Effects of melatonin on the production of GnRH and LH in luteal cells of pregnant sows

Effects of melatonin on the release and synthesis of gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) at the hypothalamus and pituitary levels have been explored in some species, but a similar study in the corpora lutea (CL) has not yet been conducted. In this study, the immunostaining for GnRH and LH was observed in luteal cells of porcine CL during pregnancy, and a significant effect of pregnant stage on the level of GnRH and LH was found; higher values for GnRH and LH immunostaining and mRNA were detected in the early- and mid- stages CL than in the later-stage CL (P < 0.01). Furthermore, the patterns of melatonin membrane receptors (MT1 and MT2) expression were consistent with those of GnRH and LH expression in the CL of pregnant sows; the relative levels of MT1 and MT2 in the early- and mid- stages were significantly higher than those in the later-stage (P < 0.01). In luteal cells, melatonin dose-dependently increased in GnRH and LH secretion and mRNA expression. Melatonin also increased the GnRH–induced accumulation of LH, and the LH–induced secretion of P4 in luteal cells. Additionally, the effects of melatonin on luteal GnRH and LH production, were blocked by luzindole, a nonselective MT1 and MT2 receptor antagonist. Our results demonstrate the stimulatory effects of melatonin on GnRH and LH production in luteal cells of pregnant sows, suggesting a potential role for melatonin in luteal function through regulating the release and synthesis of GnRH and LH in luteal cells.

Transcriptional profiling of equine endometrium before, during and after capsule disintegration during normal pregnancy and after oxytocin-induced luteostasis in non-pregnant mares

The current study used RNA sequencing to determine transcriptional profiles of equine endometrium collected 14, 22, and 28 days after ovulation from pregnant mares. In addition, the transcriptomes of endometrial samples obtained 20 days after ovulation from pregnant mares, and from non-pregnant mares which displayed and failed to display extended luteal function following the administration of oxytocin, were determined and compared in order to delineate genes whose expressions depend on the presence of the conceptus as opposed to elevated progesterone alone. A mere fifty-five transcripts were differentially expressed between samples collected from mares at Day 22 and Day 28 of pregnancy. This likely reflects the longer-term exposure to a relatively constant, progesterone-dominated environment with little change in factors secreted by the conceptus that would affect endometrial gene expression. The complement system was amongst the canonical pathways significantly enriched in transcripts differentially expressed between Day 14 and Day 22/28 of pregnancy. The expression of complement components 7 and 8 was confirmed using in situ hybridization. The expression of SERPING1, an inhibitor of the complement system, was confirmed by immunohistochemistry. In line with the resumed capacity of the endometrium to produce prostaglandin, prostaglandin G/H synthase 1 was expressed at higher levels at Days 22 and 28 than at Day 14 of pregnancy. Our data suggest that this up-regulation is enhanced by the presence of the conceptus; samples obtained from mares at Day 20 of pregnancy had significantly higher levels of prostaglandin G/H synthase 1 transcript than mares with extended luteal function.

The Crazy Ovary

From fetal life until senescence, the ovary is an extremely active tissue undergoing continuous structural and functional changes. These ever-changing events are best summarized by a quotation attributed to Plato when describing motion in space and time—‘nothing ever is but is always becoming…’. With respect to the ovary, these changes include, at the beginning, the processes of follicular formation and thereafter those of follicular growth and atresia, steroidogenesis, oocyte maturation, and decisions relating to the number of mature oocytes that are ovulated for fertilization and the role of the corpus luteum. The aims of this review are to offer some examples of these complex and hitherto processes. The ones herein have been elucidated from studies undertaken in vitro or from normal in vivo events, natural genetic mutations or after experimental inactivation of gene function. Specifically, this review offers insights concerning the initiation of follicular growth, pathologies relating to poly-ovular follicles, the consequences of premature loss of germ cells or oocytes loss, the roles of AMH (anti-Müllerian hormone) and BMP (bone morphogenetic protein) genes in regulating follicular growth and ovulation rate together with species differences in maintaining luteal function during pregnancy. Collectively, the evidence suggests that the oocyte is a key organizer of normal ovarian function. It has been shown to influence the phenotype of the adjacent somatic cells, the growth and maturation of the follicle, and to determine the ovulation rate. When germ cells or oocytes are lost prematurely, the ovary becomes disorganized and a wide range of pathologies may arise.

Latest Advances in Sow Nutrition during Early Gestation

In the pig, the establishment and maintenance of luteal function in early gestation is crucial to endometrial function, embryo development, and survival. The level of feed intake has a positive effect on formation of luteal tissue and progesterone secretion by the ovaries in the pre-implantation period, which is important for endometrial remodeling and secretion. These effects are independent of luteinising hormone (LH) and probably driven by metabolic cues, such as insulin and insulin-like growth factor (IGF-1), and seem to support progesterone secretion and delivery to the endometrium, the latter which occurs directly, bypassing the systemic circulation. Even after implantation, a high feed intake seems to improve embryo survival and the maintenance of pregnancy. In this stage, luteal function is LH-dependent, although normal variations in energy intake may not result in pregnancy failure, but may contribute to nutrient supply to the embryos, since in this phase uterine capacity becomes limiting. Feed incidents, however, such as unintended fasting of animals or severe competition for feed, may result in embryo or even pregnancy loss, especially in periods of seasonal infertility. Specific nutrients such as arginine have a role in the vascularisation of the placenta and can improve the uterine capacity in the period after implantation.

Adiposity Alters Follicle Dynamics in Women of Reproductive Age With Regular Menstrual Cycles

Obesity increases a woman’s likelihood of experiencing adverse reproductive health outcomes, including menstrual cycle irregularity, anovulation, and luteal phase dysfunction. Despite a heightened risk of reproductive dysfunction some women with obesity display ovulatory cyclicity. The degree to which adiposity affects menstrual cycle characteristics in this population is limited to endocrine assessments; evidence supports decreased luteinizing hormone pulse amplitude and reduced luteal phase progesterone. However, these endocrine disruptions have not been linked to alterations in follicular events. The objectives of the present analysis were to evaluate longitudinal changes in follicle size populations and growth kinetics of selectable follicles (6-9mm) and identify endocrine abnormalities associated with obesity in regular cycles. 14 non-obese women (BMI &lt;30 kg/m2) and 15 obese women (BMI≥ 30 kg/m2) with regular cycles were evaluated by serial ovarian transvaginal ultrasonography and venipuncture every-other-day for one complete inter-ovulatory interval (IOI). The number and diameters of all follicles ≥2 mm at each visit were documented offline using the grid method. Growth profiles of individual follicles which grew to &gt;7mm were assessed using the Identity Method. Diagnostic, morphologic, and endocrine features were compared across groups using parametric and non-parametric t-tests (i.e. cross-sectional features) and mixed models (i.e. longitudinal features). Non-obese and obese women with regular cycles showed similar IOI, follicular phase, and luteal phase lengths. The mean number of recruitment events, maximum dominant follicle diameter, and the growth rates of ovulatory follicles over time did not differ between groups, despite confirmation of compromised mean luteal progesterone production (8.23 ng/mL vs. 14.75 ng/mL, p=0.047) and decreased mean luteal FSH levels in women with obesity (2.33 mIU/mL vs. 5.83 mIU/mL, p=0.040). Over the IOI women with obesity showed an increased proportion of 2-5 mm follicles (β=5.3%; p&lt;0.05) and a decreased proportion of 6-9mm follicles (β=-5.0%; p=0.05) versus non-obese women consistent with fewer follicles transitioning from the 2-5 mm pool to the selectable stage. This is the first comparison of follicle dynamics between non-obese and obese women with regular ovulatory cycles. These data suggest that a smaller pool of selectable follicles is present in women with obesity and may result in suboptimal follicle development luteal function. Future studies are needed to understand the impact of altered follicle populations and luteal hormone dynamics on endometrial receptivity and fertility/fecundity.