An investigation into the effect of glucosamine on reproductive outcomes in the mouse.

Abstract

It is well established that conditions experienced in utero by the developing fetus can elicit permanent effects on the post natal period. Although not as well understood, a growing body of research also suggests that this can also occur in response to peri-conceptional insult. Glucosamine (GlcN) is a popular dietary supplement that is also used experimentally as a hyperglycaemic mimetic. The work contained in this thesis tests the hypothesis that pre and peri-conceptional exposure to GlcN has adverse effects on reproductive outcomes in the mouse. Preliminary experiments (Chapter 2) confirmed that the inclusion of GlcN into the in vitro maturation (IVM) media used for mouse cumulus oocyte complex (COC) maturation, reduced oocyte developmental potential. Subsequent experiments (Chapter 3) demonstrated that the inhibition of O-linked glycosylation of unknown proteins reversed the effects of GlcN. It was also shown that GlcN exposure during IVM altered Pentose phosphate pathway (PPP) activity within the oocyte. As predicted, preliminary in vivo experiments performed in Chapter 4 showed that maternal, peri-conceptional GlcN administration compromised fetal development. This was seen by a decreased mean implantation rate and litter size as well as an increase in the proportion of fetal resorptions on gestational day 18 (d18), and provided the impetus to examine the in vivo effects of GlcN exposure more carefully. It was subsequently hypothesized that these adverse effects would be heightened if given to mice with overweight-induced metabolic pathologies. In contrast to Chapter 4 outcomes, GlcN elicited no effects on d18 implantation, resorption or litter size parameters, but did reduce fetal weight. Furthermore, birth defects were higher in mice given GlcN and maintained on a low fat (LF) diet. An additional cohort of mice was allowed to give birth, and offspring were assessed for 16 weeks. There was an unexpectedly high death rate in the offspring of mice maintained on a high fat (HF) diet but not given GlcN, therefore preventing optimally controlled post natal analyses to occur. Of the remaining mice, a number of physiological differences were detected within GlcN-exposed groups. Since the principle difference between mice in Chapters 4 and 5 was maternal age, an addition experiment investigating the effects of peri-conceptional GlcN exposure in 8 week and 16 week old mice was undertaken (Chapter 6). Consistent with previous results, GlcN treatment reduced mean implantation rate and litter size only in 8 week old mice and reduced fetal weigh and length solely in 16 week old mice. Increased birth defects were also detected in the HF group given GlcN. Collectively these results provide important insights into the importance of optimal conditions during the peri-conceptional period to facilitate successful subsequent development. They also provide evidence that GlcN is a simple but effective tool that can be used to further elucidate the impact of hyperglycaemic exposure during the early developmental period. This is of key importance given the escalating instances of diabetes and obesity in current day Western society, and the associated complications that these conditions elicit on reproductive parameters.