L-PGDS Compensates for a Lack of PPARc2 Figure 3. Gene expression from epididymal and subcutaneous adipose tissue depots. Expression of adipogenic markers from; A) epididymal white adipose tissue, B) subcutaneous white adipose tissue. Expression of lipogenic markers from; C) epididymal white adipose tissue, D) subcutaneous white adipose tissue. Expression of lipases from; E) epididymal white adipose tissue, F) subcutaneous white adipose tissue. All mice n = 8 per group C57Bl/6 males 4 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.g003 independent groups. Although there was no obvious change in hepatic steatosis as assayed by histology (Figure 6C), DKO mice had a 25% increase in hepatic TG concentration compared to PPARc2 KO mice (Figure 6D), supportive of the elevated de novo lipogenic program and the elevated serum TG levels. Finally, lipidomic analysis of the livers of DKO mice revealed, when compared to PPARc2 KO mice, an up regulation in the levels of lysophosphatidylcholines, which have been associated with insulin resistance (Figure S1). Discussion We previously reported that mice lacking PPARc2 had an unexpectedly normal metabolic phenotype [1]. In this study we have demonstrated that L-PGDS was up-regulated selectively in BAT and subcutaneous white adipose tissue and that L-PGDS in part compensated for a loss of PPARc2 function. Simultaneous loss of PPARc2 and L-PGDS synergistically caused glucose intolerance. Additionally mice lacking PPARc2 and L-PGDS had elevated serum triglyceride compared to any other genotype. These biochemical parameters were associated with depot-specific changes in expression of lipases, HSL phosphorylation status and expression of inflammatory markers in white adipose tissue. They were also associated with an increased expression of the de novo lipogenic program in liver in DKO mice when compared to wild- type mice. Loss of PPARc2 resulted in an increase in L-PGDS expression in brown and subcutaneous WAT but a decrease in L-PGDS expression in epididymal WAT and liver. Given the adipose depot-specific profile of L-PGDS regulation, we expected to see the most dramatic effects of a simultaneous loss of both L-PGDS and PPARc2 in BAT and subcutaneous WAT. Although there were relatively modest changes in gene expression in the inter-scapular BAT of double knock-out mice, the subcutaneous WAT depot showed much more dramatic alterations. In subcutaneous WAT, in terms of gene expression, loss of PPARc2 led to an almost complete switching off of both the thermogenic program and the de novo lipogenic program, regardless of the presence of L-PGDS. However, the loss of L-PGDS and PPARc2 together resulted in a reduction in HSL, ATGL and LPL expression in subcutaneous WAT. These changes were qualitatively mirrored at the protein level, with a reduction in the ratio of activating and inhibitory phosphorylation levels on the lipase HSL of DKO mice compared to PPARc2 KO mice. Added to the individual effect of a loss of PPARc2 on de novo lipogenesis and thermogenesis, these results were consistent with a general impairment in subcutaneous adipose tissue function in DKO mice, suggesting this tissue may have become metabolically inert. PLoS ONE | www.plosone.org 7 July 2012 | Volume 7 | Issue 7 | e39512