The effects of maternal over-nutrition on the developing embryo

Abstract

The first 4 days of the mouse pregnancy is the preimplantation period. Cells multiply and the first differentiation occurs, establishing distinct stem cell populations; the trophectoderm (TE) which gives rise to the placenta and the inner cell mass (ICM) which gives rise to the embryo proper and yolk sac. Adaptation has been shown to occur at this early stage in response to diet and shows prolonged effects on offspring health (Wakins et al, 2008).

Mice were fed a high fat diet (HF) or high protein (HPD) diet during the preimplantation period to determine if adaptation at this stage was specific in its response to poor diet or whether default adaptation occurred to non-optimal diet. It was found that adaptation was in fact specific to dietary challenge. Maternal causes for these adaptations were investigated, with uterine growth factor expression being found to be altered.

HF embryos were further investigated with pregnancies maintained to a few days prior to birth (E17.5), with HF diet being fed throughout gestation or only for the preimplantation period (emb-HF) and compared to control fed mice. It was found that both the HF and emb-HF fetuses were proportionally larger than their placenta compared to controls, reflecting the proportions of TE and ICM cells observed in the preimplantation embryo. Bone development and glucose tolerance were also affected in these fetuses.

These results suggest that a HF environment experienced during the preimplantation period programmes the growth trajectory of the fetus and placenta. These adaptations may occur in order to establish optimal nutrient supply during gestation in anticipation of nutrient availability. Inappropriate adaptation has been linked with later life diseases such as diabetes and hypertension.

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