Leptin levels and leptin and its receptor expression in pig placenta

Leptin, an adipocyte hormone involved in energy homeostasis, is important in reproduction and pregnancy. The objective of this study was to investigate the relationship between placental leptin and its receptor gene expression and maternal plasma leptin concentration in swine, to try to understand the existence of an autocrine regulation for this hormone in placenta. This study began 15 days before the insemination of the animals and this is prolonged for the first month after the birth. The frequency of the drawings was every 15 days up to 45th day of gestation and every 7 days from 46th day up to the end of the protocol of work; an additional drawing has been executed, at parturition day. Leptin concentration was measured by the Linco Multi-Species Leptin Assay Kit; Tissue was taken at delivery, total RNA was extracted and RT-PCR was carried out with specific primers. Blood basal leptin was similar in all animals used: 1.560.03 ng/ml. Leptin levels increase during the pregnancy, but only during the last third of gestation we observed a significant rise in plasma levels (p<0.05). Maternal leptin levels are not modulated by the number of piglets and/or their weight. Results of RT-PCR studies show the expression of leptin and receptor long form: the receptor short form is not expressed. In effect the receptor long form was predicted to be the predominantly functional receptor. The presence of hormone and receptor in the same organ implies a possible autocrine/paracrine effect: these results indicate that leptin can be considered a gestational hormone implied in the endocrine function of the placenta, also with an important role in the autocrine control of the placenta function.