Visfatin in the porcine pituitary gland: expression and regulation of secretion during the oestrous cycle and early pregnancy

Abstract

Visfatin is a multifunctional protein which, besides the control of energy homeostasis, seems to be also involved in the regulation of female fertility through the influence on the endocrine hypothalamus-pituitary-gonadal axis, including the pituitary. The aim of this study was to investigate the expression of visfatin mRNA and protein in the anterior (AP) and posterior pituitary lobes of the pig during the oestrous cycle and early pregnancy. In AP, we also examined colocalisation of visfatin with pituitary tropic hormones. Moreover, we aimed to evaluate the in vitro effects of GnRH, FSH, LH, and insulin on visfatin protein concentration and secretion in AP cells during the cycle. The study showed that visfatin is present in all types of porcine pituitary endocrine cells and its expression is reliant on stage of the cycle or pregnancy. GnRH, FSH, LH and insulin stimulated visfatin secretion by AP cells on days 17 to 19 of the cycle, while on days 2 to 3 visfatin release was enhanced only by LH. Summarising, visfatin is locally produced in the pituitary in a way dependent on hormonal milieu typical for reproductive status of pigs. Further research is required to clarify the role of visfatin in the pituitary gland.

The Role of Adipokines in the Control of Pituitary Functions

“…A dependence of visfatin expression on the stage of the oestrous cycle was also found in the anterior and posterior lobe of the porcine pituitary. The adipokine was present in all types of pituitary endocrine cells, and its secretion was affected by GnRH, FSH, LH, and insulin, depending on the phase cycle; LH stimulated visfatin secretion on days 2-3, and GnRH on days 14-16, whereas FSH and insulin stimulated visfatin secretion on days 17-19 of the cycle, which strongly suggests that visfatin is locally produced in the porcine pituitary in a way that is reliant on the hormonal milieu, which is typical for the reproductive status of pigs [126].…”

The Effect of Visfatin on the Functioning of the Porcine Pituitary Gland: An In Vitro Study

“…The animals' diet was balanced according to the current Polish nutritional standards for pig breeding. The AP glands were collected from gilts (n = 5 per group, 20 in total) during specific phases of the estrous cycle: early luteal phase (luteinization phase; days 2-3), mid-luteal phase (the phase in which the activity of the corpus luteum is the highest throughout the cycle; days [10][11][12], late luteal phase (luteolysis phase, days [14][15][16] and the follicular phase (days [17][18][19]. The phase of the estrous cycle was determined by the morphology of the ovaries [15].…”

“…The procedure of APc isolation was performed as described by Szymanska et al [14]. In brief, the AP lobes were cut into small pieces.…”

“…Further, in our previous research, it has been found that VIS is also produced in both the anterior and posterior pituitary lobes of the domestic pig. Additionally, VIS expression and secretion were shown to be dependent on the phase of the estrous cycle and/or the stage of early pregnancy [14]. Furthermore, VIS secretion by porcine anterior pituitary cells (APc) was found to be influenced by gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and insulin (INS), also in a phase-dependent manner [14].…”

“…Additionally, VIS expression and secretion were shown to be dependent on the phase of the estrous cycle and/or the stage of early pregnancy [14]. Furthermore, VIS secretion by porcine anterior pituitary cells (APc) was found to be influenced by gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and insulin (INS), also in a phase-dependent manner [14]. However, the precise role of VIS in the regulation of pituitary function, especially in relation to female reproduction, remains unknown.…”