(P-331) Obesity prone mice present impaired steroidogenesis associated with SOCS3- mediated Nodal downregulation in ovarian theca-stromal compartment

Abstract Authors: Karolina Wołodko¹, Edyta Walewska¹, Elżbieta Laniecka¹, Antonio M. Galvão^1,2,3,4

< !1. Institute of Animal Reproduction and Food Research, Polish Academy of Science, Olsztyn, Poland

< !2. Royal Veterinary College, University of London, London, United Kingdom

< !3. Epigenetics Programme, The Babraham Institute, Cambridge, United Kingdom

< !4. Centre for Trophoblast Research, University of Cambridge, Cambridge, United Kingdom

Abstract Text: Obesity is a major health issue and presents multiple comorbidities, amongst them infertility. Obesity leads to systemic hormonal imbalance and diabetes, as well as ovarian failure comprising lipid accumulation, cellular stress and inflammation which culminates with decreased ovulation and infertility. Furthermore, we have previously shown that diet- induced obesity (DIO) in mice leads to the establishment of ovarian leptin resistance. Presently, we hypothesise that ovarian performance during obesity is linked to leptin and Nodal signalling disturbances. Using mouse models with contrasting responses to DIO, we unravelled the cross talk between leptin signalling modulator SOCS3 and Nodal signalling underpinning impaired steroidogenesis in obese mothers.

We treated either obesity prone C56BL/6J (B6) mice or obesity resistant 129S1 (129) mice with chow diet (CD) and high fat diet (HFD) for 16 weeks (wk), and characterised the animal phenotype, profiling body weight (BW) and food intake (FI). Additionally, after culling the animals we collected blood, gonadal fat, ovaries, ovarian granulosa cells (GC) and theca/stroma cell fraction (TC) after puncturing the ovaries. Furthermore we used pharmacologically hyperleptinemic (LEPT) mouse model, in which animals were intraperitoneally injected with saline (C) or 100mg of leptin/ day (L), as well as model of genetic obesity with leptin deficiency (ob/ob) and collected ovaries from wild type (+/+) or mutants (-/-) mice. Despite presenting greater FI then the lean counterparts (p< 0.0001), the 129 HFD mice did not gain BW, in contrast with B6 HFD mice, which doubled their BW after DIO (38g) regarding B6 CD (20g). Both strains had increased plasma levels of leptin, but to a greater extent in B6 HFD (p< 0.0001). Moreover, increased BW gain in B6 HFD after DIO was associated with the upregulation in mRNA levels of white adipose tissue expansion markers Polymerase I and transcript release factor (Cavin), Secreted frizzled-related protein 5 (Sfrp5), Mesoderm specific transcript (Mest, p< 0.01) and the proinflammatory genes NLR Family Pyrin Domain Containing 1 (Nlrp1) and C-C motif chemokine ligand 5 (Ccl5, p< 0.01). Furthermore, obesity prone B6 mice presented decreased expression of Luteinizing hormone (Lh) receptor (p< 0.05) in ovarian extracts and Prolactin receptor (Prlr) mRNA in TC (p< 0.01). Moreover mRNA expression of Steroidogenic acute regulatory protein (Star), 3 beta- hydroxysteroid dehydrogenase (3bhsd) and 17bhsd (p< 0.05) was decreased in TC in B6 HFD mice compared to CD, as well as progesterone receptor (PR, p< 0.01) and estradiol receptor a (Era, p< 0.05) mRNA. No significant differences were noted in 129 mice. Finally, we confirmed the upregulation of suppressor of cytokine signalling 3 (Socs3) from B6 HFD comparing to CD (p< 0.001) and associated downregulation of Nodal (p< 0.01) and its receptors Activin receptor type-2B (Acvr2b) and Activin A receptor (Alk7, p< 0.05). Moreover, LEPT model demonstrated increased Socs3 expression in ovarian extracts but decreased Nodal and Alk4 expression comparing to controls, while the extremely obese -/- ob/ob mice demonstrated no changes in Nodal or its receptors.

Overall, impaired steroidogenesis in obesity prone mice is associated with dysregulation of Nodal signalling in TC, which is mediated by the overexpression of SOCS3. Hence, the cross talk between leptin and Nodal signalling may suppress steroidogenesis and subsequently impact oocyte development and quality in obese mothers. Further studies are needed to explore the underlying interactions.



Research supported by the Polish National Science Centre (2019/34/E/NZ4/00349).