Endocrine Abstracts

Background : Omentin, also known as intelectin-1, is a member of the family of adipose tissue-related hormones known as adipokines, that exert anti-inflammatory, anti-atherosclerotic, and cardiovascular protective effects. Omentin expression has been detected in adipocytes as well as in a variety of extra-adipose tissues, including the ovary. Interestingly, omentin expression in the pituitary has been shown to be regulated by pituitary hormones. These observations led us to investigate whether omentin, like the other adipokines, including leptin or adiponectin, regulates pituitary cell proliferation and hormone production. Disturbances of pituitary endocrinology lead to many pathologies. Therefore, the aim of the present study was to investigate i) omentin mRNA and protein expression as well as immunolocalization in the anterior pituitary cells (APc) of sows, ii) in vitro effect of omentin on proliferation, cell cycle, and hormone secretion by pig APc.

Methods: Anterior pituitaries were collected from mature Large White sows on days 2-3, 10-12, 14-16, and 17-19 of the estrous cycle (n=6). Omentin mRNA and protein expression as well as immunolocalization in APc were determined by real-time PCR, Western Blot, and immunohistochemistry, respectively. Next, in in vitro experiments, we investigated the time- (4-72 h) and dose- (10-100 ng/ml) dependent effect of omentin on APc proliferation (alamarBlue), cell cycle (flow cytometry), and hormones’ secretion (FSH, LH, PRL, GH, TSH, ACTH). Statistical analysis was performed using the Student’s t-test, one-way ANOVA, and Tukey’s post-hoc test.

Results: Results showed fluctuations of omentin expression in AP during the estrous cycle: mRNA abundance increased from days 10-12 to 17-19, whereas protein concentration was highest on days 10-12, and lowest on days 17-19. We observed colocalization of omentin with FSH and LH in gonadotropes, with PRL in lactotropes, with GH in somatotropes, with TSH in thyrotropes, but not with ACTH in corticotropes. Interestingly, we noted the stimulatory effect of omentin on APc proliferation and an increase in the percentage of cells in the M phase of cell cycle. Additionally, we demonstrated a dose-dependent action of omentin on pituitary hormone secretion: decrease of FSH, increase of LH, GH, TSH, and no effect on PRL and ACTH.

Conclusion: Taken together, our data indicate that omentin, either locally produced or from other sources, may regulate porcine pituitary cells’ functions. Funding: National Science Centre, Poland, 2020/37/B/NZ9/01154; Excellence Initiative – Jagiellonian University “Visibility and Mobility Module”.