Abstract 295: Microsomal Prostaglandin E Synthase 1 Deficiency Attenuates Diet-Induced Obesity and Promotes the Formation of Brite Adipose Tissue

Abstract

Mice deficient in adipocyte specific phospholipases A2 have a marked reduction in prostaglandin E2 (PGE2) levels and are resistant to the development of diet-induced obesity. Clinical data suggest that obesity is a chronic low grade inflammatory disease, characterized by the influx of inflammatory cells into the adipose tissue. During a chronic inflammatory state, microsomal prostaglandin E synthase-1 (mPGES-1) is the primary source of PGE2. We have previously demonstrated that mice deficient in mPGES-1 (KO) have a marked reduction in body weight gain and adiposity compared to littermate controls (WT) fed a high fat (HF) diet with a concomitant reduction in urinary PGE2 concentrations and an increase in urinary PGI2 concentrations. The reduction in weight gain is not for accounted by alterations in food intake or locomotor activity. However, resting metabolic rate, measured by indirect calorimetry, was increased in KO mice compared to WT fed a HF diet. Moreover, body temperature was also increased in KO mice compared to WT mice (37.0 ± 0.2 vs 35.8 ± 0.2; P < 0.05) fed a HF diet. Taken together these data suggest that mPGES-1 deficiency increases energy expenditure in response to feeding a HF diet. Analysis of white adipose tissue (WAT) depots demonstrated an increase in number of smaller adipocytes per unit area in the KO mice compared to WT mice. The WAT from KO mice also had a marked decrease in triglyceride content, F4/80 staining and CD86 staining with a concomitant increase in CD206 staining suggesting an attenuation in macrophage recruitment into the WAT as well as an M2 phenotype. Additionally, COX-2 and UCP-1 and PPAR-γ expression were increased in WAT depots with a concomitant localization of multi-locular adipocytes in WAT depots, demonstrating the presence of brown adipocytes in WAT depots in KO mice fed a HF diet. These data suggest that the reduction in body weight gain in the KO mice may be due an increase in thermogenesis mediated by the formation of brite adipose tissue in WAT depots.