What is the clinical evidence from this study?

Study design: Other. Population: Healthy (evaluating brown vs white adipose tissue) (n=30). Intervention: Norepinephrine vs. Saline. Primary outcome: Iodine concentration of brown adipose tissue (BAT) (p=<0.001).

December 13, 2019Open Access

Quantification of Fat Concentration and Vascular Response in Brown and White Adipose Tissue of Rats by Spectral CT Imaging

Q: What are the key findings of this study?

Norepinephrine significantly increased the iodine concentration of brown adipose tissue compared to saline (28.75 vs. 7.49 mg/cm3, p < 0.001) on contrast-enhanced spectral CT.

Key Result

Norepinephrine significantly increased the iodine concentration of brown adipose tissue compared to saline (28.75 vs. 7.49 mg/cm3, p < 0.001) on contrast-enhanced spectral CT.

Structured PICO

Does norepinephrine stimulation increase the vascular response in brown adipose tissue compared to white adipose tissue as measured by spectral CT in rats?

Population

30 male Wistar rats (14 weeks old) were used to evaluate spectral CT for characterizing and discriminating brown from white adipose tissue.

Intervention

Intraperitoneal injection of norepinephrine (NE) at a rate of 1 μg/kg/min for 10 minutes, followed by contrast-enhanced spectral CT.

Comparator

Intraperitoneal injection of saline for 10 minutes, followed by contrast-enhanced spectral CT.

Outcome

Elevation of iodine concentration in brown adipose tissue (BAT) and white adipose tissue (WAT) after treatment, measured by enhanced spectral CT.surrogate

Spectral CT can non-invasively characterize and differentiate brown from white adipose tissue by quantifying fat concentration and norepinephrine-induced vascular responses.

Main Result

Absolute Event Rate: 28.75% vs 7.49%

p-value: p=<0.001

Limitations

Contrast agent was injected via the tail vein rather than a jugular venous line.
Only observed the difference after the first stimulation by β3 agonist; long-term effects were not investigated.
Did not combine perfusion-weighted CT imaging to monitor the responses of β3 agonists in BAT and WAT.

Abstract

OBJECTIVE: The purpose of the study was to non-invasively characterize and discriminate brown adipose tissue (BAT) from white adipose tissue (WAT) in rats using spectral computed tomography (CT) with histological validation. MATERIALS AND METHODS: , non-enhanced spectral CT scan was performed on 24 rats, and fat concentrations of BAT and WAT were measured. The rats were randomized to receive intraperitoneal treatment with norepinephrine (NE) (n = 12) or saline (n = 12). Non-enhanced and enhanced spectral CT scans were performed after treatment to measure the elevation of iodine in BAT and WAT. The BAT/aorta and WAT/aorta ratios were calculated and compared, after which isolated BAT and WAT samples were subjected to histological and uncoupling protein 1 (UCP1) analyses. RESULTS: < 0.001). Histological and UCP1 expression analyses supported the spectral CT imaging results. CONCLUSION: The study consolidates spectral CT as a new approach for non-invasive imaging of BAT and WAT. Quantitative analyses of BAT and WAT by spectral CT revealed different characteristics and pharmacologic activations in the two types of adipose tissue.

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