Dietary conjugated linoleic acid enhances spleen PPAR-γ mRNA expression in broiler chicks

1. The anti-inflammatory effects of dietary conjugated linoleic acid (CLA) on broilers repeatedly challenged with lipopolysaccharide (LPS) were investigated. 2. Day-old broiler chicks were allotted into three treatment groups and fed on a control diet or diets containing 5(.)0 or 10(.)0 g CLA/kg diet. Six chicks from each treatment were injected with LPS (0(.)25 mg/kg body weight) at 16, 18 and 20 d of age. Splenic cyclooxygenase (COX) and inducible nitric oxide synthase (iNOS) activities, and prostaglandin E-2 (PGE(2)) and nitric oxide (NO) production as well as peroxisome proliferator-activated receptor-gamma (PPAR-gamma) mRNA expression were measured at 21 d of age. 3. Chicks fed 10(.)0 g CLA/kg diet had lower COX activities and PGE2 production than the controls. Dietary CLA (10(.)0 g/kg) did not significantly diminish LPS-induced enhancement of COX-2 activity, but inhibited the subsequent increase in PGE2 production. 4. Regulation of COX-1 activity contributed to the difference in PGE2 production. 5. CLA did not markedly attenuate the increase of iNOS activity and NO production caused by LPS challenge. Chicks fed CLA had lower iNOS activity and NO production than the controls. 6. Dietary CLA activated splenic PPAR-gamma mRNA expression and increased PPAR-gamma mRNA expression after LPS injection. 7. These results suggest that dietary CLA has immunomodulatory effects in the spleen by restricting basal PGE2 and NO to lower levels and enhancing PPAR-gamma mRNA expression. During the inflammatory response, dietary CLA did not alleviate the increase in COX-2 and iNOS activities but enhanced PPAR-gamma mRNA expression.