APELIN EXPRESSION IN THE UTERUS OF SHEEP GRAZING ON SEMINATURAL PASTURE, PRELIMINARY RESULTS

Adipokines, mainly produced by adipose tissue, are molecules involved in energy metabolism and represent important links between nutritional status, and neuro-endocrine axis. Physiological levels of adipokines are necessary for the regular performance of ovarian activity, the correct embryo implantation and a healthy pregnancy. Apelin (APLN) expression in adipose tissue is regulated by factors such as fasting and refeeding and this molecule plays a role in the regulation of adiposity, food intake and body weight. However, investigation on this topic has yielded disparate results [1]. APLN and its receptor have a widespread distribution throughout the CNS and periphery. The apelinergic system is also active in the female reproductive tissues such as placenta, ovary and uterus [2] even if, differences emerged among species. APLN causes obesity increasing body weight but also leads to infertility modifying reproductive hormones in mouse [3]. In this work, the expression and localization of APLN was analyzed in the uterus of the sheep in an attempt to shed light on those cells and structures that might locally produce and secrete this peptide. A group of 15 Comisana x Appenninica adult female sheep in dry stage were fed with fresh hay from June to the pasture maximum flowering (MxF group). From this period to maximum dryness, the sheep were split into two groups: the control group (Cnt group) was fed with fresh hay while, the experimental group (Exp group) was fed with fresh hay supplemented with 600g/day/head of barely and corn (1:1). Samples of uterus were collected for each group and processed to perform PCR and immunohistochemistry. Samples for molecular biology were procedures were fixed in 10% neutral-buffered formalin solution and included in paraffin wax. Immunohistochemistry for APLN was performed with a polyclonal rabbit anti-apelin antibody. In all uterus samples analysed, PCR demonstrated the presence of the transcript for APLN. By immunohistochemical investigation, a positive staining for APLN was observed in the apical membrane of the endometrial epithelial cells and in the glands located in the connective tissue. APLN staining appeared stronger in Cnt and Exp groups respect to MxF one. To the authors' knowledge, no studies describe APLN expression in the uterus of domestic animals. Its identification in the sheep suggests that this peptide may play a role in the activity of this organ and is involved in the reproduction. This is a preliminary report that introduces APLN investigation in the sheep female genital system however, the exact role of APLN and the influence of diet needs further elucidation.