Novel measurements of periaortic adipose tissue in comparison to anthropometric measures of obesity, and abdominal adipose tissue

Multimodality Imaging in Metabolic Syndrome: State-of-the-Art Review

Metabolic syndrome comprises a set of risk factors that include abdominal obesity, impaired glucose tolerance, hypertriglyceridemia, low high-density lipoprotein levels, and high blood pressure, at least three of which must be fulfilled for diagnosis. Metabolic syndrome has been linked to an increased risk of cardiovascular disease and type 2 diabetes mellitus. Multimodality imaging plays an important role in metabolic syndrome, including diagnosis, risk stratification, and assessment of complications. CT and MRI are the primary tools for quantification of excess fat, including subcutaneous and visceral adipose tissue, as well as fat around organs, which are associated with increased cardiovascular risk. PET has been shown to detect signs of insulin resistance and may detect ectopic sites of brown fat. Cardiovascular disease is an important complication of metabolic syndrome, resulting in subclinical or symptomatic coronary artery disease, alterations in cardiac structure and function with potential progression to heart failure, and systemic vascular disease. CT angiography provides comprehensive evaluation of the coronary and systemic arteries, while cardiac MRI assesses cardiac structure, function, myocardial ischemia, and infarction. Liver damage results from a spectrum of nonalcoholic fatty liver disease ranging from steatosis to fibrosis and possible cirrhosis. US, CT, and MRI are useful in assessing steatosis and can be performed to detect and grade hepatic fibrosis, particularly using elastography techniques. Metabolic syndrome also has deleterious effects on the pancreas, kidney, gastrointestinal tract, and ovaries, including increased risk for several malignancies. Metabolic syndrome is associated with cerebral infarcts, best evaluated with MRI, and has been linked with cognitive decline. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material. See the invited commentary by Pickhardt in this issue.

Relationship Between Perivascular Adipose Tissue and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis

We conducted a systematic review and meta-analysis aimed at estimating the association between perivascular adipose tissue (PVAT) and some of the cardiovascular risk factors. A systematic search was conducted from January 1980 up to and including 2022 to identify studies that examined the relationship between PVAT and cardiovascular risk factors as obesity and its indices, hypertension, lipids, and glucose intolerance/diabetes. The Medline and Embase databases were searched using the PubMed and Scopus. Data were extracted from 23 studies that fit the criteria. To conduct meta-analysis, we used an approximation of equating the method of correlating assessment because different authors used either Pearson or Spearman correlation. Interrelations of PVAT and body mass index were analyzed in eight studies. Most studies revealed reliable direct correlation; the results of the meta-analysis also showed a significant (P = 0.37, P < 0.01, n = 12,346) correlation. PVAT and waist circumference were analyzed in six studies. Meta-analysis on the selected sample (n = 10,947) showed a significant (r = 0.45, P < 0.01) correlation. Relationship between PVAT and hypertension was revealed in three studies. Direct correlations were found in all studies. Meta-analysis showed the reliability of the correlation dependence (r = 0.21, P < 0.01, n = 3996). PVAT and blood glucose was evaluated in three studies (n = 3689). In each study a reliable (P < 0.05) direct correlation was obtained. Meta-analysis showed a significant correlation of weak strength (r = 0.24, P < 0.01). We demonstrated significant positive correlations of PVAT with the levels of total cholesterol (r = 0.05, P < 0.01), low-density lipoprotein cholesterol (r = 0.13, P < 0.01), and triglycerides (r = 0.29, P < 0.01), and a negative relationship with high-density lipoprotein cholesterol (r = -0.18, P < 0.01) in this meta-analysis. Despite some limitations, the findings of this systematic review and meta-analysis confirmed that PVAT significantly correlates with studied cardiovascular risk factors. Because PVAT presents a great interest in terms of cardiovascular remodeling and cardiovascular disease, its assessment in patients with and without cardiovascular pathology needs further research.

Aldose Reductase (AR) Mediates and Perivascular Adipose Tissue (PVAT) Modulates Endothelial Dysfunction of Short-Term High-Fat Diet Feeding in Mice

Increased adiposity of both visceral and perivascular adipose tissue (PVAT) depots is associated with an increased risk of diabetes and cardiovascular disease (CVD). Under healthy conditions, PVAT modulates vascular tone via the release of PVAT-derived relaxing factors, including adiponectin and leptin. However, when PVAT expands with high-fat diet (HFD) feeding, it appears to contribute to the development of endothelial dysfunction (ED). Yet, the mechanisms by which PVAT alters vascular health are unclear. Aldose reductase (AR) catalyzes glucose reduction in the first step of the polyol pathway and has been long implicated in diabetic complications including neuropathy, retinopathy, nephropathy, and vascular diseases. To better understand the roles of both PVAT and AR in HFD-induced ED, we studied structural and functional changes in aortic PVAT induced by short-term HFD (60% kcal fat) feeding in wild type (WT) and aldose reductase-null (AR-null) mice. Although 4 weeks of HFD feeding significantly increased body fat and PVAT mass in both WT and AR-null mice, HFD feeding induced ED in the aortas of WT mice but not of AR-null mice. Moreover, HFD feeding augmented endothelial-dependent relaxation in aortas with intact PVAT only in WT and not in AR-null mice. These data indicate that AR mediates ED associated with short-term HFD feeding and that ED appears to provoke 'compensatory changes' in PVAT induced by HFD. As these data support that the ED of HFD feeding is AR-dependent, vascular-localized AR remains a potential target of temporally selective intervention.

Exploring the Diversity of Visceral, Subcutaneous and Perivascular Adipose Tissue in a Vascular Surgery Population

The prevalence of obesity has doubled, with a concomitant increase in cardiovascular disease. This study aimed to compare the characteristics of visceral, subcutaneous and peri-aortic adipose tissue determined with computed tomography (CT) scans and to correlate them with cardiovascular risk factors, anthropometric measures and medication. An observational and prospective study was conducted, and 177 subjects were included. Peri-aortic adipose tissue had the highest density, while the subcutaneous adipose tissue had the lowest. The density of subcutaneous adipose tissue differs from the density of visceral (p = 0.00) and peri-aortic adipose tissue (p = 0.00). Smokers/ex-smokers had a lower area (p = 0.00) and density (p = 0.02) of subcutaneous adipose tissue. Multiple linear regression analysis showed that sex was a predictor of subcutaneous adipose tissue area (β = -0.27, t = -3.12, p = 0.00) but smoking habits were not. After controlling for sex, we found that the association between smokers/ex-smokers and area of subcutaneous adipose tissue was lost, but the association with density persisted. Patients with hypertension had a higher visceral adipose tissue area, and this relationship was maintained even after adjusting for gender. Peri-aortic adipose tissue is similar to visceral and distinct from subcutaneous adipose tissue. Cardiovascular risk factors have different influences in distinct adipose compartments.

Association Between Perivascular Adipose Tissue Density and Atherosclerosis in the Descending Thoracic Aorta

Radiodensity measured by computed tomography (CT) in Hounsfield Units (HU) is emerging as a clinical tool for detecting perivascular adipose tissue (PVAT) inflammation. In the present study, we hypothesized that PVAT radiodensity might predict the risk of descending thoracic aorta atherosclerosis. A total of 73 subjects who underwent CT angiography to investigate aortic disease were retrospectively analyzed. PVAT radiodensity, aortic complex plaque (ACP), mean plaque-burden score (MPBS), and plaque density were measured, and the association between them was analyzed. Perivascular adipose tissue radiodensity (HU) in patients with different aortic plaques grades (grade 1, 2, 3, and 4) were -93.71 ± 2.50, -93.63 ± 3.93, -90.24 ± 4.49, and -89.90 ± 5.18, respectively, and the difference was significant (P = .010). In the regression analysis, PVAT radiodensity was an independent predictor of ACP, with an OR of 1.263. In the linear analysis, PVAT radiodensity was an independent predictor of MPBS, with a β-coefficient of .073. In the univariate analysis, only the PVAT radiodensity was significantly associated with plaque density, with a β-coefficient of -1.666. In conclusion, PVAT density was independently related to descending thoracic aorta atherosclerosis.

The neglected association between central obesity markers and abdominal aortic aneurysm presence: A systematic review and meta-analysis

Purpose

To review the association between central obesity and abdominal aortic aneurysm (AAA).

Materials and methods

The PubMed, Web of Sciences, Embase, The China national knowledge infrastructure (CNKI), and Cochrane Library were searched up to April 30, 2022. Researches includes investigation of the relationship between central obesity markers and AAA. Included studies must use recognized measures of central obesity, i.e., waist circumference (WC) and waist-to-hip ratio (WHR), or use imaging techniques to calculate abdominal fat distribution, such as computed tomography (CT) imaging.

Results

Eleven clinical researches were identified of which eight discussed the association between physical examination and AAA, and three studies mainly focused on abdominal fat volume (AFV). Seven researches concluded that there was a positive correlation between markers of central obesity and AAA. Three studies found no significant link between markers of central obesity and AAA. One of the remaining studies reported different results for each sex. Three studies pooled in a meta-analysis identified correlation between central obesity and AAA presence (RR = 1.29; 95% confidence interval, 1.14-1.46).

Conclusion

Central obesity plays a role in the risk of AAA. Standardized central obesity markers may be predictors of AAA. However, there was no association between abdominal fat volume and AAA. Additional relevant evidence and specific mechanisms warrant further study.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?IDCRD42022332519, identifier CRD42022332519.

Changes in abdominal fat depots after bariatric surgery are associated with improved metabolic profile

BACKGROUND AND AIMS

Obesity associated with a change in the quantity and quality of fat depots. Using computed tomography (CT), we analyzed abdominal fat depots in patients with obesity after bariatric surgery according to their metabolic health status.

METHODS AND RESULTS

We recruited 79 individuals with metabolically unhealthy obesity before bariatric surgery and compared them with age-sex matched healthy controls. The volume and fat attenuation index (FAI) of fat depots were measured using CT scans that were conducted prior to and a year after bariatric surgery. 'Metabolically healthy' was defined as having no hypertension, normal fasting glucose and a waist-to-hip ratio of <1.05 for men and <0.95 for women. Individuals who achieved a metabolic health status conversion (MHC) (n = 29, 37%)-from unhealthy to healthy-were younger (p < 0.001) as compared to individuals without MHC. Pre-surgery BMI and reduction of BMI did not differ between the two groups (p = 0.099, p = 0.5730). Bariatric surgery reduced the volume and increased the FAI of fat depots. Baseline lower abdominal periaortic adipose tissue (AT) volume (p = 0.014) and great percent reduction in renal sinus AT volume after surgery (p = 0.019) were associated with MHC after surgery. Increased intraperitoneal AT FAI (p = 0.031) was also associated with MHC.

CONCLUSION

MHC was not associated with improvement in general obesity, based on indicators such as reduction of BMI after surgery. Weight reduction induced specific abdominal fat depot changes measured by CT are positively associated with MHC.

Constructing custom-made radiotranscriptomic signatures of vascular inflammation from routine CT angiograms: a prospective outcomes validation study in COVID-19

BACKGROUND

Direct evaluation of vascular inflammation in patients with COVID-19 would facilitate more efficient trials of new treatments and identify patients at risk of long-term complications who might respond to treatment. We aimed to develop a novel artificial intelligence (AI)-assisted image analysis platform that quantifies cytokine-driven vascular inflammation from routine CT angiograms, and sought to validate its prognostic value in COVID-19.

METHODS

For this prospective outcomes validation study, we developed a radiotranscriptomic platform that uses RNA sequencing data from human internal mammary artery biopsies to develop novel radiomic signatures of vascular inflammation from CT angiography images. We then used this platform to train a radiotranscriptomic signature (C19-RS), derived from the perivascular space around the aorta and the internal mammary artery, to best describe cytokine-driven vascular inflammation. The prognostic value of C19-RS was validated externally in 435 patients (331 from study arm 3 and 104 from study arm 4) admitted to hospital with or without COVID-19, undergoing clinically indicated pulmonary CT angiography, in three UK National Health Service (NHS) trusts (Oxford, Leicester, and Bath). We evaluated the diagnostic and prognostic value of C19-RS for death in hospital due to COVID-19, did sensitivity analyses based on dexamethasone treatment, and investigated the correlation of C19-RS with systemic transcriptomic changes.

FINDINGS

Patients with COVID-19 had higher C19-RS than those without (adjusted odds ratio [OR] 2·97 [95% CI 1·43-6·27], p=0·0038), and those infected with the B.1.1.7 (alpha) SARS-CoV-2 variant had higher C19-RS values than those infected with the wild-type SARS-CoV-2 variant (adjusted OR 1·89 [95% CI 1·17-3·20] per SD, p=0·012). C19-RS had prognostic value for in-hospital mortality in COVID-19 in two testing cohorts (high [≥6·99] vs low [<6·99] C19-RS; hazard ratio [HR] 3·31 [95% CI 1·49-7·33], p=0·0033; and 2·58 [1·10-6·05], p=0·028), adjusted for clinical factors, biochemical biomarkers of inflammation and myocardial injury, and technical parameters. The adjusted HR for in-hospital mortality was 8·24 (95% CI 2·16-31·36, p=0·0019) in patients who received no dexamethasone treatment, but 2·27 (0·69-7·55, p=0·18) in those who received dexamethasone after the scan, suggesting that vascular inflammation might have been a therapeutic target of dexamethasone in COVID-19. Finally, C19-RS was strongly associated (r=0·61, p=0·00031) with a whole blood transcriptional module representing dysregulation of coagulation and platelet aggregation pathways.

INTERPRETATION

Radiotranscriptomic analysis of CT angiography scans introduces a potentially powerful new platform for the development of non-invasive imaging biomarkers. Application of this platform in routine CT pulmonary angiography scans done in patients with COVID-19 produced the radiotranscriptomic signature C19-RS, a marker of cytokine-driven inflammation driving systemic activation of coagulation and responsible for adverse clinical outcomes, which predicts in-hospital mortality and might allow targeted therapy.

FUNDING

Engineering and Physical Sciences Research Council, British Heart Foundation, Oxford BHF Centre of Research Excellence, Innovate UK, NIHR Oxford Biomedical Research Centre, Wellcome Trust, Onassis Foundation.

Quantification of periaortic adipose tissue in contrast-enhanced CT angiography: technical feasibility and methodological considerations

To examine the feasibility of the quantification of abdominal periaortic fat tissue (PaFT) (tissue within - 45 to - 195 HU) in enhanced CT-angiographies compared to unenhanced CT-scans and identify methodological issues affecting its clinical implementation. Using OsirixMD, PaFT volume and mean HU value were retrospectively measured within a 5 mm periaortic ring in paired unenhanced and enhanced abdominal aortic CT-scans. The correlation between PaFT values was examined in a derivation cohort (n = 101) and linear regression analysis produced correction factors to convert values from enhanced into values from unenhanced CTs. The conversion factors were then applied to enhanced CTs in a different validation cohort (n = 47) and agreement of corrected enhanced values with values from unenhanced scans was evaluated. Correlation between PaFT Volume und Mean HU from enhanced and unenhanced scans was very high (r > 0.99 and r = 0.95, respectively, p < 0.0001 for both). The correction factors for PaFT Volume and Mean HU were 1.1057 and 1.0011. Potential confounding factors (CT-kilovoltage, slice thickness, mean intraluminal contrast density, aortic wall calcification, longitudinal variation of intraluminal contrast density, aortic diameter) showed no significant effect in a multivariate regression analysis (p > 0.05). Bland-Altman analysis of corrected enhanced and unenhanced values showed excellent agreement and Passing-Bablok regression confirmed minimal/no residual bias. PaFT can be quantified in enhanced CT-angiographies very reliably. PaFT Volume scores are very consistently slightly underestimated in enhanced scans by about 10%, while the PaFT Mean HU value remains practically constant and offers distinct methodological advantages. However, a number of methodological issues remain to be addressed.

Pericardial fat, thoracic peri-aortic adipose tissue, and systemic inflammatory marker in nonalcoholic fatty liver and abdominal obesity phenotype

Researchers have conducted many studies about the relationships between peri-cardiovascular fat, nonalcoholic fatty liver disease (NAFLD), waist circumference, and cardiovascular disease (CVD). Nevertheless, the relationship between NAFLD and pericardial fat (PCF)/thoracic peri-aortic adipose tissue (TAT) phenotypes was still unknown. This study aimed to explore whether PCF/TAT was associated with NAFLD/abdominal obesity (AO) phenotypes in different high-sensitivity C-reactive protein (hs-CRP) levels. We consecutively studied 1655 individuals (mean age, 49.44 ± 9.76 years) who underwent a health-screening program. We showed a significant association between PCF/TAT and NAFLD/AO phenotypes in the cross-sectional study. We observed that the highest risk occurred in both abnormalities' groups, and the second highest risk occurred in the AO-only group. Subjects with AO had a significantly increased risk of PCF or TAT compared to those with NAFLD. Notably, the magnitude of the associations between PCF/TAT and NAFLD/AO varied by the level of systemic inflammatory marker (hs-CRP level). We suggested that people with AO and NAFLD must be more careful about changes in PCF and TAT. Regular measurement of waist circumference (or AO) can be a more accessible way to monitor peri-cardiovascular fat (PCF and TAT), which may serve as a novel and rapid way to screen CVD in the future.

Influence of local aortic calcification on periaortic adipose tissue radiomics texture features-a primary analysis on PCCT

Perivascular adipose tissue is known to be metabolically active. Volume and density of periaortic adipose tissue are associated with aortic calcification as well as aortic diameter indicating a possible influence of periaortic adipose tissue on the development of aortic calcification. Due to better spatial resolution and signal-to-noise ratio, new CT technologies such as photon-counting computed tomography may allow the detection of texture alterations of periaortic adipose tissue depending on the existence of local aortic calcification possibly outlining a biomarker for the development of arteriosclerosis. In this retrospective, single-center, IRB-approved study, periaortic adipose tissue was segmented semiautomatically and radiomics features were extracted using pyradiomics. Statistical analysis was performed in R statistics calculating mean and standard deviation with Pearson correlation coefficient for feature correlation. For feature selection Random Forest classification was performed. A two-tailed unpaired t test was applied to the final feature set. Results were visualized as boxplots and heatmaps. A total of 30 patients (66.6% female, median age 57 years) were enrolled in this study. Patients were divided into two subgroups depending on the presence of local aortic calcification. By Random Forest feature selection a set of seven higher-order features could be defined to discriminate periaortic adipose tissue texture between these two groups. The t test showed a statistic significant discrimination for all features (p < 0.05). Texture changes of periaortic adipose tissue associated with the existence of local aortic calcification may lay the foundation for finding a biomarker for development of arteriosclerosis.

Effects of High-Fat and High-Fat/High-Sucrose Diet-Induced Obesity on PVAT Modulation of Vascular Function in Male and Female Mice

Increased adiposity in perivascular adipose tissue (PVAT) has been related to vascular dysfunction. High-fat (HF) diet-induced obesity models are often used to analyze the translational impact of obesity, but differences in sex and Western diet type complicate comparisons between studies. The role of PVAT was investigated in small mesenteric arteries (SMAs) of male and female mice fed a HF or a HF plus high-sucrose (HF + HS) diet for 3 or 5 months and compared them to age/sex-matched mice fed a chow diet. Vascular responses of SMAs without (PVAT-) or with PVAT (PVAT+) were evaluated. HF and HF + HS diets increased body weight, adiposity, and fasting glucose and insulin levels without affecting blood pressure and circulating adiponectin levels in both sexes. HF or HF + HS diet impaired PVAT anticontractile effects in SMAs from females but not males. PVAT-mediated endothelial dysfunction in SMAs from female mice after 3 months of a HF + HS diet, whereas in males, this effect was observed only after 5 months of HF + HS diet. However, PVAT did not impact acetylcholine-induced relaxation in SMAs from both sexes fed HF diet. The findings suggest that the addition of sucrose to a HF diet accelerates PVAT dysfunction in both sexes. PVAT dysfunction in response to both diets was observed early in females compared to age-matched males suggesting a susceptibility of the female sex to PVAT-mediated vascular complications in the setting of obesity. The data illustrate the importance of the duration and composition of obesogenic diets for investigating sex-specific treatments and pharmacological targets for obesity-induced vascular complications.

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.

Carotid Extra-Media Thickness in Children: Relationships With Cardiometabolic Risk Factors and Endothelial Function

Background: Emerging evidence suggests that structural adventitial modifications and perivascular adipose tissue (PAT) may have a role in early atherogenesis. In a cohort of children and adolescents, we explored (1) the association of carotid extra-media thickness (cEMT), an ultrasound measure whose main determinants are arterial adventitia and PAT, with obesity and its cardiometabolic complications; and (2) the interplay between cEMT and endothelial function. Methods: The study participants included 286 youths (age, 6-16 years; 154 boys, and 132 girls). Anthropometric and laboratory parameters, liver ultrasound, vascular structure measures [cEMT and carotid intima-media thickness (cIMT)], endothelial function [brachial artery flow-mediated dilation (FMD)] were obtained in all subjects. Non-alcoholic fatty liver disease (NAFLD) was diagnosed in the presence of hepatic fat on ultrasonography, in the absence of other causes of liver disease. Diagnosis of metabolic syndrome (MetS) was established on the basis of three or more of the following cardiovascular disease (CVD) risk variables: abdominal obesity, high triglycerides, low high-density lipoprotein cholesterol, elevated blood pressure (BP), and impaired fasting glucose. Results: cEMT demonstrated significant associations with body-mass index (BMI) and waist circumference (WC), BP, insulin resistance, NAFLD, and inflammation. No association was found between cEMT and lipid values, and between cEMT and MetS. A stepwise multivariate linear regression analysis indicated that WC (β coefficient, 0.35; P < 0.0001) was the only determinant of cEMT, independently of other major cardiometabolic risk factors. Further adjustment for cIMT did not significantly alter this association. FMD was correlated to age, Tanner stage, total and abdominal obesity, BP, NAFLD, and cEMT. The association between FMD and cEMT was independent of age, sex, Tanner stage, WC, and BMI (β coefficient, -0.14; P = 0.027). After controlling for CVD risk factors and basal brachial artery diameter, cEMT remained associated with FMD (β coefficient, -0.11; P = 0.049). Conclusions: In youths, cEMT is associated with abdominal fat, a well-established body fat depot with important implications for cardiovascular diseases. Furthermore, cEMT is related to FMD, suggesting that arterial adventitia and PAT may be involved in the early changes in endothelial function.

Advantages and disadvantages of different methods for diagnosis of visceral obesity

This analytical review is devoted to the study of visceral obesity as a risk factor for the development and progression of cardiovascular diseases. The presented review discusses the evolution of methods for diagnosis of visceral obesity, their advantages and limitation for various ectopic fat depots.

Localization of fat depots and cardiovascular risk

Despite the existing preventative and therapeutic measures, cardiovascular diseases remain the main cause of temporary disability, long-term disability, and mortality. Obesity is a major risk factor for cardiovascular diseases and their complications. However, not all fat depots have the same inflammatory, paracrine, and metabolic activities. In addition, recent studies have indicated that the accumulation of visceral fat, rather than subcutaneous fat, is associated with increased cardiometabolic risk. However, there is also evidence that increasing the area of visceral fat can help protect against lipotoxicity. This review aims to discuss the contemporary literature regarding the characteristics of the visceral, epicardial, and perivascular fat depots, as well as their associations with cardiovascular disease.

High Density of Periaortic Adipose Tissue in Abdominal Aortic Aneurysm

OBJECTIVES

Perivascular adipose tissue (PVAT) is currently seen as a paracrine organ that produces vasoactive substances, including inflammatory agents, which may have an impact on the vasculature. In this study PVAT density was quantified in patients with an aortic aneurysm and compared with those with a non-dilated aorta. Since chronic inflammation, as the pathway to medial thinning, is a hallmark of abdominal aortic aneurysms (AAAs), it was hypothesised that PVAT density is higher in AAA patients.

METHODS

In this multicentre retrospective case control study, three groups of patients were included: non-treated asymptomatic AAA (n = 140), aortoiliac occlusive disease (AIOD) (n = 104), and individuals without aortic pathology (n = 97). A Hounsfield units based analysis was performed by computed tomography (CT). As a proxy for PVAT, the density of adipose tissue 10 mm circumferential to the infrarenal aorta was analysed in each consecutive CT slice. Intra-individual PVAT differences were reported as the difference in PVAT density between the region of the maximum AAA diameter (or the mid-aortic region in patients with AIOD or controls) and the two uppermost slices of infrarenal non-dilated aorta just below the renal arteries. Furthermore, subcutaneous (SAT) and visceral (VAT) adipose tissue measurements were performed. Linear models were fitted to assess the association between the study groups, different adipose tissue compartments, and between adipose tissue compartments and aortic dimensions.

RESULTS

AAA patients presented higher intra-individual PVAT differences, with higher PVAT density around the aneurysm sac than the healthy neck. This association persisted after adjustment for cardiovascular risk factors and diseases and other fat compartments (β = 13.175, SE 4.732, p = .006). Furthermore, intra-individual PVAT differences presented the highest correlation with aortic volume that persisted after adjustment for other fat compartments, body mass index, sex, and age (β = 0.566, 0.200, p = .005).

CONCLUSION

The results suggest a relation between the deposition of PVAT and AAA pathophysiology. Further research should explore the exact underlying processes.

The relationship of perivascular adipose tissue and atherosclerosis in the aorta and carotid arteries, determined by magnetic resonance imaging

BACKGROUND AND AIMS

Imaging studies have relied on the 'overall' volumetric quantification of perivascular adipose tissue. We sought to assess the relationship of circumferential distribution between perivascular adipose tissue and adjacent wall thickness of carotid and aortic arteries using dedicated magnetic resonance imaging sequences.

METHODS

Vessel wall and perivascular adipose tissue were acquired using magnetic resonance imaging (1.5 T). Co-registered images were segmented separately, and measurements of both perivascular adipose tissue and vessel wall were obtained along radii of the vessel spaced at angles of 5° each.

RESULTS

In total, 29 patients were recruited. Perivascular adipose tissue thickness of the aorta was 3.34 ± 0.79 mm with specific pattern of 'double peaks' distribution, while carotid perivascular adipose tissue had no identifiable pattern with thickness of 0.8 ± 0.91 mm. Although statistically significant, the correlation between perivascular adipose tissue thickness and wall thickness in carotid arteries with normal (r = 0.040, p = 0.001) or with abnormal wall thickness (r = -0.039, p = 0.015) was merely nominal. Similarly, perivascular adipose tissue of the aorta had very weak correlation with normal aortic wall thickness (r = 0.010, p = 0.008) but not with the abnormal ones (r = -0.05, p = 0.29).

CONCLUSION

Dissociation between the spatial distribution of perivascular adipose tissue and arterial wall thickening in the aorta and carotid arteries does not support that perivascular adipose tissue has a causal role in promoting atherosclerotic plaque via a paracrine route. Yet, perivascular adipose tissue functional properties were not examined in this study.

Visceral and Intrahepatic Fat Are Associated with Cardiometabolic Risk Factors Above Other Ectopic Fat Depots: The Framingham Heart Study

BACKGROUND

We examined the associations among 8 different fat depots accumulated in various anatomic regions and the relationship between these fat depots and multiple cardiometabolic risk factors.

METHODS

Participants were from the Framingham Heart Study Offspring and Third Generation who also participated in the multidetector computed tomography substudy in 2002-2005. Exposures were multidetector computed tomography-derived fat depots, including abdominal subcutaneous adipose tissue, abdominal visceral adipose tissue, intramuscular fat, intrathoracic fat, pericardial fat, thoracic periaortic fat, intrahepatic fat, and renal sinus fat. Multivariable-adjusted regression analyses with a forward selection procedure were performed to identify the most predictive fat depots.

RESULTS

Of 2529 participants, 51.9% were women (mean age, 51.1 years). Visceral adipose tissue had the strongest correlations with each of the other fat measures (range, 0.26-0.77) and with various cardiometabolic risk factors (range, -0.34 to 0.39). As determined by the selection models, visceral adipose tissue was the only fat depot that was associated with all cardiometabolic risk factors evaluated in this study (all P<.05). Selection models also showed that subcutaneous adipose tissue and intrahepatic fat were associated with cardiometabolic risk factors related to the traits of dysglycemia, dyslipidemia, and hypertension (all P<.05). However, only associations with visceral adipose tissue and intrahepatic fat persisted after further adjustment for body mass index and waist circumference.

CONCLUSIONS

Visceral adipose tissue and intrahepatic fat were consistent correlates of cardiometabolic risk factors, above and beyond standard anthropometric indices. Our data provide important insights for understanding the associations between variations in fat distribution and cardiometabolic abnormalities.

Diagnostic imaging in the management of patients with metabolic syndrome

Metabolic syndrome (MetS) is the constellation of metabolic risk factors that might foster development of type 2 diabetes and cardiovascular disease. Abdominal obesity and insulin resistance play a prominent role among all metabolic traits of MetS. Because intervention including weight loss can reduce these morbidity and mortality in MetS, early detection of the severity and complications of MetS could be useful. Recent advances in imaging modalities have provided significant insight into the development and progression of abdominal obesity and insulin resistance, as well as target organ injuries. The purpose of this review is to summarize advances in diagnostic imaging modalities in MetS that can be applied for evaluating each components and target organs. This may help in early detection, monitoring target organ injury, and in turn developing novel therapeutic target to alleviate and avert them.

Perivascular Adipose Tissue as a Relevant Fat Depot for Cardiovascular Risk in Obesity

Obesity is associated with increased risk of premature death, morbidity, and mortality from several cardiovascular diseases (CVDs), including stroke, coronary heart disease (CHD), myocardial infarction, and congestive heart failure. However, this is not a straightforward relationship. Although several studies have substantiated that obesity confers an independent and additive risk of all-cause and cardiovascular death, there is significant variability in these associations, with some lean individuals developing diseases and others remaining healthy despite severe obesity, the so-called metabolically healthy obese. Part of this variability has been attributed to the heterogeneity in both the distribution of body fat and the intrinsic properties of adipose tissue depots, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, hormonal control, thermogenic ability, and vascularization. In obesity, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. The adventitial fat layer, also known as perivascular adipose tissue (PVAT), is of major importance. Similar to the visceral adipose tissue, PVAT has a pathophysiological role in CVDs. PVAT influences vascular homeostasis by releasing numerous vasoactive factors, cytokines, and adipokines, which can readily target the underlying smooth muscle cell layers, regulating the vascular tone, distribution of blood flow, as well as angiogenesis, inflammatory processes, and redox status. In this review, we summarize the current knowledge and discuss the role of PVAT within the scope of adipose tissue as a major contributing factor to obesity-associated cardiovascular risk. Relevant clinical studies documenting the relationship between PVAT dysfunction and CVD with a focus on potential mechanisms by which PVAT contributes to obesity-related CVDs are pointed out.

A histomorphometric study on the effects of antiretroviral therapy (ART) combined with a high-calorie diet (HCD) on aortic perivascular adipose tissue (PVAT)

Perivascular adipose tissue (PVAT), surrounding arteries is metabolically active. Obesity and antiretroviral therapy (ART) may cause pathophysiological conditions in the aortic wall and surrounding PVAT. The aim of the study was to determine the histological effects on the aortic wall, aortic PVAT adipocyte morphology and leptin staining intensity in obese rats treated with ART. Wistar rats (N=36) were divided into four groups; a lean control (C/ART-), ART control (C/ART+), high-calorie diet (HCD) untreated (HCD/ART-) and HCD and ART experimental (HCD/ART+). The aorta and surrounding PVAT were stained with haematoxylin and eosin (H&E) and anti-leptin antibodies for immunohistochemistry (IHC). The C/ART+ group had a thinner tunica media compared to the HCD/ART- group. The tunica adventitia was thicker in the ART groups (C/ART+ and HCD/ART+) compared to the lean control group. White adipocytes in the HCD/ART- group was larger in size compared to the other three groups. The high-calorie diet groups (HCD/ART- and HCD/ART+) had increased adipocyte sizes, for both brown and differentiating adipocytes, compared to the control groups (C/ART- and C/ART+). The unilocular and differentiating adipocytes in the C/ART+ group showed intense leptin staining. Unilocular and differentiating adipocytes in the HCD/ART- and HCD/ART+ groups showed weak to no leptin staining intensity. The present study indicated that ART and a HCD, separately and combined, altered both the tunica media and adventitia of the aortic wall, whereas the HCD alone caused adipocytes to increase in size. The leptin staining intensity suggested that ART alone may lead to increased leptin expression, whereas ART combined with a HCD may cause leptin deficiency. Changes seen with ART in a rat model suggest that aortic wall thickness and PVAT adipocyte morphology alterations should be considered by clinicians in obese individuals receiving ART.

Relation of Iliac Artery Calcium With Adiposity Measures and Peripheral Artery Disease

Arterial calcification is associated with cardiovascular morbidity and mortality. To improve the understanding of the pathogenesis involved with iliac artery calcium (IAC), we sought to examine the associations between the burden of IAC with adiposity measures and peripheral artery disease (PAD). Participants (n = 1,236, 52% women, mean age 60 years) were drawn from the Framingham Heart Study Offspring cohort who underwent multidetector computed tomography. The extent of IAC was quantified based on calcified atherosclerotic plaques detected in the iliac arteries. High IAC was defined based on gender-specific 90th percentile cut-off points from a healthy referent subsample. PAD is defined as an ankle-brachial index < 0.9, intermittent claudication, and/or history of lower extremity revascularization. The association between PAD and IAC was assessed using multivariable-adjusted logistic regression models. The burden of high IAC was 20.5% in women and 25.5% in men. High IAC was not associated with generalized (body mass index) or area-specific (waist circumference, and volumes of thoracic periaortic, abdominal subcutaneous, and visceral adipose tissue) adiposity measures (all p ≥0.22). High IAC was associated with increased odds of PAD (odds ratio 10.36, 95% confidence interval 4.28 to 25.09). This association persisted even after additionally adjusting for coronary artery calcium (odds ratio 11.25, 95% confidence interval 4.29 to 29.53). Burden of IAC was associated with an increased risk of PAD.

The association of obesity and obesity-related conditions with carotid extra-medial thickness in children and adolescents

BACKGROUND

Carotid extra-medial thickness (EMT) and carotid intima-media thickness (cIMT) provide information concerning vascular changes.

OBJECTIVES

In this study, we aimed to evaluate the association between carotid EMT and obesity and its metabolic complications in children.

METHODS

The study included 38 obese subjects and 30 age-matched and sex-matched healthy controls aged between 7 and 17 years. For all subjects, complete blood count, fasting blood glucose, serum insulin, aspartate aminotransferase, alanine aminotransferase, HDL cholesterol, total cholesterol and triglyceride levels were measured. The carotid EMT and cIMT were measured by an expert radiologist in all patients.

RESULTS

Body mass index (BMI) (28.8 ± 3 vs. 18.1 ± 2.2, p < 0.001), total cholesterol (167.9 ± 34.8 mg dL^-1 vs. 150.5 ± 28.1 mg dL^-1 , p = 0.029), homeostatic model assessment of insulin resistance (HOMA-IR) (4.3 vs. 1.7, p < 0.001), cIMT (0.51 ± 0.08 mm vs. 0.45 ± 0.06 mm, p < 0.001) and carotid EMT (0.74 ± 0.11 mm vs. 0.64 ± 0.1 mm, p < 0.001) were significantly higher in obese subjects than in controls, while HDL cholesterol (41.6 ± 6.5 mg dL^-1 vs. 49.5 ± 7.5 mg dL^-1 , p < 0.001) was lower in obesity group. Among the obese subjects, the HOMA-IR values (4.7 vs. 3.6, p = 0.027), cIMT (0.54 ± 0.07 mm vs. 0.49 ± 0.07 mm, p = 0.039) and carotid EMT (0.79 ± 0.1 mm vs. 0.7 ± 0.1 mm, p = 0.013) were significantly higher in post-pubertal children compared with prepubertal children. BMI, cut-off values of HOMA-IR and cIMT were significantly associated with increased carotid EMT (p < 0.001, p = 0.023 and p < 0.001, respectively). The only independent risk factor affecting carotid EMT was BMI (p < 0.001).

CONCLUSION

We have found that carotid EMT is associated with cIMT, obesity and insulin resistance and the assessment of carotid EMT may provide additional information concerning early vascular disease.

Association between adiposity and systemic atherosclerosis: a protocol of a cross-sectional autopsy study

INTRODUCTION

Adiposity has been associated with atherosclerosis in clinical studies. However, few autopsy studies have investigated this association, and they had only examined the coronary artery disease. Moreover, most studies had small sample sizes and were limited to middle-aged or young adults. Our aim is to investigate the association between adiposity and systemic atherosclerosis in an autopsy study.

METHODS AND ANALYSIS

A sample of 240 deceased with 30 years or more will be evaluated. The sample size was calculated using the lowest correlation coefficient found in previous studies (r=0.109), assuming a power of 90% and α=0.05. We will collect information about sociodemographics, frequency of previous contact of the deceased's next of kin and cardiovascular risk factors. We will measure neck, waist and hip circumferences, weight, height and abdominal subcutaneous tissue thickness, and then we will calculate the body mass index, waist-to-hip ratio, waist-to-height ratio and body shape index. We will also weigh the pericardial and abdominal visceral fat, the heart, and we will measure the left ventricular wall thickness. We will evaluate the presence of myocardial infarction, the degree of atherosclerosis in the aorta, carotid, coronary and cerebral arteries and plaque composition in carotid, coronary and cerebral arteries. For each individual, we will fix arterial and adipose tissue samples in 10% formalin and freeze another adipose tissue sample at -80°C for future studies.

ETHICS AND DISSEMINATION

Ethical approval was granted by the Ethics Committee of University of Sao Paulo Medical School, Brazil. Results will be submitted for publication in a peer-reviewed journal.

Insulin Signaling and Heart Failure

Heart failure is associated with generalized insulin resistance. Moreover, insulin-resistant states such as type 2 diabetes mellitus and obesity increases the risk of heart failure even after adjusting for traditional risk factors. Insulin resistance or type 2 diabetes mellitus alters the systemic and neurohumoral milieu, leading to changes in metabolism and signaling pathways in the heart that may contribute to myocardial dysfunction. In addition, changes in insulin signaling within cardiomyocytes develop in the failing heart. The changes range from activation of proximal insulin signaling pathways that may contribute to adverse left ventricular remodeling and mitochondrial dysfunction to repression of distal elements of insulin signaling pathways such as forkhead box O transcriptional signaling or glucose transport, which may also impair cardiac metabolism, structure, and function. This article will review the complexities of insulin signaling within the myocardium and ways in which these pathways are altered in heart failure or in conditions associated with generalized insulin resistance. The implications of these changes for therapeutic approaches to treating or preventing heart failure will be discussed.

Carotid extramedial thickness is associated with local arterial stiffness in children

OBJECTIVES

Experimental evidence suggests that structural changes to the arterial adventitia may be a key vascular determinant of early arterial stiffening, although this has not been directly studied. Accordingly, we hypothesized that in young children, in whom this relationship would not be altered by atheroma, carotid extramedial thickness (EMT), a measure that incorporates the thickness of the arterial adventitia, perivascular tissues and the internal jugular venous wall, would be associated with localized arterial stiffness of the same arterial region.

METHODS

We studied 248 healthy prepubescent children (aged 8 years). Carotid diameter and carotid EMT were measured by high-resolution ultrasound. Carotid blood pressure was derived from brachial blood pressure and carotid tonometry. Three measures of localized arterial stiffness (β stiffness index, distensibility coefficient and incremental modulus of elasticity) were calculated for the common carotid artery. Results were adjusted for heart rate and DBP, two important hemodynamic determinants of arterial stiffness.

RESULTS

Carotid EMT was associated with all three measures of arterial stiffness (β stiffness index: standardized β = 0.121, P = 0.03; distensibility coefficient: standardized β = -0.121, P = 0.05; incremental modulus of elasticity: standardized β = 0.140, P = 0.02). These associations remained significant after adjustment for potential confounders such as sex, height, waist circumference, BMI and body surface area.

CONCLUSION

Carotid EMT is associated with the stiffness of the same arterial segment in children, suggesting that the arterial adventitia may be involved in early changes in arterial stiffness during childhood.

Epiaortic fat pad area: A novel index for the dimensions of the ascending aorta

We sought to investigate the possible association between the area of the epiaortic fat pad (EAFP) and dimensions of the ascending aorta. A total of 193 individuals underwent transthoracic echocardiography (TTE) prospectively. The area of the EAFP was traced anterior to the aortic root and correlated with the diameter of the aorta. The mean area of the EAFP was 5.16 ± 2.28 cm(2) Absolute and indexed dimensions of the ascending aorta had a significant correlation with the area of the EAFP (p <0.001 for all). In a multivariate linear regression model, age >65 (p <0.001), body mass index >30 kg/m(2) (p = 0.02) and a history of hyperlipidemia (p = 0.003) were identified as independent predictors of the area for EAFP. In conclusion, both the absolute and indexed diameters of the ascending aorta at the different segments that directly come into contact with the EAFP linearly correlate with the area of the EAFP measured by TTE.

Evaluation of Periaortic Adiposity and Metabolic Disorders in Obese Children

OBJECTIVE

To evaluate the relationship between periaortic fat thickness (PAFT) and parameters involved in the development of metabolic complications of the cardiovascular system in obese children and to assess the usefulness of echocardiographic measurements of PAFT in correlation with cardiovascular risk factors.

METHODS

The study was conducted with 263 obese and 100 healthy children and adolescents. PAFT was measured with echocardiography method which was recently performed in obese children and adolescents.

RESULTS

PAFT was significantly higher in the obese group (0.258±0.031 mm) than in the control group (0.137±0.032 mm) (p<0.001). In multivariable regression analysis, body mass index-standard deviation score and total body fat were predictors of PAFT. The area under the receiver operating characteristic curve was 0.989 and was quite significant at p<0.001. PAFT above 0.179 mm was determined as the cut-off value in obese children and adolescents (sensitivity=1, specificity=0.97).

CONCLUSION

The measurement of PAFT in obese children and adolescents may be a good method to reveal the presence of early cardiovascular risk.

Relationship of thoracic fat depots with coronary atherosclerosis and circulating inflammatory biomarkers

OBJECTIVE

The aim of the study was to determine the relationship of various thoracic fat depots with the presence and extent of coronary artery plaque and circulating biomarkers.

METHODS

In 342 patients (52 ± 11 years, 61% male, BMI 29.1 ± 5.9 kg/m(2) ) with coronary computed tomography (CT), angiography, we measured the fat volume in four thoracic depots (pericoronary, epicardial, periaortic, extracardiac), assessed coronary plaque, and determined the circulating levels of C-reactive protein, tumor necrosis factor alpha, plasminogen activator inhibitor-1, monocyte chemoattractant protein-1, and adiponectin. The extent of coronary plaque was classified into three groups: 0, 1-3, and >3 segments.

RESULTS

Patients with plaque (n =169, 49%) had higher volumes of all four fat depots as compared to patients without plaque (all P < 0.01), despite similar BMI (P = 0.18). Extracardiac fat was most strongly correlated with BMI (r = 0.45, P < 0.001), while pericoronary fat was least (r = 0.21, P < 0.001). Only pericoronary fat remained associated with coronary plaque in adjusted analyses. Inflammatory biomarkers showed a positive correlation with pericoronary fat (all P < 0.0001), whereas adiponectin was not associated with this fat compartment (P = 0.60) and showed a negative correlation with all other fat depots (all P < 0.001).

CONCLUSIONS

Pericoronary fat is independently associated with coronary artery disease (CAD). Its correlation with inflammatory biomarkers suggests that while systemic inflammation plays a role in the pathogenesis of CAD, there are additional local effects that may exist.

Thoracic periaortic adipose tissue is increased in patients with subclinical hypothyroidism

OBJECTIVE

To evaluate thoracic periaortic adipose tissue (TAT) volume in patients with subclinical hypothyroidism (SH) in comparison with controls and in relation to cardiovascular risk factors.

METHODS

The study population consisted of 28 newly diagnosed SH patients (mean (s.d.) age: 37.3 (±11.4) years, 85.7% were females) and 37 healthy volunteers (mean (s.d.) age: 35.3 (±10.7) years, 81.5% were females). Comparisons between patient and control groups used demographic characteristics, anthropometrics, and laboratory findings. All participants underwent thoracic radiographic assessment in the supine position, using an eight-slice multidetector computed tomography scanner and TAT volume was measured.

RESULTS

The TAT volume was determined to be 27.2 (±12.7) cm(3) in the SH group and 16.3 (±8.1) cm(3) in the control group, and the difference was statistically significant (P<0.001). In addition, TSH levels were significantly higher in the patient group compared with the control group (P<0.001). A significant correlation was also found between TSH levels and TAT volume (r=0.572; P<0.001). In SH patients, no significant difference was noted in TAT levels with respect to sex (P=0.383) or concomitant smoking status (P=0.426).

CONCLUSIONS

Our findings indicate that SH patients have significantly higher TAT values than controls and that increased TAT levels correlate with increased TSH levels.

Epicardial adipose tissue volume as a marker of coronary artery disease severity in patients with diabetes independent of coronary artery calcium: findings from the CTRAD study

AIMS

The association between epicardial adipose tissue (EAT) volume and coronary artery disease (CAD) severity was evaluated, independent of traditional risk factors and coronary artery calcium (CAC) scores, in patients with diabetes type 2 (DM-2) using cardiac computed tomography angiography (CTA).

METHODS

A multivariate analysis was utilized to assess for an independent association after calculating EAT volume, CAD severity, and calcium scores in 92 patients with DM-II from the CTRAD study. We graded CAD severity as none (normal coronaries), mild-moderate (<70% stenosis), and severe (70% or greater stenosis).

RESULTS

A total of 39 (42.3%) asymptomatic patients with diabetes did not have CAD; 30.4% had mild/moderate CAD; and 27.1% had severe CAD. Mean EAT volume was highest in patients with severe CAD (143.14 cm(3)) as compared to mild/moderate CAD (112.7 cm(3)), and no CAD (107.5 cm(3)) (p = 0.003). After adjustment of clinical risk factors, notably, CAC score, multivariate regression analysis showed EAT volume was an independent predictor of CAD severity in this sample (odds ratio 11.2, 95% confidence interval 1.7-73.8, p = 0.01).

CONCLUSIONS

Increasing EAT volume in asymptomatic patients with DM-II is associated with presence of severe CAD, independent of BMI and CAC, as well as traditional risk factors.

Thoracic periaortic adipose tissue in relation to cardiovascular risk in type 2 diabetes mellitus

OBJECTIVE

To evaluate thoracic periaortic adipose tissue (TAT) burden in patients with type 2 diabetes mellitus (DM) in comparison with controls and in relation to cardiovascular risk factors.

METHODS

A total of 93 patients with type 2 DM (mean (standard deviation; SD) age: 56.7 (11.2) years, 71.0 % were men) and 85 nondiabetic control subjects (mean (SD) age: 54.6 (10.9) years, 58.8 % were men) who were admitted to Mevlana University hospital between January 2011 and June 2013 and underwent multidetector computed tomography for any reason were included in this retrospective cohort study. Patient and control groups were compared in terms of demographic characteristics, anthropometrics, and laboratory findings. TAT volume was evaluated in both groups, while correlates of TAT were determined via linear regression analysis among patients.

RESULTS

In patients with type 2 DM, TAT volume (40.1 (23.9) versus 16.9 (7.7) cm(3), p < 0.001), fasting blood glucose (p < 0.001), total cholesterol (p < 0.001), triglyceride (p = 0.017), and low-density lipoprotein (LDL) cholesterol (p = 0.034) levels were significantly higher compared with the control group. Strong positive correlation of TAT was noted with body mass index (r = 0.339, p = 0.001) and serum levels for fasting blood glucose (r = 0.343, p < 0.001), hemoglobin A1c (HbA1c; r = 0.615, p < 0.001), total cholesterol (r = 0.269, p = 0.009), and LDL cholesterol (r = 0.258, p = 0.013). In stepwise regression analysis, Hba1c emerged as a significant predictor of TAT (b = 0.610, p < 0.001), contributing to 19 % of its variability.

CONCLUSION

In conclusion, our findings indicate significantly higher values for TAT in diabetics than controls, being associated positively with body weight, poor glycemic control, and dyslipidemia and strongly predicted by HbA1c levels in diabetic patients, while not differing with respect to gender, smoking status, and concomitant hypertension.

Adipose tissue immune response: novel triggers and consequences for chronic inflammatory conditions

Adipose tissue inflammation mediates the association between excessive body fat accumulation and several chronic inflammatory diseases. A high prevalence of obesity-associated adipose tissue inflammation was observed not only in patients with cardiovascular conditions but also in patients with inflammatory bowel diseases, abdominal aortic aneurysm, or cardiorenal syndrome. In addition to excessive caloric intake, other triggers promote visceral adipose tissue inflammation followed by chronic, low-grade systemic inflammation. The infiltration and accumulation of immune cells in the inflamed and hypertrophied adipose tissue promote the production of inflammatory cytokines, contributing to target organ damages. This comorbidity seems to delimit subgroups of individuals with systemic adipose tissue inflammation and more severe chronic inflammatory diseases that are refractory to conventional treatment. This review highlights the association between adipose tissue immune response and the pathophysiology of visceral adiposity-related chronic inflammatory diseases, while suggesting several new therapeutic strategies.

Visceral adiposity is not associated with abdominal aortic aneurysm presence and growth

Previous studies in rodent models and patients suggest that visceral adipose could play a direct role in the development and progression of abdominal aortic aneurysm (AAA). This study aimed to assess the association of visceral adiposity with AAA presence and growth. This study was a case-control investigation of patients that did (n=196) and did not (n=181) have an AAA who presented to The Townsville Hospital vascular clinic between 2003 and 2012. Cases were patients with AAA (infra-renal aortic diameter >30 mm) and controls were patients with intermittent claudication but no AAA (infra-renal aortic diameter <30 mm). All patients underwent computed tomography angiography (CTA). The visceral to total abdominal adipose volume ratio was estimated from CTAs by assessing total and visceral adipose deposits using an imaging software program. Measurements were assessed for reproducibility by repeat assessments on 15 patients. AAA risk factors were recorded at entry. Forty-five cases underwent two CTAs more than 6 months apart to assess AAA expansion. The association of visceral adiposity with AAA presence and growth was examined using logistic regression. Visceral adipose assessment by CTA was highly reproducible (mean coefficient of variation 1.0%). AAA was positively associated with older age and negatively associated with diabetes. The visceral to total abdominal adipose volume ratio was not significantly associated with AAA after adjustment for other risk factors. Patients with a visceral to total abdominal adipose volume ratio in quartile four had a 1.63-fold increased risk of AAA but with wide confidence intervals (95% CI 0.71-3.70; p=0.248). Visceral adiposity was not associated with AAA growth. In conclusion, this study suggests that visceral adiposity is not specifically associated with AAA presence or growth although larger studies are required to confirm these findings.

Perivascular adipose tissue and coronary vascular disease

Coronary perivascular adipose tissue is a naturally occurring adipose tissue depot that normally surrounds the major coronary arteries on the surface of the heart. Although originally thought to promote vascular health and integrity, there is a growing body of evidence to support that coronary perivascular adipose tissue displays a distinct phenotype relative to other adipose depots and is capable of producing local factors with the potential to augment coronary vascular tone, inflammation, and the initiation and progression of coronary artery disease. The purpose of the present review is to outline previous findings about the cardiovascular effects of coronary perivascular adipose tissue and the potential mechanisms by which adipose-derived factors may influence coronary vascular function and the progression of atherogenesis.

Ectopic fat assessment focusing on cardiometabolic and renal risk

It is well known that people with high levels of body fat are at higher risk for developing diabetes mellitus, kidney disease, and cardiovascular disorders. Since individuals who are slightly overweight, or even individuals of normal weight, can vary in body fat distribution, their metabolic profiles and the degree of association of these profiles with cardiometabolic risk factors may differ. Fat distribution might be more of a predictive factor for cardiorenometabolic risk than obesity itself, which has led researchers to investigate whether ectopic fat accumulation may partially account for the development of cardiorenometabolic disorders. In addition to visceral obesity, fat can accumulate in the liver and muscle, and these intrahepatic and intramuscular lipid stores are associated with insulin resistance and adverse metabolic phenotypes. More recently, pericardial fat, perivascular fat, and perirenal fat were found to be associated with coronary atherosclerosis, cardiovascular diseases, and kidney damage, respectively. Thus, regional fat distribution may play a key role in understanding the development of cardiorenometabolic diseases in nonobese people.

Periaortic fat and cardiovascular risk: a comparison of high-risk older adults and age-matched healthy controls

Objective

Fat accumulation around the heart and aorta may impact cardiovascular (CV) health. The purpose of this study was to conduct a systematic investigation to examine potential associations of these fat depots with risk factors for CV events, which has not been done before.

Methods

Pericardial fat, periaortic fat around the ascending aorta (AA), descending aorta (DA) and aortic arch, and abdominal subcutaneous and visceral fat were measured by MRI in older adults with (n=385, 69±8 years, 52% female) and without (n=50, 69±8 years, 58% female) risk factors for a CV event.

Results

Individuals with CV risk factors exhibited greater fat volumes across all fat depots compared to those without risk factors. In analysis of covariance accounting for age, gender, race/ethnicity, diabetes, hypertension, coronary artery disease, smoking, and BMI, individuals with risk factors possessed higher epicardial, pericardial, AA, DA, and abdominal visceral fat (p<0.05). When matched one-to-one on age, gender, race/ethnicity, and BMI, AA and DA fat were higher in those with versus without CV risk factors (p<0.01).

Conclusions

Older adults with a high risk for CV events have greater periaortic fat than low-risk adults, even after accounting for BMI. More studies are needed to determine whether greater periaortic fat predicts future CV events.