Dynamic contrast‐enhanced MRI of brown and beige adipose tissues

Abstract

Purpose The vascular blood flow in brown adipose tissue (BAT) is important for handling triglyceride clearance, increased blood flow and oxygenation. We used dynamic contrast‐enhanced (DCE)‐MRI and fat fraction (FF) imaging for investigating vascular perfusion kinetics in brown and beige adipose tissues with cold exposure or treatment with β3‐adrenergic agonist. Methods FF imaging and DCE‐MRI using gadolinium‐diethylenetriaminepentaacetic acid were performed in interscapular BAT (iBAT) and beige tissues using male Wister rats (n = 38). Imaging was performed at thermoneutral condition and with either cold exposure, treatment with pharmacological agent CL‐316,243, or saline. DCE‐MRI and FF data were co‐registered to enhance the understanding of metabolic activity. Results Uptake of contrast agent in activated iBAT and beige tissues were significantly (P < .05) higher than nonactivated iBAT. The Ktrans and kep increased significantly in iBAT and beige tissues after treatment with either cold exposure or β3‐adrenergic agonist. The FF decreased in activated iBAT and beige tissues. The Ktrans and FF from iBAT and beige tissues were inversely correlated (r = 0.97; r = 0.94). Significant increase in vascular endothelial growth factor expression and Ktrans in activated iBAT and beige tissues were in agreement with the increased vasculature and vascular perfusion kinetics. The iBAT and beige tissues were validated by measuring molecular markers. Conclusion Increased Ktrans and decreased FF in iBAT and beige tissues were in agreement with the vascular perfusion kinetics facilitating the clearance of free fatty acids. The methodology can be extended for the screening of browning agents.

Comparative [18F]FDG and [18F]DPA714 PET imaging and time-dependent changes of brown adipose tissue in tumor-bearing mice

“…99m Tc-methoyl isobutyl isonitrile (MIBI) and 123 I-meta-iodobenzylguanidine (MIBG) single-photon emission computed tomography (SPECT) can also be used in BAT imaging, but the low positive rate limits their application [ 14 ]. Conventional magnetic resonance imaging (MRI) scan can also identify WAT and BAT, the principle of which is that BAT has less fat and more water [ 15 ]. But, MRI is lack of specificity and its value is also limited.…”

Contribution of perfusion to the 11C‐acetate signal in brown adipose tissue assessed by DCE‐MRI and 68Ga‐DOTA PET in a rat model

“…In mice, contrast‐enhanced ultrasound and near‐infrared fluorescence imaging also showed large effects of cold, CL316,243 and norepinephrine on perfusion 50,51 . Finally, a previous investigation of rat BAT by DCE‐MRI showed large increases in K 1 and k 2 with cold and CL316,243 stimulation 14 . These changes should have been detectable despite the variability in data.…”

“…In a previous article, we proposed a four-compartment pharmacokinetic model to distinguish oxidation and lipid synthesis. 10 However, BAT can undergo large perfusion changes along with activation by cold or sympathomimetics, [11][12][13][14] although metabolism and perfusion are sometimes uncoupled. 13,15 Perfusion affects the 11 C-acetate signal and must be considered for precise assessment of oxidation.…”

“…Moreover, combined PET‐MR scanners would allow for simultaneous perfusion and oxidation measurements. The feasibility of dynamic contrast enhanced (DCE) ‐MRI has already been demonstrated for BAT, 14 whereas non‐invasive arterial spin labeling remains technically challenging for this tissue 18 . However, while PET is inherently quantitative (it measures radioactive decay that is proportional to radiotracer concentration), the MR signal is relative, and models must be applied for quantification.…”

Magnetic Resonance Imaging Techniques for Brown Adipose Tissue Detection

“…The uptake of contrast agent was three times higher in the iBAT of the activated group compared to the control group, while no significant difference was found in the interscapular WAT. More recently, a more quantitative study of the uptake kinetics using DCE-MRI, correlated with fat fraction maps, was performed in rats (157). The volume transfer constant from blood plasma into the extracellular-extravascular spaces and the concentration of the contrast agent were calculated.…”