L-PGDS Compensates for a Lack of PPARc2 Figure 2. Energy expenditure and BAT function in DKO mice. A) Gene expression from interscapular BAT. B) Histological analysis of brown fat, analysis of lipid percentage area (right) and representative figures (left). C) Gene expression of thermogenic genes from subcutaneous WAT. D) Oxygen consumption in ml/mouse/min E) Respiratory exchange ratio (RER). All mice n = 8 per group C57Bl/6 males 4 months old. F) Levels of Eicosanoids detectable in the brown adipose tissue of all 4 genotypes n = 8 per group C57Bl/6 males 5 months old. a, P,0.05 WT vs PPARc2, b, P,0.05 WT vs DKO c, P,0.05 PPARc2 vs DKO, d P,0.05 L-PGDS vs DKO. doi:10.1371/journal.pone.0039512.g002 minor impact of a loss of L-PGDS on the function of canonical BAT depots in either WT or PPARc2 KO backgrounds. In addition to traditional BAT depots, subcutaneous WAT has recently been shown to possess significant amounts of develop- mentally distinct brown adipocytes, albeit in scWAT the levels of brown adipocyte markers are far lower than in canonical BAT depots. In scWAT, L-PGDS KO mice exhibited a 4 fold increase in UCP1 expression. Conversely, PPARc2 KO mice exhibited a 5 fold reduction in UCP1 when compared to WT, with DKO mice having similarly low UCP1 expression levels to PPARc2 KO mice (Figure 2C). Conversely, PGC1a and Deiodinase 2 were both down regulated in DKO mice compared to the PPARc2 KO mice. To determine if reduced scWAT function impacted on energy balance, indirect calorimetry was performed on all 4 genotypes. At 22uC, L-PGDS KO mice had a reduction in metabolic rate compared to WT mice (Figure 2D), whereas DKO, PPARc2 KO and WT mice had similar metabolic rates. Analysis of RER showed no overall difference in RER between groups (Figure 2E). Overall the lack of changes in metabolic rate and RER between the PPARc2 KO and DKO mice suggested there was no PLoS ONE | www.plosone.org 5 July 2012 | Volume 7 | Issue 7 | e39512