Fig. 1: [¹⁸F]F-AraG accumulates in adrenergically stimulated brown fat and bone marrow.

a Administration of β3 adrenergic receptor agonist BRL37344 (10 mg/kg) 1 h before imaging led to a high accumulation of [¹⁸F]F-AraG in iBAT (white arrowhead). No significant uptake was observed in the insulin-treated or control mice. b Signal in the iBAT of adrenergically stimulated mice (10.98 ± 1.64%ID/g) was significantly higher than the signal in the insulin treated (3.36 ± 0.62%ID/g) and control mice (4.11 ± 0.76%ID/g). No significant differences in iBAT signal were found between insulin-treated and control mice (p = 0.53). c The baseline ¹⁸FDG uptake in iBAT (white arrowheads) that was observed in control mice was increased in both insulin and BRL37344 treated mice, indicating lack of selectivity for adrenergic stimulation. d Administration of BRL37344 (10 mg/kg) for 4 consecutive days led to increased [¹⁸F]F-AraG signal in the intrascapular BAT (white arrowhead) and axillary BAT (red arrow) but also in the lumbar vertebrae region (yellow arrowhead), and the bone marrow of the tibia and femur (orange arrowhead). e–g Signal in the lumbar, thoracic, and cervical vertebrae of chronically stimulated mice was significantly different than the signal in acutely BRL37344- treated, insulin-treated and control mice. ID injected dose. [¹⁸F]F-AraG uptake in different region of interest was calculated as %ID/g. Data are plotted as mean ± SD (n = 5 or 6). Each spot represents an individual animal. *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.000.