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 PPARα 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 PPARα target genes carnitine palmitoyltransferase-1 and acyl CoA oxidase in the liver compared to control hens (P < 0.05), indicative of an activation of PPARα. 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 PPARα did not influence carnitine biosynthesis. In conclusion, this study shows that activation of PPARα 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.
Key words: Peroxisome proliferator-activated receptor α, clofibrate, laying hen, carnitine, novel organic cation transporter 2.
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