Comparisons of brown adipose tissue (BAT) of three strains during cold challenge. (A) Histological analyses of BAT by H&E staining. (B) qPCR analyses of representative brown genes expression in BAT. (C) qPCR analyses of adipocyte markers and representative white genes expression in BAT. (D) qPCR analyses of expression of browning regulators in BAT. *: p < 0.05, **: p < 0.01 for 129/Sv vs. C57BL/6; Δ: p < 0.05, ΔΔ: p < 0.01 for FVB/D vs. C57BL/6, n = 8, 8, 8.