ANGPTL3 and ApoC-III inhibitors for treating hypertriglyceridemia in context: horses for courses?

PURPOSE OF REVIEW

Hypertriglyceridemia (HTG) is an independent and casual risk factor for atherosclerotic cardiovascular disease (ASCVD). There is an unmet need for more effective treatments for patients with HTG. Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (apoC-III) are key regulators of triglyceride-rich lipoprotein (TRL) metabolism. We review recent clinical trials targeting ANGPTL3 and apoC-III with monoclonal antibody and nucleic acid therapies, including antisense oligonucleotides and small interfering RNA.

RECENT FINDINGS

ANGPTL3 and apoC-III inhibitors are effective in lowering plasma triglycerides and TRLs, with possibly greater efficacy with the inhibition of apoC-III. By contrast to ANGPTL3 inhibition that has the advantage of greater lowering of plasma low-density lipoprotein (LDL)-cholesterol and apoB levels, apoC-III inhibition only has a modest or no effect in lowering plasma LDL-cholesterol and apoB concentrations. Therapeutic inhibition of ANGPTL3 and apoC-III can correct HTG possibly by reducing production and increasing catabolism of TRL particles, but this remains to be formally investigated in patients with HTG.

SUMMARY

Novel agents targeting ANGPTL3 and apoC-III can correct HTG and potentially lower risk of ASCVD in patients with HTG. The long-term safety and cost-effectiveness of these agents await confirmation in ongoing and future studies.

Adherence to pharmacotherapy: sine qua non for reducing cumulative risk of premature coronary disease in familial hypercholesterolemia

PURPOSE OF REVIEW

Familial hypercholesterolemia (FH) is a dominant and highly penetrant monogenic disorder present from birth that markedly elevates plasma low-density lipoprotein (LDL)-cholesterol concentration and, if untreated, leads to atherosclerotic cardiovascular disease (ASCVD). The risk of ASCVD can be substantially reduced with lipid-lowering treatment (LLT). However, adherence to LLT remains a major challenge in FH patients and an under-recognized issue. We review several barriers to treatment adherence and implementation strategies for improving adherence in patients with FH.

RECENT FINDINGS

Barriers that negatively affect patient adherence to treatment include the misunderstanding of perceived and actual risk of FH and the benefits of LLT, inadequate knowledge, lack of standardization of treatment, insufficient monitoring of LDL-cholesterol level, and inequalities in healthcare resources. Education of patients, carers and healthcare providers, guideline-directed treatment goals, regular monitoring, medication regimen simplification and greater access to established and new drugs are crucial enablers for improving adherence to treatment. However, given FH is present from birth, strategies for life-long adherence from childhood or young adulthood is critically important and requires further study. To be effective, strategies should be multifaceted, targeted and patient-centred involving a multidisciplinary-team with support from family, communities and peer groups.

SUMMARY

FH confers a significant risk for ASCVD from a young age. Achieving better medication adherence is foundational for improving clinical outcomes and reducing the burden of atherosclerosis over a lifetime. Identification of key barriers and enablers are critical for implementing better adherence to treatment across the life-course of patients with FH.

An Analysis of the Gut Microbiota and Related Metabolites following PCSK9 Inhibition in Statin-Treated Patients with Elevated Levels of Lipoprotein(a)

BACKGROUND

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of global mortality, often associated with high blood levels of LDL cholesterol (LDL-c). Medications like statins and PCSK9 inhibitors, are used to manage LDL-c levels and reduce ASCVD risk. Recent findings connect the gut microbiota and its metabolites to ASCVD development. We showed that statins modulate the gut microbiota including the production of microbial metabolites involved in the regulation of cholesterol metabolism such as short chain fatty acids (SCFAs) and bile acids (BAs). Whether this pleiotropic effect of statins is associated with their antimicrobial properties or it is secondary to the modulation of cholesterol metabolism in the host is unknown. In this observational study, we evaluated whether alirocumab, a PCSK9 inhibitor administered subcutaneously, alters the stool-associated microbiota and the profiles of SCFAs and BAs.

METHODS

We used stool and plasma collected from patients enrolled in a single-sequence study using alirocumab. Microbial DNA was extracted from stool, and the bacterial component of the gut microbiota profiled following an amplicon sequencing strategy targeting the V3-V4 region of the 16S rRNA gene. Bile acids and SCFAs were profiled and quantified in stool and plasma using mass spectrometry.

RESULTS

Treatment with alirocumab did not alter bacterial alpha (Shannon index, p = 0.74) or beta diversity (PERMANOVA, p = 0.89) in feces. Similarly, circulating levels of SCFAs (mean difference (95% confidence interval (CI)), 8.12 [-7.15-23.36] µM, p = 0.25) and BAs (mean difference (95% CI), 0.04 [-0.11-0.19] log10(nmol mg-1 feces), p = 0.56) were equivalent regardless of PCSK9 inhibition. Alirocumab therapy was associated with increased concentration of BAs in feces (mean difference (95% CI), 0.20 [0.05-0.34] log10(nmol mg-1 feces), p = 0.01).

CONCLUSION

In statin-treated patients, the use of alirocumab to inhibit PCSK9 leads to elevated levels of fecal BAs without altering the bacterial population of the gut microbiota. The association of alirocumab with increased fecal BA concentration suggests an additional mechanism for the cholesterol-lowering effect of PCSK9 inhibition.

Cascade testing of children and adolescents for elevated Lp(a) in pedigrees with familial hypercholesterolaemia

Elevated plasma lipoprotein(a) [Lp(a)] is a common, inherited condition independently causing cardiovascular disease. Recent expert recommendations suggest opportunistically testing for elevated Lp(a) during cascade testing for familial hypercholesterolaemia (FH). We investigated the effectiveness of detecting elevated Lp(a) in 103 children and adolescents who were first-degree relatives of 66 adult index FH cases as part of an established FH cascade screening program. The yield of detection of elevated Lp(a) using a threshold of ≥30 mg/dL in children and adolescents was assessed. Cascade testing from FH index cases with elevated Lp(a) ≥50 mg/dL identified 1 case of Lp(a) ≥30 mg/dL for every 2 children or adolescents tested. In contrast, opportunistic screening from index cases with FH but normal Lp(a) levels demonstrated 1 case of Lp(a) ≥30 mg/dL for every 7.5 children or adolescents tested (p < 0.001). In conclusion, cascade testing for elevated Lp(a) from index cases with FH and elevated Lp(a) is effective in identifying new cases of elevated Lp(a).

The Promise of PCSK9 and Lipoprotein(a) as Targets for Gene Silencing Therapies

PURPOSE

High plasma concentrations of LDL and lipoprotein(a) (Lp[a]) are independent and causal risk factors for atherosclerotic cardiovascular disease (ASCVD). There is an unmet therapeutic need for high-risk patients with elevated levels of LDL-C and/or Lp(a). Recent advances in the development of nucleic acids for gene silencing (ie, triantennary N-acetylgalactosamine conjugated antisense-oligonucleotides [ASOs] and small interfering RNA [siRNA]) targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) and Lp(a) offer effective and sustainable therapies.

METHODS

Related articles in the English language were identified through a search for original and review articles in the PubMed database using the following key terms: cardiovascular disease, dyslipidemia, PCSK9 inhibitors, Lp(a), LDL-cholesterol, familial hypercholesterolemia, siRNA, and antisense oligonucleotide and clinical trials (either alone or in combination).

FINDINGS

Inclisiran, the most advanced siRNA-treatment targeting hepatic PCSK9, is well tolerated, producing a >30% reduction on LDL-C levels in randomized controlled trials. Pelacarsen is the most clinical advanced ASO, whereas olpasiran and SLN360 are the 2 siRNAs directed against the mRNA of the LPA gene. Evidence suggests that all Lp(a)-targeting agents are safe and well tolerated, with robust and sustained reduction in plasma Lp(a) concentration up to 70% to 90% in individuals with elevated Lp(a) levels.

IMPLICATIONS

Cumulative evidence from clinical trials supports the value of ASO and siRNA therapies targeting the synthesis of PCSK9 and Lp(a) for lowering LDL-C and Lp(a) in patients with established ASCVD or high risk of ASCVD. Further research is needed to examine whether gene silencing therapy could improve clinical outcomes in patients with elevated LDL and/or Lp(a) levels. Confirmation of the tolerability and cost-effectiveness of long-term inhibition of PCSK9 and Lp(a) with this approach is essential.

Improved arterial inflammation with high dose omega-3 fatty acids in patients with elevated lipoprotein(a): Selective effect of eicosapentaenoic acid?

Elevated lipoprotein(a) [Lp(a)] is a causal risk factor for atherosclerotic cardiovascular disease. However, there are no approved and effective treatments for lowering Lp(a) and the associated cardiovascular risks. Omega-3 fatty acids (ω-3FAs), primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have both triglyceride-lowering and anti-inflammatory properties. This pilot study investigated the effect of high dose ω-3FAs (3.6 g/day) on arterial inflammation in 12 patients with elevated Lp(a) (> 0.5 g/L) and stable coronary artery disease (CAD) receiving cholesterol-lowering treatment. Arterial inflammation was determined using 18F-fluorodexoyglucose positron emission tomography/computed tomography before and after 12-weeks intervention. ω-3FAs significantly lowered plasma concentrations of triglycerides (-17%, p < 0.01), Lp(a) (-5%, p < 0.01) as well as aortic maximum standardized uptake value (SUVmax) (-4%, p < 0.05). The reduction in SUVmax was significantly inversely associated with average on-treatment EPA (r = -0.750, p < 0.01), but not DHA and triglyceride, concentrations. In conclusion, high dose ω-3FAs decrease arterial inflammation in patients with elevated Lp(a) and stable CAD, which may involve a direct arterial effect of EPA.

Effect of Omega-3 Fatty Acid Supplementation on the Postprandial Metabolism of Apolipoprotein(a) in Familial Hypercholesterolemia

AIM

Lipoprotein(a) (Lp(a)) is a low-density lipoprotein-like particle containing apolipoprotein(a) (apo(a)) that increases the risk of atherosclerotic cardiovascular disease (ASCVD) in familial hypercholesterolemia (FH). Postprandial redistribution of apo(a) protein from Lp(a) to triglyceride-rich lipoproteins (TRLs) may also increase the atherogenicity of TRL particles. Omega-3 fatty acid (ω3FA) supplementation improves postprandial TRL metabolism in FH subjects. However, its effect on postprandial apo(a) metabolism has yet to be investigated.

METHODS

We carried out an 8-week open-label, randomized, crossover trial to test the effect of ω3FA supplementation (4 g/day) on postprandial apo(a) responses in FH patients following ingestion of an oral fat load. Postprandial plasma total and TRL-apo(a) concentrations were measured by liquid chromatography with tandem mass spectrometry, and the corresponding areas under the curve (AUCs) (0-10h) were determined using the trapezium rule.

RESULTS

Compared with no ω3FA treatment, ω3FA supplementation significantly lowered the concentrations of postprandial TRL-apo(a) at 0.5 (-17.9%), 1 (-18.7%), 2 (-32.6%), and 3 h (-19.2%) (P＜0.05 for all). Postprandial TRL-apo(a) AUC was significantly reduced with ω3FA by 14.8% (P＜0.05). By contrast, ω3FA had no significant effect on the total AUCs of apo(a), apoC-III, and apoE (P＞0.05 for all). The decrease in postprandial TRL-apo(a) AUC was significantly associated with changes in the AUC of triglycerides (r=0.600; P＜0.01) and apoB-48 (r=0.616; P＜0.01).

CONCLUSIONS

Supplementation with ω3FA reduces postprandial TRL-apo(a) response to a fat meal in FH patients; this novel metabolic effect of ω3FA may have implications on decreasing the risk of ASCVD in patients with FH, especially in those with elevated plasma triglyceride and Lp(a) concentrations. However, the clinical implications of these metabolic findings require further evaluation in outcome or surrogate endpoint trials.

Lipoprotein(a) is associated with thrombus burden in culprit arteries of younger patients with ST-segment elevation myocardial infarction

Background Lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease. The burden of thrombus in ST-segment elevation myocardial infarction (STEMI) has implications on treatment and outcomes. However, the association between Lp(a) and atherothrombosis in STEMI remains unclear. Objectives Determine the association between Lp(a) and culprit artery thrombus burden in younger patients with STEMI. Methods Single-centre study of 83 patients aged <65 years with STEMI between 2016-2018 who underwent percutaneous coronary intervention and measurement of Lp(a); those receiving thrombolytic therapy were excluded. Thrombus burden in the culprit artery was determined angiographically using the Thrombolysis in Myocardial Infarction score and classified as absent-to-small, moderate, or large. Elevated Lp(a) was defined as plasma mass concentration >30 mg/dL. Multivariate analysis was performed adjusting for cardiovascular risk factors. Results The mean age was 48.08.4 years and 78.3% were male. Thirteen (16%), 9 (11%) and 61 (73%) patients had small, moderate, or large thrombus burden, respectively, and 34 (41%) had elevated Lp(a). Elevated Lp(a) was associated with greater thrombus burden compared to normal Lp(a) (large burden 85% versus 65%; P=0.024). Elevated Lp(a) was associated with moderate or large thrombus in univariate [OR 10.70 (95% CI 1.32-86.82); P=0.026] and multivariate analysis [OR 10.33 (95% CI 1.19-89.52); P=0.034]. Lp(a) was not associated with culprit artery or stenosis location according to culprit artery. Conclusions Elevated Lp(a) is associated with greater thrombus burden in younger patients with STEMI. The finding of this observational study accords with the thrombotic and anti-fibrinolytic properties of Lp(a). A causal relationship requires verification.

Is type 2 diabetes associated dementia a microvascular early-Alzheimer's phenotype induced by aberrations in the peripheral metabolism of lipoprotein-amyloid?

There is increasing evidence of a positive association of type 2 diabetes with Alzheimer's disease (AD), the most prevalent form of dementia. Suggested pathways include cerebral vascular dysfunction; central insulin resistance, or exaggerated brain abundance of potentially cytotoxic amyloid-β (Aβ), a hallmark feature of AD. However, contemporary studies find that Aβ is secreted in the periphery by lipogenic organs and secreted as nascent triglyceride-rich lipoproteins (TRL's). Pre-clinical models show that exaggerated abundance in blood of TRL-Aβ compromises blood-brain barrier (BBB) integrity, resulting in extravasation of the TRL-Aβ moiety to brain parenchyme, neurovascular inflammation and neuronal degeneration concomitant with cognitive decline. Inhibiting secretion of TRL-Aβ by peripheral lipogenic organs attenuates the early-AD phenotype indicated in animal models, consistent with causality. Poorly controlled type 2 diabetes commonly features hypertriglyceridemia because of exaggerated TRL secretion and reduced rates of catabolism. Alzheimer's in diabetes may therefore be a consequence of heightened abundance in blood of lipoprotein-Aβ and accelerated breakdown of the BBB. This review reconciles the prevailing dogma of amyloid associated cytotoxicity as a primary risk factor in late-onset AD, with substantial evidence of a microvascular axis for dementia-in-diabetes. Consideration of potentially relevant pharmacotherapies to treat insulin resistance, dyslipidaemia and by extension plasma amyloidemia in type 2 diabetes are discussed.

Plasma Amyloid-β Homeostasis Is Associated with Body Mass Index and Weight Loss in People with Overweight and Obesity

BACKGROUND

Obesity is linked to a higher incidence of Alzheimer's disease (AD). Studies show that plasma amyloid-β (Aβ) dyshomeostasis, particularly low 42/40 ratio indicates a heightened risk for developing AD. However, the relationship between body mass index (BMI) and circulating plasma Aβ has not been extensively studied.

OBJECTIVE

We hypothesized that people with a high BMI have altered plasma Aβ homeostasis compared with people with a lower BMI. We also tested whether reducing BMI by calorie-restriction could normalize plasma concentrations of Aβ.

METHODS

Plasma concentrations of Aβ40, Aβ42, and Aβ42/40 ratio were measured in 106 participants with BMIs classified as lean, overweight, or obese. From this cohort, twelve participants with overweight or obese BMIs entered a 12-week calorie-restriction weight loss program. We then tested whether decreasing BMI affected plasma Aβ concentrations.

RESULTS

Plasma Aβ42/40 ratio was 17.54% lower in participants with an obese BMI compared to lean participants (p < 0.0001), and 11.76% lower compared to participants with an overweight BMI (p < 0.0001). The weight loss regimen decreased BMI by an average of 4.02% (p = 0.0005) and was associated with a 6.5% decrease in plasma Aβ40 (p = 0.0425). However, weight loss showed negligible correlations with plasma Aβ40, Aβ42, and Aβ42/40 ratio.

CONCLUSION

Obesity is associated with aberrant plasma Aβ homeostasis which may be associated with an increased risk for AD. Weight loss appears to lower Aβ40, but large-scale longitudinal studies in addition to molecular studies are required to elucidate the underlying mechanisms of how obesity and weight loss influence plasma Aβ homeostasis.

Effect of a PCSK9 inhibitor and a statin on cholesterol efflux capacity: A limitation of current cholesterol-lowering treatments?

BACKGROUND

Cellular cholesterol efflux is a key step in reverse cholesterol transport that may impact on atherosclerotic cardiovascular risk. The process may be reliant on the availability of apolipoprotein (apo) B-100-containing lipoproteins to accept cholesterol from high-density lipoprotein. Evolocumab and atorvastatin are known to lower plasma apoB-100-containing lipoproteins that could impact on cholesterol efflux capacity (CEC).

METHODS

We conducted a 2-by-2 factorial trial of the effects of subcutaneous evolocumab (420 mg every 2 weeks) and atorvastatin (80 mg daily) for 8 weeks on CEC in 81 healthy, normolipidaemic men. The capacity of whole plasma and apoB-depleted plasma, including ATP-binding cassette transporter A1 (ABCA1)-mediated and passive diffusion, to efflux cholesterol, was measured.

RESULTS

Evolocumab and atorvastatin independently decreased whole plasma CEC (main effect p < .01 for both). However, there were no significant effects of evolocumab and atorvastatin on apoB-depleted plasma, ABCA1-mediated and passive diffusion-mediated CEC (p > .05 in all). In the three intervention groups combined, the reduction in whole plasma CEC was significantly correlated with the corresponding reduction in plasma apoB-100 concentration (r = .339, p < .01). In the evolocumab monotherapy group, the reduction in whole plasma CEC was also significantly correlated with the corresponding reduction in plasma lipoprotein(a) concentration (r = .487, p < .05).

CONCLUSIONS

In normolipidaemic men, evolocumab and atorvastatin decrease the capacity of whole plasma to efflux cellular cholesterol. These effects may be chiefly owing to a fall in the availability of apoB-100-containing lipoproteins. Reduction in circulating lipoprotein(a) may also contribute to the decrease in whole plasma cholesterol efflux with evolocumab monotherapy.

PCSK9 inhibition with alirocumab decreases plasma lipoprotein(a) concentration by a dual mechanism of action in statin-treated patients with very high apolipoprotein(a) concentration

BACKGROUND

Inhibition of proprotein convertase subtilisin/kexin type 9 with alirocumab decreases plasma lipoprotein(a) [Lp(a)] levels. The kinetic mechanism for lowering Lp(a) by alirocumab may differ according to pre-treatment apolipoprotein(a) [apo(a)] levels.

METHODS

The effect of 12-week alirocumab (150 mg subcutaneously fortnightly) on the kinetics of apo(a) was compared in statin-treated patients with high (n = 10) and very high Lp(a) concentrations (n = 11).

RESULTS

In patients with high apo(a) concentrations, alirocumab lowered plasma apo(a) pool size (-17%, p < 0.01) chiefly by increasing the fractional catabolic rate (FCR) of apo(a) (+27%, p < 0.001). By contrast in patients with very high apo(a) concentrations, alirocumab significantly lowered plasma apo(a) pool size (-32%, p < 0.001) by both increasing apo(a) FCR (+30%, p < 0.001) and lowering production rate (-11%, p < 0.05).

CONCLUSIONS

In statin-treated patients with very high apo(a) concentrations, alirocumab lowers plasma Lp(a) concentration by a dual mode of action that increases the clearance and decreases the production of Lp(a) particles.

Familial Hypercholesterolemia and Elevated Lipoprotein(a): Cascade Testing and Other Implications for Contextual Models of Care

Elevated lipoprotein(a) [Lp(a)], a predominantly genetic disorder, is a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and calcific aortic valvular disease, particularly in patients with familial hypercholesterolemia (FH), a Tier I genomic condition. The combination from birth of the cumulative exposure to elevated plasma concentrations of both Lp(a) and low-density lipoprotein is particularly detrimental and explains the enhanced morbidity and mortality risk observed in patients with both conditions. An excellent opportunity to identify at-risk patients with hyper-Lp(a) at increased risk of ASCVD is to test for hyper-Lp(a) during cascade testing for FH. With probands having FH and hyper-Lp(a), the yield of detection of hyper-Lp(a) is 1 individual for every 2.1-2.4 relatives tested, whereas the yield of detection of both conditions is 1 individual for every 3-3.4 relatives tested. In this article, we discuss the incorporation of assessment of Lp(a) in the cascade testing in FH as a feasible and crucial part of models of care for FH. We also propose a simple management tool to help physicians identify and manage elevated Lp(a) in FH, with implications for the care of Lp(a) beyond FH, noting that the clinical use of RNA therapeutics for specifically targeting the overproduction of Lp(a) in at risk patients is still under investigation.

Cascade testing for elevated lipoprotein(a) in relatives of probands with high lipoprotein(a)

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Elevated lipoprotein(a) [Lp(a)] is a common inherited condition associated with atherosclerotic cardiovascular disease.

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Elevated Lp(a) is not routinely tested in clinical practice and most cases remain undiagnosed in the community.

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We identified 124 relatives with elevated Lp(a) (≥50 mg/dL) from 83 affected adult probands who also had dyslipidemia.

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We also demonstrate that follow-up management is effective in lowering low-density lipoprotein-cholesterol levels by 34% as a consequence of initiation of lipid-lowering therapy.

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Cascade testing families for elevated Lp(a) from affected probands with dyslipidemia is an effective and acceptable approach for identifying new cases of elevated Lp(a) who will require management of modifiable risk factors, particularly hypercholesterolemia.

Objective

Elevated lipoprotein(a) [Lp(a)] is a common inherited condition associated with cardiovascular disease. This study investigated whether cascade testing for Lp(a) was effective in detecting new cases of elevated Lp(a) in families.

Methods

Relatives from adult probands with Lp(a) concentration ≥100 mg/dL were tested for elevated Lp(a) (≥50 mg/dL) via a cascade testing program in a tertiary hospital setting. The prevalence and yield of detecting new cases of elevated Lp(a) among the relatives were assessed.

Results

Of the 83 probands, 43.4% had familial combined hyperlipidemia (FCHL) and 34.9% common hypercholesterolemia (CH). Among 182 relatives tested (151 adults and 31 children), elevated Lp(a) was found in 68.1%, with 32.9% having Lp(a) between 50 and 99 mg/dL and 35.2% having Lp(a) ≥100 mg/dL. One new case of elevated Lp(a) ≥50 mg/dL was identified for every 1.5 relatives tested and 1 new case of elevated Lp(a) ≥100 mg/dL for every 2.8 relatives tested. The proportion of relatives detected with elevated Lp(a) was significantly higher when tested from probands with Lp(a) >150 mg/dL compared with those with Lp(a) between 100 and 150 mg/dL (81.1% vs. 55.5%; P = 0.001). The concordance rates (kappa coefficient) for the detection of elevated Lp(a) with FCHL and CH were 34.8% (0.026) and 53.2% (0.099), respectively.

Conclusion

Cascade testing for elevated Lp(a) from affected probands with phenotypic dyslipidemia is highly effective in identifying new cases of high Lp(a) in families. The yield of detecting elevated Lp(a) is greater when probands have higher levels of Lp(a) and exceeds the detection of relatives with FCHL and CH.

Hypertriglyceridemia: rationale, design and implementation of the Australian Hypertriglyceridemia Registry

PURPOSE OF REVIEW

Hypertriglyceridemia (HTG) is a risk factor for atherosclerotic cardiovascular disease (ASCVD), aortic stenosis, hepatic steatosis and pancreatitis. We briefly review the aetiology and treatment of HTG and familial chylomicronemia syndrome (FCS), as well as the implementation of a clinical quality registry for improving care, the Australian Hypertriglyceridemia (AUSTRIG) Registry.

RECENT FINDINGS

There is a need to improve the detection of individuals with severe HTG and FCS, who could benefit from more intense and novel treatments to prevent end-organ damage. Patient registries provide valuable data for advancing care of individuals with severe HTG at high risk of acute pancreatitis, steatohepatitis and ASCVD. However, there is a paucity of registries of such patients. We outline the design and implementation of the AUSTRIG Registry.

SUMMARY

Clinical registries can be employed in many ways for improving outcomes for patients with HTG, through the collation and analysis of data for enabling health service planning, clinical trials and audits, and for better informing and empowering registrants.

A Tale of Two New Targets for Hypertriglyceridaemia: Which Choice of Therapy?

Angiopoietin-like protein 3 (ANGPTL3) and apolipoprotein C-III (apoC-III) are novel metabolic targets for correcting hypertriglyceridaemia (HTG). As a background to their potential clinical use, we review the metabolic aetiology of HTG, particular abnormalities in triglyceride-rich lipoproteins (TRLs) and their role in atherosclerotic cardiovascular disease (ASCVD) and acute pancreatitis. Molecular and cardiometabolic aspects of ANGPTL3 and apoC-III, as well as inhibition of these targets with monoclonal antibody and nucleic acid therapies, are summarized as background information to descriptions and analyses of recent clinical trials. These studies suggest that ANGPTL3 and apoC-III inhibitors are equally potent in lowering elevated plasma triglycerides and TRLs across a wide range of concentrations, with possibly greater efficacy with inhibition of apoC-III. ANGPTL3 inhibition may, however, have the advantage of greater lowering of plasma LDL cholesterol and could specifically address elevated LDL cholesterol in familial hypercholesterolaemia refractory to standard drug therapies. Large clinical outcome trials in relevant populations are still required to confirm the long-term efficacy, safety and cost effectiveness of these potent agents for mitigating the complications of HTG. Beyond targeting severe chylomicronaemia in the prevention of acute pancreatitis, both agents could be useful in addressing residual risk of ASCVD due to TRLs in patients receiving best standard of care, including behavioural modifications, statins, ezetimibe, fibrates and proprotein convertase subtilisin/kexin type 9 inhibitors.

Recent dynamic studies of the metabolism of atherogenic lipoproteins: elucidating the mode of action of new therapies

PURPOSE OF REVIEW

LDL, triglyceride-rich lipoprotein (TRL) and lipoprotein(a) [Lp(a)] particles are the key atherogenic lipoproteins. Deranged metabolism of these lipoproteins accounts for a spectrum of clinically important dyslipidemias, such as FH, elevated Lp(a) and diabetic dyslipidemia. We review the findings from recent dynamic and tracer studies that have contributed to expanding knowledge in this field.

RECENT FINDINGS

Deficiency in LDL receptor activity does not only impair the catabolism of LDL-apoB-100 in FH, but also induces hepatic overproduction and decreases catabolism of TRLs. Patients with elevated Lp(a) are characterized by increased hepatic secretion of Lp(a) particles. Elevation of TRLs in diabetes is partly mediated by increased production of apoB-48 and apoC-III, and impaired clearance of apoB-48 in the postprandial state. Tracer kinetic studies show that proprotein convertase subtilisin/kexin type 9 mAbs alone or in combination with statin can increase the catabolism and decrease production of LDL and Lp(a) particles. By contrast, angiopoietin-like protein 3 inhibitors (e.g. evinacumab) reduce VLDL production and increase LDL clearance in FH. Glucagon-like peptide-1 receptor agonists can improve diabetic dyslipidemia by increasing the catabolism of apoB-48 and decreasing the production of apoB-48 and apoC-III.

SUMMARY

Dynamic studies of the metabolism of atherogenic lipoproteins provide new insight into the nature of dyslipidemias and point to how new therapies with complementary modes of action may have maximal clinical impact.

Cascade testing for elevated lipoprotein(a) in relatives of probands with familial hypercholesterolaemia and elevated lipoprotein(a)

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) and elevated plasma lipoprotein(a) [Lp(a)] are inherited conditions independently associated with atherosclerotic cardiovascular disease. This study investigated the detection of new cases of elevated Lp(a) during cascade testing of relatives of probands with a definite diagnosis of FH and elevated Lp(a) (≥50 mg/dL).

METHODS

Relatives from 62 adult probands were tested for FH genetically and for elevated Lp(a) using an immunoassay. The prevalence and yield of new cases of FH with or without elevated Lp(a) among relatives and the association between the detection of elevated Lp(a) and the Lp(a) concentration of the probands were assessed.

RESULTS

Among 162 relatives tested (136 adults and 26 children), the prevalence of FH and elevated Lp(a) was 60.5% and 41.4%, respectively: FH alone was detected in 31.5%, elevated Lp(a) alone in 12.3%, FH with elevated Lp(a) in 29.0%, and neither disorder in 27.2% of the relatives. Cascade testing detected a new case of FH, elevated Lp(a) and FH with elevated Lp(a) for every 1.5, 2.1 and 3.0 relatives tested, respectively. The proportion of relatives detected with elevated Lp(a) was significantly higher when tested from probands with Lp(a) ≥100 mg/dL compared with those from probands with Lp(a) between 50 and 99 mg/dL (53% vs 34%, p = 0.018). The concordance between the detection of FH and elevated Lp(a) was 56.2% (kappa statistic 0.154), indicating a poor agreement.

CONCLUSIONS

A dual approach to cascade testing families for FH and high Lp(a) from appropriate probands can effectively identify not only new cases of FH, but also new cases of elevated Lp(a) with or without FH. The findings accord with the co-dominant and independent heritability of FH and Lp(a).

Unravelling lipoprotein metabolism with stable isotopes: tracing the flow

Dysregulated lipoprotein metabolism is a major cause of atherosclerotic cardiovascular disease (ASCVD). Use of stable isotope tracers and compartmental modelling have provided deeper understanding of the mechanisms underlying lipid disorders in patients at high risk of ASCVD, including familial hypercholesterolemia (FH), elevated lipoprotein(a) [Lp(a)] and metabolic syndrome (MetS). In patients with FH, deficiency in low-density lipoprotein (LDL) receptor activity not only impairs the catabolism of LDL, but also induces hepatic overproduction and decreases catabolism of triglyceride-rich lipoproteins (TRLs). Patients with elevated Lp(a) are characterized by increased hepatic secretion of Lp(a) particles. Atherogenic dyslipidemia in MetS patients relates to a combination of overproduction of very-low density lipoprotein-apolipoprotein (apo) B-100, decreased catabolism of apoB-100-containing particles, and increased catabolism of high-density lipoprotein-apoA-I particles, as well as to impaired clearance of TRLs in the postprandial state. Kinetic studies show that weight loss, fish oils, statins and fibrates have complementary modes of action that correct atherogenic dyslipidemia. Defining the kinetic mechanisms of action of proprotein convertase subtilisin/kexin type 9 and angiopoietin-like 3 inhibitors on lipid and lipoprotein mechanism in dyslipidemic subjects will further our understanding of these therapies in decreasing the development of ASCVD. "Everything changes but change itself. Everything flows and nothing remains the same... You cannot step twice into the same river, for other waters and yet others go flowing ever on." Heraclitus (c.535- c. 475 BCE).

Transcriptomic therapy for dyslipidemias utilizing nucleic acids targeted at ANGPTL3

Angiopoietin-like protein 3 (ANGPTL3) is a key physiological regulator of plasma lipid and lipoprotein metabolism that involves the control of enzymes, lipoprotein and endothelial lipases. Inhibition of ANGPTL3 offers a new approach for correcting the health risks of dyslipidemia, including familial hypercholesterolemia, mixed hyperlipidemia, metabolic syndrome and/or severe hypertriglyceridemia. ANGPTL3 inhibition with nucleic acid-based antisense oligonucleotide and siRNA can correct dyslipidemia chiefly by reducing production and increasing catabolism of triglyceride-rich lipoprotein and LDL particles. Early clinical trials have demonstrated that these agents can safely and effectively lower plasma triglyceride and LDL-cholesterol levels by up to 70 and 50%, respectively. However, the long-term safety and cost-effectiveness of these agents await to be confirmed in an ongoing and future clinical trials.

PCSK9 inhibition with alirocumab decreases plasma lipoprotein(a) concentration by a dual kinetic mechanism of action

Background

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein (LDL)-like particle, covalently bound to apolipoprotein(a) [apo(a)]. Recent trials show that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, such as alirocumab, decrease plasma Lp(a) levels and risk of atherosclerotic cardiovascular disease (ASCVD). The kinetic mechanism for lowering Lp(a) by PCSK9 inhibitors may differ according to pre-treatment apo(a) levels.

Purpose

We investigated the effect of alirocumab on Lp(a) metabolism in 21 long-term statin-treated patients [Lp(a) &gt;0.5 g/L in all] with moderate-high (n=10) and high (n=11) apo(a) concentrations according to a cutoff of median apo(a) levels of 145 nmol/L.

Methods

Apo(a) kinetics were studied before and after 12-week treatment with alirocumab (150 mg subcutaneously fortnightly). Apo(a) fractional catabolic rate (FCR) and production rate (PR) were determined using intravenous D3-leucine administration, mass spectrometry and compartmental modelling.

Results

The plasma concentration and PR of apo(a) were significantly higher in patients with high apo(a) than in patients with moderate-high apo(a) levels (273±30 nmol/L vs 130±4.7 nmol/L and 6.0±0.69 nmol/kg/day vs 2.6±0.15 nmol/kg/day, respectively; P&lt;0.001). The FCR of apo(a) was not significantly different between two groups (0.48±0.02 pools/day vs 0.45±0.01 pools/day, P&gt;0.05). In patients with moderate-high apo(a) levels, alirocumab significantly lowered plasma apo(a) levels (−17%, P&lt;0.01) and increased the FCR of apo(a) (+26%, P&lt;0.001), but did not alter apo(a) PR. In contrast, alirocumab significantly lowered plasma apo(a) concentrations (−31%, P&lt;0.001) via a dual mechanism that increased apo(a) FCR (+31%, P&lt;0.001) and lowered PR (−9%, P&lt;0.05) in patients with high apo(a) levels. The reductions in apo(a) concentration and PR with alirocumab in the high apo(a) group remained significant after adjusting for background statin when compared with patients with moderate-high apo(a) levels (P&lt;0.05).

Conclusions

In statin-treated patients with elevated Lp(a), alirocumab may lower elevated plasma Lp(a) concentrations by a dual mechanism of increasing the catabolism and decreasing the production of Lp(a) particles, specifically in patients with relatively high apo(a) concentrations.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This independent research was funded by an Investigator Initiated Study Concept Research Grant from Regeneron Pharmaceuticals and Sanofi (Protocol No. LPS 14508). Figure 1Figure 2

Implications of new clinical practice guidance on familial hypercholesterolaemia for Australian general practitioners

BACKGROUND

Familial hypercholesterolaemia (FH) is a monogenic lipid disorder that may be overlooked in the diagnostic process.

OBJECTIVE

The aim of this article is to review the key areas for identification and management of FH that affect Australian general practitioners (GPs).

DISCUSSION

Recent consensus advice on the care of patients with FH in Australia provides an opportunity for GPs to increase their awareness and skills in diagnosing and managing FH. New Medicare Benefits Schedule items for genetic testing and Pharmaceutical Benefits Scheme listing for the use of proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors offer GPs additional supports to improve the care of patients with FH. A shared-care approach between GPs and non-GP specialists with expertise in multiple disciplines offers the best option to facilitate genetic testing and management of index cases and affected family relatives. Implementation of this guidance in the primary care setting remains an ongoing challenge and needs to be embraced as a high priority.

Awareness of familial hypercholesterolaemia in Australian primary care: A qualitative descriptive study

BACKGROUND AND OBJECTIVES

A lack of public and health professional awareness about familial hypercholesterolaemia (FH) leads to an estimated 90,000 Australians remaining undiagnosed. The aim of this study was to establish the level of knowledge and awareness of FH in Australian general practices.

METHOD

A qualitative descriptive methodology was used to explore baseline knowledge and perceptions of practice staff about diagnosing and managing FH. Overall, 63 interviews were conducted with general practice staff at 15 practices taking part in a National Health and Medical Research Council partnership grant study (GNT1142883).

RESULTS

Data were analysed thematically and coded into themes - knowledge/awareness/recall, management, use of guidelines/referrals, and contacting family members. Most general practitioners treated the high cholesterol component as their primary focus. Guidelines and referrals were rarely used.

DISCUSSION

This research reflected a lack of knowledge, awareness and use of guidelines similar to that shown in other published studies. Improved primary care infrastructure, knowledge and awareness of FH need to be addressed.

Improving detection and management of familial hypercholesterolaemia in Australian general practice

OBJECTIVE

Familial hypercholesterolaemia (FH) is characterised by elevated low-density lipoprotein (LDL)-cholesterol and increased risk of cardiovascular disease. However, FH remains substantially underdiagnosed and undertreated. We employed a two-stage pragmatic approach to identify and manage patients with FH in primary healthcare.

METHODS

Medical records for 232 139 patients who attended 15 general practices at least once in the previous 2 years across five Australian States were first screened for potential risk of FH using an electronic tool (TARB-Ex) and confirmed by general practitioner (GP) clinical assessment based on phenotypic Dutch Lipid Clinic Network Criteria (DLCNC) score. Follow-up GP consultation and management was provided for patients with phenotypic FH.

RESULTS

A total of 1843 patients were identified by TARB-Ex as at potential risk of FH (DLCNC score ≥5). After GP medical record review, 900 of these patients (49%) were confirmed with DLCNC score ≥5 and classified as high-risk of FH. From 556 patients subsequently clinically assessed by GPs, 147 (26%) were diagnosed with phenotypic FH (DLCNC score >6). Follow-up GP consultation and management for 77 patients resulted in a significant reduction in LDL-cholesterol (-16%, p<0.01). A higher proportion of these patients attained the treatment target of 50% reduction in LDL-cholesterol (74% vs 62%, p<0.001) and absolute levels of LDL-cholesterol goals compared with baseline (26% vs 12%, p<0.05).

CONCLUSIONS

A pragmatic approach integrating electronic medical record tools and clinical GP follow-up consultation is a feasible method to identify and better manage patients with FH in the primary healthcare setting.

TRIAL REGISTRATION NUMBER

12616000630415.

Effectiveness of proprotein convertase subtilisin/kexin-9 monoclonal antibody treatment on plasma lipoprotein(a) concentrations in patients with elevated lipoprotein(a) attending a clinic

Background

Lipoprotein(a) (Lp[a]) is a causal risk factor for atherosclerotic cardiovascular disease (ASCVD). Proprotein convertase subtilisin/kexin‐9 monoclonal antibodies (PCSK9mAbs) can lower Lp(a) levels in clinical trials, but their effects in patients with elevated Lp(a) in clinical practice remain unclear.

Aims

To investigate the effectiveness and safety of PCSK9mAbs in lowering plasma Lp(a) in patients with elevated Lp(a) concentrations in a lipid clinic.

Methods

This was an open‐label study of 53 adult patients with elevated Lp(a) concentration (≥0.5 g/L). Clinical, biochemical, and safety data were collected before and on treatment with evolocumab or alirocumab over a mean period of 11 months.

Results

Treatment with a PCSK9mAb resulted in a significant reduction of 0.29 g/L (−22%) in plasma Lp(a) concentration (p<.001). There were also significant reductions in low‐density lipoprotein‐cholesterol (LDL‐C) (−53%), remnant‐cholesterol (−12%) and apolipoprotein B (−43%) concentrations. The change in Lp(a) concentration was significantly different from a comparable group of 35 patients with elevated Lp(a) who were not treated with a PCSK9mAb (−22% vs. −2%, p<.001). The reduction in Lp(a) concentration was not associated with the corresponding changes in LDL‐C, remnant‐cholesterol, and apolipoprotein B (p>.05 in all). 7.5% and 47% of the patients attained a target concentration of Lp(a) <0.5 g/L and LDL‐C <1.8 mmol/L, respectively. PCSK9mAbs were well tolerated, the common adverse effects being pharyngitis (9.4%), nasal congestion (7.6%), myalgia (9.4%), diarrhoea (7.6%), arthralgia (9.4%) and injection site reactions (11%).

Conclusion

PCSK9mAbs can effectively and safely lower plasma Lp(a) concentrations in patients with elevated Lp(a) in clinical practice; the impact of the fall in Lp(a) on ASCVD outcomes requires further investigation.

New Insights Into the Regulation of Lipoprotein Metabolism by PCSK9: Lessons From Stable Isotope Tracer Studies in Human Subjects

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a convertase enzyme mostly produced by the liver. It is a key regulator of LDL metabolism because of its ability to enhance degradation of the LDL receptor. PCSK9 also regulates the metabolism of lipoprotein(a) [Lp(a)] and triglyceride-rich lipoproteins (TRLs). Its key role in modulating atherosclerotic cardiovascular disease (ASCVD) is supported by genetic studies and clinical outcome trials. Kinetic studies provide mechanistic insight into the role of PCSK9 in regulating the physiology and pathophysiology of plasma lipids and lipoproteins. Kinetic data have demonstrated that plasma PCSK9 concentration is inversely associated with the clearance of LDL in men. Gain-of-function mutations of PCSK9 markedly increase plasma LDL-cholesterol concentrations due to impaired LDL-apoB catabolism. Conversely, PCSK9 deficiency results in low LDL-cholesterol associated with enhanced LDL-apoB clearance. Inhibition of PCSK9 with monoclonal antibodies (such as evolocumab or alirocumab) lowers plasma LDL-cholesterol and apoB levels chiefly by upregulating the catabolism of LDL particles in healthy individuals. As monotherapy, PCSK9 inhibitor reduced Lp(a) concentrations by decreasing the production rate. However, as combination therapy, it reduced the plasma concentration of Lp(a) by increasing the fractional catabolism of Lp(a) particles. In statin-treated patients with high Lp(a), PCSK9 inhibition lowers plasma Lp(a) concentrations by accelerating the catabolism of Lp(a) particles. The effect of PCSK9 inhibition on TRL metabolism has been studied in healthy individuals and in patients with type 2 diabetes. These findings suggest that PCSK9 appears to play a less important role in TRL than LDL metabolism. Kinetic studies of PCSK9 inhibition therapy on lipoprotein metabolism in diverse high risk patient populations (such as familial hypercholesterolemia) and new therapeutic combination also merit further investigation.

Lipoprotein(a) in Patients With Type 2 Diabetes and Premature Coronary Artery Disease in the Coronary Care Unit

INTRODUCTION

Lipoprotein(a) [Lp(a)] and diabetes are independently associated with premature coronary artery disease (pCAD). However, there is an inverse relationship between Lp(a) concentration and type 2 diabetes (T2D) risk. We examine whether Lp(a) distribution in patients with pCAD differs between those with or without T2D, and whether elevated Lp(a) is associated with pCAD in patients with T2D.

METHODS

Lp(a) concentration was measured in consecutive acute coronary syndrome (ACS) patients in two coronary care units (study one: ACS with or without diabetes, study two: ACS and diabetes). Elevated Lp(a) mass concentration was defined as ≥0.5 g/L and pCAD where CAD was diagnosed age <60 years. The association between elevated Lp(a) and pCAD was assessed using logistic regression.

RESULTS

Of 449 patients, 233 (51.9%) had pCAD and 278 (61.9%) had T2D. In patients with pCAD, those with T2D had a significantly lower median Lp(a) concentration (0.13 g/L versus 0.27 g/L, p=0.004). In patients with T2D, elevated Lp(a) was significantly associated with pCAD (OR 2.419, 95% CI 1.513-3.867, p<0.001). After adjusting for gender, smoking, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and triglycerides, elevated Lp(a) remained significantly associated with pCAD (OR 2.895, 95% CI 1.427-5.876, p=0.003) in patients with T2D.

CONCLUSIONS

In coronary care patients with pCAD, patients with T2D had lower Lp(a) concentrations than those without T2D. Despite this, elevated Lp(a) remained predictive of pCAD in patients with T2D. Measurement of Lp(a) should be considered in younger adults with T2D to identify who may benefit from earlier preventative therapies to reduce pCAD burden.

The Knowns and Unknowns of Contemporary Statin Therapy for Familial Hypercholesterolemia

PURPOSE OF REVIEW

Statins are first-line therapy for lowering low-density lipoprotein (LDL) cholesterol in familial hypercholesterolemia (FH), particularly in heterozygous patients. We review advances and new questions on the use of statins in FH.

RECENT FINDINGS

Cumulative evidence from registry data and sub-analyses of clinical trials mandates the value of statin therapy for prevention of atherosclerotic cardiovascular disease (ASCVD) in FH. Statins are safe in children and adolescents with FH, with longer term cardiovascular benefits. The potentially toxic effects of statins in pregnancy need to be considered, but no association has been reported in prospective cohort studies with birth defects. There is no rationale for discontinuation of statins in elderly FH unless indicated by adverse events. FH is undertreated, with > 80% of statin-treated FH patients failing to attain LDL cholesterol treatment targets. This may relate to adherence, tolerability, and genetic differences in statin responsiveness. Statin treatment from childhood may reduce the need for stringent cholesterol targets. Combination of statins with ezetimibe and PCSK9 inhibitors significantly improves the efficacy of treatment. Whether statin use could improve the clinical course of FH patients with COVID-19 and other respiratory infections remains an unsolved issue for future research. Statins are the mainstay for primary and secondary prevention of ASCVD in FH. Sustained long-term optimal statin treatment from an early age can effectively prevent ASCVD over decades of life. Despite their widespread use, statins merit further investigation in FH.

Gaps in the Care of Familial Hypercholesterolaemia in Australia: First Report From the National Registry

BACKGROUND

Familial hypercholesterolaemia (FH) is under-diagnosed and under-treated worldwide, including Australia. National registries play a key role in identifying patients with FH, understanding gaps in care and advancing the science of FH to improve care for these patients.

METHODS

The FH Australasia Network has established a national web-based registry to raise awareness of the condition, facilitate service planning and inform best practice and care services in Australia. We conducted a cross-sectional analysis of 1,528 FH adults enrolled in the registry from 28 lipid clinics.

RESULTS

The mean age at enrolment was 53.4±15.1 years, 50.5% were male and 54.3% had undergone FH genetic testing, of which 61.8% had a pathogenic FH-causing gene variant. Only 14.0% of the cohort were family members identified through cascade testing. Coronary artery disease (CAD) was reported in 28.0% of patients (age of onset 49.0±10.5 years) and 64.9% had at least one modifiable cardiovascular risk factor. The mean untreated LDL-cholesterol was 7.4±2.5 mmol/L. 80.8% of patients were on lipid-lowering therapy with a mean treated LDL-cholesterol of 3.3±1.7 mmol/L. Among patients receiving lipid-lowering therapies, 25.6% achieved an LDL-cholesterol target of <2.5 mmol/L without CAD or <1.8 mmol/L with CAD.

CONCLUSION

Patients in the national FH registry are detected later in life, have a high burden of CAD and risk factors, and do not achieve guideline-recommended LDL-cholesterol targets. Genetic and cascade testing are under-utilised. These deficiencies in care need to be addressed as a public health priority.

Lipoprotein(a) Particle Production as a Determinant of Plasma Lipoprotein(a) Concentration Across Varying Apolipoprotein(a) Isoform Sizes and Background Cholesterol-Lowering Therapy

Background

Elevated lipoprotein(a) (Lp(a)), a low‐density lipoprotein‐like particle bound to the polymorphic apolipoprotein(a) (apo(a)), may be causal for cardiovascular disease. However, the metabolism of Lp(a) in humans is poorly understood.

Methods and Results

We investigated the kinetics of Lp(a)‐apo(a) and low‐density lipoprotein‐apoB‐100 in 63 normolipidemic men. The fractional catabolic rate (FCR) and production rate PR) were studied. Plasma apo(a) concentration was significantly and inversely associated with apo(a) isoform size (r=−0.536, P<0.001) and apo(a) FCR (r=−0.363, P<0.01), and positively with apo(a) PR (r=0.877, P<0.001). There were no significant associations between the FCRs of apo(a) and low‐density lipoprotein‐apoB‐100. Subjects with smaller apo(a) isoform sizes (≤22 kringle IV repeats) had significantly higher apo(a) PR (P<0.05) and lower apo(a) FCR (P<0.01) than those with larger sizes. Plasma apo(a) concentration was significantly associated with apo(a) PR (r=0.930, P<0.001), but not with FCR (r=−0.012, P>0.05) in subjects with smaller apo(a) isoform size. In contrast, both apo(a) PR and FCR were significantly associated with plasma apo(a) concentrations (r=0.744 and −0.389, respectively, P<0.05) in subjects with larger isoforms. In multiple regression analysis, apo(a) PR and apo(a) isoform size were significant predictors of plasma apo(a) concentration independent of low‐density lipoprotein‐apoB‐100 FCR and background therapy with atorvastatin and evolocumab.

Conclusions

In normolipidemic men, the plasma Lp(a) concentration is predominantly determined by the rate of production of Lp(a) particles, irrespective of apo(a) isoform size and background therapy with a statin and a proprotein convertase subtilisin‐kexin type 9 inhibitor. Our findings underscore the importance of therapeutic targeting of the hepatic synthesis and secretion of Lp(a) particles. Lp(a) particle catabolism may only play a modest role in determining Lp(a) concentration in subjects with larger apo(a) isoform size.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02189837.

PCSK9 Inhibition with alirocumab increases the catabolism of lipoprotein(a) particles in statin-treated patients with elevated lipoprotein(a)

BACKGROUND

Lipoprotein(a) (Lp(a)) is a low-density lipoprotein (LDL) particle containing apolipoprotein(a) (apo(a)) covalently linked to apolipoprotein B-100 (apoB). Statin-treated patients with elevated Lp(a) have an increased risk of atherosclerotic cardiovascular disease (ASCVD). Recent trials show that proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition decreases Lp(a) and cardiovascular events, particularly in high risk patients with elevated Lp(a). We investigated the kinetic mechanism whereby alirocumab, a PCSK9 inhibitor, lowers Lp(a) in statin-treated patients with high Lp(a) and ASCVD.

METHODS

The effects of 12-week alirocumab treatment (150 mg every 2 weeks) on apo(a) kinetics were studied in 21 patients with elevated Lp(a) concentration (>0.5 g/L). Apo(a) fractional catabolic rate (FCR) and production rate (PR) were determined using intravenous D3-leucine administration, mass spectrometry and compartmental modelling. All patients were on long-term statin treatment.

RESULTS

Alirocumab significantly decreased plasma concentrations of total cholesterol (-39%), LDL-cholesterol (-67%), apoB (-56%), apo(a) (-25%) and Lp(a) (-22%) (P< 0.001 for all). Alirocumab also significantly lowered plasma apo(a) pool size (-26%, P <0.001) and increased the FCR of apo(a) (+28%, P< 0.001), but did not alter apo(a) PR, which remained significantly higher relative to a reference group of patients on statins with normal Lp(a) (P< 0.001).

CONCLUSIONS

In statin-treated patients, alirocumab lowers elevated plasma Lp(a) concentrations by accelerating the catabolism of Lp(a) particles. This may be consequent on marked upregulation of hepatic receptors (principally for LDL) and/or reduced competition between Lp(a) and LDL particles for these receptors; the mechanism could contribute to the benefit of PCSK9 inhibition with alirocumab on cardiovascular outcomes.

Association of Serum Lipoprotein (a) With the Requirement for a Peripheral Artery Operation and the Incidence of Major Adverse Cardiovascular Events in People With Peripheral Artery Disease

Background The aim of this study was to assess the relationship between serum lipoprotein (a) (Lp[a]) concentration and the requirement for peripheral artery disease (PAD) operations or incidence of major adverse cardiovascular events. Methods and Results A total of 1472 people with PAD presenting with intermittent claudication (n=355), abdominal aortic aneurysm (n=989) or critical limb ischemia (n=128) were prospectively recruited from 4 outpatient clinics in Australia. Lp(a) was measured in serum samples collected at recruitment using an immunoassay. Participants were followed for a median (interquartile range) of 2.4 (0.1-6.1) years to record requirement for any PAD operation, defined to include any open or endovascular PAD intervention (lower limb peripheral revascularization, abdominal aortic aneurysm repair, other aneurysm repair, or carotid artery revascularization). Myocardial infarctions, strokes, and deaths were also recorded. The association of Lp(a) with events was assessed using Cox proportional hazard analysis adjusting for traditional risk factors. Participants with Lp(a) ≥30 mg/dL had a greater requirement for any PAD operation (hazard ratio, 1.20, 95% CI, 1.02-1.41) and lower limb peripheral revascularization alone (hazard ratio 1.33, 95% CI, 1.06-1.66) but no increased risk of major adverse cardiovascular events or all-cause mortality. Lp(a) ≥50 mg/dL and a 40 mg/dL increase in Lp(a) were also associated with an increased risk of lower limb peripheral revascularization alone but not with other outcomes. Conclusions In participants with PAD referred for hospital management those with high Lp(a) had greater requirement for lower limb peripheral revascularization but Lp(a) was not consistently associated with other clinical events.

An age-matched computed tomography angiographic study of coronary atherosclerotic plaques in patients with familial hypercholesterolaemia

BACKGROUND AND AIMS

Familial hypercholesterolaemia (FH) is characterised by a high, but variable risk of premature coronary artery disease (CAD). Cardiac computed tomography angiography (CCTA) can be employed to assess subclinical coronary atherosclerosis. We investigated the features and distribution of coronary artery plaques in asymptomatic patients with and without genetically confirmed heterozygous FH.

METHODS

We undertook an aged-matched case-control study of asymptomatic phenotypic FH patients with (cases, M+) and without (controls, M-) an FH-causing mutation. Coronary atherosclerosis was assessed by CCTA and calcium scoring. Coronary segments were evaluated for global and vessel-level coronary plaques and degree of stenosis.

RESULTS

We studied 104 cases and 104 controls (mean age 49.9 ± 10.4 years), who had a similar spectrum of non-cardiovascular risk factors. Pre-treatment plasma LDL-cholesterol was higher in the M+ than M- group (7.8 ± 2.1 vs 6.2 ± 1.2 mmol/L, p<0.001). There was a greater proportion of patients with mixed and calcified plaque, as well as a higher coronary artery calcium score and segment stenosis score (all p<0.05), in the M+ compared with the M- group. M+ patients also had a significantly higher frequency of coronary artery calcium in the left main and anterior descending and right coronary arteries (all p<0.05), but not in the left circumflex.

CONCLUSIONS

Among patients with phenotypic FH, those with a genetically confirmed diagnosis had a higher frequency and severity of coronary atherosclerotic plaques, and specifically more advanced calcified plaques.

Apolipoprotein(a) Kinetics in Statin-Treated Patients With Elevated Plasma Lipoprotein(a) Concentration

BACKGROUND

Lipoprotein(a) [Lp(a)] is a low-density lipoprotein‒like particle containing apolipoprotein(a) [apo(a)]. Patients with elevated Lp(a), even when treated with statins, are at increased risk of cardiovascular disease. We investigated the kinetic basis for elevated Lp(a) in these patients.

OBJECTIVES

Apo(a) production rate (PR) and fractional catabolic rate (FCR) were compared between statin-treated patients with and without elevated Lp(a).

METHODS

The kinetics of apo(a) were investigated in 14 patients with elevated Lp(a) and 15 patients with normal Lp(a) levels matched for age, sex, and body mass index using stable isotope techniques and compartmental modeling. All 29 patients were on background statin treatment. Plasma apo(a) concentration was measured using liquid chromatography-mass spectrometry.

RESULTS

The plasma concentration and PR of apo(a) were significantly higher in patients with elevated Lp(a) than in patients with normal Lp(a) concentration (all P < 0.01). The FCR of apo(a) was not significantly different between the groups. In univariate analysis, plasma concentration of apo(a) was significantly associated with apo(a) PR in both patient groups (r = 0.699 and r = 0.949, respectively; all P < 0.01). There was no significant association between plasma apo(a) concentration and FCR in either of the groups (r = 0.160 and r = -0.137, respectively).

CONCLUSION

Elevated plasma Lp(a) concentration is a consequence of increased hepatic production of Lp(a) particles in these patients. Our findings provide a kinetic rationale for the use of therapies that target the synthesis of apo(a) and production of Lp(a) particles in patients with elevated Lp(a).

A genetic risk score predicts coronary artery disease in familial hypercholesterolaemia: enhancing the precision of risk assessment

Familial hypercholesterolaemia (FH) is associated with increased risk of coronary artery disease (CAD); however, risk prediction and stratification remain a challenge. Genetic risk scores (GRS) may have utility in identifying FH patients at high CAD risk. The study included 811 patients attending the lipid disorders clinic at Royal Perth Hospital with mutation-positive (n = 251) and mutation-negative (n = 560) FH. Patients were genotyped for a GRS previously associated with CAD. Associations between the GRS, clinical characteristics, and CAD were assessed using regression analyses. The average age of patients was 49.6 years, and 44.1% were male. The GRS was associated with increased odds of a CAD event in mutation-positive [odds ratio (OR) = 3.3; 95% confidence interval (CI) = 1.3-8.2; P = .009] and mutation-negative FH patients (OR = 1.8; 95% CI = 1.0-3.3; P = .039) after adjusting for established predictors of CAD risk. The GRS was associated with greater subclinical atherosclerosis as assessed by coronary artery calcium score (P = .039). A high GRS was associated with CAD defined clinically and angiographically in FH patients. High GRS patients may benefit from more intensive management including lifestyle modification and aggressive lipid-lowering therapy. Further assessment of the utility of the GRS requires investigation in prospective cohorts, including its role in influencing the management of FH patients in the clinic.