Docosahexaenoic acid regulates adipogenic genes in myoblasts via porcine peroxisome proliferator-activated receptor [[gamma].sup.1]

The nuclear transcription factor peroxisome proliferator-activated receptor [gamma] (PPAR[gamma]) triggers adipocyte differentiation by regulating lipogenic genes. A ligand for PPAR[gamma] is necessary to activate PPAR[gamma] function. Fatty acids are potential ligands for PPAR[gamma] activation. The current experiment was designed to determine the potential for individual fatty acids to activate porcine PPAR[gamma] ectopically expressed in myoblasts. The expression of adipocyte fatty acid binding protein (aP2) and adiponectin in myoblasts stably expressing porcine PPAR[gamma] was increased when docosahexaenoic acid (DHA) was added to the adipogenic medium. The response was positively related to DHA concentration and suggests that DHA may bind to and activate porcine PPAR[gamma], leading to increased expression of aP2 and adiponectin. The conditioned media collected from myoblasts expressing PPAR[gamma] between d 3 and 6 or between d 6 and 9, but not DHA itself, activated the aP2 gene promoter-driven luciferase activity. These results suggest that a metabolite of DHA is the ligand binding to and activating porcine PPAR[gamma]. The metabolite and pathway for its production are currently unknown. Key words: adipocyte differentiation, adipocyte fatty acid-binding protein, adiponectin, docosahexaenoic acid, peroxisome proliferator-activated receptor [gamma], pig