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

Lower estimates of myocardial perfusion are associated with greater aortic perivascular adipose tissue density in humans independent of aortic stiffness

Aortic perivascular adipose tissue (aPVAT) density is associated with age-related aortic stiffness in humans and therefore, may contribute to cardiovascular dysfunction. A lower subendocardial viability ratio (SEVR), an estimate of myocardial perfusion, indicates greater cardiovascular disease (CVD) risk and is associated with aortic stiffness in clinical populations. However, the influence of aortic stiffness on the relation between aPVAT density and SEVR/cardiovascular (CV) hemodynamics in apparently healthy adults is unknown. We hypothesize that greater aPVAT density will be associated with lower SEVR and higher CV hemodynamics independent of aortic stiffness. Fourteen (6 males/8 females; mean age, 55.4 ± 5.6 yr; body mass index, 25.5 ± 0.6 kg/m2) adults completed resting measures of myocardial perfusion (SEVR), CV hemodynamics (pulse wave analysis), aortic stiffness [carotid-femoral pulse wave velocity (cfPWV)], and a computed tomography scan to acquire aPVAT and visceral adipose tissue (VAT) density. Greater aPVAT density (i.e., higher density) was associated with lower SEVR (r = -0.78, P < 0.001) and a higher systolic pressure time integral (r = 0.49, P = 0.03), forward pulse height (r = 0.49, P = 0.03), reflected pulse height (r = 0.55, P = 0.02), ejection duration (r = 0.56, P = 0.02), and augmentation pressure (r = 0.69, P = 0.003), but not with the diastolic pressure time integral (r = -0.22, P = 0.22). VAT density was not associated with SEVR or any CV hemodynamic endpoints (all, P > 0.05). Furthermore, the relation between aPVAT density and SEVR remained after adjusting for aortic stiffness (r = -0.66, P = 0.01) but not age (r = -0.24, P > 0.05). These data provide initial evidence for aPVAT as a novel yet understudied local fat depot contributing to lower myocardial perfusion in apparently healthy adults with aging.NEW & NOTEWORTHY Aortic perivascular adipose tissue (aPVAT) density is associated with aging and aortic stiffness in humans and, therefore, may contribute to lower myocardial perfusion. We demonstrate that greater aPVAT, but not visceral adipose tissue density is associated with lower myocardial perfusion and augmentation pressure independent of aortic stiffness, but not independent of age. These data provide novel evidence for aPVAT as a potential therapeutic target to improve myocardial perfusion and cardiovascular function in humans with aging.

An Obligatory Role of Perivascular Adipose Tissue in Improved Saphenous Vein Graft Patency in Coronary Artery Bypass Grafting

The gold standard graft for coronary artery bypass grafting (CABG) is the internal thoracic artery (ITA), and the second recommendation is the radial artery. However, complete revascularization with arterial grafts alone is often difficult, and the saphenous vein (SV) is the most commonly used autologous graft for CABG, because it is easier to use without restriction for the length of the graft. On the other hand, the patency of SV grafts (SVGs) is poor compared with that of arterial grafts. The SVG is conventionally harvested as a distended conduit with surrounding tissue removed, a procedure that may cause vascular damage. A no-touch technique of SVG harvesting has been reported to result in improved long-term patency in CABG comparable to that when using the ITA for grafting. Possible reasons for the excellent long-term patency of no-touch SVGs are the physical support provided by preserved surrounding perivascular adipose tissue, preservation of the vascular wall structure including the vasa vasorum, and production of adipocyte-derived factors. In this review, we discuss recent strategies aimed at improving the performance of SVGs, including no-touch harvesting, minimally invasive harvesting and mechanical support using external stents.

Perivascular fat tissue and vascular aging: A sword and a shield

The understanding of the function of perivascular adipose tissue (PVAT) in vascular aging has significantly changed due to the increasing amount of information regarding its biology. Adipose tissue surrounding blood vessels is increasingly recognized as a key regulator of vascular disorders. It has significant endocrine and paracrine effects on the vasculature and is mediated by the production of a variety of bioactive chemicals. It also participates in a number of pathological regulatory processes, including oxidative stress, immunological inflammation, lipid metabolism, vasoconstriction, and dilation. Mechanisms of homeostasis and interactions between cells at the local level tightly regulate the function and secretory repertoire of PVAT, which can become dysregulated during vascular aging. The PVAT secretion group changes from being reducing inflammation and lowering cholesterol to increasing inflammation and increasing cholesterol in response to systemic or local inflammation and insulin resistance. In addition, the interaction between the PVAT and the vasculature is reciprocal, and the biological processes of PVAT are directly influenced by the pertinent indicators of vascular aging. The architectural and biological traits of PVAT, the molecular mechanism of crosstalk between PVAT and vascular aging, and the clinical correlation of vascular age-related disorders are all summarized in this review. In addition, this paper aims to elucidate and evaluate the potential benefits of therapeutically targeting PVAT in the context of mitigating vascular aging. Furthermore, it will discuss the latest advancements in technology used for targeting PVAT.

Influence of Perivascular Adipose Tissue on Microcirculation: A Link Between Hypertension and Obesity

Alterations in microcirculation play a crucial role in the pathogenesis of cardiovascular and metabolic disorders such as obesity and hypertension. The small resistance arteries of these patients show a typical remodeling, as indicated by an increase of media or total wall thickness to lumen diameter ratio that impairs organ flow reserve. The majority of blood vessels are surrounded by a fat depot which is termed perivascular adipose tissue (PVAT). In recent years, data from several studies have indicated that PVAT is an endocrine organ that can produce a variety of adipokines and cytokines, which may participate in the regulation of vascular tone, and the secretory profile varies with adipocyte phenotype and disease status. The PVAT of lean humans largely secretes the vasodilator adiponectin, which will act in a paracrine fashion to reduce peripheral resistance and improve nutrient uptake into tissues, thereby protecting against the development of hypertension and diabetes. In obesity, PVAT becomes enlarged and inflamed, and the bioavailability of adiponectin is reduced. The inevitable consequence is a rise in peripheral resistance with higher blood pressure. The interrelationship between obesity and hypertension could be explained, at least in part, by a cross-talk between microcirculation and PVAT. In this article, we propose an integrated pathophysiological approach of this relationship, in order to better clarify its role in obesity and hypertension, as the basis for effective and specific prevention and treatment.

Homocysteine impairs the anticontractile/vasorelaxing activity of perivascular adipose tissue surrounding human internal mammary artery

OBJECTIVES

Perivascular adipose tissue (PVAT) surrounding human internal mammary artery (IMA) possesses anticontractile property. Its function under pathological conditions is barely studied. We previously reported that homocysteine impairs the vasodilator function of IMA through endothelium and smooth muscle-dependent mechanisms. This study investigated the effect of homocysteine on the function of PVAT and the associated mechanisms.

METHODS

Residual IMA tissues were collected from patients undergoing coronary artery bypass grafting. Vasoreactivity was studied using myograph. Adiponectin was measured by ELISA. Expressions of adiponectin receptors (AdipoRs), eNOS and p-eNOS were determined by RT-qPCR and Western blot.

RESULTS

Exposure to homocysteine augmented the contractile responses of PVAT-intact IMA to U46619 and potassium chloride, regardless with or without endothelium. Such augmentation was also observed in skeletonized IMA with transferred, homocysteine-exposed PVAT. Homocysteine attenuated the relaxant response of PVAT-intact while endothelium-denuded vessels to acetylcholine. Homocysteine lowered adiponectin content in the PVAT, downregulated the expression of AdipoR1 and AdipoR2 as well as eNOS and p-eNOS in skeletonized IMA. The relaxant response of skeletonized IMA to AdipoR agonist AdipoRon was blunted by homocysteine or eNOS inhibitor, and homocysteine significantly attenuated the inhibitory effect of eNOS inhibitor on AdipoRon-induced relaxation.

CONCLUSIONS

Homocysteine impairs the anticontractile/vasorelaxing activity of PVAT surrounding the IMA through inhibiting adiponectin/AdipoR/eNOS/nitric oxide signalling pathway.

Single-Cell RNA Sequencing of Coronary Perivascular Adipose Tissue From End-Stage Heart Failure Patients Identifies SPP1+ Macrophage Subpopulation as a Target for Alleviating Fibrosis

BACKGROUND

Perivascular adipose tissue (PVAT) is vital for vascular homeostasis, and PVAT dysfunction is associated with increased atherosclerotic plaque burden. But the mechanisms underlining coronary PVAT dysfunction in coronary atherosclerosis remain elusive.

METHODS

We performed single-cell RNA sequencing of the stromal vascular fraction of coronary PVAT from 3 groups of heart transplant recipients with end-stage heart failure, including 3 patients with nonobstructive coronary atherosclerosis, 3 patients with obstructive coronary artery atherosclerosis, and 4 nonatherosclerosis control subjects. Bioinformatics was used to annotate the cellular populations, depict the cellular developmental trajectories and interactions, and explore the differences among 3 groups of coronary PVAT at the cellular and molecular levels. Pathological staining, quantitative real-time polymerase chain reaction, and in vitro studies were performed to validate the key findings.

RESULTS

Ten cell types were identified among 67 936 cells from human coronary PVAT. Several cellular subpopulations, including SPP1+ (secreted phosphoprotein 1) macrophages and profibrotic fibroadipogenic progenitor cells, were accumulated in PVAT surrounding atherosclerotic coronary arteries compared with nonatherosclerosis coronary arteries. The fibrosis percentage was increased in PVAT surrounding atherosclerotic coronary arteries, and it was positively associated with the grade of coronary artery stenosis. Cellular interaction analysis suggested OPN (osteopontin) secreted by SPP1+ macrophages interacted with CD44 (cluster of differentiation 44)/integrin on fibroadipogenic progenitor cells. Strikingly, correlation analyses uncovered that higher level of SPP1 in PVAT correlates with a more severe fibrosis degree and a higher coronary stenosis grade. In vitro studies showed that conditioned medium from atherosclerotic coronary PVAT promoted the migration and proliferation of fibroadipogenic progenitor cells, while such effect was prevented by blocking CD44 or integrin.

CONCLUSIONS

SPP1+ macrophages accumulated in the PVAT surrounding atherosclerotic coronary arteries, and they promoted the migration and proliferation of fibroadipogenic progenitor cells via OPN-CD44/integrin interaction and thus aggravated the fibrosis of coronary PVAT, which was positively correlated to the coronary stenosis burden. Therefore, SPP1+ macrophages in coronary PVAT may participate in the progression of coronary atherosclerosis.

Obesity phenotypes and cardiovascular risk: From pathophysiology to clinical management

Obesity epidemic reached the dimensions of a real global health crisis with more than one billion people worldwide living with obesity. Multiple obesity-related mechanisms cause structural, functional, humoral, and hemodynamic alterations with cardiovascular (CV) deleterious effects. A correct assessment of the cardiovascular risk in people with obesity is critical for reducing mortality and preserving quality of life. The correct identification of the obesity status remains difficult as recent evidence suggest that different phenotypes of obesity exist, each one associated with different degrees of CV risk. Diagnosis of obesity cannot depend only on anthropometric parameters but should include a precise assessment of the metabolic status. Recently, the World Heart Federation and World Obesity Federation provided an action plan for management of obesity-related CV risk and mortality, stressing for the instauration of comprehensive structured programs encompassing multidisciplinary teams. In this review we aim at providing an updated summary regarding the different obesity phenotypes, their specific effects on CV risk and differences in clinical management.

Comparison of Phenotypes in Subcutaneous Fat and Perivascular Adipose Tissue Surrounding the Saphenous Vein in Coronary Artery Bypass Grafting

BACKGROUND

The saphenous vein (SV) is used as an essential conduit in coronary artery bypass grafting (CABG), but the long-term patency of SV grafts is a crucial issue. The use of the novel "no-touch" technique of harvesting the SV together with its surrounding tissue has been reported to result in good long-term graft patency of SV grafts. We recently showed that perivascular adipose tissue (PVAT) surrounding the SV (SV-PVAT) had lower levels of metaflammation and consecutive adipose tissue remodeling than did PVAT surrounding the coronary artery. However, the difference between SV-PVAT and subcutaneous adipose tissue (SCAT) remains unclear.

METHODS AND RESULTS

Fat pads were sampled from 55 patients (38 men, 17 women; mean [±SD] age 71±8 years) with coronary artery disease who underwent elective CABG. Adipocyte size was significantly larger in SV-PVAT than SCAT. The extent of fibrosis was smaller in SV-PVAT than SCAT. There were no significant differences between SCAT and SV-PVAT in macrophage infiltration area, quantified by antibodies for CD68, CD11c, and CD206, or in gene expression levels of metaflammation-related markers. Expression patterns of adipocyte developmental and pattern-forming genes differed between SCAT and SV-PVAT.

CONCLUSIONS

The properties of SV-PVAT are close to, but not the same as, those of SCAT, possibly resulting from inherent differences in adipocytes. SV-PVAT has healthy expansion with less fibrosis in fat than SCAT.

The relation between pericoronary fat thickness and density quantified by coronary computed tomography angiography with coronary artery disease severity

OBJECTIVE

To study the correlation between epicardial fat thickness (EFT), pericoronary fat thickness (PCFT), and pericoronary fat density (PCFD) with the existence and severity of coronary artery disease (CAD).

METHODS

This cross-sectional study included 210 patients referred for multislice CT angiography. Group I normal CTCA, Group II patients had non-obstructive atherosclerosis, and Group III patients had obstructive atherosclerosis. All patients underwent a clinical examination, history taking, and multislice CT angiography.

RESULTS

The mean EFT was significantly greater in group III (10.43 ± 2.31 mm) compared to groups II (6.30 ± 1.61 mm) and I (5.06 ± 1.14 mm). The mean PCFT was significantly greater in group III (17.96 ± 2.89 mm) compared to group II (11.47 ± 2.51 mm) and group I (9.67 ± 1.99 mm). PCFD was significantly higher adjacent to the lesion (-80.47 ± 29.14) compared to the normal segment (-109.03 ± 35.24), higher in the obstructive group (-59.44 ± 20.10) compared to the non-obstructive group (-101.51 ± 20.23), but lower in calcified lesions (-89.58 ± 28.94) compared to non-calcified (-75.01 ± 29.20), and mixed lesions (-74.83 ± 26.90). EFT and PCFT cut-off values for predicting obstructive CAD were 8.3 and 12.4 mm, respectively, with 87.1% and 92.9% sensitivity and 92.9% and 86.4% specificity, respectively.

CONCLUSION

There is a significant association between epicardial fat thickness, pericoronary fat thickness and density with the severity of coronary artery disease.

Perivascular mechanical environment: A narrative review of the role of externally applied mechanical force in the pathogenesis of atherosclerosis

Atherosclerosis is promoted by systemic factors, such as dyslipidemia, hypertension, diabetes, and smoking, which cause atherosclerosis in blood vessels throughout the body. However, atherosclerotic lesions are characterized by their frequent occurrence in specific vessels and sites. Blood vessels are exposed to various mechanical forces related to blood pressure and flow. Although shear stress promotes the initiation and progression of atherosclerotic lesions, the pathogenesis of site specificity of atherosclerosis is not sufficiently explained by shear stress. We propose the concept of a perivascular mechanical environment (PVME). Compelling evidence suggests that site specificity in atherosclerotic lesions depends on a distinct local PVME. Atheroprone arteries, such as the coronary artery, are markedly affected by externally applied mechanical force (EMF), whereas atheroprotective arteries, such as the internal thoracic artery, are less affected. Recent studies have shown that the coronary artery is affected by cardiac muscle contraction, the carotid artery by the hyoid bone and the thyroid cartilage, and the abdominal aorta and lower extremity arteries by musculoskeletal motion. We speculate that the thoracic cage protects the internal thoracic artery from EMF owing to a favorable PVME. Furthermore, evidence suggests that plaque eccentricity is provided by EMF; plaques are frequently observed on an external force-applied side. In each vascular tree, site-specific characteristics of the PVME differ substantially, inducing individual atherogenicity. From the perspective of the mechanical environment, hemodynamic stress occurs in an inside-out manner, whereas EMF occurs in an outside-in manner. These inward and outward forces apply mechanical load individually, but interact synergistically. The concept of a PVME is a novel pathogenesis of atherosclerosis and also might be a pathogenesis of other arterial diseases.

Comprehensive Analysis of Differentially Expressed lncRNAs in the Perivascular Adipose Tissue of Patients with Coronary Heart Disease

Background

Coronary heart disease is a highly prevalent inflammatory disease caused by coronary atherosclerosis. Numerous studies have revealed that perivascular adipose tissue is closely associated with atherosclerosis. Here, we conducted a comprehensive analysis of long non-coding RNAs and mRNAs differentially expressed in perivascular adipose tissue in patients with coronary heart disease.

Methods

We conducted Gene Ontology term and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses of the differentially expressed genes. Furthermore, single sample gene set enrichment analysis, immune infiltration analysis, and co-expression analysis of differentially expressed long non-coding RNAs and immune gene sets were performed. Finally, the starBase and miRTarBase databases were used to construct a competing endogenous RNA network.

Results

The results show that aortic perivascular adipose tissue has higher inflammation and immune infiltration levels in patients with coronary heart disease. Dysregulated long non-coding RNAs may be related to immunity, inflammation, and hypoxia.

Conclusions

The findings of this study provide new insights into atherosclerosis and coronary heart disease.

Perivascular adipose tissue in autoimmune rheumatic diseases

Perivascular adipose tissue (PVAT) resides at the outermost boundary of the vascular wall, surrounding most conduit blood vessels, except for the cerebral vessels, in humans. A growing body of evidence suggests that inflammation localized within PVAT may contribute to the pathogenesis of cardiovascular disease (CVD). Patients with autoimmune rheumatic diseases (ARDs), e.g., systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), psoriasis, etc., exhibit heightened systemic inflammation and are at increased risk for CVD. Data from clinical studies in patients with ARDs support a linkage between dysfunctional adipose tissue, and PVAT in particular, in disease pathogenesis. Here, we review the data linking PVAT to the pathogenesis of CVD in patients with ARDs, focusing on the role of novel PVAT imaging techniques in defining disease risk and responses to biological therapies.

The Role of Angiogenesis and Arteriogenesisin Myocardial Infarction and Coronary Revascularization

Surgical myocardial revascularization is associated with long-term survival benefit in patients with multivessel coronary artery disease. However, the exact biological mechanisms underlying the clinical benefits of myocardial revascularization have not been elucidated yet. Angiogenesis and arteriogenesis biologically leading to vascular collateralization are considered one of the endogenous mechanisms to preserve myocardial viability during ischemia, and the presence of coronary collateralization has been regarded as one of the predictors of long-term survival in patients with coronary artery disease (CAD). Some experimental studies and indirect clinical evidence on chronic CAD confirmed an angiogenetic response induced by myocardial revascularization and suggested that revascularization procedures could constitute an angiogenetic trigger per se. In this review, the clinical and basic science evidence regarding arteriogenesis and angiogenesis in both CAD and coronary revascularization is analyzed with the aim to better elucidate their significance in the clinical arena and potential therapeutic use.

Macrophage Polarization in the Perivascular Fat Was Associated With Coronary Atherosclerosis

Background Inflammation of the perivascular adipose tissue (PvAT) may be related to atherosclerosis; however, the association of polarized macrophages in the pericoronary PvAT with measurements of atherosclerosis components in humans has not been fully investigated. Methods and Results Coronary arteries were dissected with surrounding PvAT. We evaluated the percentage of arterial obstruction, intima-media thickness, fibrous cap thickness, plaque components, and the number of vasa vasorum. The number of proinflammatory (M1) and anti-inflammatory (M2) macrophages in the periplaque and control PvAT were evaluated using immunohistochemistry. Regression models adjusted for sociodemographic and clinical variables were used. In 319 segments from 82 individuals, we found a correlation of the M1/M2 macrophage density ratio with an increase in arterial obstruction (P=0.02) and lipid content (P=0.01), and a decrease in smooth muscle cells (P=0.02). M1 and the ratio of M1/M2 macrophages were associated with an increased risk of thrombosis (P=0.03). In plaques with thrombosis, M1 macrophages were correlated with a decrease in fibrous cap thickness (P=0.006), an increase in lipid content (P=0.008), and the number of vasa vasorum in the adventitia layer (P=0.001). M2 macrophages were correlated with increased arterial obstruction (P=0.01), calcification (P=0.02), necrosis (P=0.03) only in plaques without thrombosis, and decrease of the number of vasa vasorum in plaques with thrombosis (P=0.003). Conclusions M1 macrophages in the periplaque PvAT were associated with a higher risk of coronary thrombosis and were correlated with histological components of plaque progression and destabilization. M2 macrophages were correlated with plaque size, calcification, necrotic content, and a decrease in the number of vasa vasorum in the adventitia layer.

Carotid Artery Perivascular Adipose Tissue Density Relates to Recanalization and Clinical Outcome After Mechanical Thrombectomy

Background: Perivascular adipose tissue (PVAT) imaging can be used in clinical practice as a surrogate marker of vascular disease. We aimed to analyze the association between the density of carotid artery PVAT and clinical features and outcomes in stroke patients treated with mechanical thrombectomy.

Methods: A total of 183 consecutive patients treated with mechanical thrombectomy due to anterior circulation large vessel occlusion were retrospectively included from January 2016 to May 2021. The density of carotid artery PVAT was evaluated by preoperative computed tomography angiography. Successful arterial recanalization was defined as a modified Thrombolysis in Cerebral Infarction score of 2b-3 on the final angiographic examination. Poor functional outcome was defined as a modified Rankin Scale (mRS) score > 2 at 3 months after stroke. We assessed the independent effect of carotid artery PVAT density on revascularization, functional outcome, and mortality using logistic regression models adjusted for relevant confounders.

Results: Patients with large artery atherosclerotic stroke have higher carotid artery PVAT density than patients with other stroke etiologies (–65.82 ± 12.96 vs. –75.77 ± 13.44, P < 0.001). Higher carotid artery PVAT density was associated with unsuccessful recanalization [adjusted odds ratio (AOR) (95% CI), 2.968 (1.292, 6.819), P = 0.010], and poor outcome [AOR (95% CI), 2.704 (1.610, 4.541), P < 0.001] and mortality [AOR (95% CI), 1.894 (1.040, 3.449), P = 0.037] at 3 months in stroke patients treated with thrombectomy.

Conclusion: Higher carotid artery PVAT density before mechanical thrombectomy is an indicator of worse postprocedural arterial revascularization and a worse functional outcome in acute stroke patients.

Association of Pericoronary Adipose Tissue Quality Determined by Dual-Layer Spectral Detector CT With Severity of Coronary Artery Disease: A Preliminary Study

Background: Pericoronary adipose tissue (PCAT) is considered as a source of inflammatory mediators, leading to the development of coronary atherosclerosis. The study aimed to investigate the correlation between PCAT quality derived from dual-layer spectral detector CT (SDCT) and the severity of coronary artery disease (CAD), and whether PCAT parameters were independently associated with the presence of CAD.

Materials and Methods: A total of 403 patients with symptoms of chest pain who underwent SDCT were included. PCAT quality including fat attenuation index (FAI) measured from conventional polychromatic CT images (FAI_120kvp) and spectral virtual mono-energetic images at 40 keV (FAI_40keV), slope of spectral HU curve (λ_HU), and effective atomic number (Eff-Z) were measured around the lesions representing the maximal degree of vascular stenosis in each patient. Meanwhile, overall epicardial adipose tissue (EAT) attenuation was acquired in the conventional polychromatic energy imaging.

Results: FAI_40keV, λ_HU, Eff-Z, and FAI_120kvp increased along with the degree of CAD in general and were superior to the overall EAT attenuation for detecting the presence of CAD. Multivariate logistic regression analysis indicated that FAI_40keV was the most powerful independent indicator (odds ratio 1.058, 95% CI 1.044–1.073; p < 0.001) of CAD among these parameters. Using an optimal cut-off (−131.8 HU), FAI_40keV showed higher diagnostic accuracy of 80.6% compared with the other parameters.

Conclusions: These preliminary findings suggest that FAI_40keV on SDCT may be an appealing surrogate maker to allow monitoring of PCAT changes in the development of CAD.

Regional Heterogeneity of Perivascular Adipose Tissue: Morphology, Origin, and Secretome

Perivascular adipose tissue (PVAT) is a unique fat depot with local and systemic impacts. PVATs are anatomically, developmentally, and functionally different from classical adipose tissues and they are also different from each other. PVAT adipocytes originate from different progenitors and precursors. They can produce and secrete a wide range of autocrine and paracrine factors, many of which are vasoactive modulators. In the context of obesity-associated low-grade inflammation, these phenotypic and functional differences become more evident. In this review, we focus on the recent findings of PVAT’s heterogeneity by comparing commonly studied adipose tissues around the thoracic aorta (tPVAT), abdominal aorta (aPVAT), and mesenteric artery (mPVAT). Distinct origins and developmental trajectory of PVAT adipocyte potentially contribute to regional heterogeneity. Regional differences also exist in ways how PVAT communicates with its neighboring vasculature by producing specific adipokines, vascular tone regulators, and extracellular vesicles in a given microenvironment. These insights may inspire new therapeutic strategies targeting the PVAT.

Overexpression of retinoid X receptor beta provides protection against oxidized low-density lipoprotein-induced inflammation via regulating PGC1α-dependent mitochondrial homeostasis in endothelial cells

Retinoid X receptor beta (RXRβ) has been poorly studied in atherosclerosis. The aim of the present study is to explore the function of RXRβ in oxidized low density lipoprotein (ox-LDL)-induced inflammation in endothelial cells and the underlying mechanism. The protein expression of RXRβ in the aorta of atherosclerotic mice was detected. A lentivirus vector for RXRβ overexpression and RNA interference for RXRβ downregulation were constructed and transfected into human aortic endothelial cells (HAECs). The results showed that RXRβ protein expression was downregulated in aorta of high fat diet (HFD)-fed LDLr^-/- mice and ox-LDL-treated HAECs. The ox-LDL-induced production of pro-inflammatory cytokines and activations of TLR9/NF-κB and NLRP3/caspase-1 inflammasome pathway were significantly decreased by RXRβ overexpression but increased by RXRβ knockdown in HAECs. The ox‑LDL‑induced mitochondrial damage indicated as the increased generation of mitochondrial ROS, decreased mitochondrial membrane potential and increased mitochondrial DNA release was abolished by RXRβ overexpression but aggravated by RXRβ knockdown. Treatment with mito-TEMPO significantly reduced the increased production of pro-inflammatory cytokines and activations of TLR9/NF-κB and NLRP3/caspase-1 inflammasome induced by RXRβ knockdown in ox-LDL treated HAECs. Moreover, peroxisome proliferator-activated receptor-γ coactivator1α (PGC1α) protein expression was reduced in HFD-fed LDLr^-/- mice. RXRβ could interact with PGC1α in HAECs. Ox-LDL-induced reduction of PGC1α was significantly inhibited by RXRβ overexpression and aggravated by RXRβ downregulation. Our further study showed that transfection of PGC1α siRNA abrogated the alleviative effects of RXRβ overexpression on mitochondrial damage and inflammation in ox-LDL treated cells. The present study indicates that RXRβ exerted protective effects against the ox-LDL-induced inflammation may through regulating PGC1α-dependent mitochondrial homeostasis.

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.

Perivascular Adipose Tissue Inflammation in Ischemic Heart Disease

OBJECTIVE

There is growing recognition that adipose tissue-derived proatherogenic mediators contribute to obesity-related cardiovascular disease. We sought to characterize regional differences in perivascular adipose tissue (PVAT) phenotype in relation to atherosclerosis susceptibility. Approach and Results: We examined thoracic PVAT samples in 34 subjects (body mass index 32±6 kg/m², age 59±11 years) undergoing valvular, aortic, or coronary artery bypass graft surgeries and performed transcriptomic characterization using whole-genome expression profiling and quantitative polymerase chain reaction analyses. We identified a highly inflamed region of PVAT surrounding the human aortic root in close proximity to coronary takeoff and adjoining epicardial fat. In subjects undergoing coronary artery bypass graft, we found 300 genes significantly upregulated (false discovery rate Q<0.1) in paired samples of PVAT surrounding the aortic root compared with nonatherosclerotic left internal mammary artery. Genes encoding proteins mechanistically implicated in atherogenesis were enriched in aortic PVAT consisting of signaling pathways linked to inflammation, WNT (wingless-related integration site) signaling, matrix remodeling, coagulation, and angiogenesis. Overexpression of several proatherogenic transcripts, including IL1β, CCL2 (MCP-1), and IL6, were confirmed by quantitative polymerase chain reaction and significantly bolstered in coronary artery disease subjects. Angiographic coronary artery disease burden quantified by the Gensini score positively correlated with the expression of inflammatory genes in PVAT. Moreover, periaortic adipose inflammation was markedly higher in obese subjects with striking upregulation (≈8-fold) of IL1β expression compared to nonobese individuals.

CONCLUSIONS

Proatherogenic mediators that originate from dysfunctional PVAT may contribute to vascular disease mechanisms in human vessels. Moreover, PVAT may adopt detrimental properties under obese conditions that play a key role in the pathophysiology of ischemic heart disease. Graphic Abstract: A graphic abstract is available for this article.

Perivascular Adipose Tissue as an Indication, Contributor to, and Therapeutic Target for Atherosclerosis

Perivascular adipose tissue (PVAT) has been identified to have significant endocrine and paracrine functions, such as releasing bioactive adipokines, cytokines, and chemokines, rather than a non-physiological structural tissue. Considering the contiguity with the vascular wall, PVAT could play a crucial role in the pathogenic microenvironment of atherosclerosis. Growing clinical evidence has shown an association between PVAT and atherosclerosis. Moreover, based on computed tomography, the fat attenuation index of PVAT was verified as an indication of vulnerable atherosclerotic plaques. Under pathological conditions, such as obesity and diabetes, PVAT shows a proatherogenic phenotype by increasing the release of factors that induce endothelial dysfunction and inflammatory cell infiltration, thus contributing to atherosclerosis. Growing animal and human studies have investigated the mechanism of the above process, which has yet to be fully elucidated. Furthermore, traditional treatments for atherosclerosis have been proven to act on PVAT, and we found several studies focused on novel drugs that target PVAT for the prevention of atherosclerosis. Emerging as an indication, contributor to, and therapeutic target for atherosclerosis, PVAT warrants further investigation.

Adipose Tissue Immunomodulation: A Novel Therapeutic Approach in Cardiovascular and Metabolic Diseases

Adipose tissue is a critical regulator of systemic metabolism and bodily homeostasis as it secretes a myriad of adipokines, including inflammatory and anti-inflammatory cytokines. As the main storage pool of lipids, subcutaneous and visceral adipose tissues undergo marked hypertrophy and hyperplasia in response to nutritional excess leading to hypoxia, adipokine dysregulation, and subsequent low-grade inflammation that is characterized by increased infiltration and activation of innate and adaptive immune cells. The specific localization, physiology, susceptibility to inflammation and the heterogeneity of the inflammatory cell population of each adipose depot are unique and thus dictate the possible complications of adipose tissue chronic inflammation. Several lines of evidence link visceral and particularly perivascular, pericardial, and perirenal adipose tissue inflammation to the development of metabolic syndrome, insulin resistance, type 2 diabetes and cardiovascular diseases. In addition to the implication of the immune system in the regulation of adipose tissue function, adipose tissue immune components are pivotal in detrimental or otherwise favorable adipose tissue remodeling and thermogenesis. Adipose tissue resident and infiltrating immune cells undergo metabolic and morphological adaptation based on the systemic energy status and thus a better comprehension of the metabolic regulation of immune cells in adipose tissues is pivotal to address complications of chronic adipose tissue inflammation. In this review, we discuss the role of adipose innate and adaptive immune cells across various physiological and pathophysiological states that pertain to the development or progression of cardiovascular diseases associated with metabolic disorders. Understanding such mechanisms allows for the exploitation of the adipose tissue-immune system crosstalk, exploring how the adipose immune system might be targeted as a strategy to treat cardiovascular derangements associated with metabolic dysfunctions.

Targeting perivascular and epicardial adipose tissue inflammation: therapeutic opportunities for cardiovascular disease

Major shifts in human lifestyle and dietary habits toward sedentary behavior and refined food intake triggered steep increase in the incidence of metabolic disorders including obesity and Type 2 diabetes. Patients with metabolic disease are at a high risk of cardiovascular complications ranging from microvascular dysfunction to cardiometabolic syndromes including heart failure. Despite significant advances in the standards of care for obese and diabetic patients, current therapeutic approaches are not always successful in averting the accompanying cardiovascular deterioration. There is a strong relationship between adipose inflammation seen in metabolic disorders and detrimental changes in cardiovascular structure and function. The particular importance of epicardial and perivascular adipose pools emerged as main modulators of the physiology or pathology of heart and blood vessels. Here, we review the peculiarities of these two fat depots in terms of their origin, function, and pathological changes during metabolic deterioration. We highlight the rationale for pharmacological targeting of the perivascular and epicardial adipose tissue or associated signaling pathways as potential disease modifying approaches in cardiometabolic syndromes.

Inflammatory cells in perivascular adipose tissue and the integrity of the tunica media in atherosclerotic coronary arteries

Obstructive coronary artery disease (CAD) is characterized by inflammation within the atherosclerotic coronary arteries. Infiltration of inflammatory cells into muscular media can lead to remodeling and weakening of the arterial wall. We examined the relationship between inflammatory infiltration in perivascular adipose tissue (PVAT), state of the external elastic membrane, and the intensity of inflammatory infiltration in the tunica media of coronary arteries obtained by endarterectomy from symptomatic patients with diffuse CAD. We analyzed endarterectomy sequesters from 22 coronary arteries that contained the intima, media, a part of the adventitia, and PVAT in at least one part of the sequester. The coronary arteries were divided into two groups according to the presence or absence of inflammatory infiltration in PVAT. Staining with hematoxylin-eosin and by the Movat's method showed atherosclerotic changes in the intima and media. Immunohistochemistry (anti-leukocyte common antigen [LCA] antibody) was used for the detection of leukocytes. We found a significant positive correlation between inflammatory infiltration in PVAT and preservation of the external elastic membrane of coronary arteries. Furthermore, we found a significant negative correlation between inflammatory infiltration in PVAT and the intensity of inflammatory infiltration in the media. It seems that the integrity of the external elastic membrane and the proinflammatory properties of PVAT restrain inflammatory cells within PVAT. Both effects may prevent the migration of inflammatory cells into the media and delay the development of CAD.

Perivascular adipose tissue in cardiovascular diseases-an update

The perivascular adipose tissue (PVAT) has been recently recognized as an important factor in vascular biology, with implications in the pathogenesis of cardiovascular diseases. The cell types and the precursor cells of PVAT appear to be different according to their location, with the component cell type including white, brown, and beige adipocytes. PVAT releases a panel of adipokines and cytokines that maintain vascular homeostasis, but it also has the ability of intervention in the pathogenesis of the atherosclerotic plaques development and in the vascular tone modulation. In this review, we summarize the current knowledge and discuss the role of PVAT as a major contributing factor in the pathogenesis of ischemic coronary disease, hypertension, obesity, and diabetes mellitus. The new perspective of PVAT as an endocrine organ, along with the recent knowledge of the mechanisms involved in dysfunctional PVAT intervention in local vascular homeostasis perturbations, nowadays represent a new area of research in cardiovascular pathology, aiming to discover new therapeutic methods.

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.

The concentration of resistin in perivascular adipose tissue after CABG and postoperative atrial fibrillation

BACKGROUND

Postoperative atrial fibrillation occurs in up to 30% of patients after coronary artery bypass graft (CABG) and its cause is unknown. The aim of the study was to evaluate whether concentration of resistin in surrounding coronary artery perivascular adipose tissue (PVAT) is related to postoperative atrial fibrillation occurrence.

METHODS

A total number of 46 patients (35 male, 11 female; median age 66.5) were qualified for elective CABG. Medical history, laboratory test results and echocardiographic parameters were noted. Patients were monitored up to 3 days after CABG and then were divided into groups with and without postoperative atrial fibrillation occurrence. Fragments of PVAT were collected intra-operatively: near the left anterior descending artery and main left coronary artery. The concentration of resistin was determined by Human Resistin Quantikine ELISA Kit and expressed as ng/g. A multivariate stepwise logistic regression analysis was performed to find variables related to postoperative atrial fibrillation occurrence.

RESULTS

Postoperative atrial fibrillation occurred in 14 (30.4%) patients. The patients with and without postoperative atrial fibrillation were similar in age, gender, epicardial adipose tissue thickness and laboratory parameters. The concentration of resistin in PVAT near the left main coronary artery was significantly higher in patients with postoperative atrial fibrillation than in those without the complication (P = 0.03). In the multivariate stepwise logistic regression analysis the concentration of resistin above cut-off point 54 ng/g in PVAT near left main coronary artery was independently related to postoperative atrial fibrillation occurrence (OR: 7.7; 95% CI:1.4-42.2 p = 0.02).

CONCLUSIONS

The higher concentrations of resistin in PVAT near the left main coronary artery which is located close to the left atrium are associated with postoperative atrial fibrillation.

Serum leptin, a potential predictor of long-term angiographic progression in Takayasu's arteritis

Aim

In patients with Takayasu's arteritis (TA), current biomarkers that properly reflect the progression of the vascular structure remain absent. We aimed to determine the serum leptin level to investigate its relationship with imaging changes and assess its value as a predictor for long‐term radiological progression.

Method

This study included 34 untreated TA patients and 40 age‐matched healthy controls. At baseline and during the 5‐year follow‐up, we assessed disease activity using Kerr's criteria and Indian Takayasu Clinical Activity Score (ITAS2010) and monitored laboratory biomarkers as well as imaging findings. Serum leptin levels were measured by enzyme‐linked immunosorbent assay.

Results

The baseline serum leptin levels were significantly higher in TA patients than in healthy controls. Leptin was significantly positively correlated with triglyceride and high‐density lipoprotein cholesterol levels and negatively correlated with fibrinogen and C‐reactive protein levels. Patients were subdivided into three groups based on their baseline leptin level. During a 5‐year follow‐up, patients in the high and medium leptin groups showed more radiological progression compared to those in the low leptin group. Cox proportional hazard regression analysis showed that a high serum leptin level was a positive predictor of radiological progression.

Conclusion

Leptin is a potential biomarker for assessing TA structural progression. Untreated patients with elevated serum leptin levels are at a higher risk of progression in the aorta. Thus, the leptin level can be a predictor of long‐term radiological progression.

Increased Lymphangiogenesis and Lymphangiogenic Growth Factor Expression in Perivascular Adipose Tissue of Patients with Coronary Artery Disease

Experimental and human autopsy studies have associated adventitial lymphangiogenesis with atherosclerosis. An analysis of perivascular lymphangiogenesis in patients with coronary artery disease is lacking. Here, we examined lymphangiogenesis and its potential regulators in perivascular adipose tissue (PVAT) surrounding the heart (C-PVAT) and compared it with PVAT of the internal mammary artery (IMA-PVAT). Forty-six patients undergoing coronary artery bypass graft surgery were included. Perioperatively collected C-PVAT and IMA-PVAT were analyzed using histology, immunohistochemistry, real time PCR, and PVAT-conditioned medium using cytokine arrays. C-PVAT exhibited increased PECAM-1 (platelet endothelial cell adhesion molecule 1)-positive vessel density. The number of lymphatic vessels expressing lymphatic vessel endothelial hyaluronan receptor-1 or podoplanin was also elevated in C-PVAT and associated with higher inflammatory cell numbers, increased intercellular adhesion molecule 1 (ICAM1) expression, and fibrosis. Significantly higher expression of regulators of lymphangiogenesis such as vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF receptor-3 was observed in C-PVAT compared to IMA-PVAT. Cytokine arrays identified angiopoietin-2 as more highly expressed in C-PVAT vs. IMA-PVAT. Findings were confirmed histologically and at the mRNA level. Stimulation of human lymphatic endothelial cells with recombinant angiopoietin-2 in combination with VEGF-C enhanced sprout formation. Our study shows that PVAT surrounding atherosclerotic arteries exhibits more extensive lymphangiogenesis, inflammation, and fibrosis compared to PVAT surrounding a non-diseased vessel, possibly due to local angiopoietin-2, VEGF-C, and VEGF-D overexpression.

Fatty Acid-Binding Protein 4 in Cardiovascular and Metabolic Diseases

Fatty acid-binding proteins (FABPs), a family of lipid chaperones, contribute to systemic metabolic regulation via several lipid signaling pathways. Fatty acid-binding protein 4 (FABP4), known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis in relation to metabolically driven low-grade and chronic inflammation, referred to as ‘metaflammation’. FABP4 is secreted from adipocytes in a non-classical pathway associated with lipolysis and acts as an adipokine for the development of insulin resistance and atherosclerosis. Circulating FABP4 levels are associated with several aspects of metabolic syndrome and cardiovascular disease. Ectopic expression and function of FABP4 in cells and tissues are also related to the pathogenesis of several diseases. Pharmacological modification of FABP4 function by specific inhibitors, neutralizing antibodies or antagonists of unidentified receptors would be novel therapeutic strategies for several diseases, including obesity, diabetes mellitus, atherosclerosis and cardiovascular disease. Significant roles of FABP4 as a lipid chaperone in physiological and pathophysiological conditions and the possibility of FABP4 being a therapeutic target for metabolic and cardiovascular diseases are discussed in this review.