The effect of nutrition and environment on the preimplantation embryo

Dynamics of inflammatory reaction and oxidative stress across maternal serum, placenta and amniotic fluid in laboratory rats and the role played by genistein aglycone

Background Genistein was reported to adversely influence fetal development although this is yet to be fully understood as a mechanism. Methods In this study, pregnant rats were divided into control (Cont.) and genistein force-fed (2-mg/kg and 4-mg/kg) groups. Each group was divided further into five subgroups: GD-0, GD-6, GD-13, GD-18, and GD-20 based on the terminal gestational day (GD). On the respective terminal GD, the rats were sacrificed and blood samples and amniotic fluid were carefully collected and separated and placenta homogenates were prepared. These samples were evaluated for oxidative stress and inflammatory reaction. The weights of embryonic implant and placenta tissue were also recorded. Heat shock protein (Hsp) (60 and 90), corticosterone, and oxidative stress biomarkers were determined in all the samples. Results Fetal and placental weights in all genistein-exposed groups were significantly decreased. A fluctuation in the level of the Hsp was recorded with a significant decrease recorded in Hsp90 level in the placenta and amniotic fluid towards GD-20 along with a concomitant increase in the corticosterone level in the amniotic fluid in all genistein groups compared to control. Maternal serum at GD-18 and GD -20 recorded a significant increase in antioxidant level (SOD, GSH, CAT) in all genistein-exposed groups. However, these antioxidants were significantly reduced in the placenta and the amniotic fluid compared to control. Conclusions Genistein enhances the placenta function in attenuating the risk of oxidative stress in the amniotic fluid and deferentially suppressed inflammatory activities in the placenta during early gestation and towards late gestation period.

Do little embryos make big decisions? How maternal dietary protein restriction can permanently change an embryo’s potential, affecting adult health

Periconceptional environment may influence embryo development, ultimately affecting adult health. Here, we review the rodent model of maternal low-protein diet specifically during the preimplantation period (Emb-LPD) with normal nutrition during subsequent gestation and postnatally. This model, studied mainly in the mouse, leads to cardiovascular, metabolic and behavioural disease in adult offspring, with females more susceptible. We evaluate the sequence of events from diet administration that may lead to adult disease. Emb-LPD changes maternal serum and/or uterine fluid metabolite composition, notably with reduced insulin and branched-chain amino acids. This is sensed by blastocysts through reduced mammalian target of rapamycin complex 1 signalling. Embryos respond by permanently changing the pattern of development of their extra-embryonic lineages, trophectoderm and primitive endoderm, to enhance maternal nutrient retrieval during subsequent gestation. These compensatory changes include stimulation in proliferation, endocytosis and cellular motility, and epigenetic mechanisms underlying them are being identified. Collectively, these responses act to protect fetal growth and likely contribute to offspring competitive fitness. However, the resulting growth adversely affects long-term health because perinatal weight positively correlates with adult disease risk. We argue that periconception environmental responses reflect developmental plasticity and ‘decisions’ made by embryos to optimise their own development, but with lasting consequences.

The effects of calcitonin on the development of and Ca2+ levels in heat-shocked bovine preimplantation embryos in vitro

Intracellular calcium homeostasis is essential for proper cell function. We investigated the effects of heat shock on the development of and the intracellular Ca²⁺ levels in bovine preimplantation embryos in vitro and the effects of calcitonin (CT), a receptor-mediated Ca²⁺ regulator, on heat shock-induced events. Heat shock (40.5 C for 10 h between 20 and 30 h postinsemination) of in vitro-produced bovine embryos did not affect the cleavage rate; however, it significantly decreased the rates of development to the 5- to 8-cell and blastocyst stages as compared with those of the control cultured for the entire period at 38.5 C (P < 0.05). The relative intracellular Ca²⁺ levels at the 1-cell stage (5 h after the start of heat shock), as assessed by Fluo-8 AM, a fluorescent probe for Ca²⁺, indicated that heat shock significantly lowered the Ca²⁺ level as compared with the control level. Semiquantitative reverse transcription PCR and western blot analyses revealed the expression of CT receptor in bovine preimplantation embryos. The addition of CT (10 nM) to the culture medium ameliorated the heat shock-induced impairment of embryonic development beyond the 5- to 8-cell stage. The Ca²⁺ level in the heat-shocked embryos cultured with CT was similar to that of the control embryos, suggesting that heat shock lowers the Ca²⁺ level in fertilized embryos in vitro and that a lower Ca²⁺ level is implicated in heat shock-induced impairment of embryonic development. Intracellular Ca²⁺-mobilizing agents, e.g., CT, may effectively circumvent the detrimental effects of heat shock on early embryonic development.