Opposing Roles of Leptin and Ghrelin in the Equine Corpus Luteum Regulation: AnIn VitroStudy

Abstract

Metabolic hormones have been associated with reproductive function modulation. Thus, the aim of this study was: (i) to characterize the immunolocalization, mRNA and protein levels of leptin (LEP), Ghrelin (GHR) and respective receptors LEPR and Ghr-R1A, throughout luteal phase; and (ii) to evaluate the role of LEP and GHR on progesterone (P4), prostaglandin (PG) E2 and PGF2α, nitric oxide (nitrite), tumor necrosis factor-α (TNF); macrophage migration inhibitory factor (MIF) secretion, and on angiogenic activity (BAEC proliferation), in equine corpus luteum (CL) from early and mid-luteal stages. LEPR expression was decreased in late CL, while GHR/Ghr-R1A system was increased in the same stage. Regarding secretory activity, GHR decreased P4 in early CL, but increased PGF2α, nitrite and TNF in mid CL. Conversely, LEP increased P4, PGE2, angiogenic activity, MIF, TNF and nitrite during early CL, in a dose-dependent manner. The in vitro effect of LEP on secretory activity was reverted by GHR, when both factors acted together. The present results evidence the presence of LEP and GHR systems in the equine CL. Moreover, we suggest that LEP and GHR play opposing roles in equine CL regulation, with LEP supporting luteal establishment and GHR promoting luteal regression. Finally, a dose-dependent luteotrophic effect of LEP was demonstrated.

Revisiting the Impact of Local Leptin Signaling in Folliculogenesis and Oocyte Maturation in Obese Mothers

“…In vivo and in vitro studies in mouse ovarian explants [ 26 ] evidenced the dose-dependent effect of leptin on progesterone (P4) synthesis, with low doses stimulating and high doses inhibiting expression of enzymes involved in P4 synthesis [ 26 ]. Also, studies in other species corroborated the aforementioned observations as the in vitro treatment of equine luteal cells with lower doses of leptin supported P4 secretion, whereas higher doses presented no effect [ 27 ]. Particularly regarding follicular dynamics, studies in mice showed that high levels of circulating leptin blocked folliculogenesis, but lower circulating levels of leptin supported the transition from primary to secondary follicle [ 28 ].…”

“…Leptin negatively affected intracellular cAMP levels, MAPK signaling, and aromatase Cyp19a1 mRNA expression with consequent downregulation of E2 synthesis [ 99 ]. Finally, we and others have also shown leptin effects on P4 synthesis, as leptin regulated, in a dose-dependent manner, the expression of cytochrome P450 side chain cleavage (P450 scc) and 3β hydroxysteroid dehydrogenase (HSD) [ 26 , 27 ]. Therefore, obesity and consequent hyperleptinemia can impair steroidogenesis in the growing antral follicle.…”

Leptin Signalling in the Ovary of Diet-Induced Obese Mice Regulates Activation of Nod-Like Receptor Protein 3 Inflammasome

“…Based on gene sequences in GenBank (National Center for Biotechnology Information), the primers for Nlrp3, Casp1, Asc,Tnf ,which sequences are presented in Table 2, were designed using Primer Express 3.0 software (Applied Biosystems). All reactions were carried out in duplicates in 384-well plate (4309849; Applied Biosystems) in 12 µl of total solution volume (Galvão et al 2014). The data were analysed using the real-time PCR Miner algorithm (S. Zhao and Fernald 2005).…”

Endothelial cells and angiogenesis in the horse in health and disease—A review

“…Last, not least, there are several cell surface molecules and receptors relevant to angiogenesis that have been identified in equine endothelial cells—although not necessarily in studies on angiogenesis but in a different context. Examples are the immunolocalization of leptin and ghrelin in equine luteal endothelial cells in vitro (Galvao et al., 2014).…”

“…During the late luteal phase, NO and progesterone 4 inhibit angiogenesis, preparing the CL for functional and structural regression (Ferreira‐Dias & Skarzynski, 2008). Leptin and ghrelin play opposing roles during development and regression of the equine CL, with leptin promoting angiogenesis and ghrelin enhancing luteolysis (Galvao et al., 2014).…”