Figure 2.

Impairment of BAT-mediated thermogenesis and sympathetic outflow in Bdnf-e1^−/−mice. (A) Hematoxylin and eosin (HE) staining of BAT in WT, Bdnf-e1^−/−, and Bdnf-e4^−/− mice at ∼5 months of age. Upper right corner, enlarged images of the red rectangular areas. Note that the lipid droplets are much larger in the BAT of Bdnf-e1^−/− mice as compared with those in WT mice. (B) Droplet number per mm² in the BAT sections of WT, Bdnf-e1^−/−, and Bdnf-e4^−/− mice. A smaller average number means larger lipid droplets in the BAT of Bdnf-e1^−/− mice. Paraffin-embedded BAT sections of those mice were used for HE staining and statistics. (C) Expression of thermogenesis-related genes (Ucp1 and Pcg1a) in the BAT of WT, Bdnf-e1^−/−, and Bdnf-e4^−/− mice at ∼5 months of age. Relative levels of Ucp1 and Pcg1a mRNAs in BAT from Bdnf-e1^−/− mice were normalized to those from WT mice after a real-time qPCR assay. (D) Rectal temperature of WT and Bdnf-e1^−/− mice at room temperature and after exposing animals to 4 °C for 1 h. (E) Levels of NE in BAT of WT, Bdnf-e1^−/−, and Bdnf-e4^−/− mice measured by the LS-MS method. (F) Immunoblotting of tyrosine hydrolase (TH), a marker for sympathetic innervation, of BAT extracts from WT and Bdnf-e1^−/− mice. β-tubulin was used as a loading control. Quantification of the immunoblot shown in a lower panel. The TH levels in BAT from Bdnf-e1^−/− mice were normalized to those from WT mice.