(123)I- or (125)I-metaiodobenzylguanidine visualization of brown adipose tissue.
(123)I-Metaiodobenzylguanidine (MIBG) accumulations that do not correspond to any tumor are observed occasionally on the medial aspect of the upper back or shoulder of children. The true nature of such accumulations is unknown, and we hypothesized that they represent interscapular brown adipose tissue (IBAT) visualized by scintigraphy.


METHODS
Wistar rats (7 wk old) received MIBG labeled with (123)I or (125)I. Autoradiography was performed, and concentrations of the tracer in the interscapular subcutaneous tissue were identified histopathologically. The effects of 6-hydroxydopamine, reserpine, and beta 3-adrenergic receptor agonist (CL316,243) on the accumulation were investigated to elucidate the mechanism of uptake into BAT.


RESULTS
Autoradiography showed well-defined distinct accumulation in the subcutaneous tissue on the upper back, and hematoxylin-eosin and anti-uncoupling protein 1 antibody staining confirmed that it was BAT. The percentage injected dose per gram in BAT was as high as that in the heart and was quite different from the concentration in white adipose tissue. Preadministration of 6-hydroxydopamine or reserpine resulted in lower MIBG concentrations in BAT. Activation of the beta 3-adrenergic receptor accelerated the washout of MIBG in BAT and caused an increase in concentration in white adipose tissue.


CONCLUSIONS
MIBG accumulates in the adrenergic nervous system in BAT, and IBAT is distinguished from the surrounding white adipose tissue. To our knowledge, BAT has not been visualized previously. We showed that MIBG scintigraphy might be suitable for the investigation of BAT and treatment of human obesity.
Okuyama
Chio
C
Department of Radiology, Kyoto Prefectural University of Medicine, Kyoto, Japan. chio@koto.kpu-m.ac.jp
Sakane
Naoki
N
Yoshida
Toshihide
T
Shima
Keiji
K
Kurosawa
Hiroyuki
H
Kumamoto
Kenzo
K
Ushijima
Yo
Y
Nishimura
Tsunehiko
T
D019797:3-Iodobenzylguanidine / Q000493:pharmacokinetics; D002001:Adipose Tissue, Brown / Q000000981:diagnostic imaging* / Q000378:metabolism; D018663:Adrenergic Agents / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D004149:Dioxoles / Q000494:pharmacology; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D016627:Oxidopamine / Q000494:pharmacology; D011877:Radionuclide Imaging; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology
D018663:Adrenergic Agents; D000318:Adrenergic beta-Agonists; D004149:Dioxoles; D007457:Iodine Radioisotopes; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; D019797:3-Iodobenzylguanidine; D012110:Reserpine; D016627:Oxidopamine