Cyclooxygenases and UCP1 Figure 5. Cold-induced UCP1 expression is attenuated in iWAT in COX2 KO mice. A B COX2 KO mice and wild-type littermates were warm- acclimated at 28–30uC for 10 days and then transferred to 4–6uC for 48 h. Rectal temperature was measured before transfer and after 24 and 48 h (A). RNA was extracted and expressions of genes were measured by RT-qPCR (B). The bars represent mean 6 standard error (n = 5–6). * indicates statistical significant difference between wild-type and KO mice (p,0.05). doi:10.1371/journal.pone.0011391.g005 supplementation for 4 weeks while keeping the mice at 28–30uC. As demonstrated in Figure 7A, indomethacin supplementation led to a higher weight gain. Energy intake was slightly, but not statistically significantly lower (data not shown). However, energy intake relative to body weight gain was significantly lower in mice that received the indomethacin-supplemented high-fat diet (Figure 7A). Mice fed the diet supplemented with indomethacin also had more WAT in different depots, but not iBAT (Figure 7B). Histological analysis revealed that the adipocytes in both iWAT and iBAT appeared normal, but adipocytes in iWAT in mice fed the high-fat diet supplemented with indomethacin were slightly larger (Figure 7C and D). As expected, feeding mice a high-fat diet lead to augmented expression of UCP1 in both iBAT and iWAT in vehicle-treated mice (Figure 7E). Importantly, diet-induced UCP1 expression was prevented in iWAT, but not in iBAT in the indomethacin-treated mice (Figure 7E). Reduced expression of UCP1 in iWAT in mice fed a high-fat diet supplemented with indomethacin was accompanied with reduced expression of Cox8b. Expression of PGC1a, Dio2, Eva1, Cidea, 4E-BP1 and RIP140 was not affected by inclusion of indomethacin with the high-fat diet (Figure 7E). Collectively, these results underscore the notion that inhibition of COX activity attenuates the acquisition of ‘‘brite’’ adipocytes in white adipose depots with an accompanying increase in feed efficiency leading to accumulation of more adipose tissue. Obviously, other mechanisms may contribute to the increase in feed efficiency, but the lack of ‘‘brite’’ adipocyte recruitment seems a key player. Discussion The unique energy-dissipating ability of UCP1 makes control of its expression and activation potential targets for the development of novel drugs for the treatment of obesity and obesity-associated diseases. Here we present evidence that COX activity and COX- derived PGE2 are intimately linked to induction of UCP1 expression in iWAT, but not in iBAT. Thus, cold-induced expression of UCP1 in iWAT was repressed in mice treated with the general COX inhibitor indomethacin, and in COX2 KO PLoS ONE | www.plosone.org 7 June 2010 | Volume 5 | Issue 6 | e11391