AJP - Endocrinology and Metabolism, Vol 272, Issue 3 E453-E460, Copyright © 1997 by American Physiological Society

ARTICLES

Transient upregulation of IGF-I gene expression in brown adipose tissue of cold-exposed rats

C. Duchamp, K. A. Burton, A. Geloen and M. J. Dauncey
UMR 5578 Centre National de la Recherche Scientifique, Universite Claude Bernard, Lyon, France.

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.

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