Non-invasive assay of amino acid turnover has the potential to improve significantly the prospective selection of the most viable embryos, or single embryo, for replacement in an IVF cycle.

Non-invasive amino acid profiling has the potential to select developmentally competent single embryos for transfer, thereby increasing the success rate and eliminating multiple births in IVF.

A model culture system for the study of follicular metabolism has been developed from existing methods of whole-follicle culture. The modified system mimics the in vivo growth and maturation of mouse ovarian follicles from primary to preovulatory stages and the modulating influences of the LH and FSH. This is the first study to demonstrate ovulation in vitro from individual ovarian follicles. The pattern of follicular lactate production relative to steroidogenesis was studied throughout in vitro follicular development over a period of 6 days. Twenty-four-hour samples of medium from individual follicles were analyzed for lactate and pyruvate by an automated analytical technique, and for estradiol and progesterone by an immunoenzymatic method. Follicles produced remarkably large quantities of lactate and estradiol during FSH-stimulated development in vitro. LH further stimulated lactate production but resulted in a significant decrease in estradiol secretion and an ovulation rate of 30%. Progesterone production was not detectable throughout the culture period, and follicles showed no evidence of pyruvate uptake. These findings demonstrate the validity of using this model culture system for the study of follicular metabolism and provide new information on the pattern of carbohydrate metabolism relative to steroidogenesis during follicular growth and maturation.

Previously, we have shown that a maternal low protein diet, fed exclusively during the preimplantation period of mouse development (Emb-LPD), is sufficient to induce by the blastocyst stage a compensatory growth phenotype in late gestation and postnatally, correlating with increased risk of adult onset cardiovascular disease and behavioural dysfunction. Here, we examine mechanisms of induction of maternal Emb-LPD programming and early compensatory responses by the embryo. Emb-LPD induced changes in maternal serum metabolites at the time of blastocyst formation (E3.5), notably reduced insulin and increased glucose, together with reduced levels of free amino acids (AAs) including branched chain AAs leucine, isoleucine and valine. Emb-LPD also caused reduction in the branched chain AAs within uterine fluid at the blastocyst stage. These maternal changes coincided with an altered content of blastocyst AAs and reduced mTORC1 signalling within blastocysts evident in reduced phosphorylation of effector S6 ribosomal protein and its ratio to total S6 protein but no change in effector 4E-BP1 phosphorylated and total pools. These changes were accompanied by increased proliferation of blastocyst trophectoderm and total cells and subsequent increased spreading of trophoblast cells in blastocyst outgrowths. We propose that induction of metabolic programming following Emb-LPD is achieved through mTORC1signalling which acts as a sensor for preimplantation embryos to detect maternal nutrient levels via branched chain AAs and/or insulin availability. Moreover, this induction step associates with changes in extra-embryonic trophectoderm behaviour occurring as early compensatory responses leading to later nutrient recovery.

Up to 40% of cattle embryos die within 3 weeks of fertilization while they are nutritionally dependent on the maternal environment provided by the oviduct and uterine fluids for their development and survival. Despite this dependence there is limited information on the composition of these fluids in cattle. Amino acids are essential for the normal growth and development of the early embryo, acting as precursors of proteins and nucleic acids and as energy sources, osmolytes and signaling molecules. The objective of this study was to measure and compare the amino acid concentrations of oviduct and uterine fluid and blood plasma on different days of the estrous cycle. Oviduct fluid was collected in situ from anaesthetised heifers on Days 0, 2, 3, 4 and 6 and uterine fluid on Days 6, 8 and 14 of the estrous cycle and the concentrations of 19 amino acids determined. Glycine was the most abundant amino acid in both oviduct and uterine fluid. However, the concentrations of many amino acids differed between oviduct and uterus and many were present at higher concentrations in oviduct and uterine fluid than in blood plasma. Oviduct fluid concentrations of amino acids were not affected by day of cycle in contrast to uterine fluid for which there was a day of cycle effect on most of the amino acids. These results provide novel information on the amino acid concentrations in the maternal environment of the early cattle embryo and could form the basis for devising improved media for the production of embryos in vitro.