLs induced lower endothelial expression of the genes encoding TLR2, Lox-1, ICAM-1, CCL2, CCL7, IL-6, IL-1β, Beclin-1, p62, and TRAF6. Collectively, these effects were associated with substantially less atherosclerosis development (>4-fold) in LTp mice. The absence of PCSK9 in LDb mice results in decreased lipid and apoB levels, fewer atherogenic LDLs, and marked reduction of atherosclerosis. The effect on atherogenesis may be mediated in part by the effects of modified LDLs on endothelial cell receptors and proinflammatory and autophagy molecules. These findings suggest that there may be clinical benefits of PCSK9 inhibition due to mechanisms unrelated to increased LDL receptor activity.

In patients with chronic hepatitis C virus (HCV) infection, viral hijacking of the host-cell biosynthetic pathways is associated with altered lipid metabolism, which contributes to disease progression and may influence antiviral response. We investigated the molecular interplay among four key regulators of lipid homeostasis [microRNA (miR)-122, miR-24, miR-223, and proprotein convertase subtilisin/kexin type 9 (PCSK9)] in HCV-infected patients (n = 72) who achieved a treatment-based viral cure after interferon-based therapy with first-generation direct-acting antivirals. Real-time PCR was used to quantify microRNA plasma levels, and ELISA assays were used to determine plasma concentrations of PCSK9. We report that levels of miR-24 and miR-223 significantly increased in patients achieving sustained virologic response (SVR), whereas the levels of miR-122, a liver-specific cofactor for HCV infection, decreased in these patients. PCSK9 concentrations were significantly increased in SVRs, suggesting that PCSK9 may help impede viral infection. The modulatory effect of PCSK9 on HCV infection was also demonstrated in the context of HCV-infected Huh-7.5.1 cells employing recombinant human PCSK9 mutants. Together, these results provide insights into a novel coordinated interplay among three important molecular players in lipid homeostasis — circulating miR-24, miR-223 and PCSK9 — whose regulation is affected by HCV infection and treatment-based viral cure.

Monitoring the expression of cell-surface receptors, their interaction with extracellular ligands, and their fate upon ligand binding is important for understanding receptor function and developing new therapies. We describe a cell-based method that utilizes bioluminescent protein complementation technology to interrogate binding of a cellular receptor with its extracellular protein ligand, specifically LDL receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9). Purified, full-length tagged PCSK9 is added to assay wells containing cells that stably express LDLR with an extracellular complementary tag. When the tagged PCSK9 binds the receptor, a bright luminescence signal is generated. The interaction is detected at the cell membrane with add-and-read simplicity, no wash steps, and flexibility, allowing data to be collected in endpoint format, kinetically, or with bioluminescent imaging. The assay is flexible, is rapid, and reports accurate biology. It is amenable to 96-well and 384-well formats, and the robustness allows for screening of new drug candidates (Z′ = 0.83). The assay reports correct potencies for antibody titrations across a 50%–150% potency range and detects potency changes due to heat stress, suggesting that it may be useful during drug development. This assay technology can be broadly applied when studying other receptors with their extracellular ligands, whether protein or small-molecule binding partners.

Background: Oxidized forms of cholesterol (oxysterols) are implicated in atherogenesis and can accumulate in the body via direct absorption from food or through oxidative reactions of endogenous cholesterol, inducing the formation of LDL particles loaded with oxidized cholesterol. It remains unknown whether drastic reductions in LDL-cholesterol (LDL-C) are associated with changes in circulating oxysterols and whether small dense LDL (sdLDL) are more likely to carry these oxysterols and susceptible to the effects of PCSK9 inhibition (PCSK9i)., Objective: We investigate the effect of LDL-C reduction accomplished via PCSK9i on changes in plasma levels of sdLDL-cholesterol (sdLDL-C) and a common, stable oxysterol, 7-ketocholesterol (7-KC), among 134 patients referred to our Preventive Cardiology clinic., Methods: Plasma lipid panel, sdLDL-C, and 7-KC measurements were obtained from patients before and after initiation of PCSK9i., Results: The intervention caused a significant lowering of LDL-C (-55.4 %). The changes in sdLDL-C levels (mean reduction 51.4 %) were highly correlated with the reductions in LDL-C levels (R = 0.829, p < 0.001). Interestingly, whereas changes in plasma free 7-KC levels with PCSK9i treatment were much smaller than (-6.6 %) and did not parallel those of LDL-C and sdLDL-C levels, they did significantly correlate with changes in triglycerides and very low-density lipoprotein-cholesterol (VLDL-C) levels (R = 0.219, p = 0.025)., Conclusion: Our findings suggest a non-preferential clearance of LDL subparticles as a consequence of LDL receptor upregulation caused by PCSK9 inhibition. Moreover, the lack of significant reduction in 7-KC with PCSK9i suggests that 7-KC may be in part carried by VLDL and lost during lipoprotein processing leading to LDL formation., (Copyright © 2023. Published by Elsevier Inc.)

The effects of cholesterol-lowering drugs, including those that reduce cholesterol synthesis (statins) and those that reduce cholesterol absorption (ezetimibe), on cholesterol absorption and synthesis are well understood. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are a novel class of cholesterol-lowering drugs that robustly reduce LDL-cholesterol (LDL-C), but little is known about their effects on cholesterol absorption and synthesis. We evaluated how treatment with evolocumab, a fully human monoclonal IgG2 antibody to PCSK9, affects markers of cholesterol synthesis and absorption by measuring these markers in patients from an evolocumab clinical trial. At 2 weeks, changes in β-sitosterol/total cholesterol (TC) from baseline were 4% for placebo, 10% for evolocumab 140 mg (nonsignificant vs. placebo), and 26% for evolocumab 420 mg (P < 0.001 vs. placebo). Changes in campesterol/TC at week 2, relative to baseline between placebo and evolocumab, were all nonsignificant. Evolocumab had a modest effect on markers of cholesterol synthesis. At 2 weeks, changes in desmosterol/TC were 1% for placebo, 7% for evolocumab 140 mg (nonsignificant vs. placebo), and 15% for evolocumab 420 mg (P < 0.01 vs. placebo). Changes from baseline in lathosterol/TC at week 2 between placebo and evolocumab were nonsignificant. These results suggest that evolocumab has a modest effect on cholesterol synthesis and absorption despite significant LDL-C lowering.

Lipoprotein (a) [Lp(a)] is independently associated with CVD risk. Evolocumab, a monoclonal antibody (mAb) to proprotein convertase subtilisin/kexin type 9 (PCSK9), decreases Lp(a). The potential mechanisms were assessed. A pooled analysis of Lp(a) and LDL cholesterol (LDL-C) in 3,278 patients from 10 clinical trials (eight phase 2/3; two extensions) was conducted. Within each parent study, biweekly and monthly doses of evolocumab statistically significantly reduced Lp(a) at week 12 versus control (P < 0.001 within each study); pooled median (quartile 1, quartile 3) percent reductions were 24.7% (40.0, 3.6) and 21.7% (39.9, 4.2), respectively. Reductions were maintained through week 52 of the open-label extension, and correlated with LDL-C reductions [with and without correction for Lp(a)-cholesterol] at both time points (P < 0.0001). The effect of LDL and LDL receptor (LDLR) availability on Lp(a) cell-association was measured in HepG2 cells: cell-associated LDL fluorescence was reversed by unlabeled LDL and Lp(a). Lp(a) cell-association was reduced by coincubation with LDL and PCSK9 and reversed by adding PCSK9 mAb. These studies support that reductions in Lp(a) with PCSK9 inhibition are partly due to increased LDLR-mediated uptake. In most situations, Lp(a) appears to compete poorly with LDL for LDLR binding and internalization, but when LDLR expression is increased with evolocumab, particularly in the setting of low circulating LDL, Lp(a) is reduced.

The transcription factors hepatic nuclear factor (HNF)1α and HNF1β can bind to the HNF1 site on the proprotein convertase subtilisin/kexin type 9 (PCSK9) promoter to activate transcription in HepG2 cells. However, it is unknown whether one or both HNF1 factors are obligatory for transactivating hepatic PCSK9 gene expression in vivo. We developed shRNA adenoviral constructs (Ad-shHNF1α and Ad-shHNF1β) to examine the effects of knockdown of HNF1α or HNF1β on PCSK9 expression and its consequent impact on LDL receptor (LDLR) protein levels in cultured hepatic cells and liver tissue. We demonstrated that infection with Ad-shHNF1α, but not Ad-shHNF1β, markedly reduced PCSK9 mRNA expression in HepG2 cells with a concomitant increase in LDLR protein abundance. Injecting Ad-shHNF1α in mice fed a normal diet significantly (∼50%) reduced liver mRNA expression and serum concentration of PCSK9 with a concomitant increase (∼1.9-fold) in hepatic LDLR protein abundance. Furthermore, we observed a modest but significant reduction in circulating LDL cholesterol after knockdown of HNF1α in these normolipidemic mice. Consistent with the observation that knockdown of HNF1β did not affect PCSK9 mRNA or protein expression in cultured hepatic cells, Ad-shHNF1β infection in mice resulted in no change in the hepatic mRNA expression or serum content of PCSK9. Altogether, our study demonstrates that HNF1α, but not HNF1β, is the primary positive regulator of PCSK9 transcription in mouse liver.

Pharmacologically increased estrogen levels have been shown to lower hepatic and plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) levels in animals and humans. We hypothesized that physiological changes in estrogen levels influence circulating PCSK9, thereby contributing to the known wide inter-individual variation in its plasma levels, as well as to the established increase in LDL cholesterol (LDL-C) with normal aging. Circulating PCSK9, estradiol, and other metabolic factors were determined in fasting samples from 206 female and 189 male healthy volunteers (age 20–85 years), The mean levels of PCSK9 were 10% higher in females than in males (P < 0.05). PCSK9 levels were 22% higher in postmenopausal than in premenopausal (P < 0.001) females. Within the group of premenopausal females, circulating PCSK9 correlated inversely to estrogen levels, and PCSK9 was higher (305 ng/ml) in the follicular phase than in the ovulatory (234 ng/ml) or the luteal (252 ng/ml) phases (P < 0.05). Changes in endogenous estrogen levels during the menstrual cycle likely contribute to the broad inter-individual variation in PCSK9 and LDL-C in normal females. PCSK9 levels increase in females after menopause but not in men during this phase in life. This likely contributes to why LDL-C in women increases in this period.

LDL cholesterol (LDL-C) contributes to coronary heart disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) increases LDL-C by inhibiting LDL-C clearance. The therapeutic potential for PCSK9 inhibitors is highlighted by the fact that PCSK9 loss-of-function carriers exhibit 15–30% lower circulating LDL-C and a disproportionately lower risk (47–88%) of experiencing a cardiovascular event. Here, we utilized pcsk9−/− mice and an anti-PCSK9 antibody to study the role of the LDL receptor (LDLR) and ApoE in PCSK9-mediated regulation of plasma cholesterol and atherosclerotic lesion development. We found that circulating cholesterol and atherosclerotic lesions were minimally modified in pcsk9−/− mice on either an LDLR- or ApoE-deficient background. Acute administration of an anti-PCSK9 antibody did not reduce circulating cholesterol in an ApoE-deficient background, but did reduce circulating cholesterol (−45%) and TGs (−36%) in APOE*3Leiden.cholesteryl ester transfer protein (CETP) mice, which contain mouse ApoE, human mutant APOE3*Leiden, and a functional LDLR. Chronic anti-PCSK9 antibody treatment in APOE*3Leiden.CETP mice resulted in a significant reduction in atherosclerotic lesion area (−91%) and reduced lesion complexity. Taken together, these results indicate that both LDLR and ApoE are required for PCSK9 inhibitor-mediated reductions in atherosclerosis, as both are needed to increase hepatic LDLR expression.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a potential novel strategy for treatment of CVD. Alirocumab is a fully human PCSK9 monoclonal antibody in phase 3 clinical development. We evaluated the antiatherogenic potential of alirocumab in APOE*3Leiden.CETP mice. Mice received a Western-type diet and were treated with alirocumab (3 or 10 mg/kg, weekly subcutaneous dosing) alone and in combination with atorvastatin (3.6 mg/kg/d) for 18 weeks. Alirocumab alone dose-dependently decreased total cholesterol (−37%; −46%, P < 0.001) and TGs (−36%; −39%, P < 0.001) and further decreased cholesterol in combination with atorvastatin (−48%; −58%, P < 0.001). Alirocumab increased hepatic LDL receptor protein levels but did not affect hepatic cholesterol and TG content. Fecal output of bile acids and neutral sterols was not changed. Alirocumab dose-dependently decreased atherosclerotic lesion size (−71%; −88%, P < 0.001) and severity and enhanced these effects when added to atorvastatin (−89%; −98%, P < 0.001). Alirocumab reduced monocyte recruitment and improved the lesion composition by increasing the smooth muscle cell and collagen content and decreasing the macrophage and necrotic core content. Alirocumab dose-dependently decreases plasma lipids and, as a result, atherosclerosis development, and it enhances the beneficial effects of atorvastatin in APOE*3Leiden.CETP mice. In addition, alirocumab improves plaque morphology.

Diabetes mellitus (DM) is strongly associated with an increased risk of atherosclerotic cardiovascular disease (ASCVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9) was recently identified as an important regulator of circulating low-density lipoprotein-cholesterol (LDL-C) levels via degradation of the LDL receptor, proving to be a valid target to improve lipoprotein profiles and cardiovascular outcomes in patients with ASCVD. Beyond LDL receptor processing and cholesterol homeostasis, the PCSK9 protein has recently been verified to be associated with glucose metabolism. Importantly, clinical trials suggest that treatment with PCSK9 inhibitors for patients with DM is more effective. Hence, in this review, we summarize the current findings derived from experimental, preclinical, and clinical studies regarding the association between PCSK9 and glucose metabolism, including the relationship of PCSK9 genetic mutations to glucose metabolism and diabetes, the link between plasma PCSK9 concentrations and glucose metabolic parameters, the effects of glucose-lowering drugs on plasma PCSK9 levels and the impacts of PCSK9 inhibitors on cardiovascular outcomes of patients with DM. Clinically, exploring this field may improve our understanding regarding the roles of PCSK9 in glucose metabolism and may offer an in-depth interpretation of how PCSK9 inhibitors exert effects on the treatment of patients with DM., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

PCSK9 proprotein convertase subtilisin/kexin type (PCSK9) is a crucial protein in LDL cholesterol (LDL-C) metabolism by virtue of its pivotal role in the degradation of the LDL receptor. In recent years, both in vitro and in vivo studies have greatly supplemented our understanding of the (patho)physiological role of PCSK9 in human biology. In the current review, we summarize studies published or in print before May 2012 concerning the physiological role of PCSK9 in cholesterol metabolism. Moreover, we briefly describe the clinical phenotypes encountered in carriers of mutations in the gene encoding PCSK9. As PCSK9 has emerged as a novel target for LDL-C lowering therapy, methods to inhibit PCSK9 will also be reviewed. Initial data from investigations of PCSK9 inhibition in humans are promising and indicate that PCSK9 inhibition may be a viable new therapeutic option for the treatment of dyslipidemia and associated cardiovascular diseases.

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. In this study, we investigated the role of the C-terminal domain for the activity of PCSK9. Experiments in which conserved residues and histidines on the surface of the C-terminal domain were mutated indicated that no specific residues of the C-terminal domain, apart from those responsible for maintaining the overall structure, are required for the activity of PCSK9. Rather, the net charge of the C-terminal domain is important. The more positively charged the C-terminal domain, the higher the activity toward the LDLR. Moreover, replacement of the C-terminal domain with an unrelated protein of comparable size led to significant activity of the chimeric protein.We conclude that the role of the evolutionary, poorly conserved C-terminal domain for the activity of PCSK9 reflects its overall positive charge and size and not the presence of specific residues involved in protein-protein interactions.

Introduction. Familial hypobetalipoproteinemia (FHBL) is an autosomal dominant disease characterized by abnormally low levels of apolipoprotein-B (apoB) containing lipoproteins. FHBL is caused by APOB, PCSK9 or ANGPTL3 mutations or is associated with loci located in chromosomes 10 and 3p21. However, other genes should be involved. This study describes the kinetic parameters of the apoB containing lipoproteins and sequence abnormalities of the APOB and PCSK9 genes of FHBL patients identified in a large hospital based survey.Material and methods. Cases with primary or secondary causes of hypobetalipoproteinemia were identified. ApoB kinetics were measured in cases with primary forms in whom truncated forms of apoB were not present in VLDL (n = 4). A primed constant infusion of [13C] leucine was administered, VLDL and LDL apoB production and catabolic rates measured by a multicompartmental model and compared to normolipemic controls. In addition, these subjects had an abdominal ultrasound and direct sequencing was carried out for the PCSK9 and apoB genes.Results. Three individuals had normal apoB production with increased catabolic rate; the remaining had reduced synthetic and catabolic rates. Various polymorphisms, some of them previously unreported (*), in the PCSK9 gene (R46L, A53V, I474V, D480N*, E498K*) and in the apoB gene (N441D*, Y1395C, P2712L, D2285E*, I2286V, T3540S*, T3799M*) were found in the FHBL patients. We found hepatic ultrasound changes of hepatic steatosis in only one of the four probands. Conclusion. FHBL without truncated apoB is a heterogeneous disease from a metabolic and a genetic perspective. Hypobetalipoproteinemia is a risk factor but not an obligate cause of steatosis.

PCSK9 degrades LDL receptor (LDLR) in liver and thereby influences the circulating level of LDL cholesterol. Hence, mechanisms inhibiting PCSK9 expression have potential for cholesterol-lowering intervention. Previously, we demonstrated that oncostatin M (OM) activates LDLR gene transcription, resulting in an increased LDL uptake in HepG2 cells and a reduction of plasma LDL in hypercholesterolemic hamsters. Here we identify the suppression of PCSK9 expression by OM as one new mechanism that increases LDLR protein in HepG2 cells. Treating HepG2 cells with OM decreases PCSK9 mRNA and protein levels. Inhibition studies and small interfering RNA -targeted depletion revealed a critical role for JAK1 and JAK2 in mediating this OM inhibitory effect. Furthermore, we showed that OM induces transient phosphorylation of STAT1, STAT3, and STAT5 and sustained activation of ERK signaling molecules. While depletion of STAT members in HepG2 cells did not affect OM inhibitory activity on PCSK9 expression, blocking activation of the MEK1/ERK signaling pathway resulted in attenuation of the OM inhibitory effect. Finally, by using an anti-hamster PCSK9 antibody, we demonstrated the in vivo suppression of liver PCSK9 mRNA and protein expression by OM in hypercholesterolemic hamsters. Our study uncovered a cytokine-triggered regulatory network for PCSK9 expression that is linked to JAKs and the ERK signaling pathway.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that regulates hepatic low-density lipoprotein receptor (LDLR) levels in humans. PCSK9 has also been shown to regulate the levels of additional membrane-bound proteins in vitro, including the very low-density lipoprotein receptor (VLDLR), apolipoprotein E receptor 2 (ApoER2) and the β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1), which are all highly expressed in the CNS and have been implicated in Alzheimer's disease. To better understand the role of PCSK9 in regulating these additional target proteins in vivo, their steady-state levels were measured in the brain of wild-type, PCSK9-deficient, and human PCSK9 overexpressing transgenic mice. We found that while PCSK9 directly bound to recombinant LDLR, VLDLR, and apoER2 protein in vitro, changes in PCSK9 expression did not alter the level of these receptors in the mouse brain. In addition, we found no evidence that PCSK9 regulates BACE1 levels or APP processing in the mouse brain. In conclusion, our results suggest that while PCSK9 plays an important role in regulating circulating LDL cholesterol levels by reducing the number of hepatic LDLRs, it does not appear to modulate the levels of LDLR and other membrane-bound proteins in the adult mouse brain.

The proprotein convertase subtilisin kexin-9 (PCSK9) circulates in plasma as mature and furin-cleaved forms. A polyclonal antibody against human PCSK9 was used to develop an ELISA that measures total plasma PCSK9 rather than only the mature form. A cross-sectional study evaluated plasma levels in normal (n = 254) and hypercholesterolemic (n = 200) subjects treated or untreated with statins or statin plus ezetimibe. In controls, mean plasma PCSK9 (89.5 ± 31.9 ng/ml) correlated positively with age, total cholesterol, LDL-cholesterol (LDL-C), triglycerides, and fasting glucose. Sequencing PCSK9 from individuals at the extremes of the normal PCSK9 distribution identified a new loss-of-function R434W variant associated with lower levels of circulating PCSK9 and LDL-C. In hypercholesterolemic subjects, PCSK9 levels were higher than in controls (99.3 ± 31.7 ng/ml, P < 0.04) and increased in proportion to the statin dose, combined or not with ezetimibe. In treated patients (n = 139), those with familial hypercholesterolemia (FH; due to LDL receptor gene mutations) had higher PCSK9 values than non-FH (147.01 ± 42.5 vs. 127.2 ± 40.8 ng/ml, P < 0.005), but LDL-C reduction correlated positively with achieved plasma PCSK9 levels to a similar extent in both subsets (r = 0.316, P < 0.02 in FH and r = 0.275, P < 0.009 in non-FH). The detection of circulating PCSK9 in both FH and non-FH subjects means that this assay could be used to monitor response to therapy in a wide range of patients.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is predominantly expressed in liver and regulates cholesterol metabolism by down regulating liver LDL receptor (LDLR) proteins. Here we report transgenic overexpression of human PCSK9 in kidney increased plasma levels of PCSK9 and subsequently led to a dramatic reduction in liver LDLR proteins. The regulation of LDLR by PCSK9 displayed tissue specificity, with liver being the most responsive tissue. Even though the PCSK9 transgene was highly expressed in kidney, LDLR proteins were suppressed to a lower extent in this tissue than in liver. Adrenal LDLR proteins were not regulated by elevated plasma PCSK9. hPCSK9 transgene expression and subsequent reduction of liver LDLR led to increases in plasma total cholesterol, LDL cholesterol, and ApoB, which were further increased by a high-fat, high-cholesterol diet. We also observed that the size distribution of hPCSK9 in transgenic mouse plasma was heterogeneous. In chow-fed mice, the majority of PCSK9 proteins were in free forms; however, feeding a high-fat, high-cholesterol diet resulted in a shift of hPCSK9 distribution toward larger complexes. PCSK9 distribution in human plasma also exhibited heterogeneity and individual variability in the percentage of PCSK9 in free form and in large complexes. We provide strong evidence to support that human PCSK9 proteins secreted from extrahepatic tissue are able to promote LDLR degradation in liver and increase plasma LDL. Our data also suggest that LDLR protein regulation by PCSK9 has tissue specificity, with liver being the most responsive tissue.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that regulates the expression of LDL receptor (LDLR) protein. Gain-of-function mutations in PCSK9 cause hypercholesterolemia, and loss-of-function mutations result in lower plasma LDL-cholesterol. Here, we investigate the kinetics and metabolism of circulating PCSK9 relative to tissue levels of LDLRs. The administration of recombinant human PCSK9 (32 μg) to mice by a single injection reduced hepatic LDLRs by ∼90% within 60 min, and the receptor levels returned to normal within 6 h. The half-life of the PCSK9 was estimated to be ∼5 min. Continuous infusion of PCSK9 (32 μg/h) into wild-type mice caused a ∼90% reduction in hepatic LDLRs within 2 h and no associated change in the level of LDLR in the adrenals. Parallel studies were performed using a catalytically inactive form of PCSK9, PCSK9(S386A), and similar results were obtained. Infusion of PCSK9(D374Y), a gain-of-function mutation, resulted in accelerated clearance of the mutant PCSK9 and a greater reduction in hepatic LDLRs. Combined, these data suggest that exogenously administrated PCSK9 in plasma preferentially reduces LDLR protein levels in liver at concentrations found in human plasma and that PCSK9's action on the LDLR is not dependent on catalytic activity in vivo.

Mutations within proprotein convertase subtilisin/kexin type 9 (PCSK9) are associated with dominant forms of familial hypercholesterolemia. PCSK9 binds the LDL receptor (LDLR), and addition of PCSK9 to cells promotes degradation of LDLR. PCSK9 mutant proteins associated with hypercholesterolemia (S127R and D374Y) are more potent in decreasing LDL uptake than is wild-type PCSK9. To better understand the mechanism by which mutations at the Ser127 and Asp374 residues of PCSK9 influence PCSK9 function, a limited vertical scanning mutagenesis was performed at both sites. S127R and S127K proteins were more potent in decreasing LDL uptake than was wild-type PCSK9, and each D374 mutant tested was more potent in reducing LDL uptake when the proteins were added exogenously to cells. The potencies of D374 mutants in lowering LDL uptake correlated with their ability to interact with LDLR in vitro. Combining S127R and D374Y was also found to have an additive effect in enhancing PCSK9's ability to reduce LDL uptake. Modeling of PCSK9 S127 and D374 mutations indicates that mutations that enhance PCSK9 function stabilize or destabilize the protein, respectively. In conclusion, these results suggest a model in which mutations at Ser127 and Asp374 residues modulate PCSK9's ability to regulate LDLR function through distinct mechanisms.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protease that regulates low density lipoprotein receptor (LDLR) protein levels. The mechanisms of this action, however, remain to be defined. We show here that recombinant human PCSK9 expressed in HEK293 cells was readily secreted into the medium, with the prosegment associated with the C-terminal domain. Secreted PCSK9 mediated cell surface LDLR degradation in a concentration- and time-dependent manner when added to HEK293 cells. Accordingly, cellular LDL uptake was significantly reduced as well. When infused directly into C57B6 mice, purified human PCSK9 substantially reduced hepatic LDLR protein levels and resulted in increased plasma LDL cholesterol. When added to culture medium, fluorescently labeled PCSK9 was endocytosed and displayed endosomal-lysosomal intracellular localization in HepG2 cells, as was demonstrated by colocalization with DiI-LDL. PCSK9 endocytosis was mediated by LDLR as LDLR deficiency (hepatocytes from LDLR null mice), or RNA interference-mediated knockdown of LDLR markedly reduced PCSK9 endocytosis. In addition, RNA interference knockdown of the autosomal recessive hypercholesterolemia (ARH) gene product also significantly reduced PCSK9 endocytosis. Biochemical analysis revealed that the LDLR extracellular domain interacted directly with secreted PCSK9; thus, overexpression of the LDLR extracellular domain was able to attenuate the reduction of cell surface LDLR levels by secreted PCSK9. Together, these results reveal that secreted PCSK9 retains biological activity, is able to bind directly to the LDLR extracellular domain, and undergoes LDLR-ARH-mediated endocytosis, leading to accelerated intracellular degradation of the LDLR.

Constitutive expression of a cholesterol-7α-hydroxylase (CYP7A1) transgene in LDL receptor-deficient mice blocked the ability of a cholesterol-enriched diet to increase plasma levels of apolipoprotein B-containing lipoproteins. LDL receptor-deficient mice expressing the CYP7A1 transgene exhibited complete resistance to diet-induced hypercholesterolemia and to the accumulation of cholesterol in the liver. Hepatic mRNA expression of liver X receptor-inducible ABCG5 and ABCG8 was decreased in CYP7A1 transgenic, LDL receptor-deficient mice fed a cholesterol-enriched diet. Thus, increased biliary cholesterol excretion could not account for the maintenance of cholesterol homeostasis. CYP7A1 transgenic, LDL receptor-deficient mice fed the cholesterol-enriched diet exhibited decreased jejunal Niemann-Pick C1-Like 1 protein (NPC1L1) mRNA expression, an important mediator of intestinal cholesterol absorption. A taurocholate-enriched diet also decreased NPC1L1 mRNA expression in a farnesoid X receptor-independent manner. Reduced expression of NPC1L1 mRNA was associated with decreased cholesterol absorption (∼20%; P < 0.05) exhibited by CYP7A1 transgenic LDL receptor-deficient mice fed the cholesterol-enriched diet. The combined data show that enhanced expression of CYP7A1 is an effective means to prevent the accumulation of cholesterol in the liver and of atherogenic apolipoprotein B-containing lipoproteins in plasma.

The efficacy of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition has broadened lipid-lowering therapy thus providing decreased risk in atherosclerotic cardiovascular disease. Unfortunately, the widespread use of PCSK9 inhibitors (PCSK9i), ie, monoclonal antibodies, has led to the findings of unusual responsiveness, ie, a phenomenon defined as an LDL-C reduction of <30% vs the average LDL-C reduction efficacy of 50-60%. This unusual responsiveness to PCSK9i is attributable to several factors, ie, lack of adherence, impaired absorption, poor distribution or early elimination as well as abnormal effects of PCSK9i in the presence of anti-antibodies or mutations in PCSK9 and LDLR. Unexpectedly increased lipoprotein (Lp)(a) also appear to contribute to the unusual responsiveness scenario. Identification of these responses and mechanisms underlying them are essential for effective management of LDL-C and cardiovascular risk. In this review, we describe plausible reasons underlying this phenomenon supported by findings of clinical trials. We also elaborate on the need for education and regular follow-up to improve adherence. Collectively, the review provides a summary of the past, present, and future of mechanisms and countermeasures revolving around unusual responses to PCSK9i therapy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Study Objective: This systematic review and meta-analysis aimed to assess the efficacy and safety profile of treatment with inclisiran, a drug that has been recently approved by the United States Food and Drug Administration (FDA) and the European Medicines Agency (EMA)., Design: A systematic literature search was conducted in order to identify randomized controlled trials (RCTs) assessing the effect on lipoproteins and the safety profile of inclisiran., Results: Data were pooled from 5 RCTs, which included 4226 subjects. Meta-analyses of data suggested that the multiple-dose regimens of inclisiran yielded a significant reduction in serum levels of proprotein convertase subtilisin/kexin type 9 (MD = -78.23%, 95%CI: -86.74, -69.71) and low-density lipoprotein cholesterol (MD = -45.48%, 95%CI: -50.36%, -40.61%) throughout the studies. Furthermore, treatment with inclisiran significantly affected total cholesterol (MD = -13.67%, 95%CI: -20.78%, -6.57%), high-density lipoprotein cholesterol (MD = 8.29%, 95%CI: 4.66%,11.93%), non-HDL cholesterol (MD = -39.45%, 95%CI: -43.6%, -35.31%), apolipoprotein B (MD = -34.58%, 95%CI: -38.78%, -30.78%) and lipoprotein(a) (MD = -20.9%, 95%CI: -25.8%, -15.99%). Multiple-dose regimens of inclisiran were associated with increased risk of injection-site reactions (any reaction: OR = 5.86, 95%CI: 3.44, 9.98; mild reactions: OR = 5.19, 95%CI: 1.68, 16.07; moderate reactions: OR = 13.37, 95%CI: 3.17, 56.46), and bronchitis (OR = 1.58, 95%CI: 1.10, 2.26), while the incidence of the pre-specified exploratory CV endpoint significantly decreased at 18 months (OR = 0.74, 95%CI: 0.58, 0.94)., Conclusion and Relevance: Inclisiran has favourable effects on serum lipid levels and an acceptable safety profile. Further well-designed RCTs are needed to explore its longer-term safety., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Authors.)

Percutaneous coronary intervention (PCI) is a standard treatment in patients with stable coronary artery disease (CAD); however, periprocedural myocardial infarction (PMI) remains a common complication of PCI. Aggressive lipid-lowering therapy with statin has shown to reduce the incidence of PMI by preventing coronary microvascular dysfunction. It is unclear whether evolocumab, a potent lipid-lowering agent, could diminish microvascular damage after PCI. The EVOCATION trial (jRCTs051180022) is a multicenter, randomized, open-label, active-controlled, parallel-group, exploratory, investigator-initiated clinical study to evaluate whether pretreatment with evolocumab could decrease the index of microvascular resistance (IMR) after PCI in patients with stable CAD. This study population consists of 100 patients with stable CAD who will undergo PCI and have high low-density lipoprotein cholesterol levels despite administration of maximum tolerated dose of statins for at least 2 weeks. Eligible patients are randomized in a 1:1 ratio to receive either evolocumab 140 mg every 2 weeks in addition to standard of care treatment or standard of care treatment only for 2-6 weeks before PCI. The primary endpoint is IMR after PCI. The EVOCATION trial will evaluate whether pretreatment with evolocumab reduces periprocedural microvascular damage in patients with stable CAD undergoing PCI., (Copyright © 2021. Published by Elsevier Ltd.)

Background and Aims: In this study, we present the status regarding molecular genetic testing for mutations in the genes encoding the low density lipoprotein receptor (LDLR), apolipoprotein B (APOB) and proprotein convertase subtilisin/kexin type 9 (PCSK9) as causes of autosomal dominant hypercholesterolemia (ADH) in Norway., Methods: We have extracted data from the laboratory information management system at Unit for Cardiac and Cardiovascular Genetics, Oslo University Hospital for the period 1993-2020. This laboratory is the sole laboratory performing molecular genetic testing for ADH in Norway., Results: A total of 29,449 unrelated hypercholesterolemic patients have been screened for mutations in the LDLR gene, in the APOB gene and in the PCSK9 gene. Of these, 2818 (9.6%) were heterozygotes and 11 were homozygotes or compound heterozygotes. Most of the 264 different mutations identified were found in the LDLR gene. Only two and three mutations were found in the APOB gene or in the PCSK9 gene, respectively. Several founder mutations were identified. After testing of 14,230 family members, a total of 8811 heterozygous patients have been identified. Of these, 94.0% had a mutation in the LDLR gene, 5.4% had a mutation in the APOB gene and 0.6% had a mutation in the PCSK9 gene., Conclusions: A large proportion of Norwegian ADH patients have been provided with a molecular genetic diagnosis. Norway is probably only second to the Netherlands in this respect. A molecular genetic diagnosis may form the basis for starting proper preventive measures and for identifying affected family members by cascade genetic screening., (Copyright © 2021. Published by Elsevier B.V.)

Background and Aims: Peripheral artery disease (PAD) affects more than 200 million people worldwide. Increased low-density lipoprotein cholesterol (LDL-C)levels are a risk factor for PAD and the concentrations are influenced by proprotein convertase subtilisin/kexin type 9 (PCSK9). PCSK9 regulates the recycling of the LDL receptors to the cell membrane surface. Only a limited number of mostly small studies investigated the association between serum PCSK9 concentrations and PAD of different definition, which revealed contrasting results., Methods: Serum PCSK9, lipoprotein(a) [Lp(a)] and other lipoprotein concentrations were measured in male participants of the CAVASIC study, a case-control study of 248 patients with intermittent claudication and 251 age and diabetes-matched controls., Results: PAD patients had significantly higher PCSK9 concentrations when compared to controls (250 ± 77 vs. 222 ± 68 ng/mL, p < 0.001). Logistic regression analysis with adjustment for age revealed that an increase in PCSK9 concentrations of 100 ng/mL was associated with a 1.78-fold higher risk for PAD (95%CI 1.38-2.33, p = 1.43 × 10 -5 ). The association attenuated, but was still significant when adjusting additionally for age, Lp(a)-corrected LDL cholesterol, HDL cholesterol, high-sensitivity-CRP, statin treatment, hypertension, diabetes mellitus and smoking (OR = 1.49, 95%CI 1.03-2.18, p = 0.035). The strongest association was observed when both PCSK9 concentrations were above the median and Lp(a) concentrations were above 30 mg/dL (OR = 3.35, 95%CI 1.49-7.71, p = 0.0038)., Conclusions: Our findings suggest an association of higher PCSK9 concentrations with PAD, which was independent of other lipid parameters and classical cardiovascular risk factors., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

After training as a gastroenterologist in the UK, the author became interested in lipidology while he was a research fellow in the USA and switched careers after returning home. Together with Nick Myant, he introduced the use of plasma exchange to treat familial hypercholesterolemia (FH) homozygotes and undertook non-steady state studies of LDL kinetics, which showed that the fractional catabolic rate of LDL remained constant irrespective of pool size. Subsequent steady-state turnover studies showed that FH homozygotes had an almost complete lack of receptor-mediated LDL catabolism, providing in vivo confirmation of the Nobel Prize-winning discovery by Goldstein and Brown that LDL receptor dysfunction was the cause of FH. Further investigation of metabolic defects in FH revealed that a significant proportion of LDL in homozygotes and heterozygotes was produced directly via a VLDL-independent pathway. Management of heterozygous FH has been greatly facilitated by statins and proprotein convertase subtilisin/kexin type 9 inhibitors but remains dependent upon lipoprotein apheresis in homozygotes. In a recent analysis of a large cohort treated with a combination of lipid-lowering measures, survival was markedly enhanced in homozygotes in the lowest quartile of on-treatment serum cholesterol. Emerging therapies could further improve the prognosis of homozygous FH; whereas in heterozygotes, the current need is better detection., Competing Interests: Conflict of interest The author declares no conflicts of interest with the contents of this article., (Copyright © 2021 The Author. Published by Elsevier Inc. All rights reserved.)

Background: There are two types of circulating proprotein convertase subtilisin/kexin type 9 (PCSK9), mature and furin-cleaved. Most types of lipoprotein(a) [Lp(a)], an independent risk factor of cardiovascular events, bind to mature PCSK9., Objective: This study examined the effects of monoclonal anti-PCSK9 antibody on plasma PCSK9 and Lp(a) levels in acute myocardial infarction (MI)., Methods: Acute MI patients (n=36) were randomly divided into evolocumab (140mg; n=17) and non-evolocumab (n=19) groups. Changes in plasma PCSK9 and Lp(a) levels were monitored before and 1, 3, 5, 10, and 20 days after evolocumab administration., Results: In the non-evolocumab group, plasma levels of mature PCSK9, furin-cleaved PCSK9, and Lp(a) (236.4±57.3ng/mL, 22.4±5.8ng/mL, and 19.2.±16.5mg/dL, respectively) significantly increased by day 3 (408.8±77.1ng/mL, p<0.001; 47.2±15.7ng/mL, p<0.001; and 39.7±21.3mg/dL, p<0.005, respectively) and returned to the baseline by day 10 or 20. In the evolocumab group, mature PCSK9 significantly increased by >1000ng/mL with a simultaneous decline of furin-cleaved PCSK9 below the measurement sensitivity level after day 3. The incremental area under the curve for plasma Lp(a) levels was significantly smaller in the evolocumab group compared with the non-evolocumab group (p=0.038)., Conclusion: Mature and furin-cleaved PCSK9 are transiently upregulated after MI onset. Evolocumab significantly increases mature PCSK9 and decreases furin-cleaved PCSK9 and might inhibit transient increase of plasma Lp(a) in acute MI., (Copyright © 2020 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)

The risk of atherosclerosis (AS) ascends among post-menopausal women, while current hormone replacement therapy exerts several adverse effects. Alisol B 23-acetate (AB23A), a tetracyclic triterpenoid isolated from the rhizome of Alisma orientale, was reported to show multiple physiological activities, including regulating lipid metabolism. According to molecular docking analysis, it was predicted to bind with estrogen receptor α (ERα). In this study, we aimed to observe the effect of AB23A on preventing post-menopausal AS and explore whether the mechanism was mediated by ERα. In vitro, free fatty acid (FFA) was applied to induce the abnormal lipid metabolism of L02 cells. In vivo, the ApoE -/- mice were ovariectomized to mimic the cessation of estrogen. The high-fat diet was also given to induce post-menopausal AS. We demonstrated AB23A attenuated the accumulation of total cholesterol and triglyceride induced by free fatty acids in hepatocytes. In high-fat diet-ovariectomy-treated ApoE -/- mice, AB23A eliminated lipids in blood and liver. AB23A not only reduced the synthesis of proprotein convertase subtilisin/kexin type 9 (PCSK9) through sterol-regulatory element binding proteins (SREBPs) but also suppressed the secretion of PCSK9 through silent information regulator 1 (SIRT1). Notably, AB23A promoted the expression of ERα in vivo and in vitro. The both ERα inhibitor and ERα siRNA were also applied in confirming whether the hepatic protective effect of AB23A was mediated by ERα. We found that AB23A significantly promoted the expression of ERα. AB23A could inhibit the synthesis and secretion of PCSK9 through ERα, lower the accumulation of triglyceride and cholesterol, and prevent post-menopausal AS., Competing Interests: Declaration of competing interest The authors confirm that this article content has no conflict of interest., (Copyright © 2020. Published by Elsevier Inc.)

A 28-year-old woman with a rare combination of homozygous LDLR and heterozygous PCSK9 mutations had a phenotype consistent with homozygous familial hypercholesterolemia. She reported a clinical history of coronary and extracoronary atherosclerosis treated with 3 coronary stenting procedures, one coronary bypass, and aortic and mitral valve replacements. Because the patient refused lipoprotein apheresis, lipid-lowering therapy with statins, ezetimibe, and evolocumab was started. The desired low-density lipoprotein cholesterol target was not achieved. Dose-escalated lomitapide therapy (up to 30 mg/d) was added, enabling achievement of low-density lipoprotein cholesterol levels of 45 mg/dL during 24 months' follow-up. During this period, no cardiovascular events or clinical evidence of side effects occurred. In this case, lomitapide has been used in combination with maximum-tolerated statin therapy to successfully treat a patient with a rare combination of mutations in both LDLR and PCSK9 genes., (Copyright © 2020 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Background: Trials have demonstrated that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are effective as an adjunct to statin therapy, but access and cost issues have limited their use in community practice., Objective: The aim of the study was to better understand patients' experiences when trying to obtain, fill, and use PCSK9 inhibitor therapy in community practice., Methods: We conducted a patient survey to evaluate patient experiences with PCSK9 inhibitors including medication initiation, indication for treatment, insurance approval status, medication persistence, and reason for discontinuation. The survey was emailed to 4740 adults who used a patient access support program., Results: Overall, 1327 of 4740 adults completed the survey (28.0% response rate). Of those, 75.0% were aged >60 years, 52.8% were male, and 92.4% were White. At the time of PCSK9 inhibitor prescription, 70.2% were not on a statin (with 84.4% of those not on a statin reporting statin intolerance). Overall, 74.6% of patients found the drug approval process to be "somewhat" or "very" burdensome. Among n = 1216 patients who initiated treatment, 33.7% discontinued by the time of the survey, with 50.0% taking the drug for 1 to 6 months. Patient out-of-pocket costs were the leading reported reason for discontinuation., Conclusions: Most PCSK9 inhibitor users in community practice were not on a statin, presumably because of statin intolerance. The drug approval process and costs continue to be strong reasons for lower initiation of PCSK9 agents, as well as higher discontinuation rates., (Copyright © 2019 National Lipid Association. Published by Elsevier Inc. All rights reserved.)

Very few studies have investigated the interrelations between proprotein convertase subtilisin/kexin type 9 (PCSK9) metabolism, cholesterol synthesis, and cholesterol absorption. We aimed to address this issue in a large clinical trial of 245 patients with hypercholesterolemia. Serum lipids, PCSK9, lathosterol (cholesterol synthesis marker), campesterol, and sitosterol (cholesterol absorption markers) were measured before and 4-8 weeks after the start of treatment with PCSK9-antibodies (alirocumab or evolocumab). The patients had mean (standard error) LDL-cholesterol and PCSK9 concentrations of 3.87 (0.10) mmol/l and 356 (17) ng/ml, respectively. Eighty-four patients received no lipid-lowering pretreatment, 26 ezetimibe, 38 statins, and 97 ezetimibe + statins. Circulating PCSK9 increased in parallel with the potency of lipid-lowering pretreatment with circulating PCSK9 being highest in the ezetimibe + statin group ( P < 0.001). Treatment with PCSK9-antibodies strongly decreased LDL-cholesterol, lathosterol, campesterol, and sitosterol (all P < 0.001) but hardly affected noncholesterol sterol to cholesterol ratios. Lipid-lowering pretreatment was not associated with the effects of PCSK9-antibodies on noncholesterol sterols (all P > 0.05). Summing up, circulating PCSK9 is increased by cholesterol synthesis and absorption inhibitors. Increased PCSK9 expression may partly explain the strong reductions of LDL-cholesterol achieved with PCSK9-antibodies after such pretreatment. On the other hand, treatment with PCSK9-antibodies does not significantly change the balance between cholesterol synthesis and absorption.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) targets the LDL receptor (LDLR) for degradation, increasing plasma LDL and, consequently, cardiovascular risk. Uptake of secreted PCSK9 is required for its effect on the LDLR, and LDL itself inhibits this uptake, though how it does so remains unclear. In this study, we investigated the relationship between LDL, the PCSK9:LDLR interaction, and PCSK9 uptake. We show that LDL inhibits binding of PCSK9 to the LDLR in vitro more impressively than it inhibits PCSK9 uptake in cells. Furthermore, cell-surface heparin-like molecules (HLMs) can partly explain this difference, consistent with heparan sulfate proteoglycans (HSPGs) acting as coreceptors for PCSK9. We also show that HLMs can interact with either PCSK9 or LDL to modulate the inhibitory activity of LDL on PCSK9 uptake, with such inhibition rescued by competition with the entire PCSK9 prodomain, but not its truncated variants. Additionally, we show that the gain-of-function PCSK9 variant, S127R, located in the prodomain near the HSPG binding site, exhibits increased affinity for HLMs, potentially explaining its phenotype. Overall, our findings suggest a model where LDL acts as a negative regulator of PCSK9 function by decreasing its uptake via direct interactions with either the LDLR or HLMs., (Copyright © 2019 Galvan and Chorba.)

Calcific aortic valve disease (CAVD) is the most common valvular disorder in the elderly, with the incidence of 3% in general population of Western countries. The initial phase of CAVD is characterized by leaflet thickening and possible spotty calcification (i.e. aortic valve sclerosis (AVSc)), while advanced stages have leaflets structure degeneration (i.e. aortic valve stenosis (AS)). The pathological cellular and molecular mechanisms, involved in CAVD, are extracellular matrix degradation, aberrant matrix deposition, fibrosis, mineralization, inflammation, lipid accumulation, and neo-angiogenesis. CAVD clinical risk shares considerable overlap with those of atherosclerosis and they include hypertension, smoking habits, and hyperlipidemia. Unfortunately, surgical aortic valve replacement and transcatheter aortic valve implantation are the only available treatments when the disease become severe and symptoms occur. Indeed, no approved pharmacological approach is available for CAVD patients. In this review, we describe the current literature evidence on possible future therapeutic targets for this debilitating and fatal disease such as PCSK9, P2Y2 receptor, cadherin 11, and DDP-4., (Copyright © 2018 Elsevier Ltd. All rights reserved.)