The role of periadventitial fat in atherosclerosis

The pathobiology of perivascular adipose tissue (PVAT), the fourth layer of the blood vessel wall

The perivascular adipose tissue (PVAT) is an adipose tissue depot which surrounds most human blood vessels. It is metabolically active and has both a protective and a pathogenic role in vascular biology and pathobiology. It regulates vascular homeostasis and promotes vascular dysfunction. The purpose of this review is to consider the origin, structure, function, and dysfunction of this unique adipose depot consisting of white (WAT), brown (BAT) and beige adipose tissue, to support the concept that PVAT may be considered the fourth layer of the normal arterial wall (tunica adiposa), in which dysfunction creates a microenvironment that regulates, in part, the initiation and growth of the fibro-inflammatory lipid atherosclerotic plaque. Experimental in-vivo and in-vitro studies and human investigations show that the adipocytes, extracellular matrix, nerve fibers and vasa vasorum found in PVAT form a functional adipose tissue unit adjacent to, but not anatomically separated from, the adventitia. PVAT maintains and regulates the structure and function of the normal arterial wall through autocrine and paracrine mechanisms, that include modulation of medial smooth muscle cell contractility and secretion of anti-inflammatory molecules. PVAT shows regional phenotypic heterogeneity which may be important in its effect on the wall of specific sections of the aorta and its muscular branches during perturbations and various injuries including obesity and diabetes. In atherosclerosis, a pan-vascular microenvironment is created that functionally links the intima-medial atherosclerotic plaque to the adventitia and PVAT beneath the plaque, highlighting the local impact of PVAT on atherogenesis. PVAT adipocytes have inflammatory effects which in response to injury show activation and phenotypic changes, some of which are considered to have direct and indirect effects on the intima and media during the initiation, growth, and development of complicated atherosclerotic plaques. Thus, it is important to maintain the integrity of the full vascular microenvironment so that design of experimental and human studies include investigation of PVAT. The era of discarding PVAT tissue in both experimental and human research and clinical vascular studies should end.

Adipocyte-Derived Serum Amyloid A Promotes Angiotensin II-Induced Abdominal Aortic Aneurysms in Obese C57BL/6J Mice

BACKGROUND

Obesity increases the risk for human abdominal aortic aneurysms (AAAs) and enhances Ang II (angiotensin II)-induced AAA formation in C57BL/6J mice. Obesity is also associated with increases in perivascular fat that expresses proinflammatory markers including SAA (serum amyloid A). We previously reported that deficiency of SAA significantly reduces Ang II-induced inflammation and AAA in hyperlipidemic apoE-deficient mice. In this study. we investigated whether adipose tissue-derived SAA plays a role in Ang II-induced AAA in obese C57BL/6J mice.

METHODS

The development of AAA was compared between male C57BL/6J mice (wild type), C57BL/6J mice lacking SAA1.1, SAA2.1, and SAA3 (TKO); and TKO mice harboring a doxycycline-inducible, adipocyte-specific SAA1.1 transgene (TKO-Tgfat; SAA expressed only in fat). All mice were fed an obesogenic diet and doxycycline to induce SAA transgene expression and infused with Ang II to induce AAA.

RESULTS

In response to Ang II infusion, SAA expression was significantly increased in perivascular fat of obese C57BL/6J mice. Maximal luminal diameters of the abdominal aorta were determined by ultrasound before and after Ang II infusion, which indicated a significant increase in aortic luminal diameters in wild type and TKO-TGfat mice but not in TKO mice. Adipocyte-specific SAA expression was associated with MMP (matrix metalloproteinase) activity and macrophage infiltration in abdominal aortas of Ang II-infused obese mice.

CONCLUSIONS

We demonstrate for the first time that SAA deficiency protects obese C57BL/6J mice from Ang II-induced AAA. SAA expression only in adipocytes is sufficient to cause AAA in obese mice infused with Ang II.

Epicardial Adipose Tissue Volume Is Associated with High Risk Plaque Profiles in Suspect CAD Patients

OBJECTIVE

To explore the association between EAT volume and plaque precise composition and high risk plaque detected by coronary computed tomography angiography (CCTA).

METHODS

101 patients with suspected coronary artery disease (CAD) underwent CCTA examination from March to July 2019 were enrolled, including 70 cases acute coronary syndrome (ACS) and 31 cases stable angina pectoris (SAP). Based on CCTA image, atherosclerotic plaque precise compositions were analyzed using dedicated quantitative software. High risk plaque was defined as plaque with more than 2 high risk features (spotty calcium, positive remolding, low attenuation plaque, napkin-ring sign) on CCTA image. The association between EAT volume and plaque composition was assessed as well as the different of correlation between ACS and SAP was analyzed. Multivariable logistic regression analysis was used to explore whether EAT volume was independent risk factors of high risk plaque (HRP).

RESULTS

EAT volume in the ACS group was significantly higher than that of the SAP group (143.7 ± 49.8 cm3 vs. 123.3 ± 39.2 cm3, P = 0.046). EAT volume demonstrated a significant positive correlation with total plaque burden (r = 0.298, P = 0.003), noncalcified plaque burden (r = 0.245, P = 0.013), lipid plaque burden (r = 0.250, P = 0.012), and homocysteine (r = 0.413, P ≤ 0.001). In ACS, EAT volume was positively correlated with total plaque burden (r = 0.309, P = 0.009), noncalcified plaque burden (r = 0.242, P = 0.044), and lipid plaque burden (r = 0.240, P = 0.045); however, no correlation was observed in SAP. Patients with HRP have larger EAT volume than those without HRP (169 ± 6.2 cm3 vs. 130.6 ± 5.3 cm3, P = 0.002). After adjustment by traditional risk factors and coronary artery calcium score (CACS), EAT volume was an independent risk predictor of presence of HRP (OR: 1.018 (95% CI: 1.006-1.030), P = 0.004).

CONCLUSIONS

With the increasing EAT volume, more dangerous plaque composition burdens increase significantly. EAT volume is a risk predictor of HRP independent of convention cardiovascular risk factors and CACS, which supports the potential impact of EAT on progression of coronary atherosclerotic plaque.

Antiatherosclerotic Phenotype of Perivascular Adipose Tissue Surrounding the Saphenous Vein in Coronary Artery Bypass Grafting

Background

Perivascular adipose tissue (PVAT) is associated with metabolically driven chronic inflammation called metaflammation, which contributes to vascular function and the pathogenesis of vascular disease. The saphenous vein (SV) is commonly used as an essential conduit in coronary artery bypass grafting, but the long‐term patency of SV grafts is a crucial issue. The use of the novel “no‐touch” technique of SV harvesting together with its surrounding tissue has been reported to result in good long‑term graft patency of SV grafts. Herein, we investigated whether PVAT surrounding the SV (SV‐PVAT) has distinct phenotypes compared with other PVATs of vessels.

Methods and Results

Fat pads were sampled from 48 patients (male/female, 32/16; age, 72±8 years) with coronary artery disease who underwent elective coronary artery bypass grafting. Adipocyte size in SV‐PVAT was significantly larger than the sizes in PVATs surrounding the internal thoracic artery, coronary artery, and aorta. SV‐PVAT and PVAT surrounding the internal thoracic artery had smaller extents of fibrosis, decreased gene expression levels of fibrosis‐related markers, and less metaflammation, as indicated by a significantly smaller extent of cluster of differentiation 11c–positive M1 macrophage infiltration, higher gene expression level of adiponectin, and lower gene expression levels of inflammatory cytokines, than did PVATs surrounding the coronary artery and aorta. Expression patterns of adipocyte developmental and pattern‐forming genes were totally different among the PVATs of the vessels.

Conclusions

The phenotype of SV‐PVAT, which may result from inherent differences in adipocytes, is closer to that of PVAT surrounding the internal thoracic artery than that of PVAT surrounding the coronary artery or that of PVAT surrounding the aorta. SV‐PVAT has less metaflammation and consecutive adipose tissue remodeling, which may contribute to high long‐term patency of grafting when the no‐touch technique of SV harvesting is used.

Clinical implications of perivascular fat stranding surrounding spontaneous isolated superior mesenteric artery dissection on computed tomography

Patients with spontaneous isolated superior mesenteric artery (SMA) dissection (SISMAD) usually present with acute or chronic abdominal pain and are admitted to the emergency or digestive diseases department to undergo auxiliary examinations, typically abdominal plain CT or contrast-enhanced CT (CECT). Plain CT is the most crucial examination in emergency radiology. An enlarged SMA diameter and perivascular fat stranding (PFS) on plain CT, though non-specific, may be the only indications for SISMAD. These results may be easily overlooked and the diagnosis of SISMAD may be missed. However, PFS around the SMA on CT may be the only indicator of the possible presence of SISMAD, particularly during the early stage when there are no massive changes in the vascular wall. The present study aimed to determine whether PFS surrounding the SMA on CT may help with the diagnosis of SISMAD by indicating the requirement for further examination. The data of 161 consecutive patients with SMA dissection who underwent abdominal CECT or underwent SMA CT angiography (CTA) after abdominal plain CT between February 2015 and February 2018 were retrospectively reviewed. SMA diameter, classification, PFS, complications, comorbidities and treatments were analyzed. The results demonstrated that SISMAD with PFS was significantly associated with admission type (emergency), clinical manifestations (abdominal pain), diagnostic modality and dissection subtype. On plain CT, PFS surrounding the SMA may be a marker for SISMAD, particularly in the emergency setting, and indicates the requirement for CTA examination.

Evaluation of Epicardial Adipose Tissue by Echocardiography and Its Correlation with Aortic Velocity Propagation and Carotid Intima-Media Thickness in Patients of Type 2 Diabetes Mellitus

Epicardial fat thickness (EFT) is associated with aortic stiffness in diabetic patients. In this study, we aimed to determine if there is an association among the parameters of EFT, aortic velocity propagation (AVP), and carotid intima-media thickness (CIMT) in patients with non-insulin dependent diabetes mellitus. This study included 55 non-insulin dependent diabetes mellitus patients and 40 non-diabetic control patients. For all participants, EFT and AVP were determined by echocardiographic method and CIMT was calculated using an ultrasonographic exam. The EFT and CIMT values were found to be significantly increased in the non-insulin dependent diabetes mellitus group. On the other hand, aortic velocity propagation was decreased in the non-insulin dependent diabetes mellitus group compared to non-diabetic patients (EFT; 8.43 ± 1.68 versus 6.36 ± 2.21 mm, p < 0.001; CIMT; 0.92 ± 0.24 versus 0.58 ± 0.18 mm, p < 0.001; and AVP; 28.20 ± 16.02 versus 58.10 ± 17.50, p < 0.01, respectively). Significantly higher EFT and CIMT values were found in addition to lower AVP values in non-insulin dependent diabetes mellitus patients. Moreover, we demonstrated that there was a strong correlation between EFT, CIMT, and AVP.

Aortic adventitial thickness as a marker of aortic atherosclerosis, vascular stiffness, and vessel remodeling in systemic lupus erythematosus

INTRODUCTION

There is limited human imaging data on the association of adventitial thickness (AT) with arterial disease. Systemic lupus erythematosus (SLE) is a prototypical disease model for studying markers of premature arterial disease.

OBJECTIVE

To determine if increased aortic AT is associated with aortic atherosclerosis [increased intima media thickness (IMT) or plaques], stiffness [increased pressure-strain elastic modulus (PSEM)], and vessel remodeling.

METHODS

In total, 70 SLE patients and 26 age- and sex-matched controls underwent transesophageal echocardiography (TEE). Two-dimensional guided M-mode images were obtained to assess AT, IMT, and plaques, and PSEM at the proximal, mid, and distal thoracic aorta. Images were interpreted by 3 observers unaware of the subjects' clinical data and each other's measurements. Abnormal aortic AT, IMT, and PSEM were defined as > 2SD above the overall mean values in controls and corresponded to > 1 mm, > 1 mm, and > 10.6 Pascal units, respectively. Plaques were defined as focal-protruding IMT > 50% of the surrounding vessel wall.

RESULTS

Abnormal aortic AT, atherosclerosis, and abnormal stiffness were more frequent in SLE patients than in controls (all p ≤ 0.02). In SLE patients, abnormal AT combined with atherosclerosis was associated with larger aortic end-diastolic diameters than in controls (p ≤ 0.05). In SLE patients, aortic AT was greater in patients with atherosclerosis and in those with abnormal stiffness than in patients without these abnormalities (all p ≤ 0.02). In patients with abnormal AT, the degree of aortic stiffness was similar to those with atherosclerosis (p = 0.22).

CONCLUSION

In patients with SLE, increased aortic AT is associated with aortic atherosclerosis, abnormal stiffness, and eccentric vessel remodeling. Key Points • In patients with SLE, abnormal aortic adventitial thickness is associated with aortic atherosclerosis, abnormal stiffness, and eccentric vessel remodeling. • In patients with SLE, aortic adventitial thickening may contribute to the extent of aortic atherosclerosis, abnormal aortic stiffness, and vessel remodeling. • To our knowledge, this is the first human imaging study to characterize the aortic adventitial layer and delineate its association with aortic disease.

[Adiponectin gene expression in local fat depots in patients with coronary heart disease depending on the degree of coronary lesion]

AIM

To determine the dependence of adiponectin gene expression by subcutaneous, epicardial and perivascular adipocytes on the degree of coronary lesion in coronary heart disease.

MATERIALS AND METHODS

84 patients with coronary artery disease were examined. Of these, 39 people showed a moderate degree of atherosclerotic lesion of the coronary bed (less than or equal to 22 points) on the SYNTAX Score scale, 20 severe (2231 points), and 25 extremely severe (more than 32 points). Upon admission to the hospital, all patients underwent an echocardiographic study (Echocardiography, Acuson, Germany) with the calculation of the ejection fraction (EF) of the left ventricle (LV) to assess its systolic function. During a planned surgical intervention (coronary bypass surgery, CABG), adipocytes of subcutaneous, epicardial (EAT) and perivascular adipose tissue (PVAT) were taken. Adiponectin gene expression was evaluated by polymerase chain reaction (real-time PCR) using TaqMan probes. Statistical analysis was performed using Statistica 9.0.

RESULTS

The maximum level of adiponectin expression was detected in adipocytes of PVAT, and the minimum EAT. With an increase in the degree of atherosclerotic lesion of the coronary bed, the expression of the adiponectin gene in adipocytes of local depots significantly decreases r=-0.82; p=0.023. Moreover, the low level of gene expression in EAT correlated with a decrease in LV EF by r=0.73; p=0.03. In adipocytes of subcutaneous and especially PVAT, gene expression was the highest in patients with a moderate degree of coronary lesion.

CONCLUSIONS

Low adiponectin gene expression in EAT is associated with an increase in the degree of atherosclerotic lesion of the coronary bed and a decrease in LV EF.

Atherosclerotic spontaneous coronary artery dissection (A-SCAD) in a patient with COVID-19: case report and possible mechanisms

Background

Spontaneous coronary artery dissection (SCAD) may be atherosclerotic (A-SCAD) or non-atherosclerotic (NA-SCAD) in origin. Contemporary usage of the term ‘SCAD’ is typically synonymous with NA-SCAD. COVID-19 could induce a vascular inflammation localized in the coronary adventitia and periadventitial fat and contribute to the development of an A-SCAD of a vulnerable plaque in a susceptible patient.

Case summary

In this report we describe a case of a COVID-19 patient with past cardiac history of CAD who was admitted for acute coronary syndrome (ACS). Coronary angiography demonstrated the culprit lesion in the proximal LAD that presented with a very complex and unusual morphology, indicative of an A-SCAD. The diagnosis of A-SCAD was supported by the presence of a mild stenosis in the same coronary segment in the last angiogram performed 3 years previously. He was successfully treated by PCI, had a favourable course of the COVID-19 with no symptoms of pneumonia, and was discharged from the hospital after two negative tests for SARS-CoV-2.

Discussion

A higher index of suspicion of A-SCAD is needed in patients with suspected or confirmed COVID-19 presenting with ACS. The proposed approach with ‘thrombolysis first’ for treating STEMI patients with suspected or confirmed COVID-19 infection could be unsafe in the case of underlying A-SCAD.

Differential Phenotypes in Perivascular Adipose Tissue Surrounding the Internal Thoracic Artery and Diseased Coronary Artery

Background

Perivascular adipose tissue (PVAT) is causally associated with vascular function and the pathogenesis of vascular disease in association with metabolically driven chronic inflammation called metaflammation. However, the difference in PVAT surrounding the coronary artery (CA‐PVAT) and that surrounding the internal thoracic artery (ITA‐PVAT), a vessel resistant to atherosclerosis, remains unclear. Herein, we investigated whether CA‐PVAT, ITA‐PVAT, and subcutaneous adipose tissue (SCAT) have distinct phenotypes.

Methods and Results

Fat pads were sampled from 44 patients (men/women, 36:8; age, 67±13 years) with CA disease who underwent elective CA bypass grafting. Adipocyte size in ITA‐PVAT and that in CA‐PVAT were significantly smaller than that in SCAT. A greater extent of fibrosis and increased gene expression levels of fibrosis‐related molecules were observed in CA‐PVAT than those in SCAT and those in ITA‐PVAT. CA‐PVAT exhibited more pronounced metaflammation, as indicated by a significantly larger extent of CD68‐positive and CD11c‐positive M1 macrophages, a lower ratio of CD206‐positive M2 to CD11c‐positive M1 macrophages, a lower gene expression level of adiponectin, and higher gene expression levels of inflammatory cytokines and inflammasome‐ and endoplasmic reticulum stress–related molecules, than did ITA‐PVAT and SCAT. Expression patterns of adipocyte developmental and pattern‐forming genes were totally different among SCAT, ITA‐PVAT, and CA‐PVAT.

Conclusions

The phenotype of ITA‐PVAT is closer to that of SCAT than that of CA‐PVAT, which may result from inherent differences in adipocytes. ITA‐PVAT appears to be protected from metaflammation and consecutive adipose tissue remodeling, which may contribute to the decreased atherosclerotic plaque burden in the ITA.

Knockout rat models mimicking human atherosclerosis created by Cpf1-mediated gene targeting

The rat is a time-honored traditional experimental model animal, but its use is limited due to the difficulty of genetic modification. Although engineered endonucleases enable us to manipulate the rat genome, it is not known whether the newly identified endonuclease Cpf1 system is applicable to rats. Here we report the first application of CRISPR-Cpf1 in rats and investigate whether Apoe knockout rat can be used as an atherosclerosis model. We generated Apoe- and/or Ldlr-deficient rats via CRISPR-Cpf1 system, characterized by high efficiency, successful germline transmission, multiple gene targeting capacity, and minimal off-target effect. The resulting Apoe knockout rats displayed hyperlipidemia and aortic lesions. In partially ligated carotid arteries of rats and mice fed with high-fat diet, in contrast to Apoe knockout mice showing atherosclerotic lesions, Apoe knockout rats showed only adventitial immune infiltrates comprising T lymphocytes and mainly macrophages with no plaque. In addition, adventitial macrophage progenitor cells (AMPCs) were more abundant in Apoe knockout rats than in mice. Our data suggest that the Cpf1 system can target single or multiple genes efficiently and specifically in rats with genetic heritability and that Apoe knockout rats may help understand initial-stage atherosclerosis.

Obesity, ectopic fat and cardiac metabolism

INTRODUCTION

Obesity is recognized as a risk factor for cardiovascular disease, expending independent adverse effects on the cardiovascular system. This relationship is complex due to several associations with cardiovascular disease risk factors/markers such as hypertension, dyslipidemia, insulin resistance/dysglycemia, or type 2 diabetes mellitus. Obesity induces a variety of cardiovascular system structural adaptations, from subclinical myocardial dysfunction to severe left ventricular systolic heart failure. Abnormalities in cardiac metabolism and subsequent cardiac energy, have been proposed as major contributors to obesity-related cardiovascular disease. Ectopic fat depots play an important role in several of the hypotheses postulated to explain the association between obesity, cardiac metabolism and cardiac dysfunction.

AREAS COVERED

In this review, we addressed with contemporary studies how obesity-associated metabolic conditions and ectopic cardiac fat accumulation, translate into cardiac energy metabolism disturbances that may lead to adverse effects on the cardiovascular system.

EXPERT COMMENTARY

Obesity and ectopic fat accumulation has long been related to metabolic diseases and adverse cardiovascular outcomes. Recent imaging advances have just started to address the complex interplays between obesity, ectopic fat depots, cardiac metabolism and the risk of obesity-related cardiovascular disease. A better comprehension of these obesity-associated metabolic disturbances will lead to earlier detection of patients at increased risk of cardiovascular disease and to the development of novel therapeutic metabolic targets to treat a wide variety of cardiovascular diseases.

Perivascular Epicardial Fat Stranding at Coronary CT Angiography: A Marker of Acute Plaque Rupture and Spontaneous Coronary Artery Dissection

Purpose To evaluate the frequency and implications of perivascular fat stranding on coronary computed tomography (CT) angiograms obtained for suspected acute coronary syndrome (ACS). Materials and Methods This retrospective registry study was approved by the institutional review board. The authors reviewed the medical records and images of 1403 consecutive patients (796 men, 607 women; mean age, 52.8 years) who underwent coronary CT angiography at the emergency department from February 2012 to March 2016. Fat attenuation, length and number of circumferential quadrants of the affected segment, and attenuation values in the unaffected epicardial and subcutaneous fat were measured. "Cases" were defined as patients with perivascular fat stranding. Patients with significant stenosis but without fat stranding were considered control subjects. Baseline imaging characteristics, ACS frequency, and results of subsequent downstream testing were compared between cases and control subjects by using two-sample t, Mann-Whitney U, and Fisher tests. Results Perivascular fat stranding was seen in 11 subjects, nine with atherosclerotic lesions and two with spontaneous coronary artery dissections, with a mean fat stranding length of 19.2 mm and circumferential extent averaging 2.9 quadrants. The mean attenuation of perivascular fat stranding, normal epicardial fat, and normal subcutaneous fat was 17, -93.2, and -109.3 HU, respectively (P < .001). Significant differences (P < .05) between cases and control subjects included lower Agatston score, presence of wall motion abnormality, and initial elevation of serum troponin level. ACS frequency was 45.4% in cases and 3.8% in control subjects (P = .001). Conclusion Recognition of perivascular fat stranding may be a helpful additional predictor of culprit lesion and marker of risk for ACS in patients with significant stenosis or spontaneous coronary artery dissection. ^© RSNA, 2018 Online supplemental material is available for this article.

Epicardial Adipose Tissue Thickness Is an Independent Predictor of Critical and Complex Coronary Artery Disease by Gensini and Syntax Scores

Epicardial adipose tissue thickness is associated with the severity and extent of atherosclerotic coronary artery disease. We prospectively investigated whether epicardial adipose tissue thickness is related to coronary artery disease extent and complexity as denoted by Gensini and Syntax scores, and whether the thickness predicts critical disease. After performing coronary angiography in 183 patients who had angina or acute myocardial infarction, we divided them into 3 groups: normal coronary arteries, noncritical disease (≥1 coronary lesion with <70% stenosis), and critical disease (≥1 coronary lesion with <70% stenosis). We used transthoracic echocardiography to measure epicardial adipose tissue thickness, then calculated Gensini and Syntax scores by reviewing the angiograms. Mean thicknesses were 4.3 ± 0.9, 5.2 ± 1.5, and 7.5 ± 1.9 mm in patients with normal coronary arteries, noncritical disease, and critical disease, respectively (P <0.001). At progressive thicknesses (<5, 5-7, and >7 mm), mean Gensini scores were 4.1 ± 5.5, 19.8 ± 15.6, and 64.9 ± 32.4, and mean Syntax scores were 4.7 ± 5.9, 16.6 ± 8.5, and 31.7 ± 8.7, respectively (both P <0.001). Thickness had strong and positive correlations with both scores (Gensini, r =0.82, P <0.001; and Syntax, r =0.825, P <0.001). The cutoff thickness value to predict critical disease was 5.75 mm (area under the curve, 0.875; 95% confidence interval, 0.825-0.926; P <0.001). Epicardial adipose tissue thickness is independently related to coronary artery disease extent and complexity as denoted by Gensini and Syntax scores, and it predicts critical coronary artery disease.

Quantification of epicardial and intrathoracic fat volume does not provide an added prognostic value as an adjunct to coronary artery calcium score and myocardial perfusion single-photon emission computed tomography

AIMS

To compare the predictive value of epicardial and intrathoracic fat volume (EFV, IFV), coronary artery calcium (CAC) score, and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) for major adverse cardiac events (MACE).

METHODS AND RESULTS

Follow-up was obtained in 275 patients with known or suspected coronary artery disease (CAD), who underwent SPECT-MPI including non-contrast cardiac computed tomography (CT) for attenuation correction to evaluate ischaemic heart disease and in whom EFV, IFV, and CAC score were calculated from non-contrast CT. Associations between fat volume, traditional cardiovascular risk factors, CAC score, and SPECT-MPI results were assessed and MACE predictors identified by Cox proportional hazard regression and global χ(2) statistics. After a median follow-up of 2.9 years, MACE were recorded in 38 patients. In univariate Cox regression analysis, EFV and IFV were predictors of MACE (P = 0.013 and P = 0.004, respectively). In multivariate analysis, EFV and IFV provided incremental predictive value beyond traditional cardiovascular risk factors (P < 0.05 and P < 0.01). However, after adjustment for CAC score and SPECT-MPI results, EFV and IFV fell short of statistical significance as independent outcome predictors.

CONCLUSION

Quantification of EFV and IFV is associated with MACE and may improve risk stratification beyond traditional cardiovascular risk factors. However, once CAC score and/or SPECT-MPI results are known, EFV and IFV do not provide any added clinically relevant prognostic value. Further studies may identify the subpopulation with the largest relative merit of EFV and IFV as an adjunct to SPECT-MPI and CAC score.

Myocardial fat as a part of cardiac visceral adipose tissue: physiological and pathophysiological view

Thoracic fat includes extra-pericardial (outside the visceral pericardium) and intra-pericardial (inside the visceral pericardium) adipose tissue. It is called ectopic adipose tissue although it is a normal anatomical structure. Intra-pericardial adipose tissue, which is predominantly composed of epicardial and pericoronary adipose tissue, has a significant role in cardiovascular system function. It provides metabolic-mechanical support to the heart and blood vessels in physiological conditions, while it represents metabolic-cardiovascular risk in case of qualitative and quantitative structural changes in the tissue: it correlates with coronary atherosclerotic disease, left ventricular mass, left atrium enlargement and atrial fibrillation presence. In the last decade there has been mounting evidence of fat cells presence in the myocardium of healthy (non-diseased) persons as well as in persons with both cardiovascular and non-cardiovascular diseases. Thus, it is necessary to clarify the incidence, aetiology, physiological role of fat cells in the myocardium, as well as the clinical significance of pathological fatty infiltration of the myocardium.

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.

Increased regional epicardial fat volume associated with reversible myocardial ischemia in patients with suspected coronary artery disease

Epicardial adipose tissue is a source of pro-inflammatory cytokines and has been linked to the development of coronary artery disease. No study has systematically assessed the relationship between local epicardial fat volume (EFV) and myocardial perfusion defects. We analyzed EFV in patients undergoing SPECT myocardial perfusion imaging combined with computed tomography (CT) for attenuation correction. Low-dose CT without contrast was performed in 396 consecutive patients undergoing SPECT imaging for evaluation of coronary artery disease. Regional thickness, cross-sectional areas, and total EFV were assessed. 295 patients had normal myocardial perfusion scans and 101 had abnormal perfusion scans. Mean EFVs in normal, ischemic, and infarcted hearts were 99.8 ± 82.3 cm(3), 156.4 ± 121.9 cm(3), and 96.3 ± 102.1 cm(3), respectively (P < 0.001). Reversible perfusion defects were associated with increased local EFV compared to normal perfusion in the distribution of the right (69.2 ± 51.5 vs 46.6 ± 32.0 cm(3); P = 0.03) and left anterior descending coronary artery (87.1 ± 76.4 vs 46.7 ± 40.6 cm(3); P = 0.005). Our results demonstrate increased regional epicardial fat in patients with active myocardial ischemia compared to patients with myocardial scar or normal perfusion on nuclear perfusion scans. Our results suggest a potential role for cardiac CT to improve risk stratification in patients with suspected coronary artery disease.

Epicardial and thoracic fat - Noninvasive measurement and clinical implications

Epicardial fat, the local visceral fat depot enclosed by the visceral pericardial sac, surrounds the coronary arteries for most of their course, and may contribute to the development of coronary atherosclerosis through local production of inflammatory cytokines. Several studies which measured epicardial fat volume noninvasively have shown a relationship of increased epicardial fat volume with coronary artery disease, with the presence and progression of coronary plaque, major adverse cardiovascular events, myocardial ischemia and atrial fibrillation. Quantitative measurement of epicardial fat volume from noninvasive imaging modalities such as CT and MRI are feasible, and may play a clinical role in cardiovascular risk assessment. The evidence to date warrants larger studies with follow-up to further investigate the role of epicardial fat as an imaging marker with prognostic importance.

Overview of epidemiology and contribution of obesity to cardiovascular disease

The prevalence of obesity has increased worldwide and is a source of concern since the negative consequences of obesity start as early as in childhood. The most commonly used anthropometric tool to assess relative weight and classify obesity is the body mass index (BMI); BMI alone shows a U- or a J-shaped association with clinical outcomes and mortality. Such an inverse relationship fuels a controversy in the literature, named the 'obesity paradox', which associates better survival and fewer cardiovascular (CV) events in patients with elevated BMI afflicted with chronic diseases compared to non-obese patients. However, BMI cannot make the distinction between an elevated body weight due to high levels of lean vs. fat body mass. Generally, an excess of body fat (BF) is more frequently associated with metabolic abnormalities than a high level of lean body mass. Another explanation for the paradox is the absence of control for major individual differences in regional BF distribution. Adipose tissue is now considered as a key organ regarding the fate of excess dietary lipids, which may determine whether or not body homeostasis will be maintained (metabolically healthy obesity) or a state of inflammation/insulin resistance will be produced, with deleterious CV consequences. Obesity, particularly visceral obesity, also induces a variety of structural adaptations/alterations in CV structure/function. Adipose tissue can now be considered as an endocrine organ orchestrating crucial interactions with vital organs and tissues such as the brain, the liver, the skeletal muscle, the heart and blood vessels themselves. Thus, the evidence reviewed in this paper suggests that adipose tissue quality/function is as important, if not more so, than its amount in determining the overall health and CV risks of overweight/obesity.

LOX-1 deletion and macrophage trafficking in atherosclerosis

BACKGROUND

Atherosclerosis is associated with macrophage accumulation. LOX-1 has been shown to induce macrophage attachment, and its deletion (LOX-1 knockout, KO) reduces atherosclerosis in LDLr KO mice fed a high cholesterol diet. We examined differences in macrophage trafficking in age-matched wild type, LOX-1 KO, LDLr KO, and LDLr/LOX-1 double KO mice.

METHODS

Sections of aortas of mice fed high cholesterol diet were collected at weeks 0, 4, 8, 12 and 19 and analyzed by immunohistochemistry and flow cytometry.

RESULTS

In the LDLr KO mice aorta, CD68 positivity (macrophage accumulation) increased over time up to 12 weeks, and then the accumulation fell modestly but significantly. The periaortal fat and adventitia showed more CD68 positivity than the media and intima. This pattern was also evident in the non-atherosclerotic areas. Importantly, LOX-1 KO and LDLr-LOX-1 double KO mice showed diminished CD68 positivity in comparison to wild type and LDLR KO mice, respectively. Further, macrophages from LOX-1 KO mice revealed a marked reduction in migration (vs. macrophages from wild type mice) in in vitro migration assay.

CONCLUSIONS

LOX-1 deletion translates into reduction in macrophage trafficking in the aorta of LDLr KO mice. Most of the macrophage trafficking appears in the subadventitial regions.

The influence of perivascular adipose tissue on vascular homeostasis

The perivascular adipose tissue (PVAT) is now recognized as an active contributor to vascular function. Adipocytes and stromal cells contained within PVAT are a source of an ever-growing list of molecules with varied paracrine effects on the underlying smooth muscle and endothelial cells, including adipokines, cytokines, reactive oxygen species, and gaseous compounds. Their secretion is regulated by systemic or local cues and modulates complex processes, including vascular contraction and relaxation, smooth muscle cell proliferation and migration, and vascular inflammation. Recent evidence demonstrates that metabolic and cardiovascular diseases alter the morphological and secretory characteristics of PVAT, with notable consequences. In obesity and diabetes, the expanded PVAT contributes to vascular insulin resistance. PVAT-derived cytokines may influence key steps of atherogenesis. The physiological anticontractile effect of PVAT is severely diminished in hypertension. Above all, a common denominator of the PVAT dysfunction in all these conditions is the immune cell infiltration, which triggers the subsequent inflammation, oxidative stress, and hypoxic processes to promote vascular dysfunction. In this review, we discuss the currently known mechanisms by which the PVAT influences blood vessel function. The important discoveries in the study of PVAT that have been made in recent years need to be further advanced, to identify the mechanisms of the anticontractile effects of PVAT, to explore the vascular-bed and species differences in PVAT function, to understand the regulation of PVAT secretion of mediators, and finally, to uncover ways to ameliorate cardiovascular disease by targeting therapeutic approaches to PVAT.

Cardiovascular disease in autoimmune rheumatic diseases

Various autoimmune rheumatic diseases (ARDs), including rheumatoid arthritis, spondyloarthritis, vasculitis and systemic lupus erythematosus, are associated with premature atherosclerosis. However, premature atherosclerosis has not been uniformly observed in systemic sclerosis. Furthermore, although experimental models of atherosclerosis support the role of antiphospholipid antibodies in atherosclerosis, there is no clear evidence of premature atherosclerosis in antiphospholipid syndrome (APA). Ischemic events in APA are more likely to be caused by pro-thrombotic state than by enhanced atherosclerosis. Cardiovascular disease (CVD) in ARDs is caused by traditional and non-traditional risk factors. Besides other factors, inflammation and immunologic abnormalities, the quantity and quality of lipoproteins, hypertension, insulin resistance/hyperglycemia, obesity and underweight, presence of platelets bearing complement protein C4d, reduced number and function of endothelial progenitor cells, apoptosis of endothelial cells, epigenetic mechanisms, renal disease, periodontal disease, depression, hyperuricemia, hypothyroidism, sleep apnea and vitamin D deficiency may contribute to the premature CVD. Although most research has focused on systemic inflammation, vascular inflammation may play a crucial role in the premature CVD in ARDs. It may be involved in the development and destabilization of both atherosclerotic lesions and of aortic aneurysms (a known complication of ARDs). Inflammation in subintimal vascular and perivascular layers appears to frequently occur in CVD, with a higher frequency in ARD than in non-ARD patients. It is possible that this inflammation is caused by infections and/or autoimmunity, which might have consequences for treatment. Importantly, drugs targeting immunologic factors participating in the subintimal inflammation (e.g., T- and B-cells) might have a protective effect on CVD. Interestingly, vasa vasorum and cardiovascular adipose tissue may play an important role in atherogenesis. Inflammation and complement depositions in the vessel wall are likely to contribute to vascular stiffness. Based on biopsy findings, also inflammation in the myocardium and small vessels may contribute to premature CVD in ARDs (cardiac ischemia and heart failure). There is an enormous need for an improved CVD prevention in ARDs. Studies examining the effect of DMARDs/biologics on vascular inflammation and CV risk are warranted.

Pentraxin 3, a novel cardiovascular biomarker, is expressed in aortic specimens of patients with coronary artery disease with and without rheumatoid arthritis

BACKGROUND

The aims were to evaluate the presence and extent of pentraxin 3 depositions in specimens from the outer layers of the aorta and from the internal thoracic artery of patients with coronary artery disease with and without rheumatoid arthritis and to search for relationships between pentraxin 3 and vascular inflammation.

METHODS

Using histochemistry and immunohistochemistry, we examined biopsies from the aortic adventitia and from the internal thoracic artery (both with adjacent perivascular tissue), removed during coronary artery bypass grafting in 19 rheumatoid arthritis and 20 non-rheumatoid-arthritis patients, for presence/extent of pentraxin 3 depositions, inflammatory cell infiltrates, and fibrosis.

RESULTS

In the aorta, pentraxin 3 deposition occurred in all specimens, mostly at sites with inflammatory cell infiltrates or fibrosis, and their extent was related to the extent of inflammatory cell infiltrates (rho=0.43, 95% confidence interval: 0.13-0.66, P=.007). The extent of pentraxin 3 and inflammatory cell infiltrates in the aorta was similar in rheumatoid arthritis and non-rheumatoid-arthritis patients, but rheumatoid arthritis patients had more fibrosis and a lower proportion of T-cells in inflammatory cell infiltrates. In the internal thoracic artery, pentraxin 3 occurred only in 36% patients, and inflammatory cell infiltrates and fibrosis occurred in none.

CONCLUSIONS

Pentraxin 3 depositions in the outer aortic layers are common and are related to the local inflammation. On the other hand, they occur less frequently in the internal thoracic artery, i.e., a vessel highly resistant to atherosclerosis. Rheumatoid arthritis patients had more pronounced fibrosis in the aortic specimens and a different leukocytic response than non-rheumatoid-arthritis patients. In theory, pentraxin 3 might modulate the inflammatory process involved in the pathogenesis of cardiovascular disease and represent a target for new therapies.

Relation of epicardial fat thickness with carotid intima-media thickness in patients with type 2 diabetes mellitus

Aims. The aim of this study was to investigate the relationship of echocardiographic epicardial fat thickness (EFT) with carotid intima-media thickness (CIMT), in patients with type 2 diabetes mellitus (T2DM). Methods and Results. A total of 139 patients with T2DM (mean age 54.3 ± 9.2 and 49.6% male) and 40 age and sex-matched control subjects were evaluated. Echocardiographic EFT and ultrasonographic CIMT were measured in all subjects. Patients with T2DM had significantly increased EFT and CIMT than those of the controls (6.0 ± 1.5 mm versus 4.42 ± 1.0 mm, P < 0.001 and 0.76 ± 0.17 mm versus 0.57 ± 0.14 mm, P < 0.001, resp.). EFT was correlated with CIMT, waist circumference, BMI, age, duration of T2DM, HbA1c in the type 2 diabetic patients. Linear regression analysis showed that CIMT (β = 3.52, t = 3.72, P < 0.001) and waist circumference (β = 0.36, t = 2.26, P = 0.03) were found to be independent predictors of EFT. A cutoff high risk EFT value of 6.3 mm showed a sensitivity and specificity of 72.5% and 71.7%, respectively, for the prediction of subclinical atherosclerosis. Conclusion. We found that echocardiographic EFT was significantly higher in patients with T2DM. Our study also showed that EFT was strongly correlated with waist circumference and CIMT as being independent of sex.

Preoperative diet impacts the adipose tissue response to surgical trauma

BACKGROUND

Short-term changes in preoperative nutrition can have profound effects on surgery-related outcomes such as ischemia/reperfusion injury in preclinical models. Dietary interventions that lend protection against stress in animal models (eg, fasting, dietary restriction [DR]) impact adipose tissue quality/quantity. Adipose tissue holds high surgical relevance because of its anatomic location and large tissue volume, and it is ubiquitously traumatized during surgery. Yet the response of adipose tissue to trauma under clinically relevant circumstances including dietary status remains poorly defined. We hypothesized that preoperative diet alters the adipose tissue response to surgical trauma.

METHODS

A novel mouse model of adipose tissue surgical trauma was employed. Dietary conditions (diet-induced obesity [DIO], preoperative DR) were modulated before application of surgical adipose tissue trauma in the context of clinically common scenarios (different ages, simulated bacterial wound contamination). Local/distant adipose tissue phenotypic responses were measured as represented by gene expression of inflammatory, tissue remodeling/growth, and metabolic markers.

RESULTS

Surgical trauma had a profound effect on adipose tissue phenotype at the site of trauma. Milder but significant distal effects on non-traumatized adipose tissue were also observed. DIO exacerbated the inflammatory aspects of this response, and preoperative DR tended to reverse these changes. Age and lipopolysaccharide (LPS)-simulated bacterial contamination also impacted the adipose tissue response to trauma, with young adult animals and LPS treatment exacerbating the proinflammatory response.

CONCLUSION

Surgical trauma dramatically impacts both local and distal adipose tissue biology. Short-term preoperative DR may offer a strategy to attenuate this response.

Human epicardial fat: what is new and what is missing?

1. Putative physiological functions of human epicardial adipose tissue (EAT) include: (i) lipid storage for the energy needs of the myocardium; (ii) thermoregulation, whereby brown fat components of EAT generate heat by non-shivering thermogenesis in response to core cooling; (iii) neuroprotection of the cardiac autonomic ganglia and nerves; and (iv) regulation of vasomotion and luminal size of the coronary arteries. Under pathophysiological circumstances, EAT may play an adverse paracrine role in cardiac arrhythmias and in lipotoxic cardiomyopathy, but of major current interest is its hypothetical role as an immunological organ contributing to inflammation around coronary artery disease (CAD). 2. The amount of EAT measured either by echocardiographic thickness over the free wall of the right ventricle or as volume by computed tomography expands in patients with obesity both without and with CAD. The mechanisms other than obesity governing the increase in EAT volume in CAD are unknown, but EAT around CAD is infiltrated by chronic inflammatory cells and overexpresses genes for adipokines that have pro- or anti-inflammatory actions and regulate oxidative stress plus angiogenesis. 3. Many cross-sectional studies have shown positive associations between increased EAT mass and stable CAD burden. One prospective population-based epidemiological study suggested that EAT volume at baseline is a predictor of acute myocardial infarction, but was without significant incremental predictive value after adjustment for established cardiovascular risk factors. However, strategies are needed to obtain robust epidemiological, interventional and experimental evidence to prove or disprove the hypothesis that EAT is a cardiovascular risk factor locally contributing to CAD.

Impact of uremia on human adipose tissue phenotype

BACKGROUND

Recognition of adipose-related signaling in surgery is increasing, although direct interrogation of human adipose has been sparse. Few scenarios rival uremia for health impact. We hypothesized that adipose from uremic patients holds a relatively higher adipose-derived hormone and proinflammatory adipokine signature; we simultaneously evaluated the impact of clinical parameters on adipose phenotype.

MATERIALS AND METHODS

Adipose was harvested from surgical patients. Histology and protein analyses were completed for select mediators.

RESULTS

In the overall cohort of 71 patients, the mean age was 63.4 y; 46.4% of patients had diabetes mellitus, 49.2% had hyperlipidemia, and 53.5% had coronary artery disease. Compared with nonuremic patients, uremic patients had one-tenth of the levels of leptin (P < 0.001), one-third of the levels of adiponectin (P < 0.001), and threefold higher levels of resistin (P < 0.001). Females had sixfold higher levels of leptin, 1.5-fold higher levels of adiponectin, and twofold higher levels of tumor necrosis factor alpha but equivalent resistin. There were differences in mediators when stratified by age. In both the obese and nonobese strata, we observed a concordant pattern of association (magnitude or significance) of uremia and leptin, adiponectin, and resistin. No differentials in other mediators emerged on body mass index stratification. Multiple regression analysis for leptin, adiponectin, and resistin (with age, gender, and uremia as independent variables) showed uremia as the highest independent predictor of all the three mediators.

CONCLUSIONS

Advanced chronic kidney disease is associated with perturbations in adipose-derived hormones (leptin, adiponectin, and resistin). Adipose adiponectin and leptin (in contrast to reported plasma levels) were lower in uremic patients; there is an inverse correlation between adipose resistin and renal function. Compared with other clinical parameters including body mass index, uremia dominates overall in determining adipose phenotype, highlighting the complex biological interplay between uremia and adipose biology.

Epicardial perivascular adipose tissue as a therapeutic target in obesity-related coronary artery disease

Adipose tissue is an active endocrine and paracrine organ that may influence the development of atherosclerosis and vascular disease. In the setting of obesity, adipose tissue produces a variety of inflammatory cytokines (or adipokines) that are known to modulate key mechanisms of atherogenesis. In particular, adipose tissue located on the surface of the heart surrounding large coronary arteries (i.e. epicardial perivascular adipose tissue) has been implicated in the pathogenesis of coronary artery disease. The present review outlines our current understanding of the cellular and molecular links between perivascular adipose tissue and atherosclerosis with a focus on potential mechanisms by which epicardial perivascular adipose tissue contributes to obesity-related coronary disease. The pathophysiology of perivascular adipose tissue in obesity and its influence on oxidative stress, inflammation, endothelial dysfunction and vascular reactivity is addressed. In addition, the contribution of specific epicardial perivascular adipose-derived adipokines (e.g. leptin, adiponectin) to the initiation and expansion of coronary disease is also highlighted. Finally, future investigative goals are discussed with an emphasis on indentifying novel therapeutic targets and disease markers within perivascular adipose tissue.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Noninvasive detection of intimal xanthoma using combined ultrasound, strain rate and photoacoustic imaging

BACKGROUND AND MOTIVATION

The structure, composition and mechanics of carotid artery are good indicators of early progressive atherosclerotic lesions. The combination of three imaging modalities (ultrasound, strain rate and photoacoustic imaging) which could provide corroborative information about the named arterial properties could enhance the characterization of intimal xanthoma.

METHODS

The experiments were performed using a New Zealand white rabbit model of atherosclerosis. The aorta excised from an atherosclerotic rabbit was scanned ex vivo using the three imaging techniques: (1) ultrasound imaging of the longitudinal section: standard ultrasound B-mode (74Hz frame rate); (2) strain rate imaging: the artery was flushed with blood and a 1.5Hz physiologic pulsation was induced, while the ultrasound data were recorded at higher frame rate (296Hz); (3) photoacoustic imaging: the artery was irradiated with nanosecond pulsed laser light of low fluence in the 1210-1230nm wavelength range and the photoacoustic data was recorded at 10Hz frame rate. Post processing algorithms based on cross-correlation and optical absorption variation were implemented to derive strain rate and spectroscopic photoacoustic images, respectively.

RESULTS

Based on the spatio-temporal variation in displacement of different regions within the arterial wall, strain rate imaging reveals differences in tissue mechanical properties. Additionally, spectroscopic photoacoustic imaging can spatially resolve the optical absorption properties of arterial tissue and identify the location of lipid pools.

CONCLUSIONS

The study demonstrates that ultrasound, strain rate and photoacoustic imaging can be used to simultaneously evaluate the structure, the mechanics and the composition of atherosclerotic lesions to improve the assessment of plaque vulnerability.

The impact of epicardial fat volume on coronary plaque vulnerability: insight from optical coherence tomography analysis

AIMS

Epicardial fat volume (EFV) has been implicated in coronary artery disease. Relationship between EFV and coronary plaque vulnerability has not been elucidated. The aim of this study was to investigate the association of EFV with coronary plaque vulnerability by using optical coherence tomography (OCT).

METHODS AND RESULTS

We enrolled 117 patients who underwent multislice computed tomography (MSCT) and OCT. EFV was quantified on MSCT. Patients were categorized according to tertiles of EFV: low tertile, EFV < 104.1 cm(3); mid-tertile, 104.1 cm(3)≤ EFV ≤ 130.7 cm(3); high tertile, EFV > 130.7 cm(3). A total of 180 vessels and 221 plaques were assessed with OCT to detect a thin-capped fibroatheroma (TCFA). TCFA was defined as a plaque with necrotic lipid pools ≥ 2 quadrants and minimum fibrous cap thickness measuring <65 μm. Patients with low computed tomographic attenuation and positive remodelling were frequently observed and patients with OCT-derived TCFA were more common in the high tertile EFV. EFV was associated with a maximal lipid arc (103.4 ± 28.2 cm(3) in 0 quadrant, 120.2 ± 35.2 cm(3) in 1-2 quadrants, and 131.5 ± 41.1 cm(3) in >2 quadrants; P= 0.01) and inversely correlated with a minimum fibrous cap thickness of the patients (r = -0.400, P<0.01). In multivariate analysis, the high tertile of EFV remained an independent predictor for patients with OCT-derived TCFA [odds ratio (OR) 2.92; 95% confidence interval (CI) 1.13-7.55; P= 0.027] and acute coronary syndrome (ACS) patients (OR 2.89; 95% CI 1.14-7.29; P= 0.025).

CONCLUSION

EFV was associated with coronary plaque vulnerability and high EFV was an independent predictor of ACS in patients with coronary artery disease.

Perivascular adipose tissue: more than just structural support

PVAT (perivascular adipose tissue) has recently been recognized as a novel factor in vascular biology, with implications in the pathophysiology of cardiovascular disease. Composed mainly of adipocytes, PVAT releases a wide range of biologically active molecules that modulate vascular smooth muscle cell contraction, proliferation and migration. PVAT exerts an anti-contractile effect in various vascular beds which seems to be mediated by an as yet elusive PVRF [PVAT-derived relaxing factor(s)]. Considerable progress has been made on deciphering the nature and mechanisms of action of PVRF, and the PVRFs proposed until now are reviewed here. However, complex pathways seem to regulate PVAT function and more than one mechanism is probably responsible for PVAT actions in vascular biology. The present review describes our current knowledge on the structure and function of PVAT, with a focus on its role in modulating vascular tone. Potential involvements of PVAT dysfunction in obesity, hypertension and atherosclerosis will be highlighted.

Clinical benefits of integrating cardiac and vascular models

INTRODUCTION

Recent advances in computational methods and medical imaging techniques have enabled non-invasive exploration of cardiovascular pathologies, from cardiac level to complex arterial networks. The potential of cardiac and vascular modeling in guiding and monitoring therapies could be further extended through the integration of the two systems.

AREAS COVERED

This review includes advances in methods for cardiac electromechanics and vascular flow simulations. The results of a literature search depicting the state of the art in cardiac and vascular modeling are reviewed. The paper goes on to address the benefits and challenges of combined cardiovascular modeling, highlighting the relevance of specific cardiovascular features and implementation. Various alternative approaches and insights on future directions are presented and analyzed with respect to their applicability to clinical practice.

EXPERT OPINION

The article has emerged from the exploration of currently available cardiac and vascular mathematical tools and their corresponding clinical application. The summarized analysis suggests that future efforts should be aimed at developing more accurate and patient-specific mathematical models integrating cardiac and vascular functions to enhance the knowledge of cardiovascular pathologies.

Thermal intravascular photoacoustic imaging

Intravascular photoacoustics (IVPA)-a minimally invasive imaging technique with contrast related to optical absorption properties of tissue, can be used to visualize atherosclerotic plaques. However, the amplitude of photoacoustic signals is also related to a temperature dependent, tissue specific parameter-the Grüneisen parameter. Therefore, photoacoustic signals measured at different temperatures may reveal information about tissue composition. In this study, thermal IVPA (tIVPA) imaging was introduced. The imaging studies were performed using an ex vivo atherosclerotic rabbit aorta. Temperature dependent photoacoustic responses from lipid in plaques and lipid in periadventitial tissue were different, thus allowing tIVPA images to delineate the location of lipid-rich plaques. The results indicate that tIVPA imaging has a potential to characterize tissue composition in atherosclerotic vessels.

Indoleamine 2,3-diooxygenase in periaortic fat: mechanisms of inhibition of contraction

Indoleamine 2,3-dioxygenase (IDO) metabolizes L-tryptophan to L-kynurenine, promotes immunosuppression, and has been described as a consumer of superoxide. We discovered IDO expression in periaortic fat and tested the hypothesis that periarterial IDO functionally reduces agonist-induced contraction. Our model was the thoracic aorta, abdominal aorta, and superior mesenteric artery of the male Sprague-Dawley rat. Periaortic fat from the thoracic aorta stained intensely for IDO, the brown fat marker uncoupling protein-1, and oil red O as a general lipid marker. White fat around the mesenteric artery and abdominal aorta stained less for IDO; brown fat was less abundant. IDO activity (kynurenine-to-tryptophan ratio via HPLC) was detected in visceral and mesenteric artery fat (ratio: ∼4) but was highest in perithoracic aortic fat (ratio: 10 ± 1.1). In isometric contractile experiments, periadventitial fat reduced ANG II-induced thoracic aortic (with fat: 34% of without fat) and mesenteric artery (with fat: 63% of without fat) maximal contraction. In contrast, periadventitial fat did not reduce agonist-induced contraction in the abdominal aorta. The IDO inhibitor 1-L-methyltryptophan (1-MT) reversed the fat-induced reduction of ANG II-induced contraction in the thoracic aorta but not in the mesenteric artery. The IDO metabolite kynurenine relaxed the thoracic aorta only at high (9 mM) concentrations, whereas the downstream metabolite quinolinic acid (1 mM) relaxed the contracted thoracic aorta (∼80%). 1-MT did not correct the reduction in basal superoxide levels observed in the presence of perithoracic aortic fat. We conclude that IDO is an enzyme active primarily in brown fat surrounding the thoracic aorta and depresses aortic contractility.

Similarity of mouse perivascular and brown adipose tissues and their resistance to diet-induced inflammation

Thoracic perivascular adipose tissue (PVAT) is a unique adipose depot that likely influences vascular function and susceptibility to pathogenesis in obesity and the metabolic syndrome. Surprisingly, PVAT has been reported to share characteristics of both brown and white adipose, but a detailed direct comparison to interscapular brown adipose tissue (BAT) has not been performed. Here we show by full genome DNA microarray analysis that global gene expression profiles of PVAT are virtually identical to BAT, with equally high expression of Ucp-1, Cidea, and other genes known to be uniquely or very highly expressed in BAT. PVAT and BAT also displayed nearly identical phenotypes upon immunohistochemical analysis, and electron microscopy confirmed that PVAT contained multilocular lipid droplets and abundant mitochondria. Compared with white adipose tissue (WAT), PVAT and BAT from C57BL6/J mice fed a high-fat diet for 13 wk had markedly lower expression of immune cell-enriched mRNAs, suggesting resistance to obesity-induced inflammation. Indeed, staining of BAT and PVAT for macrophage markers (F4/80 and CD68) in obese mice showed virtually no macrophage infiltration, and FACS analysis of BAT confirmed the presence of very few CD11b(+)/CD11c(+) macrophages in BAT (1.0%) compared with WAT (31%). In summary, murine PVAT from the thoracic aorta is virtually identical to interscapular BAT, is resistant to diet-induced macrophage infiltration, and thus may play an important role in protecting the vascular bed from inflammatory stress.

The inflammatory preatherosclerotic remodeling induced by intermittent hypoxia is attenuated by RANTES/CCL5 inhibition

RATIONALE

The highly prevalent obstructive sleep apnea syndrome (OSA) with its main component intermittent hypoxia (IH) is a risk factor for cardiovascular mortality. The poor knowledge of its pathophysiology has limited the development of specific treatments, whereas the gold standard treatment, continuous positive airway pressure, may not fully reverse the chronic consequences of OSA and has limited acceptance in some patients.

OBJECTIVES

To examine the contribution of IH-induced inflammation to the cardiovascular complications of OSA.

METHODS

We investigated systemic and vascular inflammatory changes in C57BL6 mice exposed to IH (21-5% Fi(O(2)), 60-s cycle) or normoxia 8 hours per day up to 14 days. Vascular alterations were reassessed in mice treated with a blocking antibody of regulated upon activation, normal T-cell expressed and secreted (RANTES)/CC chemokine ligand 5 (CCL5) signaling pathway, or with the IgG isotype control throughout the IH exposure.

MEASUREMENTS AND MAIN RESULTS

IH induced systemic inflammation combining increased splenic lymphocyte proliferation and chemokine expression, with early and predominant RANTES/CCL5 alterations, and enhanced splenocyte migration toward RANTES/CCL5. IH also induced structural and inflammatory vascular alterations. Leukocyte-endothelium adhesive interactions were increased, attested by leukocyte rolling and intercellular adhesion molecule-1 expression in mesenteric vessels. Aortas had increased intima-media thickness with elastic fiber alterations, mucoid depositions, nuclear factor-κB-p50 and intercellular adhesion molecule-1 overexpression, hypertrophy of smooth-muscle cells overexpressing RANTES/CCL5, and adventitial-periadventitial T-lymphocyte infiltration. RANTES/CCL5 neutralization prevented both intima-media thickening and inflammatory alterations, independently of the IH-associated proatherogenic dyslipidemia.

CONCLUSIONS

Inflammation is a determinant mechanism for IH-induced preatherosclerotic remodeling involving RANTES/CCL5, a key chemokine in atherogenesis. Characterization of the inflammatory response could allow identifying at-risk patients for complications, and its pharmacologic manipulation may represent a potential complementary treatment of sleep apnea consequences.

Emerging diagnostic and therapeutic molecular imaging applications in vascular disease

Assessment of vascular disease has evolved from mere indirect and direct measurements of luminal stenosis to sophisticated imaging methods to depict millimeter structural changes of the vasculature. In the near future, the emergence of multimodal molecular imaging strategies may enable robust therapeutic and diagnostic ('theragnostic') approaches to vascular diseases that comprehensively consider structural, functional, biological and genomic characteristics of the disease in individualized risk assessment, early diagnosis and delivery of targeted interventions.This review presents a summary of recent preclinical and clinical developments in molecular imaging and theragnostic applications covering diverse atherosclerosis events such as endothelial activation, macrophage inflammatory activity, plaque neovascularization and arterial thrombosis. The main focus is on molecular targets designed for imaging platforms commonly used in clinical medicine including magnetic resonance, computed tomography and positron emission tomography. A special emphasis is given to vascular ultrasound applications, considering the important role this imaging platform plays in the clinical and research practice of the vascular medicine specialty.

Perivascular adipose tissue and vascular disease

Perivascular adipose tissue is a local deposit of adipose tissue surrounding the vasculature. Perivascular adipose tissue is present throughout the body and has been shown to have a local effect on blood vessels. The influence of perivascular adipose tissue on the vasculature changes with increasing adiposity. This article describes the anatomy and pathophysiology of perivascular adipose tissue and the experimental evidence supporting its local adverse effect on the vasculature. Methods for quantifying perivascular adipose tissue in free-living populations will be described. Finally, the epidemiological literature demonstrating an association between perivascular adipose tissue and cardiometabolic disease will be explored.