Decreased plasma cholesterol and hypersensitivity to statins in mice lacking Pcsk9

Cell-type specific global reprogramming of the transcriptome and epigenome in induced neurons with the 16p11.2 neuropsychiatric CNVs

Copy number variants (CNVs), either deletions or duplications, at the 16p11.2 locus in the human genome are known to increase the risk for autism spectrum disorders (ASD), schizophrenia, and several other developmental conditions. Here, we investigate the global effects on gene expression and DNA methylation using an induced pluripotent stem cell (iPSC) to induced neuron (iN) cell model system derived from 16p11.2 CNV patients and controls. This approach revealed genome-wide and cell-type specific alterations to both gene expression and DNA methylation patterns and also yielded specific leads on genes potentially contributing to some of the phenotypes in 16p11.2 patients. There is global reprogramming of both the transcriptome and the DNA methylome. We observe sets of differentially expressed genes and differentially methylated regions, respectively, that are localized genome wide and that are shared, and with changes in the same direction, between the deletion and duplication genotypes. The gene PCSK9 is identified as a possible contributing factor to symptoms seen in carriers of the 16p11.2 CNVs. The protocadherin (PCDH) gene family is found to have altered DNA methylation patterns in the CNV patient samples. The iPSC lines used for this study are available through a repository as a resource for research into the molecular etiology of the clinical phenotypes of 16p11.2 CNVs and into that of neuropsychiatric and neurodevelopmental disorders in general.

Pathways and Molecular Mechanisms Governing LDL Receptor Regulation

Clearance of circulating plasma LDL (low-density lipoprotein) cholesterol by the liver requires hepatic LDLR (low-density lipoprotein receptor). Complete absence of functional LDLR manifests in severe hypercholesterolemia and premature atherosclerotic cardiovascular disease. Since the discovery of the LDLR 50 years ago by Brown and Goldstein, all approved lipid-lowering medications have been aimed at increasing the abundance and availability of LDLR on the surface of hepatocytes to promote the removal of LDL particles from the circulation. As such a critical regulator of circulating and cellular cholesterol, it is not surprising that LDLR activity is tightly regulated. Despite over half a century's worth of study, there are still many facets of LDLR biology that remain unexplored. This review will focus on pathways that regulate the LDLR and emerging concepts of LDLR biology.

Dendrobium nobile Lindl. alkaloids improve lipid metabolism by increasing LDL uptake through regulation of the LXRα/IDOL/LDLR pathway and inhibition of PCSK9 expression in HepG2 cells

Dendrobium nobile Lindl. alkaloids (DNLA) are active ingredients that can be extracted from the traditional Chinese herb Dendrobium Nobile Lindl. DNLA exhibits hypoglycemic and antihyperlipidemia effects. However, to the best of our knowledge, the specific molecular mechanism by which DNLA can regulate lipid metabolism remains unclear. The aim of the present study was to investigate the effect of DNLA on lipopolysaccharide (LPS)-induced lipid metabolism in HepG2 cells and its potential mechanism. HepG2 cells were treated with LPS with or without different concentrations of DNLA (0, 0.035, 0.35 and 3.5 µg/ml) for 48 h. Cell viability was then detected using the Cell Counting Kit-8 assay. The 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanideperchlorate-low-density lipoprotein (LDL) uptake assay was used to examine LDL uptake. In addition, possible mechanisms were explored using western blot analysis. The effect of the combination of DNLA with rosuvastatin calcium on the expression levels of the LDL receptor (LDLR) and proprotein convertase subtilisin/Kexin type 9 (PCSK9) was examined. The results indicated that LPS stimulation reduced the uptake of LDL by HepG2 cells, decreased the intracellular LDLR content, and increased the expression levels of inducible degrader of the LDLR (IDOL) and liver X receptor (LXR)α. DNLA intervention reversed all of the aforementioned LPS-induced effects in HepG2 cells. Additional mechanistic experiments revealed that DNLA exerted its effects mainly by regulating the LXRα/IDOL/LDLR pathway. It was shown that DNLA also reduced the expression levels of PCSK9, sterol regulatory element binding protein 2 and hepatocyte nuclear factor 1α. In addition, DNLA decreased the expression levels of PCSK9 in rosuvastatin calcium-induced HepG2 cells. Notably, DNLA was able to decrease 3-hydroxy-3-methylglutaryl-coenzyme A reductase and increase cytochrome p450 7A1 expression at the protein level, which are rate-limiting enzymes in cholesterol synthesis and metabolism. Collectively, these data suggested that DNLA could enhance LDL uptake of HepG2 cells by increasing LDLR expression through the LXRα/IDOL/LDLR pathway to alleviate the effects induced by LPS, suggesting the potential benefit of DNLA in improving lipid metabolism disorders.

Walking the VLDL tightrope in cardiometabolic diseases

Very-low-density lipoprotein (VLDL), a triglyceride-rich lipoprotein secreted by hepatocytes, is pivotal for supplying peripheral tissues with fatty acids for energy production. As if walking on a tightrope, perturbations in the balance of VLDL metabolism contribute to cardiometabolic dysfunction, promoting pathologies such as cardiovascular disease (CVD) or metabolic dysfunction-associated steatotic liver disease (MASLD). Despite the advent of lipid-lowering therapies, including statins and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, risks for cardiovascular events persist. With limitations to currently available CVD therapeutics and no US Food and Drug Administration (FDA)-approved treatment for MASLD, this review summarizes the current understanding of VLDL metabolism that sheds light on novel therapeutic avenues to pursue for cardiometabolic disorders.

Emerging oral therapeutic strategies for inhibiting PCSK9

Pharmacological inhibition of Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) have been firmly established to be an effective approach to reduce low-density lipoprotein (LDL) cholesterol levels and cardiovascular events. Subcutaneous administration of monoclonal antibodies (evolocumab and alirocumab) every 2 or 4 weeks determined a 60 % reduction of LDL cholesterol levels, while the GalNac-siRNA anti PCSK9 (inclisiran) provided an effective lipid lowering activity (-50 %) after an initial subcutaneous dose, repeated after 3 months and followed by a maintenance dose every 6 months. Although these two approaches have the potentiality to bring the majority of patients at high and very-high cardiovascular risk to the appropriate LDL cholesterol targets, their cost and subcutaneous administration represent a strong limitation for their large-scale use. These problems could be overcome by the development of small chemical molecules anti PCSK9 as oral therapy for controlling hypercholesterolemia. In the present review, we summarized the pharmacological properties of oral anti PCSK9 molecules that are currently under clinical development (DC371739, CVI-LM001, and AZD0780), including the mimetic peptides enlicitide decanoate (MK-0616) and NNC0385-0434.

Unraveling Estrogen and PCSK9's Roles in Lipid Metabolism Disorders among Ovariectomized Mice

We explore the interaction between estrogen and PCSK9 and their collective impact on lipid metabolism, especially concerning the regulation of low-density lipoprotein receptor levels. Utilizing both animal and cellular models, including ovariectomized mice and HepG2 cell lines, we demonstrate that estrogen deficiency leads to a disruption in lipid metabolism, characterized by elevated levels of total cholesterol and LDL-C. The study commences with mice undergoing ovariectomy, followed by a diet regimen comprising either high-fat diet or normal feed for a four-week duration. Key assessments include analyzing lipid metabolism, measuring PCSK9 levels in the bloodstream, and evaluating hepatic low-density lipoprotein receptor expression. We will also conduct correlation analyses to understand the relationship between PCSK9 and various lipid profiles. Further, a subset of ovariectomized mice on high-fat diet will undergo treatment with either estrogen or PCSK9 inhibitor for two weeks, with a subsequent re-evaluation of the earlier mentioned parameters. Our findings reveal that estrogen inhibits PCSK9-mediated degradation of low-density lipoprotein receptor, a process crucial for maintaining lipid homeostasis. Through a series of experiments, including immunohistochemistry and western blot analysis, we establish that PCSK9 is involved in lipid metabolism disorders caused by estrogen deficiency and that estrogen regulates PCSK9 and low-density lipoprotein receptor at post-transcriptional level. The study provides a mechanism for the involvement of PCSK9 in elucidating the disorders of lipid metabolism caused by estrogen deficiency due to perimenopause and ovarian decline.

PCSK9 in metabolism and diseases

PCSK9 is a serine protease that regulates plasma levels of low-density lipoprotein (LDL) and cholesterol by mediating the endolysosomal degradation of LDL receptor (LDLR) in the liver. When PCSK9 functions unchecked, it leads to increased degradation of LDLR, resulting in elevated circulatory levels of LDL and cholesterol. This dysregulation contributes to lipid and cholesterol metabolism abnormalities, foam cell formation, and the development of various diseases, including cardiovascular disease (CVD), viral infections, cancer, and sepsis. Emerging clinical and experimental evidence highlights an imperative role for PCSK9 in metabolic anomalies such as hypercholesterolemia and hyperlipidemia, as well as inflammation, and disturbances in mitochondrial homeostasis. Moreover, metabolic hormones - including insulin, glucagon, adipokines, natriuretic peptides, and sex steroids - regulate the expression and circulatory levels of PCSK9, thus influencing cardiovascular and metabolic functions. In this comprehensive review, we aim to elucidate the regulatory role of PCSK9 in lipid and cholesterol metabolism, pathophysiology of diseases such as CVD, infections, cancer, and sepsis, as well as its pharmaceutical and non-pharmaceutical targeting for therapeutic management of these conditions.

A commonly inherited human PCSK9 germline variant drives breast cancer metastasis via LRP1 receptor

Identifying patients at risk for metastatic relapse is a critical medical need. We identified a common missense germline variant in proprotein convertase subtilisin/kexin type 9 (PCSK9) (rs562556, V474I) that is associated with reduced survival in multiple breast cancer patient cohorts. Genetic modeling of this gain-of-function single-nucleotide variant in mice revealed that it causally promotes breast cancer metastasis. Conversely, host PCSK9 deletion reduced metastatic colonization in multiple breast cancer models. Host PCSK9 promoted metastatic initiation events in lung and enhanced metastatic proliferative competence by targeting tumoral low-density lipoprotein receptor related protein 1 (LRP1) receptors, which repressed metastasis-promoting genes XAF1 and USP18. Antibody-mediated therapeutic inhibition of PCSK9 suppressed breast cancer metastasis in multiple models. In a large Swedish early-stage breast cancer cohort, rs562556 homozygotes had a 22% risk of distant metastatic relapse at 15 years, whereas non-homozygotes had a 2% risk. Our findings reveal that a commonly inherited genetic alteration governs breast cancer metastasis and predicts survival-uncovering a hereditary basis underlying breast cancer metastasis.

Current and emerging PCSK9-directed therapies to reduce LDL-C and ASCVD risk: A state-of-the-art review

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide. Lowering low-density lipoprotein cholesterol (LDL-C) levels is a primary strategy to reduce ASCVD risk. Although statin therapy remains the initial therapy of choice to reduce LDL-C and ASCVD risk, statin intolerance and suboptimal LDL-C lowering response prompts the need for additional non-statin therapies. Ezetimibe and bempedoic acid are reasonable options but they modestly reduce LDL-C levels (15% to 25%). Therapies directed at the proprotein convertase subtilisin/kexin type 9 (PCSK9) enzyme, however, reduce LDL-C levels by 50%-60% when added to background statin therapy. PCSK9 is an enzyme synthesized by the liver that facilitates the degradation of LDL receptors and prevents their recycling to the hepatocyte surface to remove LDL-C from circulation. Approaches to inhibit this effect have centered on monoclonal antibodies (mAbs) (alirocumab, evolocumab) targeting PCSK9 functionality and small interfering RNA (siRNA) therapies (inclisiran) targeting the hepatic synthesis of PCSK9. Randomized controlled trials have demonstrated beneficial cardiovascular outcomes of PCSK9 mAbs, but such evidence is not yet available for inclisiran. Current clinical practice guidelines generally recommend PCSK9-directed therapies for higher-risk patients with established ASCVD and those with familial hypercholesterolemia. This approach is, in part, due to their cost and uncertain economic value, but also because these therapies require subcutaneous administration, which is not preferred by some patients. Oral therapies targeting PCSK9 are, however, in development. This scoping review covers the development of current and emerging PCSK9-directed therapies, their efficacy, safety, and role in clinical practice.

Inhibition of hepatic PCSK9 as a novel therapeutic target ameliorates metabolic steatohepatitis in mice

BACKGROUND & AIMS

Metabolic steatohepatitis (MASH) is closely related to metabolic disorders, and the main characteristics of MASH are hepatocyte steatosis with hepatocyte injury and inflammation. In severe cases, MASH can develop into liver cirrhosis. At present, there is no effective treatment for MASH. Proprotein convertase subtilisin/kexin 9 (PCSK9) is a popular target for the development of cholesterol-lowering drugs and therapeutic interventions for cardiovascular disease. The present study aimed to explore the role of PCSK9 in methionine- and choline-deficient (MCD) diet-induced MASH progression and its targeted intervention.

METHODS

PCSK9 expression was determined in a MASH mouse model, and the role of PCSK9 in the regulation of lipid metabolism, inflammation, and fibrosis was investigated using PCSK9 knockout (PCSK9-/-) mice fed a MCD diet. An adeno-associated virus was used to alter PCSK9 expression in MASH mice.

RESULTS

Following the MCD diet, C57BL/6J wild-type (WT) mice developed marked steatohepatitis and elevated hepatic PCSK9 expression, and circulating PCSK9 expression. PCSK9-/- mice showed significantly alleviated MCD-induced hepatic steatosis, with lower serum ALT levels, lower serum AST levels, smaller hepatic vacuoles, and less hepatic lipid deposition. PCSK9-/- mice on the MCD diet showed a significantly reduced levels of inflammation and fibrogenesis. Moreover, adeno-associated virus (AAV)-mediated PCSK9 silencing in mouse livers significantly relieved liver steatosis, inflammation, and fibrosis.

CONCLUSIONS

The present study demonstrated an important role of PCSK9 in MASH, suggesting that inhibition of PCSK9 may represent a novel and effective therapeutic strategy for MASH treatment.

Gene Therapy in Cardiovascular Disease: Recent Advances and Future Directions in Science: A Science Advisory From the American Heart Association

Cardiovascular disease remains the foremost cause of morbidity and mortality globally, affecting millions of individuals. Recent discoveries illuminate the substantial role of genetics in cardiovascular disease pathogenesis, encompassing both monogenic and polygenic mechanisms and identifying tangible targets for gene therapies. Innovative strategies have emerged to rectify pathogenic variants that cause monogenic disorders such as hypertrophic, dilated, and arrhythmogenic cardiomyopathies and hypercholesterolemia. These include delivery of exogenous genes to supplement insufficient protein levels caused by pathogenic variants or genome editing to correct, delete, or modify mutant sequences to restore protein function. However, effective delivery of gene therapy to specified cells presents formidable challenges. Viral vectors, notably adeno-associated viruses and nonviral vectors such as lipid and engineered nanoparticles, offer distinct advantages and limitations. Additional risks and obstacles remain, including treatment durability, tissue-specific targeting, vector-associated adverse events, and off-target effects. Addressing these challenges is an ongoing imperative; several clinical gene therapy trials are underway, and many more first-in-human studies are anticipated. This science advisory reviews core concepts of gene therapy, key obstacles, patient risks, and ongoing research endeavors to enable clinicians to understand the complex landscape of this emerging therapy and its remarkable therapeutic potential to benefit cardiovascular disease.

Investigating the Relationship Between Lipid-Lowering Agents and the Complications of Diabetic Retinopathy

BACKGROUND AND OBJECTIVE

As the therapeutic efficacy of lipid-lowering agents (LLA) against diabetic retinopathy (DR) remains controversial, this study aimed to evaluate whether various LLA therapies are associated with a reduced risk of DR progression.

PATIENTS AND METHODS

This retrospective study of the medical records of adults with type 2 diabetes mellitus and DR compared the risk of adverse progression of DR between patients who received statins, fibrates, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, and no LLA (control).

RESULTS

Patients in the statin cohort had a reduced rate of progression to proliferative DR compared to controls (HR = 0.30, CI = 0.11 to 0.83). The PCSK9 inhibitor cohort had a reduced risk of progressing to other secondary complications of DR compared to the control (RR = 0.52, CI = 0.43 to 0.64), statin (RR = 0.69, CI = 0.61 to 0.79), and fibrate (RR = 0.67, CI = 0.59 to 0.77) cohorts.

CONCLUSIONS

These findings suggest use of statins and PCSK9 inhibitors are associated with a reduced risk of adverse progression of DR. [Ophthalmic Surg Lasers Imaging Retina 2024;55:706-713.].

Rationale for Early Administration of PCSK9 Inhibitors in Acute Coronary Syndrome

Acute coronary syndromes (ACSs) represent a significant global health challenge arising from atherosclerotic cardiovascular disease (ASCVD), with elevated low-density lipoprotein cholesterol (LDL-C) levels being a primary contributor. Despite standard statin therapy, individuals with ACS remain at high risk for recurrent cardiovascular events, particularly in the initial post-ACS period. Monoclonal antibodies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9), such as evolocumab and alirocumab, offer a potential strategy to reduce LDL-C levels further and mitigate this residual risk. This review delves into the molecular mechanisms, effects on cholesterol metabolism, inflammatory modulation, and clinical outcomes associated with early administration of PCSK9 inhibitors following ACS.

Natural phytochemicals as small-molecule proprotein convertase subtilisin/kexin type 9 inhibitors

A decrease in the levels of low-density lipoprotein receptors (LDLRs) leads to the accumulation of LDL cholesterol (LDL-C) in the bloodstream, resulting in hypercholesterolemia and atherosclerotic cardiovascular diseases. Increasing the expression level or inducing the activity of LDLR in hepatocytes can effectively control hypercholesterolemia. Proprotein convertase subtilisin/kexin type 9 (PCSK9) protein, primarily produced in the liver, promotes the degradation of LDLR. Inhibiting the expression and/or function of PCSK9 can increase the levels of LDLR on the surface of hepatocytes and promote LDL-C clearance from the plasma. Thus, targeting PCSK9 represents a new strategy for developing preventive and therapeutic interventions for hypercholesterolemia. Currently, monoclonal antibodies are used as PCSK9 inhibitors in clinical practice. However, the need for oral and affordable anti-PCSK9 medications limits the perspective of choosing PCSK9 inhibitors for clinical usage. Emerging research reports have demonstrated that natural phytochemicals have efficacy in maintaining cholesterol stability and regulating lipid metabolism. Developing novel natural phytochemical PCSK9 inhibitors can serve as a starting point for developing small-molecule drugs to reduce plasma LDL-C levels in patients. In this review, we summarize the current literature on the critical role of PCSK9 in controlling LDLR degradation and hypercholesterolemia, and we discuss the results of studies attempting to develop PCSK9 inhibitors, with an emphasis on the inhibitory effects of natural phytochemicals on PCSK9. Furthermore, we provide insight into the mechanisms of action by which the reported phytochemicals exert their potential PCSK9 inhibitory effects against hypercholesterolemia.

Estimating the effect of inclisiran on hypercholesterolemia and primary prevention of cardiovascular disease: the NHANES 1999-2018 study

BACKGROUND

Hypercholesterolemia has been identified as an independent predictor of cardiovascular disease (CVD). Inclisiran, an innovative small interfering RNA agent, is anticipated to result in a notable reduction of approximately 50% in low-density lipoprotein cholesterol (LDL-C) levels. Given its transformative impact, this study scrutinized the eligibility of the US population for inclisiran treatment and evaluated its potential effects on hypercholesterolemia and the primary prevention of CVD.

METHODS

This study applied the eligibility criteria from the ORION 10 and 11 trials to the 1999-2018 National Health and Nutrition Examination Survey (NHANES) dataset to estimate the size of the eligible population for atherosclerotic cardiovascular disease (ASCVD) and ASCVD-risk equivalents. Utilizing the reduction in LDL-C levels from ORION 10, this study predicted the impact of inclisiran on LDL-C levels among ASCVD patients. Similarly, leveraging the changes in lipid levels from ORION 11, this study predicted inclisiran's effect on the 10-year change in CVD risk and preventable CVD events in the ASCVD-risk equivalents population, employing the Framingham CVD Risk Score.

RESULTS

The study identified 579 ASCVD patients (5 million) and 382 ASCVD-risk equivalents (2.66 million) who met the eligibility criteria from ORION 10 and 11. Among the ASCVD population, 3.5 million (70.2%) would achieve a ≥ 50% reduction in LDL-C levels after treatment. Furthermore, 4.6 million (91.3%) would achieve LDL-C levels < 70 mg/dL, and 3.8 million (75%) would achieve LDL-C levels < 55 mg/dL after treatment. For the ASCVD-risk equivalents population, the estimated 10-year CVD risk would decrease from 25.3 to 17.7%, an absolute reduction of 7.6% and a relative reduction of 30% following inclisiran treatment, potentially preventing 202,353 CVD events over a decade, including 138,084 coronary heart disease cases, 37,351 strokes, and 23,894 congestive heart failure cases.

CONCLUSIONS

Inclisiran has the potential to substantially reduce the prevalence of hypercholesterolemia and prevent nearly 200,000 CVD events in eligible US adults.

Time-Restricted Feeding Reduces Atherosclerosis in LDLR KO Mice but Not in ApoE Knockout Mice

BACKGROUND

Dyslipidemia increases cardiovascular disease risk, the leading cause of death worldwide. Under time-restricted feeding (TRF), wherein food intake is restricted to a consistent window of <12 hours, weight gain, glucose intolerance, inflammation, dyslipidemia, and hypercholesterolemia are all reduced in mice fed an obesogenic diet. LDLR (low-density lipoprotein receptor) mutations are a major cause of familial hypercholesterolemia and early-onset cardiovascular disease.

METHODS

We subjected benchmark preclinical models, mice lacking LDLR-knockout or ApoE knockout to ad libitum feeding of an isocaloric atherogenic diet either ad libitum or 9 hours TRF for up to 13 weeks and assessed disease development, mechanism, and global changes in hepatic gene expression and plasma lipids. In a regression model, a subset of LDLR-knockout mice were ad libitum fed and then subject to TRF.

RESULTS

TRF could significantly attenuate weight gain, hypercholesterolemia, and atherosclerosis in mice lacking the LDLR-knockout mice under experimental conditions of both prevention and regression. In LDLR-knockout mice, increased hepatic expression of genes mediating β-oxidation during fasting is associated with reduced VLDL (very-low-density lipoprotein) secretion and lipid accumulation. Additionally, increased sterol catabolism coupled with fecal loss of cholesterol and bile acids contributes to the atheroprotective effect of TRF. Finally, TRF alone or combined with a cholesterol-free diet can reduce atherosclerosis in LDLR-knockout mice. However, mice lacking ApoE, which is an important protein for hepatic lipoprotein reuptake do not respond to TRF.

CONCLUSIONS

In a preclinical animal model, TRF is effective in both the prevention and regression of atherosclerosis in LDLR knockout mice. The results suggest TRF alone or in combination with a low-cholesterol diet can be a lifestyle intervention for reducing cardiovascular disease risk in humans.

The Role of Furin and Its Therapeutic Potential in Cardiovascular Disease Risk

Furin is an important proteolytic enzyme, converting several proteins from inactive precursors to their active forms. Recently, proteo-genomic analyses in European and East Asian populations suggested a causal association of furin with ischaemic heart disease, and there is growing interest in its role in cardiovascular disease (CVD) aetiology. In this narrative review, we present a critical appraisal of evidence from population studies to assess furin's role in CVD risk and potential as a drug target for CVD. Whilst most observational studies report positive associations between furin expression and CVD risk, some studies report opposing effects, which may reflect the complex biological roles of furin and its substrates. Genetic variation in FURIN is also associated with CVD and its risk factors. We found no evidence of current clinical development of furin as a drug target for CVD, although several phase 1 and 2 clinical trials of furin inhibitors as a type of cancer immunotherapy have been completed. The growing field of proteo-genomics in large-scale population studies may inform the future development of furin and other potential drug targets to improve the treatment and prevention of CVD.

Proprotein convertase subtilisin/kexin type 9 deficiency in extrahepatic tissues: emerging considerations

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily secreted by hepatocytes. PCSK9 is critical in liver low-density lipoprotein receptors (LDLRs) metabolism. In addition to its hepatocellular presence, PCSK9 has also been detected in cardiac, cerebral, islet, renal, adipose, and other tissues. Once perceived primarily as a "harmful factor," PCSK9 has been a focal point for the targeted inhibition of both systemic circulation and localized tissues to treat diseases. However, PCSK9 also contributes to the maintenance of normal physiological functions in numerous extrahepatic tissues, encompassing both LDLR-dependent and -independent pathways. Consequently, PCSK9 deficiency may harm extrahepatic tissues in close association with several pathophysiological processes, such as lipid accumulation, mitochondrial impairment, insulin resistance, and abnormal neural differentiation. This review encapsulates the beneficial effects of PCSK9 on the physiological processes and potential disorders arising from PCSK9 deficiency in extrahepatic tissues. This review also provides a comprehensive analysis of the disparities between experimental and clinical research findings regarding the potential harm associated with PCSK9 deficiency. The aim is to improve the current understanding of the diverse effects of PCSK9 inhibition.

Protective alleles and precision healthcare in crewed spaceflight

Common and rare alleles are now being annotated across millions of human genomes, and omics technologies are increasingly being used to develop health and treatment recommendations. However, these alleles have not yet been systematically characterized relative to aerospace medicine. Here, we review published alleles naturally found in human cohorts that have a likely protective effect, which is linked to decreased cancer risk and improved bone, muscular, and cardiovascular health. Although some technical and ethical challenges remain, research into these protective mechanisms could translate into improved nutrition, exercise, and health recommendations for crew members during deep space missions.

Geranylgeranyl isoprenoids and hepatic Rap1a regulate basal and statin-induced expression of PCSK9

LDL-C lowering is the main goal of atherosclerotic cardiovascular disease prevention, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is now a validated therapeutic strategy that lowers serum LDL-C and reduces coronary events. Ironically, the most widely used medicine to lower cholesterol, statins, has been shown to increase circulating PCSK9 levels, which limits their efficacy. Here, we show that geranylgeranyl isoprenoids and hepatic Rap1a regulate both basal and statin-induced expression of PCSK9 and contribute to LDL-C homeostasis. Rap1a prenylation and activity is inhibited upon statin treatment, and statin-mediated PCSK9 induction is dependent on geranylgeranyl synthesis and hepatic Rap1a. Accordingly, treatment of mice with a small-molecule activator of Rap1a lowered PCSK9 protein and plasma cholesterol and inhibited statin-mediated PCSK9 induction in hepatocytes. The mechanism involves inhibition of the downstream RhoA-ROCK pathway and regulation of PCSK9 at the post-transcriptional level. These data further identify Rap1a as a novel regulator of PCSK9 protein and show that blocking Rap1a prenylation through lowering geranylgeranyl levels contributes to statin-mediated induction of PCSK9.

Efficient Gene Editing for Heart Disease via ELIP-Based CRISPR Delivery System

Liposomes as carriers for CRISPR/Cas9 complexes represent an attractive approach for cardiovascular gene therapy. A critical barrier to this approach remains the efficient delivery of CRISPR-based genetic materials into cardiomyocytes. Echogenic liposomes (ELIP) containing a fluorescein isothiocyanate-labeled decoy oligodeoxynucleotide against nuclear factor kappa B (ELIP-NF-κB-FITC) were used both in vitro on mouse neonatal ventricular myocytes and in vivo on rat hearts to assess gene delivery efficacy with or without ultrasound. In vitro analysis was then repeated with ELIP containing Cas9-sg-IL1RL1 (interleukin 1 receptor-like 1) RNA to determine the efficiency of gene knockdown. ELIP-NF-κB-FITC without ultrasound showed limited gene delivery in vitro and in vivo, but ultrasound combined with ELIP notably improved penetration into heart cells and tissues. When ELIP was used to deliver Cas9-sg-IL1RL1 RNA, gene editing was successful and enhanced by ultrasound. This innovative approach shows promise for heart disease gene therapy using CRISPR technology.

Function of proprotein convertase subtilisin/kexin type 9 and its role in central nervous system diseases: An update on clinical evidence

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has attracted lots of attention in preventing the clearance of plasma low-density lipoprotein cholesterol (LDL-C). PCSK9 inhibitors are developed to primarily reduce the cardiovascular risk by lowering LDL-C level. Recently, a number of pleiotropic extrahepatic functions of PCSK9 beyond the regulation of cholesterol metabolism, particularly its effects on central nervous system (CNS) diseases have been increasingly identified. Emerging clinical evidence have revealed that PCSK9 may play a significant role in neurocognition, depression, Alzheimer's disease, and stroke. The focus of this review is to elucidate the functions of PCSK9 and highlight the effects of PCSK9 in CNS diseases, with the aim of identifying the potential risks that may arise from low PCSK9 level (variant or inhibitor) in the clinical practice.

Targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): from bench to bedside

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has evolved as a pivotal enzyme in lipid metabolism and a revolutionary therapeutic target for hypercholesterolemia and its related cardiovascular diseases (CVD). This comprehensive review delineates the intricate roles and wide-ranging implications of PCSK9, extending beyond CVD to emphasize its significance in diverse physiological and pathological states, including liver diseases, infectious diseases, autoimmune disorders, and notably, cancer. Our exploration offers insights into the interaction between PCSK9 and low-density lipoprotein receptors (LDLRs), elucidating its substantial impact on cholesterol homeostasis and cardiovascular health. It also details the evolution of PCSK9-targeted therapies, translating foundational bench discoveries into bedside applications for optimized patient care. The advent and clinical approval of innovative PCSK9 inhibitory therapies (PCSK9-iTs), including three monoclonal antibodies (Evolocumab, Alirocumab, and Tafolecimab) and one small interfering RNA (siRNA, Inclisiran), have marked a significant breakthrough in cardiovascular medicine. These therapies have demonstrated unparalleled efficacy in mitigating hypercholesterolemia, reducing cardiovascular risks, and have showcased profound value in clinical applications, offering novel therapeutic avenues and a promising future in personalized medicine for cardiovascular disorders. Furthermore, emerging research, inclusive of our findings, unveils PCSK9's potential role as a pivotal indicator for cancer prognosis and its prospective application as a transformative target for cancer treatment. This review also highlights PCSK9's aberrant expression in various cancer forms, its association with cancer prognosis, and its crucial roles in carcinogenesis and cancer immunity. In conclusion, this synthesized review integrates existing knowledge and novel insights on PCSK9, providing a holistic perspective on its transformative impact in reshaping therapeutic paradigms across various disorders. It emphasizes the clinical value and effect of PCSK9-iT, underscoring its potential in advancing the landscape of biomedical research and its capabilities in heralding new eras in personalized medicine.

Novel ASO therapeutic target designed against hyperlipidemia via PCSK9 knockdown

With the gradual improvement of individuals' living standards, there has been a concurrent escalation in the consumption of fats and sugars in the daily dietary habits. Consequently, an increasing number of individuals are afflicted by hyperlipidemia, a condition that, could elevate blood viscosity, thereby engendering serious complications in a long run. Traditional lipid-lowering medications, such as statins, manifest substantial side effects, thereby imposing a significant metabolic burden on the liver and kidneys. Conversely, antisense oligonucleotides (ASOs) exhibit attributes such as rapid absorption, prolonged efficacy, and minimal side effects. In light of these considerations, a novel ASO was meticulously designed, sebsequently, its efficacy and toxicity assessments were conducted both in vitro and in vivo. The results unequivocally demonstrate the effectiveness and safety of this ASO.

Advances in nanobased platforms for cardiovascular diseases: Early diagnosis, imaging, treatment, and tissue engineering

Cardiovascular diseases (CVDs) present a significant threat to health, with traditional therapeutics based treatment being hindered by inefficiencies, limited biological effects, and resistance to conventional drug. Addressing these challenges requires advanced approaches for early disease diagnosis and therapy. Nanotechnology and nanomedicine have emerged as promising avenues for personalized CVD diagnosis and treatment through theranostic agents. Nanoparticles serve as nanodevices or nanocarriers, efficiently transporting drugs to injury sites. These nanocarriers offer the potential for precise drug and gene delivery, overcoming issues like bioavailability and solubility. By attaching specific target molecules to nanoparticle surfaces, controlled drug release to targeted areas becomes feasible. In the field of cardiology, nanoplatforms have gained popularity due to their attributes, such as passive or active targeting of cardiac tissues, enhanced sensitivity and specificity, and easy penetration into heart and artery tissues due to their small size. However, concerns persist about the immunogenicity and cytotoxicity of nanomaterials, necessitating careful consideration. Nanoparticles also hold promise for CVD diagnosis and imaging, enabling straightforward diagnostic procedures and real-time tracking during therapy. Nanotechnology has revolutionized cardiovascular imaging, yielding multimodal and multifunctional vehicles that outperform traditional methods. The paper provides an overview of nanomaterial delivery routes, targeting techniques, and recent advances in treating, diagnosing, and engineering tissues for CVDs. It also discusses the future potential of nanomaterials in CVDs, including theranostics, aiming to enhance cardiovascular treatment in clinical practice. Ultimately, refining nanocarriers and delivery methods has the potential to enhance treatment effectiveness, minimize side effects, and improve patients' well-being and outcomes.

A bibliometric analysis of PCSK9 inhibitors from 2007 to 2022

BACKGROUND

Since the approval of the proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies for marketing in 2015, PCSK9 inhibitors have attracted significant interest in the field of cardiovascular endocrinology. A large number of clinical trials have confirmed the efficacy and safety of PCSK9 inhibitors in reducing cholesterol and the risk of cardiovascular events. No bibliometric analysis of PCSK9 inhibitors has been performed as of yet. This study aims to analyze the research trends and hotspots of PCSK9 inhibitors through bibliometric analysis.

METHODS

We searched the Web of Science Core Collection (WoSCC) database for PCSK9 inhibitor-related publications from 2007 to 2022. Data visualization analysis was performed using CiteSpace software. Microsoft Excel and Graphpad software were used for the drawing of some tables and figures.

RESULTS

A total of 1072 pieces of literature were retrieved between 2007 and 2022. The number of publications concerning PCSK9 inhibitors is growing annually. The top five countries with the most articles published were the United States, England, Canada, Italy, and France. Harvard University, Amgen, Brigham & Women's Hospital, Harvard Medical School, and Imperial College London are the five institutions with the highest output. The Journal of Clinical Lipidology is the most popular journal in this field. The most frequently cited journal is the New England Journal of Medicine. As for authors, Sabatine MS and Giugliano RP from Brigham & Women's Hospital have the highest number of published articles. Amgen is the funding agency for most of the research. According to keyword analysis, "low density lipoprotein", "familial hypercholesterolemia", "PCSK9 inhibitor", "PCSK9", and "efficacy" are the five keywords with the highest frequency of co-occurrence.

CONCLUSION

The past 15 years have witnessed a rapid and fruitful development of PCSK9 inhibitors. The research trend and focus for PCSK9 inhibitors are from the mechanism of reducing low-density lipoprotein cholesterol to related clinical trials. Developed countries such as the United States have contributed prominently in this area. Coronary artery and inflammation are currently at the forefront of research in the field and are in an explosion period.

Adverse outcome pathway for pregnane X receptor-induced hypercholesterolemia

Pharmaceuticals and environmental contaminants contribute to hypercholesterolemia. Several chemicals known to cause hypercholesterolemia, activate pregnane X receptor (PXR). PXR is a nuclear receptor, classically identified as a sensor of chemical environment and regulator of detoxification processes. Later, PXR activation has been shown to disrupt metabolic functions such as lipid metabolism and recent findings have shown PXR activation to promote hypercholesterolemia through multiple mechanisms. Hypercholesterolemia is a major causative risk factor for atherosclerosis and greatly promotes global health burden. Metabolic disruption by PXR activating chemicals leading to hypercholesterolemia represents a novel toxicity pathway of concern and requires further attention. Therefore, we constructed an adverse outcome pathway (AOP) by collecting the available knowledge considering the molecular mechanisms for PXR-mediated hypercholesterolemia. AOPs are tools of modern toxicology for systematizing mechanistic knowledge to assist health risk assessment of chemicals. AOPs are formalized and structured linear concepts describing a link between molecular initiating event (MIE) and adverse outcome (AO). MIE and AO are connected via key events (KE) through key event relationships (KER). We present a plausible route of how PXR activation (MIE) leads to hypercholesterolemia (AO) through direct regulation of cholesterol synthesis and via activation of sterol regulatory element binding protein 2-pathway.

Geranylgeranyl Isoprenoids and Hepatic Rap1a Regulate Basal and Statin-Induced Expression of PCSK9

Low-density lipoprotein cholesterol (LDL-C) lowering is the main goal of atherosclerotic cardiovascular disease prevention, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is now a validated therapeutic strategy that lowers serum LDL-C and reduces coronary events. Ironically, the most widely used medicine to lower cholesterol, statins, has been shown to increase circulating PCSK9 levels, which limits their efficacy. Here, we show that geranylgeranyl isoprenoids and hepatic Rap1a regulate both basal and statin induced expression of PCSK9 and contribute to LDL-C homeostasis. Rap1a prenylation and activity is inhibited upon statin treatment, and statin mediated PCSK9 induction is dependent on geranylgeranyl synthesis and hepatic Rap1a. Accordingly, treatment of mice with a small molecule activator of Rap1a lowered PCSK9 protein and plasma cholesterol and inhibited statin mediated PCSK9 induction in hepatocytes. The mechanism involves inhibition of the downstream RhoA-ROCK pathway and regulation of PCSK9 at the post transcriptional level. These data further identify Rap1a as a novel regulator of PCSK9 protein and show that blocking Rap1a prenylation through lowering geranylgeranyl levels contributes to statin-mediated induction of PCSK9.

Brazilin from Caesalpinia sappan L. as a Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Inhibitor: Pharmacophore-Based Virtual Screening, In Silico Molecular Docking, and In Vitro Studies

Background

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a crucial regulator of low-density lipoprotein cholesterol (LDL-c) levels, as it binds to and degrades the LDL receptor (LDLR) in the lysosome of hepatocytes. Elevated levels of PCSK9 have been linked to an increased LDL-c plasma levels, thereby increasing the risk of cardiovascular disease (CVD), making it an attractive target for therapeutic interventions. As a way to inhibit PCSK9 action, we searched for naturally derived small molecules which can block the binding of PCSK9 to the LDLR.

Methods

In this study, we carried out in silico studies which consist of virtual screening using an optimized pharmacophore model and molecular docking studies using Pyrx 0.98. Effects of the candidate compounds were evaluated using in vitro PCSK9-LDLR binding assays kit.

Results

Eleven natural compounds that bind to PCSK9 were virtually screened form HerbalDB database, including brazilin. Next, molecular docking studies using Pyrx 0.98 showed that brazilin had the highest binding affinity with PCSK9 at -9.0 (Kcal/mol), which was higher than that of the other ten compounds. Subsequent in vitro PCSK9-LDLR binding assays established that brazilin decreased the binding of PCSK9 to the EGF-A fragment of the LDLR in a dose-dependent manner, with an IC50 value of 2.19 μM.

Conclusion

We have identified brazilin, which is derived from the Caesalpinia sappan herb, which can act as a small molecule inhibitor of PCSK9. Our findings suggest that screening for small molecules that can block the interaction between PCSK9 and the LDLR in silico and in vitro may be a promising approach for developing novel lipid-lowering therapy.

Proprotein convertase subtilisin/kexin type 9 targets megalin in the kidney proximal tubule and aggravates proteinuria in nephrotic syndrome

Proteinuria is a prominent feature of chronic kidney disease. Interventions that reduce proteinuria slow the progression of chronic kidney disease and the associated risk of cardiovascular disease. Here, we propose a mechanistic coupling between proteinuria and proprotein convertase subtilisin/kexin type 9 (PCSK9), a regulator of cholesterol and a therapeutic target in cardiovascular disease. PCSK9 undergoes glomerular filtration and is captured by megalin, the receptor responsible for driving protein reabsorption in the proximal tubule. Accordingly, megalin-deficient mice and patients carrying megalin pathogenic variants (Donnai Barrow syndrome) were characterized by elevated urinary PCSK9 excretion. Interestingly, PCSK9 knockout mice displayed increased kidney megalin while PCSK9 overexpression resulted in its reduction. Furthermore, PCSK9 promoted trafficking of megalin to lysosomes in cultured proximal tubule cells, suggesting that PCSK9 is a negative regulator of megalin. This effect can be accelerated under disease conditions since either genetic destruction of the glomerular filtration barrier in podocin knockout mice or minimal change disease (a common cause of nephrotic syndrome) in patients resulted in enhanced tubular PCSK9 uptake and urinary PCSK9 excretion. Pharmacological PCSK9 inhibition increased kidney megalin while reducing urinary albumin excretion in nephrotic mice. Thus, glomerular damage increases filtration of PCSK9 and concomitantly megalin degradation, resulting in escalated proteinuria.

Effect of diet and genotype on the miRNome of mice with altered lipoprotein metabolism

The molecular mechanism by which lipid/lipoprotein biosynthesis is regulated in mammals involves a very large number of genes that are subject to multiple levels of regulation. miRNAs are recognized contributors to lipid homeostasis at the post-transcriptional level, although the elucidation of their role is made difficult by the multiplicity of their targets and the ability of more miRNAs to affect the same mRNAs. In this study, an evaluation of how miRNA expression varies in organs playing a key role in lipid/lipoprotein metabolism was conducted in control mice and in two mouse models carrying genetic ablations which differently affect low-density lipoprotein metabolism. Mice were fed a lipid-poor standard diet and a diet enriched in cholesterol and saturated fat. The results obtained showed that there are no miRNAs whose expression constantly vary with dietary or genetic changes. Furthermore, it appears that diet, more than genotype, impacts on organ-specific miRNA expression profiles.

PCSK9 and the nervous system: a no-brainer?

In the past 20 years, PCSK9 has been shown to play a pivotal role in LDL cholesterol metabolism and cardiovascular health by inducing the lysosomal degradation of the LDL receptor. PCSK9 was discovered by the cloning of genes up-regulated after apoptosis induced by serum deprivation in primary cerebellar neurons, but despite its initial identification in the brain, the precise role of PCSK9 in the nervous system remains to be clearly established. The present article is a comprehensive review of studies published or in print before July 2023 that have investigated the expression pattern of PCSK9, its effects on lipid metabolism as well as its putative roles specifically in the central and peripheral nervous systems, with a special focus on cerebrovascular and neurodegenerative diseases.

Targeting PCSK9 to tackle cardiovascular disease

Lowering blood cholesterol levels efficiently reduces the risk of developing atherosclerotic cardiovascular disease (ASCVD), including coronary artery disease (CAD), which is the main cause of death worldwide. CAD is caused by plaque formation, comprising cholesterol deposits in the coronary arteries. Proprotein convertase subtilisin kexin/type 9 (PCSK9) was discovered in the early 2000s and later identified as a key regulator of cholesterol metabolism. PCSK9 induces lysosomal degradation of the low-density lipoprotein (LDL) receptor in the liver, which is responsible for clearing LDL-cholesterol (LDL-C) from the circulation. Accordingly, gain-of-function PCSK9 mutations are causative of familial hypercholesterolemia, a severe condition with extremely high plasma cholesterol levels and increased ASCVD risk, whereas loss-of-function PCSK9 mutations are associated with very low LDL-C levels and protection against CAD. Since the discovery of PCSK9, extensive investigations in developing PCSK9 targeting therapies have been performed. The combined delineation of clear biology, genetic risk variants, and PCSK9 crystal structures have been major drivers in developing antagonistic molecules. Today, two antibody-based PCSK9 inhibitors have successfully progressed to clinical application and shown to be effective in reducing cholesterol levels and mitigating the risk of ASCVD events, including myocardial infarction, stroke, and death, without any major adverse effects. A third siRNA-based inhibitor has been FDA-approved but awaits cardiovascular outcome data. In this review, we outline the PCSK9 biology, focusing on the structure and nonsynonymous mutations reported in the PCSK9 gene and elaborate on PCSK9-lowering strategies under development. Finally, we discuss future perspectives with PCSK9 inhibition in other severe disorders beyond cardiovascular disease.

Liposome-Based Carriers for CRISPR Genome Editing

The CRISPR-based genome editing technology, known as clustered regularly interspaced short palindromic repeats (CRISPR), has sparked renewed interest in gene therapy. This interest is accompanied by the development of single-guide RNAs (sgRNAs), which enable the introduction of desired genetic modifications at the targeted site when used alongside the CRISPR components. However, the efficient delivery of CRISPR/Cas remains a challenge. Successful gene editing relies on the development of a delivery strategy that can effectively deliver the CRISPR cargo to the target site. To overcome this obstacle, researchers have extensively explored non-viral, viral, and physical methods for targeted delivery of CRISPR/Cas9 and a guide RNA (gRNA) into cells and tissues. Among those methods, liposomes offer a promising approach to enhance the delivery of CRISPR/Cas and gRNA. Liposomes facilitate endosomal escape and leverage various stimuli such as light, pH, ultrasound, and environmental cues to provide both spatial and temporal control of cargo release. Thus, the combination of the CRISPR-based system with liposome delivery technology enables precise and efficient genetic modifications in cells and tissues. This approach has numerous applications in basic research, biotechnology, and therapeutic interventions. For instance, it can be employed to correct genetic mutations associated with inherited diseases and other disorders or to modify immune cells to enhance their disease-fighting capabilities. In summary, liposome-based CRISPR genome editing provides a valuable tool for achieving precise and efficient genetic modifications. This review discusses future directions and opportunities to further advance this rapidly evolving field.

Statins in Cancer Prevention and Therapy

Statins, a class of HMG-CoA reductase inhibitors best known for their cholesterol-reducing and cardiovascular protective activity, have also demonstrated promise in cancer prevention and treatment. This review focuses on their potential applications in head and neck cancer (HNC), a common malignancy for which established treatment often fails despite incurring debilitating adverse effects. Preclinical and clinical studies have suggested that statins may enhance HNC sensitivity to radiation and other conventional therapies while protecting normal tissue, but the underlying mechanisms remain poorly defined, likely involving both cholesterol-dependent and -independent effects on diverse cancer-related pathways. This review brings together recent discoveries concerning the anticancer activity of statins relevant to HNC, highlighting their anti-inflammatory activity and impacts on DNA-damage response. We also explore molecular targets and mechanisms and discuss the potential to integrate statins into conventional HNC treatment regimens to improve patient outcomes.

Evidence of an anti-inflammatory effect of PCSK9 inhibitors within the human atherosclerotic plaque

BACKGROUND AND AIMS

Preclinical evidence suggests that proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors hold anti-inflammatory properties independently of their ability to lower LDL-cholesterol (C). However, whether PCSK9 inhibitors exert anti-inflammatory effects within the atherosclerotic plaque in humans is unknown. We explored the impact of PCSK9 inhibitors, used as monotherapy, compared with other lipid-lowering drugs (oLLD) on the expression of inflammatory markers within the plaque, assessing also the subsequent incidence of cardiovascular events.

METHODS

In an observational study, we recruited 645 patients on stable therapy for at least six months and undergoing carotid endarterectomy, categorizing patients according to the use of PCSK9 inhibitors only (n = 159) or oLLD (n = 486). We evaluated the expression of NLRP3, caspase-1, IL-1β, TNFα, NF-kB, PCSK9, SIRT3, CD68, MMP-9, and collagen within the plaques in the two groups through immunohistochemistry, ELISA, or immunoblot. A composite outcome including non-fatal myocardial infarction, non-fatal stroke, and all-cause mortality was assessed during a 678 ± 120 days follow-up after the procedure.

RESULTS

Patients treated with PCSK9 inhibitors had a lower expression of pro-inflammatory proteins and a higher abundance of SIRT3 and collagen within the plaque, a result obtained despite comparable levels of circulating hs-CRP and observed also in LDL-C-matched subgroups with LDL-C levels <100 mg/dL. Patients treated with PCSK9 inhibitors showed a decreased risk of developing the outcome compared with patients on oLLD, also after adjustment for multiple variables including LDL-C (adjusted hazard ratio 0.262; 95% CI 0.131-0.524; p < 0.001). The expression of PCSK9 correlated positively with that of pro-inflammatory proteins, which burden was associated with a higher risk of developing the outcome, independently of the therapeutic regimen.

CONCLUSIONS

The use of PCSK9 inhibitors is accompanied by a beneficial remodelling of the inflammatory burden within the human atheroma, an effect possibly or partly independent of their LDL-C lowering ability. This phenomenon might provide an additional cardiovascular benefit.

Recent Advances in Translational Research for Heart Failure in Japan

Despite decades of intensive research and therapeutic development, heart failure remains a leading cause of death worldwide. However, recent advances in several basic and translational research fields, such as genomic analysis and single-cell analysis, have increased the possibility of developing novel diagnostic approaches to heart failure. Most cardiovascular diseases that predispose individuals to heart failure are caused by genetic and environmental factors. It follows that genomic analysis can contribute to the diagnosis and prognostic stratification of patients with heart failure. In addition, single-cell analysis has shown great potential for unveiling the pathogenesis and/or pathophysiology and for discovering novel therapeutic targets for heart failure. Here, we summarize the recent advances in translational research on heart failure in Japan, based mainly on our studies.

A Metabolic Enhancer Protects against Diet-Induced Obesity and Liver Steatosis and Corrects a Pro-Atherogenic Serum Profile in Mice

OBJECTIVE

Metabolic Syndrome (MetS) affects hundreds of millions of individuals and constitutes a major cause of morbidity and mortality worldwide. Obesity is believed to be at the core of metabolic abnormalities associated with MetS, including dyslipidemia, insulin resistance, fatty liver disease and vascular dysfunction. Although previous studies demonstrate a diverse array of naturally occurring antioxidants that attenuate several manifestations of MetS, little is known about the (i) combined effect of these compounds on hepatic health and (ii) molecular mechanisms responsible for their effect.

METHODS

We explored the impact of a metabolic enhancer (ME), consisting of 7 naturally occurring antioxidants and mitochondrial enhancing agents, on diet-induced obesity, hepatic steatosis and atherogenic serum profile in mice.

RESULTS

Here we show that a diet-based ME supplementation and exercise have similar beneficial effects on adiposity and hepatic steatosis in mice. Mechanistically, ME reduced hepatic ER stress, fibrosis, apoptosis, and inflammation, thereby improving overall liver health. Furthermore, we demonstrated that ME improved HFD-induced pro-atherogenic serum profile in mice, similar to exercise. The protective effects of ME were reduced in proprotein convertase subtilisin/kexin 9 (PCSK9) knock out mice, suggesting that ME exerts it protective effect partly in a PCSK9-dependent manner.

CONCLUSIONS

Our findings suggest that components of the ME have a positive, protective effect on obesity, hepatic steatosis and cardiovascular risk and that they show similar effects as exercise training.

Recent Genome-Editing Approaches toward Post-Implanted Fetuses in Mice

Genome editing, as exemplified by the CRISPR/Cas9 system, has recently been employed to effectively generate genetically modified animals and cells for the purpose of gene function analysis and disease model creation. There are at least four ways to induce genome editing in individuals: the first is to perform genome editing at the early preimplantation stage, such as fertilized eggs (zygotes), for the creation of whole genetically modified animals; the second is at post-implanted stages, as exemplified by the mid-gestational stages (E9 to E15), for targeting specific cell populations through in utero injection of viral vectors carrying genome-editing components or that of nonviral vectors carrying genome-editing components and subsequent in utero electroporation; the third is at the mid-gestational stages, as exemplified by tail-vein injection of genome-editing components into the pregnant females through which the genome-editing components can be transmitted to fetal cells via a placenta-blood barrier; and the last is at the newborn or adult stage, as exemplified by facial or tail-vein injection of genome-editing components. Here, we focus on the second and third approaches and will review the latest techniques for various methods concerning gene editing in developing fetuses.

PCSK9 attenuates efferocytosis in endothelial cells and promotes vascular aging

Aims: Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that binds to low-density lipoprotein receptors. Efferocytosis is the process by which phagocytes remove apoptotic cells. Both PCSK9 and efferocytosis play important roles in regulating redox biology and inflammation, the key factors contributing to vascular aging. This study was designed to investigate the impact of PCSK9 on efferocytosis in endothelial cells (ECs) and its implications in vascular aging. Methods and Results: Studies were performed in primary human aortic ECs (HAECs) and primary mouse aortic ECs (MAECs) isolated from male wild-type (WT) and PCSK9-/- mice, and in young and aged mice treated with saline or the PCSK9 inhibitor Pep2-8. Our findings include that recombinant PCSK9 protein induces defective efferocytosis and aging marker senescence-associated-β-galactosidase (SA-β-gal) expression in ECs, while PCSK9-/- restores efferocytosis and inhibits SA-β-gal activity. Further studies in aged mice showed that endothelial deficiency of MerTK, a critical receptor for efferocytosis that allows phagocytes to detect the presence of apoptotic cells, may be an indicator of vascular dysfunction in the aortic arch. Pep2-8 treatment markedly restored efferocytosis in endothelium from the aged mice. A proteomics study in the aortic arch from aged mice revealed that Pep2-8 administration significantly downregulates expression of NOX4, MAPK subunits, NF-κB, and secretion of pro-inflammatory cytokines, all known to promote vascular aging. Immunofluorescent staining showed that Pep2-8 administration upregulates expression of eNOS and downregulates expression of pro-IL-1β, NF-κB and p22phox compared to saline treated group. Conclusions: These findings provide initial evidence for the ability of aortic ECs to accomplish efferocytosis and argue for a role of PCSK9 in attenuating EC efferocytosis, thereby leading to vascular dysfunction and acceleration in vascular aging.

Gene transfer and genome editing for familial hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant inherited disease characterized by high circulating low-density lipoprotein (LDL) cholesterol. High circulating LDL cholesterol in FH is due to dysfunctional LDL receptors, and is mainly expressed by hepatocytes. Affected patients rapidly develop atherosclerosis, potentially leading to myocardial infarction and death within the third decade of life if left untreated. Here, we introduce the disease pathogenesis and available treatment options. We highlight different possible targets of therapeutic intervention. We then review different gene therapy strategies currently under development, which may become novel therapeutic options in the future, and discuss their advantages and disadvantages. Finally, we briefly outline the potential applications of some of these strategies for the more common acquired hypercholesterolemia disease.

High fat diet and PCSK9 knockout modulates lipid profile of the liver and changes the expression of lipid homeostasis related genes

BACKGROUND

High fat diet (HFD) increases the likelihood of dyslipidemia, which can be a serious risk factor for atherosclerosis, diabetes or hepatosteatosis. Although changes in different blood lipid levels were broadly investigated, such alterations in the liver tissue have not been studied before. The aim of the current study was to investigate the effect of HFD on hepatic triglyceride (TG), diglyceride (DG) and ceramide (CER) levels and on the expression of four key genes involved in lipid homeostasis (Pcsk9, Ldlr, Cd36 and Anxa2) in the liver. In addition, the potential role of PCSK9 in the observed changes was further investigated by using PCSK9 deficient mice.

METHODS

We used two in vivo models: mice kept on HFD for 20 weeks and PCSK9^-/- mice. The amount of the major TGs, DGs and CERs was measured by using HPLC-MS/MS analysis. The expression profiles of four lipid related genes, namely Pcsk9, Ldlr, Cd36 and Anxa2 were assessed. Co-localization studies were performed by confocal microscopy.

RESULTS

In HFD mice, hepatic PCSK9 expression was decreased and ANXA2 expression was increased both on mRNA and protein levels, and the amount of LDLR and CD36 receptor proteins was increased. While LDLR protein level was also elevated in the livers of PCSK9^-/- mice, there was no significant change in the expression of ANXA2 and CD36 in these animals. HFD induced a significant elevation in the hepatic levels of all measured TG and DG but not of CER types, and increased the proportion of monounsaturated vs. saturated TGs and DGs. Similar changes were detected in the hepatic lipid profiles of HFD and PCSK9^-/- mice. Co-localization of PCSK9 with LDLR, CD36 and ANXA2 was verified in HepG2 cells.

CONCLUSIONS

Our results show that obesogenic HFD downregulates PCSK9 expression in the liver and causes alterations in the hepatic lipid accumulation, which resemble those observed in PCSK9 deficiency. These findings suggest that PCSK9-mediated modulation of LDLR and CD36 expression might contribute to the HFD-induced changes in lipid homeostasis.

Targeting PCSK9 With Antibodies and Gene Silencing to Reduce LDL Cholesterol

The discovery of PCSK9 and its role in regulating the low-density lipoprotein (LDL) receptor, and the effect of loss-of-function mutations of its gene, identified it as a therapeutic target in 2006. Fully humanized monoclonal antibodies to PCSK9 (alirocumab and evolocumab) proved effective for lowering LDL cholesterol and subsequently for reducing atherosclerotic events in large outcome trials. Suppressing PCSK9 synthesis via gene silencing using inclisiran, a small interfering RNA, is another approach that effectively reduces LDL cholesterol, and a cardiovascular outcome trial is in progress. These treatments are given subcutaneously on a background of maximally tolerated statin treatment and are long-lasting: dosing is once or twice a month, self-administered, for alirocumab and evolocumab, and every 6 months for inclisiran, in the clinic, with an extra dose at 3 months in the initial year of therapy. These 3 agents produce mean LDL reductions of about 55% with no important adverse effects detectable to date. They are indicated in patients with atherosclerotic vascular disease or familial hypercholesterolemia who cannot achieve LDL cholesterol targets with maximally tolerated statin treatment. Such therapy can produce very low plasma LDL cholesterol and PCSK9, but there is no evidence this is harmful. Introduction into clinical practice has been impeded by economic considerations. The barrier to their use has not been scientific or medical, but rather the impact on healthcare resources. Prices have been reduced, but whether they are now cost-effective varies from country to country.

Genetics, Safety, Cost-Effectiveness, and Accessibility of Injectable Lipid-Lowering Agents: A Narrative Review

Cardiovascular disease causes significant personal, financial, and societal burden and is a major cause of mortality and morbidity globally. Dyslipidemia has proven to be a major factor that contributes to its increased incidence; thus, since a long time, low-density lipoprotein cholesterol-lowering therapies have been employed to reduce coronary artery disease-associated mortality. The first-line therapy for hyperlipidemia and dyslipidemia is statins. Evidence showed that statins decrease the level of LDL-C resulting in a lower risk of CVD (20-25% for every decrease of 1 mmol/L). However, due to statin intolerance in some patients and despite using maximal doses, they have not been successful in lowering cardiovascular-associated mortality. Moreover, bococizumab was recently suspended due to its higher immunogenicity with time, resulting in less efficacy with long-term use. Alternatives to statins are PCSK9 inhibitors which are administered subcutaneously every two or four weeks. They are injectables with considerable lipid-lowering properties. This narrative review discusses their genetics, safety, tolerability, and cost-effectiveness. It also quantifies their benefit in certain subgroups by analyzing the findings from recent randomized clinical trials. Current data from phase 2 and 3 trials (ORION, ODYSSEY, and FOURIER) suggest a favorable profile for evolocumab, alirocumab, and inclisiran with minimal tolerable side effects and superior efficacy in statin-intolerant patients. Their cost-effectiveness has not yet been established clearly, but future outcomes seem promising.

Surf4, cargo trafficking, lipid metabolism, and therapeutic implications

Surfeit 4 is a polytopic transmembrane protein that primarily resides in the endoplasmic reticulum (ER) membrane. It is ubiquitously expressed and functions as a cargo receptor, mediating cargo transport from the ER to the Golgi apparatus via the canonical coat protein complex II (COPII)-coated vesicles or specific vesicles. It also participates in ER-Golgi protein trafficking through a tubular network. Meanwhile, it facilitates retrograde transportation of cargos from the Golgi apparatus to the ER through COPI-coated vesicles. Surf4 can selectively mediate export of diverse cargos, such as PCSK9 very low-density lipoprotein (VLDL), progranulin, α1-antitrypsin, STING, proinsulin, and erythropoietin. It has been implicated in facilitating VLDL secretion, promoting cell proliferation and migration, and increasing replication of positive-strand RNA viruses. Therefore, Surf4 plays a crucial role in various physiological and pathophysiological processes and emerges as a promising therapeutic target. However, the molecular mechanisms by which Surf4 selectively sorts diverse cargos for ER-Golgi protein trafficking remain elusive. Here, we summarize the most recent advances in Surf4, focusing on its role in lipid metabolism.

Heparin Does Not Regulate Circulating Human PCSK9 (Proprotein Convertase Subtilisin-Kexin Type 9) in a General Population-Brief Report

BACKGROUND

PCSK9 (proprotein convertase subtilisin-kexin type 9) chaperones the hepatic LDLR (low-density lipoprotein receptor) for lysosomal degradation, elevating serum LDL (low-density lipoprotein) cholesterol and promoting atherosclerotic heart disease. Though the major effect on the hepatic LDLR comes from secreted PCSK9, the details of PCSK9 reuptake into the hepatocyte remain unclear. In both tissue culture and animal models, HSPGs (heparan sulfate proteoglycans) on hepatocytes act as co-receptors to promote PCSK9 reuptake. We hypothesized that if this PCSK9:HSPG interaction is important in humans, disrupting it with unfractionated heparin (UFH) would acutely displace PCSK9 from the liver and increase plasma PCSK9.

METHODS

We obtained remnant plasma samples from 160 subjects undergoing cardiac catheterization before and after administration of intravenous UFH. PCSK9 levels were determined using a commercial enzyme-linked immunosorbent assay.

RESULTS

Median plasma PCSK9 was 113 ng/mL prior to UFH and 119 ng/mL afterward. This difference was not significant (P=0.83 [95% CI, -6.23 to 6.31 ng/mL]). Equivalence testing provided 95% confidence that UFH would not raise plasma PCSK9 by > 4.7%. Among all subgroups, only subjects with the lowest baseline PCSK9 concentrations exhibited a response to UFH (8.8% increase, adj. P=0.044). A modest correlation was observed between baseline plasma PCSK9 and the change in plasma PCSK9 due to UFH (RS=-0.3634; P<0.0001).

CONCLUSIONS

Administration of UFH does not result in a clinically meaningful effect on circulating PCSK9 among an unselected population of humans. The results cast doubt on the clinical utility of disrupting the PCSK9:HSPG interaction as a general therapeutic strategy for PCSK9 inhibition. However, the observations suggest that in selected populations, disrupting the PCSK9:HSPG interaction could still affect PCSK9 reuptake and offer a therapeutic benefit.

PCSK9 deficiency alters brain lipid composition without affecting brain development and function

PCSK9 induces lysosomal degradation of the low-density lipoprotein (LDL) receptor (LDLR) in the liver, hereby preventing removal of LDL cholesterol from the circulation. Accordingly, PCSK9 inhibitory antibodies and siRNA potently reduce LDL cholesterol to unprecedented low levels and are approved for treatment of hypercholesterolemia. In addition, PCSK9 inactivation alters the levels of several other circulating lipid classes and species. Brain function is critically influenced by cholesterol and lipid composition. However, it remains unclear how the brain is affected long-term by the reduction in circulating lipids as achieved with potent lipid lowering therapeutics such as PCSK9 inhibitors. Furthermore, it is unknown if locally expressed PCSK9 affects neuronal circuits through regulation of receptor levels. We have studied the effect of lifelong low peripheral cholesterol levels on brain lipid composition and behavior in adult PCSK9 KO mice. In addition, we studied the effect of PCSK9 on neurons in culture and in vivo in the developing cerebral cortex. We found that PCSK9 reduced LDLR and neurite complexity in cultured neurons, but neither PCSK9 KO nor overexpression affected cortical development in vivo. Interestingly, PCSK9 deficiency resulted in changes of several lipid classes in the adult cortex and cerebellum. Despite the observed changes, PCSK9 KO mice had unchanged behavior compared to WT controls. In conclusion, our findings demonstrate that altered PCSK9 levels do not compromise brain development or function in mice, and are in line with clinical trials showing that PCSK9 inhibitors have no adverse effects on cognitive function.

Mechanisms of unusual response to lipid-lowering therapy: PCSK9 inhibition

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.