Effects of activation of peroxisome proliferator-activated receptor-a by clofibrate on carnitine homeostasis in laying hens

Abstract

In this study, the hypothesis was investigated that activation of peroxisome proliferator-activated receptor (PPAR)-α regulates homeostasis of carnitine in laying hens. Therefore, laying hens received either a control diet or a diet supplemented with 0.15% clofibrate as a synthetic PPAR α agonist for 4 weeks. Feed intake was not different between both groups of hens while egg production rate was slightly reduced in the group of hens treated with clofibrate (P < 0.05). Hens treated with clofibrate had an increased expression of the classical PPAR α target genes carnitine palmitoyltransferase-1 and acyl CoA oxidase in the liver compared to control hens (P < 0.05), indicative of an activation of PPAR α. In hens treated with clofibrate, mRNA concentration of novel organic cation transporter (OCTN)-2, the most important carnitine transporter, in the liver as well as carnitine concentrations in plasma, liver, egg yolk and albumen were increased compared to control hens (P < 0.05). mRNA concentrations of enzymes of hepatic carnitine synthesis as well as concentrations of the carnitine precursors trimethyllysine and γ-butyrobetaine in plasma, liver and muscle were unchanged in hens treated with clofibrate, suggesting that activation of PPAR α did not influence carnitine biosynthesis. In conclusion, this study shows that activation of PPAR α up-regulates expression of OCTN2 in the liver of laying hens, such as in mammalian species and causes an increase of carnitine concentrations in liver, plasma and egg.