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Title: Investigating the physiology of myometrium from diabetics and the actions of insulin
Author: Heath, Amanda Mary
ISNI:       0000 0004 2733 6700
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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Worldwide, a significant number of diabetic pregnancies end up in caesarean sections (CS). This has been documented in several studies, but none have ever addressed this high caesarean section rate in terms of myometrial contractility. I intended to investigate the hypothesis that the high caesarean section rate seen in diabetic pregnancies is due in part to reduced myometrial contractility, but potentially treatment of the individuals diabetic disease with insulin could also be a contributor to decreased myometrial contractions. In order to test this hypothesis I examined spontaneous contractility in and responses to high potassium depolarisation in myometrial strips dissected from myometrial biopsies obtained with full consent from women undergoing caesarean section to test if contractile activity differed between the two groups. I also investigated the histology of sections from both groups of women to see if the diabetic disease caused any alterations in myometrial muscle content and collagen deposition. To examine the effects of insulin, strips of myometrium diabetic and non-diabetic women and 22day pregnant Wistar rats were exposed to increasing doses of insulin and the response in contractility were measured. In some experiments intracellular Ca signals were simultaneously measured to also see if insulin had an effect on intracellular calcium signalling. To investigate insulin's mechanism of action Ouabain (Na pump inhibitor), tetraethylammonium (K channel inhibitor) and M~CD was added to contracting myometrium combined with insulin. The expression of insulin receptors was also examined in the myometrium from diabetic and non-diabetic women and related to the different responses to insulin seen in both groups. Preliminary experiments to examine the insulin signalling pathway in the myometrium were also carried out by examining the expression of pAkt in response to known concentrations of insulin. Myometrial contractility in diabetic women was found to be impaired compared to non- diabetic women, whereby the force of myometrial contractions was significantly reduced in diabetics. I also found that insulin caused a significant dose dependent decrease in the force of myometrial contractions in pregnant rats and both diabetic and non-diabetic women, which was mirrored in the underlying calcium transients. When Ouabain was added to contracting myometrium in combination with increasing concentrations of insulin, the negative effect of insulin on contractility was inhibited for all concentrations. TEA also significantly inhibited the negative effect of insulin on myometrial contractility. Preliminary investigations using M~CD in combination with insulin showed that there may also be a role for caveolae in the mechanism of insulin action in the myometrium. The effect of insulin on myometrial contractility was more marked in non-diabetic women compared to diabetics. To address this expression of insulin receptor beta subunit in the myometrium from both groups was quantified by immunohistochemistry and western blotting. The results showed a significant reduction in the amount of IR~ expressed in the myometrium of diabetic women compared to non-diabetics. As myometrial contractility was shown to be impaired in diabetics, the reasons for emergency caesarean sections over the last 10 years at Liverpool Women's Hospital were investigated. The results showed that diabetic women had a high chance of emergency caesarean section due to delay in the first stage of labour than non- diabetics which supported our in-vitro findings of poor myometrial contractility in diabetic women. In conclusion this study showed that myometrial contractility is reduced in diabetic women and that insulin the main treatment for diabetes further reduces contractility. Therefore these results may in part explain the high caesarean section rate seen in diabetic pregnancies.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available