TAK1 knockdown reduces differentiation of 3T3-L1 preadipocytes. (A) 3T3-L1 cells were transfected with control or Tak1 siRNA, and then cultured in differentiation medium at 0, 25, 50 and 100 ng/mL BMP2. Following 8 days of differentiation, cells were stained with Oil Red O. (B, C) 3T3-L1 cells were transfected with control or Tak1 siRNA, and stained with Oil Red O after 13 days of adipocyte differentiation. Pparγ mRNA was also measured. (D) Wild type mice were administrated with control DMSO (n=4) or TI-2 (n=3) for 6 consecutive days. Visceral fat was collected and mRNA for the indicated genes was measured. Ctr, control; *P < 0.05; ***P < 0.001.