Endocrine Abstracts

Introduction: Omentin, also known as intelectin-1 (ITLN1), is a novel adipokine produced predominantly by visceral adipose tissue, which improves insulin sensitivity. Decreased levels of ITLN1 have been reported in the serum of obese and polycystic ovary syndrome patients, as well as in the serum and adipose tissue of obese Meishan (MS) compared to normal weight Large White (LW) pigs. However, the role of ITLN1 in female reproduction at different metabolic status is still unknown.

Aims and methods: This study aimed to 1) examine the mRNA (real-time PCR) and protein (Western blot) expression and immunolocalization (immunofluorescence) of ITLN1 in the ovarian follicles as well as its concentration in follicular fluid (FF, ELISA) at different days of estrous cycle (days 2-3, 10-12 and 14-16 of estrous) in LW and MS pigs; 2) determine the in vitro effect of gonadotropin (LH, FSH) and steroids (P₄, T, and E₂) on ITLN1 expression in ovarian follicular cells and its secretion to the culture medium in LW and MS pigs; 3) the involvement of extracellular signal-regulated kinase (ERK1/2) and phosphatidylinositol 3’-kinase (PI3K) signalling pathways in the regulation of ITLN1 expression in LW pigs. Statistical analysis was performed using a one-way analysis of variance and Tukey’s test (P<0.05).

Results: We showed elevated ITLN1 expression in the ovarian follicles as well as its concentration in FF of LW compared to MS pigs; interestingly, in both breeds of pig, the level of ITLN1 increased with the progression of the estrous cycle. Immunofluorescence showed ITLN1 presence in granulosa, theca, cumulus cells, and oocytes. Both gonadotropins and steroids increased the level of ITLN1 in the ovarian follicle cells as well as in culture medium from LW pigs through kinases ERK1/2 and PI3K, while in MS pigs we observed only the stimulatory effect of LH and T on ITLN1 levels.

Conclusions: For the first time we demonstrated dependent on metabolism condition and the estrous cycle phase ITLN1 expression in the porcine ovarian follicles as well as its regulation by gonadotropins and steroid hormones through ERK1/2 and PI3K signaling pathways. Future studies will be necessary to understand the role of ITLN1 on ovarian function like steroid synthesis of animals with different metabolic states.

Funding: National Science Centre, Poland, OPUS19 project, no. 2020/37/B/NZ9/01154; Excellence Initiative – Jagiellonian University ‘Visibility and Mobility Module’.