L-PGDS Compensates for a Lack of PPARc2 Figure 1. Regulation and function of L-PGDS in models of altered PPARc activity. A) L-PGDS mRNA levels in the major metabolic tissues of PPARc2 KO mice. B) Body weights of all four genotypes from the L-PGDS x PPARc2 (DKO) double cross. C) DKO mice have reduced BAT mass compared to other genotypes. Both PPARc2 KO and DKO mice have reduced epididymal fat mass. D) DKO mice have impaired glucose tolerance compared to any other genotype. Statistics performed on area-of-curve. (Box, AOC 0–10 minutes). E) DKO mice are more insulin resistant than WT mice Statistics performed on area- of-curve. F) Serum Free fatty acid, triglyceride and insulin levels. All mice n = 8 per group C57Bl/6 males 4 months old, except mice undergoing ITT which were 4.5 months of age. *, P,0.05 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.g001 L-PGDS x PPARc2 KO (DKO) Mice have Impaired Carbohydrate and Lipid Metabolism To investigate if the up regulation of L-PGDS in BAT and scWAT was compensating for the absence of PPARc2 function, a double KO mouse lacking both L-PGDS and PPARc2 (DKO) was generated. At 16 weeks of age body weights of chow fed mice appeared similar, irrespective of genotype (Figure 1B). However, the interscapular BAT mass of the DKO mice was significantly smaller than that of wild-type or PPARc2 KO mice (Figure 1C). Epididymal WAT mass was decreased in both the DKO and PPARc2 KO mice to an equal degree when compared to WT controls. In addition to alterations in adipose tissue mass, at 16 weeks of age, DKO mice had impaired glucose tolerance when compared to WT, L-PGDS or PPARc2 KO mice (Figure 1D). Subsequent insulin tolerance tests demonstrated more severe insulin resistance in the DKO mice, when compared to wild-type mice (Figure 1E). Serum biochemistry demonstrated that DKO mice exhibited elevated serum triglycerides - nearly double that of any other genotype. Furthermore DKO mice exhibited an increase in fed free-fatty acid levels over L-PGDS single KO mice (Figure 1F). L-PGDS x PPARc2 KO Mice have Altered Levels of Markers of Brown Adipocyte Thermogenic Function Alteration in BAT mass can occur as a consequence of reduced BAT development and/or function. However, gene expression analysis failed to show many DKO-dependent alterations in markers of BAT activation. Several PPARc target genes were down regulated in response to PPARc2 ablation (including Elovl6, SCD1 and FAS), whereas UCP2 was up regulated, however the changes in these genes occurred to an equal extent in PPARc2 KO mice and DKO mice (Figure 2A). Morphologically, interscapular BAT from DKO mice exhibited greater lipid content than WT mice (Figure 2B) but was not distinct from PPARc2 KO mice. Overall, these results demonstrated that at 24uC there was a very PLoS ONE | www.plosone.org 4 July 2012 | Volume 7 | Issue 7 | e39512