High Density of Periaortic Adipose Tissue in Abdominal Aortic Aneurysm

A computed tomography angiography-based radiomics model for prognostic prediction of endovascular abdominal aortic repair

OBJECTIVE

This study aims to develop a radiomics machine learning (ML) model that uses preoperative computed tomography angiography (CTA) data to predict the prognosis of endovascular aneurysm repair (EVAR) for abdominal aortic aneurysm (AAA) patients.

METHODS

In this retrospective study, 164 AAA patients underwent EVAR and were categorized into shrinkage (good prognosis) or stable (poor prognosis) groups based on post-EVAR sac regression. From preoperative AAA and perivascular adipose tissue (PVAT) image, radiomics features (RFs) were extracted for model creation. Patients were split into 80 % training and 20 % test sets. A support vector machine model was constructed for prediction. Accuracy is evaluated via the area under the receiver operating characteristic curve (AUC).

RESULTS

Demographics and comorbidities showed no significant differences between shrinkage and stable groups. The model containing 5 AAA RFs (which are original_firstorder_InterquartileRange, log-sigma-3-0-mm-3D_glrlm_GrayLevelNonUniformityNormalized, log-sigma-3-0-mm-3D_glrlm_RunPercentage, log-sigma-4-0-mm-3D_glrlm_ShortRunLowGrayLevelEmphasis, wavelet-LLH_glcm_SumEntropy) had AUCs of 0.86 (training) and 0.77 (test). The model containing 7 PVAT RFs (which are log-sigma-3-0-mm-3D_firstorder_InterquartileRange, log-sigma-3-0-mm-3D_glcm_Correlation, wavelet-LHL_firstorder_Energy, wavelet-LHL_firstorder_TotalEnergy, wavelet-LHH_firstorder_Mean, wavelet-LHH_glcm_Idmn, wavelet-LHH_glszm_GrayLevelNonUniformityNormalized) had AUCs of 0.76 (training) and 0.78 (test). Combining AAA and PVAT RFs yielded the highest accuracy: AUCs of 0.93 (training) and 0.87 (test).

CONCLUSIONS

Radiomics-based CTA model predicts aneurysm sac regression post-EVAR in AAA patients. PVAT RFs from preoperative CTA images were closely related to AAA prognosis after EVAR, enhancing accuracy when combined with AAA RFs. This preliminary study explores a predictive model designed to assist clinicians in optimizing therapeutic strategies during clinical decision-making processes.

Sex-Specific Characteristics of Perivascular Fat in Aortic Aneurysms

Aortic aneurysms (AAs), the dilation or widening of the aorta, lead to dissection or rupture with high morbidity and mortality if untreated. AA displays gender disparities in its prevalence, progression and outcomes, with women having worse outcomes and faster aneurysm growth. However, current guidelines do not address gender dimorphism, emphasizing the urgent need for personalized treatment strategies and further research. Perivascular adipose tissue (PVAT), a unique type of fat surrounding blood vessels, plays a critical role in maintaining vasomotor tone and vascular homeostasis, with dysfunction associated with chronic inflammation and vessel-wall remodeling. Indeed, PVAT dysfunction promotes the development of aortic aneurysms, with hormonal and biomechanical factors exacerbating the pathological vascular microenvironment. The sexually dimorphic characteristics of PVAT include morphological, immunological, and hormonally mediated differences. Thus, targeting PVAT-mediated mechanisms may be a promising option for the (gender-specific) therapeutic management of cardiovascular pathologies. This review examines the emerging importance of PVAT in vascular health, its potential therapeutic implications for AA, and identifies gaps in the current state of research.

Comparative Analysis of Perivascular Adipose Tissue Attenuation on Chest Computed Tomography Angiography in Patients with Marfan Syndrome: A Case-Control Study

Background: Marfan syndrome (MFS) is a rare autosomal dominant disorder affecting connective tissues due to mutations in the fibrillin-1 gene. These genetic changes often result in severe cardiovascular conditions, including asymptomatic thoracic aortic dilation potentially leading to dissection or rupture. Perivascular adipose tissue attenuation (PVAT) observed on computed tomography may serve as a marker of localized inflammation and indicate early histopathological changes in the vascular walls of MFS patients compared to healthy individuals. Objective: This study aimed to compare PVAT values between patients with MFS and healthy controls in order to explore whether MFS patients show higher PVAT secondary to these histopathological abnormalities. Methods: This case-control study assessed PVAT on ascending aorta through computed tomography angiography (CTA) in 54 genetically confirmed MFS patients and 43 controls with low ischemic risk, excluding those with known aortic aneurysms. Results: PVAT analysis revealed significant differences between the MFS patients and healthy controls (-70.6 HU [-72.6 HU to -68.5 HU] versus -75.1 HU [-77.1 HU to -73.1 HU], p = 0.002), suggesting potential early vascular changes in the MFS group. Conclusions: The findings underscore the potential diagnostic role of PVAT in patients with genetically confirmed MFS but normal ascending aorta diameter.

Serotonin 3 receptor antagonism reduces angiotensin II-induced abdominal aortic aneurysms: Contribution of periaortic fat-derived serotonin

Serotonin (5-HT) has been implicated in cerebral aneurysm rupture, but it is unclear whether 5-HT plays a role in aortic aneurysm development and rupture, despite well known contractile effects of 5-HT through aortic 5-HT receptors. Abdominal aortic aneurysms (AAAs) induced by angiotensin II (AngII) infusion to mice exhibit periaortic inflammation and are prone to rupture. Periaortic fat (PAF), a potential source of 5-HT through tryptophan hydroxylase 1 (Tph1), has been implicated in AAA development. We quantified mRNA abundance of 5-HT receptors (Htr1b, Htr2a, Htr2b, Htr3a, and Htr7) and Tph1 in thoracic and abdominal aortas and surrounding PAF. Compared with other 5-HT receptors, we detected high levels of serotonin 3 receptor type a (Htr3a) mRNA in the abdominal aortas and abdominal PAF. Tph1 mRNA and 5-HT immunostaining were detected in aortas and PAF, with 5-HT levels higher in abdominal than thoracic PAF, and higher in epididymal white than interscapular brown fat. AngII infusion facilitated evoked [3H]5-HT release from thoracic PAF and modestly reduced 5-HT levels in thoracic PAF and brown fat. Based on a high level of Htr3a mRNA in abdominal aortas and PAF, we investigated the development of AngII-induced AAAs when serotonin 3 receptors were pharmacologically antagonized with tropisetron. Tropisetron abrogated abdominal aortic lumen diameters, aneurysm (distal thoracic aneurysm and AAA) incidence, maximal AAA diameters, and aortic weights of AngII-infused male mice. These findings indicate a novel role for serotonin 3 receptor in AAA development, with a potential clinically relevant contribution for PAF as a local source of 5-HT. SIGNIFICANCE STATEMENT: Aortic aneurysms are life-threatening vascular disorders with no effective therapeutics. This study identified antagonism of the serotonin 3 receptor as a potential therapeutic target to reduce the formation and severity of experimentally-induced aneurysms in the thoracic and abdominal aorta. Additionally, periaortic fat was identified as a potential site for serotonin production in the development of aortic aneurysms.

Assessing abdominal aortic aneurysm growth using radiomic features of perivascular adipose tissue after endovascular repair

OBJECTIVES

The study aimed to investigate the relationship between the radiomic features of perivascular adipose tissue (PVAT) and abdominal aortic aneurysm (AAA) growth after endovascular aneurysm repair (EVAR).

METHODS

Patients with sub-renal AAA who underwent regular follow-up after EVAR between March 2014 and March 2024 were retrospectively collected. Two radiologists segmented aneurysms and PVAT. Patients were categorised into growing and non-growing groups based on volumetric changes observed in two follow-up computed tomography examinations. One hundred seven radiomic features were automatically extracted from the PVAT region. Univariable and multivariable logistic regression was performed to analyse radiomic features and clinical characteristics. Furthermore, the performance of the integrated clinico-radiological model was compared with models using only radiomic features or clinical characteristics separately.

RESULTS

A total of 79 patients (68 ± 9 years, 89% men) were enroled in this study, 19 of whom had a growing aneurysm. Compared to the non-growing group, PVAT of growing AAA showed a higher surface area to volume ratio (non-growing vs growing, 0.63 vs 0.70, p = 0.04), and a trend of low dependence and high dispersion manifested by texture features (p < 0.05). The area under the curve of the integrated clinico-radiological model was 0.78 (95% confidence intervals 0.65-0.91), with a specificity of 87%. The integrated model outperformed models using only radiomic or clinical features separately (0.78 vs 0.69 vs 0.69).

CONCLUSIONS

Higher surface area to volume ratio and more heterogeneous texture presentation of PVAT were associated with aneurysm dilation after EVAR. Radiomic features of PVAT have the potential to predict AAA progression.

CLINICAL RELEVANCE STATEMENT

Radiomic features of PVAT are associated with AAA progression and can be an independent risk factor for aneurysm dilatation to assist clinicians in postoperative patient surveillance and management.

KEY POINTS

After EVAR for AAA, patients require monitoring for progression. PVAT surrounding growing AAA after EVAR exhibits a more heterogeneous texture. Integrating PVAT-related features and clinical features results in better predictive performance.

Computer tomography-based assessment of perivascular adipose tissue in patients with abdominal aortic aneurysms

This retrospective study investigates perivascular adipose tissue (PVAT) alterations in CT as a marker of inflammation in patients with abdominal aortic aneurysms (AAA). 100 abdominal CT scans of patients with abdominal aortic aneurysms and 100 age and sex matched controls without underlying aortic disease were included. Artificial Intelligence (AI) assisted segmentation of the aorta and the surrounding adipose tissue was performed. Adipose tissue density was measured in Hounsfield units (HU) close (2-5mm, HUclose) and distant (10-12mm, HUdistant) to the aortic wall. To investigate alterations in adipose tissue density close to the aorta (HUclose) as a potential marker of inflammation, we calculated the difference HUΔ = HUclose-HUdistant and the fat attenuation ratio HUratio = HUclose/HUdistant as normalized attenuation measures. These two markers were compared i) inter-individually between AAA patients and controls and ii) intra-individually between the aneurysmal and non-aneurysmal segments in AAA patients. Since most AAAs are generally observed infrarenal, the aneurysmal section of the AAA patients was compared with the infrarenal section of the aorta of the control patients. In inter-individual comparisons, higher HUΔ and a lower HUratio were observed (aneurysmal: 8.9 ± 5.1 HU vs. control: 6.9 ± 4.8 HU, p-value = 0.006; aneurysmal: 89.8 ± 5.7% vs. control: 92.1 ± 5.5% p-value = 0.004). In intra-individual comparisons, higher HUΔ and lower HUratio were observed (aneurysmal: 8.9 ± 5.1 HU vs. non-aneurysmal: 5.5 ± 4.1 HU, p-value < 0.001; aneurysmal: 89.8 ± 5.7% vs. non-aneurysmal 93.3 ± 4.9%, p-value < 0.001). The results indicate PVAT density alterations in AAA patients. This motivates further research to establish non-invasive imaging markers for vascular and perivascular inflammation in AAA.

Coronary inflammation on chest computed tomography and COVID-19 mortality

OBJECTIVES

The main factors associated with coronavirus disease-19 (COVID-19) mortality are age, comorbidities, pattern of inflammatory response, and SARS-CoV-2 lineage involved in infection. However, the clinical course of the disease is extremely heterogeneous, and reliable biomarkers predicting adverse prognosis are lacking. Our aim was to elucidate the prognostic role of a novel marker of coronary artery disease inflammation, peri-coronary adipose tissue attenuation (PCAT), available from high-resolution chest computed tomography (HRCT) in COVID-19 patients with severe disease requiring hospitalization.

METHODS

Two distinct groups of patients were admitted to Parma University Hospital in Italy with COVID-19 in March 2020 and March 2021 (first- and third-wave peaks of the COVID-19 pandemic in Italy, with the prevalence of wild-type and B.1.1.7 SARS-CoV-2 lineage, respectively) were retrospectively enrolled. The primary endpoint was in-hospital mortality. Demographic, clinical, laboratory, HRCT data, and coronary artery HRCT features (coronary calcium score and PCAT attenuation) were collected to show which variables were associated with mortality.

RESULTS

Among the 769 patients enrolled, 555 (72%) were discharged alive, and 214 (28%) died. In multivariable logistic regression analysis age (p < 0.001), number of chronic illnesses (p < 0.001), smoking habit (p = 0.006), P/F ratio (p = 0.001), platelet count (p = 0.002), blood creatinine (p < 0.001), non-invasive mechanical ventilation (p < 0.001), HRCT visual score (p < 0.001), and PCAT (p < 0.001), but not the calcium score, were independently associated with in-hospital mortality.

CONCLUSION

Coronary inflammation, measured with PCAT on non-triggered HRCT, appeared to be independently associated with higher mortality in patients with severe COVID-19, while the pre-existent coronary atherosclerotic burden was not associated with adverse outcomes after adjustment for covariates.

CLINICAL RELEVANCE STATEMENT

The current study demonstrates that a relatively simple measurement, peri-coronary adipose tissue attenuation (PCAT), available ex-post from standard high-resolution computed tomography, is strongly and independently associated with in-hospital mortality.

KEY POINTS

• Coronary inflammation can be measured by the attenuation of peri-coronary adipose tissue (PCAT) on high-resolution CT (HRCT) without contrast media. • PCAT is strongly and independently associated with in-hospital mortality in SARS-CoV-2 patients. • PCAT might be considered an independent prognostic marker in COVID-19 patients if confirmed in other studies.

Obesity and the obesity paradox in abdominal aortic aneurysm

Obesity, characterized by its complexity and heterogeneity, has emerged as a significant public health concern. Its association with increased incidence and mortality of cardiovascular diseases stems not only from its complications and comorbidities but also from the endocrine effects of adipose tissue. Abdominal aortic aneurysm (AAA), a chronic inflammatory condition, has been closely linked to obesity. Intriguingly, mild obesity appears to confer a protective effect against AAA mortality, whereas severe obesity and being underweight do not, giving rise to the concept of the "obesity paradox". This review aims to provide an overview of obesity and its paradoxical relationship with AAA, elucidate its underlying mechanisms, and discuss the importance of preoperative weight loss in severely obese patients with AAA.

Cardiovascular Disease from Pathophysiology to Risk Estimation: Is Inflammation Estimated through Perivascular Attenuation on Computed Tomography the Key?

(1) Background: Systemic inflammation stands as a well-established risk factor for ischemic cardiovascular disease, as well as a contributing factor in the development of cardiac arrhythmias, notably atrial fibrillation. Furthermore, scientific studies have brought to light the pivotal role of localized vascular inflammation in the initiation, progression, and destabilization of coronary atherosclerotic disease. (2) Methods: We comprehensively review recent, yet robust, scientific evidence elucidating the use of perivascular adipose tissue attenuation measurement on computed tomography applied to key anatomical sites. Specifically, the investigation extends to the internal carotid artery, aorta, left atrium, and coronary arteries. (3) Conclusions: The examination of perivascular adipose tissue attenuation emerges as a non-invasive and indirect means of estimating localized perivascular inflammation. This measure is quantified in Hounsfield units, indicative of the inflammatory response elicited by dense adipose tissue near the vessel or the atrium. Particularly noteworthy is its potential utility in assessing inflammatory processes within the coronary arteries, evaluating coronary microvascular dysfunction, appraising conditions within the aorta and carotid arteries, and discerning inflammatory states within the atria, especially in patients with atrial fibrillation. The widespread applicability of perivascular adipose tissue attenuation measurement underscores its significance as a diagnostic tool with considerable potential for enhancing our understanding and management of cardiovascular diseases.

CT Attenuation of Periaortic Adipose Tissue in Abdominal Aortic Aneurysms

Purpose To assess periaortic adipose tissue attenuation at CT angiography in different abdominal aortic aneurysm disease states. Materials and Methods In a retrospective observational study from January 2018 to December 2022, periaortic adipose tissue attenuation was assessed at CT angiography in patients with asymptomatic or symptomatic (including rupture) abdominal aortic aneurysms and controls without aneurysms. Adipose tissue attenuation was measured using semiautomated software in periaortic aneurysmal and nonaneurysmal segments of the abdominal aorta and in subcutaneous and visceral adipose tissue. Periaortic adipose tissue attenuation values between the three groups were assessed using Student t tests and Wilcoxon rank sum tests followed by a multiregression model. Results Eighty-eight individuals (median age, 70 years [IQR, 65-78]; 78 male and 10 female patients) were included: 70 patients with abdominal aortic aneurysms (40 asymptomatic and 30 symptomatic, including 24 with rupture) and 18 controls. There was no evidence of differences in the periaortic adipose tissue attenuation in the aneurysmal segment in asymptomatic patients versus controls (-81.44 HU ± 7 [SD] vs -83.27 HU ± 9; P = .43) and attenuation in nonaneurysmal segments between asymptomatic patients versus controls (-75.43 HU ± 8 vs -78.81 HU ± 6; P = .08). However, symptomatic patients demonstrated higher periaortic adipose tissue attenuation in both aneurysmal (-57.85 HU ± 7; P < .0001) and nonaneurysmal segments (-58.16 HU ± 8; P < .0001) when compared with the other two groups. Conclusion Periaortic adipose tissue CT attenuation was not increased in stable abdominal aortic aneurysm disease. There was a generalized increase in attenuation in patients with symptomatic disease, likely reflecting the systemic consequences of acute rupture. Keywords: Abdominal Aortic Aneurysm, Periaortic Adipose Tissue Attenuation, CT Angiography ClinicalTrials.gov registration no. NCT02229006 © RSNA, 2024.

Association Between Aneurysm Wall Inflammation Detected by Imaging Perivascular Fat and Secondary Intervention Risk for Abdominal Aortic Aneurysm Patients After Endovascular Repair

OBJECTIVE

To investigate the association between the imaging biomarker (volumetric perivascular characterization index [VPCI]) which indicates the aortic wall inflammation by mapping the spatial changes of perivascular fat attenuation on computed tomography angiography (CTA) and the reintervention risk for abdominal aortic aneurysm (AAA) patients after endovascular aortic repair (EVAR).

METHODS

This case-control study included AAA patients undergoing EVAR from a single center (n=260). Cases were AAA patients undergoing reintervention after EVAR and a 1:1 frequency-matched control group of AAA patients post-EVAR with a shrunken or ≥3-year stable sac and free of reintervention signs during the follow-up. The predictive variable (VPCI trajectory) was converted to binary variables according to the changing trend of VPCI with follow-up time. As a quasi-complete separation data pattern, least absolute shrinkage and selection operator (lasso) regression was used to screen and prove the VPCI trajectory as the best predictor, and the performance was evaluated by calculating the accuracy, sensitivity, and specificity.

RESULTS

Between 2010 and 2021, 15 AAA patients after EVAR with type I/III endoleak, aneurysm rupture, or impending rupture were included. Compared with the 1:1 frequency-matched controls with a shrunken or ≥3-year stable sac and free of reintervention signs during the follow-up, VPCI trajectories of the case group were all upward trends, whereas the controls showed 86.7% downward trends (p<0.001). The best predictive model of lasso regressions included 4 variables, and VPCI trajectory was the most outstanding, followed by the proximal landing zone, the distal landing zone, and the infrarenal β angle. The accuracy, sensitivity, and specificity of predicting the risk of reintervention were as follows, respectively: 93.3%, 100%, and 86.7%.

CONCLUSIONS

The wall inflammation detected by imaging perivascular adipose tissue based on the CTAs was strongly associated with the reintervention risk for AAA patients after EVAR, which might hold major promise as a new imaging biomarker for the mechanism and treatment study of human AAAs before and after EVAR.

CLINICAL IMPACT

The study introduces a novel imaging biomarker which indicates the aortic wall inflammation by mapping spatial changes of perivascular fat attenuation on CTA. This biomarker demonstrates a strong association with the reintervention risk in AAA patients after EVAR. Incorporation of VPCI into clinical practice has the potential to enhance the traditional surveillance methods (CT/CTAs) by providing clinicians with a non-invasive method to assess aortic wall inflammation and predict the risk of reintervention. Additionally, this study might offer a valuable tool for mechanism and treatment research in humans with AAAs both pre- and post-EVAR, ultimately improving patient outcomes and refining therapeutic strategies.

Assessing Abdominal Aortic Aneurysm Progression by Using Perivascular Adipose Tissue Attenuation on Computed Tomography Angiography

OBJECTIVE

Recent studies have highlighted the active and potential role of perivascular adipose tissue (PVAT) in atherosclerosis and aneurysm progression, respectively. This study explored the link between PVAT attenuation and abdominal aortic aneurysm (AAA) progression using computed tomography angiography (CTA).

MATERIALS AND METHODS

This multicenter retrospective study analyzed patients with AAA who underwent CTA at baseline and follow-up between March 2015 and July 2022. The following parameters were obtained: maximum diameter and total volume of the AAA, presence or absence of intraluminal thrombus (ILT), maximum diameter and volume of the ILT, and PVAT attenuation of the aortic aneurysm at baseline CTA. PVAT attenuation was divided into high (> -73.4 Hounsfield units [HU]) and low (≤ -73.4 HU). Patients who had or did not have AAA progression during the follow-up, defined as an increase in the aneurysm volume > 10 mL from baseline, were identified. Kaplan-Meier and multivariable Cox regression analyses were used to investigate the association between PVAT attenuation and AAA progression.

RESULTS

Our study included 167 participants (148 males; median age: 70.0 years; interquartile range: 63.0-76.0 years), of which 145 (86.8%) were diagnosed with AAA accompanied by ILT. Over a median period of 11.3 months (range: 6.0-85.0 months), AAA progression was observed in 67 patients (40.1%). Multivariable Cox regression analysis indicated that high baseline PVAT attenuation (adjusted hazard ratio [aHR] = 2.23; 95% confidence interval [CI], 1.16-4.32; P = 0.017) was independently associated with AAA progression. This association was demonstrated within the patients of AAA with ILT subcohort, where a high baseline PVAT attenuation (aHR = 2.23; 95% CI, 1.08-4.60; P = 0.030) was consistently independently associated with AAA progression.

CONCLUSION

Elevated PVAT attenuation is independently associated with AAA progression, including patients of AAA with ILT, suggesting the potential of PVAT attenuation as a predictive imaging marker for AAA expansion.

The Role of Non-Invasive Multimodality Imaging in Chronic Coronary Syndrome: Anatomical and Functional Pathways

Coronary artery disease (CAD) is one of the major causes of mortality and morbidity worldwide, with a high socioeconomic impact. Currently, various guidelines and recommendations have been published about chronic coronary syndromes (CCS). According to the recent European Society of Cardiology guidelines on chronic coronary syndrome, a multimodal imaging approach is strongly recommended in the evaluation of patients with suspected CAD. Today, in the current practice, non-invasive imaging methods can assess coronary anatomy through coronary computed tomography angiography (CCTA) and/or inducible myocardial ischemia through functional stress testing (stress echocardiography, cardiac magnetic resonance imaging, single photon emission computed tomography-SPECT, or positron emission tomography-PET). However, recent trials (ISCHEMIA and REVIVED) have cast doubt on the previous conception of the management of patients with CCS, and nowadays it is essential to understand the limitations and strengths of each imaging method and, specifically, when to choose a functional approach focused on the ischemia versus a coronary anatomy-based one. Finally, the concept of a pathophysiology-driven treatment of these patients emerged as an important goal of multimodal imaging, integrating 'anatomical' and 'functional' information. The present review aims to provide an overview of non-invasive imaging modalities for the comprehensive management of CCS patients.

Perivascular adipose tissue: Fine-tuner of vascular redox status and inflammation

Perivascular adipose tissue (PVAT) refers to the aggregate of adipose tissue surrounding the vasculature, exhibiting the phenotypes of white, beige and brown adipocytes. PVAT has emerged as an active modulator of vascular homeostasis and pathogenesis of cardiovascular diseases in addition to its structural role to provide mechanical support to blood vessels. More specifically, PVAT is closely involved in the regulation of reactive oxygen species (ROS) homeostasis and inflammation along the vascular tree, through the tight interaction between PVAT and cellular components of the vascular wall. Furthermore, the phenotype-genotype of PVAT at different regions of vasculature varies corresponding to different cardiovascular risks. During ageing and obesity, the cellular proportions and signaling pathways of PVAT vary in favor of cardiovascular pathogenesis by promoting ROS generation and inflammation. Physiological means and drugs that alter PVAT mass, components and signaling may provide new therapeutic insights in the treatment of cardiovascular diseases. In this review, we aim to provide an updated understanding towards PVAT in the context of redox regulation, and to highlight the therapeutic potential of targeting PVAT against cardiovascular complications.

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.

Thoracic perivascular adipose tissue inhibits VSMC apoptosis and aortic aneurysm formation in mice via the secretome of browning adipocytes

Abdominal aortic aneurysm (AAA) is a dangerous vascular disease without any effective drug therapies so far. Emerging evidence suggests the phenotypic differences in perivascular adipose tissue (PVAT) between regions of the aorta are implicated in the development of atherosclerosis evidenced by the abdominal aorta more vulnerable to atherosclerosis than the thoracic aorta in large animals and humans. The prevalence of thoracic aortic aneurysms (TAA) is much less than that of abdominal aortic aneurysms (AAA). In this study we investigated the effect of thoracic PVAT (T-PVAT) transplantation on aortic aneurysm formation and the impact of T-PVAT on vascular smooth muscle cells. Calcium phosphate-induced mouse AAA model was established. T-PVAT (20 mg) was implanted around the abdominal aorta of recipient mice after removal of endogenous abdominal PVAT (A-PVAT) and calcium phosphate treatment. Mice were sacrificed two weeks after the surgery and the maximum external diameter of infrarenal aorta was measured. We found that T-PVAT displayed a more BAT-like phenotype than A-PVAT; transplantation of T-PVAT significantly attenuated calcium phosphate-induced abdominal aortic dilation and elastic degradation as compared to sham control or A-PVAT transplantation. In addition, T-PVAT transplantation largely preserved smooth muscle cell content in the abdominal aortic wall. Co-culture of T-PVAT with vascular smooth muscle cells (VSMCs) significantly inhibited H2O2- or TNFα plus cycloheximide-induced VSMC apoptosis. RNA sequencing analysis showed that T-PVAT was enriched by browning adipocytes and anti-apoptotic secretory proteins. We further verified that the secretome of mature adipocytes isolated from T-PVAT significantly inhibited H2O2- or TNFα plus cycloheximide-induced VSMC apoptosis. Using proteomic and bioinformatic analyses we identified cartilage oligomeric matrix protein (COMP) as a secreted protein significantly increased in T-PVAT. Recombinant COMP protein significantly inhibited VSMC apoptosis. We conclude that T-PVAT exerts anti-apoptosis effect on VSMCs and attenuates AAA formation, which is possibly attributed to the secretome of browning adipocytes.

Evaluation of the relationship between para-aortic adipose tissue and ascending aortic diameter using a new method

BACKGROUND

Para-aortic adipose tissue (PAT) is the local adipose tissue that externally surrounds the aorta. It contributes significantly to aortic atherosclerosis and enlargement. Studies conducted with computed tomography and magnetic resonance have shown that individuals with aortic aneurysm had more PAT than healthy individuals. In this study, we measured PAT using transthoracic echocardiography (TTE). The aim of this study is to investigate the possible relationship of TTE measured PAT with ascending aortic width.

METHODS

PAT was defined as the hypoechoic space in front of ascending aortic 2 cm above the sinotubular junction at the end of the systole. Patients were divided into 2 groups according to the presence of dilatation in the ascending aorta using Roman's classification (aortic size index, ASI). ASI of less than 21 was considered no aortic dilation and an ASI of 21 mm/m2 or greater was considered to have aortic dilation.

RESULTS

A total of 321 unselected patients were divided into the ascending aortic dilatation (AAD) group (n = 96) and the normal ascending aorta diameter group (n = 225 patients). PAT was significantly higher in the AAD group compared with the non-ADD group (0.9 (0.48) vs. 0.7 (0.91) mm, p < 0.0001). Univariate and multivariate logistic regression analysis revealed that PAT (OR: 3.005, 95%CI (1.445-6.251)) were significantly associated with AAD.

CONCLUSIONS

This is the first study which evaluated PAT measured by TTE. We found a significant association between PAT measured by TTE and ascending aorta width.

Identification of a biomarker and immune infiltration in perivascular adipose tissue of abdominal aortic aneurysm

Objective: Abdominal aortic aneurysm (AAA) refers to unusual permanent dilation of the abdominal aorta, and gradual AAA expansion can lead to fatal rupture. However, we lack clear understanding of the pathogenesis of this disease. The effect of perivascular adipose tissue (PVAT) on vascular functional status has attracted increasing attention. Here, we try to identify the potential mechanisms linking AAA and PVAT.

Methods: We downloaded dataset GSE119717, including 30 dilated AAA PVAT samples and 30 non-dilated aorta PVAT samples from AAA cases, from Gene Expression Omnibus to identify differentially expressed genes (DEGs). We performed pathway enrichment analysis by Metascape, ClueGo and DAVID to annotate PVAT functional status according to the DEGs. A protein-protein interaction network, the support vector machine (SVM)-recursive feature elimination and the least absolute shrinkage and selection operator regression model were constructed to identify feature genes. Immune infiltration analysis was explored by CIBERSORT. And the correlation between feature gene and immune cells was also calculated. Finally, we used the angiotensin II (Ang II)-ApoE−/− mouse model of AAA to verify the effect of feature gene expression by confirming protein expression using immunohistochemistry and western blot.

Results: We identified 22 DEGs, including 21 upregulated genes and 1 downregulated gene. The DEGs were mainly enriched in neutrophil chemotaxis and IL-17 signaling pathway. FOS was identified as a good diagnostic feature gene (AUC = 0.964). Immune infiltration analysis showed a higher level of T cells follicular helper, activated NK cells, Monocytes, activated Mast cells in AAA group. And FOS was correlated with immune cells. Immunohistochemistry and western blot confirmed higher FOS expression in PVAT of the AAA mouse model compared to control group.

Conclusion: The differentially expressed genes and pathways identified in this study provide further understanding of how PVAT affects AAA development. FOS was identified as the diagnostic gene. There was an obvious difference in immune cells infiltration between normal and AAA groups.

Artificial intelligence assisted compositional analyses of human abdominal aortic aneurysms ex vivo

Quantification of histological information from excised human abdominal aortic aneurysm (AAA) specimens may provide essential information on the degree of infiltration of inflammatory cells in different regions of the AAA. Such information will support mechanistic insight in AAA pathology and can be linked to clinical measures for further development of AAA treatment regimens. We hypothesize that artificial intelligence can support high throughput analyses of histological sections of excised human AAA. We present an analysis framework based on supervised machine learning. We used TensorFlow and QuPath to determine the overall architecture of the AAA: thrombus, arterial wall, and adventitial loose connective tissue. Within the wall and adventitial zones, the content of collagen, elastin, and specific inflammatory cells was quantified. A deep neural network (DNN) was trained on manually annotated, Weigert stained, tissue sections (14 patients) and validated on images from two other patients. Finally, we applied the method on 95 new patient samples. The DNN was able to segment the sections according to the overall wall architecture with Jaccard coefficients after 65 epocs of 92% for the training and 88% for the validation data set, respectively. Precision and recall both reached 92%. The zone areas were highly variable between patients, as were the outputs on total cell count and elastin/collagen fiber content. The number of specific cells or stained area per zone was deterministically determined. However, combining the masks based on the Weigert stainings, with images of immunostained serial sections requires addition of landmark recognition to the analysis path. The combination of digital pathology, the DNN we developed, and landmark registration will provide a strong tool for future analyses of the histology of excised human AAA. In combination with biomechanical testing and microstructurally motivated mathematical models of AAA remodeling, the method has the potential to be a strong tool to provide mechanistic insight in the disease. In combination with each patients’ demographic and clinical profile, the method can be an interesting tool to in supportof a better treatment regime for the patients.

FOS gene associated immune infiltration signature in perivascular adipose tissues of abdominal aortic aneurysm

Abdominal aortic aneurysms (AAA) are pathological dilations in local aortic wall. The inflammatory infiltrates of the perivascular adipose tissue (PAT) surrounding AAAs were associated with AAAs and have been shown to contribute vascular pathology. However, the mechanism by which PAT inflammation contributes to vascular pathology in AAA remains to be clarified. This study aimed to explore the association between immune cell infiltration and key gene expression profile in PAT of AAA. For that, a gene expression dataset of human dilated perivascular adipose tissue (dPAT), non-dilated perivascular adipose tissue (ndPAT), subcutaneous abdominal fat (SAF) and omental-visceral fat (OVF) samples, as well as another microarray dataset of the abdominal perivascular adipose tissue in peripheral artery disease patients were downloaded from GEO database for analysis in this study. The CIBERSORT algorithm, weighted gene co-expression network analysis (WGCNA) and LASSO algorithm were used for the identification of immune infiltration, immune-related genes and the development of diagnostic signature. Our data discovered a significant higher proportion of activated mast cells and follicular helper T (Tfh) cells in dPAT than ndPAT, OVT and SAF samples. Moreover, AP-1 family members (FOS, FOSB, ATF3, JUN and JUNB) were found to compose the hub genes of purple module in WGCNA. Among them, FOS gene acts as a higher efficient marker to discriminate dPAT from ndPAT, OVT and SAF in AAA. Meanwhile, the expression profiles of the AP-1 family members are all significantly positive correlated with activated mast cell, plasma cell and Tfh cell infiltration in dPAT of AAA. Therefore, in the PAT surrounding AAA, the signature of inflammatory infiltration might be represented by a FOS-dominated cell network consist of activated mast cell, plasma cell and Tfh cell. Given the complicated etiology of AAA, our results are likely to shed new light on the pathophysiologic mechanism of AAA influenced by the local dPAT.

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.

Epicardial adipose tissue volume is associated with abdominal aortic aneurysm expansion

BACKGROUND

Epicardial adipose tissue volume (EATV) is associated with cardiovascular diseases such as coronary artery disease. However, no information is available regarding the relationship between EATV and abdominal aortic aneurysm (AAA) expansion. This study aimed to evaluate the association between EATV and the growth of AAA, and to identify predictors of AAA expansion.

METHODS

Between June 2009 and December 2019, a total of 906 patients underwent endovascular or open repair of AAA at our institution. Patients with previous cardiac surgery, previous ascending thoracic aortic surgery, ruptured AAA, infected AAA, inflammatory AAA, saccular aneurysm, solitary iliac aneurysm, or reintervention after treatment for AAA were excluded. Two hundred and thirty-seven patients with at least two preoperative computed tomography (CT) scans performed more than 180 days apart were included in this study. EATV within the pericardium was retrospectively quantified from preoperative non-contrast CT images using a 3D workstation. The EATV index was defined as EATV divided by body surface area. The AAA expansion rate was defined as the increase in AAA diameter per year, and patients were divided into the slow-expansion group, with an expansion rate < 5 mm/year, and the fast-expansion group, with an expansion rate ≥ 5 mm/year. The correlation between expansion rate and the EATV index was analyzed, and the cut-off value of the EATV index was determined using a receiver operating characteristics curve. Multivariate analysis was used to assess predictors of the AAA expansion rate.

RESULTS

The expansion rate of AAA was positively correlated with the EATV index (R = .237, P < .001). The initial aneurysm diameter (P < .001) and EATV index (P = .009) differed significantly between the two groups. The cut-off value of the EATV index was 60.3 cm³/m² (area under the curve, .658; 95% confidence interval [CI], .568-.749; sensitivity, 1.000; specificity, .309). Multivariate analysis revealed that the initial aneurysm diameter and an EATV index > 60.3 cm³/m² were significantly associated with the AAA expansion rate.

CONCLUSIONS

This study demonstrated that the EATV index was associated with AAA expansion.

EGR1 and KLF4 as Diagnostic Markers for Abdominal Aortic Aneurysm and Associated With Immune Infiltration

Background

Formation and rupture of abdominal aortic aneurysm (AAA) is fatal, and the pathological processes and molecular mechanisms underlying its formation and development are unclear. Perivascular adipose tissue (PVAT) has attracted extensive attention as a newly defined secretory organ, and we aim to explore the potential association between PVAT and AAA.

Methods

We analyzed gene expression and clinical data of 30 PVAT around AAA and 30 PVAT around normal abdominal aorta (NAA). The diagnostic markers and immune cell infiltration of PVAT were further investigated by WGCNA, CIBERSORT, PPI, and multiple machine learning algorisms (including LASSO, RF, and SVM). Subsequently, eight-week-old C57BL/6 male mice (n = 10) were used to construct AAA models, and aorta samples were collected for molecular validation. Meanwhile, fifty-five peripheral venous blood samples from patients (AAA vs. normal: 40:15) in our hospital were used as an inhouse cohort to validate the diagnostic markers by qRT-PCR. The diagnostic efficacy of biomarkers was assessed by receiver operating characteristic (ROC) curve, area under the ROC (AUC), and concordance index (C-index).

Results

A total of 75 genes in the Grey60 module were identified by WGCNA. To select the genes most associated with PVAT in the grey60 module, three algorithms (including LASSO, RF, and SVM) and PPI were applied. EGR1 and KLF4 were identified as diagnostic markers of PVAT, with high accurate AUCs of 0.916, 0.926, and 0.948 (combined two markers). Additionally, the two biomarkers also displayed accurate diagnostic efficacy in the mice and inhouse cohorts, with AUCs and C-indexes all >0.8. Compared with the NAA group, PVAT around AAA was more abundant in multiple immune cell infiltration. Ultimately, the immune-related analysis revealed that EGR1 and KLF4 were associated with mast cells, T cells, and plasma cells.

Conclusion

EGR1 and KLF4 were diagnostic markers of PVAT around AAA and associated with multiple immune cells.

Epicardial and periaortic fat characteristics in ischemic stroke: Relationship with stroke etiology and calcification burden

PURPOSE

We explored epicardial (EAT) and periaortic (PAT) adipose tissue characteristics in patients with acute ischemic stroke (AIS), and the relationship with stroke etiology, calcification burden, and inflammation.

METHOD

We included a retrospective cohort of consecutive patients admitted with AIS between 2015 and 2020 who underwent a chest computed tomography. We calculated volumes and attenuation of EAT and PAT, and coronary artery (CAC), and thoracic aortic (TAC) calcification. Admission's neutrophil/lymphocyte ratio (NLR) was recorded. Stroke severity was assessed using the National Institute of Health Stroke Scale (NIHSS), and patients were discriminated between cardioembolic (CE), non-CE, and embolic strokes of uncertain source (ESUS).

RESULTS

A total of 182 patients were included. EAT (non-CE 127.4 ± 47.1 cm3; CE 133.3 ± 56.7 cm3; ESUS 121.6 ± 63.5 cm3, p > 0.05) and PAT (non-CE 37.4 ± 18.6 cm3; CE 40.4 ± 17.2 cm3; ESUS 34.5 ± 14.1 cm3, p > 0.05) volumes were similar between stroke etiologies. Patients with CE stroke had higher PAT attenuation (PAT = non-CE -84.4 ± 7.0 HU; CE -78.1 ± 9.9 HU; ESUS -82.3 ± 9.3 HU, p < 0.001). Using multiple linear regression, albeit weak, we found a significant relationship between NLR and PAT attenuation [Beta 0.24; (95% CI 0.04-0.51), p < 0.05). Despite similar volume, PAT attenuation was higher (p < 0.01) among demised patients.

CONCLUSION

In this study, we identified higher periaortic fat attenuation, despite similar fat volume, in patients with CE stroke.

Different effects of high-fat and high-sucrose diets on the physiology of perivascular adipose tissues of the thoracic and abdominal aorta

Vascular diseases such as atherosclerosis and aneurysms are associated with diet. Perivascular adipose tissue (PVAT) was reportedly involved in the regulation of vascular functions. It is suggested that imbalanced diets can cause PVAT inflammation and dysfunction as well as impaired vascular function. However, the association between diets and PVAT are not clearly understood. Here, we showed that a high-fat and a high-sucrose diet affected PVAT at different sites. A high-fat diet induced increased number of large-sized lipid droplets and increased CD (Cluster of differentiation) 68+ macrophage- and monocyte chemotactic protein (MCP)-1-positive areas in the abdominal aortic PVAT (aPVAT). In addition, a high-fat diet caused decreased collagen fibre-positive area and increased CD68+ macrophage- and MCP-1-positive areas in the abdominal aorta. In contrast, a high-sucrose diet induced increased number of large-sized lipid droplets, increased CD68+ macrophage- and MCP-1-positive areas, and decreased UCP-1 positive area in the thoracic aortic PVAT (tPVAT). A high-sucrose diet caused decreased collagen fibre-positive area and increased CD68+ macrophage- and MCP-1-positive areas in the thoracic aorta. These results could be attributed to the different adipocyte populations in the tPVAT and aPVAT. Our results provide pathological evidence to improve our understanding of the relationship between diet and vascular diseases.

Clinical Significance of Increased Computed Tomography Attenuation of Periaortic Adipose Tissue in Patients With Abdominal Aortic Aneurysms

BACKGROUND

Recent imaging studies reported an association between vascular inflammation and progression of abdominal aortic aneurysm (AAA). This study investigated the clinical significance of periaortic adipose tissue inflammation derived from multidetector computed tomography angiography (MDCTA).

METHODS AND RESULTS

Patients with asymptomatic AAA (n=77) who underwent an index and >6 months follow-up MDCTA examinations were retrospectively investigated. MDCTA analysis included AAA diameter and the periaortic adipose tissue attenuation index (PAAI). The PAAI was defined as the mean CT attenuation value within a predefined range from -190 to -30 Hounsfield units of adipose tissue surrounding the AAA. The growth rate of the AAA was calculated as the change in diameter. AAA progression (AP) was defined as an AAA growth rate ≥5 mm/year. Univariate and multivariate logistic regression analysis were performed to determine the predictors of AP. AP was observed in 19 patients (24.7%), the median baseline AAA diameter was 38.9 mm (interquartile range [IQR] 32.7-42.9 mm), and the median growth rate was 3.1 mm/year (IQR 1.5-4.9 mm/year). Baseline AAA diameter (odds ratio [OR] 1.16; 95% confidence interval [CI] 1.05-1.28; P=0.001) and PAAI (OR 1.12; 95% CI 1.05-1.20; P=0.004) were independent predictors of AP.

CONCLUSIONS

PAAI was an independent and significant predictor of AP, supporting the notion that local adipose tissue inflammation may contribute to aortic remodeling.

Ovariectomy Causes Degeneration of Perivascular Adipose Tissue

Women are more resistant than men to the development of vascular diseases. However, menopause is a factor leading to deterioration of female vascular integrity, and it is reported that the risk of vascular diseases such as atherosclerosis and abdominal aortic aneurysm is increased in postmenopausal women. Although it is suggested that perivascular adipose tissue (PVAT) is deeply involved in the increased risk of vascular disease development, the effect of menopause on PVAT integrity is unknown. In this study, we aimed to elucidate the effect of menopause on PVAT in ovariectomized (OVX) rats. PVAT was divided into 4 regions based on characteristics. Hypertrophy and increased inflammation of adipocytes in the PVAT were observed in the OVX group, but the effects of OVX were different for each region. OVX induced matrix metalloproteinase (MMP) -9 which degrade extracellular matrix such as elastin and collagen fibers in PVAT. Degeneration of the arterial fibers of the thoracic and abdominal aorta were observed in the OVX group. These results indicate that OVX can cause dysfunction of PVAT which can cause degradation of arterial fibers. Appropriate management of PVAT may play an important role in the prevention and treatment of diseases originating from ovarian hypofunction.

The Histopathological Correlate of Peri-Vascular Adipose Tissue Attenuation on Computed Tomography in Surgical Ascending Aorta Aneurysms: Is This a Measure of Tissue Inflammation?

On computed tomography (CT) imaging, a peri-vascular adipose tissue attenuation (pVAT) measure has been proposed as a non-invasive correlate of inflammation in the coronary artery vessels, and a single research group provided histopathological demonstration of this radiological/pathological correspondence. Our group has shown that patients with surgical-grade ascending aorta (AA) aneurysm display higher pVAT compared with patients with smaller aneurysms or normal AA. Based on histopathological studies on coronary arteries, we speculated that this correlation may be related to a non-otherwise specified aortic inflammatory process. However, since adipose tissue around the AA is often scant, and there are no histopathological studies confirming such hypothesized association between higher pVAT and inflammation around the AA, we cannot exclude that this pVAT change is secondary to different mechanisms, unrelated to the actual presence of peri-vascular inflammation. We performed a retrospective clinical/radiological/pathological study in 78 patients who underwent AA surgery with the aim to correlate pre-operatory pVAT on CT with histopathological findings from the surgical specimens. Histopathological review and immunohistochemistry were performed on the surgical aortic samples. The AA adventitial/periadventitial adipose tissue had higher pVAT by an increasing collagen fiber deposition, which progressively makes the fat hypotrophic and, in the late stages of this process, it replaces the normal soft tissue composition in this location. In the ascending aorta, pVAT on CT imaging is probably not a proxy for the presence of current vascular inflammation, although it may track changes involving the progressive substitution of perivascular adipose cells by higher-pVAT tissues, mainly fibrotic replacement.

Perivascular Adipose Tissue Attenuation on Computed Tomography beyond the Coronary Arteries. A Systematic Review

(1) Background: Perivascular adipose tissue attenuation, measured with computed tomography imaging, is a marker of mean local vascular inflammation since it reflects the morphological changes of the fat tissue in direct contact with the vessel. This method is thoroughly validated in coronary arteries, but few studies have been performed in other vascular beds. The aim of the present study is to provide insight into the potential application of perivascular adipose tissue attenuation through computed tomography imaging in extra-coronary arteries. (2) Methods: A comprehensive search of the scientific literature published in the last 30 years (1990–2020) has been performed on Medline. (3) Results: A Medline databases search for titles, abstracts, and keywords returned 3251 records. After the exclusion of repetitions and the application of inclusion and exclusion criteria and abstract screening, 37 studies were selected for full-text evaluation. Three papers were finally included in the systematic review. Perivascular adipose tissue attenuation assessment was studied in the internal carotid artery, ascending thoracic aorta, and abdominal aorta. (4) Conclusions: Perivascular adipose tissue attenuation seems to be an applicable parameter in all investigated vascular beds, generally with good inter-observer reproducibility.

Inflammatory Gene Expression of Human Perivascular Adipose Tissue in Abdominal Aortic Aneurysms

OBJECTIVE

Perivascular adipose tissue (PVAT) contributes to vascular homeostasis and is increasingly linked to vascular pathology. PVAT density and volume were associated with abdominal aortic aneurysm (AAA) presence and dimensions on imaging. However, mechanisms underlying the role of PVAT in AAA have not been clarified. This study aimed to explore differences in PVAT from AAA using gene expression and functional tests.

METHODS

Human aortic PVAT and control subcutaneous adipose tissue were collected during open AAA surgery. Gene analyses and functional tests were performed. The control group consisted of healthy aorta from non-living renal transplant donors. Gene expression tests were performed to study genes potentially involved in various inflammatory processes and AAA related genes. Live PVAT and subcutaneous adipose tissue (SAT) from AAA were used for ex vivo co-culture with smooth muscle cells (SMCs) retrieved from non-pathological aortas.

RESULTS

Adipose tissue was harvested from 27 AAA patients (n [gene expression] = 22, n [functional tests] = 5) and five control patients. An increased inflammatory gene expression of PTPRC (p = .008), CXCL8 (p = .033), LCK (p = .003), CCL5 (p = .004) and an increase in extracellular matrix breakdown marker MMP9 (p = .016) were found in AAA compared with controls. Also, there was a decreased anti-inflammatory gene expression of PPARG in AAA compared with controls (p = .040). SMC co-cultures from non-pathological aortas with PVAT from AAA showed increased MMP9 (p = .033) and SMTN (p = .008) expression and SAT increased SMTN expression in these SMC.

CONCLUSION

The data revealed that PVAT from AAA shows an increased pro-inflammatory and matrix metallopeptidase gene expression and decreased anti-inflammatory gene expression. Furthermore, increased expression of genes involved in aneurysm formation was found in healthy SMC co-culture with PVAT of AAA patients. Therefore, PVAT from AAA might contribute to inflammation of the adjacent aortic wall and thereby plays a possible role in AAA pathophysiology. These proposed pathways of inflammatory induction could reveal new therapeutic targets in AAA treatment.

Role of Inflammation in Vascular Disease-Related Perivascular Adipose Tissue Dysfunction

Perivascular adipose tissue (PVAT) is the connective tissue around most blood vessels throughout the body. It provides mechanical support and maintains vascular homeostasis in a paracrine/endocrine manner. Under physiological conditions, PVAT has anti-inflammatory effects, improves free fatty acid metabolism, and regulates vasodilation. In pathological conditions, PVAT is dysfunctional, secretes many anti-vasodilator factors, and participates in vascular inflammation through various cells and mediators; thus, it causes dysfunction involving vascular smooth muscle cells and endothelial cells. Inflammation is an important pathophysiological event in many vascular diseases, such as vascular aging, atherosclerosis, and hypertension. Therefore, the pro-inflammatory crosstalk between PVAT and blood vessels may comprise a novel therapeutic target for the prevention and treatment of vascular diseases. In this review, we summarize findings concerning PVAT function and inflammation in different pathophysiological backgrounds, focusing on the secretory functions of PVAT and the crosstalk between PVAT and vascular inflammation in terms of vascular aging, atherosclerosis, hypertension, diabetes mellitus, and other diseases. We also discuss anti-inflammatory treatment for potential vascular diseases involving PVAT.

A Novel Hypothesis: A Role for Follicle Stimulating Hormone in Abdominal Aortic Aneurysm Development in Postmenopausal Women

An abdominal aortic aneurysm (AAA) is a dilatation of the abdominal aorta, which can potentially be fatal due to exsanguination following rupture. Although AAA is less prevalent in women, women with AAA have a more severe AAA progression compared to men as reflected by enhanced aneurysm growth rates and a higher rupture risk. Women are diagnosed with AAA at an older age than men, and in line with increased osteoporosis and cardiovascular events, the delayed AAA onset has been attributed to the reduction of the protective effect of oestrogens during the menopausal transition. However, new insights have shown that a high follicle stimulating hormone (FSH) level during menopause may also play a key role in those diseases. In this report we hypothesize that FSH may aggravate AAA development and progression in postmenopausal women via a direct and/or indirect role, promoting aorta pathology. Since FSH receptors (FSHR) are reported on many other cell types than granulosa cells in the ovaries, it is feasible that FSH stimulation of FSHR-bearing cells such as aortic endothelial cells or inflammatory cells, could promote AAA formation directly. Indirectly, AAA progression may be influenced by an FSH-mediated increase in osteoporosis, which is associated with aortic calcification. Also, an FSH-mediated decrease in cholesterol uptake by the liver and an increase in cholesterol biosynthesis will increase the cholesterol level in the circulation, and subsequently promote aortic atherosclerosis and inflammation. Lastly, FSH-induced adipogenesis may lead to obesity-mediated dysfunction of the microvasculature of the aorta and/or modulation of the periaortic adipose tissue. Thus the long term increased plasma FSH levels during the menopausal transition may contribute to enhanced AAA disease in menopausal women and could be a potential novel target for treatment to lower AAA-related events in women.

Role of Adipokines and Perivascular Adipose Tissue in Abdominal Aortic Aneurysm: A Systematic Review and Meta-Analysis of Animal and Human Observational Studies

Improved understanding of abdominal aortic aneurysms (AAA) pathogenesis is required to identify treatment targets. This systematic review summarized evidence from animal studies and clinical research examining the role of adipokines and perivascular adipose tissue (PVAT) in AAA pathogenesis. Meta-analyses suggested that leptin (Standardized mean difference [SMD]: 0.50 [95% confidence interval (CI): -1.62, 2.61]) and adiponectin (SMD: -3.16 [95% CI: -7.59, 1.28]) upregulation did not significantly affect AAA severity within animal models. There were inconsistent findings and limited studies investigating the effect of resistin-like molecule-beta (RELMβ) and PVAT in animal models of AAA. Clinical studies suggested that circulating leptin (SMD: 0.32 [95% CI: 0.19, 0.45]) and resistin (SMD: 0.63 [95% CI 0.50, 0.76]) concentrations and PVAT to abdominal adipose tissue ratio (SMD: 0.56 [95% CI 0.33, 0.79]) were significantly greater in people diagnosed with AAA compared to controls. Serum adiponectin levels were not associated with AAA diagnosis (SMD: -0.62 [95% CI -1.76, 0.52]). One, eight, and one animal studies and two, two, and four human studies had low, moderate, and high risk-of-bias respectively. These findings suggest that AAA is associated with higher circulating concentrations of leptin and resistin and greater amounts of PVAT than controls but whether this plays a role in aneurysm pathogenesis is unclear.

Preoperative anthropomorphic radiographic measurements can predict postoperative pancreatic fistula formation following pancreatoduodenectomy

BACKGROUND

Postoperative pancreatic fistulae (POPF) are a major contributing factor to pancreatoduodenectomy-associated morbidity. Established risk calculators mostly rely on subjective or intraoperative assessments. We hypothesized that various objective preoperatively determined computed tomography (CT) measurements could predict POPF as well as validated models and allow for more informed operative consent in high-risk patients.

METHODS

Patients undergoing elective pancreatoduodenectomies between January 2013 and April 2018 were identified in a prospective database. Comparative statistical analyses and multivariable logistic regression models were generated to predict POPF development. Model performance was tested with receiver operating characteristics (ROC) curves. Pancreatic neck attenuation (Hounsfield units) was measured in triplicate by pancreatic protocol CT (venous phase, coronal plane) anterior to the portal vein. A pancreatic density index (PDI) was created to adjust for differences in contrast timing by dividing the mean of these measurements by the portal vein attenuation. Total areas of subcutaneous fat and skeletal muscle were calculated at the L3 vertebral level on axial CT. Pancreatic duct (PD) diameter was determined by CT.

RESULTS

In the study period 220 patients had elective pancreatoduodenectomies with 35 (16%) developing a POPF of any grade. Multivariable regression analysis revealed that demographics (age, sex, and race) were not associated with POPF, yet patients resected for pancreatic adenocarcinoma or chronic pancreatitis were less likely to develop a POPF (10 vs. 24%; p = 0.004). ROC curves were created using various combinations of gland texture, body mass index, skeletal muscle index, sarcopenia, PDI, PD diameter, and subcutaneous fat area indexed for height (SFI). A model replacing gland texture with SFI and PDI (AUC 0.844) had similar predictive performance as the established model (p = 0.169).

CONCLUSION

A combination of preoperative objective CT measurements can adequately predict POPF and is comparable to established models relying on subjective intraoperative variables. Validation in a larger dataset would allow for better preoperative stratification of high-risk patients and improve informed consent among this patient population.

Background and Proposed Design for a Metformin Abdominal Aortic Aneurysm Suppression Trial

Abdominal aortic aneurysm (AAA) may lead to rupture and death if left untreated. While endovascular or surgical repair is generally recommended for AAA greater than 5–5.5 cm, the vast majority of aneurysms detected by screening modalities are smaller than this threshold. Once discovered, there would be a significant potential benefit in suppressing the growth of these small aneurysms in order to obviate the need for repair and mitigate rupture risk. Patients with diabetes, in particular those taking the oral hypoglycaemic medication metformin, have been shown to have lower incidence, growth rate, and rupture risk of AAA. Metformin therefore represents a widely available, non-toxic, potential inhibitor of AAA growth, but thus far no prospective clinical studies have evaluated this. Here, we present the background, rationale, and design for a randomised, double-blind, placebo-controlled clinical trial of metformin for growth suppression in patients with small AAA.

The role of perivascular adipose tissue in the appearance of ectopic adipocytes in the abdominal aortic aneurysmal wall

Abdominal aortic aneurysm (AAA) is a vascular disease characterized by the dilation of the abdominal aorta, resulting in a high mortality rate caused by vascular rupture. Previous studies have suggested that the abnormal appearance of adipocytes in the vascular wall is associated with the development of AAA. However, the mechanisms underlying the appearance of the ectopic adipocytes remain unknown. In this study, we showed that CD44⁺CD90⁺ MSCs express adipogenic transcription factors in the AAA wall of a hypoperfusion-induced AAA model. The number of CD44⁺CD90⁺ cells and adipocytes in the AAA wall significantly decreased in the perivascular adipose tissue (PVAT)-removed vascular wall. The AAA diameter significantly decreased in the PVAT-removed vascular wall compared with that in the vascular wall with PVAT. These data suggested that PVAT plays important roles in the differentiation of MSCs into adipocytes in response to vascular hypoperfusion. The decreased number of adipocytes in the PVAT-removed vascular wall might be associated with the decreased AAA diameter.

Human Perivascular Adipose Tissue as a Regulator of the Vascular Microenvironment and Diseases of the Coronary Artery and Aorta

Perivascular adipose tissue (PVAT) is an adipose depot that surrounds blood vessels in the human body and exerts local paracrine signaling. Under physiologically healthy conditions, PVAT has an anti-contractile effect on vessels, but in obesity this effect is lost. During metabolic disease, adiponectin secretion is dysregulated, influencing nitric oxide bioavailability and macrophage infiltration and inflammation, all of which mediate PVAT signaling. However, based on the location in the body, and the type of adipocyte present, PVAT has different relationships with risk factors for disease. Imaging studies in patients with cardiovascular disease have demonstrated important associations between PVAT structure and pathology, yet insight into molecular pathways regulating human PVAT function are still lacking. This review focuses on our current understanding of human PVAT and its secretory role in the vascular microenvironment. A current area of priority is defining molecular differences in the secretome between PVAT depots, as this could inform the treatment of diseases that occur in anatomically restricted locations. In addition, understanding progressive changes in PVAT structure and function during metabolic disease is required for effective targeted therapies.