The Influence of Perivascular Adipose Tissue on Vascular Function in a Rabbit Model

The recent acknowledgment of the paracrine role of perivascular adipose tissue (PVAT) in vascular modulation has been supported by many studies investigating major arteries in several animal models and humans. The influence of PVAT on the functional activity of the vascular bed has been a matter of debate, whether it is an anticontractile effect with protective roles or a pro-contractile effect, investigations are underway to address this obscurity. In this investigation, we have studied the effects of vasoconstrictors, phenylephrine and noradrenaline, and vasorelaxants, carbachol and s-nitroso-n- acetylpenicillamine (SNAP), on subclavian and iliac rings with and without PVAT attached;and concentration-response curves were constructed accordingly. Levels of nitric oxide (NO) generated due to activation of the enzyme adenosine monophosphate-activated protein kinase (AMPK) by 5-Aminoimi- dazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) were measured in sub- clavian and iliac PVAT conditioned media. Additionally, Haematoxylin and Eosin staining was performed to analyze and compare the histological characteristics of both arteries. Subclavian and iliac rings with PVAT attached showed stronger contraction to phenylephrine and noradrenaline than that of rings without PVAT attached. At the same time, relaxation tests reported lower relaxation percentages in subclavian and iliac rings with PVAT attached compared to rings without PVAT attached in response to carbachol and SNAP. PVAT treated with AICAR generated higher levels of NO compared to levels of untreated PVAT. Conclusions drawn were the pro-contractile effects demonstrated by the PVAT especially in high concentrations of drugs used. In addition, histology analysis revealed characteristics of white adipose tissue in both PVATs.

Perivascular Fat Attenuation Index on Non-Contrast-Enhanced Cardiac Computed Tomography: Comparison with Coronary Computed Tomography Angiography

Objective: Perivascular fat attenuation index (FAI) measurement on non-contrast-enhanced cardiac computed tomography (NCCT) has not been rigorously validated in previous studies. Herein, we compared perivascular FAI values between NCCT and coronary computed tomography angiography (CCTA). We also investigated the variability and reproducibility of perivascular FAI measurement. Methods: A total of 44 patients who underwent NCCT and CCTA were included in this study. For NCCT, perivascular FAI was measured using three threshold settings: from −30 to −190 Hounsfield Units (HU), −20 to −180 HU, and −10 to −170 HU. For CCTA, perivascular FAI was measured using one threshold setting: from −30 to −190 HU. Perivascular FAI measurements by NCCT were compared with those by CCTA using the paired t-test, and correlations were assessed using Pearson’s correlation coefficient. The intra- and inter-observer variabilities for the measurements with NCCT and CCTA were evaluated with the intraclass correlation coefficient. Results: Perivascular FAI measurements with the threshold setting of −30 to −190 HU were significantly lower on NCCT than on CCTA. There were no significant differences between the perivascular FAI measurements at the remaining thresholds on NCCT and those on CCTA. The perivascular FAI at all thresholds on NCCT correlated significantly with those on CCTA. The intra- and inter-observer agreements were excellent for the measurements on NCCT and CCTA. Conclusion: There were significant differences between the perivascular FAI measurements on NCCT and CCTA. However, the differences could be modified by threshold adjustment.