Investigating The Impact Of Hyperglycaemia On Early Embryo Environment And Development

The development of metabolic conditions has been associated with suboptimal nutrient provision to the embryo during pregnancy. Metabolic disorders have also been linked to subfertility; obese women produce fewer and smaller oocytes that are metabolically distinct from the oocytes of non-obese women. However, the impact of metabolic conditions on the secretions of the oviduct has not been extensively investigated. The work presented in this thesis has used an established in vitro model of the oviduct to determine the extent to which hyperglycaemia in the presence or absence of insulin modified oviduct secretions. These secretions were used to examine whether embryo survival and metabolism were also affected. Bovine oviduct epithelial cells (BOECs) were cultured under conditions designed to model acute and chronic hyperglycaemia, and in the presence or absence of physiologically relevant insulin concentrations. The fluid secreted by BOECs was analysed using ultramicrofluorometric assays and high-performance liquid chromatography, and expression of key genes was also assessed. Chronic treatment of BOECs under the above conditions modified cell secretions, since the concentrations of glucose, alanine, glycine and glutamine were significantly altered. The data on concentrations of substrates was then used to inform the composition of embryo culture medium, using 1mM, 3.6mM and 8.9mM glucose for the ‘8.5’, ‘7.3’ / ‘11+’, and ‘11-’ environments respectively, and modifying lactate, pyruvate and amino acid concentrations accordingly. The modified embryo environments did not affect preimplantation embryo cleavage and blastocyst rates; however, they modified the rates of pyruvate and glycine consumption, as well as arginine consumption/production. In summary, hyperglycaemia in the presence or absence of insulin modifies oviduct secretions, which in turn leads to altered embryo metabolism. Further experiments may elucidate whether a combination of molecules implicated in metabolic conditions exert a more pronounced effect on the composition of oviduct-derived fluid, as well as embryo survival and metabolism.