Objective: This study was designed to examine the effect of peroxisome proliferator-activated receptor-α (PPAR-α) ligands on the inflammatory changes induced by the interaction between adipocytes and macrophages in obese adipose tissue.
Methods and Procedures: PPAR-α ligands (Wy-14,643 and fenofibrate) were added to 3T3-L1 adipocytes, RAW264 macrophages, or co-culture of 3T3-L1 adipocytes and RAW264 macrophages in vitro, and monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) mRNA expression and secretion were examined. PPAR-α ligands were administered to genetically obese ob/ob mice for 2 weeks. Moreover, the effect of PPAR-α ligands was also evaluated in the adipose tissue explants and peritoneal macrophages obtained from PPAR-α-deficient mice.
Results: In the co-culture of 3T3-L1 adipocytes and RAW264 macrophages, PPAR-α ligands reduced MCP-1 and TNF-α mRNA expression and secretion in vitro relative to vehicle-treated group. The anti-inflammatory effect of Wy-14,643 was observed in adipocytes treated with macrophage-conditioned media or mouse recombinant TNF-α and in macrophages treated with adipocyte-conditioned media or palmitate. Systemic administration of PPAR-α ligands inhibited the inflammatory changes in adipose tissue from ob/ob mice. Wy-14,643 also exerted an anti-inflammatory effect in the adipose tissue explants but not in peritoneal macrophages obtained from PPAR-α-deficient mice.
Discussion: This study provides evidence for the anti-inflammatory effect of PPAR-α ligands in the interaction between adipocytes and macrophages in obese adipose tissue, thereby improving the dysregulation of adipocytokine production and obesity-related metabolic syndrome.