Figure 1. Systemic administration of BMP7 increases BAT volume and UCP-1 expression in mice at 21°C, but not at thermoneutrality.

4-week-old male C57Bl/6J mice were treated for 4 weeks with BMP7 (33 or 100 µg/kg/day) or saline via a subcutaneously located osmotic minipump at an environmental temperature of 21°C or 28°C while feeding a high-fat diet (45% fat). (A) Weight of the interscapular brown fat pads, after quantitative removal, of mice housed at 21°C (left) and 28°C (right). (B) Representative pictures of ¹⁸F-FDG PET scans that were taken in control and BMP7 (100 µg/kg/day) treated animals (housed at 21°C) after one week of treatment, from which BAT metabolic volume (C) was determined. Arrows indicate neck BAT depots. (D) Expression of Ucp1 in BAT measured by Q-RT-PCR of mice housed at 21°C (left) and 28°C (right). (E) Representative pictures of immunohistochemical UCP-1 stainings of BAT in control and BMP7 (100 µg/kg/day) treated animals housed at 21°C (top) and 28°C (bottom). Pink staining represents UCP-1 protein. Magnification 100x. Scale bar, 100 µm. Values are means+SEM (n = 9) and expression of genes was corrected for the housekeeping genes β2-microglobulin and 36b4. *P<0.05, ***P<0.001 compared to the control group.