The loss-of-function PCSK9 p.R46L genetic variant does not alter glucose homeostasis

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.

Effect of the PCSK9 R46L genetic variant on plasma insulin and glucose levels, risk of diabetes mellitus and cardiovascular disease: A meta-analysis

BACKGROUND AND AIM

The impact of the loss-of-function (LOF) genetic variant PCSK9 R46L on glucose homeostasis and cardiovascular disease (CVD) remains uncertain, despite its established correlation with diminished blood cholesterol levels. This meta-analysis aimed at exploring the effect of the PCSK9 R46L genetic variant on plasma insulin and glucose levels, risk of diabetes mellitus and CVD.

METHODS AND RESULTS

PubMed, Embase, and the Cochrane Library were searched for cohort and case-control studies published until October 1, 2023. The studies should report the association of the PCSK9 R46L genetic variant with one of the following: fasting plasma insulin, blood glucose levels, diabetes mellitus, and CVD risk. A dominant model of the PCSK9 R46L genetic variant was employed to statistical analysis. The meta-analyses were performed for continuous variables with standard mean difference (SMD), categorical variables with odds ratio (OR) using a random-effects model. A total of 17 articles with 20 studies engaging 1,186,861 population were identified and mobilized for these analyses. The overall results indicated that, compared with non-carriers of the PCSK9 R46L genetic variant, carriers of the PCSK9 R46L genetic variant did not increase or decrease the levels of fasting plasma insulin (3 studies with 7277 population; SMD, 0.08; 95% CI, -0.04 to 0.19; P = 0.270), and the levels of fasting plasma glucose (7 studies with 9331 population; SMD, 0.03; 95% CI, -0.08 to 0.13; P = 0.610). However, carriers of the PCSK9 R46L genetic variant indeed had 17% reduction in the risk of CVD (11 studies with 558,263 population; OR, 0.83; 95% CI, 0.71 to 0.98; P = 0.030), and 9% increase in the risk of diabetes mellitus (10 studies with 744,466 population; OR, 1.09; 95% CI, 1.04 to 1.14; P < 0.01). Meta-regression analyses indicated that the increased risk of diabetes mellitus and the reduced risk of CVD were positively correlated with reduction in LDL-C (P = 0.004 and 0.033, respectively).

CONCLUSIONS

PCSK9 R46L genetic variant exhibited an elevated susceptibility to diabetes mellitus alongside a reduced vulnerability to CVD.

E670G PCSK9 polymorphism in HeFH & CAD with diabetes: is the bridge to personalized therapy within reach?

Objective

To assess the distribution of PCSK9 E670G genetic polymorphism and PCSK9 levels in patients with Coronary Artery Disease (CAD) and Heterozygous Familial Hypercholesterolemia (HeFH), based on the presence of type 2 Diabetes Mellitus (T2DM).

Methods

The study included 201 patients with chronic CAD, including those with HeFH (n=57, group I) and without it (n=144, group II). DLCN was used to diagnose HeFH. The PCSK9 E670G (rs505151) polymorphism was genetically typed using the PCR-RFLP procedure. In both the patient and control groups, the genotype frequency matched the Hardy-Weinberg equilibrium distribution (P>0.05).

Results

There were twice more G alleles in group I (13, 11.4%) than in group II (17, 6.0%), and thrice more (1, 3.0%) than in the healthy control group; nevertheless, these differences weren't statistically significant. Simultaneously, PCSK9 levels were higher in HeFH patients (P<0.05) compared to non-HeFH patients not taking statins (n=63). T2DM was equally represented in groups I and II (31.6% vs. 33.3%). But carriers of AG+GG genotypes in group I had a higher chance of having a history of T2DM (RR 4.18; 95%CI 2.19-8.0; P<0.001), myocardial infarction (RR 1.79; 95%CI 1.18-2.73; P<0.05), and revascularization (RR 12.6; 95%CI 4.06-38.8; P<0.01), than AA carriers. T2DM was also more common among G allele carriers (RR 1.85; 95% CI 1.11-3.06; P<0.05) in patients with non-HeFH.

Conclusion

T2DM in patients with CAD, both with HeFH and non-HeFH, in the Uzbek population was significantly more often associated with the presence of the "gain-of-function" G allele of the PCSK9 E670G genetic polymorphism.

The association between circulatory, local pancreatic PCSK9 and type 2 diabetes mellitus: The effects of antidiabetic drugs on PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a potent modulator of cholesterol metabolism and plays a crucial role in the normal functioning of pancreatic islets and the progression of diabetes. Islet autocrine PCSK9 deficiency can lead to the enrichment of low-density lipoprotein (LDL) receptor (LDLR) and excessive LDL cholesterol (LDL-C) uptake, subsequently impairing the insulin secretion in β-cells. Circulatory PCSK9 levels are primarily attributed to hepatocyte secretion. Notably, anti-PCSK9 strategies proposed for individuals with hypercholesterolemia chiefly target liver-derived PCSK9; however, these anti-PCSK9 strategies have been associated with the risk of new-onset diabetes mellitus (NODM). In the current review, we highlight a new direction in PCSK9 inhibition therapy strategies: screening candidates for anti-PCSK9 from the drugs used in type 2 diabetes mellitus (T2DM) treatment. We explored the association between circulating, local pancreatic PCSK9 and T2DM, as well as the relationship between PCSK9 monoclonal antibodies and NODM. We discussed the emergence of artificial and natural drugs in recent years, exhibiting dual benefits of antidiabetic activity and PCSK9 reduction, confirming that the diverse effects of these drugs may potentially impact the progression of diabetes and associated disorders, thereby introducing novel avenues and methodologies to enhance disease prognosis.

Insight into the role of PCSK9 in glucose metabolism

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.

Low cholesterol states: clinical implications and management

INTRODUCTION

Hypocholesterolemia results from genetic - both monogenic and polygenic - and non-genetic causes and can sometimes be a source of clinical concern. We review etiologies and sequelae of hypocholesterolemia and therapeutics inspired from genetic hypocholesterolemia.

AREAS COVERED

Monogenic hypocholesterolemia disorders caused by the complete absence of apolipoprotein (apo) B-containing lipoproteins (abetalipoproteinemia and homozygous hypobetalipoproteinemia) or an isolated absence of apo B-48 lipoproteinemia (chylomicron retention disease) lead to clinical sequelae. These include gastrointestinal disturbances and severe vitamin deficiencies that affect multiple body systems, i.e. neurological, musculoskeletal, ophthalmological, and hematological. Monogenic hypocholesterolemia disorders with reduced but not absent levels of apo B lipoproteins have a milder clinical presentation and patients are protected against atherosclerotic cardiovascular disease. Patients with heterozygous hypobetalipoproteinemia have somewhat increased risk of hepatic disease, while patients with PCSK9 deficiency, ANGPTL3 deficiency, and polygenic hypocholesterolemia typically have anunremarkable clinical presentation.

EXPERT OPINION

In patients with severe monogenic hypocholesterolemia, early initiation of high-dose vitamin therapy and a low-fat diet are essential for optimal prognosis. The molecular basis of monogenic hypocholesterolemia has inspired novel therapeutics to help patients with the opposite phenotype - i.e. elevated apo B-containing lipoproteins. In particular, inhibitors of PCSK9 and ANGPTL3 show important clinical impact.

PCSK9 inhibition and cholesterol homeostasis in insulin producing β-cells

Low-density lipoprotein cholesterol (LDL-C) plays a central role in the pathology of atherosclerotic cardiovascular disease. For decades, the gold standard for LDL-C lowering have been statins, although these drugs carry a moderate risk for the development of new-onset diabetes. The inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9) have emerged in the last years as potential alternatives to statins due to their high efficiency and safety without indications for a diabetes risk so far. Both approaches finally eliminate LDL-C from bloodstream by upregulation of LDL receptor surface expression. Due to their low antioxidant capacity, insulin producing pancreatic β-cells are sensitive to increased lipid oxidation and related generation of reactive oxygen species. Thus, PCSK9 inhibition has been argued to promote diabetes like statins. Potentially, the remaining patients at risk will be identified in the future. Otherwise, there is increasing evidence that loss of circulating PCSK9 does not worsen glycaemia since it is compensated by local PCSK9 expression in β-cells and other islet cells. This review explores the situation in β-cells. We evaluated the relevant biology of PCSK9 and the effects of its functional loss in rodent knockout models, carriers of LDL-lowering gene variants and PCSK9 inhibitor-treated patients.

Safety of Statins and Nonstatins for Treatment of Dyslipidemia

This article reviews the safety of statins and non-statin medications for management of dyslipidemia. Statins have uncommon serious adverse effects: myopathy/ rhabdomyolysis, which resolve with statin discontinuation, and diabetes, usually in people with risk factors for diabetes. The CVD benefit of statins far exceeds the risk of diabetes. Statin myalgia, without CK elevation, is likely caused by muscle symptoms with another etiology, or the nocebo effect. Notable adverse effects of non-statin medicines include injection site reactions (alirocumab, evolocumab, inclisiran), increased uric acid and gout (bempedoic acid), atrial fibrillation/flutter (omega-3-fatty acids), and myopathy in combination with a statin (gemfibrozil).

Molecular and cellular biology of PCSK9: impact on glucose homeostasis

Proprotein convertase substilisin/kexin 9 (PCSK9) inhibitors (PCSK9i) revolutionised the lipid-lowering therapy. However, a risk of type 2 diabetes mellitus (T2DM) is evoked under PCSK9i therapy. In this review, we summarise the current knowledge on the link of PCSK9 with T2DM. A significant correlation was found between PCSK9 and insulin, homeostasis model assessment (HOMA) of insulin resistance and glycated haemoglobin. PCSK9 is also involved in inflammation. PCSK9 loss-of-function variants increased T2DM risk by altering insulin secretion. Local pancreatic low PCSK9 regulates β-cell LDLR expression which in turn promotes intracellular cholesterol accumulation and hampers insulin secretion. Nevertheless, the association of PCSK9 loss-of-function variants and T2DM is inconsistent. InsLeu and R46L polymorphisms were associated with T2DM, low HOMA for β-cell function and impaired fasting glucose, while the C679X polymorphism was associated with low fasting glucose in Black South African people. Hence, we assume that the impact of these variants on glucose homeostasis may vary depending on the genetic background of the studied populations and the type of effect caused by those genetic variants on the PCSK9 protein. Accordingly, these factors should be considered when choosing a genetic variant of PCSK9 to assess the impact of long-term use of PCSK9i on glucose homeostasis.

New Treatment Targets and Innovative Lipid-Lowering Therapies in Very-High-Risk Patients with Cardiovascular Disease

The effective and fast reduction of circulating low-density lipoprotein cholesterol (LDL-C) is a cornerstone for secondary prevention of atherosclerotic disease progression. Despite the substantial lipid-lowering effects of the established treatment option with statins and ezetimibe, a significant proportion of very-high-risk patients with cardiovascular disease do not reach the recommended treatment goal of <55 mg/dL (<1.4 mmol/L). Novel lipid-lowering agents, including the proprotein convertase subtilisin/kexin type 9 (PCSK9) antibodies alirocumab and evolocumab, the small interfering ribonucleotide acid (si-RNA) inclisiran, as well as the recently approved bempedoic acid, now complete the current arsenal of LDL-C lowering agents. These innovative therapies have demonstrated promising results in clinical studies. Besides a strong reduction of LDL-C by use of highly effective agents, there is still discussion as to whether a very rapid achievement of the treatment goal should be a new strategic approach in lipid-lowering therapy. In this review, we summarize evidence for the lipid-modifying properties of these novel agents and their safety profiles, and discuss their potential pleiotropic effects beyond LDL-C reduction (if any) as well as their effects on clinical endpoints as cardiovascular mortality. In addition to a treatment strategy of “the lower, the better”, we also discuss the concept of “the earlier, the better”, which may also add to the early clinical benefit of large LDL-C reduction after an acute ischemic event.

The Biological Relevance of PCSK9: When Less Is Better…

Proprotein Convertase Subtilisin/Kexin-type 9 (PCSK9) is a circulating negative regulator of hepatic low-density lipoprotein receptor (LDLR) which clears cholesterol from blood. Gain-of-function genetic mutations which amplify PCSK9 activity have been found to cause potentially lethal familial hypercholesterolemia. Inversely, reduction of its activity through loss-of-function genetics or with pharmaceuticals was shown to increase hepatic LDLR, to lower blood cholesterol, and to protect against cardiovascular diseases. New epidemiological and experimental evidence suggests that this reduction could also attenuate inflammation, reinforce cancer immunity, provide resistance to infections, and protect against liver pathologies. In this review, we question the relevance of this protein under normal physiology. We propose that PCSK9 is an important, but non-essential, modulator of cholesterol metabolism and immunity, and that its pathogenicity results from its chronic overexpression.

Efficacy and Safety of PCSK9 Monoclonal Antibodies in Patients With Diabetes

PURPOSE

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are novel drugs that have proven efficacy in improving cardiovascular outcomes. Roles for the PCSK9 molecule in metabolic pathways beyond LDL receptor processing and cholesterol homeostasis are well established. PCSK9 genetic variants associated with lower LDL-C levels correlate with a higher incidence of type 2 diabetes (T2DM), calling into question the appropriateness of these drugs in patients with T2DM and those at high risk of developing diabetes, and whether cardiovascular benefit seen with PCSK9 inhibitors might be offset by resultant dysglycemia. The purpose of this review was to examine the role of PCSK9 protein in glucose homeostasis, the impact of PCSK9 inhibition in relation to glucose homeostasis, and whether some of the cardiovascular benefit seen with PCSK9 inhibitors and statins might be offset by resultant dysglycemia.

METHODS

Comprehensive literature searches of electronic databases of PubMed, EMBASE, and OVID were conducted by using the search terms hyperlipidaemia, PCSK9, diabetes, and glucose as well as other relevant papers of interest collected by the authors. The retrieved papers were reviewed and shortlisted most relevant ones.

FINDINGS

Genetically determined lower circulating LDL-C and PCSK9 concentrations may have an incremental effect in increasing T2DM incidence, but any perceived harm is outweighed by the reduced risk of atherosclerotic cardiovascular disease achieved through lower lifetime exposure to LDL-C. PCSK9 monoclonal antibodies are effective and safe in patients with T2DM and those at high risk of developing it. The number-needed-to-treat to prevent one atherosclerotic cardiovascular disease event in the FOURIER (Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk) study in the subgroup with diabetes is significantly lower than for those without. Therefore, T2DM or being at high risk to develop it should not be a reason to avoid these agents. The safety of PCSK9 inhibition in relation to glucose homeostasis may depend on the method of inhibition and whether it occurs in circulation or the cells. Data from experimental studies and randomized controlled trials suggest no detrimental effect of PCSK9 monoclonal antibodies on glucose homeostasis. More data and large randomized controlled studies are needed to assess the impact of other methods of PCSK9 inhibition on glucose homeostasis.

IMPLICATIONS

PCSK9monoclonal antibodies markedly reduce LDL-C and consistently reduce cardiovascular mortality in patients with and without diabetes. Current evidence does not suggest an adverse effect of PCSK9 monoclonal antibodies on glycemic parameters.

Association between the rs615563 variant of PCSK9 gene and circulating lipids and Type 2 diabetes

Objective

Many different genetic variants of proprotein convertase subtilisin kexin 9 (PCSK9) are related to the serum levels of cholesterol and LDL cholesterol (LDL-C). The rs615563 variant of PCSK9 (a gain-of-function mutation) is associated with increased triglycerides and cholesterol levels, but its association with the incidence of diabetes is not well defined. This study aimed to investigate the relationship between the PCSK9 rs615563 variant with the incidence of type 2 diabetes. The data reported in this study are based on subsamples from a 5-year (2009–2014) cohort study of the adult population (590 subjects) aged 20 years and older. The rs615563 polymorphism was genotyped using polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis.

Results

The distribution of PCSK9 rs615563 genotypes was not significantly different between the diabetic and non-diabetic individuals. The incidence of diabetes after five-years of follow-up was not different between the genotypes. Our findings also showed no significant relationship between this polymorphism and serum lipid parameters. The data extracted from our cohort study do not support the findings that the gain-of-function mutations of PCSK9 predispose to the incidence of type 2 diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13104-021-05723-4.

How low is safe? The frontier of very low (<30 mg/dL) LDL cholesterol

Low-density lipoprotein cholesterol (LDL-C) is a proven causative factor for developing atherosclerotic cardiovascular disease. Individuals with genetic conditions associated with lifelong very low LDL-C levels can be healthy. We now possess the pharmacological armamentarium (statins, ezetimibe, PCSK9 inhibitors) to reduce LDL-C to an unprecedented extent. Increasing numbers of patients are expected to achieve very low (<30 mg/dL) LDL-C. Cardiovascular event reduction increases log linearly in association with lowering LDL-C, without reaching any clear plateau even when very low LDL-C levels are achieved. It is still controversial whether lower LDL-C levels are associated with significant clinical adverse effects (e.g. new-onset diabetes mellitus or possibly haemorrhagic stroke) and long-term data are needed to address safety concerns. This review presents the familial conditions characterized by very low LDL-C, analyses trials with lipid-lowering agents where patients attained very low LDL-C, and summarizes the benefits and potential adverse effects associated with achieving very low LDL-C. Given the potential for cardiovascular benefit and short-term safe profile of very low LDL-C, it may be advantageous to attain such low levels in specific high-risk populations. Further studies are needed to compare the net clinical benefit of non-LDL-C-lowering interventions with very low LDL-C approaches, in addition to comparing the efficacy and safety of very low LDL-C levels vs. current recommended targets.

Circulating Proprotein Convertase Subtilisin/Kexin Type 9 Levels and Cardiometabolic Risk Factors: A Population-Based Cohort Study

Aims: To evaluate the prospective association of circulating PCSK9 levels with the cardiometabolic risk profiles (high LDL-cholesterol, high triglycerides, low HDL-cholesterol, hypertension, type 2 diabetes, and metabolic syndrome).

Methods: A population-based prospective study was conducted among 7,104 Chinese individuals (age 56.2 ± 7.5 years; 32.0% men). Circulating PCSK9 levels were measured using ELISA.

Results: Circulating PCSK9 levels were higher in women than men (286.7 ± 90.1 vs. 276.1 ± 86.4 ng/ml, p < 0.001). And circulating PCSK9 was positively correlated with LDL-cholesterol, total cholesterol, and triglycerides both in men and women (all p < 0.001). The positive correlation between PCSK9 and waist circumference, fasting glucose, insulin resistance, systolic blood pressure, diastolic blood pressure and C-reactive protein (all p < 0.01) was observed in women only. According to Cox regression analysis, circulating PCSK9 was positively associated with incidence of high LDL-cholesterol both in men (HR 1.33, 95% CI 1.09–1.65, p < 0.001) and women (HR 1.36, 95% CI 1.12–1.69, p < 0.001). Moreover, PCSK9 was significantly associated with incident high triglycerides (HR 1.31, 95% CI 1.13–1.72, p < 0.001), hypertension (HR 1.28, 95% CI 1.08–1.53, p = 0.011), type 2 diabetes (HR 1.34, 95% CI 1.09–1.76, p = 0.005), and metabolic syndrome (HR 1.30, 95% CI 1.11–1.65, p = 0.009) per SD change in women only. No statistically significant association was observed between circulating PCSK9 and incidence of low HDL-cholesterol (p > 0.1).

Conclusions: Elevated circulating PCSK9 was significantly associated with cardiometabolic risk factors and independently contributed to the prediction of cardiometabolic risks in women.

Association of circulating proprotein convertase subtilisin/kexin type 9 levels and the risk of incident type 2 diabetes in subjects with prediabetes: a population-based cohort study

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol metabolism by targeting the low-density lipoprotein receptor. Recent studies have shown that circulating PCSK9 is associated with glucose homeostasis and insulin resistance. The aim of this study was to examine the association of circulating PCSK9 levels and risk for the development of type 2 diabetes in individuals with prediabetes.

METHODS

A population-based prospective study was conducted among 4205 Chinese subjects with prediabetes (average age 56.1 ± 7.5 years). Incident type 2 diabetes was diagnosed according to 2010 American Diabetes Association criteria. Circulating PCSK9 levels were measured using a commercially available enzyme-linked immunosorbent assay (ELISA). The association of circulating PCSK9 levels with the risk of incident type 2 diabetes was assessed by Cox regression analysis.

RESULTS

During a median follow-up period of 3.1 years, 568 subjects developed type 2 diabetes. Baseline circulating PCSK9 levels were significantly higher in female subjects developing incident type 2 diabetes than in those not developing incident type 2 diabetes (p < 0.001). In female subjects, the risk of incident type 2 diabetes was significantly higher in the highest PCSK9 quartile group (hazard ratio 2.16; 95% confidence interval 1.16-4.04) than in the lowest quartile group after adjustments for age, body mass index, waist circumference, C-reactive protein, γ-glutamyltransferase, triglycerides, low-density lipoprotein cholesterol, systolic blood pressure, and homeostatic model assessment of insulin resistance score. No significant association was observed between PCSK9 and incident type 2 diabetes in male subjects.

CONCLUSION

Elevated circulating PCSK9 levels are associated with an increased incidence of type 2 diabetes in female subjects with prediabetes.

Beyond cholesterol metabolism: The pleiotropic effects of proprotein convertase subtilisin/kexin type 9 (PCSK9). Genetics, mutations, expression, and perspective for long-term inhibition

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has a crucial role in lipid metabolism, particularly due to its function in low-density lipoprotein receptor degradation. Gain-of-function genetic mutations of PCSK9 result in autosomal dominant familial hypercholesterolemia, characterized by high levels of low-density lipoprotein cholesterol (LDL-C) and clinical signs of early atherosclerosis. In recent years, PCSK9 has become an important therapeutic target for cholesterol-lowering therapy. Particularly, its inhibition with monoclonal antibodies has shown excellent efficacy in decreasing LDL-C and reducing cardiovascular events. However, PCSK9, first identified in the brain, seems to be a ubiquitous protein with different tissue-specific functions also independent of cholesterol metabolism. Accordingly, it appears to be involved in the immune response, haemostasis, glucose metabolism, neuronal survival, and several other biological functions. This review provides a comprehensive overview of the genetics, biochemical structure, expression, and function of PCSK9 and discusses the potential implications of its long-term pharmacological inhibition.

Anti-PCSK9 treatment: is ultra-low low-density lipoprotein cholesterol always good?

Anti-PCSK9 (proprotein convertase subtilisin kexin 9) monoclonal antibodies (Mab) are novel, potent lipid-lowering drugs. They demonstrated to improve the lipid profile in high cardiovascular risk patients. Anti-PCSK9 Mab inhibit the targeted low-density lipoprotein (LDL)-receptor degradation induced by PCSK9 protein and are able to reduce LDL cholesterol (LDL-C) levels on top of conventional lipid-lowering therapy. Though these drugs proved to be very safe in the short-term, little is known about the possible long-term effects, due to the short period of their marketing. The genetic low cholesterol syndromes (LCS) represent the natural models of the lipid-lowering anti-PCSK9 therapy, and a valuable opportunity to predict the long-term effects of these drugs. By looking at the clinical features of such models, we could be able to foresee possible drug-induced side effects. In the present review, the correspondences and discordances between the side effects of anti-PCSK9 therapy and the corresponding LCS models will be examined in the attempt to forecast possible long-term consequences of these novel lipid-lowering agents.

C679X loss-of-function PCSK9 variant is associated with lower fasting glucose in black South African adolescents: Birth to Twenty Plus Cohort

Aim

To evaluate the association between loss-of-function (LOF) PCSK9 variants (A433T/rs28362263 and C679X/rs28362286) and biomarkers of cardiometabolic risk, specifically fasting glucose and low density lipoprotein cholesterol (LDL-C) concentrations.

Methods

Our study comprised 757 male and female black South African adolescents (mean age 18.0 ± 0.5 years) who are part of the Birth to Twenty Plus Cohort and had been genotyped for the two above-mentioned variants. Anthropometric measures were completed and fasting plasma glucose and lipid analysis were performed using standard procedures.

Results

The median and interquartile range of fasting glucose and LDL-C for the whole group were 4.60 (4.36–4.88) mmol/L and 1.67 (1.25–2.14) mmol/L, respectively. After adjusting for sex, association between the biomarkers and A443T was not significant. However, C679X carriers displayed 0.30 [95% CI (−0.57, −0.02); p = 0.035] mmol/L lower fasting glucose and 0.50 [95% CI (−0.74, −0.26); p < 0.001) mmol/L lower LDL-C concentrations compared to non-carriers.

Conclusions

Our results indicate for the first that the C679X variants associated with low fasting glucose levels during adolescents as had been known for LDL-C. In view that a similar finding was reported in older black South African adults, therefore, the correlation of lower fasting glucose and LDL-C levels with C679X is observed from an early age to adulthood.

A phenome-wide association study to discover pleiotropic effects of PCSK9, APOB, and LDLR

We conducted an electronic health record (EHR)-based phenome-wide association study (PheWAS) to discover pleiotropic effects of variants in three lipoprotein metabolism genes PCSK9, APOB, and LDLR. Using high-density genotype data, we tested the associations of variants in the three genes with 1232 EHR-derived binary phecodes in 51,700 European-ancestry (EA) individuals and 585 phecodes in 10,276 African-ancestry (AA) individuals; 457 PCSK9, 730 APOB, and 720 LDLR variants were filtered by imputation quality (r 2 > 0.4), minor allele frequency (>1%), linkage disequilibrium (r 2 < 0.3), and association with LDL-C levels, yielding a set of two PCSK9, three APOB, and five LDLR variants in EA but no variants in AA. Cases and controls were defined for each phecode using the PheWAS package in R. Logistic regression assuming an additive genetic model was used with adjustment for age, sex, and the first two principal components. Significant associations were tested in additional cohorts from Vanderbilt University (n = 29,713), the Marshfield Clinic Personalized Medicine Research Project (n = 9562), and UK Biobank (n = 408,455). We identified one PCSK9, two APOB, and two LDLR variants significantly associated with an examined phecode. Only one of the variants was associated with a non-lipid disease phecode, ("myopia") but this association was not significant in the replication cohorts. In this large-scale PheWAS we did not find LDL-C-related variants in PCSK9, APOB, and LDLR to be associated with non-lipid-related phenotypes including diabetes, neurocognitive disorders, or cataracts.

Using Human 'Experiments of Nature' to Predict Drug Safety Issues: An Example with PCSK9 Inhibitors

INTRODUCTION

When a new drug enters the market, its full array of side effects remains to be defined. Current surveillance approaches targeting these effects remain largely reactive. There is a need for development of methods to predict specific safety events that should be sought for a given new drug during development and postmarketing activities.

OBJECTIVE

We present here a safety signal identification approach applied to a new set of drug entities, inhibitors of the serine protease proprotein convertase subtilisin/kexin type 9 (PCSK9).

METHODS

Using phenome-wide association study (PheWAS) methods, we analyzed available genotype and clinical data from 29,722 patients, leveraging the known effects of changes in PCSK9 to identify novel phenotypes in which this protein and its inhibitors may have impact.

RESULTS

PheWAS revealed a significantly reduced risk of hypercholesterolemia (odds ratio [OR] 0.68, p = 7.6 × 10^-4) in association with a known loss-of-function variant in PCSK9, R46L. Similarly, laboratory data indicated significantly reduced beta mean low-density lipoprotein cholesterol (- 14.47 mg/dL, p = 2.58 × 10^-23) in individuals carrying the R46L variant. The R46L variant was also associated with an increased risk of spina bifida (OR 5.90, p = 2.7 × 10^-4), suggesting that further investigation of potential connections between inhibition of PCSK9 and neural tube defects may be warranted.

CONCLUSION

This novel methodology provides an opportunity to put in place new mechanisms to assess the safety and long-term tolerability of PCSK9 inhibitors specifically, and other new agents in general, as they move into human testing and expanded clinical use.

C679X loss-of-function PCSK9 variant lowers fasting glucose levels in a black South African population: A longitudinal study

AIMS

To determine the longitudinal association of the loss-of-function (LOF) PCSK9 variants (C679X and A443T), proxies of PCSK9 inhibitor drugs, with LDL-C, fasting glucose and glycated hemoglobin.

METHODS

We conducted a five year, longitudinal study, nested within the Prospective Urban and Rural Epidemiology study, among 737 apparently healthy, male and female black South Africans of the North West province. Genotyping of the C679X and A443T PCSK9 variants was achieved using Taqman assays from Applied Biosystems. Generalized estimating equations were used to determine longitudinal association of the A443T and C679X PCSK9 variants with LDL-C, fasting glucose and glycated hemoglobin.

RESULTS

C679X and A443T variant carriers were associated with significant reductions in LDL-C of -0.98(-1.29, -0.67) mmol/L; p < 0.001) and -0.39(-0.57, -0.20) mmol/L; p < 0.001) respectively, compared to the non-carriers. Only C679X variant was independently associated with reductions in fasting glucose of -0.37 (-0.61, -0.13) mmol/L; p = 0.002) compared to non-carriers. However, the association of the selected variants with glycated hemoglobin were not significant. C679X and A443T carriers were associated with -0.07 (-0.23, 0.09) %; p = 0.400), 0.05 (-0.13, 0.22) %; p = 0.599) of glycated haemoglobin respectively.

CONCLUSION

Our results indicated that carriers of A443T and C679X variants exhibit sustained low LDL-C levels over 5 years and have varied effects on T2D biomarkers compared to non-carriers.

Effects of evolving lipid-lowering drugs on carbohydrate metabolism

The understanding that statins reduce but not eliminate the cardiovascular risk associated with disturbed lipid metabolism and the existence of forms of dyslipidemia that are unresponsive or only partially responsive to statins have led to the development of many novel lipid-lowering drugs. Accumulating evidence suggests that the interplay between carbohydrate and lipid metabolism is bidirectional. Thus, any intervention that affects lipid metabolism has the potential to influence the homeostasis of glucose. In this review we summarize the available data on the effects of the evolving lipid-lowering drugs on carbohydrate metabolism.

Efficacy and safety of alirocumab in people with prediabetes vs those with normoglycaemia at baseline: a pooled analysis of 10 phase III ODYSSEY clinical trials

AIM

To assess the lipid-lowering efficacy and safety of alirocumab, a proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor, in people with hypercholesterolaemia and prediabetes at baseline vs people with normoglycaemia at baseline in a pooled analysis of 10 ODYSSEY phase III trials.

METHODS

People classified as having prediabetes had baseline HbA1c ≥39 mmol/mol (5.7%) and <48 mmol/mol (6.5%), or two baseline fasting plasma glucose values ≥5.6 mmol/l (100 mg/dl) but no more than one fasting plasma glucose value ≥7.0 mmol/l (126 mg/dl), or had specific terms reported in their medical history; people diagnosed with diabetes at baseline were excluded, and the remainder were classified as having normoglycaemia. Participants received alirocumab or control (placebo/ezetimibe) for 24-104 weeks, with maximally tolerated statin in most cases. The primary efficacy endpoint was LDL cholesterol reductions from baseline to week 24 in the intention-to-treat population using the mixed-effect model with a repeated measures approach.

RESULTS

Reductions in LDL cholesterol from baseline to week 24 with alirocumab were 44.0-61.8% (prediabetes group) and 45.8-59.5% (normoglycaemia group). In both subgroups, LDL cholesterol reductions were generally similar in those with and without baseline triglycerides ≥1.7 mmol/l (150 mg/dl). Alirocumab was not associated with changes in HbA1c or fasting plasma glucose over time in either subgroup (up to 24 months' follow-up). Adverse event rates were generally similar in those with and without prediabetes.

CONCLUSIONS

Over a mean follow-up of 24-104 weeks, alirocumab treatment resulted in significant LDL cholesterol reductions from baseline that were similar in participants with prediabetes and those with normoglycaemia at baseline, with no effect on glycaemia and a safety profile similar to that of the control.

Acute and Chronic Impact of Bariatric Surgery on Plasma LDL Cholesterol and PCSK9 Levels in Patients With Severe Obesity

CONTEXT

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of low-density lipoprotein cholesterol (LDL-C) concentrations. In patients with severe obesity, biliopancreatic diversion with duodenal switch (BPD-DS) surgery induces substantial weight loss and influences lipoprotein metabolism. The effect of BPD-DS on PCSK9 levels is unknown.

OBJECTIVES

To determine the acute and chronic impact of BPD-DS on PCSK9 levels and whether the acute impact of BPD-DS could be explained by BPD-DS-associated caloric restriction (CR).

DESIGN, SETTINGS, AND PARTICIPANTS

PCSK9 levels were measured in 20 men and 49 women (age, 41.5 ± 11.1 years) with severe obesity before, 24 hours, 5 days, and 6 and 12 months after BPD-DS and in a comparable control group (n = 31) at baseline and at 6 and 12 months. PCSK9 levels were also measured during 3-day CR in patients (n = 7) with severe obesity and type 2 diabetes.

RESULTS

PCSK9 levels increased 13.4% after 24 hours (248.7 ± 64.8 to 269.7 ± 63.8 ng/mL; P = 0,02) and decreased 9.5% at 12 months compared with baseline (217.6 ± 43.0 ng/mL; P < 0,0001). LDL-C levels decreased 36.2% after 24 hours (2.6 ± 0.7 to 1.7 ± 0.6 mmol/L; P < 0.0001) and 30% at 12 months compared with baseline (1.7 ± 0.5 mmol/L; P < 0.0001). Compared with baseline levels, PCSK9 levels were lower at day 2 but not at day 1 or 3 after CR.

CONCLUSION

BPD-DS is associated with acute increases in PCSK9 levels that do not appear to be explained by CR but may be due to an acute response following surgery. BPD-DS induces chronic reductions in both PCSK9 and LDL-C levels.

PCSK9: BIOLOGICAL ACTIVITY REGULATION AND CONNECTION WITH LIPID AND CARBOHYDRATE METABOLISM

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease which plays an important role in the regulation of LDL receptor (LDLR) expression and apolipoprotein B (apoB) lipoprotein cholesterol metabolism. It is well known that hepatic PCSK9 expression, its activity and secretion influence cholesterol homeostasis. An upregulation of PCSK9 causes an increase of LDLR degradation, which results in decrease of apoB lipoprotein uptake, and a consequent increase in plasma lipoprotein concentration, including LDL. Therefore, PCSK9 has become a new target for lipid lowering therapy. The aim of this review is to consider current data on metabolic and dietary regulation of PCSK9 and its effect on cholesterol and apoB lipoproteins metabolism and risk of cardiovascular disease.

PCSK9 and carbohydrate metabolism: A double-edged sword

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a paramount role in the degradation of low-density lipoprotein (LDL) receptors (LDLR) on the hepatic cells surface and subsequently affects LDL particles catabolism and LDL cholesterol (LDL-c) levels. The anti-PCSK9 monoclonal antibodies lead to substantial decrease of LDL-c concentration. PCSK9 (which is also expressed in pancreatic delta-cells) can decrease LDLR and subsequently decrease cholesterol accumulation in pancreatic beta-cells, which impairs glucose metabolism and reduces insulin secretion. Thus, a possible adverse effect of PCSK9 inhibitors on carbohydrate metabolism may be expected by this mechanism, which has been supported by the mendelian studies results. On the other hand, clinical data have suggested a detrimental association of PCSK9 with glucose metabolism. So, the inhibition of PCSK9 may be seen as a double-edged sword regarding carbohydrate metabolism. Completed clinical trials have not shown a detrimental effect of PCSK9 inhibitors on diabetes risk, but their short-term duration does not allow definite conclusions.

What is the impact of PCSK9 rs505151 and rs11591147 polymorphisms on serum lipids level and cardiovascular risk: a meta-analysis

Background

PCSK9 rs505151 and rs11591147 polymorphisms are identified as gain- and loss-of-function mutations, respectively. The effects of these polymorphisms on serum lipid levels and cardiovascular risk remain to be elucidated.

Methods

In this meta-analysis, we explored the association of PCSK9 rs505151 and rs11591147 polymorphisms with serum lipid levels and cardiovascular risk by calculating the standardized mean difference (SMD) and odds ratios (OR) with 95% confidence intervals (CI).

Results

Pooled results analyzed under a dominant genetic model indicated that the PCSK9 rs505151 G allele was related to higher levels of triglycerides (SMD: 0.14, 95% CI: 0.02 to 0.26, P = 0.021, I² = 0) and low-density lipoproteins cholesterol (LDL-C) (SMD: 0.17, 95% CI: 0.00 to 0.35, P = 0.046, I² = 75.9%) and increased cardiovascular risk (OR: 1.50, 95% CI: 1.19 to 1.89, P = 0.0006, I² = 48%). The rs11591147 T allele was significantly associated with lower levels of total cholesterol (TC) and LDL-C (TC, SMD: -0.45, 95% CI: -0.57 to −0.32, P = 0.000, I² = 0; LDL-C, SMD: -0.44, 95% CI: -0.55 to −0.33, P = 0.000, I² = 0) and decreased cardiovascular risk (OR: 0.77, 95% CI: 0.60 to 0.98, P = 0.031, I² = 59.9) in Caucasians.

Conclusions

This study indicates that the variant G allele of PCSK9 rs505151 confers increased triglyceride (TG) and LDL-C levels, as well as increased cardiovascular risk. Conversely, the variant T allele of rs11591147 protects carriers from cardiovascular disease susceptibility and lower TC and LDL-C levels in Caucasians. These findings provide useful information for researchers interested in the fields of PCSK9 genetics and cardiovascular risk prediction not only for designing future studies, but also for clinical and public health applications.

Nutritional and Lipid Modulation of PCSK9: Effects on Cardiometabolic Risk Factors

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease involved in the regulation of LDL receptor (LDLR) expression and apolipoprotein B lipoprotein cholesterol metabolism. Hepatic PCSK9 protein expression, activity, and secretion have been shown to affect cholesterol homeostasis. An upregulation of hepatic PSCK9 protein leads to increased LDLR degradation, resulting in decreased uptake of apoB lipoproteins and a consequent increase in the plasma concentration of these lipoproteins, including LDL and chylomicron remnants. Hence, PCSK9 has become a novel target for lipid-lowering therapies. The aim of this review is to outline current findings on the metabolic and dietary regulation of PCSK9 and effects on cholesterol, apoB lipoprotein metabolism, and cardiovascular disease (CVD) risk. PCSK9 gene and protein expression have been shown to be regulated by metabolic status and the diurnal pattern. In the fasting state, plasma PCSK9 is reduced via modulation of the nuclear transcriptional factors, including sterol regulatory element-binding protein (SREBP) 1c, SREBP2, and hepatocyte nuclear factor 1α. Plasma PCSK9 concentrations are also known to be positively associated with plasma insulin and homeostasis model assessment of insulin resistance, and appear to be regulated by SREBP1c independently of glucose status. Plasma PCSK9 concentrations are stable in response to high-fat or high-protein diets in healthy individuals; however, this response may differ in altered metabolic conditions. Dietary n-3 polyunsaturated fatty acids have been shown to reduce plasma PCSK9 concentration and hepatic PCSK9 mRNA expression, consistent with their lipid-lowering effects, whereas dietary fructose appears to upregulate PCSK9 mRNA expression and plasma PCSK9 concentrations. Further studies are needed to elucidate the mechanisms of how dietary components regulate PCSK9 and effects on cholesterol and apoB lipoprotein metabolism, as well as to delineate the clinical impact of diet on PCSK9 in terms of CVD risk.

Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors: A Brief Overview

Proprotein convertase subtilisin/kexin type 9 inhibitors serve as a valuable addition to the armamentarium of lipid-lowering agents and have promising potential. By inhibiting the proprotein convertase subtilisin/kexin type 9 enzyme, this novel molecule leads to increased low-density lipoprotein receptor density and decreased circulation of low-density lipoprotein. The fact the agent is a monoclonal antibody has led to limited drug interactions and minimized adverse drug events. It is critical for all providers to have a basic understanding of these novel therapies with their introduction and use for treatment.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) and metabolic syndrome: insights on insulin resistance, inflammation, and atherogenic dyslipidemia

Low-density lipoprotein (LDL) cholesterol plays a pivotal role in the pathogenesis of atherosclerotic cardiovascular disease (CVD). The discovery that proprotein convertase subtilisin/kexin type 9 (PCSK9) represents a key regulator pathway for hepatic LDL receptor (LDLR) degradation sheds light on new uncovered issues regarding LDL-C homeostasis. Indeed, as confirmed by phase II and III clinical trials with monoclonal antibodies, targeting PCSK9 represents the newest and most promising pharmacological tool for the treatment of hypercholesterolemia and related CVD. However, clinical, genetic, and experimental evidence indicates that PCSK9 may be either a cause or an effect in the context of metabolic syndrome (MetS), a condition comprising a cluster of risk factors including insulin resistance, obesity, hypertension, and atherogenic dyslipidemia. The latter is characterized by a triad of hypertriglyceridemia, low plasma concentrations of high-density lipoproteins, and qualitative changes in LDLs. PCSK9 levels seem to correlate with many of these lipid parameters as well as with the insulin sensitivity indices, although the molecular mechanisms behind this association are still unknown or not completely elucidated. Nevertheless, this area of research represents an important starting point for a better understanding of the physiological role of PCSK9, also considering the recent approval of new therapies involving anti-PCSK9. Thus, in the present review, we will discuss the current knowledge on the role of PCSK9 in the context of MetS, alteration of lipids, glucose homeostasis, and inflammation.

Association Between Low-Density Lipoprotein Cholesterol-Lowering Genetic Variants and Risk of Type 2 Diabetes: A Meta-analysis

Importance

Low-density lipoprotein cholesterol (LDL-C)-lowering alleles in or near NPC1L1 or HMGCR, encoding the respective molecular targets of ezetimibe and statins, have previously been used as proxies to study the efficacy of these lipid-lowering drugs. Alleles near HMGCR are associated with a higher risk of type 2 diabetes, similar to the increased incidence of new-onset diabetes associated with statin treatment in randomized clinical trials. It is unknown whether alleles near NPC1L1 are associated with the risk of type 2 diabetes.

Objective

To investigate whether LDL-C-lowering alleles in or near NPC1L1 and other genes encoding current or prospective molecular targets of lipid-lowering therapy (ie, HMGCR, PCSK9, ABCG5/G8, LDLR) are associated with the risk of type 2 diabetes.

Design, Setting, and Participants

The associations with type 2 diabetes and coronary artery disease of LDL-C-lowering genetic variants were investigated in meta-analyses of genetic association studies. Meta-analyses included 50 775 individuals with type 2 diabetes and 270 269 controls and 60 801 individuals with coronary artery disease and 123 504 controls. Data collection took place in Europe and the United States between 1991 and 2016.

Exposures

Low-density lipoprotein cholesterol-lowering alleles in or near NPC1L1, HMGCR, PCSK9, ABCG5/G8, and LDLR.

Main Outcomes and Measures

Odds ratios (ORs) for type 2 diabetes and coronary artery disease.

Results

Low-density lipoprotein cholesterol-lowering genetic variants at NPC1L1 were inversely associated with coronary artery disease (OR for a genetically predicted 1-mmol/L [38.7-mg/dL] reduction in LDL-C of 0.61 [95% CI, 0.42-0.88]; P = .008) and directly associated with type 2 diabetes (OR for a genetically predicted 1-mmol/L reduction in LDL-C of 2.42 [95% CI, 1.70-3.43]; P < .001). For PCSK9 genetic variants, the OR for type 2 diabetes per 1-mmol/L genetically predicted reduction in LDL-C was 1.19 (95% CI, 1.02-1.38; P = .03). For a given reduction in LDL-C, genetic variants were associated with a similar reduction in coronary artery disease risk (I2 = 0% for heterogeneity in genetic associations; P = .93). However, associations with type 2 diabetes were heterogeneous (I2 = 77.2%; P = .002), indicating gene-specific associations with metabolic risk of LDL-C-lowering alleles.

Conclusions and Relevance

In this meta-analysis, exposure to LDL-C-lowering genetic variants in or near NPC1L1 and other genes was associated with a higher risk of type 2 diabetes. These data provide insights into potential adverse effects of LDL-C-lowering therapy.

Impact of a 1-year lifestyle modification program on plasma lipoprotein and PCSK9 concentrations in patients with coronary artery disease

BACKGROUND

Patients with coronary artery disease (CAD) are characterized by an impaired cardiometabolic risk profile including high levels of atherogenic apolipoprotein (apo) B-containing lipoprotein levels. Genetic studies have highlighted a critical role for proprotein convertase subtilisin/kexin type 9 (PCSK9) in lipoprotein metabolism and CAD risk.

OBJECTIVE

To determine whether improving dietary quality and increasing physical activity levels improve parameters of the cardiometabolic risk profile such as plasma apoB and PCSK9 levels in patients with CAD.

METHODS

We recruited 86 men aged between 39 and 80 years (82 of them on statins) undergoing coronary artery bypass graft (CABG) surgery. These patients participated in a 1-year lifestyle modification program aiming at achieving a minimum of 150 minutes/week of physical activity and improving diet quality by following dietary guidelines. We used magnetic resonance imaging to measure visceral adipose tissue and a modified Bruce protocol to measure fitness levels before and after the intervention.

RESULTS

Plasma apoB and low-density lipoprotein cholesterol levels were not modified by the intervention (-3.0%, P = .08 and 1.3%, P = .56, respectively), whereas non-HDL cholesterol decreased by 4.5% (P = .04) and triglycerides by 13% (P = .002). In contrast, PCSK9 levels increased by 5.2% after the intervention (P = .05). HDL cholesterol and apolipoprotein A-I levels also increased (+12%, P < .0001 and + 6%, P < .0001, respectively). PCSK9 levels increased with improvements in fitness (r = 0.23, P = .04) and visceral fat mobilization (r = -0.23, P = .04).

CONCLUSION

In post-CABG patients, a lifestyle modification program lead to significant improvements in some parameters of the lipoprotein profile but unexpectedly increased plasma PCSK9 levels.

Association of Lipid Fractions With Risks for Coronary Artery Disease and Diabetes

IMPORTANCE

Low-density lipoprotein cholesterol (LDL-C) is causally related to coronary artery disease (CAD), but the relevance of high-density lipoprotein cholesterol (HDL-C) and triglycerides (TGs) is uncertain. Lowering of LDL-C levels by statin therapy modestly increases the risk of type 2 diabetes, but it is unknown whether this effect is specific to statins.

OBJECTIVE

To investigate the associations of 3 routinely measured lipid fractions with CAD and diabetes through mendelian randomization (MR) using conventional MR and making use of newer approaches, such as multivariate MR and MR-Egger, that address the pleiotropy of genetic instruments where relevant.

DESIGN, SETTING, AND PARTICIPANTS

Published data from genome-wide association studies were used to construct genetic instruments and then applied to investigate associations between lipid fractions and the risk of CAD and diabetes using MR approaches that took into account pleiotropy of genetic instruments. The study was conducted from March 12 to December 31, 2015.

MAIN OUTCOMES AND MEASURES

Coronary artery disease and diabetes.

RESULTS

Genetic instruments composed of 130 single-nucleotide polymorphisms (SNPs) were used for LDL-C (explaining 7.9% of its variance), 140 SNPs for HDL-C (6.6% of variance), and 140 SNPs for TGs (5.9% of variance). A 1-SD genetically instrumented elevation in LDL-C levels (equivalent to 38 mg/dL) and TG levels (equivalent to 89 mg/dL) was associated with higher CAD risk; odds ratios (ORs) were 1.68 (95% CI, 1.51-1.87) for LDL-C and 1.28 (95% CI, 1.13-1.45) for TGs. The corresponding OR for HDL-C (equivalent to a 16-mg/dL increase) was 0.95 (95% CI, 0.85-1.06). All 3 lipid traits were associated with a lower risk of type 2 diabetes. The ORs were 0.79 (95% CI, 0.71-0.88) for LDL-C and 0.83 (95% CI, 0.76-0.90) for HDL-C per 1-SD elevation. For TG, the MR estimates for diabetes were inconsistent, with MR-Egger giving an OR of 0.83 (95%CI, 0.72-0.95) per 1-SD elevation.

CONCLUSIONS AND RELEVANCE

Routinely measured lipid fractions exhibit contrasting associations with the risk of CAD and diabetes. Increased LDL-C, HDL-C, and possibly TG levels are associated with a lower risk of diabetes. This information will be relevant to the design of clinical trials of lipid-modifying agents, which should carefully monitor participants for dysglycemia and the incidence of diabetes.

Biology of proprotein convertase subtilisin kexin 9: beyond low-density lipoprotein cholesterol lowering

Proprotein convertase subtilisin kexin 9 (PCSK9) is a key regulator of low-density lipoprotein receptor levels and LDL-cholesterol levels. Loss-of-function mutations in PCSK9 gene are associated with hypocholesterolaemia and protection against cardiovascular disease, identifying PCSK9 inhibition as a valid therapeutic approach to manage hypercholesterolaemia and related diseases. Although PCSK9 is expressed mainly in the liver, it is present also in other tissues and organs with specific functions, raising the question of whether a pharmacological inhibition of PCSK9 to treat hypercholesterolaemia and associated cardiovascular diseases might be helpful or deleterious in non-hepatic tissues. For example, PCSK9 is expressed in the vascular wall, in the kidneys, and in the brain, where it was proposed to play a role in development, neurocognitive process, and neuronal apoptosis. A link between PCSK9 and immunity was also proposed as both sepsis and viral infections are differentially affected in the presence or absence of PCSK9. Despite the increasing number of observations, the debate on the exact roles of PCSK9 in extrahepatic tissues is still ongoing, and as very effective drugs that inhibit PCSK9 have become available to the clinician, a better understanding of the biological roles of PCSK9 is warranted.

No effect of PCSK9 inhibitor alirocumab on the incidence of diabetes in a pooled analysis from 10 ODYSSEY Phase 3 studies

Aims

Statins have modest adverse effects on glycaemic control. Alirocumab, a proprotein convertase subtilisin/kexin type 9 inhibitor, lowers low-density lipoprotein cholesterol. This study assessed the effects of alirocumab on new-onset diabetes and pre-diabetes incidence in individuals without diabetes at baseline.

Methods and results

Pooled analysis of 10 ODYSSEY Phase 3 trials (n = 4974) of 24–104 weeks duration. Six trials (n = 4211) were ≥52 weeks in length. Most patients received background maximally tolerated statin. Alirocumab effect on the rate of diabetes-related treatment-emergent adverse events (TEAEs), and/or fasting plasma glucose (FPG) and glycated haemoglobin A_1C (HbA_1C) was measured at baseline and every 12–24 weeks. Transition to diabetes analysis combined TEAE and FPG/HbA_1C laboratory data. At baseline, 30.7% of individuals had diabetes and were excluded from the current analysis. The remaining 3448 individuals without diabetes had pre-diabetes (39.6%) or were normoglycaemic (29.7%). The hazard ratio (HR; 95% confidence interval) for diabetes-related TEAEs in alirocumab was 0.64 (0.36–1.14) vs. placebo and 0.55 (0.22–1.41) vs. ezetimibe. The HR associated for transition from pre-diabetes to new-onset diabetes for alirocumab was 0.90 (0.63–1.29) vs. placebo and 1.10 (0.57–2.12) vs. ezetimibe. Mean change in FPG/HbA_1C over time showed no difference between treatment groups in patients without diabetes.

Conclusions

There was no evidence of an effect of alirocumab on transition to new-onset diabetes in 3448 individuals without diabetes at baseline with a follow-up period of 6–18 months, compared to either placebo or ezetimibe. Longer follow-up with larger number of individuals is needed to conclusively rule out an effect.

Genetic insights into statin-associated diabetes risk

PURPOSE OF REVIEW

Meta-analyses of major statin trials have suggested that statin therapy modestly increases the risk of developing diabetes. However, the quality of the data on which these findings are based is not without weaknesses and it has also been unclear whether this effect, if true, is an on-target or off-target effect of statins.

RECENT FINDINGS

In a major Mendelian randomization study of variants in the HMGCR gene, which encodes the protein through which statins exert their effect, two polymorphisms associated with lower LDL-cholesterol were also associated with higher weight, higher waist circumference, higher glucose and higher diabetes risk. These findings correspond with findings from the statin trials. In addition, new observational studies using a genetic risk score for LDL-cholesterol suggest that other pathways linked to LDL-cholesterol metabolism may also affect diabetes risk.

SUMMARY

Genetic studies indicate that the observed effect of statins on diabetes risk in trials is highly likely to be a true on-target effect. Although other recent studies have suggested that genetically determined lower LDL-cholesterol may be linked to diabetes risk, further data from both genetic studies and clinical trials of other LDL-cholesterol lowering agents are needed to confirm or refute this.

[PCSK9 inhibitors in hypercholesterolemia. New hope for patients with diabetes mellitus?]

The interrelation between glucose and lipid metabolism is complex and comprises many aspects. In this context diabetic dyslipidemia is of utmost importance as it represents the crucial link between diabetes and cardiovascular disease. Although hypertriglyceridemia is usually the most prominent lipid abnormality in diabetic patients, reduction of low-density lipoprotein (LDL) cholesterol is the most important strategy to prevent cardiovascular disease. Statin trials and more recently the combination of statin with ezetimibe clearly showed that diabetic patients benefit from low LDL cholesterol levels. In this context the newly developed proprotein convertase subtilisin kexin 9 (PCSK9) inhibitors are of great interest as they reduce LDL cholesterol by 50-70 % independent of co-medication and largely independent of the underlying dyslipidemia. Subgroup analyses of phase 2 and phase 3 studies indicated that diabetic patients show a similar response to PCSK9 inhibitors as non-diabetic patients. Furthermore, the overall very low rate of side effects seems to be comparable between diabetic and non-diabetic patients. In contrast to statins PCSK9 inhibitors do not lead to an increased rate of new onset diabetes. Although data from safety studies (post hoc analyses) are very promising concerning the prevention of cardiovascular events, data from outcome studies will only become available in 2016. Until then PCSK9 inhibitors should be restricted to patients with very high risk and a significant distance from the LDL cholesterol target values (despite maximum possible lipid-lowering therapy with statins and ezetimibe). This approach will most likely have to be adapted when outcome data are available.

Targeting PCSK9 for therapeutic gains: Have we addressed all the concerns?

Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) regulates the expression of low-density lipoprotein (LDL)-receptors, through reducing their recycling by binding to the receptor along with LDL and targeting it for lysosomal destruction. PCSK9 also enhances the degradation of very-low-density-lipoprotein receptor (VLDLR) and lipoprotein receptor-related protein 1 (LRP-1) in a LDL-receptor independent manner. This role in lipid homeostasis presents PCSK9 as an attractive target for the therapeutic management of familial hypercholesterolemia as well as other refractory dyslipidaemias. However, PCSK9 mediates multifarious functions independent of its role in lipid homeostasis, which can be grouped under "pleiotropic functions" of the protein. This includes PCSK9's role in: trafficking of epithelial sodium channel; hepatic regeneration; pancreatic integrity and glucose homeostasis; antiviral activity; antimalarial activity; regulation of different cell signalling pathways; cortical neural differentiation; neuronal apoptosis and Alzheimer's disease. The question that needs to be investigated in depth is "How will the pleotropic functions of PCSK9, be affected by the therapeutic intervention of the protease's LDL-receptor lowering activity?" In this review, we appraise the different lipid lowering strategies targeting PCSK9 in light of the protein's different pleiotropic functions. Additionally, we delineate the key areas that require further examination, to ensure the long-term safety of the above lipid-lowering strategies.

PCSK9 inhibitors and cardiovascular disease: heralding a new therapeutic era

PURPOSE OF REVIEW

The first monoclonal antibodies targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) have been approved for clinical use. This timely review highlights recent developments.

RECENT FINDINGS

Low-density lipoprotein cholesterol (LDL-C) is the primary driver of atherosclerosis and the key target for intervention. Yet despite best treatment including statins, attaining sufficient LDL-C lowering can be problematic for high cardiovascular risk patients. The development of PCSK9 inhibitors, driven by novel genetic and mechanistic insights, offers an answer. Removal of circulating PCSK9 increases LDL receptor availability, and thus markedly decreases plasma LDL-C levels (by ∼50-60%), and is additive to the lipid lowering effects of statins and ezetimibe. PCSK9 inhibition also reduces (by 25-30%) plasma levels of lipoprotein(a), a causal factor in atherosclerotic vascular disease, suggestive of partial catabolism of lipoprotein(a) by LDL receptors. The ODYSSEY and PROFICIO (Programme to Reduce LDL-C and Cardiovascular Outcomes Following Inhibition of PCSK9 In Different Populations) clinical trial programmes involving a wide range of high-risk patients, including statin intolerant patients, have confirmed the consistency of the LDL response, even with concomitant high-intensity statin or nonstatin therapy. Extensive evidence to date attests to a favourable safety and tolerability profile for these innovative agents.

SUMMARY

The new pharmacotherapeutic era of PCSK9 inhibition is upon us, promising major reduction in cardiovascular events across a wide spectrum of high-risk patients.