Electronic Thesis and Dissertation Repository

Thesis Format

Alternative Format

Degree

Master of Science

Program

Physiology and Pharmacology

Supervisor

Watson, Andrew J.

2nd Supervisor

Betts, Dean H.

Co-Supervisor

Abstract

Maternal diabetes increases congenital malformations due to teratogenic effects of glucose on the developing embryo. High glucose culture alters preimplantation embryo development and is associated with increased oxidative stress. Apoptosis and autophagy are programmed cell death and survival mechanisms induced by oxidative stress, but their role in preimplantation diabetic embryopathy is poorly elucidated. It was hypothesized that high glucose culture would alter autophagic and apoptotic responses, and that they are dependent on the timing of high glucose culture initiation. Embryos were cultured with 0.2 mM (control) or 25 mM (high glucose) of D-glucose starting from the early (36 hpi) or late (48 hpi) 2-cell stage. High glucose culture impaired blastocyst development and total cell number but did not result in changes in apoptotic measures. Autophagic assessments showed increased autophagosome formation and maturation in hyperglycemic embryos when cultured from the early 2-cell stage, but not the late 2-cell stage. Overall, high glucose exposure appears to induce autophagy, but not apoptosis in embryos cultured under diabetically relevant glucose concentrations in the mouse embryo. These results increased the knowledge of mechanisms involved in the etiology of diabetic embryopathy.

Summary for Lay Audience

Maternal diabetes, particularly type 1 and type 2 diabetes, is associated with increased fetal malformations or stillbirth during pregnancy. The levels of glucose in the mother’s blood affect uterine levels and increase embryo stress, negatively affecting embryonic development. My research exposed mouse preimplantation embryos to diabetically relevant concentrations of glucose and analyzed cell death (apoptosis) and cell survival (autophagy) mechanisms in response. Apoptosis mechanisms are initiated by extracellular / intracellular signaling and represent a controlled and sequential process that results in nucleus and cell membrane disintegration and cellular demise. Sometimes this occurs because of cell damage, but it can also be a normal part of controlling cell number and health during embryo development. Autophagy mechanisms promote cell survival by packaging unnecessary or damaged cellular material into a vesicle called an autophagosome, which contains specific tags for degradation. The molecules are released and can be reused as building blocks for other cellular functions. In my research I found that an elevated glucose stimulus in the embryo culture medium does not affect apoptosis, but it does induce autophagy mechanisms. This is important because it suggests the early embryo can employ autophagy to promote survival under the stressful diabetic environment. However, it is still possible the embryo is permanently altered. Additional research employing the high glucose stimulus throughout pregnancy is required to determine if elevated glucose exposure and altered autophagy leads to permanent alterations in the developing fetus.

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