LDL Cholesterol is Associated with Small Abdominal Aortic Aneurysms

Transcriptomic analysis identifies the shared diagnostic biomarkers and immune relationship between Atherosclerosis and abdominal aortic aneurysm based on fatty acid metabolism gene set

Background

Epidemiological research has demonstrated that there is a connection between lipid metabolism disorder and an increased risk of developing arteriosclerosis (AS) and abdominal aortic aneurysm (AAA). However, the precise relationship between lipid metabolism, AS, and AAA is still not fully understood. The objective of this study was to examine the pathways and potential fatty acid metabolism-related genes (FRGs) that are shared between AS and AAA.

Methods

AS- and AAA-associated datasets were retrieved from the Gene Expression Omnibus (GEO) database, and the limma package was utilized to identify differentially expressed FRGs (DFRGs) common to both AS and AAA patients. Functional enrichment analysis was conducted on the (DFRGs), and a protein-protein interaction (PPI) network was established. The selection of signature genes was performed through the utilization of least absolute shrinkage and selection operator (LASSO) regression and random forest (RF). Subsequently, a nomogram was developed using the results of the screening process, and the crucial genes were validated in two separate external datasets (GSE28829 and GSE17901) as well as clinical samples. In the end, single-sample gene set enrichment analysis (ssGSEA) was utilized to assess the immune cell patterns in both AS and AAA. Additionally, the correlation between key crosstalk genes and immune cell was evaluated.

Results

In comparison to control group, both AS and AAA patients exhibited a decrease in fatty acid metabolism score. We found 40 DFRGs overlapping in AS and AAA, with lipid and amino acid metabolism critical in their pathogenesis. PCBD1, ACADL, MGLL, BCKDHB, and IDH3G were identified as signature genes connecting AS and AAA. Their expression levels were confirmed in validation datasets and clinical samples. The analysis of immune infiltration showed that neutrophils, NK CD56dim cells, and Tem cells are important in AS and AAA development. Correlation analysis suggested that these signature genes may be involved in immune cell infiltration.

Conclusion

The fatty acid metabolism pathway appears to be linked to the development of both AS and AAA. Furthermore, PCBD1, ACADL, MGLL, BCKDHB, and IDH3G have the potential to serve as diagnostic markers for patients with AS complicated by AAA.

The effect of exercise training intervention for patients with abdominal aortic aneurysm on cardiovascular and cardiorespiratory variables: an updated meta-analysis of randomized controlled trials

OBJECTIVE

The purpose of this meta-analysis was to evaluate the effect of exercise training intervention in patients with abdominal aortic aneurysm (AAA).

METHODS

Eight randomized controlled trials (RCTs) that recruited 588 AAA patients were extracted using 4 databases (PubMed, Embase, Wanfang Data, and Cochrane Library). Physiological and biochemistry parameters that included in this study are high-sensitivity C-reactive protein (hs-CRP), respiratory peak oxygen uptake rate (VO2peak), triglyceride (TG), total cholesterol (TC), anaerobic threshold (AT), the diameter of AAA, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), and matrix metalloproteinase-9 (MMP-9). Standard mean difference (SMD) was used to assess the between group effect.

RESULTS

This meta-analysis was synthesized with findings from RCTs and found that hs-CRP (SMD, - 0.56 mg/dL; 95% CI: - 0.90 to 0.22; P = 0.001), VO2peak (SMD, 0.4 mL/kg/min; 95% CI, 0.21 to 0.60; P < 0.001), TG (SMD, - 0.39 mg/dL; 95% CI: - 0.02 to 0.77; P = 0.04), and AT (SMD, 0.75 mL/kg/min; 95% CI, 0.54 to 0.96; P < 0.001) were significantly improved in the exercise groups, while the size of AAA (SMD, - 0.15; 95% CI: - 0.36 to 0.06; P = 0.15), TC (SMD, 0.16 mg/dL; 95% CI: - 0.10 to 0.42; P = 0.23), HDL/LDL ratio (SMD, - 0.06; 95% CI: - 0.32 to 0.20; P = 0.64), HDL (SMD, - 0.09; 95% CI: - 0.39 to 0.20; P = 0.54), LDL (SMD, 0.08; 95% CI: - 0.21 to 0.38; P = 0.59), and MMP-9 (SMD, - 0.23 mg/dL; 95% CI: - 0.53 to 0.06; P = 0.12) did not differ in the exercise groups compared with the controls.

CONCLUSION

Exercise intervention improved some of the CVD risk factors but not all, hs-CRP, VO2peak and AT were significantly improved after exercise intervention, while, changes of MMP-9, the size of AAA, and the overall lipids profile were not. Exercise intervention provides an additional solution for improving cardiorespiratory capacity and health status among AAA patients, and might lead to a delay of AAA progression.

Bioinformatics-based identification of lipid- and immune-related biomarkers in abdominal aortic aneurysms

Background

Abdominal aortic aneurysm (AAA) manifest as a natural inflammatory process with permanent dilation and terminal rupture. Nevertheless, the pathogenesis of AAA remains a mystery, and treatment is still controversial. Lipid metabolism and immune system are involved in AAA progression, which has been well documented. However, lipid- and immune-related (LIR) biomarkers need to be further elucidated.

Methods

The AAA-related datasets were retrieved from the GEO database, and the datasets were analyzed for differential gene expression by NetworkAnalyst. GO and KEGG pathway enrichment analysis of differentially expressed mRNA (DE-mRNA) was performed using Metscape, and LIR DE-mRNA was further screened. AAA rat model was constructed using porcine pancreatic elastase to verify the differential expression of LIR DE-mRNA.

Results

The GSE47472 and GSE57691 datasets respectively identified 614 (containing 381 down-regulated and 233 up-regulated DE-mRNAs) and 384 (containing 218 down-regulated and 164 up-regulated DE-mRNAs) DE-mRNAs. Intersection and union of DE-mRNAs were 13 and 983, respectively. The main terms involved in the union of DE-mRNAs included "immune system process", "metabolic process", "Chemokine signaling pathway", "hematopoietic cell lineage" and "Cholesterol metabolism". In vivo experiments revealed that LIR DE-mRNAs of PDIA3, TYROBP, and HSPA1A were significantly low expression in AAA abdominal aortic tissues, and HCK and SERPINE1 were significantly high expression, which is consistent with the bioinformatics analysis.

Conclusions

PDIA3, TYROBP, HSPA1A, HCK and SERPINE1 may serve as LIR biomarkers of AAA, which provides new insights and theoretical guidance for the future treatment, early prevention and progression of AAA.

Advanced Research of Abdominal Aortic Aneurysms on Metabolism

Abdominal aortic aneurysm (AAA) is a cardiovascular disease with a high risk of death, seriously threatening the life and health of people. The specific pathogenesis of AAA is still not fully understood. In recent years, researchers have found that amino acid, lipid, and carbohydrate metabolism disorders play important roles in the occurrence and development of AAA. This review is aimed to summarize the latest research progress of the relationship between AAA progression and body metabolism. The body metabolism is closely related to the occurrence and development of AAA. It is necessary to further investigate the pathogenesis of AAA from the perspective of metabolism to provide theoretical basis for AAA diagnosis and drug development.

Hyperlipidemia does not affect development of elastase-induced abdominal aortic aneurysm in mice

BACKGROUND AND AIMS

Hyperlipidemia is a suggested risk factor for abdominal aortic aneurysm (AAA). However, whether hyperlipidemia is causally involved in AAA progression remains elusive. Here, we tested the hypothesis that hyperlipidemia aggravates AAA formation in the widely used porcine pancreatic elastase (PPE) model of AAA in mice with varying levels of plasma lipids.

METHODS

Prior to PPE-surgery, 8-week-old male C57BL/6J mice (n = 32) received 1·10¹¹ viral genomes of rAAV8-D377Y-mPcsk9 or control rAAV8 via the tail vein. Mice were fed either western type diet or regular chow. At baseline and during the 28 days following PPE-surgery, mice underwent weekly ultrasonic assessment of AAA progression. Experiments were repeated using Apolipoprotein E knockout (ApoE^-/-) mice (n = 7) and wildtype C57BL/6J mice (n = 5).

RESULTS

At sacrifice, maximal intergroup plasma cholesterol and non-HDL/HDL ratio differences were >5-fold and >20-fold, respectively. AAA diameters expanded to 150% of baseline, but no intergroup differences were detected. This was verified in an independent experiment comparing 8-week-old male ApoE^-/- mice with wildtype mice. Histological evaluation of experimental AAA lesions revealed accumulated lipid in neointimal and medial layers, and analysis of human AAA lesions (n = 5) obtained from open repair showed medial lipid deposition.

CONCLUSIONS

In summary, we find that lipid deposition in the aortic wall is a feature of PPE-induced AAA in mice as well as human AAA lesions. Despite, our data do not support the hypothesis that hyperlipidemia contributes to AAA progression.

Systems Approach to Study Associations between OxLDL and Abdominal Aortic Aneurysms

Although abdominal aortic aneurysm (AAA) is a common vascular disease and is associated with high mortality, the full pathogenesis of AAA remains unknown to researchers. Abdominal aortic aneurysms and atherosclerosis are strongly related. Currently, it is more often suggested that development of AAA is not a result of atherosclerosis, however, individual factors can act independently or synergistically with atherosclerosis. One of such factors is low-density lipoprotein (LDL) and its oxidized form (oxLDL). It is known that oxLDL plays an important role in the pathogenesis of atherosclerosis, thus, we decided to examine oxLDL impact on the development of AAA by creating two models using Petri-nets. The first, full model, contains subprocess of LDL oxidation and all subprocesses in which it participates, while the second, reduced model, does not contain them. The analysis of such models can be based on t-invariants. They correspond to subprocesses which do not change the state of the modeled system. Moreover, the knockout analysis has been used to estimate how crucial a selected transition (representing elementary subprocess) is, based on the number of excluded subprocesses as a result of its knockout. The results of the analysis of our models show that oxLDL affects 55.84% of subprocesses related to AAA development, but the analysis of the nets based on knockouts and simulation has shown that the influence of oxLDL on enlargement and rupture of AAA is negligible.

Dyslipidaemia in the elderly: to treat or not to treat?

INTRODUCTION

The elderly population (i.e. aged ≥ 65 years) is increasing worldwide. Ageing is associated with a higher incidence and prevalence of cardiovascular disease (CVD). Areas covered: The prevalence of CVD risk factors including type 2 diabetes mellitus, hypertension and dyslipidaemia also increases with advancing age, contributing to the higher absolute CVD risk observed in the elderly. The present narrative review comments on the associations of dyslipidaemia with CVD as well as the effects of lifestyle measures and lipid-lowering drugs on lipids and CVD risk with a special focus on the elderly population. Individual treatment goals and therapeutic options according to current guidelines are also reviewed. Finally, we discuss special characteristics of the elderly that may influence the efficacy and safety of drug therapy and should be considered before selection of hypolipidaemic pharmacotherapy. Expert commentary: There may be a greater CVD benefit in older patients following drug therapy compared with younger ones. Treatment goals and therapeutic options should be individualized according to current guidelines. Specific characteristics that may influence the efficacy and safety of drug therapy in the elderly should be considered in relation to dyslipidaemia treatment.

The Association of Serum Thrombomodulin with Endothelial Injuring Factors in Abdominal Aortic Aneurysm

Background. The aim of the present study was to evaluate the concentration of serum thrombomodulin (sTM) in the AAA patients and to examine its correlation with various factors which may potentially participate in the endothelial injury. Materials and Methods. Forty-one patients with AAA were involved and divided into subgroups based on different criteria. Concentration of sTM was measured using enzyme-linked-immunosorbent assay (ELISA). The results were compared with those obtained in 30 healthy age- and sex-matched volunteers. Results. The higher concentration of sTM was observed in AAA patients compared with those in controls volunteers [2.37 (1.97–2.82) ng/mL versus 3.93 (2.43–9.20) ng/mL, P < 0.001]. An elevated sTM associated significantly with increased triglycerides (TAG) [P = 0.022], cholesterol [P = 0.029], hsCRP [P = 0.031], and advanced glycation end products (AGEs) [P = 0.033]. Conclusions. The elevation of serum sTM level suggests that endothelial damage occurs in AAA pathogenesis. The correlations observed indicate that lipids abnormalities, inflammation, and oxidative stress may be involved in this destructive process.

The putative role of autophagy in the pathogenesis of abdominal aortic aneurysms

Abdominal aortic aneurysms (AAA) are a significant cause of worldwide mortality and morbidity. While the histopathological characteristics of AAA are well documented, the cellular and molecular mechanisms involved in the pathogenesis of AAA are not entirely understood. Autophagy is a highly conserved basal cellular process in eukaryotic cells that involves the turnover of organelles and proteins. It is also activated as an adaptive response to stressful conditions to promote cell survival. While autophagy typically promotes pro-survival processes, it can sometimes lead to cellular demise. Preclinical studies have revealed autophagy to be a protective mechanism in certain vascular diseases with several autophagy-related genes reported to be markedly upregulated in human aneurysmal tissue. The role autophagy plays in the pathogenesis of AAA, however, remains poorly defined. In this review, we discuss the putative role of autophagy in AAA by reviewing several in vitro and in vivo studies that address the functional significance of autophagy in cells that are involved in the pathophysiology of AAA, amongst which are macrophages, smooth muscle and endothelial cells.

Evidence of deregulated cholesterol efflux in abdominal aortic aneurysm

Previous studies indicated that lipids may be associated with abdominal aortic aneurysm (AAA); however the molecular mechanism involved is unclear. Our study aimed to investigate the expression pattern of cholesterol efflux related proteins in AAA. Liver X receptors (LXRα and LXRβ), ATP-binding-cassette transporter A1 (ABCA1), Apolipoprotein AI (ApoAI), smooth muscle α-actin (α-SM) and vimentin expression levels were evaluated in human AAA, atherosclerotic (ATH) and normal abdominal aortic tissues. We found significant differences in LXRα, LXRβ and ABCA1 mRNA expression levels between AAA, ATH and normal whole aortic tissues and also within the AAA, ATH and normal "intima-media" layers. Specifically, LXRα, LXRβ and ABCA1 mRNA levels were decreased in AAA compared to ATH-whole tissues, as well as in AAA "intima-media" compared to ATH and normal "intima-media" layers. Moreover, immunohistochemical evaluation revealed that LXRα and ABCA1 immunoreactivities (IR) were reduced in the AAA media compared to the normal and ATH media layers and that they were also reduced in the intima layer of AAA and ATH tissues, whereas ApoAI-IR was increased in the AAA and ATH aortic walls compared to normal pointing to possible deregulation of the cholesterol efflux mechanism in AAA. Furthermore, double staining for vimentin and α-SM showed vimentin expression in the intima and inner media layer of AAA with sparse vimentin positive SMCs designating possible SMCs phenotype switch from contractile to synthetic form. In addition, histochemical analysis showed excessive lipid accumulation in the AAA wall, while co-staining using Oil Red O with α-SM or CD68 revealed lipid accumulation in SMCs and macrophages, respectively. Our study provides novel evidence for impaired cholesterol efflux in AAA associated with lipid accumulation in SMCs and macrophages, as well as switch of SMCs phenotype from contractile to synthetic form.

LDL cholesterol and apolipoprotein B are associated with ascending aorta dilatation in bicuspid aortic valve patients

BACKGROUND

The factors related to ascending aorta dilation (AAD) in patients with bicuspid aortic valve (BAV) are not completely understood. In addition, the role of cholesterol metabolism in AAD has not been studied.

METHODS

We analyzed the relationship between different lipid parameters and the ascending aorta diameter/presence of aortic dilatation in 91 consecutive patients with BAV.

RESULTS

We observed a positive linear correlation between the total cholesterol, low-density lipoprotein (LDL) cholesterol and apolipoprotein B (ApoB) levels and the ascending aorta diameter. The patients with AAD had higher LDL cholesterol and ApoB levels. Whereas LDL cholesterol and ApoB were identified as independent factors predictors of the aortic root diameter, only ApoB predicted the diameter of the ascending aorta. On the other hand, the levels of ApoB were an independent factor related to the dilatation of the aortic root.

CONCLUSIONS

We have observed that cholesterol is associated with ascending aorta diameter and dilation in BAV patients. Further experimental and clinical studies are needed to explain the pathobiology of this association.

The prevalence of abdominal aortic aneurysm is consistently high among patients with coronary artery disease

OBJECTIVE

Emerging evidence suggests high prevalence of abdominal aortic aneurysm (AAA) among patients with coronary disease. Accurate characterization of the association between coronary disease and AAA and of the actual prevalence of AAA among patients with angiography-verified coronary artery disease (CAD) is needed to evaluate the possible benefits of systematic screening for AAA.

METHODS

We searched for studies that reported the association between AAA and CAD or coronary heart disease (CHD; wider phenotype definition) in the general population (randomized controlled trials, prospective population cohorts) and those that reported the prevalence of AAA among patients with angiography-verified CAD through PubMed, Embase, and reference lists for the period between 1980 and 2014. Random-effects models were applied because of the high heterogeneity between included studies.

RESULTS

Among the general population, 23 studies reported the association between CHD and the occurrence of subclinical AAA (positive ultrasound screening; meta-analyzed odds ratio of 2.38 with 95% confidence interval [CI] of 1.78-3.19; P = 4.1 × 10(-9)). According to four prospective studies, CHD is a strong predictor of future AAA events (fatal and nonfatal; meta-analyzed hazard ratio of 3.49 with 95% CI of 2.56-4.76; P = 2.4 × 10(-15)). Altogether, 10 studies reported the prevalence of AAA among patients with angiography-verified CAD or undergoing coronary artery bypass grafting. Among men, meta-analyzed prevalence was 9.5% (95% CI, 7.6%-11.7%). Among men undergoing coronary artery bypass grafting or with three-vessel disease, the prevalence was 11.4% (95% CI, 9.1%-13.9%). Among women, the prevalence was low (0.35%).

CONCLUSIONS

The risk of subclinical AAA and future AAA events is high among patients with coronary disease. Screening for AAA among CAD patients by cardiologists would be easy and inexpensive, with possible benefits to survival and risk evaluation.

Associations of ApoAI and ApoB-containing lipoproteins with AngII-induced abdominal aortic aneurysms in mice

OBJECTIVE

Dyslipidemia is implicated in abdominal aortic aneurysms (AAAs) in humans and angiotensin (Ang) II-infused mice. This study determined effects of major lipoprotein classes on AngII-induced AAAs using multiple mouse strains with dietary and pharmacological manipulations.

APPROACH AND RESULTS

Western diet had minor effects on plasma cholesterol concentrations and the low incidence of AngII-induced AAAs in C57BL/6J mice. Low incidence of AAAs in this strain was not attributed to protection from high-density lipoprotein, because apolipoprotein (apo) AI deficiency did not increase AngII-induced AAAs. ApoAI deletion also failed to alter AAA occurrence in hypercholesterolemic mice. Low-density lipoprotein receptor-/- mice fed normal diet had low incidence of AngII-induced AAAs. Western diet feeding of this strain provoked pronounced hypercholesterolemia because of increased apoB-containing lipoproteins with attendant increases of atherosclerosis in both sexes, but AAAs only in male mice. ApoE-deficient mice fed normal diet were modestly hypercholesterolemic, whereas this strain fed Western diet was severely hypercholesterolemic because of increased apoB-containing lipoprotein concentrations. The latter augmented atherosclerosis, but did not change the high incidence of AAAs in this strain. To determine whether reductions in apoB-containing lipoproteins influenced AngII-induced AAAs, ezetimibe was administered at a dose that partially reduced plasma cholesterol concentrations to ApoE-deficient mice fed Western diet. This decreased atherosclerosis, but not AAAs. This ezetimibe dose in ApoE-deficient mice fed normal diet significantly decreased plasma apoB-containing lipoprotein concentrations and reduced AngII-induced AAAs.

CONCLUSIONS

ApoB-containing lipoproteins contribute to augmentation of AngII-induced AAA in male mice. However, unlike atherosclerosis, AAA occurrence was not correlated with increases in plasma apoB-containing lipoprotein concentrations.

Systematic review of cardiovascular disease and cardiovascular death in patients with a small abdominal aortic aneurysm

Background

Screening for abdominal aortic aneurysm (AAA) has reduced the rate of AAA rupture. However, cardiovascular disease is still a major cause of death in men with an AAA. The aim of this study was to assess cardiovascular risk in patients with a small AAA.

Methods

Standard PRISMA guidelines were followed. Analysis was performed of studies reporting cardiovascular outcomes in patients with a small AAA (30–54 mm). Weighted metaregression was performed for cardiovascular death in patients with a small AAA, and the prevalence of cardiovascular disease was reviewed.

Results

Twenty-one articles were identified describing patients with an AAA, and the prevalence of, and death from, cardiovascular disease. Ten of these reported cardiovascular death rates in patients with a small AAA. Some 2323 patients with a small AAA were identified; 335 cardiovascular deaths occurred, of which 37 were due to AAA rupture. Metaregression demonstrated that the risk of cardiovascular death was 3·0 (95 per cent c.i. 1·7 to 4·3) per cent per year in patients with a small AAA (R2 = 0·902, P &lt; 0·001). The prevalence of ischaemic heart disease (44·9 per cent), myocardial infarction (26·8 per cent), heart failure (4·4 per cent) and stroke (14·0 per cent) was also high in these patients.

Conclusion

The risk of cardiovascular death in patients with a small AAA is high and increases by approximately 3 per cent each year after diagnosis. Patients with a small AAA have a high prevalence of cardiovascular disease. Patients a small AAA should be considered for lifestyle modifications and secondary cardiovascular protection.

Meta-analysis and meta-regression analysis of biomarkers for abdominal aortic aneurysm

Background

Many studies have investigated the systemic and local expression of biomarkers in patients with abdominal aortic aneurysm (AAA). The natural history of AAA varies between patients, and predictors of the presence and diameter of AAA have not been determined consistently. The aim of this study was to perform a systematic review, meta-analysis and meta-regression of studies comparing biomarkers in patients with and without AAA, with the aim of summarizing the association of identified markers with both AAA presence and size.

Methods and results

Literature review identified 106 studies suitable for inclusion. Meta-analysis demonstrated a significant difference between matrix metalloproteinase (MMP) 9, tissue inhibitor of matrix metalloproteinase 1, interleukin (IL) 6, C-reactive protein (CRP), α1-antitrypsin, triglycerides, lipoprotein(a), apolipoprotein A and high-density lipoprotein in patients with and without AAA. Although meta-analysis was not possible for MMP-2 in aortic tissue, tumour necrosis factor α, osteoprotegerin, osteopontin, interferon γ, intercellular cell adhesion molecule 1 and vascular cell adhesion molecule 1, systematic review suggested an increase in these biomarkers in patients with AAA. Meta-regression analysis identified a significant positive linear correlation between aortic diameter and CRP level.

Conclusion

A wide variety of biomarkers are dysregulated in patients with AAA, but their clinical value is yet to be established. Future research should focus on the most relevant biomarkers of AAA, and how they could be used clinically.

Interaction between widening of diameter of abdominal aorta and cardiovascular risk factors and atherosclerosis burden

The aim of this study was to investigate influence of traditional cardiovascular risk factors (CVRF) and subclinical atherosclerosis (ATS) burden on early stages of abdominal aortic diameter (AAD) widening among adults. 2,052 consecutive patients (P) (39 % women), mean age 52 ± 13 years, were prospectively screened for CVRF, ATS, and AAD. B-mode ultrasound was used to evaluate the largest AAD and to detect carotid and femoral atherosclerotic plaques. Mean AAD was 15.2 ± 2.8 mm. Atherosclerotic plaques were detected in 71 % of patients. Significant univariate correlation between AAD, traditional CVRF, and ABS was found. However, multiple regression analysis showed that only seven of them were significantly and weakly correlated with AAD (R² = 0.27, p < 0.001). On the other hand, a multivariate logistic analysis was used to evaluate CVRF impact on enlarged AAD ≥25 mm (EAAD) as compared to those with AAD <25 mm. These factors did not account for more than 30 % of interaction (R² = 0.30, p = 0.001). Furthermore, despite a large proportion of patients with high number of CVRF, and subclinical ATS, rate of patients with AAD ≥25 mm was low (1 %) and scattered regardless their CHD risk score or ATS burden. In conclusion, these results suggest that although some traditional CVRF and presence of ATS are associated with early stages of EAAD, other determinants still need to be identified for a better understanding of abdominal aortic aneurysm pathogenesis.

Autoantibodies to oxidized low-density lipoprotein in patients with aortic regurgitation: association with aortic diameter size

BACKGROUND

Aortic regurgitation (AR) is a condition associated with volume overload, causing left-ventricular (LV) remodeling, eccentric LV hypertrophy and eventually heart failure. LV remodeling associated with AR is regulated by mechanical stress, neurohormonal activation, inflammation and oxidative stress. Since anti-oxidized low-density lipoprotein (LDL) antibodies (Abs) are a measurable marker of oxidative stress, we hypothesized that an increased level of circulating oxidized LDL (oxLDL) Abs may be related to remodeling of the left ventricle in patients with significant AR.

METHODS

We assessed IgG anti-oxLDL Abs in 31 patients with significant AR and compared them to 30 patients with similar risk factors and no valvular disease. Abs to oxLDL were determined by ELISA.

RESULTS

The 2 groups had similar clinical characteristics. There was no difference between patients with AR and patients with no AR in the level of anti-oxLDL Abs. However, in all patients and controls, anti-oxLDL Abs correlated positively with the diameter of the ascending aorta (AA; r = 0.32, p = 0.016) and the level of oxLDL Abs was significantly higher in patients with an AA diameter ≥39 mm. On multivariate analysis, only white blood cell count and AA diameter were related to anti-oxLDL Abs in all patients.

CONCLUSIONS

We did not find a difference in the level of anti-oxLDL Abs between patients with AR and controls; however, there was a strong correlation between anti-oxLDL Abs and AA diameter.

Comparison of the serum lipidome in patients with abdominal aortic aneurysm and peripheral artery disease

BACKGROUND

Currently, the relationship between circulating lipids and abdominal aortic aneurysm (AAA) is unclear. We conducted a lipidomic analysis to identify serum lipids associated with AAA presence. Secondary analyses assessed the ability of models incorporating lipidomic features to improve stratification of patient groups with and without AAA beyond traditional risk factors.

METHODS AND RESULTS

Serum lipids were profiled via liquid chromatography tandem mass spectrometry analysis of serum from 161 patients with AAA and 168 controls with peripheral artery disease. Binary logistic regression was used to identify AAA-associated lipids. Classification models were created based on a combination of (1) traditional risk factors only or (2) lipidomic features and traditional risk factors. Model performance was assessed using receiver operator characteristic curves. Three diacylglycerols and 7 triacylglycerols were associated with AAA. Combining lipidomic features with traditional risk factors significantly improved stratification of AAA and peripheral artery disease groups when compared with traditional risk factors alone (mean area under the receiver operator characteristic curve [95% confidence interval], 0.760 [0.756-0.763] and 0.719 [0.716-0.723], respectively; P<0.05).

CONCLUSIONS

A group of linoleic acid containing triacylglycerols and diacylglycerols were significantly associated with AAA presence. Inclusion of lipidomic features in multivariate analyses significantly improved prediction of AAA presence when compared with traditional risk factors alone.

A Variant in LDLR Is Associated With Abdominal Aortic Aneurysm

Background—

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease among older people and demonstrates significant heritability. In contrast to similar complex diseases, relatively few genetic associations with AAA have been confirmed. We reanalyzed our genome-wide study and carried through to replication suggestive discovery associations at a lower level of significance.

Methods and Results—

A genome-wide association study was conducted using 1830 cases from the United Kingdom, New Zealand, and Australia with infrarenal aorta diameter ≥30 mm or ruptured AAA and 5435 unscreened controls from the 1958 Birth Cohort and National Blood Service cohort from the Wellcome Trust Case Control Consortium. Eight suggestive associations with P <1×10 −4 were carried through to in silico replication in 1292 AAA cases and 30 503 controls. One single-nucleotide polymorphism associated with P <0.05 after Bonferroni correction in the in silico study underwent further replication (706 AAA cases and 1063 controls from the United Kingdom, 507 AAA cases and 199 controls from Denmark, and 885 AAA cases and 1000 controls from New Zealand). Low-density lipoprotein receptor ( LDLR ) rs6511720 A was significantly associated overall and in 3 of 5 individual replication studies. The full study showed an association that reached genome-wide significance (odds ratio, 0.76; 95% confidence interval, 0.70–0.83; P =2.08×10 −10 ).

Conclusions—

LDLR rs6511720 is associated with AAA. This finding is consistent with established effects of this variant on coronary artery disease. Shared causal pathways with other cardiovascular diseases may present novel opportunities for preventative and therapeutic strategies for AAA.

Impact of Inherited Genetic Variants Associated With Lipid Profile, Hypertension, and Coronary Artery Disease on the Risk of Intracranial and Abdominal Aortic Aneurysms

Background—

Epidemiological studies show that an unfavorable lipid profile and coronary artery disease (CAD) are risk traits for abdominal aortic aneurysms (AAAs) but not for intracranial aneurysms (IAs), and that hypertension is a main risk trait for IAs but not for AAAs. To evaluate these observations, we investigated single-nucleotide polymorphisms associated with serum lipid levels, hypertension, and CAD and tested their contribution to AAA and IA risk.

Methods and Results—

We defined sets of single-nucleotide polymorphisms previously reported to be associated with serum lipid levels, CAD, and blood pressure. From previously collected genome-wide data, we extracted genotypes for these single-nucleotide polymorphism sets in 709 IA cases and 2692 controls and 807 AAA cases and 1905 controls (all of Dutch origin). We computed genetic scores for each individual by summing the observed number of risk alleles weighted by their previously published effect size. Using logistic regression, we tested the genetic scores for association with IAs and AAAs and found significant associations for genetic scores of total cholesterol ( P =3.6×10 -6 ), low-density lipoprotein-cholesterol ( P =5.7×10 -7 ), and CAD ( P =0.0014) with AAAs and for the blood pressure score with IAs ( P =0.0030).

Conclusions—

We demonstrate that genetic risk profiles of lipid factors and CAD are associated with AAAs but not with IAs, and the genetic risk profile of blood pressure is associated with IAs but not with AAAs. These findings are consistent with epidemiological observations.

Lowered postoperative ldl-c/hdl-C ratio reduces later cardiovascular events after abdominal aortic aneurysm surgery

PURPOSE

To examine the relationship between the incidence of later cardiovascular events after abdominal aortic aneurysm (AAA) surgery and postoperative lipid levels.

METHODS

Atherosclerotic risk factors including postoperative serum lipid levels were examined in 116 patients aged 70 or less undergoing an elective AAA surgery. Later cardiovascular events after AAA surgery occurred in 21 patients, including cerebral infarction (n = 4), catheter intervention or surgery for coronary artery disease (CAD) (n = 10) and other vascular disease.

RESULTS

Postoperative cholesterol levels during the average follow-up period of 55.6 ± 44.3 (months) were 49.0 ± 15.7 (mg/dL) for high-density lipoprotein cholesterol (HDL-C), 97.9 ± 31.2 (mg/dL) for low-density lipoprotein cholesterol (LDL-C), which were both significantly improved compared to preoperative values (p <0.001). Cox hazard analysis indicated that preexistent CAD significantly increased in the risk for later cardiovascular events (hazard ratio 5.67; 95%CI 1.92-16.8; p = 0.002) and lowered postoperative LDL-C/HDL-C ratio <1.5 decreased in the risk after AAA surgery (hazard ratio 0.10; 95%CI 0.01-0.83; p = 0.033). Patients with postoperative LDL-C/HDL-C ratio <1.5 (n = 22) had a significantly better cardiovascular event-free rate than those with that ratio ≥1.5 (n = 94) (p = 0.014).

CONCLUSION

Lowered postoperative LDL-C/HDL-C ratio <1.5 can decrease in the risk for later cardiovascular events after AAA surgery. These results may support the rationale for postoperative aggressive lipid-modifying therapy.

Preoperative HDL-C Predicts Later Cardiovascular Events after Abdominal Aortic Aneurysm Surgery

PURPOSE

To determine the predictive value of serum lipid levels on the development of later cardiovascular events after abdominal aortic aneurysm (AAA) surgery.

METHODS

A total of 101 patients under 70 undergoing an elective AAA surgery were divided into the following two groups: 1) those who developed later cardiovascular events after AAA surgery, including cerebral infarction (n = 4), catheter intervention (PCI) or surgery for coronary artery disease (CAD) (n = 9) and other vascular disease. (CVE group; n = 19); 2) those without later events (NoCVE group: n = 82). Preoperative atherosclerotic risk factors including serum lipid levels were subjected to univariate and multivariate analysis.

RESULTS

The CVE group showed a significantly lower high-density lipoprotein cholesterol (HDL-C) level (32.9 ± 6.6 vs 41.6 ± 12.1 mg/dL; p <0.001), higher low-density lipoprotein cholesterol (LDL-C) / HDL-C ratio (4.30 ± 1.01 vs 3.24 ± 1.15; p = 0.001), and higher prevalence of mild CAD (without an indication of PCI) (p = 0.029) preoperatively. Cox hazard analysis indicated that preexistent mild CAD (hazard ratio 4.70) and preoperative HDL-C <35 mg/dL (hazard ratio 3.07) were significant predictors for later cardiovascular events after AAA surgery.

CONCLUSION

Patients at high risk for later cardiovascular events should require a careful follow-up and may also require an aggressive lipid-modifying therapy.

Association between serum lipoproteins and abdominal aortic aneurysm

The importance of dyslipidemia in the etiology of abdominal aortic aneurysm (AAA) is poorly defined, in part because previous association analyses have often not considered the use of current lipid-modifying medications. Medications targeted at altering the concentrations of circulating lipids have an established role in occlusive atherosclerosis but are of unknown value in the primary prevention of AAA. We examined the association between fasting serum levels of triglycerides low- and high-density lipoprotein and the presence of an AAA in a cohort of 3,327 men aged 65 to 83 years. The analyses were adjusted for established risk factors of AAA and the prescription of lipid-modifying agents using multiple logistic regression analysis. Of the 3,327 men, 1,043 (31%) were receiving lipid-modifying therapy at the fasting lipid measurement. The lipid-modifying therapy was statins in most cases (n = 1,023). The serum high-density lipoprotein concentrations were lower in patients with AAAs. The serum high-density lipoprotein concentration was independently associated with a reduced risk of having an AAA in men not receiving current lipid-modifying therapy (odds ratio 0.72, 95% confidence interval 0.56 to 0.93 per 0.4-mM increase) and in the total cohort (odds ratio 0.76, 95% confidence interval 0.63 to 0.91 per 0.4-mM increase, adjusted for lipid-modifying therapy). The concentrations of low-density lipoprotein and triglycerides were not associated with the presence of AAAs. In conclusion, high-density lipoprotein appeared to be the most important lipid in predicting the risk of AAA development, with potential value as a therapeutic target. Current cardiovascular strategies aimed at lowering low-density lipoprotein might not have any effect on the prevention of AAAs.

Plasma concentrations of apolipoproteins A-I, B and M in patients with abdominal aortic aneurysms

OBJECTIVES

Apolipoproteins play important roles in the development of atherosclerosis but their involvement in the pathogenesis of abdominal aortic aneurysm (AAA) is poorly understood. The aim was to investigate whether apoA-I, apoB and apoM are independently associated with AAA.

DESIGN AND METHODS

Plasma apoA-I, apoB and apoM were measured in 343 patients with AAA and in 214 elderly apparently healthy control individuals from the background population.

RESULTS

AAA patients had lower apolipoprotein levels, as compared to healthy individuals: apoA-I, 1.62 vs. 2.08 g/L; apoB, 0.91 vs. 1.04 g/L; apoM, 0.72 vs. 0.91 mumol/L (p<0.0001 for all three). In multivariate analyses, apoA-I and apoB were associated with AAA, odds ratios (95% confidence intervals) being 0.53 (0.43-0.64) and 0.86 (0.75-0.998), respectively.

CONCLUSIONS

ApoA-I, apoB and apoM levels were significantly lower in patients with AAA than in the control individuals, but only apoA-I and apoB were independently associated to AAA.

HDL antielastase activity prevents smooth muscle cell anoikis, a potential new antiatherogenic property

Various studies using proteomic approaches have shown that HDL can carry many proteins other than its constitutive apolipoprotein A-I (apoA-I). Using mass spectrometry and Western blotting, we showed the presence of alpha(1)-antitrypsin (AAT) (SERPINA1, serpin peptidase inhibitor, clade A, an elastase inhibitor) in HDL, isolated either by ultracentrifugation or by selected-affinity immunosorption using an anti-apoA-I column. Furthermore, we report that HDL possesses potent antielastase activity. We further showed that only HDL but not LDL is able to bind AAT. HDL-associated AAT was able to inhibit extracellular matrix degradation, cell detachment, and apoptosis induced by elastase in human vascular smooth muscle cells (VSMCs) and in mammary artery cultured ex vivo. Degradation of fibronectin by elastase used as a marker of pericellular proteolysis was prevented by addition of HDL. Elastase present in aortic abdominal aneurysm (AAA) thrombus samples was also able to induce apoptosis of VSMCs in culture. This phenomenon was prevented by addition of HDL but not of LDL. Finally, we report that the proportion of AAT in HDL isolated from patients with an AAA is decreased relative to that from matched control subjects, suggesting a reduced capacity of HDL to inhibit elastase in these patients. In conclusion, our data provide evidence of a new potential antiatherogenic property of HDL attributable to AAT and its antielastase activity.

Recent advances in molecular mechanisms of abdominal aortic aneurysm formation

Abdominal aortic aneurysm (AAA) is an increasingly common clinical condition with fatal implications. It is associated with advanced age, male gender, cigarette smoking, atherosclerosis, hypertension, and genetic predisposition. Although significant evidence has emerged in the last decade, the molecular mechanisms of AAA formation remain poorly understood. Currently, the treatment for AAA remains primarily surgical with the lone innovation of endovascular therapy. With advances in the human genome, understanding precisely which molecules and genes mediate AAA development and blocking their activity at the molecular level could lead to important new discoveries and therapies. This review summarizes recent updates in molecular mechanisms of AAA formation, including animal models, autoimmune components, infection, key molecules and cytokines, mechanical forces, genetics, and pharmacotherapy. This review will be helpful to those who want to recognize the newest endeavors within the field and identify possible lines of investigation in AAA.

Are Statins an Option in the Management of Abdominal Aortic Aneurysms?

Medline was searched for studies investigating the perioperative and long-term results that derive from statin use in patients with abdominal aortic aneurysm and the clinical and experimental evidence dealing with aneurysm expansion. Data suggest that statins improve the perioperative and long-term outcomes of aneurysm operations and may also reduce expansion rates. International guidelines recommend the use of statins in these patients because abdominal aortic aneurysms are considered as a coronary heart disease equivalent. These guidelines do not appear to have been widely implemented. Preliminary results suggest that statins might play a role in the management of abdominal aortic aneurysms. Verification of these results in large-scale trials may hold implications for a more comprehensive approach of patients with abdominal aortic aneurysms as well as population-wide aneurysm screening programs. Irrespective of the role of statins on aneurysm expansion rates, it is important to ensure that all abdominal aortic aneurysm patients receive statin therapy to improve perioperative and long-term morbidity and mortality.

Growth predictors and prognosis of small abdominal aortic aneurysms

OBJECTIVE

Evidence regarding the influence of cardiovascular risk factors, comorbidities, and patient characteristics on the growth of small abdominal aortic aneurysms (AAA) is limited. We assessed, in an observational cohort study, rupture rates, risks of mortality, and the effects of cardiovascular risk factors and patient demographics on growth rates of small AAAs.

METHODS

Between September 1996 and January 2005, 5057 patients with manifest arterial vascular disease or cardiovascular risk factors were included in the Second Manifestation of ARTerial disease (SMART) study. Measurements of the abdominal aortic diameter were performed in all patients. All patients with an initial AAA diameter between 30 and 55 mm were selected for this study. All AAA measurements during follow-up until August 2007 were collected. Multivariate regression analysis was performed to calculate the effects of demographic patient characteristics, initial AAA diameter, and cardiovascular risk factors on AAA growth.

RESULTS

Included were 230 patients, with a mean age of 66 years and 90% were male. Seven AAA ruptures (six fatal) occurred in 755 patient years of follow-up (rupture rate 0.9% per patient-year). In 147 patients, AAA measurements were performed for a period of more than 6 months. The median follow-up time was 3.3 years (mean 4.0, range 0.5 to 11.1 years, standard deviation (SD) 2.5). Mean AAA diameter was 38.8 mm (SD 6.8) and mean expansion rate 2.5 mm/y. Patients using lipid-lowering drugs had a 1.2 mm/y (95% confidence interval [CI] -2.34 to -0.060 mm/y) lower AAA growth rate compared to nonusers of these drugs. Initial AAA diameter was associated with a 0.09 mm/y (95% CI 0.01 to 0.18 mm/y) higher growth rate per millimetre increase of the diameter. No other factors, including blood lipid values, were independently associated with AAA growth.

CONCLUSIONS

Lipid-lowering drug treatment and initial AAA diameter appear to be independently associated with lower AAA growth rates. The risk of rupture of these small abdominal aortic aneurysms was low, which pleads for watchful waiting.

Inhibition of development of experimental aortic abdominal aneurysm in rat model by atorvastatin through inhibition of macrophage migration

Recently, atherosclerosis has been considered to be the result of inflammation. Interestingly, hydroxymethylglutaryl-coenzyme (HMG-Co) A inhibitors (statins), which are clinically used as lipid-lowering agents, have been reported to have various anti-inflammatory effects. As abdominal aortic aneurysm (AAA) is a common degenerative condition associated with atherosclerosis, this study was designed to investigate the inhibitory effect of a statin, atorvastatin, on aneurysm formation apart from its lipid-lowering effect. We employed an elastase-induced rat AAA model, as statins do not lower cholesterol in rats. Mean aneurysm diameter was significantly smaller in the atorvastatin treatment group as compared to control at 4 weeks after surgery (P<0.05). Interestingly, atorvastatin inhibited the expression of ICAM and MCP-1, followed by the suppression of macrophage recruitment into the aortic wall at 1 week after operation. A significant reduction in MMP-12, but not MMP-2, -3 and -9, expression was also observed by treatment with atorvastatin at 1 week after surgery. In addition, synthesis of collagen and elastin in the vascular wall were significantly increased by atorvastatin. Here, the present study demonstrated a direct effect of atorvastatin to inhibit the progression of aortic aneurysm, independent of its lipid-lowering effect. This study suggests new therapeutic aspects of statins to inhibit the progression of aneurysms.

Traditional and novel risk factors for clinically diagnosed abdominal aortic aneurysm: the Kaiser multiphasic health checkup cohort study

BACKGROUND

Identification of risk factors for and early diagnosis of clinically significant abdominal aortic aneurysm (AAA) before rupture is vital to optimize outcomes in these patients. Our aim was to examine traditional and three novel potential risk factors (abdominal obesity, white blood cell count, and kidney function) for abdominal aortic aneurysm (AAA, comprising discharge diagnosis or surgical repair) in a large multiethnic population.

METHODS

Cohort study (N =104,813) conducted at an integrated health care delivery system in northern California.

RESULTS

After a median of 13 years, 605 AAA events (490 in men and 115 in women; 91 [15%] fatal) were observed. In multivariable analysis, factors significantly associated with risk of clinically detected AAA included male gender, older age, black race (inversely), low educational attainment, cigarette smoking (with dose-response relation), height, treated and untreated hypertension, high total serum cholesterol, elevated white blood cell count, known coronary artery disease, history of intermittent claudication, and reduced kidney function. A significant Asian race by gender interaction was found such that Asian race had a (borderline significant) protective association with AAA in men but not in women.

CONCLUSIONS

Our findings confirm that major atherosclerotic risk factors, except for diabetes and obesity, are also prospectively related to AAA and suggest that elevated white blood cell count and reduced kidney function may improve risk stratification for clinically relevant AAA.

The soluble forms of CD28, CD86 and CTLA-4 constitute possible immunological markers in patients with abdominal aortic aneurysm

OBJECTIVE

The T cell co-stimulatory factors CD28 and CTLA-4 and their ligands CD80 and CD86 occur as receptors on T cells and antigen-presenting cells and also in soluble forms in the circulation. We determined the levels of soluble co-stimulatory molecules in patients with abdominal aortic aneurysm (AAA) and normal individuals. We further correlated these soluble co-stimulatory molecules to other clinical parameters of importance such as age of the patient, presence of hypertension, size of the aneurysm and levels of matrix metalloproteinases-9 and C-reactive protein.

DESIGN, SETTING, SUBJECTS

This case-control study was designed to quantify the circulating levels of soluble co-stimulatory molecules by an in-house enzyme linked immunosorbent assay. A total of 314 subjects participated in the study including 100 patients and 214 normal controls. The statistical analysis was performed by Mann-Whitney test and Spearman's correlation rank test.

RESULTS

Our results show increased plasma levels of sCD28, sCD86 (P = 0.0001) and decreased plasma levels of sCTLA-4 (P = 0.0018) in the patients compared with normal individuals. The levels of these factors were not related to the age of the patient, size of aneurysm or levels of C-reactive protein in plasma. There was, however, a significant inverse relationship between the concentrations of sCTLA-4 and sCD80 with matrix metalloproteinase-9.

CONCLUSIONS

We suggest that soluble co-stimulatory molecules serve as biomarkers for the estimation of immune activation in AAA patients.

Abdominal aortic aneurysm: pathogenesis and implications for management

Abdominal aortic aneurysm (AAA) affects approximately 5% of elderly men and is responsible for a significant number of deaths in Western Countries. At present surgery by open or endovascular means is the only widely used therapy for this condition. In this review we examine the risk factors, serum, and genetic associations of AAA. Epidemiology studies suggest that smoking cessation and control of cholesterol and blood pressure should reduce the number of patients developing AAA. Natural history studies suggest that smoking cessation should reduce the rate of progression of AAA. Clear level 1 evidence for drug treatments of AAA are presently lacking; however, animal and human in vitro studies suggest that medication targeted at reducing inflammation and proteolysis are most likely to be beneficial, with limited data to support the use of statins, Angiotensin II inhibitors, and macrolides. Work has commenced in understanding which patients, identified by clinical, serum, and genotype, are more at risk of AAA progression and thus should be selected out for aggressive treatment. Well designed large multicenter randomized controlled trials are required to examine the medical treatment of AAA.

The care gap: underuse of statin therapy in the elderly

Atherosclerotic diseases are responsible for the majority of deaths in the elderly, and they can also increase the risk of disability. Statins are first-line therapies for lowering lipid levels and have been shown to reduce the risk of cardiovascular events in large-scale clinical trials. There is a growing body of evidence that statins are as efficacious at lowering lipid levels and reducing the risk of coronary heart disease (CHD) in elderly patients as in younger individuals. Furthermore, as this population is at a greater absolute risk of CHD, they may receive greater absolute benefits from treatment. However, despite these benefits, many elderly individuals at risk of CHD and stroke are not receiving adequate lipid-lowering therapy, which could help them to maintain their health and independence. Further, prospective randomised trials are required to guide physicians in the treatment of elderly patients at risk of atherosclerotic disease, thereby resolving the current undertreatment.