Epicardial Adipose Tissue May Mediate Deleterious Effects of Obesity and Inflammation on the Myocardium.

Accumulating evidence points to the existence of an inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction (HFpEF), which is characterized by biomarkers of inflammation, an expanded epicardial adipose tissue mass, microvascular endothelial dysfunction, normal-to-mildly increased left ventricular volumes and systolic blood pressures, and possibly, altered activity of adipocyte-associated inflammatory mediators. A broad range of adipogenic metabolic and systemic inflammatory disorders - e.g. obesity, diabetes and metabolic syndrome as well as rheumatoid arthritis and psoriasis - can cause this phenotype, independent of the presence of large vessel coronary artery disease. Interestingly, when compared with men, women are both at greater risk of and may suffer greater cardiac consequences from these systemic inflammatory and metabolic disorders. Women show disproportionate increases in left ventricular filling pressures following increases in central blood volume and have greater arterial stiffness than men. Additionally, they are particularly predisposed to epicardial and intramyocardial fat expansion and imbalances in adipocyte-associated proinflammatory mediators. The hormonal interrelationships seen in inflammatory-metabolic phenotype may explain why mineralocorticoid receptor antagonists and neprilysin inhibitors may be more effective in women than in men with HFpEF. Recognition of the inflammatory-metabolic phenotype may improve an understanding of the pathogenesis of HFpEF and enhance the ability to design clinical trials of interventions in this heterogeneous syndrome.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ejhf.1902

Characterization of the inflammatory-metabolic phenotype of heart failure with a preserved ejection fraction: a hypothesis to explain influence of sex on the evolution and potential treatment of the disease.

Drugs That Ameliorate Epicardial Adipose Tissue Inflammation May Have Discordant Effects in Heart Failure With a Preserved Ejection Fraction as Compared With a Reduced Ejection Fraction.

Currently, obesity is one of the leading causes death in the world. Shortly before 2000, researchers began describing metabolically active adipose tissue on cancer-surveillance 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in adult humans. This tissue generates heat through mitochondrial uncoupling and functions similar to classical brown and beige adipose tissue in mice. Despite extensive research, human brown/beige fat’s role in resistance to obesity in humans has not yet been fully delineated. FDG uptake is the de facto gold standard imaging technique when studying brown adipose tissue, although it has not been rigorously compared to other techniques. We, therefore, present a concise review of established and emerging methods to image brown adipose tissue activity in humans. Reviewed modalities include anatomic imaging with CT and magnetic resonance imaging (MRI); molecular imaging with FDG, fatty acids, and acetate; and emerging techniques. FDG-PET/CT is the most commonly used modality because of its widespread use in cancer imaging, but there are mechanistic reasons to believe other radiotracers may be more sensitive and accurate at detecting brown adipose tissue activity. Radiation-free modalities may help the longitudinal study of brown adipose tissue activity in the future.

https://www.mdpi.com/1422-0067/20/21/5509/pdf

Imaging Metabolically Active Fat: A Literature Review and Mechanistic Insights

Objective Lung transplantation (LT) for pulmonary fibrosis is related to higher mortality than other transplant indications. We aim to assess whether the amount of anterior mediastinal fat (AMF) was associated to early and long-term outcomes in fibrotic patients undergoing LT. Methods Retrospective analysis of 92 consecutive single lung transplants (SLT) for pulmonary fibrosis over a 10-year period. AMF dimensions were measured on preoperative CT-scan: anteroposterior axis (AP), transverse axis (T), and height (H). AMF volumes (V) were calculated by the formula: AP × T × H × 3.14/6. According to the radiological AMF dimensions, patients were distributed into two groups: low-AMF (V   20 cm3), and early and long-term outcomes were compared by univariable and multivariable analyses. Results There were 92 SLT: 73M/19F, 53 ± 11 [14–68] years old. 30-Day mortality (low-AMF vs. high-AMF): 5 (5.4%) vs. 15 (16.3%), p = 0.014. Patients developing primary graft dysfunction within 72 h post-transplant, and those dying within 30 days post-transplant presented higher AMF volumes: 21.1 ± 19.8 vs. 43.3 ± 24.7 cm3 (p = 0.03) and 24.4 ± 24.2 vs. 56.9 ± 63.6 cm3 (p  Factors predicting 30-day mortality were: BMI (HR = 0.77, p = 0.011), AMF volume (HR = 1.04, p = 0.018), CPB (HR = 1.42, p = 0.002), ischaemic time (HR = 1.01, p = 0.009). Factors predicting survival were: AMF volume (HR = 1.02, p  Conclusion Preoperative radiological assessment of mediastinal fat dimensions and volumes may be a useful tool to identify fibrotic patients at higher risk of mortality after single lung transplantation.

Relationship Among Radiological Measurements of Anterior Mediastinal Fat and Outcomes of Lung Transplantation in Fibrotic Patients

Quantifying the amount of brown adipose tissue (BAT) within white adipose tissue (WAT) in human depots may serve as a target to combat obesity. We aimed to quantify proton density fat fraction (PDFF) of BAT and WAT in relatively pure and in mixed preparation using water-fat imaging. Three ex-vivo experiments were performed at 3 T using excised interscapular BAT and inguinal/subcutaneous WAT from mice. The first two experiments consisted of BAT and WAT in separate tubes, and the third used mixed preparation with graded quantities of BAT and WAT. To investigate the influence of partial volume on PDFF metrics, low ( 2.66 mm 3 ) and high spatial resolution ( 0.55 mm 3 acquired voxels) in two orthogonal three-dimensional sections were compared. The low-resolution acquisitions are corrected for T2* and multipeak lipid spectrum, thus considered "quantitative," whereas the high-resolution acquisitions are not corrected but were performed to better spatially segment BAT from WAT zones. As potential BAT metrics, we quantified the average PDFF and the volume of tissue having PDFF ≤ 50 % ( VOL PDFF ≤ 50 % ) based on the PDFF histogram. In the first experiment, the average PDFF of BAT was 23 ± 6 % and 21 ± 7.6 % and the average PDFF of WAT was 76 ± 7 % and 87 ± 7 % using high- and low-resolution techniques, respectively. A similar trend with excellent reproducibility in average PDFF of BAT and WAT was observed in the second experiment. In the third experiment over the four acquisitions, the BAT-dominant tube demonstrated lower PDFF (mean ± SD) of 55 ± 2 % than WAT-dominant ( 69 ± 4 % ) and WAT-only tubes ( 88 ± 4 % ) . Estimating VOL PDFF ≤ 50 % , the BAT-dominant tube demonstrated higher volume of 0.26 cm 3 than WAT-dominant ( 0.16 cm 3 ) and WAT-only tubes ( 0.01 cm 3 ). The presence of BAT exhibits a lower PDFF relative to WAT, thus allowing segmentation of low PDFF tissue for quantification of volume representative of BAT. Future studies will determine the clinical relevance of BAT volume within human depots.

/pdf/water-fat-magnetic-resonance-imaging-quantifies-relative-4pu2eu085z.pdf

Water-fat magnetic resonance imaging quantifies relative proportions of brown and white adipose tissues: ex-vivo experiments.

Intrathoracic fat volume, more specifically, epicardial fat volume, is an emerging imaging biomarker of adverse cardiovascular events. The purpose of this work is to show the feasibility and reproducibility of intrathoracic fat volume measurement applied to contrast-enhanced multidetector computed tomography images. A retrospective cohort study of 62 subjects free of cardiovascular disease (55% females, age = 49 ± 11 years) conducted from 2008 to 2011 formed the study group. Intrathoracic fat volume was defined as all fat voxels measuring -50 to -250 Hounsfield Unit within the intrathoracic cavity from the level of the pulmonary artery bifurcation to the heart apex. The intrathoracic fat was separated into epicardial and extrapericardial fat by tracing the pericardium. The measurements were obtained by 2 readers and compared for interrater reproducibility. The fat volume measurements for the study group were 141 ± 72 cm3 for intrathoracic fat, 58 ± 27 cm3 for epicardial fat, and 84 ± 50 cm3 for extrapericardial fat. There was no statistically significant difference in intrathoracic fat volume measurements between the 2 readers, with correlation coefficients of 0.88 (P = .55) for intrathoracic fat volume and -0.12 (P = .33) for epicardial fat volume. Voxel-based measurement of intrathoracic fat, including the separation into epicardial and extrapericardial fat, is feasible and highly reproducible from multidetector computed tomography scans.

https://www.mdpi.com/2379-139X/3/1/33/pdf

Intrathoracic Fat Measurements Using Multidetector Computed Tomography (MDCT): Feasibility and Reproducibility.

Increased Epicardial Fat Volume Is Independently Associated with the Presence and Severity of Systemic Sclerosis.

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Water-fat magnetic resonance imaging quantifies relative proportions of brown and white adipose tissues: ex-vivo experiments.

Intrathoracic Fat Measurements Using Multidetector Computed Tomography (MDCT): Feasibility and Reproducibility.

Increased Epicardial Fat Volume Is Independently Associated with the Presence and Severity of Systemic Sclerosis.