Figure 3.
D-BAT induces apoptosis selectively in EC of thermogenic AT. (A) A model predicting D-BAT effect in AT. D-BAT depletes EC expressing the PEP3-tsargeted TrkA isoform while sparing SNS. Reduced BAT and SAT vascularization results in AT whitening and reduced thermogenesis. (B–F) C57BL/6 males were treated with D-BAT or PBS (control) over 2 weeks (N = 5). (B) Core body temperature maintenance at 4 °C measured 3 days after the last injection indicating reduced cold tolerance upon D-BAT treatment. Plotted are mean ± SEM; ∗P < 0.05 (Student's t-test). (C) Interscapular BAT 3 days after the last injection of D-BAT. (D) IF analysis of paraffin tissue sections from D-BAT-treated and control mice with cleaved caspase 3 IF (green) co-localized with IB4 (red). Note apoptosis in both endothelium (yellow arrow) and adipocytes (green arrow) of D-BAT-treated mice. (E) BAT IF for UCP1 (green)/perilipin1 (PLN1). Graph indicates decreased frequency of UCP1+ adipocytes, which are partly replaced by white adipocytes in D-BAT-treated mice. (F) Representative images of H/E-stained paraffin sections of BAT and SAT from treated and control mice with quantifications to the right. Arrow: beige adipocyte area. In D-F, scale bar: 50 μm. (G–L) C57BL/6 female mice treated with D-BAT were fed HFD for three months (N = 5). (G) Food consumption unchanged by D-BAT. (H) Core body temperature maintenance at 4 °C indicating reduced cold tolerance in D-BAT-treated mice. (I) Oxygen consumption (VO2) during day and night decreased by upon D-BAT treatment. Respiratory exchange ratio (RER) increase indicates that D-BAT treatment leads to lower lipid oxidation. (J) Body mass and EchoMRI indicates fat body mass increase in mice treated with D-BAT. (K) Fasted glucose tolerance test. (L) Insulin tolerance test (ITT) area under the curve (AUC). Plotted are mean ± SEM; ∗P < 0.05, ∗∗P < 0.01 (Student's t-test).