Role of melatonin on embryo viability in sheep

Melatonin is a natural hormone synthesised in the pineal gland, the activity of which is regulated by day–night perception and dictates seasonal rhythms in reproduction in ovine species. Exogenous melatonin, administered via subcutaneous implants, is used to prolong the breeding season of ewes and can increase the proportion of pregnant ewes (fertility rate) and litter size. The increased proportion of ewes that become pregnant and the number of lambs born per lambing among melatonin-treated sheep may be caused by increased embryo survival, through enhanced luteal function, reduced antiluteolytic mechanisms, or improved embryo quality. This review focuses on the effects of melatonin on embryo viability and summarises the processes by which this hormone affects the ovary, follicle, oocyte, corpus luteum and embryo. Moreover, the effects of melatonin on the mechanisms of invivo maternal recognition of pregnancy in sheep and the protective action that it appears to have on the invitro procedures that are used to obtain healthy embryos are reviewed.

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Regulation of functional and regressing stages of corpus luteum development in mice. Role of reactive oxygen species

Reproduction Fertility and Development ◽

10.1071/rd08051 ◽

2008 ◽

Vol 20 (7) ◽

pp. 760 ◽

Cited By ~ 17

Author(s):

Valeria A. Sander ◽

Lidia Piehl ◽

Graciela B. Facorro ◽

Emilio Rubín de Celis ◽

Alicia B. Motta

Keyword(s):

T Cells ◽

Corpus Luteum ◽

Ovarian Function ◽

Ovarian Tissue ◽

Radical Scavenger ◽

Luteal Function ◽

The Status ◽

Oxidant Status ◽

Total Superoxide Dismutase

The endocrine and immune systems modulate ovarian function. The aim of the present work was to compare the status of various modulating factors in two well-defined stages of corpus luteum (CL) development (the functional stage and the regressing stage) by means of a gonadotropin-synchronised mouse model. At the regressing stage of CL development, we found that ovarian tissue showed increased prostaglandin (PG) F2α and diminished PGE levels concomitantly with enhanced protein abundance of ovarian cyclooxygenase 2, the inducible isoform of the limiting enzyme of PG synthesis. We also found both enhanced lipid peroxidation and enhanced total superoxide dismutase activity, as well as inhibited catalase activity and inhibited total hydroxyl radical scavenger capacity, when compared with ovaries at the functional stage. In addition, at the regressing stage we observed an increased percentage of CD8+ (cytotoxic/suppressor) T-cells and a decreased percentage of CD4+ (helper) T-cells from ovarian-draining lymph nodes. Also, the serum interleukin (IL)-2, IL-4 and IL-10 were diminished as compared with the functional stage. We conclude that a pro-oxidant status together with a pro-inflammatory response is responsible for the loss of luteal function.

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Loss of the glucocorticoid receptor causes accelerated ovarian ageing in zebrafish

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.2190 ◽

2020 ◽

Vol 287 (1940) ◽

pp. 20202190

Author(s):

Erin Faught ◽

Helio B. Santos ◽

Mathilakath M. Vijayan

Keyword(s):

Glucocorticoid Receptor ◽

Egg Quality ◽

Oocyte Quality ◽

Fertilization Rate ◽

Wild Type ◽

Embryo Viability ◽

Embryo Survival ◽

Reproductive Ageing ◽

Inflammatory Infiltrates

Reproductive decline in mid-adult females is an established phenotype of the ageing process. Stress and the rise in glucocorticoids (GCs) accelerate reproductive ageing, but little is known about the mechanisms involved. During stress, GCs activate the glucocorticoid receptor (GR), a ubiquitously expressed, ligand-bound transcription factor, to elicit physiological changes for restoring homeostasis. Here, we tested the hypothesis that GC-GR signalling is essential for accelerating reproductive ageing. To test this, we used a ubiquitous GR knockout (GRKO) zebrafish, which is inherently hypercortisolemic, to delineate the role of high cortisol and GR signalling on reproductive ageing. The loss of GR led to premature ovarian ageing, including high frequency of typical and atypical follicular atresia in vitellogenic oocytes, yolk liquefaction and large inflammatory infiltrates. The reduction in oocyte quality was also associated with a decline in ovarian tert expression in the adult GRKO fish compared to the early adult GRKO and adult wild-type zebrafish. Accelerated ovarian ageing also impacted the progeny, including lower breeding success, fecundity, egg fertilization rate and delayed somitogenesis and embryo survival in the adult GRKO fish. We adduce that GR signalling is essential for prolonging the reproductive lifespan and improving the egg quality and embryo viability in zebrafish.

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The role of vitamin D in metabolic and reproductive disturbances of polycystic ovary syndrome: A narrative mini-review

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000691 ◽

2020 ◽

pp. 1-8

Author(s):

Daniela Menichini ◽

Gianpiero Forte ◽

Beatrice Orrù ◽

Giuseppe Gullo ◽

Vittorio Unfer ◽

...

Keyword(s):

Vitamin D ◽

Polycystic Ovary Syndrome ◽

Embryo Quality ◽

Polycystic Ovary ◽

Vitamin D Supplementation ◽

Endometrial Receptivity ◽

Metabolic Disturbances ◽

Ovary Syndrome ◽

Beneficial Role

Abstract. Vitamin D is a secosteroid hormone that plays a pivotal role in several metabolic and reproductive pathways in humans. Increasing evidence supports the role of vitamin D deficiency in metabolic disturbances and infertility in women with polycystic ovary syndrome (PCOS). Indeed, supplementation with vitamin D seems to have a beneficial role on insulin resistance and endometrial receptivity. On the other hand, exceedingly high levels of vitamin D appear to play a detrimental role on oocytes development and embryo quality. In the current review, we summarize the available evidence about the topic, aiming to suggest the best supplementation strategy in women with PCOS or, more generally, in those with metabolic disturbances and infertility. Based on the retrieved data, vitamin D seems to have a beneficial role on IR, insulin sensitivity and endometrial receptivity, but high levels and incorrect timing of administration seem to have a detrimental role on oocytes development and embryo quality. Therefore, we encourage a low dose supplementation (400–800 IU/day) particularly in vitamin D deficient women that present metabolic disturbances like PCOS. As far as the reproductive health, we advise vitamin D supplementation in selected populations, only during specific moments of the ovarian cycle, to support the luteal phase. However, ambiguities about dosage and timing of the supplementation still emerge from the clinical studies published to date and further studies are required.

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