FIGURE 1.

In response to hypoxia, brown adipocytes produce lower amounts of HIF-1α than white adipocytes but induce higher levels of hypoxia-associated genes. 3T3-L1 and brown preadipocytes were differentiated until day 7, at which stage cells were exposed to 20% or 1% O₂ for 18 h. A, nuclear (N) and cytoplasmic (C) cell fractions were prepared, and extracts were subjected to Western blot analysis. B, cells were also harvested for RNA isolation and quantitative real-time PCR analysis. Results are means ± S.E. (n = 3). *, p < 0.01; +, p < 0.05. C/EBPα, CCAAT/enhancer-binding protein α.