Pregnant glycaemic control and its effects on healthy development and aging: a role for kisspeptin

During normal healthy pregnancy insulin sensitivity in the mother decreases and in response the insulin-secreting beta-cells in the islets of Langerhans release more insulin and increase in number to maintain normal blood glucose levels. Clinically gestational diabetes can occur when the mother is unable to increase insulin release sufficiently to compensate for the insulin resistance, though the mechanisms involved are currently poorly understood. However, even if gestational diabetes does not develop, pregnancy can still be a critical period when the beta-cells are placed under stress and there is impaired control of blood glucose levels.

Kisspeptin is a recently-discovered molecule that is found, along with its receptor, in a few areas of the human body - the hypothalamic area of the brain, the placenta and the endocrine pancreas. Under normal conditions the levels of kisspeptin found in the blood are very low, but these levels increase greatly during pregnancy due to massive release from the placenta. We have previously shown that placental kisspeptin plays an important role in regulating the adaptation of beta-cell function both during pregnancy, and without it the beta-cells are less able to cope with the demands of pregnancy. We have generated data in mouse models indicating that circulating kisspeptin is involved in both increased insulin release during pregnancy and the increase in beta-cell proliferation during pregnancy. Furthermore we have recently completed a translational study to examine correlations between plasma kisspeptin levels and impaired glycaemic control in pregnant women. Preliminary data from this study indicates that there is a positive correlation between plasma kisspeptin levels during pregnancy and the extent of the insulin response to a glucose challenge as part of an oral glucose tolerance test, suggesting a role for kisspeptin in the adaptation of islets to pregnancy in humans.

However, maintaining normal control of blood glucose during pregnancy is important not just for the duration of pregnancy itself. The changes in beta-cell function that occur during pregnancy, and their long-term effects, are of great potential interest for several reasons beyond the birth of the offspring. It is well established that glucose intolerance and gestational diabetes is a strong marker for impaired glucose homeostasis and potentially type 2 diabetes in the mother in later life, although it is not known whether this represents a causative link, and the underlying mechanisms are unclear. As such the health of the pancreatic islets during pregnancy represents a critical life event with potential long term consequences on the healthy aging of the islets. Similarly, numerous previous studies have described the links between altered maternal glucose control during pregnancy and the subsequent development of metabolic dysfunction and diabetes in the adult offspring. Thus pregnancy is clearly a major physiological event in the life of both mother and offspring. An understanding of the signals involved in ensuring a healthy pregnancy is also hugely important in ensuring that the islets are able to cope with stresses later in life.

The present study aims to investigate the longer-term effects of kisspeptin signalling during pregnancy on healthy beta-cell function in both the mother and offspring after pregnancy. If kisspeptin is an important signal for maintaining normal glucose homeostasis during pregnancy per se, it may also be equally important in ensuring the continued health of the beta-cells in both the mother and the offspring in later life through preventing the development of glucose intolerance during pregnancy.
This will be done through two main objectives: (1) investigating the role of placental kisspeptin in healthy maternal aging. (2) investigating the role of placental kisspeptin in healthy glycaemic control in offspring.

The present study will use a range of different techniques to investigate the effects of plasma kisspeptin on beta-cell function both during and after pregnancy. Both in vitro and in vivo techniques will be used throughout.

The project will involve the use of a beta-cell specific GPR54 knockout mouse which has been generated by crossing floxed GPR54 allele mice with MIP-Cre-ERT mice. Both the floxed GPR54 mice and the MIP-Cre-ERT mice are currently established within the Diabetes Research Group at King's College London through collaboration with Prof Tena-Sempere in Cordoba, Spain and purchase from Jackson Laboratories respectively. Both of these mouse lines are established and have been previously published. This will provide the most specific model for studying the effects of a lack of kisspeptin signalling in the pancreas during pregnancy and the subsequent effects.

Both objectives will involve the assessment of glucose homeostasis in vivo, using techniques including glucose tolerance tests, insulin tolerance tests and collection of blood samples for the measurement of plasma hormone levels. These techniques will be used both during pregnancy itself in order to monitor the glycaemic control of the mother, but also in later life in order to track the healthy aging of the mother post-partum and in the offspring to determine whether there are any developmental differences in glucose metabolism.

Both objectives will also involve collection of tissue samples for in vitro techniques. Pancreas samples will be taken for histological assessment of beta-cell mass and islet structure. Pancreatic islets will also be isolated for the measurement of protein or mRNA levels. Finally additional tissue samples, such as liver, will also be taken to study effects in insulin target tissues.

In terms of communication with the research community the Diabetes Research Group at Guy's regularly has a strong presence presenting research at both national and international diabetes meetings such as the Diabetes UK annual professional conference and the European Association for the Study of Diabetes (EASD) annual meetings. Over recent years we have regularly presented both oral and poster presentations of research at these meetings. Going forward we anticipate continuing to regularly attend high profile scientific meetings within the field in order to disseminate our current research data. Whilst much of our research focuses on islet function and the physiological control of glucose homeostasis, which is generally of most interest to diabetes researchers, the data obtained from this project may also be of interest to researchers within the fields of reproductive function or developmental programming. Depending on the results obtained we would also look at attending meetings in these fields to disseminate our findings amongst other potentially interested groups.

In terms of translational impact, we have recently completed a cross-sectional clinical study to investigate correlations between circulating KP and glycaemic control in pregnant women undergoing a glucose tolerance test as part of their routine antenatal care in collaboration with clinical colleagues at King's College Hospital. Whilst the present project does not contain any translational element in itself we plan to discuss any relevant results with our clinical collaborators and investigate potential translational approaches to confirm our animal data in humans. Whilst translational studies would be challenging given that timescales involved in long-term human studies, the identification of a novel factor during pregnancy that was important for the long term health of the islets and their ability to cope with physiological stress would be of huge interest. Thus, whilst it would not fall within the remit of the present study, we would certainly seek to explore potential ways to move this work towards a translational impact.

Finally the Diabetes Research Group also has an excellent record of outreach activities to people with diabetes, their families and carers, and fundraisers for diabetes charities. For example JEB was recently invited to discuss his research with people with diabetes and their families at an event organised by the Diabetes, Research and Wellness Foundation in Portsmouth. We have also been involved in giving presentations to the student Biomedical Sciences society at King's College London, explaining our research and promoting academic research to those students who are interested in this as a future career. In the past six months representatives of the Group have given research-based presentations to local Diabetes UK groups and to a JDRF group, in addition to running an annual summer school at King's for A-level students who are interested in diabetes research. These presentations are designed to explain to non-scientists why we need to perform basic science studies as a foundation to developing new therapies, and they include some of the concepts and preliminary data included in this application. All of these activities are an ongoing effort on behalf of the group to engage and communicate with other researchers within the field, students enthusiastic about entering research and members of the public who will hopefully ultimately benefit from our research.