Proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors: Shaping the future after the further cardiovascular outcomes research with PCSK9 inhibition in subjects with elevated risk (FOURIER) trial

Inclisiran, Low-Density Lipoprotein Cholesterol and Lipoprotein (a)

Dyslipidemia treatment is of major importance in reducing the risk of atherosclerotic cardiovascular disease (ASCVD), which is still the most common cause of death worldwide. During the last decade, a novel lipid-lowering drug category has emerged, i.e., proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors. Apart from the two available anti-PCSK9 monoclonal antibodies (alirocumab and evolocumab), other nucleic acid-based therapies that inhibit or "silence" the expression of PCSK9 are being developed. Among them, inclisiran is the first-in-class small interfering RNA (siRNA) against PCSK9 that has been approved by both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of hypercholesterolemia. Importantly, inclisiran therapy may improve low-density lipoprotein cholesterol (LDL-C) target achievement by offering a prolonged and significant LDL-C-lowering effect with the administration of only two doses per year. The present narrative review discusses the ORION/VICTORION clinical trial program that has been designed to investigate the impact of inclisiran on atherogenic lipoproteins and major adverse cardiac events in different patient populations. The results of the completed clinical trials are presented, focusing on the effects of inclisiran on LDL-C and lipoprotein (a) (Lp(a)) levels as well as on other lipid parameters such as apolipoprotein B and non-high-density lipoprotein cholesterol (non-HDL-C). Ongoing clinical trials with inclisiran are also discussed.

Effect of alirocumab and evolocumab on all-cause mortality and major cardiovascular events: A meta-analysis focusing on the number needed to treat

AIMS

The efficacy of anti-proprotein convertase subtilisin/Kexin type 9 (PCSK9) monoclonal antibodies in patients with atherosclerotic cardiovascular disease (ASCVD) remains unclear. Therefore, this study aims to assess the effect of PCSK9 inhibitors (alirocumab and evolocumab) on ASCVD patients considering the number needed to treat (NNT).

METHODS

We reviewed randomized controlled trials (RCTs) which compared the effects of alirocumab or evolocumab and placebo or standards of care. All articles were published in English up to May 2022. Using random effect models, we estimated risk ratios (RRs), NNT, and 95% confidence intervals (CI).

RESULTS

We incorporated 12 RCTs with 53 486 patients total, of which 27 674 received PCSK9 inhibitors and 25 812 received placebos. The mean follow-up duration was 1.56 years. The effect of PCSK9 inhibitors on major adverse cardiovascular events (MACE) was statistically significant, and the corresponding mean NNT was 36. Alirocumab reduced the risk of MACE, stroke, and coronary revascularization; the corresponding mean NNT were 37, 319, and 107, respectively. Evolocumab positively affected MACE, myocardial infarction, stroke, and coronary revascularization; the corresponding mean NNT were 32, 78, 267, and 65, respectively. The effects of alirocumab or evolocumab on all-cause mortality and cardiovascular mortality were not statistically significant.

CONCLUSION

This study suggests that preventing one patient from MACE needed to treat 36 patients with ASCVD with PCSK9 inhibitors for 1.56 years. Both alirocumab and evolocumab reduced MACE, stroke, and coronary revascularization. Evolocumab had a positive effect on myocardial infarction, but no effects were noted for alirocumab. In addition, alirocumab may not be as effective as evolocumab. NNT visualizes the magnitude of efficacy to assist in clinical decisions.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=344908], identifier [CRD42022344908].

Pancreatic PCSK9 controls the organization of the β-cell secretory pathway via LDLR-cholesterol axis

BACKGROUND

Cholesterol is central to pancreatic β-cell physiology and alterations of its homeostasis contribute to β-cell dysfunction and diabetes. Proper intracellular cholesterol levels are maintained by different mechanisms including uptake via the low-density lipoprotein receptor (LDLR). In the liver, the proprotein convertase subtilisin/kexin type 9 (PCSK9) routes the LDLR to lysosomes for degradation, thus limiting its recycling to the membrane. PCSK9 is also expressed in the pancreas and loss of function mutations of PCSK9 result in higher plasma glucose levels and increased risk of Type 2 diabetes mellitus. Aim of this study was to investigate whether PCSK9 also impacts β-cells function.

METHODS

Pancreas-specific Pcsk9 null mice (Pdx1Cre/Pcsk9 fl/fl) were generated and characterized for glucose tolerance, insulin release and islet morphology. Isolated Pcsk9-deficient islets and clonal β-cells (INS1E) were employed to characterize the molecular mechanisms of PCSK9 action.

RESULTS

Pdx1Cre/Pcsk9 fl/fl mice exhibited normal blood PCSK9 and cholesterol levels but were glucose intolerant and had defective insulin secretion in vivo. Analysis of PCSK9-deficient islets revealed comparable β-cell mass and insulin content but impaired stimulated secretion. Increased proinsulin/insulin ratio, modifications of SNARE proteins expression and decreased stimulated‑calcium dynamics were detected in PCSK9-deficient β-cells. Mechanistically, pancreatic PCSK9 silencing impacts β-cell LDLR expression and cholesterol content, both in vivo and in vitro. The key role of LDLR is confirmed by the demonstration that LDLR downregulation rescued the phenotype.

CONCLUSIONS

These findings establish pancreatic PCSK9 as a novel critical regulator of the functional maturation of the β-cell secretory pathway, via modulation of cholesterol homeostasis.

Advances in biological therapies for dyslipidemias and atherosclerosis

Atherosclerosis is a multifactorial disease influenced by genetics, lifestyle and environmental factors. Despite therapeutic advances that reduce the risk of cardiovascular events, atherosclerosis-related diseases remain the leading cause of mortality worldwide. Precise targeting of genes involved in lipoprotein metabolism is an emerging approach for atherosclerosis prevention and treatment. This article focuses on the latest developments, clinical potential and current challenges of monoclonal antibodies, vaccines and genome/transcriptome modification strategies, including antisense oligonucleotides, genome/base editing and gene therapy. Multiple lipid lowering biological therapies have already been approved by the FDA with impressive results to date, while many more promising targets are being pursued in clinical trials or pre-clinical animal models.

Lipid-lowering Drugs and Neurocognitive Function: A Systematic Review

BACKGROUND/AIM

Lipid-lowering drugs have been suggested to affect neurocognitive function. This review aimed to give the latest evidence on the way these agents affect neurocognitive function based on clinical trials.

MATERIALS AND METHODS

A systematic search concerning original studies from 2015 to 2020 was performed through the databases PubMed, EMBASE and Cochrane, according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. The trials enrolled numerous patients and were conducted in different areas of the world. The terms used are cholesterol, lipid-lowering drugs, statins and cognitive function.

RESULTS

Eleven randomized trials met the inclusion criteria. The trials included patients suffering from cardiovascular conditions. In particular, patients with coronary heart disease, coronary heart disease risk equivalents and hypercholesterolemia were tested. The trials included evolocumab, alirocumab, statin, ezetimibe or placebo.

CONCLUSION

Lipid-lowering drugs seem to have no significant effect on neurocognitive function, but further research specifically focused on this matter is needed.

Obesity and dyslipidemia

Obesity, a pandemic of the modern world, is intimately associated with dyslipidemia, which is mainly driven by the effects of insulin resistance and pro-inflammatory adipokines. However, recent evidence suggests that obesity-induced dyslipidemia is not a unique pathophysiological entity, but rather has distinct characteristics depending on many individual factors. In line with that, in a subgroup of metabolically healthy obese (MHO) individuals, dyslipidemia is less prominent or even absent. In this review, we will address the main characteristics of dyslipidemia and mechanisms that induce its development in obesity. The fields, which should be further investigated to expand our knowledge on obesity-related dyslipidemia and potentially yield new strategies for prevention and management of cardiometabolic risk, will be highlighted. Also, we will discuss recent findings on novel lipid biomarkers in obesity, in particular proprotein convertase subtilisin/kexin type 9 (PCSK9), as the key molecule that regulates metabolism of low-density lipoproteins (LDL), and sphingosine-1-phosphate (S1P), as one of the most important mediators of high-density lipoprotein (HDL) particles function. Special attention will be given to microRNAs and their potential use as biomarkers of obesity-associated dyslipidemia.

PCSK9 and neurocognitive function: Should it be still an issue after FOURIER and EBBINGHAUS results?

The serine protease proprotein convertase subtilisin/kexin type 9 (PCSK9) modulates the levels of low-density lipoprotein cholesterol and cardiovascular risk. Potential risks of adverse neurological effects of intensive lipid-lowering treatment have been hypothesized, as cholesterol is a component of the central nervous system. Moreover, several observations suggest that PCSK9 might play a role in neurogenesis, neuronal migration and apoptosis. In rodents, increased expression of PCSK9 has been detected in specific areas of the central nervous system during embryonic development; also, PCSK9 modulates low-density lipoprotein receptor levels in the ischemic brain areas. Despite a putative participation of PCSK9 in nervous system physiology, the absence of PCSK9 in knockout mice or in humans with loss-of-function mutations of PCSK9 gene has not been linked to neurological alterations. In recent years, some concerns have been raised about the potential neurological side effects of cholesterol-lowering treatments and, more specifically of PCSK9 inhibitors. In this review, the evidence regarding the function of PCSK9 in neuron differentiation, apoptosis, and migration and in nervous system development and latest clinical trials evaluating the effects of PCSK9 inhibitors on neurocognitive function will be described.

Diabetes and lipid metabolism

The authors review the association between diabetes mellitus (DM) and aberrations of lipid metabolism related to DM, diabetic dyslipidemia (DD). DM is considered as a major health burden worldwide and one of the most important modifiable cardiovascular disease (CVD) risk factors. This applies to both the developed and the developing countries, especially the latter. While patients with type 1 DM, 10% of all DM cases, usually do not have dyslipidemia, DD is frequent among patients with type 2 DM (T2DM) (prevalence > 75%) and is mainly a mixed dyslipidemia [increase in triglycerides (TGs), low high-density lipoprotein cholesterol (HDL-C), and small-dense (atherogenic), low-density lipoprotein cholesterol (LDL-C) particles]. The components of DD, which is characterized by quantitative (mentioned above), qualitative, and kinetic abnormalities all contributing to CVD risk, are mostly related to insulin resistance. Statins, ezetimibe, and PCSK9 inhibitors can be used in monotherapy or consecutively in combinations if needed. Statins compose the main drug. For the residual CVD risk after statin treatment, the use of statin-fibrate combinations is indicated only in patients with mixed dyslipidemia. In conclusion, DD is a major health problem worldwide. It is a significant CVD risk factor and should be treated according to current guidelines. The means today exist to normalize all quantitative, qualitative, and kinetic aberrations of DD, thereby reducing CVD risk.

Dyslipidaemia in the elderly: to treat or not to treat?

INTRODUCTION

The elderly population (i.e. aged ≥ 65 years) is increasing worldwide. Ageing is associated with a higher incidence and prevalence of cardiovascular disease (CVD). Areas covered: The prevalence of CVD risk factors including type 2 diabetes mellitus, hypertension and dyslipidaemia also increases with advancing age, contributing to the higher absolute CVD risk observed in the elderly. The present narrative review comments on the associations of dyslipidaemia with CVD as well as the effects of lifestyle measures and lipid-lowering drugs on lipids and CVD risk with a special focus on the elderly population. Individual treatment goals and therapeutic options according to current guidelines are also reviewed. Finally, we discuss special characteristics of the elderly that may influence the efficacy and safety of drug therapy and should be considered before selection of hypolipidaemic pharmacotherapy. Expert commentary: There may be a greater CVD benefit in older patients following drug therapy compared with younger ones. Treatment goals and therapeutic options should be individualized according to current guidelines. Specific characteristics that may influence the efficacy and safety of drug therapy in the elderly should be considered in relation to dyslipidaemia treatment.

Thyroid stimulating hormone exhibits the impact on LDLR/LDL-c via up-regulating hepatic PCSK9 expression

CONTEXT

Thyroid stimulating hormone (TSH) has received increasing attention as being closely associated with increased low-density lipoprotein cholesterol (LDL-c) level and higher atherosclerotic risks. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is known for increasing circulating LDL-c level by inducing LDL receptor degradation. However, whether TSH influences hepatic PCSK9 expression and LDL-c metabolism remains unclear.

METHODS

First, the correlation between TSH and lipid profiles were investigated in euthyroid population and in subclinical hypothyroidism patients. Then, an in vitro study was conducted to validate the effects of TSH on hepatic PCSK9 expression in HepG2 cells.

RESULTS

Serum TSH concentrations positively correlated with LDL-c levels in euthyroid subjects. Subclinical hypothyroidism patients with higher serum TSH levels showed significantly increased serum PCSK9 levels than the matched euthyroid participants (151.29 (89.51-293.03) vs. 84.70 (34.98-141.72) ng/ml, P<0.001), along with increased LDL-c concentrations. In HepG2 cells, LDLR expression on the plasma membrane was decreased, and PCSK9 mRNA and protein levels were synchronously upregulated after recombinant human TSH (rhTSH) treatment, while the effects could be blocked by TSH receptor blocking antibody K1-70. Sterol regulatory element binding protein (SREBP) 1c and SREBP2 mRNA expressions were enhanced after rhTSH treatment, and specific siRNAs significantly inhibited the effects of rhTSH. Furthermore, there was a noticeable induction of PCSK9 expression by rhTSH even though HMGCR gene expression was silenced.

CONCLUSION

We conclude a regulating role of TSH on hepatic PCSK9 expression, which further contributing to a higher LDL-c level.