Transient upregulation of IGF-I gene expression in brown adipose tissue of cold-exposed rats.
The possible involvement of locally produced insulin-like growth factor I (IGF-I) in the cold-induced hyperplasia of interscapular brown adipose tissue (BAT) was investigated in 2-, 4-, and 7-day cold-exposed (CE, 4 degrees C) rats by measuring BAT IGF-I expression at a time when extensive BAT cell proliferation occurs. By comparison with thermoneutral (25 degrees C) controls, plasma IGF-I decreased in CE rats despite an increased food intake, whereas BAT IGF-I peptide increased markedly to peak after 4 days at 4 degrees C. The ratio of class 1 to class 2 IGF-I mRNA was much higher in BAT than in liver. BAT IGF-I mRNA levels per unit weight total RNA doubled after 2 days at 4 degrees C but decreased thereafter to the level in controls. Upregulation of BAT IGF-I mRNA also occurred in CE rats with a food intake restricted to the level of controls. The transient cold-induced upregulation of BAT IGF-I (per unit weight total RNA) suggests that IGF-I plays a role in the early cold-induced BAT hyperplasia that occurs in vivo.
Duchamp
C
C
UMR 5578 Centre National de la Recherche Scientifique, Université Claude Bernard, Lyon, France.
Burton
K A
KA
Géloën
A
A
Dauncey
M J
MJ
D002001:Adipose Tissue, Brown / Q000378:metabolism*; D000818:Animals; D001835:Body Weight; D003080:Cold Temperature; D002149:Energy Intake; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D015854:Up-Regulation
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I