Atherosclerosis in cholesterol-fed rabbits and in homozygous and heterozygous LDL receptor-deficient humans

FH through the retrospectoscope

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

Phylogenic Determinants of Cardiovascular Frailty, Focus on Hemodynamics and Arterial Smooth Muscle Cells

The evolution of the circulatory system from invertebrates to mammals has involved the passage from an open system to a closed in-parallel system via a closed in-series system, accompanying the increasing complexity and efficiency of life’s biological functions. The archaic heart enables pulsatile motion waves of hemolymph in invertebrates, and the in-series circulation in fish occurs with only an endothelium, whereas mural smooth muscle cells appear later. The present review focuses on evolution of the circulatory system. In particular, we address how and why this evolution took place from a closed, flowing, longitudinal conductance at low pressure to a flowing, highly pressurized and bifurcating arterial compartment. However, although arterial pressure was the latest acquired hemodynamic variable, the general teleonomy of the evolution of species is the differentiation of individual organ function, supported by specific fueling allowing and favoring partial metabolic autonomy. This was achieved via the establishment of an active contractile tone in resistance arteries, which permitted the regulation of blood supply to specific organ activities via its localized function-dependent inhibition (active vasodilation). The global resistance to viscous blood flow is the peripheral increase in frictional forces caused by the tonic change in arterial and arteriolar radius, which backscatter as systemic arterial blood pressure. Consequently, the arterial pressure gradient from circulating blood to the adventitial interstitium generates the unidirectional outward radial advective conductance of plasma solutes across the wall of conductance arteries. This hemodynamic evolution was accompanied by important changes in arterial wall structure, supported by smooth muscle cell functional plasticity, including contractility, matrix synthesis and proliferation, endocytosis and phagocytosis, etc. These adaptive phenotypic shifts are due to epigenetic regulation, mainly related to mechanotransduction. These paradigms actively participate in cardio-arterial pathologies such as atheroma, valve disease, heart failure, aneurysms, hypertension, and physiological aging.

Efficacy and Safety of PCSK9 Monoclonal Antibodies in Patients at High Cardiovascular Risk: An Updated Systematic Review and Meta-Analysis of 32 Randomized Controlled Trials

INTRODUCTION

Proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies are powerful lipid-lowering drugs which have been shown to improve clinical endpoints in patients with hypercholesterolemia. However, it is not clear how effective PCSK9 monoclonal antibodies are for patients at high cardiovascular risk. Also, whether the effectiveness of PCSK9 monoclonal antibodies varies between different drug types, dosages, race, and indications for PCSK9 monoclonal antibodies remains unclear. Therefore, we used recently published studies to systematically evaluate the efficacy and safety of PCSK9 monoclonal antibodies by analyzing the lipid profiles, adverse events, and clinical endpoints in patients at high cardiovascular risk.

METHODS

Randomized controlled trials (RCTs) comparing PCSK9 monoclonal antibodies with placebos or active drugs in patients at high cardiovascular risk were retrieved from electronic databases from their inception until November 2019. Efficacy and safety outcomes included low-density lipoprotein cholesterol (LDL-C) and other lipid profiles, treatment-emergent adverse events (TEAEs) and adverse events of interests, and clinical endpoints. Subgroup analyses based on drug types, dosing, and race were conducted. Statistical analysis was performed using STATA 15.1 and RevMan 5.0.

RESULTS

Thirty-two RCTs were included in the systematic review, and 25 of them (57,090 individuals) were included in the meta-analysis. PCSK9 monoclonal antibodies significantly improved LDL-C and other lipid profiles (P < 0.05), and no racial differences were found. A recommended dose of 140 mg of evolocumab every 2 weeks was likely to produce a relatively stronger effect than 150 mg of alirocumab every 2 weeks in terms of the absolute change (weighted mean differences (WMD) - 0.36; 95% confidence interval (CI) - 0.71 to - 0.01; P = 0.041) and percent change (WMD - 19.53; 95% CI - 32.02 to - 7.04; P = 0.002) in LDL-C levels. Overall, PCSK9 monoclonal antibodies were safe, except for the significantly increased risk of injection site reactions (relative risks (RR) 1.54; 95% CI 1.38-1.71; P < 0.001). Both alirocumab (RR 0.89; 95% CI 0.83-0.95; P < 0.001) and evolocumab (RR 0.86; 95% CI 0.80-0.92; P < 0.001) were associated with a lower risk of major cardiovascular events (MACEs), especially in secondary preventive patients (alirocumab group: RR 0.88; 95% CI 0.82-0.95; P < 0.001; evolocumab group: RR 0.86; 95% CI 0.80-0.92; P < 0.001). The reduction in MACEs was observed in White but not in Asian subjects. No significant reduction of all-cause mortality was found (RR 0.88; 95% CI 0.72-1.07; P = 0.182).

CONCLUSION

Both alirocumab and evolocumab are well tolerated and can greatly improve lipid profiles for patients at high cardiovascular risk. Both PCSK9 monoclonal antibodies significantly reduce the risk of nonfatal MACEs in patients with previous cardiovascular events, but the effect on all-cause mortality remains uncertain.

Current Role of Lipoprotein Apheresis

Purpose of Review

Lipoprotein apheresis is a very efficient but time-consuming and expensive method of lowering levels of low-density lipoprotein cholesterol, lipoprotein(a)) and other apoB containing lipoproteins, including triglyceride-rich lipoproteins. First introduced almost 45 years ago, it has long been a therapy of “last resort” for dyslipidaemias that cannot otherwise be managed. In recent years new, very potent lipid-lowering drugs have been developed and the purpose of this review is to define the role of lipoprotein apheresis in the current setting.

Recent Findings

Lipoprotein apheresis still plays an important role in managing patients with homozygous FH and some patients with other forms of hypercholesterolaemia and cardiovascular disease. In particular, patients not achieving treatment goals despite modern lipid-lowering drugs, either because these are not tolerated or the response is insufficient. Recently, lipoprotein(a) has emerged as an important cardiovascular risk factor and lipoprotein apheresis has been used to decrease lipoprotein(a) concentrations in patients with marked elevations and cardiovascular disease. However, there is considerable heterogeneity concerning the recommendations by scientific bodies as to which patient groups should be treated with lipoprotein apheresis.

Summary

Lipoprotein apheresis remains an important tool for the management of patients with severe drug-resistant dyslipidaemias, especially those with homozygous FH.