Correlations between coronary plaque tissue composition assessed by virtual histology and blood levels of biomarkers for coronary artery disease

Risk Factors for Ankle Brachial Index and Carotid Artery Stenosis in Patients with Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) significantly increases the risk of atherosclerotic cardiovascular disease. Ankle brachial index (ABI) and carotid artery stenosis are non-invasive indicators of generalized atherosclerosis. This study aimed to explore the risk factors for ABI and carotid artery stenosis and discover which factors simultaneously influence both conditions in T2DM. The study included a total of 101 patients with T2DM. ABI was performed via Doppler ultrasound, and both common carotid arteries were examined via ultrasound to obtain the percentage of carotid artery stenosis. A negative correlation was noted between the ABI and the percentage of carotid artery stenosis (p = 0.043). ABI correlated significantly negatively with waist circumference (p = 0.031), total cholesterol (p = 0.003), low-density lipoprotein (LDL) cholesterol (p = 0.003), and C-reactive protein (CRP) (p = 0.017), whereas the percentage of carotid artery stenosis correlated with the smoking habit (p = 0.017) and CRP (p = 0.042). The best model for predicting the ABI value (R2 = 0.195) obtained from stepwise regression analysis included waist circumference, LDL cholesterol, triglycerides, and CRP, while the best model for the percentage of the carotid artery stenosis (R2 = 0.112) included smoking and CRP. CRP influenced the ABI value with a negative parameter estimate of -0.008962 (p = 0.053) and the percentage of the carotid artery stenosis with a positive parameter estimate of 0.443655 (p = 0.006) relative to a one-unit change of it, presenting the negatively significant impact of CRP on the association between carotid artery stenosis and low ABI. Our results suggest that CRP is the most important risk factor that connects ABI and carotid artery stenosis, which are important non-invasive indicators of generalized atherosclerosis in T2DM.

Lipoprotein(a) and Low-Molecular-Weight Apo(a) Phenotype as Determinants of New Cardiovascular Events in Patients with Premature Coronary Heart Disease

BACKGROUND

Lipoprotein(a) (Lp(a)) is a genetic risk factor of atherosclerotic cardiovascular diseases (ASCVDs). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is related to vascular inflammation and detected in atherosclerotic plaques. A temporary increase in the circulating concentration of PCSK9 and Lp(a) was shown in patients with myocardial infarction (MI). The aim of this study was to evaluate the role of the apo(a) phenotype and the Lp(a) concentration as well as its complex with PCSK9 in the development of cardiac events and MI in patients with a premature manifestation of coronary heart disease (CHD).

METHODS

In a prospective study with retrospective data collection, we included 116 patients with premature CHD who were followed for a median of 14 years. The medical history and information on cardiovascular events after an initial exam as well as data on the levels of lipids, Lp(a), PCSK9, PCSK9-Lp(a) complex, and apo(a) phenotype were obtained.

RESULTS

The patients were divided into two groups depending on the presence of a low- (LMW, n = 52) or high-molecular weight (HMW, n = 64) apo(a) phenotype. LMW apo(a) phenotype (odds ratio 2.3 (1.1 to 4.8), p = 0.03), but not elevated Lp(a) (1.9 (0.8-4.6), p = 0.13), was an independent predictor for the development of MI after adjustment for sex, age of CHD debut, initial lipids levels, and lipid-lowering treatment. The apo(a) phenotype also determined the relationship between Lp(a) and PCSK9 concentrations. The level of the PCSK9-Lp(a) complex was higher in LMW apo(a) patients.

CONCLUSION

The LMW apo(a) phenotype is a risk factor for non-fatal MI in a long-term prospective follow-up of patients with premature CHD, and this link could be mediated via PCSK9.

CD36 down regulation by the macrophage antioxidant 7,8-dihydroneopterin through modulation of PPAR-γ activity

CD36 is the key scavenger receptor driving the formation of cholesterol loaded foam cells, the principal cellular component of atherosclerotic plaques. CD36 is down regulated by 7,8-dihydroneopterin, a potent superoxide and hypochlorite scavenging antioxidant generated by interferon-γ stimulated macrophages. 7,8-dihydroneopterin down regulates CD36 mRNA and protein levels so inhibiting macrophage foam cell formation in vitro.We examined the mechanism of 7,8-dihydroneopterin down regulation of CD36 by measuring CD36 and PPAR-γ levels by western blot analysis, in the monocyte-like U937 cells with a range of PPAR-γ stimulants and inhibitors. Lipoxygenase activity was measured by monitoring linoleic acid oxidation at 234 nm for diene formation.Between 100 and 200 μM, 7,8-dihydroneopterin decreased CD36 levels by 50% within 12 hours with levels dropping below 25% by 24 hours. CD36 levels returned to basal levels after 24 hours. Inhibition of protein synthesis by cycloheximide show 7,8-dihydroneopterin had no effect on CD36 degradation rates. PPAR-γ levels were not altered by the addition of 7,8-dihydroneopterin. MAP Kinase, P38 and NF-κB pathways inhibitors SP600125, PD98059, SB202190 and BAY 11-7082 respectively, did not restore the CD36 levels in the presence of 7,8-dihydroneopterin. The addition the lipophilic PPAR-γ activators rosiglitazone and azelaoyl-PAF prevented the CD36 down regulation by 7,8-dihydroneopterin. 7,8-dihydroneopterin inhibited soybean lipoxygenase and reduced U937 cell basal levels of cellular lipid oxides as measured by HPLC-TBARS analysis.The data shows 7,8-dihydroneopterin down regulates CD36 expression by decreasing the level of lipid oxide stimulation of PPAR-γ promotor activity, potentially through lipoxygenase inhibition.

Foam cell formation but not oxLDL cytotoxicity is inhibited by CD36 down regulation by the macrophage antioxidant 7,8-dihydroneopterin

BACKGROUND AND AIMS

Cluster of differentiation 36 (CD36) is a key scavenger receptor in the control of macrophage uptake of oxidised low-density lipoproteins (oxLDL). CD36 expression levels are not down regulated by intracellular cholesterol but are upregulated by oxidised low density lipoprotein (oxLDL) leading to the formation of lipid loaded foam cells, a major constituent of atherosclerotic plaques. We have previous shown that CD36 is down regulated by 7,8-dihydroneopterin, an antioxidant generated by γ-interferon activated macrophages. How CD36 down regulation affects oxLDL induced cytotoxicity, CD36 oxLDL upregulation and foam cell formation is examined using human monocyte like U937 cell line as a model system of human macrophages.

METHODS

Low density lipoprotein (LDL) was prepared by ultracentrifugation from human plasma and oxidised in copper chloride. CD36 levels in U937 cells were measured by western blot analysis. and lipid accumulation was measured by oil red-O staining and 7-ketocholesterol accumulation by high performance liquid chromatography. Cell viability was measured by flow cytometry analysis after propidium iodide staining.

RESULTS

7,8-dihydroneopterin concentrations above 100 μM caused a concentration and time dependent decrease in cellular CD36 levels to 20 % of the untreated cells after 24 h. Upregulation of CD36 by oxLDL was inhibited by 7,8-dihydroneopterin treatment. The CD36 down regulation was associated with decrease in foam cell formation but not a reduction on oxLDL cytotoxicity.

CONCLUSIONS

7,8-dihydroneopterin down regulated CD36 in U937 cells, inhibiting foam cell formation but not oxLDL mediated cell death. 7,8-dihydroneopterin may modulate foam cell formation in atherosclerotic plaques.

Matrix Metalloproteinase 9 as a Predictor of Coronary Atherosclerotic Plaque Instability in Stable Coronary Heart Disease Patients with Elevated Lipoprotein(a) Levels

We sought to investigate whether levels of matrix metalloproteinases (MMPs) and their inhibitors predict coronary atherosclerotic plaque instability, as assessed by intravascular ultrasound (IVUS) virtual histology during coronary angiography. Blood samples were collected before angiography in 32 subjects (mean age 56 ± 8 years) with stable coronary heart disease (CHD) and elevated lipoprotein(a) (Lp(a), 94 ± 35 mg/dL). Levels of high-sensitivity C-reactive protein (hsCRP), apolipoprotein B100 (apoB100), MMP-7, MMP-9, tissue inhibitor of metalloproteinases (TIMP)-1, and TIMP-2 were determined using commercially available enzyme-linked immunosorbent assay kits. Results. The morphology of a total of sixty coronary lesions was assessed by virtual histology IVUS imaging. Eleven (18%) plaques in nine (28%) patients were classified as plaques with an unstable phenotype or a thin-cap fibroatheroma. Age, low-density lipoprotein cholesterol, apoB100, MMP-7, and MMP-9 levels were positively associated with necrotic core volume. Conversely, there was a negative relationship between MMP-7 and -9 levels and fibrous and fibro-fatty tissue volume. Multivariate regression analysis revealed that MMP-9 is a strong independent predictor of atherosclerotic plaque instability in stable CHD patients. In stable CHD patients with elevated Lp(a), MMP-9 levels are positively associated with the size of the necrotic core of coronary atherosclerotic plaques.

Apolipoprotein B correlates with intra-plaque necrotic core volume in stable coronary artery disease

Objective

To determine the relationship between plaque composition and low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), apolipoprotein B (Apo-B), and Apo-A1 using virtual-histology intravascular ultrasound (VH-IVUS).

Methods

We assessed plaque composition in patients with stable coronary artery disease (SCD) admitted to our hospital for percutaneous coronary intervention (PCI) between November 1, 2012, and March 10, 2015. Before PCI, fibrous (FI), fibrofatty (FF), necrotic core (NC), and dense calcium (DC) regions were evaluated using VH-IVUS, and the contributions of each to the culprit lesion volume were recorded. Plasma LDL-C, HDL-C, Apo-B, and Apo-A1 levels were assessed before PCI. The relationship between the regions on VH-IVUS and plasma lipid levels was assessed. Patients were categorized into low Apo-B (LAB) and high Apo-B (HAB) groups, based on the overall cohort median Apo-B level.

Results

We enrolled 115 patients (median Apo-B, 91 mg/dL, male n = 88) with 57 and 58 patients in the LAB (Apo-B ≤ 90 mg/dL) and HAB (Apo-B ≥ 91 mg/dL) groups, respectively. Vessel, plaque, and %NC volumes were significantly greater in the HAB group than in the LAB group. The %FI, %FF, and %DC volumes were similar in both groups. In all 115 patients, the %NC volume correlated with LDL-C (r = 0.2353, P = 0.0114) and Apo-B (r = 0.2487, P = 0.0074) but not with HDL-C and Apo A-1. The high-sensitivity C-reactive protein level tended to be higher in the HAB group than in the LAB group. Multiple regression analysis showed that being male, Apo-A1, and Apo-B were significant predictors of %NC volume extent.

Conclusions

Elevated Apo-B level was related to the %NC in target coronary artery lesions in SCD patients, suggesting a role of Apo-B as a biomarker of unstable plaque in this population.

Interplay between Oxidative Stress and Platelet Activation in Coronary Thrombus of STEMI Patients

BACKGROUND

Platelet activation and oxidative stress seem to play a key role in coronary thrombus formation and are associated with thrombus burden in ST-elevation myocardial infarction (STEMI). However, the interplay between oxidative stress and platelet activation has not been fully elucidated.

MATERIALS AND METHODS

For 32 patients with STEMI undergoing primary percutaneous coronary intervention (PPCI) and 10 patients with stable angina (SA) and oxidative stress, as assessed by NADPH isoform 2 activity (soluble Nox2-derived peptide, sNox2-dp), levels of oxidized low-density lipoproteins (oxLDLs) and platelet activation markers such as soluble CD40 Ligand (sCD40L) and soluble P-selectin (sP-selectin) were measured in the retrieved material (coronary thrombi plus blood waste) of STEMI patients and in intracoronary blood of SA patients, respectively, and in peripheral blood samples of both groups.

RESULTS

In aspirated thrombi and blood waste of STEMI patients we found higher serum levels of sNox2-dp, oxLDLs, sCD40L, and sP-selectin, as compared to the intracoronary blood samples of SA patients. Moreover, in thrombi and blood waste of STEMI patients, a direct correlation between markers of oxidative stress and of platelet activation was found. Also, in STEMI patients a progressive increase of oxidative stress and platelet activation markers was observed according to the thrombus score burden. STEMI patients showed higher peripheral blood Nox2 activity and oxLDL levels as compared to SA patients.

CONCLUSION

This study shows a close relationship between oxidative stress and platelet activation in the intracoronary blood waste and aspirated thrombi of STEMI patients, suggesting a role of oxidative stress in promoting thrombus formation and growth.

Fast retrieval of calcification from sequential intravascular ultrasound gray-scale images

Intravascular ultrasound (IVUS)-based tissue characterization is invaluable for the computer-aided diagnosis and interventional treatment of cardiac vessel diseases. Although the analysis of raw backscattered signals allows more accurate plaque characterization than gray-scale images, its applications are limited due to its nature of electrocardiogram-gated acquisition. Images acquired by IVUS devices that do not allow the acquisition of raw signals cannot be characterized. To address these limitations, we developed a method for fast frame-by-frame retrieval and location of calcification according to the jump features of radial gray-level variation curves from sequential IVUS gray-scale images. The proposed method consists of three main steps: (1) radial gray-level variation curves are extracted from each filtered polar view, (2) sequential images are preliminarily queried according to the maximal slopes of radial gray-level variation curves, and finally, (3) key frames that include calcification are selected through checking the gray-level features of successive pixel columns in the preliminary results. Experimental results with clinically acquired in vivo data sets indicate key frames that include calcification can be retrieved with the advantages of simplicity, high efficiency, and accuracy. Recognition results correlate well with manual characterization results obtained by experienced physicians and through virtual histology.

Circulating Microparticles and Coronary Plaque Components Assessed by Virtual Histology Intravascular Ultrasound of the Target Lesion in Patients with Stable Angina

High levels of microparticles (MPs) circulate in the blood of patients with atherosclerotic diseases where they can serve as potential biomarkers of vascular injury and cardiovascular outcome. We used virtual histology intravascular ultrasound (VH-IVUS) to evaluate the relationship between the levels of circulating MPs and the coronary plaque composition in patients with stable angina. We included 35 patients with stable angina (22 men, age 64 ± 9 years) and a de novo target lesion. Preintervention gray-scale and VH-IVUS analysis was performed across the target lesion. Volumetric analysis was performed over a 10-mm-long segment centered at the minimum luminal site. Blood samples were obtained from the femoral artery before coronary angioplasty. MPs were measured using a solid-phase capture assay from a commercial kit. We divided participants into either a low MPs group or high MPs group based on the median value of MPs. There was no significant difference in baseline characteristics between the groups. The plaque burden and remodeling index were similar between the groups. The presence of VH-IVUS-derived thin-cap fibroatheroma was not different between the groups. The percentage of the necrotic core (NC) was significantly higher in the high MPs group than in the low MPs group, both in planar (17.0 ± 8.8% vs. 24.1 ± 6.9%, p = 0.012) and volumetric analyses (17.0 ± 4.8% vs. 22.1 ± 4.3%, p = 0.002). Circulating MPs were positively correlated with the percentage of the NC area at the minimal luminal site (r = 0.491, p = 0.003) and the percentage of the NC volume (r = 0.496, p = 0.002). Elevated levels of circulating MPs were associated with the amount of NC in the target lesion in those with stable angina, suggesting a potential role of circulating MPs as a biomarker for detecting unstable plaque in patients with stable angina.

Neopterin and 7,8-dihydroneopterin are generated within atherosclerotic plaques

Plasma neopterin correlates with the level of cardiovascular disease. Neopterin is the oxidation product of 7,8-dihydroneopterin, which is released by γ-interferon-stimulated macrophages. 7,8-Dihydroneopterin is a potent antioxidant, which inhibits lipid oxidation, macrophage cell death and scavenger receptor CD36 expression. The concentration of neopterin within atherosclerotic plaques was measured in tissue removed from carotid and femoral arteries. The excised plaques were cut into 3-mm-thick sections, and each section was analysed for neopterin, total neopterin, cholesterol, lipid peroxides, α-tocopherol and protein-bound 3,4-dihydroxyphenylalanine. Selected plaques were placed in tissue culture, and the media was analysed for 7,8-dihydroneopterin and neopterin release. Total neopterin levels ranged from 14 to 18.8 nmol/g of tissue. Large ranges of values were seen both within the same plaque and between plaques. No correlation between neopterin and any of the other analytes was observed, nor was there any significant trend in levels along the length of the plaques. γ-Interferon stimulation of cultured plaque generated total neopterin concentrations from 1 to 4 nmol/(g 24 h). The level of 7,8-dihydroneopterin generated within the plaque was within the range that inhibits lipid oxidation. The data show that atherosclerotic plaques are extremely dynamic in biochemistry and are the likely source of the plasma 7,8-dihydroneopterin and neopterin.

Correlation of high-sensitivity C-reactive protein and carotid plaques with coronary artery disease in elderly patients

The aim of this study was to explore the correlation of high-sensitivity C-reactive protein (hs-CRP) and carotid plaques with the severity of coronary artery disease (CAD). A total of 140 patients with angina who underwent coronary angiography were selected and divided into a single-vessel disease group (n=11), double-vessel disease group (n=18), multi-vessel disease group (n=71) and control group (n=40). Color Doppler ultrasound was applied to measure the intima-media thickness (IMT) of the common carotid artery (CCA) and carotid bifurcation, and to record the location and number of carotid plaques. The serum hs-CRP level was also determined. Compared with the control and single-vessel disease groups, the multi-vessel disease group showed significantly higher IMT of the CCA (P<0.05). The serum hs-CRP level was highest in the multi-vessel disease group (P<0.01). The hs-CRP level and carotid plaque characteristics were found to correlate closely with the severity of CAD. Therefore, they may be used to improve the prediction of CAD severity in elderly patients.