Does Lipoprotein(a) Inhibit Elastolysis in Abdominal Aortic Aneurysms?

Lipoprotein (a) Levels and Abdominal Aortic Aneurysm. A Systematic Review and Meta-analysis

BACKGROUND

Several studies have linked high Lipoprotein (a) (Lp(a)) concentrations to cardiovascular events, including the formation of Abdominal Aortic Aneurysms (AAA). We review and meta-analyze existing evidence on the association of Lp(a) levels with AAA.

METHODS

Studies evaluating the link of Lp(a) with AAA, up to December 27th 2021, were identified by a systematic search of PubMed, SCOPUS, and Web of Science databases. The results were qualitatively and quantitatively synthesized according to PRISMA guidelines. Results are presented as standardized mean differences (SMD) with 95% confidence intervals (CI).

RESULTS

A total of 5,078 subjects (1,637 patients with AAA vs. 3,441 controls) from 11 studies were included in the meta-analysis, with a mean age of 69.9 years and a male sex prevalence of 85.8%. Based on the qualitative synthesis, high Lp(a) concentrations are linked to abdominal aortic wall degradation and extracellular matrix disarrangement. Moreover, despite the considerable variability among races, high Lp(a) levels are related to increased AAA risk, independently of race differences. Accordingly, patients with AAA displayed significantly higher Lp(a) levels compared to controls (SMD: 0.86, 95% CI: 0.55-1.17, p < 0.001). The outcome was not affected in a sensitivity analysis excluding three outlying studies (SMD: 0.40, 95% CI: 0.22-0.58, p < 0.001).

CONCLUSION

This meta-analysis indicates the association between high Lp(a) levels and the presence of AAA, although existing literature presents high heterogeneity. Further studies are needed to standardize Lp(a) measurements and to conclude whether Lp(a) can be used as a sensitive biomarker of early presymptomatic AAA diagnosis.

Lipoprotein (a) as a treatment target for cardiovascular disease prevention and related therapeutic strategies: a critical overview

Advances in several fields of cardiovascular (CV) medicine have produced new treatments (e.g. to treat dyslipidaemia) that have proven efficacy in terms of reducing deaths and providing a better quality of life. However, the burden of CV disease (CVD) remains high. Thus, there is a need to search for new treatment targets. Lipoprotein (a) [Lp(a)] has emerged as a potential novel target since there is evidence that it contributes to CVD events. In this narrative review, we present the current evidence of the potential causal relationship between Lp(a) and CVD and discuss the likely magnitude of Lp(a) lowering required to produce a clinical benefit. We also consider current and investigational treatments targeting Lp(a), along with the potential cost of these interventions.

Lipoprotein(a) Levels in Patients With Abdominal Aortic Aneurysm

Circulating markers relevant to the development of abdominal aortic aneurysm (AAA) are currently required. Lipoprotein(a), Lp(a), is considered a candidate marker associated with the presence of AAA. The present meta-analysis aimed to evaluate the association between circulating Lp(a) levels and the presence of AAA. The PubMed-based search was conducted up to April 30, 2015, to identify the studies focusing on Lp(a) levels in patients with AAA and controls. Quantitative data synthesis was performed using a random effects model, with standardized mean difference (SMD) and 95% confidence interval (CI) as summary statistics. Overall, 9 studies were identified. After a combined analysis, patients with AAA were found to have a significantly higher level of Lp(a) compared to the controls (SMD: 0.87, 95% CI: 0.41-1.33, P < .001). This result remained robust in the sensitivity analysis, and its significance was not influenced after omitting each of the included studies from the meta-analysis. The present meta-analysis confirmed a higher level of circulating Lp(a) in patients with AAA compared to controls. High Lp(a) levels can be associated with the presence of AAA, and Lp(a) may be a marker in screening for AAA. Further studies are needed to establish the clinical utility of measuring Lp(a) in the prevention and management of AAA.

Lp(a)/apo(a) modulate MMP-9 activation and neutrophil cytokines in vivo in inflammation to regulate leukocyte recruitment

Lipoprotein(a) [Lp(a)] is an independent risk factor for cardiovascular diseases, but the mechanism is unclear. The pathogenic risk of Lp(a) is associated with elevated plasma concentration, small isoforms of apolipoprotein [apo(a)], the unique apolipoprotein of Lp(a), and a mimic of plasminogen. Inflammation is associated with both the initiation and recovery of cardiovascular diseases, and plasminogen plays an important role in leukocyte recruitment. Because Lp(a)/apo(a) is expressed only in primates, transgenic mice were generated, apo(a)tg and Lp(a)tg mice, to determine whether Lp(a)/apo(a) modifies plasminogen-dependent leukocyte recruitment or whether apo(a) has an independent role in vivo. Plasminogen activation was markedly reduced in apo(a)tg and Lp(a)tg mice in both peritonitis and vascular injury inflammatory models, and was sufficient to reduce matrix metalloproteinase-9 activation and macrophage recruitment. Furthermore, neutrophil recruitment and the neutrophil cytokines, CXCL1/CXCL2, were suppressed in apo(a)tg mice in the abdominal aortic aneurysm model. Reconstitution of CXCL1 or CXCL2 restored neutrophil recruitment in apo(a)tg mice. Apo(a) in the plasminogen-deficient background and Lp(a)tg mice were resistant to inhibition of macrophage recruitment that was associated with an increased accumulation of apo(a) in the intimal layer of the vessel wall. These data indicate that, in inflammation, Lp(a)/apo(a) suppresses neutrophil recruitment by plasminogen-independent cytokine inhibition, and Lp(a)/apo(a) inhibits plasminogen activation and regulates matrix metalloproteinase-9 activation and macrophage recruitment.

Relationship of heavy drinking, lipoprotein (a) and lipid profile to infrarenal aortic diameter

Abstract

The objective of this study was to examine the association of alcohol drinking and lipid profile with infrarenal aortic dimension. The diameter of the infrarenal aorta was measured using ultrasound in 395 individuals (mean 66.6 ± 10.3 years) with atherosclerotic diseases or risk factors. The associations between heavy drinking, serum lipoprotein (a) levels, lipid profile and infrarenal aorta diameters were examined. Heavy drinking and lipoprotein (a) were positively related with infrarenal aortic dimension, while low-density lipoprotein cholesterol (LDL-C)/high-density lipoprotein cholesterol (HDL-C), LDL-C and total cholesterol (TC)/HDL-C were negatively associated with infrarenal aortic diameter ( p < 0.05). In addition, there were negative associations of LDL-C/HDL-C, TC/HDL-C and positive associations of HDL-C and apolipoprotein AI (Apo AI) with heavy drinking ( p < 0.05). In conclusion, there was a positive association between infrarenal aortic diameters and heavy drinking, as well as lipoprotein (a) levels. Furthermore, the novel and unexpected inverse association between LDL-C/HDL-C, LDL-C, TC/HDL-C and abdominal aortic diameter may suggest a possible role for anti-atherogenic lipid profile (characterized by a higher level of HDL-C and lower level of LDL-C) in aortic dilatation processes, which need to be clarified by further studies.

Molecular Diagnoses and Treatments—Past, Present, or Future?

Use of molecular tools to diagnose and treat aortic disease, in particular, aortic aneurysms and aortic dissections, is still in its infancy, with great advancements expected in the future. Currently under investigation are the genetic markers linked to aortic disease that may help to identify patients at risk for their development prior to clinical presentation. In addition, specific gene defects may be identified that can assist in the understanding of the basic mechanisms contributing to development of aortic disease. Biomarkers are under investigation that can be used to monitor the development, progression, and possible response to therapy for aortic aneurysms and acute aortic syndromes. Equally important, further investigations into the molecular mechanisms involved in aortic pathology will result in increased understanding of the disease etiology and will lead to development of alternate therapies for these diseases prior to their catastrophic development. With advances in molecular technology, the molecular diagnosis and treatment of aortic diseases will begin to expand at a rapid rate and provide unique, improved therapies.

Relatively High Pulmonary and Cardiovascular Mortality Rates in Screening-detected Aneurysmal Patients Without Previous Hospital Admissions

BACKGROUND

Men with abdominal aortic aneurysm (AAA) who are not hospitalised for pulmonary and cardiovascular diseases may have higher mortality due to such disorders.

MATERIAL AND METHODS

Previous discharge diagnoses and causes of death were collected for 4,816 men aged 64-73 years attending mass screening for AAA. Of these, 191 (4%) had an AAA. Overall, cardiovascular- and pulmonary-disease-specific mortality was compared for men with and without AAA stratified for earlier pulmonary or cardiovascular hospitalisations by Cox's proportional hazards regression while adjusting for age. Absolute risk differences after five years were calculated by life table analysis.

RESULTS

The median observation time was 63 months. 362 men died from cardiovascular causes other than AAA, and 144 died from pulmonary causes. The cardiovascular mortality was significantly higher in aneurysm patients without previous related hospitalisation (HR=4.35, 95% CI: 2.73-6.94, P<0.001) with an absolute mortality difference after 5 years of 16.3% (95% CI: 10.2-22.5%). Pulmonary-cause mortality was higher among men with AAA both with and without previous hospitalisation for pulmonary causes (HR=3.05; 95% CI: 1.19-7.83, P=0.020, and HR=3.29; 95% CI: 1.78-6.08, P<0.001, respectively).

CONCLUSIONS

Men with AAA who had not been hospitalised for cardiovascular diseases have more than four times higher cardiovascular mortality. Studies of cohorts being offered relevant prophylaxis may clarify the potential benefits of general preventive actions.