PPARα In Tissues Research Articles

Effects of fish oil and conjugated linoleic acids on carnitine homeostasis in laying hens

1. The effects of n−3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acids (CLA) on genes involved in carnitine homeostasis were compared in laying hens. Three groups of laying hens were fed on a control diet or a diet with either 3% of fish oil or CLA for 4 weeks. 2. Feed intake and egg production rate did not differ between the three groups. Diets with fish oil or CLA had only a weak effect on mRNA levels of PPARα target genes (ACO, CPT-I) in the liver and did not influence mRNA concentrations of the most important carnitine transporter OCTN2, enzymes of involved in carnitine synthesis (TMLD, TMABA-DH, BBD) or concentrations of carnitine in plasma, liver and total egg contents. 3. Hens fed the CLA diet had lower concentrations of free and total carnitine in egg yolk but higher concentrations of carnitine in albumen than control hens (P < 0·05), whereas the amount of free and total carnitine in whole egg did not differ. 4. In conclusion, the study showed that feeding fish oil or CLA causes only a weak activation of PPARα in tissues of laying hens that probably explained the lack of effect on carnitine homeostasis. The results contrast with those in humans and mice that show a significant effect of synthetic PPARα agonists on carnitine homeostasis in humans and mice.

Expression of Peroxisome Proliferator-Activated Receptor Messenger Ribonucleic Acid and Protein in Human and Rat Testis

Peroxisome proliferator-activated receptor α (PPARα), a member of the steroid hormone receptor superfamily, has been linked to lipid homeostasis and tumorigenesis in tissues with high expression of receptor protein. On the other hand, the role of PPARα in tissues with a lower expression is not well known. Here we demonstrate the localization of PPARα messenger RNA (mRNA) and protein in developing and adult rat testis. Additionally, we demonstrate the expression of PPARα protein in adult human testis. Our experiments with Northern analysis, in situ hybridization and immunocytochemistry reveal a complex distribution of PPARα in tubular and interstitial cells of both adult and developing rat testis. The overall expression is rather low but may be modified by exogenous or endogenous stimuli. An up-regulation of PPARα mRNA could be observed after stimulation with FSH. In the developing rat testis, a clear expression of PPARα mRNA was present from the first days after birth. Additionally, PPARα mRNA and protein increased toward adulthood. In adult human testis PPARα immunoreactivity (IR) was present in interstitial Leydig cells and tubular cells. In the seminiferous epithelium of adult human testis the expression of PPARα-IR could be seen in meiotic spermatocytes, spermatids and myoid peritubular cells. The findings of our study suggest that PPARα may be involved in the regulation of growth and differentiation of tubular and interstitial cells in rat and human testis.