PET/MRI of glucose metabolic rate, lipid content and perfusion in human brown adipose tissue

• This study evaluated the MRI-derived fat fraction (FF), from a Cooling-reheating protocol, for estimating the cold-induced brown adipose tissue (BAT) metabolic rate of glucose (MRglu) and changes in lipid content, perfusion and arterial blood volume (V-A) within cervical-supraclavicular fat (sBAT). Twelve volunteers underwent PET/MRI at baseline, during cold exposure and reheating. For each temperature condition, perfusion and V-A were quantified with dynamic [O-15]water-PET, and FF, with water-fat MRI. MRglu was assessed with dynamic [F-18]fluorodeoxyglucose-PET during cold exposure. sBAT was defined using anatomical criteria, and its subregion sBAT(HI), by MRglu>11 mu mol/100 cm(3)/min. For all temperature conditions, sBAT-FF correlated negatively with sBAT-MRglu (rho <=- 0.87). After 3 h of cold, sBAT-FF decreased (- 2.13 percentage points) but tended to normalize during reheating although sBAT(HI)-FF remained low. sBAT-perfusion and sBAT-V-A increased during cold exposure (perfusion:+5.2 ml/100 cm(3)/min, V-A:+4.0 ml/100 cm(3)). sBAT-perfusion remained elevated and sBAT-V-A normalized during reheating. Regardless of temperature condition during the Cooling-reheating protocol, sBAT-FF could predict the cold-induced sBAT-MRglu. The FF decreases observed after reheating were mainly due to lipid consumption, but could potentially be underestimated due to intracellular lipid replenishment. The influence of perfusion and V-A, on the changes in FF observed during cold exposure, could not be ruled out.

Subject headings

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Radiologi och bildbehandling (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Radiology, Nuclear Medicine and Medical Imaging (hsv//eng)

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