Vascular Inflammation Stratified by C-Reactive Protein and Low-Density Lipoprotein Cholesterol Levels: Analysis with 18F-FDG PET

High-sensitivity C-reactive protein and low-density lipoprotein cholesterol association with incident of cardiovascular events: Isfahan cohort study

BACKGROUND

There are many studies on high-sensitivity C-reactive protein (hs-CRP) association with cardiovascular disease (CVD); however, just a few studies investigated whether the low-density lipoprotein cholesterol (LDL-C) could participate in hs-CRP prognostic strength. This study aimed to determine the alliance of hs-CRP and LDL-C in different concentrations in occurrence cardiovascular events in the Isfahan Cohort Study (ICS).

METHODS

3277 participants aged 35 and above were included in the current analysis. We evaluated the association of elevated hs-CRP levels (≥ 3 mg/dL) and CVD events including myocardial infarction, ischemic heart disease, stroke, CVD, CVD mortality, and all-cause mortality in those with LDL-C ≥ or < 130 mg/dL Cox frailty models was used to determine possible interactions.

RESULTS

In both crude and fully adjusted models, there was no significant interaction between LDL-C and hs-CRP levels with the incidence of MI, stroke, CVD mortality, and all-cause death. Neither elevated LDL-C alone nor elevated CRP alone were associated with the risk of all cardiovascular events and all-cause death. However, participants with elevated concentrations of both hs-CRP and LDL-C had a greater risk of ischemic heart disease (IHD) (hazards ratio (HR) 1.44; 95% CI 1.03-2.02) and CVD (HR 1.36; 95% CI 1.01-1.83) than those with low LDL-C and hs-CRP.

CONCLUSION

These results indicate that despite a null association between elevated levels of CRP or LDL-C alone and CVD events, concurrent rise in LDL-C and hs-CRP levels is associated with higher risk of IHD and CVD.

Lymphoma Severity and Type Are Associated With Aortic FDG Uptake by 18F-FDG PET/CT Imaging

Background

There is evidence that metabolic disease burden in lymphoma influences patient outcome. However, the impact of disease severity on the cardiovascular system is unknown.

Objectives

The aim of this study was to examine whether lymphoma is associated with arterial inflammation by investigating the relationship between disease metabolic burden and arterial fluorodeoxyglucose (FDG) uptake.

Methods

Sixty-two chemotherapy-naïve patients with active Hodgkin’s or non-Hodgkin’s lymphoma were matched (2:1) to individual control groups of lymphoma patients previously treated and free of active disease. All groups underwent ¹⁸F-FDG position emission tomography–computed tomography imaging. Disease severity was quantified by metabolic tumor volume (MTV) and total lesion glycolysis corresponding to standardized uptake values (SUVs) ≥41% or ≥2.5 of the maximum SUV within lymphoma regions, and aortic FDG uptake was quantified through the target-to-background ratio (TBR). Inflammatory and disease severity biomarkers were also measured.

Results

MTV and total lesion glycolysis measurements were significantly correlated with inflammatory and disease biomarkers. Aortic TBR was higher in patients with active non-Hodgkin’s lymphoma compared with control subjects (median difference 0.51; 95% confidence interval [CI]: 0.28 to 0.78; p < 0.001). Similarly, patients with active Hodgkin’s lymphoma had higher values of aortic TBR compared with control subjects (median difference 0.31; 95% CI: 0.15 to 0.49; p < 0.001). In addition, aortic TBR was modestly increased in patients with stage III to IV disease compared with those with stage I to II disease (median aortic TBR: 2.23 [interquartile range: 2.01 to 2.54] vs. 2.06 [interquartile range: 1.83 to 2.27; p = 0.050). In multivariable analysis, aortic FDG uptake and MTV_≥2.5 values were independently associated (β = 0.425; 95% CI: 0.189 to 0.662; p = 0.001; R² = 0.208), as were aortic FDG uptake and MTV_≥41% (β = 0.407; 95% CI: 0.167 to 0.649, p = 0.001; R² = 0.191).

Conclusions

Aortic wall FDG uptake is related with disease severity indicative of a possible vascular effect of lymphoma. This work highlights a new potential role of molecular imaging in cardio-oncology for evaluating disease severity and its consequences on the vasculature.

TSH suppression aggravates arterial inflammation - an 18F-FDG PET study in thyroid carcinoma patients

Purpose

We aimed to investigate the influence of both hypothyroidism and thyroid-stimulating hormone (TSH) suppression on vascular inflammation, as assessed with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT).

Methods

Ten thyroid carcinoma patients underwent an ¹⁸F-FDG PET/CT during post-thyroidectomy hypothyroidism and during thyrotropin (TSH) suppression after ¹³¹I (radioiodine) ablation therapy. We analysed the ¹⁸F-FDG uptake in the carotids, aortic arch, ascending, descending, and abdominal aorta to investigate the effects of thyroid hormone status on arterial inflammation. Target-to-background ratios (TBRs) corrected for blood pool activity were established for all arterial territories. Results were further compared to euthyroid historic control subjects.

Results

In general, there was a trend towards higher vascular TBRs during TSH suppression than during hypothyroidism (TBR_max all vessels = 1.6 and 1.8, respectively, p = 0.058), suggesting a higher degree of arterial inflammation. In concurrence with this, we found increased C-reactive protein (CRP) levels after levothyroxine treatment (CRP = 2.9 mg/l and 4.8 mg/l, p = 0.005). An exploratory comparison with euthyroid controls showed significant higher TBRs during TSH suppression for the carotids, aortic arch, thoracic descending aorta, and when all vascular territories were combined (TBR_maxp = 0.013, p = 0.016, p = 0.030 and p = 0.018 respectively).

Conclusions

Arterial inflammation is increased during TSH suppression. This finding sheds new light on the underlying mechanism of the suspected increased risk of cardiovascular disease in patients with TSH suppression.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04292-w) contains supplementary material, which is available to authorized users.

Association of serum Sestrin2 level with metabolic risk factors in newly diagnosed drug-naïve type 2 diabetes

AIMS

Previous in-vitro and in-vivo experimental studies have shown that Sestrin2 attenuates oxidative stress and the pro-inflammatory pathway, resulting in improving metabolic homeostasis. However, the relationship between circulating Sestrin2 concentration and cardiometabolic risks in humans has not been explored.

METHODS

Sestrin2 concentration was measured in 240 subjects (46 without diabetes and 194 with diabetes), and the associations between Sestrin2 level and various cardiometabolic risk factors including body composition, insulin resistance, and atherosclerosis was assessed.

RESULTS

Sestrin2 concentration showed a trend of increasing in subjects with metabolic syndrome. After adjustment for age and gender, Sestrin2 level had a positive relationship with serum triglyceride, alanine aminotransferase (ALT), and creatinine levels, but no association with carotid atherosclerosis. Especially, in subjects with type 2 diabetes Sestrin2 concentration exhibited a significant positive correlation with body mass index (P = 0.015), waist circumference (P = 0.020), high-sensitivity C-reactive protein (P = 0.008), Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) (P = 0.041), percentage body fat (P = 0.001), and truncal fat mass (P = 0.005) after adjusting age and gender. Multiple stepwise regression analysis identified age, serum ALT and creatinine levels, and percentage body fat as independent determining factors for Sestrin2 concentration in patients with type 2 diabetes (R² = 0.173).

CONCLUSIONS

This study is the first to demonstrate a trend for increased Sestrin2 level in subjects with metabolic syndrome. In particular, in subjects with type 2 diabetes, Sestrin2 was significantly related to insulin resistance and percentage body fat, suggesting its potential as a novel modulatory factor for metabolic disorders in humans.

Diet-Modulated Lipoprotein Metabolism and Vascular Inflammation Evaluated by 18F-fluorodeoxyglucose Positron Emission Tomography

Vascular inflammation plays a central role in atherosclerosis, from initiation and progression to acute thrombotic complications. Modified low-density lipoproteins (LDLs) and apoB-containing particles stimulate plaque inflammation by interacting with macrophages. Loss of function of high-density lipoprotein (HDL) for preventing LDL particles from oxidative modification in dyslipidemic states may amplify modified LDL actions, accelerating plaque inflammation. Diets are one of the most important factors that can affect these processes of lipoprotein oxidation and vascular inflammation. Recently, ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has emerged as a reliable noninvasive imaging modality for identifying and quantifying vascular inflammation within atherosclerotic lesions based on the high glycolytic activity of macrophages infiltrating active atherosclerotic plaques. Vascular inflammation evaluated by FDG PET has been positively related to metabolic syndrome components and traditional risk factors of cardiovascular disease, including high-sensitivity C-reactive protein, body mass index, and insulin resistance. A positive association of vascular inflammation with endothelial dysfunction, resistin levels, pericardial adipose tissue, and visceral fat area has also been reported. In contrast, HDL cholesterol and adiponectin have been inversely related to vascular inflammation detected by FDG PET. Because of its reproducibility, serial FDG PET shows potential for tracking the effects of dietary interventions and other systemic and local antiatherosclerotic therapies for plaque inflammation.

Vascular inflammation and aortic stiffness: potential mechanisms of increased vascular risk in chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is a complex inflammatory condition in which an important extra-pulmonary manifestation is cardiovascular disease. We hypothesized that COPD patients would have increased aortic inflammation and stiffness, as candidate mechanisms mediating increased cardiovascular risk, compared to two negative control groups: healthy never-smokers and smokers without COPD. We also studied patients with COPD due to alpha_− 1 antitrypsin deficiency (α₁ATD) as a comparator lung disease group.

Methods

Participants underwent ¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography imaging to quantify aortic inflammation as the tissue-to-blood-ratio (TBR) of FDG uptake. Aortic stiffness was measured by carotid-femoral aortic pulse wave velocity (aPWV).

Results

Eighty-five usual COPD (COPD due to smoking), 12 α₁ATD-COPD patients and 12 each smokers and never-smokers were studied. There was no difference in pack years smoked between COPD patients and smokers (45 ± 25 vs 37 ± 19, p = 0.36), but α₁ATD patients smoked significantly less (19 ± 11, p < 0.001 for both). By design, spirometry measures were lower in COPD and α₁ATD-COPD patients compared to smokers and never-smokers. Aortic inflammation and stiffness were increased in COPD (TBR: 1.90 ± 0.38, aPWV: 9.9 ± 2.6 m/s) and α₁ATD patients (TBR: 1.94 ± 0.43, aPWV: 9.5 ± 1.8 m/s) compared with smokers (TBR: 1.74 ± 0.30, aPWV: 7.8 ± 1.8 m/s, p < 0.05 all) and never-smokers (TBR: 1.71 ± 0.34, aPWV: 7.9 ± 1.7 m/s, p ≤ 0.05 all).

Conclusions

In this cross-sectional prospective study, novel findings were that both usual COPD and α1ATD-COPD patients have increased aortic inflammation and stiffness compared to smoking and never-smoking controls, regardless of smoking history. These findings suggest that the presence of COPD lung disease per se may be associated with adverse aortic wall changes, and aortic inflammation and stiffening are potential mechanisms mediating increased vascular risk observed in COPD patients.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0792-1) contains supplementary material, which is available to authorized users.

PET Molecular Targets and Near-Infrared Fluorescence Imaging of Atherosclerosis

PURPOSE OF REVIEW

With this review, we aim to summarize the role of positron emission tomography (PET) and near-infrared fluorescence imaging (NIRF) in the detection of atherosclerosis.

RECENT FINDINGS

18F-FDG is an established measure of increased macrophage activity. However, due to its low specificity, new radiotracers have emerged for more specific detection of vascular inflammation and other high-risk plaque features such as microcalcification and neovascularization. Novel NIRF probes are engineered to sense endothelial damage as an early sign of plaque erosion as well as oxidized low-density lipoprotein (oxLDL) as a prime target for atherosclerosis. Integrated NIRF/OCT (optical coherence tomography) catheters enable to detect stent-associated microthrombi. Novel radiotracers can improve specificity of PET for imaging atherosclerosis. Advanced NIRF probes show promise for future application in human. Intravascular NIRF might play a prominent role in the detection of stent-induced vascular injury.

Variability in quantitative analysis of atherosclerotic plaque inflammation using 18F-FDG PET/CT

BACKGROUND

18F-FDG-PET(/CT) is increasingly used in studies aiming at quantifying atherosclerotic plaque inflammation. Considerable methodological variability exists. The effect of data acquisition and image analysis parameters on quantitative uptake measures, such as standardized uptake value (SUV) and target-to-background ratio (TBR) has not been investigated extensively.

OBJECTIVE

The goal of this study was to explore the effect of several data acquisition and image analysis parameters on quantification of vascular wall 18F-FDG uptake measures, in order to increase awareness of potential variability.

METHODS

Three whole-body emission scans and a low-dose CT scan were acquired 38, 60 and 90 minutes after injection of 18F-FDG in six rheumatoid arthritis patients with high cardiovascular risk profiles.Data acquisition (1 and 2) and image analysis (3, 4 and 5) parameters comprised:1. 18F-FDG uptake time, 2. SUV normalisation, 3. drawing regions/volumes of interest (ROI's/VOI's) according to: a. hot-spot (HS), b. whole-segment (WS) and c. most-diseased segment (MDS), 4. Background activity, 5. Image matrix/voxel size.Intraclass correlation coefficients (ICC's) and Bland Altman plots were used to assess agreement between these techniques and between observers. A linear mixed model was used to determine the association between uptake time and continuous outcome variables.

RESULTS

1. Significantly higher TBRmax values were found at 90 minutes (1,57 95%CI 1,35-1,80) compared to 38 minutes (1,30 95%CI 1,21-1,39) (P = 0,024) 2. Normalising SUV for BW, LBM and BSA significantly influences average SUVmax (2,25 (±0,60) vs 1,67 (±0,37) vs 0,058 (±0,013)). 3. Intraclass correlation coefficients were high in all vascular segments when SUVmax HS was compared to SUVmax WS. SUVmax HS was consistently higher than SUVmax MDS in all vascular segments. 4. Blood pool activity significantly decreases in all (venous and arterial) segments over time, but does not differ between segments. 5. Image matrix/voxel size does not influence SUVmax.

CONCLUSION

Quantitative measures of vascular wall 18F-FDG uptake are affected mainly by changes in data acquisition parameters. Standardization of methodology needs to be considered when studying atherosclerosis and/or vasculitis.

Association between vascular inflammation and non-alcoholic fatty liver disease: Analysis by 18F-fluorodeoxyglucose positron emission tomography

BACKGROUND

Growing evidence suggests that non-alcoholic fatty liver disease (NAFLD) is associated with cardiovascular disease as well as metabolic syndrome. FDG-PET is a novel imaging technique that detects vascular inflammation, which may reflect rupture-prone vulnerable atherosclerotic plaques.

METHODS

Vascular inflammation was measured as the maximum target-to-background ratio (maxTBR), along with various cardiometabolic risk factors in 51 subjects with NAFLD, and compared with 100 age- and gender-matched subjects without NAFLD. The liver attenuation index (LAI), which was measured using computed tomography, was used as a parameter for the diagnosis of NAFLD.

RESULTS

After adjusting for age and sex, both maxTBR and LAI values were associated with several cardiometabolic risk parameters. Furthermore, there was a significant inter-relationship between LAI and maxTBR values (r=-0.227, P=0.005). Individuals with NAFLD had higher maxTBR values than those without NAFLD (P=0.026), although their carotid intima-media thickness (CIMT) values did not differ. The proportion of subjects with NAFLD showed a step-wise increment following the tertiles of maxTBR values (P for trend=0.015). In multiple logistic regression analysis, maxTBR tertiles were independently associated with NAFLD after adjusting for age, gender, systolic blood pressure, triglycerides, HDL-cholesterol, glucose, BUN, creatinine and homeostasis model assessment of insulin resistance (HOMA-IR) (P=0.030). However, their relationship was attenuated after further adjustment for waist circumference or high sensitive C-reactive protein.

CONCLUSION

Patients with NAFLD have an increased risk for vascular inflammation as measured via FDG-PET/CT even without difference in CIMT. (Clinical trials No. NCT01958411, http://www.clinicaltrials.gov/).

PET Imaging of Atherosclerotic Disease: Advancing Plaque Assessment from Anatomy to Pathophysiology

Atherosclerosis is a leading cause of morbidity and mortality. It is now widely recognized that the disease is more than simply a flow-limiting process and that the atheromatous plaque represents a nidus for inflammation with a consequent risk of plaque rupture and atherothrombosis, leading to myocardial infarction or stroke. However, widely used conventional clinical imaging techniques remain anatomically focused, assessing only the degree of arterial stenosis caused by plaques. Positron emission tomography (PET) has allowed the metabolic processes within the plaque to be detected and quantified directly. The increasing armory of radiotracers has facilitated the imaging of distinct metabolic aspects of atherogenesis and plaque destabilization, including macrophage-mediated inflammatory change, hypoxia, and microcalcification. This imaging modality has not only furthered our understanding of the disease process in vivo with new insights into mechanisms but has also been utilized as a non-invasive endpoint measure in the development of novel treatments for atherosclerotic disease. This review provides grounding in the principles of PET imaging of atherosclerosis, the radioligands in use and in development, its research and clinical applications, and future developments for the field.

PET/CT Imaging of Unstable Carotid Plaque with 68Ga-Labeled Somatostatin Receptor Ligand

⁶⁸Ga-labeled somatostatin receptor ligand PET imaging has recently been shown in preclinical and early human studies to have a potential role in the evaluation of vulnerable arterial plaques. We prospectively evaluated carotid plaque ⁶⁸Ga-DOTATATE uptake in patients with recent carotid events, assessed inter- and intraobserver variability of such measurements, and explored the mechanism of any plaque DOTATATE activity with immunohistochemistry in resected specimens. Methods: Twenty consecutively consenting patients with recent symptomatic carotid events (transient ischemic attack, stroke, or amaurosis fugax), due for carotid endarterectomy, were prospectively recruited. ⁶⁸Ga-DOTATATE PET/CT of the neck was performed before surgery. ⁶⁸Ga-DOTATATE uptake was measured by drawing regions of interest along the carotid plaques and contralateral plaques/carotid arteries by an experienced radionuclide radiologist and radiographer. Two PET quantification methods with inter- and intraobserver variability were assessed. Resected carotid plaques were retrieved for somatostatin receptor subtype-2 (sst2) immunohistochemical staining. Results: The median time delay between research PET and surgery was 2 d. SUVs and target-to-background ratios for the symptomatic plaques and the asymptomatic contralateral carotid arteries/plaques showed no significant difference (n = 19, P > 0.10), regardless of quantification method. The intraclass correlation coefficient was greater than 0.8 in all measures of carotid artery/plaque uptake (SUV) and greater than 0.6 in almost all measures of target-to-background ratio. None of the excised plaques was shown to contain cells (macrophages, lymphocytes, vessel-associated cells) expressing sst2 on their cell membrane. Conclusion:⁶⁸Ga-DOTATATE activity on PET in recently symptomatic carotid plaques is not significantly different from contralateral carotids/plaques. Any activity seen on PET is not shown to be from specific sst2 receptor-mediated uptake in vitro. It is therefore unlikely that sst2 PET/CT imaging will have a role in the detection and characterization of symptomatic carotid plaques.

Associations between cardiovascular disease risk factors and IL-6 and hsCRP levels in the elderly

BACKGROUND

Age-related diseases, including cardiovascular diseases (CVD) may be stimulated by microinflammation, marked by increased level of IL-6 and high-sensitivity CRP (hsCRP). We aimed to investigate whether aging "per se" independently contributes to the microinflammation, in addition to traditional and novel CVD risk factors.

METHODS/RESULTS

The research sample included 4979 participants from PolSenior Study, aged over 65years. The study consisted of three visits and included questionnaire survey, geriatric assessment and blood/urine sampling in 4101 participants (83.2% of the sample). Serum hsCRP and plasma IL-6 were measured in 4093 (99.8%) and 3895 (95.0%) subjects. Multiple logistic regression showed that advanced age (over 80years), obesity, actual/former smoking, decreased HDL-cholesterol, chronic kidney disease (CKD) and depression were associated with occurrence of increased level of IL-6 (>2.4pg/ml). For hsCRP we found that advanced age, overweight/obesity, decreased HDL-cholesterol, actual/former smoking and CKD were associated with increased level of hsCRP (>3mg/l), while high income and statins treatment were related to lower level of hsCRP.

CONCLUSIONS

Microinflammation in the elderly is not fully explained by traditional and novel CVD risk factors. Active smoking, obesity and low HDL-cholesterol among traditional risk factors, along with CKD, depression and low income among novel risk factors, are the strongest determinants of microinflammation. Also we found that statin therapy decreases hsCRP levels, which indicates a potential role of inflammation in CVD as a target for intervention in the elderly (e.g. statin use).

Association of pooled cohort risk scores with vascular inflammation and coronary artery calcification in Korean adults

OBJECTIVES

A new pooled cohort risk equation to estimate atherosclerotic cardiovascular disease (CVD) risk was recently published, but the equation is based primarily on data from Caucasian populations. The relationship of this new risk scoring system with vascular inflammation and calcification has yet to be examined.

METHODS

A total of 74 participants were retrospectively selected based on inclusion and exclusion criteria. All participants underwent (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and multi-detector computed tomography (MDCT) examination in the Korea University Guro Hospital between June 2009 and May 2013. Vascular inflammation of the carotid artery was measured as target-to-background ratio (TBR) using (18)F-FDG-PET/CT and coronary artery calcification was quantified as Agatston score by MDCT.

RESULTS

Agatston scores were not significantly associated with any metabolic risk factors, but maximum TBR values exhibited a significant positive correlation with body mass index (r=0.31, P=0.01), waist circumference (r=0.42, P<0.01), waist-to-hip ratio (r=0.49, P<0.01), and systolic (r=0.35, P<0.01) and diastolic blood pressure (r=0.39, P<0.01). Furthermore, maximum TBR values were significantly correlated with serum high-sensitivity C-reactive protein (hsCRP) levels (r=0.26, P=0.03), whereas Agatston scores had no correlation. When pooled cohort risk equation scores were divided into incremental tertiles, age, waist circumference, waist-to-hip ratio and systolic blood pressure showed significant incremental trends. In particular, pooled cohort risk scores exhibited a significant positive correlation with maximum TBR values (r=0.35, P<0.01), but not with Agatston scores (r=0.11, P=0.34).

CONCLUSIONS

The pooled cohort risk equation exhibited significant positive correlations with vascular inflammation but not with calcification in Asian subjects without CVD, suggesting that this novel risk equation may detect early inflammatory changes preceding the structural modification of vessel walls.

Implications of Pericardial, Visceral and Subcutaneous Adipose Tissue on Vascular Inflammation Measured Using 18FDG-PET/CT

Objective

Pericardial adipose tissue (PAT) is associated with adverse cardiometabolic risk factors and cardiovascular disease (CVD). However, the relative implications of PAT, abdominal visceral and subcutaneous adipose tissue on vascular inflammation have not been explored.

Method and Results

We compared the association of PAT, abdominal visceral fat area (VFA), and subcutaneous fat area (SFA) with vascular inflammation, represented as the target-to-background ratio (TBR), the blood-normalized standardized uptake value measured using ¹⁸F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸FDG-PET) in 93 men and women without diabetes or CVD. Age- and sex-adjusted correlation analysis showed that PAT, VFA, and SFA were positively associated with most cardiometabolic risk factors, including systolic blood pressure, LDL-cholesterol, triglycerides, glucose, insulin resistance and high sensitive C-reactive proteins (hsCRP), whereas they were negatively associated with HDL-cholesterol. In particular, the maximum TBR (maxTBR) values were positively correlated with PAT and VFA (r = 0.48 and r = 0.45, respectively; both P <0.001), whereas SFA showed a relatively weak positive relationship with maxTBR level (r = 0.31, P = 0.003).

Conclusion

This study demonstrated that both PAT and VFA are significantly and similarly associated with vascular inflammation and various cardiometabolic risk profiles.

PET imaging of atherosclerosis

ABSTRACT 

Atherosclerosis is a chronic, progressive, multifocal disease of the arterial wall, which is mainly fuelled by local and systemic inflammation, often resulting in acute ischemic events following plaque rupture and vessel occlusion. When assessing the cardiovascular risk of an individual patient, we must consider both global measures of disease activity and local features of plaque vulnerability, in addition to anatomical distribution and degree of established atherosclerosis. These parameters cannot be measured with conventional anatomical imaging techniques alone, which are designed primarily to identify the presence of organic intraluminal obstruction in symptomatic patients. However, molecular imaging with PET, using specifically targeted radiolabeled probes to track active in vivo atherosclerotic mechanisms noninvasively, may potentially provide a method that is better suited for this purpose. Vascular PET imaging can help us to further understand aspects of plaque biology, and current evidence supports a future role as an emerging clinical tool for the quantification of cardiovascular risk in order to guide and monitor responses to antiatherosclerosis treatments and to distinguish high-risk plaques.

Uptake of aortic 18F-FDG is correlated with low-density lipoprotein cholesterol and leptin in a general population

Objective

This study investigated the relationship between aortic ¹⁸F-fluoro-2-deoxy-D-glucose (¹⁸F-FDG) uptake and clinical and laboratory findings related to atherosclerosis in a general population.

Methods

¹⁸F-FDG uptake in the ascending aorta was measured on the positron emission tomography/computed tomography (PET/CT) scans of 211 Japanese adults. The maximum target-to-background ratio (TBR) was compared with clinical and laboratory atherosclerosis findings.

Results

By multivariate regression analysis adjusted for age and sex, TBR-ascending aorta (TBR-A) was significantly correlated with various clinical and laboratory parameters, such as body mass index, log visceral fat area, low-density lipoprotein cholesterol (LDL-C), log fasting immunoreactive insulin, log homeostasis model assessment of insulin resistance, log total adiponectin and log-leptin, in all subjects. Furthermore, by multivariate linear regression analysis adjusted for confounding factors, TBR-A was significantly correlated with LDL-C (β = 0.001, p = 0.03) and log-leptin (β = 0.336, p<0.01) in all subjects.

Conclusion

TBR-A was significantly correlated with LDL-C and log-leptin independent from confounding factors. Our results suggest that aortic ¹⁸F-FDG uptake is a good marker of atherosclerosis, even in a general population.

[18F]fluorodeoxyglucose uptake in atherosclerotic plaques is associated with reduced coronary flow reserve in mice

OBJECTIVES

Coronary microvascular dysfunction, observed as impaired coronary vasodilator capacity, is an early manifestation of coronary artery disease. Inflammation plays an important role in different stages of atherogenesis. To study the role of vessel wall inflammation in the development of coronary dysfunction, we compared [(18)F]fluorodeoxyglucose (FDG) uptake in the aorta and coronary flow reserve (CFR) in atherosclerotic mice.

METHODS

We studied healthy young C57BL/6 mice fed a normal diet (n = 7) as well as hypercholesterolemic low-density lipoprotein receptor-disrupted/apolipoprotein B100-expressing (LDLR(-/-)ApoB(100/100)) mice (n = 15) and hypercholesterolemic and diabetic LDLR(-/-)ApoB(100/100)insulinlike growth factor II-overexpressing mice (n = 14) fed a western-type diet, aged 4 to 6 months. Doppler sonography was used to measure CFR as the ratio of coronary flow velocity during isoflurane-induced hyperemia and at rest. Uptake of [(18)F]FDG into the aorta was measured by autoradiography of tissue sections.

RESULTS

Histologic sections showed extensive atherosclerosis in the aorta, but coronary arteries were not obstructed. Both hyperemic coronary flow velocity and CFR were reduced (P < .05) in hypercholesterolemic mice with and without diabetes in comparison to healthy young C57BL/6 controls. Among hypercholesterolemic mice, both hyperemic flow velocity and CFR inversely correlated with atherosclerotic plaque [(18)F]FDG uptake in the aorta (r = -0.73; P < .001; r = -0.63; P = .001, respectively). In a multivariate analysis, including animal weight, aortic plaque burden, plasma glucose, plasma cholesterol, and [(18)F]FDG uptake in atherosclerotic plaques, only [(18)F]FDG uptake remained an independent predictor of reduced CFR (β = 0.736; P = .001).

CONCLUSIONS

The inflammatory activity in atherosclerotic plaques of the aorta independently predicts reduced CFR in atherosclerotic mice without obstructive coronary artery disease. This finding suggests that atherosclerotic inflammation contributes to coronary dysfunction.

The advancing clinical impact of molecular imaging in CVD

Molecular imaging seeks to unravel critical molecular and cellular events in living subjects by providing complementary biological information to current structural clinical imaging modalities. In recent years, molecular imaging efforts have marched forward into the clinical cardiovascular arena, and are now actively illuminating new biology in a broad range of conditions, including atherosclerosis, myocardial infarction, thrombosis, vasculitis, aneurysm, cardiomyopathy, and valvular disease. Development of novel molecular imaging reporters is occurring for many clinical cardiovascular imaging modalities (positron emission tomography, single-photon emission computed tomography, magnetic resonance imaging), as well as in translational platforms such as intravascular fluorescence imaging. The ability to image, track, and quantify molecular biomarkers in organs not routinely amenable to biopsy (e.g., the heart and vasculature) open new clinical opportunities to tailor therapeutics based on a cardiovascular disease molecular profile. In addition, molecular imaging is playing an increasing role in atherosclerosis drug development in phase II clinical trials. Here, we present state-of-the-art clinical cardiovascular molecular imaging strategies, and explore promising translational approaches positioned for clinical testing in the near term.

Relationship of serum inflammatory biomarkers with plaque inflammation assessed by FDG PET/CT: the dal-PLAQUE study

OBJECTIVES

This study sought to longitudinally investigate the relationship between a broad spectrum of serum inflammatory biomarkers and plaque inflammation assessed by (18)F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT).

BACKGROUND

Both plaque inflammation and serum biomarkers of inflammation are associated with atherothrombotic events; however, the relationship between them is unclear.

METHODS

We conducted a post hoc analysis of the dal-PLAQUE (A Randomized Placebo-Controlled Study of the Effect of RO4607381 on Progression or Regression of Atherosclerotic Plaque in Patients With Coronary Heart Disease [CHD] Including Patients With Other CHD Risk Factors), a randomized, placebo-controlled study of dalcetrapib, a cholesteryl ester transfer protein inhibitor, in 130 patients with coronary heart disease, or coronary heart disease risk equivalents on stable lipid-lowering therapy. Baseline and change after 3-month follow-up in inflammatory biomarker levels and baseline and change after 3-month follow-up in aorta and carotid (18)F-FDG PET/CT (mean maximum target-to-background ratio of the most diseased segment [TBRmds]) were analyzed.

RESULTS

Baseline myeloperoxidase positively correlated with baseline carotid TBRmds (rho = 0.25, p = 0.02). This correlation remained at the 3-month follow-up and was independent of traditional cardiovascular disease risk factors. Baseline lipoprotein-associated phospholipase A2 mass correlated with aorta TBRmds (rho = 0.21, p = 0.03). However, this correlation disappeared at the 3-month follow-up and was not independent of cardiovascular disease risk factors. There was no association between change from baseline in myeloperoxidase or lipoprotein-associated phospholipase A2 mass and change from baseline in aorta and carotid TBRmds. Baseline and change from baseline in high sensitivity C-reactive protein, interleukin 6, soluble P-selectin, soluble E-selectin, soluble intracellular adhesion molecule 1, soluble vascular cell adhesion molecule 1, and matrix-metalloproteinase 3 and 9 did not correlate with baseline or change from baseline in carotid or aorta TBRmds.

CONCLUSIONS

Our data show that, in patients with coronary heart disease or at high risk of coronary heart disease on stable lipid-lowering therapy, circulating myeloperoxidase levels are associated with carotid plaque inflammation. (A Randomized, Placebo-controlled Study of the Effect of RO4607381 on Progression or Regression of Atherosclerotic Plaque in Patients With Coronary Heart Disease [CHD] Including Patients With Other CHD Risk Factors [dal-PLAQUE]; NCT00655473).

Carotid Artery FDG Uptake May Serve as a Biomarker for Cardiovascular Risk Stratification in Asymptomatic Adults

PURPOSE

We investigated the relation between carotid artery FDG uptake and cardiovascular risk based on the Framingham risk score (FRS) and evaluated the possible role of FDG uptake in terms of risk stratification of asymptomatic adults.

METHODS

We evaluated 290 adults who underwent FDG PET/CT as part of general health screens. We calculated target-to-background ratios, corrected for pre-scan blood glucose levels, and obtained "TBRglu" values for both common carotid arteries. The FRS and the presence/absence of metabolic syndrome were recorded for each subject. Relationships among TBRglu values, metabolic syndrome status, and clinical parameters were assessed.

RESULTS

Carotid artery FDG uptake was significantly associated with clinical risk factors. Stepwise multiple regression analysis revealed that triglyceride levels, diabetes, and metabolic syndrome were independent determinants of high TBRglu. Of subjects with metabolic syndrome, those exhibiting high carotid artery FDG uptake had significantly higher levels of high sensitivity C-reactive protein (hsCRP). In subjects who did not have metabolic syndrome, FRSs were significantly elevated in those exhibiting high carotid artery FDG uptake compared to those with low uptake (13.1 ± 7.0 vs. 8.2 ± 7.4), as was also true of subjects with the syndrome (21.8 ± 16.0 vs. 13.5 ± 11.9).

CONCLUSION

High carotid FDG uptake is significantly associated with clinical risk factors and a greater FRS. Of subjects with metabolic syndrome, those with high carotid uptake had significantly higher hsCRP concentrations and FRSs. Therefore, carotid artery FDG activity may serve as a possible biomarker allowing cardiovascular risk stratification of asymptomatic populations.

Apolipoprotein A-I inhibits LPS-induced atherosclerosis in ApoE(-/-) mice possibly via activated STAT3-mediated upregulation of tristetraprolin

AIM

To investigate the effects of the major component of high-density lipoprotein apolipoprotein A-I (apoA-I) on the development of atherosclerosis in LPS-challenged ApoE(-/-) mice and the underlying mechanisms.

METHODS

Male ApoE-KO mice were daily injected with LPS (25 μg, sc) or PBS for 4 weeks. The LPS-challenged mice were intravenously injected with rAAV-apoA-I-GFP or rAAV-GFP. After the animals were killed, blood, livers and aortas were collected for biochemical and histological analyses. For ex vivo experiments, the abdominal cavity macrophages were harvested from each treatment group of mice, and cultured with autologous serum, then treated with LPS.

RESULTS

Chronic administration of LPS in ApoE(-/-) mice significantly increased the expression of inflammatory cytokines (TNF-α, IL-1β, IL-6, and MCP-1), increased infiltration of inflammatory cells, and enhanced the development of atherosclerosis. In LPS-challenged mice injected with rAAV-apoA-I-GFP, viral particles and human apoA-I were detected in the livers, total plasma human apoA-I levels were grammatically increased; HDL-cholesterol level was significantly increased, TG and TC were slightly increased. Furthermore, overexpression of apoA-I significantly suppressed the expression of proinflammatory cytokines, reduced the infiltration of inflammatory cells, and decreased the extent of atherosclerotic lesions. Moreover, overexpression of apoA-I significantly increased the expression of the cytokine mRNA-destabilizing protein tristetraprolin (TTP), and phosphorylation of JAK2 and STAT3 in aortas. In ex vivo mouse macrophages, the serum from mice overexpressing apoA-I significantly increased the expression of TTP, accompanied by accelerated decay of mRNAs of the inflammatory cytokines.

CONCLUSION

ApoA-I potently suppresses LPS-induced atherosclerosis by inhibiting the inflammatory response possibly via activation of STAT3 and upregulation of TTP.

Molecular imaging in atherosclerosis: FDG PET

18F-FDG PET is a new noninvasive tool for inflammation functional imaging. Low spatial resolution is now compensated by coregistration with CT or MRI. New mechanistic insights have emerged from animal and histology to explain the obtained signals by hypoxia, macrophage infiltration, and differentiation. Mixed results have been found in biomarkers studies. Interesting data have come recently linking plaque anatomy and function in carotids and in aortic aneurysms as well as inflammation and events. In coronary arteries, plaque assessment is still hampered by myocardium uptake but developments are being made. 18-FDG PET has been able to monitor inflammation before and after several therapies in animals and humans but to date the lack of standardization and the absence of prospective event-driven studies prevent this promising technique to be used in clinical practice.

Positive association between serum level of glyceraldehyde-derived advanced glycation end products and vascular inflammation evaluated by [(18)F]fluorodeoxyglucose positron emission tomography

OBJECTIVE

Advanced glycation end products (AGEs) evoke inflammatory reactions, contributing to the development and progression of atherosclerosis. We investigated the relationship between serum AGE level and vascular inflammation.

RESEARCH DESIGN AND METHODS

The study involved 275 outpatients at Kurume University, Japan (189 males and 86 females; mean age 61.2 ± 8.8 years) who underwent complete history and physical examinations and determinations of blood chemistry and anthropometric variables, including AGEs. Serum AGE level was examined by enzyme-linked immunosorbent assay. Vascular [(18)F]fluorodeoxyglucose (FDG) uptake, an index of vascular inflammation, was measured as blood-normalized standardized uptake value, known as the target-to-background ratio (TBR), by FDG-positron emission tomography (FDG-PET). Furthermore, we examined whether the changes in serum AGE level after treatment with oral hypoglycemia agents (OHAs) were correlated with those of TBR in another 18 subjects whose AGE value was >14.2 units/mL (mean ± 2 SD).

RESULTS

Mean serum AGE level and carotid TBR values were 9.15 ± 2.53 and 1.43 ± 0.22 units/mL, respectively. Multiple stepwise regression analysis revealed that TBR was independently correlated with AGEs (P < 0.001), carotid intima-media thickness (P < 0.01), and BMI (P < 0.02). When age- and sex-adjusted AGE values stratified by TBR tertiles were compared using ANCOVA, a significant trend was observed (P < 0.01). In addition, the changes in AGEs after OHA treatment were positively (r = 0.50, P < 0.05) correlated with those in TBR value.

CONCLUSIONS

The current study reveals that serum AGE level is independently associated with vascular inflammation evaluated by FDG-PET, suggesting that circulating AGE value may be a biomarker that could reflect vascular inflammation within an area of atherosclerosis.

Glucose metabolic trapping in mouse arteries: nonradioactive assay of atherosclerotic plaque inflammation applicable to drug discovery

Background

¹⁸F-Fluorodeoxyglucose (FDG)-positron emission tomography (PET) imaging of atherosclerosis in the clinic is based on preferential accumulation of radioactive glucose analog in atherosclerotic plaques. FDG-PET is challenging in mouse models due to limited resolution and high cost. We aimed to quantify accumulation of nonradioactive glucose metabolite, FDG-6-phosphate, in the mouse atherosclerotic plaques as a simple alternative to PET imaging.

Methodology/Principal Findings

Nonradioactive FDG was injected 30 minutes before euthanasia. Arteries were dissected, and lipids were extracted. The arteries were re-extracted with 50% acetonitrile-50% methanol-0.1% formic acid. A daughter ion of FDG-6-phosphate was quantified using liquid chromatography and mass spectrometry (LC/MS/MS). Thus, both traditional (cholesterol) and novel (FDG-6-phosphate) markers were assayed in the same tissue. FDG-6-phosphate was accumulated in atherosclerotic lesions associated with carotid ligation of the Western diet fed ApoE knockout mice (5.9 times increase compare to unligated carotids, p<0.001). Treatment with the liver X receptor agonist T0901317 significantly (2.1 times, p<0.01) reduced FDG-6-phosphate accumulation 2 weeks after surgery. Anti-atherosclerotic effects were independently confirmed by reduction in lesion size, macrophage number, cholesterol ester accumulation, and macrophage proteolytic activity.

Conclusions/Significance

Mass spectrometry of FDG-6-phosphate in experimental atherosclerosis is consistent with plaque inflammation and provides potential translational link to the clinical studies utilizing FDG-PET imaging.

The effects of 3-month atorvastatin therapy on arterial inflammation, calcification, abdominal adipose tissue and circulating biomarkers

PURPOSE

(18)F-Fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT has the potential to track vascular inflammation and monitor therapeutic response. The purpose of this study was to determine the association between arterial inflammation, calcification and serological biomarkers in subjects with atherosclerosis, and to assess their therapeutic response to 12-week atorvastatin treatment.

METHODS

Forty-three statin-naïve subjects with atherosclerosis received atorvastatin (40 mg/day) for 12 weeks and underwent (18)F-FDG PET/CT, coronary calcification and abdominal adipose tissue volume measurements. A panel of serological biomarkers was analysed. Arterial inflammation was measured at seven arterial segments and normalized to venous FDG activity to produce target to background ratios (TBR). Thirty-four subjects without cardiovascular disease who repeated PET 1-4 years apart for routine health check-ups were retrospectively evaluated for comparison.

RESULTS

The baseline mean TBR values in atherosclerotic patients were positively correlated with age (R = 0.36), body mass index (R = 0.54), abdominal visceral adipose tissue volume (R = 0.65), coronary calcification score (R = 0.40), levels of low-density lipoprotein cholesterol (R = 0.54), matrix metalloproteinase (MMP)-9 (R = 0.46) and fatty acid binding protein 4 (FABP4) (R = 0.67, all p < 0.05). The TBR as well as high-sensitivity C-reactive protein (hsCRP), E-selectin, MMP-9, monocyte chemotactic protein 1, FABP4 and follistatin values were reduced significantly after the 12-week atorvastatin treatment. The TBR reduction marginally correlated with changes in MMP-9 levels (R = 0.56, p = 0.05). The control group, whose median age was younger, by comparison had lower hsCRP and arterial TBR than the subjects with atherosclerosis (all p < 0.05), and moreover had a slight but insignificant increase in mean TBR at their 2.5±0.8 year follow-up.

CONCLUSION

The medium dose of atorvastatin over a 12-week period resulted in a significant reduction of arterial inflammation as well as various circulating biomarkers.

Association between sRAGE, esRAGE levels and vascular inflammation: analysis with (18)F-fluorodeoxyglucose positron emission tomography

BACKGROUND

The receptor for advanced glycation end-products (RAGE) and its diverse ligands play a pivotal role in the development of cardiovascular disease. Soluble forms of RAGE (sRAGE), including the splice variant endogenous secretory RAGE (esRAGE), may neutralize AGE-RAGE mediated vascular damage by acting as a decoy. (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a novel imaging technique for detecting vascular inflammation.

METHODS

We examined vascular inflammation measured using FDG-PET in 41 type 2 diabetes patients and 41 healthy control subjects in the right carotid artery. Vascular (18)F-FDG uptake was measured as the blood-normalized standardized uptake value (SUV), known as the target-to-background ratio (TBR). In addition, their relationship with carotid intima-media thickness (CIMT), estimated GFR (eGFR), and other cardiovascular risk factors was evaluated.

RESULTS

Both mean and maximum TBR values were significantly higher in patients with type 2 diabetes compared to healthy subjects. After adjusting for age and gender, sRAGE levels were significantly correlated with both mean and maximum TBR values, but not with CIMT values. Multiple linear regression analysis showed that maximum TBR values were independently associated with sRAGE levels in addition to HbA1c and eGFR.

CONCLUSIONS

Circulating sRAGE showed significant association with TBR values measured using FDG-PET, which reflect vascular inflammation.

Vascular imaging with positron emission tomography

Atherosclerosis is an inflammatory disease that causes most myocardial infarctions, strokes and acute coronary syndromes. Despite the identification of multiple risk factors and widespread use of drug therapies, it still remains a global health concern with associated costs. Although angiography is established as the gold standard means of detecting coronary artery stenosis, it does not image the vessel wall itself, reporting only on its consequences such as luminal narrowing and obstruction. MRI and computed tomography provide more information about the plaque structure, but recently positron emission tomography (PET) imaging using [(18) F]-fluorodeoxyglucose (FDG) has been advocated as a means of measuring arterial inflammation. This results from the ability of FDG-PET to highlight areas of high glucose metabolism, a feature of macrophages within atherosclerosis, particularly in high-risk plaques. It is suggested that the degree of FDG accumulation in the vessel wall reflects underlying inflammation levels and that tracking any changes in FDG uptake over time or with drug therapy might be a way of getting an early efficacy readout for novel anti-atherosclerotic drugs. Early reports also demonstrate that FDG uptake is correlated with the number of cardiovascular risk factors and possibly even the risk of future cardiovascular events. This review will outline the evidence base, shortcomings and emerging applications for FDG-PET in vascular imaging. Alternative PET tracers and other candidate imaging modalities for measuring vascular inflammation will also be discussed.