(A–F) Mice underwent sham operation or transplantation with 0.1 g BAT from Il6–/– or Il6+/+mice. (A) Percent fat mass, (B) visceral WAT cell size at 12 weeks after transplantation, (C) qPCR of tyrosine hydroxylase in transplanted BAT, (D) serum FGF21, (E) endogenous BAT FGF21 protein, and (F) qPCR of Fgf21. Data are mean ± SEM. *P < 0.05 compared with sham and mice receiving 0.1 g Il6–/– BAT. **P < 0.01. n = 4–8/group.