Genetic associations with valvular calcification and aortic stenosis

Evaluation of Links Between High-Density Lipoprotein Genetics, Functionality, and Aortic Valve Stenosis Risk in Humans

Objective—

Studies have shown that high-density lipoprotein (HDL)–raising compounds induce regression of aortic valve stenosis (AVS) in animal models. However, whether patients with AVS have an impaired HDL metabolism is unknown.

Approach and Results—

A total of 1435 single nucleotide polymorphisms in genes associated with HDL cholesterol levels (in or around GALNT2, LPL, ABCA1, APOA5, SCARB1, LIPC, CETP, LCAT, LIPG, APOC4 , and PLTP ) were genotyped in 382 patients with echocardiography-confirmed AVS (aortic jet velocity ≥2.5 m/s) and 401 controls. After control for multiple testing, none of the genetic variants showed a positive association with case/control status (adjusted P ≥0.05 for all single nucleotide polymorphisms tested). In a subsample of this cohort, HDL cholesterol levels, apolipoprotein AI levels, lecithin-cholesterol acyltransferase activity, pre–β-HDL, HDL size, and 4 parameters of cholesterol efflux capacity were measured in apolipoprotein B–depleted serum samples from 86 patients with and 86 patients without AVS. Cholesterol efflux capacity was measured using J774 macrophages with and without stimulation of ATP-binding cassette A-1 expression by cAMP, and HepG2 hepatocytes for scavenger receptor class B type 1–mediated efflux. None of these parameters were different between cases and controls. However, compared with patients without coronary artery disease, sera from patients with coronary artery disease had lower HDL cholesterol levels, scavenger receptor class B type 1–mediated efflux, and HDL size ( P ≤0.003), independently of the presence or absence of AVS.

Conclusions—

Results of the present study suggest that, based on HDL genetics and HDL functionality, HDL metabolism does not seem to predict the risk of AVS. Because of our limited sample size, additional studies are needed to confirm these findings.

The association between circulating lipoprotein(a) and type 2 diabetes: is it causal?

Epidemiological evidence supports a direct and causal association between lipoprotein(a) [Lp(a)] levels and coronary risk, but the nature of the association between Lp(a) levels and risk of type 2 diabetes (T2D) is unclear. In this study, we assessed the association of Lp(a) levels with risk of incident T2D and tested whether Lp(a) levels are causally linked to T2D. We analyzed data on 18,490 participants from the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort that included adults aged 40-79 years at baseline 1993-1997. During an average 10 years of follow-up, 593 participants developed incident T2D. Cox regression models were used to estimate the association between Lp(a) levels and T2D. In Mendelian randomization analyses, based on EPIC-Norfolk combined with DIAbetes Genetics Replication And Meta-analysis data involving a total of 10,088 diabetes case participants and 68,346 control participants, we used a genetic variant (rs10455872) as an instrument to test whether the association between Lp(a) levels and T2D is causal. In adjusted analyses, there was an inverse association between Lp(a) levels and T2D: hazard ratio was 0.63 (95% CI 0.49-0.81; P trend = 0.003) comparing the top versus bottom quintile of Lp(a). In EPIC-Norfolk, a 1-SD increase in logLp(a) was associated with a lower risk of T2D (odds ratio [OR] 0.88 [95% CI: 0.80-0.95]). However, in Mendelian randomization analyses, a 1-SD increase in logLp(a) due to rs10455872, which explained 26.8% of the variability in Lp(a) levels, was not associated with risk of T2D (OR 1.03 [0.96-1.10]; P = 0.41). These prospective findings demonstrate a strong inverse association of Lp(a) levels with risk of T2D. However, a genetic variant that elevated Lp(a) levels was not associated with risk of T2D, suggesting that elevated Lp(a) levels are not causally associated with a lower risk of T2D.

Lipoprotein(a) for risk assessment in patients with established coronary artery disease

OBJECTIVES

The purpose of this study was to assess the prognostic utility of lipoprotein(a) [Lp(a)] in individuals with coronary artery disease (CAD).

BACKGROUND

Data regarding an association between Lp(a) and cardiovascular (CV) risk in secondary prevention populations are sparse.

METHODS

Plasma Lp(a) was measured in 6,708 subjects with CAD from 3 studies; data were then combined with 8 previously published studies for a total of 18,978 subjects.

RESULTS

Across the 3 studies, increasing levels of Lp(a) were not associated with the risk of CV events when modeled as a continuous variable (odds ratio [OR]: 1.03 per log-transformed SD, 95% confidence interval [CI]: 0.96 to 1.11) or by quintile (Q5:Q1 OR: 1.05, 95% CI: 0.83 to 1.34). When data were combined with previously published studies of Lp(a) in secondary prevention, subjects with Lp(a) levels in the highest quantile were at increased risk of CV events (OR: 1.40, 95% CI: 1.15 to 1.71), but with significant between-study heterogeneity (p = 0.001). When stratified on the basis of low-density lipoprotein (LDL) cholesterol, the association between Lp(a) and CV events was significant in studies in which average LDL cholesterol was ≥130 mg/dl (OR: 1.46, 95% CI: 1.23 to 1.73, p < 0.001), whereas this relationship did not achieve statistical significance for studies with an average LDL cholesterol <130 mg/dl (OR: 1.20, 95% CI: 0.90 to 1.60, p = 0.21).

CONCLUSIONS

Lp(a) is significantly associated with the risk of CV events in patients with established CAD; however, there exists marked heterogeneity across trials. In particular, the prognostic value of Lp(a) in patients with low cholesterol levels remains unclear.

Transcatheter aortic valve implantation: status and challenges

Calcific aortic valve disease of the elderly is the most prevalent hemodynamically-significant valvular disease, and the most common lesion requiring valve replacement in industrialized countries. Transcatheter aortic valve implantation is a less invasive alternative to classical aortic valve replacement that can provide a therapeutic option for high-risk or inoperable patients with aortic stenosis. These devices must be biocompatible, have excellent hemodynamic performance, be easy to insert, be securely anchored without sutures, and be durable, without increased risk of thrombosis or infection. To date, complications are related to the site of entry for insertion, the site of implantation (aorta, coronary ostia, base of left ventricle), and to the structure and design of the inserted device. However, as with any novel technology unanticipated complications will develop. Goals for future development will be to make the devices more effective, more durable, safer, and easier to implant, so as to further improve outcome for patients with severe aortic stenosis. The pathologist participating in research and development, and examination of excised devices will have a critical role in improving outcome for these patients.

Mechanisms of calcification in aortic valve disease: role of mechanokinetics and mechanodynamics

The aortic valve is highly responsive to cyclical and continuous mechanical forces, at the macroscopic and cellular levels. In this report, we delineate mechanokinetics (effects of mechanical inputs on the cells) and mechanodynamics (effects of cells and pathologic processes on the mechanics) of the aortic valve, with a particular focus on how mechanical inputs synergize with the inflammatory cytokine and other biomolecular signaling to contribute to the process of aortic valve calcification.

Familial hypercholesterolaemia is underdiagnosed and undertreated in the general population: guidance for clinicians to prevent coronary heart disease: consensus statement of the European Atherosclerosis Society

AIMS

The first aim was to critically evaluate the extent to which familial hypercholesterolaemia (FH) is underdiagnosed and undertreated. The second aim was to provide guidance for screening and treatment of FH, in order to prevent coronary heart disease (CHD).

METHODS AND RESULTS

Of the theoretical estimated prevalence of 1/500 for heterozygous FH, <1% are diagnosed in most countries. Recently, direct screening in a Northern European general population diagnosed approximately 1/200 with heterozygous FH. All reported studies document failure to achieve recommended LDL cholesterol targets in a large proportion of individuals with FH, and up to 13-fold increased risk of CHD. Based on prevalences between 1/500 and 1/200, between 14 and 34 million individuals worldwide have FH. We recommend that children, adults, and families should be screened for FH if a person or family member presents with FH, a plasma cholesterol level in an adult ≥8 mmol/L(≥310 mg/dL) or a child ≥6 mmol/L(≥230 mg/dL), premature CHD, tendon xanthomas, or sudden premature cardiac death. In FH, low-density lipoprotein cholesterol targets are <3.5 mmol/L(<135 mg/dL) for children, <2.5 mmol/L(<100 mg/dL) for adults, and <1.8 mmol/L(<70 mg/dL) for adults with known CHD or diabetes. In addition to lifestyle and dietary counselling, treatment priorities are (i) in children, statins, ezetimibe, and bile acid binding resins, and (ii) in adults, maximal potent statin dose, ezetimibe, and bile acid binding resins. Lipoprotein apheresis can be offered in homozygotes and in treatment-resistant heterozygotes with CHD.

CONCLUSION

Owing to severe underdiagnosis and undertreatment of FH, there is an urgent worldwide need for diagnostic screening together with early and aggressive treatment of this extremely high-risk condition.

Familial hypercholesterolaemia is underdiagnosed and undertreated in the general population: guidance for clinicians to prevent coronary heart disease: consensus statement of the European Atherosclerosis Society

Aims

The first aim was to critically evaluate the extent to which familial hypercholesterolaemia (FH) is underdiagnosed and undertreated. The second aim was to provide guidance for screening and treatment of FH, in order to prevent coronary heart disease (CHD).

Methods and results

Of the theoretical estimated prevalence of 1/500 for heterozygous FH, <1% are diagnosed in most countries. Recently, direct screening in a Northern European general population diagnosed approximately 1/200 with heterozygous FH. All reported studies document failure to achieve recommended LDL cholesterol targets in a large proportion of individuals with FH, and up to 13-fold increased risk of CHD. Based on prevalences between 1/500 and 1/200, between 14 and 34 million individuals worldwide have FH. We recommend that children, adults, and families should be screened for FH if a person or family member presents with FH, a plasma cholesterol level in an adult ≥8 mmol/L(≥310 mg/dL) or a child ≥6 mmol/L(≥230 mg/dL), premature CHD, tendon xanthomas, or sudden premature cardiac death. In FH, low-density lipoprotein cholesterol targets are <3.5 mmol/L(<135 mg/dL) for children, <2.5 mmol/L(<100 mg/dL) for adults, and <1.8 mmol/L(<70 mg/dL) for adults with known CHD or diabetes. In addition to lifestyle and dietary counselling, treatment priorities are (i) in children, statins, ezetimibe, and bile acid binding resins, and (ii) in adults, maximal potent statin dose, ezetimibe, and bile acid binding resins. Lipoprotein apheresis can be offered in homozygotes and in treatment-resistant heterozygotes with CHD.

Conclusion

Owing to severe underdiagnosis and undertreatment of FH, there is an urgent worldwide need for diagnostic screening together with early and aggressive treatment of this extremely high-risk condition.

Prevalence and prognosis of aortic valve disease in subjects older than 85 years of age

Although degenerative aortic valve disease is common with increasing age, limited data exist regarding prevalence and prognosis of aortic valve disease among the oldest old. Subjects were recruited from the Jerusalem Longitudinal Cohort Study. Echocardiography was performed at home in 498 randomly selected subjects. Subjects were divided into 3 groups; normal subjects, subjects with valve calcium but without stenosis (AVC), and subjects with aortic stenosis (AS). Survival status at 5-year follow-up was assessed via the centralized population registry. AVC was noted in 55% of the study subjects and AS was seen in 8.2%. There were no significant differences between the 3 groups in any of the clinical parameters examined including risk factors for atherosclerotic heart disease. Of the 498 subjects, 107 (21%) had died at the time of 5-year follow-up. Five-year mortality was similar among the normal (17%) and AVC (20%) subjects but was significantly higher among the subjects with AS (46%; p <0.0001). AS was associated with a nearly fourfold increased likelihood of mortality (hazard ratio 3.7, 95% confidence interval 1.4 to 9.3). In conclusion, among subjects ≥85 years of age, the prevalence of AS is higher than previously reported and not associated with traditional vascular risk factors. AS but not AVC alone was independently predictive of 5-year mortality.

Antisense technology: an emerging platform for cardiovascular disease therapeutics

Antisense oligonucleotides and small interfering RNAs, which suppress the translation of specific mRNA target proteins, are emerging as important therapeutic modalities for the treatment of cardiovascular disease. Over the last 25 years, the advances in all aspects of antisense technology, as well as a detailed understanding of the mechanism of action of antisense drugs, have enabled their use as therapeutic agents. These advancements culminated in the FDA approval of the first chronically administered cardiovascular antisense therapeutic, mipomersen, which targets hepatic apolipoprotein B mRNA. This review provides a brief history of antisense technology, highlights the progression of mipomersen from preclinical studies to multiple Phase III registration trials, and gives an update on the status of other cardiovascular antisense therapeutics currently in the clinic.

Efficacy and safety of mipomersen sodium (Kynamro)

INTRODUCTION

Mipomersen is a first-in-class drug indicated as an adjunct to lipid-lowering medications and diet to reduce low-density lipoprotein-cholesterol (LDL-C), apolipoprotein B (apoB), total cholesterol (TC) and non-high density lipoprotein-cholesterol (non-HDL-C) in patients with homozygous familial hypercholesterolemia (HoFH).

AREAS COVERED

This article summarizes the efficacy and safety profile of mipomersen based on literature, public materials available from the Endocrinologic and Metabolic Drugs Advisory Committee meeting (FDA) in review of the New Drug Application (NDA 203568) and the recent product label.

EXPERT OPINION

Patients suffering from HoFH are characterized by elevated levels of LDL-C and are, therefore, at severely increased risk for cardiovascular disease (CVD). Currently available lipid-lowering therapies (LLT), such as statins, have been shown to lower LDL-C levels and CVD risk. However, in patients suffering from HoFH, additional therapy is urgently needed to further decrease LDL-C levels and CVD risk. Mipomersen (Kynamro) has recently been approved by the FDA as a novel LLT modality in patients with HoFH. Mipomersen has been show to result in highly relevant absolute LDL-C reductions in HoFH patients, and given the undisputed causal relationship between LDL-C levels and CVD risk, this additional LDL-C lowering is expected to result in a robust CVD risk reduction.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.